三峡库区二叠系孤峰组硅质岩分布区土壤-农作物重金属元素地球化学特征

三峡库区二叠系孤峰组硅质岩分布区土壤、农作物具有重金属富集特征,本文选择三峡库区典型孤峰组分布区为研究对象,研究了土壤-农作物系统中重金属元素含量、赋存形态与迁移富集规律及影响因素。结果表明,研究区土壤重金属富集程度为Cd>Mo>Hg>Cr>Ni>Cu>Zn>As>Pb,含量均高于我国土壤背景值。土壤Cd平均含量12.98 mg/kg,超标率达100%,单因子污染指数和地累积指数均显示为重度污染;平均生态风险因子(Er)为4929,表现为极高生态风险,因而是研究区重点关注的特征环境元素。Cd的赋存形态主要为可交换态、残渣态和可还原态,生物有效态含量与土壤pH值以及耕种程度密切相关。农作物中Cd的含量变化为:莴笋茎>莴笋叶>胡豆>卷心菜>土豆>油菜籽,Cd、Cr等元素超标现象较为严重。重金属元素在土壤-农作物体系的迁移能力变化顺序为:Cd>Zn>Cu>Ni>Cr>Pb。不同植物类型对重金属元素的富集能力差异显著,莴笋茎和莴笋叶对重金属元素富集能力最强,其中Cd的生物富集系数最高。元素赋存形态、土壤pH值以及农作物类型可能是影响重金属元素在土壤-农作物系统中迁移转化的重要因素。

三峡库区地质高背景区土壤-油菜重金属迁移特征

三峡库区广泛分布的黑色岩系富含镉(Cd)、铬(Cr)、镍(Ni)、锌(Zn)等重金属元素,导致土壤重金属元素含量显著高于我国土壤背景值,成为典型的地质高背景区。本文选择三峡库区地质高背景区油菜种植地为研究对象,分析了土壤-油菜系统中砷(As)、Cd、Zn、铜(Cu)、铅(Pb)、Cr、Ni、汞(Hg)等重金属元素含量分布特征、富集迁移规律以及影响因素。研究结果表明,研究区油菜种植地土壤中Cd、Cr、Cu、Hg、Ni等重金属含量显著高于我国土壤背景值,单因子污染指数评价显示土壤As、Zn、Hg、Pb等重金属均属于无污染等级,Cu、Ni污染程度受到pH影响,Cd为重度污染和极高生态风险。不同重金属元素在油菜各部位含量差异明显,Pb、Cd、As等生物非必需元素更倾向进入茎、果荚,营养元素Cu和Zn则在油菜籽中含量较高,而Cr易在果荚中富集。研究区土壤中重金属元素含量、土壤pH、重金属元素间的拮抗作用以及油菜解毒机制可能是影响重金属元素在土壤-油菜各部位富集迁移的重要因素。

Experimental investigation on the cuttings formation process and its relationship with cutting force in single PDC cutter tests

The single polycrystalline diamond compact(PDC)cutter test is widely used to investigate the mecha-nism of rock-breaking.The generated cuttings and cutting force are important indexes reflecting the rock failure process.However,they were treated as two separate parameters in previous publications.In this study,through a series of rock block cutting tests,the relationship between them was investigated to obtain an in-depth understanding of the formation of cuttings.In addition,to validate the standpoints obtained in the aforementioned experiments,rock sheet cutting tests were conducted and the rock failure process was monitored by a high-speed camera frame by frame.The cutting force was recorded with the same sampling rate as the camera.By this design,every sampled point of cutting force can match a picture captured by the camera,which reflects the interaction between the rock and the cutter.The results indicate that the increase in cutting depth results in a transition of rock failure modes.At shallow cutting depth,ductile failure dominates and all the cuttings are produced by the compression of the cutter.The corresponding cutting force fluctuates slightly.However,beyond the critical depth,brittle failure occurs and chunk-like cuttings appear,which leads to a sharp decrease in cutting force.After that,the generation of new surface results in a significant decrease in actual cutting depth,a parameter proposed to reflect the interaction between the rock and the cutter.Consequently,ductile failure dominates again and a slight fluctuation of cutting force can be detected.As the cutter moves to the rock,the actual cutting depth gradually increases,which results in the subsequent generation of chunk-like cuttings.It is accompanied by an obvious cutting force drop.That is,ductile failure and brittle failure,one following another,present at large cutting depth.The transition of rock failure mode can be correlated with the variation of cutting force.Based on the results of this paper,the real-time monitoring of torque may be helpful to determine the efficiency of PDc bits in the downhole.

