136879 research outputs found
Sort by
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
Investigating the Impact of Timing of Basal Leaf Removal and Fruit Thinning on Potassium Accumulation in Red Wine Grapes
No full textIn hot climates such as Texas, high juice/wine pH represents a serious challenge for wineries. The objective of this study was to evaluate the impact of timing of basal leaf removal and cluster thinning on potassium (K+) concentration in ���Tempranillo��� and ���Camminare Noir��� grapes as a possible vineyard management practice to mitigate high pH. This research took place during the 2021 and 2022 growing seasons in two vineyards, one in the Texas Gulf Coast and the other in the North Texas region. Treatments consisted of basal leaf removal (removal of lowest three basal leaves), cluster thinning (thinning to one cluster per shoot), and leaf removal plus cluster thinning conducted at either berry set or veraison. Differences in fruiting zone canopy density were consistently observed between treatments, across years, cultivars, and sites. Leaf removal treatments averaged a 35.83% reduction in canopy density in the fruiting zone, determined by occlusion layer, leading to an increase of 124.17% in cluster exposure flux availability. However, differences in yield (yield per vine, clusters per vine), berry chemical composition (alpha amino nitrogen, ammonium, fructose, malic acid, soluble solids, tartaric acid, titratable acidity, and pH) and tissue nutrient content were only observed in singular instances, with no consistent differences between years, cultivar, or site. Berry K + concentrations and juice pH varied by rootstock, year, and cultivar, but there was no clear impact of leaf removal or cluster thinning on berry K+ or pH. In both years of the study, very low yields were observed as a result of a severe winter event and possibly negated any effects from leaf removal or cluster thinning
John Bickham field notebook: AK14501-AK15000.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK15001-AK15500 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
Technical, Economic, and Life Cycle Assessment of Membrane-Based Air-Cooling Systems
No full textThe escalating demand for space cooling in Qatar, projected to triple by 2050, underscores the urgent need to shift from traditional refrigerant-based systems to more sustainable air-cooling technologies. This transition aims to mitigate the significant contributions to global warming, with a potential increase in global temperatures by 0.44��C by the century's end. Current research in membrane-based air-cooling systems, which combine adiabatic evaporative cooling with isothermal dehumidification, shows promise for enhanced efficiency. However, existing studies often overlook key operational energy requirements, such as the energy for low-temperature condensation, leading to underestimating system costs and efficiency. Moreover, environmental assessments of these systems frequently neglect the construction phase and criteria beyond electricity consumption. Experimentally, the focus has been on developing thin-film composites and nanocomposites on unaltered support membranes, which, despite increasing selectivity, do not significantly improve overall permeance. This limitation increases the need for membrane area, raising costs for membrane-based cooling solutions.
This research employs two primary methodologies to address the challenges of space cooling in Qatar, focusing on enhancing the efficiency and environmental sustainability of membrane dehumidification systems. A comprehensive simulation of various system configurations initially underpins these systems' exhaustive technoeconomic and environmental life-cycle assessment (LCA), benchmarked against conventional cooling technologies. Utilizing the Recipe2016 methodology for both Midpoint and Endpoint analyses, this LCA reveals a significant reduction (50-66%) in human health and ecotoxicity impacts compared to traditional AC systems while highlighting the minimal (<1%) environmental impact of the construction phase. Subsequent technoeconomic analysis identifies membrane cost as a critical factor in the viability of condenser-based membrane air-cooling systems. This underscores the necessity for membranes with a water vapor permeance (WVP) above 20,000 GPU. To address this, novel mixed matrix membranes containing hydrophilic nanomaterials into a polyethersulfone matrix were designed and fabricated using phase inversion to significantly enhance permeance without compromising mechanical stability. Among these MMM, the membrane containing 0.2 wt.% sulfonated graphene oxide with exceptional WVP of ~ 25,000, now protected by a US provisional patent, was coated with a thin active Pebax layer to enhance water vapor air selectivity. Economic assessment based on this SGO-TFN revealed a minimum loss of 15% saving in the total annualized relative to conventional systems, with a 60% increase in equipment manufacturing costs
Beam Hardening and Scatter Artifact with Metal Objects Inside and Outside the Field of View in CBCT Imaging
No full textIntroduction: This study compares the objective and subjective appearance of artifacts produced by metal objects inside and outside the limited field of view (FOV) of a common region of interest (ROI).
