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Le fonctionnement hydrique et photosynthétique d’une vigne a été suivi en milieu naturel au cours de plusieurs journées à l’aide de mesures de résistance stomatique, du potentiel hydrique foliaire et des échanges de CO2. L’influence de la réhumectation du sol a pu être étudiée à l’échelle du cep entier. Par ailleurs, les études poursuivies sur les bras opposés d’un même cep ont permis de mettre en évidence des différences de comportement qui semblent en liaison avec le microclimat lumineux de ces bras., The water and photosynthetic functions of a grapevine were observed for several days under field conditions by measuring stomatal resistance, leaf water potential and C02 exchange. The influence of soil humidification was studied on the whole plant. In addition, studies carried out on opposite branches of the same vine showed behavioral differences which seem linked to the light microclimate of these branches.

Use of unvented kerosene space heaters can increase significantly the indoor levels of combustion products. To determine the amount of increase, tests have been conducted in a two-story test house using radiant and convective type space heaters. Emission rates of CO, COsub2, NO, and NOsub2 were determined. As well, each heater was placed, in turn, in the living room, bedroom, and basement, and the levels of combustion products were measured in each room. Values of mixing factor to be applied to the general ventilation equation for estimating air contaminant levels were determined from the test results., Reprinted from: ASHRAE Transactions 1987, part I, p. 173-184, ISSN: 0001-2505, v. 931., Presented at the 1987 ASHRAE Winter Meeting, New York, NY, USA, Jan 18-21, 1987

Etude comparée du comportement hydrique de quatre provenances de sapin pectine (Abies alba Mill.)

International audience

In a poorly ventilated space the occupants may be exposed to hazardous air conditions of reduced oxygen content or increased carbon dioxide concentration. If unvented fuel- burning appliances are used for heating or cooking there is the possibility of further danger from carbon monoxide poisoning. The effects of these gases in varying quantities upon smokers and non-smokers are enumerated and a method is outlined for the determination of the ventilating requirements for specific quantities of toxic gas production. Results are given of tests of typical unvented camping and boating appliances using a variety of fuels, and these indicate that certain models warrant special ventilation precautions. Guidelines are suggested for users of such equipment to avoid hazardous atmospheres in confined spaces.

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In order to optimize the carbon storage potential of agro-systems, and thereby reduce green house effect, the response of these systems to climatic variability needs to be examined in connection with agricultural practices. A list of CO2 flow measurements over a period of 6 years on 2 mid-altitude permanent grassland plots (one plot under intensive grazing conditions and the other, under extensive grazing conditions) provided some useful data. Soil carbon sequestration was higher for extensively grazed grassland compared to intensively grazed grassland (respectively 1.4 and 1.25 tC/ha). During years with a dry growing season, soil carbon sequestration was lower for the extensively grazed plot compared to the intensively grazed plot, whereas the opposite was true for years with a humid growing season: this data shows that interaction between climatic conditions and agricultural practices must be taken into consideration when evaluating grassland soil carbon storage potential. The relevance of soil characteristics (water content, nitrogen supply, microbial flora...) is determined.; Depuis 2003, les échanges de CO2 entre prairies pâturées et atmosphère sont mesurés en continu sur 2 parcelles de moyenne montagne, l’une à gestion intensive et l’autre à gestion extensive. La prairie extensive a séquestré en moyenne plus de carbone que la prairie intensive (respectivement 1,4 et 1,25 t C/ha). Les résultats indiquent qu’au cours des années présentant une saison de croissance sèche, la parcelle extensive séquestre moins de carbone que la parcelle intensive et vice versa en saisons humides. Ainsi, il est nécessaire de considérer l’interaction des facteurs climatiques et des pratiques agricoles pour évaluer le potentiel de stockage du carbone d’une prairie. L’importance des propriétés du sol (teneur en eau, ressources azotées, flore microbienne...) est identifiée.

Controlled release systems are attracting increasing interest because of their potential application in biomedical field. Indeed, such systems should enable to lower toxicity of medicines by targeting the therapeutic action and by limiting the concentration of drugs in the organism. In this research project, new nanoparticles have been developed for a thermosensitive control of drugs' delivery. These particles consist of a polynorbornene core and a polyethylene oxide shell and are developed by dispersion ring opening metathesis polymerization. As a model drug, salicylic acid has been encapsulated in those core-shell materials. This multidisciplinary project is original for two reasons. On the one hand, the nature of the particle which enables to release the drug from 35-45°C. On the other hand, the encapsulation technique that has been chosen is the impregnation under supercritical carbon dioxide., La délivrance contrôlée de médicaments constitue un enjeu thérapeutique de première importance pour le milieu médical. Elle doit, en effet, permettre de diminuer la toxicité du médicament en limitant sa concentration dans l'organisme et en ciblant son lieu de délivrance. Ce projet de recherche a conduit à la réalisation de nouveaux nano-vecteurs particulaires utilisables pour la délivrance de médicaments par hyperthermie locale. Ces objets sont constitués d'un cœur de polynorbornène et d'une écorce de poly (oxyde d'éthylène) et sont synthétisés par polymérisation par ouverture de cycle de type métathèse (ROMP) en dispersion. L'acide salicylique est encapsulé dans ces particules en tant que molécule modèle. L'originalité de ce sujet pluridisciplinaire réside : dans la nature de la particule, qui permet une libération du principe actif à partir de 35-45°C et dans la technique d'imprégnation des particules par la voie fluide supercritique.

