Articles: biological-models.
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Analysis of the mechanisms underlying the clinical effects of different drugs is a vital part of psychopharmacology. It is fair to say, however, that such analyses have thus far met with little success. This lack of success can be traced to a variety of sources that have flawed the analytical process itself. Detailed examination of these sources not only illuminates the nature of the flaws they engender, but suggests ways in which the analytic process can be modified so as to be a more fruitful one.
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Critical care medicine · Mar 1983
Pressure-time relationships of pressure-limited neonatal ventilators.
A pressure-limited ventilator (Bourns BP-200, Anaheim, CA) and a simple, manually operated constant flow ventilator were studied using a commercially available infant lung simulator (Bourns LS-130, Anaheim, CA). The characteristics of inspiratory pressure-time relationships during ventilation with these ventilators were analyzed. ⋯ Qualitatively similar tracings were obtained with the BP-200 during normal ventilation, with simulated airway obstruction and thoracic restriction. These findings suggest that monitoring pressure-time relationships may be useful in the qualitative assessment of resistance and compliance during pressure-limited ventilation of neonates.
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Light-evoked current fluctuations have been recorded from ventral photoreceptors of Limulus for light intensity from threshold up to 10(5) times threshold. These data are analyzed in terms of the adapting bump noise model, which postulates that (a) the response to light is a summation of bumps; and (b) the average size of bump decreases with light intensity, and this is the major mechanism of light adaptation. ⋯ From responses to very dim light, it is found that the average impulse response (average of a large number of responses to dim flashes) can be predicted from knowledge of both the noise characteristics under steady light and the dispersion of latencies of individual bumps. Over the range of light intensities studied, it is shown that (a) the bump rate increases in strict proportionality to light intensity, up to approximately 10(5) bumps per second; and (b) the bump height decreases approximately as the -0.7 power of light intensity; at rates greater than 10(5) bumps per second, the conductance change associated with the single bump seems to reach a minimum value of approximately 10(-11) reciprocal ohms; (c) from the lowest to the highest light intensity, the bump duration decreases approximately by a factor of 2, and the time scale of the dispersion of latencies of individual bumps decreases approximately by a factor of 3; (d) removal of calcium ions from the bath lengthens the latency process and causes an increase in bump height but appears to have no effect on either the bump rate or the bump duration.
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Acta Chir Scand Suppl · Jan 1982
The behaviour of three standard small calibre projectiles in soap blocks.
A study of three standard small calibre projectiles fired from the ranges of 30 and 100 m against soft soap blocks was performed. The assault rifles used in the tests were the Finnish M 62, the Russian AKM 47 and the American M 16 A 1 with standard ammunition. Impact velocity was measured with photocells and exist velocity with foils. ⋯ At the range of 100 m the stability of the two 7.62 projectiles is almost equal, but the 7.62 AKM 47 projectile released much more of its impact energy to the target. Furthermore, the 5.56 calibre projectile is unstable and goes on showing early tumbling and total break-up behaviour. The ratio between the volumes of cavitation was 1:2:3 (M 62:AKM 47:M 16 A 1).
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Acta Chir Scand Suppl · Jan 1982
Mechanisms of development of shot wounds caused by missiles of different initial velocity.
The investigation were carried out on blocks of 20% gelatin. Some of these models contained bones. Shots were fired from a distance of 100 m using bullets of 7.62 mm calibre and 715 m/sec initial velocity and bullets 5.52 mm of about 990 m/sec initial velocity. ⋯ The temporary and permanent changes in the block depended on the mode of bullet impact. Temporary cavity pulsation developed when air was trapped within the block. Bullets of high initial velocity convey their kinetic energy to the hit object through a much greater absolute loss of its velocity producing thus a much greater injury, especially in the second half of the bullet canal, with longer lasting and more extensive temporary changes, and greater permanent changes than in the case of wounds produced with bullets of lower initial velocity.