Morphological and allozyme variation in a collection of Cucumeropsis mannii Naudin (Cucurbitaceae) from Côte d'Ivoire

peer reviewe

On some effects of variability in the weiss epidemic model

The Weiss carrier-borne epidemic model is extended to incorporate random initial susceptible and carrier population sizes and general independent distributions for the infectious periods of the carriers. The qualitative effects of these variability factors on the spread of the disease are examined using different partial orderings for distribution functions. © 1988, Taylor & Francis Group, LLC. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Genetic diversity and germplasm conservation of three minor Andean tuber crop species

In traditional Andean agrosystems, three minor tuber crop species are of regional or local importance: oca (Oxalis tuberosa Molina), ulluco (Ullucus tuberosus Caldas) and mashua (Tropaeolum tuberosum Ruiz and Pav.). Genetic diversity within these species is very large and could result from the high ecological and cultural variability that characterizes the Andean area. Nowadays, many anthropic or ecological factors cause the loss of diversity and contribute to genetic erosion. The development of conservation strategies for genetic resources of Andean tubers, in situ as well as ex situ, includes a better knowledge of diversity in addition to the study of Andean farming strategies linked to this genetic diversity

A discrete time model for a S-I-S infectious disease with a random number of contacts between individuals

A chain-binomial deterministic model for the spread of an infectious disease of the S-I-S type is formulated that accounts explicitly for the distribution of the number of contacts made by each susceptible during one time interval. Under certain hypotheses, a threshold theorem for endemicity is derived, bounds for the endemic level are constructed, and the transient behavior of the epidemic process is investigated. © 1986.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

On linear stochastic compartmental models in discrete time

This note presents a general time-dependent study of linear stochastic compartmental models in discrete time. The transient distribution of the state of the system is obtained by adapting methods used in the continuous time analysis. Covariance functions with and without a time lag are then deduced by a simple probabilistic argument. Results are derived in the Markov case and are partly extended to the semi-Markov case. © 1985 Society for Mathematical Biology.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Amélioration des agrosystèmes intégrant le haricot commun (Phaseolus vulgaris L.) au Sud-Kivu montagneux

peer reviewedLe haricot commun, Phaseolus vulgaris L., est l'une des principales cultures de l'est de la République Démocratique du Congo. Au Sud Kivu montagneux, il est principalement produit en système d'association culturale, intégrant l'agriculture et de l'élevage, sur des terrains en pente avec des pratiques culturales inappropriées et une gestion calamiteuse de l'érosion, de la fertilité des sols. Comme modalités palliatives à la faible productivité de ce système, le bon choix de la période de semis, l'exploitation des terrains avec des cultures en couloir en intégrant des haies antiérosives de Leucaena et de Tripsacum en courbe de niveau et l'intégration de l'élevage de caprin dans le système, sont quelques pistes proposées qui permettraient de résoudre ce problème ainsi que celui de la disponibilité des terres qui se posent avec acuité dans le milieu. Ce système est présumé rentable car les déchets d'une activité sont utilisés comme intrants pour une autre au sein de la même exploitation