3,563 research outputs found
Equal-Spin Pairing State of Superfluid He in Aerogel
The equal-spin pairing (ESP) state, the so-called A-like phase, of superfluid
He in aerogels is studied theoretically in the Ginzburg-Landau (GL) region
by examining thermodynamics, and the resulting equilibrium phase diagram is
mapped out. We find that, among the ABM, planar, and robust pairing states, the
ABM state with presumably quasi long-ranged superfluid order is the best
candidate of the A-like phase with a strange lowering of the polycritical point
(PCP) observed experimentally.Comment: 4 pages, 1 figure, one reference added, accepted for publication in
Phys. Rev.
Spin melting and refreezing driven by uniaxial compression on a dipolar hexagonal plate
We investigate freezing characteristics of a finite dipolar hexagonal plate
by the Monte Carlo simulation. The hexagonal plate is cut out from a piled
triangular lattice of three layers with FCC-like (ABCABC) stacking structure.
In the present study an annealing simulation is performed for the dipolar plate
uniaxially compressed in the direction of layer-piling. We find spin melting
and refreezing driven by the uniaxial compression. Each of the melting and
refreezing corresponds one-to-one with a change of the ground states induced by
compression. The freezing temperatures of the ground-state orders differ
significantly from each other, which gives rise to the spin melting and
refreezing of the present interest. We argue that these phenomena are
originated by a finite size effect combined with peculiar anisotropic nature of
the dipole-dipole interaction.Comment: Proceedings of the Highly Frustrated Magnetism (HFM2006) conference.
To appear in a special issue of J. Phys. Condens. Matte
Noncoding RNAs and Intranuclear Positioning in Monoallelic Gene Expression
Mammalian X inactivation, imprinting, and allelic exclusion are classic examples of monoallelic gene expression. Two emerging themes are thought to be critical for monoallelic expression: (1) noncoding, often antisense, transcription linked to differential chromatin marks on otherwise homologous alleles and (2) physical segregation of alleles to separate domains within the nucleus. Here, we highlight recent progress in identifying these phenomena as possible key regulatory mechanisms of monoallelic expression
Radiative spacetimes approaching the Vaidya metric
We analyze a class of exact type II solutions of the Robinson-Trautman family
which contain pure radiation and (possibly) a cosmological constant. It is
shown that these spacetimes exist for any sufficiently smooth initial data, and
that they approach the spherically symmetric Vaidya-(anti-)de Sitter metric. We
also investigate extensions of the metric, and we demonstrate that their order
of smoothness is in general only finite. Some applications of the results are
outlined.Comment: 12 pages, 3 figure
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Are we there yet? Initial targeting of the Male-Specific Lethal and Polycomb group chromatin complexes in Drosophila
Chromatin-binding proteins must navigate the complex nuclear milieu to find their sites of action, and a constellation of protein factors and other properties are likely to influence targeting specificity. Despite considerable progress, the precise rules by which binding specificity is achieved have remained elusive. Here, we consider early targeting events for two groups of chromatin-binding complexes in Drosophila: the Male-Specific Lethal (MSL) and the Polycomb group (PcG) complexes. These two serve as models for understanding targeting, because they have been extensively studied and play vital roles in Drosophila, and their targets have been documented at high resolution. Furthermore, the proteins and biochemical properties of both complexes are largely conserved in multicellular organisms, including humans. While the MSL complex increases gene expression and PcG members repress genes, the two groups share many similarities such as the ability to modify their chromatin environment to create active or repressive domains, respectively. With legacies of in-depth genetic, biochemical and now genomic approaches, the MSL and PcG complexes will continue to provide tractable systems for understanding the recruitment of multiprotein chromatin complexes to their target loci
The Importance of Hot Corrosion and Its Effective Prevention for Enhanced Efficiency of Gas Turbines
Quantized correlation coefficient for measuring reproducibility of ChIP-chip data
<p>Abstract</p> <p>Background</p> <p>Chromatin immunoprecipitation followed by microarray hybridization (ChIP-chip) is used to study protein-DNA interactions and histone modifications on a genome-scale. To ensure data quality, these experiments are usually performed in replicates, and a correlation coefficient between replicates is used often to assess reproducibility. However, the correlation coefficient can be misleading because it is affected not only by the reproducibility of the signal but also by the amount of binding signal present in the data.</p> <p>Results</p> <p>We develop the Quantized correlation coefficient (QCC) that is much less dependent on the amount of signal. This involves discretization of data into set of quantiles (quantization), a merging procedure to group the background probes, and recalculation of the Pearson correlation coefficient. This procedure reduces the influence of the background noise on the statistic, which then properly focuses more on the reproducibility of the signal. The performance of this procedure is tested in both simulated and real ChIP-chip data. For replicates with different levels of enrichment over background and coverage, we find that QCC reflects reproducibility more accurately and is more robust than the standard Pearson or Spearman correlation coefficients. The quantization and the merging procedure can also suggest a proper quantile threshold for separating signal from background for further analysis.</p> <p>Conclusions</p> <p>To measure reproducibility of ChIP-chip data correctly, a correlation coefficient that is robust to the amount of signal present should be used. QCC is one such measure. The QCC statistic can also be applied in a variety of other contexts for measuring reproducibility, including analysis of array CGH data for DNA copy number and gene expression data.</p
Discovering Non-Abelian Weak Couplings and an Anomalous Magnetic Dipole Moment of the at LEP~2
In view of the forthcoming results on pair production at LEP~2, we
emphasize that {\em direct empirical evidence} on non-trivial properties of the
weak vector bosons can be obtained with relatively limited integrated
luminosity. An integrated luminosity of at
GeV will be sufficient to provide direct experimental evidence
for non-vanishing self-couplings of non-Abelian type among the weak vector
bosons. An integrated luminosity of at
GeV will provide direct evidence for the existence of an anomalous magnetic
dipole moment of the charged vector bosons .Comment: 6 pages LaTeX + 2 Figures; Revised Version contains correction of an
erroneous formulation made in connection with the principle of minimal
substitution; the title has been change
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