Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations

Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we want to study axisymmetric and non-axisymmetric structures, evocated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generate synthetic maps and predictions for ALMA. We performed non-ideal global 3D MHD stratified simulations of the dead-zone outer edge using the FARGO MHD code PLUTO. The stellar and disk parameters are taken from a parameterized disk model applied for fitting high-angular resolution multi-wavelength observations of circumstellar disks. The 2D temperature and density profiles are calculated consistently from a given surface density profile and Monte-Carlo radiative transfer. The 2D Ohmic resistivity profile is calculated using a dust chemistry model. The magnetic field is a vertical net flux field. The resulting dust reemission provides the basis for the simulation of observations with ALMA. The fiducial model develops a large gap followed by a jump in surface density located at the dead-zone outer edge. The jump in density and pressure is strong enough to stop the radial drift of particles. In addition, we observe the generation of vortices by the Rossby wave instability (RWI) at the jumps location close to 60 AU. The vortices are steadily generated and destroyed at a cycle of 40 local orbits. The RT results and simulated ALMA observations predict the feasibility to observe such large scale structures appearing in magnetized disks without having a planet.Comment: Language update, added comments, added citations, in press. (A&A

Enzymhistochemische Diagnostik gastrointestinaler Motilitätsstörungen: Ein Laborleitfaden

Zusammenfassung: Die enzymhistochemischen Reaktionen für Acetylcholinesterase, Laktatdehydrogenase, Succinatdehydrogenase und Nitroxidsynthetase bilden gegenwärtig den Goldstandard zur histologischen Diagnose gastrointestinaler Motilitätsstörungen. Die Acetylcholinesterase-Reaktion stellt cholinerge Nervenfasernetze der Muscularis mucosae und Muscularis propria dar und zeigt deren Acetylcholinesterase-Aktivität an. Laktatdehydrogenase, Succinatdehydrogenase und Nitroxidsynthetase dienen komplementär der selektiven Darstellung der Nervenzellen des Plexus myentericus und submucosus. Diese enzymhistochemischen Techniken erfordern natives Gewebe, sodass der direkte Transport von der gastroenterologischen oder chirurgischen Abteilung zur Pathologie ohne Zeitverzug gewährleistet sein muss. Alternativ können die Biopsien auf Trockeneis an ein weiter entfernt gelegenes Institut versendet werden. Die hier beschriebene Laboranleitung ist über 4Jahrzehnte optimiert und verfeinert worden. Die im Labor optimierten enzymhistochemischen Reaktionen zeichnen sich durch ein höchstes Maß an Zuverlässigkeit und Reproduzierbarkeit aus. Insbesondere für eine interinstitutionelle Vergleichbarkeit der Resultate ist eine standardisierte Methodik unerlässlich. Entsprechend wird in dieser Anleitung eine detaillierte Darstellung der wichtigsten enzymhistochemischen Reaktionen zur Diagnostik gastrointestinaler Motilitätsstörungen gegebe

Developing the control system of a syringe infusion pump

Infusion pumps have multiple uses according to their location. According to its use, there is a need to control specific parameters. The objective of this work is to implement and to assembly all the modules of an infusion pump, controlling all the functions. The control was implemented with the microcontroller board based Arduino and a webpage was developed to assist the user to record, retrieve and access information about the operating conditions.N/

The magnitude of educational disadvantage amongst indigenous minority groups in Australia.

Indigenous groups are amongst the most disadvantaged minority groups in the developed world. This paper examines the educational disadvantage of indigenous Australians by assessing academic performance at a relatively early age. We find that, by the age of 10, indigenous Australians are substantially behind non-indigenous Australians in academic achievement. Their relative performance deteriorates further over the next 2 years. School and locality do not appear to be important determinants of the indigenous to non-indigenous achievement gap. However, geographic remoteness, indigenous ethnicity and language use at home have a marked influence on educational achievement. A current focus of Australian indigenous policy is to increase school resources. Our results suggest that this will not eliminate indigenous educational disadvantage on its own

Modified critical correlations close to modulated and rough surfaces

Correlation functions are sensitive to the presence of a boundary. Surface modulations give rise to modified near surface correlations, which can be measured by scattering probes. To determine these correlations, we develop a perturbative calculation in deformations in height from a flat surface. The results, combined with a renormalization group around four dimensions, are also used to predict critical behavior near a self-affinely rough surface. We find that a large enough roughness exponent can modify surface critical behavior.Comment: 4 pages, 1 figure. Revised version as published in Phys. Rev. Lett. 86, 4596 (2001

Adaptive Algebraic Multigrid Methods

Our ability to simulate physical processes numerically is constrained by our ability to solve the resulting linear systems, prompting substantial research into the development of multiscale iterative methods capable of solving these linear systems with an optimal amount of effort. Overcoming the limitations of geometric multigrid methods to simple geometries and differential equations, algebraic multigrid methods construct the multigrid hierarchy based only on the given matrix. While this allows for efficient black-box solution of the linear systems associated with discretizations of many elliptic differential equations, it also results in a lack of robustness due to assumptions made on the near-null spaces of these matrices. This paper introduces an extension to algebraic multigrid methods that removes the need to make such assumptions by utilizing an adaptive process. The principles which guide the adaptivity are highlighted, as well as their application to algebraic multigrid solution of certain symmetric positive-definite linear systems