388 research outputs found
Rhythmic cluster generation in strongly driven colloidal dispersions
We study the response of a nematic colloidal dispersion of rods to a driven
probe particle which is dragged with high speed through the dispersion
perpendicular to the nematic director. In front of the dragged particle,
clusters of rods are generated which rhythmically grow and dissolve by
rotational motion. We find evidence for a mesoscopic cluster-cluster
correlation length, {\em independent} of the imposed drag speed. Our results
are based on non-equilibrium Brownian dynamics computer simulations and in line
with a dynamical scaling theory.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let
The Role of Intelligence in Mating: an Investigation of How Mating Intelligence Relates to Mate Selection and Mating-Relevant Constructs
Mating intelligence is a fairly new construct with only limited empirical examination. Yet, previous research has found important implications for the construct’s role in mating behavior. The present study sought to expand the existing body of research on mating intelligence by investigating its relationship with self-esteem, self-perceived attractiveness, and mate selection. A sample of 195 participants (83 males and 112 females) completed a survey that incorporated measures of mating intelligence, self-esteem, and self-perceived attractiveness. Additionally, participants were asked to choose between an attractive and unattractive mate to take out on a date. Significant positive relationships between mating intelligence, self-esteem, and self-perceived attractiveness were found for both sexes. For males, mating intelligence predicted self-esteem over and above selfperceived attractiveness. Both males and females with higher mating intelligence were more likely to select the attractive mate to date. Self-perceived attractiveness predicted self-esteem for both sexes, but the relationship was stronger for males
Radio Galaxy NGC 1265 unveils the Accretion Shock onto the Perseus Galaxy Cluster
We present a consistent 3D model for the head-tail radio galaxy NGC 1265 that
explains the complex radio morphology and spectrum by a past passage of the
galaxy and radio bubble through a shock wave. Using analytical solutions to the
full Riemann problem and hydrodynamical simulations, we study how this passage
transformed the plasma bubble into a toroidal vortex ring. Adiabatic
compression of the aged electron population causes it to be energized and to
emit low-surface brightness and steep-spectrum radio emission. The large infall
velocity of NGC 1265 and the low Faraday rotation measure values and variance
of the jet strongly argue that this transformation was due to the accretion
shock onto Perseus situated roughly at R_200. Estimating the volume change of
the radio bubble enables inferring a shock Mach number of M =
4.2_{-1.2}^{+0.8}, a density jump of 3.4_{-0.4}^{+0.2}, a temperature jump of
6.3_{-2.7}^{+2.5}, and a pressure jump of 21.5 +/- 10.5 while allowing for
uncertainties in the equation of state of the radio plasma and volume of the
torus. Extrapolating X-ray profiles, we obtain upper limits on the gas
temperature and density in the infalling warm-hot intergalactic medium of kT <
0.4 keV and n < 5e-5 / cm^3. The orientation of the ellipsoidally shaped radio
torus in combination with the direction of the galaxy's head and tail in the
plane of the sky is impossible to reconcile with projection effects. Instead,
this argues for post-shock shear flows that have been caused by curvature in
the shock surface with a characteristic radius of 850 kpc. The energy density
of the shear flow corresponds to a turbulent-to-thermal energy density of 14%.
The shock-injected vorticity might be important in generating and amplifying
magnetic fields in galaxy clusters. Future LOFAR observations of head-tail
galaxies can be complementary probes of accretion shocks onto galaxy clusters.Comment: 14 pages, 4 figures, ApJ, in print; v3: typos corrected to match the
published version; v2: improved presentation, added 2D numerical simulations
and exact solution to the 1D Riemann problem of a shock overrunning a
spherical bubble that gets transformed into a vortex rin
One-Bead Microrheology with Rotating Particles
We lay the theoretical basis for one-bead microrheology with rotating
particles, i.e, a method where colloids are used to probe the mechanical
properties of viscoelastic media. Based on a two-fluid model, we calculate the
compliance and discuss it for two cases. We first assume that the elastic and
fluid component exhibit both stick boundary conditions at the particle surface.
