Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41338 Publications

Activation determination for decommissioning of nuclear power plants

Barkleit, A.; Rachamin, R.; Yassin, G.; Pönitz, E.; Konheiser, J.

Due to the “German Energiewende”, all nuclear power plants (NPPs) in Germany will have been shut down by the end of 2022. Consequently, a safe, economical, and efficient dismantling of the NPPs will be an important challenge for the next decades. This is not only valid for the very particular German case but will certainly foster progress with methods for optimal planning and implementation of decommissioning.
The decommissioning strategy for an NPP requires knowledge of the neutron activation and contamination levels, which have emerged during its operation. Such knowledge can significantly minimize the radioactive waste and contribute to the safety of the operating personnel and the public.
This study considered two strategies. In the first one, the radionuclide inventory in the material of an NPP already under dismantling was investigated. Among others, Co-60 and C-14 in steel samples from the reactor pressure vessel (RPV) and Eu-152, Ba-133 and C-14 in concrete drill cores from biological shielding were quantitatively determined. C-14 was measured by liquid scintillation counting (LSC) after oxidative combustion and the other RN by gamma spectrometry. In the second strategy, the neutron flux in NPPs still under operation was determined with activation monitors. Small metal foils, covering a broad neutron energy range (i.e. thermal, epithermal, and fast energy range), e.g., Ti, Fe, Ni, Cu, In, Sn, Zn, Ta, were placed near the RPV and at the interior and exterior biological shield during the regular annual revision and irradiated for one fuel cycle (approximately one year). After the activation monitors were removed and recovered, the activation of the metal foils was quantitatively determined by gamma spectrometry. The experimental data from both strategies were compared with results from Monte-Carlo simulations.
This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant numbers 15S9412 (WERREBA) and 15S9409A (EMPRADO) and is carried out in cooperation with PreussenElektra GmbH and EWN Greifswald GmbH.

  • Lecture (Conference)
    5th International Conference on Radioecology & Environmental Radioactivity (ICRER), 04.-09.09.2022, Oslo, Norway

Publ.-Id: 34399

Electrochemical zinc corrosion studies in boric acid containing electrolytes (datafiles)

Harm, U.; Kryk, H.; Hampel, U.

Datafiles for planned publication with the title: 

"Electrochemical zinc corrosion studies in boric acid containing electrolytes"  

Further descriptions of the methods and parameters for the conducted electrochemical experiments as well as the allocation of the measurement files (xxx.asc; see above) to the figures of the planned paper see uploaded description file:


Keywords: Boric acid; corrosion; cyclic polarization; electrochemistry; zinc

Related publications


Publ.-Id: 34398

Synthesis and characterization of the two enantiomers of a chiral sigma-1 receptor radioligand: (S)-(+)- and (R)-(-)-[18F]FBFP

Wang, T.; Zhang, Y.; Zhang, X.; Chen, L.; Zheng, M.-Q.; Zhang, J.; Brust, P.; Deuther-Conrad, W.; Huang, Y.; Jia, H.

Racemic [18F]FBFP ([18F]1) proved to be a potent σ1 receptor radiotracer with superior imaging properties. The pure enantiomers of unlabeled compounds (S)- and (R)-1 and the corresponding iodonium ylide precursors were synthesized and characterized. The two enantiomers (S)-1 and (R)-1 exhibited comparable high affinity for σ1 receptors and selectivity over σ2 receptors. The Ca2+ fluorescence assay indicated that (R)-1 behaved as an antagonist and (S)-1 as an agonist for σ1 receptors. The 18F-labeled enantiomers (S)- and (R)-[18F]1 were obtained in > 99% enantiomeric purity from the corresponding enantiopure iodonium ylide precursors with radiochemical yield of 24.4% ± 2.6% and molar activity of 86 – 214 GBq/μmol. In ICR mice both (S)- and (R)-[18F]1 displayed comparable high brain uptake, brain-to-blood ratio, in vivo stability and binding specificity in the brain and peripheral organs. In micro-positron emission tomography (PET) imaging studies in rats, (S)-[18F]1 exhibited faster clearance from the brain than (R)-[18F]1, indicating different brain kinetics of the two enantiomers. Both (S)- and (R)-[18F]1 warrant further evaluation in primates to translate a single enantiomer with more suitable kinetics for imaging the σ1 receptors in humans.

Keywords: σ1 receptor; Enantiomer; Radiotracer; Positron emission tomography; Fluorine-18


Publ.-Id: 34397

Dispenser printed bismuth-based magnetic field sensors with non-saturating large magnetoresistance for touchless interactive surfaces

Oliveros Mata, E. S.; Voigt, C.; Canon Bermudez, G. S.; Zabila, Y.; Valdez-Garduño, N. M.; Fritsch, M.; Mosch, S.; Kusnezoff, M.; Faßbender, J.; Vinnichenko, M.; Makarov, D.

Printed magnetic field sensorics enable a new generation of human-machine interfaces and contactless switches for resource efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry-grade technologies are the key material science challenges. Here, we report dispenser printing of a commodity scale nonmagnetic bismuth-based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper and polymer foils. We validate experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 µT. If printed on flexible foils, our sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in-mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allowed us to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers and printed security panels.

Keywords: printed electronics; printed magnetic field sensors; high-power diode laser array processing; magnetosensitive bismuth paste; dispenser printing

Publ.-Id: 34396

Ultrafast phenomena and terahertz waves: introduction

Zhu, L.-G.; Sheng, Z.; Schneider, H.; Chen, H.-T.; Tani, M.

In this introduction, we provide an overview of the papers that were accepted for publication in the feature issue on ultrafast phenomena and terahertz (THz) waves. This feature issue presents cutting-edge research on ultrafast phenomena and highlights recent developments inTHz technology.

Keywords: terahertz technology; ultrafast phenomena

Publ.-Id: 34395

Optimization of a chemical separation strategy for trivalent actinides from rare-earth rich deep-sea archives

Fichter, S.; Koll, D.; Wallner, A.

The understanding of the formation of the elements has been an intriguing topic within the last decades. It is now approved that the heaviest naturally occurring elements on earth, the actinides, are produced in the astrophysical r-process. However, the exact site of this process is still disputed. Recently, the amount of interstellar Pu-244 (T1/2 = 80.6 Ma) in various geological archives like deep-sea ferromanganese crusts and sediments has been investigated by applying highly sensitive accelerator mass spectrometry measurements (AMS). Correlation of the influx of supernova-produced Fe-60 (T1/2 = 2.6 Ma) and Pu-244 could point to a possible origin of the r-process in the universe. To further prove this hypothesis, recent investigations focus on the determination of another long-lived radionuclide which is also produced in the r process, Cm-247 (T1/2 = 15.6 Ma), by AMS. However, the separation of the expected ultra-trace amounts of actinides (a few 100 atoms per gram) from huge amounts of matrix and interfering elements represents a major analytical challenge. Thus, this contribution aims to compare existing chemical separation strategies for trivalent actinides (Am, Cm) from deep-sea reservoirs, like ferromanganese crusts or nodules based on extraction chromatography. Our investigations show that procedures based on trivalent actinide separation by TRU™ resin fail to extract trivalent actinides from matrices with high concentrations of rare-earth elements. Thus, an alternative separation method based on anion exchange (DOWEX 1x8 for Pu separation) and solvent extraction (DGA™ resin for An/Ln separation and TEVA™ resin for the separation of Am/Cm from rare-earths) has been adapted in our studies. Am-241 and Cm-244 in kBq quantities were used as tracers to determine the yield of the full separation procedure by γ-counting and α spectrometry. The effective separation of trivalent actinides from major matrix elements, like iron and manganese, as well as various rare-earth elements allow for processing multi-gram amounts of deep-sea ferromanganese crusts. This could finally lead to the detection of live Cm-247 in geological archives. Furthermore, this adapted method can be used for the analysis of environmental samples regarding their content and isotopic ratio of anthropogenically produced Pu, Am and Cm which holds potential for nuclear safeguards and nuclear forensics studies.

  • Lecture (Conference)
    19th Radiochemical Conference, 20.05.2022, Marianske Lazne, Tschechien

Publ.-Id: 34394

From molecular oxo-hydroxo Ce clusters to crystalline CeO2

Estevenon, P.; Amidani, L.; Bauters, S.; Tamain, C.; Bodensteiner, M.; Meuer, F.; Hennig, C.; Dumas, T.; Kvashnina, K.

Due to their applications in catalysis, energy storage or biomedicine, many studies report synthesis and characterizations of CeO2 NPs and intensively use X-ray sources for characterization. In this study, we report a comprehensive interpretation of X-ray measurements on CeO2 models with atomically resolved structure, namely oxo-hydroxo polynuclear Ce complexes. A set of Ce clusters with growing size (0.6 nm to 1.2 nm) and nuclearity (from 6 to 38 Ce atoms) were synthetized and characterized by single crystal XRD. The samples were then analyzed using HEXS and HERFD technics and compared to larger CeO2 NPs and bulk CeO2. Both spectroscopic methods reveal consistent trends as the particle grows or shrink from the set of molecular Ce-{n} clusters up to bulk CeO2. HEXS reveals a broadening in distribution for the short Ce-oxygen bonds for the small clusters. Concomitantly, the HERFD performed at the Ce LIII edge indicates a gradual splitting of the cerium 5d states as the particles become more CeO2 like. From the crystallographic determination of the clusters structure, atomically resolved Ce LIII edge simulation were undertaken. These simulations allow to isolate structural and electronic properties for individual Ce sites within clusters and evidence the great difference between surface and core Ce atoms. It also shows how a combination of simulations from different sites results in the accurate reproduction of the corresponding experimental data. This approach based on clusters atomic sites was then successfully extended to model larger CeO2 NPs Ce LIII edge HERFD spectra. By linking atomically resolved structures to nanoparticles and bulk material using crystallography, X-ray technics and simulation, this work extends the knowledge on cerium oxide nanomaterial and supports a better understanding and predictability of their crystalline and electronic structure

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Publ.-Id: 34393

Data publication: Contemporary environment and historical legacy explain functional diversity of freshwater fishes in the world rivers

Su, G.; Tedesco, P.; Toussaint, A.; Villeger, S.; Brosse, S.

Script and data used for the analysis and figures plotting in paper "Contemporary environment and historical legacy explain functional diversity of freshwater fishes in the world rivers"

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Publ.-Id: 34392

How do King Cobras move across a major highway? Unintentional wildlife crossing structures may facilitate movement

Dolton Jones, M.; Marshall, B. M.; Smith, S. N.; Crane, M.; Simoes Silva, I. M.; Artchawakom, T.; Suwanwaree, P.; Waengsothorn, S.; Wüster, W.; Goode, M.; Strine, C. T.

Global road networks continue to expand, and the wildlife responses to these landscape-level changes need to be understood to advise long-term management decisions. Roads have high mortality risk to snakes because snakes typically move slowly and can be intentionally targeted by drivers.
We investigated how radio-tracked King Cobras (Ophiophagus hannah) traverse a major highway in northeast Thailand, and if reproductive cycles were associated with road hazards.
We surveyed a 15.3 km stretch of Highway 304 to determine if there were any locations where snakes could safely move across the road (e.g., culverts and bridges). We used recurse analyses to detect possible road-crossing events, and used dynamic Brownian Bridge Movement Models (dBBMMs) to show movement pathways association with possible unintentional crossing structures. We further used Integrated Step Selection Functions (ISSF) to assess seasonal differences in avoidance of major roads for adult King Cobras in relation to reproductive state.
We discovered 32 unintentional wildlife crossing locations capable of facilitating King Cobra movement across the highway. While our dBBMMs broadly revealed underpasses as possible crossing points, they failed to identify specific underpasses used by telemetered individuals; however, the tracking locations pre- and post-crossing and photographs provided strong evidence of underpass use. Our ISSF suggested a lower avoidance of roads during the breeding season, although the results were inconclusive. With the high volume of traffic, large size of King Cobras, and a 98.8% success rate of crossing the road in our study (nine individuals: 84 crossing attempts with one fatality), we strongly suspect that individuals are using the unintentional crossing structures to safely traverse the road.
Further research is needed to determine the extent of wildlife underpass use at our study site. We propose that more consistent integration of drainage culverts and bridges could help mitigate the impacts of roads on some terrestrial wildlife.

Keywords: movement ecology; conservation; bridge; drainage culvert; road mortality; Ophiophagus hannah; road crossing; space use; ecology

Publ.-Id: 34391

The speed limit of martensitic transformations

Lünser, K.; Schwabe, S.; Schmidt, D.; Nielsch, K.; Gaal, P.; Fähler, S.

Applications such as actuation by (magnetic) shape memory effects, magnetocaloric cooling and thermomagnetic energy harvesting benefit from a fast martensitic transformation, because using devices at high frequencies increases their power density. Still, data on the speed limit of theses transformations is scarce, as it is difficult to induce the phase transition in short time spans and measure it non-invasively. Up to now, shape memory wires have been heated with currents by Joule heating, which induces a transformation in as short as 20 µs. With magnetic pulses, magnetic shape memory alloys can be transformed within 13 ms. In both cases, however, transformation dynamics are limited by the duration of the current or magnetic pulse.
To increase knowledge about the speed limit of martensitic transformations, here, we heat a 500 nm thick epitaxial Ni-Mn-Ga film with a 7 ns long laser pulse and probe the martensite to austenite transformation with in situ synchrotron diffraction. With this experimental set-up, we can vary the heating rate by changing the laser fluence and additionally adjust the initial sample temperature with a furnace. We observe a linear dependence of the heating rate on the transformation speed. Thus, the transformation can be completed in as little as 10 ns; however, this requires an overheating of several hundreds of Kelvin. For most applications, only a much smaller overheating is feasible, which gives a switching time in the sub-microsecond range. The austenite to martensite transformation can be completed at least within hundreds of ns. This leaves plenty of room to speed up the performance of all applications based on martensitic transformations.

Keywords: Speed limit; epitaxial film; Ni-Mn-Ga; martensitic transformation

  • Lecture (Conference)
    12th European Symposium on Martensitic Transformations, 05.-09.09.2022, Ankara, Türkei

Publ.-Id: 34390

Recycling of refrigerators: Linking design decisions and liberation behaviour

Mütze, T.; Heibeck, M.

Recycling is part of the circular economy contributing to the sustainable and secure supply of raw materials. Most consumer products, from cars to domestic appliances, consist of multi-material structures which form complex wastes after their use phase. Therefore and with the focus on sustainability, the design decisions of product manufacturers have a significant influence on recyclability. So far, methods exist to evaluate the performance of metallurgical recycling systems through process simulation. However, there is a lack of methods to estimate the impact of design decisions on the liberation behaviour during crushing.
In a case study, a large-scale recycling campaign examined 100 refrigerators from the household sector in a commercial primary waste treatment facility. Initially, the fridges were analysed regarding e.g. initial mass, size, outer appearance, and manufacturer in order to be categorized into three fractions. Then the conventional pre-treatment steps were documented such as depollution, removal of glass shelfs, printed circuit boards and compressors. Finally, the mechanical processing started beginning with a two-stage crushing and subsequent separation in an air classifier (density sorting), magnetic and eddy current separator.
The main products of the mechanical processing are a PU rich, a ferrous, a non-ferrous and a plastics fraction. The last three of those were analysed in more detail in order to quantify the degree of liberation as well as the separation efficiency. Liberation was evaluated at particle level in terms of unliberated connections between different materials (material mixed particles) as well as connections of different components consisting of the same material (component mixed particles). This data allows deducing the liberation efficiency, which affects sorting and final product qualities.
Furthermore, the liberation efficiency of different connection types (e.g. screwing, gluing, coating, snap-fitting) was identified. Coupling these insights with a material compatibility assessment for subsequent recovery processes, design recommendations have been derived for liberation-oriented choice of connection types and specific material combinations. For example, steel in the PU rich fraction causes problems during conveying and pelletizing and is therefore regarded as hazardous pollutant for subsequent processing. In contrast to that, aluminium in the ferrous fraction deceases slightly the product quality but can be removed easily during subsequent metallurgical refinement.
As an ongoing research topic, finite element method (FEM) simulations supplement these experimental investigations to enable the analysis of various multi-material designs. In these simulations, composites of metal and fibre-reinforced plastics are modelled in a crushing process and compared to laboratory scale experiments (figure 2) regarding their liberation potential during crushing and their overall recyclability. In the future, this methodical approach will allow assessing the effects of the product design on recyclability already in the design stage assisting the development of recycling-friendly products.

Keywords: recycling; pre-treatment; liberation; crushing

  • Lecture (Conference)
    17th European Symposium on Comminution & Classification (ESCC 2022), 27.-29.06.2022, Toulouse, France

Publ.-Id: 34389

Growth and Martensitic Transformation of Ferromagnetic Co-Cr-Ga-Si Epitaxial Films

Ge, Y.; Lünser, K.; Fähler, S.

Martensitic transformations are important for many materials exhibiting magneto-, elasto- and barcaloric effects and
often the functional properties benefit from additional magnetic transformations. For caloric applications, thin films
are of particular interest due to their fast heat exchange, which promises a high cooling power. In particular epitaxial
films are a model system to understand the formation of the martensitic microstructure.[1] However, commonly
transformations from austenite to martensite only occur during cooling. The recent observation of a so-called reentrant
transformation obtained much interest, as an additional transformation from martensite to austenite was observed
during further cooling.[2,3] A reentrant transition increases both, the number of new physical effects and the possible
applications. However, reports are currently very few and only on bulk materials. Will this phenomenon occur also in
thin films? Will the martensitic transformation and microstructure differ when induced by heating or cooling? Also
for caloric applications, reentrant martensite is interesting as it may enable bidirectional caloric effects driven by
deformation and recovery of the ferromagnetic shape memory alloys (FSMA) through both, heating and cooling.
As a model system, epitaxial Co-Cr-Ga-Si ferromagnetic shape memory thin films were grown by DC magnetron
sputtering. To obtain epitaxial growth, films were deposited on different substrates as well as orientations. We identify
MgO(100) as the optimum substrate. Films were grown at different deposition temperatures and the influence of an
additional postannealing process was examined to understand the influence on elemental composition, structure,
microstructure and the transformation behavior. As a kind of summary, Fig.1-a depicts a phase diagram of all samples
prepared. Under optimum conditions, we obtain epitaxial growth, as evident from pole figure measurements of an
austenitic film (Fig. 1-b). When films are subjected to an additional heat treatment at 800°C, films are martensitic at
room temperature, which is evident the peak splitting in pole figure measurements (Fig. 2-a) and agree well with pole
figures calculated by the phenomenological theory of martensite with a c/a ratio of 1.37 (Fig. 2-b). Furthermore, the
microstructure becomes granular and twin boundaries become visible. Though annealing improves the martensitic
transformation, we observe a degradation of the ferromagnetic transition. To sum up, we could demonstrate epitaxial
growth of Co-Cr-Ga-Si films, which are martensitic and ferromagnetic at room temperature. This is a key step to
utilize the additional possibilities of reentrant martensite also for thin films.

