We investigate the asymptotic tail behavior of massive scalar fields in Schwarzschild background. It is shown that the oscillatory tail of the scalar field has the decay rate of t −5/6 at asymptotically late times, and the oscillation with the period 2π/m for the field mass m is modulated by the long-term phase shift. These behaviors are qualitatively similar to those found in nearly extreme Reissner-Nordström background, which are discussed in terms of a resonant backscattering due to the space-time curvature.

We investigate the dominant late-time tail behavior of massive scalar fields in a nearly extreme Reissner-Nordström background. It is shown that the oscillatory tail of the scalar fields has the decay rate of t Ϫ5/6 at asymptotically late times. The physical mechanism by which the asymptotic t Ϫ5/6 tail is generated and the relation between the field mass and the time scale when the tail begins to dominate are discussed in terms of resonance backscattering due to space-time curvature.

Neurofibrillary tangles, composed of hyperphosphorylated tau fibrils, are a pathological hallmark of Alzheimer's disease; the neurofibrillary tangle load correlates strongly with clinical progression of the disease. A growing body of evidence indicates that tau oligomer formation precedes the appearance of neurofibrillary tangles and contributes to neuronal loss. Here we show that tau oligomer formation can be inhibited by compounds whose chemical backbone includes 1,2-dihydroxybenzene. Specifically, we demonstrate that 1,2-dihydroxybenzene-containing compounds bind to and cap cysteine residues of tau and prevent its aggregation by hindering interactions between tau molecules. Further, we show that orally administered DL-isoproterenol, an adrenergic receptor agonist whose skeleton includes 1,2-dihydroxybenzene and which penetrates the brain, reduces the levels of detergent-insoluble tau, neuronal loss and reverses neurofibrillary tangle-associated brain dysfunction. Thus, compounds that target the cysteine residues of tau may prove useful in halting the progression of Alzheimer's disease and other tauopathies.

The observational data from some black hole candidates suggest the importance of electromagnetic fields in the vicinity of a black hole. Highly magnetized disk accretion may play an importance rule, and large scale magnetic field may be formed above the disk surface. Then, we expect that the nature of the black hole spacetime would be reveiled by magnetic phenomena near the black hole. We will start to investigate the motion of a charged particle which depends on the initial parameter setting in the black hole dipole magnetic field. Specially, we study the spin effects of a rotating black hole on the motion of the charged particle trapped in magnetic field lines. We make detailed analysis for the particle's trajectories by using the Poincaré map method, and show the chaotic properties that depend on the black hole spin. We find that the dragging effects of the spacetime by a rotating black hole weaken the chaotic properties and generate regular trajectories for some sets of initial parameters, while the chaotic properties dominate on the trajectories for slowly rotating black hole cases. The dragging effects can generate the fourth adiabatic invariant on the particle motion approximately.

We study the dominant late-time behaviors of massive scalar fields in static and spherically symmetric spacetimes. Considering the field evolution in the far zone where the gravitational field is weak, we show under which conditions the massive field oscillates with an amplitude that decays slowly as t −5/6 at very late times, as previously found in (say) the Schwarzschild case. Our conclusion is that this long-lived oscillating tail is generally observed at timelike infinity in black hole spacetimes, while it may not be able to survive if the central object is a normal star. We also discuss that such a remarkable backscattering effect is absent for the field near the null cone at larger spatial distances.

A new phase of temporal evolution of the one-dimensional selfgravitating system is numerically discovered. Fractal structure is dynamically created from non-fractal initial conditions. Implication to astrophysics and mathematical physics is discussed.

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The Pd(0)-mediated rapid trapping of methyl iodide with an excess amount of a heteroaryl-substituted tributylstannane has been investigated with the aim of incorporating a short-lived (11)C-labelled methyl group into the heteroaromatic carbon frameworks of important organic compounds, such as drugs with various heteroaromatic structures, in order to execute a positron emission tomography (PET) study of vital systems. The reaction was first performed by using our previously developed CH(3)I/stannane/[Pd(2)(dba)(3)]/P(o-CH(3)C(6)H(4))(3)/CuCl/K(2)CO(3) (1:40:0.5:2:2:2) system in DMF at 60 degrees C for 5 min (conditions A), however, the reaction gave low yields for various heteroaromatic compounds. Increasing the amount of phosphine ligand (conditions B) led to a significant improvement in the yield, but the conditions were still not suitable for a range of basic heteroaromatic structures. Use of the CuBr/CsF system (conditions C) also provided a result similar to that obtained under conditions B with an increased amount of the phosphine. Thus, pyridine and related heteroaromatic compounds remained less reactive substrates. The problem was overcome by replacing the DMF solvent with N-methyl-2-pyrolidinone (NMP). The reaction in NMP at 60-100 degrees C for 5 min using a CH(3)I/stannane/[Pd(2)(dba)(3)]/P(o-CH(3)C(6)H(4))(3)/CuBr/CsF (1:40:0.5:16:2:5) combination (conditions D) gave the methylated products in yields of more than 80 % (based on the reaction of CH(3)I) for all of the heteroaromatic compounds listed in this study. Thus, the combined use of NMP and an increased amount of phosphine is important for promoting the reaction efficiently. The use of this general approach to rapid methylation has been well demonstrated by the synthesis of the PET tracers 2- and 3-[(11)C]methylpyridines by using [Pd(2)(dba)(3)]/P(o-CH(3)C(6)H(4))(3)/CuBr/CsF (1:16:2:5) in NMP at 60 degrees C for 5 min, which gives the desired products in HPLC analytical yields of 88 and 91 %, respectively.