Biomedical subjects

Yoshio Matsui

Publications and source records attributed to Yoshio Matsui.

5 recordsLinked to original sources

PubMed2003

Practical procedure for coma-free alignment using caustic figure.

The practical procedure for coma-free alignment using a single defocused transmission electron microscopy (TEM) image is presented. Caustic figures observed in the defocused TEM image of a focused probe are utilized. Coma-free alignment can be carried out by coinciding a bright-field spot with the center of a caustic curve as observed in an underfocus TEM image. With this method, beam tilt misalignment is reduced to the sub-mrad order (e.g. 0.3mrad for 300kV FEG-TEM). This can be done without intentional beam tilting, an amorphous specimen, high-resolution TEM images, or fast Fourier transform for diffractogram or cross-correlation, which are used in previous methods. Residual coma aberration is detected using the multiple Bragg images of a known crystal. Similarity between the present coma-free alignment and well-known STEM alignment using shadow image is discussed.

Journal Article↗

PubMed2003

Experimental investigation of phase contrast formed by inelastically scattered electrons.

Phase contrast formed by inelastically scattered electrons in a crystal has been investigated using spatially resolved EELS, which enables simultaneous observation of lattice fringes formed by electrons of various energy losses. Lattice fringes produced by low-loss electrons overlap on an elastic TEM image like Fourier images. This means that the exit wave is preserved in low-loss scattering. Similar Fourier images occur for electrons suffering core-losses in the range 50-400 eV, which indicates delocalization and spatial coherence in those core-loss scattering events. The spatial coherence of inelastically scattered electrons is estimated from the focus dependence of energy-filtered lattice fringe contrast. Spatial coherence widths shorten with increasing energy-loss, and their energy-loss dependence is similar to diffraction errors derived from the characteristic angle for inelastic scattering.

Journal Article↗

PubMed2003

The study of Al-L23 ELNES with resolution-enhancement software and first-principles calculation.

Resolution-enhancement software and first-principles calculation for electron energy-loss spectroscopy (EELS) were applied for the study of aluminium (Al) coordination in alumina. Al-L23 energy-loss near-edge structures (ELNES) of alpha- and gamma-aluminas were observed using a field-emission transmission electron microscope and advanced software for EELS. The inherent energy resolution of a cold field-emission gun (FEG) of approximately 0.3 eV was realized using drift-correction software. The energy spread of the cold FEG was deconvoluted by means of maximum-entropy or Richardson-Lucy algorithms and the energy resolution of the deconvoluted spectrum became comparable with that obtained using a monochromator, whose energy resolution was < 0.2 eV. Fine structures in Al L23-edge were observed, such as 0.5 eV splitting between L3 and L2 peaks in alpha-alumina (i.e. spin-orbit splitting). The difference in Al coordination was clearly observed in Al-L23 ELNES and the major structures near the threshold were assigned using first-principles calculations.

Journal Article↗

PubMed2002

Nanoparticles of amorphous ruthenium sulfide easily obtainable from a TiO2-supported hexanuclear cluster complex [Ru6C(CO)16]2-: a highly active catalyst for the reduction of SO2 with H2.

TiO(2)-supported ruthenium-metal particles were derived from an anionic hexanuclear carbido carbonyl cluster [Ru(6)C(CO)(16)](2-) and compared with those prepared conventionally by impregnation of TiO(2) with a solution of RuCl(3) followed by reduction with H(2). The average sizes of the metal particles in both systems are similar, that is, 12 A for molecular cluster-derived particles and 15 A for those derived from the RuCl(3) precursor, although the size distribution is sharper in the former case. These supported particles efficiently promote the reduction of SO(2) with H(2) to give elemental sulfur. Their active form is ruthenium sulfide as confirmed by EXAFS and X-ray diffraction measurements. The nanoscale ruthenium sulfide particles, which originated from the cluster complex, have an amorphous character and show activity even at low temperature (463 K), whereas ruthenium sulfide formed from RuCl(3)-derived metal dispersion is a pyrite-type RuS(2) crystallite and needs a temperature above 513 K to effect the same catalysis. Amorphous ruthenium sulfide maintains its nano-sized scale (approximately 14 A) regardless of the reaction temperature, while RuS(2) crystallite aggregates to form larger nonuniform particles.

Catalysis↗

PubMed2002

Observation of magnetic domain structure in phase-separated manganites by lorentz electron microscopy.

Magnetic domain structure in manganites was investigated by Lorentz electron microscopy, in order to understand some unusual physical properties, such as a colossal magnetoresistance (CMR) effect and a metal-to-insulator (MI) transition. In particular, we examined the spatial distribution of the charge/orbital ordered (CO/OO) insulator state and the ferromagnetic (FM) metallic state in phase-separated manganites, (La5/8-xPrx)Ca3/8MnO3 for x = 0.375, by obtaining both the dark-field and Lorentz images. We found an unusual coexistence of the CO/OO and FM metallic states with micrometer size below a MI transition temperature of 60 K. Our experimental findings provide direct evidence of the phase separation found in CMR manganites.

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