Sondage archéologique sur l'oppidum du Camp de César à Laudun-l'Ardoise. Étude d'une structure du Haut-Empire réutilisée au cours de l'Antiquité tardive.

National audienceDans le cadre des recherches sur les dynamiques de peuplement dans la basse vallée de la Cèze, le sondage réalisé dans cette structure en bordure orientale de l'oppidum du Camp de César à Laudun-l'Ardoise (Gard), a permis d'établir sa construction au cours du Ier siècle de notre ère et de sa réfection au cours des Ve-VIe siècles. L'abondance de mobilier céramique tardo-républicain, et du Haut-Empire, au sein du bâti ou en stratigraphie, ne permettent pas de dater exclusivement cette structure de l'Antiquité tardive, bien que les couches tardo-antiques directement au contact de l'affleurement rocheux, sont un terminus post quem recevable pour la datation de la réfection du bâtiment. Il semble qu'au cours des Ve-VIe siècles de nouveaux constructeurs ont procédé à des terrassements mettant à jour les maçonneries préexistantes du Ier siècle, qui ont alors été réutilisées

Efficacite des Insecticides Huile de Neem, Cypermethrine et Chlorpyrifos Ethyle Contre les Principaux Ravageurs du Sorgho Poophilus costalis et Stenodiplosis sorghicola

Le sorgho Sorghum bicolor (L.) Moench est la deuxième céréale la plus cultivée après le maïs au Togo. Sa production subit des pertes de rendements de plus en plus importantes, du fait des attaques d'insectes ravageurs, principalement la cicadelle écumeuse, Poophilus costalis (Walker) (Hemiptera: Aphrophoridae) et la cécidomyie, Stenodiplosis sorghicola (Coquillett) (Cecidomyidae: Diptera). Cette étude a été réalisée en station et au champ pour évaluer l'efficacité du biopesticide Huile de Neem et des insecticides de synthèse Cyperméthrine et Chlopyrifos éthyle contre P. costalis et S. sorghicola. Trois doses d'Huile de Neem (964, 2892 et 5784 ml.ha-1), de cyperméthrine (Cypercal 50 EC : 128, 384 et 768 ml.ha-1) et de chlorpyrifos éthyle (Dursban 480 EC: 38, 114 et 228 ml.ha-1) ont été appliquées hebdomadairement dans des parcelles de sorgho contre ces deux ravageurs. Des parcelles non traitées ont représenté le témoin. Un dispositif en blocs aléatoires complets avec 4 répétitions a été utilisé. Les résultats ont montré que P. costalis a provoqué plus de 59% de perte de rendement du sorgho. Sa population a été efficacement contrôlée par l'Huile de neem, le Chlorpyrifos éthyle et la Cyperméthrine qui ont respectivement 3, 5 et 19 fois réduit l'effectif du ravageur en station et 6, 7 et 58 fois au champ, par rapport au témoin. En ce qui concerne la protection des panicules de sorgho contre S. sorghicola, la Cyperméthrine a été plus efficace que les deux autres insecticides. Appliquée à une dose de 768 ml.ha-1, la cyperméthrine a permis d'obtenir un rendement de 2802 et 1873 kg.ha-1, respectivement en station et au champ, contre 695 et 692 kg.ha-1 pour le témoin. Cette étude doit se poursuivre pour élaborer une stratégie de lutte intégrée efficace contre P. costalis et S. sorghicola. (Résumé d'auteur

New pixelized Micromegas detector with low discharge rate for the COMPASS experiment

New Micromegas (Micro-mesh gaseous detectors) are being developed in view of the future physics projects planned by the COMPASS collaboration at CERN. Several major upgrades compared to present detectors are being studied: detectors standing five times higher luminosity with hadron beams, detection of beam particles (flux up to a few hundred of kHz/mm^{2}, 10 times larger than for the present Micromegas detectors) with pixelized read-out in the central part, light and integrated electronics, and improved robustness. Two solutions of reduction of discharge impact have been studied, with Micromegas detectors using resistive layers and using an additional GEM foil. Performance of such detectors has also been measured. A large size prototypes with nominal active area and pixelized read-out has been produced and installed at COMPASS in 2010. In 2011 prototypes featuring an additional GEM foil, as well as an resistive prototype, are installed at COMPASS and preliminary results from those detectors presented very good performance. We present here the project and report on its status, in particular the performance of large size prototypes with an additional GEM foil.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous Detectors conference (MPGD2011), 29-31 August 2011, Kobe, Japa

