Yearbook 2004

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ZrAs1,4Se0,5 – A non-magnetic Kondo system with properties of a normal metal

Max Planck Institute for Chemical Physics of Solids Niewa, Rainer; Schmidt, Marcus; Cichorek, Tomasz; Auffermann, Gudrun; Ramlau, Reiner; Prots, Yurii; Schmidt, Ulrike; Völzke, Anja; Schulze, Katja; Burkhardt, Ulrich; Borrmann, Horst; Cardoso-Gil, Raúl; Schnelle, Walter; Schlechte, Andreas; Steglich, Frank; Kniep, Rüdiger
ThAsSe and UAsSe represent rare examples for non-magnetic Kondo systems. For deeper insight into this behaviour a compound with the same crystal structure type from the chemical system Zr–As–Se was studied extensively in terms of chemical composition, crystal structure and electrical resistivity at low temperatures. The results indicate the unusual behaviour of ZrAs1.4Se0.5 to be connected with dynamical phenomena within the anionic substructure. more
The INTEGRAL Gamma-Ray Observatory has provided novel insight into the nature of sources of high-energy radiation. New embedded sources were discovered, because only the high-energy part of radiation can penetrate clouds. Unexpected emission at high energies where thermal emission usually fades was found for sources with extremely high magnetic fields. Together, this leads to a re-evaluation of the relative contributions of source objects and intrinsically-diffuse emission from interstellar space. Such diffuse emission reflects cosmic radiation penetrating the interstellar gas in the Galaxy. High-resolution spectroscopy of diffuse emission addresses mainly two prominent gamma-ray lines: Antimatter annihilates into electromagnetic radiation with a line at 511 keV, and was found to have a surprisingly symmetric spatial distribution in the inner Galaxy; radiactive 26Al decays in the interstellar medium of the Galaxy, emitting a line at 1809 keV; being a by-product of cosmic element synthesis from terminal evolutionary phases of very massive stars, it was ejected into interstellar space, and thus reveals the kinematics of the interstellar gas in such regions, which are hardly accessible through other means. more

Cluster and Double Star: A fleet of 6 satellites investigating Earth's magnetosphere

Max Planck Institute for Extraterrestrial Physics Berndt Klecker; Matthias Förster, Edita, Georgescu, Stein Haaland, Arpad Kis, Goetz Paschmann, Manfred Scholer, Hans Vaith
With the missions Cluster and Double Star, coordinated measurements in Earth’s magnetosphere with up to 6 spacecraft are now becoming available for the first time. Cluster, with its 4 spacecraft in tetraeder-configuration provides data for variable distances in the range ~100 to 20000 km. These are complimented by the measurements of the Two Double Star spacecraft in polar and equatorial orbit. more
HERA, the world's first electron proton collider, has allowed scientists to look into the heart of matter with unprecedented resolution. Fascinating results have been obtained, such as the observation of a rapid increase in the number of virtual quarks, antiquarks, and gluons visible in scattering processes as the energy is increased. The HERA program has recently begun a new phase which promises a large increase in data and further exciting results. more
In this article we discuss some aspects of superstring theory. After a short introduction of string theory as unifying quantum theory of all interactions, we introduce the socalled brane world models. These models describe the universe as 3- or higher dimensional brane, embedded into the 9-dimensional space of string theory. They offer many interesting possibilities to derive the standard models of particle physics from string theory. more
The viscoselastic properties of high molecular weight polymeric liquids are dominated by topological constraints on a molecular scale. Similar to entangled ropes, polymer chains can slide past but not through each other. Tube models of polymer dynamics and rheology are based on the idea that entanglements confine a chain to small fluctuations around a primitive path. To provide a microscopic foundation for these highly successful phenomenological models, we have introduced a method for analyzing the microscopic topological state of polymeric liquids in terms of primitive paths. The resulting parameter-free predicitions for the plateau modulus agree with experiment for all major classes of synthetic polymers. more
A new cryogenic ion trap at the Max-Planck-Institut für Kernphysik in Heidelberg is able to produce and store highly charged ions. These ions are typical for extremely hot plasmas, such as those found in stellar atmospheres and nuclear fusion experimental reactors. The ion trap is mainly used for spectroscopic investigations aiming at testing current atomic structure theory. more
In early 2004, observations carried out with the H.E.S.S. array of imaging Cerenkov telescopes in Namibia confirmed with startling accuracy a prediction published in 1999 by astrophysicists at the Max-Planck-Institut für Kernphysik of the gamma-ray spectrum of the binary star system PSR B1259-63. Although these observations are a strong indication that the theory is not on the wrong track, they have also posed new puzzles. In combination with observations made in other wavelength ranges, they promise to lead to a deeper understanding of the physics involved in the production of highly relativistic pulsar winds. more

