We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V ...We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.展开更多
In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due ...In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.展开更多
Rice-duck co-culture is an integrated farming technology that benefits rice production, grain quality, and ecological sustainability in paddy fields. However, little is known about the effects of rice-duck co-culture ...Rice-duck co-culture is an integrated farming technology that benefits rice production, grain quality, and ecological sustainability in paddy fields. However, little is known about the effects of rice-duck co-culture on enzyme activity involved in the biosynthesis of 2-acetyl-1-pyrroline (2-AP), the volatile that gives fragrant rice its' distinctive and sought-after aroma. The present study aimed to examine the influence of rice-duck co-culture on the photosynthesis, yield, grain quality, rice aroma, and the enzymes involved in 2-acetyl-1-pyrroline biosynthesis in the cultivar Meixiangzhan 2 during the early and late rice growing seasons of 2016 in Guangzhou, China. We compared the rice grown in paddy fields with and without ducks. We found that rice-duck co-culture not only improved the yield and quality of fragrant rice grain, but also promoted the precursors of 2-AP biosynthesis formation and 2-AP accumulation in the grain. Grain 2-AP content in rice-duck co-culture was noticeably increased with 9.60% and 20.81% in early and late seasons, respectively. Proline and pyrroline-5-carboxylic acid (P5C) (precursors of 2-AP biosynthesis) and the activity of enzymes such as proline dehydrogenase (ProDH), ornithine aminotransferase (OAT) and Δ1 pyrroline-5-carboxylic acid synthetase (P5CS) were all improved by 10.15%–12.99%, 32.91%–47.75%, 17.81%–26.71%, 6.25%–21.78%, and 10.58%–38.87% under rice-duck co-culture in both seasons, respectively. Overall, our results suggest that rice-duck co-culture is an environmentally-friendly and sustainable approach to improving rice aroma and grain quality of fragrant rice.展开更多
Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably descr...Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface.In this paper,the time-dependent deformation characteristics of gangue under different stress levels were obtained by using lateral confinement compression,that reliably represents the compaction of goaf.The viscoelastic foundation model for gangue mechanical response is different from the traditionally used elastic foundation model,as it considers the time factor and viscoelasticity.A mechanical model using a thin plate on a fractional viscoelastic foundation was established,and the roof deflection,bending moment,time-dependent,viscous and other characteristics of SBM were included and analyzed.Compared with the existing elastic foundation model,the proposed fractional order viscoelastic foundation model has higher accuracy with laboratory data.The plate deflection increases by 50.9%and the bending moment increases by 37.9%after 100 days,which the elastic model would not have been able to predict.展开更多
The accuracy of spatial interpolation of precipitation data is determined by the actual spatial variability of the precipitation, the interpolation method, and the distribution of observatories whose selections are pa...The accuracy of spatial interpolation of precipitation data is determined by the actual spatial variability of the precipitation, the interpolation method, and the distribution of observatories whose selections are particularly important. In this paper, three spatial sampling programs, including spatial random sampling, spatial stratified sampling, and spatial sandwich sampling, are used to analyze the data from meteorological stations of northwestern China. We compared the accuracy of ordinary Kriging interpolation methods on the basis of the sampling results. The error values of the regional annual precipitation interpolation based on spatial sandwich sampling, including ME(0.1513), RMSE(95.91), ASE(101.84), MSE(-0.0036), and RMSSE(1.0397), were optimal under the premise of abundant prior knowledge. The result of spatial stratified sampling was poor, and spatial random sampling was even worse. Spatial sandwich sampling was the best sampling method, which minimized the error of regional precipitation estimation. It had a higher degree of accuracy compared with the other two methods and a wider scope of application.展开更多
Human adipose stem cells(hADSCs)are reliable sources for cell therapy.However,the clinical applications are limited by the decrease in activity during in vitro culture.We used a knockout serum replacement(KSR)medium,E...Human adipose stem cells(hADSCs)are reliable sources for cell therapy.However,the clinical applications are limited by the decrease in activity during in vitro culture.We used a knockout serum replacement(KSR)medium,Eppendorf(EP)tube culture,and a simulated microgravity(SMG)culture system to establish hADSC spheroids.We found that hADSCs aggregated and formed spheroids in the KSR culture medium.The EP tube culture method revealed many biological cell characteristics,such as good cell viabilities,rough surfaces,polar growth,fusion phenomenon,and injectability.The findings show its advantages for hADSCs spherical cultures.When cultured in SMG,hADSC spheroids produced large-scale spheroids.Additionally,confocal examination and viability assays revealed that SMG-cultured hADSC spheroids had higher cell viabilities and looser spherical structures,relative to those cultured in EP tubes.hADSC spheroids in static EP tube culture had tighter structures and more dead cells with rough and irregular surfaces,while hADSC spheroids in dynamic SMG condition exhibited looser structures and better cell viabilities with flat and regular surfaces.Therefore,the KSR media promotes spherical formation by hADSCs,which showed polar growth,fusion,and injectability in vitro.The dynamic SMG culture enhances the formation of a looser structure and better cell viabilities for hADSC spheroids.展开更多
