Testing cosmic acceleration for w(z)w(z) parameterizations using fgasf_{gas} measurements in galaxy clusters

In this paper we study the cosmic acceleration for five dynamical dark energy models whose equation of state varies with redshift. The cosmological parameters of these models are constrained by performing a MCMC analysis using mainly gas mass fraction, $f_{gas}$, measurements in two samples of galaxy clusters: one reported by Allen et al. (2004), which consists of $42$ points spanning the redshift range $0.05<z<1.1$, and the other by Hasselfield et al. (2013) from the Atacama Cosmology Telescope survey, which consists of $91$ data points in the redshift range $0.118 < \mathrm{z} < 1.36$. In addition, we perform a joint analysis with the measurements of the Hubble parameter $H(z)$, baryon acoustic oscillations and the cosmic microwave background radiation from WMAP and Planck measurements to estimate the equation of state parameters. We obtained that both $f_{gas}$ samples provide consistent constraints on the cosmological parameters. We found that the $f_{gas}$ data is consistent at the $2\sigma$ confidence level with a cosmic slowing down of the acceleration at late times for most of the parameterizations. The constraints of the joint analysis using WMAP and Planck measurements show that this trend disappears. We have confirmed that the $f_{gas}$ probe provides competitive constraints on the dark energy parameters when a $w(z)$ is assumed.Comment: 21 pages, 8 Tables, 11 Figures, accepted for publication in MNRA

The abundance of Bullet-groups in LCDM

We estimate the expected distribution of displacements between the two dominant dark matter (DM) peaks (DM-DM displacements) and between DM and gaseous baryon peak (DM-gas displacements) in dark matter halos with masses larger than $10^{13}$ Msun/h. We use as a benchmark the observation of SL2S J08544-0121, which is the lowest mass system ($1.0\times 10^{14}$ Msun/h) observed so far featuring a bi-modal dark matter distribution with a dislocated gas component. We find that $(50 \pm 10)$% of the dark matter halos with circular velocities in the range 300 km/s to 700 km/s (groups) show DM-DM displacements equal or larger than $186 \pm 30$ kpc/h as observed in SL2S J08544-0121. For dark matter halos with circular velocities larger than 700 km/s (clusters) this fraction rises to 70 $\pm$ 10%. Using the same simulation we estimate the DM-gas displacements and find that 0.1 to 1.0% of the groups should present separations equal or larger than $87\pm 14$kpc/h corresponding to our observational benchmark; for clusters this fraction rises to (7 $\pm$ 3)%, consistent with previous studies of dark matter to baryon separations. Considering both constraints on the DM-DM and DM-gas displacements we find that the number density of groups similar to SL2S J08544-0121 is $\sim 6.0\times 10^{-7}$ Mpc$^{-3}$, three times larger than the estimated value for clusters. These results open up the possibility for a new statistical test of LCDM by looking for DM-gas displacements in low mass clusters and groups.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter

The role of environment in the morphological transformation of galaxies in 9 intermediate redshift clusters

[abridged] We analyze a sample of 9 massive clusters at 0.4<z<0.6 observed with MegaCam in 4 photometric bands (g,r,i,z) from the core to a radius of 5 Mpc (~4000 galaxies). Galaxy cluster candidates are selected using photometric redshifts computed with HyperZ. Morphologies are estimated with galSVM in two broad morphological types (early-type and late-type). We examine the morphological composition of the red-sequence and the blue-cloud and study the relations between galaxies and their environment through the morphology-density relations (T-Sigma) and the morphology-radius relation (T-R) in a mass limited sample (log(M/Msol)>9.5). We find that the red sequence is already in place at z~0.5 and it is mainly composed of very massive (log(M/Msol)>11.3) early-type galaxies. These massive galaxies seem to be already formed when they enter the cluster, probably in infalling groups, since the fraction remains constant with the cluster radius. Their presence in the cluster center could be explained by a segregation effect reflecting an early assembly history. Any evolution that takes place in the galaxy cluster population occurs therefore at lower masses (10.3<log(M/Msol)<11.3). For these galaxies, the evolution, is mainly driven by galaxy-galaxy interactions in the outskirts as revealed by the T-Sigma relation. Finally, the majority of less massive galaxies (9.5<log(M/Msol)<10.3) are late-type galaxies at all locations, suggesting that they have not started the morphological transformation yet even if this low mass bin might be affected by incompleteness.Comment: A&A in pres

