Enhanced information transmission with signal dependent noise in an array of LIF neurons

Sensory cells usually transmit information to afferent neurons via chemical synapses, in which the level of noise is dependent on an applied stimulus. Taking into account such dependence, we model a sensory system as an array of LIF neurons with a common signal. We show that information transmission is enhanced by a nonzero level of noise. Moreover, we demonstrate a phenomenon similar to suprathreshold stochastic resonance with additive noise. We remark that many properties of information transmission found for the LIF neurons was predicted by us before with simple binary units [Phys. Rev. E 75, 021121 (2007)]. This confirmation of our predictions allows us to point out identical roots of the phenomena found in the simple threshold systems and more complex LIF neurons.     

The breakdown of scaling due to the possible structure of nucleonic constituents

Aside from relativistic quark model representations which correspond to the picture of point-like quarks, the current algebra also allows representations which can be interpreted in terms of quarks with structure. We speculate about the possibility that the experimentally observed small deviations from scaling for higher values of q² point out the extended nature of nucleon constituents.     

A model for the calculation of noise transmission inside dwellings: application to aircraft noise

A numerical model of sound transmission inside dwellings has been developed. It is based on a decoupled method mixing integral, modal and geometric approaches. Kropp's formulation has been adapted to take balconies into account. Architectural effects such as projected roofs or nearby buildings have been analysed. Sound transmission is strongly affected by the angle of incidence of incoming waves. The proposed approach makes use of velocity fields on windows either computed or measured with a laser vibrometer. Comparisons between computations and measurements are reported.     

Heat propagation due to torsional vibration of shafts

Torsional vibration of rotating shafts can yield substantial temperatures in the shaft due to heat generated from material damping. It has been recently observed that such a situation in electric generators can lead to insulation failures and machine outages. In the study reported here forced torsional vibration is assumed, and both lumped mass and continuous systems are considered. The hysteretic model for material damping is used to yield the heat generation in the elastic deformation range and an elastoplastic material is assumed in the plastic range. The heat conduction equation is solved for a cylindrical shaft with surface cooling. Closed form solutions and expressions for the maximum temperatures and the maximum surface temperatures are obtained and tabulated for design purposes. It is shown that substantial temperatures can develop in shafts undergoing torsional vibration.     

Measurement of the high-voltage breakdown channel propagation velocity in crystalline and amorphous quartz on a subnanosecond time scale

The formation time of a breakdown channel in 0.5- to 1.6-mm-thick crystalline and amorphous quartz samples is measured at a pulse voltage of 240 kV, and the effective velocity and direction of breakdown front propagation are determined. In the crystal, the velocity is more than 2.5 times higher than in amorphous SiO₂. This may be associated with a higher mobility of free carriers and, consequently, with a quicker motion of the avalanche breakdown front owing to a higher effective velocity of nonequilibrium carriers responsible for the high-energy tail of the distribution function.     

The WKBZ mode approach to sound propagation in the two-axis underwater channel

TheprojectissupportedbyNationalNaturalScienceFoundationofChinaI.IntroductionIndeepocean1soundpropagationstronglydependsonthesoundspeedprofileoftheseawater.Becauseoftheinfluenceoftheclimaticcondition,awell-mixedsurfacelayerofisothermalwater,whichisalsocalledsurfacechannel,canbefoundinmallyoceanareasinautumnandwinter.WhenthesurfacechannelandtheSOFARchannelexistsimultaneously,thetwo-axisunderwaterchanneloccurs.Soundpropagationinthetwo-axisunderwaterchannelisatypicalwaveproblem.Owingtothemut…     

Impact of channel baud-rate on logarithmic digital backward propagation in DP-QPSK system with uncompensated transmission links

We numerically investigate the impact of channel baud-rate on the performance of logarithmic step-size based spilt-step Fourier method (SSFM). This algorithm is used to implement digital backward propagation (DBP) to efficiently compensate fiber chromatic dispersion (CD) and non-linearities (NL). The DBP method is implemented in N-channel dual-polarization quadrature phase shift keying (DP-QPSK) transmission over 2000 km standard single mode fiber (SMF) with no in-line optical dispersion compensation. We investigate the same-capacity and same-bandwidth transmission systems with 56 Gbit/s/ch (14 GBaud), 112 Gbit/s/ch (28 GBaud) and 224 Gbit/s/ch (56 GBaud). Each system has the bandwidth occupancy of 500 GHz with a total transmission capacity of 1.12 Tbit/s. Moreover, we have also compared the multiple channel transmission performance with single channel transmission to quantify the impact of inter-channel (cross-phase modulation ‘XPM’ and four-wave mixing ‘FWM’) and intra-channel (self-phase modulation ‘SPM’) non-linearities. The logarithmic step-size based DBP algorithm (L-DBP) depicts efficient mitigation of CD and NL impairments. The benefit of the logarithmic step-size is the reduced complexity and computational time for higher baud-rate transmission systems.     

