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

Blue-Light Irradiation Regulates Proliferation and Differentiation in Human Skin Cells

Sunlight influences the physiology of the human skin in beneficial as well as harmful ways, as has been shown for UV light. However, little is known about the effects of other wavelengths of solar irradiation. In this study we irradiated human keratinocytes and skin-derived endothelial cells with light-emitting-diode devices of distinct wavelengths to study the effects on cell physiology. We found that light at wavelengths of 632–940nm has no effect, but irradiation with blue light at 412–426nm exerts toxic effects at high fluences. Light at 453nm is nontoxic up to a fluence of 500J/cm2. At nontoxic fluences, blue light reduces proliferation dose dependently by up to 50%, which is attributable to differentiation induction as shown by an increase of differentiation markers. Experiments with BSA demonstrate that blue-light irradiation up to 453nm photolytically generates nitric oxide (NO) from nitrosated proteins, which is known to initiate differentiation in skin cells. Our data provide evidence for a molecular mechanism by which blue light may be effective in treating hyperproliferative skin conditions by reducing proliferation due to the induction of differentiation. We observed a photolytic release of NO from nitrosated proteins, indicating that they are light acceptors and signal transducers up to a wavelength of 453nm

Das römische Gräberfeld von Rheingönheim

Mit den vorhandenen Funden, die nach Materialgruppen gegliedert, bestimmt und chronologisch eingeordnet wurden, war es möglich, ein Bild des Siedlungsplatzes Rheingönheim in der römischen Epoche zu zeichnen und so die Nekropole zeitlich einzuordnen. Die Hauptbelegungszeit des Gräberfeldes liegt während der Kastellzeit, also 43 bis 74 n.Chr. Sie läuft nach der Kastellzeit weiter; die Belegungsdichte ist im 2. Jahrhundert ebenfalls noch hoch. Im 3., 4. und 5. Jh. n.Chr. gibt es noch vereinzelte Bestattungen, die mit der strategischen Lage des Platzes, also mit der nachgewiesenen Beneficiarierstation und der Befestigung in Altrip, zu tun haben könnten. Durch die Terra Sigillata Funde konnte der angenommene Gründungszeitraum um 43 n.Chr. belegt werden. Bei dieser Keramik sind die frühesten Formen (Drag. 29, 30) ab der claudischen Zeit zu datieren. Die Terra Sigillata stammt in erster Linie aus südgallischen Töpfereien, aber auch mittelgallische und ostgallische Ware ist vertreten. Spätere Stücke wurden bis ins 3. Jahrhundert in Rheinzabern produziert, die spätesten Terra Sigillata Stücke aus dem 4. Jahrhundert stammen unter anderem auch aus der späten Rheinzaberner Produktion und aus Nordfrankreich (Argonnenware). In der Münzreihe von Rheingönheim sind Münzen von der republikanischen Zeit (2. Jh. v.Chr.) bis in die 2. Hälfte des 4. Jh. n. Chr. vertreten. Die Gebrauchskeramik, allem voran die Graubelgische Ware, ist im Gräberfeld sehr stark vertreten. Sie wurde während der gesamten Hauptbelegungszeit des Gräberfeldes, also in der Kastellzeit bis zum Ende des 2. Jh. n.Chr., mit ins Grab gegeben. Auffällig sind viele Imitationen, sowohl von laténezeitlicher Keramik, als auch von Terra Sigillata Gefäßen. Die graubelgische Ware mit Rollrädchenverzierung paßt einerseits zur Gründungstheorie ab 43 n.Chr., andererseits gibt es diese auch schon innerhalb von früheren Fundzusammenhängen. Weiterhin wird das Fortbestehen der Besiedlung des Areals bis ins 4. Jh. n.Chr. durch Gebrauchskeramik belegt, welche mit der aus Niederbiber vergleichbar ist, auch Mayener Ware ist anzutreffen. Die übrigen Fundgattungen, die Bronze- und Eisenobjekte, Fibeln, Gläser, Tonlampen und figürlichen Balsamarien und Terrakotten bestätigen den zeitlichen Ansatz der Besiedlung des Platzes. Durch die Auswertung der Funde des Gräberfeldes konnte also eine Gründung des Kastells vor 43 n. Chr. nicht nachgewiesen werden. Nachgewiesen werden konnte, dass der Bestattungsplatz nach der Auflassung des Kastells noch weiterhin, kontinuierlich benutzt wurde. Für eine Herkunftsbestimmung der Kastellbesatztung, konnten keine weiteren Hinweise gefunden werden

Hydrogen peroxide production of underwater nanosecond-pulsed streamer discharges with respect to pulse parameters and associated discharge characteristics

Abstract Pulsed streamer discharges submerged in water have demonstrated potential in a number of applications. Especially the generation of discharges by short high-voltage pulses in the nanosecond range has been found to offer advantages with respect to efficacies and efficiencies. The exploited plasma chemistry generally relies on the initial production of short-lived species, e.g. hydroxyl radicals. Since the diagnostic of these transient species is not readily possible, a quantification of hydrogen peroxide provides an adequate assessment of underlying reactions. These conceivably depend on the characteristics of the high-voltage pulses, such as pulse duration, pulse amplitude, as well as pulse steepness. A novel electrochemical flow-injection system was used to relate these parameters to hydrogen peroxide concentrations. Accordingly, the accumulated hydrogen peroxide production for streamer discharges ignited in deionized water was investigated for pulse durations of 100 ns and 300 ns, pulse amplitudes between 54 kV and 64 kV, and pulse rise times from 16 ns to 31 ns. An independent control of the individual pulse parameters was enabled by providing the high-voltage pulses with a Blumlein line. Applied voltage, discharge current, optical light emission and time-integrated images were recorded for each individual discharge to determine dissipated energy, inception statistic, discharge expansion and the lifetime of a discharge. Pulse steepness did not affect the hydrogen peroxide production rate, but an increase in amplitude of 10 kV for 100 ns pulses nearly doubled the rate to (0.19 ± 0.01) mol l−1 s−1, which was overall the highest determined rate. The energy efficiency did not change with pulse amplitude, but was sensitive to pulse duration. Notably, production rate and efficiency doubled when the pulse duration decreased from 300 ns to 100 ns, resulting in the best peroxide production efficiency of (9.2 ± 0.9) g kWh−1. The detailed analysis revealed that the hydrogen peroxide production rate could be described by the energy dissipation in a representative single streamer. The production efficiency was affected by the corresponding discharge volume, which was comprised by the collective volume of all filaments. Hence, dissipating more energy in a filament resulted in an increased production rate, while increasing the relative volume of the discharge compared to its propagation time increased the energy efficiency

Weighting (Version 2.0)

This contribution deals with the fundamental principles of weighting; the various types of weighting are taken into account. Terms such as design weighting and adjustment weighting are explained, and the Horvitz-Thompson estimator and the GREG estimator are presented

A New Resistive Adaptive Gate-Driving Concept with Automated Identification of Operational Parameters

This paper proposes a new adaptive gate-driving concept based on parallel-connected resistive driving stages, which allows the modification of the effective gate-resistance for every turn-on and turn-off event during operation. By selecting the appropriate gate-resistance, the switching behavior can be optimized individually for each specific operating point (Vsw, Isw, Tj). As a result, higher efficiency under partial load can be achieved. The selection of effective gate-resistance is based on the results of a here introduced automatic optimization method, which takes constraints such as dv/dt- and di/dt-limits into account. Subject of this paper is also the comparison of the new approach with the widely used single-stage resistive driver