Structure and Molecular Mechanisms of Clock Proteins

Max Planck Institute of Molecular Physiology Berndt, Alex; Breitkreuz, Helena; Hennig, Sven; Köster, Stefan; Schulze, Sabrina; Theiss, Christiane; Wolf, Eva; Yildiz, Özkan; Wittinghofer, Alfred
Most organisms exhibit day-time dependent activity cycles, referred to as circadian rhythms, which are generated and synchronized with the environmental light-dark cycle by internal biological clocks. By structurally and biochemically characterizing the clock protein PERIOD of the fruit fly Drosophila, scientists at the Max Planck Institute in Dortmund were able to obtain important insights into animal clock mechanisms. Biological, biochemical and biophysical experiments proposed by this X-ray crystal structure will assist in delineating the molecular mechanisms underlying the human circadian clockwork. more
This report details the increase in knowledge on the basic mechanisms in sugar absorption in the intestine and reabsorption in the kidney. It describes how the biophysical principles of cell asymmetry and asymmetry of the transport molecules are realized at the molecular level and how the problems of transport selectivity and transport energetics are solved by specific subdomains of the transporter. Thereby a complex series of events is described which in the end leads to the vectorial transport of sugars across the membrane and across the cell. The report also illustrates how the combination of the most modern techniques from different areas of Life Sciences is essential for the progress, this transdisciplinary research is one of the highlights of the research conducted at the Max Planck Institute in Dortmund. more
Protein modifiers are small proteins that can be covalently attached to substrate proteins. The resulting change can influence the function of the substrate protein and can thereby play a role in cellular information transfer. Attachment of modifiers is part of many developmental processes in plants, including flower induction, which depends on an interplay between a genetic program and environmental input parameters for optimal timing and execution. more
Our long-term goal is the understanding of the genetic differences between Arabidopsis accessions affecting important adaptive traits such as seed dormancy and plant growth. We expect that understanding this genetic variation will help explaining why specific variants are adapted to specific environments and that knowledge of the genetic basis of these traits will help breeding crop plants. more
Photosynthesis in green plants is the basis for all life on earth. The chlorophyll-protein complexes of photosynthesis are embedded into the thylakoid membranes of chloroplasts. Chloroplasts are capable of synthesizing a unique set of membrane lipids and isoprenoid lipids, some of which are essential for human nutrition, e.g., tocopherol (vitamin E), phylloquinone (vitamin K) and β-carotene (provitamin A). Galactolipids represent the most abundant membrane lipid class in chloroplasts. The analysis of Arabidopsis mutants revealed that galactolipids are essential for growth and photosynthesis. Furthermore, galactolipids are critical during growth on phosphate-limiting soils, because they replace phospholipids in the membranes and make phosphate available for other important cellular processes. Tocopherol (vitamin E) is one of the most important antioxidants. Thus, vitamin E is used as a major dietary supplement for human nutrition. Interestingly, growth and photosynthesis of Arabidopsis mutants carrying a defect in tocopherol biosynthesis are very similar to wild type, indicating that tocopherol can be substituted by other antioxidants in the plant cell. Employing biotechnological approaches, the natural form of vitamin E required to serve a growing population might be derived from transgenic crop plants in the near future. more
IPP’s Technology Division in Garching is conducting a development programme for the international test reactor ITER – a new ion source for plasma heating by neutral particle beams. In contrast to former devices for ITER negative ion beams are needed. Production, acceleration, and neutralisation of negative hydrogen ions, which in contrast to positive ions are very fragile objects, is accompanied by a series of challenging physics and technology problems. In addition, high particle energies and steady state is requested. The results up to now nevertheless indicate, that IPP’s ion source is well on the way to be chosen as a candidate for ITER. more
At the Greifswald Branch of IPP the linear plasma generator VINETA (Versatile Instrument for Studies on Nonlinearity, Electromagnetism, Turbulence and Application) is operated to study the basic dynamics of a magnetised plasma, i.e. the behaviour of plasmas waves, turbulence and instabilities as well as basic questions of plasma edge physics. VINETA allows one to establish precisely the respective plasma modi and to conduct detailed experimental investigations. more
By supporting metallocenes on µm-sized aggregated organic nanoparticles, prepared by emulsion polymerization, highly active catalysts for the olefin polymerization can be obtained. The influence of the support is studied by scanning confocal optical microscopy and videomicroscopy. more
Our images of organized soft matter, e.g. polymers, colloids, are dominated by static structures that provide only snapshots of the possible conformations. Since the typical energies are of the order of the thermal energy, soft matter is amenable to large fluctuations. Structural dynamics are essential for material function. The study of molecular motions over broad time and spatial ranges challenges both experimentalists and theoreticians. Three selected topics from ongoing projects should exemplify such challenges. more
Functional neuroimaging techniques provide an excellent opportunity to investigate dynamic aspects of information processing during sleep in humans. At the Max Planck Institute of Psychiatry, a method for simultaneous recordings of the electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) during sleep has been established. Subject to the respective sleep stage, acoustic stimuli led to different regional activation or deactivation patterns in cortical and subcortical brain regions, allowing conclusions on stimuli processing during sleep. Future studies and further developments of this technique will lead to a substantial progress regarding the functional neuroanatomy of sleep and the effects of sleep deprivation and psychopharmacological drugs on cognitive functioning. more
People spend a great deal of their time navigating through their environment. To be able to find our way home, we need to store important spatial information in memory. How the brain learns and retrieves the relevance of landmarks at key decision points was so far unknown. With using functional Magnetic Resonance Imaging a group at MPI for Psycholinguistic showed that the human brain automatically organises spatial information by dissociating between places carrying information necessary for wayfinding, and others. Data revealed that objects occurring at navigationally relevant locations are stored in the parahippocampal gyrus. The selective neural marking for navigationally relevant objects was observed in the absence of spatial information, and without conscious recollection of the route. This automatic neural mechanism can provide the basis for efficient and successful wayfinding. more
An investigation was conducted into how listeners compensate for deletion of word-final /t/, which may occur in fluent casual speech (‘postman’ becomes “posman”). Behavioral as well as brain-activity measures show that listeners compensate perceptually for /t/-deletion using phonological as well as world knowledge. more
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