Search results for "VISCOSITY"

1953

Sur une serie de palymethacrylates de methyl fractionnes des mesures de la diffusion lumineuse (en fonction de I'angle et de la longeur d'onde) on ete faites, puis la constante de diffusion, la constante de sedimentation dans I'ultrazentrifugeuse et la viscosite intrinshque [η] ont ete determines. Les poids moleculaires et les diametres des chaines souples sont en concordance d'apres ces methodes. La dependance des diametres des chaines sonples d,l du poids molkculaire est un peu plus forte que d'aprh la loi de Kuhn (dst ≃ M0.6). L'influence de cette decouverte sur la fonction de la diffusion lumineuse de mihe que sur l'equation de la viscosite de Kirkwood et Riseman est etudiee. Light-scat…

Plasma Viscosity and NLR in Young Subjects with Myocardial Infarction: Evaluation at the Initial Stage and at 3 and 12 Months

2018

In the “Sicilian study on juvenile myocardial infarction,” we had evaluated plasma viscosity (PV) and neutrophil/lymphocyte ratio (NLR) in patients with acute myocardial infarction (AMI) at the age of ⩽45 years. Now, we examined the relationship between these 2 parameters in 120 subjects (109 men and 11 women) aged ⩽45 years with recent AMI. The patients were classified according to the number of cardiovascular risk factors, the electrocardiographic criteria (ST-segment elevation myocardial infarction [STEMI] or non-ST-segment elevation myocardial infarction [NSTEMI]), and the extent of coronary stenosis, evaluated with coronary angiography. On fasting venous blood, we measured PV at the sh…

Characterization of blends of polypropylene with a semirigid liquid-crystal copolyester

1991

Abstract Blends with a liquid-crystal polymers (LCP) as one component show, in general, very interesting properties. Reduction of shear viscosity and improvement of mechanical properties are very remarkable. High melting temperatures and high costs of the LCP limit the use of these blends. A new class of thermotropic LCPs with flexible spaces, with relatively low melting temperatures, can overcome the first problem. In this work, rheological and mechanical properties of blends of polypropylene with low contents of this LCP are presented. Torque during extrusion and viscosity decrease with LCP content. Elastic modulus is remarkably increased when the LCP phase is oriented.

On the Measurements of Numerical Viscosity and Resistivity in Eulerian MHD Codes

2016

We propose a simple ansatz for estimating the value of the numerical resistivity and the numerical viscosity of any Eulerian MHD code. We test this ansatz with the help of simulations of the propagation of (magneto)sonic waves, Alfven waves, and the tearing mode instability using the MHD code Aenus. By comparing the simu- lation results with analytical solutions of the resistive-viscous MHD equations and an empirical ansatz for the growth rate of tearing modes we measure the numerical viscosity and resistivity of Aenus. The comparison shows that the fast-magnetosonic speed and wavelength are the characteristic velocity and length, respectively, of the aforementioned (relatively simple) syst…

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…

Solution properties of polyelectrolytes—V. Viscometric study of mixed polyanions in pure water

1990

Abstract A viscometric study of sodium polystyrene sulphonate (NaPSS) and sodium poly( l -glutamate) (NaPLG) in salt-free water has been carried out as a function of the total concentration, cm, and the concentration of one polyelectrolyte at fixed concentration of the other. The influences of the molecular weight and concentration are considered in order to establish the degree of compatibility. For the first time, an equation is proposed to define the reduced viscosity of the NaPSS + NaPLG mixture in water. The viscometric interaction parameter, Bm, taking into account the electrostatic and thermodynamic interactions between both polyions, is defined as a geometrical mean of the contribut…

Phase transitions in a colloidal dispersion flowing through a cylindrical capillary

2008

The flow of a charged-stabilized colloidal dispersion of crystalline equilibrium structure through a cylindrical capillary is investigated. The simultaneous existence of up to three differently ordered states is observed under conditions of stationary flow. The evolution of their concentric arrangement along the capillary is determined by Bragg microscopy. For sufficient low fluxes, stationary phase distributions are obtained. While the apparent viscosity is non-monotonous and non-Newtonian, the corresponding velocity profiles are found to be piecewise parabolic and are compatible to numerical calculations. Furthermore, we test the assumption of a constant yield stress determining the radia…

Toward more realistic viscosity measurements of tyre rubber–bitumen blends

2014

AbstractThe measurement of rheological properties of the tyre rubber bitumen blends is often challenging due to presence of suspended tyre rubber’s crumbs. Furthermore, the phase separation during the course of measurements makes the viscosity of these non-homogeneous blends difficult to ascertain. In this study, a new dual helical impeller was designed and manufactured to be used with a rotational viscometer in order to have a real-time control of the viscosity while performing a laboratory mixing of the blends. Layer based manufacturing techniques showed to be a convenient method to produce complex shaped impeller prototypes before manufacturing the more expensive stainless steel assembly…

Rigid Hyperbranched Polycarbonate Polyols from CO2 and Cyclohexene-Based Epoxides

2017

Hyperbranched, multifunctional polycarbonate polyols based on CO2, cyclohexene oxide (CHO), and the “inimer” (initiator–monomer) (4-hydroxymethyl)cyclohexene oxide (HCHO) were prepared in one-pot syntheses. The related linear poly(hydroxymethyl cyclohexene carbonate) structures based on protected HCHO and postpolymerization deprotection were also synthesized as model compounds. The content of hydroxyl functionalities was adjustable for both linear and hyperbranched terpolymer systems. All CO2/epoxide polymerizations were catalyzed by the (R,R)-(salcy)-Co(III)Cl complex. The polycarbonates obtained were comprehensively investigated using various 1D and 2D NMR techniques, SEC, FT-IR, UV–vis s…

Demixing of unsheared and sheared solutions of polystyrene in tert-butylacetate and the pressure influence on their flow behaviour

1979

For the system tert-butyl acetate/polystyrene (M= 670000) the phase separation behaviour (upper critical solution temperatures, upper critical solution pressures) is investigated by means of visual and turbidimetric cloud-point measurements and by viscometry. For near-critical concentrations the visually determined cloud-points are found at higher, for low concentrations at lower temperatures as compared with the turbidimetrically determined binodal temperature,Tbin Plots of the invers of the turbidity measured atTbin as a function of the polymer concentration,w2, yield a minimum from which the critical composition can be determined. The viscometrically obtained demixing points (break-down …