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Notes: A monoenergetic positron beam has been used to investigate the state of interstitial oxygen in Czochralski-grown Si with coverage of SiO2 (100 nm) and poly-Si (200 nm)/SiO2 (100 nm), respectively. It was found that (i) the growth of SiO2 gives rise to a strong Doppler broadening of positrons in the bulk of Si and (ii) such a broadening can be recovered to the original level by annealing at 450 °C, by the removal of overlayers using chemical etching and by long-term aging at room temperature. This broadening was assigned to arise from the positron trapping by oxygen interstitial clusters. It was concluded that film stress is responsible for the rearrangement of oxygen atoms in Czochralski-grown Si.

Notes: Presented are the detailed characteristics of a laser-plasma x-ray source that is successfully used for producing x-ray images of biological specimens in water by contact microscopy. The conversion efficiencies of laser energy to soft x rays are measured for various target materials using a 0.53 μm, 500 ps laser pulse. Yttrium target showed the highest conversion efficiency of around 2.5%/sr to the "water window'' region x rays at 3×1012 W/cm2. Angular distributions of x rays and ions are studied to find the best angular position of specimen for reducing the target debris. The effective x-ray spectrum contributing to making an image of a specimen in water is discussed. It is shown that an extremely small laser could be employed in high-resolution contact microscopy.

Notes: The magnetic anisotropy in Ni films deposited on Pyrex glass substrates by different sputtering methods, i.e., ion beam sputtering (IBS), triode rf sputtering, and diode rf sputtering, was studied in relation to the internal stress in the films. Strong in-plane easy magnetic anisotropy (Ku=−4.9×105 erg/cm3) was observed in IBS Ni films. The average in-plane stress in the IBS film was estimated from the radius of convex curvature of the disk substrate as large as −1.2×1010 dyn/cm2 (a negative sign implies the compressive stress), which is due to the atomic peening effect by kinetic incident atoms during deposition. The stress-induced magnetic anisotropy is calculated to be about −1.2×106 erg/cm3, which is overwhelming to the observed magnetic anisotropy in the IBS Ni film. Positive Ku and tensile internal stress, one or two order of magnitude smaller in absolute values than that in IBS film, were observed in Ni films prepared by the other sputtering methods.

Notes: It has been an earnest desire of protein crystallographers to collect fast, accurate, high resolution diffraction data from protein crystals, preferably with exposure time as short as possible. In order to meet this challenge, a new type of Weissenberg camera has been developed for the recording of diffraction intensity from protein crystals using synchrotron radiation. The BL6A2 line has a plane-bending mirror designed by Y. Sato. The optical bench with triangular tilt-cut Si crystal monochromator was designed by N. Kamiya and was installed in the BL6A2 hutch. The Weissenberg camera was set on the 2θ arm of the optical bench. This camera can be used with Fuji Imaging Plate (IP) as an x-ray detector, and the reading out of the image from the IP is carried out by using BA100. The characterization of this system was carried out using the native crystal of chicken gizzard G-actin DNase I complex and its Yb3+, PCMB, indium, and FMA derivatives. Since these crystals are very sensitive for x rays, the resolution limit of the diffraction was 5 A(ring) with a 4-circle diffractometer on a rotating anode x-ray generator (N. Sakabe et al., J. Biochem. 95, 887. This complex was crystallized in space group P2,2,2, with a=42.0, b=225.3, and c=77.4 A(ring). The data were collected with this system with the 430-mm radius cassette when Photon Factory was operated at 2.5 GeV and 270 mA and the wavelength λ=1.004 A(ring) was chosen. In order to avoid overlapping of diffraction spots, oscillation angle range and coupling constant (degree/mm) were settled on the basis of simulation patterns of diffraction spots up to the maximum resolution to be measured considering the direction of the crystal axes, wavelength, radius of the camera, and mosaicness of the crystal. When the oscillation axis was a axis, the oscillation angle range was selected at either 10° (1°/mm) or 5° (0.5°/mm) depending on the density of reciprocal lattice points along the incident beam, and typical exposure time in each IP was 50 and 25 s, respectively. The exposure was stopped after 10 times oscillation. The total range of 117.5° was recorded on 16 sheets of IP with an overlapping range 0.5°.The data processing was carried out using program weis coded by T. Higashi. Two complete data sets along the a and c axes were collected using two crystals, independently, and the merge R(F2) for native crystal was 0.068. In order to know the feasibility of the data (F+−F−), Patterson maps were calculated with data of each derivative, and heavy atom vectors clearly appeared as prominent peaks in the Harker sections of the Patterson maps of both Yb3+ and PCMB derivatives. The heavy atom positions were obtained from the combinations of different Patterson and different Fourier maps, and were refined by using least-squares techniques. The final figure of merit up to 2.5 A(ring) resolution was 0.61 with 22 700 reflections. The assignment of DNase I part on the electron density maps is progressing using the Nicholson molecular model referring to its structure reported by C. Oefner and D. Suck [J. Mol. Biol. 192, 605 (1986)]. In addition to promising results of ω-aminoacid pyruvate aminotransferase [N. Watanabe et al., Book of abstracts of second Japan-China Bilateral Symposium on Biophysics, p. 83 (1988)], these results support that this data collection system consisting of a new type of Weissenberg camera using SR, Fuji Imaging Plate, BA100, and program weis is one of the fastest and most accurate systems for protein crystallography in use today. We thank the Education Ministry and the Foundations of Yamada, Naito and Toray for the financial support of this project. We are grateful to Dr. K. Namba of ERATO for our use of BA100.

