Neuropathologically, Alzheimer’s disease is characterized by the presence of extracellular deposits of amyloid-β peptides, intracellular neurofibrillary tangles and atrophy of the basal forebrain cholinergic neurons...Neuropathologically, Alzheimer’s disease is characterized by the presence of extracellular deposits of amyloid-β peptides, intracellular neurofibrillary tangles and atrophy of the basal forebrain cholinergic neurons. The research of pathogenesis of Alzheimer’s disease inspirits potential clinical drugs for treatment. To block the progression of the disease, drugs under development have to interfere with the pathogenic steps responsible for the clinical symptoms, including cholinergic deficit, calcium dysregulation, inflammation and oxidative damage, and the deposition of amyloid- β plaques and of neurofibrillary tangles. In this review, the pertinent literature about drugs targeted on relieving symptoms above is reviewed. We aim to discuss possible research priorities in the future.展开更多
The Betula genus contains pentacyclic triterpenoid betulin known for its environmental adaptation and medicinal properties.However,the mechanisms underlying betulin biosynthesis responding to climate change remain unc...The Betula genus contains pentacyclic triterpenoid betulin known for its environmental adaptation and medicinal properties.However,the mechanisms underlying betulin biosynthesis responding to climate change remain unclear.In this study,the role of epigenetic modification(DNA methylation) in betulin biosynthesis was examined and how climatic factors influence it.Whole-genome bisulfite sequencing was performed for greenhouse-grown Chinese white birch(Betula platyphylla Sukaczev) treated with DNA methylation inhibitor zebularine(ZEB) and a natural birch population in Northeast China.ZEB treatment significantly affected the CHH methylation level of transposable elements and betulin content in a hormesis dose-dependent manner.The methylation and expression of bHLH9,a key transcriptional factor controlling betulin biosynthesis,were also consistently affected by ZEB treatment as a hormetic dose-response.In the natural population,there was a positive correlation between promoter methylation of bHLH9 and summer precipitation,while winter temperature was negatively correlated.Thus climate-dependent methylation of bHLH9 regulates the expression of downstream genes involved in betulin biosynthesis.This study highlights the role of environmental signals to induce epigenetic changes that result in betulin production,possibly helping to develop resilient plants to combat ongoing climate change and enhance secondary metabolite production.展开更多
The HfO2-based ferroelectric field effect transistors(FeFET)have been widely studied for their ability in breaking the Boltzmann limit and the potential to be applied to low-power circuits.This article systematically ...The HfO2-based ferroelectric field effect transistors(FeFET)have been widely studied for their ability in breaking the Boltzmann limit and the potential to be applied to low-power circuits.This article systematically investigates the transient response of negative capacitance(NC)fin field-effect transistors(FinFETs)through two kinds of self-built test schemes.By comparing the results with those of conventional FinFETs,we experimentally demonstrate that the on-current of the NC FinFET is not degraded in the MHz frequency domain.Further test results in the higher frequency domain show that the on-state current of the prepared NC FinFET increases with the decreasing gate pulse width at pulse widths below 100 ns and is consistently greater(about 80%with NC NMOS)than the on-state current of the conventional transistor,indicating the great potential of the NC FET for future high-frequency applications.展开更多
Nitrogen dioxide(NO_(2))poses a critical potential risk to environmental quality and public health.A reliable machine learning(ML)forecasting framework will be useful to provide valuable information to support governm...Nitrogen dioxide(NO_(2))poses a critical potential risk to environmental quality and public health.A reliable machine learning(ML)forecasting framework will be useful to provide valuable information to support government decision-making.Based on the data from1609 air quality monitors across China from 2014-2020,this study designed an ensemble ML model by integrating multiple types of spatial-temporal variables and three sub-models for time-sensitive prediction over a wide range.The ensemble ML model incorporates a residual connection to the gated recurrent unit(GRU)network and adopts the advantage of Transformer,extreme gradient boosting(XGBoost)and GRU with residual connection network,resulting in a 4.1%±1.0%lower root mean square error over XGBoost for the test results.The ensemble model shows great prediction performance,with coefficient of determination of 0.91,0.86,and 0.77 for 1-hr,3-hr,and 24-hr averages for the test results,respectively.In particular,this model has achieved excellent performance with low spatial uncertainty in Central,East,and North China,the major site-dense zones.Through the interpretability analysis based on the Shapley value for different temporal resolutions,we found that the contribution of atmospheric chemical processes is more important for hourly predictions compared with the daily scale predictions,while the impact of meteorological conditions would be ever-prominent for the latter.Compared with existing models for different spatiotemporal scales,the present model can be implemented at any air quality monitoring station across China to facilitate achieving rapid and dependable forecast of NO_(2),which will help developing effective control policies.展开更多
