Seasonal Growth Curves of Perennial Ryegrass in Mexico

An experiment was established at Colegio de Postgraduados Research Station, Texcoco, México to evaluate the seasonal pattern of growth curve of perennial ryegrass (Lolium perenne) swards. Growth rate increases rapidly from a low level immediately after defoliation, and eventually reaches an equilibrium level as the amount of green leaf in the sward stabilize. The time required to reach this state varied according to the season of year, with the four seasons ranked in the order: spring (4 weeks) \u3c summer (5 weeks) \u3c autumn and winter (6 weeks). Once swards reached equilibrium, growth rates started to decline as a consequence of an increase in dead material and pseudostem. These increases were highest in spring and lowest in winter. The results of this study suggest that sward management to maximise herbage production and utilisation in ryegrass swards must be done once the highest green leaf mass is reached. In this trial, it was reached at 5, 6, 6 and 4 weeks in summer, autumn, winter and spring, respectively

Large quantum nonlinear dynamic susceptibility of single-molecule magnets

The nonlinear dynamical response of Mn$_{12}$ single-molecule magnets is experimentally found to be very large, quite insensitive to the spin-lattice coupling constant, and displaying peaks reversed with respect to classical superparamagnets. It is shown that these features are caused by the strong field dependence of the relaxation rate due to the detuning of energy levels between which tunneling takes place. The nonlinear susceptibility technique, previously overlooked, is thus proposed as a privileged probe to ascertain the occurrence of quantum effects in mesoscopic magnetic systems.Comment: 4 pages, 4 figure

Population genetic structure and colonization sequence of Drosophila subobscura in the Canaries and Madeira Atlantic islands as inferred by autosomal, sex-linked and mtDNA traits

The genetic structure In Atlantic Islands and continental populations of Drosophila subobscura has been studied using autosomal and sex-linked allozymes and ml tochondrial DNA (mtDNA) haplotypes. From the data it Is deduced that whereas the Canary Islands have long been isolated, the neighboring island of Madeira has been subjected to continuous migration from the mainland. In addition, sex-linked allo zymes and mtDNA data show a large divergence between the geologically younger western Islands of the Canarian Archipelago and the older central ones, finding strong founder effects In the former. Divergence rates of sex-linked and mltochon drlal genes relative to autosomlc loci several times higher than expected under neutrality have been explained by differential migration between sexes. The Ca narian Archipelago colonization fits in well with a stepping-stone model of a direc tional east-west migration that parallels the geological origin of these Islands.info:eu-repo/semantics/publishedVersio

Trapping of three-dimensional electrons and transition to two-dimensional transport in the three-dimensional topological insulator Bi2Se3 under high pressure

