7,123 research outputs found
Random interactions and spin-glass thermodynamic transition in the hole-doped Haldane system YCaBaNiO
Magnetization, DC and AC bulk susceptibility of the =1 Haldane chain
system doped with electronic holes, YCaBaNiO
(0x0.20), have been measured and analyzed. The most striking
results are (i) a sub-Curie power law behavior of the linear susceptibility,
, for temperature lower than the Haldane gap
of the undoped compound (x=0) (ii) the existence of a spin-glass thermodynamic
transition at = 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 planes to a
generalized model and for large O-O hopping favors resonance-valence-bond
superconductivity of predominantly -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 , where is the particle density.Comment: 10 pages, RevTeX 3.0 + 2 PostScript figs. Accepted for publication in
Phys.Rev.
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