Front-back Asymmetry Research Articles

On the spatial symmetry of head-related transfer functions

The spatial symmetry of head-related transfer functions (HRTFs) in the horizontal and median planes was investigated using an asymmetry coefficient derived from cross-correlation analysis. Statistical results from 52 human subjects show that, for an asymmetry coefficient below 0.05, the horizontal-plane HRTFs are approximately left–right symmetric below 5.0kHz and 1.1kHz for ipsilateral and contralateral source directions, respectively, whereas the frequency limit is 5.5kHz for the median-plane HRTFs. For the horizontal-plane HRTFs, the front-back asymmetry coefficient is often greater than the left–right asymmetry coefficient. Moreover, a series of psychoacoustic experiments was conducted to evaluate the audibility of the left–right asymmetry of HRTFs in the horizontal and median planes separately. The experimental results show that the left–right asymmetry of HRTF above 4kHz is perceivable for most source directions.

Synchronization of Swimming Microorganisms

Some microorganisms, such as spermatozoa, have been observed to synchronize their flagella when swimming in close proximity. Using a two-dimensional model we show that phase-locking can arise from hydrodynamic forces alone. In a Newtonian fluid, as a consequence of the kinematic reversibility of the field equations, there must exist front-back asymmetry in the geometry of their flagellar waveform. The time-evolution of the phase difference between co-swimming cells depends only on the nature of this geometrical asymmetry, and microorganisms can phase-lock into conformations which minimize or maximize energy dissipation. In a viscoelastic fluid the presence of polymeric stresses removes the geometrical asymmetry constraint, and therefore even symmetric swimmers synchronize. Such synchronization occurs on asymptotically faster time scales than in a Newtonian fluid, and the swimmers evolve into a stable in-phase conformation minimizing the energy dissipated in the surrounding fluid. Furthermore, we show that if we consider flexible sheets, with internal symmetric forcing instead of prescribed kinematics, they deform when interacting with each other through the fluid in such a way as to systematically break the overall waveform symmetry, thereby always evolving to an in-phase conformation where energy dissipation is minimized. These dynamics are shown to be mathematically equivalent to those obtained for prescribed waveforms in viscoelastic fluids, emphasizing the crucial role of flexibility in symmetry-breaking and synchronization - be it that of the fluid, or the swimmers themselves.

Stochastic Asymmetry Properties of 3D Gauss-Lagrange Ocean Waves with Directional Spreading

In the stochastic Lagrange model for ocean waves the vertical and horizontal location of surface water particles are modeled as correlated Gaussian processes. In this article we investigate the statistical properties of wave characteristics related to wave asymmetry in the 3D Lagrange model. We present a modification of the original Lagrange model that can produce front-back asymmetry both of the space waves, i.e. observation of the sea surface at a fixed time, and of the time waves, observed at a fixed measuring station. The results, which are based on a multivariate form of Rice's formula for the expected number of level crossings, are given in the form of the cumulative distribution functions for the slopes observed either by asynchronous sampling in space, or at synchronous sampling at upcrossings and down-crossings, respectively, of a specified fixed level. The theory is illustrated in a numerical section, showing how the degree of wave asymmetry depends on the directional spectral spreading and on the mean wave direction. It is seen that the asymmetry is more accentuated for high waves, a fact that may be of importance in safety analysis of capsizing risk.

Hydrodynamic Phase Locking of Swimming Microorganisms

Some microorganisms, such as spermatozoa, synchronize their flagella when swimming in close proximity. Using a simplified model (two infinite, parallel, two-dimensional waving sheets), we show that phase locking arises from hydrodynamics forces alone, and has its origin in the front-back asymmetry of the geometry of their flagellar waveform. The time evolution of the phase difference between coswimming cells depends only on the nature of this geometrical asymmetry, and microorganisms can phase lock into conformations which minimize or maximize energy dissipation.

First Order Stochastic Lagrange Model for Asymmetric Ocean Waves

The Gaussian linear wave model, which has been successfully used in ocean engineering for more than half a century, is well understood, and there exist both exact theory and efficient numerical algorithms for calculation of the statistical distribution of wave characteristics. It is well suited for moderate seastates and deep water conditions. One drawback, however, is its lack of realism under extreme or shallow water conditions, in particular, its symmetry. It produces waves, which are stochastically symmetric, both in the vertical and in the horizontal direction. From that point of view, the Lagrangian wave model, which describes the horizontal and vertical movements of individual water particles, is more realistic. Its stochastic properties are much less known and have not been studied until quite recently. This paper presents a version of the first order stochastic Lagrange model that is able to generate irregular waves with both crest-trough and front-back asymmetries.

