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2019

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Articles 1 - 30 of 1253

Full-Text Articles in Physics

Amyloid Proteins And Fibrils Stability, Farbod Mahmoudinobar Dec 2019

Amyloid Proteins And Fibrils Stability, Farbod Mahmoudinobar

Dissertations

Compared to globular proteins that have a stable native structure, intrinsically disordered peptides (IDP) sample an ensemble of structures without folding into a native conformation.One example of IDP is the amyloid-beta(Abeta) protein which is the main constituent of senile plaques in the brain of Alzheimer's patients.Understanding the process by which IDPs undergo structural changes to form oligomers that eventually aggregate into senile plaques/amyloid fibrils may significantly advance the development of novel therapeutic methods to treat neurodegenerative diseases, for which there is no cure to date. This dissertation has two main objectives. The first one is ...


Dimension Reduction Techniques For High Dimensional And Ultra-High Dimensional Data, Subha Datta Dec 2019

Dimension Reduction Techniques For High Dimensional And Ultra-High Dimensional Data, Subha Datta

Dissertations

This dissertation introduces two statistical techniques to tackle high-dimensional data, which is very commonplace nowadays. It consists of two topics which are inter-related by a common link, dimension reduction.

The first topic is a recently introduced classification technique, the weighted principal support vector machine (WPSVM), which is incorporated into a spatial point process framework. The WPSVM possesses an additional parameter, a weight parameter, besides the regularization parameter. Most statistical techniques, including WPSVM, have an inherent assumption of independence, which means the data points are not connected with each other in any manner. But spatial data violates this assumption. Correlation between ...


Sub-Barrier And Above-Barrier Electron Transport Through Multilayer Semiconductors, Vohob R. Rasulov, Rustam Y. Rasulov, Ikbol M. Eshboltaev, Ravshan R. Sultonov Dec 2019

Sub-Barrier And Above-Barrier Electron Transport Through Multilayer Semiconductors, Vohob R. Rasulov, Rustam Y. Rasulov, Ikbol M. Eshboltaev, Ravshan R. Sultonov

Scientific Bulletin. Physical and Mathematical Research

In the article the transparency coefficients of the semiconductor structure, consisting of alternating asymmetric potential barriers and wells, where the Bastard condition is taken into account, are calculated. It is shown that in the structure there should be an oscillation of the transmission coefficient of electrons depending on their energy, which is due to the interference of the de Broglie waves reaching the barrier and reflected from the potential barrier. The electronic states of a multilayer semiconductor structure consisting of alternating potential wells and barriers are analyzed. It has been shown that both in the above-barrier and in the barrier ...


Studies Of Tribotechnical Properties Of Composite Polymeric Materials Of Machine Designation, Tojiboy O. Almataev, Nozimbek T. Almataev Dec 2019

Studies Of Tribotechnical Properties Of Composite Polymeric Materials Of Machine Designation, Tojiboy O. Almataev, Nozimbek T. Almataev

Scientific Bulletin. Physical and Mathematical Research

In the given work are experimentally investigated tribotechnical properties as intensity of wear process and factor of a friction composite epoxy the polymeric materials processed by ultrasound. Results of influence of a kind and the maintenance loading on tribotechnical properties composite epoxy polymeric materials depending on modes of ultrasonic processing are received. Correlation dependence of intensity of wear process and factor of a friction composite epoxy coverings from modes of ultrasonic processing is established. It is shown in the work that with an increase in the duration of ultrasonic exposure, the wear rate and the friction coefficient of the coatings ...


Scientific Foundation Of The Rate Of Falling Of Raw Materials On Walnut Breakage Device, Otabek A. Mirzaev, Xolhuzha A. Sobirov, Nusratillo R. Barakaev Dec 2019

Scientific Foundation Of The Rate Of Falling Of Raw Materials On Walnut Breakage Device, Otabek A. Mirzaev, Xolhuzha A. Sobirov, Nusratillo R. Barakaev

Scientific Bulletin. Physical and Mathematical Research

Today, there are many types of fruits that are separated the kernel from the shell: walnuts, almonds, filberts, chestnuts, pistachios and cashews. Nuts have a high calorific value and a rich nutrient composition. The most critical and delicate operation is shell cracking to extract the fragile whole kernel from the shell. Studies on nut rupturing are particularly focused on the following three aspects: the physical characteristics of nuts, the mechanical properties of nut rupturing, and nut rupturing equipment. Determining the velocity of the nut entered into the apparatus will allow the machine to operate normally, but will also increase its ...


