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71.
Bheemanapalli LN Akkinepally RR Pamulaparthy SR 《Chemical & pharmaceutical bulletin》2008,56(9):1342-1348
A new series of 2,3,5,7-substituted-pyrido[2,3-d]pyrimidin-4(3H)-one derivatives were prepared from 2-amino-N,6-substituted phenyl-4-(trifluoromethyl or methyl)nicotinamides. The key intermediate 2-amino-N,6-substituted phenyl-4-(trifluoromethyl or methyl)nicotinamides were synthesized from 2-bromo-N,6-disubstituted phenyl-4-(trifluoromethyl or methyl)nicotinamides as well as from ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) coupling of 2-amino-4,6-substituted nicotinic acid and substituted arylamines. All the synthesized compounds were screened for antibacterial activity against Gram +ve and Gram -ve bacteria. Compound 7c showed better antibacterial activity against Gram +ve and Gram -ve bacteria. 相似文献
72.
Ashwath Narayana Gowda 《Liquid crystals》2016,43(12):1721-1731
We have discovered that ethylenedioxythiophene (EDOT) can be used as a central unit for the synthesis of bent-core liquid crystals (BC LCs). Two series of EDOT-based BC LCs are prepared via Sonogashira coupling reaction. The mesophase behaviour of all the compounds was characterised using a combination of polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. EDOT-based three-ring compounds were found to be nonliquid crystalline, while all the four derivatives of five-ring series, including a branched alkoxy chain derivative, display enantiotropic nematic phase over wide temperature range. The bent angle of these compounds is about 153°, which falls in between typical rod-like and banana liquid crystals. The transition temperature of branched alkoxy chain compound is lower than straight alkoxy chain compounds. The detailed XRD investigations of all the mesogens corroborate the presence of nematic phase. 相似文献
73.
In vivo diffusion tensor imaging (DTI) of rat cervical and thoracic spinal cord was performed using a three-element phased array coil at 7 T. The magnetic field was shimmed over the spinal cord in real time using an in-house developed automatic algorithm. Echo planar imaging (EPI)-based diffusion-weighted images (DWIs) were acquired with 21 gradient encoding directions. The DWIs were tensor encoded, and diffusion tensor metrics, fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity (λ0) and transverse diffusivity (λ) were determined for both white matter (WM) and gray matter (GM). The results on six normal rats indicated no significant differences in the diffusion tensor metrics between thoracic and cervical regions. However, the DTI-derived metrics in cervical spinal cord from our study are somewhat different from the published results in rats. The possible reasons for these differences are suggested. 相似文献
74.
K.C. Vishnubhatla S. Venugopal Rao R. Sai Santosh Kumar Maurizio Ferrari D. Narayana Rao 《Optics Communications》2009,282(23):4537-4542
Herein we present results on the femtosecond laser direct writing and optical characterization studies of two dimensional gratings in fused silica, GE 124, and Foturan™ glasses. Varieties of structures were achieved with varying input energy and spatial orientation of the samples. Various characterization techniques including fluorescence spectroscopy, micro-Raman spectroscopy, and laser confocal microscopy were employed to analyze the structural and physical modifications at the focal volume resulting in change of refractive index. Diffraction efficiencies of 9–12% were observed from the grating structures. A broad-band emission was observed in the laser-modified region of the Foturan glass. The obtained results are analyzed in the light of recent work in similar glasses and exploring the applications of such structures in the fields of photonics. 相似文献
75.
P. Narayana Swamy 《International Journal of Theoretical Physics》2009,48(8):2432-2440
Many of us are familiar with Feynman’s “proof” of 1948, as revealed by Dyson, which demonstrates that Maxwell equations of
electromagnetism are a consequence of Newton’s laws of motion of classical mechanics and the commutation relations of coordinate
and momentum of quantum mechanics. It was Feynman’s purpose to explore the universality of dynamics of particles while making
the fewest assumptions. We re-examine this formulation in the context of quantum gravity and show how Feynman’s derivation
can be extended to include quantum gravity. 相似文献
76.
