University of South Carolina
  • Columbia, SC, United States
Recent publications
Facial amphiphilicity is an extraordinary chemical structure feature of a variety of antimicrobial peptides and polymers. Vast efforts have been dedicated to small molecular, macromolecular and dendrimer-like systems to mimic this highly preferred structure or conformation, including local facial amphiphilicity and global amphiphilicity. This work conceptualizes Facial Amphiphilicity Index (FAI) as a numerical value to quantitatively characterize the measure of chemical compositions and structural features in dictating antimicrobial efficacy. FAI is a ratio of numbers of charges to rings, representing both compositions of hydrophilicity and hydrophobicity. Cationic derivatives of multicyclic compounds were evaluated as model systems for testing antimicrobial selectivity against Gram-negative and Gram-positive bacteria. Both monocyclic and bicyclic compounds are non-antimicrobial regardless of FAIs. Antimicrobial efficacy was observed with systems having larger cross-sectional areas including tricyclic abietic acid and tetracyclic bile acid. While low and high FAIs respectively lead to higher and lower antimicrobial efficacy, in consideration of cytotoxicity, the sweet spot is typically suited with intermediate FAIs for each specific system. This can be well explained by the synergistic hydrophobic-hydrophobic and electrostatic interactions with bacterial cell membranes and the difference between bacterial and mammalian cell membranes. The adoption of FAI would pave a new avenue toward the design of next-generation antimicrobial macromolecules and peptides.
High-rate systems are defined as engineering systems that undergo accelerations of amplitudes typically greater than 100 gn over less than 100 ms. Examples include adaptive airbag deployment systems, hypersonic vehicles, and active blast mitigation systems. The use of feedback mechanisms in these high-rate applications is often critical in ensuring their continuous operations and safety. Of interest to this paper are algorithms needed to support high-rate structural health monitoring (HRSHM) to empower sub-millisecond decision systems. HRSHM is a complex task because high-rate systems are uniquely characterized by (1) large uncertainties in the external loads, (2) high levels of non-stationarities and heavy disturbances, and (3) unmodeled dynamics generated from changes in system configurations that necessitate careful crafting of adaptive strategies. This paper studies benefits of integrating a data-driven predictive model with a physics-based state observer to reduce latency and convergence time estimating actionable information. The predictive model, constructed with long short-term memory (LSTM) cells, performs multi-step ahead signal prediction acting as the input to the physical model, a model reference adaptive system (MRAS). The MRAS then performs state estimation of the predicted signal rather than the true signal. A comparison study was done between the proposed hybrid algorithm and a physics-based MRAS on a testbed involving a fast-moving boundary condition. Results showed that the hybrid algorithm could perform state estimations with zero timing deadline overshoot and with up to 50% faster convergence time when compared to the MRAS under constant boundary conditions. However, the hybrid generally underperformed the MRAS algorithm in terms of convergence accuracy during motion of the boundary condition by increasing convergence time by 20%, attributable to the lag in learning the new dynamics used in predicting. The performance of the NSE algorithm was also examined on a true high-rate system, where it was shown to be capable of qualitatively tracking actionable information.
Massive Open Online Courses (MOOCs) have been touted as a disruptive innovation with a low-cost and flexible option for opening up higher education. However, existing barriers of MOOCs such as a low retention rate and a low forum participation rate have limited their capacity of serving learners. To strengthen the potential of MOOCs, a compelling design that enables an effective learning experience is needed. This article is aimed to propose a series of design guidelines for MOOCs, namely the LITTLE, as a preliminary design framework for an effective MOOC. The LITTLE includes guidelines such as learner-centered, inquiry-based, technology-enriched, trophy-driven, literature-guided, and evidence-based strategies. Examples are provided in concert with theoretical justifications to illustrate the guidelines. © 2022 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license.
