Résumé : La capacité de décider parmi plusieurs possibilités d'actions, grâce à l'information sensorielle disponible, est essentielle à un organisme interagissant avec un environnement complexe. Les modèles actuels de sélection d'une action soutiennent que le cerveau traite continuellement l'information sensorielle afin de planifier plusieurs possibilités d'action en parallèle. Dans cette perspective, ces représentations motrices, associées à chaque possibilité d'action, sont en constante compétition entre elles. Afin qu'une alternative puisse être sélectionnée pour le mouvement, une valeur de pondération, intégrant une multitude de facteurs, doit être associée à chacun des plans moteurs afin de venir moduler la compétition. Plusieurs études se sont intéressées aux différents facteurs modulant la sélection de l'action, tels que la disposition de l'environnement, le coût des actions, le niveau de récompense, etc. Par contre, il semble qu'aucune étude n'ait rapporté ce qu'il advient lorsque la valeur de pondération de chacune des actions possibles est identique. Dans ce contexte, quel est l'élément permettant de venir moduler la sélection de l'action? De ce fait, l'objectif principal de mon projet de maitrise est d'investiguer le facteur permettant au cerveau de sélectionner une action lorsque tous les facteurs rapportés dans la littérature sont contrôlés. De récentes données ont montré que les oscillations corticales lentes dans la bande delta peuvent servir d'instrument de sélection attentionnelle en modulant l'amplitude de la réponse neuronale. Ainsi, les stimuli arrivant dans le cortex pendant une phase en delta de forte excitabilité sont amplifiés, tandis que ceux arrivant lors d'une phase en delta de faible excitabilité sont atténués. Ceci dit, il est possible que la phase en delta dans laquelle se trouve le cerveau au moment d'effectuer la sélection d'une action puisse influencer la décision. Utilisant une tâche de sélection de main, cette étude teste l'hypothèse que la sélection de la main est associée à la phase en delta des ensembles neuronaux codant le mouvement de chacune des mains, lorsque tous les facteurs connus influençant la décision sont contrôlés. L'électroencéphalographie (EEG) fut utilisée afin d'enregistrer les signaux corticaux pendant que les participants effectuaient une tâche de sélection de main dans laquelle ils devaient, à chaque essai, atteindre une cible visuelle aussi rapidement que possible en utilisant la main de leur choix. La tâche fut conçue de façon à ce que les facteurs spatiaux et biomécaniques soient contrôlés. Ceci fut réalisé enidentifiant premièrement, sur une base individuelle, l'emplacement de la cible pour laquelle les mains droite et gauche avaient une probabilité équivalente d'être choisies (point d'égalité subjective, PSE). Ensuite, dans l'expérience principale, les participants effectuaient plusieurs mouvements d'atteinte vers des cibles positionnées près et loin du PSE, toujours avec la main de leur choix. L'utilisation de cinq cibles très près du PSE a permis de collecter de nombreux essais dans lesquels la main droite et la main gauche furent sélectionnées en réponse à un même stimulus visuel. Ceci a ainsi permis d'analyser les signaux des deux cortex dans des conditions d'utilisation de la main droite et gauche, tout en contrôlant pour les autres facteurs pouvant moduler la sélection de la main. Les résultats de cette recherche révèlent que l'hémisphère cortical se trouvant dans la phase la plus excitable en delta (près du pic négatif), lors de l'apparition du stimulus, est associé à la fois à la main qui sera sélectionnée ainsi qu'au temps de réaction. Ces résultats montrent que l'excitabilité corticale momentanée (phase du signal) pourrait agir comme un facteur modulant la sélection d'une action. Dans cette optique, ces données élargissent considérablement les modèles actuels en montrant que la sélection d'une action est en partie déterminée par l'état du cerveau au moment d'effectuer un choix, d'une manière qui est indépendante de toutes les variables de décision connues. / Abstract : Action selection is thought to be achieved by competitive interactions between simultaneously co-existing motor representations associated with each potential action. Critically, selection via competition requires biasing signals to enable only one of these alternatives to be selected. Here we use electroencephalography in a unique hand selection task in which all decision variables are controlled, and show that the cortical hemisphere that is in the most excitable phase of delta frequency band at target onset dictates the hand to be selected as well as reaction time. These results demonstrate that the momentary excitability of neuronal ensembles in which motor representations are encoded can bias action selection.

