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41692 Publications

The complex chemistry of light actinides

März, J.

Abstract

The actinides (An) are located at the bottom of the periodic table. These elements are exclusively radioactive, highly chemo-toxic, and play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories. In contrast to the strongly shielded 4f electrons of the lanthanides, 5f electrons of particularly the early An are found to participate in bonding, e.g. to organic ligands. Another characteristic of the An is their huge variety of possible oxidation states, typically ranging from +II to +VII for early actinides, making their chemistry complex but interesting. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state. Observed changes in e.g. the binding situation or magnetic effects among the An series may deliver insight into their unique electronic properties mainly originating from the f-electrons. A question still remaining in the field of An chemistry is the degree of “covalency” in compounds across the actinide series, which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
We investigate the coordination chemistry of low-valent actinides using organic N-, O-, or S-donor ligands. Information on covalency trends as well as mutual ligand influences can be obtained by the analysis of solid-state structures derived by SC-XRD in combination with quantum chemical calculations (QCC) and high-energy-resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES). In solution, NMR spectroscopy permits to draw conclusions about the complex speciation in solution, the intrinsic magnetic properties of the actinides, or subtle changes in covalency in the ligand-actinide-bonding.

Keywords: actinides; transuranium; covalency; coordination chemistry

  • Invited lecture (Conferences)
    Öffentlicher Vortrag Department Chemie, 10.07.2023, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36796


Data publication: Halomonas gemina sp. nov. and Halomonas llamarensis sp. nov., two siderophore-producing organisms isolated from high-altitude salars of the Atacama Desert

Hintersatz, C.; Singh, S.; Antonio Rojas, L.; Kretzschmar, J.; Wei, T.-S.; Khambhati, K.; Kutschke, S.; Lehmann, F.; Singh, V.; Jain, R.; Pollmann, K.

Abstract

The effect of various media components on the production of desferrioxamine E by Halomonas gemina ATCH28 was investigated. Concentration of the compound was determined via HPLC using commercially available desferrioxamine E as standard for calibration.

Keywords: Halophilic bacteria; siderophores; polyphasic taxonomic; desferrioxamine E; Atacama Desert

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Permalink: https://www.hzdr.de/publications/Publ-36794


Bayes Spaces, An overview

van den Boogaart, K. G.

Abstract

Bayes Hilbert spaces \(B^2(P)\) describe a Hilbert space structure
on a set of mutally continues probability measures, improper priors
and likelihoods with origin \(P\).

The talk will give an overview of Bayes Spaces and their relation to
various concepts of mathematical statistics. Several deep results of
statistics and information theory become obvious and geometrically
intuitive corrolaries, when viewed in the light of this vector space
structure.

The name comes from the fact that vector addition in this space is
given by Bayes theorem. A distribution family is an exponential
family if and only if its a finite dimensional subspaces of a Bayes
Space. In case of regular exponential families its a Bayes Hilbert
Space. The geometry of the space is closely related to Fisher
information. There is a cannocial isometric mapping to \(L^2_0(P)\)
called centered log ratio transform, proving score functions. The
\(P\)-a.s. constant ratio of this centred log ratio transform to the
log density is Kulback Leibler Divergence. The Basis vectors of
conjugated priors can be directly interpreted in terms of
information and the basis of the original family. I.e. we explicitly
give the conjugated prior for every exponential family.

In a multivariate setting, we can identify conditional distributions
with qotient spaces, and provide a straight forward decomposition
into a sum of products of marginal spaces closely related to the
Hammersley Clifford Theorem, Graphical models and generalizing
log-linear models to continues distributions.

Keywords: Information Theory; Mathematical Statistics; Inference; Exponential Families

  • Invited lecture (Conferences)
    Olomoucian Days of Applied Mathematics 2023, 12.-14.06.2023, Olomouc, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-36792


Bioaerosols Spreading in Confined Spaces

Cavagnola, M. A.; Hampel, U.; Lecrivain, G.

Abstract

Ultraviolet germicidal irradiation has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne virus/bacteria inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between the microorganism particles and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to the physical reality of the inactivation process, i.e. that the ultraviolet inactivation effect is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against published data of inactivation of aerolized Escherichia coli bacteria in a UV-reactor.

  • Poster
    CORAERO PhD School, 07.11.2022, Technische Universität München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36791


Photonic Model for Airborne Viruses/Bacteria Inactivation by UV-Radiation

Cavagnola, M. A.; Eßlinger, F.; Hampel, U.; Ebert, G.; Lecrivain, G.

Abstract

Since the coming of the COVID-19 pandemic in 2019, virus spreading in confined spaces has been in the spotlight. Ultraviolet germicidal irradiation has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne virus/bacteria inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between the microorganism particles and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to the physical reality of the inactivation process, i.e. that the ultraviolet inactivation effect is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against published data of inactivation of aerolized Escherichia coli bacteria in a UV-reactor and will be validated experimentally using a seasonal coronavirus in a Potential Aerosol Mass Oxidation Flow Reactor at the Helmholtz-Zentrum in Munich.

  • Lecture (Conference)
    DECHEMA 2023/Aerosoltechnik, 29.03.2023, Paderborn Universität, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36790


PICMI: Simulation input meta-data standardisation for Particle-in-Cell(PIC) codes

Marre, B. E.; Tröpgen, H.; Tippey, K. E.; Kluge, T.; Schlenvoigt, H.-P.; Debus, A.

Abstract

Publishing raw PIC-simulation results according to the FAIR principle is difficult,
primarily size with a single large simulation's raw data reaching 100s TeraByte up to
1-2 PetaByte.
Fulfilling the FAIR principles therefore requires a different approach, with only
compressed results and simulation setup/initial state made directly available in direct
access public data bases.
This assures findability of simulations if initial conditions are automatically searchable, makes raw data on slow, high capacity archive storage accessible for specific simulations of interest, or allows rerunning the same simulation if additional data is required.

This is currently hindered by the different historically grown input description standards of different PIC-codes.

Simulation setups can neither be parsed, searched or understood without implementing a dedicated parser for each code and with more than 4 PIC-simulation codes, (PIConGPU, WARPX, Smilei, PICLS, ...) in use at HZDR alone this is unfeasible.
To realise the above a common standardized description for PIC-codes is needed. PICMI is being implemented and developed by HZDR and Berkley Labs for this purpose.
Besides fulfilling the above requirements, PICMI will also allow reuse of user interfaces between codes, make the simulations more accessible to users and allow using a common setup for different codes thereby al Bytelowing easy direct comparisons between codes for better reproducibility as well as lay the ground work for automated machine learning on simulations.

Keywords: PICMI; PIConGPU; meta data standarisation; simualtions; Particle in Cell; PIC; Daphne NFDI; Daphne

  • Poster
    DAPHNE4NFDI Annual meeting 2023, 03.-05.04.2023, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36789


Atomic Population Kinetics for Particle in Cell

Marre, B. E.; Huebl, A.; Bastrakov, S.; Bussmann, M.; Widera, R.; Schramm, U.; Cowan, T.; Kluge, T.

Abstract

Atomic Population Kinetics for ParticleInCell

Standard atomic physics models in PIC simulation either neglect excited states, predict
atomic state population in post processing only, or assume quasi-thermal plasma conditions.

This is no longer sufficient for high-intensity short-pulse laser generated plasmas, due
to their non-equilibrium, transient and non-thermal plasma conditions, which are now becoming
accessible in XFEL experiments at HIBEF (EuropeanXFEL), SACLA (Japan) or at MEC (LCLS/SLAC).
To remedy this, we have developed a new extension for our PIC simulation framework PIConGPU
to allow us to model atomic population kinetics in-situ in PIC-Simulations, in transient
plasmas and without assuming any temperatures.
This extension is based on a reduced atomic state model, which is directly coupled to the
existing PIC-simulation and for which the atomic rate equation is solved explicitly in
time, depending on local interaction spectra and with feedback to the host simulation.
This allows us to model de-/excitation and ionization of ions in transient plasma conditions,
as typically encountered in laser accelerator plasmas.
This new approach to atomic physics modeling will be very useful in plasma emission
prediction, plasma condition probing with XFELs and better understanding of isochoric
heating processes, since all of these rely on an accurate prediction of atomic state
populations inside transient plasmas.

Keywords: atomic physics; FLYonPIC; Particle in Cell; PIC; PIConGPU; excited atomic states

  • Lecture (Conference)
    43rd Workshop on High-Energy-Density Physics with laser and Ion beams, 30.01.-03.02.2023, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36788


Improved Planar Hall Effect sensors for fluid measurement techniques

Schmidtpeter, J.; Wondrak, T.; Makarov, D.; Zabila, Y.

Abstract

Inductive flow measurement techniques such as the Contactless Inductive Flow Tomography require sensors that provide a magnetic field resolution of 1 nT while operating in magnetic fields of several mT. With advancements in state-of-the-art magnetoresistive thin-film sensors the required behavior regarding sensitivity, precision and hysteresis can be achieved [1]. Planar Hall Effect sensor have been shown to be one of the leading sensor types in this area. Therefore we present a detailed study on the effect of different sensor layouts, geometries, magnetic flux concentrators and other parameters on the characteristics of single layer Permalloy Planar Hall Effect sensors. [1] Granell, Pablo Nicolás, et al. npj Flexible Electronics 3.1 (2019): 1-6.

Keywords: Planar Hall Effect; Sensors; DPG

  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (SKM), 31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36787


Growth twins and premartensite microstructure in epitaxial Ni-Mn-Ga films

Kar, S.; Ikeda, Y.; Lünser, K.; George Woodcock, T.; Nielsch, K.; Reith, H.; Maaß, R.; Fähler, S.

Abstract

Magnetic shape memory alloys have been examined intensively due to their multifunctionality and multitude of
physical phenomena. For both areas, epitaxial films are promising since the absence of grain boundaries is beneficial for applications in microsystems and they also allow to understand the influence of a reduced dimension on the physical effects. Despite many efforts on epitaxial films, two particular aspects remain open. First, it is not
clear how to keep epitaxial growth up to high film thickness, which is required for most microsystems. Second, it
is unknown how the microstructure of premartensite, a precursor state during the martensitic transformation,
manifests in films and differs from that in bulk.
Here, we focus on micrometer-thick austenitic Ni-Mn-Ga films and explain two distinct microstructural features
by combining high-resolution electron microscopy and X-ray diffraction methods. First, we identify pyramid-
shaped defects, which originate from {1 1 1} growth twinning and cause the breakdown of epitaxial growth.
We show that a sufficiently thick Cr buffer layer prevents this breakdown and allows epitaxial growth up to a
thickness of at least 4 μm. Second, premartensite exhibits a hierarchical microstructure in epitaxial films. The reduced dimension of films results in variant selection and regions with distinct premartensite variants, unlike its
microstructure in bulk.

Keywords: Epitaxial films; Magnetic shape memory alloy; Twinning; Premartensite; Hierarchical microstructure

Permalink: https://www.hzdr.de/publications/Publ-36786


THEREDA: Polythermal extension of the Pitzer database for strontium

Bok, F.; Moog, H. C.; Voigt, W.

Abstract

INTRODUCTION
Radioactive strontium isotopes are products of the fission of uranium in the context of nuclear energy production. Furthermore, strontium is often used in geochemical calculations as an analog for radium, both being alkaline earth metals.
In the THEREDA database [1,2], a thermodynamic Pitzer dataset for Sr in the system of oceanic salts (Na⁺, K⁺, Mg²⁺, Ca²⁺ | Cl⁻, SO₄²⁻ – H₂O) is available [3]. Yet, this dataset is valid for the temperature T = 25 °C only. However, several strontium solid phases show a large variation in solubility with temperature, e.g. strontium chloride hydrates (SrCl₂∙xH₂O with x = 6, 2 and 1) [4] or strontium hydroxide (Sr(OH)₂∙8H₂O) [5].
In this work, a polythermal extension of the existing Sr dataset for the chloride system is presented, which is valid in the range T = 0–100 °C.

DESCRIPTION OF THE WORK
Experimental data (osmotic coefficients) from literature were used to generate a temperature function for the binary Pitzer interaction coefficients (β⁰, β¹, and CΦ). Solubility data of SrCl₂ in water [4] were then used to parameterize temperature functions for the solubility products of the different strontium chloride hydrates. Consistency with the existing 25 °C data set was ensured.
Solubility data of SrCl₂ in water [4] were then used to parameterize temperature functions for the solubility products of the different strontium chloride hydrates. Polythermal expansions of the ternary Pitzer coefficients also were required for a few subsystems only.
Furthermore, the data set was extended to quaternary acidic systems (Sr²⁺, H⁺ | Cl⁻ – H₂O).

RESULTS
With the obtained dataset, it is possible to model the ternary system (Sr²⁺, Na⁺ | Cl⁻ – H₂O) in the temperature range T = 0–100 °C. The solubility of all known solid phases is correctly reproduced, see Fig. 1. The dataset now also allows polythermal calculation of higher systems such as the quaternary system (Sr²⁺, Na⁺, K⁺ | Cl⁻ – H2O) in the temperature range for which experimental solubility data are available (T = 15–50 °C), see Fig. 2. For those two systems, no adjustment of the existing ternary Pitzer interaction coefficients was necessary.
The presented polythermal extension of the strontium Pitzer model allows robust calculation of the geochemical behavior of strontium in the chloride system over a wide temperature range. This extension of the THEREDA data set will become part of the next official data release and will be complemented by polythermal data for strontium sulfate (SrSO₄) and hydroxide (Sr(OH)₂∙8H₂O) in future work.

ACKNOWLEDGMENTS
THEREDA is funded by the German “Bundesgesellschaft für Endlagerung (BGE)”, contract number 45181017.

REFERENCES
1. THEREDA – Thermodynamic Reference Database. Release 2021, https://www.thereda.de/, (2022).
2. H. C. Moog et al., “Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA)” Appl. Geochem., 55, 72–84 (2015), DOI: 10.1016/j.apgeochem.2014.12.016.
3. T. Scharge “Thermodynamic model for the systems Sr – Na, K, Mg, Ca – Cl, SO₄ – H2O at 298.15 K”, THEREDA Report (2016).
4. B. S. Krumgalz “Temperature Dependence of Mineral Solubility in Water. Part I. Alkaline and Alkaline Earth Chlorides” J. Phys. Chem. Ref. Data, 46, 043101, DOI: 10.1063/1.5006028.
5. I. Lambert et al. “Alkaline Earth Hydroxides in Water and Aqueous Solutions” IUPAC Solubility Data Series Vol. 52, Pergamon Press, Oxford, 388 p.

Keywords: THEREDA; Strontium chloride; Thermodynamic data; Solubility; Pitzer activity model

  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop VII (ABC Salt VII), 15.-16.06.2023, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-36785


Experimental prompt gamma-ray timing data for proton treatment verification in a clinical facility using a fixed beam

Werner, T.; Hueso-González, F.; Kögler, T.; Petzoldt, J.; Schellhammer, S.; Pausch, G.
Project Leader: Pausch, Guntram; ContactPerson: Schellhammer, Sonja; ContactPerson: Kögler, Toni; ResearchGroup: Berthold, Jonathan; ResearchGroup: Römer, Katja; ResearchGroup: Rinscheid, Andreas

Abstract

This dataset comprises the data reported on by Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d). Please refer to this publication for details on the experimental setup, data acquisition and preprocessing. The process is summarised in the following.

A static, pulsed pencil beam was delivered to a target without and with cylindrical air cavities of 5 to 20 mm thickness and prompt gamma-ray timing distributions were acquired.

Experimental setup:

A homogeneous cylindrical phantom comprised of poly(methylmethacrylate) was used. Air cavities of varying thickness ∆R ∈ {0 mm, 5 mm, 10 mm, 20 mm} were successively introduced into the phantom to mimic anatomical variations leading to range deviations. For each air cavity thickness, the phantom was irradiated with proton pencil beams of two different kinetic energies (E_1 = 162 MeV and E_2 = 227 MeV) and a micropulse repetition rate of 106.3 MHz. Prompt-gamma ray timing distributions were measured with a detection unit consisting of a single ∅2 ” × 2 ” CeBr_3 crystal by Scionix, a Hamamatsu R13089-100 photomultiplier and a U100 digital spectrometer by Target Systemelektronik, which was placed at a backward angle of 130° . A static pencil beam was directed centrally at the phantom. The beam was pulsed in spots with a spot duration of 69 ms, a period of 72 ms and 1e9 (!) protons per spot (corresponding approximately to the combined signal of 8 prompt-gamma ray detection units for one strongly weighted clinical pencil beam scanning spot). One measurement consisted of 100 spots. Overall, the experiment comprised eight measurements covering the set of four cavity thicknesses ∆R and two beam energies E_1 and E_2. Experiments were carried out in the patient treatment room of OncoRay, Dresden.

Data preprocessing:

The raw data of each measurement was preprocessed as follows: The binary data was converted to ROOT. The photomultiplier gain drift was corrected for and the integral signal charge was converted into deposited energy. Time digitalisation nonlinearities were corrected for. The calibrated data was then saved in list-mode format. The data was assigned to the spot number and the detection time relative to the accelerator radiofrequency (fine time) was used to populate a prompt gamma-ray timing histogram for each spot. No background or phase shift correction were applied.

Data structure:

The dataset contains one root file for each measurement, named by the detector number in the format u100-p00XX and the measurement time. The spreadsheet MeasurementIndex_20160716_SingleSpot.xlsx contains the details of each measurement. The corrected and calibrated PGT spectra can be found in the root file at analysis/05_PGT_for_Layers_and_Spots.

Each root file contains the following directories:

  • analysis

    • 01_Layers_and_Spots_Detection: association between spot number and measurement time

    • 02_Gain_Correction: energy gain drift correction curve

    • 03_Energy_Calibration: energy calibration curve

    • 04_Fine_Time_Linearization: timing non-linearity calibration curve

    • 05_PGT_for_Layers_and_Spots: final PGT spectra - for each spot of each layer:

      • PGT_*_all: timing spectrum of the whole energy range

      • PGT_*_2,5to7MeV:  timing spectrum for events between 2.5 and 7 MeV only

      • PGT_*_3to5MeV: timing spectrum for events between 3 and 5 MeV only

      • ESpec: energy spectrum

      • EoT: two-dimensional energy-timing spectrum

  • data: list-mode data (not histogrammed)

    • uncorrected: before the correction and calibration steps

    • corrected: after the correction and calibration steps

  • meta: measurement meta data (log file containing applied detector HV etc.)

