Development of a monochromatic crystal backlight imager for the recent double-cone ignition experiments

We developed a monochromatic crystal backlight imaging system for the double-cone ignition(DCI) scheme, employing a spherically bent quartz crystal. This system was used to measure the spatial distribution and temporal evolution of the head-on colliding plasma from the two compressing cones in the DCI experiments. The influence of laser parameters on the x-ray backlighter intensity and spatial resolution of the imaging system was investigated. The imaging system had a spatial resolution of 10 μm when employing a CCD detector. Experiments demonstrated that the system can obtain time-resolved radiographic images with high quality, enabling the precise measurement of the shape, size, and density distribution of the plasma.

Influence of crystal dimension on performance of spherical crystal self-emission imager

The spherical crystal imaging system,noted for its high energy spectral resolution(monochromaticity)and spatial resolution,is extensively applied in high energy density physics and inertial confinement fusion research.This system supports studies on fast electron transport,hydrodynamic instabilities,and implosion dynamics.The x-ray source,produced through laser-plasma interaction,emits a limited number of photons within short time scales,resulting in predominantly photon-starved images.Through ray-tracing simulations,we investigated the impact of varying crystal dimensions on the performance of a spherical crystal self-emission imager.We observed that increasing the crystal dimension leads to higher imaging efficiency but at the expense of monochromaticity,causing broader spectral acceptance and reduced spatial resolution.Furthermore,we presented a theoretical model to estimate the spatial resolution of the imaging system within a specific energy spectrum range,detailing the expressions for the effective size of the crystal.The spatial resolution derived from the model closely matches the numerical simulations.

Study of the toluene absorption capacity and mechanism of ionic liquids using COSMO-RS prediction and experimental verification

As green solvents,ionic liquids(ILs)are quite suitable for the absorption of volatile organic compounds(VOCs)such as benzene and its homologues.However,solvent selection is the key to the VOC absorption process.In the present study,a rapid solvent screening tool,Conductor-like Screening Model for Real Solvents(COSMO-RS),was used to predict the solubility of toluene in 816 ILs.The effects of four structure characters,namely,the type and alkyl chain length of the cations and anions on the solubility of toluene were discussed.The following conclusions were drawn from the results:(1)ILs with pyrrolidinium-based cations showed better solubility than pyridinium-and imidazoliumbased ones.(2)The solubility of toluene in PF6-based ILs increased with the increasing alkyl chain length,while its solubility in Ac-based ILs exhibited the opposite trend.(3)Toluene showed greater solubility in Cl-based ILs than those based on other anions.(4)The solubility of toluene increased with the anion alkyl chain length.Ac-based ILs were chosen as the most promising potential solvents,and further studied to determine the relationship between various interaction energy parameters and toluene solubility.The results showed that the misfit energy played a dominant role during the absorption process.Furthermore,several ILs were selected for experimental verification of the predicted solubility behavior using liquid and gaseous toluene.The results demonstrated that COSMO-RS could be used to semi-quantitatively and qualitatively predict the solubility of toluene,and this model had promising prospects in screening ILs for VOCs absorption.In summary,this study provided a fundamental basis and practical data for the control and treatment of VOCs.

Submarine volcanism in the southern margin of the South China Sea

Submarine volcanism is widely developed in the South China Sea(SCS).However,the characteristics,distribution,and genesis of submarine volcanoes in the southern margin of the SCS remain obscure.In this study,we analyzed the characteristics of submarine volcanoes and identified a total of 43 submarine volcanoes in the southern margin of the SCS,based on a newly acquired 310-km seismic reflection profile,along with previous 45 multi-channel seismic(MCS)profiles,petrological results from volcanic rocks sampled by dredging and drilling,nearby ocean bottom seismometer(OBS)wide-angle seismic profiles,and gravity and magnetic data.The study ascertains that most of these volcanoes are located in fault-block belts and graben-horst zones with strong crustal stretching and thinning.These volcanoes exhibit positive high-amplitude external seismic reflections,weak and chaotic internal seismic reflections,and are accompanied by local deformation of the surrounding sedimentary strata.Meanwhile,they have higher positive gravity anomalies and higher magnetic anomalies than the background strata.The petrological dating results show that volcanic ages are primarily in the Pliocene-Pleistocene,with geochemical characteristics indicating dominance of oceanic island basalt(OIB)-type alkali-basalts.Extensional faults have obviously spatial correspondence with post-spreading volcanism,suggesting these faults may provide conduits for submarine volcanism.The high-velocity bodies(HVBs)in the lower crust and magma underplating exist in the southern SCS,which could provide a clue of genesis for submarine volcanism.The inference is that the intensity of post-spreading volcanism in the southern margin might be affected by stretching faults,crustal thinning and magma underplating.

