Opposite Direction Of Rotation Research Articles

Controlling spiral wave and spatiotemporal chaos in cardiac tissues by slowing sodium channel activation and inactivation

Much evidence shows that the appearance and instability of the spiral wave in cardiac tissue can be linked to a kind of heart disease. Therefore there needs a method of controlling spiral wave more safely and effectively. The intelligent modification of specific ion channel to achieve desired control is the future direction of gene therapy in heart disease. The key question that has to be answered is which ion channel is the best candidate for controlling spiral wave. Modern biological technology has been able to make the mutation of sodium channel gene to change its relaxation time constant. In this paper, we adopt the Luo-Rudy phase I model to investigate how to regulate the relaxation time constant of sodium channel gate to control spiral wave and spatiotemporal chaos in cardiac tissues. We suggest a control strategy which slows down the rate of sodium current activation and inactivation by increasing the relaxation time constant of the sodium activation gate by up to times while its fast inactivation gate is clamped to 0.77. Numerical simulation results show that a gradual increase of will cause the activation gate of sodium current to reach maximum more slowly, and its amplitude is gradually reduced, so that the amplitude and duration of the action potential of cardiomyocyte are gradually reduced. When the factor is large enough, the spiral wave and spatiotemporal chaos cannot propagate in the medium except planar wave with low frequency. The reason is that the excitabilities of medium and wave speed significantly decrease. Therefore, the spiral waves and spatiotemporal chaos can be effectively eliminated when the control time is properly selected and the factor is large enough. Spiral wave and spatiotemporal chaos disappear mainly due to conduction obstacle. In some cases, spiral wave can disappear through the transition from spiral wave to target wave or tip retraction. Spatiotemporal chaos disappears after spatiotemporal chaos has evolved into meandering spiral wave. When the parameters are chosen properly, the phenomenon that spiral wave evolves into a self-sustained target wave is also observed. The corresponding target wave source is the pair of spiral waves with opposite rotation directions. These results can provide useful information for gene therapy in heart disease.

Vortices formation induced by femtosecond laser filamentation in a cloud chamber filled with air and helium

We report on the experimental observation of the airflow motion induced by an 800 nm, 1 kHz femtosecond filament in a cloud chamber filled with air and helium. It is found that vortex pairs with opposite rotation directions always form both below and above the filaments. We do not observe that the vortices clearly formed above the filament in air just because of the formation of smaller particles with weaker Mie scattering. Simulations of the airflow motion in helium are conducted by using the laser filament as a heat source, and the simulated pattern of vortices and airflow velocity agree well with the experimental results.

Competition of Azimuthally Asymmetric Modes in a Relativistic Backward-Wave Oscillator

We analyze the operation of a relativistic backward-wave oscillator, in which two waves with opposite directions of rotation of the azimuthal structure of the high-frequency field interact with the electron beam simultaneously. Based on the nonstationary model of such a tube, several characteristic features of dynamics of this system are identified, both in the autonomous regime of its operation, and under the action of an external-signal source. The list of such features includes the instability of azimuthally standing waves, the existence of stable regimes of stationary generation of two waves with different frequencies and opposite rotation directions, and the possibility of spatial self-modulation of the output radiation of a high-frequency oscillator.

自公転円板上の境界層流れの速度場に与える公転の影響

The objective of this study is to experimentally investigate the structure of the boundary layer flow over a rotating disk under orbital motion in order to reveal the generation mechanism and characteristics of disturbances. The disk diameter is 300 mm, and the orbital radius is one third of the disk radius (50mm). The velocity field in the boundary layer flow at high Reynolds number is measured by a hot-wire anemometer (as for the measurement height z = 0.65mm from the disk surface), at a fixed orbital angler portion. The structure of the three-dimensional boundary layer flow is deformed elliptically and flown away to a certain direction which is not orbital radial direction, by orbital motion. The effects on the turbulent region, the fluctuating intensity becomes larger except a certain region, as the orbital speed increases. There are observed independently of the direction of rotation. However the flown direction and the location of expecting region depend on the direction of rotation. In the coinciding orbital and rotational directions, the low frequency disturbances which have high intensity of fluctuating velocity are observed in the upstream region of transition point. The transient vortices which form streaks on the coating film are considered to be destroyed by the low frequency disturbances. However, in the opposite orbital and rotational directions, the low frequency disturbances are not observed at any section.

