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81.
Shin Y Choy N Turner TR Balachandran R Madiraju C Day BW Curran DP 《Organic letters》2002,4(25):4443-4446
[structure: see text] Two hybrid analogues of discodermolide and dictyostatin (3, 26) have been designed and synthesized. These are the first macrocyclic analogues of discodermolide and biological activities were evaluated and compared with linear discodermolide analogues. 相似文献
82.
Sandeep Ghumaan Biprajit Sarkar Mahendra P. Patil Jan Fiedler Raghavan B. Sunoj Wolfgang Kaim Goutam Kumar Lahiri 《Polyhedron》2007
The complexes (μ3-L1/L2)[Ru(acac)2]3, acac− = 2,4-pentanedionato, L1 = 2,3,8,9,14,15-hexachlorodiquinoxalino[2,3-a:2′,3′-c]phenazine and L2 = 2,3,8,9,14,15- hexamethyldiquinoxalino[2,3-a:2′,3′-c]phenazine, undergo stepwise one-electron oxidation involving a total of three electrons and stepwise one-electron reduction with three (L2) or four electrons (L1). All reversibly accessible states were characterized by UV–Vis–NIR spectroelectrochemistry. Oxidation leads to mixed-valent intermediates {(μ3-L)[Ru(acac)2]3}+ and {(μ3-L)[Ru(acac)2]3}2+ of which the RuIIIRuIIRuII combinations exhibit higher comproportionation constants Kc than the RuIIIRuIIIRuII states – in contrast to a previous report for the unsubstituted parent systems {(μ3-L3)[Ru(acac)2]3}+/2+, L3 = diquinoxalino[2,3-a:2′,3′-c]phenazine. No conspicuous inter-valence charge transfer absorptions were observed for the mixed-valent intermediates in the visible to near-infrared regions. The monocations and monoanions were characterized by EPR spectroscopy, revealing rhombic ruthenium(III) type signals for the former. Electron addition produces ruthenium(II) complexes of the reduced forms of the ligands L, a high resolution EPR spectrum with 14N and 35,37Cl hyperfine coupling and negligible g anisotropy was found for {(μ3-L1)[Ru(acac)2]3}−. DFT calculations of (μ3-L1)[Ru(acac)2]3 confirm several ligand-centered low-lying unoccupied MOs for reduction and several metal-based high-lying occupied MOs for electron withdrawal, resulting in low-energy metal-to-ligand charge transfer (MLCT) transitions. 相似文献
83.
Determination of hexavalent chromium by on-line dialysis ion chromatography in a matrix of strong colourants and trivalent chromium 总被引:3,自引:0,他引:3
Ganeshjeevan R Chandrasekar R Yuvaraj S Radhakrishnan G 《Journal of chromatography. A》2003,988(1):151-159
Hexavalent chromium detection in the presence of a high load of colourants without any false positive and in-procedure oxidation of Cr(III) is an important area of study. Colourants are a class of interfering substances in many spectroscopic analyses and chromatographic separations and detection. A purification method using an on-line dialysis technique for ion chromatography (IC) has been developed to remove water-soluble anionic dyes and particulate colourants and other substances to facilitate Cr(VI) quantification and the method is discussed. The dialysis was optimized with Cr(VI) standard solutions for quantification. The efficacy of the procedure for the removal of anionic dyes and detection of Cr(VI) was checked with a Cr(VI) spiked synthetic preparation containing a water-soluble dye and trivalent chromium. Soluble Cr(VI) extracted with organic dyes from environmental samples was analyzed. The method has a detection limit of 5 microg/l, recovery rate of 100% and analysis time less than 20 min. 相似文献
84.
M. Asai T. Aziz J. F. Bailly J. F. Baland S. Banerjee W. Bartl A. Batunin C. Caso F. Diez-Medo B. Epp A. Ferrando F. Fontanelli S. N. Ganguli V. G. Gavrjusev T. Gemesy P. Girtler A. Gurtu R. Hamatsu P. Herquet J. Hrubec Y. Iga V. Khalatyan E. Kistenev J. M. Kohli J. Mac Naughton J. C. Marin M. Markytan L. Montanet G. Neuhofer G. Pinter P. Porth R. Raghavan T. Rodrigo J. M. Salicio J. B. Singh S. Squarcia K. Takahashi L. A. Tikhonova U. Trevisan T. Tsurugai V. Yarba G. Zholobov S. Zotkin EHS-RCBC Collaboration 《Zeitschrift fur Physik C Particles and Fields》1987,34(4):429-435
Production properties and correlations forK s 0 K s 0 ,K s 0 Λ,K s 0 ¯Λ and Λ¯Λ systems in 360 GeV/cpp interactions are presented. All rapidity gap distributions are observed to peak at Δy=0 and the azimuthal angular distributions between the two particles are consistent with being flat. Experimental results are compared with the quark fusion and Lund models of particle production. 相似文献
85.