Characteristics and sources of peroxyacetyl nitrate(PAN)in the rural North China Plain:Results from1-year continuous observations

Peroxyacetyl nitrate(PAN)is an important photochemical pollutant in the troposphere,whereas long-term measurements are scarce in rural areas in North China Plain(NCP),resulting in unclear seasonal variations and sources of PAN in rural NCP.In this study,we conducted a 1-year observation of PAN during 2021-2022 at the rural NCP site.The average concentrations of PAN were 1.10,0.75,0.65,and 0.88 ppbv in spring,summer,autumn,and winter,respectively,with a 1-year average of 0.81±0.60 ppbv.Calculations indicate that the loss of PAN through thermal decomposition in summer accounts for 43.2% of the total formed PAN,which is an important reason for the low concentration of PAN in summer.We speculate that since the correlation between PAN and O_(3) in winter is significantly lower than that in other seasons,the observed regional transport of PAN cannot be ignored in winter.Through budget analysis,regional transport accounted for 12.8% and 55.9% of the observed PAN on the spring and winter pollution days,respectively,which showed that regional transport played key roles during the photochemical pollution of the rural NCP in winter.The potential source contribution function revealed that the transported PAN mainly comes from southern Hebei in spring.In winter,the transported PAN was mainly from Langfang,Hengshui,and southern Beijing.Our findings may aid in understanding PAN variations in different seasons in rural areas and highlight the impact of regional transport on the PAN budget.

Diagnosing the fast-heating process of the double-cone ignition scheme with X-ray spectroscopy

In the double-cone ignition scheme of inertial confinement fusion,the head-on collision of two compressed fuel jets from the cone-tips forms an isochoric plasma,which is then heated suddenly by a MeV relativistic electron beam produced by ultra-intense picosecond laser pulses.This fast-heating process was studied experimentally at the ShenguangⅡupgrade laser facility.By observing temporal-resolved X-ray emission and the spatial-resolved X-ray spectrum,the colliding process and heating process are carefully studied.The colliding plasma was imaged to have dimensions of approximately86μm in the implosion direction and approximately 120μm in the heating direction.By comparing the simulated plasma X-ray spectrum with experimental data,the electron temperature of the heated plasma was found to rapidly increase to 600±50 eV,almost doubling the temperature achieved before the heating laser incidence.

Investigation on relaxor-ferroelectric behavior of BNBT-KNN ceramics with Ta doping

In this study,BNBT-KNN-xTa_(2)O_(5)was designed and synthesized,successfully achieving a reduction in the relaxor-ferroelectric phase transition temperature.Synergy between temperature-dependent ferroelectric testing and dielectric spectroscopy confirmed that the depoling temperature gradually decreased with increasing doping concentration.Fitting of the relaxation parameter and freezing temperature substantiated that the incorporation of Ta_(2)O_(5)increased the degree of relaxation in BNBT-KNN-xTa_(2)O_(5),thereby effectively lowering the relaxor-ferroelectric phase transition temperature.

Enhanced energy-storage performance with optimized thermally stable dielectric property in BNT–BST ceramics modified by KNN doping

Developing environmental-friendly materials with high-density energy storage is of paramount importance to meet the burgeoning demands for energy storage.In this study,we harness the modulation of a multicomponent solid solution by introducing KNN as a third element into the BNT–BST system,thereby achieving a marked enhancement in both energy storage performance and the temperature stability of the dielectric constant.BNBST–4KNN stands out for its exceptional dielectric stability,with a dielectric constant variation rate within 10%across a broad temperature range of 40℃to 400℃,a feat attributed to the flattening and broadening of the Tm peak.BNBT–2KNN exhibits superior energy storage capabilities,with an energy storage density of 1.324 J/cm^(3)and an energy storage efficiency of 72.3%,a result of the P–E loop becoming more slender.These advancements are pivotal for the sustainable progression of energy storage technologies.

