Exact stripe, checkerboard, and droplet ground states in two dimensions

Exact static nondegenerate stripe and checkerboard ground states are obtained in a two-dimensional generalized periodic Anderson model, for a broad concentration range below quarter filling. The random droplet states, also present in the degenerate ground state, are eliminated by extending the Hamiltonian with terms of different physical origin such as dimerization, periodic charge displacements, density waves, or distorsion lines.Comment: 12 pages, 8 figure

Analytical and experimental studies of thermionically emitting electrodes in contact with dense, seeded plasmas

Interactions are considered between a moving, alkali-metal seeded, dense plasma and a metallic electrode whose surface properties are influenced by the absorption of seed particles. The plasma behavior is governed by a set of differential equations, which are coupled to the surface through the boundary conditions. These conditions are obtained by utilizing the particle desorption rate expressions of Levine and Gyftopoulos. The solution of the problem yields the state of the surface as well as the spatial distribution of plasma properties. In particular, electrode voltage drops are predicted, which indicate whether the electrode operates in a thermionic or arc mode. The method has been applied to a potassiwn-seeded argon plasma in contact with a tungsten electrode in a stagnation flow geometry. The results show that the plasma - surface interaction may lead to large electrode currents at moderate voltage drops. These currents can be up to an order of magnitude greater than what the random electron current would be at the surface under conditions of perfect thermodynamic equilibrium at the surface temperature. R.esults of a comparable experiment show reasonably good agreement with the theory

Examining a reduced jet-medium coupling in Pb+Pb collisions at the Large Hadron Collider

Recent data on the nuclear modification factor $R_{AA}$ of jet fragments in 2.76 ATeV Pb+Pb collisions at the Large Hadron Collider (LHC) indicate that the jet-medium coupling in a Quark-Gluon Plasma (QGP) is reduced at LHC energies and not compatible with the coupling deduced from data at the Relativistic Hadron Collider (RHIC). We estimate the reduction factor from a combined fit to the available data on $R_{AA}(\sqrt{s},p_T,b)$ and the elliptic flow $v_2(\sqrt{s},p_T,b)$ at $\sqrt{s}=0.2,2.76$ ATeV over a transverse momentum range $p_T$ 10-100 GeV and a broad impact parameter, b, range. We use a simple analytic "polytrope" model ($dE/dx=- \kappa E^{a} x^z T^{c}$) to investigate the dynamical jet-energy loss model dependence. Varying a=0-1 interpolates between weakly-coupled and strongly-coupled models of jet-energy dependence while z=0-2 covers a wide range of possible jet-path dependencies from elastic and radiative to holographic string mechanisms. Our fit to LHC data indicates an approximate 40% reduction of the coupling $\kappa$ from RHIC to LHC and excludes energy-loss models characterized by a jet-energy exponent with a>1/3. In particular, the rapid rise of $R_{AA}$ with $p_T$>10 GeV combined with the slow variation of the asymptotic $v_2(p_T)$ at the LHC rules out popular exponential geometric optics models (a=1). The LHC data are compatible with $0\leq a\leq 1/3$ pQCD-like energy-loss models where the jet-medium coupling is reduced by approximately 10% between RHIC and LHC.Comment: 10 pages, 7 figures, version published in Physical Review

Di-Jet Conical Correlations Associated with Heavy Quark Jets in anti--de Sitter Space/Conformal Field Theory Correspondence

We show that far zone Mach and diffusion wake ``holograms'' produced by supersonic strings in anti--de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict $N_c\to\infty$ supergravity limit if Cooper-Frye hadronization is assumed. However, a special {\em nonequilibrium} ``neck'' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly-coupled Quark-Gluon Plasma (sQGP) implied by AdS/CFT correspondence.Comment: 4 pages, 2 figures, version published in Physical Review Letter

Near Zone Navier-Stokes Analysis of Heavy Quark Jet Quenching in an N\mathcal{N} =4 SYM Plasma

The near zone energy-momentum tensor of a supersonic heavy quark jet moving through a strongly-coupled $\mathcal{N}=4$ SYM plasma is analyzed in terms of first-order Navier-Stokes hydrodynamics. It is shown that the hydrodynamical description of the near quark region worsens with increasing quark velocities. For realistic quark velocities, $v=0.99$, the non-hydrodynamical region is located at a narrow band surrounding the quark with a width of approximately $3/\pi T$ in the direction parallel to the quark's motion and with a length of roughly $10/\pi T$ in the perpendicular direction. Our results can be interpreted as an indication of the presence of coherent Yang-Mills fields where deviation from hydrodynamics is at its maximum. In the region where hydrodynamics does provide a good description of the system's dynamics, the flow velocity is so small that all the nonlinear terms can be dropped. Our results, which are compatible with the thermalization timescales extracted from elliptic flow measurements, suggest that if AdS/CFT provides a good description of the RHIC system, the bulk of the quenched jet energy has more than enough time to locally thermalize and become encoded in the collective flow. The resulting flow pattern close to the quark, however, is shown to be considerably different than the superposition of Mach cones and diffusion wakes observed at large distances.Comment: new revised version, 11 figures, as published in PR

