3,372 research outputs found
X-ray observations of the galaxy cluster PKS 0745-191: To the virial radius, and beyond
We measure X-ray emission from the outskirts of the cluster of galaxies PKS
0745-191 with Suzaku, determining radial profiles of density, temperature,
entropy, gas fraction, and mass. These measurements extend beyond the virial
radius for the first time, providing new information about cluster assembly and
the diffuse intracluster medium out to ~1.5 r_200, (r_200 ~ 1.7 Mpc ~ 15'). The
temperature is found to decrease by roughly 70 per cent from 0.3-1 r_200. We
also see a flattening of the entropy profile near the virial radius and
consider the implications this has for the assumption of hydrostatic
equilibrium when deriving mass estimates. We place these observations in the
context of simulations and analytical models to develop a better understanding
of non-gravitational physics in the outskirts of the cluster.Comment: 10 pages, 11 figures, accepted to MNRAS; expanded discussion of
analysis and uncertainties, results qualitatively unchange
Continuous Variable Quantum State Sharing via Quantum Disentanglement
Quantum state sharing is a protocol where perfect reconstruction of quantum
states is achieved with incomplete or partial information in a multi-partite
quantum networks. Quantum state sharing allows for secure communication in a
quantum network where partial information is lost or acquired by malicious
parties. This protocol utilizes entanglement for the secret state distribution,
and a class of "quantum disentangling" protocols for the state reconstruction.
We demonstrate a quantum state sharing protocol in which a tripartite entangled
state is used to encode and distribute a secret state to three players. Any two
of these players can collaborate to reconstruct the secret state, whilst
individual players obtain no information. We investigate a number of quantum
disentangling processes and experimentally demonstrate quantum state
reconstruction using two of these protocols. We experimentally measure a
fidelity, averaged over all reconstruction permutations, of F = 0.73. A result
achievable only by using quantum resources.Comment: Published, Phys. Rev. A 71, 033814 (2005) (7 figures, 11 pages
A Pleistocene Clone of Palmer's Oak Persisting in Southern California
BACKGROUND: The distribution of Palmer's oak (Quercus palmeri Engelm.) includes numerous isolated populations that are presumably relicts of a formerly larger range that has contracted due to spreading aridity following the end of the Pleistocene. PRINCIPAL FINDINGS: We investigated a recently discovered disjunct population of Palmer's oak in the Jurupa Mountains of Riverside County, California. Patterns of allozyme polymorphism, morphological homogeneity, widespread fruit abortion, and evidence of fire resprouting all strongly support the hypothesis that the population is a single clone. The size of the clone and estimates of annual growth from multiple populations lead us to conclude that the clone is in excess of 13,000 years old. CONCLUSIONS: The ancient age of the clone implies it originated during the Pleistocene and is a relict of a vanished vegetation community. Range contraction after climate change best explains the modern disjunct distribution of Q. palmeri and perhaps other plants in California
Chemical Enrichment RGS cluster sample (CHEERS): Constraints on turbulence
Feedback from AGN, galactic mergers, and sloshing are thought to give rise to
turbulence, which may prevent cooling in clusters. We aim to measure the
turbulence in clusters of galaxies and compare the measurements to some of
their structural and evolutionary properties. It is possible to measure the
turbulence of the hot gas in clusters by estimating the velocity widths of
their X-ray emission lines. The RGS Spectrometers aboard XMM-Newton are
currently the only instruments provided with sufficient effective area and
spectral resolution in this energy domain. We benefited from excellent 1.6Ms
new data provided by the CHEERS project. The new observations improve the
quality of the archival data and allow us to place constraints for some
clusters, which were not accessible in previous work. One-half of the sample
shows upper limits on turbulence less than 500km/s. For several sources, our
data are consistent with relatively strong turbulence with upper limits on the
velocity widths that are larger than 1000km/s. The NGC507 group of galaxies
shows transonic velocities, which are most likely associated with the merging
phenomena and bulk motions occurring in this object. Where both low- and
high-ionization emission lines have good enough statistics, we find larger
upper limits for the hot gas, which is partly due to the different spatial
extents of the hot and cool gas phases. Our upper limits are larger than the
Mach numbers required to balance cooling, suggesting that dissipation of
turbulence may prevent cooling, although other heating processes could be
dominant. The systematics associated with the spatial profile of the source
continuum make this technique very challenging, though still powerful, for
current instruments. The ASTRO-H and Athena missions will revolutionize the
velocity estimates and discriminate between different spatial regions and
temperature phases.Comment: 16 pages, 18 figures, 3 tables, accepted for publications in
Astronomy and Astrophysic
Searching for cool and cooling X-ray emitting gas in 45 galaxy clusters and groups
We present a spectral analysis of cool and cooling gas in 45 cool-core
clusters and groups of galaxies obtained from Reflection Grating Spectrometer
(RGS) XMM- observations. The high-resolution spectra show FeXVII
emission in many clusters, which implies the existence of cooling flows. The
cooling rates are measured between the bulk Intracluster Medium (ICM)
temperature and 0.01 keV and are typically weak, operating at less than a few
tens of in clusters, and less than 1 in groups of galaxies. They are 10-30% of the classical
cooling rates in the absence of heating, which suggests that AGN feedback has a
