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Hardware Approaches for Enabling Multi-Channel Multinuclear MRI/MRS
No full textThis dissertation addresses the challenges faced in exploring X-nuclear possibilities in magnetic resonance imaging and spectroscopy. While proton-based studies are common, the interest in other X-nuclei has grown rapidly. However, limited support from existing MR systems and the challenges in designing multinuclear RF coils hinder these studies. This dissertation proposes a multinuclear RF coil setup and implements two system modification approaches to overcome these challenges.
In X-nuclear studies, the use of double-tuned or multi-tuned RF coils is crucial for examining multiple nuclei without adjusting the setup. This work introduces a three-frequency volume transmit and array receive RF coil setup. The volume transmit coils include a 1H birdcage coil and a double-tuned 2H and 23Na saddle coil, designed to operate individually. A broadband decoupled four-channel receive array is inserted, allowing simultaneous signal reception from all three nuclei. This setup is evaluated through parallel imaging at 1H, 2H, and 23Na frequencies, offering a potential solution for triple-tuned X-nuclear RF coils.
Expanding MR scanners to multinuclear array receiving capability is also explored. This dissertation presents a hardware phase correction solution for receive-only frequency translation, addressing phase incoherence caused by different frequencies between transmit and receive. The proposed hardware utilizes passive phase detectors, a direct digital synthesizer (DDS), and an Arduino microcontroller to automatically correct the received signal phase during the scan and eliminates the need for storing individual echoes or FIDs and performing retrospective phase correction.
Furthermore, the dissertation introduces a cost-effective multinuclear add-on system for traditional MR scanners, enabling simultaneous multinuclear experiments. This system includes multiple transmit and receive mixing channels and a four-channel flexible Local Oscillator (LO) source. By interfacing with the spectrometer, the scanner can transmit and receive at different frequencies simultaneously, reducing experiment time. The results demonstrate simultaneous multinuclear transmit and receive capabilities with 2H and 23Na gradient echo images and interleaved transmit and simultaneous receive ability for 1H, 2H, and 23Na FIDs, showing comparable signal-to-noise ratio performance as the single-frequency operation
Improved Whitecap Quantification and Prediction Using Shipboard Remote Sensing and Machine Learning
No full textWhitecaps generated by wave breaking and air entrainment can be classified as active (stage A) or residual (stage B). Discrimination and measurement of each stage individually are essential for accurate parameterization of air-sea interaction processes, but conventional methods used for separation in visible images are subjective. This study provides a novel method to identify whitecap stages based on visible imagery using particle image velocimetry (PIV). A linear relationship was established between the lifetime of stage A and the timescale of averaged velocity. This novel method characterizes stage A whitecap lifetime using whitecap velocity and provides an objective approach to separate whitecap stages.
To estimate active whitecap fraction, we introduced a pipeline for active whitecap fraction measurement. In this pipeline, a new horizon detection method is developed to stabilize and rectify images and a deep learning model based on U-Net is trained and validated to identify and extract active whitecaps. The model is applied to 48 hours of video footage collected during a cruise in Gulf of Mexico. It is determined that, as a function of wind speed, active whitecap fraction has significant variability and disparity compared to previous research. This finding indicates that secondary factors should be considered for accurate whitecap parameterization. This is explored using principal component analyses and random forest, which indicate sea surface temperature, swell and wave age are important to active whitecap fraction. The precise impact of sea surface temperature is further explored using analyses of variance (ANOVA), which suggest it has a positive correlation with active whitecap fraction.
The decaying stage B foam with significant variability has been found to contribute 1.5 to 40 times more to total whitecap fraction than stage A foam. In this study, we present a novel model that describes the relationship between whitecap fraction and the evolution of whitecap area, providing a method to quantify the whitecap lifetime scale. The same data from a Gulf of Mexico cruise is processed using this method. The stage B lifetime scale shows weak positive correlation with active whitecap fraction and no correlation with sea surface temperature and wind speed
Three Essays on Climate Change Impacts on the U.S. Livestock Sector
No full textThis dissertation contains three essays and their contents are summarized as follows. The first essay contains a literature review regarding climate and climate change related decision possibilities as they impact livestock productivity and decisions. We covered impacts, emissions, adaptation possibilities and mitigation alternatives. We pointed out research gaps on non-ruminant animals and on settings involving developing countries.
