Auburn University
  • Auburn, AL, United States
Recent publications
The endomembrane system, functioning in secretion, performs many roles relating to eukaryotic cellphysiological processes and the Golgi apparatus is the central organelle in this system. An essentialassociated Golgi component is the conserved oligomeric Golgi (COG) complex, maintaining correctGolgi structure and function during retrograde trafficking. In animals, naturally occurring cogmutants provide a window into understanding it’s function(s). Eliminating even one COGcomponent impairs its function. In animals, COG mutations lead to severe cell biological anddevelopmental defects and death while far less is understood in plants which is changing. Theplant genetic model Arabidopsis thaliana COG complex functions in growth, cell expansion andother processes, involving direct interactions with other secretion system components includingthe exocyst, soluble N-Ethylmaleimide-Sensitive Factor Attachment Protein Receptor (SNARE), andthe microtubule cytoskeleton. Recent experiments have identified a defense role for the COGcomplex in plants, the focus of this review.
The internal ribosome entry site (IRES) RNA of bovine viral diarrhoea virus (BVDV), an economically significant Pestivirus, is required for the cap-independent translation of viral genomic RNA. Thus, it is essential for viral replication and pathogenesis. We applied a combination of high-throughput biochemical RNA structure probing (SHAPE-MaP) and in silico modelling approaches to gain insight into the secondary and tertiary structures of BVDV IRES RNA. Our study demonstrated that BVDV IRES RNA in solution forms a modular architecture composed of three distinct structural domains (I-III). Two regions within domain III are represented in tertiary interactions to form an H-type pseudoknot. Computational modelling of the pseudoknot motif provided a fine-grained picture of the tertiary structure and local arrangement of helices in the BVDV IRES. Furthermore, comparative genomics and consensus structure predictions revealed that the pseudoknot is evolutionarily conserved among many Pestivirus species. These studies provide detailed insight into the structural arrangement of BVDV IRES RNA H-type pseudoknot and encompassing motifs that likely contribute to the optimal functionality of viral cap-independent translation element.
Previous invasive studies indicate that human neocortical graymatter contains cytoarchitectonically distinct layers, with notable differences in their structural connectivity with the rest of the brain. Given recent improvements in the spatial resolution of anatomical and functional magnetic resonance imaging (fMRI), we hypothesize that resting state functional connectivity (FC) derived from fMRI is sensitive to layer-specific thalamo-cortical and cortico-cortical microcircuits. Using sub-millimeter resting state fMRI data obtained at 7 T, we found that: (1) FC between the entire thalamus and cortical layers I and VI was significantly stronger than between the thalamus and other layers. Furthermore, FC between somatosensory thalamus (ventral posterolateral nucleus, VPL) and layers IV, VI of the primary somatosensory cortex were stronger than with other layers; (2) Inter-hemispheric cortico-cortical FC between homologous regions in superficial layers (layers I–III) was stronger compared to deep layers (layers V–VI). These findings are in agreement with structural connections inferred from previous invasive studies that showed that: (i) M-type neurons in the entire thalamus project to layer-I; (ii) Pyramidal neurons in layer-VI target all thalamic nuclei, (iii) C-type neurons in the VPL project to layer-IV and receive inputs from layer-VI of the primary somatosensory cortex, and (iv) 80% of collosal projecting neurons between homologous cortical regions connect superficial layers. Our results demonstrate for the first time that resting state fMRI is sensitive to structural connections between cortical layers (previously inferred through invasive studies), specifically in thalamo-cortical and cortico-cortical networks.
The RAS oncogene is both the most frequently mutated oncogene in human cancer and the first confirmed human oncogene to be discovered in 1982. After decades of research, in 2013, the Shokat lab achieved a seminal breakthrough by showing that the activated KRAS isozyme caused by the G12C mutation in the KRAS gene can be directly inhibited via a newly unearthed switch II pocket. Building upon this groundbreaking discovery, sotorasib (AMG510) obtained approval by the United States Food and Drug Administration in 2021 to become the first therapy to directly target the KRAS oncoprotein in any KRAS-mutant cancers, particularly those harboring the KRAS G12C mutation. Adagrasib (MRTX849) and other direct KRAS G12C inhibitors are currently being investigated in multiple clinical trials. In this review, we delve into the path leading to the development of this novel KRAS inhibitor, starting with the discovery, structure, and function of the RAS family of oncoproteins. We then examine the clinical relevance of KRAS, especially the KRAS G12C mutation in human cancer, by providing an in-depth analysis of its cancer epidemiology. Finally, we review the preclinical evidence that supported the initial development of the direct KRAS G12C inhibitors and summarize the ongoing clinical trials of all direct KRAS G12C inhibitors.
