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91.
S-Alkyl dithioformates, generated by a cycloreversion process, react as 1,3-dipolarophiles with beta-lactam-based azomethine ylids to provide, after (net) elimination of MeSH, C(2)-unsubstituted penems. The overall cycloreversion/cycloaddition sequence was accelerated by microwave irradiation. [reaction: see text] 相似文献
92.
M.?AriasEmail author J.?Campos A.?M.?Robles-Pérez L.?Sanchez 《Calculus of Variations and Partial Differential Equations》2004,21(3):319-334
We study the existence of fast and heteroclinic solutions of an ODE that arises in connection with travelling wave solutions of Fisher-Kolmogorovs equation. They are obtained by solving a minimum or constrained minimum problem. A variational characterization of the minimum speed for which heteroclinic solutions exist is obtained.Received: 14 November 2003, Accepted: 29 January 2004, Published online: 2 April 2004M. Arias: Supported by MCYT, Acción Integrada HP2000-0039, SpainJ. Campos: Supported by MCYT, BFM2002-01308 and Acción Integrada HP2000-0039, SpainA.M. Robles-Pérez: Supported by Acção Integrada E-15/01 and Fundaçâo para a Ciência e a Tecnologia, Portugal 相似文献
93.
Phase noise characterization of a 10-W Yb fiber amplifier is presented, and we demonstrate phase locking of two fiber amplifiers with near-perfect fringe contrast at power levels of as much as 10 W per fiber. Coherent beam combining is maintained during the turn-on transient as well as in thermal steady-state operation. 相似文献
94.
Various organic moieties are homogeneously introduced in high quantities into mesostructured porous silica films through a general co-condensation process, which influences the self-assembly mechanism, depending on the physico-chemical properties of each function. 相似文献
95.
B. Ortaç A. Hideur M. Brunel T. Chartier M. Salhi H. Leblond F. Sanchez 《Applied physics. B, Lasers and optics》2003,77(6-7):589-594
The properties of an ytterbium-doped double-clad fiber laser, passively mode-locked by nonlinear polarization rotation are investigated in this work. Cartographies of mode-locking regime versus halfwave plates orientations are presented for several values of the total cavity dispersion and for different pump powers. Bistability between the continuous and the mode-locking regimes is pointed out. The effect of the total group velocity dispersion is described with a master mode-locking equation. PACS 42.55.Wd; 42.65.Re 相似文献
96.
Oxidative cleavage of the C-20/C-21 bond in apoptolidin (1) provides two fragments of similar complexity, facilitating a divide-and-diversify strategy for the determination of the structural basis for apoptolidin's biological activity, the remarkably selective induction of apoptosis in sensitive cell lines. The ability of compounds derived from this cleavage to inhibit mitochondrial F(0)F(1)-ATPase is reported. [structure: see text] 相似文献
97.
J.A. Hodges P. Bonville A. Forget J.P. Sanchez P. Vulliet M. Rams K. Królas 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):173-181
Using 170Yb and 155Gd M?ssbauer measurements down to ∼ 0.03 K, we have examined the semiconducting pyrochlore Yb2Mo2O7 where the Mo intra-sublattice interaction is anti-ferromagnetic and the metallic pyrochlore Gd2Mo2O7 where this interaction is ferromagnetic. Additional information was obtained from susceptibility, magnetisation and 172Yb perturbed angular correlation measurements. The microscopic measurements evidence lattice disorder which is important in
Yb2Mo2O7 and modest in Gd2Mo2O7. Magnetic irreversibilities occur at 17 K in Yb2Mo2O7 and at 75 K in Gd2Mo2O7 and below these temperatures the rare earths carry magnetic moments which are induced through couplings with the Mo sublattice.
In Gd2Mo2O7, we observe the steady state Gd hyperfine populations at 0.027 K are out of thermal equilibrium, indicating that Gd and Mo
spin fluctuations persist at very low temperatures. Frustration is thus operative in this essentially isotropic pyrochlore
where the dominant Mo intra-sublattice interaction is ferromagnetic.
Received 13 January 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: hodges@drecam.saclay.cea.fr 相似文献
98.
The Helmholtz equation describing the propagation of acoustic and electromagnetic waves in a nonhomogeneous media slowly varying
in the horizontal direction is considered. The contribution of the discrete and continuous spectra of the transversal Sturm-Liouville
problem to the asymptotics is studied. A uniform asymptotics for the Green function in neighborhoods of thresholds is obtained. 相似文献
99.
Tom Schoonjans Antonio Brunetti Bruno Golosio Manuel Sanchez del Rio Vicente Armando Solé Claudio Ferrero Laszlo Vincze 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(11-12):776-784
This work presents the recent developments of xraylib, an ANSI C library that provides convenient access to a large number of X-ray related databases, with a focus on quantitative X-ray fluorescence applications. The enhancements include improved X-ray fluorescence production cross sections that take into account cascade effects and M-lines, as well as revised line energies, atomic level widths, Compton broadening profiles etc. A full overview of the complete application programming interface is presented. 相似文献
100.