CPG Human Motion Phase Recognition Algorithm for a Hip Exoskeleton with VSA Actuator

Due to the dynamic stiffness characteristics of human joints, it is easy to cause impact and disturbance on normal movements during exoskeleton assistance. This not only brings strict requirements for exoskeleton control design, but also makes it difficult to improve assistive level. The Variable Stiffness Actuator (VSA), as a physical variable stiffness mechanism, has the characteristics of dynamic stiffness adjustment and high stiffness control bandwidth, which is in line with the stiffness matching experiment. However, there are still few works exploring the assistive human stiffness matching experiment based on VSA. Therefore, this paper designs a hip exoskeleton based on VSA actuator and studies CPG human motion phase recognition algorithm. Firstly, this paper puts forward the requirements of variable stiffness experimental design and the output torque and variable stiffness dynamic response standards based on human lower limb motion parameters. Plate springs are used as elastic elements to establish the mechanical principle of variable stiffness, and a small variable stiffness actuator is designed based on the plate spring. Then the corresponding theoretical dynamic model is established and analyzed. Starting from the CPG phase recognition algorithm, this paper uses perturbation theory to expand the first-order CPG unit, obtains the phase convergence equation and verifies the phase convergence when using hip joint angle as the input signal with the same frequency, and then expands the second-order CPG unit under the premise of circular limit cycle and analyzes the frequency convergence criterion. Afterwards, this paper extracts the plate spring modal from Abaqus and generates the neutral file of the flexible body model to import into Adams, and conducts torque-stiffness one-way loading and reciprocating loading experiments on the variable stiffness mechanism. After that, Simulink is used to verify the validity of the criterion. Finally, based on the above criterions, the signal mean value is removed using feedback structure to complete the phase recognition algorithm for the human hip joint angle signal, and the convergence is verified using actual human walking data on flat ground.

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.

中医药调控肿瘤相关巨噬细胞防治肺癌转移的基础研究进展

肺癌是全球死亡率最高的癌种,而转移则是导致肺癌患者死亡的主要原因,且防控效率不高。近年来研究发现,免疫疗法或许是突破转移瓶颈的方向。巨噬细胞作为固有免疫的重要组成部分,参与肿瘤发生发展的全过程。肿瘤相关巨噬细胞(tumor-associated macrophages,TAMs)是肿瘤微环境(tumor microenvironment,TME)中最丰富的免疫群体,具有抗肿瘤的M1型和促肿瘤的M2型,后者通过促进肿瘤侵袭和转移、血管和淋巴管生成、免疫抑制和介导播散肿瘤细胞(disseminated tumor cells,DTCs)休眠重激活等途径促进肿瘤转移。近年来,中医药抑制肿瘤转移疗效显著并得到诸多验证,它能通过减少TAMs的募集、抑制M2型极化和调节TME中的细胞因子和蛋白发挥抗肿瘤作用。本文综述了TAMs与肺癌转移之间的关系,梳理了中医药调控TAMs防治肺癌转移的靶点与机制,以期为肺癌防治提供思路。

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。

Autophagy in hepatic progenitor cells modulates exosomal miRNAs to inhibit liver fibrosis in schistosomiasis

Schistosoma infection is one of the major causes of liver fibrosis.Emerging roles of hepatic progenitor cells(HPCs)in the pathogenesis of liver fibrosis have been identified.Nevertheless,the precise mechanism underlying the role of HPCs in liver fibrosis in schistosomiasis remains unclear.This study examined how autophagy in HPCs affects schistosomiasis-induced liver fibrosis by modulating exosomal miRNAs.The activation of HPCs was verified by immunohistochemistry(IHC)and immunofluorescence(IF)staining in fibrotic liver from patients and mice with Schistosoma japonicum infection.By coculturing HPCs with hepatic stellate cells(HSCs)and assessing the autophagy level in HPCs by proteomic analysis and in vitro phenotypic assays,we found that impaired autophagy degradation in these activated HPCs was mediated by lysosomal dysfunction.Blocking autophagy by the autophagy inhibitor chloroquine(CQ)significantly diminished liver fibrosis and granuloma formation in S.japonicum-infected mice.HPC-secreted extracellular vehicles(EVs)were further isolated and studied by miRNA sequencing.miR-1306-3p,miR-493-3p,and miR-34a-5p were identified,and their distribution into EVs was inhibited due to impaired autophagy in HPCs,which contributed to suppressing HSC activation.In conclusion,we showed that the altered autophagy process upon HPC activation may prevent liver fibrosis by modulating exosomal miRNA release and inhibiting HSC activation in schistosomiasis.Targeting the autophagy degradation process may be a therapeutic strategy for liver fibrosis during Schistosoma infection.

