No abstract

The activity of a ZrO 2 -supported nickel catalyst promoted by silica (Ni-Si/ZrO 2 ) in CO 2 dry reforming of methane was carried out at 400 and 450 °C. The catalysts were prepared by an impregnation method and characterized by H 2 -TPR, XRD, TEM, TG-MS, Raman, XPS, and in situ XPS and DRIFTS. It was discovered that Ni-Si/ ZrO 2 showed higher initial conversion of CH 4 (0.50 s −1 ) and CO 2 (0.44 s −1 ), and stability for low temperature (400 °C) DRM reaction in comparison to an SiO 2 -supported nickel catalyst promoted by zirconia (Ni-Zr/SiO 2 ) (0.32 s −1 for both CO 2 and CH 4 ). The Ni-Si/ZrO 2 catalyst featured the formation of active nickel particles with a small size of 6−9 nm and with slightly strong electronic donor ability, stabilization of the initial metal nickel state under the reaction conditions, and the formation of easily removed C 1 coke. However, for the 450 °C DRM reaction, the coke that formed on the Ni-Si/ZrO 2 catalyst was mainly C 2 coke that was difficult to remove, because the CO 2 preferred to combine with H species rather than react with the coke. For the Ni-Zr/SiO 2 catalyst, the Ni 0 species was oxidized to a NiO species under the reaction conditions at 400 °C and could not be restored, leading to its deactivation.

No abstract

Background Many studies have shown that lipids play important roles in bone metabolism. However, the association between high-density lipoprotein cholesterol (HDL-C) and bone mineral density (BMD) is unclear. Therefore, this study aimed to investigate the linear or nonlinear relation between HDL-C levels and BMD and addressed whether the HDL-C levels had the potential values for predicting the risk of osteoporosis or osteopenia. Methods Two researchers independently extracted all information from the National Health and Nutrition Examination Survey (NHANES) database. Participants over 20 years of age with available HDL-C and BMD data were enrolled in the final analysis. The linear relationship between HDL-C levels and BMD was assessed using multivariate linear regression models. Moreover, the nonlinear relationship was also characterized by fitted smoothing curves and generalized additive models. In addition, the odds ratio (OR) for osteopenia and osteoporosis was evaluated with multiple logistic regression models. Results The weighted multivariable linear regression models demonstrated that HDL-C levels displayed an inverse association with BMD, especially among females and subjects aged 30 to 39 or 50 to 59. Moreover, the nonlinear relationship characterized by smooth curve fittings and generalized additive models suggested that (i) HDL-C levels displayed an inverted U-shaped relationship with BMD among women 30 to 39 or over 60 years of age; (ii) HDL-C levels exhibited a U-shaped association with BMD among women 20 to 29 or 50 to 59 years of age. In addition, females with high HDL levels (62-139 mg/dL) had an increased risk of osteopenia or osteoporosis. Conclusion This study demonstrated that HDL-C levels exhibit an inverse correlation with BMD. Especially in females, clinicians need to be alert to patients with high HDL-C levels, which may indicate an increased risk of osteoporosis or osteopenia. For these patients, close monitoring of BMD and early intervention may be necessary.

No abstract