Xishui National Forest Park in Heilongjiang Province hosts China's most pristine temperate forests and serves as a key site for ecotourism and forest therapy.However,the emission patterns of phytoncides(key bio ac...Xishui National Forest Park in Heilongjiang Province hosts China's most pristine temperate forests and serves as a key site for ecotourism and forest therapy.However,the emission patterns of phytoncides(key bio active compounds) remain poorly understood,limiting their therapeutic application.This study provides the first comprehensive characterization of spatiotemporal dynamics in airborne phytoncides and their synergistic interactions with environmental factors throughout the autumn-early spring seasonal transition in a temperate forest ecosystem.We analyzed the compositional dynamics of phytoncides and terpenoid content variations using thermal desorption-gas chromatography-mass spectrometry(TD-GC-MS) from September 2024 to March 2025.This period encompassed seasonal transitions from autumn to early spring,including diurnal variations in September and snowfall events in November.The method demonstrated detection limits(LODs) ranging from 1.35 to 5.33 ng m-3 and quantification limits(LOQs) from 4.09 to 16.15 ng m-3.Our results revealed pronounced seasonal fluctuations in phytoncide composition.In September,terpenoids,esters,alcohols,and alkanes displayed a diurnal "decrease-increase" trend,whereas aldehydes and ketones peaked at midday.Notably,esters and alcohols were undetectable in November and January.By January,terpenoids reached their lowest proportion(0.17±0.02%) at noon.Five terpenoids(α-pinene,myrcene,D-limonene,camphene,p-cymene) were detected in September,four(α-pinene,D-limonene,camphene,p-cymene) in November,two(D-limonene,p-cymene) in January,and only p-cymene in March.The total concentration and emission rate of the five terpenoids peaked in September afternoons at 1961.58±106.67 ng m^(-3) and653.86±35.56 ng m^(-3) h^(-1),respectively.Nocturnal emissions(32131.95±2522.21 ng m^(-3)) significantly surpassed daytime levels(14473.04±958.49 ng m^(-3)),with emission rates escalating from 1447.30±95.85 ng m^(-3) h^(-1)(day) to 5355.33±420.37 ng m^(-3) h^(-1)(night),marking a3.7-fold increase.Snowfall dramatically elevated terpenoid concentrations(pre-snowfall:158.58±14.12 ng m^(-3);post-snowfall:1080.57±57.76 ng m^(-3)) and emission rates(pre-snowfall:52.86±4.71 ng m^(-3) h^(-1);post-snowfall:360.19±19.25 ng m^(-3) h^(-1)),reflecting a 6.8-fold surge.This study underscores the profound influence of light intensity,seasonal shifts,and climatic conditions on airborne phytoncide levels,offering a scientific foundation for optimizing forest therapy and ecotourism strategies.展开更多
United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in suc...United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in such ambitious climate action roadmap.However,whether CDR technologies should be further promoted or discontinued post net-zero emission year remains unclear.In this Earth-system modelling research,we compare UN-suggested 2050 net-zero emission scenario against other common climate mitigation scenarios outlined by shared social-economic pathways(SSPs).We also simulate continued CDR implementations after net-zero emissions,which is hypothetically achieved in year 2050 and 2070 respectively,to investigate how CDR can impact the global climate throughout the whole 21st and 22nd centuries.The modelling results find if the 2050 UN net-zero emission goal is accomplished,the global average surface air temperature(SAT)in the end of 21st century is around 1.5℃higher compared to the pre-industrial level,promising an Earth environment more habitable than other scenarios without CDR.When CDR is applied to remove equal amount of anthropogenic CO_(2)emissions since industrial revolution,it restores the global average SAT close to pre-industrial level of 13.5℃.However,CDR-induced global carbon distribution within ocean,atmosphere,and land pools is different from the pre-industrial condition,causing reduced atmospheric CO_(2)concentration by 9 to 38 ppm compared to the pre-industrial cases,and more alkalinized ocean surface with pH increase of 0.004 to 0.024.This study affirms CDR cannot be viewed as a reversed process to anthropogenic CO_(2)emissions,accordingly climate policies to overcome the uncertainties after for late 21st century still require careful trade-offs for the decarbonation and the cost-benefits of CDR measures.展开更多
With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at ...With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at different temperatures in combination with real-time acoustic emission(AE)monitoring.The results show that the cumulative AE count increases stepwise with increasing cyclic stress.The peak frequency is concentrated primarily in the medium-frequency range,exhibiting a band distribution across low-,medium-,and high-frequency ranges.As the temperature increases,the proportion of low-frequency signals decreases from 14.32%to 5.76%,whereas the proportion of medium-frequency signals increases from 85.48%to 94.1%.The proportion of high-frequency signals remains relatively constant between 0.1%and 0.2%.The amplitude-count relationship of the AE signals demonstrates a strong negative power-law correlation.Furthermore,with increasing temperature,the negative power-law exponent of the amplitude gradually decreases,with the b value decreasing from 1.096 to 0.837 and the a value decreasing from 7.4871 to 6.6982.Under all four temperature conditions,the dominant failure mode in rock salt is tensile cracking.However,as the temperature increases,the proportion of tensile cracks decreases from 88.59%to 75.12%,whereas the proportion of shear cracks at 80℃is nearly double that at 20℃.This finding indicates that as the temperature increases,the ductility of the material increases,and the crack propagation mode shifts from tensile to shear.This research provides valuable insights for the design and stability assessment of salt cavern reservoirs for deep underground energy storage systems.展开更多
Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics...Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.展开更多
The detection of amino acid enantiomers holds significant importance in biomedical,chemical,food,and other fields.Traditional chiral recognition methods using fluorescent probes primarily rely on fluorescence intensit...The detection of amino acid enantiomers holds significant importance in biomedical,chemical,food,and other fields.Traditional chiral recognition methods using fluorescent probes primarily rely on fluorescence intensity changes,which can compromise accuracy and repeatability.In this study,we report a novel fluorescent probe(R)-Z1 that achieves effective enantioselective recognition of chiral amino acids in water by altering emission wavelengths(>60 nm).This water-soluble probe(R)-Z1 exhibits cyan or yellow-green luminescence upon interaction with amino acid enantiomers,enabling reliable chiral detection of 14 natural amino acids.It also allows for the determination of enantiomeric excess through monitoring changes in luminescent color.Additionally,a logic operation with two inputs and three outputs was constructed based on these optical properties.Notably,amino acid enantiomers were successfully detected via dual-channel analysis at both the food and cellular levels.This study provides a new dynamic luminescence-based tool for the accurate sensing and detection of amino acid enantiomers.展开更多
Luminescent metal-organic frameworks(MOFs)have garnered significant attention due to their structural tunability and potential applications in solid-state lighting,bioimaging,sensing,anticounterfeiting,and other field...Luminescent metal-organic frameworks(MOFs)have garnered significant attention due to their structural tunability and potential applications in solid-state lighting,bioimaging,sensing,anticounterfeiting,and other fields.Nevertheless,due to the tendency of1,4-benzenedicarboxylic acid(BDC)to rotate within the framework,MOFs composed of it exhibit significant non-radiative energy dissipation and thus impair the emissive properties.In this study,efficient luminescence of MIL-140A nanocrystals(NCs)with BDC rotors as ligands is achieved by pressure treatment strategy.Pressure treatment effectively modulates the pore structure of the framework,enhancing the interactions between the N,N-dimethylformamide vip molecules and the BDC ligands.The enhanced host-vip interaction contributes to the structural rigidity of the MOF,thereby suppressing the rotation-induced excited-state energy loss.As a result,the pressure-treated MIL-140A NCs displayed bright blue-light emission,with the photoluminescence quantum yield increasing from an initial 6.8%to 69.2%.This study developed an effective strategy to improve the luminescence performance of rotor ligand MOFs,offers a new avenue for the rational design and synthesis of MOFs with superior luminescent properties.展开更多
