Temporal verification in secure group communication system design

The paper discusses an experience in using a real-time UML/SysML profile and a formal verification toolkit to check a secure group communication system against temporal requirements. A generic framework is proposed and specialized for hierarchical groups

Impact de la variation du niveau d'eau d'un marais du lac Saint-Pierre (Québec, Canada) sur les concentrations et les flux d'hydrogène, monoxyde de carbone, méthane et dioxyde de carbone

Le but de la présente étude était d'étudier l'impact de la variation des niveaux d'eau d'un marais d'eau douce (Baie Saint-François, Québec) sur l'évolution des concentrations et des flux d'hydrogène, monoxyde de carbone, méthane et dioxyde de carbone. Une approche originale impliquant l'association d'un gradient de concentration de ces composés sur un profil vertical de 1,5 m au transfert de flux turbulent micrométéorologique fut utilisée pour la détermination des flux. L'étude démontre qu'une hausse du niveau d'eau d'un bassin versant alimentant une zone humide influence les flux de méthane, de monoxyde de carbone d'hydrogène et de dioxyde de carbone. En conditions submergées, le marais émettait du méthane et du monoxyde de carbone et consommait moins d'hydrogène troposphérique. Ainsi, cette étude démontre que des mesures in situ peuvent servir à inférer des scénarios d'impacts possibles des changements climatiques et des variations des niveaux d'eau sur les émissions des gaz à effets de serre dans l'écosystème du fleuve Saint-Laurent.Wetlands are known for their great biodiversity and the important carbon reservoir that they represent. Moreover, in the global warming context, these ecosystems represent net sources or sinks for different greenhouse gases depending of their conditions. For instance, flooded conditions favour methane production whereas they prevent hydrogen and carbon monoxide soil consumption. Baie Saint-François is a freshwater wetland that opens onto Lake Saint-Pierre (St. Lawrence River) where water levels are subject to important fluctuations due to natural processes and human activities (hydroelectricity and navigation). This study was done in order to assess the impact of the Lake Saint-Pierre water level variations on the tropospheric methane, carbon monoxide, hydrogen and carbon dioxide dynamics over the wetland. Knowledge of these dynamics should provide indications about the possible effects of the decreasing or increasing water level associated with the global warming on the production or consumption of these trace gases.Studies were carried out between June and August 2003 in Baie Saint-François where soil was subjected to successions of flooded and dry conditions. Water and carbon dioxide fluxes were obtained with a Bowen ratio micrometeorological station including a high frequency single infrared gas analyser. Hydrogen, carbon monoxide and methane fluxes were estimated with the modified Bowen method, their vertical concentration gradients (1.5 m) were measured over the plant canopy. The Bowen Ratio station was equipped with different probes to measure parameters such as net radiations, soil heat fluxes and vertical temperature gradients. The turbulent transfer coefficient (k) obtained every 20 min was assumed equal for heat, water vapour and trace gases. Hence, fluxes calculations were done by the multiplication of the turbulent transfer coefficients with the vertical concentration gradients of hydrogen, carbon monoxide and methane.The instrument used to detect hydrogen, carbon monoxide and methane was a RGA5. This analyser has two detectors: the reductive gas detector (RGD) for hydrogen and carbon monoxide and a flame ionisation detector (FID) for methane. The RGD contains an HgO bed wherein oxygen reacts with reductive gases resulting in Hg° releases detectable by differential UV absorbance. Chemicals were detected continuously in 10 min cycles with an analytical reproducibility of ±0.2, 0.3 and 2% for hydrogen, carbon monoxide and methane. Generally, vertical concentration gradients measured were greater than these limits. A calibration gas containing hydrogen, carbon monoxide and methane at 4940, 1000 and 1000 ppbv respectively in nitrogen was analysed daily to verify calibration. To ensure data integrity, linearity of the instrument was assayed by several dilutions of the standard gas and the integration of the curves gave a correction factor for hydrogen (18%) and carbon monoxide (13%). An intercomparison with NOAA (National Oceanic and Atmospheric Administration) was done to corroborate these correction factors.Background carbon monoxide, methane and carbon dioxide levels were in agreement with literature values. However, hydrogen was low, as observed by other investigators in summertime, since this season is related to minimal concentrations. Methane followed a diurnal cycle where maximum levels were observed during nighttime. In wet conditions, these nocturnal peaks reached occasionally 4000 ppbv and could be explained by specific production mechanisms and diurnal changes of vertical mixing in the boundary layer. Sensitivity of the processes responsible for methane and carbon monoxide cycling was seen between July 21st and 26th where a rain episode (total precipitation of 33.2 mm) increased their background concentrations. It seems that this precipitation was enough to favour methanogenesis and inhibit tropospheric CO and CH4 consumptions by a reduction of the diffusion of these chemicals into the soil.Our results demonstrated that four to eleven days following a variation of the Lake Saint-Pierre water level, a change in the tropospheric hydrogen, carbon monoxide and methane concentrations was observed. This lag might be explained by the distance between the lake and the research station (about 1.5 km) and the required time for the adaptation of soil microorganisms to the disruption of their environment. The concentration variations of these chemicals resulted from the inhibition of the processes responsible for their consumption or the activation of the processes accountable for their production.In June, the wetland was flooded and the CO2 median flux was -56.5 g m-2 d-1. Fluxes increased significantly (Mann-Whitney, α=0.01) in July to 5.30 g m-2 d-1, possibly due to dry conditions. Indeed, absence of water favours the activity of soil aerobic microorganisms which might produce more carbon dioxide than the quantity used by plants during photosynthesis.Methane was produced in June where the median flux was 54 mg m-2 d-1. These emissions were caused by the presence of water which maintained anaerobic conditions in the sediments, a suitable environment for methanogenic microorganisms. July was characterised by dry conditions, which generated aerobic environments in soils, an unfavourable microniche for methanogens. Therefore, methane median fluxes decreased significantly (Mann-Whitney, α=0.05) to 0.011 mg m-2 d-1 in July. In August, before the end of the investigation period, water levels had increased but methane fluxes were not significantly higher than in July. Moreover, in this period, methane concentrations tended to increase, showing that after an augmentation of the Lake Saint-Pierre water level, Baie Saint-François flooding area could represent a methane source.During summer 2003, Baie Saint-François acted as a net source of carbon monoxide. In June, the median flux was 21 µg m-2 d-1 due to presence of water which inhibited consumption by soil. Emissions were significantly (Mann-Whitney, α=0.05) lower in July (15 µg m-2 d-1) due to the absence of water, which represented a suitable environment for microorganisms consuming tropospheric carbon monoxide. In August, the median carbon monoxide flux attained 65 µg m-2 d-1 due to an increase of the Lake Saint-Pierre water level. Net carbon monoxide emissions observed in wet and dry conditions might be due to the high organic content in soil and water in addition to the presence of plants since all of these are subjected to photooxidation, generating this pollutant. Therefore, an increase of the Lake Saint-Pierre water level is associated with an augmentation of tropospheric carbon monoxide due to the inhibition of the processes responsible of its consumption.A decline in the water level might result in the activation of the soil microorganisms (or abiotic hydrogenases) able to consume tropospheric hydrogen. At the beginning of the campaign (June), the median hydrogen flux was weak (-1.37 g m-2 d-1) due to the presence of water. However, a net soil consumption was seen in July, where the median hydrogen flux decreased to -125 g m-2 d-1. The Lake Saint-Pierre water level increase observed in August was associated with a significant (Mann-Whitney, α=0.05) augmentation of the hydrogen median flux to 299 g m-2 d-1. Consequently, a rise in the Lake Saint-Pierre water levels induced an inhibition of the processes responsible of the tropospheric hydrogen consumption.This study illustrated that the water level fluctuations of the Lake Saint-Pierre have an impact on the H2, CO, CH4 and CO2 dynamics over the surrounding wetlands. When the Lake Saint-Pierre water level decreased, the wetlands acted as a carbon monoxide and carbon dioxide source, but as a consumer of tropospheric hydrogen and a minor source of methane

