New methods for high resolution 3D imaging with X-rays

In der Arbeit haben wir die Grenzen der weit verbreiteten tomographischen Rekonstruktion von 3D-Proben mittels Transmissionsröntgenmikroskopie charakterisiert. Wir zeigen, dass die 3D-Auflösung mit diesem Ansatz durch die Schärfentiefe begrenzt ist. Zur Untersuchung von Alternativen führten wir Simulationen zur Bildentstehung in einem konfokalen Röntgenmikroskop und einem FIB-SXM durch. Wir zeigen, dass FIB-SXM ein vielversprechender Ansatz ist, der eine isotrope 3D-Aulösung um die 10 nm erreichen kann und zusätzlich ein drastisch verbessertes Signal-Rausch-Verhältnis bieten könnte. Wir stellen auch eine neue Holographiemethode vor, die sich für Vollfeldabbildungen mit kurzen kohärenten Röntgenpulsen als vorteilhaft erweisen und neue Einsichten in die ultraschnelle Physik liefern könnte.We have characterized the limitations of the most powerful and widely used 3D X-ray imaging approach, transmission X-ray microscopy with tomographic reconstruction. We show that 3D resolution in this approach is limited by the depth of field. To investigate alternatives, we perform simulations of a confocal transmission X-ray microscope and a FIB-SXM. We show that FIB-SXM is a very promising approach that could o er 3D isotropic resolution at 10 nm with dramatically improved signal to noise. We also introduce a new holography method that could prove bene cial for full eld imaging with short coherent X-ray pulses and yield new insights into ultrafast physics

Towards Experimental Handbooks in Catalysis

The “Seven Pillars” of oxidation catalysis proposed by Robert K. Grasselli represent an early example of phenomenological descriptors in the field of heterogeneous catalysis. Major advances in the theoretical description of catalytic reactions have been achieved in recent years and new catalysts are predicted today by using computational methods. To tackle the immense complexity of high-performance systems in reactions where selectivity is a major issue, analysis of scientific data by artificial intelligence and data science provides new opportunities for achieving improved understanding. Modern data analytics require data of highest quality and sufficient diversity. Existing data, however, frequently do not comply with these constraints. Therefore, new concepts of data generation and management are needed. Herein we present a basic approach in defining best practice procedures of measuring consistent data sets in heterogeneous catalysis using “handbooks”. Selective oxidation of short-chain alkanes over mixed metal oxide catalysts was selected as an example.DFG, 390540038, EXC 2008: Unifying Systems in Catalysis "UniSysCat

New methods for high resolution 3D imaging with X-rays

In der Arbeit haben wir die Grenzen der weit verbreiteten tomographischen Rekonstruktion von 3D-Proben mittels Transmissionsröntgenmikroskopie charakterisiert. Wir zeigen, dass die 3D-Auflösung mit diesem Ansatz durch die Schärfentiefe begrenzt ist. Zur Untersuchung von Alternativen führten wir Simulationen zur Bildentstehung in einem konfokalen Röntgenmikroskop und einem FIB-SXM durch. Wir zeigen, dass FIB-SXM ein vielversprechender Ansatz ist, der eine isotrope 3D-Aulösung um die 10 nm erreichen kann und zusätzlich ein drastisch verbessertes Signal-Rausch-Verhältnis bieten könnte. Wir stellen auch eine neue Holographiemethode vor, die sich für Vollfeldabbildungen mit kurzen kohärenten Röntgenpulsen als vorteilhaft erweisen und neue Einsichten in die ultraschnelle Physik liefern könnte.We have characterized the limitations of the most powerful and widely used 3D X-ray imaging approach, transmission X-ray microscopy with tomographic reconstruction. We show that 3D resolution in this approach is limited by the depth of field. To investigate alternatives, we perform simulations of a confocal transmission X-ray microscope and a FIB-SXM. We show that FIB-SXM is a very promising approach that could o er 3D isotropic resolution at 10 nm with dramatically improved signal to noise. We also introduce a new holography method that could prove bene cial for full eld imaging with short coherent X-ray pulses and yield new insights into ultrafast physics

Reduced formation of peroxide and radical species stabilises iron-based hybrid catalysts in polymer electrolyte membrane fuel cells

International audienc

3D membrane segmentation and quantification of intact thick cells using cryo soft X-ray transmission microscopy: a pilot study