A Novel Model of Interaural Time Difference Based on SpatialFourier Analysis

Based on the spatial Fourier analysis, a statistical model of theindividualized interaural time difference (ITD) is derived from thehead-related transfer function database for a Chinese subject. The modelreflects the spatial left–right symmetry and front–back asymmetry ofITD. Moreover, by using three anatomical parameters of head and pinna,the model is able to predict individualized ITD in the horizontalplane. Performance of the four subjects outside the databasedemonstrates that the mean of the total error is less than 20 μs, whilethe lateral performance is inferior to that at other directions.

Idiopathic scoliosis: biomechanics and biology.

For whatever reason, right-left asymmetry has attracted an illogical proportion of research effort. Non-structural scoliosis, for example secondary to a leg length inequality, is indeed a problem of right-left asymmetry, but structural scoliosis is a complex three-dimensional deformity involving all planes. Biomechanical, biological and clinical evidence indicates clearly that the problem is one of front-back asymmetry and not right-left. The importance of biological factors lies in their ability to bring the spinal column to and beyond its buckling threshold. Thus a taller and more slender spine is more liable to bend and, being stiffer in the sagittal plane, favours movement into other planes. This epitomises the spine of the scoliosis patient who is growing faster with a spinal template similar to other family members allowing idiopathic scoliosis to express itself genetically. It is the opposite condition to idiopathic hyperkyphosis (Scheuermann's disease), but this deformity is rotationally stable, thus remaining in the sagittal plane. The presence of an adjacent area of lordo-scoliosis below the region of hyperkyphosis testifies to the common nature of the pathogenesis of idiopathic scoliosis and Scheuermann's disease. It is the area of compensatory hyperlordosis below the Scheuermann's area that has obligatorily buckled and represents a human model supporting the lordosis theory, as does surgically tethering the back of the young growing human spine, which crankshafts accelerated progression. Similarly the only successful animal model of the formation of idopathic follows creation of a lordotic spinal segment in an otherwise kyphotic spine. For centuries, engineers have recognised that the mechanical behaviour of a column under load is influenced by geometry, as well as by material properties; it is clear that the spinal column also obeys these well-described laws.

A model of water wave ‘horse-shoe’ patterns

The work suggests a simple qualitative model of the wind wave ‘horse-shoe’ patterns often seen on the sea surface. The model is aimed at explaining the persistent character of the patterns and their specific asymmetric shape. It is based on the idea that the dominant physical processes are quintet resonant interactions, input due to wind and dissipation, which balance each other. These processes are described at the lowest order in nonlinearity. The consideration is confined to the most essential modes : the central (basic) harmonic and two symmetric oblique satellites, the most rapidly growing ones due to the class I1 instability. The chosen harmonics are phase locked, i.e. all the waves have equal phase velocities in the direction of the basic wave. This fact along with the symmetry of the satellites ensures the quasi-stationary character of the resulting patterns. Mathematically the model is a set of three coupled ordinary differential equations for the wave amplitudes. It is derived starting with the integro-differential formulation of water wave equations (Zakharov’s equation) modified by taking into account small (of order of quartic nonlinearity) non-conservative effects. In the derivation the symmetry properties of the unperturbed Hamiltonian system were used by taking special canonical transformations, which allow one exactly to reduce the Zakharov equation to the model. The study of system dynamics is focused on its qualitative aspects. It is shown that if the non-conservative effects are neglected one cannot obtain solutions describing persistent asymmetric patterns, but the presence of small non-conservative effects changes drastically the system dynamics at large times. The main new feature is attructive equilibria, which are essentially distinct from the conservative ones. For the existence of the attractors a balance between nonlinearity and non-conservative effects is necessary. A wide class of initial configurations evolves to the attractors of the system, providing a likely scenario for the emergence of the long-lived threedimensional wind wave patterns. The resulting structures reproduce all the main features of the experimentally observed horse-shoe patterns. In particular, the model provides the characteristic ‘crescent’ shape of the wave fronts oriented forward and the front-back asymmetry of the wave profiles.

Monaural and binaural spectrum level cues in the ferret: acoustics and the neural representation of auditory space

