Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34752 Publications

Tuning the metal-insulator transition in epitaxial SrVO3 films by uniaxial strain

Wang, C.; Zhang, H.; Deepak, K.; Chen, C.; Fouchet, A.; Duan, J.; Hilliard, D.; Kentsch, U.; Chen, D.; Zeng, M.; Gao, X.; Zeng, Y.-J.; Helm, M.; Prellier, W.; Zhou, S.

Understanding of the metal-insulator transition (MIT) in correlated transition-metal oxides is a fascinating topic in condensed matter physics and a precise control of such transitions plays a key role in developing novel electronic devices. Here we report an effective tuning of the MIT in epitaxial SrVO3 (SVO) films by expanding the out-of-plane lattice constant without changing in-plane lattice parameters, through helium ion irradiation. Upon increase of the ion fluence, we observe a MIT with a crossover from metallic to insulating state in SVO films. A combination of transport and magnetoresistance measurements in SVO at low temperatures reveals that the observed MIT is mainly ascribed to electron-electron interactions rather than disorder-induced localization. Moreover, these results are well supported by the combination of density functional theory and dynamical mean field theory (DFT+DMFT) calculations, further confirming the decrease of the bandwidth and the enhanced electron-electron interactions resulting from the expansion of out-of-plane lattice constant. These findings provide insights into the understanding of MIT in correlated oxides and perspectives for the design of unexpected functional devices based on strongly correlated electrons.

Keywords: Oxide thin film; Strain engineering; Metal-insulator transition; Lattice distortion; Correlated electrons

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Permalink: https://www.hzdr.de/publications/Publ-29969
Publ.-Id: 29969


Confirmation of the prognostic value of pretherapeutic tumor SUR and MTV in patients with esophageal squamous cell carcinoma

Hofheinz, F.; Li, Y.; Steffen, I.; Lin, Q.; Lili, C.; Hua, W.; van den Hoff, J.; Zschaeck, S.

Purpose

The prognosis for patients with inoperable esophageal carcinoma is still poor and the reliability of individual therapy outcome prediction based on clinical parameters is not convincing. In a recent publication, we were able to show that PET can provide independent prognostic information in such a patient group and that the tumor-to-blood standard uptake ratio (SUR) can improve the prognostic value of tracer uptake values. The present investigation addresses the question of whether the distinctly improved prognostic value of SUR can be confirmed in a similar patient group that was examined and treated at a different site.
Methods

18F-FDG PET/CT was performed in 147 consecutive patients (115 male, 32 female, mean age: 62 years) with newly diagnosed esophageal squamous cell carcinoma prior to definitive radiochemotherapy. In the PET images, the metabolic active volume (MTV) of the primary tumor was delineated with an adaptive threshold method. For the resulting ROIs, SUVmax and total lesion glycolysis (TLG = MTV × SUVmean) were computed. The blood SUV was determined by manually delineating the aorta in the low-dose CT. SUR values were computed as ratio of tumor SUV and blood SUV. Univariate Cox regression and Kaplan–Meier analysis with respect to overall survival (OS), distant-metastases-free survival (DM), and locoregional control (LRC) was performed. Additionally, a multivariate Cox regression including clinically relevant parameters was performed.
Results

Univariate Cox regression revealed MTV, TLG, and SURmax as significant prognostic factors for OS. MTV as well as TLG were significant prognostic factors for LRC while SURmax showed only a trend for significance. None of the PET parameters was prognostic for DM. In univariate analysis, SUVmax was not prognostic for any of the investigated clinical endpoints. In multivariate analysis (T-stage, N-stage, MTV, and SURmax), MTV was an independent prognostic factor for OS and showed a trend for significance for LRC. SURmax was not an independent predictor for OS or LRC. When including the PET parameters separately in multivariate analysis, MTV as well as SURmax were prognostic factors for OS indicating that SURmax is independent from the clinical parameters but not from MTV. In addition, MTV was an independent prognostic factor for LRC in this separate analysis.
Conclusions

Our study revealed a clearly improved prognostic value of tumor SUR compared to tumor SUV and confirms our previously published findings regarding OS. Furthermore, SUR delivers prognostic information beyond that provided by the clinical parameters alone, but does not add prognostic information beyond that provided by MTV in this patient group. Therefore, our results suggest that pretherapeutic MTV is the parameter of choice for PET-based risk stratification in the considered setting but further investigations are necessary to demonstrate that this suggestion is correct.

Keywords: PET Esophageal cancer Definitive radiochemotherapy SUV SUR

Permalink: https://www.hzdr.de/publications/Publ-29968
Publ.-Id: 29968


HZDR Data Management Strategy — Meeting at Leibniz Institute of Polymer Research Dresden (IPF)

Knodel, O.; Gruber, T.; Müller, S.

Top-Level Architecture of the proposed HZDR Data Management Strategy with an example experiment

Keywords: data management

  • Open Access Logo Invited lecture (Conferences)
    Meeting at Leibniz Institute of Polymer Research Dresden (IPF), 15.11.2019, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-29967
Publ.-Id: 29967


Validation of an independent prognostic value of the asphericity of F18-fluorodeoxyglucose (FDG) uptake in non-small cell lung cancer (NSCLC) patients undergoing treatment in curative intent

Rogasch, J.; Furth, C.; Chibolela, C.; Hofheinz, F.; Ochsenreither, S.; Rückert, J.; Neudecker, J.; Böhmer, D.; Laffert, M.; Amthauer, H.; Frost, N.

Background

In patients with non-small cell lung cancer (NSCLC), asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) has shown prognostic significance. This study aimed at validation in an independent, sufficiently large cohort.
Patients and Methods

Retrospective study in 311 NSCLC patients undergoing FDG-PET/CT before curatively intended treatment (always including surgery). 140 patients had UICC stage I, 78 stage II, and 93 stage III (adenocarcinoma [ADC]:153; squamous cell carcinoma [SCC]:141). Primary tumor MTV was delineated with semiautomated background-adapted threshold relative to SUVmax. Cox regression (PFS/OS) for PET (MTV, ASP, SUVmax), clinical (T/N descriptor, UICC stages), histological and treatment variables (Rx/1 vs. R0 resection, chemotherapy/radiotherapy yes/no).
Results

Events (progression/relapse) occurred in 167/311 patients, 137 died (median survivor follow-up, 37 months). In multivariable Cox regression for OS, ASP>33.3% (HR, 1.58 [1.04-2.39]), male sex (1.84), age (1.04 per year), EGOG≥2 vs. 0/1 (2.68), stage II vs. I (1.96), and Rx/1 vs. R0 resection (2.1) were significant. Among separate UICC stages, ASP only predicted OS in stage II (optimal, >19.5%; median OS, 33 vs. 59 months). Regarding PFS, ASP>21.2%, male sex, EGOG≥2, stage II vs. I, and Rx/1 resection were prognostic. ASP remained prognostic in stage II (optimal, >19.5%; PFS, 12 vs. 47 months). Log-rank test for ASP was significant at any cut-off ≥18% (OS) or from 9-59% (PFS).
Conclusion

ASP was validated as prognostic factor for PFS and OS in patients with NSCLC and curative treatment intent, especially stage II. High ASP in stage II could imply intensified treatment or intensified follow-up.

Keywords: Prognosis; survival; FDG-PET; metabolic tumor volume; quantification

Permalink: https://www.hzdr.de/publications/Publ-29966
Publ.-Id: 29966


Introduction of the New Center for Radiopharmaceutical Cancer Research at Helmholtz-Zentrum Dresden-Rossendorf

Kreller, M.; Pietzsch, H.-J.; Walther, M.; Tietze, H.; Kaever, P.; Knieß, T.; Füchtner, F.; Steinbach, J.; Preusche, S.

A new Center for Radiopharmaceutical Cancer Research was established at the Helmholtz-Zentrum Dresden-Rossendorf in order to centralize radionuclide production, radiopharmaceutical production and the chemical and biochemical research facilities. The newly installed cyclotron is equipped with two beamlines, two target selectors and several liquid, gas and solid target systems. The cyclotron including the target systems and first results of beam characterization measurements as well as results of the radionuclide production are presented. The produced radionuclides are automatically distributed from the targets to the destination hot cells. This process is supervised and controlled by an in-house developed system.

Keywords: cyclotrons; radionuclide production; solid, liquid and gas targets

Permalink: https://www.hzdr.de/publications/Publ-29965
Publ.-Id: 29965


Microstructural characterization of inhomogeneity in 9Cr ODS EUROFER steel

Das, A.; Chekhonin, P.; Altstadt, E.; Bergner, F.; Heintze, C.; Lindau, R.

Ferritic-martensitic ODS steels are one of the candidate materials for Gen-IV nuclear fission and fusion reactors. Residual ferrite was often found in the microstructure of 9Cr ODS steels. This constituent was reported to be responsible for the superior creep and high-temperature strength. Using optical microscopy of an air-cooled batch of ODS EUROFER, inhomogeneous regions in the microstructure have been found with similar appearance to previously reported residual ferrite. Detailed microstructural investigations have been carried out on the inhomogeneous regions using site-specific nanoindentation, scanning electron microscopy including electron backscatter diffraction, and transmission electron microscopy. It is demonstrated that the inhomogeneous regions are formed due to imperfect mechanical alloying leading to the absence of oxide nanoparticles and consequently lower hardness. It is concluded that optical microscopy is insufficient to distinguish beneficial residual ferrite from undesired particle-free regions. The weakness of the inhomogeneous regions is attributed to the absence of nanoparticles and a lower dislocation density. Our findings are underpinned by the consistency between the calculated theoretical yield strength, the yield strength converted from the indentation hardness and the yield strength obtained from tensile testing.

Keywords: ODS steel; ferritic-martensitic steel; inhomogeneity; nanoindentation; residual ferrite

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  • Secondary publication expected from 01.05.2021

Permalink: https://www.hzdr.de/publications/Publ-29964
Publ.-Id: 29964


Molecular binding of EuIII/CmIII by Stenotrophomonas bentonitica and its impact on the safety of future geodisposal of radioactive waste

Ruiz-Fresneda, M. A.; Lopez Fernandez, M.; Martinez-Moreno, M. F.; Cherkouk, A.; Ju-Nam, Y.; Ojeda, J. J.; Moll, H.; Merroun, M. L.

Microbial communities occurring in reference materials for artificial barriers (e.g. bentonites) in future deep geological repositories of radioactive waste can influence the migration behavior of radionuclides such as curium (CmIII). This study investigates the molecular interactions between CmIII and its inactive analogue europium (EuIII) with the indigenous bentonite bacterium Stenotrophomonas bentonitica at environmentally relevant concentrations. Potentiometric studies showed a remarkable high concentration of phosphates at the bacterial cell wall compared to other bacteria, revealing a great potential of S. bentonitica for metal binding. Infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the role of phosphates and carboxylate groups from the cell envelope in the bioassociation of EuIII. The ATR-FTIR spectra also suggested a bidentate bridging EuIII complex with carboxylate groups. Additionally, time-resolved laser-induced fluorescence spectroscopy (TRLFS) identified phosphoryl and carboxyl groups from bacterial envelopes, among other released complexing agents, to be involved in the EuIII and CmIII coordination. Microscopic and kinetic Eu-binding studies indicated biosorption as the main interaction process, in addition to other mechanisms. The ability of this bacterium to form a biofilm at the surface of bentonites allow them to immobilize trivalent lanthanide and actinides in the environment.

Keywords: europium; curium; bacterial speciation; mobility; geodisposal

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  • Secondary publication expected from 13.11.2021

Permalink: https://www.hzdr.de/publications/Publ-29963
Publ.-Id: 29963


Time reversal and quantum Loschmidt echo in optical lattices

Schützhold, R.; Szpak, N.

A quantum Loschmidt echo (also referred to as quantum time mirror) corresponds to an effective time inversion after which the quantum wave function reverses its previous time evolution and eventually reaches its initial distribution again. We propose a comparably simple protocol for such an effective time reversal for ultra-cold atoms in optical lattices which should be easier to realize experimentally than previous proposals.

Keywords: Quantum Physics; Quantum Gases

Permalink: https://www.hzdr.de/publications/Publ-29961
Publ.-Id: 29961


Reply to comment on "Interaction of a BEC with a gravitational wave"

Schützhold, R.

This reply contains a brief response to the comment by R. Howl, D. Rätzel, and I. Fuentes [arXiv:1811.10306]

Keywords: Quantum Physics; General Relativity and Quantum Cosmology

Permalink: https://www.hzdr.de/publications/Publ-29960
Publ.-Id: 29960


Quantum simulation of spontaneous pair creation in 2D optical lattices

Schützhold, R.; Klar, L.; Szpak, N.

One of the fundamental predictions of Quantum Electrodynamics (QED) is the spontaneous creation of particle--antiparticle pairs from vacuum in presence of a very strong electric field. Under these extreme conditions a strongly bound state can fetch an otherwise unobservable electron from the Dirac sea, leaving behind a hole representing a positron. Although generally known for many decades, the effect has not yet been demonstrated experimentally. We propose an analogue model of the quantum Dirac field, realized by ultra--cold fermionic atoms in an optical lattice, aiming at an experimental simulation of this intriguing non--perturbative phenomenon. Numerical simulations demonstrate the effect of spontaneous pair creation in the optical analogue system, in qualitative agreement with QED: in the adiabatic regime the vacuum can be destabilized only by supercritical fields exceeding a critical threshold.

Keywords: Quantum Physics; Quantum Gases

Permalink: https://www.hzdr.de/publications/Publ-29959
Publ.-Id: 29959


Phonon Pair Creation by Inflating Quantum Fluctuations in an Ion Trap

Schützhold, R.; Wittemer, M.; Hakelberg, F.; Kiefer, P.; Schröder, J.-P.; Warring, U.; Schaetz, T.; Fey, C.

Quantum theory predicts intriguing dynamics during drastic changes of external conditions. We switch the trapping field of two ions sufficiently fast to tear apart quantum fluctuations, i.e., create pairs of phonons and, thereby, squeeze the ions’ motional state. This process can be interpreted as an experimental analog to cosmological particle creation and is accompanied by the formation of spatial entanglement. Hence, our platform allows one to study the causal connections of squeezing, pair creation, and entanglement and might permit one to cross-fertilize between concepts in cosmology and applications of quantum information processing.

Keywords: Inflation; Quantum Information with trapped Ions; Quantum simulation

Permalink: https://www.hzdr.de/publications/Publ-29958
Publ.-Id: 29958


Relaxation dynamics in a Hubbard dimer coupled to fermionic baths: phenomenological description and its microscopic foundation

Schützhold, R.; Kleinherbers, E.; Szpak, N.; König, J.

We study relaxation dynamics in a strongly-interacting two-site Fermi-Hubbard model that is induced by fermionic baths. To derive the proper form of the Lindblad operators that enter an effective description of the system-bath coupling in different temperature regimes, we employ a diagrammatic real-time technique for the reduced density matrix. An improvement on the commonly-used secular approximation, referred to as coherent approximation, is presented. We analyze the spectrum of relaxation rates and identify different time scales that are involved in the equilibration of the Hubbard dimer after a quantum quench.

Permalink: https://www.hzdr.de/publications/Publ-29957
Publ.-Id: 29957


Hydrodynamic data of an advanced inclined rotating fixed-bed reactor

Timaeus, R.; Schleicher, E.; Bieberle, A.; Hampel, U.; Schubert, M.

This publication contains the hydrodynamic data of an advanced inclined rotating fixed-bed reactor with inner tube. The phase distribution in the cross-section of the reactor and the normalized liquid filling level (normalized to the reactor diameter) were obtained with a capacitance wire-mesh sensor. Besides, the specific pressure drops for the investigated operating points are given. Furthermore, the porostiy profile of different configurations (different particle and inner tube diameter) are stored, which were obtained by gamm-ray computed tomography.

Keywords: Capacitance wire-mesh sensor; gamma-ray tomography; inclined rotating fixed-bed reactor

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-11-18
    DOI: 10.14278/rodare.203

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29956
Publ.-Id: 29956


Technetium retention by gamma alumina nanoparticles and the effect of sorbed Fe²⁺

Mayordomo, N.; Rodriguez Hernandez, D. M.; Schild, D.; Molodtsov, K.; Johnstone, E. V.; Hübner, R.; Shams Aldin Azzam, S.; Brendler, V.; Müller, K.

Technetium (Tc) retention on gamma alumina nanoparticles (gamma-Al₂O₃ NPs) has been studied in the absence (binary system) and presence (ternary system) of previously sorbed Fe²⁺ as a reducing agent. In the binary system, gamma-Al₂O₃ NPs sorb up to 6.5% of Tc from solution as Tc(VII). In the ternary system, the presence of previously sorbed Fe²⁺ on gamma-Al₂O₃ NPs significantly enhances the uptake of Tc from pH 4 to pH 11. Under these conditions, the reaction rate of Tc increases with pH, resulting in a complete uptake for pHs > 6.5. Redox potential (Eh) and X-ray photoelectron spectroscopy (XPS) measurements evince heterogeneous reduction of Tc(VII) to Tc(IV). Here, the formation of Fe containing solids was observed; Raman and scanning electron microscopy showed the presence of Fe(OH)₂, Fe(II)-Al(III)-Cl layered double hydroxide (LDH), and other Fe(II) and Fe(III) mineral phases, e.g. Fe₃O₄, FeOOH, Fe₂O₃. These results indicate that Tc scavenging is predominantly governed by the presence of sorbed Fe²⁺ species on gamma-Al₂O₃ NPs, where the reduction of Tc(VII) to Tc(IV) and overall Tc retention is highly improved, even under acidic conditions. Likewise, the formation of additional Fe solid phases in the ternary system promotes the Tc uptake via adsorption, co-precipitation, and incorporation mechanisms.

Keywords: Technetium; Al₂O₃; reduction; sorption; immobilization

Permalink: https://www.hzdr.de/publications/Publ-29955
Publ.-Id: 29955


High-Speed Data Acquisition System and Real-time Data Processing using FPGA Architecture

Bawatna, M.; Kovalev, S.; Deinert, J.-C.

