2024-03-29T11:06:50Zhttps://kuscholarworks.ku.edu/oai/requestoai:kuscholarworks.ku.edu:1808/184972020-06-24T18:42:40Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Borton, Martha Clara
2015-09-21T18:31:39Z
2015-09-21T18:31:39Z
1915
http://hdl.handle.net/1808/18497
Thesis (M.A.)--University of Kansas, Physics, 1915. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Measurement of the strength of magnetic fields by means of liquids
Thesis
Physics
M.A.
3424341
oai:kuscholarworks.ku.edu:1808/209652017-12-08T21:38:01Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Roberds, Wesley Milton
2016-06-15T15:14:37Z
2016-06-15T15:14:37Z
1926
http://hdl.handle.net/1808/20965
Thesis (M.A.)--University of Kansas, Physics, 1926.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The resistance of copper wires at very high frequencies
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/205982021-08-26T22:01:16Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Ritchie, R. Morris
2016-03-29T16:05:04Z
2016-03-29T16:05:04Z
1924
http://hdl.handle.net/1808/20598
Thesis (M.S.)--University of Kansas, Physics, 1924.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Characteristics of an electron tube supplied with an alternating plate potential
Thesis
Physics
M.S.
oai:kuscholarworks.ku.edu:1808/214622017-12-08T21:40:50Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Cannon, John Lawrence
2016-09-07T13:17:36Z
2016-09-07T13:17:36Z
1929
http://hdl.handle.net/1808/21462
Thesis (M.A.)--University of Kansas, Physics, 1929.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The thermoelectric properties of liquid alloys of mercury and tin
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/190602018-01-31T20:07:50Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Besson, David Z
Kunwar, Samridha
Allen, Christopher
Baringer, Philip S
McKay, Douglas
Tapia Takaki, Daniel
2015-12-03T04:20:17Z
2015-12-03T04:20:17Z
2015-05-31
2015
http://dissertations.umi.com/ku:13870
http://hdl.handle.net/1808/19060
The detection of ultra-high energy cosmic rays is constrained by their flux, requiring detectors with apertures of hundreds or even thousands of square kilometers and close to one hundred percent duty cycle. The sheer scale that would be required of conventional detectors, to acquire sufficient statistics for energy, composition or anisotropy studies, means that new techniques that reduce manpower and financial resources are continually being sought. In this dissertation, the development of a remote sensing technique based observatory known as bistatic radar, which aims to achieve extensive coverage of the Earth's surface, cf. Telescope Array's 700 km2 surface detector, is discussed. Construction of the radar projects transmitter station was completed in the summer of 2013, and remote receiver stations were deployed in June and November of 2014. These stations accomplish radar echo detection using an analog signal chain. Subject to less radio interference, the remote stations add stereoscopic measurement capabilities that theoretically allow unique determination of cosmic ray geometry and core location. An FPGA is used as a distributed data processing node within the project. The FPGA provides triggering logic for data sampled at 200 MSa/s, detecting Cosmic Ray shower echoes chirping at -1 to -10 Megahertz/microsecond (depending on the geometry) for several microseconds. The data acquisition system with low power consumption at a cost that is also comparatively inexpensive is described herein.
106 pages
en
University of Kansas
Copyright held by the author.
openAccess
Particle physics
Astrophysics
Chirp
Cosmic Rays
Embedded System
FPGA
Radar
UHECR
Design And Development Of An Autonomous Radar Receiver For The Detection Of Ultra High Energy Cosmic Rays
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/251592017-12-08T21:43:43Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
McFerrin, William Virgil
2017-10-19T15:06:54Z
2017-10-19T15:06:54Z
1932
http://hdl.handle.net/1808/25159
Thesis (M.A.)--University of Kansas, Physics, 1932.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Viscosities of stannic chloride-acetic acid solution
Thesis
Physics
M.A.
3425291
oai:kuscholarworks.ku.edu:1808/280522019-08-27T18:09:08Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Besson, David Z
Stockham, Jessica
Allen, Christopher
Feldman, Hume
Lewis, Ian
Zhao, Hui
2019-05-19T02:11:42Z
2019-05-19T02:11:42Z
2018-12-31
2018
http://dissertations.umi.com/ku:16297
http://hdl.handle.net/1808/28052
The ANITA (ANtarctic Impulsive Transient Antenna) experiment is a balloon-borne suite of radio frequency antennas deployed during the austral summers in 2006, 2011, 2014, and 2016 to travel on the circumpolar winds over the ice sheets of Antarctica. The goal of the ANITA experiment is to detect UHE (Ultra-High Energy) neutrinos $(10^9$ to $10^{13}$ GeV) and cosmic rays through the RF (Radio-Frequency) emission of in-ice and atmospheric particle showers initiated, respectively, by these two types of particles. Radio detection of ultra-high energy cosmic ray (UHECR) extensive air showers (EAS) above the Antarctic continent has been demonstrated by the four flights of the ANITA experiment. The majority of the detected events were received as reflections from the ice surface. In order to reconstruct the energy of these reflected events, it is necessary to quantify any decoherence in the ANITA frequency band (180-1200 MHz) due to roughness of the ice surface. The purpose of this work is to provide details on the HiCal (High-altitude Calibration) experiment implemented to measure surface reflectivities of the Antarctic ice as a part of the ANITA experiment. The first HiCal payload flew in conjunction with the ANITA-3 flight in 2014 and provided a set of direct and reflected event pairs from which an inclination angle dependent measurement of the surface reflection coefficients was determined. It was found that at the highest incidence angles (most skimming) this coefficient deviates significantly both from the Fresnel predicted coefficients and from the model derived coefficients currently used in the ANITA analysis reconstruction of UHECR events.
92 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astrophysics
Remote sensing
Geophysics
cosmic ray
surface roughness
Design, Implementation and First Results of the ANITA-HiCal Experiment
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/108632020-09-23T14:12:02Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Medvedev, Mikhail V
Keenan, Brett
Cravens, Thomas E
Rudnick, Gregory
2013-02-17T20:27:01Z
2013-02-17T20:27:01Z
2012-12-31
2012
http://dissertations.umi.com/ku:12513
http://hdl.handle.net/1808/10863
Kinetic streaming instabilities, such as the Weibel instability, occur in various HED plasma setups. Such instabilities generate strong (sub-equipartition) magnetic fields which reside at small, sub-Larmor scales. Efficient electron acceleration to relativistic energies is not uncommon in such environments. Spectra of radiation emitted by these relativistic electrons can deliver a wealth of information about the internal structure of such "Weibel turbulence". The small-scale fields simultaneously drive the particle transport via pitch-angle diffusion. Both effects are related and can be used to diagnose the plasma state. We study such a relation between transport and radiation in sub-Larmor-scale turbulence via numerical simulations and analysis.
28 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Plasma physics
Astrophysics
Diffusion
Jitter radiation
Magnetic turbulence
Pitch-angle
Small-scale
Weibel instability
Transport Properties and Radiation Production in Plasmas with Sub-Larmor-Scale Magnetic Turbulence
Thesis
Physics & Astronomy
M.S.
na
This item does not meet KU Open Access policy criteria.
8085665
oai:kuscholarworks.ku.edu:1808/298832021-03-05T16:53:01Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Cravens, Thomas E
Houston, Stephen Jeffrey
Twarog, Bruce A
Besson, David Z
Lewis, Ian M
Ackley, Brian
2020-01-17T22:04:53Z
2020-01-17T22:04:53Z
2019-05-31
2019
http://dissertations.umi.com/ku:16575
http://hdl.handle.net/1808/29883
The source of auroral X-ray emission from the Jovian polar caps, whether from electron bremsstrahlung or heavy ion precipitation, has been a topic of debate for the past 40 years, beginning with the Einstein Observatory's first measurement of X-ray emission in 1979. Since then the Roentgen satellite, Chandra X-ray Observatory, and XMM-Newton have distinguished heavy ion (oxygen and sulfur) line emission in the X-ray spectrum and measure a total power of about 1 GW. There have been many attempts to model both bremsstrahlung and ion precipitation with the goal of reproducing what is being seen; however, both have encountered push back. Electron bremsstrahlung modeling has fallen short of producing the total overall power output being observed by our earth-orbiting X-ray observatories. Whereas heavy ion precipitation has been able to reproduce strong X-ray fluxes, but the proposed incident ion energies seemed to likely be much higher (1 MeV/nucleon) than what was thought to be present above Jupiter's polar caps. Now with the National Aeronautics and Space Administration's (NASA's) Juno spacecraft arriving at Jupiter, there have been many measurements of heavy ion populations above the polar cap with energies up to 300-400 keV/nucleon (keV/u), well below predictions the of previous models. Meanwhile, Schultz et al. (2019) have provided a new outlook on how ion-neutral collisions in the Jovian atmosphere are occurring, providing an entirely new set of impact cross-sections and a total of 35 collision processes (prior models only account for 9). A model is described for the transport of magnetospheric oxygen and sulfur ions with low charge state and energies up to several MeV/nucleon (MeV/u) as they precipitate into Jupiter’s polar atmosphere. A revised and updated hybrid Monte Carlo model originally developed by Ozak et al. (2010) is used to model the Jovian X-ray aurora. The current model uses a wide range of incident oxygen ion energies (10 keV/u - 5 MeV/u) and the most up-to-date collision cross-sections. In addition, the effects of the secondary electrons generated from the heavy ion precipitation are included using a two-stream transport model that computes the secondary electron fluxes and their escape from the atmosphere. The model also determines H2 Lyman-Werner band emission intensities, including a predicted spectrum and the associated color ratio. I predict X-ray fluxes, efficiencies, and synthetic spectra for various initial ion energies considering opacity effects from two different atmospheres. The data is made available for quick X-ray calculations given an input ion flux. A calculation is given that demonstrates an in situ measured heavy ion flux above Jupiter's polar cap is capable of producing over 1 GW of X-ray emission. Implications of the new model results for the interpretation of data from NASA’s Juno mission are discussed.
299 pages
en
University of Kansas
Copyright held by the author.
openAccess
Plasma physics
Physics
Aurora
Jupiter
Monte-Carlo
Simulation
X-Ray
Comprehensive Model of Jupiter's Polar Aurora
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/302302021-03-05T19:13:26Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Chan, Wai-Lun
Kafle, Tika Ram
Besson, Dave Z.
Zhao, Hui
Wu, Judy
Caricato, Marco
2020-03-29T18:29:49Z
2020-03-29T18:29:49Z
2019-12-31
2019
http://dissertations.umi.com/ku:16894
http://hdl.handle.net/1808/30230
https://orcid.org/0000-0003-1225-7981
Organic photovoltaic (OPV) devices are environmental-friendly, lightweight, flexible and inexpensive. However, one of the setbacks for commercial application is its relative low performance in solar to electrical energy conversion compared to inorganic counterparts such as Si solar cells. Unlike typical inorganic materials in which free carriers are generated directly by the light absorption, excitons, Coulombic bound electron-hole pairs, are created upon light absorption in OPV materials. The performance of OPVs depends on how effective the bound charge transfer (CT) exciton, an exciton with its electron and hole spatially separated by the donor-acceptor interface, can dissociate to generate free charge carriers. In this thesis, the roles of the orientation of the delocalized electron wavefunction and the interfacial energy landscape in the exciton dissociation (ED) process are studied in order to understand mechanisms that control the ED efficiency. A number of donor–acceptor interfaces including organic/organic and organic/transition metal dichalcogenides (TMDs) interfaces with different molecular orientations were prepared, and exciton dynamics at these interfaces were probed. We employed time-resolved photoemission spectroscopy to measure the CT exciton dynamics, by which we were able to track the temporal evolution of the energy and the size of CT excitons. Our results on the organic-organic donor-acceptor interfaces show that the relative orientation of the delocalized electron and hole wavefunction within the CT exciton plays an important role in determining whether free carriers can be generated effectively from the CT exciton. Energy uphill, spontaneous exciton dissociation (SED) was observed on the few picosecond (ps) timescale at the zinc phthalocyanine (ZnPc)/fluorinated zinc phthalocyanine (F8ZnPc) interface with a face-on molecular orientation, at which both the electron and hole wavefunctions delocalize in the direction perpendicular to the interface. By contrast, cooling of hot CT excitons to lower energy bound CT excitons (cold excitons) was observed at the ZnPc/fullerene (C60) interface with an edge-on ZnPc orientation, at which the hole wavefunction in the CT exciton delocalizes in a direction parallel to the interface. The difference in the CT exciton dynamics suggests that free charges can be generated more effectively at the ZnPc/F8ZnPc interface with a face-on orientation. In addition, two very similar organic-TMD interfaces (ZnPc/bulk-MoS2 and ZnPc/monolayer (ML) MoS2) were studied and distinctly different CT exciton dynamics were observed. At the ZnPc/bulk-MoS2 interface, after the formation of the CT exciton, back electron transfer occurs which results in the formation of triplet excitons in the ZnPc. On the other hand, at the ZnPc/ML MoS2 interface, free carriers are generated effectively from CT excitons. This difference in the CT exciton dynamics is explained by the difference in the extent of the interfacial band bending found at the two interfaces. Overall, our study demonstrates that whether free carriers can be generated from the CT exciton depends sensitively on the local energy landscape around the interface and the electron delocalization within the CT exciton at the nanoscale. Understanding how the interfacial structure would affect the temporal evolution of the CT exciton is important for designing interfaces for effective charge generation.
157 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Condensed matter physics
charge transfer
exciton dissociation
organic-2D heterostructures
organic photovoltaics
Photoemission spectroscopy
wavefunction orientation
The role of spatial size and orientation of electronic wavefunction in exciton dissociation at van der Waals interfaces
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/185942020-06-30T01:29:39Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Lytle, William Orland
2015-10-06T18:33:46Z
2015-10-06T18:33:46Z
1917
http://hdl.handle.net/1808/18594
Thesis (M.A.)--University of Kansas, Physics, 1917. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
A study of electrostatically coupled circuits
Thesis
Physics
M.A.
3424279
oai:kuscholarworks.ku.edu:1808/278082019-08-27T18:09:08Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Bellus, Matthew Zetah
Wu, Judy
Han, Siyuan
Chan, Wai-Lun
Hui, Rongqing
2019-05-07T16:31:29Z
2019-05-07T16:31:29Z
2018-05-31
2018
http://dissertations.umi.com/ku:15813
http://hdl.handle.net/1808/27808
In the last decade or so, layered materials have attracted significant attention due to their promise for tailoring electronic properties at an atomic level. Individually, these materials have exhibited strong attributes, relevant for both electronic and optoelectronic applications. However, the real world implementation of semiconducting materials is often derived from the junctions they form with other semiconductors. Thus, much of the interest in 2D materials arises from exploiting their ability to form low dimensional heterostructures. From a structural stand point, there are two ways these heterostructures can be formed, either vertically or laterally. The more common, vertical heterostructures, are intriguing due to their van der Waals adhesion, which eliminates many of the constraints attributed to lattice matching between materials. Lateral heterostructures, on the other hand, provide the unique opportunity to form in-plane junctions within a 2D sheet, creating novel 1D interfaces. To better understand these various heterostructures, this dissertation aims to explore photocarrier dynamics, using ultrafast laser spectroscopy techniques, in several types of structures yet to be extensively studied. First, charge and energy transfer mechanisms in vertical heterostructures formed between various transition metal dichalcogenide monolayers are studied, highlighting the addition of type-I band alignment to the discussion. Next, the extent to which materials can interact electronically through van der Waals adhesion is explored at the interface between amorphous and crystalline layers. From there, the focus shifts slightly to carrier dynamics across lateral junctions formed within monolayer sheets of transition metal dichalcogenides. This includes a discussion on lateral heterostructures, formed between different materials, as well as homostructures where an electronic junction can be induced in a single material. All of these studies will provide a unique overview on the possible directions and applications for which two dimensional materials can be facilitated. This dissertation includes previously published authored material.
152 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
2D Heterostructures
Transition Metal Dichalcogenides
Charge and Energy Transfer in Different Types of Two-Dimensional Heterostructures
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/280582019-08-27T18:09:09Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Fischer, Christopher J
Deeds, Eric J
Briggs, Koan Edward Michael
Hawley, Steven A
Murray, Michael J
Shi, JiCong
2019-05-19T02:19:10Z
2019-05-19T02:19:10Z
2018-12-31
2018
http://dissertations.umi.com/ku:16249
http://hdl.handle.net/1808/28058
What follows is a pathway; a sequence of individual events, which together form a story. Yet it is still only a small part of what has come before. Biological structures also have individual stories; each composed of simple events in sequence. One story does not tell the whole, for that we must observe many stories, sample them if you will. Together, they bring understanding. Assembly is an emergent property of many individual binding events. Through this, all of the structures that make up life are created. Understanding the regime of possibilities provides insight into both the breadth and tendencies of the system. Cells contain numerous types of individual proteins many of which come together to form larger complexes. I will begin by introducing the elementary building blocks of those protein complexes. An introductory example will provide the first perspective, it will form common ground and allow the telling of the larger story with a shared perspective. Then a case study, a real biological complex and how understanding the progression of its pathways provided insight into the states which it reached. With the elementary operations described, I will move on to laying out the landscape of possible pathways; first for a specific case and then the structure of the assembly pathways themselves. Thus, providing a novel framework for the understanding of the stochastic space of protein complex assembly. Finally, I will provide an example of how making changes in the possible assembly pathways leads to non-intuitive changes in the conclusion of the protein complexes’ stories.
120 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Computational physics
Biophysics
Assembly networks
Combinatorial optimization
Graph optimization
Molecular biophysics
Numerical optimization
Protein complex assembly
Disrupted Pathways: Generating Tunable Macromolecular Assembly Pathways
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/232922020-06-23T20:18:17Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Rexroth, Byron Albert
2017-02-28T19:57:44Z
2017-02-28T19:57:44Z
1930
http://hdl.handle.net/1808/23292
Thesis (M.A.)--University of Kansas, Physics, 1930.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Method of investigating temperature coefficient of quartz oscillator crystals
Thesis
Physics
M.A.
3426819
oai:kuscholarworks.ku.edu:1808/274532018-12-04T09:01:35Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Roberds, Wesley Milton
2018-12-03T21:19:19Z
2018-12-03T21:19:19Z
1935
http://hdl.handle.net/1808/27453
Dissertation (Ph.D.)--University of Kansas, Physics, 1935.
eng
University of Kansas
This work is in the public domain and is available for users to copy,
use, and redistribute in part or in whole. No known restrictions apply to the
work.
openAccess
High frequency conductance of pyrex glass in the presence of vapors
Dissertation
Physics
Ph.D.