Keywords: epitaxial thin film; shape memory alloy; reentrant martensite

  • Lecture (Conference)
    12th European Symposium on Martensitic Transformations (ESOMAT), 05.-09.09.2022, Ankara, Turkey

Publ.-Id: 34388

Status-Quo-Erhebung zur Zyklotron-Infrastruktur für die Nuklearmedizin und Radiopharmazie in Deutschland, Österreich und der Schweiz (D-A-CH)

Zippel, C.; Ermert, J.; Patt, M.; Gildehaus, F. J.; Ross, T.; Reischl, G.; Kuwert, T.; Solbach, C.; Neumaier, B.; Kiß, O.; Mitterhauser, M.; Wadsak, W.; Schibli, R.; Kopka, K.

Zyklotrone bilden als Ressource medizinischer Radionuklide eine zentrale Infrastruktur für die Entwicklung neuer und die Produktion klinisch etablierter Radiotracer zur molekularen Hybridbildgebung. Da die letzte umfassende Veröffentlichung zu Zyklotronen ca. 15 Jahre alt ist, wurde eine Statuserhebung zu den für die Nuklearmedizin und Radiopharmazie in Deutschland, Österreich und der Schweiz (D-A-CH-Länder) betriebenen Zyklotronen angestrebt.

  • Poster
    NuklearMedizin 2022, 27.-30.04.2022, Leipzig, Deutschland

Publ.-Id: 34387

Data publication: Insights into the Electronic Structure of a U(IV) Amido and U(V) Imido Complex

Köhler, L.; Patzschke, M.; Bauters, S.; Vitova, T.; Butorin, S. M.; Kvashnina, K.; Schmidt, M.; Stumpf, T.; März, J.

This set includes single-crystal X-ray diffraction, IR, HERFD XANES and quantumchemical calculation data for the characterization of the synthesized U(IV) amido and U(V) imido complexes. Furthermore with this the inverse trans influence can be evaluated.

Keywords: uranium(V); HERFD XANES; cabenes; inverse trans influence

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Publ.-Id: 34386

Data publication: LLAMA: The Low-Level Abstraction For Memory Access

Gruber, B. M.; Amadio, G.; Blomer, J.; Matthes, A.; Widera, R.; Bussmann, M.

The performance gap between CPU and memory widens continuously. Choosing the best memory layout for each hardware architecture is increasingly important as more and more programs become memory bound. For portable codes that run across heterogeneous hardware architectures, the choice of the memory layout for data structures is ideally decoupled from the rest of a program. This can be accomplished via a zero-runtime-overhead abstraction layer, underneath which memory layouts can be freely exchanged.
We present the Low-Level Abstraction of Memory Access (LLAMA), a C++ library that provides such a data structure abstraction layer with example implementations for multidimensional arrays of nested, structured data. LLAMA provides fully C++ compliant methods for defining and switching custom memory layouts for user-defined data types. The library is extensible with third-party allocators.
Providing two close-to-life examples, we show that the LLAMA-generated AoS (Array of Structs) and SoA (Struct of Arrays) layouts produce identical code with the same performance characteristics as manually written data structures. Integrations into the SPEC CPU® lbm benchmark and the particle-in-cell simulation PIConGPU demonstrate LLAMA's abilities in real-world applications. LLAMA's layout-aware copy routines can significantly speed up transfer and reshuffling of data between layouts compared with naive element-wise copying.
LLAMA provides a novel tool for the development of high-performance C++ applications in a heterogeneous environment.

Keywords: software implementation; programming techniques; memory layout; performance portability

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Publ.-Id: 34384

Random Quantum Neural Networks (RQNN) for Noisy Image Recognition

Konar, D.; Gelenbe, E.; Bhandary, S.; Das Sarma, A.; Cangi, A.

Classical Random Neural Networks (RNNs) have demonstrated effective applications in decision making, signal processing, and image recognition tasks. However, their implementation has been limited to deterministic digital systems that output probability distributions in lieu of stochastic behaviors of random spiking signals. We introduce the novel class of supervised Random Quantum Neural Networks (RQNNs) with a robust training strategy to better exploit the random nature of the spiking RNN. The proposed RQNN employs hybrid classical-quantum algorithms with superposition state and amplitude encoding features, inspired by quantum information theory and the brain’s spatial-temporal stochastic spiking property of neuron information encoding. We have extensively validated our proposed RQNN model, relying on hybrid classical-quantum algorithms via the PennyLane Quantum simulator with a limited number of qubits. Experiments on the MNIST, FashionMNIST, and KMNIST datasets demonstrate that the proposed RQNN model achieves an average classification accuracy of 94.9%. Additionally, the experimental findings illustrate the proposed RQNN’s effectiveness and resilience in noisy settings, with enhanced image classification accuracy when compared to the classical counterparts (RNNs), classical Spiking Neural Networks (SNNs), and the classical convolutional neural network (AlexNet). Furthermore, the RQNN can deal with noise, which is useful for various applications, including computer vision in NISQ devices. The PyTorch code is made available on GitHub to reproduce the results reported in this manuscript.

Keywords: machine learning; neural networks; quantum computing; image recognition

Publ.-Id: 34383

Raw Data: Recycling of rare earth containing waste with peptide-functionalized floating glass bubbles in a phage mimicking approach

Schrader, M.

Raw data for the Publication "Recycling of rare earth containing waste with peptide-functionalized floating glass bubbles in a phage mimicking approach"


Publ.-Id: 34382

Electrical Conductivity of Iron in Earth's Core from Microscopic Ohm's Law

Ramakrishna, K.; Lokamani, M.; Baczweski, A. D.; Vorberger, J.; Cangi, A.

Understanding the electronic transport properties of iron under high temperatures and pressures is essential for constraining geophysical processes. The difficulty of reliably measuring these properties under Earth-core conditions calls for sophisticated theoretical methods that can support diagnostics. We present results of the electrical conductivity within the pressure and temperature ranges found in Earth's core from simulating microscopic Ohm's law using time-dependent density functional theory. Our predictions provide a new perspective on resolving discrepancies in recent experiments.

Keywords: transport properties; time-dependent density functional theory; Kubo-Greenwood; electrical conductivity; thermal conductivity

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Publ.-Id: 34381

Carboranyl analogues of mefenamic acid and their biological evaluation

Useini, L.; Mojic, M.; Laube, M.; Lönnecke, P.; Dahme, J.; Sárosi, M. B.; Mijatovic, S.; Maksimovic-Ivanic, D.; Pietzsch, J.; Hey-Hawkins, E.

Mefenamic acid represents a widely used nonsteroidal anti-inflammatory drug (NSAID) to treat pain of postoperative sur-gery and heavy menstrual bleeding. Like other NSAIDs, mefenamic acid inhibits the synthesis of prostaglandins by non-selectively blocking cyclooxygenase (COX) isoforms COX-1 and COX-2. For improved selectivity of the drug and thereby reduced related side effects, the carborane analogues of mefenamic acid were evaluated. The ortho-, meta- and para-carborane derivatives were synthesized in three steps: halogenation of the respective cluster, followed by a Pd-catalyzed B–N coupling and hydrolysis of the nitrile derivatives under acidic conditions. COX inhibitory activity and cytotoxicity for different cancer cell lines revealed that the carborane analogues have stronger anti-tumor potential compared to their parent organic compound.

Publ.-Id: 34380

the microbial inventory of bentonite – how does it affect the long-term integrity of repository for high-level radioactive waste?

Sushko, V.; Dressler, M.; Wei, T.-S.; Neubert, T.; Kühn, L.; Cherkouk, A.; Matschiavelli, N.

The long-term and safe storage of high-level radioactive waste (HLW) in general, remains a challenge world-wide. The deep geological repository (DGR) is a concept of applying multi barriers to store the HLW and to ensure the long-term safety. Bentonite is proposed as a potential material for sealing the space between the canister containing the HLW and the surrounding host rock. To investigate the microbial diversity and metabolic activity of naturally occurring microorganisms in Bavarian bentonite B25 as well as their influence on the used canister materials (copper & cast iron), we conducted anaerobic microcosm experiments, incubating Bavarian bentonite B25, synthetic pore waters (synthetic Opalinus Clay pore water or diluted cap rock solution) and metal plates (copper or cast iron coupons) up to 400 days at 37 °C. We also added H2 or lactate to stimulate microbial activities in certain microcosms. Geochemical analyses showed a decrease of Eh, potassium and sulfate as well as an increase of Fe(II) in microcosms that contained synthetic Opalinus Clay pore water, H2 and cast iron. Statistical analysis indicated that these observations have no significant correlation in shaping microbial communities in the respective microcosms. Moreover, SEM images provided strong evidence that no clear corrosion on cast iron and copper was observed that is due to microbial activity. Overall, this study shows that B25 bentonite may be an ideal barrier material for a DGR due to its negative microbial effects, which prolong the entire lifespan of a DGR.

  • Poster
    ISME Microbes, 14.-19.08.2022, Lausanne, Schweiz

Publ.-Id: 34379

Temperature dependent swelling transitions in MXene Ti3C2Tx

Iakunkov, A.; Nordenström, A.; Boulanger, N.; Hennig, C.; Baburin, I.; Talyzin, A.

Swelling is a property of hydrophilic layered materials, which enables the penetration of polar solvents into an interlayer space with expansion of the lattice. Here we report an irreversible swelling transition, which occurs in MXenes immersed in excess dimethyl sulfoxide (DMSO) upon heating at 362-370 K with an increase in the interlayer distance by 4.2 Å. The temperature dependence of MXene Ti3C2Tx swelling in several polar solvents was studied using synchrotron radiation X-ray diffraction. MXenes immersed in excess DMSO showed a step-like increase in the interlayer distance from 17.73 Å at 280 K to 22.34 Å above ∼362 K. The phase transformation corresponds to a transition from the MXene structure with one intercalated DMSO layer into a two-layer solvate phase. The transformation is irreversible and the expanded phase remains after cooling back to room temperature. A similar phase transformation was observed also for MXene immersed in a 2 : 1 H2O : DMSO solvent ratio but at a lower temperature. The structure of MXene in the mixed solvent below 328 K was affected by the interstratification of differently hydrated (H2O)/solvated (DMSO) layers. Above the temperature of the transformation, the water was expelled from MXene interlayers and the formation of a pure two-layer DMSO-MXene phase was found. No changes in the swelling state were observed for MXenes immersed in DMSO or methanol at temperatures below ambient down to 173 K. Notably, MXenes do not swell in 1-alcohols larger than ethanol at ambient temperature. Changing the interlayer distance of MXenes by simple temperature cycling can be useful in membrane applications, e.g. when a larger interlayer distance is required for the penetration of ions and molecules into membranes. Swelling is also very important in electrode materials since it allows penetration of the electrolyte ions into the interlayers of the MXene structure.

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Publ.-Id: 34378

Dual-Labelling Strategies for Nuclear and Fluorescence Molecular Imaging: Current Status and Future Perspectives

Kubeil, M.; Santana Martinez, I. I.; Bachmann, M.; Kopka, K.; Tuck L., K.; Stephan, H.

Molecular imaging offers the possibility to investigate biological and biochemical processes non-invasively and to obtain information on both anatomy and dysfunctions. Based on the data obtained, a fundamental understanding of various disease processes can be derived and treat-ment strategies can be planned. In this context, methods that combine several modalities in one probe are increasingly being used. Due to a comparable, very high sensitivity and provided complementary information, the combination of nuclear and optical probes has taken on a special significance. In this review article, dual-labelled systems for biomodal nuclear and optical imaging based on both modular ligands and nanomaterials are discussed. Particular attention is paid to radiometal-labelled molecules for single-photon emission computed tomography (SPECT) and positron emission tomography (PET), and metal complexes combined with fluorescent dyes for optical imaging. The clinical potential of such probes, especially for fluorescence-guided surgery is assessed.

Keywords: molecular imaging; positron emission tomography; single-photon emission computed tomography; near-infrared fluorescence

Publ.-Id: 34377

Data publication: Improved Kinetics for Mineral Dissolution Reactions in Pore-Scale Reactive Transport Modeling

Schabernack, J.; Fischer, C.

List of Data Content:

1. COMSOL Multiphysics files (.mph):
    -8 2D files:
        -2D reactive transport simulations at varying conditions
        -Conditions and some results can be seen in file "2D_Rates.xlsx"
    -4 Surface files:
        -3D reactive transport simulations over a calcite surface
        -With the classical rate equation:
            _run (model of complete surface)
            _Zoom_HighStep (model of high surface step selection as indicated in the paper)
            _Zoom_LargePit (model of large etch pit selection as indicated in the paper)
        -With the new slope factor:
            _NewSlope (model of complete surface)
    -2 3D files:
        _3DModel (model of calcite cuboid with classical rate equation)
        _3DModel_withSlope (model of calcite cuboid with slope factor rate equation)

2. Table files (.xlsx):
    -2D_Rates (Dissolution rates along the interface in all 2D simulations + experimental data for the same surface)
    -Surface-RateSpectra (Dissolution rate spectra of the surface simulations)
    -Fig7_RateSpectra (Dissolution rate spectra data for Figure 7 in the paper)

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Publ.-Id: 34376

Improved Kinetics for Mineral Dissolution Reactions in Pore-Scale Reactive Transport Modeling

Schabernack, J.; Fischer, C.

Recent numerical investigations revealed that the heterogeneity of the dissolution rate observed in numerous experiments cannot be explained by fluid transport effects. This heterogeneity is attributed to intrinsic surface reactivity. Therefore, reactive transport models (RTM) require parameterization of the surface reactivity for accurate predictions. For this purpose, a nanotopographic parametrization based on surface slope has been recently suggested. In this study, we utilize and improve this parametrization for RTMs of pore-scale systems, from the crystal surface to the single crystal geometry, going beyond the previous reactivity parametrization. 2D and 3D RTMs were developed using COMSOL Multiphysics for calcite systems based on experimental measurements. We compared the results between classically parameterized RTMs, RTMs with new slope parameterization, and experimental data. The effect of flow on dissolution under conditions far-from-equilibrium is found to be negligible, highlighting the importance of surface reactivity in the dissolution reaction. For the first time, the new slope factor was able to accurately reproduce the experimental results on a crystal surface with large field-of-view, large height variability of the topography, and over a long-term reaction period. The new parameterization had greatly improved sensitivity for intermediate reactivity ranges compared to the previous parameterization. A 3D model is used to present the general applicability of the parameterization for use in realistic geometric data sets. Thus, we also show that neglecting surface reactivity in an RTM leads to incorrect predictions regarding the porosity, pore geometry, and surface topography of the system. Our new slope factor can successfully serve as a first-order proxy for the distribution of surface reactivity in 3D pore-scale rock systems. The description of surface reactivity is crucial for accurate long-term modeling of natural rock systems.

Keywords: Pore-Scale Reactive Transport Modeling; Mineral Dissolution; Crystal Surface Reactivity; Kinetics

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Publ.-Id: 34374

Influence of Surface Nanotopography on the Adsorption of Europium on Muscovite (001)

Schabernack, J.; Faria Oliveira, A.; Heine, T.; Fischer, C.

Radionuclide migration is one of the key problems for the long-term safety of nuclear waste repositories. One possible mechanism to retard or prevent the migration of radionuclides from the repository to the biosphere is the adsorption onto mineral surfaces of the surrounding host rock. Clay rock formations such as the Opalinus Clay are being considered for potential sites for nuclear waste repositories, partly due to the strong sorption potential of clay minerals. Phyllosilicates, such as clay minerals or mica, have shown a high affinity for adsorption of various radionuclides in several experimental studies. However, mineral surfaces in natural environments are often subjected to reactions (e.g., dissolution) that may alter the surface nanotopography and, consequently, affect the overall adsorption process. Recently, it has been reported that the nanotopography of calcite surfaces leads to heterogonous sorption of europium due to differences in the atomic configuration of the adsorption sites [1].
In this study, we investigate the influence of surface site coordination on the adsorption energy barrier and the resulting overall distribution of radionuclide adsorption on the mineral surface. We utilize numerical methods to study the adsorption of Eu(OH)3 on a muscovite (001) surface with different nanotopographic structures. Density Functional Theory (DFT) calculations are performed to obtain the adsorption energy barriers of several surface sites present on muscovite. For each site, the adsorption energy is calculated based on a series of geometry optimizations with increasing Eu–site distance. The values of the site-specific adsorption energy barriers are then implemented in a Kinetic Monte Carlo (KMC) model based on a previous study [2]. In the KMC model, larger surface structures, such as steps or etch pits, are placed on the muscovite surface and a dissolution simulation is performed to create a realistic nanotopography. Based on the adsorption energy barriers obtained with DFT, Eu(OH)3 is adsorbed on the generated muscovite surface in a second KMC model step. The KMC model is then used to predict the distribution of adsorbed Eu(OH)3 and the temporal evolution of the adsorption. Using this combined numerical approach, we show the effect of surface site coordination on radionuclide adsorption reactions and the resulting adsorption heterogeneity on mineral surfaces at large scales.

Keywords: Radionuclide Adsorption; Kinetic Monte Carlo; Density Functional Theory; Muscovite; Europium

  • Lecture (Conference)
    19th Radiochemical Conference, 15.-20.05.2022, Mariánské Lázně (Marienbad), Czech Republic

Publ.-Id: 34373

Site-Specific Europium Adsorption on Muscovite (001) Surfaces

Schabernack, J.; Faria Oliveira, A.; Heine, T.; Fischer, C.

The long-term safety of nuclear waste repositories heavily depends on their potential to prevent the migration of the contained radionuclides. In the host rock, adsorption onto mineral surfaces is a key mechanism to bind radionuclides and inhibit further transport to the biosphere. Several experimental studies have shown that phyllosilicates (e.g., clay minerals or mica) provide surfaces with strong sorption potential. Therefore, clay rock formations such as the Opalinus clay are being investigated as repository sites in several countries. In the natural environment of host rock formations, the mineral surfaces are exposed to a variety of reactions altering the surface nanotopography (e.g., dissolution). These changes can affect radionuclide adsorption processes. A recent study revealed that calcite surfaces show heterogeneous europium sorption due to their nanotopography [1]. The nanotopography leads to a heterogeneous distribution of reactive sites that are available for adsorption reactions.

