Texas A&M University-Commerce
  • Commerce, Texas, United States
Recent publications
The Big Bang Nucleosynthesis (BBN) model is a cornerstone for the understanding of the evolution of the early universe, making seminal predictions that are in outstanding agreement with the present observation of light element abundances in the universe. Perhaps, the only remaining issue to be solved by theory is the so-called “lithium abundance problem". Dedicated experimental efforts to measure the relevant nuclear cross sections used as input of the model have lead to an increased level of accuracy in the prediction of the light element primordial abundances. The rise of indirect experimental techniques during the preceding few decades has permitted the access of reaction information beyond the limitations of direct measurements. New theoreticaldevelopments have also opened a fertile ground for tests of physics beyond the standard model of atomic,nuclear, statistics, and particle physics. We review the latest contributions of our group for possible solutions of the lithium problem.
Participation in experimental studies can be conceptualized as Goffmanian frames, i.e. a set of rules which include the fact the experimenter will be observing participant behavior through (the recording of) the experiment. This study is focused on frame breaches in 16 video- and audio-recorded dyadic conversations taking place in an experimental setting. Our main conclusion is that the experimental frame is conceptualized by participants as including constraints that go beyond non-experimental interactions, and in particular the need to mitigate frame breaches, which are seen as face-threatening. Analyses revealed that participants only broke the research frame after they completed the task they were assigned by the researcher, and that breaches did not necessarily correspond to changes in key. Insights gained in relation to face and mitigation are discussed, as well as the participants’ need to determine their next steps once the research purpose has been perceived complete.
Prediction of changes in biomedical signals, such as vital signs, is useful for many clinical applications. Several signal prediction (forecasting) tools were developed, but their evaluation and applicability to a specific clinical use is context dependent. In this work, we propose a novel method to tackle the problem of evaluation and comparison of vital sign predictors for intervention based clinical studies. The proposed prediction quality measures are particularly well-suited for forecasting rare events scenarios. Specifically, using the novel metrics, we measure the prediction statistics and compare nine deep learning and autoregressive forecasting models for multi-step prediction of rare bradycardia events in preterm infants, however the new concepts allow applications to other biomedical signals. We validated the novel metrics with experimental results on testing sets with several days of vital sign recordings. Our results show that simple statistical predictors could outperform state-of-the-art deep learning architectures for low-dimensional signals.
Owing to the remarkable development of deep learning technology, there have been a series of efforts to build deep learning-based climate models. Whereas most of them utilize recurrent neural networks and/or graph neural networks, we design a novel climate model based on two concepts, the neural ordinary differential equation (NODE) and the advection–diffusion equation. The advection–diffusion equation is widely used for climate modeling because it describes many physical processes involving Brownian and bulk motions in climate systems. On the other hand, NODEs are to learn a latent governing equation of ODE from data. In our presented method, we combine them into a single framework and propose a concept, called neural advection–diffusion equation (NADE). Our NADE, equipped with the advection–diffusion equation and one more additional neural network to model inherent uncertainty, can learn an appropriate latent governing equation that best describes a given climate dataset. In our experiments with three real-world and two synthetic datasets and fourteen baselines, our method consistently outperforms existing baselines by non-trivial margins.
We explored the perceptions of individuals in teams (both leaders and members) regarding shared leadership in the South Korean business context, seeking a nuanced and unique understanding of shared leadership. We examined how shared leadership in team‐based structures develops and functions. Informed by the driving and restraining forces framework, we elucidate factors that facilitate and that impede shared leadership practice and implementation. The analysis uses semi‐structured interviews with seven teams that each consist of one team leader and two team members. Findings include the four essential elements of shared leadership and the identification of the driving and restraining forces for why employees and managers welcome or refuse to accept shared leadership. We present strategies for human resource development (HRD) professionals seeking to cultivate shared leadership in the South Korean context. We also discuss the study's limitations and potential directions of inquiry for future researchers.
This paper builds on a novel methodology of lexical semantics exemplified on lexical field theory by using several translations of Ken Kesey’s One Flew Over the Cuckoo’s Nest. The present study, a large-scale collaboration, presents and compares the results for laugh, smile, grin, giggle, and other words for laughter behaviors across 14 languages and in extensive detail. The key results answer the question of what semantic dimensions the vocabularies of the various languages distinguish as marked by lexical contrasts and can inform future research in humor as well as translation studies. Based on our findings, a key marking emerges for audible (e.g., laugh) versus non-audible (e.g., smile) behaviors, as Indo-European vocabularies treat smiling as a less marked variant of laughing, e.g., German lächeln, Italian sorridere, Polish uśmiech, Turkish gülüm, but further orthogonal dimensions are documented as well, for example, aggressive, concealed, loud, or suppressed behavior. An updated hierarchy of these semantic features is proposed, and the results are presented in graphic visualizations, which also help illustrate idiosyncrasies of individual languages that go against the general trends. Exceptions to these general trends include lemmata that can cover both audible and inaudible behavior straddling what we claimed is the most important distinction (e.g., Danish grine). Finally, we outline a probabilistic method to compare word senses across languages based on aligned corpora large enough for computational approaches.
