AU Microscopii is among the most heavily spotted stars while hosting one of the best targets for atmospheric characterization of sub-Neptune worlds, given the temperature (3700 K), proximity (9.7 pc), and age (20-25 Myr) of the system. HST/WFC3 transmission spectrum observations of its innermost planet, AU Mic b, are expected to exhibit strong atmospheric absorption, but these signals are obscured by various forms of stellar activity. In this talk, I will discuss a method of decontaminating the transmission spectrum that uses chromatic information in the spectroscopic light curves to characterize the stellar surface alongside the planetary atmosphere.
Um gefährliche Auswirkungen der Sonnenaktivität geht es im Vortrag „Gefahren von Weltraumwetter für unsere moderne Infrastruktur“. Volker Bothmer vom Institut für Astrophysik und Geophysik der Universität Göttingen berichtet von den Problemen, zu den heftige Sonnenstürme auf der Erde führen können.
Biological membranes undergo dramatic shape transformations during vesicle release, organelle division, and intracellular trafficking. At the microscopic level these events require a change in membrane topology: the transformation of one continuous membrane into two separate ones. Such transitions occur on nanometre length scales where lipids must rearrange into highly curved, non-bilayer structures while still preserving the membrane’s barrier function.
In cells, specialized proteins such as dynamin catalyze these topological transitions. In this talk I will show how theoretical modelling and simulations can reveal the mechanisms and the control knobs that make them fast, reliable, and sometimes leaky. Using self-consistent field theory, coarse-grained molecular simulations, and phenomenological models, we map the energy landscapes governing membrane fusion and fission and identify the transient intermediates that dominate them, including hemifusion diaphragms, stalks, rim pores, and worm-like micelles.
A central message is that small changes in membrane composition or membrane–protein interactions can strongly reshape the energy landscape, producing large changes in the free-energy barriers and therefore in the rates and outcomes of membrane division. I will also discuss how multiple-membrane geometries, such as mitochondria and endoplasmic-reticulum contact sites, open additional pathways to membrane fission through transient inter-membrane fusion events.