In this study, we use numerical methods to investigate the adsorption of Eu(OH)3 on muscovite (001) surfaces with varying nanotopography. Density Functional Theory (DFT) is used to calculate adsorption energy barriers of several atomic sites that are present on the muscovite surface. The sites differ in their first and second order coordination environment, which influences their adsorption potential. A series of geometry optimizations with increasing Eu–site distance is computed to obtain the adsorption energy for each site. The site-specific adsorption energy barriers values are then used for the parameterization of a Kinetic Monte Carlo (KMC) model based on a previous study [2]. The KMC model allows for the simulation of adsorption on larger muscovite surfaces. It is separated into: (1) placement of structures (e.g., pits) and subsequent dissolution simulation for nanotopography generation and (2) Eu(OH)3 adsorption based on the available surface sites and their DFT-derived adsorption energy barrier. This combined numerical approach can show the effect of surface site coordination on radionuclide adsorption and predict the resulting adsorption heterogeneity on mineral surfaces.

[1] Yuan et al. (2021) Environ. Sci. Technol., 55, 15797–15809.
[2] Schabernack et al. (2021) Minerals, 11, 468.

Keywords: Radionuclide Adsorption; Kinetic Monte Carlo; Density Functional Theory; Muscovite; Europium

  • Lecture (Conference) (Online presentation)
    Goldschmidt 2022, 10.-15.07.2022, Honolulu, Hawaiʻi, United States of America

Publ.-Id: 34372

A metadata and data entry and editing tool using ontologies for knowledge graph creation

Steinmeier, L.; van den Boogaart, K. G.; Rau, F.; Schaller, T.

Making research reproducible and FAIR (Findable, Accessible, Interoperable, and Reusable) often requires more information than what is commonly published within scientific articles. There is a growing number of repositories for publishing additional material like data or code. However, articles are still at the center of most scientific work and thus efforts on gathering information which is important for reproducibility but not for the article itself are often only started at a later stage. This usually makes the collection more tedious, error-prone, and less comprehensive.

In order to lower the barrier for recording all relevant information directly when it is generated, we propose a design for a data and metadata entry and editing tool. It should allow researchers to create metadata for the files and assets which they already have and offer a possibility for structured entry of new data. To support consistent (meta)data entry over time, the user will be able to create forms which can enforce comprehensiveness and correctness. Furthermore, data FAIRness is supported through the automated usage of established ontologies for (meta)data annotation. This will be done by a background process so the user isn´t involved in these technologies. Nevertheless the tool will grant further possibilities to those who are aware of ontologies used in their domain. Resources can be referenced consistently across (meta)data sets of many stakeholders through identifiers provided by central sources. In conjunction, the usage of these common identifiers and ontologies forms large knowledge graphs of the data recorded with our tool.

This contribution will be a discussion of the various components of such a tool, potentially used metadata standards, possible variations, important features, and most relevant: How it can be useful for your work!

Keywords: metadata; tool; ontology; FAIR; research data management; data collection; knowledge graph; data annotation

  • Open Access Logo Poster
    IAMG 2022 21th Annual Conference, 29.08.-03.09.2022, Nancy, France
  • Open Access Logo Poster (Online presentation)
    HMC Conference 2022, 05.-06.10.2022, Online, Deutschland
    DOI: 10.5281/zenodo.7413894


Publ.-Id: 34371

Establishing Micro Physiological Systems by means of a radiolabeled anti-EGFR antibody for the evaluation of new radioligands

Sihver, W.; Nitt-Weber, A.-K.; Behrens, S.; Schmieder, F.; Ullrich, M.; Bachmann, M.; Kopka, K.; Pietzsch, H.-J.; Sonntag, F.

Introduction: Potential radiopharmaceuticals are usually evaluated in small animals. Aligned with the 3R principle, animal numbers could be reduced by using “Micro-Physiological Systems (MPS)” which is an organ-on-chip technology. In MPS modules, cultured cells and human organoids can be analysed in a circulatory system under defined conditions [1,2].
In this study, preliminary tests with radiolabeled anti-EGFR antibody cetuximab (C225) were performed using 2D or 3D (spheroid) cultures of A431 cells. The aim was to determine selected pharmacological parameters such as binding affinity of radiolabeled C225 using the MPS.
Methods: 104 A431 cells were placed in the 6-well chamber of the MPS module, either as monolayer or as spheroids (0.8 ± 0.3 mm) and cultured for 24 hours. The conjugate NOTA-C225 was radiolabeled with 68Ga or 64Cu (molar activity: 81.1 ± 14.7 MBq/nmol). An integrated micropump, driven by a controller, generates a pulsatile fluid flow through the fluidic channels upon the cells (Fig.1).
Medium (total binding) and medium with an EGFR blocking C225 concentration of 2 µM (nonspecific binding) (1mL) was pumped through the MPS for 5 min (80 bpm at a volume flow of 6.4 µL/s). Under saturation conditions, 1.2 to 15 nM of radiolabeled C225 were applied to cells and spheroids. Using the micropump, a total volume of 1 mL of the compound solutions were distributed through the MPS over 15 min. After washing with PBS for 10 min, the MPS modules were exposed to an imaging plate, and bound radiolabeled C225 was determined by phosphor imaging. Evaluation was realised with AIDA /GraphPadPrism.
Results/Discussion: We demonstrate that a MPS environment can be employed to determine radioligand binding parameters. The first saturation assays show high binding affinity of the radiolabeled C225 with Kd values in the low nanomolar range (1.7 to 25 nM), being in the range of previous reports [3,4]. Kd of A431 monolayers was similar to that of A431 spheroids. Nonspecific binding on the integrated channels and on empty wells was < 15% of the specifically bound tracer molecule.
Our data provides a rationale to pursue further studies with multi-organ chips using MPS in order to reduce animal numbers used in preclinical radiotracer evaluation. Further steps include trials with kidney- and liver organoids, and an investigation of how radiolabeled C225 is bound, trapped and metabolized using this preclinical model.
Conclusion: Herein, we show that binding parameters of the radiolabeled C225 can be determined in a MPS environment using 2D and 3D cell culture systems. Further studies are required to confirm these data for other EGFR positive and negative cells and for other antibody receptor pairs.
Acknowledgement: W.S. and F.S. acknowledge the financial support by the Federal Ministry of Education and Research of Germany (BMBF) in the project MPS-RP (project number AKZ161L0275A/B).
References: [1] Busek et al., J Sens Sens Syst 2016, 5, 228. [2] Schmieder et al., Proc SPIE 2020, 11268, 1126804_1. [3] Eiblmaier et al., J Nucl Med 2008, 9, 1472. [4] Bellaye et al., Clin Transl Oncol 2018, 12, 1557.

  • Contribution to proceedings
    17th European Molecular Imaging Meeting, EMIM 2022, 15.-18.03.2022, Thessaloniki, Greece
  • Open Access Logo Poster
    17th European Molecular Imaging Meeting, EMIM 2022, 15.-18.03.2022, Thessaloniki, Greece
    DOI: 10.24406/publica-13


Publ.-Id: 34370

Effect of Ca(II) on U(VI) and Np(VI) retention on Ca-bentonite and clay minerals at hyperalkaline conditions – New insights from batch sorption experiments and luminescence spectroscopy

Philipp, T.; Huittinen, N. M.; Shams Aldin Azzam, S.; Stohr, R.; Stietz, J.; Reich, T.; Schmeide, K.

In deep geological repositories for radioactive waste, interactions of radionuclides with mineral surfaces occur under complex geochemical conditions involving complex solution compositions and high pH resulting from degradation of cementitious geo-engineered barriers. Ca2+ cations have been hypothesized to play an important role as mediators for the retention of U(VI) on Ca-bentonite at (hyper)alkaline conditions, despite the anionic character of both the mineral surface and the aqueous uranyl species. To gain deeper insight into this sorption process, the effect of Ca2+ on U(VI) and Np(VI) retention on alumosilicate minerals has been comprehensively evaluated, using batch sorption experiments and time-resolved laser-induced luminescence spectroscopy (TRLFS). Sorption experiments with Ca2+ or Sr2+ and zeta potential measurements showed that the alkaline earth metals sorb strongly onto Ca bentonite at pH 8–13, leading to a partial compensation of the negative surface charge, thereby generating potential sorption sites for anionic actinyl species. U(VI) and Np(VI) sorption experiments in the absence and presence of Ca2+ or Sr2+ confirmed that these cations strongly enhance radionuclide retention on kaolinite and muscovite at pH ≥ 10. Concerning the underlying retention mechanisms, site-selective TRLFS provided spectroscopic proof for two dominating U(VI) species at the alumosilicate surfaces: (i) A ternary U(VI) complex, where U(VI) is bound to the surface via bridging Ca cations with the configuration surface ≡ Ca – OH – U(VI) and, (ii) U(VI) sorption into the interlayer space of calcium (aluminum) silicate hydrates (C-(A-)S-H), which form as secondary phases in the presence of Ca due to partial dissolution of alumosilicates under hyperalkaline conditions. Consequently, the present study confirms that alkaline earth elements, which are ubiquitous in geologic systems, enable strong retention of hexavalent actinides on clay minerals under hyperalkaline repository conditions.

Keywords: clay; C-S-H; kaolinite; muscovite; uranium; neptunium; calcium; bridging effect; TRLFS


Publ.-Id: 34369

Finding Machine-Learning Surrogates for Electronic Structures without Training

Fiedler, L.; Hoffmann, N.; Mohammed, P.; Popoola, G. A.; Yovell, T.; Oles, V.; Ellis, J. A.; Rajamanickam, S.; Cangi, A.

A myriad of phenomena in materials science and chemistry rely on quantum-level simulations of the electronic structure in matter. While moving to larger length and time scales has been a pressing issue for decades, such large-scale electronic structure calculations are still challenging despite modern software approaches and advances in high-performance computing.
The silver lining in this regard is the use of machine learning to accelerate electronic structure calculations -- this line of research has recently gained growing attention.
The grand challenge therein is finding a suitable machine-learning model during a process called hyperparameter optimization. This, however, causes a massive computational overhead in addition to that of data generation.
We accelerate the construction of machine-learning surrogate models by roughly two orders of magnitude by circumventing excessive training during the hyperparameter optimization phase. We demonstrate our workflow for Kohn-Sham density functional theory, the most popular computational method in materials science and chemistry.

Keywords: Machine learning; Neural networks; Materials science

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Publ.-Id: 34368

Data publication: Development and Biological Evaluation of the First Highly Potent and Specific Benzamide-Based Radiotracer [¹⁸F]BA3 for Imaging of Histone Deacetylases 1 and 2 in Brain

Clauß, O.; Schäker-Hübner, L.; Wenzel, B.; Toussaint, M.; Deuther-Conrad, W.; Gündel, D.; Teodoro, R.; Dukic-Stefanovic, S.; Ludwig, F.-A.; Kopka, K.; Brust, P.; Hansen, F. K.; Scheunemann, M.

The data publication contain: 1) Radiosynthesis data (Scheme of the synthesis module; RP-HPLC chromatograms of formulated [18F]BA3; MLC chromatograms of in vivo metabolism studies) 2) Biological data (Baseline TAC of CD-1 mice brain, biodistribution after i.v. injection of [18F]BA3) 3) Analytical data (1H, 13C, 19F NMR spectra; LC-MS chromatograms for final products)

Keywords: histone deacetylase inhibitor; HDAC1/2-specific; radiochemistry; fluorine-18 labelling; positron emission tomography (PET); brain-penetration; glioblastoma; glioma

Related publications


Publ.-Id: 34366

A New Class of PSMA-617-Based Hybrid Molecules for Preoperative Imaging and Intraoperative Fluorescence Navigation of Prostate Cancer

Eder, A.; Matthias, J.; Schäfer, M.; Schmidt, J.; Steinacker, N.; Bauder-Wüst, U.; Domogalla, L.; Roscher, M.; Haberkorn, U.; Eder, M.; Kopka, K.

The development of PSMA-targeting low-molecular-weight hybrid molecules aims at advancing preoperative imaging and accurate intraoperative fluorescence guidance for improved diagnosis and therapy of prostate cancer. In hybrid probe design, the major challenge is the introduction
of a bulky dye to peptidomimetic core structures without affecting tumor-targeting properties and pharmacokinetic profiles. This study developed a novel class of PSMA-targeting hybrid molecules based on the clinically established theranostic agent PSMA-617. The fluorescent dye-bearing candidates
of the strategically designed molecule library were evaluated in in vitro assays based on their PSMA-binding affinity and internalization properties to identify the most favorable hybrid molecule composition for the installation of a bulky dye. The library’s best candidate was realized with IRDye800CW providing the lead compound. Glu-urea-Lys-2-Nal-Chx-Lys(IRDye800CW)-DOTA (PSMA-927) was investigated in an in vivo proof-of-concept study, with compelling performance in organ distribution studies, PET/MRI and optical imaging, and with a strong PSMA-specific tumor uptake comparable to that of PSMA-617. This study provides valuable insights about the design of PSMA-targeting low-molecular-weight hybrid molecules, which enable further advances in the field
of peptidomimetic hybrid molecule development.

Keywords: PSMA; hybrid molecules; prostate cancer theranostics; guided surgery; theranostics

Publ.-Id: 34365

Improved calculations of mean ionization states with an average-atom model

Callow, T. J.; Kraisler, E.; Cangi, A.

The mean ionization state (MIS) is a critical property in dense plasma and warm dense matter research, for example as an input to hydrodynamics simulations and Monte--Carlo simulations. Unfortunately, however, the best way to compute the MIS remains an open question. Average-atom (AA) models are widely-used in this context due to their computational efficiency, but as we show here, the canonical approach for calculating the MIS in AA models is typically insufficient. We therefore explore three alternative approaches to compute the MIS. Firstly, we modify the canonical approach to change the way electrons are partitioned into bound and free states; secondly, we develop a novel approach using the electron localization function; finally, we extend a method which uses the Kubo--Greenwood conductivity to our average-atom model. Through comparisons with higher-fidelity simulations and experimental data, we find that any of the three new methods usually out-performs the canonical approach, with the electron localization function and Kubo--Greenwood methods showing particular promise.

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Publ.-Id: 34364

Comparison of Image Quality and Spatial Resolution Between 18F, 68Ga and 64Cu Phantom Measurements Using a Digital Biograph Vision PET/CT

Braune, A.; Oehme, L.; Freudenberg, R.; Hofheinz, F.; van den Hoff, J.; Kotzerke, J.; Hoberück, S.


The PET nuclide and reconstruction method can have a considerable influence on spatial resolution and image quality of PET/CT scans, which can, for example, influence the diagnosis in oncology. The individual impact of the positron energy of 18 F, 68 Ga and 64 Cu on spatial resolution and image quality of PET/CT scans acquired using a clinical, digital scanner was compared. Furthermore, the impact of different reconstruction parameters on image quality and spatial resolution was evaluated for 18 F-FDG PET/CT scans acquired with a scanner of the newest generation.
PET/CT scans of a Jaszczak phantom and a NEMA PET body phantom, filled with 18 F-FDG, 68 Ga-HCl and 64 Cu-HCl, respectively, were performed on a Siemens Biograph Vision. Images were assessed using spatial resolution and image quality (Recovery Coefficients (RC), coefficient of variation within the background, Contrast Recovery Coefficient (CRC), Contrast-Noise-Ratio (CNR), and relative count error in lung insert). In a subsequent analysis, the scan of the NEMA PET body phantom filled with 18 F-FDG was reconstructed applying different parameters (with/without the application of Point Spread Function (PSF), Time of Flight (ToF) or post-filtering; matrix size). Spatial resolution and quantitative image quality were compared between reconstructions.
We found that image quality was comparable between 18 F-FDG and 64 Cu-HCl PET/CT measurements featuring similar maximal endpoint energy. In comparison, RC, CRC and CNR were worse in 68 Ga-HCl data, despite similar count rates. Spatial resolution was up to 18 % worse in 68 Ga-HCl compared to 18 F-FDG images. Post-filtering of 18 F-FDG acquisitions changed image quality the most and reduced spatial resolution by 52 % if a Gaussian filter with 5 mm FWHM was applied. ToF measurements especially improved the recovery of the smallest lesion (RC mean = 1.07 compared to 0.65 without ToF) and improved spatial resolution by 29 %.
The positron energy of PET nuclides influences spatial resolution and image quality of digital PET/CT scans. Image quality of 68 Ga-HCl PET/CT images was worse compared to 18 F-FDG and 64 Cu-HCl, respectively, despite similar count rates. Reconstruction parameters have a high impact on image quality and spatial resolution and should be considered when comparing images of different scanners or centers.

Publ.-Id: 34363

Influences on PET Quantification and Interpretation

Rogasch, J.; Hofheinz, F.; van Heek, L.; Voltin, C.; Boellaard, R.; Kobe, C.

Various factors have been identified that influence quantitative accuracy and image interpretation in positron emission tomography (PET). Through the continuous introduction of new PET technology—both imaging hardware and reconstruction software—into clinical care, we now find ourselves in a transition period in which traditional and new technologies coexist. The effects on the clinical value of PET imaging and its interpretation in routine clinical practice require careful reevaluation. In this review, we provide a comprehensive summary of important factors influencing quantification and interpretation with a focus on recent developments in PET technology. Finally, we discuss the relationship between quantitative accuracy and subjective image interpretation.

Keywords: positron emission tomography; quantitative accuracy; contrast recovery; signal-to-noise ratio; image quality

Publ.-Id: 34362

Magnetism and magnetoelectricity of textured polycrystalline bulk Cr2O3 sintered in conditions far out of equilibrium

Veremchuk, I.; Makushko, P.; Hedrich, N.; Zabila, Y.; Kosub, T.; Liedke, M. O.; Butterling, M.; Attallah, A. G.; Wagner, A.; Burkhardt, U.; Pylypovskyi, O.; Hübner, R.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Magnetoelectric antiferromagnets like Cr2O3 are attractive for the realization of energy-efficient and high-speed spin-orbitronic-based memory devices. Here, we demonstrate that fabrication of polycrystalline bulk Cr2O3 samples in conditions far out of equilibrium relying on spark plasma sintering allows to realize high-quality material with density close to that of a single crystal. The sintered sample possesses a preferential [001] texture at the surface, which can be attributed to uniaxial strain applied to the sample during the sintering process. The antiferromagnetic state of the sample and linear magnetoelectric effect are accessed all-electrically relying on the spin Hall magnetoresistance effect in the Pt electrode interfaced with Cr2O3. In line with the integral magnetometry measurements, the magnetotransport characterization reveals that the sample possesses the magnetic phase transition temperature of about 308 K, which is the same as in a single crystal. The antiferromagnetic domain pattern consists of small domains with sizes in the range of several micrometers only, which is formed due to the granular structure of the sample. The possibility to access the magnetoelectric properties of the samples relying on magnetotransport measurements indicates the potential of the polycrystalline Cr2O3 samples for prospective research in antiferromagnetic spintronics.

