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1.
Jean-Michel Vierfond Yvette Mettey Raymond Joubin Marcel Miocque 《Journal of heterocyclic chemistry》1979,16(4):753-755
The introduction of polar groups in planar polycyclic systems, for the purpose of studying their intercalating action, has been realized in the benzo[c]quinolizinium series. A functionalizing synthesis has been developed from 2-picolyl-and quinaldyllithium. Intermediate ketones or imines were cyclized by a quaternization reaction involving a concerted process. Structure and physico-chemical features of the compounds prepared were studied. 相似文献
2.
Can one join both ends of a helix? A helical aromatic oligoamide was macrocyclized into a saddle-shaped bifunctional clip molecule that self-assembles into discrete circular dodecamers in the solid state and shows great potential for binding aromatic acid guests in solution. The cyclization step requires that the helix is only partly denatured in the reaction medium. 相似文献
3.
J. -M. Bismut 《Geometric And Functional Analysis》1992,2(3):285-340
LetY andY be two complex submanifolds of a complex manifoldX, and assume thatU=YY is also a submanifold ofX. Let Ñ be the excess normal bundle toU inX. We attach certain Bott-Chern currents to holomorphic Hermitian vector bundles onY, Y and to resolutions of the corresponding sheaves by holomorphic Hermitian complexes overX. We show that these currens verify natural functorial properties. Our results extend earlier results of Bismut-Gillet-Soulé to the case where Ñ is nonzero. 相似文献
4.
Baril N Lewa CJ de Certaines JD Canioni P Franconi JM Thiaudière E 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,154(1):22-27
A new method for NMR characterization of mechanical waves, based upon radiofrequency field gradient for motion encoding, is proposed. A binomial B1 gradient excitation scheme was used to visualize the mobile spins undergoing a periodic transverse mechanical excitation. A simple model was designed to simulate the NMR signal as a function of the wave frequency excitation and the periodicity of the NMR pulse sequence. The preliminary results were obtained on a gel phantom at low vibration frequencies (0-200 Hz) by using a ladder-shaped coil generating a nearly constant RF field gradient along a specific known direction. For very small displacements and/or B1 gradients, the NMR signal measured on a gel phantom was proportional to the vibration amplitude and the pulse sequence was shown to be selective with respect to the vibration frequency. A good estimation of the direction of vibrations was obtained by varying the angle between the motion direction and the B1 gradient. The method and its use in parallel to more conventional MR elastography techniques are discussed. The presented approach might be of interest for noninvasive investigation of elastic properties of soft tissues and other materials. 相似文献
5.
Lippens G Chessari G Wieruszeski JM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):242-248
Despite the use of high resolution magic angle spinning NMR, the NMR linewidth of anchored molecules on the commonly used Merrifield solid phase resins remains larger than that of the corresponding molecules in solution. We investigate the different mechanisms that might be at the origin of this line broadening. Experimentally, we use the CPMG method to determine the (15)N relaxation times of a tethered tripeptide and show that the slow resin dynamics significantly contributes to the transverse relaxation. 相似文献
6.
Jean Bellissard Anton Bovier Jean-Michel Ghez 《Communications in Mathematical Physics》1991,135(2):379-399
We study a one dimensional tight binding hamiltonian with a potential given by the period doubling sequence. We prove that its spectrum is purely singular continuous and supported on a Cantor set of zero Lebesgue measure, for all nonzero values of the potential strength. Moreover, we obtain the exact labelling of all spectral gaps and compute their widths asymptotically for small potential strength. 相似文献
7.
We report experimental and theoretical investigations of multiple laser-line emission in a distributed-feedback dye laser pumped by two coherent optical beams. We have used a Lloyd interferometer configuration with second- and third-order Bragg reflections to study the interaction between the two incident pumps in an organic thin film. We demonstrated theoretically that the number of laser emission lines can be interpreted with reference to the saturation effect in the refractive index. 相似文献
8.
We present an optical experiment which permits us to evaluate the information exchange necessary to self-induce cooperatively a well-organized pattern in a randomly activated molecular assembly. A low-power coherent beam carrying polarization and wavelength information is used to organize a surface relief grating on a photochromic polymer thin film which is photoactivated by a powerful incoherent beam. We demonstrate experimentally that less than 1% of the molecules possessing information cooperatively transmit it to the entire photoactivated polymer film. 相似文献
9.
Mid-infrared photonics in silicon needs low-loss integrated waveguides. While monocrystalline germanium waveguides on silicon have been proposed, experimental realization has not been reported. Here we demonstrate a germanium strip waveguide on a silicon substrate. It is designed for single mode transmission of light in transverse magnetic (TM) polarization generated from quantum cascade lasers at a wavelength of 5.8 μm. The propagation losses were measured with the Fabry-Perot resonance method. The lowest achieved propagation loss is 2.5 dB/cm, while the bending loss is measured to be 0.12 dB for a 90° bend with a radius of 115 μm. 相似文献
10.
Julien Lamouroux Robert R. Gamache Anne L. Laraia Jean-Michel Hartmann Christian Boulet 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(11):991-1003
The complex Robert–Bonamy (CRB) formalism was used to calculate the half-width, its temperature dependence, and the line shift for CO2 for transitions in the 30012←00001 and 30013←00001 bands with O2 as the perturbing gas. The calculations were done for rotational quantum numbers from J=0 to J=120 with no ad hoc scaling of the line shape equations. The intermolecular potential parameters are adjusted on accurate experimental measurements of the half-widths, its temperature dependence, and the pressure-induced line shifts so that a single intermolecular potential reproduces all three parameters. Using the results of this work and previous results for N2-broadening, air-broadening line shape parameters were also determined. The comparison of the CRB calculations with the experimental data available in the literature for the three line shape coefficients demonstrates the quality of the present calculations for the both bands under study. 相似文献