Results for “Hydrodynamics” — Page 61

PubMed1993

[Experimental study on the hydrodynamic performance of "valved pericardial roll"].

Optimal configuration and hydrodynamic performance of "Valved Pericardial Roll (VPR)" as an external conduit was studied using a mock circulatory system which was able to simulate a right cardiac function of infants. Results were as follows: 1) Cardiac output produced by VPR was consistently higher than that by non valved pericardial roll. This result showed the hemodynamic effectiveness of VPR at early stage of operation. 2) Cardiac output by VPR tended to decreased as an elevation of afterload and/or an increment of pulse rate. This result exhibited that VPR had a comparable performance to the Ionescu-Sihley pericardial valve, a satisfactory performance of which was recognized clinically. 3) The optimal configuration related to the length of valve leaflet (LVL) were obtained from the simulation data. VPR with two leaflets produced the best performance when each LVL was design to be 95% of the roll diameter. Among the VPR with three leaflets, the best LVL was 85%. Thus far, VPR which was developed based on the above fundamental studies, indicated satisfactory performance as compared to the conventional surgical treatment.

Animals↗

PubMed1993

Hydrodynamic properties and immunological identification of the sodium- and chloride-coupled glycine transporter.

We have recently reported the purification of the native sodium- and chloride-coupled glycine transporter from pig brain stem (López-Corcuera, B. Vázquez, J., and Aragón, C. (1991) J. Biol. Chem. 266, 24809-24814). This preparation is essentially homogeneous and contains a unique 100-kDa polypeptide based on electrophoretic migration under denaturing conditions. In this paper we report the hydrodynamic characterization of the native transporter, solubilized in two different detergents, as well as the immunological identification of the protein. On the basis of results obtained from size-exclusion chromatography, we calculated the Stokes radii of transporter 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS) and transporter-cholate complexes to be 5.5 and 6.0 nm, respectively. In addition, from H2O/D2O sucrose density gradient sedimentation analysis, we calculated the molecular weight of protein-detergent complexes to be 115,000 and 160,000 in CHAPS and cholate, respectively, and the molecular weight of the protein moiety as 86,000. Finally, polyclonal antibodies raised against the 100-kDa polypeptide were found to immunoprecipitate specifically glycine transport activity. Taken together, the results reported herein corroborate the identity of the 100-kDa band as the sodium- and chloride-coupled glycine transporter and also suggest that in its native state the transporter is a monomeric protein.

Amino Acid Transport Systems, Neutral↗

PubMedDate not supplied

Hydrodynamics of a long-body bileaflet mechanical heart valve.

A new bileaflet substitute mechanical heart valve (MHV) that incorporates an optimal length-to-annulus ratio for improved hydrodynamic efficiency was recently introduced. Efforts have been made on this new prosthesis to use the current advances in carbon materials and design technology to achieve higher net forward flow with minimal energy loss for the smaller aortic valves, while reducing regurgitant closure volume for the larger size valves by an elongated orifice. Benchtop experiments performed in a pulsatile flow loop, under simulated physiologic conditions, substantiated these improvements as claimed.

Aortic Valve↗

PubMedDate not supplied

[Effect of ciliary muscle electrical stimulation on ocular hydrodynamics and visual function in patients with glaucoma].

A course of transscleral electrostimulation of the ciliary muscle (10 sessions) using ESOF-1 device was administered to 20 patients (23 eyes) with bilateral primary open-angle glaucoma. A lens with 4 electrodes was placed on the eyeball in the ciliary body projection. Rectangular bipolar pulses up to 15 msec long were generated in the pack mode with current amplitude up to 10 mA for 3 to 7 min. Control group consisted of 17 "paired" eyes. After electrostimulation the accommodation volume increased by 54%, relative accommodation reserve by 34%, coefficient of discharge by 42%, and vision acuity by 0.1 to 0.4 diopters in 6 out of 7 eyes in which vision was lower than 1.0 diopter; intraocular pressure was 16% decreased and the number of absolute and relative scotomas in the central visual field (Humphry, 24-2) dropped by 40%. Improvement of the visual functions and hydrodynamic parameters of the eye was gradual, reaching the maximum by the end of the follow-up (6 months). In control eyes no positive changes were observed. The results indicate a positive effect of electrostimulation of the ciliary body and posterior ocular structures on intraocular fluid circulation and visual functions.

