Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

XAFS Spectroscopy Study of Microstructure and Electronic Structure of Heterosystems Containing Si/GeMn Quantum Dots

Erenburg, S. B.; Trubina, S. V.; Zvereva, A.; Zinoviev, A.; Katsyuba, V.; Dvurechenskii, V.; Kvashnina, K. O.; Voelskow, M.

Using X-ray absorption near edge structure spectroscopy, extended X-ray absorption fine structure spectroscopy, atomic force microscopy, and Rutherford backscattering spectroscopy, the features of the microstructure and elemental composition of Si/GeMn magnetic systems obtained by molecular beam epitaxy and containing quantum dots are studied. Intense mixing of Ge and Si atoms is found in all samples. The degree of mixing (diffusion) correlates with the conditions of synthesis of Si/GeMn samples. For these systems, direct contacts of germanium atoms with manganese atoms are characterized and the presence of interstitial manganese with tetrahedral coordination and substitution of manganese for germanium and silicon in the lattice sites is found. The presence of stoichiometric phases Ge8Mn11, Ge3Mn5 is not detected. The correlations of the Ge, Si, and Mn coordination numbers in the Ge environment are determined both with the Mn flux value (evaporator temperature) and with the temperature at which quantum dots are grown, as well as with other synthesis conditions. The manganese concentration in the samples is determined.

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Permalink: https://www.hzdr.de/publications/Publ-29320
Publ.-Id: 29320


Viscosity measurements in pulsed magnetic fields by using a quartz-crystal microbalance

Nomura, T.; Zherlitsyn, S.; Kohama, Y.; Wosnitza, J.

Viscosity measurements in combination with pulsed magnetic fields are developed by use of a quartz-crystal microbalance (QCM). When the QCM is immersed in liquid, the resonant frequency, f0, and the quality factor, Q, of the QCM change depending on (pn)0.5, where p is the mass density and n the viscosity. During the magnetic-field pulse, f0 and Q of the QCM are simultaneously measured by a ringdown technique. The typical resolution of (pn)>sup>0.5 is 0.5%. As a benchmark, the viscosity of liquid oxygen is measured up to 55 T.

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Permalink: https://www.hzdr.de/publications/Publ-29319
Publ.-Id: 29319


Spin Textures as Sources for Magnons with Short Wavelengths and 3D Mode Profiles

Sluka, V.; Wintz, S.

In this chapter, we will give an overview of contemporary methods for spin-wave excitation and propagation. We will focus on the exploitation of spin textures for the generation and propagation of spin waves with very short wavelengths as well as on the 3D nature of such excited waves.

Keywords: spin waves; excitation; 3D

  • Book chapter
    Gianluca Gubbiotti: Three-Dimensional Magnonics, Singapur: Jenny Stanford Publishing, 2019, 9789814800730, 219-259

Permalink: https://www.hzdr.de/publications/Publ-29318
Publ.-Id: 29318


A model of a tidally synchronized solar dynamo

Stefani, F.; Giesecke, A.; Weier, T.

We discuss a solar dynamo model of Tayler–Spruit type whose Omega-effect is conventionally produced by a solar-like differential rotation but whose alpha-effect is assumed to be periodically modulated by planetary tidal forcing. This resonance-like effect has its rationale in the tendency of the current-driven Tayler instability to undergo intrinsic helicity oscillations which, in turn, can be synchronized by periodic tidal perturbations. Specifically, we focus on the 11.07-years alignment periodicity of the tidally dominant planets Venus, Earth, and Jupiter, whose persistent synchronization with the solar dynamo is briefly touched upon. The typically emerging dynamo modes are dipolar fields, oscillating with a 22.14-years period or pulsating with a 11.07-years period, but also quadrupolar fields with corresponding periodicities. In the absence of any constant part of alpha, we prove the sub-critical nature of this Tayler–Spruit type dynamo. The resulting amplitude of the alpha oscillation that is required for dynamo action turns out to lie in the order of 1 m/s, which seems not implausible for the Sun. When starting with a more classical, non-periodic part of alpha, even less of the oscillatory alpha part is needed to synchronize the entire dynamo. Typically, the dipole solutions show butterfly diagrams, although their shapes are not convincing yet. Phase coherent transitions between dipoles and quadrupoles, which are reminiscent of the observed behavior during the Maunder minimum, can easily be triggered by long-term variations of dynamo parameters, but may also occur spontaneously even for fixed parameters. Further interesting features of the model are the typical second intensity peak and the intermittent appearance of reversed helicities in both hemispheres.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29317
Publ.-Id: 29317


Impact of the Electromagnetic Brake Position on the Flow Structure in a Slab Continuous Casting Mold: An Experimental Parameter Study

Schurmann, D.; Glavinic, I.; Willers, B.; Timmel, K.; Eckert, S.

Flow measurements are performed in a slab model for continuous casting of steel under the influence of a ruler type Electromagnetic Brake (EMBr). The Mini-LIMMCAST facility utilizes the low melting GaInSn alloy for flow modeling. Two-dimensional velocity distributions in the center plane of the rectangular mold with a cross-section of 300 x 35 mm² are determined by means of the Ultrasound Doppler Velocimetry (UDV). This study especially focuses on the influence of the vertical position of the EMBr and its magnetic flux density as well as the effect of different immersion depths of the Submerged Entry Nozzle (SEN).

The horizontal flow velocity just below the free surface can effectively be reduced by choosing an optimal position of the EMBr while an improper positioning even increases the near-surface velocity compared to the case without activated brake. A general braking effect of the EMBr on the submerged jet is not observed. The decisive mechanism for controlling the near-surface flow results from a modification of the jet geometry and a reorganization of the flow field. In terms of an effective flow control an appropriate positioning of the EMBr has at least the same significance as the regulation of the magnetic field strength.

Keywords: Continuous Slab Casting; Liquid Metal Model Experiments; Flow Measurements; Ultrasound Doppler Velocimetry (UDV); Electromagnetic Brake (EMBr); Immersion Depth

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  • Secondary publication expected from 14.01.2021

Permalink: https://www.hzdr.de/publications/Publ-29316
Publ.-Id: 29316


Micro-scale isotopic variability of low-temperature pyrite in fractured crystalline bedrock ― A large Fe isotope fractionation between Fe(II)aq/pyrite and absence of Fe-S isotope co-variation

Yu, C.; Drake, H.; Lopez Fernandez, M.; Whitehouse, M.; Dopson, M.; Åström, M. E.

This study assessed Fe-isotope ratio (56Fe/54Fe, expressed as δ56Fe relative to the IRMM-014 standard) variability and controls in pyrite that has among the largest reported S-isotope variability (maximum δ34S: 140‰). The pyrite occurs as fine-grained secondary crystals in fractures throughout the upper kilometer of granitoids of the Baltic Shield, and was analyzed here for δ56Fe by in situ secondary ion mass spectrometry (SIMS). Part of these pyrite crystals were picked from borehole instrumentation at depths of >400 m below sea level (m.b.s.l.), and thus are modern (known to have formed within 17 years) and can be compared with the δ56Fe of the source dissolved ferrous iron. The δ56Fe values of the modern pyrite crystals (−1.81‰ to +2.29‰) varied to a much greater extent than those of the groundwaters from which they formed (−0.48‰ to +0.13‰), providing strong field evidence for a large Fe isotope fractionation during the conversion of Fe(II)aq to FeS and ultimately to pyrite. Enrichment of 56Fe in pyrite relative to the groundwater was explained by equilibrium Fe(II)aq-FeS isotope fractionation, whereas depletion of 56Fe in pyrite relative to the groundwater was mainly the result of sulfidization of magnetite and kinetic isotopic fractionation during partial transformation of microsized FeS to pyrite. In many pyrite crystals, there is an increase in δ34S from crystal center to rim reflecting Rayleigh distillation processes (reservoir effects) caused by the development of closed-system conditions in the micro-environment near the growing crystals. A corresponding center-to-rim feature was not observed for the δ56Fe values. It is therefore unlikely that the groundwater near the growing pyrite crystals became progressively enriched in the heavy Fe isotope, in contrast to what has been found for the sulfur in sulfate. Other pyrite crystals formed following bacterial sulfate reduction in the time period of mid-Mesozoicum to Quaternary, had an almost identical Fe-isotope variability (total range: −1.50‰ to +2.76‰), frequency-distribution pattern, and relationship with δ34S as the recent pyrite formed on the borehole instrumentation. These features suggest that fundamental processes are operating and governing the Fe-isotope composition of pyrite crystals formed in fractured crystalline bedrock over large time scales.

Keywords: Pyrite; Iron isotopes; Equilibrium Fe-isotope fractionation; Magnetite sulfidization; Partial pyritization; Fractured crystalline bedrock

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Permalink: https://www.hzdr.de/publications/Publ-29315
Publ.-Id: 29315


Horizon-2020 ESFR-SMART project on SFR safety: status after first 15 months

Mikityuk, K.; Girardi, E.; Krepel, J.; Bubelis, E.; Fridman, E.; Rineiski, A.; Girault, N.; Payot, F.; Buligins, L.; Gerbeth, G.; Chauvin, N.; Latge, C.; Guidez, J.

Devoted to the Generation-IV European Sodium Fast Reactor safety, the Horizon-2020 ESFR-SMART project was launched in September 2017. Selected results and milestones achieved during the first fifteen months of the project are briefly reviewed in the paper, including 1)proposal of new safety measures for ESFR; 2)evaluation of ESFR core performance; 3) benchmarking of codes; 4) experimental programs; and 5) education and training.

  • Contribution to proceedings
    27th International Conference on Nuclear Engineering - ICONE27, 19.-24.05.2019, Ibaraki, Japan

Permalink: https://www.hzdr.de/publications/Publ-29314
Publ.-Id: 29314


Benchmarking KENO-VI against MCNP/Serpent using a simplified SFR pin cell problem

Fridman, E.; Jiménez-Carrascosa, A.; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.

  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Permalink: https://www.hzdr.de/publications/Publ-29313
Publ.-Id: 29313


Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent

Fridman, E.

Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent

  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Permalink: https://www.hzdr.de/publications/Publ-29312
Publ.-Id: 29312


About the impact of the Unresolved Resonance Region in Monte Carlo simulations of Sodium Fast Reactors

Jiménez-Carrascosa, A.; Fridman, E.; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.

In the last few years, and within the framework of different European projects, KENO-VI code from SCALE system has been employed to perform detailed continuous-energy Monte Carlo transport calculations for advanced fast reactors. The core characterization of both the sodium-cooled ASTRID and the lead-cooled ALFRED reactors was performed during the FP7 cross-cutting ESNII+ project; more recently, core calculations for the sodium-cooled Superphénix reactor and the improved European Sodium Fast Reactor design were performed within the HORIZON2020 ESFR-SMART project. In all cases, the effective multiplication factor predicted by KENO-VI was systematically higher (around 400-500 pcm) than the values computed by MCNP and Serpent Monte Carlo codes, using the same nuclear data library.

In order to provide insight into the origin of the observed discrepancies, a simplified 2D MOX-fueled SFR pin-cell benchmark has been launched. The multiplication factor, as well as 1-group and VITAMINJ 175-group cross-sections computed by KENO-VI, Serpent and MCNP codes employing ENDF/B-VII.1 data library, have been compared.

Significant differences between KENO-VI and the other codes have been found in the unresolved resonance regions of 239Pu and 241Pu capture and production cross sections, while negligible differences appeared outside those energy ranges. On the other hand, calculations without using probability tables have shown very good agreement. Quantita-tive comparison is presented and analyzed, along with a discussion of the impact of the probability-table treatment in the three codes for MOX-fueled systems with typical SFR spectrum.

Keywords: Unresolved Resonance Region; Probability Tables; Monte Carlo simulations of SFR

  • Contribution to proceedings
    ICAPP 2019 – International Congress on Advances in Nuclear Power Plants, 12.-15.05.2019, Juan-les-pins, France
    Proceedings of ICAPP 2019

Permalink: https://www.hzdr.de/publications/Publ-29311
Publ.-Id: 29311


In-house reference materials for the determination of low titanium concentration in SiO2 by secondary ion mass spectrometry

Ziegenrücker, R.; Belokonov, G.; Böttger, R.; Couffignal, F.; Munnik, F.; Renno, A.; Wiedenbeck, M.; Wu, H. S.

Secondary ion mass spectrometry (SIMS) is routinely used for geochemical and mineralogical applications, but quantification is still the major challenge of this method. Each analysed matrix needs its own matrix-matched reference material (RM). However, the list of available reference materials is short compared to the needs.

One approach for the production of suitable RMs is the use of ion implantation to introduce a known amount of an isotope into a matrix-matched material. This is widely used for SIMS applications in materials science, but rarely for geochemical problems. Bumett et al. (2014) [1] demonstrated the principal appropriateness and ways to calibrate nominal implant fluence. We choose the more elaborate way of implanting a box profile to allow an effectivly homogeneous distribution of the respective isotope in all three dimensions.

Silicon dioxide SiO2, a “simple” mineralogical and chemical system, can record scientificly important data e.g. the Ti-in-quartz geothermometer [2, 3]. 47Ti respectively 48Ti were implanted into synthetic ultra-high purity silica glass. Box profiles with concentrations between 10 and 1000 ppm and a maximum depth of homogeneous 47/48Ti distribution between 200 and 500 nm were produced at the Ion Beam Center in Dresden-Rossendorf. Single implantation steps with different ion-energies and –doses were simulated with the SRIM (Stopping and Range of Ions in Matter) software [4] and optimized to the target concentrations, implantation-depths and technological limitations of the implanter.

Several different implanted test-samples were characterized by means of SIMS, atomic force microscopy (AFM) and other analytical techniques. These showed that Ti is homogeneously distributed in the glass structure within ± 5% uncertainty in all 3 dimensions, while the surface-roughness remains suitable for SIMS depth profiling.

Such reference materials are also very promising for the quantification of Super-SIMS measurements [5].


[1] Bumett, D.S., et al. (2014). Ion Implants as Matrix-Appropriate Calibrators for Geochemical Ion Probe Analyses. Geostandards and Geoanalytical Research, 39(3), 265-276.
[2] Wark, D. A., Watson E. B. (2006). TitaniQ: a titanium-in-quartz geothermometer. Contributions to Mineralogy and Petrology, 152(6), 743-754.
[3] Thomas, J. B., Watson E. B., et al. (2010). TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz. Contributions to Mineralogy and Petrology, 160(5), 743–759.
[4] Ziegler, J. F. (2004). SRIM-2003. Nuclear Instruments and Methods in Physics Research Section B, 219-220, 1027-1036.
[5] Rugel, G., et al, this conference.

Keywords: Implantation; SIMS; Titanium; Quartz; Quarz; Reference material; Referenz Material

  • Poster
    Ion Beam Physics Workshop 2019, 24.-26.06.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29310
Publ.-Id: 29310


Preparation of non-oxidized Ge quantum dot lattices in amorphous Al2O3, Si3N4 and SiC matrices

Nekić, N.; Šarić, I.; Salamon, K.; Basioli, L.; Sancho-Parramon, J.; Grenzer, J.; Hübner, R.; Bernstorff, S.; Petravić, M.; Mičetić, M.

The preparation of non-oxidized Ge quantum dot (QD) lattices embedded in Al2O3, Si3N4, SiC matrices by self-assembled growth was studied. The materials were produced by magnetron sputtering deposition, using different substrate temperatures. The deposition regimes leading to the self-assembled growth type and the formation of three-dimensionally ordered Ge QD lattices in different matrices were investigated and determined. The oxidation of the Ge QDs in different matrices was monitored and the best conditions for the production of non-oxidized Ge QDs were found. The optical properties of the Ge QD lattices in different matrices show a strong dependence on the Ge oxidation and the matrix type.

Keywords: Ge QD lattices; Ge oxidation; self-assembled growth; influence of matrix

Permalink: https://www.hzdr.de/publications/Publ-29309
Publ.-Id: 29309


The magnetic structure of L10 ordered MnPt at room temperature determined using polarized neutron diffraction

Solina, D.; Schmidt, W.; Kaltofen, R.; Krien, C.; Lai, C.-H.; Schreyer, A.

Neutron scattering studies have been carried out on single crystal films of [001] orientated L10 ordered MnPt grown epitaxially onMgO(001) usingDCmagnetron sputtering. Polarized neutron diffraction studies at room temperature show that the moments in ordered MnPt are aligned perpendicular to the [001] axis with a tilt of 45° to the [100] axis and not parallel to [100] as inferred from previous powder neutron diffraction measurements.

Keywords: antiferromagnetic; neutron diffraction; platinum alloys

Permalink: https://www.hzdr.de/publications/Publ-29308
Publ.-Id: 29308


Fast neutron inelastic scattering from ⁷Li

Beyer, R.; Frotscher, A.; Gyürky, G.; Junghans, A.; Nolte, R.; Nyman, M.; Olacel, A.; Pirovano, E.; Plompen, A.; Röttger, S.; Grieger, M.; Hammer, S.; Kögler, T.; Ludwig, F.; Müller, S.; Reinicke, S.; Schulz, S.; Schwengner, R.; Trinh, T. T.; Turkat, S.; Urlaß, S.; Wagner, A.

The inelastic scattering of fast neutrons from 7Li nuclei was investigated at the nELBE neutron-time-of-flight facility. This process has technological implications in fusion and fission reactors. In the former it could create an intense γ-ray field causing heating and radiation damage, in the latter it could strongly influence the neutron energy spectrum and therefore the neutronics of e.g. novel reactor concepts like the molten salt reactor. Furthermore the γ-ray production cross section of 7Li is a very good case to be used as an alternative for neutron fluence determination to enable relative measurements of neutron-induced reactions. Inelastic neutron scattering on 7Li leads to the production of a 478 keV γ-ray from the first excited state of 7Li. The next higher lying state in this nucleus at 4630 keV already undergoes break up into an α-particle and a triton. The angular distribution of the γ-rays after inelastic neutron scattering is isotropic and has negligible internal conversion. The threshold energy is low enough to be able to cover a large range of neutron energy and the cross section of about 0.2 barn is reasonably high to enable good statistics within a feasible measurement time.
At nELBE the photon production cross section was determined by irradiated a disc of LiF with a neutrons of energies ranging from 100 keV to about 10 MeV. The target position was surounded by a setup of 7 LaBr3 scintillation detectors and 4 high-purity germanium detectors to detect the 478 keV de-excitation gamma-rays. A 235U fission chamber was used to determine the incoming neutron flux. All details of the experiment and the data analysis will be explained. The final results will be compared to previous measurement done e.g. at the GELINA facility.

Keywords: fast neutron inelastic scattering; ⁷Li; nELBE

Related publications

  • Lecture (Conference)
    2019 International Conference on Nuclear Data for Science and Technology, 19.-24.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-29307
Publ.-Id: 29307


Detection of ultra-low protein concentrations with the simplest possible field effect transistor

Georgiev, Y.; Petkov, N.; Yu, R.; Nightingale, A. M.; Buitrago, E.; Lotty, O.; Demello, J. C.; Ionescu, A.; Holmes, J. D.

Silicon nanowire (Si NW) sensors have attracted great attention due to their ability to provide fast, low-cost, label-free, real-time detection of chemical and biological species. Usually configured as field effect transistors (FETs), they have already demonstrated remarkable sensitivity with high selectivity (through appropriate functionalisation) towards a large number of analyses in both liquid and gas phases. Despite these excellent results, Si NW FET sensors have not yet been successfully employed to detect single molecules of either a chemical or biological target species. Here we show that sensors based on silicon junctionless nanowire transistors (JNTs), the simplest possible transistors, are capable of detecting the protein streptavidin at a concentration as low as 580 zM closely approaching the single molecule level. This ultrahigh detection sensitivity is due to the intrinsic advantages of junctionless devices over conventional FETs.

Apart from their superior functionality, JNTs are much easier to fabricate by standard microelectronic processes than transistors containing p-n junctions. The ability of JNT sensors to detect ultra-low concentrations (in the zeptomolar range) of target species, and their potential for low-cost mass production, will permit their deployment in numerous environments, including life sciences, biotechnology, medicine, pharmacology, product safety, environmental monitoring and security.

Keywords: Si nanowire biosensor; junctionless nanowire transistor; ultrahigh detection sensitivity; protein; streptavidin; single-molecule detection

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Permalink: https://www.hzdr.de/publications/Publ-29306
Publ.-Id: 29306


Development of nuclear and optical dual-labelled agents for cancer imaging

Stephan, H.

