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

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

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

Beta-defensin genomic copy number is not a modifier locus for cystic fibrosis

Human beta-defensin 2 (DEFB4, also known as DEFB2 or hBD-2) is a salt-sensitive antimicrobial protein that is expressed in lung epithelia. Previous work has shown that it is encoded in a cluster of beta-defensin genes at 8p23.1, which varies in copy number between 2 and 12 in different individuals. We determined the copy number of this locus in 355 patients with cystic fibrosis (CF), and tested for correlation between beta-defensin cluster genomic copy number and lung disease associated with CF. No significant association was found

Understanding the roles of gingival beta-defensins

Gingival epithelium produces β-defensins, small cationic peptides, as part of its contribution to the innate host defense against the bacterial challenge that is constantly present in the oral cavity. Besides their functions in healthy gingival tissues, β-defensins are involved in the initiation and progression, as well as restriction of periodontal tissue destruction, by acting as antimicrobial, chemotactic, and anti-inflammatory agents. In this article, we review the common knowledge about β-defensins, coming from in vivo and in vitro monolayer studies, and present new aspects, based on the experience on three-dimensional organotypic culture models, to the important role of gingival β-defensins in homeostasis of the periodontium

Agriculture de Conservation, un modèle professionnel pour la transition écologique de l'agriculture ?

Over the last decades, the agriculture has experienced the development of several alternatives that aim to achieve sustainability, environment protection, farmers' livelihood improvement, etc. Amongst these alternatives, the “Conservation Agriculture” is expanding in many countries as an attempt to maintain soil fertility and prevent soil erosion through the application of principles such as minimal soil disturbance (zero-tillage), permanent soil cover and crop rotations. Based on an empirical case study that is being carried out in the South of Belgium, the paper discusses some questions raised by the Conservation Agriculture movement in the perspective of the theory of transition and its multi-level analysis (Geels 2007). - At first, it suggests to investigate the farmers' trajectories in the adoption of the Conservation Agriculture techniques as well as the building of the movement to see how individual learnings/lock-in affect the transition. - At a collective level, we want to understand how far the associations providing technique support, advices and information to the farmers could be a source of reflexive learning : indeed, Conservation Agriculture is an ambiguous approach mixing ecological concerns with business- and industrial-oriented practices such the use of Round Up Pesticide (chemical tillage) and time saving for big cropfarmers. - In Belgium, Conservation Agriculture is a “professional” initiative with weak visibility in the public sphere (compared to organic agriculture). What are the consequences of this lack of official recognition on the public debate about the future of agriculture ? - Further, the paper tries to highlight how the network or Conservation Agriculture has or not the ability to meet wider society's concerns such as the problem of mudslides in the countryside or use of pesticide. - And finally, through this multi-level analysis, we will address the question of the building of knowledge and know-how around Conservation Agriculture

Report of the collaborative experience of the project "Sustainability stock farming and parasits management

La problématique traitée est celle de la transition des éleveurs vers des pratiques de gestion du parasitisme ayant un impact moins négatif sur l'environnement. Cette recherche est basée sur un travail collaboratif avec les éleveurs permettant d'aborder la question du parasitisme animal à travers une exploration du « système-bouse » formé par la bouse, ses insectes coprophages, leurs prédateurs, et les vermifuges. Notre première hypothèse de travail est la suivante : dans la gestion du parasitisme en élevage bovin, la mise en place de pratiques ayant un impact moins négatif sur l'environnement (et donc sur les coprophages et leurs prédateurs) nécessite que les éleveurs s'intéressent à cette problématique et que celle-ci fasse sens pour eux. Notre but premier est donc de saisir quelle est leur propre compréhension du « système-bouse » et par quels biais il est possible d'intéresser les éleveurs pour modifier leurs pratiques. Dans un second temps, nous nous intéressons à la question de la transformation des pratiques anti-parasitaires chez les éleveurs wallons. Pour ce faire, nous mobilisons le cadre analytique ESR (Hill 1995) ainsi que la typologie des conceptions de la santé animale de Cabaret et Nicourt (2011). À travers les parcours des éleveurs rencontrés, nous cherchons à comprendre comment les éleveurs gèrent le parasitisme, quelle est leur conception de la maladie animale, dans quelle logique ils se situent. Ces parcours mettennt en évidence plusieurs logiques possibles de transformation des pratiques anti-parasitaires et d'apprentissage de nouvelles pratiques. Leur analyse souligne également l'importance du rôle que peut jouer la symbolique des parasitoses dans ces transformations. Finalement, nous entamons une réflexion sur les convergences et divergences entre les alternatives proposées et le système de gestion du pâturage et du troupeau chez les éleveurs. L'étude se conclut par un bilan des avantages et limites des différentes approches du modèle ESR dans le cas de la gestion du parasitisme ainsi que des freins et obstacles à la transformation à la reconfiguration des pratiques anti-parasitaires en Région wallonne. Il apparaît enfin que les éleveurs ne sont pas les seuls acteurs dans la gestion de la maladie animale et qu'une transformation est également nécessaire au sein des autres catégories d'acteurs impliquées

Ecole d'été Internationale en agroécologie (ISSAE)

Cette année, l’ISSAE s’est déroulée à Bruxelles afn d’étudier la dynamique de l’agroécologie urbaine qui s’y développe et dont la réputation a dépassé les frontières belges: le dynamisme et la créativité des acteurs ainsi que le fort soutien institutionnel à l’agriculture urbaine en région bruxelloise ont ofert des possibilités inédites de ré exion. L’objectif de l’école d’été est d’améliorer la compréhension de l’agroécologie par les participants en leur faisant prendre conscience de l’importance des interactions entre la production de connaissances, l’action et les valeurs sans perdre de vue les autres dimensions de l’agroécologie. La formation est organisée selon les principes de l’apprentissage par projet et problème (PBL, voir rubrique III 9. du dossier de demande de fnancement). Au cours de celle-ci, les participants travaillent sur des problématiques mises en avant par le réseau des GASAP, l’entreprise « Permafungi », le projet participatif et écologique d’agriculture urbaine « Champs des Cailles » et l’association « Terre en vue ». Afn de faire prendre conscience aux participants de l’importance des politiques publiques en matière d’agriculture urbaine, deux keynotes speakers ont été invités : X. Hulhoven, responsable de l’Action Co-Create à Innoviris, et H. Renting, chercheur à l’International Network of Resources Centres on Urban Agriculture and Food Security (Pays-Bas). Ces conférences étaient ouvertes à tous.International Summer School on Agroecology 2017, “The Belgian edition of ISSAE