Magnetic Field Gradient Research Articles

A Comparison of Quality and Reliability of YouTube Videos About the MRI Technique and Its Various Aspects.

The Magnetic Resonance Imaging (MRI) machine is a subset of nuclear magnetic resonance imaging technology that produces images of the body using magnetic field gradients. The MRI Machine has two components: the computer-based control centre room and the adjacent MRI machine room where the patient undergoes the scan. This study aimed to assess the quality and reliability of YouTube videos about MRI machines, MRI scans, and MRI claustrophobia and compare the quality and reliability of the videos among different types of uploaders. Methodology: The YouTube Search Algorithm and a Google Sheets questionnaire were used to evaluate 10 videos that satisfied the inclusion criteria of the study. The video analytics included were title, number of views, likes and dislikes, comments, duration, source, and content. The quality of each video was established using the Global Quality Score (GQS), Reliability Score, and Video Power Index (VPI), where each quantifier went through statistical analysis using SPSS software, version 21.0 (IBM Corp., Armonk, NY) to determine if there was any significance. In order to determine statistical differences between the groups, the Kruskal-Wallis test was used on the quantifiers GQS, reliability score, and VPI to generate p-values. The p-valuefor VPI is 0.467, GQS is 0.277, and reliability is 0.316. All the p-values are greater than 0.05, showing that there is no statistical support for any significant difference between the groups in their VPI, GQS and reliability scores. YouTube videos with high-quality and reliable information on MRI machines, MRI procedures, and claustrophobia, especially those uploaded by clinicians and hospitals, can provide correct information, helping patients decide to undergo these procedures and alleviate claustrophobia.

Protecting coherence from the environment via Stark many-body localization in a Quantum-Dot Simulator

Semiconductor platforms are emerging as a promising architecture for storing and processing quantum information, e.g., in quantum dot spin qubits. However, charge noise coming from interactions between the electrons is a major limiting factor, along with the scalability of many qubits, for a quantum computer. We show that a magnetic field gradient can be implemented in a semiconductor quantum dot array to induce a local quantum coherent dynamical ℓ−bit exhibiting the potential to be used as logical qubits. These dynamical ℓ−bits are responsible for the model being many-body localized. We show that these dynamical ℓ−bits and the corresponding many-body localization are protected from all noises, including phonons, for sufficiently long times if electron-phonon interaction is not non-local. We further show the implementation of thermalization-based self-correcting logical gates. This thermalization-based error correction goes beyond the standard paradigm of decoherence-free and noiseless subsystems. Our work thus opens a new venue for passive quantum error correction in semiconductor-based quantum computers.

The effect of elimination of gibbs ringing, noise and systematic errors on the DTI metrics and tractography in a rat brain

Diffusion tensor imaging (DTI) metrics and tractography can be biased due to low signal-to-noise ratio (SNR) and systematic errors resulting from image artifacts and imperfections in magnetic field gradients. The imperfections include non-uniformity and nonlinearity, effects caused by eddy currents, and the influence of background and imaging gradients. We investigated the impact of systematic errors on DTI metrics of an isotropic phantom and DTI metrics and tractography of a rat brain measured at high resolution. We tested denoising and Gibbs ringing removal methods combined with the B matrix spatial distribution (BSD) method for magnetic field gradient calibration. The results showed that the performance of the BSD method depends on whether Gibbs ringing is removed and the effectiveness of stochastic error removal. Region of interest (ROI)-based analysis of the DTI metrics showed that, depending on the size of the ROI and its location in space, correction methods can remove systematic bias to varying degrees. The preprocessing pipeline proposed and dedicated to this type of data together with the BSD method resulted in an even − 90% decrease in fractional anisotropy (FA) (globally and locally) in the isotropic phantom and − 45% in the rat brain. The largest global changes in the rat brain tractogram compared to the standard method without preprocessing (sDTI) were noticed after denoising. The direction of the first eigenvector obtained from DTI after denoising, Gibbs ringing removal and BSD differed by an average of 56 and 10 degrees in the ROI from sDTI and from sDTI after denoising and Gibbs ringing removal, respectively. The latter can be identified with the amount of improvement in tractography due to the elimination of systematic errors related to imperfect magnetic field gradients. Based on the results, the systematic bias for high resolution data mainly depended on SNR, but the influence of non-uniform gradients could also be seen. After denoising, the BSD method was able to further correct both the metrics and tractography of the diffusion tensor in the rat brain by taking into account the actual distribution of magnetic field gradients independent of the examined object and uniquely dependent on the scanner and sequence. This means that in vivo studies are also subject to this type of errors, which should be taken into account when processing such data.

