Physical Rotation Research Articles

Three-Dimensional Mapping of the Rotation of Interactive Virtual Objects with Eye-Tracking Data.

We present a method for real-time recording of human interaction with three-dimensional (3D) virtual objects. The approach consists of associating rotation data of the manipulated object with behavioral measures, such as eye tracking, to make better inferences about the underlying cognitive processes. The task consists of displaying two identical models of the same 3D object (a molecule), presented on a computer screen: a rotating, interactive object (iObj) and a static, target object (tObj). Participants must rotate iObj using the mouse until they consider its orientation to be identical to that of tObj. The computer tracks all interaction data in real time. The participant's gaze data are also recorded using an eye tracker. The measurement frequency is 10 Hz on the computer and 60 Hz on the eye tracker. The orientation data of iObj with respect to tObj are recorded in rotation quaternions. The gaze data are synchronized to the orientation of iObj and referenced using this same system. This method enables us to obtain the following visualizations of the human interaction process with iObj and tObj: (1) angular disparity synchronized with other time-dependent data; (2) 3D rotation trajectory inside what we decided to call a "ball of rotations"; (3) 3D fixation heatmap. All steps of the protocol have used free software, such as GNU Octave and Jmol, and all scripts are available as supplementary material. With this approach, we can conduct detailed quantitative studies of the task-solving process involving mental or physical rotations, rather than only the outcome reached. It is possible to measure precisely how important each part of the 3D models is for the participant in solving tasks, and thus relate the models to relevant variables such as the characteristics of the objects, cognitive abilities of the individuals, and the characteristics of human-machine interface.

Measurement of microwave polarization using two polarization orthogonal local microwave electric fields in a Rydberg atom-based mixer

We propose and demonstrate what we believe to be a novel method for measuring the polarization direction of a microwave electric field in a single measurement using a Rydberg atom-based mixer with two orthogonally polarized local microwave electric fields. This approach eliminates the need for physical rotation of the local field, allowing the polarization angle of the signal field to be determined directly by measuring the ratio of the two beat signals. Furthermore, introducing a weak static magnetic field enables the utilization of the Zeeman effect and exploitation of polarization asymmetry. This distinction allows for determining the polarization direction of the microwave field is θ or 180° – θ within the 0 to 180-degree range. The capability to measure microwave polarization in real-time across this range is very valuable for applications in microwave sensing and information transmission.

A Vestibular Training to Reduce Dizziness

Many situations can induce dizziness in healthy participants, be it when riding a carrousel or when making head movements while wearing a head-mounted display. Everybody—maybe with the exception of vestibular loss patients—is prone to dizziness, albeit to widely varying degrees. Some people get dizzy after a single rotation around the body axis, while others can perform multiple pirouettes without the slightest symptoms. We have developed a form of vestibular habituation training with the purpose of reducing proneness to dizziness. The training consists of a short (8 min) exercise routine which is moderate enough that it can easily be integrated into a daily routine. Twenty volunteers performed the training over the course of two weeks. We measured subjective dizziness before and after each daily session. We also performed several vestibular tests before (pre-test) and after (post-test) the two-week training period. They included exposure to a rotating and pitching visual environment while standing upright, as well as a physical rotation that was abruptly stopped. The results show that the dizziness induced during a given daily session decreased over the course of the two weeks. The dizziness induced by the rotating visual stimulus was significantly less after completion of the training period compared with the initial pre-test. Also, postural stability and post-rotatory spinning sensations had improved when comparing the post-test with the pre-test. We conclude that a short regular vestibular training can significantly improve proneness to dizziness.

Electrophysiological signatures of veridical head direction in humans.

