26400 research outputs found
Sort by
Analysis of Additively Manufactured Inconel 718 Combustion Behavior in Promoted Oxygen Environments
No full textPromoted combustion testing is a vital tool for engineers to establish the combustion and flammability characteristics of materials (metallic or otherwise) in oxygen enriched environments. Historically, much of the established data for metallic promoted combustion has been with regards to materials in their cast and wrought forms. However, with the emergence of additive manufacturing as a preferred method of fabrication, the need exists to evaluate how metals in that form behave. Recent testing has demonstrated that even if a metal or alloy is nominally the same with regards to chemistry, flammability between samples in the wrought form can differ significantly from those which were additively manufactured. This has provided a rationale to evaluate what underlying principles and conditions may be driving such a variability in flammability response. This work will serve as an analysis and characterization of one specific alloy (the nickel-based superalloy Inconel 718), a material popular for aerospace applications such as liquid fueled rocket components and turbine engines. Promoted combustion testing (per the ASTM G124 standard) was conducted on samples of both wrought and selective laser melted (SLM) fabrication, to provide comparison of flammability response between materials produced by each manufacturing method. Additionally, post-build treatments were applied to test samples to identify any effects on performance provided by hot isostatic pressing (HIP), oxygen-getting wrapping during HIP, stress relieving, and solutionizing/aging heat treatments. This project will utilize optical and scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction, and metallography to identify the differences between flammability behavior of additively manufactured and wrought Inconel 718. This information is key for engineers to understand the safety and oxygen compatibility of this material while in use by an industry which will undoubtedly increase the adoption and use of additive manufacturing as a primary means for fabrication
Will Consumer-Generated Reviews and Electronic Word-of-Mouth Communications Affect Subjective Norm Perceptions, Attitudes Toward Social Commerce, and Social Shopping Intentions Among Gen Z Consumers?
No full textSocial commerce has become a global phenomenon in recent years. Its convenience and accessibility have revolutionized how consumers shop and interact with brands and merchants. Gen Z consumers make up the majority (55.5%) of social buyers, and they are likely to be influenced by consumer-generated reviews (CGRs) and electronic word-of-mouth (eWOM) on social media. This thesis draws on the Theory of Planned Behavior (TPB) and employs a quantitative online questionnaire to determine whether CGRs and eWOM influence subjective norms (SN) perceptions, attitudes toward social commerce (ASC), and social shopping intention (SSI) of Gen Z consumers. The theoretical framework also included three message dimensions of eWOM and CGRs (i.e., believability, credibility, and trust) as antecedents.The multiple regression results showed that credibility significantly predicts consumers’ SN. However, believability and trust did not influence the SN of consumers. After controlling the preceding variables, the multiple regression analysis found that SN is a positive and significant predictor of ASC, and ASC was also a positive and significant predictor of SSI. Discussions, implications, and future research directions were provided
Dispersal and Population Structure of Euchlanis chihuahuaensis via Anemochory in the Chihuahuan Desert
No full textDesert ecosystems present challenges for aquatic organisms as habitats are fragmented, both in space and time; however, diapausing stages of rotifers can travel hundreds of kilometers during wind events. I used the rotifer Euchlanis chihuahuaensis as a model species to investigate the influence of wind dispersal on gene flow and population genetics in Chihuahuan Desert populations. I hypothesized that anemochory facilitates gene flow from source populations in the Northern Chihuahuan Desert in Mexico and the western United States to habitats in the Trans-Pecos region via delineated wind corridors. To test this hypothesis, the genetic diversity of populations from both inside and outside of the wind corridors were compared. The corridors were constructed using data from modeled HYSPLIT trajectories of dust events over 40 years. Genetic variation in the COI gene among populations from inside and outside of the dust corridor were analyzed to determine possible isolation by distance, fixation (FST), and haplotype distributions. My results provided limited evidence for gene flow from populations