Keywords: magnetoelectric; antiferromagnet; Cr2O3; spark plasma sintering; magnetotransport

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Publ.-Id: 34361

Defect nanostructure and its impact on magnetism of α-Cr2O3 thin films

Veremchuk, I.; Liedke, M. O.; Makushko, P.; Kosub, T.; Hedrich, N.; Pylypovskyi, O.; Ganss, F.; Butterling, M.; Hübner, R.; Attallah, A. G.; Wagner, A.; Wagner, K.; Shields, B.; Maletinsky, P.; Faßbender, J.; Makarov, D.

Thin films of the magnetoelectric insulator α-Cr2O3 are technologically relevant for energy-efficient magnetic memory devices controlled by electric fields. In contrast to single crystals, the quality of thin Cr2O3 films is usually compromised by the presence of point defects and their agglomerations at grain boundaries, putting into question their application potential. Here, we study the impact of the defect nanostructure including sparse small-volume defects and their complexes on the magnetic properties of Cr2O3 thin films. By tuning the deposition temperature, we tailor the type, size, and relative concentration of defects, which we then analyze based on positron annihilation spectroscopy complemented with local electron microscopy studies. The structural characterization is correlated with magnetotransport measurements and nitrogen vacancy microscopy of antiferromagnetic domain patterns. Defects pin antiferromagnetic domain walls and stabilize complex multidomain states with a typical domain size in the sub-micrometer range. Despite their influence on the domain configuration, we demonstrate that neither small open-volume defects nor grain boundaries in Cr2O3 thin films affect the Néel temperature in a broad range of deposition parameters. Our results pave the way towards the realization of spin-orbitronic devices where magnetic domain patterns can be tailored based on defect nanostructures without affecting their operation temperature.

Keywords: Cr2O3 thin films; antiferromagnet; antiferromagnetic domains; magnetotransport; vacancy cluster; dislocations

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Publ.-Id: 34360

Investigating the complex interaction of Technetium with magnetite nanoparticles

Zimmermann, T.; Mayordomo, N.; Stumpf, T.; Scheinost, A.

Nanoparticles (NPs) are relevant in medicine, catalysis and environmental remediation. Among them, magnetite (Fe(II)Fe(III)2O4) NPs are especially interesting due to their redox and magnetic properties and their tunability of size and surface properties, which makes them suited for the removal of many redox-active pollutants. Tc is of great concern for the safety assessment of nuclear waste repositories, since 99Tc is a fission product with a long half-life (t1/2 = 2.1∙105 years). Under oxidative conditions Tc forms an anionic species, pertechnetate (Tc(VII)O4-), which is mobile due to its weak interactions with minerals. Under anaerobic conditions, pertechnetate is reduced by reducing agents to Tc(IV), which sorbs on minerals, forms insoluble oxides like TcO2, or is structurally incorporated by stable natural minerals. [1]
Previous studies by Yalcintas et al. [2] suggested that Tc(VII) reduction by magnetite resulted in the precipitation and surface adsorption of TcO2-like oligomers at pH 9, i.e. close to the pH of magnetite solubility minimum, while reduction at lower pH of 6 7 resulted in a partial incorporation of Tc(VI) in octahedral Fe sites of magnetite [3]. A working hypothesis was that the incorporation happens only at higher magnetite solubility, while the final retention mechanism remains enigmatic. Thus, our investigations are aimed to carry out a systematic approach covering a wide pH range (3 13), initial Tc concentration ([Tc] = µM-mM) and equilibration time (teq = 1 210 days).
The results show that magnetite removes at least 98 % dissolved Tc. To characterize the molecular geometry of the Tc vicinity, mainly X-ray absorption spectroscopy (XAS) has been used. XANES analysis reveals the predominance of Tc(IV) at all evaluated pH values, supporting that reductive Tc immobilization is the main retention mechanism. A detailed EXAFS analysis with different preparation methods (sorption, coprecipitation, Fe(II)-recrystallization) is currently underway to elucidate the molecular structure of the retained Tc species.
We thank the German Federal Ministry of Economic Affairs and Energy (BMWi) for funding the KRIMI project (02NUK056C).
[1] A.H. Meena, Y. Arai, ENVIRONMENTAL CHEMISTRY LETTERS, 2017, 15, 241.
[2] E. Yalcintas et al., DALTON TRANSACTIONS, 2016, 45, 17874.
[3] T. Kobayashi et al., Radiochimica Acta, 2013, 101, 323.

Keywords: Technetium; Magnetite; Nanoparticles; EXAFS

Related publications

  • Open Access Logo Poster (Online presentation)
    Goldschmidt 2022, 10.-15.07.2022, Honolulu, USA
  • Open Access Logo Poster
    ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France

Publ.-Id: 34359

Data publication: Density functionals with spin-density accuracy for open shells

Callow, T. J.; Pearce, B.
Supervisor: Gidopoulos, Nikitas

Data for the figures of the main paper ( and supplementary information, arranged by figure number.

- A few energies are given as identically zero. These are not actually zero but did not converge.
- All data is given in the units in which it appears in the paper, and columns are labelled using the same notation as in the paper.

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Publ.-Id: 34357

Ab initio modelling of magnetite surfaces for radionuclide retention

Katheras, A.; Karalis, K.; Bucher, A.; Krack, M.; Scheinost, A.; Churakov, S. V.

Thick steel casks are used for radioactive waste disposal in deep geological repositories. However, it is expected that steel corrodes over time. The corrosion products are expected to form mixed iron oxides, mainly magnetite. After tens of thousands of years, casks may breach allowing leaching of the radiotoxic elements, such as plutonium and technetium, by host rock pore-water. The dissolved radionuclides can then interact with the steel corrosion products and be adsorbed or incorporated into the solids [1]. But since these interaction mechanisms are poorly understood at the atomistic scale, our goal is to better understand them by using computer simulations alongside experiments [2].
In this computational study we identified the dominant low index surfaces on nano-magnetite particles and their termination at the relevant conditions based on Kohn-Sham density functional theory (DFT). This was done using the open source CP2K code and, for highly correlated chemical elements such as iron or plutonium, utilizing the DFT+U method because of the highly localized d and f electrons. The U parameter was determined by comparing experimental cell constants and band gaps to our result [3]. With this revised model, we examined the preferential magnetite crystal orientation plane (111) with different surface terminations as a function of oxygen and water fugacity. Based on our modelling, we found the most stable magnetite (111) surfaces under real repository conditions being Fe_oct1-O-H and Fe_tet1-O-H. Further, we used classical and ab initio MD simulations to investigate the behaviour of radionuclides at the water-magnetite interface in deep geological repositories.
[1] Dumas, T.; Fellhauer, D.; Schild, D.; Gaona, X.; Altmaier, M.; Scheinost, A. C. Plutonium Retention Mechanisms by Magnetite Under Anoxic Conditions: Entrapment Versus Sorption. ACS Earth and Space Chemistry 2019, 3 (10), 2197–2206.
[2] Yalçıntaş, E.; Scheinost, A. C.; Gaona, X.; Altmaier, M. Systematic XAS Study on the Reduction and Uptake of Tc by Magnetite and Mackinawite. Dalton Transactions 2016, 45 (44), 17874–17885.
[3] Kéri, A.; Dähn, R.; Krack, M.; Churakov, S. V. Combined XAFS Spectroscopy and Ab Initio Study on the Characterization of Iron Incorporation by Montmorillonite. Environmental Science & Technology 2017, 51 (18), 10585–10594.

Keywords: Magnetite; nuclear waste repository; EXAFS; DFT

Related publications

  • Lecture (Conference)
    Goldschmidt 2022, 08.-15.07.2022, Honolulu, USA
  • Lecture (Conference)
    Actinides revisited 2022, 21.-23.09.2022, Dresden, Germany
  • Lecture (Conference)
    Clay Conference 2022 (8th International Conference on clays in natural and engineered barriers for radioactive waste confinement), 13.-16.06.2022, Nancy, France
  • Lecture (Conference)
    ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France
  • Poster
    PACS Conference 2023, 26.-28.06.2023, Davos, Switzerland
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    Goldschmidt Conference 2023, 09.-14.07.2023, Lyon, France

Publ.-Id: 34356

Metal sorption on clay minerals aiming at the geological storage of nuclear wastes

Di Lorenzo, F.; Stotskyi, V.; Scheinost, A.; Lanson, M.; Lanson, B.; Churakov, S. V.; Marques Fernandes, M.

The design of a nuclear waste repository is a challenging technological entreprise. The reasons are intrinsically related to the nature of the problem: the storage of a variety of radioactive materials for a period longer than human history. The potential consequences of a repository failure are dramatic because they lead to high environmental impact and economical costs of remediation [1]. Repository implementation should therefore rely on deep process understanding and intrinsic passive safety of geological systems. Modern approaches to the geological storage of nuclear wastes deal with a careful site selection and a multi-barrier system. The Swiss waste disposal program is currently in the final stage of the site selection process. Three geological location identified as potential disposal sites are located in Opalinus Clay formations. The multi-barrier disposal concept is heavily relying on the physical and chemical properties of clay minerals, in particular, their interaction with radionuclides [2].
The minerals clays of interest (illite and montmorillonite) were studied over years to derive empirically the sorption properties necessary for the safety assessments. Natural systems are heterogeneous in terms of mineralogical and chemical composition. The experimental studies are limited to a finite number of scenarios, simplified chemistry and short timescale. A mechanistic description of the sorption processes is necessary to transfer the data obtained from simplified reference systems to complex natural environments using computational models based on physical and chemical process understanding. A synthetic clay, saponite, was selected as the customizable and chemically pure starting material. Sorption experiments were carried out to obtain sorption isotherms for a divalent transition metal (nickel) and a trivalent lanthanide (lutetium). The mechanistic information about the sorption processes was achieved by X-ray spectroscopy techniques that have been carried out at the Rossendorf Beamline at the European Synchrotron Radiation Facility. The spectroscopic data are interpreted with help of ab initio molecular dynamics simulations.


[1] Ilg, P., Gabbert S. and Weikard, H.P. Nuclear Waste Management under Approaching Disaster: A Comparison of Decommissioning Strategies for the German Repository Asse II. Risk Analysis 2017, 37, 7, 1213-1232.
[2] Churakov, S.V., Hummel, W. and Marques Fernandes, M. Fundamental Research on Radiochemistry of Geological Nuclear Waste Disposal. Chimia 2020, 74, 1000-1009.

Keywords: clays; nuclear waste repository; Switzerland; nickel; lutetium

Related publications

  • Lecture (Conference)
    Goldschmidt Conference 2022, 10.-15.07.2022, Honolulu, USA
  • Invited lecture (Conferences) (Online presentation)
    ROBL-Workshop, 25.01.2023, Dresden, Germany

Publ.-Id: 34355

Data Publication: What is the speed limit of martensitic transformations?

Schwabe, S.; Lünser, K.; Schmidt, D.; Nielsch, K.; Gaal, P.; Fähler, S.

Measured synchrotron data and calculated thermal evaluation during irradiation with the laser pulse.

Keywords: Syncrotron data; calculated thermal evaluation

Related publications


Publ.-Id: 34354

DNA and RNA, Electronic and electric properties

Erbe, A.

DNA and RNA offer fascinating possibilities for the self-organisation of complex patterns, which can be used in various combinations.
Since this self-organisation occurs at the nanometer scale, it can possibly offer ways for the creation of nanooptical or nanoelectronic devices.
Therefore, the quest for conductivity of DNA or RNA has inspired a vast amount of experiments which have led to a large number of diverse results.
In the recent past, a coherent picture has emerged which describes charge transport along DNA or RNA in various environments.
Based on this, electronic applications of these biomolecules have been developed.

Keywords: DNA; RNA; nanoelectronics; electronic properties

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Publ.-Id: 34353

Fine-scale variation in the effect of national border on COVID-19 spread: A case study of the Saxon-Czech border region

Mertel, A.; Vyskocil, J.; Schüler, L.; Schlechte-Welnicz, W.; Calabrese, J.

The global extent and temporally asynchronous pattern of COVID-19 spread have repeatedly highlighted the role of international borders in the fight against the pandemic. Additionally, the deluge of high resolution, spatially referenced epidemiological data generated by the pandemic provides new opportunities to study disease transmission at heretofore inaccessible scales. Existing studies of cross-border infection fluxes, for both COVID-19 and other diseases, have largely focused on characterizing overall border effects. Here, we couple fine-scale incidence data with localized regression models to quantify spatial variation in the inhibitory effect of an international border. We take as a case study the border region between the German state of Saxony and the neighboring regions in northwestern Czechia, where municipality-level COVID-19 incidence data are available on both sides of the border. Consistent with past studies, we find an overall inhibitory effect of the border, but with a clear asymmetry, where the inhibitory effect is stronger from Saxony to Czechia than vice versa. Furthermore, we identify marked spatial variation along the border in the degree to which disease spread was inhibited. In particular, the area around Löbau in Saxony appears to have been a hotspot for cross-border disease transmission. The ability to identify infection flux hotspots along international borders may help to tailor monitoring programs and response measures to more effectively limit disease spread.

Keywords: COVID-19; spatial epidemiological modeling; regression model; border effect

Publ.-Id: 34352

Dataset for Bubble identification from images with machine learning methods

Heßenkemper, H.; Starke, S.; Atassi, Y.; Ziegenhein, T.; Lucas, D.

This dataset contains the annotated training images and synthetic test images for the publication "Bubble identification from images with machine learning methods".

Related publications


Publ.-Id: 34351

Bubble identification from images with machine learning methods

Heßenkemper, H.; Starke, S.; Atassi, Y.; Ziegenhein, T.; Lucas, D.

An automated and reliable processing of bubbly flow images is highly needed to analyse large data sets of comprehensive experimental series. A particular difficulty arises due to overlapping bubble projections in recorded images, which highly complicates the identification of individual bubbles. Recent approaches focus on the use of deep learning algorithms for this task and have already proven the high potential of such techniques. The main difficulties are the capability to handle different image conditions, higher gas volume fractions and a proper reconstruction of the hidden segment of a partly occluded
bubble. In the present work, we try to tackle these points by testing three different methods based on Convolutional Neural Networks (CNN’s) for the two former and two individual approaches that can be used subsequently to address the latter. To validate our methodology, we created test data sets with synthetic images that further demonstrate the capabilities as well as limitations of our combined approach. The generated data, code and trained models are made accessible to facilitate the use as well as further developments in the research field of bubble recognition in experimental images.

Keywords: Bubbly Flows; Deep Learning; Computer Vision; CNN; Semantic Segmentation

Related publications


Publ.-Id: 34350

Software for Bubble identification from images with machine learning methods

Heßenkemper, H.; Starke, S.; Atassi, Y.; Ziegenhein, T.; Lucas, D.

This package contains the software and the trained models described in the publication "Bubble identification from images with machine learning methods". Please refer to the for installation instructions and to the Prediction_demo.ipynb for usage demonstration.


The Prediction_demo.ipynb includes now an example how to prepare the predictions for the tracking algorithm of "Fate of bubble clusters rising in a quiescent liquid". The tracking code can be found here.


Now only tensorflow models are used, so no MXNet installation required.

Keywords: Bubbly flows; Deep Learning; Computer Vision; CNN; Semantic segmentation

Related publications


Publ.-Id: 34349

Superradiance of Spin Defects in Silicon Carbide for Maser Applications

Gottscholl, A.; Wagenhöfer, M.; Klimmer, M.; Scherbel, S.; Kasper, C.; Baianov, V.; Astakhov, G.; Dyakonov, V.; Sperlich, A.

Masers as telecommunication amplifiers have been known for decades, yet their application is strongly limited due to extreme operating conditions requiring vacuum techniques and cryogenic temperatures. Recently, a new generation of masers has been invented based on optically pumped spin states in pentacene and diamond. In this study, we pave the way for masers based on spin S = 3/2 silicon vacancy (VSi) defects in silicon carbide (SiC) to overcome the microwave generation threshold and discuss the advantages of this highly developed spin hosting material. To achieve population inversion, we optically pump the VSi into their mS = ±1/2 spin sub-states and additionally tune the Zeeman energy splitting by applying an external magnetic field. In this way, the prerequisites for stimulated emission by means of resonant microwaves in the 10 GHz range are fulfilled. On the way to realising a maser, we were able to systematically solve a series of subtasks that improved the underlying relevant physical parameters of the SiC samples. Among others, we investigated the pump efficiency as a function of the optical excitation wavelength and the angle between the magnetic field and the defect symmetry axis in order to boost the population inversion factor, a key figure of merit for the targeted microwave oscillator. Furthermore, we developed a high-Q sapphire microwave resonator (Q 10^4 – 10^5) with which we find indications of superradiant stimulated microwave emission. In summary, SiC with optimized spin defect density and thus spin relaxation rates is well on its way of becoming a suitable maser gain material with wide-ranging applications.

Keywords: Quantum technology; Stimulated emission; Population inversion; Spin centers; Silicon carbide

Publ.-Id: 34347

Data publication: Laboratory investigation of tomography-controlled continuous steel casting

Glavinic, I.; Muttakin, I.; Abouelazayem, S.; Blishchik, A.; Stefani, F.; Eckert, S.; Soleimani, M.; Saidani, I.; Hlava, J.; Kenjeres, S.; Wondrak, T.

Dataset containing the raw and post-processed data used for in the associated publication. Scripts for evaluating the data are attached.

Related publications


Publ.-Id: 34346

Positrons in Material Sciences: Intense Beams for Defect Studies and Applications

Wagner, A.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Liedke, M. O.; Krause-Rehberg, R.

The Helmholtz-Center Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. The superconducting electron LINAC ELBE [2] drives a hard X-ray source, which generates positrons through pair production. The high-intensity Mono-energetic Positron Source MePS utilizes moderated positrons with adjustable kinetic energies ranging from 500 eV to 16 keV for depth profiling of defects in thin films. A magnetic beam transport system consisting of a beam chopper, a beam buncher, and a post-accelerator guides the positron beam towards the sample under investigation. Fully digital data processing of positron annihilation lifetime events generates high-quality spectra with timing resolutions down to about 210 ps and count rates in excess of 120 kcps.
The MePS facility is currently complemented by an additional beamline named Apparatus for In-situ Defect Analysis, AIDA-II, where in-situ defect studies are to be performed in a wide temperature range during thin film growth and under ion irradiation. A complimentary but functionally similar setup, AIDA-I, is operated at a 22Na-based mono-energetic continuous positron beam used for in-situ (coincidence) Doppler-broadening positron annihilation spectroscopy experiments. Recent developments figuring the formation and time dynamics of hydrogen-induced vacancies in nickel and niobium and the role of defects in magneto-ionics and ZnO semiconductor films will be presented.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; MePS

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Nuclear Probes for Materials, Medicine and Industry (NPMMI-2022), 04.-05.03.2022, Mumbai, India

Publ.-Id: 34345

Salting-Out of DNA Origami Nanostructures by Ammonium Sulfate

Hanke, M.; Hansen, N.; Ruiping, C.; Grundmeier, G.; Fahmy, K.; Keller, A.

