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51.
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Catalytic oxidation of secondary amines to nitrones using alkyl hydroperoxides as primary oxidant has been demonstrated for the first time. The titanium alkoxide catalyst is protected from co-product water by the combined use of a tightly binding trialkanolamine ligand and molecular sieves. Nitrones can be obtained in high yield (up to 98%) under homogeneous, anhydrous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity can be achieved with as little as 1% catalyst. 相似文献
53.
A time-dependent current-density-functional theory for many-particle systems in interaction with arbitrary external baths is developed. We prove that, given the initial quantum state |Psi0> and the particle-bath interaction operator, two external vector potentials A(r,t) and A'(r,t) that produce the same ensemble-averaged current density, j(r,t), must necessarily coincide up to a gauge transformation. This result greatly expands the applicability of time-dependent density-functional theory to open quantum systems, and allows for first-principles calculations of many-particle time evolution beyond Hamiltonian dynamics. 相似文献
54.
We consider higher-order QCD corrections to the production of colorless high-mass systems (lepton pairs, vector bosons, Higgs bosons, etc.) in hadron collisions. We propose a new formulation of the subtraction method to numerically compute arbitrary infrared-safe observables for this class of processes. To cancel the infrared divergences, we exploit the universal behavior of the associated transverse-momentum (qT) distributions in the small-qT region. The method is illustrated in general terms up to the next-to-next-to-leading order in QCD perturbation theory. As a first explicit application, we study Higgs-boson production through gluon fusion. Our calculation is implemented in a parton level Monte Carlo program that includes the decay of the Higgs boson into two photons. We present selected numerical results at the CERN Large Hadron Collider. 相似文献
55.
Summary In classical plasticity dissipation postulates on cycles, such as those proposed by Drucker, Martin e Il'yushin, rule the evolution of elastic-plastic deformation processes. In this paper, within the framework of the infinitesimal theory of isotropic materials with elastic range of [7], each one of those three postulates is given an equivalent local formulation; moreover, they are shown to be all equivalent.
Sommario In plasticitá classica l'evoluzione dei processi elasto-plastici é regolata da postulati di dissipazione su cicli quali quelli proposti da Drucker, Martin e Il'yushin. In questo lavoro, nell'ambito della teoria infinitesima dei materiali isotropi con dominio elastico proposta in [7], si fornisce una formulazione locale equivalent per ciascuno di quei tre postulati e si mostra che essi sono tutti tra loro equivalenti.相似文献
56.
W. Geißler 《Archive of Applied Mechanics (Ingenieur Archiv)》1974,43(6):413-425
Übersicht Es wird ein numerisches Verfahren zur Berechnung der dreidimensionalen laminaren Grenzschicht an schrägangeströmten Rotationskörpern beschrieben. Die reibungslose Geschwindigkcitsverteilung, die als äußere Randbedingung für die Grenzschichtrechnung dient, wird numerisch mittels eines Singularitätenverfahrens bestimmt. Die Grenzschichtrechnung wird in einem Stromlinienkoordinatensystem durchgeführt, d. h. die Koordinaten sind den Strom- und Potentiallinien der reibungsfreien Strömung angepaßt. Die allgemeinen Grenzschichtgleichungen werden numerisch mittels eines impliziten Differenzenverfahrens integriert. Als Ergebnis der numerischen Rechnung liegen die Grenzschicht-Geschwindigkeitsprofile in Primär- und Sekundärströmungsrichtung in allen Netzpunkten vor. Es wird dargelegt, daß mit diesem Verfahren die Bestimmung der dreidimensionalen Ablöselinie möglich ist. Die Ergebnisse der Grenzschichtrechnung und die Bestimmung der Ablöselinien stimmen sehr gut mit numerischen und analytischen Ergebnissen anderer Autoren überein.
Summary A numerical method is presented to calculate the three dimensional laminar incompressible boundary layer over bodies of revolution at incidence. The inviscid flow velocities used for the boundary condition at the outer edge of the boundary layer are determined numerically by a singularity method. The boundary layer calculation is carried out in a streamline coordinate system; the coordinates are fixed to the streamlines and equipotential lines of the inviscid flow. The boundary layer equations are integrated by an implicit finite difference method. As a result of the numerical calculation process the velocity profiles in directions of streamlines and equipotential lines are known for each mesh point of the coordinate system. It is shown that this method can be used to determine the separation lines on the body surface. The results of the boundary layer calculation and the determination of flow separation arc in very good agreement with numerical and analytical results of other investigators.相似文献
57.
58.
Direct On‐Surface Patterning of a Crystalline Laminar Covalent Organic Framework Synthesized at Room Temperature 下载免费PDF全文
Alejandro de la Peña Ruigómez David Rodríguez‐San‐Miguel Dr. Kyriakos C. Stylianou Dr. Massimiliano Cavallini Dr. Denis Gentili Dr. Fabiola Liscio Prof. Silvia Milita Dr. Otello Maria Roscioni Dr. Maria Luisa Ruiz‐González Carlos Carbonell Prof. Daniel Maspoch Dr. Rubén Mas‐Ballesté Dr. José Luis Segura Dr. Félix Zamora 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10666-10670
We report herein an efficient, fast, and simple synthesis of an imine‐based covalent organic framework (COF) at room temperature (hereafter, RT‐COF‐1 ). RT‐COF‐1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N2 and CO2. The room‐temperature synthesis has enabled us to fabricate and position low‐cost micro‐ and submicropatterns of RT‐COF‐1 on several surfaces, including solid SiO2 substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink‐jet printing. 相似文献
59.
Stabilization of Titanium Dioxide Nanoparticles at the Surface of Carbon Nanomaterials Promoted by Microwave Heating 下载免费PDF全文
Rui Zhang Prof. Dr. Saveria Santangelo Dr. Enza Fazio Prof. Dr. Fortunato Neri Dr. Massimiliano D'Arienzo Prof. Dr. Franca Morazzoni Prof. Dr. Yihe Zhang Prof. Dr. Nicola Pinna Dr. Patrícia A. Russo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14901-14910
TiO2 is frequently combined with carbon materials, such as reduced graphene oxide (RGO), to produce composites with improved properties, for example for photocatalytic applications. It is shown that heating conditions significantly affect the interface and photocatalytic properties of TiO2@C, and that microwave irradiation can be advantageous for the synthesis of carbon‐based materials. Composites of TiO2 with RGO or amorphous carbon were prepared from reaction of titanium isopropoxide with benzyl alcohol. During the synthesis of the TiO2 nanoparticles, the carbon is involved in reactions that lead to the covalent attachment of the oxide, the extent of which depends on the carbon characteristics, heating rate, and mechanism. TiO2 is more efficiently stabilized at the surface of RGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance. 相似文献
60.
Massimiliano Berti Riccardo Montalto 《Journal of Fixed Point Theory and Applications》2017,19(1):129-156
We present the result and the ideas of the recent paper (Berti and Montalto, Quasi-periodic standing wave solutions of gravity-capillary water waves, http://arxiv.org/abs/1602.02411, 2016) concerning the existence of Cantor families of small-amplitude time quasi-periodic standing wave solutions (i.e. periodic and even in the space variable x) of a 2-dimensional ocean, with infinite depth, in irrotational regime, under the action of gravity and surface tension at the free boundary. These quasi-periodic solutions are linearly stable. 相似文献