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  • Other Sources  (135)
  • GFZ, Helmholtz-Zentrum  (61)
  • 5 Abbey Square, Chester, Cheshire CH1 2HU, England  (38)
  • Univ. Bochum  (35)
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  • English  (135)
  • 1
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    INSIGHT: in situ heuristic tool for the efficient reduction of grazing‐incidence X‐ray scattering data (2024)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-04-25
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉INSIGHT〈/italic〉 is a Python‐based software tool for processing and reducing 2D grazing‐incidence wide‐ and small‐angle X‐ray scattering (GIWAXS/GISAXS) data. It offers the geometric transformation of the 2D GIWAXS/GISAXS detector image to reciprocal space, including vectorized and parallelized pixel‐wise intensity correction calculations. An explicit focus on efficient data management and batch processing enables full control of large time‐resolved synchrotron and laboratory data sets for a detailed analysis of kinetic GIWAXS/GISAXS studies of thin films. It processes data acquired with arbitrarily rotated detectors and performs vertical, horizontal, azimuthal and radial cuts in reciprocal space. It further allows crystallographic indexing and GIWAXS pattern simulation, and provides various plotting and export functionalities. Customized scripting offers a one‐step solution to reduce, process, analyze and export findings of large 〈italic〉in situ〈/italic〉 and 〈italic〉operando〈/italic〉 data sets.〈/p〉
    Keywords: ddc:548 ; grazing‐incidence X‐ray scattering ; time‐resolved studies ; in situ studies ; operando studies ; computer programs
    Language: English
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  • 2
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    Crystal diffraction prediction and partiality estimation using Gaussian basis functions (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-04
    Description: The recent diversification of macromolecular crystallographic experiments including the use of pink beams, convergent electron diffraction and serial snapshot crystallography has shown the limitations of using the Laue equations for diffraction prediction. This article gives a computationally efficient way of calculating approximate crystal diffraction patterns given varying distributions of the incoming beam, crystal shapes and other potentially hidden parameters. This approach models each pixel of a diffraction pattern and improves data processing of integrated peak intensities by enabling the correction of partially recorded reflections. The fundamental idea is to express the distributions as weighted sums of Gaussian functions. The approach is demonstrated on serial femtosecond crystallography data sets, showing a significant decrease in the required number of patterns to refine a structure to a given error.
    Description: Reflection position, size and shape prediction and partiality estimation of crystal diffraction by integrating using a Gaussian basis are described.
    Keywords: ddc:548 ; partiality estimation ; diffraction prediction ; merging ; serial snapshot crystallography
    Language: English
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  • 3
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    In situ neutron diffraction for analysing complex coarse‐grained functional materials (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-10-24
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Complex functional materials play a crucial role in a broad range of energy‐related applications and in general for materials science. Revealing the structural mechanisms is challenging due to highly correlated coexisting phases and microstructures, especially for 〈italic〉in situ〈/italic〉 or 〈italic〉operando〈/italic〉 investigations. Since the grain sizes influence the properties, these microstructural features further complicate investigations at synchrotrons due to the limitations of illuminated sample volumes. In this study, it is demonstrated that such complex functional materials with highly correlated coexisting phases can be investigated under 〈italic〉in situ〈/italic〉 conditions with neutron diffraction. For large grain sizes, these experiments are valuable methods to reveal the structural mechanisms. For an example of 〈italic〉in situ〈/italic〉 experiments on barium titanate with an applied electric field, details of the electric‐field‐induced phase transformation depending on grain size and frequency are revealed. The results uncover the strain mechanisms in barium titanate and elucidate the complex interplay of stresses in relation to grain sizes as well as domain‐wall densities and mobilities.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉This work reports 〈italic〉in situ〈/italic〉 neutron diffraction experiments on a broad range of grain sizes of barium titanate. The study reveals the grain‐size‐dependent strain mechanisms and shows the competitiveness of neutron diffraction with high‐resolution synchrotron diffraction.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2vb5054:jcr2vb5054-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:550.724 ; ddc:548 ; neutron diffraction ; in situ ; applied electric fields ; barium titanate ; strain mechanisms ; grain sizes ; complex functional materials ; microstructures ; coexisting phases
    Language: English
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  • 4
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    Energy‐dispersive X‐ray stress analysis under geometric constraints: exploiting the material's inherent anisotropy (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-09-12
    Description: Two data evaluation concepts for X‐ray stress analysis based on energy‐dispersive diffraction on polycrystalline materials with cubic crystal structure, almost random crystallographic texture and strong single‐crystal elastic anisotropy are subjected to comparative assessment. The aim is the study of the residual stress state in hard‐to‐reach measurement points, for which the sin2ψ method is not applicable due to beam shadowing at larger sample tilting. This makes the approaches attractive for stress analysis in engineering parts with complex shapes, for example. Both approaches are based on the assumption of a biaxial stress state within the irradiated sample volume. They exploit in different ways the elastic anisotropy of individual crystallites acting at the microscopic scale and the anisotropy imposed on the material by the near‐surface stress state at the macroscopic scale. They therefore complement each other, in terms of both their preconditions and their results. The first approach is based on the evaluation of strain differences, which makes it less sensitive to variations in the strain‐free lattice parameter a0. Since it assumes a homogeneous stress state within the irradiated sample volume, it provides an average value of the in‐plane stresses. The second approach exploits the sensitivity of the lattice strain to changes in a0. Consequently, it assumes a homogeneous chemical composition but provides a stress profile within the information depth. Experimental examples from different fields in materials science, namely shot peening of austenitic steel and in situ stress analysis during welding, are presented to demonstrate the suitability of the proposed methods.
    Description: The single‐crystal elastic anisotropy and the anisotropy of the near‐surface (residual) stress state of polycrystalline materials with random texture are exploited in energy‐dispersive X‐ray stress analysis to study samples under constrained measurement conditions.
    Keywords: ddc:548 ; X‐ray stress analysis ; energy‐dispersive diffraction ; polycrystalline materials ; single‐crystal elastic anisotropy
    Language: English
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  • 5
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    Use of electron backscatter diffraction patterns to determine the crystal lattice. Part 3. Pseudosymmetry (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-20
    Description: A pseudosymmetric description of the crystal lattice derived from a single wide‐angle Kikuchi pattern can have several causes. The small size (〈15%) of the sector covered by an electron backscatter diffraction pattern, the limited precision of the projection centre position and the Kikuchi band definition are crucial. Inherent pseudosymmetries of the crystal lattice and/or structure also pose a challenge in the analysis of Kikuchi patterns. To eliminate experimental errors as much as possible, simulated Kikuchi patterns of 350 phases have been analysed using the software CALM [Nolze et al. (2021). J. Appl. Cryst.54, 1012–1022] in order to estimate the frequency of and reasons for pseudosymmetric crystal lattice descriptions. Misinterpretations occur in particular when the atomic scattering factors of non‐equivalent positions are too similar and reciprocal‐lattice points are systematically missing. As an example, a pseudosymmetry prediction depending on the elements involved is discussed for binary AB compounds with B1 and B2 structure types. However, since this is impossible for more complicated phases, this approach cannot be directly applied to compounds of arbitrary composition and structure.
    Description: Distinguishing between actual and apparent pseudosymmetry in electron backscatter diffraction patterns is nearly impossible, even for simulated patterns. However, the resulting lattice is always a superlattice as long as the signal is not a superposition of multiple patterns.
    Keywords: ddc:548 ; Bravais lattices ; pseudosymmetry ; lattice point density ; ordered/disordered structures ; lattice distortion ; electron backscatter diffraction ; backscattered Kikuchi diffraction patterns ; lattice parameters ; Funk transform
    Language: English
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  • 6
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    Use of electron backscatter diffraction patterns to determine the crystal lattice. Part 2. Offset corrections (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-21
    Description: A band width determination using the first derivative of the band profile systematically underestimates the true Bragg angle. Corrections are proposed to compensate for the resulting offset Δa/a of the mean lattice parameters derived from as many Kikuchi band widths as possible. For dynamically simulated Kikuchi patterns, Δa/a can reach up to 8% for phases with a high mean atomic number Z, whereas for much more common low‐Z materials the offset decreases linearly. A predicted offset Δa/a = f(Z) is therefore proposed, which also includes the unit‐cell volume and thus takes into account the packing density of the scatterers in the material. Since Z is not always available for unknown phases, its substitution by Zmax, i.e. the atomic number of the heaviest element in the compound, is still acceptable for an approximate correction. For simulated Kikuchi patterns the offset‐corrected lattice parameter deviation is Δa/a 〈 1.5%. The lattice parameter ratios, and the angles α, β and γ between the basis vectors, are not affected at all.
    Description: Automatically determined band widths in simulated backscatter Kikuchi patterns exhibit differences from the double Bragg angles that correlate with the scatterer density. Corrections are proposed to compensate for this.
    Keywords: ddc:548 ; mean atomic number ; Kikuchi patterns ; lattice parameters ; automated Bragg angle determination ; lattice parameter determination ; dynamical theory of electron diffraction ; electron backscatter diffraction ; Funk transform
    Language: English
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  • 7
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    POWTEX visits POWGEN (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-21
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The high‐intensity time‐of‐flight (TOF) neutron diffractometer POWTEX for powder and texture analysis is currently being built prior to operation in the eastern guide hall of the research reactor FRM II at Garching close to Munich, Germany. Because of the world‐wide 〈sup〉3〈/sup〉He crisis in 2009, the authors promptly initiated the development of 〈sup〉3〈/sup〉He‐free detector alternatives that are tailor‐made for the requirements of large‐area diffractometers. Herein is reported the 2017 enterprise to operate one mounting unit of the final POWTEX detector on the neutron powder diffractometer POWGEN at the Spallation Neutron Source located at Oak Ridge National Laboratory, USA. As a result, presented here are the first angular‐ and wavelength‐dependent data from the POWTEX detector, unfortunately damaged by a 50〈italic〉g〈/italic〉 shock but still operating, as well as the efforts made both to characterize the transport damage and to successfully recalibrate the voxel positions in order to yield nonetheless reliable measurements. Also described is the current data reduction process using the 〈italic〉PowderReduceP2D〈/italic〉 algorithm implemented in 〈italic〉Mantid〈/italic〉 [Arnold 〈italic〉et al.〈/italic〉 (2014). 〈italic〉Nucl. Instrum. Methods Phys. Res. A〈/italic〉, 〈bold〉764〈/bold〉, 156–166]. The final part of the data treatment chain, namely a novel multi‐dimensional refinement using a modified version of the 〈italic〉GSAS‐II〈/italic〉 software suite [〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?aj5212"〉Toby & Von Dreele (2013). 〈italic〉J. Appl. Cryst.〈/italic〉〈bold〉46〈/bold〉, 544–549〈/ext-link〉], is compared with a standard data treatment of the same event data conventionally reduced as TOF diffraction patterns and refined with the unmodified version of 〈italic〉GSAS‐II〈/italic〉. This involves both determining the instrumental resolution parameters using POWGEN's powdered diamond standard sample and the refinement of a friendly‐user sample, BaZn(NCN)〈sub〉2〈/sub〉. Although each structural parameter on its own looks similar upon comparing the conventional (1D) and multi‐dimensional (2D) treatments, also in terms of precision, a closer view shows small but possibly significant differences. For example, the somewhat suspicious proximity of the 〈italic〉a〈/italic〉 and 〈italic〉b〈/italic〉 lattice parameters of BaZn(NCN)〈sub〉2〈/sub〉 crystallizing in 〈italic〉Pbca〈/italic〉 as resulting from the 1D refinement (0.008 Å) is five times less pronounced in the 2D refinement (0.038 Å). Similar features are found when comparing bond lengths and bond angles, 〈italic〉e.g.〈/italic〉 the two N—C—N units are less differently bent in the 1D results (173 and 175°) than in the 2D results (167 and 173°). The results are of importance not only for POWTEX but also for other neutron TOF diffractometers with large‐area detectors, like POWGEN at the SNS or the future DREAM beamline at the European Spallation Source.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The first real‐world neutron diffraction data have been collected with one of the POWTEX detectors (FRM II, Garching, Germany) mounted for testing at the Spallation Neutron Source (Oak Ridge National Laboratory, USA). They allow for angular‐ and wavelength‐dispersive Rietveld refinement using a modified version of 〈italic〉GSAS‐II〈/italic〉.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2tu5033:jcr2tu5033-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:548 ; neutron detectors ; POWGEN beamline ; POWTEX detector ; DREAM beamline ; time‐of‐flight diffraction ; angular‐dispersive refinement ; wavelength‐dispersive refinement ; powder diffraction ; Rietveld refinement ; multi‐dimensional refinement
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  • 8
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    A note on the wedge reversion antisymmetry operation and 51 types of physical quantities in arbitrary dimensions (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-21
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The paper by Gopalan [〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?ib5086"〉(2020). 〈italic〉Acta Cryst.〈/italic〉 A〈bold〉76〈/bold〉, 318–327〈/ext-link〉] presented an enumeration of the 41 physical quantity types in non‐relativistic physics, in arbitrary dimensions, based on the formalism of Clifford algebra. Gopalan considered three antisymmetries: spatial inversion, 〈overline〉1〈/overline〉, time reversal, 1′, and wedge reversion, 1〈sup〉†〈/sup〉. A consideration of the set of all seven antisymmetries (〈overline〉1〈/overline〉, 1′, 1〈sup〉†〈/sup〉, 1′〈sup〉†〈/sup〉, 〈overline〉1〈/overline〉〈sup〉†〈/sup〉, 〈overline〉1〈/overline〉′, 〈overline〉1〈/overline〉′〈sup〉†〈/sup〉) leads to an extension of the results obtained by Gopalan. It is shown that there are 51 types of physical quantities with distinct symmetry properties in total.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉It is shown that there are 51 types of physical quantities in arbitrary dimensions with distinct transformations by wedge reversion symmetry. In the paper by 〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?ib5086"〉Gopalan [(2020). 〈italic〉Acta Cryst.〈/italic〉 A〈bold〉76〈/bold〉, 318–327]〈/ext-link〉 only 41 types were enumerated.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:20532733:aya2ib5117:aya2ib5117-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:548 ; multivectors ; wedge reversion ; antisymmetry ; Clifford algebra
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  • 9
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    Use of electron backscatter diffraction patterns to determine the crystal lattice. Part 1. Where is the Bragg angle? (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-19
    Description: The derivation of a crystal structure and its phase‐specific parameters from a single wide‐angle backscattered Kikuchi diffraction pattern requires reliable extraction of the Bragg angles. By means of the first derivative of the lattice profile, an attempt is made to determine fully automatically and reproducibly the band widths in simulated Kikuchi patterns. Even under such ideal conditions (projection centre, wavelength and lattice plane traces are perfectly known), this leads to a lattice parameter distribution whose mean shows a linear offset that correlates with the mean atomic number Z of the pattern‐forming phase. The consideration of as many Kikuchi bands as possible reduces the errors that typically occur if only a single band is analysed. On the other hand, the width of the resulting distribution is such that higher image resolution of diffraction patterns, employing longer wavelengths to produce wider bands or the use of higher interference orders is less advantageous than commonly assumed.
