Physics Commons^™

Synthesis And Analysis Of Carbon-Transition Metal Oxide Composites, Binod Manandhar

Theses and Dissertations

Graphene, a two-dimensional honeycomb structure of carbon due to its high electrical and thermal conductivity, and high specific surface area, is an excellent candidate for nano-electronics and energy storage. However, it is very difficult and expensive to produce a single layered graphene by the traditional method of mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). It is mainly manufactured by chemical vapor deposition (CVD) or more economically by chemical exfoliation of graphite by Hummer’s modified method. But there is a major disadvantage in using the chemical exfoliation, instead of forming single layer of pure graphene, a non-stoichiometric and insulating graphene …

Reconstruction Of 3d Image For Particles By The Method Of Angular Correlations From Xfel Data, Sung Soon Kim

Theses and Dissertations

The world’s first X-ray Free Electron Laser (XFEL), the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC), is now generating X-ray pulses of unprecedented brilliance (one billion times brighter than the most powerful existing sources), and at the amazing rate of only a few femtoseconds. The first such experiments are being performed on relatively large objects such as viruses, which produce low resolution, low-noise diffraction patterns on the basis of the so called “diffraction before destruction” principle. Despite the promise of using XFEL for the determination of the structures of viruses, the results so far from …

Experimental Methods In Cryogenic Spectroscopy: Stark Effect Measurements In Substituted Myoglobin, Bradley Michael Moran

Theses and Dissertations

Dawning from well-defined tertiary structure, the active regions of enzymatic proteins exist as specifically tailored electrostatic microenvironments capable of facilitating chemical interaction. The specific influence these charge distributions have on ligand binding dynamics, and their impact on specificity, reactivity, and biological functionality, have yet to be fully understood. A quantitative determination of these intrinsic fields would offer insight towards the mechanistic aspects of protein functionality. This work seeks to investigate the internal molecular electric fields that are present at the oxygen binding site of myoglobin.

Experiments are performed at 1 K on samples located within a glassy matrix, using the …

Quantitative Optical Studies Of Oxidative Stress In Rodent Models Of Eye And Lung Injuries, Zahra Ghanian

Theses and Dissertations

Optical imaging techniques have emerged as essential tools for reliable assessment of organ structure, biochemistry, and metabolic function. The recognition of metabolic markers for disease diagnosis has rekindled significant interest in the development of optical methods to measure the metabolism of the organ.

The objective of my research was to employ optical imaging tools and to implement signal and image processing techniques capable of quantifying cellular metabolism for the diagnosis of diseases in human organs such as eyes and lungs. To accomplish this goal, three different tools, cryoimager, fluorescent microscope, and optical coherence tomography system were utilized to study the …

Symmetry And Reconstruction Of Particle Structure From Random Angle Diffraction Patterns, Sandi Wibowo

Theses and Dissertations

The problem of determining the structure of a biomolecule, when all the evidence from experiment consists of individual diffraction patterns from random particle orientations, is the central theoretical problem with an XFEL. One of the methods proposed is a calculation over all measured diffraction patterns of the average angular correlations between pairs of points on the diffraction patterns. It is possible to construct from these a matrix B characterized by angular momentum quantum number l, and whose elements are characterized by radii q and q’ of the resolution shells. If matrix B is considered as dot product of vectors, which …

Spatial Inhomogeneous Barrier Heights At Graphene/Semiconductor Schottky Junctions, Dushyant Tomer

Theses and Dissertations

Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors.

To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point …

Phase Sensitive Thermography Of Magnetostrictive Materials Under Periodic Excitations, Peng Yang

Theses and Dissertations

The use of giant magnetostrictive materials in actuator and sensor applications is still relatively new. Giant magnetostrictive materials, such as Terfenol-D, are unique in producing large deformation under a magnetic field. Applications of these materials in solid state actuators and transducers may require more knowledge on the interaction between geometry and material properties for a specific design. In order to gain more understanding of the magnetostriction mechanism, phase sensitive or lock-in thermography has been used to study Terfenol-D. Thermography is useful in that it allows for full field measurement of the surface of an object with a relatively simple setup. …

Variable Pathlength Cavity Spectroscopy Development Of An Automated Prototype, Ryan Schmeling

Theses and Dissertations

ABSTRACT

VARIABLE PATHLENGTH CAVITY SPECTROSCOPY

DEVELOPMENT OF AN AUTOMATED PROTOTYPE

by

Ryan Andrew Schmeling

The University of Wisconsin-Milwaukee, 2016

Under the Supervision of Professor Joseph H. Aldstadt III

Spectroscopy is the study of the interaction of electromagnetic radiation (EMR) with matter to probe the chemical and physical properties of atoms and molecules. The primary types of analytical spectroscopy are absorption, emission, and scattering methods. Absorption spectroscopy can quantitatively determine the chemical concentration of a given species in a sample by the relationship described by Beer’s Law. Upon inspection of Beer’s Law, it becomes apparent that for a given analyte concentration, …

Monsters In The Dark: High Energy Signatures Of Black Hole Formation With Multimessenger Astronomy, Alexander L. Urban

Theses and Dissertations

When two compact objects inspiral and violently merge it is a rare cosmic event, producing fantastically “luminous” gravitational wave emission. It is also fleeting, staying in the Laser Interferometer Gravitational-wave Observatory’s (LIGO) sensitive band only for somewhere between tenths of a second and several tens of minutes. However, when there is at least one neutron star, disk formation during the merger may power a slew of potentially detectable electromagnetic counterparts, such as short gamma-ray bursts (GRBs), afterglows, and kilonovae. These explosions span the full electromagnetic spectrum and are expected within seconds, hours or days of the merger event. To learn …

Intersections Of Astrophysics, Cosmology And Particle Physics, Luiz Henrique Moraes Da Silva

Theses and Dissertations

With the success of the Large Hadron Collider (LHC) at CERN, a new era of discovery has just begun. The SU(3)C x SU(2)L x U(1)Y Standard Model (SM) of electroweak and strong interactions has once again endured intensive scrutiny. Most spectacularly, the recent discovery of a particle which seems to be the SM Higgs has possibly plugged the final remaining experimental hole in the SM, cementing the theory further. Adding more to the story, the IceCube Collaboration recently reported the discovery of extraterrestrial neutrinos, heralding a new era in astroparticle physics. The collaboration was able to isolate 36 events in …

Nanostructured Organic/Inorganic Semicondutor Photovoltaics: Investigation On Morphology And Optoelectronics Performance, Aruna Wanninayake

Theses and Dissertations

Organic solar cell is a promising technology because of the versatility of organic materials in terms of tunability of their electrical and optical properties. In addition, their relative insensitivity to film imperfections potentially allows for very low-cost high-throughput roll-to-roll processing. However, the power conversion efficiency of organic solar cell is still limited and needs to be improved in order to be competitive with grid parity. This work is focused on the design and characterization of a new organic/inorganic hybrid device to enhance the efficiency factors of bilayer organic solar cells such as: light absorption, exciton diffusion, exciton dissociation, charge transportation …