High-density frustrated Lewis pairs based on Lamellar Nb2O5 for photocatalytic non-oxidative methane coupling.

Photocatalytic methane conversion requires a strong polarization environment composed of abundant activation sites with the robust stretching ability for C-H scissoring. High-density frustrated Lewis pairs consisting of low-valence Lewis acid Nb and Lewis base Nb-OH are fabricated on lamellar Nb2O5 through a thermal-reduction promoted phase-transition process. Benefitting from the planar atomic arrangement of lamellar Nb2O5, the frustrated Lewis pairs sites are highly exposed and accessible to reactants, which results in a superior methane conversion rate of 1456 µmol g-1 h-1 for photocatalytic non-oxidative methane coupling without the assistance of noble metals. The time-dependent DFT calculation demonstrates the photo-induced electron transfer from LA to LB sites enhances their intensities in a concerted way, promoting the C-H cleavage through the coupling of LA and LB. This work provides in-depth insight into designing and constructing a polarization micro-environment for photocatalytic C-H activation of methane without the assistance of noble metals.

Measurement of the mixing state of PAHs in individual particles and its effect on PAH transport in urban and remote areas and from major sources.

Although recent laboratory simulations have demonstrated that organic matter prevents the degradation of polycyclic aromatic hydrocarbons (PAHs), their role in the long-range transport of PAHs in the real atmosphere remains poorly understood. In this study, we measured the chemical composition and mixing state of PAHs-containing individual particles in aerosols from three sources, one urban area and one remote area. PAHs-containing particles were classified into five types: organic carbon (OC), potassium mixed with organic carbon (KOC), potassium mixed with sodium (KNa), Krich and PAH-rich. The PAH-rich and KOC particles were the main types of particles produced by vehicle exhaust/coal burning and biomass burning, respectively, accounting for >50% of the PAHs-containing particles. It was found that organic matter enhancement of PAHs-containing particles occurs in the ambient atmosphere, with organic-rich (OC and KOC) particles accounting for >90%. Further analysis revealed that the increase in the fractions of PAHs was related to the mixing state with organic compounds due to the protection of organics against PAHs and/or the aging of PAHs-containing particles. The results of this study improve our understanding of the chemical composition and mixing state of PAHs particles in atmospheric aerosols from emission sources and urban and remote areas, and provide field observation evidence to support the promotion of the study of long-range transport of PAHs by organics.

The association of chemical composition particularly the heavy metals with the oxidative potential of ambient PM2.5 in a megacity (Guangzhou) of southern China.

Atmospheric fine particulate matters (PM2.5) can cause adverse health effects through the generation of reactive oxygen species (ROS), which is normally characterized by the oxidative potential (OP). However, the particulate components that are mainly responsible for the ROS-induced OP remain controversial and warrant further investigation, especially in megacities where high exposure exists and particulate composition is complex. In this study, we measured the OP of PM2.5 using the dithiothreitol (DTT) assay with and without chelation of metals in a megacity in southern China, Guangzhou, in January and April. We explored the correlations between OP and various chemical components in PM2.5, including water-soluble ions, organic carbon (OC), elemental carbon (EC), and metal elements. There are strong correlations between OPDTTv (volume-normalized) and concentrations of PM2.5, OC, and EC, while the correlations between OPDTTm (mass-normalized) and mass-normalized water-soluble ions, OC, EC or metal elements are weak. The OP values with chelation were reduced by ∼90%, indicating that water-soluble heavy metals were the major contributors to OP of PM2.5 in Guangzhou. On the other hand, correlations between OPDTTm and OC improved significantly after the chelation of heavy metals, implying that OC explains the variance of OPDTTm although its contribution to OP is much smaller than that of heavy metals. We postulate that there might be synergetic effects between water-soluble heavy metals (which contribute most to OP) and OC (which explains the variance of OP) in ROS generation by PM2.5. The findings of the current study provide a better understanding on the critical components in PM2.5 and potential synergism that might be responsible for health effects in urban areas.

Effectiveness of Health-Related Behavior Interventions on Physical Activity-Related Injuries in Junior Middle School Students.

