Sense Of Rotation Research Articles

The evolutionary hypothesis of benign paroxysmal positional vertigo

Human otoliths, primarily formed from salts of calcium and carbonate, are different from bones of the skeleton, which are composed of calcium phosphate. The echinoderms, which share the earliest common ancestor with us, began to protect the body by making an endoskeleton out of calcium and carbon dioxide dissolved in the sea. In subsequent vertebrates, aerobic respiration supported strong muscle activity, but an occasional shortage of oxygen led to low pH due to the accumulation of lactate produced by anaerobic respiration, increasing the risk of melting bones composed of calcium carbonate. So, all vertebrates used calcium phosphate to increase bone strength, having a stronger ionic bonding than calcium carbonate. But otoliths, which are in the inner ear and thereby not connected to muscles, still use calcium carbonate. Benign paroxysmal positional vertigo (BPPV) is a disorder in which otoliths detached from the utricle enter the semicircular canals and cause a sense of rotation. Otoliths, the calcium carbonate ear bones retaining a long evolutionary history, can be easily broken at low pH. During sleep, shallow breathing produces mild respiratory acidosis and low pH in the blood. Since otoliths are corroded at low pH during nighttime, BPPV occurs frequently in the morning. In addition, diabetes mellitus or gout often decreases pH in the blood and increases the occurrence of BPPV.

Variations of Slot Cut and Stub Loaded Square Microstrip Antenna for Circular Polarization

Modified technique to produce circular polarization for square, nearly square microstrip antenna using diagonal slots of different shapes, slits, stub at corners of antenna is proposed. Diagonally embedded slots are perpendicular to stubs which yield orthogonal modes to give circular polarization. In-depth explanation for orthogonal mode degeneration using different slots shape, its impact on various antenna parameters and sense of rotation is discussed. VSWR, axial ratio bandwidth greater than 38% and 4.1% is obtained respectively. Resultant gain and cross polar level is 8 and 23 dBi. Antenna parameters are compared for square, nearly square microstrip antenna for different slot shapes. Major contribution of paper is empirical formulation of resonant frequencies corresponding to orthogonal modes from its surface current distribution. Close agreement is observed between simulated and calculated resonant frequency from proposed formulations.

Influence of the Yarkovsky force on Jupiter Trojan asteroids

Aims.We investigate the influence of the Yarkovsky force on the long-term orbital evolution of Jupiter Trojan asteroids.Methods.Clones of the observed population with different sizes and different thermal properties were numerically integrated for 1 Gyr with and without the Yarkovsky effect. The escape rate of these objects from the Trojan region as well as changes in the libration amplitude, eccentricity, and inclination were used as a metric of the strength of the Yarkovsky effect on the Trojan orbits.Results.Objects with radiiR≤ 1 km are significantly influenced by the Yarkovsky force. The effect causes a depletion of these objects over timescales of a few hundred million years. As a consequence, we expect the size-frequency distribution of small Trojans to show a shallower slope than that of the currently observable population (R≳ 1 km), with a turning point betweenR= 100 m andR= 1 km. The effect of the Yarkovsky acceleration on the orbits of Trojans depends on the sense of rotation in a complex way. The libration amplitude of prograde rotators decreases with time while the eccentricity increases. Retrograde rotators experience the opposite effect, which results in retrograde rotators being ejected faster from the 1:1 resonance region. Furthermore, for objects affected by the Yarkovsky force, we find indications that the effect tends to smooth out the differences in the orbital distribution between the two clouds.

Sustained rotation in a vibrated disk with asymmetric supports

A single frictional elastic disk, supported against gravity by two others, rotates steadily when the supports are vibrated and the system is tilted with respect to gravity. Rotation is here studied using molecular dynamics simulations, and a detailed analysis of the dynamics of the system is made. The origin of the observed rotational ratcheting is discussed by considering simplified situations analytically. This shows that the sense of rotation is not fixed by the tilt but depends on the details of the excitation as well.

