221 research outputs found

    Sur les limites d'application du modèle de Stephens

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    Les conséquences de l'hypothèse de la conservation de j dans le modèle de Stephens sont analysées. Les conditions de l'applicabilité de cette hypothèse dans le cas des sous-couches isolées (l'extension est faite à N = 4 et N = 3) sont discutées et des explications en sont données. Dans les autres cas, un traitement exact des états propres du mouvement intrinsèque permet néanmoins l'extension du modèle de Stephens sans élargissement de la base de diagonalisation

    SU(2) × SU(2) × U(1) basis for symmetric SO(6) representations : matrix elements of the generators

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    Matrix elements of the group generators for the symmetric irreducible representations of SO(6) are explicitly calculated in a closed form employing the decomposition chain SO(6) ⊃ SU(2) x SU(2) x U(1) (which is different from the well known Wigner supermultiplet scheme). The relation to the Gel'fand Tsetlin method using SO(6) ⊃ SO(5) ⊃ ... ⊃ SO(2) is indicated. An example of a physical application is given

    Self-consistent collective subspaces and diabatic/adiabatic motion in nuclei

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    We discuss the application of a theory of large-amplitude collective motion to a simple model mimicking the pairing-plus-quadrupole model of nuclear physics.Comment: 4 pages, RevTex using graphicx.sty, 1 postscript figures included. Talk presented at Conference on "Nuclear structure at the extremes" (June 17 - 19, 1998, Lewes, UK

    Multi-Phonon γ\gamma-Vibrational Bands and the Triaxial Projected Shell Model

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    We present a fully quantum-mechanical, microscopic, unified treatment of ground-state band and multi-phonon γ\gamma-vibrational bands using shell model diagonalization with the triaxial projected shell model. The results agree very well with data on the g- and γ\gamma-band spectra in 156170^{156-170}Er, as well as with recently measured 4+4^+ 2-phonon γ\gamma-bandhead energies in 166^{166}Er and 168^{168}Er. Multi-phonon γ\gamma-excitation energies are predicted.Comment: 4 pages, 4 figures, submitted to Phys. Lett.

    Parametrization of the octupole degrees of freedom

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    A simple parametrization for the octupole collective variables is proposed and the symmetries of the wave functions are discussed in terms of the solutions corresponding to the vibrational limit. [PACS: 21.60Ev, 21.60.Fw, 21.10.Re]Comment: 14 page

    An overview of the higher level classification of Pucciniomycotina based on combined analyses of nuclear large and small subunit rDNA sequences

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    Mycologia, Vol. 98, nº6In this study we provide a phylogenetically based introduction to the classes and orders of Pucciniomycotina (5Urediniomycetes), one of three subphyla of Basidiomycota. More than 8000 species of Pucciniomycotina have been described including putative saprotrophs and parasites of plants, animals and fungi. The overwhelming majority of these(,90%) belong to a single order of obligate plant pathogens, the Pucciniales (5Uredinales), or rust fungi. We have assembled a dataset of previously published and newly generated sequence data from two nuclear rDNA genes (large subunit and small subunit) including exemplars from all known major groups in order to test hypotheses about evolutionary relationships among the Pucciniomycotina. The utility of combining nuc-lsu sequences spanning the entire D1-D3 region with complete nuc-ssu sequences for resolution and support of nodes is discussed. Our study confirms Pucciniomycotina as a monophyletic group of Basidiomycota. In total our results support eight major clades ranked as classes (Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes,Cryptomycocolacomycetes,Cystobasidiomycetes, Microbotryomycetes,Mixiomycetes and Pucciniomycetes) and 18 orders

    AxPcoords & parallel AxParafit: statistical co-phylogenetic analyses on thousands of taxa

