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排序方式: 共有188条查询结果,搜索用时 31 毫秒
101.
A crucial point in the implementation of meshless methods such as the meshless local Petrov–Galerkin (MLPG) method is the evaluation of the domain integrals arising over circles in the discrete local weak form of the governing partial differential equation. In this paper we make a comparison between the product Gauss numerical quadrature rules, which are very popular in the MLPG literature, with cubature formulas specifically constructed for the approximation of an integral over the unit disk, but not yet applied in the MLPG method, namely the spherical, the circularly symmetrical and the symmetric cubature formulas. The same accuracy obtained with 64×64 points in the product Gauss rules may be obtained with symmetric quadrature formulas with very few points. 相似文献
102.
Philipp Gotico Bernard Boitrel Rgis Guillot Marie Sircoglou Annamaria Quaranta Zakaria Halime Winfried Leibl Ally Aukauloo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(14):4552-4557
Inspired by nature's orchestra of chemical subtleties to activate and reduce CO2, we have developed a family of iron porphyrin derivatives in to which we have introduced urea groups functioning as multipoint hydrogen‐bonding pillars on the periphery of the porphyrinic ring. This structure closely resembles the hydrogen‐bond stabilization scheme of the carbon dioxide (CO2) adduct in the carbon monoxide dehydrogenase (CODH). We found that such changes to the second coordination sphere significantly lowered the overpotential for CO2 reduction in this family of molecular catalysts and importantly increased the CO2 binding rate while maintaining high turnover frequency (TOF) and selectivity. Entrapped water molecules within the molecular clefts were found to be the source of protons for the CO2 reduction. 相似文献
103.
Alkoxy-functionalized butadienyl- and styrylboronic esters have been synthesized starting from alpha,beta-unsaturated acetals. These derivatives readily cross-couple with aryl substrates, and the obtained products can be transformed under mild conditions into aromatic ketones, achieving the same result as an acylation reaction. [reaction: see text] 相似文献
104.
Annamaria Montanari 《Journal of Differential Equations》2004,202(2):306-331
We introduce a new class of curvature PDOs describing relevant properties of real hypersurfaces of . In our setting, the pseudoconvexity and the Levi form play the same role as the convexity and the real Hessian matrix play in the real Euclidean one. Our curvature operators are second-order fully nonlinear PDOs not elliptic at any point. However, when computed on generalized s-pseudoconvex functions, we shall show that their characteristic form is nonnegative definite with kernel of dimension one. Moreover, we shall show that the missing ellipticity direction can be recovered by taking into account the CR structure of the hypersurfaces. These properties allow us to prove a strong comparison principle, leading to symmetry theorems for domains with constant curvatures and to identification results for domains with comparable curvatures. 相似文献
105.
Annamaria?Montanari Daniele?MorbidelliEmail author 《Calculus of Variations and Partial Differential Equations》2017,56(2):36
We characterize the subRiemannian cut locus of the origin in the free Carnot group of step two with three generators, giving a new, independent proof of a result by Myasnichenko (J Dyn Control Syst 8(4):573-597, 2002). We also calculate explicitly the cut time of any extremal path and the distance from the origin of all points of the cut locus. Furthermore, by using the Hamiltonian approach, we show that the cut time of strictly normal extremal paths is a smooth explicit function of the initial velocity covector. Finally, using our previous results, we show that at any cut point the distance has a corner-like singularity. 相似文献
106.
A comparison of the extraction of clove buds with supercritical carbon dioxide and superheated water 总被引:1,自引:0,他引:1
A. A. Clifford Annamaria Basile Salim H. R. Al-Saidi 《Analytical and bioanalytical chemistry》1999,364(7):635-637
Supercritical carbon dioxide and superheated water (subcritical water above 100 °C under pressure) have both been used to
extract the buds of cloves (Syzygium aromaticum). The yields of eugenol and eugenyl acetate obtained by these methods and also by steam distillation and liquid solvent (Soxhlet)
extraction are similar, but the yields of caryophyllene were lower for the methods using water.