Measuring the Dzyaloshinskii-Moriya interaction of the epitaxial Co/Ir(111) interface

The in-plane orientation of the magnetization in the center of domain walls is measured in Co/Ir(111) as a function of Co thickness via scanning electron microscopy with polarization analysis. Uncapped, thermally evaporated cobalt on an Ir(111) single-crystal surface is imaged in situ in ultra-high vacuum. The initial pseudomorphic growth with an atomically flat interface of cobalt on iridium ensures comparability to theoretical calculations and provides a study of an interface that is as ideal as possible. Below a cobalt thickness of 8.8 monolayers, the magnetic domain walls are purely N\'eel oriented and show a clockwise sense of rotation. For larger thicknesses the plane of rotation changes and the domain walls show a significant Bloch-like contribution, allowing to calculate the strength of the Dzyaloshinskii-Moriya interaction (DMI) from energy minimization. From the angle between the plane of rotation and the domain-wall normal an interfacial DMI parameter $D_s = -(1.07 \pm 0.05)$ pJ/m is determined, which corresponds to a DMI energy per bond between two Co atoms at the interface of $d_{tot} = -(1.04 \pm 0.05)$ meV.

The Gas Kinematics, Excitation, and Chemistry, in Connection with Star Formation, in Lenticular Galaxies

Abstract We present long-slit and panoramic spectroscopy of extended gaseous disks in 18 S0 galaxies, mostly in groups. The gas has often decoupled kinematics: at least five galaxies demonstrate strongly inclined large-scale ionized gas disks, seven galaxies reveal circumnuclear polar disks, and in NGC 2551 the ionized gas, although confined to the main plane, counterrotates the stars. The gas excitation analysis reveals ionization by young stars in 12 of 18 S0 galaxies; current star formation in these galaxies is confined to ring-like zones coinciding with their UV rings. Gas oxygen abundances in the rings are around 0.7 Z ⊙ and correlate neither with the ring radius nor with the metallicity of the stellar population. By applying tilted ring analysis to the velocity fields, we have traced the gas rotation plane lines of nodes along the radius. We find that current star formation proceeds usually where the gas lies strictly in the stellar disk planes and rotates circularly; the sense of the gas rotation does not matter (the counterrotating gas in NGC 2551 forms stars). In the galaxies without current star formation the extended gaseous disks either are in steady-state quasi-polar orientation or were acquired recently through the misaligned external filaments provoking shock-like excitation. Our data imply a crucial difference of the accretion regime in S0s with respect to spirals: the geometry of gas accretion in S0s is typically off-plane.

A polarization reconfigurable discontinuous ring dipole antenna

AbstractA circularly polarized antenna is realized using a discontinuous ring dipole. With the introduction of p‐i‐n diodes, it has been possible to achieve polarization reconfigurability in the antenna. The antenna is fed by a tapered feed line, which also acts as a balun and biasing structure. The sense of rotation of the electric field vector (left‐hand or right‐hand) can be controlled by switching the states of the diodes. An equivalent circuit of the antenna is proposed, which has been used to compute the input reflection coefficient of the antenna. The performance of the antenna is verified by comparing the simulated results with the measured results. It has been observed that the antenna has 8.56% overlapping CP bandwidth (a common bandwidth for |S11| ≤ −10 dB and axial ratio, AR ≤3 dB) from 5.03to 5.48 GHz. A measured gain of 3.61 dBic is obtained for all polarization states. The proposed antenna can be used for the 5.2 GHz Wi‐Fi application.

Hyperfine field of La impurity in Fe host: Experiment and theory

The magnetic hyperfine field of La impurity in ferromagnetic Fe host has been measured by time differential perturbed angular distribution (TDPAD) technique, using the 2738 keV 23/2+, isomeric state in 135La as nuclear probe, populated in the reaction \(^{128}\text {Te}\left ({~}^{11}\mathrm {B}, 4\mathrm {n}\right )^{135}\!\text {La}\) at beam energy of 52 MeV. The spin rotation spectra, R(t) measured in applied field of 2 T showed Larmor precession frequency of ωL = 93.9 ± 4.7 Mrad/sec, which corresponds to a magnetic hyperfine field, Bhf of 42.1 ± 3.3 T. From the sense of rotation observed in the R(t) spectra, the sign of the Bhf has been determined to be negative. Complimenting the experimental studies, we have performed ab-inito calculations of hyperfine field within the frame work of the density functional theory using supercell method. The calculated magnetic hyperfine field shows strong dependence with impurity concentration scaled by the supercell size. For a 2 × 2 × 2 supercell representing La concentration of 6.25 % we obtained Bhf = -21.2 T while, for a 3 × 3 × 3 supercell, corresponding to an impurity concentration of 1.8 % La, the Bhf comes out to be -48.3 T, closely agreeing with our experimental value.

