Pair Of Coils Research Articles

Equimolar Cross-Coupling Using Reactive Coiled Coils for Covalent Protein Assemblies.

Biocompatible cross-coupling reactions enable the efficient covalent attachment of large biomolecules at near-stoichiometric ratios, ensuring the stability and integrity of the resulting products. We present an affinity-based peptide platform utilizing coiled coils containing reactive side chains for proximity-driven protein cross-coupling in the presence of a cross-linking agent. This platform supports both chemical synthesis and recombinant expression, using canonical amino acids to generate reactive affinity tags. Employing the E3/R3 coiled coil pair as a scaffold, we design four complementary coils with cysteine residues as cross-linking sites, achieving >90% conversion to covalent heterodimeric coupling products using 3,4-dibromomaleimide. Equimolar mixtures of proteins with reactive coils at their termini yield near-quantitative heterodimeric cross-coupling products. The strategic selection of complementary coiled coil pairs and cross-linking agents enables orthogonal assembly of macromolecules with diverse architectures. This method offers a versatile approach for creating covalent fusion proteins, enhancing their stability and functionality for applications in chemical biology, biotechnology, and medicine.

Balancing of Resonant Differential Coils for Broadband Inductive Sensor Systems.

Differential coils are frequently implemented in inductive sensing systems. They can be considered as a single coil that is made up of two or more subcoils, wound in series opposition. They can be used on the transmit or receive side of measurement systems, and, if designed correctly, ensure no coupling between coils under background conditions. By cancelling background coupling, the receive electronics only needs to be able to measure the change in coupling produced by a target. This allows for a more efficient use of the dynamic range, and for larger receive-side amplifier gain, thereby improving SNR. When subcoils are not electrically similar, it can be hard to engineer the coil to be perfectly balanced across a wide bandwidth. This paper presents an analytical model of a resonant differential coil pair that is tested and applied on a planar metal detector for the detection of buried objects. The model demonstrates the capability to balance an arbitrary differential coil pair, which has a broad applicability across a range of inductive sensor applications such as metal detection and non-destructive testing. The method is applied to the practical system. The results show that the correction resulting from this method ensures a stable balance across a significantly enhanced bandwidth. In the case studied here, the bandwidth of the experimental system is increased from 20 kHz to 90 kHz.

Magnetic-field coils for metastability-exchange optical pumping, spectroscopy, and magnetic resonance of helium.

Optical pumping on the 23S-23P transition (1083nm) of metastable 3He or 4He atoms is used for science and applications. Gas is usually enclosed in elongated cells with lengths ranging from several centimeters to several meters for efficient absorption. Good magnetic-field homogeneity is needed for weak diffusion-induced relaxation and long nuclear magnetic resonance (NMR) signal lifetimes. A compact coil system is designed using a target-oriented numerical optimization method. It provides a suitably uniform field over cell volumes, with characteristics depending on the chosen optimization parameters. Additional pairs of coils can be used to generate transverse field components with contributions to the total field inhomogeneities that are discussed.

Biplanar coils design for spatial nonlinear magnetic fields using an enhanced target field method

The demand for spatial nonlinear magnetic fields (SNMF) spans diverse domains, encompassing medical applications like drug transportation and aerospace applications such as attitude control. Existing designs of magnetic field coils predominantly focus on uniform and gradient fields as the complexity of nonlinear magnetic field distribution often leads to intricate solution processes. This paper presents a novel approach to coil design, addressing the challenge of SNMF distribution by reconstructing the characteristic matrix within the traditional target field method (TFM). To solve the overdetermined equations involved, we incorporate an improved particle swarm optimization algorithm into the TFM framework. A pair of symmetrical and asymmetrical coils are designed and the effectiveness of this method is verified by comparing the simulated and experimental results.

Homogeneous B0 coil design method for open-access ultra-low field magnetic resonance imaging: A simulation study

A multimodal brain function measurement system integrating functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) is expected to be a tool that will provide new insights into neuroscience. To integrate fMRI and MEG, an ultra-low-field MRI (ULF-MRI) scanner that can generate a static magnetic field (B0) with an electromagnetic coil and turn off the B0 during MEG measurements is desirable. While electromagnetic B0 coil has the above advantages, it also has a trade-off between size and the broadness of the magnetic field homogeneity. In this study, we proposed a method for designing a B0 multi-stage circular coil arrangement that determines the number of coils required to maximize magnetic field homogeneity and minimize the total wiring length of the coils. The optimized multi-stage coil arrangement had an external shape of 600 mm in diameter and a maximum height of 600 mm, with an aperture of 600 mm in diameter and 300 mm in height. The magnetic field homogeneity was <100 ppm over a 210 mm diameter spherical volume (DSV). Compared to a previous two coil pairs arrangement with the same magnetic field homogeneity, the diameter was 1/1.9 times smaller, indicating that the newly designed B0 coil arrangement realized a smaller size and wider magnetic field homogeneity.

