520 research outputs found
Direct contact and authoritarianism as moderators between extended contact and reduced prejudice: Lower threat and greater trust as mediators
Using a representative sample of Dutch adults (N = 1238), we investigated the moderating influence of direct contact and authoritarianism on the potential of extended contact to reduce prejudice. As expected, direct contact and authoritarianism moderated the effect of extended contact on prejudice. Moreover, the third-order moderation effect was also significant, revealing that extended contact has the strongest effect among high authoritarians with low levels of direct contact. We identified trust and perceived threat as the mediating processes underlying these moderation effects. The present study thus attests to the theoretical and practical relevance of reducing prejudice via extended contact. The discussion focuses on the role of extended contact in relation to direct contact and authoritarianism as well as on the importance of trust in intergroup contexts
Concentration Dependen Sedimentation of Collidal Rods
In the first part of this paper, an approximate theory is developed for the
leading order concentration dependence of the sedimentation coefficient for
rod-like colloids/polymers/macromolecules. To first order in volume fraction
of rods, the sedimentation coefficient is written as .
For large aspect ratio L/D (L is the rod length, D it's thickness) is
found to very like . This
theoretical prediction is compared to experimental results. In the second part,
experiments on {\it fd}-virus are described, both in the isotropic and nematic
phase. First order in concentration results for this very long and thin
(semi-flexible) rod are in agreement with the above theoretical prediction.
Sedimentation profiles for the nematic phase show two sedimentation fronts.
This result indicates that the nematic phase becomes unstable with the respect
to isotropic phase during sedimentation.Comment: Submitted to J. Chem. Phys. See related webpage
http://www.elsie.brandeis.ed
Density profiles of a colloidal liquid at a wall under shear flow
Using a dynamical density functional theory we analyze the density profile of
a colloidal liquid near a wall under shear flow. Due to the symmetries of the
system considered, the naive application of dynamical density functional theory
does not lead to a shear induced modification of the equilibrium density
profile, which would be expected on physical grounds. By introducing a
physically motivated dynamic mean field correction we incorporate the missing
shear induced interparticle forces into the theory. We find that the shear flow
tends to enhance the oscillations in the density profile of hard-spheres at a
hard-wall and, at sufficiently high shear rates, induces a nonequilibrium
transition to a steady state characterized by planes of particles parallel to
the wall. Under gravity, we find that the center-of-mass of the density
distribution increases with shear rate, i.e., shear increases the potential
energy of the particles
Influence of different yeast cell-wall mutants on performance and protection against pathogenic bacteria (<i>Vibrio campbellii</i>) in gnotobiotically-grown <i>Artemia</i>
A selection of isogenic yeast strains (with deletion for genes involved in cell-wall synthesis) was used to evaluate their nutritional and immunostimulatory characteristics for gnotobiotically-grown Artemia. In the first set of experiments the nutritional value of isogenic yeast strains (effected in mannoproteins, glucan, chitin and cell-wall bound protein synthesis) for gnotobiotically-grown Artemia was studied. Yeast cell-wall mutants were always better feed for Artemia than the isogenic wild type mainly because they supported a higher survival but not a stronger individual growth. The difference in Artemia performance between WT and mutants feeding was reduced when stationary-phase grown cells were used. These results suggest that any mutation affecting the yeast cell-wall make-up is sufficient to improve the digestibility in Artemia. The second set of experiments, investigates the use of a small amount of yeast cells in gnotobiotic Artemia to overcome pathogenicity of Vibrio campbellii (VC). Among all yeast cell strains used in this study, only mnn9 yeast (less cell-wall bound mannoproteins and more glucan and chitin) seems to completely protect Artemia against the pathogen. Incomplete protection against the pathogen was obtained by the gas1 and chs3 mutants, which are lacking the gene for a particular cell-wall protein and chitin synthesis, respectively, resulting in more glucan. The result with the chs3 mutant is of particular interest, as its nutritional value for Artemia is comparable to the wild type. Hence, only with the chs3 strain, in contrast to the gas1 or mnn9 strains, the temporary protection to VC is not concomitant with a better growth performance under non-challenged conditions, suggesting non-interference of general nutritional effects
Kinetic pathways of the Nematic-Isotropic phase transition as studied by confocal microscopy on rod-like viruses
We investigate the kinetics of phase separation for a mixture of rodlike
viruses (fd) and polymer (dextran), which effectively constitutes a system of
attractive rods. This dispersion is quenched from a flow-induced fully nematic
state into the region where the nematic and the isotropic phase coexist. We
show experimental evidence that the kinetic pathway depends on the overall
concentration. When the quench is made at high concentrations, the system is
meta-stable and we observe typical nucleation-and-growth. For quenches at low
concentration the system is unstable and the system undergoes a spinodal
decomposition. At intermediate concentrations we see the transition between
both demixing processes, where we locate the spinodal point.Comment: 11 pages, 6 figures, accepted in J. Phys.: Condens. Matter as
symposium paper for the 6th Liquid Matter Conference in Utrech
Colloid-colloid and colloid-wall interactions in driven suspensions
We investigate the non-equilibrium fluid structure mediated forces between
two colloids driven through a suspension of mutually non-interacting Brownian
particles as well as between a colloid and a wall in stationary situations. We
solve the Smoluchowski equation in bispherical coordinates as well as with a
method of reflections, both in linear approximation for small velocities and
numerically for intermediate velocities, and we compare the results to a
superposition approximation considered previously. In particular we find an
enhancement of the friction (compared to the friction on an isolated particle)
for two colloids driven side by side as well as for a colloid traveling along a
wall. The friction on tailgating colloids is reduced. Colloids traveling side
by side experience a solute induced repulsion while tailgating colloids are
attracted to each other.Comment: 8 Pages, 8 figure
Substrate concentration dependence of the diffusion-controlled steady-state rate constant
The Smoluchowski approach to diffusion-controlled reactions is generalized to
interacting substrate particles by including the osmotic pressure and
hydrodynamic interactions of the nonideal particles in the Smoluchoswki
equation within a local-density approximation. By solving the strictly
linearized equation for the time-independent case with absorbing boundary
conditions, we present an analytic expression for the diffusion-limited
steady-state rate constant for small substrate concentrations in terms of an
effective second virial coefficient B_2*. Comparisons to Brownian dynamics
simulations excluding HI show excellent agreement up to bulk number densities
of B_2* rho_0 < 0.4 for hard sphere and repulsive Yukawa-like interactions
between the substrates. Our study provides an alternative way to determine the
second virial coefficient of interacting macromolecules experimentally by
measuring their steady-state rate constant in diffusion-controlled reactions at
low densities.Comment: 7 pages, 3 figure
Is sexism a gender issue? A motivated social cognition perspective on menâs and womenâs sexist attitudes toward own and other gender
The present research investigated the antecedents of ambivalent sexism (i.e., hostile and benevolent forms) in both men and women toward own and other gender. In two heterogeneous adult samples (Study 1: N = 179 and Study 2: N = 222), it as revealed that gender itself was only a minor predictor of sexist attitudes compared to the substantial impact of individual differences in general motivated cognition (i.e., Need for closure). Analyses further showed that the relationship between Need for closure and sexism was mediated by social attitudes (i.e., right-wing authoritarianism and social dominance orientation), which were differently related to benevolent and hostile forms of sexism. In the discussion it is argued that sexism primarily stems from individual differences in motivated cognitive style, which relates to peoples? perspective on the social world, rather than from group differences between men and women
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