Fabrication of corrosion resistant, bioactive and antibacterial silver substituted hydroxyapatite/titania composite coating on Cp Ti

The present work is aimed at developing a bioactive, corrosion resistant and anti bacterial nanostructured silver substituted hydroxyapatite/titania (AgHA/TiO₂) composite coating in a single step on commercially pure titanium (Cp Ti) by plasma electrolytic processing (PEP) technique. For this purpose 2.5 wt% silver substituted hydroxyapatite (AgHA) nanoparticles were prepared by microwave processing technique and were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) methods. The as-synthesized AgHA particles with particle length ranging from 60 to 70 nm and width ranging from 15 to 20 nm were used for the subsequent development of coating on Cp Ti. The PEP treated Cp Ti showed both titania and AgHA in its coating and exhibited an improved corrosion resistance in 7.4 pH simulated body fluid (SBF) and 4.5 pH osteoclast bioresorbable conditions compared to untreated Cp Ti. The in vitro bioactivity test conducted under Kokubo SBF conditions indicated an enhanced apatite forming ability of PEP treated Cp Ti surface compared to that of the untreated Cp Ti. The Kirby-Bauer disc diffusion method or antibiotic sensitivity test conducted with the test organisms of Escherichia coli (E. coli) for 24 h showed a significant zone of inhibition for PEP treated Cp Ti compared to untreated Cp Ti.     

Modelling and optimization of syngas production by methane dry reforming over samarium oxide supported cobalt catalyst: response surface methodology and artificial neural networks approach

The reforming of methane by carbon dioxide for the production of syngas is a potential technological route for the mitigation of greenhouse gases. However, the process is highly endothermic and often accompanied by catalyst deactivation from sintering and carbon deposition. Besides, the applications of dissimilar catalytic systems in methane dry reforming have made it difficult to obtain generalized optimum conditions for the desired products. Hence, optimization studies of any catalytic system often resulted in a unique optimum condition. The present study aimed to investigate optimum conditions of variables such as methane (CH₄) partial pressure, carbon dioxide (CO₂) partial pressure and reaction temperature that will maximize syngas yields from methane dry reforming over samarium oxide supported cobalt (Co/Sm₂O₃) catalyst. The Co/Sm₂O₃ catalyst was synthesized using wet-impregnation method and characterized by thermogravimetric analysis), field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and nitrogen (N₂) physisorption. Syngas production by methane dry reforming over the synthesized Co/Sm₂O₃ catalyst was investigated in a stainless steel fixed-bed reactor. The process variables (CH₄ partial pressure, CO₂ partial pressure and reaction temperature) for the syngas production were optimized using response surface methodology (RSM). The RSM and artificial neural networks (ANNs) were used to predict the syngas production from the experimental data. The comparative analysis between the two models showed that the ANN model has better prediction of the syngas yields compared to the RSM model as evident from the good agreement between the observed and the predicted values. At maximum desirability value of 0.97, optimum CH₄ and CO₂ partial pressures of 47.9 and 48.9 kPa were obtained at reaction temperature of 735 °C resulting in syngas yield of ~79.4 and 79.0% for hydrogen (H₂) and carbon monoxide (CO), respectively.     

Production of Glycolipid Biosurfactant from Sponge-Associated Marine Actinobacterium <Emphasis Type="Italic">Brachybacterium paraconglomeratum</Emphasis> MSA21

Potential biosurfactant producers and economic production processes are major considerations for commercialization of biosurfactants. The present study was aimed at exploring marine Actinobacteria for the production of biosurfactants using industrial and agro-industrial wastes under solid state culture (SSC). A biosurfactant producer, Brachybacterium paraconglomeratum MSA21 was isolated from a marine sponge. The strain MSA21 effectively utilized tannery pre-treated effluent as the substrate for the production of a biosurfactant under SSC. The critical control factors influence the production of biosurfactant includes glucose, yeast extract, copper sulfate and inoculum size. The glucose and yeast extract interactively increase the production maxima over a stable area. The surface active compound was characterized as a glycolipid derivative with a hydrophilic part of methyl-2-oxopropyl furan and a hydrophobic dodecanoic acid, methyl ester. The MSA21 biosurfactant displayed antibiotic activity. The domain ketosynthase in MSA21 showed that the polyketide synthase gene might be involved in the synthesis of antimicrobial compounds. The strain B. paraconglomeratum MSA21 could be used for the production of a biosurfactant as a green alternative to replace chemical surfactants.     

Semi-Empirical Molecular Modeling of Ionic Liquid Tribology: Ionic Liquid–Hydroxylated Silicon Surface Interactions

The interactions between selected ionic liquids and modified silicon surfaces are modeled in this article using semi-empirical methods. The modeled ionic liquids include a series of ionic liquids consisting of imidazolium derivatives with Cl^? as the anion interacting with hydroxylated silicon wafers. A second series consists of symmetrical and asymmetrical dicationic imidazolium derivatives with PF₆ ^? or BF₄ ^? as the anion interacting with hydroxylated single crystal silicon wafers. The tribological properties of these ionic liquids and their interactions with silicon surfaces are modeled using a rolling hydroxylated silicon surface. The ionic liquids are allowed to form a complex with this surface, and the enthalpies of complex formation are seen to correlate with the tribological properties of the ionic liquids.     

Semi-Empirical Molecular Modeling of Ionic Liquid Tribology: Ionic Liquid–Aluminum Oxide Surface Interactions

The interactions between the selected ionic liquids (ILs) and aluminum oxide surfaces are modeled in this report using theoretical methods. A wide range of ILs and their interactions with an aluminum oxide surface are modeled using the PM5 semi-empirical method. The ILs modeled in this study contain imidazolium (C_{3, 4, 6, 8 or 10}mim) or ammonium cations including (C₆H₁₃)₃NH⁺, (C₈H₁₇)₃NH⁺, C₈H₁₇NH₃ ⁺, (C₂H₅)₃NH⁺, and (C₈H₁₇)NH₃ ⁺. The anions include Cl⁻, Br⁻, PF₆ ⁻, (CF₃SO₂)₂N⁻, and (C₂F₅SO₂)₂N⁻. The interactions of these ILs with an Al–O surface are modeled in a stepwise manner. The lowest energy forms of the individual ILs are determined, and these ILs are allowed to form a complex with the Al–O surface. The resulting reaction enthalpies of ionic liquid-surface complex formation are seen to correlate with the tribological properties of the ILs. The strongest correlations occur within those ILs containing similar cations.