84 research outputs found
Variation in cold hardiness and carbohydrate concentration from dormancy induction to bud burst among provenances of three European oak species
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A parametric physical model for the intracluster medium and its use in joint SZ/X-ray analyses of galaxy clusters
We present a parameterized model of the intra-cluster medium that is suitable
for jointly analysing pointed observations of the Sunyaev-Zel'dovich (SZ)
effect and X-ray emission in galaxy clusters. The model is based on assumptions
of hydrostatic equilibrium, the Navarro, Frenk and White (NFW) model for the
dark matter, and a softened power law profile for the gas entropy. We test this
entropy-based model against high and low signal-to-noise mock observations of a
relaxed and recently-merged cluster from N-body/hydrodynamic simulations, using
Bayesian hyper-parameters to optimise the relative statistical weighting of the
mock SZ and X-ray data. We find that it accurately reproduces both the global
values of the cluster temperature, total mass and gas mass fraction (fgas), as
well as the radial dependencies of these quantities outside of the core (r >
kpc). For reference we also provide a comparison with results from the single
isothermal beta model. We confirm previous results that the single isothermal
beta model can result in significant biases in derived cluster properties.Comment: Published in MNRAS. 20 pages. 9 figure
Non-parametric modeling of the intra-cluster gas using APEX-SZ bolometer imaging data
We demonstrate the usability of mm-wavelength imaging data obtained from the
APEX-SZ bolometer array to derive the radial temperature profile of the hot
intra-cluster gas out to radius r_500 and beyond. The goal is to study the
physical properties of the intra-cluster gas by using a non-parametric
de-projection method that is, aside from the assumption of spherical symmetry,
free from modeling bias. We use publicly available X-ray imaging data from the
XMM-Newton observatory and our Sunyaev-Zel'dovich Effect (SZE) imaging data
from the APEX-SZ experiment at 150 GHz to de-project the density and
temperature profiles for the relaxed cluster Abell 2204. We derive the gas
density, temperature and entropy profiles assuming spherical symmetry, and
obtain the total mass profile under the assumption of hydrostatic equilibrium.
For comparison with X-ray spectroscopic temperature models, a re-analysis of
the recent Chandra observation is done with the latest calibration updates.
Using the non-parametric modeling we demonstrate a decrease of gas temperature
in the cluster outskirts, and also measure the gas entropy profile. These
results are obtained for the first time independently of X-ray spectroscopy,
using SZE and X-ray imaging data. The contribution of the SZE systematic
uncertainties in measuring T_e at large radii is shown to be small compared to
the Chandra systematic spectroscopic errors. The upper limit on M_200 derived
from the non-parametric method is consistent with the NFW model prediction from
weak lensing analysis.Comment: Replaced with the published version; A&A 519, A29 (2010
Substructure of the galaxy clusters in the REXCESS sample: observed statistics and comparison to numerical simulations
We study the substructure statistics of a representative sample of galaxy
clusters by means of two currently popular substructure characterisation
methods, power ratios and centroid shifts. We use the 31 clusters from the
REXCESS sample, compiled from the southern ROSAT All-Sky cluster survey REFLEX
with a morphologically unbiased selection in X-ray luminosity and redshift, all
of which have been reobserved with XMM-Newton. We investigate the uncertainties
of the substructure parameters and examine the dependence of the results on
projection effects, finding that the uncertainties of the parameters can be
quite substantial. Thus while the quantification of the dynamical state of
individual clusters with these parameters should be treated with extreme
caution, these substructure measures provide powerful statistical tools to
characterise trends of properties in large cluster samples. The centre shift
parameter, w, is found to be more sensitive in general. For the REXCESS sample
neither the occurence of substructure nor the presence of cool cores depends on
cluster mass. There is a significant anti-correlation between the existence of
substantial substructure and cool cores. The simulated clusters show on average
larger substructure parameters than the observed clusters, a trend that is
traced to the fact that cool regions are more pronounced in the simulated
clusters, leading to stronger substructure measures in merging clusters and
clusters with offset cores. Moreover, the frequency of cool regions is higher
in the simulations than in the observations, implying that the description of
the physical processes shaping cluster formation in the simulations requires
further improvement.Comment: Mauscript submitted to Astronomy and Astrophysics, 20 figure
Diurnal cycles of embolism formation and repair in petioles of grapevine (Vitis vinifera cv. Chasselas)
