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PubMedDate not supplied

[Blood viscosity and the erythrocyte charge in patients with chronic kidney failure and suppurative intoxication and during the correction of these conditions by hemosorption and hemodialysis].

Examinations of blood samples from healthy subjects and 16 patients suffering from chronic renal failure and purulent intoxication before and after hemodialysis and hemosorption showed changes in blood viscosity and red cell charges in the patients. Blood viscosity diminished following both hemodialysis and hemosorption, whereas red cell electric charge grew after hemodialysis, but fell after hemosorption. Correlations found between the viscosity, red cell charge and concentrations of urea and creatinine suggest a dependence of blood rheology and red cell surface electrostatic properties on azotemic intoxication. Thus, hemodialysis and hemosorption produce diverse effects on physiochemical characteristics of blood.

Adult↗
PubMed1996

The influence of ageing on oesophageal motility after ingestion of liquids with different viscosities.

OBJECTIVES: To verify the influence of ageing on oesophageal motility elicited by the swallowing of liquids with different viscosities. DESIGN: In order to study the effect of ageing on oesophageal function, healthy volunteers of three age groups were studied by manometric and scintigraphic methods during the swallowing of water and a high viscosity liquid. METHODS: Forty healthy volunteers (20 aged 20 to 30 years, 10 aged 50 to 60 years and 10 aged 70 to 80 years) were submitted to oesophageal manometry during 10 swallows of water, 10 swallows of sugar cane syrup and 10 "dry' swallows. Basal pressure of the upper oesophageal sphincter and the lower oesophageal sphincter, amplitude, duration and velocity of contraction and the duration of the lower oesophageal sphincter relaxation were measured. Morphology and peristalsis of contractile waves were studied. The same volunteers underwent scintigraphic oesophageal transit studies with the same boluses. Oesophageal clearance time and patterns of transit were studied. RESULTS: Water and sugar cane syrup did not differ as to quantitative contraction parameters, but sugar cane syrup led to a higher incidence of synchronous contractions. The three age groups had similar amplitude and velocity of contractile waves. The youngest group had shorter duration of contractile waves 10 and 5 cm above the lower oesophageal sphincter. The oldest group had markedly more frequent synchronous contractions and failures of contraction after both water and sugar cane syrup swallows. This was associated with a high incidence of scintigraphic transit abnormalities in this group. CONCLUSION: Abnormal oesophageal peristalsis and incomplete oesophageal emptying of both low and high viscosity liquids are significantly more frequent in healthy elderly persons than in younger persons.

Adult↗
PubMedDate not supplied

The effects of varied etching time and etching solution viscosity on bond strength and enamel morphology.

The effects of varied etching time and etching solution viscosity on bond strength were evaluated by measuring the tensile bond strength of a composite resin to bovine enamel. Also, six enamel surfaces were examined to evaluate the effect of acid treatment on the morphology of etched enamel using scanning electron microscopy. There was no significant difference in tensile bond strength between three etchants of differing viscosity or between etch times. Light microscopy revealed that most bond failures were cohesive in nature. When the three etchants of differing viscosity were compared under the scanning electron microscope, the liquid and the thin gel produced a more even etch pattern than the thick gel. In addition, the thin gel appeared to produce the most well-defined pattern of the three conditioners.

Acid Etching, Dental↗
PubMed1977

[Blood and plasma viscosity during the various phases of the acute myocardial infarction (AMI). Preliminary study (author's transl)].

In a group of 29 infarct cases, the behaviour of the same blood and plasma viscosity at the initial stage and two weeks after the AMI was. At the same time as the rheological tests, we evaluated a few parameters of the lipid (cholesterol-triglyceride), proteic (fibrinogen) and glycoproteic (haptogloben-alpha1 acid GP ceruloplasmin) balance. Though noting significant variations of all the parameters studied, the correlation between the viscosity of blood and plasm and the other humoral parameters is of little significance. In fact except for the good correlation between the blood viscosity with hematocrit and with the fibrinogen (only on 7th day and at high gradient) the other correlations, when present, are occasional or of little significance. It is our intention to continue the research undertaken, considering either the utility of the early diagnosis of a rheological change or the possibility that the latter may be a further parameter to be related to clinical, hemodynamic and humoral parameters useful for determining the prognosis of the AMI.

