לוח שנה משולב

It has long been expected theoretically that quantum fluctuations may destroy anti ferromagnetic order in certain "frustrated" systems, but it is only in the past few years that experimental systems showing this behavior have been discovered. Indeed these systems show signs of predicted "emergent' new par-ticles such as neutral spin 1/2 fermionic excitations called spinons. I shall review the recent develop-ment and discuss possible connection to superconductivity.

Cell behaviour (e.g. migration, adhesion, polarization) is regulated in many essential ways by the activity of the cytoskeletal actin microfilament. The actin filament undergoes continuous dynamic rearrangements of G-actin polymerization and F-actin depoly¬merization. Changes in cell behaviour which are governed by actin dynamics are tightly linked to changes in gene expression. The state of actin polymerization is communicated to the nucleus by proteins of the myocardin-related transcription factor (MRTF) family which are released from cytoplasmic G-actin anchorage upon stimulation of F-actin extension. Upon translocation to the nucleus, MRTF proteins activate the transcription factor SRF (serum response factor) to stimulate the transcription of a large set of cytoskeletal SRF target genes, including the actin gene itself. The seminar will discuss roles of MRTF-SRF gene control during muscle function, neuronal migration, and liver tumor formation. The results to be discussed were generated by both SRF loss-of-function and gain-of-function genetic studies using the mouse model.

Bacteria, the first and most fundamental of all organisms, lead rich social life in complex hierarchical communities. Collectively, they gather information from the environment, learn from past experience, and take decisions. To solve the new encountered problems they first assess the problem via collective sensing, recall stored information of past experience and then they all participate in distributed information processing. The billions of bacteria in the colony use sophisticated communication strategies to link the intracellular computation networks of each bacterium (including signaling pathways of billions of molecules) into a network of networks. I will then show illuminating movies of swarming intelligence of live bacteria in which they solve challenging optimization problems for collective decision making. I will explain that current game theory is too simplistic to account for bacteria's decision making and that understanding bacteria's reactions to stressful and hazardous conditions may help to understand human decision-making processes. Bacteria are simpler yet they can effectively control the individual decision process leading to group decisions for the well-being of the entire colony.

The realization of aberration-corrected lenses has triggered a quantum jump in electron optics. The re-cent generation of transmission electron microscopes with aberration-corrected optics allows materials science in atomic dimensions and to measure individual atomic positions with picometer precision. This fulfils an old dream of condensed matter physics to derive macroscopic materials properties directly from observations on the atomic level. However in order to realize this ultra-high resolution it has to be accepted that optics in atomic dimensions is based on quantum physics and that the term “image” looses its conventional meaning. As a consequence access to the atomic-resolution information requires the numerical inversion of the non-linear imaging process by quantum-mechanical and optical image calculations on the basis of solutions of the Dirac equation. After a brief introduction into the basics of aberration-corrected electron optics and the physics of atomic-resolution microscopy studies on ferroelectric perovskitic oxides will be presented which provided new insight into the subtle atom relaxations forming the basis for the particular electronic properties of these materials.