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991.
K. Roy S. Basu D. K. Pal S. Lahiri A. Ramaswami 《Journal of Radioanalytical and Nuclear Chemistry》2003,256(2):311-313
95Tc has been produced through -particle activation of a natural niobium target. The carrier-free 95Tc radionuclide has been separated from the bulk target using tri-n-octylamine (TOA) diluted by cyclohexane as extracting agent and HCl, HNO3 as aqueous phase. Solid-liquid extraction has also been carried out with TOA impregnated Kieselguhr mineral acid system. Technetium-95 was recovered from the organic phase by stripping with 0.1M EDTA above pH 9. 相似文献
992.
Chatterjee S Basu S Ghosh N Chakrabarty M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(9):2199-2201
In this communication we have reported the steric effect on the fluorescence quenching rate constants of the electron transfer (ET) process. We have done a comparative study using donor (D)-acceptor (A) systems with different exergonicity (-deltaG(f)). Different carbazole derivatives (CZ): 1,4-dicyanobenzene (DCB) systems (-deltaG(f) = 0.7-0.8 eV) were found to be among those limiting systems that show a clear-cut steric dominance in the process of fluorescence quenching. It is known that with increasing exergonicity the ET distance increases and hence steric dependence becomes insignificant. On the other hand, with decreasing exergonicity the ET distance decreases and a pronounced steric dominance should be observed. However, in the D-A systems having lower exergonicity compared to CZ-DCB systems, this steric dominance is observed only in polar medium. In non-polar medium due to exciplex formation the D-A distance effectively becomes much longer and therefore no steric dominance is observed. 相似文献
993.
We report measurements performed on the normal skin of rats in vivo, which provide information on the photobleaching kinetics and mechanisms of the photosensitizer meso-tetrahydroxyphenyl chlorin (mTHPC). Loss of mTHPC fluorescence was monitored using in vivo fluorescence spectroscopy during photodynamic therapy (PDT) performed using 650 nm laser irradiation. The bleaching was evaluated for irradiances of 5, 20 and 50 mW cm(-2). Two distinct phases of mTHPC photobleaching were observed. In the first phase there was no obvious irradiance dependence in the loss of fluorescence vs fluence. The second phase was initiated by an irradiance-dependent discontinuity in the slope of the bleaching curve, after which the photobleaching rates showed an irradiance dependence consistent with an oxygen-dependent reaction process. To investigate the unusual shape of the in vivo bleaching curves, we measured the PDT-induced changes in O2 concentrations in mTHPC-sensitized spheroids irradiated with 2, 5 and 20 mW cm(-2) of 650 nm light. The oxygen concentration data indicated no unusual features within the range of fluences where the discontinuities in fluorescence were observed during in vivo spectroscopy. The fluorescence from the in vivo bleaching experiments thus reports a phenomenon that is not reported by measurements of the photochemical oxygen consumption in the spheroids. 相似文献
994.
M. Basu Roy P. C. Mandal S. N. Bhattacharyya 《Journal of Radioanalytical and Nuclear Chemistry》1995,191(2):337-348
The yields for the loss of chromophore of Ni(II) and Cu(II) complexes of metronidazole,G(-Ni(II)M) andG(-Cu(II)M), reached almost zero when their aqueous solutions were -irradiated in the presence, of 0.4 mol·dm–3 of MeOH, EtOH,i-PrOH andt-BuOH in aerated medium. However, under N2O saturated conditions, these yields attained limiting values which suggests that the hydroxyalkyl radicals, derived from the alcohols by reaction with OH, react with the complexes in deaerated medium. But in aerated medium they react preferentially with O2. The rate constants for the reactions of the different hydroxyalkyl radicals with the complexes have been determined by the flash photolysis technique and the plausible mechanisms for the reactions have been suggested. 相似文献
995.
