Novel and simple methodology to fabricate porous and buckled fibrous structures for biomedical applications

Reproducible buckled and porous sub-micron diameter polycaprolactone (PCL) fibers were produced by simple electrospinning process for biomedical applications. In this study, six types of solvent combinations with different vapor pressures were used to study the effect of phase separation on the morphology of electrospun fibers. The fiber morphology, Infrared spectroscopy, water contact angle and tensile test were performed to study the material properties. It is evident that the fiber morphology was affected by solvent combinations used for the fabrication of sub-micron fibers. The solution viscosity, the collecting distance and the type of solvent combination used could be an optimum parameter for the generation of porous-buckled fibers with narrow pore size distribution. The simplicity of the set-up is the immense advantage for producing buckled and porous elastomeric fibers for tissue engineering applications. All the fibers were spun on a motionless collector plate to study the properties of fibers. The combination of surface pores with the buckled pattern could be of great importance in the field of biomedical engineering.     

The pLysRS-Ap4A Pathway in Mast Cells Regulates the Switch from Host Defense to a Pathological State

The innate and adaptive immune systems play an essential role in host defense against pathogens. Various signal transduction pathways monitor and balance the immune system since an imbalance may promote pathological states such as allergy, inflammation, and cancer. Mast cells have a central role in the regulation of the innate/adaptive immune system and are involved in the pathogenesis of many inflammatory and allergic diseases by releasing inflammatory mediators such as histamines, proteases, chemotactic factors, and cytokines. Although various signaling pathways are associated with mast cell activation, our discovery and characterization of the pLysRS-Ap₄A signaling pathway in these cells provided an additional important step towards a full understanding of the intracellular mechanisms involved in mast cell activation. In the present review, we will discuss in depth this signaling pathway’s contribution to host defense and the pathological state.     

Probing Ligand Structure–Activity Relationships in Pregnane X Receptor (PXR): Efavirenz and 8‐Hydroxyefavirenz Exhibit Divergence in Activation

Efavirenz (EFV), an antiretroviral that interacts clinically with co‐administered drugs via activation of the pregnane X receptor (PXR), is extensively metabolized by the cytochromes P450. We tested whether its primary metabolite, 8‐hydroxyEFV (8‐OHEFV) can activate PXR and potentially contribute to PXR‐mediated drug–drug interactions attributed to EFV. Luciferase reporter assays revealed that despite only differing from EFV by an oxygen atom, 8‐OHEFV does not activate PXR. Corroborating this, treatment with EFV for 72 h elevated the mRNA abundance of the PXR target gene, Cyp3a11, by approximately 28‐fold in primary hepatocytes isolated from PXR‐humanized mice, whereas treatment with 8‐OHEFV did not result in a change in Cyp3A11 mRNA levels. FRET‐based competitive binding assays and isothermal calorimetry demonstrated that even with the lack of ability to activate PXR, 8‐OHEFV displays an affinity for PXR (IC₅₀ 12.1 μm ; K_D 7.9 μm ) nearly identical to that of EFV (IC₅₀ 18.7 μm ; K_D 12.5 μm ). The use of 16 EFV analogues suggest that other discreet changes to the EFV structure beyond the 8‐position are well tolerated. Molecular docking simulations implicate an 8‐OHEFV binding mode that may underlie its divergence in PXR activation from EFV.     

The structural influence of aluminium ions on emission characteristics of Sm3+ ions in lead aluminium silicate glass system

Optical absorption and photoluminescence characteristics of Sm³⁺ ions in lead silicate glasses mixed with different concentrations of Al₂O₃ (5–10 mol%) have been investigated. From these studies, the radiative properties viz., spontaneous emission probability A, the total emission probability, the radiative lifetime τ_R, the fluorescent branching ratio β of emission transition of ⁴G_5/2 → ⁶H_7/2 along with other transitions for Sm³⁺ have been evaluated and found to be the highest for the glass mixed with 8.0 mol% of Al₂O₃.The IR spectral studies have indicated that Al³⁺ ions do participate in the glass network with AlO₄ and AlO₆ structural units and further revealed that the concentration of octahedral aluminium ions induce bonding defects in the glass network. Such bonding defects are assumed to be responsible for low phonon losses in these glasses and lead to higher values of radiative parameters for the glass mixed with 8.0 mol% of Al₂O₃.     