Notes: The lattice distortion and the transmuted-Ge related luminescence in neutron-transmutation-doped (NTD) GaN are studied by combining Rutherford backscattering spectroscopy/channeling, Raman scattering, and photoluminescence methods. The lattice displacement of Ga atoms of ∼0.12 Å from the 〈0001〉 row is estimated from the normalized angular yield profiles, preserving the single crystallinity in as-irradiated GaN with a minimum yield (χmin) of 7%. A 2.84 eV emission band observed in 600 °C annealed NTD-GaN is associated with the Ga interstitial, supporting the lattice distortion. Two emission bands at 2.90 eV and 2.25 eV observed in 1000 °C annealed NTD-GaN are assigned to a negatively charged DX-like center of Ge at Ga site and a complex defect attributed to Ge at Ga site and Ga vacancy, respectively. © 2002 American Institute of Physics.

Notes: α-GaN phase (wurtzite) was synthesized in GaP(100) by 140-keV N2+ ion implantation with a dose of 3.0×1017 cm−2 at 400 °C and subsequent furnace annealing at 950 °C for 20 min or rapid thermal annealing at 1000 °C for 15 s. The traces of α-GaN were recognized by glancing-angle x-ray diffraction, supporting by the observation of the planes belonging to the [0100]-zone axis in α-GaN by a selected-area electron diffraction analysis. The formation of microcrystalline GaN of 〈1000 Å in size was confirmed by using Auger electron spectroscopy and cross sectional transmission electron microscopy. A1 transverse optical phonon mode in α-GaN was observed at around 525 cm−1, indicating a nearly orientation relationship with GaN〈112¯0〉//GaP〈100〉. © 2001 American Institute of Physics.

Notes: Aims : Cyclin D1 is a target molecule transcriptionally activated by aberrant β-catenin in Wnt signalling. Thyroid papillary microcarcinoma (PMC) may be considered a precursor of papillary thyroid cancer (PTC). Ki67 is widely used as a proliferation marker. The aim of this study was to determine whether cyclin D1 overexpression is involved in early thyroid carcinogenesis.Methods and results : Thirty-five cases of PMC were examined immunohistochemically, including 11 cases less than 5 mm (PMC 〈 5) and 24 cases more than 5 mm (PMC 〉 5), and 18 PTC cases (size 11–15 mm). Cyclin D1 expression was significantly lower in PMC 〈 5 than in PMC 〉 5, while there was no significant difference between PMC 〉 5 and PTC. Statistical analysis revealed significant correlations between cyclin D1 labelling index (LI) and Ki67 LI (P = 0.0272)/cytoplasmic β-catenin expression (P 〈 0.001) in PMC and PTC. Four of five PMC 〉 5 cases with lymph node (LN) metastases displayed a high cyclin D1 LI and strong cytoplasmic β-catenin expression.Conclusions : Cyclin D1 overexpression and correlation with aberrant β-catenin expression were demonstrated in PMC. Cyclin D1 expression was significantly associated with tumour size and LN metastases in PMC. Cyclin D1 may be up-regulated at an early stage of thyroid carcinogenesis and promote tumour growth and metastatic potency in PMC through activation of the Wnt/β-catenin pathway.