Using restored two-dimensional X-ray images to reconstruct the three-dimensional magnetopause

Astronomical imaging technologies are basic tools for the exploration of the universe,providing basic data for the research of astronomy and space physics.The Soft X-ray Imager(SXI)carried by the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)aims to capture two-dimensional(2-D)images of the Earth’s magnetosheath by using soft X-ray imaging.However,the observed 2-D images are affected by many noise factors,destroying the contained information,which is not conducive to the subsequent reconstruction of the three-dimensional(3-D)structure of the magnetopause.The analysis of SXI-simulated observation images shows that such damage cannot be evaluated with traditional restoration models.This makes it difficult to establish the mapping relationship between SXIsimulated observation images and target images by using mathematical models.We propose an image restoration algorithm for SXIsimulated observation images that can recover large-scale structure information on the magnetosphere.The idea is to train a patch estimator by selecting noise–clean patch pairs with the same distribution through the Classification–Expectation Maximization algorithm to achieve the restoration estimation of the SXI-simulated observation image,whose mapping relationship with the target image is established by the patch estimator.The Classification–Expectation Maximization algorithm is used to select multiple patch clusters with the same distribution and then train different patch estimators so as to improve the accuracy of the estimator.Experimental results showed that our image restoration algorithm is superior to other classical image restoration algorithms in the SXI-simulated observation image restoration task,according to the peak signal-to-noise ratio and structural similarity.The restoration results of SXI-simulated observation images are used in the tangent fitting approach and the computed tomography approach toward magnetospheric reconstruction techniques,significantly improving the reconstruction results.Hence,the proposed technology may be feasible for processing SXI-simulated observation images.

Moisture‑Electric–Moisture‑Sensitive Heterostructure Triggered Proton Hopping for Quality‑Enhancing Moist‑Electric Generator

Moisture-enabled electricity(ME)is a method of converting the potential energy of water in the external environment into electrical energy through the interaction of functional materials with water molecules and can be directly applied to energy harvesting and signal expression.However,ME can be unreliable in numerous applications due to its sluggish response to moisture,thus sacrificing the value of fast energy harvesting and highly accurate information representation.Here,by constructing a moisture-electric-moisture-sensitive(ME-MS)heterostructure,we develop an efficient ME generator with ultra-fast electric response to moisture achieved by triggering Grotthuss protons hopping in the sensitized ZnO,which modulates the heterostructure built-in interfacial potential,enables quick response(0.435 s),an unprecedented ultra-fast response rate of 972.4 mV s^(−1),and a durable electrical signal output for 8 h without any attenuation.Our research provides an efficient way to generate electricity and important insight for a deeper understanding of the mechanisms of moisture-generated carrier migration in ME generator,which has a more comprehensive working scene and can serve as a typical model for human health monitoring and smart medical electronics design.

Uncertainty-Aware Physical Simulation of Neural Radiance Fields for Fluids

This paper presents a novel framework aimed at quantifying uncertainties associated with the 3D reconstruction of smoke from2Dimages.This approach reconstructs color and density fields from 2D images using Neural Radiance Field(NeRF)and improves image quality using frequency regularization.The NeRF model is obtained via joint training ofmultiple artificial neural networks,whereby the expectation and standard deviation of density fields and RGB values can be evaluated for each pixel.In addition,customized physics-informed neural network(PINN)with residual blocks and two-layer activation functions are utilized to input the density fields of the NeRF into Navier-Stokes equations and convection-diffusion equations to reconstruct the velocity field.The velocity uncertainties are also evaluated through ensemble learning.The effectiveness of the proposed algorithm is demonstrated through numerical examples.The presentmethod is an important step towards downstream tasks such as reliability analysis and robust optimization in engineering design.

