Magneto-optical characterization of ultrathin ferrimagnetic insulator bilayers

The demands for information storage and processing technologies continue to grow. We continue to press on for higher stability and density memory, and faster computation rates. We are even moving beyond classical computing models. Magnetic devices are prized for information storage owing to the stability of magnetization states in the absence of driving power and over many on-off cycles. Magnetic storage, however, has not been able to scale as quickly as other computing technologies. Devices such as hard disk drives tend to be one of the slowest parts of a computer because they require mechanical components and because they can only read/write from a single head. In the field of spintronics, researchers are exploring different alternative forms of storage technologies such as racetrack and skyrmion memory. These new memory devices allow for all-electrical reading and writing of bits in magnetic materials. These memory devices were first created using metallic ferromagnet films. The use of ferrimagnetic insulators as a platform for chiral domain wall motions and skyrmions are recent developments. Magnetic insulators have the potential to reduce the amount of charge current present in a working device and therefore reduce the amount of energy loss through mechanisms such as Joule heating. These materials also have several other useful characteristics such as smaller magnetizations, high tunability of anisotropy, and the potential for higher than GHz computing frequencies. However, studying ferrimagnetic thin films at the ultrathin limit necessary for room temperature skyrmion creation presents outstanding challenges in the characterization and optimization of these films. This thesis focuses on combining electrical transport and magneto-optical experimental methods in the study of thulium iron garnet (TmIG) ultrathin film systems. Detecting the presence of skyrmions in ultrathin magnetic insulating films is challenging. A standard electrical-read out method relies in the spin Hall-topological Hall effect. A heavy metal thin film, such as Pt, is deposited on the TmIG thin film and through the spin-Hall and inverse spin-Hall effects, we can detect changes to the transverse resistivity in this film generated by what is correlated to spin textures in TmIG. By using an ultra-high sensitivity Sagnac interferometer, we are able to measure the hysteresis curve for these ultrathin Pt/TmIG bilayers. The functional form of the hysteresis takes the same form as the spin-Hall anomalous Hall effect. By combining the optically determined spin Hall-anomalous Hall function with the Hall resistivity data, the anomalous contribution can be removed. For the first time, a fully quantified, room temperature spin Hall-topological Hall resistivity is presented for Pt/TmIG bilayers. A phenomenological expression for estimating skyrmion densities using the spin Hall-topological Hall resistivity is presented. The estimated skyrmion density suggests that the skyrmions in this system are on the order of 10s of nanometers in diameter. We also present work on the magnetic anisotropy of the ultrathin films as a function of magnetic layer thickness and show the large effect of the Pt layer induced interfacial anisotropy. This is necessary because one of the main parameters used to engineer a skyrmion phase is magnetic anisotropy. This work was performed by measuring three thickness of TmIG films with and without Pt, showing the anisotropy evolution. For the thicker films, in-plane hysteresis is measured using the polar MOKE configuration. The in-plane field sweeps indicate that the magnetization rotation is coherent and gives some information about in-plane saturation fields. These measurements show that without Pt, the TmIG films continue to exhibit perpendicular magnetic anisotropy to the thinnest film thickness. The interfacial anisotropy from Pt is shown to be comparable in magnitude to the volumetric anisotropy of the thickest film and produces an easy-plane anisotropy in the thinnest film. These results are discussed and estimates of the interfacial anisotropy magnitude are presented. Further avenues of study for the anisotropy are discussed with the goal of completely understanding the nature of the anisotropy for films exhibiting skyrmion phases at room temperature.Physic

Examining physical activity among US college students following COVID-19 outbreaks and lockdowns : the role of race/ethnicity and acculturation

Objective: This study examined physical activity among US college students in the context following COVID-19 outbreaks and lockdowns, with a focus on racial/ethnic and cultural determinants. Sample: This study used cross-sectional data of the COVID-19 University Research on Education and Sustainability (CURES) project. Participants were college students from 7 public universities in the US (N = 1210; 75% female; 33.5% White, 9.1% Black, 47.6% Hispanic, and 7.1% Asian; Mage = 21.06; 85.6% born in the US, 51.6% had mother born in the US, and 49% had father born in the US). Method: The International Physical Activity Questionnaire - short form (IPAQ-SF) was used to assess physical activity and the Vancouver Index of Acculturation (VIA) – the American version was used to assess levels of heritage and US acculturation. Results: White students reported statistically significant higher physical activity than Hispanic (p < .05, Cohen’s d = .19) and Asian (p < .05, Cohen’s d = .36). In sedentary level, White students reported statistically significant lower levels than Asian (p < .05, Cohen’s d = -.45). Asian reported lowest physical activity, highest sedentary level, and highest prevalence of not meeting physical activity recommendation. Small negative correlation was found between heritage cultural level and total weekly physical activity among Hispanic students (r = - .09, p < .05). Conclusion: Race/ethnicity and cultural perception and practices could play a role in determine physical activity and sedentary behaviors among college students. The study calls for more qualitative research, and racial/ethnic and cultural-specific interventions to improve physical activity among Hispanic/Latin and Asian student populations.Kinesiology and Health Educatio