The objective of this study was to determine the effectiveness of an intervention program based on Health-Related Behavior Theory (HRBT) in reducing physical activity-related injuries (PARIs) occurrence and individual risk-taking behaviors, as well as improving PA-related behaviors. A total of 1044 students from six junior middle schools in Shantou city were included and divided randomly into an intervention group (n = 550) and a control group (n = 494), respectively. The intervention group followed a prescribed PARIs intervention program based on HRBT, and the control group performed a common health education program, consisting of seven sessions and lasting seven months from May to November 2018. After the intervention, both groups showed a significantly lower prevalence of PARIs (intervention group: from 25.45% to 10.91%, control group: from 29.76% to 11.74%, both p < 0.05), but no significant between-group differences could be observed in the post-intervention PARIs prevalence (p > 0.05). Compared with the control group, students in the intervention group had a higher improvement in PA-related behaviors and a lower score of risk-taking behaviors (both p < 0.05). Thus, it could be concluded that the HRBT intervention program had a positive effect on PA-related and risk-taking behaviors in junior middle school students, though its effectiveness in reducing the occurrence of PARIs was not significant.

Nonvolatile Ferroelectric-Domain-Wall Memory Embedded in a Complex Topological Domain Structure.

The discovery and precise manipulation of atomic-size conductive ferroelectric domain walls offers new opportunities for a wide range of prospective electronic devices, and the emerging field of walltronics. Herein, a highly stable and fatigue-resistant nonvolatile memory device is demonstrated, which is based on deterministic creation and erasure of conductive domain walls that are geometrically confined in a topological domain structure. By introducing a pair of delicately designed coaxial electrodes onto the epitaxial BiFeO3  film, a center-type quadrant topological domain with conductive charged domain walls can be easily created. More importantly, reversible switching of the quadrant domain between the convergent state with highly conductive confined walls and the divergent state with insulating confined walls can be realized, resulting in an apparent resistance change with a large on/off ratio of >104  and a technically preferred readout current (up to 40 nA). Owing to restrictions from the clamped quadrant ferroelastic domain, the device exhibits excellent restoration repeatability over 108  cycles and a long retention of over 12 days (>106  s). These results provide a new pathway toward high-performance ferroelectric-domain-wall memory, which may spur extensive interest in exploring the immense potential in the emerging field of walltronics.

Association of COMT Polymorphisms with Multiple Physical Activity-Related Injuries among University Students in China.

The catechol-O-methyltransferase (COMT) is a candidate gene to provide promising evidence of psychiatric disorders, but there is a knowledge gap between the genetic factor and multiple physical activity-related injuries (PARIs). The aim of this study was to explore the contribution of COMT to the risk of PARIs among university students in the Chinese Han population. We can further search for the intrinsic risk factors for the occurrence of multiple physical activity injuries and provide a scientific basis for early screening and precise intervention for the high-risk group of college students with multiple PARIs. A 1:1 matched case-control study of 61 PARIs cases and 61 healthy controls were carried out. DNA samples of the participants were isolated from saliva and genotyped on eight SNPs of the COMT gene (rs9265, rs4680, rs6269, rs4818, rs4633, rs165655, rs165656, and rs165722) using the MALDI-TOF MS method. We found that rs6269 and rs4818 were significantly associated with PARIs, and rs6269-GG and rs4818-GG contributed to the reduced risk of PARIs. Further haplotype analysis showed a four-marker C-G-C-G haplotype (rs165722-rs6269-rs4633-rs4818) acted with a protective role in the development of PARIs (p = 0.037; OR: 0.474, 95% CI: 0.269 to 0.834). However, the interactions between club membership and rs6269 or rs4818 would significantly increase the risk of PARIs (both p < 0.001, OR: 5.121 and 4.977, respectively). This is the first study to find the contribution of COMT to PARIs occurrence, suggesting that the COMT polymorphisms and the gene-environment interactions may alter the risk of PARIs.

Quasi-one-dimensional metallic conduction channels in exotic ferroelectric topological defects.