Accommodation, Ocular↗

PubMedDate not supplied

Determination of synthetic dyes in food products by capillary zone electrophoresis in a hydrodynamically closed separation compartment.

The application of capillary zone electrophoresis (CZE) in a hydrodynamically closed separation system to determine synthetic food colorants added to food products was investigated. The CZE separations were carried out in a 300-micron-i.d. capillary tube made of fluorinated ethylene-propylene copolymer. The inner diameter of the capillary tube made it possible to enhance sample loads (100-nL injection volumes) so that 10-300 ppb limits of detection (LOD) values could be achieved for the studied dyes by a photometric absorbance detector operating at a 254-nm detection wave-length. With the exception of erythrosine (which exhibited a residual adsorption), very good reproducibilities of the determination were typical for 4- and 32-ppm concentrations of the dyes. This rapid CZE procedure (migration times of the resolved analytes were between 2.5 and 10.5 min) provided good selectivities in the determination of the dyes in various food matrices (soft drink concentrates, liqueurs, and chewing gums). Simple sample preparation steps were effective for the sample matrices used in the investigation.

Coloring Agents↗

PubMed1994

Prevention of tooth hypersensitivity caused by the hydrodynamic action of zinc phosphate and composite resin luting cements (SEM) study.

This study was done to determine the role of cement liner as a reducing factor to the fluid movement in order to prevent tooth hypersensitivity according to the hydrodynamic theory during cementation of crowns. A total of fourty freshly extracted intact lower molar were selected for this study. After conventional tooth preparation the teeth were sub-divided into four equal groups to identify the role of cement liner in preventing the penetration of used cement into the dentinal tubules. Scanning electron microscopic study proved the efficiency of glass ionomer liner on preventing cement penetration into the dentinal tubules.

Composite Resins↗

PubMedDate not supplied

[Hydrodynamic and technological bases of a new design of the automyoneoventricle in assisted blood circulation].

The paper presents evidence for and results of development of a new hydrodynamic optimized design of the automyoneoventricle (AMNV) for extracorporeal circulation in critical myocardial lesions. The chosen geometry of externally spirally braided AMNV forms a curled flow that excludes the presence of eddy and stagnant zones which present a risk for thrombogenesis. Moreover, the paper details the original process for manufacturing the prototypes of the AMNV having spiral latex ribs, which has been modified to give its thromboresistant and antibiotic properties. The proposed biomechanical system has been put through tests yielding satisfactory results and it is to undergo clinical trials.

Animals↗

PubMed1998

Hydrodynamic shear shows distinct roles for LFA-1 and Mac-1 in neutrophil adhesion to intercellular adhesion molecule-1.

The binding of neutrophil beta2 integrin to intercellular adhesion molecule-1 (ICAM-1) expressed on the inflamed endothelium is critical for neutrophil arrest at sites of tissue inflammation. To quantify the strength and kinetics of this interaction, we measured the adhesion between chemotactically stimulated neutrophils and ICAM-1-transfected mouse cells (E3-ICAM) in suspension in a cone-plate viscometer at shear rates typical of venular blood flow (100 s-1 to 500 s-1). The kinetics of aggregation were fit with a mathematical model based on two-body collision theory. This enabled estimation of adhesion efficiency, defined as the probability with which collisions between cells resulted in firm adhesion. The efficiency of beta2-integrin-dependent adhesion was highest ( approximately 0.2) at 100 s-1 and it decreased to approximately zero at 400 s-1. Both LFA-1 and Mac-1 contributed equally to adhesion efficiency over the initial 30 seconds of stimulation, but adhesion was entirely Mac-1-dependent by 120 seconds. Two hydrodynamic parameters were observed to influence integrin-dependent adhesion efficiency: the level of shear stress and the intercellular contact duration. Below a critical shear stress (<2 dyn/cm2), contact duration predominantly limited adhesion efficiency. The estimated minimum contact duration for beta2-integrin binding was approximately 6.5 ms. Above the critical shear stress (>2 dyn/cm2), the efficiency of neutrophil adhesion to E3-ICAM was limited by both the contact duration and the tensile stress. We conclude that at low shear, neutrophil adhesion is modulated independently through either LFA-1 or Mac-1, which initially contribute with equal efficiency, but differ over the duration of chemotactic stimulation.

