The unusual persistence of an ozone hole over a southern mid-latitude station during the Antarctic spring 2009: a multi-instrument study

International audienceRecord-low ozone column densities (with a minimum of 212 DU) persisted over three weeks at the Río Gallegos NDACC (Network for the Detection of Atmospheric Composition Change) station (51.5° S, 69.3° W) in November 2009. Total ozone remained two standard deviations below the climatological mean for five consecutive days during this period. The statistical analysis of 30 years of satellite data from the Multi Sensor Reanalysis (MSR) database for Río Gallegos revealed that such a long-lasting low-ozone episode is a rare occurrence. The event is examined using height-resolved ozone lidar measurements at Río Gallegos, and observations from satellite and ground-based instruments. The computed relative difference between the measured total ozone and the climatological monthly mean shows reductions varying between 10 and 30% with an average decrease of 25%. The mean absolute difference of total ozone column with respect to climatological monthly mean ozone column is around 75 DU. Extreme values of the UV index (UVI) were measured at the ground for this period, with the daily maximum UVI of around 13 on 15 and 28 November. The high-resolution MIMOSA-CHIM (Modélisation Isentrope du transport Méso-échelle de l'Ozone Stratosphérique par Advection) model was used to interpret the ozone depletion event. An ozone decrease of about 2 ppmv was observed in mid-November at the 550 K isentropic level (~22 km). The position of Río Gallegos relative to the polar vortex was classified using equivalent latitude maps. During the second week of November, the vortex was over the station at all isentropic levels, but after 20 November and until the end of the month, only the 10 lower levels in the stratosphere were affected by vortex overpasses with ozone poor air masses. A rapid recovery of the ozone column density was observed later, due to an ozone rich filament moving over Río Gallegos between 18 and 24 km in the first two weeks of December 2009

Biópsia digital em equinos com lamite induzida por sobrecarga de carboidratos

O artigo não apresenta resumo

Dilatação dos confins: caminhos, vilas e cidades na formação da Capitania de São Paulo (1532-1822)

Este ensaio analisa a formação da rede urbana das capitanias de São Vicente e Santo Amaro, depois unidas na Capitania de São Paulo. Discute o processo de apropriação do sertão, a pulsação e dilatação dos confins ao sabor dos deslocamentos humanos e de interesses políticos. Interpreta o papel de capelas, freguesias, vilas e cidades no controle e produção de territórios metropolitanos em solos ultramarinos.This essay analyzes the development of urban networks in the Captaincies of São Vicente and Santo Amaro, later merged into the Captaincy of São Paulo. It discusses the process of appropriation of the sertão (backcountry), the commotion and expansion beyond the confines to the tune of population movements and political interests. The paper also interprets the role of chapels, parishes, villages and towns in initiatives to create and control metropolitan areas on overseas soil

Infinite-Duration Poorman-Bidding Games

In two-player games on graphs, the players move a token through a graph to produce an infinite path, which determines the winner or payoff of the game. Such games are central in formal verification since they model the interaction between a non-terminating system and its environment. We study bidding games in which the players bid for the right to move the token. Two bidding rules have been defined. In Richman bidding, in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Poorman bidding is similar except that the winner of the bidding pays the “bank” rather than the other player. While poorman reachability games have been studied before, we present, for the first time, results on infinite-duration poorman games. A central quantity in these games is the ratio between the two players’ initial budgets. The questions we study concern a necessary and sufficient ratio with which a player can achieve a goal. For reachability objectives, such threshold ratios are known to exist for both bidding rules. We show that the properties of poorman reachability games extend to complex qualitative objectives such as parity, similarly to the Richman case. Our most interesting results concern quantitative poorman games, namely poorman mean-payoff games, where we construct optimal strategies depending on the initial ratio, by showing a connection with random-turn based games. The connection in itself is interesting, because it does not hold for reachability poorman games. We also solve the complexity problems that arise in poorman bidding games

Biology of Streptococcus mutans-Derived Glucosyltransferases: Role in Extracellular Matrix Formation of Cariogenic Biofilms

The importance of Streptococcus mutans in the etiology and pathogenesis of dental caries is certainly controversial, in part because excessive attention is paid to the numbers of S. mutans and acid production while the matrix within dental plaque has been neglected. S. mutans does not always dominate within plaque; many organisms are equally acidogenic and aciduric. It is also recognized that glucosyltransferases from S. mutans (Gtfs) play critical roles in the development of virulent dental plaque. Gtfs adsorb to enamel synthesizing glucans in situ, providing sites for avid colonization by microorganisms and an insoluble matrix for plaque. Gtfs also adsorb to surfaces of other oral microorganisms converting them to glucan producers. S. mutans expresses 3 genetically distinct Gtfs; each appears to play a different but overlapping role in the formation of virulent plaque. GtfC is adsorbed to enamel within pellicle whereas GtfB binds avidly to bacteria promoting tight cell clustering, and enhancing cohesion of plaque. GtfD forms a soluble, readily metabolizable polysaccharide and acts as a primer for GtfB. The behavior of soluble Gtfs does not mirror that observed with surface-adsorbed enzymes. Furthermore, the structure of polysaccharide matrix changes over time as a result of the action of mutanases and dextranases within plaque. Gtfs at distinct loci offer chemotherapeutic targets to prevent caries. Nevertheless, agents that inhibit Gtfs in solution frequently have a reduced or no effect on adsorbed enzymes. Clearly, conformational changes and reactions of Gtfs on surfaces are complex and modulate the pathogenesis of dental caries in situ, deserving further investigation

Acidulated Phosphate Fluoride Application Changes The Protein Composition Of Human Acquired Enamel Pellicle.

We evaluated, by proteomic analysis, whether the chemical changes provoked on enamel by acidulated phosphate fluoride (APF) application alter the protein composition of acquired enamel pellicle. Enamel slabs, pretreated with distilled water (negative control), phosphoric acid (active control) or APF solution, were immersed in human saliva for pellicle formation. The adsorbed proteins were extracted and analyzed by liquid chromatography-mass spectrometry/mass spectrometry. Fifty-six proteins were identified, 12 exclusive to APF and 11 to phosphoric acid. APF decreased the concentration of histatin-1, but increased the concentration of S100-A9, which is confirmed by immunoblotting. The findings suggest that APF application changes the acquired enamel pellicle composition. Copyright © 2013 S. Karger AG, Basel.47325125