This study examines the impact of natural climate variability and long-term climate change on North Atlantic tropical cyclone (TC) tracks. Using data from HURDAT for the period 1950-2007, we categorize Atlantic TCs that form in the Main Development Region into one of three track types: Straight-Moving (SM), Recurving Landfall (RCL), and Recurving Ocean (RCO) TCs. As expected, the SM storms are associated with a westward extension and strengthening of the North Atlantic Subtropical High (NASH) whereas the RCO storms coincide with a weakening of the NASH. The presence of El Nino conditions in the tropical Pacific is found to be associated with a weakening and eastward retreat of the NASH, an increase in the percentage of RCO TCs, and a decrease in the percentage of RCL TCs. Using 6-hourly wind fields from NCEP-NCAR Reanalyses, simulated tracks are computed for each historical storm in the sample using the Beta Advection Model (BAM). Using observed genesis locations, the BAM successfully reproduces the differences in TC tracks between SM, RCO and RCL storm types. When storm genesis is uniformly distributed over the MDR we find that RCL and RCO storms still exhibit a distinct difference in tracks, suggesting that differences in the large-scale steering flow over the tropical Atlantic are primarily responsible for their track differences. However the SM TCs exhibit a more northward track under the uniform genesis experiment, indicating that the more southern and western genesis location of these storms is an important contributor in determining their tracks. The observed difference between TC tracks during El Nino and La Nina events is also reproduced by the BAM under both observed and uniformly seeded genesis experiments, suggesting that it is the changes in the large-scale steering flow over the Atlantic that is responsible the larger percentage of RCO storm tracks during El Nino events. The influence of anthropogenic warming is examined using a 7 member ensemble comparing the 2xCO2 experiment to a pre-industrial control. Increased sea level pressure over the northeast and northwest quadrants of the Atlantic does not alter the average TC track.

La thèse de doctorat porte sur la physique des neutrinos de réacteurs. L'étude de plus en plus précise des spectres d'antineutrinos des réacteurs a mis à jour une déviation entre la prédiction et les mesures qui pourrait indiquer l'existence d'un nouveau neutrino, non couplé avec l'interaction faible (un neutrino stérile) et de masse autour de 1 ₑV/c². L'expérience STEREO vise à tester l'hypothèse du neutrino stérile auprès du réacteur ILL de Grenoble. Le principe de STEREO repose sur 6 cellules de détection identiques disposées entre 9 et 11.5 m de distance du cœur du réacteur de recherche de l'ILL. Le détecteur a commencé la prise de données en novembre 2016, et les premiers résultats ont été publiés dès 2018. Le travail effectué pendant la thèse a consisté dans un premier temps à caractériser la réponse en énergie du détecteur. Pendant la première phase de prise de données, des défaillances matérielles se sont manifestées entrainant le découplage optique d'une cellule et une augmentation progressive des fuites de lumière entre cellules. Ces deux aspects ont contraint l'analyse de données à développer un algorithme de reconstruction des dépôts d'énergie qui corrige les fuites lumières au premier ordre. Un important travail sur la mesure des paramètres de cette méthode a été entrepris afin d'assurer que l'échelle en énergie soit bien reproduite dans la simulation GEANT4. L'estimation des incertitudes systématiques sur l'échelle en énergie a été effectuée en se servant des bruits de fond cosmogéniques. Le second aspect majeur abordé pendant la thèse est l'analyse statistique et la génération des contours d'exclusion de l'hypothèse du neutrino stérile. La déduction statistique a été conduite en s'inspirant de la méthode de Feldman et Cousins (1999) sur la génération d'intervalles de confiance fréquentistes. Un formalise en X² a spécialement été développé pour mener une analyse d'oscillations indépendante des prédictions de flux et de forme des spectres antineutrinos. Les erreurs statistiques et systématiques ont été propagées à l'aide de matrices de covariance et les lois de X² ont été calculées en générant des pseudo-expériences. L'ensemble des travaux menés pendant cette thèse de doctorat a contribué à la publication de trois papiers présentant les résultats de l'expérience STEREO. / The doctoral thesis focuses on the physics of reactor neutrinos. The increasingly precise study of antineutrinos spectra from reactors has revealed a deviation between the prediction and the measurements, which could indicate the existence of a new neutrino. This new neutrino state would not couple with the weak interaction (a sterile neutrino) and its mass would be around 1 ₑV/c². The STEREO experiment aims at testing the sterile neutrino hypothesis at the ILL reactor in Grenoble-France. The principle of the STEREO experiment is based on 6 identical detector cells aligned between 9 and 11.5 m distance from the core of the ILL research reactor. The detector started taking data in November 2016, and the first results were published in 2018. The work carried out during the thesis initially consisted in characterizing the detector's energy response. During the first phase of data taking, hardware failures occurred leading to the optical decoupling of a cell and a gradual increase in light cross-talk between cells. These two aspects have compelled data analysis to develop a dedicated energy deposit reconstruction algorithm that corrects first-order light leaks using a matrix formalism. Significant work on the measurement of the parameters of this method was undertaken to ensure that the energy scale was well reproduced in the GEANT4 simulation. The estimation of systematic uncertainties on the energy scale was performed using cosmogenic background events. The second major aspect addressed during the thesis is the statistical analysis and generation of exclusion contours of the sterile neutrino hypothesis. The statistical inference was built using the Feldman and Cousins (1999) method by generating frequentist confidence intervals. A formalization in X² has been specially developed to conduct the oscillation analysis independently of any flux or shape prediction of the antineutrino spectra. Statistical and systematic errors were propagated using covariance matrices and X² laws were constructed by generating pseudo-experiments. All the work carried out during this doctoral thesis contributed to the publication of three papers presenting the results of the STEREO experiment.