The super radiant THz sources at TELBE facility is based on the new class of accelerator-driven terahertz (THz) radiation sources that provide high repetition rates up to 13 MHz, and flexibility of tuning the THz pulse form. The THz pulses are used for the excitation of materials of interest, about two orders of magnitude higher than state-of-the-art tabletop sources. Time-resolved experiments can be performed with a time resolution down to 30 femtoseconds (fs) using the novel pulse-resolved Data Acquisition (DAQ) system. However, the increasing demands in improving the flexibility, data throughput, and speed of the DAQ systems motivate the integration of reconfigurable processing units close to the new detectors to accelerate the processing of tens of GigaBytes of data per second. In this poster, we introduce our online ultra fast DAQ system that uses an FPGA architecture for real-time image processing, as well as interfacing the image sensors and provide a continuous data transfer.

Keywords: Ultra fast DAQ system; Pulse-resolved Data Acquisition (DAQ) system; Field Programmable Gate Array (FPGA)

  • Open Access Logo Poster
    MT ARD ST3 Annual meeting, 16.-18.10.2019, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-29954
Publ.-Id: 29954


High speed data acquisition with online analysis

Bawatna, M.; Green, B. W.; Kovalev, S.; Deinert, J.-C.

TELBE THz facility is performing ultra-fast pump-probe experiments by providing a unique combination of high pulse energies and high repetition rates. In this type of experiment, the electric or magnetic field in the THz pump pulse acts as the excitation of dynamics in the matter. This dynamic in turn is then probed by ultra-short (light) pulses, typically with the sub THz cycle resolution. A pulse resolved DAQ system has been developed at TELBE user facility to allow the performance of time-resolved THz spectroscopy measurements with sub 30 fs Full-Width Half Maximum (FHWM) time resolution with excellent dynamic range up to 120 dB.

  • Open Access Logo Poster
    The 6th Accelerator Research & Development (ARD) Workshop, 26.-28.09.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29953
Publ.-Id: 29953


High-Speed Data Acquisition and Online Analysis System at MHz Repetition Rate

Bawatna, M.; Green, B. W.; Deinert, J.-C.; Kovalev, S.

A unique high-rep-rate pulse-resolved detection scheme has been developed at TELBE that provides timing down to 12 fs by post-mortem arrival time jitter correction. This allows experiments to take full advantage of the superior properties of the light source without sacrificing the ability to perform high-resolution, high dynamic range, time-resolved experiments previously only available with tabletop sources.
One major asset is the fact that meanwhile real-time data analysis can be provided at TELBE making use of multi-thread technology.

Keywords: Real-time data analysis; Terahertz; pulse-resolve arrival time monitor

  • Open Access Logo Poster
    FELBE/TELBE User Workshop 2019, 13.-15.05.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29952
Publ.-Id: 29952


Towards the Development of FPGA-Based High-Speed Data Acquisition and Online Analysis System at MHz Repetition Rate: Proposals and Major Tradeoffs

Bawatna, M.; Green, B. W.; Kovalev, S.; Deinert, J.-C.

Pulse-resolved data acquisition and online analysis is a key ingredient in modern accelerator-based light sources because of the ever-increasing demands in data quality (e.g. signal-to-noise ratios, time resolution). Accelerator-based light sources, in particular those based on linear accelerators, are intrinsically less stable than lasers or other more conventional light sources because of their large scale. In order to achieve optimal data quality the properties of each light pulse need to be detected and implemented into the analysis of each respective experiment. Such schemes are of particular advantage in 4th generation light sources based on super-conducting radiofrequency (SRF) technology, since here the combination of pulse-resolved detection schemes with high-repetition-rates is particularly fruitful. In this case pulse-to-pulse instabilities can be utilized to perform studies of multi-dimensional parameter dependencies on very short timescales making particularly the operation of user facilities much more efficient. A unique high-rep-rate pulse-resolved arrival time monitor has been developed at the high-field high-repetition-rate THz user facility TELBE as a demonstrator for the European XFEL and routinely operates up to a repetition rate of 100 kHz in user experiments providing, among other things, a timing precision of few 10 femtoseconds. In this contribution we will outline how this existing scheme shall be upgraded based on FPGA technology so that it allows operation at MHz repetition rates and sub femtosecond timing precision. An architecture based on Field Programmable Gate Array (FPGA) technology will allow online analysis of the measured data at MHz repetition rate and will decrease the amount of data throughput and the required disk capacity for storing the data by orders of magnitude. Implementation of several novel purpose-built CMOS line array detector will enable to perform arrivaltime measurements at MHz repetition rates.

Keywords: Pulse-resolved arrival time monitor; MHz repetition rates; Terahertz; sub femtosecond timing precision

  • Open Access Logo Lecture (Conference)
    The 9th Workshop on Longitudinal Electron Bunch Diagnostics, 20.-23.02.2019, TU Dortmund, Germany

Permalink: https://www.hzdr.de/publications/Publ-29951
Publ.-Id: 29951


Pulse-resolved Data Acquisition System for THz Pump Laser Probe Experiments at TELBE using Super-radiant Terahertz Sources

Bawatna, M.; Green, B. W.; Deinert, J.-C.; Kovalev, S.; Knodel, O.; Spallek, R.; Cowan, T.

The terahertz (THz) frequency range lies between the frequency range of radio and infrared. The development of suitable detectors, detection techniques, and sources for this frequency range has much interest over the past decade. THz pulses of sufficient strength that act as an excitation of dynamics in the matter have only been available, due to the development in 4th generation light sources based on superconducting radiofrequency (SRF) technology. In the THz pump laser probe experiments the electric or magnetic field in the THz pump pulse acts as the excitation of dynamics in the matter. Ultra-short laser pulses then probe this dynamic in turn. In this contribution, we will outline the pulse-resolved data acquisition scheme of the TELBE user facility based on the characterization of a new class of accelerator-based light sources, which provide a unique combination of high pulse energies and high repetition rates.

Keywords: Ultra fast Science; High-speed Data Acqusition (DAQ) System; Terahertz; High repetition rates

  • Open Access Logo Contribution to proceedings
    2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), 16.-18.07.2019, Bochum, Germany
    2019 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), IEEE: IEEE Xplore, 978-1-7281-0936-7/19, 142-144
    DOI: 10.1109/IMWS-AMP.2019.8880116

Permalink: https://www.hzdr.de/publications/Publ-29950
Publ.-Id: 29950


Design and Development of High-Speed Data Acquisition System and Online Data Processing with a Heterogeneous FPGA/GPU Architecture

Bawatna, M.; Deinert, J.-C.; Knodel, O.; Kovalev, S.; Spallek, R.

The superradiant THz sources at TELBE facility is based on the new class of accelerator-driven terahertz (THz) radiation sources that provide high repetition rates up to 13 MHz, and flexibility of tuning the THz pulse form. The THz pulses are used for the excitation of materials of interest, about two orders of magnitude higher than state-of-the-art tabletop sources. Time-resolved experiments can be performed with a time resolution down to 30 femtoseconds (fs) using the novel pulse-resolved Data Acquisition (DAQ) system. However, the increasing demands in improving the flexibility, data throughput, and speed of the DAQ systems motivate the integration of reconfigurable processing units close to the new detectors to accelerate the processing of tens of GigaBytes of data per second. In this paper, we introduce our online ultrafast DAQ system that uses a GPU platform for real-time image processing, and a custom high-performance FPGA board for interfacing the image sensors and provide a continuous data transfer.

Keywords: Online Data Acquisition System; MHz Repetition Rates; Ultrafast; bunch diagnostics; Field Programmable Gate Array

  • Open Access Logo Contribution to proceedings
    The 39th International Free Electron Laser Conference (FEL2019), 18.08.-25.11.2019, Hamburg, Germany
    Proceedings of the 39th International Free Electron Laser Conference (FEL2019), JACoW: JACoW, 978-3-95450-210-3, 510-512
    DOI: 10.18429/JACoW-FEL2019-WEP081

Permalink: https://www.hzdr.de/publications/Publ-29949
Publ.-Id: 29949


On the Use of Statistical Entropy Analysis as Assessment Parameter for the Comparison of Lithium-Ion Battery Recycling Processes

Velázquez-Martinez, O.; van den Boogaart, K. G.; Lundström, M.; Santasalo-Aarnio, A.; Reuter, M.; Serna-Guerrero, R.

The principle of the circular economy is to reintroduce end-of-life materials back into the economic cycle. While reintroduction processes, for example, recycling or refurbishing, undoubtedly support this objective, they inevitably present material losses or generation of undesired by-products. Balancing losses and recoveries into a single and logical assessment has now become a major concern. The present work broadens the use of relative statistical entropy and material flow analysis to assess the recycling processes of two lithium-ion batteries previously published in the literature. Process simulation software, that is, HSC Sim®, was employed to evaluate with a high level of accuracy the performance of such recycling processes. Hereby, this methodology introduces an entropic association between the quality of final recoveries and the pre-processing stages, that is, shredding, grinding, and separation, by a parameter based on information theory. The results demonstrate that the pre-processing stages have a significant impact on the entropy value obtained at the final stages, reflecting the losses of materials into waste and side streams. In this manner, it is demonstrated how a pre-processing system capable of separating a wider number of components is advantageous, even when the final quality of refined products in two different processes is comparable. Additionally, it is possible to observe where the process becomes redundant, that is, where processing of material does not result in a significant concentration in order to take corrective actions on the process. The present work demonstrates how material flow analysis combined with statistical entropy can be used as a parameter upon which the performance of multiple recycling processes can be objectively compared from a material-centric perspective.

Keywords: material flow analysis; relative statistical entropy; circular economy; lithium-ion batteries; LIB recycling; process simulation

Permalink: https://www.hzdr.de/publications/Publ-29948
Publ.-Id: 29948


The energy needed to concentrate minerals from common rocks: the case of copper ore

Palacios, J.-L.; Abadias Llamas, A.; Valero, A.; Valero, A.; Reuter, M.

A way to assess today's mineral patrimony is to evaluate how much mining energy is saved today because of having concentrated mines instead of finding the minerals dispersed throughout the crust. This can be assessed through the so-called exergy replacement costs (ERC), which are a measure of the exergy required to extract and concentrate minerals from barerock. Previous studies evaluated such exergy using a theoretical approach. In this paper, from a mineral processing point-of-view through a model developed with HSC Chemistry 9.4.1, we calculated the energy needed to concentrate copper from common rocks at average crustal concentrations. In the model, current state-of-the-art technologies for copper concentration were considered. The results were then compared to the theoretical value obtained before for the ERC of copper and helped to update it. The updated ERC value is of one order of magnitude greater than the original one. This difference in magnitude enhances, even more, the issue of ore grade decline in terms of the associated spiraling energy required for mining. It also reveals the importance of valuing properly the mineral heritage of nations and the effort that should be placed for increasing secondary metal production.

Keywords: Copper; Mining energy; Ore grade decline Thanatia; Exergy replacement cost

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29947
Publ.-Id: 29947


Producing metals from common rock: the case of gold

Palacios, J.-L.; Abadias Llamas, A.; Valero, A.; Valero, A.; Reuter, M.

The depletion of the mineral capital is a topic of concern because the worldwide demand for minerals is rapidly increasing. Moreover, since the energy consumption increases as ore grades decline, there is growing stress on energy resources and the environment associated with mining activities. The energy costs associated with the exhaustion of mineral deposits is ruled by the entropy law through a negative logarithmic pattern, in which as the ore grade tends to zero, the energy tends to infinity. This study analyzes through a model developed in HSC Chemistry software, the energy that would be required to produce gold from common bare rock. In this way, we evaluate the maximum energy consumption with current technologies, to obtain gold at the final ore grade, i.e., when all mineral deposits were completely exhausted until reaching crustal concentration. The final theoretical concentration of gold is assumed to be that of the model of Thanatia, which is a resource exhausted Earth with the most abundant minerals found at crustal concentrations. The results are then compared to theoretical values obtained in previous studies for gold and serve to update with a more accurate methodology, the so-called thermodynamic rarity of minerals, as a way to assess the avoided mining energy for having minerals con- centrated in mines and not dispersed throughout the crust. This then serves to assess the mineral capital and its degradation velocity from a thermodynamic point of view.

Keywords: Mineral processing Gold; Crust; Thanatia; Exergy replacement cost Thermodynamic rarity

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29946
Publ.-Id: 29946


Linking NRP2 with EMT and chemoradioresistance in bladder cancer

Schulz, A.; Gorodetska, I.; Behrendt, R.; Fuessel, S.; Erdmann, K.; Foerster, S.; Datta, K.; Mayr, T.; Muders, M.; Dubrovska, A.

Neuropilin-2 (NRP2) is a prognostic indicator for reduced survival in bladder cancer (BCa) patients. Together with its major ligand, vascular endothelial growth factor (VEGF)-C, NRP2 expression is a predictive factor for treatment outcome in response to radiochemotherapy in BCa patients who underwent transurethral resection. Therefore, we investigated the benefit of combining cisplatin-based chemotherapy with irradiation treatment in the BCa cell line RT112 exhibiting or lacking endogenous NRP2 expression in order to evaluate NRP2 as potential therapeutic target. We have identified a high correlation of NRP2 and the Glioma-associated oncogene family zinc finger 2 (GLI2) transcripts in the cancer genome atlas (TCGA) cohort of BCa patients and a panel of 15 human BCa cell lines. Furthermore, we used in vitro BCa models to show the transforming growth factor-beta 1 (TGFb1)-dependent regulation of NRP2 and GLI2 expression levels. Since NRP2 was shown to bind TGFb1, associate with TGFb receptors and enhance TGFb1 signaling, we evaluated downstream signaling pathways using an epithelial to mesenchymal (EMT)-assay in combination with a PCR profiling array containing 84 genes related to EMT. Subsequent target validation in NRP2 knockout and knockdown models revealed secreted phosphoprotein 1 (SPP1/OPN/Osteopontin) as a downstream target positively regulated by NRP2.

Keywords: Keywords: bladder cancer; Neuropilin-2 (NRP2); Glioma-Associated Oncogene Family Zinc Finger 2 (GLI2); Secreted Phosphoprotein 1 (SPP1); Osteopontin (OPN); Epithelial to Mesenchymal Transition (EMT); RT112; J82

Permalink: https://www.hzdr.de/publications/Publ-29945
Publ.-Id: 29945


The importance of viscous and interfacial forces in the hydrodynamics of the Top-Submerged-Lance furnace

Obiso, D.; Kriebitzsch, S.; Reuter, M.; Meyer, B.

The purpose of this work is to focus on the hydrodynamics of a Top-Submerged-Lance (TSL) smelting furnace, understanding how liquid properties and operational parameters act on key factors of a TSL process, such as splashing, mixing, mass transfer area, and bubble development. A deep knowledge of all those aspects is needed since they all influence the smelting reaction rates; hence the efficiency of the reactor. The characterization and scaling of the TSL gas injection are commonly based on the modified Froude number, the ratio of dynamic and gravitational forces. Detailed literature research reveals a potential weakness of this approach, since it does not consider the effects of viscosity and surface tension. To investigate this question an extensive parametric study was performed applying computational fluid dynamics to cold and non-reactive flows, which provided a broad overview of the physics of the flow. The analysis was performed on fluid dynamic properties (liquid density, liquid viscosity, surface tension) and operational variables (gas volume flow, lance immersion depth). The coupled Level Set—Volume of Fluid model, available in the commercial solver ANSYS FluentÒ, was used to resolve the gas–liquid interface in the multiphase flow. The results of the work underscore the significance of the viscous and interfacial forces for gas injection in smelting slags, confirming the incompleteness of applying only the Froude number to describe such flows.

Permalink: https://www.hzdr.de/publications/Publ-29942
Publ.-Id: 29942


A Critical Review of Lithium-Ion Battery Recycling Processes from a Circular Economy Perspective

Velázquez-Martínez, J. V.; Santasalo-Aarnio, A.; Reuter, M.; Serna-Guerrero, R.

Lithium-ion batteries (LIBs) are currently one of the most important electrochemical energy storage devices, powering electronic mobile devices and electric vehicles alike. However, there is a remarkable difference between their rate of production and rate of recycling. At the end of their lifecycle, only a limited number of LIBs undergo any recycling treatment, with the majority go to landfills or being hoarded in households. Further losses of LIB components occur because the the state-of-the-art LIB recycling processes are limited to components with high economic value, e.g., Co, Cu, Fe, and Al. With the increasing popularity of concepts such as “circular economy” (CE), new LIB recycling systems have been proposed that target a wider spectrum of compounds, thus reducing the environmental impact associated with LIB production. This review work presents a discussion of the current practices and some of the most promising emerging technologies for recycling LIBs. While other authoritative reviews have focused on the description of recycling processes, the aim of the present was is to offer an analysis of recycling technologies from a CE perspective. Consequently, the discussion is based on the ability of each technology to recover every component in LIBs. The gathered data depicted a direct relationship between process complexity and the variety and usability of the recovered fractions. Indeed, only processes employing a combination of mechanical processing, and hydro- and pyrometallurgical steps seemed able to obtain materials suitable for LIB (re)manufacture. On the other hand, processes relying on pyrometallurgical steps are robust, but only capable of recovering metallic components.

Keywords: circular economy; recycling processes; lithium-ion battery

Permalink: https://www.hzdr.de/publications/Publ-29941
Publ.-Id: 29941


The simulation-based analysis of the resource efficiency of the circular economy – the enabling role of metallurgical infrastructure

Bartie, N. J.; Abadias Llamas, A.; Heibeck, M.; Fröhling, M.; Reuter, M.

Process metallurgy is a key enabler and the heart of the Circular Economy (CE). This paper shows the state-of-the-art approach to understanding the resource efficiency of very large-scale CE systems. Process simulation permits system-wide exergy analysis also linked to environmental footprinting. It is shown that digital twins of large CE systems can be created and their resource efficiencies quantified. This approach provides the basis for detailed estimation of financial expenditures as well as high-impact CE system innovation. The cadmium telluride (CdTe) photovoltaic technology life cycle, which brings several metal infrastructures into play, is studied. The results show that considerable work remains to optimise the CdTe system. Low exergy efficiencies resulting specifically from energy-intensive processes highlight areas with the greatest renewables-based improvement potential. This detail sheds light on the true performance of the CE and the inconvenient truth that it cannot be fully realised but only driven to its thermodynamic limits.

Keywords: Circular economy; exergy; life cycle assessment; metallurgy; photovoltaics; resource efficiency; sustainability; digital twin

Downloads:

  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29940
Publ.-Id: 29940


Simulation-based exergy analysis of large circular economy systems: Zinc production coupled to CdTe photovoltaic module life cycle

Abadias Llamas, A.; Bartie, N. J.; Heibeck, M.; Stelter, M.; Reuter, M.

