A Functionalized Covalent Organic Frameworks with Triazine and Triazole Motifs.

Covalent organic frameworks (COFs) with triazine motifs have been widely used in the field of photocatalysis due to their nitrogen-rich structure and strong chemical stability. However, their photocatalytic performances are still inadequate and need further improvement. Herein, nitrile monomers with triazole motifs are specifically chosen to as the precursor to produce a functionalized COFs with triazine and triazole motifs through microwave synthesis method. The as-prepared material exhibits broad light absorption, efficient charge separation and attractive photocatalytic hydrogen peroxide production.

Efficient photosynthesis of hydrogen peroxide by triazole-modified covalent triazine framework nanosheets.

Two-dimensional (2D) polymeric semiconductors, especially covalent triazine framework (CTF) nanosheets with aromatic triazine linkages are emerging as attractive metal-free photocatalysts owing to their predictable structures, good semiconducting properties, and high stability. However, the quantum size effect and ineffective electron screening of 2D CTF nanosheets cause an enlargement of electronic band gap and high excited electron-hole binding energies, which lead to low-level enhancements in photocatalytic performance. Herein, we present a novel triazole groups functionalized CTF nanosheet (CTF-LTZ) synthesized by facile combination of ionothermal polymerization and freeze-drying strategy from the unique letrozole precursor. The incorporation of the high-nitrogen-containing triazole group effectively modulates the optical and electronic properties, resulting in narrowed bandgap from 2.92 eV for unfunctionalized CTF to 2.22 eV for CTF-LTZ and dramatically improved charge separation, as well as highly-active sites for O2 adsorption. As a result, CTF-LTZ photocatalyst exhibits excellent performance and superior stability in H2O2 photosynthesis, with a high H2O2 production rate of 4068 µmol h-1 g-1 and a remarkable apparent quantum efficiency of 4.5 % at 400 nm. This work provides a simple and effective approach for rational design highly-efficient polymeric photocatalysts for H2O2 production.

[Mechanism of heat-clearing prescriptions in alleviating type 2 diabetes mellitus:a review].

Type 2 diabetes mellitus(T2DM), a common chronic metabolic disease, is often accompanied by internal heat syndrome. Heat-clearing prescriptions are widely used to treat different heat syndromes of T2DM from the aspects of clearing stagnant heat, excess heat, damp heat, phlegm heat, and heat toxin, demonstrating remarkable effects. The mechanism of blood sugar-lowering agents has always been a hotspot of research. Recently, the basic studies of heat-clearing prescriptions from different perspectives have been increasing year by year. To clarify the mechanisms of heat-clearing prescriptions and find specific mechanisms, we systematically reviewed the basic studies of heat-clearing prescriptions commonly used for the treatment of T2DM in the past decade, intending to provide a reference for related research.

Analysis of aerosol optical depth and relation to covariates during pre-monsoon season (2002-2019) over Pakistan using ARIMAX model and cross-wavelet analysis.

The pre-monsoon season heavily influences the precipitation amount in Pakistan. When hydrometeorological parameters interact with aerosols from multiple sources, a radiative climatic response is observed. In this study, aerosol optical depth (AOD) space-time dynamics were analyzed in relation to meteorological factors and surface parameters during the pre-monsoon season in the years 2002-2019 over Pakistan. Level-3 (L3) monthly datasets from Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-Angle Imaging Spectroradiometer (MISR) were used. Tropical Rainfall Measuring Mission (TRMM) derived monthly precipitation, Atmospheric Infrared Sounder (AIRS) derived air temperature, after moist relative humidity (RH) from Modern-Era Retrospective analysis for Research and Applications, Version-2 (MERRA-2), near-surface wind speed, and soil moisture data derived from Global Land Data Assimilation System (GLDAS) were also used on a monthly time scale. For AOD trend analysis, Mann-Kendall (MK) trend test was applied. Moreover, Autoregressive Integrated Moving Average with Explanatory variable (ARIMAX) technique was applied to observe the actual and predicted AOD trend, as well as test the multicollinearity of AOD with covariates. The periodicities of AOD were analyzed using continuous wavelet transformation (CWT) and the cross relationships of AOD with prevailing covariates on a time-frequency scale were analyzed by wavelet coherence analysis. A high variation of aerosols was observed in the spatiotemporal domain. The MK test showed a decreasing trend in AOD which was most significant in Baluchistan and Punjab, and the overall trend differs between MODIS and MISR datasets. ARIMAX model shows the correlation of AOD with varying meteorological and soil parameters. Wavelet analysis provides the abundance of periodicities in the 2-8 months periodic cycles. The coherency nature of the AOD time series along with other covariates manifests leading and lagging effects in the periodicities. Through this, a notable difference was concluded in space-time patterns between MODIS and MISR datasets. These findings may prove useful for short-term and long-term studies including oscillating features of AOD and covariates.

