Phenomenology of the little bang

I review recent selected developments in the theory and modeling of ultrarelativistic heavy-ion collisions. I explain why relativistic viscous hydrodynamics is now used to model the expansion of the matter formed in these collisions. I give examples of first quantitative predictions, and I discuss remaining open questions associated with the description of the freeze-out process. I argue that while the expansion process is now well understood, our knowledge of initial conditions is still poor. Recent analyses of two-particle correlations have revealed fine structures known as ridge and shoulder, which extend over a long range in rapidity. These correlations are thought to originate from initial state fluctuations, whose modeling is still crude. I discuss triangular flow, a simple mechanism recently put forward, through which fluctuations generate the observed correlation pattern.Comment: 10 pages, plenary talk at the International Nuclear Physics Conference (INPC 2010), Vancouver, Canada, July 4-9, 2010. (version 2: minor revision.

Pressure dependence of the upper critical field of MgB2 and of YNi2B2C

We present measurements of H$_{c2}(T)$ under pressure in MgB$_2$ and in YNi$_2$B$_2$C. The changes in the shape of H$_{c2}(T)$ are interpreted within current models and show the evolution of the main Fermi surface velocities $v_F$ and electron-phonon coupling parameters $\lambda$ with pressure. In MgB$_2$ the electron-phonon coupling strength of the nearly two dimensional $\sigma$ band, responsible for the high critical temperature, is more affected by pressure than the $\pi$ band coupling, and the hole doping of the $\sigma$ band decreases. In YNi$_2$B$_2$C, the peculiar positive curvature of H$_{c2}(T)$ is weakened by pressure.Comment: 5 pages, 5 figure

An Isotopic Fingerprint of Electron-Phonon Coupling in High-Tc Cuprates

Angle-resolved photoemission spectroscopy with low-energy tunable photons along the nodal direction of oxygen isotope substituted Bi2Sr2CaCu2O8+delta reveals a distinct oxygen isotope shift near the electron-boson coupling "kink" in the electronic dispersion. The magnitude (a few meV) and direction of the kink shift are as expected due to the measured isotopic shift of phonon frequency, which are also in agreement with theoretical expectations. This demonstrates the participation of the phonons as dominant players, as well as pinpointing the most relevant of the phonon branches.Comment: 5 pages, 3 figure

X-ray observations of PKS 0745-191 at the virial radius: Are we there yet?

We wish to reassess the properties of the ICM at large radii in the galaxy cluster PKS 0745-191 in light of the recent Suzaku measurements. We analyze an archival 10.5 ksec ROSAT/PSPC observation to extract the surface-brightness profile of PKS 0745-191 and infer the deprojected density profile. We then compare the ROSAT surface-brightness profile with the Suzaku result. We perform a mass analysis combining the ROSAT density profile and the published temperature profiles from different instruments. We find that the ROSAT surface-brightness profile is statistically inconsistent (7.7 sigma) with the Suzaku result around and beyond the value of r200 estimated by Suzaku. We argue that, thanks to its large field of view and low background, ROSAT/PSPC is to the present day the most sensitive instrument to low surface-brightness X-ray emission in the 0.4-2.0 keV band. We also note that the Suzaku temperature and mass profiles are at odds with the results from at least two other satellites (XMM-Newton and Swift). The difference in surface brightness between ROSAT and Suzaku is most likely explained by the existence of additional foreground components at the low Galactic latitude of the source, which were not taken into account in the Suzaku background modeling. In light of our mass analysis, we conclude that any estimate of the fraction of the virial radius reached by X-ray measures is affected by systematic errors of the order of 25%. As a result, the properties of the ICM at the virial radius are still uncertain, and the Suzaku results should be considered with caution.Comment: 6 pages, 5 figures, accepted for publication in A&

Substitution effects in elastic electron collisions with CH₃X (X=F, Cl, Br, I) molecules

