Polychromatic Laser Guide Star. Progress report and modeless laser

International audienceWe report the current status of the polychromatic laser guide star pro-gramme ELP-OA, and the new developments: the modeless laser allowinga continuous match of the laser FWHM with that of the Na D2 line in themesosphere, and ATTILA the ¯rst bench of the ELP-OA demonstrator

High resolution cw laser beam preamplified in a multipass cavity pumped by a CuHBr (HyBrID) laser

International audienceThe amplification of a cw high resolution (1 MHz) single-mode dye laser in a single-stage, multipass preamplifier based on a free flowing dye jet as amplifying medium is reported. The device is pumped by a homemade CuHBr laser (HyBrID laser) (18 kHz repetition rate, 30 ns pulse duration at half-maximum and 80 ns at its base) and yields pulses of duration of 10 ns (at half-maximum). In the studied pump energy domain, the gain is a linear function of pump energy and the maximum value obtained so far with pump energy of 400 μJ is 25 μJ per pulse for an input beam power of 30 mW. The corresponding gain is of the order of 10 4. We assume that a higher gain can be reached using better quality elements. The output beam is a high quality TM 00 mode. The pulse shapes of the pump beam and the output beam are compared and a phenomenological model ("switched photon lifetime") is introduced that reproduces our observations with a good agreement

Intérêt de l’amendement et du paillage pour les plantations forestières en région méditerranéenne : le projet FP7 Sustaffor

En région méditerranéenne, il est nécessaire de faire l’entretien des jeunes plantations d’arbres pour faire face à la sécheresse et à la végétation concurrente. Ces interventions ont un grand impact économique, en plus d’avoir, lors de l’utilisation de plusieurs techniques (arrosage d’urgence, dégagement chimique ou mécanique), un effet négatif sur l’environnement. Dans le cadre du projet Sustaffor, de nouveaux produits innovants sont développés : un amendement de sol et trois prototypes de paillis, dont deux sont biodégradables (un nouveau biopolymère et une toile de jute) et un réutilisable (en caoutchouc recyclé). Ces produits sont étudiés dans le nord-est de l’Espagne dans quatre bioclimats méditerranéens représentatifs : semi-aride, méditerranéen continental, méditerranéen humide et étage montagnard. Durant les deux premières saisons de végétation, le nouvel amendement de sol a eu un effet très positif pour les sols légers ayant une faible capacité de rétention d’eau. Le paillage a été très efficace dans les conditions les plus productives et, dans une moindre mesure, en conditions limitantes. Les nouveaux produits permettent de réduire entre autres les entretiens nécessaires dans les plantations d’arbres, tout en présentant un avantage environnemental

Comment bien produire en même temps des champignons et du bois dans les forêts de pin sylvestre ? Le cas pratique de la Catalogne

La production de champignons représente une des principales richesses de nos forêts. La combinaison de la production fongique et de la production de bois est un des défis les plus importants auxquels sont confrontés les gestionnaires et les propriétaires. Ceux-ci établissent des itinéraires sylvicoles qui maximisent les bénéfices que l’on peut tirer des bois, sans compromettre leur durabilité. Cet article apporte des données sur la production de champignons, et un itinéraire sylvicole multifonctionnel est proposé qui vise à maximiser les productions conjointes de bois et de champignons au sein des peuplements réguliers de Pinus sylvestris. Les résultats définis par le Centre de la Propietat Forestal de Catalunya, avec l’assistance du Centre Tecnològic Forestal de Catalunya, se basent sur le suivi des productions fongiques de parcelles permanentes au cours des quinze dernières années. Le modèle final proposé pour la production combinée de champignons et de bois avec structure régulière prévoit une période de rotation de la coupe de 120 ans (environ 50 cm de diamètre), un régime de deux éclaircies mixtes et une densité finale de 100 pieds/ha avec régénération par éclaircies successives en deux phases

Statistical Communication Theory

Contains reports on seven research projects.National Science Foundation under Grant G-1390