ORBITAL ANGULAR MOMENTUM RADIATION FROM CIRCULAR PATCHES

Orbital angular momentum (OAM) with a huge potential application in multiplexing and coding has become the subject of intense research in recent years. This paper presents a method to generate radio beams carrying OAM based on a circular patch antenna. A 3 dB quadrature hybrid is employed in the design to enable the circular patch to reconfigure opposite OAM states of a radiated field. The results of numerical simulations are presented to show that the circular patch radiates two OAM modes with opposite rotation directions simultaneously. The proposed circular patch is believed to be significant to the wireless communication applications due to its simple geometry, low cost, and OAM mode reconfiguration.

Quaternion-based finite-time control for attitude tracking of the spacecraft without unwinding

This paper investigates two finite-time controllers for the attitude tracking control of the spacecraft based on the quaternion by terminal sliding mode control. Because quaternion is unable to represent the set of attitudes both globally and uniquely, it can result in unwinding. Unwinding makes a spacecraft perform an unnecessary large-angle maneuver when a small-angle maneuver in the opposite rotational direction is sufficient to achieve the objective. The first controller converges to the equilibrium without singularity in finite time, while the second one converges to the region near the equilibrium without singularity, chattering and unwinding in finite time. Saturation function is introduced to the first controller to eliminate singularity, while a novel fast terminal sliding mode control is introduced to the second controller to eliminate singularity and unwinding. Theoretical analysis shows that the controllers can make the spacecraft follow a time-varying reference attitude signal in finite time and guarantee the stability of the overall closed-loop system. Numerical simulations also demonstrate the effectiveness of the proposed control schemes.

Case studies of EUV cyclones and their associated magnetic fields

EUV cyclones are rotating structures in the solar corona, and they are usually rooted in the underlying rotating network magnetic fields in the photosphere. However, their connection with the surrounding magnetic fields remains unknown. Here we report an observational study of four typical cyclones which are rooted in different kinds of magnetic fields. We use Solar Dynamics Observatory/Atmospheric Imaging Assembly data to investigate the rotation of EUV features in cyclones and Helioseismic and Magnetic Imager data to study the associated magnetic fields. The results show that, (1) an EUV cyclone rooted in a sunspot rotates with the photospheric magnetic field; (2) two EUV cyclones in two faculae of an active region are connected to the same sunspot of the active region but rotate oppositely; (3) an EUV cyclone is rooted in a coronal hole with weak open magnetic fields; (4) a pair of conjugated cyclones is rooted in magnetic fields that have opposite polarity with opposite directions of rotation. The differences in the spatial extent of a cyclone, characteristics of its rotation and underlying fields indicate that cyclones are ubiquitous over the solar atmosphere and that the magnetic structures relevant to the cyclones are more complicated than expected.

Chemically related 4,5-linked aminoglycoside antibiotics drive subunit rotation in opposite directions.

Dynamic remodelling of intersubunit bridge B2, a conserved RNA domain of the bacterial ribosome connecting helices 44 (h44) and 69 (H69) of the small and large subunit, respectively, impacts translation by controlling intersubunit rotation. Here we show that aminoglycosides chemically related to neomycin—paromomycin, ribostamycin and neamine—each bind to sites within h44 and H69 to perturb bridge B2 and affect subunit rotation. Neomycin and paromomycin, which only differ by their ring-I 6′-polar group, drive subunit rotation in opposite directions. This suggests that their distinct actions hinge on the 6′-substituent and the drug's net positive charge. By solving the crystal structure of the paromomycin–ribosome complex, we observe specific contacts between the apical tip of H69 and the 6′-hydroxyl on paromomycin from within the drug's canonical h44-binding site. These results indicate that aminoglycoside actions must be framed in the context of bridge B2 and their regulation of subunit rotation.

