A comprehensive analysis of the genetic diversity and environmental adaptability in worldwide Merino and Merino-derived sheep breeds

BACKGROUND: To enhance and extend the knowledge about the global historical and phylogenetic relationships between Merino and Merino-derived breeds, 19 populations were genotyped with the OvineSNP50 BeadChip specifically for this study, while an additional 23 populations from the publicly available genotypes were retrieved. Three complementary statistical tests, Rsb (extended haplotype homozygosity between-populations), XP-EHH (cross-population extended haplotype homozygosity), and runs of homozygosity (ROH) islands were applied to identify genomic variants with potential impact on the adaptability of Merino genetic type in two contrasting climate zones. RESULTS: The results indicate that a large part of the Merino's genetic relatedness and admixture patterns are explained by their genetic background and/or geographic origin, followed by local admixture. Multi-dimensional scaling, Neighbor-Net, Admixture, and TREEMIX analyses consistently provided evidence of the role of Australian, Rambouillet and German strains in the extensive gene introgression into the other Merino and Merino-derived breeds. The close relationship between Iberian Merinos and other South-western European breeds is consistent with the Iberian origin of the Merino genetic type, with traces from previous contributions of other Mediterranean stocks. Using Rsb and XP-EHH approaches, signatures of selection were detected spanning four genomic regions located on Ovis aries chromosomes (OAR) 1, 6 and 16, whereas two genomic regions on OAR6, that partially overlapped with the previous ones, were highlighted by ROH islands. Overall, the three approaches identified 106 candidate genes putatively under selection. Among them, genes related to immune response were identified via the gene interaction network. In addition, several candidate genes were found, such as LEKR1, LCORL, GHR, RBPJ, BMPR1B, PPARGC1A, and PRKAA1, related to morphological, growth and reproductive traits, adaptive thermogenesis, and hypoxia responses. CONCLUSIONS: To the best of our knowledge, this is the first comprehensive dataset that includes most of the Merino and Merino-derived sheep breeds raised in different regions of the world. The results provide an in-depth picture of the genetic makeup of the current Merino and Merino-derived breeds, highlighting the possible selection pressures associated with the combined effect of anthropic and environmental factors. The study underlines the importance of Merino genetic types as invaluable resources of possible adaptive diversity in the context of the occurring climate changes

Multispacer typing of Rickettsia isolates from humans and ticks in Tunisia revealing new genotypes

BACKGROUND: Rickettsioses are important remerging vector born infections. In Tunisia, many species have been described in humans and vectors. Genotyping is important for tracking pathogen movement between hosts and vectors. In this study, we characterized Rickettsia species detected in patients and vectors using multispacer typing (MST), proposed by Founier et al. and based on three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet), mppA-pruC) sequencing. METHODS: Our study included 25 patients hospitalized during 2009. Ticks and fleas were collected in the vicinity of confirmed cases. Serology was performed on serum samples by microimmunofluorescence using Rickettsia conorii and Rickettsia typhi antigens. To detect and identify Rickettsia species, PCR targeting ompA, ompB and gltA genes followed by sequencing was performed on 18 obtained skin biopsies and on all collected vectors. Rickettsia positive samples were further characterized using primers targeting three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet) and mppA-purC). RESULTS: A rickettsial infection was confirmed in 15 cases (60%). Serology was positive in 13 cases (52%). PCR detected Rickettsia DNA in four biopsies (16%) allowing the identification of R. conorii subsp israelensis in three cases and R. conorii subsp conorii in one case. Among 380 collected ticks, nine presented positive PCR (2.4%) allowing the identification of six R. conorii subsp israelensis, two R. massiliae and one R. conorii subsp conorii. Among 322 collected fleas, only one was positive for R. felis. R. conorii subsp israelensis strains detected in humans and vectors clustered together and showed a new MST genotype. Similarly, R. conorii subsp conorii strains detected in a skin biopsy and a tick were genetically related and presented a new MST genotype. CONCLUSIONS: New Rickettsia spotted fever strain genotypes were found in Tunisia. Isolates detected in humans and vectors were genetically homogenous despite location differences in their original isolation suggesting epidemiologic circulation of these strains

Contact Impedance Characterization of Metallized Particle Column to Copper Strip in High Frequency Domains

International audienceThe number of applications using high frequency bands up 10 GHz is in constant progression in various domains (high-speed communication, portable phone, radar...). This demand has been widely extended to connectors in automotive applications. In fact various connectors have been designed and developed in order to be used over a wide range of frequencies from a few MHz to several GHz. Among these connectors, metallized particle interconnects (MPI) used widely in interconnections (ASICs, PCs, workstations ...), constitute an interesting candidate to be developed for high frequency connectors, for frequencies up to 18 GHz. In order to simulate the connector, an MPI column was used as a terminal and compressed between two microstrip lines of copper (PCB). Signal losses measurements in the frequency band 100 MHz to 18 GHz are evaluated as a function of compression force. It was found that the impedance of the system is equivalent to an RCL circuit. By fitting experimental loss data we have analyzed each component and have established the impedance laws

