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Antimicrobial Resistance Dynamics in Poultry Environment and the Role of Insects as Vectors of Resistance
No full textThis study investigated the potential role of insects in the spread of antimicrobial resistance (AMR) within and around broiler-rearing facilities, specifically focusing on antimicrobial resistance genes (ARGs). By evaluating spatial patterns of AMR, defining the diversity and presence of ARGs, and analyzing the implications for animal and human health, we aimed to better understand AMR dynamics in broiler production environments. We employed multiple sampling techniques to collect insect and environmental samples. Shotgun sequencing was performed to examine the microbial communities and determine the presence of antimicrobial-resistant genes. Spatial variations in AMR and evaluation of elements influencing AMR dissemination were assessed by statistical analysis. Results from this research uncovered a diverse assortment of pathogens and AMR genes within the livestock environment, and highlighted insects as potential vectors for the transmission of resistant bacteria. Variations in AMR occurrence were found among the sampling sites, emphasizing the need for directed surveillance and intervention protocols. The findings of AMR in broiler farms indicated that antibiotic-resistant bacteria pose risks to food safety, human and animal health, and animal welfare, highlighting the necessity of dynamic management practices. Altogether, this study expands upon the understanding of AMR dynamics in broiler facility landscapes and showcases the significance of managing AMR in livestock environments to protect human and animal health. Additionally, our findings highlight the need for integrated management strategies considering the intricate interactions between microbes, arthropod vectors, livestock, and the environment in limiting the spread of AMR
Bifacial Passive Radiative Cooling of Silicon Solar Cells Using PDMS for Increased Efficiency
No full textWith the rising levels of pollution and environmental degradation due to fossil fuel energy, there is an urgent need for clean and renewable energy. To compete with the vastly greater generation capacity of fossil fuels, the sources of renewable energy need to be more efficient at lower cost. There has been an increasing amount of work in improving the efficiency of solar cells by using several different materials and methods to generate power more effectively. However, all standard solar cells heat up in the course of operation under the sunlight. This heat absorption comes with significant reductions in the efficiency, reliability, and overall lifespan of the solar cells. In this thesis research, we present a relatively inexpensive, energy efficient and simple way to increase the efficiency of a solar cell by using a high emissivity material showing the effectiveness of radiative cooling on the simplest monocrystalline silicon solar cell. We found that coating a high emissivity material, such as PDMS, on both top and bottom of a solar cell allows for a large amount of thermal radiation to be removed to outer space, which acts as the ultimate heat sink. With in-field tests, we found an average temperature reduction of 6��C of a 1.06% performance increase. Considering the limited power conversion efficiency of a typical solar cell, we anticipate that energy efficient radiative coolers will be ubiquitous in the upcoming generations of solar cells
Investigating Chronic Enterocolitis in Rhesus Macaques (Macaca mulatta) as a Natural Model for Post-Infectious Irritable Bowel Syndrome and the Role of Campylobacter spp. in Disease Development
No full textCampylobacter jejuni and C. coli represent the leading causes of bacterial gastroenteritis in humans worldwide and up to 20% of infections will result in post-infectious irritable bowel syndrome (PI-IBS). Investigations into the pathogenesis of PI-IBS have been hampered by lack of a complete animal model for the syndrome. We aimed to investigate the chronic diarrhea syndrome known as chronic enterocolitis (CE) in rhesus macaques (Macaca mulatta), and the potential contribution of Campylobacter infection to this syndrome, as a naturally occurring model of PI-IBS. We characterized subjective and objective variables in sections of the lower intestinal tract in 16 healthy rhesus macaques and compared these results to a cohort