Thesis (B.A.)--Haverford College, Dept. of English, 2009. / Includes bibliographical references.

Le satellite Fermi, lancé en juin 2008 par la NASA, observe le ciel dans le domaine des hautes énergies. Son instrument principal: le Large Area Telescope (LAT), récolte des données à partir de ~20 MeV jusqu'à plus de 300 GeV. Une amélioration majeure de ses algorithmes à permis récemment la mise à disposition d'un nouveau jeu de données, Pass 8. Pass 8 jette un nouvel éclairage sur le domaine méconnu de la basse énergie (E<100 MeV). En effet à basse énergie, la résolution en énergie et la résolution angulaire du LAT rendent l'analyse de données ardue.Au cours de ce travail de thèse, nous avons proposé une nouvelle paramétrisation capable de décrire la réponse en énergie du LAT sur 6 ordres de grandeur.Fort de ce travail technique et des améliorations apportées par Pass 8, nous nous sommes ensuite attelés à l'analyse des données à basse énergie. Pour cela nous avons extrapolé les modèles d'émission diffuse produits par la collaboration et nous les avons ajustés aux données. Nous avons également étudié 39 sources parmi les plus brillantes du ciel gamma. Les résultats de cette analyse de sources sont présentés dans cette thèse avec un accent particulier mis sur deux des plus brillantes sources du ciel gamma: le pulsar Vela et le pulsar du Crabe ainsi que sa nébuleuse. / Launched in June 2008 by NASA, the Fermi satellite observes the gamma-ray sky. Its main instrument, the LAT, harvests data from ~20 MeV to 300 GeV and beyond.Lately, a major upgrade of the LAT algorithms allowed the release of a reprocessed data set called Pass 8. Pass 8 sheds a new light on the low energy (E<100 MeV) regime where data analysis is difficult due to degraded angular and energy resolution.During this Phd a new parameterization was found for the energy dispersion which allowed an accurate modelisation of the LAT energy response on 6 orders of magnitude.This work, together with other Pass 8 improvements, allows us to consider low energy analysis. To do so, we extrapolated the existing diffuse models to low energy and fitted them to data together with 39 of the brightest low energy gamma-ray sources. The results of this analysis are presented in this manuscript with a particular enphasis on the Vela pulsar and the Crab pulsar plus nebula.

<p>LAT (linker for activation of T cells) is an important transmembrane adaptor protein in TCR-mediated signaling. Upon TCR engagement, LAT associates with multiple proteins which allows for the activation of downstream signaling pathways. The interaction between LAT with phospholipase C (PLC-gamma1) is especially critical for T cell receptor (TCR)-mediated Ca2+ signaling and MAPK activation. Knock-in mice harboring a mutation at the PLC-gamma1 binding site (Y136) of LAT develop a severe lymphoproliferative syndrome. These mice have defective thymic development and selection and lack natural regulatory T cells, implicating a breakdown of both central and peripheral tolerance. The phenotype observed in LAT-/- mice is even more severe.T cells are absent in the periphery of these mice due to a complete block in thymocyte development at the DN3 stage thereby making it difficult to study the physiological role of LAT in the activation and function of mature T cells. In order to bypass the developmental defects exhibited by LAT-/- and LATY136F mice, we developed conditional knock-in lines in which only a nonfunctional (ERCreLATf/-) or a LATY136F-mutated allele (ERCreLATf/m) of LAT is expressed in mature T cells after deletion of the wildtype LAT allele.</p><p>Analysis of ERCreLATf/m T cells after LAT deletion indicated that the interaction between LAT and PLC-gamma1 plays an important role in TCR-mediated signaling, proliferation, and IL-2 production. Furthermore, the deletion of LAT induced the development of the LATY136F lymphoproliferative syndrome in these mice. Although Foxp3+ natural Treg cells were present in these mice after deletion, they were unable to suppress the proliferation of conventional T cells. Our data indicated that the binding of LAT to PLC-gamma1 is essential for the suppressive function of CD4+CD25+ regulatory T cells. </p><p>We have also performed studies using ERCreLATf/- T cells to demonstrate that total LAT deficiency reduced the expression of Foxp3, CTLA4, and CD25 in peripheral Treg cells. Interestingly, mice with LAT deleted in peripheral T cells developed a lymphoproliferative syndrome similar to that observed in LATY136F mice although the disease caused by the LATY136F mutation was more severe. These data implicate LAT in both the positive and the negative regulation of mature T cells. Moreover, our findings indicate that LAT is essential in the maintenance of the regulatory T cell profile in the periphery, thereby aiding in the prevention of lymphoproliferative autoimmune disease.</p> / Dissertation