Classement vis-à-vis de l'érosion due au phénomène d'arc, des matériaux de contact électrique dans les centraux téléphoniques CP 400 et Pentaconta

L'érosion due au phénomène d'arc dans les contacts des relais électromécaniques dépend de plusieurs paramètres, entre autres la nature du matériau de contact et le type de relais dans lequel il fonctionne. L'objet de ce travail est l'étude comparative de l'érosion cathodique des contacts des centraux français du type Crossbar : CP 400 et Pentaconta. Nous avons établi une corrélation entre l'érosion cathodique ΔMc et l'énergie dissipée dans l'arc à l'ouverture W calculée à partir de la durée moyenne d'arc à l'ouverture ΔMc ≃ KW. K est une constante du matériau et sa détermination ainsi que celle de la fonction t = f(I) permettent de calculer l'érosion prévisionnelle des contacts en fonction du courant ; ceci conduit à classer vis-à-vis de l'érosion les différents matériaux pour un courant donné. Les résultats montrent que l'érosion augmente dans l'ordre suivant des matériaux : Pd, AgPd, AgAu, AgCu

Classement vis-à-vis de l'érosion due au phénomène d'arc, des matériaux de contact électrique dans les centraux téléphoniques CP 400 et Pentaconta

Arcing in electrical contacts of electromechanical relay and subsequent erosion depend on many parameters. Among these parameters : the kind of contact material and the type of relay where the contact is set. The subject of this work is to compare the cathode loss of contacts in French Crossbar telephone exchanges : CP 400 and Pentaconta. Whe have carried out a correlation between cathode loss ΔMc and energy W dissipated in the arc on break : ΔMc ≃ KW (energy is calculated from measured mean arc duration on break), K is constant depending on material. K values and the function t = f(I) have permited to calculate erosion as a function of current ; this have led to classify contacts materials, the results show that erosion increases in following order of materials : Pd, AgPd, AgAu, AgCu.L'érosion due au phénomène d'arc dans les contacts des relais électromécaniques dépend de plusieurs paramètres, entre autres la nature du matériau de contact et le type de relais dans lequel il fonctionne. L'objet de ce travail est l'étude comparative de l'érosion cathodique des contacts des centraux français du type Crossbar : CP 400 et Pentaconta. Nous avons établi une corrélation entre l'érosion cathodique ΔMc et l'énergie dissipée dans l'arc à l'ouverture W calculée à partir de la durée moyenne d'arc à l'ouverture ΔMc ≃ KW. K est une constante du matériau et sa détermination ainsi que celle de la fonction t = f(I) permettent de calculer l'érosion prévisionnelle des contacts en fonction du courant ; ceci conduit à classer vis-à-vis de l'érosion les différents matériaux pour un courant donné. Les résultats montrent que l'érosion augmente dans l'ordre suivant des matériaux : Pd, AgPd, AgAu, AgCu

OBSERVATION DE L'EMISSION DE L'EXCIPLEXE Ar H* DANS DES JETS DE PLASMAS D'ARGON-HYDROGENE RAREFIES

Les molécules de type excimères ou exciplexes suscitent depuis quelques années un intérêt considérable en partie lié à la possibilité de leur utilisation pour la réalisation de lasers. En ce exqui concerne les exciplexes de gaz rares, les plus étudiés ont été très certainement les halogénures (Xe F, Xe Br, Kr F, Ar F etc... ) et les composés alcalins gaz rares (Ar Na, Ar Cs etc...). Cependant d'autres composés sont possibles : les hydrures de gaz rares pour lesquels il existe quelques données le plus souvent théoriques, mais aussi déduites d'expériences de collisions. De façon générale, les courbes de potentiel montrent que l'état fondamental de l'hydrure neutre est répulsif et les états excités sont attractifs ; par contre l'ion moléculaire correspondant est stable |1|. Notons que pour ces hydrures, la littérature est en général plus abondante sur l'ion stable que sur la molécule neutre. C'est le cas de Ar H pour lequel il existe de nombreuses données sur Ar H+, par contre les données sont relativement réduites et de plus contradictoires sur Ar H (|2|, |3|). On peut d'ailleurs noter que les spectres moléculaires correspondant à la déexcitation radiative des états excités des hydrures neutres n'ont pratiquement jamais été observés. A notre connaissance, seule la transition 2π → 2∑ de Ar H dont la tête de bande e s t observée à 7673.2 Å est actuellement attribuée à une molécule de ce type |4|. De plus dans cette dernière étude les processus de formation de cette molécule n'ont pas été étudiés

[Antimicrobial susceptibility and frequency of occurrence of clinical blood isolates in Sfax-Tunisia (1993-1998)].