新型樟脑磺胺基肟醚衍生物的合成及抗肿瘤活性研究

利用药物设计中的活性拼接原理,以(+)-10-樟脑磺酸为原料,经酰氯化、酰胺化和缩合反应,设计合成了一系列樟脑磺胺基肟醚类衍生物,通过1HNMR、13CNMR和HRMS对其结构进行了表征.采用噻唑蓝(MTT)法对目标化合物对人肺腺癌细胞(A549)、人宫颈癌细胞(Hela)、人乳腺癌细胞(MCF-7)和人正常胚胎肝细胞(LO2)进行抗肿瘤活性评价。结果表明,大部分化合物显示出良好的抗肿瘤活性。其中,(+)-1-(7,7-二甲基-2-(苄氧基亚氨基)双环[2.2.1]庚烷-1-基)-N-(3-(三氟甲基)苯基)甲磺酰胺(4r)对三种细胞表现出最好的抗增值效果,IC50值分别为6.75、7.93和4.51μmol·L^(-1).采用流式细胞术检测细胞周期和凋亡,Hoechst染色观察细胞形态变化.荧光探针DCFH-DA和JC-1分别用于检测细胞内活性氧水平和线粒体膜电位.初步机理研究表明,化合物4r可将MCF-7细胞阻滞在G0/G1期,可诱导活性氧产生和线粒体膜电位崩溃进而诱导细胞呈剂量依赖式凋亡.

The levels, sources and reactivity of volatile organic compounds in a typical urban area of Northeast China

Air concentrations of volatile organic compounds(VOCs) were continually measured at a monitoring site in Shenyang from 20 August to 16 September 2017. The average concentrations of alkanes, alkenes, aromatics and carbonyls were 28.54, 6.30, 5.59 and9.78 ppbv, respectively. Seven sources were identified by the Positive Matrix Factorization model based on the measurement data of VOCs and CO. Vehicle exhaust contributed the most(36.15%) to the total propene-equivalent concentration of the measured VOCs,followed by combustion emission(16.92%), vegetation emission and secondary formation(14.33%), solvent usage(10.59%), petrochemical industry emission(9.89%), petrol evaporation(6.28%), and liquefied petroleum gas(LPG) usage(5.84%). Vehicle exhaust, solvent usage and combustion emission were found to be the top three VOC sources for O_3 formation potential, accounting for 34.52%, 16.55% and 11.94%, respectively. The diurnal variation of the total VOCs from each source could be well explained by their emission characteristics,e.g., the two peaks of VOC concentrations from LPG usage were in line with the cooking times for breakfast and lunch. Wind rose plots of the VOCs from each source could reveal the possible distribution of the sources around the monitoring site. The O_3 pollution episodes during the measurement period were found to be coincident with the elevation of VOCs, which was mainly due to the air parcel from the southeast direction where petrochemical industry emission was found to be dominant, suggesting that the petrochemical industry emission from the southeast was probably a significant cause of O_3 pollution in Shenyang.

Challenges and strategies for in situ endothelialization and long-term lumen patency of vascular grafts

Vascular diseases are the most prevalent cause of ischemic necrosis of tissue and organ,which even result in dysfunction and death.Vascular regeneration or artificial vascular graft,as the conventional treatment modality,has received keen attentions.However,small-diameter(diameter<4 mm)vascular grafts have a high risk of thrombosis and intimal hyperplasia(IH),which makes long-term lumen patency challengeable.Endothelial cells(ECs)form the inner endothelium layer,and are crucial for anti-coagulation and thrombogenesis.Thus,promoting in situ endothelialization in vascular graft remodeling takes top priority,which requires recruitment of endothelia progenitor cells(EPCs),migration,adhesion,proliferation and activation of EPCs and ECs.Chemotaxis aimed at ligands on EPC surface can be utilized for EPC homing,while nanofibrous structure,biocompatible surface and cell-capturing molecules on graft surface can be applied for cell adhesion.Moreover,cell orientation can be regulated by topography of scaffold,and cell bioactivity can be modulated by growth factors and therapeutic genes.Additionally,surface modification can also reduce thrombogenesis,and some drug release can inhibit IH.Considering the influence of macrophages on ECs and smooth muscle cells(SMCs),scaffolds loaded with drugs that can promote M2 polarization are alternative strategies.In conclusion,the advanced strategies for enhanced long-term lumen patency of vascular grafts are summarized in this review.Strategies for recruitment of EPCs,adhesion,proliferation and activation of EPCs and ECs,anti-thrombogenesis,anti-IH,and immunomodulation are discussed.Ideal vascular grafts with appropriate surface modification,loading and fabrication strategies are required in further studies.