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.

具有骨样微环境的压电催化可控矿化支架实现内源性骨再生

Orderly hierarchical structure with balanced mechanical,chemical,and electrical properties is the basis of the natural bone microenvironment.Inspired by nature,we developed a piezocatalytically-induced controlled mineralization strategy using piezoelectric polymer poly-L-lactic acid(PLLA)fibers with ordered micro-nano structures to prepare biomimetic tissue engineering scaffolds with a bone-like microenvironment(pcm-PLLA),in which PLLA-mediated piezoelectric catalysis promoted the in-situ polymerization of dopamine and subsequently regulated the controllable growth of hydroxyapatite crystals on the fiber surface.PLLA fibers,as analogs of mineralized collagen fibers,were arranged in an oriented manner,and ultimately formed a bone-like interconnected pore structure;in addition,they also provided bone-like piezoelectric properties.The uniformly sized HA nanocrystals formed by controlled mineralization provided a bone-like mechanical strength and chemical environment.The pcm-PLLA scaffold could rapidly recruit endogenous stem cells,and promote their osteogenic differentiation by activating cell membrane calcium channels and PI3K signaling pathways through ultrasound-responsive piezoelectric signals.In addition,the scaffold also provided a suitable microenvironment to promote macrophage M2 polarization and angiogenesis,thereby enhancing bone regeneration in skull defects of rats.The proposed piezocatalytically-induced controllable mineralization strategy provides a new idea for the development of tissue engineering scaffolds that can be implemented for multimodal physical stimulation therapy.

Nano metal-photosensitizer based on Aza-BODIPY-Cu complex for CDT-enhanced dual phototherapy

Chemodynamic therapy(CDT)combined with dual phototherapy(photothermal therapy(PTT)and photodynamic therapy(PDT))is an efficient way to synergistically improve anti-tumor efficacy.However,the combination of multiple modes often makes the composition of the system more complex,which is not conducive to clinical application.In this study,a dual phototherapy ligand carboxyl-modified Aza-BODIPY(BOD-COOH)and metal active center Cu^(2+)were used to construct multiple-modes metalphotosensitizer nanoparticles(BOD-Cu NPs)via one-step coordination self-assembly for combination therapy of CDT/PDT/PTT.In order to improve delivery efficiency,the targeted hydrophilic molecule pyridinemodified glucose derivative(G-Py)was synthesized and coated onto the BOD-Cu NPs to form a glycosylated nano metal-photosensitizer BOD-Cu@G by electrostatic interaction.The Cu^(2+)in BOD-Cu@G could not only be used as a coordination node for metal-driven self-assembly but also consume intracellular glutathione(GSH),and then catalyze Fenton-like reaction to generate hydroxyl radical(·OH)for CDT.In vitro and in vivo studies revealed that BOD-Cu@G could achieve excellent anti-tumor efficiency by CDTenhanced dual phototherapy.

Postconflict behavior among Rhinopithecus roxellana leader males in the Qinling Mountains, China

Since reconciliation was first described more than 20 years ago, a large number of postconflict be- haviors have been observed among females in many polygynous primate species. However, few studies have been conducted among males, perhaps due to the rarity with which they maintain friendly relationships with one another and their aggressive competition for resources. Although this is true for many primate males, Sichuan snub-nosed monkeys Rhinopithecus roxellana represent a potential exception as male cooperation has been known to occur. In this study, using postconfiict/ matched-control（PC-MC） and time-rule methods, we analyzed postconflict behavior among males and the possible occurrence of bystander affiliation or reconciliation. A total of 246 PC-MC pairs among leader males were obtained. On average, each leader male exhibited only 0.04 aggressive be- haviors per observation hour, and conciliation among leader males occurred at a low rate （2.03%） relative to other primate species. The occurrence of consolation-affiliation interactions between focal males and group members other than former opponents differed significantly between PCs and MCs, which is the first time this has been confirmed among R. roxellana males. We discuss the results in light of recent theories concerning consolation in primates. The patterns of postconflict contact demonstrated that R. roxellana may be a unique species among colobines.

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.