    Description: The lattice parameters of more than 350 phases have been determined from simulated backscatter Kikuchi patterns. The deviations correlating with the mean atomic number correspond to those observed previously for experimental electron backscatter diffraction patterns.
    Keywords: ddc:548 ; Bragg angles ; Kikuchi bands ; Kikuchi patterns ; first derivative ; lattice parameters ; lattice parameter determination ; Bravais lattice type ; electron backscatter diffraction ; Radon transform
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  • 10
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    Data reduction for X‐ray serial crystallography using machine learning (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
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    Publication Date: 2023-07-19
    Description: Serial crystallography experiments produce massive amounts of experimental data. Yet in spite of these large‐scale data sets, only a small percentage of the data are useful for downstream analysis. Thus, it is essential to differentiate reliably between acceptable data (hits) and unacceptable data (misses). To this end, a novel pipeline is proposed to categorize the data, which extracts features from the images, summarizes these features with the `bag of visual words' method and then classifies the images using machine learning. In addition, a novel study of various feature extractors and machine learning classifiers is presented, with the aim of finding the best feature extractor and machine learning classifier for serial crystallography data. The study reveals that the oriented FAST and rotated BRIEF (ORB) feature extractor with a multilayer perceptron classifier gives the best results. Finally, the ORB feature extractor with multilayer perceptron is evaluated on various data sets including both synthetic and experimental data, demonstrating superior performance compared with other feature extractors and classifiers.
    Description: A machine learning method for distinguishing good and bad images in serial crystallography is presented. To reduce the computational cost, this uses the oriented FAST and rotated BRIEF feature extraction method from computer vision to detect image features, followed by a multilayer perceptron (neural network) to classify the images.
    Keywords: ddc:548 ; serial crystallography ; data reduction ; machine learning ; feature extraction
    Language: English
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  • 11
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    Towards joint in situ determination of pressure and temperature in the large volume press exclusively from X‐ray diffraction (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
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    Publication Date: 2023-07-19
    Description: Since high‐pressure devices have been used at synchrotron facilities, accurate determination of pressure and temperature in the sample has been a crucial objective, particularly for experiments that simulate the Earth's interior. However, in some cases using a thermocouple may have a high likelihood of failure or is incompatible with a high‐pressure assembly. To address these challenges and similar issues, we aim to expand a previously proposed solution: to jointly estimate pressure and temperature (〈italic〉PT〈/italic〉) through 〈italic〉in situ〈/italic〉 X‐ray diffraction, to cover a wider range of internal 〈italic〉PT〈/italic〉 calibrants tested over larger 〈italic〉PT〈/italic〉 ranges. A modifiable Python‐based software is offered to quickly obtain results. To achieve these aims, 〈italic〉in situ〈/italic〉 large volume press experiments are performed on pellets of intimately mixed powders of a halide (NaCl, KCl, KBr, CsCl) or MgO and a metal (Pt, Re, Mo, W, Ni) in the pressure range 3–11 GPa and temperature range 300–1800 K. Although the pressure range was chosen for practical reasons, it also covers an equally important depth range in the Earth (down to 350 km) for geoscience studies. A thermocouple was used to validate the 〈italic〉PT〈/italic〉 conditions in the cell assemblies. The key results show that choosing the appropriate calibrant materials and using a joint 〈italic〉PT〈/italic〉 estimation can yield surprisingly small uncertainties (〈italic〉i.e.〈/italic〉 〈±0.1 GPa and 〈±50 K). This development is expected to benefit current and future research at extreme conditions, as other materials with high compressibility or high thermal pressure, stable over large 〈italic〉PT〈/italic〉 ranges, may be discovered and used as 〈italic〉PT〈/italic〉 calibrants.〈/p〉
    Description: Research in high‐pressure devices, such as the diamond anvil cell and the large volume press, requires knowledge of the pressure and temperature in the sample. Here, a large volume press and an internal resistive heater were used to generate high load and heat to various combinations of intimately mixed powders of materials. X‐ray diffraction and custom software were used to jointly estimate the pressures and temperatures in the samples and establish calibrants for 〈italic〉in situ〈/italic〉 experiments at extreme conditions.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2vl5008:jsy2vl5008-fig-0001"〉
    Description: https://gitlab.desy.de/robert.farla/eoscross
    Keywords: ddc:548 ; equations of state ; X‐ray diffraction ; large volume press ; high pressure ; resistive heating
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  • 12
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    Hard X‐ray full‐field nanoimaging using a direct photon‐counting detector (2023)
    Flenner, Silja ; Hagemann, Johannes ; Wittwer, Felix ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-03-05
    Description: Full‐field X‐ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low‐absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X‐ray microscopy with Zernike phase contrast, near‐field holography and near‐field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal‐to‐noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single‐photon‐counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz‐Zentrum Hereon. Thanks to the long sample‐to‐detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single‐photon‐counting detector in combination with a long sample‐to‐detector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal‐to‐noise level.
    Description: A direct photon‐counting detector was used for different nanoimaging phase contrast techniques, increasing the temporal resolution.
    Keywords: ddc:548 ; nanotomography ; full‐field X‐ray microscopy ; near‐field holography ; near‐field ptychography ; Zernike phase contrast ; single‐photon‐counting detector ; phase contrast
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  • 13
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    Machine learning for scattering data: strategies, perspectives and applications to surface scattering (2023)
    Hinderhofer, Alexander ; Greco, Alessandro ; Starostin, Vladimir ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-02-14
    Description: Machine learning (ML) has received enormous attention in science and beyond. Discussed here are the status, opportunities, challenges and limitations of ML as applied to X‐ray and neutron scattering techniques, with an emphasis on surface scattering. Typical strategies are outlined, as well as possible pitfalls. Applications to reflectometry and grazing‐incidence scattering are critically discussed. Comment is also given on the availability of training and test data for ML applications, such as neural networks, and a large reflectivity data set is provided as reference data for the community.
    Description: The status, opportunities, challenges and limitations of machine learning are discussed as applied to X‐ray and neutron scattering techniques, with an emphasis on surface scattering.
    Keywords: ddc:548 ; surface scattering ; X‐ray diffraction ; neutron scattering ; machine learning ; data analysis
    Language: English
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  • 14
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    Beam‐induced redox chemistry in iron oxide nanoparticle dispersions at ESRF–EBS (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
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    Publication Date: 2024-02-21
    Description: The storage ring upgrade of the European Synchrotron Radiation Facility makes ESRF–EBS the most brilliant high‐energy fourth‐generation light source, enabling in situ studies with unprecedented time resolution. While radiation damage is commonly associated with degradation of organic matter such as ionic liquids or polymers in the synchrotron beam, this study clearly shows that highly brilliant X‐ray beams readily induce structural changes and beam damage in inorganic matter, too. Here, the reduction of Fe3+ to Fe2+ in iron oxide nanoparticles by radicals in the brilliant ESRF–EBS beam, not observed before the upgrade, is reported. Radicals are created due to radiolysis of an EtOH–H2O mixture with low EtOH concentration (∼6 vol%). In light of extended irradiation times during insitu experiments in, for example, battery and catalysis research, beam‐induced redox chemistry needs to be understood for proper interpretation of insitu data.
    Description: With the increased brilliance at the European Research Facility–Extremely Brilliant Source (ESRF–EBS), a beam‐induced reduction of non‐stochiometric iron oxide nanoparticles (almost maghemite composition) to magnetite was observed in a mixture of ethanol and water with low ethanol concentration.
    Keywords: ddc:548 ; beam‐induced radiolysis ; radiation damage on inorganic materials ; ESRF–EBS
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  • 15
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    Mapping the 3D position of battery cathode particles in Bragg coherent diffractive imaging (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-12-14
    Description: In Bragg coherent diffractive imaging, the precise location of the measured crystals in the interior of the sample is usually missing. Obtaining this information would help the study of the spatially dependent behavior of particles in the bulk of inhomogeneous samples, such as extra‐thick battery cathodes. This work presents an approach to determine the 3D position of particles by precisely aligning them at the instrument axis of rotation. In the test experiment reported here, with a 60 µm‐thick LiNi0.5Mn1.5O4 battery cathode, the particles were located with a precision of 20 µm in the out‐of‐plane direction, and the in‐plane coordinates were determined with a precision of 1 µm.
    Description: A method to determine the 3D position of particles in Bragg coherent diffractive imaging experiments is proposed. Test measurements demonstrate depth‐resolution with a precision of 20 µm along the beam. image
    Keywords: ddc:548 ; extra‐thick battery cathodes ; Bragg coherent X‐ray diffractive imaging ; battery cathodes ; Bragg diffraction ; sphere of confusion ; 3D mapping
    Language: English
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  • 16
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    The soft X‐ray and XUV split‐and‐delay unit at beamlines FL23/24 at FLASH2 (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-01-12
    Description: A split‐and‐delay unit for the extreme ultraviolet and soft X‐ray spectral regions has been built which enables time‐resolved experiments at beamlines FL23 and FL24 at the Free‐electron LASer in Hamburg (FLASH). Geometric wavefront splitting at a sharp edge of a beam splitting mirror is applied to split the incoming soft X‐ray pulse into two beams. Ni and Pt coatings at grazing incidence angles have been chosen in order to cover the whole spectral range of FLASH2 and beyond, up to hν = 1800 eV. In the variable beam path with a grazing incidence angle of ϑd = 1.8°, the total transmission (T) ranges are of the order of 0.48 〈 T 〈 0.84 for hν 〈 100 eV and T 〉 0.50 for 100 eV 〈 hν 〈 650 eV with the Ni coating, and T 〉 0.06 for hν 〈 1800 eV for the Pt coating. For a fixed beam path with a grazing incidence angle of ϑf = 1.3°, a transmission of T 〉 0.61 with the Ni coating and T 〉 0.23 with a Pt coating is achieved. Soft X‐ray pump/soft X‐ray probe experiments are possible within a delay range of −5 ps 〈 Δt 〈 +18 ps with a nominal time resolution of tr = 66 as and a measured timing jitter of tj = 121 ± 2 as. First experiments with the split‐and‐delay unit determined the averaged coherence time of FLASH2 to be τc = 1.75 fs at λ = 8 nm, measured at a purposely reduced coherence of the free‐electron laser.
