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Constant Flow Rate (constant + flow_rate)
Selected AbstractsPortal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2 -type receptorsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 1 2001MaurÍcio R Loureiro-Silva Abstract Background: We have shown that the portal hypertensive response to bradykinin in normal rats is mediated by B2 receptors. Methods: By using isolated and exsanguinated rat liver perfusion, we studied the portal hypertensive response to bradykinin or des-Arg9 -bradykinin (B1 agonist) in inflamed or cirrhotic rat livers. Livers were perfused with bovine serum albumin Krebs,Henseleit buffer (pH 7.4; 37°C) at a constant flow rate, in the absence or presence of des-Arg9[Leu8]-bradykinin or HOE 140 (B1 and B2 receptor antagonists, respectively). Bradykinin (140 nmol) or des-Arg9 -bradykinin was injected as a bolus via the afferent route to the liver. Results: Basal perfusion pressure in liver-cirrhotic rats was higher than in normal rats. In normal, inflamed, or liver-cirrhotic rats, the presence of the B1 antagonist did not change the portal hypertensive response to bradykinin, while the B2 antagonist abolished this response. A 140-nmol dose of des-Arg9 -bradykinin did not change the perfusion pressure; 700 nmol of this B1 agonist produced an insignificant perfusion pressure increase. The perfusion pressure increase induced by bradykinin in cirrhotic livers was lower than in normal livers. Conclusions: The portal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2 receptors, but not B1 receptors, and there is a contracting hyporeactivity to bradykinin in cirrhotic rat livers. [source] Applicability of laser-induced Raman microscopy for in situ monitoring of imine formation in a glass microfluidic chipJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2003Moonkwon Lee Abstract Laser-induced Raman microscopy has been used to illustrate its applicability for the in situ monitoring of imine formation reaction in a glass microfluidic chip. In order to monitor the diffusion process in a micro channel, the Raman spectra were measured at various points along the channel with a constant flow rate of 2.7 µl min,1. Time-dependent Raman spectra were also measured without flow in order to monitor the variation of Raman peaks to a complete conversion. The disappearance of the CO stretching peak at 1700 cm,1 of the reactant, benzaldehyde, and the appearance of the Raman peak for the product, an imine, at 1628 cm,1 were successfully monitored. In addition, the intensity increases of three phenyl stretching modes in the 1550,1630 cm,1 region were also observed. The increase in Raman intensity for this vibrational mode is caused by an effective ,-electron conjugation between two phenyl rings through the ,CN,bridging group of the product. Laser-induced Raman microscopy enables us to monitor in situ product formation and to obtain detailed structural information in a glass microfluidic chip. Copyright © 2003 John Wiley & Sons, Ltd. [source] Rapid determination of three anticoagulant rodenticides in whole blood by liquid chromatography coupled with electrospray ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2006Mi-cong Jin A rapid, sensitive and selective method for the simultaneous determination of bromadiolone, flocoumafen and brodifacoum in whole blood using warfarin as internal standard (IS) by high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC/ESI-MS) has been developed and validated. The target compounds were extracted from the whole blood with ethyl acetate and separated on an XDB C18 column (150,mm,×,2.1,mm i.d.,×,5,µm) by using a mobile phase consisting of 0.2% acetic acid/methanol (12/88, v/v) at a constant flow rate of 0.50 mL/min. The analytes were detected using negative ESI-MS in the selected ion monitoring (SIM) mode. The molecular ions [MH], of m/z 527, 541,523 and 307 were selected for the quantification for bromadiolone, flocoumafen, brodifacoum and the IS, respectively. The calibration curves were linear (r2,>,0.995) in the concentration range of 0.50,100.00 ng/mL. The method showed a satisfactory sensitivity (0.05,0.5 ng/mL using 200 µL blood), precision (RSD,<,11.9%), accuracy (recovery: 82.0,96.1%) and selectivity. This method was successfully applied to the determination of the analytes for the diagnoses of poisoned human beings and animals. Copyright © 2006 John Wiley & Sons, Ltd. [source] Oil,water two-phase flow in microchannels: Flow patterns and pressure drop measurementsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2008Abdelkader Salim Abstract This paper investigates oil,water two-phase flows in microchannels of 793 and 667 µm hydraulic diameters made of quartz and glass, respectively. By injecting one fluid at a constant flow rate and the second at variable flow rate, different flow patterns were identified and mapped and the corresponding two-phase pressure drops were measured. Measurements of the pressure drops were interpreted using the homogeneous and Lockhart,Martinelli models developed for two-phase flows in pipes. The results show similarity to both liquid,liquid flow in pipes and to gas,liquid flow in microchannels. We find a strong dependence of pressure drop on flow rates, microchannel material, and the first fluid injected into the microchannel. On étudie dans cet article les écoulements diphasiques huile-eau dans des micro-canaux de 793 µm et 667 µm de diamètre hydraulique faits de quartz et de verre, respectivement. En injectant un fluide à un débit constant et le second à un débit variable, différents schémas d'écoulements ont été observés et représentés en diagrammes, et les pertes de charge diphasiques correspondantes ont été mesurées. Les mesures de perte de charge ont été interprétées à l'aide du modèle homogène et du modèle de Lockhart,Martinelli mis au point pour les écoulements diphasiques dans les conduites. Les résultats montrent une similarité à la fois avec l'écoulement liquide-liquide et l'écoulement liquide de gaz dans des micro-canaux. On a trouvé une forte dépendance de la perte de charge aux débits, au matériau des micro-canaux et au premier fluide injecté dans le micro-canal. [source] Second-Law Based Thermodynamic Analysis of a Novel Heat ExchangerCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2009Y.-L. He Abstract In the present investigation, second-law based thermodynamics analysis was applied to a new heat exchanger with helical baffles. The helical baffles are designed as quadrant ellipses and each baffle occupies one quadrant of the cross-section of the shell side. Experimental tests were carried out with cold water in the tube side with a constant flow rate, and hot oil on the shell side with flow rate range from 4,24,m3/h. The temperatures and pressures for the inlet and outlet of both sides were measured. The heat transfer, pressure drop, entropy generation, and exergy loss of the new heat exchanger were investigated and compared with the results for a conventional shell-and-tube heat exchanger with segmental baffles. The computed results indicated that both the entropy generation number and exergy losses of the new heat exchanger design are lower than those of the heat exchanger with segmental baffles, which means that the novel heat exchanger has a higher efficiency than the heat exchanger with segmental baffles, from the second-law based thermodynamics viewpoint. [source] | ||||||||||