Distinctive features of collisionless gradient drift instabilities in a high-β plasma in a highly nonuniform magnetic field

A set of Vlasov-Maxwell equations for collisionless electromagnetic drift instabilities of high-β plasma configurations with a nonuniform magnetic fields is solved. The effect of the transverse static magnetic field variation and magnetic field line curvature, as well as the plasma temperature and density gradients, is considered. It is shown that, in a nonuniform magnetic field, the behavior of the instabilities differs substantially from that in a uniform field. Electromagnetic modes propagating strictly transverse to the lines of the static magnetic field are analyzed in detail, and unstable solutions are obtained for both extraordinary and ordinary waves. Numerical results show that, in the latter case, instability occurs when the magnetic field decreases toward the periphery and the plasma temperature and density gradients are oppositely directed.     

磁生物学效应的研究进展

磁场作用于生物体后产生一系列的生物学效应,这种观点已被多年来的许多实验所证实。早在1896年,磁场对神经系统作用的研究就已被报道。后来,磁场抗炎,促进骨生成,促进血管神经再生等作用相继被发现。近几十年来,关于磁场对生物体的作用,从流行病学调查到实验室研究也都有了一定进展。如今,磁场的生物学效应研究已成为物理医学研究的热点。本文就近年来磁场生物学效应研究的热点与进展作一简要综述。     

Model Studies of the Magnetocardiogram

A general expression is developed for the quasi-static magnetic field outside an inhomogeneous nonmagnetic volume conductor containing internal electromotive forces. Multipole expansions for both the electric and magnetic fields are derived. It is shown that the external magnetic field vanishes under conditions of axial symmetry. The magnetic field for a dipole current source in a sphere is derived, and the effect of an eccentric spherical inhomogeneity is analyzed. Finally the magnetic dipole moment is calculated for a current dipole in a conducting prolate spheroid.     

The influence of a magnetic field on chromosome sets and cell division]

An effect of stable magnetic field on karyotype and cell division of human lymphocytes from peripheral blood was studied in tissue culture. Comparative investigations were carried out with lymphocytes, whoch were treated with magnetic field of different tension (0,179; 0,391 and 0,600 Ts) and continuance (30 sec, 30 and 60 min). Lymphocytes, treated with stable magnetic field, were suspended in donor plasma and immediately cultivated after the treatment. The stable magnetic field was found to have a distinct mutagenic effect on cultivated lymphocytes of human peripheral blood. The increase in structural impairements of chromosomes correlated with tension of magnetic field and continuance of its effect. In structural impairements of chromosomes the chromatid gaps and breaks were more often observed but chromosome ruptures and pericentric clearances occurred more rarely. The effect of stable magnetic field on lymphocytes proliferation was studie. Under weak and transient using of magnetic field the proliferation was stimulated, but in rigid conditions--mitosis and blastic transformation were decreased. Continuous effect of magnetic field with weak tension did not inhibite the blastic transformation but influenced on the survival rate of cells in tissue culture, enhancing their lethality.     

Effects of static magnetic fields at the cellular level

There have been few studies on the effects of static magnetic fields at the cellular level, compared to those of extremely low frequency magnetic fields. Past studies have shown that a static magnetic field alone does not have a lethal effect on the basic properties of cell growth and survival under normal culture conditions, regardless of the magnetic density. Most but not all studies have also suggested that a static magnetic field has no effect on changes in cell growth rate. It has also been shown that cell cycle distribution is not influenced by extremely strong static magnetic fields (up to a maximum of 10 T). A further area of interest is whether static magnetic fields cause DNA damage, which can be evaluated by determination of the frequency of micronucleus formation. The presence or absence of such micronuclei can confirm whether a particular treatment damages cellular DNA. This method has been used to confirm that a static magnetic field alone has no such effect. However, the frequency of micronucleus formation increases significantly when certain treatments (e.g., X-irradiation) are given prior to exposure to a 10 T static magnetic field. It has also been reported that treatment with trace amounts of ferrous ions in the cell culture medium and exposure to a static magnetic field increases DNA damage, which is detected using the comet assay. In addition, many studies have found a strong magnetic field that can induce orientation phenomena in cell culture.     

Magnetic field effects on the fluorescence of mutant strains of Rhodopseudomonas capsulata

The magnetic field effects on bacteriochlorophyll fluorescence in six strains of Rhodopseudomonas capsulata were investigated. All strains exhibit an increase in fluorescence upon application of a magnetic field. Large magnetic field effects are shown to arise in mutants which contain the B800–850 complex as the only bacteriochlorophyll-containing protein. These fluorescence increases are observed only with carotenoid excitation and are best described by a carotenoid singlet heterofission mechanism. Variations in the magnitudes of the magnetic field effects for the Rps. capsulata strain arise from energy differences in the excited states of the molecules involved in the process. In order to determine the contribution from reaction centers to the magnetic field effects observed in the mutants which contain all three pigment-protein complexes, reaction centers were isolated from these strains. The reaction center contribution to the magnetic field effect on fluorescence in whole cells was determined to be smaller than the antenna contribution when carotenoid excitation was employed.     