Gaseous chlorine dioxide inactivation of microbial contamination on whole black peppercorns

Black peppercorn is a common ingredient imported and used in uncooked or ready-to-eat foods in the United States. They might be exposed to fecal coliforms and other microbial contamination due to a lack of good agricultural and manufacturing practices in some developing countries under which they were grown and harvested, thus causing economic losses to the peppercorn industry in the United States. We investigated the effect of gaseous chlorine dioxide (ClO₂) on reducing the microbial population levels of coliforms, aerobic bacteria, yeasts, and molds on unprocessed black peppercorns. Treatments on peppercorns were conducted in a 30-L airtight chamber, and equal amounts of dry media precursors were used to generate gaseous ClO₂. Whole peppercorns (200 g) were exposed to 20, 30, and 40 g of precursor dose for up to 60 min at 21 ± 0.4°C and in combination with mild heat at 40 ± 2°C. Aerobic bacteria, coliforms, yeasts, and molds on peppercorns were enumerated before (7.4, 7.2, and 7.1 log CFU/g, respectively) and after treatments. Results after treatment demonstrated 0.8–1 log₁₀ (90%) reduction for all the microbes post-treatment at 21 ± 0.4°C. The treatments conducted with a 30 g precursor dose for 60 min at 21 ± 0.4°C reduced statistically higher (p < .05) microorganisms than those at 40 ± 2°C. Our work demonstrated that gaseous ClO₂ could be used as a part of an overall hurdle technology to reduce the coliforms, aerobes, yeasts, and molds on black peppercorns without affecting the visual quality.     

The fracture properties of metal-ceramic composites manufactured via stereolithography

In this work, metal-ceramic composite parts based on aluminum and alumina were manufactured in a two-stage process. First, silica was printed using a vat photopolymerization technique, followed by a curing and sintering stage, which resulted in ceramic precursors. Subsequently, these samples were subjected to a metal infiltration process to form interpenetrating metal-ceramic composites (IPCs). These composites have attracted considerable attention in the aerospace and defense sector due to the ductility associated to the metal phase and the strength offered by the ceramics. A novel application with utility includes composite tooling which requires a low coefficient of thermal expansion (CTE) for high temperatures. The investigated specimens were tested for surface quality and shrinkage, followed by a mechanical characterization. It was recorded that the samples presented a 12%–18% of shrinkage after the sintering process. The mechanical testing showed that the hardness, compression, and flexural strength of the composites were superior to the printed and sintered ceramics. A thermal analysis on the composite showed that its CTE is more than two times lower than the common composite tooling materials. It is expected that the present work can provide the foundations for further studies on these systems in the refractory, automotive, and armor-based fields.     

Performance Evaluation of Best Feature Subsets for Crop Yield Prediction Using Machine Learning Algorithms

The rapid innovations and liberalized market economy in agriculture demand accuracy in Crop Yield Prediction (CYP). In accurate prediction, machine learning (ML) algorithms and the selected features play a major role. The performance of any ML algorithm may improve with the utilization of a distinct set of features in the same training dataset. This research work evaluates the most needed features for accurate CYP. The ML algorithms, namely, Artificial Neural Network, Support Vector Regression, K-Nearest Neighbour and Random Forest (RF) are proposed for better accuracy. Agricultural dataset consists of 745 instances; 70% of data are randomly selected and are used to train the model and 30% are used for testing the model to assess the predictive ability. The results show that the RF algorithm reaches the highest accuracy by means of its error analysis values for all the distinct feature subsets using the same training agricultural data.     

Forced convection in thermally developing region of a channel partially filled with a porous material and optimal porous fraction

Local Nusselt numbers have been obtained on the porous side and the fluid side of the parallel plate channel. Plots to obtain wall heat transfer directly have been presented. Change in wall heat transfer has been examined to establish that the maximum enhancement in heat transfer occurs at a porous fraction of 0.8 at a Darcy number of 0.001. Correspondingly, the maximum enhancement per unit pressure drop occurs at a porous fraction of 0.7. As Darcy number increases, the porous fraction at which the maximum enhancement in heat transfer occurs decreases.