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 matter distribution in z ~ 0.5 redshift clusters of galaxies. II : The link between dark and visible matter

We present an optical analysis of a sample of 11 clusters built from the EXCPRES sample of X-ray selected clusters at intermediate redshift (z ~ 0.5). With a careful selection of the background galaxies we provide the mass maps reconstructed from the weak lensing by the clusters. We compare them with the light distribution traced by the early-type galaxies selected along the red sequence for each cluster. The strong correlations between dark matter and galaxy distributions are confirmed, although some discrepancies arise, mostly for merging or perturbed clusters. The average M/L ratio of the clusters is found to be: M/L_r = 160 +/- 60 in solar units (with no evolutionary correction), in excellent agreement with similar previous studies. No strong evolutionary effects are identified even if the small sample size reduces the significance of the result. We also provide a individual analysis of each cluster in the sample with a comparison between the dark matter, the galaxies and the gas distributions. Some of the clusters are studied for the first time in the optical.Comment: 25 pages, 9 figues + 11 figures in Annex, 4 tables. Accepted for publication in A&A. 1 reference correcte

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 pharmaco-economics of peri-operative beta-blocker and statin therapy in South Africa

We conducted a pharmaco-economic analysis of the prospective  peri-operative  studies of beta-blocker and statin administration for major  elective non-cardiac surgery, using the Discovery Health claims costs for 2004. This analysis shows that acute peri-operative beta-blockade and statin  therapy could result in a cost saving through a reduction in major   perioperative cardiovascular complications in patients with an expected  peri-operative major cardiovascular complication rate exceeding 10% following elective major non-cardiac surgery. The validity of these findings is dependent on whether the incidence of cardiovascular complications following major  noncardiac surgery reported in the international literature is found to be similar in South Africa

Are lipophilic beta-blockers preferable for peri-operative cardioprotection?

Atenolol has been proposed as a peri-operative cardioprotective agent in patients with coronary disease. However, recent reports have cast doubt over the cardioprotective efficacy of atenolol in patients with hypertension and coronary artery disease. There is therefore doubt whether atenolol is the correct cardioprotective drug in the surgical setting. It is possible that some of the physiochemical properties of atenolol (hydrophilic and cardioselective) may decrease it's efficacy in comparison to its more lipophilic congeners (such as propranolol, metoprolol, bisoprolol and carvedilol). The issue of prevention of perioperative cardiac events is complicated by many confounders. As a result, the role of the physicochemical properties of beta-blockers can only be determined in the simpler setting of myocardial infarction. Therefore, we conducted a restricted systematic review to evaluate the effect of initiating atenolol and metoprolol on the prevention of ventricular fibrillation following acute myocardial infarction. Neither atenolol nor metoprolol significantly decreased the incidence of in-hospital ventricular fibrillation following acute myocardial infarction. The number-needed-to-treat to prevent in-hospital ventricular fibrillation equals or exceeds 200 with metoprolol and atenolol respectively. Based on the findings of this systematic review and the recently published Clopidogrel and Metoprolol in Myocardial Infarction Trial (COMMIT), it can be concluded that the prevention of peri-operative myocardial ischaemia with a betablocker is clinically more important to peri-operative cardioprotection than whether the beta-blocker is lipo- or hydrophilic. Keywords: atenolol, metoprolol, myocardial infarction, ventricular fibrillation Southern African Journal of Anaesthesia and Analgesia Vol. 12(4) 2006: 141-14

Not all suffering is pain: sources of patients' suffering in the emergency department call for improvements in communication from practitioners

Background Provision of prompt, effective analgesia is rightly considered as a standard of care in the emergency department (ED). However, much suffering is not ‘painful’ and may be under-recognised. We sought to describe the burden of suffering in the ED and explore how this may be best addressed from a patient centred perspective. Methods In a prospective cohort study, we included undifferentiated patients presenting to the ED. We undertook two face to face questionnaires with the first immediately following triage. We asked patients: (a) if they were ‘suffering’; (b) how they were suffering; and (c) what they hoped would be done to ease this. Prior to leaving the ED, we asked patients what had been done to ease their suffering. Data were analysed thematically. Results Of 125 patients included, 77 (61.6%) reported suffering on direct questioning and 92 (73.6%) listed at least one way in which they were suffering. 90 (72.0%) patients had a pain score >0/10 but only 37 (29.6%) reported that pain was causing suffering. Patients reported suffering from both physical symptoms (especially pain, nausea, vomiting and dizziness) and emotional distress (notably anxiety). Treatment (to ease physical and emotional symptoms), information (particularly diagnosis, reassurance and explanation), care (notably friendly staff) and closure (being seen, resolving the problem and going home) were the key themes identified as important for relief of suffering. Conclusions In seeking to ease suffering in the ED, clinicians must focus not only on providing analgesia but on treating Emotional distress, Physical symptoms, providing Information, Care and Closure (EPICC)

Thickness-dependence of the electronic properties in V2O3 thin films

High quality vanadium sesquioxide V2O3 films (170-1100 {\AA}) were grown using the pulsed laser deposition technique on (0001)-oriented sapphire substrates, and the effects of film thickness on the lattice strain and electronic properties were examined. X-ray diffraction indicates that there is an in-plane compressive lattice parameter (a), close to -3.5% with respect to the substrate and an out-of-plane tensile lattice parameter (c) . The thin film samples display metallic character between 2-300 K, and no metal-to-insulator transition is observed. At low temperature, the V2O3 films behave as a strongly correlated metal, and the resistivity (\rho) follows the equation \rho =\rho_0 + A T^2, where A is the transport coefficient in a Fermi liquid. Typical values of A have been calculated to be 0.14 \mu\Omega cm K^{-2}, which is in agreement with the coefficient reported for V2O3 single crystals under high pressure. Moreover, a strong temperature-dependence of the Hall resistance confirms the electronic correlations of these V2O3 thin films samples.Comment: 4 pages, 4 figure

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