Search

Tomography is a standard and invaluable technique that covers a large range of length scales. It gives access to the inner morphology of specimens and to the three-dimensional (3D) distribution of physical quantities such as elemental composition, crystalline phases, oxidation state, or strain. These data are necessary to determine the effective properties of investigated heterogeneous media. However, each tomographic technique relies on severe sampling conditions and physical principles that require the sample to be adequately shaped. For that purpose, a wide range of sample preparation techniques is used, including mechanical machining, polishing, sawing, ion milling, or chemical techniques. Here, we focus on the basics of tomography that justify such advanced sample preparation, before reviewing and illustrating the main techniques. Performances and limits are highlighted, and we identify the best preparation technique for a particular tomographic scale and application. The targeted tomography techniques include hard X-ray micro- and nanotomography, electron nanotomography, and atom probe tomography. The article mainly focuses on hard condensed matter, including porous materials, alloys, and microelectronics applications, but also includes, to a lesser extent, biological considerations.

The Kaneshiro model proposes a role for sexual selection in peripatric speciation. During population bottlenecks, derived males lose attractive traits and become discriminated against by ancestral females, whereas derived females are selected to be less choosy. This permits novel mate choice cues to evolve in derived populations. In a quantitative analysis of laboratory experiments, we show that bottlenecked males have indeed become less attractive, but females have not lost their ancestral preferences. Contrary to the model, mating asymmetries were not limited to bottlenecks, but regularly occurred between derived and ancestral populations. The simplest explanation for the observed mating asymmetries is loss of genetic variation and inbreeding in the derived populations. The Kaneshiro process is unlikely to isolate small daughter populations from their ancestor but with slight modifications it may become a strong candidate for speciation in allopatry manifested as isolation between daughter populations in secondary contact.

We review published records of laboratory experiments on peripatric and vicariance allopatric speciation to address the following three questions: (1) What was the true effect size of reproductive isolation? (2) Was the reproductive isolation persistent? (3) What influenced the development of isolation? Contrary to popular belief, laboratory evidence for allopatric speciation is quite weak. Assortative mating was only found among derived populations in vicariance experiments. Reproductive isolation against control populations was only intermittent, so there is reason to doubt if some cases showing significant reproductive isolation really should be attributed to speciation. The method of testing was at least as important as the speciation model. Experimental populations tested against each other were the most likely to demonstrate reproductive isolation. This study suggests that allopatric speciation experiments are more likely to yield conclusive results under divergent selection than under drift, and points to the benefits of large populations and many generations.

In March 2006, a 360 km² no-take zone (NTZ) was established north of Gotland in the central Baltic Sea, with the purpose to scientifically evaluate the effects of a fishing ban on flatfish populations. A monitoring programme was set up to study the populations in the NTZ and in a reference area east of Gotland where the fishing pressure was high. The programme included fishing with multimesh survey nets, modelling of potential larval export and estimation of fish consumption by large marine predators. Overall, the results showed a clear positive effect of the NTZ on turbot Scophthalmus maximus, with higher densities in the closed area compared with the fished area and also higher densities after closure compared with before. The NTZ also had older individuals and a more even sex ratio. This, in combination with a high potential for larval export from the NTZ to Gotland, shows that the marine reserve may be important for maintaining a viable S. maximus stock at Gotland. Also, for flounder Platichthys flesus, the densities were higher in the NTZ compared to the reference area and there was a net larval export to the fished area. For both species, density-dependent growth was evident, with a lower length at age in the closed area. Potential predation by grey seal Halichoerus grypus and great cormorant Phalacrocorax carbo sinesis on flatfishes, that could hamper the evaluation of the marine reserve, was also addressed. Taken together, the results show that there are clear benefits of the fishing ban for both flatfish species within the NTZ, while the net effects on fisheries are difficult to quantify.

