A novel approach for independent budgeting of fossil fuel CO2 over Europe by 14CO2 observations

Long-term atmospheric 14CO2 observations are deployed to quantify fossil fuel derived CO2 concentrations at a regional polluted site, and at a continental mountain station in south-west Germany. Fossil fuel CO2 emission rates for the relevant catchment areas are obtained by applying the Radon-Tracer-Method. They are shown to compare well with statistical emissions inventories but reveal a larger seasonality than assumed earlier, thus contributing significantly to the observed CO2 seasonal cycle over Europe. Based on the present approach, emissions reductions on the order of 5-10% are detectable for catchment areas of several hundred kilometres radius, as anticipated within a five-years commitment period of the Kyoto Protocol. Still no significant change of fossil fuel CO2 emissions is observed at the two sites over the last 16 years

Continuous Wave Terahertz Systems Based on 1.5 μm Telecom Technologies

Terahertz systems can profit from technologies developed originally for telecom applications. Recent developments on telecom-based key devices are summarized and ways towards CW systems with highest flexibility and excellent performance at reasonable costs are sketched

Simulation of phase-controlled mode-beating lasers

Self-pulsations in Phase Controlled Mode Beating lasers (PhaseCOMB) are very attractive for all-optical clock recovery at ultra-high bit rates. In this paper we apply the comprehensive simulation tool LDSL that has been developed by us for studying the self-pulsation features of PhaseCOMB lasers considering the effects of spontaneous emission noise, longitudinal spatial hole burning, and gain dispersion. In particular the importance of mode control for adjusting the PhaseCOMB operating conditions is pointed out. The simulation results are confirmed by measurements on fabricated devices

Wege zu einer nachhaltigen und exportstarken Wasserwirtschaft : Eckpunktepapier und Empfehlungen des Projekts "Wasser 2050"

Das hier vorgelegte Eckpunktepapier befasst sich mit den Zukunftsperspektiven der deutschen Wasserwirtschaft hinsichtlich ihrer Produkte und Konzepte. Ausgehend von schwierigen Herausforderungen für die globale Wasserwirtschaft legt es dar, wie die deutsche Wasserwirtschaft diesen Herausforderungen gegenübersteht und zeigt auf, welche Maßnahmen zu ergreifen sind, um die wirtschaftlichen Perspektiven der deutschen Wasserwirtschaft dauerhaft zu verbessern. Die Abschnitte 1-5 erläutern die Ausgangslage der deutschen Wasserwirtschaft, beschreiben sich neu stellende Herausforderungen und ordnen in diesen Zusammenhang das BMBF-Verbundprojekt „Wasser 2050“ ein, in dem diese Eckpunkte und Empfehlungen erarbeitet wurden. Die Abschnitte 6-10 wenden sich dann im Einzelnen zu ergreifenden Strategien und Ansätzen zu, die dazu beitragen, die Wettbewerbsposition der deutschen Wasserwirtschaft nachhaltig zu entwickeln. Der abschließende Abschnitt 11 fasst die Empfehlungen des Projekts zusammen.Based on the difficult challenges water management is facing in the coming decades, it is outlined which measures have to be taken in order to maintain the economic perspectives of the German water industry with respect to further improving its sustainability potential. Building upon the results of the project “Water 2050” it is shown how the potential of the German water industry can be developed in order to meet the new requirements for sustainable solutions which can be understood as integrated system solutions. The German water industry’s competitive position on the international market can be improved with the help of medium- to long-term orientated innovation networks. Recommendations for action to policy-makers are geared towards a coordinated cooperation of the individual departments and an improvement of the existing instruments

Modeling of Self-Pulsating DFB Lasers

A theoretical model of a self-pulsating three section DFB-laser with an integrated phase tuning section is established. It is based on traveling wave equations and the standard carrier rate equations. As the key conditions for obtaining self-pulsations the spectral correlation of the different device sections are considered. The specific roles of each section are discussed and the theoretical results are compared to experimental measurements on these devices

Nonlinear dynamics of semiconductor lasers with active optical feedback

An in-depth theoretical as well as experimental analysis of the nonlinear dynamics in semiconductor lasers with active optical feedback is presented. Use of a monolithically integrated multi-section device of sub-mm total length provides access to the short-cavity regime. By introducing an amplifier section as novel feature, phase and strength of the feedback can be separately tuned. In this way, the number of modes involved in the laser action can be adjusted. We predict and observe specific dynamical scenarios. Bifurcations mediate various transitions in the device output, from single-mode steady-state to self-pulsation and between different kinds of self-pulsations, reaching eventually chaotic behavior in the multi-mode limit

High-frequency pulsations in DFB-lasers with amplified feedback

We describe the basic ideas behind the concept of DFB-lasers with short optical feedback for the generation of high-frequency self-pulsations (SPs) and show the theoretical background describing realized devices. It is predicted by theory that the SP frequency increases with increasing feedback strength. To provide evidence for this we propose a novel device design which employs an amplifier section in the integrated feedback cavity of a DFB-laser. We present results from numerical simulations and experiments. It has been shown experimentally that a continuous tuning of the SP frequency from 12 to 45GHz can be adjusted via the control of the feedback strength. The numerical simulations which are in good accordance with experimental investigations give an explanation for a self stabilizing effect of the SPs due to the additional carrier dynamic in the integrated feedback cavity

Observation of enhanced subthreshold K+ production in central collisions between heavy nuclei

In the very heavy collision system 197Au+197Au the K+ production process was studied as a function of impact parameter at 1 GeV/nucleon, a beam energy well below the free N-N threshold. The K+ multiplicity increases more than linearly with the number of participant nucleons and the K+/ pi + ratio rises significantly when going from peripheral to central collisions. The measured K+ double differential cross section is enhanced by a factor of 6 compared to microscopic transport calculations if secondary processes (Delta N-->K Lambda N and Delta Delta -->K Lambda N) are ignored