Interesting magnetic properties of Fe1−x_{1-x}Cox_xSi alloys

Solid solution between nonmagnetic narrow gap semiconductor FeSi and diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with long-range helical magnetic ordering, for a wide range of intermediate concentration. We report various interesting magnetic properties of these alloys, including low temperature re-entrant spin-glass like behaviour and a novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya interaction in the magnetic response of these non-centrosymmetric alloys is discussed.Comment: 11 pages and 3 figure

A New Window of Exploration in the Mass Spectrum: Strong Lensing by Galaxy Groups in the SL2S

The existence of strong lensing systems with Einstein radii (Re) covering the full mass spectrum, from ~1-2" (produced by galaxy scale dark matter haloes) to >10" (produced by galaxy cluster scale haloes) have long been predicted. Many lenses with Re around 1-2" and above 10" have been reported but very few in between. In this article, we present a sample of 13 strong lensing systems with Re in the range 3"- 8", i.e. systems produced by galaxy group scale dark matter haloes, spanning a redshift range from 0.3 to 0.8. This opens a new window of exploration in the mass spectrum, around 10^{13}- 10^{14} M_{sun}, which is a crucial range for understanding the transition between galaxies and galaxy clusters. Our analysis is based on multi-colour CFHTLS images complemented with HST imaging and ground based spectroscopy. Large scale properties are derived from both the light distribution of the elliptical galaxies group members and weak lensing of the faint background galaxy population. On small scales, the strong lensing analysis yields Einstein radii between 2.5" and 8". On larger scales, the strong lenses coincide with the peak of the light distribution, suggesting that mass is traced by light. Most of the luminosity maps have complicated shapes, indicating that these intermediate mass structures are dynamically young. Fitting the reduced shear with a Singular Isothermal Sphere, we find sigma ~ 500 km/s and an upper limit of ~900 km/s for the whole sample. The mass to light ratio for the sample is found to be M/L_i ~ 250 (solar units, corrected for evolution), with an upper limit of 500. This can be compared to mass to light ratios of small groups (with sigma ~ 300 km/s and galaxy clusters with sigma > 1000 km/s, thus bridging the gap between these mass scales.Comment: A&A Accepted. Draft with Appendix images can be found at http://www.dark-cosmology.dk/~marceau/groups_sl2s.pd

Clinical research without consent in adults in the emergency setting: a review of patient and public views

<p>Abstract</p> <p>Background</p> <p>In emergency research, obtaining informed consent can be problematic. Research to develop and improve treatments for patients admitted to hospital with life-threatening and debilitating conditions is much needed yet the issue of research without consent (RWC) raises concerns about unethical practices and the loss of individual autonomy. Consistent with the policy and practice turn towards greater patient and public involvement in health care decisions, in the US, Canada and EU, guidelines and legislation implemented to protect patients and facilitate acute research with adults who are unable to give consent have been developed with little involvement of the lay public. This paper reviews research examining public opinion regarding RWC for research in emergency situations, and whether the rules and regulations permitting research of this kind are in accordance with the views of those who ultimately may be the most affected.</p> <p>Methods</p> <p>Seven electronic databases were searched: Medline, Embase, CINAHL, Cochrane Database of Systematic Reviews, Philosopher's Index, Age Info, PsychInfo, Sociological Abstracts and Web of Science. Only those articles pertaining to the views of the public in the US, Canada and EU member states were included. Opinion pieces and those not published in English were excluded.</p> <p>Results</p> <p>Considering the wealth of literature on the perspectives of professionals, there was relatively little information about public attitudes. Twelve studies employing a range of research methods were identified. In five of the six questionnaire surveys around half the sample did <it>not </it>agree generally with RWC, though paradoxically, a higher percentage would <it>personally </it>take part in such a study. Unfortunately most of the studies were not designed to investigate individuals' views in any depth. There also appears to be a level of mistrust of medical research and some patients were more likely to accept an experimental treatment 'outside' of a research protocol.</p> <p>Conclusion</p> <p>There are too few data to evaluate whether the rules and regulations permitting RWC protects – or is acceptable to – the public. However, any attempts to engage the public should take place in the context of findings from further basic research to attend to the apparently paradoxical findings of some of the current surveys.</p

Plasma and neutrophil fatty acid composition in advanced cancer patients and response to fish oil supplementation