1. The role of the structures of the outer ear in producing monaural and binaural spectral cues to sound location was examined acoustically in the ferret. A probe microphone was introduced across the wall of the external auditory canal and its responses to digitally constructed wideband signals were recorded for a large number of free field locations. 2. In the intact animal the patterns of both monaural and binaural cues were asymmetrical for horizontal locations about the interaural axis. For anterior sound locations the monaural transformations demonstrated relative gains at middle and high frequencies and a location-dependent frequency notch. Changing elevation resulted in variations in the corner frequencies of these spectral features. Additionally, there was greater front-back asymmetry in the binaural spectral cues for locations in lateral space when compared with locations near the midline. 3. Surgical removal of the pinna and concha (pinnectomy) eliminated all the major front-back asymmetrical features in the horizon monaural and binaural spectral transformations as well as the elevation-dependent variations in the monaural spectra. Thus the residual transformations were ambiguous for sound locations in lateral space, resulting in "cones of confusion" centered on the interaural axis. 4. These cues were reflected in the topographic representation of auditory space in the deeper layers of the superior colliculus (SC). Previous studies have shown that spatial tuning at near-threshold sound levels is based on monaural pinna cues, whereas binaural inputs are utilized at higher levels that stimulate both ears. In the intact ferret we examined statistically the topography of the representation of sound azimuth for near-threshold and suprathreshold stimuli and the alignment of the auditory and visual representations in the SC. The distributions of auditory best positions within the SC for near- and suprathreshold stimulus levels were statistically indistinguishable, suggesting that both monaural and binaural cues are integrated in this neural representation of space. 5. Pinnectomy resulted in a large increase in the number of auditory units that responded best to two distinct locations in space. One lobe of the response was tuned appropriately in terms of the position of the unit within the SC, demonstrating that the residual acoustical cues are sufficient for the construction of a topographic representation of auditory space. However, the second region of space, thereby producing an ambiguous representation.(ABSTRACT TRUNCATED AT 400 WORDS)

Possibility of measuring the coupling constants of heavy quarks

The electroweak asymmetries (the front-back angular asymmetry, the right-left asymmetry, the degree of longitudinal polarization of a quark, and the degree of circular polarization of a γ-ray) in the ordinary and radiative annihilation of an electron-positron pair into a pair of heavy quarks are analyzed in the standard Weinberg-Salam model. It is shown that these P-odd asymmetries are quite sensitive to the magnitude of the right-hand coupling constant of a quark.

Probing lepton structure at the SSC

If quarks and leptons are composite objects with common constituents, then there exist two-quark-two-lepton contact interactions which could affect lepton pair production at the SSC. We show that for a range of compositeness scales and lepton pair invariant masses, the contact interaction contributions dominate the standard model contributions to the cross section. In this regime, we show that there should be a measurable and statistically significant front-back asymmetry.

Evidence for the effect of the interstellar far UV-radiation on circumstellar shells

The interstellar UV field at 1565 A is calculated around nearby OH/IR sources. The front-back asymmetry observed in the 1612 MHz maser line profile is well correlated with anisotropy of the interstellar UV flux. For some sources the spatial positions of the 1612 MHz masers are confined to the position angles for which stronger UV radiation occurs. These facts strongly support the theory of the photoproduction of OH from H2O induced by ambient interstellar UV photons penetrating the circumstellar shell. A simple model of the 1612 MHz maser with OH photoproduction suggests that the influence of the UV field on the observed maser profiles is governed by the mass loss rate and the relative abundances of OH and H2O molecules.

Properties of the W boson in some composite models

We analyze the effects of some electroweak interaction models with a composite W at present energies. We find that the width of the W into pairs of pseudoscalar bosons can be appreciable and may reduce its leptonic branching ratio by about 20%. The front-back asymmetry of leptons at the proton-antiproton collider is similar to the one obtained in the standard model.

SU(2)×U(1) effects in e +e − annihilation: Generalized charge asymmetry

The observability of the SU(2)×U(1) electroweak charge asymmetry effects in e +e − annihilation at s =29 GeV is addressed in the context of a Feynman-Field type fragmentation model. We assume three colors of five flavored quarks and one heavy lepton τ. We neglect, at this time, the hard gluon bremsstrahlung events. We take b→c+X as the b-decay mode and we assume all τ's and heavy hadrons decay within the resolution of the detector so thatonly light hadrons and leptons are detected. Allowing all these decays to occur, we then compute the expected front-back asymmetry of negatively charged particles weighted with z n for z⩾0.0175, where n = 0.5, 1…, 7, 10, and z is the light-cone momentum fraction. We find, for example, that such an asymmetry is ≈5% for n=2for sin 2 θ w=0.236 and Λ QCD=0.34 GeV. In other words, due to the large number of charge particles produced per event, this SU(2)×U(1) charge asymmetry may be accessible experimentally in e +e − → X already at PEP and PETRA energies.

Front-Back and Charge Asymmetries of Leptons from Hadronic Productions of W± and Z0-Bosons

Using the QCD perturbation theory up to O (α s ) and the standard Weinberg-Salam model we carry out numerical evaluation for the frontback asymmetry and the charge asymmetry of the leptons from the decay of the W ± - and Z 0 -bosons produced in the reactions p p , \bar p p → W ± +anything → l ± + ν l +anything and p p , \bar p p →(γ, Z 0 )+anything → l + + l - +anything. For the scale violating parton distribution we employ the Glück-Owens-Reya parametrization. We show that these asymmetries are fairly large under certain kinematical conditions.

