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21.
Angelo Albert Francesco Paolo Colonna Maurizio Guerra Bianca F. Bonini Germana Mazzanti Zoltàn Dinya Gian Franco Pedulli 《Journal of organometallic chemistry》1981,221(1):47-55
The radical adducts resulting from the reaction between group IVB organometallic radicals MR3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH2XSiH3 (X = O, S). 相似文献
22.
Andrew G McDonald Sinéad Boyce Gerard P Moss Henry BF Dixon Keith F Tipton 《BMC biochemistry》2007,8(1):14
Background
We describe the database ExplorEnz, which is the primary repository for EC numbers and enzyme data that are being curated on behalf of the IUBMB. The enzyme nomenclature is incorporated into many other resources, including the ExPASy-ENZYME, BRENDA and KEGG bioinformatics databases. 相似文献23.
24.
Kokalj A Bonini N Sbraccia C de Gironcoli S Baroni S 《Journal of the American Chemical Society》2004,126(51):16732-16733
The first two steps of methane dissociation on Rh(111) have been investigated using density-functional theory, focusing on the dependence of the catalyst's reactivity on the atomic coordination of the active metal site. We find that, although the barrier for the dehydrogenation of methane (CH4 --> CH3 + H) decreases as expected with the coordination of the binding site, the dehydrogenation of methyl (CH3 --> CH2 + H) is hindered at an ad-atom defect, where the first reaction is instead most favored. Our findings indicate that, if it were possible to let the dissociation occur selectively at ad-atom defects, the reaction could be blocked after the first dehydrogenation step, a result of high potential interest for many dream reactions such as, for example, the direct conversion of methane to methanol. 相似文献
25.
Monica L. Parentis Norberto A. Bonini Elio E. Gonzo 《Reaction Kinetics and Catalysis Letters》2001,72(2):303-308
Reaction rates of primary and secondary alcohols over chromium on silica catalysts prepared by the ion exchange method, in the presence and absence of oxygen, were measured. The effect of temperature and feed composition on activity and selectivity has been examined. 相似文献
26.
27.
Based on [19], we develop a global correspondence between immersed hypersurfaces ?:Mn→Hn+1 satisfying an exterior horosphere condition, also called here horospherically concave hypersurfaces, and complete conformal metrics e2ρgSn on domains Ω in the boundary Sn at infinity of Hn+1, where ρ is the horospherical support function, ∂∞?(Mn)=∂Ω, and Ω is the image of the Gauss map G:Mn→Sn. To do so we first establish results on when the Gauss map G:Mn→Sn is injective. We also discuss when an immersed horospherically concave hypersurface can be unfolded along the normal flow into an embedded one. These results allow us to establish general Alexandrov reflection principles for elliptic problems of both immersed hypersurfaces in Hn+1 and conformal metrics on domains in Sn. Consequently, we are able to obtain, for instance, a strong Bernstein theorem for a complete, immersed, horospherically concave hypersurface in Hn+1 of constant mean curvature. 相似文献
28.
Leszek Zalewski Dr. Michael Wykes Sergio Brovelli Dr. Massimo Bonini Dr. Thomas Breiner Dr. Marcel Kastler Dr. Florian Dötz Dr. David Beljonne Dr. Harry L. Anderson Prof. Franco Cacialli Prof. Paolo Samorì Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):3933-3941
A dithiophene rotaxane 1 ?β‐CD and its shape‐persistent corresponding dumbbell 1 were synthesized and fully characterized. 2D NOESY experiments, supported by molecular dynamics calculations, revealed a very mobile macrocycle (β‐CD). Steady‐state and time‐resolved photoluminescence experiments in solution were employed to elucidate the excited‐state dynamics for both systems and to explore the effect of cyclodextrin encapsulation. The photoluminescence (PL) spectrum of 1 ?β‐CD was found to be blueshifted with respect to the dumbbell 1 (2.81 and 2.78 eV, respectively). Additionally, in contrast to previous observations, neither PL spectra nor the decay kinetics of both threaded and unthreaded systems showed changes upon increasing the concentration or changing the polarity of the solutions, thereby providing evidence for a lack of tendency toward aggregation of the unthreaded backbone. 相似文献
29.
Bonini M Rossi S Karlsson G Almgren M Lo Nostro P Baglioni P 《Langmuir : the ACS journal of surfaces and colloids》2006,22(4):1478-1484
In this article, we report evidence of beta-cyclodextrin (beta-CD) self-aggregation in water. A critical aggregation concentration (cac) between 2 and 3 mM was determined by using dynamic (DLS) and static (SLS) light scattering to investigate the presence of beta-cyclodextrin aggregates. Transmission electron microscopy at cryogenic temperature (Cryo-TEM) was used to detect the structural features of cyclodextrin self-aggregates. The results show the occurrence of polymorphism depending on the beta-CD concentration: polydisperse nearly spherical objects with diameters of about 100 nm are present at lower concentrations, whereas micrometer planar aggregates are predominant at higher concentrations. 相似文献
30.
The geometry and the vibrational properties of missing row reconstructed O/Cu(0 0 1) and O/Ag(0 0 1) surfaces are investigated by means of density functional theory and density functional perturbation theory, using the local density and the generalized-gradient approximations. Our results predict very similar structural and vibrational properties for the two reconstructed surfaces. In the case of copper our calculations reproduce quite accurately the experimental results, while for the missing row reconstructed O/Ag(0 0 1) surface the agreement between theory and experiment is less satisfactory. 相似文献