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During the last solar cycle a number of observations of solar radio emissions were made in a wide frequency range from which an enormous amount of information has been obtained. However the results obtained so far are limited by rather poor angular resolution. Observations with much higher resolution (of the order of 1′ arc) have been required for further studies of solar radio emissions. At the present stage such observations have proceeded in the microwave range; also the radioheliograph at 80 MHz has just started at the Culgoora Observatory. At the Tokyo Astronomical Observatory a high-resolution study of radio bursts in the metre-wave range has been planned since 1960, and the construction of a new compound interferometer operating at 160.3 MHz was started in April 1967 at a new site, Nobeyama. This site, located about 150 km north-west of Tokyo, is surrounded by mountains and quite free from man-made interference. We shall give a brief description of this equipment; details will be published later.
Following an outbreak of vanA-positive Enterococcus faecium in 2005 in Kyoto prefecture, regional surveillance of vancomycin-resistant enterococci (VRE) was initiated. This revealed vanA- or vanB-positive Enterococcus gallinarum in multiple facilities. Eighty-eight vanA-positive E. gallinarum faecal carriers from 12 facilities and ten vanB-positive E. gallinarum faecal carriers from eight facilities were found. Pulsed-field gel electrophoresis profiles of the first isolate from each facility showed that 11 of the 12 vanA isolates and three of the eight vanB-positive E. gallinarum isolates belonged to a single clone. This study confirms the clonal spread of vanA- or vanB-positive E. gallinarum in a region and underlines the importance of surveillance of VRE for the presence of vancomycin resistance determinants.
In the present study, the development in vitro and in vivo of nuclear transfer (NT) embryos reconstructed with embryonic cells (blastomeres) at the 32- to 63-cell (sixth cell cycle) and 64- to 127-cell (seventh cell cycle) stages was investigated to determine the optimum range of embryonic cell cycles for yielding the highest number of identical calves in Japanese black cattle. Rates of development to the blastocyst stage (overall efficiency) were higher in the sixth cell-cycle stage (45%) than in the seventh cell-cycle stage (12%). After the transfer of the blastocysts reconstructed with blastomeres of the sixth and seventh cell cycle-stage embryos to recipient heifers, there were no differences in the pregnancy (14/35: 40% versus 3/13: 23%, respectively) or calving rates (11/39: 28% versus 3/13: 23%, respectively). These results indicate that the highest number of identical calves would be obtained by using sixth cell cycle (32- to 63-cell)-stage embryos as nuclear donors.
Electrical properties of the shallow thermal donors (TDs) in n-type
CZ-Si diodes by the electron irradiation were investigated. After
the electron irradiation, carrier concentration was decreased. From
deep level transient spectroscopy (DLTS) measurements, some peaks
related to TDs and vacancy-oxygen complexes were observed for the
irradiated samples. The peak related to V-O and/or A-center at
EC-0.18 eV increased with the electron fluence. To compare that,
the level of EC-0.09 eV related to TDs was independent of
electron fluence. In addition to that, reverse current of the diodes
was increased with increasing irradiated electron fluence.
A standard approach for structure solution of ordinary crystals begins with solving the phase problem. We show that a similar procedure can be taken even in the case of quasicrystals using single crystal X-ray diffraction by applying an ab initio structure determination method called the low density elimination method. The first picture of the occupation domains, which must be specified in a higher-dimensional structure determination of quasicrystals, is obtained from a phase-reconstructed density. We present six-dimensional densities determined by this method and give their interpretation for several different types of icosahedral quasicrystals.
Magnetism in the Zn-Mg-Ho icosahedral quasicrystal has been studied by neutron scattering. Powder samples of the icosahedral and related crystalline phases were reexamined to clarify the origin of the previously-reported long-range magnetic order [Charrier et al., Phys. Rev. Lett. 78 (1997) 4637]. The long range order was found to originate from the related crystalline phase, which is a contaminant in the previously-used samples. Whereas for high-quality icosahedral phase, we could detect only magnetic diffuse scattering. This apparently shows the absence of the long range order in the icosahedral phase. The diffuse scattering was studied in detail by using a single quasicrystalline sample. It was found that the diffuse scattering appears as satellites from intense nuclear Bragg reflections. This indicates that corresponding spin correlations can be regarded as developed between spins on the six-dimensional virtual hypercubic lattice. A magnetic modulation vector for the correlations is proposed.