Acute Disease↗
PubMedDate not supplied

Comparative viscosity and erythrocytes disaggregation shear stress of blood-radiographic contrast media mixtures in three mammalian species.

We compared blood viscosity and red blood cells (RBC) disaggregation shear stress in three mammalian species (humans, pigs and sheep) before and after adding water-soluble iodinated contrast media (CM): Ioxaglate (ionic CM) and Iopromide (non ionic CM). The two CMs had a diluting effect on the blood of the three species, which resulted in a viscosity decrease at all shear rates. However, viscosity rose slightly at low shear rates (in relation to increase of RBC aggregation) and low CM concentrations (10%), regardless of the ionic or non ionic nature of the CM. The two CMs had a similar proaggregant effect in human and pig's bloods. The proaggregant effect was slightly more pronounced with the ionic CM. We concluded that the pig is more suitable than the sheep for in vivo assessment of blood/CM mixture.

Animals↗
PubMed1976

Pathological human synovial fluids. Viscosity and boundary lubricating properties.

On human synovial fluids obtained during operations from the knee joints of 80 patients with different joing disease, relative viscosity was measured at 3 different shear rates and the boundary lubrication was tested by the coefficient of friction in an artificial rubber/glass system. The results were evaluated in relation to the operative findings. The viscosity showed statistically significant differences between the synovial fluids from the knee joints with rheumatoid arthritis, osteoarthritis, and torn menisci, being lowest in rheumatoid synovial fluid and highest in synovial fluids from knee joints with torn menisci. Correlations were found in the variations in the viscosity and the degree of synovitis. The boundary lubrication also showed different values inrelation to the different diseases. Synovial fluid from knee joints with torn menisci seemed to act as the best lubricant and significantly better than rheumatoid synovial fluid. Variations in the boundary lubrications reflect successive degrees of cartilage degeneration.

Arthritis, Rheumatoid↗
PubMed1998

Plasma viscosity in nephrotic Nigerians.

A simple and reproducible 'syringe viscometer' method was used to determine plasma viscosity, an important haemorheological parameter, in 27 (14 M, 13 F) nephrotic Nigerian patients. The plasma fibrinogen (PFC) and immunoglobulin levels (IgG, IgM, IgA) were also determined in these patients. Similar determinations were carried out in 30 (15 M, 15 F) age- and sex-matched healthy control subjects for comparison. The nephrotic patients had significantly higher relative plasma viscosity (RPV), PFC and IgM levels (2.02+/-0.17 vs. 1.66+/-0.19, 6.48+/-2.59 vs. 2.26+/-0.91 g/l; 316.2+/-169.0 vs. 186.0+/-59.5 IU/ml, p < 0.001, respectively). However, IgG and IgA levels were significantly less (151.1+/-88.7 vs. 205.7+/-77.6 IU/ml, p < 0.05, and 95.8+/-41.5 vs. 127.3+/-31.3 IU/ml, p < 0.01, respectively). In the nephrotic patients, plasma fibrinogen and IgM levels had a significant positive correlation with RPV (r=0.444, p < 0.05, and r=0.452, p < 0.02, respectively). The observed increased plasma viscosity in our nephrotic patients could on the long term predispose them to increased risk for cardiovascular morbidity.

Adolescent↗
PubMed2001

The cross-sectional study of the health effects of occupational exposure to carbon disulfide in a Chinese viscose plant.