A likely paleo-autotetraploidization event shaped the high conservation of Nyssaceae genome

Scientific knowledge about the ancestral genome of core eudicot plant kingdom can potentially have profound impacts on both basic and applied research,including evolution,genetics,genomics,ecology,agriculture,forestry,and global climate.To investigate which plant conserves best the core eudicots common ancestor genome,we compared Arcto-Tertiary relict Nyssaceae and 30 other eudicot plant families.The genomes of Davidia involucrata(a known living fossil),Camptotheca acuminata and Nyssa sinensis,one per existent genus of Nyssaceae,were performed comparative genomic analysis.We found that Nyssaceae originated from a single Nyssaceae common tetraploidization event(NCT)-autotetraploidization 28-31 Mya after the core eudicot common hexaploidization(ECH).We identified Nyssaceae orthologous and paralogous genes,determined its chromosomal evolutionary trajectory,and reconstructed the Nyssaceae most recent ancestor genome.D.involucrata genome contained the entire seven paleochromosomes and 17 ECH-generated eudicot common ancestor chromosomes and was the slowest in mutation among the analyzed 42 species of 31 plant families.Combing both its high retention of paleochromosomes and its low mutation rate,D.involucrata provides the best case in conservation of the core eudicot paleogenome.

Influence of Anteroposterior Symmetrical Aero-Wings on the Aerodynamic Performance of High-Speed Train

The running stability of high-speed train is largely constrained by the wheel-rail coupling relationship,and the continuous wear between the wheel and rail surfaces will profoundly affect the dynamic performance of the train.In recent years,under the background of increasing train speed,some scientific researchers have proposed a new idea of using the lift force generated by the aerodynamic wings(aero-wing)installed on the roof to reduce the sprung load of the carriage in order to alleviate the wear and tear of the wheel and rail.Based on the bidirectional running characteristics of high-speed train,this paper proposes a scheme to apply aero-wings with anteroposterior symmetrical cross-sections on the roof of the train.After the verification of the wind tunnel experimental data,the relatively better airfoil section and extension formof anteroposterior symmetrical aero-wing is selected respectively in this paper,and the aero-wings are fixedly connected to the roof of the train through the mounting column to conduct aerodynamic simulation analysis.The research shows that:compared with the circular-arc and oval crosssections,this paper believes that the crescent cross-section can form greater aerodynamic lift force in a limited space.Considering factors such as aerodynamic parameters,ground effect,and manufacturing process,this paper proposes to adopt aero-wings with arc type extension form and connect them to the roof of the train through mounting columns with shuttle cross-section.When the roof of the train is covered with aero-wings and runs at high speed,the sprung load of the carriages can be effectively reduced.However,there are certain hidden dangers in the tail carriage due to the large amount of lift force,so,the intervention of the aero-wing lifting mechanism is required.At the same time,it is necessary to optimize the overall aerodynamic drag force reduction in the followup work.

Allotetraploidization event of Coptis chinensis shared by all Ranunculales

Coptis chinensis Franch.,also named Chinese goldthread is a member of Ranunculaceae in the order Ranunculales and represents an important lineage of early eudicots with traditional medicinal value.In our study,by using syntenic analysis combined with phylogenomic analysis of C.chinensis and four other representative genomes from basal and core eudicots,we confirmed that the WGD event in C.chinensis was shared by Aquilegia coerulea and Papaver somniferum L.and quickly occurred after Ranunculales diverged from other eudicots,likely a Ranunculales common tetraploidization(RCT).The synonymous nucleotide substitutions at synonymous sites distribution of syntenic blocks across these genomes showed that the evolutionary rate of the P.somniferum genome is faster than that of the C.chinensis genome by approximately 13.7%,possibly due to Papaveraceaes having an additional special tetraploidization event(PST).After Ks correction,the RCT dated to 115—130 million years ago(MYA),which was close to the divergence of Ranunculaceaes and Papaveraceaes approximately115.45—130.51 MYA.Moreover,we identified homologous genes related to polyploidization and speciation and constructed multiple sequence alignments with different reference genomes.Notably,the event-related subgenomes in the basal genomes all showed genomic fractionation bias,suggesting a likely allopolyploid nature of the RCT,PST and T-Alpha and T-Beta events in Tetracentron sinense.In addition,we detected that the sixteen P450 subfamilies were markedly expanded in the genomes of Ranunculales,and most of them were related to the RCT and PST events.We constructed a new platform for Early Eudicot Comparative Genomic Research(http://www.cgrpoee.top/index.html)to store more information.In summary,our findings support the WGD of C.chinensis shared by Ranunculales,which is likely an allotetraploidization event.This present effort offered new insights into the evolution of key polyploidization events and the genes related to secondary metabolites during the diversification of early eudicots.

