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Pressure Rise (pressure + rise)
Selected AbstractsAnalysis of effect of electrolyte types on electrokinetic energy conversion in nanoscale capillariesELECTROPHORESIS, Issue 3 2010Reiyu Chein Abstract An analytical study on the effect of electrolyte types on the electrokinetic energy conversion is presented using nanoscale cylindrical capillary, which is either positively or negatively charged. The sign of surface charge determines the role and concentration magnitude of ions in the capillary and the energy conversion performance. Our study shows that the electrokinetic energy conversion performance (maximum efficiency, pressure rise and streaming potential) are approximately identical for 1:1 (KCl), 2:1 (CaCl2) and 3:1 (LaCl3) electrolytes when capillary is positively charged. For negatively charged capillary, energy conversion performance degrades significantly with the increase of counter-ion valence. For both positively and negatively charged capillaries, higher maximum efficiency can be resulted in low bulk concentration and surface charge density regimes. However, high maximum pressure rise generation for the pumping is found in the low bulk concentration and high surface charge density regimes. For the electric power generation, higher maximum streaming potential is found when both bulk concentration and surface charge density are low. [source] Peristaltic transport and heat transfer of a MHD Newtonian fluid with variable viscosityINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2010S. Nadeem Abstract The influence of temperature-dependent viscosity and magnetic field on the peristaltic flow of an incompressible, viscous Newtonian fluid is investigated. The governing equations are derived under the assumptions of long wavelength approximation. A regular perturbation expansion method is used to obtain the analytical solutions for the velocity and temperature fields. The expressions for the pressure rise, friction force and the relation between the flow rate and pressure gradient are obtain. In addition to analytical solutions, numerical results are also computed and compared with the analytical results with good agreement. The results are plotted for different values of variable viscosity parameter ,, Hartmann number M, and amplitude ratio ,. It is found that the pressure rise decreases as the viscosity parameter , increases and it increases as the Hartmann number M increases. Finally, the maximum pressure rise (,=0) increases as M increases and , decreases. Copyright © 2009 John Wiley & Sons, Ltd. [source] Design of a Protective Cage for an Intravascular Axial Flow Blood Pump to Mechanically Assist the Failing FontanARTIFICIAL ORGANS, Issue 8 2009Amy L. Throckmorton Abstract Currently, no long-term mechanical bridge-to-transplant or bridge-to-recovery therapeutic alternative exists for failing single ventricles. A blood pump that would augment pressure in the cavopulmonary circulation is needed, and would lead to a reduction in elevated systemic venous pressure, and improve cardiac output. Thus, we are developing a collapsible, percutaneously inserted, axial flow blood pump to support the cavopulmonary circulation in adult patients with a failing single ventricle physiology. This collapsible axial flow pump is designed for percutaneous positioning. The outer protective cage will be designed with radially arranged filaments as touchdown surfaces to protect the vessel wall from the rotating components. This study examined the geometric characteristics of the protective cage of filaments and the impeller through the development and numerical analysis of 13 models. A blood damage analysis was also performed on selected geometric models to assess the probability of blood trauma. All models demonstrated an acceptable hydraulic performance by delivering 2,6 L/min at a rotational speed of 6000,10 000 rpm and generating pressure rise of 5,20 mm Hg. Expected trends in the hydraulic performance of the pump models were found. This study represents the initial first design phase of the impeller and protective cage of filaments. Validation of these flow and performance predictions will be completed in the next round of experimental testing with blood bag evaluation. [source] Numerical and Experimental Analysis of an Axial Flow Left Ventricular Assist Device: The Influence of the Diffuser on Overall Pump PerformanceARTIFICIAL ORGANS, Issue 7 2005Alexandrina Untaroiu Abstract:, Thousands of adult cardiac failure patients may benefit from the availability of an effective, long-term ventricular assist device (VAD). We have developed a fully implantable, axial flow VAD (LEV-VAD) with a magnetically levitated impeller as a viable option for these patients. This pump's streamlined and unobstructed blood flow path provides its unique design and facilitates continuous washing of all surfaces contacting blood. One internal fluid contacting region, the diffuser, is extremely important to the pump's ability to produce adequate pressure but is challenging to manufacture, depending on the complex blade geometries. This study examines the influence of the diffuser on the overall LEV-VAD performance. A combination of theoretical analyses, computational fluid (CFD) simulations, and experimental testing was performed for three different diffuser models: six-bladed, three-bladed, and no-blade configuration. The diffuser configurations were computationally and experimentally investigated for flow rates of 2,10 L/min at rotational speeds of 5000,8000 rpm. For these operating conditions, CFD simulations predicted the LEV-VAD to deliver physiologic pressures with hydraulic efficiencies of 15,32%. These numerical performance results generally agreed within 10% of the experimental measurements over the entire range of rotational speeds tested. Maximum scalar stress levels were estimated to be 450 Pa for 6 L/min at 8000 rpm along the blade tip surface of the impeller. Streakline analysis demonstrated maximum fluid residence times of 200 ms with a majority of particles exiting the pump in 80 ms. Axial fluid forces remained well within counter force generation capabilities of the magnetic suspension design. The no-bladed configuration generated an unacceptable hydraulic performance. The six-diffuser-blade model produced a flow rate of 6 L/min against 100 mm Hg for 6000 rpm rotational speed, while the three-diffuser-blade model produced the same