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

Cooling Strategies for Greenhouses in Summer: Control of Fogging by Pulse Width Modulation

The possibilities for improving the control of greenhouse fogging systems, were studied by comparing several combinations of ventilation cooling techniques, shade screening and low-pressure fogging. The study was divided into three parts: experiments, modelling and simulations. In the first part of the paper, ten combinations of five cooling techniques were tested during the summers of 2002 and 2003 in a 132m2 greenhouse with a steel structure and a single-layer methacrylate cover located in Madrid, Spain. An analysis of variance of the climatic parameters was carried out to determine which combinations produced significant differences in inside temperature or relative humidity. Comparing the values for the inside to outside temperature difference, the combination of a shade screen and above-screen fogging achieved a difference in temperature almost the same as that for under-screen fogging, but the relative humidity was significantly lower. In the second part of the study a dynamic model was developed (2002) and validated (2003). The mean absolute error obtained for inside temperature was similar in the fit and the validation and it was less than 1.5 1C in both cases. The model was used to simulate the inside air temperature for a fog system working without shading, and above and under a shade screen. Control algorithms were developed for reducing system water consumption. In the three cases a simple on/off control with a fixed fogging cycle was compared with a pulse width modulation (PWM) strategy, in which the duration of the fogging pulse was increased as a function of inside temperature. The strategies with PWM applied to the fog system were able to reduce water consumption by 8–15% with respect to the strategies with a fixed fogging cycle

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

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

Experimental investigation of the stability of Fe-rich carbonates in the lower mantle

International audienceThe fate of carbonates in the Earth's mantle plays a key role in the geodynamical carbon cycle. Although iron is a major component of the Earth's lower mantle, the stability of Fe-bearing carbonates has rarely been studied. Here we present experimental results on the stability of Fe-rich carbonates at pressures ranging from 40 to 105 GPa and temperatures of 1450-3600 K, corresponding to depths within the Earth's lower mantle of about 1000-2400 km. Samples of iron oxides and iron-magnesium oxides were loaded into CO2 gas and laser heated in a diamond-anvil cell. The nature of crystalline run products was determined in situ by X-ray diffraction, and the recovered samples were studied by analytical transmission electron microscopy and scanning transmission X-ray microscopy. We show that Fe-(II) is systematically involved in redox reactions with CO2 yielding to Fe-(III)-bearing phases and diamonds. We also report a new Fe-(III)-bearing high-pressure phase resulting from the transformation of FeCO3 at pressures exceeding 40 GPa. The presence of both diamonds and an oxidized C-bearing phase suggests that oxidized and reduced forms of carbon might coexist in the deep mantle. Finally, the observed reactions potentially provide a new mechanism for diamond formation at great depth

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

Normalization of Red Cell Enolase Level Following Allogeneic Bone Marrow Transplantation in a Child with Diamond-Blackfan Anemia

We describe a girl with Diamond-Blackfan anemia with accompanying red cell enolase deficiency. At the age of 9 yr old, the patient received allogeneic bone marrow transplantation from her HLA-identical sister who had normal red cell enolase activity. While the post transplant DNA analysis with short tandem repeat has continuously demonstrated a stable mixed chimerism on follow-up, the patient remains transfusion independent and continues to show a steady increase in red cell enolase activity for over two and a half years following bone marrow transplantation