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41396 Publications

Towards standalone attitude estimation for instrumented flow followers

Buntkiel, L.; Reinecke, S.; Hampel, U.

A concept for 3D-motion tracking of instrumented flow-following sensor particles, equipped with a gyroscope, accelerometer, magnetometer and pressure sensor, has been developed. Consisting of an error state Kalman filter (ESKF) the algorithm can track the attitude of the sensor particle in relation to a reference coordinate system. In this short paper we investigated if the estimated attitude returns to the reference trajectory after experiencing motion similar to a motion that is expected to be found in the multidisperse fluid flows of a biogas fermenter or a waste water treatment basin. Results show the feasibility of the proposed method. However, the strategy of the measurement update in the ESKF needs improvement.

Keywords: error state kalman filter; motion tracking; fluid dynamics; sensor particle; soft sensor

  • Open Access Logo Contribution to proceedings
    Sensor and Measurement Science International 2021, 03.-06.05.2021, Online, Deutschland
    SMSI 2021 - Sensors and Instrumentation, Wunstorf: AMA Service GmbH, 978-3-9819376-4-0, 141-142
    DOI: 10.5162/SMSI2021/B6.3

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Permalink: https://www.hzdr.de/publications/Publ-32610
Publ.-Id: 32610


Sustainable Development Goal Conflicts in Re-Mining activities

Büttner, P.; Gutzmer, J.; Engelhardt, J.; Martin, M.

The Davidschacht tailings storage facility (TSF), operated from 1944 to 1964, represents one of the largest tailings dams in the historic Freiberg mining district. It contains a volume of 760,000 m³ of sulfidic flotation tailings, residues of former base metal and silver ore beneficiation. The tailings material still contains elevated concentrations of valuable elements such as zinc (0.4 wt.% on average), lead (0.2 wt.%) and copper (0.05 wt.%) as well as indium (10 ppm). The material has thus become the focus of efforts to enable eventual re-mining and recovery of valuable metals. However, such efforts have to take into account a number of important interests of the public. The first of these is the fact that the unrehabilitated tailings pose a significant risk to the environment. Cd (44 ppm on average) and As (0.6 wt.%) concentrations are particularly high – and have a marked influence on the adjacent water bodies, such as the Freiberg Mulde river. Curbing this influence has been the subject of multiple remediation studies, but pressure to act has risen recently due to increasing regulatory demands on the quality of surface water (EU Water Framework Directive of 2000). This is, in principle, very much in favour of re-mining the tailings in an effort to remove also hazardous components. Counteracting this reclamation scenario is the fact that the TSF is part of the UNESCO World Heritage Site “Erzgebirge / Krusne Hory” that was awarded in 2019. Another restriction pertains to the highly protected status of individual species (esp. sand lizard) settling on the TSF surface. This constellation obviously provides ample space for discussion as to how to deal with the tailings material contained in the Davidschacht TSF in future. Different sustainable development goals (SDG) have to be weighed against each other in order to find a holistic and sustainable. Airlift reactor-based bioleaching has been considered as an opportunity to maximize the sustainability of re-mining activities on the Davidschacht TSF. This innovative approach – and its circumstantial limitations – are documented in this contribution.

Keywords: Re-Mining; recomine; Tailing; Davidschacht; HIF; Resource Technology; Freiberg; Sustainable Development Goals; SDG; Bioleaching

Permalink: https://www.hzdr.de/publications/Publ-32609
Publ.-Id: 32609


Pathophysiological Changes in the Enteric Nervous System of Rotenone-Exposed Mice as Early Radiological Markers for Parkinson's Disease

Schaffernicht, G.; Shang, Q.; Stievenard, A.; Bötzel, K.; Dening, Y.; Kempe, R.; Toussaint, M.; Gündel, D.; Kranz, M.; Reichmann, H.; Vanbesien-Mailliot, C.; Brust, P.; Dieterich, M.; Funk, R. H. W.; Ravens, U.; Pan-Montojo, F.

Parkinson's disease (PD) is known to involve the peripheral nervous system (PNS) and the enteric nervous system (ENS). Functional changes in PNS and ENS appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients like constipation, that can precede the appearance of motor symptoms by years. Here we analyzed the effect of the pesticide rotenone, a mitochondrial Complex I inhibitor, on the function and neuronal composition of the ENS by measuring intestinal contractility in a tissue bath and by analyzing related protein expression. Our results show that rotenone changes the normal physiological response of the intestine to carbachol, dopamine and electric field stimulation (EFS). Changes in the reaction to EFS seem to be related to the reduction in the cholinergic input but also related to the noradrenergic input, as suggested by the non-adrenergic non-cholinergic (NANC) reaction to the EFS in rotenone-exposed mice. The magnitude and direction of these alterations varies between intestinal regions and exposure times and is associated with an early up-regulation of dopaminergic, cholinergic and adrenergic receptors and an irregular reduction in the amount of enteric neurons in rotenone-exposed mice. The early appearance of these alterations, that start occurring before the substantia nigra is affected in this mouse model, suggests that these alterations could be also observed in patients before the onset of motor symptoms and makes them ideal potential candidates to be used as radiological markers for the detection of Parkinson's disease in its early stages.

Keywords: Parkinson's disease; enteric nervous system; non-motor symptoms; pathophysiology; radiological marker

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Permalink: https://www.hzdr.de/publications/Publ-32608
Publ.-Id: 32608


Half-Auxeticity and Anisotropic Transport in Pd Decorated Two-Dimensional Boron Sheets

Ma, F.; Jiao, Y.; Wu, W.; Liu, Y.; Yang, S. A.; Heine, T.

Upon strain, most materials shrink normal to the direction of applied strain. Similarly, if a material is compressed, it will expand in the direction orthogonal to the pressure. Few materials, those of negative Poisson ratio, show the opposite behavior. Here, we show an unprecedented feature, a material that expands normal to the direction of stress, regardless if it is strained or compressed. Such behavior, namely, half-auxeticity, is demonstrated for a borophene sheet stabilized by decorating Pd atoms. We explore Pd-decorated borophene, identify three stable phases of which one has this peculiar property of half auxeticity. After carefully analyzing stability and mechanical and electronic properties we explore the origin of this very uncommon behavior and identify it as a structural feature that may also be employed to design further 2D nanomaterials.

Keywords: two-dimensional materials; auxetic materials; borophene; buckling structure; first-principle calculation

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Permalink: https://www.hzdr.de/publications/Publ-32607
Publ.-Id: 32607


Curvature-driven homogeneous Dzyaloshinskii-Moriya interaction and emergent weak ferromagnetism in anisotropic antiferromagnetic spin chains

Pylypovskyi, O.; Borysenko, Y. A.; Faßbender, J.; Sheka, D.; Makarov, D.

Chiral antiferromagnets are currently considered for a broad range of applications in spintronics, spin-orbitronics, and magnonics. In contrast to the established approach relying on materials screening, the anisotropic and chiral responses of low-dimensional antiferromagnets can be tailored relying on the geometrical curvature. Here, we consider an achiral, anisotropic antiferromagnetic spin chain and demonstrate that these systems possess geometry-driven effects stemming not only from the exchange interaction but also from the anisotropy. Peculiarly, the anisotropy-driven effects are complementary to the curvature effects stemming from the exchange interaction and rather strong as they are linear in curvature. These effects are responsible for the tilt of the equilibrium direction of vector order parameters and the appearance of the homogeneous Dzyaloshinskii–Moriya interaction. The latter is a source of the geometry-driven weak ferromagnetism emerging in curvilinear antiferromagnetic spin chains. Our findings provide a deeper fundamental insight into the physics of curvilinear antiferromagnets beyond the σ-model and offer an additional degree of freedom in the design of spintronic and magnonic devices.

Keywords: antiferromagnetism; curvilinear magnetism; Dzyaloshinskii-Moriya interaction; anisotropy

Permalink: https://www.hzdr.de/publications/Publ-32606
Publ.-Id: 32606


Diffusion of In Atoms in SiO2 Films Implanted with As+ Ions

Tyschenko, I. E.; Voelskow, M.; Si, Z.; Popov, V. P.

The diffusion of indium atoms in silicon-dioxide films previously implanted with arsenic ions with different energies is studied in relation to the temperature of postimplantation annealing. It is established that the diffusion properties of indium depend on the presence of arsenic atoms in the film and their energy. An increase in the As content in the region of the average projective range of In+ ions prevents the diffusion of In towards the SiO2 film surface at high annealing temperatures and stimulates the diffusion of In deep into the film in the form of a monovalent interstitial site. The experimentally observed effects are interpreted on the assumption of the formation of In–As pairs in neighboring substitutional positions in the SiO2 matrix.

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Permalink: https://www.hzdr.de/publications/Publ-32605
Publ.-Id: 32605


Spin polarization and magnetotransport properties of systematically disordered Fe60Al40 thin films

Borisov, K.; Ehrler, J.; Fowley, C.; Eggert, B.; Wende, H.; Cornelius, S.; Potzger, K.; Lindner, J.; Faßbender, J.; Bali, R.; Stamenov, P.

We investigate the evolution of spin polarization, spontaneous Hall angle (SHA), saturation magnetization and Curie temperature of B2-ordered Fe60Al40 thin films under varying antisite disorder, induced by Ne+-ion irradiation. The spin polarization increases monotonically as a function of ion fluence. A relatively high polarization of 46 % and the SHA of 3.1 % are achieved on 40 nm thick films irradiated with 2 ⋅ 1016 ions/cm2 at 30 keV. An interesting divergence in the trends of the magnetization and SHA is observed for low disorder concentrations. The high spin polarization and its broad tunability range make ion-irradiated Fe60Al40 a promising material for application in spin electronic devices.

Keywords: Spin polarization; Iron-Aluminium; Spintronics; Anomalous Hall Effect; Topological Hall effect; Irradiation effects; Thin films; Magnetometry; Andreev reflection

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Permalink: https://www.hzdr.de/publications/Publ-32604
Publ.-Id: 32604


Statistical position reconstruction for RPC-based thermal neutron detectors

Morozov, A.; Margato, L. M. S.; Solovov, V.; Blanco, A.; Saraiva, J.; Wilpert, T.; Zeitelhack, K.; Roemer, K.; Hall-Wilton, R.

Multilayer position-sensitive 10B-RPC thermal neutron detectors offer an attractive combination of
sub-millimeter spatial resolution and high (>50%) detection efficiency. Here we describe a new
position reconstruction method based on statistical approach. Using experimental data, we compare
performance of this method with that of the centroid reconstruction. Both methods results in a
similar image quality and spatial resolution. However, the statistical method allows to improve the
image quality at the detector periphery, offers more flexible (and more easily configurable) event
filtering and allows to develop automatic quality monitoring procedures for early detection of
situations when a change in the detector operation conditions starts to affect reconstruction quality.

Keywords: RPC; spatial resolution; neutron detection

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Permalink: https://www.hzdr.de/publications/Publ-32602
Publ.-Id: 32602


Software: Method for real-time controlled tissue theranostics using a single adaptable laser source

Podlipec, R.

Software support for real-time quantification of the treatment effect on the targeted tissue induced by a pulsed laser. Model functions used to quantify laser treatment effect are based on the calculated descriptor values from FLIM (Fluorescence lifetime imaging microscopy) and AF (autofluorescence) diagnostics images done on human retinal tissue using SPC Image software (B&H).

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Permalink: https://www.hzdr.de/publications/Publ-32601
Publ.-Id: 32601


ExPaNDS periodic progress report, September 2019 to February 2021

Servan, S.; Konrad, U.

This document presents the progress of the ExPaNDS (European Open Science Cloud Photon and Neutron Services) project after i ts first 18 months of activities, spanning from September 2019 to February 2021. It reproduces the explanation of the work carried out by the ExPaNDS partners as provided to the European Commission in the first periodic report of the project.

Keywords: EOSC; European Open Science Cloud; Photon Science; Neutron Science; Big Data; Information Technology; Forschungsdaten; Reasearch Data

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Permalink: https://www.hzdr.de/publications/Publ-32600
Publ.-Id: 32600


Dataset: Method for real-time controlled tissue theranostics using a single adaptable laser source

Podlipec, R.

Raw data of theranostics laser parameters and calculated descriptor values from FLIM (Fluorescence lifetime imaging microscopy) and AF (autofluorescence) retinal diagnostics for real-time quantification of the treatment effect.

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Permalink: https://www.hzdr.de/publications/Publ-32599
Publ.-Id: 32599


IV-data for Complex Metal Nanostructures with Programmable Shapes from Simple DNA Building Blocks

Jain, A.; Bayrak, T.; Erbe, A.

IV-curves measured on self-organized Au nanogaps. HSQ-wires are 10 nm gaps without DNA molecules, to characterise the insulating properties of HSQ resist. Au_nanowire are measurements of continuous Au nanowires. The temperature dependent measurements characterize self-organised Au contacts to DNA ensembles with 10 nm length

Keywords: Nanoelectronics; Self-Organisation; DNA Origami

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Permalink: https://www.hzdr.de/publications/Publ-32598
Publ.-Id: 32598


Method for controlled tissue theranostics using a single tunable laser source

Podlipec, R.; Mur, J.; Petelin, J.; Štrancar, J.; Petkovšek, R.

Tissue diseases and related disorders need to be first recognized using diagnostic methods and then later treated by therapeutic methods–a joint procedure called theranostics. One of the main challenges in the field of retinal therapies remains in the success of the treatment, typically improving the local metabolism, by sparing the surrounding tissue and with the immediate information of the laser effect. In our study, we present a concept for real-time controlled tissue theranostics on a proof-of-concept study capable of using a single tunable ps
laser source (in terms of irradiance, fluence, and repetition rate), done on ex-vivo human retinal pigment epithelium. We have found autofluorescence intensity and lifetime imaging diagnostics very promising for the recognition and quantification of laser effects ranging from selective non-destructive molecular tissue modification to complete tissue ablation. The main novelty of our work presents the developed algorithm for optimized theranostics based on the model function used to quantify laser-induced tissue changes through the diagnostics
descriptors, fluorescence lifetime and fluorescence intensity parameters. This approach, together with the operation of the single adaptable laser source, can serve as a new theranostics method in personalized medicine in the future not only limited to treat retinal diseases.

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Permalink: https://www.hzdr.de/publications/Publ-32597
Publ.-Id: 32597


A novel approach for the geospatial modelling and resource assessment of tailings storage facilities

Blannin, R.; Frenzel, M.; Gutzmer, J.

Tailings are the fine-grained residues of ore processing operations, typically stored in dedicated tailings storage facilities (TSFs). Despite being viewed as ‘waste’ materials, tailings can contain significant amounts of valuable metals which were not recovered by original processing techniques or were previously not of economic interest. Re-processing of tailings deposits for the recovery of remaining metals has the additional benefits of mitigation of environmental hazards posed by the TSFs, such as Acid Mine Drainage (AMD). The estimation of mineral resources requires the construction of accurate and reproducible geospatial models. However, the sedimentary-style deposition and subsequent weathering of tailings results in a complex internal structure which is challenging to model, with a laterally and vertically heterogeneous distribution of the minerals comprising the residues. The present study investigates a novel approach for the geospatial modelling of a TSF case study. The surface of the tailings deposit was densely sampled in order to assess the intrinsic horizontal variability. Drill core samples were taken from a depth of 1-3 m, on a 30 m grid and nested grids of 15 m and 7.5 m, with additional random and twin holes. The entire depth of the TSF was sampled in 2 m intervals with a total of 10 drill holes to assess vertical variability. All drill core samples were analysed with x-ray fluorescence spectrometry and inductively coupled plasma mass spectrometry. The compositional data was log-ratio-transformed and variography and subsequent ordinary kriging and co-kriging were performed on the surface samples. The variogram models obtained for the surface samples were then applied for kriging of the deeper layers. Historical photographs of the surface of the TSF were used to improve estimates with co-kriging for the corresponding layers. The entire data set will be used to determine the most efficient sampling approach for the resource estimation of TSFs.

