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Biomedical Engineering, IEEE Transactions on

Issue 6 • Date Nov. 1976

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Displaying Results 1 - 13 of 13
  • Electromechanical Transduction with Charged Polyelectrolyte Membranes

    Page(s): 421 - 433
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    Collagen and other polyelectrolyte materials in a homogeneous, aqueous electrolyte are studied and modeled as a seat of electromechanical transduction. The frequency response of collagen membranes in a range of chemical environments shows how transduction with a deformable membrane coupled hydrodynamically to an external mechanical system can lead to a mechanical response resulting from an electrical stimulus and an electrical response to a mechanical excitation. Dynamic measurements, which can more easily distinguish between membrane and electrode phenomena, result in electromechanical coupling coefficients that show reciprocity and agree with values determined by stationary techniques. A model representing the membrane at the interfibrillar level by a system of cylindrical pores is developed relating externally measured potentials, membrane deformations, currents, and mass fluxes to equivalent pore radius, fibril diameter, and polyelectrolyte charge. Measured values of the membrane coupling coefficients are then used to infer average microstructural parameters of the membrane that compare favorably to available data based on electron microscopy. View full abstract»

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  • A Mathematical Model of the Human Temperature Regulatory System - Transient Cold Exposure Response

    Page(s): 434 - 444
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    A mathematical model of the human temperature regulatory system which utilizes finite difference techniques and includes new anatomical and basal physiological information, with more detail than previous models, is presented. A cold stress control system which includes both a feedback signal based on head core temperature and feedforward signals based on the skin temperature and the skin heat flux is postulated. Model and direct experimental results (seven temperatures, cardiac output, metabolism, and arm blood flow) are compared for a transient cold exposure. The substantial agreement found suggests that the skin heat flux could be an important input to the temperature regulatory system. View full abstract»

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  • Analog Computer Simulation of Maximum Expiratory Flow Limitation

    Page(s): 445 - 452
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    This paper extends previous modeling work in our laboratory on the simulation of the panting maneuver executed in a body plethysmograph [8] to the simulation of a wider range of pulmonary function tests and, in particular, the maximum expiratory flow-volume (MEFV) curve. The simulation is implemented on an analog computer for ease of parameter manipulation; the effects of changes in several model parameters (such as large and small airway resistance, and airway and lung compliance) on the MEFV curve are discussed. The model structure presented here is much simpler than the ventilatory system models of Fry [6] and Pardaens et al. [18], and yet yields the same information in a diagnostic sense. View full abstract»

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  • Hemodynamic Phenomena in Fusiform Aneurysms - I: Steady Flow Conditions

    Page(s): 453 - 459
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    Pressure and flow distributions are reported at different steady flows for four latex fusiform aneurysm models. The accuracy of results by pitot-static techniques is examined in terms of experimental evidence and theoretical considerations. Results indicate that pressure distributions are associated with the Reynolds number, the degree of wall divergence and the degree of dilation of the sac, and that these parameters are interactive. The Reynolds number was found to have some predictive value for pressure distribution in the aneurysm, but the Bernoulli principle, based on geometrical variation and laminar flow, was usually inapplicable. Also, disturbed flow (eddies, reversal, turbulence) can occur as functions of the interactive parameters. View full abstract»

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  • Scattering of Ultrasound by Blood

    Page(s): 460 - 467
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    The ultrasonic volumetric scattering cross section of the erythrocyte has been measured over a range of frequencies by comparing the rms value of the gated backscattered signal from the blood with that of a wave reflected from a flat reflector with known reflection coefficient. It is found to be proportional to the fourth power of the frequency predicted by the wave scattering theory for small particles in the frequency range from 5 MHz to 15 MHz. The relation between the scattering coefficient and the hematocrit is also examined up to a hematocrit of 45 percent. This coefficient is found to increase along with the hematocrit until it reaches a maximum around hematocrit = 26 percent and then decreases as the hematocrit increases. Twersky's wave scattering theory is applied to describe this result. View full abstract»

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  • Techniques for Improving the Selectivity of Electromyographic Recordings

    Page(s): 467 - 472
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    Several methods aimed at obtaining highly selective electromyographic recordings are studied in human muscle with a multi-electrode technique. It was found that a small electrode size had a major effect in obtaining selective recording. High-pass filtering of the signal resulted in a further increase in the amplitude ratio of action potentials generated by close and remote fibers due to different frequency content of the action potentials. Additional improvement in selectivity could be achieved by bipolar recording. View full abstract»

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  • Determination of Oxygen Tension by Measurement of Net Charge Transport

    Page(s): 472 - 477
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    Conventional electrodes that are used to measure oxygen tension in the biological environment have been plagued by one or more of three major problems: 1) flow sensitivity, 2) instability, and 3) inadequate response time. Pulsatile operation of the electrode has the potential of eliminating these problems. A new technique of measurement using integration of output current has been developed. This new method of measurement enhances the pulsatile operation in the Po2 electrode. The technique effectively determines the difference in charge transport that occurs during the polarization potential. Using this technique, it has been possible to measure net charge transport, which is proportional to the oxygen tension level of whole blood as early as 1 ms after application of the polarization pulse. Also, the subtraction of the discharging current component appears to stabilize electrode drift. The short polarization time required allows for the elimination of flow sensitivity by reducing the extension of the oxygen diffusion gradient to less than 8 ¿m from the electrode face. The short duration of active measurement will tend to decrease poisoning by allowing use of an operating duty cycle of minimal duration. View full abstract»

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  • A Low-Powered 4-Channel Physiological Radio Telemetry System for Use in Surgical Patient Monitoring

    Page(s): 478 - 481
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    A series of 4-channel physiological radio telemetry systems with long battery life and dc response capability have been designed and built. Twenty-one of these systems are used in the operating rooms on patients undergoing surgery at the Duke University Medical Center. The features of these systems are described. View full abstract»

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  • A Moving-Trace Design for Video Systems

    Page(s): 482 - 484
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    During the past decade, closed-circuit television has become an important means of displaying images in medicine. Important concurrent physiological signals in analog form are not readily displayed simultaneously with images using standard television systems. This communication describes a moving-trace design which superimposes analog traces on video images. Investigators can thereby directly visualize and evaluate relationships between images and dynamic physiologic variables. View full abstract»

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  • A Low-Power Combination Electrocardiogram-Respiration Telemetry Transmitter

    Page(s): 484 - 486
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    An FM-FM-modulated radio-telemetry transmitter for detecting and transmitting an electrocardiogram (ECG) and respiration activity simultaneously on a single carrier frequency in the 88-108 MHz band is described. Respiration is detected by the impedance pneumographic principle by using the same pair of electrodes used for the ECG. The circuit requires less than 350 ¿A from a ± 7 V mercury battery supply and about 185 ¿A from a 1.35 V mercury battery. Signals can be transmitted over distances up to 50 ft for about 4 weeks without battery replacement and appreciable changes in calibration. View full abstract»

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  • Contributors

    Page(s): 487 - 489
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    Freely Available from IEEE
  • Author index

    Page(s): 489a - 489c
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    Freely Available from IEEE
  • Subject index

    Page(s): 489c - 489g
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    Freely Available from IEEE

Aims & Scope

IEEE Transactions on Biomedical Engineering contains basic and applied papers dealing with biomedical engineering. Papers range from engineering development in methods and techniques with biomedical applications to experimental and clinical investigations with engineering contributions.

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Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering