Large metallicity variations in the Galactic interstellar medium.

The interstellar medium (ISM) comprises gases at different temperatures and densities, including ionized, atomic and molecular species, and dust particles1. The neutral ISM is dominated by neutral hydrogen2 and has ionization fractions of up to eight per cent3. The concentration of chemical elements heavier than helium (metallicity) spans orders of magnitudes in Galactic stars4, because they formed at different times. However, the gas in the vicinity of the Sun is assumed to be well mixed and to have a solar metallicity in traditional chemical evolution models5. The ISM chemical abundances can be accurately measured with ultraviolet absorption-line spectroscopy. However, the effects of dust depletion6-9-which removes part of the metals from the observable gaseous phase and incorporates it into solid grains-have prevented, until recently, a deeper investigation of the ISM metallicity. Here we report the dust-corrected metallicity of the neutral ISM measured towards 25 stars in our Galaxy. We find large variations in metallicity over a factor of ten (with an average of 55 ± 7 per cent solar metallicity and a standard deviation of 0.28 dex), including many regions of low metallicity, down to about 17 per cent solar metallicity and possibly below. Pristine gas falling onto the Galactic disk in the form of high-velocity clouds can cause the observed chemical inhomogeneities on scales of tens of parsecs. Our results suggest that this low-metallicity accreting gas does not efficiently mix into the ISM, which may help us understand metallicity deviations in nearby coeval stars.

Entre ciência e diplomacia: a organizaçäo da influência científica francesa na América Latina, 1900-1940 / Between science and diplomacy: the organization of the French scientific influence in Latin America, 1900-1940

Mostra como o essencial das relaçöes científicas entre a França e a América Latina passou pelo Groupement des Universités et Grandes Ecoles de France pour les Relations avec l'Amérique Latine, ou foi iniciado por ele. Se esse quadro se verificou muito limitado nos anos 20, na Argentina, e nos anos 30, no Brasil e no México, permitiu, ainda assim, o desenvolvimento de ligaçöes entre cientistas em várias disciplinas (matemáticas, biologia, medicina etc.).

Le Groupement des Universités et Grandes Ecoles de France pour les relations avec l'Amérique Latine et la création d'Instituts à Rio, Säo Paulo et Buenos Aires (1907/1940) / The Groupement des Universités et Grandes Ecoles de France for the relations with Latin America, and the creation of Institutes in Rio, Säo Paulo and Buenos Aires (1907-1940)

Apresenta inicialmente as origens do Groupement des Universités et Grandes Écoles de France, suas realizaçöes antes de 1914, durante a Guerra de 1914/1918 e no período entre-guerras. Aborda, em seguida, a criaçäo do Institut de l'Université de Paris em Buenos Airese de institutos no Brasil. Conclui com um balanço comparativo entre Brasil e Argentina, apontando as diferenças existentes entre os Institutos do Rio e os de Buenos Aires, e descrevendo os contextos locais responsáveis por essas diferenças.(MAM)

Le Groupement des Universités et Grandes Ecoles de France pour les relations avec l'Amérique Latine et les échanges avec le Brésil / The Groupement des Universités et Grandes Ecoles de France for the relations with Latin America and exchanges with Brazil

Descreve o contexto e os objetivos a partir dos quais foi constituído o Groupement des Universités et Grandes Ecoles de France, suas atividades antes de 1920 no Rio e em Säo Paulo, e a retomada em 1922, após a guerra. Menciona a criaçäo do Institut Franco-Brésilien de Haute Culture no Rio e do Institut Technique Franco-Pauliste em Säo Paulo. Aborda, finalmente, o período 1932/1940 em que se dá o declínio da Associaçäo.(MAM)