Fishermen's Knowledge in the Academic Salon - How Jean-André Peyssonnel's Studies of "Marine Products" at the Coasts of Barbary and Guadeloupe Influenced Debates on the True Nature of Coral in Eighteenth-Century Europe

Conference (2012, November 01)

Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation

in Nature (2012), 491

Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris ... [more ▼]

Pluto and Eris are icy dwarf planets with nearly identical sizes, comparable densities and similar surface compositions as revealed by spectroscopic studies. Pluto possesses an atmosphere whereas Eris does not; the difference probably arises from their differing distances from the Sun, and explains their different albedos. Makemake is another icy dwarf planet with a spectrum similar to Eris and Pluto, and is currently at a distance to the Sun intermediate between the two. Although Makemake's size (1,420+/-60km) and albedo are roughly known, there has been no constraint on its density and there were expectations that it could have a Pluto-like atmosphere. Here we report the results from a stellar occultation by Makemake on 2011 April 23. Our preferred solution that fits the occultation chords corresponds to a body with projected axes of 1,430+/-9km (1σ) and 1,502+/-45km, implying a V-band geometric albedo p[SUB]V[/SUB] = 0.77+/-0.03. This albedo is larger than that of Pluto, but smaller than that of Eris. The disappearances and reappearances of the star were abrupt, showing that Makemake has no global Pluto-like atmosphere at an upper limit of 4-12nanobar (1σ) for the surface pressure, although a localized atmosphere is possible. A density of 1.7+/-0.3gcm[SUP]-3[/SUP] is inferred from the data. [less ▲]

Qualification d’un appareil d'éclairage décoratif soumis aux vibrations induites par un pont ferroviaire

Scientific conference (2012, November)

Au même titre que la plupart des pièces mécaniques soumises aux vibrations, les appareils d'éclairage installés en extérieur sont amenés à satisfaire, en fonction de leurs conditions d’utilisation, aux ... [more ▼]

Au même titre que la plupart des pièces mécaniques soumises aux vibrations, les appareils d'éclairage installés en extérieur sont amenés à satisfaire, en fonction de leurs conditions d’utilisation, aux exigences de procédures d'essais appliquées sur table vibrante. Celles-ci ont pour but de garantir l'intégrité structurelle du luminaire lorsque, une fois sur site, il est soumis aux effets du vent. Dans le cas des appareils d'éclairage décoratifs installés sur un pont de chemin de fer de structure métallique, le vent n'étant plus la source principale de vibrations en comparaison du trafic ferroviaire, on est dès lors confronté à une absence de toute indication appropriée décrivant l'essai à mener. Par conséquent, l'objectif de cette étude est d'élaborer une spécification d'essai de durée réduite, appliquée en laboratoire sur table vibrante, et représentative de l'environnement vibratoire réel de l'appareil à certifier. Sur base des essais réalisés en laboratoire, des prescriptions de montage et d'installation sont également formulées afin de garantir des conditions d’utilisation et d’essai identiques. [less ▲]

Constant 2-labelling of weighted cycles

Conference (2012, November)

We introduce the concept of constant 2-labelling of a weighted graph and show how it can be used to obtain periodic sphere packing. Roughly speaking, a constant 2-labelling of a weighted graph is a 2 ... [more ▼]

We introduce the concept of constant 2-labelling of a weighted graph and show how it can be used to obtain periodic sphere packing. Roughly speaking, a constant 2-labelling of a weighted graph is a 2-coloring (black and white) of its vertex set which preserves the sum of the weight of black vertices under some automorphisms. In this manuscript, we study this problem on weighted complete graphs and on weighted cycles. Our results on cycles allow us to determine (r,a,b)-codes in Z^2 whenever |a-b|>4 and r>1. [less ▲]

Détection d'endommagement et résonances locales sur composite CFRP par vibrothermographie

Scientific conference (2012, November)

La vibrothermographie est une technique de thermographie active capable de détecter des singularités de type délaminage ou décollement dans un matériau composite comme les laminés en fibres de carbone ... [more ▼]

