A theoretical study of the signal enhancement mechanism of coaxial DP-LIBS

In the field of dual-pulse laser-induced breakdown spectroscopy(DP-LIBS)research,the pursuit of methods for determining pulse intervals and other parameters quickly and conveniently in order to achieve optimal spectral signal enhancement is paramount.To aid researchers in identification of optimal signal enhancement conditions and more accurate interpretation of the underlying signal enhancement mechanisms,theoretical simulations of the spatiotemporal processes of coaxial DP-LIBS-induced plasma have been established in this work.Using a model based on laser ablation and two-dimensional axisymmetric fluid dynamics,plasma evolutions during aluminum–magnesium alloy laser ablation under single-pulse and coaxial dualpulse excitations have been simulated.The influences of factors,such as delay time,laser fluence,plasma temperature,and particle number density,on the DP-LIBS spectral signals are investigated.Under pulse intervals ranging from 50 to 1500 ns,the time evolutions of spectral line intensity,dual-pulse emission enhancement relative to the single-pulse results,laser irradiance,spatial distribution of plasma temperature and species number density,as well as laser irradiance shielded by plasma have been obtained.The study indicates that the main reason behind the radiation signal enhancement in coaxial DP-LIBS-induced plasma is attributed to the increased species number density and plasma temperature caused by the second laser,and it is inferred that the shielding effect of the plasma mainly occurs in the boundary layer of the stagnation point flow over the target surface.This research provides a theoretical basis for experimental research,parameter optimization,and signal enhancement tracing in DP-LIBS.

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.

Adaptive evolution of rbcL in Reaumuria soon garica(Tamaricaceae)

In the field of phylogenetic analyses, the rbcL gene encoded large subunit Ribulose-1,5-biphosphate carboxylase/oxygenase （Rubisco, EC4.1.1.39）, which plays a crucial role in the process of photosynthesis for most terrestrial plants, has been considered to be conserved; however, recent controversy regarding rbcL conservation has appeared since it was proposed to be under natural selection within all principal lineages of land plants. In this study, by examining the variation of DNA and protein sequences among 17 species in the family Tamaricaceae, three nonsynonymous mutations were identified to be under positive selection. The favored sites were located in the alph-helix domains of Rubisco, with decreased hydrophobicity and increased entropy, which could facilitate C〇 2 penetration into the active site of Rubisco. We also found that the expression level of rbcL in different genotypes of Reaumuria soongarica shifted in response to various stresses such as drought, temperature, salt, and light. This study not only sheds light on the functional/structural features of Rubisco in the evolution scenarios from 〇 3-like into C4 in Tamaricaceae but also provides useful information on directing genetic performance to enhance photosynthesis efficiency of desert plants for sustaining fragile desert ecosystems; fur-thermore, it promotes the ability to cope with desert aridification and global warming.

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.

Long-term feeding of sand rice(Agriophyllum squarrosum seed)can improve the antioxidant capacity of mice

Unhealthy eating habits with sugar-rich and high-fat foods can bring nutritional imbalance and other chronic diseases. At present, there is an increasing demand in regulating human sub-health through functional foods. Agriophyllum squarrosum(L.) Moq., a pioneer plant native to sand dunes with ecological restoration function, is a traditional food plant of sand regions and Mongolian folk medicine. Numerous studies have confirmed that A. squarrosum seed, also called sand rice, has high nutritional value. However, the long-term health effects of eating sand rice remain unclear. To better explore and evaluate its long-term effects, hereby, ICR mice were fed with sand rice flour at different ratios(control, 60% and 95%) for 100 days. Results show that the growth and blood glucose level curve of these experimental mice were lower and more stable than that of the control. In addition, mice fed pure sand rice ingredient(95%) gained more stable body weight and blood glucose after 28 days, which revealed that sand rice is a food with comprehensive nutritional value and rarely negatively impacts the body growth performance. Our data also demonstrates that, the content of triglyceride(TG), total cholesterol(TC), low-density lipoprotein cholesterol(LDL-C) and high-density lipoprotein cholesterol(HDL-C) provided the lowest level in the blood of mice with a diet of pure sand rice ingredient, 0.48, 4.14, 0.91, 3.03 mmol/L, respectively. Also, T-SOD and GSH-PX activity provided a high level in mice with pure sand rice gradient, which significantly increased by 36%(T-SOD)and 19%(GSH-PX) compared to the control. These results suggest that long term intake of the pure sand rice ingredients is more helpful for stabilizing blood lipid and improve antioxidant capacity and beneficial to people suffering from chronic disease. This study supplies the first animal evidence to support the claim that sand rice is a promising functional food with comprehensive nutrition in the future. We are confident that, with increasing demands of daily sand rice usage, planting A. squarrosum in the vast desert regions will further increase the local economy and ecological restoration when coping with global warming.

