686 research outputs found
Long hitting time, slow decay of correlations and arithmetical properties
No full textLet be the time needed for a point to enter for the first time in a ball centered in , with small radius . We construct a class of translations on the two torus having particular arithmetic properties (Liouville components with intertwined denominators of convergents) not satisfying a logarithm law, i.e. such that for generic \liminf_{r\to 0} \frac{\log \tau_r(x,x_0)}{-\log r} = \infty.
By considering a suitable reparametrization of the flow generated by a suspension of this translation, using a previous construction by Fayad, we show the existence of a mixing system on three torus having the same properties. The speed of mixing of this example must be subpolynomial, because we also show that: in a system having polynomial decay of correlations, the limsupr → 0 of the above ratio of logarithms (which is also called the upper hitting time indicator) is bounded from above by a function of the local dimension and the speed of correlation decay.
More generally, this shows that reparametrizations of torus translations having a Liouville component cannot be polynomially mixing
G. Gouvernet, G. Guieu, C. Rousset : Provence J. Peterlongo : Massif Central, Limousin, Auvergne, Velay P. Rat : Bourgogne-Morvan
No full textBonnefont Jean-Claude. G. Gouvernet, G. Guieu, C. Rousset : Provence J. Peterlongo : Massif Central, Limousin, Auvergne, Velay P. Rat : Bourgogne-Morvan. In: Revue Géographique de l'Est, tome 12, n°4, Octobre-décembre 1972. Problèmes de la protection et de la conservation de la nature dans la France de l'Est. pp. 448-449
Un guide géologique sur le Massif Central : J.-M Peterlongo, Massif Central (Limousin, Auvergne, Velay)
No full textTricart Jean. Un guide géologique sur le Massif Central : J.-M Peterlongo, Massif Central (Limousin, Auvergne, Velay). In: Annales de Géographie, t. 82, n°451, 1973. p. 350
Lossless Filter for Finding Long Multiple Approximate Repetitions Using a New Data Structure, the Bi-Factor Array
No full textSimilarity search in texts, notably biological sequences, has received substantial attention in the last few years. Numerous filtration and indexing techniques have been created in order to speed up the resolution of the problem. However, previous filters were made for speeding up pattern matching, or for finding repetitions between two sequences or occurring twice in the same sequence. In this paper, we present an algorithm called NIMBUS for filtering sequences prior to finding repetitions occurring more than twice in a sequence or in more than two sequences. NIMBUS uses gapped seeds that are indexed with a new data structure, called a bi-factor array, that is also presented in this paper. Experimental results show that the filter can be very efficient: preprocessing with NIMBUS a data set where one wants to find functional elements using a multiple local alignment tool such as GLAM ([7]), the overall execution time can be reduced from 10 hours to 6 minutes while obtaining exactly the same results
Finding Long and Multiple repetitions with Edit Distance
No full textWe present a tool for detecting long similar fragments that occur two or more times in a set of biological sequences. The problem has interesting applications in the analysis of biological sequences and their correlation, and becomes computationally challenging when a certain non negligible number of insertions, deletions and substitutions are allowed. For this reason exact exhaustive methods are hardly of practical use. In this paper we introduce a tool, FilmRed, that performs this task, and that manages instances whose size and parameters combination cannot be handled by any existing tool. This is achieved by using a filter as a preprocessing step, and by using the information that the filter has gathered also in the successive inference phase. To the best of our knowledge, FILMRED is the first ab initio tool that can deal with repeats occurring possibly several times, that have length of hundreds or thousands bases, and whose occurrences may differ in even more than 10% of their positions in terms of substitutions and indels
Filtre exact de sélection de longues répétitions approchées utilisant le tableau des bi-facteurs
No full textRIME: Repeat Identification
No full textWe present an algorithm for detecting long similar fragments occurring at least twice in a set of biological sequences. The problem becomes computationally challenging when the frequency of a repeat is allowed to increase and when a non-negligible number of insertions, deletions and substitutions are allowed. We introduce in this paper an algorithm, Rime1 1 Rime is also a reference to Coleridge's poem "The Rime of an Ancient Mariner" which contains many repetitions as a poetic device. (for Repeat Identification: long, Multiple, and with Edits) that performs this task, and manages instances whose size and combination of parameters cannot be handled by other currently existing methods. This is achieved by using a filter as a preprocessing step, and by then exploiting the information gathered by the filter in the following actual repeat inference step. To the best of our knowledge, Rime is the first algorithm that can accurately deal with very long repeats (up to a few thousands), occurring possibly several times, and with a rate of differences (substitutions and indels) allowed among copies of a same repeat of 10-15% or even more
Photoinduction of anthocyanin in maize: a genetic approach
No full textThe pathway of anthocyanin biosynthesis is well known while its regulation is less characterized. In this paper we focus our attention on the process of anthocyanin photoinduction. The results obtained following irradiation of seedling root tissues with lights of different quality disclose a significant response to blue light, apparently not attributable to phytochrome action. Even when anthocyanin accumulation is significantly increased because of the presence of Pl, a pigment intensifier, the total phytochrome content is not affected. The blue light effect is general in the sense that is observed in all genetic backgrounds tested. Photoinduction of anthocyanin accumulation in viviparous mutants blocked in carotenogenesis depends on blue light indicating that carotenoids are not involved in the blue response. Studies with calcium-channel blockers and calcium antagonists seem to exclude a requirement of Ca++ as an intermediary component of the light transduction pathway
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