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241.
242.
M. J. López P. A. Marcos A Rubio J. A. Alonso 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,40(1):385-388
The structural and thermal properties of small carbon clusters (C N , N = 13, 20, and 32) are investigated by constant energy Molecular Dynamics simulations over a wide range of temperatures, i.e., from T = 0K to above the melting point of graphitic carbon. The Tersoff interatomic potential [6] is used to mimic the covalent bond between the carbon atoms in the cluster. We find that small carbon clusters start to fragment or to evaporate atoms or C2 or C3 units before fully developing a liquidlike phase. As a consequence, some relevant isomers (such as rings, bowls, hollow cages) are thermally isolated from each other i.e., there are no thermally activated isomerization transitions between them. Possible implications of our results on the growth mechanism of fullerenes are discussed. 相似文献
243.
Angel Licea-Claverıe Simona Schwarz Frank Simon Omar Urzúa-Sánchez Jürgen Nagel Dieter Pleul Klaus-Jochen Eichhorn Andreas Janke 《Colloid and polymer science》2005,283(8):826-835
The polycation preparation of poly(dimethylaminoethylmethacrylate) hydrochloride and the multilayer formation in combination with poly(sodium 4-styrenesulphonate) as polyanion studies onto different substrates, as followed by streaming potential measurements, in situ surface plasmon resonance spectroscopy, and multi-wavelength ellipsometry, are reported. Furthermore, we studied the resulting multilayer buildup of dry surfaces by UV-Vis spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy measurements. Thereby, the layer built up at the solid/liquid-interface could be followed and quantified at the molecular level.This revised version was published online in April 2005 with corrections to the article category. 相似文献
244.
Synthesis,characterization, and metal complexes of polyacetylenes with pendant 2,2′‐bipyridyl groups
Jos Vicente Juan Gil‐Rubio Natalia Barquero 《Journal of polymer science. Part A, Polymer chemistry》2005,43(14):3167-3177
5‐Ethynyl‐2,2′‐bipyridine ( 1 ; bpyC≡CH) polymerized in the presence of catalytic amounts of [RhF(COD)(PPh3)] or [Rh(μ‐OH)(COD)]2 (COD = 1,5‐cyclooctadiene) in 74–91% yields. In contrast, [Rh(μ‐X)(NBD)]2 (X = Cl or OMe; NBD = norbornadiene) did not catalyze the polymerization of 1 or gave low yields of the polymer. The obtained polymer, poly(5‐ethynyl‐2,2′‐bipyridine) [ 2 ; (bpyC?CH)n], was highly stereoregular with a predominant cis–transoidal geometry. Random copolyacetylenes containing the 2,2′‐bipyridyl group with improved solubility in organic solvents were obtained by the treatment of a mixture of 1 and phenylacetylene ( 3 ) or 1‐ethynyl‐4‐n‐pentyl‐benzene with catalytic amounts of [RhF(COD)(PPh3)]. A block copolymer of 1 and 3 was prepared by the addition of 1 to a poly(phenylacetylene) containing a living end. The reaction of 2 with [Mo(CO)6] produced an insoluble polymer containing [Mo(CO)4(bpy)] groups, whereas with [RuCl2(bpy)2] or [Ru(bpy)2(CH3COCH3)2](CF3SO3)2, it gave soluble metal–polymer complexes containing [Ru(bpy)3]2+ groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3167–3177, 2005 相似文献
245.
The semigroup of values of irreducible space curve singularities
is the set of intersection multiplicities among hypersurfaces
and the given curve. It is an invariant of the singularity, and
for plane curves it characterizes the equisingularity type
considered by Zariski. For space curve singularities the semigroup
of values is a numerical semigroup and it can not be computed by
means of the exponents of any Puiseux parametrization, as in the
plane case. We obtain an algorithm for calculating the semigroup
of values of a space curve singularity, which determines the
generators of the semigroup and the valuation ideals associated
with the semigroup. We give a Maple version of the algorithm. 相似文献
246.
We give an example of a domain such that the sequence of iterated symmetric rings of quotients does not stabilize. This answers
a question of Passman.
The work of the first author has been partially supported by CICYT PB 86-0353-C02-01 and that of the second author by CICYT
PB87-0703 and the Institut d’Estudis Catalans. 相似文献
247.
Rubio Pablo 《Journal of Geometry》1989,34(1-2):152-171
An extension of the traditional geometry of the triangle is derived through the construction of two 30-points particular cubics. Two generation procedures founded on triangular quadratic transformations and dual associate properties of the two cubics are presented. 相似文献
248.
Complete control of single-electron states in a two-dimensional semiconductor quantum-ring model is established, opening a path into coherent laser-driven single-gate qubits. The control scheme is developed in the framework of optimal-control theory for laser pulses of two-component polarization. In terms of pulse lengths and target-state occupations, the scheme is shown to be superior to conventional control methods that exploit Rabi oscillations generated by uniform circularly polarized pulses. Current-carrying states in a quantum ring can be used to manipulate a two-level subsystem at the ring center. Combining our results, we propose a realistic approach to construct a laser-driven single-gate qubit that has switching times in the terahertz regime. 相似文献
249.
Serrano J Bosak A Arenal R Krisch M Watanabe K Taniguchi T Kanda H Rubio A Wirtz L 《Physical review letters》2007,98(9):095503
The phonon dispersion relations of bulk hexagonal boron nitride have been determined from inelastic x-ray scattering measurements and analyzed by ab initio calculations. Experimental data and calculations show an outstanding agreement and reconcile the controversies raised by recent experimental data obtained by electron-energy loss spectroscopy and second-order Raman scattering. 相似文献
250.
The effects of measuring procedures and activating additives on the electrorheological (ER) behaviour of hematite/silicone oil suspensions are analysed. The structures built up in the presence of an electric field without shear are stronger than those produced with both electric and shear fields simultaneously applied. Such differences are measurable when the field strength is not high enough to dominate over hydrodynamic interactions. Regarding the effect of additives, the ER response is enhanced by water until a certain maximum amount, beyond which the effect decreases. The increase in water concentration also leads to higher values of the electric current. Similar results are observed when Brij 30 is used. However, this surfactant only raises the yield stress at low fields. Contrary to water, the surfactant forms droplets in solution, instead of adsorbing on the hematite surface. At sufficiently high field strengths, the droplets can coalesce, enclosing the hematite particles and thus reducing the overall ER effect. 相似文献