Electrical properties of dielectric thin films of the tantalum oxide-quartz system prepared by r.f. reactive sputtering

It has been reported by many workers that tantalum oxide is one of the most useful materials for thin film capacitors. However, improvements in the design of such capacitors continue to be made; for example, in the development of TMM or TSM capacitors consisting of a film of tantalum oxide or another oxide sandwiched between electrodes.In this paper the electrical properties of mixed tantalum oxide-quartz films, prepared by reactive sputtering from tantalum-quartz composite targets with various area ratios at the target surface, are described.     

Self-phase modulation in hybridly mode-locked CW dye lasers

Largely asymmetric spectra are observed for ultrashort light pulses from a synchronously and passively mode-locked CW rhodamine 6G dye laser, with relatively high intra-cavity intensity. The spectral shape shows a broad wing on the long-wavelength side alone. When the asymmetric spectrum occurs, the conventional SHG intensity auto-correlation trace shows exponential-like long tails. Further, the temporal characteristics of the mode-locked pulses, including both the shape and phase, are also examined by a new method of SHG autocorrelation, where the SH output is spectrally resolved. These experimental results are explained with self-phase modulation (SPM) process due to the optical Kerr effect in a mixed dye jet stream inside the laser cavity. The main observed characteristics are in reasonable agreement with the theoretical expectation from the slow SPM mechanism, where the pulse width is much shorter than the relaxation time τrof refractive index. The measured nonlinear refractive index n2and τralso support the above interpretation.     

Synthesis of continuous silicon carbide fibre with high tensile strength and high Young's modulus

Polycarbosilane as the precursor of continuous SiC fibre was synthesized by thermal decomposition of polydimethylsilane. The structure of the polycarbosilane is concluded to be similar to that of polysilapropylene by the measurements of i.r. spectra, NMR spectra and chemical analyses. Its formation mechanisms are initially the formation of carbosilane by thermal decomposition of polydimethylsilane and then the increase in molecular weight by dehydrogenation-condensation of the carbosilane. Molecular structure and molecular weight distribution of the polycarbosilane depend on the reaction temperature.     

Determination of monomer reactivity ratios in copolymerizations with N-vinylpyrrolidone by means of high-speed liquid chromatography

High-speed liquid chromatography was applied to the studies of the polymerization of N-vinylpyrrolidone and its copolymerizations with vinyl acetate, glycidyl methacrylate and methyl methacrylate. The conversion was calculated from the decrease in peak-height in the chromatogram of the monomer. A small change in the amount of monomer was closely determined by using o-diphenyl benzene (o-terphenyl) as an internal standard. The calculations of the monomer reactivity ratios gave concordant results with those reported earlier. The obtained copolymer compositions agreed with the data by elementary analysis. The application of high-speed liquid chromatography to the determination of copolymerization reactivity ratios was thus found to be advantageous for saving time. The monomer reactivity ratio can be determined without the complicated processings such as separating, drying and analysing the copolymers.     

Coupled-mode analysis of anisotropic dielectric planar branching waveguides

We present a theoretical study of mode propagation in anisotropic planar branching waveguides consisting of isotropic and anisotropic layers. The characteristic equation of anisotropic five-layered structure is introduced to calculate the propagation constants and field patterns of the branching-waveguide modes. Coupled-mode analysis shows that the normalized parameter is effective for the evaluation of mode-coupling effects in the anisotropie branching waveguides as well as in the isotropic branching waveguides.     

Aortic dissection extending from the left coronary artery during percutaneous coronary angioplasty

A 72-year-old woman with acute aortic dissection as a complication of percutaneous coronary angioplasty was successfully treated. She received a graft replacement of the ascending aorta as well as triple coronary artery bypass grafts. The dissection had extended from the left coronary artery. Although acute aortic dissection is a rare complication of percutaneous coronary angioplasty, physicians and cardiac surgeons should keep its potential occurrence in mind.     

