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Design, fabrication, and development of GeTe phase-change switches for reconfigurable RF applications
Get PDFThis research is devoted to studying the chalcogenide phase change material (PCM) properties and their potential capability in RF switching applications. The goal of RF switches would be to realize the reconfigurability and adaptability of RF and microwave systems. The current RF switches are primarily based on solid-state and, more recently, micro-mechanical technologies. Each has limitations like integration compatibility, cost, reliability, or power handling. In the beginning, PCM was employed almost exclusively in non-volatile memory usage. However, PCMs exhibit properties that can improve the current state-of-the-art RF switches, like high contrast between electric conductivity in their two stable states. This means switches with low loss and high isolation subsequently translate to high cutoff frequency (fCO).
Another feature that is very suitable for RF systems is PCM switches’ very low power consumption. They require power only during state changes and can keep their state since both crystalline and amorphous phases are stable at room temperature. Among all chalcogenide PCM compounds, germanium telluride (GeTe) has features like fast switching speed and low resistivity in
the crystalline state, which makes it the best candidate for RF applications. This work presents the study of GeTe growth, crystallization, and design of RF switches utilizing it. A novel, physical vapor deposition (PVD) method called pulse electron-beam deposition (PED) was experimentally studied to investigate the requirements for the ablation of GeTe. It will be discussed
that the as-grown GeTe is amorphous and why the initial crystalline state is preferred. In order to convert the GeTe thin film into a crystalline formation, post-treatment annealing was performed. To optimize the post-annealing procedure, several annealing parameters were experimentally investigated. The thin film resistivity dropped by six orders of magnitude upon the crystallization
process. The crystallized GeTe thin films were investigated by contemplating the crystallite quality and the electrical conductivity performance. In the following, the design and fabrication of RF ohmic switches, as well as the challenges and solutions, are discussed in detail. Also, PCM-based RF switches are modeled to perceive their behavior better
Race, politics and sports history : 1960-1980
Get PDFThis thesis project encompasses the overlap of sports, political, and social history. This provides a unique insight into issues of racial inequality and how they relate to larger geopolitical context of the 1960s into the 1980s. Political engagement appeared at international events, including the Olympics. At the 1968 Olympic Games, for instance, athletes here used symbolic protests to address social unrest. In the transition into the 1970s, athletes continued to engage with issues of equality. African American athletes used domestic and international competitions in order to articulate protests against discrimination. Those athletic events held some level of politicization stemming from the Cold War. The United States used the Olympic Games to project a political stance by leading sixty-five nations by leading a boycott of the 1980 Olympics. Meanwhile, in the United Kingdom, two soccer fans, Riaz Khan and Mark Kelly provide insight into themes of sports violence, racial discrimination and other challenges within the same timeframe considered. They paradoxically engaged with hooliganism through anti-social behavior in order to find acceptance into society. This research explores how the athletes and fans used athletic competitions in domestic and international settings to critique and find new ways of coping with social inequality. The realm of sports provides a space for belonging and worthiness through community, culture and empowerment for underrepresented communities
Implementing work-from-home benefits into the workplace post-COVID-19 pandemic
Get PDFThe COVID-19 pandemic is something the world experienced together, yet altered our day-to-day lives in countless diverse ways. Some examples include how we attend school, how and where we exercise, and how we run our typical, weekly errands. For many, the biggest change caused by the pandemic was the impact on the workplace and its interior environment. Many of these changes directly impacted on full-time employees, for instance, the way work tasks were completed, as well as the location tasks were completed in. The purpose of this study is to recognize ways interior designers, architects, and even employers can help to improve employee satisfaction and productivity levels. The study compares similarities and differences of indoor environmental qualities (IEQ), as well as other interior factors like privacy and biophilic design elements, between home and workplace office environments for employees. The study focused solely on full-time employees over the age of eighteen years old who worked any amount of time at home before returning to their workplace. The method of this study used an online survey platform which made it easy to keep the data organized. Survey participants must be older than eighteen years, as well as a full-time employee. The goals of the survey included identifying positive and negative factors relating to the interior workplace environment in hopes of improving employee satisfaction and productivity. The results of this study have reassured that this topic on improving the post-pandemic workplace to better mimic the benefits found working from home is important and critical in the guaranteed improvements to employee satisfaction and productivity regarding the post-pandemic workplace environment.
