Magnetic Fields Of Different Strengths Research Articles

Analysis of the Effects of Magnetic Field on the Haemogram Profile and Protein Content of Eri Silkworm, <i>Philosamia ricini</i>

The geomagnetic field is a naturally occurring physical force that operates to sustain life on earth. However, recent advances in technology, rapid urbanization and electromagnetic pollution have led to interferences in strength of the magnetic field, which has resulted in various health hazards in several life forms. This study was carried out to understand the effect of magnetic fields that are greater than the strength of the natural geomagnetic field in Philosamia ricini, commonly known as Eri silkworm. Qualitative and quantitative analysis of the haemogram profile as well as the total protein content, were considered for analysis. The 5th instar silkworm larvae were exposed to two magnetic fields of different strengths, namely 0.4493G and 0.8345G, and changes were recorded and compared with a control group. The results revealed decrease in the number of haemocytes and disruption of haemocytes that increased with increase in strength of magnetic field along. The total protein content of haemolymph also underwent changes with changes in the strength of the magnetic field. Such studies and future in-depth analysis of different biological parameters in organisms due to the changing geomagnetic field might be beneficial in understanding and maneuvering the effects of magnetic field on organisms.

Interaction of magnetic fields with biogenic magnetic nanoparticles on cell membranes: Physiological consequences for organisms in health and disease

The interaction mechanisms between magnetic fields (MFs) and living systems, which remained hidden for more than a hundred years, continue to attract the attention of researchers from various disciplines: physics, biology, medicine, and life sciences. Revealing these mechanisms at the cellular level would allow to understand complex cell systems and could help to explain and predict cell responses to MFs, intervene in organisms’ reactions to MFs of different strengths, directions, and spatial distributions. We suggest several new physical mechanisms of the MF impacts on endothelial and cancer cells by the MF interaction with chains of biogenic and non-biogenic magnetic nanoparticles on cell membranes. The revealed mechanisms can play a hitherto unexpected role in creating physiological responses of organisms to externally applied MFs. We have also a set of theoretical models that can predict how cells will individually and collectively respond to a MF exposure. The physiological sequences of the MF – cell interactions for organisms in health and disease are discussed. The described effects and their underlying mechanisms are general and should take place in a large family of biological effects of MFs. The results are of great importance for further developing novel approaches in cell biology, cell therapy and medicine.

Magnetism and magnetic phase transition in nanowires of diamagnetically diluted superstrong magnets ε-InxFe1-xO3

The temperature dependences of magnetization of ordered arrays of diamagnetically diluted nanoparticles of superstrong ε-InxFe1-xO3 magnets (x = 0.04, 0.24) in cooling and heating mode in the permanent magnetic fields of different strengths -strong and weak compared to the magnetic anisotropy field -were measured. At temperatures of 150 K for x = 0.04 and 190 K for x = 0.24 a sharp drop in their magnetization is observed, practically to zero. Obtained evidence that the observed magnetic phase transition is accompanied by overturning of magnetization due to spin-reorientation transition of the first kind. The experimental results are described within the magnetodynamic and thermodynamic approaches.

Electrospinning and characterization of magnetoelectric NdFeO3–PbZr0.52Ti0.48O3 Core–Shell nanofibers

