Physics Commons^™

Influence Of Thickness And Capping Materials On The Static And Dynamic Properties Of Ferrimagnetic Thin Films, Noha Alzahrani

USF Tampa Graduate Theses and Dissertations

Spintronics traditionally relied on ferromagnetic materials for their strong spin properties but facedissues like large stray magnetic fields. To address these challenges, researchers turned to antiferromagnetic materials with fast spin dynamics, due to their zero net magnetic moment but the lack of a net spin moment complicated operation. In this context, ferrimagnetic materials have emerged as promising alternatives. They combine ferromagnetic and antiferromagnetic traits and feature different magnetic ions in their sublattices. This dissertation explores how film thickness and capping materials affect the properties of ferrimagnetic thin films. Rare-earth transition metal ferrimagnetic amorphous alloys have garnered attention in the realm …

Influence Of Thickness And Capping Materials On The Static And Dynamic Properties Of Ferrimagnetic Thin Films, Noha Alzahrani

USF Tampa Graduate Theses and Dissertations

Spintronics traditionally relied on ferromagnetic materials for their strong spin properties but facedissues like large stray magnetic fields. To address these challenges, researchers turned to antiferromagnetic materials with fast spin dynamics, due to their zero net magnetic moment but the lack of a net spin moment complicated operation. In this context, ferrimagnetic materials have emerged as promising alternatives. They combine ferromagnetic and antiferromagnetic traits and feature different magnetic ions in their sublattices. This dissertation explores how film thickness and capping materials affect the properties of ferrimagnetic thin films.

Rare-earth transition metal ferrimagnetic amorphous alloys have garnered attention in the realm …

Entanglements Of Teenage Food Security Within High School Pantries In Pinellas County, Florida, Karen T. Díaz Serrano

USF Tampa Graduate Theses and Dissertations

Food insecurity has the ability to shape an individual’s or a family’s everyday life and take emotional, psychological, and physical tolls. Among adolescents, not having access to nutritious food could lead to physical effects during growth and development. Moreover, the stress and anxiety of not knowing where their next meal is coming from and the social stigma associated with being food insecure can have negative effects on mental health. A recent solution to these issues is locating food pantries in high schools. Purpose: This exploratory study examined how high school students in Pinellas County, Florida perceive the use of a …

Entanglements Of Teenage Food Security Within High School Pantries In Pinellas County, Florida, Karen T. Diaz Serrano

USF Tampa Graduate Theses and Dissertations

Food insecurity has the ability to shape an individual’s or a family’s everyday life and take emotional, psychological, and physical tolls. Among adolescents, not having access to nutritious food could lead to physical effects during growth and development. Moreover, the stress and anxiety of not knowing where their next meal is coming from and the social stigma associated with being food insecure can have negative effects on mental health. A recent solution to these issues is locating food pantries in high schools. Purpose: This exploratory study examined how high school students in Pinellas County, Florida perceive the use of a …

The Applicability Of The Postmortem Submersion Interval Estimation Formula For Human Remains Found In Subtropical Aquatic Environments, Kara L. Dicomo

USF Tampa Graduate Theses and Dissertations

Within the past decade, several attempts have been made to standardize a method for estimating postmortem submersion intervals (PMSI); however, the majority of these studies have focused on data from a temperate climate which cannot be taken as representative of large portions of the globe. Thus, there are large portions of the earth in which the methodology from these studies may not be able to accurately estimate PMSI which has the potential to leave investigators in these other climatic zones at a disadvantage. This presentation presents a case study into the applicability of two Total Body Scoring Systems (TADS) utilized …

Light-Controlled Magnetism And Magnetic Sensing In Two-Dimensional Vanadium Dichalcogenides And Related Semiconductors, Valery Ortiz Jimenez

USF Tampa Graduate Theses and Dissertations

Atomically thin transition metal dichalcogenide (TMD) semiconductors hold enormous potential for modern optoelectronic devices, magnetic sensing, and quantum computing applications. By inducing long-range ferromagnetism (FM) in these semiconductors by stacking them with other magnetic TMDs or through the introduction of small amounts of a magnetic dopant, it is possible to extend their potential in emerging spintronic applications. In this dissertation, we aim to demonstrate two important applications of these materials: magnetic sensing and light-mediated, room temperature (RT) FM in V-doped WS2 (V-WS2) and V-WSe2 monolayers and in ML VSe2/TS2 (T = Mo and W) heterostructures. In this work, we developed …

