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21.
Sofiane Ben Sdira Marie-BéatriceA. Giudicelli Roger J. Lamartine 《Tetrahedron letters》2004,45(41):7801-7804
Chiral p-tert-butylcalix[4]arenes perfunctionalised at the lower rim with amino acid residues have been prepared. The 1H and 13C NMR spectra indicate that the macrocycles adopt a cone conformation. Calix[4]arenes bearing amino acid moieties 5a shows strong complexation towards Cl−, Br−, HSO4−, H2PO4− and N-tosyl-(l)-alaninate. 相似文献
22.
When high resolution convection schemes are used for discretizing chemical species mass balance equations, the mass fractions are not guaranteed to add to one. We show that a proposed remedy called χ —scheme (Darwish and Moukalled, Comput. Methods Appl. Mech. Engrg. 192 (2003): 1711) will degrade to a diffusive first‐order scheme when a chemical species vanishes from the mixture, for example, because of chemical reactions. We propose an improvement to the χ ‐scheme to overcome this problem. Furthermore, a computationally efficient alternative scheme is proposed and evaluated with several examples, to quantify the improvements in the accuracy and the computational time. Published 2013. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
23.
Nader Saad Brosse Nicolas Khadraoui Malek Fuentealba Cecilia Ziegler-Devin Isabelle Quils Fabienne El-Kirat-Chatel Sofiane Mauret Evelyne 《Cellulose (London, England)》2022,29(10):5593-5607
Cellulose - Micro- and Nano-Fibrillated Cellulose (MNFC) have gained increasing attention due to their remarkable properties, but their production usually requires an intensive multi-step process.... 相似文献
24.
Sofiane Akkouche 《Journal of Functional Analysis》2010,259(6):1443-1465
Let H(λ)=−Δ+λb be a discrete Schrödinger operator on ?2(Zd) with a potential b and a non-negative coupling constant λ. When b≡0, it is well known that σ(−Δ)=[0,4d]. When b?0, let and be the bounds of the spectrum of the Schrödinger operator. One of the aims of this paper is to study the influence of the potential b on the bounds 0 and 4d of the spectrum of −Δ. More precisely, we give a necessary and sufficient condition on the potential b such that s(−Δ+λb) is strictly positive for λ small enough. We obtain a similar necessary and sufficient condition on the potential b such that M(−Δ+λb) is lower than 4d for λ small enough. In dimensions d=1 and d=2, the situation is more precise. The following result was proved by Killip and Simon (2003) (for d=1) in [5], then by Damanik et al. (2003) (for d=1 and d=2) in [3]:
25.
Sébastien Gadat Sofiane Saadane 《Stochastics An International Journal of Probability and Stochastic Processes》2018,90(6):886-926
Narendra-Shapiro (NS) algorithms are bandit-type algorithms developed in the 1960s. NS-algorithms have been deeply studied in infinite horizon but little non-asymptotic results exist for this type of bandit algorithms. In this paper, we focus on a non-asymptotic study of the regret and address the following question: are Narendra-Shapiro bandit algorithms competitive from this point of view? In our main result, we obtain some uniform explicit bounds for the regret of (over)-penalized-NS algorithms. We also extend to the multi-armed case some convergence properties of penalized-NS algorithms towards a stationary Piecewise Deterministic Markov Process (PDMP). Finally, we establish some new sharp mixing bounds for these processes. 相似文献
26.
Ali Saberi Zahra Negahdari Sofiane Bouazza Monika Willert-Porada 《Journal of fluorine chemistry》2010,131(12):1353-1355
Nanosized MgF2 was synthesized by precipitation in microemulsions of water in cyclohexane stabilized by polyethylene glycol tert-octylphenyl ether. The synthesized MgF2 powder was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), BET specific surface area, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray diffraction (XRD). The results showed that the synthesized powder was a MgF2 powder with a crystallite size in the range of 9-11 nm and a specific surface area of 190 m2/g. 相似文献
27.
28.
Wong KM Lam SC Ko CC Zhu N Yam VW Roué S Lapinte C Fathallah S Costuas K Kahlal S Halet JF 《Inorganic chemistry》2003,42(22):7086-7097
A novel heterobimetallic alkynyl-bridged complex, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)Me(5))(dppe)], 1, and its oxidized species, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)Me(5))(dppe)][PF(6)], 2, have been synthesized and their X-ray crystal structures determined. A related vinylidene complex, [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond](H)C[double bond]C)Fe(C(5)Me(5))(dppe)][PF(6)], 3, has also been synthesized and characterized. The cyclic voltammogram of 1 shows a quasireversible reduction couple at -1.49 V (vs SCE), a fully reversible oxidation at -0.19 V, and a quasireversible oxidation at +0.88 V. In accord with the electrochemical results, density-functional theory calculations on the hydrogen-substituted model complex Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C)Fe(C(5)H(5))(dHpe) (Cp = C(5)H(5), dHpe = H(2)P[bond](CH(2))(2)[bond]PH(2)) (1-H) show that the LUMO is mainly bipyridine ligand pi* in character while the HOMO is largely iron(II) d orbital in character. The electronic absorption spectrum of 1 shows low-energy absorption at 390 nm with a 420 nm shoulder in CH(2)Cl(2), while that of 2 exhibits less intense low-energy bands at 432 and 474 nm and additional low-energy bands in the NIR at ca. 830, 1389, and 1773 nm. Unlike the related luminescent rhenium(I)-alkynyl complex [Re(bpy)(CO)(3)(C[triple bond]C[bond]C(6)H(4)[bond]C[triple bond]C[bond]H)], 4, complex 1 is found to be nonemissive, and such a phenomenon is attributed to an intramolecular quenching of the emissive d pi(Re) --> pi*(bpy) (3)MLCT state by the low-lying MLCT and LF excited states of the iron moiety. Interestingly, switching on of the luminescence property derived from the d pi(Re) --> pi*(bpy) (3)MLCT state can be demonstrated in the oxidized species 2 and the related vinylidene analogue 3 due to the absence of the quenching pathway. 相似文献
29.
Sofiane Bouarroudj 《Indagationes Mathematicae》2004,15(3):321-338
Let (M, F) be a Finsler manifold. We construct a 1-cocycle on Diff(M) with values in the space of differential operators acting on sections of some bundles, by means of the Finsler fonction F. As an operator, it has several expressions: in terms of the Chern, Berwald, Cartan or Hashiguchi connection, although its cohomology class does not depend on them. This cocycle is closely related to the conformal Schwarzian derivatives introduced in our previous work. The second main result of this paper is to discuss some properties of the conformally invariant quantization map by means of a Sazaki (type) metric on the slit bundle T Minduced by F. 相似文献
30.
Sana Zama Abdelmalek Bouraiou Sofiane Bouacida Thierry Roisnel Ali Belfaitah 《Tetrahedron letters》2013
A new class of thiazolo[3,2-a]imidazole derivatives is obtained in good yields, by reacting 1-methyl-2-bromoimidazolium salts bearing N+-CH2COAr, N+-CH2COMe, N+-CH2COOMe, or N+-CH2CN fragments, with carbon disulfide in the presence of Et3N at room temperature. The mesoionic structures of these compounds are established by NMR spectroscopy and by single-crystal X-ray analysis. 相似文献