AGRIBUSINESS MANAGEMENT OF EXCHANGE RATE RISK

This study did structured interviews with senior agribusiness executives to find out how they managed exchange rate risk and especially deep devaluations of a foreign currency. The Mexican peso crisis was the focus of the study, but the results can be informative when anticipating situations for other countries and currencies.Agribusiness, International Relations/Trade,

Photoelectric effect on dust grains across the L1721 cloud in the rho Ophiuchi molecular complex

We present ISO-LWS measurements of the main gas cooling lines, C+ 158 mum and O 63 mum towards a moderate opacity molecular cloud (Av=3), L1721, illuminated by the B2 star nu Sco (X = 5-10). These data are combined with an extinction map and IRAS dust emission images to test our understanding of gas heating and cooling in photo-dissociation regions (PDRs). This nearby PDR is spatially resolved in the IRAS images; variations in the IRAS colors across the cloud indicate an enhanced abundance of small dust grains within the PDR. A spatial correlation between the gas cooling lines and the infrared emission from small dust grains illustrates the dominant role of small dust grains in the gas heating through the photoelectric effect. The photoelectric efficiency, determined from the observations by ratioing the power radiated by gas and small dust grains, is in the range 2 to 3% in close agreement with recent theoretical estimates. The brightness profiles across the PDR in the C+ 158 mum and O 63 mum lines are compared with model calculations where the density profile is constrained by the extinction data and where the gas chemical and thermal balances are solved at each position. We show that abundance variations of small dust grains across the PDR must be considered to account for the LWS observations.Comment: 10 pages, 15 figure

Quimper – Kerlagatu

Préalablement à la construction d’un lotissement par la Ville de Quimper sur le secteur de Kerlagatu, un diagnostic archéologique a été réalisé par deux archéologues Afan du 6 juillet au 4 septembre 1998. 95 tranchées ont été implantées sur l’ensemble des 11,5 ha concernés par le projet. Le relief prononcé n’a pas permis une implantation régulière. Il s’agit en effet d’un petit plateau culminant à 33 m NGF délimité par des versants dont la pente est généralement forte, surtout au nord et à l’..

Vannes – Hôtel de Roscanvec

Du 16 mars au 3 avril 1998, un diagnostic archéologique a été réalisé dans le jardin de l’Hôtel de Roscanvec, préalablement à la construction d’une crypte-galerie reliant les bâtiments de Château-Gaillard et de l’Hôtel de Roscanvec. L’intervention a été effectuée par deux archéologues de l’Afan, avec la collaboration d’Alain Triste et de deux autres membres du CERAM. Deux sondages, de 32 m2 de superficie chacun, ont été implantés pour le premier au pied de la façade occidentale de l’Hôtel et,..

Les échanges d'enfants assistés dans les années 1830 : objets, enjeux, bilan. L'exemple des Côtes-du-Nord

Certaines familles pauvres déposent anonymement leur enfant à l’hospice pour demander par la suite qu’il leur soit confié, en tant que famille d’accueil, moyennant rétribution. Pour lutter contre cette pratique, la circulaire du 21 juillet 1827 prévoit des échanges interdépartementaux des enfants assistés afin de priver les auteurs de ces faux abandons de la possibilité de retrouver leurs nourrissons. L’auteure étudie la mise en œuvre de cette politique par le département des Côtes-du-Nord et les raisons sociales et financières de son échec

Pour mémoire – François Chappé

Il est parti le 18 novembre 2007. Insolite personnage, insolite cérémonie, toute entière voulue par François Chappé et demandée dans son testament, insolite photographie, prise lors d’un cours public organisé en plein air, devant l’Université, entre les deux tours de l’élection présidentielle de 2002. Un cours d’histoire contemporaine sur la montée des fascismes. Un cours ouvert à tous, syndicalistes, républicains, démocrates. Étudiants, bien sûr. Cette photo qu’il nous a demandé de retenir ..

Density structure of the Horsehead nebula photo-dissociation region

We present high angular resolution images of the H$_2$ 1-0 S(1) line emission obtained with the Son of ISAAC (SOFI) at the New Technology Telescope (NTT) of the Horsehead nebula. These observations are analysed in combination with H$\alpha$ line emission, aromatic dust, CO and dust continuum emissions. The Horsehead nebula illuminated by the O9.5V star $\sigma$ Ori ($\chi \sim$ 60) presents a typical photodissociation region (PDR) viewed nearly edge-on and offers an ideal opportunity to study the gas density structure of a PDR. The H$_2$ fluorescent emission observations reveal extremely sharp and bright filaments associated with the illuminated edge of the nebula which spatially coincides with the aromatic dust emission. Analysis of the H$_2$ fluorescent emission, sensitive to both the far-UV radiation field and the gas density, in conjunction with the aromatic dust and H$\alpha$ line emission, brings new constraints on the illumination conditions and the gas density in the outer PDR region. Furthermore, combination of this data with millimeter observations of CO and dust continuum emission allows us to trace the penetration of the far-UV radiation field into the cloud and probe the gas density structure throughout the PDR. From comparison with PDR model calculations, we find that i) the gas density follows a steep gradient at the cloud edge, with a scale length of 0.02 pc (or 10'') and $n_H\sim 10^4$ and $10^5$ cm$^{-3}$ in the H$_2$ emitting and inner cold molecular layers respectively, and ii) this density gradient model is essentially a constant pressure model, with $P\sim$4 $10^6$ K cm$^{-3}$. The constraints derived here on the gas density profile are important for the study of physical and chemical processes in PDRs and provide new insight into the evolution of interstellar clouds.Comment: To be published in A&

The penetration of FUV radiation into molecular clouds

The solution of the FUV radiative transfer equation can be complicated if the most relevant radiative processes such as dust scattering and gas line absorption are included, and have realistic (non-uniform) properties. We have extended the spherical harmonics method to solve for the FUV radiation field in illuminated clouds taking into account gas absorption and coherent, nonconservative and anisotropic scattering by dust grains. Our formalism allows us to consistently include: (i) varying dust populations and (ii) gas lines in the FUV radiative transfer. The FUV penetration depth rises for increasing dust albedo and anisotropy of the scattered radiation (e.g. when grains grow towards cloud interiors). Illustrative models of illuminated clouds where only the dust populations are varied confirm earlier predictions for the FUV penetration in diffuse clouds (A_V1) we show that the FUV radiation field inside the cloud can differ by orders of magnitude depending on the grain properties. We show that the photochemical and thermal gradients can be very different depending on grain growth. Therefore, the assumption of uniform dust properties and averaged extinction curves can be a crude approximation to determine the resulting scattering properties, prevailing chemistry and atomic/molecular abundances in ISM clouds or protoplanetary disks.Comment: Accepted for publication in Astronomy & Astrophysics. Section 2. Astrophysical processes. Version 2: minor language corrections added. Figs. 2, 4 and 8 bitmapped to lower resolutio