from Southern New Mexico with individuals with shared haplotypes occurring in non-hydrologically connected habitats between 100 – 200 km apart; however, many discrete haplotypes were identified which belonged to single sites or local areas. My results elucidated the population structure of E. chihuahuaensis, with three haplogroups identified with discrete geographic boundaries in Southern New Mexico, Trans Pecos, and the Mexican border area in northern Chihuahua state, along with the identification of a putative cryptic species. Regionally partitioned populations indicated that “West” (Mimbres River Delta Region -PLP) and “East” (IMRS) regions had higher levels of haplotype diversity ranging from 0.85 to 0.93. Limited evidence points to genetic differences in diversity from populations located both inside and outside the dust corridor (58% among and 42% within populations). Investigating anemochory’s role in gene flow in desert environments can help us further understand evolutionary and ecological processes in aquatic microinvertebrates inhabiting ephemeral systems
Prelimbic Cortex Neuronal Assemblies in Behaviors Predictive of Drug-Seeking Before and After Cocaine Self-Administration
No full textLiterature has established that there are certain behaviors that are predictive of drug seeking and relapse such as impulsivity, distress tolerance (DT), Pavlovian conditioned approach (PCA), anxiety and sensation-seeking. However, few studies have examined the behavioral interactions among these tasks and drug-seeking, and none have examined the neural interactions in the prelimbic cortex, which has an essential role in drug-seeking and is implicated in each of the aforementioned behaviors of interest.We therefore hypothesized that certain behaviors including high impulsivity, low distress tolerance, high anxiety, and high locomotor activity would predict high cocaine-seeking. We further hypothesized that the neuronal activity in the prelimbic cortex during these predictive behaviors would also predict cocaine-seeking.Sprague Dawley rats underwent a GCAMP6s viral infusion and lens surgery and performed various tasks upon recovery, and their prelimbic activity was recorded via calcium imaging. Afterwards, rats underwent cocaine or water self-administration for 2 weeks followed by an extinction task to measure drug-seeking, and the original behaviors were reassessed. Sex differences were observed, with females showing less anxiety and higher distress tolerance. Cocaine decreased distress tolerance.Neuronal activity didn\u27t significantly change following cocaine but correlated with self-administration behaviors. Notably, there were significant interactions between behaviors and their neuronal activity with self-administration and reward-seeking. Specifically, sensation seeking behavior predicted water and cocaine seeking, prelimbic activity during DT predicted cocaine and water self-administration, and prelimbic activity during PCA predicts cocaine and water seeking. Overall, cocaine reduced distress tolerance but had limited effects elsewhere. However, behaviors and prelimbic activity significantly predicted drug intake and reward-seeking. Understanding these connections could inform targeted therapies for individuals prone to drug seeking and relapse
The Effects of Police Culture and Procedural Justice on Citizens\u27 Perceptions of Police Legitimacy and Trustworthiness
No full textPolice departments have often cited “a few bad apples” when discussing incidents of officer misconduct or improper use of force. However, police reform organizations often posit that when the tree is bad, all fruit it bears will be rotten. Police culture serves as the root of the tree in this analogy; the basis of the characteristics and behaviors of police rely on the specifics of police culture that has been imprinted during the police academy and maintained through everyday police work. Police culture determines how police officers interact with citizens and behave on the job. Those interactions can influence how citizens perceive police officers and police institutions. How citizens perceive police officers heavily influences the relationship between police departments and the communities they police. Citizens’ perceptions of police are often determined through personal and vicarious interactions with police, media perceptions of the police, and much more. Two studies were conducted that examined the roles of police office race, procedurally just interactions with citizens, interaction outcome and an index of positive feelings about the police. Data on perceptions of the police was also collected. In Study 1, while group membership did not predict police legitimacy and police trustworthiness, positivity toward the police and enhanced personal and vicarious experiences with police officers was positively associated with police legitimacy and police trustworthiness. When perceptions of the police were added to this model, these effects disappeared. In Study 2, there were no effects of police office race, procedurally just treatment and interaction outcome on police legitimacy and police trustworthiness. When perceptions of police as added to the model, these effects emerged such that police legitimacy and police trustworthiness is enhanced when people are treated justly and when the officer is African American. Implications of using perceptions of police as a variable in future studies is discussed
