Texas A&M University
  • College Station, Texas, United States
Recent publications
One of the easiest to observe conditions where waves occur in nature is the undulatory motion of aquatic animals and micro-organisms. In these bio-mechanisms, there is oscillatory locomotion which results in propulsion as the motion is accompanied by energy transfer from one end of the specimen or structure to the other end. Recent years have also seen a rise in the replication of the propulsive capabilities of these animals into aquatic robots. The use of smart materials to actuate and mimic the fin and tail characteristics of a fish has been attempted in various ways. Miniature robots actuated by piezoelectric materials have been effectively used for propulsion due to their simplicity and innovative actuating mechanism. These miniature robots find their application in the regime of underwater propulsion because of their size, flexibility, and ability to mimic fish locomotion. In most of these studies, the undulatory motion of these aquatic robots is achieved by discretizing the fin of the robot into multiple segments and synchronizing the oscillatory motion of individual segments to replicate continuous traveling waves. As a part of such endeavors, the present work attempts to use smart materials to actuate and mimic the fin motion characteristics of a fish. The bio-inspired design of the miniature robots consists of two brass shims supported by four piezoelectric bimorphs. The undulatory motion displayed by aquatic animals is mimicked by generating anechoic traveling waves in these brass fins. Anechoic traveling waves propagate in a structure without undergoing reflections at the structural boundaries. Such waves are generated by taking advantage of the structural dynamics of the fin under multi-input excitation.
This article investigated household-level food security for Ghana, Liberia, and Senegal. Different agroclimatic, ecological, social, and farming conditions in West Africa were represented. Using data-driven Random Forest and Chi-Square Automatic Interaction Detection (CHAID) decision tree methodology, this study classified 644 Ghanaian, 323 Liberian, and 510 Senegalese households for comparison and interpretation on food security. The predictors growing Liberian and Senegalese decision trees imply community support, diverse selling channels outside villages, resolving the dispute over farmland, and increasing community-level investment for food availability and access demonstrate household food security. Predictor importance on food security for Ghana highlighted the role of independent producers and food suppliers toward stability. Household food security or insecurity was distinguished by location-specific and gender-led households in Liberia and Senegal. Practically, the results presented a need to step-up agricultural education and extension based on an empirical field survey and its interpretations. The results can add considerations to the role of farming households as independent and individual suppliers and consumers to long-standing dimensions of food security, i.e., food availability, access, and stability.
The influence of external debt on the environment is a rising issue in the rapidly developing climate crisis. This study analyzes the relationship between carbon dioxide emissions per capita, gross domestic product per capita and ecological footprint per capita by applying an autoregressive distributed lag model for the Republic of Turkey. According to the results of this study there is an inverted U relationship between carbon dioxide emissions and external debt. There is no inverted U relationship between ecological footprint per capita and external debt while there is bidirectional causal relationship between external debt and economic growth. In addition, the results reveal that economic growth has a significant impact on ecological footprint per capita in the long run. There is causal relationship from external debt to emissions. This study recommends that further analysis be done for other countries that have high foreign debt to investigate the relationship between external debt and emissions. Similar analysis may be carried out for the external debt and ecological footprint per capita nexus for future studies.
The Covid-19 has presented an unprecedented challenge to public health worldwide. However, residents in different countries showed diverse levels of Covid-19 awareness during the outbreak and suffered from uneven health impacts. This study analyzed the global Twitter data from January 1st to June 30th, 2020, to answer two research questions. What are the linguistic and geographical disparities of public awareness in the Covid-19 outbreak period reflected on social media? Does significant association exist between the changing Covid-19 awareness and the pandemic outbreak? We established a Twitter data mining framework calculating the Ratio index to quantify and track awareness. The lag correlations between awareness and health impacts were examined at global and country levels. Results show that users presenting the highest Covid-19 awareness were mainly those tweeting in the official languages of India and Bangladesh. Asian countries showed more disparities in awareness than European countries, and awareness in Eastern Europe was higher than in central Europe. Finally, the Ratio index had high correlations with global mortality rate, global case fatality ratio, and country-level mortality rate, with 21-31, 35-42, and 13–18 leading days, respectively. This study yields timely insights into social media use in understanding human behaviors for public health research.
