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At least 1,045 records · Page 58Linked to original sources
PubMed1992

Iontophoretic permeability of polyethylene glycols through hairless rat skin: application of hydrodynamic theory for hindered transport through liquid-filled pores.

The electrically-assisted transport of a homologous series of polyethylene glycols (PEGs) through hairless rat skin (HRS) was examined in order to determine the relationship between the iontophoretic permeability of flexible macromolecules and their size and conformation in free solution. Using fully hydrated HRS, the anodic transport of 26 low molecular weight oligomers of PEG was studied over a 14 hour period at a current density of 0.50 mA/cm2. Analysis of the data revealed a distinct sigmoidal relationship between iontophoretic permeability and molecular size. In addition, the reflection of a relatively small molecular weight species was significant. Accordingly, a hydrodynamic model relating the convective transport of flexible macrosolutes through cylindrical pores was fit to the data generated from the iontophoretic transport of PEGs ranging in weight from 282 to 1382 daltons. A nonlinear least squares analysis of the data demonstrated that the 'effective' mean diameter of aqueous channels within HRS is approximately 36 A.

Animals↗
PubMed2004

Microchip electrophoresis with hydrodynamic injection and waste-removing function for quantitative analysis.

Quantitative analysis is problematic for microchip electrophoresis for several reasons including chip-to-chip variation, discontinuous sample re-loading, channel reconditioning, and electrokinetic injection bias. In this study, the capability for quantitative analysis on a flow-through based microchip electrophoresis, which provides continuous sample re-loading, channel washing, reconditioning and hydrodynamic injection as well as waste removing is demonstrated to be more quantifiable and more reproducible compared to manual electrokinetic injection method. Using the flow-through microchip with waste-removing function, FITC-labeled estrogen or Rhodamine B could be continuously analyzed without significant changes (R.S.D. < 6.6%) in signal intensity for over 3 h, which is sufficient for a complete set of quantitative analysis. With the use of a phosphorylated kinase substrate as the model, a calibration curve for quantitative analysis of phosphopeptides were constructed and results indicate that both R2 value of the linearity and R.S.D. values of the peak intensity were around 0.9961 and 3.16%, respectively, without the use of an internal standard. These values were slightly improved to be around 0.9986 and 2.27%, respectively, with the use of a non-phosphopeptide counterpart as the internal standard. The potential of this flow-through device for the development of a kinase phosphorylation assay based on the quantitative method was also briefly discussed.

Amino Acid Sequence↗
PubMed2004

Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.

The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1 m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST, In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs--for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the appropriate flux rating is applied to the 1DFT estimate of the surface area.

Algorithms↗
PubMed2004

[Estimation of the hydrodynamical characteristics of the end-to-loop gastroenteroanastomosis].

The article presents the results of a study of the hydrodynamical characteristics of the end-to-loop gastroenteroanastomosis by the method of multichannel intraluminal manometry. The study was carried out on 7 outbreed dogs. The function of anastomosis was studied at the constant speed of liquid passage as well as at modeling short-term rises of pressure similar to those created by stomach and gut peristalsis. The results of the study testify that the end-to-loop anastomosis is a dosed obstacle to the antegrade passage comparable with those in the normal state and has expressed antireflux properties.

Anastomosis, Roux-en-Y↗
PubMed1975

[The influence of isoglaucon on the hydrodynamics and haemodynamics of the eye (author's transl)].

By animal experiments and clinically we could prove that isoglaucon instillation caused the decrease in IOP due to both increase in outflow and reduction of humor secretion; the IOP decrease and changes in hydrodynamics being manifested more markedly in the fellow-eye. As reoophthalmography demonstrated "Isoglaucon" produced lumen narrowing in the anterior portion of the uveal tract. "Isoglaucon" was prescribed to 20 patients having open-angle-glaucoma, Two hours after instillation the 23 decreased in 26 eyes (of 28) by 9.3 +/- 1.0 mm Hg. When prescribed regularly "Isoglaucon" raised the outflow facility coefficient from 0.10 +/- 0.01 to 0.20 +/-0.02. The secretion decreased from 2.0 +/- 0.2 to 0.9 +/- 0.15. Thus, IOP decrease after "Isoglaucon" is accounted for by both improved outflow and reduction of aqueous humor secretion. The "isoglucon" instillation produced a rather moderate decrease in the total arterial pressure, though no expected parallelism in arterial and intraocular pressure was marked.