For the past decade, nuclear and optical dual-labelled imaging agents have attracted enormous attention. Applied to cancer imaging, tumours can be tracked down by nuclear techniques such as single-photon emission tomography (SPECT) and positron emission tomography (PET), and subsequently resected using image-guided surgery with the appropriate fluorophores. Moreover, the high spatial resolution of fluorescence imaging permits the elucidation of cell-biological events and thereby gaining a deeper insight into in vitro and in vivo processes. The development of dual imaging probes can be achieved using sophisticated low-molecular compounds that combine moieties for the desired imaging modalities, e.g. dyes for fluorescence optical imaging, and appropriate bifunctional chelator agents (BFCAs) for radiometals enabling SPECT or PET. We have developed BFCAs based on bis(2-pyridylmethyl)-1,4,7-triazacyclononane (DMPTACN) and 3,7-diazabicyclo[3.3.1]nonane (bispidine) that rapidly form stable 64CuII complexes under mild conditions. These BFCAs are well-suited for in vivo application in cancer imaging. Since they are also relatively easy to functionalize with multiple modalities, they are ideal chelators for the design of targeted dual-labelled imaging agents (PET, fluorescence imaging). Moreover, these chelating agents can be easily grafted on the surface of nanomaterials that are equipped with a multitude of different functionalities, such as targeting units, solubility enhancer and fluorescent tags. Hence, higher sensitivity can be achieved compared to small molecules, and there is an almost infinite variability regarding the surface functionalization.
Examples of target-specific peptides and bio(nano)materials equipped with DMPTACN/bispidine ligands for labelling with 64Cu as an ideal positron emitter are discussed. This enables tumour imaging and the biodistribution of materials can be studied over a period of days via positron emission tomography (PET). The additional introduction of fluorescence labels allows for optical imaging with high spatial resolution, and offers the possibility to visualize cellular processes by fluorescence microscopy.

  • Lecture (Conference)
    Seventh International Conference on Radiation in Various Fields of Research, 10.-14.06.2019, Herceg Novi, Montenegro

Permalink: https://www.hzdr.de/publications/Publ-29305
Publ.-Id: 29305


Evidence for Recent Interstellar ⁶⁰Fe on Earth

Koll, D.; Faestermann, T.; Feige, J.; Fifield, L. K.; Froehlich, M. B.; Hotchkis, M. A. C.; Korschinek, G.; Merchel, S.; Panjkov, S.; Pavetich, S.; Tims, S. G.; Wallner, A.

Over the last 20 years the long-lived radionuclide ⁶⁰Fe with a half-life of 2.6 Myr was shown to be an expedient astrophysical tracer to detect freshly synthesized stardust on Earth. The unprecedented sensitivity of Accelerator Mass Spectrometry for ⁶⁰Fe at The Australian National University (ANU) and Technical University of Munich (TUM) allowed us to detect minute amounts of ⁶⁰Fe in deep-sea crusts, nodules, sediments and on the Moon [1-5]. These signals, around 2-3 Myr and 6.5-9 Myr before present, were interpreted as a signature from nearby Supernovae which synthesized and ejected ⁶⁰Fe into the local interstellar medium.
Triggered by these findings, ANU and TUM independently analyzed recent surface material for ⁶⁰Fe, deep-sea sediments and for the first time Antarctic snow, respectively [6, 7].
We find in both terrestrial archives corresponding amounts of recent ⁶⁰Fe.
We will present these discoveries, evaluate the origin of this recent influx and bring it into line with previously reported ancient ⁶⁰Fe findings.
[1] K. Knie et. al. “Indication for supernova produced ⁶⁰Fe activity on Earth”, Phys. Rev. Lett. 83 (1999) 18.
[2] K. Knie et. al. “⁶⁰Fe anomaly in a deep-sea manganese crust and implications for a nearby supernova source”, Phys. Rev. Lett. 93 (2004) 171103.
[3] P. Ludwig et. al. “Time-resolved 2-million-year-old super-nova activity discovered in Earth's microfossil record”, PNAS 113 (2016) 9232.
[4] A. Wallner et. al. “Recent near-Earth supernovae probed by global deposition of interstellar radioactive ⁶⁰Fe”, Nature 532 (2016) 69.
[5] L. Fimiani et. al. “Interstellar ⁶⁰Fe on the surface of the Moon”, Phys. Rev. Lett. 116 (2016) 151104.
[6] D. Koll et. al. “Interstellar ⁶⁰Fe in Antarctica”, Phys. Rev. Lett., submitted
[7] A. Wallner et al. in preparation

Keywords: AMS; supernova; Antarctica; radionuclide; ⁶⁰Fe

  • Lecture (Conference)
    Heavy Ion Accelerator Symposium on Fundamental and Applied Science (HIAS), 09.-13.09.2019, Canberra, Australia

Permalink: https://www.hzdr.de/publications/Publ-29304
Publ.-Id: 29304


Integrierte Entwicklungs- und Publikationsumgebung für Forschungssoftware und Daten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

Frust, T.; Konrad, U.

Mit dem Ziel den gesamten Lebenszyklus wissenschaftlicher Artikel, Forschungssoftware und Daten in Vereinbarkeit mit den FAIR-Prinzipien zu unterstützen, wurde am HZDR eine integrierte Entwicklungs- und Publikationsumgebung geschaffen. Insbesondere die Publikation von Forschungssoftware und Daten erfordert eine technische und organisatorische Infrastruktur. Oft ist auch ein intensiverer Wissensaustausch und die Unterstützung der Wissenschaftler notwendig. Die Hürde zur Veröffentlichung sollte durch Automatisierung und Integration verschiedener Plattformen möglichst klein gehalten werden. In diesem Vortrag wird der aktuelle Stand, Erfahrungen und Herausforderungen gezeigt, die bei der Bereitstellung einer derartigen Umgebung gemacht wurden.

Keywords: Publication; Data management; Research Software

  • Open Access Logo Lecture (Conference)
    deRSE19, 04.-06.06.2019, Potsdam, Deutschland
    DOI: 10.5446/42518

Permalink: https://www.hzdr.de/publications/Publ-29303
Publ.-Id: 29303


Effect of trivalent lanthanides and actinides on a rat kidney cell line

Heller, A.; Acker, M.; Barkleit, A.; Bok, F.; Wober, J.

Exposure to trivalent lanthanides (Ln) and actinides (An) poses a serious health risk to animals and humans. Since both Ln and An are mainly excreted with the urine, we investigated the effect of La, Ce, Eu, and Yb (as representatives of Ln) as well as Am (as representative of An) exposure on a rat kidney cell line (NRK-52E) for 8, 24, and 48 h in vitro. Cell viability studies using the XTT assay and fluorescence microscopic investigations were combined with solubility and speciation studies using ICP-MS and time-resolved laser-induced fluorescence spectroscopy (TRLFS). Thermodynamic modeling was applied to predict the speciation of Ln and Am in cell culture medium.
All Ln show a concentration- and time-dependent effect on NRK-52E cells with Ce being the most potent element. Effective Ln concentrations reducing the cell viability to 50 % (EC50 values) range from 340 µM for Ce to 1.1 mM for Eu. In general, light and heavy Ln seem to exhibit a greater effect than middle Ln.
In cell culture medium with 10 % fetal bovine serum (FBS), the Ln are completely soluble and complexed with proteins from FBS. Ln speciation is time-independent. Comparative experiments with Am are ongoing and will reveal analogies and/or differences in the effect of trivalent Ln and An on rat kidney cells.
This is the first study revealing the effects of Ln onto mammalian kidney cells. Furthermore, our laboratory is one of the few worldwide, which is able to perform cell culture studies using radioactive elements like Am.
The results of this study underline the importance of combining biological, chemical, and spectroscopic methods in studying the effect of Ln and An on cells in vitro and may contribute to the improvement of the current risk assessment for Ln in the human body. Furthermore, they demonstrate that Ln seem to have no effect on rat renal cells in vitro at environmental trace concentrations. Nevertheless, especially Ce has the potential for harmful effects at elevated concentrations observed in mining and industrial areas.

Keywords: cytotoxicity; f-elements; XTT; TRLFS

  • Lecture (Conference)
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-29302
Publ.-Id: 29302


Measurement, model prediction and uncertainty quantification of plasma clearance of cerium citrate in humans

Höllriegl, V.; Barkleit, A.; Spielmann, V.; Li, W. B.

Double tracer studies in healthy human volunteers with stable isotopes of cerium citrate were performed with the aim of investigating the gastro-intestinal absorption of cerium (Ce), its plasma clearance and urinary excretion. In the present work, results of the clearance of Ce in blood plasma are shown after simultaneous intravenous and oral administration of a Ce tracer. Inductively coupled plasma mass spectrometry was used to determine the tracer concentrations in plasma. The results show that about 80% of the injected Ce citrate cleared from the plasma within the 5 mins post-administration. The data obtained are compared to a revised biokinetic model of Ce, which was initially developed by the International Commission on Radiological Protection (ICRP). The measured plasma clearance of Ce citrate was mostly consistent with that predicted by the ICRP biokinetic model. Furthermore, in an effort to quantify the uncertainty of the model prediction, the laboratory animal data on which the ICRP biokinetic Ce model is based, was analyzed. The measured plasma clearance and its uncertainty was also compared to the plasma clearance uncertainty predicted by the model. It was found that the measured plasma clearance during the first 15 min after administration is in a good agreement with the modelled plasma clearance. In general, the measured clearance falls inside the 95% confidence interval predicted by the biokinetic model.

Keywords: cerium; biokinetics; systemic model; speciation; internal dosimetry; uncertainty analysis

Permalink: https://www.hzdr.de/publications/Publ-29301
Publ.-Id: 29301


Influence of common decorporation agents on the speciation of trivalent f-elements in serum – a luminescence spectroscopic study

Barkleit, A.; Heller, A.

The accidental release of radionuclides, especially actinides (An), in a nuclear facility or in the environment increases the risk of incorporation of these elements into the human body. Irrespective of the uptake pathway, via inhalation, ingestion, or through wounds or the skin, An are resorbed and transported by the bloodstream. Eventually, they are deposited in target organs (e.g., bone, liver or kidney) or partially excreted with urine or faeces. Fast and effective decorporation or chelation therapy is very important to minimize the health risk. To improve decorporation efficiency by choosing the right chelating agent or by designing new efficient chelators for different An, the understanding of their chemical speciation on a molecular level is crucial.
In this study, we investigate the chemical speciation of Cm(III) (as representative of An) and Eu(III) (as non-radioactive analogue for trivalent An) in blood serum. Subsequently, the alterations in speciation after spiking with common chelating agents often used for decorporation purposes, such as ethylenediaminetetraacetic acid (EDTA), or diethylenetriaminepentaacetic acid (DTPA), were studied and compared to biological ligands, such as citrate. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used to perform the speciation investigations. Thermodynamic calculations were carried out to support the experimental results.
The dominant chemical species of Eu in serum were identified by comparing the Eu luminescence spectra and lifetimes in serum with those obtained in reference solutions with individual components of the serum, such as the proteins albumin and transferrin as well as the inorganic anions phosphate and carbonate. Linear combination fitting analysis (LCFA) on the sample spectra indicated that Eu is mainly coordinated by albumin (~50 %) and transferrin (~35 %), and to a lesser extent by inorganic anions like carbonate (~15 %).
The shape of the Eu luminescence spectrum in serum was only slightly influenced by adding citrate and EDTA, whereas the shapes of the pure ligand spectra differ strongly. This indicates that the speciation of Eu in serum was only slightly changed by these ligands. In contrast, DTPA caused a splitting of both the 7F1 and 7F2 peak, which is very similar to the Eu spectrum with the pure DTPA ligand, indicating a strong change of the Eu speciation in serum towards Eu-DTPA complexation. LCFA indicated that about 50 % of the Eu was coordinated by DTPA. The luminescence lifetimes and thermodynamic calculations as well as the Cm luminescence data show similar tendencies. Our results follow the trend of the respective complex stability constants of Am(III) complexes with chelating agents and the findings from 241Am experiments with animals.
This study combining TRLFS and thermodynamic calculations demonstrates a fast and easy way to screen the effect of several chelating agents towards (luminescent) An in vitro. In future, this could be a useful tool to improve decorporation methods.

Keywords: serum proteins; EDTA; DTPA; laser fluorescence spectroscopy

  • Contribution to proceedings
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik
  • Lecture (Conference)
    5th International Conference on Environmental Radioactivity, ENVIRA 2019, 08.-13.09.2019, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-29300
Publ.-Id: 29300


Transverse electron beam dynamics in the beam loading regime

Köhler, A.

GeV electron bunches accelerated on a centimeter scale device exemplify the extraordinary advances of laser-plasma acceleration. The combination of high charges from optimized injection schemes and intrinsic femtosecond short bunch duration yields kiloampere peak currents. Further enhancing the current while reducing the energy spread will pave the way for future application, e.g. the driver for compact secondary radiation sources such as high-field THz, high-brightness x-ray or gamma-ray sources. One essential key for beam transport to a specific application is an electron bunch with high quality beam parameters such as low energy spread as well as small divergence and spot size. The inherent micrometer size at the plasma exit is typically sufficient for an efficient coupling into a conventional beamline. However, energy spread and beam divergence require optimization before the beam can be transported efficiently. Induced by the high peak current, the beam loading regime can be used in order to achieve optimized beam parameters for beam transport.

In this thesis, the impact of beam loading on the transverse electron dynamic is systematically studied by investigating betatron radiation and electron beam divergence. For this reason, the bubble regime with self-truncated ionization injection (STII) is applied to set up a nanocoulomb-class laser wakefield accelerator. The accelerator is driven by 150TW laser pulses from the DRACO high power laser system. A supersonic gas jet provides a 3mm long acceleration medium with electron densities from 3 × 10^18 cm^−3 to 5 × 10^18 cm^−3. The STII scheme together with the employed setup yields highly reproducible injections with bunch charges of up to 0.5 nC. The recorded betatron radius at the accelerator exit is about one micron and reveals that the beam size stays at the same value. The optimal beam loading, which is observed at around 250 pC to 300 pC, leads to the minimum energy spread of ~40MeV and a 20% smaller divergence. It is demonstrated that an incomplete betatron phase mixing due to the small energy spread can explain the experimentally observed minimum beam divergence.

Keywords: Laser wakefield acceleration; laser plasma accelerator; self-truncated ionization injection; high x-ray flux; high bunch charge; beam loading; bunch size measurement; betatron radiation; betatron spectroscopy; Transverse phase space dynamic; beam divergence; beam decoherence; betatron phase mixing; betatron decoherence

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-102 2019
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-29299
Publ.-Id: 29299


Gated targeting with a novel switchable CAR platform technology

Feldmann, A.; Hoffmann, A.; Kittel-Boselli, E.; Bergmann, R.; Koristka, S.; Arndt, C.; Loureiro, L.; Berndt, N.; Bachmann, M.

T-cells armed with conventional CARs (cCARs) are highly effective especially in hematological malignancies. However, they often fail against solid tumors, induce tumor escape variants and cause life-threatening side effects. The safety of cCAR therapy should be improved by on/off-switchable CARs. Additionally, gated targeting strategies could increase the CAR specificity, minimize on-target/off-tumor toxicities and reduce tumor escape variants. For AND gate targeting, the signaling and costimulatory motifs are split from one onto two separate CARs of different specificities. Dual-CAR-T-cells, expressing both CARs, get activated only after recognizing both antigens. However, the application of such pairs of cCARs is very challenging as the affinity and signal strength of both CARs have to be adapted accordingly. Furthermore, the cCAR size limits the number of specificities that can be simultaneously transduced into a T-cell.
Therefore, our idea was to replace the extracellular scFv domain of cCARs with a small peptide epitope. Resulting RevCARs have a small size, avoid unspecific binding and tonic signaling caused by scFv dimerization. RevCAR-T-cells can be redirected against tumors only via bispecific target modules. Such RevTMs can be used as on/off-switch of RevCAR-T-cells and flexibly replaced for targeting of any antigens. For proof of concept, two RevCARs with different peptide epitopes and a series of respective RevTMs were constructed and functionally proven for targeting of leukemic as well as solid cancers. Moreover, for gated targeting, two RevCARs were expressed in the same T-cell that differ in their extracellular peptide epitope, transmembrane and intracellular signaling domains to separately transmit isolated activation and costimulatory signals. For efficient activation of Dual-RevCAR-T-cells, both RevCARs must be engaged by respective RevTMs recognizing different epitopes and antigens.
In summary, we established a novel switchable, modular and adaptable RevCAR system characterized by small size, improved safety, easy controllability, and high flexibility allowing gated targeting strategies.

  • Lecture (Conference)
    International Conference on Lymphocyte Engineering (ICLE) 2019, 13.-15.09.2019, London, England
  • Abstract in refereed journal
    Human Gene Therapy 30(2019)12
    DOI: 10.1089/hum.2019.29091.abstracts

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29298
Publ.-Id: 29298


Extracting the Dynamic Magnetic Contrast in Time-Resolved X-ray Transmission Microscopy

Schaffers, T.; Feggeler, T.; Pile, S.; Meckenstock, R.; Buchner, M.; Spoddig, D.; Ney, V.; Farle, M.; Wende, H.; Wintz, S.; Weigand, M.; Ohldag, H.; Ollefs, K.; Ney, A.

Using a time-resolved detection scheme in scanning transmission X-ray microscopy (STXM) we measured element resolved ferromagnetic resonance (FMR) at microwave frequencies up to 10 GHz and a spatial resolution down to 20 nm at two different synchrotrons. We present different methods to separate the contribution of the background from the dynamic magnetic contrast based on the X-ray magnetic circular dichroism (XMCD) effect. The relative phase between the GHz microwave excitation and the X-ray pulses generated by the synchrotron, as well as the opening angle of the precession at FMR can be quantified. A detailed analysis for homogeneous and inhomogeneous magnetic excitations demonstrates that the dynamic contrast indeed behaves as the usual XMCD effect. The dynamic magnetic contrast in time-resolved STXM has the potential be a powerful tool to study the linear and non-linear magnetic excitations in magnetic micro- and nano-structures with unique spatial-temporal resolution in combination with element selectivity.

Keywords: x-ray microscopy; magnetic imaging

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Permalink: https://www.hzdr.de/publications/Publ-29297
Publ.-Id: 29297


Formation of Néel Type Skyrmions in an Antidot Lattice with Perpendicular Magnetic Anisotropy

Saha, S.; Zelent, M.; Finizio, S.; Mruczkiewicz, M.; Tacchi, S.; Suszka, A. K.; Wintz, S.; Bingham, N. S.; Raabe, J.; Krawczyk, M.; Heyderman, L. J.

Magnetic skyrmions are particle-like chiral spin textures found in a magnetic film with out-of-plane anisotropy and are considered to be potential candidates as information carriers in next generation data storage devices. Despite intense research into the nature of skyrmions and their dynamic properties, there are several key challenges that still need to be addressed. In particular, the outstanding issues are the reproducible generation, stabilization and confinement of skyrmions at room temperature. Here, we present a method for the capture of nanometer sized magnetic skyrmions in an array of magnetic topological defects in the form of an antidot lattice. With micromagnetic simulations, we elucidate the skyrmion formation in the antidot lattice and show that the capture is dependent on the antidot lattice parameters. This behavior is confirmed with scanning transmission x-ray microscopy measurements. This demonstration that a magnetic antidot lattice can be implemented as a host to capture skyrmions provides a new platform for experimental investigations of skyrmions and skyrmion based devices.

Keywords: skyrmion

Permalink: https://www.hzdr.de/publications/Publ-29296
Publ.-Id: 29296


Editorial for special issue "Jörg Steinbach"

Mamat, C.

This special issue of Journal of Labelled Compounds and Radiopharmaceuticals is dedicated to commemorate the outstanding scientific work of Jörg Steinbach, former director of the Institute of Radiopharmaceutical Cancer Research at the Helmholtz‐Zentrum Dresden‐Rossendorf (HZDR) and full professor for Bioinorganic and Radiopharmaceutical Chemistry at the Technical University Dresden. Current legal regulations brought to an end the formal attachment of Professor Steinbach to the TU Dresden as well as the directorship of the institute within his 65th birthday. A festive symposium has been held at the HZDR on the occasion of his retirement on September 5th, 2018, one day after the inauguration of the new Centre for Radiopharmaceutical Tumor Research at the HZDR.

  • Journal of Labelled Compounds and Radiopharmaceuticals 62(2019)8, 350-351
    DOI: 10.1002/jlcr.3773

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  • Secondary publication expected

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Publ.-Id: 29295


Prompt-gamma based range verification in proton therapy: Can we do better? Shall we do better?

Pausch, G.

Prompt gamma-ray imaging (PGI) with a knife-edge slit camera has proven to be useful for range monitoring in proton therapy (PT). It is meanwhile applied in a prostate patient study at OncoRay. Together with an improved range prediction based on dual-energy CT and robust planning methods it could finally allow reducing the range margins, thus saving normal tissue in PT treatments. Translating these emerging techniques in clinical routine is a long but important process that will require considerable efforts.
Nevertheless we are also dealing with the far end of the translational conveyer, asking if and how in-vivo range verification could be improved. So far, PGI does not allow measuring range deviations of single pencil beams with the necessary precision. The reason is the short delivery time of such a beam spot, and the poor event statistics that can be accessed in this period. It is obvious to exploit not only spatial, but also spectroscopic and timing information of the gamma rays registered for range verification. The prompt gamma-ray spectroscopy method developed at MGH in Boston and the prompt gamma-ray timing technique explored at OncoRay in Dresden represent reasonable alternatives to PGI; but can these approaches be combined in a single, preferable simple and light-weight, clinically applicable system distinguished by minimum interference with beam and patient couch? Could such a combination improve the accuracy and allow single-spot range verification, maybe even for the non-distal spots comprising much less protons?
The talk will present our thoughts and approaches to answer this question. This includes recent results concerning prompt gamma-ray timing (PGT) and single-plane Compton imaging (SPCI). Part of the research performed in this context could also affect gamma-ray imaging in nuclear medicine.