Information about heading direction is critical for navigation as it provides the means to orient ourselves in space. However, given that veridical head-direction signals require physical rotation of the head and most human neuroimaging experiments depend upon fixing the head in position, little is known about how the human brain is tuned to such heading signals. Here we adress this by asking 52 healthy participants undergoing simultaneous electroencephalography and motion tracking recordings (split into two experiments) and 10 patients undergoing simultaneous intracranial electroencephalography and motion tracking recordings to complete a series of orientation tasks in which they made physical head rotations to target positions. We then used a series of forward encoding models and linear mixed-effects models to isolate electrophysiological activity that was specifically tuned to heading direction. We identified a robust posterior central signature that predicts changes in veridical head orientation after regressing out confounds including sensory input and muscular activity. Both source localization and intracranial analysis implicated the medial temporal lobe as the origin of this effect. Subsequent analyses disentangled head-direction signatures from signals relating to head rotation and those reflecting location-specific effects. Lastly, when directly comparing head direction and eye-gaze-related tuning, we found that the brain maintains both codes while actively navigating, with stronger tuning to head direction in the medial temporal lobe. Together, these results reveal a taxonomy of population-level head-direction signals within the human brain that is reminiscent of those reported in the single units of rodents.

Optimisation strategy for coplanar array capacitance imaging in rotational scanning mode

ABSTRACT Coplanar array capacitive imaging represents a non-destructive testing technology. To address the challenge of reduced utilisation of the high-sensitivity region caused by the ‘soft field’ effect characterised by severe nonlinear and inhomogeneous distribution of coplanar array capacitance sensitivity, resulting in difficulties in solving the problem of medium distribution, the proposed approach involves coplanar array capacitance sensor rotational scanning technology. This paper establishes both a physical rotation model and a sensitive field rotation model for a coplanar array capacitance sensor, demonstrating the inability to resolve the low-sensitivity region for medium distribution and illustrating how rotary scanning detection can enhance the utilisation rate of the high-sensitivity region. In conjunction with improved regional energy contrast, the images acquired under various rotation angles are fused, and experimental verification is conducted. The experimental results underscore that rotational scanning detection techniques can increase the utilisation rate of the high-sensitivity region within the coplanar array capacitance sensor by 74.69%. This enhancement effectively captures essential information within the reconstructed image and successfully addresses the challenge of solving difficulties in dielectric distribution. The research outcomes provide valuable insights for advancing non-destructive testing technologies employing coplanar array capacitance sensors.

Controlling the charge-transfer dynamics of two-level systems around avoided crossings.

Two-level quantum systems are fundamental physical models that continue to attract growing interest due to their crucial role as a building block of quantum technologies. The exact analytical solution of the dynamics of these systems is central to control theory and its applications, such as that to quantum computing. In this study, we reconsider the two-state charge transfer problem by extending and using a methodology developed to study (pseudo)spin systems in quantum electrodynamics contexts. This approach allows us to build a time evolution operator for the charge transfer system and to show new opportunities for the coherent control of the system dynamics, with a particular emphasis on the critical dynamic region around the transition state coordinate, where the avoided crossing of the energy levels occurs. We identify and propose possible experimental implementations of a class of rotations of the charge donor (or acceptor) that endow the electronic coupling matrix element with a time-dependent phase that can be employed to realize controllable coherent dynamics of the system across the avoided level crossing. The analogy of these rotations to reference frame rotations in generalized semiclassical Rabi models is discussed. We also show that the physical rotations in the charge-transfer systems can be performed so as to implement quantum gates relevant to quantum computing. From an exquisitely physical-mathematical viewpoint, our approach brings to light situations in which the time-dependent state of the system can be obtained without resorting to the special functions appearing in the Landau-Zener approach.

