Los colosos del campo: tractores de alta potencia

Revisión y descripción de las principales características de los tractores de alta potencia en el sector agrícola español. La agricultura profesional es una empresa compleja y la inversión en formación de los agentes implicados en el sector (agricultores e ingenieros) es la llave para conseguir aprovechar toda la tecnología disponible y optimizar los recursos usados

Últimas novedades en equipos de recolección de forraje

Los equipos para la recolección de forraje comprenden un amplio espectro de máquinas y aperos entre los que se encuentran los equipos para la siega, acondicionado, esparcido, hilerado, carga y transporte, además del empacado y el picado. Los equipos empleados para esta variedad de labores son muy diversos y presentan grandes diferencias en complejidad y nivel de tecnificación, características en cuanto a las cuales podríamos situar a las picadoras de forraje autopropulsadas en la cumbre. El ritmo de desarrollo e implementación de avances técnicos es tanto mayor cuantas más posibilidades ofrezca el equipo, por lo que son las picadoras de forraje autopropulsadas, seguidas de las empacadoras, los equipos en los cuales podemos encontrar cambios más notables a lo largo de los últimos años

Pleistocene-Holocene P. nigra traces on tufa archives in the Northern Meseta of the Iberian Peninsula

Molds preserved on travertines constitute exceptional species-informative material to reconstruct past vegetation. These are common on the High Ebro region. Here, the fluvial system erosion and karstification of the Mesozoic limestone since the Late Tertiary, origins extensive travertine complexes like the one studied in Tubilla del Agua (Burgos). In this site, three different travertine complexes are observed. The older one is represented by two disconnected edifices incised by the Valoria river. The age of this structure is established between > 300,000 and 240,000 yr BP, as from the U/Th dating on its base and top. The subsequent incision lasted until at least 90,000 yr BP, when another edifice erected upstream on the older one. The second travertine group comprises three platforms aged 60,000 yr BP the lower one, and 18,000 yr BP the middle one. The third travertine group is a lake-barrier complex 12,000 yr BP old, on which Tubilla del Agua was built, and a stratified travertine body that covers the valley bottom 10,000 to 2700 cal yr BP old. Some of the ages of the oldest travertines, and the most modern ones, coincide with the principal travertine formation cycles described by Durán (1996) for Spain. The matrix of precipitated calcium carbonate of all these complexes are rich in plant remain molds (mosses, stems, leaves, cones) of the surrounding flora. Pinus nigra Arnold cone molds have been localized and identified by comparative morphology studies. These remains are of high valuable information about the Pleistocene and Holocene presence of this taxon, in a site where no natural presence can be found today. This work was funded by project CGL2008-06005

Novedades en remolques agrícolas y cisternas

Los remolques agrícolas son máquinas arrastradas cuya finalidad es la carga, transporte y descarga o distribución de materiales empleados en las explotaciones. La enorme variabilidad de materiales a transportar en las explotaciones agrícolas condiciona las características de estas máquinas, por lo que resulta necesaria una clasificación según cuatro grandes tipos de remolques que posteriormente nos permita identificar algunos de los parámetros más relevantes para cada tipo, y comentar las soluciones aportadas por los fabricantes en la actualidad

Point defect stability in a semicoherent metallic interface

We present a comprehensive density functional theory (DFT) -based study of different aspects of one vacancy and He impurity atom behavior at semicoherent interfaces between the low-solubility transition metals Cu and Nb. Such interfaces have not been previously modeled using DFT. A thorough analysis of the stability and mobility of the two types of defects at the interfaces and neighboring internal layers has been performed and the results have been compared to the equivalent cases in the pure metallic matrices. The different behavior of fcc and bcc metals on both sides of the interface has been specifically assessed. The modeling effort undertaken is the first attempt to study the stability and defect energetics of noncoherent Cu/Nb interfaces from first principles, in order to assess their potential use in radiation-resistant materials.Seventh Framework Programme (European Commission) (Project RAD-INTERFACES)Spain. Ministerio de Economia y Competividad (Project NANO-EXTREM, Ref. MAT2012-38541)United States. Dept. of Energy. Office of Basic Energy Sciences (Award 2008LANL1026

