Bibliothek

Notizen: Nonlinear dynamics of magnetic buoyancy instabilities for the Parker-type and interchange-type modes are numerically investigated with the aim of understanding the emerging mechanism of solar coronal magnetic loops. Two-dimensional nonlinear magnetohydrodynamic (MHD) simulations of the magnetic buoyancy instabilities are performed in a highly stratified domain consisting of two temperature regions corresponding to the corona and the chromosphere, respectively. First, it is revealed that the angle between the wave vector and the magnetic field at the top interface of the magnetic layer is a crucial parameter controlling the basic properties of the instability. Second, it is found that the magnetic buoyancy instability in the sheared field grows nonlinearly larger than in the shearless field, although the magnetic shear reduces the linear growth rate. This is due to the Parker-type mode being destabilized by the nonlinear effect of the interchange-type instabilities. Third, it is shown that the magnetic buoyancy instability can drive magnetic reconnections which create isolated flux regions. © 1998 American Institute of Physics.

Notizen: We present theoretical investigations of subband structures and optical absorption properties of periodic quantum wires. The calculation is based on the multiband effective mass theory, where effects such as the valence-band mixing effects, the dependence of crystallographic orientation, and the strain effect using a total energy minimization technique are duly taken into account. We use the finite element method to solve the eigenvalue problem with periodic boundary conditions for the quasitwo-dimensional quantum confinement effect. We study strain effects on subband structures and optical properties, and dependence of the optical properties on the crystallographic orientation. © 2002 American Institute of Physics.

Notizen: We have investigated the magnetic, electric, and structural properties of Mn5Ge3/Ge nanostructured films produced by solid-state reaction of Mn/Ge multilayered films. The films composed of strongly uniaxially oriented Mn5Ge3 and randomly oriented Ge were successfully produced. The average grain size of Mn5Ge3 considerably changed according to the discharging power (E) of the ion source: 15 nm for E=25 W and 50 nm for E=50 W. The temperature dependence of the conductivity for the E=25 sample showed semiconductor-type behavior over all the temperature region. Whereas the E=50 sample, the conduction type changed from a metallic type (low temperature) to a semiconductor type (high temperature) with the transition temperature TTR=360 K. We also observed the anomalous magnetic behavior of Mn5Ge3. We discuss these behaviors in conjunction with the microstructure of the annealed films. The possibility of the carrier–spin exchange interactions has also been studied. © 1999 American Institute of Physics.

Notizen: Carbon adsorption to the Si(100) surface in the atmosphere with large or with small concentrations of organic carbons is examined by using thermal desorption spectroscopy or x-ray photoelectron spectroscopy. The number of carbon atoms on a Si(100) wafer stored in the pure water, in which the total organic carbon is 285 ppb, becomes larger until a certain time with increasing time stored in pure water, and it keeps constant over that time. On the other hand, that stored in the air in the clean bench, where the concentration of the organic carbon is thought to be low, becomes small, and the increasing rate of the carbon atoms adsorbed on the Si(100) surface is very small. The difference between these results is due to whether the dominant step is the transportation of organic carbons in the atmosphere or it is the adsorption of organic carbons on the Si surface. The former process occurs for the small concentration of the organic carbons in the atmosphere, and the latter process occurs for the large concentration of them. Adsorption of the organic carbons dominates in the entire process in pure water under the present condition, and the transportation of them dominates in the entire process in the air of the clean bench under the present condition. From the relationship between C1s integral intensity and thickness of the native oxide, it is found that the adsorption of the carbon atoms has a close relationship with the growth of the native oxide on the Si surface. The adsorption site of the carbon atoms is also discussed from the viewpoint of stepped growth of the native oxide. © 1996 American Institute of Physics.

Notizen: A finite-element method is developed for the analysis of eigenstates in the valence band of quantum wires which have arbitrary potential profiles. Our method is basically based on the Galerkin procedure and triangle linear elements are used as finite elements. In our formulation the effect of the band mixing in the valence band is duly taken into account. Boundary conditions at heterointerfaces are also taken into account in the multiband envelope function space. Numerical examples are presented for circular, square, rectangular, and triangular quantum wire structures. The relation is clarified between the degeneracy in the E-ky dispersion curve and the symmetricity of the confinement potential. © 1998 American Institute of Physics.

Notizen: Aims:  A micropapillary pattern (MPP) in lung adenocarcinoma, characterized by papillary structures with epithelial tufts lacking a central fibrovascular core, has been reported to be a new pathological marker of poor prognosis. However, its clinicopathological and prognostic significance in small lung adenocarcinomas (≤20 mm) remains undetermined. A new histological classification of small lung adenocarcinoma proposed by Noguchi et al. has been found to be useful since it has defined surgically curable bronchioloalveolar carcinoma (BAC)-type tumours (Noguchi's type A and B) based on the absence of active fibroblastic proliferation. However, BAC-type tumours with active fibroblastic proliferation (Noguchi's type C), which is adenocarcinoma with mixed subtypes including BAC and invasive carcinoma in the new World Health Organization (WHO) classification, account for most of the small adenocarcinomas and represent a heterogeneous group ranging from minimal to overtly invasive cancer with variable prognoses. Therefore, in this study the aim was to investigate whether MPP can be an additional histological marker(s) to subclassify this heterogeneous group in small lung adenocarcinoma.Methods and results:  One hundred and twenty-two cases of small lung adenocarcinomas (≤20 mm in maximum dimension) classified according to the new WHO classification and Noguchi's proposal were analysed with reference to the presence of MPP. Of the 122 cases, 67 (55%) were MPP-positive and 55 (45%) were MPP-negative. Lymph node metastasis and pleural invasion were significantly more frequent in the MPP-positive group: 74% and 66% in the positive group versus 26% and 34% in the negative group, respectively. The 5-year survival of the MPP-positive group was 54%, whereas that of the MPP-negative group was 81% (P = 0.024). The 5-year survival rates of BAC (Noguchi's type A and B) (n =14), mixed BAC and invasive adenocarcinoma (Noguchi's type C) (n = 85) and invasive adenocarcinoma (Noguchi's type D and F) (n = 23) were 100%, 68% and 36%, respectively. In patients with mixed BAC and invasive adenocarcinoma (Noguchi's type C tumours), the 5-year survival of the MPP-positive group (n = 51) was 54%, significantly lower than that of the MPP-negative group (n = 23) of 100% (P = 0.02).Conclusions:  MPP is a simple and distinct pathological marker to subclassify tumours with a significantly poor prognosis within small (≤20 mm) mixed BAC and invasive adenocarcinoma (Noguchi's type C tumours).