Composition floristique et potentiel fourrager des principaux ligneux des parcours d’accueil des transhumants dans la Basse et Moyenne Vallée de l’Ouémé en zone guinéo-soudanienne du Bénin

Objectifs: Les ligneux fourragers constituent une ressource alimentaire dans la zone d’accueille des bovins transhumants en saison sèche. L’objectif de cette étude était d’inventorier les ligneux fourragers des parcours des transhumants de la Basse et Moyenne Vallée de l’Ouémé, d’évaluer leur contribution pour l'alimentation des bovins transhumants en saison sèche et d’analyser leurs modes d’utilisation en vue de l'amélioration de la gestion de l'écosystème.Méthodologie et Résultats: Des suivis des troupeaux au pâturage ont été effectués pour identifier les principaux ligneux fourragers. Les mesures sur les ligneux ont été réalisées dans 181 placeaux de 50 m X 50 m installées au hasard selon le type de sol et de végétation. La méthode non destructive été a utilisée pour évaluer la biomasse foliaire. Pterocarpus santalinoides (Teck africain), Kigelia africana (Saucissonier), Lonchocharpus sericeus (Lilas du Sénégal) Mitragyna inermis (Pied d’éléphant), Daniellia oliveri (baumier d’Ilorin) et Vitex doniana (Prunier noir) étaient les ligneux présentant un grand intérêt pastoral. La biomasse foliaire a varié de 5 à 346,90 kg MS / ha et la capacité de charge de 0,003 à 0,185 unité de bétail tropical par hectare. Le mode d'exploitation des ligneux est basé sur l'élagage des branches et l'abattage.Conclusions et application des résultats: La présente étude a montré que les ligneux fourragers tels que D. oliveri, K. africana, L. sericeus, M. inermis, P. santalinoides et V. doniana sont prioritaires pour l'alimentation des bovins transhumants pendant la saison sèche. Cependant, les modes d'utilisation et le surpâturage compromettent leur régénération naturelle. Il est nécessaire d'améliorer la gestion durable des pâturages afin de continuer à alimenter le bétail pendant la saison sèche. Il est également important de développer des moyens efficaces de régénération de ces espèces ligneuses en utilisant des politiques de gestion participative des ressources mises en oeuvre pour assurer la durabilité des services sociaux et pastoraux.Mots clés: ligneux fourragers, caractéristique structurale, biomasse foliaire, capacité de charge, végétation, BéninEnglish Title: Floristic composition and forage potential of the main tree fodder of transhumant rangeland in the Lower and Medium Oueme Valley in the Guineo-Sudanean zone of BeninEnglish AbstractObjectives: Tree forage is a feed resource in area receiving the transhumant ruminants, during the dry season. The objective of this study was to inventory fodder trees of the rangelands of the Lower and Mean Valley of Oueme, to evaluate their contribution to animal feeding and to analyze the modes of use in order for better management of the ecosystem.Methodology and Results: Grazing surveys were conducted to identify the main forage trees. The data were collected in 181 plots of 50 m X 50 m installed randomly according to type of soil and vegetation. The nondestructive method was used to evaluate tree leaf biomass. Fodder tree plants such as Pterocarpussantalinoides (African teak), Kigelia africana (Sausage tree), Lonchocharpus sericeus (Senegal lilac) Mitragyna inermis(Elephant foot), Daniellia oliveri (West African copal) and Vitex doniana (Black plum tree) have shown great pastoral interest. Leaf biomass varied from 5 to 346.90 kg MS / ha and carrying capacity from 0.003 to 0,185 Tropical Livestock Unit per ha. The mode of use of the trees leaves is based on the pruning of the branches and the felling.Conclusions and application of findings: The present study showed that the fodder trees such as D. oliveri, K. africana, L. sericeus, M. inermis, P. santalinoides, and V. doniana are priorities for rangelands feeding during dry season by transhumant farmer. However, the modes of use and the overgrazing of trees, compromise their natural regeneration. There is a need to improve sustainable management of rangelands in order to continue to feed the cattle during the dry season. So, it’s also important to develop effective means of regeneration of these woody species by using participatory resource management policies implemented to ensure sustainability of social and pastoral services.Keywords: Ligneous forage, structural characteristic, leaf biomass, carrying capacity, vegetation, Beni

The Nucleon Spectral Function at Finite Temperature and the Onset of Superfluidity in Nuclear Matter

