The many faces of the COVID-19 mask in Eastern DRC

The introduction of the mask during the COVID-19 outbreak changed daily life in eastern Democratic Republic of Congo and took many faces. From state repression in the city of Goma, to fear of the unknown in rural areas, the mask in the region generated both suspicion and humour. Christian Pole Pole Bazuzi, a researcher and one of the founding members and co-directors of Marakuja Kivu Research, shares his thoughts on the imposition of masks, which changed daily life in the provincial capital and the Kivus region more broadly

How Best Should We Manage Hybrid Poplar Plantations? Interactions of Site Preparation, Vegetation Control and Fertilization

The silviculture of hybrid poplars is a promising solution to reduce the pressure on natural forests while maintaining the wood supply to industries. However, hybrid poplars are sensitive to competing vegetation and to inadequate soil conditions and fertility. Possible management tools include mechanical site preparation (MSP), vegetation control, and fertilization. We present here the results after five years of growth for eight formerly forested sites (40 hectares total) on Podzols in the province of Quebec, Canada. The experimental design combines four MSP treatments (harrowing, scarifying, mounding, and no preparation) with four frequencies of plant competition control by brushing (from never to once a year) and N or N+P fertilization. The best growth was found in the following MSP treatments: mounding \u3e harrowing \u3e scarifying \u3e none. The effect of competition control is more evident on the more productive sites and in the less severe preparation treatments, which brings insight into the Grime-Tilman debate over the importance and intensity of competition. Fertilization can provide substantial improvement in immediate growth, although it does not seem to compensate for deficient root systems. We will discuss the causes and implications of our results for future management strategies of hybrid poplar plantations

Étude structure-fonction des transporteurs ABC de Candida albicans impliqués dans la résistance aux agents antifongiques

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Prediction of cognitive decline for enrichment of Alzheimer's disease clinical trials

A key issue to Alzheimer's disease clinical trial failures is poor participant selection. Participants have heterogeneous cognitive trajectories and many do not decline during trials, which reduces a study's power to detect treatment effects. Trials need enrichment strategies to enroll individuals who will decline. We developed machine learning models to predict cognitive trajectories in participants with early Alzheimer's disease (n=1342) and presymptomatic individuals (n=756) over 24 and 48 months respectively. Baseline magnetic resonance imaging, cognitive tests, demographics, and APOE genotype were used to classify decliners, measured by an increase in CDR-Sum of Boxes, and non-decliners with up to 79% area under the curve (cross-validated and out-of-sample). Using these prognostic models to recruit enriched cohorts of decliners can reduce required sample sizes by as much as 51%, while maintaining the same detection power, and thus may improve trial quality, derisk endpoint failures, and accelerate therapeutic development in Alzheimer's disease.Comment: 11 pages, 3 main figures, 3 main tables, supplementary material (3 tables, 2 figures), incorporated feedback from reviewers in the introduction and discussio

Biocompatible polymer-assisted dispersion of multi walled carbon nanotubes in water, application to the investigation of their ecotoxicity using Xenopus laevis amphibian larvae

Carbon nanotubes (CNTs) tend to readily agglomerate and settle down in water, while the adsorption of compounds present in natural aquatic media could enhance their dispersion and stabilization in the water column. We designed a new exposure protocol to compare the biological responses of Xenopus laevis larvae exposed in semi-static conditions to size-reduced agglomerates of multi-walled carbon nanotubes (MWCNTs) in suspension in the water column and/or to larger agglomerates. Suspensions were prepared using a combination of a non-covalent functionalization with a non-toxic polymer (either carboxymethylcellulose, CMC, or gum arabic, GA) and mechanical dispersion methods (mainly ultrasonication). The ingestion of agglomerates which have settled down was incriminated in the disruption of the intestinal transit and the assimilation of nutrients, leading to acute and chronic toxicities at the highest tested concentrations. Rise in mortality, decrease in the growth rate and induction of genotoxicity from low concentrations (1 mg/L in the presence of CMC) were evidenced in presence of suspended MWCNTs in the water column. The biological responses seemed to be modulated when GA, a potential antioxidant, was used. We hypothesized that MWCNTs should interfere mainly at the surface of the gills, acting as a potential respiratory toxicant and generally inducing indirect effects

Original hybrid control for robotic structures using magnetic shape memory alloys actuators.

International audienceMagnetic Shape Memory Alloys (MSMA) are relatively new active materials but at this time they are not actually very used as actuators despite a high strain and a small response time. This is probably due in part to a large hysteresis and a strong non-linear behaviour. In this paper, an original hybrid control is designed taking into account dynamical effects and hysteretic behaviour in order to increase static gain of the system. After a short presentation of MSMA behaviour, a modelling is proposed to obtain two different control strategies. Some experimental results are also given

Conversion d'Energie Magnéto-Thermo-Mécanique dans les Alliages à Mémoire de Forme Magnétiques.

National audienceLes alliages à mémoire de forme magnétiques sont des matériaux actifs dont les caractéristiques combinent celles des alliages à mémoire de forme classiques et celles des matériaux magnétostrictifs. Ces matériaux relativement récents sont actuellement assez peu utilisés pour des applications pratiques telles que les actionneurs et les capteurs en raison des difficultés de conception et de contrôle résultant d'un comportement complexe. Cet article se propose de présenter le mode de conversion d'énergie à l'oeuvre dans ces matériaux ainsi qu'un état de l'art des principaux travaux en termes d'actionneurs. Il se propose ensuite de présenter les réalisations des auteurs ainsi que les modèles de comportement développés pour finir par une présentation des règles de conception et de contrôle mis en évidence

Nonlinear Hamiltonian modelling of magnetic shape memory alloy based actuators.

International audienceThis paper proposes an application of the Lagrangian formalism and its Hamiltonian extension to design, model and control a mechatronic system using Magnetic Shape Memory Alloys. In this aim, an original dynamical modelling of a Magnetic Shape Memory Alloy based actuator is presented. Energy-based techniques are used to obtain a coherent modelling of the magnetical, mechanical and thermodynamic phenomena. The Lagrangian formalism, well suited in such a case, is introduced and used to take into account the dynamical effects. Hamilton equations are deduced and used for the computation of the theoretical behaviour of this actuator. These numerical simulations are compared with some experimental measurements permitting the validation of the proposed modelling. Beyond the work presented here, these results will be used to design an energy shaping nonlinear control well-adapted for a strongly nonlinear active material

Modelling Rearrangement Process of Martensite Platelets in a Magnetic Shape Memory Alloy Ni2MnGa Single Crystal under Magnetic Field and (or) Stress Action

International audienceThe aim of the paper is the modelling of the rearrangement process between martensite variants in order to use Magnetic alloys (MSMs) as actuators. In the framework of the thermodynamic of irreversible processes, an efficient choice of the internal variables in order to take into account the magnetic and the mechanical actions and a free energy function are stated. The behaviour is chosen as magnetically reversible and mechanically irreversible. An equivalence between magnetic field action H and uniaxial stress action o for the initiation of the rearrangement is established. Finally, moel predictions are compared with experimental measurements