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35179 Publications

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

Rydlewicz, W.; Fridman, E.; 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

Related publications

  • ASTRID-DYN3D (Id 32353) HZDR-primary research data are used by this (Id 29937) publication
  • Contribution to proceedings
    Physics of Reactors PHYSOR 2020, 29.03.-02.04.2020, Cambridge, United Kingdom, 978-1-5272-6447-2
  • Open Access Logo European Physical Journal Web of Conferences 247(2021), 02028
    DOI: 10.1051/epjconf/202124702028

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

Related publications

  • Contribution to proceedings
    Physics of Reactors PHYSOR 2020, 29.03.-02.04.2020, Cambridge, United Kingdom
  • Open Access Logo European Physical Journal Web of Conferences 247(2021), 02001
    DOI: 10.1051/epjconf/202124702001

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


Fine or coarse particle flotation in mineral processing? A critical assessment of the recent flotation developments

Hassanzadeh, A.; Safari, M.

Recent advances in the froth flotation circulate around whether fine or coarse particulate systems. After a century of flotation’s application to mining industry, two completely different strategies have been introduced for processing purposes. One includes pursuing the treatment of fine particles due to reduction of cut-off grades, facing with complex and poly-mineralized ores as well as achieving the acceptable degree of mineral liberation degrees using e.g. pneumatic cells such as Jameson, Imhof, oscillating grid flotation cell (OGC), Concorde and reactor/separator cell. The other school of mind deals with the coarse particle processes mainly owing to the low required energy usages employing e.g. flash, fluidized bed, hydrofloat, OGC, NovaCell and Reflux flotation cells.
These two believes have not been addressed in the literature at all. This study endeavours to evaluate these two ideologies critically considering existing technological elaborations, water and energy usages, material handling, maintenance, kinetics and circuit design. Finally, PGM, chromite and gold flotation processes were illustrated as fine treatment case studies comparing with the copper flotation given as an example of coarse flotation. It is revealed that the incorporation of coarse grinding apparatuses, mineralogical techniques together with the technologically applicable classification systems and adapted simulator tools are urgently needed for coarse flotation as the future requirement for mining industries. However, fine flotation may remain as the main focus of re-processing tailings.

Keywords: Flotation cells; Fine and coarse particles; Technology development; Kinetics

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-23.10.2020, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-29924
Publ.-Id: 29924


Recovery of iron from dry tailings dump of a processing plant using an efficient circuit

Gholami, H.; Habibollahzadeh, A.; Haghi, M.; Hassanzadeh, A.

More than half of the tailings dams worldwide contain valuable materials due to the poor performance of upstream processes. Iron ore processing plants are no exception and there has been always a transfer of iron to the tailings. This work aims to investigate the feasibility of producing a high yield product suitable for feed of the concentrate plant from the tailings dump of Zarand Steel Complex ore. For this purpose, five dumps with Fe average grade of 17-20% were studied and sampled. Six samples from each of the five dumps together with one sample from the mixture of them were taken. The representative samples were crushed by a roll crusher down to 6 mm and followed by a medium intensity magnetic separator (MIMS) and a rougher stage. The tailing of previous steps was removed and the product was concentrated by a low intensity magnetic separator (LIMS) in the cleaner stage. The product obtained was sieved by a 3 mm screen that the underflow was selected as the final product while its coarse-grained fraction was crushed by a roll crusher at the beginning of the circuit.
Experimental results showed that the iron reprocessing from tailings dumps was potentially associated with an increase of 20-25% in the iron content. The mass recovery obtained from each dump sample comprised of ca. 16- 22% with the iron grade of 40-45%. The mass recovery of the mixed dumps sample was about 20% with an average grade of 40%.

Keywords: Magnetic separator; iron grade; rougher and cleaner stages; tailings dumps

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-23.10.2020, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-29923
Publ.-Id: 29923


An improvement on selective separation by applying ultrasound to rougher and re-cleaner stages of copper flotation

Gholami, H.; Sajjadi, A.; Hassanzadehmahaleh, A.; Amini, S.; Behjat Jabbari, M.; Sanaie, S. M.

The ultrasonic treatment has been commonly used as a pre-treatment and rarely applied as an on-treatment technique to improve grade and recovery in froth flotation processes. This work aims at investigating the impact of ultrasonic wave under different conditions on a porphyry copper ore during the flotation of rougher and re-cleaner stages. For this purposes, four different operating configurations were examined as I) un-treated, II) only homogenizer, III) only ultrasonic bath and IV) homogenizer and ultrasonic bath. The ultrasonic vibration was generated during the flotation using a homogenizer (21 kHz, 1 kW) in froth zone and ultrasonic bath (35 kHz, 300 W) for the bulk zone. The rougher and re-cleaner flotation experiments were conducted at 4.2 L and 1 L Denver type mechanically agitation cells. In addition to the grade and recovery, the separation efficiency (S.E) and selectivity index (SI) criteria were used for evaluating the separation performance of the flotation trials. It was found out that combination of the ultrasonic bath and the homogenizer provided an absolute improvement of 4.0%±0.6 and 7.0%±0.5 of the S.E. compared to the untreated ore for rougher and re-cleaner stages, respectively. The detailed argument was discussed in this work regarding the role of US on both froth and bulk zone according to four configurations.

Keywords: Ultrasonic bath; homogenizer; rougher; re-cleaner; flotation; grade and recovery

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-23.10.2020, Cape Town, south Africa

Permalink: https://www.hzdr.de/publications/Publ-29922
Publ.-Id: 29922


The effect of ultrasound treatment on wettability and floatability

Hassanzadehmahaleh, A.; Haosheng, W.; Adrian, V. H.; Gülce, Ö.; Sondos, S. S. S. M. R.

Despite the three-decade study in the ultrasound (US) impact on mineral’s floatabilities, there is still not a clear image regarding its role on mineral surface characteristics. For this purpose, the current investigation studies the wettability, roughness and floatability characteristics of six mono-minerals i.e. quartz (strongly hydrophilic), cassiterite (hydrophilic), calcite (moderately hydrophilic), pyrite (slightly hydrophobic), chalcopyrite (fairly hydrophobic) and talc (strongly hydrophobic) to cover the entire spectrum of mineral hydrophobicity properties.
Ultrasound at variable amplitudes were supplied by an ultrasonic bath (35 kHz, 140/560 W, 1.5 A) and sonotrode Sonopuls (20 kHz, 200 W and 0.9 A). Sonopuls’s time (15, 30, 45, 60 and 90 s) and power levels (30, 60, 90, 120 and 180 W) as well as ultrasonic bath’s time (15, 30, 45 and 60 min) were evaluated while dissolved oxygen, temperature, conductivity and pH were monitored. Micro-flotation tests were carried out on the US pre-treated and during the ultrasound treatment. The wettability of the samples was analyzed by optical contour analysis (OCA). Surface morphology and topography were investigated by optical profilometry and atomic force microscopy (AFM) together with scanning electron microscopy (SEM).
The results obtained for the strongly/relatively hydrophobic and hydrophilic minerals confirm that the ultrasonic pre-treatment creates intensive rough surfaces inducing an increase on the mineral hydrophobicities. However, a longer ultrasonic time led to smoothening particle surface roughness and consequently reduced the mineral wetabilities/floatabilities. Naturally/slightly hydrophilic minerals behaved differently in the presence and absence of ultrasonic vibrations which were argued in detail.

Keywords: Ultrasound; wettability; floatability; roughness; contact angle

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-23.10.2020, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-29921
Publ.-Id: 29921


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.
ContactPerson: Neumann-Kipping, Martin; RightsHolder: Hampel, Uwe; DataManager: Bieberle, André

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.
ContactPerson: Neumann-Kipping, Martin; RightsHolder: Hampel, Uwe; DataManager: Bieberle, André

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.
ContactPerson: Neumann-Kipping, Martin; RightsHolder: Hampel, Uwe; DataManager: Bieberle, André

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.
ContactPerson: Neumann-Kipping, Martin; RightsHolder: Hampel, Uwe; DataManager: Bieberle, André

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.
Researcher: Neumann-Kipping, Martin; Researcher: Bieberle, Martina; Researcher: Wolf, Jan

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

  • Open Access Logo 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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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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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


Neuartige Calix[4]benzokronen zur Komplexierung von schweren Erdalkalimetallionen

Blumberg, M.