J.S. Yadav B.V. Subba Reddy G.G.K.S. Narayana Kumar B. Jagadeesh 《Tetrahedron letters》2009,50(16):1799-7160
4-Hydroxypiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using 10 mol % phosphomolybdic acid under mild reaction conditions. This is the first report on the preparation of 4-hydroxypiperidines via aza-Prins-cyclization. 相似文献
77.
Albert Koulman Gary Woffendin Vinod K. Narayana Helen Welchman Catharina Crone Dietrich A. Volmer 《Rapid communications in mass spectrometry : RCM》2009,23(10):1411-1418
Most analytical methods in metabolomics are based on one of two strategies. The first strategy is aimed at specifically analysing a limited number of known metabolites or compound classes. Alternatively, an unbiased approach can be used for profiling as many features as possible in a given metabolome without prior knowledge of the identity of these features. Using high‐resolution mass spectrometry with instruments capable of measuring m/z ratios with sufficiently low mass measurement uncertainties and simultaneous high scan speeds, it is possible to combine these two strategies, allowing unbiased profiling of biological samples and targeted analysis of specific compounds at the same time without compromises. Such high mass accuracy and mass resolving power reduces the number of candidate metabolites occupying the same retention time and m/z ratio space to a minimum. In this study, we demonstrate how targeted analysis of phospholipids as well as unbiased profiling is achievable using a benchtop orbitrap instrument after high‐speed reversed‐phase chromatography. The ability to apply both strategies in one experiment is an important step forward in comprehensive analysis of the metabolome. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
78.
Vishnu Shanker Saroj L. Samal Gopal K. Pradhan Chandrabhas Narayana Ashok K. Ganguli 《Solid State Sciences》2009,11(2):562-569
Nanocrystalline NaNbO3 and NaTaO3 have been synthesized by the reverse micellar technique for the first time. The particle size of NaNbO3 was found to be 18 nm while that of NaTaO3 was found to be 40 nm (much smaller size than most of the earlier reports on NaTaO3). Rietveld refinement of X-ray diffraction data and Raman spectroscopy confirm that the nanoparticles of NaNbO3 and NaTaO3 have orthorhombically distorted structures with Pmc21 and Pbnm space groups, respectively. The dielectric constant at 25 °C of NaNbO3 and NaTaO3 was found to be 209 and 147 at 1 kHz, respectively. The antiferroelectric transition in NaNbO3 shifts to lower temperature (325 °C) in the nanocrystalline solid. 相似文献
79.
P. Narayana Reddy A. Sreedhar M. Hari Prasad Reddy S. Uthanna J. F. Pierson 《Crystal Research and Technology》2011,46(9):961-966
Nano‐crystalline silver oxide films were deposited on glass and silicon substrates held at room temperature by RF magnetron sputtering of silver target under different oxygen partial pressures. The influence of oxygen partial pressure on the structural, morphological, electrical and optical properties of deposited films was investigated. Varying oxygen partial pressure during the sputter deposition leads to changes of mixed phase of Ag2O and Ag to a single phase of Ag2O and to AgO. The X‐ray diffraction and X‐ray photoelectron spectroscopy results showed the formation of single phase Ag2O with cubic structure at oxygen partial pressures of 2x10‐2 Pa while the films deposited at higher oxygen partial pressure of 9x10‐2 Pa showed the formation of single phase of AgO with monoclinic structure. Raman spectroscopic studies on the single phase Ag2O showed the stretching vibration of Ag‐O bonds. Single‐phase Ag2O films obtained at oxygen partial pressure of 2x10‐2 Pa were nano‐crystalline with crystallite size of 20 nm and possessed an electrical resistivity of 5.2x10‐3 Ωcm and optical band gap of 2.05 eV. The films deposited at higher oxygen partial pressure of 9x10‐2 Pa were of AgO with electrical resistivity of 1.8x10‐2 Ωcm and optical band gap of 2.13 eV. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
80.
Grzegorz Dutkiewicz B. Narayana S. Samshuddin H. S. Yathirajan Maciej Kubicki 《Journal of chemical crystallography》2011,41(10):1442-1446