A translational study of somatosensory evoked potential time–frequency components in rats,goats,and humans

Somatosensory evoked potentials(SEPs)have been widely used to assess neurological function in clinical practice.A good understanding of the association between SEP signals and neurological function is helpful for precise diagnosis of impairment location.Previous studies on SEPs have been reported in animal models.However,few studies have reported the relationships between SEP waveforms in animals and those in humans.In this study,we collected normal SEP waveforms and decomposed them into specific time–frequency components(TFCs).Our results showed three stable TFC distribution regions in intact goats and rats and in humans.After we induced spinal cord injury in the animal models,a greater number of small TFC distribution regions were observed in the injured goat and rat groups than in the normal group.Moreover,there were significant correlations(P<0.05)and linear relationships between the main SEP TFCs of the human group and those of the goat and rat groups.A stable TFC distribution of SEP components was observed in the human,goat and rat groups,and the TFC distribution modes were similar between the three groups.Results in various animal models in this study could be translated to future clinical studies based on SEP TFC analysis.Human studies were approved by the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster(approval No.UM 05-312 T/975)on December 5,2005.Rat experiments were approved by the Committee on the Use of Live Animals in Teaching and Research of Li Ka Shing Faculty of Medicine of the University of Hong Kong(approval No.CULART 2912-12)on January 28,2013.Goat experiments were approved by the Animal Ethics Committee of Affiliated Hospital of Guangdong Medical University(approval No.GDY2002132)on March 5,2018.

Electron-enriched single-Pd-sites on g-C_(3)N_(4) nanosheets achieved by in-situ anchoring twinned Pd nanoparticles for efficient CO_(2) photoreduction

Modulating electronic structures of single-atom metal cocatalysts is vital for highly active photoreduction of CO_(2),and it's especially challenging to develop a facile method to modify the dispersion of atomical photocatalytic sites.We herein report an ion-loading pyrolysis route to in-situ anchor Pd single atoms as well as twinned Pd nanoparticles on ultra-thin graphitic carbon nitride nanosheets(PdTP/Pd_(SA)-CN)for high-efficiency photoreduction of CO_(2).The anchored Pd twinned nanoparticles donate electrons to adjacent single Pd–N_(4) sites through the carbon nitride networks,and the optimized PdTP/Pd_(SA)-CN photocatalyst exhibits a CO evolution rate up to 46.5μmol g^(-1) h^(-1) with nearly 100%selectivity.As revealed by spectroscopic and theoretical analyses,the superior photocatalytic activity is attributed to the lowered desorption barrier of carbonyl species at electron-enriched Pd single atoms,together with the improved efficiencies of light-harvesting and charge separation/transport.This work has demonstrated the engineering of the electron density of single active sites with twinned metal nanoparticles assisted by strong electronic interaction with the support of the atomic metal,and unveiled the underlying mechanism for expedited photocatalytic efficiency.

Supramolecular polymer-based gel fracturing fluid with a double network applied in ultra-deep hydraulic fracturing

A gel based on polyacrylamide,exhibiting delayed crosslinking characteristics,emerges as the preferred solution for mitigating degradation under conditions of high temperature and extended shear in ultralong wellbores.High viscosity/viscoelasticity of the fracturing fluid was required to maintain excellent proppant suspension properties before gelling.Taking into account both the cost and the potential damage to reservoirs,polymers with lower concentrations and molecular weights are generally preferred.In this work,the supramolecular action was integrated into the polymer,resulting in significant increases in the viscosity and viscoelasticity of the synthesized supramolecular polymer system.The double network gel,which is formed by the combination of the supramolecular polymer system and a small quantity of Zr-crosslinker,effectively resists temperature while minimizing permeability damage to the reservoir.The results indicate that the supramolecular polymer system with a molecular weight of(268—380)×10^(4)g/mol can achieve the same viscosity and viscoelasticity at 0.4 wt%due to the supramolecular interaction between polymers,compared to the 0.6 wt%traditional polymer(hydrolyzed polyacrylamide,molecular weight of 1078×10^(4)g/mol).The supramolecular polymer system possessed excellent proppant suspension properties with a 0.55 cm/min sedimentation rate at 0.4 wt%,whereas the0.6 wt%traditional polymer had a rate of 0.57 cm/min.In comparison to the traditional gel with a Zrcrosslinker concentration of 0.6 wt%and an elastic modulus of 7.77 Pa,the double network gel with a higher elastic modulus(9.00 Pa)could be formed only at 0.1 wt%Zr-crosslinker,which greatly reduced the amount of residue of the fluid after gel-breaking.The viscosity of the double network gel was66 m Pa s after 2 h shearing,whereas the traditional gel only reached 27 m Pa s.