Low-temperature characteristicsof rubbers and performance testsof type 120 emergencyvalve diaphragms

Purpose–The type 120 emergency valve is an essential braking component of railway freight trains,butcorresponding diaphragms consisting of natural rubber(NR)and chloroprene rubber(CR)exhibit insufficientaging resistance and low-temperature resistance,respectively.In order to develop type 120 emergency valverubber diaphragms with long-life and high-performance,low-temperatureresistant CR and NR were processed.Design/methodology/approach–The physical properties of the low-temperature-resistant CR and NRwere tested by low-temperature stretching,dynamic mechanical analysis,differential scanning calorimetryand thermogravimetric analysis.Single-valve and single-vehicle tests of type 120 emergency valves werecarried out for emergency diaphragms consisting of NR and CR.Findings–The low-temperature-resistant CR and NR exhibited excellent physical properties.The elasticityand low-temperature resistance of NR were superior to those of CR,whereas the mechanical properties of thetwo rubbers were similar in the temperature range of 0℃–150℃.The NR and CR emergency diaphragms metthe requirements of the single-valve test.In the low-temperature single-vehicle test,only the low-temperaturesensitivity test of the NR emergency diaphragm met the requirements.Originality/value–The innovation of this study is that it provides valuable data and experience for futuredevelopment of type 120 valve rubber diaphragms.

Experimental Study on Anchoring Physical Properties of Different Anchoring Lengths Coupled with Temperature and Pressure

Aiming at deep roadway anchorage solids, laboratory similar model tests were used to reveal the mechanical properties of anchorage solids with different anchorage lengths under the coupling effect of temperature and pressure, and SPSS statistical analysis software was used to conduct linear regression analysis of the ultimate anchorage force obtained from the tests. The results show that: through multiple linear regression analysis, the influence degree of temperature and pressure coupling on the ultimate anchorage force is arranged in order of anchoring length > surrounding rock strength > temperature > side pressure coefficient, and the linear regression equation of the model is obtained. Compared with the linear regression equation of simulation results, the model has a high explanatory ability.

Recent Advances of Deep Learning in Geological Hazard Forecasting

Geological hazard is an adverse geological condition that can cause loss of life and property.Accurate prediction and analysis of geological hazards is an important and challenging task.In the past decade,there has been a great expansion of geohazard detection data and advancement in data-driven simulation techniques.In particular,great efforts have been made in applying deep learning to predict geohazards.To understand the recent progress in this field,this paper provides an overview of the commonly used data sources and deep neural networks in the prediction of a variety of geological hazards.

MXene terminating groups=O,–F or–OH,–F or=O,–OH,–F,or=O,–OH,–Cl?

MXenes are a novel family of two-dimensional(2D)materials that are fast gaining popularity due to their versatile characteristics.The surfaces of these materials are often functionalized by negatively charged terminal groups,such as=O,OH,and F during their synthesis,and it has been hypothesized that regulating the surface terminators enables to control the material characteristics.However,there is still a large gap between computational and experimental investigations regarding comprehending the surface functional groups.Surfaces with mixed terminations are consistently synthesized in experiments,although pure terminated surfaces are predicted by computational research.Here we summarized the nature of chemical bonding in transition metal carbide materials(MXenes)by1H and19F nuclear magnetic resonance(NMR),Raman,X-ray absorption near edge structure(XANES),extended X-ray absorption fine structure(EXAFS),ultraviolet photoelectron spectroscopy(UPS),X-ray photoelectron spectroscopy(XPS)/scanning transmission electron microscopy(STEM),and thermogravimetric analysis-mass spectrometry(TGA-MS)characterizations.Previous literature reveals that=O,–OH,–F,and–Cl are typical MXene surface terminators.However,recent comparative investigations on the valence band intensity distribution in MXenes reveal that the–OH cannot be considered an intrinsic termination species in MXenes.The surface terminals(=O,–OH,–F,and–Cl)of several MXenes,particularly V2CTxand Ti3C2Tx,will be identified and quantified here.We have also discussed different etching approaches for the synthesis of MXene,the dependence of MXene conductivity on MXene terminating groups,and the emission of various gaseous products that evolved during its chemical transformations.This paper provides significance,especially in the field of energy conversion and storage materials,where the intercalation process is crucial.

