5,552 research outputs found
Probing extra spacetime dimensions at the Tevatron
Theories with extra spacetime dimensions aiming at resolving the hierarchy
problem have recently been developed. These scenarios have provided exciting
new grounds for experimental probes. A review of the searches conducted at the
Tevatron in this framework during its first running phase and the prospects for
its second running phase are reviewed.Comment: Proceedings of the SUSY 2002 conference, Hamburg, Germany. 8 pages
corrected reference and a typ
Topology of event distribution as a generalized definition of phase transitions in finite systems
We propose a definition of phase transitions in finite systems based on
topology anomalies of the event distribution in the space of observations. This
generalizes all the definitions based on the curvature anomalies of
thermodynamical potentials and provides a natural definition of order
parameters. The proposed definition is directly operational from the
experimental point of view. It allows to study phase transitions in Gibbs
equilibria as well as in other ensembles such as the Tsallis ensemble.Comment: 4 pages, 3 figure
Analyzing Conflict Freedom For Multi-threaded Programs With Time Annotations
Avoiding access conflicts is a major challenge in the design of
multi-threaded programs. In the context of real-time systems, the absence of
conflicts can be guaranteed by ensuring that no two potentially conflicting
accesses are ever scheduled concurrently.In this paper, we analyze programs
that carry time annotations specifying the time for executing each statement.
We propose a technique for verifying that a multi-threaded program with time
annotations is free of access conflicts. In particular, we generate constraints
that reflect the possible schedules for executing the program and the required
properties. We then invoke an SMT solver in order to verify that no execution
gives rise to concurrent conflicting accesses. Otherwise, we obtain a trace
that exhibits the access conflict.Comment: http://journal.ub.tu-berlin.de/eceasst/article/view/97
Oestrogen, an evolutionary conserved regulator of T cell differentiation and immune tolerance in jawed vertebrates?
In teleosts, as in mammals, the immune system is tightly regulated by sexual steroid hormones, such as oestrogens. We investigated the effects of 17ÎČ-oestradiol on the expression of several genes related to T cell development and resulting T cell subpopulations in sea bass, Dicentrarchus labrax, for a primary lymphoid organ, the thymus, and two secondary lymphoid organs, the head-kidney and the spleen. In parallel, the oxidative burst capacity was assessed in leucocytes of the secondary lymphoid organs. Apoptosis- and proliferation-related genes, indicative of B and T cell clonal selection and lymphoid progenitor activity, were not affected by elevated oestrogen-levels. Sex-related oestrogen-responsiveness in T cell and antigen-presenting cell markers was observed, the expression of which was differentially induced by oestrogen-exposure in the three lymphoid organs. Remarkably, in the spleen, oestrogen increased regulatory T cell-related gene expression was associated with a decrease in oxidative burst capacity. To the best of our knowledge, this study indicates for the first time that physiological levels of oestrogen are likely to promote immune tolerance by modulating thymic function (i.e., T cell development and output) and peripheral T cells in teleosts, similar to previously reported oestrogenic effects in mammals.CCMAR/Multi/04326/2013; ANRfinanced project ETaT(ANR-15-CE32-0014); FR CNRS 3730 SCALE scholarshipinfo:eu-repo/semantics/publishedVersio
Practical applications of probabilistic model checking to communication protocols
Probabilistic model checking is a formal verification technique for the analysis of systems that exhibit stochastic behaviour. It has been successfully employed in an extremely wide array of application domains including, for example, communication and multimedia protocols, security and power management. In this chapter we focus on the applicability of these techniques to the analysis of communication protocols. An analysis of the performance of such systems must successfully incorporate several crucial aspects, including concurrency between multiple components, real-time constraints and randomisation. Probabilistic model checking, in particular using probabilistic timed automata, is well suited to such an analysis. We provide an overview of this area, with emphasis on an industrially relevant case study: the IEEE 802.3 (CSMA/CD) protocol. We also discuss two contrasting approaches to the implementation of probabilistic model checking, namely those based on numerical computation and those based on discrete-event simulation. Using results from the two tools PRISM and APMC, we summarise the advantages, disadvantages and trade-offs associated with these techniques
Water ice deuteration: a tracer of the chemical history of protostars
Context. Millimetric observations have measured high degrees of molecular
deuteration in several species seen around low-mass protostars. The Herschel
Space Telescope, launched in 2009, is now providing new measures of the
deuterium fractionation of water, the main constituent of interstellar ices.