Der Fokus dieser Arbeit liegt auf der Synthese neuer Chelatoren für die Komplexierung der schweren Erdalkalimetallionen Sr2+, Ba2+ und Ra2+. Ein besonderes Augenmerk liegt hierbei auf den für die Krebstherapie interessanten Radiumisotopen 223Ra und 224Ra und dem SPECT-Nuklid 131Ba als Matched Pair. Strontium besitzt mit 89Sr ebenfalls ein in der Nuklearmedizin nutzbares Nuklid. Außerdem kann auf Grundlage der Untersuchung der drei Erdalkalimetalle der Einfluss des Ionenradius auf die Komplexierungseigenschaften der Chelatoren bewertet werden. Zudem soll auch die Komplexierung mit dem ebenfalls zweiwertigen Pb2+ untersucht werden. Der β--Strahler 212Pb wird in der Radiopharmazie als in vivo-Generator des kurzlebigen α-Strahlers 212Bi in der Immuntherapie genutzt. 212Pb kommt wie 224Ra in der natürlichen Zerfallsreihe des 232Th vor.
Für die Komplexierung der genannten Metallionen sollen neuartige Calix[4]kronen synthetisiert werden, die nach dem Vorbild von Zhou et al. mit sauren Sulfonamidseitenketten funktionalisiert sind. Vorherige Extraktionsexperimente unserer Arbeitsgruppe haben gezeigt, dass Derivate mit perfluorierten Isopropylresten am Sulfonamid die effektivste Extraktion von Ba2+ und Ra2+ erlauben. Daher sollen Derivate mit diesen Seitenketten synthetisiert werden.
In dieser Arbeit soll die Modifizierung der Kronenetherüberbrückung der Calixarenderivate untersucht werden. Dafür soll ein aromatisches System in Form einer Benzokrone in den Chelator eingebaut werden. Eine solche Benzokrone bietet gegenüber der Krone-6 den Vorteil, dass sie mit zusätzlichen funktionellen Gruppen ausgestattet werden kann, um daran biologisch aktive Vektormoleküle zu binden. Die Einführung einer Amin-, Azid- oder Säurefunktion ermöglicht eine Kupplung an Peptide, Proteine oder Antikörper.

Keywords: Calixarene; Barium; Radium; Alpha-Therapie

  • Master thesis
    TU Dresden, 2019
    Mentor: Dr. habil. Constantin Mamat
    135 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29851
Publ.-Id: 29851


Neuartige Käfigverbindungen zur Komplexierung von Barium und Radium

Eiselt, E.

Calixarene sind eine Gruppe von Verbindungen, welche eine vielseitige Nutzung zur Komplexierung von Ionen und kleinen Molekülen ermöglichen. Unter anderem können sie, durch die Einführung von Donorgruppen als Chelatoren für Gruppe-2-Metalle eingesetzt werden. Für eine zielgerichtete interne α-Therapie mit den therapeutisch zugänglichen Radiumisotopen 223Ra und 224Ra, ist es von Nöten, diese ausreichend stabil zu komplexieren. Damit soll eine unerwünschte Freisetzung und Anreicherung an anderen Orten im Körper weitgehend unterbunden werden.
Im Rahmen dieser Arbeit sollen Chelatoren entwickelt werden, welche Ba2+ als Surrogat für Ra2+ stabil und selektiv binden und eine weitere Funktionalisierung mit biologisch aktiven, zielsuchenden Molekülen zulassen. Auf Basis, der von Steinberg et al. veröffentlichten Ergebnisse sollen Verbindungen synthetisiert werden, welche statt einer Krone-6-Überbrückung offenkettige Etherfunktionen als Strukturmerkmal aufweisen. Dabei sollen sowohl Derivate mit zyklischen Amidfunktionen, als auch mit verschiedenen fluorierten Sulfonamiden funktionalisierte Verbindungen hergestellt werden. Weiterhin sollen Vorstufen für Liganden synthetisiert werden, welche über eine kurze Seitenkette mit zyklischen tertiären Aminen verfügen.
Alle Liganden sowie deren Vorstufen sollen mittels NMR-Spektroskopie und Massenspektrometrie eingehend charakterisiert werden. Die fertiggestellten Chelatoren werden mit der Methode der UV-Vis-Titration hinsichtlich ihrer Komplexbildungseigenschaften mit Ba2+, Sr2+ und Pb2+ untersucht. Die ermittelten Komplexstabilitäten sollen mit den analogen Krone-6-überbrückten Derivaten verglichen werden.

Keywords: Calixarene; Barium; Radium; Alpha-Therapie

  • Master thesis
    HTW Dresden, 2019
    Mentor: Dr. habil. Constantin Mamat (HZDR) / Prof. Dr. Marina Vogel (HTW)
    94 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29850
Publ.-Id: 29850


The High-Energy-Density Physics at FAIR Collaboration: Unique Capabilities for HEDM Science

Schoenberg, K.; Bagnoud, V.; Blazevic, A.; Fortov, V. E.; Gericke, D. O.; Golubev, A.; Hoffmann, D. H. H.; Kraus, D.; Lomonosov, I. V.; Mintsev, V.; Neff, S.; Neumayer, P.; Piriz, A. R.; Redmer, R.; Rosmej, O.; Roth, M.; Schenkel, T.; Tahir, N. A.; Varentsov, D.; Zhao, Y.