  • histograms: selected example histograms

For further questions, please refer to the contact persons stated in the Contributors section.

Keywords: proton therapy; treatment verification; prompt gamma-ray timing; experimental data

Involved research facilities

  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-36784


Evidence for a High-Valent Iron-Fluoride That Mediates Oxidative C(sp3)‐H Fluorination

Panda, C.; Anny-Nzekwue, O.; Doyle, L. M.; Gericke, R.; McDonald, A. R.

Abstract

(Fe(II)(NCCH₃)(NTB))(OTf)₂ (NTB = tris(2- benzimidazoylmethyl)amine, OTf = trifluoromethanesulfonate) was reacted with difluoro(phenyl)-λ³-iodane (PhIF₂) in the presence of a variety of saturated hydrocarbons, resulting in the oxidative fluorination of the hydrocarbons in moderate-to-good yields. Kinetic and product analysis point towards a hydrogen atom transfer oxidation prior to fluorine radical rebound to form the fluorinated product. The combined evidence supports the formation of a formally Fe(IV)(F)₂ oxidant that performs hydrogen atom transfer followed by the formation of a dimeric μ-F−(Fe(III))₂ product that is a plausible fluorine atom transfer rebound reagent. This approach mimics the heme paradigm for hydrocarbon hydroxylation, opening up avenues for oxidative hydrocarbon halogenation.

Keywords: high-valent iron; fluorination; hydrogen atom transfer; proton coupled electron transfer; fluorine atom transfer

Permalink: https://www.hzdr.de/publications/Publ-36782


Laser cutting of polymer templates for water-droplet induced self-folding of micron cubes: hinge geometry optimization

Lorenz, P.; Franz, R.; Ehrhardt, M.; Lecrivain, G.; Kirchner, R.; Zimmer, K.

Abstract

Droplet-induced self-folding processes enable the easy and cost-effective fabrication of submillimeter 3D structures from planar templates. These templates were fabricated by laser cutting of polymer foils that offers a high flexibility in design. The interaction of water droplets with template surfaces induces a surface tension force that causes deformation of the laser-cut templates needed to form the 3D structures. In this study, laser patterning of 25 µm thick polyimide (PI) foils by UV ultrashort pulse laser ablation was used to systematically investigate the effect of hinge thickness on the bending and self-folding process of cubes. The deposition of water droplets on the laser-structured samples leads to forces that move the side faces of the cube template causing a defined deformation of the hinges of the PI template and resulting in a bending angle between hinged template regions. The bending angle was determined as a function of hinge geometry and water droplet volume. The bending angle is increased with increasing droplet volume below a certain maximum, but decreased with increasing hinge thickness and width. The results provide guidelines for experimental optimization and reference data for computer-aided optimization of water droplet-induced self-folding of 3D structures.

Keywords: ps-laser; laser cutting; self-folding; water droplet

Permalink: https://www.hzdr.de/publications/Publ-36781


Data publication: Enantioselective Synthesis, Structure Activity Relationship, Radiofluorination and Biological Evaluation of [18F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET

Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Bormans, G.; Kopka, K.; Brust, P.; Moldovan, R.-P.

Abstract

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation in various pathological conditions, such as neuroinflammation and cancer. Herein we report on the enantioselective synthesis of a series of highly affine fluorinated indole-2-carboxamide ligands targeting the CB2R in the brain. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity (Ki = 2.1 nM) and pronounced selectivity over CB1R (factor > 300). A fully automated copper-mediated radiofluorination of [18F]RM365 was established starting from the corresponding aryl boronic acid pinacol ester precursor. Preliminary in vitro evaluation of [18F]RM365 indicated species differences in the binding to CB2R (KD of 2.32 nM for the human CB2R vs. KD > 10000 nM for the rat CB2R). Metabolism studies in mice revealed high stability of [18F]RM365 with fractions of parent compound of > 90% in the brain and > 54% in the plasma at 30 min p.i. PET imaging in a rat model of local hCB2R(D80N) overexpression in the brain demonstrate the ability of [18F]RM365 to reach and selectively label the intracranial expressed hCB2R(D80N) with high signal-to-background ratio. Thus, [18F]RM365 is a very promising PET radioligand for the imaging of upregulated hCB2R expression under pathological conditions with high potential towards clinical application in humans.

Keywords: cannabinoid receptor type 2; indole-2-carboxamide; binding affinity; radiochemistry; fluorine-18 labeling; positron-emission tomography

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Permalink: https://www.hzdr.de/publications/Publ-36778


Unraveling the multifaceted challenges and advances in validating tray efficiency prediction models

Vishwakarma, V.; Schubert, M.; Hampel, U.

Abstract

Industrial tray columns are widely used for distillation and absorption processes globally. They are known for high energy consumption, which is often overlooked due to unavailability of an equivalent industrially viable alternative. Rising energy costs and urgent need to control greenhouse gas emissions call for improvement in the performances of tray columns globally. This can be achieved by tuning the dynamics of the two-phase dispersion on individual trays for higher efficiencies via design modifications and revamping. To do so, it becomes necessary to understand how the two-phase flow evolves over a tray and relates to the tray efficiency. Such relation can be evaluated based on mathematical models called as tray efficiency prediction models. Hitherto, the existing models only provided black box estimations and ignored maldistributions in the vapor flow. These limitations were recently targeted by a new model referred to as ‘Refined Residence Time Distribution (RRTD) model’ [1].

The proof of concept of the RRTD model demands complete information pertaining to two-phase dispersion and mass transfer on a large-scale column tray. They are not available at desired resolution in the existing literature due to several limitations in the applied measurement techniques and systems. Thus, a recently-proposed multiplex flow profiler [2] was deployed inside an air-water column mockup (DN800) for characterizing the distributions of liquid holdup, residence time and mixing over a sieve tray for several loadings at high resolution. For the same operating conditions, the efficiency data over that tray was obtained based on air-led stripping of isobutyl acetate from the aqueous solution. Both hydrodynamic and efficiency data were applied together for assessing the validity of the new RRTD and other models. This works also sets new benchmarking standards for improved validation of CFD and efficiency prediction models in the future.

[1] Vishwakarma, V., Schubert, M. and Hampel, U., 2019. Development of a refined RTD-based efficiency prediction model for cross-flow trays. Industrial & Engineering Chemistry Research, 58(8), pp.3258-3268.
[2] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., 2020. Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten. Deutsches Patent und Markenamt, DE 10 2018 124 501.

Involved research facilities

  • TOPFLOW Facility
  • Open Access Logo Invited lecture (Conferences)
    2023 AIChE Spring Meeting and 19th Global Congress on Process Safety, 13.-16.03.2023, Houston, Texas, USA

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Permalink: https://www.hzdr.de/publications/Publ-36777


Where I am – Chemical microscopy of Eu(III) in plants

Klotzsche, M.; Steudtner, R.; Drobot, B.; Vogel, M.

Abstract

The strongly luminescent Eu(III) was applied as molecular probe to retrace the distribution of trivalent lanthanides in plant cells and entire plants upon metal exposure.

Keywords: Europium; Luminescence; Chemical microscopy; Raman microscopy; Spectroscopy; Plants; Lanthanide

  • Lecture (Conference)
    ICOBTE & ICHMET 2023, 06.-10.09.2023, Wuppertal, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36775


Exploring the Eu(III) translocation in hydroponically grown plants

Klotzsche, M.; Steudtner, R.; Vogel, M.; Drobot, B.

Abstract

Various biochemical, microscopic and spectroscopic techniques were applied to unravel the macroscopic and microscopic distribution and translocation of Eu(III) in hydroponically grown plants.

Keywords: Europium; Hydroponics; Plants; Spectroscopy; Chemical microscopy; Lanthanides

  • Lecture (Conference)
    Goldschmidt Conference 2023, 08.-13.07.2023, Lyon, Frankreich
  • Poster
    10. RCA Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36774


Eignung von Bestrahlungs-Logfiles für eine phantomlose patientenspezifische Qualitätssicherung in der Protonentherapie: Untersuchung der Reproduzierbarkeit von Logfile-Auswertungen

Wolter, L. C.; Hennings, F.; Bokor, J.; Richter, C.; Stützer, K.

Abstract

Einleitung
Da Bestrahlungs-Logfiles in der Protonentherapie Informationen über Energie, Position und Monitoreinheiten (MU) aller abgestrahlten Spots enthalten, ermöglichen sie eine Rekonstruktion der applizierten Dosis und bilden damit eine wichtige Komponente für eine phantomlose, patientenspezifische Qualitätssicherung (PSQA). Für eine zuverlässige Einschätzung der Dosisapplikation innerhalb einer solchen PSQA vor oder zum Therapiebeginn muss die Reproduzierbarkeit der Logfile-Parameter gewährleistet sein, d.h. tägliche Schwankungen der Logfile-Parameter dürfen keinen relevanten Einfluss auf die Fraktionsdosis haben. Wir haben Bestrahlungslogfiles diesbezüglich retrospektiv ausgewertet und deren Dosisverteilungen verglichen.

Material und Methoden
Die Logfile-Variabilität wurde sowohl auf Spotparameter- als auch auf Dosisebene untersucht. Für 14 Bestrahlungspläne (Tab.1; unterschiedliche Tumorlokalisationen und Gantrywinkel; 100 ≤ Energie/MeV ≤ 226,7; 0,02 ≤ MU/Spot ≤ 4,75) wurden die Logfiles aller Fraktionen analysiert. Aus den Parametern x/y-Position und MU wurden für 108.610 Spots die jeweilige mittlere Abweichung vom geplanten Wert (Genauigkeit) und die Standardabweichung vom Mittelwert (Reproduzierbarkeit) über alle Fraktionen berechnet. Die aus den Logfiles der insgesamt 339 Fraktionen rekonstruierten Dosisverteilungen wurden mittels 3D Gamma-Index-Analyse ausgewertet. Die dosisbasierte Γ-Durchlassrate wurde mit einer spotbasierten Logfile-Durchlassrate Λ(d) verglichen. Diese wurde definiert als die MU-Summe aller Spots, deren Distanz zur geplanten Position ≤ d ist, relativ zur Fraktions-MU.

Ergebnisse
Die mittlere spotweise Genauigkeit bezüglich der Planposition betrug (0,6 ± 0,3) mm und bezüglich der Plan-MU (0,0001 ± 0,0023) MU. Die mittlere Reproduzierbarkeit der Einzelspots lag bei (0,2 ± 0,1) mm und (0,0004 ± 0,0004) MU (Mittelwert ± Standardabweichung der Einzelwerte). Diese Abweichungen führen in allen untersuchten Fraktionen zu minimalen Änderungen in den Dosisverteilungen mit Gamma-Durchlassraten von Γ(2mm/2%) > 99%. Die Ergebnisse für sensitivere Kriterien Γ(1mm/1%) sind planspezifisch (Abb.1), jedoch pro Plan im Mittel > 92,6% und korrelieren mit der Λ(1mm)-Durchlassrate (Tab.1; 0,51 ≤ rPearson ≤ 0,99).

Zusammenfassung
Die untersuchten Einzelspotparameter sind über alle Fraktionen durchgängig stabil. Auch größere Positionsabweichungen sind im Submillimeterbereich reproduzierbar, was eher auf systematische Abhängigkeiten zwischen den Planparametern als auf Messfehler in den Strahlmonitoren hinweist. Geringe, klinisch nicht relevante Schwankungen in den Fraktionsdosisverteilungen konnten mittels sensitiver Gamma-Index-Analyse detektiert werden. Dies qualifiziert die Logfiles des Bestrahlungssystems für eine zuverlässige phantomlose PSQA und verspricht aufgrund der hohen Sensitivität einen außerordentlichen Nutzen für eine retrospektive Kontrolle der Bestrahlungsqualität im Rahmen einer zukünftigen online-adaptiven Protonentherapie.

Keywords: Proton therapy; Pencil beam scanning; Adaptive radiotherapy; Log-file analysis; Quality assurance

Involved research facilities

  • OncoRay
  • Lecture (Conference)
    54. Jahrestagung der DGMP, 26.-29.09.2023, Magdeburg, Sachsen-Anhalt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36773


Locally addressable energy efficient actuation of magnetic soft actuator array systems

Richter, M.; Sikorski, J.; Makushko, P.; Zabila, Y.; Kalpathy Venkiteswaran, V.; Makarov, D.; Misra, S.

Abstract

Advances in magnetoresponsive composites and (electro-)magnetic actuators have led to development of magnetic soft machines (MSMs) as building blocks for small-scale robotic devices. Near-field MSMs offer energy efficiency and compactness by bringing the field source and effectors in close proximity. Current challenges of near-field MSM are limited programmability of effector motion, dimensionality, ability to perform collaborative tasks, and structural flexibility. Herein, a new class of near-field MSMs is demonstrated that combines microscale thickness flexible planar coils with magnetoresponsive polymer effectors. We apply ultrathin manufacturing and magnetic programming of effectors to tailor their response to the nonhomogeneous near-field distribution on the coil surface. The MSMs are demonstrated to lift, tilt, pull, or grasp in close proximity to each other. These ultrathin (90 um) and lightweight (100 g/m2) MSMs can operate at high frequency (25 Hz) and low energy consumption (0.5 W), required for the use of MSMs in portable electronics.

Keywords: Magnetic soft machines; Planar coils; Magnetic near-field; Independent actuation

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36772


ASL lexicon and reporting recommendations: A consensus report from the ISMRM Open Science Initiative for Perfusion Imaging (OSIPI)

Suzuki, Y.; Clement, P.; Dai, W.; Dolui, S.; Fernández-Seara, M.; Lindner, T.; Mutsaerts, H. J.; Petr, J.; Shao, X.; Taso, M.; Thomas, D. L.

Abstract

The 2015 consensus statement published by the ISMRM Perfusion Study Group and the EU COST Action ‘ASL in Dementia’ aimed to encourage the implementation of robust Arterial Spin Labeling (ASL) perfusion MRI for clinical applications and promote consistency across scanner types, sites, and studies. Subsequently, the recommended 3D pseudo-continuous ASL sequence has been implemented by most major MRI manufacturers. However, ASL remains a rapidly and widely developing field, leading inevitably to further divergence of the technique and its associated terminology, which could cause confusion and hamper research reproducibility.
On behalf of the ISMRM Perfusion Study Group, and as part of the ISMRM Open Science Initiative for Perfusion Imaging (OSIPI), the ASL Lexicon Task-Force has been working on the development of an ‘ASL Lexicon and Reporting Recommendations’ for perfusion imaging and analysis, aiming to 1) develop standardized, consensus nomenclature and terminology for the broad range of ASL imaging techniques and parameters, as well as the physiological constants required for quantitative analysis, and 2) provide a community-endorsed recommendation on the imaging parameters that we encourage authors to include when describing ASL methods in scientific reports/articles.
In this manuscript, the sequences and parameters in (pseudo-)continuous ASL, pulsed ASL, velocity-selective ASL and multi-timepoint ASL for brain perfusion imaging are included. However, the content of the lexicon is not intended to be limited to these techniques, and this paper provides the foundation for a growing online inventory that will be extended by the community as further methods and improvements are developed and established.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-36771


miniSCIDOM: a scintillator-based tomograph for volumetric dose reconstruction of single laser-driven proton bunches

Corvino, A.; Reimold, M.; Beyreuther, E.; Brack, F.-E.; Kroll, F.; Pawelke, J.; Schilz, J.; Schneider, M.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Abstract

Laser plasma accelerators enable the generation of intense and short proton bunches on a micrometer scale, thus offering new experimental capabilities to research fields like ultra-high dose rate radiobiology or material analysis. Being spectrally broadband, laser-accelerated proton bunches allow for tailored volumetric dose deposition in a sample via single bunches to excite or probe specific sample properties. The rising number of such experiments indicates a need for diagnostics providing spatially-resolved characterization of dose distributions with volumes of ∼1 cm³ for single proton bunches to allow for fast online feedback.
Here we present the scintillator-based miniSCIDOM detector for online single-bunch tomographic reconstruction of dose distributions in volumes of up to ∼1 cm³. The detector achieves a spatial resolution below 500 μm and a sensitivity of 100 mGy. The detector performance is tested at a proton therapy cyclotron and an LPA proton source. The experiments’ primary focus is the characterization of the scintillator’s ionization quenching behavior.

Keywords: laser-driven proton beams; ultra-high dose rate; beam monitoring detectors; scintillator-based diagnostics

Involved research facilities

  • OncoRay
  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36770


Development of Analysis and Visualization Methods for Next-Generation Sequencing Phage Surface Display Data, Master thesis 2022

Bloß, C.

Abstract

Efforts in the field of biomolecular probes and materials science have been accelerated by the application of phage surface display technology. A practical complement to this technology is next-generation sequencing. This combination provides deeper insight into biopanning rounds with impurity identification, display of sequence read content, visualization of phage library evolution, and methods for displaying binding motifs. To implement these approaches, a pipeline was developed to preprocess the next-generation sequencing data using Sequana and fastqjoin. The raw sequences are then extracted and the inserts of the pIII coat protein genes of the M13 phage are isolated. The inserts are translated and written into a frequency list. From this, a series of matrices are formed to detect enrichments of amino acid abundances per position in the library. Protein sequences are also clustered and written to additional matrices to create sequence logos for sequence motif discovery. The pipeline was used to analyze two data sets. In the first dataset, a customized, unamplified mini-library was created and tested for bias. No preservation of sequence motifs was detected. The second data set was used to test whether the sequence motifs QxQ and SxHS could be confirmed as conserved sequence motifs. However, this data set had serious qualitative problems and no meaningful results could be obtained. Overall, it can be concluded that the created pipeline provides good results for large data sets if
the quality is sufficient.

Keywords: Bioinformatics; Biotechnology; Next-Generation Sequencing; Phage Surface Display; Biopanning; Statistics; Stochastic; Master thesis; Vizualisation; Analysis

  • Master thesis
    Hochschule Mittweida, 2022
    Mentor: Röbbe Wünschiers, Katrin Pollmann, Franziska Lederer
    92 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36769


Challenges and advantages of an e-LINAC based positron beam facility

Wagner, A.