of 37 animals euthanized for CE. Similar to PI-IBS, animals with CE had elevated total leukocyte populations in the large intestine and significantly increased intraepithelial CD3+ T cells in the colon and rectum. Unlike PI-IBS, neutrophils were increased in CE and enteroendocrine cells, enterochromaffin cells, and mast cells displayed no differences between study groups. We then utilized culture, qPCR, and whole genome sequencing (WGS) to characterize the Campylobacter sp. circulating in the study colony. Culture and WGS of 275 samples yielded a non-clonal population of 103 C. coli and 8 C. jejuni isolates, each containing genes for all three subunits of cytolethal distending toxin. Certain MLSTs were found only in animals with intestinal disease and some only in healthy animals. Antimicrobial resistance patterns were similar between these isolates and human reports. qPCR detected a higher prevalence of both bacteria than culture, the quantity of bacteria was significantly higher in animals with intestinal disease, and nearly 1/3 of animals were positive for both C. jejuni and C. coli. Using generalized linear mixed modeling, the only significant risk factor for the presence of Campylobacter sp. or intestinal disease was young age. Ultimately, we added to the understanding of CE, identifying areas where the syndrome overlaps with PI-IBS and areas that warrant further investigation, and advanced our knowledge of Campylobacter sp. circulating in rhesus macaques, allowing honing of future studies to investigate a causal link between the bacteria and CE as exists in PI-IBS
Misc. Karyotypes: Misc_TK4525-TK15371_karyotypes.pdf
No full textEach page/AK number corresponds to a karyotype slide data and/or unique specimen.Data pages for Misc_TK4525-TK15371_karyotypes corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
Design and Evaluation of Scancap: A Low-Cost, Reusable Tethered Capsule Endoscope with Digital Chromo-Endoscopy Imaging for Unsedated Screening and Early Detection of Barrett���s Esophagus
No full textEsophageal adenocarcinoma (EAC) is the sixth leading cause of cancer death worldwide. Early detection and treatment of Barrett���s esophagus (BE), a precursor to EAC, increases the five-year survival rate from 18% to 98%. BE is a global challenge; however, current endoscopes for early detection of BE are costly and require extensive infrastructure for patient examination and sedation. We describe the design and evaluation of the first prototype of ScanCap, a high-resolution optical endoscopy system with a reusable, low-cost tethered capsule designed to provide high-definition, digital chromoendoscopic imaging for early detection of BE in unsedated patients. The tethered capsule (12.8 mm diameter, 35.5 mm length) contains a color camera and rotating mirror and is designed to be swallowed; images are collected as the capsule is retracted manually via the tether. The tether provides electrical power and illumination at wavelengths of 415 nm and 565 nm and transmits data from the camera to a tablet. The ScanCap prototype capsule was used to image the oral mucosa in normal volunteers and ex vivo esophageal resections; images were compared to those obtained using an Olympus CV-180 endoscope. Images of superficial capillaries in intact oral mucosa were clearly visible in ScanCap images. Diagnostically relevant features of BE, including irregular Z-lines, distorted mucosa, and dilated vasculature, were clearly visible in ScanCap images of ex-vivo esophageal specimens
Development of an Active Barium Vapor Notch Filter for Ultraviolet Scattering Based Diagnostics
No full textAtomic and molecular filters are proven tools in laser-based diagnostics. Their use as notch filters has greatly expanded the usefulness of scattering phenomena in both ground testing and remote sensing applications. However, current filtering technology limits researchers to the use of the frequency doubled Nd:YAG signal (532 nm) or more rare and complicated lasers such as Ti:Sapphire and Dye lasers. The visible spectrum presents eye safety issues and lacks the molecular scattering signal strength found in the UV. This work aims to develop a vapor filter functioning at the near UV wavelength of the Nd:YAG third harmonic (355 nm). The frequency required for this filter, which utilizes an excited state transition in atomic barium vapor, falls between the ozone absorption region and the retinal hazard