403 research outputs found
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
Relationship between Raman crystallinity and open-circuit voltage in microcrystalline silicon solar cells
Rough ZnO layers by LP-CVD process and their effect in improving performances of amorphous and microcrystalline silicon solar cells
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 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 and related to the
divergence of the relaxation time by and
, where is the correlation length and the
wavevector. The values determined are and for the
3D LCG and and for the 3D XY model. It is argued
that the nonlinear exponent relates to , whereas the usual
Hohenberg-Halperin classification relates to . 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 lattices, the scaling
behavior of the susceptibility and correlation length at the
Kosterlitz-Thouless phase transition is analyzed with emphasis on
multiplicative logarithmic corrections in the finite-size
scaling region and in the high-temperature phase near
criticality, respectively. By analyzing the susceptibility at criticality on
lattices of size up to we obtain , 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 in the high-temperature phase,
however, we arrive at quite a different estimate of , 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 . This method gives in
2d and 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 . We obtain preliminary results
in 3d.Comment: 4 pages, 2 figures, revte
- …