Magnon bands and transverse transport in a proposed two-dimensional [formula omitted] ferrimagnet

The copper fluoride Cu2F5 is a proposed stable compound that can be seen as a layered lattice of S=1 and S=1/2 sites, corresponding to copper ions. Intending to cast light on the transport properties of ferrimagnetic magnons, we use the linear spin wave approach to study the magnon band structure of the 2D lattice in a ferrimagnetic off-plane order, as well as the transverse transport of magnons in the crystal bulk. A magnetic field or temperature gradient can induce transverse (Hall-like) transport within the linear response theory generated by the Berry curvature of the eigenstates. As in most cases involving magnons, the Berry curvature is related to Dzyaloshinskii–Moriya interactions between next-near-neighbors The band structure of the system is non-degenerate and the transport coefficients are non-null. The novel and interesting feature of the system is that, within certain conditions, the transport coefficients versus temperature curves are non-monotonic and present a sign change, opening the exciting possibility of controlling the transverse magnon flow direction and magnitude with the temperature change.

3-D Current Density and Magnetic Field of 3-D MR Scanner Gradient Coil

The topic of this paper is to describe the 3-D current density in the windings of a 3-D coil, which fills the volume between two coaxial cylinders at a precisely defined distance from each other, and which serves to generate a magnetic field gradient in the center of the cylinder axis. The 3-D current density is considered an unknown input quantity, which is calculated from the known gradient magnetic field output. It is an inverse problem in mathematics, where the direct problems are the calculation of unknown output quantities based on known input quantities. Fourier series expansion methods in the context of cylindrical coordinates were used to describe the 3-D current density. In that case, Bessel functions are used as development components. The current densities, at each point in space, were lined up to represent current lines. Each power line is associated with a coil winding through which a current of a certain strength flows. After that, the principle of discretization of coil windings was applied. Each winding is divided into a large number of elementary segments that were considered as current elements, which create, based on Bio-Savar's law, an elementary magnetic field. In this way, the total, continuous magnetic field is broken into many elementary components, which come from different current elements. An important result of this process is that each current element can be controlled independently by a current source. This means that the output magnetic field of the gradient can be controlled by current sources, which are the input sizes, and this is what is at the core of the topic of this paper.

Advancing potential field data analysis: the Modified Horizontal Gradient Amplitude method (MHGA)

Enhancing the detection accuracy of the edges of the geological features within the subsurface remains a significant objective in geophysical data interpretation. Despite numerous advancements, approaches stemming from the directional gradients of gravity and magnetic fields still grapple with challenges such as low-resolution outcomes and susceptibility to noise contamination. In this study, we introduce a novel filtering framework based on the total horizontal gradient and its derivatives, designed to yield more precise and coherent edges free from false boundaries or disruptive artifacts. Validation using synthetic Bishop complex magnetic and gravity datasets, alongside Tuangiao aeromagnetic data from Vietnam, substantiates the robustness and applicability of our modified approach. Furthermore, recognizing the inherent susceptibility of edge detection filters to noise contamination resulting from directional derivatives, we employ the recently developed modified non-local means (MNLM) algorithm to alleviate noise effects prior to the analysis of noisy synthetic and real datasets. Our findings confirm the efficacy of the proposed method in reducing false artifacts and identifying edges with heightened precision, positioning MHGA as a valuable alternative for processing potential field data.

Toward Programmable Quantum Processors Based on Spin Qubits with Mechanically Mediated Interactions and Transport.

