Occupational Health Problem Network : the Exposome

We present a thinking on the concept of relational networks applied to the french national occupational disease surveillance and prevention network (R\'eseau National de Vigilance et de Pr\'evention des Pathologies Professionnelles, RNV3P). This approach consists in searching common exposures to occupational health problems

Ants mediate the structure of phytotelm communities in an ant-garden bromeliad

The main theories explaining the biological diversity of rain forests often confer a limited understanding of the contribution of interspecific interactions to the observed patterns. We show how two-species mutualisms can affect much larger segments of the invertebrate community in tropical rain forests. Aechmea mertensii (Bromeliaceae) is both a phytotelm (plant-held water) and an ant-garden epiphyte. We studied the influence of its associated ant species (Pachycondyla goeldii and Camponotus femoratus) on the physical characteristics of the plants, and, subsequently, on the diversity of the invertebrate communities that inhabit their tanks. As dispersal agents for the bromeliads, P. goeldii and C. femoratus influence the shape and size of the bromeliad by determining the location of the seedling, from exposed to partially shaded areas. By coexisting on a local scale, the two ant species generate a gradient of habitat conditions in terms of available resources (space and food) for aquatic invertebrates, the diversity of the invertebrate communities increasing with greater volumes of water and fine detritus. Two-species mutualisms are widespread in nature, but their influence on the diversity of entire communities remains largely unexplored. Because macroinvertebrates constitute an important part of animal production in all ecosystem types, further investigations should address the functional implications of such indirect effects

Aggregates relaxation in a jamming colloidal suspension after shear cessation

The reversible aggregates formation in a shear thickening, concentrated colloidal suspension is investigated through speckle visibility spectroscopy, a dynamic light scattering technique recently introduced [P.K. Dixon and D.J. Durian, Phys. Rev. Lett. 90, 184302 (2003)]. Formation of particles aggregates is observed in the jamming regime, and their relaxation after shear cessation is monitored as a function of the applied shear stress. The aggregates relaxation time increases when a larger stress is applied. Several phenomena have been proposed to interpret this behavior: an increase of the aggregates size and volume fraction, or a closer packing of the particles in the aggregates.Comment: 7 pages, 7 figures; added figures included in the pdf versio

Production of non-local quartets and phase-sensitive entanglement in a superconducting beam splitter

Three BCS superconductors S_a, S_b, and S and two short normal regions N_a and N_b in a three-terminal S_aN_aSN_bS_b set-up provide a source of non-local quartets spatially separated as two correlated pairs in S_a and S_b, if the distance between the interfaces N_aS and SN_b is comparable to the coherence length in S. Low-temperature dc-transport of non-local quartets from S to S_a and S_b can occur in equilibrium, and also if S_a and S_b are biased at opposite voltages. At higher temperatures, thermal excitations result in correlated current fluctuations which depend on the superconducting phases phi_a and phi_b in S_a and S_b. Phase-sensitive entanglement is obtained at zero temperature if N_a and N_b are replaced by discrete levels.Comment: 4 pages, 2 figures; technical details attached in ancillary file http://arxiv.org/src/1102.2355v4/anc/EPAPS_Freyn_2011.pdf; higher versions: minor corrections, cleanup and corrected reference

Orchestrated transcription of biological processes in the marine picoeukaryote Ostreococcus exposed to light/dark cycles

Background: Picoeukaryotes represent an important, yet poorly characterized component of marine phytoplankton. The recent genome availability for two species of Ostreococcus and Micromonas has led to the emergence of picophytoplankton comparative genomics. Sequencing has revealed many unexpected features about genome structure and led to several hypotheses on Ostreococcus biology and physiology. Despite the accumulation of genomic data, little is known about gene expression in eukaryotic picophytoplankton. Results: We have conducted a genome-wide analysis of gene expression in Ostreococcus tauri cells exposed to light/dark cycles (L/D). A Bayesian Fourier Clustering method was implemented to cluster rhythmic genes according to their expression waveform. In a single L/D condition nearly all expressed genes displayed rhythmic patterns of expression. Clusters of genes were associated with the main biological processes such as transcription in the nucleus and the organelles, photosynthesis, DNA replication and mitosis. Conclusions: Light/Dark time-dependent transcription of the genes involved in the main steps leading to protein synthesis (transcription basic machinery, ribosome biogenesis, translation and aminoacid synthesis) was observed, to an unprecedented extent in eukaryotes, suggesting a major input of transcriptional regulations in Ostreococcus. We propose that the diurnal co-regulation of genes involved in photoprotection, defence against oxidative stress and DNA repair might be an efficient mechanism, which protects cells against photo-damage thereby, contributing to the ability of O. tauri to grow under a wide range of light intensities

Cognitive ability experiment with photosensitive organic molecular thin films

We present an optical experiment which permits to evaluate the information exchange necessary to self-induce cooperatively a well-organized pattern in a randomly activated molecular assembly. A low-power coherent beam carrying polarization and wavelength information is used to organize a surface relief grating on a photochromic polymer thin film which is photo-activated by a powerful incoherent beam. We demonstrate experimentally that less than 1% of the molecules possessing information cooperatively transmit it to the entire photo-activated polymer film.Comment: 16 pages, 4 figure