Optimization of cw sodium laser guide star efficiency

Context: Sodium laser guide stars (LGS) are about to enter a new range of laser powers. Previous theoretical and numerical methods are inadequate for accurate computations of the return flux and hence for the design of the next-generation LGS systems. Aims: We numerically optimize the cw (continuous wave) laser format, in particular the light polarization and spectrum. Methods: Using Bloch equations, we simulate the mesospheric sodium atoms, including Doppler broadening, saturation, collisional relaxation, Larmor precession, and recoil, taking into account all 24 sodium hyperfine states and on the order of 100 velocity groups. Results: LGS return flux is limited by "three evils": Larmor precession due to the geomagnetic field, atomic recoil due to radiation pressure, and transition saturation. We study their impacts and show that the return flux can be boosted by repumping (simultaneous excitation of the sodium D2a and D2b lines with 10-20% of the laser power in the latter). Conclusions: We strongly recommend the use of circularly polarized lasers and repumping. As a rule of thumb, the bandwidth of laser radiation in MHz (at each line) should approximately equal the launched laser power in Watts divided by six, assuming a diffraction-limited spot size.Comment: 15 pages, 12 figures, to be published in Astronomy & Astrophysics, AA/2009/1310

Algebraic Comparison of Partial Lists in Bioinformatics

The outcome of a functional genomics pipeline is usually a partial list of genomic features, ranked by their relevance in modelling biological phenotype in terms of a classification or regression model. Due to resampling protocols or just within a meta-analysis comparison, instead of one list it is often the case that sets of alternative feature lists (possibly of different lengths) are obtained. Here we introduce a method, based on the algebraic theory of symmetric groups, for studying the variability between lists ("list stability") in the case of lists of unequal length. We provide algorithms evaluating stability for lists embedded in the full feature set or just limited to the features occurring in the partial lists. The method is demonstrated first on synthetic data in a gene filtering task and then for finding gene profiles on a recent prostate cancer dataset

A fast and accurate method to detect allelic genomic imbalances underlying mosaic rearrangements using SNP array data

<p>Abstract</p> <p>Background</p> <p>Mosaicism for copy number and copy neutral chromosomal rearrangements has been recently identified as a relatively common source of genetic variation in the normal population. However its prevalence is poorly defined since it has been only studied systematically in one large-scale study and by using non optimal <it>ad-hoc </it>SNP array data analysis tools, uncovering rather large alterations (> 1 Mb) and affecting a high proportion of cells. Here we propose a novel methodology, Mosaic Alteration Detection-MAD, by providing a software tool that is effective for capturing previously described alterations as wells as new variants that are smaller in size and/or affecting a low percentage of cells.</p> <p>Results</p> <p>The developed method identified all previously known mosaic abnormalities reported in SNP array data obtained from controls, bladder cancer and HapMap individuals. In addition MAD tool was able to detect new mosaic variants not reported before that were smaller in size and with lower percentage of cells affected. The performance of the tool was analysed by studying simulated data for different scenarios. Our method showed high sensitivity and specificity for all assessed scenarios.</p> <p>Conclusions</p> <p>The tool presented here has the ability to identify mosaic abnormalities with high sensitivity and specificity. Our results confirm the lack of sensitivity of former methods by identifying new mosaic variants not reported in previously utilised datasets. Our work suggests that the prevalence of mosaic alterations could be higher than initially thought. The use of appropriate SNP array data analysis methods would help in defining the human genome mosaic map.</p

Eruption type probability and eruption source parameters at Cotopaxi and Guagua Pichincha volcanoes (Ecuador) with uncertainty quantification

Future occurrence of explosive eruptive activity at Cotopaxi and Guagua Pichincha volcanoes, Ecuador, is assessed probabilistically, utilizing expert elicitation. Eight eruption types were considered for each volcano. Type event probabilities were evaluated for the next eruption at each volcano and for at least one of each type within the next 100&nbsp;years. For each type, we elicited relevant eruption source parameters (duration, average plume height, and total tephra mass). We investigated the robustness of these elicited evaluations by deriving probability uncertainties using three expert scoring methods. For Cotopaxi, we considered both rhyolitic and andesitic magmas. Elicitation findings indicate that the most probable next eruption type is an andesitic hydrovolcanic/ash-emission (~ 26–44% median probability), which has also the highest median probability of recurring over the next 100&nbsp;years. However, for the next eruption at Cotopaxi, the average joint probabilities for sub-Plinian or Plinian type eruption is of order 30–40%—a significant chance of a violent explosive event. It is inferred that any Cotopaxi rhyolitic eruption could involve a longer duration and greater erupted mass than an andesitic event, likely producing a prolonged emergency. For Guagua Pichincha, future eruption types are expected to be andesitic/dacitic, and a vulcanian event is judged most probable for the next eruption (median probability ~40–55%); this type is expected to be most frequent over the next 100&nbsp;years, too. However, there is a substantial probability (possibly &gt;40% in average) that the next eruption could be sub-Plinian or Plinian, with all that implies for hazard levels