DNA origami technology enables the folding of DNA strands into complex nanoscale shapes whose properties and interactions with molecular species often deviate significantly from that of genomic DNA. Here, we investigate the salting-out of different DNA origami shapes by the kosmotropic salt ammonium sulfate that is routinely employed in protein precipitation. We find that centrifugation in the presence of 3 M ammonium sulfate results in notable precipitation of DNA origami nanostructures but not of double-stranded genomic DNA. The precipitated DNA origami nanostructures can be resuspended in ammonium sulfate-free buffer without apparent formation of aggregates or loss of structural integrity. Even though quasi-1D six-helix bundle DNA origami are slightly less susceptible toward salting-out than more compact DNA origami triangles and 24-helix bundles, precipitation and recovery yields appear to be mostly independent of DNA origami shape and superstructure. Exploiting the specificity of ammonium sulfate salting-out for DNA origami nanostructures, we further apply this method to separate DNA origami triangles from genomic DNA fragments in a complex mixture. Our results thus demonstrate the possibility of concentrating and purifying DNA origami nanostructures by ammonium sulfate-induced salting-out.

Keywords: DNA origami; DNA nanotechnology; ammonium sulfate; precipitation; salting-out

Publ.-Id: 34343

Data for case studies about estimating measurement uncertainties

Pospiech, S.

These data are supplementary material for the publication "Uncertainty Estimation for Measurement Data - A Practical Guide for Earth Scientists" in the journal Geostandards and Geoanalytical Research.

Data have uncertainties. Including a good estimate of the uncertainties for data analysis might significantly change the data interpretation. Therefore, high data quality is characterized by good accuracy of measurement results, but equally important by a good estimation of data uncertainty, which includes all relevant sources of dispersion of a measurement procedure. These data are example data sets for two case studies using uncertainty models based on replicated measurements. The case studies demonstrate how the models can be parameterized by using measurement data. The case studies are accompanied by code examples for the statistical programming language R.


Publ.-Id: 34342

Stacking polymorphism in PtSe2 drastically affects its electromechanical properties

Kempt, R.; Lukas, S.; Hartwig, O.; Prechtl, M.; Kuc, A. B.; Brumme, T.; Li, S.; Neumaier, D.; Lemme, M. C.; Duesberg, G. S.; Heine, T.

PtSe2 is one of the most promising materials for the next generation of piezoresistive sensors. However, the large-scale synthesis of homogeneous thin films with reproducible electromechanical properties is challenging due to polycrystallinity. We show that stacking phases other than the 1T phase become thermodynamically available at elevated temperatures that are common during synthesis. We show that these phases can make up a significant fraction in a polycrystalline thin film and discuss methods to characterize them, including their Seebeck coefficients. Lastly, we estimate their gauge factors, which vary strongly and heavily impact the performance of a nanoelectromechanical device.

Publ.-Id: 34341

Stochastic Modelling of Mineral Exploration Targets

Talebi, H.; Mueller, U.; Peeters, L. J. M.; Otto, A.; de Caritat, P.; Tolosana Delgado, R.; van den Boogaart, K. G.

Mineral deposits are metal enrichment anomalies, occurring as local manifestations of the interplay between various geological processes that operate at a wide range of temporal and spatial scales. Mineral prospectivity maps are generated by integrating several proxy maps that represent critical geological processes in a mineral system conceptual model. The derivation of mineral prospectivity maps is subject to several types of uncertainty, including systematic (inadequate knowledge of mineralisation processes), stochastic (incomplete geoscience data), and model uncertainty (multiple choices for predictive models and their parameters). Traditional approaches to mineral prospectivity mapping often fail to fully appreciate different sources of uncertainty and spatiotemporal interdependencies between proxy maps associated with the mineral system components. Therefore, these traditional approaches are biased and understate the overall uncertainty. For instance, spatial proxies are mapped using univariate deterministic approaches that ignore stochastic uncertainty and spatial dependencies (i.e., auto- and cross-correlations). This study presents a multivariate stochastic model for prediction and uncertainty quantification of mineral exploration targets by combining multivariate geostatistical simulations and spatial machine learning algorithms. The spatial machine learning algorithm used in the stochastic model is a spatially aware random forests algorithm based on higher-order spatial statistics. It is demonstrated that the proposed approach can detect intrinsic heterogeneity, spatial interdependencies, and complex spatial patterns in proxy maps that are related to the mineralisation type of interest. The approach is illustrated using a synthetic case study with multiple geochemical, geophysical, and lithological attributes.

Keywords: Geostatistical learning; Machine learning; Mineral prospectivity mapping; Spatial data; Spatial predictive model; Uncertainty quantification

Publ.-Id: 34340

Reaction cross sections 54Fe(n,γ)55Fe and 35Cl(n,γ)36Cl at keV neutron energies investigated by Accelerator Mass Spectrometry

Slavkovska, Z.; Wallner, A.; Reifarth, R.; Bott, L.; Brückner, B.; Erbacher, P.; Fifield, K.; Froehlich, M.; Göbel, K.; Al-Khasawneh, K.; Koll, D.; Lachner, J.; Merchel, S.; Pavetich, S.; Reich, M.; Rugel, G.; Thomas, B.; Tims, S. G.; Volknandt, M.; Weigand, M.

Typical neutron energies for the astrophysical s-process follow the Maxwell-Boltzmann distribution in the keV energy range. Neutron capture cross sections highly relevant for modelling the s-process can be experimentally determined by using the Time-of-Flight (ToF) method [1] or by the activation technique. If the reaction product is a long-lived radionuclide (t1/2 ~ yr -100 Myr), the cross section can be determined by activation with a quasi-stellar neutron distribution (typically kT = 25 keV) and a subsequent accelerator mass spectrometry (AMS) measurement of the reaction product [2]. Comparison of a number of such neutron capture cross sections shows a systematic bias, i.e. AMS data being lower than the ToF data [3, 4].

To investigate this discrepancy, we repeated experiments for two reactions that allow for highly precise AMS data: Maxwellian-averaged cross sections for the reactions 54Fe(n,γ)55Fe and 35Cl(n,γ)36Cl were investigated with dedicated activations at the Frankfurt Neutron Source (FRANZ) in Germany [5] and AMS measurements at two independent facilities. Analogously to previous activations, a quasi-stellar neutron spectrum of kT = 25 keV was produced via the 7Li(p,n) reaction, but at a different neutron-producing facility. Furthermore, to complement existing ToF and AMS data, an additional neutron activation of 54Fe and 35Cl at a proton energy of 2 MeV was performed, yielding data in the not-yet explored kT = 90 keV region.

The irradiated metallic Fe foil and NaCl pellet (both of natural isotopic composition) were chemically processed and converted to AMS targets (Fe2O3 and AgCl) together with non-irradiated blanks. The subsequent AMS measurements of both radionuclides, 36Cl and 55Fe, were performed at two complementary AMS facilities, the Heavy Ion Accelerator Facility (HIAF) at the Australian National University [6] and at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany [7]. AMS allows a direct measurement of the 55Fe/54Fe and 36Cl/35Cl conversion ratios that result from the irradiation. The cross section is then deduced from the isotope ratio and the neutron fluence, which is determined using Au monitor foils.

The new experiment was designed to produce highly accurate data and, owing to the two independent AMS measurements, it minimizes unrecognized sources of uncertainties in the AMS technique. The new preliminary data obtained in this work seem to confirm the previous AMS results. Consequently, the systematic discrepancy between AMS and ToF data remains unresolved.

[1] Guber, K.H., et al., Phys. Rev. C 65, 058801 (2002).
[2] Györky, Gy., et al., Eur. Phys. J. A 55, 41 (2019).
[3] Capote, R., et al., Nucl. Data Sheets 163 (2020): 191.
[4] Slavkovská, Z., et al., EPJ Web Conf. Vol. 232, p.02005, EDP Sciences, 2020.
[5] Reifarth, R., et al., Publ. Astron. Soc. Aust. 26.3 (2009): 255.
[6] Fifield, L.K., et al. Nucl. Instr. Meth. B: 268 (2010): 858.
[7] Rugel, G., et al., Nucl. Instr. and Meth. in Phys. Res. B 370 (2016) 94.

Keywords: AMS

Related publications


Publ.-Id: 34339

Data publication: First-principles derivation and properties of density-functional average-atom models

Callow, T. J.; Hansen, S. B.; Kraisler, E.; Cangi, A.

Data for the pre-print "First-principles derivation and properties of density-functional average-atom models",

Each data folder is named according to the corresponding figure in the paper. For any questions, please contact the authors.

Related publications

Publ.-Id: 34337

Metadatamanagement - How to make your data FAIR

Schaller, T.; Steinmeier, L.; Rau, F.

The necessity of exhaustive documentation of research data arises from an increasing depth of scientific understanding and investigations of unknown phenomena with research teams of different areas and fields. Different methods and definitions and insufficient documentation of field work, experimental and numerical examinations lead to information loss, especially over time. To counteract this problem the scientific community aims to make research data Findable, Accessible, Interoperable and Reusable (FAIR). Unfortunately infrastructure, tools, personnel and acceptability for these additional steps are often missing and result in the mentioned paucity of information and data. Within the Helmholtz Association the Helmholtz Metadata Collaboration (HMC) has taken on the task of building this infrastructure to support high quality data documentation and publication throughout the entire lifecycle of research data and to raise the awareness for necessary structural changes in the wider scientific community.
One goal of HMC is the mapping of existing data management structures and demands in the different research fields of the Helmholtz Community. These fields are especially addressed with Hubs, being the connection between HMC and the specific needs of the research fields. Based on the collected information HMC will implement tools to assist scientists, data managers and IT administrators in making their research data FAIR. Furthermore members of HMC will connect with other (meta-)data initiatives to work towards necessary structural changes in the world of scientific research by e.g. defining standards.
In this poster we will discuss the FAIR principles and introduce the Helmholtz Metadata Collaboration and their tasks. Also, we will show concrete examples from the geoscientific part of Hub Energy. The Hub in which we are active.

Keywords: FAIR; Metadata; Helmholtz Metadata Collaboration; Deutsche Geophysikalische Gesellschaft

  • Poster (Online presentation)
    Jahrestagung der Deutschen Geophysikalischen Gesellschaft, 07.-10.03.2022, München, Deutschland

Publ.-Id: 34336

Complexation studies of Eu(III) with NTA at high ionic strengths

Sieber, C.; Kretzschmar, J.; Schmeide, K.; Stumpf, T.

Radionuclide speciation inside long-term radioactive waste repositories needs to be understood in order to ensure effective containment of the waste. Organic ligands originating from the degradation of organic components inside such a repository can possibly affect the mobility of radionuclides in solution. The present study focuses on nitrilotriacetic acid, NTA, as a model molecule and europium, Eu(III), as a nonradioactive analog with outstanding luminescence and magnetic properties.
The complexation of NTA with Eu(III) (in ratios of 1:2 and 1:1 Eu:NTA) as a function of pH was studied using nuclear magnetic resonance (NMR) spectroscopy in 1 M NaCl D2O solution. The 1H and 13C NMR spectra of the NTA solutions with Eu(III) show clearly distinguishable signals for the free NTA and two Eu-NTA complexes, which is indicative of a 1:1 and a 1:2 Eu-NTA complex. The interaction of Eu(III) with NTA is relatively strong and favors the 1:2 Eu-NTA complex even in solution containing 1:1 Eu-NTA ratio, unless in very acidic solutions.
As a repository relevant cationic groundwater components, the influence of Ca(II) and Al(III) on Eu(III) complexation is studied in detail.
A combination of NMR spectroscopy and time-resolved laser-induced fluorescence spectroscopy yields qualitative and quantitative information on the coordination environment from the ligand’s and the metal ion’s perspective, respectively. In subsequent studies focusing on ternary systems comprising repository relevant solid phases, radionuclides and organic ligands this will allow the identification of radionuclide speciation in solution and their sorption to solid phases.
Acknowledgement: The German Federal Ministry for Economic Affairs and Energy (BMWi) is thanked for financial support within the GRaZ II project, no. 02E11860B.

Keywords: europium; nitrilotriacetic acid; nuclear magnetic resonance

  • Poster
    19th Radiochemical Conference (RadChem), 15.-20.05.2022, Mariánské Lázně, Tschechische Republik

Publ.-Id: 34333

What is the speed limit of martensitic transformations?

Schwabe, S.; Lünser, K.; Schmidt, D.; Nielsch, K.; Gaal, P.; Fähler, S.

Structural martensitic transformations enable various applications, which range from high stroke actuation and sensing to energy efficient magnetocaloric refrigeration and thermomagnetic energy harvesting. All these emerging applications benefit from a fast transformation, but up to now the speed limit of martensitic transformations has not been explored. Here, we demonstrate that a martensite to austenite transformation can be completed in under ten nanoseconds. We heat an epitaxial Ni-Mn-Ga film with a laser pulse and use synchrotron diffraction to probe the influence of initial sample temperature and overheating on transformation rate and ratio. We demonstrate that an increase of thermal energy drives this transformation faster. Though the observed speed limit of 2.5 x 10^27 (Js)^-1 per unit cell leaves plenty of room for a further acceleration of applications, our analysis reveals that the practical limit will be the energy required for switching. Our experiments unveil that martensitic transformations obey similar speed limits as in microelectronics, which are expressed by the Margolus–Levitin theorem.

Keywords: Martensitic Transformations; Time dependency; Syncrotron Diffraction

Related publications

Publ.-Id: 34330

One-step synthesis of the hydrophobic conical Co-Fe structures – the comparison of their active areas and electrocatalytic properties

Skibińska, K.; Kornaus, K.; Yang, X.; Kutyła, D.; Wojnicki, M.; Żabiński, P.

Enhancement of the surface of the catalyst is desirable in the interest of mass transport maximizing. However, without a well-defined method of determination of its active surface, catalyst deposited with different conditions cannot be accurately compared. In this work, Co-Fe alloy cones were synthesized from the electrolyte containing ammonium chloride as a crystal modifier. It controls the direction of the deposit growth, and consequently, develops the active surface area. Moreover, the influence of the direction of the applied magnetic field on the ferromagnetic Co-Fe alloy was investigated. It affected noticeably the morphology and composition of layers and therefore, the catalytic activity of the samples in the Hydrogen Evolution Reaction (HER). Linear Sweep Voltammetry (LSV) measurements were used to test the catalytic activity in 1 M NaOH electrolyte. The expected development of the real active surface area was determined using two different methods: Brunauer-Emmett-Teller (BET) and Helmholtz Double-Layer Capacitance (DLC). Results show that no specific value of the sample surface multiplication can be found based on these methods. All conical structures were hydrophobic.

Keywords: Co-Fe cones; crystal modifier; magnetic field; hydrogen evolution reaction; active surface area

Publ.-Id: 34329

From License Consultation to Software Spotlights

Konrad, U.; Meeßen, C.; Hammitzsch, M.; Huste, T.; Jandt, U.

Presentation to the session: "Reproducible Science - Research Data and Research Software in Interaction" - "Reproduzierbare Wissenschaft – Forschungsdaten und Research Software im Zusammenspiel".
Reproducibility is a prerequisite for open science, but results must also be reusable in accordance with FAIR principles, and this applies in particular to research software! But how can research software, even if it is developed in open source projects, be made known to a broad user community? And how can better visibility and recognition be achieved for the developers of successful software solutions?
A new approach is currently being implemented in the Helmholtz Association. First of all, the necessary database is being created by building up a software directory as automatically as possible on the basis of standardised metadata. By evaluating these entries, successful solutions will be marked and prepared for a broad community. Finally, the best software products will be published in a "Software Flagship Store" and offered to a broad community.

Keywords: Research Software Engineering; Software License; HIFIS; Cloud Services; Software Development; Software Entwicklung; Forschungssoftware; Lizenzen; Helmholtz Federated IT Services

  • Open Access Logo Lecture (Conference) (Online presentation)
    RDA Deutschland Tagung 2022, 21.-25.02.2022, virtuell, Deutschland
    DOI: 10.5281/zenodo.6248895

Publ.-Id: 34327

Estimating individual uncertainties – making use of all your replicate analysis

Pospiech, S.; van den Boogaart, K. G.; Renno, A.; Möckel, R.; Fahlbusch, W.

High data quality is characterized by good accuracy of measurement results but equally important by a good estimation of data uncertainty (JCGM 100:2008). Using a good estimate of the uncertainty for data analysis might significantly change the data interpretation: Ignoring or underestimating uncertainties projects too high confidence into the measurand values, while overestimation of uncertainties could blur relevant information in the data. The information carried by the data can be exploited best, if the measurement result would be reported as original (not rounded) number accompanied by the values of the measurement uncertainty (Eggen, et al. 2019). This requires methods to calculate or estimate uncertainties for each analytical datum. Including uncertainties as separate values into the data interpretation is especially important if the data set has individual uncertainties, i.e., every data point has a its ‘own’ uncertainty.

Earth scientists need a method of estimating individual uncertainties based on a few multiple measurements. This method should consider the sample materials' characteristics for which the uncertainty should be assessed, e.g. range of potential measurand values, variability in sample material and heterogeneities. It should also allow to model several sources of uncertainties to account for the multi-step measurement procedure. And last but not least, the method should remain affordable and practical, e.g. the method should also be applicable if samples are send to external laboratories.

In this contribution, we present a method to quantify individual uncertainties with respect to the analyte level (Ellison and Williams 2012)[Annex E.5], including uncertainty model component which allows to model Poisson type error, e.g. due to heterogeneities which are typical for samples in the geosciences. Case studies and examples in data science languages are presented to facilitate the implementation.

Keywords: uncertainty; uncertainty estimation; analytics; measurement data; R-package

  • Open Access Logo Lecture (Conference)
    Geoanalysis 2022, 06.-12.08.2022, Freiberg, Germany


Publ.-Id: 34323

A comprehensive study on the interaction of Eu(III) and U(VI) with plant cells (Daucus carota) in suspension

Jessat, J.; Moll, H.; John, W.; Bilke, M.-L.; Hübner, R.; Kretzschmar, J.; Steudtner, R.; Drobot, B.; Stumpf, T.; Sachs, S.

Daucus carota suspension cells showed a high affinity towards Eu(III) and U(VI) based on a single-step bioassociation process with an equilibrium after 48 to 72 h. Cells responded with an increased metabolic activity towards heavy metal stress. Luminescence spectroscopy pointed to multiple species for both heavy metals in the culture media, providing initial hints of their interaction with cells and released metabolites. Using nuclear magnetic resonance spectroscopy, we could prove that malate, as an released metabolite in the culture medium, was found to complex with U. Luminescence spectroscopy also showed that Eu(III)-EDTA species are interacting with the cells. Furthermore, Eu(III) and U(VI) coordination is dominated by phosphate groups provided by the cells. We found that Ca ion channels of D. carota cells were involved in the uptake of U(VI), which led to a bioprecipitation of U(VI) in the vacuole of the cells, most probably as uranyl(VI) phosphates along with an intracellular sorption of U(VI) on biomembranes by lipid structures. Eu(III) could be found locally concentrated in the cell wall and in the cytoplasm with a co-localization with phosphorous and oxygen.

