On-axis Rotation Research Articles

Graviception Uncertainty, Spatial Anxiety, and Derealization in Patients with Persistent Postural-Perceptual Dizziness

Objectives: Persistent Postural-Perceptual Dizziness (PPPD) is a frequent diagnosis in patients with chronic dizziness, ineffective postural control, visual dependence, and emotional symptoms. Methods: 53 patients with PPPD (25–84 years old) and 53 adults (29–84 years old) with no vestibular disease agreed to participate in this study. Assessments included: vestibular function tests (sinusoidal yaw rotation and vestibular-evoked myogenic potentials); accuracy and precision of Subjective Visual Vertical (SVV) estimation while static and during on-axis yaw rotation; static posturography with open/closed eyes and 30° neck extension, while standing on hard/soft surface; questionnaires on symptoms of unsteadiness, spatial anxiety, dizziness-related handicap, anxiety/depression, depersonalization/derealization, and perceived stress. After preliminary bivariate analyses, analysis of covariance was performed on the measurements of postural sway, spatial anxiety, and dizziness-related handicap (p < 0.05). Results: Higher intraindividual variability (reduced precision) on SVV estimations was evident in patients with PPPD compared to adults with no vestibular disease, which was related to the length of postural sway, to velocity displacement in the sagittal plane, as well as to spatial anxiety and common mental symptoms (including depersonalization/derealization symptoms). Covariance analysis showed contribution of these factors to the dizziness-related handicap reported by the patients. Conclusions: Unprecise graviception could be a contributing factor to the postural instability and mental symptoms reported by patients with PPPD, which in turn contribute to their dizziness-related handicap.

Theoretical study of long-lived mode in tokamaks

Long-lived mode (LLM) in rotating plasmas is studied by using a alternative dispersion relation. This work offers a theoretical interpretation of LLM observed in experiments [Heidbrink, Phys. Rev. Lett. 57, 835 (1986)10.1103/PhysRevLett.57.835; Chapman, Nucl. Fusion 50, 045007 (2010)10.1088/0029-5515/50/4/045007]. It is found that in rotating plasmas, LLM can transform from the fishbone mode. The real frequency of LLM, independent of the characteristic frequency of energetic ions (EIs), is proportional to the on-axis rotation frequency of bulk plasma. The key conditions to cause transition between the fishbone mode and LLM are weak magnetic shear (for both monotonic and nonmonotonic safety factor profile) and plasma rotation. The fishbone mode can evolve into LLM only when rotating speed is bigger than a critical value in low shear plasmas. The critical beta of EIs to induce LLM is very low. LLM is nonresonantly excited by EIs, and the driving sources mainly come from plasma inertia.

Recurrent neural network reveals transparent objects through scattering media.

Scattering generally worsens the condition of inverse problems, with the severity depending on the statistics of the refractive index gradient and contrast. Removing scattering artifacts from images has attracted much work in the literature, including recently the use of static neural networks. S. Li et al. [Optica5(7), 803 (2018)10.1364/OPTICA.5.000803] trained a convolutional neural network to reveal amplitude objects hidden by a specific diffuser; whereas Y. Li et al. [Optica5(10), 1181 (2018)10.1364/OPTICA.5.001181] were able to deal with arbitrary diffusers, as long as certain statistical criteria were met. Here, we propose a novel dynamical machine learning approach for the case of imaging phase objects through arbitrary diffusers. The motivation is to strengthen the correlation among the patterns during the training and to reveal phase objects through scattering media. We utilize the on-axis rotation of a diffuser to impart dynamics and utilize multiple speckle measurements from different angles to form a sequence of images for training. Recurrent neural networks (RNN) embedded with the dynamics filter out useful information and discard the redundancies, thus quantitative phase information in presence of strong scattering. In other words, the RNN effectively averages out the effect of the dynamic random scattering media and learns more about the static pattern. The dynamical approach reveals transparent images behind the scattering media out of speckle correlation among adjacent measurements in a sequence. This method is also applicable to other imaging applications that involve any other spatiotemporal dynamics.

Depixelation and enhancement of fiber bundle images by bundle rotation.

Fiber bundles have become widely adopted for use in endoscopy, live-organism imaging, and other imaging applications. An inherent consequence of imaging with these bundles is the introduction of a honeycomb-like artifact that arises from the inter-fiber spacing, which obscures features of objects in the image. This artifact subsequently limits applicability and can make interpretation of the image-based data difficult. This work presents a method to reduce this artifact by on-axis rotation of the fiber bundle. Fiber bundle images were first low-pass and median filtered to improve image quality. Consecutive filtered images with rotated samples were then co-registered and averaged to generate a final, reconstructed image. The results demonstrate removal of the artifacts, in addition to increased signal contrast and signal-to-noise ratio. This approach combines digital filtering and spatial resampling to reconstruct higher-quality images, enhancing the utility of images acquired using fiber bundles.