La vibrothermographie est une technique de thermographie active capable de détecter des singularités de type délaminage ou décollement dans un matériau composite comme les laminés en fibres de carbone très utilisés actuellement en construction aéronautique (CFRP). Les causes physiques du mécanisme d'échauffement interne, suite à l'interaction avec les ondes élastiques, peuvent être la friction, l'hystérésis viscoélastique ou encore la déformation plastique. La méthode est efficace également sur des géométries complexes et requiert uniquement que les deux faces internes du délaminage soient libres de vibrer. Cette étude consiste à déterminer la relation entre l'échauffement observé et la fréquence d'une excitation sinusoïdale entre 8 et 27 kHz. Il apparaît clairement des pics d'échauffement pour certaines fréquences particulières. La comparaison avec les fréquences de résonance locale du défaut modélisé par éléments finis montre des similitudes avec l'apparition de certains de ces pics. Une étude expérimentale visant à exploiter la présence de ceux-ci montre l'intérêt d'un test vibrothermographique de type balayage rapide (chirp), dans l'optique de mettre sur pied un test court et fiable pour le contrôle non destructif de matériaux composites. [less ▲]

European Initiative for the Exchange of Young Officers inspired by Erasmus

in Weisserth, Hans-Bernhard; Rehrl, Jochen (Eds.) CSDP Handbook - The Common Security and Defence Policy of the European Union (2012)

Economic impact of RVF outbreaks

Conference (2012, November)

Dwarfing the direct losses due to ruminant abortions and flock mortality, the main economic impact of RVF is systemic and ensues from the trade restrictions aimed at its containment. Indeed, past ... [more ▼]

Dwarfing the direct losses due to ruminant abortions and flock mortality, the main economic impact of RVF is systemic and ensues from the trade restrictions aimed at its containment. Indeed, past outbreaks of RVF in East Africa and Middle East came as disturbing events in a commercial context of high specialization in trade of small ruminants and interdependence between East-African exporters and the Middle-Eastern importing countries. The two successive bans imposed by Middle-Eastern countries on livestock products coming from the Horn of Africa in 1998-1999 and 2000-2002 highlighted this interdependence. Both bans caused an abrupt stop in exportations from IGAD countries. Nevertheless, the impact of the outbreaks motivating these bans differed due to their unique timing with regard to the Muslim celebrations that trigger the main flow of livestock from the Horn of Africa to Mecca. Hence, in 2000, the worst impact was observed on pastoralist households because the ban was imposed in September, prior to the Haj festival, when the main seasonal export flow had not been realized yet. Regarding the 1997 outbreak, the ban was implemented only in February 1998, after the main trade flow had occurred. The impacts of the bans on Somalia were particularly severe, due to the high specialization of the concerned region in an export-oriented livestock sector, benefitting from a niche market organized around the above-mentioned religious festivals and Arab consumers preferences. The country was all the more affected, as they own two main ports involved in this trade, i.e. Berbera (Somaliland) and Bossaso (Puntland). Prior to the bans, the size of the export market from Somalia to Saudi Arabia and the United Arab Emirates was estimated around US$600 million, with Saudi Arabia representing 66% of the total. The bans led the Somali livestock market to collapse. Losses for the livestock industry were estimated at US$109 million and US$326 million, for the first and second ban respectively. The government also directly incurred an important loss around US$45 million from foregone export taxes and docking fees. In the same time, livestock exporters lost a net cumulative profit of US$330 million, whereas producers estimated their annual losses at over US$8 million. Hence, the successive RVF-related trade bans impacted the employment rate, the public treasury, the exchange rate of national currency and thus, the price of imported goods, inducing a general inflationary pressure and important socio-economic upheavals. More generally, the livestock market in the whole East Africa was affected, due to the fall in prices caused by the loss of outlets for livestock. Using market equilibrium models taking these shocks into account, the impact of the trade bans on the Somali region of Ethiopia were estimated at a 36% fall of the GDP. Other impacts originated in the closure of markets inside East Africa, being part of national control strategies. In Kenya, e.g., the closure of the Garissa Market, which is a major outlet for Somali and Ethiopian livestock, resulted in a more than 25% decrease in the price of cattle, inducing a total loss of US$10 million for the value chain. The emergency destocking response of distressed households also participated to the fall in prices and worsening of terms of trade. Together with flock mortality and abortion, destocking moreover affects the herds’ dynamics on the long run and the commercial potential of households. These mechanisms show greater impact on smallholders, due to threshold effects in livestock capitalisation and the loss in risk management ability in such variable environmental conditions. In the Middle East too, the bans showed drastic economic impacts. In Yemen, e.g., the bans caused a loss of US$15 million from foregone custom taxes and US$27 million profit losses for traders. The two bans, combined with the prolonged ban maintained till 2009 by Saudi Arabia on Somalia, contributed to a restructuration of trade within and between the two regions. Indeed, trade actors soon reorganized their activity, as highlighted through official figures, notwithstanding the importance of informal trade. Hence, Yemen and the United Arab Emirates appeared as major alternative entry points on Arab Peninsula for Somali livestock. The latter could also transit through Djibouti or Sudan to reach Saudi Arabia. Benefitting from the prolonged bans on Somalia, the port of Djibouti emerged as a major player in the region between 2006 and 2009, thanks to massive investment in port infrastructures and agreements with Saudi importers. Therefore the private sector played a considerable role in adapting to new risks. The Djibouti port diverted much of the livestock trade previously handled at the Berbera and Bossaso ports. On this occasion, as it has been the case in Somalia after ban lifting in 2009, the Middle East has been a source of investment for the Horn of Africa for biosecurity infrastructure. Finally, the second ban led to the emergence of Australia as a major livestock supplier for Saudi Arabia from 2000 till now, and to a certain a point Australia has been a country of major Saudi investments which is seen as another way of adapting for some major value chain agents. In the two last decades, the intraregional livestock trade grew rapidly in East Africa, spurred by the urban demand. Most of this trade is informal, thus lacking official figures. It nevertheless shows a great importance regarding poverty alleviation aspects, the small to medium actors being the main operators of this trade. In recent years, a considerable growth in recorded intraregional trade is noticed, mainly due to a growth of recorded exports from Ethiopia to neighboring countries, as a result of a policy aiming at the facilitation of registration procedures through the CAC/AP-system. As a conclusion, livestock export to Middle East and the growing intraregional East-African livestock trade are both threatened by RVF-linked bans due to loss of outlets and price volatility. Thus, stability of the livestock sector being crucial to human and economic development in the region, a high priority must be given to RVF prevention and control, as supported by figures of impact of past outbreaks. [less ▲]