The second essay reports on an application of econometric models to explore how climate affects livestock performance. We investigated climate impacts on the productive and reproductive performance for US cattle, hogs and chickens, using temperature humidity index (THI) as a proxy of heat stress. Our results show that climate factors play an important role in livestock productivity. Future climate projections reveal a decrease in all major livestock yield metrics, with the projected changes in yield showing geographical variations across the country.
The third essay reports on an analysis of implications of omitting or including livestock impacts within an agricultural-sector-based climate change impact appraisal. Previous agricultural sector studies have largely ignored impacts on livestock just concentrating on crops. By integrating the livestock impact projections from the second essay, we find introducing livestock impacts causes a 2.5B (22.1%) decline under RCP 4.5
Astrocytic Nik Regulates Local and Systemic Inflammatory and Metabolic Responses
No full textThough NF-��B-inducing kinase (NIK) has well-established roles in inflammatory, immune, and
metabolic regulation on a systemic level, its specific roles in the central nervous system (CNS)
are not well-defined. NIK���s tumor-intrinsic roles in glioblastoma multiforme (GBM) promoting
tumor invasion and growth suggest it could be involved in other neuroinflammatory conditions,
such as stroke and traumatic brain injury, as well as maintain tumor-extrinsic functions in GBM.
Critical in each of these conditions are astrocytes, glial cells of the CNS with diverse immune
and metabolic functions. No study has characterized the function of NIK in astrocytes. Thus, this
thesis aims to examine NIK���s roles in inflammation, immunity, and metabolism within 1) the
CNS overall and 2) specifically through astrocytes ��� critical CNS support cells.
The impact of NIK on GBM survival was investigated via orthotopic implantation of the
syngeneic GL261 GBM model in a total NIK knockout (KO) mouse model. The function of NIK
in astrocytes under basal and lipopolysaccharide-induced inflammatory conditions was explored
with a GFAP-Cre NIK KO mouse model. Output from metabolic cages, transcriptional
regulation of cytokines and metabolic markers in harvested liver and brain tissue, and protein
expression of cytokines in tissue and serum was analyzed in GFAP-Cre NIK KO and control
mice.
Loss of NIK in the GBM tumor microenvironment (TME) increased male mouse survival. With loss of NIK in astrocytes, increased signaling and decreased metabolism was noted both locally and systemically, specific to male mice. After induction of inflammation with LPS, increased astrocytic response and cytokine signaling was identified locally, and decreased tissue inflammation and metabolism systemically, again in male mice.
NIK plays a critical, pro-tumor role within the GBM TME, resulting in increased survival when knocked out. With loss of NIK in astrocytes, systemic homeostasis is impacted, specifically in signaling and metabolic regulation. These effects are significantly more pronounced in males, suggesting a critical sex-specific role of NIK in the CNS and in inflammatory CNS pathologies such as GBM
Optimal Mass Screening and Quarantine Policies in Heterogeneous Populations Under Limited Budget and Resources
No full textMass screening of populations is an indispensable public health tool that is extensively utilized in a variety of settings (e.g., screening blood transfusion, gastric cancer, sexually transmitted diseases (STDs)). The main objective is to efficiently screen a large population to accurately classify them as positive or negative for a certain binary characteristic (e.g., presence of an infectious agent). Owing to the advent of the COVID-19 pandemic, the topic of mass screening has gained considerable attention as it is a crucial aspect in effectively mitigating the spread of infectious diseases. The objective of mass screening is to maximize the overall classification accuracy under limited budget and testing resources.
We study the problem through the development of optimization-based frameworks that account for various factors, including population heterogeneity, imperfect assays, budget constraints, diverse testing schemes (individual and/or Dorfman group testing), the presence of multiple competing assays, and different testing approaches (proactive and/or reactive). These comprehensive considerations give rise to distinct optimization models. By analyzing the resulting optimization problems, we take advantage of the structure of the problem and identify efficient solution schemes.
Using real-world data, we conduct geographic-based nationwide case studies on COVID-19 screening in the United States. Our results reveal that the identified screening strategies substantially outperform conventional practices by significantly lowering misclassifications. Moreover, our results provide valuable managerial insights with regard to the distribution of testing schemes, assays, and budget across different geographic regions. Such insights can inform policy-makers with tailored and implementable data-driven recommendations.
