Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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43564 Publications
Radiative characterization of supersonic jets and shocks in a laser-plasma experiment
Bohlin, H.; Brack, F.-E.; Cervenak, M.; Chodukowski, T.; Cikhardt, J.; Dostál, J.; Dudžák, R.; Hubner, J.; Huo, W.; Jelinek, S.; Klír, D.; Kroll, F.; Krupka, M.; Krůs, M.; Pisarczyk, T.; Rusiniak, Z.; Schramm, U.; T.-H, N.-B.; Weber, S.; Zaraś-Szydłowska, A.; Zeil, K.; Kumar, D.; Schlegel, T.; Tikhonchuk, V.
Abstract
The interaction of supersonic laser-generated plasma jets with a secondary gas target was studied experimentally. The plasma parameters of the jet, and the resulting shock, were characterized using a combination of multi-frame interferometry/shadowgraphy, and x-ray diagnostics, allowing for a detailed study of their structure and evolution. The velocity was obtained with an x-ray streak camera, and filtered x-ray pinhole imaging was used to infer the electron temperature of the jet and shock. The topology of the ambient plasma density was found to have a significant effect on the jet and shock formation, as well as on their radiation characteristics. The experimental results were compared with radiation hydrodynamic simulations, thereby providing further insights into the underlying physical processes of the jet and shock formation and evolution.
Keywords: Supersonic jets; Shocks; Laser Plasma; X-ray imaging; Hydrodynamic
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Plasma Physics and Controlled Fusion 63(2021), 045026
DOI: 10.1088/1361-6587/abe526
Cited 3 times in Scopus -
Contribution to WWW
arXiv:2009.11567 [physics.plasm-ph]: https://arxiv.org/abs/2009.11567#
Downloads
Permalink: https://www.hzdr.de/publications/Publ-32883
On the study of hydrodynamic instabilities in the presence of background magnetic fields in high-energy-density plasmas
Manuel, M. J.-E.; Khiar, B.; Rigon, G.; Albertazzi, B.; Klein, S. R.; Kroll, F.; Brack, F.-E.; Michel, T.; Mabey, P.; Pikuz, S.; Williams, J. C.; Koenig, M.; Casner, A.; Kuranz, C. C.
Abstract
Blast-wave-driven hydrodynamic instabilities are studied in the presence of a background B-field through experiments and simulations in the high-energy-density (HED) physics regime. In experiments conducted at the Laboratoire pour l’utilisation des lasers intenses (LULI), a laser-driven shock-tube platform was used to generate a hydrodynamically unstable interface with a prescribed sinusoidal surface perturbation, and short-pulse x-ray radiography was used to characterize the instability growth with and without a 10-T B-field. The LULI experiments were modeled in FLASH using resistive and ideal magnetohydrodynamics (MHD), and comparing the experiments and simulations suggests that the Spitzer model implemented in FLASH is necessary and sufficient for modeling these planar systems. These results suggest insufficient amplification of the seed B-field, due to resistive diffusion, to alter the hydrodynamic behavior. Although the ideal-MHD simulations did not represent the experiments accurately, they suggest that similar HED systems with dynamic plasma-β (=2*μ_0*ρ*v^2/B^2) values of less than ∼100 can reduce the growth of blast-wave-driven Rayleigh–Taylor instabilities. These findings validate the resistive-MHD FLASH modeling that is being used to design future experiments for studying B-field effects in HED plasmas.
Keywords: Shock waves; Nebulae; Supernovae; Radiography; Magnetohydrodynamics; High pressure instruments; Magnetic fields; Fluid instabilities; Electromagnetic coils
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Matter and Radiation at Extremes 6(2021), 026904
DOI: 10.1063/5.0025374
Cited 21 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32882
robust training, adversarial examples and what it tells us about modern medical ML classifiers
Abstract
Undoubtedly, the advent of deep learning for image classification or pattern recognition has created a ecosystem stir in the
medical domain of unprecedented extension. In this talk, I'd like to discuss the question how adversarial examples can help us
quantify the quality of a Deep Learning trained classifyer. With this approach, I'd like to underline how observations and
methods from commercial applications can or cannot be transferred to medical applications. The slidedeck is meant to motivate a discussion on what we expect machine learning to leverage and how this relates to clinical applications with robustness of solutions in mind.
Keywords: robust AI; robust ML; adversarial examples; adversarial attacks; medical imaging; radiology
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Invited lecture (Conferences) (Online presentation)
EMPAIA Committee “Validation of AI solutions”, 24.06.2021, virtuell, Germany
DOI: 10.6084/m9.figshare.14838330.v1
Permalink: https://www.hzdr.de/publications/Publ-32881
Update of the EPTN atlas for CT- and MR-based (3T and 7T) contouring in Neuro-Oncology
Eekers, D. B. P.; Di, P. D.; Roelofs, E.; Postma, A.; Dijkstra, J.; Ajithkumar, T.; Alapetite, C.; Blomstrand, M.; Burnet, N. G.; Calugaru, V.; Compter, I.; Coremans, I. E. M.; Harrabi, S.; Iannalfi, A.; Klaver, Y. L. B.; Lambrecht, M.; Méndez Romero, A.; Paulsen, F.; Timmermann, B.; Vitek, P.; van der Weide, H. L.; Whitfield, G. A.; Nyström, P.; Zindler, J.; De, R. D.; Langendijk, J.; Weber, D. C.; Troost, E. G. C.
Abstract
Background and purpose:To update the digital online atlas for organs at risk (OARs) delineation in neuro-oncology based on high-quality computed tomography (CT) and magnetic resonance (MR) imaging withnew OARs.Materials and methods:In this planned update of the neurological contouring atlas published in 2018, tennew clinically relevant OARs were included, after thorough discussion between experienced neuro-radiation oncologists (RTOs) representing 30 European radiotherapy-oncology institutes. Inclusion wasbased on daily practice and research requirements. Consensus was reached for the delineation after crit-ical review. Contouring was performed on registered CT with intravenous (IV) contrast (soft tissue & bonewindow setting) and 3 Tesla (T) MRI (T1 with gadolinium & T2 FLAIR) images of one patient (1 mm slices).For illustration purposes, delineation on a 7 T MRI without IV contrast from a healthy volunteer wasadded. OARs were delineated by three experienced RTOs and a neuroradiologist based on the relevant lit-erature.Results:The presented update of the neurological contouring atlas was reviewed and approved by 28experts in the field. The atlas is available online and includes in total 25 OARs relevant to neurooncology, contoured on CT and MRI T1 and FLAIR (3 T & 7 T). Three-dimensional (3D) rendered films arealso available online.Conclusion:In order to further decrease inter- and intra-observer OAR delineation variability in the fieldof neuro-oncology, we propose the use of this contouring atlas in photon and particle therapy, in clinicalpractice and in the research setting. The updated atlas is freely available onwww.cancerdata.org.
Keywords: Atlas for neuro-oncology; Brain; Organs at risk; Particle therapy; Radiotherapy; European Particle Therapy Net
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Radiotherapy and Oncology 160(2021), 259-265
DOI: 10.1016/j.radonc.2021.05.013
Cited 37 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32880
Simultaneous localisation and mapping for laparoscopic liver navigation: a comparative evaluation study
Docea, R.; Pfeiffer, M.; Bodenstedt, S.; Kolbinger, F.; Höller, L.; Wittig, I.; Hoffmann, R.; Troost, E. G. C.; Riediger, C.; Weitz, J.; Speidel, S.
Abstract
Computer-Assisted Surgery (CAS) aids the surgeon by enriching the surgical scene with additional information
in order to improve patient outcome. One such aid may be the superimposition of important structures (such as
blood vessels and tumors) over a laparoscopic image stream. In liver surgery, this may be achieved by creating
a dense map of the abdominal environment surrounding the liver, registering a preoperative model (CT scan)
to the liver within this map, and tracking the relative pose of the camera. Thereby, known structures may be
rendered into images from the camera perspective. This intraoperative map of the scene may be constructed, and
the relative pose of the laparoscope camera estimated, using Simultaneous Localisation and Mapping (SLAM).
The intraoperative scene poses unique challenges, such as: homogeneous surface textures, sparse visual features,
specular reflections and camera motions specific to laparoscopy. This work compares the efficacies of two state-of-
the-art SLAM systems in the context of laparoscopic surgery, on a newly collected phantom dataset with ground
truth trajectory and surface data. The SLAM systems chosen contrast strongly in implementation: one sparse and
feature-based, ORB-SLAM3,1–3 and one dense and featureless, ElasticFusion.4 We find that ORB-SLAM3 greatly
outperforms ElasticFusion in trajectory estimation and is more stable on sequences from laparoscopic surgeries.
However, when extended to give a dense output, ORB-SLAM3 performs surface reconstruction comparably to
ElasticFusion. Our evaluation of these systems serves as a basis for expanding the use of SLAM algorithms in
the context of laparoscopic liver surgery and Minimally Invasive Surgery (MIS) more generally.
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Proceedings of SPIE 115980B(2021)
DOI: 10.1117/12.2582121
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32879
Value of PET imaging for radiation therapy
Lapa, C.; Nestle, U.; Albert, N.; Baues, C.; Beer, A.; Buck, A.; Budach, V.; Bütof, R.; Combs, S.; Derlin, T.; Eiber, M.; Fendler, W.; Furth, C.; Gani, C.; Gkika, E.; Grosu, A.; Henkenberens, C.; Ilhan, H.; Löck, S.; Marnitz-Schulze, S.; Miederer, M.; Mix, M.; Nicolay, N.; Niyazi, M.; Pöttgen, C.; Rödel, C.; Schatka, I.; Schwarzenboeck, S.; Todica, A.; Weber, W.; Wegen, S.; Wiegel, T.; Zamboglou, C.; Zips, D.; Zöphel, K.; Zschaeck, S.; Thorwarth, D.; Troost, E. G. C.
Abstract
This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.
Keywords: PET; radiation oncology; functional imaging; radiomics
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Strahlentherapie und Onkologie 197(2021), 757-779
DOI: 10.1007/s00066-021-01812-2
Cited 18 times in Scopus -
Nuklearmedizin 60(2021)5, 326-343
DOI: 10.1055/a-1525-7029
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32878
ROCOCO Performance Score translates dosimetric differences into clinically relevant endpoints: comparing IMPT to VMAT in pilocytic astrocytoma
In, ’. V. L.; Roelofs, E.; Cubillos, M. M.; Compter, I.; Klaver, Y.; Smeenk, R.; Janssens, G. O.; Kaanders, J. H. A. M.; Fajardo, R. D.; Oldenburger, F.; De, R. D.; Troost, E. G. C.; Eekers, D.
Abstract
Background and purpose: Proton therapy is expected to outperform photon-based treatment regarding organs at risk (OAR) sparing but to date there is no method to practically measure clinical benefit. Here, we introduce the novel ROCOCO Performance Scoring System (RPSS) translating dose differences
into clinically relevant endpoints and apply this to a treatment plan comparison of volumetric modulated arc therapy (VMAT) and intensity modulated proton therapy (IMPT) in 20 pilocytic astrocytoma patients.
Material and methods: The RPSS was developed on the basis of expert-based weighting factors and toxicity scores per OAR. The imaging datasets of 20 pilocytic astrocytoma patients having undergone radiotherapy were included in this in silico dosimetric comparison trial as proof of principle. For each of these patients, treatment plans to a total dose of 54 Gy (RBE) were generated for VMAT and IMPT and these were compared regarding radiation dose to the clinical target volume (CTV) and OARs. The RPSS was calculated for each treatment plan comparing VMAT and IMPT.
Results: In 40 analysed treatment plans, the average and low dose volumes to various OARs were significantly reduced when using IMPT compared to VMAT (p < 0.05). Using the RPSS, a significant difference between both treatment modalities was found, with 85% of the patients having a lower RPSS in favour of the IMPT plan.
Conclusion: There are dosimetric differences between IMPT and VMAT in pilocytic astrocytoma patients. In absence of clinically validated NTCP models we introduce the RPSS model in order to objectively compare treatment modalities by translating dosimetric differences in potential clinical differences.
Keywords: Low grade glioma; Pilocytic astrocytoma; Organ at risk; Proton therapy; Cognition; Scoring system
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Clinical and Translational Radiation Oncology 28(2021), 32-38
DOI: 10.1016/j.ctro.2021.02.006
Cited 3 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32877
Formation of plutonium (IV) silicate species in very alkaline reactive media
Estevenon, P.; Dumas, T.; Lorenzo Solari, P.; Welcomme, E.; Szenknect, S.; Mesbah, A.; Kvashnina, K. O.; Moisy, P.; Poinssot, C.; Dacheux, N.
Abstract
The formation of stable plutonium (IV) silicate colloidal suspension has been identified in very alkaline reactive media (pH ≥ 13). XAS measurements allowed to observe that these species exhibit a structure similar to those reported at (IV) oxidation state, like for thorium, uranium and neptunium silicates counterparts. These colloids can be stabilized in aqueous solution at concentrations around 10 2 mol·L 1 and successive filtration process allowed to evaluate that most of these silicates had a size ranging between 3 and 6 nm. This result may bring new outlooks on the behavior of plutonium in silicate ions rich reactive media
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 32876) publication
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Dalton Transactions 50(2021), 12528-12536
DOI: 10.1039/D1DT02248B
Cited 5 times in Scopus
Downloads
- Final Draft PDF 1,1 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32876
An open-access future for Journal of Synchrotron Radiation
Kvashnina, K.; Amemiya, Y.; Bhattacharyya, D.; Lindau, I.; Allen, A.
Abstract
The entire Journal of Synchrotron Radiation (JSR) editorial team would like to take this opportunity to inform all our readers, authors and supporters about the coming transition to open access. All papers submitted to JSR after 1 October 2021, will be for open-access publication. By taking this step, JSR is supporting a journey towards open science in general.
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Communication & Media Relations
Editorial from the Main Editors 01.09.2021
DOI: 10.1107/S1600577521007086
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32875
Generation of Reverse Meniscus Flow by Applying An Electromagnetic Brake
Vakhrushev, A.; Kharicha, A.; Karimi-Sibaki, E.; Wu, M.; Ludwig, A.; Nitzl, G.; Tang, Y.; Hackl, G.; Watzinger, J.; Eckert, S.
Abstract
A numerical study is presented that deals with the flow in the mold of a continuous slab caster under the influence of a DC magnetic field (electromagnetic brakes (EMBrs)). The arrangement and geometry investigated here is based on a series of previous experimental studies carried out at the mini-LIMMCAST facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The magnetic field models a ruler-type EMBr and is installed in the region of the ports of the
submerged entry nozzle (SEN). The current article considers magnet field strengths up to 441 mT, corresponding to a Hartmann number of about 600, and takes the electrical conductivity of the solidified shell into account. The numerical model of the turbulent flow under the applied magnetic field is implemented using the open-source CFD package OpenFOAM. Our numerical results reveal that a growing magnitude of the applied magnetic field may cause a reversal of the flow direction at the meniscus surface, which is related the formation of a ‘‘multiroll’’ flow pattern in the mold. This phenomenon can be
explained as a classical magnetohydrodynamics (MHD) effect: (1) the closure of the induced electric current results not primarily in a braking Lorentz force inside the jet but in an acceleration in regions of previously weak velocities, which initiates the formation of an opposite vortex (OV) close to the mean jet; (2) this vortex develops in size at the expense of the main vortex until it reaches the meniscus surface, where it becomes clearly visible. We also show
that an acceleration of the meniscus flow must be expected when the applied magnetic field is smaller than a critical value. This acceleration is due to the transfer of kinetic energy from smaller turbulent structures into the mean flow. A further increase in the EMBr intensity leads to the expected damping of the mean flow and, consequently, to a reduction in the size of the upper roll. These investigations show that the Lorentz force cannot be reduced to a simple
damping effect; depending on the field strength, its action is found to be topologically complex.
Keywords: continuous casting; mold flow; electromagnetic brake; numerical simulation
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Metallurgical and Materials Transactions B 52(2021), 3193-3207
DOI: 10.1007/s11663-021-02247-x
Cited 23 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32874
Resolution Enhancement for Drill-Core Hyperspectral Mineral Mapping
Contreras Acosta, I. C.; Khodadadzadeh, M.; Gloaguen, R.
Abstract
Drill-core samples are a key component in mineral exploration campaigns, and their rapid and objective analysis is becoming increasingly important. Hyperspectral imaging of drill-cores is a non-destructive technique that allows for non-invasive and fast mapping of mineral phases and alteration patterns. The use of adapted machine learning techniques such as supervised learning algorithms allows for a robust and accurate analysis of drill-core hyperspectral data. One of the remaining challenge is the spatial sampling of hyperspectral sensors in operational conditions, which does not allow us to render the textural and mineral diversity that is required to map minerals with low abundances and fine structures such as veins and faults. In this work, we propose a methodology in which we implement a resolution enhancement technique, a coupled non-negative matrix factorization, using hyperspectral, RGB images and high-resolution mineralogical data to produce mineral maps at higher spatial resolutions and to improve the mapping of minerals. The results demonstrate that the enhanced maps not only provide better details in the alteration patterns such as veins but also allow for mapping minerals that were previously hidden in the hyperspectral data due to its low spatial sampling.
Keywords: resolution enhancement; sampling enhancement; hyperspectral; high-spatial resolution multi-spectral; drill-cores; mineral mapping; machine learning
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Remote Sensing 13(2021), 2296
DOI: 10.3390/rs13122296
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32872
Comparative High-Field Magnetization Study of (Sm,Er)2Fe17 and Er2Fe17 Compounds and their Nitrides
Ivanov, L.; Paukov, M.; Tereshina, I.; Veselova, S.; Akimova, O.; Verbetsky, V.; Gorbunov, D.
Abstract
Magnetic properties of the R2Fe17 compounds are sensitive to the atomic substitutions and interstitial absorption of nitrogen. In our work, both were combined and their effect on the magnetization behavior of Er2Fe17 compound in magnetic fields up to 58 T was studied. Er2Fe17N2, Sm1.2Er0.8Fe17N
Involved research facilities
- High Magnetic Field Laboratory (HLD)
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Materials Science Forum 1037(2021), 148-153
DOI: 10.4028/www.scientific.net/MSF.1037.148
ISSN: 1662-9752
Permalink: https://www.hzdr.de/publications/Publ-32871
Magnetocaloric properties and specifics of the hysteresis at the first-order metamagnetic transition in Ni-doped FeRh
Chirkova, A. M.; Skokov, K. P.; Scurschii, I.; Scheibel, F.; Karpenkov, A. Y.; Volegov, A. S.; Baranov, N. V.; Nielsch, K.; Schultz, L.; Müller, K.-H.; Woodcock, T. G.; Gutfleisch, O.
Abstract
Measurements of the magnetization in quasistatic and pulsed magnetic fields with different sweep rates, measurements of the specific heat in various magnetic fields, and direct measurements of the adiabatic temperature change have been employed to study the metamagnetic phase transition from an antiferromagnetic (AF) to the ferromagnetic (FM) state in an (Fe0.98Ni0.02)49Rh51 alloy with a critical AF-FM transition temperature, Ttr, reduced to 266 K. Based on the obtained results, a magnetic phase diagram for this alloy has been constructed. The AF-FM transition induced by the magnetic field below 10 K is found to occur in a steplike fashion in contrast to smooth behavior at 10K < T < Ttr. The adiabatic temperature change ΔTad in the magnetic field of 2 T exceeds 6.5 K in pulsed fields (∼100 T/s) and in the Halbach setup (∼0.5 T/s), which is in agreement with the estimation from the S-T diagram constructed based on the specific heat measurements. The reversible ΔTad reaches −4.6 K under cyclic conditions in the Halbach setup (2 T). A complete transformation to the FM state in the whole temperature range requires a magnetic field of 14 T. Direct measurements of ΔTad in pulsed fields of 14 T revealed an irreversible part of the magnetocaloric effect associated with the presence of magnetic hysteresis and respective losses during the magnetization process.
Involved research facilities
- High Magnetic Field Laboratory (HLD)
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Physical Review Materials 5(2021), 064412
DOI: 10.1103/PhysRevMaterials.5.064412
Cited 22 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32870
Development of a high-speed ultrasonic tomography system for measurements of rising bubbles in a horizontal cross-section
Murakawa, H.; Tomoyuki, S.; Eckert, S.
Abstract
The present study deals with high-speed ultrasonic tomography (UT) as a powerful tool to characterize the behavior of multiphase flows. A major goal of the work is to improve the temporal resolution for the detection of transit flow structures and time-dependent phenomena such as the incidence of rising gas bubbles. A special transducer with a wide divergence angle of 110° and a vertical height of the measurement volume of approx. 4 mm was developed and tested. The system thus enables the acquisition of cross-sectional images at a frame rate of up to 1,000 frames/s. Scatter noise was eliminated using a time series filtering method. This UT system was applied to a chain of gas bubbles rising in a cylindrical container with an internal diameter of 50 mm. The measurement system provides qualitative observations of the turbulent dynamics of bubbly flows including bubble-bubble interactions, such as the coalescence of individual bubbles.
Keywords: full-matrix capture; reflection mode; time-series filtering; pseudo three-dimensional image; bubble column
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Measurement 182(2021), 109654
DOI: 10.1016/j.measurement.2021.109654
Cited 23 times in Scopus
Downloads
- Final Draft PDF 1005 kB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32869
Solidification and fluid convection - the story of an inseparable couple
Eckert, S.; Anders, S.; Shevchenko, N.; Keplinger, O.; Kao, A.
Abstract
In numerous processes in nature and technology, convection is caused by density differences resulting from temperature and concentration gradients. If the rates of diffusion of the two variables differ, this is called double-diffusive convection. Solidification processes under the influence of gravitational forces almost always occur in combination with convective flows. In nature, double-diffusive convection is responsible for magma flow in the mantle of planets or occurs during freezing of seawater. Thermo-solutal convection in industrial castings may result in a composition variation over distances comparable to the size of the solidification domain due to transport of rejected solute by fluid flow, the phenomenon being known as macrosegregation. This paper is dedicated to the interplay between solidification and convection, which are usually closely coupled, interacting in many different ways and thus can lead to very complex phenomena. Results from various experiments conducted both in metals and transparent analogues are presented and discussed.
