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161.
Hari Ji Singh Bhupesh Kumar Mishra Nand Kishor Gour 《Theoretical chemistry accounts》2010,125(1-2):57-64
The unimolecular decomposition reaction of CF3CCl2O radical has been investigated using theoretical methods. Two most important channels of decomposition occurring via C–C bond scission and Cl elimination have been considered during the present investigation. Ab initio quantum mechanical calculations are performed to get optimized structure and vibrational frequencies at DFT and MP2 levels of theory. Energetics are further refined by the application of a modified Gaussian-2 method, G2M(CC,MP2). The thermal rate constants for the decomposition reactions involved are evaluated using Canonical Transition State Theory (CTST) utilizing the ab initio data. Rate constants for C–C bond scission and Cl elimination are found to be 6.7 × 106 and 1.1 × 108 s?1, respectively, at 298 K and 1 atm pressure with an energy barrier of 8.6 and 6.5 kcal/mol, respectively. These values suggest that Cl elimination is the dominant process during the decomposition of the CF3CCl2O radical. Transition states are searched on the potential energy surface of the decomposition reactions involved and are characterized by the existence of only one imaginary frequency (NIMAG = 1) during frequency calculation. The existence of transition states on the corresponding potential energy surface is further ascertained by performing intrinsic reaction coordinate (IRC) calculation. 相似文献
162.
Reactions of the sulphonium ion of sulphur mustard (SM+1) at the N7, N3 and O6 sites of guanine, N7, N3 and N1 sites of adenine, O2 and N3 sites of cytosine and O2 and O4 sites of thymine were studied theoretically in gas phase and aqueous media employing density functional theory (DFT) and second order Møller–Plesset perturbation (MP2) theory. The B3LYP, B3PW91 and B1B95 functionals of DFT and the 6-31+G* and AUG-cc-pVDZ basis sets were used in the calculations. Basis set superposition error was treated using the counterpoise method by single point energy calculations at the B3LYP/6-31+G* level in gas phase. The present study explains the mechanism of alkylation of the DNA bases and shows that SM+1 would form stable adducts at the endocyclic nitrogen sites of the DNA bases, and at the O6 site of guanine and the O2 site of cytosine. Formation of adducts at the N7 site of guanine and N3 site of adenine are found to be most favored and next most favored respectively, which agrees with experimental observations. 相似文献
163.
Ashutosh Tiwari Rajendra Kumar Mani Prabaharan Ravi R. Pandey Premlata Kumari Anurag Chaturvedi A. K. Mishra 《先进技术聚合物》2010,21(9):615-620
A nanofibrous polyaniline (PANI) thin film was fabricated using plasma‐induced polymerization method and explored its application in the fabrication of NO2 gas sensor. The effects of substrate position, pressure, and the number of plasma pulses on the PANI film growth rate were monitored and an optimum condition for the PANI thin film preparation was established. The resulting PANI film was characterized with UV–visible spectrophotometer, FTIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The PANI thin film possessed nanofibers with a diameter ranging from 15 to 20 nm. The NO2 gas sensing behavior was studied by measuring the change in electrical conductivity of PANI film with respect to NO2 gas concentration and exposure time. The optimized sensor exhibited a sensitivity factor of 206 with a response time of 23 sec. The NO2 gas sensor using nanofibrous PANI thin film as sensing probe showed a linear current response to the NO2 gas concentration in the range of 10–100 ppm. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
164.
Spatially homogeneous Bianchi types V and VI0 cosmological models are studied with source cosmic cloud strings coupled with electromagnetic field in Rosen’s (Gen. Relativ.
Gravit. 4:435, 1973) bimetric theory of relativity. It is observed that Bianchi type V space time is feasible whereas Bianchi type VI0 is not feasible. In the feasible case different equations of state for cosmic strings with Maxwell fields do not survive
in this theory and the space-time turns out to be flat. 相似文献
165.
This paper presents the modeling and characterization of an optical fiber grating for maximum reflectivity. Grating length and change in refractive index are the critical parameters in contributing to the performance of fiber Bragg grating. The wavelength chosen for analysis is from the third window to minimize the attenuation. The reflection spectra, bandwidth and side lobes strength were analyzed with different lengths and change in refractive index. The simulations are based on solving coupled mode equations by transfer matrix method that describes the interaction of guided modes. 相似文献
166.
Dipsikha Bhattacharya Sumanta K. Sahu Indranil Banerjee Manasmita Das Debashish Mishra Tapas K. Maiti Panchanan Pramanik 《Journal of nanoparticle research》2011,13(9):4173-4188
In this article, we report the design and synthesis of a series of well-dispersed superparamagnetic iron oxide nanoparticles
(SPIONs) using chitosan as a surface modifying agent to develop a potential T
2 contrast probe for magnetic resonance imaging (MRI). The amine, carboxyl, hydroxyl, and thiol functionalities were introduced
on chitosan-coated magnetic probe via simple reactions with small reactive organic molecules to afford a series of biofunctionalized
nanoparticles. Physico-chemical characterizations of these functionalized nanoparticles were performed by TEM, XRD, DLS, FTIR,
and VSM. The colloidal stability of these functionalized iron oxide nanoparticles was investigated in presence of phosphate
buffer saline, high salt concentrations and different cell media for 1 week. MRI analysis of human cervical carcinoma (HeLa)
cell lines treated with nanoparticles elucidated that the amine-functionalized nanoparticles exhibited higher amount of signal
darkening and lower T
2 relaxation in comparison to the others. The cellular internalization efficacy of these functionalized SPIONs was also investigated
with HeLa cancer cell line by magnetically activated cell sorting (MACS) and fluorescence microscopy and results established
selectively higher internalization efficacy of amine-functionalized nanoparticles to cancer cells. These positive attributes
demonstrated that these nanoconjugates can be used as a promising platform for further in vitro and in vivo biological evaluations. 相似文献
167.
168.
S. K. Mohanta S. N. Mishra S. M. Davane Neeraj Kumar A. Thamizhavel S. Layek Z. Hossain S. K. Srivastava 《Hyperfine Interactions》2013,221(1-3):23-27
Employing the γ-ray perturbed angular distribution technique, we have measured the magnetic hyperfine field of 54Fe in tetragonal and orthorhombic structural phases of SrFe2As2. In the tetragonal phase, the magnetic response of 54Fe shows Curie-Weiss type local susceptibility, indicating the presence of localized moment on Fe. The temperature dependence of the hyperfine field of 54Fe reflects quasi-two dimensional first order magnetic transition at 200 K. Our data indicate that Fe moments in the magnetically ordered phase of SrFe2As2 may be canted out of the ab-plane. 相似文献
169.
170.
A simple and efficient methodology for Markovnikov addition of azoles with vinyl acetate catalyzed by potassium tert-butoxide is described.N-heterocyclic compounds are synthesized from simple and commercially available starting materials under mild conditions in high yields. 相似文献