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La Imagen del Recuerdo: Sagrada Memoria y Always from Somewhere Else de Marjorie Agos��n
No full textEl presente trabajo propone un an��lisis comparativo de Sagrada memoria (1994) y Always from somewhere else (1998) de la escritora chilena Marjorie Agos��n. Estas obras presentan los recuerdos de Frida y Mois��s Agos��n, los padres de la autora, pero constituyen un testimonio que va m��s all�� de sus vivencias personales. Estos testimonios trascienden el ��mbito familiar conformando memorias colectivas, siendo el retrato de la realidad heredada por los supervivientes del Holocausto que emigraron a Latinoam��rica. Los recuerdos, marcados por la imaginaci��n y subjetividad, son reflejo de experiencias discriminatorias antisemitas, pero tambi��n raciales y de g��nero. El presente estudio tiene como principal objetivo el an��lisis comparativo de dichas memorias en cuanto a conceptos como testimonio, memoria, postmemoria e imaginaci��n ic��nica, entre otros. Dicho an��lisis nos lleva a encontrar las siguientes tem��ticas comunes: el mandato jud��o de recordar, el trauma heredado, la imposibilidad de narrar el recuerdo, el antisemitismo, el exilio, la identidad del sujeto diasp��rico, la subjetividad, el imaginario o memoria social o colectiva y el reconocimiento. Estas tem��ticas permiten establecer nexos entre estas memorias y la concepci��n art��stica de la artista judeo-chilena Patricia Israel, cuya obra tambi��n conjuga la imagen y la palabra con el fin de abordar la memoria tanto privada como colectiva. La imaginaci��n ic��nica juega un papel importante en la elaboraci��n de im��genes verbales, lo que permite establecer relaciones entre la narraci��n y algunas de las obras del pintor jud��o Marc Chagall que propongo como un intertexto visual, as�� como entender el significado simb��lico que los tatuajes y los trenes adquirieron a partir del Holocausto. Adem��s, el contraste entre las memorias permite realizar una lectura de g��nero que manifiesta los estereotipos codificados en cuanto a la vida y funciones de la madre y del padre
Advancing Iron Catalyzed Three-Component Cross-Coupling Reactions
No full textTransition metal���catalyzed cross-coupling reactions are some of the most widely used methods in chemical synthesis. Notable advantages of iron as a potentially cheaper, more abundant, and a less toxic transition metal catalyst have drawn the interest of our lab, in particular to explore the mechanism of action in three-component radical cross-couplings. In the first project, we explored the difunctionalization of unactivated olefins with alkyl halides and Grignard reagents. The reaction tolerates a wide range of sp^2 hybridized nucleophiles, alkyl halides, and unactivated olefins bearing a diverse range of functional groups.
Our second work highlights iron���s practical application in more elaborate multicomponent cross-couplings including formation and trapping of ��-boryl radicals and allyl alkyl halides for practical synthesis of cyclic fluorous compounds. Incorporating fluorine into drug scaffolds remains of utmost importance in medicinal chemistry since it generally increases lipophilicity, stability, and overall lifetime, and ~20% of drugs on the market contain at least one C-F bond. In that vein, pinacol boronate esters and boronic acids are excellent building blocks due to their reaction efficiency, low cost, and ability to be transformed into many other desired functional groups.