A core–shell nanofiber with a neodymium orthoferrite (NdFeO3) core and lead zirconium titanate (PbZr0.52Ti0.48O3) shell was prepared in this study using the sol-gel electrospinning method. Structural properties of the nanofiber were analysed using the X-ray diffraction (XRD) method, which revealed that a perovskite structure was formed. The strain was calculated using Williamson-Hall (W–H) plot. Functional groups of the nanofiber were studied using Fourier transform infrared (FTIR) spectroscopy. Morphological studies revealed the core diameter of the nanofiber to be 65 nm and its shell diameter to be 128 nm. The elemental analysis of core-shell nanofiber was made using Energy Dispersive X-ray Spectroscopy (EDS) which proved the formation of NdFeO3 and PbZr0.52Ti0.48O3 composite in the stoichiometric ratio. Topography analysis using atomic force microscopy found the average fibre diameter to be 135 nm. The nanofiber exhibited antiferromagnetic behaviour, with a saturation magnetization of 0.48 emu/g. Dynamic contact electrostatic force microscopy (DC-EFM) studies revealed that the nanofiber showed domain-switching behaviour. The ferroelectric hysteresis plots showed that the nanofiber exhibited a maximum polarization of 5.45 μC/cm2 at 20 kV/cm. Also, its dielectric constant was 268 at 100 Hz. The leakage current study revealed a butterfly-shaped J-E loop, which further proved the ferroelectric behaviour of the nanofiber. The mechanism behind the leakage current was identified to be the Schottky emission. The P-E loops recorded under external magnetic fields of different strengths exhibited variations in the polarization, indicating the presence of cross-coupling between electric and magnetic order parameters. Because of the high dielectric constant displayed by the magnetoelectrically active NdFeO3–PbZr0.52Ti0.48O3 core–shell nanofiber, it can be a promising candidate for a number of applications, such as data storage devices, multimedia devices, spintronics and magnetic field sensors.

Technical Note: Effect of magnetic fields on the microdosimetry of carbon-ion beams.

To investigate the influence of magnetic fields on the microdosimetry of carbon-ion beams and the scaling effect of tissue equivalent proportional counter (TEPC) defined as the change of energy deposition in a TEPC from that in a microscopic scale region of interest due to the presence of a magnetic field in combination with the TEPC larger physical dimensions. Geant4-based Monte Carlo simulations were conducted to calculate the microdosimetric quantities for carbon-ion beams with different initial energies (10-290MeV/u) under magnetic fields of various strengths (0.5-3T). The calculations were performed for a 1μm spherical volume made of tissue, and for spherical TEPCs of 1 and 10mm in diameter. Then, values of dose-averaged lineal energy (yD ) were acquired for the different scenarios to analyze the effect of magnetic fields on the microdosimetry of carbon-ion beams and the scaling effect of TEPC. The yD values and lineal energy spectra in the 1μm spherical tissue volume for the scenarios without magnetic field and with magnetic fields of different strengths and directions remained nearly the same for the various energy carbon-ion beams. However, compared with those of the 1μm spherical tissue volume, an increase of of yD values and an obvious shift of the lineal energy spectra for the TEPCs of 1 and 10mm in diameter under magnetic fields were found. The application of magnetic fields under 3T has no significant influence on the microdosimetric results of carbon-ion beams. However, there is definitely a scaling effect when using TEPC for microdosimetric study, which alters the reading of TEPC in the presence of magnetic fields. Novel methods to correct the reading of TEPC or scaling effect-resistant microdosimetric measurement detectors are urgently needed to perform experimental microdosimetric studies under magnetic fields.

Dynamical response of a quantum R–L circuit in the presence of resonant tunneling

The admittance of a quantum point contact (QPC) is investigated in the ac regime. Resonance-like peaks superimposed on the commonly occurring admittance plateaus are observed. To explore the origin of these peaks, we perform measurements on the sample in perpendicular magnetic fields of different strengths. We find that as the magnetic field increases, the resonance-like peak located at the first admittance plateau disappears, while that at the third plateau becomes more pronounced. Under certain conditions, these peaks can evolve into 0.7 anomalous plateaus. We believe that these resonance-like peaks are caused by the presence of impurities in the QPC. To confirm this, a bias voltage is added to the common gate voltage to generate an asymmetric QPC confinement potential. We then observe an asymmetric evolution of the peaks for both positive and negative bias voltages. The effects of the magnetic field and the bias voltage can be described well by the results of numerical calculation using the finite difference method and taking into account the influence of the impurity. The results of this work should help provide better understanding of charge dynamic transfer and may also be useful for the study of QPC-based devices such as qubits and quantum dots.