A type system for formal verification of cyber-physical systems C/C++ software

The subject: This study focuses on improving the quality of Cyber-Physical System (CPS) software by eliminating incorrect usage of units of measurement and orientation in C/C++ programs. Incorrect usage often leads to critical errors that conventional systems cannot effectively prevent. Manual examination of code using dimensional and orientation analysis can detect these errors in physical equations, but these methods become impractical when dealing with complex physical computations. Objectives: As suggested by Siano, the proposed approach uses physical quantities and prefixes defined by the International System of Units and orientation operations on physical objects. The elaborated system incorporates dimensional and orientation analysis and metaprogramming techniques. The methods used are dimensional & orientational analysis and metaprogramming. The following results were obtained: ensuring consistency of the units, incorporating orientation operations into the programming model for accurately handling physical object rotations and alignments, and using Siano’s work to precisely manipulate object orientation, thereby reducing the likelihood of orientation-related errors. Checking physical dimensions and orientations during the compilation stage identifies potential software defects before code execution, thereby reducing debugging time and lowering the cost of addressing issues later in development. The elaborated system represents a crucial step towards safer and more dependable Cyber-Physical System applications. This approach allows us to identify approximately 90% of incorrect usage of program variables; additionally, it detects over 50% of erroneous operations during compilation and execution of large-scale programs in real-world conditions. Conclusions. Scientific novelty: it proposed and developed a specialized C++-type library for formal compile-time software verification of Cyber-Physical Systems software. The proposed C++-type library leverages dimensional and orientational analysis to enhance software quality, reliability, and real-time formal verification. Although the proposed method for formal verification is not tailor-made for cyber-physical objects and systems, given its primary focus on software-level concerns, it does exhibit adaptability for verifying general-purpose software that incorporates various physical parameters. This versatility extends to diverse domains such as educational, gaming, and simulation software.

An Evaluation of View Rotation Techniques for Seated Navigation in Virtual Reality.

Head tracking is commonly used in VR applications to allow users to naturally view 3D content using physical head movement, but many applications also support turning with hand-held controllers. Controller and joystick controls are convenient for practical settings where full 360-degree physical rotation is not possible, such as when the user is sitting at a desk. Though controller-based rotation provides the benefit of convenience, previous research has demonstrated that virtual or joystick-controlled view rotation to have drawbacks of sickness and disorientation compared to physical turning. To combat such issues, researchers have considered various techniques such as speed adjustments or reduced field of view, but data is limited on how different variations for joystick rotation influences sickness and orientation perception. Our studies include different variations of techniques such as joystick rotation, resetting, and field-of-view reduction. We investigate trade-offs among different techniques in terms of sickness and the ability to maintain spatial orientation. In two controlled experiments, participants traveled through a sequence of rooms and were tested on spatial orientation, and we also collected subjective measures of sickness and preference. Our findings indicate a preference by users towards directly-manipulated joystick-based rotations compared to user-initiated resetting and minimal effects of technique on spatial awareness.

Anatomical predictors of mental rotation with bodily and non-bodily stimuli: A lesion-symptom study

Mental rotation (MR) is widely regarded as a quintessential example of an embodied cognitive process. This viewpoint stems from the functional parallels between MR and the physical rotation of tangible objects, as well as participants' inclination to employ motor-based strategies when tackling MR tasks involving bodily stimuli. These commonalities imply that MR may depend on brain regions crucial for the planning and execution of motor programs. However, there is disagreement regarding the anatomy of MR between findings from functional imaging and lesion studies involving brain-injured patients. The former indicate the involvement of the right-hemispheric parietal cortex, while the latter underscore the significance of posterior areas in the left hemisphere. In this study, we aimed to discern the neural underpinnings of MR using lesion-symptom mapping (LSM) for both bodily (hands) and non-bodily (letters) stimuli. Behavioral results from the two MR tasks revealed impaired MR of bodily stimuli in patients with left hemisphere damage. LSM results pinpointed the left primary motor and somatosensory cortices, along with the superior parietal lobule, as the anatomical substrates of MR for both bodily and non-bodily stimuli. Furthermore, damage to the left angular gyrus, supramarginal gyrus, supplementary motor area, and retrosplenial cortex was associated with MR of non-bodily stimuli. These findings support the causal involvement of the left hemisphere in MR and underscore the existence of a common anatomical substrate in brain regions pertinent to motor planning and execution.

