Physics Commons^™

Oligomerization Of The Sterile-2 G-Protein Coupled Receptor In Yeast Cells In The Presence And Absence Of Alpha-Factor Pheromone Using Fluorescence Spectroscopy And Forster Resonance Energy Transfer Analysis, Joel David Paprocki

Theses and Dissertations

G-protein-coupled receptors (GPCRs) are the largest family of receptors that respond to a wide variety of extracellular stimuli, including molecular ligands such as odorants, neurotransmitters, and hormones, as well as physical agents sigh as light and pressure. The stimulation event results in initiating conformational changes in the structure of the receptor, which further results in the release of the heterotrimeric G-protein; the latter has a variety of functions within signaling pathways in cellular biology. The GPCR explored in this investigation is the Sterile 2 α-factor receptor (Ste2), whose natural function is that of a yeast mating pheromone receptor. Its natural …

The Structure And Ferroelectric Properties Of Iron-Doped Lead Titanate, Michael Bartlein

Theses and Dissertations

Multiferroics are a class of poorly understood, but technologically important materials. Lead(II) titanate (PbTiO$_3$) is a known perovskite ferroelectric. By doping PbTiO$_3$ with Fe$^{3+}$ at the Ti site, we produce the multiferroic PbTi$_{1-x}$Fe$_x$O$_3$ (PTFO). Using selected area electron diffraction on a transmission electron microscope, the structure of PTFO is investigated. Of particular interest is identifying the cubic-to-tetragonal transition at the Curie temperature. As the concentration of Fe increases, the crystal becomes more cubic and experiences a lower transition temperature. I also establish a procedure for preparing bulk PTFO samples for ferroelectric testing and present preliminary results establishing ferroelectricity in these …

Propagation Of An Optical Vortex In Fiber Arrays With Triangular Lattices, Muhammad Abdulrahman Mushref

Theses and Dissertations

The propagation of optical vortices (OVs) in linear and nonlinear media is an important field of research in science and engineering. The most important goal is to explore the properties of guiding dynamics for potential applications such as sensing, all-optical switching, frequency mixing and modulation. In this dissertation, we present analytical methods and numerical techniques to investigate the propagation of an optical vortex in fiber array waveguides. Analytically, we model wave propagation in a waveguide by coupled mode Equations as a simplified approximation. The beam propagation method (BPM) is also employed to numerically solve the paraxial wave Equation by finite …

Searching For Gravitational Waves Using Pulsar Timing Arrays, Justin Ellis

Theses and Dissertations

Gravitational Waves (GWs) are tiny ripples in the fabric of spacetime predicted by Einstein's theory of General Relativity. Pulsar timing arrays (PTAs) offer a unique opportunity to detect low frequency GWs in the near future. Such a detection would be complementary to both LISA and LIGO GW efforts. In this frequency band, the expected source of GWs are Supermassive Black Hole Binaries (SMBHBs) that will most likely form an ensemble creating a stochastic GW background with possibly a few nearby/massive sources that will be individually resolvable. A direct detection of GWs will open a new window into the fields of …

Design Of A Micro-Focus X-Ray Source Validated By Model Protein Crystals, Lavanya Ramachandran

Theses and Dissertations

The main objective of this thesis was to build a Laboratory Microfocus X-ray Source for Protein Crystallography (LMXS-PC), an X-ray source that would provide prospective users programmatic control and remote capability.

A study of the crystal was conducted using Photoactive Yellow protein (PYP) and cytochrome c nitrite reductase (ccNiR). The instrument was then tested by mounting the crystal in the instrument and collecting data.

The other objective of my research work was to determine the crystal structure of PYP using X-ray crystallography techniques. I attempted many trials in PYP crystal in an effort to achieve a high-quality diffraction pattern; however, …

Monitoring Changes In Hemodynamics Following Optogenetic Stimulation, Seth Thomas Frye

Theses and Dissertations

The brain is composed of billions of neurons, all of which connected through a vast network. After years of study and applications of different technologies and techniques, there are still more questions than answers when it comes to the fundamental functions of the brain. This project aims to provide a new tool which can be used to gain a better understanding of the fundamental mechanisms that govern neurological processes inside the brain. In order for neural networks to operate, blood has to be supplied through neighboring blood vessels. As such, the increase or decrease in the blood supply has been …

Nonlinear Processes In Multi-Mode Optical Fibers, Hamed Pourbeyram Kaleibar

Theses and Dissertations

Nonlinear processes in optical fibers can affect data transmission and power carried by

optical fibers and can limit the bandwidth and the capacity of optical communications.

On the other hand nonlinear phenomena could be utilized to build in-fiber all-optical

light sources and amplifiers. In this thesis new peaks inside an optical fiber have been

generated using nonlinear processes. An intense green pump laser has been launched

into a short fiber and specific modes have been excited to generate two new peaks in

red and blue wavelengths, where two pump photons are annihilated to create two new

photons in red and …

Surface X-Ray Diffraction Study On Polar Oxide Surface And Interface, Wei Han

Theses and Dissertations

An atomic scale study of surface/interface structure is required to properly understand physical and chemical phenomena such as crystal growth, lubrication and electrochemistry. The stability of polar oxide surface has long been an interesting question. A bulk-terminated polar oxide surface comprises alternating layers of opposite charges, thus resulting in diverging surface energies. In order to reduce the surface energy, various reconstruction-stabilized MgO (111) surfaces have been reported

experimentally. However, the atomic structure of the MgO (111)rt3×rt3R30o<\super> reconstructed surface remains unclear.

Using a third-generation X-ray source is one of the feasible methodologies to probe such a system due to its increase …