Vacuum Insulation and Achievement of 980 keV, 185 A/m~2 H-Ion Beam Acceleration at JAEA for the ITER Neutral Beam Injector

Vacuum insulation of 1 MV is a common issue for the HV bushing and the accel- erator for the ITER neutral beam injector (NBI). The HV bushing as an insulating feedthrough has a five-stage structure and each stage consists of double-layered insulators. To sustain 1 MV in vacuum, reduction of electric field at several triple points existing around the double-layered insulators is a critical issue. To reduce electric field simultaneously at these points, three types of stress ring have been developed. In a voltage holding test of a full-scale mockup equipped with these stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, whose target is the acceleration of a H ion beam of 1 MeV, 200 A/m 2 , the gap between the grid support was extended to suppress breakdowns triggered by electric field concentration at the edge and corner of the grid support. This modi- fication improved the voltage holding capability in vacuum, and the MeV accelerator succeeded in sustaining 1 MV stably. Furthermore, it appeared that the H ions beam was deflected and a part of the beam was intercepted at the acceleration grid. This causes high heat load on the grids and breakdowns during beam acceleration. To suppress the direct interception, a new grid was designed with proper aperture displacement based on a three dimensional beam trajectory analysis. As a result, 980 keV, 185 A/m 2 H ion beam acceleration has been demonstrated, which is close to the ITER requirement.     

EFFECTS OF DIETARY PLANT CEREBROSIDE ON GENE EXPRESSION IN THE LARGE INTESTINE OF 1,2-DIMETHYLHYDRAZINE (DMH)-TREATED MICE DETERMINED BY DNA MICROARRAY ANALYSIS

The effects of dietary plant cerebroside on colon gene expression by DNA microarray analysis in 1,2-dimethylhydrazine (DMH)-treated mice were investigated. After 9 weeks of feeding with DMH, decreases and increases in the levels of expression of 110 and 145 genes were detected, respectively. Especially, the expression of Soggy-1, which suppresses the Wnt signaling pathway, was increased, while that of Ras-associated protein, which induces the mitogen-activated protein (MAP)-kinase pathway and is responsible for the development of aberrant crypt foci (ACF), was decreased. The results of the present study indicated that dietary cerebroside in DMH-treated mice regulates the Wnt signaling and MAP-kinase pathways, and prevents the development of ACF in the large intestine.

PRACTICAL APPLICATIONS

Dietary plant cerebroside increased expression of Soggy-1 mRNA, which suppresses the Wnt signaling pathway, and decreased expression ofRas-associated protein, which induces the MAP-kinase pathway in 1,2-dimethylhydrazine (DMH)-treated mice. The results of the present study indicated that dietary cerebroside in DMH-treated mice regulates the Wnt signaling and MAP-kinase pathways, and prevents the development of aberrant crypt foci in the large intestine, thus being of potential use for nutraceutical applications.     

On the stability of control systems with randomly time-varying characteristics†

The purpose of this paper is to study the stability conditions of randomly time-varying control systems.

First we define the stability, in the stoehastic sense, of the control system with randomly time-varying characteristics and secondly we obtain the conditions for global stability in the mean for a control system which is governed in each time interval by two different differential equations with probability p and 1-q respectively.

Finally we examine the stability condition for the concrete control systems by experiments of the Monte Carlo method.     

INFLUENCE OF CELL SIZE AND CELL WALL VOLUME FRACTION ON FAILURE PROPERTIES OF POTATO AND CARROT TISSUE

This article presents the influence of cell size and cell wall volume fraction on the failure parameters of potato tuber and carrot tissue. Confocal scanning laser microscope was used for obtaining images of the cell structure of the tissues. The mean cell face area and the cell wall volume fraction obtained from the images was compared with work to failure, failure stress, failure strain and secant modulus obtained in a compression test of potato and carrot tissue at two strain rates. Bigger cells and less amount of cell wall material weakened the tissue, which was visible as a linear decrease in the parameters: work to failure, failure stress and failure strain. There were differences between potato and carrot in the secant modulus. For carrot, the secant modulus changed with microstructural parameters, whereas for potato, the secant modulus did not depend on these values. The strain rate decreases all the failure properties for potato. For carrot, only the work to failure was affected by the strain rate.     

