Charging of a quantum dot coupled to Luttinger liquid leads

Luttinger liquid behavior of one-dimensional correlated electron systems is characterized by power-law scaling of a variety of physical observables with exponents determined by a single interaction dependent parameter K. We suggest a setup to study Luttinger liquid behavior in quantum wires which allows to determine K from two independent measurements: resonant transport through a quantum dot embedded in the wire and the charge on the dot. Consistency of the two measured values of K for a single probe would provide strong experimental evidence for the Luttinger liquid paradigm.Comment: 4 pages, 4 figures included, version accepted for publication in PR

Indirect forces between impurities in one-dimensional quantum liquids

We investigate the indirect interaction between two isolated impurities in a Luttinger liquid described by a microscopic lattice model. To treat the electron-electron interaction U the functional renormalization group method is used. For comparison we also study the U=0 case. We find that for a wide range of impurity parameters the impurity interaction V_{12} as a function of their separation r oscillates with decaying amplitude between being attractive and repulsive. For half-filling of the band and in a crossover regime between weak and strong impurities the interaction becomes purely attractive. For U=0 and independent of the impurity strength the amplitude of the interaction energy falls off as 1/r. For U>0 the decay for small separations and weak to intermediate impurities is governed by a U dependent exponent larger than -1, which crosses over to -1 for large r. The crossover scale depends on the impurity strength and U. We present simple pictures which explain our results in the limits of weak and strong impurities. We finally also consider attractive interactions U<0.Comment: 8 pages, 9 figures include

Connecting biodiversity monitoring with soil inventory information - A Swiss case study

Switzerland is one of the first countries in the world to monitor its biological diversity. The Federal Office for the environment (FOEN), triggered by the Rio world summit, initiated 1995 a program for this purpose called Biodiversity Monitoring in Switzerland (BDM). According to the Convention on Biological Diversity various biodiversity targets were defined and the action plan strategy biodiversity Switzerland serves to implement these strategic goals. Unfortunately, up to very recently, soil was not part of these considerations. In the Swiss biodiversity monitoring system a core indicator, species diversity in habitats, is designed to document changes in species diversity of vascular plants and mosses in Switzerland’s major habitats. Together with the current land use and general metadata like elevation, slope, exposition and geology these data are stored in a central database. Since 2001 the totally 1’600 sites based on a regular grid (6 by 4 km) are resampled in a 5 years interval. In the third sampling campaign (2011-2015) the setting was broadened by taking soil samples at all locations possible. At each site 4 replicates 0-20 cm were taken to provide predictions on plot scale variability. All samples were prepared in the laboratory of the Swiss Soil Monitoring Network. Exploratory data analyses for pH, soil organic carbon and nitrogen revealed distinct patterns according to land use as well as to altitude; pH decreases from colline to alpine zones. Furthermore, regional analyses show enormous differences between the northern and southern side of the Alps. Connecting measured soil parameters with the outcome of the BDM survey enables to determine the impact of environmental conditions on species diversity of vascular plants and mosses as well as on soil-plant interactions. Therefore, connecting measured soil inventory data and plant and moss diversity information provide a clear added value to the Biodiversity Monitoring in Switzerland

Stochastic method for in-situ damage analysis

Based on the physics of stochastic processes we present a new approach for structural health monitoring. We show that the new method allows for an in-situ analysis of the elastic features of a mechanical structure even for realistic excitations with correlated noise as it appears in real-world situations. In particular an experimental set-up of undamaged and damaged beam structures was exposed to a noisy excitation under turbulent wind conditions. The method of reconstructing stochastic equations from measured data has been extended to realistic noisy excitations like those given here. In our analysis the deterministic part is separated from the stochastic dynamics of the system and we show that the slope of the deterministic part, which is linked to mechanical features of the material, changes sensitively with increasing damage. The results are more significant than corresponding changes in eigenfrequencies, as commonly used for structural health monitoring.Comment: This paper is accepted by European Physical Journal B on November 2. 2012. 5 pages, 5 figures, 1 tabl

Data management and GIS in the Center for Disaster Management and Risk Reduction Technology (CEDIM): from integrated spatial data to the mapping of risk

International audienceThe project "Risk Map Germany" of the Center for Disaster Management and Risk Reduction Technology (CEDIM) aims at the examination of existing and the development of new approaches for integrated risk assessment as well as the realisation of risk analyses for selected threats and regions. Hazard, vulnerability and risk maps display the results and provide valuable information for planning, insurances, emergency management, science and the public. This article describes the development of the basic information infrastructure for CEDIM and the "Risk Map Germany" providing components for the networking of participating institutions, for common data management, data dissemination and publication. While a web based project platform offers information and communication facilities for all the project members and also the presentation of CEDIM to the public, an integrated data base is prepared as foundation for cross-discipline but common risk assessment. It is made available by the spatial data service "CEDIM Data Center" which allows the project members to inform themselves about the characteristics of existing data and its applicability for their specific tasks by exploring GIS functionalities. Suitable data can be downloaded and further processed in their own work environment. The components' alignment with the principles of Spatial Data Infrastructures is required to accomplish the suppositions for long-term availability and accessibility of data, information and services

Wind Energy and the Turbulent Nature of the Atmospheric Boundary Layer

Wind turbines operate in the atmospheric boundary layer, where they are exposed to the turbulent atmospheric flows. As the response time of wind turbine is typically in the range of seconds, they are affected by the small scale intermittent properties of the turbulent wind. Consequently, basic features which are known for small-scale homogeneous isotropic turbulence, and in particular the well-known intermittency problem, have an important impact on the wind energy conversion process. We report on basic research results concerning the small-scale intermittent properties of atmospheric flows and their impact on the wind energy conversion process. The analysis of wind data shows strongly intermittent statistics of wind fluctuations. To achieve numerical modeling a data-driven superposition model is proposed. For the experimental reproduction and adjustment of intermittent flows a so-called active grid setup is presented. Its ability is shown to generate reproducible properties of atmospheric flows on the smaller scales of the laboratory conditions of a wind tunnel. As an application example the response dynamics of different anemometer types are tested. To achieve a proper understanding of the impact of intermittent turbulent inflow properties on wind turbines we present methods of numerical and stochastic modeling, and compare the results to measurement data. As a summarizing result we find that atmospheric turbulence imposes its intermittent features on the complete wind energy conversion process. Intermittent turbulence features are not only present in atmospheric wind, but are also dominant in the loads on the turbine, i.e. rotor torque and thrust, and in the electrical power output signal. We conclude that profound knowledge of turbulent statistics and the application of suitable numerical as well as experimental methods are necessary to grasp these unique features (...)Comment: Accepted by the Journal of Turbulence on May 17, 201