Schwefel-K-Kanten-Absorptionsspektroskopie an ausgewählten biologischen Systemen

Gegenstand der vorliegenden Arbeit ist die Anwendung der Schwefel-XANES-Spektroskopie auf biologische Probensysteme. Nach einer kurzen Begründung der besonderen Eignung des Verfahrens werden die physikalischen Grundlagen der Messmethodik dargelegt. Ausführlich ist der experimentelle Aufbau unter Nutzung eines Synchrotrons als Lichtquelle beschrieben. Die spektrale Selektion erfolgte durch Doppelkristallmonochromatoren. Für ortsauflösende Messungen wurde eine sog. Mikrosonde in Betrieb genommen. Die Messungen wurden in Baton Rouge / Louisiana am Center for Advanced Microstructures and Devices (CAMD) durchgeführt. Ortsauflösende Messungen dienten zur Untersuchung des Rostpilzbefalls von Weizenblättern, einer landwirtschaftlich relevanten Pflanzenkrankheit. Die Experimente liefern Informationen über die Beeinflussung des Stoffwechsels der Wirtspflanze durch den Parasiten und über die Ausdehnung des Befalls optisch gesunder Bereiche. Des weiteren wurden Messungen an mikrobiellen Matten aus sulfidischen Höhlenquellen durchgeführt. In diesen Matten herrschen Mikroorganismen vor, die eine entscheidende Rolle für den Schwefelkreislauf in diesen (verglichen mit Tiefseeobjekten) leicht zugänglichen lichtlosen Lebensräumen spielen. Außerdem wurde mit Hilfe der XANES-Spektroskopie untersucht, wie sich wurzelseitiger Sulfatmangel und eine Begasung mit H2S auf Schwefelverbindungen in Speisezwiebeln auswirken. Um Einblick in die thermische Zersetzung organischen Materials zu gewinnen, wurde das Rösten von Kaffeebohnen untersucht. Die Röntgenabsorptionsspektren erlauben einen neuen Einblick in die wirksamen Prozesse. Insgesamt zeigt die Arbeit, dass die Schwefel-XANES-Spektroskopie ein effizientes Werkzeug zur Analyse biologischer Systeme darstellt. Das Verfahren ermöglicht den ´in situ´ Einblick in Vorgänge, die auf andere Weise kaum experimentell zugänglich sind.Sulfur-K-Edge Absorption Spectroscopy of selected Biological Systems In this thesis investigations of sulfur compounds in biological samples by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. After a short elucidation of the special advantages of this method the physical basis of the technique is presented. The experimental setup including the synchrotron light source, the double crystal monochromator and a so-called microprobe for spatially resolved measurements is described in detail. The measurements were carried out in Baton Rouge / Louisiana at the Center for Advanced Microstructures and Devices (CAMD). Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi - a plant disease of considerable economic relevance. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. They are of great importance for the ecosystem in these easily accessible (compared to deep sea areas) aphotic habitats. Additionally, the influence of sulfate deprivation and H2S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting on sulfur compounds in coffee beans was studied. Several differences between XANES spectra of green and roasted coffee beans could be observed. Altogether this thesis shows that sulfur XANES spectroscopy is an efficient tool for the analysis of biological systems. The technique enables ´in situ´ insight into processes experimentally almost inaccessible by other methods.</p

Role of Iron on the Structure and Stability of Ni3.2Fe/Al2O3 during Dynamic CO2 Methanation for P2X Applications

An energy scenario, mainly based on renewables, requires efficient and flexible Power-to-X (P2X) storage technologies, including the methanation of CO₂. As active Ni⁰ surface sites of monometallic nickel-based catalysts are prone to surface oxidation under hydrogen-deficient conditions, we investigated iron as “protective” dopant. A combined operando X-ray absorption spectroscopy and X-ray diffraction setup with quantitative on-line product analysis was used to unravel the structure of Ni and Fe in an alloyed Ni-Fe/Al₂O₃ catalyst during dynamically driven methanation of CO₂. We observed that Fe protects Ni from oxidation and is itself more dynamic in the oxidation and reduction process. Hence, such “sacrificial” or“protective” dopants added in order to preserve the catalytic activity under dynamic reaction conditions may not only be of high relevance with respect to fine-tuning of catalysts for future industrial P2X applications but certainly also of general interest

Bridging the gap between industry and synchrotron: Operando study at 30 bar over 300 h during Fischer-Tropsch synthesis

