Effect of magnetic field and temperature on the ferroelectric loop in MnWO4
静磁场对细胞内蛋白质影响研究进展
Industry Review 行业综述
静磁场对细胞内蛋白质影响研究进展
Effect of Static Magnetic Field on Intracellular Protein
◎ 赵 勇 1，郭利芳 1，盛占武 2 （1. 海南职业技术学院，海南 海口 570216； 2. 中国热带农业科学院海口实验站，海南 海口 570102） Zhao Yong1, Guo Lifang1, Sheng Zhanwu2 (1.Hainan College of Vocation and Technique, Haikou 570216, China; 2.Haikou Experimental Station, Chinese Academy of Tropical Agricultural Sciences,
1 静磁场对生物膜离子通道的影响
科学家们在对生物电产生机制的研究中观察到生 物膜对离子通透性的变化。20 世纪 50 年代，英国生 物物理学家 Hodgkin 等人通过大量研究后提出离子通
XIANDAISHIPIN 现代食品 / 01
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Jovanova-Nesic 等 人 [9] 采 用 AlCl3 处 理 大 鼠 大 脑 核区神经细胞，降低 Na/K 泵的活性，再用 60 mT 磁 场处理，结果发现可增加 Na/K 泵的活性。Rosen[10] 研 究发现在增殖的 GH3 细胞中电压激活的 Na+ 通道经 125 mT 的磁场作用后缩减。并非所有离子的运输都会
细胞、分子等多个层面开展。目前，细胞内蛋白质分 子受静磁场的影响多表现在细胞膜的离子通道和细胞 内的酶蛋白中。静磁场对生物系统的影响作为一个重 要的研究领域，多年来受到国内外学者的广泛关注。 国内外关于静磁场的生物学效应已有大量研究，证据 表明静磁场对很多生物体和生物组织均存在影响。研 究静磁场作用下生物有机体的响应机制，对深入了解 静磁场的生物学效应具有重要意义。
磁学 径向克尔 英文 kerr effect
IntroductionThe Kerr effect, also known as the magneto-optic Kerr effect (MOKE), is a phenomenon that manifests the interaction between light and magnetic fields in a material. It is named after its discoverer, John Kerr, who observed this effect in 1877. The radial Kerr effect, specifically, refers to the variation in polarization state of light upon reflection from a magnetized surface, where the change occurs radially with respect to the magnetization direction. This unique aspect of the Kerr effect has significant implications in various scientific disciplines, including condensed matter physics, materials science, and optoelectronics. This paper presents a comprehensive, multifaceted analysis of the radial Kerr effect, delving into its underlying principles, experimental techniques, applications, and ongoing research directions.I. Theoretical Foundations of the Radial Kerr EffectA. Basic PrinciplesThe radial Kerr effect arises due to the anisotropic nature of the refractive index of a ferromagnetic or ferrimagnetic material when subjected to an external magnetic field. When linearly polarized light impinges on such a magnetized surface, the reflected beam experiences a change in its polarization state, which is characterized by a rotation of the plane of polarization and/or a change in ellipticity. This alteration is radially dependent on the orientation of the magnetization vector relative to the incident light's plane of incidence. The radial Kerr effect is fundamentally governed by the Faraday-Kerr law, which describes the relationship between the change in polarization angle (ΔθK) and the applied magnetic field (H):ΔθK = nHKVwhere n is the sample's refractive index, H is the magnetic field strength, K is the Kerr constant, and V is the Verdet constant, which depends on the wavelength of the incident light and the magnetic properties of the material.B. Microscopic MechanismsAt the microscopic level, the radial Kerr effect can be attributed to twoprimary mechanisms: the spin-orbit interaction and the exchange interaction. The spin-orbit interaction arises from the coupling between the electron's spin and its orbital motion in the presence of an electric field gradient, leading to a magnetic-field-dependent modification of the electron density distribution and, consequently, the refractive index. The exchange interaction, on the other hand, influences the Kerr effect through its role in determining the magnetic structure and the alignment of magnetic moments within the material.C. Material DependenceThe magnitude and sign of the radial Kerr effect are highly dependent on the magnetic and optical properties of the material under investigation. Ferromagnetic and ferrimagnetic materials generally exhibit larger Kerr rotations due to their strong net magnetization. Additionally, the effect is sensitive to factors such as crystal structure, chemical composition, and doping levels, making it a valuable tool for studying the magnetic and electronic structure of complex materials.II. Experimental Techniques for Measuring the Radial Kerr EffectA. MOKE SetupA typical MOKE setup consists of a light source, polarizers, a magnetized sample, and a detector. In the case of radial Kerr measurements, the sample is usually magnetized along a radial direction, and the incident light is either p-polarized (electric field parallel to the plane of incidence) or s-polarized (electric field perpendicular to the plane of incidence). By monitoring the change in the polarization state of the reflected light as a function of the applied magnetic field, the radial Kerr effect can be quantified.B. Advanced MOKE TechniquesSeveral advanced MOKE techniques have been developed to enhance the sensitivity and specificity of radial Kerr effect measurements. These include polar MOKE, longitudinal MOKE, and polarizing neutron reflectometry, each tailored to probe different aspects of the magnetic structure and dynamics. Moreover, time-resolved MOKE setups enable the study of ultrafast magneticphenomena, such as spin dynamics and all-optical switching, by employing pulsed laser sources and high-speed detection systems.III. Applications of the Radial Kerr EffectA. Magnetic Domain Imaging and CharacterizationThe radial Kerr effect plays a crucial role in visualizing and analyzing magnetic domains in ferromagnetic and ferrimagnetic materials. By raster-scanning a focused laser beam over the sample surface while monitoring the Kerr signal, high-resolution maps of domain patterns, domain wall structures, and magnetic domain evolution can be obtained. This information is vital for understanding the fundamental mechanisms governing magnetic behavior and optimizing the performance of magnetic devices.B. Magnetometry and SensingDue to its sensitivity to both the magnitude and direction of the magnetic field, the radial Kerr effect finds applications in magnetometry and sensing technologies. MOKE-based sensors offer high spatial resolution, non-destructive testing capabilities, and compatibility with various sample geometries, making them suitable for applications ranging from magnetic storage media characterization to biomedical imaging.C. Spintronics and MagnonicsThe radial Kerr effect is instrumental in investigating spintronic and magnonic phenomena, where the manipulation and control of spin degrees of freedom in solids are exploited for novel device concepts. For instance, it can be used to study spin-wave propagation, spin-transfer torque effects, and all-optical magnetic switching, which are key elements in the development of spintronic memory, logic devices, and magnonic circuits.IV. Current Research Directions and Future PerspectivesA. Advanced Materials and NanostructuresOngoing research in the field focuses on exploring the radial Kerr effect in novel magnetic materials, such as multiferroics, topological magnets, and magnetic thin films and nanostructures. These studies aim to uncover newmagnetooptical phenomena, understand the interplay between magnetic, electric, and structural order parameters, and develop materials with tailored Kerr responses for next-generation optoelectronic and spintronic applications.B. Ultrafast Magnetism and Spin DynamicsThe advent of femtosecond laser technology has enabled researchers to investigate the radial Kerr effect on ultrafast timescales, revealing fascinating insights into the fundamental processes governing magnetic relaxation, spin precession, and all-optical manipulation of magnetic order. Future work in this area promises to deepen our understanding of ultrafast magnetism and pave the way for the development of ultrafast magnetic switches and memories.C. Quantum Information ProcessingRecent studies have demonstrated the potential of the radial Kerr effect in quantum information processing applications. For example, the manipulation of single spins in solid-state systems using the radial Kerr effect could lead to the realization of scalable, robust quantum bits (qubits) and quantum communication protocols. Further exploration in this direction may open up new avenues for quantum computing and cryptography.ConclusionThe radial Kerr effect, a manifestation of the intricate interplay between light and magnetism, offers a powerful and versatile platform for probing the magnetic properties and dynamics of materials. Its profound impact on various scientific disciplines, coupled with ongoing advancements in experimental techniques and materials engineering, underscores the continued importance of this phenomenon in shaping our understanding of magnetism and driving technological innovations in optoelectronics, spintronics, and quantum information processing. As research in these fields progresses, the radial Kerr effect will undoubtedly continue to serve as a cornerstone for unraveling the mysteries of magnetic materials and harnessing their potential for transformative technologies.。
有研粉末新材料股份有限公司上交所科创板上市
• 56 •粉末冶金工业第31卷•行业动灸*有研粉末新材料股份有限公司上交所科创板上市2021年3月17日，有研粉末新材料股份有限公司正式在上海证券交易所科创板上市，股票代码为 688456=粉末冶金产业技术创新战略联盟(CPMA)理事长、中国钢研科技集团有限公司董事长张少明，联盟副理 事长、有研粉末新材料股份有限公司董事长汪礼敏出席上市仪式。
出席上市仪式的还有有研科技集团有限 公司的领导，联盟副理事长李普明、申承秀，联盟专家委副主任曲选辉，联盟副秘书长曹阳以及联盟理事汪 志荣、薛志生等领导和专家。
有研粉末新材料股份有限公司以先进有色金属粉体材料的设计、研发、生产和销售为主营业务，主要产 品包括铜基金属粉体材料、微电子锡基焊粉材料和3D打印粉体材料等。
此次1PO,有研粉末新材料股份有 限公司拟将4.05亿元募集资金用于有研粉末新材料股份有限公司科技创新中心建设项目、新建粉体材料基 地建设项目、泰国产业基地建设项目以及补充流动资金。
有研粉末新材料股份有限公司己经掌握众多与有色金属粉体材料制备和应用相关的核心技术，目前生 产经营应用的主要核心技术有:球形金属粉体材料制备技术;高品质电解铜粉绿色制备技术；系列无铅环保 微电子焊粉制备及材料设计技术;扩散/复合粉体材料均匀化制备技术;超细金属粉体材料制备技术;3D打 印粉体材料制备技术；高性能粉末冶金中空凸轮轴制备技术。
有研粉末新材料股份有限公司铜基金属粉体材料广泛应用于粉末冶金、超硬工具、摩擦材料、电碳制 品、电工合金等领域，主要客户包括汽车零部件供应商辉门集团，赫格纳斯集团，东睦股份，博深股份，天宜 上佳，神奇电碳集团等;微电子锡基焊粉材料专门用于微电子封装领域，主要客户包括确信爱法、铟泰科技、弘辉电子等世界知名锡焊料生产商。
有研粉末新材料股份有限公司主营产品为铜基金属粉体材料、微电子锡基焊粉材料和3D打印粉体材 料。
2020年上半年，有研粉末新材料股份有限公司以上主营业务收入分别为4.80亿元、丨.77亿元、59.29万元，占比分别为65.16%、24.03%、0.08%,铜基金属粉体材料占比超50%。
磁场流速对传感器用Cu电极电解过程及质量的影响
第31卷第2期 202丨年4月粉宋冶全工业P O W D E R M E T A L L U R G Y I N D U S T R YVol. 31，No.2,p52-56Apr. 2021DOI ： 10.13228/j.boyuan.issn 1006-6543.20200137磁场流速对传感器用C u电极电解过程及质量的影响孙娟'，孙栗2,金晗3(1.河南科技职业大学，河南周口466000; 2.国网浙江海宁市供电公司，浙江海宁314400;3.中原工学院能源与环境学院，河南郑州460000)摘要：在电解工艺制备铜的过程中加入磁场以达到协同强化效果，分析了磁场流速对传感器用C u电极电解过程及质量的影响。
结果表明：施加磁场后，形成了更复杂的铜电解反应。
当提高磁场流速后，铜阳极质量损失减小，最大阴极析出量出现于流速为0.25 m/s的情况下。
磁场流速对C u电极电解阶段的杂质离子产生着显著影响。
受到磁场作用后，杂质离子浓度减小，实际效果受到此磁场取向与流速的共同作用。
处于0.25 m/s磁场流速下，能够获得最大的阴极析出速率，从而减小电解液内的杂质离子浓度并降低铜损失。
处于垂直磁场中，在0〜0.75 m/s范围的电解液黏度基本恒定，并在0.25 m/s时达到最小值。
垂直磁场可以对电子传输发挥抑制作用，增强扩散效果。
随着流速的增大，阻碍了 Cir1扩散过程，在0.25 m/s速率下获得最大阴极析出量。