Covalent organic frameworks(COFs)are an emerging type of porous crystalline polymers formed by combining strong covalent bonds with organic building blocks.Due to their large surface area,high intrinsic pore space,goo...Covalent organic frameworks(COFs)are an emerging type of porous crystalline polymers formed by combining strong covalent bonds with organic building blocks.Due to their large surface area,high intrinsic pore space,good crystallization properties,high stability,and designability of the resultant units,COFs are widely studied and used in the fields of gas adsorption,drug transport,energy storage,photoelectric catalysis,electrochemistry,and sensors.In recent years,the rapid development of the Internet of Things and people’s yearning for a better life have put forward higher and more requirements for sensors,which are the core components of the Internet of Things.Therefore,this paper reviews the recent progress of COFs in synthesis methods and sensing applications,especially in the last five years.This paper first introduces structure,properties,and synthesis methods of COFs and discusses advantages and disadvantages of different synthesis methods.Then,the research progress of COFs in different sensing fields,such as metal ion sensors,gas sensors,biomedical sensors,humidity sensors,and pH sensors,is introduced systematically.Conclusions and prospects are also presented in order to provide a reference for researchers concerned with COFs and sensors.展开更多
Summary What is already known about this topic?In 2018,unassisted smoking cessation(USC)was the predominant method for quitting smoking among Chinese adult smokers,accounting for 90.1%of cases.The utilization of profe...Summary What is already known about this topic?In 2018,unassisted smoking cessation(USC)was the predominant method for quitting smoking among Chinese adult smokers,accounting for 90.1%of cases.The utilization of professional smoking cessation support was comparatively low in this population.What was added by this report?In 2020,the prevalence of USC methods increased to 93.1%.Concurrently,there was a slight increase in the utilization of pharmaceuticals(from 4.6%in 2018 to 5.5%in 2020)and counseling and quit line services(from 3.2%in 2018 to 7.5%in 2020).On the other hand,the use of e-cigarettes as a cessation aid decreased from 14.9%in 2018 to 9.8%in 2020.Smokers aged 15–24 years old were more likely to rely on pharmaceutical interventions(7.9%),and less likely to choose USC methods(79.0%).What are the implications for public health practice?The promotion of professional cessation support is essential for enhancing smoking cessation rates.展开更多
Vascular complications of diabetes pose a severe threat to human health.Prevention and treatment protocols based on a single vascular complication are no longer suitable for the long-term management of patients with d...Vascular complications of diabetes pose a severe threat to human health.Prevention and treatment protocols based on a single vascular complication are no longer suitable for the long-term management of patients with diabetes.Diabetic panvascular disease(DPD)is a clinical syndrome in which vessels of various sizes,including macrovessels and microvessels in the cardiac,cerebral,renal,ophthalmic,and peripheral systems of patients with diabetes,develop atherosclerosis as a common pathology.Pathological manifestations of DPDs usually manifest macrovascular atherosclerosis,as well as microvascular endothelial function impairment,basement membrane thickening,and microthrombosis.Cardiac,cerebral,and peripheral microangiopathy coexist with microangiopathy,while renal and retinal are predominantly microangiopathic.The following associations exist between DPDs:numerous similar molecular mechanisms,and risk-predictive relationships between diseases.Aggressive glycemic control combined with early comprehensive vascular intervention is the key to prevention and treatment.In addition to the widely recommended metformin,glucagon-like peptide-1 agonist,and sodium-glucose cotransporter-2 inhibitors,for the latest molecular mechanisms,aldose reductase inhibitors,peroxisome proliferator-activated receptor-γagonizts,glucokinases agonizts,mitochondrial energy modulators,etc.are under active development.DPDs are proposed for patients to obtain more systematic clinical care requires a comprehensive diabetes care center focusing on panvascular diseases.This would leverage the advantages of a cross-disciplinary approach to achieve better integration of the pathogenesis and therapeutic evidence.Such a strategy would confer more clinical benefits to patients and promote the comprehensive development of DPD as a discipline.展开更多