The crucial role of density functional nonlocality and on-axis CH3NH3 rotation induced I2 formation in hybrid organic-inorganic CH3NH3PbI3 cubic perovskite

Effects of electronic nonlocality in density functional theory study of structural and energetic properties of a pseudocubic CH3NH3PbI3 are investigated by considering coherent rotation around C–N axis of a CH3NH3 cation. A number of truly non-local and semi-local exchange correlation density functionals are examined by comparing calculated structural parameters with experimental results. The vdW-DF-cx which takes into account the non-local van der Waals correlation and consistent exchange shows the best overall performance for density functional theory study of this system. Remarkable distinctions between results from vdW-DF-cx and those from PBEsol exchange correlation functionals are observed and indicate the need of including the non-local interaction in the study of this system, especially its dynamical properties. The obtained rotational barriers are 18.56 meV/formula and 27.71 meV/formula which correspond to rotational frequencies of 3.71 THz and 2.60 THz for vdW-DF-cx and PBEsol calculations, respectively. Interestingly, the maximally localised Wannier function analysis shows the hydrogen bonding assisted covalent character of two iodide anions at a moderate rotational angle which can lead to I2 formation and then material degradation.

Broadband and compact rectangular waveguide twist by using rigid waveguide

A broadband and compact rectangular waveguide twist are presented and verified. Adopting an axially rotating 45° ridge waveguide, the rectangular waveguide twist provides a very compact interconnection of two rectangular waveguides with different on-axis angle rotation. Compared to conventional waveguide twist, the superiority of the proposed waveguide twist is the easiness for manufacturing and the overall dimension is compact, the thickness is only 0.25 times the waveguide wavelength of the TE10 mode. For verification purpose, a Ka-band 90° waveguide twist has been designed, fabricated, and tested. Measurement results show that the return loss is <−20 dB and the insertion loss is in excess of −0.2 dB. The measurements are in good agreement with simulations and demonstrate the excellent performance of the waveguide twist at the Ka-band.

Energy Landscape of Molecular Motion in Cubic Methylammonium Lead Iodide from First-Principles

Molecular A-cation dynamics are known to play a role in the electronic properties and structure of hybrid organic–inorganic ABX3 perovskites such as CH3NH3PbI3. We calculate the full energy landscape for rigid-body rotations and translations of the methylammonium cation in the cubic phase of CH3NH3PbI3. Energy barriers are calculated for combinations of molecular reorientation, on-axis rotation, and molecular translation within the unit cell. Allowing molecular translations significantly stabilizes orientations along [100] which we attribute to strong N–H···I interactions between CH3NH3+ and the inorganic Pb–I host lattice.

Unilateral otolith centrifugation by head tilt

To test for otolith asymmetries, several studies described horizontal translation of the body and head en bloc during fast vertical axis rotation. This stimulus causes one otolithic organ to rotate on-axis, and the other to experience centripetal acceleration. To test a new, more simple method of unilateral stimulation with head tilt and the body remaining on axis. During stationary and during 360 deg/s rotation, 12 healthy blindfolded subjects had their heads tilted 30 degrees sideways, positioning one otolithic organ on the axis of rotation after the other. The haptic subjective vertical (SV) was recorded several times by means of a manually adjustable rod. It was found that during stationary the SV tilted about 4 degrees on average in the direction of the head. During rotation, the SV tilted about 9 degrees on average. We therefore estimate the effect of eccentric otolith rotation to be 5 degrees on average. Tilt of the subjective vertical induced by head tilt during on-axis body rotation can provide a relatively uncomplicated alternative to test unilateral otolithic function as compared to body and head translation during rotation. Moreover, unlike eccentric rotation of the entire body, somatosensory cues are minimized by keeping the body fixed on axis and by subtracting the effect of head tilt per se.

Continuous theta-burst stimulation of the right superior temporal gyrus impairs self-motion perception

Sensory input from the semicircular canals (SCC) and otolith organs is centrally combined with signals from other sensory modalities to continuously update the internal estimate of self-motion. Constant velocity vertical on-axis rotation leads to decay of the nystagmus response from the horizontal SCC and of perceived angular velocity (PAV), and when the rotation stops, a similar oppositely directed post-rotatory response occurs. Case reports and electrical stimulation studies suggest an involvement of the temporo-peri-Sylvian vestibular cortex in generating the PAV. Here, we transiently inhibited the right superior temporal gyrus (STG) by use of continuous theta-burst stimulation (cTBS) and predicted an accelerated decay of PAV compared to controls (n=5 control session first, n=1 cTBS session first). Constant velocity (100°/s) vertical on-axis rotations were applied over 75s before (1 block) and after (3 blocks) cTBS over the right STG in six subjects. Breaks between the rotations (75s) were initiated by abrupt stops. By use of a rotating potentiometer, subjects indicated the PAV during and after the chair rotations. Simultaneously eye positions were recorded using a scleral search coil. One subject was excluded for per-rotary analysis. Early after cTBS, the post-rotary PAV decay time constant (DTC) was significantly (9.4±5.7 vs. 13.6±5.9s; p=0.049) reduced (no directionality to this effect observed). Overall, post-rotary PAV showed a trend toward shortened DTC compared to the control trials (p=0.086) in the first 25min after cTBS, while per-rotary PAV was not significantly changed. Per-rotary and post-rotary aVOR DTC were not significantly changed after cTBS (p>0.05). These findings support the hypothesis that the right STG is involved in mediating self-motion perception and can be modulated by cTBS.