纽布病毒研究概况

纽布病毒是杯状病毒科纽布病毒属的唯一成员,是引起犊牛腹泻的新发病原。其具有广泛的地域分布,目前已在美国、英国、日本等13个国家检出,在我国奶牛和牦牛中均有检出,并发现了区别于其他基因型的新毒株,其在我国的流行情况目前还不清楚。对纽布病毒的病原学、流行病学、临床症状和检测方法进行论述,以期为纽布病毒防控提供参考。

回填土质量评价体系和标准研究进展

在建筑施工领域回填土的质量标准研究已较深入,但现有标准中未关注到回填土污染物浓度问题,在今后相关标准制定中需对其加以考虑。污染场地中回填土的质量标准主要由土地用途决定,本文主要从建设用地和农业用地两方面对修复后土壤再利用的质量控制进行厘定,为污染场地回填土的质量标准建立提供建议。污泥土地利用可大致分为园林绿化、土地改良、农用和林用地4种类型,不同土地利用的质量评价指标也有所不同。有关矿山回填土的质量标准研究缺乏,从土地复垦类型、回填土性质、回填深度等方面初步建立矿山回填土的质量控制标准,认为避免地质灾害和预防污染物扩散是矿山回填土质量控制的核心,同时利用现有相关标准和规范,初步建立矿山回填土质量评价流程,为矿山回填土质量标准建立提供理论基础,为今后相关回填土标准的制定提供借鉴。

Characteristics of rare-earth elements (REE),strontium and neodymium isotopes in hydrothermal fluorites from the Bailashui tin deposit in the Furong ore field,southern Hunan Province,China

In this paper the authors present the REE concentrations and Sr and Nd isotopic compositions of fluorites from the Bailashui tin deposit of the Furong ore field,southern Hunan Province. The results showed that the total amount of REE in fluorites is usually low,ranging from 0.705 to 8.785 μg/g with the chondrite-normalized REE dis-tribution patterns similar to those of the Qitianling granites in the study area,characterized by LREE-enrichment patterns with pronounced negative Eu anomalies. The fluorites vary in Sr isotopic composition within the range of 0.7083-0.7091,the values are lower than those of the granites and higher than those of the host carbonate rocks in this area. The εNd(t) values of fluorites vary between -9.4 and +10.3,revealing that both the crust-and mantle-source materials were involved in the ore-forming hydrothermal fluids. Combined with previous studies on this ore deposit,the Bailashui tin deposit is temporally and spatially closely related with granitic magmatism in this area. The hydro-thermal fluorites are the product of fluid/rock interactions between granitic magmatic hydrothermal fluid and marine carbonate rocks. The REE and F in the ore-forming fluid were derived from the granites,whereas Sr in the ore-forming fluid came mainly from the granitic magmatic hydrothermal fluid and marine carbonate rocks,although variations in Sr isotopic composition cannot be explained by a simple mixture of these two end-members. Evidence demonstrated that the ore-forming fluids are of crustal-mantle mixing origin,but that the fluids were probably in-completely homogenized and this may be caused by inhomogeneous mixing of the fluids of different sources.

Geochemistry and environmental effect of cadmium in the super-large Jinding Pb-Zn deposit,Yunnan Province, China

The Jinding Pb-Zn deposit in Yunnan Province is the representative of a Cd-enriched area and mining activities lead to the release of Cd into the hypergenic ecosystem, resulting in Cd pollution. The concentrations of Cd vary greatly from one type to another type of rocks in the mining district. In the host rock, Cd concentrations range from 50×10-6 to 650×10-6 with an average of 310×10-6. In primary ores, Cd concentrations range from 14×10-6 to 2800×10-6 with an average of 767×10-6. However, in oxidized ores, Cd concentrations are highest, varying within the range of 110×10-6 to 8200×10-6 , averaging 1661×10-6. It is shown that the oxidized ores are the main carrier and environmental source of Cd. Leaching test showed that Pb/Zn ores are easy to oxidize and thereafter release Cd and other harmful elements. These leached elements in the leachate may be precipitated rapidly in the order of Zn>Pb>Cd. As for the concentration distribution of Cd in the Bijiang River, it is estimated to be 15.7 μg/L Cd in water, 49.3 mg/L in suspended substances, and 203.7 mg/L in sediments. The average value of Cd in soil from the polluted area is 83.0 mg/kg. Natural weathering of Cd-rich rocks and minerals imposes a potential environmental risk on the aquatic ecosystem of the Bijiang catchment.

