The Indirect Search for Dark Matter from the centre of the Galaxy with the Fermi LAT

Dark matter (DM) constitutes around a 25% of the Universe, while baryons only a 4%. DM can be reasonably assumed to be made of particles, and many theories (Super-symmetry, Universal Extra Dimensions, etc.) predict Weakly Interacting Massive Particles (WIMPs) as natural DM candidates at the weak scale. Self-annihilation (or decay) of WIMPs might produce secondary gamma-rays, via hadronization or as final state radiation. Since its launch in the 2008, the Large Area Telescope on-board of the Fermi gamma-ray Space Telescope has detected the largest amount of gamma-rays to date, in the 20MeV 300GeV energy range, allowing to perform a very sensitive indirect experimental search for DM (by means of high-energy gamma-rays). DM forms large gravitationally bounded structures, the halos, which can host entire galaxies, such as the Milky Way. The DM distribution in the central part of the halos is not experimentally know, despite a very large density enhancement might be present. As secondary gamma rays production is very sensitive to WIMP density, a very effective search can be performed from the regions where the largest density is expected. Therefore the information provided by the DM halo N-body simulations are crucial. The largest gamma-ray signal from DM annihilation is expected from the centre of the Galaxy. In the same region a large gamma-ray background is produced by bright discrete sources and the cosmic-rays interacting with the interstellar gas and the photons fields. Here we report an update of the indirect search for DM from the Galactic Center (GC).Comment: 6 pages, 2 figures. Invited talk presented at the Workshop "SciNeGHE 2010", September 8-10, 2010, Trieste, Italy. To appear in Il Nuovo Cimento C - Colloquia on physic

The conjecturing process: perspectives in theory and implications in practice

[Abstract]: In this paper we analyze different types and stages of the conjecturing process. A classification of conjectures is discussed. A variety of problems that could lead to conjectures are considered from the didactical point of view. Results from a number of research studies are used to identify and investigate a number of questions related to the theoretical background of conjecturing as well as practical implications in the learning process

Thermal dynamics of thermoelectric phenomena from frequency resolved methods

Understanding the dynamics of thermoelectric (TE) phenomena is important for the detailed knowledge of the operation of TE materials and devices. By analyzing the impedance response of both a single TE element and a TE device under suspended conditions, we provide new insights into the thermal dynamics of these systems. The analysis is performed employing parameters such as the thermal penetration depth, the characteristic thermal diffusion frequency and the thermal diffusion time. It is shown that in both systems the dynamics of the thermoelectric response is governed by how the Peltier heat production/absorption at the junctions evolves. In a single thermoelement, at high frequencies the thermal waves diffuse semi-infinitely from the junctions towards the half-length. When the frequency is reduced, the thermal waves can penetrate further and eventually reach the half-length where they start to cancel each other and further penetration is blocked. In the case of a TE module, semi-infinite thermal diffusion along the thickness of the ceramic layers occurs at the highest frequencies. As the frequency is decreased, heat storage in the ceramics becomes dominant and starts to compete with the diffusion of the thermal waves towards the half-length of the thermoelements. Finally, the cancellation of the waves occurs at the lowest frequencies. It is demonstrated that the analysis is able to identify and separate the different physical processes and to provide a detailed understanding of the dynamics of different thermoelectric effects

Understanding the management logic of private forest owners: a new approach

Recently, several typologies of non-industrial private forest owners were established in order to assess their objectives and attitudes toward forests. However, current management practices and work organization have usually not been explicitly addressed in these empirically based typologies. In a context of increasing outsourcing and decreasing family work in forests, it is important to know the forest practices, who carries them out, and with whose labour and equipment. The interrelated knowledge of these variables sheds light on the constraints faced by different forest owners and about the agents caring for their forests. Such knowledge can also improve the understanding of forest owners' behaviour and, therefore, be useful for the design and implementation of forest policies. The work models of Portuguese non-industrial private forest were identified with these goals in mind. A cluster analysis, using a representative nationwide sample and an empirically based set of variables, was instrumental in identifying six work models. The interrelation amongst these models and other variables such as landholding attributes (e.g. forest size and dominant species), owners' social profile, and their economic goals was also assessed. Finally, the main dynamics of private owners' forest management are outlined

Evaluation du procédé Oxygreen® pour son potentiel de décontamination en ochratoxine A du blé. Les effets toxiques liés à une exposition sub-chronique à l'ochratoxine A sont-ils atténués ?

