136 research outputs found
Na2O solubility in CaO–MgO–SiO2 melts
No full textThe sodium solubility in silicate melts in the CaO-MgO-SiO2 (CMS) system at 1400 C has been measured by using a closed thermochemical reactor designed to control alkali metal activity. In this reactor, Na-(g) evaporation from a Na2O-xSiO(2) melt imposes an alkali metal vapor pressure in equilibrium with the molten silicate samples. Because of equilibrium conditions in the reactor, the activity of sodium-metal oxide in the molten samples is the same as that of the source, i.e., aNa(2)O((sample)) = aNa(2)O((source)). This design also allows to determine the sodium oxide activity coefficient in the samples. Thirty-three different CMS compositions were studied. The results show that the amount of sodium entering from the gas phase (i.e., Na2O solubility) is strongly sensitive to silica content of the melt and, to a lesser extent, the relative amounts of CaO and MgO. Despite the large range of tested melt compositions (0 < CaO and MgO < 40; 40 < SiO2 < 100; in wt%), we found that Na2O solubility is conveniently modeled as a linear function of the optical basicity (A) calculated on a Na-free basis melt composition. In our experiments, gamma Na2O(sample) ranges from 7 x 10(-7) to 5 x 10(-6), indicating a strongly non-ideal behavior of Na2O solubility in the studied CMS melts (gamma Na2O(sample) << 1). In addition to showing the effect of sodium on phase relationships in the CMS system, this Na2O solubility study brings valuable new constraints on how melt structure controls the solubility of Na in the CMS silicate melts. Our results suggest that Na2O addition causes depolymerization of the melt by preferential breaking of Si-O-Si bonds of the most polymerized tetrahedral sites, mainly Q(4). (C) 2010 Elsevier Ltd. All rights reserved.ANR [BLAN06-3_134633
Suivi de la pluviométrie au Nord-Sénégal de 1954 à 2013 : étude de cas des stations synoptiques de Matam, Podor et Saint-Louis
No full textSur la série 1954-2013, le Nord-Sénégal a connu de très fortes fluctuations pluviométriques tant du point de vue de répartition intra-annuelle qu’en termes d’évolution interannuelle. Le démarrage de la véritable saison hivernale, défini par les occurrences, ainsi que sa durée reste une problématique majeure notamment dans le domaine agronomique alors que l’évolution interannuelle y est révélatrice de tendances souvent généralement observées dans tout le Sahel avec toutefois des réalités propres à la zone d’étude et qui donc l’identifient au reste de la région. Plusieurs méthodes sont utilisées dans cet article dans le but de suivre ces différentes fluctuations. Le décèlement des occurrences du maximum pluviométrique nous permet de localiser la véritable saison des pluies notamment son démarrage et sa durée. La méthode des écarts à la moyenne est utilisée dans le but de vérifier les variabilités (déficits et excédents) interannuelles. Nous avons par la suite appliqué le test non-paramétrique de Pettitt aux données de notre série (1954-2013) dans le but de détecter la/les rupture (s) de tendance dans l’évolution de la pluviométrie sur nos 60 années d’étude. La division de la série en sous-série nous a renseigné sur la tendance actuellement observée dans la région. Nous avons enfin corrélé à l’aide de la corrélation r de Pearson la hauteur d’eau annuelle et le nombre de jours de pluie afin d’exprimer l’intensité de la pluviométrie. Les résultats montrent que la saison des pluies qui dure généralement de juillet à septembre se concentre sur seulement deux mois qui enregistrent à eux seuls l’essentiel des abats annuels (juillet-Août à Matam avec 87 % et Août-septembre à Saint-Louis et Podor avec respectivement 87 et 84 %). Ces observations traduisent ainsi un démarrage de l’hivernage dans la deuxième quinzaine de juillet et une fin au plus tard dans la 1re décade du mois d’octobre. Les écarts à la moyenne révèlent une très grande variabilité interannuelle avec une forte présence d’années déficitaires (29/60 à Saint-Louis, 33/60 à Podor et la moitié de la série à Matam). L’application du test de Pettitt indique un seul point de rupture de tendance dans la série (1969 à l’ouest et à l’est de la zone et 1970 au centre) alors que la division de la série en sous-série y révèle un retour à la normale depuis les années 2000. La corrélation de Pearson montre une forte relation entre hauteur d’eau annuelle et nombre de jours de pluie (r = 0.58 à la station de Saint-Louis, r = 0,7 à la station de Podor et r = 0,59 à la station de Matam).From 1954 to 2013, the north of Senegal has experienced considerable fluctuations in rainfall from the point of view of intra-annual distribution and in terms of inter-annual evolution. The start of real winter season, defined by the occurrence and its duration remains a major problem especially in the agricultural field while the inter-annual evolution is often suggestive of general trends across all the Sahel but with the realities characteristic of the study area and therefore identify it with the rest of the region. Several methods are used in this article in order to follow these different fluctuations. The detection of occurrences of maximum rainfall allows us to locate the real rainy season particularly its start and duration. The method