Diffusive wavelets on groups and homogeneous spaces

The aim of this exposition is to explain basic ideas behind the concept of diffusive wavelets on spheres in the language of representation theory of Lie groups and within the framework of the group Fourier transform given by Peter-Weyl decomposition of $L^2(G)$ for a compact Lie group $G$. After developing a general concept for compact groups and their homogeneous spaces we give concrete examples for tori -which reflect the situation on $R^n$- and for spheres $S^2$ and $S^3$.Comment: 20 pages, 3 figure

Evaluation of Mobile Phones for Large Display Interaction

Large displays have become more and more common in the last few years. While interaction with these displays can be conducted using standard methods such as computer mouse and keyboard, this approach causes issues in multi-user environments, where the various conditions for providing multiple keyboards and mice, together with the facilities to employ them, cannot be met. To solve this problem, interaction using mobile phones was proposed by several authors. Previous solutions were specialized interaction metaphors only for certain applications. To gain more insight into general interaction patterns realizable with smart phones, we created a set of general test cases using a well-known taxonomy for interactions. These test cases were then evaluated in a user study, comparing smart phone usage against the traditional keyboard/mouse-combination. Results (time and user satisfaction) show strengths and weaknesses when using the new interaction with the smart phone. With further evaluations we draw conclusions on how to improve large display interaction using smart phones in general

Mass measurements of 238U-projectile fragments for the first time with a Multiple-Reflection Time-Of-Flight Mass Spectrometer

