Multiwavelength focusing with the Sun as gravitational lens

The light deviation caused by the gravitational potential in the vicinity of the sun could be used as a means of focussing radiation that cannot be focussed easily otherwise. The gravitational lens formed by the sun is not stigmatic, but does have the advantage of being achromatic and acts identically on all types of mass-less radiations. For a source at infinity, its geometrical characteristics present a “caustic” line starting at 550 astronomical units (UA) downstream from the sun. In a plane perpendicular to that caustic line, images of distant objects are formed.The perturbations by the solar corona plasma will significantly blur electromagnetic radiation for wavelengths longer than those of the IR domain. At shorter wavelengths, for example the γ domain, the focussing process could lead to 10⁸ amplification factors. In order to reach the regions where images are formed, long distance space missions are necessary. Once launched, missions of this type would be dedicated to a single field. Some possible targets are considered, such as Sagitarius A observed in X and γ rays.In this paper we study the point spread function (PSF) of the sun as a gravitational lens. Taking into account perturbations by the planets, the non sphericity of the sun and coronal plasma index, we derive limits within which such observations could be possible.     

Implosions and emplosions in supermassive objects

It is shown that for small velocities the time dependent evolution of massive stars may be described by a series of static models. Those are linked to each other by one continuous time dependent parameter-the relativity effect. The fate of the dynamic system is analyzed by the behaviour of the static models. The method is illustrated for general relativistic polytropes.     

Coastal coal pollution increases Cd concentrations in the predatory gastropod Hexaplex trunculus and is detrimental to its health

Parameters of environmental health, including paracellular permeability of external epithelia, functional state of lysosomes and the level of metallothioneins (MTs), were examined using fluorescent markers and vital microfluorometry in different tissues of the marine gastropod, Hexaplex trunculus, from a coal-polluted and coal-free site. Vital microfluorometrical examinations exhibited enhanced paracellular permeability of external epithelia to the anionic marker, fluorescein (FLU), lower lysosomal accumulation of neutral red (NR) as well as higher levels of MTs, when compared with epithelia of gastropods from the coal-free site. Those differences were particularly marked in the foot epithelium, which is in direct contact with the substrate. In addition, cadmium was measured by ICP-AES in the hepatopancreas of gastropods sampled from the coal-polluted site and two coal-free sites. Significantly higher levels of Cd were found in gastropod hepatopancreas from the coal-polluted site. In addition, two months feeding experiments conducted in aquaria containing: (a) coal pieces covered by barnacles; (b) natural rocks covered by barnacles; and (c) natural rocks with barnacles + bare coal pieces, demonstrated significant increase of Cd concentration in the hepatopancreas of the gastropods exposed to coal. We suggest that coal in the marine environment has detrimental effects on marine gastropods, both directly through contact with the organisms and indirectly through the food web.     

Footprints in Homogeneously and Heterogeneously Driven Boundary Layers Derived from a Lagrangian Stochastic Particle Model Embedded into Large-Eddy Simulation

A Lagrangian stochastic (LS) model, which is embedded into a parallelised large-eddy simulation (LES) model, is used for dispersion and footprint evaluations. For the first time an online coupling between LES and LS models is applied. The new model reproduces concentration patterns, which were obtained in prior studies, provided that subgrid-scale turbulence is included in the LS model. Comparisons with prior studies show that the model evaluates footprints successfully. Streamwise dispersion leads to footprint maxima that are situated less far upstream than previously reported. Negative flux footprints are detected in the convective boundary layer (CBL). The wide range of applicability of the model is shown by applying it under neutral and stable stratification. It is pointed out that the turning of the wind direction with height leads to a considerable dependency of source areas on height. First results of an application to a heterogeneously heated CBL are presented, which emphasize that footprints are severely affected by the inhomogeneity.     

The photometric period of the cataclysmic variable HV Andromedae

We present four nights of time-resolved photometry of the cataclysmic variable star HV And. Our time series analysis has revealed a prominent period at 3.368 ± 0.060 h, as well as some low frequency power. We interpret this signal, from saw-tooth waves in the light curve, as evidence of superhumps in HV And.     

Macroscopic quantum resonators (MAQRO)

Quantum physics challenges our understanding of the nature of physical reality and of space-time and suggests the necessity of radical revisions of their underlying concepts. Experimental tests of quantum phenomena involving massive macroscopic objects would provide novel insights into these fundamental questions. Making use of the unique environment provided by space, MAQRO aims at investigating this largely unexplored realm of macroscopic quantum physics. MAQRO has originally been proposed as a medium-sized fundamental-science space mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments: DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative Acceleration Sensing Experiment). The main scientific objective of MAQRO, which is addressed by the experiment DECIDE, is to test the predictions of quantum theory for quantum superpositions of macroscopic objects containing more than 10⁸ atoms. Under these conditions, deviations due to various suggested alternative models to quantum theory would become visible. These models have been suggested to harmonize the paradoxical quantum phenomena both with the classical macroscopic world and with our notion of Minkowski space-time. The second scientific objective of MAQRO, which is addressed by the experiment CASE, is to demonstrate the performance of a novel type of inertial sensor based on optically trapped microspheres. CASE is a technology demonstrator that shows how the modular design of DECIDE allows to easily incorporate it with other missions that have compatible requirements in terms of spacecraft and orbit. CASE can, at the same time, serve as a test bench for the weak equivalence principle, i.e., the universality of free fall with test-masses differing in their mass by 7 orders of magnitude.     

Anelastic convection-driven dynamo benchmarks: A finite element model

We present a fully non-linear, anelastic convection and dynamo model in a rotating spherical shell that is based on a finite element method. It is shown that both the hydrodynamic steadily drifting convection and convection-driven steadily drifting dynamo are in satisfactory agreement with the anelastic convection and dynamo benchmark based on the pseudo-spectral method (Jones, C.A., Boronski, P., Brun, A.S., Glatzmaier, G.A., Gastine, T., Miesch, M.S., Wicht, J. [2011]. Icarus, 216, 120–135).