Analytical model for reduction of deep levels in SiC by thermal oxidation

Two trap-reduction processes, thermal oxidation and C+ implantation followed by Ar annealing, have been discovered, being effective ways for reducing the Z[1/2] center (EC – 0.67 eV), which is a lifetime killer in n-type 4H-SiC. In this study, it is shown that new deep levels are generated by the trap-reduction processes in parallel with the reduction of the Z[1/2] center. A comparison of defect behaviors (reduction, generation, and change of the depth profile) for the two trap-reduction processes shows that the reduction of deep levels by thermal oxidation can be explained by an interstitial diffusion model. Prediction of the defect distributions after oxidation was achieved by a numerical calculation based on a diffusion equation, in which interstitials generated at the SiO2/SiC interface diffuse to the SiC bulk and occupy vacancies related to the origin of the Z[1/2] center. The prediction based on the proposed analytical model is mostly valid for SiC after oxidation at any temperature, for any oxidation time, and any initial Z[1/2]-concentration. Based on the results, the authors experimentally achieved the elimination of the Z[1/2] center to a depth of about 90 μm in the sample with a relatively high initial-Z[1/2]-concentration of 10[13] cm[−3] by thermal oxidation at 1400 °C for 16.5 h. Furthermore, prediction of carrier lifetimes in SiC from the Z[1/2] profiles was realized through calculation based on a diffusion equation, which considers excited-carrier diffusion and recombination in the epilayer, in the substrate, and at the surface

An intestinal bacterial metabolite (M1) of ginseng protopanaxadiol saponins inhibits tumor-induced neovascularization

The present study demonstrated that an intestinal bacterial metabolite (M1) of protopanaxadiol-type ginsenosides significantly inhibited the growth of implanted tumor and the intrahepatic metastasis by the implantation of a small fragment of colon 26-L5 tumor into the liver when it was administered orally. These findings indicates that M1 was effective for the inhibition of the growth and metastasis of colon26-L5 cells in addition to lung metastasis of B16-BL6 melanoma cells as have been reported previously. The conditioned medium of colon 26-L5 cellS (CM-L5) induced in vitro tube formation of hepatic sinusoidal endothelial (HSE) cells on Matrigel-coated substrates, which is considered to be an important step in the processes of tumor angiogenesis. \u27This activity of CML5 was abrogated by noncytotoxic concentrations of M1 in a concentration-dependent manner. Similarly, M1 eliminated the ability of CM-L5 to promote the migration of HSE cells concentration-dependently. These findings indicate that M1-induced inhibition of tumor growth and intrahepatic metastasis may be partly related to the suppression of tumor angiogenic responses including capillary tube formation and migration of HSE cells. 本研究では,薬用人参(Panax ginseng C.A.MEYER)のprotopanaxadiol-type ginsenosidesの主要な腸内細菌代謝物M1の経口投与は,マウス結腸癌colon 26-L5細胞の腫瘍小片を肝へ直接移植した後の移植部位での増殖と肝内移転に対して有意に抑制効果を示すことを明らかにした。この結果は,B16-BL6メラノーマ細胞による肺転移を抑制した以前の報告と同様に,co1on 26-L5細胞に対しても有効であることが示された。肝類洞内度細胞(HSE細胞)をマトリゲルをコートした基質上で,colon 26-L5細胞の培養上清(CM-L5)とともに培養すると,腫瘍血管新生の週程における重要なステップのひとつである,内度細胞の菅腔形成を誘導した。CM-L5による菅形成能は,細胞傷害性を示さない濃度範囲のM1により,濃度依存的に抑制された。同様に,CM-L5によるHSE細胞の移動能の亢進を,M1は濃度に依存して抑制した。以上,M1による結腸癌の肝における増殖及び肝内転移の抑制は,内度細胞の骨腔形成及ぴ移動能を含む血管新生反応の抑制と部分的に関係していることが示唆された

酸化物結晶のフォノンスペクトルにおける非調和効果に関する研究

取得学位：博士(理学)，学位授与番号：博乙第203号，学位授与年月日：平成11年9月30日,学位授与年：199

Pathophysiology and Diagnosis of Coronary Functional Abnormalities

Approximately one-half of patients undergoing diagnostic coronary angiography for angina have no significant coronary atherosclerotic stenosis. This clinical condition has recently been described as ischaemia with non-obstructive coronary arteries (INOCA). Coronary functional abnormalities are central to the pathogenesis of INOCA, including epicardial coronary spasm and coronary microvascular dysfunction composed of a variable combination of increased vasoconstrictive reactivity and/or reduced vasodilator function. During the last decade – in INOCA patients in particular – evidence for the prognostic impact of coronary functional abnormalities has accumulated and various non-invasive and invasive diagnostic techniques have enabled the evaluation of coronary vasomotor function in a comprehensive manner. In this review, the authors briefly summarise the recent advances in the understanding of pathophysiology and diagnosis of epicardial coronary artery spasm and coronary microvascular dysfunction

Mobile monitoring along a street canyon and stationary forest air monitoring of formaldehyde by means of a micro gas analysis system

A micro-gas analysis system (μGAS) was developed for mobile monitoring and continuous measurements of atmospheric HCHO. HCHO gas was trapped into an absorbing/reaction solution continuously using a microchannel scrubber in which the microchannels were patterned in a honeycomb structure to form a wide absorbing area with a thin absorbing solution layer. Fluorescence was monitored after reaction of the collected HCHO with 2,4-pentanedione (PD) in the presence of acetic acid/ammonium acetate. The system was portable, battery-driven, highly sensitive (limit of detection = 0.01 ppbv) and had good time resolution (response time 50 s). The results revealed that the PD chemistry was subject to interference from O3. The mechanism of this interference was investigated and the problem was addressed by incorporating a wet denuder. Mobile monitoring was performed along traffic roads, and elevated HCHO levels in a street canyon were evident upon mapping of the obtained data. The system was also applied to stationary monitoring in a forest in which HCHO formed naturally via reaction of biogenic compounds with oxidants. Concentrations of a few ppbv-HCHO and several-tens of ppbv of O3 were then simultaneously monitored with the μGAS in forest air monitoring campaigns. The obtained 1 h average data were compared with those obtained by 1 h impinger collection and offsite GC-MS analysis after derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA). From the obtained data in the forest, daily variations of chemical HCHO production and loss are discussed