The High-Energy-Density Science collaboration at the Facility for Antiproton and Ion Research (HED@FAIR) will utilize the World’s highest intensity relativistic beams of heavy nuclei to uniquely create and investigate highly energetic and dense-plasma states of cubic millimeter sized matter for durations of approximately 100 ns. Four principal themes of research have been identified by the HED@FAIR collaboration: Properties of materials driven to extreme conditions of pressure and temperatures, Shocked matter and material equation of state (EOS), Basic properties of strongly-coupled plasma and warm dense matter, and Nuclear photonics with a focus on the excitation of nuclear processes in plasmas, laser-driven particle acceleration, and neutron production. Collaboration research will develop over the next decade as the FAIR project is completed and the heavy ion beam and experimental capabilities evolve. The so-called "FAIR Phase 0" experiments officially began in 2018 to test the components and detectors prepared for FAIR. The HEDM Phase-0 research effort will utilize the existing and enhanced GSI infrastructure of the SIS-18 synchrotron coupled with the PHELIX laser. The FAIR experimental program, presently scheduled to begin in 2025, will commence the use of the SIS-100 synchrotron coupled with new experimental and diagnostic infrastructure to realize the envisaged unique HEDM research program.

Permalink: https://www.hzdr.de/publications/Publ-29849
Publ.-Id: 29849


Combining trace element measurements with analytical uncertainties for a better characterization of plant geochemistry

Pospiech, S.; van den Boogaart, K. G.; Tolosana Delgado, R.; Wiebke, F.

Trace element analysis in plants is often subject to a high measurement uncertainty and accordingly the variability of the geochemical composition of trace elements in plants is – especially close to the detection limit - very high. In this contribution we propose a method to estimate models respecting the uncertainty and capable of treating values below and around the detection limit. We suggest to use all measurement signals, but report it alongside with the individual uncertainties for each value. The standard descriptive and statistical analysis mainly ignores these uncertainties by simply reporting if a signal value is below the detection limit (BDL) or above. BDL-values are either ignored or replaced by an arbitrary small value. In both cases this can substantially distort the analysis. Our methodology could substantially reduce this bias.
In order to take into account the constraints of concentration data we use methods of compositional data analysis, i.e. represent population by their compositional expectation, typically represented in an log-ratio transform. The uncertainties are incorporated in statistical methods by estimating the reported value not by a simple mean, but by an estimation procedure using the model assumption that a signal observed in the geochemical analysis has two components of variability: i) A population spread that could e.g. be modeled by a compositional distribution, and ii) a signal variability to be modeled according to the measurement instrument, typically assuming additive normal or Poisson errors and calibration errors. The parameters for the model of the signal variability are estimated from blind values, duplicate analysis as well as precision and accuracy of repeatedly measured reference samples.
We will present the change of results produced by the methodology over a standard approach with reporting BDL-values by demonstrating the applicability of the methodology with simulated data and a dataset of rye, ryegrass, faba bean, triticale and amaranth from two agricultural test sites in Germany. All samples had been treated by a four-acid digestion and analyzed by ICP-MS and ICP-OES.

Keywords: plant geochemistry; compositional data; uncertainty; analytics; ICP-MS; ICP-OES; Bayesian statistics

  • Open Access Logo Poster
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29847
Publ.-Id: 29847


Microresonator-integrated magnetic tunnel junctions allowing for thermal gradient sign reversal designed using COMSOL simulations

Cansever, H.; Lindner, J.; Huebner, T.; Niesen, A.; Reiss, G.; Fassbender, J.; Deac, A. M.