[EN] This paper reports an experimental and theoretical investigation on the electronic structure of bismuth selenide (Bi2Se3) up to 9 GPa. The optical gap of Bi2Se3 increases from 0.17 eV at ambient pressure to 0.45 eV at 8 GPa. The quenching of the Burstein-Moss effect in degenerate samples and the shift of the free-carrier plasma frequency to lower energies reveal a quick decrease of the bulk three-dimensional (3D) electron concentration under pressure. On increasing pressure the behavior of Hall electron concentration and mobility depends on the sample thickness, consistently with a gradual transition from mainly 3D transport at ambient pressure to mainly two-dimensional (2D) transport at high pressure. Two-carrier transport equations confirm the trapping of high-mobility 3D electrons, an effect that can be related to a shallow-to-deep transformation of donor levels, associated with a change in the ordering of the conduction band minima. The high apparent areal density and low electron mobility of 2D electrons are not compatible with their expected properties in a Dirac cone. Measured transport parameters at high pressure are most probably affected by the presence of holes, either in an accumulation surface layer or as minority carriers in the bulk. ©2012 American Physical SocietyThis work has been done under financial support from Spanish MICINN under Grants No. MAT2008-06873-C02-02, No. MAT2007-66129, No. MAT2010-21270-C04-03/04, No. CSD2007-00045, and Prometeo No. GV2011/035. The supercomputer time has been provided by the Red Espanola de Supercomputacion (RES) and the MALTA cluster.Segura, A.; Panchal, V.; Sánchez-Royo, JF.; Marín-Borrás, V.; Muñoz-Sanjosé, V.; Rodríguez-Hernández, P.; Muñoz, A.... (2012). Trapping of three-dimensional electrons and transition to two-dimensional transport in the three-dimensional topological insulator Bi2Se3 under high pressure. Physical Review B. 85:195139-1-195139-9. https://doi.org/10.1103/PhysRevB.85.195139S195139-1195139-985Mishra, S. K., Satpathy, S., & Jepsen, O. (1997). Electronic structure and thermoelectric properties of bismuth telluride and bismuth selenide. Journal of Physics: Condensed Matter, 9(2), 461-470. doi:10.1088/0953-8984/9/2/014Hor, Y. S., Richardella, A., Roushan, P., Xia, Y., Checkelsky, J. G., Yazdani, A., … Cava, R. J. (2009). p-typeBi2Se3for topological insulator and low-temperature thermoelectric applications. Physical Review B, 79(19). doi:10.1103/physrevb.79.195208Zhang, H., Liu, C.-X., Qi, X.-L., Dai, X., Fang, Z., & Zhang, S.-C. (2009). Topological insulators in Bi2Se3, Bi2Te3 and Sb2Te3 with a single Dirac cone on the surface. Nature Physics, 5(6), 438-442. doi:10.1038/nphys1270Hasan, M. Z., & Kane, C. L. (2010). Colloquium: Topological insulators. Reviews of Modern Physics, 82(4), 3045-3067. doi:10.1103/revmodphys.82.3045Moore, J. E. (2010). The birth of topological insulators. Nature, 464(7286), 194-198. doi:10.1038/nature08916Xia, Y., Qian, D., Hsieh, D., Wray, L., Pal, A., Lin, H., … Hasan, M. Z. (2009). Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nature Physics, 5(6), 398-402. doi:10.1038/nphys1274Chen, Y. L., Analytis, J. G., Chu, J.-H., Liu, Z. K., Mo, S.-K., Qi, X. L., … Shen, Z.-X. (2009). Experimental Realization of a Three-Dimensional Topological Insulator, Bi2Te3. Science, 325(5937), 178-181. doi:10.1126/science.1173034Hsieh, D., Xia, Y., Qian, D., Wray, L., Dil, J. H., Meier, F., … Hasan, M. Z. (2009). A tunable topological insulator in the spin helical Dirac transport regime. Nature, 460(7259), 1101-1105. doi:10.1038/nature08234Alpichshev, Z., Analytis, J. G., Chu, J.