region, provides a stronger backscattered signal than visible light, and can be easily attained with the robust and commonly used high-power Nd:YAG laser. These benefits have significant implications for atmospheric measurements, including the aerosol profiling technique of High Spectral Resolution Lidar (HSRL). Through a combined theoretical and experimental effort, a barium vapor filter has been fabricated and characterized for a variety of filter conditions. The results for low vapor pressures of barium are particularly notable and represent the first reported measurements of the absorption feature of interest in the absence of a neutral buffer gas. The addition of a weak argon buffer gas reduced spatial diffusion, resulting in a more stable and deep absorption feature, capable of implementation in scattering based diagnostics. The AURa (Aggie Ultraviolet Rayleigh) Lidar facility has been developed to serve as a testbed for this and other lidar techniques. Aerosol backscatter and extinction results using the novel filter, which mark the first HSRL measurements at 355 nm with a vapor-based filter, will be presented alongside a discussion of the measurement errors and suggested improvements to this system. Finally, a few other applications of the novel filtering approach will be examined
Higher-Dimensional Data in Powder-Bed Fusion Additive Manufacturing: A Path to Improved Printability Predictions
No full textThis dissertation explores the optimization of alloy design and process parameters in metal additive manufacturing (AM), specifically focusing on powder bed fusion (PBF) processes like laser powder bed fusion (L-PBF) and electron beam powder bed fusion (EB-PBF). Conventionally, process parameters for well-known alloys were optimized in hopes of achieving properties similar to those obtained using traditional manufacturing methods. However, the potential of AM processes, particularly PBF, demands the development of alloys tailored to exploit these unique benefits. The complexity of PBF systems, with numerous design degrees of freedom, necessitates a strategic approach to alloy design and process parameter optimization.
To address these challenges, this dissertation introduces two frameworks centered around the use of higher-dimensional data. The first framework is a purely data-driven model that efficiently explores composition and process parameter spaces. Drawing from a database collected from the literature and in-house experiments, this screening tool incorporates classification techniques to predict process defects and identify regions conducive to good printability. Alloys with larger printability regions are better suited to be fabricated using PBF processes.
The second framework is a physics-based model for the fine-tuning of metal alloy printability. Overcoming challenges present in current frameworks, this model employs dimensionality reduction techniques and regression methods to predict higher-dimensional spatial thermal field outputs instead of relying on lower-dimensional melt-pool dimensions. This approach allows for predicting melt-pool dimensions at varying layer thicknesses and beam spot sizes without the need for additional experiments. This allows for the exhaustive exploration of the process parameter design space.
Overall, the dissertation���s focus on leveraging higher-dimensional data provides a comprehensive and efficient methodology for advancing alloy design and optimizing process parameters in PBF processes, contributing to the evolution of metal additive manufacturing
Spatial Transformer Network You Only Look Once (STN-YOLO) for Improved Object Detection
No full textObject detection plays a crucial role in the field of computer vision by enabling machines to identify and locate objects within images or videos. There are several state-of-the-art object detection approaches and the most common model is You Only Look Once (YOLO). YOLO is a single-shot algorithm that directly classifies an object in a single pass by having only one neural network predict the bounding boxes and class probabilities. The baseline YOLO model may encounter challenges in detecting objects within cluttered or partially occluded scenes. Furthermore, the model may face difficulty in detecting small objects or those with low contrast. To improve the performance of the baseline model, a spatial transformer network (STN) is incorporated into YOLO baseline model.
