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John Bickham field notebook: Scalaris_AK800-AK856,pdf
No full textEach page/AK number corresponds to a karyotype slide data and/or unique specimen.Data pages for Scalaris_AK800-AK856,pdf 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
Selective Modulation of Metal-Insulator Transitions Through Ion Irradiation and Ion Implantation for Neuromorphic Applications
No full textVanadium dioxide (VO2) is a strongly electronic correlated material that exhibits a metal insulator transition (MIT) at 68 ��C. The MIT can result in a up to four orders of magnitude change in electrical conductivity, which is coupled with a structural phase transition (SPT) where VO2 transforms from insulating monoclinic to metallic rutile. The nonlinear characteristics of charge transport related with this phase transition enable non-linear dynamical behavior that are of interest for neuromorphic computing applications.
Despite this interest, application of VO2 to devices and circuits for the purpose of emulating neuronal behavior is limited by 1) control over electrical transport behavior in the two phases, and 2) control over aspects of the structural transition itself, including the extent of phase coexistence. All these factors play a role in both emulating neuronal character and extending the lifetime of a VO2 memristor. Previous research has focused on either 1) chemical doping of VO2 2) use of strain via lattice mismatch and 3) creation of defects all to modify aspects of the transformation.
To address these challenges this work focuses on the intersecting effects of chemical doping, lattice strain, and irradiation induced defects on the electrical transport and neuronal oscillatory behavior of VO2. The main focus is to map material property changes to engineer nonlinear behavior in memristive devices. Chapter 2 and 3 first explore He+ irradiation as an effective method to selectively tune the �� of both phases without changing other aspects of the transformation. Chapter 4 explores trends between transport changes and electro-thermal oscillations by comparing pristine, He+ irradiated, and Ge+ implanted memristor devices
How the Presence of In-Group Peers and Experts Influence Stem Undergraduate���s Identity, Persistence, and Academic Success
No full textEfforts to confront complex societal challenges are hindered by the lack of diversity in the science, technology, engineering, and mathematics (STEM). As education is a social enterprise, investigating how social interactions support or hinder belonging and persistence is crucial for the success and retention of historically underrepresented (HU) students. This three-article dissertation sought to understand and quantify how the presence (or lack thereof) of ingroup peers and experts in a student���s network influences domain-specific motivation and persistence intentions for HU STEM students. Study 1 uses ego-centric social network analyses to evaluate how the characteristics of mentees and mentors relate to the content of support and structure of mentor networks in a large sample of White and Hispanic/Latino(a) STEM undergraduates. Mentee perceived psychological similarity with their mentor(s) predicted both dyadic and network average levels of mentor support (i.e., psychosocial, career, role modeling) and relational satisfaction. Additionally, demographic homophily and engagement in undergraduate research were related to some mentor network structures. Study 2 extended this work by evaluating how characteristics of mentees, including if they have a mentor, and the quality and structure of their individual networks related to social integration, well-being, academic success, and persistence in STEM over two years. Having a high-quality mentor network, rather than the absence or presence of one or multiple mentors, was an important predictor of domain identity and well-being for students, which ultimately led to persistence in their STEM major. Finally, Study 3 narrowed the scope of social supports by analyzing patterns of demographic and psychological factors between students in one sophomore- and junior-level undergraduate Engineering and Computer Science (ECS) classroom. LNAM results revealed the presence of network clustering based on similar levels of domain identity. Additionally, domain values were positively related to STEM persistence intentions. This work critically addresses several significant gaps in the literature at the intersection of motivation and social networks for HU STEM undergraduates. Results inform best practices for developmental mentor network support, program developments, and interventions at the classroom level aimed to enhance social supports for students, ultimately addressing the nation���s goals to broadening participation in STEM fields
Underexplored Aspects of Host Finding and Host Acceptance in Parasitoid Wasps
No full textParasitoids use sensory cues, such as olfactory infochemicals, that can be emitted directly by their potential herbivore hosts or plants as a damage response to herbivory to locate potential hosts for oviposition. Despite intensive studies on interactions between parasitoids and their host, certain aspects of chemical communication of the interaction still need to be explored. This study aimed to study the different understudied aspects of odor-mediated host finding and acceptance response of two parasitic wasps (Hymenoptera: Braconidae) with varying degrees of host specificity, Microplitis croceipes (Cresson) (specialist) and Cotesia marginiventris (Cresson) (generalist), integrating multiple tools (analytical, behavioral, electrophysiological). These aspects include the use of plant volatile to determine the parasitism status of damaging hosts, parasitoid���s use of host cuticular composition as cues for host acceptance, and the influence of associative learning of host-related odor in the odor-mediated flight behavior of specialist parasitoids.
