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Investigating Deformation and Sediment Dispersal During Andean Mountain Building in the Western Cordillera of Southern Peru
No full textThe central Andes are the archetypal modern cordilleran margin. An assessment of the timing, style, and position of deformation and associated sediment dispersal remains incomplete, especially in the Western Cordillera and forearc. Here, much of the region is overlain by Neogene extrusive igneous products from the modern Andean arc that obscure the exposures and evidence of crustal deformation. This study exploits exposures in deeply incised canyons that provide key insights into the deformational and depositional records of the Western Cordillera and forearc in southern Peru. New U-Pb zircon geochronology, structural field mapping, aerial drone 3D modeling, sediment provenance modeling, and fault kinematic forward modeling results are integrated to constrain deformation timing and style, and sediment provenance of the forearc basin. Geochronologic results from two outcrops of thrust faults that verge toward the subduction trench, paired with outcrop interpretations and forward modeling, provide detailed accounts of fault kinematics in the forearc. One fault, termed here the Aplao thrust fault, shows evidence of at least three distinct slip events throughout a long-lived history: initial compressional deformation is constrained here to between early Cretaceous and ending prior to 45.24 Ma; syndepositional deformation between 45.24 Ma and ending between 30 and 26.67 Ma; and a final episode ending before 26.67 Ma. The other structure, termed here the Toran fault, also displays multiple phases of deformation: the structure initiated as a Jurassic normal fault related to pre-Andean extension, followed by normal fault inversion and three identified compressional slip events constrained to (1) between early-middle Jurassic and ending prior to 26.67 Ma, (2) 15.98���14.07 Ma, and (3) post14.07 Ma. Sediment provenance modeling reveals upsection unroofing of the Western Cordillera and recycling of forearc basin fill, with minimal contribution from distal sources in the Altiplano or Eastern Cordillera. Results from this investigation are integrated with published depositional and deformational age constraints to place forearc deformation into context with broader orogenic controls on Andean deformation. Protracted compression in the forearc was coincident with an Eocene���early Miocene episode of flat or shallow slab subduction. This ancient slab shallowing event also drove inboard deformation of the Eastern Cordillera. This new record of shortening and unroofing in the forearc while deformation was also ongoing in the Eastern Cordillera is evidence of widespread and distributed out-of-sequence deformation and consistent with the Andean orogen being in a protracted phase of subcritical taper. The observed thrust fault geometries are consistent with a broadly bivergent Andean cordilleran system and emphasize the role of selective reactivation and inversion of inherited structures on deformation localization. These results contribute towards a complete characterization of Andean deformation, emphasizing the need for additional investigation into the cause of this long-lived compressional deformation in the forearc, even when deformation was focused far inboard from the trench
Spatial Patterns, Drivers, and Impacts of the Urban Land Expansion in Nigeria from 1985 to 2015
No full textUrbanization is reshaping landscapes worldwide, posing considerable challenges to ecosystems, climate patterns, and resource utilization. This dissertation studies the spatio-temporal patterns of urban land change, its drivers, and its implications for biodiversity and flood exposure in Nigeria from 1985 to 2015. A pivotal aspect of the methodology is the evaluation of global urban land cover products to facilitate the understanding of urban land expansion in a context where specific national data on land cover is scarce or not available. This evaluation revealed each product's ability and limitations in accurately reflecting the reality of Nigeria's urban development. The specific findings of this research also reveal significant environmental implications, such as the loss and fragmentation of natural habitats and the exposure of urban land to flooding. Thus, the dissertation provides valuable insights that can inform urban management, policy formulation, and conservation strategies in developing urban landscapes, that are particularly tailored to Nigeria, but also indicative of other rapidly urbanizing countries across Sub-Saharan Africa
Computational Fluid Dynamics Analysis of the Blockage Accident in Wire-Wrapped Fuel Rod Bundles
No full textThe purpose for reducing CO2 emissions and enhancing the safety of nuclear reactors have led to increased interest in Liquid Metal Fast Reactors (LMFRs). These reactors offer high power density, low-pressure operation, and the ability to breed fissile material. However, LMFR fuel assemblies, comprising fuel pins enclosed in hexagonal ducts with wire-wrapped spacers, are susceptible to coolant flow blockages due to debris buildup, potentially leading to reduced heat transfer and fuel cladding damage. This PhD dissertation aims to conduct a comprehensive computational fluid dynamics (CFD) analysis of blockage accidents in wire-wrapped fuel rod bundles. The objectives include the preparation and validation of CFD models for both nominal (unblocked) conditions and various blockage scenarios, considering solid and porous blockages. Conjugate heat transfer modeling is also incorporated to simulate the cladding temperature. The proposed research activities