Magnesium-induced regiospecific C-silylation of suitably substituted enoates and dienoates

The β-aryl-β-silyl and β,β-disilyl propionates have been synthesized from cinnamates and β-silyl acrylates by a regiospecific reductive C-silylation using Mg/silyl chloride/DMF system at room temperature. These reductive C-silylation conditions have also been applied to δ-aryl substituted dienoates wherein silylation took place at the δ-position leading to the synthesis of single regioisomeric allylsilanes with very high stereoselectivity.     

A study of self-quenching of lyoluminescence yield from gamma-irradiated saccharides and amino acids

Tissue equivalent (TE) lyoluminescence (LL) dosimetry requires practical amount of phosphor for dissolution, typically 5-30 mg. Pronounced mass quenching effect has been observed even in the region of 5 mg, in the cases of LL of lactose-monohydrate, d-glucose, d-mannose, raffinose, sucrose and 1-glutamine. Ordinary concentration-quenching is non-existent but yield per mg falls rapidly with increasing mass of the phosphor. The curves have been fitted with a self-absorption type formula. A well-recognised dose effect is present in quenching curves. The role of free radicals at high radiation doses has been discussed in the contribution of dose effect in quenching.     

Induction of B1 phase in binary mixtures of rod- and bent-shaped mesomorphic compounds

The miscibility of a rod-shaped (R) and a bent-shaped (BC) compound forming an induced B₁ phase is reported. B₁ phase is not present in both R and BC in the entire phase sequence. R exhibits partially bilayered smectic A_d phase with cholesteric and TGB while BC shows a B₂ phase. It is interesting to show that the B₂ phase is totally diminished in low composition (weight%) of BC, B₁ phase is induced at lower temperature range (~90-135 °C). A dielectric study is also incorporated to confirm the induction of B₁ phase in the binary mixture.     

A soft-segmentation visualization scheme for magnetic resonance images

Prevalent visualization tools exploit gray value distribution in images through modified histogram equalization and matching technique, referred to as the window width/window level-based method, to improve visibility and enhance diagnostic value. The window width/window level tool is extensively used in magnetic resonance (MR) images to highlight tissue boundaries during image interpretation. However, the identification of different regions and distinct boundaries between them based on gray-level distribution and displayed intensity levels is extremely difficult because of the large dynamic range of tissue intensities inherent in MR images. We propose a soft-segmentation visualization scheme to generate pixel partitions from the histogram of MR image data using a connectionist approach and then generate selective visual depictions of pixel partitions using pseudo color based on an appropriate fuzzy membership function. By applying the display scheme in clinical examples in this study, we could demonstrate additional overlapping regions between distinct tissue types in healthy and diseased areas (in the brain) that could help improve the tissue characterization ability of MR images.     

Stereospecific peptide folds. A rationally designed molecular bracelet

A canonical planar beta-hairpin peptide, stereochemically reengineered into a semicircular bracelet type motif by L-to-D stereochemical inversion in two pairs of its cross-strand neighbor residues, displays protein like ordering including two-state behavior in H2O, which is unusual for a small peptide of this size.     

Completeness properties of the pseudocompact-open topology on <Emphasis Type="Italic">C</Emphasis>(<Emphasis Type="Italic">X</Emphasis>)

This is a study of the completeness properties of the space C _ps (X) of continuous real-valued functions on a Tychonoff space X, where the function space has the pseudocompact-open topology. The properties range from complete metrizability to the Baire space property. Dedicated to Professor Robert A. McCoy     

Anharmonic effects on lattice resonant modes of impure metallic crystals

The effect of lattice anharmonicity on the resonant modes of dilute impurities for Au-Cu, Au-Ag and W-Cr metallic systems are studied from the poles of the double time temperature dependent impure Green’s function of these crystals. The third order force constants used in the present work are derived assuming the systems to obey the Lennard-Jones potential. The inclusion of lattice anharmonicity has been found to increase the resonant frequency which depends upon the mass defect, force constant change parameter and the impurity concentration terms. Some interesting features about the phase shift and the change in width of the vibrational spectrum are reported at room temperature for the isotopic defects and the defects interacting with host atoms. The results are found to be in qualitative agreement with the experiments on the systems considered.