Ultrafast Synthesis of Metal-Layered Hydroxides in a Dozen Seconds for High-Performance Aqueous Zn(Micro-)Battery

Efficient synthesis of transition metal hydroxides on conductive substrate is essential for enhancing their merits in industrialization of energy storage field.However,most of the synthetic routes at present mainly rely on traditional bottom-up method,which involves tedious steps,time-consuming treatments,or additional alkaline media,and is unfavorable for high-efficiency production.Herein,we present a facile,ultrafast and general avenue to synthesize transition metal hydroxides on carbon substrate within 13 s by Joule-heating method.With high reaction kinetics caused by the instantaneous high temperature,seven kinds of transition metal-layered hydroxides(TM-LDHs)are formed on carbon cloth.Therein,the fastest synthesis rate reaches~0.46 cm^(2)s^(-1).Density functional theory calculations further demonstrate the nucleation energy barriers and potential mechanism for the formation of metal-based hydroxides on carbon substrates.This efficient approach avoids the use of extra agents,multiple steps,and long production time and endows the LDHs@carbon cloth with outstanding flexibility and machinability,showing practical advantages in both common and micro-zinc ion-based energy storage devices.To prove its utility,as a cathode in rechargeable aqueous alkaline Zn(micro-)battery,the NiCo LDH@carbon cloth exhibits a high energy density,superior to most transition metal LDH materials reported so far.

In-situ oriented oxygen-defect-rich Mn-N-O via nitridation and electrochemical oxidation based on industrial-scale Mn_(2)O_(3) to achieve high-performance aqueous zinc ion battery

As a general problem in the field of batteries,materials produced on a large industrial scale usually possess unsatisfactory electrochemical performances.Among them,manganese-based aqueous rechargeable zinc-ion batteries(ARZBs)have been emerging as promising large-scale energy storage systems owing to their high energy densities,low manufacturing cost and intrinsic high safety.However,the direct application of industrial-scale Mn2O3(MO)cathode exhibits poor electrochemical performance especially at high current rates.Herein,a highly reversible Mn-based cathode is developed from the industrial-scale MO by nitridation and following electrochemical oxidation,which triples the ion diffusion rate and greatly promotes the charge transfer.Notably,the cathode delivers a capacity of 161 m Ah g^(-1) at a high current density of 10 A g^(-1),nearly-three times the capacity of pristine MO(60 m Ah g^(-1)).Impressive specific capacity(243.4 m Ah g^(-1))is obtained without Mn^(2+) additive added in the electrolyte,much superior to the pristine MO(124.5 m Ah g^(-1)),suggesting its enhanced reaction kinetics and structural stability.In addition,it possesses an outstanding energy output of 368.4 Wh kg^(-1) at 387.8 W kg^(-1),which exceeds many of reported cathodes in ARZBs,providing new opportunities for the large-scale application of highperformance and low-cost ARZBs.

Metal-organic frameworks with mixed-ligands strategy as heterogeneous nucleation center to assist crystallization for efficient and stable perovskite solar cells

