Response sigmoid

Figure 2-10 The probit transformation converts the sigmoidal response vs. log dose curve into a straight line when plotted on a linear probit scale. Source D. J. Finney, Probit Analysis, 3d ed. (Cambridge Cambridge University Press, 1971), p. 24. Reprinted by permission.

In an effort to simulate the theoretical behavior of neuron cells, researchers in the 1940 s and the 1950 s such as McCullogh, Pitts, and Rosenblatt developed functions that mimicked the threshold response of a synapse. Their theory of synapses held that the output of a neuron cell was at or near zero until the sum of all of the input potentials connected to it passed a certain threshold, at which point the cell s output would be at or near one. Mathematically, their neuron functions yielded a binary or a sigmoidal response to a linear combination of its inputs, and could be connected... 

The pmential advantage of a sigmoidal response to varying substrate is illustrated in Figure 4-49. For comparison, a normal hyperbolic velocity... 

Figure 16.4. Sigmoid response curves positive (a) and negative (b) sigmoid responses are shown.

Fig. 15.8. shows a typical sigmoid response curve. When the re-... 

Finney DJ (1952). Probit Analysis a Statistical Treatment of the Sigmoid Response Curve, 2nd Edition. Cambridge Cambridge University Press. 

The activation of pyruvate carboxylase by acetyl CoA is a sigmoidal response, with the steep part of the curve between the normal low and high ranges of acetyl CoA. Thus, as acetyl CoA increases in concentration, there is a marked stimulation of pyruvate carboxylase (Fig. 13.3). 

Why do most of the opened loops have a sigmoidal response like that of Figure 16.8a The answer is rather clear using the analysis of Chapters 10 through 12. There we noticed that almost all physical processes encountered in a chemical plant are simple first-order or multicapacity processes whose response has the general overdamped shape of Figures 11.1a and 11.6. The oscillatory underdamped behavior is produced mainly by the presence of... 

For spherical microelectrodes in the limit of low scan rates T 1), the diffusive mass transport is able to keep the surface gradient constant with time and the steady state is attained. Under these conditions, a sigmoidal response is obtained in cyclic voltammetry with the current reaching a... 

Figure 1 shows the response of enzyme activity to phosphoenolpymvate and fructose-diphosphate concmtratioa It is obvious from Fig. 1 that the response of enzyme activity to increasing concentrations of substrate is not hyperbolic (Michaelian), but sigmoid. Such a sigmoid response increases the sensitivity of enzyme to small changes in the concentration of substrate and thus increases... 

Investigation of the gelatin-SDS system by Greener et al. (see above) included fluorescence measurements in which pyrene aldehyde was the probe. The characteristic sigmoidal response referred to earlier (Fig. 9) was obtained, but the fluorescence data also showed that ... 

Fig. 8. Schematic representation of the dose dependence of the fraction of functional tissue subunits (FSU). A response can be clinically detected only, if the fraction is reduced below a certain threshold (top). This leads to the typical sigmoidal response curves, when the probability to induce a given effect is plotted as a fimction of dose (bottow)...

The erythrocyte PRPP synthetase in these patients exhibit in hemolysate, at saturating concentration of ribose-5-phosphate and ATP, a hyperbolic response to increasing inorganic phosphate concentration, as contrasted to the sigmoidal response of the enzyme of of normal control subjects (13,14) (Fig. l). 

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