Development of miniaturized SAF-LIBS with high repetition rate acousto-optic gating for quantitative analysis

The self-absorption effect in laser-induced breakdown spectroscopy(LIBS)reduces the accuracy of quantitative measurement results.The self-absorption-free LIBS(SAF-LIBS)has been proved to directly capture the optically thin plasma spectra by setting an appropriate exposure time.In this work,a novel SAF-LIBS technique with high repetition rate acousto-optic gating is developed,in which an acousto-optic modulator is used as the shutter to diffract the optically thin fluorescence,and a high repetition rate laser is used to produce quasi-continuous plasmas to enhance the integral spectral intensity,so that the CCD spectrometer can replace an intensified CCD(ICCD)and echelle spectrometer in SAF-LIBS.Experimental results show that the average absolute prediction error of aluminum is reduced to 0.18%,which is equivalent to that of traditional SAF-LIBS.This technique not only effectively shields continuous background radiation and broadened spectral lines in optically thick plasma,but also has advantages of miniaturization,low cost,convenience and reliability.

基于智能水凝胶薄膜电极构建可视化分子逻辑门的综合化学实验的课程思政设计

本案例将多种思政元素融入到智能水凝胶薄膜电极的制备、表征及其应用于构筑可视化分子逻辑门的综合化学实验中,通过多学科交叉研究搭建基础教学与前沿科技的桥梁,引导学生关心国家新兴材料研发、可持续发展和数字信息加密等问题。本案例的设计有助于培养学生服务国家战略和经济社会发展的责任感,勇于创新和攀登科学高峰的使命感等意志品质。

化学类通识课程中“科技传承”与“文化自信”的融合——以古代典籍《天工开物》在化学与人类文明中的诠释为例

文化是民族的灵魂,科技领域的进步也需要从传统文化中汲取力量,因此树立文化自信是建设科技强国的必由之路。《天工开物》作为一部中国17世纪综合性的科学技术著作,蕴含了古人在生产实践中化学知识的总结,有机结合了中国传统文化和科学观念。本文将《天工开物》中的化学科技知识与中国优秀传统文化进行提取,结合思想政治导向,在化学类通识课程“化学与人类文明”中进行整合与导入,对科技与文化的传承,尤其在学生心中确立“科技文化自信”具有重要作用。

经济政策不确定性与企业债务期限结构

基于信贷供应方视角,本文系统考察了经济政策不确定性对中国企业债务期限结构的影响。利用中国沪深A股上市企业的面板数据研究发现,伴随着经济政策不确定性上升,企业的债务期限结构呈现出短化趋势,并且这一效应在信息不对称严重的企业中更为突出。作用机制检验发现,对于财务风险较大以及无政府隐性担保的企业,金融机构提供长期负债的意愿较小,从而经济政策不确定性对企业债务期限结构短化的加剧作用更强,这表明金融机构对短期债务的供给偏好是经济政策不确定性导致企业债务期限结构短化的核心作用机制。进一步地,本文还发现经济政策不确定性引致的债务期限结构短化会造成企业长期资金出现缺口,加剧企业的投融资期限错配现象。本文的研究揭示了现阶段中国企业债务期限结构变动的背后逻辑,对于科学制定和有效实施“稳金融”政策具有一定现实意义。

Elemental and proximate analysis of coal by x-ray fluorescence assisted laser-induced breakdown spectroscopy

Although laser-induced breakdown spectroscopy(LIBS),as a fast on-line analysis technology,has great potential and competitiveness in the analysis of chemical composition and proximate analysis results of coal in thermal power plants,the measurement repeatability of LIBS needs to be further improved due to the difficulty in controlling the stability of the generated plasmas at present.In this paper,we propose a novel x-ray fluorescence(XRF) assisted LIBS method for high repeatability analysis of coal quality,which not only inherits the ability of LIBS to directly analyze organic elements such as C and H in coal,but also uses XRF to make up for the lack of stability of LIBS in determining other inorganic ash-forming elements.With the combination of elemental lines in LIBS and XRF spectra,the principal component analysis and the partial least squares are used to establish the prediction model and perform multi-elemental and proximate analysis of coal.Quantitative analysis results show that the relative standard deviation(RSD) of C is 0.15%,the RSDs of other elements are less than 4%,and the standard deviations of calorific value,ash content,sulfur content and volatile matter are 0.11 MJ kg,0.17%,0.79% and 0.41%respectively,indicating that the method has good repeatability in determination of coal quality.This work is helpful to accelerate the development of LIBS in the field of rapid measurement of coal entering the power plant and on-line monitoring of coal entering the furnace.

