Total synthesis of (+) Artemisinin

(+) Artemisinin is a sesquiterpene endoperoxide lactone with an unprecedented structure is a natural medicine for the treatment of malaria in particular drug against drug resistant malaria and cerebral malaria. The total synthesis of this novel sesquiterpene is described using an inter-molecular radical reaction on important intermediate iodolactone starting from terpene (+) isolimonene

Fabrication and Analysis of Amorphous Silicon TFT

The display technology and large area electronics got momentum with the introduction of TFT devices. TFTs can be made using different semiconducting materials or organic conducting materials as the active layer. Each one of them differ in their performance depending on the material used for the active layer. In this paper, fabrication of amorphous silicon TFT using PECVD is carried out. Simulation of the a-Si: H TFT is also carried out with the dimensions similar to that of the masks used for the fabrication. The Id-Vd plot for both the simulation and fabrication is obtained and studied

Characteristics of spectral aerosol optical depths over India during ICARB

Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Angstrom parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Angstrom coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from the adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Angstrom exponent (α) remained significantly lower (~1) over the Arabian Sea compared to Bay of Bengal (BoB) (~1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of α, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in α over the BoB

Synthetic studies toward pondaplin: total synthesis of pondaplin analogues

Syntheses of synthetic analogues of pondaplin 1 have been achieved. Final macrolide construction was accomplished using a Keck macrolactonization reaction

One pot synthesis of 4-(2-hydroxybenzoyl)-pyrazoles from 3-formylchromones under microwave irradiation in solvent free conditions

The synthesis of 4-(-2-hydroxybenzoyl)pyrazoles (3) was achieved in a single step by the reaction of 3-formylchromones (1) with Phenylhydrazine or Tosylhydrazine under microwave irradiation without a solvent

Stereoselective total synthesis of (+)-artemisinin

The total synthesis of the novel antimalarial drug, a sesquiterpene endoperoxide, (+)-artemisinin is described. The approach is flexible and stereoselective. The use of an intermolecular radical reaction on an intermediate iodolactone and a Wittig reaction on a ketone were employed for the synthesis

Investigation of Wafer Level Au-Si Eutectic Bonding of Shape Memory Alloy (SMA) with Silicon

The objective of this research work was to investigate the low temperature gold silicon eutectic bonding of SMA with silicon wafers. The research work was carried out to optimize a bond process with better yield and higher bond strength. The gold layer thickness, processing temperature, diffusion barrier, adhesive layer, and the removal of silicon oxide are the important parameters in determining a reliable and uniform bond. Based on the previous work on Au-Si eutectic bonding, 7 different Si substrates were prepared to investigate the effect of above mentioned parameters. Cantilevers with different bond sizes were prepared from SMA and steel sheets. Afterwards, these cantilevers were bonded to the prepared substrates. The bond yield and bond strength are the two parameters which establish the bond quality. Quantitative analysis was carried out by shear tests. Scanning Electron Microscopy (SEM) and Mapping were used for the analysis of the bond interface and diffusion of elements across the bond. The research has resulted in bonding of SMA cantilevers onto silicon wafers with high yield and bond strength. Steel cantilever can also be bonded by Au-Si eutectic alloy but the processing of the steel sheet is critical. Further research is needed for the fabrication of steel cantilevers and to investigate the stresses across the bond interface. It was found that the amount of gold is the key factor for reliable bonding

A highly efficient, mild, and selective cleavage of β-methoxyethoxymethyl (MEM) ethers by cerium(III) chloride in acetonitrile

A highly selective cleavage of MEM ethers has been achieved in high yields using CeCl<SUB>3</SUB>·7H<SUB>2</SUB>O in refluxing acetonitrile under mild and neutral reaction conditions. The method is very rapid and compatible with other hydroxyl protecting groups such as Bn, TBDPS, Ac, Me, Tr, PMB, benzylidene, THP, MOM, BOM, and NHAc present in the substrate

A novel, efficient, and selective cleavage of acetals using bismuth (III) chloride

Treatment of acetals with bismuth(III) chloride in methanol provides a simple, convenient and chemoselective process for deprotection, and the parent aldehyde or ketone was obtained in high yield. The acetals have been cleaved selectively in the presence of silyl, benzyl and tetrahydropyranyl ethers