Effect of Occupational Extremely Low-Frequency Electromagnetic Field Exposure on the Thyroid Gland of Workers:A Prospective Study

Objective:The aim of this study was to investigate the biological effects of occupational extremely low-frequency electromagnetic field(ELF-EMF)exposure on the thyroid gland.Methods:We conducted a prospective analysis of 85 workers(exposure group)exposed to an ELF-EMF(100μT,10-100 Hz)produced by the electromagnetic aircraft launch system and followed up on thyroid function indices,immunological indices,and color Doppler images for 3 years.Additionally,116 healthy volunteers were randomly selected as controls(control group),the thyroid function of whom was compared to the exposure group.Results:No significant difference was observed in thyroid function between the exposure and control groups.During the follow-up of the exposure group,the serum free triiodothyronine(FT3)level was found to slowly decrease and free thyroxine(FT4)level slowly increase with increasing exposure time.However,no significant difference was found in thyroid-stimulating hormone(TSH)over the three years,and no significant difference was observed in the FT3,FT4 and TSH levels between different exposure subgroups.Furthermore,no significant changes were observed in thyroid autoantibody levels and ultrasound images between subgroups or over time.Conclusion:Long-term exposure to ELF-EMF may promote thyroid secretion of T4 and inhibit deiodination of T4 to T3.ELF-EMF has no significant effect on thyroid immune function and morphology.

Protective effects of blueberry anthocyanin extracts on hippocampal neuron damage induced by extremely low-frequency electromagnetic field

The protective effects of blueberry anthocyanin extracts against damage induced by extremely lowfrequency electromagnetic field(ELF-EMF)were investigated in a rat model.Wistar rats were exposed to ELF-EMF with or without the administration of blueberry anthocyanin extracts(50,100,and 200 mg/kg per day intragastrically once a day)for 30 days.Blueberry anthocyanin extracts supplementation inhibited the decrease in Nissl substance levels,cell membrane integrity,and mitochondrial membrane potential induced by ELF-EMF;prevented the increase in nitric oxide,malondialdehyde,and Ca2+concentrations;suppressed superoxide dismutase and glutathione depletion;and enhanced the cognitive ability of the rats exposed to ELF-EMF.The protective effects of blueberry anthocyanin extracts against hippocampal neuron injury caused by ELF-EMF were dose-dependent.These results demonstrated that blueberry anthocyanin extracts suppress hippocampal neuron injury caused by ELF-EMF by inhibiting cell membrane damage and oxidative stress pathways,and suggested that blueberry anthocyanin treatment potentially prevents hippocampal neuron injury.

Effect of low-frequency electromagnetic field on the as-cast microstructure of a new super high strength aluminum alloy by horizontal continuous casting

The super high strength aluminum alloy ingots with 100 mm in diameter were cast by the process of low-frequency electromagnetic horizontal continuous casting (LFEHC) and the effect of electromagnetic field on the as-cast microstructure was studied. Results show that microstructure of the sample prepared by the LFEHC process was greatly refined. Microstructures at the border and the center of the ingots were fine, uniform and rosette-shaped. Electromagnetic frequency plays a key role in microstructure refining. Fine and uniform microstructures can be obtained with optimal electromagnetic frequency. In this experiment, under a frequency of 30 Hz the microstructure was the finest and the most uniform.

Low-frequency pulsed electromagnetic field pretreated bone marrow-derived mesenchymal stem cells promote the regeneration of crush-injured rat mental nerve

