Catalytic synthesis of biodiesel from pongamia glabra over zirconia and its modified forms

Zirconia & its modified forms such as Mo(VI)/ZrO₂, Pt-SO ₄ ^2? /ZrO₂, MgO & MgO-ZrO₂ mixed oxide were prepared by impregnation method. These catalysts were analyzed for surface acidity, surface basicity and crystallinity by using techniques such as TPD & powder X-ray diffraction. Mo(VI)/ZrO₂, Pt-SO₄ ^2?/ZrO₂ were used as solid acid catalysts for esterification of pongamia glabra (karanja) oil to reduce the concentration of free fatty acid and MgO and MgO-ZrO₂ mixed oxide were used as solid base catalysts for transesterification of karanja oil to produce biodiesel. These zirconia catalysts were found to be highly efficient for the synthesis of biodiesel with more than 90% yield of biodiesel. These solid catalysts can be effectively reactivated and reused.     

Superoxide and hydroxyl radical scavenging actions of botanical extracts of Wagatea spicata

Wagatea spicata, candy corn plant, a woody legume shrub, widespread medicinal plant found in Western Ghat of India has significant abilities to scavenge highly reactive free radicals. Shade dried leaf, bark and flower powder of this plant has been extracted with water and fractionated with different solvents. Extracts and their solvent fractions were found to be good scavengers of superoxide and hydroxyl radicals. Free radical scavenging action of W. spicata is due to its rich phenolic and flavonoid contents. Bark and leaf extracts showed significant scavenging action against superoxide radicals, where as flower extracts efficiently inhibited hydroxyl radicals.     

Synthesis and stability studies of thiophenol capped CdS nanoparticles

The results of the studies on the preparation and stability of thiophenol-capped CdS nanoparticles prepared by a non-aqueous chemical method are reported. Solutions of cadmium acetate and sodium sulphide were taken as the precursors and thiophenol was used as a capping agent to control the growth and also to prevent flocculation of the synthesized particles. The synthesized CdS nanoparticles were characterized by the optical absorption and X-ray diffraction (XRD) studies. The blue shift of the optical absorption edge indicated the formation of particles in the nanometer size regime. The particle sizes were estimated from the band gap values obtained from the optical absorption spectra using effective mass approximation (EMA). The CdS powder sample was used for the X-ray Diffraction studies. Broadening of the diffraction peaks with an increase in the stabilizer concentration also suggests the decrease in particle size with increase in the stabilizer concentration. Particle sizes calculated from the X-ray diffraction studies agree fairly well with those estimated from the optical absorption studies. The particle size could be conveniently controlled by adjusting the concentration of the stabilizer. X–ray diffraction studies were also carried out at higher temperatures. Particle size did not change with temperature as indicated by XRD. Stability of the synthesized nanoparticles was studied by recording the optical absorption spectra for 45 days. A change in particle size was observed at lower stabilizer concentrations for the first few days. But at higher stabilizer concentrations there was no change in particle size with time.     

Construction of constant fatigue life diagram for a carbon fiber composite

Using the constant amplitude fatigue data at various stress ratios, the constant fatigue life (CFL) diagram was constructed for the CFC material which is useful in prediction of fatigue life under variable amplitude fatigue loads. A quasi-isotropic lay-up sequenced carbon fiber-epoxy composite (CFC) laminate was fabricated by resin infusion technique. The tensile and compression tests were carried out to determine the static strength of the material. About 175 mm long, constant rectangular cross-sectioned fatigue test specimens were cut and prepared from the laminate. The stress-controlled, constant-amplitude fatigue tests were conducted in a 100 kN servo-hydraulic test machine, at room temperature and in lab air atmosphere. All the fatigue tests were performed with a sinusoidal waveform and a frequency of 1–3 Hz. The fatigue tests were conducted at four different stress ratio, R = σ_min/σ_max, Viz., 0.7,0.5 (tension-tension), −1.0 (tension-compression), and 4.0 (compression-compression). Anti-buckling guide was employed during the fatigue tests which involved compressive load cycles. The CFL Diagrams are material specific with predictive capability for any designed levels from selective experimental data.     