Since screening can identify infected individuals and assess the associated risk levels, these testing efforts can significantly influence quarantine policies aimed at isolating positive cases. Consequently, our research also delves into the development of risk-based quarantine strategies. Our model takes into account the trade-off between healthcare benefits and the economic implications of quarantine measures. We show our resulting formulation can be cast as a more tractable network flow problem solvable in polynomial-time. We then proceed to calibrate our model using real-life COVID-19 and census data for the state of Minnesota. Our optimal risk-based quarantine policies exhibit substantial reductions in disease spread while maintaining favorable economic outputs
Sequence Stratigraphy and Chemostratigraphy of the Middle Cretaceous Woodbine and Eagle Ford Groups on the Southeastern Margin of the East Texas Basin and East Texas Submarine Plateau
No full textWithin the East Texas Basin (ETB), the Woodbine and Eagle Ford groups are important hydrocarbon reservoirs. However, little work was done within the southeast margin of the ETB, and adjacent East Texas Submarine Plateau (ETSP) region, to properly differentiate these units. In fact, the entire succession between the Buda Formation and Austin Groups often is referred to as the ���Eaglebine���. When defined, sandstone beds, as well as underlying mudstone beds, within it, are simply lithologically assigned to the Woodbine Group. This study takes a surface-based, or sequence stratigraphic, approach using: 1) a grid of well log cross sections, 2) x-ray fluorescence (XRF) data from cuttings and cores, and 3) previously published seismic data, to chronostratigraphically define and differentiate the Woodbine and Eagle Ford Groups across the study area.
Across much of the western portions of the study area, in Grimes and Madison Counties, a regional unconformity at the base of the Lower Eagle Ford Formation (K630sb) separates the Woodbine Group below from the Eagle Ford Group above. In this area, TOC- and Ca-rich, high-resistivity mudstone of the Lower Eagle Ford Formation unconformably overlie Al-rich, moderate resistivity mudstones of the Pepper Shale, which represent the distal downdip (basinal) equivalents of the Woodbine Group Freestone Delta.
In the western portions of the study area, in Houston and Walker Counties, a regional unconformity at the base of the Upper Eagle Ford Formation (K650sb), truncates the Lower Eagle Ford Formation near the interpreted K630 depositional shelf break. In this area, Al-rich, low-resistivity mudstone, and overlying sandstone, of the Upper Eagle Ford Formation Harris Delta, unconformably overlie Al-rich, low-resistivity mudstones, and overlying sandstones, of the Woodbine Group Freestone Delta. Fortunately, a low-resistivity marker, interpreted as regional flooding surface (K650mfs), near the base of the Upper Eagle Ford Formation can be defined, mapped, and used to differentiate strata of the Upper Eagle Ford Formation Harris Delta from the underlying Woodbine Group Freestone Delta in this area.
Finally, in the southeastern portions of the study area in Polk County, a regional unconformity at the base of the Austin Group (K720sb) truncates most, or all, of the Eagle Ford Group, and the Austin Group, or the lowermost portion of the Upper Eagle Ford Formation unconformably overlie the Woodbine Group Freestone Delta. A thick succession of the Eagle Ford Group was deposited downdip of the interpreted K630sb depositional shelf break in this region
Oebalus pugnax (Hemiptera: Pentatomidae) Resistance to ��-cyhalothrin in Texas Grain Sorghum and Efficacy of Potential Alternative Insecticides
No full textAlong the Coastal Bend of Texas, the rice stink bug, Oebalus pugnax (F.), is a pest of grain sorghum and rice that is primarily managed by application of insecticides. In 2015, a rice stink bug population from Wharton County, Texas, was found to be resistant to the pyrethroid insecticide ��-cyhalothrin, a common insecticide for rice stink bug management. In more recent years, reports of control failures have spread throughout Coastal Bend, a major hub of Texas grain sorghum production. Despite growing concern from grain sorghum producers, no studies have thoroughly evaluated the extent or geographic range of pyrethroid resistance in Texas. This thesis focuses on addressing the gaps in knowledge regarding rice stink bug pyrethroid resistance in grain sorghum and improving management tools and considerations for this pest.
