Analytical and numerical methods for finite-strain elastoplasticity

An important class of finite-strain elastoplasticity is based on the multiplicative decomposition of the strain tensor $F=F_el F_pl$ and hence leads to complex geometric nonlinearities. This survey describes recent advances on the analytical treatment of time-incremental minimization problems with or without regularizing terms involving strain gradients. For a regularization controlling all of $abla F_pl$ we provide an existence theory for the time-continuous rate-independent evolution problem, which is based on a recently developed energetic formulation for rate-independent systems in abstract topological spaces. In systems without gradient regularization one encounters the formation of microstructures, which can be described by sequential laminates or more general gradient Young measures. We provide a mathematical framework for the evolution of such microstructure and discuss algorithms for solving the associated space-time discretizations. We outline in a finite-step-sized incremental setting of standard dissipative materials details of relaxation-induced microstructure development for strain softening von Mises plasticity and single-slip crystal plasticity. The numerical implementations are based on simplified assumptions concerning the complexity of the microstructures

Integration of Hyperspectral and Magnetic Data for Geological Characterization of the Niaqornarssuit Ultramafic Complex in West-Greenland

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Korpusbasierte Analyse österreichischer Parlamentsreden

Dieser Beitrag beschreibt, wie aus Plenarprotokollen des Österreichischen Nationalrats generierte Korpora computerbasiert analysiert werden können. Konkret sollen dabei mit korpuslinguistischen Methoden diskursspezifische Schlagwörter und Wortgruppen (n-Gramme) aus den Nationalratsreden extrahiert werden. In einer Fallstudie wird auf die Beiträge der Abgeordneten zweier im politischen Spektrum weit voneinander entfernter Parteien fokussiert: GRÜNE und FPÖ. Mit Hilfe der so gewonnenen Daten soll die inhaltliche Analyse der stenografischen Protokolle erleichtert werden und die kontrastive Gegenüberstellung beispielsweise von Positionen, politischen Konzepten oder Wertvorstellungen in den Reden der Abgeordneten der unterschiedlichen Parteien ermöglicht werden

C-Terminal regions of topoisomerase IIα and IIβ determine isoform-specific functioning of the enzymes in vivo

Topoisomerase II removes supercoils and catenanes generated during DNA metabolic processes such as transcription and replication. Vertebrate cells express two genetically distinct isoforms (α and β) with similar structures and biochemical activities but different biological roles. Topoisomerase IIα is essential for cell proliferation, whereas topoisomerase IIβ is required only for aspects of nerve growth and brain development. To identify the structural features responsible for these differences, we exchanged the divergent C-terminal regions (CTRs) of the two human isoforms (α 1173-1531 and β 1186-1621) and tested the resulting hybrids for complementation of a conditional topoisomerase IIα knockout in human cells. Proliferation was fully supported by all enzymes bearing the α CTR. The α CTR also promoted chromosome binding of both enzyme cores, and was by itself chromosome-bound, suggesting a role in enzyme targeting during mitosis. In contrast, enzymes bearing the β CTR supported proliferation only rarely and when expressed at unusually high levels. A similar analysis of the divergent N-terminal regions (α 1-27 and β 1-43) revealed no role in isoform-specific functions. Our results show that it is the CTRs of human topoisomerase II that determine their isoform-specific functions in proliferating cells. They also indicate persistence of some functional redundancy between the two isoforms

Numerical approach to a model for quasistatic damage with spatial BV-regularization

We address a model for rate-independent, partial, isotropic damage in quasistatic small strain linear elasticity, featuring a damage variable with spatial BV-regularization. Discrete solutions are obtained using an alternate time-discrete scheme and the Variable-ADMM algorithm to solve the constrained nonsmooth optimization problem that determines the damage variable at each time step. We prove convergence of the method and show that discrete solutions approximate a semistable energetic solution of the rate-independent system. Moreover, we present our numerical results for two benchmark problems

Cryo-EM structures reveal intricate Fe-S cluster arrangement and charging in Rhodobacter capsulatus formate dehydrogenase

Metal-containing formate dehydrogenases (FDH) catalyse the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active site. They display a diverse subunit and cofactor composition, but structural information on these enzymes is limited. Here we report the cryo-electron microscopic structures of the soluble Rhodobacter capsulatus FDH (RcFDH) as isolated and in the presence of reduced nicotinamide adenine dinucleotide (NADH). RcFDH assembles into a 360 kDa dimer of heterotetramers revealing a putative interconnection of electron pathway chains. In the presence of NADH, the RcFDH structure shows charging of cofactors, indicative of an increased electron load

Potentials of Thermal Energy Storage Integrated into Steam Power Plants

For conventional power plants, the integration of thermal energy storage opens up a promising opportunity to meet future technical requirements in terms of flexibility while at the same time improving cost-effectiveness. In the FLEXI-TES joint project, the flexibilization of coal-fired steam power plants by integrating thermal energy storage (TES) into the power plant process is being investigated. In the concept phase at the beginning of the research project, various storage integration concepts were developed and evaluated. Finally, three lead concepts with different storage technologies and integration points in the power plant were identified. By means of stationary system simulations, the changes of net power output during charging and discharging as well as different storage efficiencies were calculated. Depending on the concept and the operating strategy, a reduction of the minimum load by up to 4% of the net capacity during charging and a load increase by up to 5% of the net capacity during discharging are possible. Storage efficiencies of up to 80% can be achieved

Generation and deposition of A43 by the virtually inactive presenilin-1 L435F mutant contradicts the presenilin loss-of-function hypothesis of Alzheimer's disease

As stated by the prevailing amyloid cascade hypothesis, Alzheimer's disease (AD) is caused by the aggregation and cerebral deposition of long amyloid- peptide (A) species, which are released from a C-terminal amyloid precursor protein fragment by -secretase. Mutations in its catalytic subunit presenilin-1 (PS1) increase the A42 to A40 ratio and are the major cause of familial AD (FAD). An opposing hypothesis states that loss of essential presenilin functions underlies the disease. A major argument for this hypothesis is the observation that the nearly inactive PS1 L435F mutant, paradoxically, causes FAD. We now show that the very little A generated by PS1 L435F consists primarily of A43, a highly amyloidogenic species which was overlooked in previous studies of this mutant. We further demonstrate that the generation of A43 is not due to a trans-dominant effect of this mutant on WT presenilin. Furthermore, we found A43-containing plaques in brains of patients with this mutation. The aberrant generation of A43 by this particular mutant provides a direct objection against the presenilin hypothesis