By imitating the body structure and movement mode of the crab in nature,a novel stick–slip piezo-driven positioning platform was proposed by employing the bionic flexible hinge mechanism with a symmetrical structure ...By imitating the body structure and movement mode of the crab in nature,a novel stick–slip piezo-driven positioning platform was proposed by employing the bionic flexible hinge mechanism with a symmetrical structure and two piezoelectric stacks.The structural design and bionic motion principle were discussed,followed by analyzing the feasibility,safety,and output magnification ratio of the bionic flexible hinge mechanism via the stiffness matrix method and finite element simulation.To investigate the output performances of the positioning platform,a prototype was fabricated and an experiment system was established.Stepping characteristics of the positioning platform under various driving voltages were characterized,and the results indicated that the positioning platform could move steadily under various driving voltages.Within 1 s,the differences between the forward and reverse output displacement were less than 3%under different driving frequencies,proving the high bidirectional motion symmetry.The maximum driving speed of 5.44 mm/s was obtained under the driving voltage of 120 V and driving frequency of 5 Hz.In addition,the carrying load capacity of the positioning platform was tested by standard weights,and the results showed that when the carrying load reached 10 N,the driving speed could still reach 60μm/s.展开更多
Land surface temperature(LST),especially day-night LST difference(LSTd-LSTn),is a key variable for the stability of terrestrial ecosystems,affected by vegetation and climate change.Quantifying the contribution and fee...Land surface temperature(LST),especially day-night LST difference(LSTd-LSTn),is a key variable for the stability of terrestrial ecosystems,affected by vegetation and climate change.Quantifying the contribution and feedback of vegetation and climate to LST changes is critical to developing mitigation strategies.Based on LST,Normalized vegetation index(NDVI),land use(LU),air temperature(AT)and precipitation(Pre)from 2003 to 2021,partial correlation was used to analyze the response of LST to vegetation and climate.The feedback and contribution of both to LST were further quantifed by using spatial linear relationships and partial derivatives analysis.The results showed that both interannual LST(LSTy)and LSTd-LSTn responded negatively to vegetation,and vegetation had a negative feedback effect in areas with significantly altered.Vegetation was also a major contributor to the decline of LSTd-LSTn.With the advantage of positive partial correlation area of 94.99%,AT became the main driving factor and contributor to LSTy change trend.Pre contributed negatively to both LSTy and LSTd-LSTn,with contributions of-0.004℃/y and-0.022℃/y,respectively.AT played a decisive role in LST warming of YRB,which was partially mitigated by vegetation and Pre.The present research contributed'to,the,detection,of LST changes and improved understanding of the driving mechanism.展开更多
In recent years,past changes in global and regional land surface temperatures(LST)have been well studied,however,future LST changes have been largely ignored owing to data limitations.In this study,three climate varia...In recent years,past changes in global and regional land surface temperatures(LST)have been well studied,however,future LST changes have been largely ignored owing to data limitations.In this study,three climate variables of CMIP6,namely air temperature(AT),precipitation(Pre),and leaf area index(LAl),were spatially corrected using the Delta downscaling method.On this basis,by combining MODIS LST,elevation,slope and aspect,a random forest(RF)model was built to calculate the LST from 2022 to 2100.The absolute variability(AV)and Mann-Kendall(M-K)tests were used to quantitatively detect interannual and seasonal LST changes in different Shared Socioeconomic Pathways(SSPs)scenarios.The results showed that the AV value increased successively from SSP1-2.6 to SSP2-4.5 and then to SSP5-8.5.Compared with the base period(2003-2021),the increment in interannual,spring,summer and autumn LST during 2022-2100 was mainly between 1 and 2°℃under threescenarios.The interannual and seasonal LST were spatially characterized by significant warming over large areas,and the increasing was the fastest under SSP5-8.5.These results indicate that,in the future,LST will increase further over large areas,especially in winter.展开更多
Summary What is already known about this topic?In 2019,China CDC conducted the National Youth Tobacco Survey among secondary school students,and the prevalence rates of ever,current,and frequent smoking were 17.9%,5.9...Summary What is already known about this topic?In 2019,China CDC conducted the National Youth Tobacco Survey among secondary school students,and the prevalence rates of ever,current,and frequent smoking were 17.9%,5.9%,and 1.8%,respectively.What is added by this report?The prevalence rate of cigarette use in males decreased largely from 2019 to 2021 in China,while it increased in 18 provincial-level administrative divisions(PLADs)for females.The tobacco control situation remains challenging among vocational senior high school(VSHS)students.Significant geographical disparities existed in cigarette use.What are the implications for public health practice?Targeted tobacco control policies aimed at VSHS students are needed,specifically those PLADs with higher smoking rates.Additionally,close attention should be paid to female smokers.展开更多
Summary What is already known about this topic?Using the framework of the global youth tobacco survey(GYTS),China CDC conducted the first round of a national tobacco survey among junior high school(JHS)students in 201...Summary What is already known about this topic?Using the framework of the global youth tobacco survey(GYTS),China CDC conducted the first round of a national tobacco survey among junior high school(JHS)students in 2014,indicating that 17.9%and 5.9%of respondents were experimental and current cigarette smokers,respectively.展开更多
Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporad...Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporadically in China and have been contained relatively quickly.What is added by this report?Epidemiological investigation with genome sequence traceability analysis showed that the first case of COVID-19 in Nangong City acquired infection from a confirmed case from Shijiazhuang City.展开更多
