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Flow Profile (flow + profile)
Selected AbstractsUnusual Pulmonary Venous Flow Profile in a Patient with Mitral Valve Perforation Secondary to Bacterial EndocarditisECHOCARDIOGRAPHY, Issue 2 2006Shalini Modi M.D. Pulmonary venous flow patterns have been well described in the literature to assess severity of mitral regurgitation (MR) and the degree of diastolic dysfunction. We report a case of posterior mitral leaflet perforation due to bacterial endocarditis causing an alteration of pulmonary venous flow, not previously described in the literature. This pulmonary venous flow pattern is unique in that it reflects dynamic changes in left atrial pressure in the background of severe MR. [source] Macroporous monolithic chiral stationary phases for capillary electrochromatography: New chiral monomer derived from cinchona alkaloid with enhanced enantioselectivityELECTROPHORESIS, Issue 17 2003Michael Lämmerhofer Abstract A new chiral monomer derived from cinchona alkaloid, namely O -9-(tert -butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O -9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 ,m in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1 - co -HEMA- co -EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4 - co -HEMA- co -EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency. [source] Study of electroosmotic flow profile by processing of virtual digital Shah function mask and Fourier transformJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12-13 2003Shinya Kitagawa Abstract The electroosmotic flow in a packed capillary column (CEC) and in a rectangular capillary (CE) was observed by using a microscope-CCD-camera system. The observed image was captured to PC, and virtual digital Shah function mask processing was applied. The flow velocity was calculated by Fourier transform methods. The flow profile was analyzed by multiple measurements of the flow velocity in adjoining regions. The velocity of the electroosmotic flow in a packed capillary column (ID 150 ,m, length 18 mm, packed with cation exchanger) was 4.49 ,m/s at any point of the column, and the flow profile was flat. The effect of gravity on electroosmotic flow was also studied. The profile of the electroosmotic flow was almost flat under both 1-G and microgravity, and the electroosmotic flow velocity under microgravity was found to be significantly faster than that under 1-G. [source] Study on conical columns for semi-preparative liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 3-4 2003Ma Jiping Abstract The dynamic flow profiles and column efficiencies in conically shaped semi-preparative liquid chromatographic columns (inlet ID larger than outlet ID) with two different conical angles (7° and 15°) were studied. The dynamic flow profiles were studied by an on-column visualization method. Conical columns were compared with cylindrical column of the same length and internal volume. The results showed that the flow profile of a sample band in the conical column of 7° (50 mm×17 mm , 11 mm ID) was parabolic in shape. The sample band migrated slower in the wall region than in the central region, as in the cylindrical column (50 mm×14 mm ID). However, the sample band in the conical column of 15° (50 mm×20 mm , 7 mm ID) migrated slower in the central region than in the wall region, resulting in a reverse parabolic flow profile, in contrast to that in cylindrical column. This indicated that a flat flow profile might be realized in a conical column with a conical angle between 7° and 15°. The conical column of 15° had the highest column efficiency among the three columns under the same conditions. Compared with the cylindrical column packed with identical packing material, the conical column of 15° had 22%,45% higher column efficiency and 11%,27% higher peak height. [source] Linear instability of ideal flows on a sphereMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2009Yuri N. Skiba Abstract A unified approach to the normal mode instability study of steady solutions to the vorticity equation governing the motion of an ideal incompressible fluid on a rotating sphere is considered. The four types of well-known solutions are considered, namely, the Legendre-polynomial (LP) flows, Rossby,Haurwitz (RH) waves, Wu,Verkley (WV) waves and modons. A conservation law for disturbances to each solution is derived and used to obtain a necessary condition for its exponential instability. By these conditions, Fjörtoft's (Tellus 1953; 5:225,230) average spectral number of the amplitude of an unstable mode must be equal to a special value. In the case of LP flows or RH waves, this value is related only with the basic flow degree. For the WV waves and modons, it depends both on the basic flow degree and on the spectral distribution of the mode energy in the inner and outer regions of the flow. Peculiarities of the instability conditions for different types of modons are discussed. The new instability conditions specify the spectral structure of growing disturbances localizing them in the phase space. For the LP flows, this condition complements the well-known Rayleigh,Kuo and Fjörtoft conditions related to the zonal flow profile. Some analytical and numerical examples are considered. The maximum growth rate of unstable modes is also estimated, and the orthogonality of any unstable, decaying and non-stationary mode to the basic flow is shown in the energy inner