722 research outputs found
Investigating the cores of fossil systems with Chandra
We investigate the cores of fossil galaxy groups and clusters (`fossil
systems') using archival Chandra data for a sample of 17 fossil systems. We
determined the cool-core fraction for fossils via three observable diagnostics,
the central cooling time, cuspiness, and concentration parameter. We quantified
the dynamical state of the fossils by the X-ray peak/brightest cluster galaxy
(BCG), and the X-ray peak/emission weighted centre separations. We studied the
X-ray emission coincident with the BCG to detect the presence of potential
thermal coronae. A deprojection analysis was performed for z < 0.05 fossils to
obtain cooling time and entropy profiles, and to resolve subtle temperature
structures. We investigated the Lx-T relation for fossils from the 400d
catalogue to see if the scaling relation deviates from that of other groups.
Most fossils are identified as cool-core objects via at least two cool-core
diagnostics. All fossils have their dominant elliptical galaxy within 50 kpc of
the X-ray peak, and most also have the emission weighted centre within that
distance. We do not see clear indications of a X-ray corona associated with the
BCG unlike that has been observed for some other objects. Fossils do not have
universal temperature profiles, with some low-temperature objects lacking
features that are expected for ostensibly relaxed objects with a cool-core. The
entropy profiles of the z < 0.05 fossil systems can be well-described by a
power law model, albeit with indices smaller than 1. The 400d fossils Lx-T
relation shows indications of an elevated normalisation with respect to other
groups, which seems to persist even after factoring in selection effects.Comment: Accepted for publication in Astronomy and Astrophysic
XMM-Newton and Chandra Cross Calibration Using HIFLUGCS Galaxy Clusters: Systematic Temperature Differences and Cosmological Impact
Cosmological constraints from clusters rely on accurate gravitational mass
estimates, which strongly depend on cluster gas temperature measurements.
Therefore, systematic calibration differences may result in biased,
instrument-dependent cosmological constraints. This is of special interest in
the light of the tension between the Planck results of the primary temperature
anisotropies of the CMB and Sunyaev-Zel'dovich plus X-ray cluster counts
analyses. We quantify in detail the systematics and uncertainties of the
cross-calibration of the effective area between five X-ray instruments,
EPIC-MOS1/MOS2/PN onboard XMM-Newton and ACIS-I/S onboard Chandra, and the
influence on temperature measurements. Furthermore, we assess the impact of the
cross calibration uncertainties on cosmology. Using the HIFLUGCS sample,
consisting of the 64 X-ray brightest galaxy clusters, we constrain the ICM
temperatures through spectral fitting in the same, mostly isothermal, regions
and compare them. Our work is an extension to a previous one using X-ray
clusters by the IACHEC. Performing spectral fitting in the full energy band we
find that best-fit temperatures determined with XMM-Newton/EPIC are
significantly lower than Chandra/ACIS temperatures. We demonstrate that effects
like multitemperature structure and different relative sensitivities of the
instruments at certain energy bands cannot explain the observed differences. We
conclude that using XMM-Newton/EPIC, instead of Chandra/ACIS to derive full
energy band temperature profiles for cluster mass determination results in an
8% shift towards lower OmegaM values and <1% shift towards higher sigma8 values
in a cosmological analysis of a complete sample of galaxy clusters. Such a
shift is insufficient to significantly alleviate the tension between Planck CMB
anisotropies and SZ plus XMM-Newton cosmological constraints.Comment: Accepted by A&A; Python-Script for modification of XMM-Newton/EPIC
and Chandra/ACIS effective areas according to the stacked residual ratios:
https://wikis.mit.edu/confluence/display/iachec/Data
What difference can drop-in substitution actually make? A life cycle assessment of alternative water repellent chemicals
Per- and polyfluoroalkyl substances (PFASs) are used in durable water repellents (DWRs) on outdoor garments and manufacturers are currently phasing out hazardous PFASs. A critical question is: which alternatives should be chosen? The answer should depend on a holistic assessment, but the published inventory data and methodological guidance for assessing PFAS in products is slim and typically limited to hazard assessment. We aim to provide a holistic assessment of the potential environmental consequences of this phase out of DWRs, going beyond the more traditional hazard-focused substitution assessment to also include a broad life-cycle-based assessment of PFASs and their drop-in alternatives. In this study, potential environmental consequences of the phase out were evaluated by applying a life cycle assessment (LCA) to shell jackets with side-chain fluorinated polymer based (i.e., PFASs) or non-fluorinated alternative DWRs with the aim to support a substitution assessment. We demonstrated an innovative approach to impact assessment by inclusion of PFAS related fate and toxicity and invested effort towards contributing new primary inventory data by using a combination of industry dialogue and performance measurements from our larger project context. From a methodological point of view, this paper demonstrates the state-of-the-art in product LCA of persistent textile chemicals and identifies the current limits of this assessment approach. It also delivers new LCI data of use to other analysts. The LCA results in this paper suggest that jackets without PFASs are environmentally preferable. Potential problem shifting due to increased washing and reimpregnation of the jackets did not outweigh PFAS-related potential toxicity impacts as indicated by LCA results. Based on the results presented here, specific DWRs within the non-fluorinated DWR group could not be identified as preferable to others. This LCA does however provide a relevant starting point for more detailed studies on specific DWR systems and it supports moves to phase-out PFASs from non-essential DWR uses
Bridges over troubled waters: an interdisciplinary framework for evaluating the interconnectedness within fragmented domestic flood risk management systems
Diversification of strategies in Flood Risk Management (FRM) is widely regarded as a necessary step forward in terms of lessening the likelihood and magnitude of flooding, as well as minimizing the exposure of people and property, and in turn the disruption, economic damage, health impacts and other adverse consequences that ensue when floods occur. Thus, diversification is often heralded as an essential condition for enhancing societal resilience to flooding. However, an inevitable consequence of diversifying strategies and practices in FRM is that it can lead to fragmentation within FRM systems, in terms of the distribution of responsibilities between actors and governing rules enacted within different policy domains. This can prove detrimental to the effectiveness of FRM.
