Signal conditioner circuit for photomultiplier tube

Miniaturized circuit improves measurement of radiation dose absorbed in a scintillation crystal. The temperature coefficient of the field-effect transistor gate-source voltage in the isolation amplifier can be readily controlled

Deciphering phenotypic diversity of Ralstonia solanacearum strains pathogenic to potato : [P2-08]

Based on the phylotype classification scheme, we questioned how genetically how genetically and phenotypically diverse may strains of #Ralstonia solanacearum# pathogenic to potato are. We studied 129 representative European and Mediterranean strains of #R. solanacearum# along with 57 reference strains known to cover the genetic diversity in this species. Phylogeny analysis was done on partial endoglucanase (egl) gene sequences. Virulence and pathogenicity to potato, tomato, and eggplant was established at two ranges of temperature 24-30°C (tropical) and 15-24°C (temperate) and tests on banana were only conducted at 24-30°C. Results confirm the literature that the ability to cause wilt on Solanaceae and specially on potato was of polyphyletic nature and shared by strains in all phylotypes I, IIA, IIB, III, and IV, showing a wide genetic basis for pathogenicity on these hosts. We also noticed that strains that were known to cause wilt on Musaceae solely: phylotypes IIA sequevar 6 (IIA-6), IIB-3, and IIB-4, were also able to trigger wilt on Solanaceae, especially on susceptible potato, tomato and eggplant, and also on some resistant tomato for the phylotype IIB-4. In the same time, we isolated Brown rot potato strains belonging to phylotypes IIB-1 and IIB-2, but also strains belonging to phylotype IIB-27, from symptomless banana plants, also suggesting the polyphyletic nature of the Moko disease causing strains. That said, from an epidemiological point of view, no Moko disease causing strains have ever been isolated from a wilted tomato or potato in the field, although it is now apparent they were able to trigger wilt in these hosts. But from a phylogenetic point of view, these two well known ecotypes address the question of host adaptation mechanisms, which may have undergone a similar bottleneck evolution. On the contrary, cold-tolerance ability on Solanaceae is only shared among the clonal brown rot phylotype IIB-1, which gathered the great majority of European and Mediterranean (EuMr) strains. All other strains were not able to trigger wilt or were drastically less aggressive on these hosts. A total of 5 strains out of 106 originating or intercepted in EuMr countries were not distributed into the phylotype IIB-1 and showed that despite the great proportion of brown rot phylotypes IIB-1 strains on EuMr territory, other phylotypes may represent a potential threat to Solanaceae production. This study highlighted the strain LNPV24.25, which was isolated from a diseased tomato and belong to the phylotype IIB-4NPB that gather highly aggressive and virulent emerging strains. This indicates, from our knowledge, the first report of an emerging strain in France. These findings showed that pathogenicity traits of genetically identified strains still need to be understood, especially in the perspective of post-genomics comparative analysis to understand bacterial speciation in the #R. solanacearum# species complex. (Résumé d'auteur

Digital numerically controlled oscillator

The frequency and phase of an output signal from an oscillator circuit are controlled with accuracy by a digital input word. Positive and negative alterations in output frequency are both provided for by translating all values of input words so that they are positive. The oscillator reference frequency is corrected only in one direction, by adding phase to the output frequency of the oscillator. The input control word is translated to a single algebraic sign and the digital 1 is added thereto. The translated input control word is then accumulated. A reference clock signal having a frequency at an integer multiple of the desired frequency of the output signal is generated. The accumulated control word is then compared with a threshold level. The output signal is adjusted in a single direction by dividing the frequency of the reference clock signal by a first integer or by an integer different from the first integer

Modeling the thermal behavior of biosphere 2 in a non-controlled environment using bond graphs

Biosphere 2 is a closed ecological system of high complexity built to deepen the understanding of ecological systems, to study the dynamics of closed ecologies, and to learn to control their behavior. The use of modeling and simulation is crucial in the achievement of these goals. Understanding a physical system is almost synonymous with possessing a model of its comportment. The main goal of this study is the development of a dynamic bond graph model that represents the thermal behavior of the complex ecological system under study, Biosphere 2. In this work, a first model that captures the behavior of the ecological system in a non-controlled environment is presented.Postprint (published version

Aménagement de l’environnement parcellaire en maraîchage biologique: une nouvelle piste pour renforcer l’efficacité des auxiliaires naturels et améliorer la résistance génétique aux pucerons ?