of differences in the average is used in order to verify the variability (deficits and excesses) inter-annual. We subsequently applied the non-parametric Pettitt test to the data in our series (1954-2013) in order to detect the rupture (s) trend in the evolution of rainfall on our 60 years’ study. The division of the series in subseries has informed us about the current trend in the region. Finally the r Pearson correlation between annual water height and number of rainy days was used to show the intensity of rainfall. The results show that the rainy season, which usually lasts from July to September, concentrates during only two months which record the main part of the annual rains (July-August in Matam with 87 % and August-September in Saint-Louis and Podor with respectively 87 and 84 %). These observations reflect a start of the rainy season in the second fortnight of July and an end in the first decade of October at the latest. The values of standard deviation show a high interannual variability with a strong presence of deficit years (29/60 in Saint-Louis, Podor 33/60 and half of the series in Matam). The application of Pettitt test indicates a single break point in the trend series (1969 to the west and east of the area and in 1970 to the center), while the division of the series in sub-series reveals a return to normal since the 2000s. Pearson correlation shows a strong relationship between high annual water and number of rainy days (r = 0.58 at the station of Saint- Louis, r = 0.7 at the station of Podor and r = 0.59 at the station of Matam)
Pond management in the Podor department, Senegal
No full textSIGLEAvailable from British Library Document Supply Centre-DSC:4584.31233(72) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Calvin United Church of Christ Confirmation Class, 1958
No full textA photograph of the 1958 confirmation class of Calvin United Church of Christ with Reverend Zsiros.Bottom Row: T. Doktor, 3. Arvay, J. Nagy, J. Podor, J. Lakatos F Szymanskl
2nd Row: V. Byurko, D. Benyo, M. Pigott, M. Petrilla, C. oecivl, 3. Fejea.
3rd. Row: D. Donnal, L. Welch, Liane Kertesz, Rev. Zsiros, M. Toth 111,
N. Molnar, E. Wargo, R. Matyok.
Géomorphologie et quaternaire d'après une image R.B.V. : la vallée du Sénégal entre Bogué et Podor (Sénégal, Mauritanie)
No full textLandsat-3 R.B.V. systems, characterized by a high resolution (24 m) operates in the same wavelenghts as panchromatic films. In order to evaluate its usefulness for geographers, an example has been choosen : the Senegal Valley between Bogue and Podor, on the border between Senegal and Mauritania (West Africa), in the Sahelian belt. The area coincides roughly with the Podor sheet of the 1/200 000 map and its Quarternary and geomorphological features are fairly well known. They have been studied since 1953 by the author and teams of the C.G.A. (L.A. 95). A geological map has been published in the dissertation of P. Michel (1973).
The scene reproduced in the paper has been carefully chosen (2d of January 1979) : two and a half month after the end of the annual flood, so that the coarser and higher landforms are dry (dunes high levees, Continental Terminal plateau) but the lower units, mainly those consisting of fine material, are still wet. Atmospheric transmissivity is optimal. Sharp contrasts increase the resolution, so that this image associates the advantages of a synoptic view, proper to orbital imagery, with the accuracy of details. The comparison of the R.B.V. scene with the excellent geological map of P. Michel, gives the following results : — The eolian sand cover on the Continental Terminal plateau is more extensive than mapped. Its thickness is irregular : the common procedure of the geological map, using continuous lines for the contacts and plain colours for the outcrops is not suitable. Dots of varying density could be used as an overprint on the colour of the basement in order to show the changes in thickness of the sand cover. The longitudinal dunes which have been shaped during an arid period where the sand cover is thicker are quite clear on the R.B.V. imagery. This image could be used for mapping these dunes, the direction of which changes slightly but clearly at some distance, N. of the Senegal Valley, a fact which had remained unnoticed formerly.
— On the Continental Terminal plateau, some small outcrops of ironcrusts have been mapped. On R.B.V. scene, they can be recognized through a lower reflectibility. Their shape and the transitional features of their limits helps discriminating them from the small basins where finer deposits have retained some humidity. Once again, the solid contour line of the geological map is not suitable at all, because, usually, these ironcrust outcrops vanish gradually, transforming themselves in ferrugineous gravels. The same type of cartographical technique as mentioned above is wanted for their mapping. On R.B.V. image, too, some fossilized and relictual valleys are quite noticeable. The Loueid valley, in the N., is shown, on the topographical map, as continuous and as reaching the Senegal river, whereas, obviously, on the scene, it faints and disappears downstream about 15 km before reaching the Senegal valley. In this area, a basin, still wet, could receive its underflow in the sand cover.