Keywords: PGI; PGT; prompt gamma ray; proton therapy; range verification; treatment verification

  • Lecture (others)
    Medizinphysik-Seminar, 12.06.2019, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29293
Publ.-Id: 29293


THEREDA - Achievements, present activities, and future developments

Moog, H. C.; Altmaier, M.; Bok, F.; Brendler, V.; Freyer, D.; Gaona, X.; Marquardt, C.; Richter, A.; Scharge, T.; Seher, H.; Thoenen, T.; Voigt, W.

INTRODUCTION
Five institutions are actively maintaining the thermodynamic reference database THEREDA aiming at the calculation of solubilities in high-saline solutions. The database is designed for applications in the context of the disposal of radioactive waste in rock salt formations and clay formations featuring solutions with a higher ionic strength [1]. The project is striving to provide an internally consistent set of data, formatted for the use by several widely-used geochemical codes. With the focus on high ionic strength systems, THEREDA complements other database projects focussing on low-saline solutions, such as THERMOCHIMIE [2] or the PSI/Nagra Chemical Thermodynamic Data Base [3].
In practical terms, work for THEREDA comprises several aspects. Most importantly, the database is continuously maintained and extended, based on annual contributions to the project. Other aspects concern the implementation of internal calculation routines, export functions and measures for quality assurance.

RECENT ACTIVITIES
Data releases
In 2018 a new release (R-12) was issued covering phosphate in high-saline solutions [4-5]. Pitzer interaction coefficients were optimized using osmotic coefficients, activity coefficients, and solubility data in binary and ternary systems. To test the obtained database, experimental data from quaternary systems were successfully modelled.
Supplementary to the phosphate release, an earlier uranium release was upgraded by adding several solid phases with phosphate (R-09.1). Available experimental data for respective aqueous complexes with phosphate in high-saline solution are currently under inspection.

CURRENT ACTIVITIES
Data releases
THEREDA is working on new thermodynamic data sets, in part as extensions to existing releases, and in part representing new systems, hitherto not covered by THEREDA. In short, the systems currently in preparation are:
• Solubility of molecular oxygen (polythermal)
• Se(+VI,+IV,0,-II) – Na, K, Mg, Ca – Cl, SO4 – H2O (partially polythermal)
• Solubility of carbonates up to 100°C (upgrade for R-03)
• Extensions for the systems Na, Mg, Cl, OH- - H2O (Sorel phases)
• Cs – K, Na, Mg, Ca, – Cl, SO4 – H2O (polythermal upgrade for R-05)
• Rb - K, Na, Mg, Ca, – Cl, SO4 – H2O (25°C)
• U(VI) hydrolysis and solubility in NaCl, KCl and MgCl2 systems (25°C, upgrade of R-09.1)
• Implementation of CEMDATA 18 [8]; will not work with GWB and TOUGHREACT as they cannot handle solid solutions yet.

Preparation of new release mode
THEREDA ensures that all issued parameter files yield the results as laid out in the release papers available at the project website. To optimize the workload, we will abstain from producing release papers in the future and establish a new procedure for data releases, which ensures a high quality of issued parameter files. Future data releases will move along the following steps.
• 1. addition and modification of data sets in THEREDA;
• 2. “feature freeze” of the database: no new data sets are added, and no existing data sets modified;
• 3. All test calculations (at present 192) are automated for all supported codes, producing (at present 1131) individual results to be compared with the ones from previous releases;
• 4. If significant deviations occur, “debugging” and repetition of test calculations is started.
5. Release of one cumulative parameter file (covering all supported systems) for each supported code.

Supported codes
Due to a significantly decreasing number of downloads, the support for EQ3/6 has been abandoned. GEM-Selektor [9] is now able to import the generic JSON-export from THEREDA. As to GWB beside the traditional “Oct84” the “Jul17” format is supported.
At present we are working on the support for TOUGHREACT [10].

Assessment of current state of THEREDA
By the end of the year the management board of THEREDA is required to submit an assessment as to whether the database, related to supported systems, still represents the state-of-the-art, or to which extent updates are appropriate.

CONCLUSION
THEREDA aims for implementing additional thermodynamic data (Pitzer) for radionuclides and key matrix elements in future data releases. While THEREDA is particularly focusing on Germany, it is open for international exchange and exploiting synergies with the international scientific/technical community.

ACKNOWLEDGMENTS
THEREDA is funded by the German “Bundesgesellschaft für Endlagerung (BGE)”, contract number 45162393 (8998-3).

REFERENCES
1. 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).
2. E. GIFFAUT et al.: Andra thermodynamic data for performance assessment: ThermoChimie. Appl. Geochem., 49, 225–236 (2014).
3. T. THOENEN et al.: The PSI/Nagra Chemical Thermodynamic Database 12/07. PSI Bericht Nr. 14-04, Paul Scherrer Institut, ISSN 1019-0643 (2014). https://www.psi.ch/en/les/database
4. T. SCHARGE et al.: Thermodynamic modelling of high salinary phosphate solutions. I. Binary systems. J. Chem. Thermodynamics, 64, 249–256 (2013).
5. T. SCHARGE et al.: Thermodynamic modeling of high salinary phosphate solutions II. Ternary and higher systems. J. Chem. Thermodynamics, 80, 172-183 (2015).
6. A. P. SOLOV’JEV et al.: Rastvorimost‘ v ctevernych vzainych vodnych sistemach iz chloridov i fosfatov natrija i kalija pri 25°C, Sb. Naucn. Tr. Jarosl. Gos. Ped. Inst., 164, 136-142 (1977).
7. G. BRUNISHOLZ et al.: Contribution à L'étude du système quinaire H+-Na+-K+-Cl--PO43--H2O II. Le diagramme de solubilité du système quaternaire Na+-K+-Cl--H2PO4--H2O, Helv. Chim. Acta, 46, 2575-2587 (1963).
8. B. LOTHENBACH et al.: Cemdata18: A chemical thermodynamic database for hydrated Portland cements and alkali-activated materials. Cem. Concr. Res., 115, 472-506 (2019).
9. D. A. KULIK et al.: GEM-Selektor geochemical modeling package: revised algorithm and GEMS3K numerical kernel for coupled simulation codes. Comp. Geosc., 17, 1-24 (2013).
10: TIANFU XU et al.: TOUGHREACT—A simulation program for non-isothermal multiphase reactive geochemical transport in variably saturated geologic media: Applications to geothermal injectivity and CO2 geological sequestration. Comp.Geosc., 32, 145-165 (2006).

Keywords: THEREDA; Database; Geochemical Modelling; Thermodynamic; Nuclear Waste Repository; Pitzer

  • Lecture (Conference)
    Actinide Brine Chemistry (ABC-Salt) VI Workshop 2019, 25.-26.06.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29292
Publ.-Id: 29292


Band gap renormalization in n-type GeSn alloys made by ion implantation and flash lamp annealing

Prucnal, S.; Berencén, Y.; Wang, M.; Rebohle, L.; Kudrawiec, R.; Polak, M.; Zviagin, V.; Schmidt-Grund, R.; Grundmann, M.; Grenzer, J.; Turek, M.; Droździel, A.; Pyszniak, K.; Zuk, J.; Helm, M.; Skorupa, W.; Zhou, S.

The last missing piece of the puzzle for the full functionalization of group IV optoelectronic devices is a direct bandgap semiconductor made by CMOS compatible technology. Here, we report on the fabrication of GeSn alloys with Sn concentrations up to 4.5% using ion implantation followed by millisecond-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are realized by coimplantation of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The bandgap engineering in GeSn as a function of the doping level and Sn concentration is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully suppressed by millisecond-range nonequilibrium thermal processing.

Keywords: ion implantation; flash lamp annealing; Ge; GeSn; n-type doping

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Permalink: https://www.hzdr.de/publications/Publ-29290
Publ.-Id: 29290


Benchmarking ATHLET against TRACE as applied to Superphénix start-up tests

Di Nora, V. A.; Fridman, E.; Mikityuk, K.

ATHLET is a thermal-hydraulic (TH) system code developed at the GRS for the modeling of Light Water Reactors (LWRs). To extend the applicability of ATHLET to the analyses of Sodium Fast Reactors (SFRs), the code was recently upgraded with the thermal-physical properties of the liquid sodium. The new extension is still under verification and validation phases. The present work contributes to the verification efforts. This study investigated the perfor-mance of the extended version of ATHLET as applied to the transient analysis of a set of start-up tests conducted at the Superphénix SFR. The specifications of the corresponding tests such as the simplified SPX reactor core models and the set of reactivity coefficients were adopted primarily from a previous dedicated study performed at PSI and at KIT. The reactivity effects accounted for by ATHLET included fuel Doppler effect and thermal expansion effects of sodium, fuel, diagrid, control rods driveline, strongback, and reactor vessel. The results obtained by ATHLET for main stationary TH parameters, power evolutions, and reactivity feedback components were benchmarked against the reference solutions provided by TRACE. Employing an identical set of reactivity coefficients, either in steady-state or transient calculations, the codes produce consistent and close results.

Keywords: ATHLET against TRACE; ATHLET verification; Superphénix start-up tests

  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants - ICAPP2019, 12.-15.05.2019, Juan-les-Pins, France

Permalink: https://www.hzdr.de/publications/Publ-29289
Publ.-Id: 29289


Photon diagnostics at the FLASH THz beamline

Pan, R.; Zapolnova, E.; Golz, T.; Krmpot, A. J.; Rabasovic, M. D.; Petrovic, J.; Asgekar, V.; Faatz, B.; Tavella, F.; Perucchi, A.; Kovalev, S.; Green, B.; Geloni, G.; Tanikawa, T.; Yurkov, M.; Schneidmiller, E.; Gensch, M.; Stojanovic, N.

The THz beamline at FLASH, DESY, provides both tunable (1–300 THz) narrow-bandwidth (∼10%) and broad-bandwidth intense (up to 150 uJ) THz pulses delivered in 1 MHz bursts and naturally synchronized with free-electron laser X-ray pulses. Combination of these pulses, along with the auxiliary NIR and VIS ultrashort lasers, supports a plethora of dynamic investigations in physics, material science and biology. The unique features of the FLASH THz pulses and the accelerator source, however, bring along a set of challenges in the diagnostics of their key parameters: pulse energy, spectral, temporal and spatial profiles. Here, these challenges are discussed and the pulse diagnostic tools developed at FLASH are presented. In particular, a radiometric power measurement is presented that enables the derivation of the average pulse energy within a pulse burst across the spectral range, jitter-corrected electro-optical sampling for the full spectro-temporal pulse characterization, spatial beam profiling along the beam transport line and at the sample, and a lamellar grating based Fourier transform infrared spectrometer for the on-line assessment of the average THz pulse spectra. Corresponding measurement results provide a comprehensive insight into the THz beamline capabilities.

Keywords: Electro-optic; FLASH; FTIR; Intense THz; THz diagnostic

Permalink: https://www.hzdr.de/publications/Publ-29288
Publ.-Id: 29288


Cross section of 3He(α , γ)7Be around the 7Be proton separation threshold

Szücs, T.; Kiss, G. G.; Gyürky, G.; Halász, Z.; Szegedi, T. N.; Fülöp, Z.

Background: The 3He(α,γ)7Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations.

Purpose: Despite the high number of experimental studies, none of them addresses the 3He(α,γ)7Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the 6Li(p,γ)7Be reaction suggested a new level in 7Be, which would also have an impact on the 3He(α,γ)7Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the 3He(α,γ)7Be reaction cross section in the energy range of the proposed level.

Method: For this investigation the activation technique was used. A thin window gas-cell target confining 3He gas was irradiated using an α beam. The 7Be produced was implanted into the exit foil. The 7Be activity was determined by counting the γ rays following its decay by a well-shielded high-purity germanium detector.

Results: Reaction cross sections have been determined between Ecm=4.0and4.4 MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies.

Conclusions: A constant cross section of around 10.5 μb was observed around the 7Be proton separation energy. An upper limit of 45 neV for the strength of a 3He(α,γ)7Be resonance is derived.

Keywords: Nuclear Astrophysics; alpha induced reaction; light element nucleosynthesis

Permalink: https://www.hzdr.de/publications/Publ-29287
Publ.-Id: 29287


Electromagnetic forcing of a flow with the azimuthal wavenumber m=2 in cylindrical geometry

Stepanov, R.; Stefani, F.

In this paper, we consider a liquid metal flow generated in a cylindrical volume by AC currents in various coil configurations. The final aim of this study is to design and optimize a Rayleigh-Bénard experiment with a large scale circulation, the helicity oscillation of which is synchronized by a periodically modulated tide-like m=2 perturbation.

Keywords: Rayleigh-Bénard

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29286
Publ.-Id: 29286


Incorporation of Europium into GaN Nanowires by Ion Implantation

Faye, D. N. A.; Biquard, X. B.; Nogales, E. C.; Felizardo, M. A.; Peres, M. A.; Redondo-Cubero, A. A.; Auzelle, T. B.; Daudin, B.; Tizei, L. H. G.; Kociak, M.; Ruterana, P.; Möller, W.; Méndez, B.; Alves, E.; Lorenz, K.

Rare earth (RE)-doped GaN nanowires (NWs), combining the well-defined and controllable optical emission lines of trivalent RE ions with the high crystalline quality, versatility, and small dimension of the NW host, are promising building blocks for future nanoscale devices in optoelectronics and quantum technologies. Europium doping of GaN NWs was performed by ion implantation, and structural and optical properties were assessed in comparison to thin film reference samples. Despite some surface degradation for high implantation fluences, the NW core remains of high crystalline quality with lower concentrations of extended defects than observed in ion-implanted thin films. Strain introduced by implantation defects is efficiently relaxed in NWs and the measured deformation stays much below that in thin films implanted in the same conditions. Optical activation is achieved for all samples after annealing, and while optical centers are similar in all samples, Eu 3+ emission from NW samples is shown to be less affected by residual implantation damage than for the case of thin films. The incorporation of Eu in GaN NWs was further investigated by nano-cathodoluminescence and X-ray absorption spectroscopy (XAS). Maps of the Eu-emission intensity within a single NW agree well with the Eu-distribution predicted by Monte Carlo simulations, suggesting that no pronounced Eu-diffusion takes place. XAS shows that 70-80% of Eu is found in the 3+ charge state while 20-30% is 2+ attributed to residual implantation defects. A similar local environment was found for Eu in NWs and thin films: for low fluences, Eu is mainly incorporated on substitutional Ga-sites, while for high fluences XAS points at the formation of a local EuN-like next neighbor structure. The results reveal the high potential of ion implantation as a processing tool at the nanoscale.

Permalink: https://www.hzdr.de/publications/Publ-29285
Publ.-Id: 29285


Excitation of beam-driven plasma-waves in a hybrid L|PWFA

Schöbel, S.; Kurz, T.; Debus, A.; Kononenko, O.; Heinemann, T.; Couperus Cabadağ, J. P.; Chang, Y.-Y.; Pausch, R.; Bock, S.; Bussmann, M.; Corde, S.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Köhler, A.; Hidding, B.; Karsch, S.; Zarini, O.; Schramm, U.; Martinez De La Ossa, A.; Irman, A.

Recent progress in laser wakefield acceleration (LWFA) has demonstrated the generation of high peak current electron beams with improved shot to shot stability [1]. Using high-current electron beams from a LWFA as drivers of a beam-driven plasma wakefield accelerator (PWFA) has been proposed as a beam energy and brightness transformer [2], aiming to fulfill the demanding quality requirements for applications such as FELs. It has been demonstrated experimentaly that electron beams from LWFA can actually drive plasma wakefields by themselves [3]. In order to further study the generation of plasma waves in the PWFA stage a sub-10 fs probe pulse was deployed and installed at HZDR. We observed beam driven plasma waves at different plasma densities, showing the capability of the LWFA beam to drive plasma wakefields in the self-ionizing regime. Furthermore we observed a correlation between the energy loss of the driver beam and the shape of the plasma wave. This enables us to find an optimum parameter set towards the experimental demonstration of the hybrid LPWFA.

References
[1] J. P. Couperus, R. Pausch, A. Köhler, O. Zarini, J. M. Krämer, M. Garten, A. Huebl, R. Gebhardt, U. Helbig, S. Bock, K. Zeil, A. Debus, M. Bussmann, U. Schramm, and A. Irman. Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator. Nature Communications, pages 1-7, 2017.
[2] A. Martinez de la Ossa, R.W. Assmann, M. Bussmann, S. Corde, J. P. Couperus Cabadağ, A. Debus, A. Döpp, A. Ferran Pousa, M. F.Gilljohann, T. Heinemann, B. Hidding, A. Irman, S. Karsch, O. Kononenko, T. Kurz, J. Osterhoff, R. Pausch, and U. Schramm Hybrid LWFA | PWFA Staging as a Beam Energy and Brightness Transformer: Conceptual Design and Simulations. Phil. Trans. R. Soc. A. Accepted for publication., 2019, https://arxiv.org/abs/1903.04640.
[3] M. F. Gilljohann, H. Ding, A. Döpp, J. Götzfried, S. Schindler, G. Schilling, S. Corde, A. Debus, T. Heinemann, B. Hidding, S. M. Hooker, A. Irman, O. Kononenko, T. Kurz, A. Martinez de la Ossa, U. Schramm, and S. Karsch. Direct Observation of Plasma Waves and Dynamics Induced by Laser-Accelerated Electron Beams. Phys. Rev. X, 9:011046, Mar 2019

  • Lecture (Conference)
    Laser Plasma Accelerator Workshop (LPAW), 06.05.2019, Split, Kroatien
  • Lecture (Conference)
    EAAC (European Advanced Accelerator Concepts Workshop), 16.09.2019, Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-29284
Publ.-Id: 29284


Electron Paramagnetic Resonance in Ge/Si Heterostructures with Mn-Doped Quantum Dots

Zinovieva, A. F.; Zinovyev, V. A.; Stepina, N. P.; Katsuba, A. V.; Dvurechenskii, A. V.; Gutakovskii, A. K.; Kulik, L. V.; Bogomyakov, A. S.; Erenburg, S. B.; Trubina, S. V.; Voelskow, M.

Ge/Si quantum dot (QD) structures doped with Mn have been tested by the EPR method to find the optimal conditions for formation of the diluted magnetic semiconductor (DMS) phase inside QDs. The effect of Mn doping has been studied for two series of samples: series A with QDs grown at 450 degrees C and varied Mn concentration and series B with QDs grown at different temperature with Mn concentration x = 0.02. Several effects of modification of the EPR spectra due to Mn presence in the samples have been obtained. These effects are related to (i) strain reduction due to GeSi intermixing, (ii) QD enlargement and change in QD shape, (iii) presence of an additional magnetic field produced by Mn atoms incorporated in QDs. The data obtained allow us to understand the reasons for irreproducibility of the results available in the literature on the creation of magnetic Ge1 - xMnx quantum dots.

Permalink: https://www.hzdr.de/publications/Publ-29283
Publ.-Id: 29283


Optimizing the Utilization of Heterogeneous Systems Using a Single-Source Approach with Dynamic Resource Mapping

Knodel, O.; Charaf, N.; Stephan, J.; Göhringer, D.

The efficient execution of applications on various heterogeneous resources is an emerging challenge in the heterogeneous landscape of ongoing processing architectures. Especially the mapping of applications to available hardware --regarding to real time requirements, energy parameters, hardware resources and various other system parameters-- is a major academic mission. Based on a single-source C++ software application --only containing SYCL directives-- kernels are generated for different specialized hardware accelerators (e.g. multicore processors, Graphics Processing Units (GPUs) and Field Programmable Gate Arrays (FPGAs)). With the help of hardware emulation the behavior of the execution on different hardware platforms is simulated and a survey is created. While taking additional user objectives and demands (e.g. execution time, hardware resources, power consumption, ...) into account, a virtual Heterogeneous System (vHS) is constructed and then deployed inside a data center or resource-limited edge board. To achieve high system utilization dynamic task offloading between different accelerators and kernel migration is also considered.

Keywords: Heterogeneous Systems; Virtualization; Cloud; Edge Computing; Reconfigurable

  • Poster
    ACACES - Advanced Computer Architecture and Compilation for High-Performance and Embedded Systems, 14.-20.07.2019, Fiuggi, Italy

Permalink: https://www.hzdr.de/publications/Publ-29282
Publ.-Id: 29282


Common methods of spectral data analysis for unevenly sampled data

Seilmayer, M.

Fourier and Hilbert transforms are utilized to perform several types of spectral analysis on the supplied data. Fragmented and irregularly spaced data can be processed in terms of Lomb-Scargle method. Both, FFT as well as LOMB methods take multivariate data. A user friendly interface helps to interpret the results.

Keywords: Lomb-Scargle; Fourier, Hilbert, R

  • Software in external data repository
    Publication year 2019
    Programming language: R
    System requirements: PC, Windows, Linux, MAC
    License: GPL-2

Permalink: https://www.hzdr.de/publications/Publ-29280
Publ.-Id: 29280


Numerical modelling of air-breathing PEMFC

Weber, N.; Chaparro, A.; Ferreira-Aparicio, P.

