Effects of ageing on postreceptoral short-wavelength gain control: transient tritanopia increases with age

We investigated the effect of ageing on the neural gain control in the short-wavelength opponent channel. In order to tackle specifically postreceptoral changes, we determined the effect of ageing on transient tritanopia, a paradoxical and transient reduction of short-wavelength sensitivity after the presentation of a long-wavelength adapting light. The results demonstrate an unexpected and significant increase of transient tritanopia with age, which cannot be explained by a general decline of short-wave sensitivity or the selective reduction of retinal illumination. Instead, our data imply that ageing affects also short-wavelength gain control at the site of chromatic opponency or beyond. Age-related changes of adaptation processes should therefore be considered an important factor influencing the visual performances of the elderly.

Search for long-term radiation trends in the environs of Swiss nuclear power plants

Annually since 1989, biannually since 1994 the sites of the Swiss nuclear facilities are surveyed flying the same survey lines by airborne gamma ray spectrometry. The equipment and the data processing software used for those surveys were built and developed at the Institute of Geophysics, ETH Zurich. For mapping the ground radiation around the nuclear facilities, a pixel representation and a modified spectrum dose index (SDI) method are used. In the search for long-term trends, the local dose rates are calculated first and in turn the net dose rates. So far, no change in the radiation levels was detected over the last 13 years outside of the fenced sites of the nuclear facilities and, especially, no artificial radioactivity was present that could not be explained by nuclear weapon tests or by the Chernobyl event.

Linear cooperative binding of large ligands involving mutual exclusion of different binding modes

A rigorous treatment is given for mutually exclusive multiple mode cooperative binding on a linear structure of equivalent binding "contacts". This will be of special interest with regard to larger ligands implicating the possibility that there are different kinds of binding interactions with more than one monomeric sub unit of a linear biopolymer. Quantitative evaluation of binding properties is shown to be essentially based on calculating the largest root of an algebraic equation. The whole procedure can be practically executed by means of a fairly simple computer program. Various typical examples comprising only two modes are discussed in more detail. For some nucleotide-polylysine systems definite binding parameters have been determined from pertinent experimental data.