Organic-inorganic metal halides(OIMHs)have emerged as highly promising novel multifunctional optoelectronic materials,owing to their easily adjustable properties from a variety of combinations of different components....Organic-inorganic metal halides(OIMHs)have emerged as highly promising novel multifunctional optoelectronic materials,owing to their easily adjustable properties from a variety of combinations of different components.But it is still difficult and rare to realize highly tunable multicolor luminescence within the same material.In this work,we successfully incorporated three adjustable emission centers in OIMHs to synthesize a novel OIMH(NEA)_(2)MnBr_(4),with each emission center capable of emitting one of the primary colors—red,green,and blue.The green and red emissions originate from the tetrahedron and octahedron structures in the Mn-based frame,while the blue can be attributed to the contribution of organic components.Additionally,to achieve comparable emission intensity among the three primary colors,we enhanced the blue emission performance by optimizing the ratio of organic structure components and incorporating chirality in the OIMHs.The resulting high-quality films can be obtained by spin-coating method with a photoluminescence quantum yields of up to 96%.More interestingly,by the dual manipulation of excitation wavelength and temperature,the sample can be emitted at least seven distinct colors including a standard white luminescence at(0.33,0.33),opening up promising prospects for multicolor luminescence applications such as high-end anti-counterfeiting technology,light-emitting diodes,X-ray imaging,latent fingerprints,humidity detection,and so on.Therefore,based on application scenarios and requirements,our research on this highly tunable luminescent OIMH material lays a solid foundation for further development of various functional properties of related materials.展开更多
To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through ...To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through cyclic loading and unloading(CLU)experiments followed by cyclic drying and wetting(CDW)experiments,and finally conducted creep experiments.The study analyzed the effects of initial damage on creep mechanical behavior,crack evolution,and explored failure precursor information,revealing the damage failure mechanisms.The results show that the structural characteristics of the rock mass control its macroscopic failure mode.Initial damage promotes microcrack development,influences the fracture mode,and increases the proportion of high-frequency(200−280 kHz)acoustic emission events during creep.Meanwhile,initial damage exacerbates creep characteristics,increasing the creep rate,shortening total creep failure time,and reducing long-term strength.The damage failure is attributed to:the generation of internal cracks and pores in the rock caused by CLU;mineral hydrolysis and expansion-contraction due to CDW,resulting in weakened intergranular cementation;and full development of cracks and pores under creep stress.Additionally,the deformation difference coefficient and the coefficient of variation of RA/AF values can serve as precursor indicators for creep failure.展开更多
In the field of rock engineering,the influence of water is a dynamic process that exhibits varying effects over time and across different locations.To further understand how water influences the mechanical properties ...In the field of rock engineering,the influence of water is a dynamic process that exhibits varying effects over time and across different locations.To further understand how water influences the mechanical properties and acoustic emission(AE)behavior of rocks,this study conducted uniaxial compression experiments on sandstones with varying degrees of wetting under both natural conditions and water-chemical environments.In addition,the study combined AE equipment with digital image correlation(DIC)to monitor the entire failure process.Using the sliding window algorithm,the variation in the variance of AE characteristic parameters during the process of sandstone loading to failure is analyzed from the perspective of critical slowing down.This analysis enables the effective identification of the early warning signal before failure.The experimental findings suggest that an increase in wetting height results in a gradual decrease in peak stress,accompanied by a concomitant increase in the percentage of shear cracks.The characteristic parameters,including energy,amplitude,and ringing count,all exhibit critical slowing phenomena.The waveform of AE characteristic parameters of the same sample is similar,and the mutation time of the precursor signal is roughly the same.All signals appear in the irreversible plastic deformation stage of microcrack initiation.The integration of critical slowing down theory and the b-value early warning method facilitates a more comprehensive evaluation of the stability of rock mass,thereby significantly enhancing the efficiency and safety of disaster prevention measures.展开更多
Transforming urban spatial structures to promote green and low-carbon development is an effective strategy.Although prior studies have examined the impact of urban polycentricity on carbon emissions and economic devel...Transforming urban spatial structures to promote green and low-carbon development is an effective strategy.Although prior studies have examined the impact of urban polycentricity on carbon emissions and economic development,research on its role in the synergistic relationship between these factors regarding carbon emission efficiency is limited.Furthermore,existing literature often overlooks nonlinear effects and interactions with other urban variables.This paper analyzed data from 295 Chinese cities in 2020,calculating urban population polycentricity,population dispersion indices,and carbon emission efficiency.Utilizing local spatial autocorrelation tools,we reveal interactions among urban population polycentricity,dispersion,carbon emissions,and carbon emission efficiency.We then employ a gradient boosting decision tree model(GBDT)to explore nonlinear and synergistic effects of polycentric urbanization.Key findings include:1)polycentric urbanization in Chinese cities exhibits significant spatial differentiation characteristics.The Polycentricity index is relatively high in economically developed eastern coastal regions with an overall low level,carbon emissions are concentrated in industrialized north-central cities and some Yangtze River Delta hubs,and carbon emission efficiency is the highest in the Yangtze River Delta while relatively low in Northeast China;there are significant spatially heterogeneous interaction characteristics among population polycentricity,population dispersion,carbon emissions,and carbon emission efficiency.2)Urban population polycentricity contributes 9.42%to total carbon emissions and 6.24%to carbon emission efficiency.3)The polycentricity index has a nonlinear impact on carbon emissions and carbon emission efficiency:no significant effect when below 0.50 or above 0.55,increased carbon emissions in 0.50-0.53,and reduced carbon emissions with improved efficiency in 0.53-0.55.4)The polycentricity index has an interaction effect with other variables;specifically,when the polycentricity index is between 0.53 and 0.55,its interaction with urban gross domestic product(GDP),urban population,urban built-up area,green coverage rate in built-up areas,urban technological expenditure,and the proportion of the output value of the secondary industry will reduce carbon emissions and improve carbon emission efficiency.These findings enhance the understanding of urban spatial structures and carbon emissions,providing valuable insights for policymakers in developing green and low-carbon strategies.展开更多
Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nit...Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nitrogen addition in a Larix gmelinii forest was carried out to study the effects on soil carbon,nitrogen,and CO_(2)flux during the thawing,growing,and freezing periods.Our study found that warming(0-2.0℃)increased soil organic carbon(SOC)and total nitrogen(STN),dissolved organic carbon(DOC)and dissolved organic nitrogen(DON),and microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN).Warming played a direct role in regulating soil CO_(2)emissions,stimulated microbial and plant root respiration and soil CO_(2)flux rapidly increased.Rainfall increase initially increased soil carbon and nitrogen,but a 30%increase in mean annual rainfall caused losses of SOC,STN,DOC,and DON,while MBC and MBN accumulated.Soil CO_(2)emissions were regulated by MBC after an increase in rainfall,excess moisture inhibited microbial activity,and soil CO_(2)flux showed a trend of R2(20%rainfall increase)>R1(10%rainfall increase)>CK(control)>R3(30%rainfall increase).The addition of nitrogen increased SOC,STN,DOC,DON,MBC and MBN.Soil CO_(2)flux progressively decreased with nitrogen inputs(2.5,5.0 and 10.0 g m^(-2)a^(-1)),as more N intensified plant-microbe competition.Nitrogen addition indirectly regulated soil CO_(2)emissions by altering SOC and STN,with MBC and MBN acting as secondary regulators.The results highlight the role of cold-temperate coniferous forest soils in predicting carbon-climate feedback in high-latitude forest permafrost regions.展开更多