Background Women who carry a premutation allele of the FMR1 gene are at increased vulnerability to an array of age-related symptoms and disorders, including age-related decline in select cognitive skills. However, the risk factors for age-related decline are poorly understood, including the potential role of family history and genetic factors. In other forms of pathological aging, early decline in syntactic complexity is observed and predicts the later onset of neurodegenerative disease. To shed light on the earliest signs of degeneration, the present study characterized longitudinal changes in the syntactic complexity of women with the FMR1 premutation across midlife, and associations with family history of fragile X-associated tremor/ataxia syndrome (FXTAS) and CGG repeat length. Methods Forty-five women with the FMR1 premutation aged 35–64 years at study entry participated in 1–5 longitudinal assessments spaced approximately a year apart (130 observations total). All participants were mothers of children with confirmed fragile X syndrome. Language samples were analyzed for syntactic complexity and participants provided information on family history of FXTAS. CGG repeat length was determined via molecular genetic testing. Results Hierarchical linear models indicated that women who reported a family history of FXTAS exhibited faster age-related decline in syntactic complexity than those without a family history, with that difference emerging as the women reached their mid-50 s. CGG repeat length was not a significant predictor of age-related change. Conclusions Results suggest that women with the FMR1 premutation who have a family history of FXTAS may be at increased risk for neurodegenerative disease, as indicated by age-related loss of syntactic complexity. Thus, family history of FXTAS may represent a personalized risk factor for age-related disease. Follow-up study is needed to determine whether syntactic decline is an early indicator of FXTAS specifically, as opposed to being a more general age-related cognitive decline associated with the FMR1 premutation.
The chemical pollution crisis severely threatens human and environmental health globally. To tackle this challenge the establishment of an overarching international science–policy body has recently been suggested. We strongly support this initiative based on the awareness that humanity has already likely left the safe operating space within planetary boundaries for novel entities including chemical pollution. Immediate action is essential and needs to be informed by sound scientific knowledge and data compiled and critically evaluated by an overarching science–policy interface body. Major challenges for such a body are (i) to foster global knowledge production on exposure, impacts and governance going beyond data-rich regions (e.g., Europe and North America), (ii) to cover the entirety of hazardous chemicals, mixtures and wastes, (iii) to follow a one-health perspective considering the risks posed by chemicals and waste on ecosystem and human health, and (iv) to strive for solution-oriented assessments based on systems thinking. Based on multiple evidence on urgent action on a global scale, we call scientists and practitioners to mobilize their scientific networks and to intensify science–policy interaction with national governments to support the negotiations on the establishment of an intergovernmental body based on scientific knowledge explaining the anticipated benefit for human and environmental health.
Aim: To evaluate whether dietary pattern changes, antioxidant supplementation or 5-10% weight loss could improve disease activity (skin and joint) in patients with psoriatic arthritis (PsA). Methods: A total of 97 PsA patients were enrolled in this 12-week randomized, double-blinded, placebo-controlled trial. Patients were randomized into three groups: Diet-placebo (hypocaloric diet + placebo supplementation); Diet-fish (hypocaloric diet + 3 g/day of omega-3 supplementation; and Placebo. Food intake (3-day registry, Healthy Eating Index (HEI), and the Dietary Inflammatory Index (DII)), body composition (whole-body dual-energy X-ray absorptiometry (DXA), weight and waist circumference) and disease activity (PASI, BSA, BASDAI, DAS28-ESR, DAS28-CRP and MDA) were evaluated at baseline and after the 12-week intervention. Statistical analysis used the intention-to-treat approach. The P value was considered to indicate significance when below 0.05. Results: After 12 weeks, DAS28-CRP and BASDAI scores improved, especially in the Diet-placebo group (- 0.6 ± 0.9; p = 0.004 and - 1.39 ± 1.97; p = 0.001, respectively). In addition, a higher proportion of patients achieved minimal disease activity (MDA) in all groups. The Diet-fish group showed significant weight loss (- 1.79 ± 2.4; p = 0.004), as well as waist circumference (- 3.28 ± 3.5, p < 0.001) and body fat (- 1.2 ± 2.2, p = 0.006) reductions. There was no significant correlation between weight loss and disease activity improvement. Each 1-unit increase in the HEI value reduced the likelihood of achieving remission by 4%. Additionally, each 100-cal daily intake increase caused a 3.4-fold DAS28-ESR impairment. Conclusion: A 12-week hypocaloric intervention provided suitable control of joint disease activity in patients with PsA, regardless of weight loss. Adding omega-3 supplementation caused relevant body composition changes but not disease activity improvement. Trial registration: The study was recorded on Clinicaltrials.gov (NCT03142503).