Magnetic field assisted preconcentration of biomolecules for lateral flow assaying

Lateral flow assays (LFA) have been extensively explored for rapid and cost effective point-of-care diagnostics. Typically, LFA responses are influenced by the complexity of sample matrices containing analogues or molecules that may potentially yield non-specific responses, for instance, when assaying for biomarkers in blood, serum and plasma. Therefore, isolation of analytes of interest from sample matrices would significantly improve the LFA responses. Herein, we report a magnetic field assisted preconcentration approach for extraction and assay of proteins in an LFA format. Cardiac marker, Troponin (cTnICT complex), is utilized as a model system for validation of the proposed approach. Magnetic fields of different strengths are evaluated for retaining cTnICT on an LFA membrane utilizing magnetic beads conjugated with anti-Troponin I (anti-TnI) antibodies. The sample matrix components subsequently flows through to the absorbent pad via a hydrophilic passivation layer that is protecting the capturing anti-Troponin C (anti-TnC) antibodies in the test zone. Isolated TnI-magnetic bead complexes are then released to flow downstream along the LFA strip to the test zone upon removal of magnetic field and the passivation layer. The capture of cTnICT magnetic bead complexes at the test zone produces a characteristic brownish band, enabling concentration dependant visual detection of cTnICT. Experimental results indicate that the assay yields pM level sensitivity within 15 min using very low sample volumes (<100 μL), and with possibilities for signal enhancement. The reported assay offers a promising avenue for sensitive detection of target analytes in complex matrices at clinically relevant concentration levels without requiring tedious sample pre-treatment protocols.

Defects characterization studies of europium-substituted bismuth ferrite nanocrystals by positron annihilation and other methods

In this paper, we present a detailed study of the origin of structural defects and their role on the effects of Eu3+-substitution (x  =  0.0, 0.05…..., 0.3) in place of Bi3+ in Bi1−xEuxFeO3 nanocrystalline multiferroic perovskite samples. The samples were synthesized through a sol-gel route and characterized by x-ray diffraction and transmission electron microscopy. The energy dispersive analysis of x-rays clearly demonstrated the effective replacement of Bi3+ ions by Eu3+ and a possibility of generation of oxygen vacancies. UV–vis diffuse reflectance spectra were recorded to determine the band gap, which showed a continuous decrease on increased substitution. The phenomenon indicated the creation of defects-induced energy levels in the band gap closer to the conduction band. Positron annihilation spectroscopy revealed the presence of structural defects like trivacancies within the Bi1−xEuxFeO3 nanocrystallites. The surfaces of nanocrystallites smaller than the thermal diffusion lengths of positrons also acted as trapping centres. The transformation from the distorted rhombohedra structure to an orthorhombic configuration with an accompanying lattice contraction at x  >  0.2 influenced the positron lifetimes and the intensities. Substitution also resulted in the recombination of the pre-existed vacancies with a fraction of the doped ions. Coincidence Doppler broadening measurements confirmed cationic vacancies as the predominant defects. Magneto-electric voltages measured under a.c. magnetic fields of different strengths showed an increase until x  =  0.2 and then decreased concomitantly with the transformation of the crystallites to the orthorhombic structure.

Suspension Rheology and Magnetorheological Finishing Characteristics of Biopolymer-Coated Carbonyliron Particles

Magnetorheological (MR) finishing has been adopted as a newly ultraprecision finishing method for microparticles, an optical system, and an aspherical lens, mainly by MR fluids consisting of magnetic carbonyliron (CI) particles and a carrier fluid such as silicone oil or diwater. However, CI particles are related to corrosion problems because of their oxidation, leading to unpredictable polishing results and a short lifetime of the MR fluids. To resolve this problem, we coated CI particles with a biopolymer of xanthan gum (XG) for better MR polishing and measured their MR properties using a rotational rheometer under applied magnetic fields of different strengths. Experiments were carried out to examine the material removal depth and the surface roughness for BK7 (borosilicate) glass by changing the experimental parameters. While the material-removal depth obtained using raw CI particles was deeper than that for the XG-coated CI particles, the surface roughness obtained using the XG-coated CI particles after MR polishing was lower than that for pure CI particles. These results confirm that XG-coated CI particles can be applied for the MR polishing of a BK7 glass well.