Received: 23 December 1998 / Revised: 26 March 1999 / Accepted: 31 March 1999 相似文献
107.
Jorge Morgado Ana Charas Nunzio Barbagallo Luis Alcácer Manuel Matos Franco Cacialli 《Macromolecular Symposia》2004,212(1):381-386
We report on the use of indium-tin oxide surface modification, by grafting of highly polar p-disubstituted benzenes, in the fabrication of light-emitting diodes. The polar compounds possess COCl or SO2Cl grafting groups and CF3 or NO2 as highly electronegative groups, leading to the formation of a dipolar monolayer, which brings about an increase in ITO work function, thereby reducing the barrier for hole injection into luminescent polymers. We observe that the effect of this self-assembled monolayer, in terms of light-onset voltage, efficiency and luminance, is at least comparable to the use of a hole injection layer of doped poly[(3,4-ethylenedioxy)thiophene] for LEDs using poly({2-[(2-ethylhexyl)oxy]-5-methoxy-1,4-phenylene}vinylene) (MEH-PPV) and polyfluorene blends as active layers. 相似文献
108.
Dr. Annamaria Panniello Dr. Mariachiara Trapani Dr. Massimiliano Cordaro Carlo Nazareno Dibenedetto Prof. Raffaele Tommasi Dr. Chiara Ingrosso Prof. Elisabetta Fanizza Dr. Roberto Grisorio Prof. Elisabetta Collini Prof. Angela Agostiano Prof. Maria Lucia Curri Dr. Maria Angela Castriciano Dr. Marinella Striccoli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2371-2380
Efficient FRET systems are developed combining colloidal CdSe quantum dots (QDs) donors and BODIPY acceptors. To promote effective energy transfer in FRET architectures, the distance between the organic fluorophore and the QDs needs to be optimized by a careful system engineering. In this context, BODIPY dyes bearing amino-terminated functionalities are used in virtue of the high affinity of amine groups in coordinating the QD surface. A preliminary QD surface treatment with a short amine ligand is performed to favor the interaction with the organic fluorophores in solution. The successful coordination of the dye to the QD surface, accomplishing a short donor–acceptor distance, provides effective energy transfer already in solution, with efficiency of 76 %. The efficiency further increases in the solid state where the QDs and the dye are deposited as single coordinated units from solution, with a distance between the fluorophores down to 2.2 nm, demonstrating the effectiveness of the coupling strategy. 相似文献
109.
Annamaria Barbagallo Paolo Mauro 《Journal of Optimization Theory and Applications》2012,155(1):288-314
The paper is devoted to generalize a previous model of the dynamic oligopolistic market equilibrium problem allowing the presence of production excesses and assuming, in a more reasonable way that the total amounts of commodity shipments from a firm to all the demand markets be upper bounded. First, we give equilibrium conditions in terms of the well-known dynamic Cournot–Nash equilibrium principle. Then we show that such conditions can be expressed in terms of Lagrange multipliers; namely, by means of an utility function, prove that both equilibrium conditions can be equivalently expressed by a variational inequality. The variational formulation allows us to provide existence theorems and qualitative properties for equilibrium solutions. At last, a numerical example illustrates the results obtained. 相似文献
110.
Blangetti M Deagostino A Gervasio G Marabello D Prandi C Venturello P 《Organic & biomolecular chemistry》2011,9(7):2535-2538
Alkoxydienamides 2 have been synthesized exploiting the reactivity of α,β-unsaturated acetals 1 with isocyanates in the presence of Schlosser's superbase LIC-KOR. In a mild acidic medium, 2 can then be promptly converted both into α-ketoamides 3 and into substituted 2-pyrrolidinones 4 or imino ethers 5 by choosing the appropriate experimental conditions. 相似文献