342 research outputs found

    Evolution of sexual dimorphism of wing shape in the Drosophila melanogaster subgroup

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    Background: Sexual dimorphism of body size has been the subject of numerous studies, but few have examined sexual shape dimorphism (SShD) and its evolution. Allometry, the shape change associated with size variation, has been suggested to be a main component of SShD. Yet little is known about the relative importance of the allometric and non-allometric components for the evolution of SShD. Results: We investigated sexual dimorphism in wing shape in the nine species of the Drosophila melanogaster subgroup. We used geometric morphometrics to characterise wing shape and found significant SShD in all nine species. The amount of shape difference and the diversity of the shape changes evolved across the group. However, mapping the divergence of SShD onto the phylogeny of the Drosophila melanogaster subgroup indicated that there is little phylogenetic signal. Finally, allometry accounted for a substantial part of SShD, but did not explain the bulk of evolutionary divergence in SShD because allometry itself was found to be evolutionarily plastic. Conclusion: SShD in the Drosophila wing can evolve rapidly and therefore shows only weak phylogenetic structure. The variable contribution of allometric and non-allometric components to the evolutionary divergence of SShD and the evolutionary plasticity of allometry suggest that SShD and allometry are influenced by a complex interaction of processes

    Automatic determination of landmark coordinates for honey bee forewing venation using a new MATLAB-based tool

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    In this study, a novel and free-to-use MATLAB-based tool (WingMarks) is presented, aimed at facilitating the geometric morphometric analysis of honey bee forewing venation through automatic recognition of vein junctions. Firstly, the ability of the new software to analyze wing images obtained by different optical equipment was evaluated. Even when a low-end USB-microscope was used for image collection, it reached 100% precision in the automatic detection of the landmarks for 87% of the samples, and most of failures corresponded to a single point and were easily corrected. The measurement error of WingMarks software was studied through repeated analysis of the same wing image, evincing that landmark determination was highly repeatable, even higher than that of widely used tpsDig manual software. In addition, a field test with 720 specimens from three subspecies (A. m. iberiensis, A. m. ligustica, and A. m. carnica) and from hybrid Buckfast bees, collected from 90 different colonies, was conducted. In conjunction with MorphoJ, the coordinates of the vein junctions extracted by the program led to an accurate classification of the specimens, confirmed by canonical variate analysis methods. WingMarks software can thus be deemed as a versatile, precise, and accurate tool for the automatic recognition of A. mellifera wing vein junctions, facilitating the identification of bee genetic diversity using geometric morphometrics. The program is available under Creative Commons license and can be easily adapted to different insect species

    Spin coherence of holes in GaAs/AlGaAs quantum wells

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    The carrier spin coherence in a p-doped GaAs/(Al,Ga)As quantum well with a diluted hole gas has been studied by picosecond pump-probe Kerr rotation with an in-plane magnetic field. For resonant optical excitation of the positively charged exciton the spin precession shows two types of oscillations. Fast oscillating electron spin beats decay with the radiative lifetime of the charged exciton of 50 ps. Long lived spin coherence of the holes with dephasing times up to 650 ps. The spin dephasing time as well as the in-plane hole g factor show strong temperature dependence, underlining the importance of hole localization at cryogenic temperatures.Comment: 5 pages, 4 figures in PostScript forma

    Thermoelectric Higher Manganese Silicide: Synthetized, sintered and shaped simultaneously by selective laser sintering/Melting additive manufacturing technique

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    Complex geometry legs were advantageous to obtain higher thermoelectric potential due to a better thermal dissipation. Among all industrial processes, additive manufacturing using a selective laser sintering (SLS) or melting (SLM) techniques is the most promising to obtain such complex-shape legs without machining step. In this work, for the first time, Higher Manganese Silicide (HMS) sheet samples were synthetized, sintered and shaped simultaneously by additive manufacturing from ball milled manganese and silicon powder. Impact of surface power density and scanning rate of the laser on the microstructural and structural properties was discussed for some SLS/M parameters. Characterizations have shown that both densification and pure HMS phase can be obtained by SLS/M

    Redescription of Lemuricola (Madoxyuris) bauchoti (Nematoda, Oxyuridae) from Lemur catta in Madagascar