Deep-level defects and random oriented configuration in perovskite crystallization process would cause the nonradiative recombination and further affect the performance of perovskite solar cells(PSCs).Herein,two metal-organic frameworks(MOFs)with tunable Lewis-base passivation sites have been constructed(Cd-Httb and Cd-Httb-BDC,Httb=5-(4-(1H-1,2,4-triazole-1-yl)benzyl)-1h-tetrazole,BDC=1,4-dicarboxybenzene)to eliminate deep-level defects and simultaneously as nanostructured heterogeneous nucleation seed to assist the growth of large-grained perovskite films.Compared with the control and Cd-Httb,Cd-Httb-BDC designed with mix-ligands strategy exhibited the enhanced inducted effect on the crystallization and nucleation of high-quality perovskite films during annealing process.Consequently,the resultant Cd-Httb-BDC-modified device achieved higher power conversion efficiency(PCE)(22.18%)than the control(20.89%)and Cd-Httb(21.56%).Meanwhile,the unencapsulated Cd-Httb-BDC-modified device still maintained 90%of initial PCE after 1500 h in ambient conditions and exhibited enhanced thermal stability(85℃ in N_(2) atmosphere).This work presented a successful example of mixligands strategy on construction of high-quality MOF-assisted perovskite films for high-efficient and stable PSCs.

体重指数和血压与血管硬化的关系及护理对策

目的旨在探讨体重指数(body mass index,BMI)和血管硬化指标[包括臂踝脉搏波传导速度(brachial ankle pulse wave velocity,baPWV)和踝臂血压指数(ankle brachial index,ABI)]之间的关联,以及血压是否与之关联,并提出相关的护理对策。方法采用横断面调查研究。2019年3一12月,选取上海市张江社区医疗中心接受常规健康筛查的1894名中老年人进行调查。根据BMI将其分为3组:正常体重(n=1202)、超重(n=480)和肥胖(n=212)组。采用多变量线性回归模型和平滑曲线拟合评估BMI和血管硬化指标之间的关联。采用中介分析来检验血压是否在BMI和血管硬化指标之间起中介作用。结果多元线性回归分析显示,BMI与baPWV(m/s)[β=-0.06(-0.10,-0.03)]和ABI[β=-0.004(-0.005,-0.003)]分别显示负向关联。收缩压在BMI与baPWV关系中的交互作用检验结果有统计学意义(P=0.01)。在校正年龄和性别后,中介分析显示BMI和baPWV存在关联(β=0.090,P<0.001),收缩压(β=0.533,P<0.001)和舒张压(β=0.338,P<0.001)的中介作用有统计学意义。BMI与ABI负向关联(β=-0.135,P<0.001),收缩压(β=0.124,P<0.001)和舒张压(β=0.053,P<0.001)有部分中介作用。然而,依据血压水平进一步进行亚组分析后,多数亚组内血压中介效应无统计学意义。结论研究结果显示,BMI与不同非侵人性血管硬化测量指标之间存在矛盾的关联。在BMI和baPWV的关系中,血压可能有生物学上的交互作用。应采取针对性的健康教育和行为干预,控制血压和体质量,预防中老年人的血管硬化。

Kinetic and thermodynamic synergy of organic small molecular additives enables constructed stable zinc anode

An organic small molecule additive zinc formate is introduced to construct stable Zn metal interphase by electrochemical kinetic control and thermodynamic adjustment.It partially forms a water-formate concomitant dipole layer at the internal Helmholtz electrical double layers(HEDLs) under the preferential adsorption function of formate on Zn surface,reducing the occurrence of side reactions at phase interface.Meanwhile,free formate in HEDLs regulates the Zn^(2+) solvation sheath structure to accelerate the desolvation,transference,and deposition kinetics of Zn^(2+).Besides,the hydrolysis reaction of zinc formate increases the hydrogen evolution overpotential,inhibiting the thermodynamic tendency of hydrogen evolution.Consequently,it presents stable cycle for more than 2400 h at 5 mA cm^(-2),as well as an average Coulombic efficiency of 99.8% at 1 A g^(-1) after 800 cycles in the Zn‖VO_(2) full cell.The interphase engineering strategy zinc anode by organic small molecular brings new possibility towards high-performance aqueous zinc-ion batteries.