Abstract

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions (σt ≈100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments.
In the presentation advantages and caveats of employing a high-power electron LINAC for secondary positron beam production will be discussed.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and by the Helmholtz Energy Materials Characterization Platform.
[1] A. Wagner, et al., AIP Conference Proceedings, 1970, 040003 (2018).

Keywords: positron annihilation; electron accelerator; linac; bremsstrahlung

Involved research facilities

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  • Invited lecture (Conferences) (Online presentation)
    Theme Meeting on Scientific Opportunities of ANURIB, 25.-27.04.2023, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-36768


Investigating binary granular mixing in a rotating drum using ultrafast X-ray computed tomography

Papapetrou, T. N.; Bieberle, M.; Barthel, F.; Hampel, U.; Lecrivain, G.

Abstract

The transient mixing dynamics of an initially segregated binary granular system in a half-filled rotating drum are investigated. The granular system consists of spherical beads having identical size. The density ratio between the two granular phases is 2.8. With its ability to scan three-dimensional opaque systems with a high frequency, the ultrafast X-ray computed tomography is used to capture the transient and steady-state segregation dynamics in the bulk. The segregation dynamics are also compared to those at the circular end-wall caps, which have been captured with a high-speed camera. The results show an axial migration of the denser particles towards the bulk and, more importantly, second-order overshooting dynamics in the radial mixing index, which tend to increase with the Froude number. The results will find application in industrial systems, where rapid mixing occurs. We also believe the presented data can serve as validation for future three-dimensional simulations focusing on the transient formation of segregation patterns in the bulk.

Keywords: granular mixing; rotating drum; ultrafast X-ray computed tomography; segregation dynamics

Involved research facilities

  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-36766


Data and code: Investigating binary granular mixing in a rotating drum using ultrafast X-ray computed tomography

Papapetrou, T. N.; Bieberle, M.; Barthel, F.; Hampel, U.; Lecrivain, G.

Abstract

Original video camera data, and time-averaged, beam-hardening-corrected, drift-corrected dynamic and static UFXCT image data used in the associated publication; code used for the final processing; and the final processed data. More details are found in the publication and in the info in the respective folders.

Keywords: granular mixing; rotating drum; ultrafast X-ray computed tomography; image processing

Involved research facilities

  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-36765


Uranium(VI) reduction by a Desulfitobacterium species in pure culture and in artificial multispecies bio-aggregates

Hilpmann, S.; Jeschke, I.; Deev, D.; Zugan, M.; Lapanje, A.; Rijavec, T.; Hübner, R.; Bok, F.; Schymura, S.; Cherkouk, A.

Abstract

The reduction of highly mobile and water soluble U(VI) to less mobile U(IV) represents a key process influencing the migration of this radionuclide in the environment. Microorganisms such as for example iron and sulfate-reducers are capable of reducing U(VI) under various conditions. This interaction mechanism between microbes and U could play an important role in a final disposal site for high-level radioactive waste deposited in deep geological layers. Different host rocks are suitable for the long-term storage of nuclear waste, e.g. clay formations, crystalline rock and rock salt. Besides the geochemical, geophysical and geological properties of such a repository, little is known about the influence of naturally occurring microorganism on the safety of such a site. In a worst-case scenario, if water enters the repository, radionuclides can get distributed in the surrounding host rock and thus interact with the native microorganisms, potentially leading to an immobilization of radionuclides via bioreduction. Furthermore, a reduction of U(VI) could also play an important role in the development of different bioremediation approaches for radionuclide-contaminated environments. As a potential component of new remediation strategies, we introduce the use of artificial bio-aggregates of different bacterial genera. By the use of these artificial biofilms insights into the complex interactions in a multi-species environment can be obtained. In this study, we used derivatized polyelectrolytes to form aggregates of two different microorganisms to connect advantageous properties of the microorganisms in a complementary way and to investigate the reduction of U(VI) under different conditions.
Desulfitobacterium sp. G1-2 was chosen as an important representative of iron-reducing bacteria in anaerobic environments. This bacterial strain was isolated from bentonite samples of the Full-scale Engineered Barrier Experiment – Dismantling Project (FEBEX-DP) at the Helmholtz Center Dresden-Rossendorf. Bentonites are supposed to serve as a possible backfill material, not only for a final disposal site in clay formations but also in crystalline rock. Furthermore, Desulfitobacterium species were detected in other clay formations as well, for example in Opalinus Clay.[1] These were used to form artificial bio-aggregates with different bacterial strains (among others Desulfitobacterium sp. G1-2 and aerobic marine inhabitant Cobetia marina DSM 50416) using electrostatic modifications of surface charge of bacterial cells.
Time-dependent experiments of Desulfitobacterium sp. G1-2 alone in 30 mM bicarbonate buffer (100 µM U(VI), 10 mM lactate) showed a decrease in U concentrations in the supernatants. Moreover, artificial Opalinus Clay pore water[2] (100 µM U(VI), 10 mM lactate, pH 5.5) was used as background electrolyte, as well, to create more environment-related conditions. In both cases, approximately 80% of the uranium was removed from the supernatants after one week. In order to be able to exclude abiotic influences on the uranium(VI) reduction, experiments using heat-killed cells were carried out, as well. Thermodynamic calculations of the U(VI) speciation in both solutions revealed the predominance of different U(VI) complexes in the used media. UV/Vis studies of the dissolved cell pellets verified the formation of U(IV) by an almost complete reduction of U(VI) in bicarbonate buffer and artificial Opalinus Clay pore water. In contrast, experiments with heat-killed cells did not show any reduction of U(VI) in the samples. STEM investigations coupled with EDX analysis of U-incubated cells showed the presence of two different U-containing aggregates inside the cells of Desulfitobacterium sp. G1-2. On the one hand, spherical nanoparticles are present, which are probably containing organic uranium phosphate compounds, as shown by EDX mapping of the samples. On the other hand, rod-shaped particles consisting of inorganic uranium phosphate compounds occur inside the cells as well.
First experiments with artificial bio-aggregates that were formed from different bacterial strains (e.g. Desulfitobacterium sp. G1-2 and Cobetia marina DSM 50416) using electrostatic modification of surface charge of bacterial cells by different polyelectrolytes showed a promising U reduction capacity in bicarbonate buffer (30 mM, 100 µM U(VI), 10 mM lactate). Future investigation will focus on the elucidation of the complex interaction mechanisms in multi-species environments.
This study helps to close existing gaps in a comprehensive safeguard concept for a repository for high-level radioactive waste in clay rock. Moreover, the results of these investigations provide new insights into the U(VI) reduction by iron-reducing microorganisms and thus, contribute to new knowledge on the migration of uranium in the environment. In addition, it may help to establish new bioremediation approaches of contaminated environments, because beneficial microbes can be used for the artificial bio-aggregates, even if they do not form biofilms themselves.

References
[1] A. Bagnoud et al. (2016). Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock. Nat. Commun. 2016, 7, 1–10
[2] P. Wersin et al. (2011). Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland. Appl. Geochemistry 2011, 26, 931–953

Keywords: Uranium(VI) reduction; Iron-reducing bacteria; Multispecies bio-aggregates

  • Lecture (Conference)
    Migration 2023, 24.-29.09.2023, Nantes, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36762


Redox transformation of uranium by iron-reducing bacteria as single culture and in artificial multispecies bio-aggregates

Hilpmann, S.; Jeschke, I.; Deev, D.; Zugan, M.; Lapanje, A.; Rijavec, T.; Hübner, R.; Schymura, S.; Cherkouk, A.

Abstract

Redox transformations have a strong influence on the mobility of different metal ions in the environment. A key process in influencing the migration of uranium is the reduction of highly mobile and water-soluble uranium(VI) to less mobile uranium(IV). Especially in the surroundings of former uranium mines, this radionuclide represents an important contaminant whose entry into the environment must be prevented. Different microorganisms, e.g. sulfate- and iron-reducing bacteria, are capable of reducing uranium under various conditions. Thus, microbes can offer an environmentally friendly remediation strategy for radionuclide-contaminated environments. Moreover, in this study, we introduce the use of artificial bio-aggregates of different bacterial genera as a potential bioremediation approach combining advantageous properties of the microorganisms in a complementary way.
Desulfitobacterium sp. G1-2, which was isolated from bentonite samples, was chosen as an important representative of iron-reducing bacteria in anaerobic environments. Furthermore, different Desulfitobacterium species were found in other natural environments, like clay formations as well. These bacteria were used to form artificial bio-aggregates with different other bacterial strains (e.g. aerobic marine inhabitant Cobetia marina DSM 50416) based on electrostatic modifications of the surface charge of the bacterial cells.
Time-dependent experiments of a pure Desulfitobacterium sp. G1-2 culture in 30 mM bicarbonate buffer as background electrolyte showed a decrease in uranium concentration in the supernatants (100 µM uranium(VI), 10 mM lactate, pH 6.8/5.5). Approximately 80% of the uranium were removed from the supernatants within one week. UV/Vis studies of the dissolved cell pellets verified the reduction of uranium(VI) in the samples. STEM imaging of ultra-thin sectioned samples of uranium-incubated cells coupled with EDX spectroscopy showed the presence of two different uranium-containing aggregates inside the microbes.
First experiments with artificial bio-aggregates that were formed from different bacterial genera (e.g. Desulfitobacterium sp. G1-2 and Cobetia marina DSM 50416) revealed a promising reduction capacity of uranium. Such artificial bio-aggregates have a potential in utilizing beneficial microbes in remediation strategies, even if they do not form biofilms themselves. Moreover, these investigations offer new insights in the complex interaction processes in multi-species environments.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Iron-reducing bacteria; Multispecies bio-aggregates

  • Poster
    Goldschmidt 2023, 09.-14.07.2023, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36760


Influence of microbial uranium reduction processes on the final disposal of radioactive waste

Hilpmann, S.; Jeschke, I.; Steudtner, R.; Hübner, R.; Schymura, S.; Stumpf, T.; Cherkouk, A.

Abstract

The safe disposal of high-level radioactive waste represents a major scientific and societal challenge. In addition to geological, geochemical and geophysical properties of such a repository, the influence of naturally occurring microorganisms from deep geological layers has to be taken into account for a comprehensive safeguard concept. Various sulfate- and iron-reducing bacteria are present in different clay formations, which can serve as a potential host rock for the long-term storage of the waste, as well as in the backfill material bentonite. In the event of a worst-case scenario, if water enters the repository, those microorganisms can interact with the waste and change for example the oxidation state or the chemical speciation, which can influence the mobility of the radionuclides.
In this study, the reduction of highly-mobile, water-soluble U(VI) to less mobile U(IV) by the iron-reducing microorganism Desulfitobacterium sp. G1-2 and the sulfate-reducer Desulfosporosinus hippei DSM 8344T were investigated. Desulfitobacterium sp. G1-2 has been isolated from a bentonite sample and Desulfosporosinus hippei DSM 8344T represents a genus of sulfate-reducing bacteria present in clay rock and bentonite.
During time-dependent experiments in bicarbonate buffer (30 mM, 100/550 µM U(VI)), Desulfitobacterium sp. G1-2 showed a removal of up to 80% of U within 5 days, whereas samples of Desulfosporosinus hippei DSM 8344T showed no decrease in U concentrations over time. Therefore, experiments were carried out in artificial Opalinus Clay pore water with this bacterium (100 µM U(VI), pH 5.5). In this case, the U concentration showed a decrease of up to 80% of the radionuclide from the supernatants within 48 h. UV/Vis studies of dissolved cell pellets of both bacteria after U incubation showed an almost complete reduction to U(IV) for Desulfitobacterium sp. G1-2. On the other hand, samples of Desulfosporosinus hippei DSM 8344T exhibited only a partial reduction. TEM imaging combined with EDX analysis revealed the release of membrane vesicles from cells of Desulfosporosinus hippei DSM 8344T as a possible defense reaction against cell incrustation. Furthermore, TEM images of Desulfitobacterium sp. G1-2 cells showed the presence of two different U-containing aggregates inside the cells.
These investigations showed clear differences in the reduction behavior of sulfate- and iron-reducing bacteria relevant to nuclear waste storage. This highlights the importance of studies on the U(VI) interactions of different microorganisms present in deep geological layers. Moreover, new aspects for a safety concept for a nuclear repository in clay formations and for final disposal sites using bentonite as backfill material could be revealed.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Iron-reducing bacteria; Nuclear waste disposal

  • Poster
    Interdisziplinäres Forschungssymposium SafeND, 13.-15.09.2023, Berlin, Deutschland
  • Open Access Logo Contribution to proceedings
    Interdisziplinäres Forschungssymposium Safe ND, 13.-15.09.2023, Berlin, Deutschland
    DOI: 10.5194/sand-2-151-2023

Permalink: https://www.hzdr.de/publications/Publ-36759


A Morphology-Adaptive Multifield Two-Fluid Model

Meller, R.; Schlegel, F.; Krull, B.

Abstract

Industrial multiphase flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed (e.g., Euler-Euler) or resolved (e.g., Volume-of-Fluid) interfacial structures. A simulation method that requires less knowledge about the flow in advance would be desirable and should allow describing both interfacial structures – resolved and dispersed – in a single computational domain. Such methods that combine interface-resolving and non-resolving approaches are called hybrid models. A morphology adaptive multifield two-fluid model, named OpenFOAM-Hybrid, is proposed, which is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. An interfacial drag formulation for large interfacial structures is used to describe them in a volume-of-fluid-like manner. For the dispersed structures, the baseline model developed at Helmholtz-Zentrum Dresden - Rossendorf is applied. The functionality of the framework is demonstrated by several test cases, including a single rising gas bubble in a stagnant water column. Recent developments focus on the transition region, where bubbles are over- or under-resolved either for Euler-Euler or for Volume-of-Fluid.

  • Poster
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36758


A Morphology-Adaptive Multifield Two-Fluid Model: Recent developments and applications

Schlegel, F.; Krull, B.; Lehnigk, R.; Meller, R.; Tekavcic, M.

Abstract

Physical phenomena in industrial gas-liquid flows typically span a wide range of length
and time scales. Individual flow regimes are usually modelled using specific approaches,
which are mainly characterised by the level of detail the existing interfaces are handled
with. The cross-scale nature of multiphase flows requires the simultaneous application and
flexible switching between these methods in a single common framework.
For this reason, a morphology-adaptive model is established by combining the Euler-
Euler model with the Volume-of-Fluid (VOF) model. Interactions and transitions between
different morphologies and scales are taken into account by dedicated models. This work
gives an overview over recent advances towards a fully scalable morphology-adaptive
multiphase model (MultiMorph).
In order to be applicable to realistic, large-scale problems, special care is required to
ensure a robust model behaviour, even if the spatial resolution is not optimal in terms of
the respective flow phenomena. Large interfaces might be represented on coarse numerical
grids. The usual VOF model typically over-predicts the interfacial shear stress in such
a situation, resulting in unrealistic interface dynamics. Instead, a resolution-adaptive
interfacial coupling is proposed. In that way the phases may slip along each other in the
direction parallel to the interface, improving the prediction, i.e., of interface shape or of
bubble rising velocity.
A central building block of morphology-adaptive methods is the ability of structures to
evolve from one morphology to another. For example, unresolved bubbles may coalesce,
grow, or enter highly-refined mesh regions, such that a resolved representation becomes
possible. Therefore, a transition to a continuous representation is realised, to make optimal
use of the available numerical degrees of freedom. The opposite case, the transition from a
continuous to a dispersed representation, is handled as well. This becomes relevant in case
of mesh coarsening or if large continuous structures disintegrate into to smaller particles
which cannot longer be resolved by the given spatial resolution.
Another important feature of the model is the ability to track large numbers of dispersed
particles. A class-method based solution approach is included, providing complete
information about the size distribution, a necessity for modelling the number-conservative
transition between dispersed and resolved structures. However, the associated computational
cost is significant. Fortunately, the solution of the population balance equation could
be parallelised by outsourcing it to graphics processing units, which leads to a significant
improvement in performance.
The MultiMorph model is implemented in the software released by the OpenFOAM
Foundation with strong focus on sustainable research, including a state-of-the-art IT
approach. Both the source code and a comprehensive suite of simulation cases are publicly
available. Several multi-scale applications are presented, featuring for example a distillation
column, a swirl separator, and a impinging jet. Further details can be found at
www.hzdr.de/multimorph.

  • Poster
    19th Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 19.-23.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36757


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

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

Abstract

Simulation and literature data on the electrical and thermal conductivity of iron. The raw simulation data was generated from time-dependent density functional theory calculations. Post-processing was applied to obtain the transport properties (conductivities) as described in the associated journal publication. The literature data was compiled from available publication data as referenced in the associated journal publication.

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

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Permalink: https://www.hzdr.de/publications/Publ-36755


Current state of Na-Zn battery research

Weber, N.

Abstract

Within the Horizon 2020 project SOLSTICE, two molten salt battery concepts, based on sodium and zinc, are developed. The first cell relies on a solid Na-beta’’-alumina membrane, and is very similar to the commercially available ZEBRA batteries. Operating at 300°C, this design benefits from a wide range of knowledge available from these existing batteries. The second cell concept, a fully liquid battery, operates around 600°C. Due to its novelty, this design presents a larger number of challenges, such as corrosion, sealing and self-discharge. Once these are solved, the sodium-zinc battery can be employed as a very competitive and sustainable stationary energy storage device due to the lower costs, abundance and recyclability of the active materials. The talk will give an overview on the current state of research in the SOLSTICE consortium, the achievements and the remaining challenges in Na-Zn battery development.

  • Lecture (Conference)
    SUPHER23 (SUstainable PolyEnergy generation and HaRvesting), 06.-08.09.2023, Savona, Italy

Permalink: https://www.hzdr.de/publications/Publ-36754


Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch den Einsatz von 3D-gedruckten Zickzack-Packungen

Loll, R.; Bieberle, A.; Schubert, M.; Koop, J.; Held, C.; Schembecker, G.

Abstract

Poster zum Thema: Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch Einsatz 3D-gedruckter Zickzack-Packungen

Keywords: Zickzack-Packungen; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

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  • Poster
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36753


Neues Konzept zur Flüssigkeitsverteilung für Rotating Packed Beds

Pyka, T.; Koop, J.; Bieberle, A.; Schubert, M.; Held, C.; Schembecker, G.

Abstract

Vorstellung eines neuen Konzepts zur Flüssigkeitsverteilung für Rotating Packed Beds

Keywords: Rotating Packed Beds; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

Related publications

  • Lecture (Conference)
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36752


OCTOPOD: single bunch tomography for angular-spectral characterization of laser-driven protons

Reimold, M.; Assenbaum, S.; Beyreuther, E.; Bodenstein, E.; Brack, F.-E.; Eisenmann, C.; Englbrecht, F.; Kroll, F.; Lindner, F.; Masood, U.; Pawelke, J.; Schramm, U.; Schneider, M.; Sobiella, M.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Abstract

Laser-plasma accelerated (LPA) proton bunches are now prepared and provided for research fields ranging from ultra-high dose rate radiobiology to material science and probing of extreme states of matter. Yet, the capabilities to fully characterize the spectrally and angularly broad LPA bunches lag behind the rapidly evolving applications. The Optical Cone beam TOmograph for Proton Online Dosimetry - short OCTOPOD - translates the angularly resolved spectral characterization of LPA proton bunches into the spatially resolved detection of the volumetric dose distribution deposited in a liquid scintillator. Up to 24 multi-pinhole arrays record projections of the volumetric scintillation light distribution and allow for tomographic reconstruction of the volumetric dose deposition pattern, from which proton spectra may be retrieved in arbitrary directions by spectral deconvolution.
Applying the OCTOPOD at a cyclotron, we show the reliable retrieval of various spatial dose deposition patterns and detector sensitivity over a broad dose range from less than 1 Gy to more than 100 Gy, as required for LPA proton bunch characterization. With a dedicated vacuum housing, the OCTOPOD was installed at a LPA proton source, providing real-time data on proton acceleration performance for various laser-target interaction parameters and attesting the system optimal performance in the harsh laser plasma environment.

Keywords: laser-plasma acceleration of protons; proton detector; tomographic reconstruction

Involved research facilities

  • OncoRay
  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36751


Direct numerical simulation of a flexible fiber interacting with a fluidic interface

Lecrivain, G.

Abstract

The dynamics of fibers at a fluidic interface is of significant importance in various processes, among which stand out textile flotation, stabilization of emulsions, micro-folding of elastic structures, and clogging of feather fibers by oil droplets. A consistent formulation for the direct numerical simulation of a flexible fiber interacting with a fluidic interface is presently suggested. The fiber is geometrically decomposed into a chain of spherical beads, which undergo stretching, bending, and twisting interactions. The capillary force, acting at the three-phase contact line, is calculated using a ternary diffuse-interface model. Each ingredient of the model was validated against theoretical solutions. Partial and complete wrapping of an immersed three-dimensional drop is successfully simulated. The results show that the fiber curvature increases linearly with the square of the elasto-capillary length, for both low and large structural deformation, in-line with previously experimental observations

Keywords: Simulation; Particle at interface

  • Invited lecture (Conferences)
    Final Conference - MSCA-ITN-EID COMETE, 28.-29.03.2023, Udine, Italy

Permalink: https://www.hzdr.de/publications/Publ-36750


Effect of helium ion implantation on nanomechanical resonators in 3C-SiC

Jagtap, N.; Klaß, Y.; David, F.; Bredol, P.; Weig, E.; Helm, M.; Astakhov, G.; Erbe, A.

Abstract

Silicon carbide (SiC) is a suitable candidate for nanoelectromechanical systems due to its superior mechanical properties. It is also an interesting material platform to study the coupling of mechanical modes with localized spins associated with irradiation-induced defects. Such a spin-mechanical system can be used for quantum sensing applications [1].
The nanomechanical resonators in 3C-SiC are fabricated by standard semiconductor processing techniques such as electron beam lithography and reactive ion etching. They are characterized using Fabry-Pérot interferometer. In the preliminary experiments, we focus on the material modification by helium ion broad beam implantation on strained 3C-SiC resonators. The effect of varying fluence on resonance frequencies and quality factors is studied. With the fluence of 1 X 10^14 /cm^2 we observe decrease in resonant frequencies (~ 15%) and quality factors.

[1] A. V. Poshakinskiy and G. V. Astakhov, "Optically detected spin-mechanical resonance in silicon carbide membranes”, PhysRevB.100.094104 (2019)

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Related publications

  • Poster
    Frontiers of Nanomechanical Systems (FNS) workshop, 06.-09.06.2023, Art Center Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36749


New Cross Section Data for Radiative Proton Capture on Carbon for Nuclear Astrophysics at LUNA

Boeltzig, A.; Skowronski, J.

Abstract

The observable ratio of 12C/13C can be used as a probe for stellar nucleosynthesis as well as for mixing processes during hydrogen burning, provided that the reaction rates of 12C(p,γ)13N and 13C(p,γ)14N are known. To obtain direct cross section measurements at low energies, which are required to better constrain these rates in astrophysical scenarios, both reactions were studied in a series of experiments at the LUNA-400 accelerator. Different targets and complementary detector setups were employed for a systematic study, and the sensitivity afforded by the low-background underground environment allowed for precise measurements at lower energies than previously available. We will present these experiments and their results for both reactions.

  • Lecture (Conference)
    DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36748


MetroPOEM – Metrology for the harmonisation of measurements of environmental pollutants in Europe

Arnold, D.; Eberhardt, J.; Flierl, L.; Rienitz, O.; Pramann, A.; Zapata, D.; Vogl, J.; Prem, P. S.; Lourenço, V.; Chambon, L.; Isnard, H.; Mazánová, M.; Sochorová, J.; Zuliani, T.; Goltnik, T.; Rovan, L.; Štrok, M.; Noireaux, J.; Kamarainen, M.; Engin, B. A.; Can, S. Z.; Cankur, O.; İşleyen, A.; Hansen, V.; Ulrich, T.; Andreasen, R.; Hou, X.; Qiao, J.; Pröfrock, D.; Wippermann, D.; Zimmermann, T.; Winkler, S.; Fichter, S.; Wallner, A.; Schöpke, C.; Johansen, I.; Yasin, V.; Ioan, M.-R.; Virgolici, M.; Olaru, C.; Badea, R.; Walther, C.; Irrgeher, J.; Lancaster, S.; Epov, A.; Chernonozhkin, S.; Wagner, S.; Jerome, S.; Skipperud, L.; Jensen, K.-A.; Salminen-Paatero, S.; Vukanac, I.; Čeliković, I.; Rajačić, I.; Djurašević, M.; Nikolić, J. K.; Christl, M.; Tribouillier, H. P.; Malinovskiy, D.; Hil, S.; Goenaga-Infante, H.; Strekopytov, S.; Russell, B.; Mohamud, H.; Thompkins, H.

Abstract

Summary

The European Green Deal’s ambition for zero pollution requires the development of highly sensitive techniques to detect ultra-low amounts of pollutants. This requirement will be delivered via strategies described by the two European Metrology Network (EMN) on Pollution Monitoring (PolMo) and the EMN on Radiation Protection, supporting the Basic Safety Standards directive. Implicit in these strategies is a strong need to improve data quality for monitoring and reporting pollution in the air, water, and soil. To detect radioactive isotopes and stable polluting elements in the environment, fast, sensitive, and inexpensive analytical procedures are needed. Mass spectrometry is a key method for determination of non-radioactive polluting elements and of increasing importance for long-lived radionuclides, however, application of single collector ICP-MS, this potential cannot be fully realised unless techniques are validated with traceable multi-element reference materials. However, multi-element certified reference materials are usually not available and single-element certified reference materials are limited to very few elements. Nevertheless, these reference materials are urgently needed to calibrate mass spectrometric measurements, to overcome mass bias effects occurring during the measurements in mass spectrometers. The MetroPOEM project (21GRD09) is designed to address these problems. MetroPOEM, coordinated by the Physikalisch-Technische Bundesanstalt of Germany, will be delivered by a consortium of 22 partners from 13 countries throughout Europe.

Objectives

The overall aim of MetroPOEM is to bridge the gap between radiometric techniques and mass spectrometry for the characterisation and detection of polluting long-lived radionuclides and stable elements and element tracers by comparing and linking both techniques, thus significantly improving measurement uncertainties and detection limits. These aims and objectives will be delivered through four technical work packages, supported by project and impact management activities:

  • Establish and compare (inter-laboratory) the selectivity and detection limits of diverse types of mass spectrometers for selected radioactive pollutants (e.g., U, Np, Pu, Am) using isotope reference materials and/or activity standards. This includes assessing relative instrument performance with respect to current measurement challenges and establishing detection limits in relation to environmental regulations.
  • Develop measurement methods for isotope ratios that are traceable to the SI by using multi-collector ICP-MS and apply these methods on more commonly available techniques (ICP-MS/MS, ICP-QMS) by providing suitable operating procedures focussing on stable polluting elements (e.g., Li, B, Cr, Cd, Ni, Sb, Pb, U). To produce recommendations for sample processing, treatment, uncertainty budgets, and if feasible, the quantification of the so-called mass bias.
  • Develop two radioactive reference materials with the sample matrix containing radioactive pollutants (e.g., U, Np, Pu, Am) for use in an inter-laboratory comparison employing techniques used WP1, which will demonstrate the variations in parameters including detection limits, sample preparation, sample introduction methods, total procedural time, and uncertainty budgets.
  • Implement and validate the methods for isotope ratio measurements established in objective 2 by the development of one aqueous certified reference material that is certified for the same stable polluting elements with lowest possible uncertainties using multi-collector instruments, to facilitate the calibration of single collector ICP-MS, instrument validation, as well as quality control.
  • Facilitate the acceptance of the technology and measurement infrastructure developed in the project by the measurement supply chain (e.g., accredited laboratories), standards developing organisations and international organisations and end users (e.g., environmental monitoring agencies).

Involved research facilities

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  • Poster
    10. RCA-Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36747


Comparison of different CFD approaches for the simulation of developing free surface two-phase flow in straight and bent pipes

Döß, A.; Höhne, T.; Schubert, M.; Hampel, U.

Abstract

Two-phase flows in feed pipes of thermal separation columns have complex flow patterns and are difficult to predict during sizing and design for geometries with non-straight pipes. Numerical simulation codes have only been validated for very few pipe geometries. This work benchmarks the state-of-the-art Volume-of-Fluid model (VoF) and the Algebraic Interfacial Area Density model (AIAD) for the simulation of two-phase flows with the Eulerian/Eulerian CFD approach for straight pipes and horizontal bends as well as for different pipe diameters and flow rates. Both models are compared and shortcomings of the predicted velocity fields from AIAD in the vicinity of horizontal bends are highlighted. Predicted average phase fractions agree reasonably with experimental data. From the numerical results, recommendations for the selection of feed inlet devices are derived.

Keywords: Horizontal two-phase feeds; Flow morphology; Numerical simulation; VoF; AIAD; CFD; Wire-mesh sensors

Involved research facilities

  • TOPFLOW Facility

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  • Secondary publication expected from 18.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36746


Exploring the lowest levels of environmental 90Sr in carbonates and seawater using a new, highly sensitive Accelerator Mass Spectrometry technique

Winkler, S.; Martschini, M.; Merchel, S.; Steier, P.; Golser, R.

Abstract

1 Introduction

Strontium-90 (90Sr) is an anthropogenic radionuclide, which, due to its radiological relevance, has been most intensively monitored in the past. In terms of initial activity, over 630 PBb of this radioisotope have been distributed globally from stratospheric fallout of bomb-testing, and there are more localized contributions from test, accidents, and releases from reprocessing plants.[1] Despite of the massive spike of 90Sr from global fall-out has been very difficult to measure in the ocean, due to the massive dilution in the oceans and the low atom detection efficiency of decay counting measurements. Massive sample sizes (up to 100 l of seawater or 100 g of coral aragonite) were required even right after the peak period of global fall-out from bomb testing. On the other hand, the high amount of strontium dissolved in seawater complicates the use of mass spectrometric methods, as an isotopic abundance sensitivity of at least 1·10-15 is required to detect the estimated main signal. Here we report on the results of successful measurements of such samples using a new Accelerator Mass Spectrometry (AMS) technique [2].

2 Samples and Methods

Our interest in this study lies in the determination of 90Sr as geochemical and ocean current tracer in conjunction with another anthropogenic tracer isotope, 236U. Both the respective elements both get build into marine carbonates such a coral samples, and both are present in significant amounts in seawater. While 236U is a well-established isotope and can be measured at very low levels (<10-13 236U/U) with AMS, only recent advances in isobar separation technique in AMS at the University of Vienna have opened possibility to measure 90Sr at the required level. The new technique uses an ion-cooler and laser-photo-detachment to suppress the stable isobar 90Zr. Besides the isobar suppression in the mass spectrometer system, we also gain a boost in suppression using ion-exchange columns. Since we are interested in measuring 90Sr against 236U we developed a sample preparation technique to extract both efficiently from a calcium carbonate matrix, while suppressing 90Zr, and avoiding pre-concentration steps. In principle, this could also be applied to seawater samples, although the efficiency of uranium co-precipitation in with carbonates still needs investigation. In this study we relied on separate procedures in the case of sea water samples.

3 Results

With initial test samples we could confirm a detection limit for the method corresponding to 0.03 mBq (or better) and a 90Sr/Sr isotopic abundance sensitivity of <8·10-16. We will present results from contemporary coral skeleton material, the methods, requirements, and impact of sample preparation. Further, we explain our sample preparation scheme to extract 236U, another important anthropogenic radionuclide, simultaneously with 90Sr for multi-isotope applications of both. Finally, the sample preparation and blank levels for ocean water samples and the results will be shown.

  • Lecture (Conference)
    RCA-Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36745


Porous Magnesium Oxide by Twin Polymerization: From Hybrid Materials to Catalysis

Scharf, S.; Notz, S.; Thomas, R.; Mehring, M.; Tegenkamp, C.; Formánek, P.; Hübner, R.; Lang, H.

Abstract

Twin monomers [Mg(2-OCH2-cC6H4O)][L]0.8 (2, L=diglyme) and [Mg(2-OCH2-cC6H4O)][L]0.66 (3, L=tmeda) form by their thermal polymerization interpenetrating organic-inorganic hybrid materials in a straightforward manner. Carbonization (Ar) followed by calcination gave porous MgO (2: surface area 200 m2g-1, 3: 400 m2g-1), which showed in catalytic studies towards Meerwein-Ponndorf-Verley reductions excellent yields and complete conversions for cyclohexanone and benzaldehyde. However, with crotonaldehyde a mixture of C4–C8 compounds was obtained. When MgO was exposed to air then primarily crotyl alcohol was formed. The range of applications could be easily extended by twin polymerization of 3 in presence of [Cu-(O2CCH2O(CH2CH2O)2Me)2] (4) or [Ag(O2CCH2-cC4H3S)(PPh3)] (5), resulting in the formation of nanoparticle-decorated porous CuO@MgO or Ag@MgO materials, which showed high catalytic reactivity towards the reduction of methylene blue.

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Permalink: https://www.hzdr.de/publications/Publ-36744


How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) – A microspectroscopic study.

Klotzsche, M.; Vogel, M.; Sachs, S.; Raff, J.; Stumpf, T.; Drobot, B.; Steudtner, R.

Abstract

Herein, Eu(III) was representatively used as luminescent probe to study the chemical environment and to elucidate the molecular interactions of lanthanides with a suspension cell culture of Nicotiana tabacum BY-2. Biochemical methods were combined with luminescence spectroscopy, two-dimensional microspectroscopic mappings, and data deconvolution methods to resolve bioassociation behavior and spatial distribution of Eu(III) in plant cells.

Keywords: Europium; Tobacco BY-2; Luminescence; Chemical microscopy; Raman microscopy; Plant cells; Species analysis; Lanthanides; Bioassociation

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  • Secondary publication expected from 30.08.2024

Permalink: https://www.hzdr.de/publications/Publ-36743


Data publication: Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

Data from flow visualization experiments, results of numerical simulations and Particle Image Velocimetry image data

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36742


Laser Transmission in the Relativistically Induced Transparency Regime for High Performance Proton Acceleration at PW Laser Systems

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by laser-plasma sources promises many applications, but reaching the required beam quality parameters demands a high level of understanding and control over the interaction process. Several advanced schemes, including the Relativistically Induced Transparency (RIT) regime, have been proposed and investigated in search of a stable acceleration for proton energies beyond 100 MeV. In the RIT scheme, the absorption of the electromagnetic laser field by the target and the generated plasma is critical. In joint experiments at the DRACO PW (HZDR) and J-KAREN (KPSI) lasers, we use transmission diagnostics to study the onset of transparency and learn about the sensitivity of the laser input to improve the process’s robustness. Using ultra-short pulses on thin solid density foil targets, we observe high performance proton beams in an expanded foil case. Our analysis of the effects on the transmission and its correlation with the acceleration performance indicates changes in the plasma interaction process.

Keywords: laser plasma; laser proton acceleration; high power laser

Involved research facilities

  • Draco
  • Lecture (Conference)
    DPG-Frühjahrstagung 2023; SMuK2023, 20.-24.03.2023, Dresden, Deutschland
  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2023, Praha, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-36740


Revisiting power-law distributions in empirical outage data of power systems

Hartmann, B.; Deng, S.; Ódor, G.; Kelling, J.

Abstract

The size distribution of planned and forced outages in power systems have been studied for
almost two decades and has drawn great interest as they display heavy tails. Understanding of this
phenomenon has been done by various threshold models, which are self-tuned at their critical points,
but as many papers pointed out, explanations are intuitive, and more empirical data is needed to
support hypotheses. In this paper, the authors analyze outage data collected from various public
sources to calculate the outage energy and outage duration exponents of possible power-law fits.
Temporal thresholds are applied to identify crossovers from initial short-time behavior to power-
law tails. We revisit and add to the possible explanations of the uniformness of these exponents.
By performing power spectral analyses on the outage event time series and the outage duration
time series, it is found that, on the one hand, while being overwhelmed by white noise, outage
events show traits of self-organized criticality (SOC), which may be modeled by a crossover from
random percolation to directed percolation branching process with dissipation. On the other hand,
in responses to outages, the heavy tails in outage duration distributions could be a consequence of
the highly optimized tolerance (HOT) mechanism, based on the optimized allocation of maintenance
resources.