Keywords: work-from-home, WFH, return-to-office, RTO, return-to-workplace, COVID-19, pandemic, post-pandemic, workplace, satisfaction, production, indoor environmental quality, biophilic desig
Validation and application of a liquid chromatography-tandem mass spectrometry method for mitragynine in postmortem blood and liver
Get PDFKratom is a tree originating in Southeast Asia, and has a history of usage among farmers. The leaves of the tree were chewed and used by farmers as a stimulant in order to work long days. Over the years, the popularity of the drug spread worldwide and has risen in recent years. In 2016, kratom was put on a Drugs of Concern list by the United States Drug Enforcement Administration (DEA). A lack of research including studies for mitragynine and 7-hydroxymitragynine has been observed, and there are even fewer postmortem case studies in the literature. The rise in kratom usage was noticed in the casework of the Office of the Chief Medical Examiner (OCME) Toxicology Laboratory in Oklahoma. The number of cases involving mitragynine, an alkaloid in kratom, has risen over recent years, but the OCME did not have a validated method for quantitation. The importance of this thesis project was to validate a method for the quantitation of mitragynine and qualitative identification of 7-hydroxymitragynine, assess the stability of the two alkaloids in three different storage conditions (ambient, refrigerated, and frozen), and examine real world cases coming through the OCME. The extraction utilized in this method was a phosphate buffer followed by filtering the samples using 3 mL columns containing diatomaceous earth. Extracts were then concentrated by drying them down, reconstituted, and washed with hexanes. The samples were then analyzed using liquid chromatography paired with tandem mass spectrometry (LC/MS-MS). The method for quantitation of mitragynine was validated with the criteria of interferences, bias, precision, ion suppression/enhancement, limit of detection, carryover, calibration model, and stability taken into consideration. The validation criteria for 7-hydroxymitragynine were interferences, ion suppression/enhancement, limit of detection, carryover, and stability. All criteria were met and deemed acceptable by the OCME lab's Quality Assurance Program. The stability study demonstrated that mitragynine is more stable in refrigerator conditions as opposed to freezer, and that 7-hydroxymitragynine went through an approximate 20% decrease over 65 days in the refrigerator in blood. The case studies had ranges of 130-1,400 ng/mL for heart blood, 130-1,300 ng/mL for femoral blood, and 220-7,000 ng/mL for liver. Central/Peripheral (C/P) and Liver/Peripheral (L/P) ratios were calculated to identify the potential for mitragynine to undergo postmortem redistribution (PMR). The C/P and L/P ratios were an average of 1.0 and 2.7 respectively, suggesting that mitragynine does not experience significant PMR. This thesis project will be adding to the body of knowledge concerning mitragynine and 7-hydroxymitragynine which will help researchers and postmortem labs assess the storage conditions of their specimen and help with interpretation of toxicology results in death investigations
The Risks of Rhetoricity: Accounting for Intellectual Disability in the Rhetorical Tradition
Get PDFI am troubled by the notion that what specialists in my field call “rhetoricity”—the quality of being able to assess an audience and effectively influence their thinking—is what separates humans (“rhetors”) from non-humans. This binary is problematic when we account for individuals with intellectual/developmental disabilities (I/DD), whose rhetorical prowess diverges from our accepted models. Recent trends in rhetorical studies, however, have widened how rhetoric defines itself, including expanding not only what rhetoric is and does, but also what entities (ex. animals, objects, sounds) are able to exercise agency. Yet, little scholarship has taken up people with I/DD as sites of rhetorical possibility. My project explores this possibility by examining the intersection of rhetorical theory and profound cognitive impairment. I analyze the generative potential of the past and future of intellectual disability in order to understand not only how rhetoric has influenced the understanding of and treatment of disabled people, but how disability collides with the study of rhetoric. Each chapter of my project excavates how rhetoric shapes the material reality of disability and the ways in which the bodies and minds of people with intellectual disabilities transform our understanding of rhetoric. My findings suggest that embracing profound disability deepens the scope of rhetorical studies and challenges our understanding of rhetoric’s origins, functions, and boundaries. In doing so, I offer a richer, more diverse view of what it means not only to be rhetorical, but to be an active, valued participant in the world
Interpretable deep neural networks for more accurate predictive genomics and genome-wide association studies
Get PDFGenome-wide association studies (GWAS) and predictive genomics have become increasingly important in genetics research over the past decade. GWAS involves the analysis of the entire genome of a large group of individuals to identify genetic variants associated with a particular trait or disease. Predictive genomics combines information from multiple genetic variants to predict the polygenic risk score (PRS) of an individual for developing a disease.
Machine learning is a branch of artificial intelligence that has revolutionized various fields of study, including computer vision, natural language processing, and robotics. Machine learning focuses on developing algorithms and models that enable computers to learn from data and make predictions or decisions without being explicitly programmed. Deep learning is a subset of machine learning that uses deep neural networks to recognize patterns and relationships.
