Physical Sciences and Mathematics Commons^™

Optical Characterization Of Magnetism In Magnetic/Nonmagnetic Heterostructures, Yichun Fan

Dissertations, Theses, and Masters Projects

This thesis focuses on the study of the static and dynamic magnetic interactions in ferromagnetic/nonmagnetic heterostructures using interface-specific and time-resolved optical techniques. The goal of this thesis is to elucidate the interface exchange coupling, magnetic anisotropy, and coherent spin dynamics in these advanced material systems, crucial to the realization of high performance spintronic devices.;First, a pronounced exchange bias (EB) phenomenon is observed in Fe/MgO (001) by magnetic second harmonic generation. The bulk magnetization does not, in marked contrast to typical systems where EB is manifested only in the net magnetization. The magnitude of the exchange bias varies with interface oxygen …

Post-Release Mortality Of School-Size Atlantic Bluefin Tuna (Thunnus Thynnus) In The U.S Recreational Troll Fishery, Benjamin Jon Marcek

Dissertations, Theses, and Masters Projects

Atlantic bluefin tuna Thunnus thynnus (ABFT) support commercial and recreational fisheries throughout the North Atlantic Ocean. Due to heavy fishing pressure over the course of several decades, the eastern and western stocks of ABFT were overfished and the current biomass of the western stock is estimated to be approximately 19% of the biomass necessary for maximum sustainable yield. Despite a variety of management measures, including the implementation of minimum sizes and reductions of the total allowable catch (TAC) and country-specific quotas, little change was observed in the status of the western stock. The U.S. commercial and recreational ABFT fisheries are …

Intelligent Feature Selection Techniques For Pattern Classification Of Time-Domain Signals, Corey Alexander Miller

Dissertations, Theses, and Masters Projects

Time-domain signals form the basis of analysis for a variety of applications, including those involving variable conditions or physical changes that result in degraded signal quality. Typical approaches to signal analysis fail under these conditions, as these types of changes often lie outside the scope of the domain's basic analytic theory and are too complex for modeling. Sophisticated signal processing techniques are required as a result. In this work, we develop a robust signal analysis technique that is suitable for a wide variety of time-domain signal analysis applications. Statistical pattern classification routines are applied to problems of interest involving a …

Applications Of Holographic Dualities, Dylan Judd Albrecht

Dissertations, Theses, and Masters Projects

We introduce and review some of the building blocks to what is known as the AdS/CFT correspondence. We then present, using the framework of the correspondence, two applications: one to QCD (Chapters 2 and 3) and one to superconductivity (Chapter 4). The work presented in these chapters was carried out by the author and collaborators during the author's graduate studies.

Low Energy Tests Of The Standard Model, Benjamin Carl Rislow

Dissertations, Theses, and Masters Projects

The Standard Model describes a wide range of fundamental interactions. Searches are ongoing for experimental results that differ from the Standard Model predictions. Such disagreements would both indicate that the Standard Model is incomplete and constrain the properties of New Physics scenarios. to probe the Standard Model over a wide kinematic range, low energy tests are necessary to complement experiments in the high energy regime. We perform calculations for experiments that are representative of two general types of low energy tests. The Qweak experiment at Jefferson Lab is a low energy measurement of the weak charge of the proton. Since …

Submarine Groundwater Discharge To The York River Estuary: Quantifying Groundwater Flux And Potential For Biogeochemical Cycling, Jenna Lynn Luek

Dissertations, Theses, and Masters Projects

No abstract provided.

Surface Modifications For Gas Chromatography Micro Columns, Daniel Andre Hirtenstein

Dissertations, Theses, and Masters Projects

No abstract provided.

