Arrested kinetic Li isotope fractionation at the margin of the llimaussaq complex, South Greenland: Evidence for open-system processes during final cooling of peralkaline igneous rocks

Li contents [Li] and isotopic composition (delta Li-7) of mafic minerals (mainly amphibole and clinopyroxene) from the alkaline to peralkaline Ilimaussaq plutonic complex, South Greenland, track the behavior of Li and its isotopes during magmatic differentiation and final cooling of an alkaline igneous system. [Li] in amphibole increase from < 10 ppm in Caamphiboles of the least differentiated unit to >3000 ppm in Na-amphiboles of the highly evolved units. In contrast, [Li] in clinopyroxene are comparatively low (<85 ppm) and do not vary systematically with differentiation. The distribution of Li between amphibole and pyroxene is controlled by the major element composition of the minerals (Ca-rich and Na-rich, respectively) and changes in oxygen fugacity (due to Li incorporation via coupled substitution with ferric iron) during magmatic differentiation. delta(7) Li values of all minerals span a wide range from + 17 to - 8 parts per thousand, with the different intrusive units of the complex having distinct Li isotopic systematics. Amphiboles, which dominate the Li budget of whole-rocks from the inner part of the complex, have constant delta Li-7 of + 1.8 +/- 2.2 parts per thousand (2 sigma, n = 15). This value reflects a homogeneous melt reservoir and is consistent with their mantle derivation, in agreement with published O and Nd isotopic data. Clinopyroxenes of these samples are consistently lighter, with Delta Li-7(amph-cpx). as large as 8 parts per thousand and are thus not in Li isotope equilibrium. These low values probably reflect late-stage diffusion of Li into clinopyroxene during final cooling of the rocks, thus enriching the clinopyroxene in 6 Li. At the margin of the complex delta(7) Li in the syenites increases systematically, from +2 to high values of + 14 parts per thousand. This, coupled with the observed Li isotope systematics of the granitic country rocks, reflects post-magmatic open-system processes occurring during final cooling of the intrusion. Although the shape and magnitude of the Li isotope and elemental profiles through syenite and country rock are suggestive of diffusion-driven isotope fractionation, they cannot be modeled by one-dimensional diffusive transport and point to circulation of a fluid having a high 67 Li value (possibly seawater) along the chilled contact. In all, this study demonstrates that Li isotopes can be used to identify complex fluid- and diffusion-governed processes taking place during the final cooling of such rocks. (c) 2007 Elsevier B.V All rights reserved.

Perception du risque lié au tabagisme: données et interrogations [Smoking risk perception: facts and questions]

Based on general concepts relating to risk perception, the authors summarize in this article today's knowledge of smoking risk perception. A pluridisciplinary approach (general internal medicine, public health and anthropology) allows an improved understanding of its complexity, its utility in every day clinical practice and of the questions still pending around its use and evaluation in research projects.

Critical analysis and extension of the Hirshfeld atoms in molecules

The computational approach to the Hirshfeld [Theor. Chim. Acta 44, 129 (1977)] atom in a molecule is critically investigated, and several difficulties are highlighted. It is shown that these difficulties are mitigated by an alternative, iterative version, of the Hirshfeld partitioning procedure. The iterative scheme ensures that the Hirshfeld definition represents a mathematically proper information entropy, allows the Hirshfeld approach to be used for charged molecules, eliminates arbitrariness in the choice of the promolecule, and increases the magnitudes of the charges. The resulting "Hirshfeld-I charges" correlate well with electrostatic potential derived atomic charges

Effective atomic orbitals for fuzzy atoms

The method of extracting effective atomic orbitals and effective minimal basis sets from molecular wave function characterizing the state of an atom in a molecule is developed in the framework of the "fuzzy" atoms. In all cases studied, there were as many effective orbitals that have considerable occupation numbers as orbitals in the classical minimal basis. That is considered to be of high conceptual importance

Energy partitioning for "fuzzy" atoms

The total energy of molecule in terms of 'fuzzy atoms' presented as sum of one- and two-atomic energy components is described. The divisions of three-dimensional physical space into atomic regions exhibit continuous transition from one to another. The energy components are on chemical energy scale according to proper definitions. The Becke's integration scheme and weight function determines realization of method which permits effective numerical integrations

[Archives de la Parole]. , Hōli Song (complainte) : in maithili / [Sir George Grierson], éd. ; Linguistic survey of India ; [Ramanand Prasad Varma], voix

[Traditions. Asie. Inde. Province du Bihar. Darbhanga]

Carte du département du Pas-de-Calais / Lith. de F[éli]x Robaut

Échelle(s) : [ca 1:286 000], 2 Myriamètres [= 7 cm]

A qui li dic? : la detecció de l’abús sexual infantil i el traspàs d’informació entre professionals

Aquest treball s'estructura en una primera part de fonamentació teòrica. El procediment que s'ha seguit ha estat la recerca bibliogràfica. Es basa en els aspectes tècnics a tenir en compte per la detecció de l' Abusos Sexuals Infantils (ASI), la ubicació dels Serveis Bàsics d'Atenció Social (SBAS) dins el sistema català de serveis socials, el marc jurídic dels drets i de la protecció a la infància i l'adolescència així com de qüestions relatives al tractament de dades, de la confidencialitat de les informacions de què disposem els/les professionals, l'obligació de secret, complementat amb la deontologia professional, que ens pot orientar a l'hora de prendre les decisions més adequades a la nostra praxi. La segona part del treball és empírica. El procediment ha estat portar a terme un grup de reflexió ètica amb professionals del Consorci de Benestar Social del Pla de l'Estany-Banyoles. Partint de casos pràctics de sospita d'ASI, les persones participants han concretat els principals problemes (alguns dels quals relacionats amb l'ètica aplicada) davant els quals s'han trobat a la fase de detecció/intervenció. Les aportacions extretes de les diferents sessions en les quals es van treballar part dels objectius d'aquesta recerca ens permeten concretar la realitat i una primera deliberació sobre quina podria ser la bona pràctica general. La tercera part utilitza la fonamentació teòrica i els material del treball de camp per presentar la reflexió final que pretén donar resposta als objectius plantejats en aquesta recerca