This article presents results of carbon disulfide exposure assessment in a Chinese viscose rayon factory and represents the cross-sectional study beginning phase of the occupational epidemiological project. The authors measured external exposure levels to carbon disulfide at a Chinese viscose rayon factory and monitored results as internal exposure indexes by testing urine samples of workers exposed to carbon disulfide levels. The rate at which carbon disulfide is metabolized by exposed subjects was demonstrated by 2-thio-thiazolidine-4-carboxylic acid (TTCA) concentrations in urine of exposed subjects, which was studied to determine best time points for internal exposure sampling. Carbon disulfide concentrations in the air of the workplace were analyzed with gas chromatography with flame photometric detector (GC-FPD); presence of TTCA in urine samples of subjects was determined using a modified high-performance liquid chromatography method. Kinetics of TTCA excretion was studied by analysis at different time points during and after exposure of workers to carbon disulfide. A total of 155 personal samples were obtained. Carbon disulfide concentration at staple viscose hall was found to be 13.72 +/- 1.12 mg/m3 in terms of geometric mean and geometric standard deviation. Carbon disulfide concentration at filament spinning hall was found to be 20.05 +/- 1.33 mg/m3. TTCA values of subjects at staple spinning hall were 1.18 +/- 0.43 and 1.07 +/- 0.38 mg/g creatinine for subjects working at filament spinning hall. The best time for TTCA sampling is at the end of the exposure-working shift.

Adult↗
PubMed1999

Microstructure and Viscosity of Aggregating Colloids under Strong Shearing Force.

Disaggregation under strong shearing force is simulated for an aggregating colloid based on a sticky particle model which can describe the disaggregating and aggregating kinetics, the deformation, and the rupture of clusters with a minimum number of parameters. For a 2-dimensional system, the viscosity and coordination number of the model colloid are calculated at each time step, and the changes of microstructure with shear flow are observed directly by displaying the configuration of particles onto a monitor. The viscosity depends on both area fraction and shear rate, but coordination number depends only on shear rate. Furthermore, the viscosity and coordination number at steady state are independent of the initial state of particles, which indicates that the disaggregation and aggregation are mutually reversible. Copyright 1999 Academic Press.

Journal Article↗
PubMed1987

The kinetics of the aerobic oxidation of ferrocytochrome c by cytochrome c oxidase in solvents of increased viscosity are partially diffusion controlled.

The steady-state spectrophotometrically determined initial velocity kinetics of the aerobic oxidation of ferrocytochrome c by cytochrome c oxidase were examined for effects of diffusion control in solvents of increased viscosity. Both glycerol/water and sucrose/water proved unsatisfactory as viscosogens due to weak competitive inhibition (Ki values of 2.6 M and 1.6 M, respectively). However, polyethylene glycol (PEG) was satisfactory as a viscosogen. The measured diffusion coefficient of ferrocytochrome c in PEG/water was shown to follow closely the Stokes-Einstein equation. In PEG/water mixtures at high ionic strength the minimum association rate constant (kmin = Vmax/(Km[EO]) is partly diffusion controlled with contributions from diffusion control and chemical activation control being about equal at 5 mPa X s, a viscosity that may be physiologically relevant. This finding can be interpreted to mean that cytochrome c oxidase is an enzyme that has evolved to approach its maximum efficiency. The steady-state kinetics were also examined at low ionic strength where multiphasic kinetics are exhibited. The effect of increased viscosity was exhibited over the whole experimentally accessible region indicating that there are effects due to diffusion control on both the high-affinity and low-affinity binding of ferrocytochrome c. Several models for diffusion control were examined and a comparison is made with other diffusion-controlled reactions of proteins.

Aerobiosis↗
PubMed2003

Size distribution of colloidal silica in sodium silicate solutions investigated by dynamic light scattering and viscosity measurements.

Three types of aqueous sodium silicate solutions characterized by molar SiO(2):Na(2)O ratios of 2.2, 3.3, and 3.9 were investigated by dynamic light scattering and viscosity measurements. The solutions were prepared by diluting concentrated commercial products to SiO(2) content between 0.5 and 15 wt%. Dynamic light scattering (DLS) was used for the investigation of size distributions of colloids immediately after dilution. At least three size classes of colloidal particles were detected, which exist in parallel in the solutions. The respective radii are 0.4 to 0.6 nm, 2.5 to 13 nm, and 75 to 85 nm. The larger colloids dominate the mass distribution, whereas the smaller colloids control the surface area of the colloidal fraction. Material properties such as pH, viscosity, refractive index, and density were measured as a function of dilution. The evaluation of the viscosity data indicated that the colloids have a lower density than dense amorphous silica. Aging effects could be suppressed by measuring within 1 h after dilution.

