Stable laws and products of positive random matrices

Let $S$ be the multiplicative semigroup of $q\times q$ matrices with positive entries such that every row and every column contains a strictly positive element. Denote by $(X_n)_{n\geq1}$ a sequence of independent identically distributed random variables in $S$ and by $X^{(n)} = X_n ... X_1$, $n\geq 1$, the associated left random walk on $S$. We assume that $(X_n)_{n\geq1}$ verifies the contraction property $\P(\bigcup_{n\geq1}[X^{(n)} \in S^\circ])>0$, where $S^\circ$ is the subset of all matrices which have strictly positive entries. We state conditions on the distribution of the random matrix $X_1$ which ensure that the logarithms of the entries, of the norm, and of the spectral radius of the products $X^{(n)}$, $n\ge 1$, are in the domain of attraction of a stable law.Comment: 14 pages. To appear in Journal of Theoretical Probabilit

Desktop cutting of paper using a single emitter laser diode and inkjet printing

International audienceLaser cutting of paper is widely used in the paper conversion industry. CO 2 lasers are well suited for this type of applications. Desktop printing is a large market both for digital photography, document management and graphics applications, but it still lacks advanced cutting and scoring ability, and CO 2 lasers seem costly to be integrated in mass-market printers. For that reason, mass-scalable and low-cost semiconductor laser diodes would be very advantageous to add paper cutting and scoring features in desktop printers. However, common paper can not be cut properly using visible or Near Infrared (NIR) laser diode since it has a very poor absorption at these wavelengths. We report here an innovative solution to achieve paper cutting or scoring using a 1 W single emitter NIR laser diode, within an inkjet printer. A special ink that absorbs the NIR light, and that penetrates all through the paper, is first disposed on the lines to be cut. Then, the laser diode goes along the lines to be cut. We show that a cutting speed of 2m/min can be achieved on 80g/m 2 conventional paper. The influence of the optical properties of the ink on the cutting speed are discussed, as well as focussing issues. In particular, we show that invisible inks are suitable, and very clear-cut edges can be obtained. The perspective of this technique are discussed

User-centered visual analysis using a hybrid reasoning architecture for intensive care units

One problem pertaining to Intensive Care Unit information systems is that, in some cases, a very dense display of data can result. To ensure the overview and readability of the increasing volumes of data, some special features are required (e.g., data prioritization, clustering, and selection mechanisms) with the application of analytical methods (e.g., temporal data abstraction, principal component analysis, and detection of events). This paper addresses the problem of improving the integration of the visual and analytical methods applied to medical monitoring systems. We present a knowledge- and machine learning-based approach to support the knowledge discovery process with appropriate analytical and visual methods. Its potential benefit to the development of user interfaces for intelligent monitors that can assist with the detection and explanation of new, potentially threatening medical events. The proposed hybrid reasoning architecture provides an interactive graphical user interface to adjust the parameters of the analytical methods based on the users' task at hand. The action sequences performed on the graphical user interface by the user are consolidated in a dynamic knowledge base with specific hybrid reasoning that integrates symbolic and connectionist approaches. These sequences of expert knowledge acquisition can be very efficient for making easier knowledge emergence during a similar experience and positively impact the monitoring of critical situations. The provided graphical user interface incorporating a user-centered visual analysis is exploited to facilitate the natural and effective representation of clinical information for patient care

Expression in E. coli and characterization of the catalytic domain of Botrytis cinerea chitin synthase

<p>Abstract</p> <p>Background</p> <p>Chitin synthase 3a (CHS3a) from <it>Botrytis cinerea </it>(Bc) catalyses the multiple transfer of <it>N</it>-acetylglucosamine (GlcNAc) residues to the growing chitin chain. Chitin, a β-1,4 linked GlcNAc homopolymer, is an essential cell wall component of filamentous fungi. Chitin synthase, processive membranous protein, has been recognized as a promising target for new antifungicides. Enzymatic characterizations of chitin synthases have been limited, mainly because purity and amounts of integral enzyme obtained after purification procedures have not been sufficient.</p> <p>Findings</p> <p>We undertook the preparation of two BcCHS3a fragment proteins, containing only the central domain and devoid of the N-terminal and transmembrane C-terminal regions. The central domain of CHS3a, named SGC (Spsa GntI Core), is conserved in all UDP-glycosyltransferases and it is believed to contain the active site of the enzyme. CHS3a-SGC protein was totally expressed as inclusion bodies in <it>Escherichia coli</it>. We performed recombinant CHS3a-SGC purification in denaturing conditions, followed by a refolding step. Although circular dichroism spectra clearly exhibited secondary structures of renatured CHS3a-SGC, no chitin synthase activity was detected. Nevertheless CHS3a-SGC proteins show specific binding for the substrate UDP-GlcNAc with a dissociation constant similar to the Michaelis constant and a major contribution of the uracil moiety for recognition was confirmed.</p> <p>Conclusions</p> <p>Milligram-scale quantities of CHS3a-SGC protein with native-like properties such as specific substrate UDP-GlcNAc binding could be easily obtained. These results are encouraging for subsequent heterologous expression of full-length CHS3a.</p

Structural elements defining elongation factor Tu mediated suppression of codon ambiguity