Ferroelectric topological objects provide a fertile ground for exploring emerging physical properties that could potentially be utilized in future nanoelectronic devices. Here, we demonstrate quasi-one-dimensional metallic high conduction channels associated with the topological cores of quadrant vortex domain and center domain (monopole-like) states confined in high quality BiFeO3 nanoislands, abbreviated as the vortex core and the center core. We unveil via the phase-field simulation that the superfine metallic conduction channels along the center cores arise from the screening charge carriers confined at the core region, whereas the high conductance of vortex cores results from a field-induced twisted state. These conducting channels can be reversibly created and deleted by manipulating the two topological states via electric field, leading to an apparent electroresistance effect with an on/off ratio higher than 103. These results open up the possibility of utilizing these functional one-dimensional topological objects in high-density nanoelectronic devices, e.g. nonvolatile memory.

A step-by-step synergistic stripping approach toward ultra-thin porous g-C3N4 nanosheets with high conduction band position for photocatalystic CO2 reduction.

The pristine g-C3N4 (BCN) with a low conversion efficiency of CO2 exits with small specific surface area, weak CO2 adsorption and severe recombination of photo-generated charges. The stripping of few-layer g-C3N4 represents excellent photocatalytic performance, which attracts extensive attention in photocatalytic CO2 reduction. In the present study, the ultra-thin porous g-C3N4 (THCN) with high specific surface area and high position of conduction band was prepared using step-by-step synergistic exfoliation. Further, we treated it with HCl-assisted hydrothermal stripping and successive thermal stripping/etching in air. Our results showed that the THCN exhibited the best CO2 conversion efficiency from CO2 to CH4 and CO fuels, compared with g-C3N4 (HCN) prepared by HCl-assisted hydrothermal stripping and g-C3N4 (TCN) prepared by thermal stripping/etching in air. Further, the excellent photocatalytic performance for CO2 reduction was mainly attributed to its high specific surface area and rich pores, excellent separation and utilization efficiency of photo-generated carriers, and upper position of conduction band. Due to its wide band gap and high specific surface area, the THCN also showed significantly better degradation for Rhodamine B than BCN, HCN and TCN. Nonetheless, using a simple two-step stripping strategy, we prepared and obtained an ultra-thin porous g-C3N4 nanosheets with a high specific surface area for CO2 conversion to CH4 and CO fuels. This ultimately provided a reference for preparation of other two-dimensional ultra-thin materials for CO2 reduction.

Gender-specific physical activity-related injuries and risk factors among university students in China: a multicentre population-based cross-sectional study.

OBJECTIVES: Data on the problem of physical activity-related injury (PARI) in university students and the risk factors for PARI among different genders are rare. We conducted a multicentre population-based study to investigate the occurrence of PARI and to explore the gender-specific risk factors for PARI among Chinese university students. DESIGN: Cross-sectional study. PARTICIPANTS: A total of 5341 students in grades 1-3 at eight universities in four Chinese cities were selected to complete the online questionnaires during March and April 2017. The questionnaires assessed sociodemographic characteristics, physical activity PA) involvement, sleep duration, sedentary behaviour and PARI experiences in the past 12 months. MAIN OUTCOME MEASURES: PARI during the past 12 months. RESULTS: Among the 5341 participants, 1293 suffered from at least one PARI in the past 12 months, with an overall incidence rate of 24.2% (males: 26.2%, females: 23.2%) and an injury risk of 0.38 injuries/student/year (males: 0.48, females: 0.32). Over half of the injured (57.3%) experienced a withdrawal time of PA and nearly two-fifths (39.6%) required medical attention. Irrespective of gender, Shantou and Xi'an students, sports team members and those who engaged in sports and leisure-time vigorous-intensity PA (VPA) at a higher frequency were more likely to suffer from PARI. Male students who participated in sports and leisure-time VPA for long durations had a greater likelihood of sustaining PARI, while having a chronic condition and being involved in sports and leisure-time moderate-intensity PA at a higher frequency and longer duration were potential contributors to PARI among females. CONCLUSIONS: The occurrence of PARI and its risk factors differed by gender, which provides a direction towards developing targeted and effective gender-specific preventative programmes to protect Chinese university students from PARI.

COVID-19 outbreak prevention by early containment in Shantou, China.

