Spatial aggregation of low resolution satellite data for the monitoring of vegetation response to climatic stresses : analysis of the spatial heterogeneity of aggregated entities.

peer reviewedOur PhD research consists in analysing and modelling the vegetation response or sensitivity to climatic stresses with low satellite imagery. In that framework, the selection of optimal calibration sites is very important. These sites should be characterised by a stable and homogenous land cover over large area. Here we analyse the spatial heterogeneity of the aggregation entities (EU-NUTS 2) used by the MARSFOOD programme for the extraction of regional NDVI-means

A Non-Cytosolic Protein of Trypanosoma evansi Induces CD45-Dependent Lymphocyte Death

In a recent study dealing with a mouse model of Trypanosoma evansi-associated disease, a remarkable synchrony between the parasitaemia peak and the white-blood-cell count nadir was noticed. The present study was designed to establish whether there is a direct causal link between the parasite load during its exponential phase of growth and the disappearance of peripheral blood leukocytes. In vitro experiments performed with trypanosomes and purified peripheral blood mononucleated cells revealed the existence of a lymphotoxin embedded in the T. evansi membrane: a protein sensitive to serine proteases, with a molecular mass of less than 30 kDa. Lymphocytes death induced by this protein was found to depend on the intervention of a lymphocytic protein tyrosine phosphatase. When lymphocytes were exposed to increasing quantities of a monoclonal antibody raised against the extracellular portion of CD45, a transmembrane protein tyrosine phosphatase covering over 10% of the lymphocyte surface, T. evansi membrane extracts showed a dose-dependent decrease in cytotoxicity. As the regulatory functions of CD45 concern not only the fate of lymphocytes but also the activation threshold of the TCR-dependent signal and the amplitude and nature of cytokinic effects, this demonstration of its involvement in T. evansi-dependent lymphotoxicity suggests that T. evansi might manipulate, via CD45, the host's cytokinic and adaptive responses

Investigative safety strategies to improve success in drug development

Understanding and reducing attrition rate remains a key challenge in drug development. Preclinical and clinical safety issues still represent about 40% of drug discontinuation, of which cardiac and liver toxicities are the leading reasons. Reducing attrition rate can be achieved by various means, starting with a comprehensive evaluation of the potential safety issues associated to the primary target followed by an evaluation of undesirable secondary targets. To address these risks, a risk mitigation plan should be built at very early development stages, using a panel of in silico, in vitro, and in vivo models. While most pharmaceutical companies have developed robust safety strategies to de-risk genotoxicity and cardiotoxicity issues, partly driven by regulatory requirements; safety issues affecting other organs or systems, such as the central nervous system, liver, kidney, or gastro-intestinal system are less commonly addressed during early drug development. This paper proposes some de-risking strategies that can be applied to these target organ systems, including the use of novel biomarkers that can be easily integrated in both preclinical and clinical studies. Experiments to understand the mechanisms’ underlying toxicity are also important. Two examples are provided to demonstrate how such mechanistic studies can impact drug development. Novel trends in investigative safety are reviewed, such as computational modeling, mitochondrial toxicity assessment, and imaging technologies. Ultimately, understanding the predictive value of non-clinical safety testing and its translatability to humans will enable to optimize assays in order to address the key objectives of the drug discovery process, i.e., hazard identification, risk assessment, and mitigation

Modelling climate control on cropland and grassland development using phenologically tuned variables

