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A new effective approach to the synthesis of a small library of 2-amino-5-arylidene-1,3-thiazol-4(5H)-ones was reported using solvent-free reaction conditions under microwave irradiation. In the first step, rhodanines were subjected to Knoevenagel condensation with aryl aldimines according to a facile one-pot protocol. Then the (5Z)-5-arylidene rhodanine derivatives were transformed directly into the corresponding 2-amino-1,3-thiazol-4(5H)-ones by sulfur/nitrogen displacement reaction under microwaves with retention of configuration and good overall yields. 相似文献
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The aim of this study is to shed more light on the formation of mullite and the kinetics of mullitization from sol-gel synthesized precursors. Tetraethylorthosilicate (TEOS) and aluminum nitrate nonahydrate (ANN) were used, as a source of silica and alumina, respectively, for the synthesis of homogenous mullite precursor powder. The mullitization process was characterized by thermogravimetry (TG), differential thermal analysis (DTA), thermodilatometric analysis (TDA), and x-ray powder diffraction (XRD) techniques. It was found that mullite started to crystalize at temperatures of 1050, 1200, and 1241 °C as determined by XRD, DTA, and TDA, respectively?. Mullite crystallization kinetics was thoroughly investigated under isothermal and non-isothermal conditions using DTA. The activation energy for mullite formation was calculated, for different crystallization fractions, following the Freidman, Kissinger, Boswell, and Ozawa methods. The average values were found to be 1282.92, 1324.30, 1336.93, and 1283.09 kJ/mol, respectively. The kinetic parameters and the crystallization mechanism were determined and the results were compared with those available in the literature. The Sestak Berggren SB(m,n) model was found to be the most suitable for the determination of mullite crystallization mechanism. The calculated average values of the Gibbs free energy (ΔG#), enthalpy (ΔH#), and entropy (ΔS#) for mullite formation, at different heating rates, were 433.98 kJ/mol, 1294.20 kJ/mol, and 566.23 J/mol.K, respectively. 相似文献
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Henni Khadidja Louis Pierre-Yves Vannier Brigitte Moussa Ahmed 《Advances in Data Analysis and Classification》2020,14(3):543-570
Advances in Data Analysis and Classification - Clustering via marked point processes and influence space, Is-ClusterMPP, is a new unsupervised clustering algorithm through adaptive MCMC sampling of... 相似文献
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We prove a rgularity result, in Hölder spaces, for solutions to an elliptic problem with mixed boundary condition, namely Dirichlet on a part of the boundary and Signorini on the remaining part, in a regular or polygonal, domain of IR2 We give the behaviour of the solution near points where the boundary condition tyoe changes. Nous montrons la Régularité jusqu'au bord, dans les espaces de Hölder des solutions d'un problème aux limites de type mêlé avec une condition de Dirichlet sur une partie de la frontière et des conditions de type Signorini sur le complémentaire, et ceci dans un ouvert plan ré gulier ou polygonal. Nous donnons en particulier le comportement de la solution au volisinge d'un point de la frontiére où la condition aux limites change de type. Mots Clés: In´quations variationnells–conditions unilatélrales. Domains polygonaux. Classification AMS 35 (J) 49 (A) 相似文献
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Khadidja Bourahla Mustapha Rahmouni Joan Fraga‐Dubreuil Jean Pierre Bazureau Jack Hamelin 《Journal of heterocyclic chemistry》2007,44(1):193-199
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Samia Lamraoui Rachid Bensalem Khadidja Hacini Hocine Meradji Sebti Ghemid Fouad El Haj Hassan 《Central European Journal of Physics》2014,12(1):70-79
Structural, electronic and thermal properties of Zn1?x Mg x S ternary alloys are studied by using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The Wu-Cohen generalized gradient approximation (WC-GGA) is used in this approach for the exchangecorrelation potential. Moreover, the modified Becke-Johnson approximation (mBJ) is adopted for band structure calculations. The dependence of the lattice constant, bulk modulus and band gap on the composition x showed that the first exhibits a small deviation from the Vegard’s law, whereas, a marginal deviation of the second from linear concentration dependence (LCD). The bowing of the fundamental gap versus composition predicted by our calculations agrees well with the available theoretical data. The microscopic origins of the gap bowing are explained by using the approach of Zunger and co-workers. Thermal effects on some macroscopic properties of Zn1?x Mg x S alloys are also investigated using the quasi-harmonic Debye model, in which the phononic effects are considered. As, this is the first quantitative theoretical prediction of the thermal properties of Zn1?x Mg x S alloys, no other calculated results and furthermore no experimental studies are available for comparison. 相似文献
8.
Dutot L Gaucher A Elkassimi K Drapeau J Wakselman M Mazaleyrat JP Peggion C Formaggio F Toniolo C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(10):3154-3163
A new set of beta-amino acids that carry various crown ether receptors on their side chains of the general formula (S)-beta(3)-HDOPA(crown ether) (HDOPA: homo-3,4-dihydroxyphenylalanine; (crown ether): [15]crown-5 ([15-C-5]), [18]crown-6 ([18-C-6]), [21]crown-7 ([21-C-7]), 1,2-Benzo-[24]crown-8 ([Benzo-24-C-8]) and (R)-Binol-[20]crown-6 ([(R)-Binol-20-C-6])) was prepared. Peptides that are based on these new crowned beta-amino acids combined with (1S,2S)-ACHC (2-aminocyclohexanecarboxylic acid), which is known to be a potent 3(14)-helix inducer, to the hexamer level, with two crowned residues at the i and i+3 positions of the main-chain, were synthesized in solution by stepwise coupling using Boc-N(alpha)-protection (Boc: tert-butoxycarbonyl) and the EDC/HOAt C-activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 3(14)-helix conformation. 相似文献
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Khadidja Youce Ettoumi Yamina Zouambia Nadji Moulai-Mostefa 《Journal of Dispersion Science and Technology》2017,38(1):26-32
The present study was conducted to enhance the peel of Citrus sinensis (sweet orange) by using their essential oils (EOs) as a potential source of natural bioactive molecules. EOs were obtained by hydrodistillation and their chemical profile was determined through GC-MS analysis. O/W EO emulsions were prepared using pectin as biopolymer emulsifier at different proportions, including different amounts of ascorbic acid (0, 0.5, and 1% w/w). The effect of pectin and ascorbic acid concentrations on the stability and rheological behavior of emulsions was investigated. It was found that adding ascorbic acid to the appropriate concentration of pectin enhances the interfacial membranes surrounding the oil droplets and decreases the droplet sizes. As a result both the viscoelastic modules and the resulting viscosity of emulsions increase leading to an improvement of their stability. Antioxidant activity of orange EO emulsion in combination with ascorbic acid was found significantly higher than that without ascorbic acid, and higher than that of individual components. Overall, this study would be helpful in developing more effectives systems with promising physical and antioxidant characteristics for the preservation of foods. 相似文献
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Audoin Coralie Holderith Serge Romari Khadidja Thomas Olivier P. Genta-Jouve Grégory 《平面色谱法杂志一现代薄层色谱法》2014,27(5):328-332
JPC – Journal of Planar Chromatography – Modern TLC - Although the different practical steps of a high-performance thin-layer chromatography (HPTLC) experiment are now all automated,... 相似文献