Spontaneous generation of spin-orbit coupling in magnetic dipolar Fermi gases

The stability of an unpolarized two-component dipolar Fermi gas is studied within mean-field theory. Besides the known instability towards spontaneous magnetization with Fermi sphere deformation, another instability towards spontaneous formation of a spin-orbit coupled phase with a Rashba-like spin texture is found. A phase diagram is presented and consequences are briefly discussed

Avaliação sorológica de vacinas comerciais polivalentes contra a enterotoxemia em caprinos.

Foram avaliadas as respostas sorológicas a cinco vacinas comerciais polivalentes que continham o toxóide épsilon do Clostridium perfringens tipo D na sua formulação. Para isso, foram utilizados 84 caprinos jovens, divididos aleatoriamente em seis grupos experimentais com 14 animais em cada grupo. Os caprinos do Grupo Controle não receberam nenhuma dose de vacina e os dos Grupos 1 ao 5 receberam duas doses de vacina com intervalo de quatro semanas entre elas. A primeira dose de vacina foi aplicada aos 45 (± 3) dias de vida dos animais (início do experimento - dia zero) e a segunda aos 75 (± 3 ? dia 30). As amostras de sangue para a realização dos testes sorológicos foram colhidas antes (dia zero), e nos dias 30, 60, 90, 120 e 150 após o início do experimento. Utilizou-se a técnica de ELISA Indireto para quantificação dos anticorpos antitoxina épsilon do C. perfringens tipo D. De maneira geral ocorreu um aumento nos valores médios do título de anticorpos séricos dos caprinos no dia 60 em resposta às duas doses de vacina recebidas nos dias zero e 30, sendo que o maior número de animais considerados protegidos também foi detectado neste dia. Apenas cinco caprinos jovens do Grupo 1 e um do Grupo 3 permaneceram com títulos de anticorpos considerados protetores até o dia 150. Diante dos resultados obtidos, concluiu-se que as vacinas avaliadas apresentaram baixa capacidade de estimular uma resposta imune protetora nos caprinos avaliados

Avaliação sorológica de vacinas comerciais polivalentes contra a enterotoxemia em caprinos.

Foram avaliadas as respostas sorológicas a cinco vacinas comerciais polivalentes que continham o toxóide épsilon do Clostridium perfringens tipo D na sua formulação. Para isso, foram utilizados 84 caprinos jovens, divididos aleatoriamente em seis grupos experimentais com 14 animais em cada grupo. Os caprinos do Grupo Controle não receberam nenhuma dose de vacina e os dos Grupos 1 ao 5 receberam duas doses de vacina com intervalo de quatro semanas entre elas. A primeira dose de vacina foi aplicada aos 45 (± 3) dias de vida dos animais (início do experimento - dia zero) e a segunda aos 75 (± 3 ? dia 30). As amostras de sangue para a realização dos testes sorológicos foram colhidas antes (dia zero), e nos dias 30, 60, 90, 120 e 150 após o início do experimento. Utilizou-se a técnica de ELISA Indireto para quantificação dos anticorpos antitoxina épsilon do C. perfringens tipo D. De maneira geral ocorreu um aumento nos valores médios do título de anticorpos séricos dos caprinos no dia 60 em resposta às duas doses de vacina recebidas nos dias zero e 30, sendo que o maior número de animais considerados protegidos também foi detectado neste dia. Apenas cinco caprinos jovens do Grupo 1 e um do Grupo 3 permaneceram com títulos de anticorpos considerados protetores até o dia 150. Diante dos resultados obtidos, concluiu-se que as vacinas avaliadas apresentaram baixa capacidade de estimular uma resposta imune protetora nos caprinos avaliados

Clostridium perfringens epsilon toxin increases the small intestinal permeability in mice and rats

Epsilon toxin is a potent neurotoxin produced by Clostridium perfringens types B and D, an anaerobic bacterium that causes enterotoxaemia in ruminants. In the affected animal, it causes oedema of the lungs and brain by damaging the endothelial cells, inducing physiological and morphological changes. Although it is believed to compromise the intestinal barrier, thus entering the gut vasculature, little is known about the mechanism underlying this process. This study characterizes the effects of epsilon toxin on fluid transport and bioelectrical parameters in the small intestine of mice and rats. The enteropooling and the intestinal loop tests, together with the single-pass perfusion assay and in vitro and ex vivo analysis in Ussing's chamber, were all used in combination with histological and ultrastructural analysis of mice and rat small intestine, challenged with or without C. perfringens epsilon toxin. Luminal epsilon toxin induced a time and concentration dependent intestinal fluid accumulation and fall of the transepithelial resistance. Although no evident histological changes were observed, opening of the mucosa tight junction in combination with apoptotic changes in the lamina propria were seen with transmission electron microscopy. These results indicate that C. perfringens epsilon toxin alters the intestinal permeability, predominantly by opening the mucosa tight junction, increasing its permeability to macromolecules, and inducing further degenerative changes in the lamina propria of the bowel. © 2009 Goldstein et al