Probing the interaction between asphaltene-wax and its effects on the crystallization behavior of waxes in heavy oil via molecular dynamics simulation

High content of asphaltenes and waxes leads to the high pour point and the poor flowability of heavy oil,which is adverse to its efficient development and its transportation in pipe.Understanding the interaction mechanism between asphaltene-wax is crucial to solve these problems,but it is still unclear.In this paper,molecular dynamics simulation was used to investigate the interaction between asphaltenewax and its effects on the crystallization behavior of waxes in heavy oil.Results show that molecules in pure wax are arranged in a paralleled geometry.But wax molecules in heavy oil,which are close to the surface of asphaltene aggregates,are bent and arranged irregularly.When the mass fraction of asphaltenes in asphaltene-wax system(ω_(asp))is 0-25 wt%,the attraction among wax molecules decreases and the bend degree of wax molecules increases with the increase ofω_(asp).Theω_(asp)increases from 0 to 25 wt%,and the attraction between asphaltene-wax is stronger than that among waxes.This causes that the wax precipitation point changes from 353 to 333 K.While theω_(asp)increases to 50 wt%,wax molecules are more dispersed owing to the steric hindrance of asphaltene aggregates,and the interaction among wax molecules transforms from attraction to repulsion.It causes that the ordered crystal structure of waxes can't be formed at normal temperature.Simultaneously,the asphaltene,with the higher molecular weight or the more hetero atoms,has more obvious inhibition to the formation of wax crystals.Besides,resins also have an obvious inhibition on the wax crystal due to the formation of asphalteneresin aggregates with a larger radius.Our results reveal the interaction mechanism between asphaltene-wax,and provide useful guidelines for the development of heavy oil.

Adhesion property of AlCrNbSiTi high-entropy alloy coating on zirconium:experimental and theoretical studies

Experimental scratch tests and first-principles calculations were used to investigate the adhesion property of AlCrNbSiTi high-entropy alloy(HEA)coatings on zirconium substrates.AlCrNbSiTi HEA and Cr coatings were deposited on Zr alloy substrates using multi-arc ion plating technology,and scratch tests were subsequently conducted to estimate the adhesion property of the coatings.The results indicated that Cr coatings had better adhesion strength than HEA coatings,and the HEA coatings showed brittleness.The special quasi-random structure approach was used to build HEA models,and Cr/Zr and HEA/Zr interface models were employed to investigate the cohesion between the coatings and Zr substrate using first-principles calculations.The calculated interface energies showed that the cohesion between the Cr coating and the Zr substrate was stronger than that of the HEA coating with Zr.In contrary to Al or Si in the HEA coating,Cr,Nb,and Ti atoms binded strongly with Zr substrate.Based on the calculated elastic constants,it was found that low Cr and high Al content decreased the mechanical performances of HEA coatings.Finally,this study demonstrated the utilization of a combined approach involving first-principles calculations and experimental studies for future HEA coating development.

