4,983 research outputs found

### Large scale correlations of quasar polarisation vectors: Hints of extreme scale structures?

A survey measuring quasar polarization vectors has been started in two
regions towards the North and South Galactic Poles. Here, We review the
discovery of significant correlations of orientations of polarization vectors
over huge angular distances. We report new results including a larger sample of
the quasars confirming the existence of coherent orientations at redshifts z>1.Comment: Proc. of Astronomical Polarimetry - Current Status and Future
Directions March 15-19, 2004. Waikoloa Beach Marriott, Hawaii. 5 pages, 3
figure

### Building patterns by traveling vortices and dipoles in periodic dissipative media

We analyze pattern-formation scenarios in the two-dimensional (2D) complex
Ginzburg-Landau (CGL) equation with the cubic-quintic (CQ) nonlinearity and a
cellular potential. The equation models laser cavities with built-in gratings,
which are used to stabilize 2D patterns. The pattern-building process is
initiated by kicking a localized compound mode, in the form of a dipole,
quadrupole, or vortex which is composed of four local peaks. The hopping motion
of the kicked mode through the cellular structure leads to the generation of
various extended patterns pinned by the structure. In the ring-shaped system,
the persisting freely moving dipole hits the stationary pattern from the
opposite side, giving rise to several dynamical regimes, with the pinned
multi-soliton chain playing the role of the Newton's cradle (NC)

### Convergence to the maximal invariant measure for a zero-range process with random rates

We consider a one-dimensional totally asymmetric nearest-neighbor zero-range
process with site-dependent jump-rates - an environment. For each environment p
we prove that the set of all invariant measures is the convex hull of a set of
product measures with geometric marginals. As a consequence we show that for
environments p satisfying certain asymptotic property, there are no invariant
measures concentrating on configurations with critical density bigger than
$\rho^*(p)$, a critical value. If $\rho^*(p)$ is finite we say that there is
phase-transition on the density. In this case we prove that if the initial
configuration has asymptotic density strictly above $\rho^*(p)$, then the
process converges to the maximal invariant measure.Comment: 19 pages, Revised versio

### A strict lower-limit EBL: Applications on gamma-ray absorption

A strict lower limit flux for the extragalactic background light from
ultraviolet to the far-infrared photon energies is presented. The spectral
energy distribution is derived using an established EBL model based on galaxy
formation. The model parameters are chosen to fit the lower limit data from
number count observations in particular recent results by the SPITZER infrared
space telescope. A lower limit EBL model is needed to calculate guaranteed
absorption due to pair production in extragalactic gamma-ray sources as in TeV
blazars.Comment: Comments: 4 pages, 2 figures, submitted to proceedings of "4th
Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

### Phosphorylation of CENP-A on serine 7 does not control centromere function

CENP-A is the histone H3 variant necessary to specify the location of all eukaryotic centromeres via its CENP-A targeting domain and either one of its terminal regions. In humans, several post-translational modifications occur on CENP-A, but their role in centromere function remains controversial. One of these modifications of CENP-A, phosphorylation on serine 7, has been proposed to control centromere assembly and function. Here, using gene targeting at both endogenous CENP-A alleles and gene replacement in human cells, we demonstrate that a CENP-A variant that cannot be phosphorylated at serine 7 maintains correct CENP-C recruitment, faithful chromosome segregation and long-term cell viability. Thus, we conclude that phosphorylation of CENP-A on serine 7 is dispensable to maintain correct centromere dynamics and function

### On the equivalence of N=1 brane worlds and geometric singularities with flux

We consider Kaluza Klein reductions of M-theory on the Z_N orbifold of the
spin bundle over S^3 along two different U(1) isometries. The first one gives
rise to the familiar ``large N duality'' of the N=1 SU(N) gauge theory in which
the UV is realized as the world-volume theory of N D6-branes wrapped on S^3,
whereas the IR involves N units of RR flux through an S^2. The second reduction
gives an equivalent version of this duality in which the UV is realized
geometrically in terms of an S^2 of A_{N-1} singularities, with one unit of RR
flux through the S^2. The IR is reached via a geometric transition and involves
a single D6 brane on a lens space S^3/Z_N or, alternatively, a singular
background (S^2\times R^4)/Z_N, with one unit of RR flux through S^2 and,
localized at the singularities, an action of their stabilizer group in the U(1)
RR gauge bundle, so that no massless twisted states occur. We also consider
linear sigma-model descriptions of these backgrounds.Comment: 25 pages, LaTeX; v2: one reference added, published versio

### CENP-A Is Dispensable for Mitotic Centromere Function after Initial Centromere/Kinetochore Assembly

Human centromeres are defined by chromatin containing the histone H3 variant CENP-A assembled onto repetitive alphoid DNA sequences. By inducing rapid, complete degradation of endogenous CENP-A, we now demonstrate that once the first steps of centromere assembly have been completed in G1/S, continued CENP-A binding is not required for maintaining kinetochore attachment to centromeres or for centromere function in the next mitosis. Degradation of CENP-A prior to kinetochore assembly is found to block deposition of CENP-C and CENP-N, but not CENP-T, thereby producing defective kinetochores and failure of chromosome segregation. Without the continuing presence of CENP-A, CENP-B binding to alphoid DNA sequences becomes essential to preserve anchoring of CENP-C and the kinetochore to each centromere. Thus, there is a reciprocal interdependency of CENP-A chromatin and the underlying repetitive centromere DNA sequences bound by CENP-B in the maintenance of human chromosome segregation

### 320g Ionization-Heat Cryogenic Detector for Dark Matter Search in the EDELWEISS Experiment

The EDELWEISS experiment used in 2001 a 320g heat-and-ionization cryogenic Ge
detector operated in a low-background environment in the Laboratoire Souterrain
de Modane for direct WIMP detection. This detector presents an increase of more
than 4 times the mass of previous detectors. Calibrations of this detector are
used to determine its energy resolution and fiducial volume, and to optimize
the detector design for the 1kg phase of the EDELWEISS-I experiment. Analysis
of the calibrations and characteristics of a first series of 320g-detectors are
presented.Comment: 4 pages, 3 figure

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