R&D Productivty: an International Study

The objective of this paper is to explore the impact of R&D expenditures on company performance. R&D activities play an essential role in the future economic development and financial performance of firms. However, with the exception of some American studies, the economic effectiveness of such investment is seldom demonstrated explicitly by the literature, and to the best of our knowledge, there are no existing studies on R&D productivity taking an international approach. Our research design is based on an earnings equation associating earnings with recorded assets, R&D expenditures and selling, general and administrative (SG&A) expenses (proxying advertising expenses). We determine a rate of return on R&D for each given sample of firms in 12 developed countries. Our results corroborate previous studies of American companies, which found that reported earnings, adjusted for the expensing of R&D, reflect realized benefits from R&D. This study confirms the positive contribution of R&D activities to future company performance, although this contribution can vary from one country to another.R&D productivity; R&D profitability; international study

Le caractère de réversibilité dans l'étude de la migration

La réflexion sur les concepts de mobilité spatiale amène à dépasser le critère de "changement de résidence" pour aborder les flux migratoires contemporains sous leurs diverses formes. L'introduction du caractère de réversibilité éventuelle de la migration permet de pousser plus en avant la notion d'espace de vie, que D. Courgeau a déjà introduite lors du quatrième colloque de démographie africaine en 1975. Les auteurs essayent de centrer cet espace de vie sur la notion de "résidence-base"; ils peuvent ainsi définir divers types de flux que le concept de changement de résidence ne permettrait pas de saisir. En particulier, l'introduction du caractère de réversibilité éventuelle de la migration permet de dépasser la dichotomie utilisée jusqu'à présent entre déplacements définitifs et déplacements temporaires, bien que la définition précise de cette réversibilité reste à faire. (résumé d'auteur

Dynamique de la population et migration en Guyane

Paradoxe peu fréquent d'un territoire quasiment vierge, mais localement en voie de surpeuplement, la Guyane présente une inégale répartition de l'accumulation des hommes face à une exploitation limitée des richesses naturelles. Cette étude analyse d'une part la dynamique de la population de la Guyane et ses relations avec les phénomènes migratoires des deux dernières décennies et d'autre part aborde les problèmes méthodologiques que pose l'appréhension de ces phénomènes

Alternative life-histories in a socially polymorphic ant

Social organisms vary greatly in the number of breeders per group; yet, the causes and consequences of this variation remain poorly known. Here, we show that variation in social structure is tightly linked with changes in several fundamental life-history traits within one population of ants. Multiple-queen colonies of Formica selysi were much more populous than single-queen ones. They also occurred in areas of higher nest density, had longer colony lifespan, produced smaller queens that presumably disperse less, and invested less in reproductive individuals relative to workers. These multiple changes in life histories are consistent with a shift in the mode of colony foundation and the degree of philopatry of queens. They may also provide various fitness benefits to members of multiple-queen colonies and are likely to play a central role in the evolution and maintenance of polymorphic social structure

Investigation of suitability of the method of volume averaging for the study of heat transfer in superconducting accelerator magnet cooled by superfluid helium.

In the field of applied superconductivity, there is a growing need to better understand heat transfers in superconducting accelerator magnets. Depending on the engineering point of view looked at, either 0-D, 1-D, 2D or 3D modeling may be needed. Because of the size of these magnets, alone or coupled together, it is yet, impossible to study this numerically for computational reasons alone without simplification in the description of the geometry and the physics. The main idea of this study is to consider the interior of a superconducting accelerator magnet as a porous medium and to apply methods used in the field of por-ous media physics to obtain the equations that model heat transfers of a superconducting accelerator magnet in different configurations (steady-state, beam losses, quench, etc.) with minimal compromises to the physics and geometry. Since the interior of a superconducting magnet is made of coils, collars and yoke filled with liquid helium, creating channels that interconnect the helium inside the magnet, an upscaling method provides models that describe heat transfer at the magnet scale and are suitable for numerical studies. This paper presents concisely the method and an example of application for super-conducting accelerator magnet cooled by superfluid helium in the steady-state regime in considering the thermal point of view