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21.
A method of calculating a free-convection flow of a viscous incompressible medium in a rectangular cavity is proposed. The
lateral boundaries of the cavity have the same constant temperature, the top and bottomboundaries are thermally insulated,
and the half-width to height ratio is much smaller than unity. A decomposition of the flow domain into zones with ascending
and descending flows made it possible to formulate and solve analytically a coupled parabolic system of linear equations based
on the classic Oberbeck-Boussinesq assumptions. 相似文献
22.
A concise, efficient approach to the total synthesis of ningalin B (1) based on a heterocyclic azadiene Diels-Alder strategy (1,2,4,5-tetrazine-->1,2,-diazine-->pyrrole) ideally suited for construction of the densely functionalized pyrrole core found in the natural product is detailed. Examination of the natural product and a number of synthetic intermediates revealed that while lacking inherent cytotoxic activity, many reverse the multidrug-resistant (MDR) phenotype, resensitizing a human colon cancer cell line (HCT116/VM46) to vinblastine and doxorubicin at lower doses than the prototypical agent verapamil. 相似文献
23.
24.
Ahmed SN Anthony AE Beier EW Bellerive A Biller SD Boger J Boulay MG Bowler MG Bowles TJ Brice SJ Bullard TV Chan YD Chen M Chen X Cleveland BT Cox GA Dai X Dalnoki-Veress F Doe PJ Dosanjh RS Doucas G Dragowsky MR Duba CA Duncan FA Dunford M Dunmore JA Earle ED Elliott SR Evans HC Ewan GT Farine J Fergani H Fleurot F Formaggio JA Fowler MM Frame K Fulsom BG Gagnon N Graham K Grant DR Hahn RL Hall JC Hallin AL Hallman ED Hamer AS Handler WB Hargrove CK Harvey PJ Hazama R Heeger KM Heintzelman WJ 《Physical review letters》2004,92(18):181301
The Sudbury Neutrino Observatory has precisely determined the total active (nu(x)) 8B solar neutrino flux without assumptions about the energy dependence of the nu(e) survival probability. The measurements were made with dissolved NaCl in heavy water to enhance the sensitivity and signature for neutral-current interactions. The flux is found to be 5.21 +/- 0.27(stat)+/-0.38(syst) x 10(6) cm(-2) s(-1), in agreement with previous measurements and standard solar models. A global analysis of these and other solar and reactor neutrino results yields Deltam(2)=7.1(+1.2)(-0.6) x 10(-5) eV(2) and theta=32.5(+2.4)(-2.3) degrees. Maximal mixing is rejected at the equivalent of 5.4 standard deviations. 相似文献
25.
The total synthesis and evaluation of three key ramoplanin aglycon analogues are detailed. The first (5a) represents replacement of the labile depsipeptide ester with a stable amide (HAsn2 --> Dap2) with removal of the HAsn pendant carboxamide, and it was found to be slightly more potent than the natural aglycon in antimicrobial assays providing a new lead structure with an improved profile and a more stable and accessible macrocyclic template on which to conduct structure-function studies. In contrast, a second amide analogue 5b which contains a single additional methylene relative to 5a (HAsn2 --> Dab2) was found to be inactive in antimicrobial assays (>100-fold loss in activity). The third key analogue 5c in which the Asn1 lipid side chain was replaced with an acetyl group revealed that it contributes significantly to the antimicrobial activity (16-fold) of the ramoplanins, but is not essential. 相似文献
26.
The synthesis of the alkylating subunit of the DNA cross-linking agent, isochrysohermidin (2), and its subsequent incorporation into conjugates with distamycin A (1) are described. The DNA binding properties of these agents were compared to that of distamycin A, using a fluorescence intercalator displacement (FID) assay. 相似文献
27.
Methods based on image analysis and mathematical morphology are proposed to study fingering patterns obtained in a radial
Hele-Shaw cell. They have been used to study miscible displacement patterns obtained under various conditions of initial viscosity,
viscosity ratio and injection rate. Their application domain can be extended to other type of fingering patterns as well as
diffusion-limited aggregates.
Received: 28 October 1997/Accepted: 16 April 1998 相似文献
28.
Subbiah Meenakshisundaram RM. Sockalingam 《Journal of molecular catalysis. A, Chemical》2000,160(2):269-275
Catalytic activity of Os(VIII) in the oxidation of some twenty organic sulfides with sodium salt of N-chlorobenzenesulfonamide (CAB) has been investigated in alkaline (pH8.7) t-butanol–water (1:1 v/v) medium. Significant retarding influence of [OH−] on the reactivity is exhibited. The catalysed reaction is strongly accelerated in the presence of Hg(II). Imperfections are observed in the linear Hammett relationship in the case of –NO2 substituents. 相似文献
29.
A thixotropic recovery model has been developed that is based on consideration of the microstructural interactions that occur
between particles within a suspension particle network. The model is based on Smoluchowski coagulation rate theory, utilizing
second order kinetics to describe the thixotropic recovery behavior. The model is applied to Na-montmorillonite-based coal
tailings suspensions and is also shown to be applicable to brown coal and bauxite residue suspensions. The model describes
all the recovery data well, especially at intermediate to large recovery times. The recovery of the montmorillonite suspensions
at short times was faster than predicted, indicating the existence of additional factors in early-time structure development.
The discrepancy may have also been due to the highly anisotropic nature of the clay platelets. The recovery rate constant,
K
r
, increases with increasing solids concentration (for constant surface chemical conditions) as would be expected from the
basis of the model.
Received: 22 September 2000 Accepted: 16 March 2001 相似文献
30.
Chlorofusin, its seven chromophore diastereomers, and key analogues were comparatively examined for inhibition of MDM2-p53 binding revealing that the chromophore, but not simple replacements, contributes significantly to the natural products properties, and that this contribution is independent of its relative and absolute stereochemistry. 相似文献