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排序方式: 共有196条查询结果,搜索用时 15 毫秒
191.
Mourad Ben Braiek Faouzi Aloui Souad Moussa Moncef Tounsi Jérome Marrot Béchir Ben Hassine 《Tetrahedron letters》2013
A new helically chiral pentacyclic system containing one pyrrole ring was prepared in a good yield and purity via a three-step sequence involving Heck coupling and classical oxidative photocyclization. X-ray crystal structure analysis indicated that the conformation resembled that of unsubstituted pentahelicene, the idealized symmetry of which is C2. The optical properties of the pentacyclic helicene were investigated and show interesting behaviour. 相似文献
192.
193.
Mounir Hajji Mohamed Faouzi Zid Ahmed Driss Tahar Jouini 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):i76-i78
A new non‐centrosymmetrical form of lithium molybdyl arsenate has been synthesized and grown as a single crystal. The structure of β‐LiMoO2(AsO4) is built up of corner‐sharing AsO4 tetrahedra and MoO6 octahedra which form a three‐dimensional framework containing tunnels running along the a axis, wherein the Li+ cations are located. This novel structure is compared with the compound LiMoO2(AsO4) of the same formula, and with those of AMO2(XO4) (A is Na, K, Rb or Pb, M is Mo or V, and X is P or As) and B(MoO2)2(XO4)2 (B is Ba, Pb or Sr). 相似文献
194.
Jahouach-Rabai W Trabelsi M Van Hoed V Adams A Verhé R De Kimpe N Frikha MH 《Ultrasonics sonochemistry》2008,15(4):590-597
The effects of bleaching using high power ultrasound (20 kHz) on the quality of olive oil were considered in this study, in order to verify the modifications that can occur in fatty acid composition and minor compounds. During the treatment of olive oil under ultrasonic waves, a rancid odour has been detected. Treated olive oils show no significant changes in their chemical composition but the presence of some volatile compounds, due to ultrasonic treatment. Some off-flavour compounds (hexanal, hept-2-enal and 2(E),4(E)-decadienal) resulting from the sonodegradation of olive oil have been identified. A wide variety of analytical techniques (GLC, HPLC and GC/MS) were used to follow the quality of bleached olive oils with ultrasonic waves by the determination of the amounts of certain minor compounds such as sterols and tocopherols. Steradienes, resulting from the dehydration of sterols, were detected with small quantities especially in severe conditions of sonication. Solid phase micro-extraction (SPME) coupled to gas chromatography was known to be a sensitive technique to follow changes in the oxidative state of vegetable oils by measuring the amount of volatile materials produced during the refining process. 相似文献
195.
196.
Faouzi Triki & Tao Yin 《计算数学(英文版)》2023,41(3):482-500
This paper concerns the reconstruction of a scalar coefficient of a second-order elliptic equation in divergence form posed on a bounded domain from internal data. This problem finds applications in multi-wave imaging, greedy methods to approximate parameter-dependent elliptic problems, and image treatment with partial differential equations. We first show that the inverse problem for smooth coefficients can be rewritten as a linear transport equation. Assuming that the coefficient is known near the boundary, we study the well-posedness of associated transport equation as well as its numerical resolution using discontinuous Galerkin method. We propose a regularized transport equation that allow us to derive rigorous convergence rates of the numerical method in terms of the order of the polynomial approximation as well as the regularization parameter. We finally provide numerical examples for the inversion assuming a lower regularity of the coefficient, and using synthetic data. 相似文献