BackgroundChildren's health and health behaviour are essential for their development and it is important to obtain abundant and accurate information to understand young people's health and health behaviour. The Health Behaviour in School-aged Children (HBSC) study is among the first large-scale international surveys on adolescent health through self-report questionnaires. So far, more than 40 countries in Europe and North America have been involved in the HBSC study. The purpose of this study is to assess the test-retest reliability of selected items in the Chinese version of the HBSC survey questionnaire in a sample of adolescents in Beijing, China.MethodsA sample of 95 male and female students aged 11 or 15 years old participated in a test and retest with a three weeks interval. Student Identity numbers of respondents were utilized to permit matching of test-retest questionnaires. 23 items concerning physical activity, sedentary behaviour, sleep and substance use were evaluated by using the percentage of response shifts and the single measure Intraclass Correlation Coefficients (ICC) with 95% confidence interval (CI) for all respondents and stratified by gender and age. Items on substance use were only evaluated for school children aged 15 years old.ResultsThe percentage of no response shift between test and retest varied from 32% for the item on computer use at weekends to 92% for the three items on smoking. Of all the 23 items evaluated, 6 items (26%) showed a moderate reliability, 12 items (52%) displayed a substantial reliability and 4 items (17%) indicated almost perfect reliability. No gender and age group difference of the test-retest reliability was found except for a few items on sedentary behaviour.ConclusionsThe overall findings of this study suggest that most selected indicators in the HBSC survey questionnaire have satisfactory test-retest reliability for the students in Beijing. Further test-retest studies in a large and diverse sample, as well as validity studies, should be considered for the future Chinese HBSC study.

We report a straightforward strategy to design efficient N doped porous carbon (NPC) electrocatalyst that has a high concentration of easily accessible active sites for the CO2 reduction reaction (CO2RR). The NPC with large amounts of active N (pyridinic and graphitic N) and highly porous structure is prepared by using an oxygen‐rich metal–organic framework (Zn‐MOF‐74) precursor. The amount of active N species can be tuned by optimizing the calcination temperature and time. Owing to the large pore sizes, the active sites are well exposed to electrolyte for CO2RR. The NPC exhibits superior CO2RR activity with a small onset potential of −0.35 V and a high faradaic efficiency (FE) of 98.4 % towards CO at −0.55 V vs. RHE, one of the highest values among NPC‐based CO2RR electrocatalysts. This work advances an effective and facile way towards highly active and cost‐effective alternatives to noble‐metal CO2RR electrocatalysts for practical applications.

We report as traightforwards trategy to design efficient Nd oped porous carbon (NPC) electrocatalyst that has ahigh concentration of easily accessible active sites for the CO 2 reduction reaction (CO 2 RR). The NPC with large amounts of active N( pyridinic and graphitic N) and highly porous structure is prepared by using an oxygen-rich metalorganic framework (Zn-MOF-74) precursor.T he amount of active Ns pecies can be tuned by optimizing the calcination temperature and time.Owing to the large pore sizes,the active sites are well exposed to electrolyte for CO 2 RR. The NPC exhibits superior CO 2 RR activity with asmall onset potential of À0.35 Vand ahigh faradaic efficiency (FE) of 98.4 %towards CO at À0.55 Vvs. RHE, one of the highest values among NPCbased CO 2 RR electrocatalysts.This work advances an effective and facile wayt owards highly active and cost-effective alternatives to noble-metal CO 2 RR electrocatalysts for practical applications.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Recovery of spent graphite (SG) anode has been largely overlooked and undervalued due to the difficult regeneration process and the relative low price of graphite compared to valuable elements in the cathode. Moreover, lacking feasible low-cost techniques for the recovery of SG seriously restricts the development of all-component recycling of end-of-life batteries. Here, a novel in-depth purification process via KOH–NaOH composite alkali etching is proposed to eliminate impurities incorporated in SG. Residual acid-insoluble impurities, such as Al- and Fe-related compounds, can be removed effectively by alkali roasting treatment at 180–300 °C. Furthermore, in situ TEM investigation is conducted to unravel the gradual graphitization of the coating layer and the construction of Li+ transport channels between the newly formed structures and the original graphite bulk particles via an epitaxial growth manner during the regeneration process. After optimized purification and regeneration treatments, the recycled graphite can be used suitably as a regenerated anode, and a full cell containing commercial LiFePO4 and recycled graphite shows satisfactory capacity retention of 85.8% after 500 cycles at 1 C. This work demonstrates a promising recyclization route of SG anodes.