First-Principles-Based Modeling Of Energy Converting Properties Of Conventional And Emerging Ferroelectrics, Maggie Kingsland

USF Tampa Graduate Theses and Dissertations

Ferroelectric materials are a type of multifunctional material that exhibit spontaneous polarization reversable by the application of an electric field. They are used in many technologies such as ferroelectric RAM (FeRAM), piezoelectric devices, RFID chips, and capacitors. However, the most commonly used ferroelectrics are often made with rare, expensive elements and are not environmentally friendly. For example, many prototypical ferroelectrics contain elements such as lead, zirconium, and titanium. As technology grows more advanced, there is a need to discover or manufacture cheaper ferroelectrics and to make them less impactful on human health and the earth as a whole. We set …

Exploring Magneto-Excitons In Bulk And Mono-Layer Semiconductors Using Non-Linear Spectroscopy Techniques, Varun Mapara

USF Tampa Graduate Theses and Dissertations

The research in two-dimensional (2D) materials has evolved from ``traditional" quantum wells based on group III-V and II-VI semiconductors to atomically thin sheets of van der Waals materials such as 2D semiconducting Transition Metal Dichalcogenides (TMDs). These 2D materials remain a stimulating field that continues to introduce new challenges. From both a fundamental physics and technological perspective, magneto-optical spectroscopy has been an essential tool in this research field. TMDs, for example, pose the challenge of characterizing their spin-valley-resolved physics and deriving implications in quantum computation and information research. With the discovery of valley Zeeman effects, the spin-valley physics of TMDs …

Crystal Structure Prediction Of Materials At Extreme Conditions, Ashley S. Williams

USF Tampa Graduate Theses and Dissertations

The prediction of the structure of a crystal given only the constituent elements is one of the greatest challenges in both materials science and computational science alike. If one were to try to predict a novel crystal by brute force, meaning by arranging the atoms in every possible position of the unit cell and optimizing the geometry to find the energy minima of the potential energy surface, the amount of computer resources required to complete the calculation on the timescale of a few years would vastly exceed the currently installed computational capacity of the entire world. Fortunately, several methods have …

Carbon And Other Low-Z Materials Under Extreme Conditions, Jonathan T. Willman

USF Tampa Graduate Theses and Dissertations

This work is focused on understanding material's behavior and response to extreme conditions. Under extreme conditions, which is categorized as regions of high pressures and temperatures in (P-T) space, materials can undergo multiple types of phase transitions as well as exhibit substantial damage as well as other exotic behaviors. By studying matter at these extreme conditions, we can elucidate a broad range of fundamental physics including a material's energetic, mechanical, and electronic responses. This thesis describes work that makes contributions to the growing body of knowledge within these subsets of condensed matter physics. In the first thrust, crystal structure prediction …

Texturing In Bi2Te3 Alloy Thermoelectric Materials: An Applied Physics Investigation, Oluwagbemiga P. Ojo

USF Tampa Graduate Theses and Dissertations

Thermoelectric devices provide the means for direct conversion between heat and electricity. The device conversion efficiency, or performance, is directly related to the thermoelectric figure of merit, ZT, of the working materials. Bismuth telluride alloys are the materials currently in use in most thermoelectric devices for near room temperature solid-state refrigeration and power conversion applications. The vast majority of publications in the literature on thermoelectricity report on investigations towards developing new materials with enhanced thermoelectric properties, however Bi₂Te₃ alloys have been used in thermoelectric devices for decades.