Aims. We aim at theoretically studying the formation and the deuteration of
water, which is believed to be formed on interstellar grain surfaces in
molecular clouds. Methods. We used our gas-grain astrochemical model GRAINOBLE,
which considers the multilayer formation of interstellar ices. We varied
several input parameters to study their impact on water deuteration. We
included the treatment of ortho- and para-states of key species, including H2,
which affects the deuterium fractionation of all molecules. The model also
includes relevant laboratory and theoretical works on the water formation and
deuteration on grain surfaces. In particular, we computed the transmission
probabilities of surface reactions using the Eckart model, and we considered
ice photodissociation following molecular dynamics simulations. Results. The
use of a multilayer approach allowed us to study the influence of various
parameters on the abundance and the deuteration of water. Deuteration of water
is found to be very sensitive to the ortho-to-para ratio of H2 and to the total
density, but it also depends on the gas/grain temperatures and the visual
extinction of the cloud. Since the deuteration is very sensitive to the
physical conditions, the comparison with sub-millimetric observation towards
the low-mass protostar IRAS 16293 allows us to suggest that water ice is formed
together with CO2 in molecular clouds with limited density, whilst formaldehyde
and methanol are mainly formed in a later phase, where the condensation becomes
denser and colder.Comment: Accepted for publication to A&A. 24 pages, 10 figure
A quoi servent les expertises «RPS» » auprÚs des CHSCT ? 1: Document de travail LEST
Le droit des CHSCT de faire appel Ă un expert dans le domaine de lâanalyse des conditions de travail sâest dĂ©veloppĂ© rĂ©cemment, passant de 500 Ă 1500 par an de 2008 Ă 2014, pour environ 25 000 CHSC, mais ses usages et ses effets sont mĂ©connus. On s'appuie sur trois cas dâĂ©tudes, tirĂ©s pour une part dâune enquĂȘte rĂ©alisĂ©e Ă la demande dâun grand cabinet agrĂ©Ă© et dâun retour sur expĂ©rience sur lâune des nombreuses missions dâexpertise assumĂ©es par lâun des coauteurs de l' article. Les terrains dâenquĂȘte sont contrastĂ©s du point de vue de la configuration des rapports de force entre directions et syndicats et de la maniĂšre dont les acteurs sâemparent du rapport remis par les consultants. Dans la premiĂšre, la rĂ©appropriation de lâexpertise est des plus limitĂ©e et ne permet pas de dĂ©nouer une situation de blocage entre RP et direction : cette derniĂšre ignore les prĂ©conisations du rapport, que les reprĂ©sentants du personnel rĂ©investissent eux-mĂȘmes trĂšs peu. Dans la seconde, lâexpertise conduit les directions Ă reprendre en compte une partie des prĂ©conisations. En dĂ©pit des limites des actions entreprises par la direction, on observe que la rĂ©alisation de lâexpertise contribue Ă une dynamisation de lâaction syndicale sur les questions du travail. La mise en perspective des diffĂ©rentes missions dâexpertise Ă©tudiĂ©es aide Ă repĂ©rer la diversitĂ© des usages syndicaux et managĂ©riaux qui en sont faits, ainsi que la pluralitĂ© des facteurs qui en contraignent les effets sur les modes dâorganisation du travail
Perturbative QCD and Tau Decay
Sufficiently inclusive observables in the decay of the tau lepton can be
calculated using the methods of perturbative QCD. These include the asymmetry
parameter that determines that angular distribution of the total
hadron momentum in the decay of a polarized tau. It should be possible to
measure accurately using existing data from LEP. Reliable estimates of
theoretical errors are essential in order to determine whether a given
observable is sufficiently inclusive to be calculated using perturbative
methods. The theoretical uncertainties due to higher orders in can
be estimated using recent calculations to all orders in the large-
limit. These estimates indicate that tau decay data can be used to determine
to a precision of 2% or better.Comment: 9 pages, LaTeX with espcrc2.sty, invited talk presented at the TAU 96
Workshop, Estes Park, Colorado, in September 199
PrĂ©diction des services Ă©cosystĂ©miques dans les bois agricoles Ă partir dâimages hyperspectrales
Les services Ă©cosystĂ©miques sont devenus un enjeu social, Ă©cologique et Ă©conomique majeur dans le monde. Les forĂȘts des paysages agricoles offrent des services prĂ©cieux bien qu'ils soient souvent sous-estimĂ©s et mal utilisĂ©s. Cependant, une cartographie prĂ©cise de ces services Ă grande Ă©chelle reste difficile. Des donnĂ©es de tĂ©lĂ©dĂ©tection permettent aujourdâhui dâenvisager cette cartographie. Nous avons Ă©valuĂ© la contribution des indices de vĂ©gĂ©tation calculĂ©s Ă partir d'images hyperspectrales Ă haute rĂ©solution spatiale pour la prĂ©vision de services Ă©cosystĂ©miques par rapport aux rĂ©sultats fondĂ©es sur la couverture terrestre. 28 parcelles forestiĂšres ont Ă©tĂ© Ă©chantillonnĂ©es et des images hyperspectrales aĂ©roportĂ©es ont Ă©tĂ© acquises pour la zone d'Ă©tude, Ă une rĂ©solution de 2 m. Habituellement, les indices de vĂ©gĂ©tation dĂ©rivĂ©s de l'hyperspectral Ă lâĂ©chelle du paysage (buffer spatial autour de lâobjet considĂ©rĂ©) sont rĂ©duits en utilisant des statistiques descriptives (moyenne, Ă©cart-type, valeurs minimales et maximales). Cependant, cette approche peut perdre beaucoup d'informations, en particulier Ă l'Ă©chelle des paysages, oĂč plusieurs objets avec diffĂ©rentes signatures spectrales sont prĂ©sents. Nous proposons une description du paysage hyperspectral basĂ©e sur la rĂ©partition complĂšte des indices de vĂ©gĂ©tation Ă travers les paysages. Nous avons utilisĂ© les modĂšles de mĂ©lange gaussien (GMM) pour modĂ©liser la distribution des pixels dans chaque paysage et introduit une distance L2 entre ces mĂ©langes. Cette distance est utilisĂ©e dans lâalgorithme des plus proches voisins pour prĂ©dire les niveaux de services. La qualitĂ© des prĂ©dictions a Ă©tĂ© comparĂ©e entre trois reprĂ©sentations de paysage: occupation des sols, statistiques descriptives de donnĂ©es hyperspectrales et description de donnĂ©es hyperspectrales basĂ©es sur GMM
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