Les historiens français et la recherche historique allemande de 1865 à 1914

Québec Université Laval, Bibliothèque 201

Tests des modèles de la leptogenèse par la mesure de la violation CP leptonique au LHC

Plusieurs observations montrent une asymétrie baryons-antibaryons dans l'Univers. La principale théorie expliquant cette asymétrie est la baryogenèse qui requiert les trois conditions de Sakharov : la non-conservation du nombre baryonique, la présence de violation CP et des interactions entre particules hors de l'équilibre thermique. La baryogenèse nécessite de considérer de la physique au-delà du Modèle Standard (MS), car le MS suppose généralement une asymétrie baryonique trop petite. La baryogenèse peut être obtenue à partir de la leptogenèse, la théorie équivalente pour les leptons. De nouvelles particules et interactions impliquant des leptons généreraient une asymétrie leptonique (AL) mesurable au LHC qui serait transférable au secteur baryonique. L'ajout de neutrinos de chiralité droite (RH) au MS est un choix naturel pour expliquer l'origine de la masse des neutrinos et l'existence d'une AL, et donc d'une asymétrie baryonique. Le projet aborde certains processus détectables au LHC impliquant la désintégration de bosons W en neutrinos RH. Ces processus peuvent violer le nombre leptonique et la symétrie CP. Des facteurs d'asymétrie CP sont calculés et permettent de mesurer des invariants CP. Les invariants CP dépendent des paramètres du modèle et quantifient la violation CP. Ces invariants CP apparaissent dans les équations de Boltzmann qui décrivent l'évolution de l'AL. La résolution de ces équations permet de calculer le ratio du nombre de baryons sur le nombre de photons dans l'Univers. L'identification des invariants CP qui décrivent l'AL permet de tester les modèles de la leptogenèse par la mesure de processus impliquant de la violation CP au LHC. Pour répondre à ces objectifs, un scénario de leptogenèse résonante a été testé. Les résultats obtenus montrent que les invariants CP nécessaires pour reproduire l'asymétrie baryonique sont trop petits pour être mesurés au LHC. De futures recherches pourraient s'intéresser à d'autres modèles menant à un signal observable au LHC

Exploring the Diversity of Mechanisms Associated With Plant Tolerance to Virus Infection

Tolerance is defined as an interaction in which viruses accumulate to some degree without causing significant loss of vigor or fitness to their hosts. Tolerance can be described as a stable equilibrium between the virus and its host, an interaction in which each partner not only accommodate trade-offs for survival but also receive some benefits (e.g., protection of the plant against super-infection by virulent viruses; virus invasion of meristem tissues allowing vertical transmission). This equilibrium, which would be associated with little selective pressure for the emergence of severe viral strains, is common in wild ecosystems and has important implications for the management of viral diseases in the field. Plant viruses are obligatory intracellular parasites that divert the host cellular machinery to complete their infection cycle. Highjacking/modification of plant factors can affect plant vigor and fitness. In addition, the toxic effects of viral proteins and the deployment of plant defense responses contribute to the induction of symptoms ranging in severity from tissue discoloration to malformation or tissue necrosis. The impact of viral infection is also influenced by the virulence of the specific virus strain (or strains for mixed infections), the host genotype and environmental conditions. Although plant resistance mechanisms that restrict virus accumulation or movement have received much attention, molecular mechanisms associated with tolerance are less well-understood. We review the experimental evidence that supports the concept that tolerance can be achieved by reaching the proper balance between plant defense responses and virus counter-defenses. We also discuss plant translation repression mechanisms, plant protein degradation or modification pathways and viral self-attenuation strategies that regulate the accumulation or activity of viral proteins to mitigate their impact on the host. Finally, we discuss current progress and future opportunities toward the application of various tolerance mechanisms in the field

e-Book on plant virus infection—a cell biology perspective

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Ratification vote on taxonomic proposals to the International Committee on Taxonomy of Viruses (2016)

This article lists the changes to virus taxonomy approved and ratified by the International Committee on Taxonomy of Viruses (ICTV) in April 2016. Changes to virus taxonomy (the Universal Scheme of Virus Classification of the International Committee on Taxonomy of Viruses [ICTV]) now take place annually and are the result of a multi-stage process. In accordance with the ICTV Statutes (http://​www.​ictvonline.​org/​statutes.​asp), proposals submitted to the ICTV Executive Committee (EC) undergo a review process that involves input from the ICTV Study Groups (SGs) and Subcommittees (SCs), other interested virologists, and the EC. After final approval by the EC, proposals are then presented for ratification to the full ICTV membership by publication on an ICTV web site (http://​www.​ictvonline.​org/​) followed by an electronic vote. The latest set of proposals approved by the EC was made available on the ICTV website by January 2016 (https://​talk.​ictvonline.​org/​files/​proposals/​). A list of these proposals was then emailed on 28 March 2016 to the 148 members of ICTV, namely the EC Members, Life Members, ICTV Subcommittee Members (including the SG chairs) and ICTV National Representatives. Members were then requested to vote on whether to ratify the taxonomic proposals (voting closed on 29 April 2016)

Pest categorisation of Satsuma dwarf virus

The EFSA Panelon Plant Health performed a pest categorisation of Satsuma dwarf virus (SDV) for the EU territory. SDV is a well-known pathogen and the type species of the genus Sadwavirus in the family Secoviridae. SDV is now considered to include several other formerly distinct viruses which are therefore also covered in the present opinion. Citrus species and their relatives represent the main hosts of SDV and efficient diagnostic techniques are available. SDV is listed on some of its known hosts in Annex IIAI of Directive 2000/29/EC. It is transmitted by vegetative propagation of infected hosts and presumably through the soil, but the precise mechanism or vector(s) are still unknown. SDV is present in Asia and is not known to occur in the EU. Therefore, it does not meet this criterion to qualify as a Union regulated non-quarantine pest (RNPQ). Plants for planting represent the main pathway for the entry, but this pathway is closed by existing legislation for the main hosts (Citrus, Fortunella and Poncirus). SDV is, however, able to enter the EU on plants for plants of its unregulated rutaceous or non-rutaceous hosts. Should it be introduced, SDV has the potential to establish and subsequently spread with plants for planting and, possibly, through its poorly characterised natural spread mechanism(s). SDV is able to cause severe symptoms, quality and yield losses on a range of citrus crops. Overall, SDV meets all the criteria evaluated by EFSA to qualify as a Union quarantine pest. The main knowledge gaps and uncertainties concern (1) the potential significance of the unregulated rutaceous and non-rutaceous hosts for virus dissemination and epidemiology, (2) the origin and trade volume of the plants for planting of these host imported in the EU and (3) theefficiency of natural spread of SDV under EU conditions