Bi-planar magnetic stabilisation coils for an inertial sensor based on atom interferometry

Inertial sensors that measure the acceleration of ultracold atoms promise unrivalled accuracy compared to classical equivalents. However, atomic systems are sensitive to various perturbations, including magnetic fields, which can introduce measurement inaccuracies. To address this challenge, we have designed, manufactured, and validated a magnetic field stabilisation system for a quantum sensor based on atom interferometry. We solve for the magnetic field generated by surface currents in-between a pair of bi-rectangular coils and approximate the surface current using discrete wires. The wires are wound by-hand onto machined panels which are retrofitted onto the existing mounting structure of the sensor without interfering with any experimental components. Along the central 60mm of the y-axis, which aligns with the trajectory of the atoms during interferometry, the coils are measured to generate an independent uniform axial magnetic field with a strength of Bz=22.81±0.01μT/A [mean±2σstd. error] and an independent linear axial field gradient of strength dBz/dy=10.6±0.1μT/Am. The uniform Bz field is measured to deviate by a maximum value of 1.3% in the same region, which is a factor of three times more uniform than the previously-used on-sensor rectangular Bz compensation set.

Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle.

Combining proton and phosphorus magnetic resonance spectroscopy offers a unique opportunity to study the oxidative and glycolytic components of metabolism in working muscle. This paper presents a 7 T proton calf coil design that combines dipole and loop elements to achieve the high performance necessary for detecting metabolites with low abundance and restricted visibility, specifically lactate, while including the option of adding a phosphorus array. We investigated the transmit, receive, and parallel imaging performance of three transceiver dipoles with six pair-wise overlap-decoupled standard or twisted pair receive-only coils. With a higher SNR and more efficient transmission decoupling, standard loops outperformed twisted pair coils. The dipoles with standard loops provided a four-fold-higher image SNR than a multinuclear reference coil comprising two proton channels and 32% more than a commercially available 28-channel proton knee coil. The setup enabled up to three-fold acceleration in the right-left direction, with acceptable g-factors and no visible aliasing artefacts. Spectroscopic phantom measurements revealed a higher spectral SNR for lactate with the developed setup than with either reference coil and fewer restrictions in voxel placement due to improved transmit homogeneity. This paper presents a new use case for dipoles and highlights their advantages for the integration in multinuclear calf coils.

Experimental and theoretical study of the harmonic distortion in a ferromagnetic plate excited by a pair of air-cored coils

The harmonic distortion in a ferromagnetic plate is studied both experimentally and using numerical simulations. The electromagnetic field inside the specimen is excited by a couple of air-cored coils, and the field is measured at a specific location using a set of Hall sensors. The considered material is a typical structural steel of an intermediate mechanical and magnetic hardness. The comparison of the numerical results with carefully conducted measurements demonstrates the importance of an accurate and physically consistent hysteresis model. The absence of magnetic circuit reduces the number of the setup uncertainties thereby simplifying the characterisation procedure and making this particular configuration a good benchmark candidate for the validation of numerical codes dealing with the hysteresis problem.

Method for improving accurate measurement of the magnetic field of wireless passive micro-magnetic stimulator micro-coil

In recent years, the wireless passive micro-magnetic stimulator (WP-μMS) has emerged as a focal for implantable neuromagnetism modulation research. However, accurately measuring the magnetic field strength of the micro-coil presents a significant challenge due to its small size and low mutual inductance (M). Firstly, this paper establishes a theoretical model of magnetic coupling with a three-stage structure of transmitting coil-micro-coil-detecting coil. The calculation method of detecting the coil to measure the magnetic field is determined by calculating the M between each pair of coils. Secondly, the magnetic coupling resonance method enhances the measured value M to the nH-scale. This approach also eliminates the influence of the M between the transmitting coil-detecting coil on the measurement of the transmitting coil-micro-coil M, thereby achieving accurate measurement of the mT-scale magnetic field strength of the WP-μMS micro-coil. Finally, the effectiveness of the measured mT-scale magnitude magnetic stimulation is validated biologically.