关键词：磁化电解;强磁场;铜电解;表面质量文献标志码：A 文章编号：1006-6543(2021)02-0052-05Effect of magnetic field velocity on electrolysis process and quality of Cuelectrode used in sensorSUN Juan1,SUN Li2,JIN Han3(1. Henan Vocational University of Science and Technology, Zhoukou 466000, China; 2. State Grid HainingPower Supply Company, Haining 314400, China; 3. School of Energy and Environment, Zhongyuan Universityof Technology, Zhengzhou 460000, China)A bstract：The effect of magnetic field velocity on the electrolytic process and the quality of Cu electrode used inthe sensor was analyzed.The results show that a more complex copper electrolysis reaction is formed by applying amagnetic field.After increasing the magnetic field velocity, the mass loss of copper anode decreased, and the maximum cathode precipitation appeared at the flow rate of 0.25 m/s.The magnetic field velocity has a significant effecton the impurity ions in Cu electrode electrolysis stage.The concentration of impurity ions decreases after the magnetic field is applied, and the actual effect is influenced by the magnetic field orientation and the flow velocity.Atthe magnetic field velocity of 0.25 m/s, the maximum cathode precipitation rate can be obtained, thus reducing theconcentration of impurity ions in the electrolyte and reducing the copper loss.In the vertical magnetic field, the electrolyte viscosity in the range of 0-0.75 m/s is basically constant, and reaches the minimum value at 0.25 m/s.Vertical magnetic field can inhibit electron transport and enhance diffusion.With the increase of flow rate, C u2'diffusionprocess was hindered, and the maximum cathode precipitation was obtained at the rate of 0.25 m/s.Key w ords：magnetization electrolysis; strong magnetic field; copper electrolysis; surface quality 现阶段，电解技术己经成为一种非常广泛的铜 制备工艺。
介绍地球磁场的作文英文
介绍地球磁场的作文英文英文：The Earth's magnetic field is a fascinating and essential aspect of our planet. It plays a crucial role in protecting the Earth from harmful solar winds and cosmic radiation. The magnetic field is generated by the movement of molten iron and nickel in the Earth's outer core. This movement creates electric currents, which in turn produce a magnetic field. This field extends from the Earth'sinterior out into space and is often compared to a giant bar magnet.The Earth's magnetic field has a significant impact on our daily lives, although we may not always be aware of it. For example, it is the reason why a compass always points north. The magnetic field also affects the behavior of migratory birds and certain animal species that use it for navigation. Furthermore, it helps scientists understand the geological history of the Earth, as the magnetic mineralsin rocks align themselves with the Earth's magnetic fieldat the time of their formation.The magnetic field is not static and has undergone numerous reversals throughout Earth's history. These reversals, known as geomagnetic reversals, occur when the magnetic north and south poles switch places. This phenomenon has been studied by scientists, and the evidence of these reversals can be found in the ocean floor and in rocks.中文：地球的磁场是我们星球上一个迷人且至关重要的方面。
文献翻译(二次电流层)
激光等离子体相互作用中磁重联引起的等离子体与二次电流层生成的研究摘要:以尼尔逊[物理学家、列托人，97，255001，（2006）]为代表的科学家首次对等离子体相互作用引起的磁重联进行了研究，该研究在固体等离子体层上进行，在两个激光脉冲中间设置一定间隔，在两个激光斑点之间可以发现一条细长的电流层（CS），为了更加贴切的模拟磁重联过程，我们应该设置两个并列的目标薄层。
实验过程中发现，细长的电流层的一端出现一个折叠的电子流出区域，该区域中含有三条平行的电子喷射线，电子射线末端能量分布符合幂律法则。
电子主导磁重联区域强烈的感应电场增强了电子加速，当感应电场处于快速移动的等离子体状态时还会进一步加速，另外弹射过程会引起一个二级电流层。
正文:等离子体的磁重联与爆炸过程磁能量进入等离子体动能和热能能量的相互转换有关。
发生磁重联的薄层区域加速并释放等离子体[1-5]。
实验中磁重联速度与太阳能的观察结果大于Sweet-Parker与相关模型[4-6]的标准值，这是由霍尔电流和湍流[7-12]引起的。
二级磁岛以及该区域释放的等离子体可以提高磁重联速度，当伦德奎斯特数S﹥104[13]时二级磁导很不稳定。
这些理论预测值与近地磁尾离子扩散区域中心附近的二级磁岛观察值相符[14]，激光束与物质的相互作用的过程中，正压机制激发兆高斯磁场（▽ne×▽Te）生成[15-16]。
以尼尔逊[17]为代表的科学家首次运用两个类似的的激光产生的等离子体模拟磁重联过程。
尼尔逊[17]与Li[18]等人实验测量数据为磁重联的存在提供了决定性的证据，他们运用了随时间推移的质子偏转技术来研究磁拓扑变化，除此之外尼尔逊[17]等人观察到高度平行双向等离子喷射线与预期的磁重联平面成40°夹角。
本次研究调查了自发磁场的无碰撞重联，激光等离子体相互作用产生等离子体，为了防止磁场与等离子体连接在一起实验过程使用了两个共面有一定间隔的等离子体。
Effect of Static Magnetic Field on Extracellular P
August 2013, Vol. 7, No. 8, pp. 796-801Journal of Life Sciences, ISSN 1934-7391, USAEffect of Static Magnetic Field on Extracellular Proteins Synthesis in Escherichia coliAshti M. Amin, Fouad Houssein Kamel and Saleem S. QaderMedical Technical Institute, University of Polytechnic, Erbil 44001, IraqReceived: April 07, 2013 / Accepted: June 14, 2013 / Published: August 30, 2013.Abstract: Escherichia coli type 1 was used as a model system to determine whether static magnetic fields are a general stress factor. The bacterial broth culture were exposed to different magnetic force (400, 800, 1200 and 1600 Gauss) with incubation at 37 °C for different times (24, 48 and 72 hrs) under aerobic conditions. The response of the cells to the magnetic fields was estimated from the change in total protein synthesis by using spectrophotometer at 550 nm and by using of SDS-PAGE (Sodium dodecyl sulfate- polyacrylamide gel electrophoresis). Results concluded that was approximately no reproducible changes qualitatively in extracellular proteins were observed in the SDS-PAGE electrophoresis and did not act as a general stress factor. While, increases in the level of extra-cellular synthesis were observed using different magnetic field exposed samples when compared with the control.Key words: Magnetic field, optical density, Escherichia coli, extracellular protein, electrophoresis.1. IntroductionA magnetic field is the area of influence exerted by a magnetic force. This field is normally focused along two poles. These poles are usually designated as north and south. However these directions are not the only two that a magnetic field can have. Most magnetic objects are composed of many small fields called domains [1]. The literature on biomagnetic effects on the growth and development of various organisms has been quite extensive showing both positive and negative findings. Among the positive findings attributed to strong magnetic fields are: altered growth rate, enzyme activities, cellular metabolism, DNA synthesis and animal orientation [2].In this project, the authors tried to detect the effects of magnetic field on E. coli protein synthesis and its activity. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymesCorresponding author: Fouad Houssein Kamel, Ph.D., Assist. Prof., research fields: biophysics, nanotechnology. E-mail:*********************.that catalyze biochemical reactions and are vital to metabolism [3].In most bacteria, the most numerous intracellular structure is the ribosome, the site of protein synthesis in all living organisms. All prokaryotes have 70 S (where S = Svedberg units) ribosomes. The 70 S ribosome is made up of 50 S and 30 S subunits [4].Proteins are lengthy chains of amino acids which are folded back upon themselves. The nature of a protein is determined both by the amino acid chain and by the way in which the protein is folded [5].The mode of gene expression affects the location of the protein produced. The proteins may either be located in the cytoplasm of E. coli or secreted though the cell membrane [6].Genes encoded in DNA are first transcribed into pre-messenger RNA (mRNA) by proteins such as RNA polymerase. In prokaryotes like E. coli the mRNA may either be used as soon as it is produced, or be bound by a ribosome after having moved away from the nucleoid. The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 20 amino acids per second[7].All Rights Reserved.Effect of Static Magnetic Field on Extracellular Proteins Synthesis in Escherichia coli797The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass, which is normally reported in units of daltons (synonymous with atomic mass units), or the derivative unit kilodalton [8].To perform in vitro analysis, a protein must be purified away from other cellular components. This process usually begins with cell lysis, in which a cell’s membrane is disrupted and its internal contents released into a solution known as a crude lysate. The resulting mixture can be purified using ultracentrifugation, which fractionates the various cellular components into fractions containing soluble proteins; membrane lipids and proteins; cellular organelles and nucleic acids. Precipitation by a method known as salting out can concentrate the proteins from this lysate. Various types of chromatography are then used to isolate the protein or proteins of interest based on properties such as molecular weight, net charge and binding affinity [9].The level of purification can be monitored using various types of gel electrophoresis like SDS-PAGE if the desired protein’s molecular weight and isoelectric point are known, by spectroscopy if the protein has distinguishable spectroscopic features, or by enzyme assays if the protein has enzymatic activity. Additionally, proteins can be isolated according their charge using electro focusing [8].2. Materials and MethodsBacterial suspension of Escherichia coli which was isolated from urine sample and cultured on MacConkey agar will be inoculated in to five groups of tube containing nutrient broth media and exposed each one of these four tubes in one of magnetic field which were prepared with different forces including 400, 800, 1200, 1600 G and measured by Teslometer in Physical Department of College of Science. The tube number five as a control without magnetic power, all of these tubes incubated separately for 24, 48 and 72 hrs at 37 ºC. The inoculation of API kit (BioMerieux Company) with bacteria from each groups were performed separately to identify the enteric bacteria type [8]. A plastic strip holding twenty mini-test tubes is inoculated with a saline suspension of a pure culture. This process also rehydrates the desiccated medium in each tube. A few tubes are completely filled [7], and some tubes are overlaid with mineral oil such that anaerobic reactions can be carried out (ADH, LDC, ODC, H2S, URE) [10].After incubation in a humidity chamber for 18-24 hrs at 37 °C, the color reactions are read. Note especially the color reactions for amino acid decarboxylations (ADH through ODC) and carbohydrate fermentations (GLU through ARA). The amino acids tested are (in order) arginine, lysine and ornithine. Decarboxylation is shown by an alkaline reaction (red color of the particular pH indicator used). The carbohydrates tested are glucose, mannitol, inositol, sorbitol, rhamnose, sucrose, melibiose, amygdalin and arabinose. Fermentation is shown by an acid reaction (yellow color of indicator). Hydrogen sulfide production (H2S) and gelatin hydrolysis (GEL) result in a black color throughout the tube. A positive reaction for tryptophan deaminase (TDA) gives a deep brown color with the addition of ferric chloride [10].The identification and separation of proteins were measured by SDS-PAGE (sodium dodecyl sulfate- polyacrylamide gel electrophoresis). According to API test, it can be known which types of proteins in the experiment have effected by magnetic field, so these proteins should be separated by SDS-PAGE method. Proteins separate by charge when exposed to an electric field. In order to separate proteins electrophoretically by size, they are first mixed with SDS, a negatively charged detergent. SDS binds to all proteins in the mixture and denatures them so that each molecule assumes a random coil configuration and becomes negatively charged. Thus, each protein will migrate toward the anode during electrophoresis, and its rate of migration will depend on its size, larger protein take longer to slither through the gel matrix, while smallerAll Rights Reserved.Effect of Static Magnetic Field on Extracellular Proteins Synthesis in Escherichia coli 798one migrate more rapidly through the gel matrix. At the end, the proteins in the gel are visualized by Coomassie brilliant blue (250 R), and the particular banding pattern, or fingerprint, of each bacterial samples can be discerned by comparing with protein marker [9].The concentration and activity of the extracellular enzymes (proteins) are measured by Total Protein kit (Biuret Method Ready for use). Total proteins were measured for both treated and non treated groups by spectrophotometer and by using Biolabo reagents so high rate of proteins may be caused by an increased in the concentration of specific proteins [11]. 