Nucleon selfenergies and spectral functions are calculated at the saturation density of symmetric nuclear matter at finite temperatures. In particular, the behaviour of these quantities at temperatures above and close to the critical temperature for the superfluid phase transition in nuclear matter is discussed. It is shown how the singularity in the thermodynamic T-matrix at the critical temperature for superfluidity (Thouless criterion) reflects in the selfenergy and correspondingly in the spectral function. The real part of the on-shell selfenergy (optical potential) shows an anomalous behaviour for momenta near the Fermi momentum and temperatures close to the critical temperature related to the pairing singularity in the imaginary part. For comparison the selfenergy derived from the K-matrix of Brueckner theory is also calculated. It is found, that there is no pairing singularity in the imaginary part of the selfenergy in this case, which is due to the neglect of hole-hole scattering in the K-matrix. From the selfenergy the spectral function and the occupation numbers for finite temperatures are calculated.Comment: LaTex, 23 pages, 21 PostScript figures included (uuencoded), uses prc.sty, aps.sty, revtex.sty, psfig.sty (last included

Zero temperature string breaking in lattice quantum chromodynamics

The separation of a heavy quark and antiquark pair leads to the formation of a tube of flux, or "string", which should break in the presence of light quark-antiquark pairs. This expected zero-temperature phenomenon has proven elusive in simulations of lattice QCD. We study mixing between the string state and the two-meson decay channel in QCD with two flavors of dynamical sea quarks. We confirm that mixing is weak and find that it decreases at level crossing. While our study does not show direct effects of internal quark loops, our results, combined with unitarity, give clear confirmation of string breaking.Comment: 20 pages, 7 figures. With small clarifications and two additions to references. Submitted to Phys. Rev.

Heavy-light mesons with staggered light quarks

We demonstrate the viability of improved staggered light quarks in studies of heavy-light systems. Our method for constructing heavy-light operators exploits the close relation between naive and staggered fermions. The new approach is tested on quenched configurations using several staggered actionsn combined with nonrelativistic heavy quarks. The B_s meson kinetic mass, the hyperfine and 1P-1S splittings in B_s, and the decay constant f_{B_s} are calculated and compared to previous quenched lattice studies. An important technical detail, Bayesian curve-fitting, is discussed at length.Comment: 38 pages, figures included. v2: Entry in Table IX corrected and other minor changes, version appearing in Phys. Rev.

Modelling laser-atom interactions in the strong field regime

We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.Comment: 11 pages, 5 figure

Direct Measurement of the Pseudoscalar Decay Constant fD+

The absolute branching fraction of $D^+ \to \mu^+ \nu$ has been directly measured by an analysis of a data sample of about 33 ${\rm pb^{-1}}$ collected around $\sqrt{s}=3.773$ GeV with the BES-II at the BEPC. At these energies, $D^-$ meson is produced in pair as $e^+e^-\to D^{+} D^{-}$. A total of $5321 \pm 149 \pm 160$ $D^-$ mesons are reconstructed from this data set. In the recoil side of the tagged $D^-$ mesons, $2.67\pm1.74$ purely leptonic decay events of $D^+ \to \mu^+ \nu$ are observed. This yields a branching fraction of $BF(D^+ \to \mu^+ \nu_{\mu}) = (0.122^{+0.111}_{-0.053}\pm 0.010)$, and a corresponding pseudoscalar decay constant $f_{D^+}=(371^{+129}_{-119}\pm 25)$ MeV.Comment: 7 pages, 8 figures, Submitted to Physics Letters B in October, 200

Sex Segregation and Salary Structure in Academia

This article reports a study of aggregate unit salary levels, within a major research university. We analyze these salary levels, as they are influenced by unit sex composition, and modified by unit attainment levels—where unit refers to the departments, colleges and schools, and other academic divisions of the university. We investigate three central issues of sex and salary, previously overlooked in salary studies of academic employees: Do high proportions of women depress men's unit salary levels ("competition" hypothesis)? Are women's salary levels higher in male-dominated, and lower in female-dominated, units ("concentration" hypothesis)? Are men salary-compensated for working with women ("compensation" hypothesis)? The findings support none of these hypotheses. Rather, the relationship between unit sex composition and salary rests upon the connection between units' composition and attainment levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69126/2/10.1177_073088848100800103.pd

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair