Direct radiative effect of the Russian wildfires and its impact on air temperature and atmospheric dynamics during August 2010

International audienceIn this study, we investigate the shortwave aerosol direct radiative forcing (ADRF) and its feedback on air temperature and atmospheric dynamics during a major fire event that occurred in Russia during August 2010. The methodology is based on an offline coupling between the CHIMERE chemistry-transport and the Weather Research and Forecasting (WRF) models. First, simulations for the period 5–12 August 2010 have been evaluated by using AERONET (AErosol RObotic NETwork) and satellite measurements of the POLarization and Directionality of the Earth's Reflectance (POLDER) and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) sensors. During this period, elevated POLDER aerosol optical thickness (AOT) is found over a large part of eastern Europe, with values above 2 (at 550 nm) in the aerosol plume. According to CALIOP observations, particles remain confined to the first five kilometres of the atmospheric layer. Comparisons with satellite measurements show the ability of CHIMERE to reproduce the regional and vertical distribution of aerosols during their transport from the source region. Over Moscow, AERONET measurements indicate an important increase of AOT (340 nm) from 0.7 on 5 August to 2–4 between 6 and 10 August when the aerosol plume was advected over the city. Particles are mainly observed in the fine size mode (radius in the range 0.2–0.4 μm) and are characterized by elevated single-scattering albedo (SSA) (0.95–0.96 between 440 and 1020 nm). Comparisons of simulations with AERONET measurements show that aerosol physical–optical properties (size distribution, AOT, SSA) have been well simulated over Moscow in terms of intensity and/or spectral dependence. Secondly, modelled aerosol optical properties have been used as input in the radiative transfer code of WRF to evaluate their direct radiative impact. Simulations indicate a significant reduction of solar radiation at the ground (up to 80–150 W m−2 in diurnal averages over a large part of eastern Europe due to the presence of the aerosol plume. This ADRF causes an important reduction of the near-surface air temperature between 0.2 and 2.6° on a regional scale. Moscow has been affected by the aerosol plume, especially between 6 and 10 August. During this period, aerosol causes a significant reduction of surface shortwave radiation (up to 70–84 W m−2 in diurnal averages) with a moderate part (20–30%) due to solar absorption within the aerosol layer. The resulting feedbacks lead to a cooling of the air up to 1.6° at the surface and 0.1° at an altitude of 1500–2000 m (in diurnal averages), that contribute to stabilize the atmospheric boundary layer (ABL). Indeed, a reduction of the ABL height of 13 to 65% has been simulated during daytime in presence of aerosols. This decrease is the result of a lower air entrainment as the vertical wind speed in the ABL is shown to be reduced by 5 to 80% (at midday) when the feedback of the ADRF is taken into account. However, the ADRF is shown to have a lower impact on the horizontal wind speed, suggesting that the dilution of particles would be mainly affected by the weakening of the ABL development and associated vertical entrainment. Indeed, CHIMERE simulations driven by the WRF meteorological fields including this ADRF feedback result in a large increase in the modelled near-surface PM10 concentrations (up to 99%). This is due to their lower vertical dilution in the ABL, which tend to reduce model biases with the ground PM10 values observed over Moscow during this specific period

Helicobacter pullorum cytolethal distending toxin targets vinculin and cortactin and triggers formation of lamellipodia in intestinal epithelial cells

Helicobacter pullorum, a bacterium initially isolated from poultry, has been associated with human digestive disorders. However, the factor responsible for its cytopathogenic effects on epithelial cells has not been formally identified. The cytopathogenic alterations induced by several human and avian H. pullorum strains were investigated on human intestinal epithelial cell lines. Moreover, the effects of the cytolethal distending toxin (CDT) were evaluated first by using a wild-type strain and its corresponding cdtB isogenic mutant and second by delivering the active CdtB subunit of the CDT directly into the cells. All of the H. pullorum strains induced cellular distending phenotype, actin cytoskeleton remodeling, and G2/M cell cycle arrest. These effects were dependent on the CDT, as they were (1) not observed in response to a cdtB isogenic mutant strain and (2) present in cells expressing CdtB. CdtB also induced an atypical delocalization of vinculin from focal adhesions to the perinuclear region, formation of cortical actin-rich large lamellipodia with an upregulation of cortactin, and decreased cellular adherence. In conclusion, the CDT of H. pullorum is responsible for major cytopathogenic effects in vitro, confirming its role as a main virulence factor of this emerging human pathogen.This work was supported by the Institut national de la santé et de la recherche médicale, the University Bordeaux Segalen, the Conseil Régional d’Aquitaine (grants 20030304002FA and 20040305003 FA), the Société Nationale Française de Gastroentérologie, the European Union (FEDER no. 2003227

Quoi de neuf sur la guerre ?