The final research focus is on using a mechanistic-driven approach towards designing new chiral organoiron catalytic species capable of controlling the C-C bond formation with diverse C-centered radicals. To date, there are only three examples of enantioselective iron-catalyzed cross-coupling reactions, and all are limited to the union of only two components. We reported a practical and simple protocol that uses commercially available and inexpensive iron salts in combination with chiral bisphosphine ligands to enable the regio- and enantioselective (up to 91:9) multicomponent cross-coupling of vinyl boronates, (fluoro)alkyl halides, and Grignard reagents. Preliminary mechanistic studies are consistent with rapid formation of ��-boryl radical followed by reversible radical addition to mono-aryl bisphosphine-Fe(II) and subsequent enantioselective inner-sphere reductive elimination. Overall, my research is expected to expand the field of asymmetric iron cross-couplings and have broad implications towards the synthesis of bioactive compounds via the use of alkenes to translocate alkyl radicals, modify their steric and electronic properties, and induce stereocontrol
The Coordination Between Peptidoglycan Hydrolases and Synthases in Myxococcus xanthus
No full textPeptidoglycan (PG) defines cell shape and protects bacteria against osmotic stress. The growth and integrity of PG require coordinated actions between synthases that insert new PG strands and hydrolases that generate openings to allow the insertion. However, the mechanisms of their coordination remain elusive. Here, I show that moenomycin that inhibits a family of PG synthases known as Class-A penicillin-binding proteins (aPBPs), triggers cell lysis despite aPBPs being non- essential for cell growth. We demonstrate that inhibited PBP1a2, an aPBP, accelerates the degradation of cell poles by DacB, a hydrolytic PG peptidase, in the bacterium Myxococcus xanthus. Moenomycin reduces the mobility of DacB molecules through PBP1a2, potentially promoting the binding between DacB and PG. Conversely, DacB also regulates the distribution and dynamics of aPBPs. These findings reveal the lethal action of moenomycin and suggest that disrupting the coordination between PG synthases and hydrolases could be more lethal than eliminating individual enzymes. The process of sporulation provides a unique scenario in M. xanthus to study PG regulation. Sporulation is the process by which spherical spores are formed in M. xanthus, from its regular rod shape in vegetative cells. Surprisingly, in our model organism, there is complete degradation of PG during this rod-to-sphere transition during chemically induced sporulation as well as during the formation of fruiting bodies. During this process, there is an upregulation of PG hydrolases, enzymes which are usually redundant in bacteria. Lytic transglycosylases, which cleave the glycan backbone, are important for the process of sporulation, and our results identified MXAN_3363 (LtgA) and MXAN_4034 (LtgB) as important for the process of sporulation, the former for glycerol induced sporulation and the latter for both sporulation pathways
Improving Access to River Discharge Data Through Satellite Remote Sensing
No full textRivers are a critical engine for the transportation of water, nutrients, and sediments across landscapes, making them an integral natural resource for many ecosystems and civilizations. Historically, river discharge, the volumetric flow of water at a point, has been measured using river gauges. These gauge discharge measurements serve a vital role in water resource management by improving our understanding of river dynamics and informing flood predictions. In this dissertation, I compile the largest collection of publicly available river gauge data and analyze this database for spatial and temporal trends in river gauge availability. I find that global gauge availability has remained stable since 1980 but the gauge network is biased towards the Americas and Europe. In addition, I find that 77% of global gauge records are not available in real-time, limiting our ability to make effective water management decisions. To alleviate the issues associated with the global gauge network, I leverage satellite remote sensing to provide real-time estimates of discharge in both gauged and ungauged reaches. By developing empirical relationships between gauge discharge measurements and satellite river widths, I am able to add nearly 300 thousand daily discharge observations to the global gauge record. Along ungauged North American reaches, I develop an algorithm, RODEO, to estimate river discharge efficiently and accurately from Landsat imagery. RODEO is available as a publicly available Google Earth Engine application and provides a path forward for the accurate quantification of remote sensing of discharge uncertainty. River discharge can directly influence and be influenced by lake dynamics. With the aim of better understanding lakes and rivers as an interconnected system, I develop the LakeFlow algorithm. LakeFlow leverages satellite observations from the recently launched Surface Water and Ocean Topography (SWOT) mission and mass conservation principles to estimate discharge at river-lake boundaries. LakeFlow has been tested using synthetic datasets at three lakes and shows promising accuracy. Ultimately, LakeFlow can be used to provide discharge at approximately 35 thousand river reaches globally
Applying Topology-Based Machine Learning to Risk Stratification in Pulmonary Arterial Hypertension
No full textRisk assessment instruments such as REVEAL Lite 2 can identify patients at high risk for events related to Pulmonary Arterial Hypertension (PAH). However, some patients classified as low or intermediate risk can still experience disease-worsening events, suggesting that these patients are at increased risk beyond that specified by traditional risk stratification tools.
We utilized a dataset of 109 consecutive PAH patients seen between January 2016 and December 2019. PAH-related worsening events occurred in 22 patients. An event was defined as the initiation of parenteral prostacyclin, lung transplantation referral, or death. The 87 patients without an event were used as controls. Echocardiography and REVEAL Lite 2 variables were obtained 4-8 months prior to an event. Topological Data Analysis (TDA), a machine-learning method well-suited to finding hidden patterns in high-dimensional datasets, was used to analyze the dataset. The TDA results then guided Kolmogorov-Smirnov Two-Sample Tests to identify variables differentiating event-prone patients from low-event patients.