Application Of Optoelectron Converters Of Reflective Type For Automation Of Liquid And Gas Version Test Measuring Units, Yuriy G. Shipulin, Otabek T. Almataev Dec 2019

Application Of Optoelectron Converters Of Reflective Type For Automation Of Liquid And Gas Version Test Measuring Units, Yuriy G. Shipulin, Otabek T. Almataev

Scientific Bulletin. Physical and Mathematical Research

This work is devoted to the use of reflective optoelectronic converters for the automation of liquid and gas calibration flowmeter installations. Liquid and gas calibration flowmeter devices are widely used for verification and certification of various liquid and gas flowmeters and meters. The analysis of the principles of construction of a reflective optoelectronic converter for calibration devices is carried out and the basic principles of their construction are determined. A functional diagram of an experimental automated programmable calibration test setup of flow meters, liquid meters developed on the basis of ROC is presented. High accuracy requirements are imposed on the ...


Spectral Characteristics Of The Absorption Coefficient And Energy Position Of Defects, Sirojiddin Z. Zaynobidinov, Rustamjon G. Ikramov, Mashhurahon A. Nuriddinova, Khurshid A. Muminov Dec 2019

Spectral Characteristics Of The Absorption Coefficient And Energy Position Of Defects, Sirojiddin Z. Zaynobidinov, Rustamjon G. Ikramov, Mashhurahon A. Nuriddinova, Khurshid A. Muminov

Scientific Bulletin. Physical and Mathematical Research

In this paper, a theoretical method to study the spectral characteristics of the absorption coefficient, namely the area of ​​defective absorption of amorphous hydrogenated silicon according to the Davis-Mott approximation from the Kubo-Greenwood formula. It is shown that using the experimental spectral characteristic of the defect absorption coefficient, one can determine the energy position of defects in the mobility gap. Optical transitions of electrons, in which electronic states participate in defects, indicate that there are three types of optical transitions of electrons: between defects, between defects and tails of allowed zones, and also between defects and allowed zones. It was ...


Features Of The Physical Properties Of The Modified Surface Of The P-Cdte – Znse Film Heterostructure With Deep Impurity Levels, Yuozas Y. Vaytkus, Nodir E. Alimov, Salim M. Otajonov Dec 2019

Features Of The Physical Properties Of The Modified Surface Of The P-Cdte – Znse Film Heterostructure With Deep Impurity Levels, Yuozas Y. Vaytkus, Nodir E. Alimov, Salim M. Otajonov

Scientific Bulletin. Physical and Mathematical Research

This article analyzes the spectrum of the photocurrent in a layered film heterostructure CdTe-ZnSe with deep primesnymi levels. The experimental results demonstrated that the heterostructure CdTe-ZnSe observed a new effect in the measurement of the photoconductivity spectra, depending on the direction of the applied electric field, and the applied field stimulates the emergence of photo-emf. The spectrum of the photocurrent in a layered CdTe- ZnSe heterostructure film with deep impurity levels are considered in the article. It follows from the experimental results that a new effect is observed in the CdTe-ZnSe heterostructure when measuring the photoconductivity spectra depending on the ...


Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov Dec 2019

Definition Of Extended Structural Defects In Epitaxial Films Of Znteg‘Gaas Grown By Mbe, Muratbay B. Sharibaev, Kanatbay A. Ismailov, Ibrohim N. Karimov, Murodjon Z. Nosirov

Scientific Bulletin. Physical and Mathematical Research

The last three decades of the development of solid state physics are characterized by the fact that the main objects of research are increasingly not massive crystals, but thin films, multilayer thin-film systems, conducting filaments and crystallites of small size. Epitaxial films are grown on a substrate of a single crystal of the same or another material. In the first case, the epitaxial layer with the correct technology becomes a natural extension of the substrate. Epitaxial film can be doped with various impurities. To introduce an alloying admixture into the epitaxial film, three methods are used. According to the first ...