Mass measurements of short-lived uranium projectile fragments were performed for the first time with a Multiple-Reflexion-Time-of-Flight Mass Spectrometer (MR-TOF-MS). A major part of this doctoral work was a novel development of a data analysis method for the MR-TOF-MS mass measurements of exotic nuclei at the fragment separator FRS at GSI. The developed method was successfully applied to the data obtained from two pilot experiments with the MR-TOF-MS at the FRS in 2012 and 2014. A substantial upgrade of the experimental setup of the MR-TOF-MS was also performed in the frame work of this doctoral thesis after the first run. In the experiments projectile fragments were created with 1000 MeV/u 238U ions in a Be/Nb target at the entrance of the in-flight separator FRS. The exotic nuclei were spatially separated, energy bunched and slowed down with the ion-optical system of the FRS combined with monoenergetic and homogeneous degraders. At the final focal plane of the FRS the fragments were completely slowed down and thermalized in a cryogenic stopping cell (CSC) filled with 3-5 mg/cm^2 pure helium gas. The exotic nuclei were fast extracted from the CSC to enable mass measurements of very short-lived fragments with the MR-TOF-MS. The achievement of this goal was successfully demonstrated with the mass measurement of 220Ra ions with a half-life of 17.9 ms and 11 detected events. The mass measurements of the isobars 211Fr, 211Po and 211Rn have clearly demonstrated the scientific potential of the MR-TOF-MS for the investigation of exotic nuclei and the power of the data analysis system. Difficult measurements with overlapping mass distributions with only a few counts in the measured spectra were the challenge for the new data analysis method based on the maximum likelihood method. The drifts during the measurements were corrected with the developed time-resolved calibration method. After the improvements of the setup as a consequence of the experience of the first experiment in 2012 and the applied time-resolved calibration method a mass resolving power of 400,000 has been achieved in the experiment in 2014. The achieved mass accuracy in these pilot experiments were about $mathsf{1cdot 10^{-6}}$. The contribution of the software and the resulting systematic errors were in the 10$^{-8}$ range. The reliability of the present analysis method was carefully checked in detailed simulations with a realistic peak shape approximated by an exponentially modified Gaussian distribution. Both list mode data and measured histograms were treated in the data analysis. The analysis method was tested with strongly overlapping mass distributions and low count rates including a variable amount of back ground. In summary, the experimental setup for mass measurements of very rare and short-lived nuclei and the corresponding data analysis have reached with this work and results of the present thesis a great potential for high-resolution measurements in future experiments. There mass measurements with 10 events can be performed with a residual uncertainty of $mathsf{4.5 cdot 10^{-7}}$ at a mass resolving power of 400,000.Im Rahmen dieser Arbeit wurden erstmal mit einem Multireflexions Flugzeit-Massenspektrometer (MR-TOF-MS) Massenmessungen an kurzlebigen Uran-Projektilfragmenten durchgeführt. Ein Hauptteil dieser Arbeit war die Entwicklung einer Datenauswertemethode für die MR-TOF-MS Massenmessungen exotischer Kerne am Fragmentseparator FRS der GSI. Das entwickelte Verfahren wurde erfolgreich auf die Daten zweier Pilotexperimente des MR-TOF-MS am FRS 2012 und 2014 angewandt, in denen die Massen der Isotope 211Rn, 211Po und 220Po erstmalig direkt gemessen wurden. Ebenfalls wurden umfangreiche Verbesserungen am MR-TOF-MS nach dem ersten Experiment im Rahmen dieser Arbeit durchgeführt. In den Experimenten wurden Projektilfragmente mit 1000 MeV/u 238U Ionen in einem Be/Nb Target am Eingang des im-Flug Separators FRS erzeugt. Die exotischen Kerne wurden räumlich separiert, in der Energie komprimiert und abgebremst mit dem Ionenoptischen System des FRS in Verbindung mit monoenergetischen und homogenen Degradern. Die Fragmente wurden am finalen Fokus des FRS mittels einer kryogenen Stoppzelle (CSC) vollständig abgebremst und thermalisiert. Die CSC war dabei mit 3-5 mg/cm^2 reinem Heliumgas gefüllt. Die exotischen Kerne wurden schnell aus der CSC extrahiert, um Massenmessungen sehr kurzlebiger Fragmente mit dem MR-TOF-MS zu ermöglichen. Das Erlangen dieses Ziels wurde erfolgreich durch die Massenmessung von 220Ra Ionen mit einer Lebensdauer von 17,9 ms und 11 detektierten Ereignissen demonstriert. Die Massenmessungen der Isobare 211Fr, 211Po und 211Rn haben klar das wissenschaftliche Potential des MR-TOF-MS für die Untersuchung exotischer Kerne und die Fähigkeiten des Datenauswerteverfahrens aufgezeigt. Die Herausforderung des neuen Datenauswerteverfahrens, das auf der Maximum Likelihood Methode beruht, bestand in den Messungen mit überlappenden Verteilungen und nur wenigen Ereignissen in den Spektren. Die Drifts während der Messungen wurden mit der neu entwickelten Zeit-aufgelösten Kalibration korrigiert. Nach den Verbesserungen des Aufbaus als Konsequenz des ersten Experiments 2012 und der Anwendung der Zeit-aufgelösten Kalibration wurde im zweiten Experiment 2014 ein Massenauflösungsvermögen von 400.000 erreicht. Zusätzlich wurde eine Elektronenstoßquelle installiert, um Kalibranten aus Gasen wie Xe und SF6 erzeugen zu können. Die Verfügbarkeit zahlreicher Kalibranten ist eine Voraussetzung für Messungen über große Massenbereiche. Die erreichten Massengenauigkeiten dieser Pilotexperimente betrugen ungefähr 1*10E-6. Der Beitrag des Datenauswerteverfahrens und der resultierende systematische Fehler befanden sich im Bereich von 10E-8. Die Zuverlässigkeit der gegenwärtigen Auswertemethode wurde reiflich in detaillierten Simulationen untersucht. Die gemessene Verteilungsfunktion wurde durch die exponentiell modifizierte Gauß-Funktion angenähert. Mittels stark überlappender Massenverteilungen, niedrigen Zählraten und variablen Mengen an Untergrund wurde die Auswertemethode getestet. Zusammengefasst haben der experimentelle Aufbau für Massenmessungen sehr seltener und kurzlebiger Kerne und die zugehörige Datenauswertemethode im Rahmen dieser Dissertation ein großes Potential für hoch-aufgelöste Messungen in zukünftigen Experimenten erreicht

Bose-Einstein condensation in dense quark matter

We consider the problem of Bose condensation of charged pions in QCD at finite isospin chemical potential $\mu_I$ using the O(4)-symmetric linear sigma model as an effective field theory for two-flavor QCD. Using the 2PI $1/N$-expansion, we determine the quasiparticle masses as well as the pion and chiral condensates as a function of the temperature and isospin chemical potential in the chiral limit and at the physical point. At T=0, Bose condensation takes place for chemical potentials larger than $m_{\pi}$. In the chiral limit, the chiral condensate vanishes for any finite value of $\mu_I$.Comment: Talk given at Strong and Electroweak matter 2008, Amsterdam August 25-29 2008. Four pages and two figures. 2nd version: typos fixed and updated list of ref