1 mL of total protein reagent which contain (sodium hydroxide, Na-K tartrate, potassium iodide and copper 11 sulfate) mix with 20 µL bacterial protein for each group separately, 1 mL of reagent mix with 20 µL standard (which contain Bovine Albumin 6 g/dL) and 1 mL of reagent mix with 20 µL ddH2O as reagent blank. Mix well, let stand for 10 minutes at room temperature, record absorbance at 550 nm against reagent blank [11].3. ResultsIn this project, the E. coli was used as a model system to determine the magnetic fields (MFs) effects. Table 1 and Fig. 1 show the change in the E. coli type 1 enzymes such as ADH, CIT and GEL. It is clear from Table 1 and Fig. 1 that the bacterial exposure period 24 hrs to different forces of SMF (400, 800, 1200 and 1600 G), appears that treating bacterial cells can inhibit or promote enzyme activity according to API test, these results are in a good agreement with Gremion et al. [12]. The literature on biomagnetic effects on the growth and development of various organisms has been quite extensive showing both positive and negative findings. Among the positive findings attributed to strong magnetic fields are: altered growth rate, enzyme activities, cellular metabolism, DNA synthesis and animal orientation.Resulted in the inhibition of ADH, CIT and GEL enzymes at 24 hours incubation time (Table 1 and Fig.1) but 48 hrs and 72 hrs incubation times shows that only ADH and CIT are effected to SMF, as shown in Table 2 and Fig. 2. By this test the E. coli which were type 1 could be identified.SDS-Gel for E. coli to identify bands that affected by different forces of magnetic fields, with this experiment the authors wanted to isolate the proteins that are affected by magnetic forces. 10% SDS-PAGE stained with Coomassie for five different samples of the E. coli, as shown in Fig. 3. Indeed, normal bands of approximately 86, 78, 60, 58, 56, 43, 48, 34, 27 and 20 kDa were observed in the presence of E. coli suspension, lysozyme and magnetic fields were used in this experiment.Total proteins were measured for both treated and non treated groups by spectrophotometer at 550 nm and by using Biolabo reagents so high rate of proteins may be caused by an increased in the concentration of specific proteins, as seen in Table 3.4. DiscussionExposing of bacteria to different forces of magnetic fields leads to change the bacteria enzymes according to API test these results are in a good agreement with Gremion et al. [13]. The literature on biomagnetic effects on the growth and development of various organisms has been quite extensive showing both positive and negative findings. Among the positive findings attributed to strong magnetic fields are:Table 1 The API test for E. coli samples with magnetic forces and without at 24 hrs.24 hrsARAAMYMELSACRHASORINOManGLUGELVPINDTDAUREH2SCITODCLDCADHONDGControl+-++++-++--++---++++400+-++++-++--++--+++-+800+-++++-+++-++--+++-+1200+-++++-++--++--+++-+1600+-++++-++--++--+++-+All Rights Reserved.Effect of Static Magnetic Field on Extracellular Proteins Synthesis in Escherichia coli 799Fig. 1 The API test for E. coli samples with magnetic forces at 24 hrs.Table 2 The API test for E. coli at 48 hrs and 72 hrs.48 & 72hrs ARAAMY MEL SAC RHA SOR INO Man GLU GEL VP IND TDA URE H 2S Cit ODC LDC ADH ONDG Control + - + + + + - + + - - + + - - - + + + + 400 + - + + + + - + + - - + + - - + + + - + 800 + - + + + + - + + - - + + - - + + + -+ 1200 + - + + + + - + + - - + + - - + + + - + 1600+-++++-++--++--+++-+Fig. 2 The API test for E. coli at 48 hrs and 72 hrs.altered growth rate, enzyme activities, cellular metabolism, DNA synthesis and animal orientation. According of the SDS-PAGE, the bacterial cells were exposed to different forces of magnetic fieldunder aerobic conditions (24 hrs), no reproduciblechanges were observed in the SDS-gel when compared with the control it means that no effect ofthe different forces of magnetic fields were detectedAll Rights Reserved.800Fig. 3 SDS-g G; 4: 800 G; 5Table 3 Th measured by Samples in different MF Control 400 G 800 G 1200 G 1600 Gwhen compa 3, it can be field causes samples whe 5. Conclus The bacte are effected According t forces of ma with the c activity are total protein Effect of St gel for E. coli t 5: 1200 G; 6: 1he total protei spectrophotom ncubation in forces ared with the seen that the the increase en compared sionserial enzymes to magnetic the SDS-PAG agnetic fields ontrol. The effected by n test.tatic Magneti to identify ban 1600 G.in of E. coli meter. nTotal protein 348.5 448.4 401.2 398.3 351.01control. Acc e different fo of total prote with the cont s, such as AD field accord GE, no effect was detected concentratio magnetic fie ic Field on Ex 6nds that affecte for each grou at 550 nmcording the T orces of magn ein in all expo trol.DH, CIT and G ding to API t t of the diffe d when comp on and prot elds accordin xtracellular P5 4 ed by different up isTablenetic osed GEL ests.erent ared teins ng to Ac T the coll Cen stud Re [1][2][3][4][5]roteins Synth 3 2 1t forces of mag knowledgm The authors g Rizgari Teac lection. Grate nter staff grou dent of Scienc ferencesD. Todorovi Rauš, L. Nik field (50 mT Tenebrio (Ins (2013) 44-50E. Aarholt, low-frequenc Phys Med Bi A.R. Davis, W the Living Sy K. Mitra, C. S protein-condu Nature 438 (2C.M. Dobson folding, in:hesis in Esch 1gnetic fields. 1:mentsgratefully ack ching Hospita eful thanks f up, and also ce College fo ć, T. Markovi ćkoli ć, et al., The T) on developm secta, Coleopte .E.A. Flinn, cy magnetic fie ol 26 (4) (1981W.C.Jr. Rawls, ystem, Acres, U Schaffitzel, T. S ucting channel b 2005) 318-324.n, The nature R.H. Pain (E herichia coli: Marker; 2: C knowledge th al laboratorie for the Medi to Sazan Qad or her help in , Z. Proli ć, S. e influence of ment and moto era), Int J Radi C.W. Smith elds on bacteria ) 613-621. Magnetism and USA, Kansas Ci Shaikh, Structur bound to a trans and significan Ed.), Mechanism 150 10080 60 50 40 30 25Control; 3: 400he support of es for sample cal Research dir the Ph.D.the analysis.Mihajlovi ć, S.static magnetic or behaviour of iat Biol. 89 (1)h, Effects of al growth rate,d Its Effects on ity, 1974. re of the E. coli slating ribosom nce of protein ms of Protein 0 fe h . .c f ) f , n i m, n nAll Rights Reserved.Effect of Static Magnetic Field on Extracellular Proteins Synthesis in Escherichia coli801Folding, Oxford University Press, Oxford shire, 2000, pp.1-28.[6] F.A. Marston, The purification of eukaryotic polypeptidessynthesis in E. coli,Biochem J. 240 (1) (1986 November15) 1-12.[7]L. Potenza, L. Ubaldi, R. De Sanctis, R. De Bellis, L.Cucchiarini, M. Dachà, Effects of a static magnetic fieldon cell growth and gene expression in Escherichia coli,Mutat Res. 561 (1-2) (2004 Jul 11) 53-62.[8] A. Fulton, W. Isaacs, Titin, a huge, elastic sarcomericprotein with a probable role in morphogenesis, BioEssays13 (4) (1991) 157-161.[9]J. Wiltfang, N. Arold, V. Neuhoff, A new multiphasicbuffer system for sodium dodecyl sulfate-polyacrylamidegel electrophoresis of proteins and peptides with molecular masses 100,000-1,000, and their detection withpicomolar sensitivity, Electrophoresis 12 (5) (1991)352-366.[10]J. Hey, A. Posch, A. Cohen, Fractionation of complexprotein mixtures by liquid-phase isoelectric focusing,Methods in Molecular Biology 424 (2008) 225-239.[11]P.C. Appelbaum, J. Stavitz, M.S. Bentz, Four methodsfor identification of gram-negative no fermenting rods:Organisms more commonly encountered in clinicalSpecimens, J. Clin. Microbiol. 12 (1980) 271-278.[12] C.A. Burtis, E.R. Ashwoo, Text Book of ClinicalChemistry, 3rd ed., W.B. Saunders, 1999, pp. 477-530. [13]G. Gremion, D. Gaillard, P.F. Leyvraz, B.M. Jolles,Effect of biomagnetic therapy versus physiotherapy fortreatment of knee osteoarthritis: A randomized controlledtrial, J Rehabil Med. 41 (13) (2009 Nov) 1090-1095.All Rights Reserved.。
巨磁电阻效应的英语
巨磁电阻效应的英语Giant magnetoresistance effect, huh? That's a mouthful! But let's break it down. Basically, it's this crazy phenomenon where the resistance of certain materials changes significantly when a magnetic field is applied.It's like they're super sensitive to magnets.Now, imagine this: you've got a material and you give it a little magnetic push. Suddenly, its resistance to electricity goes up or down by a huge amount. That's what we call giant magnetoresistance. And it's not just anylittle change; it's huge!One of the coolest things about this effect is how it's being used in tech. You know, like in those tiny sensors that can detect magnetic fields with incredible precision? They rely on this effect to work. It's like having a superpower to sense magnetic fields.And speaking of superpowers, imagine if we couldharness this effect for even more amazing things. Like, controlling robots with just our thoughts or something crazy like that. The possibilities are endless, really.So, in a nutshell, giant magnetoresistance is this fascinating effect where materials change their resistance a lot when you apply a magnetic field. It's not just a science experiment; it's shaping the future of technology in ways we can only imagine.。
Effects of magnetic fields on biological systems