high level of efficiency. If cooling flows terminate at 0.7 keV in clusters,
the associated cooling rates are higher, and have a typical value of a few to a
few tens of . Since the soft X-ray emitting region,
where the temperature keV, is spatially associated with H
nebulosity, we examine the relation between the cooling rates above 0.7 keV and
the H nebulae. We find that the cooling rates have enough energy to
power the total UV-optical luminosities, and are 5 to 50 times higher than the
observed star formation rates for low luminosity objects. In 4 high luminosity
clusters, the cooling rates above 0.7 keV are not sufficient and an inflow at a
higher temperature is required. Further residual cooling below 0.7 keV
indicates very low complete cooling rates in most clusters.Comment: 17 pages, 10 figures, accepted for publication in MNRA
Suzaku Observations of Local Ultraluminous Infrared Galaxies
We report the results from our analysis of {\it Suzaku} XIS (0.5-10 keV) and
HXD/PIN (15-40 keV) observations of five well-known local ULIRGs: {\em IRAS}
F05189-2524, {\em IRAS} F08572+3915, Mrk 273, PKS 1345+12, and Arp 220. The XIS
observations of F05189-2524 and Mrk 273 reveal strong iron lines consistent
with Fe K and changes in spectral shapes with respect to previous {\it
Chandra} and {\it XMM-Newton} observations. Mrk 273 is also detected by the
HXD/PIN at 1.8-. For F05189-2524, modeling of the data from the
different epochs suggests that the change in spectral shape is likely due to
the central source switching off, leaving behind a residual reflection
spectrum, or an increase in the absorbing column. An increase in the covering
fraction of the absorber can describe the spectral variations seen in Mrk 273,
although a reduction in the intrinsic AGN luminosity cannot be formally ruled
out. The {\it Suzaku} spectra of Mrk 273 are well fit by a ~94% covering
fraction model with a column density of cm. The
absorption-corrected log[ / ] ratio is consistent
with those found in PG Quasars. The 0.5-10 keV spectrum of PKS 1345+12 and Arp
220 seem unchanged from previous observations and their hard X-ray emission is
not convincingly detected by the HXD/PIN. The large column density derived from
CO observations and the large equivalent width of an ionized Fe line in Arp 220
can be reconciled by an ionized reflection model. F08572+3915 is undetected in
both the XIS and HXD/PIN, but the analysis of unpublished {\em Chandra} data
provides a new measurement at low energies.Comment: 37 pages including 4 tables and 10 figures. Accepted for publication
in ApJ. It is tentatively scheduled to appear in the January 20, 2009 issue
of Ap
Expression of hepatocyte growth factor-like protein in human wound tissue and its biological functionality in human keratinocytes
Hepatocyte growth factor-like protein (HGFl) and its receptor, Recepteur d'Origine Nantais (RON), have been implicated in the development of wound chronicity. HGFl and RON expression was detected in acute wound tissue, chronic wound tissue and in normal skin using quantitative polymerase chain reaction (Q-PCR). HGFl and RON expression was also assessed in chronic healing and chronic non-healing wound tissues using Q-PCR and immunohistochemical staining. Expression was similarly detected in the HaCaT immortalized human keratinocyte cell line using reverse transcription polymerase chain reaction (RT-PCR). rhHGFl was used to assess the impact of this molecule on HaCaT cell functionality using in vitro growth assays and electric cell-substrate impendence sensing (ECIS) migration assays. HGFl and RON transcript expression were significantly increased in acute wound tissue compared to chronic wound tissue and were also elevated, though non-significantly, in comparison to normal skin. Minimal expression was seen in both healing and non-healing chronic wounds. Treatment of HaCaT cells with rhHGFl had no effect on growth rates but did enhance cell migration. This effect was abolished by the addition of a phospholipase C gamma (PLCγ) small molecule inhibitor. The increased expression of HGFl and RON in acute, healing wounds and the pro-migratory effect of HGFl in an in vitro human keratinocyte model, may indicate a role for HGFl in active wound healing
Deep Chandra Observations of Abell 2199: the Interplay between Merger-Induced Gas Motions and Nuclear Outbursts in a Cool Core Cluster
We present new Chandra observations of Abell 2199 that show evidence of gas
sloshing due to a minor merger, as well as impacts of the radio source, 3C 338,
hosted by the central galaxy, NGC 6166, on the intracluster gas. The new data
are consistent with previous evidence of a Mach 1.46 shock 100" from the
cluster center, although there is still no convincing evidence for the expected
temperature jump. Other interpretations of this feature are possible, but none
is fully satisfactory. Large scale asymmetries, including enhanced X-ray
emission 200" southwest of the cluster center and a plume of low entropy,
enriched gas reaching 50" to the north of the center, are signatures of gas
sloshing induced by core passage of a merging subcluster about 400 Myr ago. An
association between the unusual radio ridge and low entropy gas are consistent
with this feature being the remnant of a former radio jet that was swept away
from the AGN by gas sloshing. A large discrepancy between the energy required
to produce the 100" shock and the enthalpy of the outer radio lobes of 3C 338
suggests that the lobes were formed by a more recent, less powerful radio
outburst. Lack of evidence for shocks in the central 10" indicates that the
power of the jet now is some two orders of magnitude smaller than when the 100"
shock was formed.Comment: 17 pages, 20 figures, accepted for publication in Ap
Electrophysiological effects of 5-hydroxytryptamine on isolated human atrial myocytes, and the influence of chronic beta-adrenoceptor blockade
<b>1.</b> 5-Hydroxytryptamine (5-HT) has been postulated to play a proarrhythmic role in the human atria via stimulation of 5-HT<sub>4</sub> receptors.