Kolmogorov-Smirnov Two Sample Testing of event-prone and low-event patients across all three risk levels showed REVEAL Lite 2 had a KS-Score of 0.303, putting it below echocardiographic variables such as end-systolic eccentricity index (0.625) in terms of differentiating between the two groups.
In this single center machine learning-based study, TDA was able to identify a unique phenotype of patients defined by worsened echocardiographic parameters who were at high-risk of PAH-related events even when deemed low-risk by traditional risk assessment scoring methods. Future risk stratification studies should consider TDA and other machine learning methods
Geomicrobiology of Seafloor Basalts and Viral Metagenomes of Seafloor Habitats in the Pacific Ocean
No full textSeafloor basalts, inactive sulfides, and seamounts represent broadly distributed biospheres on the seafloor. Here, the microbial community composition, functional potential, and extracellular enzyme activity rates were assessed within these seafloor habitats, with an emphasis on seafloor basalt samples. Extracellular enzyme activity assays were performed using seafloor basalt from the East Pacific Rise (EPR) 9��50'N and Davidson Seamount, to understand their role in carbon, nitrogen, and phosphorus acquisition. Metagenomics was also used to evaluate the differences in the microbial community composition and functional potential of seafloor basalts from two different age groups represented by two separate eruptions at EPR 9��50'N. Viruses from metagenomes of seafloor basalts, inactive sulfides, and ferromanganese crust from the EPR 9��50'N, Southern Mariana Trough, PACManus, and Takuyo-Daigo Seamount were also analyzed to characterize the overall viral community composition, auxiliary metabolic gene function, and virus-host linkages. The analyses conducted here offer an insightful understanding of the resident microbial community within seafloor habitats, shedding light on their nutrient acquisition mechanisms via extracellular enzyme activity, and their genetic potential to uptake and utilize nutrients in their environment. In addition, these analyses explore the previously overlooked role of viruses in the survival of the prokaryotic community present. The abundance and importance of these seafloor habitats in the ocean emphasizes the need to understand the ecology of the resident microbial life, and their potentially significant role in marine nutrient cycling
Multi-Physics Modeling and Simulations of Heat Pipe Cooled Graphite Moderated Micro Reactor
No full textHeat pipe micro reactors are compact, innovative nuclear reactors that utilize heat pipe technology to manage heat transfer efficiently. The advantage of heat pipe micro reactors lies in their reduced complexity, high efficiency, and ability to provide stable power in various scenarios where traditional, larger reactors are not feasible or practical. This research presents a multi-physics analysis focusing on a proposed design of 0.5 MWth heat pipe cooled, graphite moderated nuclear micro reactor. The main driver of the design study was to achieve enhanced safety characteristics, while maintaining long core lifetime and excellent power producing capabilities. The envisioned outcome was a versatile design adaptable to various purposes including remote locations and space applications.
In order to assess the safety characteristics of the design, investigations of the main reactor parameters were performed through developing a multi-physics tool, that included a neutronic model, point kinetics model, thermal conduction model, heat pipe model, and mechanical model. All models were coupled through a python wrapper to allow for appropriate data exchange. The neutronic model of the design was developed using MCNP and Serpent Monte Carlo codes, in order to calculate important parameters including criticality, control devices worth, power distribution, and temperature reactivity coefficients. The thermal conduction model of the solid-state core was developed and coupled to a heat pipe model using Ansys Fluent, to calculate the temperature distribution in the reactor, while Ansys Mechanical was employed to conduct structural mechanical analysis through performing calculations of the stress, strain, and total deformation of the core. Multi-physics simulations of the design were carried out to provide analysis of both steady-state normal operating conditions and transient scenarios, including accidents related to heat pipe and control drum failures. The obtained results were used to assess the safety aspects of the proposed design and provide valuable insights necessary for the development of heat pipe micro reactors in the near future
Multi-coil Wireless Power Transfer Systems Analysis and Design
No full textWireless power transfer (WPT) technology is growing fast and has been used for various applications. experiencing rapid growth and finding applications across various sectors. Emerging markets, such as consumer electronics, electric vehicles, and medical implants, are actively exploring the integration of wireless power transfer as an energy solution. Numerous studies have advanced proposals for WPT coil designs, resonant circuit designs, and the incorporation of wide bandgap devices into WPT systems. Concurrently, multi-coil WPT systems, employing more than one coil on either the transmitter or the receiver, have gained prominence. Among these, three-phase wireless power transfer systems have demonstrated several advantages and exhibit potential as viable solutions for technical challenges encountered in the industry.