Effects of magnetic fields onbiological systems磁场对生物系统的影响磁场是我们周围的一个普遍存在的自然现象，它是指物体围绕着自己的轴旋转以创建一个绕轴旋转的电场。
磁场可以直接或间接地影响与之相互作用的物质，其中包括生物系统。
在现代科学中，人们已经开始意识到磁场对生物系统的影响，研究称为磁生物学。
磁场的来源可以是自然的，例如地球磁场，也可以是人造的，例如电磁设备和磁共振成像仪。
现代人类在各个方面离不开电磁设备，如手机、电视、电脑等，而磁共振成像仪已经成为诊断医学中不可或缺的工具。
然而，这些设备产生的磁场是否对生物系统产生负面影响是一个值得关注的问题。
生物系统受磁场影响的机制还不完全清楚，但已经发现存在一些可能的影响机制，例如：1. 对于含有大量铁分子的细胞，磁场可以改变其代谢。
铁是许多生物分子的组成部分，包括血红蛋白和储存铁的蛋白。
一些研究表明，强磁场可能会改变铁的代谢，导致其离子状态改变、释放或在组织中聚集。
2. 磁场可以改变细胞膜的状态。
细胞膜起着保护和选择性渗透的作用。
一些研究表明，磁场可能会改变细胞膜的物理状态，从而影响细胞与环境之间的交互。
3. 磁场可能会影响生物分子的活性。
生物分子的活性受其周围环境的影响，而磁场可能会改变这一环境，从而影响分子的构象、反应速率和产物选择性。
具体而言，磁场对人类和其他生物的影响方式和级别尚未完全确定。
一些研究表明，磁场可能会对人类和其他动物的生理和心理机能产生不利影响，例如：1. 磁场可能会干扰人类和动物的睡眠。
一些研究表明，磁场可能会干扰人类和动物的大脑活动，从而影响睡眠质量。
2. 磁场可能会导致头痛和其他健康问题。
一些研究表明，长时间暴露在较强的磁场中可能会导致头痛、恶心、眩晕等健康问题。
3. 磁场可能会影响人类和动物的行为。
一些研究表明，磁场可能会影响动物的迁徙和导航能力，也可能会影响人类的认知和情绪。
地球磁场对大脑的影响
地球磁场对大脑的影响英文回答：The influence of the Earth's magnetic field on the brain is a fascinating topic that has been studied by scientists for many years. While the exact mechanisms are not fully understood, there is evidence to suggest that the magnetic field can have an impact on brain function and behavior.One way in which the Earth's magnetic field may affect the brain is through its influence on the production and release of certain neurotransmitters. Neurotransmitters are chemicals that allow nerve cells to communicate with each other, and they play a crucial role in regulating mood, cognition, and other brain functions. Studies have shown that exposure to magnetic fields can alter the levels of certain neurotransmitters, such as serotonin and dopamine, in the brain. These changes in neurotransmitter levels can in turn affect mood and behavior.For example, research has found a link between magnetic field exposure and changes in sleep patterns. The Earth's magnetic field is known to fluctuate throughout the day, and these fluctuations have been shown to affect the production of melatonin, a hormone that regulates sleep-wake cycles. When the magnetic field is disrupted, it can disrupt melatonin production, leading to sleep disturbances and other sleep-related issues.In addition to neurotransmitter levels, the Earth's magnetic field may also influence the brain through its impact on electrical activity. The brain generateselectrical signals that are essential for communication between neurons. It has been suggested that magnetic fields can influence these electrical signals, potentiallyaltering brain function.One study, for instance, found that exposure to a magnetic field can affect the brain's response to visual stimuli. Participants in the study were exposed to a magnetic field while viewing images, and their brainactivity was measured using electroencephalography (EEG). The results showed that the magnetic field altered the brain's response to the visual stimuli, suggesting that magnetic fields can modulate neural activity.It is important to note that the effects of the Earth's magnetic field on the brain are still not fully understood, and more research is needed to determine the exact mechanisms at play. Additionally, it is worth mentioning that the influence of the Earth's magnetic field on the brain is likely to be subtle and may vary from person to person.中文回答：地球磁场对大脑的影响是一个引人入胜的课题，科学家们已经研究了多年。
2019年职称英语理工类A级新增文章篇目(三)
2019年职称英语理工类A级新增文章篇目（三） Solar Power without Solar Cells太阳能的太阳能电池A dramatic and surprising magnetic effect of light discovered by University of Michigan1 researchers could lead to solar power without traditional semiconductor-based solar cells.戏剧性的和令人惊讶的磁光效应发现michigan1大学研究人员可能导致太阳能没有传统的半导体太阳能电池。
The researchers found a way to make an "optical battery," said Stephen Rand, a professor in the departments of Electrical Engineering and Computer Science, Physics and Applied Physics.研究人员发现了一种使“光电池，说：”史蒂芬兰德，系教授电气工程与计算机科学，物理和应用物理。
Light has electric and magnetic components. Until now, scientists thought the effects of the magnetic field were so weak that they could be ignored. What Rand and his colleagues found is that at the right intensity, when light is traveling through a material that does not conduct electricity, the light field can generate magnetic effects that are 100million times stronger than previously expected. Under these circumstances, the magnetic effects develop strength equivalent to a strong electric effect.光的电场和磁场组成部分。
磁场的生物效应(biologicaleffectofmagneticfield)物理小百科
磁场的生物效应（biologicaleffectofmagneticfield）物理小
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快一起来阅读磁场的生物效应(biologicaleffectofmagneticfield)物理小百科吧~
磁场的生物效应（biologicaleffectofmagneticfield）
磁场的生物效应(biologicaleffectofmagneticfield)
研究磁场生物效应的领域也称为磁生物学。
其中包括地磁场和人工磁场对生物的作用。
地磁场强度较弱，小于80A/m(1Oe)生物定向是地磁场作用的事例之一。
澳大利亚指南白蚁会定向筑巢，鲨鱼通过自身产生的电场对地磁场定向，Blakemore(1981年)发现螺旋菌能准确地游向北磁极方向，鸟类根据磁场和重力场定向。
K.V.Frisch对蜜蜂的舞蹈语言和地磁场作用机理的精心研究，在1973年获得了诺贝尔奖。
大量研究报道表明，一定条件的强磁场会影响生物大分子的构象和功能，会使染色体变异，影响DNA复制和蛋白质表达，刺激或抑制细胞生长，旋转磁场可打碎体内结石。
磁效应对组织、器官、神经系统乃至整体都有影响。
磁场的生物效应研究对生物工程和现代医学具有重要的意义。
由查字典物理网独家提供磁场的生物效应(biologicaleffectofmagneticfield)物理小百科，希望给大家提供帮助。
介绍地球磁场的作文英文
介绍地球磁场的作文英文The Earth's magnetic field is a powerful force that surrounds our planet, protecting it from the harmfuleffects of solar radiation.It is generated by the movement of molten iron in the Earth's outer core, creating a complex and ever-changing magnetic field that extends into space.This magnetic field is essential for life on Earth, as it helps to protect the atmosphere from being stripped away by solar winds and cosmic rays.Without the Earth's magnetic field, life as we know it would not be possible, as the harsh conditions of space would make our planet uninhabitable.The magnetic field also plays a crucial role in navigation, as it allows animals such as birds and sea turtles to navigate across long distances.In addition, the Earth's magnetic field has been used by humans for centuries for navigation and orientation, and it continues to be an important tool for modern technology, such as compasses and GPS systems.Overall, the Earth's magnetic field is a fascinating and essential part of our planet, providing protection, navigation, and a glimpse into the inner workings of the Earth.。
地球磁场在减弱的证据
地球磁场在减弱的证据英文回答：Evidence of Earth's Weakening Magnetic Field.The Earth's magnetic field, also known as the geomagnetic field, is generated by the movement of molten iron in the outer core of the planet. This magnetic field is crucial for protecting the Earth from harmful solar radiation and maintaining a stable climate. However, there is mounting evidence that the Earth's magnetic field is weakening.One piece of evidence is the observation of the South Atlantic Anomaly (SAA). The SAA is an area in the South Atlantic Ocean where the Earth's magnetic field is significantly weaker than in other regions. Satellites passing through this anomaly experience higher levels of radiation, which can affect their electronic systems. This anomaly has been expanding over the past few decades,indicating a weakening of the Earth's magnetic field.Another piece of evidence comes from studies of ancient rocks. Rocks contain tiny magnetic minerals that align with the Earth's magnetic field at the time of their formation. By analyzing these rocks, scientists can determine the strength and direction of the Earth's magnetic field in the past. These studies have revealed that the Earth's magnetic field has been weakening over the past few centuries.Furthermore, researchers have found that the rate of decline in the Earth's magnetic field has been accelerating in recent years. This rapid decline suggests that the weakening of the magnetic field is not a gradual process but rather a more significant and concerning phenomenon. If this trend continues, it could have significantimplications for our planet.The weakening of Earth's magnetic field has several potential consequences. One of the most significant is the increased exposure to solar radiation. The magnetic field acts as a shield, deflecting charged particles from the Sunaway from the Earth. Without a strong magnetic field, more solar radiation would reach the Earth's surface, increasing the risk of skin cancer and other health issues.Additionally, a weakened magnetic field could have implications for navigation systems that rely on magnetic compasses. The accuracy of compasses could be compromised, leading to errors in navigation. This could be particularly problematic for ships and aircraft that heavily rely on magnetic compasses for direction.In conclusion, there is compelling evidence that the Earth's magnetic field is weakening. The South Atlantic Anomaly, studies of ancient rocks, and the accelerating rate of decline all point to this concerning phenomenon. The implications of a weakened magnetic field range from increased exposure to solar radiation to potential navigation issues. It is crucial for scientists to continue monitoring and studying this phenomenon to better understand its implications for our planet.中文回答：地球磁场减弱的证据。
低强度工频磁场对脑片海马区sepsc发放特性的影响
低强度工频磁场对脑片海马区sEPSC 发放特性的影响王金海1，2，杜正高1，郑羽1，2，孔莹1，洪辉1，邱倩1（1.天津工业大学电子与信息工程学院，天津300387；2.天津市医学电子诊疗技术工程中心，天津300387）摘要：为研究磁场对脑片海马区自发兴奋性突触后电流（sEPSC ）的生物刺激作用，利用实际测量、数学建模和Comsol 软件对典型磁刺激装置进行建模与仿真，确定磁场暴露区的磁场强度和分布特性，并采用膜片钳实验对磁场刺激条件下大鼠离体脑片海马区sEPSC 进行了研究.结果表明：磁场强度从刺激器舌面处到脑片区衰减125倍左右，且磁场进入溶液后分布更加均匀；磁场强度越高，sEPSC 的幅值和频率越低，当磁场强度达到2mT 时，神经元sEPSC 的幅值、频率、半波长、上升时间和衰减时间显著下降，说明随磁场磁剂量增加，磁场抑制sEPSC 的发放.关键词：工频磁暴露；磁场强度；分布特性；脑片海马区；sEPSC ；发放特性中图分类号：Q689；TP391.9文献标志码：A文章编号：１６７１－０２４Ｘ（２０15）０4－００52－０6Effects of low intensity power frequency magnetic field on payment feature ofhippocampal sEPSC in vitro brain slicesWANG Jin-hai 1，2，DU Zheng-gao 1，ZHENG Yu 1，2，KONG Ying 1，HONG Hui 1，QIU Qian 1（1.School of Electronics and Information Engineering ，Tianjin Polytechnic University ，Tianjin 300387，China ；2.Center of Tianjin Medical Electronic Engineering Technology ，Tianjin Polytechnic University ，Tianjin 300387，China ）Abstract ：In order to investigate the biological stimulation of the magnetic field on the hippocampal spontaneous ExcitatoryPostsynaptic Current （sEPSC ）of the brain slices ，the actual measurement ，mathematical modeling and Comsol software simulation were used to model and simulate a typical magnetic stimulation device,the magnetic field in 鄄tensity and distribution characteristics of the exposed area were confirmed.And the hippocampal sEPSC in the vitro brain slices under the magnetic field was studied with the patch clamp experiment.The results showed that the magnetic field intensity decreases by 125times from the simulator to the brain slice ，and the magnetic field distributes uniformly in physiological solution.The higher the magnetic field dose ，the lower the amplitude and frequency of sEPSC.When the magnetic field intensity reaches 2mT ，the amplitude ，fequency ，half -wave width ，the rise time and decay time of neuron sEPSC decrease significantly.This results illustrated that with the increase of intensity of magnetic field ，the magnetic field suppresses the sEPSC release.Key words ：exposure to power frequency magnetic ；magnetic field intensity ；distribution characteristics ；hippocampus invitro brain slices ；spontaneous Excitatory Postsynaptic Current （sEPSC ）；payment feature收稿日期：2015-04-15基金项目：国家自然科学基金资助项目（61201106）；国家级大学生创新创业训练计划项目（201410058027）通信作者：王金海（1966—），男，博士，教授，研究方向为生物信息提取.E-mail ：*******************.cn随着科学技术的高速发展和人民生活水平的迅速提高，电力的广泛应用不可避免地引起越来越严重的电磁污染.