Quantitative Inversion of REEs in Ion-Adsorbed Rare Earth Ores from the Liutang Area(South China),Based on Measured Hyperspectral Data

Rare earth minerals are important strategic resources to economic development all over the world.In this study,multiple linear regression and back propagation(BP) neural network methods are used to invert the contents of ion adsorbed rare earth elements(REEs) and exploring the feasibility of quantitative inversion of REEs through measured hyperspectral data in Liutang rare earth mines,South China.The result shows that the spectral curve of the rare earth ore samples has obvious absorption characteristics around 390,930,1 400,1 900 and 2 200 nm,and continuum removal and the 1st derivative treatment can highlight the absorption characteristics.The modeling accuracies of BP neural network are higher than that of multiple linear regression model.The BP neural network model of the 1st derivative data in 400–1 000 nm bands has the best inversion result of the total content of REEs,R2 reaches 0.98,the ratio of the performance to deviation(RPD) is larger than 3.0.The quantitative inversion model of each REE(except for Ce) has high precision,R2 is greater than 0.90 and RPD is greater than 3.0.The results indicate that quantitative inversion of REEs using measured spectra not only has great potential and feasibility in the exploration of rare earth minerals,but also provides a rapid test method for the content of ion-adsorbed rare earth elements.

Delta(B.1.617.2)inactivated vaccine candidate elicited neutralizing antibodies to SARS-CoV-2 and circulating variants in rhesus macaques

Dear Editor,The coronavirus disease 2019(COVID-19)pandemic has resulted in 763 million cases and over 6 million deaths as of April 2023.Given the high prevalence and widespread distribution of coronaviruses,the genetic diversity and frequent recombination of their genomes,as well as the increased activity at the human-animal interface,are critical for global public health and socioeconomic impact(Zhu et al.,2020).

抗原改造联合纳米肿瘤疫苗用以克服肿瘤新抗原短缺及在多种肿瘤类型上激起强效抗肿瘤免疫反应

Neoantigen cancer vaccines have been envisioned as one of the most promising means for cancer therapies.However,identifying neoantigens for tumor types with low tumor mutation burdens continues to limit the effectiveness of neoantigen vaccines.Herein,we proposed a "hit-and-run" vaccine strategy which primes T cells to attack tumor cells decorated with exogenous "neo-antigens".This vaccine strategy utilizes a peptide nanovaccine to elicit antigen-specific T cell responses after tumor-specific decoration with a nanocarrier containing the same peptide antigens.We demonstrated that a poly(2-oxazoline)s(POx) conjugated with OVA_(257-264) peptide through a matrix metalloprotease 2(MMP-2) sensitive linker could efficiently and selectively decorate tumor cells with OVA peptides in vivo.Then,a POx-based nanovaccine containing OVA_(257-264) peptides to elicit OVA-specific T cell responses was designed.In combination with this hit-and-run vaccine system,an effective vaccine therapy was demonstrated across tumor types even without OVA antigen expression.This approach provides a promising and uniform vaccine strategy against tumors with a low tumor mutation burden.

Phase forming law and electrochemical properties of A2B7-type La-Y-Ni-based hydrogen storage alloys with different La/Y ratios

The effects of different proportions of La and Y elements in the A-side on the structure and properties of A_(2)B_(7)-type La-Y-Ni hydrogen storage alloys were investigated.The(La,Y)_(2)Ni_(7)hydrogen storage alloys with different La/Y ratios were prepared by sintering the Y_(2)Ni_(4)precursor and different AB_(5)-type precursors at 1298 K for 5 h and subsequently annealed for 20 h at 1248 K.All the alloys only contain Ce_(2)Ni_(7)(2H-type)and Gd_(2)Co_(7)(3R-type)phases with different mass ratios.As the La/Y ratio decreases,the cell volume of the two phases declines and the corresponding plateau pressure gradually increases.As the proportion of Y in the alloy increases,the hydrogen storage capacity increases gradually from 1.309 wt%(La/Y=1/1)to 1.713 wt%(La/Y=1/5)and the high-rate discharge(HRD1500)ability of the alloy electrodes increases gradually from 62.7%(La/Y=1/1)to 88.6%(La/Y=1/5).The hydrogen diffusion rate in the bulk of the alloy is the controlling step of hydriding/dehydriding kinetics.The Y ele ment can effectively inhibit the hydrogen-induced amorphous(HIA)of La-Y-Ni alloys,but the poor stability of the Y element in alkaline KOH aqueous solution leads to a decrease in the electrochemical cyclic stability with increasing Y content.