In this thesis I present our recent work on gamma-ray searches for dark matter with the Fermi Large Area Telescope (Fermi-LAT). We have targeted dwarf spheroidal galaxies since they are very dark matter dominated systems, and we have developed a novel joint likelihood method to combine the observations of a set of targets. In the first iteration of the joint likelihood analysis, 10 dwarf spheroidal galaxies are targeted and 2 years of Fermi-LAT data is analyzed. The resulting upper limits on the dark matter annihilation cross-section range from about 10−26 cm3 s−1 for dark matter masses of 5 GeV to about 5 × 10−23 cm3 s−1 for dark matter masses of 1 TeV, depending on the annihilation channel. For the first time, dark matter models with a cross section above the canonical thermal relic cross section (∼ 3 × 10−26 cm3 s−1) are strongly disfavored by a gamma-ray experiment. In the second iteration we include 15 dwarf spheroidal galaxies in the combined analysis, employ 4 years of data and an improved calculation of the dark matter density. The obtained upper limits range from about 10−26 cm3 s−1 for dark matter masses of 2 GeV to about 10−21 cm3 s−1 for dark matter masses of 10 TeV, depending on the annihilation channel. I briefly describe some of the evidence for dark matter, the Fermi-LAT instrument and public data releases, dwarf spheroidal galaxies, likelihood analysis, and results from analyses of Fermi-LAT data. I also document some of the tests made to verify the method and to compare different analysis setups.

Materialinė atsakomybė atsiranda dėl teisės pažeidimo, kuriuo vienas darbo santykio subjektas padaro žalą kitam subjektui neatlikdamas savo darbo pareigų arba netinkamai jas atlikdamas. Pagrindinis materialinės atsakomybės tikslas yra atlyginti turtinę žalą, susietą su darbo pareigų vykdymu, padarytą kitam darbo teisinio santykio subjektui. Neturtinė žala šiuo atveju atlyginama palyginus retai. Kas liečia materialinės atsakomybės atsiradimo sąlygų tai naujasis Darbo kodeksas pateikia pavyzdinį ir, reiktų pažymėti, galutinį jų sąrašą – šešias materialinei atsakomybei atsirasti būtinas sąlygas nediferencijuodamas jų. Teisės literatūroje materialinės atsakomybės sąlygos tradiciškai skirstomos į bendrąsias ir specialiąsias sąlygas. Lietuvos Aukščiausiojo Teismo teisėjų kolegija konstatavo, jog materialinei atsakomybei atsirasti reikalinga šių sąlygų visuma, t.y. kad visos šios sąlygos yra neatsiejamos viena nuo kitos siekiant nustatyti materialinės atsakomybės atsiradimo faktą pagal darbo teisę. Dažniausiai darbuotojų materialinė atsakomybė yra ribota. Darbuotojas privalo atlyginti visą padarytą žalą, bet ne daugiau kaip jo trijų vidutinių mėnesinių darbo užmokesčių dydžio. Iki Darbo kodekso įsigaliojimo išieškotina žala negalėjo viršyti vieno darbuotojo vidutinio darbo užmokesčio dydžio. Ribotoji materialinė atsakomybė darbuotojui taikoma visada išskyrus tam tikrus Darbo kodekse nustatytus atvejus, kai darbuotojas privalo atlyginti visą padarytą žalą. Kai darbuotojo darbas yra... [toliau žr. visą tekstą] / Material liability due to infringement of the working relationship between one entity causes damage to another entity without work duties or performing them incorrectly. The main purpose of the material liability is to compensate material damage related to the work duties of another work subject by the law. Non - pecuniary damage in this case rarely rewarded in comparison. With regard to liability in the conditions of the new Labor Code, it provides us a model and should be noted, the final list of them - six necessary conditions for material liability as a whole and neither one of them is discriminated. Material liability in the legal literature is traditionally divided into the general and special conditions. Lithuanian Chamber of Supreme Court judges held that all these conditions are inseparable from one another in order to determine the material liability fact under labor law. In most cases, workers' material liability is limited. The employee must repay all the damage, but no more than the three average monthly salaries. Prior to the entry into force of the Labor Code recovered damages could not exceed a worker's average wage level. Limited material liability is always subject to the employee except for certain Labor Code in the cases, the worker must pay all the¬ damage. When the employee work is directly related to the material values, it may be composed of full material liability in the contract. In any case, the worker must respect the common rules of life and... [to full text]