Inspired by the adaptation of cells to the surrounding environment,the combination of cell membrane and nanomaterials has gradually become a new type of biomimetic nanocomposite.The construction of endogenous membrane...Inspired by the adaptation of cells to the surrounding environment,the combination of cell membrane and nanomaterials has gradually become a new type of biomimetic nanocomposite.The construction of endogenous membrane biomimetic nanocarriers(EMBNs)not only retains the structure of membrane surface protein,but also has the properties of nanoparticles(NPs),also provides the ability of natural interaction between nanomaterials and organisms,thus overcoming the severe challenges faced by traditional nanodelivery systems in clinical application.In this paper,the construction methods of EMBNs are reviewed,focusing on a simple method to prepare membrane proteins.Secondly,EMBNs were classified according a variety of cell membranes.Finally,the unique advantages of EMBNs in nanomedicine are introduced,including improving biocompatibility,homologous targeting ability,prolonging blood circulation time and immune escape abilty.In nanomedicine,such as targeted delivery,phototherapy,immunotherapy and tumor imaging,multifaceted biological interfaces through membrane masking provide a new approach for the development of multifunctional NPs.展开更多
The high price of state-of-the-art Pt electrocatalysts has plagued the acidic water electrolysis technique for decades. As a cheaper alternative to Pt, ruthenium is considered an inferior hydrogen evolution reaction (...The high price of state-of-the-art Pt electrocatalysts has plagued the acidic water electrolysis technique for decades. As a cheaper alternative to Pt, ruthenium is considered an inferior hydrogen evolution reaction (HER) catalyst than Pt due to its high susceptibility to oxidation and loss of activity. Herein, we reveal that the HER activity on Ru based catalysts could surpass Pt via tuning Ru oxidation state. Specifically, RuP clusters encapsulated in few layers of N, P-doped carbon (RuP@NPC) display a minimum over potential of 15.6 mV to deliver 10 mA·cm^(−2). Moreover, we for the first time show that a Ru based catalyst could afford current density up to 4 A·cm^(−2) in a practical water electrolysis cell, with voltage even lower than the Pt/C-based cell, as well as high robustness during 200 h operation. Using a combination of experiment probing and calculation, we postulate that the suitably charged Ru (∼ +2.4) catalytic center is the origin for its superior catalytic behavior. While the moderately charged Ru is empowered with optimized H adsorption behavior, the carbon encapsulation layers protect RuP clusters from over oxidation, thereby conferring the catalyst with high robustness.展开更多
Summary What is already known about this topic?Previous studies about tobacco use among college students in China were conducted at the school level or city level,with fewer than 5,000 students participating.What is a...Summary What is already known about this topic?Previous studies about tobacco use among college students in China were conducted at the school level or city level,with fewer than 5,000 students participating.What is added by this report?In 2021,China CDC conducted a national tobacco survey targeting students enrolled in the public higher education system.Overall,124,119 students from 220 colleges and universities in 31 provincial-level administrative divisions participated in this survey.Current cigarette smoking,current daily smoking,willingness to quit,and smoking cessation among college students were explored.What are the implications for public health practice?The current daily cigarette smoking rate of college students was significantly higher than that of senior high school students,especially higher vocational college students.Tobacco control interventions,such as a smoke-free school policy and smoking cessation services,need to be reinforced on college campuses.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12174034, 12047510, and 11822401)NSAF (Grant Nos. U1930402 and U1930403)。
文摘We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.
基金The authors would like to acknowledge the financial support provided by the National Natural Science Foundation of China(Grant No.41977240)the Fundamental Research Funds for the Central Universities(Grant No.B200202090).
文摘In this study, a three-dimensional (3D) finite element modelling (FEM) analysis is carried out to investigate the effects of soil spatial variability on the response of retaining walls and an adjacent box culvert due to a braced excavation. The spatial variability of soil stiffness is modelled using a variogram and calibrated by high-quality experimental data. Multiple random field samples (RFSs) of soil stiffness are generated using geostatistical analysis and mapped onto a finite element mesh for stochastic analysis of excavation-induced structural responses by Monte Carlo simulation. It is found that the spatial variability of soil stiffness can be described by an exponential variogram, and the associated vertical correlation length is varied from 1.3 m to 1.6 m. It also reveals that the spatial variability of soil stiffness has a significant effect on the variations of retaining wall deflections and box culvert settlements. The ignorance of spatial variability in 3D FEM can result in an underestimation of lateral wall deflections and culvert settlements. Thus, the stochastic structural responses obtained from the 3D analysis could serve as an effective aid for probabilistic design and analysis of excavations.