We report absolute elastic differential, integral, and momentum transfer cross sections for electron interactions with the series of molecules CH₃X (X=F, Cl, Br, I). The incident electron energy range is 50–200 eV, while the scattered electron angular range for the differential measurements is 15°–150°. In all cases the absolute scale of the differential cross sections was set using the relative flow method with helium as the reference species. Substitution effects on these cross sections, as we progress along the halomethane series CH₃F, CH₃Cl, CH3Br, and CH₃I, are investigated as a part of this study. In addition, atomic-like behavior in these scattering systems is also considered by comparing these halomethane elastic cross sections to results from other workers for the corresponding noble gases Ne, Ar, Kr, and Xe, respectively. Finally we report results for calculations of elastic differential and integral cross sections for electrons scattering from each of the CH₃X species, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements was found to be quite remarkable in each case.This work was conducted under the support of the Japanese Ministry of Education, Sport, Culture and Technology and also by the Ministerio de Educación Ciencia e Innovación Plan Nacional de Fisica, Project No. FIS2006- 00702, the Consejo de Seguridad Nuclear and the European Science Foundation COST Action No. CM0601. Additional support from the Australian Research Council, through its Centres of Excellence Program, and the Korea Science and Engineering Foundation Grant No. 2009-0052415 is further noted. One of us H.K. also acknowledges the Japan Society for the Promotion of Science JSPS for his fellowships as grants-in-aid for scientific research and, most recently, to facilitate his visit to Flinders University and the ANU

Anisotropic resistivity and Hall effect in MgB2 single crystals

We report resistivity and the Hall effect measurements in the normal and superconducting states of MgB2 single crystal. The resistivity has been found to be anisotropic with slightly temperature dependent resistivity ratio of about 3.5. The Hall constant, with a magnetic field parallel to the Mg and B sheets is negative in contrast to the hole-like Hall response with a field directed along the c-axis indicating presence of both types of charge carriers and, thus, multi-band electronic structure of MgB2. The Hall effect in the mixed state shows no sign change anomaly reproducing the Hall effect behavior in clean limit type-II superconductors.Comment: Minor changed content, 11 pages including 3 figure

Application of an endo-xylanase from Aspergillus japonicus in the fruit juice clarification and fruit peel waste hydrolysis.

The endo-xylanase from Aspergillus japonicus (UFMS 48.136) was purified in a single step using carboximethylcellulose chromatographic column and applied in fruit juice clarification process and fruit peel waste hydrolysis. This purification procedure resulted in 38.9-fold purification of endo-xylanase with 83.3% final yield. MALDITOF analysis confirmed the molecular mass of 32 kDa. The optimal purified endo-xylanase activity was at a range of pH from 5.0 to 6.0 and from 50 to 60 +-C, retaining more than 70% of its activity at all pH studied (3.0?8.0) for 24 h at room temperature. The A. japonicus endo-xylanolytic activity stimulation curve was assayed in the presence of different birchwood xylan concentrations (ranging from 0.02 to 0.5% w/v) and the endoxylanase activity presented a Vmax of 467.4 +- 30.38 μmol/min/mg, with a km of 2.59 +- 0.17 mg/mL, a kcat of 253.95 +- 16.51 s -1 and a kcat/km value of 98.05 +- 4.41 mL s -1 mg -1. The endo-xylanase was activated by Mn2þ (34.5%) and inhibited by Cu2þ (56.9%). The endo-xylanase was activated by β-mercaptoethanol, Triton X-100, Tween-20, Tween-80 and ferulic acid. In the clarification assay, endo-xylanase successfully clarified the juices of mango (51.11%), banana (9.99%) and tangerine (8.54%). Furthermore, the enzyme also hydrolysed all fruit peel wastes that were tested. In summary, A. japonicus endo-xylanase showed potential for applications in fruit juice clarification and in the treatment of fruit peel wastes, and it is a good candidate for the food industry due to its wide pH stability under acidic conditions

Elastic and total reaction cross sections of oxygen isotopes in Glauber theory

We systematically calculate the total reaction cross sections of oxygen isotopes, $^{15-24}$O, on a $^{12}$C target at high energies using the Glauber theory. The oxygen isotopes are described with Slater determinants generated from a phenomenological mean-field potential. The agreement between theory and experiment is generally good, but a sharp increase of the reaction cross sections from ^{21}O to ^{23}O remains unresolved. To examine the sensitivity of the diffraction pattern of elastic scattering to the nuclear surface, we study the differential elastic-scattering cross sections of proton-^{20,21,23}O at the incident energy of 300 MeV by calculating the full Glauber amplitude.Comment: 9 pages, 8 figure