Environmental stress linked to consumption of maternally derived carotenoids in brown trout embryos (Salmo trutta).

The yellow, orange, or red colors of salmonid eggs are due to maternally derived carotenoids whose functions are not sufficiently understood yet. Here, we studied the significance of naturally acquired carotenoids as maternal environmental effects during embryo development in brown trout (Salmo trutta). We collected eggs from wild females, quantified their egg carotenoid content, fertilized them in vitro in full-factorial breeding blocks to separate maternal from paternal effects, and raised 3,278 embryos singly at various stress conditions until hatching. We found significant sire effects that revealed additive genetic variance for embryo survival and hatching time. Dam effects were 5.4 times larger than these sire effects, indicating that maternal environmental effects play an important role in determining embryo stress tolerance. Of the eight pigment molecules that we targeted, only astaxanthin, zeaxanthin (that both affected egg redness), and lutein were detected above our confidence thresholds. No strong link could be observed between carotenoid content in unfertilized eggs and embryo mortality or hatching timing. However, the consumption of carotenoids during our stress treatment was negatively correlated to embryo survival among sib groups and explained about 14% of the maternal environmental variance. We conclude that maternally derived carotenoids play a role in the ability of embryos to cope with environmental stress, but that the initial susceptibility to the organic pollution was mainly determined by other factors

Profil electroneuromyographique des neuropathies dans une population de patients diabetiques admis dans un laboratoire de neurophysiologie

Les neuropathies périphériques constituent une complication fréquente du diabète. Plusieurs formes de neuropathies sont décrites dans cette population. L’objectif de ce travail était d’étudier la fréquence desdifférentes neuropathies dans une population de diabétiques.Nous avons réalisé une étude descriptive portant sur 110 patients diabétiques admis dans le laboratoire de Neurophysiologie du CHU de Limoges de janvier 2004 à juin 2006. Le diagnostic EMG des neuropathies démyélinisantes était basé sur les critères de l’EFNS/PNS. Il s’agit de 110 sujets dont 63 de sexe masculin, âgés de 18 à 81 ans avec un âge moyen de 57,2 ans. La durée moyenne de la maladie était de 15 ans avec un taux moyen de HbA1C de 7,9%.33 sujets (30,6%) avaient une neuropathie démyélinisante dont 20 classés défini, 8 probable et 5 possible. 25,2% avaient une neuropathie axonale, 22,7% un syndrome du canal carpien et 14 sujets avaient un EMG normal. Ces résultats comparables à certains de la littérature suggèrent une fréquence assez élevée des neuropathies démyélinisantes chez les diabétiques et imposent d’en étudier les déterminants

Percolation properties of the 2D Heisenberg model

We analyze the percolation properties of certain clusters defined on configurations of the 2--dimensional Heisenberg model. We find that, given any direction \vec{n} in O(3) space, the spins almost perpendicular to \vec{n} form a percolating cluster. This result gives indications of how the model can avoid a previously conjectured Kosterlitz-Thouless phase transition at finite temperature T.Comment: 4 pages, 3 eps figures. Revised version (more clear abstract, some new references

Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics

The dynamic critical exponent $z$ is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices $z_0$ and $z$ related to the divergence of the relaxation time $\tau$ by $\tau\propto \xi^{z_0}$ and $\tau\propto k^{-z}$, where $\xi$ is the correlation length and $k$ the wavevector. The values determined are $z_0\approx 1.5$ and $z\approx 1$ for the 3D LCG and $z_0\approx 1.5$ and $z\approx 2$ for the 3D XY model. It is argued that the nonlinear $IV$ exponent relates to $z_0$, whereas the usual Hohenberg-Halperin classification relates to $z$. Possible implications for the interpretation of experiments are pointed out. Comparisons with other existing results are discussed.Comment: to appear in PR

Logarithmic Corrections in the 2D XY Model

Using two sets of high-precision Monte Carlo data for the two-dimensional XY model in the Villain formulation on square $L \times L$ lattices, the scaling behavior of the susceptibility $\chi$ and correlation length $\xi$ at the Kosterlitz-Thouless phase transition is analyzed with emphasis on multiplicative logarithmic corrections $(ln L)^{-2r}$ in the finite-size scaling region and $(ln \xi)^{-2r}$ in the high-temperature phase near criticality, respectively. By analyzing the susceptibility at criticality on lattices of size up to $512^2$ we obtain $r = -0.0270(10)$, in agreement with recent work of Kenna and Irving on the the finite-size scaling of Lee-Yang zeros in the cosine formulation of the XY model. By studying susceptibilities and correlation lengths up to $\xi \approx 140$ in the high-temperature phase, however, we arrive at quite a different estimate of $r = 0.0560(17)$, which is in good agreement with recent analyses of thermodynamic Monte Carlo data and high-temperature series expansions of the cosine formulation.Comment: 13 pages, LaTeX + 8 postscript figures. See also http://www.cond-mat.physik.uni-mainz.de/~janke/doc/home_janke.htm

Numerical Study of Order in a Gauge Glass Model

The XY model with quenched random phase shifts is studied by a T=0 finite size defect energy scaling method in 2d and 3d. The defect energy is defined by a change in the boundary conditions from those compatible with the true ground state configuration for a given realization of disorder. A numerical technique, which is exact in principle, is used to evaluate this energy and to estimate the stiffness exponent $\theta$. This method gives $\theta = -0.36\pm0.013$ in 2d and $\theta = +0.31\pm 0.015$ in 3d, which are considerably larger than previous estimates, strongly suggesting that the lower critical dimension is less than three. Some arguments in favor of these new estimates are given.Comment: 4 pages, 2 figures, revtex. Submitted to Phys. Rev. Let

Numerical Study of Spin and Chiral Order in a Two-Dimensional XY Spin Glass

The two dimensional XY spin glass is studied numerically by a finite size scaling method at T=0 in the vortex representation which allows us to compute the exact (in principle) spin and chiral domain wall energies. We confirm earlier predictions that there is no glass phase at any finite T. Our results strongly support the conjecture that both spin and chiral order have the same correlation length exponent $\nu \approx 2.70$. We obtain preliminary results in 3d.Comment: 4 pages, 2 figures, revte