Carl Nielsen and the Radio

The Nielsen-Thurston Classification Theorem

Overview: The Nielsen-Thurston Classification Theorem asserts that every element of MCG(Sg) (g ≥ 2) exhibits one of three types of simple behavior. It either has finite order, fixes a nonempty set of of isotopy classes of essential, simple closed curves (reducible), or stretches along a pair of transverse measured foliations in an area-preserving way (pseduo-Anosov). Bers’ strategy for proving ...

Carl Woese

Not long after Carl Woese died, I received a message from Robin Gutell asking if I would contribute an article to this issue of RNA Biology. While my admiration for Carl's contributions to biology knows no bounds, I did not know him well personally. For that reason I advised Robin to strike my name off the list of contributors and replace it with that of someone who is better qualified than I a...

Yule-Nielsen effect in halftone prints: graphical analysis method and improvement of the Yule-Nielsen transform

The well-known Yule-Nielsen modified spectral Neugebauer model is one of the most accurate predictive models for the spectral reflectance of printed halftone colors which expresses the spectral reflectance of halftones raised to the power 1/n as a linear combination of the spectral reflectance of the fulltone colors (Neugebauer primaries) also raised to the power 1/n, where n is a tunable real ...

Carl Djerassi: Chemist and entrepreneur

Nielsen Number and Differential Equations

In reply to a problem of Jean Leray (application of the Nielsen theory to differential equations), two main approaches are presented. The first is via Poincaré’s translation operator, while the second one is based on the Hammerstein-type solution operator. The applicability of various Nielsen theories is discussed with respect to several sorts of differential equations and inclusions. Links wit...