Efficient Method for Computing Lower Bounds on the pp-radius of Switched Linear Systems

This paper proposes lower bounds on a quantity called $L^p$-norm joint spectral radius, or in short, $p$-radius, of a finite set of matrices. Despite its wide range of applications to, for example, stability analysis of switched linear systems and the equilibrium analysis of switched linear economical models, algorithms for computing the $p$-radius are only available in a very limited number of particular cases. The proposed lower bounds are given as the spectral radius of an average of the given matrices weighted via Kronecker products and do not place any requirements on the set of matrices. We show that the proposed lower bounds theoretically extend and also can practically improve the existing lower bounds. A Markovian extension of the proposed lower bounds is also presented

Transition and ecologisation of waloon agriculture: trajectories of farmers in conservation agriculture

peer reviewedCet article s’intéresse aux trajectoires de transition d’agriculteurs engagés dans le mouvement d'« Agriculture de Conservation des sols » en Région Wallonne (Belgique). L'agriculture de conservation vise à restaurer ou à maintenir la fertilité des sols ainsi qu'à enrayer l'érosion de ces derniers par la mise en œuvre de techniques telles que la réduction du travail du sol (techniques de non-labour), la couverture permanente des sols et les rotations de cultures appropriées. Ce modèle agricole se développe aujourd'hui dans de nombreux pays et gagne peu à peu la reconnaissance d'institutions publiques. L’interprétation du processus de transition vers l’agriculture de conservation reste néanmoins ambiguë, car cette dernière s’inscrit dans des perspectives diverses et parfois contradictoires : initiative technique, économique, agronomique ou encore écologique. Le cadre analytique choisi est celui de la théorie multi-niveaux de la transition, considérant l'agriculture de conservation comme une niche d'innovation « par retrait », se construisant par décrochages successifs du labour en tant qu'institution du régime de l'agriculture conventionnelle. À travers les trajectoires de trois agriculteurs engagés dans des techniques de non-labour, il s'agira de saisir les modalités d'articulation et de désarticulation entre l'agriculture de conservation, d'une part, et le labour et l'agriculture conventionnelle, d'autre part. Cette analyse permettra de comprendre dans quelles perspectives les agriculteurs inscrivent leur pratique de l'agriculture de conservation ainsi que la position qu'ils lui donnent par rapport à l'agriculture conventionnelle

Distribution of human beta-defensin polymorphisms in various control and cystic fibrosis populations.

Abstract Human beta defensins contribute to the first line of defense against infection of the lung. Polymorphisms in these genes are therefore potential modifiers of the severity of lung disease in cystic fibrosis. Polymorphisms were sought in the human beta-defensin genes DEFB1, DEFB4, DEFB103A, and DEFB104 in healthy individuals and cystic fibrosis (CF) patients living in various European countries. DEFB1, DEFB4, and DEFB104 were very polymorphic, but DEFB103A was not. Within Europe, differences between control populations were found for some of the frequent polymorphisms in DEFB1, with significant differences between South-Italian and Czech populations. Moreover, frequent polymorphisms located in DEFB4 and DEFB104 were not in Hardy Weinberg equilibrium in all populations studied, while those in DEFB1 were in Hardy Weinberg equilibrium. Sequencing of a monochromosomal chromosome 8 mouse-human hybrid cell line revealed signals for multiple alleles for some loci in DEFB4 and DEFB104, but not for DEFB1. This indicated that more than one DEFB4 and DEFB104 gene was present on this chromosome 8, in agreement with recent findings that DEFB4 and DEFB104 are part of a repeat region. Individual DEFB4 and DEFB104 PCR amplification products of various samples were cloned and sequenced. The results showed that one DNA sample could contain more than two haplotypes, indicating that the various repeats on one chromosome were not identical. Given the higher complexity found in the genomic organization of the DEFB4 and DEFB104 genes, association studies with CF lung disease severity were performed only for frequent polymorphisms located in DEFB1. No association with the age of first infection by Pseudomonas aeruginosa or with the FEV1 percentage at the age of 11-13 years could be found

Pkc-Mediated Stimulation of Amphibian Cftr Depends on a Single Phosphorylation Consensus Site. Insertion of This Site Confers Pkc Sensitivity to Human Cftr

Mutations of the CFTR, a phosphorylation-regulated Cl− channel, cause cystic fibrosis. Activation of CFTR by PKA stimulation appears to be mediated by a complex interaction between several consensus phosphorylation sites in the regulatory domain (R domain). None of these sites has a critical role in this process. Here, we show that although endogenous phosphorylation by PKC is required for the effect of PKA on CFTR, stimulation of PKC by itself has only a minor effect on human CFTR. In contrast, CFTR from the amphibians Necturus maculosus and Xenopus laevis (XCFTR) can be activated to similar degrees by stimulation of either PKA or PKC. Furthermore, the activation of XCFTR by PKC is independent of the net charge of the R domain, and mutagenesis experiments indicate that a single site (Thr665) is required for the activation of XCFTR. Human CFTR lacks the PKC phosphorylation consensus site that includes Thr665, but insertion of an equivalent site results in a large activation upon PKC stimulation. These observations establish the presence of a novel mechanism of activation of CFTR by phosphorylation of the R domain, i.e., activation by PKC requires a single consensus phosphorylation site and is unrelated to the net charge of the R domain

Improving statistical inference on pathogen densities estimated by quantitative molecular methods: malaria gametocytaemia as a case study