The results showcase the efficacy of the end-to-end pipeline, highlighting the innovative application of STN integrated with YOLO that demonstrates improved object detection performance through quantitative metrics (e.g., precision, accuracy, recall and intersection over union). This study also investigates of the impact of different localization network in the STN like RESNET18 and VGG16 on the object detection. The objective of incorporating the STN module into YOLO is to enhance the model���s capability not only to attend to the most relevant regions in an image but also to perform spatial transformations such that the image is aligned before the detection is performed. The detected image can be used to perform analysis by extracting relevant information in terms of features or statistics from images
Electric Powertrain Models for Small UAS Conceptual Design
No full textSmall, battery powered unmanned aerial systems (SUAS) have become indispensable tools for researchers, civilians, and warfighters. However, conceptual designers do not have rigorous tools to design and analyze their electric powertrains which consist of brushless DC motors; therefore, lid-state motor controllers, and lithium polymer batteries. Literature models to analyze the components��� efficiencies rely on detailed information that a vehicle designer cannot practically acquire at the early design stage, such as empirical test data. Therefore, engineers must rely on inaccurate constant powertrain efficiency assumptions which lead to subpar designs. Moreover, existing models ignore the influence of a component���s thermal dynamics on size and performance; therefore, these models could lead to designs that are significantly over or undersized depending on the thermal conditions in which the existing models��� underlying data was collected. Consequently, the resulting designs can overheat or add too much weight penalty in the final vehicle. We have developed a set of efficiency, thermal, and sizing models to address this literature gap in the design and analysis of electric powertrains. We validated these models using wind tunnel tests, motor teardowns, and flight tests. Individually, the models can predict a motor���s efficiency, heat transfer, mass, and electrical constants given high-level inputs which a user can easily find at the conceptual design stage. The models capture the coupled dynamics of a motor���s size, performance, and thermal response. The nuanced results enable users to size the optimal motor for a desired application and given thermal conditions. We also developed efficiency models for the motor controller and battery which rely on fewer inputs than similar literature models, and we validated them with parametric experimental tests. Finally, we developed an instrumentation system that measured and recorded a quadcopter���s propeller torque, propeller speed, and electrical power during flight. We used the flight data to validate an integrated powertrain model that combined the motor, motor controller, and battery efficiency models. The integrated model predicted the vehicle���s battery discharge within 5% of flight data for a six-minute flight. The integrated model enables a user to evaluate different powertrain configurations for an entire mission using readily available inputs
On the Security of End-to-End Encrypted Messaging and Calling Applications
No full textIn recent years, the use of end-to-end encrypted messaging and calling applications has risen, driven by the need for secure communications. While these applications protect against unauthorized access, concerns about potential vulnerabilities have emerged. End-to-end encryption (E2EE) aims to safeguard private communications, yet fears of eavesdropping and communication manipulation linger, especially from government entities or attackers. Despite its effectiveness, E2EE integrity can be compromised, like through key substitution attacks. Worries center on authentication ceremonies and potential user errors leading to man-in-the-middle (MitM) attacks. Additionally, the introduction of client-side scanning (CSS) in secure applications to detect harmful content raises privacy concerns. CSS���s local processing or endpoint filtering could undermine the promised encryption guarantees.
In this dissertation, we delve into the complexities surrounding the use of end-to-end encrypted messaging and calling applications, addressing issues of impersonations, MitM attacks, authenti-cation ceremonies, and the topic of CSS technology. Our work provides a systematic analysis of E2EE functionality and authentication ceremonies in popular applications. We propose an auto-mated approach to enhance and streamline the authentication ceremony within encrypted applications. Our work highlights vulnerabilities in voice-based authentication and stresses the need for stronger security measures. Additionally, we investigate the risks of using social media networks in the authentication ceremony and examine potential threats related to CSS technologies and their impact on E2EE principles.
Our dissertation provides the following contributions: First, we conduct a comprehensive security analysis of existing studies, identifying flaws and vulnerabilities in widely used encrypted applications, particularly focusing on authentication ceremonies. Second, we explore automated methods to enhance the authentication ceremony and reduce reliance on user interaction. Third, we undertake simulated investigations to identify potential vulnerabilities arising from exclusive reliance on a voice channel for the authentication ceremony in a real-world end-to-end encrypted application. This could compromise the security of static media and textual communications. The insights from our study suggest enhancing the security of end-to-end encrypted apps by using phonetically distinct words for codes, implementing warnings for suspicious voice code usage, employing multiple authentication channels, and prioritizing ongoing research for stronger security measures. Fourth, we introduce a novel investigation targeting social media authentication ceremonies, illustrating potential risks associated with user impersonation through counterfeit ac-counts. Our study suggests enhancing social media authentication security by displaying comprehensive user details, promoting hands-on user verification, using visual cues for unique identifiers, advocating continuous monitoring and adaptation, and fortifying end-to-end encrypted applications with multi-channel authentication. Lastly, we introduce an encrypted keyboard to address concerns related to CSS technology