Ved Singh - Academia.edu (original) (raw)
Uploads
Papers by Ved Singh
Nanotechnology, 2007
A first-principles study of the effects of spin-orbit coupling (SOI) on the structural, electroni... more A first-principles study of the effects of spin-orbit coupling (SOI) on the structural, electronic and optical properties of 16 bismuth nanowires, Bi n with n = 7-18, has been performed. The density functional theory (DFT) in the local density approximation (LDA) has been used. The inclusion of the SOI significantly alters the electronic and optical properties of the wires. The stable structures for the Bi n wires with n = 7-18 form two groups: non-helical and helical configurations. In addition to the most stable non-helical 5-Bi pentagonal, 6-Bi hexagonal and 6-Bi triple-zigzag wire configurations found in a previous report, the present study adds to this list three more non-helical structures, namely the non-helical 7-Bi hexagonal, 8-Bi heptagonal and 11-Bi pentagonal cross-sectional wire configurations. The present result is in sharp contrast to the conclusions of our previous studies of Pb-and Tl-nanowires, where it was observed that, in general, a structure possessing a high coordination number value has large binding energy and, therefore, the helical wire structures are the most stable ones. All of the wires are metallic in the LDA. The number of channels in the nanowires is large which will lead to high quantum ballistic conduction. The consideration of the many body effects such as the GW approximation (GWA) may destroy the metallicity predicted here in the Bi n wire configurations for n 7. However, for the wire configurations having n 8, we find that even in the GWA, one may not observe the opening of the energy gaps because of the violation of the electron counting principle.
Nanotechnology, 2006
Full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory ... more Full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory has been used to calculate structural, electronic and optical properties of Ca 1Àx Sr x S, an alkali earth chalcogenide, with varying compositional parameter x in the range 0oxo1. Whereas the structural properties are discussed in terms of charge transfer between the two cations, calculated electronic band structure and density of states have been analyzed in terms of contribution from the S p, Ca d and Sr d states. Furthermore, we have calculated some optical properties such as real and imaginary parts of dielectric constant, e(o), and the calculated results have been discussed in comparison with the existing experimental data and other theoretical calculations.
Chemical & Pharmaceutical Bulletin, 2010
Series of pyrazole ester prodrugs analogues have been synthesized and found to contain highly pot... more Series of pyrazole ester prodrugs analogues have been synthesized and found to contain highly potent inhibitors of the cyclooxygenase-2 (COX-2) enzyme. The paper describes synthesis of the target pyrazole analogues. The structure of the synthesized mutual ester prodrugs (6-8c) were confirmed by 1 H-, 13 C-NMR mass spectroscopy (MS) and their purity were ascertained by TLC and elemental analyses. The biological in vivo evaluation of these compounds in experimental models (carrageenan-induced oedema) proved the presence of anti-inflammatory activity. Docking studies into the catalytic site of COX-2 were used to identify potential antiinflammatory lead compounds. One lead derivative was chosen endowed with good binding energies.
Nanotechnology, 2007
A first-principles study of the effects of spin-orbit coupling (SOI) on the structural, electroni... more A first-principles study of the effects of spin-orbit coupling (SOI) on the structural, electronic and optical properties of 16 bismuth nanowires, Bi n with n = 7-18, has been performed. The density functional theory (DFT) in the local density approximation (LDA) has been used. The inclusion of the SOI significantly alters the electronic and optical properties of the wires. The stable structures for the Bi n wires with n = 7-18 form two groups: non-helical and helical configurations. In addition to the most stable non-helical 5-Bi pentagonal, 6-Bi hexagonal and 6-Bi triple-zigzag wire configurations found in a previous report, the present study adds to this list three more non-helical structures, namely the non-helical 7-Bi hexagonal, 8-Bi heptagonal and 11-Bi pentagonal cross-sectional wire configurations. The present result is in sharp contrast to the conclusions of our previous studies of Pb-and Tl-nanowires, where it was observed that, in general, a structure possessing a high coordination number value has large binding energy and, therefore, the helical wire structures are the most stable ones. All of the wires are metallic in the LDA. The number of channels in the nanowires is large which will lead to high quantum ballistic conduction. The consideration of the many body effects such as the GW approximation (GWA) may destroy the metallicity predicted here in the Bi n wire configurations for n 7. However, for the wire configurations having n 8, we find that even in the GWA, one may not observe the opening of the energy gaps because of the violation of the electron counting principle.
Nanotechnology, 2006
Full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory ... more Full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory has been used to calculate structural, electronic and optical properties of Ca 1Àx Sr x S, an alkali earth chalcogenide, with varying compositional parameter x in the range 0oxo1. Whereas the structural properties are discussed in terms of charge transfer between the two cations, calculated electronic band structure and density of states have been analyzed in terms of contribution from the S p, Ca d and Sr d states. Furthermore, we have calculated some optical properties such as real and imaginary parts of dielectric constant, e(o), and the calculated results have been discussed in comparison with the existing experimental data and other theoretical calculations.
Chemical & Pharmaceutical Bulletin, 2010
Series of pyrazole ester prodrugs analogues have been synthesized and found to contain highly pot... more Series of pyrazole ester prodrugs analogues have been synthesized and found to contain highly potent inhibitors of the cyclooxygenase-2 (COX-2) enzyme. The paper describes synthesis of the target pyrazole analogues. The structure of the synthesized mutual ester prodrugs (6-8c) were confirmed by 1 H-, 13 C-NMR mass spectroscopy (MS) and their purity were ascertained by TLC and elemental analyses. The biological in vivo evaluation of these compounds in experimental models (carrageenan-induced oedema) proved the presence of anti-inflammatory activity. Docking studies into the catalytic site of COX-2 were used to identify potential antiinflammatory lead compounds. One lead derivative was chosen endowed with good binding energies.