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1.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
2.
3.
Ciprian Borcea Xavier Goaoc Sylvain Lazard Sylvain Petitjean 《Discrete and Computational Geometry》2006,35(2):287-300
We prove that four spheres in ℝ3 have infinitely many real common tangents if and only if they have aligned centers and at least one real common tangent. 相似文献
4.
Sylvain Maillot 《Geometric And Functional Analysis》2007,17(3):839-851
We show that open 3-manifolds that have a locally finite decomposition along 2-spheres are characterized by the existence
of a Riemannian metric with respect to which the second homotopy group of the manifold is generated by small elements.
Received: November 2005 Revision: February 2006 Accepted: May 2006 相似文献
5.
The performances of two Laser Doppler Velocimetry (LDV) systems adapted for measuring the acoustic particle velocities are assessed in enclosed sound field. This assessment is performed by comparing the acoustic velocities measured by means of LDV to reference acoustic velocities estimated from sound pressure measurements. The two LDV systems are based on a single optical bench which delivers an optical signal called Doppler signal. The Doppler signal, which is frequency modulated, is analyzed by means of two signal processing systems, the BSA (Burst Spectrum Analyser from Dantec) on the one hand, and a system specifically developed for the estimation of the acoustic velocity on the other hand. Once the experimental setup has been optimized for minimizing the errors made on the reference velocities, the assessment is performed and shows that both systems can measure the acoustic velocity in enclosed field in two the frequency ranges [0-4 kHz] and [0-2 kHz] respectively for acoustic velocity amplitudes of 10 mm/s and 1 mm/s. 相似文献
6.
7.
Jacques E. Desnoyers Gérald Perron Sylvain Léger Byron Y. Okamoto Terrence H. Lilley Robert H. Wood 《Journal of solution chemistry》1978,7(3):165-178
The freezing-point depression of the ternary systems tetraalkylammonium bromides-t-butanol-water for the first five homologs of R4NBr was measured. In the case of Bu4NBr, the effect of size of the alcohol (methahol ton-butanol) was also investigated. From the corresponding freezing-point data for the binary systems the apparent salting constants
were calculated. The true salting constantsk
s were obtained by extrapolation to infinite dilution. These are all very close to zero at the freezing temperature. From the
corresponding thermochemical data the temperature dependence ofk
s was calculated, and above 5°C all the R4NBr salts int-butanol; the salting-in increases with temperature and with the size of the hydrophobic cations. The scaled-particle theory
is at present the only one which can account semiquantitatively for the temperature dependence of the salting-in effect.
On leave of absence from Chemistry Department, The University, Sheffield S3 7HF, England
To whom correspondence should be addressed. 相似文献
8.
Broussy S Bernardes-Génisson V Gornitzka H Bernadou J Meunier B 《Organic & biomolecular chemistry》2005,3(4):666-669
An ortho-metallation-electrophilic substitution sequence was employed as a key step to build the 4-benzoylpyridine framework. It was found that 4-benzoylpyridine-3-carboxamide and an N-pyridyl alkylated derivative both exist in a unique cyclized hemiamidal structure, not in the usually expected keto-amide open form. These structures represent fragment models of the Isoniazid-NAD adducts involved in the mechanism of action of the antituberculous drug Isoniazid. 相似文献
9.
Carré V Gaud O Sylvain I Bourdon O Spiro M Blais J Granet R Krausz P Guilloton M 《Journal of photochemistry and photobiology. B, Biology》1999,48(1):57-62
A series of neutral meso-arylglycosylporphyrins has been tested in order to evaluate their potency as antifungal agents against the yeast Saccharomyces cerevisiae. Photodynamic activity of these molecules results in intracellular damage as evidenced by the loss of clonogenicity and DNA fragmentation. The ability of these photosensitizers to permeate yeast cells is determined by microspectrofluorimetry and is correlated with their antifungal potency. Amphiphilic porphyrin derivatives are shown to exhibit the more pronounced photoactivity. 相似文献
10.
Lahboub Bouyazza Jean-Charles Lancelot Sylvain Rault Max Robba Marie Anne Quermonne 《Journal of heterocyclic chemistry》1991,28(2):373-377
Cyclization of 2-(1-pyrrolyl)piperonylcarboxamide derivatives gave iminium perchlorates which afforded 9-(N-substituted-imino) and 9-(N-substituted amino)-6,7-methylenedioxypyrrolo[1,2-a]indoles. 相似文献