Tuning parallel manganese dioxide to hollow parallel hydroxyl oxidize iron replicas for high-performance asymmetric supercapacitors.

A novel and facile strategy is developed to tune parallel manganese dioxide (MnO2) to hollow parallel hydroxyl oxidize iron (FeOOH) replicas, which can exactly keep its original morphology. The key factors leading to the morphology-preserved transformation are the low-temperature and dropwise strategy via a serial of controlled experiments. Benefiting from the characteristics of parallel and hollow structures, the FeOOH replica delivers remarkable specific capacitance of 186.8F g-1 at 0.5 A g-1. The electrochemical performances delivered by the asymmetric supercapacitor (parallel MnO2//hollow parallel FeOOH) are much superior to those where conventional activated graphene or FeOOH nanoneedles are used as negative electrode materials. This can be attributed to the advantages of parallel nanostructure and high electrochemical matching effect of positive and negative electrode materials. The energy density is recorded up to 46.8 Wh kg-1 at the power density of 0.5 kW kg-1, while it still remains 20.7 Wh kg-1 with the maximum power density of 10 kW kg-1. Furthermore, this strategy shows great universality and can be broadened to almost all MnO2 related researches to synthesize ideal negative electrode materials with high structural and electrochemical matching effect, thus further enhances the electrochemical performances of as-prepared asymmetric supercapacitor devices.

Analysis of risk factors of acute ischemic stroke for different ethnic groups in Changde.

OBJECTIVES: The aim of our study was to explore the risk factors of acute ischemic stroke (AIS) for different ethnic groups in Changde city (a multi-ethnic residence inhabited mainly by Han and Tujia), Hunan Province, China. DESIGN, SETTING AND PARTICIPANTS: A multicenter study was performed and the demography data, etiology data and clinical features of 5338 AIS patients from 17 hospitals in Changde city were collected from January 2011 through December 2011. MAIN MEASURES: Student's t-test and Chi2-test were used to compare the differences between the Han and Tujia ethnic group in the AIS. RESULTS: In Changde, the incidence of AIS in the Tujia ethnic group was higher than that in the Han ethnic group (233.14 per million vs. 84.38 million, respectively). We found statistically significant differences between the Tujia and Han ethnicities in demographic, etiology and clinical data (eg, sex, living environment, diet, smoking, payment methods, cerebral hemorrhage and transient ischemic attack [P < .05]). In addition, compared with the Han population, the Tujia patients had a higher rate of the incidence of the anterior circulation infarction, partial anterior circulation infarction, lacunar infarction and cerebral hemorrhage. CONCLUSIONS: Our results indicate that lifestyle choices (eg, diet, smoking cigarettes), location, family heritage, and sex are associated with AIS and is useful for informing AIS rates and treatment for AIS.