Factors controlling nitrate in ice cores: Evidence from the Dome C deep ice core

In order to estimate past changes in atmospheric NOx concentration, nitrate, an oxidation product of NOx, has often been measured in polar ice cores. In the frame of the European Project for Ice Coring in Antarctica (EPICA), a high-resolution nitrate record was obtained by continuous flow analysis (CFA) of a new deep ice core drilled at Dome C. This record allows a detailed comparison of nitrate with other chemical trace substances in polar snow under different climatic regimes. Previous studies showed that it would be difficult to make firm conclusions about atmospheric NOx concentrations based on ice core nitrate without a better understanding of the factors controlling NO3− deposition and preservation. At Dome C, initially high nitrate concentrations (over 500 ppb) decrease within the top meter to steady low values around 15 ppb that are maintained throughout the Holocene ice. Much higher concentrations (averaging 53 ppb) are found in ice from the Last Glacial Maximum (LGM). Combining this information with data from previous sampling elsewhere in Antarctica, it seems that under climatic conditions of the Holocene, temperature and accumulation rate are the key factors determining the NO3− concentration in the ice. Furthermore, ice layers with high acidity show a depletion of NO3−, but higher concentrations are found before and after the acidity layer, indicating that NO3− has been redistributed after deposition. Under glacial conditions, where NO3− shows a higher concentration level and also a larger variability, non-sea-salt calcium seems to act as a stabilizer, preventing volatilization of NO3− from the surface snow layers

Résultats préliminaires en faveur de l'existence d'un antigène majeur de surface, spécifique de LEISHMANIA BRAZILIENSIS BRAZILIENSIS

L'Etude comparative des antigènes de surface de 10 souches boliviennes de référence de la sous-espèce L. B. Braziliensis a permis de mettre en évidence une grande homogénéité au sein de ce groupe. Les souches éprouvées possèdent des profils antigéniques où domine un antigène de 72kD. (Résumé d'auteur

Year-round records of bulk and size-segregated aerosol composition in central Antarctica (Concordia site) Part 1: Fractionation of sea-salt particles

Abstract. Multiple year-round records of bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located at Dome C in East Antarctica. In parallel, sampling of acidic gases on denuder tubes was carried out to quantify the concentrations of HCl and HNO3 present in the gas phase. These time-series are used to examine aerosol present over central Antarctica in terms of chloride depletion relative to sodium with respect to freshly emitted sea-salt aerosol as well as depletion of sulfate relative to sodium with respect to the composition of seawater. A depletion of chloride relative to sodium is observed over most of the year, reaching a maximum of ~ 20 ng m−3 in spring when there are still large sea-salt amounts and acidic components start to recover. The role of acidic sulfur aerosol and nitric acid in replacing chloride from sea-salt particles is here discussed. HCl is found to be around twice more abundant than the amount of chloride lost by sea-salt aerosol, suggesting that either HCl is more efficiently transported to Concordia than sea-salt aerosol or reemission from the snow pack over the Antarctic plateau represents an additional significant HCl source. The size-segregated composition of aerosol collected in winter (from 2006 to 2011) indicates a mean sulfate to sodium ratio of sea-salt aerosol present over central Antarctica of 0.16 ± 0.05, suggesting that, on average, the sea-ice and open ocean emissions equally contribute to sea-salt aerosol load of the inland Antarctic atmosphere. The temporal variability of the sulfate depletion relative to sodium was examined at the light of air mass backward trajectories, showing an overall decreasing trend of the ratio (i.e. a stronger sulfate depletion relative to sodium) when air masses arriving at Dome C had travelled a longer time over sea-ice than over open-ocean. The findings are shown to be useful to discuss sea-salt ice records extracted at deep drilling sites located inland Antarctica. </jats:p

Simple methods for crosstalk reduction in fiber optical parametric amplifiers

International audienceWe propose and numerically demonstrate two simple methods for reduction of the crosstalk caused by four-wave mixing between the pump and the wavelength-division multiplexed channels in single-pump fiber optical parametric amplifier. The first one is based on a proper tuning of the WDM system from the pump wavelength and the second one uses the Stokes side rather than the anti-Stokes side in the gain band

Towards FAIR GNSS data: challenges and open problems

C

Pharmacokinetic modelling and development of Bayesian estimators for therapeutic drug monitoring of mycophenolate mofetil in reduced-intensity haematopoietic stem cell transplantation.