In order to reduce CO$_{2}$ emissions, it is necessary to substitute fossil fuels with renewable energy using CO$_{2}$ as a carbon feedstock. An attractive route for synthetic fuel production is the Fe- or Co-catalysed Fischer–Tropsch process. A profound knowledge of the catalyst deactivation phenomena under industrial conditions is crucial for the process optimisation. In this study, we followed the structural changes of a Co–Ni–Re/γ-Al$_{2}$O$_{3}$ catalyst for >300 hours at 30 bar and 250 °C during the Fischer–Tropsch synthesis operando at a synchrotron radiation facility. The advanced setup built for operando X-ray diffraction and X-ray absorption spectroscopy allows simultaneous and robust monitoring of the catalytic activity even over 300 h time on stream. We found three activity regimes for the Co–Ni–Re/γ-Al$_{2}$O$_{3}$ catalyst during 310 h of operation. Fast decline in activity was observed during the initiation phase in the first hours of operation due to liquid film formation (mass transport limitations). Furthermore, solid state reactions and carbon depositions were found while continuing the exposure of the catalyst to harsh temperature conditions of 250 °C. By using this advanced setup, we bridged the gap between industrially oriented catalysts and fundamental studies at synchrotron radiation facilities, opening up new possibilities for operando characterisation of industrial processes that rely on conditions of up to 450 °C and 50 bar

The CO2Image mission: retrieval studies and performance analysis

The CO2Image satellite mission, led by the German Aerospace Center (DLR), aims to demonstrate the feasibility of quantifying carbon dioxide (CO2) and methane (CH4) emissions from medium-size point sources. Several DLR institutes are currently working on the reliminary design phase (Phase B) of the mission. Here we present a performance analysis based on the current instrument specifications. The Beer InfraRed Retrieval Algorithm (BIRRA), the line-by-line radiative transfer model Py4CAtS (Python for Computational ATmospheric Spectroscopy) and a COSIS (Carbon dioxide Sensing Imaging Spectrometer) instrument model are employed to infer CO2 and CH4 concentrations from synthetic COSIS spectra. We evaluate the instrument's performance and determine if it meets the intended requirements. The study assesses uncertainties in the retrieved concentrations as well as errors in point source emission estimates caused by instrument noise. First results suggest that the detection and quantification limits stated in the mission requirements document are justified. The analysis also demonstrates that retrieval errors tend to increase when the signal-to-noise ratio is low, complicating the distinction between emission sources and background concentrations. Furthermore, we discuss non-instrumental effects and demonstrate that the fit quality significantly improves if a low-level plume is scaled instead of a background reference profile that covers the atmosphere's full vertical extent. The analysis on heterogeneous scenes (high albedo contrast) reveals that the various instrument setups perform similarly for both molecules

CO2Image retrieval studies and performance analysis

Current and planned satellite missions such as the Japanese GOSAT (Greenhouse Gases Observing Satellite) and NASA's OCO (Orbiting Carbon Observatory) series and the upcoming Copernicus Carbon Dioxide Monitoring (CO2M) mission aim to constrain national and regional-scale emissions down to scales of urban agglomerations and large point sources. The CO2Image demonstrator mission of the German Aerospace Center (DLR) is specifically designed to detect and quantify carbon dioxide (CO2) and methane (CH4) emissions from medium-size point sources. To this end its COSIS (Carbon dioxide Sensing Imaging Spectrometer) push-broom grating spectrometer measures reflected solar radiation with a high spatial resolution of 50x50 m2, covering tiles of ~50x50 km2 extent. The instrument has a moderate spectral resolution of approximately ~1 nm and observes in a single spectral window in the 2 µm region. Here we present and discuss the impact of the expected COSIS performance on the retrieved level-2 data. The level-1 data (spectra) are generated using the Py4CAtS (Python for Computational ATmospheric Spectroscopy) line-by-line radiative transfer model and the COSIS SIMulator (COSIS-SIM). Based on the COSIS instrument parameters the analysis examines the retrieval errors related to noise which allows to estimate the detection and quantification limit of CO2 and CH4 emission rates at the instrument's spatial and spectral resolution. We further discuss the effect of heterogeneous scenes, i.e. high contrast surfaces that cause an effective distortion of the spectral response function by non-uniform illumination of the entrance slit. Finally, we assess the influence of initial guess values for the plume's vertical extent and shape on the retrieval

SOLARIS National Synchrotron Radiation Centre in Krakow, Poland

The SOLARIS synchrotron located in Krakow, Poland, is a third-generation light source operating at medium electron energy. The first synchrotron light was observed in 2015, and the consequent development of infrastructure lead to the first users’ experiments at soft X-ray energies in 2018. Presently, SOLARIS expands its operation towards hard X-rays with continuous developments of the beamlines and concurrent infrastructure. In the following, we will summarize the SOLARIS synchrotron design, and describe the beamlines and research infrastructure together with the main performance parameters, upgrade, and development plans