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641.
An extension of Mulliken's charge transfer theory leads to the following correlations: the change in the transition moment of the X—H stretching vibration with the enhancement of dipole moment, and the displacement of the X—H stretching frequency with the ionization of donors. Experimental data for a number of hydrogen-bonded complexes are in accord with these predictions. 相似文献
642.
643.
We measured the Mg2+-dependent absorption spectra, emission spectra, quantum yields, and intensity decays of most presently available fluorescent magnesium probes. The lifetimes were found to be strongly Mg2+ dependent for Mag-quin-1, Mag-quin-2, magnesium green, and magnesium orange and increased 2- to 10-fold upon binding of Mg2+. The lifetimes of Mag-fura-2, Mag-fura-5, Mag-fura red, and Mag-indo-1 were similar in the presence and absence of Mg2+. Detailed timeresolved measurements were carried out for Mag-quin-2 and magnesium green using phase-modulation fluorometry. Apparent dissociation constants (K
d) were determined from the steady-state and time-resolved data. Their values were compared and discussed. Mg2+ sensing is described using phase and modulation data measured at a single modulation frequency. Phase angle and modulation data showed the possibility of obtaining a wider Mg2+-sensitive range than available from intensity measurements. A significant expansion in the Mg2+-sensitive range was found for Mag-quin-2 using excitation wavelengths from 343 to 375 nm, where the apparentK
d from the phase angle was found to vary from 0.3 to about 100 mM. Discrimination against Ca2+ was also measured for Mag-quin-2 and magnesium green. Significant phototransformation and/or photode-composition, which affect the sensitivity to Mg2+, were observed for Mag-quin-2 and magnesium green under intense and long illumination. 相似文献
644.
Tarek S. El-Bawab Chintan H. Vaishnav Anura P. Jayasumana Henryk Temkin Jon R. Sauer Heinz A. Willebrand 《Fiber and Integrated Optics》1997,16(3):237-260
The wavelength division multiplexing (WDM) network architectures, in general, are based on transmitters and/or receivers that can be precisely and speedily tuned to predetermined, fixed wavelengths. These requirements are not easy to meet in practice. Robust WDM, the subject of this paper, has been introduced as a technique to implement WDM in the local area. The strength of this novel approach is that it does not rely on wavelength-sensitive devices that are required to perform with extreme stability. This paper describes the basis of this approach and presents two types of medium access control (MAC) protocols that are suitable for Robust WDM local area networks (LANs). The performance of networks based on these protocols is discussed in detail. It is shown that the new approach has considerable promise for WDM networks in the local area. 相似文献
645.
We give some information about the action of Aut(M) on M(0), where M is a countable arithmetically saturated model of Peano Arithmetic. We concentrate on analogues of moving gaps and covering gaps inside M(0). 相似文献
646.
A formula is given for the permanent of a general Cauchy matrix ((xi?yj)?1). In a special case, where the xi and the yj are the distinct nth roots of 1 and ?1 respectively, a formula for the permanent, conjectured by R. F. Scott, is proved by computing the eigenvalues of related circulants. 相似文献
647.
648.
The enhancement of the dipole moments of hydrogen-bonded complexes are discussed using Mulliken's charge-transfer theory.A linear relation is found between the ratio a/b and the ionization potential of the donor, IVD. This behaviour is similar to that previously found for halogen charge-transfer complexes [6]. 相似文献
649.
We prove that if a global solution of the equation dXt = a(Xt) dBt, X0 = x exists for some x ? and ∫∞0a2(Xs)ds = ∞, then one must have a ≠ 0 a.e. 相似文献
650.