Are there stable long-range ordered Fe(1-x)Cr(x) compounds?

The heat of formation of Fe-Cr alloys undergoes an anomalous change of sign at small Cr concentrations. This observation raises the question whether there are intermetallic phases present in this composition range. Here we report the discovery of several long-range ordered structures that represent ground state phases at zero Kelvin. In particular we have identified a structure at 3.7% Cr with an embedding energy which is 49 meV/Cr atom below the solid solution. This implies there is an effective long-range attractive interaction between Cr atoms. We propose that the structures found in this study complete the low temperature-low Cr region of the phase diagram.Comment: 3 pages, 2 figure

Short-range order and precipitation in Fe-rich Fe-Cr alloys: Atomistic off-lattice Monte Carlo simulations

Short-range order (SRO) in Fe-rich Fe-Cr alloys is investigated by means of atomistic off-lattice Monte Carlo simulations in the semi-grand canonical ensemble using classical interatomic potentials. The SRO parameter defined by Cowley [Phys. Rev. B 77, 669 (1950)] is used to quantify the degree of ordering. In agreement with experiments a strong ordering tendency in the Cr distribution at low Cr concentrations (~< 5%) is observed, as manifested in negative values of the SRO parameters. For intermediate Cr concentrations (5% ~< c_Cr ~< 15%) the SRO parameter for the alpha-phase goes through a minimum, but at the solubility limit the alpha-phase still displays a rather strong SRO. In thermodynamic equilibrium for concentrations within the two-phase region the SRO parameter measured over the entire sample therefore comprises the contributions from both the alpha and alpha-prime phases. If both of these contributions are taken into account, it is possible to quantitatively reproduce the experimental results and interpret their physical implications. It is thereby shown that the inversion of the SRO observed experimentally is due to the formation of stable (supercritical) alpha-prime precipitates. It is not related to the loss of SRO in the alpha-phase or to the presence of unstable (subcritical) Cr precipitates in the alpha-phase.Comment: 9 pages, 8 figure

A Quantum-Classical Brackets from p-Mechanics

We provide an answer to the long standing problem of mixing quantum and classical dynamics within a single formalism. The construction is based on p-mechanical derivation (quant-ph/0212101, quant-ph/0304023) of quantum and classical dynamics from the representation theory of the Heisenberg group. To achieve a quantum-classical mixing we take the product of two copies of the Heisenberg group which represent two different Planck's constants. In comparison with earlier guesses our answer contains an extra term of analytical nature, which was not obtained before in purely algebraic setup. Keywords: Moyal brackets, Poisson brackets, commutator, Heisenberg group, orbit method, representation theory, Planck's constant, quantum-classical mixingComment: LaTeX, 7 pages (EPL style), no figures; v2: example of dynamics with two different Planck's constants is added, minor corrections; v3: major revion, a complete example of quantum-classic dynamics is given; v4: few grammatic correction

A fully automatic system for acid-base coulometric titrations

An automatic system for acid-base titrations by electrogeneration of H+ and OH- ions, with potentiometric end-point detection, was developed. The system includes a PC-compatible computer for instrumental control, data acquisition and processing, which allows up to 13 samples to be analysed sequentially with no human intervention

Estudio sobre la integracion de la prevencion en la fase de redaccion de los proyectos en España. analisis comparativo respecto de los paises - EU-15

España es uno de los países europeos con mayor índice de siniestralidad en el ámbito de la construcción, pero contradictoriamente cuenta con una normativa muy amplia y relativamente novedosa. En el ámbito europeo, también se considera esta actividad de alto riesgo, de hecho el Consejo de las Comunidades Europeas, en su Resolución de 21 de diciembre de 1987, seleccionó a la construcción entre las tres de mayor riesgo y encargó a la Comisión la elaboración de una Directiva que culminó en la identificada como 92/57 CEE, de 24 de junio de 1992, relativa a la actividad de la construcción, mientras que la transposición a nuestro ordenamiento jurídico se realizó mediante el RD 1627/97, de 24 de octubre. El estudio de las distintas transposiciones de la Directiva 92/57/CEE a cada uno de los ordenamientos jurídicos de cada uno de los países que conforman la Europa de los 15 a través de la información facilitada por distintos Organismos Europeos tales como la Agencia Europea de Seguridad y Salud en el Trabajo o el CEN - European Comité for Standardisation, nos ha proporcionado, mediante su análisis, contraste y discusión de dicha documentación, información de cómo llevar a cabo las distintas obligaciones de los agentes intervinientes en el proceso constructivo que emanan de la Directiva 92/57/CEE. Asimismo, hemos podido conocer las ventajas e inconvenientes legales de cada uno de ellos así como reflexionar sobre la idoneidad en la gestión de la prevención en las obras de construcción de España respecto de lo estipulado en estos ordenamientos jurídicos. De igual forma, en este estudio se ha analizado la metodología, conocimiento y gestión de los arquitectos españoles redactores de proyectos de ejecución a la hora de integrar la prevención en sus proyectos de ejecución a lo largo de las distintas fases del proceso de redacción. El estudio ha contado con la participación de 145 arquitectos redactores de proyectos de ejecución sobre una población aproximada de 11.844 arquitectos en España en la misma condición en los últimos años

Preliminary Characterisation of Sardinian Red Grape Cultivars (Vitis vinifera L.) According to Their Phenolic Potential

Fourteen cultivars and clones, mainly selected from the island of Sardinia (Italy) and grown in a collection field,showed significant quantitative differences in phenolic potential. An extraction method designed to reproducethe winemaking process was used to determine the amounts of extractable polyphenols, anthocyanins, catechinsand proanthocyanidins reactive to vanillin, and the proanthocyanidins in grape skins and seeds. The Sardiniancultivar Nieddera and the Spanish cultivar Graciano had the highest concentrations of extractable polyphenols,anthocyanins, catechins and proanthocyanidins reactive to vanillin. Four clones of the Cannonau cultivar (synonymGrenache) exhibited fairly high variability, with significant differences in berry and seed phenolic contents