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    Lemuricola (Madoxyuris) bauchoti Chabaud, Brygoo et Petter, 1965 is redescribed from material collected from the ring-tailed lemur, Lemur catta, from the Beza Mahafaly Special Reserve in Madagascar using the scanning electron microscope. This is a new host record and the first oxyurid reported from the ring-tailed lemur. Previously, records of each species of the subgenus Madoxyuris have been restricted to a single host species, but the close relationship between these nematodes and their Strepsirrhini hosts will only be proven when additional records fill in the gaps in their distribution.Fil: Robles, Maria del Rosario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Loudon, James E.. State University of Colorado at Boulder; Estados UnidosFil: Kinsella, John M.. Helm West Laboratory; Estados UnidosFil: Hunter Ishikawa, Mandala. State University of Colorado - Fort Collins; Estados UnidosFil: Miller, David S.. State University of Colorado - Fort Collins; Estados UnidosFil: Sauther, Michelle L.. State University of Colorado at Boulder; Estados UnidosFil: Cuozzo, Frank P.. University of North Dakota; Estados Unido

    Molecular and ecophysiological characterisation of the Tunisian bee: Apis mellifera intermissa

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    This study concerns the morphological identification, the molecular features and the eco-physiology of the Tunisian bee Apis mellifera intermissa, focused on 655 colonies from 7 populations: Kroumirie Moogod, North East Cap Bon, Ridge and Tell, high steppe, lower steppe, Atlas Chainon, Jeffara and Ouarra. The geometric morphometry of the interior wing of the bee shows polymorphism in size and shape. The size polymorphism is essentialy related to beekeeping practices. The characterization by means of a cytoplasmic molecular marker - mitochondrial DNA (DNA m t) - showed that the Tunisian bee originated from lineage A, which contradicts its membership to lineage M as demonstrated by a study based on biometric data only (Ruttner, 1988). There is a genetic polymorphism of the Tunisian bee in the presence of four haplotypes: A1, A8, A9 and A4. The distribution of the A4 and A9 haplotypes depends on ecological conditions. Foreign haplotypes are present in the region of Ghardimaou near the Algerian border (C7 haplotype). The study of some ecophysiological parameters in colonies of Apis mellifera intermissa from 5 sites showed that the Tunisian bee is endowed with a very marked disregard for all haplotypes (A1, A4, A8 and A9). However, we report the existence of a difference between these haplotypes in thermoregulation, oviposition and respiration of solitary bees. The temperature of the A1 and A8 haplotypes brood nest is around 36¬įC while the A9 and A4 haplotypes brood nest has a temperature of 34¬įC when weather conditions are extreme. The A4 and A9 haplotypes fall into hibernation, the temperature of the brood nest ranging between 22 and 28¬įC. The A1 and A8 haplotypes have a high tendency to lay A9 and A4 haplotypes, which however is variable, ranging from zero to average depending on climatic conditions. A study of respiration of isolated honeybees showed a difference in oxygen consumption between haplotypes A1/ A8 and A4/A9 at low temperatures

    Computer-aided engineering of enzymes for in vitro and in vivo production of novel precursors

