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Biomedical subjects

M Le Berre

Publications and source records attributed to M Le Berre.

17 recordsLinked to original sources
PubMed2006

Spirals and vortex lattices in quasi-self-imaging divide-by-three optical parametric oscillators.

A linear stability analysis is derived in self-imaging cavities for which the conditions for large Fresnel number are stated. In cases of both Fabry-Pérot and ring cavities a Hopf bifurcation is predicted at finite transverse wave number. The self-imaging Fabry-Pérot resonator operates as a longitudinal multimode cavity that invalidates the mean-field model. Above the bifurcation threshold, either vortex lattices, spirals, or targets occur, depending on the Fresnel number, the input intensity, and the mistunings. The time and spatial characteristics have different scales in the case of a self-imaging ring cavity, but the same sort of patterns are reported.

Journal Article↗
PubMed2003

Patterns in a quasiconfocal optical parametric oscillator.

The formation of transverse patterns in a triply resonant optical parametric oscillator is studied both numerically and analytically for a spherical cavity close to confocality. While the pump profile is Gaussian, the signal and idler intensities may be made of many rings, either stationary or time dependent. The mode selection and the time dependence are understood with the help of the linear stability analysis. It might explain observations reported for a quasiconfocal cavity with a KTP crystal.

Journal Article↗
PubMed2002

Example of a chaotic crystal: the labyrinth.

Labyrinthine structures often appear as the final steady state of pattern forming systems. Being disordered, they exhibit the same kind of short range positional order as the Newell-Pomeau turbulent crystal. Labyrinths can be seen as a limit case of the texture of disordered rolls with a coherence length of the same order as the wavelength. In the various two-dimensional model equations we looked at, labyrinths and parallel rolls are steady states for the same parameters, their occurrence depending on the initial conditions. Comparing the stability of these two structures, we find that in variational models their energy is very close, rolls always being more stable than labyrinths. For the nonvariational model we propose a numerical experiment which displays a well defined bifurcation from parallel rolls to labyrinths as the more stable state.

Journal Article↗
PubMed1988

[Intestinal flora and social relations in laboratory rats].

This paper deals with the quantitative study of the social interaction in dyads of laboratory rats. Two kinds of dyads of Rattus norvegicus were observed: one which had the conventional rat intestinal flora (S.S.C.u.p.) and the other a micro-flora (J.L.T.) derived from feral rats, each member of the dyad having the same sex. Contact-seeking and sniffing behaviour were more frequent and lasted longer in J.L.T. rats than in S.S.C.u.p.

Animals↗
PubMed1979

[Placing the activity rhythm in Araneus cornutus].

Araneus cornutus spiderling activities recorded from hatching to scattering show a particular distribution of the general motor activity over a 24-hour period. More motor activity is first observed during the light sequence, while at a nocturnal activity distribution appears after the 2nd nymphean ecdysis.

Activity Cycles↗
PubMed1977

[Response of the brown trout (Salmo trutta, L. 1766) and rainbow trout (Salmo gairdneri Richardson, 1836) to infection by a new rhabdovirus].

Intra peritoneal injection of 200 g Trout hold at + 12 degrees C with 2x10(8) p.f.u. of a new Rhabdovirus (strain 23.75) induces an interferon synthesis within 2 days. (IF titres reaching 2,000 units/ml). 1 month later, the surviving Fish exhibit a specific anti 23.75 neutralizing serum activity (titre 40 to 80) which has been demonstrated to be due to immunoglobulins. This seroneutralization is also recorded in 1/3 of the survivors of natural infection.

Animals↗
PubMed1977

[Isolation of a pathogenic rhabdovirus of brown trout (Salmo trutta L., 1766)].

A Rhabdovirus pathogenic both for Rainbow and Brown Trout has been isolated from Brown Trout suffering heavy mortalities associated with muscular haemorrages and necrotic lesions of kidney and spleen. According to seroneutralization tests and host range, this virus appears to be different from the other known salmonids rhabdoviruses. Upon the basis of its in vitro gross characteristics, it is identical to Viral Haemorragic Septicemia Virus (VHS), F1 serotype, but differs from Infectious Hematopoïetic Necrosis and VHS type II viruses.

Animals↗
PubMed1975

Infectivity of fish rhabdoviruses for Drosophila melanogaster.

Two fish rhabdoviruses, spring viraemia of Carp virus (SVC) and Pike fry rhabdovirus (PFR), have been shown to multiply in Drosophila melanogaster. The other two fish rhabdoviruses, viral haemorrhagic septicaemia (VHS) and infectious hematopoietic necrosis (IHN), did not multiply under the conditions used. Only those viruses which multiplied (i. e. SVC, PFR) conferred a CO2 sensitivity on the infected drosophila. No hereditary transmission of the fish viruses was detected.

Animals↗