Le satellite Fermi a été lancé le 11 juin 2008, avec à son bord le Large Area Telescope (LAT). Le LAT est un télescope sensible au rayonnement gamma de 20 MeV à plus de 300 GeV. Au début de l'activité de Fermi, neuf pulsars jeunes et énergétiques étaient connus dans le domaine gamma. Le nombre de détections de pulsars par le LAT prédit avant lancement était de plusieurs dizaines au moins. Le LAT permettait également l'étude des pulsars milliseconde (MSPs), jamais détectés avec certitude à très haute énergie jusqu'alors. Cette thèse aborde dans un premier temps la campagne de chronométrie des pulsars émetteurs radio et/ou X, candidats à la détection par le LAT, en collaboration avec les grands radiotélescopes et télescopes X. Cette campagne a permis la recherche de signaux gamma pulsés avec une grande sensibilité. En outre, la plupart des MSPs galactiques ont été suivis dans le cadre de cette campagne, sans biais de sélection a priori sur cette population d'étoiles. Pour la première fois, des pulsations ont été détectées pour huit MSPs galactiques au-dessus de 100 MeV. Quelques bons candidats à une détection prochaine apparaissent. Une recherche similaire a été conduite pour des MSPs d'amas globulaires, sans succès à présent. L'analyse des courbes de lumière et des propriétés spectrales des huit MSPs détectés révèle que leur rayonnement gamma est relativement similaire à celui des pulsars ordinaires, et est vraisemblablement produit dans la magnétosphère externe. Cette découverte suggère que certaines sources non identifiées sont des MSPs, pour l'instant inconnus.

Els transportadors del sistema L faciliten el moviment d'aminoàcids grans i neutres a través de les membranes cel·lulars. Fins el moment es coneixien 3 proteïnes capaces d'induir aquesta activitat de transport: LAT1, LAT2 i LAT3. En aquets treball s'ha identificat LAT4, un nou transportador d'aminoàcids de la família SLC43 que guarda un 57% i un 30% d'identitat amb LAT3 i EEG1, els altres dos membres de la família. La proteïna es glicosila i arriba a la membrana plasmàtica de les cèl·lules HeLa i dels oòcits de Xenopus laevis quan es sobreexpressa. El RNA missatger de LAT4 s'expressa majoritàriament a placenta, intestí i ronyó. Més concretament, mitjançant hibridació in situ, hem detectat el missatger de LAT4 a cèl·lules dels túbuls distals i dels conductes col·lectors del ronyó, i a les cèl·lules de la cripta i la base de l'enteròcit a l'intestí prim. L'expressió de LAT4 en oòcits de Xenopus laevis indueix una activitat de transport d'aminoàcids neutres i grans; sodi, clorur i pH independent i que s'inhibeix per l'anàleg d'aminoàcids no metabolitzable BCH. Aquestes propietats concorden amb el subsistema prèviament descrit L2 i afegeixen un quart transportador responsable de l'activitat del sistema L. L'activitat de transport induïda, no és transestimulable, i possiblement es tracti d'un mecanisme de difusió facilitada. El transport induït per LAT4 mostra una cinètica de dos components, on les constants d'afinitat són de 4,7+/-0,5 mM i 178+/-29 mil.limicres pel component de baixa i alta afinitat, respectivament. L'agent alquilant de grups sulfidrils, N-etilmaleïmida (NEM) inhibeix parcialment l'activitat de transport induïda per LAT4 i efecte específicament el component de baixa afinitat. A més a més, hem identificat el mutant LAT4 S297A insensible al pretractament amb NEM. Al model cel·lular de ronyó PCT, es detecta una activitat de transport de baixa afinitat a la cara basolateral compatible amb la descrita per LAT4.EEG1, el tercer membre de la família SLC43, es glicosila i expressat en sistemes heteròlegs arriba a la membrana plasmàtica de la cèl·lula, però no indueix activitat de transport pels aminoàcids assajats. El RNA missatger de EEG1 es detecta majoritàriament a cor, fetge, i en menor grau a ronyó, pulmó i placenta, tant en teixits humans com de ratolí. S'ha generat un anticòs contra la proteïna que permet la seva detecció a ronyó, intestí i pulmó amb diferents patrons de glicosilació. També s'ha generat un model murí amb EEG1 mutat, mitjançant l'exposició a l'agent altament mutagènic etilnitrosurea (ENU). La mutació puntual detectada, introdueix un codó stop prematur concretament a la posició de la tirosina 221, que trunca la proteïna aproximadament a la meitat. Els ratolins homozigots per la mutació són viables, fèrtils i segueixen una herència mendeliana. No existeixen diferències pel que fa al pes dels animals mutants i control. No hiperexcreten aminoàcids en orina, ni tenen nivells elevats d'aminoàcids en sang. Presenten alteracions histopatològiques al ronyó i al fetge. Suggerim que EEG1 no té un paper rellevant en la reabsorció renal d'aminoàcids sense descartar una possible compensació per altres transportadors. / System L amino acid transporters mediate the movement of bulky neutral amino acids across cell membranes. Until now, three proteins that induce system L activity have been identified: LAT1, LAT2 and LAT3. In the present study we identify a new cDNA, designated LAT4, which also mediates system L activity when expressed in Xenopus laevis oocytes. Human LAT4 exhibits 57% identity to human LAT3 and 30% to EEG1. LAT4 protein is glycosylated and reaches plasma membrane in HeLa cells and Xenopus oocytes when LAT4 is overexpressed. LAT4 mRNA is expressed mainly in placenta, small intestine and kidney. In situ hybridization experiments show that LAT4 mRNA is restricted to the epithelial cells of distal tubule and the collecting duct in the kidney and in the cells of the crypt in the intestine. Like LAT3, the amino acid transport activity induced by LAT4 is sodium-, chloride- and pH-independent, is not trans-stimulated, and shows two kinetic components. The low affinity component of LAT4 induced activity is sensitive to the sulfhydryl-specific reagent N-ethylmaleimide (NEM) but not that with high affinity. Mutation in LAT4 of the SLC43 conserved S 297 to A abolishes sensitivity to NEM.EEG1, the third member of SLC43 is glycosylated and when is expressed in heterologous system it reaches the plasma membrane. EEG1 mRNA is expressed mainly in heart and liver, but also is present in kidney, lung and placenta. We generated an antibody able to recognize EEG1 from kidney, small intestine and lung with different patterns of glycosylation. We also generated an EEG1 mutated mouse model caused by the chemical mutagen N-ethyl-N-nitrosurea (ENU) which introduced a point mutation resulting in a truncated protein in amino acid position 221. The homozygous mutant mice were born at normal Mendelian ratios when intercrossing between the heterozygous mice, indicating that there was no embryonic mortality in the mutant animals. Homozygous mice do not hyperexcrete any amino acid in urine and no high level of amino acids in plasma were found. Histopathological studies of the kidney and liver reveal damage alterations in both tissues.