Numerical simulation for heat transfer and velocity field characteristics of two-phase flow systems in axially rotating horizontal cans

Volume of fluid (VOF) element method coupled with a finite volume (FV) discretization technique was used to simulate two-dimensional, transient, two-phase flow patterns (air–water and air–food material) in an axially rotating horizontal can for rotational speeds of 10–160rpm. Rotational Reynolds number ranged from 1700 to 27200 and 0.88 to 14.1 for water and food phases, respectively. FV solution was performed on a moving mesh system representing the can motion in on-axis axial rotation with respect to an inertial-fixed frame. Since the two-phase flow pattern prediction was an important aspect of modeling fluid mixing and improved heat transfer in canning process, reliable time- and spatially-dependent flow pattern maps were given to identify the rotational effects on two-phase flow characteristics and to determine flow patterns prevailing at different rotational speeds. Single-phase and food-phase flow computations with the corresponding flow patterns were also provided for a direct comparison with air–water results to further determine the physical limitations of the rotational effects. Numerical results demonstrated that two-phase flow patterns were significantly influenced by increasing rotational speeds leading to distinguishable flow patterns in terms of air–liquid (water/food material) interface characteristics and associated headspace air bubble movement through the liquid phase.

Normative Data for the Subjective Visual Vertical Test during Centrifugation

The otoliths act as gravito-inertial force sensors and contribute to the perception of spatial orientation. The perception of gravitational vertical can be assessed by asking a subject to adjust a light bar to the vertical. Prior to clinical use of the SVV (subjective visual vertical) test, normative data and test-retest reliability must be established. To obtain normative data and d etermine the test-retest reliability for the SVV test performed in static and dynamic test conditions. A descriptive design was used to obtain normative data. Twenty-four young adults with no history of neurological disease, middle-ear pathology, open or closed head injury, cervical injury, or audiovestibular disorder participated in the study. The SVV angle was measured in the static position and in three dynamic conditions: (1) on-axis clockwise (CW) rotation, (2) off-axis CW rotation of right ear, and (3) off-axis CW rotation of left ear. In young healthy individuals, the SVV was <2° for static and on-axis rotation, and shifted up to 11° during unilateral centrifugation. Test-retest reliability of the SVV was good for all test conditions. The normative data obtained in this study may be useful in identifying patients with chronic utricular dysfunction. We recommend the use of difference angles (on-axis SVV - off-axis SVV) to remove baseline bias and decrease the variability of the SVV angles for the off-axis conditions.

Effect of radius versus rotation speed in artificial gravity

Artificial gravity by centrifugation can lead to perceptual disturbances in the form of motion sickness and/or misperception of motion during head movements, but the degree of perceptual disturbance during centrifugation in 0-g has not been thoroughly investigated. It is known that during whole-body on-axis yaw rotation in 0-g, head movements in pitch and roll cause very little disturbance, despite significant disturbance in 1-g. Therefore, 1-g experimental results do not apply directly to 0-g without further analysis. A modeling approach was used here to predict disorienting effects in 0-g and 1-g environments, with different rotation speeds, centrifuge radii, and directions of head movement. The results were based upon investigation of the stimulus itself, in the form of angular and linear accelerations, and their consequences due to linear-angular interactions in three dimensions. The results explain known differences in 0-g and 1-g, for head turns toward and away from the direction of motion, and for head movements on- and off-axis. Additional predictions include an increase in perceptual disturbance with the magnitude of the gravito-inertial acceleration (GIA), therefore an increase off-axis, but a decrease in 0-g. Also predicted is that head-movement direction makes a difference, with rotation outward relative to the centrifuge axis causing the least disturbance.

