Magnetic Field Parameters and Biological Sample Differences That Lead to Differential Bioeffects

In the scanning magnetic domain by using the conventional magnetic force microscopy (MFM), a laser beam reflection is used to detect the static magnetic force between probe and sample. Therefore, for the MFM, it is a challenge to directly detect the dynamic magnetic force between probe and sample under an external alternating-current (AC) magnetic field. In this study, it is proved that in an alternating magnetic force microscopy (A-MFM) a sensitive Co-GdO<sub><i>x</i></sub> superparamagnetic probe can be usedto detect the dynamic magnetic force under an external AC magnetic field (frequency <i>ω</i><sub>m</sub>). In the present method, the magnetization of Co-GdO<sub><i>x</i></sub> probe is modulated by an external AC magnetic field. Collecting <i>ω</i><sub>m</sub> and 2<i>ω</i><sub>m</sub> signals by using the combination of phase-locked loop (PLL) and lock in amplifiers can accurately represent the static (DC, which stands for direct current) magnetic field areas (the external AC magnetic field has no effect on the magnetized status of the sample) and dynamic (AC) magnetic field areas (the external AC magnetic field changes the magnetized status of the sample) of an anisotropic Sr ferrite sintered magnet at the same time, respectively. The Sr ferrite sample is a single-domain-type magnet where magnetization mainly changes via magnetic rotation. The A-MFM method can measure the strength and identify the polarities of the static magnetic field of sample with a DC demagnetized state. By modifying the traditional tapping-lift mode into a tapping-multiply lift mode, the A-MFM by using superparamagnetic tips can measure the static and dynamic magnetic field distribution in three-dimensional (3D) space. It is proved that the static and dynamic magnetic field as a function of the distance <i>z</i> between probe and sample are both expressed as <i>H<sub>z</sub></i>(<i>z</i>) = <i>H<sub>z</sub></i>(0)·exp(–<i>kz</i>). The experimental data are consistent with the previous theoretical calculations. The A-MFM can be used to study the dynamic magnetization process and to evaluate the magnetic homogeneity (microstructural homogeneity) of magnetic materials.

Static weak magnetic field measurements based on low-field nuclear magnetic resonance.

Magnetoreception

Solar activity regularly produces suprathermal electron bursts at energies below 1.4 keV. At 1 AU, these bursts have been detected at energies as low as 73 eV. The characteristics of such bursts vary considerably from event to event due in part to the physical processes involved in their propagation to Earth. In 2002, Advanced Composition Explorer/Solar Wind Electron Proton Alpha Monitor (ACE/SWEPAM) observed 101 solar electron bursts at energies below 1.4 keV, 40 of which exhibited broader pitch angle distributions than the preburst strahl. In general, the width of the pitch angle distribution from 73 to 1370 eV is a function of energy. In ∼65% of the events the pitch angle distribution width increased with energy during the burst, in ∼10% of the events it decreased with energy, and ∼25% of the cases demonstrated no clear energy dependence. The delay time between the onset of the burst and the onset of pitch angle distribution broadening also showed energy dependence. At 987 eV broadening almost always occurred after onset of the burst; however, at energies less than 519 eV broadening of the pitch angle distribution sometimes preceded the burst onset. Although energy dispersion was observed in the burst onset times, several events revealed nearly simultaneous broadening over an extended range of energies, in one case from 197 to 1370 eV. Broadening of the pitch angle distribution function during solar electron bursts almost certainly results from wave‐particle scattering. Scattering, in turn, should depend on solar wind plasma and magnetic field conditions. Nevertheless, we were not able to find any general statistical correlations between ACE plasma and magnetic field parameters and the burst pitch angle distribution width. Because ACE measurements are inherently local, whereas scattering can occur anywhere between the Sun and Earth, we also examined five bursts that we infer underwent relatively local scattering. These bursts exhibited maximum pitch angle distribution widths greater than 75°. Even these special cases failed to manifest any correlation with local plasma or magnetic field measurements.

In this study, for the first time, the combined effects of external magnetic, electric, and Aharonov-Bohm (AB) flux fields on quantum levels of the hydrogen atom embedded in Debye and quantum plasmas modeled by the more general exponential cosine screened Coulomb (MGECSC) potential are investigated within cylindrical coordinate formalism using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in the potential. The corresponding Schrödinger equation is solved numerically in order to examine both strong and weak regimes and confinement effects of external fields. The influence of screening parameters of the MGECSC potential on quantum levels of the hydrogen atom is also studied in detail in the presence of external magnetic, electric, and AB flux fields. As it is possible to model both Debye and quantum plasmas by using screening parameters in the MGECSC potential, the effects of each plasma environment on quantum levels of the hydrogen atom are also considered in the external fields. It is observed that there are important results of external fields on the total interaction potential profile, and the most dominant one in these fields is the magnetic field. Furthermore, the effects of confinement on the physical state of the plasma environment is a subject of this study. These details would be important in experimental and theoretical investigations in plasma and atomic physics fields.