铁硼基海绵催化电极的制备及其高效析氢性能

采用温和化学镀法在非导电基底材料聚氨酯海绵(PU)上成功制备了NiB@Fe–B/PU催化电极,并通过掺杂少量第三种元素,如钴、钼等金属元素制备了NiB@Fe–Co–B/PU和NiB@Fe–Mo–B/PU催化电极。结果表明,掺杂钴、钼可明显提升Ni B@Fe–B/PU催化电极的析氢性能,其中掺杂钴的性能更优。在0.5 mol/L缓冲液(磷酸缓冲盐溶液,PBS)中,NiB@Fe–Co–B/PU电极的析氢反应(HER)过电位仅为161 mV(电流密度, j=50 mA/cm^2),塔菲尔斜率为68.24 mV/dec,且在过电位为61 mV下能够稳定工作24 h以上,电化学稳定性良好。

Pollution levels, composition characteristics and sources of atmospheric PM2.5 in a rural area of the North China Plain during winter

The pollution levels,composition characteristics and sources of atmospheric PM2.5 were investigated based on field measurement at a rural site in the North China Plain(NCP) from pre-heating period to heating period in winter of 2017.The hourly average concentrations of PM2.5 frequently exceeded 150 μg/m3 and even achieved 400 μg/m3,indicating that the PM2.5pollution was still very serious despite the implementation of stricter control measures in the rural area.Compared with the pre-heating period,the mean concentrations of organic carbon(OG),element carbon(EC) and chlorine ion(Cl-) during the heating period increased by 20.8%,36.6% and 38.8%,accompanying with increments of their proportions in PM2.5from 37.5%,9.8% and 5.5% to 42.9%,12.7% and 7.2%,respectively.The significant increase of both their concentrations and proportions during the heating period was mainly ascribed to the residential coal combustion.The proportions of sulfate,nitrate and ammonium respectively increased from 9.9%,10.9% and 9.0% in nighttime to 13.8%,16.2% and 11.1% in daytime,implying that the daytime photochemical reactions made remarkable contributions to the secondary inorganic aerosols.The simulation results from WRF-Chem revealed that the emission of residential coal combustion in the rural area was underestimated by the current emission inventory.Six sources identified by positive matrix factorization(PMF) based on the measurement were residential coal combustion,secondary formation of inorganic aerosols,biomass burning,vehicle emission and raising dust,contributing to atmospheric PM2.5 of 40.5%,21.2%,16.4%,10.8%,8.6% and 2.5%,respectively.

Rural vehicle emission as an important driver for the variations of summertime tropospheric ozone in the Beijing-Tianjin-Hebei region during 2014-2019

Tropospheric ozone(O_(3))pollution is increasing in the Beijing-Tianjin-Hebei(BTH)region despite a significant decline in atmospheric fine aerosol particles(PM_(2.5))in recent years.However,the intrinsic reason for the elevation of the regional O_(3)is still unclear.In this study,we analyzed the spatio-temporal variations of tropospheric O_(3)and relevant pollutants(PM_(2.5),NO_(2),and CO)in the BTH region based on monitoring data from the China Ministry of Ecology and Environment during the period of 2014-2019.The results showed that summertime O_(3)concentrations were constant in Beijing(BJ,0.06μg/(m^(3)·year))but increased significantly in Tianjin(TJ,9.09μg/(m^(3)·year))and Hebei(HB,6.06μg/(m3·year)).Distinct O_(3)trends between Beijing and other cities in BTH could not be attributed to the significant decrease in PM_(2.5)(from-5.08 to-6.32μg/(m3·year))and CO(from-0.053 to-0.090 mg/(m^(3)·year))because their decreasing rates were approximately the same in all the cities.The relatively stable O_(3)concentrations during the investigating period in BJ may be attributed to a faster decreasing rate of NO_(2)(BJ:-2.55μg/(m^(3)·year);TJ:-1.16μg/(m^(3)·year);HB:-1.34μg/(m3·year)),indicating that the continued reduction of NOx will be an effective mitigation strategy for reducing regional O_(3)pollution.Significant positive correlations were found between daily maximum8 hr average(MDA8)O_(3)concentrations and vehicle population and highway freight transportation in HB.Therefore,we speculate that the increase in rural NO_(x)emissions due to the increase in vehicle emissions in the vast rural areas around HB greatly accelerates regional O_(3)formation,accounting for the significant increasing trends of O_(3)in HB.