<b>2.</b> The aims of this study were to examine the effects of 5-HT on the L-type Ca<sup>2+</sup> current (<i>I</i><sub>CaL</sub>) action potential duration (APD), the effective refractory period (ERP) and arrhythmic activity in human atrial cells, and to assess the effects of prior treatment with β-adrenoceptor antagonists.
<b>3.</b> Isolated myocytes, from the right atrial appendage of 27 consenting patients undergoing cardiac surgery who were in sinus rhythm, were studied using the whole-cell perforated patch-clamp technique at 37ºC.
<b>4.</b> 5-HT (1 n-10 μM) caused a concentration-dependent increase in <i>I</i><sub>CaL</sub>, which was potentiated in cells from β-blocked (maximum response to 5-HT, E<sub>max</sub>=299±12% increase above control) compared to non-β-blocked patients (E<sub>max</sub>=220±6%, P<0.05), but with no change in either the potency (log EC<sub>50</sub>: -7.09±0.07 vs -7.26±0.06) or Hill coefficient (<i>n</i><sub>H</sub>: 1.5±0.6 vs 1.5±0.3) of the 5-HT concentration-response curve.
<b>5.</b> 5-HT (10 μM) produced a greater increase in the APD at 50% repolarisation (APD50) in cells from β-blocked patients (of 37±10 ms, i.e. 589±197%) vs non-β-blocked patients (of 10±4 ms, i.e. 157±54%; P<0.05). Both the APD<sub>90</sub> and the ERP were unaffected by 5-HT.
<b>6.</b> Arrhythmic activity was observed in response to 5-HT in five of 17 cells (29%) studied from β-blocked, compared to zero of 16 cells from the non-β-blocked patients (P<0.05).
<b>7.</b> In summary, the 5-HT-induced increase in calcium current was associated with a prolonged early plateau phase of repolarisation, but not late repolarisation or refractoriness, and the enhancement of these effects by chronic β-adrenoceptor blockade was associated with arrhythmic potential
Discovery of O VII line emitting gas in elliptical galaxies
In the cores of ellipticals, clusters, and groups of galaxies, the gas has a
cooling time shorter than 1 Gyr. It is possible to probe cooling flows through
the detection of Fe XVII and O VII emission lines, but so far O VII has not
been detected in any individual object. The Reflection Grating Spectrometers
(RGS) aboard XMM-Newton are currently the only instruments able to detect O VII
in extended objects such as elliptical galaxies and galaxy clusters. We
searched for evidence of O VII through all the archival RGS observations of
galaxy clusters, groups of galaxies, and elliptical galaxies focusing on those
with core temperatures below 1 keV. We have discovered O VII resonance (21.6A)
and forbidden (22.1A) lines for the first time in the spectra of individual
objects. O VII was detected at a level higher than three sigma in six
elliptical galaxies: M 84, M 86, M 89, NGC 1316, NGC 4636, and NGC 5846. M 84,
M 86 and M 89 are members of the Virgo Cluster, the others are central dominant
galaxies of groups, and most them show evidence of O VI in UV spectra. We
detect no significant trend between the Fe XVII and O VII
resonance-to-forbidden line ratios, possibly because of the limited statistics.
The observed line ratios = (0.52+/-0.02, 0.9+/-0.2) indicate
that the spectra of all these ellipticals are affected by resonance scattering,
suggesting low turbulence. Deeper exposures will help to understand whether the
Fe XVII and O VII lines are both produced by the same cooling gas or by
multiphase gas. Our O VII luminosities correspond to 0.2-2 Msun/yr, which agree
with the predictions for ellipticals. Such weak cooling rates would not be
detected in clusters because their spectra are dominated by the emission of
hotter gas, and owing to their greater distance, the expected O VII line flux
would be undetectable.Comment: 5 pages, 2 figures, 2 tables, accepted for publication in Astronomy
and Astrophysic
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