Long-term manure application has the potential to alleviate soil acidification, and increase carbon sequestration and nutrient availability, thus improving cropland fertility. However, the mechanisms behind greenhouse...Long-term manure application has the potential to alleviate soil acidification, and increase carbon sequestration and nutrient availability, thus improving cropland fertility. However, the mechanisms behind greenhouse gas N_(2)O emissions from acidic soil mediated by long-term manure application remain poorly understood. Herein, we investigated N_(2)O emission and its linkage with gross N mineralization and nitrification rates, as well as nitrifying and denitrifying microbes in an acidic upland soil subjected to 36-year fertilization treatments, including an unfertilized control(CK), inorganic fertilizer(F), 2× rate of inorganic fertilizer(2F), manure(M), and the combination of inorganic fertilizer and manure(FM) treatments. Compared to the CK treatment(1.34 μg N kg^(-1) d^(-1)), fertilization strongly increased N_(2)O emissions by 34-fold on average, with more pronounced increases in the manure-amendment(10.6-169 μg N kg^(-1) d^(-1)) than those in the inorganic fertilizer treatments(3.26-5.51 μg N kg^(-1) d^(-1)). The manure amendment-stimulated N_(2)O emissions were highly associated with increased soil pH, mean weight diameter of soil aggregates, substrate availability(e.g., particulate organic carbon, NO_(3)^(-)and available phosphorus), gross N mineralization rates, denitrifier abundances and the(nirK+nirS)/nosZ ratio. These findings suggest that the increased N_(2)O emissions primarily resulted from alleviated acidification, increased substrate availability and improved soil structure, thus enhancing microbial N mineralization and favoring N_(2)O^(-)producing denitrifiers over N_(2)O consumers. Moreover, ammonia-oxidizing bacteria(AOB) rather than ammonia-oxidizing archaea(AOA) positively correlated with soil NO_(3)^(-)concentration and N_(2)O emissions, indicating that nitrification indirectly contributed to N_(2)O production by supplying NO_(3)^(-)for denitrification. Collectively, manure amendment potentially stimulates N_(2)O emissions, primarily resulting from alleviated soil acidification and increased substrate availability, thus enhancing N mineralization and denitrifier-mediated N_(2)O production. Our findings suggest that consideration should be given to the greenhouse gas budgets of agricultural ecosystems when applying manure for managing the pH and fertility of acidic soils.展开更多
During deep coal mining,an instability failure of coal usually occurs under the combined effect of initial damage and triaxial cyclic loading and unloading(TCLU).Therefore,this study investigated the impact of initial...During deep coal mining,an instability failure of coal usually occurs under the combined effect of initial damage and triaxial cyclic loading and unloading(TCLU).Therefore,this study investigated the impact of initial damage on mechanical behavior and acoustic emission(AE)characteristics of coal under TCLU.Initial damage variables(IDVs)of coal specimens were quantified using preloading,followed by TCLU experiments to assess the deformation,energy distribution,and fracture development.The results revealed that the increase in IDVs significantly reduced the structural integrity of coal specimens,increased the cumulative irreversible strain,and enhanced the dissipated energy owing to microfracture expansion.Moreover,AE monitoring showed earlier activation of fractures and a higher occurrence of large-scale rupture events of coal specimens with high IDVs,which correlated with decreasing AE b values(reflecting the different scales of fracture within specimens)and increasing S values(reflecting the AE activity within specimens).Additionally,computed tomography analysis revealed intensified fracture networks and increasing three-dimensional fractal dimensions of coal specimens with higher IDVs.Finally,the coupling effect of TCLU and initial damage on the weakening mechanism of coal was investigated.Initial damage significantly reduced the structural integrity of coal by increasing the number of weak planes within coal specimens,contributing to the earlier activation and rapid expansion of fractures at low stress levels under TCLU and eventually accelerating the weakening process of coal.This study provides a scientific basis and theoretical support for the prevention and control of dynamic disasters in deep coal mining.展开更多
The development of quantum materials for single-photon emission is crucial for the advancement of quantum information technology.Although significant advancements have been witnessed in recent years for single-photon ...The development of quantum materials for single-photon emission is crucial for the advancement of quantum information technology.Although significant advancements have been witnessed in recent years for single-photon sources in the near-infrared band(λ∼700–1000 nm),several challenges have yet to be addressed for ideal single-photon emission at the telecommunication band.In this study,we present a droplet-epitaxy strategy for O-band to C-band single-photon source-based semiconductor quantum dots(QDs)using metal-organic vaporphase epitaxy(MOVPE).By investigating the growth conditions of the epitaxial process,we have successfully synthesized InAs/InP QDs with narrow emission lines spanning a broad spectral range of λ∼1200–1600 nm.The morphological and optical properties of the samples were characterized using atomic force microscopy and microphotoluminescence spectroscopy.The recorded single-photon purity of a plain QD structure reaches g^((2))(0)=0.16,with a radiative recombination lifetime as short as 1.5 ns.This work provides a crucial platform for future research on integrated microcavity enhancement techniques and coupled QDs with other quantum photonics in the telecom bands,offering significant prospects for quantum network applications.展开更多
The geothermal resources in China are primarily found in its sedimentary basins,particularly in the large basins located in eastern China,which hold significant potential for geothermal energy development.The Songliao...The geothermal resources in China are primarily found in its sedimentary basins,particularly in the large basins located in eastern China,which hold significant potential for geothermal energy development.The Songliao,North China,and Zhangzhou basins are of special interest due to their considerable exploration depths,extensive development history,and high levels of research activity.This study focuses on the three basins to analyze their thermal reservoir characteristics in eastern China.Between 2017 and 2023,the research team carried out a comprehensive analysis involving deep boreholes that exceeded 4000 m in depth within these three basins.They meticulously created detailed physical profiles that captured essential characteristics such as porosity,permeability,and thermal properties,reaching down to the basement of each basin.The findings indicated that variations in thermal conductivity within shallow geotechnical layers significantly influence the redistribution of deep thermal energy in the upper layers of the earth.Furthermore,differences in physical properties notably affect heat transport processes.The research proposes distinct heat models tailored for each basin:For the Songliao Basin,a low-permeability model with homogeneous thermal properties is constructed;for the North China Basin,high permeability and thermal conductivity layers are highlighted;and a fracture network controlling water and heat is presented in the Zhangzhou Basin.To elucidate the thermal structure of these basins,the Curie surface and Moho surface were analyzed.The shallow Curie surface indicates ongoing intense thermal activity stemming from crustal heat sources,while a shallow Moho surface signifies historical vigorous mantle thermal activity associated with mantle source heat production.Furthermore,the research evaluates the geothermal resources and the potential for carbon emission reduction in these basins.Total volume of exploitable geothermal fluid is estimated to be 76.9×10^(9) m^(3)/a,corresponding to an annual renewable geothermal energy 1.47×10^(16)k J.The implementation of geothermal energy could lead to a reduction in annual CO_(2)emissions by nearly 2×10^(9) t,which constitutes about 17.4%of China’s national carbon emissions in 2022.This estimation provides invaluable theoretical insights and data support for geothermal exploration and sustainable development in eastern China.展开更多