PURIFICATION AND PROPERTIES OF DESMUTAGENIC FACTOR FROM BROCCOLI (BRASSICA OLERANCEA VAR. ITALICA PLENCK) FOR MUTAGENIC PRINCIPLE OF TRYPTOPHAN PYROLYSATE

A desmutagenic factor which inhibited the mutagenicity of the mutagens, Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole), Trp-P-2 (3-amino-1-methyl)-5H-pyrido[4,3-b]indole), ethidiumbromide and 2-aminoanthracene, was purified from broccoli (Brassica olerancea var. italica plenck). The factor was not sedimented by ultra-centrifugation at 200,000 xg for 2 h. It adsorbed to a DEAE-cellulose column and was eluted with low concentration of potassium chloride. The purified factor exhibited a heme-like protein absorption spectrum with a Soret band at 403 nm and α and β bands at 640 and 504 nm, respectively. The molecualr weight was estimated to be approximately 53,000 by SDS-gel electrophoresis.     

Microstructure and superelastic properties of free forged Ti–Ni shape-memory alloy

Elemental titanium (Ti) and nickel (Ni) powders were consolidated by spark plasma sintering (SPS) to fabricate Ti–51%Ni (mole fraction) shape-memory alloys (SMAs). The objective of this study is to enhance the superelasticity of SPS produced Ti–Ni alloy using free forging as a secondary process. Products from two processes (with and without free forging) were compared in terms of microstructure, transformation temperature and superelasticity. The results showed that, free forging effectively improved the tensile and shape-memory properties. Ductility increased from 6.8% to 9.2% after forging. The maximum strain during superelasticity increased from 5% to 7.5% and the strain recovery rate increased from 72% to 92%. The microstructure of produced Ti–51%Ni SMA consists of the cubic austenite (B2) matrix, monoclinic martensite (B19′), secondary phases (Ti₃Ni₄, Ti₂Ni and TiNi₃) and oxides (Ti₄Ni₂O and Ti₃O₅). There was a shift towards higher temperatures in the martensitic transformation of free forged specimen (aged at 500 °C) due to the decrease in Ni content of B2 matrix. This is related to the presence of Ti₃Ni₄ precipitates, which were observed using transmission electron microscope (TEM). In conclusion, free forging could improve superelasticity and mechanical properties of Ti–51%Ni SMA.     

自由锻Ti-Ni形状记忆合金的显微组织和超弹性（英文）

采用放电等离子烧结(SPS)法将元素钛粉和镍粉制备成Ti-51%Ni形状记忆合金(SMAs)。研究目的是采用自由锻二次加工以提高SPS合金的性能。对自由锻前后合金的显微组织、相变温度和超弹性进行比较。结果表明,自由锻可以显著提高Ti-Ni形状记忆合金的拉伸强度和形状记忆性能,自由锻后合金的韧性从6.8%提高到了9.2%,超弹性的应变范围从5%增加到7.5%,应变恢复速率从72%提高到92%。Ti-51%Ni合金显微组织中含有立方奥氏体相(B2)基体、单斜马氏体相(B19′)、第二相(Ti_3Ni_4,Ti_2Ni和TiNi_3)和氧化物相(Ti_4Ni_2O,Ti_3O_5)。自由锻后再经500°C时效处理的最终样品的马氏体相变温度向高温方向偏移,这是由于Ti_3Ni_4相(透射电镜下可以观察到)的析出而导致基体中Ni含量的减少。总之,自由锻可以提高Ti-51%Ni形状记忆合金的超弹性和力学性能。