Based on one-year observation,the concentration,sources,and potential source areas of volatile organic compounds(VOCs)were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haiko...Based on one-year observation,the concentration,sources,and potential source areas of volatile organic compounds(VOCs)were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haikou,China.The results showed that the annual average concentration of total VOCs(TVOCs)was 11.4 ppb V,and the composition was dominated by alkanes(8.2 ppb V,71.4%)and alkenes(1.3 ppb V,20.5%).The diurnal variation in the concentration of dominant VOC species showed a distinct bimodal distribution with peaks in the morning and evening.The greatest contribution to ozone formation potential(OFP)was made by alkenes(51.6%),followed by alkanes(27.2%).The concentrations of VOCs and nitrogen dioxide(NO_(2))in spring and summer were low,and it was difficult to generate high ozone(O_(3))concentrations through photochemical reactions.The significant increase in O_(3)concentrations in autumn and winter was mainly related to the transmission of pollutants from the northeast.Traffic sources(40.1%),industrial sources(19.4%),combustion sources(18.6%),solvent usage sources(15.5%)and plant sources(6.4%)were identified as major sources of VOCs through the positive matrix factorization(PMF)model.The southeastern coastal areas of China were identified as major potential source areas of VOCs through the potential source contribution function(PSCF)and concentration-weighted trajectory(CWT)models.Overall,the concentration of ambient VOCs in Haikou was strongly influenced by traffic sources and long-distance transport,and the control of VOCs emitted from vehicles should be strengthened to reduce the active species of ambient VOCs in Haikou,thereby reducing the generation of O_(3).展开更多
This study evaluates the quality of accounting information provided by Chinese multinational corporations(MNCs)in relation to the issue of earnings management.Using a combined dataset of outward foreign direct investm...This study evaluates the quality of accounting information provided by Chinese multinational corporations(MNCs)in relation to the issue of earnings management.Using a combined dataset of outward foreign direct investment and financial statements by Chinese firms publicly listed on A-share markets between 2012 and 2017,we investigate whether Chinese MNCs are more inclined to manage earnings.We discover that these firms exhibited significant earnings management behavior and typically adjusted their earnings downward.We demonstrate that these effects were more pronounced among private MNCs than state-owned firms,and in host countries with weaker institutional quality.Further research reveals that after delaying the confirmation of current earnings,Chinese MNCs received higher government subsidies,and this pattern was particularly prevalent among private MNCs.We find no evidence that Chinese MNCs manipulated earnings to avoid paying taxes.展开更多
The increasing need to monitor emergent pollutants,such as persistent organic pollutants,endocrine disruptors,and antibiotics,is driven by their impacts on environment and health.1,2 Nevertheless,instrumental methods ...The increasing need to monitor emergent pollutants,such as persistent organic pollutants,endocrine disruptors,and antibiotics,is driven by their impacts on environment and health.1,2 Nevertheless,instrumental methods based on mass spectrometry are intricate,take a considerable amount of time,and necessitate costly equipment,posing challenges for their application in field monitoring.The development of biosensors has offered a prompt,sensitive,selective,and real-time technique for the identification and monitoring of pollutants.A bioreceptor,a transducer,and a signal processor compose a biosensor,which transforms the recognition of target into detectable signals.3 The performance of biosensors relies heavily on the bioreceptor as its binding affinity and specificity are vital determinants.The most frequently used biosensors are developed with antibodies as bioreceptors that detect environmental pollutants effectively.This is due to their high specificity and binding affinity to analytes,which results from antigen−antibody immune interactions.However,screening antibodies with high specificity and affinity can be a challenging process in biosensor development for diverse pollutants.Furthermore,these antibodies may not always maintain a constant recognition performance in a harsh environmental matrix.Therefore,development of new bioreceptors with a rapid screening method that are reliable and cost-effective is essential for improving the convenience in on-site monitoring of environmental pollutants.展开更多
The development of high-efficiency peroxidase mimetics is highly desirable in view of high cost and low stability of natural enzymes.From the perspective of mimicking active site microenvironment at low cost,we herein...The development of high-efficiency peroxidase mimetics is highly desirable in view of high cost and low stability of natural enzymes.From the perspective of mimicking active site microenvironment at low cost,we herein report a novel histidine-functionalized graphene quantum dot(His-GQD)/hemin complex,which exhibits the highest catalytic rate for the peroxidase-based chromogenic reaction among the hemin-containing mimetics reported so far.Also,our peroxidase mimetic shows excellent tolerance to strongly acidic conditions and can function in a wide temperature range.Lineweaver-Burk plots and comprehensive electron paramagnetic resonance analysis reveal a ping-pong type catalytic mechanism for this mimetic.In addition,His-GQD/hemin demonstrates high efficiency and accuracy in detecting H2O2 and blood glucose.Our work provides an effective design of artificial enzymes for practical applications.展开更多