-H., Fisher, I. R., Chen, Y. L., Shen, Z. X., … Kapitulnik, A. (2010). STM Imaging of Electronic Waves on the Surface ofBi2Te3: Topologically Protected Surface States and Hexagonal Warping Effects. Physical Review Letters, 104(1). doi:10.1103/physrevlett.104.016401Roushan, P., Seo, J., Parker, C. V., Hor, Y. S., Hsieh, D., Qian, D., … Yazdani, A. (2009). Topological surface states protected from backscattering by chiral spin texture. Nature, 460(7259), 1106-1109. doi:10.1038/nature08308Butch, N. P., Kirshenbaum, K., Syers, P., Sushkov, A. B., Jenkins, G. S., Drew, H. D., & Paglione, J. (2010). Strong surface scattering in ultrahigh-mobilityBi2Se3topological insulator crystals. Physical Review B, 81(24). doi:10.1103/physrevb.81.241301Wang, Z., Lin, T., Wei, P., Liu, X., Dumas, R., Liu, K., & Shi, J. (2010). Tuning carrier type and density in Bi2Se3 by Ca-doping. Applied Physics Letters, 97(4), 042112. doi:10.1063/1.3473778Ren, Z., Taskin, A. A., Sasaki, S., Segawa, K., & Ando, Y. (2010). Large bulk resistivity and surface quantum oscillations in the topological insulatorBi2Te2Se. Physical Review B, 82(24). doi:10.1103/physrevb.82.241306Kulbachinskii, V. A., Miura, N., Nakagawa, H., Arimoto, H., Ikaida, T., Lostak, P., & Drasar, C. (1999). Conduction-band structure ofBi2−xSbxSe3mixed crystals by Shubnikov–de Haas and cyclotron resonance measurements in high magnetic fields. Physical Review B, 59(24), 15733-15739. doi:10.1103/physrevb.59.15733Analytis, J. G., McDonald, R. D., Riggs, S. C., Chu, J.-H., Boebinger, G. S., & Fisher, I. R. (2010). Two-dimensional surface state in the quantum limit of a topological insulator. Nature Physics, 6(12), 960-964. doi:10.1038/nphys1861Cho, S., Butch, N. P., Paglione, J., & Fuhrer, M. S. (2011). Insulating Behavior in Ultrathin Bismuth Selenide Field Effect Transistors. Nano Letters, 11(5), 1925-1927. doi:10.1021/nl200017fZhang, Y., He, K., Chang, C.-Z., Song, C.-L., Wang, L.-L., Chen, X., … Xue, Q.-K. (2010). Crossover of the three-dimensional topological insulator Bi2Se3 to the two-dimensional limit. Nature Physics, 6(8), 584-588. doi:10.1038/nphys1689Kong, D., Cha, J. J., Lai, K., Peng, H., Analytis, J. G., Meister, S., … Cui, Y. (2011). Rapid Surface Oxidation as a Source of Surface Degradation Factor for Bi2Se3. ACS Nano, 5(6), 4698-4703. doi:10.1021/nn200556hBenia, H. M., Lin, C., Kern, K., & Ast, C. R. (2011). Reactive Chemical Doping of theBi2Se3Topological Insulator. Physical Review Letters, 107(17). doi:10.1103/physrevlett.107.177602King, P. D. C., Hatch, R. C., Bianchi, M., Ovsyannikov, R., Lupulescu, C., Landolt, G., … Hofmann, P. (2011). Large Tunable Rashba Spin Splitting of a Two-Dimensional Electron Gas inBi2Se3. Physical Review Letters, 107(9). doi:10.1103/physrevlett.107.096802Hamlin, J. J., Jeffries, J. R., Butch, N. P., Syers, P., Zocco, D. A., Weir, S. T., … Maple, M. B. (2011). High pressure transport properties of the topological insulator Bi2Se3. Journal of Physics: Condensed Matter, 24(3), 035602. doi:10.1088/0953-8984/24/3/035602Köhler, H., & Hartmann, J. (1974). Burstein Shift of the Absorption Edge of nBi2Se3. physica status solidi (b), 63(1), 171-176. doi:10.1002/pssb.2220630116Panchal, V., Segura, A., & Pellicer-Porres, J. (2011). Low-cost set-up for Fourier-transform infrared spectroscopy in diamond anvil cell from 4000 to 400 cm−1. High Pressure Research, 31(3), 445-453. doi:10.1080/08957959.2011.594049Chervin, J. C., Canny, B., Besson, J. M., & Pruzan, P. (1995). A diamond anvil cell for IR microspectroscopy. Review of Scientific Instruments, 66(3), 2595-2598. doi:10.1063/1.1145594Piermarini, G. J., Block, S., Barnett, J. D., & Forman, R. A. (1975). Calibration of the pressure dependence of theR1ruby fluorescence line to 195 kbar. Journal of Applied Physics, 46(6), 2774-2780. doi:10.1063/1.321957Errandonea, D., Segura, A., Martínez-García, D., & Muñoz-San Jose, V. (2009). Hall-effect and resistivity measurements in CdTe and ZnTe at high pressure: Electronic structure of impurities in the zinc-blende phase and the semimetallic or metallic character of the high-pressure phases. Physical Review B, 79(12). doi:10.1103/physrevb.79.125203Errandonea, D., Martínez-García, D., Segura, A., Ruiz-Fuertes, J., Lacomba-Perales, R., Fages, V., … Mũnoz-San José, V. (2006). High-pressure electrical transport measurements on p-type GaSe and InSe. High Pressure Research, 26(4), 513-516. doi:10.1080/08957950601101787Hohenberg, P., & Kohn, W. (1964). Inhomogeneous Electron Gas. Physical Review, 136(3B), B864-B871. doi:10.1103/physrev.136.b864Kresse, G., & Hafner, J. (1993). Ab initiomolecular dynamics for liquid metals. Physical Review B, 47(1), 558-561. doi:10.1103/physrevb.47.558Kresse, G., & Hafner, J. (1994). Ab initiomolecular-dynamics simulation of the liquid-metal–amorphous-semiconductor transition in germanium. Physical Review B, 49(20), 14251-14269. doi:10.1103/physrevb.49.14251Kresse, G., & Furthmüller, J. (1996). Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 6(1), 15-50. doi:10.1016/0927-0256(96)00008-0Kresse, G., & Furthmüller, J. (1996). Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Physical Review B, 54(16), 11169-11186. doi:10.1103/physrevb.54.11169Blöchl, P. E. (1994). Projector augmented-wave method. Physical Review B, 50(24), 17953-17979. doi:10.1103/physrevb.50.17953Kresse, G., & Joubert, D. (1999). From ultrasoft pseudopotentials to the projector augmented-wave method. Physical Review B, 59(3), 1758-1775. doi:10.1103/physrevb.59.1758Perdew, J. P., Ruzsinszky, A., Csonka, G. I., Vydrov, O. A., Scuseria, G. E., Constantin, L. A., … Burke, K. (2008). Restoring the Density-Gradient Expansion for Exchange in Solids and Surfaces. Physical Review Letters, 100(13). doi:10.1103/physrevlett.100.136406Mujica, A., Rubio, A., Muñoz, A., & Needs, R. J. (2003). High-pressure phases of group-IV, III–V, and II–VI compounds. Reviews of Modern Physics, 75(3), 863-912. doi:10.1103/revmodphys.75.863Köhler, H., & Becker, C. R. (1974). Optically Active Lattice Vibrations in Bi2Se3. physica status solidi (b), 61(2), 533-537. doi:10.1002/pssb.2220610218Vilaplana, R., Santamaría-Pérez, D., Gomis, O., Manjón, F. J., González, J., Segura, A., … Kucek, V. (2011). Structural and vibrational study of Bi2Se3under high pressure. Physical Review B, 84(18). doi:10.1103/physrevb.84.184110LaForge, A. D., Frenzel, A., Pursley, B. C., Lin, T., Liu, X., Shi, J., & Basov, D. N. (2010). Optical characterization ofBi2Se3in a magnetic field: Infrared evidence for magnetoelectric coupling in a topological insulator material. Physical Review B, 81(12). doi:10.1103/physrevb.81.125120Penn, D. R. (1962). Wave-Number-Dependent Dielectric Function of Semiconductors. Physical Review, 128(5), 2093-2097. doi:10.1103/physrev.128.2093PHILLIPS, J. C. (1970). Ionicity of the Chemical Bond in Crystals. Reviews of Modern Physics, 42(3), 317-356. doi:10.1103/revmodphys.42.317Van Vechten, J. A. (1969). Quantum Dielectric Theory of Electronegativity in Covalent Systems. I. Electronic Dielectric Constant. Physical Review, 182(3), 891-905. doi:10.1103/physrev.182.891Van Vechten, J. A. (1969). Quantum Dielectric Theory of Electronegativity in Covalent Systems. II. Ionization Potentials and Interband Transition Energies. Physical Review, 187(3), 1007-1020. doi:10.1103/physrev.187.1007Larson, P., Greanya, V. A., Tonjes, W. C., Liu, R., Mahanti, S. D., & Olson, C. G. (2002). Electronic structure ofBi2X3(X=S,Se,T)compounds:  Comparison of theoretical calculations with photoemission studies. Physical Review B, 65(8). doi:10.1103/physrevb.65.085108Chang, J., Jadaun, P., Register, L. F., Banerjee, S. K., & Sahu, B. (2011). Dielectric capping effects on binary and ternary topological insulator surface states. Physical Review B, 84(15). doi:10.1103/physrevb.84.155105Suski, T., Piotrzkowski, R., Wiśniewski, P., Litwin-Staszewska, E., & Dmowski, L. (1989). High pressure andDXcenters in heavily doped bulk GaAs. Physical Review B, 40(6), 4012-4021. doi:10.1103/physrevb.40.4012Errandonea, D., Segura, A., Sánchez-Royo, J. F., Mun-|Atoz, V., Grima, P., Chevy, A., & Ulrich, C. (1997). Investigation of conduction-band structure, electron-scattering mechanisms, and phase transitions in indium selenide by means of transport measurements under pressure. Physical Review B, 55(24), 16217-16225. doi:10.1103/physrevb.55.16217Analytis, J. G., Chu, J.-H., Chen, Y., Corredor, F., McDonald, R. D., Shen, Z. X., & Fisher, I. R. (2010). Bulk Fermi surface coexistence with Dirac surface state inBi2Se3: A comparison of photoemission and Shubnikov–de Haas measurements. Physical Review B, 81(20). doi:10.1103/physrevb.81.205407Köhler, H., & Fabbicius, A. (1975). Galvanomagnetic Properties of Bi2Se3with Free Carrier Densities below 5 × 1017 cm−3. physica status solidi (b), 71(2), 487-496. doi:10.1002/pssb.222071020

