International Journal of Agricultural Research, Innovation and Technology (IJARIT)
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Online course on food environments for healthy sustainable diets
No full text3rd International Symposium on Nutrition (ISN 2022): Urban Food Policies for Sustainable Nutrition and Health, 27–28 January 2022International audienc
Accurate equilibrium structures of linear triatomic molecules from a combined theoretical-experimental method: The protonated nitrogen molecule, HN2+
No full textInternational audienc
An assessment of implicit-explicit time integrators for the pseudo-spectral approximation of Boussinesq thermal convection in an annulus
No full textInternational audienceWe analyze the behaviour of an ensemble of time integrators applied to the semi-discrete problem resulting from the spectral discretization of the equations describing Boussinesq thermal convection in a cylindrical annulus. The equations are cast in their vorticity-streamfunction formulation that yields a differential algebraic equation (DAE). The ensemble comprises 28 members: 4 implicit-explicit multistep schemes, 22 implicit-explicit Runge-Kutta (IMEX-RK) schemes, and 2 fully explicit schemes used for reference. The schemes whose theoretical order varies from 2 to 5 are assessed for 11 different physical setups that cover laminar and turbulent regimes. Multistep and order 2 IMEX-RK methods exhibit their expected order of convergence under all circumstances. IMEX-RK methods of higher-order show occasional order reduction that impacts both algebraic and differential field variables. We ascribe the order reduction to the stiffness of the problem at hand and, to a larger extent, the presence of the DAE. Using the popular Crank-Nicolson Adams-Bashforth of order 2 (CNAB2) integrator as reference, performance is defined by the ratio of maximum admissible time step to the cost of performing one iteration; the maximum admissible time step is determined by inspection of the time series of viscous dissipation within the system, which guarantees a physically acceptable solution. Relative performance is bounded between 0.5 and 1.5 across all studied configurations. Considering accuracy jointly with performance, we find that 6 schemes consistently outperform CNAB2, meaning that in addition to allowing for a more efficient calculation, the accuracy that they achieve at their operational, dissipation-based limit of stability yields a lower error. In our most turbulent setup, where the behaviour of the methods is almost entirely dictated by their explicit component, 13 IMEX-RK integrators outperform CNAB2 in terms of accuracy and efficiency
Alkyl chain length modulates antioxidant activity of gallic acid esters in spray-dried emulsions
No full textInternational audienceLipid oxidation is a well-recognized issue in dried food emulsions, such as infant milk formula. Antioxidants can be used to mitigate this issue; however, their efficiency in such complex systems is far from understood. In this study, antioxidant polarity is varied through the alkyl chain length of gallic acid esters (0–16 carbon atoms) incorporated to O/W emulsions that are subsequently spray-dried. During processing and subsequent storage of the samples, antioxidants with more than eight carbon atoms are effective. Both for encapsulated fat and surface free fat, we observe a slight cut-off effect, meaning that beyond eight alkyl groups, a more nonpolar antioxidant is slightly less effective. Depending on the antioxidant polarity, lipid oxidation is faster either in the encapsulated or in the surface free fat. The insights obtained contribute to understanding lipid oxidation in low moisture food emulsions, and thus lead to effective antioxidant strategies
plm: Linear Models for Panel Data
No full textA set of estimators for models and (robust) covariance matrices, and tests for panel data econometrics, including within/fixed effects, random effects, between, first-difference, nested random effects as well as instrumental-variable (IV) and Hausman-Taylor-style models, panel generalized method of moments (GMM) and general FGLS models, mean groups (MG), demeaned MG, and common correlated effects (CCEMG) and pooled (CCEP) estimators with common factors, variable coefficients and limited dependent variables models. Test functions include model specification, serial correlation, cross-sectional dependence, panel unit root and panel Granger (non-)causality. Typical references are general econometrics text books such as Baltagi (2021), Econometric Analysis of Panel Data, ISBN-13:978-3-030-53952-8, Hsiao (2014), Analysis of Panel Data , and Croissant and Millo (2018), Panel Data Econometrics with R, ISBN-13:978-1-118-94918-4
DETERMINANTS DE LEFFICACITE TECHNIQUE DES PRODUCTEURS DES TOMATES AU KONGO CENTRAL EN RD. CONGO