Keywords: solidification; double-diffusive convection; macrosegregation
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Invited lecture (Conferences)
(Online presentation)
TMS 2021, annual Meeting & Exhibition, 15.-18.03.2021, virtual, online, USA
Permalink: https://www.hzdr.de/publications/Publ-32868
Investigate utilization of machine-learning methods to derive drag models for Euler-Euler simulations from DNS data
Patel, H.
Abstract
Multiphase flow plays a vital role in many industrial applications. DNS simulations provide an insight
into the complexity of multiphase flows but are limited due to very high computational costs. Instead,
Euler-Euler (E-E) simulations provide a reliable prediction for a wide range of engineering applications.
E-E simulations are highly dependent on the choice of closure models for the interaction terms. Modeling
of interfacial drag force is one of the main aspect of E-E simulations. In this thesis an attempt has been
made to develop a drag model for E-E simulations by analyzing the DNS data using machine learning
techniques. The entire work was carried out at HZDR (Helmholtz Zentrum Dresden Rossendorf).
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Master thesis
TU Dresden, 2021
Mentor: Dr. Fabian Schlegel
73 Seiten
Permalink: https://www.hzdr.de/publications/Publ-32867
Experimental validation of 4D log file-based proton dose reconstruction for interplay assessment considering amplitude-sorted 4DCTs
Spautz, S.; Jakobi, A.; Meijers, A.; Peters, N.; Löck, S.; Knopf, A. C.; Troost, E. G. C.; Richter, C.; Stützer, K.
Abstract
Purpose: The unpredictable interplay between dynamic proton therapy delivery and target motion (in the thorax) can lead to severe dose distortions. A fraction-wise four-dimensional (4D) dose reconstruction workflow allows to assess the applied dose after patient treatment considering the actual beam delivery sequence extracted from machine log files, the recorded breathing pattern and the geometric information from a 4D computed tomography scan (4DCT). Such an algorithm capable of accounting for amplitude sorted 4DCTs was implemented and its accuracy as well as its sensitivity to input parameter variations was experimentally evaluated.
Methods: An anthropomorphic thorax phantom with a movable insert containing a target surrogate and a radiochromic film was irradiated with a monoenergetic field for various 1D target motion forms (sin, sin4) and peak-to-peak amplitudes (5/10/15/20/30 mm). The measured characteristic film dose distributions were compared to the respective sections in the 4D reconstructed doses using a 2D γ-analysis; γ-pass rates were derived for different dose grid resolutions (1mm/3mm) and deformable image registrations (DIR, automatic/manual) applied during the 4D dose reconstruction process. In an additional analysis, the sensitivity of reconstructed dose distributions against potential asynchronous timing of the motion and machine log files was investigated for both a monoenergetic field and more realistic 4D robustly optimized fields by artificially introduced offsets of ± 1/5/25/50/250 ms. The resulting dose distributions with asynchronized log files were compared to the those with synchronized log files by means of a 3D γ-analysis and the evaluation of absolute dose differences.
Results: The induced characteristic interplay patterns on the films were well reproduced by the 4D dose reconstruction with 2D γ-pass rates ≥95% for almost all cases with motion magnitudes ≤15 mm. In general, the γ-pass rates showed a significant decrease for larger motion amplitudes and increase when using a finer dose grid resolution but were not affected by the choice of motion form (sin, sin4). There was also a statistical trend towards the manually defined DIR for better quality of the reconstructed dose distributions in the area imaged by the film. The 4D dose reconstruction results for the monoenergetic as well as the 4D robustly optimized fields were robust against small asynchronies between motion and machine log files of up to 5 ms, which is in the order of potential network latencies.
Conclusions: We have implemented a 4D log file-based proton dose reconstruction that accounts for amplitude sorted 4DCTs. Its accuracy was proven to be clinically acceptable for target motion magnitudes of up to 15 mm. Particular attention should be paid to the synchronization of the log file generating systems as the reconstructed dose distribution may vary with log file asynchronies larger than those caused by realistic network delays.
Keywords: proton therapy; log file-based dose reconstruction; pencil beam scanning; 4D dose; interplay effect
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Medical Physics 49(2022), 3538-3549
DOI: 10.1002/mp.15625
Cited 12 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32866
5f states in UGa2 probed by x-ray spectroscopies
Kolomiets, A. V.; Paukov, M.; Valenta, J.; Chatterjee, B.; Andreev, A. V.; Kvashnina, K. O.; Wilhelm, F.; Rogalev, A.; Drozdenko, D.; Minarik, P.; Kolorenc, J.; Richter, M.; Prchal, J.; Havela, L.
Abstract
The 5f -based ferromagnet UGa2 with the Curie temperature TC = 125K was investigated by x-ray absorption
spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments at the U–M4,5 and Ga–K
edges. The position of the U–M4 white line, determined in the high-energy resolution fluorescence detection
XAS, suggests that UGa2 is neither a localized 5f 2 nor an itinerant system with 5f occupancy close to n5f = 3.
The analysis of the acquired M4,5XANES and XMCD spectra indicates the 5f occupancy close to 2.5 and a
large orbital magnetic moment of the uranium 5f states (3.18 μB) that is partly compensated by the antiparallel
spin moment (1.31 μB). Thus, the total 5f magnetic moment of 1.87 μB is obtained, which is smaller than
the known bulk magnetization of 3.0 μB per formula unit, while the magnetic moments of the Ga atoms are
negligible. Several methods based on density-functional theory were applied and the obtained results were
compared with XAS spectral features, the Sommerfeld coefficient of the electronic specific heat, and the size of
the U moments and 5f occupancies. A clear correlation is revealed between the U–M4 white-line position of three
metallic uranium compounds and the calculated uranium ionicity. It is demonstrated that only electronic structure
methods taking appropriate care of orbital magnetism and related atomic multiplet effects can successfully
describe all considered properties
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 32865) publication
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Physical Review B 104(2021)4, 045119
DOI: 10.1103/PhysRevB.104.045119
Cited 6 times in Scopus
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- Final Draft PDF 1,5 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32865
Research data: Neutralization dynamics and kinetic energy loss of highly charged ions transmitted through graphene
Abstract
This depository contains research data (measured ESA spectra and evaluated data) for highly charged ion transmission though graphene.
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32864) publication
- DOI: 10.1038/s42005-021-00686-1 references this (Id 32864) publication
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Peeling graphite layer by layer reveals the charge exchange dynamics of ions …
ROBIS: 32862 has used this (Id 32864) publication of HZDR-primary research data
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Reseach data in the HZDR data repository RODARE
Publication date: 2021-07-05 Closed access
DOI: 10.14278/rodare.1052
Versions: 10.14278/rodare.1053
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Permalink: https://www.hzdr.de/publications/Publ-32864
Peeling graphite layer by layer reveals the charge exchange dynamics of ions inside a solid
Niggas, A.; Creutzburg, S.; Schwestka, J.; Wöckinger, B.; Gupta, T.; Grande, P. L.; Eder, D.; Marques, J. P.; Bayer, B. C.; Aumayr, F.; Bennett, R.; Wilhelm, R. A.
Abstract
Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a new first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations.
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32862) publication
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Research data: Neutralization dynamics and kinetic energy loss of highly …
ROBIS: 32864 HZDR-primary research data are used by this (Id 32862) publication
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Communications Physics 4(2021), 180
DOI: 10.1038/s42005-021-00686-1
Cited 14 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32862
Autocorrelation-informed home range estimation: a review and practical guide
Simoes Silva, I. M.; Fleming, C. H.; Noonan, M. J.; Alston, J.; Folta, C.; Fagan, W. F.; Calabrese, J.
Abstract
1. Modern tracking devices allow for the collection of high-volume animal tracking data at improved sampling rates over VHF radiotelemetry. Home range estimation is a key output from these tracking datasets, but the inherent properties of animal movement can lead traditional statistical methods to under- or overestimate home range areas.
2. The Autocorrelated Kernel Density Estimation (AKDE) family of estimators were designed to be statistically efficient while explicitly dealing with the complexities of modern movement data: autocorrelation, small sample sizes, and missing or irregularly sampled data. Although each of these estimators has been described in separate technical papers, here we review how these estimators work and provide a user-friendly guide on how they may be combined to reduce multiple biases simultaneously.
3. We describe the magnitude of the improvements offered by these estimators and their impact on home range area estimates, using both empirical case studies and simulations, contrasting their computational costs.
4. Finally, we provide guidelines for researchers to choose among alternative estimators and an R script to facilitate the application and interpretation of AKDE home range estimates.
Keywords: home range; tracking data; telemetry; kernel density estimation; movement process; ecology; ctmm; AKDE; autocorrelation
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Contribution to WWW
EcoEvoRxiv Preprints: https://ecoevorxiv.org/23wq7/
DOI: 10.32942/osf.io/23wq7 -
Methods in Ecology and Evolution 13(2022)3, 534-544
Online First (2021) DOI: 10.1111/2041-210X.13786
Cited 69 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32861
Behavior of implanted Xe and Kr in nanodiamond and thin graphene stacks: experiment and modeling
Shiryaev, A. A.; Trigub, A. L.; Voronina, E. N.; Kvashnina, K. O.; Bukhovets, V. L.
Abstract
Implantation and subsequent behaviour of heavy noble gases (Ar, Kr, Xe) in few-layer graphene sheets and in nanodiamonds
is studied both using computational methods and experimentally using X-ray absorption spectroscopy. For the first time the
Xe-vacancy (Xe-V) defect is experimentally confirmed as a main site for Xe in the diamond. It is shown that noble gases in
thin graphene stacks distort the layers, forming bulges. The energy of an ion placed in between flat graphene sheets is
notably lower than in domains with high curvature. However, if the ion is trapped in the curved domain, considerable
additional energy is required to displace it.
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 32860) publication
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Physical Chemistry Chemical Physics 23(2021), 21729-21737
DOI: 10.1039/D1CP02600C
Cited 4 times in Scopus
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- Final Draft PDF 994 kB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32860
Prompt Gamma-Ray Range Verification in Particle Therapy
Abstract
Particle therapy (PT) has become a widely accepted and promising option for tumor treatment. It supplements conventional radiation therapy with MV X-rays and electrons and is becoming increasingly important for more and more applications. More than 100 clinical PT facilities are already in operation worldwide, around 40 are currently under construction and just as many are planned.
The accuracy of the prediction of the particle range in the tissue is, however, influenced by uncertainties in patient positioning, by patient movements during irradiation, by anatomical changes during one or between several fractions and by other factors that are difficult to quantify in daily clinical routine. These uncertainties are considered by conservative safety margins in the treatment planning, but these margins reduce the advantage of particle beams compared to conventional therapies in many cases. Real-time range verification is therefore a necessity in order to exploit the full potential of particle therapy.
Range verification of therapeutic ions has been investigated for over 50 years now. Many systems have been developed in this time, some devices have been tested under clinical conditions and only a few make it to clinical trials. However, so far there is no system that is used in daily clinical routine. While the first devices still made use of the annihilation radiation of the positron emitters generated in the therapy, the international community mainly concentrates on the use of prompt gamma rays today.
This talk gives an overview of the current status of prompt gamma-ray based range verification. The focus is on the three currently most promising options (Prompt Gamma Ray Imaging, Spectroscopy and Timing). The metrological fundamentals of the individual systems are presented and discussed with regard to their use in everyday clinical practice.
Keywords: Prompt Gamma Treatment Verification; Range Verification in Particle Therapy; Prompt Gamma Ray Timing; Prompt Gamma Ray Imaging; Prompt Gamma Ray Spectroscopy
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32859) publication
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Lecture (others)
(Online presentation)
Heidelberg Particle Therapy Seminar, 07.07.2021, Heidelberg, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-32859
Radiolabeled PSMA inhibitors
Neels, O.; Kopka, K.; Liolios, C.; Afshar-Oromieh, A.
Abstract
Prostate-specific membrane antigen (PSMA) has shown to be a promising target for diagnosis and therapy (theranostics) of prostate cancer. An introducing overview on the regulatory status of PSMA-targeting radiopharmaceuticals in the US and Europe is given. We review developments in the field of radio- and fluorescence-guided surgery and targeted photodynamic therapy as well as multitargeting PSMA inhibitors also addressing albumin and GRPr. Technical and quality aspects of PSMA-targeting radiopharmaceuticals are described and new radiolabeling strategies are presented. Finally, insights are given into production, application and potential of alternatives beyond the commonly used radionuclides for radiolabeling PSMA inhibitors. An additional re-finement of radiopharmaceuticals is required in order to further improve dose-limiting factors like nephrotoxicity and salivary gland uptake during endoradiotherapy. The combination of ra-dionuclide therapy with therapy options of other disciplines shows a way to improve the treat-ment of patients.
Keywords: PSMA; Prostate-specific membrane antigen; PSMA inhibitor; Radiolabeling; PET; SPECT; fluorescence; endoradiotherapy; theranostics; radioguided surgery; fluorescence-guided surgery; targeted photodynamic therapy; radionuclides
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Cancers 13(2021)24
DOI: 10.3390/cancers13246255
Cited 33 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32858
Data and code for: Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species' traits
Wells, H. B. M.; Crego, R. D.; Opedal, Ø. H.; Khasoha, L. M.; Alston, J. M.; Reed, C. G.; Weiner, S.; Kurukura, S.; Hassan, A. A.; Namoni, M.; Ekadeli, J.; Kimuyu, D.; Young, T. P.; Kartzinel, T. R.; Palmer, T. M.; Pringle, R. M.; Goheen, J. R.
Abstract
Data and code that can be used to reproduce the analyses underlying "Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species’ traits" by Wells et al. (2021) https://doi.org/10.1111/1365-2656.13565
Related publications
- DOI: 10.1111/1365-2656.13565 references this (Id 32857) publication
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Experimental evidence that effects of megaherbivores on mesoherbivore space …
ROBIS: 32807 has used this (Id 32857) publication of HZDR-primary research data
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Reseach data in the HZDR data repository RODARE
Publication date: 2021-07-03 Restricted access
DOI: 10.14278/rodare.1050
Versions: 10.14278/rodare.1051
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Permalink: https://www.hzdr.de/publications/Publ-32857
Rational Design of Two-dimensional Binary Polymers from Heterotriangulenes for Photocatalytic Water Splitting
Zhou, Z.; Springer, M.; Geng, W.; Zhu, X.; Li, T.; Li, M.; Jing, Y.; Heine, T.
Abstract
Based on first principles calculations, we report the design of three two-dimensional (2D) binary honeycomb-kagome polymers composed of B- and N-centered heterotriangulenes in the same plane with a periodically alternate arrangement as in hexagonal boron nitride. The 2D binary polymers with donor-acceptor characteristics, are semiconductors with a direct band gap of 1.98-2.28 eV. The enhanced in-plane electron conjugation contributes to high charge carrier mobilities for both electrons and holes, about 6.70 and 0.24 × 103 cm2 V-1 s-1, respectively, for the 2D binary polymer with carbonyl bridges (2D CTPAB). With appropriate band edge alignments to match the water redox potentials and pronounced light adsorption for the ultraviolet and visible range of spectra, 2D CTPAB is predicted to be an effective individual photocatalyst to promote overall water splitting.
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The Journal of Physical Chemistry Letters 12(2021), 8134-8140
DOI: 10.1021/acs.jpclett.1c02109
Cited 37 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32856
First X-ray absorption study of palladium in pentlandite and palladium minerals
Merkulova, M.; Brovchenko, V.; Sittner, J.; Borca, C.; Huthwelker, T.; Sluzhenikin, S. F.; Cnudde, V.
Abstract
Norilsk sulfide ores are one of the largest known sources of palladium (Pd) on Earth. Palladium in these ores is hosted by platinum-group minerals (PGMs) and pentlandite ((Fe,Ni)9S8). Although a number of studies demonstrated extraordinarily high concentrations along with heterogeneous distribution of Pd in sulfide minerals from Norilsk, no information is known about the exact chemical form of Pd in pentlandite. Here, we present the first evidence for Pd incorporation in the lattice of pentlandite from Norilsk ores. These results were obtained by combining synchrotron-based micro-X-ray fluorescence (μXRF) and X-ray absorption near edge structure (XANES) spectroscopy. We present the first ever measured XANES spectra of Pd in pentlandite and atokite ((Pd,Pt)3Sn), a common Pd mineral in Norilsk ores. Incorporation of divalent Pd in pentlandite was detected. Substitution of Pd for Ni in the lattice of pentlandite is supported by elemental correlations shown by μXRF and electron probe microanalysis (EPMA). The occurrence of two different forms of Pd supports the hypothesis of rapid quenching of sulfide liquids as the formation mechanism of Mount Rudnaya platinum-group elements (PGEs) ores in Norilsk region. The combination of analytical techniques used in the present study demonstrates the great potential for understanding the mechanisms of noble metal incorporation into ore minerals.
Keywords: Palladium; Pentlandite; Platinum-Group Minerals; XANES; µXRF
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American Mineralogist 108(2023)11, 2086-2095
DOI: 10.2138/am-2022-8704
Cited 3 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32855
Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier
Schönig, J.; von Eynatten, H.; Tolosana Delgado, R.; Meinhold, G.
Abstract
The major-element chemical composition of garnet provides valuable petrogenetic information about its primary host lithologies, particularly in metamorphic rocks. When facing detrital garnet, information about the bulk composition and mineral paragenesis of the initial garnet-bearing host rock is absent. This prevents the application of chemical thermobarometric techniques and calls for quantitative empirical approaches. Here we present a new garnet host-rock discrimination scheme that is based on a random forest machine-learning algorithm trained on a large dataset of 13,615 garnet analyses that covers a wide variety of garnet-bearing lithologies. Considering the out-of-bag error, the scheme correctly predicts the original garnet host-rock in (i) >95 % concerning the setting, that is mantle versus metamorphic versus igneous versus metasomatic; (ii) >84 % concerning the metamorphic facies, that is blueschist/greenschist versus amphibolite versus granulite versus eclogite/ultrahigh-pressure; and (iii) >93 % concerning the host-rock composition, that is intermediate–felsic/metasedimentary versus mafic versus ultramafic versus alkaline versus calcsilicate. The wide coverage of potential host rocks, the detailed prediction classes, the high discrimination rates, and the successfully tested real-case applications demonstrate that the introduced scheme overcomes many issues related to previous schemes. This highlights the potential of transferring the applied discrimination strategy to the broad range of detrital minerals beyond garnet, as well as many other quantitative empirical challenges in Earth sciences. For easy and quick usage, a freely accessible web app is provided that guides the user in five steps from garnet composition to prediction results including data visualization.
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Contributions to Mineralogy and Petrology 176(2022)12, 98
Online First (2021) DOI: 10.1007/s00410-021-01854-w
Cited 26 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32854
Challenges in Contactless Inductive Flow Tomography for Rayleigh-Bénard Convection Cells
Sieger, M.; Mitra, R.; Schindler, F.; Vogt, T.; Stefani, F.; Eckert, S.; Wondrak, T.
Abstract
Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.
Keywords: contactless inductive flow tomography; large scale circulation; liquid metal flow; Rayleigh-Bénard convection
Related publications
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Flow Reconstruction in a Rayleigh-Bénard Convection Cell with an Aspect Ratio …
ROBIS: 32885 cites this (Id 32853) publication
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Contribution to proceedings
Electromagnetic processing of materials 2021, 14.-16.06.2021, Riga / virtual, Latvia
Proceedings of the 10th international conference Electromagnetic Processing of Materials, Riga: The University of Latvia Press, 978-9934-18-686-8, 1-280 -
Lecture (Conference)
(Online presentation)
Electromagnetic processing of materials 2021, 16.06.2021, Riga / virtual, Latvia -
Magnetohydrodynamics 58(2022)1/2, 25-32
DOI: 10.22364/mhd.58.1-2.3
Cited 5 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32853
Strong Binding of Noble Gases to [B₁₂X₁₁]⁻: a theoretical study
Wöhner, K.; Wulf, T.; Vankova, N.; Heine, T.
Abstract
We systematically explore the stability and properties of [B₁₂X₁₁NG]⁻ adducts resulting from the binding of noble gas atoms to anionic [B₁₂X₁₁]⁻ clusters in the gas phase of mass spectrometers. [B₁₂X₁₁]⁻ can be obtained by stripping one X⁻ off the icosahedral closo-dodecaborate dianion [B₁₂X₁₂]²⁻. We study the binding of the noble gas atoms He, Ne, Ar, Kr and Xe to [B₁₂X₁₁]⁻ with substituents X = F, Cl, Br, I, CN. While He cannot be captured by these clusters and Ne only binds at low temperatures, the complexes with the heavier noble gas atoms Ar, Kr and Xe show appreciable complexation energies and exceed 1 eV at room temperature in the case of [B₁₂(CN)₁₁Xe]⁻. The predicted B–NG equilibrium distance in the complexes with Ar, Kr and Xe is only 0.10 to 0.25 Å longer than the sum of the covalent radii of the two corresponding atoms, and a significant charge transfer from the noble gas atom to the icosahedral B₁₂ cage is observed.
Keywords: Boron; Anions; Complexation; Cluster chemistry; Group 17 compounds
Related publications
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Data publication: Strong Binding of Noble Gases to [B₁₂X₁₁]⁻: a theoretical …
ROBIS: 33348 HZDR-primary research data are used by this (Id 32852) publication
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Journal of Physical Chemistry A 125(2021), 4760-4765
DOI: 10.1021/acs.jpca.1c01909
Cited 6 times in Scopus
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- Open Access Version from chemrxiv.org
- Fulltext from pubs.acs.org
- Secondary publication expected
Permalink: https://www.hzdr.de/publications/Publ-32852
Concept of High-Power CW IR-THz Source for the Radiation Source ELBE Upgrade
Evtushenko, P.; Lehnert, U.; Michel, P.; Cowan, T.
