3,845 research outputs found
K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147
We identify a sub-Neptune exoplanet ( R)
transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H]
= +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2
Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%,
and a duration of ~4 hours. Based on our analysis of high-resolution MIKE
spectra, broadband optical and NIR photometry, the cluster parallax and
interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST,
we estimate the following properties for the host star: M, R, and K. This star appears to be single, based on our modeling of the
photometry, the low radial velocity variability measured over nearly ten years,
and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry.
Applying a probabilistic mass-radius relation, we estimate that the mass of
this planet is M, which would cause a RV
semi-amplitude of m s that may be measurable with existing
precise RV facilities. After statistically validating this planet with BLENDER,
we now designate it K2-231 b, making it the second sub-stellar object to be
discovered in Ruprecht 147 and the first planet; it joins the small but growing
ranks of 23 other planets found in open clusters.Comment: 24 pages, 7 figures, light curve included as separate fil
Entanglement capability of self-inverse Hamiltonian evolution
We determine the entanglement capability of self-inverse Hamiltonian
evolution, which reduces to the known result for Ising Hamiltonian, and
identify optimal input states for yielding the maximal entanglement rate. We
introduce the concept of the operator entanglement rate, and find that the
maximal operator entanglement rate gives a lower bound on the entanglement
capability of a general Hamiltonian.Comment: 4 pages, no figures. Version 3: small change
A global view of transcriptional regulation by nuclear receptors: gene expression, factor localization, and DNA sequence analysis
Recent genomic analyses of transcription factor binding, histone modification, and gene expression have provided a global view of transcriptional regulation by nuclear receptors (NRs) that complements an existing large body of literature on gene-specific studies. The picture emerging from these genomic studies indicates that NRs bind at promoter-proximal and promoter-distal enhancers in conjunction with other transcription factors (e.g., activator protein-1, Sp1 and FOXA1). This binding promotes the recruitment of coregulators that mediate the posttranslational modification of histones at promoters and enhancers. Ultimately, signaling through liganded NRs stimulates changes in the occupancy of RNA polymerase II (Pol II) or the activation of preloaded Pol II at target promoters. Chromosomal looping and/or Pol II tracking may underlie promoter-enhancer communication. Interestingly, the direct target genes of NR signaling represent a limited subset of all the genes regulated by NR ligands, with the rest being regulated through secondary effects. As suggested by previous gene-specific analyses, NR-mediated outcomes are highly cell type- and promoter-specific, highlighting the complexity of transcriptional regulation by NRs and the value of genomic analyses for identifying commonly shared patterns. Overall, NRs share common themes in their patterns of localization and transcriptional regulation across mammalian genomes. In this review, we provide an overview of recent advances in the understanding of NR-mediated transcription garnered from genomic analyses of gene expression, factor localization, and target DNA sequences
Holographic principle in the BDL brane cosmology
We study the holographic principle in the brane cosmology. Especially we
describe how to accommodate the 5D anti de Sitter Schwarzschild (AdSS)
black hole in the Binetruy-Deffayet-Langlois (BDL) approach of brane cosmology.
It is easy to make a connection between a mass of the AdSS black hole
and a conformal field theory (CFT)-radiation dominated universe on the brane in
the moving domain wall approach. But this is not established in the BDL
approach. In this case we use two parameters in the Friedmann
equation. These arise from integration and are really related to the choice of
initial bulk matter. If one chooses a bulk energy density to account
for a mass of the AdSS black hole and the static fifth dimension, a
CFT-radiation term with comes out from the bulk
matter without introducing a localized matter distribution on the brane. This
means that the holographic principle can be established in the BDL brane
cosmology.Comment: 9 pages, a version to appear in PR
Genome-wide analysis reveals PADI4 cooperates with Elk-1 to activate c-Fos expression in breast cancer cells.
