Etude phenomenologique sur la convection naturelle au dessus d’un disque rainure par voie optique

Parmi toutes les méthodes expérimentales, l’optique a toujours occupé une place de choix grâce à son caractère non intrusif : la traversée d’un écoulement par un faisceau lumineux n’entraine pas de perturbation dans les conditions requises par la visualisation ou la mesure. C’est ce qui explique l’importance de la technique que nous allons décrire. Cette étude vise la mise en place d'un banc d'essai en vue de visualiser et traiter numériquement la convection naturelle induite par un disque rainuré et chauffée par le bas dans un système ouvert. La méthode de visualisation choisie est l'ombroscopie comme méthode non intrusive afin de ne pas perturber la convection. Il est utile aussi de rappeler que cette dernière technique délivre en fait des images qu'il faudra lire et éventuellement traiter. Ainsi, dans pratiquement tous les cas de contrôle optique, il faut, pour obtenir des images reconstituées de bonne qualité et envisager une vision nette, mettre en oeuvre un système élaboré de traitement d'images. Ce système a pour premier but d'améliorer la qualité de l'image sur le plan du contraste et du niveau de bruit; il doit en seconde lieu très souvent prendre en compte la morphologie des objectifs recherchés afin de rendre l'image reconstituée parfaitement exploitable.Mots clés: Convection naturelle, Disque rainuré, Ombroscopie, Traitement d’image, thermographi

IN VITRO EFFECT OF ACETYLSALICYLIC ACID ON CALCIUM OXALATE CRYSTALLIZATION: AN APPROACH TO ANTILITHIASIS

Objective: In recent years, significant progress has been made in identifying and counting physico-chemical processes involved in urinary stone formation. The ability of urine to inhibit calcium oxalate crystallization is considered an important mechanism against stone formation. Several natural substances were tested to inhibit calcium oxalate crystallization. In the present study, we evaluate the effects of acetylsalicylic acid, also known as Aspirin, as an inhibitor of calcium oxalate crystallization in vitro.Methods: The nucleation and aggregation of calcium oxalate crystals were studied using turbidimetric 400-sec time course measurements of optic density at 620 nm after mixing solutions containing calcium chloride and sodium oxalate at room temperature, pH 5.7. The formation of crystals is induced by the addition of the oxalate to calcium solution. The effects on calcium oxalate crystal growth of acetylsalicylic acid with various concentrations were examined. The maximum increase of optic density in the course of time reflects maximum rate of formation of new particles. After reaching equilibrium, a progressive decrease of optic density with time is observed. Rate of aggregation is derived from the maximum decrease in optic density.Results: The results showed that if a concentration of acetylsalicylic acid is more than 1,66 mM both rate of formations of new particles and Rate of aggregation decreased (P<0.05).Conclusion: acetylsalicylic acid has a significant effect on nucleation as well as on crystal growth stage; consequently, it inhibits the crystal formation of calcium oxalate urinary lithiasis. Â

SIMULATION OF A SOLAR DRIVEN AIR CONDITIONING SYSTEM FOR A HOUSE IN DRY AND HOT CLIMATE OF ALGERIA

Solar cooling technology is environmentally friendly and contributes to a significant decrease of the CO2 emissions which cause the green house effect .Currently, most of the solar cooling systems commonly used are the hot water driven lithium bromide absorption chillers. According to the operating temperature of driving thermal source, single – effect Li Br/H2O absorption chillers have the advantage of being powered by ordinary flat-plate or evacuated tubular solar collectors available in the market. The main objective of this work is to develop a computational model that allows the simulation of an hourly basis for an absorption refrigeration - single - effect used the LiBr/H2O as solution working fluid- system assisted by solar energy and natural gas as auxiliary fuel coupled with the residential building located in the hot and dry climate of Algeria. This model will be developed using the dynamic simulation program TRNSYS, considering three specifics areas of work: determination of the cooling loads for a building, implementation of the computational model for the absorption refrigeration system and the parametric optimization of components, which will make possible an approach to optimal sizing of the solar absorption system. The results of the simulation of the absorption chiller indicate that an area of 28 m2 of flat plat collectors with an inclination of 35° and 800 L for hot storage tank provides an annual solar fraction of 80% and a thermal performance coefficient COP of 0.73, getting to cover demand of air conditioning in a house of 120 m2 located in Biskra (Algeria)