3426880
oai:kuscholarworks.ku.edu:1808/209542021-08-26T22:03:29Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Emery, George Valentine
2016-06-15T15:14:29Z
2016-06-15T15:14:29Z
1924
http://hdl.handle.net/1808/20954
Thesis (M.S.)--University of Kansas, Physics, 1924.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The resistivity of liquid alloys of mercury and tin
Thesis
Physics
M.S.
oai:kuscholarworks.ku.edu:1808/103352020-09-11T14:47:41Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wilson, Graham
McGivern, Carrie Lynne
Baringer, Philip
Bean, Alice
Lerner, David
McKay, Douglas
2012-10-28T17:32:29Z
2012-10-28T17:32:29Z
2012-05-31
2012
http://dissertations.umi.com/ku:12027
http://hdl.handle.net/1808/10335
We present the results of three analyses; a WZ production cross section measurement, a search for new physics in anomalous top quark decays, and the search for the standard model Higgs boson, all with final states of three or more leptons – either electrons or muons – plus an imbalance of transverse momentum using Tevatron proton and anti-proton collisions at a center-of-mass energy of sqrt(s) = 1.96 TeV with the DZero detector at the Fermi National Accelerator Laboratory in Chicago, IL. The first analysis reports a measurement of the WZ → lνl+l− cross section. Using 4.1 fb−1 of integrated luminosity, we measure a cross section of 3.90−0.85+1.01(stat+syst) ± 0.31(lumi) pb, which is found to be in good agreement with the standard model prediction. The second analysis is an extension of the first, in which we use the same dataset and look for the flavor changing neutral current decay of t → Zq in ppbar → ttbar → WbZq → l'νl+l− + jets decays. Here q is considered to be either a u or c quark, and both the q and b quarks decay hadronically. We find no evidence of flavor changing neutral current production and set upper limits on the branching ratio of BR(t → Zq) −1, the full dataset available at DZero, we observe no excess above the standard model background prediction and extract limits on the Higgs boson production cross section times branching ratio for a Higgs boson mass range of mH = 100 - 200 GeV/c2, in intervals of 5 GeV/c2.
210 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Diboson production
Elementary particles and high energy physics
Fermilab
Flavor changing neutral current top quark decays
Higgs boson
Tevatron
Measurement of WZ production and searches for anomalous top quark decays and Higgs boson production using tri-lepton final states in ppbar collisions at √s = 1.96 TeV
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085727
oai:kuscholarworks.ku.edu:1808/173192020-06-24T19:14:30Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Griffing, Burgoyne Lee
2015-04-06T16:50:46Z
2015-04-06T16:50:46Z
1922.
http://hdl.handle.net/1808/17319
Thesis (M.A.)--University of Kansas, Physics, 1922. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Some photoactive properties of metals in electrolytic cells /
Thesis
Physics
3424430
oai:kuscholarworks.ku.edu:1808/80492020-08-18T13:13:39Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Ralston, John P
Backović, Mihailo
McKay, Douglas
Kong, Kyoungchul
Feldman, Hume A
Lerner, David
2011-09-22T01:30:38Z
2011-09-22T01:30:38Z
2011-07-04
2011
http://dissertations.umi.com/ku:11586
http://hdl.handle.net/1808/8049
Resonant dark matter annihilation drew much attention in the light of recent measurements of charged cosmic ray fluxes. Interpreting the anomalous signal in the positron fraction as a sign of dark matter annihilation in the galactic halo requires cross sections orders of magnitudes higher than the estimates coming from thermal relic abundance. Resonant dark matter annihilation provides a mechanism to bridge the apparent contradiction between thermal relic abundance and the positron data measured by PAMELA and FERMI satellites. In this thesis, we analyze a class of models which allow for dark matter to annihilate through an s-channel resonance. Our analysis takes into account constraints from thermal relic abundance and the recent measurements of charged lepton cosmic ray fluxes, first separately and then simultaneously. Consistency of resonant dark matter annihilation models with thermal relic abundance as measured by WMAP serves to construct a relationship between the full set of masses, couplings and widths involved. Extensive numerical analysis of the full four dimensional parameter space is summarized by simple analytic approximations. The expressions are robust enough to be generalized to models including additional annihilation channels. We provide a separate treatment of resonant annihilation of dark matter in the galac- tic halo. We find model-independent upper limits on halo dark matter annihilation rates and show that the most efficient annihilation mechanism involves s-channel resonances. Widths that are large compared to the energy spread in the galactic halo are capable of saturating unitarity bounds without much difficulty. Partial wave unitarity prevents the so called Sommerfeld factors from producing large changes in cross sections. In addition, the approximations made in Sommerfeld factors break down in the kinematic regions where large cross section enhancements are often cited. Simultaneous constraints from thermal relic abundance and halo annihilation serve to produce new limits on dark matter masses and couplings. Past considerations of only a part of the resonant annihilation parameter set to motivate large annihilation cross section enhancements in the halo while maintaining correct relic abundance are generally incomplete. Taking into account only the resonance mass and width to show that large cross section enhancements are possible does not in principle guarantee that the enhancement will be achieved. We extend the calculation to include the full resonant parameter set. As a result, we obtain new limits on dark matter masses and couplings.
122 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Dark matter
Indirect detection
Limits
Relic abundance
Resonance
Sommerfeld enhancements
Constraints on Resonant Dark Matter Annihilation
Dissertation
Physics & Astronomy
Ph.D.
This item does not meet KU Open Access policy criteria.
7643083
oai:kuscholarworks.ku.edu:1808/136552020-10-22T14:29:22Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Dresden, Max
Gutzwiller, Martin C.
2014-05-13T20:41:07Z
2014-05-13T20:41:07Z
1953
http://hdl.handle.net/1808/13655
142 pp.
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Quantumtheory of Wavefields in a Space of Constant Curvature
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
3428253
oai:kuscholarworks.ku.edu:1808/233052020-06-23T18:31:31Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Stranathan, Robert K.
2017-02-28T19:57:55Z
2017-02-28T19:57:55Z
1932
http://hdl.handle.net/1808/23305
Thesis (M.A.)--University of Kansas, Physics, 1932.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
A proposed method for the measurement of the loss in velocity of electrons in gases at reduced pressures
Thesis
Physics
M.A.
3425402
oai:kuscholarworks.ku.edu:1808/182822020-06-24T18:22:47Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Hull, Lewis Madison
2015-07-31T21:40:44Z
2015-07-31T21:40:44Z
1918
http://hdl.handle.net/1808/18282
Thesis (M.A.)--University of Kansas, Physics, 1918. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Dynamic characteristics of an oscillating electron tube
Thesis
3424305
oai:kuscholarworks.ku.edu:1808/260002018-05-02T19:40:40Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Sanders, Stephen J
Castle, James Robert
Takaki, Daniel
Bean, Alice L
Lewis, Ian
Elles, Christopher G
2018-02-18T20:20:55Z
2018-02-18T20:20:55Z
2017-08-31
2017
http://dissertations.umi.com/ku:15513
http://hdl.handle.net/1808/26000
https://orcid.org/0000-0002-2177-617X
The collective, anisotropic expansion of the medium created in ultrarelativistic heavy-ion collisions, known as flow, is characterized through a Fourier expansion of the final-state azimuthal particle density. In the Fourier expansion, flow harmonic coefficients $v_n$ correspond to shape components in the final-state particle density, which are a consequence of similar spatial anisotropies in the initial-state transverse energy density of a collision. Flow harmonic fluctuations are studied for PbPb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV using the CMS detector at the CERN LHC. Flow harmonic probability distributions $p(v_n)$ are obtained using particles with $0.3 < p_{\rm T} < 3.0$ GeV/$c$ and $\lvert \eta \rvert < 1.0$ by removing finite-multiplicity resolution effects from the observed azimuthal particle density through an unfolding procedure. Cumulant elliptic flow harmonics ($n=2$) are determined from the moments of the unfolded $p(v_2)$ distributions and used to construct observables in $5\%$ wide centrality bins up to $60\%$ that relate to the initial-state spatial anisotropy. Hydrodynamic models predict that fluctuations in the initial-state transverse energy density will lead to a non-Gaussian component in the elliptic flow probability distributions that manifests as a negative skewness. A statistically significant negative skewness is observed for all centrality bins as evidenced by a splitting between the higher-order cumulant elliptic flow harmonics. The unfolded $p(v_2)$ distributions are transformed assuming a linear relationship between the initial-state spatial anisotropy and final-state flow and are fitted with elliptic power law and Bessel Gaussian parametrizations to infer information on the nature of initial-state fluctuations. The elliptic power law parametrization is found to provide a more accurate description of the fluctuations than the Bessel-Gaussian parametrization. In addition, the event-shape engineering technique, where events are further divided into classes based on an observed ellipticity, is used to study fluctuation-driven differences in the initial-state spatial anisotropy for a given collision centrality that would otherwise be destroyed by event-averaging techniques. Correlations between the first and second moments of $p(v_n)$ distributions and event ellipticity are measured for harmonic orders $n=2-4$ by coupling event-shape engineering to the unfolding technique.
220 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Event-shape engineering
Heavy ions
High-density QCD
Hydrodynamic flow
Unfolding/deconvolution
Hydrodynamic Flow Fluctuations in √sNN = 5.02 TeV PbPb Collisions
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/203692021-08-26T22:02:22Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Stranathan, James Docking
2016-02-25T21:13:03Z
2016-02-25T21:13:03Z
1924
http://hdl.handle.net/1808/20369
Thesis (M.S.)--University of Kansas, Physics, 1924.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
A study of the variation of high frequency resistance with temperature
Thesis
Physics
M.S.
oai:kuscholarworks.ku.edu:1808/148192017-12-08T21:46:54Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Power, Archie Dayton
2014-07-24T13:21:12Z
2014-07-24T13:21:12Z
1912-06-01
http://hdl.handle.net/1808/14819
This is a thesis submitted to the Department of Physics of the University of Kansas, in partial fulfillment of the requirements for the degree of Master of Arts.
14 pages
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Elasticity cells. An investigation of the relation between the energy liberated by a strained metal going into solution and the potential difference resulting.
Thesis
Physics
M.A.
na
This item does not meet KU Open Access policy criteria.
oai:kuscholarworks.ku.edu:1808/279902019-08-27T18:09:08Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Takaki, Daniel T.
Boren, Samuel Steed
Takaki, Daniel T.
Baringer, Phil S.
Gavosto, Estela A.
Ralston, John P.
Sanders, Stephen J.
2019-05-18T19:12:38Z
2019-05-18T19:12:38Z
2018-08-31
2018
http://dissertations.umi.com/ku:16157
http://hdl.handle.net/1808/27990
One of the most remarkable predictions of the physics of strong interactions, and quantum chromodynamics (QCD) in particular, is gluon saturation. It is observed that the gluon density in hadrons, such as the proton, grows with energy, or equivalently with decreasing Bjorken-$x$ (the fraction of the hadron momentum carried by the parton). At some point this growth exceeds the unitarity limit and some new phenomena such as non-linear effects must set in. Data on the proton structure function, and on exclusive vector-meson photoproduction from the electron-proton collider HERA, which ended operations in 2007, have been inconclusive on whether or not gluon saturation has been observed. The search for non-linear QCD effects such as gluon saturation in both the proton and the nucleus is one of the main lines of research in high energy nuclear physics today. In nuclei the quantum fluctuations ought to be stronger than in protons. Recently, it has been found that the Quark Gluon Plasma (QGP) created in nucleus-nucleus collisions at RHIC and LHC expands with very little dissipation. The quantum fluctuations of the initial state described by the overlap of two highly Lorentz-contracted nuclei traveling on light-cone trajectories are probably imprinted upon the distribution of particles created in the QGP. Without assessing these quantum fluctuations in nuclei, fundamental properties of the QGP such as its viscosity-to-entropy ratio cannot be determined to a high precision. In this thesis we have studied, for the first time, the angular correlations of photoproduced dijets in ultra-peripheral Pb+Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV. This process has been suggested as a way to extract information of the nuclear gluon density in the Pb target, and thus provide information about the initial state of high energy nucleus-nucleus collisions.
149 pages
en
University of Kansas
Copyright held by the author.
openAccess
Nuclear physics and radiation
CMS
Heavy ion collisions
jets
Physics
Ultra-peripheral collisions
UPC
Angular correlations of dijets in ultra-peripheral Pb+Pb collisions at sqrt(s[NN])=5.02 TeV
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/54602020-06-25T16:33:37Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z
Dizon, Jonathan Reyes
Han, Siyuan
Zhao, Hui
Baringer, Phil
Johnson, Carey K.
2009-08-31T03:15:52Z
2009-08-31T03:15:52Z
2009-04-28
2009
http://dissertations.umi.com/ku:10371
http://hdl.handle.net/1808/5460
Identifying defects and non-superconducting regions in high-temperature superconductors (HTS) is of great importance because they limit the material's capability to carry higher current densities and serve as nucleation spots for "hot spots" that can evolve over time and drive a HTS from superconducting (SC) to normal state. A technique that combines near-field scanning microwave microscopy (NSMM) with transport measurement was developed to image defects and nonuniformities at room temperature and detect low-level dissipation at low temperatures. At room temperature, macroscopic and microscopic defects in both conducting and HTS films were clearly identified and imaged with adequate sensitivity and resolution. At low temperatures, low-level dissipation was detected by observing the NSMM's response during the HTS' transition from SC to normal state. Measuring the time-dependent self-heating effect due to a bias current at a fixed temperature provided insight into the dynamics of thermal instability due to hot-spot nucleation. When the HTS is far from the transition state, a bi-modal evolution of the thermal quench was observed beginning with a nucleation of a local hot spot followed by a spreading/coalescence of them via self-heating. When the HTS is brought closer to transition by increasing either temperature or bias current, this effect is diminished due to faster hot spot growth and continuous spread by self-heating. Observations were obtained for both the bulk and grain boundary regions of a HTS.
127 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
Defects
Dissipation
Grain boundary
Imaging
Microwave microscopy
Superconductors
A Combined Near-field Scanning Microwave Microscope and Transport Measurement System for Characterizing Dissipation in Conducting and High-Tc Superconducting Films at Variable Temperature
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
6857469
oai:kuscholarworks.ku.edu:1808/191322017-12-08T21:34:35Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Brown, Ben Eli
2015-12-04T15:10:05Z
2015-12-04T15:10:05Z
1921
http://hdl.handle.net/1808/19132
Thesis (M.A.)--University of Kansas, Physics, 1921. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Occlusion of water of gas-mask charcoal
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/185632020-06-25T18:25:06Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Kirby, Samuel Sylvester
2015-10-06T18:06:32Z
2015-10-06T18:06:32Z
1921
http://hdl.handle.net/1808/18563
Thesis (M.A.)--University of Kansas, Physics, 1921. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
A comparison of dynamic and static methods of determining amplification constants and internal resistance of three electrode vacuum tubes
Thesis
Physics
M.A.
3424532
oai:kuscholarworks.ku.edu:1808/123182020-09-25T14:33:17Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Cravens, Thomas E.
Richard, Matthew Scott
Baringer, Philip
Anthony-Twarog, Barbara J.
Rudnick, Gregory
Hierl, Peter
2013-09-30T19:52:06Z
2013-09-30T19:52:06Z
2013-05-31
2013
http://dissertations.umi.com/ku:12603
http://hdl.handle.net/1808/12318
The Cassini mission has collected vast amounts of in situ data within the ionosphere of Saturn's moon Titan and has shown the complexity of the interaction of Saturn's magnetospheric plasma with Titan. Models of the interactions have been created; however, none have been able to completely describe the observed phenomena. Most notably, modeled electron densities are much larger than the electron densities observed by instruments aboard the Cassini spacecraft. This thesis will explore the possible causes of this discrepancy between measured and modeled electron densities using models calculating the production of ions due to solar photons and magnetospheric electrons precipitating down magnetic field lines and into the ionosphere, temperature calculations of the thermal electron population (electrons with energies less than 2 eV), and chemical reactions in the ionosphere. The results of these models will be compared to data collected by instruments aboard Cassini. Modeled ion production rates and thermal electron temperature profiles will be shown to be in good agreement with ion production rates derived from data collected by the Ion – Neutral Mass Spectrometer (INMS) and electron temperatures measured by the Radio and Plasma Wave Science – Langmuir Probe above 1000 km. Modeled ion mass spectra will be generated near the ionospheric peak and will be compared with the INMS measured mass spectra to examine the effects of chemical loss processes on the ion densities. From this analysis it will be shown that the overabundance of modeled electrons is not caused by over production of ions and that chemical loss processes, predominantly the electron dissociative recombination coefficient of HCNH+, need to be reexamined. After the model has been proven to reproduce accurate profiles of ion production and temperature, ion production profiles will be generated using solar photons and magnetospheric electron fluxes for four canonical cases detailed in the work of Rymer et al. [2009] and a globally averaged model of the neutral densities based on INMS neutral measurements from more than 30 flybys of Titan. These generic profiles can be combined to predict ionospheric observations made by the Cassini spacecraft for a variety of solar zenith angles and magnetospheric conditions.
516 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Plasma physics
Atmospheric sciences
Electron precipitation
Ionosphere
Ion production
Saturn
Titan
Plasma Interactions in Titan's Ionosphere
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085981
oai:kuscholarworks.ku.edu:1808/209712021-08-26T22:01:45Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Barstow, John MacDonald
Nutting, Floyd Lester
2016-06-15T15:14:40Z
2016-06-15T15:14:40Z
1924
http://hdl.handle.net/1808/20971
Thesis (M.S.)--University of Kansas, Physics, 1924.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Contact potential differences as modified by gaseous atmospheres
Thesis
Physics
M.S.
oai:kuscholarworks.ku.edu:1808/191622018-01-31T20:07:51Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Murray, Michael J
Bruner, Christopher
Sanders, Stephen J
Shi, Jack
Kong, Kyoungchol
Ostermann, Russell
2015-12-11T22:08:14Z
2015-12-11T22:08:14Z
2015-08-31
2015
http://dissertations.umi.com/ku:14269
http://hdl.handle.net/1808/19162
The almost hermitic coverage of CMS is used to measure the distribution of transverse energy as a function of pseudorapidity for pPb collisions at center of mass energy of 5:02 TeV. For minimum bias collisions (1/N) dET/dη reaches 25 GeV which implies an energy density comparable to that of PbPb collisions at TeV energies. The centrality dependence of transverse energy dependence has been studied using centrality measures defined in three different angular regions. The correlations between which events are selected by are much wider than they were in PbPb collisions and are not reproduced by either the EPOS-LHC or HIJING event generators. Each centrality class was divided by the most central events in order to measure the auto-correlations induced by a centrality definition and reduce the systematic error. This variable is called SPC and the effect of the auto-correlation persists over a much wider pseudo-rapidity range than predicted by either of the event generators.
90 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Calorimetry
Energy Density
Heavy-Ion
LHC
Nuclear
Relativistic
Centrality and Pseudorapidity of the Transverse Energy Flow in pPb Collisions at Center of Mass Energy 5.02 TeV
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/191902018-01-31T20:07:51Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z.
Malek, Gary A.
Berrie, Cindy
Chan, Wai-Lun
Han, Siyuan
Shi, Jicong
2015-12-11T23:41:48Z
2015-12-11T23:41:48Z
2015-08-31
2015
http://dissertations.umi.com/ku:14260
http://hdl.handle.net/1808/19190
Due to the prodigious amount of electrical energy consumed throughout the world, there exists a great demand for new and improved methods of generating electrical energy in a clean and renewable manner as well as finding more effective ways to store it. This enormous task is of great interest to scientists and engineers, and much headway is being made by utilizing three-dimensional (3D) nanostructured materials. This work explores the application of two types of 3D nanostructured materials toward fabrication of advanced electrical energy storage and conversion devices. The first nanostructured material consists of vertically aligned carbon nanofibers. This three-dimensional structure is opaque, electrically conducting, and contains active sites along the outside of each fiber that are conducive to chemical reactions. Therefore, they make the perfect 3D conducting nanostructured substrate for advanced energy storage devices. In this work, the details for transforming vertically aligned carbon nanofiber arrays into core-shell structures via atomic layer deposition as well as into a mesoporous manganese oxide coated supercapacitor electrode are given. Another unique type of three-dimensional nanostructured substrate is nanotextured glass, which is transparent but non-conducting. Therefore, it can be converted to a 3D transparent conductor for possible application in photovoltaics if it can be conformally coated with a conducting material. This work details that transformation as well as the addition of plasmonic gold nanoparticles to complete the transition to a 3D plasmonic transparent conductor.