In this dissertation, we first compared various machine learning and statistical models for estimating breast cancer PRS. A deep neural network (DNN) was found to be the most effective, outperforming other techniques such as BLUP, BayesA, and LDpred. In the test cohort with 50% prevalence, the receiver operating characteristic curves area under the curves (ROC AUCs) were 67.4% for DNN, 64.2% for BLUP, 64.5% for BayesA, and 62.4% for LDpred. While BLUP, BayesA, and LDpred generated PRS that followed a normal distribution in the case population, the PRS generated by DNN followed a bimodal distribution. This allowed DNN to achieve a recall of 18.8% at 90% precision in the test cohort, which extrapolates to 65.4% recall at 20% precision in a general population. Interpretation of the DNN model identified significant variants that were previously overlooked by GWAS, highlighting their importance in predicting breast cancer risk.
We then developed a linearizing neural network architecture (LINA) that provided first-order and second-order interpretations on both the instance-wise and model-wise levels, addressing the challenge of interpretability in neural networks. LINA outperformed other algorithms in providing accurate and versatile model interpretation, as demonstrated in synthetic datasets and real-world predictive genomics applications, by identifying salient features and feature interactions used for predictions.
Finally, it has been observed that many complex diseases are related to each other through common genetic factors, such as pleiotropy or shared etiology. We hypothesized that this genetic overlap can be used to improve the accuracy of polygenic risk scores (PRS) for multiple diseases simultaneously. To test this hypothesis, we propose an interpretable multi-task learning approach based on the LINA architecture. We found that the parallel estimation of PRS for 17 prevalent cancers using a pan-cancer MTL model was generally more accurate than independent estimations for individual cancers using comparable single-task learning models. Similar performance improvements were observed for 60 prevalent non-cancer diseases in a pan-disease MTL model. Interpretation of the MTL models revealed significant genetic correlations between important sets of single nucleotide polymorphisms, suggesting that there is a well-connected network of diseases with a shared genetic basis
Balas y palabras: novela, testimonio y crónica sobre el sicario colombiano (1988-2023)
Get PDFThis dissertation analyzes the sociocultural phenomenon of hitmen in Colombia through its literary representation during the last 35 years. During that time, the figure of the hitman acquired great prominence both in the social reality and in the literary world of that country. More than one generation of writers has been interested in addressing the world of urban violence and has found in it an inexhaustible source of stories. Even today, the literary production on hitmen is still valid and has great commercial interest. This study analyzes the different representations of the Colombian hitman in the last decades from the genres of the novel, the testimony, and the chronicle. The narratological theories that are used here to analyze each work are those proposed by Gérard Genette and Mikhail Bakhtin. In this research, each text analyzed offers a new perspective to understand what the phenomenon of hitmen has represented for Colombian identity and imaginary. To achieve this objective, a study of the following texts is made: El sicario (1988) by Mario Bahamón Dussán, No nacimos pa’ semilla (1990) by Alonso Salazar, La Virgen de los Sicarios (1994) by Fernando Vallejo, Rosario Tijeras (1999) by Jorge Franco, Sangre Ajena (2000) by Arturo Alape, Balas por encargo by Juan Miguel Álvarez (2013) y Sobreviviendo a Escobar: «Popeye» el sicario 23 años y 3 meses de cárcel (2015) by Jhon Jairo Velásquez. Likewise, this work proposes to categorize Colombian literature on the hitman into three main groups: «the sicaresque novel», «the sicaresque testimony» and «the sicaresque chronicle». From the studies of each narrative, the importance of hitmen for Colombian identity is established, and a current autochthonous narrative of that country is identified
Frequency-agile filtering antennas for S-band and X-band applications
Get PDFMulti-functional, highly flexible, and tightly integrated Radio-Frequency Front-Ends (RFFEs) are at the forefront of the current developments to improve the performance of next-generation wireless RF systems. In the past decade, filtering antennas, or filtennas, have emerged as a potential solution to minimize the Radio-frequency system's cost and complexity while maximizing performance in a highly integrated module. The RF co-design approach of combining the filtering and radiation functionalities into a single unit is beneficial for improving a system's Signal-to-Noise (SNR) performance while limiting interference in a congested frequency spectrum. Furthermore, frequency-agile filtennas can enhance an RF system's adaptation to changing radio environments.
The work presented in this thesis utilizes conventional bandpass filter synthesis techniques to enhance the performance of tunable filtennas for next-generation RFFEs. By using high- Evanescent-mode (EVA-mode) cavity resonators and highly efficient slot antennas, multiple filtenna designs are demonstrated. First, the building blocks of the filtennas are individually developed. A novel Evanescent-mode Cavity-Backed Slot Antenna (ECBSA) with contactless capacitive tuning is designed for radiation functionality. Long-range external linear actuators are deployed to tune the critical gap size of the cavity. Experimental results of the antenna demonstrate a high power-handling capacity and wide tuning from 1.7 GHz to 2.6 GHz (40\%). The ECBSA is then integrated with a contactless-tuned EVA-mode resonator to form a 2nd-order tunable filtenna. The fabricated filtenna demonstrates frequency tuning from 2-2.6 GHz (26\%), with a peak realized gain ranging from 2.7~dB to 5.2~dB. The filtenna showed excellent tuning reliability due to the deployed closed-loop monitoring system and exhibits state-of-the-art performance in the class of tunable cavity-based filtennas.