Bone marrow-derived mesenchymal stem cells （BMSCs） have been shown to promote the regeneration of injured peripheral nerves. Pulsed electromagnetic field （PEMF） reportedly promotes the proliferation and neuronal differentiation of BMSCs. Low-frequency PEMF can induce the neuronal differentiation of BMSCs in the absence of nerve growth factors. This study was designed to investigate the effects of low-frequency PEMF pretreatment on the proliferation and function of BMSCs and the effects of low-frequency PEMF pre-treated BMSCs on the regeneration of injured peripheral nerve using in vitro and in vivo experiments.In in vitro experiments, quantitative DNA analysis was performed to determine the proliferation of BMSCs, and reverse transcription-polymerase chain reaction was performed to detect S100 （Schwann cell marker）, glial fibrillary acidic protein （astrocyte marker）, and brain-derived neurotrophic factor and nerve growth factor （neurotrophic factors） mRNA expression. In the in vivo experiments, rat models of crush-injured mental nerve established using clamp method were randomly injected with low-frequency PEMF pretreated BMSCs, unpretreated BMSCs or PBS at the injury site （1 × 106 cells）. DiI-labeled BMSCs injected at the injury site were counted under the fluorescence microscope to determine cell survival. One or two weeks after cell injection, functional recovery of the injured nerve was assessed using the sensory test with von Frey filaments. Two weeks after cell injection, axonal regeneration was evaluated using histomorphometric analysis and retrograde labeling of trigeminal ganglion neurons. In vitro experiment results revealed that low-frequency PEMF pretreated BMSCs proliferated faster and had greater mRNA expression of growth factors than unpretreated BMSCs. In vivo experiment results revealed that compared with injection of unpretreated BMSCs, injection of low-frequency PEMF pretreated BMSCs led to higher myelinated axon count and axon density and more DiI-labeled neurons in the trigeminal ganglia, contributing to rapider functional recovery of injured mental nerve. These findings suggest that low-frequency PEMF pretreatment is a promising approach to enhance the efficacy of cell therapy for peripheral nerve injury repair.

Experiment on low-frequency electromagnetic waves propagating in shock-tube-generated magnetized cylindrical enveloping plasma

We propose a method of applying a static magnetic field to reduce the attenuation of the magnetic field component(SH) of low-frequency electromagnetic(LF EM) waves in dense plasma. The principle of this method is to apply a static magnetic field to limit electron movement, thereby increasing the equivalent resistance and thus reducing the induced current and SH. We consider the static magnetic field acting on the plasma of the entire induced current loop rather than on the local plasma, where the induced current is excited by the magnetic field component of LF EM waves. Analytical expressions of SH suitable for magnetized cylindrical enveloping plasma are derived by adopting an equivalent circuit approach, by which SHis calculated with respect to various plasma parameter settings. The results show that SH can be reduced under a static magnetic field and the maximum magnetic field strength that mitigates blackout is less than 0.1 T. Experiments in which LF EM waves propagate in a shock-tubegenerated magnetized cylindrical enveloping plasma are also conducted. SH measured under the magnetic field(the magnetic field strength B0 acting on the magnetic field probe was about0.06 T) reduces at f=10 MHz and f=30 MHz when ne≈1.9×1013 cm-3, which is consistent with theoretical results. The verification of the theory thus suggests that applying a static magnetic field with a weak magnetic field has the potential to improve the transmission capacity of LF EM waves in dense plasma.

Effects of Different Electromagnetic Fields on Circadian Rhythms of Some Haematochemical Parameters in Rats

Objective To investigate the effects of different electromagnetic fields on some haematochemical parameters of circadian rhythms in Sprague-Dawley rats. Methods The study was carried out in 18 male and 18 female rats in good health conditions exposed to 50 Hz magnetic sinusoid fields at the intensity of 1000 μT, 100 μT, and 0 μT （control group） respectively, and in 18 male and 18 female rats in good health conditions exposed to 1.8 GHz electromagnetic fields at the intensity of 50 V/m, 25 V/m and 0 V/m （control group）, respectively. Following haematochemical parameters for glucose, triglycerides, and total cholesterol were measured. Results Different effects of electromagnetic fields on circadian rhythms of both male and female rats were observed. Different changes occurred in some haematochemical parameters for glucose, triglycerides, and total cholesterol （P〈0.05）. Conclusion Exposure to different electromagnetic fields is responsible for the variations of some haematochemical parameters in rats.