La biodiversité fonctionnelle consiste à favoriser autour des cultures des espèces végétales qui vont attirer, héberger, nourrir les insectes auxiliaires indigènes participant au maintien des populations de ravageurs sous le seuil de nuisibilité économique. L'objectif est donc de transposer cette technique pour améliorer la lutte contre les pucerons, qui sont parmi les principaux ravageurs dans le Sud de la France, en particulier sur melon (pour lequel aucun produit phytosanitaire n’est autorisé en AB). Par ailleurs, l'intérêt potentiel des bandes de plantes non hôtes pour protéger les cultures des virus transmis selon le mode non persistant a également été montré (Fereres, 2000 ; Hooks et Fereres, 2006). Plusieurs mécanismes pourraient être mis en jeu : « barrière physique » réduisant le nombre de pucerons ailés atteignant la culture, « filtre à virus » permettant de réduire la charge virale des pucerons avant qu'ils n'atteignent la culture, «leurre » détournant les pucerons de leur culture ou « réservoir à ennemis naturels ». Ainsi la bibliographie suggère que la manipulation de l'environnement parcellaire peut être une stratégie efficace pour diminuer à la fois la pression virus et la pression puceron. Cet essai s'inscrit dans un réseau d'expérimentations (avec l’INRA d’Avignon, le CEFEL) financées pendant 3 ans par le CTPS Parcel-R. L’attaque de pucerons a été très faible cette année dans la culture. Les effectifs observés dans la parcelle étant bas, il convient d’être prudent quant à leur interprétation. Il apparait que les aménagements réalisés (bande florale et dans une moindre mesure bande enherbée) abritent plus d’auxiliaires que l’enherbement spontané (chemin longeant la parcelle). Les aménagements ont hébergé des pucerons spécifiques, constituant des proies de substitution pour les auxiliaires contre pucerons, capables de migrer ensuite dans la parcelle. Différents auxiliaires, la plupart non spécifiques des pucerons (punaises, araignées) se déplacent dans la parcelle ; l’impact de l’aménagement est alors assez difficile à mettre en évidence. Par contre, en observant les melons, et les auxiliaires s’y étant installés, il apparaît que la bande fleurie, à la différence des deux autres modalités, a permis de renforcer la présence des micro-hyménoptères parasitoïdes

Biodiversité fonctionnelle en maraîchage biologique : mise en place de bandes florales pour favoriser les punaises prédatrices - compte-rendu d'essai 2012

Functional biodiversity can be enhanced by in settling, in the crops surroundings, specific vegetal species that will increase the occurrence of beneficial insects, by providing shelters, and alternative preys. This technique, also called biological control by habitat manipulation, was adapted in Southern France to control spider mites (Tetranychus urticae), and white flies (Trialeurodes vaporariorum and Bemisia tabaci) using two predatory mirid bugs Macrolophus pygmaeus and Dicyphus errans. Trials started in 2007, with a first step consisting in selecting adapted host-plants for these two mirids. 22 species of host-plants have been sown in strips between greenhouses at the experimental station of GRAB (Avignon – Provence). Germination rate, competition with weeds have been evaluated. Exhaustive samples of insects on these host-plants have been realised. The ratio [number of predators / number of phytophagous] has been calculated, and the number of predatory mirid bugs evaluated. Dittrichia viscosa and Calendula officinalis appeared to be the most promising species, considering their rusticity, their high ratio [predators/phytophagous] and their ability to shelter Macrolophus and Dicyphus. Works focused since 2011 on the potential of Geraniacae as host-plants for Dicyphinae, and on the interest of establishing flower strips in the shelters

Story of an array based technology designed to grasp and detect the complex plant pathogen Ralstonia solanacearum