  • Open Access Logo Contribution to proceedings
    European Geosciences Union General Assembly 2021, 26.-30.04.2021, Vienna, Austria
    DOI: 10.5194/egusphere-egu21-2992

Permalink: https://www.hzdr.de/publications/Publ-32595
Publ.-Id: 32595


[¹⁸F]JHU94620-d₈ – A new radiotracer for the noninvasive in vivo assessment of the CB₂ receptor in brain and peripheral tissues by PET

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

Introduction
An upregulation of cannabinoid receptors type 2 (₂) has been reported in association with inflammation processes, traumatic brain injury, neurodegeneration and cancer.[1] The activation of ₂ leads to an anti-inflammatory action. Therefore, the non-invasive assessment of the ₂ availability with PET can support decisions for ₂-directed therapies. Recently, we have reported on the development of the PET radiotracer [¹⁸F]JHU94620. This radioligand suffers from low metabolic stability in vivo.[2] Here, we describe the deuterated analogue [¹⁸F]JHU94620-d₈ and its biological evaluation.
Methods
The precursor for radiofluorination was obtained by coupling 4,5-dimethylthiazol-ylidene-2,2,3,3-tetramethylcyclopropane-1-carboxamide with 1,4-butandiol-1,1,2,2,3,3,4,4-d₈ bis(4-methylbenzenesulfonate) and radiofluorinated in the presence of the Kryptand K2.2.2. and K2CO3. The fraction of radiometabolites after injection of 27 to 50 MBq i.v. (AM ≈ 150 GBq/µmol) was quantified in mice plasma and brain 30 min p.i. The ₂ binding affinity (KD) and specificity (Ki) of [¹⁸F]JHU94620-d₈ was determined in vitro. Additionally, PET studies (injection of 23 ± 5 MBq i.v.) were performed to evaluate the [¹⁸F]JHU94620-d₈ uptake into the spleen of adult healthy Wistar rats and in rats overexpressing the functional inactive h₂(D𔕐N) in the right striatum[3] (h₂-rs).
Results/Discussion
[¹⁸F]JHU94620-d₈ was obtained in 10% radiochemical yield and >99% radiochemical purity, showing an improved metabolic stability of the deuterated analogue (80% vs. 36% for [¹⁸F]JHU94620, determined in the brain 30 min p.i.). It revealed a KD on rat ₂ of 0.36 nM and on human ₂ of 2.72 nM, as well as a Ki(hCB1) > 1 µM and Ki(h₂) of 0.9 nM. PET studies revealed a ₂-specific uptake of [¹⁸F]JHU94620-d₈ into the rat spleen (AUC0-30min = 33 vs. 17 SUV × min after blocking with GW405833). In the h₂-rs rats we could show a reversible and target-specific uptake of [¹⁸F]JHU94620-d₈ with an SUVmean of 6.7 ± 0.3 from 6 to 60 min p.i. and an SUVr (right striatum-to-cerebellum) of 43 ± 7 at 60 min p.i.
Conclusions
[¹⁸F]JHU94620-d₈ is a new PET tracer with improved metabolic stability as compared with the non-deuterated version, thus indicating an excellent ability to image the ₂ receptors in vivo.
Acknowledgement
This research was funded by Deutsche Forschungsgemeinschaft (DFG), grant number MO2677/4-1
Disclosure
A German patent application was filed Nr. 10 2020118 255.4
References
[1] Stasiulewicz, A., Znajdek, K., et al. 2020, ‘A Guide to Targeting the Endocannabinoid System in Drug Design’, IJMS, 2020, 21, 2778; doi:10.3390/ijms21082778
[2] Moldovan, R.-P., Deuther-Conrad, W., et al., 2015, ‘¹⁸F-JHU94620, a high affinity PET radioligand for imaging of cannabinoid subtype 2 receptors (₂R)’, J. Nucl. Med., 56, 1048
[3] Attili, B., Celen, S., et al., 2019, ‘Preclinical evaluation of [¹⁸F]MA3: a ₂ receptor agonist radiotracer for PET’, Br. J. Pharmacol., 176, 1481-1491

Keywords: PET; cannabinoid receptor 2; CB2

  • Poster
    EMIM2021, 24.-27.08.2021, Göttingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32588
Publ.-Id: 32588


Investigation of the radioactive inventory in the reactor pressure vessel of a nuclear power plant - a key for efficient nuclear waste disposal

Yassin, G.; Barkleit, A.; Brendler, V.

One of the most important activities after the decommissioning process of the nuclear power plant NPP is the determination of the neutron activated radionuclides RNs in the construction material of the reactor. Our work is mainly focused on the dismantled units of reactor pressure vessel RPV of Greifswald NPP. For this aim, both nondestructive and destructive methods were employed. Firstly, surface analysis methods based on scanning electron microscopy / energy dispersive X-ray spectroscopy SEM / EDX were performed, in order to understand the impact of the neutron fluencies on the RPV steel shielding material during the long-term operation. Furthermore, gamma spectrometry measurements were done for the analysis of the activity of the gamma emitting RN of Co-60 in the decommissioned RPV units. On the other hand, the determination of the long lived beta emitting RNs such as C-14 was determined by employing a commercial sample oxidizer, followed by liquid scintillation counting LSC measurements. Radiochemical procedure including precipitation, anion exchange chromatography and extraction steps was developed for the separation and purification of Ni-63 and Fe-55 prior to their activity determination.

  • Open Access Logo Contribution to proceedings
    9. RCA Workshop, 08.-09.06.2021, Dresden, Deutschland
    Proceedings of the 9. RCA Workshop
  • Poster
    9. RCA Workshop, 08.-09.06.2021, online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-32587
Publ.-Id: 32587


Grobstruktursimulation blasenbehafteter Strömungen mittels eines hybriden Mehrphasenmodells

Meller, R.

Kurzfassung

In einer Vielzahl industrieller Prozesse spielen Strömungen mit verschiedenen gasförmigen und flüssigen Phasen eine wichtige Rolle. Die Phasengrenzflächen bilden sehr große Strukturen aus, wie z. B. eine freie Wasseroberfläche. Gleichzeitig können kleine, s. g. disperse Strukturen wie Gasbläschen auftreten. Um auch komplexe Prozesse zu simulieren ohne die Art der Strömung im Vorhinein zu kennen, werden unterschiedliche Methoden zur numerischen Beschreibung der verschiedenen Strömungstypen miteinander kombiniert. In der vorliegenden Arbeit wird die Euler-Euler-Methode für disperse Strukturen mit der algebraischen Volume-Of-Fluid-Methode für großskalige Phasengrenzflächen kombiniert. Das auf diese Weise formulierte hybride Mehrphasenmodell wird im Mehr-Fluid-Modell für eine beliebige Anzahl von Phasen formuliert, d. h. für jede vorhandene Phase gelten individuelle Erhaltungsgleichungen für Masse und Impuls. Für disperse Strömungen werden Formulierungen aus der Literatur für den Strömungswiderstand und die virtuelle Masse von Gasblasen genutzt, um den Impulsaustausch zwischen den verschiedenen Phasen zu beschreiben. Für großskalige Phasengrenzflächen wird das Widerstandsmodell von Štrubelj und Tiselj (2011) verwendet, mit dessen Hilfe die Impulserhaltungsgleichungen der individuellen Phasen stark aneinander gekoppelt werden. Zur Beschreibung des Platzens von Gasbläschen an einer freien Oberfläche wird eine neue Formulierung des Phasentransfers eingeführt, womit disperses in kontinuierliches Gas überführt wird.
Für die numerische Lösung des resultierenden Gleichungssystems wird die kompakte Impulsinterpolation von Cubero et al. (2014) genutzt. Die starke Kopplung der phasen-spezifischen Gleichungen für den Impulserhalt erfordert besondere numerische Maßnahmen, um das gesamte Gleichungssystem effizient zu lösen. Dazu wird die Methode der partiellen Eliminierung von Spalding (1981) durch eine Summenformulierung zur näherungsweise Auflösung dieser Kopplung auf das Mehr-Fluid-Modell erweitert. Anhand von zwei- und dreidimensionalen Fällen von aufsteigenden einzelnen Gasblasen wird nachgewiesen, dass das hybride Modell das Verhalten des Ein-Fluid-Modells zur Beschreibung großskaliger Phasengrenzflächen beschreiben kann. Darüber hinaus wird die Funktionsweise der Methode demonstriert, die Interaktion zwischen kleinen Gasbläschen und großskaliger Phasengrenzflächen zu beschreiben. Dies schließt den Phasentransfer von dispersem zu kontinuierlichem Gas ein.
In der Realität sind viele Strömungen turbulent und analog zu den Phasengrenzflächen sind die turbulenten Wirbel typischerweise von sehr verschiedenen Längenskalen. Ein möglicher Weg, solche Probleme numerisch zu beschreiben, ist die Grobstruktursimulation (engl. large-eddy simulation). Dazu werden die Erhaltungsgleichungen räumlich tiefpass-gefiltert. Dadurch entstehen im hiesigen Mehr-Fluid-Modell fünf ungeschlossene Feinstrukturterme, zu denen die Terme der konvektiven Feinstrukturspannungen und der Feinstruktur-Oberflächenspannung gehören. Für die Abschätzung dieser beiden Terme werden unterschiedliche Modelle genutzt. Bei manchen dieser Modelle wird die Struktur der Phasengrenzfläche direkt berücksichtigt. Der Einfluss dieser Modelle auf die Interaktion zwischen der Turbulenz und der Phasengrenzfläche wird anhand von Testfällen einzelner aufsteigender Gasblasen a posteriori untersucht.

Abstract

Flows of gaseous and liquid phases play an important role in numerous industrial processes. The interface, which is the contact surface between different immiscible phases, may form large structures, e.g., a free water surface. At the same time small, so-called disperse structures such as micro gas bubbles may appear.In order to numerically describe such complex processes without knowing the type of flow in advance, different methods for the numerical description of different kinds of flows are combined with each other. In the present work the Euler-Euler method is applied for disperse structures and the algebraic volume-of-fluid method is used to describe large scale interfaces. The resulting hybrid multiphase model is formulated in the context of the multi-fluid model for an arbitrary number of phases, i.e., for each phase present individual conservation equations are considered for mass and momentum. This requires the definition of model forces to express the momentum transfer between different phases. For disperse flows appropriate formulations for drag and virtual mass of gas bubbles from the literature are employed. For large scale interfaces the drag model of Štrubelj and Tiselj (2011) is used, which strongly couples the momentum equations of the individual phases together. In order to describe the process of gas bubbles bursting at a free surface a new phase transfer formulation is introduced, such that disperse gas can be turned into continuous one.
The compact momentum interpolation according to Cubero et al. (2014) is utilized for the numerical solution of the resulting system of equations. The strong coupling of phase specific momentum conservation equations requires special treatment to allow the system of equations to be numerically solved in an efficient way. Therefore, the partial elimination algorithm of Spalding (1981) is expanded to the multi-field model via a sum formulation with the goal of an approximate resolution of phase coupling. The functionality of the hybrid method to reproduce the behaviour of the one-fluid model for the description of large scale interfaces is proven with several two- and three-dimensional test cases considering individual rising gas bubbles. Furthermore, the method's ability to predict interactions of small gas bubbles and large scale interfaces is demonstrated, which includes the phase transfer from disperse to continuous gas.
In reality many flows are turbulent and the according eddies are typically of widely varying length scales, just as it is the case for interfacial structures. Large-eddy simulation is a common approach to describe such problems numerically. Therefore, the conservation equations are spatially low-pass filtered, which leads to five unclosed sub-grid scale terms in the case of the presented multi-fluid model. Two of them are the convective sub-grid stress and the sub-grid surface tension term, which are modelled via several individual formulations taking the interface into account. The model influence on the interaction between turbulence and interface is assessed a posteriori considering single rising gas bubbles.

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  • Doctoral thesis
    Universität der Bundeswehr München, 2021
    Mentor: Prof. Dr.-Ing. habil. Markus Klein
    183 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32586
Publ.-Id: 32586


Classification and resolution adaptive drag modelling of gas-liquid interfaces with a multifield two-fluid model

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

Reliable techniques for the numerical simulation of gas-liquid flows at industrial scales are of great interest for safety analysis and efficiency optimisation, e.g. in nuclear power or metal processing industries. This type of simulation is hard to carry out due to the immense range of scales, which is spanned by interfacial and turbulent structures. For this purpose, hybrid morphology-adaptive numerical frameworks are being developed in the recent years, combining different well established numerical methods for individual flow regimes. The present work follows the approach of Meller et al. (Int J Numer Meth Fluids. 2021; 93: 748-773), who utilise the Euler-Euler approach to statistically describe multiphase structures in dispersed flow regimes, such as bubbly flows, as a basis. At the same time, regimes with resolved gas-liquid interfaces, such as large rising gas bubbles or horizontal interfaces in stratified flows, are captured by means of a Volume-of-Fluid-like method (Tekavčič et al., Nucl Eng Des. 2021; 379: 111223). A fully morphology-adaptive numerical framework needs to comprise transitions between the aforementioned regimes. Hence, the limits of both underlying basic numerical approaches need to be pushed towards and beyond an overlapping region of grid resolution with adequate predictive power, such that the whole spectrum of length scales is covered, forming the basis of morphology transitions.
For this purpose, the present work focuses on the extension of the Volume-of-Fluid methodology towards reliable resolved simulations of gas-liquid interfaces with very coarse grid resolutions. By means of the underlying two-fluid model, an interfacial slip velocity in the interface region becomes generally possible and can be chosen physically motivated. The flow in the vicinity of the interface needs to be classified. For this purpose, the latter is categorised to be of shear type, stagnant type or in between the two. Furthermore, a dimensionless grid spacing is evaluated based on the shear stress across the interface, similarly to the y+ value for the cell thickness of wall-bounded flows. Besides that, interface curvature is considered in relation to grid spacing. From these information, a degree of under-resolution of the interface is determined, which subsequently serves as a criterion for the drag modelling framework. On this basis, interfacial drag coupling is manipulated, such that interfacial slip can take place in the direction tangential to the interface, whenever required. While the interfacial drag formulation of Štrubelj and Tiselj (Int J Numer Methods Engng. 2011; 85: 575-590) is used in case of proper resolution, the closure formulations of Porombka and Höhne (Chem Eng Sci. 2015; 134: 348-459) or Marschall (Technical University of Munich, PhD Thesis, 2011) are considered for portions of the computational domain, where interfaces are classified to be under-resolved. The functionality of the described procedure is validated in cases of 2D and 3D rising gas bubbles, considering their shape and rising velocity. Moreover, gas and liquid velocity profiles of a stratified flow serve as a validation in an additional flow regime.
In this way, the numerical prediction of the gas-liquid interface is improved, pushing the limit of spatial resolutions with adequately reliable predictions towards extremely coarse computational grids, which is the prerequisite for efficient numerical simulations in large-scale applications.

  • Lecture (Conference)
    30th International Conference Nuclear Energy for New Europe, 06.-09.09.2021, Bled, Slowenien
  • Contribution to proceedings
    30th International Conference Nuclear Energy for New Europe, 06.-09.09.2021, Bled, Slovenija
    NENE 2021 conference proceedings, Ljubljana: Nuclear Society of Slovenia, 978-961-6207-51-5, 601.1-601.9

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Revealing inflammatory indications induced by titanium alloy wear debris in periprosthetic tissue by label-free correlative high-resolution ion, electron and optical micro-spectroscopy

Podlipec, R.; Punzón-Quijorna, E.; Pirker, L.; Kelemen, M.; Vavpetič, P.; Kavalar, R.; Hlawacek, G.; Štrancar, J.; Pelicon, P.; Fokter, S. K.

The metallic-associated adverse local tissue reactions (ALTR) and events accompanying worn-broken implant materials are still poorly understood on the subcellular and molecular lev-el. Current immunohistochemical techniques lack spatial resolution and chemical sensitivity to investigate causal relations between material and biological response on submicron or even na-noscale. In our study, new insights of titanium alloy debris-tissue interaction were revealed by the implementation of label-free high-resolution correlative microscopy approaches. Wear debris chemical and biological impact on the surrounding periprosthetic tissue obtained at revision surgery of a fractured titanium-alloy modular neck of a patient with hip osteoarthritis was suc-cessfully characterized by applying a combination of photon, electron and ion beam mi-cro-spectroscopy techniques, that includes hybrid optical fluorescence and reflectance mi-cro-spectroscopy, scanning electron microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), helium ion microscopy (HIM) and micro-particle-induced X-ray emission (micro-PIXE). Micron-sized wear debris was found as the main cause of the tissue oxidative stress exhibited through lipopigments accumulation in the nearby lysosomes. Furthermore, insights on extensive fretting and corrosion of the debris on nm scale and a quantitative measure of significant Al and V release into the tissue together with hydroxyapatite-like layer formation particularly bound to the regions with the highest Al content were revealed. The functional and structural information obtained at the molecular and subcellular level contributes to a better understanding of the mac-roscopic inflammatory processes observed on the tissue level. The established label-free correla-tive microscopy approach can efficiently be adopted to study any other clinical cases related to ALTR.

Keywords: Adverse Local Tissue Reactions (ALTR); periprosthetic tissue; Titanium alloy wear debris; correlative microscopy; confocal fluorescence and reflectance microscopy; FLIM; SEM-EDS; HIM; micro-PIXE; fHSI

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An efficient route to obtain (radio)fluorinated or (radio)iodinated 1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid (TIC(OH)) analogues as potential radiotracers for imaging of solid tumours

Maisonial-Besset, A.; Noelia Chao, M.; Debiton, E.; Canitrot, D.; Witkowski, T.; Degoul, F.; Tarrit, S.; Wenzel, B.; Miot-Noirault, E.; Serre, A.; Chezal, J.-M.

Introduction:

The use of radiolabelled amino acids (AAs) can provide high contrast SPECT/PET imaging of solid tumours. Among them, radiohalogenated tyrosine analogues ([123I]IMT, [18F]FDOPA, [123I]8-iodo-L-TIC(OH), etc) were developed mainly for imaging of neuroendocrine, prostatic and brain tumours. While radioiodinated derivatives are easily available via electrophilic aromatic substitutions with radioactive I+, radiofluorinated tyrosine analogues are difficult to obtain. Indeed, direct radiofluorination of electron-rich aromatic structures from [18F]F- remains a challenge as evidenced by the number of emerging methods recently published. The progresses reported for the radiosynthesis of the [18F]FDOPA illustrate the new opportunities to produce radiofluorinated arenes that could not be routinely accessed even a few years ago. Surprisingly, the [123I]8-iodo-L-TIC(OH), a promising radiotracer for SPECT imaging of prostatic tumours, did not benefit from these methodological advances and no corresponding radiofluorinated derivatives, which could allow the use of the TIC(OH) scaffold to PET imaging, were reported so far.

Materials and Methods:

A convergent synthetic route was developed to produce radioiodinated [125I]iodo-L-TIC(OH), and radiofluorinated [18F]fluoro-L-TIC(OH) tracers from common organotin intermediates, synthesized from iodinated analogues via palladium catalyzed I/SnMe3 exchange. The [125I]iodo-L-TIC(OH) radiotracers were obtained by electrophilic radioiododestannylation with [125I]I+, while the radiofluorinated analogues [18F]fluoro-L-TIC(OH) were produced from the organotin precursors by a copper-mediated aromatic radiofluorination using nucleophilic [18F]F-. For control of the purity, molar activity and enantiomeric excess, corresponding non-radiolabelled iodinated and fluorinated derivatives from the L and D series were synthesized.

Results:

Organotin compounds were radiolabelled using no-carrier-added [125I]NaI in the presence of Chloramine-T as mild oxidative agent at room temperature for 5 minutes with excellent labelling efficiencies (> 95%). After a two-step deprotection sequence and semipreparative RP-HPLC purification, [125I]iodo-L-TIC(OH) compounds were isolated with good radiochemical yields (RCY, 51-78%), high radiochemical purities (RCP, > 98%), molar activities (> 1.5-2.9 GBq/µmol) and enantiomeric excess (e.e., > 99%). [18F]fluoro-L-TIC(OH) derivatives were obtained by radiofluorination of organotin compounds in presence of tetrakis(pyridine)copper(II) triflate catalyst and nucleophilic [18F]F- at 110 °C for 10 minutes with high labelling efficiencies (54-92%). After purification by C18 solid phase extraction, deprotection under acidic conditions and semipreparative RP-HPLC purification, [18F]fluoro-L-TIC(OH) radiotracers were produced with good RCY (23-37% d.c.), high RCP (> 99%), molar activities (20-107 GBq/µmol) and e.e. (> 99%).