The Main Injector Neutrino Oscillation Search (MINOS) is a long baseline experiment that was built for studying the neutrino oscillation phenomena. The MINOS experiment uses high intensity muon neutrino and antineutrino beams created by Neutrinos at the Main Injector facility (NuMI) at the Fermi National Accelerator Laboratory (Fermilab). Neutrino interactions are recorded by two sampling steel-scintillator tracking calorimeters: 0.98 kton Near Detector at Fermilab, IL and 5.4 kton Far Detector at the Soudan Underground Laboratory, MN. These two detectors are functionally identical, which helps to reduce the systematic uncertainties in the muon neutrino and antineutrino disappearance measurements. The Near Detector, located 1.04 km from the neutrino production target, is used to measure the initial beam composition and neutrino energy proximal to the neutrino source. The collected data at the Near Detector is then used to predict energy spectrum in the Far Detector. By comparing this prediction to collected data at the Far Detector, which is 735 km away from the target, it enables a measurement of a set of parameters that govern the neutrino oscillation phenomenon. The flexibility of the NuMI beam configuration and the magnetization of the MINOS detectors facilitate the identification of v[subscript mu] and v̄[subscript mu] charged-current interactions on an event-by-event basis. This enables one to measure neutrino and antineutrino oscillation parameters independently and therefore allows us to test the CPT symmetry in the lepton sector. To enhance the sensitivity of the oscillation parameters measurement, a number of techniques have been implemented. Event classification, shower energy estimation and energy resolution bin fitting, which are described in this dissertation, are three of these techniques. Moreover, the most stringent constraints on oscillation parameters can be achieved by combining multiple data sets. This dissertation reports the measurement of antineutrino oscillation parameters using the complete MINOS accelerator and atmospheric data set of charged-current v̄[subscript mu] events. / text

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The Madden-Julian Oscillation (MJO) has been associated with extreme precipitation events in western North America. However, the mechanisms for, and predictability of, these associations are not clear. We have examined the influence of the MJO on North Pacific - North America (NPNA) circulation and precipitation anomalies during the boreal winter. We constructed composites of MJO events during 1979-2005 determined from the Wheeler RMM1/RMM2 index of MJO activity. Our analyses of NPNA anomalies were based primarily on the National Centers for Environmental Prediction reanalysis data set. We focused our investigations on the impacts on NPNA circulation and precipitation of: (1) the location and amplitude of the convective and subsidence components of the MJO; (2) the season of MJO occurrence; and (3) concurrent El Nino (EN) or La Nina (LN) events. We found that the NPNA response to the MJO is sensitive to the location of both the convective and subsidence components of the MJO, the season of MJO occurrence, and to the existence of concurrent EN or LN events. EN or LN events affect the extratropical response to the MJO by altering the equatorial Rossby-Kelvin wave response to the components of the MJO. This in turn affects the anomalous extratropical wave trains initiated by the MJO, and alters the strength and location of the resulting NPNA precipitation anomalies. Our results have allowed us to identify characteristic patterns associated with the MJO that can be related to the location and intensity of extreme NPNA precipitation. MJO events are relatively persistent phenomena. Thus, increased understanding of the mechanisms by which they impact the extratropics has the potential to improve extratropical extended range forecasting. Our results provide a substantial foundation for improving forecasts of NPNA circulation and precipitation.