Keywords: actinides; lanthanides; luminescence spectroscopy; malate; mobilization


  • Secondary publication expected

Publ.-Id: 34322

Charge-density reduction promotes ribozyme activity in RNA–peptide coacervates via RNA fluidization and magnesium partitioning

Iglesias-Artola, J. M.; Drobot, B.; Kar, M.; Fritsch, A. W.; Mutschler, H.; Dora Tang, T.-Y.; Kreysing, M.

It has long been proposed that phase-separated compartments can provide a basis for the formation of cellular precursors in prebiotic environments. However, we know very little about the properties of coacervates formed from simple peptides, their compatibility with ribozymes or their functional significance. Here we assess the conditions under which functional ribozymes form coacervates with simple peptides. We find coacervation to be most robust when transitioning from long homopeptides to shorter, more pre-biologically plausible heteropeptides. We mechanistically show that these RNA–peptide coacervates display peptide-dependent material properties and cofactor concentrations. We find that the interspacing of cationic and neutral amino acids increases RNA mobility, and we use isothermal calorimetry to reveal sequence-dependent Mg2+ partitioning, two critical factors that together enable ribozyme activity. Our results establish how peptides of limited length, homogeneity and charge density facilitate the compartmentalization of active ribozymes into non-gelating, magnesium-rich coacervates, a scenario that could be applicable to cellular precursors with peptide-dependent functional phenotypes.

Keywords: Ribozyme; Coacervates; Origin of llife


Publ.-Id: 34321

Cosmogenic nuclide rates and (U,Th)-He dates of denudation in the eastern Great Escarpment, South Africa

Makhubela, T. V.; Kramers, J. D.; Konyana, S. M.; van Niekerk, H. S.; Winkler, S.

In Southern Africa, cosmogenic nuclides have been used during the past two decades in determining the denudation rates, exposure dates, and burial dates of surfaces, soils, and deposits. That work has focused on the Great Escarpment in the semi-arid to arid western segment in Namibia and the humid south and southeast segments in South Africa (Makhubela et al., 2021a). We present the first cosmogenic beryllium-10 (10Be) denudation rates and uranium-thorium-helium ((U,Th)-He) dates in the very humid eastern segment of the Great escarpment in South Africa (Makhubela et al., 2021b). The 10Be denudation rates were obtained from river sediments and bedrock outcrops (2.7 – 14.1 m/Ma and 1.8 – 24 m/Ma, respectively), and they are similar in range to the values determined from the other segments of the Great Escarpment. These denudation rates are positively correlated with mean annual precipitation above 800 mm/yr, but the similarity of the denudation rates across the segments of the escarpment with different climates suggests that topography is the main driver of denudation. The (U,Th)-He dates were determined on pedogenic goethite concretions in oxisols at Graskop near the escarpment edge, using a new approach that incorporates helium data into U/Th disequilibrium dating. The ages range from 0.85 Ma to 1.05 Ma, documenting a long soil residence time. They coincide with the Mid-Pleistocene Transition and appear to indicate the last period of intensive chemical weathering on the eastern escarpment, when the climate of the region changed from wet to dry conditions whichthat lasted for ca. 600 kyr before the present humidification (Caley et al., 2018). Our results demonstrate that the combination of cosmogenic nuclides and U-series offer a novel way of dating and quantifying Earth surface processes in the context of past climate changes.
Caley, T., et al., 2018. Nature, 560, 76-79.
Makhubela, T. V., et al., 2021a. South African Geographical Journal, 103(1), 99-118.
Makhubela, T. V., et al., 2021b. Chemical Geology, 580, 120368.

  • Poster
    Goldschmidt 2022 Conference, 10.-15.07.2022, Honolulu, Hawaiʻi, USA

Publ.-Id: 34320

Uranium(VI) retention by calcium aluminosilicate hydrates (C-A-S-H) – Impact of temperature, ionic strength, and organic ligands

Schmeide, K.; Huittinen, N. M.; Shams Aldin Azzam, S.; Brendler, E.; Kretzschmar, J.

Concepts for the safe disposal of high-level radioactive waste in deep geological formations to ensure isolation from the biosphere are based on a multi-barrier system. Cementitious materials are one component of the geotechnical barrier, used as backfill material, for borehole sealing and to enforce the mechanical stability of tunnels. Calcium silicate hydrate (C-S-H), the principal binding phase of conventional concrete, is known to provide a high sorption capacity for trivalent to hexavalent actinides [1-3]. In modern concretes, Al-containing compounds such as blast furnace slag or fly ash are added, leading to formation of calcium aluminosilicate hydrate (C-A-S-H). To systematically study the influence of Al on both the structure of C-A-S-H phases and their U(VI) retention properties in comparison to C-S-H phases, three series of samples were synthesized in the absence and presence of U(VI). They comprise samples with Ca/Si molar ratios of 0.8, 1.2 and 1.6, representing different alteration stages of concrete, and increasing Al/Si molar ratios of 0, 0.06 and 0.18 within each series. Furthermore, the impact of temperature (25°C, 100°C, 200°C) on the structure of C-A-S-H phases and on the U(VI) retention mechanism was studied. Structural characteristics of the cementitious phases were obtained from powder X-ray diffraction as well as 27Al and 29Si solid-state magic angle spinning nuclear magnetic resonance spectroscopy. Al tetrahedra were identified to occupy bridging positions of the Si chain and cross-linking positions. Enhanced temperatures were found to increase the crystallinity of the material with the appearance of neoformed crystalline phases. U(VI) luminescence spectroscopy was applied to characterize the U(VI) binding. Several U(VI) species (surface-sorbed or C-A-S-H interlayer absorbed) are forming in different amounts, depending on the composition of the C-A-S-H phases.
Finally, to study the stability (or reversibility) of the U(VI) retention by the C-A-S-H phases in the presence of (i) high ionic strength pore waters and (ii) organics originally present as admixtures in cement-based materials, leaching experiments were conducted. In these experiments, simulated pore waters of complex solution composition and solutions containing gluconate as a representative of organic ligands that may be present under repository conditions, respectively, were used. The leaching experiments were conducted over extended timescales of up to 6 months. The results showed a high retention of U(VI) in the C-A-S-H phases under both abovementioned solution conditions. In conclusion, the immobilization of U(VI) by cementitious material via sorption and/or incorporation processes has important positive implications for limiting uranium migration during geological disposal of radioactive waste.

Keywords: C-S-H; C-A-S-H; cement; actinide; uranium; sorption; NMR; TRLFS; XRD; leaching

  • Lecture (Conference)
    RadChem 2022 / 19th Radiochemical Conference, 15.-20.05.2022, Mariánské Lázně, Czech Republic

Publ.-Id: 34317

Enhanced survival of high-risk medulloblastoma-bearing mice after multimodal treatment with radiotherapy, decitabine, and abacavir

Gringmuth, M.; Walther, J.; Greiser, S.; Toussaint, M.; Schwalm, B.; Kool, M.; Kortmann, R.-D.; Glasow, A.; Patties, I.

Children with high-risk SHH/TP53-mut and Group 3 medulloblastoma (MB) have a 5-year overall survival of only 40 %. Innovative approaches to enhance survival while preventing adverse effects are urgently needed. We investigated an innovative therapy approach combining irradiation (RT), decitabine (DEC), and abacavir (ABC) in a patient-derived orthotopic SHH/TP53-mut and Group 3 MB mouse model. MB-bearing mice were treated with DEC, ABC and RT. Mouse survival, tumor growth (BLI, MRT) tumor histology (H/E), proliferation (Ki-67), and endothelial (CD31) staining were analyzed. Gene expression was examined by microarray and RT-PCR (Ki-67, VEGF, CD31, CD15, CD133, nestin, CD68, IBA). The RT/DEC/ABC therapy inhibited tumor growth and enhanced mouse survival. Ki-67 decreased in SHH/TP53-mut MBs after RT, DEC, RT/ABC, and RT/DEC/ABC therapy. CD31 was higher in
SHH/TP53-mut compared to Group 3 MBs and decreased after RT/DEC/ABC. Microarray analyses showed a therapy-induced downregulation of cell cycle genes. By RT-PCR, no therapy-induced effect on stem cell fraction or immune cell invasion/activation could be shown. We showed for the first time that RT/DEC/ABC therapy improves survival of ortothopic SHH/TP53-mut and Group 3 MB-bearing mice without inducing adverse effects suggesting the potential for an adjuvant application of this multimodal therapy approach in the human clinic.

Keywords: medulloblastoma; radiation; decitabine; abacavir; in vivo study; magnetic resonance imaging; T2 mapping; bioluminescence imaging; gene expression microarray

Publ.-Id: 34316

Complexation of Eu(III) in artificial digestive media by aminopolycarboxylic acid EGTA

Friedrich, S.; Holtmann, L.; Kretzschmar, J.; Barkleit, A.; Stumpf, T.

Radionuclides released from nuclear accidents can be widely distributed and even enter the human food chain. If ingested, they interact with the fluids from the digestive system and can cause necrosis or carcinogenesis of human cells. To remove these radionuclides, decorporation agents are used. Clinical approved decorporation agents like ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) that are used against heavy metal poisoning show low oral activity.[1] Therefore, the focus of this work is set on EDTA and DTPA related compound ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA). Europium(III) is used as a non-radioactive analogue for trivalent actinides like americium and curium. The overall goal of the study is to expand the knowledge of processes underlying the interactions of radionuclides in the human digestive system in the presence of decorporation agents on a molecular level. To derive thermodynamic parameters, the Eu-EGTA-system is investigated at different physiological relevant pH values and molar ratios, using time-resolved laser-induced fluorescence spectroscopy (TRLFS), NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and isothermal titration calorimetry (ITC). Between pH 3 and 9 a very stable complex with a Eu(III)-EGTA-ratio of 1:1 is observed and comprehensively characterised from the ligands and metals perspective. Our knowledge on the speciation of Eu(III) in artificial biofluids of the human digestive system is now extended by the impact of EGTA on the speciation to measure the suitability of EGTA as possible decorporation agent for usage in radiation protection.[2] This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant number 02NUK057A and part of the joint project RADEKOR.

[1] P. W. Durbin, Health Phys. 2008, 95, 465.
[2] C. Wilke, A. Barkleit, T. Stumpf, A. Ikeda-Ohno, J. Inorg. Biochem. 2017, 175, 248.

  • Open Access Logo Lecture (Conference)
    19th Radiochemical Conference, 15.-20.05.2022, Marienbad, Tschechien


Publ.-Id: 34315

A scalable pipeline for effective forecast of COVID-19 in Germany, Czechia, and Poland

Abdussalam, W.

We develop a software system for the spatial, temporal, and strategic optimization of the use of tests for SARS-COV-2. We have built an operational data store (ODS) using PostgreSQL to continuously consolidate datasets from multiple data sources, perform collaborative work, facilitate high performance data analysis, and trace changes. The ODS has been built to store the COVID-19 data from Germany, Czechia, and other areas. We have built the schema of metadata which is capable of orderly storing the data from those regions, and is scalable to the entire world. Next, the ODS is populated using batch Extract, Transfer, and Load (ETL) jobs and SQL queries are created which reduce the need for pre-processing data. The data can then support forecasting using a version-controlled Arima and Holt Winter model and other analyses to support decision making. The jobs run at a weekly interval and plan to upgrade to a daily interval. The results are finally displayed as a web app at

  • Open Access Logo Lecture (Conference) (Online presentation)
    Software Engineering 2022, 21.-25.02.2022, Potsdam Online, Germany


Publ.-Id: 34314

From data to model: microstructure aware models for uncertainty estimation of reactive transport in granitoide rocks

Pospiech, S.; Tolosana Delgado, R.; Brendler, V.; Bachmann, K.; Krause, J.; van den Boogaart, K. G.

Safety of nuclear waste repositories in crystalline host rocks depends on realistic predictions of radionuclide migration in undisturbed geologies beyond the geotechnical barrier. There, the fluid migration paths will be - in absence of large scale connectivities like fissures, fault systems and joints - along weakzones like microcracks, alterations and grain boundaries. The retention potential of crystalline rocks is thus not only controlled by its modal mineralogy but also by the (heterogeneous) distribution of mineral grains, e.g. by contact area of different mineral surfaces to migration paths. Until now, reactive transport models assume homogeneous and isotropic distribution of minerals in the host rock. Including the spatial correlation of transport and mineralogy, especially the modal mineralogy along fluid migration paths, would significantly improve the estimation of radionuclide retention potential.
Modelling the microstructures is subject to uncertainties. Such uncertainties can be derived by estimating this spatial co-occurances from measured microstructures. The workflow requires spatially distributed data from analytical methods, which a) provide information about mineral composition including voids and b) allow to detect migrations paths and the mineral surface types with related areas. Here, information from gneissic samples is used to train a structure simulation model. The resulting variability of "accessible" mineral surfaces then allows to derive (by geochemical speciation codes) the variability of contaminant distribution coefficients based on sorption data and pore water composition. Finally, the spatial geological predictions are applied in reactive transport models to calculate the uncertainty of the radionuclide retention within a representative rock volume. In this contribution, we present a workflow from (real) samples to microstructure aware retention models, and discuss challenges of input data uncertainties, how they affect the total uncertainty of the model, and whether these models can be used for upscaling.

Keywords: nuclear waste repository; microstructure modelling; crystalline rock; geostatistics; radionuclide migration; radionuclide retention

  • Open Access Logo Lecture (Conference)
    21st Annual Conference of the International Association for Mathematical Geosciences, 29.08.-03.09.2022, Nancy, France

Publ.-Id: 34313

Energetic Au ion beam implantation of ZnO nanopillars for optical response modulation

Macková, A.; Malinský, P.; Jagerová, A.; Mikšová, R.; Lalik, O.; Nekvindová, P.; Mistrík, J.; Marvan, P.; Sofer, Z.; Holý, V.; Schutter, J. D.; Kentsch, U.; Azarov, A.; Galeckas, A.

Nanopillars of ZnO were implanted with Au-400 keV ions at various ion fluences from 1 × 10¹⁵ cm⁻² to 1 × 10¹⁶ cm⁻² and subsequently annealed at 750 °C for 15 min in order to reduce the implantation damage and to support Au nanoparticle (NP) aggregation. It was found that implantation-induced effects and thermal effects influence the Au NP coalescence as well as the quality of the ZnO nanopillars. Rutherford Back-Scattering spectrometry (RBS) showed the broader Au-depth profiles than it was theoretically predicted, but the Au-concentration maximum agrees well with prediction taking into account the effective ZnO layer density. The implantation at the higher fluences induced the morphology modification of the nanopillar layer evidenced by RBS and scanning electron microscopy (SEM). An indirect evidence of this effect was given by optical ellipsometry due to gradual refractive index changes in the ZnO nanopillars with the increased Au-ion fluence. Optical characterization of the Au-implanted and annealed nanopillars performed by means of photoluminescence (PL) and diffuse-reflectance spectroscopy (DRS) evidenced the surface plasmon resonance (SPR) activity of the embedded Au NPs. The SPR-enhanced scattering and PL emission observed in the spectral range 500–650 nm are ascribed to Au NPs or more complex Au-clusters. In addition, the ellipsometry measurements of extinction coefficient are found to corroborate well results from DRS, both indicating increase of SPR effect with the increase of Au-ion fluence and after the post-annealing.

Keywords: ZnO nanopillars; Au nanoparticles; ion implantation; SPR; doped ZnO nanostructures

Related publications


Publ.-Id: 34312

Spectroscopic investigation of the speciation of uranium(VI) in the biofluids of the human digestive system

Butscher, D.; Barkleit, A.; Stumpf, T.

In case radionuclides (RN) enter the food chain and are incorporated by humans, they pose a possible health risk due to their radio- and chemotoxicity. Therefore, it is necessary to know the biokinetic processes as well as the speciation of the RN after ingestion in order to develop and improve specific methods for their decorporation. When RN are ingested orally, they first come into contact and interact with the biofluids of the digestive tract. However, for most actinides, little is known to date about their speciation and biochemical behavior in the gastrointestinal tract. Therefore, the aim of this study was to investigate the interactions of hexavalent uranium in the digestive steps and respective biofluids in the stomach (saliva and gastric juice) and small intestine (pancreatic juice and bile fluid). The combination of these two segments was also considered. Biofluids and digestive steps were artificially simulated based on human physiology. The chemical speciation of uranium was investigated using cryogenic time-resolved laser-induced fluorescence spectroscopy (cryo-TRLFS) at 153 K. The results were compared with thermodynamic modeling.
The TRLFS experiments show that uranium is predominantly complexed with inorganic ligands, mainly carbonate and to a smaller extent phosphate, as confirmed by thermodynamic modeling. For the organic ligands, only some proteins, e.g. prancreatin, are involved in the speciation to a small extent. Based on this knowledge, specific decorporation agents can be developed and their influence on uranium speciation can be observed using cryo-TRLFS.

  • Lecture (Conference)
    RadChem 2022 / 19th Radiochemical Conference, 15.-20.05.2022, Marianske Lazne, Czech Republic

Publ.-Id: 34311

Data publication: Non-invasive assessment of locally overexpressed human adenosine 2A receptors in the heart of transgenic mice

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Teodoro, R.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Kopka, K.; Boknik, P.; Hofmann, B.; Gergs, U.; Neumann, J.; Brust, P.

PET data, mice; i.v. administration of [18F]FLUDA with and without pre-administration of istradefylline

Keywords: [18F]FLUDA; A2A adenosine receptor; PET; myocardium

Related publications


Publ.-Id: 34310

Compositional Data Analysis of Organizational Culture and Business-IT Alignment

Sieber, M. R.; van den Boogaart, K. G.