EXTREMELY LOW FREQUENCY MAGNETIC FIELD SUSCEPTIBILITY OF VISUAL DISPLAY UNITS

Extremely low frequency (ELF) magnetic field susceptibility is an index of visual display unit (VDU) quality and performance. This paper provided field measured data on the susceptibility for a large variety of VDUs. A test rig was built to study the susceptibility of VDUs to magnetic fields at fundamental and third harmonic frequencies. It was found that the susceptibility level is largely dependent on refresh rate of the VDU and the orientation of the external ELF field. It was also found that the VDU susceptibility is significantly increased in the presence of harmonic frequency magnetic fields. About 30% of the tested samples have susceptibility levels higher than that stated in IEC 1000-4-8 standard.

地中电偶极源极低频电磁场的分布与传播特征

利用层状大地中偶极源响应的正演算法,计算地中电偶极源激发的极低频地震电磁场并分析其在地球环境下的传播特征.设计了多个水平层状地球模型,分别模拟和展示了深埋地中的电偶极源的响应和空间分布特征.重点分析了含地壳波导+LAI波导模型的高阻大地中,倾斜电偶极源激励响应随观测点的偏移距和垂直位置、激励源深度、地壳波导结构和参数变化时各场量响应的幅频特征.研究表明,用倾斜电偶极源模拟和分析高阻大地中孕震电磁辐射的响应及在大地电磁系统中的传播特性是可行的;模拟的高阻大地中的电磁辐射在地壳波导和LAI波导中均表现有慢衰减或幅值增强特性,但两个波导效应具有不同的频率选择性;高阻大地中的电磁辐射在波导的高阻介质中具有幅值强、衰减慢的特点.建议在高阻地层出露的地表、井中或海底的高阻岩层中以及大气层中布设测站.

基于层次分析模型的潜艇极低频电磁场贡献率评估方法研究

潜艇极低频电磁场作为目标探测的关键特征,其形成机制复杂多样,平台工况以及在水下所处位置都会对其产生很大影响。有效操控以降低潜艇的磁特征对于提升其磁隐身性能具有重要的意义。然而,当前各种因素对电磁场影响程度的研究尚不充分。为此该文提出一种基于层次分析模型的贡献率评估方法,旨在为有效操控提供理论依据。首先深入分析潜艇极低频电磁场的威胁成因,并建立相应的威胁层次结构模型。其次,通过仿真手段获取由不同成因产生的电磁场信号特征,并构建威胁矩阵和特征矩阵。最后,计算得到不同成因电磁场对总电磁场的贡献率,在尾部测线上,尾流磁场的贡献率占比最高,达到0.7649;径向测线上轴频磁场贡献率占比最高,并逐渐衰减,最终在150 m处低于尾流电磁场,并保持在占比0.5左右。仿真结果验证了该方法的有效性,可为潜艇极低频电磁场的综合主动控制策略研究奠定技术基础。

极低频电磁场治疗对创伤性颅脑损伤患者的神经保护作用及对血清电解质水平的影响

目的:探究极低频电磁场治疗对创伤性颅脑损伤患者的神经保护作用及对血清电解质水平的影响。方法:选取80例创伤性颅脑损伤患者,根据治疗方法分为对照组(40例)和观察组(40例),对照组采用营养支持治疗,观察组在营养支持治疗基础上加用极低频电磁场治疗;测定治疗前和治疗1个月后血清神经元特异性烯醇化酶(NSE)、神经肽Y(NPY)及Na^(+)、K^(+)、Cl^(-)水平,脑干听觉诱发电位(BAEP)、体感诱发电位(SEP)。结果:2组治疗后血清NSE、NPY水平均低于治疗前;且观察组效果优于对照组(P<0.05)。治疗后观察组左、右耳BAEP的Ⅰ、Ⅲ、Ⅴ、Ⅰ~Ⅲ、Ⅲ~Ⅴ级波以及SEP的N13、N20、N13~N20波的潜伏期均短于对照组(P<0.05)。治疗后2组血清Na^(+)、Cl^(-)水平低于治疗前,K^(+)高于治疗前(P<0.05)。结论:极低频电磁场治疗对创伤性颅脑损伤患者有神经保护作用。

