Yearbook 2011

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After a brief comparison between the commutative algebra of classical observables in Hamiltonian mechanics and non-commutative quantum observables in quantum mechanics, an algebraic way of realizing the quantization process (deformation quantization) is introduced and in particular the universal formula of Kontsevich is explained in some details. Finally, some (open) problems related to deformation quantization are considered, some of which have been positively addressed at the Max Planck Institute for Mathematics in Bonn. more
Periods are a special kind of numbers, which play an outstanding role in number theory. An important aspect to consider are relations between different representations of periods. These can be studied in great detail for L-values, which are more accessible than most other examples are. more
The understanding and prediction of the behaviour of, for example, acoustic, electromagnetic, and elastic waves in different media is of great importance in a number of applications. The propagation of waves is often investigated in unbounded spatial domains. To obtain a numerical approximation in such situations the method of boundary integral equations is particularly attractive. The analysis and development of numerical methods for boundary integral equations for wave equations, in contrast to the time-harmonic Helmholtz equation, has until recently been in its infancy. more

High-performance Computing, Scientific Visualization and Data Services

Max Planck Computing and Data Facility (MPCDF) Dohmen, Renate; Kennedy, John; Lederer, Hermann; Rampp, Markus; Reuter, Klaus; Schott, Andreas
A major task of the RZG is the optimization of complex applications from plasma physics, astrophysics, materials science, and other disciplines for massively parallel high-performance computers. Moreover, the RZG provides data visualization services for the exploration and quantitative analysis of simulation results. Another key area are data management and data services. In both areas, the RZG plays a leading role in projects within the MPG and at national and European level. more
Toxin-Antitoxin (TA) systems are genetic elements that can be found in the genomes of nearly all bacteria. They encode for a toxin protein as well as its cognate antitoxin. When the antitoxin is degraded, the toxin is released and the host bacterium dies. Based on this mechanism, the epsilon/zeta TA-family not only helps pathogenic bacteria to stabilize resistance genes but also to increase their virulence. The discovery of the working principle of zeta toxins at the Max Planck Institute for Medical Research now allows to explain both of these phenomena. more
Myelin is an electrical insulator essential for the rapid conduction of nerve impulses in the central nervous system. In order to do so, myelin requires a unique lipid and protein composition. Recent findings demonstrate that oligodendrocytes generate a barrier that functions as a physical filter to form the lipid-rich myelin membrane sheets. Myelin basic protein establishes this molecular sieve and restricts the diffusion of proteins into myelin. This mechanism generates the anisotropic membrane organization of oligodendrocytes that facilitates the assembly of highly insulating membranes. more
The development of smart therapeutic interventions requires a detailed analysis of the disease progression. In the case of ischemic stroke, non-invasive positron emission tomography (PET) is combined with invasive optical methods (laser speckle flowmetry and oxymetry) to examine the complicated interaction of the pathologically induced processes and to identify potential diagnostic parameters. Since PET is common practice in the clinic, experimental results can be readily translated into application in humans. more
The Indian subcontinent is one of the most intensely irrigated regions of the world. Using the regional climate model REMO distinct feedbacks of the monsoon circulation with irrigation processes could be shown. With irrigation, a significant model bias in temperature and mean sea level pressure over NW India/Pakistan was removed. Moreover conditions were created favourable for currents from Bay of Bengal to intrude deep into western India and Pakistan that have been unrealistically suppressed before. Thus, the representation of irrigated water is unavoidable for a realistic monsoon simulation. more
Numerous bacterial species are motile and almost all of them are capable of forming sessile surface-associated communities, often referred to as biofilms. Both abilities are crucial for successful propagation and spreading in the natural environment. Using species of the soil and sediment bacteria Shewanella we study how these organisms regulate motility and biofilm formation to adapt to environmental conditions. more
Fourteen years ago, the world’s largest bacterium, Thiomargarita namibiensis, was discovered off the coast of Namibia. Since then we learned that the “Namibian sulfur pearl” has many close relatives in other parts of the sea and that it also plays an important ecological role: These bacteria can induce the formation of phosphorus-rich rocks. This process decreases the total amount of phosphate in seawater with the result that this nutrient becomes unavailable for other organisms. Thereby, the formation of these rocks counteracts the eutrophication of the ocean with respect to phosphate. more

Thermoelectric properties of porous silicon

Max Planck Institute of Microstructure Physics De Boor, Johannes; Ao, Xianyu; Kim, Dong-Sik; Schmidt, Volker
By nanostructuring silicon its thermal conductivity can be significantly reduced. Such a reduction can potentially induce a corresponding increase of the thermoelectric efficiency so that the transformation of heat into electric power could be improved. Therefore porous silicon layers were produced by electrochemical etching and the thermoelectric properties of the nanostructured material investigated. These investigations show that the thermal conductivity is indeed strongly reduced but that due to competing effects only moderate increases of the thermoelectric efficiency can be achieved. more
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