Deaf-Latina/Latino Critical (Deaf-LatCrit) Theory in Education is a new theoretical proposition for this qualitative study. Deaf-LatCrit recognizes and validates Deaf-Lat epistemology and challenges the topic of racism and linguicism in educational research. This study explores the multiple identities and experiences of five Deaf-Latina/o (Deaf-Lat) high school students. Deaf-Lat students reside at a residential school for the Deaf, "Rainy State School for the Deaf" (RSSD), during the week and go home for the weekend, traversing from the margin to the center of educational scholarship and discourses. The intention of this research is to explore the singular Deaf identity discourse and its inter-group diversity in the field of Deaf Studies, particularly in education. This study examines the main question: What are the intersectional identities and experiences of high school Deaf-Lat students enrolled in a residential school for the Deaf? The methods include demographic questionnaires, semi-structured interviews, participant observations, and cultural documents/artifacts. Using Deaf-LatCrit ethnographic techniques, the researcher worked with Deaf-Lat students and their families for over one year at each Deaf-Lat student's home and RSSD. This study emerges with two themes: cultural-emotional ties and microaggressions. First, it discusses how Deaf-Lat students' cultural-emotional ties in certain spaces make reference to their multiple intersecting identities. The second theme discusses how Deaf-Lat students experience multiple microaggressions and how their agentic behaviors help them cope. The findings suggest the need to look beyond Deaf identity by embracing the multiple intersectional race, class, gender and sexual orientation identities of Deaf-Lat students, particularly in schools. Understanding the experiences and overlapping identities of Deaf-Lat students can promote that residential school administrators and classroom teachers explore into their privilege(s) and learn about the history of institutional and individual racism and linguicism. These findings can push for the creation of safe spaces for Deaf-Lat students in the field of education and other multiple disciplines. / text