基于miRNA23/Nocth信号通路探讨极低频电磁场对缺血性脑卒中神经功能的修复作用

目的研究极低频电磁场(ELF EMF)通过对miRNA23(miR-23)/Nocth信号通路促进对缺血性脑卒中神经功能缺失恢复的机制研究。方法建立成年雄性SD大鼠缺血性脑卒中模型,进行ELF EMF干预,给予NC miR序列或miR-23抑制物侧脑室注射。评估神经功能缺失程度,脑梗死体积,检测miR-23表达水平,Notch1、Jagged1、Hes1蛋白的表达水平。结果与假手术组比较,模型组的Zea Longa评分、脑梗死体积、细胞凋亡率增加,miR-23、Notch1、Jagged1、Hes1的表达水平降低(P<0.05);与模型组比较,ELF EMF组的Zea Longa评分、脑梗死体积、细胞凋亡率降低,miR-23、Notch1、Jagged1、Hes1的表达水平增加(P<0.05);与miR-NC+ELF EMF组比较,miR-23+ELF EMF组的Zea Longa评分、脑梗死体积、细胞凋亡率增加,miR-23、Notch1、Jagged1、Hes1的表达水平降低(P<0.05)。结论ELF EMF促进缺血性脑卒中大鼠神经功能缺失恢复,这一作用与增加miR-23表达、激活下游Notch1通路有关。

电磁轨道发射装置电磁热力强耦合计算及分析

针对电磁轨道发射过程中电磁热力多物理场强耦合的计算问题,利用毕奥-沙伐定律推导了电枢和轨道的磁感应强度计算公式,建立其三维瞬态电磁场数值模型并进行求解,在此基础上求解发射过程中枢轨的瞬态电磁力。从摩擦系数瞬态变化的角度考虑轨道电阻焦耳热和滑动摩擦热共同对枢轨瞬态温升的影响;从枢轨材料非线性变化及接触压力瞬态特性的角度考虑了枢轨的应力分布情况,从而建立了动态发射状态下的电磁场-温度场-力场的三维强耦合计算模型并同时进行分析。结果表明:枢轨的电流密度、磁感应强度、温升和热应力集中分布在电枢喉部及枢轨接触面区域。强耦合计算能够获取发射过程中的实时物理量参数,为材料进一步设计制造和系统可靠性预测奠定基础。

大连地磁台极低频观测天然源电磁场数据分析

利用大连极低频电磁观测台的连续观测数据,采用天然源电磁法对观测的电磁场数据进行了处理和分析。结果表明天然源电磁场具有明显的周期性变化特征,表现为白天电磁场谱值比夜间的大,日变化和夏季谱值是冬季谱值的2倍左右的季节性的特征。对地磁台站观测天然源电磁场数据的非地震影响因素主要为雷电、磁暴以及电磁环境(如高压直流输电)等。

高压输电线环境电磁场暴露健康效应的原初作用

高压输电线环境电磁场暴露健康效应的原初作用机制是阐述电磁健康的环节,是制修订我国环境电磁标准的重要基础。为此,对220kV的高压输电线环境电磁场进行了现场监测,将SD大鼠海马神经元暴露在瑞士IT’IS系统中,观察胞内活性氧自由基(ROS)、钙离子(Ca2+)和线粒体膜电位(MMP)对磁感应强度为0.1mT、0.5mT和1.0mT的极低频电磁场的生物响应。研究结果表明:环境电场强度≤1kV/m,磁场磁感应强度≤1.5μT;神经元胞内活性氧自由基、钙离子、线粒体膜电位对磁感应强度≥0.1mT的磁场有生物反应。因此,电场能量密度和磁场能量密度可作为电磁健康效应的评价参数;ROS是电磁因果链原初作用中连接物理和生物解释的一个重要标志物;足够强度的电磁场才能对健康产生影响,笼统说"电磁场对健康有影响"会误导公众。