In this study, a dynamic model for the bearing rotor system of a high-speed train under variable speed conditions is established. In contrast to previous studies, the contact stress is simplified in the proposed model and the compensation balance excitation caused by the rotor mass eccentricity considered. The angle iteration method is used to overcome the challenge posed by the inability to determine the roller space position during bearing rotation. The simulation results show that the model accurately describes the dynamics of bearings under varying speed profiles that contain acceleration, deceleration, and speed oscillation stages. The order ratio spectrum of the bearing vibration signal indicates that both the single and multiple frequencies in the simulation results are consistent with the theoretical results. Experiments on bearings with outer and inner ring faults under various operating conditions are performed to verify the developed model.
The question about behavior of gaps between zeros of polynomials under differentiation is classical and goes back to Marcel Riesz. Recently, Stefan Steinerberger [42] formally derived a nonlocal nonlinear partial differential equation which models dynamics of roots of polynomials under differentiation. In this paper, we connect rigorously solutions of Steinerberger’s PDE and evolution of roots under differentiation for a class of trigonometric polynomials. Namely, we prove that the distribution of the zeros of the derivatives of a polynomial and the corresponding solutions of the PDE remain close for all times. The global in time control follows from the analysis of the propagation of errors equation, which turns out to be a nonlinear fractional heat equation with the main term similar to the modulated discretized fractional Laplacian (-Δ)1/2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(-\Delta )^{1/2}$$\end{document}.
Social media is commonly used by the public during election campaigns to express their opinions regarding different issues. Among various social media channels, Twitter provides an efficient platform for researchers and politicians to explore public opinion regarding a wide range of topics such as the economy and foreign policy. Current literature mainly focuses on analyzing the content of tweets without considering the gender of users. This research collects and analyzes a large number of tweets and uses computational, human coding, and statistical analyses to identify topics in more than 300,000 tweets posted during the 2020 U.S. presidential election and to compare female and male users regarding the average weight of the discussed topics. Our findings are based upon a wide range of topics, such as tax, climate change, and the COVID-19 pandemic. Out of the topics, there exists a significant difference between female and male users for more than 70% of topics.
Fossil fuels are the primary source of energy for a long period in spite of excessive environmental hazards, such as greenhouse gas emissions. Production of energy and fuel from lignocellulosic biomass has been the goal of the study in pursuit of renewable alternatives to fossil materials. Corncob is common agricultural biomass waste found in many countries. It can be utilized to produce bioenergy, but the conversion efficiency is limited. Pretreatment may be applied to improve the efficiency of corncob conversion; for example, by the fractionation of lignocellulosic biomass. Choline chloride (ChCl) and glycerol are considered as synthetic deep eutectic solvents (DESs), also known as green solvents. DESs are expected to fractionate hemicellulose and lignin from raw biomass, and the accessibility of cellulose may be enhanced. In this work, pretreatment of corncob with DES prepared from ChCl and glycerol was investigated at varying reaction temperatures (60–150 °C), residence times (6–15 h), and ChCl-to-glycerol molar ratios (1:0.5-4). The results showed that hemicellulose and lignin were effectively extracted from the raw corncob, and therefore, cellulose content in the remaining solid residue, known as cellulose-rich material (CRM), can be improved by least 140%. The reaction temperature, residence time, and presence of ChCl in the DES influenced the pretreatment of corncob significantly. Increases in reaction temperature and residence time led to a higher cellulose content in CRMs and an increased extraction of hemicellulose and lignin from the raw corncob. Without the ChCl in DES, the cellulose content in CRMs and the extraction of hemicellulose and lignin from the sample were decreased markedly. The optimal condition at 150 °C, 12-h residence time, and 1:4 ChCl-to-glycerol molar ratio could be used to improve the cellulose content of CRMs from the raw corncob by more than 150%. The CRM with improved lignocellulosic properties can be used as a feedstock in further bioenergy/fuel application.