14e édition du congrès de la Société française du génie des procédés, Lyon, FRA, 08-/10/2013 - 10/10/2013; International audience; Les fluides réfrigérants classiques sont néfastes pour l'environnement en raison de leur potentiel de réchauffement global (GWP), c'est pourquoi leur utilisation doit être réduite. L'une des solutions est d'employer des fluides frigoporteurs diphasiques, comme les coulis d'hydrates, pour transporter le froid. Le travail réalisé a pour objectif d'étudier les propriétés rhéologiques et thermiques des coulis de CO2. Le dispositif expérimental est constitué d'une boucle pilote permettant la circulation des fluides. Les hydrates sont formés par refroidissement à des températures de l'ordre de 275 K et des pressions allant jusqu'à 3 MPa. Les coefficients d'échange thermique locaux et moyens du coulis ont également été évalués par l'utilisation d'un tube chauffant. La rhéologie a montré que le coulis présentait un comportement de type rhéofluidifiant pour des fractions d'hydrates en volume allant jusqu'à 22 %. L'étude thermique a quant à elle montré que le coulis présentait des coefficients d'échange locaux de l'ordre de 2900 W.m-2.K-1 pour une fraction en hydrates de 19 %, ce qui est supérieur à l'eau et légèrement plus élevé que le coulis de glace. Ainsi, ces résultats permettent de mettre en évidence les bonnes capacités du coulis d'hydrates à stocker, à véhiculer et à restituer l'énergie emmagasinée.

