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排序方式: 共有236条查询结果,搜索用时 15 毫秒
31.
One-pot synthesis of substituted pyrroles by a cascade reaction of azides with Morita-Baylis-Hillman acetates of acetylenic aldehydes is described and the reaction is efficiently mediated by triphenyl phosphine at room temperature. Sodium azide is successfully used to provide N-unsubstituted pyrroles, while alkyl azides afforded the corresponding N-alkylated pyrroles through a sequence of allylic substitution/azide reduction/cycloisomerization reactions. The obtained products have provided a new entry to indolizino indoles, pyrrolo isoquinolines and 8-oxo-5,6,7,8-tetrahydroindolizine. 相似文献
32.
Luchezar?L.?Avramov Melvin?Hochster Srikanth?B.?IyengarEmail author Yongwei?Yao 《Mathematische Annalen》2012,353(2):275-291
It is proved that when R is a local ring of positive characteristic, \({\phi\colon R{\to} R}\) is its Frobenius endomorphism, and some non-zero finite R-module has finite flat dimension or finite injective dimension for the R-module structure induced through \({\phi}\) , then R is regular. This broad generalization of Kunz’s characterization of regularity in positive characteristic is deduced from a theorem concerning a local ring R with residue field of k of arbitrary characteristic: If \({\phi}\) is a contracting endomorphism of R, then the Betti numbers and the Bass numbers over \({\phi}\) of any non-zero finitely generated R-module grow at the same rate, on an exponential scale, as the Betti numbers of k over R. 相似文献
33.
In Alzheimer's disease, copper binds to amyloid beta (Aβ) peptide and generates oxidative stress. The coordination of histidine (His) residues to Cu(2+) is still uncertain. We studied Cu(2+) binding to Aβ1-16 peptide using the diethyl pyrocarbonate (DEPC) assay and mass spectrometry. Our results show that only one His is involved in Cu(2+) coordination, which is identified as His6 using mass spectral studies. Novel nickel displacement studies have further supported the proposal that the Cu(2+) binding site of Aβ1-16 peptide resembles the ATCUN motif of human serum albumin. 相似文献
34.
Metal foams may be used in direct methanol fuel cells to feed reactants to the catalyst layer and to collect current from
the resulting electrochemical reaction. Although the mass transfer from the metal foam to the underlying gas diffusion layer
(GDL) is diffusion-dominated, it is found that at a fixed methanol concentration, the limiting current density increases with
increasing methanol flow rates. This unexpected result is attributed to the more efficient removal of product CO2 from the GDL. A methodology is developed to estimate the effective diffusion coefficient of methanol in the anode diffusion
layer from limiting current density measurements, and to extract the fraction of GDL volume occupied by CO2. 相似文献
35.
The problem of estimating the global optimal values of intractable combinatorial optimization problems is of interest to researchers developing and evaluating heuristics for these problems. In this paper we present a method for combining statistical optimum prediction techniques with local search methods such as simulated annealing and tabu search and illustrate the approach on a single machine scheduling problem. Computational experiments show that the approach yields useful estimates of optimal values with very reasonable computational effort. 相似文献
36.
P. R. Srikanth Sharma Peiguang Zhou Harry L. Frisch 《Journal of polymer science. Part A, Polymer chemistry》1996,34(6):1049-1058
We report the synthesis and characterization of interpenetrating polymer networks (IPNs) exhibiting nonlinear optical (NLO) properties. The network consists of aliphatic polycarbonate urethane (PCU) and poly(methyl methacrylate-co-N,N-disubstituted urea), with a nonlinear optical (NLO) chromophore incorporated into N,N-disubstituted urea. The full IPNs have only one Tg, as determined by differential scanning calorimetry (DSC), together with scanning electron microscopy (SEM) observations, suggest a single phase morphology. The thin films of IPNs are transparent and the unpoled samples produced second harmonic generation (SHG) signals at room temperature. This result indicates that the NLO chromophore is oriented noncentrosymmetrically during the IPN formation process and is tightly held between the permanent entanglements of the two component networks of the IPN. © 1996 John Wiley & Sons, Inc. 相似文献
37.
M. Vijaya Bhaskara Reddy S. Madhu Sudhana B. Srikanth C. Naga Raju 《Phosphorus, sulfur, and silicon and the related elements》2016,191(1):144-149
In an effort to develop novel anti-inflammatory agents, we synthesized phosphorylated derivatives of febuxostat using various phosphates/phosphonites by Michaelis-Arbuzov reaction. Their inhibitory activity on nitric oxide (NO) production, reactive oxygen species (ROS) production and cytotoxicity were evaluated using lipopolysaccharide (LPS) activated macrophages RAW264.7 assay, flow-cytometry analysis and MTT method respectively. Some of these compounds showed potent inhibition of NO and ROS production without obvious cytotoxicity. Furthermore, docking simulations were performed to positional compounds 3g, 3h, 3i and 3j into the COX-2 active site to determine the probable binding model. Physicochemical parameters revealed that most of the compounds possessed drug-like properties. 相似文献
38.
Naidu B. Gowri Srikanth S. Raju G. J. Naga Sarita P. 《Journal of Radioanalytical and Nuclear Chemistry》2020,323(3):1307-1316
Journal of Radioanalytical and Nuclear Chemistry - Particle induced X-ray emission technique was used to obtain the serum elemental profile of healthy subjects and breast cancer patients (BCPs)... 相似文献
39.
Structural Chemistry - The MurD enzyme of Staphylococcus aureus is an attractive drug target as it is essential and ubiquitous in bacteria but absent in mammalian cells. In the present study, we... 相似文献
40.