Biological and Chemical Physics Commons^™

Creasing In Thick Hemispherical Shells As A Model For Foveal Formation, Indigo Skye Peppard

Undergraduate Honors Theses

This research experimentally investigates creasing behavior on the inner surface of hemispherical shells with the ultimate goal of modelling the formation of the foveal pit, a sharp surface deformation present in the retina of the eye of many animals. Creasing is a phenomenon observed in hyperelastic materials and is characterized by sharply localized surface deformations that appear at ~35% compressive strain. The foveal pits of anoles (small iguanian lizards) are funnel-shaped and resemble creases when cut along the central axis. Furthermore, during foveal pit formation the anole eye contracts around 35% along this same axis. Given these similarities we believe …

Outpatient Fall Prevention In Ambulatory Adults 65 Years Old And Over, Dorothy L. Osborne-White

Doctor of Nursing Practice (DNP) Scholarly Projects - Archive

Background: In the United States (U.S.), falls are the leading cause of injury among adults 65 and over, resulting in 36 million falls yearly (Moreland et al., 2020). According to the Centers for Disease Control and Prevention (CDC, 2023), one in four older adults experiences a fall each year. Falls are the world's second most prominent cause of accidental deaths (World Health Organization [WHO], 2021). Falls are the leading cause of both fatal and non-fatal injuries among older adults (Moreland et al., 2020).

Methods: A quality improvement project that included a fall bundle was implemented in a primary clinic. A …

Biosynthesis Of Mgo Nanoparticles And Their Impact On The Properties Of The Pva/Gelatin Nanocomposites For Smart Food Packaging Applications, Mohamed Morsy

Nanotechnology Research Centre

No abstract provided.

Modeling Excited State Processes In Molecular Aggregates By Constructing An Adaptive Basis For The Hierarchy Of Pure States, Leonel Varvelo

Chemistry Theses and Dissertations

Simulating excitation energy transfer (EET) in molecular materials is of crucial importance for the development of and understanding of materials such as organic photovoltaics and photosynthetic systems and further development of novel materials. The Hierarchy of Pure States (HOPS) is an exact framework for the time evolution of an open quantum system in which a hierarchy of stochastic wave functions are propagated in time. The adaptive HOPS (adHOPS) method achieves size-invariant scaling with the number of simulated molecules for sufficiently large aggregates by using an adaptive basis that moves with the excitation through the material. To demonstrate the power of …

Long-Range And Chaotic Active Mixing Of Swimming Microbes In A Vortex Chain Flow, Nghia Le

Honors Theses

We present experiments studying the motion and active mixing of swimming mi- crobes in laminar, vortex-dominated fluid flows. We are testing a theory that predicts the existence of swimming invariant manifolds (SwIMs) - invisible, one-way barriers blocking the paths of self-propelled tracers in the flow in one direction. We also pro- pose that the SwIMs together can form chute structures in three-dimensional phase space that facilitate cross-vortex transport of the microbes. We also observe evidence of how these structures promote long-range transport at different non-dimensional velocities (microbe’s velocity relative to flow velocity). Long-range transport is quan- tified by measuring the …

Coupled Oscillators: Protein And Acoustics, Angelique N. Mcfarlane

Theses

This work encompassed three different vibrational energy transfer studies of coupled resonators (metal, topological, and microtubule comparison) inspired by the lattices of microtubules from regular and cancerous cells. COMSOL Multiphysics 5.4 was utilized to design the experiment. The simulation starts with an acoustic pressure study to examine the vibrational modes present in coupled cylinders, representing α-, β-tubulin heterodimers. The Metal Study consisted of 3 models (monomer, dimer, and trimer) to choose the correct height (40 mm) and mode (Mode 1) for study. The Topological Study was run to predict and understand how the lattice structure changes over a parametric sweep …

Stability Of Group Four Monochalcogenides In Water And Air, William Shattuck

Graduate Theses and Dissertations

Previously published works have simulated the behavior of monolayer group IV monochalcogenides and predicted them to have very useful electronic properties. These simulations have also predicted that monolayers of group IV monochalcogenides will degrade quickly when exposed to water, even in extremely low concentrations. We hypothesize that thin samples of these materials will show signs of degradation if left in air and in water for an extended period of time.

Samples of each of the four monochalcogenides (GeS, GeSe, SnS and SnSe) were exfoliated onto clean oxidized silicon substrates. Chemical analysis showed the SnSe samples were contaminated, so they were …

The Structural Information Filtered Features Potential For Machine Learning Calculations Of Energies And Forces Of Atomic Systems., Jorge Arturo Hernandez Zeledon

Graduate Theses, Dissertations, and Problem Reports (ETD)

In the last ten years, machine learning potentials have been successfully applied to the study of crystals, and molecules. However, more complex materials like clusters, macro-molecules, and glasses are out reach of current methods. The input of any machine learning system is a tensor of features (the most universal type are rank 1 tensors or vectors of features), the quality of any machine learning system is directly related to how well the feature space describes the original physical system. So far, the feature engineering process for machine learning potentials can not describe complex material. The current methods are highly inefficient …

Classical Transport In Disordered Systems, Antonios Papaioannou

Dissertations, Theses, and Capstone Projects

This thesis reports on the manifestation of structural disorder on molecular transport and it consists of two parts. Part I discusses the relations between classical transport and the underlying structural complexity of the system. Both types of molecular diffusion, namely Gaussian and non-Gaussian are presented and the relevant time regimes are discussed. In addition the concept of structural universality is introduced and connected with the diffusion metrics. One of the most robust techniques for measuring molecular mean square displacements is magnetic resonance. This method requires encoding and subsequently reading out after an experimentally controlled time, a phase ϕ to the …