product. The analytical instability results obtained here can also be applied for testing the accuracy of computational programs and algorithms used for the numerical stability study. It should be stressed that Fjörtoft's spectral number appearing both in the instability conditions and in the maximum growth rate estimates is the parameter of paramount importance in the linear instability problem of ideal flows on a sphere. Copyright © 2008 John Wiley & Sons, Ltd. [source] The nuchal translucency and the fetal heart: a literature reviewPRENATAL DIAGNOSIS, Issue 8 2009S. A. Clur Abstract In this overview the current knowledge of the relationship between an increased nuchal translucency (NT) measurement and fetal heart structure and function in chromosomally normal fetuses is reviewed. Relevant pathophysiological theories behind the increased NT are discussed. Fetuses with an increased NT have an increased risk for congenital heart disease (CHD) with no particular bias for one form of CHD over another. This risk increases with increasing NT measurement. Although the NT measurement is only a modestly effective screening tool for all CHD when used alone, it may indeed be effective in identifying specific CHD "likely to benefit" from prenatal diagnosis. The combination of an increased NT, tricuspid regurgitation and an abnormal ductus venosus (DV) Doppler flow profile, is a strong marker for CHD. A fetal echocardiogram should be performed at 20 weeks' gestation in fetuses with an NT , 95th percentile but < 99th percentile. When the NT measurement is , 99th percentile, or when tricuspid regurgitation and/or an abnormal DV flow pattern is found along with the increased NT, an earlier echocardiogram is indicated, followed by a repeat scan at around 20 weeks' gestation. The resultant increased demand for early fetal echocardiography and sonographers with this special expertise needs to be planned and provided for. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experimental Fluid Dynamics of Transventricular Apical Aortic CannulationARTIFICIAL ORGANS, Issue 3 2010Ikuo Fukuda Abstract To clarify the flow pattern from a transventricular apical aortic cannula, hydrodynamic analysis of transventricular apical aortic cannulation (apical cannulation) was performed using particle-image velocimetry in a glass aortic model. Simulated apical cannulation using a 7-mm Sarns Soft-Flow cannula and the newly developed 7-mm apical aortic cannula was compared with standard aortic cannulation. The flow-velocity, streamline, and distribution of magnitude of the strain rate tensor (function of shear stress) were analyzed. Streamline analysis revealed a steady and organized flow profile in apical cannulation as compared with that in standard aortic cannulation. The magnitude of the strain rate tensor decreased within a few centimeters from the exit of the apical cannula. [source] A study of the Coriolis effect on the fluid flow profile in a centrifugal bioreactorBIOTECHNOLOGY PROGRESS, Issue 4 2009Christopher J. Detzel Abstract Increasing demand for tissues, proteins, and antibodies derived from cell culture is necessitating the development and implementation of high cell density bioreactors. A system for studying high density culture is the centrifugal bioreactor (CCBR), which retains cells by increasing settling velocities through system rotation, thereby eliminating diffusional limitations associated with mechanical cell retention devices. This article focuses on the fluid mechanics of the CCBR system by considering Coriolis effects. Such considerations for centrifugal bioprocessing have heretofore been ignored; therefore, a simpler analysis of an empty chamber will be performed. Comparisons are made between numerical simulations and bromophenol blue dye injection experiments. For the non-rotating bioreactor with an inlet velocity of 4.3 cm/s, both the numerical and experimental results show the formation of a teardrop shaped plume of dye following streamlines through the reactor. However, as the reactor is rotated, the simulation predicts the development of vortices and a flow profile dominated by Coriolis forces resulting in the majority of flow up the leading wall of the reactor as dye initially enters the chamber, results are confirmed by experimental observations. As the reactor continues to fill with dye, the simulation predicts dye movement up both walls while experimental observations show the reactor fills with dye from the exit to the inlet. Differences between the simulation and experimental observations can be explained by excessive diffusion required for simulation convergence, and a slight density difference between dyed and un-dyed solutions. Implications of the results on practical bioreactor use are also discussed. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] Numerical modeling of the Joule heating effect on electrokinetic flow focusingELECTROPHORESIS, Issue 10 2006Kuan-Da Huang Abstract In electrokinetically driven microfluidic systems, the driving voltage applied during operation tends to induce a Joule heating effect in the buffer solution. This heat source alters the solution's characteristics and changes both the electrical potential field and the velocity field during the transport process. This study performs a series of numerical simulations to investigate the Joule heating effect and analyzes its influence on the electrokinetic focusing performance. The results indicate that the Joule heating effect causes the diffusion coefficient of the sample to increase, the potential distribution to change, and the flow velocity field to adopt a nonuniform profile. These variations are particularly pronounced under tighter focusing conditions and at higher applied electrical intensities. In numerical investigations, it is found that the focused bandwidth broadens because thermal diffusion effect is enhanced by Joule heating. The variation in the potential distribution induces a nonuniform flow field and causes the focused bandwidth to tighten and broaden alternately as a result of the convex and concave velocity flow profiles, respectively. The present results confirm that the Joule heating effect exerts a considerable influence on the electrokinetic focusing ratio. [source] Prevalence of lower urinary tract symptoms in a community-based survey of men in TurkeyINTERNATIONAL JOURNAL OF UROLOGY, Issue 7 2003FAZIL TUNCAY AKI Abstract Aim: The aim of the present study was to determine the frequency of lower urinary tract symptoms (LUTS), assess the impact of LUTS on quality of life (QOL) and compare the results with recent reports from other population-based studies. Methods: A total of 266 men participated in the study. The men were stratified into 10-year age groups between 40 and 79 years. All participants were asked to complete a questionnaire that included a Turkish translation of the International Prostate Symptom Score (IPSS) with QOL questions, and void into a uroflowmeter to obtain voided urine volume, peak and mean flow rate. Results: While 14.8% of men had no symptoms (IPSS = 0), 24.9% had moderate to severe symptoms (IPSS> 7). Severity of symptoms increased with age (P= 0.0018). There was a strong relationship between bother score and IPSS (rs= 0.79, P= 0.0001). Fifty-five percent of moderately symptomatic and 78% of severely symptomatic men reported poor QOL (QOL score , 3). The results of the survey provide a general picture of the symptomatology and urinary flow profiles of elderly men living in Turkey. Conclusion: The prevalence of LUTS in the Turkish community is fairly high, it increases with age and has an impact on QOL that is not negligible. [source] Feasibility of infusion pumps for continuous spinal administration of local anesthetics in post-operative pain therapyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2009M. WENK Background and Objectives: For completion of perioperative care and for general ethical considerations, any intraoperatively used catheter technique should be utilizable for post-operative pain therapy. Continuous spinal anesthesia (CSA) is an established form of local anesthetic application. However, for its use in post-operative therapy, infusion pumps are required that are technically able to deliver low rates and are distinctive in design to avoid possible pump or medication swaps. Because of a lack of devices specifically designed for CSA, we investigated the potential deployability of infusion pumps for post-operative pain therapy via CSA microcatheters, which were originally designed and approved for different applications. Methods: The accuracy of infusion rates of three different pumps was measured in a liquor model environment. Furthermore, we investigated safety and user-friendliness by interviewing 30 anesthesiologists and 15 pain nurses. Results: Except for the first hour of infusion, all pumps provided comparable and adequate flow profiles. However, interviews revealed significant risk factors for all pumps in terms of swapping devices, lines or medications and misprogramming the units. Discussion: All pumps tested were technically able to deliver accurate flow rates; however, because the non-CSA-specific design involves the risk of medication overdosage and syringe swaps, none of the systems tested can be recommended for routine use in post-operative CSA, irrespective of the fact that it was an off-label application anyway. Therefore, to ensure patient safety, continuous spinal administration of local anesthetics via microcatheters is a questionable method of post-operative pain therapy as long as non-specific pumps are used. [source] INFLUENCE OF CHEWING AND SWALLOWING BEHAVIOR ON VOLATILE RELEASE IN TWO CONFECTIONERY SYSTEMSJOURNAL OF TEXTURE STUDIES, Issue 5 2006A. BLISSETT ABSTRACT Electromyography, electroglottography and turbine airflow technology were used to characterize the chewing, swallowing and breath flow profiles of 35 subjects during the consumption of two different (a gum Arabic- and carrageenan-based) confectionery chews. Simultaneous volatile release measurements were obtained using atmospheric pressure chemical ionization mass spectrometry. Subgroups of subjects displaying different eating characteristics were identified for both products. Parameters accounting for the maximum variance (product 1, 42% and product 2, 52%) between the subgroups were chewing force, chewing rate, proportion of work and total number of chews. Volatile release measurements were significantly different between the subgroups from product 1. The impact of the different eating characteristics on volatile release from product 2 was less defined, and postulated to be a result of the contrasting textural properties. Manipulating in vivo breakdown of chewy confectionery products, by texture modification, may influence consumer's volatile release and subsequent flavor perception. [source] The influence of power-law