The marine climate conditions are intricate and variable. In scenarios characterized by high proportions of wind and solar energy access, the uncertainty regarding the energy sources for island microgrid is significan...The marine climate conditions are intricate and variable. In scenarios characterized by high proportions of wind and solar energy access, the uncertainty regarding the energy sources for island microgrid is significantly exacerbated, presenting challenges to both the economic viability and reliability of the capacity configuration for island microgrids. To address this issue, this paper proposes a distributionally robust optimization (DRO) method for island microgrids, considering extreme scenarios of wind and solar conditions. Firstly, to address the challenge of determining the probability distribution functions of wind and solar in complex island climates, a conditional generative adversarial network (CGAN) is employed to generate a scenario set for wind and solar conditions. Then, by combining k-means clustering with an extreme scenario selection method, typical scenarios and extreme scenarios are selected from the generated scenario set, forming the scenario set for the DRO model of island microgrids. On this basis, a DRO model based on multiple discrete scenarios is constructed with the objective of minimizing the sum of investment costs, operation and maintenance costs, fuel purchase costs, penalty costs of wind and solar curtailment, and penalty costs of load loss. The model is subjected to equipment operation and power balance constraints, and solved using the columns and constraints generation (CCG) algorithm. Finally, through typical examples, the effectiveness of this paper’s method in balancing the economic viability and robustness of the configuration scheme for the island microgrid, as well as reducing wind and solar curtailment and load loss, is verified.展开更多
The compaction characteristics of biomimetic press roller with ridge structures, inspired from the geometrical features of the ventral surface of dung beetle （Copris ochus Motschulsky）, were investigated in this wor...The compaction characteristics of biomimetic press roller with ridge structures, inspired from the geometrical features of the ventral surface of dung beetle （Copris ochus Motschulsky）, were investigated in this work. Field tests were carried out at three weights （300 N, 500 N and 700 N） and two forward velocities （0.64 m·s^-1 and 1.04 m·s^-1） for biomimetic press roller and conventional press roller. To determine compaction performance, rolling resistance, soil bulk density, soil moisture content, emergence rate and percent change of plant spacing were measured. Roller weight was proved to be the major contributory factor on soil compaction. Biomimetic press roller decreased rolling resistance by 2.98% -17.69% at the velocity of 0.64 m·s^-1, and by 6.59% -18.57% at the velocity of 1.04 m·s^-1 compared with the conventional press roller. Both biomimetic roller and conventional roller can achieve proper bulk density for corn seeds under the experimental conditions. However, compared with the conventional roller, biomimetic roller helped soil conserve more moisture. The highest emergence rate was found when the biomimetic roller worked with a weight of 700 N and velocity of 0.64 m·s^-1. Percent change of plant spacing was lower using the biomimetic press roller compared with that using the conventional roller, because that adjacent ridge structures of the biomi- metic roller can well constrain the flow of soil during compacting process.展开更多
Amides,a series of significant atmospheric nitrogen-containing volatile organic compounds(VOCs),can participate in new particle formation(NPF)throught interacting with sulfuric acid(SA)and organic acids.In this study,...Amides,a series of significant atmospheric nitrogen-containing volatile organic compounds(VOCs),can participate in new particle formation(NPF)throught interacting with sulfuric acid(SA)and organic acids.In this study,we investigated the molecular interactions of formamide(FA),acetamide(AA),N-methylformamide(MF),propanamide(PA),Nmethylacetamide(MA),and N,N-dimethylformamide(DMF)with SA,acetic acid(HAC),propanoic acid(PAC),oxalic acid(OA),and malonic acid(MOA).Global minimum of clusters were obtained through the association of the artificial bee colony(ABC)algorithm and density functional theory(DFT)calculations.The conformational analysis,thermochemical analysis,frequency analysis,and topological analysis were conducted to determine the interactions of hydrogen-bonded molecular clusters.The heterodimers formed a hepta or octa membered ring through four different types of hydrogen bonds,and the strength of the bonds are ranked in the following order:SO-H···O>CO-H···O>N-H···O>C-H···O.We also evaluated the stability of the clusters and found that the stabilization effect of amides with SA is weaker than that of amines with SA but stronger than that of ammonia(NH 3)with SA in the dimer formation of nucleation process.Additionally,the nucleation capacity of SA with amides is greater than that of organic acids with amides.展开更多