The first research topic revolves around wireless lithium battery charging, a critical component of electric vehicles. The charging process for lithium batteries requires a sequential application of constant current (CC) charging succeeded by constant voltage (CV) charging. This paper presents a novel reconfigurable compensation topology designed for three-phase wireless charging systems. The reconfigurable compensation topology facilitates a seamless transition between the inductor-capacitor-capacitor-parallel (LCC-P) configuration and the inductor-capacitor-capacitor-series (LCC-S) configuration. This enables the output to exhibit CC and CV characteristics, respectively.
The second research topic delves into wireless power transfer for autonomous underwater vehicles (AUVs). Charging AUVs presents unique challenges due to insulation and water leakage issues when submerged. The application of three-phase wireless power transfer encounters complexities, primarily stemming from uncontrollable docking angles leading to rotational misalignment issues. In response to these challenges, a three-phase wireless power transfer coil resistant to rotational misalignment has been proposed, simulated, and tested
Markov Duality and Asymptotics of Interacting Particle Systems
No full textWe propose novel algebraic methods to Markov dualities. The first method produces orthogonal polynomial dualities from the ������bialgebra structure of Drinfeld���Jimbo quantum groups. The ������structure allows for the construction of certain unitary symmetries, which imply the orthogonality of the duality functions. In the case of the quantum group Uq(gln+1), the result is a nested multivariate q���Krawtchouk duality for the n���species ASEP(q, ��). The method also applies to other quantized simple Lie algebras (e.g. so2n) and to stochastic vertex models. The second method constructs duality functions for integrable dynamic models. This method will be implemented on dynamic stochastic higher spin vertex models, where we prove the duality functions between the dynamic stochastic higher spin vertex models and non dynamic stochastic higher spin vertex models are the 3��2 functions. A degeneration of these duality functions is dual q���Krawtchouk polynomials, which agree with orthogonal polynomial dualities between ASEP and dynamic ASEP of Groenevelt���Wagenaar [1]. The method involves using the universal twister of Uq(sl2), viewed as a quasi���triangular, quasi���������Hopf algebra. The algebraic method is presented very generally and is expected to produce duality functions for other dynamic integrable models.
As probabilistic applications of the duality relations found, we provide the explicit contour integral formula of the q���shifted factorial moments (namely the q-analogue of the Pochhammer symbol) for the two���species q���TAZRP (totally asymmetric zero range process). We use those contour integral formulas to find the asymptotics of the two���point correlations. In addition, we also focus on the open symmetric exclusion process with parameter m (open SEP(m/2)). Based on duality relations, we prove that the hydrodynamic limit of the density profile for a d���dimensional open SEP(m/2) solves the (d + 1)���dimensional heat equation with certain initial condition and boundary condition. Last, as an application of the duality of dynamic six vertex model, we prove ii that the asymptotic fluctuations of the dynamic stochastic six vertex model with step initial conditions are governed by the Tracy���Widom distribution
Applied and Theoretical Approaches to Decision Making in Agriculture
No full textThis work consists of three essays, each demonstrating economic approaches to decision making.
In the first essay, the choice of which Title I farm program to enroll in is modelled as a quadratic integer programming problem. This framework is used to determine optimum program selection for upland cotton producers in Hale County Texas with average risk aversion.
The second essay quantifies the gains in efficiency resulting from recent infrastructure development in the Southern Plains region of Texas. The transportation of agricultural commodities on public roads imposes a number of costs on the state. These include increased road maintenance, ecological damage and traffic congestion in urban centers. The presence of these externalities can lead to inefficient market outcomes. This paper uses a linear programming model to study recent changes to the supply chain of cottonseed and lint and the associated improvement in efficiency.
The third essay is a theoretical piece that expands traditional consumer theory, allowing it to be used in new contexts. It uses this framework to explore and reconcile opposing viewpoints on the value of work. It demonstrates that the process of producing commodities is a potentially important source of utility and failing to account for this results in a misleading evaluation of welfare changes associated with a modification of manufacturing methods