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    Development of enzyme-based synthetic processes is often hampered by the lack of natural enzymes with requisite properties or specificities. With the potential offered nowadays by computer-aided molecular design and enzyme engineering techniques, we have seen in recent years numerous examples of successful enzyme designs that enabled tremendous improvements of catalytic properties for various applications, including catalysis of novel synthetic reactions. Nonetheless, progress in this field, in particular with computational techniques, is still required in order to fasten enzyme design and accelerate the generation of efficient biocatalysts. This lecture will report and discuss recent developments and specific research projects of our laboratory. Special emphasis will be placed on the contribution of computational methods in our strategies. Several areas will be covered: (i) development of computational methods for multi-scale molecular modelling and design inspired from artificial intelligence field [1-2]; (ii) computer-aided engineering of carbohydrate-active enzymes to conceive catalysts acting on non-natural substrates, chemically protected to integrate programmed chemo-enzymatic cascades, and ultimately produce antigenic oligosaccharide precursors [3-5]; (iii) structure -based engineering of enzymes to conceive an artificial metabolic pathway dedicated to in vivo production of non-natural methionine precursor 2,4-Dihydroxybutyric acid (DHB) [6]. This work was partially funded by the French National Research Agency (PROTICAD, ANR-12-MONU-0015-03; GLUCODESIGN ANR-08-PCVI-0002-02; SYNTHACS ANR-10-BTBR-05-01). [1] Traor√© S., Roberts K.E., Allouche D., Donald B.R., Andr√© I., Schiex T., Barbe S. 2016. Fast search algorithms for Computational Protein Design. J. Comp. Chem. 37(12):1048-58 [2] Traor√© S., Allouche D., Andr√© I., de Givry S., Katsirelos G., Schiex T. and Barbe S. 2013. A New Framework for Computational Protein Design through Cost Function Network Optimization Bioinformatics, 29(17), 2129-2136 [3] Verges A., Cambon E., Barbe S., Salamone S., Le Guen Y., Moulis C., Mulard L.A., Remaud-Sim√©on M., Andr√© I. 2015. Computer-aided engineering of a transglucosylase for the glucosylation of an unnatural disaccharide of relevance for bacterial antigen synthesis.ACS Catalysis. 5(2), 1186-1198 [4] Salamone S., Guerreiro C., Cambon E., Andr√© I., Remaud-Sim√©on M., Mulard L.A. 2015. Programmed chemo-enzymatic synthesis of the oligosaccharide component of a carbohydrate-based antibacterial vaccine candidate. Chem. Comm. 51, 2581-2584. [5] Champion E., Gu√©rin F., Moulis C., Barbe S., Tran T.-H., Morel S., Descroix K., Monsan P., Mourey L., Mulard L.A., Tranier S., Remaud-Sim√©on M., Andr√© I. 2012. Applying pairwise combinations of amino acid mutations for sorting out highly efficient glucosylation tools for chemo-enzymatic synthesis of bacterial oligosaccharides. J. Am. Chem. Soc. 134 (45), 18677‚Äď18688 [6] Walther T., Topham C., Irague R., Auriol C., Baylac A., Cordier H., Dressaire C., Lozano-Huguet L., Martineau N., Stodel M., Malbert Y., Maestracci M., Huet R., Andr√© I., Remaud-Sim√©on M., Fran√ßois J.-M. 2017. Construction of a synthetic methabolic pathway for biosynthesis of the non-natural methionine precursor 2,4-dihydroxybutyric acid. Submitte

    The SPL (II) at CERN, a Superconducting 3.5 GeV H- Linac

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    A revision of the physics needs and recent progress in the technology of superconducting (SC) RF cavities have triggered major changes in the design of a SC H-linac at CERN. With up to 5MW beam power, the SPL can be the proton driver for a next generation ISOL-type radioactive beam facility (√ĘEURISOL√Ę) and/or supply protons to a neutrino () facility (conventional superbeam + beta-beam or -factory). Furthermore the SPL can replace Linac2 and the PS booster (PSB), improving significantly the beam performance in terms of brightness, intensity, and reliability for the benefit of all proton users at CERN, including LHC and its luminosity upgrade. Compared with the first conceptual design, the beam energy is almost doubled (3.5GeV instead of 2.2 GeV) while the length is reduced by 40%. At a repetition rate of 50 Hz, the linac reuses decommissioned 352.2MHz RF equipment from LEP in the low-energy part. Beyond 90MeV the RF frequency is doubled, and from 180MeV onwards high-gradient SC bulkniobium cavities accelerate the beam to its final energy of 3.5GeV. This paper presents the overall design approach, together with the technical progress since the first conceptual design in 2000

    Resonant spin amplification of hole spin dynamics in two‚Äźdimensional hole systems: experiment and simulation

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    Spins in semiconductor structures may allow for the realization of scalable quantum bit arrays, an essential component for quantum computation schemes. Specifically, hole spins may be more suited for this purpose than electron spins, due to their strongly reduced interaction with lattice nuclei, which limits spin coherence for electrons in quantum dots. Here, we present resonant spin amplification (RSA) measurements, performed on a p-modulation doped GaAs-based quantum well at temperatures below 500 mK. The RSA traces have a peculiar, butterfly-like shape, which stems from the initialization of a resident hole spin polarization by optical orientation. The combined dynamics of the optically oriented electron and hole spins are well-described by a rate equation model, and by comparison of experiment and model, hole spin dephasing times of more than 70 ns are extracted from the measured data
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