64 research outputs found
A Tool to Recover Scalar Time-Delay Systems from Experimental Time Series
We propose a method that is able to analyze chaotic time series, gained from
exp erimental data. The method allows to identify scalar time-delay systems. If
the dynamics of the system under investigation is governed by a scalar
time-delay differential equation of the form ,
the delay time and the functi on can be recovered. There are no
restrictions to the dimensionality of the chaotic attractor. The method turns
out to be insensitive to noise. We successfully apply the method to various
time series taken from a computer experiment and two different electronic
oscillators
Segmentation non supervisée d'images polarimétriques passives
Ce papier montre l'intĂ©rĂȘt de la segmentation par grille active multi-composantes dans le traitement d'images obtenues par un systĂšme d'imagerie polarimĂ©trique de Stokes. L'utilisation conjointe d'un systĂšme d'imagerie non-conventionnel performant et d'une mĂ©thode de traitement (segmentation) adaptĂ©e peut ainsi ĂȘtre mis Ă profit pour des applications de contrĂŽle non-destructif. L'exemple prĂ©sentĂ© illustre en particulier la possibilitĂ© de segmenter l'image d'un objet suivant l'orientation gĂ©omĂ©trique de ses diverses facettes
Mutations of RNA polymerase II activate key genes of the nucleoside triphosphate biosynthetic pathways
The yeast URA2 gene, encoding the rate-limiting enzyme of UTP biosynthesis, is transcriptionally activated by UTP shortage. In contrast to other genes of the UTP pathway, this activation is not governed by the Ppr1 activator. Moreover, it is not due to an increased recruitment of RNA polymerase II at the URA2 promoter, but to its much more effective progression beyond the URA2 mRNA start site(s). Regulatory mutants constitutively expressing URA2 resulted from cis-acting deletions upstream of the transcription initiator region, or from amino-acid replacements altering the RNA polymerase II Switch 1 loop domain, such as rpb1-L1397S. These two mutation classes allowed RNA polymerase to progress downstream of the URA2 mRNA start site(s). rpb1-L1397S had similar effects on IMD2 (IMP dehydrogenase) and URA8 (CTP synthase), and thus specifically activated the rate-limiting steps of UTP, GTP and CTP biosynthesis. These data suggest that the Switch 1 loop of RNA polymerase II, located at the downstream end of the transcription bubble, may operate as a specific sensor of the nucleoside triphosphates available for transcription
Inactivation of TIF1Îł Cooperates with KrasG12D to Induce Cystic Tumors of the Pancreas
Inactivation of the Transforming Growth Factor Beta (TGFÎČ) tumor suppressor pathway contributes to the progression of Pancreatic Ductal AdenoCarcinoma (PDAC) since it is inactivated in virtually all cases of this malignancy. Genetic lesions inactivating this pathway contribute to pancreatic tumor progression in mouse models. Transcriptional Intermediary Factor 1 gamma (TIF1Îł) has recently been proposed to be involved in TGFÎČ signaling, functioning as either a positive or negative regulator of the pathway. Here, we addressed the role of TIF1Îł in pancreatic carcinogenesis. Using conditional Tif1Îł knockout mice (Tif1Îłlox/lox), we selectively abrogated Tif1Îł expression in the pancreas of Pdx1-Cre;Tif1Îłlox/lox mice. We also generated Pdx1-Cre;LSL-KrasG12D;Tif1Îłlox/lox mice to address the effect of Tif1Îł loss-of-function in precancerous lesions induced by oncogenic KrasG12D. Finally, we analyzed TIF1Îł expression in human pancreatic tumors. In our mouse model, we showed that Tif1Îł was dispensable for normal pancreatic development but cooperated with Kras activation to induce pancreatic tumors reminiscent of human Intraductal Papillary Mucinous Neoplasms (IPMNs). Interestingly, these cystic lesions resemble those observed in Pdx1-Cre;LSL-KrasG12D;Smad4lox/lox mice described by others. However, distinctive characteristics, such as the systematic presence of endocrine pseudo-islets within the papillary projections, suggest that SMAD4 and TIF1Îł don't have strictly redundant functions. Finally, we report that TIF1Îł expression is markedly down-regulated in human pancreatic tumors by quantitative RTâPCR and immunohistochemistry supporting the relevance of these findings to human malignancy. This study suggests that TIF1Îł is critical for tumor suppression in the pancreas, brings new insight into the genetics of pancreatic cancer, and constitutes a promising model to decipher the respective roles of SMAD4 and TIF1Îł in the multifaceted functions of TGFÎČ in carcinogenesis and development
