Ab initio simulations of liquid systems: Concentration dependence of the electric conductivity of NaSn alloys

Liquid NaSn alloys in five different compositions (20, 40, 50, 57 and 80% sodium) are studied using density functional calculations combined with molecular dynamics(Car-Parrinello method). The frequency-dependent electric conductivities for the systems are calculated by means of the Kubo-Greenwood formula. The extrapolated DC conductivities are in good agreement with the experimental data and reproduce the strong variation with the concentration. The maximum of conductivity is obtained, in agreement with experiment, near the equimolar composition. The strong variation of conductivity, ranging from almost semiconducting up to metallic behaviour, can be understood by an analysis of the densities-of-states.Comment: LaTex 6 pages and 2 figures, to appear in J.Phys. Cond. Ma

Hirnorganoide – Modellsysteme des menschlichen Gehirns

This is the final version. Available from Deutsche Akademie der Naturforscher Leopoldina via the DOI in this record. Hirnorganoide sind Gewebestrukturen aus dem Labor, die Teile der Hirnfunktion imitieren. Sie eröffnen als vereinfachtes Modellsystem einen experimentellen Zugang zu Fragen rund um die Entwicklung und die Funktion des menschlichen Gehirns. Während die Forschung an menschlichen lebenden Gehirnen aus ethischen Gründen enge Grenzen hat und Tiermodelle viele Fragen nur bedingt beantworten können, bieten Hirnorganoide neue Forschungsmöglichkeiten. In der Stellungnahme „Hirnorganoide ‒ Modellsysteme des menschlichen Gehirns“ der Nationalen Akademie der Wissenschaften Leopoldina beschreiben Wissenschaftlerinnen und Wissenschaftler die Möglichkeiten dieses Forschungsgebietes und erörtern, ob es aus ethischen oder juristischen Gründen stärker reguliert werden sollte

Prenatal Diagnosis of Oculocutaneous Albinism by Electron Microscopy of Fetal Skin

Oculocutaneous albinism was diagnosed prenatally by electron microscopic examination of fetal skin samples taken during fetoscopy at 20 weeks of gestation. Melanosome development in hair bulb melanocytes progressed no further than stage II, indicating a lack of melanin synthesis. In 4 age-matched control fetuses, numerous stage IV melanosomes, signifying active melanin synthesis, were identified. The diagnosis was confirmed after the pregnancy was terminated at 22 weeks. Examination of the fetal eye showed absence of pigment in the retinal epithelium and uvea at a stage when ocular melanogenesis would normally be active. This study shows that oculocutaneous albinism can be detected in the second trimester using similar techniques to those employed in the prenatal diagnosis of epidermolysis bullosa and ichthyosis

Neuroenhancement von Emotionen : zum Begriff emotionaler Authentizität

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