Solid-state spin qubits are promising candidates for quantum information processing, but controlled interactions and entanglement in large, multiqubit systems are currently difficult to achieve. We describe a method for programmable control of multiqubit spin systems, in which individual nitrogen-vacancy (NV) centers in diamond nanopillars are coupled to magnetically functionalized silicon nitride mechanical resonators in a scanning probe configuration. Qubits can be entangled via interactions with nanomechanical resonators while programmable connectivity is realized via mechanical transport of qubits in nanopillars. To demonstrate the feasibility of this approach, we characterize both the mechanical properties and the magnetic field gradients around the micromagnet placed on the nanobeam resonator. We demonstrate coherent manipulation of a spin qubit in the proximity of a transported micromagnet by utilizing nuclear spin memory and use the NV center to detect the time-varying magnetic field from the oscillating micromagnet, extracting a spin-mechanical coupling of 7.7(9)Hz. With realistic improvements, the high-cooperativity regime can be reached, offering a new avenue toward scalable quantum information processing with spin qubits.

Novel Spectrometer Designs for Laser-Driven Ion Acceleration

We propose novel spectrometer designs that aim to enhance the measured spectral range of ions on a finite-sized detector. In contrast to the traditional devices that use a uniform magnetic field, in which the deflection of particles increases inversely proportional to their momentum, in a gradient magnetic field, the deflection of particles will decrease due to the reduction of the magnetic field along their propagation. In this way, low-energy ions can reach the detector because they are deflected less, compared to the uniform field case. By utilizing a gradient magnetic field, the non-linear dispersion of ions in a homogeneous magnetic field approaches nearly linear dispersion behavior. Nonetheless, the dispersion of low-energy ions, using a dipole field, remains unnecessarily high. In this article, we discuss the employed methodology and present simulation results of the spectrometer with an extended ion spectral range, focusing on the minimum detectable energy (energy dynamic range) and energy resolution.

Excitation of transverse and longitudinal thermomagnetic waves in anisotropic conducting media in the presence of a temperature gradient T   without an external magnetic fieldH

In anisotropic conducting media, the excited thermomagnetic waves at different orientations of the magnetic field and temperature gradient significantly depend on the direction of the anisotropic medium. Theoretical calculations of the electrical conductivity tensor ik  depending on the frequency of the thermomagnetic wave are of scientific interest. In this theoretical work, the frequencies of the thermomagnetic wave at k T   || and at k T ⊥   were found, and it was proven that at longitudinal (k T   || ) and at transverse (k T ⊥   ) the direction of the frequency and growth rate of these waves depends differently on the external magnetic field. The work theoretically studies the conditions for the excitation of thermomagnetic waves. It is indicated that the directions of external fields play a significant role in the appearance of growing waves in the sample. It is shown that, depending on the value of the electrical conductivity tensor ik  , thermomagnetic waves are excited in the longitudinal (i.e. k T   || ) and transverse (i.e.k T ⊥   ) directions. The frequencies of these thermomagnetic waves in both the longitudinal and transverse directions have been calculated. The growth rates of these waves are determined by the values of the inverse electrical conductivity tensor ik  . It has been proven that the excited wave is mainly of a thermomagnetic nature. In theory, the dispersion equation obtained is of algebraically high powers relative to the oscillation frequency. The dispersion equation in both cases (longitudinalk T   || and transverse k T ⊥   ) contains terms in which there are thermomagnetic frequencies in a low degree of frequency. It has been proven that if the value of the electrical conductivity tensor ik  is the same, then the propagation frequencies of thermomagnetic waves are different. The theory is constructed without an external magnetic field 0 0 =Н . In the presence of an external magnetic field, the conditions for the excitation of thermomagnetic waves, and of course the conditions for their growth, will change significantly.

