External Static Magnetic Field Research Articles

Changes of 1,2,4-triazole retention and lipophilicity descriptor values in RP-TLC and MLC—TLC systems in the presence of an external magnetic field

As it was shown in earlier experiments, magnetic field can influence various processes taking part in nature. One of them might be the permeation of chemical compounds across biological membranes. An excellent tool for investigations on that subject is chromatography. Basing on retention measurements performed using reversed-phase thin-layer chromatography (RP-TLC) and micellar liquid chromatography—thin-layer chromatography (MLC—TLC), descriptors of lipophilicity were calculated for the group of 1,2,4-triazole derivatives. The experiments were performed in moderate (≈0.4 T) magnetic field and simultaneously outside it. The analysis of the obtained data showed that the presence of an external static magnetic field can alternate the obtained descriptor values which allows to assume that the ability of passive permeation of the investigated substances across cellular membrane also changes. The intensity of changes depends on the structure of the chromatographed substance and the lipophilicity measurement method.

Influence of steady magnetic field on dynamic behavior mechanism in full penetration laser beam welding

To study influence from external static magnetic field on dynamic behavior interaction between laser beam and EH36 steel, four cases with different magnetic strength (0mT, 15mT, 25mT and 30mT) are designed to capture high-speed image series of full penetration laser welding through quartz glass. It can be observed that: (1) Part of laser welding energy is compacted in bottom of weld pool to increase penetration and bottom width of bead geometry; (2) Eruption cycle and intensity (height 2.125mm, width 1.75mm) of vapor plume are both weakened; (3) Inhomogeneity and fluctuation of energy distribution are prominently dropped off; (4) Cooling period is delayed to reduce thermal gradient, depression area of the final profile is also reduced. Meanwhile, a polynomial model is developed to reveal relationship between thermal density and distance along the weld center. Therefore, external steady magnetic field has influence on dynamic behavior mechanism (weld pool, vapor plume, energy homogeneity, cool down stage) and even the final morphology, while 15mT is an optimal value of the magnetic strength in these four cases. It can be concluded that selecting an appropriate magnetic field strength is helpful to stabilize laser process and improve welding quality.

Weld profile, microstructure, and mechanical property of laser-welded butt joints of 5A06 Al alloy with static magnetic field support

The magnetic support technology has been widely recognized to be an ideal way of improving the welding quality. In current work, the 7-mm 5A06 Al plates are laser welded with an external static magnetic field aligned vertically to the welding direction. The bead formation, grain configuration, alloying element distribution, and weld hardness are experimentally analyzed to reveal the magnetically dominated flow behavior within the weld pool. The results indicate that, under the function of the magnetostatic field, the continuity and stability of the aluminum welds are improved and the weld width especially on the bead surface diminishes obviously with increasing magnetic flux density from 0 to ~238 mT. The evolutions on weld profile are caused by the induced electromagnetic suppression on the molten convection, especially the Marangoni. The grain enlargement, remarkable grain-boundary segregation, and chemical heterogeneity are found in the seams with magnetic field applied since the blocked melt flow restrains the thermal transfer and decreases the nucleation rate and supercooling degree. The weld hardness achieves lower in fusion zone but higher in HAZ compared with the control case, which is consistent with the microstructure characteristics.

Magnetic targeting with superparamagnetic iron oxide nanoparticles for in vivo glioma

AbstractThe purpose of this study was to review the use of the magnetic targeting technique, characterized by magnetic driving compounds based on superparamagnetic iron oxide nanoparticles (SPIONs), as drug delivery for a specific brain locus in gliomas. We reviewed a process mediated by the application of an external static magnetic field for targeting SPIONs in gliomas. A search of PubMed, Cochrane Library, Scopus, and Web of Science databases identified 228 studies, 23 of which were selected based on inclusion criteria and predetermined exclusion criteria. The articles were analyzed by physicochemical characteristics of SPIONs used, cell types used for tumor induction, characteristics of experimental glioma models, magnetic targeting technical parameters, and analysis method of process efficiency. The study shows the highlights and importance of magnetic targeting to optimize the magnetic targeting process as a therapeutic strategy for gliomas. Regardless of the intensity of the patterned magnetic field, the time of application of the field, and nanoparticle used (commercial or synthesized), all studies showed a vast advantage in the use of magnetic targeting, either alone or in combination with other techniques, for optimized glioma therapy. Therefore, this review elucidates the preclinical and therapeutic applications of magnetic targeting in glioma, an innovative nanobiotechnological method.

