Investigations of mucociliary activity in vivo are based on photoelectric recordings of light reflections from the mucosa. The alterations in light intensity produced by the beating cilia are picked up by a photodetector and converted to photoelectric signals. The optimal processing of these signals is not known, but in vitro ...

We describe a programmable spatial-filtering system using bacteriorhodopsin (BR) film as a programmable, optically addressed spatial light modulator illuminated by a single wavelength of light. We use a computer-controlled mirror scanning system to write time-varying filter functions to the BR film and present proof-of-principle experimental results that demonstrate several elementary ...

Pacemakers that augment heart rate (HR) by sensing body motion have been the most frequently prescribed rate responsive pacemakers. Many comparisons between motion-based rate responsive pacemaker models have been published. However, conclusions regarding specific signal processing methods used for rate response (e.g., filters and algorithms) can be affected by device-specific ...

Direction-discrimination performance was measured for two-frame random-dot kinematograms in which one or both frames were spatial frequency filtered with a one octave band-pass filter and the centre frequency of this filter was varied in the range 0.75-9 c/deg independently for each frame. When both frames were filtered so that they ...

Three observers participated in several sessions of identification and speeded classification. Predictions from F. G. Ashby and W. T. Maddox's (1994a) response time (RT) theory of speeded classification were tested. A key theoretical concept is decisional separability (DS), that is, that the decision about the level of 1 component does ...

A comprehensive and flexible arrangement for Digital long-term Acquisition and Processing of Analog Signals (DAPAS) has been developed. It is especially designed for neurophysiological laboratories and mainly based on IBM-compatible PC components. A/D converters are used, which allow sampling rates of up to 100 kHz (up to 16 bits, 1-16 ...

BACKGROUND: Development of electrogastrography, the recording of gastric electric rhythm from cutaneous electrodes, for clinical purposes has been hampered by methodologic problems and the lack of an ambulatory technique. We have evaluated a newly developed system for ambulatory electrogastrography. METHODS: 24-Hour recordings were obtained from 30 healthy volunteers. We used ...

Thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of duration (2, 4, 6, 10, and 14 ms), level (70, 80, and 90 dB SPL) and frequency (250, 500, 1000, 2000, and 4000 Hz). Seven normally hearing listeners were tested at each frequency ...

PURPOSE: To apply digital signal acquisition and analyzing techniques to the collection and interpretation of electromyographic data of the cavernous body. MATERIALS AND METHODS: Electromyographic recordings were performed in the cavernous bodies of anesthetized, spontaneously breathing dogs under resting conditions and after intracavernous pharmacostimulation with norepinephrine, angiotensin II, phentolamine/papaverine, diethylether ...

This study demonstrates how phototransduction cascades and membranes tune photoreceptor response dynamics to image quality, and eliminate noise introduced in cell signalling. Intracellular recordings from intact retina confirm that the light-adapted photoreceptors of the crane fly Tipula paludosa (Diptera; Tipulidae) have a slow response, appropriate for their visual ecology. To ...

Light-induced molecule reorientation in dye-doped liquid crystals has been applied to nonlinear spatial filtering of periodic patterns. Photoisomerization of azo-dye molecules leads to local alignment changes in the liquidcrystal molecules because of interaction among the molecules. Consequently the polarization of transmitted light is modulated, depending on the induced light intensity. ...

A mechanical filter developed to improved the performances of an artificial heart whose electrical motor has a reciprocating motion is presented. The filter phases the mechanical load strongly reducing its inertial component (which is of the same order of magnitude as the useful load). The analysis reported for a prototype ...

A systematic study of the effects of poling time and applied voltage on second-harmonic (SH) generation in thermally poled silica glass reveals that the SH signal is proportional to the square of the applied voltage and that the speed of the poling process increases with the applied voltage. Prior treatment ...

We studied cardiac contamination of magnetoencephalographic signals in eight healthy volunteers. The signals were recorded in a magnetically shielded room while the subject was sitting under a whole-scalp neuromagnetometer and were averaged time-locked to the R wave of the electrocardiogram. The maximum amplitude of the cardiac artifact varied between the ...

The mapping of complex-valued functions onto phase-only spatial light modulators is examined. Random phase encoding effectively adds amplitude control to the phase-only filter and can be used to trade off systematic errors of the phase-only filter for random errors. This is illustrated for the problem of recognizing a threedimensional object ...

Two-frame random-element kinematograms were used to study the matching algorithm employed by the visual system to keep track of moving elements. Previous data have shown that the maximum spatial displacement detectable (dmax) for random-dot kinematogram stimuli increases both with increasing dot size and with decreasing centre frequency for spatially band-pass ...

There is recent evidence that both linear and non-linear filtering operations subserve stereoscopic localization. For example, for spatially band-pass stimuli, the overall Gaussian envelope, which is not explicitly represented by the output of linear filters, can provide coarse disparity information. Here we ask three questions about the nature of this ...

We have investigated the relative performance of an adaptive and nonadaptive 60-Hz notch filter applied to an ECG signal. We evaluated the performance of the two implementations with respect to adaptation rate (or transient response time), signal distortion, and implementation complexity. We also investigated the relative effect of adaptive and ...

OBJECTIVE: To evaluate awareness and knowledge of cigarette filter ventilation in a national probability sample of smokers of Ultra-light, Light, and regular cigarettes. DESIGN: Random-digit-dialling and computer-assisted telephone interviewing was used on a probability sample of daily cigarette smokers (ages 18 and above). SUBJECTS AND SETTING: 218 Smokers of Ultra-light ...

The application of an artificial neural network filter (ANNF) to estimate the visual evoked potential (VEP) is presented. VEP is the gross electrical response of the brain to visual stimuli. Due to the low SNR, it is difficult to extract response from individual stimulus trials. The ANNF we used estimates ...

We introduce a novel, adaptive image representation using spatially varying wavelet packets (WPs), Our adaptive representation uses the fast double-tree algorithm introduced previously (Herley et al., 1993) to optimize an operational rate-distortion (R-D) cost function, as is appropriate for the lossy image compression framework. This involves jointly determining which filter ...

The photoplethysmorgraphic signal (PPG) from forearm skin and the ECG were recorded simultaneously from healthy subjects. The optical signal was derived with a fibre-optic probe which consisted of 61 fibre pairs. The peak-to-peak averaged a.c.-signal was calculated. The dependency of this signal and the signal-to-noise ratio (SNR) on the light ...

Synchronized electrical stimulation was used to study the heart rate (HR) response to fluctuations in parasympathetic input to the sinus node in anesthetized dogs. This was obtained by varying the time interval (interpulse interval) between stimulatory vagal pulses. Spectral methods were used to estimate transfer functions between the excitatory signal ...

This study investigated the relations between theoretical auditory filters and "attentional filters" observed when measuring the detectability in noise of tones of expected or unexpected (probe) frequency. The effect of the level of the noise and the frequency range (narrow or wide) of the probes was assessed. For each 2IFC ...

Ventricular late potentials are small ECG components that have significant diagnostic importance. Temporal averaging is used to recover these signals from high levels of background noise, but is not the optimum approach. A new form of hybrid time-frequency adaptive filtering is introduced that is based on signal division into a ...

A method for quantifying the fluctuations of the QRS electrocardiogram over the flat (unrolled) thoracic surface in normal subjects is presented. Serial comparisons were performed on 32-lead ECG recordings and body surface maps from seven healthy men, using as similarity measures correlation and RMS-difference in both time-signal and 2D map ...

OBJECTIVE--To determine whether standard manual frequency filters in the ON and OFF settings affected P-QRS-T voltages, discover whether recorded P-QRS-T voltages vary between commercial electrocardiographs, assess effects of frequency filters on base-line artifact, and evaluate ECG frequency content by high-fidelity recordings subjected to digital filters with variable frequencies. DESIGN--Sequential 10-lead ...

Filtering of electrode-recorded activity before averaging is used in evoked-potential measurements to reduce background noise under the assumption that unwanted spectral components will be suppressed without substantially altering neural activity. Desired filter characteristics depend on signal and noise spectra and filter choice can affect the validity and efficiency of ABR ...

The current study investigated perceptual constancy for spectral slope discrimination when fundamental frequency (F0) and spectral shape were varied across three complex stimuli within a single trial. The three stimulus variables were global or emergent properties of a complex sound. The selection of the stimulus variables was in keeping with ...

The shape of the auditory filter was estimated at center frequencies of 4, 12, 14, and 16 kHz for normally hearing subjects, using the notched-noise method. A specially designed sound delivery system was used to generate a high-frequency masking noise with a flat spectrum. For all test frequencies, the auditory ...

An adaptive time constant filter is derived for electromyographic (EMG) signal processing in prosthetic control applications. The analysis indicates that the mean-squared estimation error can be reduced by varying the time constant of the filter as a function of the signal and its derivative. Results of several experiments indicated this ...

Reductions of the soliton interactions and jitter by the upsliding-frequency filter, the downsliding-frequency filter, and the zigzag-sliding-frequency filter are numerically studied. It is shown that the most effective filter for reducing the soliton interactions is the zigzag-sliding-frequency filter.

Butterworth filters of second or higher order periodically inserted along a soliton transmission line, although they are flat at bandpass center, give to first order a nonzero restoring force for frequency and amplitude displacements. The amplified spontaneous emission generated at the filter center frequency is significantly less than that generated ...

