SOYBEAN PRODUCTION COSTS: AN ANALYSIS OF THE UNITED STATES, BRAZIL, AND ARGENTINA

U.S. farmers' share of world soybean exports has declined, while Brazil and Argentina are gaining. There is much debate concerning the competitive advantage of U.S. versus Latin American soybean producers. A detailed analysis of soybean production costs under different systems and technologies in the United States, Argentina, and Brazil was conducted.Crop Production/Industries,

Evaluación foliar de aceites esenciales de especies de Eucalytus sp. susceptibles al daño de Gonipterus scutellatus (coleoptera: curculionidae)

- Huerta, A.; García, D. Departamento de Silvicultura, Facultad de Ciencias Forestales, Universidad de Chile. Casilla 9206, Santiago, Chile. - Chiffelle, I . Departamento de Agroindustria y Enología, Facultad de Ciencias Agronómicas, Universidad de Chile. Casilla 1004, Santiago, Chile.Dada la presencia en Chile desde 1998 del insecto defoliador Gonipterus scutellatus (Coleoptera: Curculionidae), el cual está causando serios daños en las plantaciones de Eucalipto desde las regiones IV a la VIII, se evaluó la composición de los principales aceites esenciales volátiles entre tres especies de eucalipto cultivadas en Chile (E. globulus, E. nitens y E. camaldulensis) por su rol en la resistencia al ataque de este insecto. La identificación de los aceites esenciales se hizo por cromatografía de gases. El gas de arrastre fue vapor de agua y las muestras se diluyeron 20 veces en n-hexano y se compararon con patrones preestablecidos. Se hicieron tres repeticiones por especie de eucalipto de 20 minutos a 100ºC. Como resultado se obtuvo que el componente esencial de las hojas de eucalipto más abundante fue el eucalyptol, destacándose en las hojas de E. nitens, donde tuvo una participación superior al 50%, seguido de E. globulus, con un 25% de presencia y finalmente, en E. camaldulensis con cerca del 2%. Este aceite esencial se asocia a un papel defensivo. El aceite esencial proveniente de las hojas de E. camaldulensis tuvo una mayor participación de ciclo azuleno (20%), presentándose únicamente en esta especie. También se encontraron otros aceites esenciales en menor proporción, tales como: alfa-pineno, camphino, entre otros. Por último, se recomienda proseguir con estudios conducentes a profundizar sobre el comportamiento de los aceites esenciales como factor de resistencia/susceptibilidad al daño causado por insectos

Dynamical Encoding by Networks of Competing Neuron Groups: Winnerless Competition

Following studies of olfactory processing in insects and fish, we investigate neural networks whose dynamics in phase space is represented by orbits near the heteroclinic connections between saddle regions (fixed points or limit cycles). These networks encode input information as trajectories along the heteroclinic connections. If there are N neurons in the network, the capacity is approximately e(N-1)!, i.e., much larger than that of most traditional network structures. We show that a small winnerless competition network composed of FitzHugh-Nagumo spiking neurons efficiently transforms input information into a spatiotemporal output

Entanglement and alpha entropies for a massive scalar field in two dimensions

We find the analytic expression of the trace of powers of the reduced density matrix on an interval of length L, for a massive boson field in 1+1 dimensions. This is given exactly (except for a non universal factor) in terms of a finite sum of solutions of non linear differential equations of the Painlev\'e V type. Our method is a generalization of one introduced by Myers and is based on the explicit calculation of quantities related to the Green function on a plane, where boundary conditions are imposed on a finite cut. It is shown that the associated partition function is related to correlators of exponential operators in the Sine-Gordon model in agreement with a result by Delfino et al. We also compute the short and long distance leading terms of the entanglement entropy. We find that the bosonic entropic c-function interpolates between the Dirac and Majorana fermion ones given in a previous paper. Finally, we study some universal terms for the entanglement entropy in arbitrary dimensions which, in the case of free fields, can be expressed in terms of the two dimensional entropy functions.Comment: 13 pages, 2 figure

Free Form of the Foldy-Wouthuysen Transformation in External Electromagnetic Fields

We derive the exact Foldy-Wouthuysen transformation for Dirac fermions in a time independent external electromagnetic field in the basis of the Ritus eigenfunctions, namely the eigenfunctions of the operator $(\gamma \cdot \Pi)^2$, with $\Pi^\mu = p^\mu - e A^\mu$. In this basis, the transformation acquires a free form involving the dynamical quantum numbers induced by the field.Comment: 8 pages. Accepted in J. Phys. A: Math. and Theo. (Fast Track Communication

X-ray photoelectron spectroscopy studies of non-stoichiometric superconducting NbB2+x

