Alteration and release of aliphatic compounds by the polychaete Nereis virens (Sars) experimentally fed with hydrocarbons

In the laboratory, marine worms were fed with a mixture of algae and several aliphatic hydrocarbons for 15 days. After ingestion by the worms, 34.9% of hydrocarbons are found in the faeces and only 3.1% accumulated in the gut. The comparison between the initial mixture and the faeces shows that the worm’s digestive process lead to changes in the distribution of the n-alkane mixture. These changes are different from those only due to physical processes in the experimental conditions. In our experiment, no variation in the distribution of hydrocarbons in faeces with time and no microbial hydrocarbon biodegradation were evidenced. Our results suggest that marine worm feeding can substantially affect the fate of hydrocarbons in the sedimentary marine ecosystem by predominantly stimulating dissolution processes

The First Post-Kepler Brightness Dips of KIC 8462852

We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in October 2015, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth. We distinguish four main 1-2.5% dips, named "Elsie," "Celeste," "Skara Brae," and "Angkor", which persist on timescales from several days to weeks. Our main results so far are: (i) there are no apparent changes of the stellar spectrum or polarization during the dips; (ii) the multiband photometry of the dips shows differential reddening favoring non-grey extinction. Therefore, our data are inconsistent with dip models that invoke optically thick material, but rather they are in-line with predictions for an occulter consisting primarily of ordinary dust, where much of the material must be optically thin with a size scale <<1um, and may also be consistent with models invoking variations intrinsic to the stellar photosphere. Notably, our data do not place constraints on the color of the longer-term "secular" dimming, which may be caused by independent processes, or probe different regimes of a single process

La démographie rurale : des évolutions différenciées selon les territoires ruraux

Notre analyse de l’évolution de la démographie rurale québécoise, basée sur des données objectives, permet d’illustrer des réalités souvent méconnues ou mal perçues, par exemple la croissance globalement positive de la population vivant en milieu rural. Nous proposons ici une typologie originale des milieux ruraux qui permet de mieux faire ressortir la dynamique des évolutions démographiques rurales. Dans un deuxième temps, nous étudions l’évolution des migrations selon cette typologie, qui illustre un ralentissement significatif de ce qu’on appelle l’exode rural et le ralentissement du pouvoir d’attraction de Montréal. Finalement, le vieillissement de la population rurale, avec maintenant plus de décès que de naissances, devient un facteur décisif de l’évolution de la démographie rurale du Québec.Our analysis of the evolution of Quebec’s rural demography, based on objective data, illustrates realities that are often overlooked or poorly perceived, as the generally positive growth of the population living in rural areas. Here we propose an original typology of rural areas which allows us to better highlight the dynamics of rural demographic changes. In a second step, we study the evolution of migrations according to this typology, which illustrates a significant slowdown in what is called the rural exodus and the slowdown in the attractiveness of Montreal. Finally, the aging of the rural population, now with more deaths than births, becomes a decisive factor in the evolution of Quebec’s rural demography