Microwave-Hydrothermal Synthesis of Nanophase Ferrites

This paper reports the synthesis of technologically important ferrites such as ZnFe₂O₄, NiFe₂O₄, MnFe₂O₄, and CoFe₂O₄ by using novel microwave-hydrothermal processing. Nanophase ferrites with high surface areas, in the range of 72-247m²/g, have been synthesized in a matter of a few minutes at temperatures as low as 164°C. The rapid synthesis of nanophase ferrites via an acceleration of reaction rates under microwave-hydrothermal conditions is expected to lead to energy savings.     

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.     

Screening of β1- and β2-Adrenergic Receptor Modulators through Advanced Pharmacoinformatics and Machine Learning Approaches

Cardiovascular diseases (CDs) are a major concern in the human race and one of the leading causes of death worldwide. β-Adrenergic receptors (β1-AR and β2-AR) play a crucial role in the overall regulation of cardiac function. In the present study, structure-based virtual screening, machine learning (ML), and a ligand-based similarity search were conducted for the PubChem database against both β1- and β2-AR. Initially, all docked molecules were screened using the threshold binding energy value. Molecules with a better binding affinity were further used for segregation as active and inactive through ML. The pharmacokinetic assessment was carried out on molecules retained in the above step. Further, similarity searching of the ChEMBL and DrugBank databases was performed. From detailed analysis of the above data, four compounds for each of β1- and β2-AR were found to be promising in nature. A number of critical ligand-binding amino acids formed potential hydrogen bonds and hydrophobic interactions. Finally, a molecular dynamics (MD) simulation study of each molecule bound with the respective target was performed. A number of parameters obtained from the MD simulation trajectories were calculated and substantiated the stability between the protein-ligand complex. Hence, it can be postulated that the final molecules might be crucial for CDs subjected to experimental validation.     

Highly potent and specific GSK-3beta inhibitors that block tau phosphorylation and decrease alpha-synuclein protein expression in a cellular model of Parkinson's disease

Research by Klein and co-workers suggests that the inhibition of GSK-3beta by small molecules may offer an important strategy in the treatment of a number of central nervous system (CNS) disorders including Alzheimer's disease, Parkinson's disease, and bipolar disorders. Based on results from kinase-screening assays that identified a staurosporine analogue as a modest inhibitor of GSK-3beta, a series of 3-indolyl-4-indazolylmaleimides was prepared for study in both enzymatic and cell-based assays. Most strikingly, whereas we identified ligands having poor to high potency for GSK-3beta inhibition, only ligands with a Ki value of less than 8 nM, namely maleimides 18 and 22, were found to inhibit Tau phosphorylation at a GSK-3beta-specific site (Ser 396/404). Accordingly, maleimides 18 and 22 may protect neuronal cells against cell death by decreasing the level of alpha-Syn protein expression. We conclude that the GSK-3beta inhibitors described herein offer promise in defending cells against MPP+-induced neurotoxicity and that such compounds will be valuable to explore in animal models of Parkinson's disease as well as in other Tau-related neurodegenerative disease states.     

Removal of lead contaminated dusts from hard surfaces

Government guidelines have widely recommended trisodium phosphate (TSP) or "lead-specific" cleaning detergents for removal of lead-contaminated dust (LCD) from hard surfaces, such as floors and window areas. The purpose of this study was to determine if low-phosphate, non-lead-specific cleaners could be used to efficiently remove LCD from 3 types of surfaces (vinyl flooring, wood, and wallpaper). Laboratory methods were developed and validated for simulating the doping, embedding, and sponge cleaning of the 3 surface types with 4 categories of cleaners: lead-specific detergents, nonionic cleaners, anionic cleaners, and trisodium phosphate (TSP). Vinyl flooring and wood were worn using artificial means. Materials were ashed, followed by ultrasound extraction, and anodic stripping voltammetry (ASV). One-way analysis of variance approach was used to evaluate the surface and detergent effects. Surface type was found to be a significant factor in removal of lead (p < 0.001). Vinyl flooring cleaned better than wallpaper by over 14% and wood cleaned better than wallpaper by 13%. There was no difference between the cleaning action of vinyl flooring and wood. No evidence was found to support the use of TSP or lead-specific detergents over all-purpose cleaning detergents for removal of lead-contaminated dusts. No-phosphate, non-lead-specific detergents are effective in sponge cleaning of lead-contaminated hard surfaces and childhood lead prevention programs should consider recommending all-purpose household detergents for removal of lead-contaminated dust after appropriate vacuuming.     