encompass analyzing fluid flow behavior, pressure drop, velocity, turbulent structures, and temperature profiles for the different blockage configurations. Experimental data from wire-wrapped test facilities is used to validate the CFD models. These facilities have provided high-fidelity data of velocity and pressure drop for transition and turbulent flow regimes at nominal conditions, as well as for blockage scenarios with solid and porous obstructions. The CFD methodology involves solving the incompressible Navier-Stokes equations with the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) methods. The results demonstrate the accuracy of the proposed methodology in predicting friction factors and velocity profiles in both unblocked and blocked bundles after the comparison with the experimental data. The findings reveal that the presence of blockages in wire-wrapped fuel rod bundles significantly impact the thermal-hydraulic performance of LMFRs. The analyses show that solid blockages cause an increase in pressure drop and a decrease in velocity, while porous blockages have a lesser impact. The turbulence analysis reveals that the blockages lead to the formation of vortices and eddies, which can further impact the flow behavior and heat transfer. This research yields valuable insights into blockage accidents and contribute to gain more reliability in the use of CFD models for safety assessments of LMFRs
Using Antibiotic Alternative Feed Additives to Improve Overall Duck Growth Performance and Welfare
No full textGrowing ducks with optimal efficiency, health, and welfare has become of paramount importance. While numerous antibiotic alternatives (AA) have been investigated in other poultry species to reach these goals, there has been limited research on Pekin ducks. Several experiments were conducted to determine the effects including (i) organic acids (OA), (ii) oregano oils (OO), and (iii) direct fed microbials (DFM) in ducks. Experiment 1 evaluated duck growth, health, and welfare with water supplementation of OA and OO. The OA and OO improved feed conversion ratio (FCR) and body weight (BW) (P 0.05). Experiment 2 evaluated optimum inclusion rates of a commercially available (DFM) feed additive. Duck growth, stress, fear response, welfare, and litter conditions were evaluated. Results conveyed CON had higher (P 0.05) compared to CON. Experiment 3 evaluated the use of the same treatments as Experiment 2 except for the addition of a prolonged heat stress period added during the grow out. Results indicated BW and FCR compared to CON (P > 0.05) was higher than all other treatments. Total white blood cell counts were lower than CON (P < 0.05) compared to all other treatments in the DFM heat stress trial. Heterophil counts, H/L ratio, and total plasma corticosterone levels were also lower than CON (P < 0.05) compared to all other treatments reviewed whether through water supplementation or dietary supplementation. Lymphocytes counts were higher than CON (P < 0.05) compared to all other treatments. Villus height presented differences (P < 0.05) in all other treatments compared to CON. In conclusion, these experiments indicate that Organic Acid, Oregano Oils, and Direct fed microbials can be used to improve duck growth, feed efficiency, stress susceptibility, and bird welfare
Vision-Language Models: The Overlooked Role of Synonyms
No full textIn the past few years, contrastively pre-trained Vision-Language Models (VLMs) such as CLIP, have significantly propelled advancements in multimodal applications. Pre-trained on internet scale images and captions VLMs learn to associate relevant text and images, making them key to downstream applications such as visual chatbots and text-to-image generation diffusion models. However, there has been limited analysis of these models��� pre-training datasets, primarily due to the challenges posed by their large scale. Moreover, given that these datasets lack human annotation, determining the presence of specific visual concepts within them poses a significant challenge.
We address this challenge by using a Large Language Model and count the pre-training texts that contain synonyms of any given visual concept. Contrary to popular belief we discover that these pre-training datasets exhibit a long-tailed concept distribution, resulting in biased performance in VLMs.
Next we propose a novel prompting strategy that leverages synonyms to improve the performance of VLMs for zero-shot recognition. Instead of prompting VLMs using original class names, we use the most frequent synonyms found in the pre-training texts. Finally we propose a novel light-weight retrieval augmented strategy, that achieves a new state-of-the-art for the zero-shot recognition
Impact of Organic Management Practices on Soil Greenhouse Gas Emissions from Cotton-Winter Cover Crop Systems in East-Central Texas
No full textConventional cotton production practices demand extensive management involving high pesticides, fertilizers, and tillage inputs, contributing significantly to environmental impacts. To address these concerns, we explored the potential of organic cotton systems employing diverse cover crops, manure, and biochar to mitigate soil greenhouse gas (GHG) emissions while preserving soil carbon and nitrogen. Our field experiment, conducted in the humid subtropical climate of East-Central Texas, assessed various cover crops such as oats (Avena sativa), Austrian winter pea (Pisum sativum), purple top turnip (Brassica rapa subsp. rapa), and mixed species cover crops compared against a control (no cover crop) over three consecutive years. We monitored soil GHG emissions, moisture, and temperature dynamics throughout the cover crop and cotton seasons.