Sumanta Bhattacharya Shrabanti Bhattacharya Banerjee Kalyan Ghosh Sukalyan Basu Manas Banerjee 《Journal of solution chemistry》2006,35(4):519-539
Electron donor–acceptor (EDA) complex formation of o-chloranil with six different phosphine oxides and tri-n-butyl phosphate (TBP) has been studied in CCl 4 solution by the UV-VIS absorption spectrophotometric technique. An absorption band due to a charge–transfer (CT) transition is observed in the visible region. Utilizing the CT transition energy, the electron affinity of o-chloranil in solution has been calculated. Degrees of charge transfer, and oscillator and transition dipole strengths have also been calculated for all of the investigated EDA complexes. Except for TBP, other phosphine oxides, viz., tri-n-octyl phosphine oxide, tri-n-butyl phosphine oxide, triphenyl phosphine, octyl(phenyl)-N,N-diisobutylcarbamoylphosphine oxide, octyl(phenyl)-N,N-dicyclohexylcarbamoylmethylphosphine oxide and octyl(phenyl)-N,N-diisopropylcarbamoylmethylphosphine oxide have been shown to form stable 1:1 EDA complexes with o-chloranil. The complex of TBP with o-chloranil decays slowly into a secondary product. Formation constants of the EDA complexes have been determined. 相似文献
996.
Gargi Basu Ray Indranil Chakraborty Soumen Ghosh Satya P. Moulik 《Colloid and polymer science》2007,285(4):457-469
The micellization of mixed binary surfactant systems of sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS)
has been studied by conductometry, tensiometry, fluorimetry, and microcalorimetry at different mole fractional compositions.
The counter-ion binding of micelles, micellar aggregation number, thermodynamics of micellization, interaction of components
in the mixed micelles, and their compositions therein and amphiphile packing in micelles have been examined. The adsorption
features of the surfactants at the air/solution interface have also been estimated. Correlation of the results and explanations
of the findings have been presented. The difference in the head groups of SDS and SDBS has manifested interesting solution
and interfacial behaviors. 相似文献
997.
We have measured the intrinsic fluorescence anisotropies of six photosensitizers in homogeneous solution, and we have imaged the anisotropies of these sensitizers in tumor cell monolayers using polarization-sensitive laser-scanning confocal microscopy. The intrinsic anisotropies are unremarkable and are within the approximate range of 0.2–0.27. In cells, however, very interesting behavior is exhibited by meso -tetrahydroxyphenyl chlorin (mTHPC). Polarization-sensitive images of mTHPC's fluorescence show a pronounced banding of alternating high and low anisotropy consistent with an ordering of the sensitizer in the nuclear envelope, indicating that this structure is a target of photodynamic damage with this sensitizer. None of the other sensitizers exhibits localization to the nuclear envelope. The frequency distributions of the intracellular anisotropies of the sensitizers exhibit variable peaks and widths. An unusual case is that of Photofrin, with a peak in its anisotropy frequency distribution of –0.12. The change from a positive intrinsic anisotropy in homogeneous solution to a negative value in cells suggests an environmentally induced change in the relative orientations of the absorption and emission dipole moments. 相似文献
998.
Basudeb Achari Soumitra Bandyopadhyay Krishnakali Basu Satyesh C. Pakrashi 《Tetrahedron》1985,41(1):107-110
Aristolindiquinone () , the first naturally occurring 8-methyl-juglone earlier isolated from has been synthesised from -allyl--cresol in 7% overall yield. 相似文献
999.
Kakali Sen Samita Basu Dhananjay Bhattacharyya 《International journal of quantum chemistry》2005,102(4):368-378
The exciplex is a charge transfer species formed in the process of electron transfer between an electron donor and an electron acceptor and hence is very sensitive to solvent polarity. In order to understand the role of solvent in exciplex formation between pyrene (PY) and 4,4′‐bis(dimethylamino)diphenylmethane (DMDPM), we used two types of solvent approximations: an implicit solvent model and an explicit solvent model. The difference in energies between the excited and the meta‐stable Frank–Condon state (ΔE) of the structures were assumed to correspond to the emission maximum of the exciplex in different solvents. The ΔE values show the trend of stabilization of the exciplex with an increase in solvent polarity. This trend in stabilization is substantially more prominent in the explicit solvent model than that with the implicit solvent model. The ΔE value obtained in methanol reflects equal stabilization compared to that in a more polar solvent, N,N‐dimethylformamide. This extra stabilization of the exciplex may be explained on the basis of the H‐bonding capability of the protic solvent, methanol. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
1000.
Synergistic effect of neutral donors like tri-butyl phosphate (TBP), triphenyl phosphine oxide (TPPO), trioctyl phosphine oxide (TOPO), and dimethyl sulphoxide (DMSO) on the extraction of uranium(VI) by tri-isooctyl amine into CCl4 is reported. Synergistic coefficients and adduct formation constants are calculated from distribution data and correlated with relative donor abilities of added bases. 相似文献