flow rate and pressure rise for a rotational speed of 6500 rpm. The three-bladed diffuser configuration was selected over the six-bladed, requiring only an incremental adjustment in revolution per minute to compensate for and ease manufacturing constraints. The acceptable results of the computational simulations and experimental testing encourage final prototype manufacturing for acute and chronic animal studies. [source] 3351: Influence of atmospheric pressureand temperature changes on the intraocular pressure.ACTA OPHTHALMOLOGICA, Issue 2010S VAN DE VEIRE Purpose Some patients questioned us whether diving and mountaineering can have an effect on their intraocular pressure (IOP). Since the results in the literature concerning mountaineering are often contradictory and the data concerning diving are very limited; we investigated if an increase in atmospheric pressure influences the IOP in a normal population. Since we clinically experienced higher pressures in the summer, we checked the temperature influence on the IOP simultaneously. Methods Twenty-seven healthy volunteers (aged 18 to 44) were placed in a hyperbaric chamber. Their IOP was measured with a Perkins tonometer at baseline (normal atmospheric pressure of 1 Bar and 24°C), after increasing the atmospheric pressure to 2 Bar both at 14°C and 28°C, and finally at baseline again. A multivariate regression analysis was used to evaluate the results of both eyes. Results The IOP significantly decreased from 11.75mmHg to 10.50mmHg at 2 Bar. The IOP decrease remained constant during the atmospheric pressure rise (40 minutes) and was independent of the temperature change. The IOP returned back to the baseline value when exiting from the hyperbaric chamber. Conclusion A small increase of atmospheric pressure to 2 Bar (= equal effect to diving at 10m below sea level) is sufficient to lead to a significant reduction in IOP independent of temperature changes in a healthy young population. The IOP decrease sustains for the whole hyperbaric chamber period. [source] Use of latanoprost to reduce acute intraocular pressure rise following neodymium: Yag laser iridotomyACTA OPHTHALMOLOGICA, Issue 3 2002Catherine J. Liu ABSTRACT. Purpose: To evaluate the efficacy of latanoprost in reducing acute intraocular pressure (IOP) elevation after neodymium:Yag laser iridotomy (LI). Methods: Primary angle-closure glaucoma (PACG) eyes were randomized to receive premedication with latanoprost and pilocarpine or with pilocarpine only before LI. Postoperative IOP changes were compared with Wilcoxon signed-ranks test using the fellow eyes of 47 patients who had one eye in each group. Results: Postoperative pressure spikes were significantly lower (p =,0.010) in the latanoprost group (4.1 ± 5.0 mmHg) than in the control group (6.7 ± 7.0 mmHg). Mean elevation of IOP was less in the latanoprost group than in the control group at 1 hour (2.5 ± 4.8 versus 4.1 ± 4.7 mmHg, p = 0.013) and 2 hours (0.8 ± 5.6 versus 4.4 ± 8.1 mmHg, p = 0.003) postoperatively. Eleven eyes in the latanoprost group (23.4%) and 20 eyes in the control group (42.6%) developed a rise in IOP ,,6 mmHg (p =,0.048). Conclusion: Latanoprost may reduce the pressure rise following LI in PACG eyes, but its application is limited by a late onset of effect. [source] Late intraocular pressure rise following intravitreal triamcinolone injectionCLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 4 2007Christopher PR Williams FRCOphth Abstract Most ophthalmologists are aware of the risk of elevated intraocular pressure developing 1 or 2 months after an intravitreal injection of triamcinolone. However, the two cases reported here demonstrate that such a rise can occur significantly later than this. All patients who have had intravitreal steroid injection should therefore have prolonged intraocular pressure monitoring. [source] Effects of imatinib mesylate (Glivec®) as a c-kit tyrosine kinase inhibitor in the guinea-pig urinary bladderNEUROUROLOGY AND URODYNAMICS, Issue 3 2006Yasue Kubota Abstract Aims In the gastrointestinal tract, slow wave activity in smooth muscle is generated by the interstitial cells of Cajal (ICC). Detrusor smooth muscle strips of most species show spontaneous contractions which are triggered by action potential bursts, however, the pacemaker mechanisms for the detrusor are still unknown. Recently, ICC-like cells have been found in guinea-pig bladder, using antibodies to the c-kit receptor. We have investigated the effects of Glivec, a c-kit tyrosine kinase inhibitor, on spontaneous action potentials in guinea-pig detrusor and intravesical pressure of isolated guinea-pig bladders. Methods Changes in the membrane potential were measured in guinea-pig detrusor smooth muscle using conventional microelectrode techniques. Pressure changes in the bladder were recorded using whole organ bath techniques. Results Smooth muscle cells in detrusor muscle bundles exhibited spontaneous action potentials, and spontaneous pressure rises occurred in isolated bladders. Glivec (10 ,M) converted action potential bursts into continuous firing with no effects on the shape of individual action potentials. Glivec (>50 ,M) reduced the amplitude of spontaneous pressure rises in the whole bladder in a dose dependent manner and abolished spontaneous action potentials in detrusor smooth muscle cells. Conclusions The results suggest that ICC-like cells may be responsible for generating bursts of action potentials and contractions in detrusor smooth muscle. Drugs inhibiting the c-kit receptor may prove useful for treating the overactive bladder. Neurourol. Urodynam. © 2006 Wiley-Liss, Inc. [source] Baric and temperature dependences of kinetic coefficients in p-Cd0.7Mn0.3GeAs2 at atmospheric and high pressuresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009A. Yu. Abstract The pressure dependences of the resistivity , (P) and Hall coefficient R,(P) have been measured for heavily doped Cd0.7Mn0.3GeAs2 at increasing and decreasing pressure at room temperature. To investigate temperature properties of conductivity in Cd0.7Mn0.3GeAs2, the temperature dependences , (T) and R,(T) have been defined in the temperature range 77,450 K at atmospheric pressure. The pioneering measurements of magnetoresistance ,,xx (H, P)/,0(P) in Cd0.7Mn0.3GeAs2 are presented. A hysteresis of magnetoresistive effect has been found when pressure rises and falls. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||