Perspectives pour la formation des salariés agricoles

In spite of efforts from various sides, only a small number (2 %) of salaried farm workers have benefited from existing training programs. A study in four "départements " shows that the main issue is cashing in on training efforts. Programs must lead to recognized improvements in qualification and to better pay

Evidence of unidirectional hybridization and second‐generation adult hybrid between the two largest animals on Earth, the fin and blue whales

Biodiversity in the oceans has dramatically declined since the beginning of the industrial era, with accelerated loss of marine biodiversity impairing the ocean's capacity to maintain vital ecosystem services. A few organisms epitomize the damaging and long‐lasting effects of anthropogenic exploitation: some whale species, for instance, were brought to the brink of extinction, with their population sizes reduced to such low levels that may have cause a significant disruption to their reproductive dynamics and facilitated hybridization events. The incidence of hybridization is nevertheless believed to be rare and very little information exist on its directionality. Here, using genetic markers, we show that all but one whale hybrid sample collected in Icelandic waters originated from the successful mating of male fin whale and female blue whale, thus suggesting unidirectional hybridization. We also demonstrate for the first time the existence of a second‐generation adult (male) hybrid resulting from a backcross between a female hybrid and a pure male fin whale. The incidence of hybridization events between fin and blue whales is likely underestimated and the observed unidirectional hybridization (for F1 and F2 hybrids) is likely to induce a reproductive loss in blue whale, which may represent an additional challenge to its recovery in the Atlantic Ocean compared to other rorquals

The Translational Lattice-Vibration Raman Spectrum of Single-Crystal Ice Ih

Abstract We present the Raman spectra in natural and polarized light of ice Ih monocrystals in the region of the translational frequencies. These spectra are of better quality and higher resolution than previous spectra from monocrystals, and demonstrate the value of the investigation of single crystals by this technique, in spite of the proton disorder. In order to explain the observations we use the model of simultaneous activity of the modes allowed in D 6h symmetry and the modes allowed by the proton disorder. By analogy with the interpretation of the phenomena observed in ordered piezoelectric crystals, we suggest that the existence of translation frequencies up to c. 320 cm-1 is due to the splitting between transverse and longitudinal optical modes. On this basis, an initial simple dynamical model using only three parameters permits an interpretation of the Raman spectrum. The probable presence of directional effects in ice Ih argues in favour of the proposed explanation.</jats:p

The Translational Lattice-Vibration Raman Spectrum of Single-Crystal Ice Ih

AbstractWe present the Raman spectra in natural and polarized light of ice Ih monocrystals in the region of the translational frequencies. These spectra are of better quality and higher resolution than previous spectra from monocrystals, and demonstrate the value of the investigation of single crystals by this technique, in spite of the proton disorder. In order to explain the observations we use the model of simultaneous activity of the modes allowed in D6h symmetry and the modes allowed by the proton disorder. By analogy with the interpretation of the phenomena observed in ordered piezoelectric crystals, we suggest that the existence of translation frequencies up to c. 320 cm-1 is due to the splitting between transverse and longitudinal optical modes. On this basis, an initial simple dynamical model using only three parameters permits an interpretation of the Raman spectrum. The probable presence of directional effects in ice Ih argues in favour of the proposed explanation.</jats:p

Perspectives pour la formation des salariés agricoles

In spite of efforts from various sides, only a small number (2 %) of salaried farm workers have benefited from existing training programs. A study in four "départements " shows that the main issue is cashing in on training efforts. Programs must lead to recognized improvements in qualification and to better pay.La proportion de salariés agricoles touchés par les actions de formation continue reste, malgré les efforts des différents partenaires, relativement faible : environ 2 % du public potentiel. La recherche-action que nous avons entreprise, à partir d'une étude détaillée de la situation dans quatre départements, montre que le véritable débat se situe au niveau de la valorisation de la formation. Il s'agit donc, désormais, de mettre sur pieds des itinéraires de formation débouchant sur des niveaux de qualification — et de rémunération — reconnus.Chosson Jean-François, Loupias P. Perspectives pour la formation des salariés agricoles. In: Économie rurale. N°142, 1981. p. 24

Temperature dependence of the 306 and 227 cm-1 Raman lines in hexagonal ice between 250 and 80 K

The Raman spectra of the translational vibrational modes at 227 cm -1 and 306 cm-1 in hexagonal ice were studied as a function of temperature between 250 K and 80 K. The aim of the experiment was to detect a possible coupling between acoustic and optical phonons in the range of temperature where the elastic constants display an anormal behaviour.Par diffusion Raman l'évolution de la fréquence en fonction de la température a été étudiée entre 250 K et 80 K pour les modes de vibration 227 cm -1 et 306 cm-1 dans la glace hexagonale. Le but était de déceler l'existence possible d'un couplage entre modes optiques et modes acoustiques dans la région de température où les constantes élastiques présentent un comportement anormal

Color images visible under UV light

The present contribution aims at creating color images printed with fluorescent inks that are only visible under UV light. The considered fluorescent inks absorb light in the UV wavelength range and reemit part of it in the visible wavelength range. In contrast to normal color printing which relies on the spectral absorption of light by the inks, at low concentration fluorescent inks behave additively, i.e. their light emission spectra sum up. We first analyze to which extent different fluorescent inks can be superposed. Due to the quenching effect, at high concentrations of the fluorescent molecules, the fluorescent effect diminishes. With an ink-jet printer capable of printing pixels at reduced dot sizes, we reduce the concentration of the individual fluorescent inks and are able to create from the blue, red and greenish-yellow inks the new colorants white and magenta. In order to avoid quenching effects, we propose a color halftoning method relying on diagonally oriented pre-computed screen dots, which are printed side by side. For gamut mapping and color separation, we create a 3D representation of the fluorescent ink gamut in CIELAB space by predicting halftone fluorescent emission spectra according to the spectral Neugebauer model. Thanks to gamut mapping and juxtaposed halftoning, we create color images, which are invisible under daylight and have, under UV light, a high resemblance with the original images