In most prokaryotes Asn-tRNAAsn and Gln-tRNAGln are formed by amidation of aspartate and glutamate mischarged onto tRNAAsn and tRNAGln, respectively. Coexistence in the organism of mischarged Asp-tRNAAsn and Glu-tRNAGln and the homologous Asn-tRNAAsn and Gln-tRNAGln does not, however, lead to erroneous incorporation of Asp and Glu into proteins, since EF-Tu discriminates the misacylated tRNAs from the correctly charged ones. This property contrasts with the canonical function of EF-Tu, which is to non-specifically bind the homologous aa-tRNAs, as well as heterologous species formed in vitro by aminoacylation of non-cognate tRNAs. In Thermus thermophilus that forms the Asp-tRNAAsn intermediate by the indirect pathway of tRNA asparaginylation, EF-Tu must discriminate the mischarged aminoacyl-tRNAs (aa-tRNA). We show that two base pairs in the tRNA T-arm and a single residue in the amino acid binding pocket of EF-Tu promote discrimination of Asp-tRNAAsn from Asn-tRNAAsn and Asp-tRNAAsp by the protein. Our analysis suggests that these structural elements might also contribute to rejection of other mischarged aa-tRNAs formed in vivo that are not involved in peptide elongation. Additionally, these structural features might be involved in maintaining a delicate balance of weak and strong binding affinities between EF-Tu and the amino acid and tRNA moieties of other elongator aa-tRNAs

The heterotrimeric Thermus thermophilus Asp-tRNAAsn amidotransferase can also generate Gln-tRNAGln

AbstractThermus thermophilus strain HB8 is known to have a heterodimeric aspartyl-tRNAAsn amidotransferase (Asp-AdT) capable of forming Asn-tRNAAsn [Becker, H.D. and Kern, D. (1998) Proc. Natl. Acad. Sci. USA 95, 12832–12837]. Here we show that, like other bacteria, T. thermophilus possesses the canonical set of amidotransferase (AdT) genes (gatA, gatB and gatC). We cloned and sequenced these genes, and constructed an artificial operon for overexpression in Escherichia coli of the thermophilic holoenzyme. The overproduced T. thermophilus AdT can generate Gln-tRNAGln as well as Asn-tRNAAsn. Thus, the T. thermophilus tRNA-dependent AdT is a dual-specific Asp/Glu-AdT resembling other bacterial AdTs. In addition, we observed that removal of the 44 carboxy-terminal amino acids of the GatA subunit only inhibits the Asp-AdT activity, leaving the Glu-AdT activity of the mutant AdT unaltered; this shows that Asp-AdT and Glu-AdT activities can be mechanistically separated

Etude expérimentale et numérique de joints d'étanchéité en graphite expansé matricé

Avec des réglementations de plus en plus strictes, les enjeux environnementaux deviennent une priorité pour les industries. L'un des aspects primordiaux pour limiter l'impact environnemental est la réduction des émissions fugitives, rencontrées entre autres, dans les organes de robinetterie des installations pétrolières et nucléaires. Un des produits d'étanchéité les plus utilisés dans les vannes, pompes et brides de robinetterie est le presse-garniture souvent composé de joints en Graphite Expansé Matricé (GEM).  En vue d'améliorer l'étanchéité de ces systèmes, les travaux présentés dans cette étude ont pour but de comprendre le comportement mécanique des joints en GEM. Un dispositif expérimental a été spécialement conçu pour reproduire le fonctionnement d'un presse-garniture de robinetterie composé d'un empilement de plusieurs joints. Il permet de récupérer la contrainte axiale des joints mais également, les déformations circonférentielles et longitudinales du logement. Pour cela, différents chargements au niveau du fouloir sont appliqués pour obtenir un serrage de la bague d'étanchéité. Ensuite, des mouvements de tige sont effectués afin de simuler le fonctionnement de la vanne.  Les cycles appliqués sont reproduits à l'aide d'un modèle EF, prenant en compte tous les éléments du montage. Un modèle de comportement macroscopique de type Hyperélasto-Hystérétique est utilisé pour retranscrire la réponse mécanique des joints. Ce modèle de comportement décompose la puissance mécanique en deux contributions en contrainte : une partie hyperélastique et une partie hystérésis. La partie hyperélastique est fortement non linéaire réversible. Quant à la partie hystérésis, elle introduit une non-réversibilité non visqueuse dans la modélisation du comportement du joint, les résultats expérimentaux ayant montré que la contribution visqueuse était négligeable. Le modèle d'hystérésis permet de simuler les cycles de charge-décharge. Le niveau de porosité du joint en GEM est également pris en compte via les interactions entre les parties déviatorique et sphérique des contributions hyperélastique et hystérétique en contrainte du modèle. Les comparaisons entre les données expérimentales et les simulations numériques montrent que le modèle EF est capable de reproduire le comportement du joint en GEM placé dans le corps de la vanne, pour différents chargement appliqués par le fouloir

Analysis of out-of-hospital cardiac arrest and ozone pollution: A qualitative study

Background: Air pollution is increasingly associated with cardiovascular events. As for ozone (O3) pollution, results are inconsistent though O3 levels are associated with hospital admissions, global mortality, and respiratory, and cardiovascular mortality. Methods: In this time-stratified case-crossover study, the associations between short-term exposure to O3 (on an hourly and daily scale) and out-of-hospital cardiac arrests (OHCA) were investigated. Specific subgroups were explored by sex, age, diabetes status, for OHCA during non-holiday periods. Data were collected in the Nord-Pas-de-Calais region, France, in 2015. Data were statistically analyzed using conditional logistic regression (CLR). Results: The study included 1039 cases of OHCA. Significant negative associations were found between OHCA and O3 levels measured in 3 or 4 days before the arrest for all the people, and 1, 2 or 3 days before the arrest for men. As for OHCA during non-holiday periods, there was no significant negative associations but a positive association was revealed for women between OHCA and O3 levels measured in 5 days before the arrest (OR=1.53, P = 0.008). Conclusion: According to the results, OHCA should be investigated during non-holiday periods to control potential confounders that would lead to negative associations. Women might be a susceptible subgroup to O3 pollution. Keywords: Heart arrest, Ozone, Air pollution, Epidemiology, Environmental healt