Coexistence of bulk and surface polaritons in a magnetic-semiconductor superlattice influenced by a transverse magnetic field

It is demonstrated that the effect of coexistence of bulk and surface polaritons within the same frequency band and the wavevector space can be achieved in a magnetic-semiconductor superlattice, providing a conscious choice of characteristic resonant frequencies and material fractions of the structure's underlying components as well as geometry of the external static magnetic field. The study is based on the effective medium theory, which is involved to calculate dispersion characteristics of the long-wavelength electromagnetic modes of ordinary and extraordinary bulk polaritons, and hybrid surface polaritons with dominant longitudinal component of either magnetic (HE) or electric (EH) field derived via averaged expressions with respect to the effective constitutive parameters of the superlattice.

Higgs mechanism in superconducting structures

It is shown that in equilibrium superconducting structures with s-wave pairing, the unique part of the phase of the complex ordering parameter 〈ψ↑ψ↓〉 transforms into the longitudinal component of the vector potential as in the Abelian Higgs model of relativistic field theory. This analysis is based on a microscopic Hamiltonian of the system in the presence of an external static magnetic field and infinitely small Cooper pair sources. Impurities and nonsuperconducting barriers are assumed to be present, and the quantum nature of the induced electromagnetic field is taken into account. Quantization of the latter is done under the condition A0 = 0 (A0 is the scalar potential) that the invariance with respect to time-independent gauge transformations is not broken. Exact relations determining the quasi-averages 〈ψ↑ψ↓〉 are established. These relations play a key role in the new derivation of the mean-field equations discussed in this article. A new physical treatment of the Josephson effect (without a “phase difference”) is proposed on the basis of these results and some of its consequences are discussed.

Crossing and anti-crossing effects of polaritons in a magnetic-semiconductor superlattice influenced by an external magnetic field

Crossing and anti-crossing effects in dispersion characteristics of both bulk and surface polaritons in a magnetic-semiconductor superlattice influenced by an external static magnetic field being in the Faraday geometry are discussed. The bulk polaritons are classified as eigenwaves with right-handed and left-handed elliptically polarized states, whereas the surface polaritons are considered as hybrid modes having a predominant effect of either magnetic or semiconductor subsystem, and distinctions in dispersion characteristics of such polaritons are revealed involving the concept of critical points.

Enhanced dynamics simulation and threshold analysis of multipaction in the ferrite microwave component

Multipactor discharge between dielectric and metal was investigated and experimentally verified for the first time. Moreover, multipaction electron evolution laws in the complex ferrite component were revealed, and discharge breakdown threshold was analyzed. Through reasonable approximation and by establishing the equivalent analytical model, the effects of the external static magnetic field and charge accumulation were investigated, and transient electronic trajectory was obtained. Based on the electromagnetic particle-in-cell technology, the three dimensional simulation method of electron evolution in complex ferromagnetic microwave components was implemented. The discharge threshold was obtained through the long term evolution of field to electron and electron to field interactions and verified by multipactor measurement on the circulator for the first time. Instead of the steady field condition, the steady particle condition was proposed for the threshold prediction, exhibiting great potential in the space industry application. It is demonstrated that for ferrite dielectric-metal multipaction, the phase focusing process was prolonged, and the traditional prediction criteria for the threshold analysis were invalid due to the existence of the external magnetic field and highly inhomogeneous field distribution.

Impact of an External Magnetic Field on the Shear Stresses Exerted by Blood Flowing in a Large Vessel

The aim of this paper is to provide an advanced analysis of the shear stresses exerted on vessel walls by the flowing blood, when a limb or the whole body, or a vessel prosthesis, a scaffold… is placed in an external static magnetic field B0. This type of situation could occur in several biomedical applications, such as magnetic resonance imaging (MRI), magnetic drug transport and targeting, tissue engineering, mechanotransduction studies… Since blood is a conducting fluid, its charged particles are deviated by the Hall effect, and the equations of motion include the Lorentz force. Consequently, the velocity profile is no longer axisymmetric, and the velocity gradients at the wall vary all around the vessel. To illustrate this idea, we expand the exact solution given by Gold (1962) for the stationary flow of blood in a rigid vessel with an insulating wall in the presence of an external static magnetic field: the analytical expressions for the velocity gradients are provided and evaluated near the wall. We demonstrate that the derivative of the longitudinal velocity with respect to the radial coordinate is preponderant when compared to the θ-derivative, and that elevated values of B0 would be required to induce some noteworthy influence on the shear stresses at the vessel wall.

