Mellum Island (southern North Sea): dynamic processes and sedimentary structures. I. Southern tidal flat, transition zone and high-surface.[p.72 (Blasensand) only][Translation from: Senckenbergiana Maritima 11, 59-113, 1979]

This partial translation of a longer article describes the phenomenon of ”Blasensand”. Blasensand is formed when sedimentation of dried out sand is suddenly flooded from above. A more detailed explanation of Blasensand is given in this translated part of the paper

Sedimentological studies of the "Ilha de Marchantaria" in the Solimões/Amazon River near Manaus

Sedimentological studies on the Ilha de Marchantaria an island in the Amazon river near Manaus reveal the existence of four different structural main units. A: Sandy channel bars consisting of giant ripples constitute deposits for the formation of islands or newly formed areas of the Varzea. B: Gradual accumulation on the channel bars leads to the formation of point bar ridges which consist chiefly of small-scale ripples. C: Between point bar ridges of different ages there exist swales. During rising water level the river water flows from the downward side into the swales where finegrained sediments are deposited. D: Permanent lakes are formed mainly in the centre of the islands. During low water periods the lakes may be cut of from the river. During high water periods when the whole island is flooded by the river, additional sedimentation takes place especially in the upstream area of the island. There is however, extensive erosion of the banks on the upstream side of the island. By erosion of the upstream end and sedimentation processes on the downstream end the island moves slowly downstream

Investigating the origin of time with trapped ions

Even though quantum systems in energy eigenstates do not evolve in time, they can exhibit correlations between internal degrees of freedom in such a way that one of the internal degrees of freedom behaves like a clock variable, and thereby defines an internal time, that parametrises the evolution of the other degrees of freedom. This situation is of great interest in quantum cosmology where the invariance under reparametrisation of time implies that the temporal coordinate dissapears and is replaced by the Wheeler-DeWitt constraint. Here we show that this paradox can be investigated experimentally using the exquisite control now available on moderate size quantum systems. We describe in detail how to implement such an experimental demonstration using the spin and motional degrees of freedom of a single trapped ion.Comment: 5 page

New Insights into Cosmic Ray induced Biosignature Chemistry in Earth-like Atmospheres

With the recent discoveries of terrestrial planets around active M-dwarfs, destruction processes masking the possible presence of life are receiving increased attention in the exoplanet community. We investigate potential biosignatures of planets having Earth-like (N$_2$-O$_2$) atmospheres orbiting in the habitable zone of the M-dwarf star AD Leo. These are bombarded by high energetic particles which can create showers of secondary particles at the surface. We apply our cloud-free 1D climate-chemistry model to study the influence of key particle shower parameters and chemical efficiencies of NOx and HOx production from cosmic rays. We determine the effect of stellar radiation and cosmic rays upon atmospheric composition, temperature, and spectral appearance. Despite strong stratospheric O$_3$ destruction by cosmic rays, smog O$_3$ can significantly build up in the lower atmosphere of our modeled planet around AD Leo related to low stellar UVB. N$_2$O abundances decrease with increasing flaring energies but a sink reaction for N$_2$O with excited oxygen becomes weaker, stabilizing its abundance. CH$_4$ is removed mainly by Cl in the upper atmosphere for strong flaring cases and not via hydroxyl as is otherwise usually the case. Cosmic rays weaken the role of CH$_4$ in heating the middle atmosphere so that H$_2$O absorption becomes more important. We additionally underline the importance of HNO$_3$ as a possible marker for strong stellar particle showers. In a nutshell, uncertainty in NOx and HOx production from cosmic rays significantly influences biosignature abundances and spectral appearance.Comment: Manuscript version after addressing all referee comments. Published in Ap