Random interactions and spin-glass thermodynamic transition in the hole-doped Haldane system Y2−x_{2-x}Cax_xBaNiO5_5

Magnetization, DC and AC bulk susceptibility of the $S$=1 Haldane chain system doped with electronic holes, Y$_{2-x}$Ca$_x$BaNiO$_5$ (0$\leq$x$\leq$0.20), have been measured and analyzed. The most striking results are (i) a sub-Curie power law behavior of the linear susceptibility, $\chi (T)$$\sim$ $T$$^{-\alpha}$, for temperature lower than the Haldane gap of the undoped compound (x=0) (ii) the existence of a spin-glass thermodynamic transition at $T$$_g$ = 2-3 K. These findings are consistent with (i) random couplings within the chains between the spin degrees of freedom induced by hole doping, (ii) the existence of ferromagnetic bonds that induce magnetic frustration when interchain interactions come into play at low temperature.Comment: 4 pages, 4 figures, to appear in Phys. Rev.

Complementary action of chemical and electrical synapses to perception

Acknowledgements This study was possible by partial financial support from the following agencies: Fundação Araucária, EPSRC-EP/I032606/1, CNPq No. 441553/2014-1, CAPES No. 17656-12-5 and Science Without Borders Program— Process Nos. 17656125, 99999.010583/2013-00 and 245377/2012-3.Peer reviewedPostprin

Persistence, seasonal dynamics and pathogenic potential of Vibrio communities from pacific oyster hemolymph

Bacteria of the genus Vibrio occur at a continuum from free-living to symbiotic life forms, including opportunists and pathogens, that can contribute to severe diseases, for instance summer mortality events of Pacific oysters Crassostrea gigas. While most studies focused on Vibrio isolated from moribund oysters during mortality outbreaks, investigations of the Vibrio community in healthy oysters are rare. Therefore, we characterized the persistence, diversity, seasonal dynamics, and pathogenicity of the Vibrio community isolated from healthy Pacific oysters. In a reciprocal transplant experiment we repeatedly sampled hemolymph from adult Pacific oysters to differentiate population from site-specific effects during six months of in situ incubation in the field. We characterized virulence phenotypes and genomic diversity based on multilocus sequence typing in a total of 70 Vibrio strains. Based on controlled infection experiments we could show that strains with the ability to colonize healthy adult oysters can also have the potential to induce high mortality rates on larvae. Diversity and abundance of Vibrio varied significantly over time with highest values during and after spawning season. Vibrio communities from transplanted and stationary oysters converged over time, indicating that communities were not population specific, but rather assemble from the surrounding environment forming communities, some of which can persist over longer period

Electron Spin Resonance of defects in the Haldane System Y(2)BaNiO(5)

We calculate the electron paramagnetic resonance (EPR) spectra of the antiferromagnetic spin-1 chain compound Y(2)BaNi(1-x)Mg(x)O(5) for different values of x and temperature T much lower than the Haldane gap (~100K). The low-energy spectrum of an anisotropic Heisenberg Hamiltonian, with all parameters determined from experiment, has been solved using DMRG. The observed EPR spectra are quantitatively reproduced by this model. The presence of end-chain S=1/2 states is clearly observed as the main peak in the spectrum and the remaining structure is completely understood.Comment: 5 pages, 4 figures include

Avaliação do efeito de formulações com o látex da Euphorbia tirucalli na terapêutica tópica de feridas cutâneas: aspectos clínicos e histopatológicos

Este trabalho objetiva avaliar o efeito do tratamento com soluções aquosas em diferentes concentrações do látex oriundo do aveloz (Euphorbia tirucalli) no processo cicatricial por segunda intenção, de feridas cutâneas experimentais em ratos. Foram utilizados 96 ratos divididos em oito grupos. As feridas foram confeccionadas cirurgicamente, na região lateral direita da linha dorsal. O látex da Euphorbia tirucalli foi coletado e diluído em seis concentrações: 50%, 25%, 12,5%, 6,25%, 3,12% e 1,6%. Para comparação de resultados utilizou-se para controle negativo, água destilada e para controle positivo, pomada a base de clostebol. Após 24 horas da cirurgia, iniciou-se o tratamento duas vezes ao dia. A evolução da cicatrização foi avaliada diariamente e a mensuração da área das lesões realizada a cada quatro dias. Realizou-se coleta de material para avaliação histopatológica da cicatrização. Os resultados da avaliação macroscópica foram submetidos à Análise de Variância e comparação de médias pelo Teste de Tukey ao nível de 5% de probabilidade, e os da avaliação histopatológica foram analisados pelo Teste de Kruskall-Wallis a 5% de probabilidade. O uso de formulações tópicas à base de látex de Euphorbia tirucalli, em distintas concentrações, não reduz o tempo final de cicatrização de feridas experimentais do dorso de ratos. Soluções aquosas do látex nas concentrações de 6,25% e 3,12% podem ser alternativamente empregadas na cicatrização de feridas, pois induzem menor hiperemia e exsudação e desencadeiam uma reparação tissular esteticamente melhor

Superconductivity from correlated hopping

We consider a chain described by a next-nearest-neighbor hopping combined with a nearest-neighbor spin flip. In two dimensions this three-body term arises from a mapping of the three-band Hubbard model for CuO$_2$ planes to a generalized $t-J$ model and for large O-O hopping favors resonance-valence-bond superconductivity of predominantly $d$-wave symmetry. Solving the ground state and low-energy excitations by analytical and numerical methods we find that the chain is a Luther-Emery liquid with correlation exponent $K_{\rho} = (2-n)^2/2$, where $n$ is the particle density.Comment: 10 pages, RevTeX 3.0 + 2 PostScript figs. Accepted for publication in Phys.Rev.