BACKGROUND: Quantitative molecular methods (QMMs) such as quantitative real-time polymerase chain reaction (q-PCR), reverse-transcriptase PCR (qRT-PCR) and quantitative nucleic acid sequence-based amplification (QT-NASBA) are increasingly used to estimate pathogen density in a variety of clinical and epidemiological contexts. These methods are often classified as semi-quantitative, yet estimates of reliability or sensitivity are seldom reported. Here, a statistical framework is developed for assessing the reliability (uncertainty) of pathogen densities estimated using QMMs and the associated diagnostic sensitivity. The method is illustrated with quantification of Plasmodium falciparum gametocytaemia by QT-NASBA. RESULTS: The reliability of pathogen (e.g. gametocyte) densities, and the accompanying diagnostic sensitivity, estimated by two contrasting statistical calibration techniques, are compared; a traditional method and a mixed model Bayesian approach. The latter accounts for statistical dependence of QMM assays run under identical laboratory protocols and permits structural modelling of experimental measurements, allowing precision to vary with pathogen density. Traditional calibration cannot account for inter-assay variability arising from imperfect QMMs and generates estimates of pathogen density that have poor reliability, are variable among assays and inaccurately reflect diagnostic sensitivity. The Bayesian mixed model approach assimilates information from replica QMM assays, improving reliability and inter-assay homogeneity, providing an accurate appraisal of quantitative and diagnostic performance. CONCLUSIONS: Bayesian mixed model statistical calibration supersedes traditional techniques in the context of QMM-derived estimates of pathogen density, offering the potential to improve substantially the depth and quality of clinical and epidemiological inference for a wide variety of pathogens

Contribution à la définition d’un programme de recherche global pour l’agriculture biologique en Wallonie : identification des priorités pour la période 2015-2020

In order to identify research priorities in the organic farming sector, a three step approach was performed in 2014- 2015: (A) Ninety farmers were interviewed, in 2014, on an individual basis. Sixty of these farmers performed animal production (ruminant or mono-gastric); (B) Ten focus groups were organized with representatives of (1) advisory services, (2) administrations and farmer unions and (3) research institutions; (C) Priorities identified in (A) and (B) were compared to (1) the priorities identified, in 2015, by the “producer representatives”, in the organic sector and (2) the funded or pre-called thematic of regional and European research programs. This work underlines and confirms the necessity, for organic farmers, to develop more autonomous production systems, from a livestock feeding and soil fertility maintenance point of view. The comparison of these different sources of information highlights the link existing between the definition of previous regional research programs and expectations from the field. This questions the efficiency with which research innovations are spread among the sector as these problematics remain open. Farmers are asking for action and contextualized research. Such a research posture, highly promoted by H2020 programmation, would improve the diffusion of results

Contribution to the definition of an overall research program for organic farming in Wallonia: identification of priorities for the 2015-2020 period

In order to identify research priorities in the organic farming sector, a three step approach was performed in 2014- 2015: (A) Ninety farmers were interviewed, in 2014, on an individual basis. Sixty of these farmers performed animal production (ruminant or mono-gastric); (B) Ten focus groups were organized with representatives of (1) advisory services, (2) administrations and farmer unions and (3) research institutions; (C) Priorities identified in (A) and (B) were compared to (1) the priorities identified, in 2015, by the “producer representatives”, in the organic sector and (2) the funded or pre-called thematic of regional and European research programs. This work underlines and confirms the necessity, for organic farmers, to develop more autonomous production systems, from a livestock feeding and soil fertility maintenance point of view. The comparison of these different sources of information highlights the link existing between the definition of previous regional research programs and expectations from the field. This questions the efficiency with which research innovations are spread among the sector as these problematics remain open. Farmers are asking for action and contextualized research. Such a research posture, highly promoted by H2020 programmation, would improve the diffusion of results

Survey of CF mutations in the clinical laboratory

BACKGROUND: Since it is impossible to sequence the complete CFTR gene routinely, clinical laboratories must rely on test systems that screen for a panel of the most frequent mutations causing disease in a high percentage of patients. Thus, in a cohort of 257 persons that were referred to our laboratory for analysis of CF gene mutations, reverse line probe assays for the most common CF mutations were performed. These techniques were evaluated as routine first-line analyses of the CFTR gene status. METHODS: DNA from whole blood specimens was extracted and subjected to PCR amplification of 9 exons and 6 introns of the CFTR gene. The resulting amplicons were hybridised to probes for CF mutations and polymorphisms, immobilised on membranes supplied by Roche Molecular Systems, Inc. and Innogenetics, Inc.. Denaturing gradient gel electrophoresis and sequencing of suspicious fragments indicating mutations were done with CF exon and intron specific primers. RESULTS: Of the 257 persons tested over the last three years (referrals based on 1) clinical symptoms typical for/indicative of CF, 2) indication for in vitro fertilisation, and 3) gene status determination because of anticipated parenthood and partners or relatives affected by CF), the reverse line blots detected heterozygote or homozygote mutations in the CFTR gene in 68 persons (26%). Eighty-three percent of those affected were heterozygous (47 persons) or homozygous (10 persons) for the ΔF508 allele. The only other CF-alleles that we found with these tests were the G542X allele (3 persons), the G551D allele (3 persons), the 3849+10kb C-T allele (2 persons) the R117H allele (2 persons) and the 621+1G-T allele (1 person). Of the fifteen IVS8-5T-polymorphisms detected in intron 8, seven (47%) were found in males referred to us from IVF clinics. These seven 5T-alleles were all coupled with a heterozygous ΔF508 allele, they make up 35% of the males with fertility problems (20 men) referred to us. CONCLUSIONS: In summary, the frequency of CF chromosomes in the cohort examined with these tests was 26%, with the ΔF508 allele affecting 83% of the CF chromosomes. It is a substantial improvement for routine CF diagnostics to have available a test system for 30 mutations plus the polypyrimidine length variants in intron 8. Our results show that this test system allows a routine first-line analyses of the CFTR gene status