4,714 research outputs found
Dynamisme, résultats et problèmes actuels de l’agriculture espagnole
The need to substitute capital for labor-force and the augmentation of internal demand explain the forms of expansion of spanish agriculture for the last 20 years: growth of production and changes in its composition, progression of productivity, intense mecanization, increase of imports more rapidly than exports. To day several factors disturbe this model of growth, the main ones being the slow-down or rural depopulation, the inequality on land distribution, the persistent weakness of breeding. In the crisis ' cycle, we may doubt that government and agricultors can reach, beyond their short term accommodation, a new long term compromise
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A study of the antioxidant capacity of oak wood used in wine ageing and the correlation with polyphenol composition
The antioxidant capacity of oak wood used in the ageing of wine was studied by four different methods: measurement of scavenging capacity against a given radical (ABTS, DPPH), oxygen radical absorbance capacity (ORAC) and the ferric reducing antioxidant power (FRAP). Although, the four methods tested gave comparable results for the antioxidant capacity measured in oak wood extracts, the ORAC method gave results with some differences from the other methods. Non-toasted oak wood samples displayed more antioxidant power than toasted ones due to differences in the polyphenol compositon. A correlation analysis revealed that ellagitannins were the compounds mainly responsible for the antioxidant capacity of oak wood. Some phenolic acids, mainly gallic acid, also showed a significant correlation with antioxidant capacity
Determinación de los parámetros de solubilidad de Hansen para el aceite de caña de azúcar. Uso del etanol para la refinación de la cera de caña de azúcar
Currently, the refining of sugarcane wax is carried out with 95% v/v ethanol as solvent. This process has a high rate of ethanol consumption thus, the main objective of this work was to corroborate the feasibility of 95% v/v ethanol as a solvent in the refining of sugarcane wax. The suitability of its performance over other organic solvents was evaluated through the relative energy difference (RED) determined from Hansen solubility parameters (HSPs) of sugarcane oil, which were calculated using HSPiP software. HSPs turned out to be δD = 16.24 MPa½, δP = 3.21 MPa½ and δH = 10.34 MPa½, similar to those reported for pine resin and castor oil. The best solvent was 1-decanol. 95% v/v ethanol turned out to be a bad solvent. Absolute ethanol had a RED value of 0.993, which made it a better candidate since it could reduce consumption rates, and constituted an eco-friendly solvent produced in Cuba for the refining process.La refinaciĂłn de la cera cruda de caña se realiza con etanol a 95% v/v, incurriendo en altos Ăndices de consumo, por lo que el objetivo principal de este trabajo es determinar si el etanol a 95% v/v es un solvente adecuado. Su uso respecto a otros solventes orgánicos es evaluado por la diferencia de energĂa relativa (RED) determinada a partir de los parámetros de solubilidad de Hansen (HSPs), se calcularon usando el programa HSPiP. Los HSPs fueron δD = 16.24 MPa½, δP = 3.21 MPa½ and δH = 10.34 MPa ½, siendo similares a los reportados para la resina de pino y el aceite de ricino. El mejor solvente fue 1-decanol, el etanol del 95% v/v fue un mal solvente; el etanol absoluto con un RED= 0.993 es un mejor candidato, ya que podrĂa reducir las tasas de consumo, manteniendo un solvente ecolĂłgico y producido en Cuba para el proceso de refinaciĂłn
Non-ergodic effects in the Coulomb glass: specific heat
We present a numerical method for the investigation of non-ergodic effects in
the Coulomb glass. For that, an almost complete set of low-energy many-particle
states is obtained by a new algorithm. The dynamics of the sample is mapped to
the graph formed by the relevant transitions between these states, that means
by transitions with rates larger than the inverse of the duration of the
measurement. The formation of isolated clusters in the graph indicates
non-ergodicity. We analyze the connectivity of this graph in dependence on
temperature, duration of measurement, degree of disorder, and dimensionality,
studying how non-ergodicity is reflected in the specific heat.Comment: Submited Phys. Rev.
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