Effect of static magnetic field on the molten pool dynamics during laser powder bed fusion of Inconel 718 superalloy

This research investigates Casson fluid flow over a vertical porous (absorbent) surface under a suitable applied magnetic field in the presence of a chemical reaction. The effects of various physical parameters, including the volume fraction of penetrable spheres, suction rate, Schmidt and Casson fluid numbers, magnetic field strength, and chemical concentration on the fluid mass transfer and momentum characteristics, specifically the Sherwood number and skin friction, are studied. The flow and mass-transfer equations governing the two phenomena are transformed into a nonlinear system of ordinary differential equations via similarity transformations. The velocity and concentration profiles under different parameter values are obtained by numerically solving the BVP using BVP4C in MATLAB. The quantitative results demonstrate that, while an increase in the Grashof number decreases skin friction, increases in the volume fraction, suction parameter, Schmidt number, Casson parameter, magnetic parameter, and chemical concentration increase skin friction. Conversely, the g (acceleration due to gravity) decreases with increasing Casson and magnetic field parameters, but increases with the chemical concentration, Grashof, Schmidt, suction, and volume fraction. These findings are corroborated by published literature. The current study has applications in the development of magnetic nanoparticles for targeted drug delivery, enhanced heat and mass transport phenomena in porous media processing, and the production of microfluidic devices, where control over chemically reactive, magneto-sensitive, non-Newtonian fluids is crucial.

High-altitude cusp: INTERBALL observation

In the present study, we have investigated the steady mixed convection nonaxisymmetric Homann stagnation-point flow in the presence of a magnetic field over a vertical flat wall immersed in a viscous and incompressible fluid. The magnetic field is applied in the normal direction to the plate. The governing equations are reduced to a system of nonlinear ordinary differential equations with suitable boundary conditions by applying similarity transformations to the equations and the boundary conditions. Using an efficient shooting method, the transformed equations are numerically solved. The solution involves the dimensionless governing parameters: γ representing the shear-to-strain-rate ratio, a mixed convection parameter λ, a magnetic field parameter M, and Prandtl number Pr. An important observation is that dual solutions exist for a certain range of mixed convection parameter λ. It is noticed that critical values λc of λ are found in opposing flow, which produce two solution branches by making saddle-node bifurcation at λ = λc. Numerical results are obtained for representative values of γ, λ, and M and are explored in depth. Through the use of graphs, the properties of the flow and temperature profiles for various values of the governing parameters γ, λ, and M are examined. Also, we examined how the solution varied with λ for representative values of M (magnetic field parameter). A parametric analysis is conducted to investigate how different governing parameters affect the characteristics of fluid flow and temperature. Also, we derive asymptotic results for large λ.

This paper presents an experimental exploration of the electrophysical properties of high-temperature superconductors that is based on the determination of the constitutive equation parameters for the combined model with two sources of electromagnetic field: current density and magnetization. It involves a series of experiments in different external magnetic fields and various transition modes to the superconducting state that allows the individual field sources to be distinguished. Since conditions that would enable us to maintain a homogenous current density distributions and magnetization under varying external magnetic induction in the HTSs are not available, the magnetic field parameters and its sources in the samples are determined via computational and experimental methods, in which the magnetic field parameters in the sample are calculated using their values out of the sample. A special laboratory installation equipped with the required measuring tools and magnetic system to create a controlled external magnetic field with the magnetic flux density of 1.5 T is constructed for the practical implementation of the experimental research technique.

The goal of investigation is to look at how a rotating disc affects the motion of magnetohydrodynamics micropolar nanofluid flow model (MHD-MPNFFM) in applied magnetic field and partial slip condition. Using suitable transformations, the PDEs of considered flow system are converted to ODEs. These obtained non-linear ODEs are then processed using the computational power of Lobatto IIIA approach to obtain a dataset of Artificial Intelligence neural networks model backpropagated with Bayesian Regularization procedure (AINM-BBRP) for variation of velocity slip parameters, magnetic field parameter, material parameters, Brownian motion parameter, thermophoresis parameter and Lewis number. To verify the current findings, a contrast to past study is included. Graphical representations of regression, efficiency, fit curve, error bars, and trained state analysis are presented using nftool. The velocity, temperature, microrotation, and concentration profiles were computed, and the findings were presented through graphs and tables. This is observed that velocity and microrotation or spin components are degraded by the slip action and magnetic field. Brownian motion parameter, thermophoresis parameter, and Lewis number all have rising temperature fields, however Brownian motion parameter and Lewis number have decreasing concentration profiles. The accuracy achieved in terms of relative error demonstrates the validity and significance of the solution process.