Some of the most interesting objects in the Universe are Active Galactic Nuclei. In the centre of an active galaxy is a supermassive black hole that accretes matter from the surrounding galaxy. In the process, not yet fully understood, some of the matter is ejected in two jets, perpendicular to the plane of the galaxy. The energy of the particles in the jets are extremely high, sometimes over 1019 eV. The features of an active galaxy can be very different depending on from which angle it is viewed. This means that some astronomical objects that earlier seemed to be very heterogeneous might be only different manifestations of the same type of object, namely active galactic nuclei. This thesis introduces some of these different objects. The unifying theory is described. Ways of detecting the high-energy radiation and two important instruments, H.E.S.S. and Fermi-LAT are described. Three studies of the BL Lac PKS 2155-304, an active galactic nucleus that points its jet almost straight at Earth, are made using Fermi-LAT data. The conclusion of the studies is that the source is variable at least in the time scale of days and that in order to gather further information about these objects simultaneous multi-wavelength surveys have to be done.

No description available.

An analysis is made on the Flat Spectrum Radio Quasar PKS 0426-380 using two sets of data. The first set of data is the Fermi-LAT data collected over the time 54682.66 − 59317.66 in Modified Julian Date within the energy range of 100 MeV to 500 GeV. The second set of data is a multi-wavelength spectral energy distribution within the approximate frequencies of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%0A%0A%5Cleft%5B10%5E%7B10%7D,%2010%5E%7B27%7D%20%5Cright%5D" data-classname="equation" data-title="" />. First, the Fermi-LAT data were analysed and after modelling a lightcurve over the entire available time, a period of interest was located. The next step was to obtain a multi-wavelength spectral energy distribution of said period. Then, using JetSeT modelling, the data were analysed and a model of the Synchrotron Self-Compton, External-Compton and Synchrotron curves was fitted to the data. The final model which contained the best fit provided a set of physical parameters that described the source. These parameters were finally compared to two other Flat Spectrum Radio Quasars and conclusions regarding the properties of PKS 0426-380 were eventually drawn. A discussion comparing a related work on the same source to the results in this thesis followed. With the large differences in the constrained data between the Flat Spectrum Radio Quasars as background, three predictions concluded the thesis. These are, firstly, a cautioned approach to future searches for periodicity in AGN's. Secondly, in time, local periodicity for AGN's might be more common and interesting for future research. Finally, no certain values for the physical parameters of the AGN can be assessed and the results can only be wived as indications of the actual properties. / <p>Passed</p>

System L (SL), a basolateral amino acid transporter, transports large neutral amino acids (LNAAs) in a Na+-independent manner. Previously, we identified two isoforms of transporters: L-type amino acid transporter 1 (LAT1) and 2 (LAT2) and revealed their distinct substrate selectivity and transport properties. In this study, to establish more stable human LAT1 (hLAT1) and LAT2 (hLAT2) in vitro assay systems, we established mouse cell lines stably expressing hLAT1 (S2-LAT1) and hLAT2 (S2-LAT2). Real-time quantitative RT-PCR analysis revealed that S2-LAT1 and S2-LAT2 cells express hLAT1 and hLAT2 mRNAs at 20 - 1000-fold higher levels than those of endogenous mouse Lat1 and Lat2. S2-LAT1 and S2-LAT2 mediated [14C]L-leucine transport properties were measured and corresponded to results observed via Xenopus oocytes. Using these cells, the data demonstrate that hLAT1 and hLAT2 exhibit different characters in the acceptance of α-methyl amino acids and amino acid-related compounds with bulky side chains such as thyroid hormones and melphalan. S2-LAT1 and S2-LAT2 cells are expected to facilitate hLAT1 and hLAT2 substrate recognition research and contribute to drug development by providing an efficient assay system to screen for chemical compounds that interact with hLAT1 and hLAT2.

No description available.