Exploration and Practice of the Reform of Postgraduate Award System-Taking Wuhan University of Science and Technology as an Example

China began to implement the charging policy for postgraduate students in 2014.Various universities at all levels have formulated a scholarship and stipend system for postgraduate students,which is in line with the needs of schools in talent training along with the spirit of relevant documents of the Ministry of Education and the actual situation of the schools.This study investigates and analyzes the advantages and disadvantages of the postgraduate funding by Wuhan University of Science and Technology.This article then provides advice for the reform of the scholarship and stipend system from improving the precision funding system,to increasing funding,to expanding the scope of postgraduate funding,and standardizing the treatment of deferred postgraduate students in hope that it would provide a basis for the funding system and provide guarantee for postgraduate students to complete their studies successfully.

MRI-guided photothermal/photodynamic immune activation combined with PD-1 inhibitor for the multimodal combination therapy of melanoma and metastases

Non-invasive image-guided precise photothermal/photodynamic therapy(PTT/PDT)has been proven to be an effective local treatment modality but incompetent against metastases.Hence,the combination of local PTT/PDT and systemic immunotherapy would be a promising strategy for tumor eradication.Herein,a magnetic resonance imaging(MRI)-visualized PTT/PDT agent(SIDP NMs)was constructed,and the efficacy of its multimodal combination with a programmed cell death 1(PD-1)inhibitor in the treatment of melanoma and metastases was studied.Due to the hydrophobic encapsulation of indocyanine green within the micellar core,SIDP NMs exhibited excellent photothermal/photodynamic properties and stability under an 808 nm near-infrared laser.In vitro cell experiments showed that SIDP NMs had a good killing effect.After incubating with B16-F10 cells for 24 h and irradiating with an 808-nm laser for 10 min,cell viability decreased significantly.Magnetic resonance imaging experiments in melanoma-bearing mice have shown that the dynamic distribution of SIDP NMs in tumor tissue could be monitored by T2WI and T2-MAP non-invasively due to the presence of superparamagnetic iron oxide nanocrystal in SIDP NMs.When the 808 nm laser was irradiated at the maximum focusing time point shown by MRI,the temperature of the tumor area rapidly increased from 32℃to 60.7℃in 5 min.In mouse melanoma ablation and distant tumor immunotherapy studies,SIDP NMs provided excellent MRI-guided PTT/PDT results and,when combined with PD-1 inhibitor,have great potential to cure primary tumors and eradicate metastases.

Active-transporting of charge-reversal Cu(Ⅱ)-doped mesoporous silica nanoagents for antitumor chemo/chemodynamic therapy

Fe-based Fenton agents can generate highly reactive and toxic hydroxyl radicals(·OH)in the tumor microenvironment(TME)for chemodynamic therapy(CDT)with high specificity.However,the low pH environment and insufficient endogenous hydrogen peroxide(H_(2)O_(2))of the highly efficient Fenton reaction limits its practical application in clinic.Here,a Cu(Ⅱ)-doped mesoporous silica nanoagent(Cu-MSN)with excellent dispersity was successfully developed.After loaded with doxorubicin(DOX)and ascorbate(AA),Cu-MSN@DA was coated with active targeting ligand folic acid(FA),dimethyl maleic an-hydride(DMMA)and carboxymethyl chitosan(CMC)to obtain an active transporting nanoagent(FCDC@Cu-MSN@DA)with tunable charge-reversal property,which is more adaptable to the pH value of TME than Fe-based Fenton agents,and can self-supply exogenous H_(2)O_(2)by ascorbate to produce more toxic·OH to trigger the apoptosis of cancer cells.Meanwhile,the high level of glutathione(GSH)in TME can reduce Cu(Ⅱ)to Cu(I)by Fenton-like reaction,increasing the generation rate of·OH and relieving tumor antioxidant ability.The supply of exogenous H_(2)O_(2)significantly enhanced the synergistic effect of CDT by oxidative damage.Together with DOX-induced cell apoptosis,this novel nanoagent FCDC@Cu-MSN@DA can achieve maximum therapeutic efficacy,creating a new model of safe and effective tumor treatment with high specificity.

Simultaneously improving ROP and maintaining wellbore stability in shale gas well:A case study of Luzhou shale gas reservoirs

The ROP(rate of penetration)within the horizontal section of shale gas wells in the Luzhou oil field is low,seriously delaying the exploration and development process.It is proved that reducing mud density mitigates the bottom-hole differential pressure(ΔP)and increases the ROP during overbalanced drilling.However,wellbore collapse may occur when wellbore pressure is excessively low.It is urgent to ascertain the optimal equilibrium point between improving ROP and maintaining wellbore stability.The safe mud weight window and the lower limit of mud density in the horizontal section of the Luzhou block are predicted using the piecewise fitting method based on conventional logging data.Then,the accuracy of the collapse pressure prediction was verified using the distinct element method(DEM),and the effect of wellbore pressure,in-situ stress,rock cohesion,and natural fracture density on borehole collapse was investigated.Finally,a fitting model ofΔP and ROP of the horizontal section in the Luzhou block is established to predict ROP promotion potential after mud density reduction.The field application of this approach,demonstrated in 8 horizontal wells in the Luzhou block,effectively validates the efficiency of reducing mud density for ROP improvement.This study provides a useful method for simultaneously improving ROP and maintaining wellbore stability and offers significant insights for petroleum engineers in the design of drilling parameters.

Dopamine multivalent-modified polyaspartic acid for MRI-guided near-infrared photothermal therapy

Nanophotothermal agents that provide efficient and precise treatment at tumor sites are attracting increasing attention in biomedicine.In particular,the method combination of nanophotothermal agents and magnetic resonance imaging(MRI)shows great promise for biomedical therapeutic applications.Herein,a simple nanophotothermal agent with dopamine multivalent-modified polyaspartic acid chelated superparamagnetic iron oxide(SPIO)and ferric ion(SPIO@PAsp-DAFe/PEG)was developed for MRI-guided near-infrared photothermal therapy(PTT).SPIO@PAsp-DAFe/PEG was random SPIO nanocluster with good water solubility,had a diameter of 57.8±7.8 nm in dynamic light scattering,negatively charged surface(zeta potential=−11 mV),exhibited good stability and outstanding photothermal conversion efficiency(35.4%)and produced superior magnetic resonance enhanced imaging.In the experiment with tumor-bearing mice,the MRI not only monitored the accumulation of SPIO@PAsp-DAFe/PEG nanocomposites enhanced by near-infrared irradiation after intravenous administration but also determined the appropriate time window for PTT.With the use of MRI-guided near-infrared therapy,the SPIO@PAsp-DAFe/PEG nanocomposites provided excellent therapeutic effects,confirming their great potential as effective MRI/PTT therapeutic agents.

Mineralization of the Lianhuashan Sn-polymetallic deposits associated with dynamic metamorphism:Constraints from cassiterite geochemistry and U-Pb geochronology

The Lianhuashan metallogenic belt in Eastern Guangdong Province(South China)is the most important Sn polymetallic district in the region,hosting many medium-sized deposits such as the Tashan,Xianshuili,and Jiangxikeng.However,the metallogenic mechanism of these deposits remains hotly debated.In this paper,two types of cassiterites(Cst1 and Cst2)have been identified in the Xianshuili and Jiangxikeng Sn deposits,which are hosted in the biotite-mylonite and garnetcordierite-muscovite blastomylonite,respectively.The euhedral Cst1(0.50–1.8 mm)coexists with biotite,feldspar,and quartz.It is platy and zoned with a mosaic structure.The subhedral to anhedral Cst2(0.02–0.35 mm)coexists with metamorphic minerals such as garnet and cordierite,and it is characterized by well-developed porosity and has no zonation.In-situ U-Pb dating of the Cst1 and Cst2 yielded ages of 149.5±1.0 Ma(MSWD=1.6,n=45)and 125.1±2.3 Ma(MSWD=4.5,n=43),respectively.Cst1 is most likely to be related to the intermediate-felsic magmatism that formed Gaojiping Group,whereas Cst2 has relatively high Ta,Nb,Fe,and W contents with obvious rare earth tetragroup effect,and may have formed by the late Early Cretaceous dynamic metamorphism.Results presented here,when combined with regional geology and geochemistry,led us to suggest that the Mesozoic intermediate-felsic volcanic rocks in the LMB are significantly enriched in Sn and F,with high Sn-polymetallic mineralization potential which likely have contributed to the volcanic-related Cst1.In the late Early Cretaceous period,due to the NW-dipping subduction of the paleo-Pacific plate,the intermediate-felsic volcanic rocks underwent dynamic metamorphism that led to Sn mobilization,migration,and precipitation in the regional ductile shear zones,and eventually generating Sn mineralization.We propose that areas beneath Xianshuili and Jiangxikeng have great potential for discovery of new Sn resources.Our findings likely offer practical importance to regional geological ore prospecting.