    Description: The properties of the recently installed split‐and‐delay unit at beamlines FL23 and FL24 at FLASH2 are presented. Its operational range, performance parameters and results of a first experiment are described. image
    Keywords: ddc:550.724 ; time‐resolved pump–probe ; XUV ; soft X‐rays ; free‐electron laser
    Language: English
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  • 17
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    XDSGUI: a graphical user interface for XDS, SHELX and ARCIMBOLDO (2023)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-01-12
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉XDSGUI〈/italic〉 is a lightweight graphical user interface (GUI) for the 〈italic〉XDS〈/italic〉, 〈italic〉SHELX〈/italic〉 and 〈italic〉ARCIMBOLDO〈/italic〉 program packages that serves both novice and experienced users in obtaining optimal processing and phasing results for X‐ray, neutron and electron diffraction data. The design of the program enables data processing and phasing without command line usage, and supports advanced command flows in a simple user‐modifiable and user‐extensible way. The GUI supplies graphical information based on the tabular log output of the programs, which is more intuitive, comprehensible and efficient than text output can be.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉A customizable stateless graphical user interface simplifies the processing, analysis and phasing of diffraction data.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2yr5110:jcr2yr5110-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:548 ; X‐ray diffraction ; neutron diffraction ; electron diffraction ; data processing ; graphical user interfaces ; phasing ; XDS ; ARCIMBOLDO ; SHELX
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  • 18
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    Sub‐micrometer focusing setup for high‐pressure crystallography at the Extreme Conditions beamline at PETRA III (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-06-24
    Description: Scientific tasks aimed at decoding and characterizing complex systems and processes at high pressures set new challenges for modern X‐ray diffraction instrumentation in terms of X‐ray flux, focal spot size and sample positioning. Presented here are new developments at the Extreme Conditions beamline (P02.2, PETRA III, DESY, Germany) that enable considerable improvements in data collection at very high pressures and small scattering volumes. In particular, the focusing of the X‐ray beam to the sub‐micrometer level is described, and control of the aberrations of the focusing compound refractive lenses is made possible with the implementation of a correcting phase plate. This device provides a significant enhancement of the signal‐to‐noise ratio by conditioning the beam shape profile at the focal spot. A new sample alignment system with a small sphere of confusion enables single‐crystal data collection from grains of micrometer to sub‐micrometer dimensions subjected to pressures as high as 200 GPa. The combination of the technical development of the optical path and the sample alignment system contributes to research and gives benefits on various levels, including rapid and accurate diffraction mapping of samples with sub‐micrometer resolution at multimegabar pressures.
    Description: Facing the challenges of X‐ray diffraction from tiny samples subjected to multimegabar pressures, instrumentation developments are presented that enable, among other studies, single‐crystal data collection from micrometer‐ to sub‐micrometer‐sized grains. The developments are based on a sub‐micrometer beam capability employing compound refractive lenses operating with a phase correcting plate and a precise motorization solution.
    Keywords: ddc:548
    Language: English
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  • 19
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    Robust approaches for model‐free small‐angle scattering data analysis (2022)
    Bender, Philipp ; Honecker, Dirk ; Bersweiler, Mathias ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-10-04
    Description: The small‐angle neutron scattering data of nanostructured magnetic samples contain information regarding their chemical and magnetic properties. Often, the first step to access characteristic magnetic and structural length scales is a model‐free investigation. However, due to measurement uncertainties and a restricted q range, a direct Fourier transform usually fails and results in ambiguous distributions. To circumvent these problems, different methods have been introduced to derive regularized, more stable correlation functions, with the indirect Fourier transform being the most prominent approach. Here, the indirect Fourier transform is compared with the singular value decomposition and an iterative algorithm. These approaches are used to determine the correlation function from magnetic small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles; it is shown that with all three methods, in principle, the same correlation function can be derived. Each method has certain advantages and disadvantages, and thus the recommendation is to combine these three approaches to obtain robust results.
    Description: Three different approaches are compared for determination of the correlation function from the small‐angle neutron scattering data of a powder sample of iron oxide nanoparticles.
    Keywords: ddc:548
    Language: English
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  • 20
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    Structure determination from unindexed powder data from scratch by a global optimization approach using pattern comparison based on cross‐correlation functions (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-06-16
    Description: A method of ab initio crystal structure determination from powder diffraction data for organic and metal–organic compounds, which does not require prior indexing of the powder pattern, has been developed. Only a reasonable molecular geometry is required, needing knowledge of neither unit‐cell parameters nor space group. The structures are solved from scratch by a global fit to the powder data using the new program FIDEL‐GO (`FIt with DEviating Lattice parameters ‐ Global Optimization'). FIDEL‐GO uses a similarity measure based on cross‐correlation functions, which allows the comparison of simulated and experimental powder data even if the unit‐cell parameters deviate strongly. The optimization starts from large sets of random structures in various space groups. The unit‐cell parameters, molecular position and orientation, and selected internal degrees of freedom are fitted simultaneously to the powder pattern. The optimization proceeds in an elaborate multi‐step procedure with built‐in clustering of duplicate structures and iterative adaptation of parameter ranges. The best structures are selected for an automatic Rietveld refinement. Finally, a user‐controlled Rietveld refinement is performed. The procedure aims for the analysis of a wide range of `problematic' powder patterns, in particular powders of low crystallinity. The method can also be used for the clustering and screening of a large number of possible structure candidates and other application scenarios. Examples are presented for structure determination from unindexed powder data of the previously unknown structures of the nanocrystalline phases of 4,11‐difluoro‐, 2,9‐dichloro‐ and 2,9‐dichloro‐6,13‐dihydro‐quinacridone, which were solved from powder patterns with 14–20 peaks only, and of the coordination polymer dichloro‐bis(pyridine‐N)copper(II).
    Description: A new method for the structure determination of molecular crystals from unindexed powder data has been developed and successfully applied. The method performs a global optimization using pattern comparison based on cross‐correlation functions.
    Keywords: ddc:548
    Language: English
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  • 21
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    Site dependence of the magnetocaloric effect in Mn5−xFexSi3 (2022)
    Ait Haddouch, Mohammed ; Abboushi, Nour ; Sharma, Neetika ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-12-06
    Description: The nuclear and magnetic structures of Mn3Fe2Si3 are investigated in the temperature range from 20 to 300 K. The magnetic properties of Mn3Fe2Si3 were measured on a single crystal. The compound undergoes a paramagnetic to antiferromagnetic transition at TN2 ≃ 120 K and an antiferromagnetic to antiferromagnetic transition at TN1 ≃ 69 K. A similar sequence of magnetic phase transitions is found for the parent compound Mn5Si3 upon temperature variation, but the field‐driven transition observed in Mn5Si3 is not found in Mn3Fe2Si3, resulting in a strongly reduced magnetocaloric effect. Structurally, the hexagonal symmetry found for both compounds under ambient conditions is preserved in Mn3Fe2Si3 through both magnetic transitions, indicating that the crystal structure is only weakly affected by the magnetic phase transition, in contrast to Mn5Si3 where both transitions distort the nuclear structure. Both compounds feature a collinear high‐temperature magnetic phase AF2 and transfer into a non‐collinear phase AF1 at low temperature. While one of the distinct crystallographic sites remains disordered in the AF2 phase in the parent compound, the magnetic structure in the AF2 phase involves all magnetic atoms in Mn3Fe2Si3. These observations imply that the distinct sites occupied by the magnetic atoms play an important role in the magnetocaloric behaviour of the family.
    Description: The nuclear and magnetic structures of Mn3Fe2Si3 are determined and the magnetic properties are compared with those of the parent compound Mn5Si3. The results imply that the distinct magnetic sites play an important role in the magnetocaloric behaviour of the family. image
    Keywords: ddc:548 ; magnetocaloric effect ; magnetic structure ; neutron diffraction ; synchrotron diffraction ; site dependence
    Language: English
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  • 22
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    Digitization of imaging plates from Guinier powder X‐ray diffraction cameras (2022)
    Nasir, Jamal ; Steinbrück, Nils ; Xu, Ke ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-01-15
    Description: A Guinier camera equipped with an imaging plate is used to investigate and eliminate the sources of instrumental errors affecting the quality of the obtained scanned Guinier data. A program with a graphical user interface is presented which converts the data of the scanned images into different standard file formats for powder X‐ray patterns containing intensities, their standard deviations and the diffraction angles. The program also allows for manual and automatic correction of the 2gθ scale against a known reference material. It is shown using LaB6 that the exported X‐ray diffraction patterns provide a 2gθ scale reproducible enough to allow for averaging diffractograms obtained from different exposures of the imaging plate for the same sample. As shown on a mixture of NaCl and sodalite, the quality of the produced data is sufficient for Rietveld refinement. The software including source code is made available under a free software license.
    Description: A program for the digitization of Guinier powder diffraction images is described, which works with images from both optical and laser scanners. Thus, processing of data from storage‐phosphor‐based imaging plates and Ag‐based photographic films is possible.
    Keywords: ddc:548 ; IPreader software ; Guinier cameras ; imaging plates (IPs) ; diffraction pattern conversion into data columns ; powder X‐ray diffraction ; data processing ; Guinier method
    Language: English
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  • 23
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    Small‐angle neutron scattering of long‐wavelength magnetic modulations in reduced sample dimensions (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-04
    Description: Magnetic small‐angle neutron scattering (SANS) is ideally suited to providing direct reciprocal‐space information on long‐wavelength magnetic modulations, such as helicoids, solitons, merons or skyrmions. SANS of such structures in thin films or micro‐structured bulk materials is strongly limited by the tiny scattering volume vis a vis the prohibitively high background scattering by the substrate and support structures. Considering near‐surface scattering just above the critical angle of reflection, where unwanted signal contributions due to substrate or support structures become very small, it is established that the scattering patterns of the helical, conical, skyrmion lattice and fluctuation‐disordered phases in a polished bulk sample of MnSi are equivalent for conventional transmission and near‐surface SANS geometries. This motivates the prediction of a complete repository of scattering patterns expected for thin films in the near‐surface SANS geometry for each orientation of the magnetic order with respect to the scattering plane.
    Description: Near‐surface SANS is discussed for its potential as a probe of long‐wavelength magnetic modulations in specimens with reduced sample dimensions.
    Keywords: ddc:548 ; small‐angle neutron scattering ; near‐surface SANS ; magnetism ; non‐collinear magnetism ; thin films ; skyrmions ; MnSi
    Language: English
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  • 24
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    Using diffraction losses of X‐rays in a single crystal for determination of its lattice parameters as well as for monochromator calibration (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-12-04
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉A way has been developed to measure the unit‐cell parameters of a single crystal just from an energy scan with X‐rays, even when the exact energy of the X‐rays is not well defined due to an error in the pitch angle of the monochromator. The precision of this measurement reaches 〈italic〉da〈/italic〉/〈italic〉a〈/italic〉 ∼ 1 × 10〈sup〉−5〈/sup〉. The method is based on the analysis of diffraction losses of the beam, transmitted through a single crystal (the so‐called `glitch effect'). This method can be easily applied to any transmissive X‐ray optical element made of single crystals (for example, X‐ray lenses). The only requirements are the possibility to change the energy of the generated X‐ray beam and some intensity monitor to measure the transmitted intensity. The method is agnostic to the error in the monochromator tuning and it can even be used for determination of the absolute pitch (or 2gθ) angle of the monochromator. Applying the same method to a crystal with well known lattice parameters allows determination of the exact cell parameters of the monochromator at any energy.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Diffraction losses (glitches) at certain energies of the X‐ray beam, transmitted through a single crystal, can be used for lattice parameters determination as well as for calibrating the monochromator (absolute pitch angle and the unit‐cell parameter).〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2ay5590:jsy2ay5590-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:548 ; X‐ray glitches ; diffraction losses ; unit‐cell parameter ; single‐crystal X‐ray optics ; monochromator calibration
    Language: English
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  • 25
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    Combining reverse Monte Carlo analysis of X‐ray scattering and extended X‐ray absorption fine structure spectra of very small nanoparticles (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-07-21
    Description: Finite size effects in partial pair distribution functions generate artefacts in the scattering structure factor and scattering intensity. It is shown how they can be overcome using a binned version of the Debye scattering equation. Accordingly, reverse Monte Carlo simulations are used for very small nanoparticles of LaFeO3 with diameters below 10 nm to simultaneously analyse X‐ray scattering data and extended X‐ray absorption fine structure spectra at the La K and Fe K edges. The structural information obtained is consistent regarding local structure and long‐range order.
    Description: Computing scattering intensity using the Debye scattering equation after binning interatomic distances avoids finite size artefacts and is efficient enough for simultaneous refinement of scattering data and extended X‐ray absorption spectra by reverse Monte Carlo simulations.