The impact of water deficit on stomatal conductance (gs), petiole hydraulic conductance (Kpetiole), and vulnerability to cavitation (PLC, percentage loss of hydraulic conductivity) in leaf petioles has been observed on field-grown vines (Vitis vinifera L. cv. Chasselas). Petioles were highly vulnerable to cavitation, with a 50% loss of hydraulic conductivity at a stem xylem water potential (Ψx) of –0.95 MPa, and up to 90% loss of conductivity at a Ψx of –1.5 MPa. Kpetiole described a daily cycle, decreasing during the day as water stress and evapotranspiration increased, then rising again in the early evening up to the previous morning's Kpetiole levels. In water-stressed vines, PLC increased sharply during the daytime and reached maximum values (70–90%) in the middle of the afternoon. Embolism repair occurred in petioles from the end of the day through the night. Indeed, PLC decreased in darkness in water-stressed vines. PLC variation in irrigated plants showed the same tendency, but with a smaller amplitude. The Chasselas cultivar appears to develop hydraulic segmentation, in which petiole cavitation plays an important role as a ‘hydraulic fuse’, thereby limiting leaf transpiration and the propagation of embolism and preserving the integrity of other organs (shoots and roots) during water stress. In the present study, progressive stomatal closure responded to a decrease in Kpetiole and an increase in cavitation events. Almost total closure of stomata (90%) was measured when PLC in petioles reached >90%
Sunyaev-Zel'dovich-measured Pressure Profiles from the Bolocam X-Ray/SZ Galaxy Cluster Sample
We describe Sunyaev-Zel'dovich (SZ) effect measurements and analysis of the intracluster medium (ICM) pressure profiles of a set of 45 massive galaxy clusters imaged using Bolocam at the Caltech Submillimeter Observatory. We deproject the average pressure profile of our sample into 13 logarithmically spaced radial bins between 0.07R_(500) and 3.5R_(500), and we find that a generalized Navarro, Frenk, and White (gNFW) profile describes our data with sufficient goodness-of-fit and best-fit parameters (C_(500), α, β, γ, P_0 = 1.18, 0.86, 3.67, 0.67, 4.29). We use X-ray data to define cool-core and disturbed subsamples of clusters, and we constrain the average pressure profiles of each of these subsamples. We find that, given the precision of our data, the average pressure profiles of disturbed and cool-core clusters are consistent with one another at R≳ 0.15R_(500), with cool-core systems showing indications of higher pressure at R≾ 0.15R_(500). In addition, for the first time, we place simultaneous constraints on the mass scaling of cluster pressure profiles, their ensemble mean profile, and their radius-dependent intrinsic scatter between 0.1R_(500) and 2.0R_(500). The scatter among profiles is minimized at radii between ≃ 0.2R_(500) and ≃ 0.5R_(500), with a value of ≃ 20%. These results for the intrinsic scatter are largely consistent with previous analyses, most of which have relied heavily on X-ray derived pressures of clusters at significantly lower masses and redshifts compared to our sample. Therefore, our data provide further evidence that cluster pressure profiles are largely universal with scatter of ≃ 20%-40% about the universal profile over a wide range of masses and redshifts
Sunyaev-Zel'dovich clusters in millennium gas simulations
Large surveys using the Sunyaev–Zel’dovich (SZ) effect to find clusters of galaxies are now starting to yield large numbers of systems out to high redshift, many of which are new dis- coveries. In order to provide theoretical interpretation for the release of the full SZ cluster samples over the next few years, we have exploited the large-volume Millennium gas cosmo- logical N-body hydrodynamics simulations to study the SZ cluster population at low and high redshift, for three models with varying gas physics. We confirm previous results using smaller samplesthattheintrinsic(spherical)Y500–M500relationhasverylittlescatter(σlog10Y ≃0.04), is insensitive to cluster gas physics and evolves to redshift 1 in accordance with self-similar expectations. Our preheating and feedback models predict scaling relations that are in excel- lent agreement with the recent analysis from combined Planck and XMM–Newton data by the Planck Collaboration. This agreement is largely preserved when r500 and M500 are derived using thehydrostaticmassproxy,YX,500,albeitwithsignificantlyreducedscatter(σlog10Y ≃0.02),a result that is due to the tight correlation between Y500 and YX,500. Interestingly, this assumption also hides any bias in the relation due to dynamical activity. We also assess the importance of projection effects from large-scale structure along the line of sight, by extracting cluster Y500 values from 50 simulated 5 × 5-deg2 sky maps. Once the (model-dependent) mean signal is subtracted from the maps we find that the integrated SZ signal is unbiased with respect to the underlying clusters, although the scatter in the (cylindrical) Y500–M500 relation increases in the preheating case, where a significant amount of energy was injected into the intergalactic medium at high redshift. Finally, we study the hot gas pressure profiles to investigate the origin of the SZ signal and find that the largest contribution comes from radii close to r500 in all cases. The profiles themselves are well described by generalized Navarro, Frenk & White profiles but there is significant cluster-to-cluster scatter. In conclusion, our results support the notion that Y500 is a robust mass proxy for use in cosmological analyses with clusters