Fungicides reduce fungal pathogen populations and are essential to food security. Understanding the impacts of fungicides on crop microbiomes is vital to minimizing unintended consequences while maintaining their use for plant protection. However, fungicide disturbance of plant microbiomes has received limited attention, and has not been examined in different agricultural management systems. We used amplicon sequencing of fungi and prokaryotes in maize and soybean microbiomes before and after foliar fungicide application in leaves and roots from plots under long-term no-till and conventional tillage management. We examined fungicide disturbance and resilience, which revealed consistent non-target effects and greater resiliency under no-till management. Fungicides lowered pathogen abundance in maize and soybean and decreased the abundance of Tremellomycetes yeasts, especially Bulleribasidiaceae, including core microbiome members. Fungicide application reduced network complexity in the soybean phyllosphere, which revealed altered co-occurrence patterns between yeast species of Bulleribasidiaceae, and Sphingomonas and Hymenobacter in fungicide treated plots. Results indicate that foliar fungicides lower pathogen and non-target fungal abundance and may impact prokaryotes indirectly. Treatment effects were confined to the phyllosphere and did not impact belowground microbial communities. Overall, these results demonstrate the resilience of no-till management to fungicide disturbance, a potential novel ecosystem service provided by no-till agriculture.
Preparation strategies of cellulose nanopaper were elaborated.Functionalization of cellulose nanopaper and its advanced applications were summarized.Prospects and challenges of cellulose nanopaper were discussed. Preparation strategies of cellulose nanopaper were elaborated. Functionalization of cellulose nanopaper and its advanced applications were summarized. Prospects and challenges of cellulose nanopaper were discussed. Cellulose nanopaper has shown great potential in diverse fields including optoelectronic devices, food packaging, biomedical application, and so forth, owing to their various advantages such as good flexibility, tunable light transmittance, high thermal stability, low thermal expansion coefficient, and superior mechanical properties. Herein, recent progress on the fabrication and applications of cellulose nanopaper is summarized and discussed based on the analyses of the latest studies. We begin with a brief introduction of the three types of nanocellulose: cellulose nanocrystals, cellulose nanofibrils and bacterial cellulose, recapitulating their differences in preparation and properties. Then, the main preparation methods of cellulose nanopaper including filtration method and casting method as well as the newly developed technology are systematically elaborated and compared. Furthermore, the advanced applications of cellulose nanopaper including energy storage, electronic devices, water treatment, and high-performance packaging materials were highlighted. Finally, the prospects and ongoing challenges of cellulose nanopaper were summarized.
The application of citric acid and glycerol as natural binder was investigated for the manufacturing of jute stick particleboard in this study. The effects of citric acid content (0–30 wt%), citric acid and glycerol mixture (ratio of CA–G), and pressing temperatures on the properties of jute stick particleboard were investigated. Citric acid-bonded jute stick particleboard had good mechanical properties and dimensional stability when citric acid concentration was 20 wt% at pressing temperature of 200 °C. By addition of glycerol concentration (40/60), the properties were further increased. The modulus of rupture (MOR) and thickness swelling (TS) values of CA–G (40/60) bonded jute stick particleboard were 19.67 N/mm ² and 9%, respectively, which satisfy the minimum requirement for type-18 of particleboard JIS A 5908 (2003). FTIR analysis confirmed the formation of ester linkage by polymerization reaction between carboxyl groups and alcohol groups. Citric acid and glycerol polymer reacted with jute stick particles and produced cross-linked networks with enhanced properties, hence improved the adhesiveness during particleboard production. It could be concluded that citric acid and glycerol mixture can be a potential natural binder for the production of jute stick particleboard.
