Le mouton en Martinique. II. Croissance des agneaux sous la mère

Des contrôles de performances en fermes réalisés entre 1984 et 1987 dans 5 élevages de Martinique (Antilles Françaises) fournissent les croissances entre 10 et 130 jours (âge au sevrage) de 1655 agneaux de phénotypes locaux (Black-Belly et Créole) et croisés européens. Les croisés Lacaune, et plus généralement les croisés européens, donnent de meilleures croissances et poids au sevrage que les autres phénotypes comparés. Néanmoins, cette supériorité n'est pas une règle générale dans tous les élevages. Les auteurs mettent en évidence le rôle prépondérant de la conduite du troupeau, deux fois plus important sur la croissance que le phénotype. L'étude des effets saisonniers souligne la liaison étroite qu'il y a entre la production d'herbe de qualité et la croissance des agneaux. En conclusion, les auteurs insistent sur les gains réalisables par standardisation des techniques d'élevage avant d'envisager une politique uniforme d'amélioration par croisemen

Le mouton en Martinique. I. Description des principaux phénotypes identifiés et étude de quelques caractères morphologiques

Quelques caractères morphologiques principaux (poids, hauteur au garrot et longueur) ont été comparés sur un effectif de 483 brebis réparties dans six élevages martiniquais. Les variations de ces mesures sont discutées en fonction de l'âge et du phénotype des brebis, et de l'élevage. Très peu de différences apparaissent entre les phénotypes. Les écarts de gabarit sont liés à l'âge qui permet de différencier deux groupes d'animaux : Ceux de plus d'un an et ceux de moins d'un an. L'effet âge éliminé, c'est l'influence de l'élevage qui apparaît ensuite comme prépondérante sur le gabarit des animaux. Ceci conduit à proposer aux éleveurs une grille de classification de leur élevage et met en évidence le fait que l'amélioration du niveau technique passe avant la recherche de la race idéal

Dissolved oxygen dynamics during a phytoplankton bloom in the Ross Sea polynya

The Ross Sea polynya is one of the most productive regions in the Southern Ocean. However, limited access and high spatio-temporal variability of physical and biological processes limit the use of conventional oceanographic methods to measure early season primary productivity. High-resolution observations from two Seagliders provide insights into the timing of a bloom in the southern Ross Sea polynya in December 2010. Changes in chlorophyll and oxygen concentrations are used to assess bloom dynamics. Using a ratio of dissolved oxygen to carbon, net primary production is estimated over the duration of the bloom showing a sensitive balance between net autotrophy and heterotrophy. The two gliders, observing spatially distinct regions during the same period, found net community production rates of -0.9±0.7 and 0.7±0.4 g C m-2 d-1. The difference highlights the spatial variability of biological processes and is probably caused by observing different stages of the bloom. The challenge of obtaining accurate primary productivity estimates highlights the need for increased observational efforts, particularly focusing on subsurface processes not resolved using surface or remote observations. Without an increased observational effort and the involvement of emerging technologies, it will not be possible to determine the seasonal trophic balance of the Ross Sea polynya and quantify the shelf's importance in carbon export

Neon and Helium in the Surface of Stardust Cell C2028

Previous studies of light noble gases in Stardust aerogel samples detected a variety of isotopically non-terrestrial He and Ne compositions. However, with one exception, in none of these samples was there visible evidence for the presence of particles that could have hosted the gases. The exception is materials keystoned from track 41, cell C2044, which contained observable fragments of the impacting Wild 2 comet coma grain. Here we report noble gas data from a second aerogel sample in which grains are observed, cut from the surface of a cell (C2028) riddled with tiny tracks and particles that are thought to be secondary in origin, ejected toward the cell when a parent grain collided with the spacecraft structure and fragmented. Interestingly, measured 20Ne/22Ne ratios in the track 41 and C2028 samples are similar, and within error of the meteoritic "Q-phase" Ne composition

Sigma-phase in Fe-Cr and Fe-V alloy systems and its physical properties

A review is presented on physical properties of the sigma-phase in Fe-Cr and Fe-V alloy systems as revealed both with experimental -- mostly with the Mossbauer spectroscopy -- and theoretical methods. In particular, the following questions relevant to the issue have been addressed: identification of sigma and determination of its structural properties, kinetics of alpha-to-sigma and sigma-to-alpha phase transformations, Debye temperature and Fe-partial phonon density of states, Curie temperature and magnetization, hyperfine fields, isomer shifts and electric field gradients.Comment: 26 pages, 23 figures and 83 reference

Mass-fractionation induced by the Genesis solar wind concentrator: Analysis of neon isotopes by UV laser ablation