Basic fibroblast growth factor promotes extension of regenerating axons of peripheral nerve. In vivo experiments using a Schwann cell basal lamina tube model

Schwann cell basal lamina tubes serve as attractive conduits for regeneration of peripheral nerve axons. In the present study, by using basal lamina tubes prepared by in situ freeze-treatment of rat saphenous nerve, the effects of exogenously applied basic fibroblast growth factor (bFGF) on peripheral nerve regeneration was examined 2 and 5 days after bFGF administration. Regenerating axons were observed by light and electron microscopy using PGP9.5-immunohistochemistry for specific staining of axons. In addition, the localizations of bFGF and its receptor (FGF receptor-1) were examined by immunohistochemistry using anti-bFGF antibody and anti-FGF receptor-1 antibody, respectively. Regenerating axons extended further in the bFGF-administered segment than in the bFGF-untreated control segment. Electron microscopy showed that regenerating axons grew out unaccompanied by Schwann cells. Findings concerning angiogenesis and Schwann cell migration were very similar between the bFGF treated and control nerve segment. bFGF-immunoreactivity was not detected in the control nerve segment. In contrast, bFGF-immunoreactivity was detected on the basal lamina tubes as well as on the plasmalemma of regenerating axons facing the basal lamina in the bFGF treated nerve segment up to 5 days after administration, suggesting that exogenous bFGF can be retained in the basal lamina for several days after administration. FGF receptor was detected on the plasma membrane of regenerating axons where they abutted the basal lamina. These results indicate that bFGF could promote the extension of early regenerating axons by directly influencing the axons, but not via Schwann cells or angiogenesis.     

Intraepidermal mass of M. leprae in a case of seborrheic keratosis due to Hansen's disease (LLs)

A 67-year-old patient has had exanthema in the lower right limb since 51 years ago (16 years old at onset), which underwent repeated remission and recurrence. At present, he has bilateral symmetrical widespread infiltrating exanthema and asymmetrical marked neuralhypertrophy, and has been diagnosed typical LLs (His father had the same disease). The exanthema recurred several years ago, and the patient is being treated for Hansen's disease. He had a dark brown flat elevation with a rough surface and the size of a small finger tip in his right abdominal skin for approximately 20 years. A biopsy was performed, and the specimen was fixed in 10% formalin and paraffin sections were prepared for histopathologic examination. A part of the specimen was processed forscanning electron microscopic examination. Seborrheic keratosis was diagnosed by H & E staining. Acid-fast (FITE) staining, immunohistochemical staining (keratin, S-100 protein, anti-PGL antibody and anti-BCG antibody) and scanning electron microscopy revealed the presence of bacteria (M. leprae) in the dermal foam cells, the matrix with a banded structure and the squamous epithelial cells which normally lack phagocytosis function. Compared to the basal cells of normal epidermis, the basal cells located adjacent to the dermis affected with seborrheic keratosis showed increased proliferation and more marked characteristics of a germinative cell. The degree of differentiation of the basal cells appeared regressed, and they probably possessed augmented phagocytic activity. The phagocytosed bacteria were probably carried by the epidermal cell cycle toward the surface layer. However, bacteria could not be found in the stratum corneum, probably due to an association with the lysosome.     

Mechanical properties changes of Fe-Cr alloys by fast neutron irradiation

The changes in the mechanical properties of Fe-Cr ferritic, single α-phase alloys, containing 0–15 wt% Cr, by fast neutron irradiation were studied by means of tensile tests in the temperature range between 77 and 283 K, mainly with regard to the effects of the Cr content. The temperature dependence of the yield stress decreased with increasing Cr content. The irradiation raised the thermal activated component of the yield stress in low Cr alloys severely, but not in high Cr alloys. The fracture stress in the brittle fracture mode increased with Cr content up to 10 wt%, beyond which it decreased. The frequency of twinning deformation showed an opposite tendency to the fracture stress with or without irradiation. The transition temperature of the unstable plastic flow, which occurred intensively after irradiation, decreased with increasing Cr content. The last condition mainly governed the irradiation embrittlement of Fe-Cr alloys determined from absorbed energy-temperature curves in tensile testing. Thus, high Cr alloying can make the steel more resistant to irradiation embrittlement.