Between 2021���2023, 21 rice stink bug populations across the Texas and Louisiana were evaluated for ��-cyhalothrin resistance over three grain sorghum growing seasons (2021���2023). Mortality was assessed through glass vial exposures to eight concentrations (0, 0.03, 0.1, 0.3, 1, 3, 10, and 30 ��g/vial) of the pyrethroid ��-cyhalothrin. The concentration of ��-cyhalothrin required to kill 50% (LC������) of each population was estimated by probit analysis. Furthermore, the efficacy of insecticides including pyrethroid (��-cyhalothrin), organophosphate (dimethoate), and neonicotinoid (dinotefuran) insecticides were evaluated in field experiments conducted in Nueces County, Texas in 2021. The efficacy of these insecticides was evaluated for suppression of nymph and adult rice stink bug over the course of 22 days in experimental plots.
Our results indicated numerous rice stink bug populations along the Coastal Bend were resistant to ��-cyhalothrin with LC������ values ranging from 42���1,600 times more than a susceptible population. In a 2021 field efficacy trial, ��-cyhalothrin did not provide adequate control for rice stink bugs. Dinotefuran provided excellent control of nymphs, but dimethoate provided greater control of adult rice stink bugs. This study resulted in the approval of three Section 2(ee) bulletins for dimethoate products to be used on rice stink bug in Texas grain sorghum, thereby expanding the products available for control of this pest
A Multiphysics Model for Predicting Spatiotemporal Temperature Profiles in Microwave-Heated CO2 Direct Air Capture Processes
No full textDue to alarming rise in atmospheric CO2 ppm levels, the direct air capture process has been engineered to capture low concentrations of CO2 directly from the atmosphere using chemisorbents. However, the regeneration of chemisorbents is highly energy-intensive and inefficient. To enhance this, microwave is employed for selective and targeted heating of the chemisorbent. Existing measurement techniques struggle to accurately capture the spatiotemporal temperature profile of solvent impregnated polymer (SIP) under microwave heating. Therefore, it becomes crucial to determine the spatiotemporal temperature distribution inside the polymer phase to expedite CO2 desorption, improve energy efficiency, and prevent material degradation. Motivated by these considerations, we propose a 3D-multiphysics model to study the spatiotemporal distribution of temperature inside a hybrid nanoscale multi-functional material. We focus on the microwave heating of a novel heterogeneous system comprising a SIP with a ferromagnetic additive, further solving the heat diffusion and Maxwell���s electromagnetic equations to analyze the temperature variation inside the SIP system. By coupling the physics of electromagnetism and heat transfer, our model allows for a comprehensive analysis of the temperature distribution and heating effects inside the chemisorbent. The proposed model is validated experimentally by the surface temperature findings of the SIP from IR-sensor. Additionally, we conduct sensitivity analysis of spatiotemporal temperature profile on various thermal and dielectric parameters, as well as the size and location of the Fe3O4 layer, to optimize desorption rates and make the regeneration process more energy-efficient
Ira Greenbaum field notebook: GK5001-GK5500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for GK5001-GK5500 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
Superconductivity Near a Quantum-Critical Point: Analysis of the Discrete ��-Model at Finite Temperatures
No full textNear a Quantum-Critical Point (QCP) in a metal, strong Fermion-Fermion interaction mediated by a soft collective Boson gives rise to two competing tendencies, non-Fermi Liquid behaviour and Superconductivity which differs from the standard BCS theory. In this thesis, we consider a class of models, known as ����� Model, in which the effective interaction potential takes the form V (���) ��� 1/|���| �� . We introduce some numerical and semi-analytical techniques to analyze the behaviour near QCP. Based on the mapping between Eliashberg theory and the classical spin chain, we get a discrete Hamiltonian in terms of the angles made by individual spins. 2 different numerical approaches are introduced to solve the infinite number of coupled non-linear equations resulting from minimizing the Hamiltonian, which will yield the topologically distinct minima and saddle points. We find that the minimum energy state is always a superconducting state with winding number n = 0. Other superconducting states were also found, they represent topologically different pairings with different winding numbers. These states represent the saddle points of the free energy functional. We focus our analysis mainly on the case 1 < �� < 2 at finite temperatures