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Rachida Elosrouti B. Sallek H. Chaair K. Digua et H. Oudadesse 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):124-133
Abstract Le comportement sous atmosphère humide des mélanges initiaux de la calcite et du di-ammonium hydrogénophosphate à différents rapport atomique (Ca/P)initiala été étudié. L’analyse par diffraction des rayons X (DRX) montre que les produits obtenus ont tous une structure apatitique. Il montre la présence à côté de celle de l’apatite, des raies identifiables à la calcite pour des rapports atomiques initiaux supérieurs à 1.50. Par ailleurs, la spectroscopie d’absorption infrarouge (IR) révèle dans les différents cas, la présence autre que les bandes attribuables aux ions PO4 3?dans une apatite, des bandes à 875 cm?1caractéristique des groupements HPO4 2?dans une apatite déficiente en ion calcium. De même, le traitement thermique à 1000°C des poudres synthétisés a mis en évidence que les apatites formées sont non st?chiométriques. Les analyses chimiques montrent, par ailleurs, que lorsque le rapport atomique Ca/P du mélange initial est inférieur à 1.50, l’apatite formée a un rapport atomique Ca/P égal à 1.58. Par contre, lorsque le rapport Ca/P initial est supérieur à 1.50, le produit formé est biphasique et a un rapport atomique Ca/P de 1.62. Ce rapport est dû essentiellement à la présence d’un excès de CaCO3dans le mélange initial (DRX, IR). Mots clés Apatite; atmosphère humide; calcite; hydrothermal; synthèse Abstract The behavior, in a humid atmosphere, of the initial mixtures of calcite and diammonium hydrogenophosphate at different atomic ratio (Ca/P) was studied. The X-ray diffraction (XRD) analysis shows that all the products obtained have apatite structure. For initial atomic ratios greater than 1.50, the XRD analysis shows the presence of reflections different from those of apatite, which may be attributed to calcite. Analysis by infrared (IR) absorption spectroscopy allows to distinguish between the two cases: in addition to the presence of bands due to the PO4 3?ions in apatite further bands at 875 cm?1characteristic of HPO4 2?in apatite deficient with respect to calcium ions are observed. Similarly, the powders synthesized by heat treatment at 1000°C showed that nonstoichiometric apatites are formed. Chemical analyses show, that when the atomic ratio Ca/P of the initial mixture is less than 1.50, the apatite formed has an atomic Ca/P ratio of 1.58. When the initial Ca/P ratio is greater than 1.50, the product formed is biphasic and has an atomic ratio Ca/P of 1.62. This result is mainly due to the presence of an excess of CaCO3in the original mixture (XRD, IR). 相似文献
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Rachida M’chaar Abdelaziz Sabbar Mouloud El Moudane Noureddine Ouerfelli 《哲学杂志》2020,100(11):1415-1438
ABSTRACT By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds. 相似文献
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Fadoua Hamzaoui-Azaza Mounira Zammouri Meriem Ameur Mohamedou Baba Sy Moncef Gueddari Rachida Bouhlila 《Natural Resource Modeling》2020,33(4):e12282
The study of water quality and the quantification of reserves and their variations according to natural and anthropogenic forcing is necessary to establish an adequate management plan for groundwater resources. For this purpose, a modeling approach is a useful tool that allows, after calibration phase and verification of simulation, and under different scenarios of forcing and operational changes, to estimate and control the groundwater quantity and quality. The main objective of this study is to collect all available data in a model that simulates the Jeffara of Medenine coastal aquifer system functioning. To achieve this goal, a conceptual model was constructed based on previous studies and hydrogeological investigations. The regional groundwater numerical flow model for the Jeffara aquifer was developed using MODFLOW working under steady-state and transient conditions. Groundwater elevations measured from the piezometric wells distributed throughout the study area in 1973 were selected as the target water levels for steady state (head) model calibration. A transient simulation was undertaken for the 42 years from 1973 to 2015. The historical transient model calibration was satisfactory, consistent with the continuous piezometric decline in response to the increase in groundwater abstraction. The developed numerical model was used to study the system's behavior over the next 35 years under various constraints. Two scenarios for potential groundwater extraction for the period 2015–2050 are presented. The predictive simulations show the effect of the increase of the exploitation on the piezometric levels. To study the phenomenon of salinization, which is one of the most severe and widespread groundwater contamination problems, especially in coastal regions, a solute transport model has been constructed by using MT3DMS software coupled with the groundwater flow model. The best calibration results are obtained when the connection with the overlying superficial aquifer is considered suggesting that groundwater contamination originates from this aquifer. Recommendations for water resource managers
- The results of this study show that Groundwater resources of Jeffara of Medenine coastal aquifer in Tunisia are under immense pressure from multiple stresses.
- The water resources manager must consider the impact of economic and demographic development in groundwater management to avoid the intrusion of saline water.