Übersicht über die Simulation von Luft atmenden Brennstoffzellen mit OpenFOAM

  • Lecture (others)
    Vortrag am IEK3 des Forschungszentrums Jülich, 22.05.2019, Jülich, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29279
Publ.-Id: 29279


Improved 242Pu(n,γ) thermal cross section combining activation and prompt gamma analysis

Lerendegui-Marco, J.; Guerrero, C.; Belgya, T.; Maróti, B.; Eberhardt, K.; Düllmann, C. E.; Junghans, A. R.; Mokry, C.; Quesada, J. M.; Runke, J.; Thörle-Pospiech, P.

A good knowledge of the radiative capture cross section of 242Pu is required for innovative nuclear reactor studies, especially for MoX fuel reactors. However, the experimental data available show discrepancies in the energy regions of interest: the thermal point and the keV region. Previous experimental results of the thermal cross section deviate from each other by 20% and these discrepancies are reflected also in the evaluated libraries, each of them giving more credit to different data sets. A recent measurement by Genreith et al. did not succeed to solve the existing discrepancy due to the large uncertainties and correction factors in the analysis. This work presents a new measurement of the thermal capture cross section of 242Pu carried out in the Budapest Research Reactor using the same thin targets of a previous measurement at n_TOF-EAR1, each containing 30mg of 99.995% pure 242Pu . The combined analysis of the full prompt γ-ray spectrum and the 243Pu decay has led to three compatible values for the thermal cross section. Their average value, 18.9(9)b, has an improved accuracy compared to recent measurements. Leaving aside the activation value of Genreith using an outdated intensity value for the 84 keV decay line of 243Pu , our average result is in very good agreement with the JEFF-3.2 evaluation and all the previous measurements, with the exception of the highest value 22.5(11)b reported by Marie et al., which has a strong influence in the ENDF evaluation.242

Keywords: neutron capture cross section; 242Pu; thermal neutron spectrum

Permalink: https://www.hzdr.de/publications/Publ-29278
Publ.-Id: 29278


Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development

Hildebrand, H.; Franke, K.; Fischer, C.; Schymura, S.

Exertengespräch und Präsentation der Ergebnisse aus der Literaturstudie zum Nachweis von Nanomaterialien in den verschiedenen Umweltkompartimenten, Projekt NanoExperte

Keywords: nanomaterials in environemtal media; detection; quantification

  • Invited lecture (Conferences)
    Abschlusspräsentation des Sachverständigengutachtens „NanoExperte“, 17.04.2019, Dessau-Roßlau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29277
Publ.-Id: 29277


Specific ion effects directed noble metal aerogels: Versatile manipulation for electrocatalysis and beyond

Du, R.; Hu, Y.; Hübner, R.; Joswig, J.-O.; Fan, X.; Schneider, K.; Eychmüller, A.

Noble metal foams (NMFs) are a new class of functional materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in diverse fields. Among reported synthetic methods, the sol-gel approach manifests overwhelming advantages for versatile synthesis of nanostructured NMFs (i.e., noble metal aerogels) under mild conditions. However, limited gelation methods and elusive formation mechanisms retard structure/composition manipulation, hampering on-demand design for practical applications. Here, highly tunable NMFs are fabricated by activating specific ion effects, enabling various single/alloy aerogels with adjustable composition (Au, Ag, Pd, and Pt), ligament sizes (3.1 to 142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation is also demonstrated. This study provides a conceptually new approach to fabricate and manipulate NMFs and an overall framework for understanding the gelation mechanism, paving the way for on-target design of NMFs and investigating structure-performance
relationships for versatile applications.

Permalink: https://www.hzdr.de/publications/Publ-29276
Publ.-Id: 29276


Dose-volume predictors of early esophageal toxicity in non-small cell lung cancer patients treated with accelerated-hyperfractionated radiotherapy

Bütof, R.; Löck, S.; Soliman, M.; Haase, R.; Perrin, R.; Richter, C.; Appold, S.; Krause, M.; Baumann, M.

Background and purpose: Early radiation-induced esophageal toxicity (RIET) is one of the major side effects in patients with non-small cell lung cancer (NSCLC) and can be a reason for treatment interruptions. As the age of patients with NSCLC and corresponding comorbidities continue to increase, primary radiotherapy alone is a commonly used alternative treatment in these cases. The aim of the present study is to compare dosimetric and clinical parameters from the previously reported CHARTWEL trial for their ability to predict esophagitis and investigate potential differences in the accelerated and conventional fractionation arm.

Material and methods: 146 patients of the Dresden cohort of the randomized phase III CHARTWEL trial were included in this post-hoc analysis. Side effects were prospectively scored weekly during the first 8 weeks from start of radiotherapy. To compare both treatment arms, recorded dose-volume parameters were adjusted for the different fractionation schedules. Logistic regression was performed to predict early RIET for the entire study group as well as for the individual treatment arms. Differentdosimetric and clinical parameters were tested.

Results: Patients receiving the accelerated CHARTWEL schedule experienced earlier and more severe esophagitis (e.g. 20.5% v . 9.6% ≤ grade 2 at week 3, respectively). In contrast, the median time period for recovery of grade 1 esophagitis was significantly longer for patients with conventional fractionation compared to the CHARTWEL group (median [range]: 21 [12-49] days vs. 15 [7-84] days, p=0.028). In univariable logistic regression none of the dose-volume parameters showed a significant correlation with early RIET grade  2 in the conventional irradiation group. In contrast, for patients receiving CHARTWEL, the physical dose-volumes parameters V40 and V50; and re-scaled values VEQD2,50 and VEQD2,60 were significant predictors of early RIET grade  2. Dose-volume parameters remained different between CHARTWEL and conventional fractionation even after biological rescaling.

Conclusion: Our results show a more dominant dose-volume effect in the CHARTWEL arm compared to conventional fractionation, especially for higher esophageal doses. These findings support the notion that dose-volume parameters for radiation esophagitis determined in a specific and time dependent setting of field arrangements can not be easily transferred to another setting. In clinical practice esophageal volumes receiving 40 Gy or more should be strictly limited in hyperfractionated accelerated fraction schemes.

Keywords: Dose-volume parameters; esophagitis; radiotherapy; accelerated; prediction; non-small cell lung cancer; CHARTWEL

Permalink: https://www.hzdr.de/publications/Publ-29275
Publ.-Id: 29275


Eu3+ incorporation into xenotime LnPO4: the effect of local distortion on long term stability

Schmidt, M.; Lösch, H.; Hirsch, A.; Holthausen, J.; Peters, L.; Xiao, B.; Neumeier, S.; Huittinen, N.

Ceramic matrices are considered for the immobilization of specific nuclear waste streams. Recently, our group has studied the suitability of orthophosphates with monazite structure for this purpose, and found generally good exchangeability between host and guest cation and a corresponding high stability of the materials. Nonetheless, it was evident that both bulk structure and the local coordination environment of the guest cation need to be studied in order to assess the structural strain in the ceramic
material on the molecular level. Here, we present an in-depth study of the incorporation of Eu3+ as a luminescent homologue for the trivalent actinides, such as Am3+, into xenotime orthophosphates. We combine XRD with laser-induced luminescence spectroscopy (TRLFS) as a method to probe the local structure, to understand the impact of the substitution process.
Polarization-dependent TRLFS studies with single crystalline materials show that Eu3+ occupies identical lattice sites in Tb, Y, Ho, Er, and YbPO4. The site has a distinct lower symmetry than the crystallographic cation lattice site, indicating local distortion. In LuPO4, the material with the smallest host cation, this distortion is no longer viable and Eu3+ occupies a less distorted site with similar geometry to the crystallographic lattice site. The very small site enforces a strong overlap of ligand and metal orbitals, inducing strong spectral shifts as well as coupling to lattice phonons.[1] Characterization of polycrystalline materials reveals a more complex mineralogy, including an anhydrite-type phase and monazite in addition to xenotime. Eu3+ distribution indicates a clear aversion for the xenotime lattice when other phases are present. In the absence of other phases, Eu3+ is incorporated into xenotime initially, but long term studies reveal a complex unmixing process[2].
[1] Xiao, B. et al., (2018), Chem Eur J., 24, 13368-77.
[2] Lösch, H. et al., (2019), Front. Chem., 7, 94.

Keywords: xenotime; TRLFS; luminescence; lanthanides

  • Lecture (Conference)
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Espana

Permalink: https://www.hzdr.de/publications/Publ-29274
Publ.-Id: 29274


Uranium toxicity on plant cells: Isothermal microcalorimetric studies for the differentiation between chemotoxic and radiotoxic effects of uranium

Sachs, S.; Oertel, J.; Fahmy, K.

The transfer of radionuclides into the food chain is a central concern in the safety assessment of both nuclear waste repositories and remediation strategies in radioactively contaminated sites, such as legacies of the former uranium mining. The uptake and translocation of radionuclides, e.g., uranium, is speciation dependent and induces several stress response reactions, which changes the plant metabolism. Correlating molecular information on radionuclide speciation and biomolecular interactions with physiological performance is a major challenge for radioecology.
In our previous work we applied isothermal microcalorimetry as a sensitive real-time monitor to study the interaction of U(VI) with canola (Brassica napus) cells (Sachs et al., 2017). Applying this method we were able to monitor the metabolic activity of the cells in the presence of U(VI) and to determine the U(VI) toxicity in B. napus cells. Those was correlated with the oxidoreductase activity of the cells and the U(VI) speciation in solution. Based on this work we are currently investigating the differentiation between chemotoxic and radiotoxic effects of uranium on B. napus cells applying natural uranium as well as 233U as alpha emitter. To discriminate between these effects, the metabolic heat flow of the cells at a constant total uranium concentration of 50 µmol/L is monitored by isothermal microcalorimetry applying increasing concentrations of 233U (1-15 µmol/L), which correspond to increasing radiation doses. Applying liquid scintillation counting (LSC) we determine the amount of uranium that is bioassociated to the plant cells and estimate the respective 233U doses for the cells.
Mc values provide a quantitative ranking of metabolic activities that is independent of cell number and largely unaffected by normal variations between experiments (Sachs et al., 2017). Our data are normalized to Mc values of B. napus cells that were exposed to natural uranium only. In the presence of 2 µM 233U a slight increase in the Mc values was observed, which indicates a slightly higher metabolic activity of the cells. Probably, this is an indication for a stress response of the cells to the radiotoxic effect of 233U. With increasing 233U concentration only a slight decrease of the Mc values was observed. This indicates only a slight effect of the alpha radiation on the cells compared to those cells that were exposed to natural uranium, which exhibits a predominant chemotoxic effect. These first results point to a high resistance of B. napus cells to the radiotoxicity of 233U.
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies. We will present the calorimetric determination of the U(VI) toxicity in B. napus cells that correlates with oxidoreductase activity and U(VI) speciation and will focus on the differentiation between chemotoxic and radiotoxic effects of uranium.

Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K. 2017. Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Environ. Sci. Technol. 51, 10843-10849.

Keywords: uranium; plant cells; toxicity; isothermal microcalorimetry

  • Lecture (Conference)
    ENVIRA 2019, 5th International Conference on Environmental Radioactivity, 08.-13.09.2019, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-29272
Publ.-Id: 29272


Influence of local magnification effects in the atom probe for silicon nanocrystals doped by indium

Nomoto, K.; Hiller, D.; Rebohle, L.; Ringer, S.

Atom probe tomography (APT) is a powerful tool to study the 3-dimensional structure of materials with sub-nanometer spatial resolution. This allows us to study the location of atoms such as dopant positions in nanocrystals (NCs) with high accuracy. However, one of the limitations for the spatial resolution are the effects of local magnification when there are multiple elements with different evaporation rates in the atom probe specimen. For example, in the system of silicon (Si) NCs embedded in SiO2, the difference in the local evaporation field between Si NCs and SiO2 results in a non-uniform sequence of evaporation and this affects the accuracy of the 3-dimensional reconstruction of the atom probe experiment (i.e. over/under estimation of the number of doped atoms in the Si NCs). In this study, we use indium (In) as a dopant to investigate the local magnification effects. Due to the very low solubility of In-atoms in Si, the detected In-atoms inside of Si NCs can be attributed to the local magnification effects and we can quantitatively estimate the number of atoms which are projected inside of Si NCs due to the trajectory artefact. This approach provides a model system to quantify and correct local magnification effects which allows a more precise and advanced study of Si nanostructures.

Keywords: Atom probe tomography; Si nanocrystals; ion implantation

  • Lecture (Conference)
    European Material Research Society Spring Meeting 2019, 27.-31.05.2019, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-29271
Publ.-Id: 29271


Radiobiology of high dose-rate particle beams

Beyreuther, E.; Karsch, L.; Pawelke, J.

In the past few years, the normal tissue protecting effect of Flash electron irradiation was shown for several endpoints and in different species [1], [2]. Contrary to conventional, clinical beam delivery over minutes, the therapeutic dose is administered within less than 0.5 s by Flash irradiation. Hence, this treatment regime is linked to high mean dose rates of ~100 Gy/s and high pulse dose rates of ≥105 Gy/s, clearly exceeding the parameters of a few Gy/min on time average and of ~ 102 Gy/s within one pulse of conventional, clinical Linacs. Of note, tumors were cured by electron Flash as efficient as by conventional electron beam treatment over minutes [1]. Moreover, the protecting Flash effect was recently validated for photons [3], which promises a general validity of this effect also for other types of clinically used radiation.
First attempts testing the feasibility of proton Flash were conducted at clinical proton beam facilities in France [4] and at the University Proton Therapy Dresden (UPTD), Germany. At UPTD, a setup was established that allows for the irradiation of zebrafish embryo either with dose rates of 100 Gy/s for Flash or of 5 Gy/min for conventional reference. The zebrafish embryo were treated with graded doses up to 40 Gy and embryonic survival as well as the manifestation of morphological abnormalities were followed for up to four days. However, analysing the different endpoints, a clear dependency on dose but no significant dependence on proton dose rate was revealed.
This unexpected result implies, that more studies are needed to resolve the influence on beam time structure for the induction of a protective Flash effect. Here, research facilities like FAIR with a broader parameter space regarding ion species, particle fluence, LET, pulsing and beam time structure provide the possibility to study the physical limits of Flash in more detail. Therewith also questions on a potential influence or interaction of high dose-rate particle beam, high LET and oxygen level of the irradiated tissue could be investigated systematically. The results obtained therein could help to further develop dedicated clinical accelerators, like superconducting or heavy ion synchrotrons, to make clinical use of the Flash effect.



[1] V. Favaudon et al., “Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice,” Sci. Transl. Med., vol. 6, no. 245, p. 245ra93, Jul. 2014.
[2] P. Montay-Gruel et al., “Irradiation in a flash: Unique sparing of memory in mice after whole brain irradiation with dose rates above 100Gy/s,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 124, no. 3, pp. 365–369, 2017.
[3] P. Montay-Gruel et al., “X-rays can trigger the FLASH effect: Ultra-high dose-rate synchrotron light source prevents normal brain injury after whole brain irradiation in mice,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 129, no. 3, pp. 582–588, Dec. 2018.
[4] A. Patriarca et al., “Experimental Set-up for FLASH Proton Irradiation of Small Animals Using a Clinical System,” Int. J. Radiat. Oncol. Biol. Phys., vol. 102, no. 3, pp. 619–626, Nov. 2018.

  • Contribution to proceedings
    International Biophysics Collaboration Meeting, 20.-22.05.2019, Darmstadt, Deutschland
    DOI: 10.15120/GSI-2019-00596
  • Lecture (Conference)
    International Biophysics Collaboration Meeting, 20.-22.05.2019, Darmstadt, Deutschland
    DOI: 10.15120/GSI-2019-00596

Permalink: https://www.hzdr.de/publications/Publ-29270
Publ.-Id: 29270


‘Box-Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry

Wu, H.; Böttger, R.; Couffignal, F.; Gutzmer, J.; Krause, J.; Munnik, F.; Renno, A.; Hübner, R.; Wiedenbeck, M.; Ziegenrücker, R.

EPMA (Electron Probe Microanalysis) and SIMS (Secondary Ion Mass Spectrometry) are widely used analytical techniques for geochemical and mineralogical applications. Nevertheless, metrologically rigorous quantification remains a major challenge for these methods. SIMS in particular is a matrix-sensitive method; for SIMS the use of matrix-matched reference materials (RMs) is essential in order to avoid significant analytical bias. A major problem is that the list of available RMs for SIMS is vanishingly short compared to the needs of the analyst. One approach for the production of matrix-specific RMs is the use of high-energy ion implantation that introduces a known amount of a selected isotope into a material. We chose the more elaborate way of implanting a so-called ‘box profile’ to generate a quasi-homogeneous concentration of the implanted isotope in three dimensions, which allows RMs not only to be used for ion beam analysis but also makes them suitable for EPMA. For proof of concept, we used the thoroughly studied mineralogically and chemically ‘simple’ SiO2 system, which addresses many interesting scientific challenges, such as the Ti-in-quartz geothermometer (Wark et al. 2006, Thomas et al. 2010). We implanted either 47Ti or 48Ti into synthetic, ultra-high purity silica glass. Several ‘box profiles’ with concentrations between 10 and 1000 µg g-1 Ti and maximum depths of homogeneous Ti distribution between 200 nm and 3 µm were produced at the Institute of Ion Beam Physics and Materials Research of Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Multiple implantation steps using varying ion energies and ion doses were simulated with the SRIM (Stopping and Range of Ions in Matter) software (Ziegler et al. 2008), optimizing for the target concentrations, implantation-depths and technical limits of the implanter.
We characterized several implant test-samples having different concentrations and maximum implantation depths by means of SIMS and other analytical techniques. The results show that the implant samples are suitable for use as reference materials for SIMS measurements. The multi-energy ion implantation technique also looks to be very promising procedure for the production of EPMA-suitable reference materials.

Keywords: ‘box-profile’; multi-energy ion implantation; EPMA; SIMS; synthetic reference material

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29269
Publ.-Id: 29269


Multi-Sensor Spectral Imaging of Geological Samples: A Data Fusion Approach using Spatio-Spectral Feature Extraction

Lorenz, S.; Seidel, P.; Ghamisi, P.; Zimmermann, R.; Tusa, L.; Khodadadzadeh, M.; Contreras, I. C.; Gloaguen, R.

Spectral imaging or hyperspectral reflectance mapping for mineral exploration sample analysis has evolved rapidly in the recent decade. A wide range of deployable sensors is available nowadays, providing high flexibility in spectral as well as in spatial resolution and coverage. However, the fusion of data from different customized setups and sensors is challenging and usually not conducted. In the following study, the integration of such multi-sensor datasets is demonstrated on data acquired from five commercially available hyperspectral sensors and a pair of RGB cameras. We present a workflow for the integrated image analyses using advanced machine learning methods and evaluate the procedure on a representative set of geological samples. Detailed mineralogical and spectral validation affirms the approach. The suggested workflow provides a new way for the integration of multi-source data, e.g., it allows a straight-forward integration of visible/near-infrared (VNIR), short-wave infrared (SWIR) and long-wave infrared (LWIR) data for sensors with highly different spatial and spectral resolution. Finally, we evaluate the benefits of different multi-sensor combinations for potential applications in mineral exploration.

Keywords: hyperspectral; spectral imaging; multi-sensor data; data fusion; feature extraction; Support Vector Machine (SVM); Orthogonal Total Variation Component Analysis (OTVCA); mineral exploration

Permalink: https://www.hzdr.de/publications/Publ-29268
Publ.-Id: 29268


Focused ion beam modification of non-local magnon-based transport in yttrium iron garnet/platinum heterostructures

Schlitz, R.; Helm, T.; Lammel, M.; Nielsch, K.; Erbe, A.; Goennenwein, S. T. B.

We study the impact of Ga ion exposure on the local and non-local magnetotransport response in heterostructures of the ferrimagnetic insulator yttrium iron garnet and platinum. In particular, we cut the yttrium iron garnet layer in between two electrically separated wires of platinum using a Ga ion beam, and study the ensuing changes in the magnetoresistive response. between the Pt wires is fully cut, although the local spin Hall magnetoresistance signal remains finite. This observation corroborates the notion that pure spin currents carried by magnons are crucial for the non-local magnetotransport effects observed in magnetic insulator/metal nanostructures and that possible substrate contributions to the non-local transport can be ruled out.

Keywords: nano magnetism; spin transport; focussed ion beam

Permalink: https://www.hzdr.de/publications/Publ-29267
Publ.-Id: 29267


Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

Prucnal, S.; Heera, V.; Hübner, R.; Wang, M.; Mazur, G. P.; Grzybowski, M. J.; Qin, X.; Yuan, Y.; Voelskow, M.; Skorupa, W.; Rebohle, L.; Helm, M.; Sawicki, M.; Zhou, S.

Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron-doped diamond and Si, superconductivity has been observed in gallium-doped Ge; however, the obtained specimen is in polycrystalline form [Phys. Rev. Lett. 102, 217003 (2009)]. Here we present superconducting single-crystalline Ge hyperdoped with gallium or aluminum by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is 8 times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 1021 cm−3. Using density functional theory in the local-density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon mediated. According to the ab initio calculations, the critical superconducting temperature for Al- and Ga-doped Ge is in the range of 0.45 K for 6.25at.% of dopant concentration, being in qualitative agreement with experimentally obtained values.