The Contribution of Radio Galaxy Contamination to Measurements of the Sunyaev-Zel'dovich Decrement in Massive Galaxy Clusters at 140 GHz with Bolocam
We describe in detail our characterization of the compact radio source population in 140 GHz Bolocam observations of a set of 45 massive galaxy clusters. We use a combination of 1.4 and 30 GHz data to select a total of 28 probable cluster-member radio galaxies and also to predict their 140 GHz flux densities. All of these galaxies are steep-spectrum radio sources and they are found preferentially in the cool-core clusters within our sample. In particular, 11 of the 12 brightest cluster-member radio sources are associated with cool-core systems. Although none of the individual galaxies are robustly detected in the Bolocam data, the ensemble-average flux density at 140 GHz is consistent with, but slightly lower than, the extrapolation from lower frequencies assuming a constant spectral index. In addition, our data indicate an intrinsic scatter of ≃ 30% around the power-law extrapolated flux densities at 140 GHz, although our data do not tightly constrain this scatter. For our cluster sample, which is composed of high-mass and moderate-redshift systems, we find that the maximum fractional change in the Sunyaev-Zel'dovich signal integrated over any single cluster due to the presence of these radio sources is ≃ 20%, and only ≃ 1/4 of the clusters show a fractional change of more than 1%. The amount of contamination is strongly dependent on cluster morphology, and nearly all of the clusters with ≥1% contamination are cool-core systems. This result indicates that radio contamination is not significant compared with current noise levels in 140 GHz images of massive clusters and is in good agreement with the level of radio contamination found in previous results based on lower frequency data or simulations
Reduction of serum IGF-I levels in patients affected with Monoclonal Gammopathies of undetermined significance or Multiple Myeloma. Comparison with bFGF, VEGF and K-ras gene mutation
<p>Abstract</p> <p>Background</p> <p>Serum levels of IGF-I in patients affected with multiple myeloma (MM) have been scarcely studied. The present study is aimed to explore this point comparing 55 healthy subjects, 71 monoclonal gammopaties of uncertain significance (MGUS) and 77 overt MM patients. In the same subjects, basic FGF and VEGF, have been detected. All three mediators were analyzed in function of K-<it>ras </it>mutation and melphalan response. Concerning IGF-I, two representative monitoring examples have also been added.</p> <p>Methods</p> <p>Cytokine determinations were performed by commercially available ELISA kits, while K12-<it>ras </it>mutation was investigated on genomic DNA isolated from bone marrow cell specimens by RFLP-PCR assay.</p> <p>Results</p> <p>Significant reductions of IGF-I levels were observed in MGUS and MM as compared with healthy controls. In addition, MM subjects showed significantly decreased serum IGF-I levels than MGUS. Conversely, increasing levels were observed for bFGF and VEGF, molecules significantly correlated. A multivariate analysis corrected for age and gender confirmed the significant difference only for IGF-I values (P = 0.01). K12-<it>ras </it>mutation was significantly associated with malignancy, response to therapy and with significantly increased serum bFGF levels.</p> <p>Conclusion</p> <p>IGF-I reduction in the transition: Controls→MGUS→MM and changes observed over time suggest that IGF-I should be furtherly studied in future clinical trials as a possible monitoring marker for MM.</p
IL-10 Signaling Blockade Controls Murine West Nile Virus Infection
West Nile virus (WNV), a mosquito-borne single-stranded RNA flavivirus, can cause significant human morbidity and mortality. Our data show that interleukin-10 (IL-10) is dramatically elevated both in vitro and in vivo following WNV infection. Consistent with an etiologic role of IL-10 in WNV pathogenesis, we find that WNV infection is markedly diminished in IL-10 deficient (IL-10−/−) mice, and pharmacologic blockade of IL-10 signaling by IL-10 neutralizing antibody increases survival of WNV-infected mice. Increased production of antiviral cytokines in IL-10−/− mice is associated with more efficient control of WNV infection. Moreover, CD4+ T cells produce copious amounts of IL-10, and may be an important cellular source of IL-10 during WNV infection in vivo. In conclusion, IL-10 signaling plays a negative role in immunity against WNV infection, and blockade of IL-10 signaling by genetic or pharmacologic means helps to control viral infection, suggesting a novel anti-WNV therapeutic strategy
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