Asteroseismology of exoplanets host stars: the special case of ι\iota Horologii (HD17051)

{This paper presents detailed analysis and modelisation of the star HD17051 (alias $\iota$ Hor), which appears as a specially interesting case among exoplanet host stars. As most of these stars, $\iota$ Hor presents a metallicity excess which has been measured by various observers who give different results, ranging from [Fe/H] = 0.11 to 0.26, associated with different atmospheric parameters. Meanwhile the luminosity of the star may be determined owing to Hipparcos parallax. Although in the southern hemisphere, this star belongs to the Hyades stream and its external parameters show that it could even be one of the Hyades stars ejected during cluster formation. The aim of this work was to gather and analyse our present knowledge on this star and to prepare seismic tests for future observations with the HARPS spectrometer (planned for November 2006).} {We have computed evolutionary tracks with various metallicities, in the two frameworks of primordial overmetallicity and accretion. We have concentrated on models inside the error boxes given by the various observers in the log g - log T$_{eff}$ diagram. We then computed the adiabatic oscillation frequencies of these models to prepare future observations.} {The detailed analysis of $\iota$ Hor presented in this paper already allowed to constrain its external parameters, mass and age. Some values given in the literature could be rejected as inconsistent with the overall analysis. We found that a model computed with the Hyades parameters (age, metallicity) was clearly acceptable, but other ones were possible too. We are confident that observations with HARPS will allow for a clear conclusion about this star and that it will bring important new light on the physics of exoplanet host stars.}Comment: to be published in Astronomy and Astrophysic

Comparative study of the pathogenicity of seabed isolates of Fusarium equiseti and the effect of the composition of the mineral salt medium and temperature on mycelia growth

The pathogenicity of seven strains of Fusarium equiseti isolated from seabed soil was evaluated on different host plants showing pre and post emergence damage. Radial growth of 27 strains was measured on culture media previously adjusted to different osmotic potentials with either KCl or NaCl (-1.50 to - 144.54 bars) at 15º, 25º and 35º C. Significant differences and interactive effects were observed in the response of mycelia to osmotic potential and temperature

Common causes of failure of pneumatic distributors in high precision pneumatic seeders: Proposals towards predictive maintenance

Modern precision pneumatic drills (1-500 kg/ha) used in the cultivation of high density crops such as winter cereals (up to 400 plants/m2) are very high performance equipment that triple the working width (up to 9m) and rates (up to 14 km/h) compared to those used fifteen years ago. Most of enterprises commercialize such devices using as cornerstone a central pneumatic distributor in combination with a large number of radial outlets (24-48). In spite of the unquestionable advantages of these devices with regard to more conventional gravitational distributors, the main drawback remains the lack of transversal uniformity which has proven to be fairly sensitive to seed size and shape, to slight air flow changes related to partial obstructions of outlets, elbows and grips in discharge outlets, or vibrations and inclinations of the central distributor, as well associated to inadequate maintenance of the machine by untrained operators. Moreover, the lack of behavior predictability derives in a certain discredit of the pneumatic procedure. This work proposes a theoretical-empirical methodology to analyze the pneumatic circuit and its interaction with a variety of seeds types to be delivered, and selected operational machinery settings, within the aim of elaborating a test protocol which combined with low cost instrumentation will serve a base for predictive maintenance. Experimental data gathered in static and dynamic tests performed by the authors on at least two different seeders together with published information available on technical papers will be reviewed and used for further discussion on reliable diagnosis procedure

Cargadoras telescópicas frente a tractores con cargador frontal.

Las tareas de carga y transporte suponen en la agricultura moderna hasta un 40% del trabajo to tal en la explotación agropecuaria, por lo que op timizar la velocidad y el rendimiento en las tareas de carga, descarga y manejo de materiales es im prescindible de cara a rentabitizar la actividad agroganadera.Tradicionalmente para estas tareas se han utilizado tractores con cargador frontal, pe ro es cada vez más frecuente la sustitución de es tas máquinas por cargadoras telescópicas

Nuevos desarrollos de hoy hacia el tractor de mañana

En el artículo se presentan las principales novedades, fundamentalmente orientadas a conseguir un funcionamiento más eficiente y limpio o a desarrollos electrónicos para automatizar tareas