Phytoplankton Growth Rates In The Ross Sea, Antarctica, Anna Ford Mosby

Dissertations, Theses, and Masters Projects

The Ross Sea is a highly productive region of the Southern Ocean characterized by spatially variable distribution of phytoplankton, primarily Phaeocystis antarctica, but phytoplankton growth rates in the region have not been thoroughly investigated. Variability in growth rates was investigated from January to February 2012 on a cruise to the Ross Sea using two methods: 14C-isotopic tracer incubations and dilution experiments. Because all methods of measuring growth rates may not be appropriate in all systems due to errors inherent to each method, I assessed and compared the two methods for possible sources of error by examining the effect of extended …

Effects Of Episodic Turbulence On Diatoms: With Comments On The Use Of Evans Blue Stain For Live-Dead Determinations, Haley S. Garrison

Dissertations, Theses, and Masters Projects

Episodic turbulence is a short-lived, high-intensity phenomenon in marine environments produced by both anthropogenic and natural causes, such as boat propellers, strong winds, and breaking waves. Episodic turbulence has been shown to cause mortality in zooplankton, but its effects on marine phytoplankton have rarely been investigated. This study focused on two diatoms: Thalassiosira weissflogii and Skeletonema costatum. I found that exposure for 45 s to turbulence intensities above 2.5 cm2 s-3 caused 24-32% reduction in diatom abundance and increased the amount of intact dead cells to 22%. Turbulence also caused extracellular release of optically reactive DOM. At a turbulence level …

Advanced Topographic Characterization Of Variously Prepared Niobium Surfaces And Linkage To Rf Losses, Chen Xu

Dissertations, Theses, and Masters Projects

Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. The shallow penetration (∼ 40 nm) of the RF into superconducting niobium lends great importance to SRF cavity interior surface chemistry and topography. These in turn are strongly influenced by the chemical etching "surface clean-up" that follows fabrication.;The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions …

Seasonal Nitrogen Uptake And Regeneration In The Water Column And Sea-Ice Of The Western Coastal Arctic, Steven E. Baer

Dissertations, Theses, and Masters Projects

The logistical difficulties of research in extremely low temperatures and lack of access to the Arctic have meant that there is a historic dearth of knowledge of coastal Arctic biogeochemistry, especially during winter when sea ice is present. Recent observations, however, indicate that the Arctic is changing rapidly. Changes include increased temperatures, decreased extent and volume of sea ice, and increased freshwater inputs. How these changes influence biogeochemical cycles is an open question, especially in the highly productive coastal regions of the Chukchi Sea. Here I present nitrogen (N) uptake and regeneration rates for phytoplankton and bacteria measured in the …

Experimental Generation And Manipulation Of Quantum Squeezed Vacuum Via Polarization Self-Rotation In Rb Vapor, Travis Scott Horrom

Dissertations, Theses, and Masters Projects

Nonclassical states of light are of increasing interest due to their applications in the emerging field of quantum information processing and communication. Squeezed light is such a state of the electromagnetic field in which the quantum noise properties are altered compared with those of coherent light. Squeezed light and squeezed vacuum states are potentially useful for quantum information protocols as well as optical measurements, where sensitivities can be limited by quantum noise. We experimentally study a source of squeezed vacuum resulting from the interaction of near-resonant light with both cold and hot Rb atoms via the nonlinear polarization self-rotation effect …

Improving Energy Efficiency And Security For Pervasive Computing Systems, Fengyuan Xu

Dissertations, Theses, and Masters Projects

Pervasive computing systems are comprised of various personal mobile devices connected by the wireless networks. Pervasive computing systems have gained soaring popularity because of the rapid proliferation of the personal mobile devices. The number of personal mobile devices increased steeply over years and will surpass world population by 2016.;However, the fast development of pervasive computing systems is facing two critical issues, energy efficiency and security assurance. Power consumption of personal mobile devices keeps increasing while the battery capacity has been hardly improved over years. at the same time, a lot of private information is stored on and transmitted from personal …

Methylmercury Exposure Affects Risk-Taking Behaviors In Zebra Finches: Tradeoffs Between Eating And Being Eaten, Megan Elizabeth Kobiela

Dissertations, Theses, and Masters Projects

No abstract provided.

Total Synthesis Of (+)-Malbrancheamide B Utilizing A Stereoselective Domino Reaction Sequence To Establish The Bicyclo[2.2]Diazaoctane Core, Stephen William Laws

Dissertations, Theses, and Masters Projects

No abstract provided.