L'ingestion des parties périphériques du grain de blé, dans lesquelles sont concentrés la majorité des vitamines et minéraux, par la consommation d'aliments complets (farines complètes, pain complet, pâtes complètes) constitue un atout nutritionnel évident. Cette consommation est limitée par sa faible digestibilité ainsi que par la présence de contaminants chimiques et biologiques présentant un risque pour la santé humaine et animale. L'ozonation du blé par le procédé Oxygreen® facilite la digestibilité des parties périphériques du grain de blé et en élimine les contaminants. L'objet de cette thèse consiste plus spécifiquement en l'étude du potentiel décontaminant du procédé Oxygreen® en Ochratoxine A, mycotoxine fréquemment retrouvée dans le blé et dont la présence est limitée par une réglementation Européenne. Le traitement d'une solution aqueuse d'OTA par l'ozone conduit à une dégradation rapide de l'OTA, sans formation de dérivés. L'ozonation du blé contenant de l'OTA en réduit le taux de contamination. L'étude de la cytotoxicité, de la génotoxicité in vitro révèle que l'application du procédé Oxygreen® sur un blé de bonne qualité ne conduit pas à l'apparition de phénomènes de toxicité. La connaissance des effets toxiques de l'OTA est nécessaire à la détermination des doses maximales journalières tolérables pour l'homme par extrapolation des résultats obtenus chez l'animal. L'innocuité du procédé Oxygreen® ainsi que les effets d'une exposition subchronique à de faibles doses d'OTA ont été évalués chez des rats mâles et femelles. L'exposition, même faible (40ng/kg pc/jour l'OTA conduit à l'accumulation de l'OTA dans le compartiment sanguin ainsi que dans les différents organes. Des adduits à l'ADN sont observés dans les reins et foies des animaux. Bien que l'exposition des rats recevant un blé ozoné soit réduite, les études in vitro et in vivo suggèrent des précautions dans l'utilisation de ce procédé pour la décontamination en OTA du blé. Des optimisations de ce procédé sont à envisager afin d'augmenter l'efficacité de la décontamination. ABSTRACT : Ingestion of complete flour or complete bread has the advantage of providing a food with a high nutritional value (vitamins, trace elements). The consumption of these foods is limited because bran is not easy to digest and concentrates contaminants which could impact human and animal health. Ozone application via Oxygreen® process increases their digestibility and allows reducing the contamination rate. The aim of this thesis is to analyse the safety of Oxygreen® process applied on OTA contaminated wheat. OTA is a nephrotoxic and carcinogenic mycotoxin; its amount in food is regulated by EU community. The treatment of an aqueous OTA solution by ozone rapidly destroys OTA without generating new derivatives. In the same way, ozone applied on wheat reduces OTA level. In vitro analyses of cytotoxicity and genotoxicity reveal that Oxygreen® process applied on high quality wheat does not lead to any toxic effects. Oxygreen® safety and the effects of low OTA exposure were investigated in a sub-chronic study on male and female rats. Even with exposure as low as 40 ng/kg bw/day, OTA accumulates in blood and organs, leading to DNA adducts formation in target organs (liver and kidney). The reduction of rats exposure does not result in the total decrease of OTA toxic effects. This study suggests to take care about Oxygreen® use in view of mycotoxin decontamination, and to optimize the process

Use of a managed solitary bee to pollinate almonds: Population sustainability and increased fruit set

Osmia spp. are excellent orchard pollinators but evidence that their populations can be sustained in orchard environments and their use results in increased fruit production is scarce. We released an Osmia cornuta population in an almond orchard and measured its population dynamics, as well as visitation rates and fruit set at increasing distances from the nesting stations. Honeybees were 10 times more abundant than O. cornuta. However, the best models relating fruit set and bee visitation included only O. cornuta visitation, which explained 41% and 40% of the initial and final fruit set. Distance from the nesting stations explained 27.7% and 22.1% of the variability in initial and final fruit set. Of the 198 females released, 99 (54.4%) established and produced an average of 9.15 cells. Female population growth was 1.28. By comparing our results with those of previous O. cornuta studies we identify two important populational bottlenecks (female establishment and male-biased progeny sex ratios). Our study demonstrates that even a small population of a highly effective pollinator may have a significant impact on fruit set. Our results are encouraging for the use of Osmia managed populations and for the implementation of measures to promote wild pollinators in agricultural environments