Heat diffusion optimization in high performance perovskite solar cells integrated with zeolite

Heat accumulation inside perovskite solar cells causes the decomposition of the perovskite layer and hole transport materials(HTMs)under working conditions,yielding a decrease in long-term stability.Here,we present a zeolite-assisted heat conduction strategy by introducing economic zeolite crystals(e.g.,NaX,NaY,and ZSM-5)as a cooling filter to induce heat diffusion.The fitted thermal diffusion kinetic equation from real-time infrared thermal imaging technology reveals the zeolite skeleton assisted thermal co nduction mechanism of internal lattice vibration.Additionally,the nearly twofold improved conductivity of the modified HTM film is benefited from Na^(+)hopping on the supercages of the zeolite,therefore,the best-performed device with a rapid heat diffusion and defect inhibition obtains a remarkable power conversion efficiency of 23.42%.Both of NaX modified sprio-OMeTAD and PTAA based devices exhibit excellent operational stability after heating 1000 h at 85℃under N_(2)condition.This work demonstrates the potential application of economical porous zeolite materials in improving the thermal stability of PSCs.

Two-step model of paleohexaploidy, ancestral genome reshuffling and plasticity of heat shock response in Asteraceae

An ancient hexaploidization event in the most but not all Asteraceae plants,may have been responsible for shaping the genomes of many horticultural,ornamental,and medicinal plants that promoting the prosperity of the largest angiosperm family on the earth.However,the duplication process of this hexaploidy,as well as the genomic and phenotypic diversity of extant Asteraceae plants caused by paleogenome reorganization,are still poorly understood.We analyzed 11 genomes from 10 genera in Asteraceae,and redated the Asteraceae common hexaploidization(ACH)event∼70.7–78.6 million years ago(Mya)and the Asteroideae specific tetraploidization(AST)event∼41.6–46.2 Mya.Moreover,we identified the genomic homologies generated from the ACH,AST and speciation events,and constructed a multiple genome alignment framework for Asteraceae.Subsequently,we revealed biased fractionations between the paleopolyploidization produced subgenomes,suggesting the ACH and AST both are allopolyplodization events.Interestingly,the paleochromosome reshuffling traces provided clear evidence for the two-step duplications of ACH event in Asteraceae.Furthermore,we reconstructed ancestral Asteraceae karyotype(AAK)that has 9 paleochromosomes,and revealed a highly flexible reshuffling of Asteraceae paleogenome.Of specific significance,we explored the genetic diversity of Heat Shock Transcription Factors(Hsfs)associated with recursive whole-genome polyploidizations,gene duplications,and paleogenome reshuffling,and revealed that the expansion of Hsfs gene families enable heat shock plasticity during the genome evolution of Asteraceae.Our study provides insights on polyploidy and paleogenome remodeling for the successful establishment of Asteraceae,and is helpful for further communication and exploration of the diversification of plant families and phenotypes.

The Systemic Immune Inflammatory Index Predicts No-Reflow Phenomenon after Primary Percutaneous Coronary Intervention in Older Patients with STEMI

Purpose:Coronary no-reflow phenomenon(NRP),a common adverse complication in patients with ST-segment eleva-tion myocardial infarction(STEMI)treated by percutaneous coronary intervention(PCI),is associated with poor patient prognosis.In this study,the correlation between the systemic immune-inflammation index(SII)and NRP in older patients with STEMI was studied,to provide a basis for early identification of high-risk patients and improve their prognosis.Materials and methods:Between January 2017 and June 2020,578 older patients with acute STEMI admitted to the Department of Cardiology of Hebei General Hospital for direct PCI treatment were selected for this retrospective study.Patients were divided into an NRP group and normal-flow group according to whether NRP occurred during the operation.Clinical data and the examination indexes of the two groups were collected.Logistic regression was used to analyze the independent predictors of NRP,and the receiver operating characteristic curve was used to further analyze the ability of SII to predict NRP in older patients with STEMI.Results:Multivariate logistic analysis indicated that hypertension(OR=2.048,95%CI:1.252–3.352,P=0.004),lymphocyte count(OR=0.571,95%CI:0.368–0.885,P=0.012),platelet count(OR=1.009,95%CI:1.005–1.013,P<0.001),hemoglobin(OR=1.015,95%CI:1.003–1.028,P=0.018),multivessel disease(OR=2.237,95%CI:1.407–3.558,P=0.001),and SII≥1814(OR=3.799,95%CI:2.190–6.593,P<0.001)were independent predictors of NRP after primary PCI in older patients with STEMI.Receiver operating characteristic curve analysis demonstrated that SII had a high predictive value for NRP(AUC=0.738;95%CI:0.686–0.790),with the best cut-off value of 1814,a sensitivity of 52.85%and a specificity of 85.71%.Conclusion:For older patients with STEMI undergoing primary PCI,SII is a valid predictor of NRP.