西南高镉地质背景区农田土壤与农作物的重金属富集特征

为探明高地质背景区农田土壤与农作物系统中重金属富集与转运特征,通过对采自重庆黑色岩系高镉地质背景区的土壤和农作物样品进行分析,并与其他典型黑色页岩区域进行对比研究.发现研究区部分农田土壤pH极低; Cd、Cr、Ni和Zn显著富集.土壤样品Cd的超标率为100%,其次为Cr和Ni,91. 3%的土壤样品Cd污染级别为严重污染及以上.土壤Zn、Cu、Cr和Ni的残渣态占比为80%以上,Cd和Pb较低;弱酸提取态Cd占比27. 0%±6. 4%,Zn和Ni次之.黑色岩系母质风化导致研究区土壤重金属富集,Cd是区域内的特征污染元素,其生物有效性较高,并易于在农作物中富集. Cd的转运系数高于其他元素,农作物中Cd的富集和污染程度最高,特别是叶类蔬菜,平均Cd含量(干重)高达11. 5 mg·kg^(-1),不适于种植和食用;部分农作物Cr超标,存在一定风险.因此,有必要对研究区农田土壤进行污染等级划分,实行科学管控,并进行农作物种植结构调整,以保障当地人群健康.

粮农生产行为调整动机:效益还是效用——基于2290份农户的追踪调查样本

本文根据效用最大化理论重新审视了粮农在农业生产中的行为调整动机,除了生产效益带来的货币收益,农户在土地规模和种植结构上的调整行为背后还蕴含着家庭成员在收支方面综合效用的最大化效应。通过对2290份粮农在6年中生产行为调整追踪调查样本的分析发现,粮农的生产调整行为有利于农户家庭效用水平达到最优值,而且当效用水平处于最优状态时,调整行为显著减少。通过多元选择Logit回归分析发现,粮户的生产调整路径存在显著差异,原因是效用影响因素水平的结构差异所致。

锂离子电容电池关键电极材料

锂离子电容电池兼具锂离子电池和超级电容器的优势,凭借高能量密度、高功率密度、长循环寿命和快速充放电等优势成为具有前景的新型储能系统。然而,电池型电极和电容型电极之间的动力学不平衡、能量密度不太理想和循环稳定性较差等关键问题仍然存在,若要有效解决该问题需要在该领域开发出新型正负极电极材料。因此,本文详细介绍了锂离子电容电池正负极材料(例如金属氧化物、碳材料、硫化物等)的研究进展以及技术路线,并针对目前存在的问题进行了分析,同时对电极材料未来的研究方向进行了展望,以及对其他化学电源的研究提供了新思路和手段。

Association between large artery stenosis,cerebral small vessel disease and risk of ischemic stroke