Acoustic And Sedimentological Investigations Of Seabed Conditions And Related Bio-Geological Parameters In A Tidally Energetic, Fine-Grained Environment: York River Estuary, Virginia, Lindsey M. Kraatz

Dissertations, Theses, and Masters Projects

The transport and fate of fine-grained sediments is a critical factor affecting the physical, chemical, and biological health of estuaries, coastal embayments, riverine, lacustrine, and continental shelf environments. A geophysical and sedimentological study of the York River as a part of the NSF Multi-disciplinary Benthic Exchange Dynamics (MUDBED) project was conducted to determine: 1) the primary drivers of sediment erodibility within a fine-grained system, 2) if these drivers can be accurately measured through sedimentological and acoustic information, and 3) the spatial and seasonal variability of erosion within the estuary. Previous studies indicate that increased erodibility within the York River Estuary …

Multi-Meson Systems From Lattice Quantum Chromodynamics, Zhifeng Shi

Dissertations, Theses, and Masters Projects

Systems of non-zero isospin chemical potential ( muI), where the chemical potential for up and down quarks is equal in magnitude but of opposite sign, do not suffer from the sign problem, and normal LQCD techniques can be successfully adapted to study such systems. From chiral perturbation theory (chiPT), in addition to the deconfined phase transition at high temperature at zero chemical potential, another phase transition from ordinary hadronic states to a Bose Einstein Condensate (BEC) state has been conjectured [1] at non-zero isospin chemical potential. Such a BEC phase is of phenomenological relevance in the interior of neutron stars.;In …

Improving Security And Privacy In Online Social Networks, Wei Wei

Dissertations, Theses, and Masters Projects

Online social networks (OSNs) have gained soaring popularity and are among the most popular sites on the Web. With OSNs, users around the world establish and strengthen connections by sharing thoughts, activities, photos, locations, and other personal information. However, the immense popularity of OSNs also raises significant security and privacy concerns. Storing millions of users' private information and their social connections, OSNs are susceptible to becoming the target of various attacks. In addition, user privacy will be compromised if the private data collected by OSNs are abused, inadvertently leaked, or under the control of adversaries. as a result, the tension …

Electroless Gold Deposition With Self-Assembled Monolayers For Gas Chromatography Stationary Phases, Jessica Lynn Belton

Dissertations, Theses, and Masters Projects

No abstract provided.

Synthesis And Fluorescence Studies Of Ph-Responsive Rhodamine B Derivatives, William Lawrence Czaplyski

Dissertations, Theses, and Masters Projects

No abstract provided.

Tracelab: Reproducing Empirical Software Engineering Research, Evan Alexander Moritz

Dissertations, Theses, and Masters Projects

No abstract provided.

Food Availability And Utilization For Cultured Hard Clams, Richard Garrik Secrist

Dissertations, Theses, and Masters Projects

Aquaculture of the hard clam Mercenaria mercenaria is a valuable industry on the east coast. At high planting densities, cultured bivalves can become limited by food availability, resulting in reduced growth. Centric diatoms are considered the dominant food source to cultured bivalves. Alternative sources may also be important, including resuspended benthic microalgae (pennate diatoms) and detritus from macroalgae growing on predator exclusion nets. This study measured (1) the availability of different food sources in clam beds at Cherrystone Inlet in Chesapeake Bay, including the effects of macroalgae on food availability, and (2) the clearance rates and absorption efficiencies by cultured …

Analysis Of Extreme Water Levels In The Lower Chesapeake Bay, Carissa N. Wilkerson

Dissertations, Theses, and Masters Projects

In order to better understand storm tides in the Lower Chesapeake Bay, water levels during eleven storms at eight stations were analyzed using several methods. Storm tide was separated into individual components: predicted tide, storm surge, and local anomaly. These components were quantified and then analyzed for spatial trends. Trends were verified using Principal Component Analysis (PCA). The predicted tide and the storm surge each exhibited spatial variability, while the anomaly was spatially uniform. Anomaly values varied from storm to storm, ranging from 0.01m to 0.3m.

