8,502 research outputs found
Local transient rheological behavior of concentrated suspensions
This paper reports experiments on the shear transient response of
concentrated non-Brownian suspensions. The shear viscosity of the suspensions
is measured using a wide-gap Couette rheometer equipped with a Particle Image
Velocimetry (PIV) device that allows measuring the velocity field. The
suspensions made of PMMA particles (31m in diameter) suspended in a
Newtonian index- and density-matched liquid are transparent enough to allow an
accurate measurement of the local velocity for particle concentrations as high
as 50%. In the wide-gap Couette cell, the shear induced particle migration is
evidenced by the measurement of the time evolution of the flow profile. A
peculiar radial zone in the gap is identified where the viscosity remains
constant. At this special location, the local particle volume fraction is taken
to be the mean particle concentration. The local shear transient response of
the suspensions when the shear flow is reversed is measured at this point where
the particle volume fraction is well defined. The local rheological
measurements presented here confirm the macroscopic measurements of
Gadala-Maria and Acrivos (1980). After shear reversal, the viscosity undergoes
a step-like reduction, decreases slower and passes through a minimum before
increasing again to reach a plateau. Upon varying the particle concentration,
we have been able to show that the minimum and the plateau viscosities do not
obey the same scaling law with respect to the particle volume fraction. These
experimental results are consistent with the scaling predicted by Mills and
Snabre (2009) and with the results of numerical simulation performed on random
suspensions [Sierou and Brady (2001)]. The minimum seems to be associated with
the viscosity of an isotropic suspension, or at least of a suspension whose
particles do not interact through non-hydrodynamic forces, while the plateau
value would correspond to the viscosity of a suspension structured by the shear
where the non-hydrodynamic forces play a crucial role
On realizing diagrams of Pi-algebras
Given a diagram of Pi-algebras (graded groups equipped with an action of the
primary homotopy operations), we ask whether it can be realized as the homotopy
groups of a diagram of spaces. The answer given here is in the form of an
obstruction theory, of somewhat wider application, formulated in terms of
generalized Pi-algebras. This extends a program begun in [J. Pure Appl. Alg.
103 (1995) 167-188] and [Topology 43 (2004) 857-892] to study the realization
of a single Pi-algebra. In particular, we explicitly analyze the simple case of
a single map, and provide a detailed example, illustrating the connections to
higher homotopy operations.Comment: This is the version published by Algebraic & Geometric Topology on 21
June 200
JAPANESE DEMAND FOR WHEAT PROTEIN QUANTITY AND QUALITY
Ladd and Martin's hedonic pricing model is extended to include the interactive effect of noncontracted characteristics on the value of contracted characteristics. Marginal values of wheat protein in the Japanese import market are estimated using the interactive effects of noncontracted dough/flour characteristics typically proxied by protein. Protein value is linked positively to farinograph stability, a prime factor in blending different flours. Three high protein wheats maintained about the same marginal value of protein. The marginal value for the two low protein wheats appear more end-use dependant. They varied in a $2.00/ton range depending on protein absorption, stability, and extensibility.Demand and Price Analysis,
Higher homotopy operations and cohomology
We explain how higher homotopy operations, defined topologically, may be
identified under mild assumptions with (the last of) the Dwyer-Kan-Smith
cohomological obstructions to rectifying homotopy-commutative diagrams.Comment: 28 page
Nonlinear instability of density-independent orbital-free kinetic energy functionals
We study in this article the mathematical properties of a class of
orbital-free kinetic energy functionals. We prove that these models are
linearly stable but nonlinearly unstable, in the sense that the corresponding
kinetic energy functionals are not bounded from below. As a matter of
illustration, we provide an example of an electronic density of simple shape
the kinetic energy of which is negative.Comment: 14 pages, 1 figur
Alien Registration- Le Blanc, Arthur W. (Gorham, Cumberland County)
https://digitalmaine.com/alien_docs/31594/thumbnail.jp
Changing molecular epidemiology of methicillin-resistant Staphylococcus aureus in an Algerian hospital.
INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of both hospital- and community-acquired infections worldwide. However, data about the molecular epidemiology of MRSA in North Africa are still scarce.
METHODOLOGY: All MRSA isolates recovered between January 2006 and July 2011 from one Algerian hospital were genetically and phenotypically characterized.
RESULTS: The predominance of a European community-associated-MRSA (CA-MRSA) clone (ST80-SCCmec IV-PVL positive) was revealed by this analysis.
CONCLUSION: Our data suggest that a CA-MRSA clone recently invaded the hospital setting in Algiers and replaced a typical hospital-associated pandemic clone such as the Brazilian clone (ST239-SCCmec IIImercury-PVL negative)
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