The existing literature on the chemical ecology of host selection behavior of parasitoid wasps was discussed, the understudied aspects were identified, and a rationale for the study was provided. Behavioral bioassays were conducted to test the ability of specialist M. croceipes to utilize plant volatiles as host-discrimination cues and found that parasitoids can discriminate and show a preference for volatiles from plants infested by unparasitized hosts over volatiles from plants infested by parasitized hosts and was mediated by the alteration in plant volatile emission due to infestation by parasitized hosts. Behavioral and electrophysiological studies were performed to evaluate the role of host cuticular composition in mediating host recognition and acceptance behavior of M. croceipes and C. marginiventris and reported that specialist parasitoids are more dependent on host-specific kairomonal cues than generalist during host acceptance. The effect of associative learning on the odor-mediated flight behavior of M. croceipes was evaluated by performing a wind tunnel bioassay using two host-related compounds, ��-pinene, and ��-farnesene, and found that odor learning results in enhanced and directed upwind flight towards the learned odors. Results from this dissertation have contributed to our understanding of the understudied but essential aspects of semiochemical-mediated behavior and foraging strategies employed by parasitoids during odor-mediated host findings
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
Investigating Vaccinia Virus D10 and Its Homologs
No full textRNA decapping is a fundamental step in eukaryotic mRNA metabolism facilitating the regulation of gene expression by initiating mRNA decay or translational repression. Poxviruses and other nucleocytoplasmic large DNA viruses (NCLDV) encode mRNA decapping enzymes to modulate host and viral RNA levels during infection. The decapping activity is catalyzed by the nudix motif in the protein, which removes the 5��� end m7G cap structure of eukaryotic mRNA by hydrolysis. The prototype poxvirus, vaccinia virus (VACV), encodes two mRNA decapping enzymes: D9 and D10. Previous research has demonstrated the importance of these enzymes by showing a reduction in viral replication when the nudix motif is disabled by mutating key amino acids. Our lab recently showed that VACV D10 colocalizes with mitochondria and that colocalization is also required for VACV replication, hinting at important regulatory mechanisms for D10���s decapping function. Here, we characterized a recombinant VACV with both D9 and D10 knocked out (v���D9���D10). We compared the viral replication dynamics and plaque sizes between v���D9���D10 and the nudix mutant virus (vD9muD10mu). We found that v���D9���D10 showed a significant decrease in both plaque size and viral replication as compared to vD9muD10mu. This result suggests critical regulatory mechanisms of D9/D10 decapping activity that are required for efficient VACV replication. The v���D9���D10 recombinant virus was then used to investigate the ability of D10 homologs to compensate for the loss of D9 and D10. Our findings suggest that the ability of mRNA decapping enzymes to compensate for lack of D10 is unlikely to correlate to the overall sequence similarity, suggesting a more complex regulation mechanism of decapping enzyme���s functions. Additionally, investigation into structural homology led to the discovery that the mitochondrial localization motif recently identified in D10 is structurally conserved in many of the tested homologs. These findings also indicate the possibility that decapping enzymes homologous to D10 may also possess unique functions which aid in their effectiveness