The changes of mechanical properties and biological activities of monomeric erythrocytes are studied using optical tweezers micromanipulation technology.Firstly,the mechanical properties of irradiated erythrocyte memb...The changes of mechanical properties and biological activities of monomeric erythrocytes are studied using optical tweezers micromanipulation technology.Firstly,the mechanical properties of irradiated erythrocyte membranes are obtained.Weaker power laser irradiation can delay the decay of the mechanical properties of erythrocytes and promote the biological activity of erythrocytes,while higher power laser irradiation damages erythrocytes.The stronger the laser irradiation is,the more obvious and rapid the damage will be.The temperature of the cell surface will be changed by regulating the laser power and irradiation time,so the biological functions of erythrocyte can be controlled.Secondly,the finite element simulation of the temperature change on the cell surface under the condition of laser irradiation is carried out using simulation software,and the precise temperature of the cell surface irradiated cumulatively by a laser with different powers is obtained.Finally,the processes of abscission,unfolding,and denaturation of hemoglobins in erythrocytes at different temperatures due to the photothermal effect are analyzed using the model.The mechanism of laser irradiation on the elasticity of erythrocyte membranes is also obtained.展开更多
In this work,we investigate the tracking control problem of asymmetrical underactuated surface vessels with parameter uncertainties.The tracking error model is frst derived via appropriate coordinate transformations,a...In this work,we investigate the tracking control problem of asymmetrical underactuated surface vessels with parameter uncertainties.The tracking error model is frst derived via appropriate coordinate transformations,and is considered as a cascade structure composed of two subsystems.The Lyapunov redesign approach is employed to construct the control laws separately to stabilize the two subsystems with unknown model parameters.The cascade system theory is applied to prove the global uniform asymptotic convergence of the state trajectory to the reference one provided the desired yaw velocity is not vanishing.The effectiveness of the proposed control laws is verifed by simulation examples.展开更多
As a new type of nanomaterial,carbon dots(CDs)have been recognized as a versatile nanoplatform with enormous potential for biomedical and optoelectronic applications because of low cytotoxicity,photostability,biocompa...As a new type of nanomaterial,carbon dots(CDs)have been recognized as a versatile nanoplatform with enormous potential for biomedical and optoelectronic applications because of low cytotoxicity,photostability,biocompatibility and versatility in addition to their tunable photoluminescence.In this review,we aim at updating the latest research on preparation,optoelectronic and chemical properties of CDs as well as their biomedical and optoelectronic applications.We highlight the applications of CDs for stem cell imaging,cell nucleus imaging,two-photon fluorescence imaging,tumor diagnosis and therapy and their optoelectronic applications including light-emitting diodes(LEDs),solar cells and electrocatalysis.Furthermore,we also discuss current challenges and breakthroughs on machine-learning-driven synthesis of CDs as well as nucleic acid detection with an eye towards the future.Finally,we hope that this review will give further impulses to target-oriented research on CDs for biomedical and optoelectronic applications.展开更多
In recent years,carbon dots(CDs),including carbon nanodots,carbonized polymer dots,carbon quantum dots,and graphene quantum dots have attracted a mounting interest as readily accessible,nontoxic,and relatively inexpen...In recent years,carbon dots(CDs),including carbon nanodots,carbonized polymer dots,carbon quantum dots,and graphene quantum dots have attracted a mounting interest as readily accessible,nontoxic,and relatively inexpensive carbon-based nanomaterials.Yet,despite intense research for a number of years,a unifying picture is still lacking to clarify the exact definition,clear chemical structure,and unique optical properties of this family of nanomaterials.In this review,we systematically summarize the recent development of CDs from molecular design to related properties of excited states as well as their applications in optoelectronic devices and biology.We point out the current challenges,including exploring precise synthesis,clarifying the structure-property relationship,and regulating singlet and triplet states of fluorescence,phosphorescence,and delayed fluorescence.Moreover,the structural optimization of optoelectronic devices,tumor targeting mechanism,selective imaging,and drug delivery of CDs are also highlighted.We hope that the information provided in this review will inspire more exciting research on CDs from a brand-new perspective and promote practical application of CDs in multiple directions of current and future research.展开更多
基金supported by the Major Program of Science and Technology of Hainan Province,China(No.ZDKJ202007)the Special Foundation of Government Financial of Hainan Province,China(No.ZC2018-196)the Youth Innovation Foundation of Hainan Research Academy of Environmental Sciences,China(No.QNCX2021002)。
文摘Based on one-year observation,the concentration,sources,and potential source areas of volatile organic compounds(VOCs)were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haikou,China.The results showed that the annual average concentration of total VOCs(TVOCs)was 11.4 ppb V,and the composition was dominated by alkanes(8.2 ppb V,71.4%)and alkenes(1.3 ppb V,20.5%).The diurnal variation in the concentration of dominant VOC species showed a distinct bimodal distribution with peaks in the morning and evening.The greatest contribution to ozone formation potential(OFP)was made by alkenes(51.6%),followed by alkanes(27.2%).The concentrations of VOCs and nitrogen dioxide(NO_(2))in spring and summer were low,and it was difficult to generate high ozone(O_(3))concentrations through photochemical reactions.The significant increase in O_(3)concentrations in autumn and winter was mainly related to the transmission of pollutants from the northeast.Traffic sources(40.1%),industrial sources(19.4%),combustion sources(18.6%),solvent usage sources(15.5%)and plant sources(6.4%)were identified as major sources of VOCs through the positive matrix factorization(PMF)model.The southeastern coastal areas of China were identified as major potential source areas of VOCs through the potential source contribution function(PSCF)and concentration-weighted trajectory(CWT)models.Overall,the concentration of ambient VOCs in Haikou was strongly influenced by traffic sources and long-distance transport,and the control of VOCs emitted from vehicles should be strengthened to reduce the active species of ambient VOCs in Haikou,thereby reducing the generation of O_(3).
