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Astronauts experience osteoporosis‐like loss of bone mass because of microgravity conditions during space flight. To prevent bone loss, they need a riskless and antiresorptive drug. Melatonin is reported to suppress osteoclast function. However, no studies have examined the effects of melatonin on bone metabolism under microgravity conditions. We used goldfish scales as a bone model of coexisting osteoclasts and osteoblasts and demonstrated that mRNA expression level of acetylserotonin O‐methyltransferase, an enzyme essential for melatonin synthesis, decreased significantly under microgravity. During space flight, microgravity stimulated osteoclastic activity and significantly increased gene expression for osteoclast differentiation and activation. Melatonin treatment significantly stimulated Calcitonin (an osteoclast‐inhibiting hormone) mRNA expression and decreased the mRNA expression of receptor activator of nuclear factor κB ligand (a promoter of osteoclastogenesis), which coincided with suppressed gene expression levels for osteoclast functions. This is the first study to report the inhibitory effect of melatonin on osteoclastic activation by microgravity. We also observed a novel action pathway of melatonin on osteoclasts via an increase in CALCITONIN secretion. Melatonin could be the source of a potential novel drug to prevent bone loss during space flight.

In this paper, a new constitutive model is proposed to describe the mechanical behaviors of soils under diŠerent loading conditions. New evolution equations for the development of stress-induced anisotropy and the change of overconsolidation of soils are proposed. By combining systematically the above two evolution equations with the evolution equation for the structure of soil proposed by Asaoka et al. (2002), the newly proposed model is able to describe not only the mechanical behavior of soils under monotonic loading, but also the behavior of soils under cyclic loading with diŠerent drained condition. Special attention is paid to the behavior of sand subjected to cyclic loading under undrained condition. That is, for given sand with diŠerent densities, very loose sand may liquefy without cyclic mobility, medium dense sand will liquefy with cyclic mobility while dense sand will not liquefy, which is just controlled by the density, the structure and the anisotropy of the sand. A suitable model should uniquely describe this behavior without changing its parameters. Present research will show the possibility of the proposed model.

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Nascent volatiles from the pyrolysis of a type of woody biomass were reformed in a bed of charcoal at 750À850 °C. While the volatiles passed through the bed together with air at an air ratio of 0.115, the concentration of heavy tar (bp > 336 °C) decreased from 910 000 to 6À1020 mg/Nm 3 dry . This rapid and almost total decomposition of the tar can be ascribed to its deposition onto the charcoal surface, forming coke. The coke formation leads to the loss of the charcoal micropores that provide active sites. Therefore, simultaneous creation of micropores by gasification is necessary to maintain the charcoal activity. Steam played the role of gasifying agent, while O 2 was consumed mainly by gas-phase oxidation that supplied the heat for the reaction.