Importance of the Two Dissimilatory (Nar) Nitrate Reductases in the Growth and Nitrate Reduction of the Methylotrophic Marine Bacterium Methylophaga nitratireducenticrescens JAM1

Methylophaga nitratireducenticrescens JAM1 is the only reported Methylophaga species capable of growing under anaerobic conditions with nitrate as electron acceptor. Its genome encodes a truncated denitrification pathway, which includes two nitrate reductases, Nar1 and Nar2; two nitric oxide reductases, Nor1 and Nor2; and one nitrous oxide reductase, Nos; but no nitrite reductase (NirK or NirS). The transcriptome of strain JAM1 cultivated with nitrate and methanol under anaerobic conditions showed the genes for these enzymes were all expressed. We investigated the importance of Nar1 and Nar2 by knocking out narG1, narG2 or both genes. Measurement of the specific growth rate and the specific nitrate reduction rate of the knockout mutants JAM1ΔnarG1 (Nar1) and JAM1ΔnarG2 (Nar2) clearly demonstrated that both Nar systems contributed to the growth of strain JAM1 under anaerobic conditions, but at different levels. The JAM1ΔnarG1 mutant exhibited an important decrease in the nitrate reduction rate that consequently impaired its growth under anaerobic conditions. In JAM1ΔnarG2, the mutation induced a 20-h lag period before nitrate reduction occurred at specific rate similar to that of strain JAM1. The disruption of narG1 did not affect the expression of narG2. However, the expression of the Nar1 system was highly downregulated in the presence of oxygen with the JAM1ΔnarG2 mutant. These results indicated Nar1 is the major nitrate reductase in strain JAM1 but Nar2 appears to regulate the expression of Nar1

Le Trait de Nacera Belaza

Le Trait – ainsi qu’une ligne dessine un trajet, livre un desse(i)n jeté telle une adresse à l’espace, le geste chorégraphique de Nacera Belaza, précis et tenace, tenu à sa violence sans jamais la défaire, affirme avec insistance comme un retrait – un retrait qui repousse tout horizon pour venir creuser en soi un vide qui élargit les marges au cœur de la nuit. Et qui donne cette expansion si singulière à l’espace alors que le spectateur apprivoise le silence au début du spectacle, et que lent..