近年来，人们开始关心这些弥散于我们周围的电磁场会对生物体尤其是人类产生何种影响，对电磁场生物效应的研究得到了各国学者的广泛关注.有研究表明，利用工频磁场对人体的中枢神经系统进行暴露辐射，结果显示人体的学习和预测能力出现下降、反应迟钝等现象[1]；且有报道显示，工频电磁场影响大鼠的空间记忆力[2]和小鸡的迂回学习能力[3].海马区是神经系统中主管学习和记忆的重要区域[4]，例如空间记忆、工作记忆和联系记忆等，临床新生儿的双侧海马损伤会造成严重的学习记忆障碍[5]；海马区还与一些神经疾病有关，报道显示其是阿尔兹海默病、癫痫等精神疾病主要的病变位置[6-7].也有报道显示，30mT 恒定磁场能够明显延长海马区神经细胞的平均存活时间，且平均存活时间是对照组的一倍以上[8].磁场作为一种物理因素，对运动的带电物质有洛伦兹力的作用.工频磁场刺激是否对细胞间的带电粒天津工业大学学报ＪＯＵＲＮＡＬＯＦＴＩＡＮＪＩＮＰＯＬＹＴＥＣＨＮＩＣＵＮＩＶＥＲＳＩＴＹ第34卷第4期２０15年8月Vol.34No.4August 2015DOI ：10.3969/j.issn.1671-024x.2015.04.011第4期子有磁场导向移动作用，从而影响到海马区神经元sEPSC 的电生理学特性？另外，研究低强度工频磁场对海马区脑片影响的报道也很少见.基于此，本文提出一种精确计算工频磁场作用于脑片区的磁剂量及其分布特性的研究方案，分析从磁场源到脑片区的磁剂量和分布特性，并讨论在该剂量下工频磁场对大鼠海马区sEPSC 发放特性的影响，为揭示工频磁场在海马区的生物效应奠定一定的理论和实验基础.1磁场刺激器建模仿真sEPSC 发放特性是衡量大脑海马组织功能强弱的一个重要指标，sEPSC 的发放反映海马神经元功能是否正常.通过上文可知，工频磁场对中枢神经及海马区神经细胞具有较大的影响.因此，精确计算作用在脑片上的工频磁场磁剂量对sEPSC 的检测具有重要的意义.本节将从实际测量、数学建模及Comsol 仿真3个方面对脑片区磁场强度进行建模仿真，考察脑片区的磁场强度和分布特性，保证脑片放置在暴磁区的最佳刺激位置，并从微观上定量确定磁场特性，为后续采用膜片钳技术分析sEPSC 的发放特性奠定基础.1.1磁场实际测量本实验自制磁场刺激器，磁路示例及等效电路如图1所示.磁路由马蹄形硅钢铁芯载体、培养皿中溶液、铁芯和培养皿间的空气3段材料组成.培养皿玻璃介质相应参数与空气相似，且所占空间很小，基本不影响磁场分布.其具体尺度参数为：铁芯采用冷轧硅钢片，厚2cm ，宽4cm ；线圈由直径0.8mm 漆包铜线绕制，匝数为310匝，舌面积为8cm 2；培养皿为玻璃材质，外壁和底部厚度均为1mm ，培养皿中装有人工脑脊液（arificial cerebrospinal fluid ，ACSF ）[9].具体材料参数如表1所示.自制圆形线圈外接50Hz 交流稳压电源，可产生0～100mT 交变磁场，通过改变线圈中电流大小，可以调节线圈产生的磁场强度.在实际应用工频磁场对脑片区进行磁场刺激时，首先需要通过PF-035型数字特斯拉计测得暴磁区即培养皿处的磁场强度，和实验所需磁场强度进行对比，然后通过调节线圈输入电流大小，得到实验所需磁场刺激强度.当线圈中输入电流分别为0.21、0.32和0.56A 时，测得中心暴露区的磁场大小为0.5、1和2mT ；且通过多点测量证实，在中心暴露区磁场分布基本均匀，满足实验要求.但是，在进行多组试验时，由于每组实验所需的磁场刺激强度是不相同的，通过不断对比磁场强度和调节线圈电流大小来得到所需磁场强度的方法不够严谨，既耗费人力又浪费大量时间.因此，本文尝试采用数学建模的方法，建立线圈电流强度与暴磁区磁场强度之间的关系式，通过确定输入电流的强度，使得暴磁区即培养皿处能够获得所需的磁场强度.1.2数学建模针对如图1所示的磁刺激器，假设磁性材料内磁感应强度是均匀的，其值等于平均半径处的磁感应强度.设磁路平均长度为L ，截面积为A ，磁导率为μ，若线圈为N 匝，有电流I ，则外加磁动势为V m .具体参数为：铁芯磁路长L 1=220mm 、铁芯和培养皿顶部空气磁路长L 2=8mm 、培养皿中溶液磁路长L 3=32mm ；培养皿、铁芯舌面积和空气截面积分别为A 1=7.52πmm 2、A 2=20×40mm 2、A 2.由于培养皿和铁芯之间的缝隙只有4mm 的距离，因此，铁芯中磁感线设定都通过培养皿，这里设定空气截面积和铁芯舌面积相同.根据磁路的计算原理，外加磁动势V m 为：V m =NI =t乙H 軖·d l 軆（1）磁性材料内的磁通为：椎=s乙B 軑·d S 軋=BA =μNIA L=V mL /μA（2）如果磁路由n 段组成，则：ni =1移椎iRm i=V m （3）式中：椎i 为第i 段的磁通；R m i 为第i 段的磁阻，磁阻计表1材料参数Tab.1Material parameters材料名电导率/（S ·m -1）介电常数/（F ·m -1）磁导率/（H ·m -1）空气1.0011铜线59980000.0011铁芯70000000.0012530人工脑脊液 1.79109[10]1玻璃培养皿1.0021图1实际工频磁路示例及其等效电路Fig.1Actual circuit and equivalent cicuit（a ）磁路示例（b ）等效电路V m =NI+-L 2+L 2′椎L 3L 1L 1A 1L 2L 3L 2′A 2NIL 1王金海，等：低强度工频磁场对脑片海马区sEPSC 发放特性的影响53——天津工业大学学报第34卷算如下：R =R 1+R 2+R 3（4）式中：R 1=L 1/u 1A 2；R 2=（L 2+L 2′）/u 2A 2；R 3=L 3/u 3A 1；L 1、L 2+L 2′、L 3分别为铁芯、空气间隙和培养皿溶液中的磁路长度；u 1、u 2和u 3分别为铁芯、空气、溶液中的磁导率；A 2和A 1分别为铁芯（空气）和溶液的截面积；R 1、R 2和R 3分别为铁芯、空气和溶液中的磁阻.由式（1）—（4）得培养皿中磁场强度（B ）计算公式为：B =V m /（RA 1）（5）根据式（5）计算可知，当线圈中分别通入0.083、0.85和1.65A 的电流时，空气间隙中磁场强度为0.5、1和2mT.通过数学建模，可以很快获得实验所需的暴磁区磁场强度.但是，该数学模型是以模型中的几何中心线为磁路的，和实际磁路相差明显；模型中没有考虑溶液的浓度、离子密度、电导率等参数，建模得到的结果和实际测量有一定误差.另一方面，实际测量中，由于特斯拉计精确度和灵敏度的限制以及空间上具体测量的难度，磁场分布的均匀性很难测量，数学建模也很难精确地确定磁场分布的情况，而磁场对脑片的刺激是整个区域的刺激，对于磁场均匀性需做进一步研究.因此，本文采用Comsol 软件进行进一步建模分析.1.3Comsol 建模仿真Comsol Multiphysics 是一款强大的有限元法分析软件.研究者可以根据实际情况选择不同的仿真环境和变量值，在结果中可清晰地看到物理场的分布情况.本文所研究的离体脑片及细胞的磁场辐射剂量在几个mT 范围内，在磁场刺激的时间段内，溶液的温度热效应忽略不计.在磁场刺激的过程中，脑片存活的环境是人工脑脊液.人工脑脊液和空气的区别在于前者介质为弱导体，对作用到脑片上的磁剂量和分布会产生一定影响，因为其包含生理溶液等因素的干扰，增加了磁场计算的复杂性.Comsol 仿真中能够设置溶液电导率、磁导率和密度等实际参数，通过仿真计算得到与实际所需磁场应输入电流大小最接近的电流值，并且从仿真结果中可以看到磁场强度和磁场强弱分布特性.为精确定量作用于脑片上各点磁场的剂量值，对sEPSC 发放特性测量提供精确的磁场刺激环境，本文采用Comsol Multiphysics 中的AC/DC 模块仿真建模与计算求解.建模时，对磁场刺激器采取1×1的比例建模，设定培养皿中装入空气和ACSF 两种不同的材料，材料参数根据实际参数设置，仿真出空气间隙磁场强度的大小和分布特性以及该磁场强度进入溶液中的大小和分布特性，并最终针对孵育环境中脑片上磁场的定量精确分布特性展开研究.当线圈中电流大小分别为0.105、0.20和0.42A 时，经Comsol 仿真得到暴磁区磁场强度为0.5、1和2mT 的磁场分布状况，进而确定脑片区的磁场分布特性，结果如图2所示.图2脑片区磁场强度的分布图Fig.2Distribution of magnetic field intensity in brain area（b ）培养皿中介质为人工脑脊液（a ）培养皿中介质为空气0.5mT1mT2mT0.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.1250.1240.1230.1220.1210.1200.1190.1180.1170.1160.1150.1560.1600.1640.1580.1620.51mT 0.510.470.480.490.50 1.07mT 1.071.061.051.041.031.021.011.000.990.992.09mT 2.082.062.042.022.001.981.961.941.936.36×10-3mT 6.3×10-36.2×10-36.1×10-36.0×10-35.9×10-35.8×10-35.79×10-30.01mT 14×10-312.7×10-30.010.03mT 27.3×10-324.9×10-30.02弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m弧长/m54——第4期根据离体海马区膜片钳实验，选择溶液中间直径1cm圆形区为脑片区，由于实验所用的脑片厚度范围在350~500μm，考虑到溶液中磁场在此厚度内的强度或分布性相差很小，且小尺度模型在Comsol画网格时大大增加了自由度数量，增加求解过程和时间，所以本文采取截面形式进行分析.图上方0.5、1和2mT数值表示舌面处磁场强度大小.对比图2（a）和图2（b）可以看出，磁场在铁芯舌面处的磁场强度是脑片上磁场强度的125倍左右，且磁场在溶液中分布更加均匀.2脑片sEPSC发放特性的测量膜片钳技术是测量脑片或细胞电生理特性的主要方法，具有高精度高稳定性的特点.本文通过建模仿真得到实验所需的准确磁场刺激强度，在此磁场强度刺激下通过膜片钳技术记录脑片的sEPSC，分析磁场刺激对sEPSC发放特性的影响.2.1膜片钳实验本实验采用中国医学科学院所属放射医学研究所实验动物中心提供的SD（Sprague Dawley）大鼠[11]，鼠龄18~25d，雄性.并根据文献[12]的方法配置ACSF、切片液和全细胞记录sEPSC电极内液.对大鼠进行断头取脑，置于0~4°C的ACSF中1~2min，取出后置于震动切片机上切成350μm厚的脑片.室温下，将脑片放入ACSF中，并通入95% O2+5% CO2混合气体，孵育45min[13].孵育后，在显微镜下选取活性较好的脑片进行磁场刺激.准备好磁刺激装置并设定磁刺激器暴磁区的磁场强度（0、0.5、1和2mT），将培育好的脑片放入培养皿中，并移到刺激器的暴磁区.实验中脑片分为4组，分别是对照组（0mT）和工频磁场刺激实验组（0.5、1和2mT），10片一组，每片脑片上取活性最好的4个神经细胞来做实验，每组实验磁场暴露20min.经过40d试验后，最终得到142个有sEPSC发放的神经元细胞，本文从中选取122个发放幅值较大的数据进行论述.在室温下（20~23°C），利用EPC10-USB膜片钳放大器（HEKA，德国）进行全细胞膜片钳记录，通过Pulse软件设定好实验参数、刺激波形及数据采集.采用Minianalysis软件和Origin8.0统计软件分析实验数据.数据经P/N漏减处理后，进行统计与分析，结果用Means±SD表示.差异显著性检验采用单因素方差（one-way ANOVE）分析，post-hoc检验采用Scheffe检验方法进行统计，*P<0.05，**P<0.01，***P<0.001为显著性的3个层次[14].2.2脑片sEPSC的发放特性分析在本文试验条件下，大鼠海马CA1区锥体神经元sEPSC经0、0.5、1和2mT磁场刺激下的波形如图3所示，其幅值和频率如图4所示.由图3和图4可知，在0.5、1、2mT磁场强度下分别刺激20min后，大鼠海马CA1区锥体神经元sEPSC 发放的幅值和频率均下降；且随磁场剂量增高，sEPSC 的幅值和频率降低.由数据分析可知，在0.5mT磁场刺激下，sEPSC的幅值与正常对照组相比下降2046.37 4000350030002500200015001000500幅值/pA0.512图4sEPSC的幅值和频率Fig.4Amplitude and frequeney of sEPSC54321频率/Hz0.5121pA1280ms（a）0mT（b）0.5mT（c）1mT（d）2mT图3不同磁场强度刺激后sEPSC的波形Fig.3Waveform of sEPSC by different magnetic field intensity stimulation磁场强度/mT磁场强度/mT（a）幅值（b）频率王金海，等：低强度工频磁场对脑片海马区sEPSC发放特性的影响55——天津工业大学学报第34卷pA ，降幅达到49.8%；而在1和2mT 磁场刺激下，降幅增至80.3%和98%，说明1和2mT 磁场刺激显著抑制sEPSC 发放的幅度.在频率发放方面，0.5、1和2mT 磁场刺激下，频率的降幅达到40%、67.3%和75.6%，同样说明工频磁场对海马区CA1区神经元sEPSC 的频率发放发挥抑制作用.根据单因素方差（one-way ANOVE ）分析显示，磁场作用明显抑制sEPSC 的幅值和频率发放，并且均有显著性差异（F （3，471）=137.32，P <0.01；F （3，526）=7.03156，P <0.05）.2mT 磁场作用下神经元sEPSC 的幅值明显低于对照组，通过post-hoc 检验表明，2mT 磁场刺激后，对sEPSC 幅值和频率的抑制程度尤为显著（F =73.52，P <0.001；F =5.85，P <0.05）.说明磁场已经影响到神经元的活性，导致神经元细胞膜的电生理特性降低.图5所示为大鼠海马CA1区锥体神经元单个sEPSC 的半波宽、上升时间和衰减时间的发放特性.由图5可知，0.5、1、2mT 磁场作用20min 后，大鼠海马CA1区锥体神经元单个sEPSC 的半波宽、上升时间和衰减时间的发放特性相似.与对照组相比，0.5和1mT 磁场作用后，sEPSC 的半波宽分别上升了0.29和0.64ms ，上升时间分别上升了0.27和0.49ms ，衰减时间上升了0.4和1.0ms .单因素方差（one -way ANOVE ）分析显示，0.5、1mT 磁场作用使sEPSC 的半波宽、上升时间和衰减时间显著性增加（F （2，468）=67.49，P <0.01；F （2，468）=20.51，P <0.01；F （2，468）=87.12，P <0.01）.由此说明，磁场刺激延长了海马CA1区锥体神经元sEPSC 的发放周期，从而降低了其发放频率，说明磁场刺激对脑片sEPSC 的频率发放有抑制作用.当增加磁场刺激剂量至2mT 后，与对照组相比，sEPSC 的半波宽、上升时间和衰减时间分别下降了0.63、0.79和0.3ms ，降幅达到42.3%、50.3%和23.4%.post-hoc 检验表明，与对照组相比，2mT 磁场作用显著抑制了sEPSC 半波宽、上升时间和衰减时间的发放（F =13.19，P <0.001；F =6.71，P <0.001；F =25.31，P <0.001）.在2mT 磁场刺激下，脑片上神经元活性下降，细胞膜上离子通道活性随之下降，细胞突触间离子交换能力下降，因此，sEPSC 的半波宽、上升时间和衰减时间显著下降，说明2mT 磁场刺激显著抑制了sEPSC 的半波宽、上升时间和衰减时间的发放.综上所述，工频磁场抑制海马区神经元sEPSC 的发放特性，且随磁场强度的增加，磁场对sEPSC 幅值和频率的抑制越来越强，随之抑制sEPSC 半波、上升时间和衰减时间特性.这可能是由于：磁场的洛仑兹力能够影响带电粒子的移动，因此，磁场能够影响细胞膜的离子通透性和膜两侧的电位，导致机体内细胞内外电位失衡，从而影响带电物质的转移过程，产生一些生物效应.另外，在一些生物学的系统里，反磁体分子以高度规则方式排列，并以平行的反磁体矢量连接发挥作用[15].低强度工频磁场产生的洛伦兹力使得突触间带电状态的谷氨酸和Ca 2+、Na +、K +等离子非正常移动，不能与突触后膜上相应受体结合，从而影响到sEPSC 的放电特性.本实验结果提示，低强度磁场的生物刺激作用与细胞突触膜离子通道特性及通道构形变化有关，但仍需进一步从分子生物学及细胞信号转导方面进行分子层面的理论和实验验证.3结束语为了研究磁场对脑片sEPSC 电生理特性的生物刺激作用，本文设计了适用于离体脑片实验的50Hz 、21衰减时间/m s0.5122.01.51.00.50.0上升时间/m s0.51221半波宽/m s0.512图5单个sEPSC 半波宽、上升时间和衰减时间的发放特性Fig.5Issuance characteristics of half-wave width,rise time and decay time of single sEPSC磁场强度/mT（b ）上升时间磁场强度/mT（a ）半波宽磁场强度/mT（c ）衰减时间56——第4期0～100mT磁信号发生器，通过实际测量、理论公式计算及Comsol建模仿真，得到磁场刺激器暴磁区的磁场强度和分布，最终确定作用到脑片上的磁场强度大小及分布情况.在此基础上，采用全细胞膜片钳技术，针对大鼠海马CA1区的锥体神经元细胞，记录由工频磁场诱发的sEPSC幅值及发放频率，在细胞水平上研究工频磁场对兴奋性突触后电流传递的影响.以sEPSC 的幅值、频率、半波长、上升时间和衰减时间为指标，研究工频磁场抑制兴奋性突触传递的可能机制.结果表明：在0.5和1mT磁场刺激下，神经元sEPSC的频率和幅值均有大幅度的下降，半波长、上升时间和衰减时间均高于未经过磁场刺激的神经元，说明细胞的兴奋性传递频率明显降低；当磁场强度达到2mT时，神经元sEPSC的幅值、频率、半波长、上升时间和衰减时间显著下降.参考文献：[1]段冠民，杨立新，李敬录，等.工频电磁场对中枢神经系统影响的观察[J].中国水电医学，2002（3）：132-133.[2]MAJID J，SEYED M F，ALI R P，et al.Acute exposure to a50Hz magnetic field impairs consolidation of spatial memory in rats[J].Neurobiology of Learning and Memory，2007，88（4）：387-392.[3]CHE Yi，SUN Huaying，CUI Yonghua，et al.Effects of expo－sure to50Hz magnetic field of1mT on the performance of de－tour learning task by chicks[J].Brain Research Bulletin，2007，74（5）：178-182.[4]BROADBENT N J，SQUIRE L R，CLARK R E.Spatial memory，recognition memory，and the hippocampus[J].Proceedings of the National Academy of Sciences of the United States of 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Effect of magnetic field on texture evolution in titanium
