Even though there are several deterministic methods for the modeling of linear systems, there is no standard method for the modeling of nonlinear systems. Most biological systems can be thought of as nonlinear systems...
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Even though there are several deterministic methods for the modeling of linear systems, there is no standard method for the modeling of nonlinear systems. Most biological systems can be thought of as nonlinear systems. For the modeling of biological systems the authors have studied nonlinear systems using genetic programming. Time series were generated from the simple known nonlinear dynamics. Then nonlinear dynamics was estimated from these time series using genetic programming. For the tested nonlinear systems this suggested method estimated the nonlinear dynamics correctly. This method also has been applied for the modeling of the dynamics of the 24-hour electrocardiogram.
We describe initial results of a new hybrid digital and analog design for tracking the retina and controlling the laser beam. The results demonstrate tracking rates which exceed the equivalent of 50 degrees per second...
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We describe initial results of a new hybrid digital and analog design for tracking the retina and controlling the laser beam. The results demonstrate tracking rates which exceed the equivalent of 50 degrees per second in the eye, with automatic lesion pattern creation and robust loss of lock detection. Robotically-assisted laser surgery to treat conditions such as diabetic retinopathy, macular degeneration, and retinal tears can now be realized under clinical conditions with requisite safety using standard video hardware and inexpensive optical components.
This paper emphasizes the statistical properties of the wavelet transform (WT) and discusses some examples of applications in medicine and biology. The redundant forms of the transform (continuous wavelet transform (C...
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This paper emphasizes the statistical properties of the wavelet transform (WT) and discusses some examples of applications in medicine and biology. The redundant forms of the transform (continuous wavelet transform (CWT) and wavelet frames) are well suited for detection tasks (e.g., spikes in EEG, or microcalcifications in mammograms). The CWT, in particular, can be interpreted as a prewhitening multi-scale matched filter. Redundant wavelet decompositions are also very useful for the characterization of singularities, as well as for the time-frequency analysis of non-stationary signals. We discuss some examples of applications in phonocardiography, electrocardiography (EGG), and electroencephalography (EEG). Wavelet bases (WB) provide a similar, non-redundant decomposition of a signal in terms of the shifts and dilations of a wavelet. This makes WB well suited for any of the tasks for which block transforms have been used traditionally. Wavelets, however, may present certain advantages because they can improve the signal-to-noise ratio, while retaining a certain degree of localization in the time (or space) domain. We present three illustrative examples. The first is a denoising technique that applies a soft threshold in the wavelet domain. The second is a more refined version that uses generalized Wiener filtering. The third is a statistical method for detecting and locating patterns of brain activity in functional images acquired using magnetic resonance imaging (MRI). We conclude by describing a wavelet generalization of the classical Karhunen-Loeve transform.
Three different frequency-domain techniques, the Spectral F-Test (SFT), Component Synchrony Measure (CSM) and Magnitude-Squared Coherence (MSC) have been studied for the detection of responses in the EEG to repetitive...
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Three different frequency-domain techniques, the Spectral F-Test (SFT), Component Synchrony Measure (CSM) and Magnitude-Squared Coherence (MSC) have been studied for the detection of responses in the EEG to repetitive somatosensitive stimulation (RSSS). In simulations, the three techniques were tested and the performance of the detectors compared. In real EEG data (approximately 10 second segments), spectral changes under RSSS at 4 and 8 Hz were found; CSM and MSC performed better than SFT, as was also found in simulations.
作者：
M. UnserImage Processing Group
Biomedical Engineering and Instrumentation Program National Institutes of Health DHHS MD USA
The order of a wavelet transform is typically given by the number of vanishing moments of the analysis wavelet. The Strang-Fix (1971) conditions imply that the error for an orthogonal wavelet approximation at scale a=...
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The order of a wavelet transform is typically given by the number of vanishing moments of the analysis wavelet. The Strang-Fix (1971) conditions imply that the error for an orthogonal wavelet approximation at scale a=2/sup -i/ globally decays as a/sup L/, where L is the order of the transform. This is why, for a given number of scales, higher order wavelet transforms usually result in better signal approximations. We show that this result carries over for the general biorthogonal case and that the rate of decay of the error is determined by the order properties of the synthesis scaling function alone. We also derive asymptotic error formulas and show that biorthogonal wavelet transforms are equivalent to their corresponding orthogonal projector as the scale goes to zero. These results strengthen Sweldens (see Numer. Math., vol.68, no.3, p.377-401, 1994) earlier analysis and confirm that the approximation power of biorthogonal and (semi-)orthogonal wavelet expansions is essentially the same. Finally, we compare the asymptotic performance of various wavelet transforms and briefly discuss the advantages of splines. We also indicate how the smoothness of the basis functions is beneficial in reducing the approximation error.
The utilization of 12 neonatal intensive care technologies was recorded in 193 patients. An index of utilization (P(u)) was adopted to classify these technologies into three sub-groups corresponding to low (P(u) 85%)...
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The utilization of 12 neonatal intensive care technologies was recorded in 193 patients. An index of utilization (P(u)) was adopted to classify these technologies into three sub-groups corresponding to low (P(u) < 15%), medium (15% ≤ P(u) ≤ 85%), and high (P(u) > 85%) intensity of use. No models were developed for technologies with high intensity of use (intravenous hydration, warming, micro-haematocrit, heart rate monitoring). Multiple linear regression was used to predict the utilization of technologies with medium intensity of use (gasometry, oxygen hood, CPAP, mechanical ventilation), and multiple logistic regression was used with the same purpose for technologies with low intensity of use (exchange transfusion, bicarbonate, adrenaline, echocardiography). Both methods yielded significant models (P < 0.05) which can be used to improve planning and management of technology in neonatal intensive care units.
For a microcomputer-based tutorial system, algorithms based on Surfaces have been implemented, using classification procedures for spatial position and normals of faces of anatomical structures, in order to establish ...
For a microcomputer-based tutorial system, algorithms based on Surfaces have been implemented, using classification procedures for spatial position and normals of faces of anatomical structures, in order to establish a priori knowledge of visibility, distance and colouring. With the proposed approach reductions in computing time are always obtained, but the degree depends on the viewing angle. For a lateral-anterior view of the skull (31,873 faces), reductions of 33% were obtained in the number of read operations and 59% for visibility test.
In this work the authors present a quantitative comparison of the four Nearest-Neighbour, Planar Spline and Spherical Spline interpolation techniques. Simulated distributions of scalp potentials derived from dipoles i...
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In this work the authors present a quantitative comparison of the four Nearest-Neighbour, Planar Spline and Spherical Spline interpolation techniques. Simulated distributions of scalp potentials derived from dipoles inside a model consisting of three concentric spherical shells were evaluated using global error measures. Differences in the performance of the three interpolation techniques depending on the location of the source were found. The results indicate that for electrode densities similar to those provided by the 10-20 system, none of the interpolation technique is clearly superior, with relative performance depending strongly on electrode location.
During pregnancy, painful problems of posture are common. With the alterations in weight and weight-distribution, changes in body balance may also be expected. In the present work, postural sway of normal pregnant wom...
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During pregnancy, painful problems of posture are common. With the alterations in weight and weight-distribution, changes in body balance may also be expected. In the present work, postural sway of normal pregnant women was analysed through stabilometric exams. Taking parameters of power in frequency bands in the forward/backward and lateral directions, it was found that alterations only occurred below 0.5 Hz under eyes closed/feet apart and eyes open/feet together protocols. The authors conclude that the mechanisms of balance control generally seem able to compensate body sway for the physical changes during pregnancy.
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