A Proof of Tarski’s Fixed Point Theorem by Application of Galois Connections

Two examples of Galois connections and their dual forms are considered. One of them is applied to formulate a criterion when a given subset of a complete lattice forms a complete lattice. The second, closely related to the first, is used to prove in a short way the Knaster-Tarski’s fixed point theore

La dimension migratoire des Antilles

Forcée, dirigée, volontaire... la migration a toujours été au coeur des processus adaptatifs qui ont forgé l'actuelle société antillaise, soumise à rude épreuve au cours des dernières décennies : mutation statutaire, explosion démographique et exutoire migratoire massif, révolution des transports aériens et émergence d'une société "bipolaire", passage de l'économie de plantation à l'économie de transferts...Ainsi la migration, vecteur de tous ces changements et moyen d'ajustement entre espaces économiques hiérarchisés, s'articule avec de nouvelles normes de mobilité que la seule observation des phénomènes démographiques et des mouvements de population ne suffit plus à appréhender. Par son approche multidisciplinaire, cet ouvrage constitue un essai scientifique de "migratologie", qui appréhende la dimension migratoire des Antilles comme un fait de société, au travers des processus résultant des facteurs spatio-temporels caraïbéens (première partie), des déterminants institutionnels et économiques (deuxième partie), et de la dynamique des courants migratoires (troisième partie). (Résumé d'auteur

Biclosed Binary Relations and Galois Connections.

Given two closure spaces (E,j) and (E',j'), a relation R inclue dans E x E' is said biclosed if every row of its matrix representation corresponds t o a closed subset of E', and every column to a closed subset of E. An isomorphism between, on the one hand, the set of all biclosed relations and, on the other hand, the set of all Galois connections between the two lattices of closed sets is established. Several computational applications are derived from this result.DATA ANALYSIS ; MATHEMATICS ; CONNECTIONS

Isoptopic evidence of the transfer of nitrogen fixed by legumes to coffee trees

The use of isotopic methods has made it possible to quantify the contribution of nitrogen fixed by a coffee plantation. Thanks to the use of the natural 15N abundance assessment technique, we were able to show that, in field condition, roughly 30/ of the nitrogen effectively fixed by a legume (including biomass, roots and root exudates) were transferred to the associated coffee trees. The quantities of N transferred by legume prunings to sole coffee trees were measured to evaluate the amount of N transferred to coffee via litter fall or soil

Leaf natural 15N abundance and total N concentration as potential indicators of plant N nutrition in legumes and pioneer species in a rain forest of French Guiana

The suitability of the natural 15N abundance and of total N concentration of leaves as indicators of the type of plant N nutrition in a rain forest of French Guiana were tested. Leaf samples from primary legume species, non-legumes (pioneer species) and from the non-N2-fixing species Dicorynia guianensis were analyzed. Both '15N and total leaf N varied widely (m1 r '15N (‰) r 7 and 1 r leaf N(%) r 3.2) suggesting possible distinctions between diazotrophic and non-fixing plants. The '15N also revealed two statistically distinct groups of non-N2-fixing species ('15N = 5.14 - 0.3 vs '15Nv=v1.65 - 0.17) related to the different ecological behaviors of these species in the successional processes. We conclude that the '15N signature of plant leaves combined with their total N concentration may be relevant indicators for identifying functional groups within the community of non-N2-fixing species, as well as for detecting diazotrophy. Despite the variability in the '15N of the non-N2-fixing species, N2-fixing groups can still be identified, provided that plants are simultaneously classified taxonomically, by their leaf '15N and total N concentration and by the presence or absence of nodules. The variability in the '15N of the non-fixing species is discussed