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31.
M. Di Vece A.B. LaursenL. Bech C.N. MadenM. Duchamp R.V. MateiuS. Dahl I. Chorkendorff 《Journal of photochemistry and photobiology. A, Chemistry》2012,230(1):10-14
The plasmon resonance of metal nanostructures affects neighboring semiconductors, quenching or enhancing optical transitions depending on various parameters. These plasmonic properties are currently investigated with respect to topics such as photovoltaics and optical detection and could also have important consequences for photocatalysis. Here the effect of silver nanoparticles of a size up to 30 nm and at maximum 0.50 monolayers on the photocatalytic oxidation of ethylene on TiO2 is studied. Since the plasmon resonance energy of silver nanoparticles is comparable with the TiO2 band gap, dipole-dipole interaction converts excitons into heat at the silver nanoparticle. This indicates that plasmonic interaction with TiO2 semiconductor catalysts can reduce the photo catalytic activity considerably. 相似文献
32.
Zhang J Fuhrer T Fu W Ge J Bearden DW Dallas J Duchamp J Walker K Champion H Azurmendi H Harich K Dorn HC 《Journal of the American Chemical Society》2012,134(20):8487-8493
The nanoscale parameters of metal clusters and lattices have a crucial influence on the macroscopic properties of materials. Herein, we provide a detailed study on the size and shape of isolated yttrium carbide clusters in different fullerene cages. A family of diyttrium endohedral metallofullerenes with the general formula of Y(2)C(2n) (n = 40-59) are reported. The high field (13)C nuclear magnetic resonance (NMR) and density functional theory (DFT) methods are employed to examine this yttrium carbide cluster in certain family members, Y(2)C(2)@D(5)(450)-C(100), Y(2)C(2)@D(3)(85)-C(92), Y(2)C(2)@C(84), Y(2)C(2)@C(3v)(8)-C(82), and Y(2)C(2)@C(s)(6)-C(82). The results of this study suggest that decreasing the size of a fullerene cage with the same (Y(2)C(2))(4+) cluster results in nanoscale fullerene compression (NFC) from a nearly linear stretched geometry to a constrained "butterfly" structure. The (13)C NMR chemical shift and scalar (1)J(YC) coupling parameters provide a very sensitive measure of this NFC effect for the (Y(2)C(2))(4+) cluster. The crystal structural parameters of a previously reported metal carbide, Y(2)C(3) are directly compared to the (Y(2)C(2))(4+) cluster in the current metallofullerene study. 相似文献
33.
Turibio Kuiate Tabopda Anne‐Claire Mitaine‐Offer Tomofumi Miyamoto Chiaki Tanaka Bonaventure Tchaleu Ngadjui Jean‐François Mirjolet Olivier Duchamp Marie‐Aleth Lacaille‐Dubois 《Helvetica chimica acta》2011,94(5):914-922
Three new medicagenic acid saponins, micranthosides A–C ( 1 – 3 ), were isolated from the roots of Polygala micrantha Guill . & Perr ., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D‐ and 2D‐NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 1 ), 3‐O‐β‐D ‐glucopyranosylmedicagenic acid 28‐[O‐6‐O‐acetyl‐β‐D ‐galactopyranosyl‐(1→4)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl] ester ( 2 ), and 3‐O‐{O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐[β‐D ‐glucopyranosyl‐(1→6)]‐β‐D ‐glucopyranosyl}medicagenic acid 28‐{O‐β‐D ‐apiofuranosyl‐(1→3)‐O‐β‐D ‐xylopyranosyl‐(1→4)‐O‐[β‐D ‐apiofuranosyl‐(1→3)]‐O‐α‐L ‐rhamnopyranosyl‐(1→2)‐β‐D ‐fucopyranosyl} ester ( 3 ). Compounds 1 – 3 were evaluated against HCT 116 and HT‐29 human colon cancer cells, but they did not show any cytotoxicity. 相似文献
34.
We prove a conjecture of A. Connes, which gives a rationality criterion for elements of the closure of ℂΓ (Γ a free group) in the space of bounded operators in l
2
(Γ). We show that this criterion applies also to the ring of Malcev–Neumann series on Γ.
Oblatum 2-VIII-1996 & 20-IX-1996 相似文献
Oblatum 2-VIII-1996 & 20-IX-1996 相似文献
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Summary A moduli space for the class of pointed strictly linearly convex domains in
n
is obtained. It is shown that the space of pointed smoothly bounded strictly linearly convex domains with a fixed indicatrix is parameterized by a class of deformations of the CR structure of the boundary of the indicatrix. These deformations are constructed by using the circular representation of a domain to pull back its complex structure tensor to the indicatrix. A careful study of the pull back structure shows that the allowable deformations are parameterized by a class of complex Hamiltonian vector fields. The proof of this fact is based on the Folland-Stein estimates for the
complex of the boundary of the indicatrix.The paper is related to one of László Lempert, Holomorphic invariants, normal forms and moduli space of convex domains. Ann. Math128, 47–78 (1988), where other modular data for pointed convex domains were constructed. A method of recovering Lempert's modular data from the deformation moduli is given.Oblatum 26-IX-1989 & 22-III-1990Partially supported by an NSERC grant.The second author wishes to thank the University of Toronto and the Mathematical Sciences Research Institute at Berkeley, where portions of the paper were written. 相似文献