It has been known that twin symmetry occurs in small metal crystals and it could lead to ultrahigh mechanical properties. In this research, we first found out the formation of nanoscale twin crystals in polymers under cylindrical confinement. The nylon-6 nanorods are fabricated by infiltrating the melt into cylindrical nanopores of an anodized alumina oxide template. The α-phase nanotwin of nylon-6 under cylindrical confinement has been examined by both two-dimensional wide-angle X-ray diffraction and transmission electron microscopy (TEM) selected-area electron diffraction (SAED) techniques. The 45°angle between two 200 reflections in the TEM SAED pattern of individual nylon-6 nanorods precisely confirms that nanocrystals in the nylon-6 rod are twins. The twin axis is along the a-axis orientation, which is also the hydrogen-bond direction of the unit cell. The (001) composition (twin) plane is the hydrogen-bonded sheet.

Shape amphiphiles are a class of molecules, which contain distinct shapes of building blocks with competing interactions. The building blocks in one molecule are forced connected through chemical bonds, resulting in competition and cooperation of interactions and packings, which leads to interesting assembled structures. In this work, we have designed and synthesized sphere–triangle shape amphiphiles composed of C60 and triphenylene (C60–TP). C60–TP exhibits a hexagonal lattice with unit cell parameters of a = b = 1.98 nm, c = 4.52 nm, and γ = 120°. Also, for the first time, we demonstrated a three-dimensional layered structure with novel honeycomb C60 scaffolds. The coordination number of C60 in the hexagonal lattice plane is tuned to be four, instead of six in a traditional hexagonal close packing. This new type of hexagonal nonclose packing formed by the spatial packing effect of TP moiety could provide general implications for tuning symmetry in hierarchical structures.

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Background With the progress of urbanization and technology advancement in China, this study aimed to examine the trends in and correlates of PA and sedentary behaviors among Chinese children. Methods Self-reported physical activity data were extracted from the “China Health and Nutrition Survey” project. A total of 6,936 observations (4341 subjects) aged 6–17 years old who participated in at least one round of follow-up surveys from 2004 to 2015 were included. Random-effects ordinal regression models were applied to investigate the trends in the levels of PA, and repeated measures mixed models were applied to examine the trends in and distribution characteristics of PA and sedentary behaviors, controlling for the random effect of communities and adjusting for socio-demographic differences. Quantile regression models were applied to explore the influencing factors at each quartile of PA volume and time spent in sedentary behaviors. Results The prevalence of physical inactivity among Chinese Children aged 6–17 years increased from 76.0% in 2004 to 81.5% in 2015 (OR = 1.51, 95% CI: 1.19 ~ 1.90, p < 0.001). The average weekly volume of PA declined from 41.7 ± 1.6 to 35.9 ± 1.7 MET-hrs/week (P < 0.001) from 2004 to 2015, of which, in-school PA declined significantly by 4.6 MET-hrs/week (P < 0.001). The time spent in sedentary behaviors rose from 23.9 ± 0.6 hrs/week in 2004 to 25.7 ± 0.6 hrs/week in 2015 (p < 0.001), with more profound increases observed for the time on screen-based entertainment (increased by 2.9 hrs/week, P < 0.001). Age, ethnicity, and region showed significant effects on the volume of PA across quartiles (p < 0.001). Compared with children residing in rural area or with low urbanization level, sedentary time was significantly higher than those residing in urban areas (p < 0.001) or with high urbanization level (p ≤ 0.005) across quartiles. Conclusions To improve PA and curb sedentary behaviors among Chinese children aged 6–17 years old, urgent actions should be taken to promote in-school PA and to reduce their screen time. The findings also suggest certain subgroups and geographical areas that are at higher risk of physical inactivity, which warrants more attention when designing and implementing physical activity-promoting policy and action.