Removal of the rate table: MEMS gyrocompass with virtual maytagging

High-performance micro-electro-mechanical system (MEMS) gyrocompasses for north-finding systems have been very popular for decades. In this paper, a MEMS north-finding system (NFS) based on virtual maytagging (VM) is presented for the first time. In stark contrast to previous schemes of MEMS-based NFSs (e.g., carouseling, maytagging) and the abandoning rate table, we developed a honeycomb disk resonator gyroscope (HDRG) and two commercial accelerometers for azimuth detection. Instead of the physical rotation of the integrated turntable in traditional NFSs, the vibratory working modes of the HDRG are rotated periodically with electronic control to reduce the uncertainty in the azimuth. After systematically analyzing the principle of NFSs with VM, we designed tests to verify the practicability at the sensor level. A bias instability of 0.0078°/h can be obtained during one day with VM in an HDRG. We also implemented comparative north-finding experiments to further check our strategy at the system level. The accuracy in the azimuth can reach 0.204° for 5 min at 28.2° latitude with VM and 0.172° with maytagging. The results show that without any mechanical turning parts, VM technology makes it possible to develop high-precision handheld MEMS NFSs.

Does a concurrent motor process influence representational momentum?

Whether the direction of a hand motion that is congruent or incongruent with a concurrent target motion can influence representational momentum for that target was examined. Participants viewed a leftward or rightward moving target while moving their hand rightward, leftward, or not moving their hand. Prior studies of mental rotation found that congruency or incongruency of the direction of mental rotation and the direction of a concurrent physical rotation of a stimulus influenced mental rotation. As mental rotation and representational momentum each involve extrapolation of target motion, it could be predicted that congruency of the direction of hand motion and the direction of target motion might influence representational momentum of the target. Robust representational momentum occurred in all conditions, but there was no effect of congruency of hand motion and target motion, nor of the presence or absence of hand motion, on representational momentum. The results are consistent with a hypothesis that the generation of representational momentum involves sensory processes rather than motor processes.

The time course of planar and non-planar rotations in a letter rotation task

Mental rotation (MR) of character letters requires participants to mentally rotate the letter in their minds’ eyes through a process akin to the physical rotation of the stimulus. It has been suggested that different cognitive processes are engaged during such MR of both canonical and mirror-reversed letters. In addition to the planar rotation of the canonical letters, an additional “flip-over” process (non-planar rotation) has been assumed during the MR of mirror-reversed letters. However, the temporal relationship between planar and non-planar rotation has not been systematically investigated. In this study, the occurrence of both planar and non-planar rotations were examined through the analysis of the event-related brain potentials (ERPs) elicited by canonical or mirror-reversed letters presented at different rotation angles between 300 and 1000 ms post-stimulus onset over consecutive 50ms time-windows. For smaller rotation angles (30° and 60°), non-planar rotation preceded planar rotation. For letters rotated by 90°, planar and non-planar rotation occurred at the same time. For larger angles (120° and 150°), the letter was first rotated within the plane (planar rotation) and afterwards it was also rotated out-of-the-plane (non-planar rotation) until it was fully canonicalized. Thus, the temporal relationship between planar and non-planar rotation differed for each rotation angle, with the non-planar rotation occurring at increasingly later intervals for different points in time for progressively larger rotation angles. These findings have relevant methodological implications for studies investigating the psychophysiological correlates of the mental rotation of mirror letters.

SU(2) symmetry of coherent photons and application to Poincaré rotator

Lie algebra is a hidden mathematical structure behind various quantum systems realised in nature. Here, we consider SU(2) wavefunctions for polarisation states of coherent photons emitted from a laser source, and discuss the relationship to spin expectation values with SO(3) symmetry based on isomorphism theorems. In particular, we found rotated half-wave-plates correspond to mirror reflections in the Poincaré sphere, which do not form a subgroup in the projected O(2) plane due to anti-hermitian property. This could be overcome experimentally by preparing another half-wave-plate to realise a pristine rotator in SU(2), which allows arbitrary rotation angles determined by the physical rotation. By combining another 2 quarter-wave-plates, we could also construct a genuine phase-shifter, thus, realising passive control over the full Poincaré sphere.