The second law of thermodynamics (2LT) helps to quantify the limits as well as the resource efficiency of the circular economy (CE) in its transformation of resources, which include materials, energy or water, into products and residues, some of which will be irreversibly lost. Furthermore, material and energy losses will also occur, as well as the residues and emissions that are generated have an environmental impact. Identifying the limits of circularity of large-scale CE systems, i.e. flowsheets, is necessary to understand the viability of the CE. With this deeper understanding, the full social, environmental and economic sustainability can be explored. Exergy dissipation, a measure of resource consumption, material recoveries and environmental impact indicators together provide a quantitative basis for designing a resource efficient CE system. Unique and very large simulation models, linking up to 223 detailed modelled unit operations, over 860 flows and 30 elements and all associated compounds apply this thermoeconomic (exergy-based) methodology showing (i) the resource efficiency limits, in terms of material losses and exergy dissipation of the CdTe photovoltaic (PV) module CE system (i.e. from ore to metal production, PV module production, and end- of-life recycling the original metal into the system again), and (ii) the analysis of the zinc processing subsystem of the CdTe PV system, for which the material recovery, resource consumption and environmental impacts of the different processing routes were evaluated and the most resource-efficient alternative to minimize the residue production during zinc production was selected. The paper also quantifies the key role that metallurgy plays in enabling sustainability. Therefore, it highlights the criticality of the metallurgical infrastructure to the CE, above and beyond simply focusing on the criticality of the elements.

Keywords: Exergy; Thermoeconomics; Circular economy; Geometallurgy, Process simulation; Digital twin; Sustainability; Jarosite; CdTe photovoltaic (PV) modules

Downloads:

  • Secondary publication expected from 01.03.2021

Permalink: https://www.hzdr.de/publications/Publ-29939
Publ.-Id: 29939


Towards Real-time Data Processing using FPGA Technology for High-speed Data Acquisition System at MHz Repetition Rates

Bawatna, M.; Arnold, A.; Green, B. W.; Deinert, J.-C.; Kovalev, S.

Accelerator-based light sources, in particular, those based on linear accelerators, are intrinsically less stable than lasers or other more conventional light sources be-cause of their large scale. In order to achieve optimal data quality, the properties of each light pulse need to be de-tected and implemented into the analysis of each experi-ment. Such schemes are of particular advantage in 4th gen-eration light sources based on superconducting radiofre-quency (SRF) technology, since here the combination of pulse -resolved detection schemes with high -repetition-rate is particularly fruitful. Implementation of several different pur pose -built CMOS linear array detector will enable to perform arrival-time measurements at MHz repetition rates. An architecture based on FPGA technology will al-low an online analysis of the measured data at MHz repe-tition rate and will decrease the amount of data throughput and disk capacity for storing the data by orders of magni-tude. In this contribution, we will outline how the pulse-resolved data acquisition scheme of the TELBE user facil-ity shall be upgraded to allow operation at MHz repetition rates and sub-femtosecond timing precision.

Keywords: Real-Time Data Processing; High-speed Data Acquisition System; High Repetition Rates

  • Open Access Logo Contribution to proceedings
    The 19th International Conference on RF Superconductivity (SRF2019), 23.-30.06.2019, Dresden, Germany
    Proceedings of SRF 2019, JACoW: JACoW, 978-3-95450-211-0, 907-912
    DOI: 10.18429/JACoW-SRF2019-THP029

Permalink: https://www.hzdr.de/publications/Publ-29938
Publ.-Id: 29938


Modelling ASTRID-Like Sodium-Cooled Fast Reactor with Serpent DYN3D Code Sequence

Rydlewicz, W.; Fridman, Emil; Shwageraus, E.

This study explores the feasibility of applying the Serpent-DYN3D sequence to the analysis of Sodium-cooled Fast Reactors (SFRs) with complex core geometries, such as the ASTRID-like design. The core is characterised by a highly heterogeneous configuration and was likely to challenge the accuracy of the Serpent-DYN3D sequence. It includes axially heterogeneous fuel assemblies, non-uniform fuel assembly heights and large sodium plena. Consequently, the influence of generation and correction methods of various homogenised, few-group cross-sections (XS) on the accuracy of the full-core nodal diffusion DYN3D calculations is presented. An attempt to compare the approximate time effort spent on models preparation against the accuracy of the result is made. Results are compared to reference full-core Serpent MC (Monte Carlo) solutions. Initially, XS data was generated in Serpent using traditional methods (2D single assemblies and 2D super-cells). Full core calculations and MC simulations offered a moderate agreement. Therefore, XS generation with 2D fuel-reflector models and 3D single assembly models was verified. Super-homogenisation (SPH) factors for XS correction were applied. In conclusion, the performed work suggests that Serpent-DYN3D sequence could be used for the analysis of highly heterogeneous SFR designs similar to the studied ASTRID-like, with an only small penalty on the accuracy of the core reactivity and radial power distribution prediction. However, the XS generation route would need to include the correction with SPH factors and generation of XS with various MC models, for different core regions. At a certain point, there are diminishing returns to using more complex XS generation methods, as the accuracy of full-core deterministic calculations improves only slightly, while the time effort required increases significantly.

Keywords: Group constant generation; Serpent; DYN3D; Monte Carlo; ASTRID

  • Contribution to proceedings
    Physics of Reactors PHYSOR 2020, 29.03.-02.04.2020, Cambridge, United Kingdom, 978-1-5272-6447-2

Permalink: https://www.hzdr.de/publications/Publ-29937
Publ.-Id: 29937


Case study of bilayered spin-1/2 square lattice compound VO(HCOO)2 · (H2O)

Guchhait, S.; Arjun, U.; Anjana, P. K.; Sahoo, M.; Thirumurugan, A.; Medhi, A.; Scurschii, I.; Koo, B.; Sichelschmidt, J.; Schmidt, B.; Baenitz, M.; Nath, R.

We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline VO(HCOO)2 · (H2O) by means of x-ray diffraction, magnetic susceptibility, high-field magnetization, heat capacity, and electron-spin-resonance measurements. The compound crystallizes in an orthorhombic structure with space group Pcca. The crystal lattice features distorted VO6 octahedra connected via HCOO linkers (formate anions), forming a two-dimensional square lattice network with a bilayered structure. Analysis of magnetic susceptibility, high-field magnetization, and heat capacity data in terms of the frustrated square lattice model unambiguously establish the quasi-two-dimensional nature of the compound with nearest-neighbor interaction J1/kB ≃ 11.7 K and next-nearest-neighbor interaction J2/k ≃ 0.02 K. A Néel antiferromagnetic ordering sets in at TN ≃ 1.1 K. The ratio θCW/TN ≃ 10.9 reflects excellent two-dimensionality of the spin-lattice in the compound. A strong in-plane anisotropy is inferred from the linear increase of TN with magnetic field, consistent with the structural data.

Permalink: https://www.hzdr.de/publications/Publ-29936
Publ.-Id: 29936


Evaluation of the ESFR End of Cycle State and Detailed Spatial Distributions of Reactivity Coefficients

Davies, U.; Margulis, M.; Shwageraus, E.; Fridman, E.; Garcia-Herranz, N.; Jimenez-Carrascosa, A.; Cabellos, O.; Gregg, R.

The ESFR-SMART project is the latest iteration of research into the behaviour of a commercial-size SFR core throughout its lifetime. As part of this project the ESFR core has been modelled by a range of different reactor physics simulation codes at its end of cycle state, and the important safety relevant parameters evaluated. These parameters are found to agree well between the different codes, giving good confidence in the results.
A detailed mapping of the local sodium void worth is also performed due to the problems associated with the positive void coefficient seen in large SFR designs. The local void worth maps show that the use of zone-wise coefficients replicates the important reactivity feedbacks, with a trend towards conservatism.

Keywords: ESFR; sodium-cooled fast reactor; spatial reactivity coefficients; sodium void worth

  • Contribution to proceedings
    Physics of Reactors PHYSOR 2020, 29.03.-02.04.2020, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29935
Publ.-Id: 29935


One- and three-dimensional quantum phase transitions and anisotropy in Rb2CuMo3O12

Hayashida, S.; Blosser, D.; Povarov, K. Y.; Yan, Z.; Gvasaliya, S.; Ponomaryov, O.; Zvyagin, S.; Zheludev, A.

Single crystal samples of the frustrated quasi-one-dimensional quantum magnet Rb2Cu2Mo3O12 are investigated by magnetic, thermodynamic, and electron spin resonance (ESR) measurements. Quantum Phase transitions between the gapped, magnetically ordered, and fully saturated phases are observed. Surprisingly, the former has a distinctive three-dimensional character, while the latter is dominated by one-dimensional Quantum spin fluctuations. The entire H-T phase diagram is mapped out and found to be substantially anisotropic. In particular, the lower critical fields differ by over 50% depending on the direction of applied field, while the upper ones are almost isotropic, as is the magnetization above saturation. The ESR spectra are strongly dependent on field orientation and point to a helical structure with a rigidly defined spin rotation plane.

Permalink: https://www.hzdr.de/publications/Publ-29933
Publ.-Id: 29933


Bioflotation of sulfides in sea water: Sailing towards up-scaling the process

Luque Consuegra, G.

Halophilic bacteria were tested in microflotation experiments with minerals pyrite and chalcopyrite and in 1 litre batch flotation experiments with mafic complex sulphide mineral from El teniente mine. Results in microflotation experiments show that Halomonas sp. depresses pyrite from 80% floated pyrite to 10% floated pyrite in single mineral microflotation experiments and slightly improves the flotation of chalcopyrite in single mineral microflotation experiments. It is notable to mention that in these experiments, no lime or pH modifier was used to alter the pH of artificial sea water (ASW), leading to milder flotation conditions which could be potentially beneficial in large scale flotation processes. Due to these results, flotation experiments in 1L were performed on a core sample from El Teniente mine with halophilic bacteria as pyrite biodepressant instead of lime. Results from the XRD and MLA from the batch flotation experiments will be displayed in the presentation at the IBS 2019 in Fukuoka, Japan.

Keywords: Bioflotation; Biodepression; Pyrite; Halophilic Bacteria

  • Lecture (Conference)
    International Biohydrometallurgy Symposium Fukuoka, 20.-23.10.2019, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-29932
Publ.-Id: 29932


Halophilic bacteria as potential pyrite bio-depressants in Cu-Mo bioflotation

Luque Consuegra, G.; Kutschke, S.; Rudolph, M.; Pollmann, K.

Five halophilic bacteria have been studied as potential pyrite biodepressants. Microflotation experiments, as well as hydrophobicity and adhesion experiments were performed in order to assess the potential of these bacteria in the sulfide flotation process. It was shown that bacteria with hydrophobic properties in the Microbial Adhesion To Hydrocarbons (MATH) test adhere to pyrite and that Halomonas boliviensis and Halomonas sp. adhere to chalcopyrite in artificial sea water medium. Selective pyrite biodepression was greatly enhanced in the presence of Halobacillus sp. and Halomonas sp., and Halomonas boliviensis whilst chalcopyrite flotation was unaffected and in fact, enhanced by Halobacillus sp., Marinobacter spp. and Marinococcus sp. showing that the potential of this family of bacteria is yet to be untapped and could be an interesting development in sulfide bioflotation/biodepression processes.

Keywords: Halophilic bacteria; bioflotation; biodepression; pyrite; chalcopyrite; biobeneficiation

Permalink: https://www.hzdr.de/publications/Publ-29931
Publ.-Id: 29931


Effect of background electrolyte composition on the formation of Th(IV) nanoparticles on mica (001)

Neumann, J.; Qiu, C.; Hellebrandt, S.; Eng, P.; Skanthakumar, S.; Steppert, M.; Soderholm, L.; Stumpf, T.; Schmidt, M.

Actinides are known to form nanoparticles (NP), which may enhance[1] or decrease radionuclide mobility in the environment. Understanding these processes on the molecular level is therefore of particular interest for a reliable safety assessment for nuclear waste repositories. Previous results showed a strong and unusual influence of the background electrolyte composition on Th sorption on the mica (001) basal plane based on surface x-ray diffraction (SXD) data. Uptake was shown to be significantly lower (~0.04 Th/AUC; AUC = 46.72 Ų, the area of the mica (001) unit cell) for NaClO4 solution compared to NaCl (0.4 Th/AUC). An exceptional high coverage was detected for LiClO4 (4.9 Th/AUC) and surprisingly intermediate sorption occurs for KClO4 (~0.1 Th/AUC) under otherwise identical solution conditions.[2,3] The measured Th coverage from LiClO4 medium far exceeds the amount needed for surface charge compensation (0.25 Th/AUC), which suggests the formation of Th NP.[3] The mechanism of the reaction remains unclear, for instance whether the reaction occurs at the interface or in solution and if anion and cation effect occur independently. We applied SXD as well as electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) and in situ atomic force microscopy (AFM) to address these questions. ESI-TOF-MS measurements show no NP formation or other electrolyte influence in solution over a broad concentration range of Th in all media, which proofs the processes happen on the mica surface. From Cl- media higher coverages are found for LiCl (8.8 Th/AUC) and KCl (3.6 Th/AUC) compared to Na (0.4 Th/AUC), confirming the trend observed with perchlorates. All samples with Cl- electrolytes show higher coverages than the corresponding ClO4- samples, which confirms two independent effects for the electrolyte cation and anion. In situ AFM images show the Th-NP to have a variable lateral size and a height of a few nanometers. For higher Th(IV) concentrations the formation of Th-nanochains is observed. In the suggested mechanism the formation of Th NP occurs on the mica surface in a first step and the particles move along the surface in a second step to form band like structures of up to several hundred nanometer length. Formation of Thnanochains occurs at lower Th concentrations in the presence of LiCl (0.5 mM) compared to NaCl (1 mM). The findings suggest that the electrolyte cation influences oligomerization at the mineral-water-interface.
References:
[1] A. Kersting, Nature, 1999, 397, 56-59.
[2] M. Schmidt, Geochim. Et Cosmochim. Acta. 2015, 165, 280-293.
[3] M. Schmidt, Geochim. Et Cosmochim. Acta. 2012, 88, 66-76.

Keywords: Sorption; Thorium; Nanoparticles; Surface X-ray Diffraction; Background Electrolyte

  • Poster
    GDCh Fachgruppentagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29930
Publ.-Id: 29930


Radionuclide sorption in heterogeneous systems: Form model mineral oxides to complex rock

Schierz, A.; Stockmann, M.; Jordan, N.; Foerstendorf, H.; Steudtner, R.; Bok, F.; Brendler, V.

The fate of radionuclides in natural rocks is governed by their sorption reactions onto heterogeneous systems. Fundamental process understanding of the retardation mechanisms is crucial in the long-term safety assessment of nuclear waste repositories.
The “Component Additivity” (CA) approach is widely used to model radionuclide sorption onto rocks or soils in a realistic manner. This bottom up approach is based on the principle that the sorption in a complex material is determined by competitive sorption effects from the individual minerals. In the context of repository safety assessment the CA approach is used in the smart Kd concept, which is developed for complex geochemical transport models to describe the radionuclide migration in the far-field of a repository more realistically [1].
In this work, batch sorption experiments of radionuclides, e.g. Np(V) and U(VI) onto mixtures of different mineral oxides, such as iron oxides, silicium dioxide, manganese oxides were performed varying the ratio of mineral oxides, solid-liquid-ratios and geochemical conditions. Vibrational (IR) and luminescence spectroscopy (TRLFS) were performed to identify sorbed species and to gain mechanistic understanding of the radionuclide sorption processes. Surface complexation parameters (such as surface protolysis and complex formation constants) of single minerals and mixtures thereof were derived, namely from titration and batch sorption experiments.
Finally, the experimental results were compared with results obtained from sorption predictions to verify the robustness and applicability of the CA approach. Based on the results obtained, estimations on the applicability of the CA approach for radionuclide sorption processes are presented.

  • Poster
    GDCh, Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29929
Publ.-Id: 29929


Radionuclide sorption in heterogeneous systems: From model mineral oxides to complex rocks

Schierz, A.; Stockmann, M.; Jordan, N.; Foerstendorf, H.; Steudtner, R.; Bok, F.; Brendler, V.

The fate of radionuclides in natural rocks is governed by their sorption reactions onto heterogeneous systems. Fundamental process understanding of the retardation mechanisms is crucial in the long-term safety assessment of nuclear waste repositories.
The “Component Additivity” (CA) approach is widely used to model radionuclide sorption onto rocks or soils in a realistic manner. This bottom-up approach is based on the principle that the sorption in a complex material is determined by competitive sorption effects from the individual minerals. In the context of repository safety assessment the CA approach is used in the smart Kd-concept, which is developed for complex geochemical transport models to describe the radionuclide migration in the far-field of a repository more realistically [1].
In this work, batch sorption experiments of radionuclides, e.g. Np(V) and U(VI) onto mixtures of different mineral oxides, such as iron oxides, silicium dioxide, manganese oxides were performed varying the ratio of mineral oxides, solid-liquid-ratios and geochemical conditions. Vibrational (IR) and luminescence spectroscopy (TRLFS) were performed to identify sorbed species and to gain mechanistic understanding of the radionuclide sorption processes. Surface complexation parameters (such as surface protolysis and complex formation constants) of single minerals and mixtures thereof were derived, namely from titration and batch sorption experiments.
Finally, the experimental results were compared with results obtained from sorption predictions to verify the robustness and applicability of the CA approach. Based on the results obtained, a first estimation on the applicability of the CA approach for radionuclide sorption processes is presented.
[1] Stockmann et al. (2017), Chemosphere 187, 277-285.

Keywords: Sorption

  • Poster
    Goldschmidt2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29928
Publ.-Id: 29928


Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles

Neumann, J.; Qiu, C.; Hellebrandt, S.; Eng, P.; Skanthakumar, S.; Steppert, M.; Soderholm, L.; Stumpf, T.; Schmidt, M.