基金supported by the Science and Technology Project of Guangdong Province (2015B090903077, 2016A020210094, 2017A090905030), Chinathe Science and Technology Project of Guangzhou (201604020062), China+1 种基金the Innovation Team Construction Project of Modern Agricultural Industry Technology System of Guangdong Province (2016LM1100), Chinathe Overseas Joint Doctoral Training Program of South China Agricultural University (2018LHPY010), China
文摘Rice-duck co-culture is an integrated farming technology that benefits rice production, grain quality, and ecological sustainability in paddy fields. However, little is known about the effects of rice-duck co-culture on enzyme activity involved in the biosynthesis of 2-acetyl-1-pyrroline (2-AP), the volatile that gives fragrant rice its' distinctive and sought-after aroma. The present study aimed to examine the influence of rice-duck co-culture on the photosynthesis, yield, grain quality, rice aroma, and the enzymes involved in 2-acetyl-1-pyrroline biosynthesis in the cultivar Meixiangzhan 2 during the early and late rice growing seasons of 2016 in Guangzhou, China. We compared the rice grown in paddy fields with and without ducks. We found that rice-duck co-culture not only improved the yield and quality of fragrant rice grain, but also promoted the precursors of 2-AP biosynthesis formation and 2-AP accumulation in the grain. Grain 2-AP content in rice-duck co-culture was noticeably increased with 9.60% and 20.81% in early and late seasons, respectively. Proline and pyrroline-5-carboxylic acid (P5C) (precursors of 2-AP biosynthesis) and the activity of enzymes such as proline dehydrogenase (ProDH), ornithine aminotransferase (OAT) and Δ1 pyrroline-5-carboxylic acid synthetase (P5CS) were all improved by 10.15%–12.99%, 32.91%–47.75%, 17.81%–26.71%, 6.25%–21.78%, and 10.58%–38.87% under rice-duck co-culture in both seasons, respectively. Overall, our results suggest that rice-duck co-culture is an environmentally-friendly and sustainable approach to improving rice aroma and grain quality of fragrant rice.
基金funded by the National Science Fund for Distinguished Young Scholars(No.51725403)the National Natural Science Foundation of China(No.52004271)+1 种基金the China PostdoctoralScienceFoundation(Nos.2019M661990and 2018M632410)the Fundamental Research Funds for the Central Universities(No.2020QN05)。
文摘Solid backfill mining(SBM)is a form of green mining,the core of which is to control and minimize the deformation and movement of strata above longwall coal mines.Establishing a mechanical model that can reliably describe roof deformation by considering the viscoelastic properties of waste gangue is important as it assists in improving mine designs and reducing the environmental impact on the surface.In this paper,the time-dependent deformation characteristics of gangue under different stress levels were obtained by using lateral confinement compression,that reliably represents the compaction of goaf.The viscoelastic foundation model for gangue mechanical response is different from the traditionally used elastic foundation model,as it considers the time factor and viscoelasticity.A mechanical model using a thin plate on a fractional viscoelastic foundation was established,and the roof deflection,bending moment,time-dependent,viscous and other characteristics of SBM were included and analyzed.Compared with the existing elastic foundation model,the proposed fractional order viscoelastic foundation model has higher accuracy with laboratory data.The plate deflection increases by 50.9%and the bending moment increases by 37.9%after 100 days,which the elastic model would not have been able to predict.
基金conducted within the National Major Scientific Research Project (No. 2013CBA01806)the National Natural Science Foundation of China (No. 41271085)the National Scientific and Technological Support Project (No. 2013BAB05B03)
文摘The accuracy of spatial interpolation of precipitation data is determined by the actual spatial variability of the precipitation, the interpolation method, and the distribution of observatories whose selections are particularly important. In this paper, three spatial sampling programs, including spatial random sampling, spatial stratified sampling, and spatial sandwich sampling, are used to analyze the data from meteorological stations of northwestern China. We compared the accuracy of ordinary Kriging interpolation methods on the basis of the sampling results. The error values of the regional annual precipitation interpolation based on spatial sandwich sampling, including ME(0.1513), RMSE(95.91), ASE(101.84), MSE(-0.0036), and RMSSE(1.0397), were optimal under the premise of abundant prior knowledge. The result of spatial stratified sampling was poor, and spatial random sampling was even worse. Spatial sandwich sampling was the best sampling method, which minimized the error of regional precipitation estimation. It had a higher degree of accuracy compared with the other two methods and a wider scope of application.