The Effect of Combined Convective and Microwave Heating on Mechanical Behaviour of Wood during Drying

ABSTRACT: A numerical study is performed in order to analyse the effect of combined microwave and convective drying on the wood rheology behaviour. The stress model takes into account the free shrinkage, elastic deformation, viscoelasticity and mechanosorptive creep. Stress equations were solved using an implicit finite differential scheme and Thomas algorithm. Results showed that, combined convective and microwave drying reduce the drying time of wood and increasing the drying efficiency. It was found that the moisture content of wood below the fiber saturation point affect the drying stress and there was a significant effect between the drying condition and the mechanical properties of wood. The variation of moisture content during drying intended to produce a mechano-sorptive creep that is able to reduce drying stress. The stress model is used to optimize drying process and to effectively relieve the residual stresses after drying

SPECTROPHOTOMETRIC DETERMINATION OF PHENOL BY CHARGE-TRANSFER COMPLEXATION

The phenol is used in pharmaceutical domain as agent of preservation, a rapid and reliable spectrophotometric method was validated for its determination in routine control. This method is based on the formation of a charge transfer complex between phenol and 2,6-dichloroquinone-4-chloroimide (DCQ) in basic medium. This produced a blue product with maximum absorption at 610nm. Beer's law is obeyed and the calibration curve was linear (r = 0.999) over the range 7.5 10 -6 M -7.5 10 -

Lactate released by inflammatory bone marrow neutrophils induces their mobilization via endothelial GPR81 signaling.

Neutrophils provide first line of host defense against bacterial infections utilizing glycolysis for their effector functions. How glycolysis and its major byproduct lactate are triggered in bone marrow (BM) neutrophils and their contribution to neutrophil mobilization in acute inflammation is not clear. Here we report that bacterial lipopolysaccharides (LPS) or Salmonella Typhimurium triggers lactate release by increasing glycolysis, NADPH-oxidase-mediated reactive oxygen species and HIF-1α levels in BM neutrophils. Increased release of BM lactate preferentially promotes neutrophil mobilization by reducing endothelial VE-Cadherin expression, increasing BM vascular permeability via endothelial lactate-receptor GPR81 signaling. GPR81-/- mice mobilize reduced levels of neutrophils in response to LPS, unless rescued by VE-Cadherin disrupting antibodies. Lactate administration also induces release of the BM neutrophil mobilizers G-CSF, CXCL1 and CXCL2, indicating that this metabolite drives neutrophil mobilization via multiple pathways. Our study reveals a metabolic crosstalk between lactate-producing neutrophils and BM endothelium, which controls neutrophil mobilization under bacterial infection

Inside and out: the activities of senescence in cancer.

The core aspect of the senescent phenotype is a stable state of cell cycle arrest. However, this is a disguise that conceals a highly active metabolic cell state with diverse functionality. Both the cell-autonomous and the non-cell-autonomous activities of senescent cells create spatiotemporally dynamic and context-dependent tissue reactions. For example, the senescence-associated secretory phenotype (SASP) provokes not only tumour-suppressive but also tumour-promoting responses. Senescence is now increasingly considered to be an integrated and widespread component that is potentially important for tumour development, tumour suppression and the response to therapy.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nrc377

Caracterisation et analyse du comportement thermohydrique d'une serre horticole. Identification in situ des parametres d'un modele dynamique

* INRA Centre de Recherche d'Avignon, URD, Domaine St Paul, BP 91, 84143 Montfavet cedex Diffusion du document : INRA Centre de Recherche d'Avignon, URD, Domaine St Paul, BP 91, 84143 Montfavet cedex Diplôme : Dr. d'Universit

In situ calibration of a greenhouse climate control model including sensible heat, water vapour and CO2 balances

International audienc

Natural ventilation of a greenhouse with continuous roof vents : measurements and data analysis

International audienc