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    Background Current tools for Co-phylogenetic analyses are not able to cope with the continuous accumulation of phylogenetic data. The sophisticated statistical test for host-parasite co-phylogenetic analyses implemented in Parafit does not allow it to handle large datasets in reasonable times. The Parafit and DistPCoA programs are the by far most compute-intensive components of the Parafit analysis pipeline. We present AxParafit and AxPcoords (Ax stands for Accelerated) which are highly optimized versions of Parafit and DistPCoA respectively. Results Both programs have been entirely re-written in C. Via optimization of the algorithm and the C code as well as integration of highly tuned BLAS and LAPACK methods AxParafit runs 5–61 times faster than Parafit with a lower memory footprint (up to 35% reduction) while the performance benefit increases with growing dataset size. The MPI-based parallel implementation of AxParafit shows good scalability on up to 128 processors, even on medium-sized datasets. The parallel analysis with AxParafit on 128 CPUs for a medium-sized dataset with an 512 by 512 association matrix is more than 1,200/128 times faster per processor than the sequential Parafit run. AxPcoords is 8–26 times faster than DistPCoA and numerically stable on large datasets. We outline the substantial benefits of using parallel AxParafit by example of a large-scale empirical study on smut fungi and their host plants. To the best of our knowledge, this study represents the largest co-phylogenetic analysis to date. Conclusion The highly efficient AxPcoords and AxParafit programs allow for large-scale co-phylogenetic analyses on several thousands of taxa for the first time. In addition, AxParafit and AxPcoords have been integrated into the easy-to-use CopyCat tool

    Internet of Things for Sustainable Forestry

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    Forests and grasslands play an important role in water and air purification, prevention of the soil erosion, and in provision of habitat to wildlife. Internet of Things has a tremendous potential to play a vital role in the forest ecosystem management and stability. The conservation of species and habitats, timber production, prevention of forest soil degradation, forest fire prediction, mitigation, and control can be attained through forest management using Internet of Things. The use and adoption of IoT in forest ecosystem management is challenging due to many factors. Vast geographical areas and limited resources in terms of budget and equipment are some of the limiting factors. In digital forestry, IoT deployment offers effective operations, control, and forecasts for soil erosion, fires, and undesirable depositions. In this chapter, IoT sensing and communication applications are presented for digital forestry systems. Different IoT systems for digital forest monitoring applications are also discussed

    Molecular techniques revolutionize knowledge of basidiomycete evolution

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    Desafíos políticos de los países de inmigración

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    13 págs.-- Publicado en "Confluencia XXI. Revista de Pensamiento Político" (México), nº 3 (Oct-Dic 2008) bajo el título monográfico "Migrantes: ¿Por qué se van? ¿Por qué se quedan?".Las migraciones, una práctica tan antigua como la propia condición humana, se han convertido en un factor estructural de primer orden, en uno de los macrofenómenos más definitorios de nuestra época y en un complejo reto para las sociedades contemporáneas. En prácticamente todos los países del mundo, todo lo que concierne a este complejo fenómeno ocupa un lugar destacado en la agenda política. La gestión, el control y la integración de los movimientos internacionales de personas se presentan como un policy field de creciente y prioritaria relevancia. No se trata, sin embargo, de una cuestión de mera moda: el número de países implicados de manera significativa en las migraciones internacionales ha aumentado considerablemente, hasta el punto de que resulta realmente difícil encontrar algún Estado que no sea bien un país de inmigración, bien un país de emigración o bien ambas cosas a la vez, cuando no al menos un país de tránsito. No ha de extrañar entonces que la mayoría de los gobiernos haya tomado conciencia de la necesidad de ofrecer una respuesta en términos legales e institucionales a un fenómeno de carácter permanente que puede llegar a alterar la estructura demográfica, social, cultural, económica y laboral de un país. Dada la complejidad de la cuestión, y por cuestiones de economía argumentativa, aquí se abordará de manera fundamental desde la perspectiva de los países receptores, que, por lo demás, es también la adoptada en forma habitual por los países europeos que registran mayor inmigración. Sin embargo, el fenómeno migratorio es fundamentalmente transnacional y tiene fehacientes repercusiones en los países de emigración.Peer reviewe
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