Conclusion:

A short and efficient synthetic pathway was developed to easily produce [125I]iodo-L-TIC(OH) and [18F]fluoro-L-TIC(OH) compounds from common organotin intermediates. In vitro studies on human cancer cell lines are ongoing to evaluate the potential of these radioligands to target AAs transporters.

  • Lecture (Conference) (Online presentation)
    34th Annual EANM Congress, 20.10.2021, virtuell, virtuell

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Publ.-Id: 32583


SEM-EDS datasets of titanium alloy wear debris in periprosthetic tissue

Podlipec, R.; Pirker, L.

SEM-EDS images and datasets of titanium alloy wear debris found in periprosthetic tissue obtained at revision surgery of a fractured titanium-alloy modular neck of a patient with hip osteoarthritis.

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Publ.-Id: 32582


Pump-probe data for "A Two‐Dimensional Polyimide‐Graphene Heterostructure with Ultra‐fast Interlayer Charge Transfer"

Li, J.; Pashkin, O.; Schneider, H.; Helm, M.

Pump-probe traces of transient absorption change for graphene, protonated 2DPI and protonated 2DPI on graphene

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Dynamics of Single Hydrogen Bubbles at Pt Microelectrodes in Microgravity

Bashkatov, A.; Yang, X.; Mutschke, G.; Fritzsche, B.; Hossain, S. S.; Eckert, K.

The dynamics of single hydrogen bubbles electrogenerated in acidic electrolytes at a Pt microelectrode under potentiostatic conditions is investigated in microgravity during parabolic flights. Three bubble evolution scenarios have been identified depending on the electric potential applied and the acid concentration. The dominant scenario, characterized by lateral detachment of the grown bubble, is studied in detail. For that purpose, the evolution of the bubble radius, electric current and bubble trajectories, as well as the bubble lifetime are comprehensively addressed for different potentials and electrolyte concentrations. We focus particularly on analyzing bubble-bubble coalescence events which are responsible for reversals of the direction of bubble motion. Finally, as parabolic flights also permit hypergravity conditions, a detailed comparison of the characteristic bubble phenomena at various levels of gravity is drawn.

Keywords: hydrogen; bubble; bubble dynamics; electrolysis; microgravity; microelectrode; force balance; parabolic flight; energy

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Publ.-Id: 32580


Solutions for the Ages – a Short Crash Course on Sustainable Software Development

Huste, T.

As part of the International Virtual Covid Challenge this talk gives an introduction on sustainable software development. Basing on the HIFIS course "Let's Make Your Script Ready for Publication" it details the steps necessary to build a sustainable software application that can easily be cited in a scientific publication.

Keywords: Software; Sustainability; Licensing; Open Source

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    International Virtual Covid Data Challenge 2021, 29.04.2021, Online, Deutschland
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    HIDA Annual Conference 2021, 30.11.2021, Berlin, Deutschland

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Publ.-Id: 32579


Data for: Sensitivity of PS/CoPd Janus particles to an external magnetic field

Eichler-Volf, A.; Alsaadawi, Y.; Vazquez Luna, F.; Khan, Q. A.; Stierle, S.; Xu, C.; Heigl, M.; Fekri, Z.; Zhou, S.; Zahn, P.; Albrecht, M.; Steinhart, M.; Erbe, A.

Movies show the 90-degrees rotation of PS/CoPd Janus particles in weak and strong magnetic fields

EDX/SEM/XRD data were used  to characterize the the CoPd particles

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HELIPORT (HELmholtz ScIentific Project WORkflow PlaTform)

Voigt, M.; Ufer, R.; Schacht, W.; Knodel, O.; Pape, D.; Lokamani, M.; Müller, S.; Gruber, T.; Kelling, J.

The guidance system HELIPORT aims to make the entire life cycle of a project at the HZDR searchable, accessible, complete and reusable according to the FAIR principles, mentioned below. In particular, our data management solution deals with the areas from the generation of the data to the publication of primary research data, the workflows carried out and the actual research results. For this purpose, a concept was developed which shows the various essential components and their connections. Descriptions of the individual components can be found in our RODARE publication: 10.14278/rodare.193

Keywords: metadata; HELIPORT; project lifecycle; FAIR; data managment

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Publ.-Id: 32577


Update on Radiation Studies for MU2E-II (and MU2E)

Müller, S.

Presentation at "Mu2e-II Snowmass22 Workshop", 28.04.2021

Keywords: FLUKA; MU2E

  • Lecture (Conference) (Online presentation)
    Mu2e-II Snowmass22 Workshop, 28.04.2021, FERMILAB (virtual), USA

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Publ.-Id: 32576


Data for: Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Seidel, P.

The uploaded XRF, OES, and LIBS data served as base for the publication by Seidel et al. 2021 in the journal Metals.

Keywords: Metals; Element analysis; XRF

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Demonstration of a compact plasma accelerator powered by laser-accelerated electron beams

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

Plasma wakefield accelerators are capable of sustaining gigavolt-per-centimeter accelerating
fields, surpassing the electric breakdown threshold in state-of-the-art accelerator modules by
3-4 orders of magnitude. Beam-driven wakefields offer particularly attractive conditions for
the generation and acceleration of high-quality beams. However, this scheme relies on
kilometer-scale accelerators. Here, we report on the demonstration of a millimeter-scale
plasma accelerator powered by laser-accelerated electron beams. We showcase the acceleration
of electron beams to 128 MeV, consistent with simulations exhibiting accelerating
gradients exceeding 100 GVm⁻¹. This miniaturized accelerator is further explored by
employing a controlled pair of drive and witness electron bunches, where a fraction of the
driver energy is transferred to the accelerated witness through the plasma. Such a hybrid
approach allows fundamental studies of beam-driven plasma accelerator concepts at widely
accessible high-power laser facilities. It is anticipated to provide compact sources of energetic
high-brightness electron beams for quality-demanding applications such as free-electron
lasers.

Keywords: Laser; Plasma; High energy electrons; X-Rays; Hybrid; High brightness

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Publ.-Id: 32574


Discovery and development of brain-penetrant 18F-labeled radioligands for neuroimaging of the sigma-2 receptors

Zhang, Y.; Wang, T.; Zhang, X.; Deuther-Conrad, W.; Fu, H.; Cui, M.; Zhang, J.; Brust, P.; Huang, Y.; Jia, H.

Six indole-based derivatives with a methoxy group at the indole ring were synthesized and evaluated as σ2 receptor ligands with nanomolar affinity (Ki (σ2) = 4.40-9.46 nM) and moderate subtype selectivity (Ki(σ2)/Ki(σ1) = 7-102). Radioligands 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-4-(2-[18F]fluoroethoxy)-1H-indole ([18F]3) and 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-5-(2-[18F]fluoroethoxy)-1H-indole ([18F]4) with high σ2 receptor affinity and subtype selectivity were synthesized through a direct SN2 displacement reaction, with radiochemical yields of 36-50% and 20-29%, radiochemical purity of >99%, and molar activities of 29-151 GBq/μmol and 55-72 GBq/μmol, respectively. Radioligand [18F]3 displayed high brain uptake, high brain-to-blood ratio and slow washout from the brain in male ICR mice. Administration of compound CM398 5 min prior to the radiotracer injection led to a significantly dose-dependent reduction of the brain accumulation (29-54%) and the brain-to-blood ratio (60-88%) at 30 min, indicating high specific binding of [18F]3 to the σ2 receptors in the brain. Ex vivo autoradiography in male ICR mice showed widely and heterogeneous distribution of [18F]3 in the brain. Small animal positron emission tomography imaging in rats confirmed different distribution and high specific binding of [18F]3 to σ2 receptors in rat brain. These findings warrant [18F]3 as a potential probe used for neuroimaging of the σ2 receptors in the brain.

Keywords: indole-based derivatives; σ2 receptor; fluorine-18; positron emission tomography; neuroimaging

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Publ.-Id: 32573


Large eddy simulation of the fluid–structure interaction in an abstracted aquatic canopy consisting of flexible blades

Tschisgale, S.; Löhrer, B.; Meller, R.; Fröhlich, J.

The paper addresses the fluid–structure interaction of submerged aquatic canopies, with particular focus on the complex interplay between coherent flow structures and the motion of vegetation elements. New insights into the underlying mechanisms are gained from a large eddy simulation of a submerged model canopy flow. The model canopy is made up of 800 highly flexible blades, each individually resolved by an immersed boundary method. The obtained high-resolution flow data reveal well-known coherent turbulent structures, including velocity streaks, Kelvin–Helmholtz (KH) vortices in the mixing layer as well as hairpin (HP) vortices in the outer flow region. The present results show that the interaction of these prototypical structures plays a key role creating unique turbulent features such as composite KH/HP vortices located between a high-speed and low-speed streak. Under the influence of these pronounced eddies, groups of blades respond by a strong local reconfiguration. Due to the convection of the coherent structures by the mean flow this causes an apparent wave-like motion of the canopy in streamwise direction, known as monami. A frequency analysis of this phenomenon shows that the vegetation responds almost passively, merely reflecting local flow conditions.

Keywords: flow–structure interactions; turbulent boundary layers

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Publ.-Id: 32572


An experimental investigation of light emission produced in the process of positronium formation in matter

Pietrow, M.; Zaleski, R.; Wagner, A.; Słomski, P.; Hirschmann, E.; Krause-Rehberg, R.; Liedke, M. O.; Butterling, M.; Weinberger, D.

The excess energy emitted during the positronium (Ps) formation in condensed matter may be released as light. Spectroscopic analysis of this light can be a new method of studying the electronic properties of materials. We report the first experimental attempt, according to our knowledge, to verify the existence of this emission process. As a result, the possibility of the emission of photons during Ps formation is within the experimental uncertainty in two different solids: an n-alkane and porous silica. However, it seems that the Ps formation on the alkane surface is not accompanied by the emission of photons with energy in the detection range of 1.6 – 3.8 eV. Various processes that can influence the energy of the photon emitted during the Ps formation are discussed to elucidate this issue. To aid future experiments, equations were developed to estimate the expected ratio of light emission events to annihilation events with the presence or absence of a photon during the Ps formation.

Keywords: positron annihilation lifetime spectroscopy; ELBE; MePS; EPOS; porosity; positronium

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A combination of advanced ion beam techniques reveals detailed physico-chemical properties of collected Saharan dust particles

Podlipec, R.; Munnik, F.; Klingner, N.; Hlawacek, G.; Rigler, M.; Heller, R.

The diverse physical and chemical properties of aerosols can cause a diverse impact on air quality, cloud nucleation, planetary radiation balance, public health, etc. Besides carbon particles from incomplete combustion, mineral particles from Saharan dust also present a significant contribution to the changes. It is estimated that 400 to 700 million tons of dust is transported from Sahara every year and with the particular wind directions it is carried to the Mediterranean or even to the north of Europe (Prospero, 1996). It has recently been shown that these particles induce serious problems for asthmatics (Gutierrez et al., 2020).
To understand the origin of pollution, necessary input information presents knowing the source apportionment of aerosols. Techniques such as non-destructive particle induced X-ray emission (PIXE) (Lucarelli et al., 2018) and energy dispersive x-ray spectroscopy (SEM-EDS) (Longoria-Rodríguez et al., 2021) have been successfully applied for chemical microanalysis of individual particles. However, knowing both the physical and chemical properties of particles towards nm scales, which would cover all aerosol sizes, is still a challenging task.
In our study, we have thus implemented the correlative approach using advanced ion beam techniques to study both physical and chemical properties of mineral particles from Saharan dust collected on quartz fiber filters on Cyprus Atmospheric Observatory (35.04oN,33.06 Eo; 535 m a.s.l.) using a combination of the virtual impactor and Aethalometer AE33 (Aerosol d.o.o.). We have implemented Helium Ion Microscopy (HIM), capable of sub-nm resolution imaging with high depth-of-field contrast, followed by micro-PIXE elemental analysis done on the same filter region. Information from backscattered high-energy ions was found particularly suitable for the registration and overlap of complementary images (Figure 1).
The study has revealed the size, shape, architecture, and surface topography of individual mineral particles on nm scale, while micro-PIXE their chemical composition. Additionally, HIM resolution and surface sensitivity enabled the detection and identification of individual black carbon (BC) soot attached to the surface of mineral particles. This information can have a significant impact on our understanding of the optical properties of mineral dust and its relevance to climate changes and health effects. This finding urges for further investigations where additional focused ion beam techniques and instrumentation have been implemented and will be discussed.

Keywords: HIM; micro-PIXE; Saharan dust; BC soot; correlative microscopy

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  • Lecture (Conference)
    European Aerosol Conference (EAC 2021), 30.08.-03.09.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-32570
Publ.-Id: 32570


Examining out-of-plane expansion of aggregate minerals in ion-irradiated concrete.

Roode-Gutzmer, Q. I.; Schymura, S.; Barkleit, A.; Stumpf, T.

1 Introduction

Concrete consists primarily of the mineral quartz as coarse and fine aggregates to a weight of 50-60 %. After quartz, feldspar is generally contained in a weight quantity of 15-20 %. Quartz in its pristine state is the least soluble of the silicates, thereby providing concrete the highest possible chemical durability. Biological shielding concrete that surrounds nuclear reactor pressure vessels are exposed to neutron radiation over decades during the course of nuclear power plant (NPP) operation. Minerals that are subjected to radiation, whether it be neutrons, electrons, or ions, of sufficient fluence and energy, accumulate defects in their crystal lattices. Once the threshold concentration of defects has been reached, structural relaxation occurs, which is a volume expansive amorphization process. Of all the minerals examined for neutron radiation-induced volume expansion, quartz exhibits the highest, followed by feldspar with volume expansion maxima respectively being 17.8 and 7.7 % [1]. Irradiated quartz accumulates E’-center defects [2], which are essentially unpaired sp³ dangling bonds and chemically reactive in aqueous solution, particularly at the higher pH values typically prevailing in pore water in concrete. It is the objective of this research to investigate the increased dissolution rates of irradiated silicate minerals, particularly in the context of the alkali-silica reaction (ASR), which is the most significant degradation reaction known to occur in concrete.

2 Experimental

Polished sections of concrete partially masked with aluminium foil were subjected to Si-ion irradiation with a fluence of 5·1014 ions/cm2 at 300 keV under vacuum without cooling. Changes in the vertical profiles of the irradiated samples were examined by Vertical Scanning Interferometry (VSI) and Confocal Microscopy.

3 Results

The minerals making up the aggregate were identified by µ Raman spectroscopy to be α-quartz and potassium feldspar (microcline: KAlSi₃O₈), the latter always intergrown with quartz. Quartz (grain A) exhibited an out-of-plane expansion of ~ 80 nm. No observable difference in average height between radiated and non-radiated areas on the aggregate containing feldspar (grain B) could be ascertained. This is mainly attributable to the surface roughness of feldspar (> 1 µm), which is essentially out of range for interferometric techniques. Furthermore, the penetration depths estimated in the Kinchin-Pease calculation by SRIM [3] for Si-ion irradiation at 300 keV are 429 and 604 nm, respectively for α-quartz and microcline. As the damage to the structure occurs initially at the point where the ion stops, structural relaxation in the feldspar begins much further away from the surface than it does for quartz. In our case, it is likely that the expansion in the feldspar has not detectably reached the surface.

Literature:

[1] Le Pape, Y., Alsaid, F., Alain, B. and Giorla, B.: J. Adv. Conc. Technol. (2018) 16, 191-209.
[2] Douillard, L. and Duraud, J. P.: Nucl. Instrum. Methods Phys. Res. (1996) B16, 191-209.
[3] Ziegler, J. F., Ziegler, M. D. and Biersack, J. P.: Nucl. Instrum. Methods Phys. Res. (2010) B268, 1818-1823. (http://www.SRIM.org)

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  • Lecture (Conference) (Online presentation)
    9. Radiochemischer Analytik Workshop, 08.-09.06.2021, Rossendorf, Germany

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Publ.-Id: 32569


An updated status and trends in actinide metal-organic frameworks (An-MOFs): from synthesis to application

Lyu, K.; Fichter, S.; Gu, M.; März, J.; Schmidt, M.

Actinide metal-organic frameworks (An-MOFs) consisting of actinide nodes and organic linkers represent an underexplored category of coordination polymers due to challenges in their synthetic and characterization. The unparalleled coordination chemistry of actinide elements confers a huge opportunity to explore the rational design, chemical reactivity, and versatile properties of An-MOFs as one of the most intriguing class of metal-organic frameworks (MOFs). Significant advances in this “juvenile” MOF research field have been witnessed in recent years and progress in the An-MOFs area since 2003 has been reviewed from the aspects of the synthesis, structure, and applications. The preparative handling and synthetic strategies implemented in constructing An-MOFs are illustrated. Their structure motifs are then classified and expounded by actinide building blocks and organic linkers. The modularity, topology, and porosity of An-MOFs are specified to highlight a great potential to tune their electronic structures and ensuing properties. Ultimately, applications of An-MOFs as
selective adsorbents, heterogenous catalysts, luminescent sensors, conducting, and semiconducting materials, and nuclear targets are underlined. This updated review is envisaged to guide in-depth investigation of largely elusive transuranium MOFs and the development of thorium or uranium-based MOFs towards practical applications.

Keywords: Actinide coordination chemistry; Metal-Organic Frameworks; Actinide MOF; Transuranium elements; Uranium and Thorium; Properties and Applications

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Modulation of γ-secretase activity by a carborane-based flurbiprofen analogue

Saretz, S.; Basset, G.; Useini, L.; Laube, M.; Pietzsch, J.; Draca, D.; Maksimović-Ivanić, D.; Trambauer, J.; Steiner, H.; Hey-Hawkins, E.

