Search

Developing highly active catalysts, which possess highly dispersed small active particles, strong metal–support interaction (MSI) and abundant oxygen vacancies, has attracted much attention in the steam reforming of biomass tar. In this study, a series of Ce-promoted lignite-char-supported Co catalysts (Co–Ce/C) was prepared via ion exchange combined with an impregnation method. A smaller average metal particle size (4.22 nm), higher reduction degree (90%), larger number of oxygen vacancies (58%) and stronger MSI were obtained when the Ce content was 5 wt %. For steam reforming of toluene, Co-5Ce/C exhibited the highest activity, such that toluene conversion and H2yield reached 100% and 4137 μmol·min–1·gCo–1, respectively, and good stability such that the toluene conversion remained at 92% after 100 h of continuous reaction at 450 °C. The low apparent energy (45.8 kJ/mol) was consistent with the high activity of Co-5Ce/C, while less carbon deposition and slighter growth of metal particle size (5.45 nm) over the spent catalyst corresponded to its good stability. In short, the formation of oxygen vacancies due to the introduction of Ce not only increased the dispersion of active metal but also promoted the adsorption and activation of H2O molecule and accelerated the carbon removal. The reported catalyst can be promising for highly efficient conversion of the real biomass tar, especially at relatively low temperatures.

Aim: Sleep-disordered breathing (SDB) is common among adolescents and is associated with short- and long-term consequences. Data on the prevalence and epidemiologic characteristics of SDB in Chinese adolescents are limited. The purpose of this study was to examine the prevalence, epidemiologic characteristics, and associated factors of SDB using a large sample of Chinese adolescents. Subjects and methods: Participants were from the baseline of the Shandong Adolescent Behavior and Health Cohort (SABHC) and included 11,831 adolescents (aged 14.97 ± 1.46 years old) from five middle schools and three high schools in Shandong Province, China. Adolescents completed a self-administered questionnaire on sleep-related variables, demographics, general health, family, and school information. SDB was defined as report of loud snoring or snorting/gasping or stopping breathing during sleep occurring weekly. Results: In this sample, 8.3% of the adolescents snored loudly at least once per week and 2.1% snored loudly almost every night. Snorting/gasping and stopping breathing at least once a week affected 6.6% and 2.0% of adolescents, respectively. The prevalence of weekly SDB was 13.4% according to adolescent report. Multiple logistic regression analysis revealed that SDB was independently associated with male gender, body mass index (BMI), chronic diseases, ever smoking, ever drinking, insomnia, daytime sleepiness, poor family economic status, and low father education level. Conclusion: SDB is prevalent in Chinese adolescents, and multiple factors are associated with SDB. These associations also require longitudinal epidemiologic studies to clarify the complex nature of their relationships and opportunities for and effects of intervention.

Aluminum fluoride (AlF3)-modified HZSM-5 obtained by simple mechanical mixing and calcination was used to enhance the conversion of the lignite pyrolysis volatiles to light aromatics. The results revealed that the appropriate amount of AlF3modification can simultaneously dealuminize and aluminize to enhance the catalytic performance, in which dealumination considerably enlarged the pores while realumination generated more midstrength acid sites to compensate for the loss of acid sites caused by dealumination. HZ-2 (HZSM-5 mixed with 2 wt % AlF3) obtained the maximum light aromatics yield of 31.0 mg/g as a result of its abundant mesopores and suitable midstrength acid sites, especially the yield of benzene increased by 6.3 mg/g in comparison with that of the original HZSM-5. However, mixing with only a small amount of AlF3generated the most serious carbon depositions because of the acidity enhancement by the critical role of alumination. Moreover, excessive AlF3etched more framework Al that dramatically reduced the midstrength acid sites, inhibiting the formation of light aromatics, although the enlargement of pore size facilitated mass transfer. This one-step modification combining the expansion of the pore size and the optimization of acid sites provides a promising strategy for upgrading the lignite pyrolysis volatiles.

Plasma surface alloying technology was applied to introduce Ni element into Ti6Al4V to improve its tribological property. The microstructure, composition, phase constituent and hardness of the alloyed layer were examined. Wear mechanisms were discussed on the basis of wear scar observations. The tribological performance of the alloyed layer was investigated by ball-on-disk sliding tests in different environments. The results showed that the Ti-Ni alloyed layer was about 12μm in thickness and the content of Ni element reached to 28% on the surface. The surface hardness of the layer was 677HV, nearly twice as the untreated Ti6Al4V. The wear resistance of the modified Ti6Al4V substrate was improved obviously in different environments.

Menstrual problems and daytime sleepiness are prevalent in adolescent girls. Little is known about the associations between age at menarche, menstrual problems, and daytime sleepiness. This study aimed to examine the associations of age at menarche and menstrual problems with daytime sleepiness among Chinese adolescent girls.

Daytime sleepiness is associated with poor daytime functioning and adverse cognitive and emotional consequences, such as impaired decision-making and increased impulsivity. Little is known about the association between daytime sleepiness and suicidal behaviors. This study examined the prospective relationship between daytime sleepiness and suicidal behaviors, including suicidal thought (ST), suicide plan (SP), and suicide attempt (SA), in a large sample of adolescents.