Coil Position Research Articles

Chromatographic properties of deamidated peptides with Asn-Gly sequences in proteomic bottom-up experiments

Studies surrounding deamidation have relied on the chromatographic and mass spectrometric differentiation of Asn containing peptides and their isomeric Asp and iso-Asp products. The development of mass spectrometry analytical techniques and characterization of isomer specific fragmentation patterns has permitted the investigation of some deamidation species but has struggled to remain effective when applied and on complex samples or in high throughput scenarios. On the other hand, chromatographic separations can provide additional information to facilitate detection of deamidation. In this work the retention characteristics of deamidation products have been reported in reversed-phase separations using formic acid as an ion-pairing modifier. We found three major elution patterns depending on primary and secondary structure of Asn-Gly containing tryptic peptides. Random coil, helical conformations, and N-terminal positioning of Asn usually result in Asn < iso-Asp < Asp, iso-Asp < Asn < Asp, and Asn < Asp < iso-Asp elution order, respectively. These trends, found from the analyses of proteomic samples, were subsequently confirmed via analytical scale UV-HPLC. Additionally, we determined the retention shifts following deamidation for twenty various separation settings used as a first-dimension fractionation for high-throughput proteomic 2D LC-MS/MS analyses.

A Receiver Position Estimation Method Based on LSTM for Multi-Transmitter Single-Receiver Wireless Power Transfer Systems

The multi-transmitter single-receiver wireless power transfer (MTSR-WPT) system has good tolerance for coil misalignment because the magnetic fields generated by multiple transmitters can be shaped to adapt to position changes in the receiver coil. In order to achieve magnetic field shaping of the MTSR-WPT system and increase power transfer efficiency, accurately estimating the position of the receiver coil is a key issue that needs to be addressed. In this article, a receiver position estimation method based on long short-term memory (LSTM) is proposed, which utilizes a data-driven approach to establish a neural network model. By learning the relationship between the measured time-series voltage data of the transmitter coils and the position of the receiver coil, the proposed model can achieve accurate position estimation of the receiver. Compared with previous works, the proposed method does not require communication between the transmitter and receiver, which is conducive to simplifying the system structure and reducing costs. In addition, the proposed LSTM-based method requires less derivation of complex formulas and the internal mechanism analysis of the system. Finally, a MTSR-WPT prototype is built to verify the proposed method. The experimental results show that the proposed LSTM-based method can achieve high-accuracy position estimation of the receiver. When the receiver moves within a range of 160 mm × 160 mm, the average error between the estimated receiver coil position using the proposed method and the actual receiver coil position is less than 2.40 mm.

Evaluation of an integrated variable flip angle protocol to estimate coil B1 for hyperpolarized MRI

AbstractPurposeThe purpose of this work is to validate a simple and versatile integrated variable flip angle (VFA) method for mapping B1 in hyperpolarized MRI, which can be used to correct signal variations due to coil inhomogeneity.Theory and MethodsSimulations were run to assess performance of the VFA B1 mapping method compared to the currently used constant flip angle (CFA) approach. Simulation results were used to inform the design of VFA sequences, validated in four volunteers for hyperpolarized xenon‐129 imaging of the lungs and another four volunteers for hyperpolarized carbon‐13 imaging of the human brain. B1 maps obtained were used to correct transmit and receive inhomogeneity in the images.ResultsSimulations showed improved performance of the VFA approach over the CFA approach with reduced sensitivity to T1. For xenon‐129, the B1 maps accurately reflected the variation of signal depolarization, but in some cases could not be used to correct for coil receive inhomogeneity due to a lack of transmit‐receive reciprocity resulting from suboptimal coil positioning. For carbon‐13, the B1 maps showed good agreement with a separately acquired B1 map of a phantom and were effectively used to correct coil‐induced signal inhomogeneity.ConclusionA simple, versatile, and effective VFA B1 mapping method was implemented and evaluated. Inclusion of the B1 mapping method in hyperpolarized imaging studies can enable more robust signal quantification.

