Single generator problem

Using the Stone-\v{C}ech compactification of integers, we introduce a free extension of an almost periodic flow. Together with some properties of outer functions, we see that, in a certain class of ergodic Hardy spaces , , the corresponding subspaces are all singly generated. This shows the existence of maximal weak- Dirichlet algebras, different from of the disc, for which the single generator problem is settled.

     

Simultaneous Measurement of Individual ATPase and Mechanical Reactions by a Single Myosin Molecule at Work

Based on techniques for single molecule imaging and nanomanipulation by optical tweezers, we have developed a new technique that allows simultaneous measurement of individual ATPase and mechanical reactions from a single myosin molecule during force generation. We show how the ATPase reaction couples to the mechanical reaction directly at the single molecule level. The results show that the myosin head can produce force even after releasing the bound nucleotide, probably ADP, suggesting that the chemical energy driven by ATP hydrolysis can be hysteretically stored in the myosin molecule. This view does not support a widely accepted hypothesis in which the force generation is tightly coupled to ligand dissociation.This paper was originally presented as an invited paper at the seventh Meeting on Near Field Optics, which was held on July 1, 1998 at Nagoya University, Nagoya, organized by the Research Group on Near Field Optics of the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics.     

Photoemission study of Ag nanofilm grown on pseudomorphic fcc Fe(1 0 0)

An angle-resolved photoemission study for Ag nanofilm grown on pseudomorphic metastable-fcc-phase Fe(1 0 0) has been done in order to investigate in detail the quantized electronic structures. From the low-energy electron-diffraction and angle-resolved photoemission spectra, it is found that the present Ag nanofilms were grown in the direction of [1 1 1] on pseudomorphic fcc Fe(1 0 0) substrates. The angle-resolved photoemission spectra of Ag nanofilms grown on pseudomorphic fcc Fe(1 0 0) exhibit the features derived from Shockley-type surface state and additional fine-structures derived from the quantized state of Ag sp valence electron. The experimental nanofilm-thickness dependence of binding energies of these quantized states is compared with the theoretical calculation based on the phase accumulation model, taking into account the phase shifts of electron reflection at both interfaces of the Ag nanofilm. From these results, we discuss the quantized electronic structure in Ag nanofilm grown on pseudomorphic fcc Fe(1 0 0).     

Mössbauer study on a two-dimensional triangular antiferromagnet YFeMnO4

Magnetic ordering of YFeMnO₄ has been studied with Mössbauer spectroscopy in the temperature range between 4.2 K and 300 K on the conditions of gamma rays parallel to and perpendicular to thec-axis. It is revealed that the spin system orders like a Heisenberg spin system in a triangular antiferromagnet with an anisotropic axis parallel to thec-axis.     

Phase behavior and fluid-solid surface tension of argon in slit pores and carbon nanotubes

Phase behaviors of argon in several types of cylindrical and slit pores are examined by grand-canonical Monte Carlo simulations. Condensation processes in single- and multi-walled carbon nanotubes along with those in hard-wall tubes are compared. Effects of the pore size on pressure-tensor components, the fluid-wall surface tension, and the adsorption are also compared for the different fluid-pore interactions. The chemical potential at which the fluid begins to condense in the single-walled nanotube is greater than that in the multi-walled nanotube by an amount nearly equal to the difference in the potential-well depth of the fluid-pore interaction, and the adsorption isotherms overlap each other almost completely for narrow pores and partially for wider pores. Similar analyses are performed for slit pores of two different hydrocarbon models.     

Isomer-selected photoreactions of gas-phase cluster ions

We have developed an apparatus for investigating isomer-selected photodissociation reactions by ion mobility spectrometry coupled with time-of-flight mass spectrometry. By using this apparatus we optimized ion intensities under isomer-separation condition for carbon cluster ions. Among ions having linear and cyclic isomers, we demonstrated dissociation of isomer-selected C₉ ⁺ ion at 355-nm photon irradiation. As a result we observed marked difference in the dissociation pathways between from linear isomer and from cyclic isomer. For the purpose of adopting this technique to metal-ligand cluster ions, we also investigated mobility spectrometry of vanadium metal ions with Ar, in addition to electronic state separation for free atomic ions.