Exosomes are highly important in clinical diagnosis due to their high homology with their parental cells.However,conventional exosome detection methods still face the challenges of expensive equipment,low sensitivity,...Exosomes are highly important in clinical diagnosis due to their high homology with their parental cells.However,conventional exosome detection methods still face the challenges of expensive equipment,low sensitivity,and complex procedures.Field effect transistors(FETs)are not only the most essential electronic component in the modern microelectronics industry but also show great potential for biomolecule detection owing to the advantages of rapid response,high sensitivity,and label-free detection.In this study,we proposed a Si nanowire field-effect transistor(Si-NW Bio-FET)device chemically modified with specific antibodies for the electrical and label-free detection of exosomes.The Si-NW FETs were fabricated by standard microelectronic processes with 45 nm width nanowires and packaged in a polydimethylsiloxane(PDMS)microfluidic channel.The nanowires were further modified with the specific CD63 antibody to form a Si-NW Bio-FET.The use of the developed Si-NW Bio-FET for the electrical and labelfree detection of exosomes was successfully demonstrated with a limit of detection(LOD)of 2159 particles/mL.In contrast to other technologies,in this study,Si-NW Bio-FET provides a unique strategy for directly quantifying and realtime detecting exosomes without labeling,indicating its potential as a tool for the early diagnosis of cancer.展开更多
Interactions of the three common atmospheric bases,dimethylamine((CH3)2 NH),methylamine(CH3 NH2),ammonia(NH3),all considered to be efficient stabilizers of binary clusters in the Earth’s atmosphere,with H2 SO4,the ke...Interactions of the three common atmospheric bases,dimethylamine((CH3)2 NH),methylamine(CH3 NH2),ammonia(NH3),all considered to be efficient stabilizers of binary clusters in the Earth’s atmosphere,with H2 SO4,the key atmospheric precursor,and 14 common atmospheric organic acids(COAs)(formic,acetic,oxalic,malonic,succinic,glutaric acid,adipic,benzoic,phenylacetic,pyruvic,maleic acid,malic,tartaric and pinonic acids)have been studied using the density functional theory(DFT)and composite high-accuracy G3 MP2 method.The thermodynamic stability of mixed(COA)(H2 SO4),(COA)(B1),(COA)(B2)and(COA)(B3)dimers and(COA)(H2 SO4)(B1),(COA)(H2 SO4)(B2)and(COA)(H2 SO4)(B3)trimers,where B1,B2 and B3 refer to(CH3)2 NH,CH3 NH2 and NH3,respectively,have been investigated and their impacts on the thermodynamic stability of clusters containing H2 SO4 have been studied.Our investigation shows that interactions of H2 SO4 with GOA,(CH3)2 NH,CH3 NH2 and NH3 lead to the formation of more stable mixed dimers and trimers than(H2 SO4)2 and(H2 SO4)2(base),respectively,and emphasize the importance of common organic species for early stages of atmospheric nucleation.We also show that although amines are generally confirmed to be more active than NH3 as stabilizers of binary clusters,in some cases mixed trimers containing NH3 are more stable thermodynamically than those containing CH3 NH2.This study indicates an important role of COA,which coexist and interact with that H2 SO4 and common atmospheric bases in the Earth atmosphere,in formation of stable prenucleation clusters and suggests that the impacts of COA on new particle formation(NPF)should be studied in further details.展开更多
Sea salt particles containing NaCl are among the most abundant particulate masses in coastal atmosphere. Reactions involving sea salt particles potentially generate Cl radicals, which are released into coastal atmosph...Sea salt particles containing NaCl are among the most abundant particulate masses in coastal atmosphere. Reactions involving sea salt particles potentially generate Cl radicals, which are released into coastal atmosphere. Cl radicals play an important role in the nitrogen and O3 cycles, sulfitr chemistry and particle formation in the troposphere of the polluted coastal regions. This paper aimed at .the heterogeneous reaction between gaseous HNO3 .and solid NaCl. The mech.anis.m was in.vestigatedby density functional theory （DFT）. The results imply that water molecules induce the surface reconstruction, which is essential for the heterogeneous reaction. The surface reconstruction on the defective （710） surface has a barrier of 10.24 kcal.mol-1 and is endothermic by 9.69 kcal.mol-1, whereas the reconstruction on the clean （100） surface has a barrier of 18.46 kcal.mol-1 and isendothermic by 12.96 kcal.mol-1. The surface reconstruction involved in water-adsorbed （710） surface is more energetically favorable. In comparison, water molecules adsorbed on NaCl （100） surface likely undergo water diffusion or desorption. Further, it reveals that the coordination number of the Cl-out is reduced after the surface reconstruction, which assists Clout to accept the proton from HNO3. HCl is released from heterogeneous reactions between gaseous HNO3 and solid NaCl and can react with OH free radicals to produce atomic Cl radicals. The results will offer further insights into the impact of gaseous HNO3 on the air quality of the coastal areas.展开更多