基金This study was supported by the National Natural Science Foundation of China(21318261 and 3201101202 to JC)National Natural Science Foundation of China(82000943 to YG)+1 种基金the Joint Fund of Basic and Applied Basic Research Fund of Guangdong Province(2019A1515110355 to YG)the Project funded by China Postdoctoral Science Foundation(2019M663391 and 2021T140273 to YG).
文摘Human adipose stem cells(hADSCs)are reliable sources for cell therapy.However,the clinical applications are limited by the decrease in activity during in vitro culture.We used a knockout serum replacement(KSR)medium,Eppendorf(EP)tube culture,and a simulated microgravity(SMG)culture system to establish hADSC spheroids.We found that hADSCs aggregated and formed spheroids in the KSR culture medium.The EP tube culture method revealed many biological cell characteristics,such as good cell viabilities,rough surfaces,polar growth,fusion phenomenon,and injectability.The findings show its advantages for hADSCs spherical cultures.When cultured in SMG,hADSC spheroids produced large-scale spheroids.Additionally,confocal examination and viability assays revealed that SMG-cultured hADSC spheroids had higher cell viabilities and looser spherical structures,relative to those cultured in EP tubes.hADSC spheroids in static EP tube culture had tighter structures and more dead cells with rough and irregular surfaces,while hADSC spheroids in dynamic SMG condition exhibited looser structures and better cell viabilities with flat and regular surfaces.Therefore,the KSR media promotes spherical formation by hADSCs,which showed polar growth,fusion,and injectability in vitro.The dynamic SMG culture enhances the formation of a looser structure and better cell viabilities for hADSC spheroids.
基金funded by the National Natural Science Foundation of China(No.21964016)Xinjiang National Science Fund for Distinguished Young Scholars(No.2022D01E37)+1 种基金Key programs of Xinjiang Natural Science Foundation(No.2022B02051)Tianshan Innovation Team Program of Xinjiang Uygur Autonomous Region(No.2020D14038).
文摘Covalent organic frameworks(COFs)are an emerging type of porous crystalline polymers formed by combining strong covalent bonds with organic building blocks.Due to their large surface area,high intrinsic pore space,good crystallization properties,high stability,and designability of the resultant units,COFs are widely studied and used in the fields of gas adsorption,drug transport,energy storage,photoelectric catalysis,electrochemistry,and sensors.In recent years,the rapid development of the Internet of Things and people’s yearning for a better life have put forward higher and more requirements for sensors,which are the core components of the Internet of Things.Therefore,this paper reviews the recent progress of COFs in synthesis methods and sensing applications,especially in the last five years.This paper first introduces structure,properties,and synthesis methods of COFs and discusses advantages and disadvantages of different synthesis methods.Then,the research progress of COFs in different sensing fields,such as metal ion sensors,gas sensors,biomedical sensors,humidity sensors,and pH sensors,is introduced systematically.Conclusions and prospects are also presented in order to provide a reference for researchers concerned with COFs and sensors.
基金Supported by the China CDC scientific research project(JY22-3-09).
文摘Summary What is already known about this topic?In 2018,unassisted smoking cessation(USC)was the predominant method for quitting smoking among Chinese adult smokers,accounting for 90.1%of cases.The utilization of professional smoking cessation support was comparatively low in this population.What was added by this report?In 2020,the prevalence of USC methods increased to 93.1%.Concurrently,there was a slight increase in the utilization of pharmaceuticals(from 4.6%in 2018 to 5.5%in 2020)and counseling and quit line services(from 3.2%in 2018 to 7.5%in 2020).On the other hand,the use of e-cigarettes as a cessation aid decreased from 14.9%in 2018 to 9.8%in 2020.Smokers aged 15–24 years old were more likely to rely on pharmaceutical interventions(7.9%),and less likely to choose USC methods(79.0%).What are the implications for public health practice?The promotion of professional cessation support is essential for enhancing smoking cessation rates.
基金supported by the National Outstanding Youth Natural Science Foundation of China (82022076)the Young Qihuang Scholar of the“Tens of millions”talent project of China.