The purpose of this paper is to analytically evaluate and compare two of the most common methods for measuring respiration-related heart rate fluctuations: linear detrended heart rate power spectral analysis and the Porges technique of filtered variance. Low-frequency power was removed from instantaneous 4-Hz R-R interval signals using either a ...

The present work introduces a running discrete Fourier transform (RDFT) for time-frequency analysis (TFA) of nonstationary short-term signals. The RDFT algorithm adapts a window function, which has adjustable time-frequency characteristics. A generalized weighting filter was proposed, which maps the time-dependent signal into the time-frequency plane. As an example the weighting ...

The ability of listeners to detect the temporal asynchrony of a single harmonic in complex sounds was measured. The listeners discriminated an asynchronous complex from one in which all harmonics were synchronous (standard). The asynchrony was created either at the onset or offset of the complex. In the asynchronous complex, ...

An algorithm for computing correlation filters based on synthetic discriminant functions that can be displayed on current spatial light modulators is presented. The procedure is nondivergent, computationally feasible, and capable of producing multiple solutions, thus overcoming some of the pitfalls of previous methods.

There is a need for methods capable of increasing the detectability of transient-evoked otoacoustic emissions (TEOAE). Detection of an emission is based commonly on either visual inspection and cross-correlation between replicate recordings or cross-spectral analysis. Performance of these methods is obviously influenced by the residual noise level. Residual noise is ...

The aim of the paper is to determine the speed of the neurological response to cerebral artery occlusion by monitoring transient changes in somatosensory evoked potentials (SEPs). SEPs, continuously monitored during temporary clipping of the middle cerebral artery (MCA) in anaesthetised cats, are analysed. The SEP signals are modelled by ...

A new method to detect steady-state evoked potentials (EPs) is presented. The technique is based on a two-weight recursive least squares (RLS) adaptive filter and the Tcirc2 statistic. Simulations with known sinusoids buried in Gaussian noise and in EEG noise indicate that the adaptive filter can detect signals at 3 ...

A concept for optical temperature sensing based on the differential spectral reflectivity/transmittance from a multilayer dielectric edge filter is described and demonstrated. Two wavelengths, λ(1) and λ(2), from the spectrum of a broadband light source are selected so that they are located on the sloped and flat regions of the ...

A 2-weight adaptive filter that determines the amplitude and phase of steady-state evoked potentials is presented. Reference signals are derived from the visual stimulator that are related to corresponding harmonics of the response and the filter weights are adjusted so as to minimize the squared estimation error between the reference ...

Recent investigations of texture and motion perception suggest two early filtering stages: an initial stage of selective linear filtering followed by rectification and a second stage of linear filtering. Here we demonstrate that there are differently scaled second-stage filters, and we measure their contrast modulation sensitivity as a function of ...

The ensemble average of Pattern Shift Visual Evoked Potentials (PSVEP) signals is seriously affected by random latency variations encountered in each individual sweep which is modeled as a continuous signal with linear segments and well-shaped triangular peaks. This effect is causing the smoothed peaks of the averaged PSVEP waveforms. It ...

The effect of combining low-pass spatial filtering with the first-arriving-light method for imaging through a scattering medium was investigated. The modification is highly effective for media having a significant specular transmission component but is essentially ineffective for media without a specular component.

This paper describes a real time digital adaptive filter for processing myoelectric signals. The filter time constant is automatically selected by the adaptation algorithm, giving a significant improvement over linear filters for estimating the muscle force and controlling a prosthetic device. Interference from mains sources often produces problems for myoelectric ...

An amplitude-modulated circular-harmonic filter is proposed for rotation-invariant pattern recognition. We investigate the filter characteristics by varying two design parameters, A(ρ) and B(ρ), and select optimum values to design an amplitude-modulated circular-harmonic filter. When compared with the phase-only circular-harmonic filter, the amplitude-modulated circular-harmonic filter is found to yield a sharper ...

Computer simulations of photorefractive thresholding filters for the reduction of artifact or dust noise demonstrate an increase in signal-to-noise ratio (SNR) of 70% to 95%, respectively, of that provided by the Wiener filter for inputs with a SNR of approximately 3. These simple, nearly optimal filters use a spectral thresholding ...

A new adaptive postprocessing algorithm to enhance the quality of a noisy video sequence is presented. The algorithm recognizes that the visibility of noise depends on local signal characteristics. It therefore classifies the video signal into different classes and uses separate nonlinear filters matched to each class. The most general ...

The power-line frequency interference in electrocardiographic signals is eliminated to enhance the signal characteristics for diagnosis. The power-line frequency normally varies +/- 1.5 Hz from its standard value of 50 Hz. In the present work, the performances of the linear FIR filter, Wave digital filter (WDF) and adaptive filter for ...