基金the National Natural Science Foundation of China(Nos.72203061,72303157,and 72173082)the Ministry of Education Project of Key Research Institute of Humanities and Social Sciences at Universities in China(No.22JJD790011)the Fundamental Research Funds for the Central Universities(No.2021ECNU-HLYT033).
文摘This study evaluates the quality of accounting information provided by Chinese multinational corporations(MNCs)in relation to the issue of earnings management.Using a combined dataset of outward foreign direct investment and financial statements by Chinese firms publicly listed on A-share markets between 2012 and 2017,we investigate whether Chinese MNCs are more inclined to manage earnings.We discover that these firms exhibited significant earnings management behavior and typically adjusted their earnings downward.We demonstrate that these effects were more pronounced among private MNCs than state-owned firms,and in host countries with weaker institutional quality.Further research reveals that after delaying the confirmation of current earnings,Chinese MNCs received higher government subsidies,and this pattern was particularly prevalent among private MNCs.We find no evidence that Chinese MNCs manipulated earnings to avoid paying taxes.
基金supported by National Natural Science Fund for Excellent Young Scientists Fund Program(Overseas)the National Natural Science Foundation of China(Grant no.22276199).
文摘The increasing need to monitor emergent pollutants,such as persistent organic pollutants,endocrine disruptors,and antibiotics,is driven by their impacts on environment and health.1,2 Nevertheless,instrumental methods based on mass spectrometry are intricate,take a considerable amount of time,and necessitate costly equipment,posing challenges for their application in field monitoring.The development of biosensors has offered a prompt,sensitive,selective,and real-time technique for the identification and monitoring of pollutants.A bioreceptor,a transducer,and a signal processor compose a biosensor,which transforms the recognition of target into detectable signals.3 The performance of biosensors relies heavily on the bioreceptor as its binding affinity and specificity are vital determinants.The most frequently used biosensors are developed with antibodies as bioreceptors that detect environmental pollutants effectively.This is due to their high specificity and binding affinity to analytes,which results from antigen−antibody immune interactions.However,screening antibodies with high specificity and affinity can be a challenging process in biosensor development for diverse pollutants.Furthermore,these antibodies may not always maintain a constant recognition performance in a harsh environmental matrix.Therefore,development of new bioreceptors with a rapid screening method that are reliable and cost-effective is essential for improving the convenience in on-site monitoring of environmental pollutants.
基金The authors acknowledge financial support for this work from the National Key R&D Program"nanotechnology"special focus(No.2016YFA0201600)the National Natural Science Foundation of China(Nos.21422303,21573049,21872043,81602643)+1 种基金Beijing Natural Science Foundation(No.2142036)the Knowledge Innovation Program,Youth Innovation Promotion Association,and Special Program of"One Belt One Road"of CAS.The authors thank Dr.Dexing Li for the technique support and many helpful discussions for the ITC testing.
文摘The development of high-efficiency peroxidase mimetics is highly desirable in view of high cost and low stability of natural enzymes.From the perspective of mimicking active site microenvironment at low cost,we herein report a novel histidine-functionalized graphene quantum dot(His-GQD)/hemin complex,which exhibits the highest catalytic rate for the peroxidase-based chromogenic reaction among the hemin-containing mimetics reported so far.Also,our peroxidase mimetic shows excellent tolerance to strongly acidic conditions and can function in a wide temperature range.Lineweaver-Burk plots and comprehensive electron paramagnetic resonance analysis reveal a ping-pong type catalytic mechanism for this mimetic.In addition,His-GQD/hemin demonstrates high efficiency and accuracy in detecting H2O2 and blood glucose.Our work provides an effective design of artificial enzymes for practical applications.