To understand the size-resolved aerosol ionic composition and the factors influencing secondary aerosol formation in the upper boundary layer in South Central China, size-segregated aerosol samples were collected usin...To understand the size-resolved aerosol ionic composition and the factors influencing secondary aerosol formation in the upper boundary layer in South Central China, size-segregated aerosol samples were collected using a micro-orifice uniform deposit irnpactor （MOUDI） in spring 2009 at the summit of Mount Heng （1269 m asl）, followed by subsequent laboratory analyses of 13 inorganic and organic water-soluble ions. During non- dust-storm periods, the average PM1.8 concentration was 41.8 μg·m^-3, contributing to 55% of the PM10. Sulfates, nitrates, and ammonium, the dominant ions in the fine particles, amounted to 46.8% of the PM1.8. Compared with Mount Tai in the North China Plain, the concentrations of both fine and coarse particles and the ions contained therein were substantially lower. When the air masses from Southeast Asia prevailed, intensive biomass burning there led to elevated concentrations of sulfates, nitrates, ammonium, potassium, and chloride in the fine particles at Mount Heng. The air masses originating from the north Gobi brought heavy dust storms that resulted in the remarkable production of sulfates, ammonium, methane sulfonic acid, and oxalates in the coarse particles. Generally, the sulfates were primarily produced in the form of （NH4）2SO4 in the droplet mode via heterogeneous aqueous reactions. Only approximately one-third of the nitrates were distributed in the fine mode, and high humidity facilitated the secondary formation of fine nitrates. The heterogeneous formation of coarse nitrates and ammonium on dry alkaline dust surfaces was found to be less efficient than that on the coarse particles during non-dust-storm periods.展开更多
Fluorine-containing halogenated fluorophenol may have effect as intermediate species involved in the formation of polyfluorinated dibenzo-p-dioxin/dibenzofurans （PFDDs/Fs）. The mechanism for the atomic H initiated r...Fluorine-containing halogenated fluorophenol may have effect as intermediate species involved in the formation of polyfluorinated dibenzo-p-dioxin/dibenzofurans （PFDDs/Fs）. The mechanism for the atomic H initiated reactions with complete series of nineteen fluorophenol congeners was studies using the density functional theory. At the MPWB1K,/6-31＋G（d,p） level, the geometries and frequencies of reactants, transition states, and products were obtained, and the accurate energetic values were acquired at the MPWB 1K/6-311 ＋G（3df,2p） level. The rate constants were evaluated by the canonical variational transition-state theory with the small curvature tunneling contribution over a wide temperature range of 600-1000 K. The study shows that the intramolecular hydrogen-bond in the ortho-substituted FPs as well as the inductive effect of the electron-withdrawing fluorine and steric repulsion of multiple substitutions may ultimately be responsible for the relative strength of the O-H bonds in FPs. The results can be used for further studies on PFDD/Fs formation mechanism.展开更多
In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states ...In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states and products were performed at the MPWB1K/6-311＋G（3df,2p）//MPWB1K/6- 31＋G（d,p） level of theory. Several energetically favorable reaction pathways were revealed. The formation mechanisms of secondary pollutants were presented and discussed. The rate constants were deduced over the temperature range of 273-333 K using canonical variational transition-state （CVT） theory with the small curvature tunneling （SCT） method. Our study shows that H abstraction from the alkyl group and NO3 addition to the Ca atom of the benzene ring are the dominant reaction pathways. The rate-temperature formula of the overall rate constants is k（T）（DDT＋NO3） = （7.21 ~ 10-15）exp（-153.81/T） cm3/（mol.sec） over the possible atmospheric temperature range of 273-333 K. The atmospheric lifetime of DDT determined by NO3 radical is about 52.5 days, which indicates that it can be degraded in the gas phase within several months.展开更多
文摘Neuropathologically, Alzheimer’s disease is characterized by the presence of extracellular deposits of amyloid-β peptides, intracellular neurofibrillary tangles and atrophy of the basal forebrain cholinergic neurons. The research of pathogenesis of Alzheimer’s disease inspirits potential clinical drugs for treatment. To block the progression of the disease, drugs under development have to interfere with the pathogenic steps responsible for the clinical symptoms, including cholinergic deficit, calcium dysregulation, inflammation and oxidative damage, and the deposition of amyloid- β plaques and of neurofibrillary tangles. In this review, the pertinent literature about drugs targeted on relieving symptoms above is reviewed. We aim to discuss possible research priorities in the future.
