Yearbook 2005

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Geometry studies geodesics in various settings, in particular on hyperbolic surfaces. The distribution of geodesics on arithmetic hyperbolic surfaces gives information on the arithmetic of quadratic forms, an important branch of number theory. more
In the sixties and seventies of the last century physicists developed procedures to renormalize infinities appearing in quantum field theory. We explain recent work of Connes-Kreimer and Connes-Marcolli, giving a conceptual understanding of these procedures and indicating unexpected links to number theory. more
General relativity and quantum theory have not been merged into a consistent theory of quantum gravity yet. Unfortunately, to date, there are no experiments available that may disclose parts of the unified theory. Nevertheless, mathematics is already in a position to provide us with rigorous statements on how quantum gravity may look like. more
At the MPI for Mathematics in the Sciences general principles that underlie the robustness of evolved systems are studied and formalized. The aim is to formulate a mathematical theory of robustness that can be used for developing artificial adaptive systems. more
A dogma in the Neurosciences states that learning causes long-lasting changes in chemical synapses of the brain. The goal of the Department of Molecular Neurobiology at the MPI for Medical Research is to describe the function of key molecules for such changes. Most synapses in the brain are excitatory in nature and operate with the chemical transmitter L-glutamate, which when released upon an impulse from the sending part of the synapse (presynaptic specialization), diffuses across the synaptic cleft and binds to postsynaptically localized specific receptors. Binding of glutamate opens an inherent pore in the receptors, such that for a brief moment (several msec) positively charged ions (cations) flow into the nerve cell, shifting the cell from its resting state to an excited state by depolarizing its membrane potential. Genetic manipulation of glutamate receptors (GluRs) in the mouse alters synaptic function and may impair or – more rarely – enhance learning abilities. The following investigations highlight important functional aspects of glutamate receptors in spatial learning for which the hippocampus, a prominent brain structure, is essential, and also in olfactory learning in olfactory synapses. Moreover, the expression of functionally altered GluRs can evoke neurodegenerative diseases such as epilepsy and amyotrophic lateral sclerosis. more
SIP1 is a transcription factor that has been implicated in the genesis of Mowat-Wilson syndrome – a disease that affects normal brain development in humans. In order to uncover molecular mechanisms of Sip1 gene action scientists of the MPI for experimental medicine created a mutant mouse as a model for the syndrome. In this mouse Sip1 gene was inactivated in the cerebral cortex only, while in other organs it remained intact. The mutant mice showed loss of the entire hippocampus, which was based on elevated cell death and decreased proliferation during development. more
Research of the in vivo NMR laboratory focusses on the regeneration potential of stem cells after stroke. This therapeutical strategy of cell replacement acts during several days or weeks after the onset of the primary disease event. One of the fundamental prerequisites for a causal based therapy development is the understanding of the lesion in its chronic development. Inflammatory activity is an essential factor during this period. Investigations into the functional brain activation are expected to provide information about the spontaneous and the therapy induced recovery potential of the brain after stroke. These various pathophysiologically relevant phases of the disease development are followed and characterized in the experimental animal system using highly resolved magnetic resonance imaging. New therapeutic strategies of stem cell based regeneration are analyzed for their effectiveness, based on such detailed longitudinal studies. On the methodological end, development and application – achieved in international cooperations – of intelligent contrast agents as well as generation of transgenic cell lines which produce their own contrast agent utilizing suitable promotors, will essentially improve the detectability and the information content of functional characteristics of the implanted stem cells, facilitated by in vivo high field MRI. more

Earth System Research Partnership

Max Planck Institute for Meteorology Marotzke, Jochem; Andreae, Meinrat; Heimann, Martin
Earth system research is the science of global change, whether caused naturally or by humans. Earth system research requires the amalgamation of previously unrelated scientific disciplines and the appreciation of the Earth as a system of interacting compartments. In-situ measurements, satellite remote sensing, and numerical modelling are the pillars of Earth system research and have advanced dramatically in recent years. The Earth System Research Partnership is the association of the Max Planck Institutes dedicated to Earth system research, with further contributions by several Max Planck and other institutes. more
Many environmental pollutants are slowly degrading (persistent) and very mobile. Results of simulations using a global multicompartment model which is based on an atmosphere general circulation model are presented. The integration of soils, vegetation, air, ocean and ice is mandatory in order to describe the environmental fate, i.e. transports and transformations, of slowly degrading and semivolatile substances. This class of substances includes the so-called persistent organic pollutants (POPs) and other pesticides and industrial chemicals. The investigations elucidate the combined effects of climate and substance properties on transport and distribution of pollutants and allow to quantify persistence and long-range transport potential. more
Denitrifying microorganisms play a key role in the global nitrogen cycle. Denitrification is one of the main processes of this cycle and trace gases originating from it cause climatic effects. Application of molecular techniques in the field of microbial ecology allowed fundamental insights into diversity and structure of denitrifier communities. This is a prerequisite to understand the interrelationship of structure and function of denitrifier communities and the influence of parameters that drive the development of these microbial communities and their activity in the environment. more
The advent of high throughput sequencing technologies in the last years is set out to unravel the diversity and function of marine microorganisms on a whole genome level. It is the objective of the microbial genomics group to take advantage of this development and learn more about the mechanisms coded in the genome enabling the organisms to adapt to changing environmental conditions. To reach the goal it is necessary to not only generate sequences but to force functional genomic analysis. To reveal ecological relevant gene functions the genomic potential has to be correlated with on site microbial diversity and physical-chemical measurements on a geospatial level. This in turn should uncover specific niche adaptations and give hints how the organisms influence the global cycling of matters. The knowledge obtained will lead to a better understanding of the complexity, interaction and stability of marine habitats. The long term perspective is to predict the impact of local anthropogenic influences as well as global changes, like the green house effect, on the marine ecosystem. more
Using surface sensitive x-ray diffraction the geometric structure of the Fe/MgO/Fe(001) Tunneling-Magneto-Resistance (TMR) device was investigated. Evidence for the formation of an FeO-like interface layer could be provided, which significantly influences the magnitude of the TMR-effect more

New methods of X-ray analysis of protein structure and dynamics

Max Planck Research Unit for Structural Molecular Biology at DESY Bartunik, Hans D.
Protein function is determined by the three-dimensional structure and dynamical changes in the conformation during biological reactions. The structure-function relationships currently may be investigated in atomic detail even in the case of complex multi-protein systems. Such studies involve methods of X-ray crystal structure analysis that are based on the use of highly intense synchrotron radiation. The methods recently have been further developed, opening the way to structural genomics applications. The construction of free-electron lasers (FELs) at DESY provides the basis for entirely new types of applications in biological structural research. The VUV-FEL that recently has become operational at DESY may be used for Raman spectroscopic studies in the vacuum-UV on femtosecond time scales. The hard X-ray regime will be made accessible by the planned construction of an X-ray laser (X-FEL) at DESY. The X-FEL may be used for a number of applications including structural analysis of transient states on short time scales down to the femtosecond range, combined use of Mößbauer effect and diffraction for solving highly complex structures and simultaneous analysis of dynamical processes, and determination of the three-dimensional structures of non-crystalline matter and single (virus) particles. more
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