Studies on novel bioactive glasses and bioactive glass-nano-HAp composites suitable for coating on metallic implants

A series of novel zinc oxide (ZnO) containing bioactive glass compositions in SiO₂-Na₂O-CaO-P₂O₅ system and composite with hydroxyapatite (HAp) nano-particles were developed and applied as coating on Ti-6Al-4V substrates. The bioactive glasses and their composites were also processed to yield dense scaffolds, porous scaffolds and porous bone filler materials. The coating materials and the coatings were characterized and evaluated by different in vitro techniques to establish their superior mechanical properties. The cytotoxicity test of the coating material, porous and dense scaffolds and coated specimens showed non-cytotoxicity, biocompatibility and promising in vitro bioactivity for all tested samples. The dissolution behaviour studies of the bioactive glasses and the composites in simulated body fluid showed promising in vitro release pattern and bioactivity for all tested samples. Addition of nanosized HAp improves mechanical properties of the bioactive glass coating without affecting the in vitro bioactivity.     

Fatigue mitigation through the optimization of ergonomic positional parameters in massage therapy using virtual instrumentation

This paper reports a research in which a setup was developed to determine the optimal values of ergonomic positional parameters that would mitigate the development of fatigue while performing massage therapy. This setup was based on virtual instrumentation principles and consisted of a sphygmomanometer bulb, an air sac, a pressure sensor, a data acquisition card and a personal computer installed with the Laboratory Virtual Instrumentation Engineers Workbench software (LABView software). The air sac fitted in this setup is equalised with the muscles and other human body parts which a human therapist is required to press while performing massage therapy. After constructing the air sac fatigue monitoring virtual instrumentation setup, 25 participants who were not actually massage therapists were asked to press the air sac to mimic the behaviour of the massage therapists during the time of their works. After drawing necessary data by performing this activity and by entering the data in Minitab 16 software, regression models to specify optimal values of ergonomic positional parameters were developed. These regression models were practically validated by conducting experiments involving five other participants. The method of utilizing these regression models in determining the optimum values of positional parameters that would mitigate fatigue development while performing massage therapy is illustrated by presenting two cases. While concluding, it is suggested to involve actual massage therapists for testing the performance of the fatigue monitoring virtual instrumentation setup developed during the research reported in this paper.     

Physicochemical Studies of 4-Substituted N-(2-Mercaptophenyl)-Salicylideneimines: Corrosion Inhibition of Mild Steel in an Acid Medium

A series of 4-substituted N-(2-mercaptophenyl)salicylideneimine Schiff bases were synthesized and investigated for corrosion inhibition of mild steel in hydrochloric acid medium. Inhibition through adsorption mechanism is proposed for these inhibitors, which is well supported by electrochemical impedance spectroscopy, the Langmuir adsorption isotherm and Scanning Electron Microscope morphologies of inhibited and uninhibited mild steel specimens. The negative ?G _ads indicates the spontaneous adsorption of the inhibitor on a mild steel surface. Among all the examined inhibitors, 5-bromo-N-(2-mercaptophenyl)salicylideneimine showed a higher inhibition efficiency. In order to reveal the usefulness of these Schiff bases as corrosion inhibitors under various circumstances, weight loss measurements were performed at various temperatures, acid concentrations and immersion times.     

Stacking of nanocrystalline graphene for nano-electro-mechanical (NEM) actuator applications

Graphene nano-electro-mechanical switches are promising components due to their excellent switching performance such as low pull-in voltage and low contact resistance. Mass fabrication with an appropriate counter electrode remains challenging. In this work, we report the stacking of nanocrystalline graphene (NCG) with a 70-nm dielectric separation layer. The buried NCG layer is contacted through the formation of vias and acts as actuation electrode. After metallization, the top 7.5-nm thin NCG layer is patterned to form double-clamped beams, and the structure is released by hydrofluoric acid etching. By applying a voltage between the top and buried NCG layer, a step-like current increase is observed below 1.5 V, caused by the contact of the movable beam with the buried NCG. No pull-out is observed due to the thin sacrificial layer and high beam length, resulting in low mechanical restoring force. We discuss the possible applications of the NCG stacking approach to realize nano-electro-mechanical contact switches and advanced logical components such as a AND logic.

     

Effect of natural antioxidants on the oxidation stability of methyl ester of rubber seed oil

Biodiesel has been proved as a promising solution amidst other alternate fuels in terms of its characteristics compared to diesel. The oxidation property of biodiesel results in the degradation of its quality. This problem can be solved by the addition of suitable antioxidants which improves the oxidation stability of the fuel. Usage of natural antioxidants offsets the defects in synthetic antioxidants, because they are renewable, nontoxic as well as cost effective. The effect of natural antioxidant additives on the oxidation stability of the Methyl Ester of non-edible Rubber Seed oil (MERB) has been experimentally investigated in this study. Natural antioxidants Ginger, Moringa oleifera Lam, Basil and Oregano have been mixed in varying proportions (500, 1000, 1500 and 2000 ppm) and the antioxidant characteristics of the additives were identified by using Fourier Transform Infra-Red (FTIR) analysis. The induction period, which denotes the oxidation stability was worked out with Rancimat apparatus. From this study it was found out that the oxidation stability of MERB increased when natural antioxidant additives were added. Among the antioxidants used, Ginger was found to be more effective in enhancing the oxidation stability, with induction period values of 11.5 h, 18.5 h, 23 h and 26.5 h for proportions 500, 1000, 1500 and 2000 ppm respectively.     

Pt nanoparticles supported on NiTiO3/C as electrocatalyst towards high performance Methanol Oxidation Reaction

Pt nanoparticles supported on NiTiO₃/C has been synthesized by a wet chemical method, using the corresponding metal precursors and citric acid as a complexing reagent. The nanocomposite has been characterized using X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. The electrocatalytic Methanol Oxidation Reaction (MOR) has been performed using Pt-NiTiO₃/C catalyst in both alkaline and acid medium. Analysis using cyclic voltammetry (CV), steady state polarization (SSP), and chronoamperometry (CA) techniques clearly demonstrate that Pt-NiTiO₃/C catalyst exhibits higher performance in methanol oxidation in alkaline medium compared to acid medium. The results demonstrate that NiTiO₃ has significant promotion effect on the electrocatalytic activity and stability for the methanol electro-oxidation. The enhanced activity is attributed to the ability of NiTiO₃ to promote CO_ads oxidation through strong interaction with Pt (which is in close proximity to NiTiO₃). Pt-NiTiO₃/C appears to be a promising anode catalyst for direct methanol fuel cells.