Potential water levels were determined for each storm by applying a time-shift to match …

Habitat And Fish Population Dynamics: Advancing Stock Assessments Of Highly Migratory Species, Patrick D. Lynch

Dissertations, Theses, and Masters Projects

Fisheries sustainability is inherently linked to an understanding of the population-level effects of fishing. With an accurate characterization of historical fish and fishery dynamics, management agencies are more equipped to create regulations that sustain fishery resources over the long term. The overarching goal of this dissertation is to contribute to the advancement of fisheries stock assessment and promote resource sustainability. My research focused on highly migratory species (HMS), particularly fishes that reside in the open ocean. These species constitute some of the highest valued global fisheries; however, numerous factors compromise HMS stock assessment and management. These challenges are fully described …

Magnetic Order And Dimensional Crossover In Optical Lattices With Repulsive Interaction, Jie Xu

Dissertations, Theses, and Masters Projects

One of the most interesting and challenging problems in physics is understanding strongly correlated many-body systems, where strong interactions can yield many remarkable phenomena such as superfluidity in 4He, high-temperature superconductivity, etc. In order to attack these problems, we often need to reduce the complexity of the systems to simple models in hopes of getting better insights into the properties of the systems. The Hubbard model, the focus of this dissertation, is one of the most famous examples of such model, which describes a tunneling of electrons between nearest neighbor sites of a lattice with on-site interactions. This simple model …

Epidemic Models On Adaptive Networks With Network Structure Constraints, Ilker Tunc

Dissertations, Theses, and Masters Projects

Spread of infectious diseases progresses as a result of contacts between the individuals in a population. Therefore, it is crucial to gain insight into the pattern of connections to better understand and possibly control the spread of infectious diseases. Moreover, people may respond to an epidemic by changing their social behaviors to prevent infection. as a result, the structure of the network of social contacts evolves adaptively as a function of the disease status of the nodes. Recently, the dynamic relationships between different network topologies and adaptation mechanisms have attracted great attention in modeling epidemic spread. However, in most of …

Real-Time High-Quality Image To Mesh Conversion For Finite Element Simulations, Panagiotis Foteinos

Dissertations, Theses, and Masters Projects

Technological Advances in Medical Imaging have enabled the acquisition of images accurately describing biological tissues. Finite Element (FE) methods on these images provide the means to simulate biological phenomena such as brain shift registration, respiratory organ motion, blood flow pressure in vessels, etc. FE methods require the domain of tissues be discretized by simpler geometric elements, such as triangles in two dimensions, tetrahedra in three, and pentatopes in four. This exact discretization is called a mesh . The accuracy and speed of FE methods depend on the quality and fidelity of the mesh used to describe the biological object. Elements …

A Search For A New Gauge Boson, Eric Lyle Jensen

Dissertations, Theses, and Masters Projects

In the Standard Model, gauge bosons mediate the strong, weak, and electromagnetic forces. New forces could have escaped detection only if their mediators are either heavier than O (TeV) or weakly coupled to charged matter. New vector bosons with small coupling a' arise naturally from a small kinetic mixing with the photon and have received considerable attention as an explanation of various dark matter related anomalies. Such particles could be produced in electron-nucleus fixed-target scattering and then decay to e+ e -- pairs. New light vector bosons and their associated forces are a common feature of Standard Model extensions, but …

Holocene Sedimentation On The Lanyang Plain And Adjacent Continental Shelf, Northwestern Taiwan, Chia-Yu Wu

Dissertations, Theses, and Masters Projects

The Lanyang Plain, along the northeastern Taiwan orogen, provides an excellent example of the tectonic and climatic controls on erosion and subsequent riverine sediment supply to the coastal ocean and deep sea. 12 deep borings on the Lanyang Plain and 2 long cores in Southern Okinawa Trough (MD12403, ODP1202), together with high-resolution seismic data on Ilan Shelf, provide a good record of the depositional history during Holocene, in both on-land and offshore areas. Based on these data, we find the sediment thickness reaches 216 m in Lanyang Plain, and the average sediment rate is estimated to be 3.6 Mt/yr - …

Improvements In Triploid Crassostrea Virginica Production: Characterizing The Diploid Parent, Brian R. Callam

Dissertations, Theses, and Masters Projects

The effect of triploidy to effect faster growth and increased survival compared to diploid oysters is called the ‘triploid advantage’ and this advantage in the Chesapeake Bay for Crassostrea virginica is the principal reason for the value of triploid C. virginica in the Chesapeake Bay, USA. The triploid advantage is hypothesized to be the result of genetic effects, physiological changes, or a combination of both. The causative genetic mechanisms at play may include additive genetic effects and heterosis while the physiological changes obtain from triploid sterility. The triploid advantage was examined by comparing 13 diploid and 13 triploid crosses across …