基金supported by the National Natural Science Foundation of China (No.61575087)the Natural Science Foundation of Jiangsu Province (No.BK20151164)+2 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No.16KJB140005)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)Jiangsu Collaborative Innovation Center of Advanced Laser Technology and Emerging Industry for the generous financial support
文摘The changes of mechanical properties and biological activities of monomeric erythrocytes are studied using optical tweezers micromanipulation technology.Firstly,the mechanical properties of irradiated erythrocyte membranes are obtained.Weaker power laser irradiation can delay the decay of the mechanical properties of erythrocytes and promote the biological activity of erythrocytes,while higher power laser irradiation damages erythrocytes.The stronger the laser irradiation is,the more obvious and rapid the damage will be.The temperature of the cell surface will be changed by regulating the laser power and irradiation time,so the biological functions of erythrocyte can be controlled.Secondly,the finite element simulation of the temperature change on the cell surface under the condition of laser irradiation is carried out using simulation software,and the precise temperature of the cell surface irradiated cumulatively by a laser with different powers is obtained.Finally,the processes of abscission,unfolding,and denaturation of hemoglobins in erythrocytes at different temperatures due to the photothermal effect are analyzed using the model.The mechanism of laser irradiation on the elasticity of erythrocyte membranes is also obtained.
基金supported by National Science and Technology Major Project(No.2012CB821202)the Beijing Natural Science Foundation(Nos.4122043,4112034)the National Natural Science Foundation of China(Nos.60874012,61174057)
文摘In this work,we investigate the tracking control problem of asymmetrical underactuated surface vessels with parameter uncertainties.The tracking error model is frst derived via appropriate coordinate transformations,and is considered as a cascade structure composed of two subsystems.The Lyapunov redesign approach is employed to construct the control laws separately to stabilize the two subsystems with unknown model parameters.The cascade system theory is applied to prove the global uniform asymptotic convergence of the state trajectory to the reference one provided the desired yaw velocity is not vanishing.The effectiveness of the proposed control laws is verifed by simulation examples.
基金the National Natural Science Foundation of China(NSFC 21573019,21872010)the Fundamental Research Funds for the Central Universities(2020NTST11)We also acknowledge the support from Key Laboratory of Radiopharmaceuticals and Key Laboratory of Theoretical and Computational Photochemistry,Ministry of Education.
文摘As a new type of nanomaterial,carbon dots(CDs)have been recognized as a versatile nanoplatform with enormous potential for biomedical and optoelectronic applications because of low cytotoxicity,photostability,biocompatibility and versatility in addition to their tunable photoluminescence.In this review,we aim at updating the latest research on preparation,optoelectronic and chemical properties of CDs as well as their biomedical and optoelectronic applications.We highlight the applications of CDs for stem cell imaging,cell nucleus imaging,two-photon fluorescence imaging,tumor diagnosis and therapy and their optoelectronic applications including light-emitting diodes(LEDs),solar cells and electrocatalysis.Furthermore,we also discuss current challenges and breakthroughs on machine-learning-driven synthesis of CDs as well as nucleic acid detection with an eye towards the future.Finally,we hope that this review will give further impulses to target-oriented research on CDs for biomedical and optoelectronic applications.
基金National Natural Science Foundation of China,Grant/Award Numbers:21573019,21872010National Key Research and Development Program of China,Grant/Award Number:2019YFE0112200FundamentalResearch Funds for the Central Universities,Grant/Award Number:2020NTST11。
文摘In recent years,carbon dots(CDs),including carbon nanodots,carbonized polymer dots,carbon quantum dots,and graphene quantum dots have attracted a mounting interest as readily accessible,nontoxic,and relatively inexpensive carbon-based nanomaterials.Yet,despite intense research for a number of years,a unifying picture is still lacking to clarify the exact definition,clear chemical structure,and unique optical properties of this family of nanomaterials.In this review,we systematically summarize the recent development of CDs from molecular design to related properties of excited states as well as their applications in optoelectronic devices and biology.We point out the current challenges,including exploring precise synthesis,clarifying the structure-property relationship,and regulating singlet and triplet states of fluorescence,phosphorescence,and delayed fluorescence.Moreover,the structural optimization of optoelectronic devices,tumor targeting mechanism,selective imaging,and drug delivery of CDs are also highlighted.We hope that the information provided in this review will inspire more exciting research on CDs from a brand-new perspective and promote practical application of CDs in multiple directions of current and future research.