Then, the compliance fulfills a generalized Stokes law with a complex shear
modulus whose validity is only limited by inertial effects, in contrast to
translational motion. Secondly, we find that the validity of the Stokes regime
is reduced when the elastic network is not coupled to the particleComment: 7 pages, 5 figures, submitted to Europhys. Let
Public Participation Organizations and Open Policy:A Constitutional Moment for British Democracy?
This article builds on work in Science and Technology Studies and cognate disciplines concerning the institutionalization of public engagement and participation practices. It describes and analyses ethnographic qualitative research into one “organization of participation,” the UK government–funded Sciencewise program. Sciencewise’s interactions with broader political developments are explored, including the emergence of “open policy” as a key policy object in the UK context. The article considers what the new imaginary of openness means for institutionalized forms of public participation in science policymaking, asking whether this is illustrative of a “constitutional moment” in relations between society and science policymaking
The Influence of Environment on the Star Formation Rates of Galaxies
We have used a sample of 15749 galaxies taken from the Las Campanas Redshift
Survey to investigate the effects of environment on the rate of star formation
(SFR) in galaxies. The size and homogeneity of this data set allows us to
sample, for the first time, the entire range of galactic environment, from the
voids to the clusters, in a uniform manner, thus, we could decouple the local
galaxy density from the membership in associations. This decoupling is very
crucial for constraining the physical processes responsible for the
environmental dependencies of SFR. On the other hand, the use of an
automatically-measured concentration index (C), rather than Hubble type, allows
us to cleanly separate the morphological component from the SFR vs. environment
relationship. We find that cluster galaxies exhibit lower SFR for the same C
than field galaxies, while a further division of clusters by `richness' reveals
a new possible excitation of `starbursts' in poor clusters. Meanwhile, a more
general environmental investigation reveals that the SFR of a given C shows a
continuous correlation with the local density. Interestingly, this trend is
also observed both inside and outside of clusters, implying that physical
processes responsible for this correlation might not be intrinsic to the
cluster environment. On the other hand, galaxies with differing levels of SFR
appear to respond differently to the local density. Low levels of SFR are more
sensitive to environment inside than outside of clusters. In contrast, high
levels of SFR, identified as ``starbursts'', are as sensitive to local density
in the field as in clusters. We conclude that at least two separate processes
are responsible for the environmental sensitivity of the SFR.Comment: 25 pages, 10 figures, submitted to Ap
Spatial variations of the Sr i 4607 {\AA} scattering polarization peak
Context. The scattering polarization signal observed in the photospheric Sr i
4607 {\AA} line is expected to vary at granular spatial scales. This variation
can be due to changes in the magnetic field intensity and orientation (Hanle
effect), but also to spatial and temporal variations in the plasma properties.
Measuring the spatial variation of such polarization signal would allow us to
study the properties of the magnetic fields at subgranular scales, but
observations are challenging since both high spatial resolution and high
spectropolarimetric sensitivity are required.
Aims. We aim to provide observational evidence of the polarization peak
spatial variations, and to analyze the correlation they might have with
granulation.
Methods. Observations conjugating high spatial resolution and high
spectropolarimetric precision were performed with the Zurich IMaging
POLarimeter, ZIMPOL, at the GREGOR solar telescope, taking advantage of the
adaptive optics system and the newly installed image derotator.
Results. Spatial variations of the scattering polarization in the Sr i 4607
{\AA} line are clearly observed. The spatial scale of these variations is
comparable with the granular size. Small correlations between the polarization
signal amplitude and the continuum intensity indicate that the polarization is
higher at the center of granules than in the intergranular lanes.Comment: 5 pages, 4 figure
Structure of Polyelectrolytes in Poor Solvent
We present simulations on charged polymers in poor solvent. First we
investigate in detail the dilute concentration range with and without imposed
extension constraints. The resulting necklace polymer conformations are
analyzed in detail. We find strong fluctuations in the number of pearls and
their sizes leading only to small signatures in the form factor and the
force-extension relation. The scaling of the peak in the structure factor with
the monomer density shows a pertinent different behavior from good solvent
chains.Comment: 7 pages, 5 figures. submitted to EP
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