Excitons in InGaAs Quantum Dots without Electron Wetting Layer States

The Stranski-Krastanov (SK) growth-mode facilitates the self-assembly of quantum dots (QDs) using lattice-mismatched semiconductors, for instance InAs and GaAs. SK QDs are defect-free and can be embedded in heterostructures and nano-engineered devices. InAs QDs are excellent photon emitters: QD-excitons, electron-hole bound pairs, are exploited as emitters of high quality single photons for quantum communication. One significant drawback of the SK-mode is the wetting layer (WL). The WL results in a continuum rather close in energy to the QD-confined-states. The WL-states lead to unwanted scattering and dephasing processes of QD-excitons. Here, we report that a slight modification to the SK-growth-protocol of InAs on GaAs -- we add a monolayer of AlAs following InAs QD formation -- results in a radical change to the QD-excitons. Extensive characterisation demonstrates that this additional layer eliminates the WL-continuum for electrons enabling the creation of highly charged excitons where up to six electrons occupy the same QD. Single QDs grown with this protocol exhibit optical linewidths matching those of the very best SK QDs making them an attractive alternative to standard InGaAs QDs

Earthworm management in tropical agroecosystems

Data of 145 and 69 earthworm communities from managed and natural ecosystems, respectively, of four continents and 15 tropical countries were analysed. The aim of the study was to separate the influence of phylogenetic, environmental and agricultural factors on the structure of earthworm communities in agroecosystems, and to evaluate their relative importance in the whole soil macrofauna community. Earthworms comprise 40-90% of macrofaunal biomass in most ecosystems except for annually cropped systems. Three major conclusions were drawn from the analysis of community structure (regional analysis) : (i) crops were, independently of region, characterized by a loss of native species and by the dominance of exotic endogeics ; (ii) pastures were highly heterogenous in terms of native or exotic species dominance ; (iii) native species survived better in management ecosystems of India and Africa than in Mexico-Central America. Local analysis in selected countries indicated that, as a general rule, the intensity of agricultural practices is negatively correlated with the amount of native species and the total abundance and biomass of earthworms ; the only exception was found in the conversion of savannas to pastures, in Colombian llanos. (Résumé d'auteur

Insect Net on High Tunnel as an Effective Technology to Protect Tomato Crops against Major Pests in the Highlands of Kenya

Tomato crop is a agricultural precious commodity worldwide due to high economic returns, nutritive value and role in agricultural and economic diversification. Therefore, tomato demand is booming in sub-Saharan Africa to feed the growing urban populations. But high pest pressure throughout the year, insecticide resistance and the arrival of new species such as tomato leaf miner Tuta absoluta are major constraints in management. Consequently, in sub-Saharan Africa, tomato yield, quality and environmental health practices remain way below international standards. To increase marketable production and quality sustainable pest control is essential. Several alternatives including biopesticide, semiochemical and insect nets are being explored. This study was carried out to evaluate the effectiveness of a high tunnel covered by insect net combined with biopesticides to protect tomato crop against major pests. A statistic block design was implemented in the research centre of KALRO Mwea in Central Kenya during two seasons. Biopesticides based on Bacillus thuringiensis and Metarizium anisopliae were used to complete the physical protection against caterpillars and sucking pests respectively. The results showed that correctly used, insect nets used on high tunnel protect tomatoes against T. absoluta. Whiteflies (Trialeurodes vaporariorum), serpentine leaf miner (Liriomyza spp.) and brown thrips (Frankliniella spp) populations remained at a significantly lower level or arrived later inside the tunnel as compared to open cultivation, but the dark thrips species were much more inside at the flowering stage. Net treatment with permethrin did not provide a significant reduction in pests population as compared to non treated net. Biopesticides recorded significantly low pest populations as compared to the untreated control in open field. The yield was significantly improved mainly due to greenhouse effect. Demonstrations in farmer fields confirmed the effectiveness and affordability of this technology. With higher ventilation, reduction of dryness and a capacity to use rain, high tunnel high tunnel covered by net appeared effective against pests, adaptable and affordable to smallholder farmers to produce good quality tomatoes in the highlands of Kenya. (Résumé d'auteur

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let

A novel role for the root cap in phosphate uptake and homeostasis

The root cap has a fundamental role in sensing environmental cues as well as regulating root growth via altered meristem activity. Despite this well-established role in the control of developmental processes in roots, the root cap's function in nutrition remains obscure. Here, we uncover its role in phosphate nutrition by targeted cellular inactivation or phosphate transport complementation in Arabidopsis, using a transactivation strategy with an innovative high-resolution real-time P-33 imaging technique. Remarkably, the diminutive size of the root cap cells at the root-to-soil exchange surface accounts for a significant amount of the total seedling phosphate uptake (approximately 20%). This level of Pi absorption is sufficient for shoot biomass production (up to a 180% gain in soil), as well as repression of Pi starvation-induced genes. These results extend our understanding of this important tissue from its previously described roles in environmental perception to novel functions in mineral nutrition and homeostasis control

An aqueous one-pot route to gold/quantum rod heterostructured nanoparticles functionalized with DNA

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