Methods: Metal objects (titanium rods, zirconium rods, zirconium crucibles) were positioned in the human cadaver���s left maxilla and imaged using Accuitomo 170 CBCT with limited FOV. Sixteen scans (7 with metal inside the FOV, 7 with metal outside the FOV, and two controls) were obtained. The artifacts were objectively evaluated by calculating the standard deviation (SD) of grayscale values using ImageJ software. For the subjective test, two observers rated paired images for beam hardening/scatter artifacts.
Results: The Wilcoxon signed rank test showed no difference in the SD of grayscale values with the metal objects inside or outside the FOV (p=.2882). However, a subjective comparison of the two image groups (metal objects inside and outside FOV) showed subtle differences in beam hardening intensity in the region immediately adjacent to the metal objects. The SD of grayscale values for slices at the level of metal objects were higher than those apical to the level of metal objects (p<0.001). Conclusion: Strategic repositioning of a limited FOV CBCT to avoid metal objects did not significantly reduce the image noise. However, it reduced the beam hardening artifact on the area of the image immediately adjacent to the metal object. Additionally, selectively tilting the patient���s chin to keep metal objects in a different horizontal plane from ROI may reduce artifact appearance
Optical Distortion in Hypersonic True Flight Enthalpy Flows
No full textA simplified, blunt-nose wedge model was tested over a range of realistic hypersonic flight conditions to evaluate several aero-optic diagnostic measurement techniques. A two-dimensional 10��� half angle wedge of width 0.47 m and blunt-nose radius 1 cm test article was designed and tested in an experimental campaign in Texas A&M University���s hypervelocity expansion wind tunnel. The aero-optic diagnostic techniques employed in this work included schlieren photography, linear array focused laser differential interferometry, Michelson interferometry, and optical emission spectroscopy. Experimental test conditions comprised Mach numbers of 6, 9, 12, and 15, realistic-flight flow enthalpy, and static temperatures between 200 K and 270 K. Hypersonic flow features such as bow shocks, natural light emission, and boundary layers were captured in schlieren recordings. Index of refraction fluctuation power spectral density data were recorded between frequencies of 100 kHz and 10 MHz at multiple points near the surface of the test arti-cle. The data suggested that eddies causing density fluctuations at rates greater than 2 MHz and between 7.30 mm and 10.63 mm tall developed in the boundary layer for unit Reynolds numbers between 11 �� 106 m���1 and 12 �� 106 m���1
Anger-Induced Early Childhood Respiratory Sinus Arrhythmia and Parenting Style: Predictors of Toddler Externalizing Behavior Problems and School Readiness
No full textEarly childhood emotional regulation has been linked to favorable academic, behavioral and socioemotional outcomes. Respiratory sinus arrhythmia (RSA) in response to an emotion induction has been studied as an indicator of emotional regulation. This study investigated children���s dynamic RSA change in response to a negative-affect evoking laboratory episode, and how RSA relates to behavior problems and school readiness. The sample consisted of 58 typically developing children (males = 24, mean age = 3.1, SD = .02) and their parents (mothers = 56, mean age = 35.04, SD = 5.25) in the Bryan-College Station area. Greater RSA suppression during the anger induction was associated with lower externalizing behavioral problem scores and higher school readiness scores. Children of authoritarian parents had the highest school readiness scores across levels of RSA suppression but the highest externalizing problems for those with low emotional regulation. Girls showed more pronounced patterns of RSA suppression whereas boys��� RSA levels remained comparatively flat over the anger induction. My study contributes to the emotion regulation literature from a family study perspective while employing multi-method assessments of child temperament. The findings shed further insight to the relationship between emotion regulation and cognitive performance. This research has implications for preschool readiness, cognition and behavioral interventions
Improving the Accuracy, Reliability, and Throughput of Nanoindentation Hardness and Modulus
No full textInstrumented nanoindentation is a form of load and depth sensing indentation that characterizes material properties on the micro- and nanoscale. This form of indentation is widely used for its ability to measure a variety of material properties on very small scales in a high-throughput manner without extensive sample preparation and with minimal sample damage after testing. However, this versatility introduces a level of complexity, and due to the various methods for performing nanoindentation tests and collecting data, there are inevitably opportunities to encounter and cause experimental errors. Common sources of error include not accounting for pile-up or other area-related issues, frame stiffness and sample mounting issues, and using improper sample preparation and testing parameters as well as testing non-ideal samples. This thesis provides a background for these sources of error and expands on best practices from research and literature to overcome or avoid these sources of error. To this end, a highly ordered pyrolytic graphite sample was tested and the lack of residual indent impression and sample anisotropy was examined in detail, with methods used to account for such sample non-idealities and provide more reliable data presented. This thesis further investigates how sample mounting conditions affect and can sometimes produce error in the compliance of the nanoindentation system. Such research expands and improves the minimal research that currently exists in the literature by providing concrete methods for avoiding issues caused by sample mounting in order to produce accurate and reliable data
Evaluating the Attentional Demand of Visual and Auditory Stimuli on Adolescents with ADHD Using a Dual Task Paradigm
No full textAttention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder defined by impaired levels of inattention and/or hyperactivity ��� characterized by being unable to stay focused in the face of distraction or think flexibly when presented more than one stimulus. This inability to remain focused may make it difficult to do two things at one time, or dual task.