A molecular propeller effect for chiral separation and analysis.

Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

Mixed lag synchronization in chaotic oscillators and experimental observations

We report mixed lag synchronization in coupled counter-rotating oscillators. The trajectories of counter-rotating oscillators has opposite directions of rotation in uncoupled state. Under diffusive coupling via a scalar variable, a mixed lag synchronization emerges when a parameter mismatch is induced in two counter-rotating oscillators. In the state of mixed lag synchronization, one pair of state variables achieve synchronization shifted in time while another pair of state variables are in antisynchronization, however, they are too shifted by the same time. Transition point of mixed-phase synchronization is estimated analytically using approximation theory. Numerical example of the paradigmatic Rossler oscillator is presented and supported by electronic experiment.

Surface waves in a square container due to its resonant horizontal elliptic motion

Surface waves in a square container due to its resonant horizontal elliptic or linear motion are investigated theoretically. The motion of the container is characterized by the ratio, expressed as , of the length of the minor axis to the length of the major axis of its elliptic orbit, and by the angle θ between the directions of the major axis and one of its sidewalls. Using the reductive perturbation method, non-linear time evolution equations for the complex amplitudes of two degenerate modes excited by this motion are derived with the inclusion of linear damping. When is small, for any θ these equations have two kinds of stable stationary solutions corresponding to regular co-rotating waves whose direction of rotation is the same as that of the container and regular counter-rotating waves of the opposite direction of rotation. As increases to one, the region of forcing frequency in which stable regular counter-rotating waves are observed shrinks and then disappears for any θ. Solutions with chaotic or periodic slow variations in amplitude and phase of excited surface waves are also obtained for forcing frequencies where no stable stationary solutions exist. Non-stationary solutions are either unidirectionally or bidirectionally rotating waves. For , chaotic waves and bidirectionally rotating waves are observed more frequently for smaller . For , for sufficiently small fluid depth, regular non-rotating waves are expected to occur for any forcing frequency. Moreover, stable stationary and non-stationary solutions obtained for are found to agree fairly well with the experimental results in a preceding study.

Direct measurement of the intrinsic ankle stiffness during standing

Ankle stiffness contributes to standing balance, counteracting the destabilizing effect of gravity. The ankle stiffness together with the compliance between the foot and the support surface make up the ankle-foot stiffness, which is relevant to quiet standing. The contribution of the intrinsic ankle-foot stiffness to balance, and the ankle-foot stiffness amplitude dependency remain a topic of debate in the literature. We therefore developed an experimental protocol to directly measure the bilateral intrinsic ankle-foot stiffness during standing balance, and determine its amplitude dependency. By applying fast (40ms) ramp-and-hold support surface rotations (0.005–0.08rad) during standing, reflexive contributions could be excluded, and the amplitude dependency of the intrinsic ankle-foot stiffness was investigated. Results showed that reflexive activity could not have biased the torque used for estimating the intrinsic stiffness. Furthermore, subjects required less recovery action to restore balance after bilateral rotations in opposite directions compared to rotations in the same direction. The intrinsic ankle-foot stiffness appears insufficient to ensure balance, ranging from 0.93±0.09 to 0.44±0.06 (normalized to critical stiffness ‘mgh’). This implies that changes in muscle activation are required to maintain balance. The non-linear stiffness decrease with increasing rotation amplitude supports the previous published research. With the proposed method reflexive effects can be ruled out from the measured torque without any model assumptions, allowing direct estimation of intrinsic stiffness during standing.

