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31.
Anirudh Pradhan Purnima Pandey Kanti Jotania Mahesh Kumar Yadav 《International Journal of Theoretical Physics》2007,46(11):2774-2787
Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The
viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear
viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear
viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations.
Some physical and geometric properties of the models are also discussed. 相似文献
32.
Midde SreekanthGavinolla Pranitha Bharatam JagadeeshTushar Kanti Chakraborty 《Tetrahedron letters》2011,52(14):1709-1712
Stereoselective construction of highly substituted five-membered carbocycles with multiple chiral centres is described. Sharpless kinetic resolution was applied as the key step to prepare the required 2,3-epoxy alcohols and a Ti(III) radical mediated opening of the epoxide ring followed by intramolecular trapping of the generated radical with a suitably placed α,β-unsaturated ester resulted in the formation of five-membered carbocycles with up to three consecutive new chiral centres stereoselectively fixed. 相似文献
33.
An elegant and fast method for the calculation of geometrical structure coefficients needed for an expansion of a few-body
wavefunction and interaction in hyperspherical harmonics has been proposed. A sum rule for the GSC has also been derived,
which is useful for an independent check of the coefficients. The proposed method of computation is many orders of magnitude
faster than conventional methods. 相似文献
34.
One-pot transition-metal-free synthesis of aromatic aldehydes and ketones via oxidative decarboxylation of arylacetic acids in water is developed. Protocol relies on the direct decarboxylation of sp3-hybridized carbon in water without any over oxidation into carboxylic acids with minimal waste. Reaction mechanism is investigated and application of this protocol is demonstrated on a gram scale. 相似文献
35.
A stereoselective synthesis of the C1-C15 fragment of a G-actin binding natural macrodiolide, rhizopodin was achieved using, as key steps, highly stereoselective acetate aldol reactions to build the C1-C7 fragment, one pot oxazole synthesis and an asymmetric Keck allylation reaction to build the C8-C15 fragment and finally, a Stille reaction to couple both the fragments. 相似文献
36.
Sengupta P Sarkar AK Bhaumik U Chatterjee B Roy B Chakraborty US Pal TK 《Biomedical chromatography : BMC》2010,24(12):1342-1349
A simple, high‐throughput and specific high‐performance liquid chromatography tandem mass spectrometry method has been developed and validated according to the FDA guidelines for simultaneous quantification of olmesartan and pioglitazone in rat plasma. The bioanalytical method consists of liquid–liquid extraction and quantitation by triple quadrupole mass spectrometry using electrospray ionization technique, operating in multiple reaction monitoring and positive ion modes. The compounds were eluted isocratically on a C18 column with a mobile phase consisting of a mixture of methanol and water (containing 0.5% formic acid) in a ratio of 9:1. The response to olmesartan and pioglitazone was linear over the range 0.01–10 µg/mL. The validation results demonstrated that the method had satisfactory precision and accuracy across the calibration range. Intra‐ and inter‐day precisions ranged from 0.66 to 3.32 and from 0.94 to 2.93% (%CV), respectively. The accuracy determined at three quality control levels was within 91.27–107.28%. There was no evidence of instability of the analytes in rat plasma following the stability studies. The method proved highly reproducible and sensitive and was successfully applied in a pharmacokinetic study after single dose oral administration of olmesartan and pioglitazone to the rat. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
37.
Mrinal Kanti Paira Tapan Kumar Mondal Elena López-Torres Joan Ribas Chittaranjan Sinha 《Polyhedron》2010
Copper(II) complexes of 3-((2-(alkylthio)phenylazo)-2,4-pentanedione, tridentate O, N, S donor ligands, are described in this work. Chloride bridged copper(II) polymers (1) and thiocyanato bridged copper(II) dimmers (2) are characterized by a single crystal X-ray diffraction study. The complexes show antiferromagnetic interactions, with J = −0.5 ± 0.1 cm−1 (1a) and −25.8 ± 0.5 cm−1 (2b), which implies stronger coupling in the –SCN-bridging compound. The spectra, redox and magnetism are explained by DFT studies. 相似文献
38.
Célia Fonseca Guerra Tushar van der Wijst Jordi Poater Marcel Swart F. Matthias Bickelhaupt 《Theoretical chemistry accounts》2010,125(3-6):245-252
We have investigated the performance of the dispersion-corrected density functionals (BLYP-D, BP86-D and PBE-D) and the widely used B3LYP functional for describing the hydrogen bonds and the stacking interactions in DNA base dimers. For the gas-phase situation, the bonding energies have been compared to the best ab initio results available in the literature. All dispersion-corrected functionals reproduce well the ab initio results, whereas B3LYP fails completely for the stacked systems. The use of the proper functional leads us to find minima for the adenine quartets, which are energetically and structurally very different from the C4h structures, and might explain why adenine has to be sandwiched between guanine quartets to form planar adenine quartets. 相似文献
39.
Karmakar S Das O Ghosh S Zangrando E Johann M Rentschler E Weyhermüller T Khanra S Paine TK 《Dalton transactions (Cambridge, England : 2003)》2010,39(45):10920-10927
A new dicompartmental dioxime ligand (H(2)L) with m-xylyl spacer between the donor sites has been synthesised by Schiff-base condensation of α,α'-diamino-m-xylene and diacetyl monooxime. The ligand reacts with copper(ii) salts giving rise to hexanuclear tricationic copper(II) cage complexes [Cu(II)(6)(μ(3)-O···H···O-μ(3))L(3)(H(2)O)(6)]X(3) (X = BF(4), 1a; X = ClO(4), 1b). The complexes have been characterised by different analytical and spectroscopic techniques and confirmed the hexanuclear structure even in solution. Single crystal X-ray diffraction studies of both the complexes revealed a very similar core structure with three dicompartmental ligands supporting two triangular Cu(3)O cores that share a proton, located on their common threefold axis and involved in a strong hydrogen bond interaction (O···O distance of 2.517(2) ?). Two Cu(3)O units do not superimpose but are staggered and disposed with the formation of a helicate structure. However both the enantiomers are present in the centrosymmetric space group. The facing Cu(3)-planes in 1a are separated at a distance of 3.476 ?. The temperature dependence of the magnetic behaviour of the hexanuclear complex 1a clearly indicates an overall antiferromagnetic exchange interaction between the spin carriers in the cage having two Cu(3)O subunits and leaves a single unpaired electron in each triangular unit. The unpaired electrons in the two Cu(3)O units interact antiferromagnetically through hydrogen bonding giving rise to an overall singlet-spin ground state. 相似文献
40.
A simple electrochemical process has been implemented to fabricated fractal structured leaf-like metallic zinc. The fabricated material was structurally characterized using X-ray diffraction that reveals the hexagonal unit cell structure. Also the growth of the structure is anisotropic. Field emission scanning electron microscopic images revealed clearly the leaf-like morphology of the fabricated material is fern like and ∼500 μm in length, ∼50-60 μm wide and the platelets thickness is ∼5 μm. The growth of this structure is diffusion controlled and locally accomplished with the oriented attachment. Raman shift measurement revealed the existence of surface optical phonon modes which is very significant for surface defects. 相似文献