All over the world, societies are facing rapidly aging populations combined with a growing num-ber of patients suffering from Alzheimer’s disease (AD). One focus in pharmaceutical research to address this issue is on the reduction of the longer amyloid-β (Aβ) fragments in brain by modula-tion of γ-secretase, a membrane-bound protease. R-Flurbiprofen (tarenflurbil) was studied in this regard, but failed to show significant improvement in AD patients in a phase 3 clinical trial. This was mainly attributed to its low ability to cross the blood-brain barrier (BBB). We here present the synthesis and in vitro evaluation of a racemic meta-carborane analogue of flurbiprofen. By intro-ducing the carborane moiety, the hydrophobicity could be shifted into a more favourable range for the penetration of the blood-brain barrier, evident by a logD7.4 value of 2.0. Furthermore, our analogue retained γ-secretase modulator activity in comparison to racemic flurbiprofen in a cell-based assay. These findings demonstrate the potential of carboranes as phenyl mimetics also in AD research.

Keywords: Alzheimer; Carborane; Flurbiprofen; γ-Secretase modulator (GSM); Small molecule; Amyloid-β (Aβ) peptide; Phenyl mimetic

Permalink: https://www.hzdr.de/publications/Publ-32567
Publ.-Id: 32567


A Fluorometric Investigation of a Peptide-assisted Interaction between Composite Magnetic Beads and Phosphors for the Recycling of Rare Earth Elements

Hinman, N. R.

The recovery of rare earth elements through recycling of end-of-life electronics has become a goal of increasing importance as this helps create a more sustainable economy. Nevertheless, the recycling rates are still low. Rare earth elements could potentially be recovered from phosphors in end-of-life compact fluorescent lamps. In this thesis, LAP-specific peptides were immobilized on composite magnetic beads and these were brought in contact with LAP to see how much LAP interacts with the magnetic beads. LAP is an inorganic phosphor particle that emits green light when exposed to ultraviolet radiation. To be able to interpret the binding experiments, the fluorescent spectra of five different phosphors were measured and a simple quantification method was developed. In addition to this, the ratio of elements present in five different phosphors was investigated. This thesis has provided several insights into the fluorometric properties of suspended phosphors, single or in mixture, and into the effect of media on binding experiments. These insights can help in future work e.g. to be able to adapt the binding experiments for a mixture of phosphors. Furthermore, the proof-of-concept for binding experiments developed in this thesis could easily be applied for the investigation of other peptides phosphors as well.

Keywords: Phosphor; Compact Fluorescent Lamps; Lamp Powder; Fluorescence; Rare Earth Element

  • Bachelor thesis
    Hochschule Bonn-Rhein-Sieg, 2021
    Mentor: Dr. Ulf Ritgen
    68 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32566
Publ.-Id: 32566


Spin-wave frequency combs

Hula, T.; Schultheiß, K.; Trindade Goncalves, F. J.; Körber, L.; Bejarano, M.; Copus, M.; Flacke, L.; Liensberger, L.; Buzdakov, A.; Kakay, A.; Weiler, M.; Camley, R.; Faßbender, J.; Schultheiß, H.

We experimentally demonstrate the generation of spin-wave frequency combs based on the non-
linear interaction of propagating spin waves in a microstructured waveguide. By means of time- and space-resolved Brillouin light scattering spectroscopy, we show that the simultaneous excita- tion of spin waves with different frequencies leads to a cascade of four-magnon scattering events which ultimately results in well-defined frequency combs. Their spectral weight can be tuned by the choice of amplitude and frequency of the input signals. Furthermore, we introduce a model for stimulated four-magnon scattering which describes the formation of spin-wave frequency combs in the frequency and time domain.
Frequency

Keywords: magnetism; magnetization dynamics; spin waves; magnons; spin dynamics; micromagnetic modeling; Brillouin light scattering; spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-32565
Publ.-Id: 32565


A novel and open-source illumination correction for hyperspectral digital outcrop models

T. Thiele, S.; Lorenz, S.; Kirsch, M.; Gloaguen, R.

The widespread application of drones and associated miniaturization of imaging sensors has led to an explosion of remote sensing applications with very high spatial and spectral resolutions. Three dimensional (3-D) ultra-high resolution digital outcrop models created using drones and oblique imagery from ground-based sensors are now commonly used in the academic and industrial sectors. While the generation of spatially accurate models has been greatly facilitated by the development of com- puter vision tools such as Structure from Motion, correction of spectral attributes to achieve material reflectance measurements remains challenging. Following the development of a topograph- ical correction toolbox (mephysto), we now propose a series of new tools that can leverage the detailed geometry captured by digital outcrop models to correct for illumination effects caused by oblique viewing angles and the interaction of light with complex 3-D surfaces. This open source code is integrated into hylite, a python toolbox for the full 3-D processing and fusion of digital outcrop models with hyperspectral imaging data. We validate the performance of our novel method using a case study at an open pit mine in Tharsis, Spain, and demonstrate the importance of accurate illumination corrections for quantitative spectral analyses. Significantly, we show that commonly applied spectral analysis techniques can yield erroneous results for data corrected using current state of the art approaches. Our proposed method ameliorates many of the issues with these established approaches.

Keywords: Digital outcrop models; Geology; Illumination correction; Hyperspectral imaging

Permalink: https://www.hzdr.de/publications/Publ-32564
Publ.-Id: 32564


Reactivation of magma pathways: Insights from field observations, geochronology, geomechanical tests and numerical models

Thiele, S. T.; Cruden, A. R.; Zhang, X.; Micklethwaite, S.; Matchan, E. L.

Field observations and unmanned aerial vehicle surveys from Caldera Taburiente (La Palma, Canary Islands, Spain) show that pre-existing dykes can capture and re-direct younger ones to form multiple dyke composites. Chill margins suggest that the older dykes were solidified and cooled when this occurred. In one multiple dyke example, an 40Ar/39Ar age difference of 200 kyr was determined between co-located dykes. Petrography and geomechanical measurements (ultrasonic pulse and Brazilian disc tests) show that a microscopic preferred alignment of plagioclase laths and sheet-like structures formed by non-randomly distributed vesicles give the solidified dykes anisotropic elastic moduli and fracture toughness. We hypothesise that this anisotropy led to the development of margin-parallel joints within the dykes, during subsequent volcanic loading. Finite element models also suggest that the elastic contrast between solidified dykes and their host rock elevated and re-oriented the stresses that governed subsequent dyke propagation. Thus, the margin-parallel joints, combined with local concentration and rotation of stresses, favoured the deflection of subsequent magma-filled fractures by up to 60° to form the multiple dykes. At the edifice scale, the capture and deflection of active intrusions by older ones could change the organisation of volcanic magma plumbing systems and cause unexpected propagation paths relative to the regional stress. We suggest that reactivation of older dykes by this mechanism gives the volcanic edifice a structural memory of past stress states, potentially encouraging the re-use of older vents and deflecting intrusions along volcanic rift zones or towards shallow magma reservoirs.

Keywords: multiple dyke; elastic anisotropy; fracture deflection; mechanical discontinuity; reactivation; Quaternary; basalt Ar-Ar dating; Canary Islands

Permalink: https://www.hzdr.de/publications/Publ-32563
Publ.-Id: 32563


Data: Finite-element dynamic-matrix approach for spin-wave dispersions in magnonic waveguides with arbitrary cross section

Körber, L.; Quasebarth, G.; Otto, A.; Kakay, A.

This repository contains data generated to showcase our developed micromagnetic method described in our paper "Finite-element dynamic-matrix approach for spin-wave dispersions in magnonic waveguides with arbitrary cross section". For each example in Section V, we provide

  • .clc and .spc files containing important material and experimental parameters
  • .geo files containing the sample geometry (gmsh files)
  • .csv files containing the dispersions calculated using our eigensolver 

     
  • only for example A: linescans of the mode profiles along the width of the waveguide
  • only for example B: .dat file of the obtained mumax dispersion

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Permalink: https://www.hzdr.de/publications/Publ-32562
Publ.-Id: 32562


Finite-element dynamic-matrix approach for spin-wave dispersions in magnonic waveguides with arbitrary cross section

Körber, L.; Quasebarth, G.; Otto, A.; Kakay, A.

We present a numerical approach to efficiently calculate spin-wave dispersions and spatial mode profiles in magnetic waveguides of arbitrarily shaped cross section with any non-collinear equilibrium magnetization which is translationally invariant along the waveguide. Our method is based on the propagating-wave dynamic-matrix approach by Henry et al. and extends it to arbitrary cross sections using a finite-element method. We solve the linearized equation of motion of the magnetization only in a single waveguide cross section which drastically reduces computational effort compared to common three-dimensional micromagnetic simulations. In order to numerically obtain the dipolar potential of individual spin-wave modes, we present a plane-wave version of the hybrid finite-element/boundary-element method by Frekdin and Koehler which, for the first time, we extend to a modified version of the Poisson equation. Our method is applied to several important examples of magnonic waveguides including systems with surface curvature, such as magnetic nanotubes, where the curvature leads to an asymmetric spin-wave dispersion. In all cases, the validity of our approach is confirmed by other methods. Our method is of particular interest for the study of curvature-induced or magnetochiral effects on spin-wave transport but also serves as an efficient tool to investigate standard magnonic problems.

Keywords: spin wave; eigensolver; micromagnetic simulation; dispersion; finite-element method; FEM

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Permalink: https://www.hzdr.de/publications/Publ-32561
Publ.-Id: 32561


Magneto-ionics in single-layer transition metal nitrides

de Rojas, J.; Salguero, J.; Ibrahim, F.; Chshiev, M.; Quintana, A.; Lopeandia, A.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Wagner, A.; Abad, L.; Costa-Krämer, J. L.; Menéndez, E.; Sort, J.

Magneto-ionics allows for tunable control of magnetism by voltage-driven transport of ions, traditionally oxygen or lithium, and, more recently, hydrogen, fluorine or nitrogen. Here, magneto-ionic effects in single-layer iron nitride films are demonstrated, and their performance is evaluated at room temperature and compared with previously studied cobalt nitrides. Iron nitrides require an increased activation energy and, under high bias, exhibit more modest rates of magneto-ionic motion than cobalt nitrides. Ab initio calculations reveal that, based on the atomic bonding strength, the critical field required to induce nitrogen-ion motion is higher in iron nitrides (≈ 6.6 V nm-1) than in cobalt nitrides (≈ 5.3 V nm-1). Nonetheless, under large bias (i.e., well above the magneto-ionic onset and, thus, when magneto-ionics is fully activated), iron nitride films exhibit enhanced coercivity and larger generated saturation magnetization, surpassing many of the features of cobalt nitrides. The microstructural effects responsible for these enhanced magneto-ionic effects are discussed. These results open up the potential integration of magneto-ionics in existing nitride semiconductor materials in view of new memory system architectures.

Keywords: FeN; magneto-ionics; positron annihilation spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-32560
Publ.-Id: 32560


Origin of the 30 T transition in CeRhIn5 in tilted magnetic fields

Mishra, S.; Gorbunov, D.; Campbell, D. J.; Leboeuf, D.; Hornung, J.; Klotz, J.; Zherlitsyn, S.; Harima, H.; Wosnitza, J.; Aoki, D.; McCollam, A.; Sheikin, I.

We present a comprehensive ultrasound study of the prototypical heavy-fermion material CeRhIn5, examining the origin of the enigmatic 30 T transition. For a field applied at 2° from the c axis, we observed two sharp anomalies in the sound velocity, at Bm ≈ 20 T and B ≈ 30 T, in all the symmetry-breaking ultrasound modes at low temperatures. The lower-field anomaly corresponds to the well-known first-order metamagnetic incommensurate-to-commensurate transition. The higher-field anomaly takes place at 30 T, where an electronic-nematic transition was previously suggested to occur. Both anomalies, observed only within the antiferromagnetic state, are of similar shape, but the corresponding changes of the ultrasound velocity have opposite signs. Based on our experimental results, we suggest that a field-induced magnetic transition from a commensurate to another incommensurate antiferromagnetic state occurs at B. With further increasing the field angle from the c axis, the anomaly at B slowly shifts to higher fields, broadens, and becomes smaller in magnitude. Traced up to 30° from the c axis, it is no longer observed at 40° below 36 T.

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Permalink: https://www.hzdr.de/publications/Publ-32559
Publ.-Id: 32559


Accelerator Programming Using Directives 7th International Workshop, WACCPD 2020, Virtual Event, November 20, 2020, Proceedings

Bhalachandra, S.; Wienke, S.; Chandrasekaran, S.; Juckeland, G.

This book constitutes the proceedings of the 7th International Workshop on Accelerator Programming Using Directives, WACCPD 2020, which took place on November 20, 2021. The workshop was initially planned to take place in Atlanta, GA, USA, and changed to an online format due to the COVID-19 pandemic.
WACCPD is one of the major forums for bringing together users, developers, and the software and tools community to share knowledge and experiences when programming emerging complex parallel computing systems. The 5 papers presented in this volume were carefully reviewed and selected from 7 submissions. They were organized in topical sections named: OpenMP; OpenACC; and Domain-specific Solvers.

Keywords: Compilers; computer networks; CUDA; distributed computer systems; embedded systems; Graphics Processing Unit (GPU); Hardware accelerators; Heterogeneous (hybrid) systems; Massively parallel algorithms; Massively parallel and high-performance simulations

Permalink: https://www.hzdr.de/publications/Publ-32558
Publ.-Id: 32558


Development of [18F]LU14 for PET Imaging of Cannabinoid Receptor Type 2 in the Brain

Teodoro, R.; Gündel, D.; Ueberham, L.; Toussaint, M.; Bormans, G.; Brust, P.; Deuther-Conrad, W.; Moldovan, R.-P.

Cannabinoid receptors represent an attractive therapeutic target for neurodegenerative diseases and cancer. Aiming at a positron emission tomography (PET) radiotracer to monitor neuronal changes of receptor density and/or occupancy during the CB2R-tailored therapy, we developed here cis-[18F]1-(4-fluorobutyl-N-((1s,4s)-4-methylcyclohexyl)-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamide ([18F]LU14) starting from the corresponding mesylate precursor. First biological evalua-tion revealed that [18F]LU14 is a highly affine CB2R radioligand with optimal metabolic stability (>80% intact tracer in brain at 30 min p.i.). Its further evaluation in a well-established rat model of CB2R overexpression by PET demonstrated its ability to selectively image the CB2R in the brain and its potential as tracer to further investigate diseased related CB2R alterations.

Keywords: Cannabinoid receptor type 2; naphtyrid-2-one; binding affinity; radiochemistry; fluorine-18 labeling; brain; positron emission tomography (PET)

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Permalink: https://www.hzdr.de/publications/Publ-32557
Publ.-Id: 32557


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

Matschiavelli, N.

Durch den Ausstieg Deutschlands aus der Kernkraft tritt immer mehr die dauerhafte und sichere Lagerung der noch hoch-radioaktiven Brennelemente in den Fokus. Aber wie beeinflussen Mikroorganismen die Metalle und Gesteine, aus denen ein Endlager aufgebaut ist? Als Mikrobiologen/innen in der Abteilung für Biogeochemie zeigen wir dir, wie mit modernen biologischen Methoden diese Fragen beantwortet werden.

  • Lecture (others) (Online presentation)
    Gils`& Boys`day am HZDR, 22.04.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32556
Publ.-Id: 32556


Evaluation of a sensitive, reasonable, and fast detection method for ⁵⁵Fe in steel

Merchel, S.; Rugel, G.; Lachner, J.; Wallner, A.; Walther, D.; Ziegenrücker, R.

A pilot study to quantify ⁵⁵Fe in steel from a reactor vessel of a nuclear power plant by accelerator mass spectrometry (AMS) without any chemical sample preparation was validated by liquid scintillation counting (LSC) and AMS after radiochemical separation. AMS reaches an uncertainty <10% at the 1 kBq gFe -1 level within less than 10 min measuring time. The background was <3 Bq gFe -1, presently limited by the short measurement time. The new instrumental AMS method for analysing ⁵⁵Fe from neutron capture production is reasonable and fast compared to other analytical methods.

Keywords: Accelerator mass spectrometry; nuclear decommissioning; nuclear waste; ⁵⁵Fe; radiochemical separation

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Permalink: https://www.hzdr.de/publications/Publ-32555
Publ.-Id: 32555


Proton beam quality enhancement by spectral phase control of a PW-class laser system

Ziegler, T.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T. E.; Dover, N. P.; Garten, M.; Gaus, L.; Gebhardt, R.; Goethel, I.; Helbig, U.; Irman, A.; Kiriyama, H.; Kluge, T.; Kon, A.; Kraft, S.; Kroll, F.; Loeser, M.; Metzkes-Ng, J.; Obst-Huebl, L.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

This repository contains the experimental raw data, the analyzed data and corresponding scripts as well as figures for the "Proton beam quality enhancement by spectral phase control of a PW-class laser system" publication.

https://doi.org/10.1038/s41598-021-86547-x

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Permalink: https://www.hzdr.de/publications/Publ-32554
Publ.-Id: 32554


ExPaNDS Training Catalogue Demo

Knodel, O.

This entry contains a demo video introducing the ExPaNDS/PaNOSC training catalogue used as  PaN Training Portal developed by HZDR. The video is also part of the ExPaNDS WP5 Deliverable 5.4.

One of the goals of ExPaNDS (European Open Science Cloud (EOSC) Photon and Neutron Data Service) is to train research scientists to better use available computational RI infrastructures to address critical research questions. This requires access both to face-to-face training opportunities and to disparate training materials and resources, currently dispersed across Europe.

The ambitious ExPaNDS project itself is a collaboration between 10 national Photon and Neutron Research Infrastructures (PaN RIs) as well as EGI. The project aims to deliver standardised, interoperable, and integrated data sources and data analysis services for Photon and Neutron facilities. ExPaNDS collaborates with PaNOSC (Photon and Neutron Open Science Cloud). 

