How to integrate geochemistry at affordable costs into reactive transport for large-scale systems: Abstract Book

This international workshop entitled “How to integrate geochemistry at affordable costs into reac-tive transport for large-scale systems” was organized by the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden Rossendorf in Feb-ruary 2020. A mechanistic understanding and building on that an appropriate modelling of geochemical processes is essential for reliably predicting contaminant transport in groundwater systems, but also in many other cases where migration of hazardous substances is expected and consequently has to be assessed and limited. In case of already present contaminations, such modelling may help to quantify the threads and to support the development and application of suitable remediation measures. Typical application areas are nuclear waste disposal, environmental remediation, mining and milling, carbon capture & storage, or geothermal energy production. Experts from these fields were brought together to discuss large-scale reactive transport modelling (RTM) because the scales covered by such pre-dictions may reach up to one million year and dozens of kilometers. Full-fledged incorporation of geochemical processes, e.g. sorption, precipitation, or redox reactions (to name just a few important basic processes) will thus create inacceptable long computing times. As an effective way to integrate geochemistry at affordable costs into RTM different geochemical concepts (e.g. multidimensional look-up tables, surrogate functions, machine learning, utilization of uncertainty and sensitivity analysis etc.) exist and were extensively discussed throughout the workshop. During the 3-day program of the workshop keynote and regular lectures from experts in the field, a poster session, and a radio lab tour had been offered. In total, 40 scientists from 28 re-search institutes and 8 countries participated

Stability of the shell structure in 2D quantum dots

We study the effects of external impurities on the shell structure in semiconductor quantum dots by using a fast response-function method for solving the Kohn-Sham equations. We perform statistics of the addition energies up to 20 interacting electrons. The results show that the shell structure is generally preserved even if effects of high disorder are clear. The Coulomb interaction and the variation in ground-state spins have a strong effect on the addition-energy distributions, which in the noninteracting single-electron picture correspond to level statistics showing mixtures of Poisson and Wigner forms.Comment: 7 pages, 8 figures, submitted to Phys. Rev.

Optically nonlinear energy transfer in light-harvesting dendrimers

Dendrimeric polymers are the subject of intense research activity geared towards their implementation in nanodevice applications such as energy harvesting systems,organic light-emitting diodes, photosensitizers, low-threshold lasers, and quantum logic elements, etc. A recent development in this area has been the construction of dendrimers specifically designed to exhibit novel forms of optical nonlinearity, exploiting the unique properties of these materials at high levels of photon flux. Starting from a thorough treatment of the underlying theory based on the principles of molecular quantum electrodynamics, it is possible to identify and characterize several optically nonlinear mechanisms for directed energy transfer and energy pooling in multichromophore dendrimers. Such mechanisms fall into two classes: first, those where two-photon absorption by individual donors is followed by transfer of the net energy to an acceptor; second, those where the excitation of two electronically distinct but neighboring donor groups is followed by a collective migration of their energy to a suitable acceptor. Each transfer process is subject to minor dissipative losses. In this paper we describe in detail the balance of factors and the constraints that determines the favored mechanism, which include the excitation statistics, structure of the energy levels, laser coherence factors, chromophore selection rules and architecture, possibilities for the formation of delocalized excitons, spectral overlap, and the overall distribution of donors and acceptors. Furthermore, it transpires that quantum interference between different mechanisms can play an important role. Thus, as the relative importance of each mechanism determines the relevant nanophotonic characteristics, the results reported here afford the means for optimizing highly efficient light-harvesting dendrimer devices

Light emission patterns from stadium-shaped semiconductor microcavity lasers

We study light emission patterns from stadium-shaped semiconductor (GaAs) microcavity lasers theoretically and experimentally. Performing systematic wave calculations for passive cavity modes, we demonstrate that the averaging by low-loss modes, such as those realized in multi-mode lasing, generates an emission pattern in good agreement with the ray model's prediction. In addition, we show that the dependence of experimental far-field emission patterns on the aspect ratio of the stadium cavity is well reproduced by the ray model.Comment: 5 pages, 4 figure

