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Prapti Saxena Sankar P. Sanyal 《Physica E: Low-dimensional Systems and Nanostructures》2004,24(3-4):244-248
We report a detailed study of the phonon properties of hexagonal boron nitride (BN) monolayers as well as nanotubes by using De Launay type of angular force model. The force constants used for calculation of phonon dispersion relations of the nanotube are derived from those for the monolayers of hexagonal by employing force constant method. These force constants have been modified to include the effect of curvature of the tubule. The results are then used to derive the phonon dispersion relations for (10,10) BN nanotubes using ‘zone-folding’ method. Calculated phonon modes are in good agreement with the experimental values obtained so far, for (10,10) armchair BN nanotubes. 相似文献
3.
N. K. Sanyal A. N. Pandey H. S. Singh B. P. Singh 《Journal of Quantitative Spectroscopy & Radiative Transfer》1970,10(12):1343-1345
The generalized mean-square amplitudes of vibration and mean amplitudes of vibration have been computed for CrO3-4, Mn18O-4, MoSe2-4 and WSe2-4 ions at three temperatures, T = 0°K, T = 298°K, T = 500°K, employing Cyvin's method. The results have been discussed in the light of atomic weight and electronegativity of the atom in the ionic system. 相似文献
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Isocratic reversed-phase liquid chromatography (LC) method was developed using acetonitrile and water for the determination of diospyrin, a pharmacologically important bisnaphthoquinonoid plant-product. The method was validated for precision, accuracy and reproducibility, and was found to be linear over the concentration range of 1-1000 microg/ml; the limits of detection and quantitation were 8 and 20 ng, respectively. The technique was used to determine the amount of diospyrin in plant extracts from four climatic regions in India. It was also applied for differentiation and separation of 27 naphthyl compounds. While a composition of 50:50 was preferable for dimeric compounds, the composition 40:60 was a better choice for the monomers. Also, the isomeric alpha- and beta-naphthols and their dimers could be distinguished by conversion into the respective methyl ethers. 相似文献
6.
Sanyal A Rautaray D Bansal V Ahmad A Sastry M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7220-7224
We show here that reaction of the fungus, Fusarium oxysporum, with the aqueous heavy-metal ions Pb2+ and Cd2+ results in the one-step formation of the corresponding metal carbonates. The metal carbonates are formed by reaction of the heavy-metal ions with CO2 produced by the fungus during metabolism and thus provide a completely biological method for production of crystals of metal carbonates. The PbCO3 and CdCO3 crystals thus produced have interesting morphologies that are shown to arise because of interaction of the growing crystals with specific proteins secreted by the fungus during reaction. An additional advantage of this approach is that the reaction leads to detoxification of the aqueous solution and could have immense potential for bioremediation of heavy metals. Under conditions of this study, the metal ions are not toxic to the fungus, which readily grows after exposure to the metal ions. 相似文献
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Summary The use of chrome azurol S for the colorimetric determination of quadrivalent vanadium is described. The reagent forms a violet coloured chelate (
max = = 580 nm) with the metal at pH 4.0±0.2. Beer's law is followed with 0.203 to 3.40 ppm of metal. The sensitivity is 0.02g/cm2 (Sandell) and 0.2g/cm2 (practical). Many ions interfere.
Zusammenfassung Die kolorimetrische Bestimmung von Vanadin(IV) mit Chromazurol S wurde beschrieben. Das Reagens bildet mit Vanadin(IV) einen violetten ChelatkompleX ( max = 580 nm) bei pH 4,0±0,2. Zwischen 0,203 und 3,40 ppm Metall ist das Beersche Gesetz erfüllt. Die Empfindlichkeit beträgt 0,02g/cm2 (Sandell) bzw. 0,2g/cm2 (praktisch). Viele Fremdionen stören.
Résumé On décrit l'emploi du chrome-azurol S pour le dosage colorimétrique du vanadium-IV. Le réactif forme un chélate coloré en violet ( max = 580 nm) avec le métal à pH 4,0 ± 0,2. La loi de Beer est vérifiée de 0,203 à 3,40 p. p. m. de métal. La sensibilité est de 0,02g/cm3 (Sandell) et 0,2g/cm3 (en pratique). De nombreux ions interfèrent.相似文献
9.
Rhenium and uranium hexafluorides oxidise iodine in iodine pentafluoride at ambient temperature to give the I2+ cation. With UF6 additional reaction occurs to give β-uranium pentafluoride as one product (J.A. Berry, A. Prescott, D.W.A. Sharp, and J.M. Winfield, ., 1977, , 247). Further work on the latter reaction together with an electronic spectroscopic study of the oxidation of I2 by phosphorus pentafluoride in IF5, suggests that the fate of the I2+ cation depends on the nature and quantity of the oxidising agent. Oxidation of I2 by PF5 can be conveniently followed by monitoring its visible spectrum. The reaction occurs over several hours and eventually an apparent equilibrium between I2 and I2+ results. Formation of I2+UF6?is rapid and, with the mole ratio UF6:I2 > 10:1, UF5 is precipitated rapidly from solution, I2+ being oxidised further, apparently to IF5. With a smaller UF6:I2 mole ratio UF5 is contaminated by I2, the latter is presumed to result from the disproportion-ation of an II or IIII fluoride.β-UF5 is very soluble in acetonitrile and reacts with thallium(I) fluoride in this solvent to give TlIUF6. It reacts with trimethyl(methoxo)silane to give (CH3)3SiF, U(OCH3)5, and an insoluble solid, believed to be a mixture of UV methoxide, fluorides. Both reactions are conveniently followed by near i.r. spectroscopy. 相似文献
10.
Uzun O Sanyal A Nakade H Thibault RJ Rotello VM 《Journal of the American Chemical Society》2004,126(45):14773-14777
Polystyrene functionalized with diamidopyridine (DAP) recognition units self-assembles in nonpolar media to form thermally reversible micrometer-scale spherical aggregates. The size and the thermal stability of these microspheres can be controlled by the molecular weight of the polymer. The addition of thymine-functionalized polymer to these self-assembled microspheres converted them into vesicular aggregates with a controlled size. The morphology change was reversible: the addition of DAP-functionalized polymer converted the vesicles back to microspheres. 相似文献