No description available.

La cellule de Purkinje constitue la seule sortie du cortex cérébelleux. En étudiant les caractéristiques de sa décharge spontanée sur l’animal éveillé, nous pouvons avoir un aperçu de l’intégration par le cortex cérébelleux de ses deux entrées excitatrices, les fibres moussues et les fibres grimpantes. Les souris transgéniques constituent une opportunité réelle de mieux comprendre le fonctionnement et les dysfonctionnements du cortex cérébelleux. Dans ce travail, nous décrivons la décharge spontanée des cellules de Purkinje chez l’animal normal et dans différents modèles de souris ataxiques. Nous avons ainsi mis en évidence différents patterns d’activité correspondant à différents degrés d’ataxie. Ainsi, sur les souris consommant chroniquement de l’éthanol et sur les souris SCA1, qui présentent un très léger trouble de la coordination motrice, nous avons trouvé une fréquence de décharge diminuée des spikes simples et des spikes complexes, sans augmentation de la rythmicité ni émergence d’oscillation du potentiel de champ de local. Les souris déficientes en calbindine, en calrétinine, en parvalbumine, en Ube 3A maternelle, ou ayant subi in utero un syndrome d’alcoolisme fœtal présentent un trouble de la coordination plus net, mais nécessitant toujours des tests adaptés pour être mis en évidence. Ces souris présentent une oscillation rapide soutenue par la décharge rythmique et synchrone des cellules de Purkinje. Cette oscillation est synchronisée dans l’axe des fibres parallèles, et est inhibée par les inhibiteurs des gap junctions, des récepteurs GABAA et NMDA. Par contre, les souris BK-/- dont l’ataxie est évidente même en conditions standards, présentent une oscillation lente synchronisée dans les axes sagittal et frontal, en phase avec les bursts des cellules de Purkinje et avec la décharge des cellules de Golgi. L’existence de ces différents patterns qui regroupent des conditions physiopathologiques qui n’ont pas d’autre point commun qu’un même niveau de déficit de la coordination motrice suggère que les troubles cérébelleux puissent être classifiés en un nombre limité de catégories permettant ainsi une approche thérapeutique plus ciblée.

No description available.

T2K is a long baseline neutrino experiment which uses a beam of muon neutrinos, produced at J-PARC and detected at Super-Kamiokande, to study the neutrino oscillation parameters. The measurement of cross-sections in the T2K energies can constrain the uncertainties on the model predictions and help the oscillation analyses reach the necessary sensitivity to measure CP violation in the lepton sector. This thesis describes the measurement of the CC1 + cross-section in water using Run II-IV T2K data. The T2K near detector, ND280, is used to select a sample of CC1 + events having vertices in the water layers of the downstream ne-grained detector (FGD). The Time Projection Chambers (TPC) are used for the particle identi cation and to measure their momenta. The Electromagnetic Calorimeters (ECals) are used to reject events that produce electromagnetic showers coming from neutral pions. A Bayesian unfolding method with background subtraction and two control samples is used to extract the cross-section. The control samples constrain the background coming from interactions on carbon and deep inelastic scattering. The single di erential cross-section is presented as a function of the muon kinematics, the pion kinematics, the angle between the muon and the pion, and the reconstructed neutrino energy. A future long baseline experiment between J-PARC and Hyper-Kamiokande is presented as a natural continuation to the T2K experiment. Hyper- Kamiokande will be a next generation water Cherenkov detector with a total ( ducial) mass of 0.99 (0.56) million metric tons. A total exposure of 7.5MW 107 sec integrated beam power will lead to the measurement of CP to better than 19 degrees for all possible values of CP . CP violation in the lepton sector could be established at better than 3 (5 ) for 76% (58%) of the CP parameter space.

