Two-dimensional layered semiconductors such as MoS₂ and WSe₂ have attracted considerable interest in recent times. Exploring the full potential of these layered materials requires precise spatial ...modulation of their chemical composition and electronic properties to create well-defined heterostructures. Here, we report the growth of compositionally modulated MoS₂-MoSe₂ and WS₂-WSe₂ lateral heterostructures by in situ modulation of the vapour-phase reactants during growth of these two-dimensional crystals. Raman and photoluminescence mapping studies demonstrate that the resulting heterostructure nanosheets exhibit clear structural and optical modulation. Transmission electron microscopy and elemental mapping studies reveal a single crystalline structure with opposite modulation of sulphur and selenium distributions across the heterostructure interface. Electrical transport studies demonstrate that the WSe₂-WS₂ heterojunctions form lateral p-n diodes and photodiodes, and can be used to create complementary inverters with high voltage gain. Our study is an important advance in the development of layered semiconductor heterostructures, an essential step towards achieving functional electronics and optoelectronics.
Purpose： This study presents the most recent estimates of prevalence of overweight, obesity, and screen-time viewing among Chinese school-aged children. Demographic differences in these estimates ...between sexes and resident locales were also examined. Methods： Cross-sectional analyses of 116,615 Chinese school children 9 to 17 years of age who participated in the 2016 Physical Activity and Fitness in China--The Youth Study project. Outcomes were the prevalence of children＇s overweight （85th 〈 body mass index （BMI） 〈 95th percentile） and obesity （BMI _〉95th percentile） （defined by the Working Group on Obesity in China） and not meeting screen-time viewing recommendations （＂not meeting＂ was defined as more than 2 h per day of viewing activities after school）. Analyses were conducted on the whole sample and by school grade cohorts （primary, junior middle, and junior high schools）, sex, and residence locales （urban, rural）. Results＇： Overall, 14.4% （95% confidence interval （Cl）： 13.8% 15.0%） of children and adolescents were overweight, 11.9% （95%CI： 11.0% 13.0%） were obese, and 36.8% （95%CI： 34.7%-38.9%） did not meet screen-time viewing recommendations. Across the 3-grade cohorts, boys were more likely to be obese than girls, and primary and junior middle school children living in urban areas were more likely to be obese than those living in rural areas. Primary and junior middle school boys were less likely to meet screen-time recommendations than girls, and junior high school children living in urban areas were less likely to meet screen-time recommendations than school children of the same grades living in rural areas. Conclusion： In 2016, the prevalence of obesity among Chinese school children was about 12%, and about 37% of them did not meet screen-time viewing recommendations. The prevalence of obesity and sedentary behavior was generally higher among boys than among girls, and it was higher for children living in urban areas than for those living in rural areas. 2017 Production and hosting by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license （http：//creativecommons.org/licenses/by-nc-nd/4.0/）.
IntroductionThe world’s population is ageing. Age-related declines in physical function negatively affect the quality of life but may be ameliorated by certain types of exercise. The purpose of this ...study is to investigate the effects of combining resistance training (RT) with balance training on physical function in older community-dwelling adults to provide a reference for this type of exercise compared with other exercises and to provide a theoretical basis for optimising exercise plans to improve physical function among older adults.MethodsThis single-blind randomised controlled trial will recruit 66 community dwelling adults 60–89 years of age with normal cognition. Participants will be randomly assigned to one of three groups: RT, RT combined with balance training or a control group with usual daily activities. Exercise interventions will be conducted in three 45 min sessions per week for 24 weeks. Primary physical function outcomes will be assessed using the timed up and go test, usual walking speed, maximal walking speed, 30 s chair stand and 30 s arm curl. Secondary assessments will be conducted using the 2 min step test, back scratch test and chair sit-and-reach test. All physical function assessments will be performed at baseline and after 12 and 24 weeks of exercise interventions. Exercise intensity will be monitored to maintain moderate intensity by heart rate, ratings of perceived exertion and OMNI-Resistance Exercise Scale. Data that conform to a normal distribution will be expressed as means±SD, otherwise as medians and interquartile intervals. Pretest, mid-test and post-test outcomes will be analysed for within-group and between-group comparisons using two-way repeated measures analyses of variance.Ethics and disseminationThis proposal was reviewed and approved by the Shanghai University of Sport Research Ethics Committee (102772021RT067). The results will be disseminated to the trial participants and as a peer-reviewed publication.Trial registration numberChiCTR2200056090.