Understanding actinide nanoparticle (NP) formation and its influence on their mobility in ecosystems is essential for the reliable safety assessment of nuclear waste repositories. Previous surface x-ray diffraction (SXD) results showed a strong and unusual influence of the background electrolyte composition on Th sorption on the mica (001) basal plane.
Uptake was shown to be significantly lower (0.04 Th/AUC; AUC = 46.72 Å2, area of mica (001) unit cell) for NaClO4 solution compared to NaCl (0.4 Th/AUC). An exceptionally high coverage was detected for LiClO4 (4.9 Th/AUC), which far exceeds the amount needed for surface charge compensation (0.25 Th/AUC), suggesting the formation of Th-NP. However, it remained unclear, if the reaction occurs at the interface or in solution and if anion and cation effect occur independently. We applied SXD as well as electrospray-ionization time-offlight mass spectrometry (ESI-TOF-MS) and in situ AFM to address these questions. ESI-TOF-MS measurements show no influence on solution speciation, indicating the processes happen on the mica surface. In all media, only monomers are observed. From Cl- media higher coverages are found for LiCl (8.8 Th/AUC) and KCl (3.6 Th/AUC) compared to NaCl (0.4 Th/AUC), confirming the trend observed with perchlorates and the occurrence of two independent effects for the electrolyte cation and anion. In situ AFM images show the Th-NP to have variable lateral size and a height of a few nanometers. For higher Th(IV) concentrations the formation of Th nanochains is observed. In the suggested mechanism the formation of Th-NP occurs on the mica surface. In a first step, Th is adsorbed on the surface, where large local concentrations lead to the formation of Th-NP in some media. These particles move along the surface in a second step to form band-like structures of up to several hundred nanometer length.

Keywords: Sorption; Thorium; Nanoparticles; Surface X-ray Diffraction; Background electrolyte

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

Permalink: https://www.hzdr.de/publications/Publ-29927
Publ.-Id: 29927


New insights into 99Tc(VII) removal by pyrite: A spectroscopic approach

Rodriguez Hernandez, D. M.; Mayordomo, N.; Scheinost, A.; Schild, D.; Brendler, V.; Müller, K.; Stumpf, T.

99Tc(VII) uptake by synthetic pure pyrite was studied in a wide pH range from 3.5 to 10.5 using batch experiments at 21°C combined with scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) and Raman microscopy. We found that pyrite removes Tc quantitatively from solution (log Kd = 5.0 ± 0.1) within one day at pH ≥ 5.5. At pH < 5.5 the uptake process is slower, leading to 98% Tc removal (log Kd = 4.5 ± 0.1) after 35 days. The slower Tc uptake was explained by higher pyrite solubility under acidic conditions. After two months in contact with oxygen at pH 6 and 10, Tc was neither re-oxidized nor re-dissolved. XAS showed that the uptake mechanism involves the reduction from Tc(VII) to Tc(IV) and subsequent inner-sphere complexation of Tc(IV)-Tc(IV) dimers onto a Fe oxide like hematite at pH 6, and Tc(IV) incorporation into magnetite via Fe(III) substitution at pH 10. Calculations of Fe speciation under the experimental conditions predict the formation of hematite at pH < 7.5 and magnetite at pH > 7.5, explaining the formation of the two different Tc species depending on the pH. XPS spectra showed the formation of TcSx at pH 10, being a small fraction of a surface complex, potentially a transient phase in the total redox process.

Permalink: https://www.hzdr.de/publications/Publ-29925
Publ.-Id: 29925


Freestanding and positionable microwave-antenna device for magneto-optical spectroscopy experiments

Hache, T.; Vaňatka, M.; Flajšman, L.; Weinhold, T.; Hula, T.; Ciubotariu, O.; Albrecht, M.; Arkook, B.; Barsukov, I.; Fallarino, L.; Hellwig, O.; Faßbender, J.; Urbánek, M.; Schultheiß, H.

Modern spectroscopic techniques for the investigation of magnetization dynamics in micro- and nano- structures or thin films use mostly microwave antennas which are directly fabricated on the sample by means of electron-beam-lithography (EBL). Following this approach, every magnetic structure on the sample needs its own antenna, resulting in additional EBL steps and layer deposition processes. We demonstrate a new device for magnetization excitation that is suitable for optical and non-optical spectroscopic techniques. By patterning the antenna on a separated flexible glass cantilever and insulating it electrically, we solved the be- fore mentioned issues. Since we use flexible transparent glass as a substrate, optical spectroscopic techniques like Brillouin-light-scattering microscopy (μBLS), time resolved magneto-optical Kerr effect measurements (TRMOKE) or optical detected magnetic resonance (ODMR) measurements can be performed at visible laser wavelengths. As the antenna is detached from the sample it can be freely positioned in all three dimensions to get access to all desired magnetic sample structures, while being brought in close contact with the sample for an effective excitation. We show the functionality of these antennas using μBLS. We compare with thermally excited magnons to show the enhancement of the signal by a factor of about 400 demonstrating the high impact of the magnetization excitation by the antenna. Moreover, we show the possibility to characterize yttrium iron garnet thin films by doing optical ferromagnetic resonance (FMR) experiments allowing for the characterization of magnetic properties spatially resolved. Additionally, we show the spatial excitation profile of the antenna by measuring the magnetization dynamics in two dimensions. Furthermore, injection-locking of spin Hall nano-oscillators could be shown.

Keywords: magnetism; magnetization dynamics; spin Hall; spin waves; microwave; antenna; yttrium iron garnet; CoFeB; spin Hall nano-oscillators; optical FMR; antenna device; radio frequency; solid state physics; physics; experimental physics; injection locking; phase locking

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 31.03.-05.04.2019, Universität Regensburg, Deutschland
  • Physical Review Applied 13(2020)5, 054009
    DOI: 10.1103/PhysRevApplied.13.054009

Permalink: https://www.hzdr.de/publications/Publ-29920
Publ.-Id: 29920


Determination of electron effective mass in InN by cyclotron resonance spectroscopy

Fang, X.; Zheng, F.; Drachenko, O.; Zhou, S.; Zheng, X.; Chen, Z.; Wang, P.; Ge, W.; Shen, B.; Feng, J.; Wang, X.

We report the determination of electron effective mass in InN by using cyclotron resonance (CR) spectroscopy. To avoid the influence of sapphire substrate on CR measurements, InN epilayer with low residual electron concentration of 5 × 1017 cm−3 was grown on silicon substrate. Together with analyzing the effect of non-parabolic band structure, we derive that the isotropy c-plane electron effective mass of InN epilayer is 0.050±0.002 m0 and 0.058±0.002 m0 at temperatures of 4.2 and 50 K, respectively, which is in good agreement with our theoretical predication of the effective mass near the Γ point.

Keywords: Cyclotron resonance spectroscopy; Effective mass; InN

Permalink: https://www.hzdr.de/publications/Publ-29918
Publ.-Id: 29918


Two types of axisymmetric helical magnetorotational instability in rotating flows with positive shear

Mamatsashvili, G.; Stefani, F.; Hollerbach, R.; Rüdiger, G.

We reveal and investigate a type of linear axisymmetric helical magnetorotational instability which is capable of destabilizing viscous and resistive rotational flows with radially increasing angular velocity, or positive shear. This instability is double-diffusive by nature and is different from the more familiar helical magnetorotational instability, operating at positive shear above the Liu limit, in that it works instead for a wide range of the positive shear when (i) a combination of axial and azimuthal magnetic fields is applied and (ii) the magnetic Prandtl number is not too close to unity. We study this instability first with radially local Wentzel-Kramers-Brillouin (WKB) analysis, deriving the scaling properties of its growth rate with respect to Hartmann, Reynolds, and magnetic Prandtl numbers. Then we confirm its existence using a global stability analysis of the magnetized flow confined between two rotating coaxial cylinders with purely conducting or insulating boundaries and compare the results with those of the local analysis. From an experimental point of view, we also demonstrate the presence of this instability in a magnetized viscous and resistive Taylor-Couette flow with positive shear for such values of the flow parameters, which can be realized in upcoming experiments at the DRESDYN facility. Finally, this instability might have implications for the dynamics of the equatorial parts of the solar tachocline and dynamo action there, since the above two necessary conditions for the instability to take place are satisfied in this region. Our global stability calculations for the tachocline-like configuration, representing a thin rotating cylindrical layer with the appropriate boundary conditions—conducting inner and insulating outer cylinders—and the values of the flow parameters, indicate that it can indeed arise in this case with a characteristic growth time comparable to the solar cycle period.

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Permalink: https://www.hzdr.de/publications/Publ-29917
Publ.-Id: 29917


Hierarchy of double-time correlations

Queißer, F.; Schützhold, R.

The hierarchy of correlations is an analytical approximation method which allows us to study non-equilibrium phenomena in strongly interacting quantum many-body systems on lattices in higher dimensions. So far, this method was restricted to equal-time correlators ⟨A ^ μ (t)B ^ ν (t)⟩ . In this work, we generalize this method to double-time correlators ⟨A ^ μ (t)B ^ ν (t ′ )⟩ , which allows us to study effective light cones and Green functions and to incorporate finite initial temperatures.

Permalink: https://www.hzdr.de/publications/Publ-29916
Publ.-Id: 29916


Boltzmann relaxation dynamics of strongly interacting spinless fermions on a lattice

Queißer, F.; Schützhold, R.; Schreiber, S.; Kratzer, P.

Motivated by the recent interest in non-equilibrium phenomena in quantum many-body systems, we study strongly interacting fermions on a lattice by deriving and numerically solving quantum Boltzmann equations that describe their relaxation to thermodynamic equilibrium.The derivation is carried out by inspecting the hierarchy of correlations within the framework of the 1/Z-expansion. Applying the Markov approximation, we obtain the dynamic equations for the distribution functions. Interestingly, we find that in the strong-coupling limit, collisions between particles and holes dominate over particle-particle and hole-hole collisions -- in stark contrast to weakly interacting systems. As a consequence, our numerical simulations show that the relaxation time scales strongly depend on the type of excitations (particles or holes or both) that are initially present.

Permalink: https://www.hzdr.de/publications/Publ-29915
Publ.-Id: 29915


Doublon bottleneck in the ultrafast relaxation dynamics of hot electrons in 1T-TaS_2

Queißer, F.; Schützhold, R.; Avigo, I.; Zhou, P.; Ligges, M.; Rossnagel, K.; Bovensiepen, U.

Employing time-resolved photoelectron spectroscopy we analyze the relaxation dynamics of hot electrons in the charge density wave / Mott material 1T-TaS_2. At 1.2 eV above the Fermi level we observe a hot electron lifetime of 12 +- 5 fs in the metallic state and of 60 +- 10 fs in the broken symmetry ground state - a direct consequence of the reduced phase space for electron-electron scattering determined by the Mott gap. Boltzmann equation calculations which account for the interaction of hot electrons in a Bloch band with a doublon-holon excitation in the Mott state provide insight into the unoccupied electronic structure in the correlated state.

Permalink: https://www.hzdr.de/publications/Publ-29914
Publ.-Id: 29914


Stability of a Flow Under Electromagnetic Forcing in a Cylindrical Vessel

Jüstel, P.; Röhrborn, S.; Schindler, F.; Stefani, F.

We investigate the flow excited by electromagnetic forcing in a unit aspect ratio Rayleigh-Bénard cylinder. Flow structure and velocities dependent on AC frequency and coil current amplitude have been analysed. The unstable impinging jet flow bears interesting features, and a possible stochastic resonance is still under investigation.

Keywords: electromagnetic; forcing; flow stability; impinging jet; stochastic resonance

  • Poster
    N2 Event 2019, 13.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29913
Publ.-Id: 29913


Environment induced pre-thermalization in the Mott-Hubbard model

Queißer, F.; Schützhold, R.

Via the hierarchy of correlations, we study the strongly interacting Fermi-Hubbard model in the Mott insulator state and couple it to a Markovian environment which constantly monitors the particle numbers \hat n_\mu^\uparrow and \hat n_\mu^\downarrow for each lattice site \mu. As expected, the environment induces an imaginary part \gamma (i.e., decay rate) of the quasi-particle frequencies \omega_{\mathbf{k}}\to\omega_{\mathbf{k}}-i\gamma and tends to diminish the correlations between lattice sites. Surprisingly, the environment does also steer the state of the system on intermediate time scales \mathcal{O}(1/\gamma) to a pre-thermalized state very similar to a quantum quench (i.e., suddenly switching on the hopping rate J). Full thermalization occurs via local on-site heating and takes much longer.

Permalink: https://www.hzdr.de/publications/Publ-29912
Publ.-Id: 29912


Low-energy electron irradiation induced synthesis of molecular nanosheets: An influence of the electron beam energy

Neumann, C.; Wilhelm, R. A.; Küllmer, M.; Turchanin, A.

Aromatic self-assembled monolayers (SAMs) can be cross-linked into molecular nanosheets  carbon nanomembranes (CNMs)  via low-energy electron irradiation. Due to their favorable mechanical stability and tunable functional properties, they possess a high potential for various applications including nanosensors, separation membrane for osmosis or energy conversion devices. Despite this potential, the mechanistic details of the electron irradiation induced cross-linking process still need to be understood in more detail. Here we studied the cross-linking of 4'-nitro-1,1 ́-biphenyl-4-thiol SAM on gold. The SAM samples were irradiated with different electron energies ranging from 2.5 to 100 eV in ultra-high vacuum and subsequently analysed by complementary techniques. We present results obtained via spectroscopy and microscopy characterization by high-resolution X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction with micrometre sized electron beams (LEED) and low-energy electron microscopy (LEEM). To demostrate the formation of CNMs, the formed two-dimensional molecular materials were transferred onto grids and oxidized wafer and analyzed by optical, scanning electron (SEM) and atomic force microscopy (AFM). We found a strong energy dependence for the cross section for the cross-linking process, which rates decrease exponentially towards lower electron energies by about four orders of magnitude. We conduct a comparative analysis of the cross sections for the C-H bond scission via electron impact ionization and dissociative electron attachment and find out that these different ionization mechnisms are responsible for the variation of the cross-linking cross section with electron energy.

Permalink: https://www.hzdr.de/publications/Publ-29910
Publ.-Id: 29910


Dynamically assisted nuclear fusion

Queißer, F.; Schützhold, R.

We consider deuterium-tritium fusion as a generic example for general fusion reactions. For initial kinetic energies in the keV regime, the reaction rate is exponentially suppressed due to the Coulomb barrier between the nuclei, which is overcome by tunneling. Here, we study whether the tunneling probability could be enhanced by an additional electromagnetic field, such as an x-ray free electron laser (XFEL). We find that the XFEL frequencies and field strengths required for this dynamical assistance mechanism should come within reach of present-day or near-future technology.

Permalink: https://www.hzdr.de/publications/Publ-29909
Publ.-Id: 29909


Charge calibration of DRZ scintillation phosphor screens

Schwinkendorf, J.-P.; Bohlena, S.; Couperus Cabadağ, J. P.; Ding, H.; Irman, A.; Karsch, S.; Köhler, A.; Krämer, J. M.; Kurz, T.; Kuschel, S.; Osterhoff, J.; Schaper, L. F.; Schinkel, D.; Schramm, U.; Zarini, O.; D'Arcy, R.

As a basic diagnostic tool, scintillation screens are employed in particle accelerators to detect charged particles. In extension to the recent revision on the calibration of scintillation screens commonly applied in the context of plasma acceleration [T. Kurz et al., Rev. Sci. Instrum. 89 (2018) 093303], here we present the charge calibration of three DRZ screens (Std, Plus, High), which promise to offer similar spatial resolution to other screen types whilst reaching higher conversion efficiencies. The calibration was performed at the Electron Linac for beams with high Brilliance and low Emittance (ELBE) at the Helmholtz-Zentrum Dresden-Rossendorf, which delivers picosecond-long beams of up to 40 MeV energy. Compared to the most sensitive screen, Kodak BioMAX MS, of the aforementioned recent investigation by Kurz et al., the sample with highest yield in this campaign, DRZ High, revealed a 30% increase in light yield. The detection threshold with these screens was found to be below 10 pC/mm². For higher charge-densities (several nC/mm²) saturation effects were observed. In contrast to the recent reported work, the DRZ screens were more robust, demonstrating higher durability under the same high level of charge deposition.

Keywords: Beam-line instrumentation; beam-intensity monitors; bunch length monitors; beam position and profile monitors; Detector alignment and calibration methods (lasers and sources and particle-beams); Scintillators; Wake-field acceleration (laser-driven and electron-driven); scintillation and light emission processes (solid and gas and liquid scintillators)

Permalink: https://www.hzdr.de/publications/Publ-29908
Publ.-Id: 29908


Antibacterial activity of selenium nanoparticles studied by calorimetry, flow cytometry and electron microscopy

Schäfer, S.; Fahmy, K.; Merroun, M. L.

Nanoparticles (NPs) are of growing interest for various applications due to their unique properties, such as elevated surface-to-volume-ratio and variability of composition surface features and charge. Moreover, certain metal NPs possess antimicrobial activity and are therefore considered as an alternative to common antibiotics to overcome the recently emerging issue of bacterial resistance against common antibiotics [1].
Silver (Ag) NPs are well-studied concerning their antimicrobial activity and already applied in medicine and household products. However, cellular interaction mechanisms and consequent toxicity are not entirely elucidated. It is proposed, that NPs either interact with the cell membrane via intermolecular interactions, such as charge-charge interactions or intracellular accumulation. Once interacting with the cell extra- or intracellularly, NPs release reactive oxygen species and metal ions, which subsequently damage the cell membrane and affect enzymatic activity, ultimately leading to cell death. [1]
Besides AgNPs, selenium (Se) NPs exhibit prominent antimicrobial activity, without being studied into more detail [2,3]. In our approach, gram-positive and gram-negative bacterial strains are chosen their putatively differing response to the metal NPs based on differing cell wall compositions. Calorimetric studies of differentially-coated Se NPs exhibited a decrease in growth rate of the bacterial model strains, indicating their antimicrobial activity. To further investigate the cytotoxicity, the influence on reactive oxygen species and enzymatic activity, fluorescence-based flow cytometry is being performed. Furthermore, electron microscopy is exploited to localize the NPs and to elucidate putative metal ion release.

References:
[1] Brandelli et al. (2017) Springer Int Publ 337-363.
[2] Piacenza et al. (2017) Microb Biotechnol 10, 804-818.
[3] Srivastava & Mukhopadhyay (2015) Bioprocess Biosyst Eng 38, 1723-1730.

  • Open Access Logo Lecture (Conference)
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29907
Publ.-Id: 29907


Antibacterial activity of selenium nanoparticles studied by calorimetry, flow cytometry and electron microscopy

Schäfer, S.; Fahmy, K.; Merroun, M. L.