In this thesis, an investigation of crystallographic texturing on large …

The Early Medieval Transition: Diet Reconstruction, Mobility, And Culture Contact In The Ravenna Countryside, Northern Italy, Anastasia Temkina

USF Tampa Graduate Theses and Dissertations

This research project evaluates the effects of increased mobility and culture contact on dietary practices, and on dietary variation among people buried at two northern Italian sites, Chiunsano di Ficarolo and Chiesazza di Ficarolo, located near the ancient Roman capital of Ravenna and dating 4th to 7th century CE. The Early Medieval period was a time of change, political instability, migration and invasion of the “barbarian” tribes, and diet was not unaffected. In particular, it is hypothesized that a new staple crop, millet, was introduced and that meat consumption had increased. The goal of this research is to use stable …

Pregnancy And Fertility Amongst Women With The Mthfr C677t Polymorphism: An Anthropological Review, Caroline A. Maclean

USF Tampa Graduate Theses and Dissertations

Effects of the MTHFR C677T allele on reproduction include multiple complications. The frequency of births with neural tube defects, Down Syndrome, or recurrent pregnancy loss of CC, CT, and TT mothers was measured using data collected from existing literature. Total participants n=2605 (n=1111 cases, n=1494 controls). Results show that folic acid supplementation did not prevent the incidence of NTD pregnancy in CT women. Furthermore, CT women are more fecund overall, producing more pregnancies than CC and TT women. While CT case women did have higher incidences of RPL, NTD pregnancy and DS pregnancy, this is due to the overall greater …

Identifying Skeletal Puberty Stages In A Modern Sample From The United States, Jordan T. Wright

USF Tampa Graduate Theses and Dissertations

Investigating the onset and progression of puberty can provide insight and evidence for social changes regarding the transition to adulthood. There are also many social factors that can lead to variation in the timing of the onset and progression of puberty. Methods created by Mary Lewis and Fiona Shapland for assessing changes in skeletal development associated with pubertal timing were applied to computerized tomography scans (n=400) from the New Mexico Decedent Image Database and recorded in an attempt to identify adolescent growth trends in a modern skeletal sample from the United States. This is a novel study using the methods …

Listening To Women: Using A Mixed-Methods Approach To Understanding Women’S Desires And Experience During Childbirth, Nicole Loraine Falk Smith

USF Tampa Graduate Theses and Dissertations

This dissertation is based on evolutionary medicine and applied anthropological research where the narratives and biology of modern women are used to inform evolutionary theory, specifically obligate midwifery, and modern birth practices. Improvements to the US maternity care systems are needed as rates of maternal mortality and morbidity are continually higher than rates in other technologically advanced nations. Additionally, women birthing under the technocratic model of care, as is predominant in the US, report trauma and post-traumatic stress disorders due to their birthing experience, and more women are experiencing postpartum depression. Thus, I seek to use an evolutionary medicine perspective …

Probing The Ground State Magnetism In Materials With Competing Magnetic Interactions, Richa Pokharel Madhogaria

USF Tampa Graduate Theses and Dissertations

Materials with competing magnetic interactions provide a unique combination of intriguing physics originating from structural, magnetic, and electronic degrees of freedom, along with their technological applications. The complex oxides and helimagnets also share an interesting physics involving competitive interactions and understanding the behavior of one helps us to yield an insight into the other system. A rigorous understanding about the competing interactions in strongly correlated magnetic systems provide an opportunity to explore the related effects like spin frustration, glassiness, metamagnetism, which play an essential role in manipulating their magnetic properties and functionality. In this dissertation, we combine dc magnetization [M(H,T)], …

Third-Order Frequency-Resolved Photon Correlations From A Single Quantum Dot's Resonance Fluorescence, Yamil A. Nieves González

USF Tampa Graduate Theses and Dissertations

The ability to control the photon emission from light sources has sparked an increasing interest in the field of quantum optics due to potential applications in the development of quantum technologies. Motivated by such applications, photon statistics have been a powerful investigative tool used to characterize the properties of light sources capable of emitting a bundle of N photons. As such, the first-order and second-order photon correlations continue to be researched extensively providing invaluable information about the light and the mechanism underlying its generation. Meanwhile, third-order photon correlations have remained majorly unexplored due to the high degree of experimental challenges …

Characterizing Childhood And Diet In Migration Period Hungary, Kirsten A. Verostick

USF Tampa Graduate Theses and Dissertations

This project investigates children, childhood and diet of two different Migration Period (4^th-8^th century AD) populations, the Gepids and the Avars, in the Great Hungarian Plain. The main goal was to assess whether there are differences in treatment of children and differences in breastfeeding and weaning practices in these distinct sites and populations. Secondarily, this research also focused on characterizing diet for the Gepids and the Avars at four different sites from the Migration Period, to understand how the migration and settling into the region and the assimilation of other groups into the two populations affected their …