閉殻重原子系における外部静磁場によって誘起される電子スピン密度の解析

We present a clear equation and a simple display method to analyze theoretically the spin density induced by an external static magnetic field in closed-shell molecules containing heavy atoms (Xe and HI). We showed that the magnitude of the spin density in a heavy-atom-light-atom (HALA) system is proportional to the mixing of the opposite spin orbital caused by the spin-orbit interaction.

Optimization of processing parameters of AISI 316L laser welding influenced by external magnetic field combining RBFNN and GA

The external static magnetic field has significant influence on the microstructure and mechanical properties of weld bead during 316L stainless steel laser welding. The quality of a weld joint of laser welding supported by external magnetic field (LWSMF) is significantly influenced by the processing parameters. Hence, how to choose appropriate processing parameters for a good-quality weld joint of LWSMF is significantly important. This paper develops a hybrid methodology by combining radial basis function neural network (RBFNN) and genetic algorithm (GA) to address this issue. Firstly, the bead appearance, which is the external manifestation of the weld geometrical imperfection and weld quality, is quantitatively described and selected as the indices to judge the weld quality of LWSMF. Then the physical experiments are conducted, where laser power (LP), laser welding speed (WS), and the flux density of magnetic field (MFD) are taken into consideration as the input process parameters. Secondly, the RBFNN model, as its excellent global prediction performance, is adopted to establish the relationships between the inputs and outputs. Thirdly, based on the constructed RBFNN model, the effects of different input parameters on the bead appearance are analyzed and the global process parameter space exploration is performed by using GA. At last, the verification experiments are conducted to verify the effectiveness of the calculated optimal process parameters. Results demonstrate that the spatter defects decrease and the grains are refined under the influence of external magnetic after optimization. On the whole, the proposed hybrid methodology shows great promise for improving the effectiveness and stability of LWSMF.

Magnetically and Photonically Tunable Double Waveguide Inverter

We consider a system of two parallel quantum waveguides that coupled via a coupling window. The coupled waveguide system is exposed to an external magnetic field and coupled to a photon field. We take into account both the electron–electron and electron–photon interactions in the system and an exact diagonalization technique is used to treat these interactions. We investigate electron switching between the waveguides using external static magnetic field, side-dot gate, and quantized photon field. The role of the Coulomb interaction in electron switching is also presented. Furthermore, we show how a single photon can enhance electron transport between the waveguides where the photon is polarized in the same direction of electron motion.

Effect of static magnetic field on the hemodynamic properties of blood flow containing magnetic substances

The use of magnetic fields in targeted drug delivery, especially for treatment of cancers and tumoral regions, is one of the significant techniques in the field of modern methods of treatment. Considering that many vital biological tissues have been located deep in the body, then for targeted drug delivery and effective treatment in these tissues, it is required to bring therapeutic agent to the desired location and focus on that location. The purpose of this study is to evaluate the static magnetic field interaction with hemodynamic properties of blood flow containing a magnetic carrier substance as a bio magnetic fluid. The finite element method (FEM) is used for 2D numerical simulation of magnet with different tip shapes and evaluating of external static magnetic field and its effects on the blood flow with aforementioned properties. The results show that the static magnetic fields generated from magnets with different tip shapes have different effects on the distribution of the fluid velocity field. Furthermore it can be concluded that when magnetic field flux density is concentrated around the magnet tip, the intensity of these hemodynamic effects become more concentrated within the fluid and the location of the magnet tip on the tissue, though the hemodynamic variables have been changed.

Effects of magnetic field on photon-induced quantum transport in a single dot-cavity system

In this study, we show how a static magnetic field can control photon-induced electron transport through a quantum dot system coupled to a photon cavity. The quantum dot system is connected to two electron reservoirs and exposed to an external perpendicular static magnetic field. The propagation of electrons through the system is thus influenced by the static magnetic and the dynamic photon fields. It is observed that the photon cavity forms photon replica states controlling electron transport in the system. If the photon field has more energy than the cyclotron energy, then the photon field is dominant in the electron transport. Consequently, the electron transport is enhanced due to activation of photon replica states. By contrast, the electron transport is suppressed in the system when the photon energy is smaller than the cyclotron energy.