Keywords: superconductivity; ion implantation; Germanium; flash lamp annealing

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Permalink: https://www.hzdr.de/publications/Publ-29266
Publ.-Id: 29266


Antimonite binding to natural organic matter: Spectroscopic evidence from a mine water impacted peatland

Besold, J.; Eberle, A.; Noël, V.; Kujala, K.; Kumar, N.; Scheinost, A.; Lezama Pacheco, J.; Fendorf, S.; Planer-Friedrich, B.

Peatlands and other wetlands are sinks for antimony (Sb). Solid natural organic matter (NOM) has thus been suggested to play an important role in controlling Sb binding in wetland sediments. However, direct spectroscopic evidence for this sequestration mechanism in natural peat samples is still lacking. In order to investigate Sb binding in peat, we sampled and characterized three profiles up to a depth of 80 cm in an Sb-impacted peatland in northern Finland. We used bulk K-edge X-ray absorption spectroscopy to study the speciation of Fe, S and Sb in the peat solid phase. Additionally, we determined the aqueous speciation of Sb in surface and pore waters. Based on linear combination fittings of extended X-ray absorption fine structure spectra, we found that Sb associated to the solid-phase is up to 100% coordinated to organic phenol and/or thiol groups. Even in the presence of iron, organically-bound Sb(III) was the dominant fraction in all peat profiles and across all depths. While aqueous antimonite concentrations were low, Sb(III) species were dominating solid-phase speciation, suggesting a high reactivity of Sb(III) towards peat surfaces. Our findings therefore confirm that Sb binding to solid NOM acts as an important sequestration mechanism under reducing conditions in NOM-rich wetlands.

Keywords: EXAFS; sulfur; iron; antimony; peat

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Permalink: https://www.hzdr.de/publications/Publ-29265
Publ.-Id: 29265


Monolithic waveguide laser mode-locked by embedded Ag nanoparticles operating at 1 μm

Li, R.; Pang, C.; Li, Z.; Dong, N.; Wang, J.; Ren, F.; Akhmadaliev, S.; Zhou, S.; Chen, F.

Monolithic waveguide laser devices are required to achieve on-chip lasing. In this work, a new design of a monolithic device with embedded Ag nanoparticles (NPs) plus the Nd:YAG ridge waveguide has been proposed and implemented. By using Ag+ ion implantation, the embedded Ag NPs are synthesized on the near-surface region of the Nd:YAG crystal, resulting in the significant enhancement of the optical nonlinearity of Nd:YAG and offering saturable absorption properties of the crystal at a wide wavelength band. The subsequent processing of the O5+ ion implantation and diamond saw dicing of crystal finally leads to the fabrication of monolithic waveguide with embedded Ag NPs. Under an optical pump, the Q-switched mode-locked waveguide lasers operating at 1 μm is realized with the pulse duration of 29.5 ps and fundamental repetition rate of 10.53 GHz, owing to the modulation of Ag NPs through evanescent field interaction with waveguide modes. This work introduces a new approach in the application of monolithic ultrafast laser devices by using embedded metallic NPs.

Permalink: https://www.hzdr.de/publications/Publ-29264
Publ.-Id: 29264


Ion acceleration from ultra-thin foil targets with on-shot monitored temporal contrast

Ziegler, T.; Bernert, C.; Brack, F.-E.; Bussmann, M.; Cowan, T.; Garten, M.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Obst-Hübl, L.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

Laser-driven ion acceleration promises to provide a compact solution for demanding applications like particle therapy, proton radiography or inertial confinement research. Controlling the particle beam parameters to achieve these goals is currently pushing the frontier of laser driven particle accelerators.

The performance of the plasma acceleration is strongly dependent on the complex pre-plasma formation process at the target front surface which is determined by the temporal intensity contrast. Particularly low-density targets require an enhanced temporal contrast to remain overcritical until the main pulse arrives. Plasma mirror setups have proven to significantly improve the temporal contrast by reducing pre-pulse intensity and steepening the rising edge of the main laser pulse, enabling the investigation of laser proton acceleration and proton energy scaling using ultra-thin targets.

We present new experimental results on the interaction of the DRACO Petawatt ultra-short pulse laser with ultra-thin foil targets. Efficient and on-demand contrast cleaning established through a re-collimating plasma mirror setup facilitated thickness scans from the µm range down to several tens of nm. The combination of a complex set of diagnostics, consisting of proton detectors in target normal, laser forward and laser backward axis, laser pulse transmission and reflection diagnostics as well as detection of front surface electrons, delivered concrete indicators for the acceleration conditions. Furthermore, tremendous progress has been achieved by successfully implementing a novel laser contrast diagnostic by means of self-referenced spectral interferometry with extended time excursion (SRSI-ETE), allowing to characterize the temporal contrast in the experimental area on a single-shot base with unprecedented dynamic and temporal range.

  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien

Permalink: https://www.hzdr.de/publications/Publ-29263
Publ.-Id: 29263


Beam quality optimization in a beam loaded nanocoulomb-class laser wakefield accelerator

Couperus Cabadağ, J. P.; Köhler, A.; Zarini, O.; Pausch, R.; Debus, A.; Chang, Y.-Y.; Kurz, T.; Schöbel, S.; Bussmann, M.; Schramm, U.; Irman, A.

Here we report on optimization of both energy spread and beam divergence in a laser wakefield accelerator (LWFA) operating in the beam loading regime. The self-truncated ionization injection scheme is employed, enabling a precise control over the amount of injected electrons with charges up to 0.5 nC (FWHM) at a quasi-monoenergetic peak.
By employing the optimal beam loading condition, the accelerating gradient is flattened and we eliminate additional energy spread contribution from the acceleration process1,2. This point of minimized finite energy spread is used to limit the betatron oscillations of bunch electrons, leading to a decrease of the normalized beam divergence. Meanwhile, an ultrafast single-shot electron beam diagnostic based on Coherent Transition Radiation reveals ~10 femtosecond bunch lengths yielding peak currents of over 10 kA. Such peak currents are one to two orders of magnitude larger than those found in conventional RF accelerators. Control of the energy spread and beam divergence of LWFA beams with the beam loading condition together with the scaling to high peak currents paves the road for driving secondary superradiant lights sources.

References:
1. J.P. Couperus, et.al., “Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator”, Nature Communication, 8, 487 (2017)
2. A. Irman et al., “Improved performance of laser wakefield acceleration by tailored self-truncation ionization injection”, Plasma Physics and Controlled Fusion, 60, 044015 (2018)

Keywords: beam loading; plasma acceleration; electron acceleration; LWFA; laser wakefield acceleration; LPA; betatron

  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop (LPAW) 2019, 05.-10.05.2019, Split, Republika Hrvatska
  • Poster
    4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Repubblica Italiana

Permalink: https://www.hzdr.de/publications/Publ-29262
Publ.-Id: 29262


Laser-driven proton beam profiles in ultra-high fields

Obst-Hübl, L.; Bernert, C.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cochran, G.; Cowan, T.; Curry, C. B.; Gaus, L.; Fiuza, F.; Garten, M.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Hübl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Macdonald, M. J.; Metzkes-Ng, J.; Mishra, R.; Pausch, R.; Poole, P.; Prencipe, I.; Rehwald, M.; Rödel, C.; Ruyer, C.; Schlenvoigt, H.-P.; Sommer, P.; Schoenwalder, C.; Schumaker, W.; Ziegler, T.; Schramm, U.; Schumacher, D. W.; Zeil, K.

Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact multi-MeV proton accelerators with unique bunch characteristics. Protons are accelerated in TV/m fields that are established within the micrometer-scale vicinity of the high-power laser focus. This initial acceleration phase is followed by ballistic proton bunch propagation with negligible space-charge effects over millimeters to hundreds of centimeters to the particle detector or a proton target at a dedicated irradiation site. The detected proton emission distribution can be influenced by the spatio-temporal intensity distribution in the laser focus, electron transport through the target, potential plasma instabilities, as well as local and global target geometry and surface properties.
Substantially extending this picture, our recent results show a critical influence of the milimeter scale vacuum environment on the accelerated proton bunch, where residual gas molecules are ionized by the remnant laser light that is not absorbed into the target plasma but reflected or transmitted. In an experiment with µm-sized hydrogen jet targets, this effect lead to the counter-intuitive observation of laser near-field feature imprints in the detected proton beam profiles. Our results show that the remnant laser pulse induces a quasi-static deflecting field map in the ionized residual background gas that serves as a memorizing medium and allows for asynchronous information transfer to the naturally delayed proton bunch. Occurring under typical experimental laser, target and vacuum conditions, all-optical imprinting needs to be taken into account for sensible interpretation of modulated proton beam profiles.

Keywords: laser-driven plasmas; high-power lasers; novel accelerator concepts; laser-ion acceleration; plasma mirrors

  • Invited lecture (Conferences)
    Laser Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien
  • Lecture (others)
    Seminar talk, 27.06.2019, London, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29261
Publ.-Id: 29261


First demonstration of a hybrid laser-electron-beam driven plasma wakefield accelerator

Kurz, T.; Heinemann, T.; Schöbel, S.; Couperus Cabadağ, J. P.; Kononenko, O.; Chang, Y.-Y.; Bussmann, M.; Corde, S.; Debus, A.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Hidding, B.; Karsch, S.; Köhler, A.; Pausch, R.; Zarini, O.; Schramm, U.; Martinez De La Ossa, A.; Irman, A.

Plasma based electron acceleration is widely considered as a promising concept for a compact electron accelerator with broad range of future applications from high energy physics to photon science.
These accelerators can be powered by either ultra-intense laser beams (LWFA) or relativistic high-current-density particle beams (PWFA).
Here, we report on a novel approach which combines both schemes in a truly compact experimental setup.
In our “LWFA + PWFA” hybrid accelerator, the electron beam generated by a LWFA stage drives a subsequent PWFA stage where a witness beam is trapped and accelerated.
This strategy aims to combine the unique features of both plasma acceleration techniques, the LWFA stage provides with a compact source of high-current electron beams required as PWFA drivers, while the PWFA stage acts as an energy and brightness transformer for the LWFA output.
In this work, we show the first experimental evidence of accelerating a distinct witness bunch in a LWFA-driven PWFA (LPWFA), within only about one millimeter acceleration distance.
In the beam self-ionizing case, we observe witness energies of around 50 MeV.
By utilizing a counter-propagating pre-ionization laser, the interaction with the plasma becomes stronger, increasing the final energies to around 120 MeV.
Thus, yielding a field gradient of (46+-11) GeV/m which is comparable to what has been shown at large scale facilities.

Keywords: Laser; Plasma Accelerator; Hybrid; Electron beam; Peak Current

  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien

Permalink: https://www.hzdr.de/publications/Publ-29260
Publ.-Id: 29260


Synthetic radiation diagnostics as a pathway for studying plasma dynamics from advanced accelerators to astrophysical observations

Pausch, R.

In this thesis, two novel diagnostic techniques for the identi1cation of plasma dynamics and thequanti cation of essential parameters of the dynamics by means of electromagnetic plasmaradiation are presented. Based on particle-in-cell simulations, both the radiation signatures of micrometer-sized laser plasma accelerators and light-year-sized plasma jets are simulated with the same highly parallel radiation simulation framework, in-situ to the plasma simulation.
The basics and limits of classical radiation calculation, as well as the theoretical and technical foundation of modern plasma simulation using the particle-in-cell method, are brie2y introduced. The combination of previously independent methods in an in-situ analysis code as well as its validation and extension with newly developed algorithms for the simultaneous quantitative prediction of both coherent and incoherent radiation and the prevention of numerical artifacts is outlined in the initial chapters.
For laser wake1eld acceleration, a hitherto unknown off-axis beam signature is observed,which can be used to identify the so-called blowout regime during laser defocusing. Since signi cant radiation is emitted only after the minimum spot size is reached, this signature is ideally suited to determine the laser focus position itself in the plasma to below 100 _m and thus to quantify the in2uence of relativistic self-focusing. A simple semi-analytical scattering model was developed to explain the blowout radiation signature. The spectral signature predicted by the model is veri1ed using both a large-scale explorative simulation and a simulation parameter study, based on an experiment conducted at the HZDR. Identi1ed by the simulations, a temporal asymmetry in the scattered laser light, which cannot be described by state of the art quasi-static models of the blowout regime, makes it possible to determine the focus position precisely by using this radiation signature.
For the so-called Kelvin-Helmholtz instability, a polarization signature is identi1ed that allows both identifying the linear phase of the instability and quantifying its most important parameter, the growth rate. This plasma instability is suspected to occur in the shear region between plasma jets of active galactic nuclei or supernova remnants and the surrounding plasma and causes strong magnetic 1elds to grow along the shear surface. The measurement of the growth rate of these elds allows deducing the internal structure and dynamics of these jets and gaining an insight into previously inaccessible regions. A microscopic model of the electron dynamics was developed which describes the main radiation properties. With an unprecedentedly large and accurate simulation of the relativistic Kelvin-Helmholtz instability, the microscopic model was validated. The discovered polarization signature can be clearly identi1ed even under arbitrary Lorentz transformations for observers on Earth and poses thus an ideal method for astronomical observations.
These very different physical scenarios clearly exemplify the possibilities of synthetic radiation diagnostics and represent the 1rst step towards future explorative studies of plasmas and their radiation in other scenarios using simulations.

Keywords: PhD defense

  • Lecture (others)
    Disputation, 25.03.2019, Dresden, Deutschland
  • Doctoral thesis
    TU Dresden / HZDR, 2019
    173 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-107 2019
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-29259
Publ.-Id: 29259


Modeling hybrid plasma accelerator experiments with PIConGPU

Pausch, R.; Bussmann, M.; Garten, M.; Hübl, A.; Steiniger, K.; Widera, R.; Kurz, T.; Schöbel, S.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Köhler, A.; Zarini, O.; Heinemann, T.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Kononeko, O.; Raj, G.; Corde, S.; Hidding, B.; Karsch, S.; Martinez De La Ossa, A.; Irman, A.; Schramm, U.; Debus, A.

Utilizing laser-wakefield accelerated (LWFA) electrons to drive aplasma-wakefield accelerator (PWFA) holds great promise for realizingcentimeter-scale electron accelerators providing ultra-high brightnessbeams. Recent experiments at HZDR could demonstrate for the first timesuch an electron acceleration in a nonlinear PWFA plasma wakefield. Fordriving this compact hybrid accelerator setup, high-charge electronbunches from LWFA self-truncated ionization injection were used.In this talk, we present recent results of the accompanying simulationcampaign performed with the 3D3V particle-in-cell code PIConGPU. Thesesimulations model the geometry, density distributions, laser modes, andgas dopings as determined in the experiments. The simulation conditionsresemble the experiment to a very high degree and thus provide goodcomparability between experiment and simulation. Additionally, thewealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamics, otherwise inaccessible inexperiments.From an algorithmic and computational perspective, we modeled the hybridaccelerator from start to end in a single simulation scenario. Wediscuss the associated challenges in maintaining numerical stability andexperimental comparability of these long-duration simulations.

Keywords: LPWFA; hybrid; PIConGPU

  • Lecture (Conference)
    Laser-Plasma AcceleratorWorkshop 2019, 05.-10.05.2019, Split, Croatia

Permalink: https://www.hzdr.de/publications/Publ-29258
Publ.-Id: 29258


Hybrid plasma accelerators - LWFA-PWFA simulations with PIConGPU

Pausch, R.; Debus, A.; Garten, M.; Hübl, A.; Steiniger, K.; Widera, R.; Kurz, T.; Schöbel, S.; Couperus Cabadağ, J. P.; Irman, A.; Schramm, U.; Bussmann, M.

Utilizing laser-wakefield accelerated (LWFA) electrons to drive a plasma-wakefield accelerator (PWFA) holds great promise for realizing centimeter-scale electron accelerators providing ultra-high brightness beams. Recent experiments at HZDR could demonstrate for the first time such an electron acceleration in a nonlinear PWFA plasma wakefield using this compact setup.

On this poster, we show recent results of the accompanying simulation campaign performed with the 3D3V particle-in-cell code PIConGPU. These simulations model the geometry, density distributions, laser modes, and gas dopings as determined in the experiments. The simulation conditions resemble the experiment to a very high degree and thus provide precise comparability between experiment and simulation. Additionally, the wealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamic, otherwise inaccessible in experiments. Algorithmic and computational challenges essential for the numerical stability of these long-duration simulations will be presented as well.

Keywords: PIConGPU; LPWFA; hybrid; ISAAC

  • Poster
    The fifth annual meeting of the programme "Matter and Technologies", 05.-07.03.2019, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29257
Publ.-Id: 29257


Approaching predictive capabilities for LWFA experiments with PIConGPU

Pausch, R.; Couperus Cabadağ, J. P.; Garten, M.; Hübl, A.; Köhler, A.; Kurz, T.; Schöbel, S.; Schramm, U.; Steiniger, K.; Widera, R.; Zarini, O.; Irman, A.; Bussmann, M.; Debus, A.

State-of-the-art particle-in-cell simulations are becoming faster in terms of time to solution by utilizing modern hardware accelerators like GPUs and more accurate by improving the underlying algorithms. However, in order to model experiments, methods to include realistic laser pulses and gas distributions as well as efficient techniques to predict experimental observables, so-called synthetic diagnostics, need to be included in these simulations.

In this talk, we present extensions to the particle-in-cell code PIConGPU that were essential to accurately model LWFA experiments based on self-truncated ionization injection performed at HZDR. We discuss the significant impact of the implementation of higher order laser modes on the plasma dynamics and the resulting acceleration process. Furthermore, we discuss in detail the advantage of efficient in situ data analysis on the example of studying electron phase space evolution and of predicting spectrally and directionally radiation emission by all particles.

These improvements set the stage for quantitatively predicting the results of experiments in the near future.

Keywords: PIConGPU; LWFA; radiation; synthetic diagnostics

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29256
Publ.-Id: 29256


Radiation imprint of ultra-intense laser heating of solids

Garten, M.; Hübl, A.; Widera, R.; Göthel, I.; Obst-Hübl, L.; Ziegler, T.; Zeil, K.; Cowan, T.; Schramm, U.; Bussmann, M.; Kluge, T.

Laser-accelerated ions are increasingly recognized as a promising alternative to conventionally accelerated ion beams. Possible applications range from fast ignition in laser fusion to ion tumor therapy as well as studies of transient high-current and high-field phenomena in laboratory astrophysics and material science. A combination of ultra-short duration and very high charge density is the most sought-after characteristic of these beams which are produced in the violent interaction of an ultra-intense short pulse laser with a solid target. We have performed the – to our knowledge – very first full 3D particle-in-cell simulations of this interaction that includes the picosecond time span prior to the arrival of the main laser pulse. This time period is thought to be decisive for the following main pulse interaction, yet it is poorly explored – partly due to the immense computational needs to resolve the plasma kinetically with full precision. Here, we bridge scales hitherto inaccessible, from attosecond plasma oscillations over few-femtosecond laser oscillations and transient, non-equilibrium plasma dynamics on the tens of femtosecond laser duration to picosecond pre-plasma development. We study the influence of pre-pulse laser conditions and material on the ion acceleration performance. Additionally, we aim to infer radiative signatures of the plasma dynamics and link them to isochoric heating, instability development, and other complex dynamics. Beyond gaining a fundamental understanding of the governing fundamental principle plasma dynamics, the results will be used in the ongoing development of novel diagnostics analyzing the bremsstrahlung and synchrotron radiation in order to experimentally probe the sub-ps interaction. The simulations have been performed at Piz Daint at CSCS, Switzerland, using the 3D particle-in-cell code PIConGPU developed at HZDR.

Keywords: laser ion acceleration; laser-driven proton sources; particle-in-cell; PIConGPU; openPMD; HPC; throughput; PRACE; CSCS; Piz Daint

  • Invited lecture (Conferences)
    EuroHPC Summit Week 2019 / PRACEdays19, 13.-17.05.2019, Poznań, Polska

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Permalink: https://www.hzdr.de/publications/Publ-29255
Publ.-Id: 29255


Synthetic radiation simulations as a path to study the relativistic Kelvin-Helmholtz instability in interstellar jets

Pausch, R.; Bussmann, M.; Hübl, A.; Schramm, U.; Steiniger, K.; Widera, R.; Debus, A.

The relativistic Kelvin-Helmholtz instability (KHI) is expected in shear flow regions of astrophysical plasma jets originating from AGNs and SNR. It generates magnetic fields that influence the jet dynamics significantly.

We present 3D3V particle-in-cell simulations of unprecedented resolution and extent that not only allow studying the plasma dynamics during the KHI but also making quantitative predictions on the emitted radiation. We present a diagnostic method that allows identifying the linear phase of the instability via a polarization anisotropy observable light years away on Earth and to quantify the growth rate of the instability.

A microscopic model, that describes the fundamental origin of the radiation signature, will be covered in detail during the talk. Technical aspects relevant for performing these large-scale simulations with the particle-in-cell code PIConGPU and for making quantitative predictions with synthetic radiation diagnostics, based on Liénard-Wiechert potentials, will be discussed, and observation limits both for interstellar jets and in lab astrophysics experiments will be covered.