We aimed to assess the associations of large artery stenosis(LAS)and cerebral small vessel disease(CSVD)with the risk of ischemic stroke and to investigate their respective and combined contributions.In the prospective population-based Shunyi Study,1,082 stroke-free participants aged 55.9±9.1 years were included.Participants were followed for incident stroke throughout the study period(2013-2019).Total small vessel disease score was used to measure CSVD burden.Cervico-cerebral large artery stenosis was evaluated via brain magnetic resonance angiography and carotid ultrasound.We estimated the risk of ischemic stroke in relation to LAS and CSVD with Cox regression models.During a mean follow-up of 4.2 years,34 participants(3.1%)experienced at least one ischemic stroke.Severe LAS(≥50% stenosis versus no stenosis:HR=3.27(95%CI:1.31-8.18))and high CSVD burden(total small vessel disease score 2-4 versus 0 point:HR=12.73(4.83-33.53))were associated with increased stroke risk independently.In multivariate models,CSVD burden(7.72%)explained a larger portion of the variation in stroke risk than severity of LAS(3.49%).Our findings identified that both LAS and CSVD were associated with future ischemic stroke in asymptomatic subjects,while those with high CSVD burden deserve more attention in primary prevention of stroke.

IFITM3 inhibits virus-triggered induction of type I interferon by mediating autophagosome-dependent degradation of IRF3

Interferon-induced transmembrane protein 3 (IFITM3) is a restriction factor that can be induced by viral infectionand interferons (IFNs). It inhibits the entry and replication of many viruses, which are independent of receptorusage but dependent on processes that occur in endosomes. In this study, we demonstrate that IFITM3 playsimportant roles in regulating the RNA-virus-triggered production of IFN-β in a negative-feedback manner.Overexpression of IFITM3 inhibited Sendai virus-triggered induction of IFN-β, whereas knockdown of IFITM3 hadthe opposite effect. We also showed that IFITM3 was constitutively associated with IRF3 and regulated thehomeostasis of IRF3 by mediating the autophagic degradation of IRF3. These findings suggest a novel inhibitoryfunction of IFITM3 on the RNA-virus-triggered production of type I IFNs and cellular antiviral responses.

An ultrahigh-sensitivity and selective sensing material for ethanol： α-/γ-Fe2O3 mixed-phase mesoporous nanofibers

A process for synthesizing Fe2O3 based on electrospinning and the hard-template method was proposed such that the crystal phase of Fe2O3 could be tailored with precision. Mesoporous γ-Fe2O3, α-/γ-Fe2O3, and α-Fe2O3 nanofibers could be fabricated successfully by changing the synthesis parameters. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction analyses, Raman spectroscopy, and nitrogen adsorption-desorption analyses were used to characterize the structures of the synthesized products. The optimal calcination conditions for preparing α-/γ-FeaO3 nanofibers with the highest ethanol response were determined through ethanol-sensing measurements. The mixed-phase material exhibited a significantly higher sensitivity than the corresponding purephase ones. The superior ethanol-sensing performance of the α-/γ-Fe2O3 nanofibers suggested that they may be suitable for use in alcohol sensing. Hence, a novel strategy for improving the sensing performance of metal oxide semiconductors is to assemble the different crystalline forms of the same metal oxide in one structure. Finally, the mechanism responsible for the sensing performance of α-/γ-Fe2O3 being higher than those of γ-Fe2O3 and α-Fe2O3 was elucidated on the basis of data from X-ray photoelectron spectroscopy and resistance measurements.

Multi-functions of exonuclease 1 in DNA damage response and cancer susceptibility

Exonuclease 1(EXO1)can catalyze nucleotide chain excision with its conserved N-terminal domain of 5′ to 3′ exonuclease activity,enabling it to influence diverse biological processes facing the challenges of genotoxic environmental factors such as ionizing radiation.This nuclease activity enables EXO1 to maintain replication forks and telomeres length,to facilitate post-replication DNA repair and to process the end resection step of homologous recombination of DNA double-strand breaks-induced by ionizing radiation.When DNA replication is disrupted or blocked,EXO1 can cleave the broken DNA ends to form 3’ssDNA,leading to repair pathways activation.Excess EXO1-mediated nucleotide excision,however,can introduce an abundance of single-stranded DNA that can cause mutation and recombination via micro-homology-mediated end joining or single-strand annealing mechanisms,contributing to a loss of genetic information.EXO1 activity must therefore be carefully regulated within healthy cells.The mutations and dysregulations of EXO1 can increase the sensitivity of cells to radiation injury and risk of oncogenic transformation,limit the adoption of specific treatments in a range of human diseases.As such,EXO1 represents a promising target for the treatment and prevention of cancer.In the present review,we delineate the structural properties and functional characteristics of EXO1,discuss the relationship between this exonuclease and cancer susceptibility as well as the second cancers related to radiotherapy.