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861.
Visualization studies were performed both experimentally and theoretically to observe stress wave propagation in a material
and its interaction with the free surface of the material in a blasting process. PMMA (polymethyl-methacrylate) plates were
used as a transparent material. The stress wave was generated by initiation of an electric detonator. The stress waves in
the PMMA specimen with the right-angled corner were observed by means of the shadowgraph system using a Q switched ruby laser
as a light source. In addition to the experiment, a numerical analysis using smoothed particle hydrodynamics (SPH) was also
carried out to clarify the dynamic behavior of stress waves in the blasting process. Transmittance and reflection of the stress
wave at the free surface could be visualized by both the experiment and the numerical analysis. 相似文献
862.
Maeda A Matsumoto S Kishida H Takenobu T Iwasa Y Shiraishi M Ata M Okamoto H 《Physical review letters》2005,94(4):047404
We measured third-order nonlinear susceptibility (chi(3)) spectra in semiconducting single-walled carbon nanotubes (SWNTs) by the Z-scan method. |Imchi(3)| is remarkably enhanced under resonant excitation to the lowest interband transition, reaching 4.2 x 10(-6) esu and 1.5 x 10(-7) esu in SWNTs grown by the laser ablation and HiPco methods, respectively. A comparison of the transient absorption changes evaluated by degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of |Imchi(3)| is dominated by a coherent process rather than by saturation of absorption. 相似文献
863.
Schibli TR Minoshima K Hong EL Inaba H Bitou Y Onae A Matsumoto H 《Optics letters》2005,30(17):2323-2325
We present an arbitrary optical single-frequency generator based on a femtosecond optical frequency comb. The functions of this device are comparable to those of a radio-frequency synthesizer. However, this device operates at hundreds of terahertz. The absolute frequency accuracy of this synthesizer is approximately 1 kHz at a 282 THz carrier frequency. The stability is approximately 2 x 10(-14) at 100 s, and the tuning speed exceeds 30 GHz/s. This source demonstrates the integration of a phase-locked optical comb into a versatile and easy-to-use system for the generation of tunable, absolute optical frequencies. By using downconversion, one could generate tunable terahertz frequencies that are phase locked to a microwave reference, such as a Cs atomic clock, and high-precision interferometry could benefit greatly from the stability and accuracy of this widely tunable source. 相似文献
864.
[reaction: see text] Bu2Sn(OTf)H (1a), easily prepared from Bu2SnH2 and TfOH, was found to be very valuable for highly regio- and stereoselective hydrostannylation of various propargyl alcohols leading to (Z)-gamma-stannylated allyl alcohols. The stannylation with 1a is applicable to the synthesis of hydroxy-substituted (Z)-vinylstannanes from terminal alkynes bearing a hydroxy group at the homoallylic or bishomoallylic position. The coordination of the hydroxy group to the Lewis acidic tin center plays an important role for the observed regio- and stereochemistry. 相似文献
865.
A comparative spectral study of the fluorescence of the m-oxybenzoate anion versus the electron-transfer-initiated chemiluminescence (CIEEL) of the same anion derived from the bicyclic dioxetanes in various solvents is reported. The present study reveals that the fluorescence of this oxyanion is blue-shifted in protic versus aprotic solvents, while the CIEEL-spectral maximum is independent of the medium. The same phenomenon has been recently observed for the m-oxybenzoate ion derived from CIEEL-active spiroadamantyl dioxetanes. The reported spectral differences between the fluorescence and chemiluminescence emissions cannot be attributed to exciplex formation in the CIEEL process, but result from the differences in hydrogen-bonding effects on the photo- and chemiexcited oxyanion species. The observed solvatochromism is qualitatively rationalized in terms of the semiempirical AM1 calculations. 相似文献
866.
A simplified and efficient encapsulation-dehydration protocol, which is a compromise between vitrification and encapsulation-dehydration, was presented for plant cryopreservation. In this protocol, during the encapsulation process, the apices precultured with 0.3 M sucrose for 16 h were simultaneously osmoprotected with a mixture of 02 M glycerol plus 0.4 M sucrose for 1 h. These encapsulated apices were directly dehydrated with dry silica gel prior to a plunge into LN without the pretreatment of 0.8M sucrose for 16 h. This protocol produced much higher rates of recovery growth in the three plant species tested (wasabi, chrysanthemum, and mint) than those cryopreserved by the conventional encapsulation-dehydration. This protocol also considerably reduced the time needed for the cryogenic procedure. Thus, this new protocol appears promising for cryopreservation of shoot apices and other explants. 相似文献
867.