Multi-Label Image Classification Based on Object Detection and Dynamic Graph Convolutional Networks

Multi-label image classification is recognized as an important task within the field of computer vision,a discipline that has experienced a significant escalation in research endeavors in recent years.The widespread adoption of convolutional neural networks(CNNs)has catalyzed the remarkable success of architectures such as ResNet-101 within the domain of image classification.However,inmulti-label image classification tasks,it is crucial to consider the correlation between labels.In order to improve the accuracy and performance of multi-label classification and fully combine visual and semantic features,many existing studies use graph convolutional networks(GCN)for modeling.Object detection and multi-label image classification exhibit a degree of conceptual overlap;however,the integration of these two tasks within a unified framework has been relatively underexplored in the existing literature.In this paper,we come up with Object-GCN framework,a model combining object detection network YOLOv5 and graph convolutional network,and we carry out a thorough experimental analysis using a range of well-established public datasets.The designed framework Object-GCN achieves significantly better performance than existing studies in public datasets COCO2014,VOC2007,VOC2012.The final results achieved are 86.9%,96.7%,and 96.3%mean Average Precision(mAP)across the three datasets.

Fermi Surface Nesting with Heavy Quasiparticles in the Locally Noncentrosymmetric Superconductor CeRh_(2)As_(2)

The locally noncentrosymmetric heavy fermion superconductor CeRh_(2)As_(2) has attracted considerable interests due to its rich superconducting phases,accompanied by possible quadrupole density wave and pronounced antiferromagnetic excitations.To understand the underlying physics,here we report measurements from highresolution angle-resolved photoemission.Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure,as well as a quasi-two-dimensional Fermi surface(FS)with strong 4f contributions.The FS shows signs of nesting with an in-plane vector q_(1)=(π/α,π/α),which is facilitated by the heavy bands nearˉ𝑋arising from the characteristic conduction-X hybridization.The FS nesting provides a natural explanation for the observed antiferromagnetic spin fluctuations at(π/α,π/α),which might be the driving force for its unconventional superconductivity.Our experimental results can be reasonably explained by density functional theory plus dynamical mean field theory calculations,which can capture the strong correlation effects.Our study not only provides spectroscopic signature of the key factors underlying the field-induced superconducting transition,but also uncovers the critical role of FS nesting and lattice Kondo effect in the underlying magnetic fluctuations.

Cases Report of Atypical Aortic Dissection

Background: Aortic dissection (AD) is one of the common causes of fatal chest pain in emergency medicine. The main and most common clinical manifestation is pain, with about 90% of patients experiencing sudden persistent, tearing or cutting-like pain in the chest or back. However, there have also been reports of myocardial infarction, heart failure, renal failure, syncope, shock, stroke, paraplegia and other cases. Clinical misdiagnosis is common. Aim: Alert clinicians to aortic dissection with shock and chest tightness as the main clinical presentations. Case Presentation: Report on two cases of aortic dissection with syncope and shock as the main manifestations. Conclusion: Aortic dissection is a highly dangerous cardiovascular emergency with a high mortality rate. In clinical practice, awareness of the clinical manifestations of aortic dissection should be increased. Careful inquiry about medical history, attention to atypical clinical presentations of aortic dissection, thorough physical examination, and comprehensive diagnostic evaluation can improve the success rate of diagnosing aortic dissection.

A Study on the Pedagogical Application of Chinese New Year Culture in International Chinese Language Education

Culture teaching is an inseparable part of International Chinese Language Education,and it has great significance in international Chinese language teaching.Students can enhance their interest in Chinese language learning and improve their learning effect through understanding the excellent traditional Chinese culture,at the same time,culture teaching can help to disseminate the Chinese culture and promote the development of a multicultural world.Taking the teaching of Chinese New Year culture as an example,we analyze the current teaching materials involving Chinese New Year culture with high popularity and acceptance,put forward effective teaching methods matching the feasibility of teaching Chinese New Year culture,and then present the specific teaching design of Chinese New Year culture,in order to provide references for the teaching of culture in International Chinese Language Education.

