12,672 research outputs found
Microscopic surface structure of C/SiC composite mirrors for space cryogenic telescopes
We report on the microscopic surface structure of carbon-fiber-reinforced
silicon carbide (C/SiC) composite mirrors that have been improved for the Space
Infrared Telescope for Cosmology and Astrophysics (SPICA) and other cooled
telescopes. The C/SiC composite consists of carbon fiber, silicon carbide, and
residual silicon. Specific microscopic structures are found on the surface of
the bare C/SiC mirrors after polishing. These structures are considered to be
caused by the different hardness of those materials. The roughness obtained for
the bare mirrors is 20 nm rms for flat surfaces and 100 nm rms for curved
surfaces. It was confirmed that a SiSiC slurry coating is effective in reducing
the roughness to 2 nm rms. The scattering properties of the mirrors were
measured at room temperature and also at 95 K. No significant change was found
in the scattering properties through cooling, which suggests that the
microscopic surface structure is stable with changes in temperature down to
cryogenic values. The C/SiC mirror with the SiSiC slurry coating is a promising
candidate for the SPICA telescope.Comment: 25 pages, 6 figure
Warranted Skepticism: A Dynamic Model of Infant Industry Protection
The neo-classical model of infant industry protection is limited in that agents have static expectations. This paper incorporates a fundamental behavioral assumption, that agents base their decisions on future expectations. An analysis of the global perfect foresight dynamics exposes the rich relationship between protection and outcome, and new policy implications. If an industry is to be protected until its good is competitive in the world market, its success is as likely as its failure, explaining the unreliability of protection programs in practice. The industry's decline after an initial take-off can also be an equilibrium. For the industry's growth to be an equilibrium, protection can be removed before the industry achieves international competitiveness. For the industry's growth to be the unique equilibrium, protection has to continue even after international competitiveness.
The DNA methylation inhibitor 5-aza-2’-deoxycytidine retards cell growth and alters gene expression in canine mammary gland tumor cells
Disruption of gene expression by DNA methylation changes is widely involved in tumorigenesis. Here,to investigate DNA methylation changes in canine, we treated a canine mammary gland tumor cell line with a DNA methylation inhibitor, 5-aza-2’-deoxycytidine (5-aza). Cell growth was significantly retarded following 5-aza treatment and the epithelial marker genes CDH1 and KRT18 were significantly up-regulated, whereas the mesenchymal marker genes CDH2 and VIM were significantly downregulated. We also found a significant decrease in DNA methylation level in the CDH1 promoter region by 5-aza treatment. These results showed for the first time in canine mammary gland tumor cells that inhibition of DNA methylation caused cell growth retardation and affected epithelial mesenchymal transition-related gene expression via changes in DNA methylation level
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