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961.
962.
Yuet Tsang Fung Ming Siu Ngai Ling Ma Chun Wai Tsang 《Rapid communications in mass spectrometry : RCM》2002,16(3):229-237
Using a refined Gaussian-3 (G3) protocol, the highest level of ab initio calculations reported so far, we have established the Li+ cation binding enthalpy (affinity) at 0 K (in kJ mol-1) for formamide (195.7), N-methylformamide (209.2), N,N'-dimethylformamide (220.0), acetamide (211.7), N-methylacetamide (222.5), and N,N'-dimethylacetamide (230.1), with an estimated maximum uncertainty of +/-8 kJ mol-1. With these six theoretical lithium cation binding affinities as reference values, the absolute Li+ affinities of imidazole and dimethoxyethane were determined by the extended kinetic method, and by adopting the statistical data treatment protocol recently proposed by Armentrout. The Li+ affinities obtained for these two ligands are in good agreement (within 6 kJ mol-1) with recent values determined by the threshold collision-induced dissociation method, and consistent with the Li+ basicity values first reported by Taft and co-workers in 1990. Our study confirms that the previously suggested, and recently implemented, downward revision of Taft's original basicity scale by 10.9 kJ mol-1 is justified for ligands with revised basicities less than 151 kJ mol-1. However, for selected ligands with Li+ basicities greater than 151 kJ mol-1, including some of the six amides studied in this work, the reported discrepancy between theoretical and experimental estimates in the revised Li+ basicity scale of Burk et al. is likely to arise from experimental uncertainties. 相似文献
963.
Catalytic user-friendly approach to the syntheses of various functionalized aromatic phosphines from their corresponding substituted aryl triflates and triarylphosphines was accomplished. This method is carried out in neutral media and compatible with many functional groups including aldehyde, keto, ester, nitrile, ether and pyridyl groups. 相似文献
964.
In this paper, the problem of estimating the scale matrix and their eigenvalues in a Wishart distribution and in a multivariate F distribution (which arise naturally from a two-sample setting) are considered. A new class of estimators which shrink the eigenvalues towards their arithmetic mean are proposed. It is shown that the new estimator which dominates the usual unbiased estimator under the squared error loss function. A simulation study was carried out to study the performance of these estimators. 相似文献
965.
966.
Transient parametric scattering is investigated theoretically using density matrix perturbation theory. Emphasis is placed on the effects of population and transverse or dephasing relaxation on the scattered parametric pulse durations. Pulse duration measurement provides important insight into the actual transient temporal behavior of four-wave mixing processes and is shown to be a potentially useful technique for the characterization of material time constants and incident pulse shape. 相似文献
967.
Absolute stereochemistry of panaxynol was determined by exciton chirality method. The circular dichroism spectra of panaxynol p-bromobenzoate and p-dimethylaminobenzoate show the negative exciton chirality at λext indicating the S configuration of the chiral center. 相似文献
968.
Chung BH Oh HJ Piao SG Sun IO Kang SH Choi SR Park HS Choi BS Choi YJ Park CW Kim YS Cho ML Yang CW 《Experimental & molecular medicine》2011,43(11):630-637
The aim of this study was to evaluate whether the Th17 and Treg cell infiltration into allograft tissue is associated with the severity of allograft dysfunction and tissue injury in acute T cell-mediated rejection (ATCMR). Seventy-one allograft tissues with biopsy-proven ATCMR were included. The biopsy specimens were immunostained for FOXP3 and IL-17. The allograft function was assessed at biopsy by measuring serum creatinine (Scr) concentration, and by applying the modified diet in renal disease (MDRD) formula, which provides the estimated glomerular filtration rate (eGFR). The severity of allograft tissue injury was assessed by calculating tissue injury scores using the Banff classification. The average numbers of infiltrating Treg and Th17 cells were 11.6 ± 12.2 cells/mm2 and 5.6 ± 8.0 cells/mm2, respectively. The average Treg/Th17 ratio was 5.6 ± 8.2. The Treg/Th17 ratio was significantly associated with allograft function (Scr and MDRD eGFR) and with the severity of interstitial injury and tubular injury (P < 0.05, all parameters). In separate analyses of the number of infiltrating Treg and Th17 cells, Th17 cell infiltration was significantly associated with allograft function and the severity of tissue injury. By contrast, Treg cell infiltration was not significantly associated with allograft dysfunction or the severity of tissue injury. The results of this study show that higher infiltration of Th17 cell compared with Treg cell is significantly associated with the severity of allograft dysfunction and tissue injury. 相似文献
969.
Kempaiah R Salgado S Chung WL Maheshwari V 《Chemical communications (Cambridge, England)》2011,47(41):11480-11482
Graphene sheets (chemically reduced), a high modulus and high thermal and electrically conductive material are coupled with yeast cells to form an encapsulating inorganic functional layer. The coupling of the high modulus sheets with the cells increases their stability to osmotic stresses. The sheets also allow the direct visualization of the cells in an electron microscope. 相似文献
970.
Yee GM Kowolik K Manabe S Fettinger JC Berben LA 《Chemical communications (Cambridge, England)》2011,47(42):11680-11682
Synthesis of substituted phenylacetylide ligands 2,6-bis(trimethylsilyl)phenylacetylene (H1) and 2-(triphenylsilyl)phenylacteylene (H2) is reported. Ligand 1 supports tetrahedral complexes of V(III), Fe(II), and Mn(II) (3-5). Complexes 3-5 are high-spin and redox active. 相似文献