INTRODUCTION: To report about the successful outbreak containment of COVID-19 in Shantou, one of the prefectural cities of Guangdong province in the mainland China. METHODOLOGY: All patients confirmed as having COVID-19 between 23 January and 25 March 2020 by RT-PCR assay in the clinical lab of Shantou CDC were included and divided into three groups based on the source of identification: hospital diagnosis, contact tracing, and community screening. Collected data was analyzed and compared among these three groups. RESULTS: A total of 25 COVID-19 cases were identified in Shantou. The first case was identified on 14 January 2020 at one of two COVID-19 dedicated hospitals in Shantou. The majority of the cases were either imported from Wuhan or linked to Wuhan/Hubei. The median lag time for diagnosis (i.e., the time between symptom onset and case confirmation) was 2 days (IQR, 2.0-4.0) for all cases, 9 days (IQR, 7.0-10.0) for the cases diagnosed in hospitals, 2 days (IQR, 1.5-2.0) for the cases in contact tracing, and 4 days (IQR, 2.5-4.5) for cases in community screening, with a significantly longer diagnosis lag time in hospitals (p = 0.003). Multivariate linear regression models showed larger family size and severe cases as the significant predictor for increasing number of close contacts. CONCLUSIONS: The current pandemic appears to exist for an uncertain period. The early containment measures applied in Shantou, a city with insufficient healthcare resources for COVID-19, seems to be appropriate for cities or areas with similar profiles.

Predicting cloud condensation nuclei number concentration based on conventional measurements of aerosol properties in the North China Plain.

Cloud condensation nuclei (CCN) play an important role in the formation and evolution of cloud droplets. However, the dataset of global CCN number concentration (NCCN) is still scarce due to the lack of direct CCN measurements, hindering an accurate evaluation of its climate effects. Alternative approaches to determine NCCN have thus been proposed to calculate NCCN based on measurements of other aerosol properties, such as particle number size distribution, bulk aerosol chemical composition and aerosol optical properties. To better understand the interaction between haze pollution and climate, we performed direct CCN measurements in the winter of 2018 at the Gucheng site, a typical polluted suburban site in North China Plain (NCP). The results show that the average CCN concentrations were 3.81 × 103 cm-3, 5.35 × 103 cm-3, 9.74 × 103 cm-3, 1.27 × 104 cm-3, 1.44 × 104 cm-3 at measured supersaturation levels of 0.114%, 0.148%, 0.273%, 0.492% and 0.864%, respectively. Based on these observational data, we have further investigated two methods of calculating NCCN from: (1) bulk aerosol chemical composition and particle number size distribution; (2) bulk aerosol chemical composition and aerosol optical properties. Our results showed that both methods could well reproduce the observed concentration (R2 > 0.88) and variability of NCCN with a 9% to 23% difference in the mean value. Further error analysis shows that the estimated NCCN tends to be underestimated by about 20% during the daytime while overestimated by <10% at night compared with the measured NCCN. These results provide quantitative instructions for the NCCN prediction based on conventional aerosol measurements in the NCP.

Characteristics and associated factors of physical activity-related injuries among university students in southern China.

This cross-sectional study aimed to describe the characteristics of physical activity-related injury (PARI) and to explore its associated factors among university students in Chaoshan district. Selected from the baseline survey in March and April, 434 students graded 1-3 from two universities were interviewed face-to-face in April and May 2017. Socio-demographics, physical activity (PA) participation, risk-taking behaviors, and PARI occurrences in the past 12 months were collected. Group Lasso logistic regression was applied to identify the risk factors of PARI. Totally, 317 PARI episodes were reported by 184 subjects with an overall injury risk of 0.73 injuries/student/year (males: 1.00, females: 0.63) and an injury incidence density of 0.81 injuries per 1000 PA exposure hours (males: 1.13, females: 0.69). Most injuries involved the lower extremities and were sprains and strains. Males, sports team members, and those with high-risk rebellious and anti-social behaviors were more likely to sustain PARI compared to their counterparts. Those who participated in vigorous-intensity PA with longer duration (particularly ≥ 150 min/week) were at a higher risk for PARI. This study indicates that PARI is a health concern among university students and great efforts should be taken to prevent them from PARI when promoting a physically active lifestyle.

Gender-Specific Risk Factors of Physical Activity-Related Injuries among Middle School Students in Southern China.

