Lichtgedanken 02

Editorial 58 Insights into the atom Physicists present new mechanism for examining ato- mic nuclei Dry rot as chemist How bacteria switch on the synthesis of certain natural substances in pillar-fungi Old buildings often suffer from dry rot. This fungus (pho- to above) attacks wood, thereby endangering the stabili- ty of construction materials containing wood. The dry rot fungus Serpula lacrymans is also a good »chemist«, how- ever: various types of bacteria are able to trigger the for- mation of dyes in it. New results from Prof. Dr Dirk Hoff- meister and his team are now casting light on the complex molecular interrelations between fungus and bacteria. As the researchers together with their colleagues working with Prof. Dr Axel Brakhage from the Leibniz Institute for Natural Product Research and Infection Biology write in the magazine »Environmental Microbiology«, they have been able to prove that the bacteria switch on certain fungus genes responsible for colour in the fungus. This »communication« between fungi and bacteria can even be seen with the naked eye: Fungal mycelium and substrate turn bright yellow. MR It is not easy to view the smallest components of matter. Whi- le the outlines of atoms can be revealed with scanning tun- neling microscopes, direct close-ups of atomic nuclei have so far been totally impossible to achieve: just as distant planets are often shrouded in a thick atmosphere, a cloud of electrons circling the atomic nucleus obscure the view into the inside of an atom. Researchers have to resort to ingenious methods in order to gain direct access to atomic nuclei. And that is precisely what Prof. Dr Stephan Fritzsche and his colleagues from the Institute of Theoretical Physics at the university and the Helmholtz Institute in Jena have done. In the specialist magazine »Physical Review Letters«, they present a me- thod by which they are able to lift the veil provided by the cloud of electrons and directly excite the atomic nuclei. The examination method is based on so-called two-photon emission spectroscopy. The method consists in directing an electromagnetic beam into a sample of the element to be examined. The electrons in the atomic shell are excited and move into a higher energy state from where they fall back again into their original state. In the process, every atom excited in this way gives off its energy in the form of two light particles (photons). »However, one of these photons is absorbed by the atomic nucleus which is then itself exci- ted,« says lead author PD Dr Andrey Volotka. This exci- tement of the atomic nucleus – like that of the remaining second photon – can be spectroscopically recorded. The signals observable in the photon spectra give researchers insights into the structure of the atomic nucleus and the way in which it interacts with the electrons. US What is growing in the savanna? Satellite and terrestrial data reveal information on the biomass in the Kruger National Park in South Africa Savannas form one of the largest habitats on earth. »In ad- dition, they play a crucial role in the global carbon cycle,« says Victor Odipo (photo below). According to the doctoral student from the Chair of Earth Observation, the volume of plant biomass above ground is decisive in determining the savannas’ ability to store CO 2 . Odipo and colleagues from the universities in Jena and Oxford as well as the Federal Institute for Geosciences and Natural Resources have esta- blished a method by which the biomass of the savannas can be very precisely measured. To do so, researchers use both radar data recorded by satellites and laser scanning data surveyed from the ground. They have published their re- sults in the specialist magazine »Forests«. US Ticke