Dual task is a paradigm used to quantify allocation of attention by asking subjects to perform two tasks consecutively and measuring the difference in their performance individually to completing them together. Usually done with walking and a cognitive task. The type of cognitive task may be important in ADHD because of poorer responses to visual vs auditory stimuli.
This study sought out to examine the difference in dual task cost (DTC) between auditory and visual stimuli-based tasks in older adolescents with ADHD tendencies. The hypothesis was people with ADHD tendencies would experience a higher DTC under visual than the auditory tasks.
Nineteen subjects completed five randomized, one-minute collections of single task (ST) walking, ST visual, ST auditory, dual task (DT) visual (walking while performing the test), and DT auditory. The cognitive DTC was calculated using the percent correct answer difference. The gait DTC was calculated for step width and gait speed. Both the signed and absolute DTC values were analyzed to examine both the direction of the cost as well as the magnitude of the change. Comparisons were made between visual and auditory DTC for percent correct, gait speed, and step width. The absolute value of the cognitive DTC was found to have significance (p<0.001), with the auditory having a higher magnitude of DTC than the visual. Other comparisons were not significant.
Little to no evidence was found to support the hypothesis. This was likely due to the use of preferred gait speed, which may not have challenged attentional resources. Further, it is feasible that there is a cognitive benefit of walking on working memory. Future studies should investigate or control for subtypes or comorbidities of ADHD, the mechanisms of auditory processing in those with ADHD, and the cognitive benefits associated with walking
Methods for Large-Scale Inference with Application to Genomics Data
No full textGenomic data are subject to various sources of confounding, such as demographic variables, biological heterogeneity, and batch effects. To identify genomic features associated with a variable of interest in the presence of confounders, the traditional approach involves fitting a confounder-adjusted regression model to each genomic feature, followed by multiplicity correction. The first project shows that the traditional approach is sub-optimal and proposes a new two-dimensional false discovery rate control framework (2dFDR+) that provides significant power improvement over the conventional method and applies to a wide range of settings. 2dFDR+ uses marginal independence test statistics as auxiliary information to filter out less promising features, and FDR control is performed based on conditional independence test statistics in the remaining features. 2dFDR+ provides (asymptotically) valid inference from samples in settings where the conditional distribution of the genomic variables given the covariate of interest and the confounders is arbitrary and completely unknown. In genome-wide epigenetic studies, exposures (e.g., Single Nucleotide Polymorphisms) affect outcomes (e.g., gene expression) through intermediate variables such as DNA methylation. Mediation analysis offers a way to study these intermediate variables and identify the presence or absence of causal mediation effects. Testing for mediation effects leads to a composite null hypothesis. Existing methods like Sobel���s test or the Max-P test are often underpowered because 1) statistical inference is often conducted based on distributions determined under a subset of the null, and 2) they are not designed to shoulder the multiple testing burden. To tackle these issues, we introduce a technique called MLFDR (Mediation Analysis using Local False Discovery Rates) for high dimensional mediation analysis, which uses the local false discovery rates based on the coefficients of the structural equation model specifying the mediation relationship to construct a rejection region. We have shown theoretically as well as through simulation studies that in the high-dimensional setting, the new method of identifying the mediating variables controls the false discovery rate asymptotically and performs better with respect to power than several existing methods