The development of long-term preservation methods of somatic embryos was investigated as a contribution to synthetic seed technology, Thus, cryopreservation in liquid nitrogen was attempted with somatic embryos of two species. Coffea canephora Pierre and Daucus carota L. Cryopreservation of carrot embryos simply required a 21-h sucrose pretreatment followed by a prefreezing step at -20°C. A freeze-hardening treatment consisting of embryo culture in the presence of high sucrose molarity and 1 μM ABA was developed for coffee embryos. Following desiccation at 75% relative humidity (RH) and +24°C for 7 d, embryos were frozen by rapid immersion in liquid nitrogen. Direct regrowth of frozen-thawed embryos was obtained for the majority of both carrot and coffee embryos. Even large carrot embryos were able to survive cryopreservation. The size of embryos and the age of the embryogenic strain from which the embryos originated determined their ability to develop into normal plantlets. Direct regrowth without any secondary callogenesis and/or embryogenesis is a prerequisite for practical use of preserved embryos either in a nursery or through direct planting.

The aim of this work is the analysis of a front end approach of optical interconnects on SOI wafers. Design and fabrication of elementary integrated optical devices used for optical clock signal distribution and experimental results will be discussed.

The paper presents the adopted concept in implementing the supervision, control, monitoring and protection functions for 110 kV and 20 kV substations. The article describes the structure of the existing SCADA system, the approach adopted in implementing new facilities, the main performances of RTUs and the main functions of the computer-based control and monitoring centre. The concept of open systems architecture adopted for the SCADA system inherently offers an increased control system availability and improved upgradeability. The authors also present the development and the main algorithms used to achieve a digital protection equipment for medium voltage (MV) power systems. The equipment includes protection functions, automation functions as well as metering functions for isolated neutral networks or earthing through a resistor or an arc suppression coil. An important task of the equipment is the capability to be integrated in SCADA systems.

ResumeLa duree du cycle et le coefficient de proliferation ont ete determines par differentes methodes de cinetique cellulaire dans les meristemes de la racine seminale de Vigna radiata cv Tai 1. L'analyse des relations entre la valeur absolue en ADN par noyau, les durees du cycle, de G1, S et M, a mis en evidence certaines caracteristiques communes a d'autres especes de Legumineuses.Les mesures des contenus en ADN des noyaux a chromocentres de Vigna radiata, standardisees par rapport a des erythrocytes de poulet ou des lymphocytes humains ont ete realisees par cytophotometrie apres reaction de Feulgen. La valeur absolue en ADN 2C a ete estimee a 1,23 ± 0,26 pg. La population cellulaire, distribuee en quatre classes, 2C, 2C-4C, 4C et 8C, est caracterisee par un mode principal de niveau 4C et par la presence de cellules a contenu en ADN superieur a 4C.

Copolymerization of ethylene and hexene has been carried out using Phillips' catalysts (chromium oxide deposited on silica) modified with small amounts of triethylaluminium [Al(C2H5)3], without solvent other than hexene itself and under constant ethylene pressure. The copolymers are highly disperse, not only in molecular weight but also in composition; the amount of hexene incorporated in the solid fraction is always less than 4%. Most of the hexene units are in a waxy fraction, which may account for a very high proportion of the copolymer produced. The behaviour of the catalyst is strongly dependent upon the amount of Al(C2H5)3 used.

Copolymers of ethylene with hexene-1 have been prepared by catalytic polymerization. Three types of specimens were studied: (a) as the polymerized material; (b) the same after extraction with heptane; (c) the low molecular weight extract. These specimens were subjected to one or more of the following characterization techniques: Mn by several methods, X-ray diffraction, GPC, DSC, Rheovibron at 110 Hz, and Tg by an ESR spin probe technique. The hexene content of the extracted polymer did not exceed 4 mol%; that in the extract was as high as 89.5%. The characterization data and dynamic mechanical loss results in this paper have been examined in the context of an exhaustive study of ethylene-ethylene-α-olefin copolymers by Shirayama et al. with some additional details by Wilson et al. All Tg data are summarized in the form of a plot of temperature vs log (wt% hexene-1). It is emphasized that increasing hexene content decreases crystallinity, crystallite size and molecular weight, so that caution is required in interpreting results. For high mol wt low hexene-1 whole and extracted polymers, the spin probe method gives Tg for the amorphous phase whereas Rheovibron data reflect Tβ( >Tg) for the composite amorphous-crystallite specimens. The ESR data indicate that Tg for amorphous PE, called Tg(L), is very close to 200 K which is above and distinct from Tγ at c, 150 K. It would still be desirable to investigate a series of ethylene-hexene-1 copolymers over the entire composition range at essentially constant, high molecular weight.

