Etude de la morbidité palustre et de la gravité des accès pernicieux chez les porteurs du trait drépanocytaire

Une étude a été conduite en zone de forte transmission permanente du paludisme à #Plasmodium falciparum$ pour comparer la fréquence et la gravité des accès palustres chez les enfants de la naissance à 15 ans appartenant à différents groupes hémoglobiniques; 291 enfants se présentant dans un dispensaire périphérique et 467 à l'hôpital ont été examinés. Le diagnostic des accès palustres a été établi sur des critères cliniques, parasitologiques et évolutifs. Le seuil de parasitémie pathogène paraît similaire pour tous les types d'hémoglobine. Il a été estimé à 3000 hématies parasitées par mm3. Les accès palustres simples ou pernicieux sont significativement plus fréquents chez les sujets ayant une hémoglobine normale que chez les autres. La létalité due au paludisme est supérieure à 3 % chez les enfants AA, alors qu'aucun décès n'a pu être attribué au paludisme chez les porteurs du trait drépanocytaire. La fréquence du gène S s'est révélée significativement moindre (p < 0,05) chez des enfants présentant un accès palustre que dans tous les autres groupes d'enfants. Il apparaît que la plus faible fréquence et la moindre gravité des accès palustres chez les porteurs du trait drépanocytaire pourraient expliquer, en zone d'holoendémie, une mortalité réduite dans l'enfance chez ces sujets par rapport aux autres sujets. (Résumé d'auteur

Molecular outflows in the young open cluster IC348

We present a wide-field survey of the young open cluster IC348 for molecular H2 outflows. Outflow activity is only found at its south-western limit, where a new subcluster of embedded sources is in an early phase of its formation. If the IC348 cluster had been built up by such subclusters forming at different times, this could explain the large age-spread that Herbig (1998) found for the IC348 member stars. In addition to several compact groups of H2 knots, our survey reveals a large north-south oriented outflow, and we identify the newly discovered far-infrared and mm-object IC348MMS as its source. New deep images in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet as highly-collimated chains of knots, resembling the interferometric CO and SiO jets. This jet system appears rotated counter-clockwise by about 3 degrees with respect to the prominent H2 bow shocks. Furthermore, we resolve HH211-mm as a double point-like source in the mm-continuum.Comment: 10 pages, 9 figures, accepted for publication in Ap

Visible to near-infrared down-shifting in Tm3+ doped fluoride glasses for solar cells efficiency enhancement

In this paper, down-conversion of Tm3+ doped fluoride ZLAG glasses with composition of 70.2ZrF4–(23.4−x)LaF3–0.6AlF3–5.8GaF3–xTmF3 (x = 0.25, 0.5, 0.75, 1, 2, 3 and 5 mol%) were tested as encapsulation materials for solar cells. The current density – voltage (J-V) characterizations were performed under solar simulator irradiation. The influence of Tm3+ concentration on the mono crystalline silicon solar cells performances was investigated. A slight increase of the solar cell efficiency was observed in the case of fluoride ZLAG for Tm3+ doping concentrations up to 1 mol% Tm3+. Further increase of the Tm3+ concentration leads to a decrease of solar cell conversion efficiency as a result of concentration quenching

Star formation in the vicinity of the IC 348 cluster

Aims. We present molecular line observations of the southwestern part of the IC 348 young cluster, and we use them together with NIR and mm continuum data to determine the distribution of dense gas, search for molecular outflows, and analyze the ongoing star formation activity in the region. Methods. Our molecular line data consists of C18O(1--0) and N2H+(1--0) maps obtained with the FCRAO telescope at a resolution of about 50'' and CO(2--1) data obtained with the IRAM 30m telescope at a resolution of 11''. Results. The dense gas southwest of IC 348 is concentrated in two groups of dense cores, each of them with a few solar masses of material and indications of CO depletion at high density. One of the core groups is actively forming stars, while the other seems starless. There is evidence for at least three bipolar molecular outflows in the region, two of them powered by previously identified Class 0 sources, while the other one is powered by a still not well characterized low-luminosity object. The ongoing star formation activity is producing a small stellar subgroup in the cluster. Using the observed core characteristics and the star formation rate in the cluster we propose that that similar episodes of stellar birth may have produced the subclustering observed in the halo of IC 348.Comment: 10 pages, 6 figures, A&A accepte