疫情背景下“完全线上”远程混合式教学的实践与思考

为应对新型冠状病毒肺炎疫情,教师通过在线直播和线上交互讨论等形式,积极探索有效的线上教学方式,为在家自主学习的学生提供良好的学习体验。本文以“无机化学与化学分析”课程为例,面对疫情期间的特殊性,将以往的“线上线下融合”的混合式教学模式进行相应调整,提供给大家“完全线上”的远程混合式教学案例,以获得实时高效的教学效果。

价值引领融入“无机化学与化学分析”的课程思政建设

将课程思政应用到“无机化学和化学分析”教学中,更好发挥其价值引领作用。开展课程思政建设,应做到守正与创新。本文以价值引领为切入点,介绍如何将思想政治教育有机融入课程内容设置和课堂讲授等环节,力求培养学生的家国情怀、国际视野、法治意识、生态意识、工程伦理、人文关怀等科学素养,深入践行立德树人,提高本科教学质量。

多维度信息化无机化学实验的资源构建与教学实践探索

面对大一化类专业学生化学基础、理论与实验联系能力和实验操作水平等存在较大差异的现状,天津大学无机化学教学团队从课堂演示实验、实验课在线开放、实验安全管理与教育及虚拟仿真实验的制作与应用等多个维度构建无机化学信息化实验资源,并应用于无机化学教学实践中,解决学生在学习过程中的困难,提高教学效果和效率。

无机化学与化学分析课程在线期末考试的探索与实践

为应对新型冠状病毒肺炎疫情,在线期末考试的探索与实践成为一个新的研究热点。本文以"无机化学与化学分析"课程为例,面对疫情期间的特殊性,从在线考试设计、在线考试准备、考试实施和学生反馈等方面对于在线考试进行了多维度的介绍,总结了经验并进行了反思,提出了切实可行的考试流程,为高校开展学生较多的公共基础课的在线考试提供了参考和借鉴。

加压氢化反应虚拟仿真实验的建设与应用

为扩大加压氢化这一实用技术在本科教学中的应用,使学生能够熟练使用氢气这种易燃易爆气体,提出并建设了加压氢化反应的虚拟仿真实验。基于三位诺贝尔奖获得者在氢化反应领域的相关工作,开展加压氢化反应的虚拟仿真实验。该实验建设包括仿真软件资源、学习共享平台、移动端学习资源、流程建设、评价体系建设,充分发挥虚拟仿真技术在化学化工领域中的作用,为一些难以在教学中开展的化学化工实验课程开辟了新的道路。

Recent Advances in Space-Deployable Structures in China

Deployable space structure technology is an approach used in building spacecraft,especially when realizing deployment and folding functions.Once in orbit,the structures are released from the fairing,deployed,and positioned.With the development of communication,remote-sensing,and navigation satellites,space-deployable structures have become cutting-edge research topics in space science and technology.This paper summarizes the current research status and development trend of spacedeployable structures in China,including large space mesh antennas,space solar arrays,and deployable structures and mechanisms for deep-space exploration.Critical technologies of space-deployable structures are addressed from the perspectives of deployable mechanisms,cable-membrane form-finding,dynamic analysis,reliable environmental adaptability analysis,and validation.Finally,future technology developments and trends are elucidated in the fields of mesh antennas,solar arrays,deployable mechanisms,and on-orbit adjustment,assembly,and construction.

浅析气排球技、战术特点

气排球是在室内排球基础上,衍生而出的一种新型体育运动,是我国自主发明的一项融观赏、娱乐、健身、竞技为一体的新兴体育项目。气排球作为现代排球项目的分支,是一项比赛难度小、运动强度低、趣味性能浓、观赏性能高、参与性能强的综合性有氧运动。本文运用文献资料法、比较分析法等研究方法,就二者发展历程、球本身特性及临场比赛技、战术应用等方面进行比较研究,创新性地提出有关气排球基本技、战术的优化策略,旨在丰富气排球运动技术含量,为气排球向全国范围内推广、实施提供一定的理论参考依据。

Transcriptomic comparison to identify rapidly evolving genes in Braya humilis

The Brassicaceae species Braya humilis shows broad adaptation to different climatic zones and latitudes. However, the molecular adaptation mechanism of B. humilis is poorly understood. In China, B. humilis is mainly distributed on the QinghaiTibetan Plateau(QTP) and in the adjacent arid region. Previous transcriptome analysis of B. humilis has revealed that 39 salt and osmotic stress response genes are subjected to purifying selection during its speciation. To further explore the adaptation mechanism of B. humilis to an arid environment, OrthoMCL program was employed in this study and 6,268 pairs of orthologous gene pairs with high confidence were obtained between B. humilis and Arabidopsis thaliana. A comparative evolutionary analysis based on nonsynonymous to synonymous substitution ratio(Ka/Ks) was then conducted. There were 64 pairs exhibiting a Ka/Ks ratio more than 0.5 and among which, three instrumental candidate genes, T20487,T22576, and T23757, were identified with strong selection signatures(Ka/Ks >1). The corresponding A. thaliana orthologs are double-stranded RNA-binding domain protein, MADS-box family protein, and NADH-dehydrogenase subunit6, which is encoded by mitochondria genome. This report not only demonstrates the adaptation contribution of fast evolving nuclear genes, but also highlights the potential adaptive value of mitochondria gene to the speciation and adaptation of B. humilis toward the extreme environment in an arid region.