Heterogeneous ice nucleation on atmospheric aerosols strongly affects the earth’s climate, and at the microscopic level, surface-irregularity-induced ice crystallization behaviors are common but crucial. Because of the lack of visual evidence and effective experimental methods, the mechanism of atomic-structure-dependent ice formation on aerosol surfaces is poorly understood. Here we chose highly oriented pyrolytic graphite (HOPG) to represent soot (a primary aerosol), and environmental scanning electron microscopy (ESEM) was performed for in situ observations of ice formation. We found that hexagonal ice crystals show an aligned growth pattern via a two-stage pathway with one a axis coinciding with the direction of atomic step edges on the HOPG surface. Additionally, the ice crystals grow at a noticeably higher speed along this direction. This study reveals the role of atomic surface defects in heterogeneous ice nucleation and may pave the way to control icing-related processes in practical applications.

In this study, we report on the thermal oxidation of few-layer ZrS 3 flakes as a function of temperature and heating time. We characterize the changes to the material crystal structure caused by the thermal treatment using atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and electrical transport measurements and link these results to the observed changes in optical contrast for on-substrate flakes. Importantly, we observe a very strong photoluminescence emission enhancement in the heated samples, with intensities comparable to those of direct-gap monolayer MoS 2 . We attribute this enhancement to mid-gap states in the thermally synthesized oxides of zirconium which form on the flake surface. We show that this emission is isotropic, unlike that of the untreated ZrS 3 , which unlocks an additional degree of freedom to the modulation of the optoelectronic properties of quasi-one-dimensional van der Waals materials.

A microscopic understanding of the mechanism of direct ice formation from water vapor has a significant benefit for controlling the processes involving ice condensation and evaporation. However, previous studies on this topic have been limited to theoretical simulations or optical observations. Here, by in situ observation via environmental scanning electron microscopy (ESEM), we revealed that hexagonal ice crystals are developed by a step-by-step pathway in a supersaturated water vapor environment. Furthermore, we also discerned that such steps came from two different origins, which are screw dislocations and initial steps. In addition, the relationship between the edge-length (of hexagonal ice crystals) and the growth time was quantitatively studied at controlled temperatures and pressures by experimental data fitting. This study shows that qualitative and quantitative observations of ice formation can be made with simple setups, and it should inspire future investigations toward important physicochemical processes using ESEM, especially those that simultaneously involve two or more phases.

The gate dielectric layer is an important component in building a field-effect transistor. Here, we report the synthesis of a layered rhombohedral-structured MnAl2S4 crystal, which can be mechanically exfoliated down to the monolayer limit. The dielectric properties of few-layered MnAl2S4 flakes are systematically investigated, whereby they exhibit a relative dielectric constant of over 6 and an electric breakdown field of around 3.9 MV/cm. The atomically smooth thin MnAl2S4 flakes are then applied as a dielectric top gate layer to realize a two-dimensional van der Waals stacked field-effect transistor, which uses MoS2 as a channel material. The fabricated transistor can be operated at a small drain–source voltage of 0.1 V and gate voltages within ranges of ±2 V, which exhibit a large on–off ratio over 107 at 0.5 V and a low subthreshold swing value of 80 mV/dec. Our work demonstrates that the few-layered MnAl2S4 can work as a dielectric layer to realize high-performance two-dimensional transistors, and thus broadens the research on high-κ 2D materials and may provide new opportunities in developing low-dimensional electronic devices with a low power consumption in the future.