Effect of a constant magnetic field on biological systems]

The effect of magnetic field on biological systems is discussed. A number of existing theories are evaluated, and a conclusion is made that it is difficult to explain from the standpoint of physics, neglecting the specifies of the living cell, the effect of the constant magnetic field on biological systems at the microscopic level.     

Effect of physiological parameters of blood on magnetophoretic mobility of erythrocytes

Magnetophoresis is the process of the particle motion under the influence of a magnetic field. The magnetic particle and medium are considered responsive to the imposed magnetic field, and the material property that describes the response to the external magnetic field is relative magnetic permeability, and the magnetic susceptibility. The present work aims to evaluate the effect of internal and external physiological parameters on the erythrocytes' magnetophoretic mobility (MM) using Cell Tracking Velocimetry (CTV). The results of this study showed that there are a strong correlation between MM and several physiological blood parameters such as mean corpuscle hemoglobin (MCH), red blood cells distribution width (RDW), mean corpuscle hemoglobin concentration (MCHC), and fibrinogen.     

Effect of physiological parameters of blood on magnetophoretic mobility of erythrocytes

Magnetophoresis is the process of the particle motion under the influence of a magnetic field. The magnetic particle and medium are considered responsive to the imposed magnetic field, and the material property that describes the response to the external magnetic field is relative magnetic permeability, and the magnetic susceptibility. The present work aims to evaluate the effect of internal and external physiological parameters on the erythrocytes' magnetophoretic mobility (MM) using Cell Tracking Velocimetry (CTV). The results of this study showed that there are a strong correlation between MM and several physiological blood parameters such as mean corpuscle hemoglobin (MCH), red blood cells distribution width (RDW), mean corpuscle hemoglobin concentration (MCHC), and fibrinogen.     

磁场对金针菇菌丝生长的影响及磁受体和铁离子转运蛋白的鉴定表达

磁场作为一种无法避免的自然因子,对生物的生长发育有重要影响。然而,目前磁场对大型真菌影响的研究还鲜有报道。本研究采用铷磁铁对金针菇菌丝进行处理,检测金针菇菌丝在不同磁极刺激下的生长和基因表达规律。结果显示：磁场是铷磁铁抑制金针菇菌丝生长的主要原因,且在磁感应强度0.003T以上对菌丝生长的抑制作用较强。通过同源比对获得一个金针菇磁受体和一个铁离子转运蛋白的编码基因,分别命名为ff-magr和ff-fief。定量PCR结果显示ff-magr在N极和S极均出现显著下调表达,N极和S极磁场对ff-fief 的表达均无显著影响。结果表明：磁受体蛋白参与了金针菇菌丝受磁场抑制的应答过程,而磁受体不仅仅是通过调控铁的含量来调控菌丝的生长发育。以上结果为合理利用磁场调控真菌生长发育奠定基础,同时也为深入研究磁场对真菌生长发育的分子机理提供参考。     

Thermodynamic properties of bulk knitted structures

The mechanism of interaction of an external magnetic field with liquid was proposed. The statistical integral and configurational contributions for a free energy, entropy and specific heat for the soliton model of bulk knitted structures in a magnetic field were calculated. It was shown that the concentration of solitons depends on the effect of external fields. In the specific case of bulk knitted structures (liquid water without magnetic field), the theoretical data are consistent with experimental. The memory effects in systems with hydrogen bonds in magnetic field was explained in the framework of the continuum soliton concept.     

静磁场保健寝具磁参数的评价

基于对生物磁学效应的研究,磁疗成为替代医学和补充医学的一种有效的治疗方法,本文通过对现有静磁场（恒定磁场）保健寝具磁标准和磁剂量的评述,首次提出磁保健寝具三围空间磁场的概念,指出采用磁感应强度在空间的强度分布作为磁保健剂量标准。论述了三围空间磁场具体磁参数的评价,包括所用磁源的表面磁感应强度,寝具织物表面磁场的穿透力、梯度、有效磁通量和空间能量等磁场分布的描述性指标。指出了静磁场保健寝具磁参数的合理的评价参量：为确保织物表面磁感应强度在目前认知的400～1100Gs有效安全剂量内,依据使用时的织物厚度,磁保健寝具选用的磁体表磁应在1000-3000Gs左右．且磁场的梯度不宜过大,磁场的平均穿透力在25-30cm左右,以确保空间磁场能量的有效作用于人体深处。     

Magnetoreception in fish

Magnetoreception is the ability of organisms to perceive magnetic fields in the surrounding environment and changes in its properties such as field direction, intensity and gradient, where the effect on organisms can manifest as an array of reactions. As the magnetic sense is found in many taxa, both evolutionarily young and old, it can be assumed that magnetoreception came into existence as one of the first sensory systems. Many studies on the effect of magnetic fields on fishes have considered both fishes that migrate for long distances and those that are more or less sedentary. Research has focused on tracing the perception of the geomagnetic field by fishes and understanding magnetic fields that are smaller and larger than the ambient Earth's geomagnetic field. The question of the effect of magnetic fields of values higher than the Earth's is gaining importance with the increasing effect of anthropogenic magnetic and electromagnetic fields in aquatic ecosystems. This review draws together the results of studies on the effect and reception of natural and human-generated magnetic fields on fishes at various stages of ontogeny, chronologically arranged from gametes, through embryonic development, embryonic and larval motor function, directional reactions of embryos and larvae, orientation of fishes, to the mechanisms of magnetic field reception. The present state of knowledge indicates a common nature of effect on various ontogenetic stages of fishes. However, understanding of the mechanisms of magnetic sense in fishes and its relevance for ecological outcomes highlights that further progress requires more detailed research.     