No full textInternational audienceThis study aimed to measure the level of technical efficiency of Congolese tomato producers and to identify its main determinants. A sample of 120 tomato producers in the territories of Kasangulu and Kisantu in the province of Kongo Central was drawn using the voluntary sampling technique. The result of the stochastic frontier model revealed that more than half of the tomato producers in these territories are technically efficient with an average technical efficiency score of 99%. As for the determinants of the level of efficiency, the result reveals that the level of efficiency found is influenced by the quantity of fertilizers (NPK), the quantity of seeds, as well as certain household assets such as paid labor and the cart.Cette étude a eu comme objectifs de mesurer le niveau d’efficacité technique des producteurs Congolais de la tomate et d’identifier ses principaux déterminants. Un échantillon de 120 producteurs des tomates des territoires de Kasangulu et Kisantu dans la province du Kongo central a été tiré à l’aide de la technique d’échantillonnage à participation volontaire. Le résultat du modèle stochastique de frontière a révélé que plus de la moitié des producteurs des tomates de ces territoires sont techniquement efficaces avec un score moyen d’efficacité technique de 99%. Quant aux déterminants du niveau d’efficacité, le résultat revèle que le niveau d’efficacité trouvé est influencé par la quantité des fertilisants (NPK), la quantité des semences, ainsi que certains actifs du ménage tels que la main d’œuvre salariale et la charrette
Tropical cyclones and economic growth : the importance of considering small island developing states
No full textInternational audienceTropical cyclones are arguably one of the most damaging and threatening natural disasters for human systems. Among other examples, the 2005 Hurricane Katrina caused the displacement of approximately 650,000 people and destroyed more than 200,000 homes along the US Gulf Coast. A number of empirical studies have explored the short and long-run economic relationship between tropical cyclones and national growth rates, but no general conclusion can be drawn from them so far. While negative effects are found in samples of exposed countries worldwide, cyclone shocks also show no significant influence in other national-level analyses. This suggests that, beyond inequalities in the exposure to cyclonic risk between countries, there is also inequality regarding these extreme weather events' impacts
Stress oxydant et pathologie diabétique : impact de la glycation des érythrocytes sur leur morphologie, statut redox et capacité à moduler la fonctionnalité de cellules vasculaires humaines en culture.
No full textDiabetes constitutes an enhanced prevalent disease, associated with a dramatic mortality rate due to its vascular complications. Chronic hyperglycemia in diabetes leads to enhanced oxidative stress and glycation phenomena affecting circulating components. Despite erythrocytes represent determinant actors in vascular complications, very little is known about how glycation can affect their structures, capacities to be phagocytosed and impair endothelial cell functioning. The objective of my thesis was to evaluate the impact of glycation on erythrocytes characteristics and capacities to affect endothelial cell function following erythrophagocytosis. In vitro glycated erythrocytes were prepared in the absence or presence of increasing concentrations of glucose. To get insight into the in vivo relevance of our results, these data were compared to that of erythrocytes purified from diabetic or non-diabetic subjects. Oxidative damages and deformability capacities were measured on the different erythrocyte preparations by using dot blot techniques and ektacytometry, respectively. Protective effects of Antirhea borbonica (Ab) extracts against erythrocyte glycation damages were tested in vitro and in vivo by using zebrafish animals. Human umbilical vascular endothelial cells and EA.hy926 cell lines were incubated with glycated or nonglycated erythrocytes, previously labelled with fluorescent probes. Erythrophagocytosis together with reactive oxygen species (ROS) production, iron accumulation and cellular permeability were determined in endothelial cells. Artificial microvessels were created to test the effects of circulating glycated erythrocytes on endothelial cells in a dynamic incubation condition. Structure alteration, redox status and oxidative modifications were found to be enhanced in glycated erythrocytes after determination of their deformability, hemolysis sensibility, ROS production and eryptosis phenomenon. These modifications were associated with reduced antioxidant defence enzymatic activities in glycated erythrocytes. Most of these oxidative damages identified in in vitro glycated