129 pages
en
University of Kansas
Copyright held by the author.
openAccess
Condensed matter physics
Atomic Layer Deposition
Electrochemical Storage Devices
Plasmonics
Three-Dimensional Substrate
Transparent Conductors
Vertically Aligned Carbon Nanofibers
Conformal Coating of Three-Dimensional Nanostructures via Atomic Layer Deposition for Development of Advanced Energy Storage Devices and Plasmonic Transparent Conductors
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/173142020-06-24T18:14:10Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Taylor, Henry William
Yoder, Paul R.
2015-04-06T16:50:44Z
2015-04-06T16:50:44Z
1922.
http://hdl.handle.net/1808/17314
Thesis (M.A.)--University of Kansas, Physics, 1922. ; Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
An investigation of the electrical and mechanical phenomena in the Rochelle salt crystal /
Thesis
Physics
3424634
oai:kuscholarworks.ku.edu:1808/186642018-10-29T15:36:25Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Kumar, Nardeep
Zhao, Hui
Chiu, Hsin-Ying
Chan, Wai-Lun
Kong, Kyoungchul
Ren, Shenqiang
2015-10-13T04:23:23Z
2015-10-13T04:23:23Z
2014-12-31
2014
http://dissertations.umi.com/ku:13659
http://hdl.handle.net/1808/18664
https://orcid.org/0000-0002-8078-6669
Layered materials in which atomic sheets are stacked together by weak van der Waals forces can be used to fabricate two-dimensional systems. They represent a diverse and rich, but largely unexplored, source of materials. Atomically-thin structures derived from these materials possess a number of interesting electrical, optical, and mechanical properties, and are attractive for new nanodevices. For their applications in semiconductor industry, it is necessary to understand the dynamics of photoexcited quasiparticles that occur on ultrafast time scales of less than one nanosecond. In this dissertation, I discuss ultrafast optical experimental techniques and results from various two-dimensional materials, which provide information about electronic dynamics. First, a second harmonic generation technique that can be used to find the crystalline orientation, thickness uniformity, layer stacking, and single-crystal domain size is discussed, with results presented on exfoliated and chemical vapor deposition MoS2 samples. Second, a third harmonic generation technique is discussed, which can be used to explore nonlinear optical properties of materials, and results are presented on graphene and few-layer graphite films. Third, a spatially resolved femtosecond pump-probe is described, which can be used to study hot carrier and photoexcited phonon dynamics and results are presented on Bi2 Se3 sample. Then, exciton dynamics in MoS2 and MoSe2 are explored by using transient absorption microscopy with a high spatiotemporal resolution. Finally, a polarization-resolved femtosecond transient absorption spectroscopy that can be used to study valley and spin dynamics is discussed, with results presented on monolayer, few-layer, and bulk MoSe2 samples.
142 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Excitons
Quasiparticles
Second harmonic generation
Third harmonic generation
Two-dimensional crystals
Ultrafast laser
Spatiotemporal dynamics of photoexcited quasiparticles in two-dimensional crystals studied by ultrafast laser techniques
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/45432018-01-31T20:08:02Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z
Wang, Xiang
Han, Siyuan
Zhao, Hui
Baringer, Philip
Nordheden, Karen J
2009-05-08T22:36:40Z
2009-05-08T22:36:40Z
2008-01-01
2008
http://dissertations.umi.com/ku:10069
http://hdl.handle.net/1808/4543
The most promising characteristic of a High Temperature Superconductor (HTS) is its ability to carry larger electrical current at liquid nitrogen boiling temperature and strong applied magnetic field with minimal dissipation. Numerous large scale applications such as HTS transmission cables, HTS magnets and HTS motors have been developed using HTS materials. The major limitation that prevents its wide commercialization is its high cost-to-performance ratio. However, the effort to further improve HTS current carrying capability is jeopardized by a mysterious thickness dependence of the critical current density (Jc) --- Jc monotonically decreases with increasing thickness (t) at 77 K and self-field (SF). This poses a great challenge for both HTS applications and the understanding of vortex dynamics. What further complicates this issue is the complex defect structure in HTS films as well as the creep nature of magnetic vortices at a finite temperature. After a systematic study of the temperature and magnetic field effects on Jc-t, we conclude that Jc-t is most likely the result of a collective pinning effect dictated by a random pinning potential. Besides that, thermal fluctuations also alter Jc-t in a predictable way. Therefore, by either modifying the vortex structure or pinning structure, Jc-t can be eliminated. Indeed, a thin film Jc has been restored in a HTS/insulator/HTS trilayer while the magnetic coupling is weakened. Moreover, Jc-t has been removed when the random distributed point pins are overpowered by strong linear defects.
104 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
Critical current density
Defects
Film
High tc superconductor
Thickness
Mechanism of Thickness Dependence of Critical Current Density in HTS YBaCuO7-x Film and Its Elimination Using Nano-Engineering
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
oai:kuscholarworks.ku.edu:1808/315032024-01-16T16:42:58Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Rudnick, Gregory H.
Deger, Sinan
Blumenstiel, Justin
Cravens, Thomas E.
Feldman, Hume A.
Twarog, Bruce A.
2021-02-27T21:03:28Z
2021-02-27T21:03:28Z
2019-12-31
2019
http://dissertations.umi.com/ku:16808
http://hdl.handle.net/1808/31503
https://orcid.org/0000-0003-1943-723X
In this work, we present our analysis attempting to constrain the prevalence of tidal interaction and merger (TIM) events on the evolution of intermediate redshift galaxies. The main focus of this work is the effect of such events on the star formation properties of galaxies. Such an undertaking requires the precise selection of tidal interactions and mergers (TIMs), in a wide range of environments to account for environmental effects. As such, in the first part of this work we study the fraction of tidal interactions and mergers with well identified observability timescales ($f_{\rm TIM}$) in group, cluster, and accompanying field galaxies and its dependence on redshift ($z$), cluster velocity dispersion ($\sigma$), and environment. We analyze images from the Hubble Space Telescope (HST), and catalogs from the ESO Distant Cluster Survey (EDisCS) for our work. Our data sample consists of 11 clusters, 7 groups, and accompanying field galaxies at $0.4 \leq z \leq 0.8$. We select our TIM sample using both a visual classification of galaxy morphologies and an automated method, the $G-M_{20}$ method. We calibrate this method using the visual classifications that were performed on a subset of our sample. After this calibration, we label visual TIMs also picked by our $G-M_{20}$ selection criterion as \textquotedblleft $G-M_{20}$ TIM \textquotedblright, and gather our visually undisturbed galaxies plus the visual TIMs that are not $G-M_{20}$ selected under the \textquotedblleft undisturbed \textquotedblright label. Our tests indicate that these subpopulations are well-seperated in the $G-M_{20}$ space, and that our results are robust against different $G-M_{20}$ TIM selection criteria. Next, we investigate whether the fraction of $G-M_{20}$ TIMs, or $f_{\rm TIM}$, shows any strong trends with redshift ($z$), cluster velocity dispersion ($\sigma$), and the global environment the in which our galaxies reside. We find marginal evidence for a trend between $f_{\rm TIM}$ and $z$, in that higher $z$ values correspond to higher $f_{\rm TIM}$. However, we also cannot rule out the null hypothesis of no correlation at higher than 68\% confidence. No trend is present between $f_{\rm TIM}$ and $\sigma$. We find that $f_{\rm TIM}$ shows suggestive peaks in groups, and tentatively in clusters at $R > 0.5\times R_{200}$, implying that $f_{\rm TIM}$ gets boosted in these intermediate density environments. However, our analysis of the local densities of our cluster sample does not reveal a trend between $f_{\rm TIM}$ and density, except for a potential enhancement at the very highest densities. We also perform an analysis of projected radius-velocity phase space for our cluster members. Our results reveal that tidal interactions and mergers (TIM), and undisturbed galaxies only have a 6\% probability of having been drawn from the same parent population in their velocity distribution and 37\% in radii, in agreement with the modest differences obtained in $f_{\rm TIM}$ at the clusters. After classifying our sample into $G-M_{20}$ TIMs and undisturbed galaxies, we investigate the stellar populations of our sample. To this purpose, we perform a full spectral fitting on the deep EDisCS spectroscopy data. We use the publicly available pPXF code for the spectral fitting, obtaining the details of the stellar populations, and the gas present in our sample, as results of our spectral fitting. We extract the fraction of the total stellar mass contained in stellar populations of different ages in our sample from this information. We also derive age-sensitive spectral indices, the strength of the narrow 4000$\mbox{\AA}$ break strength, $D_{n,4000}$, and the Balmer H$\mathrm{\delta}$ absorption line index using the results of the spectral fitting. The final part of our analysis attempts to combine our morphological analysis, and our stellar population analysis. We search for trends in our $G-M_{20}$ TIMs and undisturbed galaxies with respect to the ages of their stellar populations. We find that our $G-M_{20}$ TIM galaxies are predominantly star-forming, as derived from multi-band photometric data. A larger fraction of the $G-M_{20}$ TIM galaxies also have features in their galaxy spectra indicating that their light is dominated by young stars. We then analyze the mass-weighted age fractions in the last 0.5 Gyr ($f_{Age 0.5\times R_{200}$, implying that $f_{\rm TIM}$ gets boosted in these intermediate density environments. However, our analysis of the local densities of our cluster sample does not reveal a trend between $f_{\rm TIM}$ and density, except for a potential enhancement at the very highest densities. We also perform an analysis of projected radius-velocity phase space for our cluster members. Our results reveal that tidal interactions and mergers (TIM), and undisturbed galaxies only have a 6\% probability of having been drawn from the same parent population in their velocity distribution and 37\% in radii, in agreement with the modest differences obtained in $f_{\rm TIM}$ at the clusters. After classifying our sample into $G-M_{20}$ TIMs and undisturbed galaxies, we investigate the stellar populations of our sample. To this purpose, we perform a full spectral fitting on the deep EDisCS spectroscopy data. We use the publicly available pPXF code for the spectral fitting, obtaining the details of the stellar populations, and the gas present in our sample, as results of our spectral fitting. We extract the fraction of the total stellar mass contained in stellar populations of different ages in our sample from this information. We also derive age-sensitive spectral indices, the strength of the narrow 4000$\mbox{\AA}$ break strength, $D_{n,4000}$, and the Balmer H$\mathrm{\delta}$ absorption line index using the results of the spectral fitting. The final part of our analysis attempts to combine our morphological analysis, and our stellar population analysis. We search for trends in our $G-M_{20}$ TIMs and undisturbed galaxies with respect to the ages of their stellar populations. We find that our $G-M_{20}$ TIM galaxies are predominantly star-forming, as derived from multi-band photometric data. A larger fraction of the $G-M_{20}$ TIM galaxies also have features in their galaxy spectra indicating that their light is dominated by young stars. We then analyze the mass-weighted age fractions in the last 0.5 Gyr ($f_{Age < 0.5~\mathrm{Gyr}}$), and between 0.5 Gyr and 1 Gyr ($f_{0.5 < Age < 1.0~\mathrm{Gyr}}$). Our results imply an enhanced $f_{Age < 0.5~\mathrm{Gyr}}$ value for the $G-M_{20}$ TIMs. This time interval is comparable in length to merger timescales reported by many studies, thereby this result is indicative of the TIM event boosting the star formation of these galaxies.
1113 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Astronomy
Galaxy Clusters and Groups
Galaxy Evolution
Galaxy Mergers and Interactions
Star Formation in Galaxies
The Role of Tidal Interactions and Mergers on the Evolution of Intermediate Redshift Galaxies
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/42202020-07-21T16:07:21Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Ralston, John P
Schiel, Rainer W.
Marfatia, Danny
McKay, Douglas
Feldman, Hume A
Lerner, David
2008-09-29T04:15:29Z
2008-09-29T04:15:29Z
2008-08-15
2008
http://dissertations2.umi.com/ku:2646
http://hdl.handle.net/1808/4220
Neutrino oscillation experiments rely on the knowledge of neutrino-nucleus cross-sections. Generally, just one scattering process is used to model these cross-sections. However, it is not sufficient to describe the cross-sections by only one scattering process. In the region of momentum transfers Q^2 < 10^5 MeV, there are two dominant processes, charged-current quasi-elastic scattering and charged-current whole-nucleus scattering. Both of these processes must be accounted for in the analysis. Determining the neutrino cross-sections experimentally is difficult. In most experiments, only the scattering angle and energy of the charged lepton in the final state are known, although neither the recoiled target nor the energy of the incoming neutrino are measured. The Multi-Beam Strategy presented in this dissertation is a novel data-based analysis tool. It can incorporate several nuclear processes in the analysis and simultaneously reduce the model-dependence of the analysis.
107 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Theory
Elementary particles and high energy physics
Neutrino nucleus interactions
Neutrino oscillations
Multi-Beam Strategy for Neutrino-Nucleus Cross-Sections
Dissertation
Physics & Astronomy
PH.D.
na
This item does not meet KU Open Access policy criteria.
6857231
oai:kuscholarworks.ku.edu:1808/218852018-01-31T20:07:52Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Besson, Dave
Prohira, Steven
Kong, KC
Bean, Alice
Ralston, John P.
2016-11-10T23:10:02Z
2016-11-10T23:10:02Z
2016-05-31
2016
http://dissertations.umi.com/ku:14549
http://hdl.handle.net/1808/21885
The Telescope Array RADAR experiment is a bi-static radar search for Ultra-High-Energy Cosmic Rays (UHECR). Here we describe an upgrade and re-deployment of two of our detectors, which, owing to their isolation from the main detector apparatus on Long Ridge, Millard County, UT, are called the Remote Stations (RS). The upgrade described here comprises a total overhaul of the trigger and timing systems, with improvements in signal-to-noise ratio sensitivity of approximately 30 dB. Our new firmware-based trigger method is sensitive to expected signals at SNR of -4 dB at high efficiency. Bench-top tests indicate that this new system is sensitive to a Radar Cross Section (RCS) of order one square meter. Deployment of the overhauled stations took place in February 2016, with a planned data-taking duration of 3-6 weeks.
41 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Particle physics
Astrophysics
Astroparticle physics
Cosmic Rays
Firmware
Radio
Software triggering
Upgrade and Re-Deployment of the Telescope Array RADAR (TARA) Cosmic Ray Observatory Remote Stations
Thesis
Physics & Astronomy
M.S.
oai:kuscholarworks.ku.edu:1808/106722020-09-15T14:35:24Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Medvedev, Mikhail V
Reynolds, Sarah J
Cravens, Thomas E
Rudnick, Gregory
Anthony-Twarog, Barbara J
Richter, Mark L
2013-01-20T17:12:50Z
2013-01-20T17:12:50Z
2012-05-31
2012
http://dissertations.umi.com/ku:12175
http://hdl.handle.net/1808/10672
Relativistic charged particles moving within regions of small-scale magnetic field turbulence radiate as they undergo transverse accelerations reflective of the magnetic field variation along the particle's path. For a particle of Lorentz factor (gamma), relativistic beaming concentrates the bulk of the particle's emission within a small angle 1/(gamma) from the particle's forward direction. Synchrotron radiation is produced when large-scale magnetic fields cause the charged particles to gyrate, with the resulting radiation spectrum being primarily determined by the intermittent sweep of the relativistic beaming cone past the direction to the observer. In small-scale magnetic field turbulence, magnetic fields may be locally strong but varies over sufficiently small scales that the particle's emission is more consistently oriented towards a particular direction. Consequently, deflection effects cease to dominate the observed spectrum and the standard synchrotron model no longer applies. In this dissertation, we focus on the strong jitter radiation regime, in which the field varies over sufficiently short scales that the particle is never substantially deviated from a straight line path and an observer in the particle's forward direction receives consistently strong radiation over many correlation lengths of the magnetic field. We develop the general jitter radiation solutions for such a case and demonstrate that the resulting radiation spectrum differs notably from the synchtrotron spectrum and depends directly on the spectral distribution of the magnetic field encountered by the particle. The Weibel-like filamentation instability generates small-scale magnetic field turbulence through current filamentation in counterstreaming particle populations, such as may be found at or near propagating shock fronts, in outflow from regions of magnetic reconnection, or from a variety of other scenarios producing an anisotropic particle velocity distribution. The current filamentation produces an anisotropy in magnetic field distribution that causes the jitter radiation spectrum to be sensitive to the radiating particle's orientation with respect to the filamentation axis. Because the spectrum observed from any given direction will be dominated by emission from particle's moving along that particular line-of-sight, this results in a natural angular dependence of the jitter radiation spectrum. We explore the implications of jitter radiation's spectral sensitivity to the field anisotropy produced by the Weibel-like filamentation instability to relevant astrophysical and laboratory plasma scenarios. We calculate the jitter radiation spectra that may be produced in a high-energy density laboratory plasma by using quasi-monoenergetic electron beams to generate and then probe a region of current filamentation, and show that the jitter radiation may be used as a radiative diagnostic to determine features of the magnetic field distribution within this region. For gamma-ray bursts, this instability may play a significant role in generating magnetic field strength from relativistic collisionless shocks or other particle acceleration mechanisms. We show that the viewing angle dependence of the jitter radiation spectrum can result in a rapidly time-evolving spectrum whose hard-to-soft evolution, synchrotron-violating low-energy spectral indices, and correlation between low-energy spectral hardness and the flux at peak energy may explain trends noticed in time-resolved GRB spectral evolution. We generate the jitter radiation spectra as would be produced in the co-moving frame by a single, instantantaneously-illuminated shock front, which may then be relativistically transformed with appropriate geometry into a time-evolving spectrum and multiple such signals assembled to produce "synthetic" GRB for comparison with observations.
156 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Astrophysics
Plasma physics
Physics
Gamma-ray bursts
Laboratory astrophysics
Magnetic field turbulence
Plasma instabilities
Radiation mechanisms
Relativistic collisionless shocks
Radiation from Small-Scale Magnetic Field Turbulence: Implications for Gamma-Ray Bursts and Laboratory Astrophysical Plasmas
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085769
oai:kuscholarworks.ku.edu:1808/260152018-05-01T17:23:39Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Fischer, Christopher J.
LeGresley-Rush, Sarah Elizabeth
Anthony-Twarog, Barbara J.
Murray, Michael J.
Shi, Jack J.
Stetler, Dean A.
2018-02-19T03:20:25Z
2018-02-19T03:20:25Z
2017-08-31
2017
http://dissertations.umi.com/ku:15482
http://hdl.handle.net/1808/26015
https://orcid.org/0000-0002-7576-7295
Deoxyribnucleic Acid (DNA) damage can lead to health related issues such as developmental disorders, aging, and cancer. It has been estimated that damage rates may be as high as 100,000 per cell per day. Because of the devastating effects that DNA damage can have, DNA repair mechanisms are of great interest yet are not completely understood. To gain a better understanding of possible DNA repair mechanisms, my dissertation focused on mathematical methods for understanding the interactions between DNA and proteins. I developed a damaged DNA model to estimate the probabilities of damaged DNA being located at specific positions. Experiments were then performed that suggested that the damaged DNA may be repositioned. These experimental results were consistent with the model's prediction that damaged DNA has preferred locations. To study how proteins might be moving along the DNA, I studied the use of the uniform motion “n-step” model. The n-step model has been used to determine the kinetics parameters (e.g. rates at which a protein moves along the DNA, how much energy is required to move a protein along a specified amount of DNA, etc.) of proteins moving along the DNA. Monte Carlo methods were used to simulate proteins moving with different types of non-uniform motion (e.g. backward, jumping, etc.) along the DNA. Estimates for the kinetics parameters in the n-step model were found by fitting of the Monte Carlo simulation data. Analysis indicated that non-uniform motion of the protein may lead to over or underestimation of the kinetic parameters of this n-step model.