ExPaNDS WP5: Training activities through EOSC platforms will organise workshops and deliver training materials through the e-learning platforms made available on the EOSC.

Keywords: data management; training; ExPaNDS

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Permalink: https://www.hzdr.de/publications/Publ-32553
Publ.-Id: 32553


Thermocapillary Effects at Gas Bubbles Growing on Electrodes

Mutschke, G.; Hossain, S. S.; Bashkatov, A.; Yang, X.; Eckert, K.

The contribution summarizes recent progress obtained in our group when studying the dynamics of
hydrogen gas bubbles growing during electrolysis in an aqueous electrolyte. We find that thermocapillary
effects are important to be considered, which lead to characteristic vortical electrolyte flow close to the
bubble [1,2]. We further discuss the resulting force on the bubble and conclude on how the bubble
departure is affected at electrodes of different sizes [3]. This knowledge might contribute to advancing
the efficiency of electrolyzers.

References:

[1] X. Yang et al., Marangoni convection at electrogenerated hydrogen bubbles, Phys. Chem. Chem.
Phys. 20 (2018) 11542.
[2] J. Massing et al., Thermocapillary convection during hydrogen evolution at microelectrodes,
Electrochim. Acta 297 (2019) 929-940.
[3] S.S. Hossain et al., On the thermocapillary effect on gas bubbles growing on electrodes of different
sizes, Electrochim. Acta 353 (2020) 136461.

Keywords: electrolysis; water splitting; gas evolution; thermocapillary effect

  • Lecture (Conference) (Online presentation)
    29th Topical Meeting of the International Society of Electrochemistry, 19.-21.04.2021, Mikulov, Tschechische Republik
  • Poster
    International Congress of Theoretical and Applied Mechanics (ICTAM 2020+1), 26.08.2021, Milano, Italien, 22.-27.08.2021, Milano, Italien
  • Lecture (Conference) (Online presentation)
    72nd Annual Meeting of the International Society of Electrochemistry, 29.08.-03.09.2021, Jeju, Südkorea

Permalink: https://www.hzdr.de/publications/Publ-32552
Publ.-Id: 32552


Macro to generate muon (g-2) summary plot

Müller, S.

This macro gives the status of the muon (g-2) just after the FERMILAB seminar on April 7, 2021.

The theoretical values use the different contributions as given in the

[White Paper](https://arxiv.org/pdf/2006.04822.pdf) of the

[Theory Initiative](https://muon-gm2-theory.illinois.edu/). Since the leading

order hadronic contribution is dominating the uncertainty of the

theoretical values, several values for a$_\mu$ are plotted which use the

different evaluations for the leading order hadronic contribution given in

Table 4 of the White Paper as well as the White Paper average.

Keywords: ROOT; (g-2); Macro

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Permalink: https://www.hzdr.de/publications/Publ-32551
Publ.-Id: 32551


A Two‐Dimensional Polyimide‐Graphene Heterostructure with Ultra‐fast Interlayer Charge Transfer

Liu, K.; Li, J.; Qi, H.; Hambsch, M.; Rawle, J.; Romaní Vázquez, A.; Shaygan Nia, A.; Pashkin, O.; Schneider, H.; Polozij, M.; Heine, T.; Helm, M.; Mannsfeld, S. C. B.; Kaiser, U.; Dong, R.; Feng, X.

Two‐dimensional polymers (2DPs) are a class of atomically/molecularly thin crystalline organic 2D materials. They are intriguing candidates for the development of unprecedented organic‐inorganic 2D van der Waals heterostructures (vdWHs) with exotic physicochemical properties. In this work, we demonstrate the on‐water surface synthesis of large‐area (cm 2 ), monolayer 2D polyimide (2DPI) with 3.1‐nm lattice. Such 2DPI comprises metal‐free porphyrin and perylene units linked by imide bonds. We further achieve a scalable synthesis of 2DPI‐graphene (2DPI‐G) vdWHs via a face‐to‐face co‐assembly of graphene and 2DPI on the water surface. Remarkably, femtosecond transient absorption spectroscopy reveals an ultra‐fast interlayer charge transfer (~60 fs) in the resultant 2DPI‐G vdWH upon protonation by acid, which is equivalent to that of the fastest reports among inorganic 2D vdWHs. Such large interlayer electronic coupling is ascribed to the interlayer cation‐π interaction between 2DP and graphene. Our work opens opportunities to develop 2DP‐based vdWHs via the on‐water surface synthesis strategy and highlights the unique interface‐induced optoelectronic properties.

Keywords: 2D polymer; graphene; van der Waals heterostructure; transient absorption spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-32550
Publ.-Id: 32550


A tunable autocorrelator for pulse measurements at IR FEL-oscillator facilities

Cicek, E.; Seidel, W.; Ketenoglu, B.

Radiation characteristics of a Free-Electron Laser (FEL) such as pulse length, timestructure, intensity, bandwidth, wavelength, power, frequency, etc., which were measured on adiagnostics table, are thoroughly discussed. In this respect, pulse length measurements of an InfraredFEL (IR-FEL) beam are evaluated through an intensity autocorrelator, designed and installed as adiagnostics tool at the “Helmholtz-Zentrum Dresden-Rossendorf (HZDR)-Radiation Source ELBE”of Germany. In addition, the autocorrelator was designed as a unique, cost-effective, and in-housesetup. It operates within the wavelength range of 3–35 microns, using Cadmium-Telluride (CdTe)crystals in the Second Harmonic Generation (SHG) medium. The intensity autocorrelation curveswere obtained for the FEL beam with the wavelength of 26.2 microns, indicating an FWHM pulseduration ranging between 3.29–8.03 ps with different optical cavity detuning values. Furthermore,the pulse duration of Ti: sapphire laser beam is measured between 1–3 ps through the designedautocorrelator at the ELBE light source. On the other hand, the setup may pave the way for pulselength measurements of the Turkish infrared FEL-oscillator facility (TARLA) as well, which iscurrently under the hardware installation phase. Finally, it is elaborated in section 3 that the uniqueautocorrelator design fully meets all requirements for pulse length measurements of an infraredFEL source.Radiation characteristics of a Free-Electron Laser (FEL) such as pulse length, timestructure, intensity, bandwidth, wavelength, power, frequency, etc., which were measured on adiagnostics table, are thoroughly discussed. In this respect, pulse length measurements of an InfraredFEL (IR-FEL) beam are evaluated through an intensity autocorrelator, designed and installed as adiagnostics tool at the “Helmholtz-Zentrum Dresden-Rossendorf (HZDR)-Radiation Source ELBE”of Germany. In addition, the autocorrelator was designed as a unique, cost-effective, and in-housesetup. It operates within the wavelength range of 3–35 microns, using Cadmium-Telluride (CdTe)crystals in the Second Harmonic Generation (SHG) medium. The intensity autocorrelation curveswere obtained for the FEL beam with the wavelength of 26.2 microns, indicating an FWHM pulseduration ranging between 3.29–8.03 ps with different optical cavity detuning values. Furthermore,the pulse duration of Ti: sapphire laser beam is measured between 1–3 ps through the designedautocorrelator at the ELBE light source. On the other hand, the setup may pave the way for pulselength measurements of the Turkish infrared FEL-oscillator facility (TARLA) as well, which iscurrently under the hardware installation phase. Finally, it is elaborated in section 3 that the uniqueautocorrelator design fully meets all requirements for pulse length measurements of an infraredFEL source.

Keywords: Beam-line instrumentation (beam position and profile monitors; beam-intensity monitors; bunch lengt

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Permalink: https://www.hzdr.de/publications/Publ-32549
Publ.-Id: 32549


Ion Microprobe analysis of wear processes in tribological ta-C coatings.

Munnik, F.; Habenicht, C.; Lorenz, L.; Krause, M.

Solid lubricants are an active research topic due to many factors, an important one being the elimination of current liquid lubrication because of its environmental impact. The tribological behaviour of different solid lubricants depends on the gas en¬vironment while testing. The most often-used solid lubricant coating is MoS2. A newer one still under research is ta-C (hydrogen-free, tetra-edic, amorphous carbon) that behaves like a polar opposite to MoS2. ta-C relies on free hydrogen and hydroxide ions to passivate free bonds resulting from the wear testing.
In a first test, a ta-C coating has been subjected to tribological tests with counter bodies made of various materials. The aim is to study tribological surface changes like material loss of the coating or material transfer from the counter body, processes which aren’t fully understood yet. Both the wear tracks on the ta-C coating and the counter bodies have been subjected to Ion Beam Analysis using a high energy ion microprobe. Both PIXE (Particle Induced X-ray Emission) and RBS (Rutherford Backscattering Spectrometry) measurements have been performed using a 2 MeV He ion beam and a 3 MeV H ion beam. Results for the wear tracks obtained with a brass and a Al2O3 counter body are presented as well as results on the counter bodies themselves. The advantages and drawbacks of the results obtained with different ions and different methods are presented. These results show that it is important to combine the measurements in order to obtain a complete picture of the damage caused by the wear tests.

Keywords: Tribilogy; Ion beam analysis

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  • Lecture (Conference) (Online presentation)
    Ion beam workshop 2021 - virtual meeting, 24.-25.03.2021, online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32548
Publ.-Id: 32548


Terahertz-wave decoding of femtosecond extreme-ultraviolet light pulses

Ilyakov, I.; Agarwal, N.; Deinert, J.-C.; Liu, J.; Yaroslavtsev, A.; Foglia, L.; Kurdi, G.; Mincigrucci, R.; Principi, E.; Jakob, G.; Kläui, M.; Seifert, T.; Kampfrath, T.; Kovalev, S.; Carley, R.; Scherz, A.; Gensch, M.

In recent years, femtosecond extreme-ultraviolet (XUV) and X-ray pulses from free-electron lasers have developed into important probes to monitor processes and dynamics in matter on femtosecond-time and Angstroem-length-scales. With the rapid progress of versatile ultra-fast X-ray spectroscopy techniques and more sophisticated data-analysis tools, accurate single-pulse information on the arrival time, duration and shape of the probing X-ray and XUV pulses becomes essential. Here, we demonstrate for the first time that XUV pulses can be converted into terahertz electromagnetic pulses. We observe that the duration, arrival time and energy of each individual XUV pulse is encoded in the waveform of the associated terahertz pulses and can, thus, be readily deduced from single-shot terahertz time-domain detection.

Keywords: Terahertz; Extreme Ultraviolet; Pulse-resolved; ultrafast; terahertz tomography; electron bunch diagnostics

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Permalink: https://www.hzdr.de/publications/Publ-32547
Publ.-Id: 32547


Modelling on the very large-scale connectome

Ódor, G.; Gastner, M.; Kelling, J.; Deco, G.

In this review we discuss critical dynamics of simple nonequilibrium models on large connectomes, obtained by diffusion MRI, representing the white matter of the human brain. In the first chapter we overview graph theoretical and topological analysis of these networks, pointing out certain universality, which allows to select a representative one, the KKI-18, which has been used for dynamical simulation subsequently. The critical and sub-critical behavior of simple, two or three state threshold models is discussed with special emphasis of rare-region effects leading to robust Griffiths Phases (GP). Numerical results of synchronization phenomena, studied by the Kuramoto model, are also shown, leading to a continuous analog of GP, termed frustrated synchronization in Chimera states. The models presented here exhibit avalanche scaling behavior with exponents in agreement with brain experimental data if local homeostasis is provided.

Permalink: https://www.hzdr.de/publications/Publ-32546
Publ.-Id: 32546


The Helmholtz cloud services as well suited platform for sustainable OpenFOAM_RCS development

Schlegel, F.; Greenshields, C.; Huste, T.; Lehnigk, R.; Lucas, D.; Peltola, J.

The presentation gives a comprehensive overview about sustainable software development strategies for OpenFOAM_RCS and how this will be supported by the Helmholtz cloud services in the frame of HIFIS.

Keywords: OpenFOAM; HIFIS; Computational Fluid Dynamics; software development

  • Lecture (Conference) (Online presentation)
    32nd Meeting of German CFD Network of Competence, 16.-17.03.2021, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32544
Publ.-Id: 32544


Experimental electronic stopping cross section of tungsten for light ions in a large energy interval

Moro, M. V.; Wolf, P. M.; Bruckner, B.; Munnik, F.; Heller, R.; Bauer, P.; Primetzhofer, D.

Electronic stopping cross section of tungsten for light ions was experimentally measured in a wide energy interval (20 to 6000 keV for protons and 50 to 9000 keV for helium) in backscattering and transmission geometries. The measurements were carried out in three laboratories (Austria, Germany and Sweden) using five different set-ups, the stopping data deduced from different data sets showed excellent agreement amongst each other, with total uncertainty varying within 1.5–3.8% for protons and 2.2–5.5% for helium, averaged over the respective energy range of each data set. The final data is compared to available data and to widely adopted semi-empirical and theoretical approaches, and found to be in good agreement with most adopted models at energies around and above the stopping maximum. Most importantly, our results extend the energy regime towards lower energies, and are thus of high technological relevance, e.g., in fusion research. At these low energies, our findings also revealed that tungsten – featured with fully and partially occupied f- and d-subshells, respectively – can be modeled as an electron gas for the energy loss process.

Keywords: Stopping power; Tungsten; Free electron gas; Bragg peak; Protons; Helium; Fusion

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Permalink: https://www.hzdr.de/publications/Publ-32543
Publ.-Id: 32543


Data/Software for: Dynamics of mono- and poly-disperse two-dimensional foams flowing in an obstructed channel

Lecrivain, G.

This archive contains selected raw data and the original code described in the manuscript "Dynamics of mono- and poly-disperse two-dimensional foams flowing in an obstructed channel", submitted in 2020 to Journal of Fluid Mechanics by Thales Carl Lavoratti, Sascha Heitkam, Uwe Hampel, and Gregory Lecrivain. The archive contains the following data:

- C++ code used to simulate the foam dynamics and create the raw data (petsc.tar.gz)

- selected raw data in petsc format. The mono-disperse scenarios V125.tar.gz, V200.tar.gz, V250.tar.gz, V350.tar.gz correspond to the gas fractions \varepsilon = 0.44, 0.68, 0.83, and 0.99, respectively. The poly-disperse scenarios V125r.tar.gz, V200r.tar.gz, V250r.tar.gz, V350r.tar.gz correspond to the gas fractions 0.44, 0.69, 0.84, and 0.99, respectively

- bash and python scripts used to create bubble contours from the petsc raw data (scripts.tar.gz)

- extracted bubble contours (contours.tar.gz)

- python codes used to make figures and animations (figures.tar.gz)

- Mathematica notebook testing the wall potential f(\phi_w) = 0 (potential.nb)

- manuscript data (manuscript.tar.gz)

For further questions, feel free to contact me (g.lecrivain@hzdr.de).

Keywords: Flowing foam; Phase-field simulation; Obstructed channel

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Publ.-Id: 32542


X-ray and neutron radiography of optically opaque fluid flows: experiments with particle-laden liquid metals and liquid foams

Lappan, T.

Multi-phase flows of small solid particles and gas bubbles in optically opaque fluids play a key role in both mineral and metallurgical processing, which use the principle of froth flotation and bubble flotation, respectively. To gain visual insight into such particle-laden multi-phase flows, this dissertation investigates the application of radiographic techniques, employing both X-rays and neutron radiation. Lab-scale experiments are performed with model particles in liquid foams and liquid metals, focussing on the time-resolved measurement of the particles’ motion in the multi-phase flows, aiming for a sufficient contrast-to-noise ratio in the X-ray or neutron image sequences.

The model experiments in this dissertation demonstrate the capabilities of X-ray and neutron radiography to image multi-phase flow in particle-laden and optically opaque fluids, especially to measure the motions of small particles with high spatial and temporal resolution. X-ray radiography enables to track custom-tailored tracer particles acting as tools for experimental investigations of flow phenomena in three-dimensional liquid foams. Both radiographic techniques supplement each other for imaging measurements of multi-phase flows with gas bubbles and solid particles in liquid metals. However, to visualise smallest model particles in liquid metal flows, neutron radiography proves to be the more promising technique compared to X-ray radiography. All in all, this dissertation contributes to paving the way for systematic radiographic measurements and further studies of particle-laden flows in optically opaque fluids.

Keywords: X-ray radiography; neutron radiography; liquid metal; liquid foam; flotation

  • Doctoral thesis
    TU Dresden, 2021
    Mentor: Dr. Sven Eckert, Dr. Sascha Heitkam, Prof. Kerstin Eckert

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Publ.-Id: 32539


Speciation of Pd in minerals from Norilsk ores by X-ray absorption spectroscopy

Brovchenko, V. D.; Merkulova, M.; Sittner, J.; Renno, A. D.

Определены спектры рентгеновского поглощения (XANES) для Pd в пентландите, Pd в металлической форме (Pd фольга) и Pd в минералах платиновой группы, показывающие большие различия в форме всех спектров. Доказано, что палладий в пентландите не имеет ни металлической формы, ни микропримесей минералов платиновой группы, но входит в кристаллическую решетку пентландита. Энергетическое положение белой линии (3173.8 eV) спектра Pd в пентландите аналогично положению белой линии спектров Pd в минералах платиновой группы. Это свидетельствует о том, что палладий в пентландите имеет номинальное состояние окисления +2. Поэтому можно предположить, что палладий замещает атомы железа или никеля в кристаллической структуре пентландита.
X-ray absorption spectra (XANES) for Pd in pentlandite, Pd in metallic form (Pd foil) and Pd in platinum-group minerals were determined showing large differences in the shape of all spectra. It was proved that palladium in pentlandite is neither in its metal form nor in microinclusions of platinum-group minerals, but is included in the crystal lattice of pentlandite. Energy position of white line (3173.8 eV) of Pd spectrum in pentlandite is similar to the position of white line of Pd spectra in platinum group minerals. This indicates that palladium in pentlandite has a nominal oxidation state of +2. Therefore, we can assume that palladium replaces iron or nickel atoms in the crystal structure of pentlandite.