yes / Interpretations of living apart together (LAT) have typically counter-posed 'new family form' versus 'continuist' perspectives. Recent surveys, however, construct LAT as a heterogeneous category that supports a 'qualified continuist' position - most people live apart as a response to practical circumstances or as a modern version of 'boy/girlfriend', although a minority represents something new in preferring to live apart more permanently. This article interrogates this conclusion by examining in depth why people live apart together, using a nationally representative survey from Britain and interview accounts from 2011. Our analysis shows that LAT as a category contains different sorts of relationship, with different needs and desires. While overall coupledom remains pivotal and cohabitation remains the goal for most, LAT allows people flexibility and room to manoeuvre in adapting couple intimacy to the demands of contemporary life. Hence, we suggest, LAT is both 'new' and a 'continuation'. / ESRC / The full text of the published article is open access. Full text of the author's final draft was released to the Repository 09/10/2014 at the end of the publisher's embargo period.

Lat est clé dans le développement des cellules T. En l'absence de Lat, le développement des cellules T au niveau du thymus est complètement bloqué au stade DN3. Le développement des lymphocytes T est très diminué dans des souris knockin LatY136F dans lesquelles la tyrosine présente en position 136 de la protéine Lat est remplacée par une phénylalanine. De manière paradoxale, le petit nombre de cellules T qui émergent dans la périphérie des souris LatY136F donnent naissance à un syndrome lymphoprolifératif Th2 sévère. Ce projet vise à identifier les facteurs génétiques qui contribuent au développement d'un tel syndrome lymphoprolifératif. A la suite d'un crible génétique basée sur une mutagenèse à l'ENU (N-éthyl-N-nitrosurea), des lignées de souris mutantes LatY136F présentant une pathologie atténuée ou exacerbée ont été fixées et les mutations induites chimiquement ont été cartographiées et identifiées. En particulier, nous avons obtenu une lignée mutante appelée Basilic dépourvue du syndrome lymphoprolifératif. Le clonage positionnel assisté par les techniques de séquençage à haut-débit de l'ADN ont permis l'identification d'un gène appelé, Rltpr ou Lrrc16c, et ne possédant aucune fonction immunologique connue. Nous avons montré que Rltpr constitue un élément clé de la voie de signalisation opérée par la molécule de costimulation CD28. Les résultats principaux obtenus au cours de la thèse sont présentés sous forme d'un article publié. Un chapitre de perspective est consacré ensuite aux améliorations que nous pourrions apporter au type d'approche que nous avons réalisé. Enfin une dernière rubrique traite des outils permettant la manipulation du génome de la souris. / Lat is essential for proper T cell development. In the absence of Lat, intra thymic T cell development is completely blocked at an early stage known as the DN3 stage. LatY136F mice in which the tyrosine found at position 136 of Lat was replaced by a phenylalanine, also showed an impaired sequence of intrathymic T cell development. Paradoxically, the small number of improperly selected T cells that reach the periphery of LatY136F mice expand in an uncontrolled manner and trigger a severe Th2 lymphoproliferative disorder. The present thesis project aimed at identifying genetic factors contributing to the development of such a lymphoproliferative disorder. Using a sensitized ENU mutagenesis screen, we identified and characterized mutations that dampened or exacerbated the LatY136F pathology. A mutation that is called Basilic and that acts in a T cell intrinsic manner and completely prevented the LatY136F lymphoproliferative disorder was characterized in a comprehensive manner. Positional cloning assisted by next generation DNA sequencing demonstrated that Basilic corresponds to a mutation in a gene called Rltpr or Lrrc16c, the function of which was previously completely unknown in the frame of the immune system. Further functional studies performed during this project showed that Rltpr corresponded to a “missing link” involved in the signaling cascade that mediates the function of the co-stimulatory molecule CD28. Consistent with that view, nullozygous Cd28 mutant mice were found to be a phenocopy of the Basilic mice and as such prevented lymphoproliferative disorder in LatY136F mice. The Basilic mutation also resulted in a defect in regulatory T cell development.

