Radiation hydrodynamics integrated in the code PLUTO

The transport of energy through radiation is very important in many astrophysical phenomena. In dynamical problems the time-dependent equations of radiation hydrodynamics have to be solved. We present a newly developed radiation-hydrodynamics module specifically designed for the versatile MHD code PLUTO. The solver is based on the flux-limited diffusion approximation in the two-temperature approach. All equations are solved in the co-moving frame in the frequency independent (grey) approximation. The hydrodynamics is solved by the different Godunov schemes implemented in PLUTO, and for the radiation transport we use a fully implicit scheme. The resulting system of linear equations is solved either using the successive over-relaxation (SOR) method (for testing purposes), or matrix solvers that are available in the PETSc library. We state in detail the methodology and describe several test cases in order to verify the correctness of our implementation. The solver works in standard coordinate systems, such as Cartesian, cylindrical and spherical, and also for non-equidistant grids. We have presented a new radiation-hydrodynamics solver coupled to the MHD-code \PLUTO that is a modern, versatile and efficient new module for treating complex radiation hydrodynamical problems in astrophysics. As test cases, either purely radiative situations, or full radiation-hydrodynamical setups (including radiative shocks and convection in accretion discs) have been studied successfully. The new module scales very well on parallel computers using MPI. For problems in star or planet formation, we have added the possibility of irradiation by a central source.Comment: 13 pages, 11 figures, accepted by Astronomy & Astrophysic

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Cationic palladium allyl complexes [η3-C3H5)Pd(k2P^O)]+SbF6- (2[SbF6],P^O= Ph2P(CH2)2C-(=O)OEt; 3[SbF6], o-Ph2PC6H4C(=O)OEt; 4[SbF6], Ph2P(CH2)2P(=O)Ph2) have been prepared. In all complexes the oxygen donor can be displaced by other ligands such as carbon monoxide and ethylene. Displacement of an ester donor occurs much more readily than displacement of the phosphine oxide function. Above 0°C, the resulting ethylene complexes [η3-C3H5)Pd(C2H4)(k1P~O)]+ react to give (1,2,5-η3)-pent-1-en-5-yl complexes [(H2C=CH(CH2)3Pd(k2P^O)]+. A rate constant of e.g. k(17°C) = (2.27 ± 0.11) × 10-4 s-1 was determined for P,O ≡ Ph2P(CH2)2C(O)OEt by 1H NMR spectroscopy. Using 2-4 as catalyst precursors for ethylene dimerization, the allyl moiety is ultimately cleaved from the metal center as 1,4-pentadiene

Morphological structures relate to the location and extent of the seismogenic zone - bathymetric studies of the Sunda margin, Indonesia

Earthquake history shows that the Sunda subduction zone of the Indonesian margin produces great earthquakes offshore Sumatra, whereas earthquakes of comparable magnitude are lacking offshore Java and the Lesser Sunda islands. Morphological structures from multibeam bathymetric data across the forearc relate with the extent of the seismogenic zone (SZ). Off Java and the Lesser Sunda islands the Indo-Australian plate subducts almost normal underneath the oceanic plate of the Indonesian archipelago. Landward of the trench, the outer wedge of the slope break is ~50 km uniformly wide with uniform bathymetric gradients. The slope of the outer wedge is locally cut by one/two steeper ridges of ~5 km extent. The sharp slope break corresponds to the updip limit of the SZ, which is also associated with the seawardmost part of the outer arc high. Landward of the slope break we find narrow, uniform outer arc ridges. The landward termination of these ridges coincides with the downdip limit of the SZ. The intersection of the shallow upper plate mantle with the subduction thrust fault marks the downdip limit of the SZ beneath the forearc. Off Sumatra the Indo-Australian plate subducts obliquely underneath the continental part of the Indonesian Sunda margin. Landward of the trench, the outer wedge varies, being mostly ~70 km wide, in some areas narrowing to 50 km width. The lower slope bathymetric gradients are steep. The outer wedge slope is made up of several steeper ridges of ~5 km extent. The slope break is only locally sharp, and corresponds to the updip limit of the SZ. The outer arc ridges off Sumatra are, in comparison with the forearc structures off Java and the Lesser Sunda islands, wider and partly elevated above sea level forming the Mentawai forearc islands. The downdip limit of the SZ coincides with the intersection of a deeper upper plate mantle with the subduction thrust fault beneath the forearc. Sunda Strait marks a transition zone between the Sumatra and Java margins. Seafloor morphology enables the identification of the seismogenic zone (SZ) across the entire Sunda margin. The SZ is uniformly wide for the Sumatra margin and narrows off Sunda Strait. Sunda Strait is the transition between the Sumatra margin and the uniformly narrow extent of the SZ of the Java/Lesser Sunda margin. Comparing the Java and Lesser Sunda islands with the Sumatra margin we find the differences along the Sunda margin, especially the wider extent of the SZ off Sumatra, producing larger earthquakes, to result from the combination of various causes: The sediment income on the oceanic incoming plate and the subduction direction; we attribute a major role to the continental/oceanic upper plate nature of Sumatra/Java influencing the composition and deformation style along the forearc and subduction fault. Off Sumatra the SZ is up to more than twice as wide as off Java/Lesser Sunda islands, enlarging the unstable regime off Sumatra and thus the risk of sudden stress release in a great earthquake

Unkrautbekämpfung durch Stoppel-bearbeitung – Ergebnisse aus zwei Jahren Praxisversuche im Ökologischen Landbau

Einleitung In den Zeiten vor Einführung der Herbizide war der Schälpflug das gängige Gerät zur Stoppelbearbeitung. Aus verschiedenen Gründen verschwand er weitestgehend aus der Praxis, um vor allem durch den Grubber ersetzt zu werden. Unter den Produktionsbedingungen des konventionellen Landbaus hat der Verzicht auf den Schälpflug vermutlich keine negativen Folgen, während er im Ökologischen Landbau, besonders zur Bekämpfung mehrjähriger Unkräuter (z. B. Acker-kratzdistel, Ampfer, Quecke) durch seine flächig abschneidende und wendende Arbeitsweise durchaus ein wertvolles Gerät darstellen könnte