Rare-earth-activated glasses for solar energy conversion

The solar cells efficiency may be improved by better exploitation of the solar spectrum, making use of the down-conversion mechanism, where one high energy photon is cut into two low energy photons. The choice of the matrix is a crucial point to obtain an efficient down-conversion process with rare-earth ions. When energy transfer between rare earth ions is used to activate this process, high emission and absorption cross sections as well as low cut-off phonon energy are mandatory. In this paper we present some results concerning 70SiO2-30HfO2 glass ceramic planar waveguides co-activated by Tb3+/Yb3+ ions, fabricated by sol gel route using a top-down approach, and a bulk fluoride glass of molar composition 70ZrF4 23.5LaF3 0.5AlF3 6GaF3 co-activated by Pr3+/Yb3+ ion. Attention is focused on the assessment of the energy transfer efficiency between the two couples of rare earth ions in the different hosts

Microclimat sous bâche à plat et son impact sur une culture de pomme de terre

Deux traitements ont été effectués dans un dispositif en blocs aléatoires complets avec quatre répétitions. Le premier sans bâche sert de témoin et le second utilise la bâche à plat comme couverture de la culture. La bâche en film polyéthylène perforé a été installée quinze jours après la plantation d’une culture de pomme de terre (Solanum tuberosum cv. Nicola) ayant reçu un traitement préventif contre le mildiou. La bâche a été retirée juste avant la récolte de la pomme de terre. Sous bâche à plat, les températures et les hygrométries de l’air ainsi que les températures du sol ont été supérieures à celles de l’extérieur. Les gouttelettes de condensation formées sous bâche ont réduit considérablement la transmission lumineuse. Les résultats agronomiques sont, par conséquent, affectés par ces conditions climatiques. Une nette amélioration de la croissance végétative de la pomme de terre a été observée sous bâche, mais l’attaque du mildiou a été plus importante sous bâche à plat que dans les parcelles témoins non couvertes qui ont été bien traitées. Ceci a affecté le rendement de pomme de terre sous bâche qui a enregistré une perte de 23% par rapport au témoin non couvert

Studies on Pr3+–Yb3+ codoped ZBLA as rare earth down convertor glasses for solar cells encapsulation

The non-absorption of photons with energies below the bandgap (Eg) and the thermalization of photons with energies higher than Eg are the dominant loss processes of single-junction solar cells. Rare earth doped glasses give the opportunity to convert the incident photons wavelength and hence to increase or decrease their energies. The conversion of photons energies by “up or down conversion” leads to the possibility to increase the efficiencies of all classes of single-junction solar cells. Depending on the nature of doping materials, two low energy photons can be converted into one high-energy photon (up-conversion), or one high energy photon, can be converted into two low energy photons (down-conversion). In this paper, Pr3+–Yb3+ down-conversion co-doped ZBLA glasses were tested as encapsulation materials for silicon solar cells. The J–V characterizations were done under solar simulator irradiation. The influence of Yb3+ concentration on the solar cells performances was investigated, showing that an optimum value between 0.5 and 2 mol% conducts to an increase of the device efficiency comparing to mono-doped ZBLA material

Site selection spectroscopy in Eu3+-doped lanthanum fluorozirconate glass and glass-ceramic

The optical properties of Eu3+-doped glass and transparent glass-ceramic with composition (in mol%) 70.2ZrF4–23.4LaF3–0.6AlF3–5.8GaF3 were investigated by site selective spectroscopy in order to study the effect of ceramization on the symmetry of Eu3 + sites. The glass-ceramic obtained after thermal treatment of the glass ZLAG contains a unique crystalline phase of unknown structure. The analysis and comparison of FLN spectra in these materials are presented and different classes of sites are discussed. We found the presence of two main site distributions for Eu3+ ions of equivalent symmetry (C2v or lower) in the glass and two sites of different symmetry (C2v or lower and C4v or lower) in tthe glass-ceramic (GC). The estimated average crystal field strength for glass and GC decreases with the 5D0 → 7F0 energy. The results suggest that the two kinds of sites identified in the glass correspond to Eu3+ ions in and out of the former network. Decay-time measurements of 5D0 level of Eu3 + evidenced energy transfer between high and low energy sites and showed an increase of lifetime from the glass to the glass-ceramic