Abstract
The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is a user facility based on a 1 mA - 40 MeV CW SRF LINAC. Presently HZDR is considering upgrade options for the ELBE or its replace- ment with a new CW, SRF LINAC-based user facility. A part of the user requirements is the capability to generate IR and THz pulse in the frequency range from 0.1 through 30 THz, with pulse energies in the range from 100 J through a few mJ, at the repetition rate between 100 kHz and 1 MHz. This corresponds to the pulse energy in- crease, dependent on the wavelength, by a factor from 100 through 1000. In this contribution, we outline key aspects of a concept, which would allow to achieve such parameters. These aspects are: 1 - use of a beam with longitudinal density modulation and bunching factor of about 0.5 at the fundamental frequency; 2 - achieving the density modulation through the mechanism similar to the one used in optical klystron (OK); 3 – generating the necessary for the modulation optical beam by an FEL oscillator, and 4 - using two electron injectors. First injec- tor would provide a beam for the FEL oscillator. Second high charge injector would provide the beam for the high pulse energy generation for users. All-in-all the concept of the new radiation source is very similar to an OK, but operating with two beams simultaneously.
Keywords: ELBE; THz; superradiant; undulator radiation; high power; SRF linac
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32851) publication
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Contribution to proceedings
39th International Free Electron Laser Conference (FEL2019), 26.-30.08.2019, Hamburg, Germany
Proceedings, 39th International Free Electron Laser Conference (FEL2019)
DOI: 10.18429/JACoW-FEL2019-TUP008
Cited 1 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32851
Design of High-Power CW IR-THz Source for the Radiation Source ELBE Upgrade
Evtushenko, P.; Lehnert, U.; Michel, P.; Cowan, T.
Abstract
The Radiation Source ELBE at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is a user facility based on a 1 mA - 40 MeV CW SRF LINAC. Presently HZDR is considering upgrade options for the ELBE or its replace- ment with a new CW, SRF LINAC-based user facility. A part of the user requirements is the capability to generate IR and THz pulse in the frequency range from 0.1 through 30 THz, with pulse energies in the range from 100 J through a few mJ, at the repetition rate between 100 kHz and 1 MHz. This corresponds to the pulse energy in- crease, dependent on the wavelength by a factor from 100 through 1000. In this contribution, we outline key aspects of a concept, which would allow to achieve such parame- ters. Such key aspects are: 1 - use of a beam with longitu- dinal density modulation and bunching factor of about 0.5 at the fundamental frequency; 2 - achieving the density modulation through the mechanism similar to the one used in optical klystron (OK) and HGHG FEL; 3 - gener- ating necessary for the modulation optical beam by an FEL oscillator, and 4 - using two electron injectors, where one injector provides beam for the FEL oscillator while second high charge injector provides beam for the high energy per pulse generation for user experiments. All-in- all the concept of the new radiation source is very similar to an OK, but operating with two beams simultaneously.
Keywords: Superradiant Undulator; THz; SRF LINAC; Undulator radiation; modulated beam
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32850) publication
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Contribution to proceedings
10th International Particle Accelerator Conference - IPAC 19, 19.-24.05.2019, Melbourne, Australia
IAPC2019 Proceedings, 1702-1704
DOI: 10.18429/JACoW-IPAC2019-TUPRB012
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Permalink: https://www.hzdr.de/publications/Publ-32850
Probing the local coordination of hexavalent uranium and the splitting of 5f orbitals induced by chemical bonding.
Amidani, L.; Retegan, M.; Volkova, A.; Popa, K.; Martin, P. M.; Kvashnina, K.
Abstract
We report here the first detailed experimental and theoretical investigation of hexavalent uranium in various local configurations with high-energy-resolution fluorescence-detected X-ray absorption near-edge structure at the M4 edge. We demonstrate the pronounced sensitivity of the technique to the arrangement of atoms around the absorber and provide a detailed theoretical interpretation revealing the nature of spectral features. We show that for all local configuration analyzed, the main peak corresponds to non-bonding 5f orbitals, and the highest energy peak corresponds to anti-bonding 5f orbitals. Our findings are in agreement with the accepted interpretation of uranyl spectral features and embed the latter in the broader field of view where the spectra of a larger variety of U6+-containing samples are interpreted on the same theoretical ground.
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Analytical Chemistry 60(2021)21, 16286-16293
DOI: 10.1021/acs.inorgchem.1c02107
Cited 17 times in Scopus
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- Final Draft PDF 1,2 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32849
To form or not to form: PuO2 nanoparticles at acidic pH
Gerber, E.; Romanchuk, A. Y.; Weiss, S.; Kuzenkova, A.; Hynault, M.; Bauters, S.; Egorov, A.; Butorin, S. M.; Kalmykov, S. N.; Kvashnina, K. O.
Abstract
Properties of the PuO2 nanoparticles (NPs) formed under acidic conditions (pH 1-4) are explored in this study at the atomic scale. High-resolution transmission electron microscopy (HRTEM) was applied to characterize the crystallinity, morphology and size of the precipitates. It was found that 2 nm crystalline NPs are formed with a crystal structure similar to bulk PuO2. High energy resolution fluorescence detected (HERFD) X-ray absorption spectroscopy at the Pu M4 edge has been used to identify the Pu oxidation states and recorded data are analyzed using the theory based on the Anderson Impurity Model (AIM). The experimental data obtained on NPs show that Pu(IV) oxidation state dominates in all NPs formed at pH 1-4. However, the suspension at pH 1 demonstrate the presence of Pu(III) in addition to the Pu(IV), which is associated with redox dissolution of PuO2 NPs under acidic conditions. As shown by UV-Vis the contribution of Pu(III) in the HERFD spectrum for the sample at pH 1 originates from the solution rather than from NPs themselves. We discuss in detail the mechanism that affects the PuO2 NP synthesis under acidic conditions and compare it with one in neutral and alkaline conditions. Future investigations of plutonium chemistry will fundamentally benefit from the insights this work provides and further applied to various environmental and technological applications
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 32848) publication
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Environmental Science: Nano 9(2022), 1509-1518
DOI: 10.1039/d1en00666e
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32848
Emergence of cobalt oxide nano-assemblies: X-ray in situ studies bridging the molecular- and macro- length scales
Grote, L.; Zito, C. A.; Frank, K.; Dippel, A.-C.; Reisbeck, P.; Pitala, K.; Kvashnina, K. O.; Bauters, S.; Detlefs, B.; Ivashko, O.; Pandit, P.; Rebber, M.; Harouna-Mayer, S. Y.; Nickel, B.; Koziej, D.
Abstract
The key to fabricate complex, hierarchical materials is the control of chemical reactions at various length scales. The classical model of nucleation and growth fails to provide sufficient information. Here, we illustrate how modern X-ray spectroscopic and scattering in situ studies bridge the molecular- and macro- length scales for an assembly of CoO polyhedral shape nanocrystals. By combining high energy-resolution fluorescence-detected X-ray absorption near edge structure (HERFD-XANES) measurements and FEFF simulation, we directly access the molecular level of the reaction. We reveal that initially Co(acac)3 rapidly reduces to Co(acac)2 and coordinates to oxygen atoms of two solvent molecules, forming a bis-adduct of the square-planar Co(acac)2 with octahedral coordination. Unlike a classical nucleation and growth mechanism, we observe that nuclie as small as 2 nm assemble into superstructures of 20 nm. The individual nanoparticles and assemblies continue growing at a similar pace. The final assemblies are smaller than 100 nm and maintain their spherical shape, while the nanoparticles reach a size of 6 nm and adopt various polyhedral, edgy shapes. Our work thus provides a comprehensive perspective on the emergence of nano-assemblies in solution
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
Related publications
- DOI: 10.1107/S1600577520014265 is cited by this (Id 32847) publication
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Nature Communications 12(2021), 4429
DOI: 10.1038/s41467-021-24557-z
Cited 18 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32847
HERFD-XANES and RIXS study on the electronic structure of trivalent lanthanides across a series of isostructural compounds
Zasimov, P. V.; Amidani, L.; Retegan, M.; Walter, O.; Caciuffo, R.; Kvashnina, K. O.
Abstract
We performed a systematic study of the complexes of trivalent lanthanide cations with the hydridotris(1-pyrazolyl)borato (Tp) ligand (LnTp3; Ln = La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu) using both high-energy-resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES) and resonant inelastic X-ray scattering (RIXS) at the lanthanide L3 absorption edge. Here, we report the results obtained and we discuss them against simulations performed with the density functional theory and atomic multiplet theory computational approaches. The spectral shape and the elemental trends observed in the experimental HERFD-XANES spectra are well reproduced by density functional theory calculations, whilst the pre-edge energy interval is well better described by atomic multiplet theory. The RIXS data show a generally rather complex pattern that originates from the intra-atomic electron-electron interactions in the intermediate and final states, as demonstrated by the good agreement obtained with simulations considering exclusively the atomic configuration. Guided by theoretical predictions, we discuss possible origins of the observed spectral features and the trends in energy splitting across the series. The insight in the electronic structure of trivalent lanthanides compounds demonstrated here and obtained with advanced X-ray spectroscopies coupled with theoretical simulations can be applied to any lanthanide-bearing compound and be of great interest for all research fields involving lanthanides
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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Inorganic Chemistry 61(2022)4, 1817-1830
DOI: 10.1021/acs.inorgchem.1c01525
Cited 18 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32846
Valence fluctuations in the 3D+3 modulated Yb3Co4Ge13 Remeika Phase
Feig, M.; Akselrud, L.; Motylenko, M.; Bobnar, M.; Wagler, J.; Kvashnina, K. O.; Rafaja, D.; Leithe-Jasper, A.; Gumeniuk, R.
Abstract
Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group
P43n(a,0,0)000(0,a,0)000(0,0,a)000; a = 8:72328(1) Å, Q1 = Q2 = Q3 = 0:4974(2)]
modulated crystal structure. A slight shift of the composition towards higher Ybcontent
(i:e: Yb3:2Co4Ge12:8) leads to the disappearance of the satellite reflections and
stabilization of the disordered primitive cubic [space group Pm3n, a = 8:74072(2) Å]
Remeika prototype structure. The stoichiometric structurally modulated germanide is
a metal with hole-like charge carriers, where Yb-ions are in a temperature dependent
intermediate valence state of +2:60+2:66 for the temperature range 85-293 K. The
valence fluctuations have been investigated by means of temperature dependent X-ray
absorption spectroscopy, magnetic susceptibility and thermopower measurements
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32845) publication
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Dalton Transactions 50(2021), 13580
DOI: 10.1039/D1DT01972D
Cited 9 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32845
Towards The Bottom of The Periodic Table
Kvashnina, K.
Abstract
Towards the Bottom of the Periodic Table
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32844) publication
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Invited lecture (Conferences)
(Online presentation)
Monday Meetings, 22.03.2021, Washington State University, USA
Permalink: https://www.hzdr.de/publications/Publ-32844
XAS Towards the Bottom of the Periodic Table
Kvashnina, K.
Abstract
Understanding the mechanisms of different chemical reactions with actinides (An) at the atomic level is a key step towards safe disposal of nuclear wastes and towards the identification of physical-chemical processes of radionuclides in the environment. X-ray absorption spectroscopy in high energy resolution fluorescence detection (HERFD) mode at the An M4,5 edges is now a common technique to probe the electronic structure and the An 5f states. I will provide an overview of the recently performed studies on Uranium, Thorium and Plutonium-containing materials at the European Synchrotron (ESRF) in Grenoble (France). I will show how the detailed information about the An oxidation state, electron-electron interactions, hybridization between molecular orbitals can be obtained by a combination of experimental data and electronic structure calculations. It might be of interest for fundamental research in chemistry and physics of actinides as well as for applied science.
Reading:
[1] K. O. Kvashnina, S. M. Butorin, P. Martin, and P. Glatzel, “Chemical State of Complex Uranium Oxides,” Phys. Rev. Lett., vol. 111, no. 25, p. 253002, Dec. 2013, doi: 10.1103/PhysRevLett.111.253002.
[2] K. O. Kvashnina, Y. O. Kvashnin, and S. M. Butorin, “Role of resonant inelastic X-ray scattering in high-resolution core-level spectroscopy of actinide materials,” J. Electron Spectros. Relat. Phenomena, vol. 194, pp. 27–36, Jun. 2014, doi: 10.1016/j.elspec.2014.01.016.
[3] S. M. Butorin, K. O. Kvashnina, J. R. Vegelius, D. Meyer, and D. K. Shuh, “High-resolution X-ray absorption spectroscopy as a probe of crystal-field and covalency effects in actinide compounds,” Proc. Natl. Acad. Sci., vol. 113, no. 29, pp. 8093–8097, Jul. 2016, doi: 10.1073/pnas.1601741113.
[4] K. O. Kvashnina et al., “A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO 2 Nanoparticles,” Angew. Chemie Int. Ed., vol. 58, no. 49, pp. 17558–17562, Dec. 2019, doi: 10.1002/anie.201911637.
[5] E. Gerber et al., “The missing pieces of the PuO 2 nanoparticle puzzle,” Nanoscale, vol. 12, no. 35, pp. 18039–18048, 2020, doi: 10.1039/D0NR03767B.
[6] I. Pidchenko, J. März, M. O. J. Y. Hunault, S. Bauters, S. M. Butorin, and K. O. Kvashnina, “Synthesis, Structural, and Electronic Properties of K 4 Pu VI O 2 (CO 3 ) 3(cr) : An Environmentally Relevant Plutonium Carbonate Complex,” Inorg. Chem., vol. 59, no. 17, pp. 11889–11893, Sep. 2020, doi: 10.1021/acs.inorgchem.0c01335.
[7] L. Amidani et al., “The Application of HEXS and HERFD XANES for Accurate Structural Characterisation of Actinide Nanomaterials: The Case of ThO 2,” Chem. – A Eur. J., vol. 27, no. 1, pp. 252–263, Jan. 2021, doi: 10.1002/chem.202003360.
[8] E. Gerber et al., “Insight into the structure–property relationship of UO 2 nanoparticles,” Inorg. Chem. Front., p. accepted, 2021, doi: 10.1039/D0QI01140A.
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32843) publication
-
Invited lecture (Conferences) (Online presentation)
GlobalXAS, 04.02.2021, Washington, USA
Downloads
Permalink: https://www.hzdr.de/publications/Publ-32843
Bubble coalescence and breakup mechanism in a vertical pipe with an obstacle
Liao, Y.; Sibel, T.-K.; Martin, N.-K.; Lucas, D.
Abstract
One of the major issues in numerical study of bubbly flows is the prediction of bubble size. Among other physical processes coalescence and breakup represents a huge challenge. A variety of investigations on bubble coalescence and breakup in turbulent flows has been motivated, and a remarkable diversity of mechanisms has been observed. However, knowledge on the superposition of multiple mechanisms remains insufficient. The purpose of this work is to investigate the effect of a sudden change of flow fields on coalescence and breakup events. Turbulent bubbly flows in a vertical pipe with a ring obstacle are analyzed with ultrafast x-ray computed tomography and a generalized population balance model. The results show that coalescence and breakup are in equilibrium before the obstacle leading to a nearly unchanged bubble size distribution (BSD) and quasi fully-developed flow, which is destroyed by the presence of the obstacle. Immediately behind it, both the coalescence and breakup rates are enhanced due to intensified turbulence and recirculation, and as a result, the BSD becomes broader. At first, the increase in coalescence exceeds that in breakup such that the mean bubble size increases. After about ten millimeters downstream from the obstacle (L/D≈0.2), breakup overtakes coalescence and the BSD shifts to the direction of small bubble size. At L/D≈0.4, the bubble size before the obstacle is almost recovered, but it decreases further downstream. The predicted and measured BSDs agree well with each other upstream and downstream, where the bubble coalescence and breakup is majorly controlled by turbulence. Difficulties are encountered in capturing the drastic change in the region directly downstream of the obstacle in particular the rapid increase in coalescence rate. The test of turbulence single-phase flow through a sudden expansion reveals that it is difficult for a RANS model to reproduce the turbulence structure in the recirculation zone reliably, which directly affects the performance of coalescence and breakup models. Furthermore, coalescence resulting from other mechanisms such as wake entrainment or laminar shear is shown to have a minor contribution, and turbulence is dominant. Further investigations concerning bubble coalescence and breakup, turbulence as well as its effect on interfacial momentum transfer are necessary for the obstructed flow.
Keywords: bubble coalescence and breakup; computational fluid dynamics; obstacle; turbulence; vertical pipe flow
Involved research facilities
- TOPFLOW Facility
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Contribution to proceedings
The 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brussels, Belgium -
Lecture (Conference)
The 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brussels, Belgium
Permalink: https://www.hzdr.de/publications/Publ-32842
X-ray Spectroscopy for Actinide Science
Kvashnina, K.
Abstract
X-ray spectroscopy is a widely used technique at synchrotron radiation sources for analyses of the electronic and structural parameters of materials. This includes the determination of the oxidation state and local symmetry of the absorbing atom. This lecture aimed at PhD students and postdocs who are interested in learning about the principles and practicalities of X-ray spectroscopy, as applied to actinide science. Experimental measurements can be performed on materials in a variety of states, including liquids and solids. The high intensity and tunability of X-rays allow the investigation of a wide range of materials, including thin films, nanoparticles, amorphous materials, solutions, disordered minerals and soils. Moreover, I will provide an overview of the advanced spectroscopic techniques, such as resonant inelastic X-ray scattering (RIXS) and high-energy-resolution fluorescence detected (HERFD) absorption spectroscopy (XAS) that are available at the synchrotrons for studies of actinide systems. I will cover basic principles of X-ray spectroscopy theory and instrumental setups and I will show several examples of the studies performed on the uranium, thorium and plutonium containing materials in the hard and tender X-ray range
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32841) publication
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Invited lecture (Conferences)
(Online presentation)
JDA-2021: 13th School on the Physics and Chemistry of Actinides, 22.-25.03.2021, Rennes, France
Permalink: https://www.hzdr.de/publications/Publ-32841
High energy resolution X-ray spectroscopy on uranium compounds
Kvashnina, K.
Abstract
Understanding the mechanisms of different chemical reactions with uranium at the atomic level is a key step towards safe disposal of nuclear wastes and towards the identification of physical-chemical processes of radionuclides in the environment. X-ray absorption spectroscopy in high energy resolution fluorescence detection (HERFD) mode at the U L3 and M4,5 edges together with resonant inelastic X-ray scattering (RIXS) are now common techniques for probing the uranium electronic structure and for studying the physics and chemistry of uranium-containing compounds[1], [2]. I will provide an overview of the recently performed studies[3]–[5] on uranium-containing materials at the European Synchrotron (ESRF) in Grenoble (France). I will show how the detailed information about the U oxidation state and electron-electron interactions can be obtained by a combination of experimental data and electronic structure calculations. In connection with latest results, the capabilities and limitations of the HERFD and RIXS experimental methods will be discussed in details. It might be of interest for fundamental research in chemistry and physics of actinides as well as for applied science
References:
[1] K. O. Kvashnina, S. M. Butorin, P. Martin, and P. Glatzel, “Chemical State of Complex Uranium Oxides,” Phys. Rev. Lett., vol. 111, no. 25, p. 253002, Dec. 2013, doi: 10.1103/PhysRevLett.111.253002.
[2] K. O. Kvashnina, Y. O. Kvashnin, and S. M. Butorin, “Role of resonant inelastic X-ray scattering in high-resolution core-level spectroscopy of actinide materials,” J. Electron Spectros. Relat. Phenomena, vol. 194, pp. 27–36, Jun. 2014, doi: 10.1016/j.elspec.2014.01.016.
[3] N. Boulanger et al., “Enhanced Sorption of Radionuclides by Defect-Rich Graphene Oxide,” ACS Appl. Mater. Interfaces, vol. 12, no. 40, pp. 45122–45135, Oct. 2020, doi: 10.1021/acsami.0c11122.
[4] E. Gerber et al., “Insight into the structure–property relationship of UO 2 nanoparticles,” Inorg. Chem. Front., vol. 8, no. 4, pp. 1102–1110, 2021, doi: 10.1039/D0QI01140A.
[5] A. S. Kuzenkova et al., “New insights into the mechanism of graphene oxide and radionuclide interaction,” Carbon N. Y., vol. 158, pp. 291–302, Mar. 2020, doi: 10.1016/j.carbon.2019.10.003.
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32840) publication
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Invited lecture (Conferences)
(Online presentation)
Uranium Science, 28.06.-01.07.2021, Bristol, UK
Permalink: https://www.hzdr.de/publications/Publ-32840
Thermoelectricity and electronic properties of Y1-xCexCrB4
Flipo, S.; Rosner, H.; Bobnar, M.; Kvashnina, K.; Leithe-Jasper, A.; Gumeniuk, R.
Abstract
Boron-rich materials combine chemical stability with refractory properties and, consequently, are interestingfor high-temperature thermoelectric applications. Therefore, the magnetic, electrical, and thermal transportproperties of the Y1−xCexCrB4series have been investigated here to employ the concept of correlation-enhancedthermoelectric properties. Combining x-ray diffraction and energy- or wavelength-dispersive spectrometry,we find a rather narrow stability range of Y1−xCexCrB4, only samples on the Y- and Ce-rich substitutionlimits (x=0,0.05,0.95,and 1) were obtained. Electrical resistivity data show a change from semiconducting(x=0) to metallic behavior upon Ce substitution (x0.95). From magnetic susceptibility measurements andx-ray absorption spectroscopy, we find a temperature-dependent intermediate valence state of Ce of about+3.5.However, a fit of the magnetic susceptibility data to the Coqblin-Schrieffer model yields a surprisingly highKondo temperature of about 1100 K. Together with the good thermal conductivity for the studied substitutionseries this impedes a suitable thermoelectric performance. Electronic structure calculations for YCrB4supportits narrow gap semiconducting nature in contrast to previous studies. Surprisingly, its electronic structure ischaracterized by pronounced van Hove singularities very close to the Fermi-levelEF. They originate fromnearly dispersionless Cr 3dz2−r2-derived bands in a large part of the Brillouin zone, suggesting the appearance ofelectronic instabilities upon rather small electron doping into these states
Involved research facilities
- Rossendorf Beamline at ESRF DOI: 10.1107/S1600577520014265
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- DOI: 10.1107/S1600577520014265 is cited by this (Id 32839) publication
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Physical Review B 103(2021), 195121
DOI: 10.1103/PhysRevB.103.195121
Cited 8 times in Scopus
Downloads
- Final Draft PDF 3,1 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32839
Uptake of niobium by cement systems relevant for nuclear waste disposal: impact of ISA and chloride
Cevirim-Papaioannou, N.; Jo, Y.; Franke, K.; Fuss, M.; de Blochouse, B.; Altmaier, M.; Gaona, X.