rheology on flow distribution in coathanger manifolds,POLYMER ENGINEERING & SCIENCE, Issue 3 2003J. D. Reid Coathanger dies are effective in delivering uniform flow if a polymer melt; however, when the fluid flow index varies from the design values, the flow is not uniform. Although mechanisms such as die lip adjustments have been effective tools for adjusting flow profiles, the issue of a variable flow index has not been fully addressed at the design stage. An analytical solution, based on the assumptions present in the 1-D design equation, has been developed for the flow distribution in a coathanger manifold. This solution determines the flow distribution for a power-law fluid with a flow index n* in a manifold designed for a separate flow index n*. From this solution, a uniformity index and a critical design angle are defined. The critical design angle is the angle at which the local derivative of the uniformity index with respect to n* approaches a maximum (for n* < n) or a minimum (for n* > n) as a function of the design angle. The critical design angle is independent of n and is presented as a function of the manifold aspect ratio. [source] Cold and hot gas filtration using a novel mobile granular bed with an inner fluidized sectionTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2002Nicolas Abatzoglou Abstract Two experimental studies were conducted with a novel moving granular bed filter (NMGBF). The first one was performed on a cold and dry mock-up module operated at room temperature and was aimed at a) proving the concept, b) establishing the operating patterns and flow profiles and c) optimizing the operating conditions. The gas flowrate and the geometry of the filter were the main variables studied. The second study was conducted on a prototype hot filter PDU (Process Development Unit) under real time operating conditions. The filter was one of the modules of a hot-gas-conditioning-train in a fluidized bed gasifier. Results showed similar particles collection efficiency for hot- and cold-dry filtration. The filter showed an efficiency of 99.9% over 55 h filtration time for particles larger than 1 ,m, while for submicronic particles the efficiency is between 84% and 96% (weight basis). This paper presents and discusses the apparatus, the experimental methods and conditions as well as characteristic results on the two prototypes used. Deux études expérimentales ont été menées à I'aide d'un nouveau filtre à lit granulaire mobile (NMGBF). La premiére a été menée sur une maquette froide et séche à la température ambiante et visait a (a) prouver le concept, (b) établir les modéles de fonctionnement et les profus d'écoulement et (c) optimiser les conditions opératoires. Les variables étudiées sont le débit de gaz et la géométrie du filtre La seconde étude a été menée sur une unite de développement de procédes prototype à filtre chaud dans des conditions opératoires en temps réel. Le filtre est un des modules du train de conditionnement à gaz chaud dans un gazéificateur à lit fluidise. Les résultats montrent une efficacite de collecte des particules comparable pour la filtration sèche chaude et froide. Le filtre montre une efficacité de 99,9 % pour un temps de filtration de 55 h avec des particules au-dessus de 1 ,m, alors qu'avec des particules inférieur au micron I'efficacite' se situe entre 84 et 96 % (sur la base massique). On décrit dans cet article I'appareil, les méthodes expérimentales et les conditions, ainsi que les résultats caractéristiques des deux prototypes utilisés. [source] Prediction of prognosis by echocardiography in patients with midgut carcinoid syndrome,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 6 2001G. Westberg Background: The association between malignant midgut carcinoid tumours and right-sided cardiac lesions is well known, but the pathogenetic link between tumour secretion and valvular disease is still obscure. The purpose of this investigation was to describe the morphological and functional changes of valvular heart disease in a large patient series and to correlate these findings with hormonal secretion and prognosis. Methods: Of 64 consecutive patients with the midgut carcinoid syndrome followed between 1985 and 1998, valvular heart disease was evaluated in 52 patients by two-dimensional echocardiography, Doppler estimation of valvular regurgitation and flow profiles. A majority was also evaluated with exercise electrocardiography and spirometry. Results: Structural and functional abnormalities of the tricuspid valve were found in 65 per cent of patients, while only 19 per cent had pulmonary valve regurgitation. Long-term survival was related to excessive urinary excretion of 5,hydroxyindole acetic acid of over 500 µmol in 24 h, but the main predictor of prognosis was the presence of severe structural and functional abnormalities of the tricuspid valve. Although advanced tricuspid abnormalities were prevalent in this series, only one patient died from right ventricular heart failure. Conclusion: Tricuspid valvular disease is a common manifestation of the midgut carcinoid syndrome and advanced changes are associated with poor long-term survival. Active surgical and medical therapy of the tumour disease reduced the hormonal secretion and, combined with cardiological surveillance, made right ventricular heart failure a rare cause of death in these patients. © 2001 British Journal of Surgery Society Ltd [source] | ||||||||||||||||