Resolution changes of MCP-PMTs in magnetic fields

Micro-channel plate photomultiplier tubes (MCP-PMTs) are chosen in many applications that have to cope with strong magnetic fields. The DIRC detectors of the PANDA experiment plan to employ them as they show excellent timing characteristics, radiation hardness, relatively low dark count rates and sufficient lifetime. This article mainly focuses on the performance of the position reconstruction of detected photons. Two different MCP-PMTs with segmented anode geometries have been tested in magnetic fields of different strengths. The variation of their performance has been studied. The measurements show improved position resolution and image shifts with increasing magnetic field strength.

MAGNETIC FIELDS AND GALACTIC STAR FORMATION RATES

The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of giant molecular clouds (GMCs) within a kiloparsec patch of a disk galaxy and resolving scales down to $\simeq0.5\:{\rm{pc}}$. Including an empirically motivated prescription for star formation from dense gas ($n_{\rm{H}}>10^5\:{\rm{cm}^{-3}}$) at an efficiency of 2\% per local free-fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated $B$-field case of $80\:{\rm{\mu}}$G. However, our chosen kpc-scale region, extracted from a global galaxy simulation, happens to contain a starbursting cloud complex that is only modestly affected by these magnetic fields and likely requires internal star formation feedback to regulate its SFR.

The influence of material properties on the assembly of ferrite nanoparticles into 3D structures

The fabrication of patterned arrays consisting of magnetic nanoparticles is gaining more and more research activities due to the possibility of enhancing a material's properties for the use in various fields (i.e. magneto-electrics). Here we present the influence of the particle size, the magnetic interactions between the particles and the strength of the applied magnetic field on the magnetically-directed assembly of ferrite nanoparticles. The assemblies were prepared from cobalt ferrite and maghemite suspensions using the drop-deposition technique without or with applied magnetic fields of different strengths. The cobalt ferrite particles with diameter of 6, 8, 10, 12, 20 nm, and maghemite nanoparticles with a diameter of 14 nm were used. The particles' size influences their magnetic properties, the magnetic interactions between the particles and, consequently, the assemblies' morphology. At an applied magnetic field of 0.5 T the morphology of the assembled structures was gradually changing as the particles' size was increasing from flat films for the 6 nm-sized cobalt ferrite nanoparticles to ordered 3-dimensional structures with columnar shape for the 20 nm-sized cobalt ferrite and 14 nm-sized maghemite nanoparticles. The assembled 3-dimensional structures displayed promising magnetic properties and can be used as a basis for the preparation of magneto-electric composites.

RADIATIVE INTERACTION OF SHOCKS WITH SMALL INTERSTELLAR CLOUDS AS A PRE-STAGE TO STAR FORMATION

Cloud compression by external shocks is believed to be an important triggering mechanism for gravitational collapse and star formation in the interstellar medium. We have performed MHD simulations to investigate whether the radiative interaction between a shock wave and a small interstellar cloud can induce the conditions for Jeans instability and how the interaction is influenced by magnetic fields of different strengths and orientation. The simulations use the NIRVANA code in three dimensions with anisotropic heat conduction and radiative heating/cooling at an effective resolution of 100 cells per cloud radius. Our cloud has radius 1.5 pc, has density 17 cm{sup -3}, is embedded in a medium of density 0.17 cm{sup -3}, and is struck by a planar Mach 30 shock wave. The simulations produce dense, cold fragments similar to those of Mellema et al. and Fragile et al. We do not find any regions that are Jeans unstable but do record transient cloud density enhancements of factors {approx}10{sup 3}-10{sup 5} for the bulk of the cloud mass, which then decline and converge toward seemingly stable net density enhancement factors {approx}10{sup 2}-10{sup 4}. Our run with a weak, initial magnetic field ({beta} = 10{sup 3}) perpendicular to the shock normal standsmore » out as producing the most lasting density enhancements. We interpret this field strength as being the compromise between weak internal magnetic pressure preventing compression and sufficiently strong magnetic field to thermally insulate the condensations, thus helping them cool radiatively.« less