Li depletion in solar analogues with exoplanets: Extending the sample

We want to study the effects of the formation of planets and planetary systems on the atmospheric Li abundance of planet host stars. In this work we present new determinations of lithium abundances for 326 Main Sequence stars with and without planets in the T$_\mathrm{eff}$ range 5600-5900 K. 277 stars come from the HARPS sample, the remaining targets have been observed with a variety of high resolution spectrographs. We confirm significant differences in the Li distribution of solar twins (T$_\mathrm{eff}$ = T$_{\odot} \pm$ 80 K, log g = log g$_{\odot}$ $\pm$ 0.2 and [Fe/H] = [Fe/H]$_{\odot} \pm$ 0.2): the full sample of planet host stars (22) shows Li average values lower than "single" stars with no detected planets (60). If we focus in subsamples with narrower ranges in metallicity and age, we observe indications of a similar result though it is not so clear for some of the studied subsamples. Furthermore, we compare the observed spectra of several couples of stars with very similar parameters which show different Li abundances up to 1.6 dex. Therefore we show that neither age, nor mass nor metallicity of a parent star is the only responsible for enhanced Li depletion in solar analogues. We conclude that another variable must account for that difference and suggest that this could be the presence of planets which causes additional rotationally induced mixing in the external layers of planet host stars. Moreover, we find indications that the amount of depletion of Li in planet host solar-type stars is higher when the planets are more massive than Jupiter.Comment: 16 pages, accepted for publication in A&

Structure and evolution of the mitochondrial DNA complete control region in the Drosophila subobscura subgroup

The complete A + T-rich region of mitochondrial DNA (mtDNA) has been cloned and sequenced in the species of the Drosophila subobscura subgroup D. subobscura, D. madeirensis and D. guanche. Comparative analysis of these sequences with others already published has identified new sequence motifs that are conserved in Drosophila and other insects. A putative bi-directional promoter and a stop signal are proposed to be involved in the primary mtDNA strand replication of Drosophila. This region strongly resolves relationships of the species included in a phylogenetic analysis, both for closely related species and also at deeper phylogenetic levels when only the left and central domains are taken into account.info:eu-repo/semantics/publishedVersio