    Keywords: ddc:548 ; extended X‐ray absorption fine structure ; EXAFS ; wide‐angle X‐ray scattering ; WAXS ; reverse Monte Carlo ; RMC ; nanocrystals ; LaFeO3
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  • 26
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    HTD2: a single‐crystal X‐ray diffractometer for combined high‐pressure/low‐temperature experiments at laboratory scale (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-12-15
    Description: High‐pressure (HP) X‐ray diffraction experiments at low temperature (LT) require dedicated instruments as well as non‐standard sample environments and measuring strategies. This is especially true when helium cryogenic temperatures below 80 K are targeted. Furthermore, only experiments on single‐crystalline samples provide the prerequisites to study subtle structural changes in the p–T phase diagram under extreme LT and HP conditions in greater detail. Due to special hardware requirements, such measurements are usually in the realm of synchrotron beamlines. This contribution describes the design of an LT/HP diffractometer (HTD2) to perform single‐crystal X‐ray diffraction experiments using a laboratory source in the temperature range 400 〉 T 〉 2 K while applying pressures of up to 20 GPa.
    Description: The design and operation of a newly commissioned single‐crystal X‐ray diffractometer (HTD2) are presented. The device enables experiments under simultaneous low‐temperature and high‐pressure conditions using a laboratory X‐ray source.
    Keywords: ddc:548 ; HTD2 ; low temperature ; high pressure ; single crystals ; instrumentation
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  • 27
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    X‐ray diffraction with micrometre spatial resolution for highly absorbing samples (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-01-21
    Description: X‐ray diffraction with high spatial resolution is commonly used to characterize (poly)crystalline samples with, for example, respect to local strain, residual stress, grain boundaries and texture. However, the investigation of highly absorbing samples or the simultaneous assessment of high‐Z materials by X‐ray fluorescence have been limited due to the utilization of low photon energies. Here, a goniometer‐based setup implemented at the P06 beamline of PETRA III that allows for micrometre spatial resolution with a photon energy of 35 keV and above is reported. A highly focused beam was achieved by using compound refractive lenses, and high‐precision sample manipulation was enabled by a goniometer that allows up to 5D scans (three rotations and two translations). As experimental examples, the determination of local strain variations in martensitic steel samples with micrometre spatial resolution, as well as the simultaneous elemental distribution for high‐Z materials in a thin‐film solar cell, are demonstrated. The proposed approach allows users from the materials‐science community to determine micro‐structural properties even in highly absorbing samples.
    Description: A demonstration of high‐resolution micro X‐ray diffraction at high photon energies for highly absorbing samples.
    Keywords: ddc:548 ; X‐ray diffraction ; high spatial resolution ; high photon energy ; X‐ray fluorescence ; goniometers
    Language: English
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  • 28
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    Domain Auto Finder (DAFi) program: the analysis of single‐crystal X‐ray diffraction data from polycrystalline samples (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-01-21
    Description: This paper presents the Domain Auto Finder (DAFi) program and its application to the analysis of single‐crystal X‐ray diffraction (SC‐XRD) data from multiphase mixtures of microcrystalline solids and powders. Superposition of numerous reflections originating from a large number of single‐crystal domains of the same and/or different (especially unknown) phases usually precludes the sorting of reflections coming from individual domains, making their automatic indexing impossible. The DAFi algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC‐XRD data. Further indexing of all found subsets can be easily performed using widely accessible crystallographic packages. As the algorithm neither requires a priori crystallographic information nor is limited by the number of phases or individual domains, DAFi is powerful software to be used for studies of multiphase polycrystalline and microcrystalline (powder) materials. The algorithm is validated by testing on X‐ray diffraction data sets obtained from real samples: a multi‐mineral basalt rock at ambient conditions and products of the chemical reaction of yttrium and nitrogen in a laser‐heated diamond anvil cell at 50 GPa. The high performance of the DAFi algorithm means it can be used for processing SC‐XRD data online during experiments at synchrotron facilities.
    Description: This paper presents the Domain Auto Finder (DAFi) program and its application to the analysis of single‐crystal X‐ray diffraction (SC‐XRD) data from multiphase mixtures of microcrystalline solids and powders. The DAFi algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC‐XRD data and neither requires a priori crystallographic information nor is limited by the number of phases or individual domains.
    Keywords: ddc:548 ; single‐crystal domain auto finder ; DAFi ; single‐crystal X‐ray diffraction ; polycrystalline samples ; multiphase mixtures
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  • 29
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    High‐resolution XEOL spectroscopy setup at the X‐ray absorption spectroscopy beamline P65 of PETRA III (2022)
    Levcenko, S. ; Biller, R. ; Pfeiffelmann, T. ; [et al.]
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-01-25
    Description: A newly designed setup to perform steady‐state X‐ray excited optical luminescence (XEOL) spectroscopy and simultaneous XEOL and X‐ray absorption spectroscopy characterization at beamline P65 of PETRA III is described. The XEOL setup is equipped with a He‐flow cryostat and state‐of‐the‐art optical detection system, which covers a wide wavelength range of 300–1700 nm with a high spectral resolution of 0.4 nm. To demonstrate the setup functioning, low‐temperature XEOL studies on polycrystalline CuInSe2 thin film, single‐crystalline GaN thin film and single‐crystalline ZnO bulk semiconductor samples are performed.
    Description: X‐ray excited optical luminescence (XEOL) spectroscopy is increasingly important to understand the interplay between the optical properties, structure and chemical composition, providing insights into the mechanism of radiative recombination for a wide range of materials. This study demonstrates a newly implemented setup to perform steady‐state XEOL and simultaneous XEOL and XAFS characterizations at beamline P65 of PETRA III.
    Keywords: ddc:550.2 ; XEOL ; XAS ; CuInSe2 ; ZnO ; GaN
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  • 30
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    Automatic bad‐pixel mask maker for X‐ray pixel detectors with application to serial crystallography (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-02-14
    Description: X‐ray crystallography has witnessed a massive development over the past decade, driven by large increases in the intensity and brightness of X‐ray sources and enabled by employing high‐frame‐rate X‐ray detectors. The analysis of large data sets is done via automatic algorithms that are vulnerable to imperfections in the detector and noise inherent with the detection process. By improving the model of the behaviour of the detector, data can be analysed more reliably and data storage costs can be significantly reduced. One major requirement is a software mask that identifies defective pixels in diffraction frames. This paper introduces a methodology and program based upon concepts of machine learning, called robust mask maker (RMM), for the generation of bad‐pixel masks for large‐area X‐ray pixel detectors based on modern robust statistics. It is proposed to discriminate normally behaving pixels from abnormal pixels by analysing routine measurements made with and without X‐ray illumination. Analysis software typically uses a Bragg peak finder to detect Bragg peaks and an indexing method to detect crystal lattices among those peaks. Without proper masking of the bad pixels, peak finding methods often confuse the abnormal values of bad pixels in a pattern with true Bragg peaks and flag such patterns as useful regardless, leading to storage of enormous uninformative data sets. Also, it is computationally very expensive for indexing methods to search for crystal lattices among false peaks and the solution may be biased. This paper shows how RMM vastly improves peak finders and prevents them from labelling bad pixels as Bragg peaks, by demonstrating its effectiveness on several serial crystallography data sets.
    Description: Attention is focused on perhaps the biggest bottleneck in data analysis for serial crystallography at X‐ray free‐electron lasers, which has not received serious enough examination to date. An effective and reliable way is presented to identify anomalies in detectors, using machine learning and recently developed mathematical methods in the field referred to as `robust statistics'. image
    Keywords: ddc:548 ; bad‐pixel masks ; robust mask maker ; machine learning ; robust statistics ; serial crystallography
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    Updates in SASfit for fitting analytical expressions and numerical models to small‐angle scattering patterns (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-02-22
    Description: Small‐angle scattering is an increasingly common method for characterizing particle ensembles in a wide variety of sample types and for diverse areas of application. SASfit has been one of the most comprehensive and flexible curve‐fitting programs for decades, with many specialized tools for various fields. Here, a selection of enhancements and additions to the SASfit program are presented that may be of great benefit to interested and advanced users alike: (a) further development of the technical basis of the program, such as new numerical algorithms currently in use, a continuous integration practice for automated building and packaging of the software, and upgrades on the plug‐in system for easier adoption by third‐party developers; (b) a selection of new form factors for anisotropic scattering patterns and updates to existing form factors to account for multiple scattering effects; (c) a new type of a very flexible distribution called metalog [Keelin (2016). Decis. Anal.13, 243–277], and regularization techniques such as the expectation‐maximization method [Dempster et al. (1977). J. R. Stat. Soc. Ser. B (Methodological), 39, 1–22; Richardson (1972) J. Opt. Soc. Am.62, 55; Lucy (1974). Astron. J.79, 745; Lucy (1994). Astron. Astrophys.289, 983–994], which is compared with fits of analytical size distributions via the non‐linear least‐squares method; and (d) new structure factors, especially for ordered nano‐ and meso‐scaled material systems, as well as the Ornstein–Zernike solver for numerical determination of particle interactions and the resulting structure factor when no analytical solution is available, with the aim of incorporating its effects into the small‐angle scattering intensity model used for fitting with SASfit.
    Description: Recent enhancements and additions to the SASfit program are discussed, including anisotropic scattering models, flexible distributions, regularization techniques such as the expectation‐maximization method, and new structure factors, especially for ordered nano‐ and meso‐scaled material. The Ornstein–Zernike solver for numerical structure factors is also introduced. image
    Keywords: ddc:548 ; small‐angle scattering ; SASfit ; numerical models ; structure factors ; form factors ; regularization techniques
    Language: English
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    Extending MIEZE spectroscopy towards thermal wavelengths (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-02-05
    Description: A modulation of intensity with zero effort (MIEZE) setup is proposed for high‐resolution neutron spectroscopy at momentum transfers up to 3 Å〈sup〉−1〈/sup〉, energy transfers up to 20 meV and an energy resolution in the microelectronvolt range using both thermal and cold neutrons. MIEZE has two prominent advantages compared with classical neutron spin echo. The first is the possibility to investigate spin‐depolarizing samples or samples in strong magnetic fields without loss of signal amplitude and intensity. This allows for the study of spin fluctuations in ferromagnets, and facilitates the study of samples with strong spin‐incoherent scattering. The second advantage is that multi‐analyzer setups can be implemented with comparatively little effort. The use of thermal neutrons increases the range of validity of the spin‐echo approximation towards shorter spin‐echo times. In turn, the thermal MIEZE option for greater ranges (TIGER) closes the gap between classical neutron spin‐echo spectroscopy and conventional high‐resolution neutron spectroscopy techniques such as triple‐axis, time‐of‐flight and back‐scattering. To illustrate the feasibility of TIGER, this paper presents the details of its implementation at the RESEDA beamline at FRM II by means of an additional velocity selector, polarizer and analyzer.
    Description: A modulation of intensity with zero effort (MIEZE) setup is proposed for high‐resolution neutron spectroscopy at momentum transfers up to 3 Å〈sup〉−1〈/sup〉, energy transfers up to 20 meV and an energy resolution in the microelectronvolt range using both thermal and cold neutrons.
    Keywords: ddc:548 ; neutron resonant spin echo ; MIEZE ; quasielastic scattering ; thermal neutrons
    Language: English
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    Extreme conditions research using the large‐volume press at the P61B endstation, PETRA III (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-02-05
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Penetrating, high‐energy synchrotron X‐rays are in strong demand, particularly for high‐pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high‐energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front‐end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high‐energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six‐ram Hall‐type large‐volume press, Aster‐15, at a synchrotron facility is described for research with synchrotron X‐rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy‐dispersive X‐ray diffraction and radiography techniques are presented.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The operation of the P61B endstation large‐volume press and optics of P61 are reviewed. The instrumentation at P61B, including the large‐volume press, detection systems and data acquisition for 〈italic〉in situ〈/italic〉 high‐pressure experiments are described.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2ju5040:jsy2ju5040-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:550.724 ; extreme conditions ; high‐pressure ; large‐volume press ; energy‐dispersive X‐ray diffraction ; radiography ; resistive heating ; ultrasonic interferometry ; acoustic emissions detection
    Language: English
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    Quantifying electron cascade size in various irradiated materials for free‐electron laser applications (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2023-12-12
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Studying electron‐ and X‐ray‐induced electron cascades in solids is essential for various research areas at free‐electron laser facilities, such as X‐ray imaging, crystallography, pulse diagnostics or X‐ray‐induced damage. To better understand the fundamental factors that define the duration and spatial size of such cascades, this work investigates the electron propagation in ten solids relevant for the applications of X‐ray lasers: Au, B〈sub〉4〈/sub〉C, diamond, Ni, polystyrene, Ru, Si, SiC, Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 and W. Using classical Monte Carlo simulation in the atomic approximation, we study the dependence of the cascade size on the incident electron or photon energy and on the target parameters. The results show that an electron‐induced cascade is systematically larger than a photon‐induced cascade. Moreover, in contrast with the common assumption, the maximal cascade size does not necessarily coincide with the electron range. It was found that the cascade size can be controlled by careful selection of the photon energy for a particular material. Photon energy, just above an ionization potential, can essentially split the absorbed energy between two electrons (photo‐ and Auger), reducing their initial energy and thus shrinking the cascade size. This analysis suggests a way of tailoring the electron cascades for applications requiring either small cascades with a high density of excited electrons or large‐spread cascades with lower electron densities.〈/p〉
    Description: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Studying electron‐ and X‐ray‐induced electron cascades in solids is essential for various research areas at free‐electron laser facilities, such as X‐ray imaging, crystallography, pulse diagnostics or X‐ray‐induced damage. To better understand the fundamental factors that define the duration and spatial size of such cascades, this work investigates the electron propagation in ten solids relevant for the applications of X‐ray lasers. Using classical Monte Carlo simulation in the atomic approximation, the dependence of the cascade size on the incident electron or photon energy and on the target parameters is studied.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2gb5123:jsy2gb5123-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Keywords: ddc:548 ; electron cascades ; X‐ray free‐electron lasers ; Monte Carlo ; photon‐induced cascade ; electron transport
    Language: English
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    The PERCIVAL detector: first user experiments (2022)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2024-03-13
    Description: The PERCIVAL detector is a CMOS imager designed for the soft X‐ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free‐electron laser, holographic imaging at a storage ring and preliminary tests on X‐ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X‐ray science.