Abstract
The isotope 94 of niobium (t1/2= 2.04·104 a) is produced during the operation of nuclear reactors due to the neutron activation of 93Nb, which is present in some structural components in nuclear reactor vessels. Related waste streams will be disposed of in repositories for low and intermediate level wastes (L/ILW), where cement is widely used for the stabilization of the waste and for construction purposes.
The retention of niobium by young cement was investigated in a series of sorption experiments using a combination of active (95Nb + 91mNb) and inactive (93Nb) niobium isotopes. Sorption experiments assessed also the impact of iso-saccharinic acid (ISA, main degradation product of cellulose) and chloride on Nb retention, both expected in specific L/ILW.
A pyrochlore-structure Ca-Nb(V) oxide was found to control the solubility of Nb(V) in cement pore water at pH= 13.5, defining [Nb(V)]aq = 2∙10-6 - 7·10–8 M. Sorption experiments revealed a strong uptake of Nb(V) by cement (5 ≤ log Rd ≤ 7, Rd in L·kg–1), in spite of the predominance of anionic hydrolysis species in the cement pore water. Sorption isotherms were found to be linear within 10–14 M ≤ [Nb(V)]aq ≤ 10–9 M. Calcium silicate hydrate (C-S-H) phases are defined as main sink of Nb(V) in cement, with Ca2+ playing a key role in bridging the negatively charged Nb(V) species to C-S-H. ISA significantly decreases the uptake of Nb(V) at [ISA]aq ≥ 10–4 M, reflecting the formation of stable (Ca-)Nb(V)-ISA complexes in the aqueous phase. Sorption is not affected by chloride within the investigated concentration range (10–5 M ≤ [Cl–] ≤ 1.0 M).
This work represents the first experimental evidence on the uptake of niobium by young cement in the absence and presence of ISA and Cl–, thus providing key inputs for the assessment of 94Nb retention in the context of the Safety Case for repositories for nuclear waste.
Keywords: niobium; cement; ISA; chloride; sorption
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Data publication: Uptake of niobium by cement systems relevant for nuclear …
ROBIS: 33416 HZDR-primary research data are used by this (Id 32838) publication
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Cement and Concrete Research 153(2022), 106690
DOI: 10.1016/j.cemconres.2021.106690
Cited 11 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32838
Novel Radionuclides - Don’t Forget the Regulatory Side
Abstract
Recent years have seen many efforts to investigate several novel radionuclides, currently neither commercially available nor clinically used. Especially with the advent of theranostics aims are to improve therapeutic efficacy, to adapt the physical half live to the target under investigation or to improve the “matched pair” concept, i.e. eliminating differences in chemistry between a diagnostic and therapeutic radionuclides. This pre-Congress symposium will discuss, which candidates are promising, how technical and organisational advances may lead to better availability, where are major challenges, what is clinically required and desired, where are regulatory hurdles and where we currently stand in the development. The views from the producers, preclinical radiopharmaceutical researchers and the clinician will be included to provide an up to date status.
Keywords: Radionuclides; Theranostics; Accelerators; Mass separation; Radiopharmaceutical development
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Invited lecture (Conferences) (Online presentation)
Annual Congress of the European Association of Nuclear Medicine, 11.-13.10.2021, Virtuell, Österreich
DOI: 10.1007/s00259-021-05547-1
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32837
Regulatory Aspects of Cold Kit-Based Radiopharmaceuticals in the EU
Abstract
The cold kit approach is a fast and easy method for labeling tracers with radiometals used in Nuclear Medicine for 99mTc-radiopharmaceuticals since decades. The clinical success of some radiopharmaceutical labelled with Ga-68, a generator-based PET isotope, followed by the availability of registered generators and the development of new chelators, boosted the interest in development of cold kit-based 68Ga- radiopharmaceuticals as for 99mTc. The aluminium fluoride-18 (Al[18F]F) radiolabelling is an interesting “one-pot” method which involves the formation of 18F-metal complex trapped by a suitable chelator. This approach simplifies the 18F-labeling methodology along with the possibility to obtain a kit-based radiofluorination. In this session, the recent developments in kit-based labeling of 68Ga- radiopharmaceuticals and in Al[18F]F labeling will be discussed. Finally, since the regulatory aspect is an important issue for using cold kit preparations in clinical practice, an overview of the different regulations in European countries will be showed and discussed.
Keywords: Cold kit; radiolabeling; 68Ga-radiopharmaceuticals; Al[18F]F; regulatory aspects; PET
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Invited lecture (Conferences) (Online presentation)
Annual Congress of the European Association of Nuclear Medicine, 20.-23.10.2021, Virtuell, Österreich
DOI: 10.1007/s00259-021-05547-1
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32836
Optimization and automation of radiolabeling FAPI-74 using [18F]AlF chemistry
Laube, M.; Pietzsch, J.; Knieß, T.; Kopka, K.; Neels, O.
Abstract
Aim/Introduction:
In recent years quinoline-based small molecules targeting the fibroblast activation protein alpha (FAP) have gained interest for imaging a variety of tumor entities (1). A number of radiotracers for SPECT and PET have been developed, but so far only three FAP inhibitor (FAPI) radioligands have been reported to be radiolabeled with fluorine-18 (2,3,4). This study shows the optimization and automation of the radiofluorination of FAPI-74.
Materials and Methods:
(S)-(4-Carboxymethyl-7-{2-[4-(3-{4-[2-(2-cyano-pyrrolidin-1-yl)-2-oxoethylcarbamoyl]-quinolin-6-yloxy}-propyl)-piperazin-1-yl]-2-oxo-ethyl}-[1,4,7]triazonan-1-yl)-acetic acid, commonly referred to as FAPI-74, was radiolabeled using the [18F]AlF chelation method. Starting from [18F]fluoride, the reaction with AlCl3, chelate formation and subsequent purification was initially optimized by manual syntheses. Optimization included the examination of different anion exchangers (QMA light, PSHCO3) and elution solutions (NaOAc buffer pH4, 0.9% NaCl) as well as careful adjustment of the reaction parameters time (0-20 min), temperature (r.t. to 100°C), amount of AlCl3 and NaOAc buffer pH4, solvents (DMSO, EtOH), and precursor concentration (1-350 µM). Radiochemical conversion (RCC) was determined by radio-UPLC of the crude reaction mixtures. Selected reaction mixtures were analyzed after decay using UPLC-MS to identify non-radioactive byproducts. The optimized radiosynthetic procedure was transferred to a fully automated radiosynthesizer (TRACERlab FXFN) and the final product was purified and formulated using semi-preparative HPLC and SPE.
Results:
Under optimized conditions, RCC of [18F]AlF-FAPI-74 of > 99% was still observed at precursor concentrations as low as 12 µM FAPI-74 after reaction in a 1:1 molar ratio with AlCl3 in DMSO/sodium acetate buffer at pH 4 at 80°C for 15 minutes. Transfer of optimized conditions and upscaling was successfully achieved and delivered radiochemical pure [18F]AlF-FAPI-74 formulated in EtOH suitable for further preclinical experiments. Work on a more rapid SPE-purification and full characterization according to GMP guidelines is in progress.
Conclusion:
The radiosynthesis of [18F]AlF-FAPI-74 was optimized and automated, which in the future will allow the production of large quantities and the distribution of this promising radiotracer to other (clinical) centers.
References:
(1) Altmann A et al. The latest developments in imaging fibroblast activation protein (FAP). J. Nucl. Med. 2021, 62(2) 160-167.
(2) Giesel FL et al. FAPI-74 PET/CT Using Either 18F-AlF or Cold-Kit 68Ga Labeling: Biodistribution, Radiation Dosimetry, and Tumor Delineation in Lung Cancer Patients. J. Nucl. Med. 2021, 62(2) 201-207.
(3) Jiang X et al. FAPI-04 PET/CT using [18F]AlF Labeling Strategy: Automatic Synthesis, Quality Control, and in vivo Assessment in Patient. Front. Oncol. 2021, 11:649148.
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Lecture (Conference) (Online presentation)
Annual Congress of the European Association of Nuclear Medicine, 20.-23.10.2021, Virtuell, Österreich
DOI: 10.1007/s00259-021-05547-1
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32835
Resonance behavior of embedded and freestanding microscale ferromagnets
Cansever, H.; Anwar, M. S.; Stienen, S.; Lenz, K.; Narkovic, R.; Hlawacek, G.; Potzger, K.; Hellwig, O.; Faßbender, J.; Lindner, J.; Bali, R.
Abstract
The ferromagnetic resonance of a disordered A2 Fe60Al40 of ferromagnetic strip, of dimensions 5 µm × 1 µm x 32 nm, has been observed in two vastly differing surroundings: in the first case, the ferromagnetic region was circumferenced by ordered B2 Fe60Al40, and in the second case it was free standing, adhering only to the oxide substrate. The embedded ferromagnet possesses a periodic magnetic domain structure, which transforms to a single domain structure in the freestanding case. The two cases differ in their dynamic response, for instance, the resonance field for the uniform (k = 0) mode at ~ 14 GHz excitation displays a shift from 209 to 194 mT, respectively for the embedded and freestanding cases, with the external magnetic field applied along the long axis. The resonant behavior of a microscopic ferromagnet can thus be finely tailored via control of its near-interfacial surrounding.
Keywords: Embedded nanomagnets; microresonator; ferromagnetic resonance; ion irradiation
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32834) publication
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Scientific Reports 12(2022), 14809
DOI: 10.1038/s41598-022-15959-0
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32834
Two-dimensional magneto-photoconductivity in non-van der Waals manganese selenide
Hu, L.; Cao, L.; Li, L.; Duan, J.; Liao, X.; Long, F.; Zhou, J.; Xiao, Y.; Zeng, Y.-J.; Zhou, S.
Abstract
Deficient intrinsic species and suppressed Curie temperatures (Tc) in two-dimensional (2D) magnets are major barriers for future spintronic applications. As an alternative, delaminating non-van der Waals (vdW) magnets can offset these shortcomings and involve robust bandgaps to explore 2D magneto-photoconductivity at ambient temperature. Herein, non-vdW a-MnSe2 is first delaminated as quasi-2D nanosheets for the study of emerging semiconductor, ferromagnetism and magneto-photoconductivity behaviors. Abundant nonstoichiometric surfaces induce the renormalization of the band structure and open a bandgap of 1.2 eV. The structural optimization strengthens ferromagnetic super–exchange interactions between the nearest-neighbor Mn2+, which enables us to achieve a high Tc of 320 K well above room temperature. The critical fitting of magnetization and transport measurements both verify that it is of quasi-2D nature. The above observations are evidenced bymultiplemicroscopic andmacroscopic characterization tools, in line with the prediction of firstprinciples calculations. Profiting from the negative magnetoresistance effect, the self-powered infrared magneto-photoconductivity performance including a responsivity of 330.4 mA W-1 and a millisecondlevel response speed are further demonstrated. Such merits stem from the synergistic modulation of magnetic and light fields on photogenerated carriers. This provides a new strategy to manipulate both charge and spin in 2D non-vdW systems and displays their alluring prospects in magneto-photodetection.
Keywords: Manganese selenide; two dimensional non van der Waals
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32833) publication
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Materials Horizons 8(2021), 1286-1296
DOI: 10.1039/d1mh00009h
Cited 57 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32833
How to study nonlinear dynamics in semiconductors by terahertz wave free electron laser
Abstract
This tutorial talk covers the study of nonlinear dynamics in semiconductor nanostructures in strong terahertz and mid-infrared fields involving a free-electron laser.
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
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- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32832) publication
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Invited lecture (Conferences)
(Online presentation)
International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPT2021), 16.-19.06.2021, Chengdu, China
Permalink: https://www.hzdr.de/publications/Publ-32832
Interfacial behavior of particle-laden bubbles under asymmetric shear flow
Eftekhari, M.; Schwarzenberger, K.; Heitkam, S.; Javadi, A.; Bashkatov, A.; Ata, S.; Eckert, K.
Abstract
The interfacial properties of air bubbles have mostly been studied in quiescent fluids or in an axisymmetric flow field. To extend the knowledge to technologically relevant conditions, we investigate the behavior of surfactant- and particle-laden bubbles under asymmetric shear forces. Experiments are performed with a buoyant bubble at the tip of a capillary placed in a defined flow field. The response of the interface to the surrounding asymmetric flow is measured under successive reduction of the surface area. Profile analysis tensiometry is utilized to investigate the dynamic surface tension and the surface rheology of the surfactant- and particle-laden interfaces. The bulk flow and the interfacial mobility of the buoyant bubble are studied using microscopic particle image and tracking velocimetry. According to our findings, under asymmetric shear flow, surfactant-laden interfaces remain mobile regardless of the surfactant concentration. In contrast, particle-laden interfaces adopt a solid-like state and resist the interfacial flow at certain surface coverages. Elasticity measurements during successive reduction of the surface area indicate a significant change in the structure of the interface that changes its mobility. The immobilization of the interface is characterized by the ratio of the interfacial elasticity to shear forces. This dimensionless number provides an estimate the interfacial forces required to initiates interfacial immobility at defined flow field. Our findings can serve as a basis to model the boundary conditions and to modulate the hydrodynamics of bubbles and droplets with different adsorbed material.
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Langmuir 37(2021)45, 13244-13254
DOI: 10.1021/acs.langmuir.1c01814
Cited 12 times in Scopus
Downloads
- Final Draft PDF 2,2 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32831
Enhanced trion emission in monolayer MoSe2 by constructing a type-I van der Waals heterostructure
Duan, J.; Chava, P.; Ghorbani Asl, M.; Krasheninnikov, A.; Erb, D.; Hu, L.; Schneider, H.; Rebohle, L.; Erbe, A.; Helm, M.; Zeng, Y.-J.; Zhou, S.; Prucnal, S.
Abstract
Trions, quasi-particles consisting of two electrons combined with one hole or of two holes with one electron, have recently been observed in transition metal dichalcogenides (TMDCs) and drawn increasing attention due to potential applications of these materials in light-emitting diodes, valleytronic devices as well as for being a testbed for understanding many-body phenomena. Therefore, it is important to enhance the trion emission and its stability. In this study, we construct a MoSe2/FePS3 van der Waals heterostructure (vdWH) with type-I band alignment, which allows for carriers injection from FePS3 to MoSe2. At low temperatures, the neutral exciton (X0) emission in this vdWH is almost completely suppressed. The ITrion/Ix0 intensity ratio increases from 0.44 in a single MoSe2 monolayer to 20 in this heterostructure with the trion charging state changing from negative in the monolayer to positive in the heterostructure. The optical pumping with circularly polarized light shows a 14% polarization for the trion emission in MoSe2/FePS3. Moreover, forming such type-I vdWH also gives rise to a 20-fold enhancement of the room temperature photoluminescence from monolayer MoSe2. Our results demonstrate a novel approach to convert excitons to trions in monolayer 2D TMDCs via interlayer doping effect using type-I band alignment in vdWH
Keywords: type-I; van der Waals heterosturcture; photoluminescence enhancement; trion/exciton intensity ratio; polarization
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32827) publication
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Advanced Functional Materials 31(2021)40, 2104960
DOI: 10.1002/adfm.202104960
Cited 27 times in Scopus -
Lecture (Conference)
(Online presentation)
2021 Fall Meeting of the European Materials Research Society (E-MRS), 20.-23.09.2021, Warsaw, Poland
Permalink: https://www.hzdr.de/publications/Publ-32827
Log file-based 4D proton dose reconstruction for interplay assessment in clinical routine and simulation studies
Stützer, K.; Spautz, S.; Thiele, J.; Tschiche, M.; Troost, E. G. C.; Richter, C.
Abstract
We have implemented the reconstruction of interplay-affected dose distributions from the log files of the dynamic PBS proton beam delivery and of the breathing-induced intra-fractional motion. For the first time, such an algorithm is capable to consider amplitude-sorted 4DCT phases. We have validated the reconstruction accuracy by phantom experiments for several motion patterns and magnitudes. The module is applied in combination with weekly repeat 4DCTs to routinely monitor the PBS treatments of NSCLC patients in our clinic department. Further use cases are occasional pre-treatment interplay estimations and the interplay effect evaluations within a plan comparison study investigating the benefit of 4D robustly optimized proton plans for NSCLC patients with large breathing motion (>5mm).
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Lecture (others)
(Online presentation)
European RayStation user meeting 2021, 30.11.-01.12.2021, Stockholm, Sweden
Permalink: https://www.hzdr.de/publications/Publ-32826
Attention based deep 3d multiple instance survival models for oropharyngeal carcinoma patients
Starke, S.; Leger, S.; Zwanenburg, A.; Löck, S.
Abstract
Introduction
Attention-based convolutional neural networks (CNNs) have the capability to use multiple parts of the same image to predict outcomes of interest. Especially in the domain of medical image analysis, where whole images are typically described by a single label but the identification of important image regions is unclear, this approach allows to combine competitively performing CNNs with enhanced interpretability of the decision-making process.
Materials & Methods
We developed risk models for the prediction of overall survival (OS) for 518 patients of a publicly available oropharyngeal carcinoma (OPC) cohort. Patients were randomly split into training, validation, and test cohorts (388/30/100 patients). A baseline Cox model using clinical information only and three attention-based CNNs using different likelihood functions were trained on multiple 3D instances of the pre-treatment computed tomography (CT) images. Subsequently, patients were stratified into groups at low and high risk of death using median cutoff values based on predictions determined on the training cohort. Model performance was measured using the concordance index (C-index) and differences between Kaplan-Meier curves were assessed by the log-rank test.
Results
The baseline Cox model achieved a C-Index of 0.22 and the CNN models based on the Cox, Weibull and Lognormal likelihood functions achieved C-indices of 0.34, 0.35 and 0.35, respectively, on the test cohort. All models stratified the patients into two risk groups with a statistically significant difference in OS. Attention scores between the multiple instances of a patient were similar, suggesting that all CT instances were equally important for the network decision.
Summary
We investigated the potential of attention-based multiple-instance learning for prediction of OS on an OPC cohort. Since all attention-based CNNs generated risk groups with significantly different OS based on imaging data alone, we consider this approach promising for future validation studies.
Keywords: Deep learning; Survival analysis; Oropharyngeal carcinoma; Attention
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Lecture (Conference)
(Online presentation)
Dreiländertagung der Medizinischen Physik, 19.-21.09.2021, digital, digital
Permalink: https://www.hzdr.de/publications/Publ-32825
THEREDA - Thermodynamic Reference Database
Moog, H. C.; Bok, F.; Freyer, D.; Gaona, X.; Thoenen, T.
Abstract
Part of the process to ensure the safety of radioactive waste disposal is the predictive modeling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modeling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA [1].
THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients which allow for the calculation of solubilities in high-saline solutions. Registered users may either download single thermodynamic data or ready-to-use parameter files for the geochemical speciation codes PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. Data can also be downloaded in a generic JSON-format to allow for the import into other codes. The database can be accessed via the world wide web: www.thereda.de
Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side effects on calculations are caused. Furthermore, our website offers an increasing number of examples for applications, including graphical representation, which can be filtered by components of the calculated system.
[1] H. C. Moog, F. Bok, C. M. Marquardt, V. Brendler (2015): Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55) 72-84. http://dx.doi.org/10.1016/j.apgeochem.2014.12.016
Keywords: THEREDA; Thermodynamic Reference Database; Datenbasis; Datenbank; Pitzer; Löslichkeiten; Modellierung
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Poster
(Online presentation)
Goldschmidt2021, 04.-09.07.2021, Lyon, Frankreich
Permalink: https://www.hzdr.de/publications/Publ-32824
Uranium carbonates removal by Layered Double Hydroxides
Padberg, G.
Abstract
Uranium as a radionuclide and heavy metal has strong negative health effects on all living beings.
Since uranium salts display a high solubility in water, its mobility in aquifers is immense
and leads to the risk of ingestion by water consuming organisms. Sources of uranium contamination
in the environment are military and mining activities as well as leaking repositories.
The objective of this work is to analyze the uranium removal properties of two double layered
hydroxides (LDH) with different redox properties in absence and presence of carbonate. The
LDH phases selected are Ca(II)-Al(III)-Cl and Fe(II)-Al(III)-Cl, hereafter named Ca-LDH and
Fe-LDH. These LDHs play a crucial role in the geosphere, as they consist of the most abundant
elements in the earth crust. Furthermore, Ca-LDH is a product of bentonite weathering, which
is an essential process considered in repository safety management.
The first aim of this work is to synthesize and characterize Ca-LDH and Fe-LDH with respect
to their stoichiometry (inductively coupled plasma mass spectrometry, Mössbauer spectroscopy,
thermogravimetric analysis, energy-dispersive X-ray spectroscopy), their structure
(X-ray diffraction, Brunauer-Emmett-Teller theory, dynamic light scattering, scanning electron
microscopy, Raman microscopy) and their electronic state (X-ray photoelectron spectroscopy,
electrophoretic mobility).
The ultimate goal is to determine the best conditions under which uranium is removed from
solution by these LDHs. This will be achieved by analyzing the parameters that influence the
process (carbonate presence, redox processes, pH, ionic strength and uranium concentration).
In comparison to Ca-LDH, Fe(II)-LDH contains a redox active moiety, so that a different mechanism
for the interaction of these LDH phases with aqueous uranium is expected. For a comprehensive
understanding of these molecular uranium reactions occuring at the LDH phase,
various spectroscopic techniques (attenuated total reflexion Fourier-transform infrared, cryo
time-resolved laser-induced fluorescence, energy-dispersive X-ray, X-ray photelectron spectroscopy)
and microscopies (Raman microscopy, scanning electron microscopy) are applied
and combined. The synthesis of Ca-LDH and Fe-LDH was successful and structurally characterized by different
techniques (XRD, DLS, electrophoretic mobility, BET, SEM, EDXS, Raman microscopy,
XPS and Mössbauer). The stoichiometry under consideration of the corresponding oxidation
states was determined as
Ca(II)₀.₅₉Al(III)₀.₄₁Cl₀.₈₂(OH)₂ · 3.0 H2O and
Fe(II)₀.₆₀Al(III)₀.₄₀Cl₀.₈₀(OH)₂ · 1.8 H2O.
