Kaoru Mizuno

Selective expansion of CD16highCCR2- subpopulation of circulating monocytes with preferential production of haem oxygenase (HO)-1 in response to acute inflammation

Monocytes are composed of two distinct subpopulations in the peripheral blood as determined by their surface antigen expressions, profiles of cytokine production and functional roles played in vivo. We attempted to delineate the unique functional roles played by a minor CD16highCCR2– subpopulation of circulating monocytes. They produced significant levels of interleukin (IL)‐6 and tumour necrosis factor (TNF)‐α, but very low levels of IL‐10 upon in vitro stimulation. Characteristic profiles of cytokine production were confirmed by stimulating purified subpopulations of monocytes after cell sorting. It was noteworthy that freshly isolated CD16highCCR2– monocyte subpopulations produced significant levels of haem oxygenase (HO)‐1, whereas the major CD16lowCCR2+ subpopulation produced little. These results were contrary to the generally accepted notion that the CD16highCCR2– monocyte subpopulation plays a predominantly proinflammatory role in vivo. The CD16highCCR2– subpopulation increased in Kawasaki disease and influenza virus infection. In accord with this, HO‐1 mRNA expression by mononuclear cells was significantly increased in these illnesses. These results indicate that CD16highCCR2– subpopulations are of a distinct lineage from CD16lowCCR2+ monocytes. More importantly, they may represent a monocyte subpopulation with a unique functional role to regulate inflammation by producing HO‐1 in steady state in vivo.

Effect of hydrogen on the formation of interstitial loops in hydrogen-irradiated aluminum

Abstract The role of hydrogen atoms in the formation of interstitial type dislocation loops in aluminum irradiated with 15 keV hydrogen ions was investigated by electron microscopy. It was found that the loop density satisfied and Arrhenius relation with the pre-irradiation temperature, yielding an apparent activation energy of about 0.3 eV. Experimental results are interpreted in terms of the mechanism that small hydrogen-vacancy complexes formed by the pre-irradiation of hydrogen ions act as nucleation sites of dislocation loops in the subsequent electron irradiation. A basically identical mechanism seems to be acting in the irradiation with hydrogen ions at room temperature.

Vacancy Source in Nearly Perfect Crystals

Vacancy generation process in nearly perfect aluminum single crystals was investigated by X-ray diffraction topography technique of Lang. A lot of small black dots were observed in the topograph taken after the temperature rise from room temperature to 200°C, and these dots are confirmed to be small interstitial type dislocation loops. It was concluded that the thermal generation process of vacancies in nearly perfect crystals consists of the following two steps. Small interstitial clusters are formed in the perfect lattice first, and then these grow to interstitial type dislocation loops emitting vacancies into lattice.

In-situ observation of the migration and growth of helium bubbles in aluminum

Abstract Brownian motion of helium bubbles, their disappearance, and coalescence in high purity aluminum were demonstrated in real time by electron microscopy and the recording of these whole processes on VTR. It was experimentally established for the first time that the mean square of the migration distance of the bubble during the time duration, t , is proportional to t at least for t ≥ 1 min. The growth of the bubble was caused by the coalescence between bubbles during Brownian motion and also by annealing at higher temperature unless the coalescence takes place. A dependence of the diffusivity of the bubble on its diameter and a rapid formation of new bubble by the coalescence of two bubbles seem to be supported through the surface diffusion of aluminum on the bubble surface.

Antiphase Domain Structure in Gd75Sc25 Single-Crystal Alloys

Magnetization, low field ac susceptibility, electrical resistivity, ultrasonic attenuation and specific heat have been measured for Gd75Sc25 single crystals. Low field ac susceptibility curves for the c-axis sample exhibit a sharp peak at the highest ordering temperature Tc (= 187 K) and a drop between Tc and T2 (= 126 K), which suggest the existence of an antiphase domain ferrimagnetic structure. A similar conclusion has been reached from the results of electrical resistivity, elastic property and specific heat measurements.