Animals↗
PubMed2005

[Design and adjustment of a hydrodynamic model of turbulent flow separation area for in vitro experiment on the downstream of tubal stenosis].

This paper reports the establishment of a model of turbulent flow separation area for experiment on the downstream of tubal stenosis, and adjust it to cooperate with the velocity and turbulent shear stress (TSS) detection by means of the particle image velocimetry (PIV), and with the pressure detection of pressure sensor in vitro. The velocity, TSS and wall pressure characteristics of the downstream of tubal stenosis were quantitatively detected and analyzed via the PIV and pressure sensor. And the hydrodynamic characteristics of the velocity, TSS and wall pressure in the flow separation area were primarily understood. The model can cooperate smoothly with the PIV and pressure sensor to detect the velocity, TSS and wall pressure; there exist low velocity, low TSS and low pressure in the flow separation area downstream of tubal stenosis.

Blood Flow Velocity↗
PubMedDate not supplied

[Effects of pressure and flow rate of irrigation liquid on hydrodynamics of the upper urinary tract in contact ureterolithotripsy].

We studied the influence of pressure and rate of irrigative liquid flow on hydrodynamics of the upper urinary tracts in contact pneumatic lithotripsy (Litoclast lithotriptor) in 68 patients with ureteroliths and nephrostomic drainage. To a nephrostome the device was attached on which the linear change of pressure inside the pelvis was measured at the moment of visualization of the stone, its destruction and final ureteroscopy. 45 patients had nephrostome with a pelvis curl. In this group of patients at the moment of stone destruction the pressure inside the pelvis and the speed of irrigative flow were increased. In patients with marked local inflammation on the place of stone location the pressure inside the pelvis was the highest. The effect of communicating vessels was seen. The stone was completely destroyed in 34 (75.5%) patients, in 9 (20%) patients the stone was destroyed partially. In 2 cases the stone migrated in the cavitary system of the kidney. A nephrostome-intubator was placed antegradely in 23 patients. The balloon-obturator was placed in the ureter above the stone through the nephrostome. The pressure inside the pelvis during contact lithotripsy was not increased. Full destruction of the stone was achieved in 26 patients (92.8%), migration of the stone in the cavitary system and partial destruction of the stone was observed in 2 (2.2%) patients.

Aged↗
PubMed2005

Suspended solids transport: an analysis based on turbidity measurements and event based fully calibrated hydrodynamic models.

Modelling suspended solids transport is a key issue for predicting the pollution load discharged by CSOs. Nonetheless, there is still much debate on the main drivers for suspended solids transport and on the modelling approach to be adopted. Current sewer models provide suspended solids transport models. These models, however, rely upon erosion-deposition criteria developed in fluvial environments, therewith oversimplifying the sewer sediment characteristics. Consequently, the performance of these models is poor from a theoretical point of view. To get an improved understanding of the temporal and spatial variations in suspended solids transport, a measuring network was installed in the sewer system of Loenen in conjunction with a hydraulic measuring network from June through December 2001. During the measuring period, 15 storm events rendered high-quality data on both the hydraulics and the turbidity. For each storm event, a hydrodynamic model was calibrated using the Clemens' method. The conclusion of the paper is that modelling of suspended solids transport has been and will be one of the challenges in the field of urban drainage modelling. A direct relation of either shear stress or flow velocity with turbidity could not be found, likely because of the time varying characteristics of the suspended solids.

Calibration↗
PubMed1991

Hydrodynamic properties of the purified glutamate-binding protein subunit of the N-methyl-D-aspartate receptor.