The instability strip of ZZ Ceti white dwarfs and its extension to extremely low mass pulsators

Conference (2012, November)

Kinetic and crystallographic studies of extended-spectrum GES-11, GES-12, and GES-14 β-lactamases.

in Antimicrobial Agents and Chemotherapy (2012), 56(11)

GES-1 is a class A extended-spectrum β-lactamase conferring resistance to penicillins, narrow- and expanded-spectrum cephalosporins, and ceftazidime. However, GES-1 poorly hydrolyzes aztreonam and ... [more ▼]

GES-1 is a class A extended-spectrum β-lactamase conferring resistance to penicillins, narrow- and expanded-spectrum cephalosporins, and ceftazidime. However, GES-1 poorly hydrolyzes aztreonam and cephamycins and exhibits very low k(cat) values for carbapenems. Twenty-two GES variants have been discovered thus far, differing from each other by 1 to 3 amino acid substitutions that affect substrate specificity. GES-11 possesses a Gly243Ala substitution which seems to confer to this variant an increased activity against aztreonam and ceftazidime. GES-12 differs from GES-11 by a single Thr237Ala substitution, while GES-14 differs from GES-11 by the Gly170Ser mutation, which is known to confer increased carbapenemase activity. GES-11 and GES-12 were kinetically characterized and compared to GES-1 and GES-14. Purified GES-11 and GES-12 showed strong activities against most tested β-lactams, with the exception of temocillin, cefoxitin, and carbapenems. Both variants showed a significantly increased rate of hydrolysis of cefotaxime, ceftazidime, and aztreonam. On the other hand, GES-11 and GES-12 (and GES-14) variants all containing Ala243 exhibited increased susceptibility to classical inhibitors. The crystallographic structures of the GES-11 and GES-14 β-lactamases were solved. The overall structures of GES-11 and GES-14 are similar to that of GES-1. The Gly243Ala substitution caused only subtle local rearrangements, notably in the typical carbapenemase disulfide bond. The active sites of GES-14 and GES-11 are very similar, with the Gly170Ser substitution leading only to the formation of additional hydrogen bonds of the Ser residue with hydrolytic water and the Glu166 residue. [less ▲]

Thermal effect characterization in the excavation damaged zone around tunnels for the nuclear waste disposal in argillaceous rocks

Conference (2012, November)