Objective Long INterspersed Element-1 (L1) is an autonomous transposable element in the genome. L1 transcripts that are not reverse transcribed back into the genome can accumulate in the cytoplasm and activate an inflammatory response via the cyclic GMP-AMP (cGAS)-STING pathway. We examined skeletal muscle L1 markers as well as STING protein levels in 10 older individuals (63 ± 11 y, BMI = 30.2 ± 6.8 kg/m ² ) with end-stage osteoarthritis (OA) undergoing total hip (THA, n = 4) or knee (TKA, n = 6) arthroplasty versus 10 young, healthy comparators (Y, 22 ± 2 y, BMI = 23.2 ± 2.5 kg/m ² ). For OA, muscle was collected from surgical (SX) and contralateral (CTL) sides whereas single vastus lateralis samples were collected from Y. Results L1 mRNA was higher in CTL and SX compared to Y (p < 0.001 and p = 0.001, respectively). Protein expression was higher in SX versus Y for ORF1p (p = 0.002) and STING (p = 0.022). While these data are preliminary due to limited n-sizes and the lack of a BMI-matched younger control group, higher L1 mRNA expression, ORF1p and STING protein are evident in older versus younger adults. More research is needed to determine whether cGAS-STING signaling contributes to heightened muscle inflammation during aging and/or OA.
Classifying the sentiments of online reviews of products or services is important in that it provides the analysts with the ability to extract critical information which can be used to improve the corresponding product or service. The objective of this study is to classify the customer reviews (on a five-star and binary scale) that were collected for four different types of products/services. To achieve this goal, a novel classification framework is built by devising a unique classifier (composite variable), which includes rich information gathered by using all of the extracted features. The proposed framework is compared to commonly used Singular Value Decomposition (SVD) and chi-square-based feature selection (selected features, SF). These approaches are separately deployed in tree-based machine learning algorithms and Logistic Regression using a five-fold cross validation strategy. The results indicate that the proposed methodology outperforms the alternatives for each dataset employed.
Bi2Te3-based materials are remarkable thermoelectric renewable energy harvesters. The measurement of their thermal conductivity (κ) is a critical phase toward the realization of the material's energy conversion efficiency. However, the experimental techniques involved in the measurements of κ, particularly for thin films, are incredibly challenging. Herein, we introduce a pioneering technique using support vector regression and decision tree regression machine learning models where the values of κ can be predicted based on the structural crystal lattice constants of the material and its electrical properties. A decision tree regression (DTR) and support vector regression (SVR) models using both radial basis function (RBF) and polynomial kernels were developed. The performance of the models was evaluated based on the correlation coefficient (CC) between the predicted and actual values of κ, R² values, mean absolute error (MAE), and mean square error (MSE). Our results revealed that the DTR outperforms the SVR models in estimating the values of κ with CC of 98.7% and R² of 97.5% for the testing phase. The models were validated by solving some real-world problems such as predicting the thermal conductivity of transition metal-doped Cu–Bi2Te3, effects of doping non-metals (Se–Bi2Te3), and the role of toxic elements (Pb–Bi2Te3) on the values of κ. The model was further employed to investigate the effects of pulsed laser deposition substrate temperature on the thermal conductivity of Bi2Te3. The performance of the models in predicting the thermal conductivity of Bi2Te3-based materials makes it a useful tool for thermoelectric energy research.
Research regarding the pros and cons of returns policy changes is limited. We use psychological contract theory and organizational justice theory to explore the effect of a returns policy change on customer intentions to spread negative word of mouth, switch to a different retailer’s website, and switch to the retailer’s physical store. We follow a mixed-method sequential method. In Study 1, an experiment tests our theoretically developed hypotheses. In Study 2, qualitative data provides additional insight into our findings. Results indicate that the type of returns policy change was significantly related to customer intent to spread negative word of mouth. Further, the intensity of a retailer’s communication to convey returns policy changes plays an important moderating role and a moderated mediation role regarding customer intentions. Contextually, the research provides important theoretical and managerial insights into factors to consider when implementing returns policy changes.
