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A 180-nm-thick boron (B) layer was deposited on a 300-nm-thick a-axis-oriented BaSi2 epitaxial film grown by molecular beam epitaxy on Si(111) and was annealed at different temperatures in ultrahigh vacuum. The depth profiles of B were investigated using secondary ion mass spectrometry (SIMS) with O2+, and the diffusion coefficients of B were evaluated. The B profiles were reproduced well by taking both the lattice and the grain boundary (GB) diffusions into consideration. The cross-sectional transmission electron microscopy (TEM) image revealed that the GBs of the BaSi2 film were very sharp and normal to the sample surface. The plan-view TEM image exhibited that the grain size of the BaSi2 film was approximately 0.6 μm. The temperature dependence of lattice and GB diffusion coefficients was derived from the SIMS profiles, and their activation energies were found to be 4.6 eV and 4.4 eV, respectively.

2013-04-04 08:31:50
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1 0 0 0 OA Effect of silicon deficiency on secondary cell wall synthesis in rice leaf

著者: Yamamoto Tsuyoshi Nakamura Atsuko Iwai Hiroaki Ishii Tadashi Ma Jian Feng Yokoyama Ryusuke Nishitani Kazuhiko Satoh Shinobu Furukawa Jun
出版者: Springer Japan
雑誌: Journal of plant research (ISSN:09189440)
巻号頁・発行日: vol.125, no.6, pp.771-779, 2012-11
被引用文献数: 64 3

Rice (Oryza sativa L.) is a typical Si-accumulating plant and is able to accumulate Si up to >10 % of shoot dry weight. The cell wall has been reported to become thicker under Si-deficient condition. To clarify the relationship between Si accumulation and cell wall components, the physical properties of, and macromolecular components and Si content in, the pectic, hemicellulosic, and cellulosic fractions prepared from rice seedlings grown in hydroponics with or without 1.5 mM silicic acid were analyzed. In the absence of Si (the −Si condition), leaf blades drooped, but physical properties were enhanced. Sugar content in the cellulosic fraction and lignin content in the total cell wall increased under −Si condition. After histochemical staining, there was an increase in cellulose deposition in short cells and the cell layer just beneath the epidermis in the −Si condition, but no significant change in the pattern of lignin deposition. Expression of the genes involved in secondary cell wall synthesis, OsCesA4, OsCesA7, OsPAL, OsCCR1 and OsCAD6 was up-regulated under −Si condition, but expression of OsCesA1, involved in primary cell wall synthesis, did not increase. These results suggest that an increase in secondary cell wall components occurs in rice leaves to compensate for Si deficiency.

2013-04-04 08:31:45
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1 0 0 0 OA Smoking cessation and COPD mortality among Japanese men and women: The JACC study

著者: Li Yuanying Yamagishi Kazumasa Yatsuya Hiroshi Tamakoshi Akiko Iso Hiroyasu
出版者: Elsevier Inc.
雑誌: Preventive medicine (ISSN:00917435)
巻号頁・発行日: vol.55, no.6, pp.639-643, 2012-12
被引用文献数: 11 4

ObjectiveTo investigate an effect of smoking cessation on chronic obstructive pulmonary disease (COPD) mortality in Asians.MethodsThe data was obtained from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study). A total of 41465 Japanese men and 52662 Japanese women aged 40–79 years who had no history of COPD, asthma, other chronic lung diseases, cardiovascular disease or cancer were followed between 1988 and 2008.ResultsDuring median 18-year of follow-up, there were 285 (251 men and 34 women) documented deaths from COPD. Multivariable-adjusted hazard ratios with 95% confidence intervals of COPD death were 4.46 (2.72–7.29) and 9.26 (4.19–20.5), respectively for current male and female smokers when compared to never smokers. Compared with current smokers, the multivariable HRs for 5–9 years and 10 years or more smoking cessation prior to baseline were 0.44 (0.22–0.87) and 0.36 (0.22–0.58) in men, respectively while the HR for never smokers was 0.30 (0.16–0.57). There were an insufficient number of COPD deaths in women to clarify this association.ConclusionSmoking cessation for ten years or more prior to enrollment reverses the excess risk of COPD mortality to a level similar to that observed among never smokers in men.

2013-04-04 08:31:39
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1 0 0 0 OA In-situ heavily p-type doping of over 1020 cm−3 in semiconducting BaSi2 thin films for solar cells applications

著者: Khan M. Ajmal Hara K. O. Du W. Baba M. Nakamura K. Suzuno M. Toko K. Usami N. Suemasu T.
出版者: American Institute of Physics
雑誌: Applied physics letters (ISSN:00036951)
巻号頁・発行日: vol.102, no.11, pp.112107, 2013-03
被引用文献数: 72 15

B-doped p-BaSi2 layer growth by molecular beam epitaxy and the influence of rapid thermal annealing (RTA) on hole concentrations were presented. The hole concentration was controlled in the range between 1017 and 1020 cm−3 at room temperature by changing the temperature of the B Knudsen cell crucible. The acceptor level of the B atoms was estimated to be approximately 23 meV. High hole concentrations exceeding 1 × 1020 cm−3 were achieved via dopant activation using RTA at 800 °C in Ar. The activation efficiency was increased up to 10%.