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排序方式: 共有368条查询结果,搜索用时 15 毫秒
1.
Mark Webber 《Mathematical Methods in the Applied Sciences》2006,29(7):819-838
We investigate the influence of slip boundary conditions on the onset of Bénard convection in an infinite fluid layer. It is shown that the critical Rayleigh number is a decreasing function of the slip length, and therefore boundary slip is seen to have a destabilizing effect. Chebyshev‐tau and compound matrix formulations for solving the eigenvalue problem are presented. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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R. E. Ansorge B. ?sman C. N. Booth L. Burow P. Carlson R. S. De Wolf B. Eckart G. Ekspong C. Fuglesang J. Gaudaen C. Geich-Gimbel B. Holl R. Hospes K. Jon-And D. P. Johnson F. Lotse N. Manthos D. J. Munday J. E. V. Ovens W. Pelzer J. G. Rushbrooke F. Triantis L. Van hamme C. Walck C. P. Ward D. R. Ward C. J. S. Webber T. O. White G. Wilquet N. Yamdagni UA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,41(2):179-190
A detailed analysis ofK s 0 production in \(\bar pp\) |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheK s 0 production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity. 相似文献
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A method for the selective detection and determination of hydrogen sulfide in the atmosphere is presented. This method utilizes the reversible adsorption of H2S on a piezoelectric quartz crystal coated with an acetone extract of soots resulting from the burning of organochlorine compounds. The extract of a soot prepared from chlorobenzoic acid provided the best substrate. The method is useful in the concentration range 1–60 ppm. 相似文献
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Wender PA Baryza JL Bennett CE Bi FC Brenner SE Clarke MO Horan JC Kan C Lacôte E Lippa B Nell PG Turner TM 《Journal of the American Chemical Society》2002,124(46):13648-13649
Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer. 相似文献
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Kaale E Govaerts C Hoogmartens J Schepdael AV 《Rapid communications in mass spectrometry : RCM》2005,19(20):2918-2922
Aminoglycoside antibiotics are widely used to treat serious Gram-negative and Gram-positive bacterial infections. The lack of a UV chromophore presents a problem in the analysis of aminoglycosides. Derivatization with 1,2-phthalic dicarboxaldehyde (OPA) in the presence of a thiol made it possible to introduce a UV chromophoric thioisoindole moiety. A qualitative mass spectrometry study was carried out to confirm the molecular identity of the products formed. The conditions described earlier to derivatize gentamicin and kanamycin yielded products in which all primary amino groups are fully derivatized. On the other hand, with tobramycin and amikacin, there was also formation of incompletely derivatized products that contained one thioisoindole group less than the fully derivatized product. This study has therefore brought an additional insight into the nature of the OPA-aminoglycoside derivatives studied. 相似文献
8.
Yates MZ Shah PS Johnston KP Lim KT Webber S 《Journal of colloid and interface science》2000,227(1):176-184
Steric stabilization and flocculation of colloids with surface-grafted poly(dimethylsiloxane) (PDMS) chains are examined in liquid and supercritical carbon dioxide with and without hexane as a cosolvent. Neither poly(methyl methacrylate) (PMMA) nor silica particles with grafted 10,000 g/mol PDMS could be stabilized in pure CO(2) at pressures up to 345 bar at 25 degrees C and 517 bar at 65 degrees C without stirring. The addition of 15 wt% hexane to CO(2) led to stable dispersions with sedimentation velocities of 0.2 mm/min for 1-2 μm PMMA particles. The critical flocculation pressure of the colloids in the hexane/CO(2) mixture, determined from turbidity versus time measurements, was found to be the same for silica and PMMA particles and was well above the upper critical solution pressure for the PDMS-CO(2) system. The addition of a nonreactive cosolvent, hexane, eliminates flocculation of PMMA particles synthesized through dispersion polymerization in CO(2) with PDMS-based surfactants. Copyright 2000 Academic Press. 相似文献
9.
Abstract— –The high intensity laser induced photochemistry of phenanthrene is complex and appears to be non-linear with respect to laser intensity. Photochemical products primarily involve the solvent (CH2 C12 ) and phenanthrene coupling. These species exhibit strong absorption and emission which are red-shifted from that of phenanthrene. In the presence of a-methyl styrene, styrene oligomers are formed, but no dimers, indicating that there are no a-methyl styrene cation radical reactions. In all cases of laser irradiation the solutions become acidic, which is ascribed to the deprotonation of the phenanthrene cation radical. Acid formation does not occur in the presence of a-methyl styrene under CW irradiation with a conventional Xe lamp. These differences are ascribed to photoionization from the singlet state for laser irradiation while under CW conditions triplet-triplet annihilation can produce the phenanthrene cation radical. 相似文献
10.
Total synthesis of polycavernoside A, a lethal toxin of the red alga Polycavernosa tsudai 总被引:1,自引:0,他引:1
Blakemore PR Browder CC Hong J Lincoln CM Nagornyy PA Robarge LA Wardrop DJ White JD 《The Journal of organic chemistry》2005,70(14):5449-5460
[structure: see text] Two approaches to the synthesis of the aglycon 120 of polycavernoside A (1) were developed, only one of which was completed. The successful "second-generation" route assembled the aglycon seco acids 102 and 106 via Nozaki-Hiyama-Kishi coupling of aldehyde 70, prepared from methyl (S)-3-hydroxy-2-methylpropionate (72) and (S)-pantolactone (73), with vinyl bromide 71. The latter was obtained from a sequence which commenced from the silyl ether 24 of 3-hydroxypropionaldehyde and entailed cyclization of (Z)-zeta-hydroxy-alpha,beta-unsaturated ester 82. Regioselective Yamaguchi lactonization of trihydroxycarboxylic acids 102 and 106 and subsequent functional-group adjustments led to macrolactone 120, to which the fucopyranosylxylopyranoside moiety was attached. Stille coupling of the glycosidated aglycon 128 with dienylstannane 129 furnished polycavernoside A in a synthesis for which the longest linear sequence was 25 steps. The overall yield to lactone 120 was 4.7%. 相似文献