Effect of magnetic field on texture evolution in titaniumD.A.Molodova,*,A.D.Sheikh-Ali b aInstitute of Physical Metallurgy and Metal Physics,Aachen University,Kopernikusstr.14,D-52056Aachen,Germany b National High Magnetic Field Laboratory and FAMU-FSU College of Engineering,1800E.Paul Dirac Drive,Tallahassee,FL 32310,USAReceived 18February 2004;received in revised form 1June 2004;accepted 3June 2004Available online 24June 2004AbstractThe effect of a high magnetic field on texture development in titanium is addressed.Cold rolled (82%)titanium shows a typical rolling texture with two components in the {0002}pole figure,which remains after recrystallization and subsequent grain growth.The annealing of titanium sheet samples in the hexagonal phase field (750°C)in a magnetic field of 19.4T with the sheet normal parallel or perpendicular to the field direction does not change the final texture.In contrast,the same thermo-magnetic treatment results in a distinct difference between usually symmetrical texture peaks when the sample is tilted by +30°or )30°to the magnetic field direction around the rolling direction leading to a configuration where the c ðh 0001iÞaxis of grains corresponding to one texture component is aligned normal to the magnetic field direction.This observation is attributed to grain growth affected by an additional driving force arising in a magnetic field by the anisotropy of the magnetic susceptibility of titanium.Ó2004Acta Materialia Inc.Published by Elsevier Ltd.All rights reserved.Keywords:Texture;Magnetic anisotropy;Titanium;Grain growth1.IntroductionThe effect of a magnetic field on grain growth in non-magnetic materials was first studied by Mullins [1]inter magnetically induced grain boundarymotion was measured in specially grown bismuth andzinc bicrystals containing specific individual grainboundaries [2–5].The driving force for grain boundarymotion in these experiments was provided by a magneticfield due to the magnetic anisotropy of the respectivematerial.It has also been shown that a magnetic drivingforce can cause selective grain growth in locally de-formed zinc single crystals during their annealing in amagnetic field [6].This experiment clearly indicates thepossibility to effectively change the orientation distri-bution of grains in a magnetically anisotropic poly-crystalline material by means of annealing in highmagnetic fields.This has been recently proved in ex-periments with zinc-1.1%aluminum alloy [7].For thefirst time,it has been demonstrated that annealing of cold rolled zinc alloy sheet in a high magnetic field can make significant changes in crystallographic texture.These results were interpreted in terms of selective grain growth induced by a magnetic driving force [7].Ac-cording to this interpretation the magnetically affected texture development is not confined to zinc,but any magnetically anisotropic material is liable for the con-trol of texture by means of annealing in a high magnetic field.The current study addresses the effect of a mag-netic field on texture evolution in cold rolled titanium when exposed to high magnetic field at elevated temperatures.2.Experimental procedure 2.1.Material and thermomechanical treatment The titanium sheet (3mm in thickness)used in this experiment was cut out from a 10mm plate prior hot rolled in a phase field followed by annealing at 700°C.It showed fully recrystallized structure having equiaxed *Corresponding author.Tel.:+49-241-802-6873;fax:+49-241-802-2301.E-mail address:molodov@imm.rwth-aachen.de (D.A.Molodov).1359-6454/$30.00Ó2004Acta Materialia Inc.Published by Elsevier Ltd.All rights reserved.doi:10.1016/j.actamat.2004.06.004Acta Materialia 52(2004)4377–4383grains of about 35l m in size (Fig.6).Table 1shows thechemical composition of the used titanium.This startingmaterial was rolled at room temperature to total re-duction of 82%.A reduction in thickness for each passvaried from 12%to 28%.The direction of rolling wasreversed after each pass.The final sheet thickness was0.53mm.These cold rolled specimens were annealed at 750°C.The heating time to raise the temperature from RT to750°C varied from 12to 14min.Subsequently thesamples were annealed for 15min without any magneticfield and then for 59min within the applied magneticfield.The reference specimens were annealed at 750°Cfor the same time without any magnetic field.In order toavoid an oxidation during the heat treatment,thespecimens were encapsulated under a vacuum of2Â10À5Pa in quartz tubes (four specimens of size13mm Â12mm per tube)before annealing (Fig.1).The annealing in the magnetic field was carried outusing the high magnetic field facilities of the NationalHigh Magnetic Field Laboratory in Tallahassee,Flor-ida,USA.A resistive,steady-state 20T magnet with195mm bore diameter was used,and a field strength1.54Â107A/m was applied.The specimens were an-nealed in the field being oriented differently with respect to the field direction (Fig.2).The rolling direction (RD)of all specimens was kept perpendicular to the field,while the transverse direction (TD)was kept perpen-dicular,parallel (Fig.2(a)and (b))and tilted by +30°and )30°to the field direction (Fig.2(c)and (d))for the four sample sets,respectively.To characterize the microstructure before and after annealing,the samples were mechanically polished and analysed by means of optical microscopy.2.2.Texture characterisation Texture was determined from the normal direction (ND)in the mid-layer of the sheet before and after an-nealing.After wet grinding with SiC papers of 1200,2400and 4000grit the samples were etched in a solution of 30ml HNO 3,10ml HF and 50ml H 2O to remove a surface layer of at least 20l m.Incomplete X-ray pole figures were measured with Co K a radiation (k ¼1:79 A)from an area of 24Â13mm 2composed of two samples (each 12mm (RD)Â13mm (TD))in the range of the pole distance angle a from 5°to 70°by means of a fully automatic texture goniometer in the back reflection mode.From a set of six pole figures {0002},f 10 10g ,f 11 20g ,f 10 11g ,f 10 12g and f 10 13g the orientation distribution function (ODF)was calculated using the series expansion method with I max ¼22,employing a positivity criterion to determine even and odd series coefficients [8,9].Sample symmetry was regarded tri-clinic to represent asymmetric textures after annealing inthe magnetic field.The pole figures shown in Figs.3–5were calculated according to the obtained ODFs.3.ResultsAs shown in Fig.3(a),the material after 82%rollingreduction became highly textured exhibiting the typicalrolling texture of titanium,as indicated by the two peaksin the {0002}pole figure.This has been observed byseveral investigators [10–12].The obtained peaksare Fig.1.Vacuum sealed (2Â10À5Pa)quartz ampul with four sheet ti-tanium samples placed in a tilted 30°configuration in a stainless steelcontainer.Table 1Chemical composition of commercially pure titanium (99.8%)used inthe experimentElementFe O N C H Content (wt%)0.060.080.010.010.0034378 D.A.Molodov,A.D.Sheikh-Ali /Acta Materialia 52(2004)4377–4383rather wide-spread,but the main feature of this texture can be described by the ideal orientation{0001} h10 10iÆ30°TD.This means that the hexagonal c axes are tilted at an angle ofÆ30°from the sheet normal direction to the transverse direction around the rolling direction while the h10 10i direction is mostly parallel to the rolling direction.In other words,this texture is characterized by a high density of the ODF around the orientation f u1¼0;U¼30°;u2¼0g,i.e.,around f 12 15g h10 10i.The main component of deformation texture{0001} h10 10iÆ30°TD also remains in the recrystallization texture after the annealing at750°(Fig.3(b)).In addi-tion,the texture in Fig.3(b)is characterized by a high level of the orientation{0001}h 12 10iÆ30°TD which is typical for the recrystallization texture in commercially pure titanium,identified as the orienta-tion f10 13gh 12 10i or f u1¼0;U¼30°;u2¼30g [10,12–14].A very similarfinal texture with symmetrical peaks as observed in Fig.3(b)is obtained after annealing in magneticfield for specimen configurations shown in Fig.2(a)and(b).The resulting polefigures are presented in Fig.4.In contrast,the same heat treatment in a magneticfield of equal strength(19.4T)results in a distinct difference between usually symmetricaltexture Fig.6.Microstructure of the investigated titanium:(a)as-received;(b)cold rolled to82%reduction in thickness;(c)annealed at750°C(12min heating up to750°C and15+59min annealing).4380 D.A.Molodov,A.D.Sheikh-Ali/Acta Materialia52(2004)4377–4383peaks when the sample is tilted by+30°or)30°to the field direction around the rolling direction(Fig.5).The ratio of intensity for the two(0002)reflections amounts to a factor of1.9(Figs.5and7).Fig.6presents optical micrographs of the investi-gated titanium specimens before and after annealing at 750°C.The average grain size of recrystallized grains is $70l m.OIM analysis and a study of grain boundary character distribution in these specimens are in progress, and will be reported elsewhere.4.DiscussionIt is known from literature that texture in a-titanium introduced by cold working(e.g.,rolling)cannot be erased by annealing in the hexagonal phasefield(below 882°C),even after recrystallization and subsequent grain growth[10,11].This is also confirmed by our own experiments as shown by the polefigures of Fig.3.This texture also persists after annealing in the high temper-ature bcc region[10,13,15].The results of the present study,however,provides an unambiguous evidence that the texture development in a-titanium can be effectively changed by a magneticfield.The effect of the magneticfield clearly depends on the orientation of the specimen with respect to thefield di-rection.Annealing in a magneticfield for sample con-figurations shown by Fig.2(a)and(b)does not change thefinal texture(Fig.4),when compared to the texture after annealing without a magneticfield(Fig.3(b)).Pole figures remain symmetrical with practically equal h0002i reflection intensities.In contrast,annealing of the specimens in magneticfield for both the tilted con-figurations drastically affects the h0002i pole intensities.Main peaks in the{0002}polefigures obtained from the recrystallized specimens(Figs.3(b),4and5)repre-sent orientations around both f 12 15gh10 10i and f10 13gh 12 10i locations.These orientations are related to each other by a30°rotation about the hexagonal c-axis.Their common feature is that the c axes in the corresponding grains are tilted at aboutÆ30°towards TD.It is easy to see that c axes in grains of differently oriented specimens(Fig.2)are tilted differently to the field.For samples with the configurations shown in Fig.2(a)and(b),the angles between c axes of each component in{0002}polefigures and thefield direc-tion are equal to each other and amounts to$30°and 60°,respectively.The c-axis of component B1in specimens shown in Fig.2(c)is nearly perpendicular to thefield.A rotation TD by)30°around RD makes the c-axis of component A almost normal to thefield direction.Therefore,the magnetic annealing of samples in both the tilt-positions results in strengthening of the texture peak corre-1For convenience we refer in the following to texture components inthe{0002}polefigures as to A and B components(Fig.3).D.A.Molodov,A.D.Sheikh-Ali/Acta Materialia52(2004)4377–43834381sponding to grains with the c -axis perpendicular to thefield,while the intensity of the other texture componentdecreases.We attribute the observed effect of a magnetic field onthe texture development to grain growth affected by anadditional driving force exerted in the magnetic field dueto the anisotropy of the magnetic susceptibility of tita-nium.Studies of recrystallization kinetics in pure andlow alloyed titanium revealed that primary recrystalli-zation after high rolling reductions (70–90%)in thetemperature range over 600°C proceeds very fast[14,15].In Inoue and Inakazu [15],a recrystallizedstructure with fine grains in 90%rolled titanium sheetwas observed after annealing at 600°C for $100s.According to Wagner et al.