Leptonic front-back asymmetry in [formula omitted] and [formula omitted

We study the differential cross sections d 2 σ/d zd p T 2, d σ/d p T, d σ/d z for p p ̄ → B(→ ℓ 1ℓ 2)+ jet+ X with B = Z 0, W ±at √ s = 540 GeV, and the corresponding quantities for the pp case. The corresponding leptonic front-back asymmetry A( z, p T 2) for these first-order QCD processes is then calculated for the pp̄ case. A( z, p T 2) is found to be p T independent to a very good approximation for p T(jet) ⩾ 3 GeV/ c, with a magnitude similar to that of the zeroth-order process. Since zeroth- and first-order total cross sections are comparable in magnitude, the first-order asymmetry should be an experimentally testable quantity.

Front-Back Asymmetry for the W -Boson Produced in Formulap Collision

Front-Back Asymmetry for the W -Boson Produced in Formulap Collision

Detection of intermediate vector bosons and high-energy weak interactions from decay of hadron resonances

We discuss the detection of parity violating effects in the production of hadron resonances as a way to identify weak interactions at high energies. Numerical results indicate that such effects due to the production of W's and Z's should be observable at Isabelle energies. Observation of such effects may be the best method to establish that high-mass resonances or new behavior of cross sections are not hadronic in origin. By observing hadron resonances with different quantum numbers, it is possible to study the flavor dependence of high-energy weak effects; the energy dependence of the ~0[*r ratio may even be a useful signal of W production. We also calculate predictions for polarized beams. The possibility of observing unconventional kinds of weak interactions is briefly considered. In this paper we want to discuss how weak interactions can be studied at high energies. We will concentrate on productions of W's and Z's but also include some discussion of the possibility of seeing unconventional effects. The usual methods [1-3] involve the production of W's and Z's and their decays into leptons or hadron jets. In particular, the charge asymmetry in pp -~/l+/a - + X, or the frontback asymmetry in p~ ~/a -+ + X would signal a weak-interaction effect [3]. These may well be the best methods, particularly to detect a Z ° by its g+/.t- decay, and they have been studied in some detail. The method we want to emphasize here is the detection of weak effects v/a the parity-violating production of hadron resonances. One can see very simply that such effects may occur. For example, a W decay into q?:l will give a left-handed q in a V- A theory. When making a meson resonance by picking up a ?:1 from the vacuum it will form (say) p's only of helicity 0 and -1 ,'while the strong interactions give equal amounts of helicity 1 and -1. Thus, appropriate comparison of the amounts of helicity 1 and -1 p's can signal a

Production and signature of intermediate vector bosons

The front-back asymmetry of outgoing muons in the inclusive reaction p p → Z(→ μ +μ −)+ anything is calculated in the framework of the Drell-Yan model. We get very general expressions for the front-back asymmetry and the differential cross section in terms of the weak coupling constants and the parton distributions. Results for W ± production and proton-proton collisions are also given. Numerical estimates are made using various parton distributions and the Weinberg-Salam model for definiteness. We comment on the predictions of gauge theories that accommodate the absence of parity violating effects in atomic physics. We also give a new estimate of the inclusive cross sections p p or pp → Z(→ μ + μ −) or W ±(→ μ ± ν μ ) + anything. The effects of asymptotic freedom in the frontback asymmetries and the total cross sectons are investigated. We reanalyze results for the purely leptonic reaction e + e − → γ, Z → μ + μ −.

Photoproduction of Neutral Pions from Hydrogen at Forward Angles from 240 to 480 Mev

Recoil protons from the process $\ensuremath{\gamma}+p\ensuremath{\rightarrow}p+{\ensuremath{\pi}}^{0}$ have been detected by nuclear emulsions placed within a hydrogen-gas target and used to measure the differential cross section for production of neutral pions. In this manner protons of energies as low as 5 Mev can be detected at laboratory angles corresponding to emission of a pion at center-of-momentum (c.m.) angles as low as 26\ifmmode^\circ\else\textdegree\fi{}. This experiment thus supplements that of Oakley and Walker which is in the same range of photon energies (240-480 Mev), but is restricted to pion c.m. angles greater than about 70\ifmmode^\circ\else\textdegree\fi{} owing to higher minimum detectable proton energy. Common experimental points provide intercomparison of absolute values. Angular distributions are analyzed in the form $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}=A+Bcos\ensuremath{\theta}+C{cos}^{2}\ensuremath{\theta}$ in the c.m. system. The combined Oakley-Walker and present data give the average value of the ratio $\frac{A}{C}$ as -1.60\ifmmode\pm\else\textpm\fi{}0.10 in the energy range from 260 to 450 Mev. The coefficient $B$, which gives the front-back asymmetry, passes through zero below the resonance energy of 320 Mev and is positive at higher energies. These results are consistent with magnetic dipole absorption leading to a state of the pion-nucleon system of angular momentum $\frac{3}{2}$, together with a finite amount of $S$-wave interference.