The solar wind (SW) concentrator, a key instrument onboard the Genesis mission, was designed to provide larger fluences of implanted SW for precise isotope analyses of oxygen and nitrogen [1]. SW ions in the mass range 4–28 amu were accelerated and focused on a “concentrator target” by an electrostatic mirror. This concentration process caused some instrumental mass fractionation of the implanted SW ions as function of the radial position on the target. Correction of this fractionation will be based on a combination of the measured radial fractionation of Ne isotopes with results of simulations of the implantation process using the actual performance of the concentrator and the SW conditions during exposure. Here we present He and Ne abundance and Ne isotopic composition data along one arm of the gold cross that framed the 4 concentrator subtargets

Localization-delocalization transition of a reaction-diffusion front near a semipermeable wall

The A+B --> C reaction-diffusion process is studied in a system where the reagents are separated by a semipermeable wall. We use reaction-diffusion equations to describe the process and to derive a scaling description for the long-time behavior of the reaction front. Furthermore, we show that a critical localization-delocalization transition takes place as a control parameter which depends on the initial densities and on the diffusion constants is varied. The transition is between a reaction front of finite width that is localized at the wall and a front which is detached and moves away from the wall. At the critical point, the reaction front remains at the wall but its width diverges with time [as t^(1/6) in mean-field approximation].Comment: 7 pages, PS fil

The pressure-volume-temperature relationship of cellulose

Pressure–volume–temperature (PVT) mea- surements of a-cellulose with different water contents, were performed at temperatures from 25 to 180 °C and pressures from 19.6 to 196 MPa. PVT measurements allowed observation of the combined effects of pressure and temperature on the specific volume during cellulose thermo-compression. All isobars showed a decrease in cellulose specific volume with temperature. This densification is associated with a transition process of the cellulose, occurring at a temperature defined by the inflection point Tt of the isobar curve. Tt decreases from 110 to 40 °C with pressure and is lower as moisture content increases. For isobars obtained at high pressures and high moisture contents, after attaining a minimum, an increase in volume is observed with temperature that may be related to free water evaporation. PVT a-cellulose experimental data was compared with predicted values from a regression analysis of the Tait equations of state, usually applied to synthetic polymers. Good correla- tions were observed at low temperatures and low pressures. The densification observed from the PVT experimental data, at a temperature that decreases with pressure, could result from a sintering phenomenon, but more research is needed to actually understand the cohesion mechanism under these conditions

Comparative genomic analysis of Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis

BACKGROUND: The Leishmania (Viannia) braziliensis complex is responsible for most cases of New World tegumentary leishmaniasis. This complex includes two closely related species but with different geographic distribution and disease phenotypes, L. (V.) peruviana and L. (V.) braziliensis. However, the genetic basis of these differences is not well understood and the status of L. (V.) peruviana as distinct species has been questioned by some. Here we sequenced the genomes of two L. (V.) peruviana isolates (LEM1537 and PAB-4377) using Illumina high throughput sequencing and performed comparative analyses against the L. (V.) braziliensis M2904 reference genome. Comparisons were focused on the detection of Single Nucleotide Polymorphisms (SNPs), insertions and deletions (INDELs), aneuploidy and gene copy number variations. RESULTS: We found 94,070 variants shared by both L. (V.) peruviana isolates (144,079 in PAB-4377 and 136,946 in LEM1537) against the L. (V.) braziliensis M2904 reference genome while only 26,853 variants separated both L. (V.) peruviana genomes. Analysis in coding sequences detected 26,750 SNPs and 1,513 indels shared by both L. (V.) peruviana isolates against L. (V.) braziliensis M2904 and revealed two L. (V.) braziliensis pseudogenes that are likely to have coding potential in L. (V.) peruviana. Chromosomal read density and allele frequency profiling showed a heterogeneous pattern of aneuploidy with an overall disomic tendency in both L. (V.) peruviana isolates, in contrast with a trisomic pattern in the L. (V.) braziliensis M2904 reference. Read depth analysis allowed us to detect more than 368 gene expansions and 14 expanded gene arrays in L. (V.) peruviana, and the likely absence of expanded amastin gene arrays. CONCLUSIONS: The greater numbers of interspecific SNP/indel differences between L. (V.) peruviana and L. (V.) braziliensis and the presence of different gene and chromosome copy number variations support the classification of both organisms as closely related but distinct species. The extensive nucleotide polymorphisms and differences in gene and chromosome copy numbers in L. (V.) peruviana suggests the possibility that these may contribute to some of the unique features of its biology, including a lower pathology and lack of mucosal development. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-015-1928-z) contains supplementary material, which is available to authorized users