[14],the recrystallization inlow alloyed titanium rolled to 80%reduction at 700°Ctakes less than one minute.These results clearly indicatethat the primary recrystallization in the current experi-ment has been completed during the ramping the tem-perature up to 750°C (12–14min)and annealing at thistemperature ($15min),i.e.,before the magnetic fieldwas turned on.Therefore,it can be concluded that themicrostructural development in the investigated tita-nium sheet is affected by the magnetic field in the stageof grain growth.In magnetically anisotropic materials an additionaldriving force,p m ,for grain growth (or grain boundarymotion)can be given by the difference in magnetic freeenergy,x ,in neighboring grains when being differentlyoriented with respect to the magnetic field direction [1]p m ¼x 1Àx 2¼l0H 22v 1ðÀv 2Þ;ð1Þwhere v 1and v2are the magnetic susceptibilities ofneighboring grains 1and 2,respectively,along themagnetic field,H .This driving force depends only on thestrength of the magnetic field and its orientation withrespect to the two neighboring crystals.The direction ofp m remains the same when the sense of the field is re-versed.According to elementary crystallography themagnetic susceptibility of a single crystal can be writtenas v ¼v ?þD v cos 2h ,where D v is the difference in sus-ceptibilities parallel vk and perpendicular v?to theprincipal (or c )axis.Here h is the angle between the c -axis and the magnetic field.Substituting this expressioninto Eq.(1)leads top m ¼12l 0D v H 2cos 2h 1ÀÀcos 2h 2Á:ð2ÞA maximum magnetic driving forcep max m ¼1D v H 2ð3Þis attained when the angles between the field and the c -axis in both neighboring grains are h 1¼0and h 2¼90°.For p m ¼0,the grain orientations need not be identical,rather the condition h 1¼h 2is sufficient.The sign of p mdepends on the magnetic anisotropy of a material ðD v Þand the asymmetry of the spatial orientation of both neighboring grains with respect to the magnetic field direction.Paramagnetic a -titanium possesses the magnetic an-isotropy with v k >v ?[16,17].The difference in suscep-tibilities parallel and perpendicular to the c -axis at 750°C amounts to D v ¼1:18Â10À5[17].According to Eq.(3),the maximum magnetic driving force for grain boundary migration in titanium in our case (field strength H ¼1:54Â107A/m)is p max m ;750°C ¼1:77kJ/m 3.This force is related to a boundary with a misorientation angle of 90°between grains with basal planes (or h 0001i directions)oriented parallel and perpendicular to the field direction.For boundaries with other misorienta-tion angles,as well as for another orientation of the bicrystal with respect to the magnetic field,the driving force will be lower.When the c -axis of the grains of one texture compo-nent in our experiment is oriented perpendicular to the field,then these grains experience an additional driving force for growth (or for the motion of their boundaries)in the direction of differently oriented grains,particu-larly in the direction of grains of another component.In this case,the orientation of c -axis of the second com-ponent,with respect to the field direction,is about 30°and the magnetic force,according to Eq.(2),amounts to about 1.5kJ/m 3.It can be shown that the magnetic driving force is comparable to the driving force for normal (continuous)grain growth arising due to the gain of grain boundary energy.The driving force for normal grain growth reads p c ¼2r R ;ð4Þwhere r the grain boundary energy and R is the radius of curvature,which usually exceeds the grain size by about an order of magnitude.In the current experiment the mean grain size after the annealing at 750°C was measured to be about 70l m.Assuming grain boundary energy of typically 0.3J/m 2,the driving force for normal grain growth at the final stage of the magnetic annealing amounts to about p c ffi1kJ/m 3.It is evident from a comparison of the respective driving forces that the magnetic force is at least of the order of the curvature force and therefore is able to affect the grain growth significantly,increasing the growth rate of those grains whose h 0001i axis is perpendicular to the field.In our experiment,for the configurations where samples are parallel or perpendicular to the field direc-tion (Fig.2(a)and (b)),the c axes of each component in {0002}pole figures are symmetrical with respect to the field direction.The magnetic free energy of the grains of both components is equal and neither grains A nor grains B experience an additional force to grow.In the tilted configuration this symmetry gets lost and c axes of grains which belong to one texture component become4382 D.A.Molodov,A.D.Sheikh-Ali /Acta Materialia 52(2004)4377–4383almost perpendicular to thefield.The magnetic free energy of these grains reaches to its minimum and be-comes lower than the energy of any other grain with different orientations of c axes.Consequently,an addi-tional magnetic driving force arises and enhances the growth of such grains.Since a rise in intensity of one texture component corresponds to a decrease in inten-sity of another component,as shown in Figs.5and7,it is reasonable to suggest that grains with the preferable orientation grow mainly at the expense of grains of another texture component.5.SummaryIn the present investigation,the effect of a magnetic field on texture development in titanium has been studied.The annealing of82%rolled titanium sheet samples at750°C in a magneticfield of19.4T does not change thefinal texture for the samples with their sheet normal either parallel or perpendicular to the magnetic field direction.In contrast,the same heat treatment in the same magneticfield results in a distinct difference between usually symmetrical texture peaks when the sample is tilted by+30°or)30°to thefield direction around the rolling direction leading to a configuration where the c-axis of grains corresponding to one texture component is aligned normal to thefield direction.This effect is due to an additional driving force for grain growth arising in the magneticfield by the anisotropy of the magnetic susceptibility of titanium.The results of this study demonstrate that the texture in paramagnetic titanium can be effectively changed by means of annealing in a high magneticfield.This would provide a new method to control the development of crystallographic texture in magnetically anisotropic non-magnetic materials.AcknowledgementsThe authors express their gratitude to the Deutsche Forschungsgemeinschaft forfinancial support(Grant MO848/4-1).Critical reading of the manuscript by Dr. Satyam Suwas is gratefully acknowledged. References[1]Mullins WW.Acta Metall1956;4:421.[2]Molodov DA,Gottstein G,Heringhaus F,Shvindlerman LS.Scripta Mater1997;37:1207.[3]Molodov DA,Gottstein G,Heringhaus F,Shvindlerman LS.Acta Mater1998;46:5627.[4]Konijnenberg PJ,Molodov DA,Gottstein G,Shvindlerman LS.NHMFL Ann Res Rev2000:266–7.[5]Sheikh-Ali AD,Molodov DA,Garmestani H.Appl Phys Lett2003;82:3005.[6]Konijnenberg PJ,Molodov DA,Gottstein G,Shvindlerman LS.NHMFL Ann Res Rev2002:303–4.[7]Sheikh-Ali AD,Molodov DA,Garmestani H.Scripta Mater2002;46:854.[8]Dahms M,Bunge HJ.J Appl Crystallogr1989;22:439.[9]Dahms M.Appl Crystallogr1992;25:258.[10]Singh AK,Schwarzer RA.Z Metallkd2000;91:702.[11]Davis GJ,Kallend JS,Knight FI.In:Gottstein G,L€u cke K,editors.Proceedings of the Fifth International Conference on Texture of Materials.Berlin:Springer;1978.p.245.[12]Naka S,Penelle R,Valle R,Lacombe P.In:Gottstein G,L€u ckeK,editors.Proceedings of the Fifth International Conference on Texture of Materials.Berlin:Springer;1978.p.405.[13]McHargue CJ,Hammond JP.Trans AIME1953;197:57.[14]Wagner F,Bozzolo N,Van Landuyt O,Grosdidier T.Acta Mater2000;50:1245.[15]Inoue H,Inakazu N.In:Chandra T,editor.Recrystallization90.Warrendale:The Minerals,Metals&Materials Society;1990.p.687.[16]Collings EW,Ho JC.Phys Rev B1970;2:235.[17]Vol’kenshtein NV,Galoshina EV,Panikovskaya EB.Sov PhysJETP1975;40:730.D.A.Molodov,A.D.Sheikh-Ali/Acta Materialia52(2004)4377–43834383。
电磁场英语作文
电磁场英语作文The electromagnetic field is a fundamental aspect of our world that plays a crucial role in numerous aspects of our daily lives. 电磁场是我们世界的一个基本方面，在我们日常生活的许多方面起着至关重要的作用。
From the electricity that powers our homes to the magnetic fields that guide our compasses, the influence of the electromagnetic field is pervasive. 从为我们家庭供电的电力到引导我们指南针的磁场，电磁场的影响是无处不在的。
One of the most fascinating aspects of the electromagnetic field is its ability to transmit information through electromagnetic waves. 电磁场最迷人的一个方面是它通过电磁波传输信息的能力。
This is the basis of modern communication systems, allowing us to send messages, make phone calls, and access the internet wirelessly. 这是现代通讯系统的基础，使我们能够无线发送信息、打电话和访问互联网。
However, the increasing reliance on electromagnetic technology raises concerns about potential health risks associated withprolonged exposure to electromagnetic fields. 然而，对电磁技术的日益依赖引发了对长期暴露于电磁场可能带来的健康风险的关注。
人体磁场的作用及其与能量的关系
人体磁场的作用及其与能量的关系The human body has an electromagnetic field that is generated by the electrical activity of cells, tissues, and organs. This field, also known as the biofield, is composed of various frequencies and intensities of electromagnetic waves. It is believed that this biofield plays a crucial role in maintaining the overall health and well-being of an individual.The human body's electromagnetic field interacts with external electromagnetic fields, such as those emitted by electronic devices and the Earth's magnetic field. Some studies suggest that exposure to electromagnetic fields can have both positive and negative effects on the body's energy levels and overall health.In terms of energy, the human body is often described as having a subtle energy system. This system consists of energy centers, known as chakras, and energy pathways, known as meridians. These energy channels are believed to facilitate the flow of vital energy, also known as qi or prana, throughout the body. It is believed that disruptions or imbalances in this energy flow can lead to physical, mental, and emotional health issues.Practices such as acupuncture, qigong, and Reiki aim to balance and enhance the body's energy flow, thereby promoting overall health and well-being. These practices work by stimulating specific points or areas on the body, which are believed to correspond to the energy centers and pathways. By restoring the balance and flow of energy, these practices can help alleviate symptoms and improve the body's natural healing abilities.中文回答:人体具有由细胞、组织和器官的电活动所产生的电磁场，也被称为生物场。
介质中的恒定磁场与边界条件(双语)
medium, and it shows that in the medium the circulation of the
magnetic field intensity around a closed curve irent enclosed by the curve.
