脆性金属材料の理想的な表面清浄状態での真強度の測定と環境脆化現象の解明

材料の強度特性が試験環境のような外部的な要因により、左右されることが最近わかってきている。このことは、これまでの材料強度の測定値は見かけの性質である場合が多いことを示唆している。本研究の目的は理想的な環境の下で、真の材料強度を測定し、環境脆化の問題を実験的および理論的に解明することにある。このため我々が作製した「試料表面清浄用イオン銃付き超高真空雰囲気引張り試験機」を使って、純金属のCr、Mo、Ti、Ni、Al、およびTi- 6%Al-4%V合金、Fe-3%Si合金の強度特性を調べた。特に、純Ni、純Al、Fe-3mass%Si合金の[001]方位の単結晶について、電解研磨後Arスパッタを行った試料と、高温大気中で表面に酸化物を生成させた試料の強度特性の比較を行った。さらに、DV-Xα分子軌道計算を行い、Cr 中の水素、酸素、窒素、炭素、ボロン原子の電子状態を計算した。これらの研究より、以下の結果が得られた。 1、酸化物をはじめとする試料表面の状態や試験環境が高温金属材料の強度特性に影響を及ぼすことがわかった。すなわち、超高真空下で引っ張り試験をした結果、いずれの材料においても、その0.2%耐力は表面を清浄にしたとき増加した。この傾向は引張り強度(最大応力値)においてより顕著であった。 2、炭素やボロンなどはクロムと強い化学結合を形成し、高温金属素材の強度特性を左右する重要な元素であることが示唆された。本研究により、試料表面の酸化物は明らかに材料強度に影響を及ぼすことが分かった。今後、Arスパッタの試料の表面状態への影響についても詳しく検討していくことにより、材料の強度特性が明らかになるものと考えられる。科学研究費補助金 研究種目:基盤研究(B)(2) 課題番号:07455279 研究代表者:森永 正彦 研究期間:1995-1996年度research repor

Antibiotic-resistant Escherichia coli isolated from dairy cows and their surrounding environment on a livestock farm practicing prudent antimicrobial use

application/pdfOn a livestock farm where antimicrobial administration and its history had been managed for prudent use of antimicrobials, we surveyed antibiotic-resistant Escherichia coli strains isolated from cow feces and the surrounding environment （i.e., rat and crow feces, and water samples from a drainage pit and wastewater processing tank） every month for 1 year. Two strains （1.7%） in cow feces were resistant to tetracycline, whereas all other strains were susceptible to all other antimicrobials. Among 136 strains isolated from cows and wild animals, only one ampicillin-resistant strain was identified. The antibiotic resistance rate in the drainage from the barn was 8.3% （10/120）, and all strains showed susceptibility for 8 months of the year. Tetracycline resistance was common in all resistant strains isolated from animal feces and water samples; all tetracycline-resistant strains carried tetA. These results strongly support the proper use and management of antibiotics on farms to minimize the outbreak and spread of antibiotic-resistant bacteria

Observation of the ηc(2S) in Exclusive B→KKSK-π+ Decays

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Characterization of the Surface of AIkali Metaｌ-modified MgO by IR spectroscopy

application/pdfCO_2 gas was employed to characterize the surface of alkali metal-modified MgO by IR spectroscopy.　Doses of alkali metals changed the composition of CO_2-derived species　because of the enchanced basicity of the surfaces. Li showed the highest modification effect of the three alkali metals used ； this result was in the reverse order of electron-donating　ability. Taking inso account the fact that Li^+ can be substituted for Mg^^ due to their　similar sizes，and that alkali metal oxide and hydroxide were shown by XRD patterns， the　existence of an Li site strongly-connected with oxygen was considered.　The data from both lR spectra and TPD profiles leads to the possibility of quantitative evaluation of basicity of　the surface only by IR spectroscopy to a certain degree.departmental bulletin pape

Correlation between cellular and viral RNA encapsidation and APO3G packaging

<p><b>Copyright information:</b></p><p>Taken from "Analysis of the contribution of cellular and viral RNA to the packaging of APOBEC3G into HIV-1 virions"</p><p>http://www.retrovirology.com/content/4/1/48</p><p>Retrovirology 2007;4():48-48.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1948019.</p><p></p> HeLa cells were co-transfected with pcDNA-APO3G-MycHis together with -defective variants of either pNL4-3 (43ΔVif), pC-Help (C-HelpΔVif), or mS.1 (mS.1ΔVif). Viruses were harvested 24 h after transfection and purified as described in Methods. Virus production and packaging of APO3G was monitored by immunoblot analysis using an aliquot of the purified, concentrated virus preparations. APO3G encapsidation was identified using a polyclonal APO3G-specific peptide antibody. Viral capsid proteins (CA) were identified using an HIV-positive human patient serum (APS). APO3G-specific bands in panel A were quantified by densitometric scanning and corrected for fluctuations in capsid levels. Results were calculated relative to APO3G associated with NL4-3ΔVif particles, which was defined as 100%. RNAs were extracted from purified, concentrated viruses and amplified by RT-PCR using primer pairs specific for HIV-1 RNA or host RNAs as indicated on the left and detailed in table 1. RT-PCR products were separated on 1% agarose gels and visualized by staining with ethidium bromide