Among renewable and sustainable energy resources, biomass plays a vital role. Agricultural residues/wastes, energy crops, and lignocellulosic biomass could potentially be major feedstocks for biorefineries. In Thailand, one of the most interesting energy crops is hybrid giant Juncao grass (GJG) or Pennisetum purpureum × Pennisetum typhoideum. GJG can be easily grown and has relatively high yields under tropical climates. Herein, conversion of GJG to biofuels via hydrothermal liquefaction (HTL) was investigated using batch reactors under varying reaction temperatures of 250–350 °C and biomass-to-deionized water concentrations of 15–25 wt% at a fixed residence time of 30 min. Changes in temperature and GJG-to-deionized water concentration were found to markedly affect the yields and distribution of products from HTL of GJG. Yields of the liquid product, or bio-oil, can be up to 50 wt% at 350 °C and 25 wt% GJG-to-deionized water concentration. The yields of solid char and gas products fluctuated within 10–25 wt% and 30–45 wt%, respectively. Higher heating values of the resulting bio-oil and char were remarkably better than those of the raw material. An energy recovery of over 50% from the bio-oil, as well as about 35% from the char, can be obtained. By gas chromatograph-mass spectrometry and nuclear magnetic resonance, the bio-oil obtained was found to be a complex chemical mixture, consisting mainly of phenols, nitrogenous compounds, aliphatic compounds, ketones, carboxylic acids, and aldehydes. The finding is useful in future utilization of GJG via HTL for biofuel and/or biochemical production.
In this article, I review the academic literature on the economics of plug-in electric vehicles (PEVs), with a focus on PEV policy, benefits, and equity. PEVs are one of the most promising technologies for decarbonizing the transportation sector. As such, many government policies exist to promote their adoption. Understanding the effectiveness and equity of existing policies, what the realized environmental benefits are, and how these benefits compare to costs is crucial to improving future PEV policy. This review suggests that consumer PEV subsidies are not cost-effective and are often expensive relative to estimated environmental benefits. Furthermore, higher-income households who make up a larger share of the PEV market receive both a disproportionate amount of government subsidies as well as PEV benefits. There is considerable room for policy improvement. Expected final online publication date for the Annual Review of Resource Economics, Volume 14 is October 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Awareness that high-status adolescents can be targets of aggression has grown in recent years. However, questions remain about the associations of the confluence of victimization and popularity with adjustment. The current study fills this gap by examining the joint and unique effects of victimization and popularity on aggression and alcohol use. Participants were 804 Dutch adolescents (50.2% boys, Mage = 13.65) who were followed for one year. High-status victims were more aggressive and drank more alcohol than lower-status victims. High-status victims were also more proactively and indirectly aggressive and self-reported more bullying than high-status non-victims. Thus, the findings demonstrated a conjoined risk of victimization and popularity for some types of aggression.
Information technology developments have combined traditional face-to-face counseling with online- or cyber-counseling. As digital natives, Generation Z has easy access to cyber-counseling. However, their attitudes toward cyber-counseling remain unknown. This study explored these attitudes and relevant influencing factors among 1216 Chinese adolescents using self-report questionnaires. Descriptive analyses and structural equation modeling were used for data analysis. The model explained 27.7 % of the total variance, attitudes toward psychological help was the most influential, followed by attitudes toward the Internet and perceived behavioral control. The model was effective in explaining attitudes toward cyber-counseling, emphasizing the influence of attitudes toward psychological help.
The problem of observables and their supposed lack of change has been significant in Hamiltonian quantum gravity since the 1950s. This paper considers the unrecognized variety of ideas about observables in the thought of constrained Hamiltonian dynamics co-founder Peter Bergmann, who trained many students at Syracuse and invented observables. Whereas initially Bergmann required a constrained Hamiltonian formalism to be mathematically equivalent to the Lagrangian, in 1953 Bergmann and Schiller introduced a novel postulate, motivated by facilitating quantum gravity. This postulate held that observables were invariant under transformations generated by each individual first-class constraint. While modern works rely on Bergmann's authority and sometimes speak of “Bergmann observables,” he had much to say about observables, generally interesting and plausible but not all mutually consistent and much of it neglected. On occasion he required observables to be locally defined (not changeless and global); at times he wanted observables to be independent of the Hamiltonian formalism (implicitly contrary to a definition involving separate first-class constraints). But typically he took observables to have vanishing Poisson bracket with each first-class constraint and took this result to be justified by the example of electrodynamics. He expected observables to be analogous to the transverse true degrees of freedom of electromagnetism. Given these premises, there is no coherent concept of observables which he reliably endorsed, much less established. A revised definition of observables that satisfies the requirement that equivalent theories should have equivalent observables using the Rosenfeld–Anderson–Bergmann–Castellani gauge generator G, a tuned sum of first-class constraints that changes the canonical action ∫dt(pq̇−H) by a boundary term. Bootstrapping from theory formulations with no first-class constraints, one finds that the “external” coordinate gauge symmetry of GR calls for covariance (a transformation rule and hence a 4-dimensional Lie derivative for the Poisson bracket), not invariance (0 Poisson bracket), under G (not each first-class constraint separately).
