Neutral Theory and Relative Species Abundance in Ecology

The theory of island biogeography[1] asserts that an island or a local community approaches an equilibrium species richness as a result of the interplay between the immigration of species from the much larger metacommunity source area and local extinction of species on the island (local community). Hubbell[2] generalized this neutral theory to explore the expected steady-state distribution of relative species abundance (RSA) in the local community under restricted immigration. Here we present a theoretical framework for the unified neutral theory of biodiversity[2] and an analytical solution for the distribution of the RSA both in the metacommunity (Fisher's logseries) and in the local community, where there are fewer rare species. Rare species are more extinction-prone, and once they go locally extinct, they take longer to re-immigrate than do common species. Contrary to recent assertions[3], we show that the analytical solution provides a better fit, with fewer free parameters, to the RSA distribution of tree species on Barro Colorado Island (BCI)[4] than the lognormal distribution[5,6].Comment: 19 pages, 1 figur

Unary enhancements of inherently nonfinitely based semigroups

We exhibit a simple condition under which a finite involutary semigroup whose semigroup reduct is inherently nonfinitely based is also inherently nonfinitely based as a unary semigroup. As applications, we get already known as well as new examples of inherently nonfinitely based involutory semigroups. We also show that for finite regular semigroups, our condition is not only sufficient but also necessary for the property of being inherently nonfinitely based to persist. This leads to an algorithmic description of regular inherently nonfinitely based involutory semigroups.Comment: 11 pages, 1 figure. Section 4 has been improved and expanded according to suggestions of an anonymous referee of the journal version. A few minor improvements have been done in Section

Towards a Complete Twistorization of the Heterotic String

In $D=3,4,6$ and 10 space--time dimensions considered is a string model invariant under transformations of $N=1$ space--time supersymmetry and $n=D-2$ local worldsheet supersymmetry with the both Virasoro constraints solved in the twistor form. The twistor solution survives in a modified form even in the presence of the heterotic fermions.Comment: 11 pages, latex, report no. Goteborg-ITP-94-1

Transfert de connaissances dans les entreprises multinationales : efficacité et influence des facteurs contextuels

Dans la présente recherche, nous nous sommes penchés sur le processus du transfert intra-organisationnel de connaissances au sein d’entreprises multinationales (EM). Partant du triple constat suivant : les connaissances organisationnelles constituent un avantage stratégique (Barney, 1991 ; Bartlett et Ghoshal, 1998), les transferts intra-organisationnels constituent la raison d’être des EM (Gupta et Govindarajan, 2000), lesquelles ont accès à un vaste bassin de connaissances disséminées à travers le monde par le biais de leurs filiales et les mécanismes organisationnels internes sont plus efficaces que ceux du marché (Williamson, 1987 ; Casson, 1976) pour transférer des connaissances entre unités organisationnelles; nous nous sommes intéressés aux facteurs pouvant affecter l’efficacité de ce processus de transfert. Ayant identifié, lors de notre revue des écrits théoriques, une multitude d’approches permettant d’appréhender ce phénomène, nous proposons, dans notre recherche, un modèle théorique intégrant les trois étapes propres au processus de transfert, soit : la détermination des connaissances à transférer, la sélection des mécanismes de transfert appropriés et, finalement, l’évaluation, d’une part, de l’efficacité des transferts et, d’autre part, de l’ensemble des facteurs contextuels ayant un impact sur l’efficacité de ce processus. Sur le plan théorique, cette recherche oppose deux courants dominant ce champ disciplinaire. L’approche stratégique, exprimée par la théorie des ressources, met l’accent sur l’importance prépondérante des facteurs organisationnels internes sur l’efficacité de toute action organisationnelle (Bartlett et Ghoshal, 1998 ; Barney, 1991). Cette approche s’oppose au courant institutionnel, lequel considère plutôt que les choix et les actions organisationnels sont surtout conditionnés par les contraintes de l’environnement externe (Ferner, 1997; Kostova, 1999; Scott, 1991). Les résultats de notre recherche démontrent que, malgré l’existence de contraintes de nature institutionnelle et culturelle, l’efficacité du processus de transfert des connaissances associées à la gestion des ressources humaines relève davantage des conditions organisationnelles internes et, plus particulièrement, de l’implication de la haute direction, du rôle accordé à la fonction RH et de l’alignement entre la stratégie corporative, la stratégie RH et la culture organisationnelle. Sur le plan méthodologique, il s’agit d’une recherche exploratoire qualitative menée auprès de trois EM (2 canadiennes et 1 française) oeuvrant dans les secteurs de la métallurgie et des télécommunications. Les données empiriques proviennent de 17 entrevues approfondies que nous ont accordées, au Canada, en France, en Allemagne et en Suisse des cadres responsables de la gestion des ressources humaines, affectés au siège social des EM en question ou œuvrant au sein de leurs filiales, et de sources documentaires secondaires.The aim of this research is to investigate the process of transfer of intra-organizational knowledge within multinational corporations. Taking into consideration the following three postulates: that organizational knowledge represents a source of competitive advantage for a firm (Barney, 1991; Bartlett and Ghoshal, 1998); that access to a large pool of knowledge disseminated across the world and the transfer of this knowledge across the organization constitutes la raison d’être of MNC (Gupta and Govindarajan, 2000); and that internal organizational mechanisms are more efficient than the market (Williamson, 1987) for the transfer of this knowledge between organizational units, for the purpose of this study we were particularly interested in the factors that can affect the effectiveness of this process of transfers. Having identified in past research various theoretical approaches to study this phenomena, we proposed and tested the integrative theoretical model helping to analyse the impact of contextual factors on each of the following three stages of the process of transfer: the determination of knowledge to be transferred, the selection of mechanisms of knowledge transfer and finally, the evaluation of the effectiveness of transfer. Our research confronts two theoretical perspectives currently dominating the field of knowledge transfer in multinational corporations. The strategic approach and the resource-based view of the firm emphasize the importance of internal organizational factors for the effectiveness of any organizational action (Bartlett and Ghoshal, 1998; Barney, 1991). On the other hand, the institutional approach considers rather that organizational choices and actions are conditioned by the external environment (Ferner, 1997; Kostova, 1999; Scott, 1991). The results of our research show that in spite of the existence of institutional and cultural constraints, the effectiveness of the entire process of transfer of knowledge related to HRM is determined by internal organizational conditions, such as the involvement of top management, the role of RH function and the alignment between corporative strategy, HR strategy and the organizational culture. Our methodological approach is based on a qualitative case-study of three multinational companies (two Canadian and one French) working in metallurgical and telecommunications sectors. Our empirical data stems from seventeen semi-structured interviews conducted with the top HR managers of these companies, who are actively involved in the process of knowledge transfer at HQ or at its subsidiaries in Canada, France, Germany and Switzerland. We also used a large amount of publicly available information from these companies

Matrix identities involving multiplication and transposition

We study matrix identities involving multiplication and unary operations such as transposition or Moore-Penrose inversion. We prove that in many cases such identities admit no finite basis. © European Mathematical Society 2012