Pathwise uniqueness for stochastic differential equations with singular drift and nonconstant diffusion

von der Lühe K. Pathwise uniqueness for stochastic differential equations with singular drift and nonconstant diffusion. Bielefeld: Universität Bielefeld; 2017

Improved alkaline extraction method for biogenic silica determination in volcanic soils

Here we present the first results obtained with an innovative technique aiming at measuring biogenic and lithogenic amorphous silica contents in soils developed on basaltic parent material. Biogenic silica (BSi) has become important to many research domains like soil science, biogeochemistry, aquatic sciences, palaeoecology, and agricultural sciences. In most soils, BSi is a small but highly reactive Si pool in comparison to lithogenic Si sources. This high reactivity makes it a key component of the soil-plant Si cycle. In the last decade, the continental cycle of Si has been increasingly studied, because of (1) the importance of Si as a nutrient for plants and diatoms (studies include e.g., impact of land-use change, export through harvest, influence on crops resistance to various kinds of stress) and (2) the major role of Si during chemical weathering. Constraining Si reservoirs in soils is, however, not an easy task due to the ubiquity of Si. Many methods have been developed to quantify BSi content in soils (mostly alkaline extraction techniques) and other Si pools in soils (e.g., mobile Si, adsorbed Si, … with the sequential Si extraction by Georgiadis et al. 2013 [1]). BSi extraction methods that are based only on solubility are, however, difficult to apply to environments where large amounts of lithogenic amorphous or poorly crystalline aluminosilicates are present, like e.g. in volcanic soils, as their solubility is close to that of BSi. In order to study the soil/plant Si cycle in such soils, leaching methods, quasi-continuously analysing both the dissolution kinetics and the chemistry of the dissolving phases, provide better control of the dissolving Si sources. Several authors successfully used methods similar to the one applied here on various materials. This is however the first study that applies such method with quasi-continuous monitoring of released elements on the challenging material that is volcanic soils

Simulation algorithm to model the visible tunable filter for the Daniel K. Inouye Solar Telescope

Journal of astronomical telescopes, instruments, and systems : JATIS 3 (2017), Nr. 0

Surface engineering of magnetic nanoparticles: synthesis, reversibility, and applications

In der vorgelegten Arbeit wurden ausgehend von Poly(tert-Butoxycarbonylamino methacrylat) anionische (PtBAA) sowie zwitterionische (Polydehydroalanin, PDha) Polyelektrolyte synthetisiert und charakterisiert. Die erhaltenen Polyelektrolyte wurden neben weiteren Polymeren zur Oberflächenfunktionalisierung von magnetischen Eisenoxid Nanopartikeln mittels Adsorption verwendet. Die erhaltenen Hybridpartikel wurden mittels dynamischer Lichstreuung, Transmissionselektronikroskopie, Zeta Potentials Messungen sowie Thermogravimetrie charakterisiert. Mit zwitterionischem Polydroalanin funktionalisierte Partikel weisen pH abhängige Oberflächenladungen auf und konnten erfolgreich für die Adsorption weiterer Polyelektrolytlagen mit kationischen und anionischen Polyelektrolyten verwendet werden. Unter sauren Bedingungen können Polyanionen, unter alkalischen Bedingungen Polykationen adsorbiert werden. Die äußeren lagen der so erhaltenen Multilagen Partikel können unter geeigneten Bedingungen selektiv wieder von den Partikeln abgelöst werden. Dieses Verfahren konnte erfo lgreich auf ein niedermolekulares Modelsystem, den kationischen Farbstoff Methylenblau übertragen werden. Anhand dieser Modelverbindung konnte die Reversibilität der Ad- und desorption bis zu neun Zyklen gezeigt werden. Des weiteren konnte durch Inkubationsexperimente in fötalem Kälberserum unter variierten Bedingungen gezeigt werden, dass eine PDha Hülle die Proteinadsorption auf die Partikel im vergleich zu Partikeln ohne Oberflächenmodifikation deutlich reduziert

Oscillatory behavior in the quiet Sun observed with the New Solar Telescope

Surface photometry of the quiet Sun has achieved an angular resolution of $0".1$ with the New Solar Telescope at Big Bear Solar Observatory revealing that a disproportionate fraction of the oscillatory events appear above observed bright point-like structures. During the tracking of these structures, we noted that the more powerful oscillatory events are cospatial with them, indicating that observed flux tubes may be the source of many observed oscillatory events.Comment: 5 pages 4 figure

Substructure of Quiet Sun Bright Points

Since photospheric bright points (BPs) were first observed, there has been a question as to how are they structured. Are they just single flux tubes or a bundle of the flux-tubes? Surface photometry of the quiet Sun (QS) has achieved resolution close to 0.1" with the New Solar Telescope at Big Bear Solar Observatory. This resolution allowed us to detect a richer spectrum of BPs in the QS. The smallest BPs we observed with TiO 705.68 nm were 0.13", and we were able to resolve individual components in some of the BPs clusters and ribbons observed in the QS, showing that they are composed of the individual BPs. Average size of observed BPs was 0.22".Comment: 4 pages, 3 figures, presented as poster at IAU Symposium 273, 201

The Position of High Frequency Waves with Respect to the Granulation Pattern

High frequency velocity oscillations were observed in the spectral lines Fe I 543.45nm and 543.29nm, using 2D spectroscopy with a Fabry- Perot and speckle reconstruction, at the VTT in Tenerife. We investigate the radial component of waves with frequencies in the range 8 - 22mHz in the internetwork, network and a pore. We find that the occurrence of waves do not show any preference on location and are equally distributed over down-flows and up-flows, regardless of the activity of the observed area in the line of Fe I 543.45nm. The waves observed in the lower formed line of Fe I 543.29nm seem to appear preferentially over down-flows.Comment: Article has 12 pages and 7 images. It is accepted in Solar Physics Journa