Keywords: Norilsk; X-Ray Absorption Spectroscopy; Palladium; Pentlandite

  • Open Access Logo Lecture (Conference)
    Металлогения древних и современных океанов – 2021. Сингенез, эпигенез, гипергенез Metallogeny of ancient and modern oceans - 2021. Syngenesis, epigenesis, hypergenesis, 26.-30.04.2021, Миасс - Miass, Russland

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Publ.-Id: 32538


Example Project Plan generated by HELIPORT

Voigt, M.; Knodel, O.

This dataset contains the metadata for an example project generated using the project export button in our prototype scientific project lifecycle and workflow management system HELIPORT (HELmholtz ScIentific Project WORkflow PlaTform). The metadata schema is still under development and this entry will be updated to reflect further developments.

Keywords: metadata; HELIPORT; project livecycle; FAIR

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Publ.-Id: 32537


Variable relative biological effectiveness (RBE) in proton therapy of benign brain tumors

Klünder, L.; Lühr, A.; Troost, E. G. C.; Liheng, T.; Krause, M.; Löck, S.; Eulitz, J.

Introduction
Currently, there is an intense debate on the need to consider a variable clinical relative biological effectiveness (RBE) in proton therapy. Here, a variable clinically derived RBE-model was applied in-silico to predict the risk for late radiation-induced brain injuries (RIBI) in benign brain tumor patients having undergone proton therapy.

Materials & Methods
In total, 23 patients with benign brain tumors of WHO grade I-II, who received (adjuvant) proton radio(chemo)therapy between 2015 and 2017, were analyzed. Dose and linear energy transfer distributions were retrospectively simulated and used to calculate variable RBE-weighted dose in brain tissue. The variable RBE-model was previously derived for RIBI observed after proton therapy in grade II-IV gliomas. RBE-weighted dose, dose-volume parameters and normal tissue complication probabilities (NTCP) were calculated in brain tissue within and outside the clinical target volume (CTV) using the variable RBE-model and the clinically applied RBE of 1.1, excluding brainstem, gross tumor volume and surgical cavity from analysis.

Results
The average difference in maximum RBE-weighted dose between the variable and constant RBE-model was 12 Gy(RBE) [range: 7.9-15 Gy(RBE)] and 14.8 Gy(RBE) [8.9-19.2 Gy(RBE)] within and outside the CTV. In the same regions, values of 9.2 Gy(RBE) [5.8-12.6 Gy(RBE)] and 1.0 Gy(RBE) [0.2-3.2 Gy(RBE)] were obtained for the difference of the mean dose. Using the variable RBE-model the cohort average D4ml (minimum dose to the hottest 4 ml) and NTCP increased by 10.8 Gy(RBE) [7.4-16.0 Gy(RBE)] and 25.4% [0.6-53.4%], respectively (figure 1).

Summary
A substantial increase in high dose and predicted RIBI risk was found in normal and normal-appearing brain tissue using the assumption of a variable RBE-model instead of a generic RBE of 1.1. After correlation of predicted with occurring RIBI on follow-up MRI scans, our results may help to verify and extend clinical RBE-models established for proton therapy of gliomas.

Keywords: Variable proton RBE; Radiation-induced brain injury; Benign brain tumors

  • Lecture (Conference) (Online presentation)
    Dreiländertagung der Medizinischen Physik, 19.-22.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32536
Publ.-Id: 32536


Agility of spin Hall nano-oscillators

Trindade Goncalves, F. J.; Hache, T.; Bejarano, M.; Hula, T.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

Data repository for manuscript submitted to Physical Review Applied: Agility of spin Hall nano-oscillators.

DATA fingerprint for resubmitted: md5:a9bbd503a5370963b835d3c40cdf8ba8
Ignore the older onesmd5:36e53eb278f8c3073a51de6c709f72c8   (Ignore md5:3e2ddf76473149ad1d58cf100f90321f , I am unable to remove it, it is just an incomplete submission)

Data organised on a figure by figure basis. The provided file- How to navigate the data- links all the data sets and data handling scripts utilised on each figure. Ipython notebook was used in the data handling and Omnigraffle was used to assemble the sub-figures and label the plots produced in via the Ipython notebooks. Data shown in the corresponding plots can be found in the .txt files with same labelling as figures.

Abstract. 

We investigate the temporal response of constriction-based spin Hall nano-oscillators driven by pulsed stimuli using time-resolved Brillouin light scattering microscopy. The growth rate of the magnetization auto-oscillations, enabled by spin Hall effect and spin orbit torque, is found to vary with the amplitude of the input voltage pulses, as well as the synchronization frequency set by an external microwave input. The combination of voltage and microwave pulses allows to generate auto-oscillation signals with multi-level amplitude and frequency in the time-domain. Our findings suggest that the lead time of processes such as synchronization and logic using spin Hall nano-oscillators can be reduced to the nanosecond time-scale.

Keywords: Spintronics; Magnons; Spin waves; Brillouin scattering & spectroscopy; Microwave techniques

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Publ.-Id: 32535


3D CT image

Da Assuncao Godinho, J. R.

3D image, experiment 2

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Publ.-Id: 32534


Dataset for: Chemical absorption measurements in a lab scale bubble column

Kipping, R.; Hampel, U.

This data set contains gas phase hydrodynamic data obtained from ultrafast X-ray tomography measurements in a bubble column. Global and local gas holdups, as well as bubble size distributions are given for I) non reactive conditions with nitrogen (gas) and sodium hydroxide solution (liquid) and II) reactive conditions with carbon dioxide (gas) and sodium hydroxide solution (liquid). Additionally the data set contains the corresponding consumption rates obtained from wire-mesh sensor measurements.

Furhter details on the experiments are explained in the corresponding journal paper.

Keywords: bubble columns; wire-mesh sensor; UFXCT

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Permalink: https://www.hzdr.de/publications/Publ-32533
Publ.-Id: 32533


Isolation, identification and selection of bacteria with the proof-of-concept for bioaugmentation of whitewater from wood-free paper mills

Verdel, N.; Rijavec, T.; Rybkin, I.; Erzin, A.; Velišček, Ž.; Pintar, A.; Lapanje, A.

In the wood-free paper industry, whitewater is usually a mixture of additives for paper production. We are currently lacking an efficient, cost-effective purification technology for their removal. In closed whitewater cycles the additives accumulate, causing adverse production problems, such as the formation of slime and pitch. The aim of our study was to find an effective bio-based strategy for whitewater treatment using a selection of indigenous bacterial isolates. We first obtained a large collection of bacterial isolates and then tested them individually for their ability to degrade the papermaking additives, i.e., carbohydrates, resin acids, alkyl ketene dimers, polyvinyl alcohol, latex, and azo and fluorescent dyes. Of the 318 bacterial isolates, we selected a consortium of four strains (Xanthomonadales bacterium sp. CST37-CF, Sphingomonas sp. BLA14-CF, Cellulosimicrobium sp. AKD4-BF and Aeromonas sp. RES19-BTP) that degrade the entire spectrum of tested additives. A proof-of-concept study on a pilot scale was then performed by immobilizing the artificial consortium of the four strains and inserting them into a 33-litre, tubular flow-through reactor with a retention time of <15 h. The consortium caused an 88% reduction in the COD of the whitewater, even after 21 days.

Keywords: Aeromonas; azo dye; bioaugmentation; Cellulosimicrobium; PCA; water treatment

Permalink: https://www.hzdr.de/publications/Publ-32532
Publ.-Id: 32532


Advancing laser plasma accelerators by means of femto-scale diagnostics for a pilot study of high dose rate in-vivo irradiation

Schramm, U.

Talk on Advancing laser plasma accelerators by means of femto-scale diagnostics for a pilot study of high dose rate in-vivo irradiation

Keywords: laser proton acceleration; high dose rate radiobiology

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  • Invited lecture (Conferences) (Online presentation)
    4th international symposium on high power laser science and engineering, HPLSE, 12.-15.04.2021, Suzhou, China

Permalink: https://www.hzdr.de/publications/Publ-32531
Publ.-Id: 32531


Development of fluorinated and methoxylated benzothiazole derivatives as highly potent and selective cannabinoid CB2 receptor ligands

Aly, M. W.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.; Abadi, A. H.; Moldovan, R.-P.; Osman, N. A.

Numerous studies have indicated the upregulation of the cannabinoid type 2 receptors (CB2 receptors) in neuroinflammation and cancer, and that their visualization with PET (Positron emission tomography) could provide a valuable diagnostic and/or therapy-monitoring tool in such disorders. However, the availability of reliable CB2-selective imaging probes is still lacking in clinical practice. Encouraged by promising CB2 affinity results obtained for a benzothiazole lead compound, 6a, further structural optimizations led to the development of a series of fluorinated and methoxylated benzothiazole derivatives, endowed with extremely high CB2 binding affinity and an exclusive selectivity to the CB2 receptor, along with structural sites suitable for radiolabeling. Compounds 20, 21, 24, 25, 29, 32 and 33 displayed subnanomolar CB2 Ki values (ranging from 0.16 nM to 0.68 nM) while lacked affinity to the CB1 receptor subtype. The fluorinated analogs, 21 and 29, were evaluated for their in vitro metabolic stability in mouse and human liver microsomes (MLM and HLM). Both 21 and 29 displayed an exceptionally high stability (98% and 91% intact compounds, respectively) after 60 min incubation with MLM.
Contrastingly, compound 29 revealed an almost 2-fold greater metabolic stability after incubation with HLM for 60 min. Taken together, our data represent remarkably potent and selective CB2 ligands as credible leads that can be further exploited for 18F- or 11C-radiolabeling and utilization as PET tracers.

Keywords: Benzothiazole; Cannabinoid receptor type 2; CB2 ligands; Fluorine; Metabolic studies; PET

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Permalink: https://www.hzdr.de/publications/Publ-32530
Publ.-Id: 32530


Data for: Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

Pawelke, J.; Brand, M.; Hans, S.; Hideghéty, K.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Szabo, E. R.; Beyreuther, E.

Primary data and data description to publication:

Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

Abstract:

Background and purpose
In consequence of a previous study, where no protecting proton Flash effect was found for zebrafish embryos, potential reasons and requirements for inducing a Flash effect should be investigated with the beam pulse structure and the partial oxygen pressure (pO2) as relevant parameters.
Materials and methods
The experiments were performed at the research electron accelerator ELBE, whose variable pulse structure enables dose delivery as electron Flash and quasi-continuously (reference). Zebrafish embryos were irradiated with ~26 Gy either continuously with a dose rate of ~6.7 Gy/min or in one 111 µs long pulse with a pulse dose rate of 109 Gy/s and a mean dose rate of 105 Gy/s, respectively. Using the OxyLite system to measure the pO2 a low- (pO2 ≤ 5 mmHg) and a high-pO2 group were defined on basis of the oxygen depletion kinetics in sealed embryo samples.
Results
A protective Flash effect was seen for most endpoints ranging from 4 % less reduction in embryo length to about 20 – 25 % less embryos with spinal curvature and pericardial edema, relative to reference irradiation. The reduction of pO2 below atmospheric levels (148 mmHg) resulted in higher protection, which was however more pronounced in the low-pO2 group.
Conclusion
The Flash experiment at ELBE showed that the zebrafish embryo model is appropriate for studying the radiobiological response of high dose rate irradiation. Pulse dose and pulse dose rate as important beam parameters were confirmed as well as the pivotal role of pO2 during irradiation.

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Publ.-Id: 32529


A Robust PtNi Nanoframe/N-Doped Graphene Aerogel Electrocatalyst with Both High Activity and Stability

Yang, J.; Hübner, R.; Zhang, J.; Wan, H.; Zheng, Y.; Wang, H.; Qi, H.; He, L.; Li, Y.; Aregahegn Dubale, A.; Sun, Y.; Liu, Y.; Peng, D.; Meng, Y.; Zheng, Z.; Rossmeisl, J.; Liu, W.

Insufficient catalytic activity and stability and high cost are the barriers for Pt-based electrocatalysts in wide practical applications. Herein, a hierarchically porous PtNi nanoframe/N-doped graphene aerogel (PtNiNF-NGA) electrocatalyst with outstanding performance toward methanol oxidation reaction (MOR) in acid electrolyte has been developed via facile tert-butanol-assisted structure reconfiguration. The ensemble of high-alloying-degree-modulated electronic
structure and correspondingly the optimum MOR reaction pathway, the structure superiorities of hierarchical porosity, thin edges, Pt-rich corners, and the anchoring effect of the NGA, endow the PtNiNF-NGA with both prominent electrocatalytic activity and stability. The mass and specific activity (1647 mAmgPt -1, 3.8 mAcm-2) of the PtNiNF-NGA are 5.8 and 7.8 times higher than those of commercial Pt/C. It exhibits exceptional stability under a 5-hour chronoamperometry test and 2200-cycle cyclic voltammetry scanning.

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Permalink: https://www.hzdr.de/publications/Publ-32527
Publ.-Id: 32527


60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

Wallner, A.; Froehlich, M. B.; Hotchkis, M. A. C.; Kinoshita, N.; Paul, M.; Martschini, M.; Pavetich, S.; Tims, S. G.; Kivel, N.; Schumann, D.; Honda, M.; Matsuzaki, H.; Yamagata, T.

Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust: 60Fe (half-life 2.6 million years, Myr), predominantly produced in massive stars and ejected in SN explosions; and 244Pu, (half-life 80.6 Myr) produced solely in r-process events. We detect two distinct influxes of 60Fe to Earth in the last 10 Myr and accompanying lower quantities of 244Pu. The 244Pu/60Fe influx ratios are similar for both events. The 244Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, implying some contribution from other sources.

Keywords: r process; Supernova; interstellar medium; accelerator mass spectrometry; deep-sea archive; 60Fe; 244Pu

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32525
Publ.-Id: 32525


Combining X-ray diffraction, X-ray absorption spectroscopy, and molecular dynamics simulations to probe metals in zeolites: the case of intergrown Cd2+-LEV/ERI.

Cametti, G.; Scheinost, A.; Churakov, S. V.

Despite cadmium being a toxic element for environmental and human health, it is widely used in industries for fabrication of nickel-cadmium batteries, as anticorrosive agent, color pigment, etc. The most common and effective techniques for Cd removal from wastewater include filtration, chemical precipitation, bio-remediation and ion exchange. Because of their microporous structure and extremely efficient cation exchange capacity, natural zeolites are good candidates for use as ionic filters. Moreover, heavy-metal exchanged zeolites show improved catalytic properties that can be exploited in post remediation processes. Therefore, the chemical reactivity and stability of heavy-metal enriched zeolite is of paramount importance. Additionally, the nature of the metal species and their interaction with the zeolite framework play a fundamental role. Nevertheless, the correct determination of the aforementioned aspects can be compromised by the high disorder of the extraframework species, making difficult an unequivocal interpretation of the coordination chemistry of the metal cations. In this respect, the combination of X-ray diffraction (XRD) based techniques together with X-ray absorption spectroscopy (XAS) represents a valid tool to probe the long and short-range order of the species of interest.
In this contribution, we used a complementary experimental and theoretical approach to investigate in detail the structure of two Cd2+ -exchanged zeolites, levyne (LEV) and erionite (ERI). These two minerals are classified as small-pore zeolites (pore size between 0.35 and 40 nm) and, due to their structural similarity, they are often found as intergrown phase in nature [4]. In this study, experimental data from single crystal XRD and XAFS were coupled with Molecular Dynamics (MD) simulations to determine the distribution and coordination chemistry of Cd2+ in the two framework types (LEV and ERI). Our results showed that in Cd-LEV, Cd2+ ions have a fairly ordered distribution, resembling that characteristic of the pristine material [5]. In contrast, a strong disorder of the extraframework species (Cd2+ and H2O) is detected in Cd-ERI pores, where the occupancy of the EF sites is lower than 20%. Such disorder was attributed to the presence of Cd+2(H2O)6 complexes, which are only partially coordinated to framework oxygen and, therefore, more mobile. To discriminate between the effect of thermal and structural disorder in the measured and theoretically calculated EXAFS spectra, we propose a theoretical approach based on a set of geometry optimizations performed starting from the uncorrelated atomic configuration of MD simulations. Moreover, based on EXAFS analysis, the formation of metallic Cd within the pores of both zeolites could be ruled out.
Finally, we present the effect of Cd2+ incorporation on the thermal stability of Cd-LEV. The structural changes were monitored in situ from 25 to 400°C by single crystal X-ray diffraction. Our results demonstrated that, even if Cd had little influence on the room temperature structure, the dehydration behaviour drastically changes compared to that of the pristine material (natural levyne-Ca). The most relevant differences can be summarized by: i) a stronger volume contraction of the unit-cell volume (8% and 5% for Cd-LEV and levyne-Ca, respectively) in the investigated temperature range, and ii) the lack, at high temperatures, of the phase transformation to levyne B’ topology, characteristic of natural levyne-Ca.

Keywords: zeolite; Cd; XRD; XAFS

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  • Lecture (Conference) (Online presentation)
    XXV General Assembly and Congress of the International Union of Crystallography - IUCr 2021, 14.-22.08.2021, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-32524
Publ.-Id: 32524


Metal-induced progressive alteration of conducting states in memristors for implementing an efficient analog memory: a DFT-supported experimental approach

Das, D.; Barman, A.; Sarkar, P. K.; Rajput, P.; Jha, S. N.; Hübner, R.; Kanjilal, D.; Johari, P.; Kanjilal, A.

Advancement of the memristor-based artificial synapse (AS) is urgently needed for rapid progress in neuromorphic devices. The precise structural and chemical engineering of metal oxide layers by metal dopants (Ni) is presented as an innovative way to set off a decent performance of the AS. An ON/OFF ratio of 103 as well as data retention and endurance capabilities of 104 s and 103 cycles, respectively, are achieved. With these properties, the symmetric alteration in conductance states, short-term plasticity (STP) and long-term plasticity (LTP) are realized within the same device, and compared with the reported values to establish its excellent cognitive behavioural ability. Our combined experimental and the DFT-based first-principles calculation results reveal that the rational designing of AS using metal cations (Ni) can promote an ultra-low-power of about 2.55 fJ per pulse (lower than human brain about 10 fJ per pulse) for STP, promising for next-generation smart memory devices. Here, Ni endorses strong electronic localization, which in turn familiarizes trap states within the forbidden energy gap and improves short-term memory loss. Further, it modifies the local electrostatic barriers to stimulate modulatory action (as commonly observed in the mammalian brain) for LTP. Overall, this work provides a novel pathway to overcome the technological bottleneck.