The configuration and detection characteristics of a 3D holographic LWD instrument antenna system based on multi-component EM induction theory

In order to improve the precision of electromagnetic resistivity logging, while ensuring the reliability of boundary detection and anisotropy identification, this study starts from the theory of multi-component electromagnetic induction. Through deriving the formula of component responses, the analytical expressions of electromagnetic wave fields are obtained for various coil pairs of azimuthal instruments. A 3D holographic LWD instrument antenna configuration is constructed, with co-planar and non-coplanar, tilted and orthogonal coil combinations, all components of the magnetic field tensor Hxx,Hxy,Hxz,Hyx,Hyy,Hyz,Hzx,Hzx,HzzHxx,Hxy,Hxz,Hyx,Hyy,Hyz,Hzx,Hzx,Hzz are successfully resolved. With the combination of some or all components, functional signals are generated for specific detection objectives. Numerical simulation of the response of those signals shows that the distance of boundary detection and anisotropy identification capability are superior to traditional geo-signals. The response relationship shows that as the contrast of the formation resistivity decreases and the well deviation angle increases, the anisotropy identification capability gradually strengthens, and the signal strength and identification capability are better at frequency in the range of 400–600 kHz. The proposed antenna configuration has the potential to significantly enhance formation evaluation and to improve geo-steering capability, contributing technology-wise to the optimal landing trajectory and best wellbore position, resulting in cost saving and maximize oil & gas production.

Three-dimensional wireless measurement of float–sink object motions in a gas–solid fluidized bed

We developed a Lagrangian sensor system capable of wirelessly measuring the 3D motions of objects and applied it to examine the floating and sinking behaviors in a gas–solid fluidized bed. The system consisted of a sensor particle, comprising a 9-axis sensor and a wireless module integrated into a spherical outer shell, and three pairs of magnetic coils. By utilizing this system, we can non-invasively measure the 3D motions of objects, which cannot be observed from the outside. In this study, we examined the motions of objects with various densities in the gas–solid fluidized bed. We found the similarity and dissimilarity between the float–sink motions of objects in fluidized beds and those in liquids. The experimental results revealed that the vertical motion of an object in the fluidized bed depends on its density and can be categorized into two distinct states: floating near the surface or settling down at the bottom. However, within a specific range of object densities close to the apparent density of the fluidized bed, the object exhibited complicated motions in the bed. In such cases, slight density variations induced unpredictable changes between the floating and sinking states. The results also suggested that the settling velocity of the objects in the fluidized bed varies with their vertical positions in the bed.

Enhanced beam extraction system at the U-120M cyclotron

Since its commissioning in 1977, the U-120M cyclotron was initially equipped with a single pair of harmonic coils aimed at optimizing beam quality at lower accelerating radii. In 2022, a significant upgrade introduced a second pair of harmonic coils, positioned at a radius of approximately 50 cm, aligning with the outermost beam orbit. This addition is essential for the efficient extraction of positively accelerated ions and serves as the basis for the newly developed extraction system, which, unlike the original fully electrostatic system, consists of electrostatic deflectors and magnetic channels. This paper describes the design and installation of new harmonic coils in the accelerator vacuum chamber and presents a new extraction system using precession and linear integer resonance methods. Basic properties of these two extraction methods are given and finally, an evaluation of their advantages and limitations concerning their possible use in the cyclotron and an estimation of the efficiency of the new extraction system is made.

The method for noninvasive investigation of the boundaries of homogeneous magnetizable inclusions inside a biological object

Currently, in modern medicine and related areas of medical technology, the problem of noninvasive investigation of the internal structure of a biological object with the aim of detecting and subsequently visualizing hidden metallic foreign inclusions in the body is becoming increasingly important. Determining the spatial position and identifying the boundaries of such inclusions in the body can be a rather time-consuming process, as solving this problem is mainly done through noninvasive methods of introscopy, which require very careful application. Thus, a method for noninvasive investigation of hidden differently oriented homogeneous inclusions that allow for magnetization by an externally periodically time-varying magnetic field inside a biological object, is proposed in the study. This is achieved by representing the investigated volume as a set of parallel sections and measuring the distribution of the vector function of magnetic field induction in each of them using a working element in the form of spatially oriented contours based on a pair of inductance coils with an equal number of turns and opposing winding inclusion. This allows for non-invasive tomographic scanning of a biological object aimed at detecting the refraction effect of the altered vector field of magnetic field induction, followed by the reconstruction of inclusions based on projection data. The reconstruction is carried out using the back-projection method with prior spatial filtering in the original area through convolution of projection data with a convolution function.