Expansion of Armatimonadetes through marine sediment sequencing reveals three classes with unique ecological roles

Marine sediments comprise one of the largest environments on the planet, and their microbial inhabitants are significant players in global carbon and nutrient cycles. With the advent of improved sampling techniques, recent scientific studies have shown the complexity of these communities and identified novel microorganisms from the ocean floor. Here we add to our understanding of understudied microbes by obtaining 77 metagenome-assembled genomes from the bacterial phylum Armatimonadetes in the Guaymas Basin, Gulf of California, and the Bohai Sea, coastal China. Seven of these MAGs are not classified at the class level. Thus, we propose to name these organisms Zipacnadia. Searches of public databases revealed that the 77 Armatimonadetes described in this study (including Zipacnadia) are globally distributed in hypoxic and anoxic environments and are dominant members of deep-sea sediments (up to 1.95% of the GB metagenomic raw reads). The Armatimonadetes described here also have unique metabolic capabilities for this phylum. They have pathways to reduce CO₂ to acetate via the Wood-Ljungdahl pathway (WLP) and generate energy through the oxidative branch of the Embden-Meyerhof-Parnas pathway using CO2 as an electron sink, maintaining the redox balance via WLP. Some of these organisms may also have an autotrophic lifestyle not previously identified in Armatimonadetes. Furthermore, these Armatimonadetes may play a role in sulfur and nitrogen cycling, using the intermediate compounds hydroxylamine and sulfite. The description of the Armatimonadetes identified in this study enhances our understanding of the diversity and metabolic potential of anoxic habitats worldwide.Marine Scienc

Microdroplet assay development for metabolic engineering and synthetic biology applications

Sustainable, efficient production of societally relevant chemicals in microorganisms is the epicenter of the field of metabolic engineering. Modern developments in DNA synthesis and sequencing have enabled high-information gene perturbation and protein engineering libraries that require reliable, reproducible, high throughput screening assays. Detailed herein are examples of utilizing growth-based assays and microfluidic screening to extract pertinent information from different gene perturbation libraries, microbial consortia, and engineered proteins. The first study details an approach to regulate gene expression in S. cerevisiae through utilization of a single-guide RNA library paired with dCas9 fused to either Mxi1 or VPR. Through these fusions and targets of guide RNAs, genes are either up or down regulated at increasing degrees. Using this library it was possible to identify target genes for moderate up and down regulation to improve growth on alternative carbon sources, namely glycerol and galactose. Final analysis of enriched guides via next generation sequencing identified moderate down regulation of essential genes, novel perturbations that would not have been isolated in traditional gene knock-out approaches. The studies detailed in chapters 3 and 4 delve into technical applications of microfluidics to screen for improved small molecule production. In chapter 2, the library detailed above is utilized to screen for gene targets that improve small molecule production in S. cerevisiae. This study also results in the development of a pico-injection microdroplet approach that utilizes cell-based biosensors to transduce small molecule production into a fluorescent signal. The study in chapter three characterizes this application further, ultimately leading identifying gene perturbations that improve early productivity or higher overall production, based on the time at which they were screened. In the fourth study, a previously developed CuAAC probe for extracellular electron transfer (EET) is ported into droplets to analyze an environmental microbial consortium. This study centers on the development of an oxygen-limited platform for anaerobic microbe cultivation in microdroplets, ultimately enriching environmental microorganisms previously uncharacterized for EET. This work expands the range of microorganisms compatible with this microdroplet system. In the final study, the microorganism array is expanded further through the development of a cytotoxicity assay for Sf9 insect cells is developed for use in microdroplets. This work lays a foundation for future applications to identify novel insecticidal toxins from engineered protein libraries. Collectively, these studies establish generalizable assays for high throughput screening of a wide array of organisms related to the field of synthetic biology.Biochemistr

“The City Residents Do Not Get Involved”: Understanding Barriers to Community Participation in a Small Texas Boomtown

