Tropical river fisheries valuation: a global synthesis and critical review

River fisheries / Inland fisheries / Economic impact / Cost benefit analysis / Developing countries / River basin management / Wetlands / Valuation

Thermal entanglement in the nanotubular system Na_2V_3O_7

Macroscopic entanglement witnesses have been put forward recently to reveal nonlocal quantum correlations between individual constituents of the solid at nonzero temperatures. Here we apply a recently proposed universal entanglement witness, the magnetic susceptibility [New J. Phys. {\bf 7}, 258 (2005)] for the estimation of the critical temperature $T_c$ in the nanotubular system ${\rm Na_2V_3O_7}$ below which thermal entanglement is present. As a result of an analysis based on the experimental data for dc-magnetic susceptibility, we show that $T_c \approx 365$ K, which is approximately three times higher than the critical temperature corresponding to the bipartite entanglement.Comment: 6 pages, 3 figures, REVTeX

Réflexion sur la notion de services écologiques : étude de cas à Kotoudéni (Burkina Faso)

La notion de "services écosystémiques" a été introduite dans un but de conservation pour éclairer les liens entre la dynamique de la biodiversité et les valeurs que les humains lui accordent. L'article examine comment les propos des habitants d'un village de la province du Kénédougou au Burkina Faso, Kotoudéni, peuvent être traduits en termes de services écosystémiques. Des enquêtes semi-structurées menées auprès de 23 personnes ont eu pour but de situer socialement les interlocuteurs et de susciter leur discours sur les divers espaces de leur terroir, leur importance relative, les utilisations propres à chacun, mais également sur les religions, la "tradition" et les changements environnementaux et sociaux en cours. L'analyse de ces discours a permis de dégager une conception locale et paysanne des "services écosystémiques" qui a été confrontée aux catégories de la classification du MEA (2005). Les usages matériels mentionnés correspondent assez bien aux catégories du MEA, mais le principal service rendu par les écosystèmes est d'ordre spirituel : organiser le monde et assurer son harmonie par l'intermédiaire d'êtres invisibles (ancêtres et génies). Vouloir faire entrer ce service spirituel dans la catégorie des services culturels revient à le défigurer et à en nier la portée. La conclusion est qu'une telle catégorisation standardisée ne peut permettre de rendre compte des services culturels : pour ceux-ci le recours à des approches plus large de type anthropologique reste nécessaire

The Kohn mode for trapped Bose gases within the dielectric formalism

The presence of undamped harmonic center of mass oscillations of a weakly interacting Bose gas in a harmonic trap is demonstrated within the dielectric formalism for a previously introduced finite temperature approximation including exchange. The consistency of the approximation with the Kohn theorem is thereby demonstrated. The Kohn modes are found explicitly, generalizing an earlier zero-temperature result found in the literature. It is shown how the Kohn mode disappears from the single-particle spectrum, while remaining in the density oscillation spectrum, when the temperature increases from below to above the condensation temperature.Comment: 6 pages revte

A two-qubit Bell inequality for which POVM measurements are relevant

A bipartite Bell inequality is derived which is maximally violated on the two-qubit state space if measurements describable by positive operator valued measure (POVM) elements are allowed rather than restricting the possible measurements to projective ones. In particular, the presented Bell inequality requires POVMs in order to be maximally violated by a maximally entangled two-qubit state. This answers a question raised by N. Gisin.Comment: 7 pages, 1 figur

Assessment of Growth Support Potentials of Different Substrates for the Cultivation of Volvoriella Volvaceae

Four substrates (banana leaves, sawdust, palm trunk fibre and coconut coir) were screened for the cultivation of straw mushroom (Volvoriella volvaceae). Palm trunk fibre and coconut coir substrates did not support spawning and fruit body production of the test mushroom. Proximate analyses of the composted and spent substrates revealed marked reduction in crude fibre and increase in the protein content of the spent substrates. Treatment of the substrates with CaCO3 and rice bran increased the alkalinity of the banana and sawdust substrates. On banana leaves, spawn run took 21 days while sawdust substrate was totally colonized in 28 days. Pinheads appeared three days after transfer of the fully colonized substrates to the cropping room. Thirty one (31) flushes (each spanned 7 days) were recorded in 210 days. However, sawdust did not support the production of fruit bodies beyond the 24th flush which corresponded to day 161 from the initiation of pinheads. The biological efficiency was 19.93% for banana leaves and 10.05% for sawdust. The total fresh weight of fruit bodies produced from banana leaves and sawdust were 21.62kg and 10.91kg respectively. The mean length of stipe, area of pileus, fresh and dry weights of V. volvaceae cultivated on banana leaves substrate doubled those produced on sawdust substrate and were significantly different at P<0.05 Key words: Sawdust, banana leaves, nutrient composition, pH, Volvoriella volvaceae

Lower bound on the communication cost of simulating bipartite quantum correlations

Suppose Alice and Bob share a maximally entangled state of any finite dimension and each perform two-outcome measurements on the respective part of the state. It is known, due to the recent result of Regev and Toner, that if a classical model is augmented with two bits of communication then all the quantum correlations arising from these measurements can be reproduced. Here we show that two bits of communication is in fact necessary for the perfect simulation. In particular, we prove that a pair of maximally entangled four-dimensional quantum systems cannot be simulated by a classical model augmented by only one bit of communication.Comment: 5 pages, no figures. v2: filled gap in the proof of Sec. II

Anion emission from water molecules colliding with positive ions: Identification of binary and many-body processes

It is shown that negative ions are ejected from gas-phase water molecules when bombarded with positive ions at keV energies typical of solar-wind velocities. This finding is relevant for studies of planetary and cometary atmospheres, as well as for radiolysis and radiobiology. Emission of both H- and heavier (O- and OH-) anions, with a larger yield for H-, was observed in 6.6-keV 16O+ + H2O collisions. The ex-perimental setup allowed separate identification of anions formed in collisions with many-body dynamics from those created in hard, binary collisions. Most of the ani-ons are emitted with low kinetic energy due to many-body processes. Model calcu-lations show that both nucleus-nucleus interactions and electronic excitations con-tribute to the observed large anion emission yield.Comment: 5 pages, 4 figure

Stationary Properties of a Randomly Driven Ising Ferromagnet

We consider the behavior of an Ising ferromagnet obeying the Glauber dynamics under the influence of a fast switching, random external field. Analytic results for the stationary state are presented in mean-field approximation, exhibiting a novel type of first order phase transition related to dynamic freezing. Monte Carlo simulations performed on a quadratic lattice indicate that many features of the mean field theory may survive the presence of fluctuations.Comment: 5 pages in RevTex format, 7 eps/ps figures, send comments to "mailto:[email protected]", submitted to PR