Éditeur(s) : HAL CCSD
Résumé : International audience
This paper deals with data structures within GIS. Continuous phenomenons are usually represented by raster structures for simplicity reasons. With such structures spatial repartitions of the data is not easily interpretable. Moreover, in an overlapping clustering context these structures remove the links between the data and the algorithms. We propose a vector representation of such data based on non-regular multi-rings polygons. The structure requires multipart nested polygons and new set operations. We present the formalism based on belief theory and uncertainty reasoning. We also detail the implementation of the structures and the set operations. The structures and the set operations are illustrated in the context of forest classification having diffuse transitions.
IF&GIS
Shangai, China

hal-01514239
https://hal.archives-ouvertes.fr/hal-01514239

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The quasi-equilibrium approximation is acceptable when molecular interactions are fast enough compared to circuit dynamics, but is no longer allowed when cellular activities are governed by rare events. A typical example is the lactose operon (lac), one of the most famous paradigms of transcription regulation, for which several theories still coexist to describe its behaviors. The lac system is generally analyzed by using equilibrium constants, contradicting single-event hypotheses long suggested by Novick and Weiner (1957). Enzyme induction as an all-or-none phenomenon. Proc. Natl. Acad. Sci. USA 43, 553-566) and recently refined in the study of (Choi et al., 2008. A stochastic single-molecule event triggers phenotype switching of a bacterial cell. Science 322, 442-446). In the present report, a lac repressor (LacI)-mediated DNA immunoprecipitation experiment reveals that the natural LacI-lac DNA complex built in vivo is extremely tight and long-lived compared to the time scale of lac expression dynamics, which could functionally disconnect the abortive expression bursts and forbid using the standard modes of lac bistability. As alternatives, purely kinetic mechanisms are examined for their capacity to restrict induction through: (i) widely scattered derepression related to the arrival time variance of a predominantly backward asymmetric random walk and (ii) an induction threshold arising in a single window of derepression without recourse to nonlinear multimeric binding and Hill functions. Considering the complete disengagement of the lac repressor from the lac promoter as the probabilistic consequence of a transient stepwise mechanism, is sufficient to explain the sigmoidal lac responses as functions of time and of inducer concentration. This sigmoidal shape can be misleadingly interpreted as a phenomenon of equilibrium cooperativity classically used to explain bistability, but which has been reported to be weak in this system.
ISSN: 0022-5193

inserm-00818506
http://www.hal.inserm.fr/inserm-00818506
http://www.hal.inserm.fr/inserm-00818506/document
http://www.hal.inserm.fr/inserm-00818506/file/LacI-TeX.pdf
ARXIV : 1312.5566