El Ni??o-Southern Oscillation (ENSO) is the most important coupled ocean-atmospheric phenomenon to cause global climate variability on interannual time scales. Efforts to understand recent, apparently anomalous ENSO behaviour are hampered by the lack of long, high-quality climate records. While instrumental data generally covers the past 150 years, record length is insufficient for the assessment of past changes in the frequency, magnitude, and duration of ENSO. Here, multiproxy networks of high-resolution tree-ring, coral, ice and documentary records derived from eastern and western Pacific ENSO ???centres of action??? are analysed (A.D. 1525-2002). Considerable improvements in ENSO reconstruction are achieved from expanding the use of records from the western Pacific. In particular, ~500 years of a continuous 3,722 year ENSO sensitive tree-ring record from New Zealand is introduced. Although extreme ENSO events are seen throughout a 478-year discrete event analysis, 43% of extreme, 20% of very strong and 28% of all protracted ENSO events occur within the 20th century. Principal component analysis was used to extend instrumental records of the Southern Oscillation Index (SOI) Ni??o 3.4 Sea Surface Temperature (Ni??o 3.4 SST) and a newly developed coupled ocean-atmospheric ENSO index (CEI) by 347 years. Significantly, of the three indices reconstructed here, CEI reconstructions were largely found to be the best predictors of ENSO. The results suggest that ENSO may be more effectively characterised using a coupled ocean-atmosphere index, particularly for December-May periods. Compared to the pre-instrumental period, the late 19th and early 20th centuries indicate a clear trend toward increased ENSO variability over the past 150 years. Significantly, spectral analysis of reconstructed indices reveals a marked change in the frequency and intensity of ENSO beginning ~A.D. 1850, coinciding with the end of the Little Ice Age and the boom in global industrialisation. This suggests that ENSO may operate differently under natural (pre-industrial) and anthropogenically influenced background states. This study asserts that recent ENSO variability appears anomalous in the context of the past five centuries. Given the considerable socio-economic impacts of ENSO events, future investigation into the implications an increasingly anthropogenically-warmed world may have on ENSO is vital.

The NOMAD experiment is a neutrino oscillation experiment, capable of identifying \nm, \nmb, \nel, \neb\ and \nt\ for use in oscillation analyses. A search for \mutoe\ oscillations is conducted, emphasising the development of two separate beam simulators, to provide the background, (no oscillation), \nel\ signal. Both beam descriptions include fits to the results of the SPY experiment that measured hadron production from a 450~GeV proton beam on beryllium target. An independent analysis of the raw SPY data to produce the particle yield is reported. A series of criteria are described for the selection and classification of neutrino events. These produce the data samples necessary for both tuning the beam simulation and determining the oscillation signal. The development of a GEANT and FLUKA based Monte Carlo beam simulator is presented, providing good agreement to the measured neutrino beam. This simulation method has sizeable variations depending on the beamline geometry, which is not known precisely. This causes large systematic errors. An empirical parametrisation is proposed and used for the first time in a NOMAD oscillation search. It uses the measured neutrino spectra at NOMAD, except the \nel, to infer the meson production at the target, and then predict the \nel\ spectrum. This method has good agreement with the data and is also insensitive to alterations of the beamline geometry, resulting in much smaller systematic errors. The reduction of the systematic errors allows the \mutoe\ oscillations search to be performed with much greater precision. Comparisons of the \nel/\nm\ ratio between the empirical parametrisation and data yields no evidence for \mutoe\ oscillations, setting a limit on the mixing parameter, $sin^2(2 \theta) &lt 1.9 \times 10^{-3} \mbox{(90\% CL)}$ at high $\Delta m^2$. The present sensitivity of the analysis on the mixing parameter is 0.0017.

This thesis has been performed in the university context for Master thesis 30 credits,which is a compulsory exercise in order to gain a degree in electrical engineering. The thesis main objectives were to investigate how the damping and the stiffness of ahydroelectric generator changed depending on different parameter values, and to testa new mathematical model to calculate the damping and stiffness constants Kd and Ks.The work has been performed at the request of VG Power, but has been performedat the division for electricity at Uppsala University. The reason for undertaking thisthesis was to ensure that generators are robust. But also when building future modelsfor generators, to have a system that can be used to compute robustness. During this thesis a power cabinet has also been constructed to be able to test thesimulated model on a real generator. Under the first five weeks a power cabinet wasconstructed in the laboratory at the division for electricity. The tests were thenperformed at a generator with a rated power of 75 kVA.

Photoreflectance (PR) spectra of a GaN thin film and an AlGaN/GaN heterostructure were measured by using a HeCd laser or a mercury lamp as a pump beam. The wavelengths (£f) of the HeCd laser and the mercury lamp are 325 nm and 253.7 nm, respectively. The energy of the HeCd laser is lower than band-gap energy of AlxGa1-xN (x > 0.2) so that electron-hole pairs cannot be generated in the AlGaN layer. Hence, the PR of the AlGaN was measured by using Argon ion laser (£f=300 nm) or quadrupled Nd:YAG (£f=266 nm) rather than HeCd laser in the previous works. In this work, the mercury lamp (£f=254 nm)was used as the pump beam. The problem with using the mercury lamp as the pump beam is because it is a diffused source so that it cannot be focused to a small spot. Nevertheless, defocused pump and probe beams were used in the PR measurement to improve signal to noise ratio. Hence, the diffused property of the mercury lamp is not a hindrance to the PR measurements.