erythrocytes were retrieved on erythrocytes from diabetic patients. Ab extract was shown to significantly preserve erythrocytes from methylglyoxal (MGO)-induced damages in terms of restored membrane deformability, reduced oxidative stress and eryptosis phenomenon. Antioxidant capacities of Ab extract on erythrocytes were retrieved in vivo in zebrafish previously infused with MGO. Erythrophagocytosis by endothelial cells was found to be about 2 fold increased when incubated in the presence of glycated erythrocytes compared with non-glycated erythrocytes. In addition, higher iron accumulation, ROS production and enhanced endothelial cell permeability were evidenced in cells previously incubated in the presence of glycated erythrocytes. Experiments in flow conditions evidenced a significant impact of glycated erythrocytes at specific zones of our 3D artificial micro vessel, the bifurcation zone preferential to vascular complication occurrence. This work highlights the impact of glycation on erythrocyte structure and capacity to interact with endothelial cells and open doors to research perspectives. Enhanced phagocytosis of glycated erythrocytes may impact endothelial cell function with putative consequences on the development of diabetic vascular complications. Further experiments are highly needed to reach better mechanistic insights on glycated erythrocytes impact on endothelial cell functioning and contributing to the research of therapeutic strategies against vascular disorders in diabetes.Le diabète, maladie de plus en plus prévalente, est associée à des complications vasculaires fortement augmentées et souvent mortelles. L’hyperglycémie chronique de la maladie induit la glycation de composés circulants dont les dommages, de type oxydatif, peuvent participer à l’altération des vaisseaux sanguins. Bien que les érythrocytes représentent les constituants majeurs du sang, peu de choses sont connues quant à l’impact de la glycation sur leur capacité à participer aux désordresvasculaires. L’objectif de mon travail de thèse a été de préciser l’impact de la glycation sur les caractéristiques morphologiques des érythrocytes et sur leur capacité à être phagocyté et altérer la fonctionnalité de cellules endothéliales humaines en culture. Des érythrocytes humains ont été glyqués par incubation en présence de concentrations croissantes en glucose. Aussi, des érythrocytes glyqués « in vivo » ont été purifiés de patients diabétiques. Les dommages oxydatifs et les capacités de déformabilité de nos préparations ont été mesurés par des techniques de biochimie, de cytométrie et d’ektacytométrie. L’emploi du modèle poisson zèbre a permis d’appréhender l’effet in vivo d’extrait d’Antirhea borbonica (Ab) sur la glycation des érythrocytes. Des cellules endothéliales humaines de lignée (EA.hy926) et purifiées à partir de cordons ombilicaux (HUVEC) ont été utilisées. Des microvaisseaux artificiels ont été développés pour l’étude de l’impact en condition de flux, des érythrocytes glyqués. Les érythrocytes glyqués, in vitro ou purifiés de patients diabétiques, présentent une augmentation deleurs dommages oxydatifs, une réduction de leur capacité de déformabilité ainsi que de leurs défenses antioxydantes et une éryptose accrue. Ces dommages oxydatifs induits par la glycation des érythrocytes sont prévenus par des extraits d’Ab à la fois in vitro et in vivo dans le modèle animal poisson zèbre. Une phagocytose significativement augmentée a été observée dans les cellules endothéliales incubées avec des érythrocytes glyqués. Cette érythrophagocytose accrue s’accompagne d’une accumulation de fer, d’un stress oxydant accru et d’une augmentation de la perméabilité des cellules endothéliales incubées avec les érythrocytes glyqués. Nos expériences d’incubation des microvaisseaux avec les érythrocytes en condition dynamique a révélé leur impact significatif sur l’endothélium à des points spécifiques, les bifurcations, zones préférentielles de l’apparition de complications vasculaires. Les résultats de ma thèse apportent quelques éléments d’information nouveaux quant à l’implication des phénomènes de glycation sur les propriétés des érythrocytes et sur leur capacité à altérer la fonctionnalité de cellules endothéliales et offrent des pistes de perspectives de recherche mécanistique. Une meilleure compréhension de l’impact des phénomènes de glycation et de leurs conséquences tissulaires, ainsi que des moyens de les limiter, pourrait participer dans l’effort de recherche des stratégies thérapeutiques contre les désordres vasculaires de la personne diabétique
Évaluation de l’efficacité de l’aromathérapie par une revue systématique de la littérature