With increases in inactive lifestyles and mounting pressure for academic excellence in Chinese younger populations, lack of physical activity and increased prevalence of obesity have become a major ...public health concern in China. The purpose of this study is to provide updated estimates on the prevalence of meeting moderate-vigorous physical activity (MVPA) and screen viewing time guidelines, and overweight and obesity among Chinese school-aged children and adolescents, with a secondary aim examining variations in prevalence by sex, grade groupings, and residential location.
The study sample came from the 2017 Physical Activity and Fitness in China-The Youth Study, a cross-sectional and national survey of 131,859 students (aged 7 to 19 years) from 986 public schools in China. Measures of MVPA, screen viewing time, and age- and sex-specific overweight and obese body mass index were used to calculate national prevalence estimates of Chinese school-aged children and adolescents.
In 2017, 34.1% (95% confidence interval CI, 34.09-34.11%) of children and adolescents met MVPA guidelines and 65.4% (95% CI, 65.39-65.41%) adhered to screen viewing time guidelines. The prevalence of overweight and obesity was 15.1% (95% CI, 15.09-15.11%) and 10.7% (95% CI, 10.69-10.71%), respectively. Prevalence estimates differed by sex (boys, girls), grade grouping (primary schools, junior middle schools, junior high schools), and residential location (rural, urban).
There remains a low prevalence of meeting MVPA guidelines and high prevalence of overweight and obesity in Chinese school-aged children and adolescents. Future efforts should focus on monitoring the trend of these behavioral and health risk factors to inform school policies and programs aimed at increasing physical activity and reducing and preventing obesity in younger populations in China.
Maintaining both walking speed and cognitive function is essential for active, healthy aging. This study investigated age-related differences in walking speed and global cognitive function with aging ...and the association between them among older adults residing in the developing country of China.
This cross-sectional study measured usual (UWS) and maximal walking speed (MWS) of participants for six meters. The Chinese version of the Montreal Cognitive Assessment was used to evaluate global cognition through in-person interviews. Analyses of variance were used to compare the differences in UWS, MWS, and global cognition between genders and age groups. Multiple linear regression models were used to determine the association between walking speed and global cognitive function.
In total, 791 Chinese adults (252 men and 539 women) aged 60-89 years were included in this study. Markedly slowed UWS and worse global cognitive function scores were observed for both genders among adults ≥80 years of age. MWS slowed considerably in men ≥85 years of age and in women ≥80 years of age. There was a significant gender difference in MWS-with men walking faster than women-but not in UWS. Linear regression analysis adjusted for the confounding factors of gender, height, weight, years of education, and chronic disease indicated that MWS, but not UWS, was significantly associated with global cognitive function (β = 0.086, 0.177, 1.657,
= 0.015) such that slower maximal walking speed was associated with poorer cognitive performance. This association was statistically significant only for adults aged 75-79 years (β = 0.261 0.647, 4.592,
= 0.010).
Walking speed was slower in the older age groups. Global cognitive function deteriorated markedly after 80 years of age. After controlling for confounding variables, slower MWS, but not UWS, was associated with poorer global cognitive function. MWS may serve as a potential indicator for earlier identification of poor cognition and motoric cognitive risk syndrome in an older Chinese population.
Band gap engineering of transition-metal dichalcogenides is an important task for their applications in photonics, optoelectronics, and nanoelectronics. We report for the first time the continuous ...lateral growth of composition graded bilayer MoS2(1–x)Se2x alloys along single triangular nanosheets by an improved chemical vapor deposition approach. From the center to the edge of the nanosheet, the composition can be gradually tuned from x = 0 (pure MoS2) to x = 0.68, leading to the corresponding bandgap being continuously modulated from 1.82 eV (680 nm) to 1.64 eV (755 nm). Local photoluminescence scanning from the center to the edge gives single band edge emission peaks, indicating high crystalline quality for the achieved alloy nanosheets, which was further demonstrated by the microstructure characterizations. These novel 2D structures offer an interesting system for probing the physical properties of layered materials and exploring new applications in functional nanoelectronic and optoelectronic devices.
Objective: By copying the uric acid nephropathy rat model, the oxidative stress injury of mitochondria was caused in renal tubular epithelial cells and the relationship between the injury and the ...induction of cell apoptosis was identified.
Methods: All rats were randomly divided into NC (normal control, NC) group, HUA (high uric acid, HUA) group and GSH (reductive glutathione, GSH) group. The values were quantitatively tested in the kidney tissues, including 24-h urinary protein quantity, serum creatinine, blood uric acid, the MDA (malondialdehyde, MDA) and SOD (superoxide dismutase, SOD) oxidative stress indicators. The expression of p53, Bax and caspase-9/-3 were detected by immunoblotting. TUNEL assays were used to detect the apoptosis of renal tubular epithelial cells.