This cross-sectional study was carried out to explore the potential risk factors of physical activity-related injuries (PARI) among middle-school students of different genders. Selected by the random cluster sampling method, students aged from 12 to 16 years old in grades 7-8 from six middle schools in Shantou, southern China, were recruited for this investigation in November 2017. Information about socio-demographics, physical activity (PA) exposure time, individual exercise behaviors, risk-taking behaviors, and PARI experiences in the past 12 months was collected. A multivariate logistic regression model was used to explore the risk factors of PARI. A total of 1270 students completed valid questionnaires, with an overall injury incidence of 33.6% (boys: 42.0%; girls: 25.0%), an injury risk of 0.68 injuries/student/year, and an injury rate of 1.43 injuries per 1000 PA exposure hours. For boys, living in a school dormitory, participating in sports teams, exercising on a wet floor, rebellious behavior, and having longer PA exposure time were the risk factors of PARI. For girls, those who were sports team members, whose parents were divorced or separated, and those with longer PA exposure time were more vulnerable to suffer from PARI. In conclusion, PARI was a health problem among middle school students in southern China. Boys and girls differed in PARI occurrence and were affected by different risk factors, which provides a basis for targeted gender-specific intervention programs to reduce the occurrence of PARI among middle-school students.

Epidemiology of physical activity-related injuries in Chinese university students.

Knowledge gaps of the physical activity-related injury (PARI) problem among general undergraduates exist. We conducted a study in four universities, where 1421 students graded 1-3 were interviewed face-to-face during April and May after their completion of the baseline survey in March and April 2017, aiming to describe the incidence and characteristics of PARI. PARI experience and physical activity (PA) participation in the past 12 months were collected. Injury incidence density (IID) and risk, and injury characteristics were evaluated for the overall sample and by gender. Pearson chi-square or Fisher's exact tests and independent-sample t tests were used to test between-group differences. We found that 486 PARIs were reported totally by 289 participants, with an overall IID of 0.57 per 1000 hours of exposure (males: 1.07, females: 0.45) and an injury risk of 0.34 injuries/student/y (males: 0.52; females: 0.28). Higher IIDs were found in roller skating, football, and basketball. The majority of injuries occurred outdoors and involved the lower extremities, with sprain and strain being the primary injury types. Moreover, most injuries were new, acute, and happened in non-contact situations. Of all injuries, 52.1% required medical attention and 64.6% resulted in inactivity of one or more days. Some significant differences were observed between males and females. Our study indicates that PARI is a public health concern among Chinese university students, which can provide direction for targeted prophylactic interventions to underpin the sex-specific injury mechanism to reduce PARI.

Topological domain states and magnetoelectric properties in multiferroic nanostructures.

Multiferroic nanostructures have been attracting tremendous attention over the past decade, due to their rich cross-coupling effects and prospective electronic applications. In particular, the emergence of some exotic phenomena in size-confined multiferroic systems, including topological domain states such as vortices, center domains, and skyrmion bubble domains, has opened a new avenue to a number of intriguing physical properties and functionalities, and thus underpins a wide range of applications in future nanoelectronic devices. It is also highly appreciated that nano-domain engineering provides a pathway to control the magnetoelectric properties, which is promising for future energy-efficient spintronic devices. In recent years, this field, still in its infancy, has witnessed a rapid development and a number of challenges too. In this article, we shall review the recent advances in the emergent domain-related exotic phenomena in multiferroic nanostructures. Specific attention is paid to the topological domain structures and related novel physical behaviors as well as the electric-field-driven magnetic switching via domain engineering. This review will end with a discussion of future challenges and potential directions.

[HONO Pollution Characteristics and Nighttime Sources During Autumn in Guangzhou, China].