Journal Article↗
PubMed2003

Shear rate and viscosity corrections for a Casson fluid in cylindrical (Couette) geometries.

Shear rate and viscosity correction factors for a Casson fluid in cylindrical (Couette) geometries--type I, concentric cylinder with a narrow gap, and type II, cylinder in a semi-infinite medium--are developed in this work. The analytical correction factors compare well with published data corrected by general methods. Corrected viscosities were also compared to viscosity-shear rate data on chocolate in an absolute viscometer (cone-and-plate), which requires no corrections. This comparison showed excellent agreement of the corrected data in the higher shear rate range, but not very good agreement in the lower shear rate range. Reasons for this are discussed. In addition, a Reiner-Riwlin type formulation was developed for determination of model constants directly from rotational viscometry data without the need to correct for non-Newtonian shear rate, but this method is less accurate than existing slope-intercept methods for determining model constants. The analytical correction procedure developed here is expected to be useful wherever the Casson model is used to describe the rheology of a fluid, particularly one exhibiting yield-stress pseudoplastic behavior.

Journal Article↗
PubMed2004

Structure of colloid silica determined by viscosity measurements.

The viscosity of nanosized colloid silica suspensions, used as binders in the investment casting, was determined as a function of their weight fraction reaching 52%. A new capillary viscometer was used whose construction eliminated sedimentation effects. The experiments have been carried out at fixed pH 10.0 and controlled ionic strength. It was found that for a low silica concentration range (weight fraction below 5%) the suspension viscosity increased more rapidly than the Einstein theory predicts. This anomalous behavior could not be explained in terms of the primary electroviscous effect predicted to be a few orders of magnitude smaller as observed. This discrepancy was accounted for by postulating a fuzzy, gel-like structure of colloid silicas used in our experiments. Hence, the apparent hydrodynamic radius of silica particles in aqueous suspensions was found to be larger than the primary particle size in accordance with previous observations. Based on this postulate, an apparent density of the silica sols was found to be 1.32-1.37 g/cm(3) instead of 2.2-2.32 g/cm(3) as determined from the suspension dilution method. This behavior was interpreted in terms of the core/shell model with high shell porosity, reaching 85%. Similarly, for higher concentration ranges, silica viscosity increased more rapidly with increased sol concentration than predicted by the Batchelor model derived for hard particles. The deviation was attributed to the secondary electroviscous effect stemming from the electrostatic interactions among silica particles in sheared suspensions. This effect has quantitatively been interpreted in terms of Russel's theory. On the other hand, for the high concentration range the experimental results were well accounted for by the Dougherty-Krieger model. By exploiting our experimental findings a sensitive method of determining the structure and apparent density of silica sols in aqueous media was proposed.

Journal Article↗
PubMed2005

Comparison between theoretical values and simulation results of viscosity for the dissipative particle dynamics method.

In order to investigate the validity of the dissipative particle dynamics method, which is a mesoscopic simulation technique, we have derived an expression for viscosity from the equation of motion of dissipative particles. In the concrete, we have shown the Fokker-Planck equation in phase space, and macroscopic conservation equations such as the equation of continuity and the equation of momentum conservation. The basic equations of the single-particle and pair distribution functions have been derived using the Fokker-Planck equation. The solutions of these distribution functions have approximately been solved by the perturbation method under the assumption of molecular chaos. The expressions of the viscosity due to momentum and dissipative forces have been obtained using the approximate solutions of the distribution functions. Also, we have conducted nonequilibrium dynamics simulations to investigate the influence of the parameters, which have appeared in defining the equation of motion in the dissipative particle dynamics method. The theoretical values of the viscosity due to dissipative forces in the Hoogerbrugge-Koelman theory are in good agreement with the simulation results obtained by the nonequilibrium dynamics method, except in the range of small number densities. There are restriction conditions for taking appropriate values of the number density, number of particles, time interval, shear rate, etc., to obtain physically reasonable results by means of dissipative particle dynamics simulations.