Structural and vibrational study of Bi2Se3 under high pressure

The structural and vibrational properties of bismuth selenide (Bi2Se3) have been studied by means of x-ray diffraction and Raman scattering measurements up to 20 and 30 GPa, respectively. The measurements have been complemented with ab initio total-energy and lattice dynamics calculations. Our experimental results evidence a phase transition from the low-pressure rhombohedral (R-3m) phase (B-Bi2Se3) with sixfold coordination for Bi to a monoclinic C2/m structure (B-Bi2Se3) with sevenfold coordination for Bi above 10 GPa. The equation of state and the pressure dependence of the lattice parameters and volume of a and B phases of Bi2Se3 are reported. Furthermore, the presence of a pressure-induced electronic topological phase transition in B-Bi2Se3 is discussed. Raman measurements evidence that Bi2Se3 undergoes two additional phase transitions around 20 and 28 GPa, likely toward a monoclinic C2/c and a disordered body-centered cubic structure with 8-fold and 9- or 10-fold coordination, respectively. These two high-pressure structures are the same as those recently found at high pressures in Bi2Te3 and Sb2Te3. On pressure release, Bi2Se3 reverts to the original rhombohedral phase after considerable hysteresis. Symmetries, frequencies, and pressure coefficients of the Raman and infrared modes in the different phases are reported and discussed.This work was done under financial support from Spanish Ministry of Science and Innovation under Projects No. MAT2007-66129, No. MAT2010-21270-C04-03/04, and No. CSD-2007-00045 and from the Valencian government under Project No. Prometeo/2011-035. It is also supported by the Ministry of Education, Youth and Sports of the Czech Republic Project No. MSM 0021627501

DEFINICIÓN DE UN PROTOCOLO PARA LA REALIZACIÓN DE AUDITORÍAS ENERGÉTICAS EN INSTALACIONES GANADERAS: APLICACIÓN EN PEQUEÑAS Y MEDIANAS EXPLOTACIONES

En el presente trabajo se muestran los resultados de un proyecto desarrollado en España bajo los auspicios del Instituto para la Diversificación y Ahorro de la Energía (IDAE), el Ente Regional de la Energía de Castilla y León (EREN) y la Unión de Pequeños Agricultores (UPA), y aplicado en la región de Castilla y León, zona con un perfil productivo eminentemente agrícola y ganadero, cuyo objetivo fue la definición de un protocolo para la realización de auditorías energéticas en instalaciones ganaderas, focalizando aquellas de tamaño pequeño y mediano. En el protocolo se desarrolló la metodología para la caracterización y la formulación de mejoras de los siguientes elementos: Características constructivas, suministros energéticos, iluminación, motores eléctricos, calefacción, refrigeración y ventilación, energías renovables, equipamientos de aprovechamiento energético de residuos y equipamientos de control. El protocolo fue validado con la realización de auditorías energéticas en 15 explotaciones: 5 de vacuno lechero, 5 de ovino lechero, 3 de porcino de engorde y 2 de pollos de carne. Los resultados obtenidos muestran que con las medidas de eficiencia energética propuestas se consiguen ahorros medios en los consumos energéticos del 18 %, lo cual significa una disminución media del coste económico del 24,28 %

Improving Cognitive Visual-Motor Abilities in Individuals with Down Syndrome

Down syndrome causes a reduction in cognitive abilities, with visual-motor skills being particularly affected. In this work, we have focused on this skill in order to stimulate better learning. The proposal relies on stimulating the cognitive visual-motor skills of individuals with Down Syndrome (DS) using exercises with a gestural interaction platform based on the KINECT sensor named TANGO:H, the goal being to improve them. To validate the proposal, an experimental single-case study method was designed using two groups: a control group and an experimental one, with similar cognitive ages. Didactic exercises were provided to the experimental group using visual cognitive stimulation. These exercises were created on the TANGO:H Designer, a platform that was designed for gestural interaction using the KINECT sensor. As a result, TANGO:H allows for visual-motor cognitive stimulation through the movement of hands, arms, feet and head. The “Illinois Test of Psycholinguistic Abilities (ITPA)” was applied to both groups as a pre-test and post-test in its four reference sections: visual comprehension, visual-motor sequential memory, visual association, and visual integration. Two checks were made, one using the longitudinal comparison of the pre-test/post-test of the experimental group, and another that relied on comparing the difference of the means of the pre-test/post-test. We also used an observational methodology for the working sessions from the experimental group. Although the statistical results do not show significant differences between the two groups, the results of the observations exhibited an improvement in visual-motor cognitive skills

La casa de Alicia en el país de las maravillas: la casa del SER en su contexto

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