Optimized wavelets for blind separation of nonstationary surface myoelectric signals

Surface electromyography (EMG) signals detected over the skin surface may be mixtures of signals generated by many active muscles due to poor spatial selectivity of the recording. In this paper, we propose a new method for blind source separation (BSS) of nonstationary signals modeled as linear instantaneous mixtures. The method is based on whitening of the observations and rotation of the whitened observations. The rotation is performed by joint diagonalization of a set of spatial wavelet distributions (SWDs). The SWDs depend on the selection of the mother wavelet which can be defined by unconstrained parameters via the lattice parameterization within the multiresolution analysis framework. As the sources are classically supposed to be mutually uncorrelated, the design parameters of the mother wavelet can be blindly optimized by minimizing the average (over time lags) cross correlation between the estimated sources. The method was tested on simulated and experimental surface EMG signals and results were compared with those obtained with spatial time-frequency distributions and with second-order statistics (only spectral information). On a set of simulated signals, for 10-dB signal-to-noise ratio (SNR), the cross-correlation coefficient between original and estimated sources was 0.92 +/- 0.07 with wavelet optimization, 0.74 +/- 0.09 with the wavelet leading to the poorest performance, 0.85 +/- 0.07 with Wigner-Ville distribution, 0.86 +/- 0.07 with Choi-Williams distribution, and 0.73 +/- 0.05 with second-order statistics. In experimental conditions, when the flexor carpi radialis and pronator teres were concomitantly active for 50% of the time, crosstalk was 55.2 +/- 10.0% before BSS and was reduced to 15.2 +/- 6.3% with wavelet optimization, 30.1 +/- 15.0% with the worst wavelet, 28.3 +/- 12.3% with Wigner-Ville distribution, 26.2 +/- 12.0% with Choi-Williams distribution, and 35.1 +/- 15.5% with second-order statistics. In conclusion, the proposed approach resulted in better performance than previous methods for the separation of nonstationary myoelectric signals.     

Phonon density of states of LaFeAsO(1-x)Fx

We have studied the phonon density of states (PDOS) in LaFeAsO(1-x)Fx with inelastic neutron scattering methods. The PDOS of the parent compound (x=0) is very similar to the PDOS of samples optimally doped with fluorine to achieve the maximum Tc (x approximately 0.1). Good agreement is found between the experimental PDOS and first-principles calculations with the exception of a small difference in Fe mode frequencies. The PDOS reported here is not consistent with conventional electron-phonon mediated superconductivity.     

Investigation of the Kr + Au system at 22 MeV/u

With laser-atomic-beam-spectroscopy the hyperfinestructure splitting constants A, B and the lifetimes τ of the Mn I levels 3d⁵4s4p z⁴p_3/2,5/2 were determined from the UV intercombination lines 321,7 nm and 322,5 nm. We obtained: A=?821(3)MHz, B=?40(30)MHz, τ=1120(50)nsec for the J=3/2 level and A=?607,8(1,5)MHz, B=+75(15)MHz, τ=970(50)nsec for the J=5/2 level.     

Calculation and analysis of electromagnetic scattering by helicopter rotating blades

This paper describes an application of physical optics and the method of equivalent currents to the calculation of radar cross section (RCS) of a helicopter rotor. The problem is treated using a quasi-stationary approach. The calculation can be parameterized as a function of the locations of the radar transmitter and receiver in relation to the rotor center. Therefore, this offers the possibility of monostatic and bistatic simulations in the far field and near field. Blade geometry is taken into account using a triangular meshing generated by the I-DEAS meshing software. Digital applications are presented and the effects on the RCS spectrum of incidence, frequency, blade number, and the near field are analyzed.     

Preparative separation of pyrogens from proteins by isoelectric focusing using a multicompartment electrolyser with Immobiline membranes

Due to the nature of lipopolysaccharide endotoxin structures of bacterial pyrogens, their removal from solutions containing therapeutic proteins is often a problem in the pharmaceutical industry. In this report we describe the application of electromotive force to dislodge lipopolysaccharide endotoxins from proteins. This was performed by employing a multicompartment electrolyzer fitted with Immobiline membranes of specified pIs. A thousand-fold reduction of endotoxin could be achieved in the model test system described. This contribution describes the use of a new recycling isoelectric focusing approach without the use of carrier ampholytes.     

Modifications chimiques du polyallylbenzène influence sur ses propriétés électriques

Polyallylbenzene [2] exhibits interesting dielectric characteristics. Chemical modifications of the material are made in order to increase the dielectric constant while preserving low dielectric losses as compared to those of usual polymers. The study of the synthesis, molecular and structural characterizations of the modified polymers as well as electrical measurements are presented.     

Plasmon-mediated interaction between physically adsorbed atoms — curvature effect

The quantum-mechanical formulation of the non-retarded interaction of a single atom with a metallic surface is extended to the study of two neighboring atoms in the presence of a metallic surface. The atoms are represented as fluctuating three-dimensional oscillators, whereas the metal gives a dynamical response through the interaction of the surface plasma oscillations with the external fluctuating dipole. In the total energy balance, one finds, besides the two-body atom-atom and atom-surface interactions, a three-body contribution arising from the surface mediated atom-atom interaction. The flat-surface case is first treated to illustrate how this plasmon-mediated interaction takes place. Then for the general case of two atoms in presence of a curved surface, the three-body interaction term is evaluated. Application is made to the case of a surface having the shape of a spherical particle or a spherical cavity. Numerical evaluation for the case of two argon atoms on solid aluminium has been made in order to determine the relative importance of the modified lateral interaction and the dependence on the radius for the particle or the cavity configuration.     

Spartanburg, S.C.: Testing the Effectiveness of Video, Voice, and Data Feedback

The experiment "points to the broad and pleasant conclusion that return voice and data functions can probably be used effectively for most forms of education and training programs."     

Angular distributions of fission and deep inelastic products of the system Ar+Au at 285 MeV

The angular distribution of the heavy products from the interaction of 285 MeV ions⁴⁰Ar on an Au target has been analysed through a large angular range (4°–165° lab angles). The results exhibit two components: the fission component corresponding to relatively symmetric masses, and a deep inelastic one which peaks in the angular range 100°–140° (c.m angles). The fission component exhibit the usual 1/sinθ pattern, proving that, in spite of a zero fission barrier, the life time of the system exceeds the rotation period. The relative cross sections for the fission and deep inelastic processes are discussed.