Wigner molecules in quantum dots

We perform unrestricted Hartree-Fock (HF) calculations for electrons in a parabolic quantum dot at zero magnetic field. The crossover from Fermi liquid to Wigner molecule behavior is studied for up to eight electrons and various spin components $S_z$. We compare the results with numerically exact path-integral Monte Carlo simulations and earlier HF studies. Even in the strongly correlated regime the symmetry breaking HF solutions provide accurate estimates for the energies and describe the one-particle densities qualitatively. However, the HF approximation favors the formation of a Wigner molecule and produces azimuthal modulations of the density for even numbers of electrons in one spatial shell.Comment: 5 pages, figures include

Beitrag zur Kenntnis der Gewässergüte im Hahnenmoorkanalgebiet (Landkreis Osnabrück) anhand der Wirbellosenfauna

Über die Zusammensetzung der substratgebundenen Wirbellosenfauna zahlreicher Fließgewässer des Hahnenmoorkanalgebietes, etwa 50 km nordwestlich von Osnabrück in Niedersachsen, wird berichtet. Der jeweilige ökologische Zustand wird beschrieben. Vorschläge werden gemacht, wie mögliche Schadwirkungen auf aquatische Ökosysteme, die nach dem geplanten Gewässerausbau zu erwarten sind, vermieden werden können.The composition of benthic invertebrate communities is determined in numerous running waters in the Hahnenmoorkanalgebiet, about 50 km north-west of Osnabrück, Lower Saxony. Discriptions of the individual ecological situations are given. Proposals are formulated how possible destructive effects on aquatic ecosystems by planned brook regulations can be avoided

MAGED2: the gene associated with Bartter syndrome type 5 is a key regulator of Gαs signalling in the developing kidney

Pathogenic variants in the Melanoma-Associated Antigen D2 (MAGED2) gene have been identified as the cause of the severe but transient antenatal Bartter syndrome type 5 (BS5) accounting for approximately 10% of all Bartter syndrome cases. The disorder is characterized by severe polyhydramnios leading to premature delivery and still birth as well as postnatal polyuria that declines after a few weeks or months followed by normal further development. The underlying molecular mechanisms of BS5 and especially the function of MAGED2 in kidney physiology had been largely unknown so far. In this study, we show that Maged2 expression in mouse embryonic kidneys declines during development. As MAGED2 interacts with G-protein alpha subunit Gαs (GNAS), it was inferred to play a role in G-protein coupled receptor (GPCR) signalling. Accordingly, we showed that knockdown of MAGED2 in HEK293T cells induces major changes in protein phosphorylation but not in protein abundance. In the murine collecting duct cell line mpkCCD, Maged2 knockdown modulated vasopressin type 2 receptor (V2R)-induced phosphorylation-dependent signalling in terms of cAMP kinetics and weakened phosphorylation on downstream targets like cAMP response element-binding protein (CREB). Unexpectedly, Maged2 knockdown resulted in vitro in a marked increase of the water channel aquaporin-2 (AQP2) abundance upon long-term V2R activation, which was mediated transcriptionally. To further analyse Maged2 function in vivo, we generated a knock-in mouse model of the human mutation p.R446C via CRISPR/Cas9. Mendelian ratio of Maged2R446C/Y mice was clearly skewed towards the wildtype genotype. Affected male mice also showed impaired embryonic development in form of general paleness as well as slightly decreased body and kidney weight. On the proteome level MAGED2 loss in P0 kidneys led to significant alterations of abundance of 307 proteins, with 112 proteins showing increased and 195 proteins showing decreased expression. Remarkably, Gαs was significantly upregulated, while the Thiazide-Sensitive Sodium-Chloride Cotransporter (NCC) was significantly downregulated. Localization studies in kidneys from P0 Maged2R446C/Y mice could not show an aberrant localization of targets defective in other types of BS like the cotransporters Na-K-2Cl Cotransporter 2 (NKCC2), NCC and the Potassium Inwardly Rectifying Channel Subfamily J Member 1 (ROMK), while the apical localization of AQP2 and also its phosphorylated form pAQP2 were clearly impaired. A similar diffuse instead of apical AQP2 distribution was observed in the only available kidney sections from a stillborn BS5 infant. Taken together, MAGED2 modulates GPCR-signalling at a specific period of time and acts as a desensitizer of V2R in vitro. Moreover, we demonstrate that Maged2 loss in vivo impairs the abundance and the targeting of numerous renal proteins which could explain the overall severe character of the disease in comparison to other forms of Bartter syndrome. The studies presented here serve as a basis for further research on BS5, potentially allowing the development of targeted treatments for this disease. Especially the mouse model will help us to dissect the complex effects of MAGED2 in health and disease and integrate the discovery in the context of tubulopathies and general fluid homeostasis. Ultimately, backtracking the reductive cascade of MADED2 functions will yield a more precise understanding of fluid and electrolyte homeostasis during embryonic development and beyond

Organismen von morgen im Experiment von heute – experimentelle Evolution mit Phytoplankton

Der globale Wandel erfasst zunehmend auch die Weltmeere und ihre Lebewelt. Insbesondere Erwärmung und Ozeanversauerung könnte den Beginn der Nahrungskette beeinträchtigen, die mikroskopisch kleinen Pflanzen des Phytoplanktons. Diese Einzeller tragen zur Hälfte der gesamten Biomasse - Produktion auf unserem Planeten bei. Das allermeiste Wissen über ihre Reaktionen auf die globalen Umweltveränderungen hat die Meeresbiologie aus Kurzzeit-Experimenten. Doch die Organismen von morgen könnten auch ganz anders auf die neuen Bedingungen reagieren, sofern sie sich evolutiv anpassen. Der Vortrag stellt den neuen Ansatz von Evolutionsexperimenten in der Meereskunde vor. Dieser ermöglicht es, die Organismen von morgen heute im Labor zu untersuchen. Wie erwartet können sich einige Arten rechtzeitig anpassen, ihre Anpassungsrate ist dabei schneller als die prognostizierten Umweltänderungen. In einem Ausblick werden die evolutionsbiologischen Konzepte auch auf andere Bereiche in der Meeresbiologie übertragen wie die Fischerei