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Permalink: https://www.hzdr.de/publications/Publ-32523
Publ.-Id: 32523


Electric Quadrupolar Contributions in the Magnetic Phases of UNi4B

Yanagisawa, T.; Matsumori, H.; Saito, H.; Hidaka, H.; Amitsuka, H.; Nakamura, S.; Awaji, S.; Gorbunov, D.; Zherlitsyn, S.; Wosnitza, J.; Uhlirova, K.; Valiska, M.; Sechovsky, V.

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi4B. The transverse ultrasonic mode C66 shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to ∼0.33 K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that Γ6 (E2g) electric quadrupolar degrees of freedom in localized 5f2 (J = 4) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi4B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

Permalink: https://www.hzdr.de/publications/Publ-32522
Publ.-Id: 32522


Data for: Effective diffusivity prediction of radionuclides in clay formations using an integrated upscaling workflow

Yuan, T.; Fischer, C.

The effective diffusivity is a key parameter in the diffusive transport calculations, thus decisive for predicting the radionuclide migration in low-permeable clay-rich formations. Potential host rocks such as the Opalinus clay exhibit pore network heterogeneities, critically modified due to compositional variability in the sandy facies and owing to diagenetic minerals. Meaningful estimation of the effective diffusivity requires an understanding of transport mechanisms at the nanometer-scale as a starting point and a combination with upscaling strategies for considering compositional heterogeneities at the micrometer-scale.

In this study, we propose an upscaling workflow that integrates transport simulations at both the nanometer-scale and the micrometer-scale to predict the effective diffusivities of radionuclides in the sandy facies of the Opalinus clay. The respective synthetic digital rocks provide conceptually two types of materials at the pore scale, in which the pore space and pore network in the clay matrix at the nanometer scale and mineral complexity in shales at the micrometer scale are considered. The numerical approach using the introduced digital rocks is validated with published experimental data that confirm the general applicability of the models. Sensitivity studies reveal the increase of effective diffusivity of shales as a function of increased pore space, reduced tortuosity, and an increased sheet silicate concentration compared to other rock components. Thus, such spatial variabilities at the pore scale of more complex sedimentary rocks are now addressed in the proposed approach and available for studying heterogeneous diffusion patterns compared to commonly assumed homogeneous behavior. Finally, and as a starting point for further upscaling strategies, we investigate anisotropic diffusion by studying the effect of lamination of the shales towards enhanced predictability of radionuclide migration.

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Permalink: https://www.hzdr.de/publications/Publ-32519
Publ.-Id: 32519


Analysis of heterogeneity and anisotropy of diffusivity in the sandy facies of Opalinus Clay host rocks using multi-scale digital rock physics

Yuan, T.; Yang, Y.; Deissmann, G.; Fischer, C.

The effective diffusivity is a key parameter in numerical tools required for the simulation of radionuclide migration in low-permeable rocks. Potential host rocks for deep geological repositories for nuclear waste such as the Opalinus Clay (OPA) exhibit pore network heterogeneities at the nanometer to micrometer scale. In the sandy facies of OPA, this pore network is critically modified due to compositional variability and owing to diagenetic reaction products, e.g., carbonate minerals. Such spatial variability is responsible for heterogeneous and anisotropic diffusion patterns contrary to the commonly assumed homogeneous conditions in the shaly facies. At the continuum scale, the representative elementary volume (REV) is a fundamental parameter for the quantification of the effective diffusivity. Therefore, meaningful modeling of heterogeneous and anisotropic diffusion in the sandy facies of OPA at the continuum scale requires an accurate estimation of the REV.
Here, we first utilize digital rock physics and propose an upscaling workflow that integrates transport simulations at both the nanometer-scale and the micrometer-scale to estimate the effective diffusivity of radionuclides in the sandy facies of OPA. In the proposed upscaling workflow, the lattice Boltzmann method (LBM) is used to solve the Poisson-Nernst-Planck (PNP) equation at the nanometer-scale [1]. The nanometer-scale results are then used as input parameters in the micrometer-scale model for diffusive transport calculations. At the micrometer-scale, the three-dimensional (3D) diffusion-sorption equation is numerically solved by a previously developed numerical simulator [2]. The diffusivity is calculated using the proposed upscaling approach, which is validated with published experimental data that confirm the general applicability of the models. Next, we determine the REV for diffusivity by analyzing the calculated diffusivity of the selected regions of interest (ROIs) as a function of the length scale [3]. The determined REV provides critical insight into the heterogeneity and anisotropy of the diffusivity in the sandy facies of OPA, which contributes to enhanced predictability of radionuclide migration.

  • Lecture (Conference) (Online presentation)
    Goldschmidt 2021, 04.-09.07.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-32518
Publ.-Id: 32518


Range verification in proton therapy: Feasibility of CNN-based detection and classification of treatment deviations from realistic prompt-gamma-imaging data

Pietsch, J.; Khamfongkhruea, C.; Berthold, J.; Janssens, G.; Stützer, K.; Löck, S.; Richter, C.

Introduction
Within a clinical study, we investigate the potential benefit of prompt-gamma-imaging (PGI) based range verification in proton therapy. As the manual interpretation of detected spot-wise range-shift information is time-consuming and complex, we aim to automatically detect and classify treatment deviations from realistic PGI data using convolutional neural networks (CNNs).

Materials & Methods
For 12 head-and-neck cancer patients and an anthropomorphic head phantom, monitoring of single fields from pencil-beam-scanning plans with the IBA slit camera was considered. In total, 386 treatment deviations were simulated on planning and control CTs and manually classified into 7 classes: non-relevant changes (NRC) and relevant changes triggering treatment intervention due to range-prediction errors (±RPE), setup errors in beam direction (±SE), anatomical changes (AC), or a combination of such errors (CE). The spatial maps of filtered PGI-determined range deviations were converted to 16x16x16 voxel grids. Three complexity levels were investigated using 3D-CNNs [training cohort (n=9), test cohort (n=4), Fig.1]: (A) optimal PGI data, (B) realistic PGI data with simulated Poisson noise based on the locally delivered proton number, (C) realistic PGI data with additional positioning uncertainty of the slit camera.

Results
During validation on the independent test data, the 3D-CNNs achieved multi-class accuracies of 81%, 77%, 76% and binary accuracies of 97%, 95%, 93% for the respective complexity levels (A,B,C) (Fig.2). In the most realistic scenario (C), relevant treatment deviations were detected with 97% sensitivity and 82% specificity. Misclassifications of the AC class were caused by similar PGI characteristics of the CE class.

Conclusion
CNNs can reliably detect and classify relevant treatment deviations from realistically simulated PGI data. While validation on measured patient data is needed, our study highlights the potential of automated PGI interpretation, which is desired for broad clinical application and a prerequisite for including PGI in an automated feedback loop for online adaptation.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference) (Online presentation)
    Dreiländertagung der Medizinischen Physik 2021, 19.-21.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32517
Publ.-Id: 32517


Prompt-gamma-based verification in proton therapy: CNN-based classification of treatment deviations

Pietsch, J.; Khamfongkhruea, C.; Berthold, J.; Janssens, G.; Stützer, K.; Löck, S.; Richter, C.

Purpose & Objective
Prompt-gamma imaging (PGI) based range verification has been utilized in first pencil-beam scanning (PBS) proton therapy treatments and is under systematic investigation concerning its potential benefit in a clinical study at our institution. Manual interpretation of the detected spot-wise range shift information is time-consuming, highly complex, and therefore not feasible in a broad routine application. Here, we present an approach to automatically detect and classify treatment deviations in realistically simulated PGI data for head and neck cancer treatments using convolutional neural networks (CNNs).

Materials & Methods
For 12 patients and an anthropomorphic head phantom, PBS treatment plans were generated and one field per plan was assumed to be monitored with the IBA slit camera. In total, 386 scenarios resembling different relevant or non-relevant treatment deviations were simulated on planning and control CTs and manually classified into 7 classes: non-relevant changes (NRC) and relevant changes triggering treatment intervention due to range prediction errors (±RPE), setup errors in beam direction (±SE), anatomical changes (AC), or a combination of such errors (CE). After filtering of PBS spots with reliable PGI information, the 3D spatial maps of PGI-determined range deviations (reference vs. change scenario) were converted to 16x16x16 voxel grids. Three complexity levels of simulated PGI data were investigated: (A) optimal PGI data, (B) realistic PGI data with simulated Poisson noise based on the locally delivered proton number, (C) realistic PGI data with an additional positioning uncertainty of the slit camera following an experimentally determined distribution.
For each complexity level, 3D-CNNs (6 convolutional & 2 downsampling layers) were trained on a subset of 8 patients and the phantom dataset using patient-specific leave-one-out cross-validation and tested on an independent test cohort of 4 patients.

Results
On the test data, the CNN ensemble achieved an accuracy of 0.81, 0.77, and 0.76 for the complexity levels (A), (B), and (C), respectively. Similarly, for the task to solely differentiate relevant from non-relevant changes, the binary accuracy was 0.97, 0.95, and 0.93. The trained ensemble provided fast (<1 s) predictions and detected treatment deviations in the most realistic scenario (C) with a sensitivity of 0.97 and a specificity of 0.82. Misclassifications of the AC class were likely due to similar PGI characteristics to the CE class.

Conclusion
This study demonstrates that CNNs can reliably detect relevant changes in realistically simulated PGI data and classify most of the underlying sources of treatment deviations. While validation on measured patient data is needed, our study highlights the potential of a reliable, automatic interpretation of PGI data, which is highly desired for broad clinical application and a prerequisite for the inclusion of PGI in an automated feedback loop for online adaptation.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference)
    ESTRO 2021, 27.-31.08.2021, Madrid, Spanien
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Supplement, 134-136
    DOI: 10.1016/S0167-8140(21)06819-5

Permalink: https://www.hzdr.de/publications/Publ-32516
Publ.-Id: 32516


Synthesis of novel fluorinated xanthine derivatives with high adenosine A2B receptor binding affinity

Lindemann, M.; Dukic-Stefanovic, S.; Hinz, S.; Deuther-Conrad, W.; Teodoro, R.; Juhl, C.; Steinbach, J.; Brust, P.; Müller, C. E.; Wenzel, B.

The G protein-coupled adenosine A2B receptor is suggested to be involved in various patholog-ical processes accompanied by increased levels of adenosine as found in inflammation, hypoxia, and cancer. Therefore, the adenosine A2B receptor is currently in the focus as a novel target for cancer therapy as well as for noninvasive molecular imaging via positron emission tomography (PET). Aiming at the development of a radiotracer labeled with the PET radionuclide fluorine-18 for imaging the adenosine A2B receptor in brain tumors, one of the most potent and selective an-tagonists, the xanthine derivative PSB-603, was selected as a lead compound. As initial biodis-tribution studies in mice revealed a negligible brain uptake of [3H]PSB-603 (SUV3min: 0.2), struc-tural modifications were performed to optimize the physicochemical properties regarding blood-brain barrier penetration. Two novel fluorinated derivatives bearing a 2-fluoropyridine (7) and a 4-fluoropiperidine (8) moiety have been synthesized, and their affinities for the four adenosine receptor subtypes were determined in competition binding assays. Both compounds showed high affinity towards the adenosine A2B receptor (Ki (7) = 9.97 ± 0.86 nM; Ki (8) = 12.3 ± 3.6 nM) with moderate selectivities versus the other adenosine receptor subtypes.

Keywords: xanthine; adenosine A2B receptor; adenosine; PSB-603

Permalink: https://www.hzdr.de/publications/Publ-32515
Publ.-Id: 32515


Precise measurement of gas parameters in a realistic RPC configuration: the currently used R134a gas and a potential alternative eco-gas

Fan, X.; Naumann, L.; Siebold, M.; Löser, M.; Stach, D.; Kalipoliti, L.; Kämpfer, B.

In this work, we present a comprehensive method to measure the gas parameters, such as the effective Townsend coefficient and electron drift velocity in homogeneous high electric fields (up to 100 kV/cm}) at atmospheric pressure and room temperature. A pulsed laser facility with micro-meter spatial accuracy and picosecond pulse duration is used to ignite primary ionizations at specific positions in the gas gap of a Resistive Plate Chamber (RPC) detector prototype. The gas parameters are determined solely by the RPC signals. The main component of the current standard gas for RPC is Tetrafluoroethane (R134a) which has a high Global Warming Potential. Therefore, using Tetrafluoropropene (HFO-1234ze) is under research as an eco-friendly substance. We measure the parameters of these two types of working gases.It is the first direct measurement of the gas parameters of timing RPCs under working conditions. By comparison with existing data from other investigation points, we observe a dependence of gas parameters on the pressure.

Keywords: Resistive Plate Chambers; Townsend coefficient; Electron drift velocity; HFO

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Permalink: https://www.hzdr.de/publications/Publ-32514
Publ.-Id: 32514


Multi-channel detector module for multi-energy computed gamma ray tomography

Bieberle, A.; Berger, R.; Stave, P.; Hampel, U.

In this paper an enhanced signal processing electronics for an existing multi-channel detector module for gamma ray computed tomography is presented. The detector electronics is able to evaluate gamma photon energies by measuring pulse duration times, which makes it perfectly suitable for attenuation measurements with multi-energy and/or multiple isotopic sources.
The duration time of each voltage pulse generated by a gamma photon within the radiation detector is measured using a complex programmable logic device (CPLD). A sophisticated logic circuit for eight detector channels is designed to acquire the pulse duration time spectra in a total of 256 channels per detector channel. This paper introduces the basic concept, describes the general and the specific CPLD design, provides an analysis of the accuracy and presents measured pulse duration time spectra.

Keywords: gamma ray computed tomography; radiation detection; complex programmable logic device

Permalink: https://www.hzdr.de/publications/Publ-32513
Publ.-Id: 32513


Critical role of electrical resistivity in magnetoionics

de Rojas, J.; Salguero, J.; Quintana, A.; Lopeandia, A.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Abad, L.; Costa-Krämer, J. L.; Sort, J.; Menéndez, E.

The critical role of electrical resistivity in governing ion motion in magneto-ionic thin-film systems is demonstrated. A series of highly nanocrystalline cobalt-nitride (Co-N) thin films (85 nm thick) with similar composition but a broad range of electrical properties exhibit markedly different magneto-ionic behavior. Semiconducting, near stoichiometric films show the best performance, better than their metallic- and insulating- counterparts. Resistivity reflects the interplay between atomic bonding, carrier localization and structural defects, which in turn determines the strength and distribution of applied electric fields inside the actuated films. This fact, generally overlooked, reveals that resistivity is a good indicator of the potential of a system to exhibit optimal magneto-ionic effects, while also opening interesting challenges.

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Permalink: https://www.hzdr.de/publications/Publ-32512
Publ.-Id: 32512


Boundary conditions for the Neel order parameter in a chiral antiferromagnetic slab

Pylypovskyi, O.; Tomilo, A.; Sheka, D.; Faßbender, J.; Makarov, D.

Understanding of the interaction of antiferromagnetic solitons including domain walls and skyrmions with boundaries of chiral antiferromagnetic slabs is important for the design of prospective antiferromagnetic spintronic devices. Here, we derive the transition from spin lattice to micromagnetic nonlinear σ model with the corresponding boundary conditions for a chiral cubic G-type antiferromagnet and analyze the impact of the slab boundaries and antisymmetric exchange (Dzyaloshinskii-Moriya interaction) on the vector order parameter. We apply this model to evaluate modifications of antiferromagnetic domain walls and skyrmions upon interaction with boundaries for different strengths of the antisymmetric exchange. Due to the presence of the antisymmetric exchange, both types of antiferromagnetic solitons become broader when approaching the boundary and transform to a mixed Bloch-Néel structure. Both textures feel the boundary at the distance of about five magnetic lengths. In this respect, our model provides design rules for antiferromagnetic racetracks, which can support bulklike properties of solitons.

Keywords: antiferromagnetism; slab; Dzyaloshinskii-Moriya interaction; domain wall; skyrmion

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Permalink: https://www.hzdr.de/publications/Publ-32511
Publ.-Id: 32511


Effects of geometry on curvilinear antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Roessler, U. K.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets are technologically promising materials for spintronic and spinorbirtonic devices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2]. Here, we explore geometry-induced effects in curvilinear antiferromagnets. We demonstrate theoretically that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI [3]. The geometry-driven easy axis anisotropy determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve.

[1] V. Baltz et al., Rev. Mod. Phys. 90, 015005 (2018).
[2] R. Streubel et al., J. Phys. D.: Appl. Phys. 49, 363001 (2016).
[3] O. V. Pylypovskyi et al., Nano Lett. (2020) DOI: 10.1021/acs.nanolett.0c03246.

Keywords: spin chain; antiferromagnetism; Dzyaloshinskii-Moriya interaction; curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    APS March Meeting 2021, 15.-19.03.2021, Online, USA

Permalink: https://www.hzdr.de/publications/Publ-32510
Publ.-Id: 32510


Proton PBS delivery within the treatment volume of an in-beam MR scanner

Sepúlveda, C.; Gebauer, B.; Schneider, S.; Hoffmann, A. L.; Lühr, A.; Burigo, L.

