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61.
Alexandros Vakalopoulos Xanthoula Kavazoudi Joachim Schoof 《Tetrahedron letters》2006,47(48):8607-8610
A novel method for the synthesis of diaryl ethers with phenols and arylstannanes under mild conditions is described. This copper-mediated O-arylation is feasible using DMAP in acetonitrile and is complementary to the use of boronic acids as aryl donors. The reaction is tolerant of a wide range of substituents and sterically hindered coupling partners. 相似文献
62.
The selective biocatalyzed synthesis of 2-monoacylglycerols (2-MAGs) through the use of commercially available immobilized Candida antarctica (Novozym435) and Rhizomucor miehei is explored. Reactions at room temperature result in the formation of a 2-MAG and a corresponding ethyl ester of the fatty acid with immobilized Candida antarctica within 2h with yields ranging from 36%-83%. Similar reaction conditions with immobilized Rhizomucor miehei yielded exclusively the 2-MAG after 24h with yields ranging from 37% to 88%. Yields vary on the acyl group at the sn-2 position and choice of enzyme involved. 相似文献
63.
George Mavrotas José Rui Figueira Alexandros Antoniadis 《Journal of Global Optimization》2011,49(4):589-606
We propose a methodology for obtaining the exact Pareto set of Bi-Objective Multi-Dimensional Knapsack Problems, exploiting
the concept of core expansion. The core concept is effectively used in single objective multi-dimensional knapsack problems
and it is based on the “divide and conquer” principle. Namely, instead of solving one problem with n variables we solve several sub-problems with a fraction of n variables (core variables). In the multi-objective case, the
general idea is that we start from an approximation of the Pareto set (produced with the Multi-Criteria Branch and Bound algorithm,
using also the core concept) and we enrich this approximation iteratively. Every time an approximation is generated, we solve
a series of appropriate single objective Integer Programming (IP) problems exploring the criterion space for possibly undiscovered,
new Pareto Optimal Solutions (POS). If one or more new POS are found, we appropriately expand the already found cores and
solve the new core problems. This process is repeated until no new POS are found from the IP problems. The paper includes
an educational example and some experiments. 相似文献
64.
Gallos JK Stathakis CI Kotoulas SS Koumbis AE 《The Journal of organic chemistry》2005,70(17):6884-6890
An improved approach to enantiomerically pure hydroxylated cyclopentenones is reported here, which involves intramolecular nitrone cycloaddition of sugar-derived chiral pent-4-enals and hex-5-en-ones-2 followed by N-O bond cleavage, quaternization of the amine thus produced, and finally oxidative elimination of the amino group. Synthesis of pentenomycin I and neplanocin A is described following this methodology. 相似文献
65.
In a series of polymethoxy benzaldehydes and acetophenones it was found that diortho-substitution distorts the ArOCH3 conformation. This distortion is accompanied by a downfield shift in the corresponding methoxyl 13C frequencies and an increase in their spin-lattice relaxation times. 相似文献
66.
Coarse-grained models of poly(ethylene oxide) oligomer-grafted nanoparticles are established by matching their structural distribution functions to atomistic simulation data. Coarse-grained force fields for bulk oligomer chains show excellent transferability with respect to chain lengths and temperature, but structure and dynamics of grafted nanoparticle systems exhibit a strong dependence on the core-core interactions. This leads to poor transferability of the core potential to conditions different from the state point at which the potential was optimized. Remarkably, coarse graining of grafted nanoparticles can either accelerate or slowdown the core motions, depending on the length of the grafted chains. This stands in sharp contrast to linear polymer systems, for which coarse graining always accelerates the dynamics. Diffusivity data suggest that the grafting topology is one cause of slower motions of the cores for short-chain oligomer-grafted nanoparticles; an estimation based on transition-state theory shows the coarse-grained core-core potential also has a slowing-down effect on the nanoparticle organic hybrid materials motions; both effects diminish as grafted chains become longer. 相似文献
67.
For the development of novel endocannabinoid templates with potential resistance to hydrolytic and oxidative metabolism, we are targeting the bis-allylic carbons of the arachidonoyl skeleton. Toward this end, we recently disclosed the synthesis and preliminary biological data for the (13S)-methyl-anandamide. We report now the total synthesis of the (10S)- and (10R)-methyl-counterparts. Our synthetic approach is stereospecific, efficient, and provides the analogs without the need for resolution. Peptide coupling, P-2 nickel partial hydrogenation, and cis-selective Wittig olefination are the key steps. 相似文献
68.
We report the first experimental study of a model system of a two-dimensional colloidal crystal in a random pinning potential. The colloidal crystal consists of monodispersed charged polystyrene microspheres suspended in deionized aqueous media and confined near a rough charged surface. It is found that the static orientational correlation function g6(r) decays exponentially for intermediate and strong pinning, in agreement with theories. The driven depinning is dominated by thermally activated creep motion along 1D-like channels between regions with short-range order. A coexistence model is proposed for describing the observations. 相似文献
69.
Emmanouil Kasotakis Athanasia Kostopoulou Miguel Spuch-Calvar Maria Androulidaki Nikos Pelekanos Antonios G. Kanaras Alexandros Lappas Anna Mitraki 《Applied Physics A: Materials Science & Processing》2014,116(3):977-985
We present a chemical process for the decoration of self-assembled two-dimensional peptide fibrils with two different sizes of CdSe@ZnS core–shell quantum dots (Qdots) capped with trioctylphosphine oxide molecules. The attachment of the semiconducting nanoparticles to the fibrils is directed via disulfide bond between the quantum dot and cysteine aminoacids that are deliberately impeded in the peptide structures. A significant red shift in the emission spectra of the quantum dots is observed and attributed to the synergistic interaction between adjacent nanoparticles arranged on peptide film templates extending over hundreds of nanometers. 相似文献
70.
Odysseas Tsilipakos Alexandros Pitilakis Anna C. Tasolamprou Traianos V. Yioultsis Emmanouil E. Kriezis 《Optical and Quantum Electronics》2011,42(8):541-555
The finite element and the beam propagation method, two widely used methods in photonics, are utilized for the analysis of
plasmonic components based on the dielectric-loaded plasmonic waveguide. Two components are chosen as examples and are subsequently
numerically investigated by employing the aforementioned methods, in order to demonstrate their applicability in plasmonics.
Specifically, a microring resonator add-drop filter and a Mach–Zehnder interferometric switch are analyzed by means of the
finite element and the beam propagation method, respectively. The formulation adopted is clearly presented in both cases and
the case-dependent implementation details are thoroughly discussed. 相似文献