Structure And Electro Physical Properties Of Solid Solution (Si2)1-X(Cds)X (0 £ X £ 0.01), Xurshidjon M. Madaminov Dec 2019

Structure And Electro Physical Properties Of Solid Solution (Si2)1-X(Cds)X (0 £ X £ 0.01), Xurshidjon M. Madaminov

Scientific Bulletin. Physical and Mathematical Research

This paper shows the possibility of obtaining a single-crystal solid solution for the substitution of p-Si-n-(Si2)1-x (CdS)x (0 £ x £ 0.01) on silicon substrates with a diameter of 20 mm and thickness » 400, with a crystallographic orientation (111) n-types of conductivity with a specific resistance of 1 Ω cm, by the method of liquid phase epitaxy from Sn – Si – CdS solution – melt in a hydrogen atmosphere purified by palladium. Perfect epitaxial layers with mirror surfaces and with the best parameters are grown under the following technological conditions: temperatures start crystallization –1150 ОС, speed of forced cooling is ...


Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni Dec 2019

Magnetic And Structural Transitions In Euag4as2 Studied Using 151eu Mössbauer Spectroscopy, D. H. Ryan, Sergey L. Bud’Ko, Chaowei Hu, N. Ni

Ames Laboratory Accepted Manuscripts

151Eu Mössbauer spectroscopy confirms that the europium in EuAg4As2 is fully divalent and that the spectrum at 5 K consists of a single, sharp magnetic pattern with a hyperfine field (Bhf) of 27.1(1) T and an isomer shift of −11.04(3) mm/s (relative to EuF3). The temperature dependence of the spectra shows that the ordering of the Eu moments proceeds via an incommensurate sine modulated structure starting at 15 K. The structure squares up below 9 K. A search for charge density or phonon softening signatures at the 120 K ...


Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel Dec 2019

Optimizing Measurement Strengths For Qubit Quasiprobabilities Behind Out-Of-Time-Ordered Correlators, Razieh Mohseninia, José Raúl González Alonso, Justin Dressel

Mathematics, Physics, and Computer Science Faculty Articles and Research

Out-of-time-ordered correlators (OTOCs) have been proposed as a tool to witness quantum information scrambling in many-body system dynamics. These correlators can be understood as averages over nonclassical multitime quasiprobability distributions (QPDs). These QPDs have more information and their nonclassical features witness quantum information scrambling in a more nuanced way. However, their high dimensionality and nonclassicality make QPDs challenging to measure experimentally. We focus on the topical case of a many-qubit system and show how to obtain such a QPD in the laboratory using circuits with three and four sequential measurements. Averaging distinct values over the same measured distribution reveals either ...


First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma Dec 2019

First-Principles Study Of High-Pressure Phase Stability And Superconductivity Of Bi4i4, Shiyu Deng, Xianqi Song, Quan Li, Yu Xie, Changfeng Chen, Yanming Ma

Physics & Astronomy Faculty Publications

Bismuth iodide Bi4I4 exhibits intricate crystal structures and topological insulating states that are highly susceptible to influence by environments, making its physical properties highly tunable by external conditions. In this work, we study the evolution of structural and electronic properties of Bi4I4 at high pressure using an advanced structure search method in conjunction with first-principles calculations. Our results indicate that the most stable ambient-pressure monoclinic α−Bi4I4 phase in C2/m symmetry transforms to a trigonal P31c structure (ɛ−Bi4I4) at 8.4 GPa, then to a tetragonal P4/mmm structure (ζ−Bi4I4) above 16.6 GPa. In contrast to ...


Protein And Polysaccharide-Based Magnetic Composite Materials For Medical Applications., Elizabeth J Bealer, Kyril Kavetsky, Sierra Dutko, Samuel Lofland, Xiao Hu Dec 2019

Protein And Polysaccharide-Based Magnetic Composite Materials For Medical Applications., Elizabeth J Bealer, Kyril Kavetsky, Sierra Dutko, Samuel Lofland, Xiao Hu

Faculty Scholarship for the College of Science & Mathematics

The combination of protein and polysaccharides with magnetic materials has been implemented in biomedical applications for decades. Proteins such as silk, collagen, and elastin and polysaccharides such as chitosan, cellulose, and alginate have been heavily used in composite biomaterials. The wide diversity in the structure of the materials including their primary monomer/amino acid sequences allow for tunable properties. Various types of these composites are highly regarded due to their biocompatible, thermal, and mechanical properties while retaining their biological characteristics. This review provides information on protein and polysaccharide materials combined with magnetic elements in the biomedical space showcasing the materials ...