Introduction: The magnetic fringe field of an in-beam MR scanner integrated with a proton pencil beam scanning (PBS) beamline needs to be taken into account for accurate dose delivery of IMPT plans. This work investigates corrections to proton pencil beams when delivered in the treatment volume of an in-beam MR imager.
Materials and Methods: Monte Carlo (MC) simulations using TOPAS version 3.5 were applied to model the PBS dose delivery to the treatment volume of an in-beam MR imager at the PBS beamline at OncoRay. A 3D map of the full magnetic fringe field of the 0.33 T (vertical field) open MR imager was mapped out and incorporated in the MC simulations. To estimate the distortion of the beam profile in the treatment volume, the delivery of a 10x10 cm2 spot pattern for beam energies of 100, 150 and 200 MeV was simulated in air at the MR isocenter positioned 57 cm downstream of the beam isocenter. The energy-dependent mean lateral deflection was used to correct the beam delivery by a rigid shift of the field.
Results: Lateral deflections of 32.2 mm (100 MeV), 25.6 mm (150 MeV) and 22.2 mm (200 MeV) were observed for all spots. When correcting for these deflections, the mean error in the spot positions were 0.9  0.2 mm (100 MeV), 0.5  0.6 mm (150 MeV) and 0.7  0.1 mm (200 MeV), with maximum differences of 2.0, 2.3 and 0.9 mm, respectively. No distortion of the spot pattern was found.
Conclusions: A submillimeter error in the spot position at the isocenter of the in-beam MR scanner can be achieved for a 10x10 cm2 field when applying energy-dependent corrections in the delivery of the spots. Ongoing research will consider larger fields sizes and corrections needed to account for the beam stopping in water.

Keywords: MRiPT

  • Lecture (Conference) (Online presentation)
    Joint Conference of the ÖGMP, DGMP and SGSMP Dreiländertagung der Medizinischen Physik, 19.-22.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32509
Publ.-Id: 32509


First steps towards dosimetric commissioning of an in-beam MR system for proton pencil beam scanning

Gebauer, B.; Sepúlveda, C.; Burigo, L.; Pawelke, J.; Bodenstein, E.; Schneider, S.; Hoffmann, A. L.; Lühr, A.

Introduction: A prototype system for MR‐integrated proton therapy (MRiPT) with an in-beam MR scanner is currently under investigation at our facility. The commissioning thereof requires an accurate beam model, a 3D map of the full static magnetic field (MF) of the MR scanner and consideration of their interaction. This work describes measurements of the proton beam, the MF and beam modeling performed to set up a proton beam model for the MRiPT prototype system.

Materials & Methods: Measurements of central proton beam spot sizes in air at 10 distances from the beam isocenter (between -15 and 54 cm) and integral depth-dose profiles (100 to 226.7 MeV) in water were obtained without MF using a scintillation detector and a water phantom with a Bragg peak chamber, respectively. A beam model was fitted to these measurements by utilizing an automated regularization-based optimization process. A 3D magnetic field map of the 0.33 T open MR scanner was acquired using spatially resolved Hall probe measurements.

Results: In the absence of the MF, the optimized beam model reproduced the measured beam spot sizes in air with an error <0.5 mm for 100 – 226.7 MeV and depth dose curves in water with an error <0.1 g/cm² for 100 – 226.7 MeV. The magnetic field measuring approach delivers reproducible results with high accuracy and an uncertainty <±5 mT.

Summary: A proton beam model for the MRiPT prototype system without MF was established and a high-precision method for mapping the 3D MF of the MR scanner was developed. The MF map and the beam model will be used to establish an experimental treatment planning system providing a correction algorithm accounting for the influence of the MF of the MR scanner on proton beams. Further investigations are necessary to validate the beam model in the presence of the MF.

Keywords: MRiPT

  • Lecture (Conference) (Online presentation)
    Joint Conference of the ÖGMP, DGMP and SGSMP Dreiländertagung der Medizinischen Physik, 19.-22.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32508
Publ.-Id: 32508


Data for: Bubble formation from a microscale submerged orifice- A numerical approach

Mohseni, E.

We developed a mechanistic model for calculation of bubble volume from orifices in the range from 0.03 mm to 0.193 mm under the constant gas flow conditions in a quiescent liquid. It is known that for such small orifices, the mechanism of bubble formation is highly dependent on the gas momentum force and the liquid inertia force. Accordingly, the model incorporates these forces to calculate the bubble volume in three consecutive stages. Moreover, the model includes the influence of the bubble base expansion and bubble rising induced liquid velocity on the formation of bubbles. Eventually the model is validated with own experimental data using air and deionized water. Experimental validation of the model confirms that the maximum deviation of the model is less than 10%.

Keywords: Bubble formation; Micro-scale orifice; Mechanistic model; Stainless steel orifice; Force balance

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Permalink: https://www.hzdr.de/publications/Publ-32507
Publ.-Id: 32507


Highly sensitive ²⁶Al measurements by Ion-Laser-InterAction Mass Spectrometry

Lachner, J.; Martschini, M.; Kalb, A.; Kern, M.; Marchhart, O.; Plasser, F.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The method of Ion-Laser InterAction Mass Spectrometry (ILIAMS) offers new options for the determination of ²⁶Al by Accelerator Mass Spectrometry (AMS) and improves the sensitivity and efficiency for the detection of this isotope in artificial and environmental samples. In ILIAMS, a laser is overlapped with the ion beam during its passage through a radiofrequency quadrupole ion cooler. Those ions with electron affinity lower than the energy of the photons are selectively neutralized in a photodetachment process. Because the electron affinity of MgO is lower than that of AlO, ILIAMS can suppress the isobar ²⁶Mg by 14 orders of magnitude. No further isobar suppression on the high-energy side of the spectrometer is necessary, so that the more prolific AlO⁻ beam can now also be used at facilities with terminal voltages < 5 MV. At the 3 MV Vienna Environmental Research Accelerator (VERA) routine ²⁶Al AMS measurements assisted by ILIAMS are performed utilizing AlO⁻ extracted from the ion source and charge states 2+ and 3+ for the Al ions after the accelerator on the high-energy side of the spectrometer. The most efficient generation of AlO- currents (in the range of several mA) is realized when mixing the Al₂O₃ sample material with Fe powder. Blank materials are measured down to ²⁶Al/²⁷Al ratios of 5*10⁻¹⁶. The efficiency relative to the use of Al⁻ extraction is improved typically by a factor 3-5 and thus the new method is useful for measurements with highest sensitivity and down to very low ²⁶Al/²⁷Al ratios.

Permalink: https://www.hzdr.de/publications/Publ-32506
Publ.-Id: 32506


Cisplatin - A more Efficient Drug in Combination with Radionuclides?

Reissig, F.; Runge, R.; Naumann, A.; Kotzerke, J.

The combination of conventional chemotherapeutic drugs with radionuclides or external radiation is discussed for a long period of time. The major advantage of a successful combination therapy is the reduction of severe side effects by decreasing the needed dose and simultaneously increasing therapeutic efficiency. In this study, pUC19 plasmid DNA was incubated with the cytostatic drug cisplatin and additionally irradiated with 99mTc, 188Re and 223Ra. DNA damages, such as single- and double strand breaks were determined by agarose gel electrophoresis. The threshold concentration value of cisplatin, which was tolerated by pUC19 plasmid DNA was determined to be 18-24 nM. Nevertheless, even at higher dose values (>100 Gy) and simultaneous incubation of cisplatin to 200 ng plasmid DNA, no significant increase in the number of induced single- and double-strand breaks was obtained, compared to the damage solely caused by the radionuclides. We thereby conclude that there is no direct dependence of the mechanism of strand break induction to the absence or presence of platinum atoms attached to the DNA. Reported increasing DNA damages in therapy approaches on a cellular level strongly depend on the study design and are mainly influenced by repair mechanisms in living cells. Nevertheless, the use of radioactive cisplatin, containing the Auger electron emitter 191Pt, 193mPt or 195mPt, is a bright prospect for future therapy by killing tumor cells combining two operating principles: a cytostatic drug and a radiopharmaceutical at the same time.

Keywords: Auger Therapy; Cisplatin; Chemotherapy; Radiotherapy

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Permalink: https://www.hzdr.de/publications/Publ-32504
Publ.-Id: 32504


A critical analysis of drag force modelling for disperse gas-liquid flow in a pipe with an obstacle

Tas-Köhler, S.; Liao, Y.; Hampel, U.

The accuracy of gas-liquid flow modelling strongly depends on an appropriate modelling of interfacial forces. Among those, the drag is dominating. Most drag models reported in the literature have been derived and validated for laminar or low-turbulence flow conditions only. In this study, we evaluated different drag models from the literature for a highly turbulent gas-liquid flow around an obstacle in a pipe that produces a pronounced vortex region. We compared void fraction, as well as gas and liquid velocity profiles with experimental data obtained by means of Ultrafast X-ray Computed Tomography. We found that all the models except Bakker and Feng, predict the void fraction well compared to experimental data upstream of the obstacle, that is, for a developed two-phase pipe flow with axial symmetry. However, the void fraction downstream is grossly overestimated by all of the models. Based on the results, a hybrid drag model is proposed, which improves void fraction predictions considerably.

Keywords: CFD; bubbly flow; drag force coefficient; turbulence; vortex; hybrid drag model

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Permalink: https://www.hzdr.de/publications/Publ-32503
Publ.-Id: 32503


Multidisciplinary Characterization of Mine Water from a Former Uranium Mine for Bioremediation Purposes

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

In Saxony and Thuringia (Germany), an intensive uranium mining took place for decades until 1990. After the stop of the mining activities, the mines have been flooded for remediation purposes, which continues in many mines to this day. The resulting release of the soluble U into the mine water represents a major health risk. Remediation approaches using indigenous microbial communities are an efficient strategy1,2. In this study, we have characterized the microbial diversity and geochemistry of water from two German former uranium mines (Schlema-Alberoda and Pöhla) to design a bioremediation approach.
ICP-MS and Ion-Chromatography studies showed that the mine waters exhibited a higher concentration of U, sulfate, iron and manganese in Schlema-Alberoda compared to that of Pöhla (U: 1.01 and 0.11mg/L, sulfate: 335 and 0.26mg/L, iron: 0.99 and 0.13mg/L and manganese: 1.44 and 0.16mg/L, respectively). The 16S rRNA gene and the ITS1 rRNA analyses of both mine waters revealed a high microbial diversity. The total bacterial community composition combining both mine waters indicated an average relative abundance of sulfate-reducing-bacteria (e.g., Sulfuricuvum 9.5%, Sulfurimonas 4.5% and Sulfurovum 6.5%) and iron-oxidizing-bacteria (e.g., Gallionella 3%, Sideroxydans 3%). These bacterial groups are reported to be involved in U(VI) reduction as a key process in the bioremediation of anoxic U contaminated sites2. Therefore, to design bioremediation strategies for these U-contaminated waters, the Schlema-Alberoda water was used as a reference for setting anoxic-microcosms. Concretely, U-reducing-bacteria were biostimulated by supplementing with glycerol (10mM) as electron donor. ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of U (≈89%), sulfate (≈99%), iron (≈86%) and manganese (≈88%). In addition, a drop of Eh and pH of the system was detected. A thermodynamical Eh-pH predominance diagram was calculated by Geochemist´s Workbench, indicating the formation of U(IV) precipitates, probably uraninite, after 3 months at the latest.
These results show that the U enzymatic reduction of soluble U(VI) to insoluble U(IV), as uraninite, is favored by the addition of an electron donor (such as glycerol) in low concentrated U-contaminated mine waters. Therefore, this strategy might be an efficient bioremediation approach relevant for U-contaminated waters, by biostimulating their native microbial community.

Keywords: uranium; reduction; bioremediation; 16S rRNA; ITS1 rRNA; bacteria

  • Lecture (Conference) (Online presentation)
    Goldschmidt Conference 2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32502
Publ.-Id: 32502


Design of U mine water bioremediation strategy through U(VI) bioreduction process: Multidisciplinary characterization

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

The present study describes a U(VI) bioremediation strategy of a U mine water through the stimulation of the growth of U(VI) reducing bacteria (e.g. sulfate reducing bacteria). Thus, anoxic-microcosms of mine water amended with glycerol, as electron donor, were elaborated and incubated for 3 months. The original U mine water exhibit relatively high concentration of sulfate and iron. Furthermore, 16S and ITS1 rRNA gene analyses indicated a relative abundance of natural microbial groups with U(VI)-reduction ability. After 3 months, ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease around the 90% of U, sulfate, iron and manganese. A thermodynamical Eh-pH predominance diagram was calculated by Geochemist´s Workbench, showing the solid U ore (uraninite) after 3 months.
The results obtained revealed the U-enzymatic-reduction of U(VI) to U(IV), as uraninite, by the addition of an electron-donor in low concentrated U-contaminated-mine-waters. Thus, this strategy might be an efficient bioremediation approach for U-contaminated-mine-waters, by biostimulating their native microbial community.

Keywords: uranium; bioremediation; reduction; bacteria; 16S rRNA; ITS1 rRNA

  • Lecture (Conference) (Online presentation)
    10th International Symposium on Biomining (Biomining '21), 07.-09.06.2021, Falmouth, Cornwall, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-32501
Publ.-Id: 32501


Investigation of an opposed-contact GaAs photoconductive semiconductor switch at 1-kHz excitation

Xu, M.; Dong, H.; Liu, C.; Wang, Y.; Hu, L.; Lan, C.; Luo, W.; Schneider, H.

The transient performance of gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) triggered by laser diodes (LDs) at nano-joules (nJ) energy is of great significance for the potential high-power applications at high repetition rates. An opposed-contact GaAs PCSS with Ni/AuGe/WTi/Au electrodes is presented at single-shot and 1-kHz excitation. The influences of bias electric field up to 80 kV/cm on nonlinear characteristics are investigated quantitatively with a carriers' avalanche multiplication factor as high as 0.8 x 10⁴. The effect of electric field on the carriers' dynamic process and thermal accumulation in repetitive operation is analyzed. The transient electric field distribution is demonstrated by an ensemble Monte Carlo simulation.

Keywords: Avalanche multiplication; gallium arsenide GaAs; photoconductive semiconductor switch PCSS

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Permalink: https://www.hzdr.de/publications/Publ-32500
Publ.-Id: 32500


Review mr image changes of normal-appearing brain tissue after radiotherapy

Witzmann, K.; Raschke, F.; Troost, E. G. C.

Radiotherapy is part of the standard treatment of most primary brain tumors. Large clinical target volumes and physical characteristics of photon beams inevitably lead to irradiation of surrounding normal brain tissue. This can cause radiation-induced brain injury. In particular, late brain injury, such as cognitive dysfunction, is often irreversible and progressive over time, resulting in a significant reduction in quality of life. Since 50% of patients have survival times greater than six months, radiation-induced side effects become more relevant and need to be balanced against radiation treatment given with curative intent. To develop adequate treatment and prevention strategies, the underlying cause of radiation-induced side-effects needs to be understood. This paper provides an overview of radiation-induced changes observed in normal-appearing brains measured with conventional and advanced MRI techniques and summarizes the current findings and conclusions. Brain atrophy was observed with anatomical MRI. Changes in tissue microstructure were seen on diffusion imaging. Vascular changes were examined with perfusion-weighted imaging and susceptibility-weighted imaging. MR spectroscopy revealed decreasing N-acetyl aspartate, indicating decreased neuronal health or neuronal loss. Based on these findings, multicenter prospective studies incorporating advanced MR techniques as well as neurocognitive function tests should be designed in order to gain more evidence on radiation-induced sequelae.

Keywords: radiotherapy; radiation-induced brain injuries; normal-appearing brain tissue; functional MRI; anatomical MRI; perfusion; diffusion; spectroscopy; atrophy

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Permalink: https://www.hzdr.de/publications/Publ-32499
Publ.-Id: 32499


Proton beam quality enhancement by spectral phase control of a PW-class laser system

Ziegler, T.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Dover, N. P.; Garten, M.; Gaus, L.; Gebhardt, R.; Goethel, I.; Helbig, U.; Irman, A.; Kiriyama, H.; Kluge, T.; Kon, A.; Kraft, S.; Kroll, F.; Löser, M.; Metzkes-Ng, J.; Nishiuchi, M.; Obst-Hübl, L.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

We report on experimental investigations of proton acceleration from solid foils irradiated with PW‑class laser‑pulses, where highest proton cut‑off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto‑optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses. The paper further proves the robustness and applicability of this enhancement effect for the use of different target materials and thicknesses as well as laser energy and temporal intensity contrast settings. We demonstrate that application relevant proton beam quality was reliably achieved over many months of operation with appropriate control of spectral phase and temporal contrast conditions using a state‑of‑the‑art high‑repetition rate PW laser system.

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Permalink: https://www.hzdr.de/publications/Publ-32498
Publ.-Id: 32498


Experimental and numerical study of particles resuspension

Banari, A.; Eidt, R.; Lecrivain, G.; Hampel, U.

One of the first fundamental investigations on the resuspension of micron-sized particles in shear flows probably dates back to the 1930s, when Shields reported the existence of a threshold wall shear, beyond which particle re-entrainment into the flow occurs. Improvements have since been made, yet they do not provide all ingredients for a complete description of all mechanisms occurring at the particle scale. In this work, we experimentally discover, that the inter-particle collisions are key to the resuspension of a mono-layer bed of 40 micrometer glass beads in a gas flow. Our experimental findings, supported by simulations, stress the need to account for the role of inter-particle collisions, that all models have so far neglected.

Keywords: paticle resuspension; Inter-particle collisions; experimental test

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen und Computational Fluid Dynamics, 09.-10.04.2021, Online Conference, Germany

Permalink: https://www.hzdr.de/publications/Publ-32497
Publ.-Id: 32497


Dynamics of non-spherical particles at fluidic interface

Lecvrivain, G.

During this talk, I will report about my experimental and numerical results on the attachement of non-spherical particles on and off fluidic interfaces. The results apply to the field of mineral flotation, where hydrophobic particles are separated from water by rising gas bubbles.

  • Invited lecture (Conferences)
    Seminar at the Institute for Nano- and Microfluidics, Center of Smart, Interfaces, TU Darmstadt, 25.04.2019, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-32496
Publ.-Id: 32496


Recovery of non-spherical solid particles by rising bubbles

Lecrivain, G.

During this invited lecture, I will discuss the dynamics of glass particles settling on the gas-liquid interface of an immersed gas bubbles.

  • Invited lecture (Conferences)
    Seminar über Nichtlinearität und Unordnung in komplexen Systemen, 02.07.2018, Magdeburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32495
Publ.-Id: 32495


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