老龄化与媒介研究:现代社会转型与学科未来方向

人口老龄化是目前中国社会面对的结构性变化之一。“老龄化与媒介”研究作为跨学科研究领域,需要对新的社会现象作出理论与方法上的回应。本研究通过检视中国在老龄化进程与老年学建设上的位置,提出老龄化问题的社会意涵应该得到更多学术关注,未来研究应该更多采取文化批判视角,对数字媒体、智能技术、平台治理等与老年人的关系加以审视。

Study on Horizontal Well Layout Boundary Considering Wellbore Pressure Loss

Based on the Dikken analytical calculation method of wellbore pressure loss under single-phase fluid and turbulent flow conditions, the correlation model between horizontal well output and horizontal section length and horizontal section distributed pressure difference is constructed. The influence degree of wellbore pressure loss on daily oil production of horizontal well, horizontal section pressure and production effect of horizontal well under different horizontal well lengths is analyzed, which provides certain reference for the design of horizontal well length and well layout.

关节镜下可调节袢钢板全内技术重建前交叉韧带的临床疗效分析

目的探讨关节镜下可调节袢钢板全内技术重建前交叉韧带(ACL)的临床疗效。方法回顾性分析2018年1月-2019年7月湖南省人民医院集团澧县人民医院21例ACL损伤患者的临床资料,均行关节镜下可调节袢全内技术ACL重建。其中,男13例,女8例,年龄41~56岁,平均46岁,Lachman试验Ⅲ度阳性伴软性终止点18例,Lachman试验Ⅱ度阳性伴硬性终止点3例。观察移植物粗细、术前及术后影像学、术前及术后Lachman试验情况,比较术后健侧与患侧屈膝活动度以及术前、术后半年及术后2年的国际膝关节文献委员会(IKDC)评分、Lysholm评分和Larson评分等指标,以综合评估临床疗效。结果21例患者随访时间24个月。术前Lachman试验Ⅲ度阳性伴软性终止点和LachmanⅡ度阳性伴硬性终止点的病例,术中均证实ACL完全或大部分断裂。术后半年Lachman试验阳性0例,阴性21例。术中所使用的移植物平均直径(8.59±0.44)mm,术后三维CT测量股骨粗骨道长度(21.66±2.51)mm,移植物进入股骨骨道长度(19.82±2.29)mm,胫骨粗骨道长度(19.67±1.02)mm,移植物进入胫骨骨道长度(17.69±1.26)mm。术后半年MRI显示:移植物固定牢靠,与骨道贴合良好,信号均匀。术后末次随访,健侧、患侧最大屈膝角度分别为(131.42±3.59)°和(130.71±3.64)°,两者比较,差异无统计学意义(P>0.05)。术后半年Lysholm评分、IKDC评分和Larson评分分别为(88.19±1.97)、(74.05±2.36)和(67.52±2.23)分,术后2年分别为(97.76±1.97)、(88.62±3.07)和(90.57±2.46)分,均较术前的(22.00±3.35)、(41.67±1.85)和(39.81±1.81)分明显提高,术后半年和术后2年分别与术前比较,差异均有统计学意义(P<0.05)。结论关节镜下可调节袢钢板全内技术重建ACL,肌腱利用率高,稳定性好,中远期膝关节功能恢复满意,疗效肯定。

基于1 m尺度甲醇油池火模拟计算的不同辐射模型数值评估研究

池火是火灾灾害中最常遇到的火焰类型之一,发展油池火的精细化建模有利于液体火灾事故危害性的精准分析及评估。众所周知,热辐射建模是准确模拟各种火灾场景的关键环节。因此,为建立合适的辐射模型,在这项工作中,通过将四个不同的辐射模型耦合到开源火灾模拟代码FDS中,并使用有限体积法求解辐射强度传输方程,对大尺度甲醇池火开展了LES仿真研究。结合NIST的实验数据,对不同辐射模型的影响特性及结果进行了对比分析。关于温度计算,基于WSGG的辐射模型和Cassol的模型表现更好。此外,所有模型都能很好地预测脉动频率。然而,关于辐射热通量的预测,Cassol的两个模型和FDS默认模型的表现优于其他模型,获得每个组分的准确光谱信息数据和确定混合气体的WSGG系数的方法是成功预测火焰辐射的重要因素。