Keywords: power grid; self-organized criticality; highly optimized tolerance

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Permalink: https://www.hzdr.de/publications/Publ-36739


Optimizing PW Laser-Driven Proton Acceleration by Characterizing Laser Transmission of Relativistically Transparent Targets

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by compact laser-plasma sources has great potential for a range of applications, including those with medical relevance and fusion experiments. However, in order to achieve the necessary beam quality parameters for these applications, a thorough understanding and control over the laser-plasma interaction process is required.
Therefore, we are exploring laser plasma acceleration around the promising regime of Relativistically Induced Transparency (RIT) through joint studies at DRACO PW (HZDR) and the J-KAREN-P laser system at KPSI. We have performed thickness scans to investigate the relation between proton acceleration performance and target transparency, revealing high-performance proton beams (> 60 MeV) in an expanded foil case, with an optimum at the onset of target transparency. [1] Subsequent experiments showed even higher proton energies.
Clearly, the relationship between the transparency onset time and the acceleration performance is crucial for achieving optimal beam parameters, improving our understanding of the sensitivity of laser input parameters, and increasing the process’s robustness. Thus, we are using a combination of particle and laser diagnostics to investigate this correlation. In this contribution, we present a summary of our studies in which we use spectral interferometry with the unperturbed laser beam as a reference to evaluate the output of reflected and transmitted light diagnostics. Obtaining features like shown in Bagnoud et al. [2] and Williamson et al. [3], we additionally correlate these measures with the proton acceleration performance and show first results of spectral, spatial, and energy analysis of the effects on the laser transmission through the target.

References
[1] Dover, N. P. et al.: Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities. Light Sci. Appl. in press (2023).
[2] Bagnoud, V. et al.: Studying the Dynamics of Relativistic Laser-Plasma Interaction on Thin Foils by Means of Fourier-Transform Spectral Interferometry. Phys. Rev. Lett. 118, 255003 (2017).
[3] Williamson, S. D. R. et al.: Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions. Phys. Rev. Appl. 14, 034018 (2020).

Keywords: laser plasma; laser proton acceleration; high power laser

Involved research facilities

  • Draco
  • Poster
    Laser and Plasma Accelerators Workshop 2023, 06.-10.03.2023, Lagos, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36738


State-of-the-Art Room Temperature Operable Zero-Bias Schottky Diode-Based Terahertz Detector up to 5.56 THz

Yadav, R.; Ludwig, F.; Faridi, F. R.; Klopf, J. M.; Roskos, H. G.; Preu, S.; Penirschke, A.

Abstract

We present the characterization of a Zero-bias Schottky diode-based Terahertz (THz) detector up to 5.56 THz. The detector was operated with both a table-top system until 1.2 THz and at a Free-Electron Laser (FEL) facility at singular frequencies from 1.9 to 5.56 THz. We used two measurement techniques in order to discriminate the sub-ns-scale (via a 20 GHz oscilloscope) and the ms-scale (using the lock-in technique) responsivity. While the lock-in measurements basically contain all rectification effects, the sub-ns-scale detection with the oscilloscope is not sensitive to slow bolometric effects caused by changes of the IV characteristic due to temperature. The noise equivalent power (NEP) is 10 pW/√Hz in the frequency range from 0.2 to 0.6 THz and 17 pW/√Hz at 1.2 THz and increases to 0.9 μW/√Hz at 5.56 THz, which is at the state of the art for room temperature zero-bias Schottky diode-based THz detectors with non-resonant antennas. The voltage and current responsivity of ∼500 kV/W and ∼100 mA/W, respectively, is demonstrated over a frequency range of 0.2 to 1.2 THz with the table-top system.

Keywords: FELBE; THz detectors; FEL; Schottky; ultrafast

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Permalink: https://www.hzdr.de/publications/Publ-36737


Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

We performed an experimental and numerical investigation of a convective buoyancy-driven instability that arises during the injection of a denser miscible fluid into a less dense one in a rectilinear geometry. We visualized the instability using a shadowgraph technique and we obtained quantitative information using micro-Paricle Image Velocimetry. Numerical simulations provided further insights into the 3D velocity field. We suggest scalings of the critical time, TC and dimensionless wavelength, λ/h of the instability by using the Péclet and Rayleigh numbers. Finally, we investigated the interactions of the instability vortices with each other and the geometry boundaries.

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36736


Positron beams for materials research

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

Abstract

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions (σt ≈100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and by the Helmholtz Energy Materials Characterization Platform.
[1] A. Wagner, et al., AIP Conference Proceedings, 1970, 040003 (2018).

Keywords: positron annihilation; lifetime spectroscopy; superconducting linear accelerator; defect characterization; porosity; vacancies

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  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 26.-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36735


Quasi-2D FCC lithium crystals inside defective bi-layer graphene: insights from first-principles calculations

Zhang, X.; Ghorbani Asl, M.; Zhang, Y.; Krasheninnikov, A.

Abstract

Quasi-2D crystals inside bilayer graphene have been observed in in-situ TEM experiments [Nature 564 (2018) 234]. It was also revealed that Li crystals have the FCC structure, nucleate at point defects in graphene and contain impurity atoms. Using first-principles calculations, we systematically study the interaction of isolated Li atoms and those assembled in FCC crystals with vacancy-type defects in graphene and show that quasi-2D Li crystals encapsulated between graphene sheets must indeed nucleate at the defects and that the interaction of not only isolated Li atoms but also Li crystals with the defects in graphene is strong. We further demonstrate that a moiré pattern develops at the graphene/Li interface. Finally, we investigate the behavior of impurities most likely to be found in the encapsulated Li crystals, such as O, N, S, and F and show that all impurity atoms take octahedral interstitial positions and strongly interact with atoms in Li crystals, thus impeding the de-lithiation process. Our theoretical work focused on the fundamental aspects of the behavior of Li inside bilayer graphene should help rationalize the results of in-situ TEM experiments and shed light on the role of impurities in the degradation of anode materials during Li-ion battery operation.

Keywords: Li intercalation; graphene; defects; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-36733


Hydrodynamics in a bubble column – Part 1: Two-phase flow

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

Multiphase computational fluid dynamics (CFD) simulation is a useful tool to study the hydrodynamics in a bubble column, if appropriate closure models are known. Systematic assessment of different models is an ongoing venture that benefits from improved validation data. The present study accumulates a database on two-phase flow experiments in a bubble column. This is achieved by using a combination of Particle Image Velocimetry and Shadowgraphy to measure the liquid velocity field and gas dispersion properties simultaneously. This methodology is applied for different needle diameters and gas flow rates.

A detailed description of the experimental

The experimental data (Table 1) described in this repository is structured into different folders and files as follows:
Level 1: Folders classified by measurement configuration: TX_Jg_Y_Di_ZZZ as outlined in Table 1

  • TX = Identifier
  • Jg_Y = Superficial gas velocity in mm/s
  • Di_ZZZ = Inner diameter of the needle in µm

Level 2: Folders classified by measurement height: Z_XXX

  • Z_XXX = Measurement height in mm

Level 3: csv files classified by their analysis parameter:

  • Gas_Eg_ub_over_x.csv: Each csv file consists of five columns, namely the x-coordinate (in m), the gas holdup, the uncertainty of the gas holdup, the averaged bubble rising velocity (in m/s) and the corresponding uncertainty (in m/s).
  • Liquid_v_z_over_x.csv: Each csv file consists of three columns, namely the x-coordinate (in m), the averaged liquid velocity (in m/s) and the corresponding uncertainty (in m/s).

Table 1: Overview of the measurement cases in this repository.

| ID | Diameter of needle orifice in µm | Superficial gas velocity in mm/s |
|----|----------------------------------|----------------------------------|
| T1 | 200                              | 2                                |
| T2 | 200                              | 4                                |
| T3 | 200                              | 6                                |
| T4 | 600                              | 2                                |
| T5 | 600                              | 4                                |
| T6 | 600                              | 6                                |

Keywords: Particle Image Velocimetry (PIV); Shadowgraphy; Two-phase bubble column

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Permalink: https://www.hzdr.de/publications/Publ-36732


Data publication: Deconvoluting Cr States in Cr-Doped UO2 Nuclear Fuels via Bulk and Single Crystal Spectroscopic Studies

Murphy, G. L.; Gericke, R.; Gilson, S.; Bazarkina, E.; Roßberg, A.; Kaden, P.; Thümmler, R.; Klinkenberg, M.; Henkes, M.; Kegler, P.; Svitlyk, V.; Marquardt, J.; Lender, T.; Hennig, C.; Kvashnina, K.; Huittinen, N. M.

Abstract

Experimental and fitted EPR data of Cr-UO2 single crystal grains, EXAFS data Cr-UO2 single crystal grain and powder with Cr redox standards, XANES data Cr-UO2 single crystal grain and powder with Cr redox standards

Keywords: Cr-doped UO2; Nuclear Fuel; Uranium; EPR; HERFD-XANES; EXAFS

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36731


StarDist Models for "Hydrodynamics in a bubble column – Part 1: Two-phase flow"

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Hessenkemper, H.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

This package contains the software and the trained models described in the publication "Hydrodynamics in a bubble column – Part 1: Two-phase flow". Please refer to the readme.md for installation instructions and to the Prediction_demo.ipynb for usage demonstration.

Keywords: StarDist; Bubble detection; Shadowgraphy

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Permalink: https://www.hzdr.de/publications/Publ-36730


Klassifikation von Pulsdaten mit neuronalen Netzwerken auf einer FPGA Accelerator Card

Ufer, R.; Auer, B.; Hoffmann, H.; Knodel, O.; Lokamani, M.; Müller, S.

Abstract

Zur Analyse der entstehenden Detektordaten bei dem Mu2e Experiment am Fermilab soll die Datenauswertung mit Field Programmable Gate Array (FPGA) erfolgen. Diese übernehmen die notwendige Vorverarbeitung und Reduktion der Messdaten, noch während der Durchführung der Messung. Die dabei ausgeführten Anwendungen werden standardmäßig durch Algorithmen realisiert. Eine dieser Anwendungen führt die Klassifikation der ermittelten Pulsdaten durch. Mit den Testläufen an der gELBE Bremstrahlungs-Beamline am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) konnte für das zukünftige Experiment eine große Menge dieser Datensätze erfasst werden. Diese dienen zur Charakterisierung des Detektorsystems und wurden mit einem Lanthanbromid (LaBr) Detektor gemessen. Für die Pulsdatenklassifikation wird auf der Basis des Algorithmus und der erfassten Datensätze, ein neuronales Netzwerk erstellt, trainiert und validiert. Um bei diesen Schritten etablierte Machine Learning Frameworks zu verwenden, wird für die Portierung des Netzwerks in eine High-Level Synthese (HLS) Sprache die Software hls4ml verwendet. Dabei werden verschiedene Konfigurationen genutzt, um unterschiedlich optimierte Implementierungen zu generieren. Zum Evaluieren erfolgt die Ausführung der Implementierungen auf einer Xilinx Alveo Accelerator Card.

Keywords: FPGA; ML; CI; Mu2e

  • Lecture (Conference)
    86. Jahrestagung der DPG und DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36729


Investigation of contrast mechanisms for MRI phase signal-based proton beam visualization in water phantoms

Schieferecke, J.; Gantz, S.; Hoffmann, A. L.; Pawelke, J.

Abstract

Purpose: The low sensitivity and limitation to water phantoms of convection-dependent MRI
magnitude signal-based proton beam visualization hinder its in-vivo applicability in MR-integrated
proton beam therapy. The purpose of the present study was therefore to assess possible contrast
mechanisms for MRI phase signal-based proton beam visualization that can potentially be exploited
to enhance the sensitivity of the method and extend its applicability to tissue materials.
Methods: To assess whether proton beam-induced magnetic field perturbations, changes in material
susceptibility or convection result in detectable changes in the MRI phase signal, water phantom
characteristics, experiment timing and imaging parameters were varied in combined irradiation and
imaging experiments using a time-of-flight angiography pulse sequence on a prototype in-beam MRI
scanner. Velocity encoding was used to further probe and quantify beam-induced convection.
Results: MRI phase signal-based proton beam visualization proved feasible. The observed phase
difference contrast was evoked by beam-induced buoyant convection with flow velocities in the mm/s
range. Proton beam-induced magnetic field perturbations or changes in magnetic susceptibility did not
influence the MRI phase signal. Velocity encoding was identified as a means to further enhance the
detection sensitivity.
Conclusion: Because the MRI phase difference contrast observed during proton beam irradiation of water phantoms is caused by beam-induced convection, this method will unlikely be transferable to tightly compartmentalized tissue wherein flow effects are restricted. Strongly velocity encoded pulse
sequences, however, were identified as promising candidates for the future development of MRI-
based methods for water phantom-based geometric quality assurance in MR-integrated proton beam
therapy.

Keywords: in-beam MRI; proton therapy; proton beam visualization; phase difference imaging; velocity encoding; convection

Involved research facilities

  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-36728


Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by High-Pressure Torsion using Positron Annihilation Spectroscopy and a High Resolution X-ray Diffraction

Bibimoune, I.; Bourezg, Y. I.; Abib, K.; Liedke, M. O.; Wagner, A.; Matej, Z.; Huang, Y.; Langdon, T. G.; Bradai, D.

Abstract

Two MgRE (RE=Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was
characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DBVEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an
as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ~115 nm for the as-received state to ~207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations
(positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4 - 6e14 m-2).

Keywords: Mg; rare earthhtp; dislocations; positron annihilation spectroscopy; VEPfit

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36727


Techno-economic assessment of PEM electrolysis for O2 supply in activated sludge systems – a simulation study based on the BSM2 wastewater treatment plant

Parra Ramirez, M. A.; Fogel, S.; Reinecke, S.; Hampel, U.

Abstract

The conversion of renewable energy into hydrogen (H2) by power-to-gas technologies involving electrolysis is seen today as a key element in the transition to a renewable energy sector. Wastewater treatment plants (WWTP) could make use of oxygen (O2) produced alongside H2 in biological treatment steps, however, production costs of electrolysis O2 should be competitive with respect to those of conventional O2 production processes. In this study, mathematical models of a polymer electrolyte membrane electrolyser (PEME) plant and the WWTP of the Benchmark Simulation Model Nr. 2 (BSM2) were used to simulate electrolysis O2 supply to an activated sludge (AS) system and estimate net costs of production (NCP) via a techno-economic assessment (TEA). Assuming that produced H2 is sold to a nearby industry, NCPs for O2 were calculated for two scenarios regarding PEME plant dimensions, which correspond to average (scenario 1) and optimal (scenario 2) electricity availability, i.e. medium and high number of full load hours per year. For each scenario, estimations were made for four alternatives for electricity supply and costs, namely conventional sources, photovoltaic (PV), and on/off shore wind energy, and using sets of optimistic, neutral and pessimistic data regarding system performance and market conditions. The analyses were done for 2020 as reference year and again for 2030 based on forecasts of relevant data. The results of the dimensioning of the PEME plant in scenario 1 show that a 6.4 MW PEME operated for 4,073 full load hours per year is able to cover the O2 demand of the AS system during more than 99% of the simulated period. The same is true for a 4.8 MW PEME operated for 6,259 full load hours per year in scenario 2. The TEA shows that investment costs for the PEME stacks and the operational costs for electricity make up most of the NCP of electrolysis O2. Although NCP for electrolysis O2 are always higher than those of conventional O2 sources for the year 2020, in 2030 estimated NCPs for the smaller PEME plant of scenario 2 become competitive for PV and wind on shore electricity supply under optimistic market conditions. Potential minimum selling prices were also calculated for the produced O2, however, they were above those of conventional O2 sources both in 2020 and 2030. The approach described in this study can be applied to analyse O2 supply to biological wastewater treatment in WWTPs with different characteristics, in processes different to conventional AS, and under different assumptions regarding economic conditions.

Keywords: Wastewater treatment; Activated sludge; PEM electrolysis; Techno-economic assessment

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Permalink: https://www.hzdr.de/publications/Publ-36725


Influence of Eu(III) and U(VI) on rat and human kidney cells

Butscher, D.; Senwitz, C.; Heller, A.; Stumpf, T.; Barkleit, A.

Abstract

Radionuclides (RNs) that enter the human body, for example through ingestion or inhalation, pose a potential health risk due to their radio- and chemotoxicity. The kidneys are especially exposed to the incorporated RNs, as they are mainly responsible for the excretion of toxic substances from the blood stream. Therefore, the effect of uranium(VI) and europium(III), an analogue for trivalent actinides such as Am or Cm, on rat (NRK-52E) and human (HEK-293) kidney cells was studied in vitro at the cellular and molecular levels.
Exposure experiments were carried out in which cells were incubated with these metal ions (10−9 – 10−3 M) for 7, 24 and 48 hours. The cell viability after exposure to the metal ions was measured using the XTT-assay. The half-maximum effective concentration (EC50) was calculated on the basis of the dose-response curves. In addition, morphological changes due to metal ion exposure were investigated by staining selected cell compartments and intracellular uptake was determined by ICP-MS. The speciation of a metal determines its bioavailability, influencing both the effect on cells and its uptake into cells. Therefore, time resolved laser-induced fluorescence spectroscopy (TRLFS) was used to investigate the speciation of Eu(III) and U(VI) in the cell culture medium, in the cell-exposed medium and in cell suspension. The obtained results on the cellular and molecular level contribute to a better understanding of the toxic effects of RNs.
This work is funded in the frame of the RADEKOR project by the German Federal Ministry of Education and Research (BMBF, grant number: 02NUK057A and 02NUK057B).

Keywords: Cytotoxicity; Kidney cells; Uranium; Europium; EC50; Speciation

  • Lecture (Conference)
    7th International Conference on Environmental Radioactivity (ENVIRA), 17.-22.09.2023, Seville, España

Permalink: https://www.hzdr.de/publications/Publ-36723


Theorien und Experimente zur Entstehung und Wirkung kosmischer Magnetfelder

Stefani, F.

Abstract

Der Vortrag beschäftigt sich mit Theorien und Experimenten zur Entstehung und Wirkung kosmischer Magnetfelder. Ein besonderer Schwerpunkt liegt auf der Vorstellung des DRESDYN-Experiments am HZDR.

Involved research facilities

  • DRESDYN
  • Invited lecture (Conferences)
    Öffentlicher Vortrag im Palitzsch-Museum Dresden, 23.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36720


Finite Elemente Simulation der Aufschlusszerkleinerung von Verbundstrukturen im Recycling

Heibeck, M.; Richter, J.; Mütze, T.; Filippatos, A.

