64 research outputs found
Clones in Graphs
Finding structural similarities in graph data, like social networks, is a
far-ranging task in data mining and knowledge discovery. A (conceptually)
simple reduction would be to compute the automorphism group of a graph.
However, this approach is ineffective in data mining since real world data does
not exhibit enough structural regularity. Here we step in with a novel approach
based on mappings that preserve the maximal cliques. For this we exploit the
well known correspondence between bipartite graphs and the data structure
formal context from Formal Concept Analysis. From there we utilize
the notion of clone items. The investigation of these is still an open problem
to which we add new insights with this work. Furthermore, we produce a
substantial experimental investigation of real world data. We conclude with
demonstrating the generalization of clone items to permutations.Comment: 11 pages, 2 figures, 1 tabl
Les jardins-vergers familiaux d'Amazonie centrale : un exemple d'utilisation de l'espace
Analyse structurale, floristique, sanitaire et socio-culturelle de trois vergers polyspécifiques d'Amazonie centrale brésilienne (environs de Manaus). L'installation de vergers destinés à la consommation familiale et éventuellement à la vente est une pratique courante dans cette région, elle succède à la culture du manioc sur brûlis. Dans la plaine alluviale, de tels vergers peuvent être une reconversion de systèmes arborés antérieurs. Les espèces utilisées sont d'origines diverses, les amazoniennes étant prédominantes : 40 sur un total de 60 espèces recensées. Longtemps ignorée, l'arboriculture amazonienne, aménagement relevant de l'agroforesterie, devrait être, en raison de ses caractéristiques et dans les conditions actuelles, encouragée. (Résumé d'auteur
Efficient Enumeration of Bipartite Subgraphs in Graphs
Subgraph enumeration problems ask to output all subgraphs of an input graph
that belongs to the specified graph class or satisfy the given constraint.
These problems have been widely studied in theoretical computer science. As
far, many efficient enumeration algorithms for the fundamental substructures
such as spanning trees, cycles, and paths, have been developed. This paper
addresses the enumeration problem of bipartite subgraphs. Even though bipartite
graphs are quite fundamental and have numerous applications in both theory and
application, its enumeration algorithms have not been intensively studied, to
the best of our knowledge. We propose the first non-trivial algorithms for
enumerating all bipartite subgraphs in a given graph. As the main results, we
develop two efficient algorithms: the one enumerates all bipartite induced
subgraphs of a graph with degeneracy in time per solution. The other
enumerates all bipartite subgraphs in time per solution
Monalysin, a Novel ß-Pore-Forming Toxin from the Drosophila Pathogen Pseudomonas entomophila, Contributes to Host Intestinal Damage and Lethality
Pseudomonas entomophila is an entomopathogenic bacterium that infects and kills Drosophila. P. entomophila pathogenicity is linked to its ability to cause irreversible damages to the Drosophila gut, preventing epithelium renewal and repair. Here we report the identification of a novel pore-forming toxin (PFT), Monalysin, which contributes to the virulence of P. entomophila against Drosophila. Our data show that Monalysin requires N-terminal cleavage to become fully active, forms oligomers in vitro, and induces pore-formation in artificial lipid membranes. The prediction of the secondary structure of the membrane-spanning domain indicates that Monalysin is a PFT of the ß-type. The expression of Monalysin is regulated by both the GacS/GacA two-component system and the Pvf regulator, two signaling systems that control P. entomophila pathogenicity. In addition, AprA, a metallo-protease secreted by P. entomophila, can induce the rapid cleavage of pro-Monalysin into its active form. Reduced cell death is observed upon infection with a mutant deficient in Monalysin production showing that Monalysin plays a role in P. entomophila ability to induce intestinal cell damages, which is consistent with its activity as a PFT. Our study together with the well-established action of Bacillus thuringiensis Cry toxins suggests that production of PFTs is a common strategy of entomopathogens to disrupt insect gut homeostasis
Frequency fluctuations in silicon nanoresonators
Frequency stability is key to performance of nanoresonators. This stability
is thought to reach a limit with the resonator's ability to resolve
thermally-induced vibrations. Although measurements and predictions of
resonator stability usually disregard fluctuations in the mechanical frequency
response, these fluctuations have recently attracted considerable theoretical
interest. However, their existence is very difficult to demonstrate
experimentally. Here, through a literature review, we show that all studies of
frequency stability report values several orders of magnitude larger than the
limit imposed by thermomechanical noise. We studied a monocrystalline silicon
nanoresonator at room temperature, and found a similar discrepancy. We propose
a new method to show this was due to the presence of frequency fluctuations, of
unexpected level. The fluctuations were not due to the instrumentation system,
or to any other of the known sources investigated. These results challenge our
current understanding of frequency fluctuations and call for a change in
practices
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