Simultaneously, we conducted multiple laboratory incubations to assess the carbon and nitrogen mineralization of these cover crops in combination with poultry litter manure, examining associated GHG emissions. Our laboratory simulations also considered the impact of tillage practices on residue mineralization. Additionally, we investigated the potential of cotton residue biochar to mitigate GHG emissions during cover crop and manure decomposition.
Our findings revealed that cover crops with a lower C:N ratio, especially legume and mixed species, exhibited higher GHG emissions. However, incorporating biochar alongside cover crops demonstrated significant emission reduction. Furthermore, we observed that cover crops led to reduced soil moisture during their growth phase but contributed to increased water retention during cotton seasons
Mechanisms of Circadian Clock Control of Rhythmic Translation in Neurospora crassa
No full textThe circadian clock in Neurospora crassa regulates daily rhythms in the phosphorylation and daytime inactivation of the conserved translation initiation factor eIF2��. Clock control of eIF2�� activity is responsible for the rhythmic translation of ~15% of mRNAs. Cycling phosphorylated eIF2�� levels require rhythmic activation of the eIF2�� kinase CPC-3 (the homolog of yeast and mammalian GCN2). However, how the clock controls the activity of CPC-3 is not known, and this information is critical to determine the mechanisms underlying rhythmic protein synthesis. To be activated, CPC-3 forms a complex with GCN1, which helps to bring uncharged tRNAs to the tRNA binding domain on CPC-3. In Saccharomyces cerevisiae, activation of GCN2 under stress conditions requires direct interaction of GCN1 and GCN2 with ribosomes. Furthermore, CPC-3 and GCN1 levels are clock-controlled in N. crassa. Based on these data, I hypothesized that N. crassa CPC-3 and GCN1 rhythmically interact with the ribosome, and that this interaction is necessary for rhythmic CPC-3 activity and eIF2��-controlled translation initiation. To test this hypothesis, the interaction of CPC-3 and GCN1 with ribosomes was examined in WT and the clock mutant ��frq. Ribosomes were pelleted from cultures grown in constant dark (DD) and harvested every 4 hours in a circadian time course. I found that CPC-3 and GCN1 interact with monosomes and polysomes, and that the interaction is clock-regulated with peak levels during the subjective day. We showed previously that rhythms in uncharged tRNA levels, and rhythms in CPC-3 activity are abolished in a valyl tRNA synthetase temperature sensitive mutant (un-3ts). The rhythmic interaction of CPC-3 and GCN1 with ribosomes was abolished in the un-3ts mutant, suggesting that rhythmic levels of uncharged tRNA drives the rhythmic interaction of CPC-3 and GCN1 with ribosomes. I found that disrupting the interaction between GCN1 and uncharged tRNA in the absence of GCN20, affects rhythmic CPC-3 activity. Taken together, these data support that clock regulation of rhythms in uncharged tRNA levels and rhythms in the interaction between CPC-3 and GCN1 with ribosomes are necessary for rhythmic CPC-3 activity that leads to rhythms in the translation of target mRNAs
Electrokinetic Convection-Enhanced Delivery of Macromolecules to the Brain
No full textElectrokinetic convection-enhanced delivery (ECED) utilizes an external electric field to drive the delivery of molecules and bioactive substances to local regions of the brain through electroosmosis and electrophoresis, without the need for an applied pressure. We studied the implementation of ECED to direct a neutrally charged fluorophore (3 kDa) from a doped biocompatible acrylic acid/acrylamide hydrogel placed on the cortical surface. Ex vivo (N = 18) and in vivo (N = 12) experiments were conducted to compare fluorophore infusion using ECED (time = 30 min, current = 50 ��A) and diffusion-only control trials. The linear intensity profile of infusion was significantly higher in ECED compared to control trials, both for in vivo and ex vivo. The linear distance of infusion, area of infusion, and the displacement of peak fluorescence intensity along the direction of infusion in ECED trials compared to control trials were significantly larger for in vivo trials, but not for ex vivo trials. These results demonstrate the effectiveness of ECED to direct a solute from a surface hydrogel towards inside the brain parenchyma based predominantly on the electroosmotic vector
Functional Analyses of TMTC-Type O-Mannosyltransferases in Drosophila
