Sensor systems for a changing ocean

The papers in this special section focus on sensor system deployment in the field of oceanography. Oceans regulate the Earth's climate and are integral to all known sources of life. Ocean processes are of biological, geological, chemical, or physical nature, occurring at micro- to kilometer scales, from less than seconds to centuries, turning the understanding and the sustainable management of the ocean into a multiscale and multidisciplinary effort. Collection of in situ observation of a volume that covers over 70% of the planet is also inherently challenging and remains generally difficult and costly in time and resources, with so far a rather unsatisfactory result, in particular with respect to space-time resolution. Over the past decade, there has been a steady crescendo of interest to support the development of a truly integrated and sustainably funded Ocean Observing System. This will be achieved with more long-term measurements of key parameters but is impaired by the costs and lack of reliability of ocean sensors in general.Postprint (author's final draft

Porous Coordination Polymers based on (bi)pyridinium Ligands

International audienc

N-Methyl-4,4-bipyridinium and N-Methyl-N -oxide-4,4 -bipyridinium Bismuth Complexes - Photochromism and Photoluminescence in the Solid State

Three bismuth complexes based on N-methyl-4,4-bipyridinium (hMV(+)), (hMV)[Bi(hMV)Cl-5] (1), and N-methyl-N-oxide-4,4-bipyridinium (MVO+), [Bi(MVO)X-4(dmso)]center dot dmso [X = Cl (2), Br (3)], are reported. All three compounds show luminescence in the solid state with maxima at 545 nm (yellow for 1) and 560 nm (orange for 2 and 3) with quantum yields up to 10 %. Upon UV irradiation, 1 undergoes a color change from white to blue accompanied by a reduction of the photoluminescence intensity. The analysis of the crystal structure of the three complexes points to a photoinduced charge-transfer (PICT) process at the origin of the photochromism in 1

Rayleigh–Taylor instability in two-component relativistic jets

Relativistic jets associated with active galactic nuclei and gamma-ray bursts propagate over huge distances without significant loss of momentum. At the same time they are bright emitters, which is indicative of strong energy dissipation. This points towards a mechanism of internal dissipation which does not result in a global disruption of the flow. One possibility is internal shocks and another one is turbulence driven by local instabilities. Such instabilities can be triggered when a freely expanding jet is reconfined by either the cocoon or external gas pressure. In this paper, we study the dynamics of two-component spine-sheath hydrodynamic jets coming into pressure equilibrium with external gas using 2D computer simulations. We find that the jet oscillations lead to a rapid onset of Rayleigh–Taylor-type instabilities, which results in additional internal dissipation and mixing of the jet components. Although slightly different in details, this outcome holds both for the heavy-spine-light-sheath and light-spine-heavy-sheath configurations. The results may provide an explanation to the spatial flaring observed in some AGN jets on kpc-scales

Photochromism and Solid State Photoluminescence of Bi and Pb Complexes and Coordination Polymers based on N-R-4,4’-bipyridinium entities (R= O-, CH3, CH2CN)

Date du colloque : 05/2013</p

Bipyridinium Ligands: Highly Luminescent Bismuth Complexes

International audienc

Optical and morphological properties of thermally vacuum evaporated cdte thin films for photovoltaic apllications

International audienc

Optical and Morphological Studies of Thermally Vacuum Evaporated ZnSe Thin Films

Zinc selenide (ZnSe) thin films were deposited on optical glass substrates using thermal vacuum evaporation, by sublimation of zinc selenide powder from a single quartz crucible heated at 600 degrees C. The substrates temperatures were maintained constant during deposition at 220 degrees C. All the samples were subjected to post - deposition thermal treatments in the same deposition chamber, at 250 degrees C for 20 minutes. AFM and SEM studies confirmed that post - deposition annealing improved the grains growth and their distribution over the entire surface of the film. Optical constants (refraction indices and extinction coefficients) of semiconducting ZnSe thin films were measured by spectroscopic ellipsometry in the range of 190 nm to 500 nm. Optical measurements were completed with the spectral dependencies of transmission and absorption using a double beam UV - VIS spectrophotometer. The values for optical bandgaps calculated from the absorption spectra were found to be around 2.7 eV. All these results lead to the conclusion, that ZnSe thin films are good candidates to replace the conventional CdS thin films used as n-type window layers in the thin film heterojunction solar cells

Researches on corrosion cracking phenomenon that occurs on welded of agricultural equipment

Welded construction equipments for agriculture are strongly stressed in terms of mechanics, but also in terms of environmental action and thus in many cases appears their wear by corrosion cracking phenomenon. After research it was noted that after a certain period of use of equipment, metallographic structure of welded steel structures has changed substantially and at the same time a change in the chemical composition of steel was also observed. In terms of chemical composition a reduction in carbon content was mainly observed, and an increase in sulfur content,determined mainly by the presence of large quantities of sulfur in the atmosphere. This sulfur in the atmosphere at the same time determines the acid action on metallic materials, by forming with water from precipitation of H2S. Key words