Érotique du couple lesbien à l'époque moderne : Diane et ses nymphes

En amont de l’invention de l’homosexualité féminine, la recherche porte sur la visibilité d’un éros lesbien dans l’art de l’époque moderne, autour de la figure du couple, dans les représentations des Métamorphoses d’Ovide liées aux récits de Diane et Actéon et de Diane et Callisto. Le regard critique se porte moins sur la métamorphose elle-même comme mutation des genres, que sur des figures de bord, qui mettent en jeu dans le dispositif visuel des couples de nymphes autour de Diane au bain. L’érotique lesbienne associée à une gestuelle de l’intimité interroge les affects à l’origine des œuvres, un certain désir de voir véhiculé par l’imaginaire patriarcal, comme elle questionne la place du regardeur contemporain : qu’est-ce que regarder selon son genre et sa sexualité ?Upstream the invention of female homosexuality, research focuses on the visibility of a lesbian éros in modern art, around the figure of the couple, in the representations of Ovid's Metamorphoses linked to the stories of Diana and Actaeon and of Diana and Callisto. The critical gaze is less on the metamorphosis itself as mutation of genders, than on edge figures, which bring into play in the visual device couples of nymphs around Diana at the bath. Lesbian erotica associated with gesture of intimacy questions the affects at the origin of the works, a certain desire to see conveyed by the patriarchal imagination, as it questions the place of the contemporary viewer: how to gaze according to its gender and sexuality

Christian Rizzo : Le bénéfice du doute

Il y a un tournant dans la création de Christian Rizzo, que sa dernière production au Festival d’Avignon (D’après une histoire vraie, 2013) est venue confirmer, tournant qui s’est trouvé avec Le bénéfice du doute (2012), après Mon amour (2008) et L’oubli, toucher du bois (2010). Nous revenons sur cette pièce créée à l’Opéra de Lille, où l’association fragile de Christian Rizzo a été en résidence de septembre 2007 à juin 2012, manière de clore un cycle dont on voit qu’il s’ouvre aujourd’hui à ..

Cornelia Butler, Wack ! Art and the Feminist Revolution, Los Angeles, Museum of Contemporary Art, 2007, 512 pages. Maura Reilly, Linda Nochlin, Global Feminisms:New Directions inContemporary Art, New York, Merrell, 2007, 304 pages.

Deux ouvrages croisent la création des femmes artistes et les luttes féministes, liés à deux expositions à Los Angeles et à New York. Le premier dresse pour les années 1960 et 1970 un bilan rétrospectif des rapports entre la création des femmes et les mouvements féministes aux États-Unis et en Europe occidentale, le second partant des années 1990 jusqu’à aujourd’hui se veut tourné vers l’avenir et ouvert aux autres cultures. Wack ! Art and the Feminist Revolution : le titre exclamatif entend ..

Catherine Gonnard, Élisabeth Lebovici, Femmes/artistes, artistes femmes. Paris, de 1880 à nos jours

En limitant leur sujet au Paris de la fin du XIXe siècle au début du XXIe siècle, Catherine Gonnard et Élisabeth Lebovici montrent non seulement que le XXe siècle est le siècle où les femmes prennent place dans l’histoire de l’art, mais que l’histoire de leur visibilité ne suit pas le découpage des courants artistiques conçus par l’histoire de l’art. On pourrait regretter que le cadre géographique ne soit pas plus élargi dans la deuxième moitié du siècle, alors que New York l’emporte sur Pari..

Soapéra de Mathilde Monnier et Dominique Figarella

Au commencement, il y aurait un fluide universel, non un déluge, mais cette mousse aérienne, envahissante, par où prendre corps et forme. Au début, il y aurait donc une scène déjà occupée – mais sans danseurs. Et nous spectateurs, en train d’avancer, nous verrions se déverser cette grande coulée blanche d’en-haut qui nappe la scène jusqu’à son bord pour s’arrêter presque à nos pieds. Seule la mousse, compacte et vibratile, emplirait l’obscurité de la scène. À partir de cette blancheur incondi..

Odile foucaud, La côte d’Ève, une histoire des femmes artistes, 1970-2006

Odile Foucaud analyse la présence des femmes artistes sur la scène new-yorkaise depuis la fin des années 1960. Quelle place occupent-elles dans les circuits institutionnels et commerciaux, dans les expositions et les musées ? Quel fut leur rôle dans le renouvellement de la création plastique ? L’auteur, qui enseigne l’histoire de l’art contemporain, a recueilli le témoignage d’artistes de toutes nationalités qui ont une visibilité institutionnelle, en comparant les générations. Ainsi, Martha ..