peer reviewedMany studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Using time series of remote sensing and climate data, Nemani et al. (2003) analyzed trends in Net Primary Production in relation with changes in climate and showed that, between 1982 and 1999, primary productivity increased by 6% globally in response to climate change. This study also stressed the need to take into account the spatial variability of climatic constraints to plant growth when analyzing the climate change impact on vegetation. Others authors described different phenomenon linked with climate change such as increases of seasonal NDVI amplitude and growing season duration in the Northern high latitude or changes in circumpolar photosynthetic activities. Understanding the interactions between climate and vegetation is also a key issue in our PhD research. Our objective is to identify the meteorological factors which limit the development of croplands and grasslands in relation with their geographical localization. For that purpose, we acquired 10-daily time series of the Normalized Difference Vegetation Index, NDVI, derived from SPOT-VEGETATION and 7 meteorological parameters (Tmean, Tmin, Tmax, Rain, Rad, ETP, Rain-ETP) derived from ERA40 re-analyses and the operational ECMWF (European Centre for Medium-Range Weather Forecast) atmospheric model. Cross-correlations between NDVI and each one of the meteorological parameters were analysed for a set of 25 regions over Europe and Africa: 15 agricultural regions and 10 regions covered by grassland or savannas. Unlike others studies, we did not consider the vegetation globally but we focussed on two types of vegetation: croplands and grasslands. This is quite important considering the role of phenology on the vegetation cycle and its relation with climate. Moreover the analysis was not realised using yearly estimates but using 10-daily products. In order to avoid stationarity related issue, a specific methodology was developed taking into account the phenological cycle of the vegetation under consideration. Preliminary results showed that the relation between a meteorological limiting factor, e.g. precipitation, and NDVI can not be considered as linear during the year or even during the growing season. Interactions must to be studied at a smaller time scale than the growing season in order to identify properly the limiting factors to plant growth taking into account its phenology. Moreover the main limiting factors are variable from a region to another. In our analysis we also considered the possibility of a delayed response of the vegetation or a cumulated effect of meteorological events (up to 3 months). Our methodology will be presented during the conference and results will be discussed and illustrated by some test cases

Validation d'une batterie de tests neuropsychologiques informatisés auprès d'une population sourde et malentendante de 4 à 18 ans

Des troubles affectant le traitement visuo-spatial peuvent exister dans la population sourde ou malentendante. Ils peuvent être handicapants dans la vie quotidienne de ce dernier. Pourtant, très peu de tests neuropsychologiques sont adaptés pour les personnes ayant une déficience auditive. C’est pour cette raison que la batterie Visuo Spatial Abilities in Deafness (VSAD) a été développée. Elle inclut six tâches visuo-spatiales sur tablette pour enfants et adolescents sourds. L’utilisation d’un format informatisé dans un test neuropsychologique comporte plusieurs avantages : elle permet une passation du test plus rigoureuse ainsi que des mesures comportementales plus précises. Le but de ce mémoire était de tester la validité de la batterie VSAD auprès d’enfants et d’adolescents sourds et malentendants, de 4 à 18 ans. Nous nous sommes également intéressés à l’impact de la déprivation auditive sur les fonctions visuo-spatiales. Ce faisant, nous avons pu constater que 4 tâches VSAD avaient la potentialité d’être utilisables dans la pratique clinique. De plus, nous avons observé que la présence de troubles vestibulaires pouvait avoir une influence négative sur les performances des enfants et adolescents ayant une surdité aux tâches VSAD. Cependant, la population des sourds et des malentendants est fortement hétérogène. Cette hétérogénéité est discutée dans ce mémoire.Master [120] en sciences psychologiques, Université catholique de Louvain, 201

Climatological characteristics of NDVI time series: challenges and constraints

Many studies already investigated the impact of climate change and climate variability on vegetation at global and continental scales. Low resolution satellite imagery is one of the main sources of information. In this paper, we describe a strategy to improve the quality of 10-daily time series of Normalized Difference Vegetation Index derived from SPOT-VEGETATION. A specifi c methodology was also defi ned in order to identify optimal test sites for the analysis of climate control on intra-annual dynamic of croplands. Finally two cases studies are presented to illustrate this research and in particular the non linear relationship between NDVI and meteorological parameters during the growing season

Studying Interactions between Climate Variability and Vegetation Dynamic Using a Phenology Based Approach

In this paper we investigated if and how a signature of climate control on vegetation growth can be individualized at regional scale using time series of SPOT-VEGETATION NDVI and ECMWF meteorological data. Twelve regions characterized by dominant and stable cropland or grassland covers were selected in Europe and Africa. Our results show that the relationship between NDVI and meteorological parameters is highly complex and significantly vary trough the phenological cycle of the plants. Hence, interactions between vegetation dynamics and climate variability must be studied at a smaller time scale in order to identify properly the limiting factors to vegetation growth. Using NDVI metrics, vegetative phases (from green-up to maximum NDVI) and reproductive phases (from maximum NDVI to maturity) were identified for each region. Cross-correlation analysis revealed that, in most of the cases, the best scores of Pearson's r are obtained when we considered the vegetative phase (from green-up to maximum of NDVI) and the reproductive phase (from maximum of NDVI to maturity) separately. We also showed that climatic constraints identified using yearly proxies of climate and vegetation do not depict correctly or completely the climate control on vegetation development. In that sense the complexity of the climate-vegetation relationship, which is spatially and temporally variable, is well underlined in this study.JRC.H.7-Climate Risk Managemen