the relative value as
r
0
1 m
After a diamagnetic 抗磁性 material is magnetized the composite magnetic field will be decreased, thus
m 0, 0 , r 1
A paramagnetic 顺磁性 material is magnetized, the composite magnetic field will be increased, thus
Since the magnetic field intensity is only related to the conducting current 传导电流 , the magnetic field intensity simplifies the calculation of the magnetic fields in medium just likes the electric flux density simplified that of the electrostatic fields in dielectric.
current I in vacuum. In this way, the circulation of the magnetic flux
density B around a closed curve is
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Effect of magneticfield and temperature on the ferroelectric loop in MnWO4Bohdan Kundys,*Charles Simon,and Christine MartinLaboratoire CRISMAT,CNRS UMR6508,ENSICAEN,6Boulevard du Maréchal Juin,14050Caen Cedex,FranceThe ferroelectric properties of MnWO4single crystal have been investigated.Despite a relatively low remanent polarization,we show that the sample is ferroelectric.The shape of the ferroelectric loop of MnWO4 strongly depends on magneticfield and temperature.While its dependence does not directly correlate with the magnetocapacitance effect before the paraelectric transition,the effect of magneticfield on the ferroelectric polarization loop supports magnetoelectric coupling.PACS number͑s͒:72.55.ϩs,75.80.ϩq,75.30.KzThe mutually exclusive nature of magnetism and electric polarization phenomena in most solids1,2has recently at-tracted attention in the scientific community.This is essen-tially due to both the basic physics challenges posed and the possible magnetoelectric͑ME͒applications for memory stor-age and electricfield-controlled magnetic sensors.The idea of having the two order parameters͑magnetic and electric͒at the same temperature and magnetically controlled electrical polarization͑or vice versa͒has stimulated a vast research of new materials,3–8as well as reinvestigation of previously known compounds.9It becomes evident that many canted antiferromagnets may develop electric polarization as a re-sult of the overlap of the electronic wave functions and as a result of the spin orbit interaction.10Among materials in which magnetoelectric effects have been recently reported, MnWO4is a particularly interesting material as the electric polarization in a single crystal may be switched from the b to a direction when a strong magneticfield is applied.11–14A similar phenomenon has been observed in rare-earth manganites.15,16The antiferromagnetic͑AF͒phase transi-tions of MnWO4were already studied a long time ago.17,18 With decreasing temperature,MnWO4undergoes a collinear antiferromagnetic state͑AF1phase͒at T NϷ13.5K with fur-ther transformation to the noncollinear incommensurate an-tiferromagnetic phase͑AF2phase͒at12.7K,andfinally tocollinear incommensurate antiferromagnetic phase͑AF3phase͒at7.6K.Among the three antiferromagnetic states,only the noncollinear one͑AF2phase͒appears to develop anelectric polarization that can be explained within the frame-work of the phenomenological10,19–21and microscopicmodels.22Polarity alone,however,does not guarantee ferro-electricity that is sometimes difficult to experimentallydemonstrate.9,23For example,the reversibility of the electricdipoles could require electricfields larger than the break-downfield,or it might be due to asymmetric irreversiblearrangements of the atoms.In this Brief Report,the electricfield-induced dipole reversibility͑ferroelectricity͒ofMnWO4is shown,along with the measures of its depen-dence on magneticfield and temperature.dc ferroelectricmeasurements were performed in a Physical Property Mea-surement System͑PPMS͒Quantum Design cryostat by usinga Keithley6517A electrometer.The used technique is ouradaptation of the already known method,24wherein program-ming technology has been applied to the Keithley6517Aelectrometer and PPMS to provide the possibility oftemperature-and magneticfield-dependent studies of the ferroelectric polarization loops.Its quasistatic͑dc͒opera-tional nature allows ferroelectric loops to be observed with a small electric fatigue risk at ultralow frequency measuring signals.A0.37mm sized along the b axis single crystal of MnWO4,which is grown by thefloating zone method,has been cut for ferroelectric loop measurements.The magnetic and electricfields were applied parallel to the direction of the crystalline b axis.The electrical contacts with the sample were made by using a conductive silver paint.Figure1pre-sents the ferroelectric hysteresis loops͓P͑E͔͒as a result of current-voltage͓I͑E͔͒integration with respect to time atdif-FIG.1.͑Color online͒͑a͒Ferroelectric loops obtained as a result of current integration at different temperatures.͑b͒Corresponding voltage-current characteristics taken at different temperatures.1ferent temperatures recorded after a zero electric and mag-netic field cooling procedure.The remanent polarization of about 39C /m 2at 10K agrees well with the reported forced polarization in this material.11,12Remanent polarization ͑Fig.2͒and ferroelectric coercive force ͑inset of Fig.2͒extracted from ferroelectric loops go through a maximum and decrease to zero for temperatures close to the magnetic transitions ͑i.e.,7.6and 12.7K ͒.We have also measured the forced polarization upon heating ͓electric field ͑520kV/m ͒cooling procedure ͔͑Fig.2͒.Near 7.6K,the forced polarization more rapidly increases than the remanent one ͑Fig.2͒and the maximum is reached at 8and 10K for the forced and remanent polarizations,respectively.This experimental result indicates that the ability to switch the ferroelectric polarization with electric field more quickly vanishes than the forced electric polarization in the sample in this temperature region.The effect of the external magnetic field applied along the b axis on ferroelectric switching processes ͓I ͑E ͒and P ͑E ͒loops ͔at 10K is shown in Fig.3.The ferroelectric coercive force and the remanent polarization decreased upon external magnetic field application,and the ferroelectric loop is no more observed at 12T.The magnetic field dependence of the dielectric permittivity at 10K and the magnetic field depen-dence of the ferroelectric coercive force ͑along the b axis ͒are shown in Fig.4.The position of the peak in the dielectric permittivity shows no hysteresis with respect to the magnetic field and agrees well with the magnetic field dependence of the both the ferroelectric coercive force and the remanent polarization ͑not shown ͒.While the peak in the magnetic field dependence of dielectric permittivity is very narrow along the a axis,11a rather broad anomaly in the dielectric permittivity is observed along the b crystallographic direc-tion ͑Fig.4͒.It is also worth noting that practically no mag-netodielectric effect is seen in magnetic fields up to 9T ͑Fig.4͒,while the magnetic field-induced change in the shape of a ferroelectric loop ͑values of the remanent polarization and of the ferroelectric coercive force ͒indicates a magnetoelectric coupling in this magnetic field range ͓see Fig.3͑a ͔͒.Thisbehavior is in agreement with the identical slope of ferro-electric loops near zero electric field for magnetic fields less than 9T ͓Fig.3͑a ͔͒.These results,therefore,imply that mag-netoelectric interactions are present without noticeable mag-netodielectric effects in magnetic field region of 0–9T.Mag-FIG.2.Remanent polarization extracted from ferroelectric P ͑E ͒loops and the forced polarization recorded at heating with the pre-vious electric ͑520kV/m ͒cooling procedure.The inset shows the ferroelectric coercive force as a function oftemperature.FIG.3.͑Color online ͒͑a ͒Ferroelectric loops obtained as a result of the ferroelectric current integration at different magnetic fields at 10K.͑b ͒V oltage-current characteristics taken at 10K at different magneticfields.FIG.4.͑Color online ͒The magnetic field dependence of the dielectric permittivity at 500kHz ͑left scale ͒and ferroelectric coer-cive force ͑right scale ͒at 10K.The electric and magnetic fields applied parallel to the crystallographic b axis.2netocapacitance effects may also be accompanied with stray contributions that do not necessarily reflect intrinsic magne-toelectric interactions.25–27Therefore,observing a magnetic field effect on the ferroelectric polarization loop may be an effective alternative method for studying in depth magneto-electric coupling.In support of this,the ferroelectric loop at a magneticfield of11T͓Fig.3͑a͔͓͒region where magneto-dielectric effect is big͑see Fig.4͔has a different slope near zero electricfield compared to the other loops for magnetic fields less than9T,where the magnetodielectric effect is small͑Fig.4͒.It has to be noted that,similarly,magnetic field induced ferroelectric loop has recently been found in Sr substituted BiFeO3accompanied with no magnetocapaci-tance effect in this compound.28In conclusion,a quasistatic technique has been used to investigate ferroelectric properties of a single crystal of MnWO4.It was shown that the sample is indeed ferroelectric and that the shape of its ferroelectric loop strongly depends on both temperature and magneticfield.Increasing the exter-nal magneticfield along the b axis decreased both the rem-anent polarization and ferroelectric coercive force.These ef-fects are not accompanied by any noticeable changes in the magneticfield dependence of dielectric permittivity before the transition to the paraelectric state at about10.5T.There-fore,our results also suggest that magnetoelectric coupling may be present without obvious 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