PubMed · 5669037
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M P Pudiuk, A S Kapel'tsov. 1968. [External hysterography].. https://pubmed.ncbi.nlm.nih.gov/5669037/
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We study the impact of correlated neuronal firing rate variability on the accuracy with which an encoded quantity can be extracted from a population of neurons. Contrary to widespread belief, correlations in the variabilities of neuronal firing rates do not, in general, limit the increase in coding accuracy provided by using large populations of encoding neurons. Furthermore, in some cases, but not all, correlations improve the accuracy of a population code.
Constant electric fields and constant ion currents are often considered in theories of ion transport. Therefore, it is important to understand the validity of these helpful concepts. The constant field assumption requires that the charge density of permeant ions and flexible polar groups is virtually voltage independent. We present analytic relations that indicate the conditions under which the constant field approximation applies. Barrier models are frequently fitted to experimental current-voltage curves to describe ion transport. These models are based on three fundamental characteristics: a constant electric field, negligible concerted motions of ions inside the channel (an ion can enter only an empty site), and concentration-independent energy profiles. An analysis of those fundamental assumptions of barrier models shows that those approximations require large barriers because the electrostatic interaction is strong and has a long range. In the constant currents assumption, the current of each permeating ion species is considered to be constant throughout the channel; thus ion pairing is explicitly ignored. In inhomogeneous steady-state systems, the association rate constant determines the strength of ion pairing. Among permeable ions, however, the ion association rate constants are not small, according to modern diffusion-limited reaction rate theories. A mathematical formulation of a constant currents condition indicates that ion pairing very likely has an effect but does not dominate ion transport.
The effect of 11 sulfosuccinic acid ester surfactants on the abiotrophic developmental forms of the asexual spores of Plasmopara halstedii was determined. The strength and the selectivity of the effect was separated by the spectral mapping technique and the relationship between the biological activities and physico-chemical parameters of anionic surfactants was elucidated by stepwise regression analysis. It was established that the plasmalemma of cell wall less zoospores showed the highest and the resting zoosporangia the lowest average sensitivity toward the surfactants. The biological efficacy of surfactants was highly different the di-n-octyl ester being the most effective. Calculations proved that both the strength and selectivity of the biological activity mainly depends on the lipophilicity of the molecule and, to a lesser extent, on the electronic parameters.