재질과 자기장 세기가 자기유변유체의 마찰 특성에 미치는 영향

Magnetorheological (MR) fluid belongs to the group of smart materials. In MR fluid, iron particles in base oil form chains in the direction of the applied magnetic field, thus resulting in a variation in the stiffness and damping characteristics of the fluid. Research is being carried out on controlling the stiffness and damping characteristics as well as the tribological characteristics of the MR fluid. In this study, the friction characteristics of MR fluid have been evaluated using three types of materials and magnetic fields of different strengths. The coefficients of friction of the three types of MR fluid are measured, and the relationship between the coefficient of friction and the strength of the applied magnetic field is obtained.

Calculation of magnetization curves and probability distribution for monoclinic and uniaxial systems

We present the application of a simple classical statistical mechanics-based model to selected monoclinic and hexagonal model systems. In this model, we treat the magnetization as a classical vector whose angular orientation is dictated by the laws of equilibrium classical statistical mechanics. We calculate for these anisotropic systems, the magnetization curves, energy landscapes and probability distribution for different sets of relevant parameters and magnetic fields of different strengths and directions. Our results demonstrate a correlation between the most probable orientation of the magnetization vector, the system's parameters, and the external magnetic field.

Conductivity enhancement induced by casting of polymer electrolytes under a magnetic field

We recently presented a procedure for orienting the polyethylene-oxide (PEO) helices in a direction perpendicular to the film plane by casting the polymer electrolytes (PE) under a magnetic field (MF). Here we study the influence of magnetic fields of different strengths and configurations on the structural properties and ionic conductivity of concentrated LiCF 3SO 3 (LiTf) and LiAsF 6:P(EO) pristine and composite polymer electrolytes containing γ-Fe 2O 3 nanoparticles. Some data of LiI:P(EO) system are shown for comparison. We suggest that the effect of type of salt (LiI, LiTf and LiAsF 6) on the structure–conductivity relationship of the polymer electrolytes cast under magnetic field is closely connected to the crystallinity of the PEO–LiX system. It was found that the higher the content of the crystalline phase and the size of spherulites in the typically cast salt-polymer system, the stronger the influence of the magnetic field on the conductivity enhancement when the electrolyte is cast and dried under MF. Casting of the PE from a high-dielectric-constant solvent results in disentanglement of the PEO chains, which facilitates even more the perpendicular orientation of helices under applied MF. The enhancement of ionic conductivity was appreciably higher in the PEs cast under strong NdFeB magnets than under SmCo. Both bulk (intrachain) and grain-boundary conductivities increase when a MF is applied, but the improvement in the grain-boundary conductivity – associated with ion-hopping between polymer chains – is more pronounced. For LiAsF 6:(PEO) 3 at 65 °C, the interchain conductivity increased by a factor of 75, while the intrachain conductivity increased by a factor of 11–14. At room temperature, the SEI resistance of these PEs, cast under NdFeB HMF, decreased by a factor of up to 7, as compared to the typically cast polymer electrolytes. The effect of MF on orientation is observed directly down to the molecular level by 7Li nuclear magnetic resonance measurements.

