The role of abiotic and biotic mechanisms controlling the dynamics of the dissolved organic matter in pelagic ecosystem (NW Mediterranean)

Memoria de tesis doctoral presentada por Elvia Denisse Sánchez Pérez para obtener el título de Doctora en Oceanographie por la Université Pierre et Marie Curie (UPMC), realizada bajo la dirección del Dr Pascal Conan de la Université Pierre et Marie Curie (UPMC) y de la Dra. Celia Marrasé Peña del Institut de Ciències del Mar (ICM-CSIC).-- 156 pages[EN] Chromophoric dissolved organic matter (CDOM) is a major fraction of dissolved organic matter (DOM). CDOM absorbs light over a broad range of ultraviolet (UV-R) and visible wavelengths. A small fraction of CDOM can emit fluorescence when excited by ultraviolet radiation; so called fluorescent dissolved organic matter (FDOM). CDOM plays a key role in regulating light penetration into the ocean, absorbing high-energy electromagnetic spectrum (visible and ultraviolet light) waves. On one hand, it protects aquatic organisms of potential photo-damage; in the other hand it induces a negative effect by reducing light for photosynthesis. [...][FR] La matière organique dissoute chromophorique (CDOM) est une fraction significative du pool global de matière organique dissoute (MOD) dans les océans. La CDOM absorbe une partie de la lumière dans le domaine du rayonnement ultraviolet (UV-R) et du visible. Une fraction de cette CDOM peut émettre une fluorescence lorsqu'elle est excitée par un UV-R. Cette fraction est alors appelée matière organique dissoute fluorescente (FDOM). La CDOM a donc d'une part, un effet positif, en protégeant les cellules contre les dommages causés par les UV-R, mais d'autre part, un effet négatif en réduisant la quantité de radiation disponible pour la photosynthèse. [...]Peer Reviewe

A radio and infrared exploration of the Cygnus X-3 environments

To confirm, or rule out, the possible hot spot nature of two previously detected radio sources in the vicinity of the Cygnus X-3 microquasar. We present the results of a radio and near infrared exploration of the several arc-minute field around the well known galactic relativistic jet source Cygnus X-3 using the Very Large Array and the Calar Alto 3.5~m telescope. The data this paper is based on do not presently support the hot spot hypothesis. Instead, our new observations suggest that these sources are most likely background or foreground objects. Actually, none of them appears to be even barely extended as would be expected if they were part of a bow shock structure. Our near infrared observations also include a search for extended emission in the Bracket $\gamma$ (2.166 $\mu$m) and $H_{2}$ (2.122 $\mu$m) lines as possible tracers of shocked gas in the Cygnus X-3 surroundings. The results were similarly negative and the corresponding upper limits are reported.Comment: Accepted for publication in A&A; 5 pages, 4 figure

Chandra X-ray counterpart of KS 1741-293

We aim to investigate the nature of the high energy source KS 1741-293 by revisiting the radio and infrared associations proposed in the early 1990s. Our work is mostly based on the analysis of modern survey and archive data, including the NRAO, MSX, 2MASS and Chandra archives, and catalogues. We also have obtained deep CCD optical observations by ourselves. The coincidence of KS 1741-293 with an extended radio and far-infrared source, tentatively suggested in 1994, is no longer supported by modern observational data. Instead, a Chandra source is the only peculiar object found to be consistent with all high-energy error circles of KS 1741-293 and we propose it to be its most likely X-ray counterpart. We also report the existence of a non-thermal radio nebula in the vicinity of the KS 1741-293 position with the appearance of a supernova remnant. The possibility of being associated to this X-ray binary is discussed.Comment: 5 pages, 4 figures, 2 tables. Accepted for publication in Astronomy & Astrophysic

Mechanical detection of carbon nanotube resonator vibrations

Bending-mode vibrations of carbon nanotube resonator devices were mechanically detected in air at atmospheric pressure by means of a novel scanning force microscopy method. The fundamental and higher order bending eigenmodes were imaged at up to 3.1GHz with sub-nanometer resolution in vibration amplitude. The resonance frequency and the eigenmode shape of multi-wall nanotubes are consistent with the elastic beam theory for a doubly clamped beam. For single-wall nanotubes, however, resonance frequencies are significantly shifted, which is attributed to fabrication generating, for example, slack. The effect of slack is studied by pulling down the tube with the tip, which drastically reduces the resonance frequency

Effect of thermal and high-pressure treatments on the antirotaviral activity of human milk fractions

Rotaviral gastroenteritis is associated with high rate of infant mortality and morbidity. Antirotaviral activity has been associated with some glycoproteins, such as immunoglobulins A (IgA), lactoferrin (LF), mucins and lactadherin of human milk. Although holder pasteurization (HoP, 63 degrees C for 30 min) is the treatment currently applied to human milk, it may lead to a decrease of its bioactive properties. The antirotaviral capacity of human milk showed to be mainly associated with the whey fraction, focusing on IgA and LF, with neutralizing values of 100, 100 and 62%, at 1 mg protein/mL, respectively. HoP reduced the antirotaviral activity of human whey, IgA and LF, 30, 98 and 60%, respectively. Interestingly, high temperature-short time (HTST) pasteurization at 75 degrees C for 20 s did not affect the antirotaviral activity of samples, while the highest HHP treatment at 600 MPa for 15 min only reduced the activity of human whey, IgA and LF, 9, 40 and 10%, respectively

Potential use of split-beam echosounder angular information for bivalve banks cartography: a critical evaluation

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