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The ensemble-averaged characteristics of the turbulent near-wake flow around two side-by-side identical square cylinders at a Reynolds number approximate to 23100 have been studied using a two-component laser-Doppler velocimeter s...
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The ensemble-averaged characteristics of the turbulent near-wake flow around two side-by-side identical square cylinders at a Reynolds number approximate to 23100 have been studied using a two-component laser-Doppler velocimeter system. The work focuses on a single case with a gap/diameter ratio of 2, for which the resulting individual vortex streets are coupled so as to yield a flow predominantly symmetric about the line midway between the two cylinders. Data sorting or conditioning according to phase was performed with the aid of pressure signals taken from taps on a sidewall of each cylinder. The two-cylinder results are compared in detail to results from a previous study of the one-cylinder case. Vortex structures shed on the side towards the flow centreline, termed inner structures, are distinguished from those shed on the free-stream side, termed outer structures, and the differences between the features associated with the two different structures are examined. The circulation associated with outer structures evolves downstream in a manner similar to that observed in the one-cylinder case, but the circulation of the inner structures is found to decrease dramatically downstream. This not only gives support to previous theoretical predictions but also reconciles these with previously apparently conflicting experimental observations. Information regarding vortex structure motion and the relevant length and time scales is obtained. Differences between momentum and vorticity transport, particularly across the flow centreline are pointed out, and effective turbulent vorticity fluxes are defined. Similarities in local flow topologies in one-and two-cylinder cases are discussed, and the role of local velocity-gradient invariants and their relationship to critical points and turbulence statistics are examined. [References: 26]
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The present experimental work is concerned with "twin jets in crossflow" (TJICF) concentrating upon the vorticity distribution and turbulent vorticity transport associated with the dominant vortical structure of the TJICF. The con...
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The present experimental work is concerned with "twin jets in crossflow" (TJICF) concentrating upon the vorticity distribution and turbulent vorticity transport associated with the dominant vortical structure of the TJICF. The configuration of the TJICF consists of a pair of identical jet nozzles and jet-flow conditions at the nozzle exits. The twin jets are issuing normally into a crossflow. The mean-flow velocity vector and associated turbulence statistics of the TJICF are determined using the standard crossed hot-wire anemometry technique. In the present contribution two geometrically symmetric TJICF arrangements, namely tandem and side-by-side arrangements (both with a nozzle centre-to-centre separation of 5D). are examined, focusing upon the dominant vortical structure rather similar to that of the ell-known contrarotating vortex pair of the single JICF. The formation and decay of this dominant cortical structure is closely associated with the turbulent vorticity transport. The two TJICF arrangements under consideration have their own specific vorticity transport features which are. firstly, visualized and interpreted in terms of turbulent vorticity fluxes. Secondly, the vorticity transport analysis shows the vortex-strength decay (i.e. circulation decay) as described by the corresponding integral decay-rate formula. The similarities and differences between the vorticity (distribution and transport) features associated with the two different TJICF arrangements. tandem and side-by-side, and the single-jet case are examined and discussed. The TJICF flow phenomenon represents an interaction of two single JICF and the gross qualitative features of the vortex formation process of the resulting (mean-flow) dominant vortical structure are described. (C) 2003 Elsevier Science Inc. All rights reserved. [References: 24]
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A sequential injection instrument (ALITEA, USA) with a photometric and fluorometric detection unit S2000 (Ocean Optics) was employed for the development of flow injection immunoanalysis (FIIA). The monoclonal antibodies against at...
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A sequential injection instrument (ALITEA, USA) with a photometric and fluorometric detection unit S2000 (Ocean Optics) was employed for the development of flow injection immunoanalysis (FIIA). The monoclonal antibodies against atrazine, simazine and 2,4-D were immobilized on aminopropyl glass particles by means of avidin/biotin system and packed in plexiglass column of 18 mu l volume. Assay characteristics for individual antibody-reactors and regeneration effectivities for acid and alkaline solutions are described. An attempt to prepare a functional mixed antibody-reactor has not achieved success since regeneration conditions found for individual reactors were not compatible with one performance protocol. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 23]
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The affinity biosensor system IAsys based on the resonant mirror optical structure was tested as a direct immunosensor for determination of atrazine in soil. Atrazine as a ligand was immobilized to the aminosilane surface of the m...
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The affinity biosensor system IAsys based on the resonant mirror optical structure was tested as a direct immunosensor for determination of atrazine in soil. Atrazine as a ligand was immobilized to the aminosilane surface of the measuring cuvette through albumin as a bridge molecule. The interaction of the monoclonal antibody (MAb) D6F3 with the immobilized atrazine was studied, the kinetic affinity equilibrium constant K-A was 1.18 x 10(9) mol(-1) l. The immunosensor was applied to the competitive assay of atrazine in real soil samples. The methanolic extracts of soil were preincubated with MAb (5 min) and the mixture was allowed to interact with the immunosensitive surface of the measuring cuvette (5 min). Thus obtained binding curve was processed with the kinetic program FastFit and the calculated extent of binding served as the parameter for further evaluation. The sensing surface was successfully regenerated using 100 mM NaOH (2 min), the same sensor was used repeatedly for 120 assays. Detection of atrazine concentrations from 0.1 mu g l(-1) to 10 mg l(-1) was evaluated, a practical limit of determination for soil samples was 1 mu g l(-1). The contents of atrazine in 14 real soil samples were determined with the immunosensor and compared to the results of ELISA and gas chromatography. Though correlation between these methods was achieved, the reproducibility of immunosensor data was rather low and further optimization of the measuring procedure is needed. (C) 1999 Elsevier Science B.V. All rights reserved. [References: 19]
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Seventeen rabbits and forty mice were immunized with immunogens prepared by derivatizing atrazine and simazine and conjugating them via aminohexanecarboxylic acid and thiopropanecarboxylic acid substituents to proteins. Six rabbit...
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Seventeen rabbits and forty mice were immunized with immunogens prepared by derivatizing atrazine and simazine and conjugating them via aminohexanecarboxylic acid and thiopropanecarboxylic acid substituents to proteins. Six rabbit antisera and one murine monoclonal antibody were incorporated into the ELISA (enzyme linked immunosorbent assay) format using peroxidase and alkaline phosphatase tracers. Superior antisera for atrazine, simazine and ametryn exhibited in optimized assays a 50% binding inhibition at 0.16, 0.25 and 0.45 mu g l(-1), respectively. The IC50 value for the monoclonal antibody to atrazine was about 1.0 mu g l(-1). The most sensitive antiserum Atr-(CH2)(5)-OV-3C exhibited 74.1% cross-reactivity with propazine and 26.3% with deethylatrazine. Antisera produced in response to the simazine-S-(CH2)(2)-determinant showed a remarkable variety in s-triazine recognition selectivity. Antiserum Sim-S-(CH2)(2)-KLH-C was extremely sensitive to ametryn, terbutryn and prometryn with cross-reactivities based on simazine (= 100%) 2200, 1100 and 1480%, respectively. Structural aspects of these findings are discussed. ELISA for atrazine was evaluated on surface water and ground water samples collected from a contaminated area. The amounts of atrazine found by ELISA were in good agreement with GC-MS analysis. Starting data for the application of ELISA to juice and milk samples are also presented. [References: 14]
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