This research project examines the relationship between organizational culture and business-
IT alignment. With the Fourth Industrial Revolution and digitalization, this relationship is
changing. IT and its management tend to evolve from a service provider to a value creator. The
research question is about typical management culture characteristics and their contributions to
the strategic alignment to the business of the IT departments, teams, and solution providers.
For answering the research question, this study juxtaposes two four-quadrants models. First,
it applies Cameron and Quinn’s (2011) Competing Values Framework for examining organiza-
tional culture. This model attributes culture to the four types of clan culture, adhocracy culture,
market culture, and hierarchy culture with the dimensions of flexibility vs. stability and an in-
ternal vs. external focus. Similarly, Henderson and Venkatraman’s (1993) Strategic Alignment
Model differs four perspectives for business-IT alignment with the dimensions of functional inte-
gration into IT or business and the strategic fit, i.e., the internal vs. external orientation. These
strategic alignment perspectives and their performance criteria equal a cost center, an investment
center, a profit center, and a service center.
In a survey, respondents had to divide 100 points between four options. For example, the
dominant IT management culture type: is it a clan, adhocracy, market, or hierarchy? The
corresponding ipsative scales originate from the Competing Values Framework and result in
compositional data. After eliminating missing values and imputing zeroes, the analysis calculated
a linear model with the ilr-transformed variables in R with the package compositions. Converting
ilr coefficients into the clr space revealed a variance-/covariance-matrix with the weights of IT
management culture and its alignment as the mapping of clan culture to cost center at 0.05,
adhocracy culture to investment center at 0.13, market culture to profit center at 0.17 and
hierarchy culture to service center at 0.19.

Keywords: Organizational culture; business-IT alignment; Competing Values Framework; Strategic Alignment Model; Compositional Data

  • Poster
    CoDaWork2022, 28.06.-01.07.2022, Toulouse, France

Publ.-Id: 34308

Kinetic Aspects of the Electrochemical Reduction of Uranyl in HCl Solutions

Munoz, A.; Weiß, S.

The interfacial mechanism of uranyl electroreduction at Au-electrodes in HCl solutions was discussed on the light of systematic studies of cyclovoltammetry, normal pulse voltammetry, UV-vis spectroscopy and published electroanalytical research. Voltammetric waves were numerically deconvoluted on the basis of a reaction model consisting of a first masscontrolled, quasi-reversible first electron transfer and a subsequent reduction of interfacial U(V) intermediate species with adsorption of generated U(IV) products. The dependence of the kinetic parameters on [HCl] indicates an electron transfer following an inner-sphere type mechanism assisted by electrosorption of chloride ligands. The interfacial accumulation of chloride exerts a strong electrostatic repulsion of complexed uranyl and a consequent edged drop of electron transfer rates at [HCl] ∼ 0.5 mol l-1. The electron transfer steps are followed by a chemical desorption reaction of the unstable tetravalent uranyl in U(H2O)94+ species. It is shown that the numerical reproduction of voltammetric waves suits as a method for calculating kinetic parameters in multi-steps electrochemical reactions.

Keywords: Cell proliferation; Cyclic voltammetry; Electron transitions; Gold compounds; Reaction intermediates; Interfacial mechanism


Publ.-Id: 34307

A critical review of the solution chemistry, solubility, and thermodynamics of Eu(III)

Jordan, N.; Thoenen, T.; Starke, S.; Spahiu, K.; Brendler, V.

New materials showing specific magnetic and/or electrooptic properties incorporate critical raw materials such as Rare Earth Elements (REE). Due to their very specific technological application, it is necessary to separate the REE from each other and enrich them. The optimization of physico-chemical conditions for the design of effective extraction and recycling processes of REE relies on accurate and reliable thermodynamic data. However, no consolidated and internationally recognized Thermodynamic Database (TDB) is currently available for REE.

Several reviews and reports [1-5] on the aqueous chemistry/geochemistry of europium were published, but had several drawbacks, for example:

→ insufficient transparency about the selection procedure,
→ lack of systematic screening to gather primary literature sources,
→ too high reliance on the analogy with trivalent actinides,
→ for weak complexes such as chloride and nitrate, changes in the activity coefficients due to the replacement of up to 100 % of the background electrolyte anion by Cl− or NO3− was either completely overlooked or, if recognized, not handled properly,
→ too high reliance on the charge analogy for the estimation of missing ion interaction coefficients when the Specific ion Interaction theory (SIT) was applied.

This study aims at significantly improving the situation by carefully addressing all aforementioned issues in order to provide a reliable, robust, and internally consistent TDB for europium. All available primary literature sources for Eu(III) complexation constants and solubility products for the OH−, Cl−, NO3−, PO43−, SO42−, and CO32− inorganic ligands were thoroughly evaluated. This allowed deriving a recommended set of thermodynamic data at infinite dilution and 25 °C using the SIT. Results concerning the chloride, sulfate, and phosphate ligands will be presented [6].

[1] P.L. Brown, C. Ekberg, Hydrolysis of Metal Ions. Vol. 1, Wiley-VCH, Weinheim, 2016.
[2] W. Hummel, et al., Nagra/PSI Chemical Thermodynamic Data Base 01/01, Technical Report 02-16, 2002.
[3] J.A. Rard, Chemical Reviews, 85(6) (1985) 555-582.
[4] K. Spahiu, J. Bruno, A selected thermodynamic database for REE to be used in HLNW performance assessment exercises, SKB Technical Report, 1995.
[5] S.A. Wood, Chemical Geology, 82(1-2) (1990) 159-186.
[6] N. Jordan et al., Coordination Chemistry Review (2022) (under revision).

Keywords: Europium; Thermodynamic database; complexation; solubility; SIT

  • Contribution to proceedings
    Goldschmidt 2022, 10.-15.07.2022, Hawaiʻi, USA
  • Lecture (Conference) (Online presentation)
    Goldschmidt 2022, 10.-15.07.2022, Hawaiʻi, USA

Publ.-Id: 34305

Growth factor receptor and β1 integrin signaling differentially regulate basal clonogenicity and radiation survival of fibroblasts via a modulation of cell cycling

Vehlow, A.; Cordes, N.

Cell adhesion to extracellular matrix proteins mediates resistance to radio- and chemotherapy by activating integrin signal-
ing. In addition, mutual and cooperative interactions between integrin and growth factor receptor signaling contribute to
the cellular radiation response. Here, we investigate to which extend the crosstalk between β1 integrins and growth factor
receptor signaling determines the cellular radiation response of fibroblasts by assessing clonogenic survival and cell cycling.
By utilizing growth factor signaling competent and either β1 integrin wildtype GD25β1A fibroblasts or β1 integrin mutant,
signaling incompetent GD25β1B fibroblasts, we show basal clonogenic survival to depend on growth factor receptor but not
integrin signaling. Our data further suggest the cooperation between β1 integrins and growth factor receptors to be critical
for enhancing the radiation-induced G2/M cell cycle block leading to improved clonogenic radiation survival. By pharmaco-
logical inhibition of EGFR and PI3K, we additionally show that the essential contribution of EGFR signaling to radiogenic
G2/M cell cycle arrest depends on the co-activation of the β1 integrin signaling axis, but occurs independent of PI3K. Taken
together, elucidation of the signaling circuitry underlying the EGFR/β1 integrin crosstalk may support the development of
advanced molecular targeted therapies for radiation oncology.

Keywords: beta1 integrin; Growth factor receptor; Cell cycle; Ionizing radiation

Publ.-Id: 34303

Nuclear Magnetic Resonance of Actinides

Kaden, P.

This book chapter covers all aspects of nuclear magnetic resonance spectroscopy observing actinides and nuclei in actinide-containing compounds with this spectroscopic technique.

Keywords: NMR; actinides

  • Book chapter
    Stephen T Liddle, David P Mills, Louise S Natrajan: The Lanthanides and Actinides Synthesis, Reactivity, Properties and Applications, London / UK: World Scientific Europe, 2022, 978-1-80061-015-6, 617-631
    DOI: 10.1142/9781800610163_0016

Publ.-Id: 34302

Radiation studies for MU2E-II

Müller, S.

Presentation at MU2E-II Workshop (virtual), February 22, 2022

Keywords: MU2E; FLUKA; Simulation

  • Open Access Logo Lecture (others) (Online presentation)
    Mu2e-II Snowmass22 Workshop (xi), 22.02.2022, virtuell, USA


Publ.-Id: 34301

Future Knowledge in Geometallurgical Mining Optimization

van den Boogaart, K. G.

Mining and processing involves a lot of decision making, on capacity
building, mine scheduling, blending, process parameters, and
contracted sales. Traditionally stochastic mine planning and
predictive Geometallurgy use stochastic knowledge provided e.g. by
conditional geostatistical simulations of the conditional
distributions of ore properties to infere optimal decisions through
stochastic optimization. Stochastic knowledge is however no fixed
fact, but can rather increase by later aquisition of information,
automatically as a direct consequence of the operation itself, and
optionally through additional exploration.

The contribution shows with simple and easy to comprehend sand box
examples how and why such future knowledge and even the option to
obtain future knowledge already changes, what is an optimal decision
even before this knowledge is obtained. In case of optional knowledge,
the decision to obtain it and when, becomes an integral part of the
decision problem. This radically changes what algorithms can be
feasibly used to compute optimal decissions. Straight forward
stochastic optimization is not yet computationally feasible, for
situations with increasing knowledge. The state of the art for models
using increasing information is to use reinforcement learning based

This contribution explores the idea of making a stochastic
optimizating possible by exploiting certain structures of the mining
related increasing knowledge optimization problem. Possible speedup
are based on 1) inequality relations in stochastic optimization
allowing for advanced branch and bound techniques, 2) exploiting the
fact that certain values are equivalent in different branches which
simplifies comparisions and precomputation, and 3) explicit
computation of conditional expectations in a partial separation of the
processing optimization and the scheduling optimization.

Keywords: geometallurgical optimization; branch and bound; inequalities; mining geostatistics

  • Lecture (Conference)
    IAMG 2022, 29.08.-02.09.2022, Nancy, France

Publ.-Id: 34300

Np(V) uptake by the cladding corrosion product zirconia: a combined batch, spectroscopic, and modeling approach

Jessat, I.; Roßberg, A.; Scheinost, A.; Lützenkirchen, J.; Foerstendorf, H.; Jordan, N.

When assessing the safety of a nuclear waste repository, the interactions of dissolved long-lived radionuclides, such as the actinide neptunium, with corrosion products in the near-field of the repository are crucial processes that have to be taken into account. Zirconia (ZrO₂), the main corrosion product of the zircaloy cladding material of nuclear fuel rods, constitutes a first barrier against the release of radionuclides into the environment.
A multimethod approach was pursued to gain a thorough understanding of the Np(V) sorption processes on the water−zirconia interface. For the macroscopic description of the Np(V)−ZrO₂ system, pH-dependent batch sorption experiments (varying ionic strength, Np(V) concentration, and the solid-to-liquid ratio) as well as a sorption isotherm experiment at pH 6 were conducted. The uptake of Np(V) was pH-dependent, with an increased sorption starting from pH 3 and being at a maximum at pH 6 and above. The Np(V) sorption was independent of ionic strength, hinting to the presence of Np(V) inner-sphere complexes on the zirconia surface. This was supported by zeta potential measurements in the presence of neptunium, where a shift to higher pH values of the isoelectric point of the neat ZrO₂ was observed. The Np(V) sorption edge was shifted towards lower pH values with increasing solid-to-liquid ratio, indicating the presence of different kinds of sorption sites, which was also deduced from the shape of the sorption isotherm.
Molecular information of the surface species were obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and in situ Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) revealing the predominant formation of inner-sphere Np(V) surface complexes. A short Np−Zr distance derived from EXAFS spectra suggested the presence of Np(V) bidentate complexes at the zirconia surface.
Reliable information about the number and denticity of surface species obtained by macroscopic and molecular spectroscopic investigations potentially facilitate modeling approaches such as surface complexation modeling (SCM) that in turn will contribute to a more profound prediction of the environmental behavior of neptunium.

Keywords: neptunium(V); zirconia; ZrO₂; sorption; spectroscopy; EXAFS; IR

Related publications

  • Lecture (Conference) (Online presentation)
    Goldschmidt Conference, 10.-15.07.2022, Honolulu, Hawaiʻi, USA

Publ.-Id: 34299

Neutron-irradiated concrete: Structural characterisation and gamma dosimetry.

Roode-Gutzmer, Q. I.; Barkleit, A.; Rachamin, R.; Hennig, C.; Weiß, S.; Paasch, S.; Konheiser, J.; Stumpf, T.

Increased reactivity of radiation-damaged quartz in the alkaline pore water of concrete and its role in radionuclide transport is a subject that is becoming increasingly important as nuclear power plants (NPPs) around the world reach end-of-life. Quartz contributes more than half the weight of most concretes and up to 40 % of the total radioactive waste volume associated with the dismantling of an NPP.

The gamma-emitting radionuclides are the major contributors to the radiation dose rate in the concrete biological shield in the intermediate term after NPP shut-down. The appreciable activity and associated half-lives of these radionuclides pose a problem not only during the safe dismantling of NPPs, but also in terms of processing the concrete to reduce the active waste volume for final disposal in a repository.

While thermal neutrons are captured by atomic nuclei according to their thermal neutron cross-sections, fast neutrons undergo collision cascades, which cause defects in the structure of materials. The concentration of defects accumulates as a function of neutron energy and fluence. The high covalency and the density of Si-O bonds in tectosilicates, primarily quartz, followed by feldspars, makes these minerals very susceptible to radiation damage.

In this study, two inactive concrete powder samples were placed inside an instrumentation channel passing through the first biological shielding of an operating German NPP, respectively for a half- and a full fuel cycle. Using a plant-specific 3D-reactor model in conjunction with Monte Carlo neutron transport calculations, neutron fluences at the sample positions and the resulting gamma activities are calculated. We compare the measured and calculated activities of the gamma-emitting radionuclides

Synchrotron X-ray powder diffractometry was used to examine structural changes on sub-nanoscale. The local structure of the silicate aggregate minerals was investigated by solid-state magic angle spinning nuclear magnetic resonance (NMR) Spectroscopy using 27Al and 29Si as probes.

With this work we wish to gain insights into the potential for alkali-silica reaction (ASR) in radiation-damaged concrete and the role this plays in the transport or sorption of radionuclides either present in situ via neutron activation or ex situ due to transport of leaked reactor cooling water.

Keywords: concrete biological shield; neutron activation; gamma dosimetry; Monte Carlo neutron transport calculations; radionuclides; radiation damage; quartz; alkali silica reaction

Related publications

  • Lecture (Conference)
    RadChem 2022 / 19th Radiochemical Conference, 15.-20.05.2022, Marianske Lazne, Czech Republic

Publ.-Id: 34298

Die Rolle von Mikroorganismen bei der Lagerung von hoch-radioaktiven Abfällen - Mikrobiologie am HZDR - (2022)

Matschiavelli, N.

Der Vortrag gibt einen Überblick über mikrobielle Prozesse in einem Endlager für hoch-radioaktiven Müll

  • Lecture (others) (Online presentation)
    Girl´s & Boy´s day 2022, 28.04.2022, HZDR, Deutschland

Publ.-Id: 34297

Microbial influence on cast iron corrosion under repository-relevant conditions

Matschiavelli, N.

Darstellung und Presentation von Daten innerhalb des UMB-II Projektes

  • Lecture (others)
    UMB-II 3rd workshop, 09.-10.03.2022, Greifswald, Dresden
  • Lecture (others)
    UMB-II 4th projectmeeting, 26.10.2022, Braunschweig, Deutschland
  • Lecture (others)
    UMB-II 5th project meeting, 03.-04.05.2023, Garching, Deutschland
  • Open Access Logo Lecture (others)
    UMB-II 6th project meeting, 05.-06.12.2023, Hannover, Deutschland

Publ.-Id: 34296

Beam pulse structure and dose rate as determinants for the Flash effect observed in zebrafish embryo

Karsch, L.; Pawelke, J.; Brand, M.; Hans, S.; Hideghety, K.; Jansen, J.; Leßmann, E.; Löck, S.; Schürer, M.; Schurig, R.; Seco, J.; Szabo, E. R.; Beyreuther, E.

Background and purpose
Continuing recent experiments at the research electron accelerator ELBE at the Helmholtz-Zentrum Dresden-Rossendorf the influence of beam pulse time structure on the Flash effect should be investigated in a zebrafish embryo model.
Materials and methods
The pulse structures of an isochronous and a synchrocyclotron were mimicked at ELBE with mean dose rates of 287 Gy/s and 177 Gy/s and pulse dose rates of 106 Gy/s and 109 Gy/s, respectively; and a macro pulsing for the latter. For comparison, a maximum (mean dose rate 2.5 x 105 Gy/s, pulse dose rate ~109 Gy/s) and a reference (mean dose rate of ~8 Gy/min) regime were applied. Radiation induced changes were assessed in zebrafish embryos over four days post irradiation.
A significant protecting Flash effect with a clear dependence on mean dose rate was revealed for almost all endpoints and all electron pulse regimes relative to the reference. The macro pulse dependent prolongation of treatment time of the synchrotron-like regime reduce the protecting effect compared to the maximum regime delivered at same pulse but higher mean dose rate. The protecting Flash effect of the cyclotron-like regime was confirmed at a clinical isochronous proton cyclotron comparing the effects induced by 300 Gy/s relative to conventional proton beam delivery.
The mean dose rate or treatment time are more important than pulse dose rate for the extent of the normal tissue protecting Flash effect.

Related publications


Publ.-Id: 34295

Spin-aware quantum-accurate interatomic potentials for heavy elements

Lokamani, M.; Ramakrishna, K.; Nikolov, S.; Tranchida, J.; Juckeland, G.; Wood, M.; Cangi, A.

Studying matter under extreme conditions using density functional theory (DFT) is computationally expensive, since the degrees of freedom and consequently the configurational space grows rapidly with increasing temperature and pressure. Therefore, the use of DFT for such simulations is limited to fairly small simulation cells and time scales. Machine learning-based interatomic potentials (ML-IAP) provide access to much larger spatial and temporal domains, thus enabling the discovery of new and exotic magnetic materials. A majority of existing descriptors required to construct ML-IAPs neglect the spin degrees of freedom. Here, we present our preliminary ideas/workflows to construct "spin-aware" ML-IAP using the SNAP[1] descriptors and the coupled spin-molecular dynamics framework implemented in LAMMPS [2]. This modeling capability will complement upcoming experiments to magneto-structural properties in shock- compressed or laser-driven samples at elevated temperatures and pressures exposed to strong, pulsed magnetic fields, which are planned at photon sources such as within the HIBEF consortium at the European XFEL.

Keywords: matter under extreme conditions; Machine learning-based interatomic potentials; coupled spin-molecular dynamics; High-throughput; Advanced data science; Hyperparameter optimization

  • Open Access Logo Poster
    DFT Methods for Matter under Extreme Conditions, 21.-22.02.2022, Görlitz, Saxony, Germany


Publ.-Id: 34294

Fe+ ion irradiation effects in Fe-10at%Cr films irradiated at 300 °C

Pantousa, S.; Mergia, K.; Ionescu, A.; Manios, E.; Dellis, S.; Kinane, C.; Langridge, S.; Caruana, A.; Kentsch, U.; Messoloras, S.