The identification procedure can greatly affect eyewitness performance, but this may be contingent upon a relatively weak memory for the perpetrator. In a large preregistered experiment (N = 13,728), we manipulated memory strength and tested participants with a target‐present or ‐absent showup or lineup (size 3 or 6). All fillers were description‐matched but were of low or high similarity with the target. We replicated the advantage of fair simultaneous lineups over showups and the advantage of low‐ over high‐similarity fillers when memory for the perpetrator's face was weaker (short exposure duration), but both effects were significantly reduced when memory was stronger. There was no effect of lineup size regardless of memory strength or filler similarity. We conclude that some recommendations to police may be more robust than others across changes in estimator variables such as memory strength and that more research is needed on interactions between estimator and system variables. This article is protected by copyright. All rights reserved.
Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio‐oil at high temperature (200–400 °C) and high pressure (10–25 MPa). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ethanol (1:1 vol. ratio) in a 100 ml reactor. Bio‐oils produced are characterized via elemental analysis, thermogravimetric analysis, and GC–MS. HTL of Chlorella was investigated at 240 °C & 250 °C for 0 min & 15 min under air or H2 atmosphere and with and without 5% zeolite Y. Temperature increased the bio‐oil yield from 38.75% at 240 °C to 43.04% at 250 °C for 15 min reaction time. Longer reaction time increased the bio‐oil yield at 250 °C from 39.14% for 0 min to 43.04% for 15 min. H2 atmosphere had a significant effect for HTL at 240 °C. Zeolite Y increased the bio‐oil yield significantly from 32.03% to 43.06% at 250 °C for 0 min. The carbon content of bio‐oil increased with the temperature while the oxygen content decreased. The boiling point distribution of bio‐oils in the range of 110–300 °C varies with temperature, and atmosphere. At 240 °C for 15 min, the 110–300 °C range increased from 31.19% in air (240‐15‐air) to 39.25% in H2 (240‐15‐H2). H2 atmosphere increased the content of hydrocarbons, alcohols, and esters from 69.61% in air (240‐0‐air) to 82.83% in H2 (240‐0‐H2). Overall, temperature, reaction time, atmosphere, and catalyst all significantly influenced the yield and/or the quality of bio‐oils from HTL of Chlorella. This article is protected by copyright. All rights reserved.
Interbasin water transfer projects (IBWT's) have emerged as dispersal corridors for aquatic species. However, little is known about how water transfer affects regional spread dynamics, or shapes the genetic diversity patterns of non-native populations. Shimofuri Goby Tridentiger bifasciatus is a globally introduced fish species with many well-established populations in IBWT's. Here, we used nuclear microsatellites to assess the genetic diversity and population structure of the Shimofuri Goby in its native and introduced sites belonging to two IBWT's in China. Our objectives were to (1) reveal the genetic diversity patterns of the Shimofuri Goby during regional spread, and (2) identify its mode of spreading in water transfer systems. We observed (1) a high level of genetic diversity in non-native populations without evidence of bottleneck effects, (2) that non-native populations with a longer water transfer times had a higher private allele richness, and (3) that non-native populations showed a highly mixed genetic structure, low level of genetic differentiation, and no significant relationship between geographical and genetic distances. Our results indicate that the genetic patterns of diversity of non-native populations are mainly shaped by a linear cascade spread processes due to long-distance movement of larvae, and are probably related to propagule pressure caused by the construction of water transfer. To manage the non-native populations of T. bifasciatus, preventive actions and physical removal should be implemented in IBWT's.
With the need to increase Science, Technology, Engineering, and Mathematics (STEM) graduates, higher education institutions need to identify and improve ways to increase underrepresented STEM student retention rates. Cypress College in Southern California implemented a program called STEM ² (Strengthen Transfer Education and Matriculation in Science, Technology, Engineering, and Mathematics) to give students the support and the resources to continue with their intended majors. In this study, we examined the impact of the STEM ² participation for 1,113 students on multiple core outcomes of retention, four-year transfer, and associates of arts (AA) degree completion of STEM students. Logistics regression was used to determine the significance of input variables and the odds that the desired outcome was achieved. Results indicated there is a difference in student outcomes based on the students’ ethnicity, enrollment in the STEM ² program, and use of student support programs. Implications for practice and future research were also included.
While universities across the globe differ in their assessment practices and processes, program assessment has become a foundation for policy makers, universities, and other stakeholders to demonstrate the quality of their programs. Globally, there are 550 accreditation/quality assurance bodies in 170 countries. The purpose of this study was to examine the relationship between espoused and enacted values related to assessment based on an analysis of academic department bylaws at a large university in the Midwest of the United States. If program assessment is truly valued, program assessment activities should be reflected in a university’s procedures that govern promotion and tenure. The assessment policies were reviewed using the department bylaws as observable artifacts. A summative content analysis of 1,106 pages of contractual bylaws for 7 colleges and 40 departments was conducted. The study found a disparity in the espoused value of assessment at MWU compared to the actual or enacted values found in department bylaws. Until a university’s enacted values (as seen through artifacts like bylaws) align with espoused values, a tension exists that reinforces assessment as a top-down compliance mandate rather than a continuous improvement effort to increase and ensure student learning. Implications for research and practice follow.
