Single crystal growth, structural and transport properties of bad metal RhSb2

We have successfully grown an arsenopyrite marcasite type RhSb2 single crystal, and systematically investigated its crystal structure, electrical transport, magnetic susceptibility, heat capacity, and thermodynamic properties. We found that the temperature-dependent resistivity exhibits a bad metal behavior with a board peak around 200 K. The magnetic susceptibility of RhSb2 shows diamagnetism from 300 K to 2 K. The low-temperature specific heat shows a metallic behavior with a quite small electronic specific-heat coefficient. No phase transition is observed in both specific heat and magnetic susceptibility data. The Hall resistivity measurements show that the conduction carriers are dominated by electrons with ne = 8.62 × 10^(18) cm^(-3) at 2 K, and the electron carrier density increases rapidly above 200 K without change sign. Combining with ab-initio band structure calculations, we showed that the unusual peak around 200 K in resistivity is related to the distinct electronic structure of RhSb_2. In addition, a large thermopower S(T) about -140 μV/K is observed around 200 K, which might be useful for future thermoelectric applications.

Effect of extracts from Stachys sieboldii Miq. on cellular reactive oxygen species and glutathione production and genomic DNA oxidation

Objective: To evaluate the antioxidant activity of extracts and fractions from Stachys sieboldii Miq., and to examine its effect on the cellular reactive oxygen species(ROS) and glutathione(GSH) production and genomic DNA oxidation in HT-1080 cells. Methods: The ROS generation induced by H2 O2 was measured by the dichlorofluorescein-diacetate assay. GSH levels were measured using a fluorescent method with mBBr. Genomic DNA oxidative damage was measured with levels of oxidative DNA induced by the reaction of ferritin with H2 O2. Results: The n-hexane, 85% aqueous methanol and n-butanol fractions(0.05 mg/mL concentrations) inhibited H2 O2-induced ROS generation by 63%, 35% and 45%, respectively. GSH levels were significantly increased in both acetone+methylene chloride and methanol extracts(P<0.05). Supplementation of cells with n-hexane significantly increased GSH levels at concentrations of 0.05 mg/mL(P<0.05). Both the acetone+methylene chloride and methanol extracts, as well as all fractions significantly inhibited oxidative DNA damage(P<0.05). Conclusions: These results indicate that cellular oxidation was inhibited by the n-hexane fraction and this fraction may contain valuable active compounds.