Spontaneous Raman Scattering Enhancement With Microcavities And Multipass Resonators For Trace Gas Detection, Juan Sebastian Gomez Velez

USF Tampa Graduate Theses and Dissertations

The continual increase in production and use of chemicals in an ever-growing field of applications naturally brings forth the necessity to accurately and efficiently measure molecular composition. Spontaneous Raman scattering is a reliable technique which can optically identify molecules based on their intrinsic rotational-vibrational energy structure. The Raman emission from a substance can be spectrally analyzed to detect molecular species simultaneously and with isotopic sensitivity using a single laser source. However, even though the process is non-invasive and effective, the rate at which the emission occurs is notoriously low due to a weak scattering cross-section. Therefore, research into the development …

Maternal Social Status, Offspring 2d:4d Ratio And Postnatal Growth, In Macaca Mulatta (Rhesus Macaques), Juan Pablo Arroyo

USF Tampa Graduate Theses and Dissertations

Early life exposure to stressors can disrupt growth and development, resulting in long-term compromised function and increased risk for disease throughout the lifecourse. Maternal exposure to psychosocial stressors (i.e., stressors derived from social status, social inequalities, and social interactions) during pregnancy has been associated with reduced fetal growth, adverse birth outcomes, and increased morbidity for the offspring later in life. Maternal hormonal responses to stress, such as fluctuations in glucocorticoids (e.g., cortisol) and androgens (e.g., testosterone), can result in increased developmental instability, interfere with offspring growth in-utero, and may alter developmental processes of sexual dimorphism. Second digit to fourth digit …

Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh

USF Tampa Graduate Theses and Dissertations

Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion process …

A Novel Magnetic Respiratory Sensor For Human Healthcare, Kee Young Hwang

USF Tampa Graduate Theses and Dissertations

Breathing is vital to life. Therefore, the real-time monitoring of a patient’s breathing pattern is crucial to respiratory rehabilitation therapies such as magnetic resonance exams for respiratory-triggered imaging, chronic pulmonary disease treatment, and synchronized functional electrical stimulation. While numerous respiratory devices have been developed, they are often in direct contact with a patient, which can yield inaccurate or limited data. In this study, we developed a novel, non-invasive, and contactless magnetic sensing platform that can precisely monitor a patient’s breathing, movement, or sleep patterns, thus providing efficient monitoring at a clinic or home. A magneto-LC resonance (MLCR) sensor converts the …

Van Der Waals Epitaxy Of Ultrathin Early Transition Metal (Ti & V) (Di)Selenides: Charge And Magnetic Order In The Ultrathin Limit, Manuel Bonilla Lopez

USF Tampa Graduate Theses and Dissertations

Since the isolation of graphene in 2004, two-dimensional (2D) layered materials, specially the transition metal dichalcogenides (TMDs), have attracted immense interest from theoreticians and experimentalist due to the diversity of properties presented in this family of materials. The main reason for the interest in such materials has been the observation of emergent properties as a consequence of the reduced dimensions, i.e. the monolayer regime. Initially the monolayer regime was obtained via the scotch-tape method. The implementation of exfoliation techniques was successful since layered 2D materials are composed of stacked layers held together by weak van der Walls forces that permits …

Investigation Into Reduced Thermal Conductivity For Half-Heusler Alloys And Identification Of Novel Multinary Chalcogenides Possessing Intrinsically Low Thermal Conductivity, Dean Hobbis

USF Tampa Graduate Theses and Dissertations

The current climate makes the need for sustainable energy production a priority, leading to keen interest towards the advancement of “green” energy sources and technology. This necessity has led to a multidisciplinary scientific approach with collaborations across various fields that are looking to solve this extremely important problem. One such technology is thermoelectric devices, which are attractive due to the fact that they provide direct solid-state conversion of heat to electrical power, and vice versa. This in turn allows for both waste heat recovery and sustainable refrigeration. One key aspect that is preventing the wide scale commercial use of thermoelectric …