基金the National Non-profi t Institute Research Grant of the Chinese Academy of Forestry(CAFYBB2019ZY003)the National Natural Science Foundation of China(31871220 and 31801444)+2 种基金the Innovation Project of State Key Laboratory of Tree Genetics andBreeding(Northeast Forestry University)(2013A06)the Fundamental Research Funds for the Central Universities(2572017DA06 and 2572020DP01)Heilongjiang Provincial Natural Science Foundation of China(LH2021C005).
文摘The Betula genus contains pentacyclic triterpenoid betulin known for its environmental adaptation and medicinal properties.However,the mechanisms underlying betulin biosynthesis responding to climate change remain unclear.In this study,the role of epigenetic modification(DNA methylation) in betulin biosynthesis was examined and how climatic factors influence it.Whole-genome bisulfite sequencing was performed for greenhouse-grown Chinese white birch(Betula platyphylla Sukaczev) treated with DNA methylation inhibitor zebularine(ZEB) and a natural birch population in Northeast China.ZEB treatment significantly affected the CHH methylation level of transposable elements and betulin content in a hormesis dose-dependent manner.The methylation and expression of bHLH9,a key transcriptional factor controlling betulin biosynthesis,were also consistently affected by ZEB treatment as a hormetic dose-response.In the natural population,there was a positive correlation between promoter methylation of bHLH9 and summer precipitation,while winter temperature was negatively correlated.Thus climate-dependent methylation of bHLH9 regulates the expression of downstream genes involved in betulin biosynthesis.This study highlights the role of environmental signals to induce epigenetic changes that result in betulin production,possibly helping to develop resilient plants to combat ongoing climate change and enhance secondary metabolite production.
基金This project was supported in part by the Science and Technology program of Beijing Municipal Science and Technology Commission under grant Z201100006820084,in part by the National Natural Science Foundation of China(NSFC)under grants 92064003,61904194,91964202 and 61874135,in part by the Youth Innovation Promotion Association,Chinese Academy of Sciences under grants Y9YQ01R004 and Y2020037,in part by the Opening Project of Key Laboratory of Microelectronic Devices and Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences under grants E0YS01X001 and E0290X03.
文摘The HfO2-based ferroelectric field effect transistors(FeFET)have been widely studied for their ability in breaking the Boltzmann limit and the potential to be applied to low-power circuits.This article systematically investigates the transient response of negative capacitance(NC)fin field-effect transistors(FinFETs)through two kinds of self-built test schemes.By comparing the results with those of conventional FinFETs,we experimentally demonstrate that the on-current of the NC FinFET is not degraded in the MHz frequency domain.Further test results in the higher frequency domain show that the on-state current of the prepared NC FinFET increases with the decreasing gate pulse width at pulse widths below 100 ns and is consistently greater(about 80%with NC NMOS)than the on-state current of the conventional transistor,indicating the great potential of the NC FET for future high-frequency applications.
基金supported by the Taishan Scholars (No.ts201712003)。
文摘Nitrogen dioxide(NO_(2))poses a critical potential risk to environmental quality and public health.A reliable machine learning(ML)forecasting framework will be useful to provide valuable information to support government decision-making.Based on the data from1609 air quality monitors across China from 2014-2020,this study designed an ensemble ML model by integrating multiple types of spatial-temporal variables and three sub-models for time-sensitive prediction over a wide range.The ensemble ML model incorporates a residual connection to the gated recurrent unit(GRU)network and adopts the advantage of Transformer,extreme gradient boosting(XGBoost)and GRU with residual connection network,resulting in a 4.1%±1.0%lower root mean square error over XGBoost for the test results.The ensemble model shows great prediction performance,with coefficient of determination of 0.91,0.86,and 0.77 for 1-hr,3-hr,and 24-hr averages for the test results,respectively.In particular,this model has achieved excellent performance with low spatial uncertainty in Central,East,and North China,the major site-dense zones.Through the interpretability analysis based on the Shapley value for different temporal resolutions,we found that the contribution of atmospheric chemical processes is more important for hourly predictions compared with the daily scale predictions,while the impact of meteorological conditions would be ever-prominent for the latter.Compared with existing models for different spatiotemporal scales,the present model can be implemented at any air quality monitoring station across China to facilitate achieving rapid and dependable forecast of NO_(2),which will help developing effective control policies.