Theoretical study of the dynamic magnetic response of ferrofluid to static and alternating magnetic fields

The dynamic magnetic response of ferrofluid in a static uniform external magnetic field to a weak, linear polarized, alternating magnetic field is investigated theoretically. The ferrofluid is modeled as a system of dipolar hard spheres, suspended in a long cylindrical tube whose long axis is parallel to the direction of the static and alternating magnetic fields. The theory is based on the Fokker-Planck-Brown equation formulated for the case when the both static and alternating magnetic fields are applied. The solution of the Fokker-Planck-Brown equation describing the orientational probability density of a randomly chosen dipolar particle is expressed as a series in terms of the spherical Legendre polynomials. The obtained analytical expression connecting three neighboring coefficients of the series makes possible to determine the probability density with any order of accuracy in terms of Legendre polynomials. The analytical formula for the probability density truncated at the first Legendre polynomial is evaluated and used for the calculation of the magnetization and dynamic susceptibility spectra. In the absence of the static magnetic field the presented theory gives the correct single-particle Debye-theory result, which is the exact solution of the Fokker-Planck-Brown equation for the case of applied weak alternating magnetic field. The influence of the static magnetic field on the dynamic susceptibility is analyzed in terms of the low-frequency behavior of the real part and the position of the peak in the imaginary part.

Spectra of Microwave Oscillations in Ferrospinel Films

The absorption spectra of ferrospinel single crystal films obtained by the method of chemical transport reactions are considered. It is demonstrated that along with a homogeneous resonance, additional absorption peaks corresponding to exchange spin modes localized in the surface layer are observed in the absorption spectrum investigated with an EPR spectrometer in the case of perpendicular orientation of the film with respect to an external static magnetic field. Resonant interaction of magnetostatic oscillations with exchange spin modes in the surface layer is detected in the case of tangent magnetization. The width of the magnetostatic layer and the ranges of existence of the surface and volume modes depend on the relationship between the constants of uniaxial surface anisotropy and crystallographic magnetic anisotropy. The wave numbers of the magnetostatic and exchange spin modes, the parameters of inhomogeneous exchange, and the effective magnon masses are calculated.

Low-frequency surface waves on semi-bounded magnetized quantum plasma

The propagation of low-frequency electrostatic surface waves on the interface between a vacuum and an electron-ion quantum plasma is studied in the direction perpendicular to an external static magnetic field which is parallel to the interface. A new dispersion equation is derived by employing both the quantum magnetohydrodynamic and Poisson equations. It is shown that the dispersion equations for forward and backward-going surface waves are different from each other.

Dynamical Torque in CoxFe3-xO4 Nanocube Thin Films Characterized by Femtosecond Magneto-Optics: A π-Shift Control of the Magnetization Precession.

For spintronic devices excited by a sudden magnetic or optical perturbation, the torque acting on the magnetization plays a key role in its precession and damping. However, the torque itself can be a dynamical quantity via the time-dependent anisotropies of the system. A challenging problem for applications is then to disentangle the relative importance of various sources of anisotropies in the dynamical torque, such as the dipolar field, the crystal structure or the shape of the particular interacting magnetic nanostructures. Here, we take advantage of a range of colloidal cobalt ferrite nanocubes assembled in 2D thin films under controlled magnetic fields to demonstrate that the phase, ϕPrec, of the precession carries a strong signature of the dynamical anisotropies. Performing femtosecond magneto-optics, we show that ϕPrec displays a π-shift for a particular angle θH of an external static magnetic field, H. θH is controlled with the cobalt concentration, the laser intensity, as well as the interparticle interactions. Importantly, it is shown that the shape anisotropy, which strongly departs from those of equivalent bulk thin films or individual noninteracting nanoparticles, reveals the essential role played by the interparticle collective effects. This work shows the reliability of a noninvasive optical approach to characterize the dynamical torque in high density magnetic recording media made of organized and interacting nanoparticles.

Polaritons dispersion in a composite ferrite-semiconductor structure near gyrotropic-nihility state

In the context of polaritons in a ferrite-semiconductor structure which is influenced by an external static magnetic field, the gyrotropic-nihility can be identified from the dispersion equation related to bulk polaritons as a particular extreme state, at which the longitudinal component of the corresponding constitutive tensor and bulk constant simultaneously acquire zero. Near the frequency of the gyrotropic-nihility state, the conditions of branches merging of bulk polaritons, as well as an anomalous dispersion of bulk and surface polaritons are found and discussed.

3-D Gaussian beam scattering from a gyromagnetic perforated layer: Quasi-static approach

This paper is devoted to the study of the scattering of a three-dimensional (3-D) Gaussian beam with the circular cross section from a double periodic perforated gyromagnetic layer with polarization independent unit-cell, in the quasi-static approximation. We used the plane-wave spectrum representation for Gaussian beam field representation and reduced it to a single integral representation. The phenomena of the lateral beam shift influenced by Faraday rotation and the nearly total beam transmission when passing through gyromagnetic slab biased with an external static magnetic field in the Faraday configuration were considered.