Showing papers by "Amit Singh published in 2004"

Biological synthesis of triangular gold nanoprisms

Abstract: The optoelectronic and physicochemical properties of nanoscale matter are a strong function of particle size. Nanoparticle shape also contributes significantly to modulating their electronic properties. Several shapes ranging from rods to wires to plates to teardrop structures may be obtained by chemical methods; triangular nanoparticles have been synthesized by using a seeded growth process. Here, we report the discovery that the extract from the lemongrass plant, when reacted with aqueous chloroaurate ions, yields a high percentage of thin, flat, single-crystalline gold nanotriangles. The nanotriangles seem to grow by a process involving rapid reduction, assembly and room-temperature sintering of 'liquid-like' spherical gold nanoparticles. The anisotropy in nanoparticle shape results in large near-infrared absorption by the particles, and highly anisotropic electron transport in films of the nanotriangles.

Anti-HIV and cytotoxic ruthenium(II) complexes containing flavones: biochemical evaluation in mice.

Abstract: Ru(II) polypyridyl complexes containing 3-hydroxyflavone derivatives as coligands were screened for anti-HIV and cytotoxic activities against eleven tumor cell lines. In order to check the effect of flavones containing Ru(II) complexes in vivo on a mammal, a representative complex Ru(L) 2 (DMSO) 2 .5H 2 O (LH-3-Hdroxy-4'-benzyloxyflavone; M 5 ) was orally administered to adult male mice. Its effects on protein content and LDH were studied in different tissues of the animal. The compound got absorbed and retained in the blood between 1-3 hr after feeding. As compared to the normal and DMSO control sets, tissue specific significant reversible changes in the protein content as well as in LDH activity were observed between 1-4 hr of treatment. However, on polyacrylamide gel electrophoresis, except some tissue specific transitory alterations, expression patterns of five LDH isozymes were unchanged after feeding the compound. The present results suggested that in addition to its potent cytotoxic and anti-HIV effects on cell lines in vitro, M 5 inhibited LDH activity, but reversibly with a little effect on biosynthetic status of the enzyme in mice.

Depillaring of a thick coal seam using cable bolts under shallow depth cover - a case study

Abstract: Coal resources occurring in thick seams1 in India account for 70 percent of the total workable coal reserves. Evaluation of suitable techniques to extract thick seams has been the main concern of the mining engineers in this country, perhaps, since the coal mining began in India around 200 years ago and more seriously since 1930s. Thick coal seams with a higher concentration of coal reserve, economically a boon, have posed a serious problem of exploitation due to their low level of recovery, difficult strata control, problem of heating and fire, gradient and nature of strata and coal seam. The convenient working height by the conventional method was 3 to 3.5m due to restricted maneuverability in loosening of coal. The resistance of the conventional props/chocks also decreases with height due to high slenderness ratio. The problem is more acute in Raniganj and Jharia Coalfields, where a number of good quality coal seams were developed on pillars leaving a coal band mainly along the roof horizone. A cable bolting based semi-mechanised depillaring method has been developed at Central Mining Research Institute (CMRI) to tackle the problem of thick seam mining. This method was successfully experimented at NCPH mine of M/s South Eastern Coalfields Limited (SECL). Upper Kajora seam of 6.5 to 7.5m thickness developed on pillars in Madhusudanpur 7 pit & Incline colliery of M/s Eastern Coalfields Limited (ECL) was selected for further trial of this method. This paper presents the field trial of this method at Madhussudanpur colliery along with the results of strata behaviour study done in a panel under shallow depth of cover.