Behavior of plasma parameters under mirror and cusp magnetic fields in DC glow discharge – a numerical study

Abstract The plasma parameters in DC glow discharge can easily be controlled by externally applied magnetic field without disturbing internal / built-in process parameters. Though several works have been carried out to study the influence of the magnetic field at different configurations on the plasma parameters, a complete understanding on the behaviour of the plasma discharge under the mirror and cusp fields could not be achieved. Further studies on the same are needed to improve the efficiency of the DC glow discharge system for existing applications and to find the new applications. In this work, a 2D axis-symmetric non-equilibrium plasma model with drift-diffusion approach is developed to study the characteristics of the plasma in DC glow discharge through various plasma parameters under mirror and cusp fields. The effects of current and position of magnetic coils on electric potential, ionization rate, electron temperature and electron number density are predicted and discussed. The distribution of electron number density at various coil currents and positions under both mirror and cusp fields are presented and the operating conditions favorable for applications in surface modification are suggested.

Acceptability, tolerability and safety of the BRIGhTMIND trial: Connectivity-guided intermittent theta-burst stimulation versus F3- repetitive transcranial magnetic stimulation for treatment-resistant depression

BackgroundThe BRIGhTMIND study was a double-blind RCT comparing repetitive transcranial magnetic stimulation at a standard simulation site (the “F3” location given by the International 10–20 system, F3-rTMS) versus connectivity-guided intermittent theta burst stimulation (cgiTBS) for treatment-resistant depression. This present study reports the acceptability, safety, and tolerability of F3-rTMS versus cgiTBS. MethodsThe present study used quantitative and qualitative methods. Two hundred fifty-four participants were included in the quantitative BRIGhTMIND acceptability and safety analysis (n = 126 F3-rTMS, n = 128 cgiTBS). Qualitative analysis included interviews for 15 participants (n = 7 F3-rTMS, n = 8 cgiTBS) and 582 written comments made by any participant randomised to the BRIGhTMIND trial regarding their experience of TMS and the study. Statistical analyses were used to explore differences between F3-rTMS and cgiTBS, as well as associations between acceptability, impression of change and safety. Qualitative data was analysed using an inductive thematic framework approach. OutcomesAcceptability, TMS benefits/negative effects and impression of improvement ratings did not differ across the two treatment protocols, with ratings maintained long-term (71.4 % rated TMS acceptable, 48.8 % indicated benefits of TMS outweighed negative effects and 52.2 % feeling somewhat or much better at 26 week follow-up n = 203). Impression of improvement was positively associated with acceptability and TMS benefits. Qualitative themes included participants' TMS experience, TMS response variability, and lay theories of effectiveness. Safety profiles were comparable between F3-rTMS and cgiTBS, with 74.5 % of participants (n = 190/254) experiencing at least one adverse event possibly, probably, or definitely related to TMS. The majority of adverse events were transient and mild, with a sizeable number requiring simple treatments or small adjustments to TMS intensity and coil positioning. The F3-rTMS group had a significantly greater proportion of participants that required small adjustments to TMS to tolerate treatment compared to the cgiTBS group. Serious adverse events were rare, with one serious event in each treatment arm possibly related to TMS (F3-rTMS- psychotic episode, cgiTBS-manic episode). ConclusionF3-rTMS and cgiTBS are comparably safe, tolerable and highly acceptable interventions for treatment-resistant depression. BRIGhTMIND systematically collected data from a large sample, providing evidence to meet the information needs of patients, clinicians and policy makers.

Repeatability of alkaline inorganic phosphate quantification in the skeletal muscle using 31P-magnetic resonance spectroscopy at 3T.

The detection of a secondary inorganic phosphate (Pi) resonance, a possible marker of mitochondrial content in vivo, using phosphorus magnetic resonance spectroscopy (31P-MRS), poses technical challenges at 3Tesla (T). Overcoming these challenges is imperative for the integration of this biomarker into clinical research. To evaluate the repeatability and reliability of measuring resting skeletal muscle alkaline Pi (Pialk) using with 31P-MRS at 3 T. After an initial set of experiments on five subjects to optimize the sequence, resting 31P-MRS of the quadriceps muscles were acquired on two visits (~4days apart) using an intra-subjects design, from 13 sedentary to moderately active young male and female adults (22 ± 3years old) within a whole-body 3T MR system. Measurement variability attributed to changes in coil position, shimming procedure, and spectral analysis were quantified. 31P-MRS data were acquired with a 31P/-proton (1H) dual-tuned surface coil positioned on the quadriceps using a pulse-acquire sequence. Test-retest absolute and relative repeatability was analyzed using the coefficient of variation (CV) and intra-class correlation coefficients (ICC), respectively. After sequence parameter optimization, Pialk demonstrated high intra-subject repeatability (CV: 10.6 ± 5.4%, ICC: 0.80). Proximo-distal change in coil position along the length of the quadriceps introduced Pialk quantitation variability (CV: 28 ± 5%), due to magnetic field inhomogeneity with more distal coil locations. In contrast, Pialk measurement variability due to repeated shims from the same muscle volume (0.40 ± 0.09mM; CV: 6.6%), and automated spectral processing (0.37 ± 0.01mM; CV: 2.3%), was minor. The quantification of Pialk in skeletal muscle via surface coil 31P-MRS at 3T demonstrated excellent reproducibility. However, caution is advised against placing the coil at the distal part of the quadriceps to mitigate shimming inhomogeneity.

