Recent progress in the synthesis of Mg-based metallic glasses (MGs) has allowed them to be considered as potential candidates for biodegradable and bioabsorbable implant materials. In this work, we use the Mg-Zn-Ca system as a representative to investigate the effect of composition on the atomic-level structure and local chemical environment in Mg-based MGs from ab initio molecular dynamics simulations. The results suggest that the short-range order of Mg(95-x)Zn(x)Ca5 (x = 21, 25, 29, and 33) MGs is characterized by Zn-centered icosahedral and icosahedral-like clusters, which show an increasing number and a rising tendency to interpenetrate each other with the enrichment of Zn constituents. A considerable degree of charge transfer between Zn and the surrounding Mg/Ca atoms is observed through electronic structure and bonding character analysis. At Zn-rich compositions, a percolated Zn-Zn network extended throughout the entire sample is formed, upon which the accumulated charges around Zn atoms are associated into a continuous conductivity path. Such results may shed light on the improved corrosion resistance of the Zn-rich Mg-Zn-Ca MGs.

ABSTRACT. In order to investigate how photoperiod affects the expression of KiSS-1/G-protein-coupled receptor 54 (GPR54), the hypothalamus, the ovaries and testicles of the striped hamster were studied following photoperiod treatment and melatonin injection. We found that the melatonin concentration in the blood of the striped hamster was consistent with the treated photoperiods and that the photoperiod had significant effects on KiSS-1 expression, but the effect of photoperiod on GPR54 expression differed among tissues and sexes. The relative expression of KiSS-1 in the gonads of the male and female striped hamster was significantly higher than that in the hypothalamus, while the difference in GPR54 between the gonads and hypothalamus was inconsistent between the male and female striped hamster. In the striped hamster injected with melatonin, the expression level of KiSS-1 in the gonads and hypothalamus of the male and female striped hamster was significantly decreased; the expression level of GnRH in the gonads was also significantly decreased; the expression of GPR54 in the hypothalamus was increased. In the hypothalamus, a significant positive correlation existed between KiSS-1 and GnRH expression, while a negative correlation was observed between 13895 Photoperiod regulates expression of KiSS-1 and GPR54 ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 13894-13905 (2015) GPR54 and GnRH expression. These results suggest that the photoperiodmelatonin-KiSS-1-GnRH pathway plays an important role in the seasonal reproduction mechanism of the striped hamster. Additionally, photoperiod or melatonin may not be a direct regulatory factor of GPR54 expression.