Hartmann boundary layer in peristaltic flow for viscoelastic fluid: Existence

Cable-less micro-robots have exhibited promising potential for conducting tasks in small and constrained environments through remote controlling approaches. Soft robots formed by magnetic composites have drawn rising attention, and have demonstrated their capability to be wirelessly controlled in both dry and wet working environments. This paper presents a swimmer propelled by its undulatory deformation using a magnetoelastic composite material. The swimmer can move freely on water surface driven through magnetic field generated by 3D Helmholtz coils, allowing forward and backward motion as well as steering with different velocity ranging from 0 to 14.9 mm s−1. To further study the characteristics of the swimmer, the force and torque equilibrium equations were established, and deformation of swimmer in response to different magnetic field was analyzed and described. The relationship between the parameters of magnetic field and the properties of the swimmer was obtained through analytical calculation, finite element modeling (FEM) and experiments. Furthermore, a closed-loop controlled system was developed to allow automatic path tracking and PID control of the swimmer, leading to distance errors and steering errors within ±0.36 mm and ±18.2° respectively. The swimmer and its mathematical model have suggested effective control through changing the parameters of external magnetic field. The swimmer may serve as soft surgical robots and drug delivers for biomedical and healthcare applications.

The therapeutic application of magnetic fi elds has experienced signifi cant growth in recent years. A small number of contraindications, as well as the lack of side effects makes both permanent magnets and alternating magnetic fi elds frequently used in physical therapy practice. In a signifi cant number of clinical studies the effi cacy of this physical factor as both an independent method, as well as supporting treatment programs has been confi rmed. In the last few years, a lot of emphasis is put on the fact that all therapeutic methods should have a scientifi c basis and their usage should meet the evidence based medicine criteria (EBM). Therefore, this work will focus on comparison of the use of permanent magnets and alternating low-frequency magnetic fi eld on the basis of the available literature, including mainly, a randomized double-blind trial. Analysis of the available literature on permanent magnet usage has shown clinical effi cacy in many diseases, however, placebo-controlled studies confi rm mainly the analgesic effect in patients after liposuction surgery, with diabetic neuropathy and with chronic pelvic pain. The use of the alternating low-frequency magnetic fi eld also leaves many questions to which scientists have still not found the answer. Randomized double-blind trial proved its therapeutic effi cacy in patients after knee arthroscopy, fractures and delayed bone unions, knee and cervical spine osteoarthritis as well as in case of leg ulceration. Alternating magnetic fi eld application has a wider therapeutic range in comparison to permanent magnets and its effectiveness is much better documented, both in clinical studies as well as randomized double-blind trials. Cite this article as: Głąb G., Dudek J., Klimek K., Skalska-Dulińska B., Chrabota U., Chojak-Fijałka K., Ridan T., Glodzik J. Static or dynamic low-frequency magnetic field? A review of literature. Med Rehabil 2016; 20(2): 31-35.

The spatial distribution of the lithospheric magnetic anomalies field carries information about its sources – deep tectonic structures – and reflects the processes occurring at mantle depths. Based on the geomagnetic data measured by the CHAMP satellite at an observation altitude of ~290 km, the lithospheric magnetic field parameters over the territory of the African continent were calculated. A lot of maps of the lithospheric magnetic anomalies field total intensity Ta based on various scales and degrees have been constructed. The distribution of Ta over the territories of South and East Africa is given. An analysis of lithospheric magnetic anomalies maps over the territories of African superplume influence showed good agreement with the existing hypothesis about the mantle superplume flow intrusion from the lower mantle to the upper mantle in the northeast direction and its further spread under the East African rift zone. The obtained parameters of the anomalous lithospheric magnetic field contain information about the magnetization of the lithosphere deep layers, reflecting the magnetic properties of large regional tectonic structures and the topography of the Curie surface, which is associated with the geothermal regime and tectonic setting at different levels of the lithosphere. The work shows the perspective of the geomagnetic field satellite observations using in the study of the active zones tectonics and mapping of deep lithosphere heterogeneities in hard-to-reach areas.