No full textBackground : Aromatherapy is increasingly popular, both for patients and for healthcare professionals. However, its use is based on ancestral knowledge and its effectiveness is not described as scientifically proven. Even so, the literature provides many clinical studies on essential oils, what is the level of scientific proof of these studies?.Method : In order to take stock of scientific knowledge on the subject, a litterature review was carried out to retrieve all randomized controlled trials on aromatherapy from the following databases: GOOGLE SCHOLAR, PUBMED, COCHRANE. The "MESH" keywords used were ‘’Études cliniques et aromathérapie’’, ‘’Études cliniques et huile essentielle’’, ‘’Clinical trial and aromatherapy’’, ‘’Clinical trial and essential oil’’. The methodology and quality of the trials was assessed. All articles were independently assessed and data was extracted in a predefined fashion. Result : 67 studies were selected and were sorted by symptoms: pain, anxiety, sleep disorder, menopause disorder, dementia, vomiting. These studies show fluctuating results and have a lot of bias. Details essential to the use of essential oils were missing in the methodology.Discussion : The hypothesis of efficacy must be supplemented by more rigorous studies and meta-analysis.Introduction : L’aromathérapie est de plus en plus populaire, que ce soit pour les patients ou pour les professionnels de la santé. Toutefois, son utilisation repose sur des connaissances ancestrales et son efficacité n’est pas décrite comme scientifiquement prouvée. La littérature fournie pourtant de nombreuses études cliniques sur les huiles essentielles, quel est le niveau de preuve scientifique de ces études ?Méthode : Afin de faire un état des lieux des connaissances scientifiques sur le sujet, une revue de la littérature a été effectuée pour identifier tous les essais contrôlés randomisées sur l’aromathérapie à partir des bases de données suivantes : GOOGLE SCHOLAR, PUBMED, COCHRANE. Les mots clés ‘’MESH‘’ utilisés étaient : ‘’Études cliniques et aromathérapie’’, ‘’Études cliniques et huile essentielle’’, ‘’Clinical trial and aromatherapy’’, ‘’Clinical trial and essential oil’’. La méthodologie et la qualité des essais ont été évaluées. Tous les articles ont été évalués indépendamment et les données ont été extraites de manière prédéfinie.Résultats : Soixante-sept études ont été retenues et ont été classées par symptômes : douleur, anxiété, trouble du sommeil, trouble de la ménopause, démence, vomissements. Ces études montrent des résultats fluctuants et comportent beaucoup de biais, leurs méthodologies manquent de détails indispensables à l’application des huiles essentielles.Discussion : L’hypothèse d’une efficacité doit être complétée par des études plus rigoureuses et des méta analyses
Hydrochemistry (major and trace elements) of Lake Malawi (Nyasa), Tanzanian Northern Basin: local versus global considerations
No full textInternational audienceThis paper presents the first inventory of dissolved minor and trace element (F, Al, Fe, Mn, Ba, Cd, Cr, Cu, Pb, Mo, Bi, Sr, Zn) concentrations in Lake Malawi, the second largest African lake. Sampling was carried out during 1993 dry season in the northern part of the lake. Trace metal concentrations were measured, together with Ca, Mg, Na, K, Cl, SO4, Alkalinity and Si, along three profiles in the lake northern extremity, in five tributaries and two on-land hydrothermal springs. Water profiles show similar elemental distributions and concentrations that are influenced by lake physical-chemical stratification. Stratification, assessed using temperature, conductivity, Si and Mn profiles, is characterised by two boundaries: the thermocline (70-90 m) and the oxicline (150-190 m). Elemental water concentrations are discussed using simple covariance analyse. Epilimnetic concentrations and distribution are also influenced by atmospheric deposition and river diving. Comparison of dissolved concentrations for potentially polluting elements with World Health Organisation Guidelines and those reported for other East African lakes shows that this reservoir is uncontaminated despite an increasing human stress. Major element behaviour is assessed through a 3 boxes model. In this model Cl and K are conservative elements whereas Si is removed from the solution by diatom productivity and sedimentation. Ca, Na, Mg and alkalinity show low reactivity. Evaporation is one of the controlling factors of lake element concentration that superimposes on the watershed control. Hydrothermal activity, not evidenced in the lake, controls the chemistry of one of the main northern tributary. Chemical comparison between Northern rivers and other tributaries characterises the geographical and geological specificity of studied northern watershed. Moreover the lake annual chemical budget shows that northern watershed generates the main elemental input to the lake, illustrating the dual importance of this area in terms of water and ionic recharge to the lake