一种联轴器动力学简化计算方法与验证

为快速得到联轴器的固有频率,采用结构动力学理论简化联轴器计算模型,得到一阶弯曲固有频率理论计算方法。采用三维有限元分析方法进行联轴器的模态分析,并针对理论和有限元计算结果进行比对核算。该理论方法仅需少量的结构参数便可快速获得联轴器的一阶弯曲固有频率值。后续又分别针对11款联轴器进行分析与比对,发现当联轴器中段长径比大于3、中段长度占比大于60%、中段质量占比大于50%的联轴器,用该理论方法的计算偏差一般能控制在15%以内,能够较好的应对快速计算的需求。

脓毒血症小鼠致肺损伤模型的研究

目的:探讨盲肠结扎穿刺建造的脓毒血症小鼠模型中肺组织损伤的相关机制。方法:选取42只C57BL/6雄性小鼠,随机分为正常对照组、假手术组及脓毒血症组,各14只。正常对照组不做处理,假手术组行盲肠结扎,脓毒血症组予以盲肠结扎穿刺。24 h收集各组肺组织,观察脓毒血症情况评分(MSS)、生存率、肺组织形态改变情况、肺组织损伤评分、中性粒细胞以及肺组织中炎症因子肿瘤坏死因子α(TNF-α)和白细胞介素(IL)-6表达水平的差异。结果:脓毒血症组MSS评分、肺损伤评分、中性粒细胞数、TNF-α及IL-6表达水平均较正常对照组、假手术组升高(P<0.01)。结论:脓毒血症可造成病理学层面的小鼠肺组织损伤,致炎症因子表达升高,降低小鼠的生存率。通过观察该模型中反映肺损伤程度的相关指标的变化,可评估脓毒血症严重程度和研究损伤相关机制。

Deferoxamine promotes recovery of traumatic spinal cord injury by inhibiting ferroptosis

Ferroptosis is an iron-dependent novel cell death pathway. Deferoxamine, a ferroptosis inhibitor, has been reported to promote spinal cord injury repair. It has yet to be clarified whether ferroptosis inhibition represents the mechanism of action of Deferoxamine on spinal cord injury recovery. A rat model of Deferoxamine at thoracic 10 segment was established using a modified Allen's method. Ninety 8-week-old female Wistar rats were used. Rats in the Deferoxamine group were intraperitoneally injected with 100 mg/kg Deferoxamine 30 minutes before injury. Simultaneously, the Sham and Deferoxamine groups served as controls. Drug administration was conducted for 7 consecutive days. The results were as follows:(1) Electron microscopy revealed shrunken mitochondria in the spinal cord injury group.(2) The Basso, Beattie and Bresnahan locomotor rating score showed that recovery of the hindlimb was remarkably better in the Deferoxamine group than in the spinal cord injury group.(3) The iron concentration was lower in the Deferoxamine group than in the spinal cord injury group after injury.(4) Western blot assay revealed that, compared with the spinal cord injury group, GPX4, xCT, and glutathione expression was markedly increased in the Deferoxamine group.(5) Real-time polymerase chain reaction revealed that, compared with the Deferoxamine group, mRNA levels of ferroptosis-related genes Acyl-CoA synthetase family member 2(ACSF2) and iron-responsive element-binding protein 2(IREB2) were up-regulated in the Deferoxamine group.(6) Deferoxamine increased survival of neurons and inhibited gliosis. These findings confirm that Deferoxamine can repair spinal cord injury by inhibiting ferroptosis. Targeting ferroptosis is therefore a promising therapeutic approach for spinal cord injury.

Effect of Zr content on crack formation and mechanical properties of IN738LC processed by selective laser melting

Two batches of commercial IN738LC alloy powders with different Zr contents were printed under the same parameters.The influences of Zr content(0.024 wt.% and 0.12 wt.%,respectively) in powders on crack density,distribution,formation mechanism and mechanical properties of selective laser melting(SLM)-treated parts were systematically studied.It was found that the crack density(area ratio) increases from 0.15% to 0.87% in the XOY plane and from 0.21% to 1.81% in the XOZ plane along with the Zr content increase from 0.024 wt.% to 0.12 wt.% in the original powders.Solidification cracks are formed along the epitaxially grown <001>-oriented columnar grain boundaries in molten pool center.The ultimate tensile strength of Sample 1(0.024 wt.% Zr) is 1113 MPa,and there are dimples in tensile fracture.With an increase in the Zr content to 0.12 wt.%(Sample 2),the ultimate tensile strength of Sample 2 decreases to 610 MPa,and there are numerous original cracks and exposed columnar grain boundaries in tensile fracture.The optimization of printing parameters of Sample 2 considerably increases the ultimate tensile strength by 55.2% to 947 MPa,and the plasticity is greatly improved.

