scholarly journals Investigation of the temporal and spatial dynamics of muscular action potentials through optically pumped magnetometers

2021 ◽  
Author(s):  
Philip J. Broser ◽  
Justus Marquetand ◽  
Thomas Middelmann ◽  
Davide Sometti ◽  
Christoph Braun
Keyword(s):  
Magnetic Field ◽  
Action Potential ◽  
Muscle Fiber ◽  
Stretch Reflex ◽  
Rectus Femoris ◽  
List Type ◽  
Contractile Apparatus ◽  
Optically Pumped ◽  
The Magnetic Field ◽  
Muscular Action

ABSTRACTAimThis study aims to simultaneously record the magnetic and electric components of the propagating muscular action potential.MethodA single-subject study of the monosynaptic stretch reflex of the musculus rectus femoris was performed; the magnetic field generated by the muscular activity was recorded in all three spatial directions by five optically pumped magnetometers. In addition, the electric field was recorded by four invasive fine-wire needle electrodes. The magnetic and electric fields were compared, and modelling and simulations were performed to compare the magnetic field vectors with the underlying muscular anatomy of the rectus femoris muscle.ResultsThe magnetomyography (MMG) signal can reliably be recorded following the stimulation of the monosynaptic stretch reflex. The MMG signal shows several phases of activity inside the muscle, the first of which is the propagating muscular action potential. As predicted by the finite wire model, the magnetic field vectors of the propagating muscular action potential are generated by the current flowing longitudinal to the muscle fiber. Based on the magnetic field vectors, it was possible to reconstruct the pinnation angle in the muscle. The later magnetic components are linked to the activated contractile apparatus.InterpretationMMG allows to analyze the muscle physiology from the propagating muscular action potential to the initiation of the contractile apparatus. At the same time this methods reveal information about muscle fiber direction and extend. With the development of high-resolution magnetic cameras, it will be possible to image the function and structure of any skeletal muscle with high precision. This method could be used in clinical medicine but also in sports and training science.What this paper adds-A robust technique for triggering a muscular action potential that can be recorded by MMG and needle EMG simultaneously-The correlation of the MMG signal with the needle EMG signal-A method for detecting the direction of the propagating muscular action potential-A method for correlating the magnetic field vectors with the pinnation angle of the examined muscle

P 52. Optically pumped magnetometers disclose magnetic field components of the muscular action potential

2021 ◽  
Vol 132 (8) ◽  
pp. e24-e25
Author(s):  
P.J. Broser ◽  
T. Middelmann ◽  
D. Sometti ◽  
C. Braun
Keyword(s):  
Magnetic Field ◽  
Action Potential ◽  
Optically Pumped ◽  
Muscular Action

scholarly journals Muscle fatigue revisited - Insights from optically pumped magnetometers

2021 ◽  
Author(s):  
Davide Sometti ◽  
Lorenzo Semeia ◽  
Hui Chen ◽  
Juergen Dax ◽  
Cornelius Kronlage ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Muscle Fatigue ◽  
Isometric Contraction ◽  
Muscle Fibers ◽  
Muscular Activity ◽  
Rectus Femoris ◽  
Optically Pumped ◽  
Rectus Femoris Muscle ◽  
The Magnetic Field ◽  
Femoris Muscle

Muscle fatigue is well characterized electromyographically, nevertheless only information about summed potential differences is detectable. In contrast, recently developed quantum sensors optically pumped magnetometers (OPMs) offer the advantage of recording both the electrical current propagation in the muscle as well as its geometry, by measuring the magnetic field generated by the muscular action potentials. Magnetomyographic investigation of muscle fatigue is still lacking and it is an open question whether fatigue is characterized similarly in magnetomyography (MMG) compared to electromyography (EMG). Herein, we investigated the muscle fatigue during a 3x1-min strong isometric contraction of the rectus femoris muscle of 12 healthy subjects using simultaneous EMG-MMG (4-channel surface EMG and 4 OPM along the rectus femoris muscle). Both EMG and MMG showed the characteristic frequency decrease in the signal magnitude during isometric contraction, which is typical for muscle fatigue. In addition, it was shown that the main part of this frequency decrease seems to occur in the circular component of the magnetic field around the muscle fibers and less longitudinally along the muscle fibers. Overall, these results show not only that magnetomyography is capable of reproducing the electromyographic standards in identifying muscular fatigue, but it also adds relevant information about the spatial characterization of the signal. Therefore, OPM-MMG offers new insights for the study of muscular activity and might serve as a new, supplementary neurophysiological method.

scholarly journals Optically pumped magnetometers disclose magnetic field components of the muscular action potential

2021 ◽  
Vol 56 ◽  
pp. 102490
Author(s):  
Philip J. Broser ◽  
Thomas Middelmann ◽  
Davide Sometti ◽  
Christoph Braun
Keyword(s):  
Magnetic Field ◽  
Action Potential ◽  
Optically Pumped ◽  
Muscular Action

scholarly journals Optically pumped magnetometers disclose magnetic field components of the muscular action potential.

2020 ◽  
Author(s):  
Philip Broser ◽  
Thomas Middelmann ◽  
Davide Sometti ◽  
Christoph Braun
Keyword(s):  
Magnetic Field ◽  
Action Potential ◽  
Electric Dipole ◽  
Temporal Dynamics ◽  
Signal Transduction Pathway ◽  
Electric Activity ◽  
Dipole Model ◽  
Dipole Source ◽  
Optically Pumped ◽  
The Magnetic Field

Aim: To track the magnetic field generated by the propagating muscle action potential (MAP). Method: In this prospective, proof of principle study, the magnetic activity of the intrinsic foot muscle after electric stimulation of the tibial nerve was measured using optically pumped magnetometers (OPMs). A classical biophysical electric dipole model of the propagating MAP was implemented to model the source of the data. Results: The signal profile generated by the activity of the intrinsic foot muscles was measured by four OPM devices. Three devices were located above the same muscle to compare the direction and the strength of the magnetic signal while propagating along the muscle. Interpretation: OPM devices allow for a new, non-invasive way to study MAP patterns. Since magnetic fields are less altered by the tissue surrounding the dipole source compared to electric activity, a precise analysis of the spatial characteristics and temporal dynamics of the MAP is possible. The classic electric dipole model explains major but not all aspects of the magnetic field. The field has longitudinal components generated by intrinsic structures of the muscle fibre. By understanding these magnetic components, new methods could be developed to analyse the muscular signal transduction pathway in greater detail.

scholarly journals Practice and perspectives of using ultrasensitive magnetometers in biomedical research.

2021 ◽  
Author(s):  
Yu.V. Maslennikov ◽  
◽  
◽  
Keyword(s):  
Magnetic Field ◽  
Biomedical Research ◽  
Magnetic Measurements ◽  
Signal To Noise Ratio ◽  
Frequency Range ◽  
Optically Pumped ◽  
Technical Solutions ◽  
Further Development ◽  
The Magnetic Field

There are a large number of sensors for measuring the magnetic field of biological objects. They are characterized by the type of the measured physical parameter (magnetic field strength, magnetic flux, etc.), the level of intrinsic sensitivity, and the frequency range of the recorded signals. The long-term practice of studying biomagnetic signals shows that only SQUID-based magnetometers and optically pumped magnetometers have sensitivity levels sufficient for recording biomagnetic signals with the required signal-to-noise ratio. This chapter reflects the main directions of using such magnetometers and methods of magnetic measurements in biomedical research, gives examples of existing technical solutions, and shows possible ways of their further development.

scholarly journals Properties of the Solar Filigree Structure

1974 ◽  
Vol 56 ◽  
pp. 45-47
Author(s):  
R. B. Dunn ◽  
J. B. Zirker ◽  
J. M. Beckers
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Solar Physics ◽  
List Type ◽  
Blue Wing ◽  
One To One ◽  
Granulation Pattern ◽  
Network Patterns ◽  
The Magnetic Field ◽  
The Continuum

A number of observers have noted the presence of bright structures near the cores of the chromospheric rosettes when observed in the far wings of the Hα line (eg Hα ±7/8 Å). Dunn and Zirker observed these bright structures with the highest possible resolution using the Sacramento Peak vacuum solar telescope. They find that these bright regions exhibit a very intricate fine structure which can be followed out much further into the Hα line wing (eg Hα + 2 Å) and even into the continuum. They called this fine structure ‘solar filigree’, the name referring mainly to the collective appearance of the fine structure elements. The elements themselves appear as dot-like structures and frequently also as small wiggly structures called ‘crinkles’. The properties of the filigree structure are summarized as follows: (i)Size: Measured diameter of the crinkles and dots equals 0.25, 0.40 and 0.60″ at Hα + 2 Å, Hα ± 7/8 Å and Hα ±5/8 Å respectively. The telescope resolution equals 0.22″ so that at Hα + 2 Å the structure is extremely small. The drawings in Figure 1 show typical sizes of the crinkles and network patterns in the filigree.(ii)Contrast: Filigree is enhanced in the blue wing of the Hα line. Measured contrast, uncorrected for seeing, equals 5–10%.(iii)Relation to the Granulation: The filigree structures tend to lie between the granules. This is, however, not a strict rule. It seems that in the course of their lifetime the granules move the filigree structures around with velocities of about 1.5 km s-1. Some of the crinkles also seem to wash out temporarily until compressed again by a new granule. The detailed structure of the filigree, therefore, changes significantly over times comparable to the granule lifetime. The overall structure is, however, preserved over much longer periods of time. The granulation pattern when observed in the continuum well outside the Hα line appears very peculiar in that it has substantially decreased in contrast. It appears ‘soft’ similar to granulation washed-out by seeing. This abnormal granulation can be traced over long times (> 30 min) and coincides in location to the filigree location. It is, therefore, definitely real.(iv)Relation to the spicules: The filigree structure falls near the center of the Hα chromospheric rosettes. These rosettes consist of dark elongated mottles which should probably be identified with spicules. There is, therefore, at least a coarse relation between the occurrence of spicules and the filigree. There is no clear evidence that variations in the filigree pattern are related to the generation of spicules. Some spicules seem to originate from the spaces between the crinkles. Too few, however, to conclude a definite relation.(v)Relation to the magnetic field: Beckers studied the filigree with the Universal Birefringent Filter in the magnesium b1 and b2 lines. It is very well visible in the far wing of the lines (eg. b1 ±0.8 Å). When traced into the line core the structures increase somewhat in size, as they do in Hα, and form structures similar to, and perhaps identical with, the so-called photospheric network. In the magnetically sensitive b2 line one sees a one-to-one correspondence between these network structures and the magnetic field so that, at least in the layers seen near the core of the b2 line, there is a one-to-one correspondence between the filigree structures and the enhancements in the magnetic field. Simon and Zirker (Solar Physics, submitted for publication) using a spectrograph also found that the filigree occurs in regions of enhanced magnetic field. However, in contrast to the filter observations, they found the magnetic field regions to be much more diffuse (2–3″) so that there is not a one-to-one spatial correspondence between filigree and magnetic field structure.

scholarly journals Muscle Fatigue Revisited – Insights From Optically Pumped Magnetometers

2021 ◽  
Vol 12 ◽  
Author(s):  
Davide Sometti ◽  
Lorenzo Semeia ◽  
Sangyeob Baek ◽  
Hui Chen ◽  
Giulia Righetti ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Rectus Femoris ◽  
Field Vector ◽  
Optically Pumped ◽  
Potential Alternative ◽  
Spectral Compression ◽  
Rectus Femoris Muscle ◽  
The Magnetic Field ◽  
Healthy Participants ◽  
Femoris Muscle

So far, surface electromyography (sEMG) has been the method of choice to detect and evaluate muscle fatigue. However, recent advancements in non-cryogenic quantum sensors, such as optically pumped magnetometers (OPMs), enable interesting possibilities to flexibly record biomagnetic signals. Yet, a magnetomyographic investigation of muscular fatigue is still missing. Here, we simultaneously used sEMG (4 surface electrode) and OPM-based magnetomyography (OPM-MMG, 4 sensors) to detect muscle fatigue during a 3 × 1-min isometric contractions of the left rectus femoris muscle in 7 healthy participants. Both signals exhibited the characteristic spectral compression distinctive for muscle fatigue. OPM-MMG and sEMG slope values, used to quantify the spectral compression of the signals, were positively correlated, displaying similarity between the techniques. Additionally, the analysis of the different components of the magnetic field vector enabled speculations regarding the propagation of the muscle action potentials (MAPs). Altogether these results show the feasibility of the magnetomyographic approach with OPMs and propose a potential alternative to sEMG for the study of muscle fatigue.

scholarly journals An electromagnetic arrayed pump to create arbitrary velocity profiles in fluid

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Seyed Peyman Hashemi ◽  
Mohammad Reza Karafi ◽  
Mohammad Hossein Sadeghi ◽  
Vahid Rezaei Esfedan
Keyword(s):  
Magnetic Field ◽  
Fluid Velocity ◽  
Rectangular Channel ◽  
Velocity Profiles ◽  
List Type ◽  
Finite Element Software ◽  
Electromagnetic Pump ◽  
Naoh Solution ◽  
Arbitrary Velocity ◽  
The Magnetic Field

AbstractThe present paper is conducted to develop a new structure of an electromagnetic pump capable of controlling the magnetic field in a rectangular channel. Common electromagnetic pumps do not create uniform velocity profiles in the cross-section of the channel. In these pumps, an M-shape profile is created since the fluid velocity in the vicinity of the walls is higher than that in its center. Herein, the arbitrary velocity profiles in the electromagnetic pump are generated by introducing an arrayed structure of the coils in the electromagnetic pump and implementing 3D numerical simulation in the finite element software COMSOL. The dimensions of the rectangular channel are 5.5 × 150 mm2. Moreover, the magnetic field is provided using a core with an arrayed structure made of low-carbon iron, as well as five couples of coils. 20% NaoH solution is utilized as the fluid (conductivity: 40 S/m). The arrayed pump is fabricated and experimentally created an arbitrary velocity profile. The pressure of the pump in every single array is 12 Pa and the flow rate is equal to 3375 mm3/s. According to the results, there is a good agreement between the experimental test carried out herein and the simulated models.Article highlights This is the first time that the idea of arrayed electromagnetic pump is presented. This pump uses a special arrayed core with coils; by controlling the current of each coil and the direction of the currents, the magnetic field under the core could be adjusted. By changing the magnetic field at any position in the width of the channel, the Lorentz force alters, which leads to different velocity and pressure profiles. Using COMSOL multiphysics software, the electromagnetic pump was simulated in real size compared to the experimental model. Subsequently, the simulation model was verified and different velocity profiles were generated by activation and deactivation of different coils. The pressure and velocity curves and contours were extracted. The experimental setup was manufactured and assembled. NaOH solution was utilized as the fluid. Afterwards, different modes of coil activations were investigated and the pressure and velocity profiles of the pump were calculated.

Non‐oriented cesium sensors for airborne magnetometry and gradiometry

Geophysics ◽  
1984 ◽  
Vol 49 (11) ◽  
pp. 2024-2031 ◽  
Author(s):  
C. D. Hardwick
Keyword(s):  
Magnetic Field ◽  
National Research Council ◽  
Larmor Frequency ◽  
High Sensitivity ◽  
Field Vector ◽  
Error Characteristic ◽  
Optically Pumped ◽  
Optimal Angle ◽  
Multiple Sensor ◽  
The Magnetic Field

Optically pumped magnetometers are characterized by an optimal angle between their optical axes and the direction of the magnetic field they are sensing. Departure from the optimal angle causes a shift in the Larmor frequency with a corresponding error in the scalar value of the magnetic field being measured. To minimize this error, magnetometers are conventionally either mounted in multiple sensor clusters such that the errors tend to cancel, or they are mechanically oriented to maintain the optimal angle with respect to the magnetic field vector. Recent cesium vapor magnetometers using a split‐beam technique have a sufficiently flat error characteristic that they can be flown in a non‐oriented or “strap‐down” configuration. This configuration has advantages with respect to conventional methods in terms of reduced size and weight and of greatly reduced cost. This paper describes two fixed orientations for a particular split‐beam magnetometer and calculates the allowable maneuver envelope for all dip angles from 0 to 90 degrees. It is shown that the residual orientation errors can best be handled by the conventional type of magnetic interference compensation model that must, in any case, be implemented in digital form for high‐sensitivity magnetometry or for any type of gradiometry. The National Aeronautical Establishment (NAE) of the National Research Council of Canada has flown strap‐down magnetometers in a three‐axis gradiometer array in a Convair 580 for several years. Results for the entire normal maneuver envelope of the aircraft, including 30 degree bank turns, have equalled or surpassed those obtained with oriented magnetometers. Several typical maneuver compensation results are presented that gave root‐mean‐square (rms) (one‐sigma) residual errors as low as 0.03 gammas (γ) for total field and 3.5 mgammas/m (mγ/m) for lateral gradient.

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