Building upon the notion of fragmentation developed in legal and governance literature, this paper introduces the concept of âbridging mechanismsâ, i.e. instruments that remedy fragmentation by enhancing interconnectedness between relevant actors through information transfer, coordination and cooperation. This paper develops a typology of both fragmentation and bridging mechanisms and analyzes their relations, partly drawing upon empirical research conducted within the EU âSTAR-FLOODâ project. In turn, this paper outlines a novel interdisciplinary methodological framework for evaluating the degree and quality of the interconnectedness within fragmented domestic FRM systems. A pragmatic, flexible and broadly applicable tool, this framework is both suited for academic purposes, as well as for practically oriented analysis and (re)development of fragmented FRM systems, and potentially other fragmented systems, within the EU and abroad
HSP90-CDC37-PP5 forms a structural platform for kinase dephosphorylation.
Activation of client protein kinases by the HSP90 molecular chaperone system is affected by phosphorylation at multiple sites on HSP90, the kinase-specific co-chaperone CDC37, and the kinase client itself. Removal of regulatory phosphorylation from client kinases and their release from the HSP90-CDC37 system depends on the Ser/Thr phosphatase PP5, which associates with HSP90 via its N-terminal TPR domain. Here, we present the cryoEM structure of the oncogenic protein kinase client BRAFV600E bound to HSP90-CDC37, showing how the V600E mutation favours BRAF association with HSP90-CDC37. Structures of HSP90-CDC37-BRAFV600E complexes with PP5 in autoinhibited and activated conformations, together with proteomic analysis of its phosphatase activity on BRAFV600E and CRAF, reveal how PP5 is activated by recruitment to HSP90 complexes. PP5 comprehensively dephosphorylates client proteins, removing interaction sites for regulatory partners such as 14-3-3 proteins and thus performing a 'factory reset' of the kinase prior to release
A detached double X-ray tail in the merging galaxy cluster Z8338 with a large double tail
When subhalos infall into galaxy clusters, their gas content is ram pressure
stripped by the intracluster medium (ICM) and may turn into cometary tails. We
report the discovery of two spectacular X-ray double tails in a single galaxy
cluster, Z8338, revealed by 70 ks Chandra observations. The brighter one, with
an X-ray bolometric luminosity of , is a
detached tail stripped from the host halo and extended at least 250 kpc in
projection. The head of the detached tail is a cool core with the front tip of
the cold front 30 kpc away from the nucleus of its former host galaxy.
The cooling time of the detached cool core is Gyr. For the detached
gas, the gravity of the once-associated dark matter halo further enhances the
Rayleigh-Taylor (RT) instability. From its survival, we find that a magnetic
field of a few G is required to suppress the hydrodynamic instability. The
X-ray temperature in the tail increases from 0.9 keV at the front tip to 1.6
keV in the wake region, which suggests the turbulent mixing with the hotter
ICM. The fainter double X-ray tail, with a total X-ray luminosity of , appears to stem from the cool core of a
subcluster in Z8338, and likely was formed during the ongoing merger. This
example suggests that X-ray cool cores can be displaced and eventually
destroyed by mergers, while the displaced cool cores can survive for some
extended period of time.Comment: 11 pages, 8 figures, MNRAS accepte
ICM cooling, AGN feedback and BCG properties of galaxy groups-Five properties where groups differ from clusters
Using Chandra data for a sample of 26 galaxy groups, we constrained the
central cooling times (CCTs) of the ICM and classified the groups as strong
cool-core (SCC), weak cool-core (WCC) and non-cool-core (NCC) based on their
CCTs. The total radio luminosity of the brightest cluster galaxy (BCG) was
obtained using radio catalog data and literature, which was compared to the CCT
to understand the link between gas cooling and radio output. We determined
K-band luminosities of the BCG with 2MASS data, and used it to constrain the
masses of the SMBH, which were then compared to the radio output. We also
tested for correlations between the BCG luminosity and the overall X-ray
luminosity and mass of the group.
The observed cool-core/non-cool-core fractions for groups are comparable to
those of clusters. However, notable differences are seen. For clusters, all
SCCs have a central temperature drop, but for groups, this is not the case as
some SCCs have centrally rising temperature profiles. While for the cluster
sample, all SCC clusters have a central radio source as opposed to only 45% of
the NCCs, for the group sample, all NCC groups have a central radio source as
opposed to 77% of the SCC groups. For clusters, there are indications of an
anticorrelation trend between radio luminosity and CCT which is absent for the
groups. Indications of a trend of radio luminosity with black hole mass
observed in SCC clusters is absent for groups. The strong correlation observed
between the BCG luminosity and the cluster X-ray luminosity/cluster mass
weakens significantly for groups.
We conclude that there are important differences between clusters and groups
within the ICM cooling/AGN feedback paradigm.Comment: Accepted for publication in Astronomy and Astrophysic
GLAMM: Genome-Linked Application for Metabolic Maps
The Genome-Linked Application for Metabolic Maps (GLAMM) is a unified web interface for visualizing metabolic networks, reconstructing metabolic networks from annotated genome data, visualizing experimental data in the context of metabolic networks and investigating the construction of novel, transgenic pathways. This simple, user-friendly interface is tightly integrated with the comparative genomics tools of MicrobesOnline [Dehal et al. (2010) Nucleic Acids Research, 38, D396âD400]. GLAMM is available for free to the scientific community at glamm.lbl.gov
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