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771.
Raquet B Avriller R Lassagne B Nanot S Escoffier W Broto JM Roche S 《Physical review letters》2008,101(4):046803
We report on the onset of Landau-level formation in a carbon nanotube-based Fabry-Perot resonator. Supported by excellent agreement between calculated and measured magnetoconductance patterns, the applied perpendicular magnetic field is shown to modulate the Fabry-Perot conductance oscillations consistently with the formation of a Landau level in the 1D massless Dirac fermions particle excitations. 相似文献
772.
Nuzillard JM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,190(2):292-297
The biselective spin echo technique allows the signals of coupled proton pairs to be extracted from crowded liquid state proton NMR spectra. Its use as a preparation sequence in heteronuclear chemical shift correlation experiments requires the removal of the heteronuclear coupling interaction during the biselective echo time. The discrimination between coupled and uncoupled protons signals is achieved by double quantum filtration, which delivers antiphase magnetization states. The latter are not directly compatible with the design of an HSQC-like pulse sequence. The conversion of antiphase to in-phase magnetization states by a second biselective echo sequence solves this problem. The optimization of spin echo delays is also discussed. Lastly, the article presents modified HSQC and HMBC pulses sequences in which information is obtained solely for the biselectively selected proton pairs. A peracetylated trisaccharide was used as a test molecule. 相似文献
773.
774.
Marie-Elodie Godard Jean-Marc Saiter Pilar Corts Salvador Montserrat John M. Hutchinson Fabrice Burel Claude Bunel 《Journal of Polymer Science.Polymer Physics》1998,36(4):583-593
In this work, we have investigated by DSC the structural relaxation of amorphous polymethyl(α-n-alkyl)acrylates in which it is possible to change the length of the alkyl chain. We have evaluated the Narayanaswamy parameter, x, which controls the relative contribution of temperature and of structure to the relaxation time, the apparent activation energy, Δh*, and the nonexponentiality parameter, β, of the stretched exponential response function. The results suggest that x increases while Δh* decreases and β remains constant as the length of the side chain increases. This allows us to comment on the effect of chemical modification on the relaxation kinetics. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 583–593, 1998 相似文献
775.
Louis Godeffroy Dr. Paolo Ciocci Dr. Nathaly Ortiz Peña Dr. Damien Alloyeau Dr. Jean-Marc Noël Dr. Jean-François Lemineur Dr. Frédéric Kanoufi 《Angewandte Chemie (International ed. in English)》2023,62(29):e202304950
This work proposes a novel method for measuring the intrinsic activity of single metal-based nanoparticles towards water reduction in neutral media at industrially relevant current densities. Instead of using gas nanobubbles as proxy, the method uses optical microscopy to track the local footprint of the reaction through the precipitation of metal hydroxide, which is associated to the local pH increase during electrocatalysis. The results show the electrocatalytic activities of different types of metal nanoparticles and bifunctionnal core-shell nanostructures made of Ni and Pt, and demonstrate the importance of metal hydroxide nano-shells in enhancing electrocatalysis. This method should be generalizable to any electrocatalytic reaction involving pH changes such as nitrate or CO2 reduction. 相似文献
776.
Interpenetrating polymer systems based on crosslinked polyurethane (PU) and polystyrene (PS) were prepared at room temperature by a one-shot (in situ) method, starting from an initial homogeneous mixture of reagents via non interfering mechanisms. Both polymerizations were performed either simultaneously or one after the other. Crosslinks and/or covalent bonds between components were deliberately introduced by the addition of appropriate monomers, in order to tailor the degree of microphase separation. Depending on the formation process, transluscent or transparent films were obtained, despite the difference in refractive index of the components. The maximum of miscibility, taken as from the glass transition criterion, was obtained for sequential tightly graft interpenetrating networks. 相似文献