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Effect of water vapor on static fatigue behavior of a nickel/yttria-stabilized zirconia composite
MATSUDAIRA, Tsuneaki,JANG, Byung-Koog,KIM, Sun-Dong,WOO, Sang-Kuk Ceramic Society of Japan 2017 JOURNAL OF THE CERAMIC SOCIETY OF JAPAN - Vol.125 No.5
<P>The effect of water vapor on the mechanical properties of a porous nickel/yttria- stabilized zirconia (Ni-YSZ) composite ( volume ratio of Ni:YSZ = 40: 60) was evaluated at 850 degrees C, a typical operating temperature of a reversible solid oxide cell. Both the flexural strength and static fatigue limit of Ni-YSZ obtained from the static fatigue lifetime under a wet atmosphere (containing 4% H2O) were lower than those under a dry atmosphere. This can be explained by absorption of H2O molecules into YSZ particles, resulting in accelerated crack growth. The fatigue limit of Ni-YSZ was confirmed to be extremely low, corresponding to almost one-third of the flexural strength. (C) 2017 The Ceramic Society of Japan. All rights reserved.</P>
Total Synthesis of Pactalactam, an Imidazolidinone-Type Pactamycin Analogue
Kim, Taejung,Matsushita, Shohei,Matsudaira, So,Doi, Tsuyoshi,Hirota, Shinji,Park, Young-Tae,Igarashi, Masayuki,Hatano, Masaki,Ikeda, Noriko,Ham, Jungyeob,Nakata, Masaya,Saikawa, Yoko THE AMERICAN CHEMICAL SOCIETY 2019 ORGANIC LETTERS Vol.21 No.10
<P>The first total synthesis of pactalactam was accomplished using substrate-controlled stereoselective aziridination and regioselective aziridine ring-opening to construct three continuous amino groups on an octasubstituted cyclopentane core. The cyclopentane framework was obtained by ring-closing metathesis and aldol coupling using a <SMALL>L</SMALL>-threonine-derived oxazoline compound. Cyclic urea formation, <I>m</I>-acetylphenyl group introduction by Chan-Lam coupling, and primary alcohol-selective acylation yielded the reported pactalactam structure. The presence of pactalactam in the fermentation broth of pactamycin-producing bacteria was also confirmed.</P> [FIG OMISSION]</BR>
Calcium Regulation of an Actin Spring
Tam, B.K.,Shin, J.H.,Pfeiffer, E.,Matsudaira, P.,Mahadevan, L. Biophysical Society ; Published for the Biophysica 2009 Biophysical journal Vol.97 No.4
Calcium is essential for many biological processes involved in cellular motility. However, the pathway by which calcium influences motility, in processes such as muscle contraction and neuronal growth, is often indirect and complex. We establish a simple and direct mechanochemical link that shows how calcium quantitatively regulates the dynamics of a primitive motile system, the actin-based acrosomal bundle of horseshoe crab sperm. The extension of this bundle requires the continuous presence of external calcium. Furthermore, the extension rate increases with calcium concentration, but at a given concentration, we find that the volumetric rate of extension is constant. Our experiments and theory suggest that calcium sequentially binds to calmodulin molecules decorating the actin filaments. This binding leads to a collective wave of untwisting of the actin filaments that drives bundle extension.