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We give a purely algebro-geometric proof of the fact that every nonsingular
projective curve can be defined over a finite extension of its moduli field.
This extends a result byWolfart [7] to curves over fields of arbitrary
characteristic.
Received: 30 November 2001 相似文献
5.
We say that a vertexx of a graph is predominant if there exists another vertexy ofG such that either every maximum clique ofG containingy containsx or every maximum stable set containingx containsy. A graph is then called preperfect if every induced subgraph has a predominant vertex. We show that preperfect graphs are perfect, and that several well-known classes of perfect graphs are preperfect. We also derive a new characterization of perfect graphs. 相似文献
6.
Time and spatially resolved absorption measurements of Xe* particle number densities performed at an X-ray preionized self-sustained XeCl*-laser discharge were used to investigate the reaction kinetics of such discharges and to test the validity of the commonly-made assumption that they are fit well by spatially homogeneous numerical models. It turned out that the Xe* density distribution over the discharge cross section remains homogeneous for less than 100 ns only. Comparing the experimental results of the homogeneous discharge phase with zero-dimensional model calculations, we conclude that induced emission modeled using two excited xenon levels must be taken into account for the quantitative interpretation of the absorption measurements. For the interpretation of the Xe 6s-6p absorption measurements even a multilevel model will be necessary. Further we conclude from the relative courses and the absolute values of the Xe* particle number densities that realistic HCl kinetics should contain three vibrationally excited levels and stepwise excitation processes as proposed by Dem'yanov et al. [8]. 相似文献
7.
Zusammenfassung Die Darstellung sämtlicher am mittleren Benzolkern p-substitutierten Verbindungen (C6H5)2
MC6H4
M(C6H5)2 mitM=N, P, As, Sb und Bi wird beschrieben. Für die bereits bekannte Stickstoff-bzw. Arsen-Verbindung konnte ein neuer Darstellungs-weg mit guten Ausbeuten gefunden werden, während die Antimon-und Wismutverbindung erstmals beschrieben werden. Durch Dipolmomentmessungen, UV- und IR-Aufnahmen ist ein Vergleich mit den einfachen Triphenylderivaten der genannten Elemente möglich.
Herrn Prof. Dr.F. Wessely zum 70. Geburtstag gewidmet. 相似文献
The compounds p-(C6H5)2 MC6H4 M(C6H5)2,M=N, P, As, Sb, and Bi, were prepared. New methods for the preparation of the N and As compound with good yields were found. The Sb and Bi compound were synthesized for the first time. Dipole moments, IR- and UV-spectra of these compounds were compared with those of the triphenyl derivates.
Herrn Prof. Dr.F. Wessely zum 70. Geburtstag gewidmet. 相似文献
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Abdolhassen Talebian Alem Ghiorghis Charles F. Hammer Evelyn A. Murril Frank Pallas 《Journal of heterocyclic chemistry》1992,29(4):979-984
The syntheses and spectroscopic properties (ir, 1H nmr, 13C nmr, uv and ms) of pure samples of 2-chloro-4,6-bis(dimethylamino)-s-triazine 1 , 4,6-dichloro-2-dimethylamino-s-triazine 2 , 4,6-bis(dimethylamino)-s-triazin-2(lH)-one 3 , 4-chloro-6-dimethylamino-s-triazin-2(1H)-one 4 , 6-dimethylamino-s-triazine-2,4(1H,3H)-dione 5 , and 2,4,6-tris(dimethylamino)-s-triazine (altretamine, HMM) are reported. Evidence for enol-keto equilibria are also presented for 3 , in which the enol form exhibits as an H-bonded dimer structure similar to the dimer of organic carboxylic acids. 相似文献
10.
Hammer NI Hinde RJ Compton RN Diri K Jordan KD Radisic D Stokes ST Bowen KH 《The Journal of chemical physics》2004,120(2):685-690
Results of experimental and theoretical studies of dipole-bound negative ions of the highly polar molecules ethylene carbonate (EC, C3H4O3, mu=5.35 D) and vinylene carbonate (VC, C3H2O3, mu=4.55 D) are presented. These negative ions are prepared in Rydberg electron transfer (RET) reactions in which rubidium (Rb) atoms, excited to ns or nd Rydberg states, collide with EC or VC molecules to produce EC- or VC- ions. In both cases ions are produced only when the Rb atoms are excited to states described by a relatively narrow range of effective principal quantum numbers, n*; the greatest yields of EC- and VC- are obtained for n*(max)=9.0+/-0.5 and 11.6+/-0.5, respectively. Charge transfer from low-lying Rydberg states of Rb is characteristic of a large excess electron binding energy (Eb) of the neutral parent; employing the previously derived empirical relationship Eb=23/n*(max)(2.8) eV, the electron binding energies are estimated to be 49+/-8 meV for EC and 24+/-3 meV for VC. Electron photodetachment studies of EC- show that the excess electron is bound by 49+/-5 meV, in excellent agreement with the RET results, lending credibility to the empirical relationship between Eb and n*(max). Vertical electron affinities for EC and VC are computed employing aug-cc-pVDZ atom-centered basis sets supplemented with a (5s5p) set of diffuse Gaussian primitives to support the dipole-bound electron; at the CCSD(T) level of theory the computed electron affinities are 40.9 and 20.1 meV for EC and VC, respectively. 相似文献