4,452 research outputs found
HST-COS Spectroscopy of the Cooling Flow in Abell 1795 - Evidence for Inefficient Star Formation in Condensing Intracluster Gas
We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the
Hubble Space Telescope of a cool, star-forming filament in the core of Abell
1795. These data, which span 1025A - 1700A, allow for the simultaneous modeling
of the young stellar populations and the intermediate-temperature (10^5.5 K)
gas in this filament, which is far removed (~30 kpc) from the direct influence
of the central AGN. Using a combination of UV absorption line indices and
stellar population synthesis modeling, we find evidence for ongoing star
formation, with the youngest stars having ages of 7.5 +/- 2.0 Myr and
metallicities of 0.4 +/- 0.2 Zsun. The latter is consistent with the local
metallicity of the intracluster medium. We detect the O VI (1038) line,
measuring a flux of 4.0 +/- 0.9 x 10^-17 erg s^-1 cm^-2. The O VI (1032) line
is redshifted such that it is coincident with a strong Galactic H2 absorption
feature, and is not detected. The measured O VI (1038) flux corresponds to a
cooling rate of 0.85 +/- 0.2 (stat) +/- 0.15 (sys) Msun/yr at ~10^5.5 K,
assuming that the cooling proceeds isochorically, which is consistent with the
classical X-ray luminosity-derived cooling rate in the same region. We measure
a star formation rate of 0.11 +/- 0.02 Msun/yr from the UV continuum,
suggesting that star formation is proceeding at 13 +/- 3% efficiency in this
filament. We propose that this inefficient star formation represents a
significant contribution to the larger-scale cooling flow problem.Comment: 6 pages, 4 figures. Accepted for publication in ApJ Letter
FAIRness and Usability for Open-access Omics Data Systems
Omics data sharing is crucial to the biological research community, and the last decade or two has seen a huge rise in collaborative analysis systems, databases, and knowledge bases for omics and other systems biology data. We assessed the FAIRness of NASAs GeneLab Data Systems (GLDS) along with four similar kinds of systems in the research omics data domain, using 14 FAIRness metrics. The range of overall FAIRness scores was 6-12 (out of 14), average 10.1, and standard deviation 2.4. The range of Pass ratings for the metrics was 29-79%, Partial Pass 0-21%, and Fail 7-50%. The systems we evaluated performed the best in the areas of data findability and accessibility, and worst in the area of data interoperability. Reusability of metadata, in particular, was frequently not well supported. We relate our experiences implementing semantic integration of omics data from some of the assessed systems for federated querying and retrieval functions, given their shortcomings in data interoperability. Finally, we propose two new principles that Big Data system developers, in particular, should consider for maximizing data accessibility
Bond-order modulated staggered flux phase for the model on the square lattice
Motivated by the observation of inhomogeneous patterns in some high-T
cuprate compounds, several variational Gutzwiller-projected wave-functions with
built-in charge and bond order parameters are proposed for the extended
model on the square lattice at low doping. First, following a recent
Gutzwiller-projected mean-field approach by one of us (Phys. Rev. B. {\bf 72},
060508(R) (2005)), we investigate, as a function of doping and Coulomb
repulsion, the stability of the staggered flux phase with respect to small
spontaneous modulations of squared unit cells ranging from to
. It is found that a bond-order (BO)
modulation appears spontaneously on top of the staggered flux pattern for hole
doping around 1/8. A related wave-function is then constructed and optimized
accurately and its properties studied extensively using an approximation-free
variational Monte Carlo scheme. Finally, the competition of the BO-modulated
staggered flux wave-function w.r.t. the d-wave RVB wave-function or the
commensurate flux state is investigated. It is found that a short range Coulomb
repulsion penalizes the d-wave superconductor and that a moderate Coulomb
repulsion brings them very close in energy. Our results are discussed in
connection to the STM observations in the under-doped regime of some cuprates.Comment: 10 pages, 9 figure
Vacuum Decay on a Brane World
The bubble nucleation rate for a first order phase transition occurring on a
brane world is calculated. Both the Coleman-de Luccia thin wall instanton and
the Hawking-Moss instanton are considered. The results are compared with the
corresponding nucleation rates for standard four-dimensional gravity.Comment: 5 page
Bounding bubbles: the vertex representation of 3d Group Field Theory and the suppression of pseudo-manifolds
