3. Eventos hidrológicos extremos en la cuenca amazónica peruana: presente y futuro

Recientemente, severos eventos hidrológicos extremos han ocurrido en el Río Amazonas, como intensas sequías e inundaciones, las cuales han perjudicado a las principales ciudades amazónicas y a las zonas rurales. Esos eventos hacen parte de una tendencia hacia estiajes siempre más bajos. Mientras que el caudal más bajo fue observado en septiembre de 2010 (8 300m3/s) en la estación hidrométrica de Tamshiyacu, una rápida transición hacia uno de los caudales más altos fue observado en abril 2011 (45 000 m3/s). Finalmente en abril de 2012, durante el siguiente periodo de aguas altas, el Río Amazonas experimentó su caudal histórico más elevado (55 400m3/s). Los modelos climatológicos e hidrológicos permiten prever caudales futuros. Para la mitad del siglo 21 se calcula un aumento de 7% de los caudales de crecida, lo que significa extremos aún mayores que los actuales e inundaciones más amplias.La région du fleuve Amazone a récemment connu de sévères événements hydrologiques extrêmes: des inondations et des sécheresses qui ont porté préjudice tant aux villes amazoniennes qu’aux zones rurales. Ces événements s’inscrivent dans une tendance vers des étiages toujours plus prononcés. Alors que le débit le plus bas a été observé en septembre 2008 (8 300 m3/s) a la station hydrométrique de Tamshiyacu, celui-ci a été rapidement suivi d’une rapide transition vers l’un des débits les plus hauts en avril 2011 (45 000 m3/s). Finalement en avril 2012, lors de la saison suivante de hautes eaux, le fleuve Amazone a présenté un débit historique très élevé (55 400 m3/s). Les modelés climatologiques et hydrologiques permettent de prévoir les débits futurs. D’ici la moitié du 21ème siècle, on estime qu’il y aura une augmentation de 7% des débits de crue, ce qui signifie des extrêmes encore plus élevés qu’actuellement et des inondations de plus grande ampleur.The Amazon River has recently experienced severe extreme hydrological events -such as floods and droughts- that have harmed both the main Amazonian cities as rural areas. These events are part of a continuous trend towards low flow. While the lowest rate was observed in September 2008 (8,300 m3/s) at the Tamshiyacu hydrometric station, it was observed a rapid transition to one of the highest rates in April 2011 (45,000m3/s). In April 2012, during the next period of high water, the Amazon River experienced it highest flow in its history (55 400 m3/s). Climatological and hydrological models are used to predict future rates. An increase of 7% of flood flows is calculated by the middle of the 21st century, which means even greater extreme floods than the current ones and larger

Fast energy transfer mediated by multi-quanta bound states in a nonlinear quantum lattice

By using a Generalized Hubbard model for bosons, the energy transfer in a nonlinear quantum lattice is studied, with special emphasis on the interplay between local and nonlocal nonlinearity. For a strong local nonlinearity, it is shown that the creation of v quanta on one site excites a soliton band formed by bound states involving v quanta trapped on the same site. The energy is first localized on the excited site over a significant timescale and then slowly delocalizes along the lattice. As when increasing the nonlocal nonlinearity, a faster dynamics occurs and the energy propagates more rapidly along the lattice. Nevertheless, the larger is the number of quanta, the slower is the dynamics. However, it is shown that when the nonlocal nonlinearity reaches a critical value, the lattice suddenly supports a very fast energy propagation whose dynamics is almost independent on the number of quanta. The energy is transfered by specific bound states formed by the superimposition of states involving v-p quanta trapped on one site and p quanta trapped on the nearest neighbour sites, with p=0,..,v-1. These bound states behave as independent quanta and they exhibit a dynamics which is insensitive to the nonlinearity and controlled by the single quantum hopping constant.Comment: 28 pages, 8 figure