International audienceBACKGROUND: Mycophenolate mofetil, a prodrug of mycophenolic acid (MPA), is used during non-myeloablative and reduced-intensity conditioning haematopoetic stem cell transplantation (HCT) to improve engraftment and reduce graft-versus-host disease (GVHD). However, information about MPA pharmacokinetics is sparse in this context and its use is still empirical. OBJECTIVES: To perform a pilot pharmacokinetic study and to develop maximum a posteriori Bayesian estimators (MAP-BEs) for the estimation of MPA exposure in HCT. PATIENTS AND METHODS: Fourteen patients administered oral mycophenolate mofetil 15 g/kg three times daily were included. Two consecutive 8-hour pharmacokinetic profiles were performed on the same day, 3 days before and 4 days after the HCT. One 8-hour pharmacokinetic profile was performed on day 27 after transplantation. For these 8-hour pharmacokinetic profiles, blood samples were collected predose and 20, 40, 60, 90 minutes and 2, 4, 6 and 8 hours post-dose. Using the iterative two-stage (ITS) method, two different one-compartment open pharmacokinetic models with first-order elimination were developed to describe the data: one with two gamma laws and one with three gamma laws to describe the absorption phase. For each pharmacokinetic profile, the Akaike information criterion (AIC) was calculated to evaluate model fitting. On the basis of the population pharmacokinetic parameters, MAP-BEs were developed for the estimation of MPA pharmacokinetics and area under the plasma concentration-time curve (AUC) from 0 to 8 hours at the different studied periods using a limited-sampling strategy. These MAP-BEs were then validated using a data-splitting method. RESULTS: The ITS approach allowed the development of MAP-BEs based either on 'double-gamma' or 'triple-gamma' models, the combination of which allowed correct estimation of MPA pharmacokinetics and AUC on the basis of a 20 minute-90 minute-240 minute sampling schedule. The mean bias of the Bayesian versus reference (trapezoidal) AUCs was 20%. AIC was systematically calculated for the choice of the most appropriate model fitting the data. CONCLUSION: Pharmacokinetic models and MAP-BEs for mycophenolate mofetil when administered to HCT patients have been developed. In the studied population, they allowed the estimation of MPA exposure based on three blood samples, which could be helpful in conducting clinical trials for the optimization of MPA in reduced-intensity HCT. However, prior studies will be needed to validate them in larger populations

Resistance to Dihydroartemisinin

International audienc

Influence de l'accessibilité des ressources anthropiques sur les paramètres reproducteurs de deux colonies de Goélands leucophées Larus michahellis

Cette étude a consisté à suivre la chronologie de reproduction et les paramètres reproducteurs (taille des pontes, volume des oeufs, taux d'éclosion et taux de survie des poussins) de deux colonies de Goélands leucophées Larus michahellis présentant dans leur environnement proche une accessibilité aux ressources anthropiques nettement différente. Ainsi, l'une des colonies sélectionnées, établie sur l'île de Ratonneau, est située à proximité immédiate du continent et des importantes décharges péri-marseillaises, tandis que la seconde colonie, implantée sur l'île de Bagaud, est éloignée de près de 30 km de la décharge la plus proche. La chronologie de ponte du premier oeuf montre l'existence d'un décalage phénologique significatif entre les deux colonies. Bien que les tailles moyennes de pontes (nombre moyen d'oeufs par nid) ne soient pas significativement différentes, la fréquence des pontes complètes (de 3 oeufs) est plus élevée lorsque l'accessibilité aux ressources est supérieure. Le volume moyen des oeufs est significativement différent entre les deux colonies, particulièrement en ce qui concerne le troisième oeuf, qui s'avère nettement plus petit pour la colonie ayant le moins accès aux ressources alimentaires anthropiques. De même, les taux d'éclosion et les taux de survie des poussins sont significativement inférieurs pour la colonie de Bagaud. Ainsi, ces disparités dans les paramètres reproducteurs semblent pouvoir être reliées à des différences notables d'accessibilité aux ressources alimentaires, expliquant en partie la nette différence de dynamique démographique des deux colonies observée sur les vingt dernières années. Enfin, ces résultats devraient permettre de calibrer plus justement les modèles démographiques destinés à orienter les opérations de gestion des populations de cette espèce parfois surabondante.This study aims at determining breeding chronology and reproductive parameters (clutch-size, egg volume, hatching success and chick survival rates) in two Yellow-legged Gull Larus michahellis colonies showing a marked difference in anthropogenic food resources accessibility. For instance, one of the colonies studied, established on Ratonneau island, is very close to the large refuse dumps of Marseille city white the other, established on Bagaud island, is 30 km distant from the nearest refuse dump. The mean laying date of the first egg showed a significant difference between the two colonies. Although mean clutch-size does not significantly differ between the two colonies, complete 3-egg clutches were more frequent at Ratonneau. Mean egg volume was significantly different between the two colonies with a markedly smaller volume for the C-egg in the colony that was farther from human food sources. Moreover, hatching success and chick survival rates were significantly lower on Bagaud than on Ratonneau. All these differences may be linked to marked differences in resource accessibility, and in this way, anthropogenic food resources accessibility may be partly responsible for the clear difference in the demographic patterns of the two colonies for the last twenty years. These results could be used to calibrate more accurately certain demographic modelling in order to improve the population management of this superabundant bird species

Molecular analysis of two local falciparum malaria outbreaks on the French Guiana coast confirms the msp1 B-K1/varD genotype association with severe malaria

BACKGROUND: Plasmodium falciparum outbreaks can occur in the coastal area of French Guiana, where the population is essentially non-immune. Two sporadic outbreaks were observed, including one with severe malaria cases. To characterize these outbreaks and verify previous observations of specific genotype characteristics in severe malaria in this area, all cases from each outbreak were studied. METHODS: P. falciparum genotypes for six genetic loci were determined by PCR amplification from peripheral blood parasites. The msp1/block2 and msp2 genotypes were determined by DNA sequencing. Microsatellite and varD genotyping was based on size polymorphism and locus-specific amplification. RESULTS: The outbreak including severe malaria cases was associated with a single genotype. The other mild malaria outbreak was due to at least five distinct genotypes. CONCLUSION: Two distinct types of outbreak occured despite systematic and sustained deployement of malaria control measures, indicating a need for reinforced vigilance. The varD/B-K1 msp1 linkage and its association with severe malaria in this area was confirmed