Dédié à l'étude du ciel en rayons gamma, le satellite Fermi comporte à son bord le Large Area Telescope (LAT), sensible au rayonnement gamma de 20 MeV à 300 GeV. Les données recueillies par le LAT depuis son lancement en 2008 ont permis de multiplier par 10 le nombre de noyaux actifs de galaxie (NAG) détectés dans le domaine du GeV. Les rayons gamma observés dans les NAGs proviennent de processus énergétiques faisant intervenir des particules chargées de très haute énergie. Ces particules sont confinées dans un jet de plasma magnétisé qui prend sa source dans une région proche du trou noir supermassif habitant la zone centrale de la galaxie hôte. Ce jet s’éloigne à des vitesses aussi élevées que 0.9999c, formant dans de nombreux cas des lobes radio sur des échelles du kiloparsec voire du mégaparsec. Les NAGs dont le jet fait un angle faible avec la ligne de visée sont appelés blazars. La combinaison de cette très faible inclinaison du jet par rapport à la ligne de visée et de vitesses d’éjection relativistes donne lieu à des effets relativistes : mouvements apparents superluminiques, amplification de la luminosité et modification des échelles de temps. Les blazars sont caractérisés par une extrême variabilité à toutes les longueurs d’onde, sur des échelles de temps allant de quelques minutes à plusieurs mois. Une étude temporelle et spectrale du plus brillant d'entre ceux détectés par le LAT, 3C 454.3, a été réalisée afin de contraindre les modèles d'émission. Une nouvelle méthode de génération de courbes de lumière à échantillonnage adaptatif est également proposée dans cette thèse. Celle-ci permet d'extraire le maximum d'information des données du LAT quel que soit l'état de flux de la source. / The Fermi Gamma-ray Space Telescope was launched on 2008 June 11, carrying the Large Area Telescope(LAT), sensitive to gamma-rays in the 20 MeV – 300 GeV energy range. The data collected since then allowed to multiply by a factor of 10 the number of Active Galactic Nuclei (AGN) detected in the GeV range. Gamma-rays observed in AGNs come from energetic precesses bringing into play very high energy charged particles. These particles are confined in a magnetized plasma jet rising in a region close to the supermassive black hole in the center of the host galaxy. This jet moves away with velocities as high as 0.9999c, forming in many cases radio lobes on kiloparsec or even megaparsec scales. Among the AGNs, those whose jet inclination angle to the line of sight is small are called blazars. The combination of this small inclination angle with relativistic ejection speeds leds to relativistic effects : apparent superluminal motions, amplification of the luminosity and modification of the time scales. Blazars are characterized by extreme variability at all wavelengths, on time scales from a few minutes to several months. A temporal and spectral study of the most luminous of those detected by the LAT, 3C 454.3, was done so as to constrain emission models. A new method for generating adaptive-binning lightcurves is also suggested in this thesis. It allows to extract the maximum of information from the LAT data whatever the flux state of the source.

Dédié à l’étude du ciel en rayons gamma, le satellite Fermi comporte à son bord le Large AreaTelescope (LAT), sensible au rayonnement de 20 MeV à plus de 300 GeV. Sa sensibilité et ses performances grandissantes apportent de plus en plus de contraintes sur les nébuleuses à vent de pulsar. Ces nébuleuses sont alimentées par l’injection permanente d’un vent d’électrons et de positrons relativistes accélérés par l’onde de choc délimitant la nébuleuse. Ces particules chargées rayonnent dans les différents domaines du spectre électromagnétique et notamment dans le domaine des rayons gamma à l’aide du processus de diffusion Compton inverse. Cette thèse présente l’étude morphologique et spectrale détaillée de deux sources potentiellement associées à des nébuleuses : MSH 11-62 et HESS J1857+026, afin de déterminer si l’émission gamma est produite par des nébuleuses de pulsar. Dans un deuxième temps, l’analyse de toutes les sources reliées à des contreparties détectées par les télescopes Cerenkov permet la détection de six nouvelles nébuleuses de pulsars et candidats dans la gamme de Fermi. Ceci permet d’apporter de nouvelles contraintes sur les propriétés physiques des nébuleuses de pulsar ainsi que sur les mécanismes d’émission à l’aide de modèles et d’études sur la population totale détectée par le LAT. / The Fermi Gamma-ray Space Telescope was launched on 2008 June 11, carrying the Large Area Telescope (LAT), sensitive to gamma-rays from 20 MeV to more than 300 GeV. Its constantly improving sensitivity and performance offer a new opportunity to understand the sources of the gamma-ray sky including Pulsar Wind Nebulae (PWNe). PWNe are powered by the constant injection of a relativistic wind of electrons and positrons from their central pulsars. These charged particles are accelerated at the shock front forming the PWN and emit photons which can be observed along the entire electromagnetic spectrum, including the highenergy gamma-ray domain via inverse Compton scattering.This thesis present the detailed analysis of two sources of gamma-ray emission potentially asso4021ciated to PWNe : MSH 11-62 and HESS J1857+026. The combination of the spatial and spectral analyses provide new elements to confirm these associations.In a second step, we describe a search for counterparts to sources detected by Cerenkov telescopes.This search led to the detection of six new LAT sources potentially associated with PWNe. These studies bring new insights and constraints on the physical properties of the sources as well as on emitting processes by constraining the models and allowing population studies.