— In the alluvial valley, the levees and basins can be mapped in detail, without loosing the synoptic vision which enables the reconstruction of the geomorphic evolution. Downstream Bogue, along the N. side of the valley, a former course of the Senegal River has built an important and continuous system of levees. A section of the former course is still drained during floods (Marigot de Koundi). Later on, after the small post-dunkerquian regression, the Senegal main branch has abandonned this course and has run somewhat more in the South, along the basins at the foot of these high levees. Where it cuts them, it meanders in their coarser material. Some ox-bow lakes are quite visible. The basins, still wet, as a result of the high retention capacity of their silty and clayed deposits, can be seen with a dark coulour.
The most valuable information that R.B.V. imagery can yield is in the fields of geomorphology and superficial deposits. Information about vegetative cover is scanty and very incomplete. For instance, in this densely populated valley, no field pattern and crops can be identified.Les clichés R.B.V. de Landsat-3, pris d'une manière très différente de ceux des Landsat 1 et 2, ont une excellente résolution qui permet, à la fois, d'avoir la vue synoptique propre aux enregistrements de satellites, et une précision de détails permettant de bien caractériser le milieu naturel. Bien que la région prise comme exemple soit bien connue, l'étude du cliché du 2 janvier 1979 (pris environ deux mois et demi après la fin de la crue annuelle) fournit une quantité appréciable d'informations nouvelles qui précisent ou complètent la carte géologique au 1/200 000 de P. Michel principalement sur les points suivants :
— Existence de deux orientations différentes dans les dunes longitudinales dans le N.O. du cliché, qui était inconnue.
— Irrégularité et extension de la couverture sableuse sur les plateaux du Continental Terminal (S. du fleuve, N.E. du cliché).
— Passage des cuirasses ferrugineuses à des nappes de graviers ferrugineux, avec transitions très graduelles, ignorées de la carte.
— Existence et tracé de plusieurs vallées mortes, fossilisées sous les sables et absence de raccord entre la vallée du Loueïd et le Sénégal, contrairement à ce que figure la carte topographique.
— Disposition des levées et des cuvettes de décantation dans la vallée du Sénégal, que les levées de terrain de P. Michel n'avaient pu figurer que de manière très grossière.
Par contre, la couverture végétale apparaît peu et le parcellaire et les cultures ne sont pas visibles.Tricart Jean. Géomorphologie et quaternaire d'après une image R.B.V. : la vallée du Sénégal entre Bogué et Podor (Sénégal, Mauritanie). In: Annales de Géographie, t. 90, n°499, 1981. pp. 311-326
A Service of zbw Health Status and the Allocation of Time Health Status and the Allocation of Time
No full textStandard-Nutzungsbedingungen: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden. Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen. Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. www.econstor.eu The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit organization supported by Deutsche Post Foundation. The center is associated with the University of Bonn and offers a stimulating research environment through its international network, workshops and conferences, data service, project support, research visits and doctoral program. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. Terms of use: Documents in D I S C U S S I O N P A P E R S E R I E S IZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. ABSTRACT Health Status and the Allocation of Time In this paper, we quantify the effects of health on time allocation. We estimate that improvements in health status have large and positive effects on time allocated to home and market production and large negative effects on time spent watching TV, sleeping, and consuming other types of leisure. We find that poor health status results in about 300 additional hours allocated to unproductive activities per year. Plausible estimates of the cost of this lost time exceed 0.37. JEL Classification: I1, J
Development and validation of an interface for automated image acquisition during high-temperature environmental scanning electron microscopy experiments
No full textInternational audienceAn interface that enables automatic image acquisition during high-temperature experiments in an environmental SEM is developed. It is optimized to work on multiple regions of interest at multiple magnifications, performing image focusing (focus and astigmatism) and automatic recentering of regions of interest. Its operation has been validated by monitoring two regions of interest of a nickel-based superalloy undergoing oxidation at 950°C at different magnifications. Recording series of images at different magnifications on different regions of interest makes it possible to qualify the behavior of different areas of the sample in a single operation and/or to validate the reproducibility of the observations
Influence of annealing conditions on the formation of hollow Al2O3 microspheres studied by in situ ESEM
No full textInternational audienceThe transformation of Al microparticles into hollow and broken Al2O3 microspheres was investigated by in situ environmental scanning electron microscopy (ESEM) up to 1150°C under different heating rates and 120 Pa of gas atmospheres. Slow heating rates (2°C min-1) resulted in a better coverage of the particles shell than with fast heating rates (20°C min-1) that delayed the threshold temperature at which the particles opened. Above this threshold, the amount of opened spheres increased with heating rate, with the coarser particles opening more than the small ones. It appeared that inert atmospheres (He-4%H2) increased the temperature at which the particles transformed, while air and pure oxygen tended to lower it. In contrast, the temperature interval was larger and was size-dependent when using water vapour. Irrespective of the gas atmosphere, opening of the spheres allowed molten Al to flow out from the core and aluminise the substrate while leaving behind a top coat of hollow alumina spheres
Nucleation and Growth of Oxide Constituents on NiCoCrAlY Bond Coats During the Different Stages of EB-PVD TBC Deposition and Upon Thermal Loading
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