167 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Biophysics
deoxyribonucleic acid (DNA)
kinetics
motor proteins
nucleosome
nucleosome breathing
translocation
Mathematical Methods for studying DNA and Protein Interactions
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/271772018-11-07T21:33:06Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Hall, Wayne Curtis
2018-11-02T14:18:46Z
2018-11-02T14:18:46Z
1936
http://hdl.handle.net/1808/27177
Dissertation (Ph.D.)--University of Kansas, Physics, 1936.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Measurements on the thermal conductivities of mercury, sodium, and sodium amalgams
Dissertation
Physics
Ph.D.
3425521
oai:kuscholarworks.ku.edu:1808/102592020-09-21T13:13:51Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Cravens, Thomas E
Ozak Munoz, Nataly
Anthony-Twarog, Barbara J
Hawley, Steven A.
Rudnick, Gregory
Johnson, Carey K.
2012-10-28T15:18:26Z
2012-10-28T15:18:26Z
2012-08-31
2012
http://dissertations.umi.com/ku:12210
http://hdl.handle.net/1808/10259
Auroral emissions from Jupiter have been observed across the photon spectrum including ultraviolet and x-ray wavelengths. UV observations suggest an input flux power of 1013 - 1014 W for the aurora in each hemisphere. X-ray emissions with a total power of about 1 GW were observed by the Einstein Observatory, the Roentgen satellite, Chandra x-ray Observatory (CXO), and XMM-Newton. Previous theoretical studies have shown that precipitating energetic sulfur and oxygen ions can produce the observed x-rays. This study focuses on the ion precipitation of the polar region and its effects in the ionosphere. We present the results of a hybrid Monte Carlo model for sulfur and oxygen ion precipitation at high latitudes, look at differences with the continuous slowdown model, and compare the results to synthetic spectra fitted to observations. We concentrate on the effects of altitude on the observed spectrum and find that the opacity of the atmosphere to the outgoing x-ray photons is important for incident ion energies greater than about 1.2 MeV per nucleon for both sulfur and oxygen. Quenching of longer-lived excited states of the oxygen ions is also found to be important. Opacity considerably diminishes the outgoing x-ray intensity calculated, particularly when the viewing geometry is not favorable. We estimate an emission efficiency for the x-ray aurora of &epsilon ~ 7 x 10-5. Secondary electrons from the ion precipitation as well as photoelectrons and auroral electrons also affect the polar cap atmosphere. We calculated the secondary electron production due to the oxygen ion precipitation for the first time. We analyze the secondary electron fluxes due to the ion aurora and estimate their effects on the ionosphere and field aligned electrical currents. We find that the secondary electrons affect the ionosphere similarly to auroral electrons responsible for the diffuse UV aurora and are therefore important for the magnetospheric dynamics and our better understanding of the ionosphere-magnetosphere coupling.
446 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Plasma physics
Aurora
Ionosphere
Jupiter
Magnetosphere
X-ray
Models of Jupiter's Polar Aurora
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085851
oai:kuscholarworks.ku.edu:1808/217772017-12-08T21:38:01Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Smith, Homer Paul
2016-11-01T14:38:45Z
2016-11-01T14:38:45Z
1927
http://hdl.handle.net/1808/21777
Thesis (M.A.)--University of Kansas, Physics, 1927.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The convection of heat from thin wires in air
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/41172020-07-15T15:07:10Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z.
Zhao, Hua
Zhao, Hui
Han, Siyuan
McKay, Douglas
Laird, Brian
2008-09-08
2008-09-08
2007-12-17
2007
http://dissertations.umi.com/ku:2301
http://hdl.handle.net/1808/4117
The record high superconducting transition temperature (Tc) in Hg-based High temperature superconducting (HTS) cuprates make them very promising for both fundamental physics and practical applications. The high volatile nature of Hg presents a major challenge in epitaxy of high quality Hg-based HTS films. In a novel cation exchange process developed by our group recently, epitaxial HgBa2CaCu2O6+δ (Hg-1212) films can be obtained by diffusing volatile Tl cations out of, and simultaneously diffusing Hg cations into, the lattice of epitaxial Tl2Ba2CaCu2O8 (Tl-2212) or TlBa2CaCu2O7 (Tl-1212) precursor films. Aiming at the remained issues in understanding the mechanism of the cation exchange (CE) process, this thesis work has studied the reversibility of CE. We have found that the CE process is completely reversible between Hg-1212 and Tl-2212, confirming further the thermal perturbation diffusion model. One of the experimental works unveiled that the conversion from Hg-1212 to Tl-2212 involves two steps: conversion from Hg-1212 to Tl-1212 via CE followed by Tl intercalation to form double Tl-O plans in each unit cell. Two improvements have been made in raising the quality of the Hg-1212 films. First, by successfully introducing micro-channels in Tl-1212 precursor with reversible CE, purer HTS Hg-1212 thin films have been obtained. Secondly, by pinning lattice with nonvolatile Re atoms, the surface morphology of Hg-1212 films have been improved. In addition to making the high quality Hg-1212 films, we have fabricated a two-pole X-band Hg-1212 microstrip filter and then investigated its nonlinearity by measuring the third-order intermodulation (IM3) signals since the major limitation for real application still comes from the nonlinearity. By a comparison between different structural materials of Hg-1212, Tl-2212 and YBa2Cu3O7 (YBCO), the third-order intercept (IP3) of the Hg-1212 filter is consistently higher than that in the YBCO and Tl-2212. The surprising similarity in the curves of dc critical current density Jc and the rf JIP3 derived from the IP3 against reduced temperature suggests that the magnetic vortex depinning in HTS materials dominates the microwave nonlinearity at elevated temperatures. These encouraging results have marked Hg-1212 out as a promising alternative material for passive microwave devices at above 77 K operating temperature.
129 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
High temperature superconductors
Mechanism of Cation Exchange Process for Epitaxy of Superconducting HgBa2CaCu2O6 Films and Passive Microwave Devices
Dissertation
Physics & Astronomy
PH.D.
na
This item does not meet KU Open Access policy criteria.
6599237
oai:kuscholarworks.ku.edu:1808/122872020-10-08T14:19:15Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Murray, Michael
Wood, Jeffrey Scott
Sanders, Stephen
Baringer, Philip
Han, Siyuan
Ostermann, Russ
2013-09-29T17:50:48Z
2013-09-29T17:50:48Z
2013-05-31
2013
http://dissertations.umi.com/ku:12490
http://hdl.handle.net/1808/12287
The centrality of PbPb collisions is derived using correlations from the zero degree calorimeter (ZDC) signal and pixel multiplicity at the Compact Muon Solenoid (CMS) Experiment using data from the heavy ion run in 2010. The method to derive the centrality takes the two-dimensional correlation between the ZDC and pixels and linearizes it for sorting events. The initial method for deriving the centrality at CMS uses the energy deposit in the HF detector, and it is compared to the centrality derived by the correlations in ZDC and pixel multiplicity. This comparison highlights the similarities between the results of both methods in central collisions, as expected, and deviations in the results in peripheral collisions. The ZDC signals in peripheral collisions are selected by low pixel multiplicity to obtain a ZDC neutron spectrum, which is used to effectively gain match both sides of the ZDC.
158 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Nuclear physics
Particle physics
Centrality
CMS
Lhc
Nuclear
Physics
Zdc
The Development of the CMS Zero Degree Calorimeters to Derive the Centrality of AA Collisions
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8086143
oai:kuscholarworks.ku.edu:1808/205272021-08-26T21:04:14Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Elvey, Christian Thomas
2016-03-18T16:18:09Z
2016-03-18T16:18:09Z
1923
http://hdl.handle.net/1808/20527
Thesis (M.A.)--University of Kansas, Astronomy, 1923.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The spectroscopic binary "2 monocerotis"
Thesis
Astronomy
M.A.
oai:kuscholarworks.ku.edu:1808/273452020-10-13T20:11:05Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy
Wilt, Jamie Samantha
Berrie, Cindy
Chan, Wai-Lun
Han, Siyuan
Sanders, Stephen
2018-11-14T00:08:08Z
2018-11-14T00:08:08Z
2017-12-31
2017
http://dissertations.umi.com/ku:15658
http://hdl.handle.net/1808/27345
https://orcid.org/0000-0003-0913-2889
Metal-Insulator-Metal tunnel junctions (MIMTJ) are a core building block for a variety of microelectronics including Magnetic Tunnel Junctions (MTJs) for magnetic memory and Josephson Junctions (JJs) for quantum computers. The performance of MIMTJ devices critically depends on the insulator which should have few defects and an atomic-scale thickness. However, the current state of the art insulators are both high-defect and atomic-scale (thermal or plasma assisted AlOx), or low defect and ultrathin (epitaxial MgO or Al2O3). In this work, we develop a novel Atomic Layer Deposition (ALD) process which enables the growth of atomically-thin and low-defect density Al2O3 for MIMTJ devices. Exceptional control of the metal-insulator interface is required to achieve this end as any interfacial layer (IL) which develops is catastrophic, introducing defects and impairing the insulator growth. Specifically, two critical issues of pre-ALD IL formation and ALD nucleation on the metal surface were resolved by integrating ALD with sputtering in situ under High Vacuum (HV) along with a pre-ALD H2O pulse to hydroyxlate the Al surface. Ab-initio molecular dynamics simulations were run to shed light on the mechanisms of IL formation in the HV environment and the hydroxylation of the metal surface using this pre-ALD H2O pulse. In tandem, in situ Scanning Tunneling Spectroscopy (STS) quantified the quality of the Al2O3 as the IL was systematical reduced by optimizing the pre-ALD H2O pulse, sample temperature, and pre-ALD heating time. After optimizations, STS revealed a remarkably high ALD Al2O3 tunnel barrier height which was constant down to the single monolayer scale of 1 ALD cycle with a band gap comparable to ultrathin epitaxial Al2O3. In addition, the highest known ALD Al2O3 dielectric constant, in the ultrathin thickness range, was measured in fabricated capacitors. Amazingly, capacitance fittings along with STS imaging discovered that the IL thickness is sub-monolayer after our optimizations. Thus this work has achieved the first atomically-thin and low defect insulator for MIMTJ devices. Fabricated JJs show promise and preliminary tests reveal that this in situ ALD Al2O3 process can be grown on other metals such as Fe, which is essential for MTJ devices.
130 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Materials Science
Atomic Layer Deposition
Interfacial Layer Growth
Josephson Junction
Magnetic Tunnel Junction
Tunnel Junction
Ultrathin
Atomically-thin Al2O3 dielectric films for metal-insulator-metal tunnel junctions
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/207342021-08-26T21:00:48Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Long, Chester H.
2016-05-03T17:00:22Z
2016-05-03T17:00:22Z
1923
http://hdl.handle.net/1808/20734
Thesis (M.A.)--University of Kansas, Physics, 1923.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Nature of white light
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/262552018-03-29T08:01:50Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Strickler, Paul M.
2018-03-28T15:17:54Z
2018-03-28T15:17:54Z
1937
http://hdl.handle.net/1808/26255
Dissertation (Ph.D.)--University of Kansas, Physics, 1937.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The effects of pressure, time, frequency, and cleaning, on the conductivity and capacity of adsorbed water films on pyrex glass
Dissertation
Physics
Ph.D.
3423761
oai:kuscholarworks.ku.edu:1808/280122020-10-08T16:21:39Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Shandarin, Sergei F
Ramachandra, Nesar Soorve
Feldman, Hume
Anthony-Twarog, Barbara
Twarog, Bruce
Shontz, Suzanne
2019-05-18T19:46:46Z
2019-05-18T19:46:46Z
2018-08-31
2018
http://dissertations.umi.com/ku:16136
http://hdl.handle.net/1808/28012
https://orcid.org/0000-0001-7772-0346
Spatial distribution of dark matter displays a variety of intricate three dimensional structures on the largest scales in the Universe, notably the massive haloes, long tubular filaments, flattened walls and the vast under-dense voids. Galaxies embedded in the dark matter structures have illuminated the rich geometry of these structures currently known as the cosmic web. Cosmological N-body simulations are indispensable tools for understanding the evolution of the dark matter web. Recent developments in the numerical analysis of these simulations have hinted towards incorporating the dynamical information of gravitational clustering of collisionless dark matter. This is inferred from a six-dimensional Lagrangian sub-manifold -- comprising of initial and final coordinates of the dark matter particles. Velocity multistream field derived from this sub-manifold sheds new light on the nature of gravitational collapse. Geometrical, topological, morphological and heuristic diagnostic tools used in this novel parameter space reveal features of the dark matter distribution. For instance, a single void structure not only percolates the multistream field in all the directions, but also occupies over 99 per cent of all the single-streaming regions. On the other hand, connected filaments display a rapid topological transition to isolated islands at high multistream values. Hessian analysis delineates structures with different shapes: tubular, sheet-like, or globular -- enabling detection of the dark matter haloes without ad hoc parameters related to matter density or distance field.
222 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astrophysics
Physics
Astronomy
Cosmic web
Cosmology
Dark matter
Geometry
Large scale structure
Topology
Topology, Geometry and Morphology of the Dark Matter Web
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/74072020-08-06T14:32:42Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Marfatia, Danny
Soleimani, Ali
Ralston, John
McKay, Douglas
Feldman, Hume A
Lerner, David
2011-04-26T02:11:23Z
2011-04-26T02:11:23Z
2010-05-07
2010
http://dissertations.umi.com/ku:10955
http://hdl.handle.net/1808/7407
The MSSM is often augmented by heavy singlets, in order to account for neutrino masses via the seesaw mechanism. However, these singlets can significantly impact predictions for neutralino relic density via RG effects on the SUSY mass spectrum and the concomitant changes to annihilation and detection rates. We study the interplay between these RG-mediated neutrino sector effects on relic density and constraints from lepton flavor violation, in CMSSM/mSUGRA-like models using several different GUT-inspired schemes for choosing neutrino sector parameters and mixings. We find that these effects can be very important for predictions of LFV rates; proper consideration of the changes to relic density bounds alters the predicted LFV rates by factors from a few up to two orders of magnitude, depending on the location in parameter space. Surprisingly, our results indicate that a large neutrino Yukawa unification parameter Rν u = 3 is not ruled out by current LFV bounds as was commonly thought. We also discuss our code Isajet-M, a modification and extension of standard Isajet, which we used to solve the RGEs. Isajet-M handles both the neutrino and quark sectors in complex matrix form, integrates out all particles at their individual scales, and calculates the sparticle spectrum, neutrino masses and mixings, rates for LFV processes, contributions to (g-2)μ, and neutralino relic density and cross-sections.
119 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Particle physics
Theoretical physics
Dark matter
Lfv
Mssm
Neutrino mass
Relic density
Seesaw
Supersymmetric Dark Matter and Lepton Flavor Violation
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7642735
oai:kuscholarworks.ku.edu:1808/241742018-01-31T20:07:52Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Rudnick, Gregory H
Lee-Brown, Donald
Anthony-Twarog, Barbara J
Hawley, Steven A
2017-05-15T03:08:07Z
2017-05-15T03:08:07Z
2016-12-31
2016
http://dissertations.umi.com/ku:15003
http://hdl.handle.net/1808/24174
Understanding how galaxies stop forming stars is a principle pursuit of extragalactic astrophysics. Here, I present a study of the relation between galaxy stellar age and mass in the $z=1.62$ protocluster IRC 0218. After separating star forming and quiescent galaxies on the basis of their $UVJ$ colors, we find that at stellar masses $M_* \ge 10^{10.8} M_{\odot}$, the quiescent fraction in IRC 0218 is $f_Q=1.0^{+0.00}_{-0.36}$, approximately $2-3 \times$ higher than the field value. At lower masses, $f_Q$ is consistent with the field. Using galaxy $D_{n}(4000)$ values as measures of stellar age, we find no relation between age and mass. This may indicate that the mass dependence of $f_Q$ was imprinted early in IRC 0218's history. Alternatively, the lack of a relation may be due to mass redistribution through gasless merging. Ultimately, our results place constraints on the mechanism(s) responsible for quenching in dense environments at $z\ge 1.5$.
49 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astronomy
Astrophysics
Galaxies
Galaxy Clusters
Galaxy Evolution
The Ages of Passive Galaxies in a z=1.62 Protocluster
Thesis
Physics & Astronomy
M.S.
oai:kuscholarworks.ku.edu:1808/103102020-09-15T13:57:02Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Ruzicka, Brian Andrew
Wu, Judy
Han, Siyuan
Chiu, Hsin-Ying
Ren, Shenqiang
2012-10-28T16:56:41Z
2012-10-28T16:56:41Z
2012-05-31
2012
http://dissertations.umi.com/ku:11999
http://hdl.handle.net/1808/10310
The dynamics of charge carriers in semiconductors are of fundamental importance for semiconductor applications. This includes studies of energy relaxation, carrier recombination, and carrier transport (both diffusive and ballistic). Due to their limited temporal resolution, electron measurement techniques cannot be used to study these processes on time scales in which the carrier-lattice system is not in equilibrium. However, in contemporary semiconductor devices with nanometer dimensions, this is the regime that is of interest. In this dissertation, ultrafast optical experimental techniques and results from various semiconductors are presented, which provide information about nonequilibrium electronic dynamics. First, a time resolved pump-probe technique is discussed, which can be used to measure carrier energy relaxation and carrier lifetime, and results are presented on reduced graphene oxide, Si/SiGe quantum wells, and single walled carbon nanotubes. Then, a spatially and temporally resolved pump-probe technique is discussed, which can be used to study carrier diffusion, and results are presented on GaAs, graphene, Si/SiGe quantum wells and single walled carbon nanotubes. Next, a quantum interference and control technique and a differential pump-probe technique that can be used to inject and detect ballistic currents are discussed along with results for the efficiency of such an injection technique and a demonstration of an AC spin polarized charge current in GaAs that was injected and detected using these techniques. Finally, a current-induced second harmonic generation technique that can be used to directly study currents is discussed, with results presented on both steady state and transient currents in GaAs.