‘Warrant’ revisited: Integrating mathematics teachers’ pedagogical and epistemological considerations into Toulmin’s model for argumentation

In this paper, we propose an approach to analysing teacher arguments that takes into account field dependence—namely, in Toulmin’s sense, the dependence of warrants deployed in an argument on the field of activity to which the argument relates. Freeman, to circumvent issues that emerge when we attempt to determine the field(s) that an argument relates to, proposed a classification of warrants (a priori, empirical, institutional and evaluative). Our approach to analysing teacher arguments proposes an adaptation of Freeman’s classification that distinguishes between: epistemological and pedagogical a priori warrants, professional and personal empirical warrants, epistemological and curricular institutional warrants, and evaluative warrants. Our proposition emerged from analyses conducted in the course of a written response and interview study that engages secondary mathematics teachers with classroom scenarios from the mathematical areas of analysis and algebra. The scenarios are hypothetical, grounded on seminal learning and teaching issues, and likely to occur in actual practice. To illustrate our proposed approach to analysing teacher arguments here, we draw on the data we collected through the use of one such scenario, the Tangent Task. We demonstrate how teacher arguments, not analysed for their mathematical accuracy only, can be reconsidered, arguably more productively, in the light of other teacher considerations and priorities: pedagogical, curricular, professional and personal

Pairing Fluctuation Theory of Superconducting Properties in Underdoped to Overdoped Cuprates

We propose a theoretical description of the superconducting state of under- to overdoped cuprates, based on the short coherence length of these materials and the associated strong pairing fluctuations. The calculated $T_c$ and the zero temperature excitation gap $\Delta(0)$, as a function of hole concentration $x$, are in semi-quantitative agreement with experiment. Although the ratio $T_c/\Delta(0)$ has a strong $x$ dependence, different from the universal BCS value, and $\Delta(T)$ deviates significantly from the BCS prediction, we obtain, quite remarkably, quasi-universal behavior, for the normalized superfluid density $\rho_s(T)/\rho_s(0)$ and the Josephson critical current $I_c(T)/I_c(0)$, as a function of $T/T_c$. While experiments on $\rho_s(T)$ are consistent with these results, future measurements on $I_c(T)$ are needed to test this prediction.Comment: 4 pages, 3 figures, REVTeX, submitted to Phys. Rev. Let

Superconducting phase coherence in the presence of a pseudogap: Relation to specific heat, tunneling and vortex core spectroscopies

In this paper we demonstrate how, using a natural generalization of BCS theory, superconducting phase coherence manifests itself in phase insensitive measurements, when there is a smooth evolution of the excitation gap \Delta from above to below Tc. In this context, we address the underdoped cuprates. Our premise is that just as Fermi liquid theory is failing above Tc, BCS theory is failing below. The order parameter \Delta_{sc} is different from the excitation gap \Delta. Equivalently there is a (pseudo)gap in the excitation spectrum above Tc which is also present in the underlying normal state of the superconducting phase, and can be directly inferred from specific heat and vortex core experiments. At the same time many features of BCS theory, e.g., fermionic quasiparticles below Tc, are clearly present. These observations can be reconciled by a natural extension of BCS theory, which includes finite center-of-mass momentum pair excitations, in addition to the usual fermionic quasiparticles. Applying this theory we find that the Bose condensation of Cooper pairs, which is reflected in \Delta_{sc}, leads to sharp peaks in the spectral function once $T \le T_c$. These are manifested in ARPES spectra as well as in specific heat jumps, which become more like the behavior in a \lambda transition as the pseudogap develops. We end with a discussion of tunneling experiments and condensation energy issues. Comparison between theoretical and experimental plots of C_v, and of tunneling and vortex core spectroscopy measurements is good.Comment: 12 pages, 8 figures, ReVTeX 3.

Evidence of Doping-Dependent Pairing Symmetry in Cuprate Superconductors

Scanning tunneling spectroscopy (STS) studies reveal long-range spatial homogeneity and predominantly $d_{x^2-y^2}$-pairing spectral characteristics in under- and optimally doped $\rm YBa_2Cu_3O_{7-\delta}$ superconductors, whereas STS on $\rm YBa_2(Cu_{0.9934}Zn_{0.0026}Mg_{0.004})_3O_{6.9}$ exhibits {\it microscopic} spatial modulations and strong scattering near the Zn or Mg impurity sites, together with global suppression of the pairing potential. In contrast, in overdoped $\rm (Y_{0.7}Ca_{0.3})Ba_2Cu_3O_{7-\delta}$, $(d_{x^2-y^2}+s)$-pairing symmetry is found, suggesting significant changes in the superconducting ground-state at a critical doping value.Comment: 4 pages, 4 figures. Published in Physical Review Letters. Corresponding author: Nai-Chang Yeh (e-mail address: [email protected]