Opposite Rotation Directions in the Synthesis and Hydrolysis of ATP by the ATP Synthase: Hints from a Subunit Asymmetry

The ATP synthase can be imagined as a reversible H(+)-translocating channel embedded in the membrane, FO portion, coupled to a protruding catalytic portion, F1. Under physiological conditions the F1FO complex synthesizes ATP by exploiting the transmembrane electrochemical gradient of protons and their downhill movement. Alternatively, under other patho-physiological conditions it exploits ATP hydrolysis to energize the membrane by uphill pumping protons. The reversibility of the mechanism is guaranteed by the structural coupling between the hydrophilic F1 and the hydrophobic FO. Which of the two opposite processes wins in the energy-transducing membrane complex depends on the thermodynamic balance between the protonmotive force (Δp) and the phosphorylation potential of ATP (ΔG P). Accordingly, while Δp prevalence drives ATP synthesis by translocating protons from the membrane P-side to the N-side and generating anticlockwise torque rotation (viewed from the matrix), ΔG P drives ATP hydrolysis by chemomechanical coupling of FO to F1 with clockwise torque. The direction of rotation is the same in all the ATP synthases, due to the conserved steric arrangement of the chiral a subunit of FO. The ability of this coupled bi-functional complex to produce opposite rotations in ATP synthesis and hydrolysis is explained on the basis of the a subunit asymmetry.

Composite structure of vortices in two-component Bose-Einstein condensate

Abstract In contrast to one-component Bose-Einstein condensate case, the vortices in two-component condensate can have various complicated structures. The vortices in a space-homogeneous Bose-Einstein condensate have been studied in this paper. It is shown that the vortex structure is described by three dimensionless parameters. This is totally different from the usual one-component condensate case,where an isolated vortex is described by a parameterless dimensionless equation. The two-component vortex structure strongly depends on the sign of “interaction” constant of the components. A few types of vortices with different qualitative structure are explored. We show that the “super-density vortices” can exist, when the “interaction” constant is positive. The “super-density vortices” have the near-axis density greater than the equilibrium density of a homogeneous space Bose-Einstein condensate. We also show that the vortices with opposite direction of the condensate component rotation near the axis and far off the axis can exist.

The a subunit asymmetry dictates the two opposite rotation directions in the synthesis and hydrolysis of ATP by the mitochondrial ATP synthase

The main and best known role of the mitochondrial ATP synthase is to synthesize ATP by exploiting the transmembrane electrochemical gradient of protons and their downhill movement. However, under different conditions, the same enzyme can also switch to the opposite function of ATP hydrolysis and exploits its energy to pump protons against their gradient and energize the membrane. The change in functionality is linked to the change of direction of rotation of the two matched sectors of this unique complex, namely the hydrophilic F1, which performs the catalysis, and the hydrophobic membrane-embedded FO, which channels protons. Accordingly, viewed from the matrix side, ATP synthesis is driven by counterclockwise rotation and ATP hydrolysis by clockwise rotation of the FO rotor which is transmitted to F1. ATP dissipation through this mechanism features some diseases such as myocardial ischemia. Increasing evidence shoulders the hypothesis that the asymmetry of the a subunit of FO and particularly the steric arrangement of the two inner semi-channels for protons, play a key role in conferring to the coupled bi-functional complex the ability to reverse rotation by switching from ATP synthesis to ATP hydrolysis and vice versa. Accordingly, the conserved steric arrangement of the chiral a subunit of FO yields the same direction of rotation for all the ATP synthases. According to this hypothesis, the a subunit chirality imposes the direction of rotation of the rotor according to the proton gradient across the membrane. It seems likely that the direction of rotation of the membrane-embedded c-ring, which is adjacent to the a-subunit and acts as a rotor, may be under multiple control, being rotation essential to make the whole enzyme machinery work. However, the asymmetric features of the a subunit would make it the master regulator, thus directly determining which of the two functions, ATP production or ATP dissipation, will be performed. The handedness of a subunit should be considered in drug design to counteract tissue damage under all pathological conditions linked to functional impairment of ATP synthase.

Manifold configurations of the director field formed by topological defects in free and confined geometry in smectic films.

We study the topology of the c-director field near topological defects with point core and with a droplet in the core of the defect in nonpolar smectic-C and ferroelectric smectic-C* freestanding films using polarized optical microscopy. Free and confined geometry of topological defects and droplets with strong outer boundary condition are compared. The c-director field can be remarkably different around a point defect and a droplet with the same topological charge S=+1. In ferroelectric films, splay deformation of the c-director transforms into bend deformation after droplet nucleation. Heating a ferroelectric film with an S=+1 droplet leads to a dramatic change of the c-director topology from bend to splay. In confined geometry we found spiral structures in which the c-director has opposite direction of rotation along the inner and outer boundaries of the island. Our observations are discussed on the basis of theories taking into account both the influence of polarity and of confined geometry on elasticity and topology of the c-director field.

