17,407 research outputs found
Further search for a neutral boson with a mass around 9 MeV/c2
Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1
transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In
the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0
level at 18.15 MeV, a significant deviation from IPC was observed at large pair
correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the
12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9
MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table
Ideal Embodiment: Kant's Theory of Sensibility
A Review of: Ideal Embodiment: Kant's Theory of Sensibility, by Angelica Nuzzo. Bloomington and Indianapolis: Indiana University Press, 2008, 414 pp. ISBN: 978-0-253-35229-3 hb, 27.95
Sum rules for correlation functions of ionic mixtures in arbitrary dimension
The correlations in classical multi-component ionic mixtures with spatial
dimension are studied by using a restricted grand-canonical ensemble
and the associated hierarchy equations for the correlation functions. Sum rules
for the first few moments of the two-particle correlation function are derived
and their dependence on is established. By varying continuously near
it is shown how the sum rules for the two-dimensional mixture are related
to those for mixtures at higher .Comment: 19 page
Application of superspace symmetry to optical and magnetic resonance spectra of incommensurably modulated crystals
Application of superspace symmetry to optical and magnetic resonance spectra of incommensurably modulated crystals
BROCKMAN: deciphering variance in epigenomic regulators by k-mer factorization
Background: Variation in chromatin organization across single cells can help shed important light on the mechanisms controlling gene expression, but scale, noise, and sparsity pose significant challenges for interpretation of single cell chromatin data. Here, we develop BROCKMAN (Brockman Representation Of Chromatin by K-mers in Mark-Associated Nucleotides), an approach to infer variation in transcription factor (TF) activity across samples through unsupervised analysis of the variation in DNA sequences associated with an epigenomic mark. Results: BROCKMAN represents each sample as a vector of epigenomic-mark-associated DNA word frequencies, and decomposes the resulting matrix to find hidden structure in the data, followed by unsupervised grouping of samples and identification of the TFs that distinguish groups. Applied to single cell ATAC-seq, BROCKMAN readily distinguished cell types, treatments, batch effects, experimental artifacts, and cycling cells. We show that each variable component in the k-mer landscape reflects a set of co-varying TFs, which are often known to physically interact. For example, in K562 cells, AP-1 TFs were central determinant of variability in chromatin accessibility through their variable expression levels and diverse interactions with other TFs. We provide a theoretical basis for why cooperative TF binding – and any associated epigenomic mark – is inherently more variable than non-cooperative binding. Conclusions: BROCKMAN and related approaches will help gain a mechanistic understanding of the trans determinants of chromatin variability between cells, treatments, and individuals. Keywords: Single-cell, Epigenome, Chromatin, scATAC-seq, K-mer, N-gram, Factorization, Decomposition, Clustering,
Transcription factorNational Human Genome Research Institute (U.S.) (Centers of Excellence in Genomic Science Grant)Howard Hughes Medical Institute (Centers of Excellence in Genomic Science Grant
Enhanced sensitivity of postsynaptic serotonin-1A receptors in rats and mice with high trait aggression
Individual differences in aggressive behaviour have been linked to variability in central serotonergic activity, both in humans and animals. A previous experiment in mice, selectively bred for high or low levels of aggression, showed an up-regulation of postsynaptic serotonin-1A (5-HT1A) receptors, both in receptor binding and in mRNA levels, in the aggressive line. The aim of this experiment was to study whether similar differences in 5-HT1A receptors exist in individuals from a random-bred rat strain, varying in aggressiveness. In addition, because little is known about the functional consequences of these receptor differences, a response mediated via postsynaptic 5-HT1A receptors (i.e., hypothermia) was studied both in the selection lines of mice and in the randomly bred rats. The difference in receptor binding, as demonstrated in mice previously, could not be shown in rats. However, both in rats and mice, the hypothermic response to the 5-HT1A agonist alnespirone was larger in aggressive individuals. So, in the rat strain as well as in the mouse lines, there is, to a greater or lesser extent, an enhanced sensitivity of postsynaptic 5-HT1A receptors in aggressive individuals. This could be a compensatory up-regulation induced by a lower basal 5-HT neurotransmission, which is in agreement with the serotonin deficiency hypothesis of aggression.
Proper identification of RR Lyrae Stars brighter than 12.5 mag
RR Lyrae stars are of great importance for investigations of Galactic
structure. However, a complete compendium of all RR-Lyraes in the solar
neighbourhood with accurate classifications and coordinates does not exist to
this day. Here we present a catalogue of 561 local RR-Lyrae stars V_max less
equal 12.5 mag according to the magnitudes given in the Combined General
Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue
contains about 100 RR Lyr stars. However, many objects have inaccurate
coordinates in the GCVS, the primary source of variable star information, so
that a reliable cross-identification is difficult. We identified RR Lyrae from
both catalogues based on an intensive literature search. In dubious cases we
carried out photometry of fields to identify the variable. Mennessier and
Colome (2002) have published a paper with Tyc2-GCVS identifications, but we
found that many of their identifications are wrong.
Keywords: astrometry -- Stars: RR Lyrae stars -- Catalogues: Tycho-2
catalogue -- Catalogues: The HST Guide Star Catalogue, Version 1.2 --
Catalogues: Combined General Catalogue of Variable StarsComment: 5 pages with 2 figures; A and A accepted Online-Data are available
under http://www.astro.uni-bonn.de/~gmaint
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