The nosocomial pathogen Clostridioides difficile is a burden to the healthcare system. Gut microbiome disruption, most commonly by broad-spectrum antibiotic treatment, is well established to generate a state that is susceptible to CDI. A variety of metabolites produced by the host and/or gut microbiota have been shown to interact with C. difficile. Certain bile acids promote/inhibit germination while other cholesterol-derived compounds and amino acids used in the Stickland metabolic pathway affect growth and CDI colonization. Short chain fatty acids maintain intestinal barrier integrity and a myriad of other metabolic compounds are used as nutritional sources or used by C. difficile to inhibit or outcompete other bacteria in the gut. As the move toward non-antibiotic CDI treatment takes place, a deeper understanding of interactions between C. difficile and the host's gut microbiome and metabolites becomes more relevant.
Understanding the pore system and the geological factors controlling the adsorption of gas in mudstones and shales is a key element in predicting the gas accumulation potential of an unconventional reservoir. A series of integrated methods, including basic geochemistry, X-ray diffraction, scanning electron microscopy, low-pressure gas (CO2 and Ar) physisorption, and high-pressure methane adsorption were performed on a set of mudstones from the Triassic Yanchang Formation in Ordos Basin, to characterize the pore system and gas adsorption capacity and their geological controlling factors. The results show that the studied Yanchang Mudstones are mainly siliceous rocks with high total organic carbon concentration (average of 7.63%) and low to moderate thermal maturity (vitrinite reflectance of 0.55–0.92 %). The microscopic visible pores are mainly intergranular pores between organic matter and rigid mineral grains, while organic matter pores are less well-developed. The pore volume is mainly contained in micropores (diameter < 2 nm) and mesopores (diameter = 2–50 nm), while much of the specific surface area occurs in the micropores, mainly in the organic matter pores. The occurrence of rigid minerals can inhibit the compaction of the intergranular pores. The abundant organic matter can provide potential adsorption sites for gas molecules, while clays and rigid minerals also have a limited positive effect on adsorption capacity. The adsorbed methane is mainly stored in micropores, which accounts for about 55%–90% of the total adsorbed methane content.
Background River damming inevitably reshapes water thermal conditions that are important to the general health of river ecosystems. Although a lot of studies have addressed the damming’s thermal impacts, most of them just assess the overall effects of climate variation and human activities on river thermal dynamics. Less attention has been given to quantifying the impact of climate variation, damming and flow regulation, respectively. In addition, for rivers that have already faced an erosion problem in downstream channels, an adjustment of the hydroelectric power plant operation manner is expected, which reinforces the need for understanding of flow regulation’s thermal impact. To fill this gap, an air2stream -based approach is proposed and applied at the Włocławek Reservoir in the Vistula River in Poland. Results In the years of 1952–1983, downstream river water temperature rose by 0.31 ℃ after damming. Meanwhile, the construction of dam increased the average annual water temperature by 0.55 ℃, while climate change oppositely made it decreased by 0.26 ℃. In addition, for the seasonal impact of damming, autumn was the most affected season with the warming reached 1.14 ℃, and the least affected season was winter when water temperature experienced a warming of 0.1 ℃. The absolute values of seasonal average temperature changes due to flow regulation were less than 0.1 ℃ for all the seasons. Conclusions The impacts of climate variation, damming, and flow regulation on river water temperatures can be evaluated reasonably on the strength of the proposed methodology. Climate variation and damming led to general opposite impacts on the downstream water temperature at the Włocławek Reservoir before 1980s. It is noted that the climate variation impact showed an opposite trend compared to that after 1980s. Besides, flow regulation below dam hardly affected downstream river water temperature variation. This study extends the current knowledge about impacts of climate variation and hydromorphological conditions on river water temperature, with a study area where river water temperature is higher than air temperature throughout a year.