Investigating the Production and Perception of Lexical Stress in English as a Second Language: A Cue-Weighting Approach
No full textThe Cue-Weighting Transfer Hypothesis states that (a) listeners weight acoustic cues according to how informative they are in signaling a lexical contrast in their L1, and (b) that listeners transfer their cue weightings from the L1 to the L2, using those cues that are important in the L1 to perceive lexical stress in the L2 (Tremblay et al., 2021). Most of the Spanish-English bilinguals in our region are highly proficient in both languages, but differ in their language dominance spectrums. That is, they can handle both languages with ease, but are usually more dominant in one of them. Because of the bilingual uniqueness of this region, the present study tests the Cue-Weighting Transfer Hypothesis from a language dominance perspective, as opposed to doing so from an L2 proficiency perspective, like previous cue-weighting research has done. We tested Spanish-dominant and English-dominant speakers from our region using a lexical stress perception task and a lexical stress production task to investigate if these participants show evidence of cue-weighting transfer from the dominant into the non-dominant language in the perception and production of lexical stress. Our results revealed various differences manifested as a result of language dominance effects, two of the most salient ones being that (i) English-dominant speakers use vowel reduction to a significantly higher degree than Spanish-dominant speakers, and that (ii) in the absence of vowel reduction use, Spanish-dominant speakers increase their reliance on other acoustic cues like duration and pitch instead when producing and perceiving lexical stress in English. Our results provide support for the Cue-Weighting Transfer Hypothesis. We suggest that the differences in cue weightings across languages can be modulated by language dominance, and not just by L2 proficiency, like previous research has shown. That is, cue-weighting differences can be observed in speakers who are highly proficient in both languages, but differ in their dominance continuum
Assessing Urban Tree Coverage Along the U.S.-Mexico Border: A GIS Analysis of Paso Del Norte
No full textIn recent years, researchers have extensively studied the spatial distribution of social demographics and urban tree canopy (UTC) in urban cities, but very few, to this date, address U.S.-Mexico border cities. To date, there is no research that assesses the distribution of urban tree canopy (UTC) in the city of El Paso, Texas, and Ciudad Juarez, Chihuahua, along the U.S.- Mexico border. Leveraging advanced mapping techniques and GIS tools, the study performs comparisons between countries (Juárez vs. El Paso urbanized areas and intra-country (within each country). It compares land cover classifications, assesses variations in UTC distribution across census tracts and Área GeoEstadística Básica (AGEBs), and explores potential spatial clusters. Drawing on landcover data with a resolution of 0.6m and 8.5m, the research contributes to the global understanding of urban green infrastructure (UGI) distribution, such as UTC. Also, using census data, the study addresses the distribution of vulnerability through the construction of the Binational Social Vulnerability Index (BSVI) for Paso Del Norte. The analysis confirms previous studies’ assessment of urban morphology in Paso Del Norte, identifying clustering along the international boundary and city centers. Results reveal inequitable access to UTC across Paso Del Norte, with higher social vulnerability in Ciudad Juarez and census units closer to the border in El Paso. By employing GIS, this study advances knowledge on UTC distribution, addresses environmental injustices, and sheds light on trends in U.S.-Mexico border cities\u27 UTC distribution
Atlas-Based Analysis of the Neural Projections From the Lateral Hypothalamic Area to the Lower Brainstem in the Adult Male Rat