Uranium removal by Ca-LDH and Fe-LDH was evaluated as a function of pH (5.5 to 11.0),
ionic strength (H2O, 0.01 M NaCl, and 0.1 M NaCl), carbonate concentration (0, 0.013 mM,
0.2 mM, 0.24 mM and 2 mM) and U(VI) concentration (from nM to mM). As a general statement,
uranium removal was higher than 95% for pH > 6.0 for both Ca-LDH and Fe-LDH under
all studied conditions. Uranium removal decreased for pH < 6 in both LDH, as these mineral
phases are only stable under alkaline conditions. Uranium removal by Ca-LDH decreased at high ionic strength (0.1 M NaCl) and carbonate
concentration (2 mM and 20 mM). For the sorption mechanism of uranium to Ca-LDH, redox
potential measurements indicate a pH, carbonate and ionic strength dependency of the sorbed
minerals. In all studied cases, uranium associated to Ca-LDH is found as U(VI). Two different
U(VI) species are detected by ATR-IR measurements at pH 9.5 in presence of carbonate. Most
tentatively, one species is corresponding to U(VI) precipitation, which is also suggested by Raman
microscopy. The other species could be correlated to U(VI) outer-sphere complexation,
which is also supported by the lack of changes in the isoelectric point of Ca-LDH in presence
of U(VI) and the decrease of chloride content on the Ca-LDH after being in contact with U(VI).
The presence of outer-sphere complexation might be the reason of the decreased U(VI) removal
at higher ionic strengths and carbonate concentrations.
Three different species of U(VI) associated to Ca-LDH are detected by TRLFS from pH 8.0
to pH 11.0 in presence and absence of carbonate. Species 1 could be related to [UO₂(OH)₃]⁻
complexation according to uranium speciation diagrams. Species 2 identity is challenging to
hypothesize. It is assumed that U(VI) incorporation occurs due to an increased Ca concentrationin solution. Species 3 is assigned to [UO₂(CO₃)₂]²⁻ complexation. A reliable identification of
this species would need the use of additional techniques, like XAS.
In contrast, uranium removal by Fe-LDH occurs via Fe(II) promoted reduction of U(VI) to
U(IV). This is confirmed by redox potential values, the detection of Fe(III) by XPS and the
observation of Fe(III) minerals (ferrihydrite, hematite and iron aluminate) by Raman. Changes
on the Fe-LDH structure after contact with U(VI) are also observed in SEM images. The confirmation
of possible stepwise uranium removal by Fe-LDH (anion exchange followed by U(VI)
reduction) would need further verification by ATR FT-IR.
To sum up, the synthesized Ca-LDH and Fe-LDH phases are found to exhibit excellent and effective
uranium removal properties under alkaline conditions, being able to remove negatively
charged uranium species from solutions. Sorption mechanisms could be suggested in a multispectroscopic
approach as outer-sphere surface complexation and incorporaton for Ca-LDH and
as uranium reductive immobilization for Fe-LDH.
This study shows, that the examined Ca-LDH and Fe-LDH can act as a naturally occuring retention
barrier in geosphere against uranium release from repositories. Therefore, these LDH
phases can possibly be part of a technical multi-barrier system preventing uranium leaking into
the biosphere. Further experiments need to be carried out by TRLFS, ATR-IR and XAS in
order to have a comprehensive identification of the uranium sorption mechanisms on Ca-LDH
and Fe-LDH.
Keywords: uranium; Reductive immobilization; Sorption; LDH
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Master thesis
TU Dresden, 2021
Mentor: Prof. Dr. Thorsten Stumpf (1. Prüfer) Dr. Natalia Mayordomo (2. Prüfer)
65 Seiten
Permalink: https://www.hzdr.de/publications/Publ-32823
The pure paramagnetism in graphene oxide
Zhang, X.; Li, G.; Li, Q.; Shaikh, M. S.; Li, Z.
Abstract
Magnetic properties of graphene and its derivatives are very fascinating because of their promising application in
spintronics. Among the graphene family materials, graphene oxide is quite typical and special for the magnetic
performance. Herein we report a systematic and detailed investigation on the magnetic properties of graphene
oxide. Compared to the previous reports on the ferromagnetism, our results show that graphene oxide is indeed
only paramagnetic. The magnetic properties can be well described by the Curie-Weiss law. This study is not only
revealing the paramagnetism in graphene oxide but also calling a revisit about the magnetic properties of graphene
oxides, graphene and the other derivatives of graphene.
Keywords: Graphene oxide; Micro-Raman; Magnetization; Paramagnetism
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32822) publication
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Results in Physics 26(2021), 104407
DOI: 10.1016/j.rinp.2021.104407
ISSN: 2211-3797
Cited 16 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32822
Bonding Trends in a Series of Tetravalent Th-Pu Monosalen Complexes
Abstract
Actinides (An) play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories.[1] Coordination chemistry of An using small model ligands is a useful tool to get a profound basic knowledge about fundamental physico-chemical properties of the An binding. Observed changes in e.g. the binding situation or magnetic effects among an isostructural An series with the An in the same oxidation state may deliver insight into the unique electronic An properties mainly originating from their f-electrons.
In this study we investigate the coordination chemistry of tetravalent actinides (An(IV)), which are dominant particularly under anoxic environmental conditions, using the organic salen ligand as a small N,O donor.[2] All syntheses were conducted under inert, water-free atmosphere using pyridine based solvents (Pyx). SC-XRD results prove that three isostructural complex series were achieved in each case, dependent on the solvent used. In all complexes, one salen ligand coordinates to the An (An = Th, U, Np, Pu) tetradentately with both nitrogen and deprotonated oxygen donor atoms. The vacant coordination sites are occupied by two chloro ligands for charge compensation as well as two respective solvent molecules, either pyridine (Py), 4-methylpyridine (Pic) or 3,5-lutidine (Lut), resulting in an eightfold coordination environment (see [AnCl2(salen)(Pic)2] as representatives in Figure 1).
The acquired experimental SC-XRD and IR results as well as supporting QC calculations point to a different bonding situation of the individual donor atoms to the actinide. Whereas the An–Nsalen/Pyx and the An–Cl bond lengths follow the decrease of the ionic radii, the An–Osalen bonds remarkably diverge from this behavior. These rather follow the trend of decreasing covalent radii, indicating an exceptionally strong bond here. QC calculations additionally indicate a weaker binding strength in the An–NPyx bonds compared to An–Nsalen. This explains the potential solvent exchange (e.g. to the other pyridine based solvents) and opens up the possibility of further chemical modification at these positions.
Keywords: Actinides; bonding analysis; thorium; uranium; neptunium; plutonium
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Lecture (Conference)
(Online presentation)
Journées des Actinides, 22.-25.03.2021, Rennes, France
Permalink: https://www.hzdr.de/publications/Publ-32821
Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles on the Muscovite (001) Basal Plane
Neumann, J.; Qiu, C.; Eng, P.; Skanthakumar, S.; Soderholm, L.; Stumpf, T.; Schmidt, M.
Abstract
Understanding the impact of actinide nanoparticle (NP) formation is important to assess radionuclide mobility in the environment. We combined Surface X-ray Diffraction (SXRD) and in situ AFM to investigate the previously reported unusual electrolyte effects on Th uptake on mica. At low [Th] (0.1 mM), interfacial structures show a broad Th electron density (~50 Å). A linear decrease of Th uptake with decreasing hydration enthalpy of the electrolyte cation (Li⁺, K⁺, NH₄⁺, Cs⁺) indicates a competitive effect between Th and the electrolyte cation. Na⁺ is a clear outlier from this trend. In situ AFM imaging confirms the results. Particles show a vertical size of ~1 – 2 nm and larger lateral dimensions of ~10 – 20 nm, which is typical for particles formed at interfaces (heterogeneous nucleation). At high [Th] = 1 and 3 mM, all investigated electrolytes (ACl, A = Li⁺, Na⁺, K⁺) show similar Th uptake, indicating a much smaller impact of electrolyte composition. The interfacial structures are dominated by a high Th loading at a distinct distance (~6.5 Å) from the surface. Therefore, the main retention mechanism at high [Th] is suggested to be the sorption of Th NPs aggregated from Th oligomers present in solution (homogeneous nucleation).
Keywords: CTR; RAXR; SXRD; AFM; surface X-ray diffraction; nanoparticles; nucleation; thorium
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Journal of Physical Chemistry C 125(2021)30, 16524-16535
DOI: 10.1021/acs.jpcc.1c03997
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32820
Research data: THz harmonic generation from ultraclean graphene
Deinert, J.-C.; Kovalev, S.
Project Leader: Tielrooij, Klaas-Jan; DataCollector: Kovalev, Sergey; Project Member: Soavi, Giancarlo; Project Member: Klimmer, Sebastian
Abstract
Research data from the June 2021 TELBE beamtime for scientific exchange.
Keywords: Terahrtz; graphene; encapsulated graphene; nonlinear optics; harmonic generation
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32819) publication
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Reseach data in the HZDR data repository RODARE
Publication date: 2021-06-22 Restricted access
DOI: 10.14278/rodare.1035
Versions: 10.14278/rodare.1036
Downloads
Permalink: https://www.hzdr.de/publications/Publ-32819
Analyse eines Energiespeichersystems basierend auf geologischer Unter-grundspeicherung von CO2 und CH4
Fogel, S.; Yeates, C.; Unger, S.; Hampel, U.
Abstract
Die Speicherung von überschüssiger Elektroenergie aus regenerativen Energiequellen in relevanten Größenordnungen stellt eine wesentliche technologische Hürde der Energiewende in der Bundes-republik Deutschland dar. Der nationale Strombedarf in Zeiten unzureichender regenerativer Er-zeugung kann zukünftig mit Speicherkraftwerken auf Basis von aus CO2 und Elektrolysewasser-stoff produziertem synthetischen Methan (Power-to-Gas) und methangefeuerten, hocheffizienten Kraftkreisläufen (Gas-to-Power) basierend auf dem Allam-Kreislauf gedeckt werden. Durch die Nutzung von überkritischem CO2 als Kreislaufmedium lassen sich Wirkungsgrade von bis zu 66% für den Gas-to-Power-Pfad und Gesamtwirkungsgrade des Speicherzyklus von >50% erzielen. Zur Umsetzung dieses Konzeptes sind ausreichende Speicherkapazitäten für CO2, CH4 und O2 sowie regenerative Erzeugungskapazitäten vorzuhalten. Der vorliegende Beitrag untersucht den vorge-stellten Energiespeicherzyklus unter Annahme eines geschlossenen CO2-Kreislaufs gekoppelt mit geologischer Untergrundspeicherung von CO2 und CH4 im Sinne des Carbon Capture, Utilization and Storage (CCUS). Zur technischen Bewertung des Konzeptes wurde das Potential der Speiche-rung von CO2 in Aquiferen in Deutschland analysiert und eine Studie des deutschen Energiesys-tems im Jahre 2050 für verschiedene Orientierungsszenarien durchgeführt. Mit Hilfe der erstellten Szenarien konnten die zur Erlangung einer CO2-neutralen Energiespeicherung benötigen Kapazitä-ten der regenerativen Stromerzeugung, elektrolytischen Wasserstoffbereitstellung und Rekonversi-on von CH4 sowie Speicherkapazitäten für CO2, CH4 und O2 abgeleitet werden.
Involved research facilities
- TOPFLOW Facility
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Lecture (Conference)
53. Kraftwerkstechnisches Kolloquium, 05.-06.10.2021, Dresden, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-32818
Effects of Substituents on the Molecular Structure and Redox Behavior of Uranyl(V/VI) Complexes with N3O2‑Donating Schiff Base Ligands
Takeyama, T.; Tsushima, S.; Takao, K.
Abstract
Uranyl(VI) complexes with pentadentate N3O2-donating Schiff base ligands having various substituents at the ortho (R1) and/or para (R2) positions on phenolate moieties, R1,R2-Mesaldien2−, were synthesized and thoroughly character-ized by 1H NMR, IR, elemental analysis, and single crystal X-ray diffraction. Molecular structures of UO2(R1,R2-Mesaldien) are more or less affected by electron-donating or -withdrawing nature of the substituents. The redox be-havior of all UO2(R1,R2-Mesaldien) complexes were investigated to understand how substituents introduced onto the ligand affect redox behavior of these uranyl(VI) complexes. As a result, the redox potentials of UO2(R1,R2-Mesaldien) in DMSO increased from −1.590 V to −1.213 V with an increase in the electron-withdrawing nature of the substituents at the R1 and R2 positions. The spectroelectrochemical measurements and theoretical calculation (DFT and TD-DFT calculations) revealed that the center U6+ of each UO2(R1,R2-Mesaldien) complex undergoes one-electron reduction to afford the corresponding uranyl(V) complex, [UO2(R1,R2-Mesaldien)]−, regardless of difference in the substituents. Consequently, the redox active center of uranyl(VI) complexes seems not to be governed by the HOMO/LUMO gap, but to be determined by whether the LUMO is centered on a U 5f orbital or on one π* of a surrounding ligand.
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Inorganic Chemistry 60(2021)15, 11435-11449
DOI: 10.1021/acs.inorgchem.1c01449
Cited 18 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32817
Describing chain-like assembly of ethoxygroup-functionalized organic molecules on Au(111) using high-throughput simulations
Lokamani, M.; Kelling, J.; Ohmann, R.; Meyer, J.; Kühne, T.; Cuniberti, G.; Wolf, J.; Juckeland, G.; Huhn, T.; Zahn, P.; Moresco, F.; Gemming, S.
Abstract
Due to the low corrugation of the Au(111) surface, 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB) molecules can form
quasi interlocked lateral patterns, which are observed in scanning tunneling microscopy (STM) experiments at low temperatures.
We demonstrate a multi-dimensional clustering approach to quantify the anisotropic pair-wise interaction of molecules and
explain these patterns. We perform high-throughput calculations to evaluate an energy function, which incorporates the
adsorption energy of single PEEB molecules on the metal surface and the intermolecular interaction energy of a pair of PEEB
molecules. The analysis of the energy function reveals, that, depending on coverage density, specific types of pattern are
preferred which can potentially be exploited to form one-dimensional molecular wires on Au(111).
Keywords: DFTB; 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB); STM; High-Throughput; Meta-Structures
Related publications
-
Data publication: Describing chain-like assembly of ethoxygroup-functionalized …
ROBIS: 33955 HZDR-primary research data are used by this (Id 32816) publication
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Scientific Reports 11(2021), 14649
DOI: 10.1038/s41598-021-93724-5
Cited 2 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32816
Transport in tight material enlightened by process tomography
Kulenkampff, J.; Bollermann, T.; Cardenas Rivera, M. A.; Fischer, C.
Abstract
The analysis of fluid transport through tight barrier materials poses two major challenges: (i) Long equilibration periods require long minimum experiment durations, and, (ii) the fluid transport frequently results in complex pattern formation. Too short measuring times may feign too small transport rates; intact homogeneous samples are often missing problematic features, e.g. fractures. Both issues are detected and analyzed by using process tomography techniques, hence providing an improved understanding of transport processes in complex materials.
We thus continuously develop and apply the positron emission tomography (PET) method for geomaterials (Kulenkampff et al., 2016). It is able to trace very low concentrations of β+-emitting radionuclides during their passage through drill cores of barrier material with reasonable resolution (1 mm) and over variable periods (hours to years). The method yields time-resolved quantitative tomographic images of the tracer concentration (e.g. https://doi.org/10.5281/zenodo.166509), in contrast to input-output experiments like common permeability measurements, diffusion cells, or break-through curves.
Our current research includes the analysis of diffusive transport in heterogeneous shales (sandy facies of the Opalinuston) (BMBF and HGF iCross project), the reactive flow in fracture-filling materials of crystalline rocks (Eurad FUTURE project), and transport in engineered barriers and the contact zone (Euratom Cebama, Eurad Magic, as well as MgO and Stroefun BMWi projects). The efforts combine flow field tomography, structural imaging and reactive transport modelling for improving process understanding and to provide a bridge from the molecular to the macroscopic scale.
The benefits include:
- Insight into temporal stability and spatial heterogeneity of the observed transport process
- Parameterization of local velocity distribution and effective volume, comparability with pore-scale model simulations
- Ability to quantify multiple internal transport rates without necessity to register the delayed output signal
- Transparent and palpable visualization of processes hidden in the opaque material
References
Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J., Solid Earth 7, 1217-1231, DOI: 10.5194/se-7-1217-2016
Kulenkampff, J.: Geophysical Research Abstracts, Vol. 20, EGU2018-8813-1, 2018.
Keywords: radioactive waste disposal; geological barrier; transport experiments; positron emission tomography
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Contribution to proceedings
Interdisziplinäres Forschungssymposium safeND, 10.-12.11.2021, Berlin, Deutschland
Safety of Nuclear Waste Disposal, Göttingen: Copernicus Publications
DOI: 10.5194/sand-1-293-2021
Permalink: https://www.hzdr.de/publications/Publ-32815
Electrical control of orbital and vibrational interlayer coupling in bi- and trilayer 2H-MoS2
Klein, J.; Wierzbowski, J.; Soubelet, P.; Brumme, T.; Maschio, L.; Kuc, A. B.; Müller, K.; Stier, A. V.; Finley, J. J.
Abstract
Manipulating electronic interlayer coupling in layered van der Waals (vdW) mate- rials is essential for designing opto-electronic devices. Here, we control vibrational and electronic interlayer coupling in bi- and trilayer 2H-MoS2 using large external electric fields in a micro-capacitor device. The electric field lifts Raman selection rules and activates phonon modes in excellent agreement with ab-initio calculations. Through polarization resolved photoluminescence spectroscopy in the same device, we observe a strongly tunable valley dichroism with maximum circular polarization degree of ∼ 60% in bilayer and ∼ 35% in trilayer MoS2 that are fully consistent with a rate equation model which includes input from electronic band structure calculations. We identify the highly delocalized electron wave function between the layers close to the high symmetry Q points as the origin of the tunable circular dichroism. Our results demonstrate the possibility of electric field tunable interlayer coupling for controlling emergent spin-valley physics and hybridization driven effects in vdW materials and their heterostructures.
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Physical Review Materials 6(2022), 024002
DOI: 10.1103/PhysRevMaterials.6.024002
Cited 4 times in Scopus
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- Secondary publication expected
Permalink: https://www.hzdr.de/publications/Publ-32814
Towards harmonizing clinical linear energy transfer (LET) reporting in proton radiotherapy: A European multi-centric study
Hahn, C.; Ödén, J.; Dasu, A.; Vestergaard, A.; Fuglsang Jensen, M.; Sokol, O.; Pardi, C.; Bourhaleb, F.; Leite, A.; de Marzi, L.; Smith, E.; Aitkenhead, A.; Rose, C.; Merchant, M.; Kirkby, K.; Grzanka, L.; Pawelke, J.; Lühr, A.
Abstract
Background: Clinical data suggest that the relative biological effectiveness (RBE) in proton therapy (PT) varies with linear energy transfer (LET). However, LET calculations are neither standardized nor available in clinical routine. Here, the status of LET calculations among European PT institutions and their comparability are assessed and a consensus for harmonized LET reporting is presented.
Materials and methods: Eight European PT institutions used suitable treatment planning systems with their centre-specific beam model to create treatment plans in a water phantom covering different field arrangements and fulfilling commonly agreed dose objectives. They employed their locally established LET simulation environments and procedures to determine the corresponding LET distributions. Dose distributions D1.1 and DRBE assuming constant and variable RBE, respectively, and LET were compared among the institutions. Inter-centre variability was assessed based on dose- and LET-volume-histogram parameters.
Results: Treatment plans from six institutions fulfilled all clinical goals and were eligible for common analysis. D1.1 distributions in the target volume were comparable among PT institutions with variability <2.7%. However, corresponding LET values varied substantially between institutions for all field arrangements (≤57.1%), primarily due to differences in LET averaging technique and considered secondary particle spectra. Consequently, DRBE using nonharmonized LET calculations increased inter-centre dose variations substantially compared to D1.1 and significantly in mean dose to the target volume of perpendicular and opposing field arrangements (p<0.05). Harmonizing LET reporting (dose-averaging, all protons, LET to water) reduced the inter-centre variability in LET to the order of 10-15% within and outside the target volume for all beam arrangements. Consequentially, inter-institutional variability in DRBE decreased to that observed for D1.1 (p>0.05).
Conclusion: Harmonizing the reported LET among PT centres is feasible and allows for consistent multi-centric analysis and reporting of tumour control and toxicity in view of a variable RBE. It may serve as basis for harmonized variable RBE dose prescription in PT.
Keywords: proton therapy; multi-centric study; linear energy transfer (LET); relative biological effectiveness (RBE)
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Acta Oncologica 61(2022)2, 206-214
Online First (2021) DOI: 10.1080/0284186X.2021.1992007
Cited 34 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32813
Comprehensive microstructural and optical characterization of the thermal stability of aluminum-titanium oxynitride thin films after high temperature annealing in air
Escobar Galindo, R.; Heras, I.; Guillén, E.; Munnik, F.; Azkona, I.; Krause, M.
Abstract
The thermal stability of two AlyTi1-y(OxN1-x) layers prepared by cathodic vacuum arc deposition with different oxygen content was studied after high temperature annealing of the samples in air. These layers were designed to be part of solar-selective coating (SSC) stacks. Compositional and microstructural characterization of the thin films was performed before and after the thermal treatment by elastic recoil detection (ERD), transmission electron microscopy and Raman spectroscopy.
AlyTi1-yN sample was stable after 2 hours of annealing at 450ºC. Initial stages of the formation of a surface oxide layer after annealing at 650 ºC were observed both by ERD and Raman analysis. Contrarily, no changes were found after 2 hours annealing treatment either at 450 and 650ºC in the composition and microstructure of AlyTi1-y(OxN1-x) sample. In both samples the formation of a surface anatase TiO2 film was reported after 2 hours annealing at 800°C. These compositional and microstructural changes were correlated with the optical properties determined by spectroscopic ellipsometry. A transition from metallic to dielectric behaviour with increasing annealing temperature was observed. These results complete the durability studies on the designed SSCs based on AlyTi1-y(OxN1-x) materials, confirming that these stacks withstand breakdown at 600ºC in air.