Membrane Based Measurement Technology for in situ Monitoring of Gases in Soil

The representative measurement of gas concentration and fluxes in heterogeneous soils is one of the current challenges when analyzing the interactions of biogeochemical processes in soils and global change. Furthermore, recent research projects on CO2-sequestration have an urgent need of CO2-monitoring networks. Therefore, a measurement method based on selective permeation of gases through tubular membranes has been developed. Combining the specific permeation rates of gas components for a membrane and Dalton's principle, the gas concentration (or partial pressure) can be determined by the measurement of physical quantities (pressure or volume) only. Due to the comparatively small permeation constants of membranes, the influence of the sensor on its surrounding area can be neglected. The design of the sensor membranes can be adapted to the spatial scale from the bench scale to the field scale. The sensitive area for the measurement can be optimized to obtain representative results. Furthermore, a continuous time-averaged measurement is possible where the time for averaging is simply controlled by the wall-thickness of the membrane used. The measuring method is demonstrated for continuous monitoring of O2 and CO2 inside of a sand filled Lysimeter. Using three sensor planes inside the sand pack, which were installed normal to the gas flow direction and a reference measurement system, we demonstrate the accuracy of the gas-detection for different flux-based boundary conditions

Self-reported medication in community-dwelling older adults in Germany: results from the Berlin Initiative Study

Background: Older adults have the highest drug utilization due to multimorbidity. Although the number of people over age 70 is expected to double within the next decades, population-based data on their medication patterns are scarce especially in combination with polypharmacy and potentially inappropriate medication (PIM). Our objective was to analyse the frequency of polypharmacy, pattern of prescription (PD) and over-the-counter (OTC) drug usage, and PIMs according to age and gender in a population-based cohort of very old adults in Germany. Methods: Cross-sectional baseline data of the Berlin Initiative Study, a prospective cohort study of community-dwelling adults aged ≥70 years with a standardized interview including demographics, lifestyle variables, co-morbidities, and medication assessment were analysed. Medication data were coded using the Anatomical Therapeutic Chemical (ATC) classification. Age- and sex-standardized descriptive analysis of polypharmacy (≥5 drugs, PD and OTC vs. PD only and regular and on demand drugs vs regular only), medication frequency and distribution, including PIMs, was performed by age (</≥80) and gender. Results: Of 2069 participants with an average age of 79.5 years, 97% (95%CI [96%;98%]) took at least one drug and on average 6.2 drugs (SD = 3.5) with about 40 to 66% fulfilling the criteria of polypharmacy depending on the definition. Regarding drug type more female participants took a combination of PD and OTC (male: 68%, 95%CI [65%;72%]); female: 78%, 95%CI [76%;80%]). Most frequently used were drugs for cardiovascular diseases (85%, 95%CI [83%;86%]). Medication frequency increased among participants aged ≥80 years, especially for cardiovascular drugs, antithrombotics, psychoanaleptics and dietary supplements. Among the top ten prescription drugs were mainly cardiovascular drugs including lipid-lowering agents (simvastatin), beta-blockers (metoprolol, bisoprolol) and ACE inhibitors (ramipril). The most common OTC drug was acetylsalicylic acid (35%; 95%CI [33%;37%])). Dose-independent PIM were identified for 15% of the participants. Conclusions: Polypharmacy was excessive in older adults, with not only PD but also OTC drugs contributing to the high point prevalence. The medication patterns reflected the treatment of chronic diseases in this age group. There was even an increase in medication frequency between below and above 80 years especially for drugs of cardiovascular diseases, antithrombotic medication, psychoanaleptics, and dietary supplements

Operational Experience of a Centrifugal Particle Receiver Prototype

The centrifugal particle receiver “CentRec” is a solar tower receiver development by DLR based on a direct absorption receiver concept especially suitable for high temperature process heat and electricity generation applications. Ceramic particles are used as heat transfer and storage medium for temperatures up to 1000°C. A centrifugal particle receiver system including a CentRec receiver prototype has been tested up to 965°C average receiver outlet temperature in the research platform of DLR’s test facility Juelich Solar Tower, Germany. This paper describes the first test results with a focus on first operational experiences