Showing papers in "Journal of the Indian Institute of Science in 2001"

Selected chemo - ecological studies of marine opisthobranchs from indian coasts.

Abstract: A new synthesis of 2 , 2 - dimethyl - 12 - [ 3 - methylbut - 2 - enyl ] - 2H , 6H - pyrano [ 3 , 2 - b ] xanthen - 6 - one (7) is described from 1 , 3 - dihydroxyxanthone and involved the preparation of a linear dihydropyranoxanthone (26) , its conversion into the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7).

Macrocyclic musk compounds: Synthetic approaches to key intermediates for exaltolide, exaltone and dilactones †

Abstract: A new synthesis of 2 , 2 - dimethyl - 12 - [ 3 - methylbut - 2 - enyl ] - 2H , 6H - pyrano [ 3 , 2 - b ] xanthen - 6 - one (7) is described from 1 , 3 - dihydroxyxanthone and involved the preparation of a linear dihydropyranoxanthone (26), its conversion into the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7).

Mifepristone (RU-486), the recently developed antiprogesterone drug and its analogues

Abstract: A new synthesis of 2 , 2 - dimethyl - 12 - [ 3 - methylbut - 2 - enyl ] - 2H , 6H - pyrano [ 3 , 2 - b ] xanthen - 6 - one (7) is described from 1 , 3 - dihydroxyxanthone and involved the preparation of a linear dihydropyranoxanthone (26), its conversion into the pyranoxanthone (14) and its prenylated derivative (31) followed by a Claisen rearragement leading to the target substrate (7).

PMMA As an etch mask for silicon micromachining a feasibility study.

Abstract: Silicon micromachining requires a proper etch mask, which can withstand the action of etchant during the fabrication of typical structures. Widely used etch mask materials are SiO2 , Si3N4, gold (Au), chromium (Cr) and boron diffusion. Deposition of these on substrates requires expensive equipment. Mihaela Ilie et al. [Proc. SPIE Materials and Device Characterization in Micromachining, 1998, 3512, 4221] reported PMMA as a mask layer on the backside during silicon etching by KOH solution. This etch mask is cheap and is easy to use. In the present work, PMMA is deposited on silicon substrate with a simple technique of spin-coating. The adhesion of spincoated film of PMMA on silicon wafer is an important parameter for its use as an etch mask, while etching in aqueous KOH solution for silicon micromachining. Pre- and posttreatments have been performed on silicon substrate and the mask layer to achieve greater adhesion of the mask material. Feasibility is demonstrated of the use of PMMA as etch mask.made to crystallize the thin films at as low a processing temperature as possible. The properties studied include dielectric measurements and hysteresis. Thin films of calcium-modified lead titanate (PCT) were also prepared by the sol gel technique and their pyroelectric characteristics were studied for use in infrared detectors.film was coated. These results show that the crystalline quality and deposition rate can be controlled over a wide range by this method.

Design and fabrication of bulk silicon-based temperature sensor.

Abstract: Highly conductive and transparent aluminum-doped zinc oxide thin films were prepared by ablating the target containing 2 wt% Al2O3 with ArF excimer laser (lamda=193 nm). The films were grown at a repetition rate of 10 Hz, energy density of 2-3 J/cm2 and irradiation time of 10-60 min (6000-36000 laser shots). The optical and electrical properties of the films depend on the substrate temperature and oxygen pressure during film deposition. The lowest resistivity was found to be at 1.44 Wcm for films deposited at 300oC and in 1mtorr of oxygen ambient. The average transmittance was found to be in the range of 84-92%. Sharp decrease in transmittance and sharp increase in reflectance near the plasma edge in the near-infrared range are due to impurity scattering, which is caused by aluminum doping.