175 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Condensed matter physics
Carrier dynamics
Carrier transport
Graphene
Pump-probe
Second harmonic generation
Ultrafast
Ultrafast optical studies of electronic dynamics in semiconductors
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085754
oai:kuscholarworks.ku.edu:1808/191922018-07-23T16:16:24Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Wu, Judy Z
Al-mebir, Alaa Ayad Khedhair
Wu, Judy Z
Murray, Michael J
Chan, Wai Lun
Guanggen, Zeng
2015-12-11T23:51:32Z
2015-12-11T23:51:32Z
2015-08-31
2015
http://dissertations.umi.com/ku:14188
http://hdl.handle.net/1808/19192
https://orcid.org/0000-0001-9255-0891
Cadmium Telluride has long been recognized as the second lowest- cost material after Si in the world photovoltaic market, specifically for thin-film solar cells. The two attractive properties of the CdTe are its nearly ideal band gap of ~1.5 eV for single p-n junction photovoltaic and its high optical absorption coefficient up to 〖10〗^5 cm-1. Therefore, a thickness of ~1 µm of CdTe can absorb up to 90% of the incident light. The key to high-performance thin film CdTe-based solar cells is controlling microstructure of the CdS/CdTe through obtaining high-quality crystalline CdTe thin films that have low density pinholes and other defects and form high-quality p-n heterojunction interfaces on the CdS or other window layers. Considering these, the relative high temperatures used for CdTe thick film growth may not be suitable in the thin film case due to lack of control in CdTe microstructure evolution. Therefore, development of low-temperature processes for CdTe thin film solar cells is important to achieving a precise control of the CdS/CdTe microstructure and optoelectronic properties. In addition, low temperatures provide benefits in wider selection of substrates especially those for low-cost, flexible solar cells applications. However, the CdS/CdTe solar cells based on thin CdTe films fabricated at low temperature have generally poor performance as a result of increased density of grain boundaries and defects. In order to address this issue, we have developed an in situ thermal annealing process (iTAP) immediately after the CdS/CdTe deposition using Pulsed laser deposition (PLD) at 200 °C and before the common ex situ CdCl2 annealing typically employed for optimization of the CdTe-based solar cells. A systematic study on the microstructure, optical and optoelectronic properties of CdS/CdTe solar cells processed under different iTAP conditions has been carried out. It has been found that these physical properties depend sensitively on the iTAP processing conditions and appropriate iTAP in the optimal window enhances grain growth, improves grain boundary connectivity, and reduces crystal defects. This leads to considerably improved CdTe crystallinity and as a result, improved optoelectronic properties of the CdS/CdTe solar cells. Our result suggests that the iTAP is important for optimizing the chemical composition and microstructure of CdTe thin films and its heterojunction with CdS, both of which are critical to the performance of the CdS/CdTe thin film solar cells. In addition, it was found that smaller CdTe thickness provides advantages in reduced charge recombination.
80 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Philosophy of science
Pulsed Laser Deposition
Solar Cells
Thin Film
Effect of In Situ Thermal Annealing Process on Structural, Optical and Electrical Properties of CdS\CdTe Thin-Film Solar Cells Fabricated by Pulsed Laser Deposition
Thesis
Physics & Astronomy
M.S.
oai:kuscholarworks.ku.edu:1808/279912020-10-13T15:13:53Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Murray, Michael J.
BOWEN, JAMES LEE SMITH
Baringer, Philip S.
Fischer, Christopher
Lerner, David
Tapia Takaki, Daniel
2019-05-18T19:14:00Z
2019-05-18T19:14:00Z
2018-08-31
2018
http://dissertations.umi.com/ku:16137
http://hdl.handle.net/1808/27991
https://orcid.org/0000-0002-7020-9198
The Compact Muon Solenoid Experiment measured dijets produced in photon-nuclear collisions using data taken at the Large Hadron Collider in late 2015. Dijet measurements are potentially useful in constraining the gluon density over a wide range of x and Q, which is needed in order to measure the quark-gluon plasma viscosity and to search for the color-glass condensate. Recently it has been suggested by several theoretical groups that photon induced dijets can also be used to examine the correlation between the gluons in the nucleus. This analysis focused on the latter, examining azimuthal correlations between the total transverse momentum of the dijets and the momentum difference of the dijets. Following the prescription suggested by theorists, a positive correlation was found.
158 pages
en
University of Kansas
Copyright held by the author.
openAccess
Nuclear physics and radiation
Particle physics
Heavy Ion Nuclear Physics
High Energy Nuclear Physics
Ultra-Peripheral Collisions
Measuring Dijets From Ultra-Peripheral Heavy Ion Collisions
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/236612017-12-08T21:43:44Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Rodine, Milward T.
2017-04-13T15:16:01Z
2017-04-13T15:16:01Z
1930
http://hdl.handle.net/1808/23661
Thesis (M.A.)--University of Kansas, Physics, 1930.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The thermal conductivity of mercury-cadmium liquid alloys
Thesis
Physics
M.A.
3426821
oai:kuscholarworks.ku.edu:1808/123122020-10-07T14:25:31Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Ralston, John
Middaugh, Russ
Maddux, Nathaniel R.
Han, Siyuan
Fischer, Chris
Antonik, Matthew
Van Vleck, Erik
2013-09-30T19:29:35Z
2013-09-30T19:29:35Z
2013-05-31
2013
http://dissertations.umi.com/ku:12784
http://hdl.handle.net/1808/12312
The field of pharmaceutical chemistry is currently struggling with the question of how to relate changes in the physical form of a macromolecular biopharmaceutical, such as a therapeutic protein, to changes in the drug's efficacy, safety, and long term stability (ESS). A great number of experimental methods are typically utilized to investigate the differences between forms of a macromolecule, yet conclusions regarding changes in ESS are frequently tentative. An opportunity exists, however, to relate changes in form to changes in ESS. At least once during the development of a new drug, a study is undertaken (at great expense) of the ESS of the drug upon perturbation by multiple manufacturing, formulation, storage and transportation variables. The data acquired is then used to build a model that relates changes in ESS to manufacturing, formulation, storage and transportation variables. It is not common in the pharmaceutical industry, however, to relate changes in comprehensive ESS data sets to comprehensive measurements of changes in macromolecular form. We bridge the gap between physical measurements of a macromolecule's form and measurements of its long term stability, utilizing two data sets collected in a collaboration between our group at the University of Kansas and a group at the Ludwig Maximilians University in Munich, Germany. The long term stability data, collected by the team in Germany, contains measurements of the chemical and conformation stability of Granulocyte Colony Stimulating Factor (GCSF) over a period of two years in 16 different liquid formulations. The short term physical data, collected in our lab, is comprised of spectroscopic characterization of the response of GCSF to thermal unfolding. The same 16 liquid formulations of GCSF were used in each study, allowing us to fit models predicting the long term stability of GCSF from short term measurements. We first apply a novel data reduction method to the short term data. This method selects data in the neighborhood of thermal unfolding transitions, and automates traditional comparative analyses. We then model the long term stability measurements using a linear technique, least squares fits, and a nonlinear one, radial basis function networks (RBFN). Using a Pearson correlation coefficient permutation test, we find that many of the fitted results have less than a 1 percent probability of occurring by chance.
190 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Pharmaceutical sciences
High throughput prediction of the long term stability of pharmaceutical macromolecules from short term multi-instrument spectroscopic data
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8086133
oai:kuscholarworks.ku.edu:1808/76712020-08-07T17:17:48Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Melott, Adrian L
Atri, Dimitra
Johnson, Carey K.
Murray, Michael J
Thomas, Brian C
Wilson, Graham
2011-06-21T19:30:07Z
2011-06-21T19:30:07Z
2011-04-26
2011
http://dissertations.umi.com/ku:11432
http://hdl.handle.net/1808/7671
On geological timescales, the Earth is likely to be exposed to higher than the usual flux of high energy cosmic rays (HECRs) from astrophysical sources such as nearby supernovae, gamma ray bursts or by galactic shocks. These high-energy particles strike the Earth's atmosphere, initiating an extensive air shower. As the air shower propagates deeper, it ionizes the atmosphere by producing charged secondary particles and photons. Increased ionization leads to changes in atmospheric chemistry, resulting in ozone depletion. This increases the flux of solar UVB radiation at the surface, which is potentially harmful to living organisms. Increased ionization affects the global electrical circuit, which could enhance the low-altitude cloud formation rate. Secondary particles such as muons and thermal neutrons produced as a result of hadronic interactions of the primary cosmic rays with the atmosphere are able to reach the ground, enhancing the biological radiation dose. The muon flux dominates the radiation dose from cosmic rays causing damage to DNA and an increase in mutation rates and cancer, which can have serious biological implications for surface and sub-surface life. Using CORSIKA, we perform massive computer simulations and construct lookup tables for 10 GeV - 1 PeV primaries, which can be used to quantify these effects from enhanced cosmic ray exposure to any astrophysical source. These tables are freely available to the community and can be used for other studies. We use these tables to study the terrestrial implications of galactic shock generated by the infall of our galaxy toward the Virgo cluster. Increased radiation dose from muons could be a possible mechanism explaining the observed periodicity in biodiversity in paleobiology databases.
124 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Astrobiology
Cosmic rays
Terrestrial Effects of High Energy Cosmic Rays
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7642954
oai:kuscholarworks.ku.edu:1808/53242020-07-23T13:31:02Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Shi, Jack
Bilgen, Mehmet
Alenezy, Mohammed D.
Shi, Jack
Bilgen, Mehmet
Fischer, Chris
Cook, Larry
Smirnova, Irina
2009-07-30T04:39:18Z
2009-07-30T04:39:18Z
2009-04-17
2009
http://dissertations.umi.com/ku:10236
http://hdl.handle.net/1808/5324
A two-parameter computational model is proposed for the study of the regional motion of the left ventricle (LV) wall using tagged magnetic resonance imaging (tMRI) data. In this model, the LV wall motion is mathematically decomposed into two components, an isotropic deformation of the LV wall tissues along the short axis of LV and a non-uniform rotation of the tissues along the long axis of LV. The deformation and rotation parameters are determined by fitting the model to tMRI images of the short-axis planes of the LV wall. To validate this model, the tMRI images of the LV wall at the midventricular, apical and basal levels from eight subjects including healthy human, healthy and diabetic rats were studied. The result showed that this model is very effective in studying the LV wall motion and function in both small animals and human. With this model, the torsion, strain, and strain rate of the LV wall tissues can easily be calculated analytically at different phases of a cardiac cycle. It was found that the ratio of the torsion at endocardium to the torsion at epicardium is a constant during the cardiac motion even though the torsion varies with time significantly. The value of this constant of motion equals the ratio of the end diastolic radii of the LV wall at endocardium and epicardium and, therefore, is approximately the same for rats and human. This dissertation also includes a study of effects of exercise training on diabetic heart. In that study, global cardiac functions were measured using high field MRI and it was found that the global functions of diabetic heart could be improved by the training.
83 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Medical biophysics
Health sciences
Radiology
Diabetes
Left ventricle
Magnetic resonance imaging
Strain
Tagged magnetic resonance imaging
Torsion
Modeling Left Ventricle Wall Motion Using Tagged Magnetic Resonance Imaging
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
6857438
oai:kuscholarworks.ku.edu:1808/108712020-09-23T14:53:30Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Medvedev, Mikhail V
Ford, Alexander L.
Cravens, Thomas E
Feldman, Hume A
2013-02-17T20:56:13Z
2013-02-17T20:56:13Z
2012-12-31
2012
http://dissertations.umi.com/ku:12504
http://hdl.handle.net/1808/10871
The existence of flavor-mixed particles is well established. We discuss the dynamics of a stable particle with flavor mixing scattering off of a weak potential. We demonstrate that conversion from one mass state to another is possible through scattering and calculate the associated differential cross sections. The mass conversion is not analogous to flavor oscillations or particle decay. The implications of mass conversion, in general, and with respect to flavor-mixed dark matter and the cosmic neutrino background is discussed.
25 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Theoretical physics
Cosmic neutrinos
Dark matter
Flavor mixed
Theory of Interactions of Non-Relativistic Flavor-Mixed Particles and its possible Implications to the Physics of Dark Matter and the Cosmic Neutrino Background
Thesis
Physics & Astronomy
M.S.
na
This item does not meet KU Open Access policy criteria.
8085658
oai:kuscholarworks.ku.edu:1808/215092017-12-08T21:45:29Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Horak, Henry G.
Talley, Robert L.
2016-09-13T13:20:12Z
2016-09-13T13:20:12Z
1956
http://hdl.handle.net/1808/21509
Thesis (M.A.)--University of Kansas, Physics and Astronomy, 1956.
eng
University of Kansas
This work is in the public domain and is available for users to copy,
use, and redistribute in part or in whole. No known restrictions apply to the
work.
openAccess
The analysis of eclipsing binary systems
Thesis
Physics and Astronomy
M.A.
oai:kuscholarworks.ku.edu:1808/186692018-11-29T20:04:37Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z
Elliot, Alan J.
Han, Siyuan
Zhao, Hui
Nordheden, Karen
Chiu, Hsin-Ying
2015-10-13T04:33:30Z
2015-10-13T04:33:30Z
2014-12-31
2014
http://dissertations.umi.com/ku:13807
http://hdl.handle.net/1808/18669
Since the 1970's, silicon technology has increased processing power by increasing the density of silicon transistors according to Moore's Law. However, silicon transistor feature sizes are approaching a minimum size limit, and a new paradigm is required to continue progress. Quantum computing is a promising paradigm that relies on the entanglement of macroscopic quantum objects, called qubits, to perform calculations. Josephson junction (JJ) based qubits are a promising candidate for the implementation of quantum computers. However, JJ qubits have suffered from poor coherence. A major source of decoherence in JJ qubits is two-level fluctuators in the insulating materials of the JJ circuit, particularly oxygen vacancies and interstitials in the thermally oxidized tunnel barrier. In order to realize the full potential of JJ qubits, an alternative method to thermal oxidation must be found for tunnel barrier growth. This work explores using atomic layer deposition (ALD) for the growth of ultrathin (~ 1 nm) tunnel barriers in JJs. A unique thin film deposition tool was built which integrates ultra-high vacuum sputtering with ALD in situ. The growth of ALD-Al2O3 on in situ sputtered Al films was studied in depth. Atomic force microscopy and ellipsometry were used to determine that ALD-Al2O3 grows conformally on Al, but a ~ 2 nm thermally oxidized interfacial layer (IL) develops between the Al and Al2O3 for ALD films > 2 nm. The thickness of this IL decreased when the Al film was 2 nm. The thickness of this IL decreased when the Al film was < 2 nm, confirming the IL is a thermal oxide. As a proof of concept, Nb/Al/ALD-Al2O3/Nb trilayers with ultrathin (< 1 nm) tunnel barriers were grown and processed into JJs. The junction specific resistance and gap current density were found to depend exponentially on the ALD film thickness, indicating that the tunnel barrier thickness can be controlled by ALD. Despite evidence for an estimated 0.8 nm interfacial layer in the ultrathin tunnel barrier, this work incontrovertibly concludes that ALD can be used to produce quality JJs.
94 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Engineering
Materials Science
Atomic layer deposition
Josephson junction
superconductivity
thin films
Josephson Junctions with Tunnel Barriers Grown Via In Situ Atomic Layer Deposition
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/306742020-08-27T08:01:15Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Friesen, Abraham Penner
2020-08-26T14:20:21Z
2020-08-26T14:20:21Z
1935-05-31
http://hdl.handle.net/1808/30674
Dissertation (Ph.D.)--University of Kansas, Physics, 1935.
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Pure sciences
The optical constants of liquid sodium, liquid sodium amalgams, liquid thallium, and liquid thallium-bismuth alloys
Dissertation
Physics
Ph.D.
3426781
oai:kuscholarworks.ku.edu:1808/263402018-04-24T18:33:13Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Cravens, Thomas E
Madanian, Hadi
McLaughlin, Craing A
Hawley, Steve A
Fischer, Chris J
Shi, JiCong
2018-04-20T22:23:21Z
2018-04-20T22:23:21Z
2017-05-31
2017
http://dissertations.umi.com/ku:15361
http://hdl.handle.net/1808/26340
The absence of a protecting magnetic field, such as the dipole magnetic field around Earth, makes the interaction of solar wind with unmagnetized objects particularly interesting. Long-term evolution of the object’s surface and atmosphere is closely tied to its interaction with the outer space environment. The ionospheric plasma layer around unmagnetized objects acts as an electrically conducting transition layer between lower atmospheric layers and outer space. This study considers two distinct types of unmagnetized objects: Titan and comet 67P/Churyumov-Gerasimenko (67P/CG). For many years, Titan has been a key target of the National Aeronautics and Space Administration (NASA) Cassini mission investigations; and the European Space Agency (ESA) Rosetta spacecraft explored comet 67P/CG for more than two years. Ionospheric composition and primary ion production rate profiles for Titan are modeled for various solar activity conditions. Photoionization is the main source of ion production on the dayside; on the nightside, electron-impact ionization is the main ionization source. This dissertation uses model results and in-situ measurements by the Ion and Neutral Mass Spectrometer (INMS) and the Langmuir Probe (LP) onboard the Cassini spacecraft to show that while the solar activity cycle impacts the primary ion species significantly, there is little effect on heavy ion species. Solar cycle modulates the Titan’s ionospheric chemistry. The solar cycle effects of on each ion species are quantified n this work. In some cases the solar zenith angle significantly overshadows the solar cycle effects. How each individual ion reacts to changes in solar activity and solar zenith angle is discussed in details. A method to disentangle these effects in ion densities is introduced. At comet 67P/CG, the fast-moving solar wind impacts the neutral coma. Two populations of electrons are recognizable in the cometary plasma. These are the hot suprathermal electrons, created by photoionization or electron-impact ionization, and the cold/thermal electrons. Even though photoionization is the dominant source of ion production, electron-impact ionization can be as high as the photoionization for certain solar events. At 3 AU, electron energy spectra from in-situ measurements of the Ion and Electron Sensor (IES) instrument exhibit enhancement of electron fluxes at particular energies. Model-data comparisons show that the flux of electrons is higher than the typical solar wind and pure photoionization fluxes. The probable cause of this enhancement is the ambipolar electric field and/or plasma compression. This research also discusses formation of a new boundary layer around the comet near perihelion, similar to the diamagnetic cavity at comet 1P/Halley. At each crossing event to the diamagnetic cavity region, flux of suprathermal electrons with energies between 40 to 250 eV drops. The lower flux of solar wind suprathermal electrons in that energy range can cause this flux drop.
262 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Aeronomy
Plasma physics
Comet 67P
Ionosphere
Plasma
Solar Wind
Space Physics
Titan
External Plasma Interactions with Nonmagnetized Objects in the Solar System
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/54532020-06-25T20:06:33Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Melott, Adrian L
Atri, Dimitra
Medvedev, Mikhail V
Thomas, Brian C
2009-08-31T02:45:30Z
2009-08-31T02:45:30Z
2009-04-27
2009
http://dissertations.umi.com/ku:10298
http://hdl.handle.net/1808/5453
A variety of events such as gamma-ray bursts and supernovae may expose the Earth to an increased flux of high-energy cosmic rays, with potentially important effects on the biosphere. Existing atmospheric chemistry software does not have the capability of incorporating the effects of substantial cosmic ray flux above 10 GeV. An atmospheric code, the NASA-Goddard Space Flight Center two-dimensional (latitude, altitude) time-dependent atmospheric model (NGSFC), is used to study atmospheric chemistry changes. We have created a table that, with the use of the NGSFC code can be used to simulate the effects of high energy cosmic rays (10 GeV to 1 PeV) ionizing the atmosphere. By interpolation, the table can be used to generate values for other uses which depend upon atmospheric energy deposition by ensembles of high-energy cosmic rays. We discuss the table, its use, weaknesses, and strengths.
28 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Astronomy and astrophysics
Atmospheric chemistry
Atmospheric ionization
Cosmic rays
A Lookup Table to Compute High Energy Cosmic Ray Effects on Terrestrial Atmospheric Chemistry
Thesis
Physics & Astronomy
M.S.
na
This item does not meet KU Open Access policy criteria.
6857582
oai:kuscholarworks.ku.edu:1808/260082018-05-01T18:11:27Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Medvedev, Mikhail V
Ford, Alexander L.