Polycrystalline samples of NbB2+x with nominal composition (B/Nb) = 2.0, 2.1, 2.2, 2.3, 2.4 and 2.5 were studied by X-ray photoelectron spectroscopy (XPS). The spectra revealed Nb and B oxides on the surface of the samples, mainly B2O3 and Nb2O5. After Ar ion etching the intensity of Nb and B oxides decreased. The Nb 3d5/2 and B 1s core levels associated with the chemical states (B/Nb) were identified and they do not change with etching time. The Binding Energy of the Nb 3d5/2 and B 1s core levels increase as boron content increases, suggesting a positive chemical shift in the core levels. On the other hand, analysis of Valence Band spectra showed that the contribution of the Nb 4d states slightly decreased while the contribution of the B 2p(pi) states increased as the boron content increased. As a consequence, the electronic and superconducting properties were substantially modified, in good agreement with band-structure calculations.Comment: 10 pages, 7 figures, 1 tabl

Dolomite crystal morphologies in dolocretes and lacustrine deposits from the Madrid and Almazán basins

Comunicación presentada en el IX Congreso Geológico de España, Huelva, 12-14 septiembre 2016.[ES] Este trabajo describe morfologías de cristales de dolomita, observados tanto en microscopio petrográfico como electrónico, de dolocretas y de depósitos carbonático-evaporíticos de ambientes lacustres someros, tanto del Paleógeno de la Cuenca de Almazán como del Mioceno de la Cuenca de Madrid. Se han identificado 6 morfotipos: 1) Tubos de dolomita; 2) Cilindros de dolomita vacuolar; 3) Romboedros de dolomita; 4) Cristales de dolomita esferoidal; 5) Cristales de dolomita con forma de capullo; y 6) Dolomita en mancuerna. Las morfologías dominantes en dolocretas son los romboedros, los esferoides, y las mancuernas. Por otro lado, en los depósitos lacustres la variedad de morfologías es mucho mayor, siendo las más comunes: los tubos, los cilindros de dolomita vacuolar, los esferoides y los cristales de dolomita con forma de capullo. La morfología de los cristales de dolomita puede ser un indicador de procesos bióticos o abióticos en su precipitación, aunque han de tenerse en cuenta otros indicadores para comprender la influencia de dichos procesos.[EN] This paper describes the dolomite crystal morphologies, observed under petrographic microscope and SEM, from dolocretes and carbonate-evaporitic lacustrine deposits. Samples analysed come from the Paleogene of the Almazán basin and the Miocene of the Madrid basin. Six morphotypes have been identified: 1) Dolomite tubes; 2) Vacuolar dolomite cylinders; 3) Rhombohedral dolomite crystals; 4) Spheroidal dolomite crystals; 5) Cocoon-shaped dolomite crystals; and 6) Dolomite dumbbells. Dominant morphotypes in dolocretes are: rhomboids; spheroids, and dumbbells. In lacustrine deposits the variety is higher and includes tubes, vacuolar dolomite cylinders, spheroids and cocoon-shaped dolomite crystals. Dolomite crystal morphology can be indicative of biotic or abiotic processes in dolomite precipitation, but other evidences must be taken into account to understand the influence of the mentioned processes.Este trabajo ha sido financiado por los proyectos de investigación CGL-2011-27826-CO2-02 y CGL2014- 54818-P del Ministerio de Economía y Competitividad.Peer reviewe

Entanglement and alpha entropies for a massive Dirac field in two dimensions

We present some exact results about universal quantities derived from the local density matrix, for a free massive Dirac field in two dimensions. We first find the trace of powers of the density matrix in a novel fashion, which involves the correlators of suitable operators in the sine-Gordon model. These, in turn, can be written exactly in terms of the solutions of non-linear differential equations of the Painlev\'e V type. Equipped with the previous results, we find the leading terms for the entanglement entropy, both for short and long distances, and showing that in the intermediate regime it can be expanded in a series of multiple integrals. The previous results have been checked by direct numerical calculations on the lattice, finding perfect agreement. Finally, we comment on a possible generalization of the entanglement entropy c-theorem to the alpha-entropies.Comment: Clarification in section 2, one reference added. 15 pages, 3 figure

A detailed determination of the a priori mixing angles in non-leptonic decays of hyperons

Non-leptonic Decays of Hyperons can provide a detailed determination of the a priori mixing angles that appear in physical hadrons in the approach in which non-perturbative flavor and parity violations are present in tiny pieces of the hadron mass operator. The determination of such angles in these decays will provide a bench mark to test their necessary universality-like property in other types of decays. Our main result is that the magnitudes of the a priori mixing angles can be determined quite accurately