Noise estimation for head-mounted 3D binocular eye tracking using Pupil Core eye-tracking goggles.

Head-mounted, video-based eye tracking is becoming increasingly common and has promise in a range of applications. Here, we provide a practical and systematic assessment of the sources of measurement uncertainty for one such device - the Pupil Core - in three eye-tracking domains: (1) the 2D scene camera image; (2) the physical rotation of the eye relative to the scene camera 3D space; and (3) the external projection of the estimated gaze point location onto the target plane or in relation to world coordinates. We also assess eye camera motion during active tasks relative to the eye and the scene camera, an important consideration as the rigid arrangement of eye and scene camera is essential for proper alignment of the detected gaze. We find that eye camera motion, improper gaze point depth estimation, and erroneous eye models can all lead to added noise that must be considered in the experimental design. Further, while calibration accuracy and precision estimates can help assess data quality in the scene camera image, they may not be reflective of errors and variability in gaze point estimation. These findings support the importance of eye model constancy for comparisons across experimental conditions and suggest additional assessments of data reliability may be warranted for experiments that require the gaze point or measure eye movements relative to the external world.

Relaxation spectral analysis in multi-contrast vascular magnetic particle imaging.

Magnetic nanoparticles (MNPs) are used as tracers without ionizing radiation in vascular imaging, molecular imaging, and neuroimaging. The relaxation mechanisms of magnetization in response to excitation magnetic fields are important features of MNPs. The basic relaxation mechanisms include internal rotation (Néel relaxation) and external physical rotation (Brownian relaxation). Accurate measurement of these relaxation times may provide high sensitivity for predicting MNP types and viscosity-based hydrodynamic states. It is challenging to separately measure the Néel and Brownian relaxation components using sinusoidal excitation in conventional MPI. We developed a multi-exponential relaxation spectral analysis method to separately measure the Néel and Brownian relaxation times in the magnetization recovery process in pulsed vascular MPI. Synomag-D samples with different viscosities were excited using pulsed excitation in a trapezoidal-waveform relaxometer. The samples were excited at different field amplitudes ranging from 0.5 to 10 mT at intervals of 0.5 mT. The inverse Laplace transform-based spectral analysis of the relaxation-induced decay signal in the field-flat phase was performed by using PDCO, a primal-dual interior method for convex objectives. Néel and Brownian relaxation peaks were elucidated and measured on samples with various glycerol and gelatin concentrations. The sensitivity of viscosity prediction of the decoupled relaxation times was evaluated. A digital vascular phantom was designed to mimic a plaque with viscous MNPs and a catheter with immobilized MNPs. Spectral imaging of the digital vascular phantom was simulated by combining a field-free point with homogeneous pulsed excitation. The relationship between the Brownian relaxation time from different tissues and the number of periods for signal averages was evaluated for a scan time estimation in the simulation. The relaxation spectra of synomag-D samples with different viscosity levels exhibited two relaxation time peaks. The Brownian relaxation time had a positive linear relationship with the viscosity in the range 0.9 to 3.2 mPa · s. When the viscosity was >3.2 mPa · s, the Brownian relaxation time saturated and did not change with increasing viscosity. The Néel relaxation time decreased slightly with an increase in the viscosity. The Néel relaxation time exhibited a similar saturation effect when the viscosity level was >3.2 mPa · s for all field amplitudes. The sensitivity of the Brownian relaxation time increased with the field amplitude and was maximized at approximately 4.5 mT. The plaque and catheter regions were differentiated from the vessel region in the simulated Brownian relaxation time map. The simulation results show that the Néel relaxation time was 8.33±0.09 μs in the plaque region, 8.30±0.08 μs in the catheter region, and 8.46±0.11 μs in the vessel region. The Brownian relaxation time was 36.60±2.31 μs in the plaque region, 30.17±1.24 μs in the catheter region, and 31.21±1.53 μs in the vessel region. If we used 20 excitation periods for image acquisition in the simulation, the total scan time of the digital phantom was approximately 100 s. Quantitative assessment of the Néel and Brownian relaxation times through inverse Laplace transform-based spectral analysis in pulsed excitation, highlighting their potential for use in multi-contrast vascular MPI.