Питание сверхпроводящих систем динамическим вращением трехфазного поля

In this work a device for powering superconducting systems by pumping magnetic flux is presented. The pumping is carried out by dynamic rotation of the 3-phase magnetic field in the motor stator, which has three pairs of coils.

Particle simulation of the confinement of the plasma blanket in the magnetic mirror

A new guiding center particle code Guiding center Mirror Simulation is developed to simulate the evolution and confinement of the axisymmetric plasma blanket in the magnetic mirror field generated by a pair of Helmholtz coils. The simulation results indicate that this plasma blanket maintains its shape throughout evolution, and the steady state distributions of both density and electrostatic potential are obtained. The correlation between the plasma density and the characteristic confinement time is also investigated. Generally, the characteristic confinement time decreases with increasing density. When the density is low enough, it is approximately the pitch angle scattering time of the trapped electrons. When the density increases, it comes to several times of the ion transit time evaluated with the Bohm velocity. These results have the potential for experimental applications.

Evaluation of the performance of a 7-T 8 × 2 transceiver array.

The decoupled 8 × 2 transceiver array has been shown to achieve a mean B1 + of 11.7 uT with a coefficient of variation of ~11% over the intracranial brain volume for 7-T MR imaging. However, this array may be thought to give lower signal-to-noise ratio (SNR) and higher g-factors for parallel imaging compared with a radio frequency (RF) receive-only coil due to the latter's higher coil count and use of coil overlap to reduce the mutual impedance. Nonetheless, because the transceiver's highly decoupled design (pertinent for transmission) should also be constructive for reception, we measured the noise correlation, g-factors, and SNR for the decoupled transceiver in comparison with a commercial reference coil. We found that although the transceiver has half the number of receive elements in comparison with the reference coil (16 vs. 32), comparable g-factors and SNR over the head were obtained. From five subjects, the transceiver versus reference coil SNR was 65 ± 10 versus 67 ± 15. The mean noise correlation for all coil pairs was 10% ± 5% and 12% ± 9% (transceiver and reference coil, respectively). As changes in load impedance may alter the S parameters, we also examined the performance of the transceiver with tuned and matched (TM) versus untuned and unmatched (UTM) conditions on five subjects. We found that the noise correlation and SNR are robust to load variation; a noise correlation of 10% ± 5% and 10% ± 6% was determined with TM versus UTM conditions (SNRUTM/SNRTM = 0.97 ± 0.08). Finally, we demonstrate the performance of the array in human brain using T2-weighted turbo spin echo imaging, finding excellent SNR performance in both caudal and rostral brain regions.

Trapping paramagnetic molecules in a dynamic magnetic trap

Trapping molecules in strong-field-seeking states is particularly attractive to scientists in the field of molecular optics. If the external field is strong enough, all molecules are strong-field seekers. Contrary to the weak-field-seeking states, molecules trapping in strong-field-seeking states can avoid the loss caused by the inelastic collision which is a stumbling block for evaporative and sympathetic cooling. Unfortunately, the formation of a magnetostatic maximum in free space is forbidden according to Maxwell’s equations and Earnshaw’s theory. In this paper, a dynamic magnetic trap consisting of three pairs of Helmholtz coils is proposed. The time-sequence control is given together with the distribution of the magnetic field in space. The influence of the switching frequency and electric current flowing through the wires on the number of trapped molecules is investigated. We obtain the changes in the locations and the phase-space distribution within a switching cycle by trajectory simulation. Finally, the influence of the time during which the field is off on the performance of our trap is studied.