Observation of Dislocation Lines in a Transistor by Electron-Acoustic Microscopy

Electron acoustic images, EAIs, by electron-acoustic microscopy were studied by in situ observation at the same area of a Si transistor-chip Tr-chip under several bias conditions applied between the collector and the emitter. The results confirmed that the EAI contrast varies depending not only on the difference in the materials and the flatness of the surface but also on the bias conditions. Dislocation lines were clearly observed at the base region of the Tr-chip and were induced by the thermal diffusion process of the base layer production. However, dislocation lines were not observed from the structually same emitter region.

Investigation of Surface Damage in Si Exposed to Ar Plasma by Spectroscopic Ellipsometry and Grazing X-Ray Diffraction

Low-damage processes in plasma-surface interactions, particularly lattice deformation and the degree of damage in a single-crystal Si surface exposed to Ar plasma, are investigated by spectroscopic ellipsometry (SE) and grazing X-ray diffraction. The dielectric function spectrum of the damaged Si layer in nano-depth is obtained by use of damage depth estimated by a method based on SE model analysis and confirmed by step etching combined with SE measurement. The third-derivative lineshape of the imaginary part e2 of the complex-dielectric function provides the damage dependences of interband transition energy and broadening parameter for the E1 (Λ3→Λ1) optical interband transition. The result shows that the surface damage proceeds through lattice expansion and relaxation. The lattice deformation in the damaged surface is also investigated by grazing X-ray diffraction. The X-ray rocking curve around (422)Si is asymmetric and involves small subsidiary curves corresponding to the lattice expansion and relaxation. These observations are in good agreement with the lattice deformation process obtained from the SE analysis.

Vacancy-type dislocation loops observed at fairly high temperatures in nearly perfect Al crystals

Vacancy-type dislocation loops appeared at 230°C even during a slow-cooling process from 300°C in nearly perfect aluminum crystals when examined by synchrotron radiation topography with white radiation. The temperature of the specimen was cyclicly varied between 300 and 230°C at a cooling rate of 2000°C/h and a heating rate of 1000°C/h. Almost all of these vacancy loops appeared at the same place at each repetition of the cooling process, and some of the loops were formed along the dislocation lines observed in the preceding stage. Formation of these loops cannot be explained by homogeneous nucleation theory. Therefore, it is concluded that the vacancy loops grown at fairly high temperatures were nucleated heterogeneously, and the nucleation site appears to be inclusions in the specimen. Almost all vacancy loops that remained in a nearly perfect aluminum crystal are formed by heterogeneous nucleation during the cooling process.

Conversion of hydrogen bubbles to disk-shaped defects in hydrogen irradiated aluminum

Abstract Electron microscopy was carried out on hydrogen bubbles in high purity aluminum. It was found for the first time that small hydrogen bubbles formed by irradiation with 15 keV hydrogen ions at 423 K converted to disk-shaped defects by annealing at higher temperature, depending on the initial concentration of bubbles. The many beam lattice image of the defects suggested that they mostly lay over multiple layers of (111) planes, containing characteristic distortions of the lattice on (111) planes. The formation of the disk-shaped defects is interpreted in terms of small hydrogen bubble coalescence during a random migration and collapse on (111) planes, losing their internal pressure, which may be allowed by the formation of aluminum hydride at high temperature.

Anisotropy of Superconducting Energy Gap in Aluminium Determined by Ultrasonic Method

The attenuation of 10 MHz ultrasound in aluminum has been measured by the pulse reflection method at temperatures between 0.4 and 1.2 K. Three cylindrical single-crystal specimens of high purity and perfection, having 99.9999% of purity and low density of dislocations, were used and their crystallographic orientations were [100], [110] and [111]. The temperature dependence of attenuation in the superconducting state was analyzed on the basis of the BCS theory, and the apparent superconducting energy gap was determined for the above three sound propagation directions. By using these results, the energy gap anisotropy in the electronic k -space was derived. The gap value ranged between 3.56 and 3.14 in units of (1/2) k B T c . The gap was largest for the [100] direction, somewhat smaller for the [110] direction, and especially small for the [111] direction. These conclusions were in agreement with existing experimental and theoretical results.