National audienc

Alleanze e parentele Le “affinità elettive” nella storiografia sulla Sicilia antica. Atti del Convegno internazionale Palermo 14-15 aprile 2010

Nel 1966, parlando della Sicilia, Fernand Braudel la definiva un “continente in miniatura”, assegnandole già quelle caratteristiche di microcosmo che ne hanno fatto, nel corso dei secoli, un laboratorio privilegiato d’indagine sulle dinamiche d’interazione tra le civiltà antiche. Per la sua posizione, centrale e facilmente accessibile dal mare, per le sue dimensioni, per la fertilità del suo territorio, l’isola diventò presto crocevia di uomini, terreno d’incontro e di scontro tra città ma anche tra ethne di origine diversa. Se, da un lato è vero che le vicende della Sicilia possono leggersi attraverso i momenti di conflitto e di cesura che, di volta in volta, la attraversarono; dall’altro, altrettanto paradigmatici sono quei fenomeni di convergenza e di “associazione” che ne segnarono la storia. La chiave delle alleanze e delle parentele costituisce dunque una lente, come un’altra, attraverso cui rileggere la storiografia antica e moderna sull’isola: il modo in cui forme di aggregazioni reali o fittizie si autorappresentarono o vennero rappresentate dagli storici antichi e dalle riletture dei moderni

Effects of difficulties experienced on self-efficacy and attributions in a study task with tablet

International audienc

Kinship diplomacy between Sicily and Rome

"The phenomenon of kinship diplomacy, if not perfectly defined, is nonetheless widely understood and extensively studied. The presence of kinship diplomacy in the political interactions between Rome and other Mediterranean states has in turn received specific treatment. At the same time, the extent of kinship claims in the island of Sicily and the associated claims about origines made by many of the communities on the island have also been studied in very considerable detail. In other words, this paper does not intend to cover new ground – indeed, the individual case studies upon which I shall focus have themselves been the objects of considerable attention. However, it is fair to state that the several instances of kinship diplomacy which can be documented between Sicilian communities and Rome have so far not been considered as an ensemble (although individually often considered in relation to one or more of the other instances). In itself, that would not necessarily be sufficient reason to justify a fresh study. The further argument that the Sicilian cases deserve to be better known, not least because they present a number of unusual features, could likewise be dismissed as special pleading. A more serious argument however remains, and this is that consideration of the Sicilian cases in their own right, and as a group, strongly suggests a more diverse and earlier use of the phenomenon of kinship diplomacy, in relation to Rome, than is commonly accepted." (From the Introduction

Influence of the aerosol solar extinction on photochemistry during the 2010 Russian wildfires episode

In this work, impact of aerosol solar extinction on the photochemistry over eastern Europe during the 2010 wildfires episode is discussed for the period from 5 to 12 August 2010, which coincides to the peak of fire activity. The methodology is based on an online coupling between the chemistry-transport model CHIMERE (extended by an aerosol optical module) and the radiative transfer code TUV. Results of simulations indicate an important influence of the aerosol solar extinction, in terms of intensity and spatial extent, with a reduction of the photolysis rates of NO₂ and O₃ up to 50 % (in daytime average) along the aerosol plume transport. At a regional scale, these changes in photolysis rates lead to a 3–15 % increase in the NO₂ daytime concentration and to an ozone reduction near the surface of 1–12 %. The ozone reduction is shown to occur over the entire boundary layer, where aerosols are located. Also, the total aerosol mass concentration (PM₁₀) is shown to be decreased by 1–2 %, on average during the studied period, caused by a reduced formation of secondary aerosols such as sulfates and secondary organics (4–10 %) when aerosol impact on photolysis rates is included. In terms of model performance, comparisons of simulations with air quality measurements at Moscow indicate that an explicit representation of aerosols interaction with photolysis rates tend to improve the estimation of the near-surface concentration of ozone and nitrogen dioxide as well as the formation of inorganic aerosol species such as ammonium, nitrates and sulfates