The geodynamo for non-geophysicists

The geodynamo usually appears as a somewhat intimidating subject. Its understanding seems to require the intricate theory of magnetohydrodynamics. The solution of the corresponding equations can only be achieved numerically. It seems to be a subject for the specialist. We show that one can understand the basics of the functioning of the geodynamo solely by using the well-known laws of electrodynamics. The topic is not only important for geophysicists. The same physics is the cause for the magnetic fields of sun-like stars, of the very strong fields of neutron stars, and also of the cosmic magnetic fields

Terahertz Laser Radiation Induced Resistivity Oscillations in GaAs Heterostructures

This thesis reports on the observation and analysis of microwave induced resisitivity oscillations induced by THz laser radiation in GaAs heterostructures. By selective excitation of the bulk and boundaries of the GaAs 2DEG samples, the study demonstrates that MIRO are caused in the bulk for all applied frequencies in the THz range. The oscillations are analyzed in the framework of the inelastic and the displacement mechanism. It is shown furthermore, that the dependence of the oscillations’ magnitude on the polarization’s helicity is weaker than theoretically expected. Lastly, the work demonstrates that MIRO are very robust even for illumination with high power radiation. The intensity dependence of the oscillations’ amplitude is intensively studied, revealing that electron gas heating is the dominant mechanism causing saturation in this frequency range

Estimating Thermal Material Properties Using Step-Heating Thermography Methods in a Solar Loading Thermography Setup

This work investigates solar loading thermography applications using active thermography algorithms. It is shown that active thermography methods, such as step-heating thermography, present good correlation with a solar loading setup. Solar loading thermography is an approach that has recently gained scientific attention and is advantageous because it is particularly easy to set up and can measure large-scale objects, as the sun is the primary heat source. This work also introduces the concept of using a pyranometer as a reference for the evaluation algorithms by providing a direct solar irradiance measurement. Furthermore, a recently introduced method of estimating thermal effusivity is evaluated on ambient-derived thermograms

Tropospheric Aqueous-Phase Oxidation of Isoprene-Derived Dihydroxycarbonyl Compounds

The dihydroxycarbonyls 3,4-dihydroxy-2-butanone (DHBO) and 2,3-dihydroxy-2-methylpropanal (DHMP) formed from isoprene oxidation products in the atmospheric gas phase under low-NO conditions can be expected to form aqSOA in the tropospheric aqueous phase because of their solubility. In the present study, DHBO and DHMP were investigated concerning their radical-driven aqueous-phase oxidation reaction kinetics. For DHBO and DHMP the following rate constants at 298 K are reported: k(OH + DHBO) = (1.0 ± 0.1) × 109 L mol-1 s-1, k(NO3 + DHBO) = (2.6 ± 1.6) × 106 L mol-1 s-1, k(SO4-+ DHBO) = (2.3 ± 0.2) × 107 L mol-1 s-1, k(OH + DHMP) = (1.2 ± 0.1) × 109 L mol-1 s-1, k (NO3 + DHMP) = (7.9 ± 0.7) × 106 L mol-1 s-1, k(SO4- + DHMP) = (3.3 ± 0.2) × 107 L mol-1 s-1, together with their respective temperature dependences. The product studies of both DHBO and DHMP revealed hydroxydicarbonyls, short chain carbonyls, and carboxylic acids, such as hydroxyacetone, methylglyoxal, and lactic and pyruvic acid as oxidation products with single yields up to 25%. The achieved carbon balance was 75% for DHBO and 67% for DHMP. An aqueous-phase oxidation scheme for both DHBO and DHMP was developed on the basis of the experimental findings to show their potential to contribute to the aqSOA formation. It can be expected that the main contribution to aqSOA occurs via acid formation while other short-chain oxidation products are expected to back-partition into the gas phase to undergo further oxidation there

Die Distribution des geschlossenen und offenen l-Graphems im Tschechischen des 18. Jahrhunderts: Druckersprache und -usus zweier Exemplare von Martin von Cochems Zlatý Nebeský Kljč im Vergleich

Die Arbeit untersucht die Distribution des geschlossenen und offenen l-Graphems im Druckerusus des Tschechischen des 18. Jahrhunderts beispielhaft anhand zweier Exemplare von Martin von Cochems Zlatý Nebeský Kljč. Auf Grundlage der Verteilung wird eingeordnet, ob |l| und |ł| als eigene Grapheme oder als Allographe zu klassifizieren sind. In dem aus Südböhmen stammenden Exemplar liegt eine Distribution vor, die auf eine Unterscheidung von zwei l-Phonemen zurückgeführt werden kann, ⟨l⟩ und ⟨ł⟩ also als eigene Grapheme zu betrachten sind. Der Ausgabe aus Mittelböhmen liegt hingegen eine Distribution zugrunde, die diesen Rückschluss nicht zulässt und |l| und |ł| als Allographe zu werten sind. Vergleichend wird auch herausgearbeitet, warum die Phonologie als Erklärung für die Distributionsmuster einer konfessionell motivierten Interpretation vorzuziehen ist

Two-stage, low noise quantum frequency conversion of single photons from silicon-vacancy centers in diamond to the telecom C-band

The silicon-vacancy center in diamond holds great promise as a qubit for quantum communication networks. However, since the optical transitions are located within the visible red spectral region, quantum frequency conversion to low-loss telecommunication wavelengths becomes a necessity for its use in long-range, fiber-linked networks. This work presents a highly efficient, low-noise quantum frequency conversion device for photons emitted by a silicon-vacancy (SiV) center in diamond to the telecom C-band. By using a two-stage difference-frequency mixing scheme SPDC noise is circumvented and Raman noise is minimized, resulting in a very low noise rate of $10.4 \pm 0.7$ photons per second as well as an overall device efficiency of $35.6\, \%$. By converting single photons from SiV centers we demonstrate the preservation of photon statistics upon conversion.Comment: 12 pages, 3 figure

Position paper: Runtime Model for Role-based Software Systems

In the increasingly dynamic realities of today's software systems, it is no longer feasible to always expect human developers to react to changing environments and changing conditions immediately. Instead, software systems need to be self-aware and autonomously adapt their behavior according to their experiences gathered from their environment. Current research provides role-based modeling as a promising approach to handle the adaptivity and self-awareness within a software system. There are established role-based systems e.g., for application development, persistence, and so on. However, these are isolated approaches using the role-based model on their specific layer and mapping to existing non-role-based layers. We present a global runtime model covering the whole stack of a software system to maintain a global view of the current system state and model the interdependencies between the layers. This facilitates building holistic role-based software systems using the role concept on every single layer to exploit its full potential, particularly adaptivity and self-awareness

Optimal box-covering algorithm for fractal dimension of complex networks

The self-similarity of complex networks is typically investigated through computational algorithms the primary task of which is to cover the structure with a minimal number of boxes. Here we introduce a box-covering algorithm that not only outperforms previous ones, but also finds optimal solutions. For the two benchmark cases tested, namely, the E. Coli and the WWW networks, our results show that the improvement can be rather substantial, reaching up to 15% in the case of the WWW network.Comment: 5 pages, 6 figure