A modular optically pumped magnetometer system

To address the demands in healthcare and industrial settings for spatially resolved magnetic imaging, we present a modular optically pumped magnetometer (OPM) system comprising a multi-sensor array of highly sensitive quantum magnetometers. This system is designed and built to facilitate fast prototyping and testing of new measurement schemes by enabling quick reconfiguration of the self-contained laser and sensor modules as well as allowing for the construction of various array layouts with a shared light source. The modularity of this system facilitates the development of methods for managing high-density arrays for magnetic imaging. The magnetometer sensitivity and bandwidth are first characterised in both individual channel and differential gradiometer configurations before testing in a real-world magnetoencephalography environment by measuring alpha rhythms from the brain of a human participant. We demonstrate the OPM system in a first-order axial gradiometer configuration with a magnetic field gradient sensitivity of 10fT/cm/Hz at a baseline of 4.5 cm. Single-channel operation achieved a sensitivity of 65fT/Hz . Bandwidths exceeding 200Hz were achieved for two independent modules. The system’s increased temporal resolution allows for the measurement of spinal cord signals, which we demonstrate by using phantom signal trials and comparing with an existing commercial sensor.

Properties of magnetic null points associated with X-class flares during solar cycle 24

ABSTRACT Since the launch of the Solar Dynamics Observatory (SDO) in 2010 and throughout the solar cycle 24, the Sun has produced few tens of X-class flares, which are the most energetic solar events. Those flares are produced in regions where the magnetic flux/energy is large and the magnetic configurations are complex. To provide more insights into the flaring process, we investigate the properties of magnetic null points (MNPs) and their correlation with the energy release sites. During solar cycle 24, we identify 17 X-class flares satisfying selection criteria. From SDO/HMI magnetograms, we perform potential extrapolations around the peak time of the flare to access the 3D coronal magnetic field and thus investigate the existence of coronal MNPs. We then correlate the flaring sites with the existing MNPs using SDO/AIA 171 Å; EUV observations, and deduce their properties (sign, spine, and fan). Six active regions out of 10 possess at least one MNP which is stable and with large magnetic field gradients: this implies that 35 per cent of X-class flares are associated with an MNP; of which 87.5 per cent of MNPs are of positive type. The MNPs associated with the flare sites are predominantly located at a height between 0.5 and 2 Mm, and with a vertical/radial spine field line. We also find a slight correlation between the MNPs not associated with a flare and negative-type MNPs (55 per cent) within the active region. Regarding the physics of flares, the association between the enhanced intensity at the flaring site and an MNP represents about a third of the possible scenarios for triggering X-class flares.

Super-X and conventional divertor configurations in MAST-U ohmic L-mode; a comparison facilitated by interpretative modelling

Measurements are presented, alongside corresponding interpretative SOLPS-ITER simulations, of the first MAST-U experiments comparing ohmically heated L-mode fuelling scans in Conventional divertor (CD) and Super-X divertor (SXD) configurations. In experiment, at comparable outer mid-plane separatrix electron density, ne,sep,OMP , the maximum lower outer target heat load was found to be a factor 16 ±7 lower in SXD compared to CD. In simulation, a factor 26.8 reduction was found (slightly higher than the experimental range), suggesting an additional reduction in SXD compared to the factor 9.3 expected from geometric considerations alone. According to the simulations, this additional reduction in the SXD is due to a net radial transport of the energy remaining downstream of the Te=5 eV location. This energy is carried out of the critical (highest heat load) flux tube by deuterium atoms, demonstrating the importance of a longer legged divertor which provides space for this to occur. Importantly, in both simulation and experiment, the SXD has minimal impact on the upstream ne and Te profiles. Spectral inferences of detachment front movement in SXD compare well between simulation and experiment. In regions of high magnetic field gradient, the parallel movement of the front towards the X-point becomes less sensitive to increasing ne,sep,OMP , in qualitative agreement with simplified models and previous predictive simulations. Additional aspects, regarding the target ion flux rollover, upstream separatrix temperature and drift effects, are also presented and discussed.