Peptidylarginine deiminase IV (PADI4) catalyzes the conversion of positively charged arginine and methylarginine residues to neutrally charged citrulline, and this activity has been linked to the repression of a limited number of target genes. To broaden our knowledge of the regulatory potential of PADI4, we utilized chromatin immunoprecipitation coupled with promoter tiling array (ChIP-chip) analysis to more comprehensively investigate the range of PADI4 target genes across the genome in MCF-7 breast cancer cells. Results showed that PADI4 is enriched in gene promoter regions near transcription start sites (TSSs); and, surprisingly, this pattern of binding is primarily associated with actively transcribed genes. Computational analysis found potential binding sites for Elk-1, a member of the ETS oncogene family, to be highly enriched around PADI4 binding sites; and coimmunoprecipitation analysis then confirmed that Elk-1 physically associates with PADI4. To better understand how PADI4 may facilitate gene transactivation, we then show that PADI4 interacts with Elk-1 at the c-Fos promoter and that, following Epidermal Growth Factor (EGF) stimulation, PADI4 catalytic activity facilitates Elk-1 phosphorylation, histone H4 acetylation, and c-Fos transcriptional activation. These results define a novel role for PADI4 as a transcription factor co-activator
Cosmology of intersecting brane world models in Gauss-Bonnet gravity
We study the cosmological properties of a codimension two brane world that
sits at the intersection between two four branes, in the framework of six
dimensional Einstein-Gauss-Bonnet gravity. Due to contributions of the
Gauss-Bonnet terms, the junction conditions require the presence of localized
energy density on the codimension two defect. The induced metric on this
surface assumes a FRW form, with a scale factor associated to the position of
the brane in the background; we can embed on the codimension two defect the
preferred form of energy density. We present the cosmological evolution
equations for the three brane, showing that, for the case of pure AdS
backgrounds, they acquire the same form of the ones for the Randall-Sundrum II
model. When the background is different from pure AdS, the cosmological
behavior is potentially modified in respect to the typical one of codimension
one brane worlds. We discuss, in a particular model embedded in an AdS
black hole, the conditions one should satisfy in order to obtain standard
cosmology at late epochs.Comment: 19 pages, no figures, JHEP style. v2: Typos corrected and references
adde
PARP inhibitors and the treatment of breast cancer: beyond BRCA1/2?
Poly(ADP-ribose) polymerase (PARP) inhibitors have been explored as therapeutic agents for the treatment of hereditary breast and ovarian cancers harboring mutations in BRCA1 or BRCA2. In a new study, Inbar-Rozensal and colleagues show that phenanthridine-derived PARP inhibitors promote cell cycle arrest and cell death in breast cancer cells lacking BRCA1 and BRCA2 mutations and prevent the growth of tumors from xenografts of these cells in immunocompromised mice. These results suggest a potential broader utility of PARP-1 inhibitors in the treatment of breast cancer, although further mechanistic studies are needed
No chiral truncation of quantum log gravity?
At the classical level, chiral gravity may be constructed as a consistent
truncation of a larger theory called log gravity by requiring that left-moving
charges vanish. In turn, log gravity is the limit of topologically massive
gravity (TMG) at a special value of the coupling (the chiral point). We study
the situation at the level of linearized quantum fields, focussing on a unitary
quantization. While the TMG Hilbert space is continuous at the chiral point,
the left-moving Virasoro generators become ill-defined and cannot be used to
define a chiral truncation. In a sense, the left-moving asymptotic symmetries
are spontaneously broken at the chiral point. In contrast, in a non-unitary
quantization of TMG, both the Hilbert space and charges are continuous at the
chiral point and define a unitary theory of chiral gravity at the linearized
level.Comment: 20 pages, no figures, references adde
Self-consistent non-Markovian theory of a quantum state evolution for quantum information processing
It is shown that the operator sum representation for non-Markovian dynamics
and the Lindblad master equation in Markovian limit can be derived from a
formal solution to quantum Liouville equation for a qubit system in the
presence of decoherence processes self-consistently. Our formulation is the
first principle theory based on projection-operator formalism to obtain an
exact reduced density operator in time-convolutionless form starting from the
quantum Liouville equation for a noisy quantum computer. The advantage of our
approach is that it is general enough to describe a realistic quantum computer
in the presence of decoherence provided details of the Hamiltonians are known.Comment: 5page
Strangeness dynamics in relativistic nucleus-nucleus collision
We investigate hadron production as well as transverse hadron spectra in
nucleus-nucleus collisions from 2 GeV to 21.3 TeV within two
independent transport approaches (UrQMD and HSD) that are based on quark,
diquark, string and hadronic degrees of freedom. The comparison to experimental
data demonstrates that both approaches agree quite well with each other and
with the experimental data on hadron production. The enhancement of pion
production in central Au+Au (Pb+Pb) collisions relative to scaled
collisions (the 'kink') is well described by both approaches without involving
any phase transition. However, the maximum in the ratio at 20 to 30
AGeV (the 'horn') is missed by 40%. A comparison to the
transverse mass spectra from and C+C (or Si+Si) reactions shows the
reliability of the transport models for light systems. For central Au+Au
(Pb+Pb) collisions at bombarding energies above 5 AGeV, however,
the measured -spectra have a larger inverse slope parameter
than expected from the calculations. The approximately constant slope of
spectra at SPS (the 'step') is not reproduced either. Thus the pressure
generated by hadronic interactions in the transport models above 5
AGeV is lower than observed in the experimental data. This finding
suggests that the additional pressure - as expected from lattice QCD
calculations at finite quark chemical potential and temperature - might be
generated by strong interactions in the early pre-hadronic/partonic phase of
central Au+Au (Pb+Pb) collisions.Comment: 10 pages, 5 figures, Invited talk presented by H. Stocker at
ERICE-2003 (Sep. 2003, Erice, Italy), to be published in Prog. Part. Nucl.
Phys. 52 (2004
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