The ancient soil borne plant vascular pathogen Ralstonia solanacearum evolved and adapted to cause severe damage on an unusually wide range of plants. Based on the phylotype classification, it was questioned how genetically and phenotypically diverse strains of Ralstonia solanacearum may be, in an attempt to produce adapted diagnostic tools. A pangenomic microarray was first used to better describe and understand the phylogeny of R. solanacearum, especially three particular ecotypes in the phylotype II: (i) Brown rot strains from sequevars IIB-1 and IIB-2, historically known as race 3 biovar 2 and clonal; (ii) new pathogenic variants from sequevar IIB-4NPB that lack pathogenicity to Cavendish banana but can infect many other plant species; and (iii) Moko disease-causing strains from sequevars IIB-3, IIB-4, and IIA-6, historically known as race 2, that cause wilt on banana, plantain, and Heliconia. Results revealed a phylogeographic structure within Brown rot strains, allowing European outbreak strains of Andean and African origins to be distinguished, and also showed a close but distinct relationship between Moko ecotype IIB-4 and the emerging IIB-4NPB strains. Based on those results, it is proposed to develop new DNA-based diagnostic tools, including array and routine PCR, to ensure better detection of this complex plant pathogen. (Résumé d'auteur

Glancing at host adaptation in Ralstonia solanacearum through comparative genomics of host-adapted lineages

Ralstonia solanacearum is a vascular soil-born plant pathogen with an unusually broad host range. This globally distributed, economically destructive organism has thousands of distinct lineages within a heterogeneous and taxonomically disputed species complex. Some of those lineages can be assigned to ecotypes that include highly host-adapted strains such as the banana Moko disease-causing strains, the cold-tolerant potato brown rot strains (R3bv2) and the recently emerged NPB strains (Not Pathogenic to Banana). The polyphyletic nature of the Moko ecotype and the unexpected closeness of some its lineages to the paraphyletic brown-rot and NPB ecotypes make those highly adapted strains a robust model for study of host adaptation and speciation in general (Cellier, Remenant et al.2012). Genomes of 10 new strains were produced to complement the 12 publicly available ones. Using a panel of bioinformatics methods, we looked for genetic or evolutionary features that discriminate between ecotypes. There were relatively few divergent features. Those related to known virulence factors were further analyzed for functional clues about host adaptation and ecotype emergence mechanisms. These analyses yield no clear signal, suggesting that the large biological differences between these closely related strains result from differences in gene expression rather than from differences in gene content. Transcriptomic analyses of these strains during host infection are underway to test this hypothesis

Fouille de données pour associer des noms de sessions aux articles scientifiques

National audienceIn this paper, we present a proposition based on data mining to tackle the DEFT 2014 challenge. We focus on task 4 which consists of identifying the right conference session for scientific papers. The proposed approach is based on a combination of two data mining techniques. Sequence mining extracts frequent phrases in scientific papers in order to build paper and session descriptions. Then, those descriptions of papers and sessions are used to create a graph which represents shared descriptions. A graph mining technique is applied on the graph in order to extract a collection of homogenous sub-graphs corresponding to sets of papers associated to sessions.Nous décrivons dans cet article notre participation à l'édition 2014 de DEFT. Nous nous intéressons à la tâche consistant à associer des noms de session aux articles d'une conférence. Pour ce faire, nous proposons une approche originale, symbolique et non supervisée, de découverte de connaissances. L'approche combine des méthodes de fouille de données séquentielles et de fouille de graphes. La fouille de séquences permet d'extraire des motifs fréquents dans le but de construire des descriptions des articles et des sessions. Ces descriptions sont ensuite représentées par un graphe. Une technique de fouille de graphes appliquée sur ce graphe permet d'obtenir des collections de sous-graphes homogènes, correspondant à des collections d'articles et de noms de sessions

Hybridizing direct and indirect optimal control approaches for aircraft conflict avoidance

Aircraft conflict avoidance is a crucial issue arising in air traffic management. The problem is to keep a given separation distance for aircraft along their trajectories. We focus on an optimal control model based on speed regulation to achieve aircraft separation. We propose a solution strategy based on the decomposition of the problem and on the hybridization of a direct and an indirect method applied on the obtained subproblems. Numerical results show that the proposed approach is promising in terms of reduction of computing time for conflict avoidance