Abstract

Die Kombination von Materialien wie Metallen und Kunststoffen in Verbundstrukturen ermöglicht funktionsintegrative Designs. Im Recycling müssen die unterschiedlichen Materialien jedoch wieder aufgeschlossen werden, um materialspezifisch hohe Recyclingraten zu erzielen. Typischerweise erfolgt der Aufschluss durch mechanische Zerkleinerungsprozesse. Derzeit gibt es keine adäquate Beschreibung dieser Prozesse, die zu einer recyclingorientierten Produktgestaltung beitragen könnte. Im Beitrag wird ein Ansatz zu physikalisch basierten numerischen Simulationen mit der Finite-Elemente-Methode (FEM) vorgestellt.

Keywords: FEM; Aufschluss; Zerkleinerung; Rotorreißer; Verbundwerkstoff

  • Lecture (Conference)
    DECHEMA - Fachgruppentreffen Zerkleinern & Klassieren 2023, 21.-22.03.2023, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36719


Hands-on training on machine learning

Fiedler, L.

Abstract

Hands-on training on machine learning and the MALA library.

  • Lecture (others)
    Theoretical Chemistry Seminar, 21.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36718


Demonstrating temperature transferability of neural network models replacing modern density functional theory

Fiedler, L.; Cangi, A.

Abstract

Due to its balance between accuracy and computational cost, Density Functional Theory (DFT) is one of the most important computational methods within materials science and chemistry. However, current research efforts such as the modeling of matter under extreme conditions demand the application of DFT to larger length scales as well as higher temperatures. Such investigations are currently prohibited due to the computational scaling of DFT.

We have recently introduced a machine-learning workflow that replaces modern DFT calculations [1,2,3]. This workflow uses neural networks to predict the electronic structure locally. We show that by employing such an approach, models can be trained to predict the electronic structure of matter across temperature ranges. This paves the way for large-scale simulations of thermodynamically sampled observables relevant to modeling technologically important phenomena such as radiation damage in fusion reactor walls.

Keywords: Density Functional Theory; Surrogate Models; Machine Learning

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 27.03.2023, Dresden, Deutschland
  • Invited lecture (Conferences)
    Electronic Structure Workshop, 13.-16.06.2023, Merced, USA

Permalink: https://www.hzdr.de/publications/Publ-36717


Monte Carlo simulation studies of background contributions in the Mu2e experiment

Rachamin, R.; Di Falco, S.; Ferrari, A.; Giusti, V.; Müller, S. E.; Pronskikh, V. S.

Abstract

The Mu2e experiment is currently being constructed at Fermilab to search for the direct conversion of muons into electrons in the field of a nucleus without the emission of neutrinos. The experiment aims at a sensitivity of four orders of magnitude higher than previous related experiments, which implies highly demanding accuracy requirements both in the design and during the operation. Hence, it is essential to estimate precisely the backgrounds that could mimic the monoenergetic conversion electron signal and the particle yields relevant to the experiment sensitivity. In that regard, Monte Carlo simulations were performed to investigate key yields and beam-related and cosmic rays-related backgrounds. The investigation includes: (I) an evaluation of the antiproton and charged pion yields from an 8 GeV proton pencil beam impinging on a tungsten cylindrical target, (II) an evaluation of the transmission of cosmic neutrons and neutral kaons in a block of concrete. The simulations were performed using the FLUKA2021, MCNP6, GEANT4, PHITS, and MARS15 codes. The presentation will show the simulation results with a focus on the prediction obtained from each code and their impact on the experiment.

Keywords: Charged Lepton Flavor Violation; Muon to Electron conversion; Mu2e experiment; Monte Carlo; GEANT4; PHITS; MARS15; FLUKA; MCNP

  • Lecture (Conference)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36716


The Stopping Target Monitor of the Mu2e experiment

Müller, S.; Ferrari, A.; Knodel, O.; Rachamin, R.

Abstract

The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless direct conversion of a muon to an electron in the field of an aluminum nucleus, aiming for a sensitivity four orders of magnitude better than previous experiments. The observation of a clear signal would imply Charged Lepton Flavor Violation, and hint at physics beyond the Standard Model.

The normalization of the signal events will be done by monitoring the rate of muons stopping on aluminum target discs. This will be accomplished with a detector system made of an HPGe detector and a Lanthanum Bromide detector, which detect the characteristic X- and γ-rays of energies up to 1809 keV produced when the muons are stopped or captured on the aluminum.

At the Helmholtz-Zentrum Dresden-Rossendorf, we have used a pulsed Bremsstrahlung photon beam at the ELBE radiation facility to study the performance of the detectors under conditions very similar to the ones expected at Mu2e.

In the presentation, a short overview of design and status of the Mu2e experiment and its detectors will be given, and results of the ELBE beamtime campaigns will be presented.

Keywords: Mu2e; STM; CLFV; FNAL

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  • Lecture (Conference)
    DPG Meeting SMuK, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36715


Activation calculations for decommissioning planning of NPPs

Rachamin, R.; Konheiser, J.; Barkleit, A.; Seidl, M.

Abstract

By the middle of 2023, all German nuclear power plants (NPPs) will have been shut down. The final shutdown is followed by a post-operational phase in which measures can be carried out to prepare for the NPPs dismantling and decommissioning. One of the essential tasks in planning and preparing an NPP for decommissioning is to obtain precise knowledge of the activation levels in its reactor pressure vessel (RPV), the biological shielding, and other internal components. In that regard, a novel method based on the combined use of two Monte Carlo codes, MCNP6 and FLUKA2021, was developed to serve as a non-destructive tool for evaluating the activation in an NPP. The presentation will give an overview of the methodology and demonstrate its application through the activation calculations of selected components of a German pressurized water reactor (PWR), which is the most common NPP type in Germany.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; FLUKA

  • Invited lecture (Conferences)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36714


Sensing strategies for determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

The gas flow modulation technique (GFM) is a recently proposed approach for measuring the axial gas dispersion coefficient in bubble columns. It bases on a time-resolved measurement of the modulated gas holdup at different axial positions in the column and a subsequent calculation of the axial dispersion coefficient from amplitude damping and the phase lag of a gas holdup wave. In recent studies holdup has been measured with gamma-ray densitometry, which is advantageous in terms of measurement accuracy. However, the application of radiative measurement techniques in industrial settings poses several logistical and safety challenges. This study investigates the potential of non-radiative measurement techniques in the context of GFM. In particular, differential pressure sensors, conductivity needle probes and optical probes are considered. The results obtained using these alternative techniques are compared with gamma-ray measurements. The comparison qualifies differential pressure sensors as a particular viable alternative to gamma-ray densitometry.

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36713


Determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique and several sensing strategies

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

Collected data refer to gas flow modulation measurements in a D=100 mm bubble column. The axial holdup wave is determined at three axial positions using different sensing stategies (gamma-ray densitometry, differential pressure sensors, transmittance optical probes and conductivity needle probes). Average gas holdup as well as amplitude damping and phase-shift have been determined at three different gas flow rates in the homogeneous regime. A description of the experimental setup is provided in the file "Experimental_setup.pdf". An overview of the performed experiments is provided in the Excel file "DataDescription.xlsx"

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

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  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36712


Halomonas gemina sp. nov. and Halomonas llamarensis sp. nov., two siderophore-producing organisms isolated from high-altitude salars of the Atacama Desert

Hintersatz, C.; Singh, S.; Antonio Rojas, L.; Kretzschmar, J.; Wei, T.-S.; Khambhati, K.; Kutschke, S.; Lehmann, F.; Singh, V.; Jain, R.; Pollmann, K.

Abstract

This study aimed to discover novel siderophore-producing organisms with the ability to produce high amounts of the iron-binding compounds. In the course of this, two not yet reported halophilic strains designated ATCHAT and ATCH28T were isolated from hypersaline, alkaline surface waters of Salar de Llamará and Laguna Lejía, respectively. As an alkaline milieu greatly reduces the bioavailability of iron, organisms native to those environments were suspected to produce greater amounts of siderophores to sequester the essential element. Both strains were characterized utilizing a polyphasic approach and further investigated to assess their ability to secrete siderophores. Comparative analysis of the 16S rRNA gene sequences revealed that the isolates belonged to the genus Halomonas. ATCHAT was closely related to Halomonas. salicampi and Halomonas vilamensis, while ATCH28T was related closest to Halomonas ventosae and Halomonas salina. Utilizing the chromeazurol S liquid assay, both strains were shown to produce iron-binding compounds. Via NMR and genomic analysis, the siderophore synthesized by strain ATCH28T has been determined to be desferrioxamine E (DFOE). Although this siderophore is common for various terrestrial microorganisms, it has not yet been reported to occur within Halomonas, making strain ATCH28T first member of the genus to produce a non-amphiphilic siderophore. Furthermore, the effect of various media components on the secretion of DFOE was investigated and obtained concentrations could be increased to more than 1000 µM of the compound. Genomic analysis of strain ATCHAT revealed the presence of a not yet reported NRPS-dependant gene cluster responsible for the secretion of siderophore. However, the strain only secreted small amounts of the iron-binding compound and therefore its siderophore was not investigated exhaustively within the scope of this study. Based on their phenotypic and genotypic characteristics, both strains unambiguously differed from other described members of the genus Halomonas. Average nucleotide identity (ANI) values and levels of DNA-DNA relatedness clearly indicated that the strains represented two novel species. Hence, both species should be added as new representatives of the genus Halomonas, for which the designations Halomonas llamarensis sp. nov. (type strain ATCHAT=DSM 114476=LMG 32709) and Halomonas gemina sp. nov. (type strain ATCH28T=DSM 114418=LMG 32708) are proposed.

Keywords: Halophilic bacteria; siderophores; polyphasic taxonomic; desferrioxamine E; Atacama Desert

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Permalink: https://www.hzdr.de/publications/Publ-36711


Concepts of statistical entropy for the evaluation of comminution and separation processes

Tolosana Delgado, R.; Schach, E.; Peuker, U.

Abstract

Statistical entropy, corresponding to Shannon entropy in information theory or Gibbs entropy in physical thermodynamics, can be used to evaluate the additional disorder in a system induced by its subdivision in components or subsystems. Several variations of this concept have been introduced in the last 20 years to quantify the efficiency of a separation process (or a chain of it) within the context of minerals processing both in mining and recycling. This contribution presents a coherent frame connecting these concepts, and extends them to evaluate comminution processes, in such a way that joint thermoeconomic zoptimization of whole beneficiation plants becomes possible.

The main idea is to split the system simultaneously into three dimensions: (1) mineral or chemical components, (2) particles or particle classes, and (3) output streams. In each of these dimensions, a different ratio can be defined to describe the way the mass (or volume or matter) of the system is split into the subsystems: (1) a composition; (2) a particle-wise distribution; a (3) set of partition coefficients. Entropy contributions can then be defined for each of these dimensions at different levels of integration, e.g. (1) component-wise or for a total, (2) particle-wise or bulk-wise, (3) per stream or per stage feed.

By systematically considering all possible entropy decompositions, the following results were found. Total stage entropy does not depend on the ordering of integration through the three dimensions. Comminution cannot decrease the stage entropy; a comminution that would generate perfectly liberated particles without overgrinding would keep the stage entropy constant. A separation process cannot decrease stage entropy, and perfect separation would keep it constant. However, once the masses of the output streams are measured, the output entropy does indeed decrease for any moderately good separation process. The difference between the stage entropy with and without controlling output masses can then be understood as the information value of the output mass flow measurements.

  • Open Access Logo Contribution to proceedings
    22nd Annual Conference of the International Association for Mathematical Geosciences, 05.-12.08.2023, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-36710


In-situ flow visualization with Geo-Positron-Emission-Tomography in a granite fracture from Soultz-sous-Forêts, France

Pingel, J. L.; Kulenkampff, J.; Jara-Heredia, D.; Zhou, W.; Fischer, C.; Schäfer, T.

Abstract

We investigate the fluid flow field in a fractured granite core sample. Sequential imaging with Positron-Emission-Tomography (PET) allows direct reconstruction of flow streamlines, thus providing a unique insight into the fluid dynamics of complex fractured crystalline materials. Pulse migration experiments using the positron-emitting radionuclide 18F- as tracer were conducted on a fractured granitic drill core, originating from a depth of 1958 m of the Enhanced Geothermal System (EGS) reference site at Soultz-sous-Forêts, France. The flow field was analyzed as a function of in- and outlet positions across the fracture, as well as applied flow rates. Different flow path characteristics were identified. Both the fracture aperture variation and the topography of the fracture surface affect the flow field with consequences on flow channeling and preferential flow paths. Furthermore, pulse migration experiments were also numerically simulated with a 2.5D model using COMSOL Multiphysics®.
While the higher flow rate experiments show wider and higher dispersion of the flow path, lower velocity results in more localized flow and channeling behavior. This type of study thus yields enhanced experimental insights into the hydrodynamics of fracture flow and its relation to the rough structure of natural single fractures, compared to input‑output experiments. It can help to validate model simulations and experimentally determine hydrodynamic parameters needed for reactive transport modeling that are otherwise estimated with a high degree of uncertainty.

Keywords: Positron Emission Tomography; single fracture; fluid flow; flow channeling; fracture aperture; COMSOL

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Permalink: https://www.hzdr.de/publications/Publ-36709


Influence of soil microbiology on radionuclide transport and uptake into plants

Linares Jimenez, R. E.; Flemming, K.; Matschiavelli, N.; Cherkouk, A.; Raff, J.; Stumpf, T.; Sachs, S.

Abstract

Deep geological repositories (DGR) will be used for the final disposal of highly radioactive waste. For the safety assessment of the DGR, it is important to consider accident scenarios such as the ingress of water, which might lead to a release of radionuclides (RNs) from the repository into the groundwater. RNs in groundwater can migrate to the surface soil where they can interact with indigenous microorganisms and plants, entering the food chain and posing a health risk to humans. The reliable modelling of the RN uptake into plants requires more than just transfer factors. A more detailed process understanding of the RN uptake into plants, including the effects of soil microorganisms, is necessary. RNs may affect the soil microbial community altering the natural community composition and interactions. Root exudates from plants and microorganisms can alter the speciation of RNs, affecting their bioavailability and mobility.
We study the impact of soil microorganisms on the RN transport and uptake into plants at the molecular level. The experiments discussed focus on studying the modulation of soil microbial diversity in the presence of RNs and selected root exudates. In addition, radiation-resistant soil microorganisms will be isolated to study their interaction with RNs and their effect on the degradation of root exudates. This will include characterization of the degradation products and their interactions with RNs. These findings will be used to elaborate radioecological models for the assessment of the RN transport and uptake into the food chain.

Keywords: Soil; Radionuclides; Microbial diversity; Root exudates; Plants

  • Poster
    ENVIRA 2023 - 7th International Conference on Environmental Radioactivity, 17.-22.09.2023, Sevilla, España

Permalink: https://www.hzdr.de/publications/Publ-36708


A continuous multiphase model for liquid metal batteries

Godinez-Brizuela, O. E.; Duczek, C.; Weber, N.; Nash, W.; Sarma, M.; Einarsrud, K. E.

Abstract

Liquid metal batteries (LMBs) are a promising candidate for large-scale stationary storage of renewably generated energy. Their Earth-abundant electrode materials and highly conductive molten salt electrolytes confer the low costs and high power densities required for grid-scale storage. LMB operation involves a complex interplay between mass transport mechanisms, and as a result their performance potential and operational limits are not fully understood. In this study, a multiphase numerical model is presented that simulates the charge and discharge processes of an LMB based on the Na-Zn couple. The model computes the changes in electrode and electrolyte volume, and resolves the spatial variations in the chemistry of the electrolyte that accompany the interfacial reactions. Volume change and species redistribution were found to be important in predicting the maximum theoretical capacity of the cell when neglecting other transport mechanisms.

Keywords: liquid metal battery; energy storage; multiphase flow; Na-Zn

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Permalink: https://www.hzdr.de/publications/Publ-36707


Multiobjective tuning technique for MPC in grinding circuits

Yamashita, A. S.; Martins, W. T.; Pinto, T.; Raffo, G. V.; Melo Euzebio, T. A.

Abstract

We investigate the control challenges in grinding circuits---slow dynamics, long dead times, variable coupling--- and the controller tuning challenge, that is, the difficulty in translating operating goals into tuning goals and closed-loop performance. A tuning algorithm for DMC (dynamic matrix control), suitable for the mineral processing industry, is proposed. The tuning problem is posed as a multiobjective optimization problem, in which the tuning goals are directly related to the desired closed-loop performance of process variables. The problem is solved using a compromise optimization, which minimizes the Euclidian distance between a feasible solution and the Utopia solution. Three case studies are presented, which validate the tuning algorithm for DMC in linear and non-linear grinding circuit models. The closed-loop performance obtained with the proposed tuning algorithm is compared to the one obtained through a benchmark tuning technique from the literature. The proposed tuning method has the following features: i) it shapes the closed-loop response according to the goal definitions for linear systems; ii) it requires tailored initial guesses and search spaces to converge to a stabilizing solution in non-linear applications; and iii) it allows the user to specify the desired closed-loop performance behavior in the tuning procedure, allowing the implementation of an adequate controller for each situation.

Keywords: grinding circuit; model predictive control; dynamic matrix control; controller tuning; multiobjective optimization; compromise optimization

Permalink: https://www.hzdr.de/publications/Publ-36706


Superconducting radio frequency Photoinjectors for CW-XFEL

Xiang, R.; Arnold, A.; Lewellen, J. W.

Abstract

A dependable and consistent electron source is a crucial requirement for the achievement of high-power free electron lasers (FELs). Over the past two decades, it has been demonstrated that photoinjectors based on SRF technology (SRF guns) are suitable for continuous wave (CW) beam generation. SRF guns possess both the high accelerating field gradients of normal conducting RF photoinjectors and the low power dissipation thanks to mature SRF cavity technology, and therefore have the potential to provide the high-brightness, high-current beams required for CW-XFELs.
After the demonstration of the first SRF gun in Dresden-Rossendorf, several SRF gun programs based on different approaches have achieved promising progress and even succeeded in routine operation. SRF guns are expected to play an important role in XFEL facilities in the near future. In this paper, we give an overview of design concepts, important parameters and development status of the worldwide SRF gun projects.