Result: In HUA and GSH groups, the 24-h urinary protein(24UTP), serum creatinine, and blood uric acid increased gradually with the increase of the replication cycle and the increase was significant compared to the NC group (p < .05). Compared to the NC group, MDA increased whereas SOD decreased. The expression of apoptotic proteins, such as p53, Bax, and caspase-9/-3 in the mitochondria was significantly different (p < .05). TUNEL assay revealed that the renal tubular epithelial cells in HUA group were largely apoptotic, whereas the GSH group improved significantly.
Conclusion: Mitochondria incurred the substantial damage due to being in a state of oxidative stress, which was the primary cause of apoptosis in the renal tubule epithelial cells. GSH exhibited the effective resistance to the influence of oxidative stress and can restore the damage in the renal tubular epithelial cells.
Two-dimensional (2D) layered metal dichalcogenides can form spiral nanostructures by a screw-dislocation-driven mechanism, which leads to changes in crystal symmetry and layer stackings that ...introduce attractive physical properties different from their bulk and few-layer nanostructures. However, controllable growth of spirals is challenging and their growth mechanisms are poorly understood. Here, we report the controllable growth of WS2 spiral nanoplates with different stackings by a vapor phase deposition route and investigate their formation mechanisms by combining atomic force microscopy with second harmonic generation imaging. Previously not observed “spiral arm” features could be explained as covered dislocation spiral steps, and the number of spiral arms correlates with the number of screw dislocations initiated at the bottom plane. The supersaturation-dependent growth can generate new screw dislocations from the existing layers, or even new layers templated by existing screw dislocations. Different number of dislocations and orientation of new layers result in distinct morphologies, different layer stackings, and more complex nanostructures, such as triangular spiral nanoplates with hexagonal spiral pattern on top. This work provides the understanding and control of dislocation-driven growth of 2D nanostructures. These spiral nanostructures offer diverse candidates for probing the physical properties of layered materials and exploring new applications in functional nanoelectronic and optoelectronic devices.
An activation process for developing the surface and porous structure of palygorskite/carbon（PG/C） nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was ...characterized by X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, field-emission scanning electron microscopy（SEM）, and Brunauer-Emmett-Teller analysis（BET） techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C-H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold（1201 m2/g for activated PG/C vs. 106 m2/g for PG/C） after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.
In the Loess Plateau of China, conventional tillage is defined as the tillage without crop residues left on the soil surface and ploughed twice a year. The use of alternative practices is a way to ...reduce soil erosion. Our objectives were to assess the long-term impacts of different soil tillage systems on soil physical and hydraulic characteristics, emphasizing management practices to improve the soil physical qualities (reduce bulk density and increase stability of aggregate) under the conservation tillage system in the Loess Plateau of China. Conventional tillage (CT), no tillage (NT), and sub-soiling (SS) were applied in this experiment. Soil wet aggregates distribution and stability, soil organic carbon (SOC) content, soil water retention curves and pore size distributions were measured. The results showed that in the 0–10 cm and 10–20 cm depth soil layers, NT and SS treatments showed a significantly higher proportion of wet aggregates >250 μm (macroaggregates) compared to CT. In these two layers, the proportion of wet aggregates <53 μm (microaggregates) was significantly higher in CT with respect to NT and SS. SOC content increased as the aggregate fraction size increased, and was higher within wet aggregates >250 μm than within the 250–53 μm and < 53 μm (silt + clay) fractions at both depths. In addition, the conservation tillage (NT and SS) can result in improved total porosity and reduced soil bulk density compared with CT in the surface layer. Pore size distribution in CT soil was unimodal, with the maximum in the 10–30 μm matrix pores of the surface layer. However, in the surface layer the pore size distributions from NT and SS showed a dual porosity curve, with two peaks in the matrix and structural pore areas. The 10–20 cm layer showed similar pore size distributions in each treatment. After scanning the soils by micro-computed tomography, we visualized the pore characteristics. The images showed that CT reduced the long and connected macropores compared with conservation tillage. Overall, soil aggregate stability and soil macropores are most improved under conservation tillage. Conservation tillage with crop residues should be adopted instead of conventional tillage, as an effort to improve crop yield and control soil erosion in the Loess Plateau of China.
•Long-term conservation tillage had more macro-aggregates than CT.•Conservation tillage had higher total porosity than CT.•Pore size distribution of CT was unimodal.•Pore size distribution of conservational tillage showed a dual porosity curve with two peaks.•CT reduced the long and connected macropores compared with conservation tillage.
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