Trade-offs among ecosystem services and productivity in coffee-based agroforestry systems in Nicaragua

Many studies have measured biodiversity loss across the coffee intensification gradient; some studies have shown, with contradictory results, the trade-offs between biodiversity loss and coffee production increments. Plot assessments of tree diversity, soil conservation, carbon sequestration and coffee production are lacking. We characterized the structure, productivity, diversity, soil conservation and carbon sequestration of 40 coffee agroforestry systems in two different areas in Northern Nicaragua. Coffee management, environmental conditions and soils properties were also characterized to better understand the trade-offs among services within the plots and their dependence on the local environment. These agroforestry systems were chosen to maximize contrasts in terms of biophysical context, botanical composition and management practices. Results (preliminary) showed significant differences in the vegetation structure that enabled us to identify main clusters: CAFS with dense and diverse overstorey canopy, CAFS with high Musa density and CAFS with low density of overstorey canopy. Changes in vegetation structure reflected differences in farmers' strategies but did not affect the overall coffee yield or the conservation of soils. Coffee yields had strong variations among the plots, and this was mainly related to the amount of fertilizer applied. Neither carbon sequestered, soil conserved nor tree diversity have a significant negative relationship with coffee productivity. However, coffee yields were low comparing with other coffee areas in the region. These results open new perspectives to improve coffee agroforestry systems' structural complexity and their relative ecosystem services without affecting their overall productivity. Further investigations and a more stratified sampling to get a good grasp of the whole range of variability (in highly productive areas with less shade canopy) are needed to fully understand the mechanisms involved in trade-offs

Microscopic calculations of double and triple Giant Resonance excitation in heavy ion collisions

We perform microscopic calculations of the inelastic cross sections for the double and triple excitation of giant resonances induced by heavy ion probes within a semicalssical coupled channels formalism. The channels are defined as eigenstates of a bosonic quartic Hamiltonian constructed in terms of collective RPA phonons. Therefore, they are superpositions of several multiphonon states, also with different numbers of phonons and the spectrum is anharmonic. The inclusion of (n+1) phonon configurations affects the states whose main component is a n-phonon one and leads to an appreacible lowering of their energies. We check the effects of such further anharmonicities on the previous published results for the cross section for the double excitation of Giant Resonances. We find that the only effect is a shift of the peaks towards lower energies, the double GR cross section being not modified by the explicity inclusion of the three-phonon channels in the dynamical calculations. The latters give an important contribution to the cross section in the triple GR energy region which however is still smaller than the experimental available data. The inclusion of four phonon configurations in the structure calculations does not modify the results.Comment: Revtex4, to be published in PR

Electronic structure and magnetic properties of epitaxial FeRh(001) ultra-thin films on W(100)

Epitaxial FeRh(100) films (CsCl structure, $\sim 10\ ML\$ thick), prepared {\it in-situ} on a W(100) single crystal substrate, have been investigated via valence band and core level photoemission. The presence of the temperature-induced, first-order, antiferromagnetic to ferromagnetic (AF$\rightarrow$ FM) transition in these films has been verified via linear dichroism in photoemission from the Fe 3$p$ levels. Core level spectra indicate a large moment on the Fe atom, practically unchanged in the FM and AF phases. Judging from the valence band spectra, the metamagnetic transition takes place without substantial modification of the electronic structure. In the FM phase, the spin-resolved spectra compare satisfactorily to the calculated spin-polarized bulk band structure.Comment: 7 pages, 5 figure

Distribution spatio-temporelle des précipitations de type PMP utilisant un modèle de champ de pluie : application en Suisse