文摘Vascular complications of diabetes pose a severe threat to human health.Prevention and treatment protocols based on a single vascular complication are no longer suitable for the long-term management of patients with diabetes.Diabetic panvascular disease(DPD)is a clinical syndrome in which vessels of various sizes,including macrovessels and microvessels in the cardiac,cerebral,renal,ophthalmic,and peripheral systems of patients with diabetes,develop atherosclerosis as a common pathology.Pathological manifestations of DPDs usually manifest macrovascular atherosclerosis,as well as microvascular endothelial function impairment,basement membrane thickening,and microthrombosis.Cardiac,cerebral,and peripheral microangiopathy coexist with microangiopathy,while renal and retinal are predominantly microangiopathic.The following associations exist between DPDs:numerous similar molecular mechanisms,and risk-predictive relationships between diseases.Aggressive glycemic control combined with early comprehensive vascular intervention is the key to prevention and treatment.In addition to the widely recommended metformin,glucagon-like peptide-1 agonist,and sodium-glucose cotransporter-2 inhibitors,for the latest molecular mechanisms,aldose reductase inhibitors,peroxisome proliferator-activated receptor-γagonizts,glucokinases agonizts,mitochondrial energy modulators,etc.are under active development.DPDs are proposed for patients to obtain more systematic clinical care requires a comprehensive diabetes care center focusing on panvascular diseases.This would leverage the advantages of a cross-disciplinary approach to achieve better integration of the pathogenesis and therapeutic evidence.Such a strategy would confer more clinical benefits to patients and promote the comprehensive development of DPD as a discipline.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52075221)the Research Foundation of Education Department of Jilin Province,China(Grant No.JJKH20231153KJ)the Fundamental Research Funds for the Central Universities(2019-2023).
文摘By imitating the body structure and movement mode of the crab in nature,a novel stick–slip piezo-driven positioning platform was proposed by employing the bionic flexible hinge mechanism with a symmetrical structure and two piezoelectric stacks.The structural design and bionic motion principle were discussed,followed by analyzing the feasibility,safety,and output magnification ratio of the bionic flexible hinge mechanism via the stiffness matrix method and finite element simulation.To investigate the output performances of the positioning platform,a prototype was fabricated and an experiment system was established.Stepping characteristics of the positioning platform under various driving voltages were characterized,and the results indicated that the positioning platform could move steadily under various driving voltages.Within 1 s,the differences between the forward and reverse output displacement were less than 3%under different driving frequencies,proving the high bidirectional motion symmetry.The maximum driving speed of 5.44 mm/s was obtained under the driving voltage of 120 V and driving frequency of 5 Hz.In addition,the carrying load capacity of the positioning platform was tested by standard weights,and the results showed that when the carrying load reached 10 N,the driving speed could still reach 60μm/s.
基金supported by the National key R&D plan[grant no 2022YFF0802101]the National Natural Science Foundation of China[grant no 42171175]+1 种基金the Natural Science Foundation of Chongqing[grant no CSTB2022NSCQ-MSX0753]the Key Project of Innovation LREIS[grant no KPI001].
文摘Land surface temperature(LST),especially day-night LST difference(LSTd-LSTn),is a key variable for the stability of terrestrial ecosystems,affected by vegetation and climate change.Quantifying the contribution and feedback of vegetation and climate to LST changes is critical to developing mitigation strategies.Based on LST,Normalized vegetation index(NDVI),land use(LU),air temperature(AT)and precipitation(Pre)from 2003 to 2021,partial correlation was used to analyze the response of LST to vegetation and climate.The feedback and contribution of both to LST were further quantifed by using spatial linear relationships and partial derivatives analysis.The results showed that both interannual LST(LSTy)and LSTd-LSTn responded negatively to vegetation,and vegetation had a negative feedback effect in areas with significantly altered.Vegetation was also a major contributor to the decline of LSTd-LSTn.With the advantage of positive partial correlation area of 94.99%,AT became the main driving factor and contributor to LSTy change trend.Pre contributed negatively to both LSTy and LSTd-LSTn,with contributions of-0.004℃/y and-0.022℃/y,respectively.AT played a decisive role in LST warming of YRB,which was partially mitigated by vegetation and Pre.The present research contributed'to,the,detection,of LST changes and improved understanding of the driving mechanism.
基金supported by the National Natural Science Foundation of China(U2244216)the National key R&D plan(2022YFF0802101)+1 种基金the Fundamental Research Funds for the Central Universities(SWU-KT22009)the Key Project of Innovation LREIS(KPI001).
文摘In recent years,past changes in global and regional land surface temperatures(LST)have been well studied,however,future LST changes have been largely ignored owing to data limitations.In this study,three climate variables of CMIP6,namely air temperature(AT),precipitation(Pre),and leaf area index(LAl),were spatially corrected using the Delta downscaling method.On this basis,by combining MODIS LST,elevation,slope and aspect,a random forest(RF)model was built to calculate the LST from 2022 to 2100.The absolute variability(AV)and Mann-Kendall(M-K)tests were used to quantitatively detect interannual and seasonal LST changes in different Shared Socioeconomic Pathways(SSPs)scenarios.The results showed that the AV value increased successively from SSP1-2.6 to SSP2-4.5 and then to SSP5-8.5.Compared with the base period(2003-2021),the increment in interannual,spring,summer and autumn LST during 2022-2100 was mainly between 1 and 2°℃under threescenarios.The interannual and seasonal LST were spatially characterized by significant warming over large areas,and the increasing was the fastest under SSP5-8.5.These results indicate that,in the future,LST will increase further over large areas,especially in winter.