Effect Of Electrolyte Concentration On The Capacitance And Mobility Of Graphene, Flint A. Martino

Senior Theses

The use of graphene field-effect transistors as a biosensor is increasingly being used to study biological phenomena, due to the sensitivity and low reactivity of graphene. To further improve sensitivity in biological environments, we examined how different salt concentrations affect the mobility of capacitance of the graphene. Samples were also measured after an annealing process. We report on the positive correlation between sensitivity and electrolyte concentration and speculate on methods to improve future detectors. Mobility of the device was found to change from 1.07*10³cm²/ (V*s) in de-ionized water to 2.78*10³cm²/ (V*s) in …

Modeling The Behavior Of The Graphene To Liquid Interfaces In An Electrolytic Liquid, Caitlin Duffner

Senior Theses

Understanding the mechanism for charge transfer between a graphene biosensor and its electrodes within an electrolyte solution is vital to better understand the sources of electrical noise in the system. By measuring the effective resistance and capacitance of the system at different frequencies, it is possible to develop a circuit model of the system's electrical behavior. This model provides a deeper understanding of the fundamental interactions that occur in a top-­gated graphene device and provides opportunities to improve a signal. To reduce noise created at the liquid to graphene interface, a buffer layer of Yttrium Oxide was applied. While the …

Characteristic Length Scales Of The Secondary Relaxations In Glass-Forming Glycerol, Sudipta Gupta, Eugene Mamontov, Niina Jalarvo, Laura Stingaciu, Michael Ohl

Faculty Publications

We investigate the secondary relaxations and their link to the main structural relaxation in glass-forming liquids using glycerol as a model system. We analyze the incoherent neutron scattering signal dependence on the scattering momentum transfer, Q , in order to obtain the characteristic length scale for different secondary relaxations. Such a capability of neutron scattering makes it somewhat unique and highly complementary to the traditional techniques of glass physics, such as light scattering and broadband dielectric spectroscopy, which provide information on the time scale, but not the length scales, of relaxation processes. The choice of suitable neutron scattering techniques depends …

Hydrogen Bond-Mediated Structural Order In Hydroxylated Bis-Mpa Dendritic Polymers: Experimental And Molecular Dynamics Simulation Study, Maliha N. Syed

Dissertations

Dendritic architectures are echoed throughout nature. While the significance of these pervasive patterns is not entirely clear, connections between their structures and physical properties are fascinating to contemplate. Particular interest has been paid to a family of synthetically manufactured and commercially available dendritic polymers based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) as a monomer. Composed of two hydroxyls and a carboxyl group, bis-MPA based structures hydrogen bond (H-bond) profusely. Given the high concentration and unique spatial orientation of end-groups, as well as the multitude of carbonyl, ester, and ether interior H-bond acceptors, a set of distinct H-bond organizations may be observed …

Measuring Charge Carrier Mobility In Graphene, Christina A. Harmon

Senior Theses

This research reports measurements of electron mobility in Graphene Field Effect Transistors (GFET), gated with liquid. Mobility is a quantity describing how easily charge carriers move through a material. GFET biosensors have the greatest sensitivity when the mobility is high; therefore, increasing mobility should improve sensitivity of these and similar devices. An optimal method was established for preparing samples and taking measurements of a liquid-gate device. Sheet conductivity was measured using van der Pauw geometry and carrier density was determined from measurements of the liquid-gate capacitance. It is shown that mobility improves after the graphene surface is cleaned by an …

Wave Function For Harmonically Confined Electrons In Time-Dependent Electric And Magnetostatic Fields, Hong-Ming Zhu, Jin-Wang Chen, Xiao-Yin Pan, Viraht Sahni

Publications and Research

We derive via the interaction “representation” the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field—the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement – the uniform electron gas – the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKTwave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide …

Wave Function For Time-Dependent Harmonically Confined Electrons In A Time-Dependent Electric Field, Yu-Qi Li, Xiao-Yin Pan, Viraht Sahni

Publications and Research

The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential.

Magnetic Ordering And Structural Phase Transition In Strained Ultrathin Srruo3/Srtio3 Superlattice, Mingquiang Gu, Xiaoshan Wu, Guoping Zhang

Symposium 2012

No abstract provided.

Spectroscopic Studies Of Melamine At High Pressure, Martin Donald Galley

UNLV Theses, Dissertations, Professional Papers, and Capstones

We have performed mid- and far- Infra Red (IR) absorption, Raman spectroscopy, and angular dispersive x-ray diffraction (XRD) studies on melamine under high pressure and room temperature. We have verified the presence of two prior reported phase transitions, the first between 1-2 GPa, and the second between 7-9 GPa. We have also found evidence of a third unreported phase transition between 14-16 GPa, during which, there was a sudden disappearance of all low energy peaks (^-1 ) in both the Raman and IR spectra. The far-IR peak movement experiences a discontinuity as the rate of peak movement suddenly changes. …

Photon Density Of States Of 47-Iron And 161-Dysprosium In Dyfe3 By Nuclear Resonant Inelastic X-Ray Scattering Under High Pressure, Elizabeth Anne Tanis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The dual partial phonon density of states (DOS) from two different Mossbauer isotopes (161Dy and 57Fe) in the same material (DyFe3) was successfully measured using the nuclear resonant inelastic x-ray scattering (NRIXS) technique at high pressure. Nuclear inelastic scattering measurements yield an in-depth understanding of the element-specific dynamic properties. The Debye temperatures, the Lamb-Mossbauer factor (fLM), and the vibrational contributions to the Helmholtz free energy (Fvib), specific heat (cV ), entropy (Svib) and internal energy (Uvib) are calculated directly from the phonon density of states.