960 resultados para Nuclear counters
Resumo:
Se analizan los neologismos que la Junta de Energía Nuclear Española publica en la revista 'Energía Nuclear', en la sección sobre vocabulario científico con el fin de dar a conocer a la comunidad de científicos de Hispanoamérica la relación de éstos términos con los originales de los que proceden. La sección se divide en dos apartados: 1.Palabras recomendadas, términos que ya tienen un bagaje de utilización y un peso en el léxico científico. 2.Palabras propuestas: términos que no han sido demasiado usados y cuya definición puede dar lugar a controversia. En el análisis de cada uno de los neologismos, dentro de los dos apartados, se incluye: el término en la lengua original (normalmente inglés), la traducción al castellano, la definición, procedencia etimológica, otros términos en los que deriva o con los que se relaciona.
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Se expone la situación actual de la investigación nuclear para usos pacíficos y sus posibilidades para el futuro, así como, la exigencia de grandes recursos científicos y tecnológicos para su aplicación. La experiencia británica con este tipo de energía puede ser de utilidad para España, que, también tiene limitados recursos propios de energía y se enfrenta con una creciente y acelerada demanda.
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Resumen basado en el de la publicación
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A simple extended finite field nuclear relaxation procedure for calculating vibrational contributions to degenerate four-wave mixing (also known as the intensity-dependent refractive index) is presented. As a by-product one also obtains the static vibrationally averaged linear polarizability, as well as the first and second hyperpolarizability. The methodology is validated by illustrative calculations on the water molecule. Further possible extensions are suggested
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An analytic method to evaluate nuclear contributions to electrical properties of polyatomic molecules is presented. Such contributions control changes induced by an electric field on equilibrium geometry (nuclear relaxation contribution) and vibrational motion (vibrational contribution) of a molecular system. Expressions to compute the nuclear contributions have been derived from a power series expansion of the potential energy. These contributions to the electrical properties are given in terms of energy derivatives with respect to normal coordinates, electric field intensity or both. Only one calculation of such derivatives at the field-free equilibrium geometry is required. To show the useful efficiency of the analytical evaluation of electrical properties (the so-called AEEP method), results for calculations on water and pyridine at the SCF/TZ2P and the MP2/TZ2P levels of theory are reported. The results obtained are compared with previous theoretical calculations and with experimental values
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Electrical property derivative expressions are presented for the nuclear relaxation contribution to static and dynamic (infinite frequency approximation) nonlinear optical properties. For CF4 and SF6, as opposed to HF and CH4, a term that is quadratic in the vibrational anharmonicity (and not previously evaluated for any molecule) makes an important contribution to the static second vibrational hyperpolarizability of CF4 and SF6. A comparison between calculated and experimental values for the difference between the (anisotropic) Kerr effect and electric field induced second-harmonic generation shows that, at the Hartree-Fock level, the nuclear relaxation/infinite frequency approximation gives the correct trend (in the series CH4, CF4, SF6) but is of the order of 50% too small
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The performance of the SAOP potential for the calculation of NMR chemical shifts was evaluated. SAOP results show considerable improvement with respect to previous potentials, like VWN or BP86, at least for the carbon, nitrogen, oxygen, and fluorine chemical shifts. Furthermore, a few NMR calculations carried out on third period atoms (S, P, and Cl) improved when using the SAOP potential
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A set of connections among several nuclear and electronic indexes of reactivity in the framework of the conceptual Density Functional Theory by using an expansion ofthe energy functional in terms of the total number of electrons and the normal coordinates within a canonical ensemble was derived. The relations obtained provided explicit links between important quantities related to the chemical reactivity of a system. This paper particularly demonstrates that the derivative of the electronic energy with respect to the external potential of a system in its equilibrium geometry was equal to the negative of the nuclear repulsion derivative with respect to the external potential