Animals↗

PubMed1998

Comparative kinematics and hydrodynamics of odontocete cetaceans: morphological and ecological correlates with swimming performance.

Propulsive morphology and swimming performance were compared for the odontocete cetaceans Delphinapterus leucas, Orcinus orca, Pseudorca crassidens and Tursiops truncatus. Morphological differences were apparent among the whales. The general body contour and low-aspect-ratio caudal flukes of D. leucas indicated that this species was a low-performance swimmer compared with the other species. Propulsive motions were video-taped as animals swam steadily in large pools. Video tapes were analyzed digitally using a computerized motion-analysis system. Animals swam at relative velocities ranging from 0.4 to 2.4 body lengths s-1. The stroke amplitude of the flukes decreased linearly with velocity for D. leucas, but amplitude remained constant for the other species. Tail-beat frequencies were directly related to relative swimming velocity, whereas the pitch angle of the flukes was inversely related to relative swimming velocity. Unsteady lifting-wing theory was used with regression equations based on kinematics to calculate thrust power output, drag coefficients and propulsive efficiency. Compared with other species, O. orca generated the largest thrust power (36.3 kW) and had the lowest drag coefficient (0.0026), whereas T. truncatus displayed the largest mass-specific thrust power (23.7 W kg-1) and P. crassidens had the highest efficiency (0.9). D. leucas did not swim as rapidly as the other species and had a comparatively higher minimum drag coefficient (0.01), lower mass-specific thrust power (5.2 W kg-1) and lower maximum efficiency (0.84). Minimum drag coefficients were associated with high swimming speeds, and maximum efficiencies corresponded with velocities in the range of typical cruising speeds. The results indicate that the kinematics of the propulsive flukes and hydrodynamics are associated with the swimming behaviors and morphological designs exhibited by the whales in this study, although additional factors will influence morphology.

Journal Article↗

PubMed1998

Comparative kinematics and hydrodynamics of odontocete cetaceans: morphological and ecological correlates with swimming performance.

Propulsive morphology and swimming performance were compared for the odontocete cetaceans Delphinapterus leucas, Orcinus orca, Pseudorca crassidens and Tursiops truncatus. Morphological differences were apparent among the whales. The general body contour and low-aspect-ratio caudal flukes of D. leucas indicated that this species was a low-performance swimmer compared with the other species. Propulsive motions were video-taped as animals swam steadily in large pools. Video tapes were analyzed digitally using a computerized motion-analysis system. Animals swam at relative velocities ranging from 0.4 to 2.4 body lengths s-1. The stroke amplitude of the flukes decreased linearly with velocity for D. leucas, but amplitude remained constant for the other species. Tail-beat frequencies were directly related to relative swimming velocity, whereas the pitch angle of the flukes was inversely related to relative swimming velocity. Unsteady lifting-wing theory was used with regression equations based on kinematics to calculate thrust power output, drag coefficients and propulsive efficiency. Compared with other species, O. orca generated the largest thrust power (36.3 kW) and had the lowest drag coefficient (0.0026), whereas T. truncatus displayed the largest mass-specific thrust power (23.7 W kg-1) and P. crassidens had the highest efficiency (0.9). D. leucas did not swim as rapidly as the other species and had a comparatively higher minimum drag coefficient (0.01), lower mass-specific thrust power (5.2 W kg-1) and lower maximum efficiency (0.84). Minimum drag coefficients were associated with high swimming speeds, and maximum efficiencies corresponded with velocities in the range of typical cruising speeds. The results indicate that the kinematics of the propulsive flukes and hydrodynamics are associated with the swimming behaviors and morphological designs exhibited by the whales in this study, although additional factors will influence morphology.

Animals↗

PubMed1963