Identification and Classification of Conserved RNA Secondary Structures in the Human Genome
The discoveries of microRNAs and riboswitches, among others, have shown functional RNAs to be biologically more important and genomically more prevalent than previously anticipated. We have developed a general comparative genomics method based on phylogenetic stochastic context-free grammars for identifying functional RNAs encoded in the human genome and used it to survey an eight-way genome-wide alignment of the human, chimpanzee, mouse, rat, dog, chicken, zebra-fish, and puffer-fish genomes for deeply conserved functional RNAs. At a loose threshold for acceptance, this search resulted in a set of 48,479 candidate RNA structures. This screen finds a large number of known functional RNAs, including 195 miRNAs, 62 histone 3âČUTR stem loops, and various types of known genetic recoding elements. Among the highest-scoring new predictions are 169 new miRNA candidates, as well as new candidate selenocysteine insertion sites, RNA editing hairpins, RNAs involved in transcript auto regulation, and many folds that form singletons or small functional RNA families of completely unknown function. While the rate of false positives in the overall set is difficult to estimate and is likely to be substantial, the results nevertheless provide evidence for many new human functional RNAs and present specific predictions to facilitate their further characterization
Dermacentor reticulatus: a vector on the rise
Dermacentor reticulatus is a hard tick species with extraordinary biological features. It has a high reproduction rate, a rapid developmental cycle, and is also able to overcome years of unfavourable conditions. Dermacentor reticulatus can survive under water for several months and is cold-hardy even compared to other tick species. It has a wide host range: over 60 different wild and domesticated hosts are known for the three active developmental stages. Its high adaptiveness gives an edge to this tick species as shown by new data on the emergence and establishment of D. reticulatus populations throughout Europe. The tick has been the research focus of a growing number of scientists, physicians and veterinarians. Within the Web of Science database, more than a fifth of the over 700 items published on this species between 1897 and 2015 appeared in the last three years (2013â2015). Here we attempt to synthesize current knowledge on the systematics, ecology, geographical distribution and recent spread of the species and to highlight the great spectrum of possible veterinary and public health threats it poses. Canine babesiosis caused by Babesia canis is a severe leading canine vector-borne disease in many endemic areas. Although less frequently than Ixodes ricinus, D. reticulatus adults bite humans and transmit several Rickettsia spp., Omsk haemorrhagic fever virus or Tick-borne encephalitis virus. We have not solely collected and reviewed the latest and fundamental scientific papers available in primary databases but also widened our scope to books, theses, conference papers and specialists colleaguesâ experience where needed. Besides the dominant literature available in English, we also tried to access scientific literature in German, Russian and eastern European languages as well. We hope to inspire future research projects that are necessary to understand the basic life-cycle and ecology of this vector in order to understand and prevent disease threats. We conclude that although great strides have been made in our knowledge of the eco-epidemiology of this species, several gaps still need to be filled with basic research, targeting possible reservoir and vector roles and the key factors resulting in the observed geographical spread of D. reticulatus. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1599-x) contains supplementary material, which is available to authorized users
SIGN LANGUAGE FORMAL DESCRIPTION AND SYNTHESIS
International audienceSpecial needs of deaf people appeal henceforward tosign language synthesis. The system presented here is basedon a hierarchical description of sign, trying to take thedifferent grammatical processes into account. Stress is laidon hand configurations specification thanks to finger shapesprimitives and hand global properties, and on location andorientation computation issues. We then expose the resultsachieved from the corresponding written form of signs,leading to their computer virtual animation
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