Understanding Strain Signals from Low-Frequency Distributed Acoustic Sensing In-Well Measurements: Experimental and Numerical Modeling

Summary Over the past few decades, the potential of distributed measurements using in-well fiberoptic data has been demonstrated. In particular, low-frequency distributed acoustic sensing (LF-DAS) has experienced rapid growth toward monitoring wells for integrity and production purposes. Despite technological advancements, applications in this space have been hindered by a limited understanding of the data. The richness of detail in the data is a double-edged sword; while it provides substantial amounts of information to guide the operator, it simultaneously complicates the task of deciphering the underlying signals. To address this issue, it would be advantageous to devise a straightforward approach to understand the nature of common signals due to strain encountered during routine well operations. We present an experimental method for interpreting tubing strain signals using a long spring that is fixed at both ends, mimicking the tubing in a well. Tracking the position of coils over time allows us to record the displacement when a force is applied to the spring. We show that the displacement observed from such an experiment is similar to what we observe in LF-DAS data from wells in operation. Typical signals, such as the pistoning effect on a valve or strain caused by fluid flow, are compared with experimental data. More complex phenomena, such as stick/slip friction and thermal expansion, are modeled using a mass-spring system and compared with wellbore examples. Developing a fundamental understanding of the signals will allow for real-time identification of events, facilitated by fiber-optic data, substantially enhancing operational outcomes by preempting integrity issues and promoting production optimization.

High-Quality SiC Crystal Growth by Temperature Gradient Control at Initial Growth Stage

A modified process condition has been proposed for the growth of high-quality 6-inch 4H-SiC single crystal. Temperature gradient (dT[°C] = Tbottom-Tupper) was controlled by changing coil position in order to investigate the effect of the temperature gradient on the SiC crystal quality. SiC ingot surface and etch pit density (EPD) of etched SiC wafer were investigated according to different dT conditions at the initial stage of SiC crystal growth. The surface of SiC crystal ingots grown with different dT for 10h were observed by OM and etched SiC wafers were prepared from SiC crystal ingots after main growth step for 100h. Different dT conditions in the initial growth stage resulted in dramatically different surface images and the crystal quality evaluated by EPD.

Real-time estimation of the optimal coil placement in transcranial magnetic stimulation using multi-task deep learning

Transcranial magnetic stimulation (TMS) has emerged as a promising neuromodulation technique with both therapeutic and diagnostic applications. As accurate coil placement is known to be essential for focal stimulation, computational models have been established to help find the optimal coil positioning by maximizing electric fields at the cortical target. While these numerical simulations provide realistic and subject-specific field distributions, they are computationally demanding, precluding their use in real-time applications. In this paper, we developed a novel multi-task deep neural network which simultaneously predicts the optimal coil placement for a given cortical target as well as the associated TMS-induced electric field. Trained on large amounts of preceding numerical optimizations, the Attention U-Net-based neural surrogate provided accurate coil optimizations in only 35 ms, a fraction of time compared to the state-of-the-art numerical framework. The mean errors on the position estimates were below 2 mm, i.e., smaller than previously reported manual coil positioning errors. The predicted electric fields were also highly correlated (r> 0.97) with their numerical references. In addition to healthy subjects, we validated our approach also in glioblastoma patients. We first statistically underlined the importance of using realistic heterogeneous tumor conductivities instead of simply adopting values from the surrounding healthy tissue. Second, applying the trained neural surrogate to tumor patients yielded similar accurate positioning and electric field estimates as in healthy subjects. Our findings provide a promising framework for future real-time electric field-optimized TMS applications.

Increasing the Dynamic Characteristics of the Locomotive by Changing the Position of the End Coils of the Springs of the Body Spring Suspension

Increasing the Dynamic Characteristics of the Locomotive by Changing the Position of the End Coils of the Springs of the Body Spring Suspension

Machine learning approaches to predict whether MEPs can be elicited via TMS

BackgroundTranscranial magnetic stimulation (TMS) is a valuable technique for assessing the function of the motor cortex and cortico-muscular pathways. TMS activates the motoneurons in the cortex, which after transmission along cortico-muscular pathways can be measured as motor-evoked potentials (MEPs). The position and orientation of the TMS coil and the intensity used to deliver a TMS pulse are considered central TMS setup parameters influencing the presence/absence of MEPs. New methodWe sought to predict the presence of MEPs from TMS setup parameters using machine learning. We trained different machine learners using either within-subject or between-subject designs. ResultsWe obtained prediction accuracies of on average 77 % and 65 % with maxima up to up to 90 % and 72 % within and between subjects, respectively. Across the board, a bagging ensemble appeared to be the most suitable approach to predict the presence of MEPs. ConclusionsAlthough within a subject the prediction of MEPs via TMS setup parameter-based machine learning might be feasible, the limited accuracy between subjects suggests that the transfer of this approach to experimental or clinical research comes with significant challenges.

Superconductor based, tomographic, neutron diagnostics for fusion power monitoring.

We propose a scalable system of compact, superconducting neutron monitors, which can be embedded in any existing cryogenic infrastructure of a fusion system. The pixel-based nature of the detectors allows them to be placed at intervals following the circumference of a cooled zone, e.g., a field coil, thus allowing for a tomographic measurement of the neutron flux surrounding the plasma. An early stage prototype of the superconducting bolometer is described, and the key results of a previous feasibility study of this prototype performed with cold neutrons are summarized. The bolometer can be adapted for use with fast neutrons by altering the composition and geometry of the neutron-to-heat conversion layer. This paper describes the initial feasibility considerations for implementation in a superconducting tokamak. The sensor is based on a high-temperature superconductor, making it possible to select the operation temperature in the range 1-90K. Neutron flux numbers were found using the ITER MCNP reference model, and these were embedded in a TOPAS model to find the expected signal measured by the bolometer at the position of a toroidal field coil. The results at the coil position indicate suitable operation levels in terms of the magnitude of the measured signal, with a measurable signal of several ohm, which is much smaller than the saturation energy of the detector. Radiation hardness is estimated and found to be on the order of at least 40 years for the relevant radiation levels. The upcoming investigation activities of the project are described for both radiation testing and analytical modeling.

MR-Safe Cartesian Platform for Active Cardiac Shimming: Preliminary Validation.

Implanted Cardioverter Defibrillators (ICDs) induce a large (100 parts per million) inhomogeneous magnetic field in the magnetic resonance imaging (MRI) scanner which cannot be corrected by the scanner's built-in shim coils, leading to significant image artifacts that can make portions of the heart unreadable. To compensate for the field inhomogeneity, an active shim coil capable of countering the field deviation in user-defined regions was designed that must be optimally placed at patient-specific locations. We aim to develop and evaluate an MR-safe robotic solution for automated shim coil positioning. We designed and fabricated an MR-safe Cartesian platform that holds the shim coil inside the scanner. The platform consists of three lead screw stages actuated by pneumatic motors, achieving decoupled translations of 140 mm in each direction. The platform is made of plastics and fiberglass with the control electronics placed outside the scanner room, ensuring MR safety. Mechanical modeling was derived to provide design specifications. Experiments show that the platform achieves less than 2 mm average motion error and 0.5 mm repeatability in all directions, and reduces the adjustment time from 5 min to a few seconds. Phantom and animal trials were conducted, showing that the proposed system is able to position a heavy shim coil ( kg) for improved ICD artifact suppression. This robotic platform provides an effective method for reliable shim coil positioning inside the scanner. This work contributes to improving cardiac MRI quality that could facilitate accurate diagnosis and treatment planning for patients with implanted ICDs.

Transcranial magnetic stimulation of primary motor cortex elicits an immediate transcranial evoked potential

BackgroundTranscranial evoked potentials (TEPs) measured via electroencephalography (EEG) are widely used to study the cortical responses to transcranial magnetic stimulation (TMS). Immediate transcranial evoked potentials (i-TEPs) have been obscured by pulse and muscular artifacts. Thus, the TEP peaks that are commonly reported have latencies that are too long to be caused by direct excitation of cortical neurons. MethodsIn 25 healthy individuals, we recorded i-TEPs evoked by a single biphasic TMS pulse targeting the primary motor hand area (M1HAND) or parietal or midline control sites. Sampling EEG at 50 kHz enabled us to reduce the duration of the TMS pulse artifact to a few milliseconds, while minor adjustments of the TMS coil tilt or position enabled us to avoid cranial muscular twitches during the experiment. ResultsWe observed an early positive EEG deflection starting after approx. 2 ms followed by a series of superimposed peaks with an inter-peak interval of ∼1.1–1.4 ms in multiple electrodes surrounding the stimulated sensorimotor region. This multi-peak i-TEP response was only evoked by TMS of the M1HAND region and was modified by changes in stimulation intensity and current direction. DiscussionSingle-pulse TMS of the M1HAND evokes an immediate local multi-peak response at the cortical site of stimulation. Our results suggest that the observed i-TEP patterns are genuine cortical responses evoked by TMS caused by synchronized excitation of pyramidal neurons in the targeted precentral cortex. This notion needs to be corroborated in future studies, including further investigations into the potential contribution of instrumental or physiological artifacts.

Investigation of intrinsic error fields in MAST-U device

In magnetic fusion devices, undesired non-axisymmetric magnetic field perturbations, typically called error fields (EF), have been observed to have a detrimental effect on plasma stability and confinement and can lead to brute plasma terminations, i.e. plasma disruption events. The main strategies that can be adopted to minimize the effect of EFs on the plasma dynamics consist in a careful alignment of the coils, when assembling the fusion device, and, most commonly, in the use of EF correction coils which counteract the non-axisymmetric fields by prescribing properly designed correction currents. In this work, an assessment of the n=1 EF source in MAST-U is presented. When constructing the MAST-U device, an optimization of poloidal and divertor coil positions has been adopted to reduce the n=1 EF source. This optimization consisted in the application of coil shifts and tilts, of the order of mms and mrads, respectively. To investigate the presence of a residual n=1 EF dedicated studies have been performed during the first MAST-U campaign. The compass scan method was employed to identify the n=1 EF, relying on the detection of the locked mode (LM) onset, which proved to be a challenging task. Therefore, a methodology based on Transfer Functions (TFs) among each coil and the n=1 radial magnetic field has been developed which allows the detection of LM formation. Such method is described here, complemented with the experimental results achieved, which suggest that the intrinsic n=1 EF source on MAST-U is relatively small with respect to MAST. Indeed, the empirical correction currents for n=1 EF minimization are smaller, about 0.2 kA, than the ones used in MAST, 1 kA range. This proves that the optimal coil alignment for n=1 EF minimization has been a successful strategy in MAST-U.

Design and Optimization of Coil for Transcutaneous Energy Transmission System

This article presents a coil couple-based transcutaneous energy transmission system (TETS) for wirelessly powering implanted artificial hearts. In the TETS, the performance of the system is commonly affected by the change in the position of the coupling coils, which are placed inside and outside the skin. However, to some extent, the influence of coupling efficiency caused by misalignment can be reduced by optimizing the coil. Thus, different types of coils are designed in this paper for comparison. It has been found that the curved coil better fits the surface of the skin and provides better performance for the TETS. Various types of curved coils have been designed in response to observed bending deformations, dislocations, and other coupling variations in the curved coil couple. The numerical model of the TETS is established to analyze the effects of the different types of coils. Subsequently, a series of experiments are designed to evaluate the resilience to misalignment and to verify the heating of the coil under conditions of severe coupling misalignment. The results indicated that, in the case of misalignment of the coils used in artificial hearts, the curved transmission coil demonstrated superior efficiency and lower temperature rise compared to the planar coil.

Customized modulation on plasma uniformity by non-uniform magnetic field in capacitively coupled plasma

A two-dimensional fluid model based on COMSOL Multiphysics is developed to investigate the modulation of static magnetic field on plasma homogeneity in a capacitively coupled plasma (CCP) chamber. To generate a static magnetic field, direct current is applied to a circular coil located at the top of the chamber. By adjusting the magnetic field’s configuration, which is done by altering the coil current and position, both the plasma uniformity and density can be significantly modulated. In the absence of the magnetic field, the plasma density exhibits an inhomogeneous distribution characterized by higher values at the plasma edge and lower values at the center. The introduction of a magnetic field generated by coils results in a significant increase in electron density near the coils. Furthermore, an increase in the sets of coils improves the uniformity of the plasma. By flexibly adjusting the positions of the coils and the applied current, a substantial enhancement in overall uniformity can be achieved. These findings demonstrate the feasibility of using this method for achieving uniform plasma densities in industrial applications.

Identifying the plane position of the receiver coil in a multi‐transmitter IPT system through the identification of parameters

AbstractThe study introduces a method for identifying the location of receiver coils within a multi‐transmitter IPT system that utilizes shared transmitter coils. In contrast to the conventional receiver coil position recognition methods, this approach eliminates the need for additional detection coils and position sensors. Identifying the location of the receiver coil in a multi‐transmitter IPT system is achieved through the concurrent optimization of the transmitter coil and its electrical characteristics. The study presents the design of coil grouping and control mechanisms for a 3×3 multi‐transmitter. A mathematical model has been developed for the mutual inductance between receiver and transmitter coils on the X–Y plane. Adaptive cooperative particle swarm optimizer (ACPSO) facilitates the identification of mutual inductance and load parameters in a multi‐transmitter IPT system, positioning the receiver coil in a 2D plane using genetic particle swarm optimization (GAPSO) and a mutual inductance mathematical model. The discrepancy in accuracy between the receiver coil's test coordinates and the absolute coordinates remains below 3.5%.

Simulation and test for the micro-newton electromagnetic calibration force measurement

For micro-Newton (μN) level thrust measurement, achieving highly accurate calibration forces is crucial as an initial step. To provide high-precision and wide-range electromagnetic calibration forces, this study introduces a C-type magnetic circuit structure and a rectangular coil combination method. The magnetic field distribution within the device’s characteristic region was examined using the finite element method, and the impact of the relative positions of the rectangular coil and magnet was explored. Subsequently, calibration experiments were conducted on a specially developed platform. The primary findings are as follows: The electromagnetic force calibration range is from 0.097 to 237.32 μN, with the maximum error between experimental measurement data and simulation results being 1.73%. With a coil current resolution of 10 μA, the measured resolution of the calibration force exceeds 0.1 μN. Within the characteristic region, the magnetic field distribution exhibits high uniformity, with a maximum deviation rate of only 0.7%. This research establishes a technique for micro-Newton level thrust measurement.

MR Safety of Inductively Coupled and Conventional Intraoral Coils.

Intraoral coils (IOCs) in magnetic resonance imaging (MRI) significantly improve the signal-to-noise ratio compared with conventional extraoral coils. To assess the safety of IOCs, we propose a 2-step procedure to evaluate radiofrequency-induced heating of IOCs and compare maximum temperature increases in 3 different types of IOCs. The 2-step safety assessment consists of electric field measurements and simulations to identify local hotspots followed by temperature measurements during MRI. With this method, 3 different coil types (inductively coupled IFC, transmit/receive tLoop, and receive-only tLoopRx) were tested at 1.5 T and 3 T for both tuned and detuned coil states. High SAR and regular MRI protocols were applied for 2 coil positions. The measured E field maps display distinct hotspots for all tuned IOCs, which were reduced by at least 40-fold when the IOCs were detuned. Maximum temperature rise was higher when the coils were positioned at the periphery of the phantom with the coil planes parallel to B 0 . When neither active nor passive detuning was applied, maximum temperature increase of ΔT = 1.3/0.5/1.8 K was found for IFC/tLoop/tLoopRx coils. Hotspots detected by E field measurements, and simulations were consistent. In the simulations, the results were different for homogeneous phantoms compared with full anatomical models. The 2-step test procedure is applicable to different coil types. The results indicate that a risk for radiofrequency-induced heating exists for tuned IOCs, so that adequate detuning circuits need to be integrated in the coils to ensure safe operation.