The hydrodynamic properties of the previously purified glutamate-binding protein from rat synaptic membranes were determined in order to estimate the molecular size of the protein in its native state. This protein is apparently a subunit of a multisubunit complex that forms the N-methyl-D-aspartate subtype of glutamate receptor and has a molecular size of approximately 70 kDa based on electrophoretic migration under denaturing conditions. On the basis of results obtained from H2O/D2O sucrose density gradient sedimentation and gel filtration chromatography of the purified glutamate-binding protein we calculated the partial specific volume of the protein-detergent complex to be 0.766 cc3/g, the Stokes radius of the complex as 4.9 nm, the Mc of the complex as 203,000 +/- 22,000 and the Mr of the protein as 182,000 +/- 19,000. These results are indicative of stable self-association of the glutamate-binding protein and are in agreement with recent studies indicating that more than one molecule of glutamate may be required to activate the N-methyl-D-aspartate receptor-associated ion channel.

Animals↗
PubMed1991

Avian myeloblastosis virus reverse transcriptase. Effect of glycerol on its hydrodynamic properties.

Although reverse transcriptase has been the subject of intensive investigation, minimal information is available regarding the physical properties of the enzyme. The basic hydrodynamic properties of avian myeloblastosis virus reverse transcriptase in solution were measured by both sedimentation velocity and equilibrium measurements in two buffer systems. In a 0.3 M potassium phosphate buffer system, pH 7.8, the enzyme sedimented as a homogenous particle with a sedimentation coefficient of (7.1 +/- 0.3) S with a weight-average molecular weight, Mw, of (1.52 +/- 0.05) x 10(5). Since the enzyme consists of an alpha and beta subunit of equal molar ratio with Mw of 6.3 x 10(4) and 9.4 x 10(4), respectively, it was concluded that the enzyme exists as an alpha beta heterodimer in this buffer system. In a Tris buffer system, pH 7.9, containing 0.46 M NaCl and 4% glycerol, the native enzyme also sedimented as a homogeneous particle with an apparent sedimentation coefficient of (10.1 +/- 0.5) S, without considering the effect of glycerol on solvent-protein interaction. Based on the results of Gekko and Timasheff (Gekko, K., and Timasheff, S. N. (1981) Biochemistry 20, 4667-4676) and the polarity of the enzyme, it was estimated that there is significant solvent-protein interaction even at 4% glycerol leading to a value of -0.06 g/g in the preferential solvent interaction parameter. When the solvent effect was taken into consideration, the value for s020,w increased from 10.1 to 11.9 S, implying that the native enzyme dimerizes in the presence of 4% glycerol. The combined results of gel filtration and sedimentation velocity showed that the dimerization of the enzyme to form (alpha beta)2 is favored at 20 degrees C with the alpha beta form predominating at 4 degrees C. The secondary structure of the reverse transcriptase was measured by circular dichroism. Results showed that the enzyme consists of (16 +/- 2)% alpha-helix, (24 +/- 2)% beta-sheet, (24 +/- 2)% beta-turn, and (36 +/- 4)% undefined structures.

Avian Myeloblastosis Virus↗
PubMedDate not supplied

[The prevention of the development of the collagen-induced microembolic syndrome by decreasing the hydrodynamic resistance of the blood with special polymers under flow].

The search for antiaggregatory compounds is undertaken, as a rule, under in vitro conditions which do not reflect the dynamics of the real process. The present work deals with study of the peculiarities of the development of the collagen induced microembolic syndrome and the effect produced on it by hydrodynamic resistance reducing polymers under conditions modelling real circulation. The authors show the formation of a developed microembolic syndrome under the effect of collagen with accumulation of vasoconstrictors in the environment and increase of red cell hemolysis. Reduction of blood flow turbulence by the addition of solutions of neutral high-molecular linear polymers revealed the inhibiting effect of these polymers on the development of intracellular aggregate formation and concomitant red cell microhemolysis, which was attended by sharp reduction of thromboxane A2 production in the experiment. The authors show the significance of hemodynamic conditions in the development of the microembolic syndrome and the possibility of preventing it under conditions of modification of the blood flow with polymers, which may be of high prophylactic importance.

Blood Flow Velocity↗
PubMed1990

[Effects of impulse hydrodynamic influences on blood cells in vitro and in vivo].