    Keywords: ddc:548 ; X‐ray detectors ; soft X‐rays ; ptychography ; holographic imaging ; XPCS ; detectors
    Language: English
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    Crystal structure of a calcium(II)–pyrroloquinoline quinone (PQQ) complex outside a protein environment (2021)
    5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2021-04-14
    Description: Pyrroloquinoline quinone (PQQ) is an important cofactor of calcium‐ and lanthanide‐dependent alcohol dehydrogenases, and has been known for over 30 years. Crystal structures of Ca–MDH enzymes (MDH is methanol dehydrogenase) have been known for some time; however, crystal structures of PQQ with biorelevant metal ions have been lacking in the literature for decades. We report here the first crystal structure analysis of a Ca–PQQ complex outside the protein environment, namely, poly[[undecaaquabis(μ‐4,5‐dioxo‐4,5‐dihydro‐1H‐pyrrolo[2,3‐f]quinoline‐2,7,9‐tricarboxylato)tricalcium(II)] dihydrate], {[Ca3(C14H3N2O8)2(H2O)11]·2H2O}n. The complex crystallized as Ca3PQQ2·13H2O with Ca2+ in three different positions and PQQ3−, including an extensive hydrogen‐bond network. Similarities and differences to the recently reported structure with biorelevant europium (Eu2PQQ2) are discussed.
    Description: Pyrroloquinoline quinone (PQQ) is an important cofactor of calcium‐ and lanthanide‐dependent alcohol dehydrogenases. The crystal structure of a Ca–PQQ complex (Ca3PQQ2·13H2O) is reported for the first time outside a protein environment. image
    Description: research
    Keywords: 548 ; pyrroloquinoline quinone ; calcium ; PQQ ; methanol dehydrogenase ; crystal structure ; FID-GEO-DE-7
    Language: English
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    On incoherent diffractive imaging (2021)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-04-07
    Description: Incoherent diffractive imaging (IDI) promises structural analysis with atomic resolution based on intensity interferometry of pulsed X‐ray fluorescence emission. However, its experimental realization is still pending and a comprehensive theory of contrast formation has not been established to date. Explicit expressions are derived for the equal‐pulse two‐point intensity correlations, as the principal measured quantity of IDI, with full control of the prefactors, based on a simple model of stochastic fluorescence emission. The model considers the photon detection statistics, the finite temporal coherence of the individual emissions, as well as the geometry of the scattering volume. The implications are interpreted in view of the most relevant quantities, including the fluorescence lifetime, the excitation pulse, as well as the extent of the scattering volume and pixel size. Importantly, the spatiotemporal overlap between any two emissions in the sample can be identified as a crucial factor limiting the contrast and its dependency on the sample size can be derived. The paper gives rigorous estimates for the optimum sample size, the maximum photon yield and the expected signal‐to‐noise ratio under optimal conditions. Based on these estimates, the feasibility of IDI experiments for plausible experimental parameters is discussed. It is shown in particular that the mean number of photons per detector pixel which can be achieved with X‐ray fluorescence is severely limited and as a consequence imposes restrictive constraints on possible applications.
    Description: Starting from a simple model of stochastic fluorescence emission, a theory is derived of contrast formation and signal‐to‐noise ratio for incoherent diffractive imaging; its feasibility for plausible experimental parameters is discussed. image
    Keywords: ddc:548
    Language: English
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    Recent developments in the Inorganic Crystal Structure Database: theoretical crystal structure data and related features (2019)
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Details
    Publication Date: 2022-03-24
    Description: The Inorganic Crystal Structure Database (ICSD) is the world's largest database of fully evaluated and published crystal structure data, mostly obtained from experimental results. However, the purely experimental approach is no longer the only route to discover new compounds and structures. In the past few decades, numerous computational methods for simulating and predicting structures of inorganic solids have emerged, creating large numbers of theoretical crystal data. In order to take account of these new developments the scope of the ICSD was extended in 2017 to include theoretical structures which are published in peer‐reviewed journals. Each theoretical structure has been carefully evaluated, and the resulting CIF has been extended and standardized. Furthermore, a first classification of theoretical data in the ICSD is presented, including additional categories used for comparison of experimental and theoretical information.
    Description: The article discusses how theoretical crystal data are supplementing experimental data for simulation and prediction of structures of inorganic solids in the Inorganic Crystal Structure Database.
    Keywords: ddc:548
    Language: English
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  • 39
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    The LUCIFER control software (2010)
    Univ. Bochum
    Details
    Publication Date: 2020-10-07
    Description: Die Dissertation behandelt die Konzepte sowie die Implementierung der operativen Aspekte der Kontrollsoftware des LUCIFER Instruments. Diese ist in vier Schichten aufgeteilt. Die Schnittstelle zwischen Software und Hardware bildet die Control-Schicht. In der Instrument-Schicht sind alle Komponenten des Instruments als Software-Dienste abgebildet und erfüllen die jeweils für diese Komponente notwendigen Aufgaben. In der obersten Schicht sind die wesentlichen Manager-Dienste beheimatet. Durch Beobachtungsskripte ist eine automatische Steuerung von Instrument und Teleskop möglich. Weiterhin wurden die stellaren Populationen im Zentrum von vier Galaxien untersucht. Ein Vergleich mit publizierten Werten für ähnliche Galaxien zeigt keinen signifikanten Trend zu jüngeren Populationen in den Galaxien, die einen Pseudo-Bulge zeigen. Eine Galaxie zeigt deutliche Hinweise auf eine sehr alte stellare Population im Buge, deutlich älter als die Populationen von elliptischen Galaxien.
    Description: thesis
    Keywords: 520 ; TCM 000 ; TIE 400 ; Mathematische und EDV-Verfahren {Astronomie} ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 142 S.
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  • 40
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    The formation of massive stars (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 523 ; TEG 000 ; THT 800 ; Kosmogonie {Astronomie} ; Massenreiche Sterne {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 131 S.
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  • 41
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    Nonlinear electron synchrotron cooling and synchrotron self Compton flaring of TeV blazars (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: We investigate the double-peak profile of the emission of powerful cosmic non-thermal radiation sources with dominant magnetic field self-generation like TeV blazars. Therefore, we assume a flare to occur in the emission knot due to the uniform instantaneous injection of monoenergetic ultra-relativistic electrons via a relativistic pick-up process. The electrons are subjected to a linear or nonlinear synchrotron radiation cooling and the synchrotron photons are multiple Thomson scattered off their generating electrons (SSC process). We work out the differences between single and multiple instantaneous injections of monoenergetic relativistic electrons. This is of great interest, because it is very likely that injections into the plasmoids occur repeatedly, so that this would explain the short-time energy variability of blazars. We also compute for the first time the nonlinear SSC radiation quantities using a Thomson limit approximation and the full Klein-Nishina cross section.
    Description: thesis
    Keywords: 523 ; TIE 900 ; Sonstige Sternensysteme {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 84 S.
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  • 42
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    Search for tidal streams in disk and halo (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: This work deals with the search for substructures in four nearby galaxies (NGC 300, NGC 7793, M 33, M 83) in which it is possible to resolve single stars in their outer parts.The search is based on the photometry of wide field imaging data. This photometry is further analysed by the use of classical methods (colour-magnitude-diagrams, star counts) and by the use of data-mining tools (fuzzy c-means clustering). Finally, it could be shown that three out of four galaxies show signs of substructure. In NGC 300 the analysis of the red-giant-branch stars revealed a truncation in the outer parts, while in NGC 7793 hints for a tidal stream or spiral arm were found. In case of M 83 it was possible to recover an already known surface brightness arc first seen on old photographic plates.
    Description: thesis
    Keywords: 523 ; TIE 400 ; TIE 500 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Aufbau und Struktur von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 151 S.
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  • 43
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    Gas kinematics in the haloes of nearby irregular Dwarf galaxies (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Die vorliegende Dissertation untersucht, ob heiße und expandierende Gasstrukturen gravitativ an ihre Galaxie gebunden sind (Ausfluss) oder ob sie das Gravitationspotential der Galaxie verlassen können (galaktischer Wind). Galaktische Winde, d.h. Massenverlust für die Galaxie und Anreicherung des intergalaktischen Mediums haben direkte Auswirkungen auf die Entwicklung von Galaxien und Galaxienhaufen. Spektroskopische Untersuchungen des neutralen und ionisierten Wasserstoffs wurden in einer Auswahl von vier nahen irregulären Zwerggalaxien durchgeführt. In allen vier Galaxien wurden expandierende Gasstrukturen gefunden und ihre Expansionsgeschwindigkeiten vermessen. Aus Dunkle Materie Halo Modellen wurde das Gravitationspotential der Galaxien abgeschätzt. Dadurch konnte gezeigt werden, dass das Gas in allen Fällen gravitativ gebunden bleibt. Dieses Ergebnis ist in Übereinstimmung mit hydrodynamischen Simulationen und legt nahe, dass galaktische Winde in masseärmeren Galaxien zu finden sind.
    Description: thesis
    Keywords: 523 ; TII 500 ; Emissionsnebel {Astronomie: Interstellare Materie}
    Language: English
    Type: monograph , publishedVersion
    Format: 136 S.
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    Cosmic rays and the magnetic field in the nearby starburst galaxy NGC 253 (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Beim Ras-RasGAP-Komplex ist die Hydrolyse des Guanosintriphosphats stark beschleunigt im Vergleich zu Ras allein. Dies wird hauptsächlich durch den Argininfinger R789 verursacht, der direkt zur Triphosphatgruppe zeigt. QM/MM-Simulationen wurden durchgeführt, bei denen das Triphosphat quantenmechanisch mithilfe der DFT behandelt wurde, während der Proteinkomplex und die Wasserumgebung klassisch beschrieben wurden. Im Vergleich zu Ras sind beim Ras-RasGAP-Komplex die entscheidende Elektronenverschiebung, die Bindungsverlängerung und die Verdrillung hin zu einer ekliptischen gamma-beta-Orientierung wesentlich stärker ausgeprägt. Der Argininfinger interagiert durch Verdrängung von Wassermolekülen aus der Bindenische. Das resultierende verstärkte elektrische Feld katalysiert den Bindungsbruch. Eine hypothetische Protonierung des beta-Phosphats führt zum Bindungsbruch. Nach Abschluss der Hydrolyse sind die Schwingungen des Mono- und Diphosphats über Dipol-Dipol-Wechselwirkung gekoppelt.
    Description: thesis
    Keywords: 523 ; TIE 400 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 149 S.
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  • 45
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    Non-circular motions in dark matter halos (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Diese Dissertation untersucht, ob die Dynamik von Galaxien in Einklang mit den Ergebnissen aus CDM (cold dark matter) Simulationen ist. Im Wesentlichen wurden 19 Galaxien hinsichtlich Abweichungen von kreisförmigen Bewegungen analysiert. Diese nicht-kreisförmigen Bewegungen werden von den Simulationen vorhergesagt, um das lang bestehende cusp/core Problem zu erklären. Es konnte jedoch gezeigt werden, dass die Abweichungen von den kreisförmigen Bewegungen zu klein sind, um die Ergebnisse von CDM Simulationen mit den Beobachtungen in Einklang zu bringen. Große nicht-kreisförmige Bewegungen finden sich vor allem in den Zentren von massereichen Galaxien und Balkengalaxien. Dies lässt jedoch vermuten, dass diese Bewegungen durch baryonische Materie hervorgerufen werden und nicht durch den DM Halo. Die vorliegende Dissertation unterstreicht die Notwendigkeit, die CDM Simulationen zu verändern, bzw. alternative Lösungen zu CDM Modellen zu suchen.