教育公平对省域经济增长的影响研究

本文使用地级市人均财政性教育支出构建省级教育基尼系数衡量教育横向公平,基于双向固定效应模型探究教育公平对省域经济增长的影响,并分别以夜间灯光亮度和性别间教育差异作为经济发展水平和教育公平的代理变量进行稳健性检验。研究发现:教育公平程度和省域经济发展水平呈倒U型关系,以地区生产总值为因变量的回归结果显示,当教育基尼系数为0.236时,教育公平程度对省域经济发展最为有利;以夜间灯光亮度为因变量的模型,教育基尼系数的最优值为0.288。研究还显示,教育公平对省域经济发展水平的影响存在滞后效应。基于此,各省政府应统筹安排地区间教育财政投入,优化教育资源配置。对于地市间教育投入差异较大的省份,应通过转移支付、政策支持等方式缩小地区间的教育财政投入差异。

·CO3^–在基于太阳光驱动的TiO2-贝壳粉降解盐酸四环素中的作用:降解机理和转化路径

抗生素的滥用和不当排放对水陆生生态系统造成了严重威胁,在世界各地水环境污染物调研中普遍检测到盐酸四环素的存在.如何解决水体中高稳定、难降解的盐酸四环素污染问题是当前环境领域重点研究的课题之一.在各种去除方法中,利用光化学反应生成活性氧物种如·CO3–,·OH,·O2–,·SO4–和1O2等实现对有机污染物的降解在众多研究方法中脱颖而出.·CO3–在水体中具有较高的稳态浓度且其对有机物降解具有高选择性.CO32–或HCO3–与活性物种如·OH, h+,·O2–,·SO4–等反应可以生成·CO3–.传统的半导体光催化剂TiO2在光照下会产生·OH,·O2–及h+等活性物种,能有效地降解有机污染物,已有研究发现添加CO32–/HCO3–有利于提高UV/TiO2体系降解有机物的反应速率.贝壳中含有95%以上的碳酸钙,由于其具有低成本、生态友好、无毒性等特点而越来越受到人们的关注.贝壳与TiO2复合,利用贝壳在水相中提供的CO32–/HCO3–与TiO2在光照下产生的·OH,·O2–及h+等活性物种反应生成·CO3–促进光催化反应速率的提高,对盐酸四环素的有效去除具有显著意义.本文通过溶胶-凝胶法合成TiO2-贝壳粉,采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、红外光谱和氮气吸附-脱附测试等技术对所得样品进行了表征.考察了TiO2-贝壳粉在模拟太阳光下对盐酸四环素的降解性能.结果表明,在模拟太阳光的作用下, 40%TS-300在30 min内能降解94.0%的盐酸四环素,优于纯TiO2的降解效率(88.6%).通过自由基捕获实验比较了TiO2和TiO2-贝壳粉体系降解盐酸四环素机理的差异,在TiO2光催化降解盐酸四环素体系中,·O2–和h+是主要活性物种.而在TiO2-贝壳粉体系中, TiO2在光照条件下产生的·OH,·O2–及h+通过与贝壳粉在水相中提供的CO32–/HCO3–进一步产生·CO3–,·CO3–、·O2–和h+协同作用实现盐酸四环素的有效降解.采用HRESI-TOF-MS研究了40%TS-300光降解盐酸四环素的中间转化产物,提出TiO2-贝壳粉光降解盐酸四环素可能的降解路径.对40%TS-300样品进行了光降解盐酸四环素长效循环测试,结果表明该样品能够保持稳定有效的降解盐酸四环素性能,此为该材料今后的潜在应用奠定了可靠基础.