An Analysis Of The Atmospheric Propagation Of Underground-Explosion-Generated Infrasonic Waves Based On The Equations Of Fluid Dynamics: Ground Recordings, Roberto Sabatini, Jonathan B. Snively, Michael P. Hickey, J. L. Garrison Dec 2019

An Analysis Of The Atmospheric Propagation Of Underground-Explosion-Generated Infrasonic Waves Based On The Equations Of Fluid Dynamics: Ground Recordings, Roberto Sabatini, Jonathan B. Snively, Michael P. Hickey, J. L. Garrison

Publications

An investigation on the propagation of underground-explosion-generated infrasonic waves is carried out via numerical simulations of the equations of fluid dynamics. More specifically, the continuity, momentum, and energy conservation equations are solved along with the Herzfeld-Rice equations in order to take into account the effects of vibrational relaxation phenomena. The radiation of acoustic energy by the ground motion caused by underground explosions is initiated by enforcing the equality, at ground level, between the component of the air velocity normal to the Earth's surface and the normal velocity of the ground layer. The velocity of the ground layer is defined ...


The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky Dec 2019

The First-Order Magnetoelastic Transition In Eu2in: A 151eu Mössbauer Study, D. H. Ryan, Durga Paudyal, Francois Guillou, Yaroslav Mudryk, Arjun K. Pathak, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

Our 151Eu Mössbauer investigation of Eu2In and Eu2Sn shows that the europium in both materials is fully divalent. We confirm the distinct thermodynamic orders of the magnetic transitions and reveal a remarkable difference between the magnetic environments of the europium atoms in the two compounds. Possible structural and electronic origins for these differences are discussed using DFT calculations.


Constraints On Parton Distribution Functions Imposed By Hadronic Experiments, Boting Wang Dec 2019

Constraints On Parton Distribution Functions Imposed By Hadronic Experiments, Boting Wang

Physics Theses and Dissertations

The theoretical uncertainties of the Large Hadron Collider (LHC) observables are decreasing with the increasing statistics of the LHC experiments, and it is becoming more and more important to reduce the uncertainties in the knowledge of the nucleon structure. The latest LHC high-energy experiments, future experimental proposals, and computational tools are expected to enhance the knowledge of the nucleon structure. However, the global analysis that assesses their impact on Parton Distribution Functions (PDFs) knowledge is computationally expensive due to the corresponding large size of data. I developed a new approach that can make a quick preliminary evaluation to help the ...


Detection Of Whale Acoustic Signals In The Northern Gulf Of Mexico Ladc-Gemm Database, Yingxue Gao Dec 2019

Detection Of Whale Acoustic Signals In The Northern Gulf Of Mexico Ladc-Gemm Database, Yingxue Gao

University of New Orleans Theses and Dissertations

Low-pass Fourier filter, wavelet filter, as well as matched filter detection methods were used to detect baleen whale signals in northern Gulf of Mexico data collected by the Littoral Acoustic Demonstration Center (LADC) consortium. Some potential low frequency signals appeared on the matched filter output figure. The shape of the signals is in line with one of the typical signal shapes of fin whales--vertical down-sweeps with 18s-time interval. Another shape of the signals is in line with one of the call type shapes of Bryde's whales--down-sweeps with 7s-time interval. A high-pass Fourier filter was also used to find toothed ...


Vertical Acoustic Propagation In The Non-Homogeneous Layered Atmosphere For A Time-Harmonic, Compact Source, Edward J. Yoerger Jr Dec 2019

Vertical Acoustic Propagation In The Non-Homogeneous Layered Atmosphere For A Time-Harmonic, Compact Source, Edward J. Yoerger Jr

University of New Orleans Theses and Dissertations

In this work we study vertical, acoustic propagation in a non-homogeneous media for a spatially-compact, time-harmonic source. An analytical, 2-layer model is developed representing the acoustic pressure disturbance propagating in the atmosphere. The validity of the model spans the distance from the Earth's surface to 30,000 meters. This includes the troposphere (adiabatic), ozone layer (isothermal), and part of the stratosphere (isothermal). The results of the model derivation in the adiabatic region yield pressure solutions as Bessel functions of the First (J) and Second (Y) Kind of order $-\frac{7}{2}$ with an argument of $2 \Omega \tau$ (where ...


Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig Dec 2019

Magnetic Structure Of Nd In Ndfeaso Studied By X-Ray Resonant Magnetic Scattering, M. G. Kim, J.-W. Kim, J.-Q. Yan, Alan I. Goldman, Andreas Kreyssig

Ames Laboratory Accepted Manuscripts

The magnetic structure of Nd in NdFeAsO compound has been investigated by x-ray resonant magnetic scattering at the Nd L2 edge (E=6.725 keV) at 1.7≤T≤15 K. At T=1.7 K we find that the Nd moments are aligned along the crystallographic c direction with the (1, 0, 0) propagation vector, and are arranged antiferromagnetically along the a direction and ferromagnetically along the b and c directions. At 1.7


Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan Dec 2019

Exploratory Measurements Of Large Winds And Shears In The Lower Thermosphere And Their Variability Using An Enhanced Sodium Lidar, Tao Yuan

Funded Research Records

No abstract provided.


Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann Dec 2019

Is Contact Nucleation Caused By Pressure Perturbation?, Fan Yang, Will Cantrell, Alexander Kostinski, Raymond Shaw, Andrew M. Vogelmann

Michigan Tech Publications

The reason why ice nucleation is more efficient by contact nucleation than by immersion nucleation has been elusive for over half a century. Six proposed mechanisms are summarized in this study. Among them, the pressure perturbation hypothesis, which arose from recent experiments, can qualitatively explain nearly all existing results relevant to contact nucleation. To explore the plausibility of this hypothesis in a more quantitative fashion and to guide future investigations, this study assessed the magnitude of pressure perturbation needed to cause contact nucleation and the associated spatial scales. The pressure perturbations needed were estimated using measured contact nucleation efficiencies for ...


Development Of A Low-Cost, Open Source Miniature Rotary Cell Culture System To Simulate Microgravity Within An Irradiated Environment, Elizabeth Vargis, Jr Dennison Dec 2019

Development Of A Low-Cost, Open Source Miniature Rotary Cell Culture System To Simulate Microgravity Within An Irradiated Environment, Elizabeth Vargis, Jr Dennison

Browse all Datasets

A major challenge for astronauts in long-duration space travel is combatting the hazardous spaceflight environment caused by microgravity and increased levels of ionizing radiation. Microgravity damages cellular DNA by increasing the production of harmful reactive oxygen species, while ionizing radiation damages DNA by creating double-stranded DNA (dsDNA) breaks. Cellular damage due to microgravity and radiation has been investigated using ground-based models, but most models consider microgravity and ionizing radiation alone, or asynchronously. Synchronous modeling better mimics spaceflight conditions and can be used to understand the combined effects of microgravity and ionizing radiation. However, commercially available devices to model microgravity and ...


Effects Of Impurities On Calcium Oxalate Crystallization As Measured By Atomic Force Microscopy, Himasha Wijesekara Dec 2019

Effects Of Impurities On Calcium Oxalate Crystallization As Measured By Atomic Force Microscopy, Himasha Wijesekara

Electronic Thesis and Dissertation Repository

Calcium oxalate crystals are found in kidney stones as either calcium oxalate monohydrate (COM) or calcium oxalate dihydrate (COD). COM crystals are the most abundant form as they are thermodynamically more stable than COD crystals under physiological conditions. Certain aspartic acid-rich molecules such as osteopontin (OPN) are known to affect stone formation by inhibiting COM and COD growth. We have studied COM {010} and COD {100} faces in the presence of OPN, poly-aspartic acid (poly-ASP) and synthetic peptides derived from OPN to investigate the inhibitor mechanism.

We observed that poly-ASP preferentially inhibits one particular direction of {010} faces on COM ...


Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield Dec 2019

Magnetoelastoresistance In Wte2: Exploring Electronic Structure And Extremely Large Magnetoresistance Under Strain, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield

Physics and Astronomy Publications

Strain describes the deformation of a material as a result of applied stress. It has been widely employed to probe transport properties of materials, ranging from semiconductors to correlated materials. In order to understand, and eventually control, transport behavior under strain, it is important to quantify the effects of strain on the electronic bandstructure, carrier density, and mobility. Here, we demonstrate that much information can be obtained by exploring magnetoelastoresistance (MER), which refers to magnetic field-driven changes of the elastoresistance. We use this powerful approach to study the combined effect of strain and magnetic fields on the semimetallic transition metal ...