4. HYBAM: un observatorio para medir el impacto del Cambio Climático sobre la erosión y los flujos de sedimentos en la zona Andino-Amazónica

La cuenca Amazónica es la más grande del mundo. La instalación del observatorio HYBAM con una amplia red de estaciones hidrológicas ubicadas desde el piedemonte andino hasta el océano Atlántico permite, desde el 2003, la generación de registros periódicos y confiables (nivel del agua, caudal, concentración de sedimentos y otros parámetros físico-químicos de la calidad del agua) a lo largo de toda la cuenca. Hoy en día, el desarrollo de técnicas satelitales, como la altimetría, permite completar eficientemente los datos obtenidos por las redes de medición en los ríos. El recrudecimiento de eventos extremos en la Amazonia (Inundaciones, sequias,) por efecto del cambio climático actual asociado a un cambio acelerado de ocupación de los suelos (deforestación, prácticas agrícolas), tiene una incidencia directa sobre la producción sedimentarla. Conocer los flujos de materiales transportados por los ríos es esencial tanto para la navegación fluvial como para guiar la explotación de los recursos naturales (agua, petróleo, minerales), para conocer el transporte de partículas contaminantes o para diseñar infraestructuras.Le bassin de l’Amazone est le plus grand du monde. La mise en œuvre de l’observatoire HYBAM avec un vaste réseau de stations hydrologiques situées sur les contreforts des Andes jusqu’á l’océan Atlantique permet de générer, depuis 2003, des données régulières et fiables tout le long du bassin (hauteur d’eau, débit, concentration de sédiments et d’autres paramètres physico-chimiques de qualité de l’eau). De nos jours, la mise au point des techniques par satellite, tels que l’altimétrie, permet de compléter efficacement les données obtenues par les réseaux de mesure dans les rivières. L’intensification des événements extrêmes dans la région amazonienne (inondations, sécheresses), liés au changement climatique actuel associé á un changement rapide de l’utilisation des terres (déforestation, pratiques agricoles), ont un impact direct sur la production de sédiments. Connaître les flux de matières transportés par les rivières est essentiel pour la navigation fluviale ainsi que pour guider l’exploitation des ressources naturelles (eau, pétrole, minéraux), connaître le trajet de particules polluantes ou concevoir des infrastructures.The Amazon basin is the largest basin in the world. The implementation of the HYBAM observatory, which has installed a large network of hydrological stations located from the Andean foothills down to the Atlantic Ocean, allows since 2003, generate periodical and reliable records (such as water level, flow, sediment concentration and other physicochemical parameters of water quality) along the entire basin. Nowadays, the development of satellite techniques, (such as altimetry), makes it possible to efficiently complete the data obtained by the measurement networks in rivers. The intensification of extreme events in the Amazon region (floods, droughts) occurred as a result of the current Climate Change associated with a more rapid change of land use (deforestation, agricultural practices) have a direct impact on sediment production. It is essential to know the flows of the materials transported by rivers, both for river navigation as well as to guide the exploitation of natural resources (water, oil, minerals), to know the transport of particulate pollutants, or to design infrastructures

Relaxation channels of two-vibron bound states in \alpha-helix proteins

Relaxation channels for two-vibron bound states in an anharmonic alpha-helix protein are studied. It is pointed out that the relaxation originates in the interaction between the dressed anharmonic vibrons and the remaining phonons. This interaction is responsible for the occurrence of transitions between two-vibron eigenstates mediated by both phonon absorption and phonon emission. At biological temperature, it is shown that the relaxation rate does not significantly depends on the nature of the two-vibron state involved in the process. Therefore, the lifetime for both bound and free states is of the same order of magnitude and ranges between 0.1 and 1.0 ps for realistic parameters. By contrast, the relaxation channels strongly depend on the nature of the two-vibron states which is a consequence of the breather-like behavior of the two-vibron bound states.Comment: octobre 2003 - soumis Phys. Rev.

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results