MINOS is a long baseline neutrino oscillation experiment. A manmade beam of predominantly muon neutrinos is detected both 1 km and 735 km from the production point by two functionally identical detectors. A comparison of the energy spectra measured by the two detectors shows the energy-dependent disappearance of muon neutrinos characteristic of oscillations and allows a measurement of the parameters governing the oscillations. This thesis presents work leading to measurements of disappearance in the 6% ∇_μ background in that beam. A calibration is developed to correct for time-dependent changes in the responses of both detectors, reducing the corresponding uncertainty on hadronic energy measurements from 1.8% to 0.4% in the near detector and from 0.8% to 0.4% in the far detector. A method of selecting charged current ∇_μ events is developed, with purities (efficiencies) of 96.5% (74.4%) at the near detector, and 98.8% (70.9%) at the far detector in the region below 10~GeV reconstructed neutrino energy. A method of using the measured near detector neutrino energy spectrum to predict that expected at the far detector is discussed, and developed for use in the ∇_μ analysis. Sources of systematic uncertainty contributing to the oscillation measurements are discussed. In the far detector, 32 ∇_μ events are observed below a reconstructed energy of 30 GeV, compared to an expectation of 47.8 for Δm̄²_atm = Δm²_atm, sin²(2‾θ₂₃) = sin²(2θ₂₃). This deficit, in such a low statistics sample, makes the result difficult to interpret in the context of an oscillation parameter measurement. Possible sources for the discrepancy are discussed, concluding that considerably more data are required for a definitive solution. Running MINOS with a dedicated ∇_μ beam would be the ideal continuation of this work.

Winter storms can have devastating social and economic impacts in Europe. The severity of storms and the region they influence (southern or northern Europe) is related to the index of the North Atlantic Oscillation (NAO). However recent findings indicate that over the last millennium the relationship between the NAO and storminess varied and the forcings over centennial timescales are debated. Therefore in this research storminess has been reconstructed from NAO-sensitive regions of southern Europe (Galicia, Spain) and northern Europe (Outer Hebrides, Scotland), to investigate the Late Holocene NAO-storminess relationship and the causes of observed variability. Reconstructions were based on measurements of aeolian sand deposits within ombrotrophic peat bogs and a lake sedimentary archive from the Hebrides. The elemental composition of the lake sediments were analysed (using ITRAX XRF core scanning) to identify aeolian/in-washed sediment resulting from storms, as confirmed by correlations with instrumental data. As this is a relatively new technique there was a methodological focus on assessing its applicability for storm reconstructions and the maximum resolution achievable. It is concluded the reconstruction had a 10-year resolution (equivalent to 2-5 mm sampling resolution). The peat bog reconstructions span 4000 cal yr BP to present and indicate that there was a Late Holocene northward storm track shift. The results suggest that storminess was high in Galicia between 4000-1800 cal yr BP, after which it decreased and then gradually increased in the Outer Hebrides after 1500 cal yr BP. Comparison with an NAO reconstruction supports a consistent NAO-storm relationship through the Late Holocene. Orbital forcing is suggested as causing a steepening of the latitudinal temperature gradient and increasingly zonal circulation. Superimposed on this trend are centennial variations, which spectral analysis and visual comparisons suggest are primarily the result of solar minima (suggested as causing a weakened latitudinal temperature gradient and meridional circulation patterns), with some additional forcing from volcanic and oceanic changes. Therefore there has been a consistent storm-NAO relationship through the Late Holocene; however there appear to have been millennial and centennial shifts as the result of hemispheric circulation reorganisations.