Abstract B026: Rotational magnetic drug targeting for leptomeningeal metastases

Abstract Background: Magnetic nanoparticles (MNPs) have potential for enhancing the delivery of therapeutic molecules to cancer cells and micronodules, including non-obstructing metastases within cerebrospinal fluid (CSF) pathways. Rotational magnetic drug targeting (rMDT) takes advantage of the surface-walking capability of clusters of MNPs, which can be activated remotely. Here, we present data related to 1) the creation, characterization, and in vitro testing of a variety of MNPs utilized with bound or unbound chemotherapeutic agents, and 2) the design and construction of four different magnetomotive systems used to propel MNPs at clinically-relevant distances. The goal was to create an in vitro model mimicking conditions found in patients with leptomeningeal metastases. Methods: Gold-iron alloy nanoparticles were combined with biotinylated etoposide via the streptavidin-biotin interaction. Unbound MNPs were tested with etoposide and doxorubicin. MNPs were characterized by techniques including electron microscopy, Zeta potential analysis, and dynamic light scattering. 3D-printed and acrylic trays were used as conduits for measuring translational motion over distances up to 30 cm through saline, culture media, and artifical CSF. MNP velocities were determined by videography. For propelling the MNPs, one electromagnetic system used a Helmholtz pair of coils on each side of an underlying perpendicular coil. The second electromagnetic system utilized 2 angled coils. Two rotating permanent magnet systems used neodymium-boron-iron magnets of different sizes and rotational speeds. Cultured cells included fibroblasts, lung cancer, glioblastoma, and medulloblastoma cell lines. Light microscopy and cytotoxicty assays (by MTT and trypan blue exclusion) were used to assess preservation of tumoricidal activity. Results: In unbound MNP studies, both etoposide and doxorubin could be dispersed over physiologic distances through saline and artificial CSF at velocities exceeding 1 cm/sec - much faster than by diffusion alone. Drugs conveyed in this manner could be transported at 37°C across cell surfaces and retain tumoricidal effect on cultured cells. With rotating magnets, MNPs could be moved against a saline flow rate of 1 cm/sec. In bound MNP studies, true rMDT was possible - all four magnetomotive systems could be shut off, depositing the MNP-drug conjugate at the desired location. Rotating permanent magnets were found to be advantageous for unilateral device design; electromagnetic devices, however, are more likely to be compatible with concurrent magnetic particle imaging (currently under development). Conclusions: These in vitro findings indicate that rMDT within CSF pathways is feasible and should advance to animal studies. Bound MNPs may prove to be more useful for intrathecal use (administered via lumbar puncture or Ommaya reservoir), considering dilutional effects and CSF flow. An improved ability to direct therapeutic agents within CSF would represent a major step forward in the treatment of patients with leptomeningeal metastases. Citation Format: Herbert Engelhard, Alexander Willis, Tolou Shokuhfar, Lamar Mair. Rotational magnetic drug targeting for leptomeningeal metastases [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B026.

Three-Axis Vector Magnetometer with a Three-Dimensional Flux Concentrator.

This research proposes a magnetic field sensor with spatial orientation ability. Through the assistance of a magnetic flux concentrator, out-of-plane magnetic flux can be concentrated and guided into the planar magnetic cores of a fluxgate sensor. A printed circuit board is used to construct the basic planar structure, on which the proposed three-dimensional magnetic flux concentrator and magnetic cores are assembled. This reduces the alignment error of the coils and improves the reliability of the sensor. Three-axis sensing is achieved by using the second harmonic signals from selected sensing coil pairs. The magnetometer exhibits a linear range to 130 μT. At an excitation frequency of 50 kHz, the measured sensitivities are 257.1, 468.8, and 258.8 V/T for the X-, Y-, and Z-axis sensing modes, respectively. This sensor utilizes only one sensing mechanism for the vector field, making it suitable for IoT applications, especially for assessing mechanical posture or position.

Estimation of defect depth on plates by eddy-current coil array

Eddy-current (EC) testing is one of the contactless nondestructive testing techniques that has been frequently applied to evaluate the defects on metallic objects. In this paper, an estimation method of defect depth on metallic plates is proposed based on the approximate analytical model. An EC coil array sensitive to various defect orientation is designed to scan the plate surface. The independent inductance from various ferrite-core coil pairs can be found by the approximate analytical model. The influence of defect on measurements, including depth and edges, is regarded as the variation of probe lift-off in the tested region, defined as the equivalent lift-off. Based on the approximate analytical model, when defect edges have relatively smaller influence, the defect depth on the plate surface can be approximately obtained by estimating the equivalent probe lift-off through optimization. In numerical simulations and experiments, the proposed method is evaluated by testing the aluminum and stainless-steel plates with cracks by the coil array. The reconstructed equivalent lift-off distribution closely relates to the position and dimensions of defects on plates.