44,135 research outputs found
Au9+ swift heavy ion irradiation of Zn[CS(NH2)2]3SO4 crystal: Crystalline perfection and optical properties
The single crystal of tris(thiourea)zinc sulphate (Zn[CS(NH2)2]3SO4) was
irradiated by 150 MeV Au9+ swift heavy ions and analyzed in comparison with
pure crystal for crystalline perfection and optical properties. The Fourier
transform infrared and x-ray powder diffraction inferred that swift ions lead
the disordering and breaking of molecular bonds in lattice without formation of
new structural phases. High resolution X-ray diffraction (HRXRD) revealed the
abundance of point defects, and formation of mosaics and low angle grain
boundaries in the irradiated region of crystal. The swift ion irradiation found
to affect the lattice vibrational modes and functional groups significantly.
The defects induced by heavy ions act as the color centers and resulted in
enhance of photoluminescence emission intensity. The optical transparency and
band gap found to be decreased.Comment: 7 page
Statistical Mechanics of DNA Rupture: Theory and Simulations
We study the effects of the shear force on the rupture mechanism on a double
stranded DNA. Motivated by recent experiments, we perform the atomistic
simulations with explicit solvent to obtain the distributions of extension in
hydrogen and covalent bonds below the rupture force. We obtain a significant
difference between the atomistic simulations and the existing results in the
iterature based on the coarse-grained models (theory and simulations). We
discuss the possible reasons and improve the coarse-grained model by
incorporating the consequences of semi-microscopic details of the nucleotides
in its description. The distributions obtained by the modified model
(simulations and theoretical) are qualitatively similar to the one obtained
using atomistic simulations.Comment: 18 pages, 9 figures. Accepted in J. Chem. Phys. (2013). arXiv admin
note: text overlap with arXiv:1104.305
Electronic structure studies of Fe- ZnO nanorods by x-ray absorption fine structure
We report the electronic structure studies of well characterized
polycrystalline Zn_{1-x}Fe_xO (x = 0.0, 0.01, 0.03, and 0.05) nanorods
synthesized by a co-precipitation method through x-ray absorption fine
structure (XAFS). X-ray diffraction (XRD) reveals that Fe doped ZnO
crystallizes in a single phase wurtzite structure without any secondary phase.
From the XRD pattern, it is observed that peak positions shift towards lower
2\theta value with Fe doping. The change in the peak positions with increase in
Fe contents clearly indicates that Fe ions are replacing Zn ions in the ZnO
matrix. Linear combination fittings (LCF) at Fe K-edge demonstrate that Fe is
in mixed valent state (Fe3+/Fe2+) with a ratio of ~ 7:3 (Fe3+:Fe2+). XAFS data
is successfully fitted to wurtzite structure using IFEFFIT and Artemis. The
results indicate that Fe substitutes Zn site in the ZnO matrix in tetrahedral
symmetry.Comment: 7 pages, 5 figures, 2 tables, regular articl
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