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Alkali-earth-doped yttrium orthoaluminate crystals grown in a reducing atmosphere are found to show bright photoluminescence (PL) in visible wavelength regions under the excitation by UV light source. From the results of transmission, PL, PL excitation and time-resolved PL spectra for the samples with different types and concentrations of dopants and the comparison to the results for the samples grown under different conditions, the origin of principal emission is determined to be color centers stabilized by heterovalent ions. The observed fast lifetime and high quantum yield of the luminescence can be explained by dipole-allowed transition between the levels localized in a vacancy. Comparing the effects on the optical properties from several types of dopant ions and taking influence from the UV irradiation into account, a model for the structure of emission centers is proposed.

In adult human beings, remodeling creates nearly all of new bone tissue. However, Frost hypothesized that modeling can go on in trabeculae throughout life. As this hypothesis has not been verified, we looked for histologic evidence of trabecular modeling (minimodeling) during bone histomorphometry of transiliac bone biopsy specimens obtained from 34 patients (age range, 38-81 years; mean age, 58.4 years; female, 31/34) at the time of total hip arthroplasty. Before the bone biopsy study, we performed quantitative bone scintigraphy of bilateral hip joints and bilateral iliac crests in 10 other patients with unilateral hip disease and confirmed that the bone biopsy site was not affected by ipsilateral hip joint disease. Patients who had metabolic bone diseases or who had taken medications known to affect bone metabolism were excluded from the study. During modeling where bone formation and bone resorption are not coupled, bone formation can occur on quiescent bone surfaces without preceding bone resorption and create smooth cement lines. Therefore, the combination of fluorochrome labeling and a smooth cement line without interruption of surrounding collagen fibers was regarded as evidence of minimodeling. Histologic evidence of minimodeling was detected in 21 of the entire 34 specimens (62%) and 17 of 27 specimens obtained from postmenopausal patients (63%). Bone volume of minimodeling sites was less than 1% of the trabecular bone volume, and these sites accounted for less than 2% of the entire bone surface on average. However, osteoid volume of minimodeling sites comprised approximately one-tenth of the entire osteoid volume, and their labeled surface constituted one-fourth to half of the entire labeled surface on average. Therefore, when performing bone histomorphometry of adult cancellous bone, minimodeling should be taken into account when dealing with parameters related to osteoid volume and mineralization. A comparison of specimens with and without minimodeling demonstrated that the presence of minimodeling was correlated with smaller physique of patients, accelerated mineralization (as indicated by the higher mean MS/BS and MAR values and the shorter mean Omt), and higher metabolic turn-over of bone (as indicated by the higher mean BFR/BV value). Although the findings still need to be verified in a larger number of normal subjects without hip joint disease, they support Frost's hypothesis that minimodeling can continue throughout human life.

C H dissociation is known to be responsible for the formation of radiation damage of hydrocarbon crystals such as color centers or radicals. Recently, Auger electron photoion coincidence (AEPICO) spectroscopy has allowed us to get detailed information on microscopic processes of radiation damage, because AEPICO spectroscopy can pick up only the fundamental processes, excluding effects due to secondary electrons. In this work, in an attempt to study which electronic state is responsible for the C H bond dissociation, AEPICO spectra of benzene solid were measured at 80 K as a function of photon energy. AEPICO measurements were examined at three photon energies, i.e. 285 eV(π*(e2u) ← 1s), 287 eV(σ*(C H) ← 1s), and 430 eV(ionization← 1s). Relative magnitudes of the AEPICO yieldY(hv), which reflects the C H dissociation yield, were estimated by dividing AEPICO signals with intensities of Auger electron yield. Experimental results showed thatY(287eV)/Y(430eV)≈ 1, whereasY(287eV)/Y(430eV)≈ 0.13. A relation between the small value ofY(287eV)/Y(430eV) with the small values of the radiation damage yieldη(hv) near 285 eV is discussed. In that case,η(nearKedge)η(overKedge)≈ 0.1∼0.3 [5] [A. Kimura, K. Nakagawa, K. Tanaka, M. Kotani, R. Katoh, Nucl. Instr. and Meth. in Phys. Res. B91 (1994) 67].

We have examined the reactions of fluorinated layers on Si(100) induced by hyperthermal Xe atoms. Thick fluorinated layers were prepared by the exposure of XeF 2 on silicon surfaces at 480 K. The incident kinetic energies of the Xe atoms varied up to about 5 eV. When the Xe atom beams were impinged on the fluorinated surfaces with an energy exceeding 2 eV, desorption of fluoride (SiF 3 or SiF 4 ) from the fluorinated layers was observed. After the Xe irradiation the SiF 3 + peak disappeared in the temperature-programmed desorption spectra. A collision-induced reaction of the fluorinated layer by hyperthermal Xe atoms is clearly demonstrated.