Background Teen pregnancy prevention in the United States has traditionally focused on the development, testing, and subsequent implementation of a set of evidence-based programs (EBPs), recommended nationally. However, these existing EBPs often do not prioritize the most at-risk or vulnerable populations. Methods The Innovative Teen Pregnancy Prevention Programs (iTP 3 ) project was funded to facilitate the development of new, innovative programs to reach disparate populations. Through a mixed methods design, iTP 3 evaluated the process and resulting innovative programs from five iterative cohorts of funded organizations, referred to as Innovators. iTP 3 utilized both a traditional funding model with more traditional methods of capacity building assistance, but transitioned over time to a design-focused funding model in which organizations and individuals developed innovative programs through an intensive human centered design process. Results Evaluation results showed that the resulting portfolio of programs had differences in the types of programs resulting from the differing funding models. Notable differences among programs from the two funding models include program length, along with personnel, time, and resources needed to develop and manage. Conclusion Both traditional and design funding models led to innovative programs, with notable differences in the development process and resulting programs.
The field of plasmonics explores the interaction between light and metallic micro/nanostructures and films. The collective oscillation of free electrons on metallic surfaces enables subwavelength optical confinement and enhanced light–matter interactions. In optoelectronics, perovskite materials are particularly attractive due to their excellent absorption, emission, and carrier transport properties, which lead to the improved performance of solar cells, light-emitting diodes (LEDs), lasers, photodetectors, and sensors. When perovskite materials are coupled with plasmonic structures, the device performance significantly improves owing to strong near-field and far-field optical enhancements, as well as the plasmoelectric effect. Here, we review recent theoretical and experimental works on plasmonic perovskite solar cells, light emitters, and sensors. The underlying physical mechanisms, design routes, device performances, and optimization strategies are summarized. This review also lays out challenges and future directions for the plasmonic perovskite research field toward next-generation optoelectronic technologies.
The impact of climate extremes upon human settlements is expected to accelerate. There are distinct global trends for a continued rise in urban dwellers and associated infrastructure. This growth is occurring amidst the increasing risk of extreme heat, rainfall, and flooding. Therefore, it is critical that the urban development and architectural communities recognize climate impacts are expected to be experienced globally, but the cities and urban regions they help create are far more vulnerable to these extremes than nonurban regions. Designing resilient human settlements responding to climate change needs an integrated framework. The critical elements at play are climate extremes, economic growth, human mobility, and livability. Heightened public awareness of extreme weather crises and demands for a more moral climate landscape has promoted the discussion of urban climate change ethics. With the growing urgency for considering environmental justice, we need to consider a transparent, data-driven geospatial design approach that strives to balance environmental justice, climate, and economic development needs. Communities can greatly manage their vulnerabilities under climate extremes and enhance their resilience through appropriate design and planning towards long-term stability. A holistic picture of urban climate science is thus needed to be adopted by urban designers and planners as a principle to guide urban development strategy and environmental regulation in the context of a growingly interdependent world.
Diagnosis codes are used to study SARS-CoV2 infections and COVID-19 hospitalizations in administrative and electronic health record (EHR) data. Using EHR data (April 2020–March 2021) at the Yale-New Haven Health System and the three hospital systems of the Mayo Clinic, computable phenotype definitions based on ICD-10 diagnosis of COVID-19 (U07.1) were evaluated against positive SARS-CoV-2 PCR or antigen tests. We included 69,423 patients at Yale and 75,748 at Mayo Clinic with either a diagnosis code or a positive SARS-CoV-2 test. The precision and recall of a COVID-19 diagnosis for a positive test were 68.8% and 83.3%, respectively, at Yale, with higher precision (95%) and lower recall (63.5%) at Mayo Clinic, varying between 59.2% in Rochester to 97.3% in Arizona. For hospitalizations with a principal COVID-19 diagnosis, 94.8% at Yale and 80.5% at Mayo Clinic had an associated positive laboratory test, with secondary diagnosis of COVID-19 identifying additional patients. These patients had a twofold higher inhospital mortality than based on principal diagnosis. Standardization of coding practices is needed before the use of diagnosis codes in clinical research and epidemiological surveillance of COVID-19.