文摘Summary What is already known about this topic?In 2019,China CDC conducted the National Youth Tobacco Survey among secondary school students,and the prevalence rates of ever,current,and frequent smoking were 17.9%,5.9%,and 1.8%,respectively.What is added by this report?The prevalence rate of cigarette use in males decreased largely from 2019 to 2021 in China,while it increased in 18 provincial-level administrative divisions(PLADs)for females.The tobacco control situation remains challenging among vocational senior high school(VSHS)students.Significant geographical disparities existed in cigarette use.What are the implications for public health practice?Targeted tobacco control policies aimed at VSHS students are needed,specifically those PLADs with higher smoking rates.Additionally,close attention should be paid to female smokers.
基金financially supported by the National Natural Science Foundation of China (51972230, 51802217, 61835014, 51890864 and 51890865)the Natural Science Foundation of Tianjin (19JCZDJC38200)the National Key Research and Development Project (2016YFB0402103)
文摘Summary What is already known about this topic?Using the framework of the global youth tobacco survey(GYTS),China CDC conducted the first round of a national tobacco survey among junior high school(JHS)students in 2014,indicating that 17.9%and 5.9%of respondents were experimental and current cigarette smokers,respectively.
文摘Summary What is known about this topic?Coronavirus disease 2019(COVID-19)is widespread globally.In China,COVID-19 has been well controlled and has appeared only in importationrelated cases.Local epidemics occur sporadically in China and have been contained relatively quickly.What is added by this report?Epidemiological investigation with genome sequence traceability analysis showed that the first case of COVID-19 in Nangong City acquired infection from a confirmed case from Shijiazhuang City.
基金This work was supported by the Development Plan of Youth Innovation Team in Colleges and Universities of Shandong Province(2020KJC003).
文摘Inspired by the adaptation of cells to the surrounding environment,the combination of cell membrane and nanomaterials has gradually become a new type of biomimetic nanocomposite.The construction of endogenous membrane biomimetic nanocarriers(EMBNs)not only retains the structure of membrane surface protein,but also has the properties of nanoparticles(NPs),also provides the ability of natural interaction between nanomaterials and organisms,thus overcoming the severe challenges faced by traditional nanodelivery systems in clinical application.In this paper,the construction methods of EMBNs are reviewed,focusing on a simple method to prepare membrane proteins.Secondly,EMBNs were classified according a variety of cell membranes.Finally,the unique advantages of EMBNs in nanomedicine are introduced,including improving biocompatibility,homologous targeting ability,prolonging blood circulation time and immune escape abilty.In nanomedicine,such as targeted delivery,phototherapy,immunotherapy and tumor imaging,multifaceted biological interfaces through membrane masking provide a new approach for the development of multifunctional NPs.
基金The authors acknowledge funding from the National Key R&D Program of China (No. 2018YFB1502400)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDA21090400)the Jilin Province Science and Technology Development Program (Nos. 20190201300JC and 20180101030JC).
文摘The high price of state-of-the-art Pt electrocatalysts has plagued the acidic water electrolysis technique for decades. As a cheaper alternative to Pt, ruthenium is considered an inferior hydrogen evolution reaction (HER) catalyst than Pt due to its high susceptibility to oxidation and loss of activity. Herein, we reveal that the HER activity on Ru based catalysts could surpass Pt via tuning Ru oxidation state. Specifically, RuP clusters encapsulated in few layers of N, P-doped carbon (RuP@NPC) display a minimum over potential of 15.6 mV to deliver 10 mA·cm^(−2). Moreover, we for the first time show that a Ru based catalyst could afford current density up to 4 A·cm^(−2) in a practical water electrolysis cell, with voltage even lower than the Pt/C-based cell, as well as high robustness during 200 h operation. Using a combination of experiment probing and calculation, we postulate that the suitably charged Ru (∼ +2.4) catalytic center is the origin for its superior catalytic behavior. While the moderately charged Ru is empowered with optimized H adsorption behavior, the carbon encapsulation layers protect RuP clusters from over oxidation, thereby conferring the catalyst with high robustness.
文摘Summary What is already known about this topic?Previous studies about tobacco use among college students in China were conducted at the school level or city level,with fewer than 5,000 students participating.What is added by this report?In 2021,China CDC conducted a national tobacco survey targeting students enrolled in the public higher education system.Overall,124,119 students from 220 colleges and universities in 31 provincial-level administrative divisions participated in this survey.Current cigarette smoking,current daily smoking,willingness to quit,and smoking cessation among college students were explored.What are the implications for public health practice?The current daily cigarette smoking rate of college students was significantly higher than that of senior high school students,especially higher vocational college students.Tobacco control interventions,such as a smoke-free school policy and smoking cessation services,need to be reinforced on college campuses.
