16 research outputs found
Über die Stärke mehrelektronischer Resonanzen bei der Photorekombination und -ionisation
Die Beiträge trielektronischer Prozesse zur resonanten Rekombination hochgeladener Ionen sowie der zur Rekombination zeitumgekehrte Prozess der resonanten Photoionisation wurden mit hoher Auflösung experimentell untersucht. Bei den bisher wenig beachteten Anregungskanälen der resonanten Elektron-Ion-Rekombination einer höheren Ordnung als der dielektronischen Rekombination (DR) wurden überraschend hohe Resonanzstärken gefunden, die den Zustand astrophysikalischer und erdgebundener Plasmen deutlich beeinflussen können. Die systematische Untersuchung dieser zwischen zwei Hauptschalen wirkenden Trielektronischen Rekombination (TR) an L-Schalen Ionen von Argon und Eisen – zwei astrophysikalisch bedeutende Elemente – ermöglichte die Aufstellung entsprechender Skalierungsregeln in Abhängigkeit von Z. Diesen folgend nimmt die Bedeutung der TR für niedrige Z stark zu, so dass die TR den zugehörigen dielektronischen Prozess erster Ordnung (DR) an Stärke übertreffen kann. Das physikalische Bild dieser Vorgänge wurde weiter vervollständigt durch Untersuchungen des zeitumgekehrten Prozesses, nämlich der Photoionisation von Natriumartigem Eisen. Die erstmals gleichzeitig detektierte radiative Relaxation photoangeregter Zustände durch weiche Röntgenstrahlung führte zu einer Bestimmung absoluter Resonanzenergien einer wichtigen Gruppe von in der astrophysikalischen Spektroskopie bisher unaufgelösten Übergängen. Der Vergleich mit eigenen Configuration Interaction-Rechnungen ermöglichte eine detaillierte Analyse der Einflüsse von Elektronen-Korrelation und Konfigurationsmischungen auf beide dynamischen Prozesse und zeigte unerwartet hohe Einflüsse der Breit-Wechselwirkung bereits bei Ionen mittlerer Kernladung
Streptomyces polyketides mediate bacteria–fungi interactions across soil environments
Although the interaction between prokaryotic and eukaryotic microorganisms is crucial for the functioning of ecosystems, information about the processes driving microbial interactions within communities remains scarce. Here we show that arginine-derived polyketides (arginoketides) produced by Streptomyces species mediate cross-kingdom microbial interactions with fungi of the genera Aspergillus and Penicillium, and trigger the production of natural products. Arginoketides can be cyclic or linear, and a prominent example is azalomycin F produced by Streptomyces iranensis, which induces the cryptic orsellinic acid gene cluster in Aspergillus nidulans. Bacteria that synthesize arginoketides and fungi that decode and respond to this signal were co-isolated from the same soil sample. Genome analyses and a literature search indicate that arginoketide producers are found worldwide. Because, in addition to their direct impact, arginoketides induce a secondary wave of fungal natural products, they probably contribute to the wider structure and functioning of entire soil microbial communities
Energy Storage as Part of a Secure Energy Supply
The current energy system is subject to a fundamental transformation:
A system that is oriented towards a constant
energy supply by means of fossil fuels is now expected to
integrate increasing amounts of renewable energy to achieve
overall a more sustainable energy supply. The challenges
arising from this paradigm shift are currently most obvious
in the area of electric power supply. However, it affects all
areas of the energy system, albeit with different results. Within
the energy system, various independent grids fulfill the
function of transporting and spatially distributing energy or
energy carriers, and the demand-oriented supply ensures
that energy demands are met at all times. However, renewable
energy sources generally supply their energy independently
from any specific energy demand. Their contribution
to the overall energy system is expected to increase significantly.
Energy storage technologies are one option for temporal
matching of energy supply and demand. Energy storage
systems have the ability to take up a certain amount of
energy, store it in a storage medium for a suitable period of
time, and release it in a controlled manner after a certain
time delay. Energy storage systems can also be constructed as
process chains by combining unit operations, each of which
cover different aspects of these functions. Large-scale
mechanical storage of electric power is currently almost
exclusively achieved by pumped-storage hydroelectric power
stations. These systems may be supplemented in the future
by compressed-air energy storage and possibly air separation
plants. In the area of electrochemical storage, various technologies
are currently in various stages of research, development,
and demonstration of their suitability for large-scale
electrical energy storage. Thermal energy storage technologies
are based on the storage of sensible heat, exploitation of
phase transitions, adsorption/desorption processes, and
chemical reactions. The latter offer the possibility of permanent
and loss-free storage of heat. The storage of energy in
chemical bonds involves compounds that can act as energy
carriers or as chemical feedstocks. Thus, they are in direct
economic competition with established (fossil fuel) supply
routes. The key technology here – now and for the foreseeable
future – is the electrolysis of water to produce hydrogen
and oxygen. Hydrogen can be transformed by various processes
into other energy carriers, which can be exploited in
different sectors of the energy system and/or as raw materials
for energy-intensive industrial processes. Some functions of
energy storage systems can be taken over by industrial processes.
Within the overall energy system, chemical energy
storage technologies open up opportunities to link and interweave
the various energy streams and sectors. Chemical
energy storage not only offers means for greater integration
of renewable energy outside the electric power sector, it also
creates new opportunities for increased flexibility, novel
synergies, and additional optimization. Several examples of
specific energy utilization are discussed and evaluated with
respect to energy storage applications.
The article describes various technologies for energy storage
and their potential applications in the context of Germany’s
Energiewende, i.e. the transition towards a more sustainable
energy system. Therefore, the existing legal framework
defines some of the discussions and findings within the
article, specifically the compensation for renewable electricity
providers defined by the German Renewable Energy
Sources Act, which is under constant reformation. While the
article is written from a German perspective, the authors
hope this article will be of general interest for anyone
working in the areas of energy systems or energy technology
Complete measurements of anisotropic x-ray emission following recombination of highly charged ions
Synopsis We report the first systematic measurement of x-ray emission anisotropies following dielectronic, trielectronic and quadroelectronic recombination into He-like through O-like iron and krypton ions. Using the experimental data we calculated the polarization of the Kα x rays in an anisotropic plasma as a function of the plasma temperature. Unexpectedly, we found that the degree of polarization is dominated by previously neglected trielectronic and quadroelectronic recombination resonances
Strong higher-order resonant contributions to x-ray line polarization in hot plasmas
We studied angular distributions of x rays emitted in resonant recombination
of highly charged iron and krypton ions, resolving dielectronic, trielectronic,
and quadruelectronic channels. A tunable electron beam drove these processes,
inducing x rays registered by two detectors mounted along and perpendicular to
the beam axis. The measured emission asymmetries comprehensively benchmarked
full-order atomic calculations. We conclude that accurate polarization
diagnostics of hot plasmas can only be obtained under the premise of inclusion
of higher-order processes that were neglected in earlier work.Comment: 8 pages, 3 figure
Measurement of the angular distribution of Dielectronic Recombination into highly charged Krypton ions
Angular distribution of x-rays emitted in the process of Dielectronic Recombination (DR) was studied at the Electron Beam Ion Trap. For this the photon emission spectra were observed along and perpendicular the electron beam propagation direction. X-ray line intensities differ drastically between the two acquired spectra. This indicates a strong alignment of the total angular momentum vector of the excited states populated by DR with respect to the electron beam propagation direction