Keywords: CW; FEL; SRF gun; low emittance

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36705


Corrosion of Cast Iron for High-Level Nuclear Waste Containers in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Cast iron containers are currently used for the temporary storage of nuclear waste. At the current stage of research, it is not clear whether cast iron, together with coating materials, also is an option for long-time storage. In this study, we want to investigate its potential as a container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on cast iron. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupons showed surface corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron

  • Poster
    Goldschmidt, 09.-14.07.2023, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36704


Corrosion of Container Material for High-Level Nuclear Waste in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Ductile cast iron is investigated as a potential container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on a potential container material. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2 atmosphere, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupon showed mild to severe pitting corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron.

  • Poster
    EUROCORR, 27.-31.08.2023, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-36703


Fostering quality improvement for RSE projects through consulting offers

Förster, T.

Abstract

To promote FAIR principles and to improve the value and knowledge from data innovation, HIFIS – a Helmholtz IT platform, provides a wide variety of services. This talk focuses on the lessons learned and the impact of integrating a variety of RSE offers, including educational resources and consulting on the research community in Helmholtz. We discuss the structure of the HIFIS consulting service and the resources needed to provide a good and fruitful environment for improving our clients’ software projects.

Keywords: RSE; consulting; software development

Permalink: https://www.hzdr.de/publications/Publ-36702


Fracture mechanics investigation of reactor pressure vessel steels by means of sub-sized specimens (KLEINPROBEN)

Das, A.; Altstadt, E.; Chekhonin, P.; Houska, M.

Abstract

The embrittlement of reactor pressure vessel (RPV) steels due to neutron irradiation restricts the operating lifetime of nuclear reactors. The reference temperature 𝑇0, obtained from fracture mechanics testing using the Master Curve concept, is a good indicator of the irradiation resistance of a material. The measurement of the shift in 𝑇0 after neutron irradiation, which accompanies the embrittlement of the material, using the Master Curve concept, enables the
assessment of the reactor materials. In the context of worldwide life time extensions of nuclear power plants, the limited availability of neutron irradiated materials (surveillance materials) is a challenge. Testing of miniaturized 0.16T C(T) specimens manufactured from already tested standard Charpy-sized specimens helps to solve the material shortage problem. In this work, four different reactor pressure vessel steels with different compositions were
investigated in the unirradiated and in the neutron-irradiated condition. A total number of 189 mini-C(T) samples were fabricated and tested. An important component of this study is the transferability of fracture mechanics data from mini-C(T) to standard Charpy-sized specimen. Our results demonstrate good agreement of the reference temperatures from the mini-C(T) specimens with those from standard Charpy-sized specimens. RPV steels containing higher Cu and P contents exhibit a higher increase in 𝑇0 after irradiation. The fracture surfaces were investigated using SEM in order to record the location of the fracture initiators. The fracture modes were also determined. A large number of test results formed the basis for a censoring probability function, which was
used to optimally select the testing temperature in Master Curve testing. The effect of the slow stable crack growth censoring criteria from ASTM E1921 on the determination of 𝑇0 was analysed and found to have a minor effect. Our results demonstrate the validity of mini-C(T) specimen testing and confirm the role of the impurity elements Cu and P in neutron embrittlement. We anticipate further research linking microstructure to the fracture properties of materials before and after neutron irradiation and the optimization of Master Curve testing using the results from our statistical analysis.

Keywords: reactor pressure vessel steel; neutron embrittlement; Master Curve testing; mini-CT specimens; small specimen test technology

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-125 2023
    ISSN: 2191-8708, eISSN: 2191-8716
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-36701


Visualizing Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering

Ordyna, P.; Bussmann, M.; Gaus, L.; Grenzer, J.; Gutt, C.; Huang, L.; Laso García, A.; Garten, M.; Höppner, H.; Humpries, O.; Marre, B. E.; Metzkes-Ng, J.; Nakatsutsumi, M.; Öztürk, Ö.; Pan, X.; Paschke-Brühl, F.-L.; Pelka, A.; Prencipe, I.; Randolph, L.; Schlenvoigt, H.-P.; Smid, M.; Stefanikova, R.; Thiessenhusen, E.; Toncian, T.; Zeil, K.; Schramm, U.; Cowan, T.; Kluge, T.

Abstract

Ultra-intense lasers that ionize and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration.
These instabilities can be difficult to characterize, but a novel approach using X-ray scattering at keV energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale.
Our experiments on laser-driven flat silicon membranes show the development of structure with a dominant scale of $~60\unit{nm}$ in the plane of the laser axis and laser polarization, and $~95\unit{nm}$ in the vertical direction with a growth rate faster than $0.1/\mathrm{fs}$.
Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced instability development, indicating the excitation of surface plasmons and the growth of a new type of filamentation instability.
These findings provide new insight into the ultra-fast instability processes in solids under extreme conditions at the nanometer level with important implications for inertial confinement fusion and laboratory astrophysics.

Keywords: laser; proton; ion; acceleration; HIBEF; HED; European; XFEL; SAXS

Involved research facilities

  • HIBEF

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Permalink: https://www.hzdr.de/publications/Publ-36700


Dataset: Basic verification of an industrial type of wire-mesh sensor

Wiedemann, P.; Trepte, M.

Abstract

The experimental data presented here was recorded with an industrial type of wire-mesh sensor and additional equipment. The experiments aim at verifying the main functionalities of the developed sensor and include tests of

  • Temperature compensation
  • Flow pattern identification in vertical gas-liquid flow
  • Flow pattern identification in horizontal gas-liquid flow

The experimental procedure and the results are described in detail in Wiedemann et al.: Towards Real-Time Analysis of Gas-Liquid Pipe Flow: A Wire-Mesh Sensor for Industrial Applications, Sensors 23 (2023) 4067, https://doi.org/10.3390/s23084067

Keywords: wire-mesh sensor; indWMS; two-phase flow

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Permalink: https://www.hzdr.de/publications/Publ-36699


International Standardization of Basic Industrial Radiotracer and Radiation Applications – Current State

Jentsch, T.; Thereska, J.; Jin, J.-H.; Brisset, P.

Abstract

The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. On behalf of IAEA and ISTRA experts from many countries employed in leading research centers and renowned industrial companies analyze existing international standards regarding the necessity of their update or amendment as well as the need for new standards in this field.
In June 2020, a new international standard on “Non-destructive testing - Gamma ray scanning method on process columns” was published as ISO 23159. About three years before, the experts detected the need to standardize this method, which is widely used in petrochemical and chemical plants to identify and locate the cause of malfunction inside various process columns.
In the field of flow rate measurements of fluids in conduits using radioactive tracers, a proposal for a new international standard was prepared in 2021. It united several old international standards in this technical field: measurement of water flow in closed conduits (ISO 2975), measurement of gas flow in conduits (ISO 4053) and measurement of liquid flow in open channels (ISO 9555). The new international standard with the title “Measurement of Fluid Flow Rate in Closed Conduits – Radioactive Tracer Methods” has now the state of a Draft International Standard (DIS) and will be published as ISO 24460 in this year.
Furthermore, two other international standards using radioactive tracer methods are under development. One of them is on leak testing in pressured vessels and underground pipelines, another one is on determination of concentration or density of suspended and deposited sediment in water bodies by radiometric methods. Both has already passed the New Work Item Proposal (NWIP) stage. The first one is being edited in ISO Technical Committee 135, Sub Committee 6, Working Group 1 (ISO TC 135/SC 6/WG 1), has the stage of a Committee Draft (CD) now and will be published as ISO 6640 in the middle of next year. The second one is being edited in ISO TC 113/SC 6/WG 5, has still the stage of a Working Draft (WD) and will be published as ISO 6366 also next year.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.

Keywords: International standards; ISO; radioactive tracers; radiometric methods

  • Lecture (Conference)
    NUTECH 2023 International Conference on Development and Applications of Nuclear Technologies, 20.-22.09.2023, Krakow, Polska

Permalink: https://www.hzdr.de/publications/Publ-36698


Trimorphic TaCrP – A diffraction and 31P solid state NMR spectroscopic study

Paulsen, C.; Maximilian Gerdes, J.; Svitlyk, V.; Kai Reimann, M.; Rabenbauer, A.; Nilges, T.; Ryan Hansen, M.; Pöttgen, R.

Abstract

The metal-rich phosphide TaCrP forms from the elements by step-wise solid state reaction in an alumina crucible (maximum annealing temperature 1180 K). TaCrP is trimorphic. The structural data of the hexagonal ZrNiAl high-temperature phase (space group P¯62m) was deduced from a Rietveld refinement. At room temperature TaCrP crystallizes with the TiNiSi type (Pnma, a = 623.86(5), b = 349.12(3), c = 736.78(6) pm, wR = 0.0419, 401 F2 values, 20 variables) and shows a Peierls type transition below ca. 280 K to the monoclinic low-temperature modification (P121/c1, a = 630.09(3), b = 740.3(4), c = 928.94(4) pm, β = 132.589(5)°, wR = 0.0580, 1378 F2 values, 57 variables). The latter phase transition is driven by pairwise Cr–Cr bond formation out of an equidistant chain in o-TaCrP. The phase transition was monitored via different analytical tools: differential scanning calorimetry, powder synchrotron X-ray diffraction, magnetic susceptibility measurements and 31P solid state NMR spectroscopy.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36697


A van der Waals Heterostructure with an Electronically Textured Moiré Pattern: PtSe₂/PtTe₂

Li, J.; Ghorbani Asl, M.; Lasek, K.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

Abstract

The interlayer interaction in Pt-dichalcogenides strongly affects their electronic structures. The modulations of the interlayer atom-coordination in vertical heterostructures based on these materials are expected to laterally modify these interlayer interactions and thus provide an opportunity to texture the electronic structure. To determine the effects of local variation of the interlayer atom coordination on the electronic structure of PtSe₂, van der Waals heterostructures of PtSe₂ and PtTe₂ have been synthesized by molecular beam epitaxy. The heterostructure forms a coincidence lattice with 13-unit cells of PtSe₂ matching 12-unit cells of PtTe₂, forming a moiré superstructure. The interaction with PtTe₂ reduces the band gap of PtSe₂ monolayers from 1.8 to 0.5 eV. While the band gap is uniform across the moiré unit cell, STS and dI/dV mapping identify gap states that are localized within certain regions of the moiré unit cell. Deep states associated with chalcogen pz-orbitals at binding energies of ~-2 eV also exhibit lateral variation within the moiré unit cell, indicative of varying interlayer chalcogen interactions. Density functional theory calculations indicate that local variations in atom coordination in the moiré unit cell causes variations in the charge transfer from PtTe2 to PtSe2 thus affecting the value of the interface dipole. Experimentally this is confirmed by measuring the local work function by field emission resonance spectroscopy, which reveals a large work function modulation of ~0.5 eV within the moiré structure. These results show that the local coordination variation of the chalcogen atoms in the PtSe2/PtTe2 van der Waals heterostructure induces a nanoscale electronic structure texture in PtSe₂.

Keywords: platinum dichalcogenides; van der Waals heterostructure; work function modulation; scanning tunneling microscopy; density functional theory

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Permalink: https://www.hzdr.de/publications/Publ-36696


Event generation in Julia and the path to GPUs

Hernandez Acosta, U.; Steiniger, K.; Reinhard, A.; Jungnickel, T.; Ehrig, S.; Bussmann, M.

Abstract

The inventors of the Julia programming language proclaim, that one can use high-level syntax to solve demanding numerical tasks. In order to evaluate this claim, we present possible applications of Julia by using it for the implementation of our Monte-Carlo event generator for laser-matter interaction. Especially the possible deployment of modern GPUs for demanding computing tasks during several stages of the event generation is discussed. In order to elaborate on these GPU capabilities, we show benchmarks of Julia's main programming interface for NVIDIA CUDA GPUs, namely `CUDA.jl`, and compare them with native CUDA-C++ implementations. Finally, Julia's capabilities for high-level abstraction for computations on heterogenous architectures are discussed and compared to low-level solutions like the `alpaka` library for C++.

Keywords: Julia programming language

  • Invited lecture (Conferences) (Online presentation)
    Compute Accelerator Forum, 08.03.2023, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36695


Biogenic minerals formation by an Fe(III)-reducing Desulfitobacterium sp. isolate

Cardaio, I.; Kluge, S.; Cherkouk, A.; Müller, K.; Stumpf, T.; Mayordomo, N.

Abstract

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe(III)) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe(III)-species [1]. This may lead to the formation of minerals such as magnetite (Fe(II)Fe(III)₂O₄) and siderite (Fe(II)CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc(VII)O₄⁻) to insoluble oxides (Tc(IV)O₂) [3].
The genus Desulfitobacterium contains obligate anaerobic bacteria that are capable of utilizing a wide range of electron acceptors, including nitrite, sulfite, metals, humic acids and halogenated organic compounds [4].
In this work, the Fe(III) reduction of a Desulfitobacterium species was examined. The microorganism has been isolated from bentonite, which is potentially used as geotechnical barrier in deep geological repositories for radioactive waste [5].
The cultivation conditions included DSMZ 579 medium with Na-acetate as electron donor to reduce Fe(III) citrate [6]. During cultivation, the formation of white precipitates was observed. The phases were collected both under aerobic and anaerobic conditions and repeatedly investigated by using Raman microscopy and powder X-ray diffraction (pXRD). It was noticed that the phases turned immediately to blue-greenish overnight under oxic conditions. Both Raman spectra and pXRD diffractograms can be attributed to vivianite (Fe(II)₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe(II)S₂), siderite, magnetite and hematite (FeIII₂O₃). These results suggest the ability of the bacterium of forming different Fe(II)-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe(II)-minerals formation by this microorganism depending on Fe(III)-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc(VII)O₄⁻.

The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of NukSiFutur TecRad young investigator group (02NUK072).

[1] Lovley, 1993, Annual Review of Microbiology, 47:263-290
[2] Lee, et al., 2007, Geomicrobiology Journal, 24:1, 31-41
[3] Lloyd, et al., 2000, Appl Environ Microbiol., 66(9):3743-9
[4] Villemur et al., 2006, FEMS Microbiol Rev. 2006, 30(5):706-33
[5] Drozdowski J., et al., 2018, HZDR Annual Report, pp. 40, ISSN 2191-870
[6] https://www.dsmz.de/microorganisms/medium/pdf/DSMZ_Medium579.pdf. Accessed on 27.02.23

Keywords: iron reducing bacteria; technetium; biogenic minerals; Raman microscopy; X-ray diffraction

  • Open Access Logo Poster
    Goldschmidt 2023, 09.-14.07.2023, Lyon, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-36694


Messebericht ACHEMA 2022: Klassieren und Sortieren

Mütze, T.

Abstract

Auf der ACHEMA 2022 waren in Frankfurt 25 Anbieter von Klassierer-, Sortier-, Recycling- oder Aufbereitungsanlagen im engeren Sinne vertreten. Der vorliegende Bericht fasst kurz zusammen, welche Aussteller ihr Portfolio im Bereich der Mechanischen Prozesse vorstellten und was an Neuerungen gezeigt wurde. Schwerpunkte stellten u. a. Plan- und Taumelsiebmaschinen sowie Technologien für schnelle Siebbelagswechsel und zum Entfernen von Körnern außerhalb der Produktspezifikation dar.

Keywords: Automatische Klaubung; Hydrozyklone; Klassieren; Magnetscheidung; Sichter; Siebe; Sortieren

Permalink: https://www.hzdr.de/publications/Publ-36693


Messebericht ACHEMA 2022: Zerkleinern

Mütze, T.

Abstract

Auf der ACHEMA 2022 waren in Frankfurt 38 Anbieter von Zerkleinerungstechnik vertreten. Der vorliegende Bericht fasst kurz zusammen, welche Aussteller vertreten waren und was – vor allem an Neuerungen – gezeigt wurde. Schwerpunkte waren einerseits Maschinen zum Dispergieren verklumpter bzw. sehr feinkörniger Pulver zur besseren Verarbeitbarkeit oder zum Einmischen in Flüssigkeiten sowie andererseits Mahlkörpermühlen zur Fein- und Feinstmahlung.

Keywords: Zerkleinern; Brecher; Mühlen

Permalink: https://www.hzdr.de/publications/Publ-36692


Fluctuation Electron Microscopy on Amorphous Silicon and Amorphous Germanium

Radić, D.; Peterlechner, M.; Posselt, M.; Bracht, H.

Abstract

Variable resolution fluctuation electron microscopy experiments were performed on self-ion implanted amorphous silicon and amorphous germanium to analyze the medium-range order. The results highlight that the commonly used pair-persistence analysis is influenced by the experimental conditions. Precisely, the structural correlation length Λ, a metric for the medium-range order length scale in the material, obtained from this particular evaluation varies depending on whether energy filtering is used to acquire the data. In addition, Λ depends on the sample thickness. Both observations can be explained by the fact that the pair-persistence analysis utilizes the experimentally susceptible absolute value of the normalized variance obtained from fluctuation electron microscopy data. Instead, plotting the normalized variance peak magnitude over the electron beam size offers more robust results. This evaluation yields medium-range order with an extent of approximately (1.50± 0.50)nm for the analyzed amorphous germanium and around (1.10±0.20)nm for amorphous silicon

Keywords: amorphous germanium; amorphous silicon; fluctuation electron microscopy; medium-range order

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Permalink: https://www.hzdr.de/publications/Publ-36691


An experimental study of boiling two-phase flow in a vertical rod bundle with a spacer grid-Part 2: Effects of vane angle

Tas-Köhler, S.; Boden, S.; Franz, R.; Liao, Y.; Hampel, U.

Abstract

We performed boiling flow experiments and measured the void fraction in a 3 x 3 rod bundle including a spacer grid with split type vanes using X-ray computed tomography, which provides high-resolution time-averaged void data without disturbing the flow. We studied the effects of mixing vanes with different vane angles, namely, 20°, 29° and 40°, for a mass flux between 535 and 1950 kg/m2 s and the central rod being heated giving a heat flux of 85.7 kW/m2. The presence of vanes leads to an increase of the cross-sectional averaged void fraction up to an axial position of Z≈〖0.8D〗_h. After that, the void fraction decreases until 3D_h

Involved research facilities

  • TOPFLOW Facility

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  • Secondary publication expected from 01.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36690


Frontiers of challenging studies utilizing accelerator mass spectrometry in geoscience

Honda, M.; Martschini, M.; Lachner, J.; Wieser, A.; Marchhart, O.; Steier, P.; Golser, R.; Sakaguchi, A.

