Energy transport in the medium of interacting two-level systems

This thesis investigates a medium of interacting two-level systems with dipolar interaction. This investigation is relevant to the dynamics of nuclear spins 1/2 in solids and to the dynamics of low temperature glasses. Our main tool is a hybrid quantum classical simulation, which enables us to study the time evolution of three-dimensional systems consisting of up to 1000 two-level systems. The results indicate, that the dynamics of the full system is delocalized up to very large disorders. We derive an estimate for the time scale of energy transport. When the disorder is larger than a certain value, this time scale becomes proportional to the disorder

An alternative to the conventional micro-canonical ensemble

Usual approach to the foundations of quantum statistical physics is based on conventional micro-canonical ensemble as a starting point for deriving Boltzmann-Gibbs (BG) equilibrium. It leaves, however, a number of conceptual and practical questions unanswered. Here we discuss these questions, thereby motivating the study of a natural alternative known as Quantum Micro-Canonical (QMC) ensemble. We present a detailed numerical study of the properties of the QMC ensemble for finite quantum systems revealing a good agreement with the existing analytical results for large quantum systems. We also propose the way to introduce analytical corrections accounting for finite-size effects. With the above corrections, the agreement between the analytical and the numerical results becomes very accurate. The QMC ensemble leads to an unconventional kind of equilibrium, which may be realizable after strong perturbations in small isolated quantum systems having large number of levels. We demonstrate that the variance of energy fluctuations can be used to discriminate the QMC equilibrium from the BG equilibrium. We further suggest that the reason, why BG equilibrium commonly occurs in nature rather than the QMC-type equilibrium, has something to do with the notion of quantum collapse.Comment: 25 pages, 6 figure

How do sand addition, soil moisture and nutrient status influence greenhouse gas fluxes from drained organic soils?

Drainage turns peatlands from natural carbon sinks into hotspots of greenhouse gas (GHG)emissions from soils due to alterations in hydrological and biogeochemical processes. As a consequence of drainage-induced mineralisation and anthropogenic sand addition, large areas of former peatlands under agricultural use have soil organic carbon (SOC)contents at the boundary between mineral and organic soils. Previous research has shown that the variability of GHG emissions increases with anthropogenic disturbance. However, how and whether sand addition affects GHG emissions remains a controversial issue. The aim of this long-term incubation experiment was to assess the influence of hydrological and biogeochemical soil properties on emissions of carbon dioxide (CO 2 ), nitrous oxide (N 2 O)and methane (CH 4 ). Strongly degraded peat with sand addition (peat-sand mixtures)and without sand addition (earthified peat)was systematically compared under different moisture conditions for fen and bog peat. Soil columns originating from both the topsoil and the subsoil of ten different peatlands under grassland use were investigated. Over a period of six months the almost saturated soil columns were drained stepwise via suction to −300 hPa. The CO 2 fluxes were lowest at water-saturated and dry soil moisture conditions, resulting in a parabolic dependence of CO 2 fluxes on the water-filled pore space (WFPS)peaking at 56–92% WFPS. The highest N 2 O fluxes were found at between 73 and 95% WFPS. Maximum CO 2 fluxes were highest from topsoils, ranging from 21 to 77 mg C m −2 h −1 , while the maximum CO 2 fluxes from subsoils ranged from 3 to 14 mg C m −2 h −1 . No systematic influence of peat type or sand addition on GHG emissions was found in topsoils, but CO 2 fluxes from subsoils below peat-sand mixtures were higher than from subsoils below earthified peat. Maximum N 2 O fluxes were highly variable between sites and ranged from 18.5 to 234.9 and from 0.2 to 22.9 μg N m −2 h −1 for topsoils and subsoils, respectively. CH 4 fluxes were negligible even under water-saturated conditions. The highest GHG emissions occurred at a WFPS that relates – under equilibrium conditions – to a water table of 20–60 cm below the surface in the field. High maximum CO 2 and N 2 O fluxes were linked to high densities of plant-available phosphorus and potassium. The results of this study highlight that nutrient status plays a more important role in GHG emissions than peat type or sand addition, and do not support the idea of peat-sand mixtures as a mitigation option for GHG emissions