    Description: thesis
    Keywords: 523 ; TII 100 ; Dunkle Materie {Astronomie: Interstellare Materie}
    Language: English
    Type: monograph , publishedVersion
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  • 46
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    Confinement and anisotropy of ultrahigh-energy cosmic rays in isotropic plasma wave turbulence (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: We have investigated the implications of isotropically distributed interstellar magnetohydrodynamic plasma waves on the scattering mean free path and the spatial anisotropy of high-energy cosmic rays. We demonstrate a drastic modification of the energy dependence of both cosmic ray transport parameters compared to previous calculations that have assumed that the plasma waves propagate only parallel or antiparallel to the ordered magnetic field (slab turbulence).
    Description: thesis
    Keywords: 539.7223 ; 523 ; 550 ; TFE 000 ; TFG 000 ; Kosmische Elektrodynamik {Astrophysik} ; Magnetohydrodynamik und Plasma-Astrophysik
    Language: English
    Type: monograph , publishedVersion
    Format: 91 S.
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  • 47
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    Numerical investigation of the turbulent ISM (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: In this work we introduced basic turbulence theory into the framework of the interstellar medium. In many cases turbulence simulations are applied to the interstellar medium (ISM) merely because it is a medium, where extremely high Reynolds numbers are actually realised, and the parameters of the ISM are only taken into account as far as they are needed for the turbulence research. Here, however, we investigated the basic turbulence properties, while at the same time we modelled the properties of the ISM as thoroughly as possible. The important point is that there are many physical processes going on in the ISM, which should be incorporated in the corresponding simulations. These processes reachfrom external influences of the radiation field originating from hot stars to the internal interaction of the particles culminating in the intricate chemistry of the molecular cloud medium. Each of the different phases of the ISM has its own dominant processes to be taken into account for a realistic modelling...
    Description: thesis
    Keywords: 523 ; TII 000 ; Interstellare Materie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 141 S.
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  • 48
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    The narrow line region of active galaxies (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: This thesis presents an imaging and spectroscopic study of the narrow-line region (NLR) in active galactic nuclei (AGNs). We find a correlation between size and luminosity of the NLR with different slopes for type-1 and type-2 AGNs which can be explained by the observers viewing angle and a receding torus. The radial properties of the NLR gas, such as reddening, electron density, ionization parameter, and velocity field are analyzed. We derive pure emission-line spectra and use the resulting absorption-line free ratios for spatially resolved spectral diagnostics. We find a transition between the AGN-excited NLR and the surrounding star-forming regions, allowing us to determine the NLR size independent of stellar contamination. The electron density and ionization parameter decrease with radius indicating that the NLR is photoionized by the central source only.The velocity fields suggest a disky NLR gas distribution with the torus axis lying in the galaxy disk.
    Description: thesis
    Keywords: 523 ; TIE 400 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 222 S.
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  • 49
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    The vertical structure of thickened bars in disk galaxies (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: In der vorliegenden Dissertation wird die vertikale Struktur von edge-on Scheibengalaxien mit einer 'box or peanut shaped' (B/PS) Struktur in der Bulgeregion unter Verwendung von nahinfrarot Beobachtungen untersucht. Durch Nutzung von Konturhervorhebungsverfahren und Flaechenhelligkeitsprofilen entlang der Hauptachse der Galaxie kann gezeigt werden, dass Material aus der Scheibe in vertikaler Richtung umverteilt wird, und zur Entstehung der B/PS Struktur fuehrt. Dies ist in Einklang mit dem auf der vertikalen Ausdehnung eines in der Galaxie vorhandenen stellaren Balkens sich stuetzenden sekulaeren Evolutionsmodell. Die Analyse der vertikalen Flaechenhelligkeitsverteilung zeigt eine Variation der Skalenhoehe entlang der radialen Ausdehnung der stellaren Scheibe. Diese Variation wird hier zum ersten Mal deutlich beobachtet, wobei an der Position der B/PS Struktur ein lokales Maximum der Skalenhoehe festzustellen ist, im Einklang mit dem sekulaeren Evolutionsmodell.
    Description: thesis
    Keywords: 523 ; TBG 000 ; TIE 400 ; TIE 500 ; Infrarot-Astronomie ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Aufbau und Struktur von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 178 S.
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  • 50
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    Acceleration and spatial diffusion of galactic cosmic rays (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: In the present work analytical solutions of the transport equation for hadronic cosmic rays are calculated. With these, it is possible for the first time to fit the energy spectra of the cosmic protons measured at the position of the earth. A focus lies on the investigation of the spatial diffusion of the galactic cosmic ray nuclei and their stochastic reacceleration by plasma waves superimposed on the interstellar medium. A realistic spatial distribution of supernova remnants as primary sources of the galactic cosmic rays and, as an additional process, the solar modulation are taken into account. Different fit parameters are obtained. Additionally, analytical approximations of the momentum solution for a power law injection spectrum for small and large momenta are calculated for the case without and for the case with spallation losses.
    Description: thesis
    Keywords: 523 ; TFE 000 ; Kosmische Elektrodynamik {Astrophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 192 S.
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  • 51
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    Mechanical behavior of synthetic omphacite aggregates at high temperature and high pressure (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Triaxial compression experiments were performed on the synthesized samples and Fe-bearing clinopyroxenite in a solid medium apparatus at a confining pressure of 0.75 to 2.5 GPa, temperatures 900 to 1175oC, and strain rates between 1.1x10-6 s-1 to 8.5x 10-5 s-1. Samples of calcic compositions deformed at high differential stresses reveal abundant mechanical (100)[001] twins, whereas jadeite aggregates deformed at low differential stress show well developed subgrain boundaries. Combining the mechanical data and observed microstructures for deformed synthetic samples reveal that the deformation of diopside aggregates is controlled by dislocation glide, while the kinetics of dislocation climb controls the deformation of jadeite aggregates. The variation in strength with composition obeys scaling by the dependence of melting temperature and shear modulus on composition. In contrast to climb-controlled deformation, glide-controlled deformation should be insensitive to impurity concentrations.
    Description: thesis
    Keywords: 549 ; TQL 000 ; VAE 140 ; VGF 300 ; Sonstige Verfahren {Geophysik} ; Gesteinsdeformation {Strukturgeologie} ; Experimentelle Mineralogie
    Language: English
    Type: monograph , publishedVersion
    Format: 99 S.
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  • 52
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    Mineral solubility measurements at high pressures (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Löslichkeitsdaten gesteinsbildender Minerale unter hohen Drücken sind für unser Verständnis von Fluideigenschaften und Massentransport von Mineralen in der Erdkruste und oberen Mantel von großer Wichtigkeit. In dieser Arbeit wurden neue in situ Masseverlust Methoden entwickelt um Löslichkeiten zu bestimmen, die dann in einer hydrothermalen Diamant Stempel Zelle getestet wurden. In der ersten Methode wird die Tendenz von Kristallen ausgenutzt während eines Experiments eine idiomorphe Form anzunehmen. Die zweite Methode basiert auf Messung und Analyse der Doppelbrechung eines Kristalls um dessen Dicke zu bestimmen. Masseverluste von wenigen æg können so bestimmt werden. Beide Methoden sind bis in den ppm Bereich anwendbar. Die Ergebnisse dieser Arbeit tragen sowohl zu unserem technischen Verständnis von Hockdruck/Hochtemperatur Equipment bei als auch zu unserem allgemeinen Verständnis der chemischen Eigenschaften von Fluiden in Hochdruck Umgebungen wie z.B. in Subduktionszonen.
    Description: thesis
    Keywords: 549 ; TQL 000 ; VGF 300 ; VAE 140 ; Sonstige Verfahren {Geophysik} ; Experimentelle Mineralogie ; Gesteinsdeformation {Strukturgeologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 232 S.
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  • 53
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    Development of pull apart basins and associated structures by the Riedel shear mechanism (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Die physikalischen und mechanischen Eigenschaften von tonartigen Materialien, die für die Skalierung von Analogexperimenten relevant sind, werden mit Hilfe von Konzepten der modernen Bodenmechanik analysiert. Ein Verfahren zur Bestimmung dieser Eigenschaften wird vorgestellt. Skalierte Tonexperimente mit Riedelschem Mechanismus wurden durchgeführt. Sie erzeugen typische Pull-apart Strukturen entlang Riedel Frakturen sowie Push-up Strukturen in dazwischen liegenden Flachen. Die Scherfestigkeit und die Dicke des Tonkuchens beeinflussen sowohl die Geometrie der Scherzonen als die benötigte Hauptverschiebungsgröße für die Entstehung der Riedel Scherfrakturen an der Oberflache des Tonkuchens. Pull-apart Becken, die durch Riedelschen Mechanismus erzeugt wurden, lassen sich auf der Insel Gozo (Strait of Sicily rift zone) beobachten. Die gleichzeitige Entwicklung der Push-up Horste ist im komplexen Blattverschiebungsbecken des Meers von Marmara zu finden.
    Description: thesis
    Keywords: 551.8 ; VAE 130 ; VAE 400 ; Geomechanik ; Tektogenese {Geologie}
    Language: English
    Type: monograph , publishedVersion
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  • 54
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    Inversion of gravity data with application to density modeling of the Hellenic subduction zone (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Diese Arbeit beschäftigt sich mit der Verknüpfung von manuellen und automatischen Inversionmethoden für die Interpretation gravimetrischer Anomalien. Eine neue Software mit dem Namen 3GRAINS wird vorgestellt. Sie wurde für das manuelle Modellieren entwickelt und benutzt rechteckförmige Prismen zur Berechnung des gravimetrischen Effekts eines Modells. Die Software bietet eine graphische Benutzeroberfläche, um eine komfortable Arbeit mit einer modellierten Struktur zu ermöglichen. Ein automatischer Inversionsalgorithmus basiert auf der Idee der evolutionären Berechnung. Die dargestellten Methoden werden auf die Interpretation der gravimetrischen Anomalien der Hellenischen Subduktionszone angewendet. Die tektonische Situation dieser Region und seismische Beobachtungen werden vorgestellt. Der Prozess der Datengewinnung und der Datenbearbeitung wird beschrieben. Schließlich werden die Ergebnisse der Interpretation der gravimetrischen Anomalien präsentiert.
    Description: thesis
    Keywords: 551 ; 622.15 ; 550 ; TOF 000 ; TQA 000 ; TSF 300 ; VAE 880 ; VEF 300 ; Schwerkraft {Geophysik} ; Gravimetrische Verfahren {Geophysik} ; Griechenland und griechische Inseln {Geophysik} ; Passive und aktive Kontinentalränder {Geologie} ; Griechenland und griechische Inseln {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 139 S.
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  • 55
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    Indentation methods in experimental rock deformation (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: In dieser Studie wird das Potential von Indentationsexperimenten bei erhöhten Temperaturen in der Gesteinsmechanik erkundet. Mikrohärtemessungen mit einem pyramidenförmigen Indenter werden an Olivin- und Klinopyroxen-Körnern innerhalb eines Gesteinsaggregates durchgeführt. Die Abhängigkeit der Härte der Olivin-Kristalle von der Kristallorientierung wird untersucht und die Orientierung von Gleitstufen auf der Probenoberfläche verwendet, um die während der Indentationsexperimente aktivierten Gleitsysteme zu ermitteln. Mikrohärtemessungen an Jadeit und Diopsid dienen dazu, die relative Festigkeit dieser Mitglieder einer Mischkristallreihe zu analysieren. Indentationskriechexperimente mit einem zylindrischen Indenter werden verwendet, um das rheologische Verhalten einer Legierung zu untersuchen, die als Modelmaterial für ein silikatisches Gesteinsaggregat dient. Die Ergebnisse dieser Tests an der TiAl-Legierung werden mit denen einachsiger Kriechversuche am gleichen Material verglichen.
    Description: thesis
    Keywords: 551.1 ; 550 ; VAE 140 ; VAE 120 ; VBB 000 ; VAE 140 ; VAE 120 ; VBB 000 ; Gesteinsdeformation {Strukturgeologie} ; Methodik {Strukturgeologie} ; Experimentelle Geologie
    Language: English
    Type: monograph , publishedVersion
    Format: 78 S.
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  • 56
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    Multi-component evolution, age and plate tectonic setting of high MG lamprophyric dikes and small gabbroic intrusions on Isla Margarita (Venezuela) (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Die Isla Margarita (Venezuela) am Südrand der Karibischen Platte besteht aus einem heterogenen Krustenkomplex aus Peridotiten, Metamorphiten, diversen Magmatiten und sedimentärem Deckgebirge. Die jüngsten Magmatite sind Lamprophyrgänge und Gabbros basaltisch-andesitischer Zusammensetzung, deren hoher Anteil an kompatiblen Elementen und intermediärer Zusammensetzung auf starke Fraktionierung bei relativ hohen partiellen Aufschmelzgraden deutet. Variable Anreicherung an leichten Seltenen Erden und LILE sowie erhöhte Strontium- und Blei-Isotopenverhältnisse lassen auf eine zusätzliche Subduktionskomponente schließen. Die Entstehung der Magmen und die zeitliche Einordnung der Platznahme sind wichtige Anhaltspunkte für die Aufschlüsselung der tektonischen Entwicklung des Südrandes der Karibischen Platte und erlauben eine Korrelation mit plattentektonischen Modellen.
    Description: thesis
    Keywords: 552.1 ; 551.701 ; 550 ; VBN 500 ; VKB 130 ; VEW 200 ; Geochronologie einzelner Regionen im allgemeinen ; Petrologie der Ganggesteine ; Karibischer Raum {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 233 S.
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  • 57
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    Different styles of deformation of the fore-arc wedge along the Chilean convergent margin (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VAE 890 ; VAE 130 ; VBE 000 ; TOE 000 ; TSX 500 ; VEX 500 ; Ozeanische Kruste {Tektonik} ; Geomechanik ; Modellierung von Prozessen in der Geosphäre ; Physikalisches Verhalten der Erde {Geophysik} ; Chile {Geophysik} ; Chile {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 118 S.
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  • 58
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    Neogene seismotectonics of the south-central Chile margin (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; TSX 500 ; VEX 100 ; VEX 500 ; VAE 500 ; TOH 800 ; Chile {Geophysik} ; Anden {Geologie} ; Chile {Geologie} ; Geotektonische Entwicklung der Erdkruste {Geologie} ; Paläoerdbeben {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 108 S.
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  • 59
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    Seismic structure of the Arava Fault, Dead Sea Transform (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: Ein transversales Störungssystem im Nahen Osten, die Dead Sea Transform (DST), trennt die Arabische Platte von der Sinai-Mikroplatte und erstreckt sich von Süden nach Norden vom Extensionsgebiet im Roten Meer über das Tote Meer bis zur Taurus-Zagros Kollisionszone. Die sinistrale DST bildete sich im Miozän vor etwa 17 Ma und steht mit dem Aufbrechen des Afro-Arabischen Kontinents in Verbindung. Das Untersuchungsgebiet liegt im Arava Tal zwischen Totem und Rotem Meer, mittig über der Arava Störung (Arava Fault, AF), die hier den Hauptast der DST bildet. Eine Reihe seismischer Experimente, aufgebaut aus künstlichen Quellen, linearen Profilen über die Störung und entsprechend entworfenen Empfänger-Arrays, zeigt die Untergrundstruktur in der Umgebung der AF und der Verwerfungszone selbst bis in eine Tiefe von 3-4 km. Ein tomographisch bestimmtes Modell der seismischen Geschwindigkeiten von P-Wellen zeigt einen starken Kontrast nahe der AF mit niedrigeren Geschwindigkeiten auf der westlichen Seite als im Osten. Scherwellen lokaler Erdbeben liefern ein mittleres P-zu-S Geschwindigkeitsverhältnis und es gibt Anzeichen für Änderungen über die Störung hinweg ...
    Description: thesis
    Keywords: 551 ; VAE 850 ; TQC 220 ; TSI 000 ; VEI 400 ; Festländische Lineamente {Geologie} ; Reflexionsseismik {Geophysik} ; Vorderasien {Geophysik} ; Israel, Palästina {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 142 S.
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  • 60
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    Regional geoid determination (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TQH 000 ; TQA 000 ; TOF 000 ; Aerogeophysik ; Gravimetrische Verfahren {Geophysik} ; Schwerkraft {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 48 S.
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  • 61
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    Advanced algorithms of inversion of GPS radio limb sounding data (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 106 S.
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  • 62
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    About the influence of a possible relative rotation of the earth's inner core on the polar motion, the geomagnetic field and the gravity field (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 300 ; TOD 500 ; TOF 000 ; TOT 400 ; Polbewegungen {Geophysik: Erde} ; Erdkern {Geophysik} ; Schwerkraft {Geophysik} ; Magnetfeld der Erde im allgemeinen {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 15 S.
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  • 63
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    Lecture and exercise notes (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: lecture
    Keywords: 551
    Language: English
    Type: anthology , publishedVersion
    Format: 675 S.
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  • 64
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    Seasonal oscillations in length-of-day (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 100 ; Drehbewegungen {Geophysik: Erde}
    Language: English
    Type: article , publishedVersion
    Format: 8 S.
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  • 65
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    Polar motion at seasonal frequencies (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 300 ; Polbewegungen {Geophysik: Erde}
    Language: English
    Type: article , publishedVersion
    Format: 9 S.
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  • 66
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    Radioholographic analysis of radioocculation data (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 39 S.
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  • 67
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    On the contribution of the Geodetic Institute Potsdam to the International Latitude Service (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 28 S.
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  • 68
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    Glacial isostatic adjustment and sea level change near Berkner Island, Antarctica (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wiss.-Parks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: The glacial-isostatic adjustment in Iceland resulting from the recent melting of the Vatnajökull ice cap is controlled by the viscosity distribution in the earth's interior and by the details of the melting history. Interpretations of the results of GPS and gravity measuring campaigns in the time interval 1991-2000 and 1992-1999, respectively, by means of laterally homogeneous earth models for the determination of the lithosphere thickness, the asthenosphere thickness and the asthenosphere viscosity have so far been not fully satisfactory. In particular near the ice margin, the fitting of the computed land uplift and gravity change to the observational data was inadequate, which may be related to the neglegt of the Iceland plume in the laterally homogeneous earth models. In the present study, a program package is used for the modelling of the land uplift and gravity change that allows the computation of load-induced perturbations of a Maxwell-viscoelastic, incompressible, self-gravitating, spherical earth model. To simulate the presence of the plume below the Vatnajökull, an axisymmetric viscosity distribution is used, where the plume radius and the plume viscosity are free parameters. Based on seismic results, a 6-km-thick lithosphere is assumed above the plume, which thickens to 35 km in the peripheral region of the plume. The melting history of the Vatnajökull is founded on interpretations of geomorphological and climatological investigations and is simulated by a load co-axial with the plume with parabolic profile and time-dependent radius. The results of the modelling favour a plume radius of ~80 km and a plume viscosity of (0.3-1.0) x 10^{18} Pa s.
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 20 S.
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  • 69
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    GPS data processing at GFZ for monitoring the vertical motion of global tide gauge benchmarks (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wiss.-Parks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; VAE 300 ; TQI 000 ; UNH 100 ; Epirogenese {{Geologie}} ; Geophysikalische Satellitenfernerkundung ; GPS {Praktische Geodäsie}
    Language: English
    Type: article , publishedVersion
    Format: 28 S.
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  • 70
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    Theory of elastic waves (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wiss.-Parks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 228 S.
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  • 71
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    On the relation of stress and deformation fields to natural and induced seismicity (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; TOH 530 ; VAE 200 ; VAE 130 ; Häufigkeit und Verbreitung von Erdbeben {Geophysik} ; Geodynamik der Lithosphäre {Geologie} ; Geomechanik
    Language: English
    Type: monograph , publishedVersion
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  • 72
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    Three-dimensional finite element modeling of slip rate variations on faults caused by glacial interglacial changes in ice and water volumes (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Paläoseismologische Daten lassen vermuten, dass viele aktive Störungen in unterschiedlichen tektonischen Settings eine Veränderung in der Bewegungsrate auf der Störung kurz nach dem Ende des letzten glazialen Maximums erfahren haben. Als Beispiel seien die postglazial entstandenen oder reaktivierten Pärve Überschiebung oder die Stuoragurra Überschiebung in Nord Skandinavien (Lappland Fault Province), aber auch die über Millionen Jahre aktive Wasatch Abschiebung in der Basin and Range Province oder die Tote Mehr Transform Störung genannt. In dieser Arbeit werden dreidimensionale Finite Elemente Modelle benutzt um den Einfluss von Lastwechseln auf der Erdoberfläche auf das Verhalten einzelner Störungen zu untersuchen. Die Resultate dieser Arbeit zeigen, dass klimabedingte Volumenänderungen von Gletschern und Seen auf der Erdoberfläche das Spannungsfeld der Kruste beeinflussen. Generell gilt: Lastzunahme führt zu verringerten, Entlastung zu erhöhten Bewegungsraten auf der Störung.
    Description: thesis
    Keywords: 551 ; 550 ; VAE 130 ; VAE 140 ; TOH 800 ; Paläoerdbeben {Geophysik} ; Geomechanik ; Gesteinsdeformation {Strukturgeologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 94 S.
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  • 73
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    Microstructural criteria for synseismic loading and postseismic creep in the uppermost plastosphere (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Anhand des Modellfalls der Sesia Zone in den West-Alpen werden mikrostrukturelle Kriterien für syn- und postseismische Deformation in der oberen Plastosphäre in Folge eines großen Erdbebens in der überlagernden Schizosphäre ausgearbeitet. Die Orientierungsverteilung von mechanisch verzwillingten Jadeiten liefert Hinweise auf Spitzten-Spannungen 〉0,5 GPa. Die Vielfalt unterschiedlicher Quarz-Mikrostrukturen spiegelt progressive Deformation bei relaxierenden Spannungen in einem Temperaturbereich von 300-350 ʿC wider. Ein dazu konsistentes Bild liefert die kataklastische Deformation von Granat. Verheilte Mikrorisse in Quarz, verfüllte Risse in Granat sowie mesoskopische, diskordante Quarz-Gänge mit rekristallisierter Füllung geben Hinweise auf einen fluktuierenden Porenfluiddruck. Dieses Beispiel aus der Sesia Zone veranschaulicht die Bedeutung nicht-stationärer Deformation in der oberen Plastosphäre, entgegen konventionellen Vorstellungen von dominierend stationärem Fließen.
    Description: thesis
    Keywords: 551.8 ; 551.1 ; 552.4 ; 551 ; 550 ; VAE 400 ; VAE 811 ; VAE 140 ; VEB 169 ; VAE 400 ; VAE 811 ; VAE 140 ; VEB 169 ; Tektogenese {Geologie} ; Alpidische Orogene {Geologie} ; Gesteinsdeformation {Strukturgeologie} ; Französisch-italienische Westalpen {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 97 S.
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  • 74
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    Experimental deformation of jadeite (2010)
    Univ. Bochum
    Details
    Publication Date: 2021-03-29
    Description: Zur Untersuchung der Rheologie der Mischkristallreihe Jadeit-Diopsid wurden experimentelle Untersuchungen am Endglied Jadeit durchgeführt. Polykristalline Jadeit Proben wurden aus einem Glas in einer Stempel-Zylinder-Apparatur synthetisiert. Diese Proben wurden in einer modifizierten Griggs-Apparatur bei einem Umschließungsdruck von 2.5 GPa bei verschiedenen Temperaturen und Verformungsraten in axialer Richtung deformiert. Parameter für ein Fließgesetz für Versetzungskriechen wurden abgeleitet. Deformation im Regime des Versetzungskriechens konnte aus einer Analyse der Mikrogefüge abgeleitet werden. Die erzeugten Mikrostrukturen wurden mit denen von natürlichen, deformierten Omphaziten verglichen. Anwendung des Fließgesetzes erlaubt eine Abschätzung von Spannungsmagnituden in der Eklogitschicht in Subduktionszonen. Aus Experimenten an natürlichen Proben wurde die kritische Scherspannung für mechanische Zwillingsbildung in Jadeit abgeleitet.
    Description: thesis
    Keywords: 549 ; VAE 140 ; VGF 300 ; VAE 130 ; Gesteinsdeformation {Strukturgeologie} ; Experimentelle Mineralogie ; Geomechanik
    Language: English
    Type: monograph , publishedVersion
    Format: 162 S.
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  • 75
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    Seasonal variations in length of day and atmospheric-angular-momentum (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 30 S.
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  • 76
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    Retrieval of earthquake source parameters in inhomogeneous anisotropic media with application to swarm events in West Bohemia in 2000 (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 190 S.
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  • 77
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    Teleseismic tomographic images of the Central Andes at 21°S and 25.5°S (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VEX 100 ; VAE 811 ; TSX 100 ; TQC 200 ; Anden {Geologie} ; Alpidische Orogene {Geologie} ; Anden {Geophysik} ; Prospektionsseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 139 S.
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  • 78
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    Fracture toughness determination and micromechanics of rock under Mode I and Mode II loading (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VAE 120 ; VAE 140 ; VBP 500 ; VBP 200 ; Methodik {Strukturgeologie} ; Gesteinsdeformation {Strukturgeologie} ; Bodenmechanik, Erdbaumechanik, Baugrunddynamik ; Ingenieurgeologische Bewertung von Gesteinen als Baugrund und Baustoff
    Language: English
    Type: monograph , publishedVersion
    Format: 95,S.
