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1.
Barua  A. Gohain  Boruah  B. R.  Bhattacharyya  S.  Baruah  G. D. 《Pramana》2003,60(1):47-52
Analysis of a part of the meteorite which fell at Dergaon (India) on March 2, 16.40 local time (2001) is presented with the help of FTIR, absorption and atomic spectra. The FTIR spectrum exhibits prominent absorption bands in the region 800–1100 cm−1, originating from the valence vibration of SiO4, a basic component of the silicate lattice.  相似文献   
2.
A mild and efficient protocol for the coupling of indoles and pyrroles with allyl halides such as allyl bromide, crotyl bromide and propargyl bromide in the presence of gallium metal in a Bu4NBr-DMF-H2O system has been developed. The reaction is equally effective when cadmium is used in lieu of gallium and the corresponding 3-allyl indoles and 3-allyl pyrroles were obtained in almost comparable yields.  相似文献   
3.
Al(OTf)3 catalyzed the alkylation of indoles using secondary/tertiary propargylic alcohols to produce 3-propargylated indoles in excellent yields with high selectivity. The reactions were performed in air with commercial grade solvents, and water was the only side product of the process. The catalyst was recovered after completion of the reaction and re-used with minimum loss of activity over three cycles.  相似文献   
4.
We study projective curvature tensor in K-contact and Sasakian manifolds. We prove that (1) if a K-contact manifold is quasi projectively flat then it is Einstein and (2) a K-contact manifold is ξ-projectively flat if and only if it is Einstein Sasakian. Necessary and sufficient conditions for a K-contact manifold to be quasi projectively flat and φ-projectively flat are obtained. We also prove that for a (2n + 1)-dimensional Sasakian manifold the conditions of being quasi projectively flat, φ-projectively flat and locally isometric to the unit sphere S 2n+1 (1) are equivalent. Finally, we prove that a compact φ-projectively flat K-contact manifold with regular contact vector field is a principal S 1-bundle over an almost Kaehler space of constant holomorphic sectional curvature 4.  相似文献   
5.
The premicellar and micelle formation behaviors of four cationic triphenylmethane dyes, viz, Pararosaniline (RN), Crystal violet (CV), Ethyl violet (EV), and Malachite green (MG), in aqueous anionic surfactant solutions of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium dodecyl sulfonate (SDSN) have been studied by spectral and surface tension measurements. The study was carried out within a pH range where the dyes are stable in their quinoid forms. The dyes have been found to form dye–surfactant ion pairs (DSIPs) with the surfactants, at the surfactant concentrations well below their critical micelle concentration, CMC*. The DSIPs behave like nonionic surfactants and form an air–water interfacial monolayer. The DSIPs have a lower critical micelle concentration (CMCIP), greater efficiency, and lower effectiveness than the corresponding pure surfactants. As the surfactant concentration is increased below the CMC*, the DSIPs start forming micelles of their own where the dye gets protonated and exists as a protonated dye–surfactant ion pair (PDSIP) in the ion pair micelles. As the concentration of the surfactant exceeds the CMC* of the pure surfactant, the protonation reverses gradually with the dye remaining in the micelles in solubilized form and the DSIPs in the air–water interfacial monolayer are replaced by pure surfactants. The distorted helical isomeric form (isomer B) of the dyes is favored in the PDSIPs. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
6.
In this paper, we obtain some sufficient conditions for a 3-dimensional compact trans-Sasakian manifold of type (α, β) to be homothetic to a Sasakian manifold. A characterization of a 3-dimensional cosymplectic manifold is also obtained.  相似文献   
7.
Number of bonds formed by sharing an electron pair between two atoms is not restricted to one, it can go beyond four and six is the maximum. While homopolar sextuple bond in Mo2 and W2 has been reported, such a high bond order in heteropolar diatomics has remained elusive. In the pursuit of the sextuple bond in polar diatomics, the present study depicts the existence of such multiple bonds in Rhodium-Scandium hetero-diatom based on relativistic quantum chemical calculations. The bonding comprises of three normal electron sharing covalent bonds and three dative covalent bonds.  相似文献   
8.
Comparison of structural, morphological and spectroscopic properties of zinc vanadate Zn3(VO4)2 phosphor synthesized via two different methods, viz. citrate-gel combustion and hydrothermal reaction, is presented. Highly crystalline and pure phase micro-rods are achieved by citrate-gel combustion route. The hydrothermal reaction products exhibit ribbon like structures. X-ray photoelectron spectroscopic investigation reveals the presence of multiple oxidation states of vanadium in the hydrothermally synthesized phosphor. Luminescence properties have also been compared and the effect of divalent cationic substitution (Ca, Mg) is presented.  相似文献   
9.
10.

Abstract  

Iodine catalyzes the pseudo four-component reaction of an aldehyde, a urea or thiourea, and cyclic 1,3-dicarbonyl compounds under microwave irradiation in a solvent-free condition to yield various σ symmetric spiro heterobicyclic rings in excellent yields.  相似文献   
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