Heterogeneous Distribution of Ecto-Ca-ATPases in Primary Cultures of Human Adenohypophyseal Cells

The aim of this study was to investigate the localization of ecto-Ca-adenosine-triphosphatase (ecto-Ca-ATPase) in different parenchymal cells of the human pituitary in tissue culture. The distribution of ecto-ATPases on the surface membrane of a particular parenchymal cell varied with the type of cells in contact with this parenchymal cell; the membrane portions immediately exposed to the medium showed low if any ecto-ATPase activity. These results suggest that ecto-Ca-ATPases of the parenchymal cells may be involved in cell adhesion processes and may be of crucial importance in the organization (in vivo) and reorganization (in vitro) of human adenohypophyseal tissue

The common truncation variant in pancreatic lipase related protein 2 (PNLIPRP2) is expressed poorly and does not alter risk for chronic pancreatitis

A nonsense variant (p.W358X) of human pancreatic lipase related protein 2 (PNLIPRP2) is present in different ethnic populations with a high allele frequency. In cell culture experiments, the truncated protein mainly accumulates inside the cells and causes endoplasmic reticulum stress. Here, we tested the hypothesis that variant p.W358X might increase risk for chronic pancreatitis through acinar cell stress. We sequenced exon 11 of PNLIPRP2 in a cohort of 256 subjects with chronic pancreatitis (152 alcoholic and 104 non-alcoholic) and 200 controls of Hungarian origin. We observed no significant difference in the distribution of the truncation variant between patients and controls. We analyzed mRNA expression in human pancreatic cDNA samples and found the variant allele markedly reduced. We conclude that the p.W358X truncation variant of PNLIPRP2 is expressed poorly and has no significant effect on the risk of chronic pancreatitis

Heavy Quark Radiative Energy Loss - Applications to RHIC

Heavy quark energy loss in a hot QCD plasma is computed taking into account the competing effects due to suppression of zeroth order gluon radiation bellow the plasma frequency and the enhancement of gluon radiation due to transition energy loss and medium induced Bremsstrahlung. Heavy quark medium induced radiative energy loss is derived to all orders in opacity, $(L/\lambda_g)^n$. Numerical evaluation of the energy loss suggest small suppression of high $p_\perp$ charm quarks, and therefore provide a possible explanation for the null effects observed by PHENIX in the prompt electron spectrum in $Au+Au$ as $\sqrt{s}=130$ and 200 AGeV.Comment: 4 pages, 4 figures, Contributed to 17th International Conference on Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California, 11-17 Jan 200

Microsatellite Markers Isolated From Cabomba Aquatica Sl (cabombaceae) From An Enriched Genomic Library

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Premise of the study: Microsatellite primers were designed for the submersed aquatic plant Cabomba aquatica s.l. (Cabombaceae) and characterized to estimate genetic diversity parameters. Methods and Results: Using a selective hybridization method, we designed and tested 30 simple sequence repeat loci using two natural populations of C. aquatica s.l., resulting in 13 amplifiable loci. Twelve loci were polymorphic, and alleles per locus ranged from two to four across the 49 C. aquatica s.l. individuals. Observed heterozygosity, expected heterozygosity, and fixation index varied from 0.0 to 1.0, 0.0 to 0.5, and -1.0 to -0.0667, respectively, for the Manaus population and from 0.0 to 1.0, 0.0 to 0.6, and -1.0 to 0.4643 for the Virua population. Conclusions: The developed markers will be used in further taxonomic and population studies within Cabomba. This set of microsatellite primers represents the first report on rapid molecular markers in the genus.311Post-Graduate program in Plant Biology of the Instituto de Biologia (UNICAMP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)CAPES [PNADB 457/2010

Jet Quenching in Non-Conformal Holography

We use our non-conformal holographic bottom-up model for QCD described in 1012.0116 to further study the effect of the QCD trace anomaly on the energy loss of both light and heavy quarks in a strongly coupled plasma. We compute the nuclear modification factor $R_{AA}$ for bottom and charm quarks in an expanding plasma with Glauber initial conditions. We find that the maximum stopping distance of light quarks in a non-conformal plasma scales with the energy with a temperature (and energy) dependent effective power.Comment: 4 pages, 1 figure. Proceedings for Quark Matter 201