Vortical structures and turbulent bursts behind magnetic obstacles in transitional flow regimes

The present paper reports on numerical investigations of vortical structures in transient flow regimes generated by the local action of the Lorentz force on an electrically conductive fluid. The locally imposed non-uniform magnetic field generates similar effects as observed for flows over submerged solid obstacles. It is demonstrated that complex flow patterns can be generated by imposing magnetic fields of different strengths. The initial validation of the electromagnetically extended Navier–Stokes solver on unstructured numerical grids is performed in the low-Reynolds number range 100 ⩽ Re ⩽ 400 for different values of the magnetic interaction parameter. A generally good agreement is obtained in comparison with similar numerical studies of Votyakov et al. (2007, 2008) for the low-Reynolds number cases. Then, a series of simulations are performed in transitional flow regimes ( Re = 900) for different values of the interaction parameter ( N = 3, … , 25). Simulations demonstrated the appearance of vortex-shedding phenomena similar to the flows behind solid obstacles. In contrast to the solid obstacles, the magnetic obstacles also generated the vortical flow patterns inside the magnetically affected regions. This feature can be used for the flow control of electrically conductive fluids, for efficient enhancements of the wall-heat transfer or for better mixing of passive scalars. Despite the laminar inflow conditions, turbulent bursts are observed in the magnetic wake region for the Re = 900 case. The velocity spectra and spatial distributions of the long-time averaged second-moments of the velocity field demonstrated that turbulence was locally sustained in the proximity of the magnetic wake edge.

Influence of static magnetic fields on nerve regeneration in vitro

Our research involves determining how non-invasive electric and magnetic fields influence neuronal growth in vitro. In previous studies we have shown that pulsed electromagnetic fields (PEMF) as well as direct current (DC) alone stimulate neurite outgrowth from dorsal root ganglion explants [Sisken et al. 1984; Sisken et al. (Restor Neurol Neurosci 1:303–309, 1990); Greenebaum et al. (Bioelectromagnetics 17:293–302, 1996)]. A maximum response was obtained when nerve growth factor (NGF) was also present in the medium. The results of our experiments using static magnetic fields of different strengths are presented below and indicate that fields of high magnetic strength (450–900 gauss) with added NGF stimulate neurite outgrowth comparable to the response obtained with PEMF plus NGF.

Field-dependent postdepositional grain realignment in the PDRM process: experimental evidence and implications

The field dependence of postdepositional remanent magnetization (PDRM) has been investigated by two-component PDRM acquisition experiments in deviating magnetic fields of different strengths. The experiments have been performed on samples consisting of crushed, natural magnetite grains in pseudo-single-domain (PSD) states embedded (< 0.1% by weight) in a slowly curing epoxy (Araldite). The increasing viscosity with time of the epoxy is thought to mimic consolidation processes in sediments, which gradually inhibits magnetic grain realignment. Resulting PDRM directions are partly intermediate between final and initial field directions which are unresolvable by alternating field demagnetization to 60 mT. The results suggest that partial PDRM acquired in initial low fields are modified by subsequent exposure to stronger fields. This may be due to alignment of grains not affected by the initial field or by remobilization of grains previously aligned in the weaker initial field. The suggested field-dependent PDRM smoothing may prevent improvement of paleomagnetic records by deconvolution procedures, and may imply that longitudinally confined paleomagnetic records in sediments of transitional polar paths during reversals may partly be artifacts of the PDRM recording process.

Measurement of lightning currents with different signs by magnetic links

AbstractIn regions experiencing intense thunderstorm activity, there are frequent failures of communication lines and equipment due to direct lightning strokes. For the effective application of lightning protection measures, it is extremely important that we have a good understanding of lightning current distributions. The magnetic link is known to be a convenient method of measuring lightning currents at a large number of grounding points. However, when currents of different sign are flowing, due to fluctuation in residual magnetism of the magnetic link, in regions experiencing concentrated lightning strokes it has not been possible to measure the lightning current by means of magnetic links.Using the nonlinearity of the magnetization curve, this paper examines the measurement of currents of different signs using magnetic links. We place magnetic links at two locations having magnetic fields of different strengths and when currents of different signs are present, from the measured values of the residual magnetism in the two magnetic links, we prepared a calibration curve from which we can determine the magnitudes of the currents in each direction. In addition, this method was used in the west central region of Africa to measure cable sheath currents, obtaining lightning crest value distributions which can be considered to be essentially the same as the distributions in Europe and America. This work has verified the effectiveness of this method of lightning current measurement.