地震监测人工源极低频电磁技术(CSELF)新试验

2009年利用大功率人工源极低频电磁技术(CSELF)在位于华北、华南、东北、西北和西南的12个地震台站和几个流动观测点进行了连续30天新的观测试验.结果表明,利用CSELF技术可以在1700 km之外测量到人工源电磁场信号,计算得到的电、磁场功率谱密度和视电阻率与天然源信号相比,抗干扰能力更强,观测信号更稳定,特别有利于识别和捕捉地震等诱发的电磁异常现象,在地震预测监测中具有很大的研究应用潜力.试验还发现,各地震台站和流动测点观测的CSELF信号的强度,与台站或者测量的电、磁场分量相对于发射源的距离、方位有明显的关系;发现在离开发射源的相对近区,场强随距离的衰减,比在相对远区更快;发现接收磁场信号比电场信号较易获得更高信噪比的数据.

天然超低频电磁场日夜交替及其稳定性分析

利用北京大学研制的BD-6型超低频电磁探测仪,在北京地热119井按不同时段和方位对天然场源超低频电磁信号进行观测,经数据处理得到不同时段和不同方位的电压-深度曲线和差分视电阻率-深度曲线,经分析与解译发现:太阳辐射在一定程度上影响天然场源超低频电磁信号的强度,但太阳辐射对其稳定性影响程度不大;天然源超低频电磁信号强度存在明显的方向性,磁北方向信号最强,随仪器探头方向与磁北方向夹角的增大信号强度降低;实验表明超低频电磁信号的差分视电阻率-深度法明显优于电压-深度法的反演与解译精度。

工作场所极低频电磁辐射对作业人员健康状况影响的调查分析

目的:通过调查工作场所中极低频电磁场的暴露水平,分析工作场所中极低频电磁辐射对职业人群健康状况的影响。方法:使用EFA-300工频电磁场场强测试仪测量某工厂的2个不同车间(对照组与暴露组)的电场强度和磁感应强度,同时使用AWA5610D型积分声级计测量噪声。通过多中心单纯随机抽样的方法对183名对照组和521名暴露组作业人员进行问卷调查,调查2组人员的个人职业信息、家居信息及健康状况,采用SPSS17.0软件对资料进行统计学分析。结果:监测结果显示,暴露组车间电场强度和磁感应强度明显高于对照组(P<0.05);两车间噪声比较差异无统计学意义(P>0.05)。问卷调查结果显示,与对照组比较,暴露组作业人员脱发症状发生率高于对照组(P<0.05);听力减退症状发生率低于对照组(P<0.05),其他指标差异无统计学意义(P>0.05)。结论:极低频电磁辐射暴露可能会对作业人员神经系统有一定影响。

静态和极低频电磁场非热生物效应的研究动态

人为电磁场对人类健康可能的影响尤其是电磁辐射与肿瘤发生的关系,日益引起人们的关注,电磁场的生物学效应得到全世界的广泛研究。我们着重介绍近5年来关于静态磁场和极低频电磁场生物效应的研究进展,包括信号转导、基因表达、染色体畸变、基因突变等细胞学和分子水平研究,以及致癌风险和健康危害评价等内容,并对该领域的未来研究进行了探讨。

极低频率电磁场对离体肿瘤细胞的诱导凋亡作用

目的探讨极低频率电磁场对体外培养肿瘤细胞的抑制作用。方法将人成骨肉瘤细胞(MG63)、乳腺癌细胞(MCF7)和肝癌细胞(HepG2)接种到96孔板中,并置于磁场强度分别为10mT、20mT、40mT、60mT的磁场中进行干预,每天刺激2次,每次1h,作用3天,同时每种细胞设置正常条件下的对照组。3天后以MTT法检测细胞活性(OD值),并采用流式细胞技术(AnnexinV—FITC和PI双标)检测3种细胞的凋亡情况。结果72h后以MTT法检测3种细胞的OD值,并于正常对照组进行比较,SPSS软件统计结果显示,磁场组的OD值较正常组低(P<0.05);流式细胞技术结果显示,磁场组肿瘤细胞凋亡细胞的阳性比例高于正常组,两组之间的差异有显著性统计学意义。结论极低频率电磁场对肿瘤细胞有明显抑制作用,在一定程度上诱导肿瘤细胞的凋亡。