Converging photospheric vortex flows close to the polarity inversion line of a fully emerged active region

Abstract. We report on the occurrence of vortexes in flow fields obtained from the evolution of the line-of-sight component of the photospheric magnetic field in a region around the polarity inversion line (PIL) of a fully emerged active region. Based on a local linear approximation for the flow field, we identify the presence of critical points and classify them according to the eigenvalues of the Jacobian matrix of the linear transformation. Converging vortexes are associated with the presence of a particular kind of critical point, known as the attracting focus. We identified 12 converging vortexes in the analyzed period and detected the occurrence of other types of critical points, which indicate the complexity of the flow field around the PIL. The detected vortexes show a clockwise preferred sense of rotation with approximately 67 % of the cases. A geometrical analysis of the velocity structures produced an average value of D‾=1.63±0.05 for the fractal dimension, which is very close to the one obtained for isotropic homogeneous turbulence (D=5/3). This suggests that the flow around the PIL is turbulent in nature.

Deformation of the moving magnetic skyrmion lattice in MnSi under electric current flow

Topological defects are found ubiquitously in various kinds of matter, such as vortices in type-II superconductors, and magnetic skyrmions in chiral ferromagnets. While knowledge on the static behavior of magnetic skyrmions is accumulating steadily, their dynamics under forced flow is still a widely open issue. Here, we report the deformation of the moving magnetic skyrmion lattice in MnSi under electric current flow observed using small-angle neutron scattering. A spatially inhomogeneous rotation of the skyrmion lattice, with an inverse rotation sense for opposite sample edges, is observed for current densities greater than a threshold value jt ~ 1 MA m−2 (106 A m−2). Our result show that skyrmion lattices under current flow experience significant friction near the sample edges due to pinning, this being a critical effect that must be considered for anticipated skyrmion-based applications at the nanoscale.

Hydrodynamics of Vortex Generation during Bell Contraction by the Hydromedusa Eutonina indicans (Romanes, 1876).

Swimming bell kinematics and hydrodynamic wake structures were documented during multiple pulsation cycles of a Eutonina indicans (Romanes, 1876) medusa swimming in a predominantly linear path. Bell contractions produced pairs of vortex rings with opposite rotational sense. Analyses of the momentum flux in these wake structures demonstrated that vortex dynamics related directly to variations in the medusa swimming speed. Furthermore, a bulk of the momentum flux in the wake was concentrated spatially at the interfaces between oppositely rotating vortices rings. Similar thrust-producing wake structures have been described in models of fish swimming, which posit vortex rings as vehicles for energy transport from locations of body bending to regions where interacting pairs of opposite-sign vortex rings accelerate the flow into linear propulsive jets. These findings support efforts toward soft robotic biomimetic propulsion.

Interlayer Dzyaloshinskii-Moriya Interactions

The interfacial Dzyaloshinkii-Moriya interaction defines a rotational sense for the spin structure in two-dimensional magnetic films and can be used to create chiral magnetic structures like spin spirals and skyrmions in those films. Here, we show by means of atomistic calculations that in heterostructures an interlayer coupling of the Dzyaloshinskii-Moriya type across a spacer can emerge. We quantify this interaction in the framework of the Lévy-Fert model for trilayers consisting of two ferromagnets separated by a nonmagnetic spacer and show that such an interlayer Dzyaloshinkii-Moriya interaction yields nontrivial three-dimensional spin textures across the entire trilayer, which evolve within as well as between the planes and, hence, combine intraplane and interplane chiralities. This analysis opens new perspectives for three-dimensional tailoring of magnetic chirality in multilayers.

Sign change of polarization rotation under time or space inversion in magnetoelectric YbAl3(BO3)4

Materials with optical activity can rotate the polarization plane of transmitted light. The most typical example is the natural optical activity, which has the symmetry property of changing sign after space inversion but being invariant to time inversion. Faraday rotation exhibits the opposite: it is invariant to space inversion but changes sign after time reversal. Here, we demonstrate that in a magnetoelectric material, another type of polarization rotation is possible. This effect is investigated in magnetoelectric YbAl3(BO3)4 under the viewpoint of time and space inversion symmetry arguments. We observe the sign change of the rotation sense under either time or space reversal. This investigation proves that the polarization rotation in YbAl3(BO3)4 must be classified as gyrotropic birefringence, which has been discussed within the idea of time-reversal breaking in underdoped cuprates. The diagonal terms in the magnetoelectric susceptibility are responsible for the observed signal of gyrotropic birefringence. Further analysis of the experimental spectra reveals a substantial contribution of the natural optical activity to the polarization rotation. We also demonstrate that the observed activity originates from the magnetoelectric susceptibility.