Special Emergency Resources Preallocation Concerning Demand Time for Tunnel Collapse

Lacking timely access to rescue resources is one of the main causes of casualties in tunnel collapse.To provide timely rescue,this study proposed a multi-objective preallocation model of special emergency resources for tunnel collapse based on demand time.Efficiency,multiple coverage,and cost-effectiveness are taken as the key objectives of the model;the demand time service range is used as a coverage decision factor considering the unique nature of tunnel collapse.The weight of potential disaster-affected points and other general factors are also considered in this model in order to thoroughly combine the distribution of disaster points and service areas.Further,we take 15 main tunnel projects under construction in China as an example.When the relative proximity to the ideal point of the selected optimal schemeε_(a)is smaller than 0.5,we will adjust the weight of three objectives and reselect the optimal scheme untilε_(a)>0.5.Compared with the not preallocated case,the number of rescue rigs needed is reduced by 8.3%,the number of covered potential disaster-affected points is increased by 36.36%,the weighted coverage times are increased from 0.853 to 1.383,and the weighted distance is significantly reduced by 99%when the rescue rigs are preallocated,verifying the feasibility and superiority of the proposed model.

Toward atomistic models of intact severe acute respiratory syndrome coronavirus 2 via Martini coarsegrained molecular dynamics simulations

The causative pathogen of coronavirus disease 2019(COVID-19),severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),is an enveloped virus assembled by a lipid envelope and multiple structural proteins.In this study,by integrating experimental data,structural modeling,as well as coarse-grained and all-atom molecular dynamics simulations,we constructed multiscale models of SARS-CoV-2.Our 500-ns coarse-grained simulation of the intact virion allowed us to investigate the dynamic behavior of the membrane-embedded proteins and the surrounding lipid molecules in situ.Our results indicated that the membrane-embedded proteins are highly dynamic,and certain types of lipids exhibit various binding preferences to specific sites of the membrane-embedded proteins.The equilibrated virion model was transformed into atomic resolution,which provided a 3D structure for scientific demonstration and can serve as a framework forfuture exascale allatom molecular dynamics(MD)simulations.A short all-atom molecular dynamics simulation of 255 ps was conducted as a preliminary test for largescale simulationsofthis complexsystem.

格氏栲天然林林窗植物物种多样性与系统发育多样性

林窗环境异质性导致群落物种多样性与系统发育多样性(phylogeneticdiversity,PD)存在差异,研究不同大小的林窗中群落的物种多样性与系统发育多样性有助于揭示林下生物多样性的形成及维持机制。本文以格氏栲(Castanopsiskawakamii)天然林为研究对象,通过Pearson相关性分析与广义线性模型探讨了林窗内物种多样性与系统发育多样性间的相互关系及其环境影响因素。结果表明:(1)大林窗(面积>200 m^(2))植物种类及多度均高于中林窗(50 m^(2)≤面积<100 m^(2))、小林窗(30 m^(2)≤面积<50 m^(2))和非林窗(面积=100 m^(2))。大林窗群落系统发育结构趋于发散,中、小林窗和非林窗群落系统发育结构受到生境过滤和竞争排斥综合作用。(2)群落系统发育多样性指数与物种丰富度(speciesrichness,SR)、Margalef丰富度指数和Shannon-Wiener指数均呈显著正相关,这与林窗内稀有种种类组成多于优势种有关。(3)林窗面积对物种多样性存在显著正效应;土壤全氮含量对系统发育多样性和系统发育结构存在显著正效应。林窗形成提高了格氏栲天然林群落物种多样性和系统发育多样性,林窗面积与土壤全氮共同驱动了格氏栲天然林林窗物种多样性和系统发育多样性的变化。

Facial expression recognition in golden snub-nosed monkeys

For socialized animals,such as prinlates,emotions arc the expression of internal states,which may be recognized by others to adjust an in dividual's potential actions(Girard and Bellone 2020).Facial expressions are therefore important signals in communication(e.g.,happy or in pain)and can help individuals understand potential meanings between each other(Dolensek et al.2020).Facial expressions can be expressed and processed freely and are useful in social interactions and bonding(Waller et al.2016).

Sexual interference and allomaternal behavior as predictors of rank recognition in female golden snub-nosed monkeys

Rank recognition allows social animals to adapt to complex and changeable environments and to cope with hierarchical relationships within their societies(Crone 2017).Rank recognition can improve the distribution of advantageous resources,individual adaptation,and social cohesion among group-living animals(Marmolejo-Ramos and Angiulli 2014).Empirical evidence suggests that rank recognition is a basic behavioral manifestation of social cognition adopted by a wide range of insects,birds,and mammals,including nonhuman primates(Schmitt and Fischer 2011;Smith et al.2017).Unlike most other vertebrates,primates have unusually large brains and form complex social groups.