A novel strategy of selective gene delivery by using a uniform magnetic field

The application of a magnetic field to enhance the transfection efficiency has been reported to be mainly dependent on the magnetic force generated by a magnetic field gradient to attract paramagnetic bead-conjugated carrier and polynucleotide complexes. This strategy has the advantage of targeting a point or an area on the culture vessel. However, it is difficult to target deeply placed tissues in vivo. Uniform magnetic field-correlated effect is applicable to such a purpose. Here, we attempted to establish a novel procedure for uniform magnetic field-dependent enhancement of transfection efficiency. We examined the effect of a 1.5 mT uniform magnetic field on cellular reactive oxygen species (ROS) level and transfection efficiency mediated by a ROS-sensitive transfection carrier. Our experimental results revealed that a 1.5 mT uniform magnetic field transiently decreased cellular ROS levels and strongly enhanced transfection efficiency mediated by polyethylenimine (PEI). The uniform magnetic field-dependent enhancement of PEI-mediated in vivo transfection was confirmed in the livers of mice. Local intensification of a uniform magnetic field in a culture dish resulted in selective gene delivery into cells on the target area. Although further examination and improvement are necessary for this procedure, our findings provide a novel option for spatial control of gene delivery.     

Mechanism of erythrocyte aggregate formation in presence of magnetic field and dextrans as analyzed by laser light scattering

The mechanism of erythrocyte aggregation has been studied in normal plasma, dextran 40 and dextran 70 suspensions in presence and absence of magnetic field at a concentration of 5 percent by laser light scattering. The inhomogeneous magnetic field enhances the aggregating tendency of normal erythrocytes. The growth of aggregates due to dextran 70 is enhanced in presence of magnetic field. On the other hand the disaggregating effect of dextran 40 is reduced due to this field. The induced changes due to magnetic field during the development of erythrocyte aggregates in these media are determined.     

The susceptibility of pure tubulin to high magnetic fields: a magnetic birefringence and x-ray fiber diffraction study.

The orientational behavior of microtubules assembled in strong magnetic fields has been studied. It is shown that when microtubules are assembled in a magnetic field, they align with their long axis parallel to the magnetic field. The effect of several parameters known to affect the microtubule assembly are investigated with respect to their effect on the final degree of alignment. Aligned samples of hydrated microtubules suitable for low-resolution x-ray fiber diffraction experiments have been produced, and the results obtained from the fiber diffraction experiments have been compared with the magnetic birefringence experiments. Comparisons with earlier fiber diffraction work and small-angle x-ray solution scattering experiments have been made.     

Movement of dissolved oxygen in a constant magnetic field

Some regularities of the movement of liquid-solved oxygen in the constant magnetic field have been studied. Redistribution and specific dynamics of the changes of pO2 in a vessel with a physiological solution under the effect of the magnetic field are shown. The data obtained make us to believe that when interpreting the results of biological experiments applying magnets movement of oxygen in the magnetic field should be taken into account as well as possible change of metabolic processes in this case.     

The effect of static magnetic field on fibrinogen degradation products level in rabbits with thrombosis

The effect of static magnetic field of induction 0.005 T, 0.12 T and 0.3 T applied in daily rhythm (one hour every day) for the period of 2 weeks and 4 weeks produces an increase of FDP level in the serum. Especially, the effect elicited by the magnetic field applied 2 weeks prior to experimental thrombosis development. The range of changes was related to the duration of the exposure to the magnetic field. No dependence of the degree of induction of the magnetic field was established.     

Effects of a homogeneous magnetic field on erythrocyte sedimentation and aggregation

Effects of a homogeneous static magnetic field on erythrocyte sedimentation rate (ESR) have been assessed by using the standard Westergren method. A magnetic field of 6.3 T in the vertical direction only slightly enhanced ESR in saline solution, which was consistent with an effect on cell orientation. On the other hand, the magnetic field greatly enhanced ESR in plasma. It took a long time (about 20 min) for an ESR change to occur in plasma in response to the magnetic field. The effects in plasma were too large to originate only from cell orientation and were clearly distinct from a magnetic field-induced Boycott effect under an inhomogeneous magnetic field. A morphological examination and the nonlinear time course of the sedimentation in plasma indicated that the magnetic field increased cell aggregation and thereby enhanced ESR in plasma. Bioelectromagnetics 18:215–222, 1997. © 1997 Wiley-Liss, Inc.