Les précipitations maximales probables (PMP) représentent les pluies extrêmes les plus élevées raisonnablement possibles (période de retour d'environ 10'000 ans) qui sont notamment utilisées pour dimensionner des barrages contre des crues extrêmes. En Suisse, ces précipitations sont représentées sous forme des cartes avec une résolution horizontale de 2 km. Cet article présente la méthode nécessaire pour utiliser les cartes de type PMP dans le but final d'estimer la crue maximale probable (PMF) pour les barrages. Cette méthode a été développée suite aux problèmes rencontrés avec une application inadéquate des PMP. Ces problèmes peuvent être résolus par la distribution spatio-temporelle des PMP avec une résolution affinée conservant les données physiques. La conception de la méthode de distribution spatio-temporelle des précipitations se base sur la création de champ de pluie. Cette méthode a été validée en s'appuyant sur des évènements extrêmes de type supercellulaire et confirme la possibilité de reproduire des structures réelles de pluie en utilisant un algorithme de champ de pluie

Modeling the thickness dependence of the magnetic phase transition temperature in thin FeRh films

FeRh and its first-order phase transition can open new routes for magnetic hybrid materials and devices under the assumption that it can be exploited in ultra-thin-film structures. Motivated by experimental measurements showing an unexpected increase in the phase transition temperature with decreasing thickness of FeRh on top of MgO, we develop a computational model to investigate strain effects of FeRh in such magnetic structures. Our theoretical results show that the presence of the MgO interface results in a strain that changes the magnetic configuration which drives the anomalous behavior

New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products

In this paper, we study the impact of the inclusion of the recently measured beta decay properties of the $^{102;104;105;106;107}$Tc, $^{105}$Mo, and $^{101}$Nb nuclei in an updated calculation of the antineutrino energy spectra of the four fissible isotopes $^{235, 238}$U, and $^{239,241}$Pu. These actinides are the main contributors to the fission processes in Pressurized Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo and Nb isotopes have been found to play a major role in the $\gamma$ component of the decay heat of $^{239}$Pu, solving a large part of the $\gamma$ discrepancy in the 4 to 3000\,s range. They have been measured using the Total Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations are performed using the information available nowadays in the nuclear databases, summing all the contributions of the beta decay branches of the fission products. Our results provide a new prediction of the antineutrino energy spectra of $^{235}$U, $^{239,241}$Pu and in particular of $^{238}$U for which no measurement has been published yet. We conclude that new TAS measurements are mandatory to improve the reliability of the predicted spectra.Comment: 10 pages, 2 figure

Anharmonic vibrations in nuclei

In this letter, we show that the non-linearitites of large amplitude motions in atomic nuclei induce giant quadrupole and monopole vibrations. As a consequence, the main source of anharmonicity is the coupling with configurations including one of these two giant resonances on top of any state. Two-phonon energies are often lowered by one or two MeV because of the large matrix elements with such three phonon configurations. These effects are studied in two nuclei, 40Ca and 208Pb

Les Jessour dans le Sud-Est tunisien : un système hydro-agricole ancestral dans un milieu aride

Malgré un bilan hydrique largement déficitaire dans le Sud-Est tunisien à climat aride, l'Homme a pu pratiquer l'agriculture en développant la technique des Jessour. Cette technique est confrontée aujourd'hui au risque d'abandon suite aux changements socio-économiques qu'a connus cette région au cours des cinq dernières décennies. Cet article fait le point de l'intérêt hydro-agricole des Jessour et présente les grandes lignes d'une recherche visant à évaluer le bilan hydrique de parcelles utilisant cette technique. Le but est de participer à la conservation de ce savoir-faire ancestral et d'optimiser son utilisation

Instability of the rhodium magnetic moment as origin of the metamagnetic phase transition in alpha-FeRh

Based on ab initio total energy calculations we show that two magnetic states of rhodium atoms together with competing ferromagnetic and antiferromagnetic exchange interactions are responsible for a temperature induced metamagnetic phase transition, which experimentally is observed for stoichiometric alpha-FeRh. A first-principle spin-based model allows to reproduce this first-order metamagnetic transition by means of Monte Carlo simulations. Further inclusion of spacial variation of exchange parameters leads to a realistic description of the experimental magneto-volume effects in alpha-FeRh.Comment: 10 pages, 13 figures, accepted for publication in Phys. Rev.