Limiting FCNC induced by a CP symmetry of order 4

CP4 3HDM is a three-Higgs-doublet model based on the CP symmetry of order 4 (CP4). Imposing CP4 leads to remarkable connections between the scalar and Yukawa sectors and unavoidably generates tree-level flavor-changing neutral couplings (FCNC). It remains unclear whether FCNC can be sufficiently suppressed in the CP4 3HDM. In this paper, we systematically explore this issue. We first develop an efficient scanning procedure which takes the quark masses and mixing as input and expresses the FCNC matrices in terms of physical quark observables and quark rotation parameters. This procedure allows us to explore the FCNC effects for all the Yukawa sectors possible within the CP4 3HDM. We find that, out of the eight possible CP4 Yukawa sectors, only two scenarios are compatible with the K, B, Bs and, in particular, D-meson oscillation constraints. The results of this work serve as clear guidelines for future phenomenological scans of the model.

Extending arterial stiffness assessment along the circumference using beam-steered ARFI and wave-tracking: A proof-of-principle study in phantoms and ex vivo

BackgroundTo fully quantify arterial wall and plaque stiffness, acoustic radiation force impulse (ARFI)-induced wave-tracking along the entire vessel circumference is desired. However, attenuation and guided wave behavior in thin vessel walls limits wave-tracking to short trajectories. This study investigated the potential of beam-steered ARFI and wave-tracking to extend group velocity estimation over a larger proportion of the circumference compared to conventional 0° ARFI-induced wave-tracking. MethodsSeven vessel-mimicking polyvinyl alcohol cryogel phantoms with various dimensions and compositions and an ex vivo human carotid artery were imaged in a dedicated setup. For every 20⁰ phantom rotation, transverse group wave velocity measurements were performed with an Aixplorer Ultimate system and SL18–5 transducer using 0⁰/20⁰/−20⁰-angled ultrasound pushes. Transmural angular wave velocities were derived along 60⁰-trajectories. A 360⁰-angular velocity map was composed from the top-wall 60⁰-trajectories 0°-data, averaged over all physical phantom rotations (reference). For each phantom rotation, 360⁰-angular velocity maps were composed using 0°-data (0⁰-approach) or data from all angles (beam-steered approach). Percentages of rotations with visible waves and relative angular velocity errors compared to the reference map as function of the circumferential angle were determined for both approaches. ResultsReference 360°-angular velocity maps could be derived for all samples, representing their stiffness. Beam-steering decreased the proportion of the circumference where waves were untraceable by 20% in phantoms and 10% ex vivo, mainly at 0° push locations. Relative errors were similar for both approaches (phantoms: 10–15%, ex vivo: 15–35%). ConclusionBeam-steering enables wave-tracking along a higher proportion of the wall circumference than 0⁰ ARFI-induced wave-tracking.

Contactless superconducting field exciter with active current control using hybrid magnet for high-temperature superconducting rotating machine

Rotary-type high-temperature superconducting (HTS) flux pumps using permanent magnets (PMs) are effective contactless superconducting excitation devices used for generating excitation in the field winding of HTS rotating machines. Although contactless superconducting excitation devices overcome the disadvantages of conventional contact-type excitation systems, those based on PMs are not the ideal solution because current supply to the field winding is allowed only when the HTS rotating machine is rotating in the same direction: a rapid discharge occurs when the rotation direction is reversed. They do not meet the practical operational requirements of rotating machines, viz., initial start, load fluctuation, and direction change, and alternatives to actively control excitation of field winding are essential. In this study, novel functions to improve the application feasibility in various HTS rotating machine operation modes have been proposed. Based on a numerical analysis, a prototype contactless superconducting active excitation device (CSAED) comprising PMs, alternating current (AC) and direct current (DC) electromagnets was developed using the hybrid magnet concept. The operational characteristics of active control functions in the CSAED were experimentally analysed for stationary, forward, reverse, and compensation operations of the HTS rotating machine and the qualitative effectiveness for active control of the charged current was verified. The first novel function CSAED using AC electromagnet was successfully demonstrated in initial current excitation by generating the alternating magnetic field without physical rotation for a small-scale HTS magnet. However, upgrading of the AC electromagnet is required to apply for large-scale load magnet due to small value in saturation current of the CSAED. The second novel function of CSAED using DC electromagnet worked well in current-adjustment and current-conservation modes by controlling the magnetic field density using the hybrid magnet. By controlling the current of DC electromagnets without any change in the rotation speed, the saturation current was adjusted within the ranges from 61.4 A to 1.7 A, which are 86.6 and 2.4 % of critical current for load HTS magnet, respectively. In the reverse rotation, the current discharging time of CSAED using activation of DC electromagnet increased by 2474 % compared to without energizing the DC electromagnet.