Keywords: KHI; PIConGPU; radiation; synthetic diagnostics; polarization; AGN; SNR

  • Invited lecture (Conferences)
    DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29254
Publ.-Id: 29254


Large-scale simulations of plasma acceleration

Pausch, R.; Hübl, A.; Bastrakov, S.; Debus, A.; Garten, M.; Matthes, A.; Steiniger, K.; Schramm, U.; Widera, R.; Zenker, E.; Bussmann, M.

A brief presentation of the MuT/DMA activities of the Computational radiation group and solutions that might be of interest for the Matter in the Universe community.

Keywords: DMA; MUT; ARD; PIConGPU; alpaka

  • Lecture (Conference)
    "Matter and the Universe" Days 2019, 14.-15.02.2019, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29253
Publ.-Id: 29253


From studying the self-truncated ionization injection during LWFA to hybrid LPWFA simulations

Pausch, R.; Debus, A.; Bussmann, M.; Couperus Cabadağ, J. P.; Garten, M.; Heinemann, T.; Hübl, A.; Martinez De La Ossa, A.; Irman, A.; Kurz, T.; Schöbel, S.; Steiniger, K.; Schramm, U.

This talk gives a brief summary of the current status of the start-to-end simulations of the hybrid LPWFA setup using PIConGPU.

Keywords: PIConGPU; hybrid; LPWFA; LWFA; PWFA

  • Lecture (others)
    hybrid collaboration meeting, 09.-11.01.2019, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29252
Publ.-Id: 29252


T cells engrafted with a UniCAR 28/ζ outperform UniCAR BB/ζ-transduced T cells in the face of regulatory T cell-mediated immunosuppression

Kegler, A.; Koristka, S.; Bergmann, R.; Berndt, N.; Arndt, C.; Feldmann, A.; Hoffmann, A.; Bornhäuser, M.; Schmitz, M.; Bachmann, M.

Adoptive transfer of chimeric antigen receptor (CAR)-equipped T cells has demonstrated astonishing clinical efficacy in hematological malignancies recently culminating in the approval of two CAR T cell products. Despite this tremendous success, CAR T cell approaches have still achieved only moderate efficacy against solid tumors. As major obstacle, engineered conventional T cells (Tconvs) face an anti-inflammatory, hostile tumor microenvironment often infiltrated by highly suppressive regulatory T cells (Tregs). Thus, potent CAR T cell treatment of solid tumors requires efficient activation of Tconvs via their engrafted CAR to overcome Treg-mediated immunosuppression. In that regard, selecting an optimal intracellular signaling domain might represent a crucial step to achieve best clinical efficiency. To shed light on this issue and to investigate responsiveness to Treg inhibition, we engrafted Tconvs with switchable universal CARs (UniCARs) harboring intracellularly the CD3ζ domain alone or in combination with costimulatory CD28 or 4-1BB. Our studies reveal that UniCAR ζ- and UniCAR BB/ζ-engineered Tconvs are strongly impaired by activated Tregs, whereas UniCARs providing CD28 costimulation overcome Treg-mediated suppression both in vitro and in vivo. Compared to UniCAR ζ- and UniCAR BB/ζ-modified cells, UniCAR 28/ζ-armed Tconvs secrete significantly higher amounts of Th1-related cytokines and, furthermore, levels of these cytokines are elevated even upon exposure to Tregs. Thus, in contrast to 4-1BB costimulation, CD28 signaling in UniCAR-transduced Tconvs seems to foster a pro-inflammatory milieu, which contributes to enhanced resistance to Treg suppression. Overall, our results may have significant implications for CAR T cell-based immunotherapies of solid tumors strongly invaded by Tregs.

Permalink: https://www.hzdr.de/publications/Publ-29251
Publ.-Id: 29251


Investigations on stationary measurements at COSMEA-I facility - CT part

Bieberle, A.; Beyer, M.; Pietruske, H.; Hampel, U.; Boden, S.

This repository contains reconstructed and analysed CT data obtained from the COSMEA-I test facility that is operated under stationary operating conditions. Furthermore, a full CAD drawing set is provided.

Keywords: Passive Heat Transfer; Stream Condensation; Heat Flux Probe; Process Computed Tomography

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-05-20
    DOI: 10.14278/rodare.126

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Permalink: https://www.hzdr.de/publications/Publ-29250
Publ.-Id: 29250


Thallium contamination, health risk assessment and source apportionment in common vegetables

Liu, J.; Wei, X.; Zhou, Y.; Tsang, D. C. W.; Bao, Z.; Yin, M.; Lippold, H.; Yuan, W.; Wang, J.; Feng, Y.; Chen, D.

As an element with well-known toxicity, excessive thallium (Tl) in farmland soils may threaten food security and induce extreme risks to human health. Identification of key contamination sources is a prerequisite for remediation technologies. This study aims to examine the contamination level, health risks and source apportionment of Tl in common vegetables from typical farmlands distributed over a densely populated residential area in a pyrite mine city, which has been exploiting Tl-bearing pyrite minerals for over 50 years. Results showed excessive Tl levels in most of the vegetables (0.16-20.33 mg/kg) and alarming health risks induced by the vegetables via the food chain. Source apportionment of Tl contamination in vegetables was then evaluated by using the Pb isotope fingerprinting technique. Both vegetables and soils were characterized by overall low 206Pb/207Pb ratios. This indicated that a significant contribution may be ascribed to anthropogenic activities for pyrite deposit exploitation, whose raw material and slags were featured with lower 206Pb/207Pb ratios. Further calculations by the binary mixing model suggested that pyrite mining and smelting activities contributed 54-88% to the thallium contamination in vegetables. The results highlighted that Pb isotope tracing is a suitable technique for source apportionment of Tl contamination in vegetables and that contamination from pyrite mining/smelting activities urges authorities to initiate proper practices of remediation.

Keywords: Metal contamination; Isotopic analysis; Source apportionment; Food safety; Plant uptake

Permalink: https://www.hzdr.de/publications/Publ-29249
Publ.-Id: 29249


Nitric oxide-releasing selective estrogen receptor modulators (NO-SERMs): a bifunctional approach to improve the therapeutic index

Bechmann, N.; Knieß, T.; Pietzsch, J.

When using selective estrogen receptor modulators (SERMs) in cancer therapy adverse effects such as endothelial dysfunction have to be considered. Estrogens and, consequently, SERMs regulate the synthesis of vasoactive nitric oxide (•NO). We hypothesized that a bifunctional approach combining the antagonistic action of SERMs with a targeted NO-release could diminish vascular side effects. We synthesized a series of NO-releasing SERMs (NO-SERMs) and the corresponding SERMs (after NO-release) derived from a triaryl olefin lead. Compounds showed antagonistic activity for ERβ (IC50(ERβ)=0.2–2.7µM), but no interaction with ERα. Growth of ERβpositive breast cancer and melanoma cells was significantly decreased by treatment with SERM 5d. This anti-proliferative effect was diminished by the additional release of •NO by the corresponding NO-SERM 4d. Moreover, targeted release of •NO by 4d counteracted the antiproliferative effect of 5d in normal vascular tissue cells. Summarizing, the therapeutic index of SERMs might be improved by this bifunctional approach.

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Permalink: https://www.hzdr.de/publications/Publ-29248
Publ.-Id: 29248


Breaking the Doping Limit in Silicon by Deep Impurities

Wang, M.; Debernardi, A.; Berencen, Y.; Heller, R.; Xu, C.; Yuan, Y.; Xie, Y.; Böttger, R.; Rebohle, L.; Skorupa, W.; Helm, M.; Prucnal, S.; Zhou, S.

n-type doping in Si by shallow impurities, such as P, As, and Sb, exhibits an intrinsic limit due to the Fermi-level pinning via defect complexes at high doping concentrations. Here, we demonstrate that doping Si with the deep chalcogen donor Te by nonequilibrium processing can exceed this limit and yield higher electron concentrations. In contrast to shallow impurities, the interstitial Te fraction decreases with increasing doping concentration and substitutional Te dimers become the dominant configuration as effective donors, leading to a nonsaturating carrier concentration as well as to an insulator-to-metal transition. First-principles calculations reveal that the Te dimers possess the lowest formation energy and donate two electrons per dimer to the conduction band. These results provide an alternative insight into the physics of deep impurities and lead to a possible solution for the ultrahigh electron concentration needed in today’s Si-based nanoelectronics.

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Permalink: https://www.hzdr.de/publications/Publ-29247
Publ.-Id: 29247


Nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films for in-plane asymmetric micro-supercapacitors with ultrahigh energy density

He, Y.; Zhang, P.; Wang, M.; Wang, F.; Tan, D.; Li, Y.; Zhuang, X.; Zhang, F.; Feng, X.

In-plane micro-supercapacitors (MSCs) with high power density, remarkable rate capability, and long cycling stability, exhibit promising application potential in modern electronic devices. To satisfy the fast-growing energy demands for the next-generation advanced micro-devices, increasing the energy density of MSCs is urgently desirable but still remains a great challenge. In this work, a series of in-plane asymmetric MSCs (AMSCs) are rationally constructed using a family of nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films with interdigital patterns. The voltage output window of the resultant AMSCs is able to reach up to 1.8 V, delivering superior areal capacitances of up to 19.84 mF cm-2, and ultrahigh energy density of 44.6 mW h cm-3 which is among the best performances of the state-of-the-art MSCs. Moreover, the achieved AMSCs show outstanding mechanical flexibility and integration capability. Thus, this work will promote the development of novel high-performance AMSCs.

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Permalink: https://www.hzdr.de/publications/Publ-29246
Publ.-Id: 29246


Interface stability, mechanical and corrosion properties of AlCrMoNbZr/(AlCrMoNbZr)N high-entropy alloy multilayer coatings under helium ion irradiation

Zhang, W.; Wang, M.; Wang, L.; Liu, C. H.; Chang, H.; Yang, J. J.; Liao, J. L.; Yang, Y. Y.; Liu, N.

High entropy alloy (HEA) coatings are promising for use as accident-tolerant fuel cladding due to their outstanding high-temperature corrosion resistance. In this work, we investigated the interface stability, mechanical properties and corrosion resistance of AlCrMoNbZr/(AlCrMoNbZr)N multilayer coatings with individual layer thickness of 5 nm, 10 nm and 50 nm, subjected to helium (He) ion irradiations: 400 keV He+ ions with fluences of 8×1015 ion/cm2 and 8×1016 ion/cm2. We determined that He bubbles are not observed in any of the multilayer coatings after a helium ion irradiation process with 400 keV He ions and a fluence as high as 8×1016 ion/cm2. Although intermixing and chemical reaction in the peak damage region of the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with 5 nm monolayer thickness are induced by the high fluence He ion irradiation, the FCC structure remained, and no intermetallic compounds are detected. Moreover, we found that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with the monolayer thickness of 50 nm has better interface stability during the irradiation process. Nanoindentation tests reveal that the hardness of all multilayer coatings decreased for low and high fluences, which is mainly due to the thermal effect caused by irradiation. In addition, the electrochemical corrosion test show that AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 50 nm coatings has better corrosion resistance than AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 5 nm coatings under high fluence He irradiation. The corrosion resistance of the multilayer coating depends on the stability of the multilayer interface. Our results show that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a monolayer thickness of 50 nm had better interface stability, mechanical properties and corrosion resistance than the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a per layer thickness of 5 nm under high fluence He irradiation. This work reveals that high-entropy alloy multilayer coatings have potential applications as an accident-tolerant fuel cladding coating in light water reactors.

Keywords: AlCrMoNbZr/(AlCrMoNbZr)N; Multilayer coating; High-entropy alloy; Ion irradiation; Interfaces; Nanoindentation; Electrochemical corrosion; Accident-tolerant fuel (ATF)

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Permalink: https://www.hzdr.de/publications/Publ-29245
Publ.-Id: 29245


Cortical microinfarcts in memory clinic patients are associated with reduced cerebral perfusion

Ferro, D.; Mutsaerts, H.; Hilal, S.; Kuijf, H.; Petersen, E. T.; Petr, J.; van Veluw, S.; Venketasubramanian, N.; Yeow, T. B.; Biessels, G. J.; Chen, C.

Cerebral cortical microinfarcts (CMIs) are small ischemic lesions associated with cognitive impairment and dementia. CMIs are frequently observed in cortical watershed areas suggesting that hypoperfusion contributes to their development. We investigated if presence of CMIs was related to a decrease in cerebral perfusion, globally or specifically in cortex surrounding CMIs. In181 memory clinic patients (mean age 72 ± 9 years, 51% male) CMI presence was rated on 3 T-MRI. Cerebral perfusion was assessed from cortical gray matter of the anterior circulation using pseudo-continuous arterial spin labeling parameters cerebral blood flow (CBF) (perfusion in mL blood/100g tissue/minute) and spatial coefficient of variation (CoV) (reflecting arterial transit time (ATT)) . Patients with CMIs had a 12% lower CBF (beta=-.20) and 22% higher spatial CoV (beta= .20) (both p<.05) without a specific regional pattern on voxel based CBF analysis. CBF in a 2 cm region-of-interest around the CMIs did not differ from CBF in a reference zone in the contralateral hemisphere. These findings show that CMIs in memory clinic patients are primarily related to global reductions in cerebral perfusion, thus shedding new light on the etiology of vascular brain injury in dementia.

Permalink: https://www.hzdr.de/publications/Publ-29244
Publ.-Id: 29244


Interaction of curium(III) with plant cells (Brassica napus)

Moll, H.; Sachs, S.; Raff, J.

The accumulation of radionuclides and toxic heavy metals into plants and thus into the food chain represents a potential pathway for human exposure. Hence, detailed knowledge of the fate of these elements in the ecosphere including the food chain is required for a reliable assessment of the resulting risk potential for humans and wildlife. Our aim is to explore the complex interaction of trivalent actinides with plant cells on a molecular level using curium(III) as an excellent luminescence probe.
We studied the response of canola (Brassica napus) cells to curium(III) exposure (0.7 µM). TRLFS was used as direct speciation technique to explore the Cm(III) speciation on the cells and in the supernatants. Liquid scintillation counting (LSC) was applied to measure the Cm(III) content in the supernatants. The possible release of plant cell metabolites was probed by solid phase extraction (SPE) with subsequent HPLC analysis.
The bioassociation experiments were performed in 0.154 M NaCl in a glove box over a time period up to 168 h. After defined time steps the Cm(III) concentration in the supernatants was determined as well as luminescence spectra from washed cells and the supernatants were taken. The Cm(III) concentration in the supernatants as a function of time points to a multi-stage bioassociation process on the plant cells. Red shifted Cm(III) luminescence spectra (+8.6 nm compared to Cm3+(aq)) in the supernatants indicated a Cm(III) complexation by substances that were released by the plant cells already after an exposure time of 5 h. Cell metabolites could be enriched and extracted by SPE. TRLFS studies (spectra and lifetime) showed a different Cm(III) speciation on cells compared to those found in the supernatants. To further describe the spectroscopic Cm(III) speciation in the B. napus system all spectra were evaluated with iterative transformation factor analysis (ITFA, Roßberg et al. 2003). The so obtained results (single component spectra and time-dependent species distributions) will be discussed in order to describe the fate of Cm(III) in the presence of plant cells (B. napus).
This new knowledge contributes to an improved understanding of trivalent actinide interactions with plants on a molecular level.

The authors are indebted to the U.S. Department of Energy, Office of Basic Energy Sciences, for the use of 248Cm via the transplutonium element production facilities at Oak Ridge National Laboratory; 248Cm was made available as part of collaboration between HZDR and the Lawrence Berkeley National Laboratory (LBNL). This study is part of the project TRANS-LARA which is funded by the Federal Ministry of Education and Research under contract number 02NUK051B.

Roßberg, A., Reich, T., Bernhard, G. 2003. Complexation of uranium(VI) with protocatechuic acid –
application of iterative transformation factor analysis
to EXAFS spectroscopy. Anal. Bioanal. Chem. 376, 631–638.

Keywords: curium; plant cells; Brassica napus; luminescence spectroscopy

  • Lecture (Conference)
    Envira 2019, 08.-13.09.2019, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-29243
Publ.-Id: 29243


Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background

Ullrich, M.; Richter, S.; Seifert, V.; Hauser, S.; Calsina, B.; Martínez-Montes, A. M.; Ter Laak, M.; Ziegler, C. G.; Timmers, H.; Eisenhofer, G.; Robledo, M.; Pietzsch, J.

Cyclooxygenase 2 (COX-2) is a key enzyme of the tumorigenesis-inflammation interface and can be induced by hypoxia. A pseudohypoxic transcriptional signature characterizes pheochromocytomas and paragangliomas (PPGLs) of the cluster I, mainly represented by tumors with mutations in von Hippel-Lindau (VHL), endothelial PAS domain-containing protein 1 (EPAS1), or succinate dehydrogenase (SDH) subunit genes. The aim of this study was to investigate a possible association between underlying tumor driver mutations and COX-2 in PPGLs. COX-2 gene expression and immunoreactivity were examined in clinical specimens with documented mutations as well as in spheroids and allografts derived from mouse pheochromocytoma (MPC) cells. COX-2 in vivo imaging was performed in allograft mice. We observed significantly higher COX-2 expression in cluster I, especially in VHL-mutant PPGLs, however, no specific association between COX-2 mRNA levels and a hypoxia-related transcriptional signature was found. COX-2 immunoreactivity was present in about 60 % of clinical specimens as well as in MPC spheroids and allografts. A selective COX-2 tracer specifically accumulated in MPC allografts. This study demonstrates that, although, pseudohypoxia is not the major determinant for high COX-2 levels in PPGLs, COX-2 is a relevant molecular target. This potentially allows for employing selective COX-2 inhibitors as targeted chemotherapeutic agents and radiosensitizers. Moreover, available models are suitable for preclinical testing of these treatments.

Keywords: VHL; NF1; EPAS1; hypoxia-inducible factor; inflammation; radiosensitization; succinate dehydrogenase; mouse pheochromocytoma cells; immunohistochemistry; fluorescence imaging

Permalink: https://www.hzdr.de/publications/Publ-29242
Publ.-Id: 29242


Radiumdotierte Bariumsulfat-Nanopartikel für die zukünftige Alphatherapie

Reissig, F.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.

1. Zielstellung: Durch die Alterung der Bevölkerung ist eine stetige Zunahme an Tumorneuerkrankungen zu verzeichnen und die Therapieoptimierung daher unabdingbar. Ein diskutierter Ansatz ist die Therapie mit Alphaemittern. Radionuklide wie 223/224Ra sind in der Lage, Tumorgewebe aufgrund ihres hohen linearen Energietransfers infolge einer Kaskade von Alpha-Zerfällen effizient zu zerstören ohne Beinflussung des gesunden Gewebes. Die stabile Fixierung von Barium- und Radiumionen kann durch Co-Fällung radiomarkierter [133Ba223/224Ra]Ba(Ra)SO4 Nanopartikel (NP) erfolgen, welche mit Alendronat funktionalisiert und anschließend mit einer targetspezifischen Einheit modifiziert werden.

2. Methodik
Die Synthese der BaSO4-NP wurde durch Fällung realisiert. Die Partikelgröße wurde in Abhängigkeit der Reaktionsparameter (Lösungsmittelsystem, Verhältnis der Reaktanden, Fließgeschwindigkeit bei der Zugabe des zweiten Reaktanden) untersucht. NP-Größenverteilungen wurden mittels Dynamic Light Scattering (DLS) ermittelt. Radiomarkierungen wurden unter analogen Bedingungen unter Zugabe von [133Ba]Ba2+ und [224Ra]Ra2+ durchgeführt. 224Ra wurde als [224Ra]Ra(NO3)2 aus einer 228Th-Quelle durch Ionenaustauschchromatographie separiert. 133Ba wurde als [133Ba]BaCl2 kommerziell bezogen.

3. Ergebnisse
Nach Auswertung aller Syntheseansätze wurde die Fällung der Partikel mit einem sechsfachen Bariumüberschuss in einer Ethanol/Wasser-Mischung (1/11) bei Raumtemperatur als beste Methode identifiziert. Die Einlagerung von [133Ba]Ba2+- und [224Ra]Ra2+-Ionen konnte nachgewiesen werden. Die radiomarkierten NP zeigten über 7 Tage keinen relevanten Release. Die Modifikation der Partikel mit Alendronat konnte mittels IR-Spektroskopie, EDXS-Analyse und UV/Vis-Spektroskopie nachgewiesen werden. Die Partikelgröße wurde mittels DLS (140 ± 50 nm) analysiert und durch TEM verifiziert. Die weitere Funktionalisierung der NP wurde mittels Aktivesterkupplung eines fluoreszierenden NBD-Derivates und Fluoreszenzspektroskopie nachgewiesen.

4. Schlussfolgerungen
Die Co-Fällung von Barium- und Radiumisotopen zur Gewinnung von NP definierter Größe ist ein Ausgangspunkt zukünftiger Therapieansätze. Die Funktionalisierung mit biologischen Targetmolekülen ermöglicht das zielgerichtete Aufspüren von Tumorzellen. Zukünftige Arbeiten fokussieren die Optimierung der Synthesemethode hinsichtlich der Verringerung der Partikelgröße und Ausbeute bei der Radiomarkierung sowie die anschließende Oberflächenmodifikationen bezüglich verschiedener biologischer Targets.