No full textOxygen-linked mannosylation, also known as Protein O-mannosylation, is a type of glycosylation, obstruction of which has been shown to cause severe phenotypes in humans, from neurological abnormalities to congenital muscular dystrophies. O-mannose modifications are of special interest due to their essential role in nervous system development. Protein O-mannosyltransferases (POM) are the enzymes responsible for O-mannosylation. They are highly conserved in metazoans. A majority of human O-mannosyltransferase enzymes have homologs present in Drosophila, including canonical protein O-mannosyltransferases, POMT1 and 2, (designated as Rt and Tw in Drosophila), and recently discovered non-canonical O-mannosyltransferases, transmembrane O-mannosyltransferases targeting cadherins 1-4 (TMTC1- TMTC4), all of which share conserved sequence, and structure with their human counterparts. TMTCs have been shown to selectively modify cadherins and protocadherins in humans. Yet the functions of the O-mannose modifications from individual TMTCs in humans and Drosophila are not well understood. In order to address this, we focus on elucidating the molecular mechanisms and functions of O-mannosylation mediated by TMTC1 & 2 in Drosophila. Using the advantages of the Drosophila model, I investigate the effect of TMTC-mediated modifications on the development of the nervous system, behavior, and neurological functions. In my project, I focus on a deeper understanding of how O-mannose modifications affect cadherin function at the molecular, cellular, and organismal levels. Investigating the localization, expression levels, and functional effects of TMTC targets in TMTC mutants will shed light on the function of O-mannose. I analyzed mutant alleles of TMTC1 and TMTC2 and employed rescue constructs to restore functions using both Drosophila and human constructs. I investigated possible redundancy and collaboration within the TMTC gene family by combining the downregulation of different TMTCs and using various transgenic approaches. My results revealed that TMTC1 & TMTC2 function in a partially redundant manner to establish sensory axon connections in the larval brain. My results shed light on the in vivo functions of TMTCs, their role in the regulation of cadherin functions, and have built a Drosophila model for further elucidation of the mechanism of thus highly conserved non-canonical O-mannosylation pathway in animals, including the role of TMTC genes in human biology and pathological conditions
Design, Development, and Characterization of a 3D Solar Heat Exchanger
No full textThis thesis presents a multifaceted approach to the design, characterization, and development of a 3D Solar heat exchanger, employing state-of-the-art Computational Fluid Dynamics (CFD) and experimental techniques. The Solar Model represents a compact and innovative multi-level heat exchanger, incorporating intricate design elements such as pin-fins, vanes, multiple fluid passages, or channels. The primary objective of this design is to bolster heat transfer efficiency by prolonging the contact duration between the fluid and the heat transfer surfaces. To substantiate the theoretical models and designs, a comprehensive CFD and experimental study of the 3D model was conducted. CFD has proven to be an effective tool in the design and optimization of heat exchangers by considering thermal properties and it has been employed to study different modifications, compare results, and present the best possible combination of variables to ensure optimum performance. The proposed experimental procedure was implemented, with a step-by-step guide for system setup, including the installation of a solar collector, heat exchanger, and fluid circulation system. Measurement devices, comprising of thermocouples and pressure transducers, were placed throughout the system to monitor temperatures, pressure drop, and heat transfer rates under varying experimental conditions.
This comprehensive research endeavor not only explores the theoretical aspects of solar design and optimization using CFD but also validates these models through practical experimentation. The findings emphasize the paramount role of design configurations and parameters, particularly the aspect ratios and how they influence the overall thermal performance of solar systems. This combined approach paves the way for the advancement of efficient solar thermal systems, contributing to sustainable and eco-friendly energy solutions.
Steady state CFD simulations were conducted to study the fluid flow patterns, velocity profiles and temperature distribution of the solar at different aspect ratios. The modified geometry with an aspect ratio of 0.5 led to a more homogenous temperature distribution within the computational domain characterized by well-distributed fluid flow patterns. The modified geometry was then selected for fabrication so a prototype could be characterized experimentally. Experimental results revealed that the overall heat transfer coefficient, U, increased with flow rate. Furthermore, U reached an optimum value between 2.8 and 3.0 l/min, suggesting that the flow behavior inside the solar heat exchanger reached an optimum condition despite depicting higher pressure drop at higher flow rates. In summary, designing, numerically simulating, and experimentally characterizing a solar heat exchanger with features such as long fins and guide vanes proved to be a successful heat exchanger development approach. Such an approach should help the development of heat exchangers for renewable energy applications