Search results for " viscosity"

Formation of Levan from Raffinose by Levansucrase ofZymomonas mobilis

2004

Levansucrase (EC 2.4.1.10.) of Zymomonas mobilis 113S can perform the polymerisation of fructose moiety from raffinose to levan concomitantly with a release of non-catabolised melibiose into the medium. The kinetic parameters of the levansucrase-catalysed reaction provide even higher reaction velocities on raffinose as compared to sucrose, particularly at low substrate concentrations. A decreased value in the number of the average molecular mass (Mn = 1693 kDa), an increased intrinsic viscosity (η = 49.47 cm3/g), and a diminished Huggin's constant (K' = 0.67) are intrinsic to the levan synthesis from raffinose, indicating certain structural peculiarities compared to a polysaccharide obtaine…

Dynamic evaluation of aggregation and agglutination of red blood cells.

1984

Viscoelastic evaluation of aggregation and agglutination of red blood cells was attempted. A concentric double cylinder viscoelastometer was used for determining the dynamic rigidity modulus and loss modulus of blood sample. The dynamic rigidity modulus of horse blood were measured over a wide range of hematocrit. The relation between the viscoelastic behavior and the erythrocyte sedimentation was examined. The change in the amount of surface charge of enzyme treated red blood cells was qualitatively estimated from the measurements of dynamic viscoelasticity of red blood cells suspension with added poly-L-lysine. The dynamic rigidity modulus of red blood cells agglutinated by adding lectin …

Red Cell Membrane Protein Lateral Mobility in Vascular Atherosclerotic Disease: Preliminary Report

1993

Rheological blood behaviour is not related to gender in morbidly obese subjects.

2012

To the Editor. We have read with interest the recently published article by Wiewiora et al. [7] regarding hemorheological differences related to gender in morbidly obese subjects. In this study authors found several hemorheological differences between male and female. In this sense, males showed higher blood viscosity and higher erythrocyte deformability than females and native blood viscosity correlated with several erythrocyte aggregation parameters evaluated with the Laser-Assisted Optical Rotational Cell Analyser (LORCA) [3]. In studies with small sample sizes (18 men and 20 women) there is always the risk that differences in certain variables may appear by chance or by imbalances in th…

Comparison between whole blood viscosity measured and calculated in subjects with monoclonal gammopathy of undetermined significance and in patients …

2021

BACKGROUND: in this study, with a re-evaluation of the hemorheological determinants previously described in MGUS subjects and in MM patients, we have detected the calculated whole blood viscosity, according whether to the hematocrit and total plasma protein concentration (de Simone formula) or to the haematocrit and plasma fibrinogen level (Merrill formula), and a marker of the erythrocyte aggregation (albumin/fibrinogen level). METHODS: data were expressed as means±standard deviation. Student’s t test for unpaired data was used to compare MGUS subjects and MM patients. The correlation coefficient between mean erythrocyte aggregation (MEA) and hematocrit (Ht) was evaluated in MGUS, MM and M…

Blood rheology at term in normal pregnancy and in patients with adverse outcome events.

2009

Plasma volume expansion of more than 1.5 1 and sustainable activation of the hemostatic system that results in a steady rise of the fibrinogen/fibrin turnover are contemporary physiological events during normal pregnancy. In contrast, adverse outcome of pregnancy i.e. pre-eclampsia commonly coincide with hemo concentration and over activation of blood coagulation both of which alter blood rheology. On the basis of 4,985 consecutively recorded singleton pregnancies values range of blood rheological parameters in women with normal and complicated outcome of pregnancy at the time of their delivery were compared. Plasma viscosity (pv) was determined using KSPV 1 Fresenius and RBC aggregation (s…

Objective function design for robust optimality of linear control under state-constraints and uncertainty

2009

We consider a model for the control of a linear network flow system with unknown but bounded demand and polytopic bounds on controlled flows. We are interested in the problem of finding a suitable objective function that makes robust optimal the policy represented by the so-called linear saturated feedback control. We regard the problem as a suitable differential game with switching cost and study it in the framework of the viscosity solutions theory for Bellman and Isaacs equations. © 2009 EDP Sciences, SMAI.

The capillary waves' contribution to wind-wave generation

2022

Published theories and observations have shown that dissipation of gravity waves implies frequency downshifting of wave energy. Hence, for wind-waves, the wind energy input to the highest frequencies is of special interest. Here it is shown that this input is vital, because the direct wind energy input obtained by the air-pressure’s work on most gravity waves is slightly less than what the waves need to grow. Further, the wind’s input of the angular momentum that waves need to grow is found to be absent at most gravity wave frequencies. The capillary waves that appear at the surface of the sea when the wind is blowing solve these problems. To demonstrate this, an extension of linear wave th…

Viscosity Arrhenius parameters correlation: extension from pure to binary fluid mixtures

2015

Knowledge of fluids’ physicochemical properties is mandatory for the design and optimisation of industrial processes and products. A data quantity of most importance, in this regard, turns out to be the value of fluid viscosity. Many empirical and semi-empirical formulas have been proposed in the literature to describe the viscosity of pure liquids and binary liquid mixtures. Recently, an interesting equation is proposed for pure solvents correlating the two parameters in the viscosity Arrhenius-type equation, namely the activation energy (Ea) and the pre-exponential factor (As). This paper aims to extend the said correlation to binary liquid mixtures. To achieve this purpose, statistical m…

Solution properties of polyelectrolytes. III. Effect of sodium polystyrene sulfonate concentration on viscometric and size exclusion chromatographic …

1988

The effect of sodium polystyrene sulfonate concentration on the shape of its molecules in aqueous solution at different NaNO3 ionic strengths has been analyzed by viscometry and size-exclusion chromatography (s.e.c). An equation has been developed which predicts the intrinsic viscosity, [η] p.cp.cs, at finite concentration of both polyion (cp) and electrolyte (cs). The experimental results obtained by both techniques can be accounted for in terms of the theory. Several factors involved in the elution mechanism have been considered and the variation of the slopes of s.e.c. calibration curves with cp and cs has been discussed in terms of polyion conformation changes.