Growth And Characterization Of 2d Layered Materials, Algene Fryer Ii

USF Tampa Graduate Theses and Dissertations

2D layered materials are becoming an important area of research due to their exceptional electrical and optical properties. Specifically, 2D layered monochalcogenides are known for their high carrier motilities, whereas layered metal halides have been shown to have noteworthy photoresponsivity. Despite the assortment of 2D layered materials, the search for reliable and scalable synthesis methods is still a challenge in this family of materials. Often a certain growth technique will compromise a desirable trait needed for further fabrication, such as the quality of the crystal or its coverage on a substrate. In this study, two growth techniques that incorporate changeable …

Laser-Induced Breakdown Spectroscopy For Elemental Analysis In Bioarchaeology And Forensic Anthropology, Kelsi N. Kuehn

USF Tampa Graduate Theses and Dissertations

Within bioarchaeology and forensic anthropology, the current processes of differentiating between individual human skeletal remains are imprecise, costly, and inefficient. A novel analytical technique within anthropology, laser-induced breakdown spectroscopy (LIBS) can aid in the identification of human remains using rapid laser ablation occurring at the micro-scale, making the technique virtually non-destructive to the sample. Considering this, LIBS could offer a superior method for materials discrimination and human identification. This research sought to examine whether LIBS can be used to obtain elemental signatures within bones to distinguish individuals from one another in a rapid, non-destructive manner. Seven human skeletal donors and …

First-Principles Simulations Of Materials Under Extreme Conditions, Kien Nguyen Cong

USF Tampa Graduate Theses and Dissertations

The investigation of materials at extreme conditions of high pressure and temperature (high-PT), has been one of the greatest scientific endeavors in condensed mater physics, chemistry, astronomy, planetary, and material sciences. Being subjected to high-PT conditions, materials exhibit dramatic changes in both atomic and electronic structure resulting in an emergence of exceptionally interesting phenomena including structural and electronic phase transitions, chemical reactions, and formation of novel compounds with never-previously observed physical and chemical properties. Although new exciting experimental developments in static and dynamic compression combined with new diagnostics/characterization methods allow to uncover new processes and phenomena at high P-T conditions, …

Millimeter-Wavelength Characterization Of The Co Emission Of Comets 174p/Echeclus, 29p/Schwassmann-Wachmann, And C/2016 R2 (Panstarrs), Kacper Wierzchos

USF Tampa Graduate Theses and Dissertations

Comets are fascinating minor solar system bodies. They contain some of the most pristine and unprocessed material found in the solar system. As a comet approaches the Sun it displays the characteristic cometary coma and tail. This is due to the release of volatile species through a variety of processes. In the present work I studied the carbon monoxide emission of three very unique comets; 174P/Echeclus, 29P/Schwassmann-Wachmann and C/2016 R2 (PanSTARRS) with different radio telescopes at millimeter wavelengths. After molecular hydrogen, carbon monoxide is the second most abundant molecule in the universe, and is also the most volatile of the …

Measuring And Utilizing High-Dimensional Information Of Optical Fields, Ziyi Zhu

USF Tampa Graduate Theses and Dissertations

Currently, many areas of optical techniques including imaging, inspection and communication emphasize the utilization of the high-dimensional information encoded in optical fields. There is also a requirement for novel measurement techniques to extract this high-dimensional information with high-speed and accuracy. We firstly introduce a scan-free direct measurement technique that is capable of simultaneously characterizing the amplitude and phase of a coherent scalar optical field. Our direct measurement approach is constituted of a weak polarization perturbation which is followed by the recording of a polarization-resolving imaging process. The weak perturbation rotates the linear polarization on the spatial frequency domain of the …

Modulations Of Lipid Membranes Caused By Antimicrobial Agents And Helix 0 Of Endophilin, Nawal Kishore Khadka

USF Tampa Graduate Theses and Dissertations

Understanding the cellular membrane interaction with membrane active biomolecules and antimicrobial agents provides an insight in their working mechanism. Here, we studied the effect of antimicrobial agents; a recently developed peptidomimetics E107-3 and colistin as well as the N-terminal helix H0, of Endophilin A1 on the lipid bilayer.

It is important to discern the interaction mechanism of antimicrobial peptides with lipid membranes in battling multidrug resistant bacterial pathogens. We study the modification of structural and mechanical properties with a recently reported peptidomimetic on lipid bilayer. The compound referred to as E107-3 is synthesized based on the acylated reduced amide scaffold …