Cycling in mixed traffic on the carriageway on urban main roads

Für die Förderung des Radverkehrs in Städten ist ein attraktives und sicheres Radverkehrsnetz unabdingbar. Dabei gewinnt die Führung des Radverkehrs im Mischverkehr auf Hauptverkehrsstraßen sowie insbesondere Schutzstreifen als Form der Führung im Mischverkehr zunehmend an Bedeutung. Mit einem Schutzstreifen wird dem Radfahrer auf der Fahrbahn eine Fläche zur Verfügung gestellt werden, die von anderen Fahrzeugen nur bei Bedarf und ohne Gefährdung des Radverkehrs befahren werden darf. Erstes Ziel des Forschungsvorhabens war es, das Gefährdungspotenzial für Radfahrer auf Hauptverkehrsstraßen im Mischverkehr mit und ohne Schutzstreifen zu bestimmen. Das zweite Ziel war die Bewertung der Einflüsse von Radverkehr im Mischverkehr mit und ohne Schutzstreifen auf die Leistungsfähigkeit und die Verkehrsqualität von Straßenabschnitten. Im Rahmen der Bearbeitung wurde der Erkenntnisstand zur Radverkehrsführung im Mischverkehr recherchiert und aufbereitet. Dazu gehörte auch eine Kommunalrecherche zur aktuellen und zukünftig geplanten Anwendung von Schutzstreifen. Für die Bestimmung des Gefährdungspotentials erfolgte eine Verkehrssicherheitsanalyse durch die Auswertung von Unfalldaten. Die Auswertungen erfolgten für definierte Querschnittstypen. Gleichzeitig wurde das Verkehrsverhalten anhand von Videobeobachtungen auf Strecken mit und ohne Schutzstreifen analysiert. Dazu wurden u.a. Geschwindigkeiten von Kfz- und Radverkehr sowie Überholvorgänge und Abstände erfasst und ausgewertet. Die Videobeobachtungen erfolgten sowohl an zweistreifigen als auch an vierstreifigen Strecken. Da nicht alle denkbaren Verkehrsmengenkonstellationen beobachtet werden konnten, wurde aufbauend auf den Erhebungsdaten eine mikroskopische Simulation durchgeführt, bei der die Verkehrsqualität mit Radeinfluss auch für gegenwärtig nicht beobachtbare Verkehrsstärken von Kfz- und Radverkehr bestimmt wurde. Im Ergebnis werden das Unfallgeschehen und Einflussfaktoren auf das Unfallgeschehen für Radverkehrsführungen im Mischverkehr mit und ohne Schutzstreifen bewertet. Für die verschiedenen untersuchten Querschnittstypen werden die wesentlichen Einflussfaktoren auf die Verkehrsqualität benannt und teilweise quantifiziert. Für den Kfz-Verkehr wurden Qualitätsstufen für die Querschnittstypen und Verkehrsstärkenkombinationen Kfz-Rad entsprechend der HBS-Kategorisierung ermittelt.A precondition for the promotion of cycling in cities and urban areas is to provide an attractive and safe cycling network. In this regard the role of cycle lanes forming part of the carriageway itself or as marked paths is increasingly important. On Road cycling facilities are classified in cycle lanes ("Radfahrstreifen"), which are reserved for bicycles only, and protective lanes ("Radschutzstreifen"), which can be used by vehicles as well. A protective lane provides a space on the carriageway for bicycles, which vehicles are only allowed to use if needed and without posing a danger to cyclists. The first goal of the project was to determine the potential danger for cyclists on main roads with and without protective lanes. The second goal was the evaluation of the influence of cycling on the capacity and level of service of road sections in dependency of protective lanes. As part of the processing the state of knowledge regarding cycling in mixed traffic was researched and processed. This included a municipal research for current and future planned use of protective strips. For the determination of hazard potential traffic safety analysis was performed by the analysis of accident data. Evaluations were made for defined section types. At the same time, the transport behaviour was analyzed based on video observations on carriageways with and without protective strips. For those were, amongst others speeds of vehicle and bicycle traffic as well as overtaking and spacings recorded and evaluated. The video observations were carried out both on two-lane and four-lane routes. Since not all possible traffic volume constellations could be observed, a microscopic simulation was carried out based on the survey data. With the simulation traffic quality as a function of bicycle influence could be determined also for currently unobservable traffic volumes of vehicle and bicycle traffic. As a result the accident occurrence and influence factors on accidents for cycling in mixed traffic with and without protective strips are evaluated. For the different studied section types, the main influencing factors are named on the traffic quality and partially quantified. For motor vehicle traffic quality levels for the cross-section types and traffic volume combinations (vehicles/bicycles) were determined according to the HBS - categorization

Structural and functional dissection of the DH and PH domains of oncogenic Bcr-Abl tyrosine kinase

The two isoforms of the Bcr-Abl tyrosine kinase, p210 and p190, are associated with different leukemias and have a dramatically different signaling network, despite similar kinase activity. To provide a molecular rationale for these observations, we study the Dbl-homology (DH) and Pleckstrin-homology (PH) domains of Bcr-Abl p210, which constitute the only structural differences to p190. Here we report high-resolution structures of the DH and PH domains and characterize conformations of the DH-PH unit in solution. Our structural and functional analyses show no evidence that the DH domain acts as a guanine nucleotide exchange factor, whereas the PH domain binds to various phosphatidylinositol-phosphates. PH-domain mutants alter subcellular localization and result in decreased interactions with p210-selective interaction partners. Hence, the PH domain, but not the DH domain, plays an important role in the formation of the differential p210 and p190 Bcr-Abl signaling networks

Application Of Monte Carlo Simulations To System Reliability Analysis

Lecturepg. 91Monte Carlo analysis is a powerful tool for modeling the reliability of systems. Proper application of this tool requires an understanding of its underlying principles. In this paper, Monte Carlo analysis is explained at a fundamental level with special emphasis on its application in estimating the reliability of pump systems. The first part of the paper explains step-by-step how to perform a Monte Carlo simulation. In the second part of the paper, examples are given to demonstrate the analysis techniques, what inputs are required, and how to use the information obtained from the analysis