Memory Effect and Fast Spinodal Decomposition

We consider the modification of the Cahn-Hilliard equation when a time delay process through a memory function is taken into account. We then study the process of spinodal decomposition in fast phase transitions associated with a conserved order parameter. The introduced memory effect plays an important role to obtain a finite group velocity. Then, we discuss the constraint for the parameters to satisfy causality. The memory effect is seen to affect the dynamics of phase transition at short times and has the effect of delaying, in a significant way, the process of rapid growth of the order parameter that follows a quench into the spinodal region.Comment: 4 pages, 3 eps figure

Projection effects in galaxy cluster samples: insights from X-ray redshifts

Up to now, the largest sample of galaxy clusters selected in X-rays comes from the ROSAT All-Sky Survey (RASS). Although there have been many interesting clusters discovered with the RASS data, the broad point spread function (PSF) of the ROSAT satellite limits the amount of spatial information of the detected objects. This leads to the discovery of new cluster features when a re-observation is performed with higher resolution X-ray satellites. Here we present the results from XMM-Newton observations of three clusters: RXCJ2306.6-1319, ZwCl1665 and RXCJ0034.6-0208, for which the observations reveal a double or triple system of extended components. These clusters belong to the extremely expanded HIghest X-ray FLUx Galaxy Cluster Sample (eeHIFLUGCS), which is a flux-limited cluster sample ($f_\textrm{X,500}\geq 5\times10^{-12}$ erg s$^{-1}$ cm$^{-2}$ in the $0.1-2.4$ keV energy band). For each structure in each cluster, we determine the redshift with the X-ray spectrum and find that the components are not part of the same cluster. This is confirmed by an optical spectroscopic analysis of the galaxy members. Therefore, the total number of clusters is actually 7 and not 3. We derive global cluster properties of each extended component. We compare the measured properties to lower-redshift group samples, and find a good agreement. Our flux measurements reveal that only one component of the ZwCl1665 cluster has a flux above the eeHIFLUGCS limit, while the other clusters will no longer be part of the sample. These examples demonstrate that cluster-cluster projections can bias X-ray cluster catalogues and that with high-resolution X-ray follow-up this bias can be corrected

Patterns of resistance to β-lactams and β-lactamase inhibitors in uropathogenic Escherichia coli strains isolated from animals in Portugal

FMV 1953 uropathogenic Escherichia coli isolate was extremely resistant to amoxicillin, co-amoxiclav, ticarcillin, mecillinam, cefoxitime, cefixime, cefuroxime, cefotaxime, ceftazidime, ceftriaxone and aztreoname. From the resistance patterns observed we deduce the phenotype as producing a TEM-1 β-lactamase, a hyperproduced Amp-C β-lactamase and an OXA-3 β-lactamase or a PBP-2 mutation isolate.Key words: Antibiotic resistance, uropathogenic Escherichia coli, phenotype characterization

Λ(1405)\Lambda(1405) production in the π−p→K0πΣ\pi^-p\to K^0\pi\Sigma reaction

We discuss the mechanisms that lead to $\Lambda(1405)$ production in the $\pi^-p\to K^0\pi\Sigma$ reaction. The problem has gained renewed interest after different works converge to the conclusion that there are two resonances around the region of 1400 MeV, rather than one, and that they couple differently to the $\pi\Sigma$ and $\bar{K}N$ channels. We look at the dynamics of that reaction and find two mechanisms which eventually filter each one of the resonances, leading to very different shapes of the $\pi\Sigma$ invariant mass distributions. The combination of the two mechanisms leads to a shape of this distribution compatible with the experimental measurements.Comment: RevTeX4, 10 pages, 8 figures, 2 tables, Version to appear in Phys. Rev.

Latest results for the antikaon-nucleon optical potential

The key question of this letter is whether the K-nucleus optical potential is deep, as it is prefered by the phenomenological fits to kaonic atoms data, or shallow, as it comes out from unitary chiral model calculations. The current experimental situation is reviewed.Comment: 3 pages, 1 figure. Presented at the 21st European Conference on the Few-Body problems in Physics (EFB21), Salamanca, Spain, August 29 - September 3, 201