Cravens, Thomas E
Feldman, Hume A
Shandarin, Sergei F
Lerner, David E
2018-02-19T02:40:24Z
2018-02-19T02:40:24Z
2017-08-31
2017
http://dissertations.umi.com/ku:15465
http://hdl.handle.net/1808/26008
https://orcid.org/0000-0001-6805-9787
Electromagnetic, radiative, and plasma processes around black holes in active galaxies determine how relativistic jets are launched and the efficiency at which the black hole energy is extracted via the Blandford-Znajek mechanism, which converts the black hole rotational energy into Poynting flux. The crucial assumption is the force-free condition, which is the presence of plasma with a density at or above the Goldreich-Julian density. Unlike neutron stars, which in principle can supply electrons from their surface, black holes cannot supply plasma at all, they are only a sink. Therefore, the plasma needed must be generated in situ. The essential process is the plasma production via an electron-position cascade in the so-called “gap” region in the force-free magnetosphere around the black hole. This multi-stage process, involving particle acceleration, photon Compton up-scattering, and production of electron-positron secondaries, is explored numerically by computing the radial development of the entire cascade. It is shown how the electron-positron plasma production depends on the black hole mass and spin, the energy density of the ambient photons, and seed magnetic field strength. Presented is the full, two-dimensional structure of the gap, along with empirical scaling relations for the two-dimensional gap structure. Observational predictions for X-ray and γ-ray fluxes and spectra, which can be compared with observations of the inner regions near jets and estimations of the structure of the gaps in several galaxies, e.g., Messier 87, using the empirical scaling relations are discussed.
177 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astrophysics
Plasma physics
Astronomy
AGN
black hole
plasma cascade
Plasma Cascade in Kerr Black Hole Magnetospheres
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/313652024-01-16T16:44:30Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy
Gautam, Bibek
Murray, Michael J.
Han, Siyuan
Chan, Wai-Lun
Berrie, Cindy L.
2021-02-07T20:14:58Z
2021-02-07T20:14:58Z
2019-08-31
2019
http://dissertations.umi.com/ku:16729
http://hdl.handle.net/1808/31365
https://orcid.org/0000-0002-3406-8965
A Superconductor exhibits dc zero-resistance below a critical temperature (Tc). The possible uses of superconductors in a high temperature range of 50-77 K are greatly expanded by the discovery of high temperature superconductors (HTS) in 1986. One of the most important parameters for the industrial applications of high temperature superconductors (HTS) is a high value of critical current density Jc, in applied magnetic fields (H) up to tens of Teslas. In HTS, magnetic flux would be expected to penetrate the superconductor in the form of filaments containing one flux quantum (Φo) in each filament. These flux lines are surrounded by circulating current that acts as screening current and give rise to the mixed state known as vortex state. Application challenges involve preventing vortex motion in HTS and determining the high value of Jc at the high magnetic field (H). The vortex motion increases with increasing applied field and hence decreases the Jc due to dissipation induced by the vortex motion. Obtaining a high Jc(H) requires stoppage of vortex motion in HTS. This can be done using pinning centers which capture the vortices and prevent their motion. Therefore, reaching high Jc(H) in HTS requires the insertion of strong pinning centers of dimension comparable to the superconducting coherence length on the order of few nanometers. Such pinning centers improve the critical current density and strengthen the pinning force density. Various innovative approaches have been developed in the last decade to generate optimally efficient artificial pinning centers (APCs) in YBa2Cu3O7-x (YBCO) nanocomposite films. However, controllable generation of self-assembled nanostructures during sample growth stage remains a challenge. Therefore, in this study, we generate a landscape of one-dimensional (1D) plus three-dimensional (3D) APCs of flexible elastic materials to improve strong and isotropic pinning which is beneficial for many industrial applications such as motors and generators. Specifically, a study of 3 vol.% Y2O3+2-6 vol.% BaHfO3 (BHO) double doped YBa2Cu3O7-x epitaxial thin films is carried out and compared to the same concentration of BaZrO3 (BZO) doping materials to explore the morphologic adaptation of the c-axis aligned 1D APCs to the 3D APCs. A significant reduction of Jc anisotropy is found for low doping BaHfO3 and 3 vol.% Y2O3 doped YBCO nanocomposite films (BHO double doped films). The self-assembly of 1D APCs in YBCO film matrix driven by the strain field is influenced by the lattice mismatch at the APC/YBCO interface. To answer the fundamental question on how the pinning efficiency of 1D APCs is affected by the APC/YBCO interface, electrical transport properties Jc (H, T) of the comparable diameter of BaZrO3 and BaHfO3 1D APCs on single doped YBCO nanocomposite films have been studied. The pinning force density is found to be significantly larger for a coherent, a less defective, BHO 1D APC/YBCO interface compared to a semicoherent, defective and oxygen deficient, BZO 1D APC/YBCO interface of epitaxial YBCO nanocomposite thin films. Transmission Electron Microscopy (TEM) images are utilized to study the difference of the nanostructures’ morphology, and 1D APC/YBCO interface of single and double doped nanocomposite thin films. It is found that less rigid BHO material forms a mixed APCs morphology reducing Jc anisotropy to about 20 % for 2 vol.% BHO double doped YBCO thin film at temperature of 65 K and at magnetic field of 9.0 T. A coherent APC/YBCO interface enhances the pinning efficiency of 1D APCs in BHO doped YBCO thin films. Significantly reduced pinning efficiency of BZO 1D APCs is observed for a defective BZO/YBCO interface. A method of repairing defective APC/YBCO interface through calcium doping is explored and recommended to enhance the pinning efficiency of one-dimensional APCs.
130 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Condensed matter physics
Artificial Pinning Center
Calcium Diffusion
Flux Pinning
High Tempertaure Superconductor
Isotropic Pinning
Pinning Efficiency
Controllable Self-Assembly of Nanostructured Artificial Pinning Centers (APCs) in High Temperature Superconductor Epitaxial Thin Films
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/213862017-12-08T21:40:50Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Pistorius, Grant Lewis
2016-08-23T17:11:05Z
2016-08-23T17:11:05Z
1928
http://hdl.handle.net/1808/21386
Thesis (M.A.)--University of Kansas, Physics, 1928.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The Joule-Thomson effect in air
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/206002021-08-27T17:47:15Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Bennett, James Lawton
2016-03-29T16:05:05Z
2016-03-29T16:05:05Z
1925
http://hdl.handle.net/1808/20600
Thesis (M.A.)--University of Kansas, Physics, 1925.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
An investigation of the selective hot-wire microphone
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/182122020-06-24T19:11:26Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Whittemore, Laurens Ellis
2015-07-11T03:52:29Z
2015-07-11T03:52:29Z
1915
http://hdl.handle.net/1808/18212
Notes: Includes bibliographical references.
eng
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Some characteristics of crystal detectors
Thesis
3424633
oai:kuscholarworks.ku.edu:1808/190312018-01-31T20:07:50Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Fischer, Christopher J
Eastlund, Allen
Baringer, Phillip
Hawley, Steven
Johnson, Carey
Melott, Adrian
2015-12-03T03:26:25Z
2015-12-03T03:26:25Z
2015-05-31
2015
http://dissertations.umi.com/ku:14072
http://hdl.handle.net/1808/19031
Chromatin remodelers perform a necessary and required function for the successful expression of our genetic code. By modifying, shifting, or ejecting nucleosomes from the chromatin structure they allow access to the underlying DNA to the rest of the cell’s machinery. This research has focused on two major remodeler motors from major families of chromatin remodelers: the trimeric motor domain of RSC and the motor domain of the ISWI family, ISWI. Using primarily stopped-flow spectrofluorometry, I have categorized the time-dependent motions of these motor domains along their preferred substrate, double-stranded DNA. Combined with collected ATP utilization data, I present the subsequent analysis and associated conclusions that stem from the underlying assumptions and models. Interestingly, there is little in common between the investigated proteins aside from their favored medium. While RSC exhibits modest translocation characteristics and highly effective motion with the ability for large molecular forces, ISWI is not only structurally different but highly inefficient in its motion leading to difficulties in determining its specific translocation mechanics. While chromatin remodeling is a ubiquitous facet of eukaryotic life, there remains much to be understood about their general mechanisms.
107 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Biophysics
biophysics
Chromatin
Fluorescence
Remodelers
Revealing Remodeler Function: Varied and Unique
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/269372018-10-25T19:59:48Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Ceballos, Frank
Han, Siyuan
Wu, Judy
Chan, Wai-Lun
Tao, Franklin
2018-10-22T22:19:59Z
2018-10-22T22:19:59Z
2017-05-31
2017
http://dissertations.umi.com/ku:15197
http://hdl.handle.net/1808/26937
Since the discovery of graphene and its outstanding chemical, optical, and mechanical properties, other layered materials have been fiercely hunted for through physical and chemical means. Thanks to their van der Waals interaction, acting as weak glue, different types of layered materials can be stacked without considering their lattice mismatch. The properties of the resulting multilayer structures can be tuned by choice of the materials, layer thicknesses, sequence in which they are arranged, the relative orientation between the layers, and by external electrical, mechanical, and optical controls. This opens the possibility for a large array of applications across many different fields. With the vision to obtain the ability to precisely engineer materials with desired properties, using two-dimensional materials as Lego-blocks, early studies have shown that research in van der Waals stacked two-dimensional materials to be rich in discoveries and still on its early stages due to their abundant diversity. In order to characterize, understand, and improve the properties of van der Waals stacked two-dimensional materials, we first introduce and discuss the noninvasive laser spectroscopy techniques utilized to study them. To correctly interpret the data and to understand the limits of our ultrafast laser spectroscopy system, the dynamics the photocarriers undergo after the pump photoexcitation is examined. Next, the van der Waals stacked two-dimensional materials are introduced by order complexity. First, we discuss the results obtained from bilayers of MoS2–MoSe2 and MoSe2–WS2, which set the groundwork needed to understand more complex structures. We then move on to discuss trilayer MoS2–WS2–MoSe2 and are able to time resolve the electron transfer process as electrons relocate from the MoSe2 into the MoS2 layer. Finally, in the spirit of trying to engineer a new ultrathin material with a high absorption of light in the visible regime as well as extended the photocarrier lifetimes, we fabricated a set of samples that grew in complexity as additional layers were added. It was discovered that in our more complex multilayer structure WSe2–MoSe2–WS2–MoS2, that the absorbance peaked at 50% with about just 2.5 nm of material. Moreover, the photocarrier lifetimes were extended up to a few nanoseconds. With all these we show that van der Waals stacked two-dimensional materials can be engineered layer by layer with the resulting stack having desired properties.
142 pages
en
University of Kansas
Copyright held by the author.
openAccess
Condensed matter physics
exciton
monolayer
transient absorption
transition metal dichalcogenide
two-dimensional material
van der Waals heterostructure
Interlayer Charge Transfer in van der Waals Heterostructures Formed by Transition Metal Dichalcogenide Monolayers
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/280532019-08-27T18:09:09Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Besson, David
Stockham, Mark
Allen, Christopher
Cravens, Thomas
McKay, Douglas
Ralston, John
2019-05-19T02:12:53Z
2019-05-19T02:12:53Z
2018-12-31
2018
http://dissertations.umi.com/ku:16180
http://hdl.handle.net/1808/28053
The flux and cross section of high energy neutrinos is an active area of research. Due to the expected low flux and cross section, interactions are rare and direct detection is ruled out. Large detector volumes with detection signals that can be observed from far away represent a reasonable and economical way to combat this problem. A currently popular detection strategy is to use a large, dense medium -- such as ice -- for the detector volume and radio antennas as the detectors. These radio antennas are sensitive to Cherenkov radiation produced via the Askaryan effect when a neutrino interacts in the detector volume. To determine the absolute amplitude of radio frequency (RF) emissions from high energy physics processes observed by Antarctic detectors, the bulk attenuation and surface reflection properties of Antarctic ice must be estimated. Neutrino experiments that intend to use polar ice as the detector volume must consider the depth-dependent attenuation length of the ice. Airborne experiments, such as the balloon-borne ANtarctic Impulsive Transient Antenna (ANITA), additionally need to consider the effects of the ice-air transition for both refracted signals produced by neutrino collisions in ice and reflected signals generated by cosmic ray-induced extensive air showers (EAS). Combining radar depth sounding (RDS) data for the estimation of attenuation length with radar scatterometer measurements for the estimation of surface roughness, we seek to create Antarctica-wide attenuation models. Though models and estimates for attenuation and reflection are motivated by ANITA analysis, the methods and results should have general use for the treatment of radio frequency signals interacting with ice and similar media.
136 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
Geophysics
Remote sensing
attenuation
polar
radio
Bulk and Surface Radio-Frequency Response of Ice
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/102602020-09-21T13:06:18Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy
Rochford, Caitlin
Han, Siyuan
Zhao, Hui
Chiu, Hsin-Ying
Berrie, Cindy
2012-10-28T15:19:55Z
2012-10-28T15:19:55Z
2012-08-31
2012
http://dissertations.umi.com/ku:12257
http://hdl.handle.net/1808/10260
https://orcid.org/0000-0002-5070-209X
There is a great deal of interest in carbon nanostructures such as graphene and various forms of carbon nanotubes due to their exceptional physical, electronic, and optical properties. Many technological applications have been proposed for these nanostructures, but despite the promise many carbon nanostructure-based optoelectronic devices fail to compete with their conventional counterparts. This is often due in large part to a non-optimized material or device microstructure. Factors such as crystallinity, contact quality, defect structure, and device configuration can critically affect device performance due to the high sensitivity and extreme surface to volume ratio of carbon nanostructures. In order for the exceptional intrinsic properties of the nanostructures to be exploited, a clear understanding of the microstructure and its correlation with device-relevant optoelectronic properties is needed. This dissertation presents four projects which demonstrate this principle. First, a TiO2-coated carbon nanofiber is studied in order to optimize its structure for use in a novel dye-sensitized solar cell. Second, the electrode configuration of an individual multiwall carbon nanotube infrared sensor is investigated in order to surpass the limitations of disordered nanotube film-based infrared sensors. Third, the properties of defect structures in large area transferred graphene films grown by chemical vapor deposition are correlated with carrier diffusion in order to understand the film's low mobility compared to exfoliated graphene. Fourth, the effect of deposition conditions on graphene-metal contact was studied with the goal of achieving sufficiently transparent contacts for investigation of the superconducting proximity effect. All four projects highlight the unique properties of carbon nanostructures as well as the need to correlate their optoelectronic properties with microstructural details in order to achieve the desired device performance.
176 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Carbon
Carbon nanotube
Graphene
Microstructure
Nanoscience
Optoelectronics
Correlating Microstructure and Optoelectronic Performance of Carbon-Based Nanomaterials
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085839
oai:kuscholarworks.ku.edu:1808/218872018-01-31T20:07:47Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Cravens, Thomas E
Rahmati, Ali
Baringer, Philip S
Braaten, David
Medvedev, Mikhail V
Sanders, Stephen J
2016-11-10T23:12:36Z
2016-11-10T23:12:36Z
2016-05-31
2016
http://dissertations.umi.com/ku:14448
http://hdl.handle.net/1808/21887
Mars possesses a hot oxygen exosphere that extends out to several Martian radii. The main source for populating this extended exosphere is the dissociative recombination of molecular oxygen ions with electrons in the Mars ionosphere. The dissociative recombination reaction creates two hot oxygen atoms that can gain energies above the escape energy at Mars and escape from the planet. Oxygen loss through this photochemical reaction is thought to be one of the main mechanisms of atmosphere escape at Mars, leading to the disappearance of water on the surface. In this work the hot oxygen exosphere of Mars is modeled using a two-stream/Liouville approach as well as a Monte-Carlo simulation. The modeled exosphere is used in a pickup ion simulation to predict the flux of energetic oxygen pickup ions at Mars. The pickup ions are created via ionization of neutral exospheric oxygen atoms through photo-ionization, charge exchange with solar wind protons, and electron impact ionization. Once ionized, the pickup ions are accelerated by the solar wind motional electric field to high energies, thus detectable by spacecraft instruments. The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft arrived at Mars in September of 2014 and has been taking measurements in the upper atmosphere of Mars, with the goal of determining the drivers and rates of atmospheric escape. In this work comparisons are made between the pickup ion model results and the MAVEN data from the SEP (Solar Energetic Particle) and SWIA (Solar Wind Ion Analyzer) instruments. It is shown that these model-data comparisons can be used to constrain the hot oxygen exospheric densities and the associated escape rates of oxygen from Mars.
214 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
exosphere
Mars
MAVEN
oxygen escape
pickup ion
upper atmosphere
Oxygen Exosphere of Mars: Evidence from Pickup Ions Measured by MAVEN
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/280472020-10-08T15:46:20Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Shi, Jack J
Deeds, Eric J
Nariya, Maulik
Shi, Jack J
Deeds, Eric J
Fischer, Christopher
Baringer, Philip
De Guzman, Roberto
2019-05-19T02:05:06Z
2019-05-19T02:05:06Z
2018-12-31
2018
http://dissertations.umi.com/ku:16164
http://hdl.handle.net/1808/28047
https://orcid.org/0000-0001-6646-2353
Type III secretion secretion (T3SS) system is a protein export pathway that helps bacterial cells construct many structures, like the flagellar hook and the injectisome, that aid in crucial physiological processes such as locomotion and pathogenesis. Both, the flagellar hook and the injectisome, involve long extracellular channels and the length of these channels is highly regulated to allow these structures to perform their intended functions. Numerous experiments have been performed to understand the structural details of this nanomachine during the past decade. Despite the concerted efforts of molecular and structural biologists, several crucial aspects of the assembly of these structure, such as the regulation of the length of the needle and the flagellar hook, remain unclear. There are two leading models for how length control is achieved in the flagellar hook and T3SS needle: the substrate switching model, where the length is controlled by assembly of an inner rod, and the ruler model, in which a molecular ruler controls the length. While there is qualitative experimental evidence to support both models, there is a lack of detailed quantitative characterization of these models that could be used to unambiguously test these mechanisms experimentally. In this work, we used a combination of mathematical and computational techniques to better understand these length control mechanisms. Based on a set of straightforward assumptions, we constructed a mathematical model for length control based on the timing of substrate switching. Our model made predictions about commonly measured quantities such as the average needle lengths and the variance in lengths. In particular our model predicted for the substrate switching mechanism that the variance scales quadratically with the average length. Our model also predicted the form of the needle length distribution based on this mechanism, and found excellent agreement with available experimental data from Salmonella typhimurium with only a single free parameter. We also constructed a mathematical model of length control based on the ruler mechanism, and found that the predictions of this model are consistent with experimental data not just for the scaling of the average length with the ruler protein length, but also the variance. Interestingly, we found that the ruler mechanism allows for the evolution of needles with large average lengths without the concomitant large increase in variance that occurs in the substrate switching mechanism. In addition to making further predictions that can be tested experimentally, these findings shed new light on the trade-offs that may have lead to the evolution of different length control mechanisms in different bacterial species.