The dynamic behavior of laced reinforced concrete (LRC) T‐beams could give high‐energy absorption capabilities without significantly affecting the cost, which was offered through a combination of high strength and ductile response. In this paper, LRC T‐beams, composed of inclined continuous reinforcement on each side of the beam, were investigated to maintain high deformations as predicted in blast resistance. The beams were tested under four‐point loading to create pure bending zones and obtain the ultimate flexural capacities. Transverse reinforcement using lacing reinforcement and conventional vertical stirrups were compared in terms of deformation, strain, and toughness changes of the tested beams. The inclination angles of the used lacing reinforcement with respect to the longitudinal reinforcement were 45° and 60°. The lacing reinforcement was efficient and participated actively in resisting the bending moments and shear forces at the same time. For the same diameter of lacing reinforcement, the 60° inclination angle imposed more ductility before failure than beams with lacing reinforcement of a 45° inclination angle. Moreover, the lacing bar diameter was more effective in improving the load‐carrying capacities when using the inclination angle of 45°. A finite element (FE) model was developed and validated using the experimental results based on the measured deformations and strains to conduct a parametric study. The investigated parameters included the effect of the arrangements of the applied loads, laced rebar diameter, inclination angle, tension reinforcement ratio, and concrete strength.
A green and efficient approach for the difunctionalization of ynamides by merging the electrochemical and organoselenium-catalyzed processes is described. This strategy features mild reaction conditions, broad functional group tolerance and high atom-economy, and requires no external chemical oxidant. Hence, we provide a sustainable alternative for the synthesis of polysubstituted oxazoles.
COVID-19 remains a public health emergency with prevention guidelines and mitigation strategies being constantly updated to curb the rapid spread of the disease. Despite proven successes of recommended preventive behaviors, there is low uptake of wearing a mask, washing of hands, and social distancing in the United States (US). The purpose of this study was to examine factors that influence COVID-19 preventive behaviors. We used data from the nationally representative COVID-19 Household Impact Survey (n = 19,815) conducted in the US from April to June 2020. Chi-square (χ2) test and bivariate analyses were performed to compare study participants who used all COVID-19 related preventive behaviors and those who did not, and multivariate logistic regressions to determine associations across demographic and social characteristics. Of the 19,815 participants, 79.2% of participants reported practicing the aforementioned COVID-19 preventive behaviors. Further, non-Hispanic white, Spanish speaking, living in urban areas, of older age (60+), being female, having an education above an undergraduate, those with income levels $100K or more, living in the urban northeast region that trust and communicate frequently with family and neighbors were more likely to use all three preventive behaviors. Findings suggest a need for continued provision of information on prevention and vaccination importance, but expand efforts to target adopters of these behaviors and encourage them to share their uptake and adherence efforts. This type of horizontal communication where information is shared within trusted social networks can shape social norms that influence the uptake of COVID-19 preventive behaviors and slowly curb communal spread.
Introduction Eastern migratory monarch butterflies (Danaus plexippus) have declined over 80% in recent years, but little is known about fall reproduction in the southern U.S. where monarchs may compete with queen butterflies (Danaus gilippus). Aims/methods We provide data on the survival to third instar, associated arthropods, and phenology of fall breeding monarchs and queens in Texas. Results Monarch and queen survival was relatively high, but varied among years. Oleander aphids (Aphis nerii), spiders, and red imported fire ants (Solenopsis invicta) had minor negative effects on survival. The abundance of monarchs and queens on the study site peaked three to four weeks before the main passage of monarchs in the area. Queens had similar phenology and exhibited a migratory pattern similar to monarchs but on a smaller scale. Discussion Survival of fall monarchs is relatively high and potentially important for winter roost recruitment. Fall survival was not greatly affected by any particular arthropod taxon, but may be affected by precipitation. Fall reproduction is a response to available host plants and its timing enables pupae to eclose in time for migration to winter roosts. Implications for insect conservation Management of Asclepias viridis and other native milkweeds to facilitate fall reproduction could facilitate recovery of monarchs if it buffers variable productivity further north. Management should use mowing and burn schedules that promote high quality host plants. Populations of queens should be monitored for their potential to compete with monarchs especially in response to the potential impacts of parasite resistance and climate change.
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2,293 members
Andrei Kochegarov
  • Department of Biological and Environmental Science
Izhar A. Khan
  • Department of Biological and Environmental Science
Jun Xu
  • Department of Physics and Astronomy
Curt A Carlson
  • Department of Psychology, Counseling, and Special Education
Kurtis A. Williams
  • Department of Physics and Astronomy
Information
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2200 Campbell Street, TX 75428, Commerce, Texas, United States
Website
tamuc.edu
Phone
+1 903-886-5102