451 research outputs found
Globaliseringen av kontroll: Fremveksten av registrerings- og overvåkningssystemer i Europa
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Comparing the temperatures of galaxy clusters from hydro-N-body simulations to Chandra and XMM-Newton observations
Theoretical studies of the physical processes guiding the formation and
evolution of galaxies and galaxy clusters in the X-ray are mainly based on the
results of numerical hydrodynamical N-body simulations, which in turn are often
directly compared to X-ray observations. Although trivial in principle, these
comparisons are not always simple. We demonstrate that the projected
spectroscopic temperature of thermally complex clusters obtained from X-ray
observations is always lower than the emission-weighed temperature, which is
widely used in the analysis of numerical simulations. We show that this
temperature bias is mainly related to the fact that the emission-weighted
temperature does not reflect the actual spectral properties of the observed
source. This has important implications for the study of thermal structures in
clusters, especially when strong temperature gradients, like shock fronts, are
present. Because of this bias, in real observations shock fronts appear much
weaker than what is predicted by emission-weighted temperature maps, and may
even not be detected. This may explain why, although numerical simulations
predict that shock fronts are a quite common feature in clusters of galaxies,
to date there are very few observations of objects in which they are clearly
seen. To fix this problem we propose a new formula, the spectroscopic-like
temperature function, and show that, for temperature larger than 3 keV, it
approximates the spectroscopic temperature better than few per cent, making
simulations more directly comparable to observations.Comment: Submitted for publication in MNRAS; 15 pages, 10 color figures and 13
BW figures,mn2e.cls. High resolution figures available here:
http://people.roma2.infn.it/~mazzotta/preprints/mazzotta.pd
Can simulations reproduce the observed temperature-mass relation for clusters of galaxies?
It has become increasingly apparent that traditional hydrodynamical
simulations of galaxy clusters are unable to reproduce the observed properties
of galaxy clusters, in particular overpredicting the mass corresponding to a
given cluster temperature. Such overestimation may lead to systematic errors in
results using galaxy clusters as cosmological probes, such as constraints on
the density perturbation normalization sigma_8. In this paper we demonstrate
that inclusion of additional gas physics, namely radiative cooling and a
possible preheating of gas prior to cluster formation, is able to bring the
temperature-mass relation in the innermost parts of clusters into good
agreement with recent determinations by Allen, Schmidt & Fabian using Chandra
data.Comment: 5 pages, submitted to MNRA
Antagonism of the prostaglandin D(2 )receptor CRTH2 attenuates asthma pathology in mouse eosinophilic airway inflammation
BACKGROUND: Mast cell-derived prostaglandin D(2 )(PGD(2)), may contribute to eosinophilic inflammation and mucus production in allergic asthma. Chemoattractant receptor homologous molecule expressed on TH(2 )cells (CRTH2), a high affinity receptor for prostaglandin D(2), mediates trafficking of TH(2)-cells, mast cells, and eosinophils to inflammatory sites, and has recently attracted interest as target for treatment of allergic airway diseases. The present study involving mice explores the specificity of CRTH2 antagonism of TM30089, which is structurally closely related to the dual TP/CRTH2 antagonist ramatroban, and compares the ability of ramatroban and TM30089 to inhibit asthma-like pathology. METHODS: Affinity for and antagonistic potency of TM30089 on many mouse receptors including thromboxane A(2 )receptor mTP, CRTH2 receptor, and selected anaphylatoxin and chemokines receptors were determined in recombinant expression systems in vitro. In vivo effects of TM30089 and ramatroban on tissue eosinophilia and mucus cell histopathology were examined in a mouse asthma model. RESULTS: TM30089, displayed high selectivity for and antagonistic potency on mouse CRTH2 but lacked affinity to TP and many other receptors including the related anaphylatoxin C3a and C5a receptors, selected chemokine receptors and the cyclooxygenase isoforms 1 and 2 which are all recognized players in allergic diseases. Furthermore, TM30089 and ramatroban, the latter used as a reference herein, similarly inhibited asthma pathology in vivo by reducing peribronchial eosinophilia and mucus cell hyperplasia. CONCLUSION: This is the first report to demonstrate anti-allergic efficacy in vivo of a highly selective small molecule CRTH2 antagonist. Our data suggest that CRTH2 antagonism alone is effective in mouse allergic airway inflammation even to the extent that this mechanism can explain the efficacy of ramatroban
Quantitative transcript analysis of the inducible expression system pSIP: comparison of the overexpression of Lactobacillus spp. β-galactosidases in Lactobacillus plantarum
<p>Abstract</p> <p>Background</p> <p>Two sets of overlapping genes, <it>lacLMReu </it>and <it>lacLMAci</it>, encoding heterodimeric β-galactosidases from <it>Lactobacillus reuteri </it>and <it>Lactobacillus acidophilus</it>, respectively, have previously been cloned and expressed using the pSIP vector system and <it>Lactobacillus plantarum </it>WCSF1 as host. Despite the high similarity between these <it>lacLM </it>genes and the use of identical cloning and expression strategies, strains harboring <it>lacLMReu </it>produced about twenty-fold more β-galactosidase than strains containing <it>lacLMAci</it>.</p> <p>Results</p> <p>In this study, the plasmid copy numbers (PCN) of expression vectors pEH9R (<it>lacLMReu</it>) and pEH9A (<it>lacLMAci</it>) as well as the transcription levels of both <it>lacLM </it>genes were compared using quantitative PCR methods. Analyses of parallel fermentations of <it>L. plantarum </it>harboring either pEH9R or pEH9A showed that the expression plasmids were present in similar copy numbers. However, transcript levels of <it>lacLM </it>from <it>L. reuteri </it>(pEH9R) were up to 18 times higher than those of <it>lacLM </it>from <it>L. acidophilus </it>(pEH9A). As a control, it was shown that the expression levels of regulatory genes involved in pheromone-induced promoter activation were similar in both strains.</p> <p>Conclusion</p> <p>The use of identical expression strategies for highly similar genes led to very different mRNA levels. The data indicate that this difference is primarily caused by translational effects that are likely to affect both mRNA synthesis rates and mRNA stability. These translational effects thus seem to be a dominant determinant for the success of gene expression efforts in lactobacilli.</p
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