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排序方式: 共有136条查询结果,搜索用时 203 毫秒
131.
Suresh Palla G. Ravi J. R. Reddy Naveen Kumar Veldurthi Radha Velchuri G. Prasad N. R. Munirathnam M. Vithal 《Journal of Sol-Gel Science and Technology》2013,67(3):507-518
Materials belonging to NASICON family of compositions NaHfM(PO4)3 and AgHfM(PO4)3 (M = Ti and Zr) are prepared by sol–gel and ion exchange methods, respectively. Ethylene glycol is used as a gelating agent. All the compositions are characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, 31P MAS NMR, UV–Vis DRS, XPS and energy dispersive spectral methods. All these phosphates are crystallized in rhombohedral lattice with space group $R\overline{3} c$ R 3 ¯ c . These compounds exhibit characteristic PO4 vibrational modes in their FT-IR spectra. The 31P MAS NMR gave broad signals indicating distribution of chemical environments around P ion. The dc and ac conductivity of AgHfM(PO4)3 (M = Ti and Zr) are higher compared to their sodium containing compounds. The Cole–Cole plots of impedance show semicircles between 373 and 623 K. The variation of dc conductivity with temperature follows the Arrhenius equation. The photocatalytic activity of all the samples was studied against methylene blue decomposition using sun light. AgHfM(PO4)3 (M = Ti and Zr) have shown higher photoactivity than the sodium containing Nasicons. 相似文献
132.
Renuka H. Sankhe Arijit Sengupta N. N. Mirashi 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):617-622
A rapid extraction chromatography based methodology was developed for simultaneous recovery of plutonium and americium from various kinds of analytical waste obtained during chemical quality control of plutonium based nuclear materials using sulphonic acid based actinide? resin. Efforts were made to understand the effect of initial feed acidity, gamma radiation and the concentrations of Am3+ and Pu4+ on their k d. values. Processing of assorted analytical waste solutions through this method revealed that more than 95 % of Am3+ and 90 % of Pu4+ were adsorbed on the resin while iso- propanol can be successfully employed for the quantitative recovery of both the actinides from the loaded resin phase. 相似文献
133.
Ashok K. Yadav Meera Manju Manoj Kumar Tripti Yadav Renuka Jain 《Tetrahedron letters》2008,49(40):5724-5726
The diastereoselective intramolecular electroreductive coupling of several β-ketoesters and β-ketoamides has been accomplished at a tin cathode in ionic liquids and isopropanol (9:1). The ionic liquids used are 1-butyl-3-methylimidazolium bromide [BMIM]Br, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4, 1-methoxyethyl-3-methylimidazolium trifluoroacetate [MOEMIM]CF3COO and 1-methoxyethyl-3-methylimidazolium mesylate [MOEMIM]Ms. This methodology offers a clean and green process for the synthesis of functionalized carbocycles in good yields with excellent stereochemical control at three stereogenic centres. 相似文献
134.
The influence of the polyamines putrescine (Put), spermine (Spr) and spermidine (Spd) on growth and furanocoumarin production was investigated by exogenous addition, at different concentrations, to shoot cultures of Ruta graveolens at different phases of growth. Preliminary studies indicated that addition of Put (20 microM) and Spr (80 microM) had a promotive effect on shoot multiplication rate and number of multiple shoots formed. Spd was toxic, even at lower concentrations. The growth-phase of the culture at the time of exogenous addition of polyamines was found to be an important factor. Put was most effective when added at the lag phase, while Spr was most effective when added in the log phase. Time course studies of growth and furanocoumarin content were carried out for each polyamine and phase of addition. It was seen that maximum production of furanocoumarins (256.8 mg/10 g DW) occurred in the second week when Put was added in the lag phase and 260.5 mg/10 g DW in the fourth week when Spr was added in the log phase. Put addition resulted in a 3.10 fold increase in psoralen, 6.12 in xanthotoxin and 1.46 fold in bergapten production. Spr addition resulted in a 1.31 fold increase in psoralen, 4.11 fold in xanthotoxin and 1.49 fold in bergapten production. Results indicate that alteration of growth and furanocoumarin production kinetics is a combined outcome of choice of polyamine and the phase of culture at the time of exogenous addition. Polyamine addition enabled significant enhancement in production of pharmaceutically important bergapten and xanthotoxin in shoot cultures of Ruta graveolens, which could be explored for commercial production. 相似文献
135.
Rotational diffusion of coumarin 6 (C6) laser dye has been examined in n-decane and methanol as a function of temperature. The rotational reorientation of this probe has been measured in these solvents.
It is observed that the decrease in viscosity of the solution is responsible for the decrease in the rotational relaxation
time of the probe molecule. The molecule C6 has long reorientation times in n-decane solvent as compared to methanol over all temperatures. It is found that the coumarin 6 rotates slower in n-decane than in methanol especially at higher values of viscosity over temperature. Two methods are chosen to determine the
ground state and excited state dipole moments. The change in dipole moments is estimated from Bakhshiev-Chamma-Viallet equations
and, the ground and excited state dipole moments from Kawski et al. equations, by using the variations of the Stokes shifts
with the dielectric constant and refractive index of the solvent. Our results are quite reliable which are solvatochromic
correlation obtained using solvent polarity functions. The reported results show that excited state dipole moment is greater
than ground state dipole moment, which indicates that the excited state is more polar than the ground state. 相似文献
136.