Bibliothek

Notizen: We have developed a reflection optical second harmonic (SH) microscope as a new surface probe. Using the combination of the developed SH microscope, a near infrared microscope, a confocal laser microscope, a Raman microprobe spectrometer, and an electron probe microanalyzer for x-ray fluorescence, we have observed microstructures on cleaved GaAs(110) surfaces. We have demonstrated that slab structures on these surfaces are unambiguously identified by the analysis using a combination of these microscopes. We have found that the reflection SH microscope is especially sensitive to the slab structures. The enhancement of second harmonic generation by the slab structure could be well accounted for by an electromagnetic calculation of the SH intensity. © 2000 American Institute of Physics.

Notizen: Two-dimensional magnetohydrodynamic simulations study the spontaneous fast reconnection evolution in a force-free current sheet system where the magnetic field simply rotates by 180 deg across the central current sheet without changing its magnitude. It is demonstrated that, as in the conventional coplanar case, the fast reconnection mechanism drastically evolves because of the positive feedback between (current-driven) anomalous resistivity and global reconnection flow; also, the fast reconnection evolution becomes more drastic for the lower plasma β. Once an anomalous resistivity is ignited and a sufficient amount of the sheared field component Bz is ejected from near the X reconnection point, the ambient magnetic field collapses into the X point, giving rise to the drastic buildup of the fast reconnection mechanism. On the nonlinear saturation phase, the Bz field is completely swept away from the reconnection region, so that coplanar slow shocks extend outward, and a large-scale plasmoid swells and propagates. The resulting plasmoid has a double structure that is quite different from the well-known coplanar one or from the so-called flux rope. In the backward half of the plasmoid, the plasma pressure is enhanced in the butterfly-shaped region, and (coplanar) slow shocks stand along the plasmoid boundary. On the other hand, in the forward half of the plasmoid a finite-amplitude intermediate wave stands along the plasmoid boundary; hence, across the plasmoid boundary, the magnetic field simply rotates without changing plasma quantities nor magnetic field magnitude. © 2002 American Institute of Physics.

Notizen: In contrast to the Petschek reconnection model, the plasma outflow jet in front of the plasmoid associated with the spontaneous fast reconnection model is found to exceed steadily the Alfvén velocity measured in the upstream magnetic field region. According to two-dimensional magnetohydrodynamic simulations, the final velocity of the plasma jet is observed to be superfast and can reach 1.4 times of the Alfvén velocity, which is maintained until the jet encounters a fast shock generated in front of the plasmoid. On the basis of the Rankine Hugoniot relation and the Bernoulli equation, it is theoretically found that the superfast plasma jet generated by slow shocks associated with the reconnection process is effectively accelerated beyond the Alfvén velocity by the adiabatic expansion of the plasma jet without any magnetic effect. In the plasma accelerations, the initial plasma acceleration caused in the slow shock is consistent with that of the Petschek reconnection model, but the subsequent plasma acceleration caused by the adiabatic expansion is not considered in his model. In association with the new acceleration mechanism, one pair of low-pressure regions emerges in the upstream magnetic field region. The generation of the low-pressure regions indicates that the significant adiabatic expansion results from the distortion of the surrounding magnetic field lines associated with the swelling plasmoid. © 2000 American Institute of Physics.

Notizen: Background The authors have carried out questionnaire surveys of health symptoms in school children (aged 7–12 years) in Osaka Prefecture, Japan. In this study, the geographical distribution of and trends in the prevalence of atopic dermatitis were evaluated. Objectives To assess the relationship between the prevalence of atopic dermatitis in children and the environmental factors, and to estimate future changes of the prevalence of atopic dermatitis. Methods A total of seven population surveys were carried out at 2-year intervals between 1985 and 1997 in a total of about 4 million primary school children (460 000–740 000 per survey). Results The lifetime prevalence of atopic dermatitis increased from 15·0% in 1985 to 24·1% in 1993 but levelled off thereafter. According to the school year, the prevalence was higher in lower-year pupils. However, the prevalence stopped rising earlier in lower-year pupils and began to decrease in 1997 in first- to third-year pupils. The prevalence according to areas was significantly correlated negatively with air pollution and positively with the income index. According to the income classes, the prevalence increased until 1993 but levelled off thereafter in all classes, which reduced the differences among the classes. Conclusions The increase of the prevalence of atopic dermatitis in school children stopped in 1993 in Osaka Prefecture, Japan. It is conceivable that the prevalence had reached the saturation level.

Notizen: Keratosis follicularis squamosa (KFS) is a keratinizing disorder, which is well recognized in Japan but rarely reported in other countries. KFS is characterized by asymptomatic small scaly patches with a follicular plug that is scattered on the trunk and thighs. It is easily diagnosed by its characteristic appearance that was originally described in Japanese as ‘lotus leaves on the water’. We report a typical case of KFS and review the mainly Japanese literature. We conclude that KFS is a distinct clinical entity of unknown origin. World-wide recognition of this disease should further clarify the prevalence and pathogenesis of this skin condition.

Notizen: Background H1-receptor antagonists are often effective in the treatment of allergic disorders such as atopic dermatitis. Cetirizine, a putative H1-receptor antagonist, has recently been shown to have anti-inflammatory properties through the inhibition of leucocyte recruitment and activation, and by the reduction of ICAM-1 expression on keratinocytes.Objective To further elucidate the anti-inflammatory properties of cetirizine, we first examined its effects on antigen-induced eosinophilia and neutrophila in vivo. We then examined the anti-inflammatory effects of cetirizine on a human keratinocyte A431cell line.Methods Mice were sensitized subcutaneously with ragweed pollen and were challenged intraperitoneally with the allergen. Cetirizine diluted in sterile water (0–20 mg/kg) or only sterile water was administered orally. Peritoneal cells were obtained at 8 and 24 h after challenge. The eosinophilia and neutrophilia induced by ragweed pollen extract were quantitated. Macrophage migration inhibitory factor (MIF), macrophage inflammatory protein 2 (MIP-2) and eotaxin contents of peritoneal fluid were also measured by mouse ELISA. The effects of cetirizine on MIF-induced IL-8 production in A431 cells were examined by ELISA. The effects of cetirizine on MIF expression and production in A431 cells were examined by human MIF ELISA and Northern blot analysis.Results Eosinophilia and neutrophilia induced by ragweed pollen extract were found to be significantly reduced in cetirizine-treated mice (20 mg/kg). MIF, a pleuripotent cytokine, was significantly decreased at 8 and 24 h in the peritoneal fluid by cetirizine treatment. MIP-2 and eotaxin were also decreased 8 and 24 h, respectively, after challenge in the peritoneal fluid with cetirizine treatment. MIF stimulates IL-8 production in A431 cells. We found that MIF production in A431 cells was inhibited by 10 μm cetirizine. Consistent with this, cetirizine significantly inhibited MIF-induced IL-8 production.Conclusion These results suggest that cetirizine exerts its anti-inflammatory effects by inhibiting MIF as well as IL-8 production, such as those involved in inflammatory allergic skin disease, suggesting a broad spectrum of action beyond its mere H1-receptor-antagonistic function.