Keywords: Solar energy; Concentrated solar power; Solar selective coatings; Temperature stability
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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Emergent Materials 4(2021), 1559-1568
DOI: 10.1007/s42247-021-00298-z
Permalink: https://www.hzdr.de/publications/Publ-32812
Effects of surface roughness and mineralogy on the sorption of Cm(III) on crystalline rock
Demnitz, M.; Molodtsov, K.; Schymura, S.; Schierz, A.; Müller, K.; Jankovsky, F.; Havlova, V.; Stumpf, T.; Schmidt, M.
Abstract
Crystalline rock is one of the considered host rocks for a future deep geological repository for highly active radiotoxic nuclear waste. The safety assessment requires reliable information on the retention behavior of minor actinides. In this work, we applied various spatially resolved techniques to investigate the sorption of Curium onto crystalline rock (granite, gneiss) thin sections from Eibenstock, Germany and Bukov, Czech Republic. We combined Raman-microscopy, calibrated autoradiography and µTRLFS (micro-focus time-resolved fluorescence spectroscopy) with vertical scanning interferometry to study in situ the impact of mineralogy and surface roughness on Cm(III) uptake and molecular speciation on the surface. Heterogeneous sorption of Cm(III) on the surface depends primarily on the mineralogy. However, for the same mineral class sorption uptake and strength of Cm(III) increases with growing surface roughness around surface holes or grain boundaries. When competitive sorption between multiple mineral phases occurs, surface roughness becomes the major retention parameter on low sorption uptake minerals. In high surface roughness areas primarily Cm(III) inner-sphere sorption complexation and surface incorporation are prominent and in select sites formation of stable Cm(III) ternary complexes is observed. Our molecular findings confirm that predictive radionuclide modelling should implement surface roughness as a key parameter in their simulations.
Keywords: curium; luminescence; crystalline rock; granite; sorption; correlative spectroscopy
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Data publication: Effects of surface roughness and mineralogy on the sorption …
ROBIS: 33137 HZDR-primary research data are used by this (Id 32811) publication
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Journal of Hazardous Materials 423(2021)Part A, 127006
DOI: 10.1016/j.jhazmat.2021.127006
Cited 8 times in Scopus
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- Final Draft PDF 1,5 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32811
Solar-selective coatings for high-temperature solar applications based on a selective transmitter on top of a black body absorber
Krause, M.; Lungwitz, F.; Mendez, A.; Hoppe, M.; Sonnenberg, J.; Garcia Valenzuela, A.; Munnik, F.; Grenzer, J.; Hübner, R.; Escobar Galindo, R.
Abstract
An alternative concept to achieve solar selectivity for solar thermal materials and applications consists in the use of spectrally selective transmitter coatings.[1] These are characterized by a high transmittance in the solar range and a high reflectance in the thermal range of the electromagnetic spectrum. Suitable materials for selective transmitters are dielectric/metal/dielectric multilayers and transparent conductive oxides (TCOs).[2] The concept has a series of advantages compared to multilayer- or cermet-based solar-selective coatings (SSCs) like the easiness of manufacturing, the possibility to use standard materials as transmitter (e.g., indium tin oxide (ITO)) and absorber (e.g. Pyromark or black chrome), and the adaptability to specific requirements with respect to receiver temperature and solar concentration factor.
After a conceptual introduction, an analysis of solar plant parameters, i.e., operation temperature and solar concentration, for which this concept provides a better solar efficiency than state-of-the-art bare black body absorber, will be given.[3] We will then review the recent developments in the field, which include an excellent high-temperature in-air stability of such type of solar coatings.[4] In the second part of the talk, we will report own results toward a new TCO on black body absorber coating. Vacuum and in-air stability of the TCO SnO2:Ta at 800 °C and its structural properties before and after heat exposure are demonstrated. As potential absorber, the formation, structure, and optical properties of dense, PVD-grown CuCr2O4 thin films are studied. They are obtained in high purity from as-deposited samples by a simple in-air annealing step at 800 °C and absorb light in the whole solar range from 300 nm to 2500 nm.
[1] C.E. Kennedy, Review of Mid- to High-Temperature Solar Selective Absorber Materials, NREL Technical Reports, NREL - National Renewable Energy Laboratory, Golden, Colorado, USA, 2002.
[2] J.C.C. Fan, F.J. Bachner, Transparent heat mirrors for solar-energy applications, Applied Optics 15(4) (1976) 1012-1017.
[3] F. Lungwitz, R. Escobar-Galindo, D. Janke, E. Schumann, R. Wenisch, S. Gemming, M. Krause, Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Materials and Solar Cells 196 (2019) 84-93.
[4] H. Wang, I. Haechler, S. Kaur, J. Freedman, R. Prasher, Spectrally selective solar absorber stable up to 900 degrees C for 120 h under ambient conditions, Solar Energy 174 (2018) 305-311.
Keywords: Solar energy; Concentrated solar power; Solar selective coatings; Transparent conductive oxides; Spinel type absorber
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32810) publication
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Invited lecture (Conferences)
(Online presentation)
Virtual MRS Spring Meeting 2021, Symposium EN05: Materials Challenges and Opportunities in Concentrated Solar Power Technologies, 19.-23.04.2021, Virtuell, USA
Permalink: https://www.hzdr.de/publications/Publ-32810
Formation, structure, and optical properties of copper chromite thin films for high-temperature solar absorbers
Krause, M.; Sonnenberg, J.; Munnik, F.; Grenzer, J.; Hübner, R.; Garcia Valenzuela, A.; Gemming, S.
Abstract
CuCr2O4 thin films grown by physical vapour deposition were studied in order to evaluate their potential as absorber material for the next generation of concentrated solar power plants. A series of Cu-Cr-O thin films was deposited by reactive ion beam sputtering. The Cr/Cu ratio in the sputter target is demonstrated as the most important parameter to achieve the intended film stoichiometry. In-air annealing at 800 °C leads to structural transformations of the as-deposited films and results in phase compositions according to those expected from the ternary Cu-Cr-O phase diagram. Tetragonal CuCr2O4 with 98.6 at.% phase purity regarding the solid film constituents is obtained for the appropriate Cr/Cu ratio in the sputter target. CuCr2O4 thin films absorb light in the entire solar spectral range from 300 nm to 2500 nm. Their energy gap is found to be < 0.5 eV, and their solar absorptance is estimated to be (0.85 +/- 0.03). The dense microstructure with good thermal conductivity, full adhesion to the substrate, and a relatively low surface roughness are discussed as technological advantages of CuCr2O4 thin films grown by physical vapour deposition.
Keywords: solar absorber; spinels; sputtering; phase transformations; optical materials
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32809) publication
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Materialia 18(2021), 101156
DOI: 10.1016/j.mtla.2021.101156
Cited 7 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32809
Environmental drivers of body size in North American bats
Abstract
Bergmann’s Rule—which posits that larger animals live in colder areas—is thought to influence variation in body size within species across space and time, but evidence for this claim is mixed. We tested four competing hypotheses for spatio-temporal variation in body size within bat species during the past two decades across North America. Bayesian hierarchical models revealed that spatial variation in body mass was most strongly correlated with mean annual temperature, supporting the heat conservation hypothesis (the mechanism historically believed to underlie Bergmann’s Rule). Across time, variation in body mass was most strongly correlated with net primary productivity, supporting the resource availability hypothesis. Climate change may influence body size in animals but will likely do so through both changes in mean annual temperature and in resource availability. Rapid reductions in body size alongside climate change have occurred in short-lived, fecund species, but such reductions may transpire more slowly in longer-lived species.
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Invited lecture (Conferences)
(Online presentation)
Annual Meeting of the American Society of Mammalogists, 14.-18.06.2021, Virtual, USA
Permalink: https://www.hzdr.de/publications/Publ-32808
Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species’ traits
Wells, H. B. M.; Crego, R. D.; Opedal, Ø. H.; Khasoha, L. M.; Alston, J.; Reed, C. G.; Weiner, S.; Kurukura, S.; Hassan, A. A.; Namoni, M.; Ekadeli, J.; Kimuyu, D. M.; Young, T. P.; Kartzinel, T. R.; Palmer, T. M.; Pringle, R. M.; Goheen, J. R.
Abstract
1. The extinction of 80% of megaherbivore (>1,000 kg) species towards the end of the Pleistocene altered vegetation structure, fire dynamics, and nutrient cycling worldwide. Ecologists have proposed (re)introducing megaherbivores or their ecological analogues to restore lost ecosystem functions and reinforce extant but declining megaherbivore populations. However, the effects of megaherbivores on smaller herbivores are poorly understood.
2. We used long-term exclusion experiments and multispecies hierarchical models fitted to dung counts to test 1) the effect of megaherbivore (elephant and giraffe) presence-absence on the occurrence (dung presence) and use intensity (dung-pile density) of mesoherbivores (2–1,000 kg), and 2) the extent to which the responses of each mesoherbivore species was predictable based on their traits (diet and shoulder height) and phylogenetic relatedness.
3. Megaherbivores increased the predicted occurrence and use intensity of zebras but reduced the occurrence and use intensity of several other mesoherbivore species. The negative effect of megaherbivores on mesoherbivore occurrence was stronger for shorter species, regardless of diet or relatedness.
4. Megaherbivores substantially reduced the expected total use intensity (i.e., cumulative dung density of all species) of mesoherbivores, but only minimally reduced the expected species richness (i.e., cumulative predicted occurrence probabilities of all species) of mesoherbivores (by <1 species).
5. Simulated extirpation of megaherbivores altered use intensity by mesoherbivores, which should be considered during (re)introductions of megaherbivores or their ecological proxies. Species’ traits (in this case shoulder height) may be more reliable predictors of mesoherbivores’ responses to megaherbivores than phylogenetic relatedness, and may be useful for predicting responses of data-limited species.
Keywords: African savanna; biotic interactions; competition; elephant; facilitation; giraffe; megafauna; trophic rewilding
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Data and code for: Experimental evidence that effects of megaherbivores on …
ROBIS: 32857 HZDR-primary research data are used by this (Id 32807) publication
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Journal of Animal Ecology 90(2021)11, 2510-2522
DOI: 10.1111/1365-2656.13565
Cited 7 times in Scopus
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Daily torpor reduces the energetic consequences of habitat selection for a widespread bat
Alston, J.; Dillon, M. E.; Keinath, D. A.; Abernethy, I. M.; Goheen, J. R.
Abstract
Homeothermy requires increased metabolic rates as temperatures decline below the thermoneutral zone, so homeotherms typically select microhabitats within or near their thermoneutral zones during periods of inactivity. However, many mammals and birds are heterotherms that relax internal controls on body temperature when maintaining a high, stable body temperature is energetically costly. Such heterotherms should be less tied to microhabitats near their thermoneutral zones, and because heterotherms spend more time in torpor and expend less energy at colder temperatures, heterotherms may even select microhabitats in which temperatures are well below their thermoneutral zones. We studied how temperature and daily torpor influence selection of diurnal roosts by a heterothermic bat (Myotis thysanodes). We (1) quantified the relationship between ambient temperature and daily duration of torpor, (2) simulated daily energy expenditure over a range of microhabitat (roost) temperatures, and (3) quantified the influence of roost temperature on roost selection. While warm roosts substantially reduced energy expenditure of simulated homeothermic bats, heterothermic bats modulated their use of torpor to maintain a constant level of energy expenditure over the course of a day. Daily torpor expanded the range of energetically economical microhabitats, such that roost selection was independent of roost temperature. Our work adds to a growing literature documenting functions of torpor beyond its historical conceptualization as a last-resort measure to save energy during extended or acute energetic stress.
Keywords: Bayesian hierarchical models; climate change; daily torpor; fringed myotis (Myotis thysanodes); temporal heterothermy; thermal ecology; VHF telemetry
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Data, code, and metadata for: Daily torpor reduces the energetic consequences …
ROBIS: 33865 HZDR-primary research data are used by this (Id 32806) publication
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Ecology 103(2022)6, e3677
DOI: 10.1002/ecy.3677
Cited 6 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32806
Dimeric and Trimeric Uranyl(VI)–Citrate Complexes: ¹⁷O-, ²³Na-, and ¹³⁹La-NMR – Helpful Probes for (Super-)Structure Determination
Kretzschmar, J.; Tsushima, S.; Drobot, B.; Steudtner, R.; Schmeide, K.; Brendler, V.; Stumpf, T.
Abstract
Although being investigated for more than 70 years by various methods, the uranyl(VI)–citrate (U(VI)–Cit) system still reveals interesting structural and spectroscopic features. The aqueous chemistry of the system is complex, as evidenced by the still controversial discussions on speciation and structures.
Upon complexation, a chiral center is induced in Cit’s central carbon, yielding two diastereomeric pairs of enantiomers, whereupon the 2:2 complexes exhibit syn- and anti-configured isomers. In fact, the combination of ¹⁷O-NMR (at natural abundance) and DFT calculations allowed an unambiguous discrimination. Hereby symmetry and especially deviation from regular pentagonal bipyramidal coordination geometry affect the O=U=O entities’ (Oyl) chemical shifts. In aqueous solution, the syn-isomer is favored, in contrast to the preferably crystallizing anti-isomer. Both isomers interconvert mutually with exchange rates of about 30 s–¹ at −6 °C and 249 s–¹ at 60 °C in acidic solution, corresponding to an activation barrier of about 24 kJ mol–¹.[1]
At circumneutral conditions, above 3 mM uranyl(VI) citrate concentrations, two trimeric 3:3 U(VI)–Cit complex molecules associate upon sandwiching a metal ion (Mn+) as a O=U=O→Mn+ Lewis acid–base adduct. The coordination shell formed by the six (inner) Oyl restricts the size of the enclosed Lewis acid. Among the studied metal ions, only Na+, Ca²+, and La³+ with ionic radii close to 1.0 Å match the formed cavity, while Li+ is too small, and K+ and Rb+ are too large. This cavity constitutes an anhydrous environment that shields the Mn+ from the aqueous phase, causing the sandwiched Na+ and La³+ to resonate 25 ppm and 430 ppm up-field relative to their corresponding aquo ions, respectively.
Upon increasing Mn+ charge/radius ratio, the sandwiched Lewis acids more and more withdraw electron density from those Oyl acting as Lewis base, and thus the latter sense a remarkable de-shielding. Increasing the charge of the sandwiched cation from +1 to +3, ΔδO between signals of the coordinating Oyl and the outer Oyl increases remarkably (12, 69, and 93 ppm, respectively), as the O=U=O units become progressively polarized.[2]
Literature:
[1] J. Kretzschmar et al., Inorg. Chem. 2021, 60, 7998.
[2] J. Kretzschmar et al., Chem. Commun. 2020, 56, 13133.
Keywords: NMR spectroscopy; Uranium; U(VI); Uranyl(VI); Citrate; Complex; Chirality; Diastereomers; Sandwich complex; Lewis acid-base adduct
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Dimeric and Trimeric Uranyl(VI)–Citrate Complexes in Aqueous Solution
ROBIS: 28980 is cited by this (Id 32805) publication -
Trimeric uranyl(VI)–citrate forms Na+, Ca2+, and …
ROBIS: 31389 is cited by this (Id 32805) publication
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Lecture (Conference)
(Online presentation)
GDCh Jahrestagung der Fachgruppe Magnetische Resonanz (FGMR), 27.09.-01.10.2021, online, Deutschland
Permalink: https://www.hzdr.de/publications/Publ-32805
Bentonite alteration in batch reactor experiments with and without fertilizing agents: implications for the disposal of radioactive waste
Podlech, C.; Matschiavelli, N.; Peltz, M.; Kluge, S.; Arnold, T.; Cherkouk, A.; Meleshyn, A.; Grathoff, G.; Warr, L. N.
Abstract
Bentonite is currently proposed as a potential backfill material for sealing high-level-radioactive waste in underground repositories due to its low hydraulic conductivity, self-sealing ability and high adsorption capability. High saline pore waters, high temperatures and the influence of microbes may cause mineralogical changes and affect the long-term performance of the bentonite barrier system. In this study, long-term diffusion batch experiments were carried out at 25°C and 90°C for one and two years using two different industrial bentonites (SD80 from Greece, B36 from Slovakia) and two types of aqueous solutions, which simulated a) Opalinus clay pore water with a salinity of 19 g·L-1 and b) saline cap rock solution with a salinity of 155 g·L-1. The bentonites were supplemented with and without organic substrates to study the microbial community and their potential influence on the bentonite mineralogy. Smectite alteration was dominated by metal ion substitutions, changes in layer charge and delamination during water-clay interaction. The degree of smectite alteration and changes in the microbial diversity depended largely on the respective bentonite and the experimental condition. Thus, the low charged SD80 with 17% tetrahedral charge showed nearly no structural change, whereas B36 as a medium charged smectite with 56% tetrahedral charge became more beidellitic with increasing temperature reacted in saline cap rock solution. Based on these experiments, the alteration of the smectite is mainly attributed to the nature of the bentonite, pore water chemistry and temperature. A significant microbial influence on the here analyzed parameters was not observed within the two years of experimentation, but should not be excluded, as the detected genera are known to potentially influence geochemical processes.
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Minerals 11(2021), 932
DOI: 10.3390/min11090932
Cited 10 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32803
Tailoring crystalline structure of titanium oxide films for optical applications using non-biased filtered cathodic vacuum arc deposition at room temperature
Guillén, E.; Krause, M.; Heras, I.; Rincón-Llorente, G.; Escobar-Galindo, R.
Abstract
Titanium oxide films were deposited at room temperature and with no applied bias using a filtered cathodic vacuum arc (FCVA) system in a reactive oxygen environment. The dependence of film growth on two process parameters, the working pressure (Pw) and the O2 partial pressure (pO2), is described in detail. The composition, morphological features, crystalline structure, and optical properties of the deposited films were systematically studied by Rutherford Back Scattering (RBS), Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Raman Spectroscopy, UV-vis spectroscopy, and spectroscopic ellipsometry. This systematic investigation allowed the identification of three different groups or growth regimes according to the stoichiometry and to the phase structure of the titanium oxide films. RBS analysis revealed that a wide range of TiOx stoichiometries (0.6 < x < 2.2) were obtained, including oxygen-deficient, stoichiometric TiO2 and oxygen-rich films. TiO, Ti2O3, rutile-type TiO2, and amorphous TiO2 phase structures could be achieved, as confirmed both by Raman and XRD. Therefore the results showed a highly versatile approach, in which different titanium oxide stoichiometries and crystalline phases especially suited for diverse optical applications can be obtained by changing only two process parameters, in a process at room temperature and without applied bias. Of particular interest are crystalline rutile films with high density to be used in ultra-high reflectance metal-dielectric multilayered mirrors, and reduced-TiO2 rutile samples with absorption in the visible range as a very promising photocatalyst material.
Keywords: titanium oxide films; filtered cathodic vacuum arc; rutile; optical coatings
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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Coatings 11(2021), 233
DOI: 10.3390/coatings11020233
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32800
Data publication: Detecting bacterial cell viability in few μl solutions from impedance measurements on silicon‐based biochips
Bhat, V. J.; Vegesna, S. V.; Kiani, M.; Zhao, X.; Blaschke, D.; Du, N.; Vogel, M.; Kluge, S.; Raff, J.; Hubner, U.; Skorupa, I.; Rebohle, L.; Schmidt, H.
Abstract
Der Datensatz umfasst mikroskopische Bilder und Fotos zur Bestimmung der Zelldichte sowie lebender und toter Zellen inklusive Berechnungen, Protokolle und Auswertungen dazu.
Keywords: Cell viability; Dead bacterial cells; Dead bacterial cells; Impedance biochips; Live bacterial cells; Lysinibacillus sphaericus; Membrane potential
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32799) publication
- DOI: 10.3390/ijms22073541 references this (Id 32799) publication
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Detecting bacterial cell viability in few μl solutions from impedance …
ROBIS: 32782 has used this (Id 32799) publication of HZDR-primary research data
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Reseach data in the HZDR data repository RODARE
Publication date: 2021-06-23 Open access
DOI: 10.14278/rodare.1039
Versions: 10.14278/rodare.1040
License: CC-BY-4.0
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Permalink: https://www.hzdr.de/publications/Publ-32799
Structure and luminescence of a-plane GaN on r-plane sapphire substrate modified by Si implantation
Huang, L.; Li, L.; Shang, Z.; Wang, M.; Kang, J.; Luo, W.; Liang, Z.; Prucnal, S.; Kentsch, U.; Ji, Y.; Zhang, F.; Wang, Q.; Yuan, Y.; Sun, Q.; Zhou, S.; Wang, X.
Abstract
We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation. Upon gradually raising Si fluences from 5*10¹³ /cm² to 5*10¹⁵ /cm², the n-type dopant concentration gradually increases from 4.6*10¹⁸ /cm² to 4.5*10²⁰ /cm², while the generated vacancy density accordingly raises from 3.7*10¹³ /cm² to 3.8*10¹⁵ /cm². Moreover, despite that the implantation enhances structural disorder, the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements. The monotonical uniaxial lattice expansion along the a direction (out-of-plane direction) is observed as a function of fluences till 1*10¹⁵ /cm², which ceases at the overdose of 5*10¹⁵ /cm² due to the partial amorphization in the surface region. Upon raising irradiation dose, a yellow emission in the as-grown sample is gradually quenched, probably due to the irradiation-induced generation of non-radiative recombination centers.
Keywords: ion implantation; GaN; defects
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
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- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32797) publication
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Chinese Physics B 30(2021)5, 056104
DOI: 10.1088/1674-1056/abd76a
ISSN: 1674-1056
Cited 1 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32797
New insights into U(VI) sorption onto montmorillonite from batch sorption and spectroscopic studies at increased ionic strength
Stockmann, M.; Fritsch, K.; Bok, F.; Marques Fernandes, M.; Baeyens, B.; Steudtner, R.; Müller, K.; Nebelung, C.; Brendler, V.; Stumpf, T.; Schmeide, K.