A Sm 2 Fe 17 C block sample produced by solidification of Sm 2 Fe 17 and C exhibited a much higher stability than a pulverized Sm 2 Fe 17 C sample after a heat treatment in Ar at 1373 K for 15-20 h. The powder sample was fully decomposed into a-Fe and Sm oxycarbide. The powder samples of partially substituted Sm 2 (Fe 1-x Co x ) 17 M Y C (M=Be, Mg, Al, Si, V, Cr, Mn, Ni, Ga, Ge, Mo, In, Ta or W) exhibited similar decompositions after a similar heat treatment. Sm 2 (Fe 1 - x CO x ) 17 Cr O.5 C exhibited decreasing saturation magnetization at x>0.3 and increasing coercivity at 0.2

The effects of N, C and B additions on the crystal structure of Sm 2 Fe 17 were investigated using X-ray diffraction. Also, the changes in the saturation magnetization, Curie temperature and magnetic anisotropy of Sm 2 Fe 17 N x , Sm 2 Fe 17 C , and Sm 2 Fe 17 B x were measured as functions of the concentrations of N, C or B interstitial atom. The basic Sm 2 Fe 17 lattice structure was found to be decomposed by the excess solutions of C at x>1.5 for Sm 2 Fe 17 C x , and by those of B at x>0.2 for Sm 2 Fe 17 B x . The measurements of the magnetic anisotropies of these interstitial compounds yielded concentration regions where the anisotropy field changes from the basal plane to the c axis at x>0.4-0.8 for Sm 2 Fe 17 N x , at x>0.3-0.4 for Sm 2 Fe 17 C x and at x>0.01-0.03 for Sm 2 Fe 17 B x .

Crystallographic analyses have revealed a new “domain structure” in YBa 2 Cu 3 O 7− x (123) prepared by the quench and melt growth (QMG) process. The analyses were carried out by X-ray diffractometry: a kind of pole figure method and an improved technique of microarea X-ray diffraction. The “domain structure” is composed of crystallographic units which are aligned in two-dimensions; the c-axes of them are parallel to each other and there is a slight deviation in directions of their a -and b -axes. The degree of deviation of them differs in scale: macrograins (∼ 10 mm), subgrains (∼ mm) and crystallites (∼ 100 μm) and it is about a few degrees in scale of crystallites. The “domain structure” in QMG-processed materials is closely related to their high J c values, J c > 10 4 A/cm 2 at 77 K under a magnetic field of 1 T. Crystallographic units in the “domain structure” are more strongly linked in superconducting than those in conventionally sintered specimens. The control of the “domain structure” is one of the most important factors for improving properties of superconductors.

Poly(dimethylsiloxane)s (PDMS) of molecular weight, M w , = 8 × 10 4 −1.15 × 10 6 were found to be partially miscible with poly(methylethylsiloxane)s (PMES) of M w = 4 × 10 3 −9 × 10 3 , exhibiting the upper critical solution temperature. The extremum temperature, T cl,ex , of the cloud-point curve ranged from room temperature to 100°C, and the T cl,ex of ternary blends consisting of PDMS and PMES having a bimodal molecular weight distribution could be controlled by changing the composition of the low and high molecular weight fractions in PMES. The temperature dependence of the interaction parameter χ between PDMS and PMES could be reasonably determined from the molecular weight dependence of T cl,ex . The result is expressed as χ ( per PMES monomer unit ) = 4.07 T( K ) − 2.00 × 10 −3 , showing that the enthalpy term in χ is dominant. For a particular mixture with very narrow molecular weight distributions, the critical point was determined by measuring the volume ratio of two demixed phases and was found to shift from the extremum of the cloud point curve, indicating that the location of the critical point is very sensitive to the polydispersity.

The general explicit formula of the exact amplitude of the composite particle scattering in the one-dimensional delta-force model is derived. The composite particles are composed of Fermions with an arbitrary SU h internal symmetry. The derivation is made by the use of the recoupling technique of the unitary group and by setting up the recurrence relation with respect to the Fermion number. The exact equivalent local potential which reproduces the exact scattering amplitude is constructed by the use of the soliton solutions of the Kortewegde Vries equation. In most cases the potential is energy-dependent. The accuracy of the time-dependent Hartree-Fock (TDHF) approximation for the composite particle scattering is investigated by comparing the TDHF scattering amplitude with the exact scattering amplitude. While at low energy limit the approximation is not good for small Fermion numbers, at high energy it is good for all Fermion numbers.