Emission characteristics of biogenic volatile organic compounds(BVOCs)from dominant tree species in the subtropical pristine forests of China are extremely limited.Here we conducted in situ field measurements of BVOCs...Emission characteristics of biogenic volatile organic compounds(BVOCs)from dominant tree species in the subtropical pristine forests of China are extremely limited.Here we conducted in situ field measurements of BVOCs emissions from representative mature evergreen trees by using dynamic branch enclosures at four altitude gradients(600-1690ma.s.l.)in the Nanling Mountains of southern China.Composition characteristics as well as seasonal and altitudinal variations were analyzed.Standardized emission rates and canopyscale emission factors were then calculated.Results showed that BVOCs emission intensities in the wet season were generally higher than those in the dry season.Monoterpenes were the dominant BVOCs emitted from most broad-leaved trees,accounting for over 70%of the total.Schima superba,Yushania basihirsuta and Altingia chinensis had relatively high emission intensities and secondary pollutant formation potentials.The localized emission factors of isoprene were comparable to the defaults in the Model of Emissions of Gases and Aerosols fromNature(MEGAN),while emission factors of monoterpenes and sesquiterpenes were 2 to 58 times of those in the model.Our results can be used to update the current BVOCs emission inventory in MEGAN,thereby reducing the uncertainties of BVOCs emission estimations in forested regions of southern China.展开更多
Carbon emissions resulting from energy consumption have become a pressing issue for governments worldwide.Accurate estimation of carbon emissions using satellite remote sensing data has become a crucial research probl...Carbon emissions resulting from energy consumption have become a pressing issue for governments worldwide.Accurate estimation of carbon emissions using satellite remote sensing data has become a crucial research problem.Previous studies relied on statistical regression models that failed to capture the complex nonlinear relationships between carbon emissions and characteristic variables.In this study,we propose a machine learning algorithm for carbon emissions,a Bayesian optimized XGboost regression model,using multi-year energy carbon emission data and nighttime lights(NTL)remote sensing data from Shaanxi Province,China.Our results demonstrate that the XGboost algorithm outperforms linear regression and four other machine learning models,with an R^(2)of 0.906 and RMSE of 5.687.We observe an annual increase in carbon emissions,with high-emission counties primarily concentrated in northern and central Shaanxi Province,displaying a shift from discrete,sporadic points to contiguous,extended spatial distribution.Spatial autocorrelation clustering reveals predominantly high-high and low-low clustering patterns,with economically developed counties showing high-emission clustering and economically relatively backward counties displaying low-emission clustering.Our findings show that the use of NTL data and the XGboost algorithm can estimate and predict carbon emissionsmore accurately and provide a complementary reference for satellite remote sensing image data to serve carbon emission monitoring and assessment.This research provides an important theoretical basis for formulating practical carbon emission reduction policies and contributes to the development of techniques for accurate carbon emission estimation using remote sensing data.展开更多
Civil aviation is one of the industries facing the greatest challenge in reaching carbon neutrality by the middle of this century,and this sector also contributes to adverse impacts on the regional air quality and hum...Civil aviation is one of the industries facing the greatest challenge in reaching carbon neutrality by the middle of this century,and this sector also contributes to adverse impacts on the regional air quality and human health.China exhibits the second highest air passenger turnover worldwide.Our understanding of civil aviation emissionsmust be urgently enhanced,and themitigation potential should be explored.In this study,on the basis of real domestic flight information for 2019,we built a greenhouse gas and air pollution emission inventory for the civil aviation sector in China with the fuel flowmethod based on the cruise and other phases.We thoroughly analyzed emissions by region,aircraft and engine types,and aircraft age,based on which we designed four measures to evaluate the abatement potential.We found that the hydrocarbon(HC),CO,NO_(x),SO_(2),particulate matter(PM)and CO_(2)emissions in 2019 reached 79.9 kt(95%CI[51.6–114.5]),176.3 kt(95%CI[114.5–248.2]),304.2 kt(95%CI[203.4–420.7]),23.2 kt(95%CI[14.2–33.7]),1.0 kt(95%CI[0.61–1.44])and 87.0 Mt(95%CI[57.4–119.6]),respectively.The cruise phase was the major emission phase,accounting for 67%-87%of the total pollutant emissions.If four measures were jointly implemented,the HC,CO,NO_(x),SO_(2),PM and CO_(2)emissions could be reduced by 61%,54%,55%,45%,32%and 38%,respectively.Utilizing lower-emission aircraft and switching travel modes could substantially reduce civil aviation emissions in China.展开更多
Biliary tract cancer(BTC)is a group of heterogeneous sporadic diseases,including intrahepatic,hilar,and distal cholangiocarcinoma,as well as gallbladder cancer.BTC is characterized by high invasiveness and extremely p...Biliary tract cancer(BTC)is a group of heterogeneous sporadic diseases,including intrahepatic,hilar,and distal cholangiocarcinoma,as well as gallbladder cancer.BTC is characterized by high invasiveness and extremely poor prognosis,with a global increased incidence due to intrahepatic cholangiocarcinoma(ICC).The 18Ffludeoxyglucose positron emission tomography(PET)computed tomography(18F-FDG PET/CT)combines glucose metabolic information(reflecting the glycolytic activity of tumor cells)with anatomical structure to assess tumor metabolic heterogeneity,systemic metastasis,and molecular characteristics noninvasively,overcoming the limitations of traditional imaging in the detection of micrometastases and recurrent lesions.18F-FDG PET/CT offers critical insights in clinical staging,therapeutic evaluation,and prognostic prediction of BTC.This article reviews research progress in this field over the past decade,with a particular focus on the advances made in the last 3 years,which have not been adequately summarized and recognized.The research paradigm in this field is shifting from qualitative to quantitative studies,and there have been significant breakthroughs in using 18F-FDG PET/CT metabolic information to predict gene expression in ICC.Radiomics and deep learning techniques have been applied to ICC for prognostic prediction and differential diagnosis.Additionally,PET/magnetic resonance imaging is increasingly demonstrating its value in this field.展开更多
基金supported by the Key Research and Development Plan Project of Heilongjiang Province (2022ZX02C13)。
文摘Xishui National Forest Park in Heilongjiang Province hosts China's most pristine temperate forests and serves as a key site for ecotourism and forest therapy.However,the emission patterns of phytoncides(key bio active compounds) remain poorly understood,limiting their therapeutic application.This study provides the first comprehensive characterization of spatiotemporal dynamics in airborne phytoncides and their synergistic interactions with environmental factors throughout the autumn-early spring seasonal transition in a temperate forest ecosystem.We analyzed the compositional dynamics of phytoncides and terpenoid content variations using thermal desorption-gas chromatography-mass spectrometry(TD-GC-MS) from September 2024 to March 2025.This period encompassed seasonal transitions from autumn to early spring,including diurnal variations in September and snowfall events in November.The method demonstrated detection limits(LODs) ranging from 1.35 to 5.33 ng m-3 and quantification limits(LOQs) from 4.09 to 16.15 ng m-3.Our results revealed pronounced seasonal fluctuations in phytoncide composition.In September,terpenoids,esters,alcohols,and alkanes displayed a diurnal "decrease-increase" trend,whereas aldehydes and ketones peaked at midday.Notably,esters and alcohols were undetectable in November and January.By January,terpenoids reached their lowest proportion(0.17±0.02%) at noon.Five terpenoids(α-pinene,myrcene,D-limonene,camphene,p-cymene) were detected in September,four(α-pinene,D-limonene,camphene,p-cymene) in November,two(D-limonene,p-cymene) in January,and only p-cymene in March.The total concentration and emission rate of the five terpenoids peaked in September afternoons at 1961.58±106.67 ng m^(-3) and653.86±35.56 ng m^(-3) h^(-1),respectively.Nocturnal emissions(32131.95±2522.21 ng m^(-3)) significantly surpassed daytime levels(14473.04±958.49 ng m^(-3)),with emission rates escalating from 1447.30±95.85 ng m^(-3) h^(-1)(day) to 5355.33±420.37 ng m^(-3) h^(-1)(night),marking a3.7-fold increase.Snowfall dramatically elevated terpenoid concentrations(pre-snowfall:158.58±14.12 ng m^(-3);post-snowfall:1080.57±57.76 ng m^(-3)) and emission rates(pre-snowfall:52.86±4.71 ng m^(-3) h^(-1);post-snowfall:360.19±19.25 ng m^(-3) h^(-1)),reflecting a 6.8-fold surge.This study underscores the profound influence of light intensity,seasonal shifts,and climatic conditions on airborne phytoncide levels,offering a scientific foundation for optimizing forest therapy and ecotourism strategies.
