Rotation Measurements Research Articles

A fast radio burst source at a complex magnetized site in a barred galaxy.

Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts1-3. Recent observations of a Galactic FRB4-8 suggest that at least some FRBs originate from magnetars, but the origin of cosmological FRBs is still not settled. Here we report the detection of 1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref. 9). These observations show irregular short-time variation of the Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (AU; Earth-Sun distance) of the source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy10-12 show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.

Magnetic fields on FIRE: Comparing B-fields in the multiphase ISM and CGM of simulated L* galaxies to observations

ABSTRACT The physics of magnetic fields (B) and cosmic rays (CRs) have recently been included in simulations of galaxy formation. However, significant uncertainties remain in how these components affect galaxy evolution. To understand their common observational tracers, we analyse the magnetic fields in a set of high-resolution, magnetohydrodynamic, cosmological simulations of Milky-Way-like galaxies from the FIRE-2 project. We compare mock observables of magnetic field tracers for simulations with and without CRs to observations of Zeeman splitting and rotation/dispersion measures. We find reasonable agreement between simulations and observations in both the neutral and the ionized interstellar medium (ISM). We find that the simulated galaxies with CRs show weaker ISM |B| fields on average compared to their magnetic-field-only counterparts. This is a manifestation of the effects of CRs in the diffuse, low density inner circumgalactic medium (CGM). We find that equipartition between magnetic and cosmic ray energy densities may be valid at large (> 1 kpc) scales for typical ISM densities of Milky-Way-like galaxies, but not in their haloes. Within the ISM, the magnetic fields in our simulated galaxies follow a power-law scaling with gas density. The scaling extends down to neutral hydrogen number densities < 300 cm−3, in contrast to observationally derived models, but consistent with the observational measurements. Finally, we generate synthetic rotation measure (RM) profiles for projections of the simulated galaxies and compare to observational constraints in the CGM. While consistent with upper limits, improved data are needed to detect the predicted CGM RMs at 10–200 kpc and better constrain theoretical predictions.

Irregular Workpiece Template-Matching Algorithm Using Contour Phase

The current template-matching algorithm can match the target workpiece but cannot give the position and orientation of the irregular workpiece. Aiming at this problem, this paper proposes a template-matching algorithm for irregular workpieces based on the contour phase difference. By this, one can firstly gain the profile curve of the irregular workpiece by measuring its radius in orderly fashion and then, calculate the similarity of the template workpiece profile and the target one by phase-shifting and finally, compute the rotation measure between the two according to the number of phase movements. The experimental results showed that in this way one could not only match the shaped workpiece in the template base accurately, but also accurately calculate the rotation angle of the irregular workpiece relative to the template with the maximum error controlled within 1%.

Direction-sensitive rotational speed measurement based on the rotational Doppler effect of cylindrical vector beams.

The Doppler effect has inspired numerous applications since its discovery, initially enabling measurement of the relative velocity between a moving object and a wave source. In recent years, it has been found that scalar vortex beams with orbital angular momenta can produce the rotational Doppler effect, which can be used to measure the rotational speeds of rotating objects. However, in practice, only the absolute value of the rotational Doppler frequency shift can be obtained, and it is difficult to distinguish the direction of the object directly by a single measurement. This difficulty can be solved by using cylindrical vector beams with spatially varying polarization states. The cylindrical vector beam is formed by coaxial superposition of two vortex beams with opposite orbital angular momenta and orthogonal polarization states. By using two different polarization channels, the rotation direction can be directly recognized according to the relative phase difference between the two channels. In this paper, the scattering point model is employed to analyze the rotational Doppler effect of cylindrical vector beams, and a variety of cylindrical vector beams are generated by using vortex half-wave plates. The scheme can realize measurement of the rotational speed and direction simultaneously, and the system has simple construction, high accuracy of angular velocity measurement, and accurate direction identification.

Collimation of the kiloparsec-scale radio jets in NGC 2663

ABSTRACT We present the discovery of highly collimated radio jets spanning a total of 355 kpc around the nearby elliptical galaxy NGC 2663, and the possible first detection of recollimation on kiloparsec scales. The small distance to the galaxy (∼28.5 Mpc) allows us to resolve portions of the jets to examine their structure. We combine multiwavelength data: radio observations by the Murchison Widefield Array (MWA), the Australian Square Kilometre Array Pathfinder (ASKAP) and the Australia Telescope Compact Array (ATCA), and X-ray data from Chandra, Swift, and SRG/eROSITA. We present intensity, rotation measure, polarization, spectral index, and X-ray environment maps. Regions of the southern jet show simultaneous narrowing and brightening, which can be interpreted as a signature of the recollimation of the jet by external, environmental pressure, though it is also consistent with intermittent active galactic nuclei or complex internal jet structure. X-ray data suggest that the environment is extremely poor; if the jet is indeed recollimating, the large recollimation scale (40 kpc) is consistent with a slow jet in a low-density environment.

Measurement of idlers rotation speed in belt conveyors based on image data analysis for diagnostic purposes

It is a challenge for mining enterprises to diagnose the belt conveyors, which length can be tens of kilometres and the number of idlers reaches several thousand. All of them require inspection, which is infeasible to perform using monitoring sensors, such as accelerometers. The authors proposed a novel method for the rotational speed measurement of idlers based on image data analysis. The relation is assumed of the rotation speed decrease due to internal defects. The procedure of visual data processing is verified on the real conveyor idlers. The remote sensing method can be applied in mobile inspection robots such as UAVs or UGVs as well as for manual camera recordings. The accuracy of the proposed method is 0.13-0.67% error depending on the speed range, which is provided by the standard sampling rates (30-60 FPS) and video resolution (1280 x 720 px). Recommendations are formulated for method implementation in practice.

Computational Study on Thermal Motion Sensors That Can Measure Acceleration and Rotation Simultaneously.

In this study, a new technique has been proposed by numerical simulations by which multiple physical quantities can be simultaneously measured. The sensor is a modification of existing physical sensors such as a thermal motion sensor. Simultaneous measurement of acceleration and rotation is presented herein. Cross-axis sensitivity is employed such that output sensitivities observed at two perpendicular axes, X and Y sensor data, are related to the input physical quantities. The physics involved in measurement is similar to that of a conventional thermal accelerometer, hence the governing equations predicting the sensor response are based on the conservation of mass, momentum, and energy, and are discretized by using a commercially available software FLUENT. A series of computational studies are conducted and using these studies a novel idea is proposed in which the maximum temperature values are obtained at various positions around a heating source and are correlated with the applied acceleration and rotational speed. A parametric study is also presented to find the optimum distance between the heater and sensors. The influence of changing gas medium on the temperature curves has also been examined and it has been concluded that CO2 generates the maximum performance due to its higher density and lower viscosity.

Predicting Pedicle Screw Pullout and Fatigue Performance: Comparing Lateral Dual-Energy X-Ray Absorptiometry, Anterior to Posterior Dual-Energy X-Ray Absorptiometry, and Computed Tomography Hounsfield Units.

As the prevalence and associated health care costs of osteoporosis continue to rise in our aging population, there is a growing need to continue to identify methods to predict spine construct integrity accurately and cost-effectively. Dual-energy x-ray absorptiometry (DEXA) in both anterior to posterior (AP) and lateral planes, as well as computed tomography (CT) Hounsfield units (HU), have all been investigated as potential preoperative predictive tools. The purpose of this study is to determine which of the 3 bone density analysis modalities has the highest potential for predicting pedicle screw biomechanics. Lumbar spine specimens (L2, L3, and L4) from 6 fresh frozen cadavers were used for testing. AP-DEXA, lateral-DEXA, and CT images were obtained. Biomechanical testing of pedicle screws in each vertebrae was then performed including pullout strength and fatigue testing. Statistical analysis was performed. Pullout strength was best predicted by CT HU, followed by AP-DEXA, then lateral-DEXA (R 2 = 0.78, 0.70, and 0.40, respectively). Fatigue testing showed a significant correlation of relative rotation between HU value and AP-DEXA bone mineral density (R 2 = 0.54 and R 2 = 0.72, respectively), and there was a significant correlation between relative translation and HU value (R 2 = 0.43). There was a poor correlation between relative rotation and lateral-DEXA (R 2 = 0.13) as well as a poor correlation between relative translation and both AP- and lateral-DEXA (R 2 = 0.35 and R 2 = 0.02). CT is the only modality with a statistically significant correlation to all biomechanical parameters measured (pullout strength, relative angular rotation, and relative translation). AP-DEXA also predicts the biomechanical measures of screw pullout and relative angular rotation and is superior to lateral-DEXA. CT may provide an incremental benefit in assessing fatigue strength, but this should be weighed against the disadvantages of cost and radiation. The results of this study can help to inform clinicians on different bone density analyses and their implications on pedicle screw failure.

Cooperative pointing control of collinear double-integrators without angular velocity

We deal with the cooperative pointing control problem of collinear double-integrators with unknown rotational inertia in this paper. In particular, we consider the case that the rotational angular velocity information is not available for this coordination task. First, we propose a cooperative pointing control protocol without using the rotational angular velocity measurements. By means of the passivity tool, a distributed estimation scheme is devised to access the relative rotational angular velocity information at each agent via the relative rotational angle information of the agent and its left and respectively right neighbors. Subsequently, we redesign the cooperative pointing control protocol as well as the distributed estimation scheme in the presence of saturated relative rotational angle information. It turns out that, here the unknown rotational inertia does not prevent the coordination task because of the bidirectional interactions. Meanwhile, two local estimation schemes are also presented respectively for the above two control protocols. Besides the rigorous convergence analysis, the effectiveness of our obtained theoretical results is illustrated through numerical simulations.

The Spiderweb Protocluster is Being Magnetized by Its Central Radio Jet

We present deep broadband radio polarization observations of the Spiderweb radio galaxy (J1140-2629) in a galaxy protocluster at z = 2.16. These yield the most detailed polarimetric maps yet made of a high-redshift radio galaxy. The intrinsic polarization angles and Faraday rotation measures (RMs) reveal coherent magnetic fields spanning the ∼60 kpc length of the jets, while ∼50% fractional polarizations indicate these fields are well ordered. Source-frame ∣RM∣ values of ∼1000 rad m−2 are typical, and values up to ∼11,100 rad m−2 are observed. The Faraday-rotating gas cannot be well mixed with the synchrotron-emitting gas, or stronger-than-observed depolarization would occur. Nevertheless, an observed spatial coincidence between a localized ∣RM∣ enhancement of ∼1100 rad m−2 , a bright knot of Lyα emission, and a deviation of the radio jet provide direct evidence for vigorous jet-gas interaction. We detect a large-scale RM gradient totaling ∼1000 s rad m−2 across the width of the jet, suggesting a net clockwise (as viewed from the active galactic nuclei) toroidal magnetic field component exists at tens-of-kiloparsec scales, which we speculate may be associated with the operation of a Poynting–Robertson cosmic battery. We conclude the RMs are mainly generated in a sheath of hot gas around the radio jet, rather than the ambient foreground protocluster gas. The estimated magnetic field strength decreases by successive orders of magnitude going from the jet hotspots (∼90 μG) to the jet sheath (∼10 μG) to the ambient intracluster medium (∼1 μG). Synthesizing our results, we propose that the Spiderweb radio galaxy is actively magnetizing its surrounding protocluster environment, with possible implications for theories of the origin and evolution of cosmic magnetic fields.

High Sensitivity and Full-Circle Optical Rotary Sensor for Non-Cooperatively Tracing Wrist Tremor With Nanoradian Resolution

In this article, a novel optical rotary sensor based on laser self-mixing interferometry is developed for the full-circle rotation measurement. The proposed sensor is convenient to use for it does not need any contact with the target or a cooperative mirror. A prototype is fabricated and tested. The measured results demonstrate good performance compared with other optical rotary sensors, in terms of the 0.1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> rad resolution, the 2.33 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> linearity, and 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> rad stability over 1 h. Additionally, the repeatability error is below 14.66 mrad under nine-group full-circle tests, which exhibits the potential to be instrumentalized reliably. Error analysis and limitation discussion have been also carried out. Although the accuracy needs further improvement compared with the best rotary sensor, this method has its unique advantages of high resolution, non-cooperative target sensing, and electromagnetic immunity. Hence, the proposed optical rotary sensor provides a promising alternative in precise rotation measurement, tremor tracing, and nanomotion monitoring.

Real-time bridge monitoring using ultrasonic techniques combined with six-component (6-C) measurements

This study aims to develop a real time structural health monitoring method by ultrasonic tests combined with advanced six component (6C) translation and rotation measurements. Conventionally, the investigation of the velocity and acceleration response in the translation direction is used to obtain the eigenfrequencies of structures. Recently the measurement of rotation has been considered to fully characterize the dynamic behavior of structures. This research undertakes the evaluation of a novel 6C sensor (IMU50-iXblue) with components originally developed for navigation for the purpose of bridge monitoring. However, as for all vibration recordings, there is a certain influence of environmental conditions (mainly temperature) which may affect evaluation and the results of structural assessment. We propose applying the cross-correlation function to the 6C ambient vibration signals to reconstruct wave propagation and using coda wave interferometry (CWI) to obtain internal velocity variation from waveforms. A field experiment on a large-scale prestressed concrete bridge model is presented. To verify that we are able to identify the pre-stress loss even in presence of temperature effects, we perform measurements in two different scales: the ultrasonic and output-only, vibration measurements. The change in the structural properties due to the pre-stress loss should be detected by the pulse velocity change. The results reveal both the performance and advantages of ultrasonic techniques and the capabilities of 6C sensors. To conclude, the application of CWI to wave signals contributes to a comprehensive assessment for bridge monitoring.

Angular Kinematics of Chiropractic Supine Cervical Spine Manipulation: Rotational Measures and Comparisons to Doctor and Recipient Perceptions

ObjectivesThe primary purposes of this study were to measure axial rotation during supine cervical spinal manipulative therapy (cSMT) and to record recipients’ and doctors’ perceptions of rotational magnitudes. MethodsExperienced doctors of chiropractic (DCs) provided supine cSMT and acted as recipients of cSMT. Participants who received SMT wore inertial measurement units attached to the forehead and sternum for motion capture. Afterward, recipients and DCs completed questionnaires asking about their perceptions of motion. Data were analyzed for magnitudes of axial rotation at peak thrust and correlations with patient and doctor perceptions. Secondary analyses included angular velocity, angular acceleration, and other kinematic variables. ResultsWe recorded 23 SMT events with 14 DCs. Rotation at thrust peaks averaged 32.4° (17.4°). Doctors’ and recipients’ perceptions of rotation were higher than measured values 45% and 50% of the time, respectively. Maximum angular velocity and acceleration averaged 221.9°/s (124.9) and 4786.5°/s2 (2456.6), respectively. We found no correlation between perceptions and velocity or acceleration; doctors’ perceptions had an inverse correlation with measurements. ConclusionOn average, we found rotation during supine cSMT to be 32°. Both DCs and SMT recipients overestimated rotation compared with actual measurements. These factors should be considered in discussions of rotation and SMT.

Rotational and Gas Temperature Measurements for He-C Plasma: Application to Heterogeneous Carbon Nanotubes Synthesis

Plasmas containing carbon cover a wide range of application, either using graphite electrodes or carbon containing plasma gas. The study of the C2 molecule is an interesting way to get information on moderate temperature part of the discharge. In the case of heterogeneous carbon nanotubes (CNTs) synthesis by electric arc, reasonable yield can be achieved with substitution of boron and/or nitrogen atoms by optimizing synthesis parameters. This is based on the knowledge of the plasma and gas temperatures in the synthesis chamber. While electrodes material is vaporized through the arc, nanotubes formed in the growth zone a few centimeters away, when temperature decreases down to 1200 °C–1500 °C. Molecular temperature is particularly relevant since it corresponds to the outer part of the arc, in contact with the growth zone. In this article, Abel inversion is used on side-on integrated spectral profiles for C2(0,0) Swan band, in order to get radial rotational temperature profiles. In addition, gas temperature measurements are performed using thermocouples in the arc chamber. Results show that a strong plasma temperature gradient is associated with favorable synthesis conditions for carbon-bore-nitrogen nanotubes. Gas thermal homogeneity is reached in the chamber after about 30 s, mainly through convection processes.

Using machine learning to automatically measure axial vertebral rotation on radiographs in adolescents with idiopathic scoliosis.

Adolescent idiopathic scoliosis is a 3D lateral spinal curvature coupled with axial vertebral rotation (AVR). Measuring AVR during clinic is important because it affects treatment options and predicts the risk of scoliosis progression. However, manual measurements are time consuming and have high inter-rater and intra-rater errors. This study aimed to develop a machine learning algorithm based on convolutional neural networks (CNNs) to automatically calculate AVR on posteroanterior radiographs using three different segmentations including spinal column, individual vertebra, and pedicles. Separate labeling and training processes were performed on each of the developed segmentation algorithms. The final machine learning software was tested on 221 vertebrae from 17 spinal radiographs. An experienced rater with over 25 years of experience measured the 221 vertebral rotations manually. By comparing the manual and the fully automatic measurements, 81% (178/221) of the automatic measurements were within the clinical acceptance error (±5°). The mean absolute difference and the standard deviation between the manual and automatic measurements was 4.3°±5.7°. Based on the Bland-Altman plot, the manual and automatic measurements had a strong correlation and no bias. The error did not relate to the severity of the rotation. This method is fully automatic, and the result is comparable to others.

A simple setup for in situ alkali metal electronic spin polarimetry.

Faraday rotation is considered a gold standard measurement of the electronic spin polarization of an alkali metal vapor produced under optical pumping. However, during the production of large volumes of hyperpolarized xenon gas, transmission monitoring measurements, otherwise known as field cycling measurements, are generally employed to measure the spin polarization of alkali metal atoms in situ as this method is easier to implement than Faraday rotation on standard polarizer setups. Here, we present a simple, low-cost experimental setup to perform Faraday rotation measurements of the electronic spin polarization of alkali metal atoms that can be easily implemented on standard polarizer setups. We then compare Rb polarization measurements obtained with the Faraday rotation method to those obtained with the transmission monitoring method. To our knowledge, a direct comparison of these methods has never been made. Overall, we found good agreement between the two methods, but at low Rb density and high laser power, we found evidence of nonlinear magneto-optical effects that may prevent Faraday rotation from being used under these conditions.

Orbital motion near Sagittarius A*

We report on the polarized light curves of the Galactic Center supermassive black hole Sagittarius A*, obtained at millimeter wavelength with the Atacama Large Millimeter/submillimeter Array (ALMA). The observations took place as a part of the Event Horizon Telescope campaign. We compare the observations taken during the low variability source state on 2017 Apr. 6 and 7 with those taken immediately after the X-ray flare on 2017 Apr. 11. For the latter case, we observe rotation of the electric vector position angle with a timescale of ∼70 min. We interpret this rotation as a signature of the equatorial clockwise orbital motion of a hot spot embedded in a magnetic field dominated by a dynamically important vertical component, observed at a low inclination ∼20°. The hot spot radiates strongly polarized synchrotron emission, briefly dominating the linear polarization measured by ALMA in the unresolved source. Our simple emission model captures the overall features of the polarized light curves remarkably well. Assuming a Keplerian orbit, we find the hot spot orbital radius to be ∼5 Schwarzschild radii. We observe hints of a positive black hole spin, that is, a prograde hot spot motion. Accounting for the rapidly varying rotation measure, we estimate the projected on-sky axis of the angular momentum of the hot spot to be ∼60° east of north, with a 180° ambiguity. These results suggest that the accretion structure in Sgr A* is a magnetically arrested disk rotating clockwise.

Radio Nebulae from Hyperaccreting X-Ray Binaries as Common-envelope Precursors and Persistent Counterparts of Fast Radio Bursts

Roche lobe overflow from a donor star onto a black hole or neutron star binary companion can evolve to a phase of unstable runaway mass transfer, lasting as short as hundreds of orbits (≲102 yr for a giant donor) and eventually culminating in a common-envelope event. The highly super-Eddington accretion rates achieved during this brief phase ( are accompanied by intense mass loss in disk winds, analogous to but even more extreme than ultraluminous X-ray (ULX) sources in the nearby universe. Also in analogy with the observed ULX, this expanding outflow will inflate an energetic “bubble” of plasma into the circumbinary medium. Embedded within this bubble is a nebula of relativistic electrons heated at the termination shock of the faster v ≳ 0.1c wind/jet from the inner accretion flow. We present a time-dependent, one-zone model for the synchrotron radio emission and other observable properties of such ULX “hypernebulae.” If ULX jets are sources of repeating fast radio bursts (FRB), as recently proposed, such hypernebulae could generate persistent radio emission and contribute large and time-variable rotation measure to the bursts, consistent with those seen from FRB 20121102 and FRB 20190520B. ULX hypernebulae can be discovered independently of an FRB association in radio surveys, such as VLASS, as off-nuclear point sources whose fluxes can evolve significantly on timescales as short as years, possibly presaging energetic transients from common-envelope mergers.

Improvement on Faraday rotation measurement affected by the stray lights on the HL-2A tokamak

Formic-acid (HCOOH, λ = 432.5 μm) laser P olarimeter- I nterferomet er ( PIer ) has been developed on the HL-2A tokamak, which provides 4 channels of line-integrated electron densities and 4 channels of Faraday rotation angles, respectively. Affected by the stray lights arising from the reflection of the probe waves in the optical system, the measurement of Faraday rotation angles was drastically contaminated during the HL-2A experiments, showing an obvious oscillation modulation during the electron density ramp-up/down. This paper introduces an effective correction approach used to improve the accuracy of Faraday rotation measurement on the HL-2A tokamak. Based on the method, the deviation term originating from the stray lights can be effectively subtracted from the contaminated Faraday rotation measurement. The preliminary result indicates that the interference amplitude on Faraday rotation angle is reduced by about 80%, and the corrected data is consistent with the experimental measurement by using the optical isolator that consists of a λ/4 wave-plate and polarizer under the similar discharges.

Enhanced room-temperature spin-valley coupling in V-doped MoS2

Achieving room-temperature valley polarization in two-dimensional (2D) atomic layers (2D materials) by substitutional doping opens new avenues of applications. Here, monolayer ${\mathrm{MoS}}_{2}$, when doped with vanadium at low (0.1 atomic %) concentrations, is shown to exhibit high spin-valley coupling, and hence a high degree of valley polarization at room-temperature. The atomic layers of ${\mathrm{MoS}}_{2}$ (MS) and V-doped ${\mathrm{MoS}}_{2}$ (VMS) are grown via the chemical vapor deposition-assisted method. The formation of new energy states near the valence band is confirmed from band gap calculations and also from the density functional theory--based band structure analyses. Time-reversal symmetry broken energy shift in the equivalent valleys is predicted in VMS, and the room-temperature chirality-controlled photoluminescent (PL) excitation measurements indicate such a shift in valley exciton energies (\ensuremath{\sim}35 meV). An enhanced valley polarization in VMS (\ensuremath{\sim}42%) is observed in comparison to that in MS (12%), while in MS, the chirality-controlled excitations did not show the difference in emission energies. Spin Hall effect of light--based optical rotation measurements indicate the asymmetric absorption among the two different chiralities of the incident light, hence supporting the existence of room-temperature valley polarization. This study opens possibilities of room-temperature opto-spintronics using stable 2D materials.