Journal Article↗
PubMed2006

Intrinsic viscosity of SiO2, Al2O3 and TiO2 aqueous suspensions.

The viscosity of dilute suspensions of several metal oxides (SiO2, Al2O3 and TiO2) was measured at different pH values. The intrinsic viscosity, [eta], was derived from the concentration dependence of the viscosity. This magnitude was pH-dependent. A correlation with the shape of the kinetic unity has been proposed.

Journal Article↗
PubMed2006

Measurement of the viscosity-density product using multiple reflections of ultrasonic shear horizontal waves.

We have developed an on-line computer-controlled sensor, based on ultrasound reflection measurements, to determine the product of the viscosity and density of a liquid or slurry for Newtonian fluids and the shear impedance of the liquid for non-Newtonian fluids. A 14 MHz shear wave transducer is bonded to one side of a 45-90 degrees fused silica wedge and the base is in contract with the liquid. Twenty-eight echoes were observed due to the multiple reflections of an ultrasonic shear horizontal (SH) wave within the wedge. The fast Fourier transform of each echo was obtained for a liquid and for water, which serves as the calibration fluid, and the reflection coefficient at the solid-liquid interface was obtained. Data were obtained for 11 sugar water solutions ranging in concentration from 10% to 66% by weight. The viscosity values are shown to be in good agreement with those obtained independently using a laboratory viscometer. The data acquisition time is 14s and this can be reduced by judicious selection of the echoes for determining the reflection coefficient. The measurement of the density results in a determination of the viscosity for Newtonian fluids or the shear wave velocity for non-Newtonian fluids. The sensor can be deployed for process control in a pipeline, with the base of the wedge as part of the pipeline wall, or immersed in a tank.

Journal Article↗
PubMed2003

Viscosity of emulsions: influence of flocculation.

A model has been suggested by Raijinder Pal (J. Colloid Interface Sci. 231 (2000) 168) that describes experimental data on the viscosity of concentrated emulsions reasonably well. To deduce the final equation the author assumed that droplets are covered with a layer of surfactant molecules. This means that the effective volume of a single emulsion droplet is increased by a factor K>1. It has been found that K should vary between 1.166 and 2.070 to fit the experimental data. If the drop radii are around 1 microm (for an estimate) then the drops would be covered with a layer which thickness should range from 550 A (which is 10 times of the size of SDS micelles) to 3570 A. No doubt adsorption of surfactant molecules results in an increase of the effective drop radius but not by that much. We present an alternative theoretical model for description of the viscosity-volume fraction of droplets behavior of emulsions. The model is based on the assumption that clusters of drops (doublets, triplets, and so on) are formed under the influence of colloidal, hydrodynamic interactions and/or applied shear. According to the proposed model clustering determines the volume fraction dependency of the effective viscosity of emulsions. Two limiting cases are considered: a developed flocculation and a low-flocculated emulsion. In the first case the final equation is close to that deduced by Pal; however, the physical meaning of the equation is substantially different. Comparison with available experimental data shows good agreement with the equations deduced in both the cases of a developed flocculation and a low-flocculated emulsion.

Journal Article↗
PubMed2003

Effect of salts on water viscosity in narrow membrane pores.

The effect of various salts on the viscosity, and by implication structure, of water in polymeric membrane pores of radius approximately 1.69 nm and low charge density has been studied. Permeation of pure water and various electrolyte solutions was analyzed using the Hagen-Poiseuille equation expressed in a ratio form to exclude membrane-specific quantities such as pore radius and length. The analysis produced viscosity ratios of electrolyte to pure water inside the membrane pores. Comparing the viscosity ratios inside the pores with their bulk counterparts showed that confinement significantly increased the sensitivity of water structure to the presence of ions. It has been found that, in relative terms in the pores, Cl- was a strong structure breaker, K+ was a moderately strong structure breaker, Na+ was a weak structure breaker, SO4(2-) was a weak structure maker, and Mg2+ was a strong structure maker. Predictive modeling of membrane separation performance would benefit from such effects being taken into account in cases where the pore ion concentrations may be high.

Journal Article↗