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151.
K. C. Mishra B. N. Dev S. M. Mohapatra W. M. Gibson T. P. Das 《Hyperfine Interactions》1983,16(1-4):997-1000
The electronic energy levels and wave functions of fluorine and chlorine atoms adsorbed at the <111> surface of silicon are obtained by the Hartree-Fock procedure applied to clusters simulating the surface structure. Minimising the total energy with respect to the positions of the halogen atoms, the Si-Cl distance in the adsorbed system was found to be in good agreement with that from a recent SEXAFS measurement, there being no corresponding data presently available for fluorine on silicon surface. The calculated19 f * nuclear quadrupole coupling constants using the electronic wave functions for SiH3F and the larger cluster Si4H9F, simulating the surface, differed substantially in contrast to the situation for the Si-F distance, indicating that the quadrupole coupling is a more sensitive indicator of the adequacy of the cluster chosen to represent the surface system. Experimental results for the coupling constants are awaited for comparison with theory. 相似文献
152.
P.B. Das 《Thermochimica Acta》1980,41(3):371-373
Studies of electrolytic conductance in dioxane—water mixtures of varying dioxane content were initiated in 1978 [1]. In the present communication, an attempt has been made to evaluate the thermodynamic function ΔG0t for the transfer of Mg(ClO4)+, Mg(NO3)+, BaCl+, BaBr+, Ba(ClO4+, Ba(NO3)+, SrCl+, Sr(NO3)+, CaCl+ and Ca(NO3)+ from water to dioxane—water media, which would give some information regarding ionic solvation. 相似文献
153.
Summary In aqueous solution [Cu(bigH)2]2+ (bigH=biguanide) reacts with 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen) through intermediate formation of ternary complexes [Cu(bigH)(L)]2+ and [Cu(bipy)(phen)]2+ and binary complexes [CuL2]2+ (L=bipy, phen). The rates of the different steps have been followed in borax buffer (pH 8.0±0.1) by stopped-flow spectrophotometry. For each step kobs=k0+kL[L] and the kL path appears to be associative. H and S values for the kL path conform to an isokinetic trend. 相似文献
154.
Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous. 相似文献
155.
Spectroscopic constants and molecular properties of selected diatomic anions namely CN?, SiH?, PO?, SO?, SF?, and SiS? in their ground states have been studied in detail using the hybrid HF/DF B3LYP method. The consistency of the calculated values has been verified with four different basis sets, with improved quality. The spectroscopic constants and molecular properties calculated with the aug‐cc‐pVTZ basis set agree very well with the experimental and theoretical values wherever available. Most of the spectroscopic constants and molecular properties of the selected diatomic anions, particularly the spectroscopic constants and molecular properties of SO? and SiS? are reported for the first time. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
156.
UVB irradiation of normal human skin favors the development of type-2 T-cells in vivo and in primary dermal cell cultures 总被引:1,自引:0,他引:1
Di Nuzzo S Sylva-Steenland RM Koomen CW Nakagawa S van Breemen M de Rie MA Das PK Bos JD Teunissen MB 《Photochemistry and photobiology》2002,76(3):301-309
To determine the effect of UVB exposure on the balance of type-1 or type-2 T-cells in skin, we examined the expression of key markers interferon (IFN)-gamma and interleukin (IL)-4 in cryostat sections. IFN-gamma mRNA was clearly detectable in nonirradiated control skin, and IFN-gamma protein was found in 2% of the dermal CD3pos T-cells, whereas IL-4 mRNA was hardly detectable, and no IL-4 protein was found. In contrast, IL-4 mRNA expression increased upon irradiation, and IL-4 was found in 2% of the T-cells at day 2 after UVB-exposure. Concomitantly, IFN-gamma mRNA expression decreased, and IFN-gamma protein became absent. We also analyzed T-cells present in primary dermal cell cultures, which were used as an in vitro equivalent of the in vivo situation. As compared with T-cells from control skin, T-cells in dermal cell cultures from UVB-exposed skin displayed an increased IL-4 and decreased IFN-gamma expression. No such skewing occurred when the T-cells from irradiated skin were cloned in the absence of a dermal microenvironment. Except for an occasional positive T-cell, type-1-associated cell-surface markers (CCR5, CXCR3) or type-2 markers (CCR3, CD30, CRTH2) were undetectable in situ. But these markers were expressed on cultured dermal T-cells from UVB-exposed and control skin at a comparable level, but did not correlate with the IFN-gamma and IL-4 production. Altogether, UVB-induced changes of the dermal microenvironment favor the development of type-2 T-cells. 相似文献
157.
Cesium and potassium were determined in muscle-tissues of squid, dover sole, albacore, and bocaccio by NAA. Potassium was
measured instrumentally, while cesium was radio-chemically separated. For the separation of cesium, hydrated antimony pentoxide
(HAP) was used to retain24Na, and ammonium molybdophosphate (AMP) was used to absorb quantitatively the radiocesium,134mCs. The cesium and potassium contents were based on measuring the short-lived radionuclide of cesium, 2.90 h-134mCs, and 12.4 h-42K. The mean concentrations of cesium found, based on 3–4 replicate measurements for each fish, were: 4.18±0.32 ng/g squid,
11.51±0.30 ng/g dover sole, 43.64±1.03 ng/g albacore, and 56.85±3.61 ng/g bocaccio. The mean concentrations of potassium found
were: 1.28±0.10 mg/g squid, 2.78±0.29 mg/g dover sole, 3.69±0.06 mg/g albacore, and 4.18±0.10 mg/g bocaccio. 相似文献
158.
Partha Sarathi Das Basudam Adhikari Sukumar Maiti 《Journal of polymer science. Part A, Polymer chemistry》1994,32(1):39-45
Fluorination of low-density polyethylene, polyacetylene, and poly(vinyl alcohol) was carried out using SF6 gas under electric discharge. The polymers were partially fluorinated and the extent of fluorination was more in the case of poly (vinyl alcohol) than the other two polymers. The fluorinated polymers were characterized by elemental analysis (Fluorine), IR, and x-ray diffraction. Optical transparency of the films was also measured. The fluorinated polymers show better solvent resistance and decreased transparency than the virgin polymer. © 1994 John Wiley & Sons, Inc. 相似文献
159.
B. Saha T. K. Mukherjee A. K. Das P. K. Mukherjee 《International journal of quantum chemistry》2003,91(5):626-632
Dipole‐allowed transitions have been studied for the first few members of the Si isoelectronic sequence. Transition energies, oscillator strengths, transition probabilities and quantum defect values have been estimated for the low‐ and high‐lying excited states of s and d symmetries up to the principal quantum number n=7 for these 3p open shell ions from P+ to Cr10+. Time‐dependent coupled Hartree–Fock (TDCHF) theory has been utilized to calculate such transition properties. Most of the results for transition energies, oscillator strengths, and transition probabilities for higher excited states are new. The transition energies for low‐lying excited states agree well with experimental data wherever available. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 相似文献
160.
A highly efficient strategy for Cu(OTf)2 mediated SN2-type nucleophilic ring opening followed by [4+2] cycloaddition reactions of enantiopure 2-phenyl-N-tosylazetidines with various aldehydes and ketones afforded a variety of substituted 1,3-oxazinanes and 1,3-amino alcohols in excellent yields, excellent de and good to excellent ee. The proposed SN2-type mechanism of the cycloaddition reaction is supported by experimental evidence. 相似文献