A high-resolution transmission electron microscope study of a zinc oxide varistor

Investigations were made of varistor microstructure, the morphology of Bi₂O₃ at multiple ZnO grain junctions, Bi₂O₃/ZnO grain boundaries and ZnO/ZnO grain boundaries (especially whether Bi₂O₃ is present or not at the ZnO/ZnO grain boundary) by means of high-resolution transmission electron microscopy and X-ray microanalysis in the scanning transmission electron microscope. Bi₂O₃ at multiple ZnO grain junctions consists of small particles of 0.1m in diameter, and they are vitrified to some extent. It is suggested that bismuth ions dissolve into ZnO grains over a 30 nm range from a Bi₂O₃/ZnO grain boundary; however, there is no bismuth at ZnO/ZnO grain boundaries.     

A case of foramen magnum meningioma in which case enhanced three-dimensional CT scan was valuable for preoperative evaluation of the surgical approach

We report a case of foramen magnum meningioma in which case enhanced three-dimensional CT scan was valuable for preoperative evaluation of the surgical approach. A 53-year-old woman had suffered from stiffness and pain in the left occipital region and numbness of the left side of the face for about 2 years before admission. She had also weakness and numbness of the left side of her body for about 2 months before admission, and dysphagia and pain in the occipital region and in the posterior region of the neck produced by straining for about 1 month before admission. Neurological examination revealed left hemiparesis, and hypalgesia and tactile hypesthesia of the left side of the body, including the face. Plain X-P was normal. Enhanced CT scan and gadolinium enhanced MRI revealed a well-enhanced mass attached to the left anterolateral part of the foramen magnum. The left occipital condyle was observed at the lateral side of the attachment part of this mass. Angiography revealed tumor feeders from the meningeal branches of the left vertebral artery and the left ascending pharyngeal artery. Enhanced three-dimensional CT scan clearly showed that the tumor was attached to the left anterolateral part of the foramen magnum, that the left occipital condyle was at the lateral side of the attachment part of this mass and that the jugular foramen and jugular tubercle were situated superolateral to the attachment part of this mass. Considering these factors, we decided that removal of the posterior part of the left occipital condyle was necessary, but removal of the left jugular tubercle was not necessary for a good operative view from the left posterior lateral direction. The tumor was totally removed successfully and good results were obtained by the transcondylar approach without removal of the jugular tubercle. Histology of the tumor revealed meningothelial meningioma. In this case, preoperative evaluation with enhanced three-dimensional CT scan was helpful for deciding the surgical approach. With enhanced three-dimensional CT scan, it is easy to judge whether removal of the posterior part of the occipital condyle and/or the jugular tubercle is necessary for a good operative view, and we can get good images revealing the relationships between the tumor and surrounding structures. Preoperative evaluation with enhanced three-dimensional CT scan is very useful especially in this kind of situation.     

In vitro spontaneous and UVB-induced lymphocyte apoptosis are not specific to SLE

We studied in vitro spontaneous and ultraviolet light (UV)-induced lymphocyte apoptosis in patients with systemic lupus erythematosus (SLE, n = 11), cutaneous lupus erythematosus (CLE, n = 8), and other collagen diseases (n = 6), as well as normal individuals (n = 6). Apoptosis was confirmed by the presence of a 180 bp DNA ladder on gel electrophoresis. UVB-induced apoptosis was observed in 4 of 11 patients with SLE (36.3%), 3 of 8 patients with CLE (37.5%) and 2 of 6 patients (33.3%) with other collagen diseases. There was no clinical correlation between clinical photosensitivity and UV-induced apoptosis. Similarly, spontaneous apoptosis was also found in lymphocytes from patients with diseases other than SLE. No apoptosis was found in normal subjects with or without UVB irradiation (25 mJ/cm2). These data suggest that UV-induced lymphocyte apoptosis may not be specific to SLE but may be common in collagen diseases.     

Test of the local effect model using clinical data: tumour control probability for lung tumours after treatment with carbon ion beams

The treatment planning approach used within the heavy ion tumour therapy project at GSI Darmstadt includes a biological optimisation, which is based on a biophysical model, the Local Effect Model (LEM). Here we show that the predictions of the LEM are in good agreement with clinical data obtained at the HIMAC in Chiba for the treatment of non-small-cell lung cancer, and the steep dose response for carbon ions is reproduced correctly. This steeper increase corresponds to an increasing RBE with increasing dose, which apparently is in contradiction to the systematics observed in general for in vitro measurements. A possible explanation of this discrepancy is based on the interindividual variation of photon sensitivity.     

Characterization of sputtered triple layer photoactive coating with a glass-like appearance

Photocatalytic activity of sputtered TiO₂ single layer was investigated. From the results on the optical constants analyses and dark- and photo-conductivity measurements, it is revealed that the photocatalytic activities of TiO₂ films depend on the defect density of the TiO₂ films; the atomic defects act as recombination sites for photo-generated carriers diffusing to the TiO₂ surface. A three-layer system with a layer construction of SnO₂/TiO₂/Si₃N₄/Glass was designed for realizing the glass-like appearance, namely almost the same transmission and reflection spectra in visible wavelength region as those of glass, and its photocatalytic activity was investigated. The experimental results indicate that the interface between TiO₂ and SnO₂ acts as a potential barrier for the carriers photo-generated in the TiO₂ and the photo-generated species pass through the SnO₂ overlayer depending on the SnO₂ film characteristics.     

Response of multiwire proportional counter for energy loss measurement

A multiwire proportional counter has been developed in order to experimentally simulate the energy deposited by high-energy heavy ions, such as C, Ne, and Ar of several hundred MeV/nucleon, in length as small as 5 μm in soft tissue of a human body. Four sensors with wire spacings of 2, 3, 4, and 5 mm have been prepared for comparison. To estimate the performance of these sensors, the collimated alpha particle beam from ²⁴¹Am is used as a substitute for heavy ion beams in this work. The relative gas multiplication factor and the response to the position of the incident particles are measured for these four sensors with a tissue equivalent gas, and for the 5 mm spacing sensor with various gases. The signal-to-noise ratio is also estimated. For the 5 mm spacing sensor, P-10 gas shows the best performance among the gases examined in this work. The uniformity of the response is not so good for a tissue equivalent gas that is often used to simulate measurements in a human body. The response of the sensor, which depends strongly on the gas used, can be understood qualitatively by the electronegativity of the gas. The energy loss in soft tissue is obtained by multiplying the value measured in P-10 gas by the ratio of the energy loss in a tissue equivalent gas to that in P-10 gas.     

Scintillation properties of Cs2LiLaBr6 (CLLB) crystals with varying Ce concentration

Investigations of Ce³⁺-doped Cs₂LiLaBr₆ (CLLB) crystals show a systematic trend in their scintillation properties with varying Ce concentrations. The concentration studies provide input in the optimization of growth of the CLLB crystals. Scintillation properties viz. radioluminescence, energy resolution, light yield, decay times, and non-proportionality are discussed for samples from 0% to 20% Ce concentration.