Biomedical subjects

Kenji Tamasaku

Publications and source records attributed to Kenji Tamasaku.

9 recordsLinked to original sources

PubMed2006

Nearly perfect large-area quartz: 4 meV resolution for 10 keV photons over 10 cm(2).

The perfection of two commercial top-grade quartz crystal wafers has been investigated using Bragg reflection at theta(B)=89.77 degrees of a 2.0 meV bandwidth beam of 9.979 keV X-rays by the (7\bar4\bar34) lattice planes. Topographic images show small defect concentrations (<or=5 cm(-2)). Energy scan widths are below 3 meV over 8 mm x 8 mm areas and 4 meV over the whole wafer ( approximately 11 cm(2)). This suggests that quartz can be a useful optical material.

Journal Article↗

PubMed2005

Wave-optical evaluation of interference fringes and wavefront phase in a hard-x-ray beam totally reflected by mirror optics.

The intensity flatness and wavefront shape in a coherent hard-x-ray beam totally reflected by flat mirrors that have surface bumps modeled by Gaussian functions were investigated by use of a wave-optical simulation code. Simulated results revealed the necessity for peak-to-valley height accuracy of better than 1 nm at a lateral resolution near 0.1 mm to remove high-contrast interference fringes and appreciable wavefront phase errors. Three mirrors that had different surface qualities were tested at the 1 km-long beam line at the SPring-8/Japan Synchrotron Radiation Research Institute. Interference fringes faded when the surface figure was corrected below the subnanometer level to a spatial resolution close to 0.1 mm, as indicated by the simulated results.

Journal Article↗

PubMed2005

On a phase problem of high-resolution Fourier transform X-ray spectroscopy.

A phase problem is discussed for high-resolution Fourier transform X-ray spectroscopy where the phase of the interferogram is missing. A numerical iterative method and an analytic logarithmic Hilbert transform method were tested for recovery of the missing phase information from the modulus of the interferogram. These methods were applied to measured data of the Si 14 6 0 back reflection and a calculated interferogram from an X-ray Fabry-Perot interferometer. The iterative method experienced an ambiguity of reconstruction; however, the ambiguity was relatively small and may be acceptable. The logarithmic Hilbert transform method gave a poorer reconstruction for the measured data owing to a lower signal-to-noise ratio, whereas it recovered the original spectrum from the calculated data without noise.

Artifacts↗

PubMed2005

Element array by scanning X-ray fluorescence microscopy after cis-diamminedichloro-platinum(II) treatment.

Minerals are important for cellular functions, such as transcription and enzyme activity, and are also involved in the metabolism of anticancer chemotherapeutic compounds. Profiling of intracellular elements in individual cells could help in understanding the mechanism of drug resistance in tumors and possibly provide a new strategy of anticancer chemotherapy. Using a recently developed technique of scanning X-ray fluorescence microscopy (SXFM), we analyzed intracellular elements after treatment with cis-diamminedichloro-platinum(II) (CDDP), a platinum-based anticancer agent. The images obtained by SXFM (element array) revealed that the average Pt content of CDDP-resistant cells was 2.6 times less than that of sensitive cells, and the zinc content was inversely correlated with the intracellular Pt content. Data suggested that Zn-related detoxification is responsible for resistance to CDDP. Of Zn-related excretion factors, glutathione was highly correlated with the amount of Zn. The combined treatment of CDDP and a Zn(II) chelator resulted in the incorporation of thrice more Pt with the concomitant down-regulation of glutathione. We propose that the generation of an element array by SXFM opens up new avenues in cancer biology and treatment.

Antineoplastic Agents↗

PubMed2004

Valence transition of YbInCu4 observed in hard X-ray photoemission spectra.

Yb 3d and valence-band photoemission spectra of the first-order valence-transition compound YbInCu4 have been measured with hard x ray at an excitation energy of 5.95 keV. Abrupt changes are clearly observed in both spectra around the transition temperature T(V)=42 K, in comparison with ultraviolet and soft x-ray photoemission (VUV-PES and SX-PES) spectra. From the Yb 3d spectra, the Yb valence has been estimated to be approximately 2.90 from 220 down to 50 K and approximately 2.74 at 30-10 K. We propose that Yb 3d hard x-ray photoemission spectroscopy is a very powerful method to estimate the valence of Yb with high accuracy. On the other hand, the Yb2+ 4f-derived peaks in the valence-band spectra exhibit a remarkable enhancement below T(V). The shape of the valence-band spectra is different from those of the VUV-PES and SX-PES spectra above T(V), reflecting the In 5s and 5p contributions.

Journal Article↗

PubMed2004

An X-ray BBB Michelson interferometer.

A new X-ray Michelson interferometer based on the BBB interferometer of Bonse and Hart and designed for X-rays of wavelength approximately 1 A was described in a previous paper. Here, a further test carried out at the SPring-8 1 km beamline BL29XUL is reported. One of the BBB's mirrors was displaced by a piezo to introduce the required path-length difference. The resulting variation of intensity with piezo voltage as measured by an avalanche photodiode could be ascribed to the phase variation resulting from the path-length change, with a small additional contribution from the change of the position of the lattice planes of the front mirror relative to the rest of the crystal. This 'Michelson fringe' interpretation is supported by the observed steady movement across the output beam of the interference fringes produced by a refractive wedge when the piezo voltage was ramped. The front-mirror displacement required for one complete fringe at the given wavelength is only 0.675 A; therefore, a quiet environment is vital for operating this device, as previous experiments have shown.

Journal Article↗

PubMed2004

Image quality improvement in a hard X-ray projection microscope using total reflection mirror optics.

A new figure correction method has been applied in order to fabricate an elliptical mirror to realize a one-dimensionally diverging X-ray beam having high image quality. Mutual relations between figure errors and intensity uniformities of diverging X-ray beams have also been investigated using a wave-optical simulator and indicate that figure errors in relatively short spatial wavelength ranges lead to high-contrast interference fringes. By using a microstitching interferometer and elastic emission machining, figure correction of an elliptical mirror with a lateral resolution close to 0.1 mm was carried out. A one-dimensional diverging X-ray obtained using the fabricated mirror was observed at SPring-8 and evaluated to have a sufficiently flat intensity distribution.

Equipment Design↗

PubMed2002

Nearly diffraction-limited line focusing of a hard-X-ray beam with an elliptically figured mirror.

An elliptical mirror for X-ray microfocusing was manufactured using the new fabrication methods of elastic emission machining and plasma chemical vaporization machining. Surface profiles measured using stitching interferometry showed a maximum deviation around the ideal figure of 7 nm peak-to-valley. The mirror showed nearly diffraction-limited focusing performance, with a 200 nm line width at the focus. Wave-optical calculations, taking the measured surface profile into consideration, reproduced well the measured focusing properties both at and around the beam waist.

Journal Article↗

PubMed2002

The Goos-Hänchen effect at Bragg diffraction.

The strong incident-angle dependence of the phase of complex reflectivity causes a shift of the reflected beam from the geometrically expected path. This effect, known as the Goos-Hänchen effect in the visible region, was observed for Bragg-case diffraction in the hard X-ray region. The shift was found to be in good agreement with the theory.

Journal Article↗