A schlieren method for ultra-low angle light scattering measurements

We describe a self calibrating optical technique that allows to perform absolute measurements of scattering cross sections for the light scattered at extremely small angles. Very good performances are obtained by using a very simple optical layout similar to that used for the schlieren method, a technique traditionally used for mapping local refraction index changes. The scattered intensity distribution is recovered by a statistical analysis of the random interference of the light scattered in a half-plane of the scattering wave vectors and the main transmitted beam. High quality data can be obtained by proper statistical accumulation of scattered intensity frames, and the static stray light contributions can be eliminated rigorously. The potentialities of the method are tested in a scattering experiment from non equilibrium fluctuations during a free diffusion experiment. Contributions of light scattered from length scales as long as Lambda=1 mm can be accurately determined.Comment: 7 pages, 3 figure

Electric birefringence study of reaction-limited colloidal aggregation

The kinetics of slow irreversible aggregation of monodisperse polystyrene latex spheres is investigated by means of the transient electric birefringence (TEB) technique. The amplitude of the TEB signal is connected with the anisotropy of fractal clusters; the decay of the signal after the electric field is switched off contains information about average cluster size and size distribution. The TEB results are compared with static and dynamic light scattering data

Kerr effect from fractal aggregates of polystyrene microspheres

We study the slow aggregation of aqueous suspensions of optically isotropic microspheres by means of transient electric birefringence. Aggregating clusters exhibit large Kerr constants, and consequently we provide direct experimental evidence that the clusters do posses form anisotropy. From the birefringence relaxation time we derive information on the average cluster size and on the size distribution, and determine their evolution during the aggregation process. Static and dynamic light scattering data confirm the validity of the transient electric birefringence results

The role of habitat in the facilitation of Ostreopsis spp. blooms

International audienceIn recent decades, recurrent Ostreopsis spp. blooms have been recorded throughout the globe, causing public health issues and mass mortalities of invertebrates. Ostreopsis species are benthic and develop in shallow waters in close relation with a substrate, but possible substrate preferences are still ambiguous. Bloom develops on both living and dead substrates and several interacting biotic and abiotic factors acting at different spatial scales can potentially foster or regulate Ostreopsis spp. development. The objective of this review is to collect and summarize information on Ostreopsis spp. blooms related to the habitat at different spatial scales, in order to assess preferences and trends. References including Ostreopsis spp. samplings in the field were analysed in this review, as potentially including information about the micro- (substrate), meso‑ (community) and macrohabitat (ecosystem) related to Ostreopsis spp. blooms. The sampled substrate and the ecosystem where Ostreopsis spp. were collected were generally reported and described in the studies, while the description of the mesohabitat was rarely reported. Ostreopsis spp. were generally described as attached to biotic substrates and in particular, macroalgae, even in studies conducted in coral reefs, where macroalgae are generally not dominant (but they can be in case of coral reef degradation). In both temperate and tropical areas, Ostreopsis spp. were mostly sampled on algal species usually forming medium or low complexity communities (erect or turf-forming algae), often characteristic from post-regime shift scenarios, and rarely on canopy-forming species (such as fucoids and kelps). This literature review highlights the need of collecting more information about the mesohabitat where important Ostreopsis spp. blooms develop, as much as of the underlying mechanisms driving eventual differences on Ostreopsis spp. abundances. This knowledge would allow a better risk assessment of Ostreopsis spp. blooms, identifying areas at high risk on the base of the benthic habitat

Comparing CT colonography and flexible sigmoidoscopy: A randomised trial within a population-based screening programme

The role of CT colonography (CTC) as a colorectal cancer (CRC) screening test is uncertain. The aim of our trial was to compare participation and detection rate (DR) with sigmoidoscopy (flexible sigmoidoscopy (FS)) and CTC in a screening setting

CoCoNet: Towards coast to coast networks of marine protected areas (From the shore to the high and deep sea), coupled with sea-based wind energy potential

This volume contains the main results of the EC FP7 "The Ocean of Tomorrow" Project CoCoNet, divided in two sections: 1) a set of guidelines to design networks of Marine Protected Areas in the Mediterranean and the Black Seas; 2) a smart wind chart that will allow evaluating the possibility of installing Offshore Wind Farms in both seas. The concept of Cells of Ecosystem Functioning, based on connectivity, is introduced to define natural units of management and conservation. The definition of Good Environmental Status, as defined in the Marine Strategy Framework Directive, is fully embraced to set the objectives of the project, by adopting a holistic approach that integrates a full set of disciplines, ranging from physics to bio-ecology, economics, engineering and many sub-disciplines. The CoCoNet Consortium involved scientist sfrom 22 states, based in Africa, Asia, and Europe, contributing to build a coherent scientific community