Single-Phase and Two-Phase Flow Visualization Experiments in Molten Salt Natural Circulation Loop
No full textA natural circulation loop facility was designed to mitigate major challenges in flow visualization experiments of molten salt. Single-phase and two-phase flow experiments were conducted for molten salt and compared to experiments with water as a benchmark study. Particle image velocimetry (PIV) measurements and continuous temperature measurements were obtained. In single-phase flow experiments, the full velocity field and near wall velocity field were captured and analyzed as a function of the Prandtl number. The friction factor and Nusselt number were determined and compared with correlations found in literature. System Analysis Module (SAM) code validation was performed using a one-dimensional fluid flow model of the experimental facility. Two model types were developed using the default friction factor in SAM and user input of the experimental friction factor. The accuracy of the model improved in predicting the velocity in the loop with input of the experimental friction factor. Successful validation was found for developed flow cases of water and molten salt. A cooling transient due to heater failure and subsequent salt solidification in the natural circulation loop facility was presented as a scaled-down accident scenario of a salt plug blockage during reactor shutdown. A main heater failure resulted in immediate cooling of temperatures around the loop, and available backup heaters were not able to compensate for the initial loss of power. The transient was analyzed in seven phases to describe the overall behavior in the loop as salt cooled to the freezing point. Two-phase flow visualization experiments were conducted for three argon bubble sizes injected into a co-current stream of molten salt in the natural circulation loop facility. Similar bubble sizes were injected in experiments with water to compare the bubble shape, trajectory, and wake flow behavior of the fluids. The bubble region of interest (ROI) was found to determine the equivalent diameter and terminal velocity as the bubble traveled through the test section. PIV analysis was performed and used with the bubble ROI to determine the slip ratio and slip velocity between the liquid phase and gaseous phase
Selective Modulation of Metal-Insulator Transitions Through Ion Irradiation and Ion Implantation for Neuromorphic Applications
No full textVanadium dioxide (VO2) is a strongly electronic correlated material that exhibits a metal insulator transition (MIT) at 68 ��C. The MIT can result in a up to four orders of magnitude change in electrical conductivity, which is coupled with a structural phase transition (SPT) where VO2 transforms from insulating monoclinic to metallic rutile. The nonlinear characteristics of charge transport related with this phase transition enable non-linear dynamical behavior that are of interest for neuromorphic computing applications.
Despite this interest, application of VO2 to devices and circuits for the purpose of emulating neuronal behavior is limited by 1) control over electrical transport behavior in the two phases, and 2) control over aspects of the structural transition itself, including the extent of phase coexistence. All these factors play a role in both emulating neuronal character and extending the lifetime of a VO2 memristor. Previous research has focused on either 1) chemical doping of VO2 2) use of strain via lattice mismatch and 3) creation of defects all to modify aspects of the transformation.