Abstract

The fission-product 90Sr (half-life 28.9 years) and 135Cs (half-life 2.3×106 years) are present in the environment. Strontium-90 is one of the most concerning nuclides in the assessment of internal exposure of residents because it can accumulate in bones and cause health problems. Therefore, it is essential to study the distribution of 90Sr in the environment and its temporal variation (90Sr enrichment in organisms and plants). On the other hand, 135Cs, which has a longer physical half-life than 137Cs (30.1 years), is expected to be utilized as a tracer to follow the long-term environmental fate of 137Cs, which is difficult to measure due to decay. These studies require high-throughput multi-sample analysis. However, as 90Sr and 135Cs are pure β-emitters, other β-emitters in the environmental samples (e.g., Ra isotopes, 137Cs, and 210Pb) must be entirely removed, which would interfere with β-ray detection. While this is impossible for the conventional β-ray detection method of 135Cs, it does work for 90Sr. Still, it requires a large sample volume due to the low concentrations of 90Sr in general environmental samples1). Therefore, the chemical separation of the target nuclide is very time-consuming and challenging for reliable quantification.
This study addressed solving these problems using accelerator mass spectrometry (AMS) for sensitive analysis of 90Sr and 135Cs in environmental samples2,3). AMS has the advantage of allowing more precise analysis of small sample volumes. However, the most concerning aspect of AMS for 90Sr and 135Cs is the interference of the isobars 90Zr and 135Ba. Therefore, the measurements of 90Sr and 135Cs were carried out at the University of Vienna (VERA). The AMS system is equipped with an "Ion cooler" that can effectively separate the isobars. For 90Sr, various molecular ions such as SrFn− and ZrFn− (n ≥ 1) were extracted from the target (a mixture of SrF2 and PbF2 in a weight ratio of 1:8) by Cs sputtering, and then the molecular ions with an m/q of 147 (90SrF3− and 90ZrF3−) were selectively passed through a 90° bending magnet. The ion beam (200-300 nA) was decelerated to ~30 eV and injected into the Ion cooler, an isobaric separation system with built-in radio-frequency quadrupole (RFQ). Collisions with a buffer gas mixture of He and O2 gas inside the RFQ reduced the ion energy to <1 eV. In addition, the O2 gas produces oxide ions and separated Zr. Here, a 12 W laser (532 nm) further suppressed Zr (neutralized 90ZrF3− by photo-detachment). In this isobaric separation system, Zr was suppressed by >107 for Sr (current ratio), and the overall Zr suppression is >1012 (ion source >105). The overall transmission efficiency of Sr was 0.4‰. Meanwhile, a simple chemical separation scheme was developed which efficiently separates Zr to maximize the isobaric separation performance of AMS: acid leaching → two-step chromatography with crown ether and anion exchange → SrF2 precipitation (2 days for the precipitation) to environmental reference materials (soil, beef bones, fish meat) with known 90Sr concentrations. The results showed that the 90Sr concentrations quantified by the AMS method agreed with the nominal values (quantified by the β-ray detection method) within a margin of error. Furthermore, based on the measurements of 1 mg of Sr carrier treated in the same manner as environmental samples, the detection limit of 90Sr by the AMS method achieved 1/10 (< 0.1 mBq, 90Sr/88Sr = 2.5×10-15) of the general detection limit of the β-ray detection method4). The highly sensitive analysis of 90Sr by AMS is promising for studies on the detailed distribution of 90Sr in individual (and even site-specific) corals and fishes with limited sample volumes. As for 135Cs, significant issues remain, such as efficient Ba separation in chemical separation, cross-contamination between samples in AMS ion sources, and preparing 135Cs reference materials. However, the detection limit for 135C was 0.3 µBq (135Cs/Cs atomic ratio was 7×10-12), demonstrating excellent results. Therefore, this study showed that the 135Cs AMS has the potential to apply geoscience.

Keywords: Accelerator Mass Spectrometry; Isobar; Chemical Separation; Laser photo-detachment; 90Sr; 135Cs

  • Invited lecture (Conferences)
    71st Annual Conference on Mass Spectrometry, Japan, 15.-17.05.2023, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-36689


Immunotargeting of Cancer Stem Cells.

Köseer, A. S.; Di Gaetano, S.; Arndt, C.; Bachmann, M.; Dubrovska, A.

Abstract

The generally accepted view is that CSCs hijack the signaling pathways attributed to normal stem cells that regulate the self-renewal and differentiation processes. Therefore, the development of selective targeting strategies for CSC, although clinically meaningful, is associated with significant challenges because CSC and normal stem cells share many important signaling mechanisms for their maintenance and survival. Furthermore, the efficacy of this therapy is opposed by tumor heterogeneity and CSC plasticity. While there have been considerable efforts to target CSC populations by the chemical inhibition of the developmental pathways such as Notch, Hedgehog (Hh), and Wnt/β-catenin, noticeably fewer attempts were focused on the stimulation of the immune response by CSC-specific antigens, including cell-surface targets. Cancer immunotherapies are based on triggering the anti-tumor immune response by specific activation and targeted redirecting of immune cells toward tumor cells. This review is focused on CSC-directed immunotherapeutic approaches such as bispecific antibodies and antibody-drug candidates, CSC-targeted cellular immunotherapies, and immune-based vaccines. We discuss the strategies to improve the safety and efficacy of the different immunotherapeutic approaches and describe the current state of their clinical development.

Keywords: CAR-T cells; CSC; bsAB; cancer stem cells; cancer vaccines; immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-36685


Synthesis and Characterization of a Masked Terminal Nickel-Oxide Complex

Heim, P.; Spedalotto, G.; Lovisari, M.; Gericke, R.; O’Brien, J.; Farquhar, E. R.; McDonald, A. R.

Abstract

In exploring terminal nickel-oxo complexes, postulated to be the active oxidant in natural and non-natural oxidation reactions, we report the synthesis of the pseudo-trigonal bipyramidal Ni(II) complexes (K)[Ni(II)(LPh)(DMF)] (1[DMF]) and (NMe₄)₂[Ni(II)(LPh)(OAc)] (1[OAc]) (LPh = 2,2’,2’’-nitrilo-tris-(N-phenylacetamide); DMF = N,N-dimethylformamide; OAc = acetate). Both complexes were characterized using NMR, FTIR, ESI-MS, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate fashion, together with an ancillary donor. The reaction of 1[OAc] with peroxyphenyl acetic acid (PPAA) resulted in the formation of [(LPh)Ni(III)-O-H···OAc]²-, 2, that displays many of the characteristics of a terminal Ni=O species. 2 was characterized by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a Ni(II)-phenolate complex 3 (through aromatic electrophilic substitution) that was characterized by NMR, FTIR, ESI-MS, and X-ray crystallography. 2 was capable of hydroxylation of hydrocarbons and epoxidation of olefins, as well as oxygen atom transfer oxidation of phosphines at exceptional rates. While the oxo-wall remains standing, this complex represents an excellent example of a masked metal-oxide that displays all of the properties expected of the ever elusive terminal M=O beyond the oxo-wall.

Keywords: bioinorganic chemistry; high-valent nickel; hydrocarbon oxidation; oxo-wall; peracid activation

Permalink: https://www.hzdr.de/publications/Publ-36684


High-Throughput Gel Microbeads as Incubators for Bacterial Competition Study

Nguyen Le, T. A.; Zhao, X.; Bachmann, M.; Ruelens, P.; de Visser, J. A. G. M.; Baraban, L.

Abstract

Bacteria primarily live in structured environments, such as colonies and biofilms, attached to surfaces or growing within soft tissues. They are engaged in local competitive and cooperative interactions impacting our health and well-being, for example, by affecting population-level drug resistance. Our knowledge of bacterial competition and cooperation within soft matrices is in-complete, partly because we lack high-throughput tools to quantitatively study their interactions. Here, we introduce a method to generate a large amount of agarose microbeads that mimic the natural culture conditions experienced by bacteria to co-encapsulate two strains of fluores-cence-labeled Escherichia coli. Focusing specifically on low bacterial inoculum (1–100 cells/capsule), we demonstrate a study on the formation of colonies of both strains within these 3D scaffolds and follow their growth kinetics and interaction using fluorescence microscopy in highly replicated experiments. We confirmed that the average final colony size is inversely proportional to the inoculum size in this semi-solid environment as a result of limited available resources. Further-more, the colony shape and fluorescence intensity per colony are distinctly different in mono-culture and co-culture. The experimental observations in mono- and co-culture are compared with predictions from a simple growth model. We suggest that our high throughput and small foot-print microbead system is an excellent platform for future investigation of competitive and co-operative interactions in bacterial communities under diverse conditions, including antibiotics stress.

Keywords: millifluidic; high-throughput; agarose microbeads; co-culture; bacterial co-existence; fluorescence

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Permalink: https://www.hzdr.de/publications/Publ-36682


Unraveling the Np(V) Sorption on the Nuclear Fuel Cladding Corrosion Product ZrO₂: a Batch, Spectroscopic and Modeling Combined Approach

Jessat, I.; Foerstendorf, H.; Roßberg, A.; Scheinost, A.; Lützenkirchen, J.; Heim, K.; Stumpf, T.; Jordan, N.

Abstract

Zirconia (ZrO₂), the main corrosion product of the zircaloy cladding material of nuclear fuel rods, might potentially act as the first barrier for radionuclides. Thus, the interactions of radionuclides, such as the long-lived actinide neptunium, with zirconia have to be considered in the safety assessment process of a repository for radioactive waste. The sorption of Np(V) onto zirconia (ZrO₂) was investigated in the absence of carbonate at the macroscopic and molecular scale. For the macroscopic description, pH-dependent batch sorption experiments under varying ionic strength (0.1 and 0.01 mol∙L⁻¹ NaCl), Np(V) concentration (1∙10⁻⁶ or 6∙10⁻⁶ mol∙L⁻¹) and solid-to-liquid ratio (m/V = 0.5 or 4 g∙L⁻¹ ZrO₂) were conducted. Np(V) sorption isotherms at pH 4.5 and 6.0 were additionally obtained at 0.01 mol∙L⁻¹ NaCl. The Np(V) uptake on zirconia strongly depends on pH, with sorption starting from acidic pH and maximum sorption was reached at pH 6 and above. Increasing the m/V ratio caused a significant shift of the sorption edge towards lower pH values. This indicates the presence of different kinds of sorption sites, which was supported by the results of the Np(V) sorption isotherms, where the shape of the isotherm suggested the presence of strong and weak sorption sites. The Np(V) uptake was independent of ionic strength, suggesting the presence of inner-sphere Np(V) surface complexes on zirconia. This was also supported by zeta potential measurements where a shift of the isoelectric point of the pristine zirconia towards higher pH values in the presence of Np(V) was observed.
Molecular level investigations by means of spectroscopic techniques, namely in situ attenuated total reflection Fourier transform Infrared Spectroscopy (ATR FT-IR) and extended X-ray absorption fine structure spectroscopy (EXAFS), confirmed the predominant presence of Np(V) inner-sphere complexes on the zirconia surface. EXAFS experiments conducted in the weak sorption site regime revealed the formation of one Np(V) bidentate inner-sphere surface complex. Spectroscopic techniques could not be applied to gain information about the presence and structure of Np(V) surface species at such low Np(V) concentrations, where the strong site regimes could be investigated.
The derived information at the macroscopic and molecular levels were used to parameterize a surface complexation model. The Np(V) sorption edges and isotherms could be described with a 1-pK three plane CD-MUSIC model. The derived thermodynamic constants are expected to help to better predict the environmental fate of Np(V) in the context of nuclear waste repository assessments and will also support the appraisal of safety-relevant scenarios for the extended interim storage of spent nuclear fuel.

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

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Permalink: https://www.hzdr.de/publications/Publ-36679


Data publication: Membrane-free alkali metal-iodide battery with a molten salt

Lee, J.; Monrrabal Marquez, G.; Sarma, M.; Lappan, T.; Hofstettet, Y. J.; Trtik, P.; Landgraf, S.; Ding, W.; Kumar, S.; Vaynzof, Y.; Weber, N.; Weier, T.

Abstract

Raw data from experiments with membrane-free alkali metal-iodide cells containing XPS results, phase-diagram calculations, neutron radiography images, electrochemical cycling data, and electron microscope images of the carbon felt used.

Keywords: liquid metal batteries; alkali metal-iodide batteries; liquid metal electrodes; low-temperature molten salt; membrane-free energy storage; neutron radiography

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Permalink: https://www.hzdr.de/publications/Publ-36678


Band-to-band tunneling switches based on two-dimensional van der Waals heterojunctions

Chava, P.; Fekri, Z.; Vekariya, Y. N.; Mikolajick, T.; Erbe, A.

Abstract

Quantum mechanical band-to-band tunneling (BTBT) is a type of carrier injection mechanism that is responsible for the electronic transport in devices like tunnel field effect transistors (TFETs), which hold great promise in reducing the subthreshold swing below the Boltzmann limit. This allows scaling down the operating voltage and the off-state leakage current at the same time, and thus reducing the power consumption of metal oxide semiconductor transistors. Conventional group IV or compound semiconductor materials suffer from interface and bulk traps, which hinders the device performance owing to the increased trap induced parasitics. Alternatives like two-dimensional materials (2DMs) are beneficial for realizing such devices due to their ultra-thin body and atomically sharp interfaces with van der Waals interactions, which significantly reduce the trap density, compared to their bulk counterparts, and hold the promise to finally achieve the desired low voltage operation. In this review, we summarize the recent progress on such devices, with a major focus on heterojunctions made of different 2DMs. We review different types of emerging device concepts, architectures and the tunneling mechanisms involved by analytically studying various simulations and experimental devices. We present our detailed perspective on the current developments, major roadblocks and key strategies for further improvements of the TFET technology based on 2D heterojunctions to match industry requirements. The main goal of this paper is to introduce the reader to the concept of tunneling especially in van der Waals devices and provide an overview of the recent progress and challenges in the field.

Keywords: 2D materials; heterojunctions; band-to-band tunneling; tunnel field effect transistor; tunnel diode

Permalink: https://www.hzdr.de/publications/Publ-36676


Generalized Laguerre Mosaics as versatile toolbox for microstructure modelling

van den Boogaart, K. G.; Tolosana Delgado, R.; Ballani, F.

Abstract

The particle based simulation of minerals processing often requires
models of 3D particles, while only insufficiently resolved 3D
information from CT or sufficiently resolved 2D information on the
structure of the material is available. Fitted and simulated
microstructure models can support us with relevant 3D microstructures.

The contribution proposes several steps to generalize 3D
Laguerre mosaics that allow to recreate various typical features of
microstructures with meaningful parameters to the simulation process:
Multiple phases with different abundance, preferred contacts, different
grain sizes, spatial variation of properties, flattened crystallites,
preferred orientation, flat and rounded boundaries, etc.

A special feature of the model is the possibility to change the parameters
gradually for the same simulation, such that one can track the effect
of the parameters visually and for estimation algorithms with lower
variability than with a resimulation.

The same microstructure can be computed for 3D voxel spaces, in 2D
sections and on MPS type patterns for estimation of high order
statistics.

Keywords: Geometallurgy; Stochastic Geometry; Microstructure Simulation

  • Lecture (Conference)
    IAMG2023, 05.-12.08.2023, Trontheim, Kongeriket Noreg

Permalink: https://www.hzdr.de/publications/Publ-36675


Structural MATerias research on parameters influencing the material properties of RPV steels for safe long-term operation of PWR NPPs

Kolluri, M.; Martin, O.; Naziris, F.; D’Agata, E.; Gillemot, F.; Brumovsky, M.; Ulbricht, A.; Autio, J.-M.; Shugailo, O.; Horvath, A.

Abstract

This article provides a comprehensive overview of the STRUMAT-LTO project. Embrittlement of the reactor pressure vessel (RPV) due to neutron irradiation and high temperature conditions impose critical challenges for long-term operation (LTO) of pressurized water reactors (PWRs). Significant amount of past research conducted on RPV ageing phenomena has helped to enhance the understanding of the flux effect and the impact of chemical/microstructural heterogeneities on RPV embrittlement. Nonetheless, several unresolved questions regarding RPV embrittlement persist, such as the conflicting viewpoints on the underlying mechanisms that lead to accelerated embrittlement at high fluence conditions in certain low-copper (Cu) RPV steels and the synergistic
effect between nickel, manganese, and silicon (Ni-Mn-Si). Also, the accuracy of embrittlement trend curves (ETCs) for LTO beyond 60 years and the applicability of the master curve approach at high fluences for small/sub-sized specimens require further study. The aim of the STRUMAT-LTO is to address the above-mentioned scientific gaps in RPV embrittlement by employing a unique set of RPV steel specimens constituting systematic variations in Ni, Mn, and Si content, which are irradiated to high fluences resembling reactor operation beyond 60 years within the LYRA-10 experiment at high flux reactor (HFR) in Petten. The STRUMAT-LTO project has received funding from the Euratom research and training programme 2019–2020 under grant agreement
n◦945272. The project has a duration of 48 months.

Keywords: STRUMAT-LTO; RPV embrittlement; LYRA-10; HFR; mini-CT; LWRs; Long term operation; Embrittlement trent curve

Permalink: https://www.hzdr.de/publications/Publ-36674


Vacancy complexes in Cd3As2

Rice, A. D.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Wagner, A.; Haegel, N. M.; Alberi, K.

Abstract

Epitaxial growth of the three-dimensional topological semimetal Cd3As2 on semiconductor substrates enables its use and integration in device applications. Epitaxy also provides an avenue for varying and controlling point defects through modification of the chemical potential during growth. In turn, knowledge of the point defects that are generated in Cd3As2 epilayers will aid the interpretation of electron transport behavior and guide growth efforts to produce material with low defect densities. Point defects in Cd3As2 epilayers grown by molecular beam epitaxy with varying As/Cd flux ratios are probed by positron annihilation spectroscopy. We find that lower As/Cd flux ratios produce higher concentrations of point defects. Remarkably, the measurements indicate that the average defect size is larger than a monovacancy. The data presented here contribute to an evolving picture of vacancy point defects in Cd3As2 and can be used to direct future investigation of the defect-transport relationships in this emerging electronic material.

Keywords: Cd3As2; semiconductors; defects; positron annihilation spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-36673


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