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71.
T. Matsui A.S.-C. Cheung K. Yoshino W.H. Parkinson J.E. Murray T. Imajo 《Journal of Molecular Spectroscopy》2003,219(1):45-57
The photoabsorption spectrum of the O2 Schumann-Runge bands was measured with resolution comparable to the Doppler widths by using the VUV Fourier transform spectrometer from Imperial College, London, combined with synchrotron radiation as a continuum light source at the Photon Factory, KEK, Japan. The analysis of the (12,0)-(17,0) bands of the Schumann-Runge system provides accurate rotational line positions as well as the line intensities from 185 to 175 nm. Molecular constants of the levels of the state have been determined. The (v′,0) band oscillator strengths were determined as 2.38, 2.62, 2.70, 2.66, 2.40, and 2.12×10−5 for the bands from v′=12 to 17, respectively. 相似文献
72.
Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) are two novel Ca(2+) messengers derived respectively from NAD and NADP. Since their discovery in sea urchin eggs, both have now been shown to serve messenger functions in a wide range of cells from plant to human. In this article, a series of fluorimetric assays for cADPR, NAADP and their metabolic enzymes is compiled. The enzyme assay makes use of an analog of NAD, nicotinamide guanine dinucleotide, which is non-fluorescent but is cyclized by the enzymes to a fluorescent analog of cADPR, cyclic GDP-ribose. Other NAD utilizing enzymes are not capable of catalyzing the cyclization and thus produce no interference. The fluorimetric assays for cADPR and NAADP make use of coupled-enzyme amplification and can readily detect nanomolar concentrations of either messenger. All the assays described can be performed in multi-well format, allowing ready automation and use in high throughput screening. An added advantage of these assays is that all the required reagents are commercially available, facilitating general adoption of the techniques by all those who are interested in the physiology and enzymology of the novel Ca(2+) signaling pathways mediated by cADPR and NAADP. 相似文献
73.
[reaction: see text] A ruthenium porphyrin-catalyzed stereoselective intramolecular carbenoid C[bond]H insertion is described. Using [Ru(II)(TTP)(CO)] as catalyst, aryl tosylhydrazones are converted to 2,3-dihydrobenzofurans, 2,3-dihydroindoles, and beta-lactams in good yields and remarkable cis selectivity (up to 99%). Enantioselective synthesis of 2,3-dihydrobenzofurans is also achieved with [Ru(II)(D(4)-Por*)(CO)] as catalyst, and up to 96% ee is attained. 相似文献
74.
[reaction: see text] To provide experimental evidence on the relationship between stucture and reactivity in 1,4-hydroxybiradical intermediates, the Norrish type II photochemistry of a homologous series of spirobenzoyladamantane derivatives was investigated in the crystalline state and the outcome correlated with the structures of the compounds as determined by X-ray crystallography. The results provide an unusually detailed and compelling picture of the geometric factors responsible for the partitioning of these reactive intermediates among cleavage, cyclization, and reverse hydrogen transfer. 相似文献
75.
X.M. Liu Paul K. Chu C.Y. Chung K.W.K. Yeung K.M.C. Cheung 《Applied Surface Science》2007,253(6):3154-3159
Water plasma immersion ion implantation (PIII) was conducted on orthopedic NiTi shape memory alloy to enhance the surface electrochemical characteristics. The surface composition of the NiTi alloy before and after H2O-PIII was determined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was utilized to determine the roughness and morphology of the NiTi samples. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were carried out to investigate the surface electrochemical behavior of the control and H2O-PIII NiTi samples in simulated body fluids (SBF) at 37 °C as well as the mechanism. The H2O-PIII NiTi sample showed a higher breakdown potential (Eb) than the control sample. Based on the AFM results, two different physical models with related equivalent electrical circuits were obtained to fit the EIS data and explain the surface electrochemical behavior of NiTi in SBF. The simulation results demonstrate that the higher resistance of the oxide layer produced by H2O-PIII is primarily responsible for the improvement in the surface corrosion resistance. 相似文献
76.
V.N. Wijayathunga R.S. Blackburn E.L.V. Lewis V. Cheung 《Optics & Laser Technology》2007,39(7):1301-1309
Laser irradiation has been previously investigated for achieving uniform heating of polyethylene terephthalate (PET) fibres in the hot-drawing stage of the production process, so as to obtain better fibre mechanical properties. The optical properties and dye uptake of PET fibres also depend on the polymer chain orientation and crystallinity within the fibre structure. This paper reports an investigation of a concept whereby laser irradiation and interferometry could be used to modify and trace a small change in the optical properties of a PET monofilament fibre, but the corresponding change in the dye uptake would not be detected visually. A copper vapour laser (550-580 nm wavelengths) was used to expose consecutive 4 mm lengths along a running length of monofilament to 39.8 W cm−2, at a pulse rate of 9.89 kHz in order to modify, in a controlled way, the polymer crystallinity and orientation. A 3D finite element simulation, based on uncoupled heat-transfer analysis, indicated that rapid heating and cooling could be obtained with the laser to give the small changes required. Irradiated and untreated samples were analysed by interferometry and a 0.16% change was detected in the birefringence profiles, corresponding to a small reduction in the degree of orientation and crystallinity of the irradiated samples. Density measurements and wide-angle X-ray scattering (WAXS) analysis confirmed the change in crystallinity. Tests conducted for dye adsorption and tensile strength showed a small increase in the former and only a very small decrease in the latter. It was concluded that these changes in property provide the opportunity for a laser-irradiated PET monofilament fibre to be used as a subtle tracer element in brand labels for textile garments as an anti-counterfeit measure. 相似文献
77.
The mass Δm removed per pulse in laser ablation was shown to correlate with the acoustic signal A and the beam diameter ?. The functional forms of Δm(A, ?) were deduced for aluminum and polyvinyl chloride, for fluence ranging from 1.5 through 88 J cm− 2. Δm so computed agreed with empirical values within experimental error. For samples whose mass is sensitive to environmental factors, off-line measurement of Δm was shown to be unreliable and real-time measurements such as acoustic monitoring became essential. 相似文献
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80.
In the present paper we establish some new Opial-type inequalities involving higher order partial derivatives. Our results in special cases yield some of the recent results on Opial’s inequality and provide new estimates on inequalities of this type. As an application, we prove the uniqueness of the solution of the initial value problem involving higher order partial differential equations. 相似文献