Nitrous acid (HONO) plays an important role in atmospheric photochemistry processes because its photolysis provides an efficient source of hydroxyl (OH) radicals in the troposphere. However, few studies exist on HONO in nocturnal chemistry processes. Using the observation data of HONO and related parameters for a super site at Guangzhou Jinan University in October 2015, the pollution processes and sources of HONO during nighttime were analyzed in this study. The results showed that the average concentration of HONO was 4.32 µg ·m-3 during the nighttime, which was 2.6 times its concentration of 1.67 µg ·m-3 in the daytime. The conversion rate of HONO, CHONO, during the nighttime was 0.0068 h-1, and the average contribution of vehicle emissions to HONO was 15.1%, with a peak of 37.8% at 20:00. The average net HONO generation rate from the reaction of NO and OH radicals during the night was 0.44 µg ·(m3 ·h)-1. Correlation analysis suggested that particles could not be the major HONO source, but that relative humidity (RH; 33%-78%) was a key factor. Relevant calculation indicated that the heterogeneous reaction of deposited NO2 on humid ground surfaces could be the main source of HONO during nighttime.

[Characteristics and Source Apportionment of Volatile Organic Compounds in the Rainy Season of Guangzhou City].

Atmospheric volatile organic compounds (VOCs) were measured in an urban area of Guangzhou on July 2016 using an on-line gas chromatography mass spectrometry/fire ion detector. Seventy-three VOCs were detected with an average concentration of (118.83±79.40) µg·m-3, a maximum concentration of 492.42 µg·m-3, and a minimum concentration of 10.54 µg·m-3 during the period. The peak value of the TVOC concentration appeared at about 07:00 in the morning, indicating that motor vehicle pollution had a significant contribution at the site. The minimum value appeared at about 14:00 in the afternoon, related to photochemical losses. High concentrations were also observed from 21:00 to 24:00, which was probably related to pollution emissions and boundary layer compression. Source analysis by PMF showed that the site was mainly affected by five VOC sources: vehicle exhaust, solvent use, fuel loss at fuel stations, plant emissions, and cooking exhaust, the contributions of which were 29.79%, 26.61%, 24.86%, 9.91%, and 8.84%, respectively. Vehicle exhaust was the largest source of VOCs during the daytime, while the contribution of plant emissions increased significantly at noon. The contribution of solvent uses and fuel loss at fuel stations rose during the night and became the main source of VOCs until early morning.

Electrically Driven Reversible Magnetic Rotation in Nanoscale Multiferroic Heterostructures.

Electrically driven magnetic switching (EDMS) is highly demanded for next-generation advanced memories or spintronic devices. The key challenge is to achieve repeatable and reversible EDMS at sufficiently small scale. In this work, we reported an experimental realization of room-temperature, electrically driven, reversible, and robust 120° magnetic state rotation in nanoscale multiferroic heterostructures consisting of a triangular Co nanomagnet array on tetragonal BiFeO3 films, which can be directly monitored by magnetic force microscope (MFM) imaging. The observed reversible magnetic switching in an individual nanomagnet can be triggered by a small electric pulse within 10 V with an ultrashort time of ∼10 ns, which also demonstrates sufficient switching cycling and months-long retention lifetime. A mechanism based on synergic effects of interfacial strain and exchange coupling plus shape anisotropy was also proposed, which was also verified by micromagnetic simulations. Our results create an avenue to engineer the nanoscale EDMS for low-power-consumption, high-density, nonvolatile magnetoelectric memories and beyond.

Physical Activity-Related Injury and Its Associated Factors among Middle School Students in Southern China.

Physical activity (PA) promotion is beneficial to gain and maintain optimal health, but might increase risks for physical activity-related injury (PARI). This cross-sectional study aimed to investigate the incidence rate and identify risk factors of PARI among Chinese middle school students. Selected via the method of cluster random sampling, students graded 7⁻8 (junior) and 10⁻11 (senior) from five middle schools (aged from 10 to 18 years old) in Shantou were invited to participate in the survey. Information on socio-demography, PA involvement, sleep duration, individual safety awareness and exercise behavior, and PARI experiences in the past 12 month was collected. Multivariate logistic regression model was performed to estimate the risk factors of PARI. A total of 3082 participants completed the valid questionnaires, with an overall incidence rate of 25.1%. Boys, junior school students, sports team members, and those with lower safety awareness, living with single parent, and without any chronic conditions were at higher risks for PARI. Moreover, exercising on wet floor or with illness frequently would also be more likely to experience injury, especially those with at least 120 min per day. In conclusion, PARI was prevalent among middle school students in southern China. The above data provide insights that were focused and effective actions should be taken to prevent school-aged adolescents from PARI and maximize the benefits of PA.