Understanding atypical emotions among children with autism

Children with autism are said to be poor mind readers: They have a limited understanding of the role that mental states play in determining emotions and behavior. In this research, 23 high-functioning children from the autistic spectrum (M age 9 years 3 months), 42 6-year-old controls, and 43 10-year-old controls were presented with six emotion-evoking stories and they were asked to explain protagonists' typical and atypical emotions. In the case of typical emotions, as expected on the basis of the mindblind hypothesis, children from the autistic spectrum gave few mental state explanations, referring to fewer than even the 6-year-old control group. However, in the case of atypical emotions, the autistic group performed as well as the 10-year-old controls. Their explanations for the atypical emotions demonstrate that children from the autistic spectrum indeed have the capacity to mind read (with respect to both desires and beliefs), although they do not always use this capacity in the same way as normally developing children. It is argued that the mind-reading capacity of high-functioning children from the autistic spectrum might be basically intact; unused in everyday circumstances but not necessarily defective

Attention to facial emotion expressions in children with autism

High-functioning children in the autism spectrum are frequently noted for their impaired attention to facial expressions of emotions. In this study, we examined whether attention to emotion cues in others could be enhanced in children with autism, by varying the relevance of children's attention to emotion expressions. Twenty-eight high-functioning boys with autism and 31 boys from a control group were asked to sort photos depicting smiling or frowning faces of adults. As found in earlier studies, in neutral conditions children with autism were less attentive to emotion expressions than children from a control group. This difference disappeared when children were explicitly asked to make a socially relevant decision. These findings suggest that the attention of children with autism to emotion expressions in others is influenced by situational factors. Theoretical implications of these findings are discussed. © 2006 SAGE Publications and The National Autistic Society

Universal Statistics of the Scattering Coefficient of Chaotic Microwave Cavities

We consider the statistics of the scattering coefficient S of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental S data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized, complex scattering coefficient whose Probability Density Function (PDF) is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We compare experimental PDFs of the normalized scattering coefficients with those obtained from Random Matrix Theory (RMT), and find excellent agreement. The results apply to scattering measurements on any wave chaotic system.Comment: 10 pages, 8 Figures, Fig.7 in Color, Submitted to Phys. Rev.

Geometric and impurity effects on quantum rings in magnetic fields

We investigate the effects of impurities and changing ring geometry on the energetics of quantum rings under different magnetic field strengths. We show that as the magnetic field and/or the electron number are/is increased, both the quasiperiodic Aharonov-Bohm oscillations and various magnetic phases become insensitive to whether the ring is circular or square in shape. This is in qualitative agreement with experiments. However, we also find that the Aharonov-Bohm oscillation can be greatly phase-shifted by only a few impurities and can be completely obliterated by a high level of impurity density. In the many-electron calculations we use a recently developed fourth-order imaginary time projection algorithm that can exactly compute the density matrix of a free-electron in a uniform magnetic field.Comment: 8 pages, 7 figures, to appear in PR

Personality composition and performance in entrepreneurial teams:understanding the impact of stability and plasticity traits in a relative contribution model

Considering that personalities of entrepreneurs are diverse, we examine how the personality composition of entrepreneurial teams affects team performance. Given the specific challenges of the entrepreneurship setting, we suggest a new understanding of the team composition-team performance link by (1) taking a meta-perspective to personality that considers the stability vs. plasticity underlying the Big Five traits and by (2) applying a relative contribution (minimum/maximum) conceptualisation of team composition. We conduct a quantitative study with 104 entrepreneurial teams. Our findings indicate that high entrepreneurial team performance requires all team members to have minimum levels of stability-related traits (agreeableness, emotional stability, conscientiousness), but only one team member with high plasticity-related traits (openness, extraversion)

The Potential of iPS Cells in Synucleinopathy Research

α-synuclein is a protein involved in the pathogenesis of several so-called synucleinopathies including Parkinson's disease. A variety of models have been so far assessed. Human induced pluripotent stem cells provide a patient- and disease-specific model for in vitro studies, pharmacotoxicological screens, and hope for future cell-based therapies. Initial experimental procedures include the harvest of patients' material for the reprogramming process, the investigation of the patients genetic background in the cultured cells, and the evaluation of disease-relevant factors/proteins under various cell culture conditions