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  • 79
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    Atmospheric, oceanic and hydrological contributions to seasonal variations in length of day (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TVI 000 ; Jahreszeiten als meteorologische Erscheinung
    Language: English
    Type: article , publishedVersion
    Format: 16 S.
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  • 80
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    Interannual variations in length-of-day and atmospheric-angular-momentum with respect to ENSO cycles (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TVI 000 ; TM 600 ; Jahreszeiten als meteorologische Erscheinung ; Grenzgebiete. Beziehungen. Einflüsse. Wirkungen {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 17 S.
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  • 81
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    Seasonal length of day changes and atmospheric angular momentum oscillations in their temporal variability (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 100 ; Drehbewegungen {Geophysik: Erde}
    Language: English
    Type: article , publishedVersion
    Format: 43 S.
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  • 82
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    Anatomy of an ancient subduction channel in the depth range of its seismogenic coupling zone - insights from field studies in the Swiss Alps and Southern Chile (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VBN 500 ; VAE 811 ; VEB 168 ; VEX 100 ; VEX 500 ; TSX 500 ; TSB 168 ; VKB 270 ; VAE 880 ; Geochronologie einzelner Regionen im allgemeinen ; Alpidische Orogene {Geologie} ; Schweizer Alpen {Geologie} ; Anden {Geologie} ; Chile {Geologie} ; Chile {Geophysik} ; Schweizer Alpen {Geophysik} ; Produkte mechanischer Deformation {Petrologie} ; Passive und aktive Kontinentalränder {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 179 S.
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  • 83
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    Lithospheric and upper mantle structure beneath the western Bohemian Massif obtained from teleseismic P and S receiver functions (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; TOD 200 ; TOD 410 ; TSB 000 ; VAE 812 ; VEB 130 ; TOH 100 ; Erdkruste {Geophysik} ; Oberer Erdmantel {Geophysik} ; Mitteleuropa {Geophysik} ; Variszisch-herzynische Orogene {Geologie} ; Böhmische Masse {Geologie} ; Seismometrie {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 149 S.
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  • 84
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    A high resolution global gravity field model combining CHAMP and GRACE satellite mission and surface data: EIGEN-CG01C (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
    Format: 12 S.
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  • 85
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    Deformation, erosion and natural resources in continental collision zones (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551 ; VAE 500 ; VBB 000 ; VAJ 400 ; Geotektonische Entwicklung der Erdkruste {Geologie} ; Experimentelle Geologie ; Abtragung durch Erosion {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 141 S.
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  • 86
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    Probabilistic seismic hazard assessment for Vanuatu (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein], Potsdam
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOH 530 ; TST 000 ; VET 600 ; Häufigkeit und Verbreitung von Erdbeben {Geophysik} ; Ozeanien {Geophysik} ; Sonstige Inselgruppen {Geologie}
    Language: English
    Type: article , publishedVersion
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  • 87
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    Thermomechanical polythermal ice-sheet model (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], [Potsdam]
    Details
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 511.8 ; 551 ; TOO 000 ; VAQ 400 ; Geothermik {Geophysik} ; Morphologie, Ausmaß und Dicke, Masse und Energiegleichgewicht {Glaziologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 106 S.
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  • 88
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    Mean annual and seasonal atmospheric tide models based on 3-hourly and 6-hourly ECMWF surface pressure data (2010)
    GFZ, Helmholtz-Zentrum | [Bibliothek des Wissenschaftsparks Albert Einstein] [Vertrieb], Potsdam
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 511.8 ; 551
    Language: English
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  • 89
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    Core surface flow models from decadal and subdecadal secular variation of the main geomagnetic field (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: The main objective of this thesis is an investigation and description of the secular variation of the Earth's magnetic field between 1980 and 2000. In particular, in the first part of this study the phenomenon of geomagnetic jerks are investigated by means of a deterministic model, which basically gives a description of the secular variation as a parameterization of typical periodicities of the external field. I argue that the conclusion drawn from this approach is not valid for explaining jerks as caused by external events and not valid to describe the global secular variation. In the second part a time--dependent model of the secular variation between 1980 and 2000 is developed. The endpoints of the time interval were chosen, because of the availability of high quality field models from satellite data for these epochs. The Gauss coefficients are expanded in time as function of cubic B--splines. This model is forced to fit field models from high quality vector measurements from MAGSAT in 1980 and OERSTED in 2000. The methodology is new. The model is a valuable extension of the hitherto existing time--dependent description of the secular variation, the GUFM which was valid until 1990. Unlike GUFM the model is based on observatory monthly means, and the knot spacing of the cubic B--Splines tighter than GUFM. Therefore it reveals a short term secular variation on subdecadal time scale, which was not as yet resolved. The model is also valuable to test the frozen flux hypothesis and to link some of the morphology of the radial field at the core--mantle boundary to the geodynamo. The third part of this thesis deals with the inversion of the time--dependent field and secular variation model for different kinds of core surface flow ...
    Description: thesis
    Keywords: 551 ; TOT 500 ; TOD 500 ; Ursprung und säkulare Änderungen des Erdmagnetfeldes {Geophysik} ; Erdkern {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 90
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    MFGsoft (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TM 300 ; Methodik. Arbeitsmittel. Abkürzungsverzeichnisse {Geophysik}
    Language: English
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  • 91
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    Correlations between the geomagnetic field variations, the fluctuations of the earth's rotation and climate change (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 000 ; TOT 500 ; Periodische Bewegungen der Erde {Geophysik} ; Ursprung und säkulare Änderungen des Erdmagnetfeldes {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 41 S.
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  • 92
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    Engineering geological rock mass characterisation of granitic gneisses based on seismic in-situ measurements (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: For deep underground excavations, the prediction of locations of small-scale geotechnical hazardous structures such as faults is nearly impossible when exploration is restricted to surface based methods. Therefore, for many base tunnels, exploration ahead of the advancing tunnel face is an essential component of the excavation plan. This PhD thesis aims at improving the technology for geological interpretations of seismic data, collected in underground excavations. For that purpose GeoForschungsZentrum Potsdam carried out a series of seismic measurements along the 2600 m long and up to 1400 m deep Faido access tunnel, an adit to the 57 km long Gotthard base tunnel in Switzerland.
    Description: thesis
    Keywords: 551 ; TQC 500 ; VBP 400 ; VBP 100 ; Untertageseismik {Geophysik} ; Felsmechanik, Gebirgsmechanik, Gebirgsdruck ; Methodik, Untersuchungsverfahren und Instrumente {Ingenieurgeologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 127 S.
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  • 93
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    Glacial isostatic contributions to present day sea level change around Greenland (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: Present-day sea-level change around Greenland is examined by assessing the roleplayed by glacial-isostatic adjustment (GIA). We consider the contributions from: (1) the ongoing GIA due to changes in the extent and thickness of the Greenland Ice Sheet (GIS) following the Last Glacial Maximum (LGM), (2) the equivalent signal associated with the continental ice masses located outside of Greenland, and (3) present-day changes in the GIS. Changes in the GIS arising from the last glacial-interglacial transition generally result in falling sea level today. The contribution from ice-load changes outside of Greenland causes rising sea level, owing to Greenland's location on the collapsing forebulge that surrounds the former North American ice sheets. Combining predictions of these contributions gives results showing rising sea level in the southwest and falling sea level in the north and east. However, this is strongly dependent upon the neoglacial part of the GIS's history. The present-day behaviour of the GIS is predicted to cause falling sea level with rates of several mm yr?1 around areas experiencing the larger ice-load changes. The available tide-gauge data are considered unusable by the standards of many workers. Nevertheless, we compare rates of local sea-level change inferred from this type of data with our predictions. In Southern Greenland, where the tide-gauge stations are located, sea level is predicted to be rising at a rate of 4 to 5 mm yr?1. Our predictions match most of the rates obtained from the tide-gauge time series, with the exception of Qaqortoq where the inferred rates may also reect additional oceanic and meteorological effects. Similarly, our predictions are consistent with GPS observations, with again the exception of Qaqortoq.
    Description: report
    Keywords: 551 ; TOG 000 ; VSY 000 ; Isostasie {Geophysik} ; Polargebiete {Fossile Energieträger}
    Language: English
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  • 94
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    A reanalysis and reinterpretation of geodetic and geological evidence of glacial isostatic adjustment in the Churchill region, Hudson Bay. (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: We review the historical, geological, tide-gauge, GPS and gravimetric evidence advanced in favour of or against continuing land uplift around Hudson Bay, Canada. After this, we reanalyse the tide-gauge and GPS data for Churchill using longer time series than those available to previous investigators. The dependence of the mean rate of relative sea-level change obtained on the length and mid-epoch of the observation interval considered is investigated by means of the newly developed linear-trend analysis diagram. For studying the shorter-period variability of the tide-gauge record, the continuous-wavelet transform is used. The mean rate of land uplift obtained from GPS is based on a new analysis using IGS solutions of GFZ. Furthermore, sea-level indicators from the Churchill region representing the relative sea-level history during the past 8000 a are included. Finally, the four types of observable are jointly inverted in terms of mantle viscosity. The optimum values are 3×10^20 Pa s and 1.6 × 10^22 Pa s for the upper- and lower-mantle viscosities, respectively.
    Description: report
    Keywords: 551
    Language: English
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  • 95
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    Geostrophic ocean surface velocities from TOPEX Altimetry, and CHAMP and GRACE satellite gravity models (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: Recently released global gravity field models generated solely from CHAMP and GRACE satellite observations allow with an unprecedented accuracy and resolution the recovery of the mean sea surface topography from the difference between an altimetry-based mean sea surface height model and the gravity model's derived geoid. Here the CHAMP EIGEN-2 gravity field model, and the first GFZ GRACE gravity model, EIGEN-GRACE01S, are used. The mean sea surface height model has been compiled from four years'; worth of TOPEX altimeter data. To evaluate the accuracy and resolution limits of the CHAMP and GRACE geoids for the envisaged application, a low pass filter in the spatial domain with different cut-off wavelengths has been applied to the geoid and sea surface data before subtraction. The minimum wavelength, where noisy and erroneous features in the recovered sea surface topography are minimised, can be interpreted as an indicator for the best suited common spatial resolution. The EIGEN-2 model's geoid has been tested to have a resolution of 1800 km, which corresponds to a truncation degree of l = 22 in terms of spherical harmonics. Using the EIGEN-GRACE01S model, the resolution could be extended to 1000 km (l = 40). These boundaries can be attributed to the geoid's error, exceeding 2 cm in case of the CHAMP model, and in case of the GRACE model to spurious systematic signals increasing with increasing spherical harmonic degree. The calculated sea surface topography models have been used to derive absolute geostrophic sea surface velocities. An error propagation shows that the requirement of 1 cm/s for geoid induced velocity errors is fulfilled at the given resolutions for all latitudes excluding a narrow equatorial band. Maximum geostrophic velocities are derived in the 1000 km-resolution model for the Kuroshio region with 40 cm/s, and for the Gulf Stream east off Cape Hatteras with 25 cm/s.
    Description: report
    Keywords: 551 ; TQI 000 ; Geophysikalische Satellitenfernerkundung
    Language: English
    Type: article , publishedVersion
    Format: 22 S.
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  • 96
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    The effect of the geocentric gravitational constant on scale (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOF 000 ; Schwerkraft {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 17 S.
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  • 97
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    Zur Theorie der Multipole und ihre Anwendung bei der Schwerefeldberechnung (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551
    Language: English
    Type: article , publishedVersion
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  • 98
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    CHICAGO (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: This report describes the set-up, logistics and results of the CHICAGO (Chilean Coastal AeroGeophysical Observations) survey. It gives a short overview about the scientific intentions, detailed documentation of all technical aspects starting from the survey equipment via the aircraft installation to the GPS stations set-up and the experiences in flight. All processing results for the individual profiles are discussed in detail. Finally, the data is compared and combined with available recent marine gravity data and altimetry derived solutions.
    Description: report
    Keywords: 551 ; TQH 000 ; TSX 500 ; Aerogeophysik ; Chile {Geophysik}
    Language: English
    Type: article , publishedVersion
    Format: 100 S.
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  • 99
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    Parameter variability of the observed polar motions with smaller amplitudes (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 300 ; Polbewegungen {Geophysik: Erde}
    Language: English
    Type: article , publishedVersion
    Format: 33 S.
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  • 100
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    Polar motions with a half-Chandler period and less in their temporal variability (2010)
    GFZ, Helmholtz-Zentrum
    Details
    Publication Date: 2021-03-29
    Description: report
    Keywords: 551 ; TOB 300 ; VBF 000 ; Polbewegungen {Geophysik: Erde} ; Elektronische Datenverarbeitung in der Geologie
    Language: English
    Type: article , publishedVersion
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