基金supported by the Fundamental Research Funds for the Central Universities(No.202242001)the Mount Tai Research Grant。
文摘United Nations(UN)encourages sovereign states to take prompt and concrete measures to accomplish net-zero emissions by year 2050,requesting carbon dioxide removal(CDR)technologies to be prepared and implemented in such ambitious climate action roadmap.However,whether CDR technologies should be further promoted or discontinued post net-zero emission year remains unclear.In this Earth-system modelling research,we compare UN-suggested 2050 net-zero emission scenario against other common climate mitigation scenarios outlined by shared social-economic pathways(SSPs).We also simulate continued CDR implementations after net-zero emissions,which is hypothetically achieved in year 2050 and 2070 respectively,to investigate how CDR can impact the global climate throughout the whole 21st and 22nd centuries.The modelling results find if the 2050 UN net-zero emission goal is accomplished,the global average surface air temperature(SAT)in the end of 21st century is around 1.5℃higher compared to the pre-industrial level,promising an Earth environment more habitable than other scenarios without CDR.When CDR is applied to remove equal amount of anthropogenic CO_(2)emissions since industrial revolution,it restores the global average SAT close to pre-industrial level of 13.5℃.However,CDR-induced global carbon distribution within ocean,atmosphere,and land pools is different from the pre-industrial condition,causing reduced atmospheric CO_(2)concentration by 9 to 38 ppm compared to the pre-industrial cases,and more alkalinized ocean surface with pH increase of 0.004 to 0.024.This study affirms CDR cannot be viewed as a reversed process to anthropogenic CO_(2)emissions,accordingly climate policies to overcome the uncertainties after for late 21st century still require careful trade-offs for the decarbonation and the cost-benefits of CDR measures.
基金supported by the Major Research Development Program of Hubei Province,China(Grant Nos.2022BAA093 and 2022BAD163)the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.SKLGME023008).
文摘With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at different temperatures in combination with real-time acoustic emission(AE)monitoring.The results show that the cumulative AE count increases stepwise with increasing cyclic stress.The peak frequency is concentrated primarily in the medium-frequency range,exhibiting a band distribution across low-,medium-,and high-frequency ranges.As the temperature increases,the proportion of low-frequency signals decreases from 14.32%to 5.76%,whereas the proportion of medium-frequency signals increases from 85.48%to 94.1%.The proportion of high-frequency signals remains relatively constant between 0.1%and 0.2%.The amplitude-count relationship of the AE signals demonstrates a strong negative power-law correlation.Furthermore,with increasing temperature,the negative power-law exponent of the amplitude gradually decreases,with the b value decreasing from 1.096 to 0.837 and the a value decreasing from 7.4871 to 6.6982.Under all four temperature conditions,the dominant failure mode in rock salt is tensile cracking.However,as the temperature increases,the proportion of tensile cracks decreases from 88.59%to 75.12%,whereas the proportion of shear cracks at 80℃is nearly double that at 20℃.This finding indicates that as the temperature increases,the ductility of the material increases,and the crack propagation mode shifts from tensile to shear.This research provides valuable insights for the design and stability assessment of salt cavern reservoirs for deep underground energy storage systems.
基金supported by National Natural Science Foundation of China(61921002 and 92163204)。
文摘Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.
基金the financial support from the National Natural Science Foundation of China(Nos.22377097,22307036,22074114)Natural Science Foundation of Hubei Province of China(Nos.2020CFB623,2021CFB556)Engineering Research Center of Phosphorus Resources Development and Utilization of Ministry of Education(No.LCX202305)。
文摘The detection of amino acid enantiomers holds significant importance in biomedical,chemical,food,and other fields.Traditional chiral recognition methods using fluorescent probes primarily rely on fluorescence intensity changes,which can compromise accuracy and repeatability.In this study,we report a novel fluorescent probe(R)-Z1 that achieves effective enantioselective recognition of chiral amino acids in water by altering emission wavelengths(>60 nm).This water-soluble probe(R)-Z1 exhibits cyan or yellow-green luminescence upon interaction with amino acid enantiomers,enabling reliable chiral detection of 14 natural amino acids.It also allows for the determination of enantiomeric excess through monitoring changes in luminescent color.Additionally,a logic operation with two inputs and three outputs was constructed based on these optical properties.Notably,amino acid enantiomers were successfully detected via dual-channel analysis at both the food and cellular levels.This study provides a new dynamic luminescence-based tool for the accurate sensing and detection of amino acid enantiomers.
基金supported by the National Key R&D Program of China(Grant No.2023YFA1406200)the National Natural Science Foundation of China(No.12274177 and 12304261)the China Postdoctoral Science Foundation(No.2024M751076)。
文摘Luminescent metal-organic frameworks(MOFs)have garnered significant attention due to their structural tunability and potential applications in solid-state lighting,bioimaging,sensing,anticounterfeiting,and other fields.Nevertheless,due to the tendency of1,4-benzenedicarboxylic acid(BDC)to rotate within the framework,MOFs composed of it exhibit significant non-radiative energy dissipation and thus impair the emissive properties.In this study,efficient luminescence of MIL-140A nanocrystals(NCs)with BDC rotors as ligands is achieved by pressure treatment strategy.Pressure treatment effectively modulates the pore structure of the framework,enhancing the interactions between the N,N-dimethylformamide vip molecules and the BDC ligands.The enhanced host-vip interaction contributes to the structural rigidity of the MOF,thereby suppressing the rotation-induced excited-state energy loss.As a result,the pressure-treated MIL-140A NCs displayed bright blue-light emission,with the photoluminescence quantum yield increasing from an initial 6.8%to 69.2%.This study developed an effective strategy to improve the luminescence performance of rotor ligand MOFs,offers a new avenue for the rational design and synthesis of MOFs with superior luminescent properties.