Le but de la présente étude était d'étudier l'impact de la variation des niveaux d'eau d'un marais d'eau douce (Baie Saint-François, Québec) sur l'évolution des concentrations et des flux d'hydrogène, monoxyde de carbone, méthane et dioxyde de carbone. Une approche originale impliquant l'association d'un gradient de concentration de ces composés sur un profil vertical de 1,5 m au transfert de flux turbulent micrométéorologique fut utilisée pour la détermination des flux. L'étude démontre qu'une hausse du niveau d'eau d'un bassin versant alimentant une zone humide influence les flux de méthane, de monoxyde de carbone d'hydrogène et de dioxyde de carbone. En conditions submergées, le marais émettait du méthane et du monoxyde de carbone et consommait moins d'hydrogène troposphérique. Ainsi, cette étude démontre que des mesures in situ peuvent servir à inférer des scénarios d'impacts possibles des changements climatiques et des variations des niveaux d'eau sur les émissions des gaz à effets de serre dans l'écosystème du fleuve Saint-Laurent., Wetlands are known for their great biodiversity and the important carbon reservoir that they represent. Moreover, in the global warming context, these ecosystems represent net sources or sinks for different greenhouse gases depending of their conditions. For instance, flooded conditions favour methane production whereas they prevent hydrogen and carbon monoxide soil consumption. Baie Saint-François is a freshwater wetland that opens onto Lake Saint-Pierre (St. Lawrence River) where water levels are subject to important fluctuations due to natural processes and human activities (hydroelectricity and navigation). This study was done in order to assess the impact of the Lake Saint-Pierre water level variations on the tropospheric methane, carbon monoxide, hydrogen and carbon dioxide dynamics over the wetland. Knowledge of these dynamics should provide indications about the possible effects of the decreasing or increasing water level associated with the global warming on the production or consumption of these trace gases.Studies were carried out between June and August 2003 in Baie Saint-François where soil was subjected to successions of flooded and dry conditions. Water and carbon dioxide fluxes were obtained with a Bowen ratio micrometeorological station including a high frequency single infrared gas analyser. Hydrogen, carbon monoxide and methane fluxes were estimated with the modified Bowen method, their vertical concentration gradients (1.5 m) were measured over the plant canopy. The Bowen Ratio station was equipped with different probes to measure parameters such as net radiations, soil heat fluxes and vertical temperature gradients. The turbulent transfer coefficient (k) obtained every 20 min was assumed equal for heat, water vapour and trace gases. Hence, fluxes calculations were done by the multiplication of the turbulent transfer coefficients with the vertical concentration gradients of hydrogen, carbon monoxide and methane.The instrument used to detect hydrogen, carbon monoxide and methane was a RGA5. This analyser has two detectors: the reductive gas detector (RGD) for hydrogen and carbon monoxide and a flame ionisation detector (FID) for methane. The RGD contains an HgO bed wherein oxygen reacts with reductive gases resulting in Hg° releases detectable by differential UV absorbance. Chemicals were detected continuously in 10 min cycles with an analytical reproducibility of ±0.2, 0.3 and 2% for hydrogen, carbon monoxide and methane. Generally, vertical concentration gradients measured were greater than these limits. A calibration gas containing hydrogen, carbon monoxide and methane at 4940, 1000 and 1000 ppbv respectively in nitrogen was analysed daily to verify calibration. To ensure data integrity, linearity of the instrument was assayed by several dilutions of the standard gas and the integration of the curves gave a correction factor for hydrogen (18%) and carbon monoxide (13%). An intercomparison with NOAA (National Oceanic and Atmospheric Administration) was done to corroborate these correction factors.Background carbon monoxide, methane and carbon dioxide levels were in agreement with literature values. However, hydrogen was low, as observed by other investigators in summertime, since this season is related to minimal concentrations. Methane followed a diurnal cycle where maximum levels were observed during nighttime. In wet conditions, these nocturnal peaks reached occasionally 4000 ppbv and could be explained by specific production mechanisms and diurnal changes of vertical mixing in the boundary layer. Sensitivity of the processes responsible for methane and carbon monoxide cycling was seen between July 21st and 26th where a rain episode (total precipitation of 33.2 mm) increased their background concentrations. It seems that this precipitation was enough to favour methanogenesis and inhibit tropospheric CO and CH4 consumptions by a reduction of the diffusion of these chemicals into the soil.Our results demonstrated that four to eleven days following a variation of the Lake Saint-Pierre water level, a change in the tropospheric hydrogen, carbon monoxide and methane concentrations was observed. This lag might be explained by the distance between the lake and the research station (about 1.5 km) and the required time for the adaptation of soil microorganisms to the disruption of their environment. The concentration variations of these chemicals resulted from the inhibition of the processes responsible for their consumption or the activation of the processes accountable for their production.In June, the wetland was flooded and the CO2 median flux was -56.5 g m-2 d-1. Fluxes increased significantly (Mann-Whitney, α=0.01) in July to 5.30 g m-2 d-1, possibly due to dry conditions. Indeed, absence of water favours the activity of soil aerobic microorganisms which might produce more carbon dioxide than the quantity used by plants during photosynthesis.Methane was produced in June where the median flux was 54 mg m-2 d-1. These emissions were caused by the presence of water which maintained anaerobic conditions in the sediments, a suitable environment for methanogenic microorganisms. July was characterised by dry conditions, which generated aerobic environments in soils, an unfavourable microniche for methanogens. Therefore, methane median fluxes decreased significantly (Mann-Whitney, α=0.05) to 0.011 mg m-2 d-1 in July. In August, before the end of the investigation period, water levels had increased but methane fluxes were not significantly higher than in July. Moreover, in this period, methane concentrations tended to increase, showing that after an augmentation of the Lake Saint-Pierre water level, Baie Saint-François flooding area could represent a methane source.During summer 2003, Baie Saint-François acted as a net source of carbon monoxide. In June, the median flux was 21 µg m-2 d-1 due to presence of water which inhibited consumption by soil. Emissions were significantly (Mann-Whitney, α=0.05) lower in July (15 µg m-2 d-1) due to the absence of water, which represented a suitable environment for microorganisms consuming tropospheric carbon monoxide. In August, the median carbon monoxide flux attained 65 µg m-2 d-1 due to an increase of the Lake Saint-Pierre water level. Net carbon monoxide emissions observed in wet and dry conditions might be due to the high organic content in soil and water in addition to the presence of plants since all of these are subjected to photooxidation, generating this pollutant. Therefore, an increase of the Lake Saint-Pierre water level is associated with an augmentation of tropospheric carbon monoxide due to the inhibition of the processes responsible of its consumption.A decline in the water level might result in the activation of the soil microorganisms (or abiotic hydrogenases) able to consume tropospheric hydrogen. At the beginning of the campaign (June), the median hydrogen flux was weak (-1.37 g m-2 d-1) due to the presence of water. However, a net soil consumption was seen in July, where the median hydrogen flux decreased to -125 g m-2 d-1. The Lake Saint-Pierre water level increase observed in August was associated with a significant (Mann-Whitney, α=0.05) augmentation of the hydrogen median flux to 299 g m-2 d-1. Consequently, a rise in the Lake Saint-Pierre water levels induced an inhibition of the processes responsible of the tropospheric hydrogen consumption.This study illustrated that the water level fluctuations of the Lake Saint-Pierre have an impact on the H2, CO, CH4 and CO2 dynamics over the surrounding wetlands. When the Lake Saint-Pierre water level decreased, the wetlands acted as a carbon monoxide and carbon dioxide source, but as a consumer of tropospheric hydrogen and a minor source of methane.