Seasonal and diurnal variations of atmospheric peroxyacetyl nitrate, peroxypropionyl nitrate, and carbon tetrachloride in Beijing

Atmospheric peroxyacetyl nitrate （PAN）, peroxypropionyl nitrate （PPN）, and carbon tetrachloride （CCl4） were measured from September 2010 to August 2011 in Beijing. PAN exhibited low values from mid-autumn to early spring （October to March） with monthly average concentrations ranging from 0.28 to 0.73 ppbV, and increased from early spring to summer （March to August）, ranging from 1.37-3.79 ppbV. The monthly variation of PPN was similar to PAN, with low values （below detection limit to 0.18 ppbV） from mid-autumn to early spring, and a monthly maximum in September （1.14 ppbV）. The monthly variation of CCl4 was tightly related to the variation of temperature, exhibiting a minimum in winter （69.3 pptV） and a maximum of 180.6 pptV in summer. Due to weak solar intensity and short duration, PAN and O3 showed no distinct diurnal patterns from morning to night during winter, whereas for other seasons, they both exhibited maximal values in the late afternoon （ca. 15：00 to 16：00 local time） and minimal values during early morning and midnight. Good linear correlations between PAN and PPN were found in autumn （R = 0.91）, spring （R = 0.94）, and summer （R = 0.81）, with slopes of 0.130, 0.222, and 0.133, respectively, suggesting that anthropogenic hydrocarbons dominated the photochemical formation of PANs in Beijing. Positive correlation between PAN and O3 in summer with the low slopes （AO3/APAN） ranging from 9.92 to 18.0 indicated serious air pollution in Beijing, and strong negative correlation in winter reflected strong O3 consumption by NO titration and less thermal decompositin of PAN.

The pollution levels, var iation character istics, sources and implications of atmospheric carbonyls in a typical rural area of North China Plain during winter

Atmospheric carbonyls were measured at a typical rural area of the North China Plain(NCP)from November 13 to December 24,2017 to investigate the pollution characteristics,sources and environmental implications.Fifteen carbonyls were detected,and formaldehyde,acetaldehyde and acetone accounted for about 81% at most.The concentration of the total carbonyls in heavily polluted days was twice more than that in clean days.In contrast to other carbonyls,m-tolualdehyde exhibited relatively high concentrations in the clean days in comparison with the polluted days.The ratios of three principal carbonyls to CO showed similar daily variations at different pollution levels with significant daytime peaks.Multiple linear regression analysis revealed that the contributions of background,primary and secondary sources to three principal carbonyls showed similar variation trends from the clean level to the heavily polluted level.The OH formation rate of formaldehyde showed a similar variation trend to its photodegradation rate,reaching the peak value at noon,which is important to maintain relatively high OH levels to initiate the oxidation of various gas-phase pollutants for secondary pollutant formation at the rural site.OH radical consumption rate and ozone formation potential(OFP) calculations showed that formaldehyde and acetaldehyde were the dominant oxidative species among measured carbonyls.As for OH radical consumption,n-butyraldehyde and m-tolualdehyde were important contributors,while for ozone formation potential,n-butyraldehyde and propionaldehyde made significant contributions.In addition,the contribution of carbonyl compounds to secondary organic aerosol(SOA) formation was also important and needs further investigation.

A machine learning model for textured X-ray scattering and diffraction image denoising

With the advancements in instrumentations of next-generation synchrotron light sources,methodologies for small-angle X-ray scattering(SAXS)/wide-angle X-ray diffraction(WAXD)experiments have dramatically evolved.Such experiments have developed into dynamic and multiscale in situ characterizations,leaving prolonged exposure time as well as radiation-induced damage a serious concern.However,reduction on exposure time or dose may result in noisier images with a lower signal-to-noise ratio,requiring powerful denoising mechanisms for physical information retrieval.Here,we tackle the problem from an algorithmic perspective by proposing a small yet effective machine-learning model for experimental SAXS/WAXD image denoising,allowing more redundancy for exposure time or dose reduction.Compared with classic models developed for natural image scenarios,our model provides a bespoke denoising solution,demonstrating superior performance on highly textured SAXS/WAXD images.The model is versatile and can be applied to denoising in other synchrotron imaging experiments when data volume and image complexity is concerned.

