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Raman Spectroscopy Of Inas/Gaas Quantum Dots Patterned By Nano-Indentation, Lindsay K. Hussey

USF Tampa Graduate Theses and Dissertations

Patterns of InAs/GaAs quantum dots (QDs) grown by the combination of nanoindentation technique and molecular beam epitaxy were studied. The resulting QDs tend to preferentially nucleate on indented areas rather than other regions. We studied the strain on the indentations, regions surrounding the indents, and non-indented areas. The QD LO mode for the patterned areas shifts by 7 cm-1 when compared to the non-patterned area. The biaxial strain in the indented areas producing this shift is four times larger than that in non-indented areas, explaining the QD preferential formation within these areas. This larger strain suggests that QDs on the …

A Cross-Cultural, Multilevel Study Of Inquiry-Based Instruction Effects On Conceptual Understanding And Motivation In Physics, Meiko Negishi

Theses and Dissertations

Student achievement and motivation to learn physics is highly valued in many industrialized countries including the United States and Japan. Science education curricula in these countries emphasize the importance and encourage classroom teachers to use an inquiry approach. This dissertation investigated high school students? motivational orientations and their understanding of physics concepts in a context of inquiry-based instruction. The goals were to explore the patterns of instructional effects on motivation and learning in each country and to examine cultural differences and similarities. Participants consisted of 108 students (55 females, 53 males) and 9 physics teachers in the United States and …

Determining The Agn Fraction Of Galaxy Groups, Rachel Paterno-Mahler

Pomona Senior Theses

Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction …

Fuzzy Blackholes, Anand Murugan

Pomona Senior Theses

The fuzzball model of a black hole is an attempt to resolve the many paradoxes and puzzles of black hole physics that have revealed themselves over the last century. These badly behaved solutions of general relativity have given physicists one of the few laboratories to test candidate quantum theories of gravity. Though little is known about exactly what lies beyond the event horizon, and what the ultimate fate of matter that falls in to a black hole is, we know a few intriguing and elegant semi-classical results that have kept physicists occupied. Among these are the known black hole entropy …

Coupling Down Converted Light Into Single Mode Fibers, David A. Niemi

Theses and Dissertations

We investigate the influence of the pump and collection mode parameters on the collection efficiency of Type I down converted photons into single mode fibers. For best single and coincidence counting rates, we find that the mode sizes should be close to the same size and that the mode waists should be located near the down-conversion crystal. Larger collection waists give higher collection efficiencies, but lower singles counts.

Generation And Measurement Of Surface Plasmon Coupled Emission, Kathleen E. Hamilton

Master's Theses and Capstones

Surface plasmon coupled emission (SPCE) is a process by which isotropic fluorescent emission, from a fluorescent dye or biological agent labeled with a fluorescent dye, is channeled into highly directional emission. This process relies on the interaction between fluorescent dye molecules and thin silver films in close proximity to each other. Recent studies have shown that SPCE greatly increases the sensitivity of spectroscopic methods by increasing the amount of light that can be collected from a fluorescent molecule. The work described in this thesis encompasses the study of new materials for SPCE sample manufacture as well as the design and …

Kaon Nucleon Scattering In Lattice Qcd, Anthony Charles Marcolongo

Master's Theses and Capstones

In this paper I discuss why one would want to study meson baryon interactions within the framework of lattice QCD, and what I have contributed to this area of research. I begin with a little background on QCD, and Chiral theories. I analyze Kaon Nucleon scattering, and calculate the Kaon Nucleon scattering length from data obtained using a lattice QCD simulation. Therefore, I show that it is possible to use Lattice QCD simulation to extract observables. This is important in areas where experiments are challenging or impossible with current technologies.

Self -Assembly On Strained Metallic Interfaces, And, Novel Collective Excitations On Metal Surfaces, Bogdan Diaconescu

Doctoral Dissertations

Recent interest in novel physical properties of reduced dimensional systems is spurred by the advance of investigation methods at the nanoscale. Understanding bottom-up techniques for the growth of nanomaterials with novel physical, chemical, and mechanical properties require specialized investigation tools.

I am presenting a novel design and performance of an ultra high vacuum scanning tunneling microscope (STM) that allows for large scale (8 mum x 8 mum), fast scanning (3 s for a 100 A x 100 A frame), and atomically resolved studies of reduced dimensional systems on metallic surfaces. The STM proved excellent performance, allowing for variable temperature (100 …

Inclusive Scattering Of Polarized Electrons From Polarized Protons In The Delta-Excitation Region With Blast, Octavian Florin Filoti

Doctoral Dissertations

Inclusive scattering of polarized electrons from polarized protons has been studied using the BLAST detector at MIT-Bates Linear Accelerator Center. The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study in a comprehensive and precise way the spin-dependent electromagnetic response in one and few-body systems over a large kinematic range. It has been used to measure spin-dependent scattering from the elastic to the nucleon resonance region for hydrogen and deuterium using a longitudinally polarized electron beam at a beam energy of 850 MeV stored in the MIT-Bates South Hall Ring, and polarized internal gas targets of hydrogen …

Solar Wind Entry Into The Magnetosphere Under Northward Imf Conditions, Wenhui Li

