RESUMEN
The main key to the future transition to a hydrogen economy society is the development of hydrogen production and storage methods. Hydrogen energy is the energy produced via the reaction of hydrogen with oxygen, producing only water as a by-product. Hydrogen energy is considered one of the potential substitutes to overcome the growing global energy demand and global warming. A new study on CH4 conversion into hydrogen and hydrogen storage was performed using a magnesium-based alloy. MgH2-12Ni (with the composition of 88 wt% MgH2 + 12 wt% Ni) was prepared in a planetary ball mill by milling in a hydrogen atmosphere (reaction-involved milling). X-ray diffraction (XRD) analysis was performed on samples after reaction-involved milling and after reactions with CH4. The variation of adsorbed or desorbed gas over time was measured using a Sieverts'-type high-pressure apparatus. The microstructure of the powders was observed using a scanning transmission microscope (STEM) with energy-dispersive X-ray spectroscopy (EDS). The synthesized samples were also characterized using Fourier transform infrared (FT-IR) spectroscopy. The XRD pattern of MgH2-12Ni after the reaction with CH4 (12 bar pressure) at 773 K and decomposition under 1.0 bar at 773 K exhibited MgH2 and Mg2NiH4 phases. This shows that CH4 conversion took place, the hydrogen produced after CH4 conversion was then adsorbed onto the particles, and hydrides were formed during cooling to room temperature. Ni and Mg2Ni formed during heating to 773 K are believed to cause catalytic effects in CH4 conversion. The remaining CH4 after conversion is pumped out at room temperature.
RESUMEN
Ferroelectric and piezoelectric polymers have attracted great attention from many research and engineering fields due to its mechanical robustness and flexibility as well as cost-effectiveness and easy processibility. Nevertheless, the electrical performance of piezoelectric polymers is very hard to reach that of piezoelectric ceramics basically and physically, even in the case of the representative ferroelectric polymer, poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)). Very recently, the concept for the morphotropic phase boundary (MPB), which has been exclusive in the field of high-performance piezoelectric ceramics, has been surprisingly confirmed in P(VDF-TrFE) piezoelectric copolymers by the groups. This study demonstrates the exceptional behaviors reminiscent of MPB and relaxor ferroelectrics in the feature of widely utilized electrospun P(VDF-TrFE) nanofibers. Consequently, an energy harvesting device that exceeds the performance limitation of the existing P(VDF-TrFE) materials is developed. Even the unpoled MPB-based P(VDF-TrFE) nanofibers show higher output than the electrically poled normal P(VDF-TrFE) nanofibers. This study is the first step toward the manufacture of a new generation of piezoelectric polymers with practical applications.
RESUMEN
BACKGROUND: This study aimed to investigate the relationship between leisure time physical activities (LTPA) and metabolic syndrome (MS). METHODS: Five thousand seven hundred and thirty two adults 40 years old or older were enrolled in the study from April 2009 to December 2010. National Cholesterol Education Program's Adult Treatment Panel III was used for the criteria of MS, and Minnesota Leisure Time Physical Activity Questionnaire was used to measure LTPA. After adjusted covariates (age, hypertension, smoking, drinking, education level, household income level, work time physical activities, and menopause for females), the relationship between LTPA and MS was analyzed using logistic regression analysis. RESULTS: The prevalence of MS was 22.8% in men, and 14.1% in women. Average LTPA was 1,498 kcal/wk in men, and 1,308 kcal/wk in women. After adjustment for covariates, the odds ratios of middle and low LTPA compared with high LTPA were 1.06 (0.87-1.34), 1.54 (1.08-1.75), for women, this same association was not seen in men. The prevalence of MS was 22.8% in men and 14.1% in women, and their LTPA burned 1,498 and 1,308 kcal/wk, respectively. When the odds ratio of MS for the high LTPA group was set at 1.0, the odds ratio of MS was 1.06 (0.87-1.34) in the middle LTPA group and 1.54 (1.08-1.75) in the low LTPA group in women, which showed that the MS risk increased when the LTPA was lower. This same association was not seen in men. CONCLUSION: LTPA was independently associated with metabolic syndrome, but only for women.