Electrical conductivity and thermoelectric power of amorphous Sb2Te3 thin films and amorphous-crystalline transition

The results of electrical conductivity and thermoelectric studies on antimony telluride, a promising thermoelectric material, in the thin film state are reported. Films were vacuum-deposited on to clean glass substrates with thickness between 50 and 200 nm and studied in the temperature interval 300 to 470 K. On heating the as-grown films, there is a sharp fall both in the Seebeck coefficient and the electrical resistivity at around 340 to 370 K for all the films. This is attributed to an amorphous to crystalline transition, which is confirmed by X-ray diffractogram and electron diffraction patterns.[/p]     

Ageing studies of discontinuous copper and silver thin films

The results of experiments carried out on the post-deposition resistance changes in discontinuous films of copper and silver with and without overlayers of SiO and Al₂O₃ are presented. The changes in the sheet resistance of the films with time and pressure were studied for the above combinations. Mobility coalescence is assumed to be responsible for the resistance increase of an uncovered copper film of initial resistance 1.9 M/. On exposure to the atmosphere, it was found that an Ag/SiO combination of initial resistance of 0.1 M/ achieved stability in the sheet resistance much quicker than a Cu/Al₂O₃ combination of initial resistance 20 M/. The fall in resistance of the Cu/Al₂O₃ composite is attributed to the formation of Al₂(OH)₆ due to the interaction of Al₂O₃ with the water vapour in atmosphere. Copper films with and without overlayers of Al₂O₃ show an abrupt increase in the sheet resistance as a function of pressure at a pressure of about 5 × 10^–2 torr with the maximum rate of change of resistance occurring at higher pressure for the higher resistance film. This indicates that the overlayer of Al₂O₃ is very porous in nature. Field effect studies were carried out on an uncovered copper film of initial resistance 10 M/ and the behaviour was found to be ohmic up to a field of 800 V cm^–1.     

Effect of overlayers on the instability of copper island films

The results of investigations carried out on the effect of overlayers of Al₂O₃, SiO₂ and MoO₃ on the instability of discontinuous copper films at room temperature and at 125 K, are reported. For one film, long-term stability was studied for more than 1500 h. The overlayers are inadequate in preventing movement of the islands both at room temperature and at 125 K and in providing protection against attack by atmospheric gases. The films, when exposed to the atmosphere, show a large increase in resistance in a well-defined pressure range of 5 × 10^–2 torr, corroborating our earlier findings. TheI-V characteristics at 125 K were nonlinear, the non-linearity being attributed to field-induced structural changes.     

Hypolipidemic and Antioxidant Effects of Dietary Curcumin and Capsaicin in Induced Hypercholesterolemic Rats

Health beneficial hypolipidemic and antioxidant influences of dietary spice principles—curcumin, capsaicin alone and in combination included in the diet for 8 weeks were evaluated in induced hypercholesterolemic rats, in order to verify if there is any additive or synergistic effect of these two bioactive compounds. Dietary curcumin (0.2%), capsaicin (0.015%) or their combination significantly countered the hypercholesterolemia brought about by high cholesterol feeding. Hepatic cholesterol was lowered by dietary spice principles only in normal rats. Liver triglyceride levels were lowered in both normal and hypercholesterolemic rats by capsaicin. Curcumin and capsaicin lowered hepatic and blood lipid peroxides in hypercholesterolemic rats, while the effect in blood was additive with their combination. Hepatic ascorbic acid was enhanced by dietary spice principles in normal rats; glutathione was enhanced by their combination only in hypercholesterolemic rats. Activities of serum glutathione reductase, glutathione transferase and catalase and hepatic glutathione reductase in normal rats and serum glutathione peroxidase in hypercholesterolemic rats were enhanced by dietary spice principles. While dietary curcumin and capsaicin normalized the changes in the levels of antioxidant molecules and activities of antioxidant enzymes to a significant extent, this effect was not generally additive when given in combination, and was higher than the individual effects only in a few instances.