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Regen SL Janout V Stedronsky ER Zhang Lh Blum JS Boyajian AR Butow ME Carbonelli KL Liebentritt S Rouse RK Shay DT Vincent GA Warholic HM Yanagisawa H 《Organic letters》2000,2(14):2157-2160
The use of partially quaternized, chloromethylated polystyrene as a covalent scavenger of cholate ion in aqueous media has been demonstrated. The ability of such polymers to scavenge organic anions by covalent as well as by ionic means has important implications in the areas of medicinal and environmental chemistry, which are briefly discussed. 相似文献
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A. Günther D. V. Papavassiliou M. D. Warholic T. J. Hanratty 《Experiments in fluids》1998,25(5-6):503-511
A two-component laser Doppler velocimeter with high spatial and temporal resolution was used to obtain measurements for fully
developed turbulent flow of water through a channel with an aspect ratio of 12 : 1 at Re=5700 (based on the centerline velocity and the half-height of the channel). Statistical quantities that were determined are
the mean streamwise velocity, the root-mean-square of the fluctuations of the streamwise and the normal velocities, the Reynolds
shear stress and higher order moments. Turbulence production is calculated from these quantities. Turbulence statistics obtained
from experiments are compared with results from a direct numerical simulation at the same Reynolds number. The good agreement
validates a recent DNS, at Re=5700, which is approximately twice as large as used in most previous studies.
Received: 12 May 1997 / Accepted: 8 April 1998 相似文献
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Measurements of turbulence properties of solutions of polymers have been made over a large range of drag-reduction, in a
fully-developed channel flow. At flows close to maximum drag-reduction the Reynolds stresses were approximately zero over
the whole cross section of the channel. Added mean polymer stresses were observed in the viscous wall region for small drag-reduction
and over the whole cross-section for large drag-reduction. Even though the Reynolds stresses are zero, the velocity profile
is not parabolic because of the presence of these mean stresses. We interpret the results by arguing that the interaction
of turbulence with the polymers introduces mean and fluctuating polymer stresses which can create turbulence. The observation
that the turbulence modification depends on the manner by which the polymers are introduced into the flow supports the notion
that the polymers need to form aggregates in order to be effective.
Received: 29 September 1998 / Accepted: 10 February 1999 相似文献
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Particle-image velocimetry has been used to study the effect of drag-reducing polymers on the structure of turbulence in
a channel flow, under conditions of 41% and 55% drag reduction. The fluctuating velocity fields in the x-y plane and in one
x-z plane were measured. The striking features of these results are the damping of small scales and the repression of fluctuations
of the velocity component normal to the wall. The role of the wall in creating turbulence diminishes greatly at large drag
reductions; Warholic et al. (1999) have shown that a turbulent flow with zero Reynolds stress exists at maximum drag reduction.
Velocity fields presented for conditions approaching this critical behavior are of particular interest.
Received: 23 April 1999/Accepted: 12 February 2001 相似文献
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An analytical system was developed for detection of antibiotic residues in bovine milk. The method is based on competitive fluorescent immunoassays in glass capillary tubes (U.S. Patent No. 5,624,850). The system consists of an assay cartridge containing 4 glass capillaries, a reagent tray with 4 wells of dried reagents, and a Parallux processor, which processes the assay, reads fluorescent output, and reports test results. Minimum sensitivity for detection of 6 beta-lactam antibiotics in bovine milk was determined to be penicillin-G, 3.2 ppb; ampicillin, 2.9 ppb; amoxicillin, 3.6 ppb; cloxacillin, 7.4 ppb; cephapirin, 16.3 ppb; and ceftiofur, 33.7 ppb. The assay system was also specific and sensitive for detection of incurred residues at U.S. Food and Drug Administration tolerance levels: penicillin-G, 5 ppb; ampicillin, 10 ppb; amoxicillin, 10 ppb; cloxacillin, 10 ppb; cephapirin, 20 ppb; and ceftiofur, 50 ppb. There was no interference in detection of minimum sensitivity levels of antibiotic by the presence of somatic cells at approximately 1 x 10(6) cells/mL. Milk containing 3 x 10(6) cells/mL bacteria commonly found in mastitic milk also showed no interference when tolerance levels of antibiotic were present. There was no detectable interference on results by a wide variety of non-beta-lactam drugs. 相似文献
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