Structural analysis of biological membranes is important for understanding cell and sub-cellular organelle function as well as their interaction with the surrounding environment. Imaging of whole cells in three dimension at high spatial resolution remains a significant challenge, particularly for thick cells. Cryo-transmission soft X-ray microscopy (cryo-TXM) has recently gained popularity to image, in 3D, intact thick cells (∼10μm) with details of sub-cellular architecture and organization in near-native state. This paper reports a new tool to segment and quantify structural changes of biological membranes in 3D from cryo-TXM images by tracking an initial 2D contour along the third axis of the microscope, through a multi-scale ridge detection followed by an active contours-based model, with a subsequent refinement along the other two axes. A quantitative metric that assesses the grayscale profiles perpendicular to the membrane surfaces is introduced and shown to be linearly related to the membrane thickness. Our methodology has been validated on synthetic phantoms using realistic microscope properties and structure dimensions, as well as on real cryo-TXM data. Results demonstrate the validity of our algorithms for cryo-TXM data analysis.R.C. was partially funded by the Instituto de Salud Carlos III, Spain (FIS- PI11/01709), and BE-DGR 2012 BE1 00308 from AGAUR, Catalonia, Spain. C.Z. acknowledges the financial support from the Spanish Ministry of Economy and Competitiveness, through the Maria de Maeztu Programme for Centres/Units of Excellence in R&D (MDM-2015-0502). O.K. was supported by the Seventh Framework Program of the European Commission, grant agreement 278486: DEVELAGE. The research leading to these results has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under BioStruct-X (grant agreement N283570), the Spanish Ministry of Economy and Competitiveness (grant TIN2014-52923-R) and FEDER

Correlation between Electronic Structure, Microstructure, and Switching Mode in Valence Change Mechanism Al2O3/TiOx‐Based Memristive Devices

Abstract Memristive devices with valence change mechanism (VCM) show promise for neuromorphic data processing, although emulation of synaptic behavior with analog weight updates remains a challenge. Standard filamentary and area‐dependent resistive switching exhibit characteristic differences in the transition from the high to low resistance state, which is either abrupt with inherently high variability or gradual and allows quasi‐analog operation. In this study, the two switching modes are clearly correlated to differences in the microstructure and electronic structure for Pt/Al2O3/TiOx/Cr/Pt devices made from amorphous layers of 1.2 nm Al2O3 and 7 nm TiOx by atomic layer deposition. For the filamentary mode, operando spectromicroscopy experiments identify a localized region of ≈50 nm in diameter of reduced titania surrounded by crystalline rutile‐like TiO2, highlighting the importance of Joule heating for this mode. In contrast, both oxide layers remain in their amorphous state for the interfacial mode, which proves that device temperature during switching stays below 670 K, which is the TiO2 crystallization temperature. The analysis of the electronic conduction behavior confirms that the interfacial switching occurs by modulating the effective tunnel barrier width due to accumulation and depletion of oxygen vacancies at the Al2O3/TiOx interface. The results are transferable to other bilayer stacks

Average profiles for the phantom with thickness 15 nm, with variable <i>μ</i>_<i>m</i>.

<p>G: Upper profile area with variable <i>μ</i>.</p

Schematic drawing of the profile area (grey region) based on membrane profile.

<p>Schematic drawing of the profile area (grey region) based on membrane profile.</p

(a) Reconstruction from simulated X-ray microscope data and overlaid with known contours from the ideal geometry; (b) <i>left</i>: XY slice overlaid with the segmentation, using the found compatible ridges only (<i>green</i>) or using all ridges (<i>red</i>); <i>middle</i> and <i>right</i>: YZ and XZ slices overlaid with segmentation results before (<i>white</i>) and after (<i>red</i>) the refinement step for the membrane of organelle 1; (c) reconstruction overlaid with the final segmentation.

<p>(a) Reconstruction from simulated X-ray microscope data and overlaid with known contours from the ideal geometry; (b) <i>left</i>: XY slice overlaid with the segmentation, using the found compatible ridges only (<i>green</i>) or using all ridges (<i>red</i>); <i>middle</i> and <i>right</i>: YZ and XZ slices overlaid with segmentation results before (<i>white</i>) and after (<i>red</i>) the refinement step for the membrane of organelle 1; (c) reconstruction overlaid with the final segmentation.</p