Measurement of the rotational sense and velocity of an object using OAM wave in the radio‐frequency band

A method is presented to improve the determination of the rotational velocity of an on-axis spinning object. It uses the Orbital Angular Momentum (OAM) of an electromagnetic wave at 2.47 GHz, and measures the rotational Doppler frequency shift of a reflected wave. From this shift, the rotational velocity and the direction of rotation can be directly estimated with very good accuracy.

Asteroid pairs: A complex picture

We studied a sample of 93 asteroid pairs, i.e., pairs of genetically related asteroids that are on highly similar heliocentric orbits. We estimated times elapsed since separation of pair members (i.e., pair age) that are between 7 × 103 yr and a few 106 yr. With photometric observations, we derived the rotation periods P1 for all the primaries (i.e., the larger members of asteroid pairs) and a sample of secondaries (the smaller pair members). We derived the absolute magnitude differences of the studied asteroid pairs that provide their mass ratios q. For a part of the studied pairs, we refined their WISE geometric albedos and collected or estimated their taxonomic classifications. For 17 asteroid pairs, we also determined their pole positions. In two pairs where we obtained the spin poles for both pair components, we saw the same sense of rotation for both components and constrained the angles between their original spin vectors at the time of their separation. We found that the primaries of 13 asteroid pairs in our sample are actually binary or triple systems, i.e., they have one or two bound, orbiting secondaries (satellites). As a by-product, we found also 3 new young asteroid clusters (each of them consisting of three known asteroids on highly similar heliocentric orbits). We compared the obtained asteroid pair data with theoretical predictions and discussed their implications. We found that 86 of the 93 studied asteroid pairs follow the trend of primary rotation period vs mass ratio that was found by Pravec et al. (2010). Of the 7 outliers, 3 appear insignificant (may be due to our uncertain or incomplete knowledge of the three pairs), but 4 are high mass ratio pairs that were unpredicted by the theory of asteroid pair formation by rotational fission. We discuss a (remotely) possible way that they could be created by rotational fission of flattened parent bodies followed by re-shaping of the formed components. The 13 asteroid pairs with binary primaries are particularly interesting systems that place important constraints on formation and evolution of asteroid pairs. We present two hypotheses for their formation: The asteroid pairs having both bound and unbound secondaries could be “failed asteroid clusters”, or they could be formed by a cascade primary spin fission process. Further studies are needed to reveal which of these two hypotheses for formation of the paired binary systems is real.

A polarization and band reconfigurable cross-slot antenna for multiband application

AbstractA polarization and band reconfigurable cross-slot antenna for multiband applications is presented in this paper. The antenna consists of four p–i–n diodes embedded in the cross-shaped slot in a ground plane and excited by a microstrip feed line. The p–i–n diodes are placed in such a way that they produce multiple bands, with linearly and circularly polarized (CP) radiation. By switching the states of the p–i–n diodes, the sense of rotation of the electric field in CP radiation can be reconfigured. The proposed structure can be configured to produce two bands that radiate linearly polarized waves or three bands, where, two are linearly polarized and one is CP. The proposed design concepts are validated bythe CST studio suite as well as measurementsare carried out on fabricated prototypes.

Inverse cascade of the vortical structures near the contact line of evaporating sessile droplets

Microscopic imaging as well as the particle image velocimetry (PIV) are carried out to evaluate the concentration, velocity and vorticity fields near the contact line of the nano-particles-laden evaporating sessile droplets. After the onset of the linear thermocapillary instabilities due to the Marangoni perturbations, the non-linear state sets in and the micro-scale jet-like vortex structures are ejected from the contact line towards the center of the droplet. Afterwards, the jet-like vortical structures expand in the spanwise directions and start to interact with the neighbouring structures. Two types of the inverse cascade mechanisms are found to occur. In the first kind, the vortices of the similar length scale merge and continuously produce larger vortices and corresponding wavelength growth. The second inverse cascade mechanism takes place due to the entrainment of the smaller vortices into the larger structures. Both inverse cascade processes are identified as the continuous feeding of the kinetic energy from the smaller scales to the larger scales. For individual micro-jets the velocity field characterizes the jet-like vortex structures ejected from the contact line towards the droplet center opposing the bulk flow from the center towards the contact line. In addition, the vorticity field overlaid by the velocity streamlines identify the sense of rotation of the low pressure zones on either side of the micro-jet as well as the high pressure stagnation point at the tip.