Nanoparticles are of growing interest for various applications due to their unique properties, such as elevated surface-to-volume-ratio and variability of material, surface features, and charge. Therefore, they are applied in industry as catalysts and are investigated concerning their feasibility in drug delivery [1]. Moreover, certain metal nanoparticles possess antimicrobial activity and are therefore considered as an alternative to common antibiotics [2]. Especially due to increasing bacterial resistance against common antibiotics and the lack of the development of novel ones, metal nanoparticles attracted interest in biomedical research.
Silver nanoparticles are well-studied concerning their antimicrobial activity and already applied in medicine and household products. However, cellular interaction mechanisms and consequent toxicity are not entirely elucidated. It is proposed, that nanoparticles either interact with the cell membrane via intermolecular interactions, such as charge-charge interactions or penetrate it. Thus, the size and charge of the nanoparticles are the main properties to influence interaction and antimicrobial activity. Once interacting with the cell extra- or intracellularly, nanoparticles release reactive oxygen species and metal ions, which subsequently damage the cell membrane and affect enzymatic activity, consequently leading to cell death. [2]
Besides silver nanoparticles, selenium nanoparticles exhibit prominent antimicrobial activity, without being studied into more detail [3,4]. In our approach, gram-positive (Lysinibacillus sphaericus) and gram-negative (Stenotrophomonas bentonitica) bacterial strains are chosen due to their different cell wall composition and their putatively differing response to the metal nanoparticles. Calorimetric studies of BSA- and Chitosan-coated selenium nanoparticles exhibited a decrease in growth rate of the bacterial model strains, indicating their antimicrobial activity. To further investigate the cytotoxicity, influence of reactive oxygen species and enzymatic activity, the bacterial model strains are incubated with selenium nanoparticles with different surface coatings and charges and studied via fluorescence-based flow cytometry. Furthermore, electron microscopy is performed to characterize interaction mechanisms, to localize the nanoparticles and to elucidate putative metal ion release.

References:
[1] Faraji, A. H. & Wipf, P. Nanoparticles in cellular drug delivery. Bioorganic Med. Chem. 17, 2950–2962 (2009).
[2] Brandelli, A., Ritter, A. C. & Veras, F. F. in Metal Nanoparticles in Pharma 337–363 (Springer International Publishing, 2017). doi:10.1007/978-3-319-63790-7_1
[3] Piacenza, E. et al. Antimicrobial activity of biogenically produced spherical Se-nanomaterials embedded in organic material against Pseudomonas aeruginosa and Staphylococcus aureus strains on hydroxyapatite-coated surfaces. Microb. Biotechnol. 10, 804–818 (2017).
[4] Srivastava, N. & Mukhopadhyay, M. Green synthesis and structural characterization of selenium nanoparticles and assessment of their antimicrobial property. Bioprocess Biosyst. Eng. 38, 1723–1730 (2015).

  • Open Access Logo Lecture (Conference)
    Congreso Nacional de Microbiología, 01.-05.07.2019, Málaga, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29906
Publ.-Id: 29906


Fractionation of geochemical twins (Zr/Hf, Nb/Ta and Y/Ho) and HREE-enrichment during magmatic and metamorphic processes in peralkaline nepheline syenites from Norra Kärr (Sweden).

Atanasova, P.; Marks, M. A. W.; Frenzel, M.; Gutzmer, J.; Krause, J.; Markl, G.

The Norra Kärr complex (Sweden) consists of deformed and metamorphosed peralkaline nepheline syenites that contain eudialyte-group minerals as the major host of high field strength elements and rare earth elements. Petrographic studies have revealed the presence of paragenetically distinct generations of eudialyte-group minerals and clinopyroxene of magmatic and metamorphic origin. In this study, we present the trace element characteristics of these different generations of rock-forming minerals in the three major lithological subunits of the Norra Kärr complex.
The trace element chemistry of eudialyte-group minerals mimic whole-rock compositions and display well-developed negative Eu-anomalies and strong Sr- and Ba-depletions in chondrite-normalized diagrams. They imply that the Norra Kärr rocks developed by intense fractional crystallization from an alkali basaltic parental magma. Our data also illustrate that eudialyte-group minerals do not significantly fractionate the geochemical twins Zr/Hf, Y/Ho and Nb/Ta during magmatic processes. In contrast, magmatic clinopyroxene shows a clear preference for Hf over Zr.
The transition from magmatic to metamorphic crystallization is clearly marked in the trace element chemistry of clinopyroxene by decreasing Zr/Hf and Y/Ho ratios. This accompanies the change in major element composition from aegirine sensu strictu to Al-aegirine. The transition from a magmatic to a metamorphic environment is also recorded by an increase of the rare earth element content of eudialyte-group minerals, especially the heavy rare earth elements. The exceptional enrichment of heavy rare earth elements in late metamorphic eudialyte may result from residual enrichment, whereby light rare earth elements were preferentially mobilized to form local secondary light rare earth-rich rinkite-group mineral assemblages.

Keywords: fractionation; geochemical twins; rare earth elements; clinopyroxene; eudialyte-group minerals; nepheline syenite

Permalink: https://www.hzdr.de/publications/Publ-29905
Publ.-Id: 29905


Comparison of Static and Dynamic 18F-FDG PET/CT for Quantification of Pulmonary Inflammation in Acute Lung Injury

Braune, A.; Hofheinz, F.; Bluth, T.; Kiss, T.; Wittenstein, J.; Scharffenberg, M.; Kotzerke, J.; Gama De Abreu, M.

PET imaging with 18F-FDG followed by mathematic modeling of the pulmonary uptake rate (Ki) is the gold standard for assessment of pulmonary inflammation in experimental studies of acute respiratory distress syndrome (ARDS). However, dynamic PET requires long imaging and allows the assessment of only 1 cranio-caudal field of view (∼15 cm). We investigated whether static 18F-FDG PET/CT and analysis of SUV or standardized uptake ratios (SURstat, uptake time-corrected ratio of 18F-FDG concentration in lung tissue and blood plasma) might be an alternative to dynamic 18F-FDG PET/CT and Patlak analysis for quantification of pulmonary inflammation in experimental ARDS.

Methods: ARDS was induced by saline lung lavage followed by injurious mechanical ventilation in 14 anesthetized pigs (29.5-40.0 kg). PET/CT imaging sequences were acquired before and after 24 h of mechanical ventilation. Ki and the apparent volume of distribution were calculated from dynamic 18F-FDG PET/CT scans using the Patlak analysis. Static 18F-FDG PET/CT scans were obtained immediately after dynamic PET/CT and used for calculations of SUV and SURstat Mean Ki values of the whole imaged field of view and of 5 ventro-dorsal lung regions were compared with corresponding SUV and SURstat values, respectively, by means of linear regression and concordance analysis. The variability of the 18F-FDG concentration in blood plasma (arterial input function) was analyzed.

Results: Both for the whole imaged field of view and ventro-dorsal subregions, Ki was linearly correlated with SURstat (r2 ≥ 0.84), whereas Ki-SUV correlations were worse (r2 ≤ 0.75). The arterial input function exhibited an essentially invariant shape across all animals and time points and can be described by an inverse power law. Compared with Ki, SURstat and SUV tracked the same direction of change in regional lung inflammation in 98.6% and 84.3% of measurements, respectively.

Conclusion: The Ki-SURstat correlations were considerably stronger than the Ki-SUV correlations. The good Ki-SURstat correlations suggest that static 18F-FDG PET/CT and SURstat analysis provides an alternative to dynamic 18F-FDG PET/CT and Patlak analysis, allowing the assessment of inflammation of whole lungs, repeated measurements within the period of 18F-FDG decay, and faster data acquisition. © 2019 by the Society of Nuclear Medicine and Molecular Imaging.

Keywords: Animal Imaging; PET/CT; Radiotracer; Tissue Kinetics Respiratory; 18-F-FDG; positron emission tomography; pulmonary inflammation standard; uptake value tumor-to-blood standard; Image Processing; uptake ratio (SUR)

Permalink: https://www.hzdr.de/publications/Publ-29904
Publ.-Id: 29904


Metal deportment and ore variability of the Bolcana porphyry Au–Cu system (Apuseni Mts, Romania) – Implications for ore processing

Blannin, R.; Tusa, L.; Birtel, S.; Gutzmer, J.; Gilbricht, S.; Ivascanu, P.

The maiden resource estimate for the Bolcana gold-copper porphyry defines 381 Mt at 0.53 g/t gold and 0.18% copper. The early stage of exploration provides the perfect opportunity for the application of geometallurgical studies, to enable optimisation of future mine and plant operations. Quantitative mineralogy and microfabric characterisation of crushed material and thin sections from seven 40 m drill core intervals were accomplished by Scanning Electron Microscopy based Mineral Liberation Analysis, complemented by X-ray Powder Diffraction. The mineralogy of the studied samples is highly variable, depending on lithology, mineralisation and alteration. The main Cu-bearing mineral is chalcopyrite, predominantly occurring in B and C veins. At shallow depths, secondary bornite and covellite form rims around chalcopyrite. Primary bornite occurs at greater depths in the system. Native gold grains are typically <10 μm and hosted by chalcopyrite or, to a lesser extent, pyrite. Electron Probe Microanalysis on four samples determined that gold concentrations in solid solution in selected sulphide minerals are <100 ppm. Copper and associated gold should be recoverable by flotation of chalcopyrite. The recovery of free gold and gold associated with pyrite may require additional processing steps.

  • Open Access Logo Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.08.2019, Glasgow, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29903
Publ.-Id: 29903


Metal deportment and ore variability of the Bolcana porphyry Au–Cu system (Apuseni Mts, Romania) – Implications for ore processing

Blannin, R.; Tusa, L.; Birtel, S.; Gutzmer, J.; Gilbricht, S.; Ivascanu, P.

The maiden resource estimate for the Bolcana gold-copper porphyry defines 381 Mt at 0.53 g/t gold and 0.18% copper. The early stage of exploration provides the perfect opportunity for the application of geometallurgical studies, to enable optimisation of future mine and plant operations. Quantitative mineralogy and microfabric characterisation of crushed material and thin sections from seven 40 m drill core intervals were accomplished by Scanning Electron Microscopy based Mineral Liberation Analysis, complemented by X-ray Powder Diffraction. The mineralogy of the studied samples is highly variable, depending on lithology, mineralisation and alteration. The main Cu-bearing mineral is chalcopyrite, predominantly occurring in B and C veins. At shallow depths, secondary bornite and covellite form rims around chalcopyrite. Primary bornite occurs at greater depths in the system. Native gold grains are typically <10 μm and hosted by chalcopyrite or, to a lesser extent, pyrite. Electron Probe Microanalysis on four samples determined that gold concentrations in solid solution in selected sulphide minerals are <100 ppm. Copper and associated gold should be recoverable by flotation of chalcopyrite. The recovery of free gold and gold associated with pyrite may require additional processing steps.

  • Open Access Logo Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29902
Publ.-Id: 29902


Antiferromagnetic domain wall control via surface spin flop in fully tunable synthetic antiferromagnets with perpendicular magnetic anisotropy

Böhm, B.; Fallarino, L.; Pohl, D.; Rellinghaus, B.; Nielsch, K.; Kiselev, N. S.; Hellwig, O.

Antiferromagnetic (AF) domain walls have recently attracted revived attention, not only in the emerging field of AF spintronics, but also more specifically for offering fast domain wall velocities and dynamic excitations up to the terahertz frequency regime. Here, we introduce an approach to nucleate and stabilize an AF domain wall in a synthetic antiferromagnet (SAF). We present experimental and micromagnetic studies of the magnetization reversal in [(Co/Pt)X-1/Co/Ir]N-1(Co/Pt)X SAFs, where interface-induced perpendicular magnetic anisotropy (PMA) and AF interlayer exchange coupling (IEC) are completely controlled via the individual layer thicknesses within the multilayer stack. By combining strong PMA with even stronger AF-IEC, the SAF reveals a collective response to an external magnetic field applied normal to the surface, and we stabilize the characteristic surface spin-flop (SSF) state for an even number N of AF-coupled (Co/Pt)X-1/Co multilayer blocks. In the SSF state our system provides a well-controlled and fully tunable vertical AF domain wall, easy to integrate as no single-crystal substrates are required and with uniform two-dimensional magnetization in the film plane for further functionalization options, such as lateral patterning via lithography.

Permalink: https://www.hzdr.de/publications/Publ-29901
Publ.-Id: 29901


Unveiling Electronic Properties in Metal−Phthalocyanine-Based Pyrazine-Linked Conjugated Two-Dimensional Covalent Organic Frameworks

Mingchao, W.; Marco, B.; Wang, M.; Hung-Hsuan, L.; Bishnu, P. B.; Xiaocang, H.; Silvia, P.; Eike, B.; Pan, L.; Mingwei, C.; Mischa, B.; Heine, T.; Zhou, S.; Enrique, C.; Renhao, D.; Xinliang, F.

π-Conjugated two-dimensional covalent organic frameworks (2D COFs) are emerging as a novel class of electroactive materials for (opto)electronic and chemiresistive sensing applications. However, understanding the intricate interplay between chemistry, structure, and conductivity in π-conjugated 2D COFs remains elusive. Here, we report a detailed characterization for the electronic properties of two novel samples consisting of Zn− and Cu−phthalocyaninebased pyrazine-linked 2D COFs. These 2D COFs are synthesized by condensation of metal−phthalocyanine (M =Zn and Cu) and pyrene derivatives. The obtained polycrystalline-layered COFs are p-type semiconductors both with a band gap of ∼1.2 eV. A record device-relevant mobility up to ∼5 cm2/(V s) is resolved in the dc limit, which represents a lower threshold induced by charge carrier localization at crystalline grain boundaries. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10−7 S/cm), charge carrier density (∼1012 cm−3), charge carrier scattering rate (∼3 × 1013 s−1), and effective mass (∼2.3m0) of majority carriers (holes). Notably, charge carrier transport is found to be anisotropic, with hole mobilities being practically null in-plane and finite out-of-plane for these 2D COFs.

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Permalink: https://www.hzdr.de/publications/Publ-29900
Publ.-Id: 29900


Nonsaturating extreme magnetoresistance and large electronic magnetostriction in LuAs

Juraszek, J.; Bochenek, L.; Rudenko, A.; Hosen, M. M.; Daszkiewicz, M.; Wang, Z.; Wosnitza, J.; Henkie, Z.; Samsel-Czekala, M.; Neupane, M.

In the known topological semimetals, conventional charge carriers exist in addition to relativistic quasiparticles, and thus a disentangling of their conduction properties remains challenging. Here, we address an unsaturated extreme magnetoresistance (XMR) with a marked deviation from the semiclassical B2 behavior that is commonly credited to the presence of topologically protected electronic states. For the topologically trivial semimetal LuAs, we observe a nonsaturating XMR with a nonquadratic magnetic-field dependence gained up to nearly 60 T. Remarkably, this diamagnetic material exhibits a very large magnetostriction that provides solid evidence for a field-dependent variation of electron and hole concentrations. We show that an underlying strain-induced change in the charge-carrier densities can give rise to an unsaturated XMR even in a moderately imbalanced semimetal. Our finding is of importance as well for topological semimetals in which the number of conventional charge carriers can be continuously altered with increasing field, and hence some of their high-field properties may not necessarily reflect the presence of massless quasiparticles.

Permalink: https://www.hzdr.de/publications/Publ-29899
Publ.-Id: 29899


Bose-Einstein condensation of triplons close to the quantum critical point in the quasi-one-dimensional spin-1/2 antiferromagnet NaVOPO4

Mukharjee, P. K.; Ranjith, K. M.; Koo, B.; Sichelschmidt, J.; Baenitz, M.; Scurschii, I.; Inagaki, Y.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.

Structural and magnetic properties of a quasi-one-dimensional spin-½ compound NaVOPO4 are explored by x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, electron spin resonance, and 31P nuclear magnetic resonance measurements, as well as complementary ab initio calculations. Whereas magnetic susceptibility of NaVOPO4 may be compatible with the gapless uniform spin chain model, detailed examination of the crystal structure reveals a weak alternation of the exchange couplings with the alternation ratio α 󠆪≃ 0.98 and the ensuing zero-field spin gap Δ0/kB ≃ 2.4 K directly probed by field-dependent magnetization measurements. No long-range order is observed down to 50 mK in zero field. However, applied fields above the critical field Hc1 ≃ 1.6 T give rise to a magnetic ordering transition with the phase boundary TN ∝ (H – Hc1) 1/φ, where φ ≃ 1.8 is close to the value expected for Bose-Einstein condensation of triplons.With its weak alternation of the exchange couplings and small spin gap, NaVOPO4 lies close to the quantum critical point.

Permalink: https://www.hzdr.de/publications/Publ-29898
Publ.-Id: 29898


High Energy Lasers – embedded intelligence

Bock, S.; Püschel, T.; Gebhardt, R.; Helbig, U.; Schramm, U.

Workshop presentation on requirements for assistance on running high power lasers

  • Lecture (Conference)
    High Energy Lasers - Ideas & Future (HELIF), 05.05.2019, Split, Croatia

Permalink: https://www.hzdr.de/publications/Publ-29897
Publ.-Id: 29897


Characterization of measurement devices for temporal laser pulse contrast with high dynamic range

Püschel, T.; Herrmann, F. M.; Lötfering, J. J.; Gebhardt, R.; Helbig, U.; Toncian, T.; Schramm, U.; Bock, S.

We demonstrate a protocol for the absolute calibration of third-order autocorrelator (TO-AC) response to the temporal profile of a high contrast high power laser pulse based on either artificially generated coherent pre- and post-pulses or incoherent background. The dynamic range provided by the protocol exceeds more than eight orders of magnitude. For cross-calibration, the technique of self-referenced spectral interferometry with extended time excursion (SRSI-ETE) is used.

Keywords: Ultra-short high peak power lasers; contrast; SRSI-ETE; third-order autocorrelator

  • Poster
    Ultrafast Optics XII, 06.-11.10.2019, Bol, Brac, Croatia

Permalink: https://www.hzdr.de/publications/Publ-29896
Publ.-Id: 29896


Influence of APOE genotype on α4β2 nicotinic acetylcholine receptor binding in mild Alzheimer‘s dementia as assessed by (-)-[18F]Flubatine PET

Meyer, P.; Wilke, S.; Hesse, S.; Becker, G.; Rullmann, M.; Patt, M.; Wagenknecht, G.; Hoepping, A.; Smits, R.; Sattler, B.; Deuther-Conrad, W.; Barthel, H.; Schönknecht, P.; Brust, P.; Sabri, O.