The COVID‐19 pandemic drastically impacted the Texas Division of Adult Education. As a result, Texas's grant‐funded adult education and literacy (AEL) programs transitioned to remote instruction. There was a need to understand how this unfolded. Thus, the purpose of this case study was to explore how the Texas Division of Adult Education guided AEL programs in the transition to remote services. Several published records were collected and analyzed using document and content analysis. The research findings revealed effective crisis management strategies and professional development interventions implemented by state leadership. This study also highlights the challenges and potential advantages of remote learning. These outcomes are helpful because they could guide other state agencies in incorporating remote learning courses. Ultimately, professional development training evaluations indicated the need for further program support to foster training transfer. This article concludes with implications for AEL programs and suggestions for future research.
Adult learning facilitators in any setting (ALFAS) seek to facilitate learning that is lifelong and meaningful. The purpose of this interpretive research study was to explore how instructional designers (IDs) construct knowledge when preparing graduate faculty to develop and teach courses online. The study involved five IDs and their perceptions of their knowledge construction when collaborating with graduate faculty to transition their courses to online instruction. The four main themes that emerged from the data were learning community or community of practice, individual experiences as adult educators, individual experiences as adult learners, and challenges to the learning process. These themes broaden the understanding of IDs’ perceived knowledge construction within a constructivist framework, an area that can inform adult educators and workplace learning as online instruction continues to gain much momentum.
Background The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato ( Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen ‘ Candidatus Liberibacter solanacearum’ (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant’s responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies. Results To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato ‘Moneymaker’ leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection. Conclusion The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis.
In the laser-based directed energy deposition (DED) process, blown powder additive manufacturing (AM), either spherical or irregular metal particles can be used as the feedstock to be delivered into a melt pool for fabrication. The delivered particles will interact with the melt flow in different regions of melt pool, and the interactions between the liquid melt pool and the spherical particles are different from those between the melt pool and irregular particles. The objective of this investigation is to reveal the mechanisms and dynamics of pore formation unique to spherical-powder delivery in the laser DED AM process. In situ high-speed and high-resolution X-ray imaging showed that delivered spherical particles could induce pore formation mechanisms through the interactions between the melt pool and the particle front surface, the particle side surface, or the particle back surface. These results indicate that spherical particles induce different pore formation mechanisms than irregular particles. This fundamental understanding will benefit further investigations into reducing porosity and improving DED-fabricated part quality.
Epigenetic abnormalities in DNA hydroxymethylation (5hmC) have been detected in patients with myeloid neoplasms, suggesting that 5hmC might act as a valuable epigenetic mark to reflect the disease status of myeloid neoplasms. Here, we report systematic genome-wide mapping of the DNA hydroxymethylomes in over 70 patients with myeloid neoplasms. Our integrative analysis leads to the identification of distinct 5hmC signatures that can sensitively discriminate patients from healthy individuals. At the molecular level, we unveiled dynamic 5hmC changes within key transcription factor (e.g., the CEBP family) binding motifs that are essential for hematopoiesis and myeloid lineage specification. 5hmC redistribution was found to alter the genome-wide binding of CEBP-α, thereby reprogramming transcriptional outputs to affect leukemia cell survival and stemness. Taken together, we provide a comprehensive 5hmC atlas representative of myeloid neoplasms, which sets the stage for future exploration on the epigenetic etiology of hematological malignancies. Mechanistically, our study further furnishes important insights into how abnormal 5hmC distribution in patients directly interrupts the binding of transcription factors to reshape transcriptional landscapes and aggravate leukemogenesis.
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20,183 members
Paul G Harms
  • Department of Animal Science
Haili Zhang
  • Department of Veterinary Pathobiology
Gaya Prasad Yadav
  • Department of Biochemistry/Biophysics
Anne Raymond
  • Department of Geology and Geophysics
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