基金supported by supported by the Basic Research Project of State Key Laboratory of Photovoltaic Science and Technology(No.202401020302)funding support from the National Natural Science Foundation of China(No.62274040 and No.62304046)Shanghai science and technology innovation action plan(No.24DZ3001200)。
文摘Organic-inorganic metal halides(OIMHs)have emerged as highly promising novel multifunctional optoelectronic materials,owing to their easily adjustable properties from a variety of combinations of different components.But it is still difficult and rare to realize highly tunable multicolor luminescence within the same material.In this work,we successfully incorporated three adjustable emission centers in OIMHs to synthesize a novel OIMH(NEA)_(2)MnBr_(4),with each emission center capable of emitting one of the primary colors—red,green,and blue.The green and red emissions originate from the tetrahedron and octahedron structures in the Mn-based frame,while the blue can be attributed to the contribution of organic components.Additionally,to achieve comparable emission intensity among the three primary colors,we enhanced the blue emission performance by optimizing the ratio of organic structure components and incorporating chirality in the OIMHs.The resulting high-quality films can be obtained by spin-coating method with a photoluminescence quantum yields of up to 96%.More interestingly,by the dual manipulation of excitation wavelength and temperature,the sample can be emitted at least seven distinct colors including a standard white luminescence at(0.33,0.33),opening up promising prospects for multicolor luminescence applications such as high-end anti-counterfeiting technology,light-emitting diodes,X-ray imaging,latent fingerprints,humidity detection,and so on.Therefore,based on application scenarios and requirements,our research on this highly tunable luminescent OIMH material lays a solid foundation for further development of various functional properties of related materials.
基金Project(U22A20603)supported by the National Natural Science Foundation of ChinaProject(2023YFC3008300)supported by the National Key Research and Development Program of China。
文摘To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting,this study prepared samples with different initial damage through cyclic loading and unloading(CLU)experiments followed by cyclic drying and wetting(CDW)experiments,and finally conducted creep experiments.The study analyzed the effects of initial damage on creep mechanical behavior,crack evolution,and explored failure precursor information,revealing the damage failure mechanisms.The results show that the structural characteristics of the rock mass control its macroscopic failure mode.Initial damage promotes microcrack development,influences the fracture mode,and increases the proportion of high-frequency(200−280 kHz)acoustic emission events during creep.Meanwhile,initial damage exacerbates creep characteristics,increasing the creep rate,shortening total creep failure time,and reducing long-term strength.The damage failure is attributed to:the generation of internal cracks and pores in the rock caused by CLU;mineral hydrolysis and expansion-contraction due to CDW,resulting in weakened intergranular cementation;and full development of cracks and pores under creep stress.Additionally,the deformation difference coefficient and the coefficient of variation of RA/AF values can serve as precursor indicators for creep failure.
基金support from the National Natural Science Foundation of China(Grant Nos.52104207 and 52374214)the Shandong Provincial Youth Innovation Team Development Program for Higher Education Institutions(Grant No.2023KJ305).
文摘In the field of rock engineering,the influence of water is a dynamic process that exhibits varying effects over time and across different locations.To further understand how water influences the mechanical properties and acoustic emission(AE)behavior of rocks,this study conducted uniaxial compression experiments on sandstones with varying degrees of wetting under both natural conditions and water-chemical environments.In addition,the study combined AE equipment with digital image correlation(DIC)to monitor the entire failure process.Using the sliding window algorithm,the variation in the variance of AE characteristic parameters during the process of sandstone loading to failure is analyzed from the perspective of critical slowing down.This analysis enables the effective identification of the early warning signal before failure.The experimental findings suggest that an increase in wetting height results in a gradual decrease in peak stress,accompanied by a concomitant increase in the percentage of shear cracks.The characteristic parameters,including energy,amplitude,and ringing count,all exhibit critical slowing phenomena.The waveform of AE characteristic parameters of the same sample is similar,and the mutation time of the precursor signal is roughly the same.All signals appear in the irreversible plastic deformation stage of microcrack initiation.The integration of critical slowing down theory and the b-value early warning method facilitates a more comprehensive evaluation of the stability of rock mass,thereby significantly enhancing the efficiency and safety of disaster prevention measures.
基金Under the auspices of National Natural Science Foundation of China(No.42571300)。
文摘Transforming urban spatial structures to promote green and low-carbon development is an effective strategy.Although prior studies have examined the impact of urban polycentricity on carbon emissions and economic development,research on its role in the synergistic relationship between these factors regarding carbon emission efficiency is limited.Furthermore,existing literature often overlooks nonlinear effects and interactions with other urban variables.This paper analyzed data from 295 Chinese cities in 2020,calculating urban population polycentricity,population dispersion indices,and carbon emission efficiency.Utilizing local spatial autocorrelation tools,we reveal interactions among urban population polycentricity,dispersion,carbon emissions,and carbon emission efficiency.We then employ a gradient boosting decision tree model(GBDT)to explore nonlinear and synergistic effects of polycentric urbanization.Key findings include:1)polycentric urbanization in Chinese cities exhibits significant spatial differentiation characteristics.The Polycentricity index is relatively high in economically developed eastern coastal regions with an overall low level,carbon emissions are concentrated in industrialized north-central cities and some Yangtze River Delta hubs,and carbon emission efficiency is the highest in the Yangtze River Delta while relatively low in Northeast China;there are significant spatially heterogeneous interaction characteristics among population polycentricity,population dispersion,carbon emissions,and carbon emission efficiency.2)Urban population polycentricity contributes 9.42%to total carbon emissions and 6.24%to carbon emission efficiency.3)The polycentricity index has a nonlinear impact on carbon emissions and carbon emission efficiency:no significant effect when below 0.50 or above 0.55,increased carbon emissions in 0.50-0.53,and reduced carbon emissions with improved efficiency in 0.53-0.55.4)The polycentricity index has an interaction effect with other variables;specifically,when the polycentricity index is between 0.53 and 0.55,its interaction with urban gross domestic product(GDP),urban population,urban built-up area,green coverage rate in built-up areas,urban technological expenditure,and the proportion of the output value of the secondary industry will reduce carbon emissions and improve carbon emission efficiency.These findings enhance the understanding of urban spatial structures and carbon emissions,providing valuable insights for policymakers in developing green and low-carbon strategies.
基金funded by the Science and Technology Programme of Inner Mongolia Autonomous Region(Grant No.:2023YFDZ0026 and 2024KYPT0003)the 2024 Postgraduate Research and Innovation Programme of Inner Mongolia Agricultural University。
文摘Changes in the soil environment induced by major global changes in climate are affecting carbon emissions in cold-temperate coniferous forests.A randomized block experiment simulating warming,rainfall increase and nitrogen addition in a Larix gmelinii forest was carried out to study the effects on soil carbon,nitrogen,and CO_(2)flux during the thawing,growing,and freezing periods.Our study found that warming(0-2.0℃)increased soil organic carbon(SOC)and total nitrogen(STN),dissolved organic carbon(DOC)and dissolved organic nitrogen(DON),and microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN).Warming played a direct role in regulating soil CO_(2)emissions,stimulated microbial and plant root respiration and soil CO_(2)flux rapidly increased.Rainfall increase initially increased soil carbon and nitrogen,but a 30%increase in mean annual rainfall caused losses of SOC,STN,DOC,and DON,while MBC and MBN accumulated.Soil CO_(2)emissions were regulated by MBC after an increase in rainfall,excess moisture inhibited microbial activity,and soil CO_(2)flux showed a trend of R2(20%rainfall increase)>R1(10%rainfall increase)>CK(control)>R3(30%rainfall increase).The addition of nitrogen increased SOC,STN,DOC,DON,MBC and MBN.Soil CO_(2)flux progressively decreased with nitrogen inputs(2.5,5.0 and 10.0 g m^(-2)a^(-1)),as more N intensified plant-microbe competition.Nitrogen addition indirectly regulated soil CO_(2)emissions by altering SOC and STN,with MBC and MBN acting as secondary regulators.The results highlight the role of cold-temperate coniferous forest soils in predicting carbon-climate feedback in high-latitude forest permafrost regions.