Activity maintenance of the excised branches and a case study of NO_2 exchange between the atmosphere and P.nigra branches

The efficient maintenance of the activity of excised branches is the powerful guarantee to accurately determine gas exchange flux between the detached branches of tall trees and the atmosphere. In this study, the net photosynthetic rate(NPR) of the excised branches and branches in situ were measured simultaneously by using two photosynthetic instruments to characterize the activity of the excised branches of Phyllostachys nigra. The ratio of normalized NPR of excised branches to NPR in situ was used to assess the photosynthetic activity of detached branches. Based on photosynthetic activity, an optimal hydroponics protocol for maintaining activity of excised P. nigra branches was presented:1/8 times the concentration of Gamborg B5 vitamin mixture with p H = 6. Under the best cultivation protocol, photosynthetic activity of excised P. nigra branches could be maintained more than 90% within 6 hr in the light intensity range of 200–2000 μmol/(m2·sec) and temperature range of 13.4–28.7°C. The nitrogen dioxide(NO2) flux differences between in situ and in vitro branches and the atmosphere were compared using double dynamic chambers.Based on the maintenance method of excised branches, the NO2 exchange flux between the excised P. nigra branches and the atmosphere(from-1.01 to-2.72 nmol/(m2·sec) was basically consistent with between the branches in situ and the atmosphere(from-1.12 to-3.16 nmol/(m2 sec)) within 6 hr. Therefore, this study provided a feasible protocol for in vitro measurement of gas exchange between tall trees and the atmosphere for a period of time.

Structural-functional unit ordering for high-performance electron-correlated materials

Electron-correlated materials have been drawing ever-increasing attention due to their fascinating physical behaviors and extensive application scenarios.In this review,a new method for material research and design(R&D),named structural-functional unit ordering(SFU ordering),which is presented,overcomes the shortcomings—for example,the limitation of finite chemical elements and long R&D circle-of conventional strategy and thus provides guidance for the design of these high-performance functional materials on demand.Meanwhile,with the development of material characterization technologies,SFUs of different scales and types can be directly observed,which,moreover,regulate the corresponding orderings.The review,starts with an introduction of the profile for SFU ordering and the synergistic effect between SFUs.Then,studies on several new high-performance electronic-correlated materials,for example,a ferromagnetic semiconductor with local spin,ferromagnetic metals with spin topologies,ferroelectric thin films with polar topologies,piezoelectric thin films with nanopillars enclosed by charged boundaries,thermoelectric materials with local ferromagnetic nanoparticles and topotactic phase transformation with conducting nanofilaments are stated in detail one by one.The vital aspect is the breaking of local symmetry,the construction,the structure,of SFUs and their orderings existing or theoretically existing,together with the enhanced/new performance.All in all,the main comments of the review tend to the remaining challenges,promising design approaches for the SFUs,and their orderings for high-performance functional materials.

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing

Atmospheric mixing ratios of carbonyl sulfide（COS） in Beijing were intensively measured from March 2011 to June 2013. COS mixing ratios exhibited distinct seasonal variation, with a maximum average value of 849 ± 477 pptv in winter and a minimal value of 372 ± 115 pptv in summer. The seasonal variation of COS was mainly ascribed to the combined effects of vegetation uptake and anthropogenic emissions. Two types of significant linear correlations（R2〉 0.66） were found between COS and CO during the periods from May to June and from October to March, with slopes（ΔCOS/ΔCO） of 0.72 and 0.14 pptv/ppbv, respectively. Based on the emission ratios of COS/CO from various sources, the dominant anthropogenic sources of COS in Beijing were found to be vehicle tire wear in summer and coal burning in winter. The total anthropogenic emission of COS in Beijing was roughly estimated as 0.53 ± 0.02 Gg/year based on the local CO emission inventory and the ΔCOS/ΔCO ratios.