99 pages
en
University of Kansas
Copyright held by the author.
openAccess
Computational physics
Biology
Systems science
Biochemical simulations
Mathematical model
Ruler model
Salmonella
Yersinia
Substrate switching
Type III secretion system
Mathematical Modeling of Length Control in the Type III Secretion System
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/260392018-10-31T16:24:38Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Shi, Jack
Rush, Wade Drury
Wilson, Graham
Han, Siyuan
Chan, Wai-Lun
Miller, James
2018-02-19T23:20:01Z
2018-02-19T23:20:01Z
2017-05-31
2017
http://dissertations.umi.com/ku:15232
http://hdl.handle.net/1808/26039
https://orcid.org/0000-0002-1839-8921
In 2016, Fermilab Accelerator and Technology Facility (FAST) conducted an experiment to generate a discrete and potentially tunable hard X-ray channeling radiation emissions in the 40-150 KeV energy range using a new 50 MeV rated linear accelerator. There are two current models (one-dimensional (1-D) Planar and the two-dimensional (2-D) Axial model) that numerically simulate the physics involved in generating channeling radiation. FAST decided to use the 1-D Planar model in designing the experiment using a diamond crystal lattice with a (110) plane orientation. However, this study shows that the 1-D Planar model is fraught with inconsistencies and applies excessive approximations. Using this approach will obfuscate the analysis in properly identifying the mechanism that generate these discrete energy emissions. The 2-D Axial model would be a much better model to properly predict spectrum emissions energies. However, the 2-D Axial model is complex and appears to also contain unnecessary approximations as well. This study's goal was to develop a better 2-D Generic model for the experiment based on a more fundamental and accurate approach than the existing 2-D Axial model. Unfortunately the FAST experiment was unable to generate channeling radiation data. Thus, this study had to compare its 2-D Generic model predictions with the published experimental results that were based on the 2-D Axial model. Our 2-D Generic model produced a rich amount of spectrum. But, ultimately, it had poor agreement with these published experimental data results. On the other hand, the 2-D axial model provided very good agreement with their published experimental data. The failure for this new 2-D Generic model indicates two possibilities. First, the accelerator's electron beam distribution of the transverse momentum to the beam direction directly impacts spectrum data. In all published results, this beam transverse momentum distribution is unknown. Therefore, if this transverse momentum distribution was published, then a more definitive conclusion can be made on whether this model agrees with the published experimental data or not. Second, since this model is based on a more fundamental concept, the 2-D Generic model should have very good agreement. However, since the model is unable to accurately predict discrete channeling emission energies, this discrepancy indicates that there are perhaps additional mechanisms unaccounted for in the generation of channeling radiation. Attached files DATA.zip
186 pages
en
University of Kansas
Copyright held by the author.
openAccess
Quantum physics
Physics
Axial Channeling
Axial Potential
Channeling Radiation
Electron Channeling
Lattice
Planar Channeling
"A New and Generic Two-Dimensional Model for Studying Channeling Radiation with Relativistic Electron Beams"
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/270222020-10-12T14:19:11Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Murray, Michael J
Al-Bataineh, Ayman Ahmad
Baringer, Philip S
Fischer, Chris
Takaki, Daniel T
Laird, Brian B
2018-10-24T22:47:28Z
2018-10-24T22:47:28Z
2017-12-31
2017
http://dissertations.umi.com/ku:15665
http://hdl.handle.net/1808/27022
https://orcid.org/0000-0003-4026-7626
This thesis reports on photoproduction of exclusive J/ψ mesons in ultra-peripheral PbPb and pPb collisions at √sNN = 2.76 TeV, and 5.02 TeV, respectively, from the CMS experiment at the LHC. For PbPb collisions, there is a correlation between the directions of the produced J/ψ and the neutron emitted by the struck nucleus. For J/ψ mesons with pT 100 MeV/c, the ratio of the pT distributions for J/ψ is moving in the opposite direction as the neutrons emitted from the target nucleus to those for J/ψ is moving in the same direction as the neutrons, suggests significant shadowing in the lead nucleus. For pPb collisions, the distributions of the J/ψs in transverse momentum have a similar form to previous measurements at HERA. The average pT increases with the photon-proton center of mass energy W . This implies that the spatial distribution of the gluons within the proton depends upon the gluon momentum. The cross-section also increases as W increases from 57 to 439 GeV implying that the proton becomes more and more opaque to photons as the photon energy increases. Parametrizing the growth ofthecrosssectionbytheformσ(W)∝Wδ yieldsavalueofδ =0.636±0.063. This result is consistent with the world average and has a precision comparable to other experiments.
219 pages
en
University of Kansas
Copyright held by the author.
openAccess
Nuclear physics and radiation
Physics
CMS detector at LHC
J/Psi Vector Meson
Parten Distribution Functions
Photo-nuclear interaction
Quark Gluon Plasma
Saturation and Shadowing
J/Ψ production in ultra-peripheral proton-lead and lead-lead collisions with CMS
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/69292020-08-05T14:26:41Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Marfatia, Danny
Sessolo, Enrico Maria
Feldman, Hume A
Lerner, David
McKay, Douglas
Ralston, John
2010-12-29T03:39:57Z
2010-12-29T03:39:57Z
2010-01-01
2010
http://dissertations.umi.com/ku:11040
http://hdl.handle.net/1808/6929
We introduce recent research topics in beyond the Standard Model particle physics with Supersymmetry. In the first part we implement a new, extended approach to placing bounds on trilinear R-parity violating couplings. We focus on a limited set of leptonic and semi-leptonic processes involving neutrinos, combining multidimensional plotting and cross-checking constraints from different experiments. This allows us to explore new regions of parameter space and to relax a number of bounds given in the literature. We look for qualitatively different results compared to those obtained previously using the assumption that a single coupling dominates the R-parity violating contributions to a process. In the second part we investigate the prospects for indirect detection of fermion WIMPless dark matter at the neutrino telescopes IceCube and DeepCore. The dark matter annihilating in the Sun is a hidden sector Majorana fermion that couples through Yukawa couplings to a connector particle and a visible sector particle, and it exhibits only spin-dependent scattering with nuclei via couplings to first generation quarks. We consider cases where the annihilation products are taus, staus, or sneutrinos of the three generations. To evaluate the muon fluxes incident at the detector, we propagate the neutrino spectra through the solar medium and to the Earth and account for the effects of neutrino oscillations, energy losses due to neutral- and charged-current interactions, and tau regeneration. We find that for the stau and sneutrino channels, a 5 yr 3$sigma$ detection of dark matter lighter than about 300~GeV is possible at IceCube for large Yukawa couplings or for dark matter and connector particles with similar masses. The tau channel offers far better detection prospects. However, due to its lower energy threshold and better muon background rejection capability, DeepCore is able to detect signals in all annihilation channels and for a wider range of dark matter masses.
100 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Elementary particles and high energy physics
Dark matter
Phenomenology
Supersymmetry
Beyond the Standard Model with Supersymmetry
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085577
oai:kuscholarworks.ku.edu:1808/234652017-12-08T21:43:43Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Davis, Rex Harry Allen
2017-03-21T14:33:57Z
2017-03-21T14:33:57Z
1932
http://hdl.handle.net/1808/23465
Thesis (M.A.)--University of Kansas, Physics, 1932.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Effects of corona ionization on isotherms about a heated wire in air
Thesis
Physics
M.A.
3425251
oai:kuscholarworks.ku.edu:1808/246362017-12-08T21:40:50Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
James, Harry Raymond
2017-06-26T21:11:54Z
2017-06-26T21:11:54Z
1929
http://hdl.handle.net/1808/24636
Thesis (M.A.)--University of Kansas, Physics, 1929.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The use of the hot wire anemometer in measuring coefficients of absorption of sound
Thesis
Physics
M.A.
3427739
oai:kuscholarworks.ku.edu:1808/64662020-08-03T15:33:00Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Melott, Adrian L
Overholt, Andrew
Anthony-Twarog, Barbara J
Twarog, Bruce A
2010-07-30T10:55:03Z
2010-07-30T10:55:03Z
2010-04-19
2010
http://dissertations.umi.com/ku:10783
http://hdl.handle.net/1808/6466
We re-examine past suggestions of a close link between terrestrial climate change and the Sun's transit of spiral arms in its path through the Milky Way galaxy. These links produced concrete fits, deriving the unknown spiral pattern speed from terrestrial climate correlations. We test these fits against new data on spiral structure based on CO data that does not make simplifying assumptions about symmetry and circular rotation. If we compare the times of these transits to changes in the climate of Earth, not only do the claimed correlations disappear, but also we find that they cannot be resurrected for any reasonable pattern speed.
15 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Astrophysics
Physics
Astronomy and astrophysics
Climate
Earth
Galaxies
Testing the Link Between Terrestrial Climate Change and Galactic Spiral Arm Transit
Thesis
Physics & Astronomy
M.S.
na
This item does not meet KU Open Access policy criteria.
7078879
oai:kuscholarworks.ku.edu:1808/63082020-07-28T12:07:12Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z
Emergo, Rose Lyn S.
Nordheden, Karen J
Baringer, Philip
Zhao, Hui
Han, Siyuan
2010-06-09T04:23:28Z
2010-06-09T04:23:28Z
2009-04-29
2009
http://dissertations.umi.com/ku:10372
http://hdl.handle.net/1808/6308
Critical current density (Jc) has been identified as one of the most critical parameters for the practical application of high temperature superconductors such as YBa2Cu3O7-δ (YBCO). Unfortunately, the Jc of optimized un-doped YBCO films barely satisfies the criteria for these applications. High J¬c can be achieved by introducing strong artificial pinning centers in YBCO which can inhibit flux motion and prevent dissipation. However, insertion of strong pins has been observed to strain and poison the YBCO lattice resulting in unnecessary degradation of Tc and low field Jc. In this work, two types of strong pinning centers with negligible effect on the Tc and low field Jc were incorporated in YBCO films via strain engineering on the nanoscale. The nanotube pores were generated by depositing YBCO films on vicinal SrTiO3 (STO) substrates. A close correlation between Jc and the magnetic pinning potential Up of the nanotube pores has been demonstrated below the accommodation field, suggesting that nanotube pores are strong pins on the magnetic vortices. Splayed BaZrO3 nanorords (BZO-NRs) were generated in YBCO film by depositing 2 vol.% BZO-doped YBCO on vicinal STO substrates. The interplay between the lattice strain caused by the large lattice mismatch between YBCO and BZO and the anisotropic strain due to vicinal growth resulted in the dispersed orientation of BZO-NRs. The splayed BZO-NRs led to an enhanced Jc in the entire range of the magnetic field orientation up to 5 T as compared to the non-splayed case of YBCO/BZO-NRs films.
131 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
Angular dependence of jc
Critical current density
Flux pinning
High temperature superconductors
Nano-engineering
Ybco
Enhancing Jc(B,theta) in YBa2Cu3O7-delta via nano-engineering of pinning structures
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7078975
oai:kuscholarworks.ku.edu:1808/190452018-01-31T20:07:54Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Rudnick, Gregory
Henke, Brittany Nicole
Rudnick, Gregory
Twarog, Bruce
Medvedev, Mikhail
2015-12-03T03:48:39Z
2015-12-03T03:48:39Z
2015-05-31
2015
http://dissertations.umi.com/ku:13850
http://hdl.handle.net/1808/19045
This is a feasibility study for the analysis of Hubble Space Telescope observations of galaxy cluster IRC 0218A at a redshift of z = 1.62. The main goals were as follows: to investigate any systematic biases in D(4000) and Dn(4000), commonly used indices for probing a galaxy's average stellar age, for different star formation histories, ages, metallicities, and dust extinctions; to determine the precision with which D(4000) and Dn(4000) can be measured for galaxies at a range of magnitudes; and to constrain the conditions under which a measurement of D(4000) or Dn(4000) is a reliable probe of a galaxy's average stellar age. A grid of template galaxies was constructed using the GALAXEV package described by Bruzual & Charlot (2003), and the Hubble observations were simulated using the Space Telescope Science Institute's aXeSIM software package. No obvious systematic biases in D(4000) or Dn(4000) were observed. D(4000) and Dn(4000) could be accurately measured within a 10% uncertainty up to the study's J-band magnitude limit of 22.8 and within a 5% uncertainty up to a J-band magnitude of 21.6. However, even these small errors in D(4000) correspond to large errors in calculated stellar age. A measurement of D(4000) or Dn(4000) can only roughly constrain the age of a galaxy's stellar population for J-band magnitudes brighter than ∼ 21.6.
106 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astrophysics
Astronomy
D(4000)
feasibility
galaxy
Hubble
WFC3
Measuring D(4000) n z~1.6 galaxies using WFC3/G102L observations with HST: a feasibility study
Thesis
Physics & Astronomy
M.S.
oai:kuscholarworks.ku.edu:1808/280492020-10-13T19:36:33Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Besson, David
Prohira, Steven
Ralston, John P
Kong, KC
Bean, Alice
McKay, Doug
Allen, Christopher
2019-05-19T02:07:39Z
2019-05-19T02:07:39Z
2018-12-31
2018
http://dissertations.umi.com/ku:16277
http://hdl.handle.net/1808/28049
https://orcid.org/0000-0002-8814-6607
An ultra high energy particle, incident upon the earth, will produce a cascade of particles upon interaction. Detection of this cascade holds the key to understanding the properties of the primary-what it was, how much energy it carried, and maybe even where it came from. Of the many strategies developed over the course of the last century to detect such cascades, the radar technique is one of the latest to be explored with interest. For high enough incident energies, the relativistic progression of the cascade through a medium will produce a cloud of ionization that may become dense enough to reflect incident radio-frequency (RF) fields. If so, a broadcasting transmitter and distant receiver could feasibly detect cascades at very long baselines, thereby converting a massive volume of air or ice or sand or salt into a sensitive detector. Such an increase in volume opens up possibility of detecting events which occur on the order of 1km −2 yr −1 or less. In this dissertation, we present a detailed discussion of the radar detection method, focusing specifically on the detection of ultra high energy cosmic rays in the atmosphere, and ultra high energy neutrinos in dense material, such as ice. We will present the history and experimental efforts to date, and include the latest results from recent models and experiments seeking to address the radar problem. Ultimately, we suggest that the radar method is a promising one for the detection of 10 15 eV neutrinos which have interacted in a dense medium, such as the Antarctic ice.
167 pages
en
University of Kansas
Copyright held by the author.
openAccess
Physics
astroparticle
cosmic-ray
neutrino
physics
radar
radio
Radar detection of cosmic-ray and neutrino induced cascades
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/263202018-04-24T18:39:45Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Cui, Qiannan
Han, Siyuan
Wu, Judy
Chan, Wai-Lun
Hui, Rongqing
2018-04-20T21:29:03Z
2018-04-20T21:29:03Z
2017-05-31
2017
http://dissertations.umi.com/ku:15176
http://hdl.handle.net/1808/26320
Nonlinear optical properties of two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), graphene, black phosphorus, and so on, play a key role of understanding nanoscale light-matter interactions, as well as developing nanophotonics applications from solar cells to quantum computation. With ultrafast lasers, we experimentally study nonlinear optical properties of 2D materials. Employing transient absorption microscopy, we study several members of 2D materials, such as WSe2, TiS3 and ReS2. The dynamical saturable absorption process of 2D excitons is spatiotemporally resolved. Intrinsic parameters of these 2D materials, such as exciton lifetime, exciton diffusion coefficient, and exciton mobility, are effectively measured. Especially, in-plane anisotropy of transient absorption and diffusive transport is observed for 2D excitons in monolayer ReS2, demonstrating the in-plane degree of freedom. Furthermore, with quantum interference and control nanoscopy, we all-optically inject, detect and manipulate nanoscale ballistic charge currents in a ReS2 thin film. By tuning the phase difference between one photon absorption and two photon absorption transition paths, sub-picosecond timescale of ballistic currents is coherently controlled for the first time in TMDs. In addition, the spatial resolution is two-order of magnitude smaller than optical diffraction limit. The second-order optical nonlinearity of 2D monolayers is resolved by second harmonic generation (SHG) microscopy. We measure the second-order susceptibility of monolayer MoS2. The angular dependence of SHG in monolayer MoS2 shows strong symmetry dependence on its crystal lattice structure. Hence, second harmonic generation microscopy can serve as a powerful tool to noninvasively determine the crystalline directions of 2D monolayers. The real and imaginary parts of third-order optical nonlinearity of 2D monolayers are resolved by third harmonic generation (THG) microscopy and two-photon transient absorption microscopy, respectively. With third harmonic generation microscopy, we observe strong and anisotropic THG in monolayer and multilayer ReS2. Comparing with 2D materials with hexagonal lattice, such as MoS2, the third-order susceptibility is higher by one order of magnitude in ReS2 with a distorted 1T structure. The in-plane anisotropy of THG is attributed to the lattice distortion in ReS2 after comparing with a symmetry analysis. With two-photon transient absorption microscopy, we observe a giant two-photon absorption coefficient of monolayer WS2.
144 pages
en
University of Kansas
Copyright held by the author.
openAccess
Condensed matter physics
Optics
Materials Science
2D materials
Coherent control
Second harmonic generation
Third harmonic generation
Transient absorption
Ultrafast lasers
Nonlinear Optical Spectroscopy of Two-Dimensional Materials
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/251732017-12-08T21:43:43Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Hoecker, Frank Edward
2017-10-19T15:07:02Z
2017-10-19T15:07:02Z
1932
http://hdl.handle.net/1808/25173
Thesis (M.A.)--University of Kansas, Physics, 1932.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
Measurement of the dielectric constants of dilute solutions of alcohol in nonpolar solvents
Thesis
Physics
M.A.
3425277
oai:kuscholarworks.ku.edu:1808/74292020-08-06T15:32:00Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Han, Siyuan
Mao, Bo
Marfatia, Danny
Wu, Judy
Zhao, Hui
Hui, Rongqing
2011-04-26T03:18:27Z
2011-04-26T03:18:27Z
2010-09-12
2010
http://dissertations.umi.com/ku:11154
http://hdl.handle.net/1808/7429
A radio frequency (rf) superconducting quantum interference device (SQUID) is a macroscopic quantum object consisting of a superconducting loop interrupted by a Josephson junction. Superconducting phase quantum bits (qubits) based on rf SQUIDs have been proven to be one of the most promising candidates for building a quantum computer. They exploit the unique resources of quantum superposition and entanglement and are exponentially faster than classical computers in solving certain problems, such as factoring. Compared to other approaches to quantum computing, superconducting phase qubits allow stronger and more flexible inter-qubit coupling and thus are easier to scale up. However, phase qubits couple to the environment and are subject to considerable decoherence. The resulting coherence time (also called decoherence time) is on the order of 100 ns, about two orders of magnitude shorter than that required for fault-tolerant quantum computing. One possible solution is to develop faster quantum gates in phase qubits. In this dissertation, coherent manipulation of multi-partite quantum states via Landau-Zener (LZ) transitions was investigated in a phase qubit, which was coupled to two microscopic two-level systems (TLSs) embedded in the tunnel barrier of the Josephson junction. The qubit chip was measured at temperatures below 30 mK in an ultra-low noise environment with excellent electrical and magnetic filtering and shielding. All parameters of the phase qubit were calibrated independently. The phase qubit's decoherence times have been carefully measured as well. Fast and precise coherent control of the tripartite quantum states has been successfully demonstrated by the observation of the Landau-Zener-Stückelberg (LZS) interference in the coupled qubit-TLS system. Furthermore, it is shown that utilizing LZ transitions to create multi-partite entangled states, such as the W state, is significantly more efficient than conventional methods which require a sequence of single-qubit and two-qubit gates. Hence, coherent manipulation of multi-partite quantum states via LZ transitions is a promising basis for a new family of fast multi-qubit quantum gates.
95 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
Coherent control
Lz transition
Qubit-tls
Rf squid phase qubit
Tri-partite quantum system
Coherent Manipulation of Multi-Partite Quantum States in a Qubit-TLS System via Landau-Zener Transition
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7642742
oai:kuscholarworks.ku.edu:1808/203802021-08-26T22:02:59Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Isely, Frank C.