Testing utricular function by means of on-axis rotation

Conclusions. Subjective visual vertical (SVV) estimation during on-axis rotation provides an efficient screening test of utricle function. The survey demonstrates that isolated disorders of peripheral utricular function can occur while SCC function appears normal. Objective. The present study aimed to investigate estimation of SVV during constant velocity yaw rotation (with the head held on-axis – to enhance any asymmetry between right and left utricular responses), as a useful screening test. Materials and methods. In all, 230 patients were recruited from the dizziness clinic. For each patient, the SVV was estimated (a) while held stationary, and (b) during constant angular velocity (240°/s), with the head centred on-axis. Bithermal caloric testing was also performed in 201 of the patients. Results. Of those patients with normal SVV results during stationary testing, 18.3% were pathological during rotation testing. In those cases with pathological SVV during stationary testing, a significantly greater deviation from the norm was observed during rotation (p<0.001). Of those patients with normal caloric responses, 44.4% showed pathological SVV estimates; this increased to 54.3% for cases with unilateral weakness, and 56.5% for unilateral loss. No clear correlation was found between reports of tilt illusion and pathological SVV, respectively, between rotatory vertigo and pathological caloric responses.

Experimental study of the dependence of the damping rate of n = 1 TAEs on the on-axis safety factor and toroidal rotation shear

The dependence of the measured damping rate (γ/ω) on the value of the safety factor on axis (q0) and of the toroidal rotation shear has been experimentally determined for n = 1 toroidal Alfvén eigenmodes (TAEs) in JET limiter plasmas with a monotonic safety factor profile and low edge magnetic shear. For q0 < 1, the n = 1 TAE damping rate can reach values up to γ/ω > 8%, whereas for q0 > 1.1, γ/ω < 2% for similar experimental conditions. The existence of these two separate regimes is suggestive of a possible role of the sawteeth on the damping of low-n TAEs, for example, via a redistribution of the core plasma current, which would, in turn, affect the magnetic shear profile. The value of the toroidal rotation shear affects the n = 1 TAE damping rate only at high neutral beam injection power (PNBI): for PNBI > 6.5 MW we find that γ/ω > 2% in plasmas with a higher rotation shear, whereas for lower PNBI we do not observe any appreciable effect of the rotation shear on the damping rate. These observations indicate that different damping mechanisms for low-n TAEs may be active at low and high performance.

Full-wave design of broad-band compact waveguide step-twists

Rectangular waveguide twists are components that provide an on-axis rotation of the transverse waveguide section. In this letter, a step twist configuration, obtained by the direct connection of rotated rectangular waveguide lengths, is considered. The advantages of this configuration are the easy manufacturing with tight control on the relative rotation angles and the reduction of the overall dimensions. By means of a full-wave synthesis approach various wide-band devices were designed and reported in the letter. In particular, a couple of 45/spl deg/ twists was manufactured and integrated in the Ka-band OMT realized for the SPOrt project. The experimental results match the excellent predicted data.

Perceptual disturbances predicted in zero-g through three-dimensional modeling

Perceptual disturbances in zero-g and 1-g differ. For example, the vestibular coriolis (or "cross-coupled") effect is weaker in zero-g. In 1-g, blindfolded subjects rotating on-axis experience perceptual disturbances upon head tilt, but the effects diminish in zero-g. Head tilts during centrifugation in zero-g and 1-g are investigated here by means of three-dimensional modeling, using a model that was previously used to explain the zero-g reduction of the on-axis vestibular coriolis effect. The model's foundation comprises the laws of physics, including linear-angular interactions in three dimensions. Addressed is the question: In zero-g, will the vestibular coriolis effect be as weak during centrifugation as during on-axis rotation? Centrifugation in 1-g was simulated first, with the subject supine, head toward center. The most noticeable result concerned direction of head yaw. For clockwise centrifuge rotation, greater perceptual effects arose in simulations during yaw counterclockwise (as viewed from the top of the head) than for yaw clockwise. Centrifugation in zero-g was then simulated with the same "supine" orientation. The result: In zero-g the simulated vestibular coriolis effect was greater during centrifugation than during on-axis rotation. In addition, clockwise-counterclockwise differences did not appear in zero-g, in contrast to the differences that appear in 1-g.

Nystagmus Responses in Normal Subjects during Eccentric Sinusoidal Rotation

Earth vertical axis rotation provides a method of stimulating the horizontal semicircular canals. By placing subjects off from the axis of rotation, the otolith organs may also be stimulated by additional linear acceleration forces. In the present study, we compared the rotation with subjects placed on axis to those placed in an eccentric position, either facing outward or turned 90 degrees facing the direction of the rotation. When the subject was facing outward, sinusoidal eccentric rotation at 0.64 Hz produced a significantly higher vestibulo-ocular reflex (VOR) gain than did on-axis rotation. No increase in VOR gain was observed during eccentric rotation with the subject facing the direction of the rotation. These findings suggest that the gain enhancement due to eccentric rotation is a result of tangential linear acceleration, probably sensed by the utriculus. This study raises the possibility of using eccentric rotation for the diagnosis of the patients with otolith dysfunction.