The aim of this experiment was to evaluate the feasibility of dilution of the cryoprotectant by a sucrose solution in the straw followed by direct transfer without any selection of the embryos. A comparison was made between the method described by Renard et al. (7) and a method slightly modified from that published by Leibo (8). The feasibility is proved by a mean pregnancy rate of 41.4%. Although the difference was not statistically significant, the method described by Renard et al. (7) led to a higher pregnancy rate (44.7%) than that of Leibo (8) (38.5%).

Début février 2011, alors que les opposants au régime du président Moubarak occupaient la place Tahrir au Caire, le journal Destour titrait : " Mûlid al-hurriya midan Tahrir " (Mûlid de la liberté place de la Libération). De fait, si un mûlid est littéralement une célébration, dans le sens commun égyptien le terme prend aussi la forme et la signification d'un grand rassemblement associé à l'investissement d'un lieu. C'est probablement ce caractère tendancieux qui a valu aux mûlids d'être considérés et traités par les autorités, tant gouvernementales que religieuses, comme des phénomènes suspects voire séditieux, de l'occupation britannique jusqu'à l'époque contemporaine. Présents dans la plupart des localités d'Égypte, les mûlids ne sont pourtant pas -- loin s'en faut -- au cœur de la cité ; comme objets de recherche, ils peuvent de ce fait être déclinés depuis les champs de leurs marginalisations. Ils conjuguent en effet des registres divers de marginalités : sociale, spatiale, temporelle, et de sens.

International audience; Erbil est l'une des plus anciennes cités de la planète. Sa vieille ville, qui semble avoir été habitée sans interruption depuis le 2 e millénaire avant J-C, se situe au somment d'un « tell » (une colline archéologique) qui domine la plaine environnante. Longtemps dans l'ombre de Mossoul, Erbil se développe surtout depuis que le Kurdistan d'Irak a accédé à une large autonomie. Nommée Hawler en langue kurde, elle est la capitale du Kurdistan irakien autonome depuis les années 1990.

International audience; Mossoul est la deuxième ville irakienne de par son poids démographique soit près de 3 millions d'habitants selon les estimations des autorités irakiennes avant la guerre de 2014. Traversée par le Tigre, elle se situe dans le nord du pays en Haute Mésopotamie, l'une des régions du monde où le phénomène urbain a très tôt fait son apparition. La plaine de Mossoul correspond à l'ancien territoire agricole de l'antique Ninive, qui fut, un temps, capitale du vaste empire assyrien. Mossoul a été, durant la deuxième guerre civile d'Irak (2014-2017), une nouvelle fois capitale, mais cette fois d'un proto-état terroriste dominé par l'Organisation État islamique (OEI).

International audience

International audience; La quantité de déchets produits dans le monde explose : celle-ci devrait augmenter de 69 % entre 2012 et 2025, selon une étude publiée par la Banque mondiale. Cette progression, liée à la croissance démographique et urbaine, est plus forte dans les pays du Sud. Or, les municipalités de ces pays manquent souvent de moyens. Dans les années 1990, des réformes ont tenté d'améliorer la gestion des déchets en expérimentant la délégation de service public et en modernisant les équipements. Leur succès mitigé ainsi que la conscience d'une dégradation de l'environnement et du climat ont conduit dans les années 2010 à de nouvelles orientations. L'heure est aujourd'hui à la promotion de l'économie circulaire (cf. Objectif de développement durable n° 12). Dans ce cercle vertueux, les déchets ne sont plus des rebuts mais des ressources, qui pourraient devenir lucratives. Comment la valorisation recompose-t-elle les jeux d'acteurs ? À qui profitent les bénéfices ? Quelle concurrence entre récupérateurs artisanaux et recycleurs industriels ? Quels outils et principes pour la régulation des activités de valorisation ? De Buenos Aires à Lomé, en passant par Port-au-Prince et Casablanca, l'ouvrage interroge les recompositions du secteur des déchets et l'articulation entre gestion d'un service public et marchandisation de la valorisation. Cette tension est envisagée selon quatre perspectives : (i) la confrontation entre logiques sociales et rentabilité économique ; (ii) l'insertion spatiale des activités de recyclage dans les espaces urbains ; (iii) la contribution des revenus de valorisation au financement du service public ; (iv) la promesse environnementale d'un recyclage infini des objets et des matières. direction scientifique Sylvy Jaglin, Lise Debout, Irène Salenson