Keywords: Barium; Radium; Bariumsulfat; Nanopartikel

  • Lecture (Conference)
    Jahrestagung der GDCh-Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29241
Publ.-Id: 29241


Damage accumulation and implanted Gd and Au position in a- and c-plane GaN

Macková, A.; Malinský, P.; Jagerová, A.; Mikšová, R.; Sofer, Z.; Klímová, K.; Mikulics, M.; Böttger, R.; Akhmadaliev, S.; Oswald, J.

(0001) c-plane and (11−20) a-plane GaN epitaxial layers were implanted with 400 keV Au+ and Gd+ ions using ion implantation fluences of 5×1014, 1×1015 and 5×1015 cm-2. Rutherford Back-Scattering spectrometry in channelling mode (RBS/C) was used to follow the dopant depth profiles and the introduced disorder; the angular dependence of the backscattered ions (angular scans) in c- and a-plane GaN was measured to get insight into structural modification and dopant position in various crystallographic orientations. Defect-accumulation depth profiles exhibited differences for a- and c-plane GaN, with a-plane showing significantly lower accumulated disorder in the buried layer, accompanied by the shift of the maximum damage accumulation into the deeper layer with respect to the theoretical prediction, than c-plane GaN. Angular scans showed channelling preservation in as-implanted samples and better channelling recovery in the annealed a-plane GaN compared to cplane GaN. The angular scan widths were simulated by FLUX code as well as the half-width modifications of angular scans were discussed in connection to the damage accumulation. Photoluminescence measurement followed in detail yellow band and band edge luminescence decline after the implantation and the recovery of luminescence spectra features after annealing.

Keywords: Implanted (0001) and (11–20) GaN; Damage accumulation asymmetry in GaN; Ion implantation in semiconductors; RBS channelling; Damage-depth profiling

Permalink: https://www.hzdr.de/publications/Publ-29240
Publ.-Id: 29240


Tc immobilization by Fe(II)-Al(III)-Cl layered double hydroxide phase

Mayordomo Herranz, N.; Rodriguez Hernandez, D. M.; Roßberg, A.; Scheinost, A.; Foerstendorf, H.; Heim, K.; Brendler, V.; Müller, K.

⁹⁹Tc is a long half-life isotope (2.13×10⁵ years) that can be found in the environment due to anthropogenic sources - nuclear energy production, tests of nuclear weapons and radiopharmacy - as it is a fission product from ²³⁵U and ²³⁹Pu and the daughter of 99mTc, used for diagnosis [1].
Although Tc has several oxidation states, Tc(VII) and Tc(IV) are the more stable ones found under oxidizing and reducing conditions, respectively, but their chemical behavior differs. While the Tc(VII) main species (TcO₄⁻) is a highly mobile anion that hardly interacts with minerals, Tc(IV) is usually found as a low soluble solid (TcO₂) whose precipitation avoids the Tc migration [2]. Therefore, in order to reduce Tc mobility it is essential to understand the conditions that favor the three electrons donation step switching between these two oxidation states.
Several works report that Fe²⁺ promotes the Tc reduction, especially when found in Fe(II)-minerals or sorbed on mineral surfaces [3], [4].
If corrosion of the nuclear waste canisters occurs, Fe²⁺ will be present in the near-field of a deep geological repository. In that case, Fe²⁺ could not only act as reducing agent but also interact with different minerals, getting sorbed or forming new mineral phases.
In fact, it has been observed that when Fe²⁺ interacts with Al₂O₃, it forms Fe(II)-Al(III)-Cl, a layered double hydroxide (LDH) [5]. The LDH phases are known to retain pollutants by different mechanisms: anion exchange, incorporation, surface complexation and, in Fe(II)-Al(III)-Cl, reduction promoted by the structural Fe²⁺ [6].
Therefore, we analysed the ⁹⁹Tc retention by Fe(II)-Al(III)-Cl LDH phase under different conditions (pH, ionic strength and Tc concentration). We observed that the affinity of the Fe(II)-Al(III)-Cl LDH phase for Tc has two different trends. For pH < 6.5, Tc retention increases with increasing pH and decreasing ionic strength, being complete in water, suggesting anion exchange as the main retention mechanism. At pH > 6.5, Tc uptake is complete and independent from the ionic strength and the pH value, suggesting Tc reduction as main uptake mechanism.
This work has been performed in the frame of VESPA II project (02E11607B), supported by the German Federal Ministry for Economic Affairs and Energy (BMWi).
References:
[1] A. H. Meena and Y. Arai, Environ. Chem. Lett., vol. 15, no. 2, pp. 241–263, 2017.
[2] K. H. Lieser and C. Bauscher, Radiochim. Acta, vol. 42, pp. 205–213, 1987.
[3] T. Peretyazhko et al., Geochim. Cosmochim. Acta, vol. 72, no. 6, pp. 1521–1539, 2008.
[4] D. Cui and T. E. Eriksen, Environ. Sci. Technol., vol. 30, no. 7, pp. 2263–2269, 1996.
[5] E. J. Elzinga, Environ. Sci. Technol., vol. 46, no. 9, pp. 4894–4901, 2012.
[6] C. Forano, et al , Layered double hydroxides (LDH), vol. 5. 2013.

Keywords: Technetium; immobilization; LDH; reduction

  • Lecture (Conference)
    Gesellschaft Deutscher Chemiker Nuclearchemie 2019, 25.-27.09.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29239
Publ.-Id: 29239


⁹⁹Tc retention on Fe(II)Al(III)-Cl layered double hydroxides

Mayordomo Herranz, N.; Rodriguez Hernandez, D. M.; Scheinost, A.; Roßberg, A.; Brendler, V.; Müller, K.

To assess the safety of nuclear waste repositories, possible incidents have to be considered like canister corrosion and as a consequence the release of radionuclides.Among them,the fission product ⁹⁹Tc is of high concern due to its long half-life (2.13∙10⁵years) and the high mobility of the Tc(VII)O₄⁻ oxoanion that is barely adsorbed by common mineral phases. However, Tc migration decreases under reducing conditions due to formation of Tc(IV), whose main species is a highly insoluble solid TcO₂.Under the reducing and corrosive conditions in the near-field of the repository, Fe²⁺ will act as a reducing agent for redox sensitive radionuclides (when present in the groundwater or sorbed on mineral surfaces). Furthermore,secondary mineral phases like Fe(II)-Al(III)-Cl, a layered double hydroxide (LDH),can be formed when Fe²⁺ interacts with Al₂O₃ at circumneutral-alkaline pH [1]. LDH phases are so-called anionic clays and they are known to retain pollutants by anion exchange, incorporation, surface complexation and in the case of Fe(II)-Al(III)-Cl via reduction promoted by the structural Fe²⁺ [2]. We have analysed the ⁹⁹Tc uptake by Fe(II)-Al(III)-Cl LDH under varying pH (4 to 11), ionic strength (0 to 0.1 M) and Tc concentration(10⁻⁹to 10⁻³ M). At pH < 6.5, the solid to liquid distribution coefficient, (log Kd in mL/g),ranges from (2 to 6) and increases with decreasing ionic strength and increasing pH. At pH > 6.5, log Kd (6.5±0.3) are independent of pH and ionic strength.Tc K-edge X-ray absorption spectroscopy showed in all cases a reduction to Tc(IV) and enabled us to elucidate the surface bound speciation of Tc on a molecular level.


[1]E. J. Elzinga,”Environ. Sci. Technol., vol. 46, no. 9, pp. 4894–4901, 2012.
[2]C. Forano, U. Costantino, V. Prévot, and C. T. Gueho, Layered double hydroxides (LDH), vol. 5. 2013.

Keywords: Technetium; retention; LDH; reduction

  • Lecture (Conference)
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29238
Publ.-Id: 29238


Uncovering the Origin of the Emitting States in Bi³⁺-Activated CaMO₃ (M=Zr, Sn, Ti) Perovskites: Metal-to-Metal Charge Transfer versus s-p Transitions

Back, M.; Ueda, J.; Xu, J.; Asami, K.; Amidani, L.; Trave, E.; Tanabe, S.

After more than a century of studies on the optical properties of Bi³⁺ ion, the assignment of the nature of the emissions and the bands of the absorption spectra remain ambiguous. Here we report an insight into the spectroscopy of Bi³⁺-activated CaMO₃ perovskites (M=Zr, Sn, Ti), discussing the factors driving the metal-to-metal charge transfer and sp → s2 transitions. With the aim to figure out the whole scenario, a combined experimental and theoretical approach is employed. The comparison between the temperature dependence of the PL emissions with the temperature dependence of the exciton energy of the systems has led to an unprecedent evidence of the charge transfer character of the emitting states in Bi³⁺-activated phosphors. Low temperature VUV spectroscopy together with the design of the vacuum referred binding energy diagram of the luminescent center are exploited to shed light on the origin of the absorption bands. In addition, the X-ray absorption near edge structure, unambiguously confirmed the stabilization of Bi³⁺ in Ca²⁺ site in both CaSnO₃ and CaZrO₃ perovskites. This breakthrough into the understanding of the excited state origin of Bi3+ could pave the way towards the design of a new generation of effective Bi³⁺-activated phosphors.

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Permalink: https://www.hzdr.de/publications/Publ-29236
Publ.-Id: 29236


Plutonium retention mechanisms by magnetite under anoxic conditions: Entrapment versus sorption

Dumas, T.; Fellhauer, D.; Schild, D.; Gaona, X.; Altmaier, M.; Scheinost, A.

The reliable prediction of possible plutonium migration into the geological environment is crucial for the safety assessment of radioactive waste repositories. Fe(II)-bearing corrosion products like magnetite, which form on the surface of steel waste containers, can effectively contribute to the retardation of the potential radionuclide release by sorption and redox reactions, eventually followed by formation of secondary precipitates. A retardation process even more efficient - especially when considering the required long time scales for nuclear waste reposition - is structural incorporation by magnetite, as has been demonstrated for Tc and U. Here we show that this mechanism might not be as relevant for Pu retention: after a rapid reduction of Pu(V) to Pu(III) in acidic Fe(II)/Fe(III) solution, base-induced magnetite precipitation (pHexp ≈ 12.5) leads only to a partial (≈ 50%) incorporation, while the other half remains at the surface by forming tridentate sorption complexes. Neither solid nor sorbed Pu(IV) species were observed in the starting solution and after precipitation. With Fe(II)-inforced re-crystallization at pHexp = 6.5, a process potentially mimicking long-term, thermodynamically controlled aging, the equilibrium between both Pu species is even further shifted towards the sorption complex. A detailed analysis of the incorporated species by Pu LIII-edge X-ray absorption fine-structure (XAFS) spectroscopy shows a pyrochlore-like coordination environment (split eight-fold oxygen coordination shell with Pu-O distances of 2.22 and 2.45 Å, and an edge-sharing linkage to Fe-octahedra with Pu-Fe distances of 3.68 Å), which is embedded in the magnetite matrix (Pu-Fe distances of 3.93, 5.17 and 5.47 Å). This suggests that the reason for the partial incorporation is the structural incompatibility of the large Pu(III) ion for the octahedral Fe site in magnetite. The adoption of a pyrochlore-like local environment within the magnetite long-range structure might be induced by the rapid coprecipitation rather than being a thermodynamically stable state (kinetic entrapment). For the sake of conservatism, safety assessments should rely on the formation of the Pu(III) sorption complex only.

Keywords: solid solutions; radioactive waste disposal; plutonium; magnetite; EXAFS; XANES; XPS

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Permalink: https://www.hzdr.de/publications/Publ-29235
Publ.-Id: 29235


Experiments on the magnetic enrichment of rare-earth metal ions in aqueous solutions in a microflow device

Kolczyk-Siedlecka, K.; Wojnicki, M.; Yang, X.; Mutschke, G.; Zabinski, P.

An attempt is made to achieve a continuous enrichment of rare-earth metal ions from aqueous solutions in a microflow device by applying magnetic forcing. An aqueous solution containing holmium(III) ions is pumped through a small channel which was exposed to a strong inhomogeneous magnetic field. At the outflow, the near- and far-field parts of the flow are separated and analyzed using UV-Vis spectroscopy. The relative change of ion concentration is determined from the measured absorbance. Results are reported for three different types of flow cells at different flow rates and magnetic field strengths and for a cascaded application of cells. The change of concentration is found to be small, and no clear trend can currently be stated due to the error margin of the concentration measurement.

Keywords: microflow; spectrophotometry; rare-earth elements; magnetic field; continuous separation

Permalink: https://www.hzdr.de/publications/Publ-29233
Publ.-Id: 29233


Surface nanobubbles on the rare earth fluorcarbonate mineral synchysite

Owens, C. L.; Schach, E.; Heinig, T.; Rudolph, M.; Nash, G. R.

Surface nanobubbles have been identified to play an important role in a range of industries from mineral processing to food science. The formation of surface nanobubbles is of importance for mineral processing in the extraction of complex ores, such as those containing rare earth elements. This is due to the way minerals are extracted utilising froth flotation. In this study, surface nanobubbles were imaged using non-contact atomic force microscopy on a polished cross section containing rare earth minerals. Nanobubbles were found on synchysite under reagent conditions expected to induce hydrophobicity in rare earth minerals, which is required for efficient processing.

Synchysite –(Ce) is a rare earth fluorcarbonate mineral containing over 30% rare earth elements. Relatively little research has been conducted on synchysite, with only a few papers on its surface behaviour and flotation. The resulting nanobubbles were analysed and showed an average contact angle of 24 degrees± 8. These are in line with contact angles found on dolomite and galena by previous studies.

Keywords: non-contact atomic force microscopy; synchysite; bastnäsite; rare earth elements; fluorcarbonate; surface nanobubbles; carbonatite

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Permalink: https://www.hzdr.de/publications/Publ-29231
Publ.-Id: 29231


Refinement of the Hounsfield look‐up table by retrospective application of patient‐specific direct proton stopping‐power prediction from dual‐energy CT

Wohlfahrt, P.; Möhler, C.; Enghardt, W.; Krause, M.; Kunath, D.; Menkel, S.; Troost, E. G. C.; Greilich, S.; Richter, C.

Background and Purpose:
Proton treatment planning relies on an accurate determination of stopping-power ratio (SPR) from x-ray computed tomography (CT). A clinically applicable refinement of the heuristic CT-based SPR prediction using a state-of-the-art Hounsfield look-up table (HLUT) is proposed, which incorporates patient-specific SPR information obtained from dual-energy CT (DECT) in a retrospective patient-cohort analysis.

Material and Methods:
SPR datasets of 25 brain-tumor, 25 prostate-cancer and three non-small cell lung-cancer (NSCLC) patients were directly derived from clinical DECT scans with the DirectSPR approach. Based on the median frequency distribution of voxelwise correlations between CT number and SPR within the irradiated volume, a piecewise linear function was specified (DirectSPR-based adapted HLUT). Differences in dose distribution and proton range were assessed for the non-adapted and adapted HLUT compared with the DirectSPR method.

Results:
The application of the DirectSPR-based adapted HLUT instead of the non-adapted one reduced systematic range deviations from 1.2% (1.1 mm) to -0.1% (0.0 mm) for brain-tumor, 1.7% (4.1 mm) to 0.2% (0.5 mm) for prostate-cancer and 2.0% (2.9 mm) to -0.1% (0.0 mm) for NSCLC patients. Due to the intra- and inter-patient tissue variability, range deviations larger than 1% are still present for the adapted HLUT.

Conclusions:
The incorporation of patient-specific correlations between CT number and SPR, derived from a retrospective application of DirectSPR to a broad patient cohort, improves the accuracy of the current state-of-the-art HLUT approach. The DirectSPR-based adapted HLUT has been clinically implemented at our institution, which represents a further step toward full integration of the DECT-based DirectSPR method for treatment planning in proton therapy.

Keywords: dual-energy CT; proton range prediction; proton therapy

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  • Secondary publication expected from 09.02.2021

Permalink: https://www.hzdr.de/publications/Publ-29230
Publ.-Id: 29230


Synthesis of Mg and Zn diolates and their use in metal oxide deposition

Frenzel, P.; Preuß, A.; Bankwitz, J.; Georgi, C.; Ganss, F.; Mertens, L.; Schulz, S.; Hellwig, O.; Mehring, M.; Lang, H.

The synthesis of complexes [M(OCHMeCH₂NMeCH₂)₂] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH₂NMeCH₂)₂ (3), which upon reaction with equimolar amounts of MR₂ (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH𔔢N+, C₂H𔔢N+, C₂H₅N+, CH₂O+, C₂H₂O+ and C₂H₃O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

Permalink: https://www.hzdr.de/publications/Publ-29229
Publ.-Id: 29229


Residual gammaH2AX foci in head and neck squamous cell carcinomas as predictors for tumour radiosensitivity: Evaluation in pre-clinical xenograft models and clinical specimens

Meneceur, S.; Löck, S.; Gudziol, V.; Hering, S.; Bütof, R.; Rehm, M.; Baumann, M.; Krause, M.; von Neubeck, C.

Background and purpose: Predictive biomarkers can be instrumental to treatment individualisation of cancer patients and improve therapy outcome. Residual γH2AX foci represent a promising biomarker to predict tumour radiosensitivity. In this pre-clinical study, the slope of the dose–response curve was evaluated for its predictive relevance in head and neck squamous cell carcinoma xenografts (HNSCC). Additionally, the feasibility of the translated assay was tested in a clinical setting in patient derived HNSCC samples, and associations between residual γH2AX foci and clinical parameters were analysed. Materials and methods: Seven HNSCC xenografts models (FaDu, SAS, SKX, UT-SCC-5, UT-SCC-14, UT-SCC-45, XF354)were used. Tumour bearing NMRI nude mice were randomly distributed to five treatment arms (0–8 Gy). Residual γH2AX foci (24 h post irradiation)were counted by visual scoring in a micromilieu dependent manner (assessed with BrdU and pimonidazole). The local tumour control values measured as TCD 50 (tumour control dose 50%)have previously been published. Patient derived HNSCC biopsies were cultivated ex vivo for 24 h including 4 h of pimonidazole and BrdU treatment, subsequently irradiated with 0–8 Gy and fixed after 24 h. Results: In the pre-clinical study, the dose–response curve slopes negatively correlated with the tumour control dose after fractionated irradiation (TCD 50,fx , R 2 = 0.63, p = 0.032)and after single dose irradiation under homogeneous hypoxia (TCD 50,SD,clamp , R 2 = 0.66, p = 0.027). The γH2AX assay in clinical HNSCC samples showed a dose–response relationship, with the values of the slopes ranging from 0.099 Gy −1 to 0.920 Gy −1 (coefficient of variation = 52.8%). Slopes derived from patients were in the same ranges as the sensitive, moderate and resistant models of the pre-clinical study. Statistical analysis revealed a significant negative correlation between the slope and the patients’ age (R 2 = 0.65, p = 0.001). Conclusion: These results further support the promise of the slope of the residual γH2AX foci dose–response as a biomarker for radiosensitivity. In the clinical samples, the variation in the slopes reveals patients’ specific repair capacities, which could hold potential value for treatment individualisation. © 2019 Elsevier B.V.

Keywords: Clinical specimens; HNSCC; Predictive biomarker; Radiosensitivity; Xenograft modelsγH2AX

Permalink: https://www.hzdr.de/publications/Publ-29228
Publ.-Id: 29228


Cancer stem cells in radiation response: current views and future perspectives in radiation oncology

Peitzsch, C.; Kurth, I.; Ebert, N.; Dubrovska, A.; Baumann, M.

Purpose: Despite technological improvement and advances in biology-driven patient stratification, many patients still fail radiotherapy resulting in loco-regional and distant recurrence. Tumor heterogeneity remains a key challenge to effective cancer treatment, and reliable stratification of cancer patients for prediction of outcomes is highly important. Intratumoral heterogeneity is manifested at the different levels, including different tumorigenic properties of cancer cells. Since John Dick et al. isolated leukemia initiating cells in 1990, the populations of tumor initiating or cancer stem cells (CSCs) were identified and characterized also for a broad spectrum of solid tumor types. The properties of CSCs are of considerable clinical relevance: CSCs have self-renewal and tumor initiating potential, and the metastases are initiated by the CSC clones with the ability to disseminate from the primary tumor site. Conclusion: Evidence from both, experimental and clinical studies demonstrates that the probability of achieving local tumor control by radiation therapy depends on the complete eradication of CSC populations. The number, properties and molecular signature of CSCs are highly predictive for clinical outcome of radiotherapy, whereas targeted therapies against CSCs combined with conventional treatment are expected to provide an improved clinical response and prevent tumor relapse. In this review, we discuss the modern methods to study CSCs in radiation biology, the role of CSCs in personalized cancer therapy as well as future directions for CSC research in translational radiooncology.

Keywords: Cancer stem cells; model systems; radiosensitivity

Permalink: https://www.hzdr.de/publications/Publ-29227
Publ.-Id: 29227


Widely tunable GaAs bandgap via strain engineering in core/shell nanowires with large lattice mismatch

Balaghi, L.; Bussone, G.; Grifone, R.; Hübner, R.; Grenzer, J.; Ghorbani-Asl, M.; Krasheninnikov, A.; Schneider, H.; Helm, M.; Dimakis, E.