Doctoral Dissertations

The state of the plasma sheet in the magnetosphere is usually observed to be hot (1-10 keV) and tenuous (∼0.1 cm-3). However, sometimes part of it is observed to be colder (< 1 keV) and denser (∼1 cm-3), and the plasma flow is almost stagnant. Much higher density (∼10 cm-3) plasma material (superdense plasma sheet) is also sometimes observed near the geosynchronous orbit. The cold dense plasma sheet (CDPS) is usually observed after a period of northward interplanetary magnetic field (IMF), which is also a necessary condition for the formation of a superdense plasma sheet (SDPS). Since the CDPS is generally absent of a cold O+ component, and the ionospheric outflow is strong only under southward IMF condition, the source of the CDPS is thought to be the solar wind.

Usually, solar wind plasma and energy entry into the magnetosphere is considered to occur mainly during the southward IMF condition through reconnection processes that first occur at the dayside magnetopause and then in the magnetotail. However, the formation of CDPS suggests that there are also certain processes that let solar wind enter the magnetosphere when the IMF is northward. The purpose of this dissertation study is to find …

Structural And Functional Pulmonary Imaging Using Hyperpolzarized Xenon-129, Iga Muradyan

Doctoral Dissertations

We describe applications of hyperpolarized 129 Xe to pulmonary imaging. Unique characteristics of this gas such as its polarizability and diffusibility in tissue allow probing important properties of the lungs. Three methods that study structure and function of the lungs, Chemical Shift Saturation Recovery (CSSR), Xenon polarization Transfer Contrast (XTC) and Dixon, and their application to human studies for the first time are the focus of this work.

CSSR measures the global fractional gas transport, F(t) in the lungs. Using this method the dynamics of gas exchange were studied. A model describing this process was derived and used to interpret …

Measurement Of Parity Violation In Thermal Neutron Capture On A Proton, Mikayel Dabaghyan

Doctoral Dissertations

The NPDGamma experiment is measuring the directional parity violating asymmetry in the emission of gamma rays from the capture of cold neutrons on protons. The asymmetry can be related in a straightforward way to effective couplings within an appropriate NN weak interaction theory, such as chiral perturbation based effective field theories.

Since this is a measurement within a two body system, the observables are calculable without uncertainties from few to many body (large nuclei) effects. The experiment consists of two phases. The first one, at the Los Alamos Neutron Science Center (LANSCE), has just been completed, providing a measurement of …

Ring Current -Atmosphere Interactions Model With Stormtime Magnetic Field, Alexander Emilov Vapirev

Doctoral Dissertations

An improved version of the ring current-atmosphere interactions kinetic model (RAM) is presented in this thesis. The recent stormtime empirical model T04s and the IGRF model are used to represent the Earth's external and internal magnetic fields respectively. Particle drifts, losses due to charge exchange with geocoronal hydrogen and atmospheric losses are included in the model as they are considered the main mechanisms of ring current development and its following decay. A numerical technique for bounce-averaging along the field lines is introduced and results for the calculated bounce-averaged hydrogen densities and magnetic gradient-curvature drift velocities (general case) for the moderate …

A Descriptive Framework For The Problem-Solving Experiences Of Physics Students, Sherry Savrda

Electronic Theses and Dissertations

This study investigated the applicability of a general model of physics students' problem-solving experiences that suggests there are four dynamic factors affecting the problem-solving process: categorization, goal interpretation, resource relevance, and complexity. Furthermore, it suggests an overarching control factor called stabilization, which describes the inter-relatedness of the other factors over the problem-solving process. Think-aloud protocols of problem-solving experiences were used to investigate the model. Results of the study showed that conceptual resources had a significant impact on the success of problem-solving attempts. Participants who exhibited a lack of understanding of physics concepts were less likely to check their work, use …

Improving High School Physical Science Students' Understanding Of The Electromagnetic Spectrum: A Modified Diagram Approach, James Edward Quebedeaux

LSU Doctoral Dissertations

The focus of this study was to identify major conceptual difficulties that selected public high school physical science students encounter in understanding a standard electromagnetic spectrum diagram. A research-driven, modified version of that standard diagram was used in this study to determine the value added to student understanding of electromagnetic waves. A content analysis was performed on electromagnetic spectrum diagrams found in US textbooks from the 1950s through the present. A class of public high school physical science students participated in a study consisting of four activities conducted during a three-week unit. Students were given a pre- and post-achievement test …

Using Power Spectra To Look For Anisotropies In Ultra-High Energy Cosmic Ray Distributions, Megan Alicia Mcewen

LSU Doctoral Dissertations

The origins and compositions of ultra-high energy cosmic rays (UHECR) remains a mystery to this day. The Pierre Auger Observatory (PAO) is being constructed now in the hopes that it will help solve this mystery by detecting more UHECR than any previous experiment. In this dissertation, I will discuss this experiment, and analyze the data collected so far by comparing it with simulated data from possible source distributions. In these simulations, I will track antiprotons, along with other possible cosmic ray primaries, through various models of galactic and extragalactic magnetic fields. Once they reach a certain distance, I will record …