Impulse hydrodynamic influences (IHDI) resulted in an increase of accumulation of acridine organ, degranulation of neutrophils, decrease in adenylate cyclase and Na+, K+, Mg2(+)-dependent ATPase activities in the white blood cells of man and rat in vitro and in vivo. It was found that the cell's response to one-fold IHDI was more pronounced than to 5-fold IHDI. It was suggested that in certain conditions IHDI could lead to a decrease in reactivity of white blood cells.

Acridine Orange↗
PubMed1990

Determination of molecular weight and related hydrodynamic parameters of high molecular weight protein fraction from a few oilseeds.

The hydrodynamic parameters of the major protein fraction, viz. arachin from groundnut, alpha-globulin from sesame seed, brassin (M) from mustard seed and helianthinin from sunflower seed, have been determined in a single solvent system (0.05 M Tris-HCl buffer, pH 7.5 containing 0.5 M sodium chloride): sedimentation coefficient (s0(20,w)) and diffusion coefficient (D0(20,w)) by analytical ultracentrifugation, intrinsic viscosity [eta] by Ostwald viscometry and partial specific volume (V) by densimetry. The molecular weights (M) of the four proteins, calculated using the sedimentation-viscosity and sedimentation-diffusion coefficient methods, were found close to each other. The values have been compared with those in the literature and the reasons for discrepancies have been discussed.

Chemical Phenomena↗
PubMed1990

[Ocular hydrodynamics in patients with infiltrative-edematous exophthalmos in Graves' disease].

Hydrodynamics of the eyes was investigated in 57 patients with exophthalmos, with various degree of infiltrative changes. Open angle glaucoma was not found in any case. In 12 eyes (10.5 p.c.) one observed a raised IOP (over 21 mm Hg)--checked by means, of an applanation tonometer with the patient looking straight on; in 24 eyes (18.4 p.c.) the IOP was near the upper limit of the normal pressure. Characteristic for glaucoma pathological changes of the optic disc and the visual field were absent in examined patients. All of them had the filtration angle open. The authors found a statistically significant dependency between the IOP and the degree of changes in the motor muscles, conjunctival tissue and in the lids. The authors suggest that the changes in the intraocular pressure have an external cause and stem from the disturbances of the venous circulation with exclusion of the primary hypertension.

Adult↗
PubMedDate not supplied

[Computerized hydrodynamic system "Flow" for testing artificial heart valves].

The computerized mock circulation system is described for analyzing the hydrodynamic characteristics of artificial heart valves. Flow studies have been carried out on 6 mechanical valves of various types. The volumetric flow, pressure upstream and downstream were measured and the mean systolic pressure drop and energy losses were calculated. The commercial model of the EMIKS valve shows much lower values of pressure drop and one of the smallest value of energy losses among the tested artificial heart valves.

Heart Valve Prosthesis↗
PubMedDate not supplied

[Design aspects and hydrodynamic characteristics of the Bionics heart valves].

It has been shown that Bionics prostheses compare very favorably with bioprostheses based on rigid supporting frameworks. The advantages of the above prostheses lie in the fact that the supporting frameworks of changed stiffness used in their modelling possess damping capacities at minute physical loadings, which considerably improves the hydrodynamic characteristics of biovalves.

Animals↗
PubMedDate not supplied

[Hydrodynamic and optical behavior of DNA molecule in the range of high ionic strength].

The hydrodynamic and optical properties (intrinsic viscosity and optical anisotropy of DNA) have been studied at the high ionic strength mu greater than or equal to 1 M. It has been shown that the effective volume of DNA molecule doesn't depend of mu when mu greater than or equal to 1 M. In these conditions the electrostatical interactions in DNA disappear. But thermodynamic excluded volume effects do not depend on mu and play also an important role in this range of mu (mu greater than or equal to 1 M). It has been concluded that the condensation of DNA in solutions of high salt concentration is the result of local denaturation of DNA. It has been shown that the optical anisotropy of DNA increases drastically at mu congruent to 2 M but the persistence length of DNA does not change under these conditions.

DNA↗