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51.
García Ruano JL Gamboa AE Gutiérrez LG Martín Castro AM Rodríguez Ramos JH Yuste F 《Organic letters》2000,2(6):733-736
A new kind of chiral dienophiles, cyclic vinyl-p-tolylsulfilimines (2a and 2b), were obtained from the corresponding (Z)-sulfinylacrylonitriles with HBF(4) and methanol. The asymmetric Diels-Alder reaction of optically pure 2a with cyclopentadiene under mild thermal or catalyzed conditions afforded only the endo-4a adduct with complete endo and pi-facial selectivities. The ability of the sulfilimine moiety to enhance the dienophilic reactivity of the double bond is similar to that of the sulfinyl group. 相似文献
52.
O. A. Godin 《Acoustical Physics》2008,54(3):346-352
Acoustic transmission between points onshore or in very shallow water and points in deep water is strongly influenced by the
shear rigidity of marine sediments, which control the parameters and the very existence of seismoacoustic surface waves. Previously,
it was found that coupling between acoustic modes and the seismoacoustic surface waves is normally weak, although not negligible
in the case of a gently sloping seafloor and soft sediments. In this paper, the previous work is extended by accounting for
the small-scale roughness of the seafloor. The significant role of roughness in coupling between volume and surface waves
is demonstrated. The combined effect of bottom topography, roughness, and wave attenuation in soft marine sediments on the
sound propagation between points in shallow and deep water is discussed.
Published in Russian in Akusticheskiĭ Zhurnal, 2008, Vol. 54, No. 3, pp. 400–407.
The article was translated by the author. 相似文献
53.
O. A. Godin 《Acoustical Physics》2007,53(6):714-720
Marine sediments support seismoacoustic surface waves, which can propagate along the seafloor, in deep and shallow water,
and even onshore. Because of the strong attenuation of compressional and especially shear waves in the sediments, the surface
waves can significantly contribute to the acoustic field far from the shore only through their coupling with volume waves
in the water. We theoretically study the excitation of acoustic normal modes by seismoacoustic surface waves in a shallow-water
waveguide with a sloping bottom consisting of unconsolidated marine sediments. It is found that the coupling primarily occurs
in the vicinity of a modal cutoff. The effects of geoacoustic parameters and stratification of soft marine sediments on the
efficiency of surface-to-volume conversion are investigated.
Published in Russian in Akusticheskiĭ Zhurnal, 2007, Vol. 53, No. 6, pp. 809–816.
The article was translated by the author. 相似文献
54.
Toledano P Figueiredo Neto AM de Sant'Ana ZA 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(1):486-492
Experimental investigations of lyotropic cholesterics fluids are presented which show that changes in the shape anisotropy and chirality of the micellar population determine the topology of the temperature-concentration phase diagrams. For given amounts of the substances which induce the chirality and modify the shape anisotropy of the micelles, two distinct biaxial cholesteric phases are disclosed in the phase diagrams. This is interpreted in the framework of the catastrophe theory of phase transitions. 相似文献
55.
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57.
Acoustical Physics - An approach is proposed for estimating the dispersion characteristics of waveguide modes from analysis of ship noise recorded by two closely spaced and synchronized vertical... 相似文献
58.
59.
Godin OA 《The Journal of the Acoustical Society of America》2011,130(4):EL135-EL141
Wave scattering by objects that are small compared to the wavelength (Rayleigh scattering) is usually studied for plane incident waves. However, knowledge of the full Green's function of the problem becomes necessary when the separation of scatterers from either an interface or each other is comparable to the scatterers' dimensions. Here, an elementary analytic solution is derived for diffraction of a spherical sound wave by a small, soft sphere. The approximate solution is obtained from asymptotic expansions of an exact solution, holds everywhere outside the sphere, and reduces to classical results due to Kelvin and Rayleigh in appropriate special cases. 相似文献
60.
Dr. Benjamin C. M. Martindale Georgina A. M. Hutton Prof. Christine A. Caputo Sebastian Prantl Dr. Robert Godin Prof. James R. Durrant Dr. Erwin Reisner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6559-6563
Single-source precursor syntheses have been devised for the preparation of structurally similar graphitic carbon dots (CDs), with (g-N-CD) and without (g-CD) core nitrogen doping for artificial photosynthesis. An order of magnitude improvement has been realized in the rate of solar (AM1.5G) H2 evolution using g-N-CD (7950 μmolH2 (gCD)−1 h−1) compared to undoped CDs. All graphitized CDs show significantly enhanced light absorption compared to amorphous CDs (a-CD) yet undoped g-CD display limited photosensitizer ability due to low extraction of photogenerated charges. Transient absorption spectroscopy showed that nitrogen doping in g-N-CD increases the efficiency of hole scavenging by the electron donor and thereby significantly extends the lifetime of the photogenerated electrons. Thus, nitrogen doping allows the high absorption coefficient of graphitic CDs to be translated into high charge extraction for efficient photocatalysis. 相似文献