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71.
Experiments in a refractive index matched pipe flow facility were conducted using state-of-the-art laser-Doppler anemometry to study turbulent drag reduction by dilute addition of high polymers. The results were analyzed employing the invariant theory of turbulence. It was thus possible to confirm the major conclusion of preceding theoretical work, namely that the mechanism of drag reduction by long-chain polymers is associated with an increase in anisotropy of turbulence at the wall. Furthermore, theoretical considerations based on the elastic behavior of a polymer and spatial intermittency of turbulence at small scales enabled quantitative estimates to be made for the relaxation time of a polymer and its concentration that ensures maximum drag reduction. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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76.
Bettina Eick 《Mathematische Zeitschrift》1997,224(1):103-111
Dedicated to W. Gaschütz on the occasion of his 75th birthday
Received 26 January 1995; in final form 2 May 1995 相似文献
77.
Pill J Kloetzer HM Issaeva O Kraenzlin B Deus C Kraemer U Sadick M Fiedler F Gretz N 《Analytical and bioanalytical chemistry》2005,382(1):59-64
There is an obvious and growing medical need for an accurate determination of kidney function in the diagnosis and management of renal diseases. The glomerular filtration rate (GFR) is the accepted gold standard measurement of kidney function. Several approaches to estimate the GFR are available, but most of them are inconvenient and, therefore, of limited acceptance. A new method of quantification with fluorescein-isothiocyanate (FITC) sinistrin (FS), a novel GFR marker, has been evaluated. The method is based on the fluorescence label of FS and can be performed with a standard fluorometer. To control the interference of protein with the fluorescence signal, a calibration function was developed. The accuracy of the fluorometric method established is comparable to the so-called gold standard of enzymatic determination of polyfructosan. Moreover, FS is easy to handle and requires low-cost instruments. Our results demonstrate the potential of the direct fluorometric analysis of the new FITC-labelled marker of being a precise, simple, rapid and cost-effective method for diagnosing disturbed kidney function and monitoring its treatment efficacy. The dramatic decrease in analytical effort will result in a significantly higher acceptability of GFR determination. 相似文献
78.
Hans R. Kricheldorf Bettina Weegen-Schulz 《Journal of polymer science. Part A, Polymer chemistry》1995,33(13):2193-2201
Numerous BuSnCl, Bu2SnCl, and Bu3SnCl-initiated polymerizations of cyclo(tri-methylene carbonate) (TMC) were conducted in bulk. In addition to the initiator, reaction time, temperature, and monomer/initiator (M/I) ratio were varied. Yields above 90% were obtained with all three initiators, but their reactivities decrease in the order BuSnCl3 > Bu2SnCl2 > Bu3SnCl. The maximum molecular weights decrease in the same order. With BuSnCl3 Mws up to 250,000 were obtained. These molecular weights were determined by GPC on the basis of the universal calibration method. In this connection Mark-Houwink equations for two solvents, tetrahydrofuran (THF) and CH2Cl2 were determined and compared with literature data. Furthermore, mechanistic aspects were studied. 1H- and 13C- NMR spectra revealed that BuSnCl3 forms complexes with the CO-group of TMC, whereas Bu2SnCl3 do not cause NMR spectroscopic effects. Kinetic studies in chloroform and nitrobenzene and a comparison with Bu3SnOMe suggest that at least BuSnCl3 initiates a cationic mechanism. However, in contrast to SnCl4 (or SnBr4), BuSnCl3 does not cause decarboxylation. Regardless of the initiator 1H-NMR spectroscopy revealed CH2OH and CH2CI endgroups in all cases. © 1995 John Wiley & Sons, Inc. 相似文献
79.
A novel method is proposed for the detection and quantification of protein-protein interactions in solution. In this approach, one protein binding partner is tagged with a ligand binding domain, and protein-protein interaction is monitored via changes in the NMR relaxation of a reporter ligand which reversibly binds to the ligand binding domain. The particular benefit of the method is that only minute amounts of protein material and no isotope labeling are required. Its ease of implementation and the high-throughput capabilities make the method an attractive complement to existing proteomic methodology. 相似文献
80.
Cyril A. Grob Bettina Günther Reinhard Hanreich Adrian Waldner 《Tetrahedron letters》1981,22(9):835-838
Solvolysis of 6-exo- and 6-endo-substituted 2-exo-norbornyl tosylates and , respectively, yields identical or different product mixtures depending on the inductive effect of the substituent, indicating that induction involves graded σ-participation. 相似文献