Prediction of noise changes due to traffic speed control

The effects of vehicle speed variation on road traffic noise are analyzed. The steady speed motion is replaced by deceleration, cruise, and acceleration. Because of a relatively loud acceleration noise, such a speed variation results not only in the noise decrease zones, but in the noise increase zones as well. The location of these zones depends slightly upon the ground covering (grass, concrete, etc.). Conversely, their boundaries change dramatically with the parameters describing noise emission during deceleration, cruise, and acceleration. For example, the Japanese and Polish models of noise emission have been applied. The critical length L(*) of the cruise segment of the road is introduced: for L>L(*) the sound energy decline (due to speed reduction) compensates the sound energy growth (due to acceleration). The results obtained could be useful for road administrators.     

Application of the beam propagation method to diffused transmission gratings

In this paper results for the diffraction characteristics of phase gratings calculated by the beam propagation method and by a rigorous integral equation method are presented, with the latter results serving as a reference. The configurations under consideration have refractive index changes which are realistic for ion exchange processes in glass. Thus, multiple reflections have only little influence which makes the beam propagation method applicable to the problem. Typically, the diffraction efficiencies computed by both methods differ by less than 2%. In contrast to the integral equation method, the beam propagation method works with a definable lateral field profile, enabling the modelling of a grating within a complete device design including the near field pattern. This revised version was published online in November 2006 with corrections to the Cover Date.     

Inversion of spin photocurrent due to resonant transmission

We report on the inversion of spin-dependent photocurrent via interface localized states formed at the interface of an Fe/n-AlGaAs/GaAs quantum well heterostructure by means of an optical spin orientation technique. A careful adjustment of the excitation photon energy, which is determined by a separate analysis of electroluminescence spectra under a spin injection condition, enables us to explore the spin-dependent characteristics of photoelectron transmission from the quantum well into Fe. The bias dependence of the spin-dependent photocurrent shows clear spikelike features at the voltage which is compatible with the formation of the interface localized resonant states in the Schottky depletion layer.     

Self-reported sleep disturbances due to railway noise: exposure-response relationships for nighttime equivalent and maximum noise levels

The objective of the present survey was to study self-reported sleep disturbances due to railway noise with respect to nighttime equivalent noise level (L(p,A,eq,night)) and maximum noise level (L(p,A,max)). A sample of 1349 people in and around Oslo in Norway exposed to railway noise was studied in a cross-sectional survey to obtain data on sleep disturbances, sleep problems due to noise, and personal characteristics including noise sensitivity. Individual noise exposure levels were determined outside of the bedroom facade, the most-exposed facade, and inside the respondents' bedrooms. The exposure-response relationships were analyzed by using logistic regression models, controlling for possible modifying factors including the number of noise events (train pass-by frequency). L(p,A,eq,night) and L(p,A,max) were significantly correlated, and the proportion of reported noise-induced sleep problems increased as both L(p,A,eq,night) and L(p,A,max) increased. Noise sensitivity, type of bedroom window, and pass-by frequency were significant factors affecting noise-induced sleep disturbances, in addition to the noise exposure level. Because about half of the study population did not use a bedroom at the most-exposed side of the house, the exposure-response curve obtained by using noise levels for the most-exposed facade underestimated noise-induced sleep disturbance for those who actually have their bedroom at the most-exposed facade.     

The effect of additive noise on the signal phase noise in radio over fiber links

The effect of additive noise on the signal phase noise in radio over fiber links was studied and the theory model of the output signal phase noise was proposed. The theory model was verified by experiments. The results suggest that the signal phase-noise performance decreases due to enhancing the average photocurrent of the photodiode. In practical applications, in order to reduce the deterioration of reference's phase noise, it is necessary to improve the average photocurrent when the opto–electro modulator works at quadrature points.     

Low noise amplification of an optically carried microwave signal: application to atom interferometry

In this paper, we report a new scheme to amplify a microwave signal carried on a laser light at λ=852 nm. The amplification is done via a semiconductor tapered amplifier and this scheme is used to drive stimulated Raman transitions in an atom interferometer. Sideband generation in the amplifier, due to self-phase and amplitude modulation, is investigated and characterized. We also demonstrate that the amplifier does not induce any significant phase-noise on the beating signal. Finally, the degradation of the performances of the interferometer due to the amplification process is shown to be negligible.     

Motion reversal of molecular motor assemblies due to weak noise

Bidirectional motion is an example of collective behavior of molecular motors. It occurs at finite noise level in a nonequilibrium system. We consider this problem as a first exit problem. We identify the noise strength by doing an expansion of a master equation and apply the Wentzell-Freidlin theory to define an effective nonequilibrium potential and provide analytical estimates of the reversal time. Our results match very well with the results of stochastic simulations.     

Experimental study of annoyance due to low frequency environmental noise

We have carried out a study of a particular environmental noise phenomenon which appears to be a cause of real and severe disturbance to certain people. The study has been based on field measurements and on laboratory studies and questioning involving two people who have suffered from this problem for some years. The disturbance is heard by them as a ‘throbbing’ sound and is particularly prevalent indoors, rather than out-of-doors.The study has indicated that the phenomenon arises with a broad band spectrum which lies close to the hearing threshold and which is unbalanced to the extent that the major stimulus occurs in the frequency range 20–100 Hz. It is suggested that the unbalanced spectrum may arise as a result of low frequency noise generated by distant industrial sources.