基金funded by the National Natural Science Foundation of China(Grant/Award Numbers:52177107 and 52222704)Science and Technology Project of Tianjin Municipality,China(22JCZDJC00780).
文摘The marine climate conditions are intricate and variable. In scenarios characterized by high proportions of wind and solar energy access, the uncertainty regarding the energy sources for island microgrid is significantly exacerbated, presenting challenges to both the economic viability and reliability of the capacity configuration for island microgrids. To address this issue, this paper proposes a distributionally robust optimization (DRO) method for island microgrids, considering extreme scenarios of wind and solar conditions. Firstly, to address the challenge of determining the probability distribution functions of wind and solar in complex island climates, a conditional generative adversarial network (CGAN) is employed to generate a scenario set for wind and solar conditions. Then, by combining k-means clustering with an extreme scenario selection method, typical scenarios and extreme scenarios are selected from the generated scenario set, forming the scenario set for the DRO model of island microgrids. On this basis, a DRO model based on multiple discrete scenarios is constructed with the objective of minimizing the sum of investment costs, operation and maintenance costs, fuel purchase costs, penalty costs of wind and solar curtailment, and penalty costs of load loss. The model is subjected to equipment operation and power balance constraints, and solved using the columns and constraints generation (CCG) algorithm. Finally, through typical examples, the effectiveness of this paper’s method in balancing the economic viability and robustness of the configuration scheme for the island microgrid, as well as reducing wind and solar curtailment and load loss, is verified.
基金This work was supported by the National Natural Science Foundation of China （Grant No. 51475204）, the Development Program of Science and Technology of Jilin Province of China （Grant No. 20100711）, the Pro- ject of Graduate Innovation Fund of Jilin University （Grant No. 20121093 and Grant No. 20121096） and the Natioanal “985 Project” in Jilin University.
文摘The compaction characteristics of biomimetic press roller with ridge structures, inspired from the geometrical features of the ventral surface of dung beetle （Copris ochus Motschulsky）, were investigated in this work. Field tests were carried out at three weights （300 N, 500 N and 700 N） and two forward velocities （0.64 m·s^-1 and 1.04 m·s^-1） for biomimetic press roller and conventional press roller. To determine compaction performance, rolling resistance, soil bulk density, soil moisture content, emergence rate and percent change of plant spacing were measured. Roller weight was proved to be the major contributory factor on soil compaction. Biomimetic press roller decreased rolling resistance by 2.98% -17.69% at the velocity of 0.64 m·s^-1, and by 6.59% -18.57% at the velocity of 1.04 m·s^-1 compared with the conventional press roller. Both biomimetic roller and conventional roller can achieve proper bulk density for corn seeds under the experimental conditions. However, compared with the conventional roller, biomimetic roller helped soil conserve more moisture. The highest emergence rate was found when the biomimetic roller worked with a weight of 700 N and velocity of 0.64 m·s^-1. Percent change of plant spacing was lower using the biomimetic press roller compared with that using the conventional roller, because that adjacent ridge structures of the biomi- metic roller can well constrain the flow of soil during compacting process.
基金the National Natural Science Foundation of China(Nos.91644214,21677089,21876102)the Shenzhen Science and Technology Research and Development Funds(No.JCYJ20160510165106371)+2 种基金the Fundamental Research Funds of Shandong University(Nos.2016WLJH51,2017JC033)The China Postdoctoral Science Foundation funded project(Nos.2017M612277,2017T100493)The open foundation of state key laboratory of environmental criteria and risk assessment,Chinese Research Academy of Environmental Sciences(Nos.2016OFP09)。
文摘Amides,a series of significant atmospheric nitrogen-containing volatile organic compounds(VOCs),can participate in new particle formation(NPF)throught interacting with sulfuric acid(SA)and organic acids.In this study,we investigated the molecular interactions of formamide(FA),acetamide(AA),N-methylformamide(MF),propanamide(PA),Nmethylacetamide(MA),and N,N-dimethylformamide(DMF)with SA,acetic acid(HAC),propanoic acid(PAC),oxalic acid(OA),and malonic acid(MOA).Global minimum of clusters were obtained through the association of the artificial bee colony(ABC)algorithm and density functional theory(DFT)calculations.The conformational analysis,thermochemical analysis,frequency analysis,and topological analysis were conducted to determine the interactions of hydrogen-bonded molecular clusters.The heterodimers formed a hepta or octa membered ring through four different types of hydrogen bonds,and the strength of the bonds are ranked in the following order:SO-H···O>CO-H···O>N-H···O>C-H···O.We also evaluated the stability of the clusters and found that the stabilization effect of amides with SA is weaker than that of amines with SA but stronger than that of ammonia(NH 3)with SA in the dimer formation of nucleation process.Additionally,the nucleation capacity of SA with amides is greater than that of organic acids with amides.