- The results obtained presented some reference information that can serve as a basis for water resources planning.
- The model runs to provide information that managers can use to regulate and adequately control the Jeffara of Medenine water resources.
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Lahcen Hssaini Francisca Hernandez Manuel Viuda-Martos Jamal Charafi Rachid Razouk Karim Houmanat Rachida Ouaabou Said Ennahli Driss Elothmani Ilham Hmid Marie Laure Fauconnier Hafida Hanine 《Molecules (Basel, Switzerland)》2021,26(9)
In the present study, chromatic coordinates, phenolic acids, flavonoids and antioxidant capacity assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate (ABTS) and lipid peroxidation inhibition capacity (LPIC) essays and their relative IC50 were investigated in 25 fig cultivars growing in Morocco. The aims of this study were to determine (i) the variation in these compounds among light and dark-colored cultivars, (ii) their partitioning between fruit peel and pulp and (iii) to display network connections among these variables. Twelve phenolic compounds (PCs) were isolated in peel extract versus eight in pulp samples. Anthocyanins, mainly cyanidin-3,5-diglucoside and cyanidin-3-O-rutinoside, were the predominant compounds in peels, where the mean concentrations were 75.90 ± 18.76 and 77.97 ± 18.95 µg/g dw, respectively. On the other hand, (−)-epicatechin and cyanidin-3-O-rutinoside were the major compounds in the pulp extracts, where the mean values were 5.23 ± 4.03 and 9.01 ± 5.67 µg/g dw, respectively. A two-dimensional hierarchically clustered heatmap was applied to the dataset to explore correlations in the dataset and similarities between cultivars, without dimensionality reduction. Results showed that anthocyanins, particularly pelargonidin-3-O-rutinoside, cyanidin-3,5-diglucoside and cyanidin-3-O-rutinoside, were the main contributors to the peels’ free radical scavenging capacity. This capacity was particularly higher in the peel of dark-colored figs compared to the fruit pulp. The local cultivar “INRA 1301” showed the most promising phenolic profile due to its very high levels of almost all detected PCs, especially (−)-epicatechin, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, cyanidine-3,5-diglucoside, cyanidine-3-O-rutinoside and pelargonidin-3-O-rutinoside (54.66, 141.08, 35.48, 494.08, 478.66, 12.56 µg/g dw, respectively). Having the darkest figs in the collection (L* = 25.72, c* = 22.09 and h° = 20.99), this cultivar has also combined promising IC50 values, which were of 19.85, 40.58 and 124.78 µg/mL for DPPH, ABTS and LPIC essays, respectively. 相似文献
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A study of the spatial and temporal evolution of auto-ignition kernels using time-resolved tomographic OH-LIF 总被引:1,自引:0,他引:1
Jhon Pareja Ayane Johchi Tao Li Andreas Dreizler Benjamin Böhm 《Proceedings of the Combustion Institute》2019,37(2):1321-1328
In this paper, the spatial and temporal evolution of auto-ignition kernels from methane jets propagating into a NOx-vitiated, high-turbulence, hot air co-flow was studied by means of time-resolved tomographic laser-induced fluorescence of OH (Tomo OH-LIF). Measurements were performed using a burst dye laser system at 10 kHz for volumetric laser illumination and a multi-camera arrangement (8-views) for detection of the fluorescence signal. Auto-ignition kernels were detected three-dimensionally and tracked using a robust algorithm based on the intensity gradient of the volumetrically reconstructed signals. The size and location of the detected kernels were evaluated for operating conditions with different Reynolds numbers of the fuel jet. Results showed that auto-ignition randomly occurred with high probability in a well defined fairly axisymmetric radial region with strong fluctuations in the main direction of the flow. The increase of the Reynolds number of the fuel jet resulted in a radial spread of the location of auto-ignition events. The statistical evaluation of the orientation and growth of auto-ignition kernels with respect to the mean flow field showed that the kernels were oriented tangentially to the flow and temporally evolve towards this preferential direction as the ignition events progressed. 相似文献
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J. Yves Laronze Rachida El Boukili Dominique Patigny Seloua Dridi Dominique Cartier Lean L vy 《Tetrahedron》1991,47(48):10003-10014
Upon acid catalyzed rearrangement after Sheradsky, the aryloximes A gave the tricyclic aminals C, which suffered hydrolysis to lactols E. The unique alcohol 29 was then prepared through a highly stereoselective equilibration-reductive alkylation of the epimeric mixture of lactols 22a,b. Two routes, one of which was stereospecific, allowed cyclization of 29 to (±)-aplysin 34. The yield was 2.5 % from oximes 2a,b. The isomeric epi-aplysin 35 and filiformin 36 were also obtained from 29. The debromo analogues 37,38 and 39 and their trideutero derivatives 41,42 and 43 were synthesized along similar line and allowed unequivocal structure elucidation by NMR spectroscopy. 相似文献