Aim/Introduction: The question of whether the presence of the APOE ε4 allele impacts α4β2 nicotinic acetylcholine receptor (α4β2-nAChR) availability in Alzheimer’s dementia (AD) was so far mainly studied post-mortem, and is subject of a controversial debate. We aimed to answering this question in vivo using the recently developed α4β2-nAChR-specific radioligand (-)-[18F] Flubatine and PET.
Materials and Methods: Non-smoking, drug-naïve AD-APOE ε4+ (n=7; 76±6ys; 6 females; MMSE 24±3) and AD-APOE ε4- (n=9; 75±7ys; 7 females; MMSE 24±2, n. sign. vs. AD-APOE ε4+) were investigated using (-)-[18F]Flubatine (370 MBq, ECAT Exact HR+, 0-90min p.i.) and compared with non-smoking healthy controls (HC; n=13; 72±4ys; 7 females). For quantification of the α4β2-nAChR availability, kinetic modeling (1TCM, Logan) was performed and the distribution volume (VT) was calculated. VOI analyses of a-priori selected brain regions and exploratory SPM analyses were carried out (ANCOVA, significance at P<0.05 and T>3.0; P<0.003).
Results: Compared with HC, in AD-APOE ε4+, there was significantly lower VT within the basal forebrain, hippocampus, amygdala, and fronto-temporal cortices. Compared with HC, in ADAPOE ε4-, voxel-based analysis revealed significantly lower VT in minor clusters within the fronto-temporo-parietal and posterior cingulate cortices. In AD-APOE ε4+, directly compared with AD-APOE ε4-, there was significantly lower VT within the basal forebrain, hippocampus, amygdala, fronto-temporal, and cingulate cortices. Conclusion: Using the recently developed (-)-[18F]Flubatine and PET, we demonstrated for the first time in-vivo the influence of APOE ε4 on α4β2-nAChR availability in mild AD. In contrast to earlier studies, we show that the APOE ε4 genotype modulates the α4β2-nAChR pathophysiology in AD. If replicated in larger cohorts, our findings encourage adjusting cholinergic drug therapy to the APOE genotype in patients with AD. References: None.

  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 46(2019)Suppl 1, EPS-037

Permalink: https://www.hzdr.de/publications/Publ-29895
Publ.-Id: 29895


Model Experiments for Flow Phenomena in Crystal Growth

Dadzis, K.; Pätzold, O.; Gerbeth, G.

The concept of a physical model experiment is introduced and discussed in the context of melt and gas flows in bulk crystal growth processes. Such experiments allow one to "extract" selected physical phenomena from the full complexity of a real crystal growth process and “transfer” them to material systems with an easier access for experimental measurements. Model experiments for the main techniques of melt growth are summarized in a literature review, and the applicability of the results to real crystal growth systems is analyzed. Recent examples of model experiments for melt and gas flows in Czochralski growth of silicon are used to demonstrate the state of the art and show the potential of such experiments to improve the understanding of complex multi-physical multi-scale phenomena occurring in every crystal growth process.

Keywords: crystal growth; melt flows; model experiments; numerical simulation

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Permalink: https://www.hzdr.de/publications/Publ-29894
Publ.-Id: 29894


Magnetocaloric effect and spin-strain coupling in the spin-nematic state of LiCuVO4

Gen, M.; Nomura, T.; Gorbunov, D.; Yasin, S.; Cong, P. T.; Dong, C.; Kohama, Y.; Green, E. L.; Law, J. M.; Henriques, M. S.; Wosnitza, J.; Zvyagin, A. A.; Cheranovskii, V. O.; Kremer, R. K.; Zherlitsyn, S.

We report on the magnetocaloric effect and ultrasound studies of the frustrated quasi-one-dimensional spin-1/2 compound LiCuVO4, evidencing a spin-nematic state. The magnetic Grüneisen parameter diverges at the transition to the spin-nematic phase, μ0Hc3 ≈ 40 T, showing quantum criticality accompanied by entropy accumulation. The observed high-field anomalies in the acoustic properties clearly evidence a strong involvement of the lattice in the spin dynamics. The theoretical approach, based on exchange-striction coupling with dipolar and quadrupolar contributions, suggests that the spin-dipole-strain and quadrupole-strain interactions govern the
spin-nematicity in LiCuVO4.

Permalink: https://www.hzdr.de/publications/Publ-29892
Publ.-Id: 29892


Fermi surface of LaFe2P2—a detailed density functional study

Förster, T.; Kraft, I.; Sheikin, I.; Bianchi, A. D.; Wosnitza, J.; Rosner, H.

Angular-dependent de Haas-van Alphen measurements allow the mapping of Fermi surfaces in great detail with high accuracy. Density functional electronic-structure calculations can be carried out with high precision, but depend crucially on the used structural information and the applied calculational approximations. We report in a detailed study the sensitivity of the calculated electronic band structure of the 122 compound LaFe2P2 on (i) the exact P position in the unit cell, parametrized by a so-called z parameter, and on (ii) the treatment of the La 4f states. Depending on the chosen exchange and correlation-potential approximation, the calculated z parameter varies slightly and corresponding small but distinctive differences in the calculated band structure and Fermi-surface topology appear. Similarly, topology changes appear when the energy of the mostly unoccupied La 4f states is corrected regarding their experimentally observed position. The calculated results are compared to experimental de Haas-van Alphen data. Our findings show a high sensitivity of the calculated band structure on the pnictide z position and the need for an accurate experimental determination of this parameter at low temperatures, and a particular need for a sophisticated treatment of the La 4f states. Thus, this is not only crucial for the special case of LaFe2P2 studied here, but of importance for the precise determination of the band structure of related 122 materials and La containing compounds in general.

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Permalink: https://www.hzdr.de/publications/Publ-29891
Publ.-Id: 29891


The Helmholtz Innovation Lab for ultra-short time annealing

Rebohle, L.; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.; Skorupa, W.

Der Vortrag stellt das Helmholtz Innovation Lab für Ultrakurzzeitausheilung vor. Im zweiten Teil werden experimentelle Ergebnisse bei der Kristallisation von dünnen amorphen Halbleiterschichten (Si, Ge, NiGe) mittels magnetron sputtering und Blitzlampenausheilung diskutiert.

Keywords: Helmholtz Innovation Lab; flash lamp annealung; ultra-short time annealing; magnetron sputtering; nickel germanide

  • Lecture (Conference)
    43. Nutzertreffen Heißprozesse und RTP, 23.10.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29890
Publ.-Id: 29890


Crystallization of thin Si, Ge and NiGe films on SiO2 by flash lamp annealing

Rebohle, L.; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.; Skorupa, W.

There is a broad palette of applications for thin Si and Ge films ranging from photovoltaics over various microelectronic devices to sensor applications. Both amorphous and polycrystalline thin films are of interest for thin film photovoltaics, and thin film poly-Si transistors are the heart piece for driving LCDs and OLEDs [1]. In addition, the ability to deposit SiO2 and Si layers in an alternating order and to process them allows to extend the device density without further downscaling [2]. Amorphous thin film deposition methods are the most cost-effective ones, the subsequent crystallization is the most critical process step with regard to microstructure, defect density, and electrical properties.

Potentially, flash lamp annealing (FLA) is a very suitable method due to the short process time, the qualification for temperature-sensible substrates and the possibility to take advantage of non-equilibrium crystallization modes [3]. In this work thin amorphous Si and Ge films have been deposited on SiO2 by DC-magnetron sputtering and crystallized by in-situ FLA in a new FLA sputter tool recently installed by the Rovak GmbH at HZDR (Fig. 1). The in-situ-processing suppresses the influence of surface oxidation effects after deposition prior to FLA. In order to investigate the crystallization behaviour, the thin films have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements. Based on these results and in combination with temperature simulations, a model for the crystallization of thin amorphous Si and Ge films is derived.

Keywords: flah lamp annealing; magnetron sputtering; nickel germanide; crystallization

  • Lecture (Conference)
    Gettering and Defect Engineering in Semiconductor Technology 2019, 22.-27.09.2019, Zeuthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29888
Publ.-Id: 29888


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a semi-circular constriction

Neumann-Kipping, M.; Hampel, U.

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.195
    License: CC-BY-NC-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29887
Publ.-Id: 29887


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a ring-shaped constriction

Neumann-Kipping, M.; Hampel, U.

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.197
    License: CC-BY-NC-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29886
Publ.-Id: 29886


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a semi-circular constriction

Neumann-Kipping, M.; Hampel, U.

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.137
    License: CC-BY-NC-4.0

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Permalink: https://www.hzdr.de/publications/Publ-29885
Publ.-Id: 29885


Structural, Magnetocaloric, and Critical Behavior of La0.5Ca0.5Mn1−xVxO3 Manganites Prepared by High-Energy Ball Milling

Mansouri, M.; Fallarino, L.; M'Nassri, R.; Cheikhrouhou-Koubaa, W.; Cheikhrouhou, A.

The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model.

Keywords: Critical exponents; High-energy ball milling; Magnetocaloric effect; Manganites

Permalink: https://www.hzdr.de/publications/Publ-29884
Publ.-Id: 29884


The formation of Ni germanides by magnetron sputtering and flash lamp annealing

Rebohle, L.; Begeza, V.; Garcia Munoz, A.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.

Silicides have been widely used for CMOS devices in order to provide a stable Ohmic contact with a low contact resistivity. With the integration of Ge on Si the focus also shifted to germanides as a low resistivity contact material. In addition, ferromagnetic germanides may serve as spin injector materials for Ge-based spintronic devices. Usually, germanides have been fabricated by furnace or rapid thermal annealing in literature.

In this contribution we investigate the formation process of Ni germanides using a combination of magnetron sputtering and flash lamp annealing (FLA). Three different types of Ge served as a substrate for the deposition of the transition metal: amorphous Ge made by magnetron-sputtering on a SiO2-Si substrate, polycrystalline Ge made by magnetron-sputtering followed by FLA, and monocrystalline Ge in the form of a (100) Ge wafer. After metal deposition samples are in-situ annealed by FLA without breaking the vacuum, which triggers the formation of germanides and prevents a possible, but unwanted oxidation. In order to investigate the crystallization behavior, the structures have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements.

Keywords: flash lamp annealing; magnetron sputtering; nickel germanide

  • Lecture (Conference)
    EMRS 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29883
Publ.-Id: 29883


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a ring-shaped constriction

Neumann-Kipping, M.; Hampel, U.

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.139
    License: CC-BY-NC-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29882
Publ.-Id: 29882


Measurement of f orbital hybridization in rare earths through electric dipole-octupole interference in X-ray Absorption Spectroscopy

Juhin, A.; Collins, S. P.; Joly, Y.; Diaz-Lopez, M.; Kvashnina, K.; Glatzel, P.; Brouder, C.; de Groot, F.

This work provides a direct route to measure the degree of hybridization of f states in rare earths. The interference between electric dipole and octupole transitions is measured at the L1 edge of Gd in Gd3Ga5O12 using X-ray Natural Linear Dichroism (XNLD) and high energy resolution fluorescence detection. The Gd 4f-6p admixture is quantiffed through the integral of the dipole-octupole XNLD using a new sum rule easily applicable to experimental data. The mixing of the Gd valence states with the O ligand orbitals, calculated from first-principles, reveals that despite their localized character, the Gd 4f orbitals mix with the O 2p and 2s orbitals with an antibonding and bonding character, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-29881
Publ.-Id: 29881


Nanoscale mechanism of UO2 formation through uranium reduction by magnetite

Pan, Z.; Bártová, B.; Lagrange, T.; Shen, T.; Tileli, V.; Butorin, S.; Hyatt, N. C.; Stennett, M. C.; Kvashinina, K. O.; Bernier-Latmani, R.

Significance:
Uranium (U) biogeochemical behavior is constrained by redox transformations. In anoxic environments, soluble hexavalent U is reduced and immobilized as tetravalent U. During abiotic U reduction, the formation of tetravalent U oxide (UO2) has been demonstrated and the persistence of an intermediate (pentavalent) valence state invoked. However, despite decades of study, there is little insight into the molecular mechanistic details of UO2 formation. Here, we show the formation of transient nanowires composed of randomly oriented UO2 nanoparticles followed by rearrangement into ordered UO2 nanoclusters. We also evidence the persistence of pentavalent U on the magnetite surface. These findings have implications for uranium isotopic fractionation, nuclear waste, and uranium remediation.

Abstract:
Uranium (U) is a ubiquitous element, present in the Earth’s crust at ~2 ppm. In anoxic environments, soluble hexavalent uranium (U(VI)) is reduced and immobilized. The underlying reduction mechanism is unknown but is likely of critical importance to explain variability in isotopic fractionation depending on the reducing agent and the chemical conditions. Here, we tackle the mechanism of reduction of U(VI) by the mixed-valence iron oxide, magnetite (Fe3O4). Through a combination of high-end spectroscopic and microscopic tools, we demonstrate that the reduction of U(VI) proceeds first through surface-associated U(VI) to form pentavalent U, U(V). U(V) persists on the surface of magnetite and is further reduced to tetravalent UO2 in the form of nanocrystals (~1-2 nm) arranged at random orientations in nanowires that extend hundreds of nanometers from the magnetite surface. Through re-orientation of the nanoparticles and their coalescence into larger nanoparticles, the nanowires collapse after several weeks to generate ordered UO2 nanoclusters. Thus, this work provides evidence for a transient U nanowire structure that may have implications for uranium isotope fractionation as well as for molecular-scale understanding of nuclear waste temporal evolution and the reductive remediation of uranium contamination.

Permalink: https://www.hzdr.de/publications/Publ-29880
Publ.-Id: 29880


Pathways to a nuclear waste repository in Germany

Foerstendorf, H.

Pathways to a nuclear waste repository in Germany

  • Invited lecture (Conferences)
    The Chemistry of f-Elements Autumn School, 12.-16.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29879
Publ.-Id: 29879


Stratified & Segregated Flow Modelling – Algebraic Interfacial Area Density

Höhne, T.

Optimization of large-scale multiphase processes requires adequate and efficient CFD-tools.

  • Large scales flow behavior depend on sub-grid physical phenomena that have to be described by closure models.
  • Different models necessary for dispersed particles and separated continuous phases (interfacial drag etc.)
  • Applications: Flow patterns in horizontal pipes, separation processes in rectification columns, stirred tank reactors etc.

Keywords: AIAD; Two phase flow; CFD; stratified; Gas; Liquid

  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland
  • Poster
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29878
Publ.-Id: 29878


Neuroprogressive character of sigma-1 receptor pathophysiology in unmedicated patients with acute major depressive disorder as investigated by (-)-[18F]Fluspidine PET

Meyer, P.; Strauss, M.; Becker, G.; Hesse, S.; Bednasch, K.; Ettrich, B.; Wilke, S.; Zientek, F.; Rullmann, M.; Luthardt, J.; Fischer, S.; Patt, M.; Wünsch, B.; Brust, P.; Sabri, O.

Aim/Introduction:
We have previously shown that the sigma-1 receptor(Sig-1R) availability is increased in unmedicated acute MDD (MDD) using (-)-[18F]Fluspidine PET. In order to assess whether this pathophysiology is progressive, we investigated the relationship between Sig-1R availability and duration of disease (DD), number of depressive episodes (DE) and severity of acute depressive symptoms (Hamilton Depression Rating Scale, HAMD) in this now completed first-in-human (-)-[18F]Fluspidine PET trial.
Materials and Methods:
Patients with moderate to severe MDD (n=18; 32±12 years; 9 females; DD 6±8 years; DE 3±1 years; HAMD: 20±4) were studied using (-)-[18F]Fluspidine PET (300 MBq, ECAT Exact HR+) and compared with sex-/age-matched healthy controls (HC; n=16; 32±13ys [n.s.]; 9 females [n.s.]). VOI analyses were performed and regional distribution volumes (VT) were estimated by kinetic modeling (0-210 min p.i.; 2TCM; metabolite correction).
Results:
In MDD, compared with HC, VT was higher especially within the fronto-temporal, anterior cingulate and insular cortices, amygdala, striatum, thalamus and ncl. raphe (P<0.005). Positive correlations were found between HAMD and VT within the anterior and posterior cingulate and insular cortices, ncl. caudatus and thalamus (r=0.43 to 0.57, P<0.05, adjusted for DD, BMI).Negative correlations were found between DD and VT within the orbitofrontal cortex and hypothalamus (r=-0.40 to -0.47, P<0.05, adjusted for severity of MDD) and between DE and VT within the hypothalamus, orbitofrontal, temporo-parietal and cingulate cortices, striatum, thalamus and cerebellum (r=-0.42 to -0.60, P<0.05, adjusted for severity of MDD).
Conclusion:
Using (-)-[18F]Fluspidine PET, we showed for the first time increased cortico-(para-)limbic Sig-1R availability during the DE of MDD, as compared with HC, that was associated with the severity of acute depressive symptoms (HAMD). Remarkably, in MDD, there is a negative correlation between DE or DD and Sig1-R availability, especially within orbitofrontal cortices and hypothalamus as well as within various (sub)cortical-(para)limbic and cerebellar brain regions. Although verification by longitudinal (-)-[18F]Fluspidine PET studies is needed, our findings suggest a neuroprogressive character of Sig-1R pathophysiology in MDD.

Keywords: sigma-1 receptor; acute major depressive disorde; (-)-[18F]Fluspidine; PET

  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine, 12.-16.10.2019, Barcelona, Barcelona, Spain
    DOI: 10.1007/s00259-019-04486-2

Permalink: https://www.hzdr.de/publications/Publ-29877
Publ.-Id: 29877


Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

Dubs, C.; Surzhenko, O.; Thomas, R.; Osten, J.; Schneider, T.; Lenz, K.; Grenzer, J.; Hübner, R.; Elke, W.