基金support from the National Key Research and Development Program of China(2020YFC2004503)Beijing Nova Program(Z2011006820083,Z2011006820084)Beijing Municipal Natural Science Foundation(No.4192062).
文摘Exosomes are highly important in clinical diagnosis due to their high homology with their parental cells.However,conventional exosome detection methods still face the challenges of expensive equipment,low sensitivity,and complex procedures.Field effect transistors(FETs)are not only the most essential electronic component in the modern microelectronics industry but also show great potential for biomolecule detection owing to the advantages of rapid response,high sensitivity,and label-free detection.In this study,we proposed a Si nanowire field-effect transistor(Si-NW Bio-FET)device chemically modified with specific antibodies for the electrical and label-free detection of exosomes.The Si-NW FETs were fabricated by standard microelectronic processes with 45 nm width nanowires and packaged in a polydimethylsiloxane(PDMS)microfluidic channel.The nanowires were further modified with the specific CD63 antibody to form a Si-NW Bio-FET.The use of the developed Si-NW Bio-FET for the electrical and labelfree detection of exosomes was successfully demonstrated with a limit of detection(LOD)of 2159 particles/mL.In contrast to other technologies,in this study,Si-NW Bio-FET provides a unique strategy for directly quantifying and realtime detecting exosomes without labeling,indicating its potential as a tool for the early diagnosis of cancer.
基金supported by the Science Foundation of Chinese Research Academy of Environmental Science(No.JY41375133)the National Natural Science Foundation of China(No.41375133)+1 种基金Russian Science Foundation(No.18-71-00137)the Russian Ministry of Science and Education(Nos.1.6198.2017/6.7 and 1.7706.2017/8.9)for support
文摘Interactions of the three common atmospheric bases,dimethylamine((CH3)2 NH),methylamine(CH3 NH2),ammonia(NH3),all considered to be efficient stabilizers of binary clusters in the Earth’s atmosphere,with H2 SO4,the key atmospheric precursor,and 14 common atmospheric organic acids(COAs)(formic,acetic,oxalic,malonic,succinic,glutaric acid,adipic,benzoic,phenylacetic,pyruvic,maleic acid,malic,tartaric and pinonic acids)have been studied using the density functional theory(DFT)and composite high-accuracy G3 MP2 method.The thermodynamic stability of mixed(COA)(H2 SO4),(COA)(B1),(COA)(B2)and(COA)(B3)dimers and(COA)(H2 SO4)(B1),(COA)(H2 SO4)(B2)and(COA)(H2 SO4)(B3)trimers,where B1,B2 and B3 refer to(CH3)2 NH,CH3 NH2 and NH3,respectively,have been investigated and their impacts on the thermodynamic stability of clusters containing H2 SO4 have been studied.Our investigation shows that interactions of H2 SO4 with GOA,(CH3)2 NH,CH3 NH2 and NH3 lead to the formation of more stable mixed dimers and trimers than(H2 SO4)2 and(H2 SO4)2(base),respectively,and emphasize the importance of common organic species for early stages of atmospheric nucleation.We also show that although amines are generally confirmed to be more active than NH3 as stabilizers of binary clusters,in some cases mixed trimers containing NH3 are more stable thermodynamically than those containing CH3 NH2.This study indicates an important role of COA,which coexist and interact with that H2 SO4 and common atmospheric bases in the Earth atmosphere,in formation of stable prenucleation clusters and suggests that the impacts of COA on new particle formation(NPF)should be studied in further details.
基金This work was supported by the National High Technology Research ＆ Development Program of China （No. 2012AA06A301） and the National Natural Science Foundation of China （Grant Nos. 21337001 and 21177076）.