Abstract
The influence of ionic strength up to 3 mol/kg (background electrolytes NaCl or CaCl2) on U(VI) sorption onto montmorillonite was investigated as function of pHc in absence and presence of CO2. A multi-method approach combined batch sorption experiments with spectroscopic methods (time-resolved laser-induced fluorescence spectroscopy (TRLFS) and in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy). In the absence of atmospheric carbonate, U(VI) sorption was nearly 99% above pHc 6 in both NaCl and CaCl2 and no significant effect of ionic strength was found. At lower pH, cation exchange was strongly reduced with increasing ionic strength. In the presence of carbonate, U(VI) sorption was reduced above pHc 7.5 in NaCl and pHc 6 in CaCl2 system due to formation of aqueous UO2(CO3)x
(2-2x) and Ca2UO2(CO3)3 complexes, respectively, as verified by TRLFS. A significant ionic strength effect was observed due to the formation of Ca2UO2(CO3)3
(aq), which strongly decreases U(VI) sorption with increasing ionic strength.
The joint analysis of determined sorption data together with literature data (giving a total of 213 experimental data points) allowed to derive a consistent set of surface complexation reactions and constants based on the 2SPNE SC/CE approach, yielding log K⁰ = 2.42 ± 0.04 (≡SSOUO2
+), log K⁰ = −4.49 ± 0.7 (≡SSOUO2OH), and log K⁰ = −20.5 ± 0.4 (≡SSOUO2(OH)3
2-). Ternary uranyl carbonate surface complexes were not required to describe the data. With this reduced set of surface complexes, an improved robust sorption model was obtained covering a broad variety of geochemical settings over wide ranges of ionic strengths and groundwater compositions, which subsequently was validated by an independent original dataset. This model improves the understanding of U(VI) retention by clay minerals and enables now predictive modeling of U(VI) sorption processes in complex clay rich natural environments.
Keywords: argillaceous rock; surface complexation modeling; uranium; specific ion interaction theory (SIT); ATR FT-IR; TRLFS; 2SPNE SC/CE
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Science of the Total Environment 806(2022), 150653
Online First (2021) DOI: 10.1016/j.scitotenv.2021.150653
Cited 24 times in Scopus
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- Final Draft PDF 1,6 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32796
Pharmacokinetic studies of [⁶⁸Ga]Ga‑PSMA‑11 in patients with biochemical recurrence of prostate cancer: detection, differences in temporal distribution and kinetic modelling by tissue type
Strauss, D. S.; Sachpekidis, C.; Kopka, K.; Pan, L.; Haberkorn, U.; Dimitrakopoulou‑Strauss, A.
Abstract
Purpose: [⁶⁸Ga]Ga-PSMA-11 is a promising radiopharmaceutical for detecting tumour lesions in prostate cancer, but knowledge of the pharmacokinetics is limited. Dynamic PET-CT was performed to investigate the tumour detection and differences in temporal distribution, as well as in kinetic modelling of [⁶⁸Ga]Ga-PSMA-11 by tissue type.
Methods: Dynamic PET-CT over the lower abdomen and static whole-body PET-CT 80–90 min p.i. from 142 patients with biochemical recurrence were retrospectively analysed. Detection rates were compared to PSA levels. Average time-activity curves were calculated from tumour lesions and normal tissue. A three-compartment model and non-compartment model
were used to calculate tumour kinetics.
Results: Overall detection rate was 70.42%, and in patients with PSA > 0.4 ng/mL 76.67%. All tumour lesions presented the steepest standardised uptake value (SUV) incline in the first 7–8 min before decreasing to different degrees. Normal tissue presented with a low uptake, except for the bladder, which accumulated activity the steepest 15–16 min. p.i.. While all tumour
lesions continuously increased, bone metastases showed the steepest decline, resulting in a significantly lower SUV than lymph node metastases (60 and 80–90 min). Transport rate from the blood and tracer binding and internalisation rate were lower in bone metastases. Heterogeneity (fractal dimension) and vascular density were significantly lower in bone metastases.
Conclusion: Even at low PSA between 0.51 and 0.99 ng/mL, detection rate was 57%. Dynamic imaging showed a time window in the first 10 min where tumour uptake is high, but no bladder activity is measured, aiding accuracy in distinction of local recurrence. Kinetic modelling provided additional information for tumour characterisation by tissue type.
Keywords: Ga-PSMA; PSMA; PSMA Kinetic; Recurrent prostate cancer
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European Journal of Nuclear Medicine and Molecular Imaging 48(2021), 4472-4482
DOI: 10.1007/s00259-021-05420-1
Cited 29 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32794
Cation non-stoichiometry in Fe:SrTiO3 thin films and its effect on the electrical conductivity
Morgenbesser, M.; Taibl, S.; Kubicek, M.; Schmid, A.; Viernstein, A.; Bodenmüller, N.; Herzig, C.; Baiutti, F.; de Dios Sirvent, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Artner, W.; Limbeck, A.; Tarancon, A.; Fleig, J.
Abstract
The interplay of structure, composition and electrical conductivity was investigated for Fe-doped SrTiO3 thin films prepared by pulsed laser deposition. Structural information was obtained by reciprocal space mapping while solution-based inductively-coupled plasma optical emission spectroscopy and positron annihilation lifetime spectroscopy were employed to reveal the cation composition and the predominant point defects of the thin films, respectively. A severe cation non-stoichiometry with Sr vacancies was found in films deposited from stoichiometric targets. The across plane electrical conductivity of such epitaxial films was studied in the temperature range of 250 - 720 °C by impedance spectroscopy. This revealed a pseudo-intrinsic electronic conductivity despite the substantial Fe acceptor doping, i.e. conductivities being several orders of magnitude lower than expected. Variation of PLD deposition parameters causes some changes of the cation stoichiometry, but the films still have conductivities much lower than expected. Targets with significant Sr excess (in the range of several percent) were employed to improve the cation stoichiometry in the films. The use of 7 % Sr-excess targets resulted in near-stoichiometric films with conductivities close to the stoichiometric bulk counterpart. The measurements show that a fine-tuning of the film stoichiometry is required in order to obtain acceptor doped SrTiO3 thin films with bulk-like properties. One can conclude that, although RSM experiments give a first hint whether or not cation non-stoichiometry is present, conductivity measurements are more appropriate for assessing SrTiO3 film quality in terms of cation stoichiometry.
Keywords: SrTiO3 thin films; pulsed laser deposition; structure-property relations; cationic non-stoichiometry; positron annihilation spectroscopy
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
- P-ELBE
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- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32792) publication
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Nanoscale Advances 3(2021), 6114-6127
DOI: 10.1039/D1NA00358E
Cited 6 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32792
Automated mineralogy as a novel approach for the compositional and textural characterization of spent lithium-ion batteries
Vanderbruggen, A.; Gugala, E.; Blannin, R.; Bachmann, K.; Serna-Guerrero, R.; Rudolph, M.
Abstract
Mechanical recycling processes aim to separate particles based on their physical properties, such as size, shape and density, and physico-chemical surface properties, such as wettability. Secondary materials, including electronic waste, are highly complex and heterogeneous, which complicates recycling processes. In order to improve recycling efficiency, characterization of both recycling process feed materials and intermediate products is crucial. Textural characteristics of particles in waste mixtures cannot be determined by conventional characterization techniques, such as X-ray fluorescence and X-ray diffraction spectroscopy. This paper presents the application of automated mineralogy as an analytical tool, capable of describing discrete particle characteristics for monitoring and diagnosis of lithium ion battery (LIB) recycling approaches. Automated mineralogy, which is well established for the analysis of primary raw materials but has not yet been tested on battery waste, enables the acquisition of textural and chemical information, such as elemental and phase composition, morphology, association and degree of liberation. For this study, a thermo-mechanically processed black mass (<1 mm fraction) from spent LIBs was characterized with automated mineralogy. Each particle was categorized based on which LIB component it comprised: Al foil, Cu foil, graphite, lithium metal oxides and alloys from casing. A more selective liberation of the anode components was achieved by thermo-mechanical treatment, in comparison to the cathode components. Therefore, automated mineralogy can provide vital information for understanding the properties of black mass particles, which determine the success of mechanical recycling processes. The introduced methodology is not limited to the presented case study and is applicable for the optimization of differentseparation unit operations in recycling of waste electronics and batteries.
Keywords: Automated mineralogy; Black mass; Characterization; Liberation; Lithium-ion batteries; Mineral processing; Recycling
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Minerals Engineering 169(2021), 106924
DOI: 10.1016/j.mineng.2021.106924
Cited 42 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32791
Understanding the M₄ edge HERFD XANES of U⁶⁺
Amidani, L.; Volkova, A.; Retegan, M.; Martin, P.; Kvashnina, K.
Abstract
Hexavalent uranium is of considerable importance in the actinide field, and its characterization, consequently, of fundamental concern. The application of High-Energy-Resolution Fluorescence-Detected X-ray Absorption Near-Edge Structure (HERFD XANES) at the M4 edge of actinides is gaining great popularity, as it allows to probe the 5f electronic structure with augmented resolution compared to conventional XANES, for which M4 spectra are broad and featureless. If, from one side, the extreme sensitivity of M4 HERFD XANES to actinides’ oxidation state is well-established [1], its sensitivity to the local environment has been less extensively explored [2,3]. The partially filled 5f subshell makes intra-atomic electron interactions the primary force shaping the spectrum, and simulations treating multi-electronic effects can only approximately account for the local environment.
In these regards, U6+, with its empty 5f shell, is a fortunate exceptional case. Simulation approaches based on the one-electron approximation can then be applied, and the dependence on the local environment be carefully investigated. We report here the first investigation where experimental and simulated M4 HERFD XANES are obtained on a set of U6+ compounds with different local environment. The coordination of U6+ represented by the set of samples comprises an almost perfect UO6 octahedral bipyramid (Sr3UO6), two UO6 featuring the uranyl ion (Cs2UO2Cl4 and SrUO4), and a UO8 distorted hexagonal bipyramid (CaUO4).
Experimental M4 HERFD are shown in Figure 1. The spectral shape has a similar structure, made of three or four peaks of decreasing intensity. At the same time, it presents significant differences indicating the substantial impact on the spectral shape of the local environment. We simulated the set of U6+ compounds with the DFT-based code FDMNES [4]. The good agreement between theory and experiment, see Fig. 1, makes it reasonable to have a closer look at the underlying f-density of states and to assign spectral features to specific f-orbitals.
Simulations allow to rationalize how the local coordination of U6+ affects the M4 HERFD XANES and demonstrate its high sensitivity to the local environment. Simulations based on crystal field theory were also performed. Their comparison to FDMNES results will be discussed during the conference.
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Lecture (Conference)
(Online presentation)
Uranium Science, 29.06.-01.07.2021, University of Bristol, United Kingdom
Permalink: https://www.hzdr.de/publications/Publ-32790
Exploring the anti-site disorder and oxygen vacancies in Sr₂FeMoO₆ thin films
Saloaro, M.; Liedke, M. O.; Angervoa, I.; Butterling, M.; Hirschmann, E.; Wagner, A.; Huhtinen, H.; Paturi, P.
Abstract
To address the importance of nanoscale defects in complex magnetic oxides, we present an effective tool, variable energy positron annihilation spectroscopy, for probing the relatively small changes in anti-site disorder and oxygen vacancies of the in situ annealed double perovskite Sr₂FeMoO₆ thin films. By controlling the annealing conditions in wide pressure and temperature ranges and thus affecting the amount of nanoscale defects, we show that the magnetic properties of Sr₂FeMoO₆ thin films can be modified, particularly with the oxygen nonstoichiometry, and hence their spintronic functionality can be improved. On the basis of our findings together with proposed mechanism, we suggest that the annealing treatments can also be scaled to other complex magnetic perovskites to engineer nanoscale defects and thus improve their usability in future spintronic applications.
Keywords: spintronics; SFMO; defect engineering; oxygen vacancy; positron annihilation spectroscopy; magnetic properties; anti-site disorder
Involved research facilities
- Radiation Source ELBE DOI: 10.17815/jlsrf-2-58
- P-ELBE
Related publications
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 32789) publication
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Journal of Magnetism and Magnetic Materials 540(2021), 168454
DOI: 10.1016/j.jmmm.2021.168454
Cited 9 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32789
An Introduction to the Materials Learning Algorithms Package (MALA)
Fiedler, L.; Cangi, A.; Ellis, J. A.; Rajamanickam, S.
Abstract
Density Functional Theory (DFT) is one of the most popular quantum mechanical simulation methods, since it balances sufficient accuracy with reasonable computational cost. It is often used in material science applications at ambient and extreme conditions. Nonetheless, DFT approaches its limits in terms of computational feasbility when faced with simulation problems at larger time and length scales, especially at temperatures >> 0K. Surrogate models based on neural networks can circumvent these limitations. By training a neural network to predict properties of interest (total energy, atomic forces) based on atomic configurations, predictions with DFT-like accuracy can be done at a fraction of the computational cost.
To facilitate the creation and usage of these surrogate models, the Materials Learning Algorithms package (MALA) provides modular open-source toolbox that allows users to preprocess of DFT data, train models and postprocess model predictions using only a few lines of code. MALA is jointly developed by the Center for Advanced Systems Understanding (CASUS), Sandia National Laboratories (SNL) and Oak Ridge National Laboratory (ORNL).
Keywords: Density Functional Theory; Machine Learning
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Poster
(Online presentation)
Mixed-gen Session 5: Machine Learning, 06.05.2021, Lausanne, Schweiz
DOI: 10.13140/RG.2.2.19692.49286
Permalink: https://www.hzdr.de/publications/Publ-32788
Imaging neutron capture cross sections: i-TED proof-of-concept and future prospects based on Machine-Learning techniques.
Babiano-Suárez, V.; Lerendegui-Marco, J.; Balibrea-Correa, J.; Caballero, L.; Calvo, D.; Ladarescu, I.; Real, D.; Domingo-Pardo, C.; Calviño, F.; Casanovas, A.; Tarifeño-Saldivia, A.; Alcayne, V.; Guerrero, C.; Millán-Callado, M. A.; Rodriguez-González, T.; Barbagallo, M.; Aberle, O.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Bennett, S.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Busso, M.; Caamaño, M.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Dominguez, B.; Ferrari, A.; Finocchiaro, P.; Furman, V.; Göbel, K.; Garg, R.; Gawlik, A.; Gilardoni, S.; Gonçalves, I. F.; González-Romero, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Junghans, A.; Käppeler, F.; Kadi, Y.; Kimura, A.; Knapova, I.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kurtulgil, D.; Lederer-Woods, C.; Leeb, H.; Lonsdale, S. J.; Macina, D.; Manna, A.; Martinez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Persanti, L.; Petrone, C.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos-Doval, D.; Rauscher, T.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N. V.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tassan-Got, L.; Thomas, T.; Torres-Sánchez, P.; Tsinganis, A.; Ulrich, J.; Urlaß, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T.; Žugec, P.
Abstract
i-TED is an innovative detection system which exploits Compton imaging techniques to achieve a superior signal-to-background ratio in (n, γ ) cross-section measurements using time-of-flight technique. This work presents the first experimental validation of the i-TED apparatus for highresolution time-of-flight experiments and demonstrates for the first time the concept proposed for background rejection. To this aim, the 197 Au(n, γ ) and 56 Fe(n, γ ) reactions were studied at CERN n_TOF using an i-TED demonstrator based on three position-sensitive detectors. Two C6 D6 detectors were also used to benchmark the performance of i-TED. The i-TED prototype built for this study shows a factor of ∼3 higher detection sensitivity than state-of-the-art C6 D6 detectors in the 10 keV neutron-energy region of astrophysical interest. This paper explores also the perspectives of further enhancement in performance attainable with the final i-TED array consisting of twenty position-sensitive detectors and new analysis methodologies based on Machine-Learning techniques.
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European Physical Journal A 57(2021), 197
DOI: 10.1140/epja/s10050-021-00507-7
Cited 14 times in Scopus
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- Open Access Version from arxiv.org
- Fulltext from doi.org
- Secondary publication expected
Permalink: https://www.hzdr.de/publications/Publ-32787
First Results of the 140Ce(n,gamma)141Ce Cross-Section Measurement at n_TOF
Amaducci, S.; Colonna, N.; Cosentino, L.; Cristallo, S.; Finocchiaro, P.; Krtička, M.; Massimi, C.; Mastromarco, M.; Mazzone, A.; Mengoni, A.; Valenta, S.; Aberle, O.; Alcayne, V.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Busso, M.; Caamaño, M.; Caballero-Ontanaya, L.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Chiaveri, E.; Cortés, G.; Cortés-Giraldo, M.; Damone, L.-A.; Davies, P.-J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Dominguez, B.; Ferrari, A.; Furman, V.; Göbel, K.; Garg, R.; Gawlik, A.; Gilardoni, S.; Gonçalves, I.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D.; Junghans, A.; Käppeler, F.; Kadi, Y.; Kimura, A.; Knapova, I.; Kokkoris, M.; Kopatch, Y.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Leeb, H.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martinez, T.; Masi, A.; Mastinu, P.; Maugeri, E.-A.; Mendoza, E.; Michalopoulou, V.; Milazzo, P.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Piersanti, L.; Petrone, C.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J.-M.; Ramos-Doval, D.; Rauscher, T.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Ulrich, J.; Urlaß, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P.; Wright, T.; Žugec, P.
Abstract
An accurate measurement of the 140Ce(n,g) energy-dependent cross-section was performed
at the n_TOF facility at CERN. This cross-section is of great importance because it represents a
bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in
stars. The measurement was motivated by the significant difference between the cerium abundance
measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy
can be ascribed to an overestimation of the 140Ce capture cross-section due to a lack of accurate
nuclear data. For this measurement, we used a sample of cerium oxide enriched in 140Ce to 99.4%.
The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which
allowed us to overcome the difficulties present in the previous measurements, thanks to their very
low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their
average parameters are fundamental to improve the evaluation of the 140Ce Maxwellian-averaged
cross-section.
Keywords: cerium; 140Ce; neutron capture; cross-section; n_TOF; MACS; nucleosynthesis
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Universe 7(2021), 200
DOI: 10.3390/universe7060200
Cited 5 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32785
Time evolution of Molecular Binding in Mechanically controlled Break-Junctions
Lokamani, M.; Günther, F.; Kilibarda, F.; Kelling, J.; Gemming, S.; Erbe, A.
Abstract
Mechanically controllable break junctions (MCBJs) are devices, in which the electrical properties of single molecules can be investigated with extreme precision using atomically structured metallic electrodes. The current-voltage (IV) characteristics in such junctions are considerably affected by the binding positions of the anchoring groups on the tip-facets and the configuration of the molecule. Hence, characterizing the electronic transport properties during a single tip-tip opening provides interesting insights in to the tip-molecule interaction.
In this contribution/poster, we present a novel, high-throughput approach to reproduce the time evolution of the electronic transport characteristics. For this, we performed transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB)[1] approach and the Green’s function formalism. In particular, we evaluated the energy level E0 and the coupling Γ of the dominating transport channel using the single level model[2]. In contrast to standard approaches, we consider not just one molecule orientation but many thermodynamically relevant configurations. The obtained parameters were averaged using statistical weights obtained from Metropolis simulation considering up to 80.000 different configurations for selected tip-tip distances. The dependence of the averaged quantities with respect to the tip-tip separation reveals characteristic features also observed in experiments for similar molecular systems.
Our approach allows us to relate these features to binding-site and molecule-curvature effects and therefore provides a better interpretation of the experimental results.
1. M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, T. Frauenheim, S. Suhai, and G. Seifert, Self-consistent-charge density-functional tight-binding method for simulations of complex materials properties, Phys. Rev. B 58, 7260 (1998)
2. Cuevas, J. C.; Scheer, E. In Molecular Electronics: An Introduction to Theory and Experiment; Reed, M., Ed.; World Scientific Series in Nanoscience and Nanotechnology, Vol. 1; World Scientific: Singapore,Hackensack, NJ, 201
Keywords: mechanically controlled break junctions; high-throughput simulations; density-functional-based tight binding; Salen; PEEB; single-level-model
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Poster (Online presentation)
Nanotech France 2021 The 6th ed. of Nanotech France 2021 Int. Conference and Exhibition, 23.-25.06.2021, Paris, France
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Permalink: https://www.hzdr.de/publications/Publ-32783
Detecting bacterial cell viability in few μl solutions from impedance measurements on silicon‐based biochips
Bhat, V. J.; Vegesna, S. V.; Kiani, M.; Zhao, X.; Blaschke, D.; Du, N.; Vogel, M.; Kluge, S.; Raff, J.; Hubner, U.; Skorupa, I.; Rebohle, L.; Schmidt, H.
Abstract
Using two different types of impedance biochips (PS5 and BS5) with ring top electrodes, a distinct change of measured impedance has been detected after adding 1–5 μL (with dead or live Gram‐positive Lysinibacillus sphaericus JG‐A12 cells to 20 μL DI water inside the ring top electrode. We relate observed change of measured impedance to change of membrane potential of L. sphaericus JG‐A12 cells. In contrast to impedance measurements, optical density (OD) measurements cannot be used to distinguish between dead and live cells. Dead L. sphaericus JG‐A12 cells have been obtained by adding 0.02 mg/mL of the antibiotics tetracycline and 0.1 mg/mL chloramphenicol to a batch with OD0.5 and by incubation for 24 h, 30 °C, 120 rpm in the dark. For impedance measurements, we have used batches with a cell density of 25.5 × 10⁸ cells/mL (OD8.5) and 270.0 × 10⁸ cells/mL (OD90.0). The impedance biochip PS5 can be used to detect the more resistive and less capacitive live L. sphaericus JG‐A12 cells. Also, the impedance biochip BS5 can be used to detect the less resistive and more capacitive dead L. sphaericus JG‐A12 cells. An outlook on the application of the impedance biochips for high‐throughput drug screening, e.g., against multi‐drug‐resistant Gram‐positive bacteria, is given.