No full textWithin the last decade, the number of diseases associated with dysregulation of the neural circuits responsible for energy balance, glucosensing, and feeding control has increased. One brain region containing these circuits is the lateral hypothalamic area (LHA), which plays an important role in the sleep/wake cycle, energy balance, and motivated behavior. Although the LHA has been termed a “feeding center”, other regions within the hindbrain are known for the regulation of similar functions including energy balance, glucosensing, and feeding control. While many studies have explored and reported projections from the LHA to the hindbrain, few have further investigated the interconnections between neighboring cytoarchitectonically defined LHA subdivisions. To address this gap in our understanding, we have surveyed three distinct regions within the LHA, as characterized in the standardized atlas, Brain Maps 4.0 (BM4.0). We injected a cocktail consisting of the retrograde tracer, cholera toxin subunit B (CTb), and the anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L), in three adult male Sprague-Dawley rats to visualize their LHA interconnections with the hindbrain. We mapped the traced interconnections to hindbrain atlas levels 52–73. Of the three cases, subject 19-054 displayed unique connectional patterns for various HB subregions. Through various IHC preparations, we observed sources of LHAd inputs in the form of CTb-ir perikarya, and LHAd outputs in the form of PHA-L-ir axons in reticular nuclei and regions within the dorsal vagal complex (DVC). Hence, bidirectional communication, as evident from both retrograde and anterograde labeling, exists for the proposed LHAd–HB neural circuits. We also phenotyped some of the neuronal populations in the hindbrain overlapping with these regions. Overall, this provides evidence for the existence of bidirectional structural connectivity for the LHAd–DVC neural circuit, and provides a foundation for its further elucidation. Obtaining accurate standardized maps in addition to molecular information of this neural circuit in relation to the regulation of gastrointestinal function and feeding behavior will be critical for generating effective therapies. The further delineation of this neural circuit may also prove critical for the development of novel therapeutic strategies aimed for the treatment of diabetic patients. Furthermore, by confirming LHAd connections to the hindbrain DVC, we can create and test hypotheses about how these connections work, supplemented by standardized maps of the entire network that may be utilized for large-scale projects such as deep brain stimulation, optogenetics, and even the use of light-sheet microscopy to produce a 3-D map of this important neural circuit
Dispersal And Population Structure Of Euchlanis Chihuahuaensis Via Anemochory In The Chihuahuan Desert
Get PDFDesert ecosystems present challenges for aquatic organisms as habitats are fragmented, both in space and time; however, diapausing stages of rotifers can travel hundreds of kilometers during wind events. I used the rotifer Euchlanis chihuahuaensis as a model species to investigate the influence of wind dispersal on gene flow and population genetics in Chihuahuan Desert populations. I hypothesized that anemochory facilitates gene flow from source populations in the Northern Chihuahuan Desert in Mexico and the western United States to habitats in the Trans-Pecos region via delineated wind corridors. To test this hypothesis, the genetic diversity of populations from both inside and outside of the wind corridors were compared. The corridors were constructed using data from modeled HYSPLIT trajectories of dust events over 40 years. Genetic variation in the COI gene among populations from inside and outside of the dust corridor were analyzed to determine possible isolation by distance, fixation (FST), and haplotype distributions. My results provided limited evidence for gene flow from populations from Southern New Mexico with individuals with shared haplotypes occurring in non-hydrologically connected habitats between 100 â?? 200 km apart; however, many discrete haplotypes were identified which belonged to single sites or local areas. My results elucidated the population structure of E. chihuahuaensis, with three haplogroups identified with discrete geographic boundaries in Southern New Mexico, Trans Pecos, and the Mexican border area in northern Chihuahua state, along with the identification of a putative cryptic species. Regionally partitioned populations indicated that West (Mimbres River Delta Region -PLP) and East (IMRS) regions had higher levels of haplotype diversity ranging from 0.85 to 0.93. Limited evidence points to genetic differences in diversity from populations located both inside and outside the dust corridor (58% among and 42% within populations). Investigating anemochoryâ??s role in gene flow in desert environments can help us further understand evolutionary and ecological processes in aquatic microinvertebrates inhabiting ephemeral systems