Novel integration of adsorption followed by catalytic oxidation is expected to be more beneficial for higher Mn (II) removal performance. We prepared self-assembled 3D flower-like Mg(OH) 2 coated on granular-sized polyurethane (namely FMHP) via hydrothermal method at 120°C under a facile synthesis route. The optimized material, FMHP prepared with 7 g MgO and 20 g polyurethane (FMH 0.35 P), achieved up to 351.2 mg g -1 Mn(II) removal capacity by Langmuir isotherm model. Besides, FMHP exhibited high Mn(II) removal in a wide range of NaCl concentration (0 ~ 0.1 M) and pH 2~9. Notably, through consecutive kinetics, BET, XPS, XRD, FESEM, and TEM analyses, it was found that the MnO x layer grows in-situ via ion exchange with Mg(II) on FMHP and further boosts the Mn(II) removal via catalytic oxidation during the Mn(II) removal process. Further, column experiments revealed that the FMH 0.35 P exhibited superior Mn(II) removal capacities up to 135.9 mg g -1 and highly compatible treatment costs ($0.062 m -3 ) compared to conventional chemical processes. The granular-sized FMH 0.35 P prepared by economic precursors and simple synthesis route revealed a high potential for Mn(II) containing water treatment due to its high removal capacities and easy operation.
Tropospheric attenuations can be significant in the millimeter wave (mmWave) frequency bands; hence, accurate prediction modeling of tropospheric attenuation is important for reliable mmWave communication. Several models have been established by the International Telecommunication Union (ITU), yet estimation accuracy is limited due to the large spatial scales used for model input parameters. In this paper, we address this and apply local precipitation data to analyze tropospheric attenuation statistics and compare to results when using ITU regional input rain data. Specifically, tropospheric attenuation is predicted via simulations using the ITU method at 30, 60, and 90 GHz in four distinct geographic locations with different climate types. From our simulations, we gather statistics for annual average rain attenuation, worst month rain attenuation, and rain attenuation per decade. Our results indicate that when using local measured rain data, for 1 km link distance, mean rain event attenuation increases from 0.5 to 2 dB. Local rain data yield larger attenuations at essentially all percentages of time not exceeded (essentially corresponding to all probability values): for example, for 0.1% of time not exceeded, in Columbia, SC, rain attenuation for 30 GHz frequency increases to 9 dB with local rain data, compared to 5 dB with ITU's regional data, corresponding to rain rates of 38.2 and 17.5 mm/h, respectively; at the same probability and location, the 90 GHz attenuation increases by 10 dB, from 10 to 20 dB when local rain data are used. Fog attenuations are also appreciable, reaching 8 dB for the 90 GHz frequency. Moreover, for the example locations, peak rain attenuations have increased at a rate of approximately 2 dB/decade over the past 50 years. Our results indicate that actual tropospheric attenuations may be substantially larger than that predicted by the ITU model when using regional rain rate data.
It is controversial whether the cardiac type-2 ryanodine receptor harboring a catecholaminergic polymorphic ventricular tachycardia-associated point mutation is regulated by luminal or cytosolic Ca2+. This commentary discusses new findings supporting the cytosolic Ca2+-dependent regulation.
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Paul Vrana
  • Peromyscus Genetic Stock Center
Joshua Cooper
  • Department of Mathematics
Sujit Pujhari
  • School of Medicine
Brandon Bookstaver
  • Clinical Pharmacy and Outcomes Sciences
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29208, Columbia, SC, United States
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Dr. Harris Pastides
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