基金financially supported by the National Science & Technology Fundamental Resources Investigation Project of China (2021FY100501)the Youth Innovation of Chinese Academy of Agricultural Sciences (Y2023QC16)。
文摘Long-term manure application has the potential to alleviate soil acidification, and increase carbon sequestration and nutrient availability, thus improving cropland fertility. However, the mechanisms behind greenhouse gas N_(2)O emissions from acidic soil mediated by long-term manure application remain poorly understood. Herein, we investigated N_(2)O emission and its linkage with gross N mineralization and nitrification rates, as well as nitrifying and denitrifying microbes in an acidic upland soil subjected to 36-year fertilization treatments, including an unfertilized control(CK), inorganic fertilizer(F), 2× rate of inorganic fertilizer(2F), manure(M), and the combination of inorganic fertilizer and manure(FM) treatments. Compared to the CK treatment(1.34 μg N kg^(-1) d^(-1)), fertilization strongly increased N_(2)O emissions by 34-fold on average, with more pronounced increases in the manure-amendment(10.6-169 μg N kg^(-1) d^(-1)) than those in the inorganic fertilizer treatments(3.26-5.51 μg N kg^(-1) d^(-1)). The manure amendment-stimulated N_(2)O emissions were highly associated with increased soil pH, mean weight diameter of soil aggregates, substrate availability(e.g., particulate organic carbon, NO_(3)^(-)and available phosphorus), gross N mineralization rates, denitrifier abundances and the(nirK+nirS)/nosZ ratio. These findings suggest that the increased N_(2)O emissions primarily resulted from alleviated acidification, increased substrate availability and improved soil structure, thus enhancing microbial N mineralization and favoring N_(2)O^(-)producing denitrifiers over N_(2)O consumers. Moreover, ammonia-oxidizing bacteria(AOB) rather than ammonia-oxidizing archaea(AOA) positively correlated with soil NO_(3)^(-)concentration and N_(2)O emissions, indicating that nitrification indirectly contributed to N_(2)O production by supplying NO_(3)^(-)for denitrification. Collectively, manure amendment potentially stimulates N_(2)O emissions, primarily resulting from alleviated soil acidification and increased substrate availability, thus enhancing N mineralization and denitrifier-mediated N_(2)O production. Our findings suggest that consideration should be given to the greenhouse gas budgets of agricultural ecosystems when applying manure for managing the pH and fertility of acidic soils.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3004704)the National Natural Science Foundation of China(Grant No.52174166)Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYB23031),which were gratefully acknowledged.
文摘During deep coal mining,an instability failure of coal usually occurs under the combined effect of initial damage and triaxial cyclic loading and unloading(TCLU).Therefore,this study investigated the impact of initial damage on mechanical behavior and acoustic emission(AE)characteristics of coal under TCLU.Initial damage variables(IDVs)of coal specimens were quantified using preloading,followed by TCLU experiments to assess the deformation,energy distribution,and fracture development.The results revealed that the increase in IDVs significantly reduced the structural integrity of coal specimens,increased the cumulative irreversible strain,and enhanced the dissipated energy owing to microfracture expansion.Moreover,AE monitoring showed earlier activation of fractures and a higher occurrence of large-scale rupture events of coal specimens with high IDVs,which correlated with decreasing AE b values(reflecting the different scales of fracture within specimens)and increasing S values(reflecting the AE activity within specimens).Additionally,computed tomography analysis revealed intensified fracture networks and increasing three-dimensional fractal dimensions of coal specimens with higher IDVs.Finally,the coupling effect of TCLU and initial damage on the weakening mechanism of coal was investigated.Initial damage significantly reduced the structural integrity of coal by increasing the number of weak planes within coal specimens,contributing to the earlier activation and rapid expansion of fractures at low stress levels under TCLU and eventually accelerating the weakening process of coal.This study provides a scientific basis and theoretical support for the prevention and control of dynamic disasters in deep coal mining.
基金supported by the National Natural Science Foundation of China (Grant Nos.12494604,12393834,12393831,62274014,6223501662335015)the National Key R&D Program of China (Grant No.2024YFA1208900)。
文摘The development of quantum materials for single-photon emission is crucial for the advancement of quantum information technology.Although significant advancements have been witnessed in recent years for single-photon sources in the near-infrared band(λ∼700–1000 nm),several challenges have yet to be addressed for ideal single-photon emission at the telecommunication band.In this study,we present a droplet-epitaxy strategy for O-band to C-band single-photon source-based semiconductor quantum dots(QDs)using metal-organic vaporphase epitaxy(MOVPE).By investigating the growth conditions of the epitaxial process,we have successfully synthesized InAs/InP QDs with narrow emission lines spanning a broad spectral range of λ∼1200–1600 nm.The morphological and optical properties of the samples were characterized using atomic force microscopy and microphotoluminescence spectroscopy.The recorded single-photon purity of a plain QD structure reaches g^((2))(0)=0.16,with a radiative recombination lifetime as short as 1.5 ns.This work provides a crucial platform for future research on integrated microcavity enhancement techniques and coupled QDs with other quantum photonics in the telecom bands,offering significant prospects for quantum network applications.
基金supported by the National Key R&D Program of China(2023YFA1406200)the National Natural Science Foundation of China(T2521005,12174144,12474009,12174146,and 124B2059)the Special Construction Project Fund for Shan-dong Province Taishan Scholars.
文摘Multifunctional optical responsive materials have grown increasingly pivotal in addressingthe escalating demands of sensing,detection,and anti-counterfeiting applications[1,2].These materials exhibit distinct visible optical variations upon exposure to external stimuli,such as pressure,temperature,light,solvents,pH fluctuations,or mechanical force.Fluorescent sensing and anti-counterfeiting technologies leveraging these optical responses have emerged as highly promising solutions.