Background: Professional communication researchers have engaged communities through community research and interventions, such as town halls, charettes, and participatory design work. Such interventions rely on community members who are willing to get involved, voicing their perspectives, and engaging in productive dialogue. Yet, some communities do not have these precursor conditions for intervention: they face significant social barriers that make such interventions unlikely to succeed. In an interview- and document-based study, we examine the social barriers described by interviewees in “Permia,” a small town in the Texas Permian Basin region. In contrast to the five other communities we studied, Permia participants demonstrate little readiness to engage in community dialogue. We explore how Permia interviewees made sense of unwillingness to participate in its public life, how their understandings contrasted with the other communities we investigated, and how this research might guide professional communicators as they plan future community-based interventions. Literature review: We review the professional communication research on community interventions as well as relevant sociological literature on boomtowns. Research questions: 1. How do community leaders understand their community heritage as constraining or enabling development? 2. Where do community leaders and members see potential for change and growth in community development? Where do they see barriers, threats, and hard choices? 3. How do community leaders describe the relations among community development stakeholders? How do they describe expectations and trust among them on interpersonal, intergroup, and interorganizational levels? Research methodology: We collected documents and statistics about six small Texas towns, then interviewed community leaders about the towns’ advantages and challenges. Based on those interviews, we collected further documents. We analyzed the data using deductive and inductive coding, as well as narrative analysis. Results/discussion: Through coding, we determined that interviewees saw Permia’s residents as unwilling to engage in deliberations in traditional forums such as city council meetings, and that their explanations for this unwillingness fell into three categories of barriers: distrust of institutions, dwindling personal ties, and lack of moral expectations for residents to engage in community dialogue. These three categories contrast with the other communities we studied. Through narrative analysis, we identify stories that were told by the interviewees to explain how these barriers developed in Permia. Conclusion: We conclude by discussing how professional communicators might survey barriers to community dialogue. Such surveys can help professional communicators choose a pathway for intervention in their community projects.IC2 Institut

Development of a new laser doppler vibrometer-based non-contact damage detection system for cracks in rail head

Rail defects are one of the dominant causes of train derailments and an essential factor affecting transportation safety. Among the rail defects, transverse defects (TDs), which are cracks located transversely in rail heads, are one of the main causes of derailments. When TDs are left undetected, their size expands, leading to rail breaks. Therefore, the railway transportation community is interested in the detection of such defects at speeds that do not obstruct the routine railroad operation. The goal of this research is to develop a novel LDV-based noncontact damage detection system for TDs. The tasks performed herein to achieve this goal (i.e., the objective of the study) were: (i) extensive literature review and in-situ testing to understand the vibrations resulting from the propagating waves in rail, (ii) numerical modeling of the damage detection system, (iii) rigorous laboratory and in-situ testing to understand the noise in LDV measurements as well as to evaluate the performance of the damage detection system, and (iv) analytical work to develop filters to minimize the noise in the LDV measurements. Accordingly, the configuration of the developed damage detection consists of two LDVs attached vertically in front of a rail car to measure guided waves in the rail head, which are induced by rail-wheel interaction. This system uses the LDV measurements to detect a change in the relative amplitudes of the recorded waves caused by a defect in the frequency range between 30 kHz to 100 kHz. The lower cut-off frequency was selected conservatively since it was shown in the literature that guided waves start to localize in the rail head after approximately 15 kHz. The higher cut-off frequency was selected since (i) the guided waves below 100 kHz can be used for transverse defect detection (as the frequency exceeds 100 kHz, waves are susceptible to surface defects), and (ii) the measurements collected from rail during the passage of operating trains showed that the power of the excitations induced by wheel-rail interactions is dominant up to approximately 100 kHz. The main challenge during the development of the system was speckle noise, which is inevitable due to the inherent nature of the measurements performed by LDVs placed on a moving platform. Consequently, the damage detection framework associated with the system operates as follows: 1) in the pre-processing stage, time-varying mean and impulsive noise in the recorded LDV signals are filtered and then the changes in the LDV signals in the frequency range of interest are quantified and monitored using moving standard deviation, 2) in the post-processing stage, two damage features, which are based on the relative change in the moving standard deviations and transfer functions between two measurement points are combined using multivariate statistical analysis to create a damage index that shows the location of rail segments which are affected by a defect. The goal of impulsive noise filtering and transfer functions in the framework is to minimize the speckle noise. The field tests demonstrated that rail segments consisting of a defect can be identified by the developed system.Civil, Architectural, and Environmental Engineerin

Under the aegis of the Archangel : fascism and divine kingship in interwar Romania

