11,241 research outputs found
Exact Results for Average Cluster Numbers in Bond Percolation on Lattice Strips
We present exact calculations of the average number of connected clusters per
site, , as a function of bond occupation probability $p$, for the bond
percolation problem on infinite-length strips of finite width $L_y$, of the
square, triangular, honeycomb, and kagom\'e lattices $\Lambda$ with various
boundary conditions. These are used to study the approach of , for a given
and , to its value on the two-dimensional lattice as the strip
width increases. We investigate the singularities of in the complex $p$
plane and their influence on the radii of convergence of the Taylor series
expansions of about and .Comment: 16 pages, revtex, 7 eps figure
Probing protein-protein interactions by dynamic force correlated spectroscopy (FCS)
We develop a formalism for single molecule dynamic force spectroscopy to map
the energy landscape of protein-protein complex (). The joint
distribution of unbinding lifetimes and
measurable in a compression-tension cycle, which accounts for the internal
relaxation dynamics of the proteins under tension, shows that the histogram of
is not Poissonian. The theory is applied to the forced unbinding of
protein , modeled as a wormlike chain, from . We propose a new
class of experiments which can resolve the effect of internal protein dynamics
on the unbinding lifetimes.Comment: 12 pages, 3 figures, accepted to Phys. Rev. Let
An experimental investigation of the structural dynamics of a torsionally soft rotor in vacuum
An extensive data base of structural dynamic characteristics has been generated from an experimental program conducted on a torsionally soft two-bladed model helicopter rotor system. Measurements of vibratory strains for five modes of vibration were made at twenty-one locations on the two blades at speeds varying from 0 to 1000 RPM and for several combinations of precone, droop and flexure stiffness. Tests were conducted in vacuum under carefully controlled conditions using a unique excitation device with a system of piezoelectric crystals bonded to the blade surface near the root. Frequencies, strain mode shapes and dampings are extracted from the time histories and can be used to validate structural dynamics codes. The dynamics of the system are such that there is a clear tendency for the first torsion and second flap modes to couple within the speed range considered. Strain mode shapes vary significantly with speed and configuration. This feature is important in the calcualtion of aeroelastic instabilities. The tension axis tests confirmed that the modulus-weighted centroid for the nonhomogeneous airfoil is slightly off the mass centroid and validated previous static tests done to determine location of the tension axis
The good, the bad and the ugly .... of Horava gravity
I review the good, the bad and the ugly of the non-projectable versions of
Horava gravity. I explain how this non-relativistic theory was constructed and
why it was touted with such excitement as a quantum theory of gravity. I then
review some of the issues facing the theory, explaining how strong coupling
occurs and why this is such a problem for both phenomenology and the question
of renormalisability. Finally I comment on possible violations of Equivalence
Principle, and explain why these could be an issue for Blas et al's "healthy
extension". This paper was presented as a talk at PASCOS 2010 in Valencia.Comment: 7 page
SED-inferred properties and morphology of Lyman-break galaxies at in the CDF-S
After carefully cross-identifying a previously discovered GALEX-selected
Lyman Break Galaxy (LBG) candidates one-to-one with their optical counterparts
in the field of the CDF-S, we re-estimate their photometric redshifts using
multi-wavelength data from UV, optical to NIR. We refine a new updated sample
of 383 LBGs at 0.7\la z \la 1.4.
Most LBGs are classified as starburst and irregular types. Ages spread from
several Myr to 1.5Gyr. Their dust-corrected star formation rates (SFRs) and
stellar masses () are from 4\my to 220\my and from 2.3\times 10^8
\msun to 4 \times 10^{11} \msun. The rest-frame FUV luminosity function of
LBGs are presented. LBGs of irregular types mainly distribute along the "main
sequence" of star forming galaxies while most LBGs of starburst types locate in
the starburst region. A "downsizing" effect is clearly found and LBGs
distribute in the "blue" cloud.
HST images in F606W ( band) and F850LP ( band) are taken from the GEMS
and GOODS-S surveys. SExtractor and GALFIT are applied to get their
morphological parameters. A morphological sample of 142 LBGs with reliable
results of \sersic and sizes in both bands is defined. We find that LBGs at
are dominated by disk-like galaxies. Correlations between
photometric and morphological properties of LBGs are investigated. Strong
correlations between their half-light radii and , i.e., size-stellar mass
relations, are found in both bands. Physical connections between correlations
and the "downsizing" effect are discussed.Comment: 26 pages, 30 figures, 6 tables, accepted by MNRA
Electroweak Beautygenesis: From b {\to} s CP-violation to the Cosmic Baryon Asymmetry
We address the possibility that CP-violation in mixing may
help explain the origin of the cosmic baryon asymmetry. We propose a new
baryogenesis mechanism - "Electroweak Beautygenesis" - explicitly showing that
these two CP-violating phenomena can be sourced by a common CP-phase. As an
illustration, we work in the Two-Higgs-Doublet model. Because the relevant
CP-phase is flavor off-diagonal, this mechanism is less severely constrained by
null results of electric dipole moment searches than other scenarios. We show
how measurements of flavor observables by the D0, CDF, and LHCb collaborations
test this scenario.Comment: 4 pages, 1 figure, 1 tabl
Convection and AGN Feedback in Clusters of Galaxies
A number of studies have shown that the convective stability criterion for
the intracluster medium (ICM) is very different from the Schwarzchild criterion
due to the effects of anisotropic thermal conduction and cosmic rays. Building
on these studies, we develop a model of the ICM in which a central active
galactic nucleus (AGN) accretes hot intracluster plasma at the Bondi rate and
produces cosmic rays that cause the ICM to become convectively unstable. The
resulting convection heats the intracluster plasma and regulates its
temperature and density profiles. By adjusting a single parameter in the model
(the size of the cosmic-ray acceleration region), we are able to achieve a good
match to the observed density and temperature profiles in a sample of eight
clusters. Our results suggest that convection is an important process in
cluster cores. An interesting feature of our solutions is that the cooling rate
is more sharply peaked about the cluster center than is the convective heating
rate. As a result, in several of the clusters in our sample, a compact cooling
flow arises in the central region with a size R that is typically a few kpc.
The cooling flow matches onto a Bondi flow at smaller radii. The mass accretion
rate in the Bondi flow is equal to, and controlled by, the rate at which mass
flows in through the cooling flow. Our solutions suggest that the AGN regulates
the mass accretion rate in these clusters by controlling R: if the AGN power
rises above the equilibrium level, R decreases, the mass accretion rate drops,
and the AGN power drops back down to the equilibrium level.Comment: 41 pages, 7 figures, accepted for publication in ApJ. Changes in this
version: extended discussion of Bondi accretion in clusters, better mass
model, new numerical solution
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