Keywords: Cell viability; Dead bacterial cells; Dead bacterial cells; Impedance biochips; Live bacterial cells; Lysinibacillus sphaericus; Membrane potential
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32782) publication
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Data publication: Detecting bacterial cell viability in few μl solutions from …
ROBIS: 32799 HZDR-primary research data are used by this (Id 32782) publication
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International Journal of Molecular Sciences 22(2021)71, 3541
DOI: 10.3390/ijms22073541
Cited 4 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32782
Data publication: Creep Properties of 9Cr and 14Cr ODS Tubes Tested by Inner Gas Pressure
Sornin, D.; Ehrnsten, U.; Mozzani, N.; Rantala, J.; Walter, M.; Hobt, A.; Aktaa, J.; Onorbe, E.; Hernandez-Mayoral, M.; Ulbricht, A.; Gicquel, S.; Frank, L.; de Carlan, Y.
Abstract
Skript Messdata Online ILL data’’ https://doi.ill.fr/10.5291/ILL-DATA.1-01-146. 2015.
Keywords: ODS steel; Tube creep test; Inner gas pressure
Related publications
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Creep Properties of 9Cr and 14Cr ODS Tubes Tested by Inner Gas Pressure
ROBIS: 32777 has used this (Id 32780) publication of HZDR-primary research data
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Reseach data in external data repository
Publication year 2021
License: CC-BY-4.0
DOI: 10.5291/ILL-DATA.1-01-146
Permalink: https://www.hzdr.de/publications/Publ-32780
Creep Properties of 9Cr and 14Cr ODS Tubes Tested by Inner Gas Pressure
Sornin, D.; Ehrnsten, U.; Mozzani, N.; Rantala, J.; Walter, M.; Hobt, A.; Aktaa, J.; Onorbe, E.; Hernandez-Mayoral, M.; Ulbricht, A.; Gicquel, S.; Frank, L.; de Carlan, Y.
Abstract
Oxide-dispersion strengthened steels are promising materials for extreme service conditions including nuclear reactors core. In service conditions, nuclear fuel claddings are exposed to the fission gas pressure at temperatures about 700°C. This paper presents novel results on ODS creep properties from a round robin of inner gas pressure creep test. A gas pressure creep test, simulating fission gas loading, was designed and achieved by four different European teams. Lifetime and specific behavior of ODS steel tube are prospected. Based on a mechanical clamping achieving gas tightness, short length tubes samples are tested by different laboratories. In situ laser measurements exhibit the radial expansion of ODS steel tubes before failure. Post-mortem, geometrical characterizations are performed to determine hoop strains at failure. A consistent creep lifetime is observed by all the teams even with slightly different testing apparatus and clamping systems. Under inner gas pressure, ODS steels exhibit a typical failure by leakage associated to a very small radial expansion. This behavior results from a brutal failure (burst) without evidence of tertiary creep stage. This failure mode of ODS cladding in creep conditions is consistently observed on all samples of the study. Inner gas pressure creep tests were compared, for the first time, by four European laboratories on ODS steel tube. This technique, simulating the fission gas pressure loading, is applied on small and mechanically clamped samples. This technique shows a remarkable consistency between the different laboratories results and demonstrates to be efficient for ODS steel cladding tube qualification. The results show a correlation between the creep properties and the microstructure.
Keywords: ODS steel; Tube creep test; Inner gas pressure
Related publications
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Data publication: Creep Properties of 9Cr and 14Cr ODS Tubes Tested by Inner …
ROBIS: 32780 HZDR-primary research data are used by this (Id 32777) publication
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Metallurgical and Materials Transactions A 52(2021), 3541-3552
DOI: 10.1007/s11661-021-06327-0
Cited 2 times in Scopus
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Permalink: https://www.hzdr.de/publications/Publ-32777
Mechanically flexible magnetoelectronics for human-machine interfaces and soft robotics
Abstract
In this presentation I review our activities on flexible, printable and stretchable functional elements for human-machine interfaces, interactive electronics, soft robotics and cancer research.
Keywords: flexible magnetic field sensors; printable magentic field sensors; flexible heater
Involved research facilities
- Ion Beam Center DOI: 10.17815/jlsrf-3-159
Related publications
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 32775) publication
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Invited lecture (Conferences)
(Online presentation)
International School on Programmable Smart Sensors based on Bio-compatible Nanocomposite Materials (NanoSens), 17.-24.06.2021, Chemnitz, Germany
Permalink: https://www.hzdr.de/publications/Publ-32775
Does the uncertainty in relative biological effectiveness affect patient treatment in proton therapy?
Sørensen, B. S.; Pawelke, J.; Bauer, J.; Burnet, N. G.; Dasu, A.; Høyer, M.; Karger, C. P.; Krause, M.; Schwarz, M.; Underwood, T. S. A.; Wagenaar, D.; Whitfield, G.; Lühr, A.
Abstract
Clinical treatment with protons relies on the concept of relative biological effectiveness (RBE) to convert the absorbed dose into an RBE-weighted dose that equals the dose for radiotherapy with photons causing the same biological effect. Currently, in proton therapy a constant RBE of 1.1 is generically used. However, empirical data indicate that the RBE is not constant, but increases at the distal edge of the proton beam. This increase in RBE is of concern, as the clinical impact is still unresolved, and clinical studies demonstrating a clinical effect of an increased RBE are emerging.
Within the European Particle Therapy Network (EPTN) work package 6 on radiobiology and RBE, a workshop was held in February 2020 in Manchester with one day of discussion dedicated to the impact of proton RBE in a clinical context. Current data on RBE effects, patient outcome and modelling from experimental as well as clinical studies were presented and discussed. Furthermore, representatives from European clinical proton therapy centres, who were involved in patient treatment, laid out their current clinical practice on how to consider the risk of a variable RBE in their centres. In line with the workshop, this work considers the actual impact of RBE issues on patient care in proton therapy by reviewing preclinical data on the relation between linear energy transfer (LET) and RBE, current clinical data sets on RBE effects in patients, and applied clinical strategies to manage RBE uncertainties. A better understanding of the variability in RBE would allow development of proton treatments which are safer and more effective.
Keywords: proton therapy; relative biological effectiveness (RBE)
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Radiotherapy and Oncology 163(2021), 177-184
DOI: 10.1016/j.radonc.2021.08.016
Cited 55 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32773
Self-discharge mitigation in a liquid metal displacement battery
Mushtaq, K.; Zhao, J.; Weber, N.; Mendes, A.; Sadoway, D. R.
Abstract
Recently, a disruptive idea was reported about the discovery of a new type of battery named Liquid Displacement Battery (LDB) comprising liquid metal electrodes and molten salt electrolyte. This cell featured a novel concept of a porous electronically conductive faradaic membrane instead of the traditional ion-selective ceramic membrane. LDBs are attractive for stationary storage applications but need mitigation against self-discharge. In the instant battery chemistry, Li|LiCl-PbCl2|Pb, reducing the diffusion coefficient of lead ions can be a way forward and a solution can be the addition of PbO to the electrolyte. The latter acts as a supplementary barrier and complements the function of the faradaic membrane. The remedial actions improved the cell’s coulombic efficiency from 92% to 97% without affecting the voltage efficiency. In addition, the limiting current density of a 500 mAh cell increased from 575 to 831 mA/cm² and the limiting power from 2.53 to 3.66 W. Finally, the effect of PbO on the impedance and polarization of the cell was also studied.
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Journal of Energy Chemistry 66(2022), 390-396
Online First (2021) DOI: 10.1016/j.jechem.2021.08.015
Cited 8 times in Scopus
Downloads
Permalink: https://www.hzdr.de/publications/Publ-32771
First direct limit on the 334 keV resonance strength in 22Ne(α,γ)26Mg reaction
Piatti, D.; Masha, E.; Aliotta, M.; Balibrea-Correa, J.; Barile, F.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Ciani, G. F.; Compagnucci, A.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Lugaro, M.; Marigo, P.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Rapagnani, D.; Schiavulli, L.; Skowronski, J.; Stöckel, K.; Straniero, O.; Szücs, T.; Takacs, M. P.; Zavatarelli, S.
Abstract
In stars, the fusion of 22Ne and 4He may produce either 25Mg, with the emission of a neutron, or 26Mg and a γ ray. At high temperature, the (α,n) channel dominates, while at low temperature, it is energetically hampered. The rate of its competitor, the 22Ne(α,γ)26Mg reaction, and, hence, the minimum temperature for the (α,n) dominance, are controlled by many nuclear resonances. The strengths of these resonances have hitherto been studied only indirectly. The present work aims to directly measure the total strength of the resonance at E_{r}=334keV (corresponding to E_{x}=10949keV in 26Mg). The data reported here have been obtained using high intensity 4He+ beam from the INFN LUNA 400 kV underground accelerator, a windowless, recirculating, 99.9% isotopically enriched 22Ne gas target, and a 4π bismuth germanate summing γ-ray detector. The ultra-low background rate of less than 0.5 counts/day was determined using 67 days of no-beam data and 7 days of 4He+ beam on an inert argon target. The new high-sensitivity setup allowed to determine the first direct upper limit of 4.0×10−11 eV (at 90% confidence level) for the resonance strength. Finally, the sensitivity of this setup paves the way to study further 22Ne(α,γ)26Mg resonances at higher energy.
Keywords: Nuclear reactions; Nucleosynthesis; abundances – Stars: AGB and post-AGB
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European Physical Journal A 58(2022), 194
DOI: 10.1140/epja/s10050-022-00827-2
Cited 14 times in Scopus -
Contribution to WWW
ArXiV Preprint-Server: https://arxiv.org/abs/2209.03051
Permalink: https://www.hzdr.de/publications/Publ-32770
Nachhaltiges Bauen in der Praxis: Bestandserhalt und ökologische Sanierung
Dirlich, S.; Schweiker, K.
Abstract
Nachhaltiges Bauen ist immer noch eine Nische im Baubereich, obwohl es zahlreiche Vorteile bietet. Mittlerweile wünscht sich auch die Präsidentin der EU-Kommission zur Umsetzung des „Green Deals“ einen Aufbruch auch im Baubereich, der als „New European Bauhaus“ bezeichnet wird in Anlehnung an die Ideen des Bauhauses im 20. Jahrhundert. Auch der Bund Deutscher Architekten (BDA) fordert in seinem Manifest zum klimagerechten Bauen aus dem Jahr 2020 eine Abkehr vom konventionellen Bauen und schlägt eine Reihe von Maßnahmen zu dessen Umsetzung vor, so u. a. „Achtung des Bestands“, „einfach intelligent“ oder „vollständige Entkarbonisierung“.
Beim nachhaltigen Bauen geht es u. a. darum, den gesamten genutzten Wohnraum zu reduzieren, möglichst natürliche und regionale Baustoffe mit geringem Energieinhalt zu nutzen, eine zukunftsfähige Medienversorgung einzusetzen und klimaangepasst zu bauen, also den Bedingungen, die das Klima vorgibt, mit architektonischen statt ingenieurtechnischen Lösungen zu begegnen. Eine Möglichkeit, auf diese Anforderungen einzugehen, besteht im traditionellen Bauen und der Übertragung auf zukunftsfähiges Bauen. Traditionelles Bauen kann als ein Vorbild dienen, um nachhaltig und klimagerecht zu bauen. In früheren Zeiten wurde so gebaut, wie es die regionalen Baustoffe hergaben und die klimatischen Verhältnisse erforderten. Einerseits können in den tropischen Klimazonen Häuser errichtet werden, die den lokal vorhandenen Gegebenheiten gerecht werden und den Menschen trotz der oftmals großen Hitze einigermaßen angenehme Wohnverhältnisse ermöglichen. Andererseits können in den arktischen Gebieten Menschen durch die geschickte Ausnutzung von Bauprinzipien bei eisigen Temperaturen für akzeptable Wärme in den eigenen Wänden zu sorgen. Dabei kann gerade Holz als sehr variabler und in vielfältigen Bereichen einsetzbarer Baustoff dienen, der mittlerweile auch in den Bauordnungen der Länder stärker anerkannt wird. Holz ist zudem noch eine Kohlenstoffsenke und hat insbesondere im Gegensatz zu sehr CO2-intensiven Bauprodukten auf Zementbasis wie Beton große Vorteile bezüglich der Klimarelevanz. In Verbindung mit dem ebenfalls traditionellen Baumaterial Lehm können regionale Rohstoffe genutzt werden, die sich darüber hinaus gut ergänzen und nicht zuletzt auch hohen ästhetischen Ansprüchen genügen.
In der Praxis setzt die Umsetzung nachhaltiger Bauprinzipien oftmals den Willen der Bauherren ebenso voraus wie die Erfahrungen der Bauplanerin/des Bauplaners mit nachhaltigem Bauen. Wenn beides gegeben ist, wie bei der Sanierung einer Doppelhaushälfte in einer Siedlung in Dresden-Reick, kann Wohnraum entstehen, der sowohl aus architektonischer als auch ökologischer Sicht überzeugend ist. Im Verlauf des Bauprozesses mussten teilweise auch die Handwerker überzeugt werden, da die bauseitigen Lösungen beim Einsatz ökologischer Materialien und Bauprinzipien nicht immer mit der konventionellen Herangehensweise zu erzielen sind. Durch entsprechende intensive Absprachen mit den betreffenden Handwerkern konnte aber immer eine überzeugende Lösung erreicht werden und dadurch konnten zudem beide Seiten voneinander lernen.
Keywords: Nachhaltiges Bauen; sustainable building; Bestandserhalt; preservation of existing buildings
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Book chapter
Leal Filho, Walter: Theorie und Praxis der Nachhaltigkeit, Berlin: Springer Spektrum, 2022, 9783631871645
Permalink: https://www.hzdr.de/publications/Publ-32769
Nachhaltige Ressourcengewinnung aus Haldenmaterial
Dirlich, S.; Büttner, P.
Abstract
Die Bergbauindustrie verursacht beim Abbau von Rohstoffen große Umweltauswirkungen. Allerdings sind moderne Industriegesellschaften ohne die Gewinnung von Rohstoffen nicht denkbar. Hochtechnologie und insbesondere auch Umwelttechnologien benötigen in der Herstellung in nicht unerheblichem Maße Metalle und Minerale wie Kupfer, Indium, Lithium, Gallium, Germanium aber auch Seltene Erden und viele weitere Elemente. Die Hinterlassenschaften des Bergbaus in Form von Halden, die fortwährend bei der Rohstoffgewinnung entstehen, sorgen aber für extreme Umweltbelastungen und enthalten zudem noch immer zahlreiche Wertminerale in oft recht hohen Konzentrationen. Diese können durch verschiedene physikalische, chemische und/oder biotechnologische Aufbereitungsverfahren rückgewonnen werden. Solche Technologien sind aus den folgenden Gründen als nachhaltig zu bezeichnen.
Durch die (erneute) Aufbereitung des Haldenmaterials, bei der eine bessere Ressourcennutzung erzielt wird, lässt sich die Ressourceneffizienz erhöhen. Insbesondere Halden, die vor längerer Zeit entstanden sind, enthalten noch beträchtliche Konzentrationen an wertvollen Stoffen mit wirtschaftlicher Bedeutung. Diese aus den Halden zu gewinnen bedeutet damit, dass insgesamt weniger primärer Rohstoffe aus dem Boden gewonnen werden müssen.
Neben der Rohstoffgewinnung hat die Behandlung des Haldenmaterials auch noch zum Ziel, die potenziellen Schadstoffemissionen und anderen Umweltwirkungen zu vermindern. Teilweise kommen dabei die gleichen Verfahren zum Zuge wie bei der Gewinnung der Wertminerale. Die Sanierung solcher Bergbauhinterlassenschaften ist in vielen Fällen gesetzlich vorgeschrieben und zudem sind in den vergangenen Jahrzehnten weltweit zahlreiche katastrophale Unfälle mit Halden vorgefallen, so dass eine Haldensanierung in vielen Fällen sowieso betrieben werden muss.
Aus wirtschaftlicher Sicht ist dabei aber zu beachten, dass die Rohstoffgewinnung in aller Regel nur als eine zusätzliche Einnahmequelle dienen kann, um einen Teil der Kosten für die Haldensanierung zu decken. Theoretische Annahmen zeigen regelmäßig, dass die in den Haldenvolumina enthaltenen Wertstoffkonzentrationen zwar durchaus relevante Größenordnungen erreichen, diese aber bei genauerer Betrachtung insbesondere der Gegenrechnung der Kosten für die erforderlichen Verfahrensschritte standhalten müssen, so dass in vielen Fällen letztendlich – wenn überhaupt – ein Nullsummenspiel gegeben ist.
Am Helmholtz-Institut Freiberg wurde und wird in zahlreichen Projekten an entsprechenden Verfahren geforscht. Darüber hinaus koordiniert das HIF ein großes regionales Netzwerk (recomine), das sich den Bergbaualtlasten an der Schnittstelle von Umwelttechnologie, Ressourcentechnologie und Digitalisierung widmet und unter dessen Schirm Lösungen entwickelt werden, die regional getestet und weiterentwickelt, letztlich auf dem Weltmarkt angeboten werden sollen.
Keywords: remining; Ressourcentechnologie; Nachhaltigkeit; Haldensanierung
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Book chapter
Leal Filho, Walter: Theorie und Praxis der Nachhaltigkeit, Berlin: Springer Spektrum, 2022, 9783631871645
Permalink: https://www.hzdr.de/publications/Publ-32768
Nonreciprocity of spin waves in magnetic nanotubes with helical equilibrium magnetization
Salazar-Cardona, M. M.; Körber, L.; Schultheiß, H.; Lenz, K.; Thomas, A.; Nielsch, K.; Kakay, A.; Otálora, J. A.
Abstract
Spin waves (SWs) in magnetic nanotubes have shown interesting nonreciprocal properties in their dispersion relation, group velocity, frequency linewidth, and attenuation lengths. The reported chiral effects are similar to those induced by the Dzyaloshinskii–Moriya interaction but originating from the dipole–dipole interaction. Here, we show that the isotropic-exchange interaction can also induce chiral effects in the SW transport; the so-called Berry phase of SWs. We demonstrate that with the application of magnetic fields, the nonreciprocity of the different SW modes can be tuned between the fully dipolar governed and the fully exchange governed cases, as they are directly related to the underlying equilibrium state. In the helical state, due to the combined action of the two effects, every single sign combination of the azimuthal and axial wave vectors leads to different dispersions, allowing for a very sophisticated tuning of the SW transport. A disentangle- ment of the dipole–dipole and exchange contributions so far was not reported for the SW transport in nanotubes. Furthermore, we propose a device based on coplanar waveguides that would allow to selectively measure the exchange or dipole induced SW nonreciprocities. In the context of magnonic applications, our results might encourage further developments in the emerging field of 3D magnonic devices using curved magnetic membranes.
Keywords: spin wave; nanotube; nonreciprocity; transducer
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Applied Physics Letters 118(2021), 262411
DOI: 10.1063/5.0048692
Cited 20 times in Scopus
Downloads
- Final Draft PDF 1,6 MB Secondary publication
Permalink: https://www.hzdr.de/publications/Publ-32767
Structured membrane formation via biopolymer-surfactant coacervation
Schwarzenberger, K.; Keshavarzi, B.; Stergiou, Y.; Javadi, A.; Eckert, K.
Abstract
Coacervation can yield membranes with different permeabilities, making it attractive for technological applications in encapsulation or separation processes. During coacervation, oppositely charged species like polymers and surfactants form complexes due to coulombic attraction. These polymer-surfactant complexes are insoluble in the aqueous phase leading to phase separation. As a result, a structured membrane can form in the contact zone between a polymer and a surfactant solution. However, the details of the structure formation processes are only poorly understood.
In this study, we use a combination of the anionic biopolymer xanthan gum and cationic CnTAB surfactants. The quasi 2D-geometry of the Hele-Shaw cell allows us to observe the membrane formation and the growth dynamics in-situ. By this, we can link the membrane properties for different surfactant types and concentrations to the underlying mass transfer and structure formation processes.
The results show that the density and permeability of the formed membrane significantly depend on surfactant chain length and concentration. In a wide range of experiments, the formation of a porous structure is observed whose characteristics depend on the process parameters. The pore formation can be explained as instability of the growing membrane surface in interaction with the supply of polymer across the depleted zone in the vicinity of the membrane front. Our insights provide the basis to control membrane thickness, density, porosity and pore structure. These properties are essential for technological applications since they determine the selectivity, permeability and mechanical stability of the membrane.
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Lecture (Conference)
ECIS 2021, 06.-10.09.2021, Athens, Greece
Permalink: https://www.hzdr.de/publications/Publ-32766
Comparative therapeutic exploitability of acute adaptation mechanisms to photon and proton irradiation in 3d head and neck squamous cell carcinoma cell cultures
Meerz, A.; Deville, S. S.; Muller, J.; Cordes, N.
Abstract
For better tumor control, high-precision proton beam radiation therapy is currently being intensively discussed relative to conventional photon therapy. Here, we assumed that radiation type-specific molecular response profiles in more physiological 3D, matrix-based head and neck squamous cell carcinoma (HNSCC) cell cultures can be identified and therapeutically exploited. While proton irradiation revealed superimposable clonogenic survival and residual DNA double strand breaks (DSB) relative to photon irradiation, kinome profiles showed quantitative differences between both irradiation types. Pharmacological inhibition of a subset of radiation-induced kinases, predominantly belonging to the mitogen-activated protein kinase (MAPK) family, failed to sensitize HNSCC cells to either proton or photon irradiation. Likewise, inhibitors for ATM, DNA-PK and PARP did not discriminate between proton and photon irradiation but generally elicited a radio-sensitization. Conclusively, our results suggest marginal cell line-specific differences in the radio-sensitivity and DSB repair without a superiority of one radiation type over the other in 3D grown HNSCC cell cultures. Importantly, radiation-induced activity changes of cytoplasmic kinases induced during the first, acute phase of the cellular radiation response could neither be exploited for sensitization of HNSCC cells to photon nor proton irradiation.
Keywords: 3D cell culture; HNSCC; Molecular targeting; Photon irradiation; Proton beam irradiation
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Cancers 13(2021)6, 1190
DOI: 10.3390/cancers13061190
Cited 13 times in Scopus
Permalink: https://www.hzdr.de/publications/Publ-32765
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