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1.
Dorina Mitrea Marius Mitrea Jill Pipher 《Journal of Fourier Analysis and Applications》1997,3(2):131-192
We study boundary value problems for the time-harmonic form of the Maxwell equations, as well as for other related systems
of equations, on arbitrary Lipschitz domains in the three-dimensional Euclidean space. The main goal is to develop the corresponding
theory for Lp-integrable bounday data for optimal values of p's. We also discuss a number of relevant applications in electromagnetic scattering. 相似文献
2.
One of the successful transformations within the field of organocatalysis, the organocatalytic asymmetric addition of nitromethane to α,β‐unsaturated aldehydes and ketones, has been studied by quantum chemical modeling. The level of accuracy of the hybrid density functional theory method B3LYP/6‐31G(d) was compared to a high level ab initio benchmark for this reaction. It is concluded that B3LYP/6‐31G(d) performs very well for this reaction type, giving good estimates of critical energies. The reaction between acrolein and nitromethane was studied in detail. The reaction mechanism revealed an intermediate oxazolidin structure, which is currently unknown. Alkyl substitution in various positions on the amine catalyst or α,β‐unsaturated carbonyl compound influences the reactivity in a predictive fashion. The iminium ion, prop‐2‐en‐iminium, is less activated towards nucleophilic attack compared to protonated acrolein. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
3.
Dans ce travail on détermine quelques probabilités géométriques concernant des réseaux irréguliers dans le plan euclidienE
2 et dans l'espace euclidienE
n
. Les propriétés généralisent certains résultats de Buffon, Deltheil et Stoka.
Travail effectué avec l'aide du MURST (40%, 60%). 相似文献
4.
Using recursive variants of Baire notions of nowhere dense and meagre sets we study the topological size of speedable and infinitely often speedable functions in a machine-independent framework. We show that the set of speedable functions is not “small” whereas the set of infinitely often speedable functions is “large”. In this way we offer partial answers to a question in [4]. 相似文献
5.
In this paper we study the Navier–Stokes boundary‐initial value problem in the exterior of a rotating obstacle, in two and three spatial dimensions. We prove the local in time existence and uniqueness of strong solutions. Moreover, we show that the solutions are global in time, in two spatial dimensions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
6.
A novel Cu(II)-Mn(II) hexanuclear complex of formula [[MnCuL](3)(tma)](ClO(4))(3).8H(2)O [H(2)L = macrocyclic Robson proligand; H(3)tma = trimesic acid] has been obtained by connecting three heterobinuclear [Cu(II)Mn(II)L](2+) cationic species through the trimesate anion. The complex exhibits a C(3) rotational symmetry, imposed by the geometry of the bridging ligand. The interaction within each Mn(II)-Cu(II) pair is antiferromagnetic (J = -16.7 cm(-1)). A weak ferromagnetic coupling among the three S = 2 resulting spins through the tricarboxylato bridge leads to a S = 6 ground spin state, for which the spin polarization mechanism is responsible. 相似文献
7.
Rudzevich Y Vysotsky MO Bohmer V Brody MS Rebek Jr J Broda F Thondorf I 《Organic & biomolecular chemistry》2004,2(21):3080-3084
The dimerization of tetratolyl- and tetratosyl-urea derivatives 1 and 2, derived from a tetrapentoxy calix[4]arene in the cone conformation and of the corresponding tetra-urea derivatives 3 and 4, in which the cone conformation is rigidified by the two crown-3 tethers, have been studied. All six possible equimolar mixtures were examined by 1H NMR using CDCl3 and CD2Cl2 as solvents. While no heterodimers are found for the combinations 1/3 and 2/4 in either solvent, all remaining combinations lead to the (exclusive) formation of heterodimers in CD2Cl2. In CDCl3 heterodimers are only observed for the combinations of 3 with 2 or 4. These results are discussed in terms of entropic and enthalpic contributions and compared with MD-simulations in a box of chloroform solvent molecules. 相似文献
8.
Marius Rebek Josef Schurz Walter Stöger Wolfgang Popp 《Monatshefte für Chemie / Chemical Monthly》1969,100(2):532-539
Zusammenfassung Die vorliegende Arbeit stellt eine Beschreibung von Experimenten dar, die die Erhöhung der Pfropfbereitschaft von trägen Komponenten durch Beimischung von aktiveren zum Ziele hatten.Das Trägermolekül war in allen Fällen Cellulose in Form von hochgradig gereinigtem Zellstoff. Durch die Verwendung von Mischsystemen aus Styrol und Methylmethacrylat gelang es, das trägere Styrol in bedeutend größerer Menge auf die Cellulose aufzupfropfen, als es bei Abwesenheit des aktiven Methylmethacrylats der Fall war.
Nach einem Vortrag, den der erstgenannte der Autoren im Rahmen der Arbeitstagung des Vereins Österreichischer Chemiker am 27. September 1968 in Wien gehalten hat. 相似文献
Grafting Polymerization of Cellulose with Two Vinyl Monomers
This paper describes experiments to increase the grafting of cellulose with components of poor reactivity by mixing them with highly reactive ones. A highly purified wood pulp was used as backbone. Using combinations of styrene and methyl methacrylate it was possible to graft considerably higher amounts of the poorly reacting styrene than in the absence of the highly reactive methyl methacrylate.
Nach einem Vortrag, den der erstgenannte der Autoren im Rahmen der Arbeitstagung des Vereins Österreichischer Chemiker am 27. September 1968 in Wien gehalten hat. 相似文献
9.
Czechoslovak Mathematical Journal - We say that a subgroup H is isolated in a group G if for every x ∈ G we have either x ∈ H or 〈x〉 ∩ H = 1. We describe the set of... 相似文献
10.
Boumendjel A Roberts JC Hu E Pallai PV Rebek J 《The Journal of organic chemistry》1996,61(13):4434-4438
We describe the asymmetric synthesis of non-peptidic compounds that feature rigid backbone conformations and present various side-chain functions. The key step in the synthesis of these compounds is the C-acylation of an appropriate ketone with a suitably protected aspartic acid derivative. The resulting dipeptide modules may be connected to form tetrapeptide mimics. Specifically is described the mimicry of a four-residue segment of CD4, the cellular receptor of HIV-1. The design was based on molecular modeling and the X-ray crystal structures of CD4 and intended to present the most important side chains and backbone elements of the Phe43-Lys46 segment. 相似文献