Resumo: Este trabalho tem a finalidade de investigar a incineração de resíduos sólidos na presença de ondas acústicas para incrementar o processo de combustão. Para tanto foi projetado e construído um forno rotativo para incineração de resíduo sólido industrial. Um combustor do tipo sintonizável foi desenvolvido e acoplado ao forno rotativo para indução de oscilações acústicas, além de outros acessórios utilizados no processo de combustão (alimentador de resíduos, ejetor, sonda para análise de gases). Os resultados obtidos mostram que a presença do campo acústico melhora o processo de combustão. Estes resultados foram avaliados principalmente através da análise de gases de combustão, permitindo uma redução da quantidade de combustível utilizado. / Abstract: This work has the objective of investigating the incineration of solid wastes with acoustics oscillations to improve the combustion process. A rotary kiln was designed and built for the research. A tunable combustor was developed and connected to the rotary kiln for induction of the acoustics oscillations. Accessories were also built and used in the combustion process (feeder of waste, air ejector, probe for gas analysis). The results show that the presence of the acoustic field improves the combustion process. These results had been evaluated mainly through the analysis of gas combustion, allowing a reduction of the amount of used fuel. / Orientador: João Andrade de Carvalho Junior / Coorientador: Galdenoro Botura Júnior / Banca: Marco Aurélio Ferreira / Banca: Cristiane Aparecida Martins Andraus / Banca: José Antonio Perrella Balestieri / Banca: Luiz Roberto Carrocci / Doutor

The impact of the Madden Julian Oscillation (MJO), a major source of intraseasonal variability in the tropical atmosphere, on the Indonesia Seas is investigated using satellite-derived, reanalysis and mooring data. The MJO footprint on the Indonesian Seas is evident from the surface layer into the pycnocline. In the surface, MJO air-sea heat fluxes govern the intraseasonal sea surface temperature (SST) variations. Within the pycnocline, the MJO reduces the transfer of the Pacific water to the Indian Ocean, the Indonesian Throughflow (ITF). In addition to the ocean’s response, the oceanic feedback to the MJO is also examined. Warmer SST in the Indonesian Seas during the suppressed phase of the MJO promotes the MJO convective phase to propagate eastward over the maritime continent (MC). Intraseasonal SST variation accounts for 55 - 60% of the total non-seasonal SST variance across the Indonesian Seas. It is most energetic in Banda and Timor Seas, with its standard deviation varying between 0.4 – 0.5°C. Coupled to the MJO surface fluxes, the intraseasonal SST exhibits stronger variation in boreal winter than in summer. A slab ocean model indicates that MJO surface heat fluxes account for 69-78% of the intraseasonal SST variability. The SST increases by 1.1° - 2°C, on average, in response to intense surface heating and weak winds over the suppressed (dry) MJO phase, and then decreases by 1.8° - 2.1°C over the course of the ensuing MJO active phase that is characterized by enhanced convective cooling and westerly wind bursts. Intraseasonal variability is also significant in the Sulawesi Sea SST, but it is mostly derived from eddies and local winds. Over the period 1980 - 2012, we observe 86 significant MJO (Real-time Multi variate MJO index > 1) events occurring in the Indian Ocean, of which 51 events achieve eastward propagation (EP) over the MC, while 35 events attentuate in the eastern Indian Ocean, or show no propagation (NP) over the MC. Eastward propagation (EP) MJO events occur more frequently during La Niña years than during El Niño years. Analyses of SST across the Indonesian Seas during the suppressed phase of the MJO events indicate that the SST in Java, Banda, and Timor Seas attributed to the EP MJO events is warmer by 0.5oC that associated with the NP MJO events. The warmer SST corresponds with enhanced surface latent heat flux, sensible heat flux, and low-level moisture in the atmospheric boundary layer, driven by diurnal activity. The EP MJO events are more frequent during La Niña, as the SST response to MJO events is influenced by the thermocline depth: shallower thermocline during El Niño enables cooler subsurface water under the MJO forcing to reduce SST that then attenuates MJO activity, with deeper thermocline of La Niña having the opposite outcome. Moored velocity data in Makassar Strait between 2004 – August 2011 and August 2013 – August 2015 document substantial direct impacts of the MJO on the ITF, particularly with the surface layer (< 80 m ). A composite of the along-strait velocity within the surface layer for 10 MJO events observed during the observational period exhibits strong northward velocity within days, following the peak of MJO wind stress. The MJO forces both northward along-strait pressure gradient and the resultant of northward wind stress and turbulent stress at the base of the surface layer that, together with the seasonal forcing, maintain the reduction or even reversal of the ITF southward transport on timescales of 1-3 months during boreal winter.