2016-02-25T21:13:06Z
2016-02-25T21:13:06Z
1924
http://hdl.handle.net/1808/20380
Thesis (M.A.)--University of Kansas, Physics, 1924.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The relation between the mechanical and piezo-electrical properties of a Rochelle salt crystal
Thesis
Physics
M.A.
oai:kuscholarworks.ku.edu:1808/307012020-09-02T08:01:01Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Reinhart, Raymond E.
2020-09-01T15:01:52Z
2020-09-01T15:01:52Z
1933-05-31
http://hdl.handle.net/1808/30701
Dissertation (Ph.D.)--University of Kansas, Physics, 1933.
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Pure sciences
A study of the propagation of large Barkhausen discontinuities as a function of longitudinal field, circular field, and intensity of magnetization
Dissertation
Physics
Ph.D.
3549397
oai:kuscholarworks.ku.edu:1808/73932020-07-30T13:12:40Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Haugan, Timothy J.
Baca, Francisco Javier A.
Baringer, Philip
Han, Siyuan
Williams, Susan M.
Zhao, Hui
2011-04-25T22:04:48Z
2011-04-25T22:04:48Z
2009-11-20
2009
http://dissertations.umi.com/ku:10627
http://hdl.handle.net/1808/7393
With the ability to carry very high electrical currents per unit area in kilometer length wires, high temperature superconductors (HTS) are especially promising candidates for applications where size and weight constraints are priorities. From military aircraft and naval applications to energy production by wind power, many types of power generation applications may operate under strenuous conditions, requiring current densities on the order of 105 A/cm2 while subjected to magnetic fields of 3 - 5 T. In the absence of a magnetic field, this current density requirement is well within the intrinsic limits of YBa2Cu3O7-x (YBCO), but operation in high magnetic fields makes the problem of vortex motion a limiting factor to the critical current density, Jc. Vortex pinning by the insertion of non-superconducting oxides like BaZrO3 (BZO) or BaSnO3 (BSO) into the YBCO matrix is an effective means of addressing this problem since these defects self-assemble into columnar structures (nanorods) that provide strong pinning along the length of the flux-line. However, only limited control of nanorod geometry is possible by current growth methods. To meet the requirements of applications that operate in magnetic fields of varying intensity or orientation, this thesis aims to produce a defect landscape that may be designed to meet these demands, as the thin film is grown. Achieving this represents a major challenge in the development of HTS cables and power devices, requiring correlation of material synthesis and characterization on a nanometer scale. The microstructure of BZO- and BSO-doped YBCO thin films was studied using Transmission Electron Microscopy and the findings indicate that it is possible to produce a controllable defect landscape by manipulation of the strain relationships using vicinal substrates, as well as through controlled growth dynamics by varying growth temperature.
131 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Condensed matter physics
Nanoscience
Bzo nanorods
High temperature superconductivity
Microstructure engineering
Tem
Vortex pinning
Ybco
In-Situ Control of BaZrO<sub>3</sub> and BaSnO<sub>3</sub> Nanorod Alignment and Microstructure in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> Thin Films by Strain Modulated Growth
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7078718
oai:kuscholarworks.ku.edu:1808/64162020-08-03T15:10:49Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Bean, Alice
Clutter, Justace Randall
Baringer, Phil
Wilson, Graham
Ralston, John
Lerner, David
2010-07-25T22:09:09Z
2010-07-25T22:09:09Z
2010-04-28
2010
http://dissertations.umi.com/ku:10931
http://hdl.handle.net/1808/6416
A search for dijet resonance production in a four-jet all-hadronic final state from the DO detector at Fermilab's Tevatron is presented. The data set, acquired at a ppbar center-of-mass energy of sqrt{s}=1.96 TeV, contains primarily multijet events and represents approximately 1 fb-1 of data. The cross section limits for associated Higgs production and Technicolor processes are determined through a background subtraction method using data to estimate the background. This four-jet channel is potentially very powerful, but is extremely challenging due to the large multijet background from QCD processes. Background rejection is performed by utilizing b-tagging, pre-selection cuts, a multi-variate boosted decision tree discriminant, and the correlated information contained in the M(bb) and M(jj) dijet invariant masses. The search for VH (WH+ZH) processes yields a 95% confidence level observed upper limit of 20.4 pb on the VH cross section for a Higgs mass of 115 GeV/c2. Additionally, a 95% confidence level observed upper limit of 16.7 pb was set for a Higgs boson mass of 125 GeV/c2 and 24.6 pb was set for a Higgs boson mass of 135 GeV/c2. The same data set was used to place limits on the Technicolor process ρTC→ WπTC where the technirho mass was fixed to 240 GeV/c2. For a technipion mass of 115 GeV/c2 we find a 95% confidence level observed upper limit on the cross section of 49 pb. The technipion masses of 125 GeV/c2 and 140 GeV/c2, the 95% confidence level observed upper limits are 57 pb and 71 pb, respectively.
201 pages
EN
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Elementary particles and high energy physics
Fermilab
Hadronic
Higgs boson
Technicolor
Tevatron
Search for VH and Technicolor Production in the qqbb Final State Using the RunII D0 Detector
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
8085490
oai:kuscholarworks.ku.edu:1808/226512020-06-23T18:33:31Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Strickler, Paul M.
2017-01-19T14:56:17Z
2017-01-19T14:56:17Z
1929
http://hdl.handle.net/1808/22651
Thesis (M.A.)--University of Kansas, Physics, 1929.
eng
University of Kansas
This work is in the public domain and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
A redetermination of the dielectric constant of benzene
Thesis
Physics
M.A.
3426475
oai:kuscholarworks.ku.edu:1808/314982024-01-16T16:42:58Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Wu, Judy Z
Acharya, Jagaran
Han, Siyuan
Murray, Michael J.
Chan, Wai-Lun
Berrie, Cindy L.
2021-02-27T20:55:30Z
2021-02-27T20:55:30Z
2019-12-31
2019
http://dissertations.umi.com/ku:16923
http://hdl.handle.net/1808/31498
https://orcid.org/0000-0003-1129-0974
The miniaturization of future microelectronics demands the development of high quality ultrathin (few to sub-nm) dielectric films for application in metal-insulator-metal (MIM) architectures. Among all other approaches employed for ultrathin dielectric film fabrication, atomic layer deposition (ALD) provides a unique approach for the fabrication of ultrathin TBs with several advantages including an atomic-scale control on the TB thickness, conformal coating, and low defects density. Despite extensive efforts in ALD devices, the figure-of-merit dielectric constant (r) exhibits a significant monotonic decrease with the film thickness as compared to bulk single crystal value. Primarily, the control over metal-insulator (M-I) interface, specifically in ultrathin thickness range, remains a challenge due to the formation of defective oxides and interfacial layer (IL). This work demonstrates the development of high quality Al/ALD Al2O3/Al MIM trilayers using a unique in-house integrated in situ deposition (sputtering/ALD) method. These trilayers devices were characterization to understand and control the IL formation with atomic precision. To the best of our knowledge, high r ~8.9 that is within 3% of the bulk value ~9.2 has been achieved for the first time on the ALD Al2O3 films in thickness range ~3.3-4.4 nm. This corresponds to an effective oxide thickness ~1.4-1.9 nm comparable to High-K HfO2 of 3-4 nm. The low leakage current density (J) ~10-9 A/cm2 is an order of magnitude lower than the best previously reported values. These results suggest that the optimal ultrathin high quality ALD Al2O3 provides a much lower-cost alternative for gate dielectric. Also, ALD Al2O3 seed layer (SL) approach was used to illustrate the critical importance of control over M-I interface to obtain dense hydroxylation and reduce incubation period, improving the dielectric properties of ultrathin ALD MgO films. ALD MgO with SL demonstrated r ~8.8-9.4 in thickness range ~3.8-4.9 nm comparable to bulk MgO ~9.4. In contrast, low r ~3.6-4.7 was observed for ALD MgO without Al2O3 SL in a similar thickness range. Both the scanning tunnelling spectroscopy and ab-initio molecular dynamics studies point out that SL allows the initial dense nucleation and perfect interface resulting in a high quality dielectric with tunnel barrier height (Eb)~1.5 eV compared to 0.8 eV for MgO without SL. This result provides an approach to engineering incompatible M-I interface using a SL for obtaining high quality dielectric as required for applications in MIM tunnel junctions and CMOS. In addition, tuning thickness of Al wetting layer (t_Al) in capacitors consisting of Nb (25 nm)/Fe (20 nm)/ALD Al2O3 (2.2 nm)/ t_Al/Fe (20 nm)/Nb (50 nm) shows switching between pure dielectric behavior for t_Al >1 nm and ferroelectric/dielectric (FE/DE) bilayer at t_Al≤ 1 nm. These FE/DE bilayer gate with ultrathin DE are promising for low power microelectronic devices. This helps to realize FE/DE bilayer capacitors with a total FE/DE total thickness 1 nm and ferroelectric/dielectric (FE/DE) bilayer at t_Al≤ 1 nm. These FE/DE bilayer gate with ultrathin DE are promising for low power microelectronic devices. This helps to realize FE/DE bilayer capacitors with a total FE/DE total thickness < 3-4 nm that show a dynamic switching on/off of the negative capacitance under the application of an external force. This result not only provides a viable approach for generating ultrathin FE/DE bilayer capacitors but also offers a promising solution to low-power consumption microelectronics and piezoelectric sensors applications. Pinhole-free and defect-free ultrathin dielectric tunnel barriers (TBs) is a key to obtaining high tunnelling magnetoresistance (TMR) and efficient switching in magnetic tunnel junctions (MTJs). Motivated by this, this work explores fabrication and characterization of spin-valve Fe/ALD-Al2O3/Fe MTJs with ALD Al2O3 TB thickness of 0.55 nm using in situ ALD. Remarkably, high TMR values of ~77% and ~ 90% have been obtained respectively at room temperature and at 100 K, which are comparable to the best reported on MTJs having thermal AlOx TBs with optimized device structures. In situ scanning tunnelling spectroscopy characterization of the ALD Al2O3 TBs has revealed a higher tunnel barrier height Eb of 1.33 eV, in contrast to Eb~0.3-0.6 eV for their AlOx TB counterparts, indicative of significantly lower defect concentration in the former. This first success of the MTJs with sub-nm thick ALD Al2O3 TBs demonstrates the feasibility of in situ ALD for the fabrication of pinhole-free and low-defect ultrathin TBs for practical applications and the performance could be further improved through device optimization.
157 pages
en
University of Kansas
Copyright held by the author.
openAccess
Condensed matter physics
Atomic layer deposition
dielectric constant
magnetic tunnel junction
scanning tunnelling spectroscopy
tunnelling magnetoresistance
ultrathin dielectric
Controlling Interface for Metal-Insulator-Metal Architectures with Ultrathin Dielectric Fabricated Using Atomic Layer Deposition and Sputtering
Dissertation
Physics & Astronomy
Ph.D.
oai:kuscholarworks.ku.edu:1808/84002020-08-17T14:03:22Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Zhao, Hui
Werake, Lalani Kumari
Zhao, Hui
Han, Siyuan
Wu, Judy
Antonik, Matthew
Elles, Christopher
2011-11-13T02:05:20Z
2011-11-13T02:05:20Z
2011-08-31
2011
http://dissertations.umi.com/ku:11714
http://hdl.handle.net/1808/8400
Abstract Exploring the spin degree of freedom of electrons has been recognized as a promising solution to several limitations in semiconductor device industry. Injection, transport, detection and manipulation of "spin" in materials are the key elements of this new electronic technology, known as spintronics. Despite the extensive efforts in recent years, there are still significant challenges and spintronics is still in the research phase. This dissertation is devoted to study one of these key processes: spin transport. We used quantum interference and control technique to inject spin currents. Two techniques are developed to detect the spin transport, namely a pump probe technique and a second-harmonic generation technique. Spin transport in several materials and structures are studied, including GaAs bulk, quantum wells, and germanium wafers. We observed the intrinsic inverse spin-Hall effect by time-resolving the ballistic spin and charge transport. We found that the Hall current appeared before the first scattering event. We discovered a new nonlinear optical effect, second-harmonic generation, induced by the pure spin current, and demonstrated that it can be used to directly detect pure spin currents. We have also discovered a charge-current-induced second-harmonic generation process, and used it to study plasma oscillation in GaAs. Finally, we also attempted to observe the second harmonic generation induced by spin polarized and spin unpolarized carrier populations. We did not observe a significant change in the observed second harmonic generation induced by spin polarized and spin unpolarized carrier populations.
132 pages
en
University of Kansas
This item is protected by copyright and unless otherwise specified the copyright of this thesis/dissertation is held by the author.
openAccess
Physics
Semiconductor
Spintronics
Ultrafast lasers
BALLISTIC CARRIER TRANSPORT IN SEMICONDUCTORS STUDIED BY ULTRAFAST LASER TECHNIQUES
Dissertation
Physics & Astronomy
Ph.D.
na
This item does not meet KU Open Access policy criteria.
7643087
oai:kuscholarworks.ku.edu:1808/104882019-07-26T16:59:12Zcom_1808_109com_1808_1260col_1808_14164col_1808_7158
Beal, A. F.
2012-12-10T20:57:36Z
2012-12-10T20:57:36Z
1912-05-29
http://hdl.handle.net/1808/10488
41 pages
en_US
University of Kansas
This work is in the public domain according to U.S. copyright law and is available for users to copy, use, and redistribute in part or in whole. No known restrictions apply to the work.
openAccess
The Experimental Investications of the Gibbs's Theory of Surface-Concentration
Thesis
Physics
M.A.
na
This item does not meet KU Open Access policy criteria.
oai:kuscholarworks.ku.edu:1808/258302018-01-31T23:29:56Zcom_1808_109com_1808_1260col_1808_14164col_1808_1951
Anthony-Twarog, Barbara J
Symons, Teresa Anne
Feldman, Hume A
Wilson, Graham W
2018-01-30T03:49:17Z
2018-01-30T03:49:17Z
2017-05-31
2017
http://dissertations.umi.com/ku:15190
http://hdl.handle.net/1808/25830
As CCD’s have drastically increased the amount of information recorded per frame, so too have they increased the time and effort needed to sift through the data. For observations of a single star, information from millions of pixels needs to be distilled into one number: the magnitude. Various computer systems have been used to streamline this process over the years. The CCDPhot photometer, in use at the Kitt Peak 0.9-m telescope in the 1990’s, allowed for user settings and provided real time magnitudes during observation of single stars. It is this level of speed and convenience that inspired the development of the Python-based software analysis system photPARTY, which can quickly and efficiently produce magnitudes for a set of single- star or un-crowded field CCD frames. Seeking to remove the need for manual interaction after initial settings for a group of images, photPARTY automatically locates stars, subtracts the background, and performs square-aperture photometry. Rather than being a package of available functions, it is essentially a self-contained, one-click analysis system, with the capability to process several hundred frames in just a couple of minutes. Results of comparisons with present systems such as IRAF are presented.
64 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astronomy
Computer science
Physics
astronomy
computational physics
photometry
python
photPARTY: Python Automated Square-Aperture Photometry
Thesis
Physics & Astronomy
M.S.
oai:kuscholarworks.ku.edu:1808/308162020-11-11T09:00:48Zcom_1808_109col_1808_14164
Fields, Brian D.
Melott, Adrian L.
Ellis, John
Ertel, Adrienne F.
Fry, Brian J.
Lieberman, Bruce S.
Liu, Zhenghai
Miller, Jesse A.
Thomas, Brian C.
2020-11-10T15:43:19Z
2020-11-10T15:43:19Z
2020-08-18
Fields, B. D., Melott, A. L., Ellis, J., Ertel, A. F., Fry, B. J., Lieberman, B. S., Liu, Z., Miller, J. A., & Thomas, B. C. (2020). Supernova triggers for end-Devonian extinctions. Proceedings of the National Academy of Sciences of the United States of America, 117(35), 21008–21010. https://doi.org/10.1073/pnas.2013774117
http://hdl.handle.net/1808/30816
10.1073/pnas.2013774117
https://orcid.org/0000-0002-4188-7141
https://orcid.org/0000-0002-7399-0813
https://orcid.org/0000-0002-3876-2057
https://orcid.org/0000-0002-4353-7874
https://orcid.org/0000-0002-8056-2526
https://orcid.org/0000-0001-5071-0412
https://orcid.org/0000-0001-9091-0830
PMC7474607
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian–Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to ∼100 ky. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at ∼20pc, somewhat beyond the “kill distance” that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes Sm146 or Pu244 in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosynthesis. Other possible tests of the supernova hypothesis are discussed.
UK Science and Technology Facilities Council
Estonian Research Council
National Academy of Sciences
Copyright © 2020 the Author(s). Published by PNAS.
http://creativecommons.org/licenses/by-nc-nd/4.0/
openAccess
Extinction
Supernova
Cosmic rays
Ozone
Isotope geology
Supernova triggers for end-Devonian extinctions
Article
Melott, Adrian L.
Physics and Astronomy
Scholarly/refereed, publisher version
This item meets KU Open Access policy criteria.
oai:kuscholarworks.ku.edu:1808/275272018-12-19T20:18:37Zcom_1808_1260com_1808_109col_1808_1952col_1808_14164
Melott, Adrian L
Overholt, Andrew
Lieberman, Bruce
Thomas, Brian
Twarog, Bruce
Wilson, Graham
2018-12-18T17:46:44Z
2018-12-18T17:46:44Z
2013-05-31
2013
http://dissertations.umi.com/ku:12640
http://hdl.handle.net/1808/27527
The Earth is constantly bombarded by cosmic rays. These high energy particles collide with target nuclei, producing a shower of secondary particles. These secondaries contribute significantly to the radiation background at sea level and in the atmosphere, as well as producing rare cosmogenic nuclides. This contribution is variable over long time scales as astrophysical events change the cosmic ray flux incident on the Earth. Our work re-examines a previously proposed climate effect of increased cosmic ray flux due to galactic location. Although our work does not support this effect, cosmic ray secondaries remain a threat to terrestrial biota. We calculate the cosmogenic neutron flux within the atmosphere as a function of primary spectrum. This work is pivotal in determining the radiation dose due to any arbitrary astrophysical event where the primary spectrum is known. Additionally, this work can be used to determine the cosmogenic nuclide production from such an event. These neutrons are the fundamental source of cosmogenic nuclides within our atmosphere and extraterrestrial matter. We explore the idea that excursions in 14C and 10Be abundances in the atmosphere may arise from direct deposition by long-period comet impacts, and those in 26Al from any bolide. We find that the amount of nuclide mass on large long-period comets entering the Earth's atmosphere may be sufficient for creating anomalies in the records of 14C and 10Be from past impacts. In particular, the estimated mass of the proposed Younger Dryas comet is consistent with its having deposited sufficient isotopes to account for recorded nuclide increases at that time. The 26Al/10Be ratio is much larger in extraterrestrial objects than in the atmosphere, and so, we note that measuring this ratio in ice cores is a suitable further test for the Younger Dryas impact hypothesis. This portion of our work may be used to find possible impact events in the geologic record as well as determination of a large bolide impact rate.
88 pages
en
University of Kansas
Copyright held by the author.
openAccess
Astrophysics
Physics
Comet
Cosmogenic
Impact
Neutrons
Sprial Arms
Younger Dryas
Cosmogenic nuclide production within the atmosphere and long period comets
Dissertation
Physics & Astronomy
Ph.D.
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