MISSTEC-S: A fast 1H pulse calibration from spectra simultaneously produced by a spin echo and a stimulated echo

Radio-Frequency (RF) pulse calibration is an essential step in guaranteeing both optimum acquisition quality in multi-pulse NMR and accurate results in quantitative experiments. Most existing methods are based on a series of spectra for which the flip angle of one or more pulses is progressively incremented, implying a significant experiment time. In order to circumvent this drawback, we have previously proposed an approach based on the acquisition of a spin echo and a stimulated echo − the MISSTEC sequence − which requires only 8 s to determine the PW90-1H, while it is several minutes in the case of the use of a nutation curve.In this work, a new sequence for RF calibration is presented: MISSTEC-S. It is derived from the previously proposed MISSTEC sequence, but the observation of echoes in presence of magnetic field gradient is replaced by the observation of FIDs.This modification allows both spectra to be phased, while imposing a strong constraint on the Mixing Time (TM). However, the relationship used to calculate the flip angle is only correct when TM is small enough to neglect longitudinal relaxation during this delay. In order to reduce TM, the first FID is truncated during acquisition and subsequently lengthened using points from the second FID. Results obtained with MISSTEC-S were compared to those obtained from a complete nutation curve and an excellent correlation was observed, although the experimental time to obtain the PW90 is dramatically reduced.

Exploring the stabilization mechanism of NH3/CH4 non-premixed flames under gradient magnetic fields

This study explores the stabilization of non-premixed NH3/CH4 flames using gradient magnetic fields, overcoming challenges like low flame speed and instability inherent in ammonia—a carbon-free fuel and efficient hydrogen carrier. The action of the magnetic field modified the flame flow field, resulting in the suppression of emissions. By applying magnetic fields, the blending ratio of ammonia in the diffusion flame was elevated, resulting in an increase of 69% in the limit concentration to a near-pure level of 0.914. Measurements with Particle Image Velocimetry and schlieren system, alongside computational fluid dynamics, reveal how gradient magnetic fields mitigate flame detachment, lift-off, and blowout by altering flame root stabilization mechanisms. Specifically, gradient magnetic fields reduce localized flow velocity at the flame root and improve mass transfer. This indicates that gradient magnetic fields can significantly enhance the stability of NH3/CH4 flames, suggesting a promising route toward cleaner energy production and environmental sustainability.

Design and application of environmentally friendly composite magnetic particles for microplastic extraction from water media

The widespread presence of microplastic particles in aquatic environments requires methods of their extraction from water for counting and analysis and for water purification technologies. In this study, new magnetic composite nanoparticles (FNP) were designed, characterized and explored to be used as magnetic seeds for extracting polyethylene terephthalate microparticles (MPET, 5–30 μm) from water by magnetic sedimentation. The engineered seeds have a complex morphology, with magnetic cores of Fe3O4 dispersed in an environmentally compatible polymer matrix of silicon dioxide, chitosan or gelatine. Mechanisms of the heteroaggregation of FNP and MPET are considered and the main influencing factors (particles concentrations, major ions, duration of the preliminary exposure and of the sedimentation) are studied. The heteroaggregates are removed from water using a gradient magnetic field (Bzmax = 0.44 T) generated by a system of permanent magnets. The mass concentration of magnetic nanoseeds for more than 98 % capture of PET particles in pure and in salted water after 0.5 hour of magnetic sedimentation was detected to be 0.002 g/L. It is two orders of magnitude lower than that reported for uncovered magnetite-based particles. Using magnetic composite seeds with ecofriendly coatings allows to perform a high efficient magnetic separation of microplastic particles from water both for analytical purpose and for potential water cleaning technologies, while strongly reducing the synthetic flocculant sludge volume.

The Xe isotope nuclear resonance frequency shift of NMR angular velocity sensors due to transverse gradient magnetic fields

The nuclear magnetic resonance (NMR) angular velocity sensor detects angular velocity by measuring the shift in the nuclear spin precession frequency, which is of fundamental interest. Recent studies have revealed the parameter dependency of nuclei frequency shifts induced by non-uniformly distributed polarized pump beams, temperature, and magnetic field properties. In this study, we investigated the effect of the linear transverse gradient magnetic field on the frequency ratio shift of the Xe isotope nuclear resonance frequency in the NMR sensors. A theoretical analysis method was proposed based on the Fermi contact interaction in atomic polarization and the spin-diffusion relaxation of 129Xe and 131Xe nuclei. The frequency ratio shift of the Xe isotope under different x-axis gradient magnetic fields was measured experimentally. Furthermore, we eliminated the equivalent residual magnetic field through a feedback system and compensated for the original gradient magnetic field in the system, which contributed to accurately revealing the frequency shift induced by the magnetic field gradient. The results indicate that the frequency ratio shift of the Xe isotope is proportional to the strength of the second-order linear transverse gradient magnetic field. This study provides a reference for the analysis and evaluation of the presence of the gradient magnetic field in the NMR angular velocity sensor.