This report aims to take a decisive first step towards an analysis of fascism as a resuscitated form of that archaic political figuration known to religious studies scholars as divine kingship. I take this aspirational first step through a case study of The Legion of the Archangel Michael and Corneliu Zelea Codreanu, Romania’s interwar fascist movement and its founder. The report first situates itself within the ‘new consensus’ of fascist studies as represented by the theories of Roger Griffin and Emilio Gentile before delving into a history of the Legion of the Archangel Michael and C.Z. Codreanu. With this historical data in hand, I turn to an exegesis and application of some key theories on divine kingship from Ernst Kantorowicz’s The King’s Two Bodies (1957) and David Graeber & Marshall Sahlins’ On Kings (2017) to the Legion. What emerges is a distinct vision of the necessarily modern political phenomenon of fascism as in fact a kind of reboot of divine kingship for an era of mass, electoral politics.Religious Studie

The lettuce monster : a history of state violence, carceral geography and industrial agriculture in the Salinas Valley

This dissertation is a descriptive account of state violence in the Salinas Valley, a rural agricultural area on California’s Central Coast, from the 1930s to the 2010s. Chapter 1 recounts the 1934 Filipino lettuce strike and the 1936 Dust Bowl migrant strike to track how valley law enforcement departments expanded in man- and fire-power, and instituted surveillance tactics that were advanced for their time. It also examines how agribusiness leaders funded and directed strike suppression activities, and facilitated law enforcement’s acquisition of tear gas and long-range guns. These events contributed to making Salinas Valley law enforcement one of the most armed and organized forces in the nation by the end of the 1930s. Chapter 2 highlights valley law enforcement’s partnerships with federal and military agencies during World War II, as well as agribusiness’s use of Bracero and Prisoner of War labor. This chapter argues that the Salinas Valley developed a carceral geography that enabled high levels of agricultural production during the war. Chapter 3 follows the transformation of the carceral geography to include field and factory worksites, as undocumented immigrants were housed in labor camps resembling prison camps and were surveilled by growers’ private security guards, regional Border Patrol agents, and United Farm Workers strikers. Undocumented immigrants constituted a marginalized workforce that was exploited and faced dangerous work and living conditions into the 1980s. Formerly incarcerated people also form part of this workforce, and are subject to hyper-surveillance inside agricultural packing factories, and in public spaces subject to city ordinances and state probation laws. Chapter 4 examines Salinas Valley law enforcement’s increased militarization post-9/11, which was facilitated by the expansion of the Department of Defense’s 1033 Program and state and federal funding. A culture of impunity in the valley enabled law enforcement to engage in a series of unethical policing practices and financial scams, ultimately escalating to a spate of police shootings from 2014 to 2019. This dissertation ends considering how current pandemic-related measures affect policing and surveillance in the valley.American Studie

Methods for matrix completion

In this paper, we are going to provide major results for two sorts of Matrix Completion problems. One involves the recovery of a low rank matrix and the other involves the recovery of an approximately low rank matrix based on a small number of observed entries. In the end of the paper, we are going to demonstrate the feasibility of the recovery methods discussed on randomly generated low rank and approximately low rank matrices.Computer Scienc

Factors associated with food delivery app use in young adults

Food delivery apps are highly popular among young adults and are often used to purchase calorie-dense foods, which are associated with a variety of health issues such as increased risk for obesity. Limited research exists on the use of food delivery apps and the research that has been conducted, focused on adults, suggests that food delivery app use differs by sociodemographic factors. Thus, the purpose of this study is 1) to describe food delivery app use among young adults, and 2) to examine the association between young adult food delivery app use and factors including age, race, ethnicity, sex, SES, food insecurity, living arrangement, financial responsibility, and full-time student status. Data are from the Promoting Young Adult Health Survey, a cross-sectional online survey with 1,038 young adults online from the Qualtrics panel January-February 2022. Poisson regression was used to examine the relationship between food delivery app use and the sociodemographic variables. Our results suggest that participants who reported being non-Hispanic Black and Hispanic had greater food delivery app use frequency as compared to participants who reported being white. Having higher perceived subjective social status, being food insecure, being financially responsible, and being a full-time student were all significantly associated with greater food delivery app use frequency. Living with someone else was significantly associated with lower food delivery app use frequency. Age, sex, and ‘Other’ Race/ethnicity were not associated with food delivery app use frequency. Overall, young adults use food delivery apps approximately twice a week with vulnerable groups such as Black and Hispanic young adults and young adults reporting food insecurity having greater frequency of use. This study provides a first step in understanding the characteristics of young adults who use food delivery apps more frequently. Given that this new technology can both increase access to unhealthy food options as well as healthy food options, future research is needed to better understand the types of food purchased through food delivery apps and the differences by the sociodemographic factors explored in this study.Kinesiology and Health Educatio