Investigation Of Isomer Ratios In The Reactions (Γ, N) And (N, 2N) On Nuclei 76Ge And 82Se, Satimbay Palvanov, Turgunali Akhmadzhanov Dec 2019

Investigation Of Isomer Ratios In The Reactions (Γ, N) And (N, 2N) On Nuclei 76Ge And 82Se, Satimbay Palvanov, Turgunali Akhmadzhanov

Bulletin of National University of Uzbekistan: Mathematics and Natural Sciences

The method of the induced activity measured the isomeric yield ratios and cross-sections ratios of reactions (γ, n) and (n, 2n) on nuclei 76Ge and 82Se. Samples of natural have been irradiated in the bremsstrahlung beam of the betatron SB-50 of National University of Uzbekistan in the energy range of 10-35 MeV with energy step of 1 MeV. For 14 MeV neutron irradiation, we used the NG-150 neutron generator of Institute of Nuclear Physics. The gamma spectra reactions products were measured with a spectroscopic system consisting of HPGe detector CANBERRA with energy resolution of 1.8 keV ...


Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He Dec 2019

Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He

Engineering and Applied Science Theses & Dissertations

Photoacoustic (PA) tomography (PAT) is a novel imaging modality that combines the fine lateral resolution from optical imaging and the deep penetration from ultrasonic imaging, and provides rich optical-absorption–based images. PAT has been widely used in extracting structural and functional information from both ex vivo tissue samples to in vivo animals and humans with different length scales by imaging various endogenous and exogenous contrasts at the ultraviolet to infrared spectrum. For example, hemoglobin in red blood cells is of particular interest in PAT since it is one of the dominant absorbers in tissue at the visible wavelength.The main ...


Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed Dec 2019

Pressure Driven Electronic Band Gap Engineering In Tin(Iv)-O,N Compounds, Daniel Thomas Sneed

UNLV Theses, Dissertations, Professional Papers, and Capstones

The intrinsic link between long-range order, coordination geometry, and the electronic properties of a system must be understood in order to tailor function-specific materials. Although material properties are typically tailored using chemical dopants, such methods can cause irreversible changes to the structure, limiting the range of functionality. The application of high pressure may provide an alternative “clean” method to tune the electronic properties of semiconducting materials by tailoring their defect density and structure.

We have explored a number of optoelectronic relevant materials with promising characteristics, specifically Sn-(O,N) compounds which have been predicted to undergo pressure-mediated opening of their ...


Cyclotron Resonance In Graphene Heterostructurescyclotron Resonance In Graphene Heterostructures, Billy Jordan Russell Dec 2019

Cyclotron Resonance In Graphene Heterostructurescyclotron Resonance In Graphene Heterostructures, Billy Jordan Russell

Arts & Sciences Electronic Theses and Dissertations

We present observations of cyclotron resonance in graphene Van der Waals heterostructure devices. Such devices provide dramatic improvements in sample quality and allow for ad- vanced electronic control, opening windows on previously inaccessible physics. The design and construction of a dedicated system for the measurement of electronic transport and infrared magnetospectroscopy in microscopic samples of atomically thin materials at cryogenic temperatures is presented. In high-mobility encapsulated monolayer graphene, electron- electron interaction effects are unambiguously observed to impact the interband cyclotron resonance as the Landau level filling factor is varied in a quantizing magnetic field. Additionally, a splitting of transitions involving ...


Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu Dec 2019

Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu

Engineering and Applied Science Theses & Dissertations

Aggregation of nanoparticles in aerosols is a fundamental phenomenon with important implications to diverse fields ranging from material synthesis to pollutant control. The past few decades have witnessed extensive research on investigating the structure and growth mechanism of aerosol aggregates with sizes spanning across several orders of magnitude. This dissertation focuses on some contemporary problems that remain unaddressed in this topical area. Aerosol aggregates in sub-micron regimes, which are formed via the irreversible collision and aggregation of solid nanoparticle monomers, are fractal-like in their morphology. A mathematical description of this seemingly random structure dates to the seminal works by Forest ...