文摘Sea salt particles containing NaCl are among the most abundant particulate masses in coastal atmosphere. Reactions involving sea salt particles potentially generate Cl radicals, which are released into coastal atmosphere. Cl radicals play an important role in the nitrogen and O3 cycles, sulfitr chemistry and particle formation in the troposphere of the polluted coastal regions. This paper aimed at .the heterogeneous reaction between gaseous HNO3 .and solid NaCl. The mech.anis.m was in.vestigatedby density functional theory （DFT）. The results imply that water molecules induce the surface reconstruction, which is essential for the heterogeneous reaction. The surface reconstruction on the defective （710） surface has a barrier of 10.24 kcal.mol-1 and is endothermic by 9.69 kcal.mol-1, whereas the reconstruction on the clean （100） surface has a barrier of 18.46 kcal.mol-1 and isendothermic by 12.96 kcal.mol-1. The surface reconstruction involved in water-adsorbed （710） surface is more energetically favorable. In comparison, water molecules adsorbed on NaCl （100） surface likely undergo water diffusion or desorption. Further, it reveals that the coordination number of the Cl-out is reduced after the surface reconstruction, which assists Clout to accept the proton from HNO3. HCl is released from heterogeneous reactions between gaseous HNO3 and solid NaCl and can react with OH free radicals to produce atomic Cl radicals. The results will offer further insights into the impact of gaseous HNO3 on the air quality of the coastal areas.
文摘To understand the size-resolved aerosol ionic composition and the factors influencing secondary aerosol formation in the upper boundary layer in South Central China, size-segregated aerosol samples were collected using a micro-orifice uniform deposit irnpactor （MOUDI） in spring 2009 at the summit of Mount Heng （1269 m asl）, followed by subsequent laboratory analyses of 13 inorganic and organic water-soluble ions. During non- dust-storm periods, the average PM1.8 concentration was 41.8 μg·m^-3, contributing to 55% of the PM10. Sulfates, nitrates, and ammonium, the dominant ions in the fine particles, amounted to 46.8% of the PM1.8. Compared with Mount Tai in the North China Plain, the concentrations of both fine and coarse particles and the ions contained therein were substantially lower. When the air masses from Southeast Asia prevailed, intensive biomass burning there led to elevated concentrations of sulfates, nitrates, ammonium, potassium, and chloride in the fine particles at Mount Heng. The air masses originating from the north Gobi brought heavy dust storms that resulted in the remarkable production of sulfates, ammonium, methane sulfonic acid, and oxalates in the coarse particles. Generally, the sulfates were primarily produced in the form of （NH4）2SO4 in the droplet mode via heterogeneous aqueous reactions. Only approximately one-third of the nitrates were distributed in the fine mode, and high humidity facilitated the secondary formation of fine nitrates. The heterogeneous formation of coarse nitrates and ammonium on dry alkaline dust surfaces was found to be less efficient than that on the coarse particles during non-dust-storm periods.
基金supported by the National Natural Science Foundation of China(No.21177077,21177076)the Independent Innovation Foundation of Shandong University(No.2012JC030)
文摘Fluorine-containing halogenated fluorophenol may have effect as intermediate species involved in the formation of polyfluorinated dibenzo-p-dioxin/dibenzofurans （PFDDs/Fs）. The mechanism for the atomic H initiated reactions with complete series of nineteen fluorophenol congeners was studies using the density functional theory. At the MPWB1K,/6-31＋G（d,p） level, the geometries and frequencies of reactants, transition states, and products were obtained, and the accurate energetic values were acquired at the MPWB 1K/6-311 ＋G（3df,2p） level. The rate constants were evaluated by the canonical variational transition-state theory with the small curvature tunneling contribution over a wide temperature range of 600-1000 K. The study shows that the intramolecular hydrogen-bond in the ortho-substituted FPs as well as the inductive effect of the electron-withdrawing fluorine and steric repulsion of multiple substitutions may ultimately be responsible for the relative strength of the O-H bonds in FPs. The results can be used for further studies on PFDD/Fs formation mechanism.
基金supported by the National Natural Science Foundation of China(No.21337001,21377073)the Independent Innovation Foundation of Shandong University(IIFSDU)(No.2012JC030)
文摘In this article, the NO3 radical-initiated atmospheric oxidation degradation of DDT was theoretically investigated using molecular orbital theory calculations. All the calculations of intermediates, transition states and products were performed at the MPWB1K/6-311＋G（3df,2p）//MPWB1K/6- 31＋G（d,p） level of theory. Several energetically favorable reaction pathways were revealed. The formation mechanisms of secondary pollutants were presented and discussed. The rate constants were deduced over the temperature range of 273-333 K using canonical variational transition-state （CVT） theory with the small curvature tunneling （SCT） method. Our study shows that H abstraction from the alkyl group and NO3 addition to the Ca atom of the benzene ring are the dominant reaction pathways. The rate-temperature formula of the overall rate constants is k（T）（DDT＋NO3） = （7.21 ~ 10-15）exp（-153.81/T） cm3/（mol.sec） over the possible atmospheric temperature range of 273-333 K. The atmospheric lifetime of DDT determined by NO3 radical is about 52.5 days, which indicates that it can be degraded in the gas phase within several months.