再生混凝土研究发展现状及评述

由于城市化的不断推进,建筑废料急剧增加,废弃混凝土的回收与利用已成为全世界关注的一个重要问题。此外,日益增长的全球建筑需求,敦促寻找可持续资源,以取代生产混凝土的天然材料。在过去的几十年中,人们对利用建筑和拆除废物生产可再次利用的混凝土产品进行了研究,并取得众多的成果。本文综述了国内外再生混凝土的最新研究情况,系统地分析了再生混凝土的制备方法、工作性、力学性能、收缩性以及耐久性五个方面的研究进展情况和目前存在的问题。结果表明:已有研究体系中应加强实验室的研究成果向实际工程应用的转化研究,同时在实际工程与制定再生骨料标准时,优先考虑含水量和孔隙率的影响因素。

Microstructure,anticorrosion,biocompatibility and antibacterial activities of extruded Mg−Zn−Mn strengthened with Ca

To find suitable biodegradable materials for implant applications,Mg−6Zn−0.3Mn−xCa(x=0,0.2 and 0.5,wt.%)alloys were prepared by semi-continuous casting followed by hot-extrusion technique.The microstructure and mechanical properties of Mg−6Zn−0.3Mn−xCa alloys were investigated using the optical microscope,scanning electron microscope and tensile testing.Results indicated that minor Ca addition can slightly refine grains of the extruded Mg−6Zn−0.3Mn alloy and improve its strength.When 0.2 wt.%and 0.5 wt.%Ca were added,the grain sizes of the as-extruded alloys were refined from 4.8 to 4.6 and 4.2μm,respectively.Of the three alloys studied,the alloy with 0.5 wt.%Ca exhibits better combined mechanical properties with the ultimate tensile strength and elongation of 334 MPa and 20.3%.The corrosion behaviour,cell viability and antibacterial activities of alloys studied were also evaluated.Increasing Ca content deteriorates the corrosion resistance of alloys due to the increase of amount of effective cathodic sites caused by the formation of more Ca2Mg6Zn3 phases.Cytotoxicity evaluation with L929 cells shows higher cell viability of the Mg−6Zn−0.3Mn−0.5Ca alloy compared to Mg−6Zn−0.3Mn and Mg−6Zn−0.3Mn−0.2Ca alloys.The antibacterial activity against Staphylococcus aureus is enhanced with increasing the Ca content due to its physicochemical and biological performance in bone repairing process.

Effect of isothermal heat treatment on semi-solid microstructure of AZ91D magnesium alloy containing rare earth Gd

The AZ91 D magnesium alloy containing rare earth Gd was prepared in this study, and the effect of semi-solid isothermal heat treatment on the microstructure of the alloy was investigated to obtain an optimum semi-solid structure. Results show that Gd can refine the microstructure of AZ91 D magnesium alloy, and the optimum semi-solid AZ91 D microstructure can be achieved by adding 1.5wt.% Gd. After treated at 585 °C for 30 min, the well distributed rose-shaped and near-spherical semi-solid microstructures of AZ91D+1.5wt.%Gd alloy can be obtained. The liquid phase of the semi-solid alloy consists of three components, namely, the molten pool, the "entrapped liquid" pool and the liner liquid film which separates two neighbor particles. The solid phase is composed of two phases, the primary α-Mg particles and the α-Mg phase formed in the second stage of solidification. With the increase of holding time, melting which causes the decrease of the primary α-Mg particle size is the dominant mechanism in the initial stage while coalescence and Ostwald ripening tend to be the principles later.