Matsumoto A. Nishimura K. Utaka K. Usami M. 《Quantum Electronics, IEEE Journal of》2006,42(3):313-323
Using the newly developed time-dependent transfer matrix method with nonlinear effects, we analyzed the characteristics of cross-phase modulation (XPM), cross-gain modulation and gain recovery time of a semiconductor optical amplifier (SOA) with an assist light injection, which is introduced to speed up the gain recovery of the SOA. Particularly for the application to high-speed wavelength converters using XPM with an interferometer structure where /spl pi/-phase change is required, various parameters such as SOA lengths, wavelengths and powers of injected lights, and their propagation directions are designed via numerical simulation. Discussions concerning the conditions of an SOA structure and the parameters of injected lights for high-speed operation are described to show the potential of fast gain recovery with a response time as low as 25 ps. 相似文献
868.
Takashi Iida Toshitake Tamura Taro Matsumoto Frederic C. Chang 《Magnetic resonance in chemistry : MRC》1983,21(5):305-309
Carbon-13 NMR signals were assigned for the complete set of the 26 theoretically possible isomers of methyl 5β-cholanates having one to three hydroxy groups at positions C-3, C-7 and/or C-12 in the nucleus. Substituent effects on the 13C NMR shielding data serving to characterize the position and configuration of the hydroxy groups are discussed. 相似文献
869.
We prepared a phenobarbital (PB) solid dispersion (SD) with phosphatidylcholine (PC). PB was present in an amorphous state in SD if its mole fraction was under 0.75. An infrared (IR) spectra study suggested a hydrogen bond between NH in PB and phosphate in PC, with a ratio of about 1:1. When the mole fraction of PB was less than 0.50, differential scanning calorimetry (DSC) curves showed endothermic peaks at 57, 90 and 145 degrees C, and an exothermic peak at 60 degrees C. The IR spectrum and X-ray diffraction pattern changed after holding at 70 degrees C, so at this point it is considered that the metastable state of SD changed into a stable state, and extra energy was released. When the mole fraction of PB was high, PB also arranged near hydrophobic group because an endothermic peak was observed at 46-52 degrees C, which was lower than fully hydrated PC. PB is similar to indomethacin (IM) in molecular shape and to phenytoin (PHT) in chemical structure. Its DSC curve and IR spectra are similar to PHT, and the limit ratio of its amorphous state is the same as IM. It is considered that the chemical structure is an important factor in its interaction to PC, and also, the molecular shape is important to arrange into PC lattice. 相似文献
870.
M. Asai J. L. Bailly H. B?ttcher F. Bruyant C. Caso Y. Chiba H. Dibon B. Epp A. Ferrando F. Fontanelli S. N. Ganguli T. Gémesy R. Hamatsu P. Hidas T. Hirose J. Hrubec T. Kageya N. Khalatyan E. Kistenev I. Kita S. Kitamura V. Kubik J. MacNaughton M. Markytan S. Matsumoto I. S. Mittra L. Montanet G. Neuhofer G. Pinter P. Porth T. Rodrigo J. Singh S. Squarcia K. Takahashi R. Tanaka L. A. Tikhonova U. Trevisan R. Wischnewski T. Yamagata S. A. Zotkin NA EHS-RCBC Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,46(4):593-598
Properties of proton diffractive dissociation have been investigated for four-prong final states in proton-proton reactions at 360 GeV/c, in particular forpp→ppπ +π? mπ 0(m=0,1,2). Mass distributions and decay angular distributions are given. The decay of the diffractive system is seen to be very anisotropic, and largep T is suppressed at higher masses. It is found that the “pomeron” couples with a single valence quark of the incident proton, but indications for a diquark-pomeron coupling are also found. Similarities with fragmentation in lepton-hadron deep inelastic scattering are underlined. 相似文献