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A robust acrylamide (AAm) hydrogel reinforced by imogolite (IG), a perfect rigid nanotubular clay mineral, exhibited distinct tensile stress-strain characteristics and strain-induced birefringence in accordance with the compositions of the gels. The gel showed a reversible anisotropic/isotropic structural transition in response to stretching/releasing before the breakdown strain. The strain-induced birefringence of the IG-reinforced gels could be fixed by the in situ interpenetrating polymerization of other AAm monomers that were impregnated into the gels in the stretched states. This resulted in gels with nonvolatile anisotropic birefringence, and therefore, the fixed anisotropic IG ordering showed specific stress-strain characteristics depending on the orientation of IG.

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In the course of our screening for new antibiotic, newmembersof benz[a]anthraquinone antibiotics (I and II), which showed antibacterial activity against Gram-positive bacteria were isolated from a culture broth of Streptomyces tsusimaensis MI310-38F7. This strain produced nonactin and a minor yellow compound (III) which was identical with X-14881 E1}. This report describes the isolation, characterization and structure determination of these compounds, named 6-deoxy-8-0-methylrabelomycin (I) and 8-0-methylrabelomycin (II).

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