Lyxo-phytosphingosine and erythro-sphingosine have been elaborated from a common intermediate. The key step in the reaction sequence involves stereo- and regiospecific functionalization of an olefin by intramolecular nucleophilic sulfinyl group participation. 相似文献
86.
The time dependent performance of extended surfaces subjected to fouling is addressed in this work. Where fins are used for
augmenting boiling heat transfer, the interaction of local values of temperature excess, fouling resistance and surface characteristics
of the deposit can be quite complex. Taking typical asymptotic fouling growth parameters from literature for reverse solubility
salts, three kinds of fin geometry are analysed – rectangular, triangular and annular. For various values of the fin parameter
mL, the temperature distribution and variation of fouling resistance are obtained as a function of time. To interpret the
performance of a fouled fin, a new term `cleanliness efficiency' is introduced. The necessity of choosing an optimal value
of mL for the fin is also highlighted here. It is shown that for all three fin configurations, cleanliness efficiency differs
little, thus simplifying the geometry dependence. The approach set out in this work will help in the design of finned heat
exchangers subjected to fouling and thereby minimise their overdesign.
Received on 12 July 2000 相似文献
87.
88.
J. L. Bailly S. Banerjee F. Bruyant B. Buschbeck C. Caso H. Dibon B. Epp A. Ferrando F. Fontanelli T. Gemesy A. Gurtu R. Hamatsu Ph. Herquet T. Hirose J. Hrubec Yu. Ivanysherkov E. P. Kistenev N. Khalatyan S. Kitamura T. Kreuzberger V. Kubik P. Lipa P. K. Malhotra M. Markytan I. S. Mittra L. Montanet G. Neuhofer G. Pinter P. Porth R. Raghavan T. Rodrigo J. B. Singh S. Squarcia U. Trevisan K. Takahashi L. A. tikhonova T. Yamagata G. Zholobov J. Zoll S. A. Zotkin NA EHS - RCBC Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(1):13-24
Two particle correlations of hadrons produced in 360 GeV/cpp interactions are investigated in the transverse plane and in rapidity. The data were obtained at the European hybrid spectrometer equipped with a rapid cycling bubble chamber. The observed transverse and rapidity correlations are compared with the one string LUND-and a two string dual parton-model. These models predict in general stronger correlations in the transverse plane and much weaker correlations in rapidity than found in the data. The LUND-FRITIOF-and multichain dual parton models provide a better reproduction of the data, although the agreement is not yet satisfactory. Only the UA5 cluster model GENCL shows agreement with the data. 相似文献
89.
A previously described procedure for the determination of the positions of coupling in the dimeric one-electron reduction products of 1-alkylpyridinium ions has been extended to the examination of the coupling positions in the dimeric species resulting from one-electron reduction of ring-substituted 1-alkylpyridinium ions. 相似文献
90.
Raghava S Aquil S Bhattacharyya S Varadarajan R Gupta MN 《Journal of chromatography. A》2008,1194(1):90-95
The maltose binding protein (MBP) affinity tag has been extensively used for protein purification. A commercial grade cationic starch could precipitate MBP or an MBP-tagged protein quantitatively by simultaneous addition of 10% (w/v) polyethylene glycol (PEG) and 50 mM calcium chloride. The precipitated MBP or MBP-tagged protein could be selectively dissociated by suspending the precipitate in 1 M NaCl. In the case of a soluble MBP fusion with a fragment of human immunodeficiency virus protein gp120, 38% of the contaminating proteins could be removed by precipitation with PEG/CaCl(2) and 100% of the fusion protein was recovered. In all cases, the purified proteins showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the expected changes in fluorescence emission spectra upon binding to maltose. 相似文献