Magnetoresistance and Magnetocapacitance Effect in Magnetic Tunnel Junction with Perpendicular Anisotropy of Magnetic Electrodes Tb22−δCo5Fe73/Pr6O11/Tb19−δCo5Fe76

This paper presents the results of studies of the effects of magnetoresistance and magnetocapacitance in magnetic tunnel junctions [Formula: see text]Co5[Formula: see text]/Pr6[Formula: see text]/[Formula: see text]Co5[Formula: see text] with perpendicular anisotropy of magnetic electrodes and a paramagnetic barrier layer. Experimentally measured values of tunnel magnetic resistance and tunnel magnetic capacitance in such contacts exceed 100% at room temperature. The paper analyzes the effect of magnetization reversal of one of the electrodes on the conductivity of magnetic tunnel junctions with electrodes that have perpendicular anisotropy. It is shown that significant changes in tunnel magnetic resistance and tunnel magnetic capacity in such contacts can be explained by the separation of electrons with major and minor spin polarization in the inverse nanolayer in the interface region. The separation of polarized electrons is caused by the magnetomotive force acting on the electron spin in a strongly gradient magnetic field. Such a magnetomotive force occurs with antiparallel magnetization of the magnetic electrodes and it has opposite directions for major and minor polarized electrons. As a result of the spatial separation of polarized electrons in the inversion layer, an inhomogeneous distribution of the electron density along the direction of magnetization of the magnetic contacts occurs. As a result, an additional Coulomb barrier between the magnetic electrodes and the dielectric nanolayer appears in the tunnel contacts and an additional spin capacitance appears.

Octopus-Inspired Soft Robot for Slow Drug Release.

Octopus tentacles are equipped with numerous suckers, wherein the muscles contract and expel air, creating a pressure difference. Subsequently, when the muscular tension is released, objects can be securely adhered to. This mechanism has been widely employed in the development of adhesive systems. However, most existing octopus-inspired structures are passive and static, lacking dynamic and controllable adhesive switching capabilities and excellent locomotion performance. Here, we present an octopus-inspired soft robot (OISR). Attracted by the magnetic gradient field, the suction cup structure inside the OISR can generate a strong adsorption force, producing dynamically controllable adsorption and separation in the gastrointestinal (GI) tract. The experimental results show that the OISR has a variety of controllable locomotion behaviors, including quick scrolling and rolling motions, generating fast locomotion responses, rolling over gastric folds, and tumbling and swimming inside liquids. By carrying drugs that are absorbable by GI epithelial cells to target areas, the OISR enables continuous drug delivery at lesions or inflamed regions of the GI tract. This research may be a potential approach for achieving localized slow drug release within the GI tract.

Gradient magnetic field measurement using first-order gradiometers equipped with 50 mm diameter pickup coils made out of a 2G high-Tc superconducting tape

Two types of first-order gradiometers equipped with 50 mm diameter pickup coils were made out of an REBaCuO High-Tc superconducting (HTS) flexible tape. The HTS tapes were formed into the HTS gradiometers by ``cut-and-wind'' method without cable jointing.The HTS gradiometers were examined at 77 K for magnetic sensitivity to a gradient field applied by an external coil. The axial-type HTS gradiometer eliminated the magnetic field output of the device induced by a uniform field, and enhanced the magnetic field output induced by a gradient field on the axis of the pickup coil. The planar-type HTS gradiometer made it possible to detect a 20 mm diameter steel cylinder placed beside the pickup coil in a uniform field of 100 µT by detecting the spatial field gradient in the vicinity of a ferromagnetic object.

Numerical design of transverse gradient coil with transformed magnetic gradient field over an effective imaging area

Numerical design of transverse gradient coil with transformed magnetic gradient field over an effective imaging area