&lt;p&gt;Antimicrobial susceptibility and frequency of occurrence of clinical blood isolates in Sfax-Tunisia (1993-1998). The choice of antimicrobial therapy for the treatment of bacteremia is often empirical and based on the knowledge of susceptibility profiles of the most common bacteria causing such infections. This study determines the bacterial etiology of bacteremic episodes and antimicrobial susceptibility patterns recorded at a teaching hospital, from January 1993 to December 1998. We collected 2979 strains responsible for bacteremia. Gram negative bacteria were predominant (60%). The organisms recovered most frequently were Staphylococcus aureus (18.9%), Escherichia coli (14.7%), Klebsiella pneumoniae (14%) and Pseudomonas aeruginosa (7.6%). The incidence of resistance to methicillin were 17.4% for Staphylococcus aureus and 26.8% for coagulase negative Staphylococcus. No resistance to glycopeptides was observed among the enterococci and staphylococci studied. 27.7% of enterobacteriaceae were resistant to third generation cephalosporins. Imipenem was the most active agent against gram negative bacteria. To carry out a surveillance of bacteremic episodes occurring at every hospital, it is necessary to provide valuable information which should be the basis for effective empiric therapy.&lt;/p&gt;</p

Étude de l'érosion due au phénomène d'arc dans les contacts de relais des centraux electromécaniques - Corrélation érosion-durée d'arc. Influence de la vapeur d'eau atmosphérique sur la durée d'arc

Arcing in electrical contacts of telephone switching relays and subsequent erosion has been the subject of a great deal of work. Nevertheless the problem depends on many parameters (electrical circuits, environmental, mechanical, contact shapes...), of which the knowledge is incomplete. This is the case for the contacts used in Crossbar telephone exchanges. The aim of this work is to show that erosion and arc duration on break are correlated, and to apply the results of this correlation to calculate the erosion of two Ag/Cu (90/10) contact shapes operating in ambient atmosphere (80 % relative humidity) or in ambient dried atmosphere (15 % relative humidity).Le phénomène d'arc dans les contacts des relais téléphoniques et l'érosion qui en résulte, ont été l'objet d'un grand nombre de travaux. Néanmoins, le problème dépendant de plusieurs paramètres (circuits électriques, atmosphère environnante, paramètres mécaniques, formes de contacts...), les connaissances restent encore partielles. C'est le cas pour les contacts utilisés dans les centraux téléphoniques du type Crossbar. Le but de cette étude est de montrer que l'érosion et la durée d'arc à l'ouverture sont corrélées et d'appliquer les résultats de cette corrélation pour calculer l'érosion sur deux formes différentes de paires de contacts en AgCu (90/10), fonctionnant en atmosphère ambiante 80 % d'humidité relative ou en atmosphère ambiante desséchée (15 % d'humidité relative)

Étude de l'érosion due au phénomène d'arc dans les contacts de relais des centraux electromécaniques - Corrélation érosion-durée d'arc. Influence de la vapeur d'eau atmosphérique sur la durée d'arc

Le phénomène d'arc dans les contacts des relais téléphoniques et l'érosion qui en résulte, ont été l'objet d'un grand nombre de travaux. Néanmoins, le problème dépendant de plusieurs paramètres (circuits électriques, atmosphère environnante, paramètres mécaniques, formes de contacts...), les connaissances restent encore partielles. C'est le cas pour les contacts utilisés dans les centraux téléphoniques du type Crossbar. Le but de cette étude est de montrer que l'érosion et la durée d'arc à l'ouverture sont corrélées et d'appliquer les résultats de cette corrélation pour calculer l'érosion sur deux formes différentes de paires de contacts en AgCu (90/10), fonctionnant en atmosphère ambiante 80 % d'humidité relative ou en atmosphère ambiante desséchée (15 % d'humidité relative)

Minimum fretting amplitude in medium force for connector coated material and pure metals

WOS:000287418800016International audienceFor automotive applications, the mechanical behaviour of the contact area under vibrations is one of the key factors for connector reliability. Such vibrations are typically in the range of 10-2000Hz and result in displacements of only a few microns, at the contact interface. In the present study, a bench test has been developed to control more representative motions down to 1 mu m. The objective is to determine the minimum amplitude for fretting-corrosion degradation based on the evolution of contact resistance and to study the effects of the material, the contact force, the coating for these low displacement amplitudes. To obtain the limit of the appearance of fretting, a sub-micrometer incrementing displacement amplitude methodology was applied on high stiffness bench test including a double PZT actuator. It was found that the fretting degradation starts to occur from 2 mu m to 6 mu m when the contact force is from 0.5N to 2.5N with a tin coated terminal. Moreover pure copper, tin and nickel have similar amplitude fretting limits while noble metals confirm the absence of fretting up t