Poiseuille flow of a Quincke suspension

The controversy of models of dielectric particle suspensions with antisymmetric stress, which predict a nonphysical cusp of the velocity profile in plane Poiseuille flow under the action of the electrical field, is resolved. In the mean-field approximation, the nonlinear kinetic equation is derived for coupled due to the flow translational and rotational motion of the particles. By its numerical solution, it is shown that the velocity profile is smeared due to the translational diffusion of the particles with opposite directions of rotation. The obtained results for the velocity profiles and flow rates as a function of the electric field strength are in qualitative agreement with the existing experimental results.

Rotating Snakes Illusion - Quantitative analysis reveals islands in luminance space with opposite illusory rotation

The "Rotating Snakes" illusion is based on patterns with repeated asymmetric luminance steps, arranged in concentric bands forming a "snake wheel". In the underlying luminance sequence "black – darker grey (g1) – white – lighter grey (g2)" we varied the luminances of g1 and g2, and measured illusion strength via a nulling task: On a gamma-corrected VDU, repetitive saccades were performed passing a "snake wheel" that physically rotated, and the participants adjusted rotation direction and speed until a stationary percept obtained. We found that our participants performed perceptual nulling (in the range of ± 1°/s) of the seeming rotation quite reliably and convincingly; when the gaze was directed to the center of the wheel after null-adjustment, the actual rotation could be quite surprising (depending on the levels [g1, g2]). Typical settings for [g1, g2] as measured from images by A. Kitaoka, are around [20%, 60%]. Indeed, we found a marked illusion in an "island" region [g1≈{0–25%}, g2≈{20–75%}]. Unexpectedly, we detected a second island around [60%, 90%] with opposite rotation direction, although the relative order of g1 and g2 stayed the same. Furthermore, there was also some rotation illusion when altogether only 3 luminance levels were visible, e.g.: 0–0–50–100%. These quantitative measurements of illusion strength have revealed new phenomena in this illusion, which challenge the two explanatory models put forth so far. Meeting abstract presented at VSS 2014

3-D measurements of separated flow over rigid plates with spanwise periodic cambering at low Reynolds number

Measurements of the flow field around a flat plate and rigid plates with spanwise periodic cambering were performed using volumetric three-component velocimetry (V3V) at a Reynolds numbers of 28,000 at α=12° where the flow is fully separated. The Reynolds normal and shear stresses, and the streamwise, spanwise and normal components of the vorticity vector are investigated for three-dimensionality. Flow features are discussed in context of the periodic cambering and corresponding aerodynamic force measurements. The periodic cambering results in spanwise variation in the reversed-flow region, Reynolds stresses and spanwise vorticity. These spanwise variations are induced by streamwise and normal vortices of opposite directions of rotation. Moreover, measurements were carried out for the cambered plates at α=8°, where a long separation bubble exists, to further understand the behavior of the streamwise and normal vortices. These vortices become more organized and increase in strength and size at the lower angle of attack. It is also speculated that these vortices contribute to the increase in lift at and beyond the onset of stall angle of attack.

Deflection of light due to rotating mass – a comparison among the results of different approaches

It is known that light gets deflected due to mass. Value of deflection of light for static body is not same as it is in the case of rotating body. The deflection for a static body entirely depends on the gravitational mass where in case of a rotating body new terms will be included due to rotation. The bending angle of light is also not same in the equatorial plane and non equatorial plane for rotating Kerr body. The light bending angle is also direction of motion dependent i.e. if the motion of the light ray is in the direction of rotation, bending angle is greater than the static case and if the ray is in the opposite direction of rotation, the bending angle is smaller than the static case in equatorial plane. There are two approaches to obtain the bending angle, null geodesic of photon and change of effective refractive index. In this paper a comparison will be made among the results of different approaches.