The realization of photonic devices for different energy ranges demands materials with different bandgaps, sometimes combined even within the same device as in multi-junction photovoltaic cells. The optimal solution in terms of integration, device performance and device economics would be a simple material system with widely tunable bandgap and compatible with the mainstream silicon technology. Here, we show that gallium arsenide nanowires grown epitaxially on silicon substrates exhibit a sizeable reduction of their bandgap by up to 40% when overgrown with lattice-mismatched indium gallium arsenide or indium aluminium arsenide shells. Specifically, we demonstrate that the gallium arsenide core sustains unusually large tensile strain with hydrostatic character and its magnitude can be engineered via the composition and the thickness of the shell. The resulted bandgap reduction renders gallium arsenide nanowires suitable for photonic devices across the near-infrared range, including telecom photonics at 1.3 and potentially 1.55 μm, with the additional possibility of monolithic integration in silicon-CMOS chips.

Permalink: https://www.hzdr.de/publications/Publ-29226
Publ.-Id: 29226


Advanced Methods for Temporal Reconstruction of Modulated Electron Bunches

Zarini, O.; Köhler, A.; Couperus Cabadağ, J. P.; Pausch, R.; Kurz, T.; Schöbel, S.; Meißner, H.; Bussmann, M.; Schramm, U.; Irman, A.; Debus, A.

We describe optimizations of phase-retrieval algorithms for the reconstruction of the temporal structure of highly modulated electron bunches from coherent transition radiation (CTR) spectra. Synthetic data is used to quantitatively analyze capabilities and limitations of the approach taking into account realistic bandwidth constraints of ultra-broadband spectrometers. Established algorithms are combined with information from independent channels as charge calibrated electron spectra and absolute intensity calibration of the spectrometer. With this set of data, in principle available in experiments, we demonstrate a promising fidelity for the detailed analysis of substructured laser wakefield accelerated electron bunches.

Keywords: Electron bunch duration; reconstruction algorithm; transition radiation

  • Contribution to proceedings
    Advanced Accelerator Concepts Workshop (AAC2018), 12.-17.08.2018, Breckenridge, Colorado, USA: IEEE, 978-1-5386-7721-6
    DOI: 10.1109/AAC.2018.8659388

Permalink: https://www.hzdr.de/publications/Publ-29225
Publ.-Id: 29225


Synthesis and in vitro evaluation of 8-pyridinyl substituted benzo[e]imidazo[2,1-c][1,2,4]triazines as phosphodiesterase 2A (PDE2A) inhibitors

Ritawidya, R.; Ludwig, F.-A.; Briel, D.; Brust, P.; Scheunemann, M.

Phosphodiesterase 2A (PDE2A) is highly expressed in distinct areas of the brain which are known to be related to neuropsychiatric diseases. The development of suitable PDE2A tracers for Positron Emission Tomography (PET) would permit the in vivo imaging of the PDE2A and evaluation of disease- mediated alterations of its expression. A series of novel fluorinated PDE2A inhibitors on the basis of a benzoimidazotriazine (BIT) scaffold was prepared leading to a promising inhibitor for further development of a PDE2A PET imaging agent. BIT derivatives (BIT1-9) were obtained by a seven-step synthesis route and their inhibitory potency towards PDE2A and selectivity over other PDEs have been evaluated. BIT1 demonstrated much higher inhibition than other BIT derivatives (82.9% inhibition of PDE2A at 10 nM). BIT1 displayed an IC50 for PDE2A of 3.33 nM with 16-fold selectivity over PDE10A. This finding revealed that a derivative bearing both a 2-fluoro-pyridin-4-yl and 2-chloro-5-methoxy-phenyl unit at 8- and 1-position, respectively, appeared to be the most potent inhibitor. In vitro studies of BIT1 using mouse liver microsomes (MLM) disclosed BIT1 as a suitable ligand for 18F-labeling. Nevertheless, future in vivo metabolism studies are required.

Keywords: Phosphodiesterase 2A (PDE2A); positron emission tomography (PET); benzoimidazotriazine (BIT); fluorinated; mouse liver microsomes (MLM)

Permalink: https://www.hzdr.de/publications/Publ-29224
Publ.-Id: 29224


Experimental investigations of bubble chains in a liquid metal under the influence of a horizontal magnetic field

Keplinger, O.; Shevchenko, N.; Eckert, S.

We present an experimental study on bubble chains ascending in the eutectic GaInSn alloy under the influence of a horizontal magnetic field. Argon gas bubbles are injected through a single nozzle positioned in the middle at the bottom of a flat Plexiglas vessel. Bubble size distribution, shape deformation, velocities, etc. are obtained by post-processing of X-ray radiographs measured with a high-speed video-camera for a wide range of Argon gas flow rates. In the case without a magnetic field, the typical zigzag movement of the rising bubbles is observed. This movement and the integrity of the bubble chain are significantly disturbed with increasing gas flow by the turbulent flow in the liquid metal. The main effect of the magnetic field consists in a stabilization of the bubble trajectories. The application of a magnetic field at moderate field strength dampens the turbulent fluctuations in the bubble wake and stabilizes the zigzag movement. The application of a sufficiently strong magnetic field suppresses the zig-zag motion of the bubbles and forces them to follow a straight path. The rising velocity is gradually reduced with increasing magnetic field strength. The motion of the individual bubbles within the chain becomes highly correlated. Ellipsoidal bubbles tend to align their major axes along the magnetic field lines.

Keywords: Liquid metal; Two-phase flow; Bubble chain; Horizontal magnetic field; X-ray radiography

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  • Secondary publication expected from 01.12.2020

Permalink: https://www.hzdr.de/publications/Publ-29223
Publ.-Id: 29223


Measuring sub-femtosecond temporal structures in multi-ten kiloampere electron beams

Zarini, O.

In laser wakefield acceleration, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m.
This scheme advances a novel concept for compact and less expensive electron accelerators, which can be hosted in a typical university size laboratory. Furthermore, laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer size with duration ranging from several fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top X-ray light-sources and remains a big challenge due to the resolution limit of existing diagnostic techniques.

Spectral measurement of broadband coherent and incoherent transition radiation (TR) produced when electron bunches passing through a metal foil is a promising way to analyze longitudinal characteristics of these bunches. Due to the limited reproducibility of the electron source this measurement highly requires single-shot capability.
An ultra-broadband spectrometer combines the TR spectrum in UV/NIR (200-1000 nm), NIR (0.9-1.7 µm) and mid-IR (1.6-12 µm). A high spectral sensitivity, dynamic bandwidth and spectral resolution are realized by three optimized dispersion and detection systems integrated into a single-shot spectrometer.
A complete characterization and calibration of the spectrometer have been done concerning wavelengths, relative spectral sensitivities, and absolute photometric sensitivities, also taking into account for the light polarization.
The TR spectrometer is able to characterize electron bunches with charges as low as 1pC and can resolve time-scales of 0.4 fs. Electron bunches up to 16 fs (rms width) can be reconstructed from their TR spectrum.

In the presented work, the self-truncated ionization induced injection (STII) scheme has been explored to study the relevant beam parameters especially its longitudinal bunch profile and the resulting peak current.
Proper focusing of a high power laser pulse into a supersonic gas-jet target and tailoring the conditional laser and plasma density and taking advantage of the relativistic self-focusing effects are investigated in this PhD thesis in order to study the final beam parameters as well as the consequent beam loading effects by producing nC-class mono-energetic electron beams.

In the experiment at HZDR, the DRACO 100TW Ti:Sa based laser system is used in conjunction with a He-N₂ mixed, supersonic gas-jet target. Under optimized conditions, mono-energetic electron bunches are accelerated, which are massively loaded up to several 100 pC at 300 MeV peak energy with a narrow energy spread of a few 10 MeV. Reconstruction results of TR spectra, measured by TR spectrometer, show that the shortest electron bunch duration is at about 13 fs FWHM corresponding to a peak current as high as 20 kA.
Such peak current is about one order of magnitude higher than those generated by conventional RF linear accelerator. This landmarks a significant finding of this thesis.

Keywords: Laser wakefield acceleration; laser plasma accelerator; self-truncated ionization injection; high peak current; high bunch charge; beam loading; bunch duration measurement; coherent transition radiation; broadband spectrometer; infrared spectrometer; prism spectrometer; echelle spectrometer; phase reconstruction algorithm; Foldwrap reconstruction algorithm; PIConGPU

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-100 2019
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-29222
Publ.-Id: 29222


Recent application of the solid targetry system

Mansel, A.; Franke, K.

The solid targetry system was used both, at port 4 directly mounted at the yoke and at the beamline at port 3. We will give an overview about the purification or separation of n.c.a. radionuclides like Sr-85, V-48, Cu-64, Cr-51, Co-56, Y-88, La-135, Zr-89, Ce-139 and Pb-203.

  • Lecture (Conference)
    14th CYCLEUR workshop 2019, 08.-10.05.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29221
Publ.-Id: 29221


Competence Center for Ion Beams in Materials Research and Medicine

Faßbender, J.

Competence Center for Ion Beams in Materials Research and Medicine

Keywords: ion beams; high-energy; materials research; user facility

  • Invited lecture (Conferences)
    Competence Center for Ion Beams in Materials Research and Medicine, 02.05.2019, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29220
Publ.-Id: 29220


Pool CFD Modelling: Lessons from the SESAME Project

Moreau, V.; Profir, M.; Alamberti, A.; Frignani, M.; Merli, F.; Belka, M.; Frybort, O.; Melichar, T.; Tarantino, M.; Franke, S.; Eckert, S.; Class, A.; Yanez, J.; Grishchenko, D.; Jeltsov, M.; Kudinov, P.; Roelofs, F.; Zwijsen, K.; Visser, D. C.; Badillo, A.; Niceno, B.; Martelli, D.

The Computational Fluid-Dynamics (CFD) modelling of Heavy Liquid Metal (HLM) flows in pool configuration is investigated.
We describe how the argument is treated within the SESAME project in its specific work package. The work package structure, based on a systematic approach of redundancy and diversification, is explained along with its motivation. The main achievements obtained and the main lessons learned are illustrated.
The paper focuses on the strong coupling between experimental activity and CFD simulation performed within the SESAME project. Two HLM fluids are contemplated: pure lead and Lead-Bismuth Eutectic. The objective is to make CFD a valid instrument in support to the design of safe and innovative Gen-IV nuclear plants.
Some effort has also been devoted to a highly challenging and innovative approach, the Proper Orthogonal Decomposition (POD) with Galerkin projection modelling, potentially able to cover some CFD applications at a much lower computational cost.
To reach sufficient maturity, the method requires however input from sufficiently complex CFD simulations such as those produced in the present context.
Dedicated experimental campaigns on heavily instrumented facilities have been conceived with the specific objective to build a series of datasets suited for the calibration and CFD modelling validation. In pool configuration, the attention is focused on the balance between conductive and convective heat transfer phenomena, on transients representative of incidental scenarios and on the possible occurrence of solidification phenomena. Four test sections have been selected for the dataset production: (i) the CIRCE facility from ENEA, (ii) the TALL-3D pool test section from KTH, (iii) the TALL-3D Solidification Test Section (STS) from KTH and (iv) the SESAME Stand facility from CVR. While CIRCE and TALL-3D were existing facilities, the STS and SESAME Stand facility have been conceived, built and operated within the project, heavily relying on the use of CFD support. We give an outlook on the work performed, the results achieved and remaining or new uncovered issues.

Keywords: GenIV reactors; Pool-type configuration; Heavy liquid metals; CFD

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  • Secondary publication expected from 15.12.2020

Permalink: https://www.hzdr.de/publications/Publ-29219
Publ.-Id: 29219


Adjuvant drug-assisted bone healing: Part III – Further strategies for local and systemic modulation

Rothe, R.; Schulze, S.; Neuber, C.; Hauser, S.; Rammelt, S.; Pietzsch, J.

In this third in a series of reviews on adjuvant drug-assisted bone healing, further approaches aiming at influencing the healing process are discussed. Local and systemic modulation of bone metabolism is persued with use of a number of drugs with completely different indications, which are characterized by a pleiotropic spectrum of action. These include drugs used to treat lipid disorders (HMG-CoA reductase inhibitors), hypertension (ACE inhibitors), osteoporosis (bisphosphonates), cancer (proteasome inhibitors) and others. Potential applications to enhance bone healing are discussed.

Keywords: bisphosphonates; bone metabolism; critical-size bone defects; small molecules; statins; strontium; Wnt signaling

  • Clinical Hemorheology and Microcirculation 73(2019), 439-488
    DOI: 10.3233/CH-199104

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29218
Publ.-Id: 29218


Adjuvant drug-assisted bone healing: Part II – Modulation of angiogenesis

Rothe, R.; Schulze, S.; Neuber, C.; Hauser, S.; Rammelt, S.; Pietzsch, J.

The treatment of critical-size bone defects following complicated fractures, infections or tumor resections is a major challenge. The same applies to fractures in patients with impaired bone healing due to systemic inflammatory and metabolic diseases. Despite considerable progress in the development and establishment of new surgical techniques, the design of bone graft substitutes and imaging techniques, these scenarios still represent unresolved clinical problems. However, the development of new active substances gives cause for hope. This work discusses therapeutic approaches that influence angiogenesis or hypoxic situations in healing bone and surrounding tissue. In particular, the literature on sphingosine-1-phosphate receptor modulators and nitric oxide (NO•) donors, including bi-functional (hybrid) compounds like NO•-releasing cyclooxygenase-2 inhibitors, was critically reviewed with regard to their local and systemic mode of action.

Keywords: critical-size bone defects; neovascularization; nitric oxide donors; signaling; small molecules; sphingosine-1-phosphate receptor

  • Open Access Logo Clinical Hemorheology and Microcirculation 73(2019), 409-438
    DOI: 10.3233/CH-199103

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Permalink: https://www.hzdr.de/publications/Publ-29217
Publ.-Id: 29217


Adjuvant drug-assisted bone healing: Part I – Modulation of inflammation

Rothe, R.; Schulze, S.; Neuber, C.; Hauser, S.; Rammelt, S.; Pietzsch, J.

Critical-size bone defects after compound fractures, infection, or tumor resection are challenging to treat. The same is true for fractures in patients with impaired bone healing due to metabolic diseases and cancer. Despite considerable progress over the last decade in surgical techniques, material design, and dedicated imaging approaches, these scenarios represent unsolved clinical problems. The high socioeconomic burden of such conditions justifies increasing interest in novel osteoinductive drugs for adjuvant therapeutic approaches. There is an increasing body of experimental and clinical literature on potentially promising effects of growth factors, anti-resorptive, and anabolic agents. The true clinical efficacy of these, however, is discussed controversially. Therefore, we aimed to critically examine the hypothesis that targeted adjuvant therapies have the potential to enhance bone regeneration in critical-size bone defects and under systemic conditions that impair bone healing. This first approach to the topic deals with small molecule drugs and compounds that influence the immune response and inflammatory processes. In particular, literature reporting on selective cyclooxygenase-2 inhibitors has been reviewed with respect to their local and systemic mode of action and to stimulate further research on bone healing under critical conditions.

Keywords: biomaterials; critical-size bone defects; cyclooxygenase-2; innate immunity; prostanoids; signaling; small molecules

  • Clinical Hemorheology and Microcirculation 73(2019), 381-408
    DOI: 10.3233/CH-199102

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29216
Publ.-Id: 29216


Experimental and computational studies of the influence of grain boundaries and temperature on the radiation-induced damage and hydrogen behavior in tungsten

Panizo-Laiz, M.; Díaz-Rodríguez, P.; Rivera, A.; Valles, G.; Martín-Bragado, I.; Perlado, J. M.; Munnik, F.; González-Arrabal, R.

We study the influence of grain boundaries on radiation-induced vacancies, as well as, on the hydrogen (H) behavior in tungsten (W) samples with different grain sizes in the temperature range from 300 K to 573 K, both experimentally and by computer simulations. For this purpose, coarse-grained and nanostructured W samples were sequentially irradiated with carbon (C) and H ions at energies of 665 keV and 170 keV, respectively. A first set of the implanted samples was annealed at 473 K and a second set at 573 K. Object kinetic Monte Carlo simulations were performed to account for experimental outcomes. Results show that the number of vacancies for nanostructured W is always larger than for single crystal W samples in the whole studied temperature range and that the number of vacancies is only reduced in samples with a large density of grain boundaries and at temperatures high enough to activate the vacancy motion (around 573 K). Results also indicate that the migration of H along vacancy free grain boundaries is more effective than along the bulk, and that the retained H is trapped in vacancies located within the grains. These results are used to explain the experimental outcomes.

Permalink: https://www.hzdr.de/publications/Publ-29215
Publ.-Id: 29215


Improvement of UniCAR T cell effectiveness against EGFR+ tumor cells by using different αEGFR targeting module formats

Jureczek, J.; Feldmann, A.; Albert, S.; Bergmann, R.; Berndt, N.; Arndt, C.; Koristka, S.; Bachmann, M.

Since epithelial growth factor receptor (EGFR) mutations or overexpression is linked with variety of malignancies, including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas as well as glioblastomas it is an attractive target for tailored treatment of solid cancer. Thus over the last twenty years many strategies targeting EGFR were developed and even clinically approved, including disrupting intracellular signalling involving tyrosine kinase inhibitors (TKIs) or the inhibition of ligand binding using therapeutic monoclonal antibodies like e.g. Cetuximab, Panitumumab or Necitumumab. Unfortunately, cancers treated with these targeted drugs commonly become resistant to them. These limitations justify the need of more efficient therapy options. As chimeric antigen receptor (CAR) engineered T cells highly effectively eliminate hematological malignancies already in the clinics, one idea is to redirect CAR T cells also against EGFR expressing solid cancers. However, CAR T cell therapy can lead to severe even life-threatening side effects and its effectiveness against solid tumors is still limited. Particular worrying is that EGFR is a widespread antigen commonly expressed also on healthy tissues bearing a high risk of severe on-target/off-tumor side effects due to EGFR-targeted therapies, which cannot be controlled in patients. In order to overcome these challenges our UniCAR technology might be an appropriate answer combining high anti-tumor effectiveness, tumor specificity, flexibility, and safety control mechanisms. In contrast to conventional CARs, UniCAR T cells are per se inert because UniCARs are directed against a small peptide epitope, which is not present on living cells. The redirection of UniCAR T cells to tumor cells occurs only in the presence of a tumor specific targeting module (TM). TMs, on one hand carry the specificity for a certain tumor antigen and on the other hand contain the UniCAR peptide epitope recognized by UniCARs mediating the cross-linkage of UniCAR T cells and antigen presenting tumor cells. As TMs have a very short half-life in vivo they can be used as a switch to control UniCAR T cell activity on demand in patients. In detail, UniCAR T cells are only switched on in the presence of antigen specific TMs realized by permanent TM infusion, but could be rapidly switched off when the application of the TM is stopped and the TM is eliminated. Meanwhile we successfully generated a series of different TMs against different tumor antigens and entities. Interestingly, TMs can be made of different molecules showing various structures and can flexible be exchanged in order to target any tumor antigen and overcome tumor escape variants. Commonly our TMs consist of a humanized single-chain variable fragment (scFv) derived from the variable heavy and light chain domains of a murine monoclonal antibody. In addition, we successfully generated TMs based on different monovalent and bivalent antibody derivatives, nanobodies derived from one variable camelid antibody domain, affibodies and even small peptide molecules.
Recently we demonstrated proof-of-concept for the redirection of UniCAR T cells to EGFR expressing tumor cells by a nanobody based αEGFR TM derived from the camelid αEGFR antibody 7C12. Considering that the affinity and anti-tumor efficiency of the eucaryotically expressed αEGFR nanobody based TM was limited, we therefore asked the question, whether we could further improve the therapeutic effect against EGFR positive tumor cells using the UniCAR technology. In order to answer this question, we generated a novel TM based on a scFv derived from the clinically used chimeric monoclonal antibody Cetuximab (IMC C-225). In detail, we designed a murine and humanized αEGFR scFv TM, successfully expressed them in mammalian cell lines and compared their functionality with the eucaryotic αEGFR nanobody-based TM in vitro and in vivo. In principle, we observed that both TM formats, the αEGFR nanobody as well as the scFv-based TM, are able to redirect UniCAR T cells eliminate EGFR-expressing tumor cells in an antigen-specific and TM-dependent manner. As both the murine and humanized scFv TM variants worked equally well, obviously humanization of the αEGFR scFv does not affect its functionality. However most interestingly, the tumor killing efficiency of the αEGFR scFv TM was significantly superior in comparison to the αEGFR nanobody based TM. Here, the half maximal effective TM concentration (EC50) value of scFv based TM was improved 1000-fold, from nM to pM range. Consequently, UniCAR T cells in combination with the scFv based TM efficiently eliminate also target cells expressing a low EGFR density level, while UniCAR T cells redirected by the nb based TM clearly attack only highly EGFR expressing tumor cells. Furthermore, the high anti-tumor efficacy of the αEGFR scFv TM over nb TM was manifested in experimental mice.
In summary, we successfully established different αEGFR TM formats that are able to redirect UniCAR T cells to eliminate EGFR-positive tumor cells. However, the analysed αEGFR TM formats differ with respect to their anti-tumor efficiency, which might decide whether UniCAR T cells attack target cells showing different EGFR density levels.

  • Poster
    Tumor immunology meets oncology (TIMO XV), 25.-27.04.2019, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29214
Publ.-Id: 29214


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