The field of magnon spintronics is experiencing increasing interest in the development of solutions for spin-wave-based data transport and processing technologies that are complementary or alternative to modern CMOS architectures. Nanometer-thin yttrium iron garnet (YIG) films have been the gold standard for insulator-based spintronics to date, but a potential process technology that can deliver perfect, homogeneous large-diameter films is still lacking. We report that liquid phase epitaxy (LPE) enables the deposition of nanometer-thin YIG films with low ferromagnetic resonance losses and consistently high magnetic quality down to a thickness of 10 nm. The obtained epitaxial films are characterized by an ideal stoichiometry and perfect film lattices, which show neither significant compositional strain nor geometric mosaicity, but sharp interfaces. Their magneto-static and dynamic behavior is similar to that of single crystalline bulk YIG. We found, that the Gilbert damping coefficient  is independent of the film thickness and close to 1  10-4, and that together with an inhomogeneous peak-to-peak linewidth broadening of H0|| = 0.4 G, these values are among the lowest ever reported for YIG films with a thickness smaller than 40 nm. Only for the 10-nm-thin film a significantly reduced saturation magnetization was observed. These results suggest, that nanometer-thin LPE films can be used to fabricate nano- and micro-scaled circuits with the required quality for magnonic devices. The LPE technique is easily scalable to YIG sample diameters of several inches.

Keywords: YIG; ferromagnetic resonance; linewidth; damping; thin films; liquid phase epitaxy

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Permalink: https://www.hzdr.de/publications/Publ-29876
Publ.-Id: 29876


Spektroskopische Methoden für die Endlagerforschung

Drobot, B.

Spektroskopische Methoden generieren molekulares Prozessverständnis. Dies ist wichtig für die Erhöhung der Belastbarkeit von Risokoanalysen im Endlager-Kontext.

Keywords: Endlager; Spektroskopie

  • Invited lecture (Conferences)
    Kraftwerkstechnisches Kolloquium, 23.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29875
Publ.-Id: 29875


HZDR Data Management Strategy — Top-Level Architecture

Knodel, O.; Gruber, T.; Müller, S.; Juckeland, G.

Top-Level Architecture of the proposed HZDR Data Management Strategy

Keywords: data management

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-12
    DOI: 10.14278/rodare.193
    License: CC-BY-NC-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29873
Publ.-Id: 29873


Hydrodynamic investigations of gas-liquid two-phase flow in centrifugal pumps - reconstructions (selected data)

Schäfer, T.; Bieberle, A.; Hampel, U.

This data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:

  • Reconstructed raw data (FBP) sets for selected two-phase flow operating conditions at constant 1480 rpm with static and rotating impeller, respectively
  • Corresponding quantitative gas fraction data sets (for static impeller position)
  • Averaged gas fraction distributions
  • Standard deviations of the gas fraction mean values
  • Data evaluation scripts

Keywords: centrifugal pump; gas-liquid two-phase flow; ultrafast X-ray computed tomography

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-10-30
    DOI: 10.14278/rodare.189

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29872
Publ.-Id: 29872


Cross section of α-induced reactions on 197Au at sub-Coulomb energies

Szücs, T.; Mohr, P.; Gyürky, G.; Halász, Z.; Huszánk, R.; Kiss, G. G.; Szegedi, T. N.; Török, Z.; Fülöp, Z.

Statistical model calculations have to be used for the determination of reaction rates in large-scale reaction networks for heavy-element nucleosynthesis. A basic ingredient of such a calculation is the a-nucleus optical model potential. Several different parameter sets are available in literature, but their predictions of a-induced reaction rates vary widely, sometimes even exceeding one order of magnitude.
This paper presents the result of a-induced reaction cross-section measurements on gold which could be carried out for the first time very close to the astrophysically relevant energy region. The new experimental data are used to test statistical model predictions and to constrain the a-nucleus optical model potential.
For the measurements the activation technique was used. The cross section of the (a,n) and (a,2n) reactions was determined from g-ray counting, while that of the radiative capture was determined via X-ray counting.
The cross section of the reactions was measured below Ea=20.0~MeV. In the case of the 197Au(a,2n)199Tl reaction down to 17.5~MeV with 0.5-MeV steps, reaching closer to the reaction threshold than ever before. The cross section of 197Au(a,n)200Tl and 197Au(a,g)201Tl was measured down to Ea=13.6 and 14.0~MeV, respectively, with 0.5-MeV steps above the (a,2n) reaction threshold and with 1.0-MeV steps below that.
The new dataset is in agreement with the available values from the literature, but is more precise and extends towards lower energies. Two orders of magnitude lower cross sections were successfully measured than in previous experiments which used g-ray counting only, thus providing experimental data at lower energies than ever before. The new precision dataset allows us to find the best-fit a-nucleus optical model potential and to predict cross sections in the Gamow window with smaller uncertainties.

Keywords: Nuclear Astrophysiscs; Heavy element nucleosynthesis; Alpha induced reactions

Permalink: https://www.hzdr.de/publications/Publ-29871
Publ.-Id: 29871


Impact of milling condition on the flotation of Vietnamese silicaceous carbonaceous apatite ore

Hoang, D. H.; Saquran, S. S.; Hassanzadeh, A.; Kupka, N.; Michaux, B.; Schach, E.; Sprenger, H.; Rudolph, M.

This study aims to endeavor the role of milling environment on the output particle properties and on the batch flotation behavior of a siliceous carbonaceous sedimentary apatite ore. For this purpose, the milling prior to the flotation was performed in three conditions, i.e. dry, wet and wet-conditioned using a rod mill and finding the milling times in order to have the same particle size distribution (PSD). Flotation experiments were carried out in a 4 L agitating mechanical cell at pH10 adjusted by Na2CO3, sodium silicate (400 g/t) and corn starch (200 g/t) as depressants. Atrac 922 (350 g/t) and MIBC (15 g/t) were added as collector and frother, respectively. Concentrates and tailings were mineralogically and chemically characterized by automated mineralogy (Mineral Liberation Analyzer - MLA) and inductively coupled plasma - optical emission spectrometry (ICP - OES), respectively. It was shown that the flotation feed particle size distributions (PSDs), apatite and dolomite liberation degrees (LDs) and water properties were remained constant for all three milling configurations which allowed to eliminate their effectiveness on floatability responses.
The experimental results showed that the different particle properties (i.e., particle size, mineral liberation), pulp/ froth properties (Ca2+/ Mg2+ ions concentration, pulp rheology, froth structure) under different milling conditions, which in turn influences on the flotation response (grade, recovery, flotation kinetics and selectivity between apatite and carbonate minerals). A feed ore containing about 12.4 % P2O5 and 7.3 % MgO, after rougher flotation, achieved concentrates with a P2O5 content of about 16.7-17 % at the recoveries of 88.6-92.3 %. However, the MgO content of 7.9-8.3 % in the apatite concentrates is higher compared to the feed, where only 24-29 % of dolomite was removed. Hence, the separation between apatite-carbonates is very challenging for fine intergrowth sedimentary siliceous carbonaceous apatite ores, which will need further investigation on optimization of reagent regime, especially, depressants of carbonates minerals.

Keywords: Dry and wet milling; Ca2+/ Mg2+ concentration; flotation; calcium-bearing minerals; carbonate depressant

  • Open Access Logo Contribution to proceedings
    IMPC-Eurasia 2019, 31.10.-02.11.2019, Antalya, Turkey
    IMPC-Eurasia 2019, 1st regional Mineral Processing Conference, 978-975-7946-44-1

Permalink: https://www.hzdr.de/publications/Publ-29870
Publ.-Id: 29870


Interactive effect of particle size, liberation and hydrophobicity on the flotation kinetics of a carbonaceous phosphate deposit

Hoang, D. H.; Schach, E.; Hassanzadehmahaleh, A.; Kupka, N.; Pereira, L.; Rudolph, M.

Selective separation of apatite from the associated minerals (quartz, calcite and dolomite) in a carbonaceous phosphate ore type strongly depends on the interactive effect of particle size, hydrophobicity and mineral liberation degree (LD). This study aims to investigate these parameters by paying close attention to distinguishing true flotation (attachment) and entrainment phenomena respectively in pulp and froth zones. Modified flotation kinetics (kM) were used for estimating flotation rates of the different minerals on size-by-liberation in terms of taking the combination of infinitive recovery (Rmax) and k into account. The results indicate that the LD plays an insignificant role on kM of fine apatite particles (< 20 µm) due to transporting to the concentrate by both true flotation and entrainment mechanisms. In contrast, kM of the coarse apatite particles (> 20 µm) is strongly influenced by the LD. Additionally, the recovery of fully liberated apatite in the four studied size ranges was found fairly similar. However, both size and LD are significantly affecting the recovery of liberated gangue minerals where both true flotation and entrainment occurred for carbonates and entrainment for silicates.

  • Contribution to proceedings
    Procemin-Geomet 2019, 20.-22.11.2019, Santiago, Chile
    Procemin-Geomet 2019

Permalink: https://www.hzdr.de/publications/Publ-29868
Publ.-Id: 29868


Neutron radiography of particle-laden liquid metal flow driven by an electromagnetic induction pump

Lappan, T.; Sarma, M.; Heitkam, S.; Trtik, P.; Mannes, D.; Eckert, K.; Eckert, S.

Ladle metallurgy treatment affects the chemical composition and the impurities in molten steel. To remove non-metallic inclusions, gas injection into the ladle and intense stirring by bubbly flows are essential in the refining process. This paper reports on a model experiment that provides an insight into the bubble – particle interaction in liquid metal at room temperature. We apply neutron radiography as imaging technique for particle-laden liquid metal flow around a cylindrical obstacle representing a single rising bubble. The experimental setup is tailored to both the measurement principle of neutron transmission imaging and the design of the disc-type induction pump driving the flow. A liquid metal loop of 30 mm x 3 mm rectangular cross section is filled with low-melting gallium-tin alloy. Gadolinium oxide particles (0.3 – 0.5mm) are employed because of their superior neutron attenuation compared to liquid gallium-tin. The neutron image sequences visualise the particle trajectories in the opaque liquid metal with high temporal resolution (100 fps). Up- and downstream the cylindrical obstacle, we analyse the velocity field as a function of the pump’s rotational speed by particle image velocimetry (PIV). The time-averaged particle velocity measured by PIV is lower than the circumferential velocity of the pump’s discs. This velocity deficit arises from the particles’ buoyancy and the pressure drop in the liquid metal loop. In the further analysis of these neutron image data, we will focus on the fluid flow in the wake of the cylindrical obstacle.

Keywords: neutron radiography; liquid metal; gadolinium oxide; induction pump; particle image velocimetry

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  • Secondary publication expected from 26.09.2021

Permalink: https://www.hzdr.de/publications/Publ-29867
Publ.-Id: 29867


X-ray particle tracking velocimetry in liquid foam flow

Lappan, T.; Franz, A.; Schwab, H.; Kühn, U.; Eckert, S.; Eckert, K.; Heitkam, S.

In this work, we introduce a novel approach to measure the flow velocity of liquid foam by tracking custom-tailored 3D-printed tracers in X-ray radiography. In contrast to optical observations of foam flow in flat cells, the measurement depth equals 100mm in X-ray beam direction. Light-weight tracers of millimetric size and tetrapod-inspired shape are additively manufactured from stainless steel powder by selective laser melting. Matching with the foam structure and bubble size, these tracers follow the foam flow minimally invasively. An X-ray beam passes through the radiotransparent foam channel and is detected by an X-ray image intensifier. The X-ray transmission images show the two-dimensional projections of the radiopaque tracers. Employing particle tracking velocimetry algorithms, the tracer trajectories are measured with both high spatial (0.2 mm) and temporal (25 fps) resolution. Fine-pored and coarse-pored liquid foam flow of different velocities are studied in a partly curved channel with rectangular cross section. The simultaneous time-resolved measurement of the tracers' translational motion and their intrinsic rotation reveal both the local velocity and vorticity of the foam flow. In the semi-circular curved channel section, the rigid-body-like flow pattern is investigated. Moreover, a relaxation of the foam structure in the transition zone between straight and curved section is observed.

Keywords: X-ray radiography; particle tracking velocimetry; liquid foam; flow tracer

  • Soft Matter 16(2020)8, 2093-2103
    DOI: 10.1039/C9SM02140J
  • Lecture (Conference) (Online presentation)
    EUFoam 2020, 07.-10.07.2020, Aberystwyth, United Kingdom

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  • Secondary publication expected from 04.02.2021

Permalink: https://www.hzdr.de/publications/Publ-29866
Publ.-Id: 29866


Status and innovations in pre-treatment CT imaging for proton therapy

Wohlfahrt, P.; Richter, C.

Pre-treatment CT imaging is a topic of growing importance in particle therapy. Improvements in the accuracy of stopping-power prediction are demanded to allow for a dose conformality that is not inferior to state-of-the-art image-guided photon therapy. Although range uncertainty has kept practically constant over the last decades, recent technological and methodological developments, like the clinical application of dualenergy CT, have been introduced or arise at least on the horizon to improve the accuracy and precision of range prediction. This review gives an overview of the current status, summarizes the innovations in dual-energy CT and its potential impact on the field as well as potential alternative technologies for SPR prediction.

Keywords: Dual-energy CT; range prediction; stopping-power ratio; stopping-power prediction; SPR; proton therapy

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29865
Publ.-Id: 29865


Dynamical freeze-out phenomena: The case of K±,ϕ transverse momentum spectra in collisions of Au(1.23 A GeV) + Au

Rabe, B.; Kämpfer, B.

We argue on a continuous (dynamical) kinetic freeze-out of K±,ϕ observed at midrapidity in collisions Au(1.23 A GeV) + Au. The simulations by means of a transport model of BUU type point to time independent transverse momentum slope parameters after 20 fm/c. The complex interplay of expansion dynamics and strangeness production/exchange/absorption as well as elastic scatterings involved in the reaction network does not support the previous interpretation of a late freeze-out of K− due to larger cross sections.

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Permalink: https://www.hzdr.de/publications/Publ-29863
Publ.-Id: 29863


Entangling continuous variables with a qubit array

Navez, P.; Sowa, A.; Zagoskin, A.

We show that an array of qubits embedded in a waveguide can emit entangled pairs of microwave photon beams. The quadratures obtained from the homodyne detection of these outputs beams form a pair of correlated continuous variables similar to the Einstein-Podolsky-Rosen experiment. The photon pairs are produced by the decay of plasmonlike collective excitations in the qubit array. The maximum intensity of the resulting beams is bounded by only the number of emitters. We calculate the excitation decay rate both into a continuum of the photon state and into a one-mode cavity. We also determine the frequency of Rabi-like oscillations resulting from a detuning.

Permalink: https://www.hzdr.de/publications/Publ-29862
Publ.-Id: 29862


Plasmonic nonlinearity in GaAs/In0.20Ga0.80As core/shell nanowires

Rana, R.; Balaghi, L.; Fotev, I.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.

We have investigated the plasmonic response of GaAs/In0.20Ga0.80As core/shell nanowires driven resonantly by strong THz fields with the amplitude of few MV/cm. The plasmon mode exhibits a systematic redshift with the suppression of the spectral weight with the increase of the driving THz field. Interestingly, the scaling of the plasmon parameters does not follow the usual quadratic behavior, indicating an inhomogeneous intervalley electron scattering across the nanowire.

Keywords: Plasmons; Nanowires; Nonlinear optics

  • Contribution to proceedings
    44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 01.-06.09.2019, Paris, France
    2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), IEEE Xplore: IEEEE, 978-1-5386-8285-2
    DOI: 10.1109/IRMMW-THz.2019.8874085

Permalink: https://www.hzdr.de/publications/Publ-29861
Publ.-Id: 29861


Mobility of radionuclides enhanced by complexing agents used in a repository: Modeling sorption and transport

Karimzadeh, L.; Lippold, H.; Fischer, C.

Among the organic inventory of a nuclear waste repository, aminopolycarboxylic acids, which are used as decontamination agents during operation, are of particular concern in view of their chelating capability and high persistence, but data regarding their impact on the mobility of radionuclides in geological barriers are missing so far. Migration in the host rock is controlled by sorption reactions on mineral surfaces, potentially affected by organic complexing ligands. As a case study, using 152Eu as a short-lived tracer analogue of actinides, we investigated sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of the complexant diethylenetriaminepentaacetic acid (DTPA). The transport behavior was studied in column experiments (up- and down-flooding) at neutral pH in order to detect possible inconsistencies between sorption in batch systems and retardation in dynamic systems.
The effect of DTPA on sorption of Eu(III) was found to be strongly dependent on pH. At neutral and alkaline conditions, sorption is considerably decreased, resulting in accelerated breakthrough and facilitated elution in column experiments. Sorption as a function of DTPA concentration and pH was completely described by surface complexation modeling based on the Diffuse Double Layer Model of Dzombak and Morel, using the speciation program PHREEQC coupled with the parameter estimation code PEST. Results of column experiments were simulated in 1D calculations by means of the obtained surface complexation parameters. Breakthrough and elution curves were perfectly reproduced without readjustments.

  • Poster
    Jahrestagung der GDCh, Fachgruppe Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29859
Publ.-Id: 29859


Thermo-physical properties of coatings in the Ti(B,N) system grown by chemical vapor deposition

Kainz, C.; Schalk, N.; Tkadletz, M.; Saringer, C.; Winkler, M.; Stark, A.; Schell, N.; Julin, J.; Czettl, C.

Hard protective coatings are commonly subjected to temperatures exceeding 1000 °C, which has significant influence on their thermo-physical properties and the associated performance in application. Within the present work, temperature dependent physical properties of coatings within the Ti(B,N) system grown by chemical vapor deposition were correlated with their chemical composition. High-energy X-ray diffraction experiments in inert atmosphere proved that TiN, TiB₂ and ternary TiBxNy coatings with varying B contents are thermally stable up to 1000 °C. First order lattice strains of TiN and TiBxNy coatings diminish during heating, whereas TiB₂ exhibits compressive strain enhancement up to the deposition temperature. Nanocrystalline TiB₂ exhibits more pronounced grain growth during annealing compared to coarse grained columnar TiN. Within the investigated coatings, the mean thermal expansion coefficient decreases as the B content increases. The same trend was observed for the thermal conductivity, which correlates with the grain size of the coatings.

Keywords: Chemical vapor deposition; X-ray diffraction; Ti(B,N); thermal conductivity; strain

Permalink: https://www.hzdr.de/publications/Publ-29858
Publ.-Id: 29858


Produktion und Reinigung von n.c.a. 48V am Leipziger Zyklotron für Extraktionsstudien

Mansel, A.; Franke, K.