基金funded by the Basic Scientific Research of China Geological Academy(YK202305)National Key R&D Program of China(2019YFB1504101)+1 种基金National Natural Science Foundation of China(41602271)China Geological Survey(DD20160207 and DD20189112)。
文摘The geothermal resources in China are primarily found in its sedimentary basins,particularly in the large basins located in eastern China,which hold significant potential for geothermal energy development.The Songliao,North China,and Zhangzhou basins are of special interest due to their considerable exploration depths,extensive development history,and high levels of research activity.This study focuses on the three basins to analyze their thermal reservoir characteristics in eastern China.Between 2017 and 2023,the research team carried out a comprehensive analysis involving deep boreholes that exceeded 4000 m in depth within these three basins.They meticulously created detailed physical profiles that captured essential characteristics such as porosity,permeability,and thermal properties,reaching down to the basement of each basin.The findings indicated that variations in thermal conductivity within shallow geotechnical layers significantly influence the redistribution of deep thermal energy in the upper layers of the earth.Furthermore,differences in physical properties notably affect heat transport processes.The research proposes distinct heat models tailored for each basin:For the Songliao Basin,a low-permeability model with homogeneous thermal properties is constructed;for the North China Basin,high permeability and thermal conductivity layers are highlighted;and a fracture network controlling water and heat is presented in the Zhangzhou Basin.To elucidate the thermal structure of these basins,the Curie surface and Moho surface were analyzed.The shallow Curie surface indicates ongoing intense thermal activity stemming from crustal heat sources,while a shallow Moho surface signifies historical vigorous mantle thermal activity associated with mantle source heat production.Furthermore,the research evaluates the geothermal resources and the potential for carbon emission reduction in these basins.Total volume of exploitable geothermal fluid is estimated to be 76.9×10^(9) m^(3)/a,corresponding to an annual renewable geothermal energy 1.47×10^(16)k J.The implementation of geothermal energy could lead to a reduction in annual CO_(2)emissions by nearly 2×10^(9) t,which constitutes about 17.4%of China’s national carbon emissions in 2022.This estimation provides invaluable theoretical insights and data support for geothermal exploration and sustainable development in eastern China.
基金supported by the National Natural Science Foundation of China (NSFC)Projects (Nos.42205105,42121004,and 42077190)the Science and Technology Project of Shaoguan (No.210811164532141)+3 种基金the National Key R&D Program of China (2022YFC3700604)the Science and Technology Program of Guangzhou City (No.202201010400)the Fundamental Research Funds for the Central Universities (No.21622319)the Research Center of Low Carbon Economy for Guangzhou Region (No.22JNZS50).
文摘Emission characteristics of biogenic volatile organic compounds(BVOCs)from dominant tree species in the subtropical pristine forests of China are extremely limited.Here we conducted in situ field measurements of BVOCs emissions from representative mature evergreen trees by using dynamic branch enclosures at four altitude gradients(600-1690ma.s.l.)in the Nanling Mountains of southern China.Composition characteristics as well as seasonal and altitudinal variations were analyzed.Standardized emission rates and canopyscale emission factors were then calculated.Results showed that BVOCs emission intensities in the wet season were generally higher than those in the dry season.Monoterpenes were the dominant BVOCs emitted from most broad-leaved trees,accounting for over 70%of the total.Schima superba,Yushania basihirsuta and Altingia chinensis had relatively high emission intensities and secondary pollutant formation potentials.The localized emission factors of isoprene were comparable to the defaults in the Model of Emissions of Gases and Aerosols fromNature(MEGAN),while emission factors of monoterpenes and sesquiterpenes were 2 to 58 times of those in the model.Our results can be used to update the current BVOCs emission inventory in MEGAN,thereby reducing the uncertainties of BVOCs emission estimations in forested regions of southern China.
基金supported by the Key Research and Development Program in Shaanxi Province,China(No.2022ZDLSF07-05)the Fundamental Research Funds for the Central Universities,CHD(No.300102352901)。
文摘Carbon emissions resulting from energy consumption have become a pressing issue for governments worldwide.Accurate estimation of carbon emissions using satellite remote sensing data has become a crucial research problem.Previous studies relied on statistical regression models that failed to capture the complex nonlinear relationships between carbon emissions and characteristic variables.In this study,we propose a machine learning algorithm for carbon emissions,a Bayesian optimized XGboost regression model,using multi-year energy carbon emission data and nighttime lights(NTL)remote sensing data from Shaanxi Province,China.Our results demonstrate that the XGboost algorithm outperforms linear regression and four other machine learning models,with an R^(2)of 0.906 and RMSE of 5.687.We observe an annual increase in carbon emissions,with high-emission counties primarily concentrated in northern and central Shaanxi Province,displaying a shift from discrete,sporadic points to contiguous,extended spatial distribution.Spatial autocorrelation clustering reveals predominantly high-high and low-low clustering patterns,with economically developed counties showing high-emission clustering and economically relatively backward counties displaying low-emission clustering.Our findings show that the use of NTL data and the XGboost algorithm can estimate and predict carbon emissionsmore accurately and provide a complementary reference for satellite remote sensing image data to serve carbon emission monitoring and assessment.This research provides an important theoretical basis for formulating practical carbon emission reduction policies and contributes to the development of techniques for accurate carbon emission estimation using remote sensing data.
基金supported by the National Natural Science Foundation of China(Nos.42375171 and 42105157)the Interdisciplinary Research Project for Young Teachers of USTB(No.06600083)+1 种基金Energy Foundation(Nos.G-2109-33379 and G-2306-34754)the Fundamental Research Funds for the Central Universities(No.06500166).
文摘Civil aviation is one of the industries facing the greatest challenge in reaching carbon neutrality by the middle of this century,and this sector also contributes to adverse impacts on the regional air quality and human health.China exhibits the second highest air passenger turnover worldwide.Our understanding of civil aviation emissionsmust be urgently enhanced,and themitigation potential should be explored.In this study,on the basis of real domestic flight information for 2019,we built a greenhouse gas and air pollution emission inventory for the civil aviation sector in China with the fuel flowmethod based on the cruise and other phases.We thoroughly analyzed emissions by region,aircraft and engine types,and aircraft age,based on which we designed four measures to evaluate the abatement potential.We found that the hydrocarbon(HC),CO,NO_(x),SO_(2),particulate matter(PM)and CO_(2)emissions in 2019 reached 79.9 kt(95%CI[51.6–114.5]),176.3 kt(95%CI[114.5–248.2]),304.2 kt(95%CI[203.4–420.7]),23.2 kt(95%CI[14.2–33.7]),1.0 kt(95%CI[0.61–1.44])and 87.0 Mt(95%CI[57.4–119.6]),respectively.The cruise phase was the major emission phase,accounting for 67%-87%of the total pollutant emissions.If four measures were jointly implemented,the HC,CO,NO_(x),SO_(2),PM and CO_(2)emissions could be reduced by 61%,54%,55%,45%,32%and 38%,respectively.Utilizing lower-emission aircraft and switching travel modes could substantially reduce civil aviation emissions in China.
文摘Biliary tract cancer(BTC)is a group of heterogeneous sporadic diseases,including intrahepatic,hilar,and distal cholangiocarcinoma,as well as gallbladder cancer.BTC is characterized by high invasiveness and extremely poor prognosis,with a global increased incidence due to intrahepatic cholangiocarcinoma(ICC).The 18Ffludeoxyglucose positron emission tomography(PET)computed tomography(18F-FDG PET/CT)combines glucose metabolic information(reflecting the glycolytic activity of tumor cells)with anatomical structure to assess tumor metabolic heterogeneity,systemic metastasis,and molecular characteristics noninvasively,overcoming the limitations of traditional imaging in the detection of micrometastases and recurrent lesions.18F-FDG PET/CT offers critical insights in clinical staging,therapeutic evaluation,and prognostic prediction of BTC.This article reviews research progress in this field over the past decade,with a particular focus on the advances made in the last 3 years,which have not been adequately summarized and recognized.The research paradigm in this field is shifting from qualitative to quantitative studies,and there have been significant breakthroughs in using 18F-FDG PET/CT metabolic information to predict gene expression in ICC.Radiomics and deep learning techniques have been applied to ICC for prognostic prediction and differential diagnosis.Additionally,PET/magnetic resonance imaging is increasingly demonstrating its value in this field.
