Yearbook 2009

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We explain the important idea of L-function in mathematics and Deligne-Beilinson conjectures about values of L-functions at integral points. As main examples we consider here the Riemann zeta function and L-functions of elliptic curves. In the end we explain relation between values of L-functions of elliptic curves at 2 and logarithmic Mahler measures. more
Open books are particular decompositions of manifolds which are useful for the construction of foliations. There are also important applications to the theory of contact structures. more
Many living systems can survive thanks to sophisticated and flexible information processing capabilities enabling them to act autonomously. Even though this ability is increasingly demanded from technical systems, it is still largely unknown which properties are required for a system to obtain autonomy. To fill this gap, an information theoretic measure of autonomy is proposed here. For illustration the autonomy of simple systems is measured and a close relationship between autonomy and memory is established. more

High-performance computing, long-term archiving, visualization, international projects

Max Planck Computing and Data Facility (MPCDF) Lederer, Hermann; Rampp, Markus; Reuter, Harmut; Dohmen, Renate; Dannert, Tilman; Egger, Matthias; Kennedy, John; Heimann, Peter
A major task has been the optimization of complex applications from materials science, plasma physics and other disciplines for massively parallel high-performance computers. The RZG provides data visualization services for the exploration and quantitative analysis of HPC data. Several institutes of humanities research also use our long-term data archive. The RZG has a leading role within MPG, national and European projects. more

In vivo acetylcholine receptor dynamics at neuromuscular junctions

Max Planck Institute for Medical Research Yampolsky, Pessah; Pacifici, Pier-Giorgio; Chevessier, Frédéric; Mersdorf, Ulrike; Barenhoff, Karina; Koenen, Michael; Witzemann, Veit
Synaptogenesis and synaptic plasticity require interactions between pre- and postsynaptic components. The neuromuscular synapse as model and genetically manipulated mice were used to study the dynamics of acetylcholine receptors. Direct in vivo analysis shows how newly synthesized receptors are integrated into the existing synapse and how receptor stability changes when muscle is inactivated by innervation. more
Fast neuronal communication in the central nervous system takes place at excitatory and inhibitory synapses. The accuracy and efficiency of synaptic transmission rely on the proper assembly of specific adhesion, scaffold, receptor, and signaling proteins. Postsynaptic adhesion proteins of the Neuroligin family were identified as key regulators of this assembly process at excitatory glutamatergic synapses. Recent studies showed that Neuroligins also regulate the formation of GABAergic and glycinergic synapses. Thus, Neuroligins are essential regulators of synaptogenesis at all fast synapses in the central nervous system. more
Anticipation, required in both prognosis and planning, occurs on different time scales, and we also become differently aware of being engaged in it. Recent findings of scientists at the MPI for Neurological Research corroborate the view that the frontal lobes play a crucial role in anticipation in general. In particular, the frontal brain’s function in integrating relations into superordinate ones seems reflected by its hierarchical functional-anatomical architecture. Interestingly, even highly abstract kinds of prognoses still call for regions that, on demand, spell out our expectations in the seconds range. more
Scientists are currently puzzled by the behavior of Arctic sea ice: Following a sharp and unexpected decline in summer 2007, the ice-covered area has increased both in 2008 and in 2009. At MPI for Meteorology, scientists carry out research to understand these ups and downs. They also examine what their results mean for the future evolution of the polar bear's habitat. For their studies, the researchers use sophisticated computer models, but they also carry out field measurements in the Arctic to better understand the physical properties of sea ice. more
Members of the third domain of life, the Archaea, exhibit a number of different cell surface structures which are similar in assembly and function to bacterial type IV pili. Type IV pili play an important role in surface motility and adhesion, DNA transfer and invasion of eukaryotic host cells. Archaeal type IV pili like filaments are build from a minimal set of subunits facilitating the progress of understanding the mechanism of how these and other bacterial type IV pili are assembled. more
The fungus Ustilago maydis is the causative agent of maize smut disease. During this biotrophic interaction, plant defense is suppressed immediately upon penetration. We identified the secreted effector-protein Pep1. Pep1 deletion mutants failed to suppress plant defense and are not able to colonize maize tissue. Therefore, Pep1 is an essential factor for the compatible interaction between U. maydis and its host plant. Elucidation of the Pep1 function will help to understand the molecular mechanisms that determine compatibility in biotrophic plant-fungal interactions. more
The Max Planck Research Group for Marine Geochemistry studies dissolved organic matter in the ocean, an important component of global element cycles. Marine dissolved organic matter accumulates since thousands of years to the largest organic carbon pool in the oceans and is mainly of microbial origin. The controlling mechanisms behind its turnover, however, are unknown. The Max Planck Research Group applies ultra high resolution mass spectrometry to obtain answers to the fundamental questions regarding the cycling of marine organic matter. more

Photoemission by ultrashort laser pulses

Max Planck Institute of Microstructure Physics Winkelmann, Aimo; Chiang, Cheng-Tien; Lin, Wen-Chin; Kirschner, Jürgen
The investigation of possibilities to influence electrons in solids and at surfaces on the femtosecond (10-15 s) time scale is an important area of research. This is also relevant for the steering of magnetic switching processes by ultrashort laser pulses and for the control of the spin of excited electrons. At the MPI of Microstructure Physics, the control of the spin of optically excited photoelectrons is investigated by the absorption of multiple photons at metal surfaces. more

An enzyme structurally closely related to human monoamine oxidases enables a soil bacterium to live on nicotine

Max Planck Research Unit for Structural Molecular Biology at DESY Bartunik, Hans D.
The soil bacterium Arthrobacter nicotinovorans grows on nicotine. Degradation of L-nicotine and D-nicotine involves two genetically unrelated flavoenzymes, 6HLNO and 6HDNO. Their crystal structures may explain the stereospecificity of their enzymatic reactions. 6HLNO by its structure and mechanism is closely related to human monoamine oxidases (MAO), which play central roles in degradation of neurotransmitters. Structural analysis of 6HLNO reaction intermediates and the inhibition mechanism extends the basis for possible development of new leads for MAO. more
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