Pressures to maximize survey space or mitigate respondent fatigue can lead researchers to employ abbreviated during data collection. This is problematic because short-form measures can suffer from reduced reliability and validity. Thus, we conducted a meta-analysis to determine whether the use of brief measures of the Big Five in business research tends to produce psychometrically sound and criterion-valid results. We compared scale internal consistencies and effect size estimates from our study with meta-analytic estimates for long measures of the Big Five, as established in the literature. Our results indicated that, in general, internal consistency estimates were not substantively different. However, the criterion-related validity comparisons indicated that several point estimates for individual measures did not fall within the credibility intervals obtained from prior meta-analyses. This suggests that although brief measures of the Big Five might appear acceptable for use in business research, caution should be exercised when choosing a brief measure.
The production of clean oil products from oily waste can help the oil industry to become more efficient and sustainable. A novel technique is developed that takes waste refinery oily sludge (ROS) as feedstock to produce a clean high quality oil product. The cost of the feedstock supply is very low as ROS is a waste product that is costly to dispose of with potential adverse consequences for the ecosystem if improperly discarded. The novel process involves a two-stage tubular fixed-bed reactor capable of converting the ROS into a clean oil product and simultaneously upgrade its quality. To systematically optimize the process variables, the response surface methodology (RSM) is applied. A meticulous mathematical model with an error of less than 5% estimates the optimum point for achieving the maximum product yield. The upgrading process involves a specifically synthesized, highly selective metal (Ni/Co/Mo) loaded zeolite catalysts. The synthesized catalysts are carefully characterized using XRD, FTIR, ICP, and SEM analysis. The detailed compositions of the upgraded products are also characterized using GC–MS CHNS/O elemental, and GC techniques. Among the synthesized catalysts, the 3 wt% Ni/HZSM-5 catalyst exhibited superior performance in reducing unfavorable oxygen, sulfur, and nitrogen contents in the oil products. Notably, the higher heating value of the upgraded product generated with nickel-zeolite catalysts (Ni/HZSM-5) is 44.24 MJ/kg which is in the range of naturally occurring crude oils (typically 42 to 47 MJ/kg). This feature highlights the quality and value of the final product.
In the platform economy, digital labor platforms (DLPs) enable remote work by intermediating transactions between platform-dependent entrepreneurs (PDEs) and clients. Information asymmetry arises, however, because PDEs engaged in remote work often are more informed about their abilities than clients are, which may lead to the “lemons problem” and cause market failure. Applying transaction cost economics, we develop a framework that incorporates propositions about what conditions allow different forms of trust to emerge among PDEs, DLPs, and clients. We also delineate how building and sustaining trust should help mitigate market failure threats on DLPs, and, in turn, improve outcomes for PDEs, platforms, and clients. Our framework makes important conceptual extensions by highlighting the relevance of information asymmetry, linking trust development within the DLP-facilitated service triad, and underscoring transaction frequency’s importance, which has been largely overlooked in extant literature. It also provides practical implications for remote work involving PDEs, DLPs, and clients.
Cellulose nanofibers (CNFs) have been shown to assemble at oil/water interface and act as Pickering emulsions stabilizers. Developing a simple approach to fabricate CNFs with tunable surface properties and elucidating the influence of the surface properties of the CNFs on their emulsifying performance are of great significance and highly demanded. Herein, a facile approach, namely FeCl3-catalyzed formic acid hydrolysis in combination with high pressure homogenization was reported to produce CNFs using industrial Kraft pulp as raw materials. The surface properties, especially the surface wettability of the CNFs could be easily adjusted by changing the hydrolysis time. Additionally, the emulsifying performance of the CNFs and the stability of CNF-stabilized Pickering emulsions were also evaluated. The obtained CNF-stabilized Pickering emulsions demonstrated great stability under various ionic strengths ranging from 0 to 1 M NaCl and high temperature of 80 °C. This work would greatly improve the possibility of sustainable production of CNFs for practical emulsions.
Over the last decades, renewable energy sources have increased considerably their generation share in power systems. As a consequence, in terms of frequency deviations, both grid reliability and stability have raised interest. By considering the absence of a consensual set of models for frequency control analysis, both for the different generation units (conventional and renewables) and the power system itself, this paper provides extensive and significant information focused on the models and parameters for studies about frequency control and grid stability. An extensive analysis of supply-side and power system modeling for frequency stability studies over the last decade is presented and reviewed. Parameters commonly used and assumed in the specific literature for such simulations are also given and compared. Modeling of generation units are described as well, including both conventional and renewable power plants.
The focus of this study is thermal responses of a clamped composite laminated beam with arbitrary layer numbers under non-uniform temperature boundary conditions. Analytical solutions of temperature, stresses, and displacements are derived based on the theory of thermoelasticity. The temperature distribution in the laminated beam is divided into two parts. The first part is constructed to satisfy the inhomogeneous temperature boundary conditions, while the second part is obtained on the basis of the Fourier law of heat conduction and the temperature environment. On the other hand, the unit pulse function and the Dirac delta function are introduced to translate the clamped support into the simply support with an unknown horizontal stress. According to the continuities at the interface and the state space method, the relationships of displacements and stresses between the top and bottom surfaces of the laminated beam are derived. Finally, the unknown coefficients of displacements and stresses are determined by the mechanical boundary conditions. It can be observed from the numerical results that this method has excellent convergence performance. The accuracy of this method is verified by comparing with the results of the finite element method. Furthermore, the effects of surface temperature, material properties, length-to-thickness ratio and layer numbers on the distributions of temperature, displacements and stresses in the laminated beam are in depth investigated.
To combat the severity of neurological conditions (NCs), limit the complications, and reduce the cost of treatment, researchers have turned to hybrid exoskeletons such as functional electrical stimulation (FES) cycling. In this work, closed-loop FES/motor controllers are developed that compensate for time-varying, nonlinear, and uncertain dynamics, unknown disturbances, switching between actuators (e.g., between muscle groups and the motor), fatigue, and the unknown time-varying muscle delay between stimulation application and the production of muscle force, called the electromechanical delay (EMD). Control authority is maintained and efficient muscle contractions are produced through the development of FES/motor switching conditions that are both EMD and state dependent. Contributions are that the controllers implement a modular time-varying estimate of the EMD and yield exponential cadence tracking as verified by a Lyapunov-like stability analysis. An example EMD estimate is presented that varies with cycling time to account for fatigue. Furthermore, experiments were conducted to validate the developed control system, which produced an average cadence error of -0.01 ± 1.35 revolutions per minute (RPM) across five able-bodied participants and -0.05 ± 1.38 RPM across four participants with NCs.
Carbon Fiber Reinforced Polymer (CFRP) composite materials are a class of advanced materials widely used in versatile applications, including aerospace and automotive industries, due to their exceptional physical and mechanical properties. Owing to the heterogeneous nature of the composites, it is often a challenging task to machine them unlike metals. Drilling in particular, the most commonly used process for component assembly, is critical especially in the aerospace sector that demands parts of highest quality and surface integrity. Conventionally, all composites are machined under dry conditions. While there are drawbacks related to dry drilling, for example, poor surface roughness, there is a need to develop processes that yield good quality parts demonstrating improved surface integrity. This study aims at investigating the machining performance when drilling CFRP composite material under cryogenic (Cryo), minimum quantity lubrication (MQL) and hybrid (CryoMQL) conditions and comparing the performance with dry drilling in terms of the thrust force, torque, delamination, geometric error such as diametric variation, and surface integrity assessment including average surface roughness, hardness and sub-surface damage analysis. Additionally, the effects of varying the feed on the drilling performance were examined. Based on the results, it was concluded that drilling of CFRP composite material using coolant/lubricant outperformed dry drilling by producing better quality parts. Also, varying the feed proved to be advantageous over drilling at constant feed.
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7,840 members
Anh Nguyen
  • Department of Computer Science & Software Engineering
Stephen ("Ash") Bullard
  • School of Fisheries, Aquaculture, and Aquatic Sciences
Vitaly Vodyanoy
  • Department of Anatomy, Physiology and Pharmacology
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Dr. Mario Eden
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