A relationship between hexagonal phases in the Zn-Mg-RE (RE=rare earth) system and icosahedral quasicrystalline phase is discussed. There are three hexagonal phases in the vicinity of Zn6Mg3RE1 which are related with a lattice parameters by a ratio 3:5:7 but with approximately the same c parameters. A structural model for the phase with medium a lattice parameter is proposed based on the structures of the other two phases recently determined. We also show a preliminary result of X-ray diffraction study of the Zn-Mg-Ho icosahedral phase.
In this paper the unitary equivalence of unbounded
*-representations of *-algebras
is investigated. It is shown that if closed *-representations
π1 and π2 of a *-algebra
[Ascr ] satisfy a certain density condition for the intertwining spaces
[Jscr ](π1, π2) and
[Jscr ](π2, π1), then a *-isomorphism
Φ between the
O*-algebras π1([Ascr ]) and π2([Ascr ])
defined by Φ(π1(x))=π2(x),
x∈[Ascr ] and it induces a
*-isomorphism Φ¯, between the von Neumann algebras
and (π2([Ascr ])′w)′,
further if Φ¯, is spatial (that is, it is
unitarily implemented), then π1 and π2
are unitarily equivalent.
The surface microroughness of Si(100) wafers has been studied by FT-IR-ATR. The final wafer clean in an 0.1% HF + 1% H2O2 aqueous solution significantly improves the hydrogenterminated surface morphology as demonstrated by a sharp SiH2 stretching vibration peak accompanied with the weak SiH and SiH3 peaks. The ultra-thin gate oxide grown on such surface exhibits nearly ideal tunneling current transport. The cleaning in 4.5% HF reduces the SiH2 peak height and enhances SiH3, making the surface rough. Nevertheless, the tunneling characteristics are hardly influenced with such spectral change.
HF-treated Si surfaces and the oxidation kinetics in pure water or in clean room air have systematically been studied by x-ray photoelectron spectroscopy (XPS). The oxidation of heavily-doped n-type Si appears to proceed parallel to the surface, resulting in the layer-by-layer oxidation. The oxide growth rate in pure water for heavily-doped n-type Si is significantly higher than that of heavily-doped ptype Si. This is explained by the electron tunneling from the Si conduction band to adsorbed O2 molecules to form the O2 state. O2 ions easily decompose and induce a surface electric field, enhancing the oxidation rate. The growth rate of native oxide on heavily-doped n-type Si is less sensitive to the crystallographic orientations than the case of lightly doped Si where the steric hindrance against oxygen molecules significantly lowers the oxidation rate of the (110) and (111) surfaces. We suggest that the decomposed oxygen can penetrate into Si without steric hindrance. It is also found that the oxidation of heavily-doped n-type Si in pure water is effectively suppressed by adding a small amount (10 ∼ 3600 ppm) of HCI.
Chemical bonding features and suboxide compositions in native oxide grown on chemically-cleaned hydrogen-terminated Si(100) surfaces stored in pure water have been studied by using surface sensitive infrared spectroscopy and x-ray photoelectron spectroscopy. The LO phonon peak for the native oxide is located at 1210cm−1, which is shifted to a significantly lower wavenumber side than the ultrathin thermal oxide peak at 1250cm−1. This is because an appreciable amount of SiHx bonds are incorporated in the native oxide/Si interface and such hydrogen termination in the network dramatically reduces strained bonds in the interface. Very weak Si2+ suboxide signal from the oxide grown in pure water is also explained by the incorporated SiHx bonds which interrupt the Si2+ suboxide formation in the interface.
Growth kinetics of native oxide on HF-treated Si surfaces terminated with Si-H bonds has been studied by angle-resolved x-ray photoelectron spectroscopy. The oxide growth rate in pure water for an n+ Si(100) surface is significantly high compared to that of p+, and the n or p type Si oxidation rate is in between. This is explained by the formation of ions through electron transfer from Si to adsorbed O2 molecules and the resulting enhancement of the oxidation rate. The oxide growth on Si(100) is faster than (110) and (111) as interpreted in terms of the steric hindrance for molecular oxygen adsorption on the hydrogen terminated silicon 1×1 surface structures.