Mental object rotation based on two-dimensional visual representations

The discovery of mental rotation was one of the most significant landmarks in experimental psychology, leading to the ongoing assumption that to visually compare objects from different three-dimensional viewpoints, we use explicit internal simulations of object rotations, to 'mentally adjust' one object until it matches the other1. These rotations are thought to be performed on three-dimensional representations of the object, by literal analogy to physical rotations. In particular, it is thought that an imagined object is continuously adjusted at a constant three-dimensional angular rotation rate from its initial orientation to the final orientation through all intervening viewpoints2. While qualitative theories have tried to account for this phenomenon3, to date there has been no explicit, image-computable model of the underlying processes. As a result, there is no quantitative account of why some object viewpoints appear more similar to one another than others when the three-dimensional angular difference between them is the same4,5. We reasoned that the specific pattern of non-uniformities in the perception of viewpoints can reveal the visual computations underlying mental rotation. We therefore compared human viewpoint perception with a model based on the kind of two-dimensional 'optical flow' computations that are thought to underlie motion perception in biological vision6, finding that the model reproduces the specific errors that participants make. This suggests that mental rotation involves simulating the two-dimensional retinal image change that would occur when rotating objects. When we compare objects, we do not do so in a distal three-dimensional representation as previously assumed, but by measuring how much the proximal stimulus would change if we watched the object rotate, capturing perspectival appearance changes7.

Micro-extruded LaSrCuFeO-based polystyrene magnetic composites: Morphological and magnetic characterization

Novel magnetic composites consisting of a polystyrene matrix containing La 0.80 Sr 0.20 Fe 0.90 Cu 0.10 O 3-w (LSFC10) and La 0.80 Sr 0.20 Fe 0.80 Cu 0.20 O 3 -w (LSFC20) particles, each with two weight concentrations, 0.5% and 1.0%, are prepared by extrusion technique. The LSFC10 and LSFC20 filler phases are synthetized by citrate auto-combustion technique. From the XRD data, only a single crystalline phase, namely an orthorhombic perovskite structure, is observed. Additionally, the TEM images and EDX analysis show single phase compounds, confirming the absence of other phases. SEM images of the composites show the presence of perovskite nanoparticles, aggregated in structures with dimensions in the order of ten microns or lower, probably due to their magnetic interactions. Differently to bare particles, showing a single-phase hysteresis loop, the room temperature field-dependent magnetization loops of polymer composites exhibit a wasp-waisted-like magnetic hysteresis loops, which may origin from different mechanisms that likely emerge when the particles are dispersed in the matrix, such as the particle surface spin canting and the interparticle interactions, along with a physical rotation of the particles that are not firmly blocked in the polymer matrix. • magnetic polymer-based composites were prepared using micro-extrusion. • single phase, nanosized La 0.8 Sr 0.2 Fe 1 -x Cu x O 3 was dispersed in a polystyrene matrix. • magnetic loops of La 0.8 Sr 0.2 Fe 1 -x Cu x O 3 show a strong irreversible behaviour. • the composites exhibit a peculiar wasp-waisted-like magnetic hysteresis loops.