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Mean Voltage (mean + voltage)

Distribution by Scientific Domains

Medical Sciences	80%

Selected Abstracts

Measuring masticatory performance using a new device and ,-carotene in test gummy jelly

JOURNAL OF ORAL REHABILITATION, Issue 11 2010
T. NOKUBI
Summary, Objective methods for evaluating masticatory performance are invaluable for quantitative comparisons between various dental treatments as well as diagnosing masticatory disorder. The purpose of this study was to develop an accurate method for automatically measuring masticatory performance using a new measuring device consisting of light-emitting diodes and a photodiode and test gummy jelly. First, the relationship between six known ,-carotene concentrations in aqueous solution and the voltage values exhibited on a photodiode was investigated. Mean voltage obtained by red light incident on the photodiode indicated a significantly high correlation (r = 0·999 in a cubic function, P < 0·01) with ,-carotene concentration in the aqueous solution. Second, to establish the optimal measuring conditions for evaluating masticatory performance, factors influencing mean voltage were investigated, such as water temperature and times for rinsing the gummy jelly and dissolving ,-carotene from the jelly. A stable mean voltage was obtained by measuring under the following conditions: rinsing water temperature, 35 °C; rinsing time, 30 s; water dissolving temperature, 35 °C; dissolving time, 10 s. Finally, the relationship between seven surface area values of divided gummy jelly and ,-carotene concentrations dissolved from the divided jellies was investigated. The increase in surface area of divided test gummy jelly particles was accurately calculated (r = 0·992, P < 0·001) from mean voltage on the photodiode to change with ,-carotene concentration dissolved from the jelly surface. This new method using test gummy jelly and an automatic measuring device appears useful for precisely evaluating masticatory performance. [source]

A Pilot Study of a Low-Tilt Biphasic Waveform for Transvenous Cardioversion of Atrial Fibrillation: Improved Efficacy Compared with Conventional Capacitor-Based Waveforms in Patients

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008
BENEDICT M. GLOVER M.D.
Background:The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. Methods:We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for ,30 seconds. Results:The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). Conclusion:The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage). [source]

The time course of the motoneurone afterhyperpolarization is related to motor unit twitch speed in human skeletal muscle

THE JOURNAL OF PHYSIOLOGY, Issue 2 2003
E. Roderich Gossen
The relationship between the electrophysiological properties of motoneurones and their muscle units has been established in animal models. A functionally significant relationship exists whereby motoneurones with long post-spike afterhyperpolarizations (AHPs) innervate slow contracting muscle units. The purpose of this study was to determine whether the time course of the AHP as measured by its time constant is associated with the contractile properties of its muscle unit in humans. Using an intramuscular fine wire electrode, 46 motor units were recorded in eight subjects as they held a low force contraction of the first dorsal interosseus muscle for approximately 10 min. By applying a recently validated transform to the interspike interval histogram, the mean voltage versus time trajectory of the motoneurone AHP was determined. Spike-triggered averaging was used to extract the muscle unit twitch from the whole muscle force with strict control over force variability and motor unit discharge rate (interspike intervals between 120 and 200 ms). The AHP time constant was positively correlated to the time to half-force decay (,= 0.36, P < 0.05) and twitch duration (,= 0.57, P < 0.001); however, time to peak force failed to reach significance (,= 0.27, P < 0.07). These results suggest that a similar functional relationship exists in humans between the motoneurone AHP and the muscle unit contractile properties. [source]