Le virus de l’herpès simplex de type 1 (HSV1) établit une infection latente dans le système nerveux de l'homme, au cours de laquelle un type de transcrits, appelés LATs (pour latency associated transcripts), s'accumule dans les neurones infectés. Le rôle clef des LATs dans le contrôle de la latence virale est reconnu. Cependant, depuis leur découverte dans les années 80, leur mécanisme d'action reste non élucidé.Le gène des LATs est transcrit en un LAT primaire de 8,3kb, qui est épissé, conduisant à la formation de deux LATs stables : le LAT2kb et le LAT1.5kb. De façon remarquable, le LAT2kb et le LAT1.5kb sont des introns. Leur stabilité est la conséquence d'un branchement non canonique qui se traduit par le maintien de la structure en lariat. Par ailleurs, la région du génome codant les LATs contient également le gène RL2 qui code ICP0, la protéine la plus en amont dans la cascade de réactivation du virus. Des études précédentes ont montré qu’au moment de la latence, des transcrits RL2 non épissés, s'accumulent au site principal de la latence (le ganglion de Gasser).Nous avons caractérisé ces transcrits non épissés du gène RL2 dans les tissus infectés de façon latente. Ils contiennent de façon reproductible l’intron 1 et sont d’autant plus abondants dans les tissus infectés de façon latente que les LAT s’accumulent. On peut ainsi distinguer plusieurs types de tissus infectés de façon latente, dont les deux exemples les plus représentatifs sont d’une part le ganglion de Gasser (forte expression des LAT et accumulation de transcrits RL2 non-épissés) et d’autre part le ganglion cervical supérieur (pas d’accumulation de LAT par rapport aux quantités exprimées pendant la phase aiguë de l’infection, et très peu d’expression dans transcrits non-épissés). Dans tous les cas, la réalité du caractère latent de l’infection était confirmé par la présence de génome viral sans expression de transcrits matures de gène viral précoce (représenté par celui de la thymidine kinase) ni tardif (gène UL18). Ces résultats suggèrent une relation entre la présence des LAT et l’accumulation de transcrits RL2 non-épissés, ce qui pourrait être en relation avec le maintien de l’infection à l’état latent dans ces tissus. / The herpes simplex virus type 1 (HSV-1) establishes a latent infection in the nervous system of humans, in which latency associated transcripts (LATs) accumulate in infected neurons. The key role of LATs in the control of viral latency is well established. However, since their discovery in the 80s, their mechanism of action remains unclear.The LAT gene is transcribed into a 8.3 kb primary LAT that is rapidly spliced, leading to the formation of two stable LATs; LAT2kb and LAT1.5kb. Remarkably, the LAT2kb and LAT1.5kb are introns. Their stability is the result of a non-canonical sequence of the branching point, which results in maintaining the lariat structure.Moreover, the region of the genome encoding the LATs also contains the RL2 gene, encoding ICP0 that acts upstream in the cascade of viral reactivation. Previous studies have shown that RL2 unspliced transcripts may accumulate in the main site of HSV-1 latency (trigeminal ganglia). We have characterized these unspliced transcripts RL2 gene in latently infected tissues. They reproducibly contain intron 1 and are particularly abundant in latently infected tissues where LATs also accumulate. We distinguished several types of latently infected tissues, the two most representative examples being the trigeminal ganglion (strong expression of LATs and accumulation of non-spliced transcripts RL2) and, in the opposite, the superior cervical ganglion (no accumulation of LAT compared with the amounts expressed during the acute phase of infection, and little expression in non-spliced RL2 transcripts). In all cases, the reality of the latent nature of the infection was confirmed by the presence of viral genome with no expression of mature transcripts from early viral gene (represented by the thymidine kinase gene) or late (UL18 gene).These results suggest a relationship between the presence of LAT and the accumulation of non-spliced RL2 transcripts, which could be related to the maintenance of latent infection in these tissues.

Le Gallid herpesvirus 2 est un virus oncogène responsable des lymphomes T chez les poulets. L´infection par ce virus est divisée en une phase lytique dépendante de l´expression des gènes très précoces ICP4 et ICP27 et une phase latente, caractérisée par l´expression de l’ARN long non codant LAT. Nous avons montré que le gène LAT exprime de transcrits épissés alternativement, plaçant le cluster de microARN mdv1-miR-M8-M10 dans leur premier intron. Un microARN de ce cluster régule l’expression d’ICP4 et ICP27. L’étude du promoteur d’ICP27 a permis d’identifier plusieurs éléments de réponse (ER) importants, dont une boîte GC et des ER AP1 et CRE, et montré que le promoteur n’est pas transactivé par la protéine virale VP16. Nous avons identifié un transcrit épissé d’ICP27, piloté par le promoteur gK et encodant une isoforme tronquée d’ICP27. Les deux isoformes d’ICP27 colocalise avec les protéines SR du splicéosome dans le noyau, mais sont associées à des localisations différentes. / Gallid herpesvirus2 (GaHV-2) is an oncogenic herpesvirus responsible of T-cell lymphoma in chicken. GaHV-2 infections are divided into a lytic phase, depending on the expression of immediate earky genes like ICP4 and ICP27, and a latent phase characterized by the expression of the long non-coding RNA LAT. In this study, we have shown that the LAT is expressed as several highly spliced transcripts, all placing the microRNA clyster mdv1-miR-M8-M10 in their first intron. One of those microRNAs regulated the expression of ICP4 and ICP27. Studies on the ICP27 promoter allowed us to identify several important response elements (REs), including a GC box and AP1 and CRE REs, and to show that the viral protein VP16 does not transactivate the promoter. We identified a spliced transcript driven by the gK promoter that encodes a truncated ICP27 isoforms. Both isoforms of ICP27 are colocalized with spliceosomal SR proteins in the nucleus, but show a slightly different localization.

<p>Linker for Activation of T cells, LAT, is a transmembrane adaptor protein that is vital for integrating TCR-mediated signals that modulate T cell development, activation, and proliferation. Upon engagement of the T cell receptor, LAT is phosphorylated and associates with Grb2, Gads, and PLC&#947;1 through its four distal tyrosine residues. Mutation of tyrosine 136 abolishes LAT binding to PLC&#947;1. This results in impaired TCR-mediated calcium mobilization and Erk activation. LATY136F knock-in mice have a severe but incomplete block in T cell development. Yet, CD4+ &#945;&#946; T cells undergo uncontrolled expansion in the periphery, resulting in a severe autoimmune syndrome characterized by Th2 skewing and resultant B cell autoreactivity. Here, we further studied the role of LAT-PLC&#947;1 signaling in T cell lineage commitment, cytokine production, and autoimmunity.</p><p>First, we investigated the importance of the LAT-PLC&#947;1 interaction in &#947;&#948; T cells by crossing LATY136F mice with TCR&#946;-deficient mice. Our data showed that the LATY136F mutation had no major effect on the homeostasis of epithelial &#947;&#948; T cells, which could be found in the skin and small intestine. Interestingly, a population of CD4+ &#947;&#948; T cells in the spleen and lymph nodes underwent continuous expansion and produced elevated amounts of IL4, resulting in an autoimmune syndrome similar to that caused by &#945;&#946; T cells in LATY136F mice. Development of these hyperproliferative &#947;&#948; T cells was not dependent on expression of MHC class II or CD4, and their proliferation could be partially suppressed by regulatory T cells. Our data indicated that a unique subset of CD4+ &#947;&#948; T cells could hyperproliferate in LATY136F mice and suggested that LAT-PLC&#947;1 signaling may function differently in various subsets of &#947;&#948; T cells. </p><p>In addition to examining &#947;&#948; and &#945;&#946; T cell development, we also were interested in further exploring the role of LAT in cytokine production. While our previous data have demonstrated that T cells in LATY136F mice are Th2 skewed, producing large amounts of IL4, we investigated other cytokines that may be important for autoimmunity and found that these CD4+ &#945;&#946; T cells could also produce the proinflammatory cytokine IL6. Analysis of whole cell lysates from CD4+ &#945;&#946; LATY136F T cells demonstrated that NF&#954;B, AKT, and p38 were constitutively phosphorylated, and inhibition of these pathways resulted in reduced IL6 production. By crossing LATY136F mice with IL6 deficient mice, we demonstrated that early T cell survival was diminished in the absence of IL6. We further showed that this reduced CD4+ T cell pool was not due to further blocks in development, or an increase in FoxP3+ regulatory T cells. Finally, we demonstrated that over time, CD4+ T cells do hyperproliferate, yet B cell class switching and autoreactivity remains low. Our data uncovered a novel role for LAT-PLC&#947;1 signaling in regulating IL6 production by T cells during autoimmunity. </p><p>Finally, we wanted to further examine IL4 production and T helper cell differentiation in LATY136F mice. We examined IL4 production using KN2 reporter mice, where huCD2 marks T cells that have recently produced IL4 protein. We demonstrated that only a small proportion of the LATY136F T cells were actively secreting IL4. This subset of T cells were Tfh cells that expressed BCL6 and localized to B cell-rich germinal centers within the spleen. Most studies to date have examined Tfh cells in infection models, and have demonstrated that Tfh cells have very low expression of GATA3. Our results revealed in a spontaneous T cell-mediated autoimmune model system, that Tfh cells express both high levels of BCL6 and GATA3. Additionally, using an inducible deletion system, where normal development occurs, we showed that Tfh cells differentiation is the result of aberrant LAT signaling, rather than autoreactive TCRs with high affinity for self-peptide-MHC. LATY136F Tfh cells did require B cells for their development. Together, these results displayed a novel role for tonic LAT-PLC&#947;1 signaling in modulating Tfh cell differentiation and BCL6 expression.</p> / Dissertation