Effects of roxarsone on CYP4501A and CYP4502B in earthworm Eisenia andrei

The interface between two immiscible electrolyte solutions (ITIES) provides a well-defined platform for fundamental studies of adsorption processes and molecular reactivity in general. Two bio-inspired systems are considered in the present work: adsorbed phospholipid monolayers at the classical water-1,2-dichloroethane interface and photosensitized reduction of carbon dioxide at the novel water-supercritical CO2 interface. In first instance, theoretical modeling of adsorption processes at an ideally polarizable ITIES was carried out. In this part of the work, extension of previous models was performed in order to account for the ionic partition of the surface-active molecule. For the sake of simplicity, only a potential-dependent Langmuir isotherm was considered. A general model was then obtained in which prediction of triangular-shaped adsorptive peaks in voltammetric measurements arises naturally. Additionally, the interplay between the Gibbs energies of adsorption and ion-transfer was shown to be especially important for intermediate values between -20 to -40 kJ·mol-1. Adsorbed phospholipid monolayers at the ITIES were employed as a model for mimicking half of a cell membrane. Interactions between peptides and L-α-dipalmitoylphosphatidylcholine (DPPC), the most abundant phospholipid in cell membranes, were proven to occur by voltammetry. Further confirmation of the existence of non-covalent complexes was obtained by the complementary use of biphasic electrospray ionization mass spectrometry (BESI-MS); a technique recently developed in the Laboratoire d'Electrochimie Physique et Analytique (LEPA). Cationization of neutral peptides was equally observed to induce the complex formation with DPPC observed as a net current across the ITIES. Antimicrobial peptides were also considered given their high affinity to cell membranes. Therefore, melittin, selected as model antimicrobial peptide, exhibited a well-defined ion-transfer process accompanied by adsorptive signals. Contact angle estimation of supported interfaces over a platinum electrode indicated that these signals are reversible and induce deformation of deposited aqueous droplets. Earlier desorption of phospholipids was equally observed in presence of the antimicrobial peptide, confirming its membrane-disrupting ability by cyclic voltammetry. Finally, reduction of carbon dioxide was studied at the water-supercritical interface, in an attempt to mimic natural photosynthetic systems. As a first approach, the reduction of CO2 to formate was obtained in presence of decamethylferrocene, an organometallic compound which is capable of reducing protons under anaerobic conditions in 1,2-dichloroethane. However, the reaction follows a different pathway in presence of supercritical CO2 and formate is detected as the most abundant product. Taking one step further the application of water-supercritical CO2 interfaces, the photosensitized reduction of CO2 was conducted. In this approach, nickel(II)-1,4,8,11-tetraazacyclotetradecane (Ni(II)cyclam) was employed as catalyst, ruthenium(II)tris(2,2'-bipyridyl) ([Ru(bpy)3]2+) as photosensitizer and sodium ascorbate as sacrificial electron donor. All the components of the catalytic cycle are dissolved in water. Hence, the presence of supercritical CO2 provides with adsorption sites in which intermediates are hypothesized to be adsorbed, leading to increased efficiency and selectivity simultaneously. Adsorption of the catalyst was observed at the air-water interface and further corroborated by pendant drop shape analysis at the water-supercritical CO2 interface. In what is considered as a very promising approach, modification of the supercritical phase with co-solvents opens the route for the study of many different systems in presence of large amounts of CO2 with the long-term goal of conceiving an efficient artificial leave.

National audience

National audience; l'extrusion est un procédé largement utilisé industriellement pour la mise en forme de matériaux. Dans ce travail, nous nous intéressons plus particulièrement à l'utilisation du dioxyde de carbone supercritique (CO 2 SC) comme agent moussant pour la fabrication de mousses polymères par extrusion. Dans une première étape, une extrudeuse monovis (capacité de l'ordre de 1 kg.h-1) a été modifiée afin de pouvoir injecter du CO 2 SC au sein de la matière extrudée. Ensuite, de premières expériences ont été réalisées sur du polystyrène. Abstract : extrusion is a widely used process in industry for material design. This work deals with the use of supercritical carbon dioxide (SC CO 2) as foaming agent for manufacturing polymeric foams by extrusion. In a first step, a single-screw extruder (capacity of about 1 kg.h-1) was modified to be able to inject SC CO 2 within the extruded matter. Then, preliminary experiments were performed on polystyrene.