Cobalt(III)-catalyzed C-H amidation of N,N-dialkyl thiobenzamides by sulfur coordination.

An efficient inexpensive cobalt(III)-catalyzed intermolecular amidation of N,N-dialkyl thiobenzamides with 1,4,2-dioxazol-5-ones via C-H bond activation is described. The reaction proceeds with high functional group tolerance under external oxidant free conditions, providing a straightforward approach for the direct modification of thioamide derivatives, which are prevalent organic motifs found in vital biological and pharmaceutical molecules.

Determinants of student's physical activity: a 12-month follow-up study in Ningxia province.

BACKGROUND: Physical activity has many health benefits for children and adolescents. However, the prevalence of physical inactivity in school-aged children and adolescents remains high in China. Many factors impact the levels of moderate and vigorous physical activity (MVPA) among students. This study investigated the factors associated with students' MVPA levels and the determinants of changes in their MVPA behaviour. METHODS: This is a longitudinal study with a 12-month follow-up. The study samples were obtained from 2016 and 2017 Physical Activity and Fitness in China-The Youth Study, and they included 1597 students (aged 9-18 years) from 31 primary, junior high, and high schools in Ningxia Province. Factors related to the individual (Age, Sex, BMI and attitude to PA), school (school exercise facility, PE class, teacher support, PA time and PA environment) and neighbourhood (free skill training, sport events, sport organization, sport facility) factors were measured via questionnaire at baseline and after 12 months. Multiple logistic regression was performed to examine the factors that impact students' MVPA level and the determinants of changes in students' MVPA behaviour. RESULTS: There was no difference in students' MVPA levels between 2016 and 2017. Boys were more physically active than girls at baseline (RR 1.55, 95% CI 1.10, 2.20). Neighbourhood factors associated students' MVPA levels were significant, but all of these factors (neighbourhood sport events, organizations, facilities, etc.) were removed from the longitudinal model. Individual and school factors were important for students' MVPA maintenance and positive development (e.g., gender, attitude, school PE class and PA time). CONCLUSIONS: In conclusion, both neighbourhood and school factors may affect students' MVPA, but school appears to plays a more critical role in maintaining and promoting students' MVPA levels. In addition, individual factors may be more important than school and neighbourhood factors in influencing students' MVPA levels. Our research demonstrates that students' attitudes towards PA and school factors should be considered targets for future intervention programmes to promote MVPA. More education programmes may help enhance students' attitudes towards PA, but more studies with large samples and objective assessments are needed to explore the determinants of MVPA.

Thermal-dynamical analysis of blister formation in chirped mirror irradiated by single femtosecond lasers.

The laser-induced damage behaviors of chirped mirrors (CMs) are studied by single 800 nm, 38 fs lasers. The CMs provide group delay dispersion of around -60 fs² and average reflectivity of about 99.4% with bandwidth range of 200-300 nm at a central wavelength of 800 nm. Interestingly, a circular blister feature appears in the CMs at a wide range of laser fluence. An optical microscope, atomic force microscope, scanning electron microscope, and surface profiler are applied to describe the blister characteristics. An adiabatic expansion model of ideal gas is adopted to illustrate the formation dynamics of blisters. The evolution of blisters can be explained by partial evaporation of the film and a subsequent gas expansion, driving the bulging of the film stack up to the stress limit, where the blister fractures. According to this model, the energy absorption ratio of blisters increases monotonously with increasing laser fluence before the occurrence of the focal spot confinement effect.