人工智能时代下成人教育的现实困境及转变路径探究

人工智能技术的发展使教育的标准不断提高,人们对自身能力与职业发展的诉求也逐渐多样化。成人教育为适应时代发展,须突破当下现实困境,即传统教育观念的禁锢、教学内容与方式的固化、学习场所的固定单一,并积极寻求与之相对应的合理转变路径,即教育观念由终结型、再现型、学历型转变为终身型、创新型、能力型;教学内容由实用性转向多元性,教学方式由传统型转向个性化;学习场所由固定场所转向智能空间。

Deployment analysis of composite thin-walled lenticular tubes with effect of storage time and temperature

Composite Thin-walled Lenticular Tube(CTLT)is increasingly utilized in small satellites missions as a lightweight,foldable,and rollable structural material that facilitates the construction of large deployable systems.The CTLT is initially flattened and coiled around a central hub for storage before launch,during which elastic energy is stored as deformation energy,allowing it to be self-deployed on demand for use in orbit.This work presents a comprehensive investigation into the coiling,storage and deployment behaviors of CTLT that wraps around a central hub.A nonlinear explicit dynamic finite element model was developed with both deformable CTLT and rigidbodies mechanisms including the central hub and guide rollers,as well as the complex interactions among them.The coiling mechanics characteristics such as stored strain energy and rotational moment were presented and validated against experimental data in the literature.Then,the dynamic deployment behaviors were analyzed in terms of two different deployment methods,namely,controlled deployment and free deployment.The effect of material property change during storage was also discussed through numerical experiments.

Hyaluronic acid-based dual-responsive nanomicelles mediated mutually synergistic photothermal and molecular targeting therapies

Precise clinical treatment of triple-negative breast cancer(TNBC)is an obstacle in clinic.Nanotechnology-assisted photothermal therapy(PTT)is a superior treatment modality for TNBC in terms of precision.However,thermoresistance arising from PTT and insufficient drug release from nanocarriers decrease the efficacy of PTT.AT13387 is a novel HSP90 inhibitor that can weaken thermoresistance and undergoing clinic II phase study,showing satisfactory antitumour activity through molecularly targeted therapy(MTT).Whereas,it has poor solubility.Hence hyaluronic acid and stearic acid were connected by hydrazone bonds and disulfide bonds,forming an amphipathic copolymer that could self-assembled into nanomicelles,followed by encapsulating Cypate and AT13387.These nanomicelles exhibited great features,including achieving mutually synergistic PTT/MTT for overcoming thermoresistance and promoting translocation of drugs,increasing the solubility of Cypate and AT13387,showing a pH/redox dual response that contributes to drug release,and having the ability of active targeting.Thus,the nanomicelles developed in this study may be a promising strategy for the precise treatment of TNBC.

建构中国民艺思想史——杭间教授专访

《民艺》杂志:您曾对中国的工艺美学思想进行了系统的梳理,出版了专著《中国工艺美学史》。实际上,您在著作中对中国民艺思想的脉络也进行了阐发。能否请您简要总结中国民艺思想的演进历程呢?杭间:中国民艺思想是一个非常重要的研究课题,张道一先生、吕品田研究员、潘鲁生教授、左汉中编审、孙建君研究员等学者分别从不同的角度展开了研究,取得了丰富的研究成果,如张道一先生既有宏阔的《张道一论民艺》,对民艺思想进行了高屋建瓴式的观察与总结,也有《孝道图—二十四孝图等考析》《麒麟送子》等专论从个案角度进行的深入解析。

民艺研究的历程与展望——杭间访谈

《民艺》杂志编辑马晓飞于2018年10月2日在北京就民艺的概念、范畴等问题,采访了中国美术学院副院长杭间教授。杭间教授作为见证者回顾了中国民艺研究的基本历程,论证了相关概念,并对今后民艺研究的主要方法与主要路径给出了建议。

21世纪以来的英国手工艺发展——《手工艺市场报告》导读

2020年4月,英国《手工艺》(《Crafts》)杂志在其网站刊发《手工艺市场报告》(The Market for Craft),报告由杂志主办方—英国手工艺理事会(Craft Council)组织编写。报告从用户画像、消费模式、市场规模、出口市场等不同侧面,通过112页的篇幅、丰富的图表、翔实的数据,对英国手工艺市场进行了全景扫描。报告指出:手工艺不再只是收藏家关注的小众领域,已经演变为主流消费,成为人们生活的必需品。

民间陶瓷与民众生活

民间陶瓷与民间生活密不可分,无论是结实、厚重的粗瓷杂器,还是精工细琢的民间陶塑,都体现在日用行常之间。尽管其器型、其装饰、其色彩随着时间的推移而跌宕变化,但始终与民间的风俗习惯、爱憎协调一致,并且折射出最本质的华夏文化。当人们端详陶瓷纹样的时候就会发现,趋利避害是民间装饰最为重要的主题,民间所谓的'图个吉利',这个好彩头在民间包含金榜题名、荣华富贵、多子多福等心愿。