The Many-Interacting-Worlds (MIW) approach to a quantum theory without wave functions proposed in [8] leads naturally to numerical integrators of the Schrödinger equation on comoving grids. As yet, little is known about concrete MIW models for more than one spatial dimension and/or more than one particle. In honour of Detlef Dürr, we report on a further development of the MIW approach to treat arbitrary degrees of freedom and provide a numerical proof of concept for ground states in 2d. The latter (...) is part of a systematic numerical study [22] that includes also 1d ground and excited states. With this step towards the treatment of higher degrees of freedom we hope to stimulate their further study. (shrink)

This text explores how we understand living and other complex systems. The conventional basis of understanding rests on abstract general theories, but this book proposes conceptual continuity as a new means of comparing systems of divergent complexity and resolving problems in complex systems.

It has been tacitly assumed that certain fundamental “laws” of science have the same meaning and significance in the different scientific disciplines. Outside of quantum physics the law of causality was regarded as such a concept which was most generally applicable in the description of the systems of nature. However, the role of causality in recent research in biology seems not quite clear. There an explanation of the specific properties of biological systems does not assume the form of a simple (...) law such as a mathematical expression relating different states of one and the same system. Rather it is attempted to show how the properties of the system as a whole are established by the specific interaction of the parts of the system. (shrink)

It may seem trivial to state that one of the major trends in biological investigation consists in an attempt to explain the structural and functional aspects of living matter in chemical terms, in an effort to obtain insight into the equivalent of macroscopic phenomena on the molecular level. I am sure you are aware of, and this meeting of the Association has brought ample additional evidence, in how many fields this tendency has become apparent. It can be recognized in genetics (...) with the molecular analysis of chromosomes and the enzymatic or metabolic interpretation of hereditary properties like the eyecolor of Drosophila. In a purely morphological branch like histology we do not ask merely for a differentiation of stained cell structure but we ask for the nature of the staining reaction; in nerve physiology we try to interpret conduction as alterations of protein lipoid layers; or in pathology where the age old syndrome of inflammation is explored with biochemical methods. I should mention molecular models of membranes and cell surfaces, the molecular interpretation of secretion and of the macroscopic phenomena of metabolism. Yet insofar as this yield of data could be designated as a trend, it would rather seem to be the natural outcome to be expected from the application of the analytic method of science. In one instance, however, this approach has been carried farther than in all the other fields, and it would seem to be worthwhile to pause for one moment to ask whether this case is important merely because of its technical implications or whether it is meaningful in a wider sense. (shrink)

The 24 components of the relativistic spin tensor consist of 3 + 3 basic spin fields and 9 + 9 constitutive fields. Empirically only three basic spin fields and nine constitutive fields are known. This empirem can be expressed by two spin axioms, one of them denying purely relativistic spin fields, and the other one relating the three additional basic fields and the nine additional constitutive fields to the known (and measurable) ones. This identification by the spin axioms is material-independent (...) and does not mix basic spin fields with constitutive properties. The approaches to the Weyssenhoff fluid and the Dirac-electron fluid found in literature are discussed with regard to these spin axioms. The conjecture is formulated, that another reduction from six to three basic spin fields which does not obey the spin axioms introduces special material properties by not allowed mixing of constitutive and basic fields. (shrink)

Changes in the shape and structural organization of the cell nucleus occur during many fundamental processes including development, differentiation and aging. In many of these processes, the cell responds to physical forces by altering gene expression within the nucleus. How the nucleus itself senses and responds to such mechanical cues is not well understood. In addition to these external forces, epigenetic modifications of chromatin structure inside the nucleus could also alter its physical properties. To achieve a better understanding, we need (...) to elucidate the relationship between nuclear structure and material properties. Recently, new approaches have been developed to systematically investigate nuclear mechanical properties. These experiments provide important new insights into the disease mechanism of a growing class of tissue‐specific disorders termed ‘nuclear envelopathies’. Here we review our current understanding of what determines the shape and mechanical properties of the cell nucleus. BioEssays 30:226–236, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Together with microtubules and actin microfilaments, ∼11 nm wide intermediate filaments (IFs) constitute the integrated, dynamic filament network present in the cytoplasm of metazoan cells. This network is critically involved in division, motility and other cellular processes. While the structures of microtubules and microfilaments are known in atomic detail, IF architecture is presently much less understood. The elementary ‘building block’ of IFs is a highly elongated, rod‐like dimer based on an α‐helical coiled‐coil structure. Assembly of cytoplasmic IF proteins, such as (...) vimentin, begins with a lateral association of dimers into tetramers and gradually into the so‐called unit‐length filaments (ULFs). Subsequently ULFs start to anneal longitudinally, ultimately yielding mature IFs after a compaction step. For nuclear lamins, however, assembly starts with a head‐to‐tail association of dimers. Recently, X‐ray crystallographic data were obtained for several fragments of the vimentin dimer. Based on the dimer structure, molecular models of the tetramer and the entire filament are now a possibility. BioEssays 25:243–251, 2003. © 2003 Wiley Periodicals, Inc. (shrink)