1,042 research outputs found
Genetic structure of the common sole Solea vulgaris at different geographic scales
The genetic structure of the flatfish #Solea vulgaris was investigated on several spatial scales and at the temporal level through analysis of electrophoretic variation at 8 to 12 polymorphic enzyme loci. No differentiation was apparent at the temporal scale. Some differentiation was detected at and above the regional scale. Isolation by distance was evidenced by the significant correlation between genetic and geographic distances, and by the consistency of the results of multiple-locus correspondence analysis with geographic sampling patterns. The analysis suggested that the geographic unit of population structure (i.e. a geographical area corresponding to a panmictic or nearly panmictic population) lies within a radius of the order of 100 km. The isolation-by-distance pattern in #S. vulgaris contrasted with the known genetic structures of other flatfish species of the northeastern Atlantic and Mediterranean in a way that may be related to the range of their respective temperature tolerances for eggs and larvae. (Résumé d'auteur
Génétique des populations de Beryx splendens de la zone économique de la Nouvelle-Calédonie : distribution des haplotypes du gène du cytochrome b de l'ADN mitochondrial et analyse phylogénétique de leurs séquences
La délimitation géographique des populations, établie sur les bases biologiques, est nécessaire à toute gestion rationnelle des pêcheries. Tel est le cas pour #Beryx splendens, ressource pour laquelle la mise en évidence de différentes populations dans la zone économique (ZE) de Nouvelle-Calédonie serait essentielle pour en éviter la surexploitation. L'ADN mitochondrial a été choisi comme marqueur génétique de la structure géographique de #B. splendens sur les monts sous-marins de la ZE de Nouvelle-Calédonie. (D'après résumé d'auteur
Formation of convective cells in the scrape-off layer of the CASTOR tokamak
Understanding of the scrape-off layer (SOL) physics in tokamaks requires
diagnostics with sufficient temporal and spatial resolution. This contribution
describes results of experiments performed in the SOL of the CASTOR tokamak
(R=40 cm, a = 6 cm) by means of a ring of 124 Langmuir probes surrounding the
whole poloidal cross section. The individual probes measure either the ion
saturation current of the floating potential with the spatial resolution up to
3 mm. Experiments are performed in a particular magnetic configuration,
characterized by a long parallel connection length in the SOL, L_par ~q2piR. We
report on measurements in discharges, where the edge electric field is modified
by inserting a biased electrode into the edge plasma. In particular, a complex
picture is observed, if the biased electrode is located inside the SOL. The
poloidal distribution of the floating potential appears to be strongly
non-uniform at biasing. The peaks of potential are observed at particular
poloidal angles. This is interpreted as formation of a biased flux tube, which
emanates from the electrode along the magnetic field lines and snakes q times
around the torus. The resulting electric field in the SOL is 2-dimensional,
having the radial as well as the poloidal component. It is demonstrated that
the poloidal electric field E_pol convects the edge plasma radially due to the
E_pol x B_T drift either inward or outward depending on its sign. The
convective particle flux is by two orders of magnitude larger than the
fluctuation-induced one and consequently dominates.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Elastic instability in stratified core annular flow
We study experimentally the interfacial instability between a layer of dilute
polymer solution and water flowing in a thin capillary. The use of microfluidic
devices allows us to observe and quantify in great detail the features of the
flow. At low velocities, the flow takes the form of a straight jet, while at
high velocities, steady or advected wavy jets are produced. We demonstrate that
the transition between these flow regimes is purely elastic -- it is caused by
viscoelasticity of the polymer solution only. The linear stability analysis of
the flow in the short-wave approximation captures quantitatively the flow
diagram. Surprisingly, unstable flows are observed for strong velocities,
whereas convected flows are observed for low velocities. We demonstrate that
this instability can be used to measure rheological properties of dilute
polymer solutions that are difficult to assess otherwise.Comment: 4 pages, 4 figure
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