Metabolic demand and altered supply of essential nutrients is poorly characterised in patients with advanced cancer. A possible imbalance or deficiency of essential fatty acids is suggested by reported beneficial effects of fish oil supplementation. To assess fatty acid status (composition of plasma and neutrophil phospholipids) in advanced cancer patients before and after 14 days of supplementation (12±1 g day−1) with fish (eicosapentaenoic acid, and docosahexaenoic acid) or placebo (olive) oil. Blood was drawn from cancer patients experiencing weight loss of >5% body weight (n=23). Fatty acid composition of plasma phospholipids and the major phospholipid classes of isolated neutrophils were determined using gas liquid chromatography. At baseline, patients with advanced cancer exhibited low levels (<30% of normal values) of plasma phospholipids and constituent fatty acids and elevated 20 : 4 n-6 content in neutrophil phospholipids. High n-6/n-3 fatty acid ratios in neutrophil and plasma phospholipids were inversely related to body mass index. Fish oil supplementation raised eicosapentaenoic acid and docosahexaenoic acid content in plasma but not neutrophil phospholipids. 20 : 4 n-6 content was reduced in neutrophil PI following supplementation with fish oil. Change in body weight during the supplementation period related directly to increases in eicosapentaenoic acid in plasma. Advanced cancer patients have alterations in lipid metabolism potentially due to nutritional status and/or chemotherapy. Potential obstacles in fatty acid utilisation must be addressed in future trials aiming to improve outcomes using nutritional intervention with fish oils

Les propriétés magnétiques des substances mésomorphes

Mesures : Elimination des impuretés ferromagnétiques par filtration de la solution chloroformique et recristallisation. Contrôle magnétique de la pureté. Mesure de χ à diverses températures par la méthode de Faraday à l'aide d'un appareil de Foëx et Forrer. Nématiques : Le solide pulvérisé et le liquide isotrope ont un diamagnétisme indépendant de la température. Pour la phase nématique |χ| est plus petit et croit avec la température. La petitesse est due à ce que les molécules possèdent une direction commune, sa croissance à ce que l'agitation thermique détruit progressivement leur orientation. L'orientation des molécules nématiques et l'aimantation des ferro-magnétiques varient avec la température suivant des lois très voisines. Cependant la courbe d'orientation est interrompue avant sa rencontre avec l'axe des températures par une brusque disparition de l'orientation. Le même caractère existe dans les courbes d'aimantation des ferro-cobalt. Le passage de l'état nématique à l'état liquide peut donc être considéré aussi bien comme un changement d'état que comme un passage par un point de Curie analogue à celui des ferro-colbalt, sans changement de phase. Des mesures de chaleur spécifique pourraient peut-être élucider la question. Smectiques. - L'orientation d'ensemble des molécules et la diminution brusque du diamagnétisme qui en résulte se produisent si un champ intense agit au cours du passage de l'état liquide à l'état smectique. Les caractères de la discontinuité montrent qu'il s'agit bien d'un changement d'état. Cristallisation dans le champ : Les nématiques refroidis dans le champ de manière à éviter la surfusion donnent un solide formé de cristaux ayant une direction commune et fortement anisotrope au total χ reste invariable pendant la cristallisation. Avec les smectiques le solide obtenu dans le champ est anisotrope mais son orientation n'est pas celle qu'on prévoyait. Le cristal d'azoxyanisol : Mesure des trois χ principaux. Le grand axe des molécules coïncide avec la direction suivant laquelle χ est minimum. Les mesures, qui permettent de trouver cette direction, renseignent complètement sur l'orientation des molécules dans le cristal. Propriétés du paraazoxyanisol et théorie du diamagnétisme : Le diamagnétisme dû à un électron circulant sur une orbite fermée est plus grand lorsque le plan de l'orbitre est perpendiculaire au champ que lorsqu'il lui est parallèle. |χ| étant le plus faible possible lorsque les molécules ont leur axe parallèle au champ, les orbites électroniques dont les plans sont parallèles à l'axe sont prépondérantes. C'est là une donné sur la structure de la molécule. La variation de χ au passage d'un état isotrope à l'état orienté est trop grande pour être compatible avec les résultats de la théorie classique appliquée à des orbites circulaires. L'existence de la précession de Larmor dans le cristal en est rendue peu vraisemblable. L'additivité du diamagnétisme montre que pour les molécules des éléments, la précession existe dans la même mesure que pour l'azoxyanisol. La comparaison des rayons atomiques déduits du diamagnétisme avec ceux que fournit l'analyse cristalline par rayons X est plutôt en faveur de la validité du théorème de Larmor et de la théorie de Langevin. Toutefois le calcul du rayon qui ne tient pas compte de l'elliplicité des orbites ne peut pas conduire à une conclusion ferme