Search results for "Viscosity."

Dynamic anomalies at the glass transition of organic van der Waals liquids

1993

Abstract The paper discusses the question of whether there is a characteristic temperature T c above the calorimetric glass transition temperature T g . Mode-coupling theory (MCT) predicts a crossover from liquid- to solid-like dynamics at T c . Neutron scattering and gradient NMR experiments have been carried out to test MCT using the molecular van der Waals liquid ortho -terphenyl as a model system. A significant anomaly of the Debye—Waller factor and a “decoupling” of self-diffusion from viscosity support the MCT predictions. A critical discussion of the relevance of such tests and of the limitations of neutron scattering is presented.

Gelation of smectic liquid crystal phases with photosensitive gel forming agents.

2020

This paper studies the potential of 3 newly synthesized low molecular weight gelling agents (2 of them with azo groups) with the semicarbazide group as a H-bonding motif to gel the smectic phase of a commercial chiral smectic C material. To detect gelation two methods were used: the stabilization of the director pattern, which measures the interaction of the physical gel network with the LC-director, and the suppression of the onset of electrohydrodynamic instabilities, which measures the increase of viscosity. Special emphasis was put on the influence of the photochemical - isomerization of the gelling agents on gelation.From the stabilization of the director pattern an elastic component c…

Power Consumption in Uncovered Unbaffled Stirred Tanks: Influence of the Viscosity and Flow Regime

2013

Notwithstanding the increasing industrial interest toward unbaffled tanks, available experimental information on their behavior is still scant, even for basic quantities such as the mechanical power drawn. In this work, the influence of the Reynolds and Froude numbers on the power consumption characteristics is presented for unbaffled stirred tanks operating both in nonaerated conditions (subcritical regime) and in aerated conditions (supercritical regime), i.e., when the free surface vortex has reached the impeller and the gas phase is ingested and dispersed inside the reactor. Experimental results obtained at various liquid viscosities show that power numbers obtained in subcritical condi…

MR2410211 (2009b:47107) Păcurar, Mădălina Viscosity approximation of fixed points with $\phi$-contractions. Carpathian J. Math. 24 (2008), no. 1, 88-…

2009

Let T be a nonexpansive self-mapping of a closed bounded convex subset Y of a Hilbert space. For l in (0, 1), the author considers the iteration xl = lf(xl)+(1−l)Txl, where f from Y to Y is a $\phi$-contraction. Then, the author proves that (xl)l converges strongly as l goes to 0 to the unique fixed point of the $\phi$-contraction Pof, where P is the metric projection of Y onto the set FT of fixed points of T. The viscosity approximation method of the paper is obtained from the method proposed by A. Moudafi [J. Math. Anal. Appl. 241 (2000), no. 1, 46–55; MR1738332 (2000k:47085)] for mappings in Hilbert spaces, and by H. K. Xu [J. Math. Anal. Appl. 298 (2004), no. 1, 279–291; MR2086546 (2005…

Techniques to evaluate erythrocyte deformability in diabetes mellitus

2005

Using several rheological techniques, we examined the erythrocyte deformability in different groups of diabetic subjects. The macrorheological techniques used for this evaluation were respectively whole-blood filtration, filtration of erythrocyte suspensions, polyviscosimetry and diffractometry. Whole-blood filterability, at a negative pressure of 20 cm water, was decreased in type 2 diabetics; no difference was evident at a negative pressure of 10 cm water. The filtration of erythrocyte suspensions at low haematocrit (5%) did not show differences between normal and diabetic subjects. The polyviscosimetry, which explores the filterability of erythrocyte suspensions at high haematocrit (80%)…

Healon®5: A New Viscoadaptive Formulation

2000

To relate the practical relevance of our study results, specific requirement profiles for individual procedures have been correlated to the desired physicochemical characteristics. Healon®5 demonstrated the statistically significant highest zero shear viscosity of all OVD and a long relaxation time (Dick et al., 2000). It therefore most effectively creates and maintains a deep anterior chamber in order to facilitate safe surgical maneuvers (e.g., in case of vitreous pressure). Additionally, the high viscosity of Healon®5 exhibits a dynamic frequency dependence, which has not been observed in any pure hyaluronic acid formulation before. Healon®5’s properties change in response to surgical ma…

Rheological Characterization of Low-calorie Milk-based Salad Dressings

1992

Oil-in-water emulsions of different quantitative composition, containing milk powder and locust bean gum. as stabilizing agents, showed similar rheological behavior: time-dependent thixotropic character and yield stress. Thixograms obtained for each sample could be modelled through the Hahn equation for the different shear rates. The analysis of the Hahn parameter variation for each sample as a function of shear rate led to a function σ= f(γ, t). Predicted shear stress values had relative errors lower than 10% in 99.9% of the samples studied. Analysis of composition influence on the rheological parameters showed an interactive role of gum, milk and acetic acid concentrations on emulsion con…

Do we understand the solid-like elastic properties of confined liquids?

2021

Recently, in polymeric liquids, unexpected solid-like shear elasticity has been discovered, which gave rise to a controversial discussion about its origin (1⇓–3). The observed solid-like shear modulus G depends strongly on the distance L between the plates of the rheometer according to a power law G ∝ L − p with a nonuniversal exponent ranging between p = 2 and p = 3 . Zaccone and Trachenko (4) have published an article in which they claim to explain these findings by a nonaffine contribution to the liquid shear modulus. The latter is represented as Δ G ∝ − ∑ λ = L , T 1 V … [↵][1]1To whom correspondence may be addressed. Email: giancarlo.ruocco{at}roma1.infn.it. [1]: #xref-corresp-1-1

Publisher's Note: "Thermodynamic formalism for transport coefficients with an application to the shear modulus and shear viscosity" [J. Chem. Phys. 1…

2017

Rheological studies of moderately concentrated polystyrene solutions. I. A new method for the extrapolation of the zero-shear viscosity

1983

Measurements of the viscosity coefficient η of solutions of polystyrene (Mw = 6.0 × 105 and 1.77 × 106) in trans-decalin (TD, θ solvent) and toluene (TL, good solvent) as function of shear rate (11−104 s−1), concentration (4.24−11.21 wt %), and temperature (10–50°C) are reported. As a new theoretically grounded method for the determination of the zero-shear viscosity η0 it is proposed to plot η as a function of . The intercepts of the straight lines obtained by this procedure give η0 in good agreement with directly measured values.