Based on recent work on simplicial diffeomorphisms in colored group field
theories, we develop a representation of the colored Boulatov model, in which
the GFT fields depend on variables associated to vertices of the associated
simplicial complex, as opposed to edges. On top of simplifying the action of
diffeomorphisms, the main advantage of this representation is that the GFT
Feynman graphs have a different stranded structure, which allows a direct
identification of subgraphs associated to bubbles, and their evaluation is
simplified drastically. As a first important application of this formulation,
we derive new scaling bounds for the regularized amplitudes, organized in terms
of the genera of the bubbles, and show how the pseudo-manifolds configurations
appearing in the perturbative expansion are suppressed as compared to
manifolds. Moreover, these bounds are proved to be optimal.Comment: 28 pages, 17 figures. Few typos fixed. Minor corrections in figure 6
and theorem
Bethe Ansatz for the Weakly Asymmetric Simple Exclusion Process and phase transition in the current distribution
The probability distribution of the current in the asymmetric simple
exclusion process is expected to undergo a phase transition in the regime of
weak asymmetry of the jumping rates. This transition was first predicted by
Bodineau and Derrida using a linear stability analysis of the hydrodynamical
limit of the process and further arguments have been given by Mallick and
Prolhac. However it has been impossible so far to study what happens after the
transition. The present paper presents an analysis of the large deviation
function of the current on both sides of the transition from a Bethe ansatz
approach of the weak asymmetry regime of the exclusion process.Comment: accepted to J.Stat.Phys, 1 figure, 1 reference, 2 paragraphs adde
Characterization of Plum Procyanidins by Thiolytic Depolymerization
The phenolic compounds of ?Green Gage? (GG) plums (Prunus domestica L.), ?Rainha Cla?udia Verde?, from a ?protected designation of origin? (PDO), in Portugal, were quantified in both flesh and skin tissues of plums collected in two different orchards (GG-V and GG-C). Analyzes of phenolic compounds were also performed on another GG European plum obtained in France (GG-F) and two other French plums, ?Mirabelle? (M) and ?Golden Japan? (GJ). Thiolysis was used for the first time in the analysis of plum phenolic compounds. This methodology showed that the flesh and skin contain a large proportion of flavan-3-ols, which account, respectively, for 92 and 85% in GJ, 61 and 44% in GG-V, 62 and 48% in GG-C, 54 and 27% in M, and 45 and 37% in GG-F. Terminal units of procyanidins observed in plums are mainly (+)-catechin (54?77% of all terminal units in flesh and 57?81% in skin). The GJ plums showed a phenolic composition different from all of the others, with a lower content of chlorogenic acid isomers and the presence of A-type procyanidins as dimers and terminal residues of polymerized forms. The average degree of polymerization (DPn) of plum procyanidins was higher in the flesh (5?9 units) than in the skin (4?6 units). Procyanidin B7 was observed in the flesh of all GG plums and in the skin of the Portuguese ones. Principal component analysis of the phenolic composition of the flesh and skin of these plums obtained after thiolysis allowed their distinction according to the variety and origin, opening the possibility of the use of phenolic composition for variety/origin identification
New Results from a Near-Infrared Search for Hidden Broad-Line Regions in Ultraluminous Infrared Galaxies
This paper reports the latest results from a near-infrared search for hidden
broad-line regions (BLRs: FWHM >~ 2,000 km/s) in ultraluminous infrared
galaxies (ULIGs). The new sample contains thirty-nine ULIGs from the 1-Jy
sample selected for their lack of BLRs at optical wavelengths. The results from
this new study are combined with those from our previous optical and
near-infrared surveys to derive the fraction of all ULIGs with optical or
near-infrared signs of genuine AGN activity (either a BLR or [Si VI] emission).
Comparisons of the dereddened emission-line luminosities of the optical or
obscured BLRs detected in the ULIGs of the 1-Jy sample with those of optical
quasars indicate that the obscured AGN/quasar in ULIGs is the main source of
energy in at least 15 -- 25% of all ULIGs in the 1-Jy sample. This fraction is
30 -- 50% among ULIGs with L_ir > 10^{12.3} L_sun. These results are compatible
with those from recent mid-infrared spectroscopic surveys carried out with ISO.
(abridged)Comment: 40 pages including 10 figures and 3 tables (Table 3 should be printed
in landscape mode
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