Fe-Cr alloys constitute the model systems for the investigation of radiation damage effects in ferritic-martensitic steels which are candidate structural materials for fusion reactors. In the current study Fe-10at%Cr alloy films of 70 nm thickness were irradiated by 490 keV Fe+ ions at 300 °C at doses ranging from 0.5 up to 20 displacements per atom (dpa). The Fe+ ion energy chosen corresponds to the energy of primary Fe(Cr) knock-on atoms from 14 MeV neutrons. The irradiation effects were investigated employing X-ray diffraction and X-ray and polarized neutron reflectivity. The irradiation produced dose dependent: a) lattice constant increase, b) grain size growth and c) Cr depletion in the matrix. These changes occur largely up to 4 dpa and afterwards the system attains a dynamic equilibrium.

Keywords: Fe-Cr alloys; ion irradiation; lattice damage; Cr depletion; polarized neutron reflectivity; magnetization

Related publications

Publ.-Id: 34293

The role of crustal thickness on magma composition in arcs: An example from the pre-Andean, South American Cordillera

Alasino, P. H.; Paterson, S. R.; Kirsch, M.; Larrovere, M. A.

We explore the temporal evolution of pre-Andean Cordilleran arcs in central and northwestern Argentina and northern Chile (27°-34°S) with a focus on the geochemical characteristics of the episodic magmatism and the relationship with crustal thickness. A compilation of ca. 5000 U-Pb bedrock and detrital zircon ages, with ages from 600 to 130 Ma, reveals seven temporal magmatic accretions with main peaks at ~526 Ma (Pampean); ~471 Ma (Famatinian); ~340 and ~305 Ma (Early Gondwanan); ~253 and ~221 Ma (Gondwanan); and ~ 160 Ma (Early Andean). We show that most of the magmatic episodes were developed in 30-50 km thick crust. Magmatism experienced fractional crystallization (r = 0) combined with variable degrees of assimilation (r > 0) that mostly did not exceed 30% crust. We conclude that increasing crustal thickness not only promotes more extensive differentiation by fractionation but also establishes conditions near host rock solidi at shallow crustal levels promoting further contamination in magmas.

Keywords: Cordilleran arc; Crust; Magmatic tempos; Mantle procceses

Publ.-Id: 34292

Roadmap on Spin-Wave Computing

Chumak, A. V.; Kabos, P.; Wu, M.; et al.; Schultheiß, H.; Schultheiß, K.

Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors that covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with Boolean digital data, unconventional approaches like neuromorphic computing, and the progress towards magnon-based quantum computing. The article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.

Keywords: Spin wave; Magnon; Magnonics; Computing; Data processing

Publ.-Id: 34291

Data publication: Multisite Dopamine Sensing with Femtomolar Resolution Using a CMOS Enabled Aptasensor Chip

Baraban, L.; Seichepine, F.; Sessi, V.; Ibarlucea, B.; Klinghammer, S.; Ibrahim, I.; Heinzig, A.; Szabo, N.; Mikolajick, T.; Reinhold Hierlemann, A.; Frey, U.; Weber, W.; Cuniberti, G.

Data describe the graphs summarized into the figures with a possibility of opening the figures and direct data access.

Related publications


Publ.-Id: 34290

Lab Scale Experimental Studies For Modeling Possible Zinc Removal Efforts in LOCA Situations

Harm, U.; Kryk, H.; Hampel, U.; Seeliger, A.; Alt, S.; Kästner, W.

During the sump recirculation phase after a postulated LOCA in PWR, the coolant in the reactor sump is recirculated to the reactor core by residual-heat removal pumps as part of the emergency core cooling system. Long-term contact of the boric acid containing coolant with hot-dip galvanized containment internals (e.g. grating treads) is assumed to cause corrosion of corresponding materials with the consequence of rising concentrations of dissolved zinc in coolant. As it was shown in previous research projects, subsequently formed zinc borates may precipitate within hot spots of the reactor core in the late phase of the LOCA causing thermal hydraulic effects. In PWR, ion exchange columns are installed as part of the coolant cleaning system, having potential to be used to remove dissolved zinc ions.
For evaluation of such approach, lab scale investigations with ion exchange resins to remove dissolved zinc ions from the coolant are carried out under typical conditions of the post LOCA phase (sump recirculation). The usability of the coolant cleaning system for this purpose was proven successfully. The further aim is to model the zinc removal process by the coolant cleaning system by means of data of the ion exchange capacity of different ion exchange resins and kinetic data for the zinc removal under LOCA conditions.

The investigations are carried out as joint research project of Helmholtz-Zentrum Dresden - Rossendorf, TU Dresden, and Hochschule Zittau/Goerlitz. The goal is to build up a database for extensions of thermo-hydraulic simulation tools by the project partner GRS.

Keywords: PWR; LOCA; coolant cleaning system; zinc; modeling

  • Contribution to proceedings
    The 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brussels, Belgium
    Proceedings of NURETH-19
  • Lecture (Conference) (Online presentation)
    The 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brussels, Belgium

Publ.-Id: 34289

Understanding the M4 edge HERFD XANES of U6+

Amidani, L.; Volkova, A.; Retegan, M.; Popa, K.; Martin, P.; Kvashnina, K.

Hexavalent uranium is of considerable importance in the actinide field, and its characterization, consequently, of fundamental concern. The application of High-Energy-Resolution Fluorescence-Detected X-ray Absorption Near-Edge Structure (HERFD XANES) spectroscopy at the M4 edge of actinides probes the 5f electronic structure with augmented resolution compared to conventional XANES and is gaining great popularity. If, from one side, the extreme sensitivity of M4 HERFD XANES to actinides’ oxidation state is well-established [1], its sensitivity to the local environment has been less extensively explored [2,3]. The partially filled 5f subshell makes intra-atomic electron interactions the primary force shaping the spectrum, and simulations treating multi-electronic effects can only approximately account for the local environment.
In these regards, U6+, with its empty 5f shell, is a fortunate exceptional case. Simulation approaches based on the one-electron approximation can then be applied, and the dependence on the local environment be carefully investigated. We recently reported a detailed investigation where experimental and simulated M4 HERFD XANES are obtained on a set of U6+ compounds with different local environments [4]. The coordination of U6+ represented by the set of samples comprises an almost perfect UO6 octahedral bipyramid (Sr3UO6), two UO6 featuring the uranyl ion (Cs2UO2Cl4 and SrUO4), and a UO8 distorted hexagonal bipyramid (CaUO4).
Experimental M4 HERFD are shown in Figure 1. The spectral shape has a similar structure, made of three or four peaks of decreasing intensity. At the same time, it presents significant differences indicating the substantial impact on the spectral shape of the local environment. We simulated the set of U6+ compounds with the DFT-based code FDMNES [5]. The good agreement between theory and experiment, see Fig. 1, makes it reasonable to have a closer look at the underlying f-density of states and to assign spectral features to specific f-orbitals.
Simulations allow to rationalize how the local coordination of U6+ affects the M4 HERFD XANES and demonstrate its high sensitivity to the local environment. Simulations based on crystal field theory were also performed. Their comparison to FDMNES results will be discussed.

  • Lecture (Conference)
    JdA 51 - Journées des Actinides, 10.-14.04.2022, Santa Margherita, Italia

Publ.-Id: 34288

State-resolved ultrafast charge and spin dynamics in [Co/Pd] multilayers

Le Guyader, L.; Higley, D. J.; Pancaldi, M.; Liu, T.; Chen, Z.; Chase, T.; Granitzka, P. W.; Coslovich, G.; Lutman, A. A.; Dakovski, G. L.; Schlotter, W. F.; Shafer, P.; Arenholz, E.; Hellwig, O.; Lalieu, M. L. M.; Koopmans, B.; Reid, A. H.; Bonetti, S.; Stöhr, J.; Dürr, H. A.

We use transient absorption spectroscopy with circularly polarized x-rays to detect laser-
excited hole states below the Fermi level and compare their dynamics with that of unoc-
cupied states above the Fermi level in ferromagnetic [Co/Pd] multilayers. While below
the Fermi level an instantaneous and significantly stronger demagnetization is observed,
above the Fermi level the demagnetization is delayed by 35 ± 10 fs. This provides a direct
visualization of how ultrafast demagnetization proceeds via initial spin-flip scattering of
laser-excited holes to the subsequent formation of spin waves

Publ.-Id: 34287

Multisite Dopamine Sensing with Femtomolar Resolution Using a CMOS Enabled Aptasensor Chip

Baraban, L.; Seichepine, F.; Sessi, V.; Ibarlucea, B.; Klinghammer, S.; Ibrahim, I.; Heinzig, A.; Szabo, N.; Mikolajick, T.; Reinhold Hierlemann, A.; Frey, U.; Weber, W.; Cuniberti, G.

Many biomarkers including neurotransmitters are found in external body fluids, such as sweat or saliva, but at lower titration levels than they are present in blood. Efficient detection of such biomarkers thus requires, on the one hand, to use techniques offering high sensitivity, and, on the other hand, to use a miniaturized format to carry out diagnostics in a minimally invasive way. Here, we present the hybrid integration of bottom-up silicon-nanowire Schottky-junction FETs (SiNW SJ-FETs) with complementary-metal–oxide–semiconductor (CMOS) readout and amplification electronics to establish a robust biosensing platform with 32 x 32 aptasensor measurement sites at a 100 µm pitch. The applied hetero-junctions yield a selective biomolecular detection down to femtomolar concentrations. Selective and multi-site detection of dopamine is demonstrated at an outstanding sensitivity of ~ 1 V/fM. The integrated platform offers great potential for detecting biomarkers at high dilution levels and could be applied, for example, to diagnosing neurodegenerative diseases or monitoring therapy progress based on patient samples, such as tear liquid, saliva, or eccrine sweat.

Related publications

Publ.-Id: 34286

Design and production of tungsten-carbide rich coating layers

Racz, A. S.; Fogarassy, Z.; Kentsch, U.; Panjan, P.; Menyhard, M.

Ion beam induced mixing (IBM) can be used for making protecting coating layers at room temperature. We have studied the production of tungsten-carbide, having high strength and low friction, by IBM since this material is also a candidate for protective coatings. WC rich layers have been produced by irradiating C/W multilayer of various structures (with individual layer thicknesses from 10 to 20 nm) by noble gases using medium energy projectiles. The resulting alterations of the samples have been measured by Auger electron spectroscopy (AES) depth-profiling. TRIDYN simulations, with some parametrization, were applied to determine the elemental in-depth distribution after IBM; the compound formation was calculated by a simple model. The calculated and measured depth profiles were compared and excellent agreement has been found for a rich dataset differing in layer structures, projectiles, ion fluences and energies. The good agreement in a wide parameter range validates our procedure and allows the design of the WC-rich layers and also enables the significant decrease of the experimental work.

Keywords: Tungsten-carbide; WC; Coating; Simulation; Ion irradiation; TRIDYN

Related publications

Publ.-Id: 34285

A perfect match between borophene and aluminium in the AlB3heterostructure with covalent Al-B bonds, multiple Dirac points and a high Fermi velocity

Jiao, Y.; Ma, F.; Zhang, X.; Heine, T.

By performing a swarm-intelligent global structure search combined with first-principles calculations, a stable twodimensional (2D) AlB3 heterostructure with directed, covalent Al-B bonds forms due to a nearly perfect lattice match between 2D borophene and the Al(111) surface. The AlB3 heterosheet with the P6mm space group is composed of a planar Al(111) layer and a corrugated borophene layer, where the in-plane coordinates of Al covalently link with the corrugated B atoms. The resulting structure shows a similar interlayer interaction energy to that of the Al(111) surface layer to the bulk and high mechanical and thermal stability, possesses multiple Dirac points in the Brillouin zone with a remarkably high Fermi velocity of 1.09 × 106 m s-1, which is comparable to that of graphene. Detailed analysis of the electronic structure employing the electron localisation function and topological analysis of the electron density confirm the covalent Al-B bond with high electron localisation between the Al and B centres and with only little interatomic charge transfer. The combination of
borophene with metal monolayers in 2D heterostructures opens the door to a rich chemistry with potentially unprecedented properties.

Keywords: Calculations; Charge transfer; Electronic structure; Graphene; Topology; Dirac point

Publ.-Id: 34284

Quantifying the Dzyaloshinkii-Moriya Interaction Induced by the Bulk Magnetic Asymmetry

Zhang, Q.; Liang, J.; Bi, K.; Zhao, L.; Bai, H.; Cui, Q.; Zhou, H.-A.; Bai, H.; Feng, H.; Song, W.; Chai, G.; Gladii, O.; Schultheiß, H.; Zhu, T.; Zhang, J.; Peng, Y.; Yang, H.; Jiang, W.

A broken interfacial inversion symmetry in ultrathin ferromagnet/heavy metal (FM/HM) bilayers is generally believed to be a prerequisite for accommodating Dzyaloshinskii-Moriya interaction (DMI) and for stabilizing chiral spin textures. By contrast, we present an approach for engineering both the sign and amplitude of DMI in relatively thick films without involving interfacial asymmetry, which is achieved through incorporating the composition gradient-induced bulk magnetic asymmetry (BMA) combined with strong spin-orbit coupling (SOC). The pivotal roles of BMA and SOC are theoretically examined based on the three-site Fert-Lévy model and the first principles calculations. Experimentally, both the sign and amplitude of DMI in films with controllable composition gradients along the growth direction, in the presence/absence of SOC are studied by using a Brillouin light scattering spectroscopy. Our results suggest that the appreciable value of DMI (±0.15 mJ/m2) could be established through combining BMA and SOC into relatively thick films. It is expected that our findings may help to further understand chiral magnetism and to design novel non-collinear spin textures.

Keywords: Dzyaloshinskii-Moriya interaction; Brillouin light scattering; spin-wave non-reciprocity; bulk magnetic asymmetry; spin-orbit coupling


Publ.-Id: 34283

Electron-ion temperature relaxation in warm dense hydrogen observed with picosecond resolved X-ray scattering

Fletcher, L. B.; Vorberger, J.; Schumaker, W.; Ruyer, C.; Goede, S.; Galtier, E.; Zastrau, U.; Alves, E. P.; Baalrud, S. D.; Baggott, R. A.; Barbrel, B.; Chen, Z.; Döppner, T.; Gauthier, M.; Granados, E.; Kim, J. B.; Kraus, D.; Lee, H. J.; Macdonald, M. J.; Mishra, R.; Pelka, A.; Ravasio, A.; Roedel, C.; Fry, A. R.; Redmer, R.; Fiuza, F.; Gericke, D. O.; Glenzer, S. H.

Angularly resolved X-ray scattering measurements from fs-laser heated hydrogen have been
used to determine the equilibration of electron and ion temperatures in the warm dense matter
regime. The relaxation of rapidly heated cryogenic hydrogen is visualized using 5.5 keV X-ray
pulses from the Linac Coherent Light (LCLS) source in a 1 Hz repetition rate pump-probe setting.
We demonstrate that the electron-ion energy transfer is faster than quasi-classical Landau-Spitzer
models that use ad hoc cutoffs in the Coulomb logarithm.

Keywords: warm dense matter; x-ray scattering; relaxation; femtosecond; hydrogen jet

Related publications

Publ.-Id: 34282

Quantitative assessment of radionuclide production yields in in-beam1 and offline PET measurements at different proton irradiation facilities

Bauer, J.; Hildebrandt, M.; Baumgartl, M.; Fiedler, F.; Robert, C.; Buvat, I.; Enghardt, W.; Parodi, K.

Objective: Reliable radionuclide production-yield data are a prerequisite for positron-emission-1
tomography (PET) based in-vivo proton treatment verification. In this context, activation data acquired2
at two different treatment facilities with different imaging systems were analyzed to provide3
experimentally determined radionuclide yields in thick targets and were compared with each other to4
investigate the impact of the respective imaging technique.5
Approach: Homogeneous thick targets (PMMA, gelatine, and graphite) were irradiated with mono-6
energetic proton pencil-beams at two distinct energies. Material activation was measured (i) in-beam7
during and after beam delivery with a double-head prototype PET camera and (ii) offline shortly after8
beam delivery with a commercial full-ring PET/CT scanner. Integral as well as depth-resolved +-9
emitter yields were determined for the dominant positron-emitting radionuclides 11C, 15O, 13N and (in-10
beam only) 10C. In-beam data were used to investigate the qualitative impact of different monitoring11
time schemes on activity depth profiles and their quantitative impact on count rates and total activity.12
Main results: Production yields measured with the in-beam camera were comparable to or higher13
compared to respective offline results. Depth profiles of radionuclide-specific yields obtained from the14
double-head camera showed qualitative differences to data acquired with the full-ring camera with a15
more convex profile shape. Considerable impact of the imaging timing scheme on the activity profile16
was observed for gelatine only with a range variation of up to 3.5 mm. Evaluation of the coincidence17
rate and the total number of observed events in the considered workflows confirmed a strongly18
decreasing rate in targets with a large oxygen fraction.19
Significance: The observed quantitative and qualitative differences between the datasets underline20
the importance of a thorough system commissioning. Due to the lack of reliable cross-section data, in-21
house phantom measurements are still considered a gold standard for careful characterization of the22
system response and to ensure a reliable beam range verification

Keywords: offline PET; positron emitter production yield; in-beam PET; particle therapy; in-vivo range verification

Publ.-Id: 34281

Scale dependent anisotropy & intermittency in bubble laden turbulent flows

Ma, T.; Hessenkemper, H.; Lucas, D.; Ott, B.; Fröhlich, J.; Bragg, A.

-- Anisotropy
DNS data of disperse bubbly flows in a vertical channel are used to study scale-dependent anisotropy for flows dominated by bubble-induced turbulence. We developed a new method, based on an extension of the barycentric map approach, that allows to quantify and visualize the anisotropy and componentiality of the flow at any scale. Using this we found that the bubbles significantly enhance anisotropy in the flow at all scales compared with the unladen case, and that for some bubble cases, very strong anisotropy persists down to the smallest scales of the flow. The strongest anisotropy observed was for the cases involving small bubbles.

-- intermittency
We experimentally explore the properties of bubble-laden turbulent flow at different scales, considering how the bubbles effect the extreme events of the flow. To this end, high-resolution Particle Shadow Velocimetry measurements are carried out in a bubble column in which the flow generated by a homogeneous distributed bubble swarm rising in water for two different bubble diameters (2.7 mm & 3.9 mm) and moderate gas volume fractions (0.26% - 1.31%). We considered the intermittency quantified by the normalized probability density functions of the longitudinal velocity increments. The results reveal that extreme values in the velocity increments become more probable with decreasing Reynolds number, the opposite of the behavior in single-phase turbulence. We visualize those extreme events and find that regions of intense small-scale velocity increments occur near the turbulent/non-turbulent interface at the boundary of the bubble wake.

Keywords: Bubbly flow; Turbulence

  • Invited lecture (Conferences)
    Special Seminar at Johns Hopkins University Center for Environmental & Applied Fluid Mechanics, 23.02.2022, Baltimore, USA

Publ.-Id: 34280

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