Adaptive demodulation of dynamic signals from fiber Bragg gratings using two-wave mixing technology

A two-wave mixing (TWM) interferometer using photorefractive (PRC) InP:Fe crystal is configured to demodulate the spectral shift of a fiber Bragg grating (FBG) sensor. The FBG is illuminated with a broadband source, and any strain in the FBG is encoded as a wavelength shift of the light reflected by the FBG. The wavelength shift is converted into phase shift by means of an unbalanced TWM interferometer. TWM wavelength demodulation is attractive for monitoring dynamic strains because it is adaptive and multiplexable. Adaptivity implies that it can selectively monitor dynamic strains without active compensation of large quasi-static strains and large temperature drifts that otherwise would cause system to drift. Multiplexability implies that several FBG sensors can be simultaneously demodulated using a single demodulator. TWM wavelength demodulation is therefore a cost-effective method of demodulating several spectrally encoded FBG sensors.     

Polysaccharide nanofibrous scaffolds as a model for in vitro skin tissue regeneration

Tissue engineering and nanotechnology have advanced a general strategy combining the cellular elements of living tissue with sophisticated functional biocomposites to produce living structures of sufficient size and function at a low cost for clinical relevance. Xylan, a natural polysaccharide was electrospun along with polyvinyl alcohol (PVA) to produce Xylan/PVA nanofibers for skin tissue engineering. The Xylan/PVA glutaraldehyde (Glu) vapor cross-linked nanofibers were characterized by SEM, FT-IR, tensile testing and water contact angle measurements to analyze the morphology, functional groups, mechanical properties and wettability of the fibers for skin tissue regeneration. The cell-biomaterial interactions were studied by culturing human foreskin fibroblasts on Xylan/PVA Glu vapor cross-linked and Xylan/PVA/Glu blend nanofibrous scaffolds. The observed results showed that the mechanical properties (72 %) and fibroblast proliferation significantly increased up to 23 % (P < 0.05) in 48 h Glu vapor cross-linked nanofibers compared to 24 h Glu vapor cross-linked Xylan/PVA nanofibers. The present study may prove that the natural biodegradable Xylan/PVA nanofibrous scaffolds have good potential for fibroblast adhesion, proliferation and cell matrix interactions relevant for skin tissue regeneration.     

Experimental analysis of spatio-temporal behavior of anodic dead-end mode operated polymer electrolyte fuel cell

During the anodic dead-end mode operation of fuel cells, the inert gases (nitrogen and water) present in the cathode side gas channel permeate to the anode side and accumulate in the anode gas channel. The inert gas accumulation in the anode decreases the fuel cell performance by impeding the access of hydrogen to the catalyst. The performance of fuel cell under potentiostatic dead-end mode operation is shown to have three distinct regions viz. time lag region, transient current region and a steady state current region. A current distribution measurement setup is used to capture the evolution of the current distribution as a function of time and space. Co- and counter-flow operations of dead-end mode confirm the propagation of inert gas from the dead-end of anode channel to the inlet of anode. Experiments with different oxidants, oxygen and air, under dead-end mode confirm that nitrogen which permeates from cathode to anode causes the performance drop of the fuel cell. For different starting current densities of 0.15 A cm⁻², 0.3 A cm⁻² and 0.6 A cm⁻² the inert gas occupies 35%, 45% and 57%, respectively of anode channel volume at the end of 60 min of dead-end mode operation.     

Effects of Small Additions of Tin on High-Temperature Oxidation of Fe-Cu-Sn Alloys for Surface Hot Shortness

Steel produced in an electric arc furnace contains a high amount of copper (Cu) that causes a surface-cracking phenomenon called surface hot shortness. It is known that tin (Sn) can exacerbate the hot shortness problem. A series of iron (Fe)-0.3 wt pct Cu-x wt pct Sn alloys with an Sn content ranging from 0.03 to 0.15 wt pct was oxidized in air at 1423 K (1150 °C) for 60 seconds, 300 seconds, and 600 seconds using thermogravimetry. A numerical model developed in a previous article was applied to predict the liquid–γFe interface concentrations and interface morphology in the Fe-Cu-Sn ternary system. Scanning electron microscopy investigations show that (1) The interface between the oxide and the metal is planar as predicted by the numerical model, (2) Sn leads to severe Cu-rich liquid penetration and cracking along the grain boundaries, and (3) open cracks with Fe oxides were found beneath the oxide–metal interface. The focused ion beam serial-sectioning technique was used to reveal a three-dimensional structure of cracks in the grain boundary containing Cu-rich liquid and Fe oxides.     

Dielectric and dynamic mechanical relaxation behavior of exfoliated nano graphite reinforced flouroelastomer composites

Dynamic mechanical analysis and dielectric relaxation spectra of exfoliated nano graphite reinforced flouroelastomer composites were used to study their relaxation behavior as a function of temperature (−80°C to +40°C) and frequency (0.01 to 10⁵ Hz). The effect of filler loadings on glass transition temperature was marginal for all the composites and T_g value was in the narrow range of 7.8–8.4°C, which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain‐dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.01–10%. The nonlinearity in storage modulus has been explained on the concept of filler‐polymer interaction and filler aggregation of the nano graphite platelets. The variation in real and complex part of impedance with frequency has been studied as a function of filler. The percolation of the nano graphite as studied by conductivity measurements is also reported. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.