The frequency scalability of the tunable filtenna is next investigated in the X-band (8-12~GHz) frequency regime. A new filtenna structure and tuning scheme is conceptualized by incorporating varactor diodes on a novel superstrate-loaded cavity-backed slot antenna. The performance trade-offs and loss analysis is completed by analyzing the resistive losses associated with tuning varactors. In addition, a new technique is proposed to estimate a varactor's quality factor for high-frequency applications. The proposed method does not require any calibration or de-embedding processes. The varactor- estimation technique can effectively estimate the bias and frequency-dependent varactor quality factor for any reconfigurable RF application
Characteristics and Lifecycles of Anticyclonic Tropopause Polar Vortices
Get PDFTropopause polar vortices (TPVs) are sub-synoptic, long-lived, closed circulation features located in the upper-troposphere and lower-stratosphere region. Although TPV circulations can be cyclonic or anticyclonic, most previous studies have focused only on cyclonic TPVs, especially due to their direct influence on weather systems, including Arctic cyclones, but also cold air outbreaks and severe convection in middle latitudes. Cyclonic TPV longevity is unique to polar regions due to the relatively limited role of latent heating and the more dominant role of longwave radiative cooling. TPVs are also important to global circulations as recent studies have shown that cyclonic TPVs can exit the Arctic and interact with the polar jet, causing the initiation of Rossby wave packets on the polar jet. Rossby wave initiation and subsequent Rossby wave breaks (RWBs) and blocking patterns cause high-impact weather from droughts and floods to heatwaves and cold air outbreaks. However, current models have low skill when forecasting RWBs and blocking patterns, especially in the sub-seasonal to the seasonal timeframe.
This study aims to determine if anticyclonic TPVs are associated with RWBs and impact the development and persistence of blocking patterns. It is hypothesized that anticyclonic TPVs form from poleward RWBs and are important potential vorticity anomalies that aid in the maintenance of blocking patterns. It is also hypothesized that examining the lifecycles and characteristics of anticyclonic TPVs can improve understanding and forecasting of RWBs and blocking patterns. ERA5 data are used to create cyclonic and anticyclonic TPV and block tracks. The characteristics and lifecycles of all three are compared. Results show that anticyclonic TPVs have significantly shorter lifetimes than their cyclonic counterparts while decreasing in maximum intensity on average throughout their lifetime. Anticyclonic TPVs have less seasonal variability than cyclonic TPVs. The maxima in anticyclonic TPV genesis locations overlap the maxima in RWB and blocking frequencies. Anticyclonic TPVs are found to be in close spatial and temporal proximity to known blocks. Composites of multiple blocking and RWB indices show that ATPVs are most commonly associated with cyclonically sheared, poleward RWBs
Comparative analysis of survey methodologies for population-level studies of Texas horned lizards (Phrynosoma cornutum)
Get PDFTexas horned lizards (Phrynosoma cornutum) are classified by the Oklahoma Department of Wildlife Conservation as a Tier 1 Species of Greatest Conservation Need and have similar designations throughout their range. Updated population assessments are needed range-wide to understand the current state of Texas horned lizard populations. However, most Texas horned lizard studies have relied upon fortuitous encounters and the lack of a standardized approach for population monitoring has significantly hampered our understanding of population trends. I carried out, with the assistance of field technicians, two summers of Texas horned lizard field research in western Oklahoma. I performed a comparative assessment of strategic survey methods: road cruising, drift fence arrays, and foot searches using transects and plots. Effort (person-hours) was logged for all methodologies. Road cruising surveys performed the best, with an average of 3.5 person-hours/Texas horned lizard followed by drift fence arrays (38.2 person-hours/Texas horned lizard) and plot foot searches (42.2 person hours/Texas horned lizard). Not all road types performed equally; one-lane gravel/dirt roads had the highest number of Texas horned lizards/km. Occupancy analyses using road cruising survey data indicated that the number of observers (one vs. two) did not significantly impact detection, whereas observer identity did affect detection, regardless of prior experience. Occupancy analyses indicated that time of day and time of year were important detection factors, with earlier in the day and in the spring/early summer showing higher detection probability. The number of recaptured lizards was inadequate to generate reliable population estimates using mark-recapture methodologies, and obtaining enough recaptures for these methods may be problematic. When comparing all methods, road cruising surveys are the most efficient and effective way to strategically survey Texas horned lizards, and care should be taken to plan surveys in a way that optimizes detection, limits bias, and ensures datasets are comparable across the range