Vanadium ist ein Bestandteil in Eisen-Chromschlacken und gilt als strategisches Wertmetall. Um effiziente Abtrennungsverfahren von fünfwertigem Vanadium vom dreiwertigen Chrom bzw. sechswertigem Chromat mit Hilfe der Ionenchromatographie zu entwickeln, wurde die Radiotracertechnik eingesetzt [48V; T1/2 = 15,97 d; E = 984 keV; 99,97 %]. Die Produktion dieses Radionuklides wurde am Leipziger Zyklotron CYCLONE 18/9® durch die Kernreaktion natTi(p,n)48V realisiert. Eine Titanfolie (natürliche Isotopenzusammensetzung; 140 mg) wurde mit Protonen der Energie 12 MeV bei einem Strom von 22 µA für zwei Stunden bestrahlt. Das bestrahlte Target wurde für einen Tag zum Abklingen des kurzlebigen Radionuklides 47V (T1/2 = 32,6 min) aufbewahrt und anschließend in konzentrierter Schwefelsäure und wenigen Tropfen Flußsäure in einem Teflonbecher aufgelöst. Nach dem Eindampfen wurde der Rückstand mit 3 g Natriumcarbonat / 80 mg Natriumnitrat in einem Platintiegel für 30 Minuten bei 800 °C aufgeschlossen. Durch mehrmaliges Anlösen mit Wasser wurde das 48V in Form von Natriumvanadat vom Targetmaterial Titandioxid herausgelöst. Spuren von Titan wurden mit Hilfe eines Kationenaustauschers (DOWEX 50 W X-8) bei pH 3 abgetrennt und das Vanadylion in Form von Vanadat mit 20 %igem Ammoniak eluiert. Die radiochemische Ausbeute betrug (95 ± 8) %. Die Aktivität betrug fünf Stunden nach Bestrahlungsende ~ 245 MBq und die Nachweisgrenze wurde zu 8 fM (~0,4 pg/L) für n.c.a. 48V ermittelt.

  • Poster
    GDCh Jahrestagung der Fachgruppe Nuklearchemie, 24.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29857
Publ.-Id: 29857


MRI based measurement of pancreas motion reduction with an MR- and particle therapy compatible abdominal corset

Schneider, S.; Stefanowicz, S.; Lohaus, F.; Jentsch, C.; Troost, E. G. C.; Hoffmann, A. L.

Introduction:
In particle beam therapy (PBT) respiratory-induced tumor motion is commonly accounted for by the definition of an internal target volume[1] to cover the tumor in all respiratory phases. Consequentially, also a relatively large volume of healthy tissue surrounding the tumor is exposed to radiation. An appropriate immobilization of the target volume can improve the sparing of healthy tissues. Immobilization of target volumes located in the upper gastro-intestinal tract has been accomplished through abdominal compression bands or pressure plates. These, however, can exacerbate the proton beam range uncertainties when these devices extend into the treatment fields, thereby compromising an accurate dose delivery[2]. For this study, an MR- and PBT-compatible patient-individualized abdominal corset was developed to test its efficacy to reduce respiratory-induced pancreas motion as measured by means of orthogonal 2D-cine and 4D-MRI.

Methods:
Nine patients (6 female, 3 male; average age 72.9 ± 9.6 years) with abdominal tumors of the pancreas (7 patients), gallbladder (1 patient), or liver (1 patient) provided written informed consent (study number DRKS00010966) to be scanned by means of orthogonal 2D-cine (2 min acquisition time) and 4D-MRI (9 min acquisition time) utilizing a balanced steady-state free precession sequence. For 2D-cine MRI coronal and sagittal slices were positioned to image the pancreatic head. The 4D-MRI dataset was reconstructed by retrospectively resorting a multi-slice 2D acquisition into 10 respiratory phases by amplitude based sorting[3], thereby imaging the full volume of the pancreas. Two MRI scans were acquired per patient, one without and one with a patient-individualized abdominal corset to reduce respiratory motion. The corset was manufactured from polyethylene (Orthopädie- und Rehatechnik Dresden GmbH, Dresden, Germany) based on an optical 3D-surface scan of the patient (Artec Eva®, Artec3D, Luxembourg, Luxemburg). From the nine patients, eight orthogonal 2D-cine datasets and seven 4D-MRI datasets were successfully acquired on a 3.0T MRI scanner (Ingenuity TF PET/MR scanner, Philips Healthcare, Best, The Netherlands). The patients were scanned in supine position on a flat tabletop using an anterior coil holder to avoid anatomical deformations of the chest wall due to the weight of the receiver coils. Pancreas motion was determined as center-of-mass displacement in three orthogonal directions (inferior-superior (IS), anterior-posterior (AP), left-right (LR)) for both orthogonal 2D-cine and 4D-MRI (Fig. 1). The motion amplitude extracted from the 2D-cine dataset was evaluated as the mean peak-to-peak amplitude M95, for which the lower and upper 2.5 % of the data was discarded to reduce the effect of possible outliers.

Results:
Orthogonal 2D-cine MRI showed that pancreas motion was dominant in IS direction (Fig. 2). For the 8 patients analyzed, the abdominal corset reduced the motion M95 in IS direction by in average 42 % (5 mm ± 3.7 mm (standard deviation) without corset, 3.8 mm ± 1.1 mm with corset; p<0.05). Similarly, the patients’ intrafraction motion variability decreased by 40 % (from in average 1.5 mm ± 0.4 mm to 0.9 mm ± 0.2 mm, p<0.01). Pancreas motion in AP and LR direction was small without corset (1.5 mm ± 0.2 mm and 1.8 mm ± 0.7 mm for AP and LR, respectively) and was not significantly reduced by the use of the corset (Fig. 2).
In general, 4D-MRI (Fig. 3) showed larger motion amplitudes than 2D-cine MRI. For the 7 patients analyzed based on 4D-MRI, mean peak-to-peak motion in IS direction was reduced from 8.6 mm ± 3.7 mm without corset to 5.0 mm ± 2.4 mm with corset (42 % reduction, p<0.05).

Discussion:
Both orthogonal 2D-cine and 4D-MRI show that by use of a patient-individualized abdominal corset, respiratory-induced pancreas motion as well as the patient’s intrafraction motion variability can be significantly reduced in IS direction. The slightly different results retrieved with 2D-cine and 4D-MRI can be attributed to the different volume of the pancreas imaged in the respective modality. However, the main effect explaining this difference seems to be the amplitude-based sorting algorithm used for 4D-MRI, which naturally reflects larger motion amplitudes.

Conclusion:
MRI-based motion analysis showed that respiratory-induced pancreas motion could be significantly reduced in IS direction by the use of a patient-individualized MR- and PTB-compatible abdominal corset. The results suggest that patients would benefit from a patient-individualized abdominal corset allowing for improved healthy tissue sparing due to the consequentially smaller margins surrounding the target volume.

References
[1] Chang JY, Zhang X, Knopf A et al. Consensus Guidelines for Implementing Pencil-Beam Scanning Proton Therapy for Thoracic Malignancies on Behalf of the PTCOG Thoracic and Lymphoma Subcommittee. Int J Radiat Oncol Biol Phys 2017; 99(1): 41-50.
[2] Wroe AJ, Bush DA and Slater JD. Immobilization Considerations for Proton Radiation Therapy. Technol Cancer Res Treat 2014; 13: 217–226.
[3] Von Siebenthal K, Székely G, Gamper U, Boesiger P, Lomax A and Cattin P. 4D MR imaging of respiratory organ motion its variability. Phys Med Biol 2007; 52: 1547–64.

Keywords: Pancreatic adenocarcinoma; respiratory motion; MR guided particle therapy; 4D MRI

  • Lecture (Conference)
    ISMRM 28th Annual Meeting & Exhibition, 18.04.2020, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-29856
Publ.-Id: 29856


Coupled processes across a claystone-concrete interface: results of a combined X-ray CT and PET transport experiment

Mäder, U.; Bernard, E.; Kulenkampff, J.; Jenni, A.

Interfaces between dense clay materials and cementitious materials are studied in the context of deep disposal of radioactive waste for one main reason: mineral reactions due to contrasting chemistries will modify the pore network and affect transport of water, solutes and gas. Substantial research efforts were directed towards mineralogical and physical characterisation of interface regions (e.g. Mäder et al. 2018) but little evidence exists on direct observations of transport behaviour across such skins. This study aims at providing evidence on how mineralogical-physical changes at such an interface affect transport of water and solutes, and linking mineralogical-physical characterisation, X-ray computed tomography and positron emission tomography (PET).

We developed an X-ray transparent core infiltration apparatus whereby a sample core subject to a hydraulic confining pressure can be tested with a hydraulic gradient (Mäder, 2018, for details of method and design in steel and titanium). This compact apparatus uses a carbon fibre tube as pressure vessel and various polymer plastics for other components. Several small pressure tanks integrated into the apparatus allow for self-contained operation for several days, and switching of the percolating fluid. A further extension in form of an integrated lead-shielded pressure container allows also for using radioactive tracers such that the equipment can be used for positron-emission tomography (PET). PET is a superb method to directly image the mobile phase in 3D, and its time evolution (Kuhlenkampff et al., 2017).

A 14 year-old sample core was recovered by stabilized drilling from a long term in situ experiment (CI) at the Mont Terri rock laboratory (Mäder et al., 2018), containing a physically preserved interface between Opalinus Clay and OPC concrete. This larger sample (101 mm DM) was sub-sampled and a 50x50 mm core was stabilised and cored from it. The clay part shows pre-existing bedding-parallel weak jointing that can also be seen in high resolution X-ray CT. The aged interface shows mineral transformations at the mm scale with complex mineral alteration patterns in both clay and cement matrix at a sub-mm scale, including porosity re-distribution and net reduction. The OPC concrete contains aggregate and gas pores. The compound sample may represent a repository situation of a claystone somewhat disturbed by excavation, in contact with a concrete liner, with pore water transport from clay across concrete.

A long-term transport experiment was set up by injecting a synthetic claystone pore water into the core sample on the clay-side, and force advection/diffusion across the interface and out of the cement-side. The fluid is traced with deuterium as water tracer, and periodically sampled for chemical and isotopic analysis. The sample was monitored frequently by high resolution X-ray CT during the first few days, and then regularly for the first 4 months. The running experiment was then transported to Leipzig and prepared for PET. 124I was used as PET tracer, and the chosen dose allowed for continuous PET scanning during two weeks, initially every 3 hrs.

A very large data set of 2D interface characterisation (SEM/EDX mapping, etc.) and time-resolved 3D CT and PET is presently being evaluated, enhanced, imaged and interpreted. Preliminary results document an initial self-sealing effect of the joint system in the Opalinus Clay, permeation into the diffusion-controlled pore network in claystone and cement matrix, and partial filling of gas pores. PET captures some preferential flow across claystone along some remaining joints, a spreading of the tracer plume at the clay/cement interface, and some moderate preferential flow across OPC.

This approach provides much more detailed information of coupled processes in complex porous media by imaging both the stationary and the mobile phase. Compared to summation parameters, such as tracer breakthrough, there is infinitely more information obtained about the localisation of flow and the nature of the pore network and its temporal evolution.

The research leading to these results has also received funding from the European Union's European Atomic Energy Community's (Euratom) Horizon 2020 Programme (NFRP-2014/2015) under grant agreement, 662147 – Cebama. Uni Bern acknowledges funding contributions by Nagra and the Mont Terri Consortium (CI Experiment).

Kulenkampff, J., Gründig, M., Zakhnini, A., Lippmann-Pipke, J. (2016). Geoscientific process monitoring with positron emission tomography (GeoPET). Solid Earth 7, 1207-2015.
U. Mäder (2018). Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone, Geofluids, 2018.
U. Mäder, A. Jenni, C. Lerouge, S. Gaboreau, S. Miyoshi, Y. Kimura, V. Cloet, M. Fukaya, F. Claret, T. Otake, M. Shibata, B. Lothenbach (2017). 5-year chemico-physical evolution of concrete-claystone interfaces, Swiss Journal of Geosciences, 110, 307-327.

Keywords: radioactive waste disposal; clay-cement interface; transport experiments; positron emission tomography; x-rax computed tomography

  • Open Access Logo Lecture (Conference)
    Decovalex 2019, 04.-05.11.2019, Brugg, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-29855
Publ.-Id: 29855


Novel fiducial marker has optimal characteristics for image-guided radiotherapy of abdominal tumours

Stefanowicz, S.; Mieke, L. M.; Julia, T.; Michael, J.; Cordelia, H.; Troost, E. G. C.

Introduction
Most solid tumours originate from and amidst soft tissues and are localised in direct proximity of radiation sensitive organs at risk. That is why, e.g., in pancreatic cancer, the full potential of radio(chemo)therapy has not been exploited yet. In the era of highly conformal radiation techniques and hypofractionated treatment schedules, it is of increasing importance to accurately and precisely localise the tumour, both at treatment planning and delivery. Solid fiducial markers to be implanted in (the proximity of) the tumour have been available for some time, but have been shown to be suboptimal for particle therapy [1]. A novel liquid fiducial marker, BioXmark® (Nanovi A/S, Kgs. Lyngby, Denmark), was found to visible on x-ray, (conebeam)CT, and MRI, and to hardly interfere with particle beam irradiation [1-3]. The aim of this study was to assess the visibility and severity of imaging artefacts of BioXmark® in a tissue-equivalent phantom of the upper abdomen.

Material and Methods
In a dedicated phantom of the upper abdomen (CIRS, Norfolk, VA), including liver, vertebrae and soft tissue mimicking material, different radiopaque component concentrations (67%, 100%, 133%, 167% in relation to the currently available product), and quantities (25µl, 50µl, 100µl, 150µl) of BioXmark® were deposited at equi-distance in a gelatine-filled vial and inserted at the putative site of the pancreas. These vials were subjected to kV-X-ray (80; 100), single- and dual-energy computed tomography (SECT/DECT; Somatom Definition AS, Siemens Healthineers, Erlangen, Germany) and conebeam-CT (CBCT; VARIAN, Palo Alto, CA). The significant visibility of the markers on kV-imaging was assessed in coronal and sagittal projection using a contrast-to-noise-ratio (CNR) of at least 2.0 [4]. Moreover, a radiation oncologist, a medical physicist and two radiotherapy technicians scored the marker visibility using a four-point scale (0=not visible; 3=visible, suitable for clinical use). The degree of artefacts was determined calculating the Streaking Index (SI; [4]).

Results
Except for small marker quantities of low radiopaque component concentration, all BioXmark® passed the CNR-threshold (Fig. 1). Even though the experts scored the visibility of BioXmark® with a 2.5, only the 25µl with 67% radiopaque component concentration was deemed invisible (score: 1; Fig. 1). The artefacts seen on CBCT, SECT and DECT were small, with SI-values ranging from 8.2-52.2, 9.1-44.2, and 4.4-50.1, respectively (Fig. 2).

Conclusion
For targets in the upper abdomen, the trade-off between visibility and imaging artefacts is optimal using 50µl or 100µl of the BioXmark® at 100% or 133% radiopaque component concentrations. Monte-Carlo simulations on the interference of the different concentrations of BioXmark® with proton beam irradiation are ongoing.

References
[1] Rydhög JS et al. Radiother Oncol 2017;122:393-399
[2] Schneider S et al. Med Phys 2018;45:37-47
[3] De Roover R et al. Med Phys 2018;2205-2217
[4] Rydhög JS et al. Med Phys 2015;42:2818-2826

  • Poster (Online presentation)
    ESTRO 2020 - 39th Congress of the European Society for Radiotherapy and Oncology, 03.-07.04.2020, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29854
Publ.-Id: 29854


Lichtinduzierte Freisetzung von Kohlenstoffmonoxid aus Ruthenium(II)-Komplexen und deren biologische Bewertung

Geri, S.

Der Schwerpunkt der vorliegenden Masterarbeit liegt auf der Synthese neuer Ru(II)-basierter PhotoCORMs der Summenformel [RuL(CO)2Cl2] (L = Ligand). Als Liganden sollen 4,4‘-substituierte Derivate des 2,2‘-Bipyridins verwendet werden. 2,2‘-Bipyridine sind zweizähnige Lewis-Basen mit σ-Donor-Charakter, die mit Ruthenium in der Oxidationsstufe II stabile Chelatkomplexe bilden. Geeignete Funktionalisierung und strukturelle Erweiterung an den 4,4‘-Positionen des 2,2‘-Bipyridins soll den entstehenden PhotoCORMs neue Eigenschaften verleihen.
Der Schwerpunkt dieser Masterarbeit wird zunächst auf die Synthese eines Alkin-funktionalisierten PhotoCORMs gelegt. Alkin-Gruppen stellen eine Basis für die Bindung eines Azid-funktionalisierten Peptides mittels kupferkatalysierter Azid-Alkin 1,3-dipolarer Cycloaddition (CuAAC, „Click-Reaktion“) dar. Peptide geeigneten Designs können eine erhöhte Spezifität gegenüber bestimmtem Zelltyp induzieren, sodass das Peptid-funktionalisierte PhotoCORM bevorzugt in diesen Zellen angereichert wird.
Auch im zweiten Teil dieser Masterarbeit steht die Synthese eines Alkin-funktionalisierten PhotoCORMs im Vordergrund, allerdings soll hierbei der Fokus auf dessen Weiterfunktionalisierung mit einem Fluoreszenzfarbstoff gelegt werden. Durch direkte Substitution eines Fluoreszenzfarbstoffes am Grundgerüst des Bipyridins soll eine Erweiterung des bestehenden π-Systems erzielt werden. Als Folge werden eine bathochrome Verschiebung der MLCT-Bande, größere Quantenausbeuten sowie starke Fluoreszenz des neu synthetisierten PhotoCORMs erwartet. Letztere soll eine einfache visuelle Verfolgung der zellulären Aufnahme des in vitro verabreichten PhotoCORMs ermöglichen. Alternativ zu dieser Herangehensweise soll ein PhotoCORM synthetisiert werden, bei dem der Fluoreszenzfarbstoff mit dem Bipyridin-Grundgerüst über einen Amid-Linker verbunden ist.

Keywords: CO; Ru(II)-Komplexe; Therapie

  • Master thesis
    TU Dresden, 2019
    Mentor: Dr. Manja Kubeil / Dr. habil. Constantin Mamat
    108 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29852
Publ.-Id: 29852


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