Heavy-atom effects on hydrogen-atom transfer reaction from monohalogenated phenols to triplet 7,8-benzoquinoline

The rate constants and the radical yields for the hydrogen-atom transfer reaction from four monohalogenated phenols to triplet 7,8-benzoquinoline were determined by an emission—absorption flash technique. The rate constants are of the order of 10⁹ M⁻¹ s⁻¹ except for 2-bromophenol, and the radical yield Φ_rt decreases on halogen substitution. In the case of monobromophenols, Φ_rt is sensitive to the position of the bromine atom. The rate constant of free radical recombination increases with decreasing Φ_rt. Such heavy-atom effects are explained in terms of the heavy-atom-induced spin relaxation of the triplet radical pair.     

Asymptotic behaviour of solutions for the wave equation with an effective dissipation around the boundary

We consider the initial-boundary value problem for the wave equation with a dissipation a(t,x)u_t in an exterior domain, whose boundary meets no geometrical condition. We assume that the dissipation a(t,x)u_t is effective around the boundary and a(t,x) decays as |x|→∞. We shall prove that the total energy does not in general decay, and the solution is asymptotically free as the time goes to infinity. Further, we shall show that the local energy decays like O(t⁻¹) (t→∞).     

Generation of nearly diffraction-free laser beams

Laser beams which behave like the so-called diffraction-free beams have been generated by an argon ion laser with a new type of cavity. They have almost the same intensity distributions and propagation characteristics as those predicted for the Bessel-Gauss beams which were introduced recently. Beams corresponding not only to the lowestorder but also to higher-order Bessel-Gauss beams have been obtained.     

Infrared Optical Fiber Sensors

Notably improved performance as well as extended application areas is expected in the technology of optical fiber sensors using infrared fibers that transmit radiation in a wavelength range beyond 2 μm. Measurement of infrared radiation is particularly important in thermometry and spectrometry. In these areas, the use of infrared fibers has been studied extensively not only as a transmission waveguide but also as a sensor chip. Of various infrared fibers, fluoride glass fibers exhibit the lowest transmission loss and hence are useful for remote sensing that requires light transmission over a long distance. The wide transmission range of chalcogenide glass fibers and halide crystalline fibers is valuable for thermometry in a low temperature range and for spectrometry of various molecules. Hollow waveguides are useful as a capillary flow cell that realizes fast-response spectrometry. The advantages and disadvantages of infrared fibers must be considered carefully in the development of fiber sensors. In this paper, the progress of infrared optical fiber sensors is reviewed with particular interest in thermometry and spectroscopy.     

Paeonilactone-A, -B,and -C,new monoterpenoids from paeony root

Three new monoterpenoids named paeonilactone-A, -B, and -C were isolated from Paeony root (roots of Paeonia albiflora PALLAS var. trichocarpa BUNGE) and their structures were determined to be $\text{2}$, $\text{3}$, and $\text{4}$, respectively, by means of chemical and spectroscopic studies.     

Continuous Displacement Formulation of Alloys

The conventional permutational statistics of cooperative phenomena is extended to include displacement of atoms from their reference lattice points. The formulation is done in the cluster variation method (CVM) framework, by changing summations in energy and entropy to integrals. It is demonstrated for the pair approximation of CVM on phase-separating fcc binary alloys. The treatment can take into account local lattice distortion due to atomic size difference, the elastic effects, and the pressure effects. To compare stability of states under pressure, the grand potential (T, V, { _i}) is extended to Z(T, p, { _i}) by a Legendre transform. Although the new function Z(T, p, { _i}) vanishes in equilibrium, and is called the ZERO-potential in the paper, it remains nonzero and is used to determine the coexisting phases when the chemical potentials are modified. Numerical calculations are done using the natural iteration technique on model inter-atomic potentials of the Lennard-Jones type. The numerical results of using (T, V, { _i}) and Z(T, p, { _i}) potentials for phase-separating diagrams, for composition and pressure dependence of the lattice constant, and for the bulk modulus are reported and discussed.