Stochastic Feedback and the Regulation of Biological Rhythms

We propose a general approach to the question of how biological rhythms spontaneously self-regulate, based on the concept of ``stochastic feedback''. We illustrate this approach by considering the neuroautonomic regulation of the heart rate. The model generates complex dynamics and successfully accounts for key characteristics of cardiac variability, including the $1/f$ power spectrum, the functional form and scaling of the distribution of variations, and correlations in the Fourier phases. Our results suggest that in healthy systems the control mechanisms operate to drive the system away from extreme values while not allowing it to settle down to a constant output.Comment: 15 pages, latex2e using rotate and epsf, with 4 ps figures. Submitted to PR

Poem to Dear Pastor Leraar

A brief poem is addressed to Dear Pastor (Leraar). There is no indication who the Pastor is, but the document is found in the Van Raalte Collection at Calvin College. Apparently the signers are students in a class which Rev. Albertus C. Van Raalte or someone close to the family taught. The names of the students are appended as well as the date. The students are: J. Wakker, J. Kroes, N. Kanters, A. Phanstiehl, L. Binnekant, R. Struik, G. Wakker, and K. Plugger, all familiar Holland names of that period.https://digitalcommons.hope.edu/vrp_1860s/1189/thumbnail.jp