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51.
Titan, the largest moon of Saturn, is enveloped in a reddish brown organic haze. Titan haze is presumed to be formed from methane and nitrogen (CH(4) and N(2)) in Titan's upper atmosphere through energetic photochemistry and particle bombardment. Though Titan haze has been directly investigated using methods including the Cassini mission, its formation mechanism and the contributing chemical structures and prebiotic potential are still not well developed. We report here the structural investigation of the (13)C and (15)N labeled, simulated Titan haze aerosol (tholin) by solution-state NMR. The one-dimensional (1)H, (13)C, and (15)N NMR spectra and decoupling experiments indicate that the tholin sample contains amine, nitrile, imine, and N-heteroaromatic compounds of tremendous import in understanding complex organic chemistry in anaerobic, extraterrestrial environments. 相似文献
52.
Computed tomography (CT) has the potential to greatly enhance our understanding of the turbulent flow structures, the combustion
chemistry, and the interactions between the two, which challenge us in our attempts to understand and model the details of
turbulent combustion. Here, we present high-resolution and fully three-dimensional measurements of the flame surface of a
turbulent reacting flow. The CT-reconstructed images show the flame front, at a single instant in time, of a turbulent, premixed
propane/air flame. The significance of this powerful experimental tool is to provide new insight into turbulent combustion,
allowing for the development of cleaner burning, higher power, and more efficient combustors. 相似文献
53.
H. S Upton 《Fresenius' Journal of Analytical Chemistry》1921,60(1-2):73-74
Ohne Zusammenfassung 相似文献
54.
Calibrated multichannel electronic interferometry, a new technique for quantitative flow visualization of transient phenomena, is discussed. This technique uses an interferometer combined with diffraction gratings to generate three phase shifted interferograms simultaneously which are used to perform multichannel phase shifting. The optical system is calibrated with no phase object present using standard piezoelectric phase shifting, and this calibration information is stored as an electro-optic hologram. The calibration information is used along with the three phase-shifted interferograms that exist with a phase object present to perform time-resolved phase shifting. Examples using natural convection and separated flows are presented. 相似文献
55.
56.
Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co2+Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed. 相似文献
57.
58.
A deuterated cavitand host was examined for its affinity to a series of guests; for halogenated, preorganized guests binding was significantly stronger than the corresponding protium host. 相似文献
59.
Gram-Schmidt orthogonalization of the Zernike polynomials on apertures of arbitrary shape 总被引:1,自引:0,他引:1
An orthonormal hexagonal Zernike basis set is generated from circular Zernike polynomials apodized by a hexagonal mask by use of the Gram-Schmidt orthogonalization technique. Results for the first 15 hexagonal Zernike polynomials are shown. The Gram-Schmidt orthogonalization technique presented can be extended to both apertures of arbitrary shape and other basis functions. 相似文献
60.
Zhou SZ Sey M De Clercq PJ Milanesio M Viterbo D 《Angewandte Chemie (International ed. in English)》2000,39(16):2861-2863