To address these challenges this work focuses on the intersecting effects of chemical doping, lattice strain, and irradiation induced defects on the electrical transport and neuronal oscillatory behavior of VO2. The main focus is to map material property changes to engineer nonlinear behavior in memristive devices. Chapter 2 and 3 first explore He+ irradiation as an effective method to selectively tune the �� of both phases without changing other aspects of the transformation. Chapter 4 explores trends between transport changes and electro-thermal oscillations by comparing pristine, He+ irradiated, and Ge+ implanted memristor devices
Influence of Dietary Saccharomyces cerevisiae Fermentation Product on Markers of Inflammation and Cartilage Metabolism in Young Exercising Horses Challenged with Intra-Articular Lipopolysaccharide
No full textThe objective was to evaluate dietary Saccharomyces cerevisiae fermentation product (SCFP) on joint inflammation and cartilage metabolism in exercising yearlings challenged with intra-articular lipopolysaccharide (LPS), hypothesizing SCFP (TruEquine��C, Diamond V Mills, Inc.) would ameliorate inflammation and increase cartilage metabolism. Thirty Quarter Horse yearlings were stratified by bodyweight (BW), age, sex, and assigned to (n =10/dietary treatment): control (0), 46, or 92 mg/kg BW/d SCFP. Treatments were top-dressed to 1% BW concentrate. Horses were stalled, offered ad libitum Coastal bermudagrass hay, and exercised for 30 min/d, 5 d/wk. Every 21 d, wither height (WH), hip height (HH), heart girth (HG), body length (BL), and BW were obtained. On d 46, horses underwent an LPS challenge with each radial carpal joint receiving 0.8 mL of a 0.5 ng LPS solution or sterile lactated Ringer���s solution (LRS). Synovial fluid was collected pre (h 0), and 6, 12, 24, and 336 h post-injection, and analyzed for prostaglandin E2 (PGE2), carboxypropeptide of type II collagen (CPII) and collagenase cleavage neopeptide (C2C) via ELISA, and chemokines (CCL2, and CCL11) and cytokines (TNF�� and IL-10) via multiplex platform. Rectal temperature (RT), heart rate (HR), respiration rate (RR), and carpal circumference (CC) were recorded prior to arthrocentesis. Data were analyzed using MIXED procedure of SAS. By d 56, growth parameters increased (P < 0.01) where control had a greater increase in BW than SCFP groups (P < 0.01). Clinical parameters were uninfluenced by diet (P ��� 0.29) but varied over time (P ��� 0.03). Treatments didn���t influence CPII, C2C, CPII:C2C (P ��� 0.46) or logPGE2, logCCL2, CCL11, and logIL-10 (P ��� 0.23). There was an interaction for CCL11 (P = 0.04) where control was greater than SCFP groups at h 6. Furthermore, logIL-10 had an interaction where 46 mg/kg was lower at h 12 compared to control and 92 mg/kg (P = 0.05). There was a treatment effect for TNF�� (P = 0.04) where 92 mg/kg was lower than 46 mg/kg and tended to be lower than control. Although SCFP didn���t influence cartilage metabolism or logPGE2, SCFP may ameliorate inflammatory cytokines and chemokines following an acute, intra-articular insult
Single-Phase and Two-Phase Flow Visualization Experiments in Molten Salt Natural Circulation Loop
No full textA natural circulation loop facility was designed to mitigate major challenges in flow visualization experiments of molten salt. Single-phase and two-phase flow experiments were conducted for molten salt and compared to experiments with water as a benchmark study. Particle image velocimetry (PIV) measurements and continuous temperature measurements were obtained. In single-phase flow experiments, the full velocity field and near wall velocity field were captured and analyzed as a function of the Prandtl number. The friction factor and Nusselt number were determined and compared with correlations found in literature. System Analysis Module (SAM) code validation was performed using a one-dimensional fluid flow model of the experimental facility. Two model types were developed using the default friction factor in SAM and user input of the experimental friction factor. The accuracy of the model improved in predicting the velocity in the loop with input of the experimental friction factor. Successful validation was found for developed flow cases of water and molten salt. A cooling transient due to heater failure and subsequent salt solidification in the natural circulation loop facility was presented as a scaled-down accident scenario of a salt plug blockage during reactor shutdown. A main heater failure resulted in immediate cooling of temperatures around the loop, and available backup heaters were not able to compensate for the initial loss of power. The transient was analyzed in seven phases to describe the overall behavior in the loop as salt cooled to the freezing point. Two-phase flow visualization experiments were conducted for three argon bubble sizes injected into a co-current stream of molten salt in the natural circulation loop facility. Similar bubble sizes were injected in experiments with water to compare the bubble shape, trajectory, and wake flow behavior of the fluids. The bubble region of interest (ROI) was found to determine the equivalent diameter and terminal velocity as the bubble traveled through the test section. PIV analysis was performed and used with the bubble ROI to determine the slip ratio and slip velocity between the liquid phase and gaseous phase