Sulphur and Carbon Isotopes as Tracers of Past Sub-seafloor Microbial Activity

Microbial life below the seafloor has changed over geological time, but these changes are often not obvious, as they are not recorded in the sediment. Sulphur (S) isotope values in pyrite extracted from a Plio- to Holocene sequence of the Peru Margin (Ocean Drilling Program, ODP, Site 1229) show a down-core pattern that correlates with the pattern of carbon (C) isotopes in diagenetic dolomite. Early formation of the pyrite is indicated by the mineralogical composition of iron, showing a high degree of pyritization throughout the sedimentary sequence. Hence, the S-record could not have been substantially overprinted by later pyrite formation. The S- and C-isotope profiles show, thus, evidence for two episodes of enhanced microbial methane production with a very shallow sulphate-methane transition zone. The events of high activity are correlated with zones of elevated organic C content in the stratigraphic sequence. Our results demonstrate how isotopic signatures preserved in diagenetic mineral phases provide information on changes of past biogeochemical activity in a dynamic sub-seafloor biosphere

Naturen er bedre i økologiske hegn og skel

Det glædelige er at selv ret unge økologiske hegn og relativt nyomlagte bedrifter tilsyneladende også har stor betydning for agerlandets natur. En mere varieret hegnsvegetation giver flere levemuligheder også for andre arter, både insekter og højere dyr. Med omtanke kan landmanden altså påvirke og beskytte naturen i skel og hegn via sin daglige drift og dermed bidrage til at forbedre naturen i agerlandskabet

Experimental evidence of solitary wave interaction in Hertzian chains

We study experimentally the interaction between two solitary waves that approach one to another in a linear chain of spheres interacting via the Hertz potential. When these counter propagating waves collide, they cross each other and a phase shift respect to the noninteracting waves is introduced, as a result of the nonlinear interaction potential. This observation is well reproduced by our numerical simulations and it is shown to be independent of viscoelastic dissipation at the beads contact. In addition, when the collision of equal amplitude and synchronized counter propagating waves takes place, we observe that two secondary solitary waves emerge from the interacting region. The amplitude of secondary solitary waves is proportional to the amplitude of incident waves. However, secondary solitary waves are stronger when the collision occurs at the middle contact in chains with even number of beads. Although numerical simulations correctly predict the existence of these waves, experiments show that their respective amplitude are significantly larger than predicted. We attribute this discrepancy to the rolling friction at the beads contacts during solitary wave propagation

act up Controls Actin Polymerization to Alter Cell Shape and Restrict Hedgehog Signaling in the Drosophila Eye Disc

AbstractCells in the morphogenetic furrow of the Drosophila eye disc undergo a striking shape change immediately prior to their neuronal differentiation. We have isolated mutations in a novel gene act up (acu), that is required for this shape change. acu encodes a homolog of yeast cyclase-associated protein, which sequesters monomeric actin; we show that acu is required to prevent actin filament polymerization in the eye disc. In contrast, profilin promotes actin filament polymerization, acting epistatically to acu. However, both acu and profilin are required to prevent premature Hedgehog-induced photoreceptor differentiation ahead of the morphogenetic furrow. These findings suggest that dynamic changes in actin filaments alter cell shape to control the movement of signals that coordinate a wave of differentiation

Factors Affecting Adoption of Improved Crops by Rural Farmers in Niger

Improved crops are advocated to meet the dual challenge of food security and the fight against poverty in developing countries. As most poor people in developing countries live in rural areas and depend on agriculture for their livelihood, an important key to get them out of poverty is to increase agricultural productivity by using technologies such as improved crops. However, the rate of improved crops adoption remains surprisingly low in Niger, one of the world poorest countries. In this paper, we examine the factors affecting adoption of improved crops by rural farmers focusing on Niger. Using the 2014’s National Survey on Households Living Conditions and Agriculture, we investigate the effect of farmers’ socioeconomic characteristics, the farm’s quality, the geographic location, the production system, the access to improved seeds and the land tenure on the probability to use improved crops rather than local crops. Our results suggest that the ownership of a government land title is the most important driver in the adoption of improved crops by rural farmers. In addition, being a female, educated, practicing polyculture, having access to improved seed increase the probability to adopt improved crops. In contrast, household size, operating on the parcel for a long period and the parcel size reduces the probability to use improved crops. These determinants of improved crops adoption should be considered in Niger’s agricultural policy to succeed in the dissemination of improved crops among rural farmers. Keywords: Adoption, Improved crops, Farm, Farmer, Nige