Non-periodic phase-space trajectories of roughness-driven secondary flows in high- boundary layers and channels

Turbulent flows respond to bounding walls with a predominant spanwise heterogeneity – that is, a heterogeneity parallel to the prevailing transport direction – with formation of Reynolds-averaged turbulent secondary flows. Prior experimental and numerical work has determined that these secondary rolls occur in a variety of arrangements, contingent only upon the existence of a spanwise heterogeneity (i.e. from complex, multiscale roughness with a predominant spanwise heterogeneity, to canonical step changes, to different roughness elements). These secondary rolls are known to be a manifestation of Prandtl’s secondary flow of the second kind: driven and sustained by the existence of spatial heterogeneities in the Reynolds (turbulent) stresses, all of which vanish in the absence of spanwise heterogeneity. Herein, we show results from a suite of large-eddy simulations and complementary experimental measurements of flow over spanwise-heterogeneous surfaces. Although the resultant secondary cell location is clearly correlated with the surface characteristics, which ultimately dictates the Reynolds-averaged flow patterns, we show the potential for instantaneous sign reversals in the rotational sense of the secondary cells. This is accomplished with probability density functions and conditional sampling. In order to address this further, a base flow representing the streamwise rolls is introduced. The base flow intensity – based on a leading-order Galerkin projection – is allowed to vary in time through the introduction of time-dependent parameters. Upon substitution of the base flow into the streamwise momentum and streamwise vorticity transport equations, and via use of a vortex forcing model, we are able to assess the phase-space evolution (orbit) of the resulting system of ordinary differential equations. The system resembles the Lorenz system, but the forcing conditions differ intrinsically. Nevertheless, the system reveals that chaotic, non-periodic trajectories are possible for sufficient inertial conditions. Poincaré projection is used to assess the conditions needed for chaos, and to estimate the fractal dimension of the attractor. Its simplicity notwithstanding, the propensity for chaotic, non-periodic trajectories in the base flow model suggests similar dynamics is responsible for the large-scale reversals observed in the numerical and experimental datasets.

Propensity rules in photoelectron circular dichroism in chiral molecules. I. Chiral hydrogen

Photoelectron circular dichroism results from one-photon ionization of chiral molecules by circularly polarized light and manifests itself in forward-backward asymmetry of electron emission in the direction orthogonal to the light polarization plane. What is the physical mechanism underlying asymmetric electron ejection? How "which way" information builds up in a chiral molecule and maps into forward-backward asymmetry? We introduce instances of bound chiral wave functions resulting from stationary superpositions of states in a hydrogen atom and use them to show that the chiral response in one-photon ionization of aligned molecular ensembles originates from two propensity rules: (i) Sensitivity of ionization to the sense of electron rotation in the polarization plane. (ii) Sensitivity of ionization to the direction of charge displacement or stationary current orthogonal to the polarization plane. In the companion paper we show how the ideas presented here are part of a broader picture valid for all chiral molecules and arbitrary degrees of molecular alignment.

Asteroid collisions as origin of debris disks: Asteroid shape reconstruction from BNAO Rozhen photometry

AbstractAs a result of collisions during their lifetimes, asteroids have a large variety of different shapes. It is believed that high velocity collisions or rotational spin-up of asteroids continuously replenish the Sun’s zodiacal cloud and debris disks around extrasolar planets (Jewitt (2010)). Knowledge of the spin and shape parameters of the asteroids is very important for understanding collision asteroid processes. Lately photometric observations of asteroids showed that variations in brightness are not accompanied by variations in colour index which indicate that the shape of the lightcurve is caused by varying illuminations of the asteroid surface rather than albedo variations over the surface. This conclusion became possible when photometric investigations were combined with laboratory experiments (Dunlap (1971)). In this article using the convex lightcurve inversion method we obtained the sense of rotation, pole solutions and preliminary shape of 901 Brunsia.