In magnetic tunnel junctions (MTJs), it was theoretically predicted that magnetization dynamics can be induced by thermal gradients via thermal-spin transfer torques (T-STTs), similar to STTs induced by applied voltages[1]. We recently proposed an approach based on microresonators (µR) in order to detect T-STT terms acting on the free layer of an MTJ device by means of investigating the ferromagnetic response of an MTJ exposed to a cw laser in open-circuit conditions. The linewidth of the ferromagnetic signal is modified by the damping-like torque induced by thermal gradient, while the frequency is subject to changes induced by the field-like torque[2]. Here, we used COMSOL simulations to determine the temperature profile of Co2FeAl/MgO/CoFeB MTJs, when the MR structure is considered, see Fig 1. In this design, the structure is defined with laterally larger Co2FeAl (CFA) layer below CoFeB (CFB) layer. This allows for the laser beam to be focused on the CFA layer surface, in order to heat the bottom electrode of the MTJ rather than the top, as commonly investigated[3-6]. The temperature of both layers and temperature differences (ΔT) as a function of lateral width are shown in Fig 2. The temperature on the CFA layer decreases laterally about 25K towards to center of the structure and yields a ΔT over the barrier of about 680mK, if a gold pad is placed on the CFA layer, in the position where the laser is shined on (Fig 2). Without the gold pad and leaving the MgO on the CFA unpatterned, the ΔT over the barrier is reduced almost by factor of 2, and is estimated to be around 320mK and 270mK respectively. When both layers have gold contacts, ΔT drops to 20mK (Fig 2). Consequently, the magnitude and the sign of ΔT over the barrier can be engineered by appropriately designing the design of the device, which would allow for T-STTs induced by thermal gradients of different sign to be investigated experimentally in a single MTJ.

*Figure 1 2D sketch of an MTJ structure considered for COMSOL modelling, where the loop of µR was taken into account and only the bottom layer is exposed to the laser.

*Figure 2 Temperature profile of the MTJ versus lateral size, ΔT dependence on designed structure.
References
[1] Jia X, Xia K and Bauer G E W 2011 Phys. Rev. Lett.107 176603
[2] H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac, 2018 J. Phys. D: Appl. Phys. 51 22400
[3] N. Liebing, S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker, H. W. Schumacher, 2011, Phys. Rev. Lett. 107, 177201.
[4] J. C. Leutenantsmeyer, M. Walter, V. Zbarsky, M. Münzenberg, R. Gareev, K. Rott, A. Thomas, G. Reiss, P. Peretzki, H. Schuhmann, M. Seibt, M. Czerner, C. Heiliger, 2013, Spin 3, 1350002.
[5] A. Boehnke, M. Milnikel, M. Ehe, C. Franz, V. Zbarsky, M. Czerner, K. Rott, A. Thomas, C. Heiliger, G. Reiss, M. Münzenberg, 2015, Sci. Rep. 5, 8945.
[6] H. Cansever, J. Lindner, T. Huebner, A. Niesen, G. Reiss, J. Fassbender, A. M. Deac, 2019, IEEE Trans.Magn. 51(17) Early Access

Keywords: COMSOL; thermal spin-transfer torque; magnetic tunnel junction; microresonator

  • Lecture (Conference)
    Annual Conference on Magnetism and Magnetic Materials, MMM Las Vegas 2019, 04.-08.11.2019, Las Vegas, USA

Permalink: https://www.hzdr.de/publications/Publ-29846
Publ.-Id: 29846


Spectral Random Masking für PIV in Mehrphasenströmung

Anders, S.; Noto, D.; Eckert, S.

Im vorliegenden Beitrag wird eine neuartige Maskierungsmethode für die Particle Image Velocimetry (PIV) von Mehrphasenströmungen vorgestellt. Mit diesem neuen Ansatz können Geschwindigkeitsfelder einer unmaskierten Partikelfraktion (z. B. PIV-Tracer) unabhängig von der Bewegung einer zweiten, maskierten Partikel-Fraktion (z. B. Blasen oder Feststoffpartikel) bestimmt werden.
Ausgehend von einer segmentierten Bilderserie in welcher die verschiedenen Partikelfraktionen für alle Einzelbilder detektiert wurden, werden verschiedene Maskierungsverfahren diskutiert. Hierbei werden die Probleme, welche durch Standardverfahren für den Fall dynamischer Maskierung unter realen Belichtungsbedingungen entstehen besonders hervorgehoben. Als entsprechende Lösung stellen wir unseren Ansatz des Spectral Random Masking (vgl. Anders et al. 2019) vor, bei welchem maskierte Bildbereiche durch spektral angepasste, zufällige Intensitätsverteilungen ersetzt werden. Damit sollen die maskierten Bereiche für eine anschließende PIV-Analyse “unsichtbar” gemacht werden. Die Vorteile dieser Methode gegenüber konventionellen Maskierungsverfahren werden anhand eines Modellexperimentes dargestellt, bei welchem wässrige Ammonium-Chlorid Lösungen (NH₄Cl(aq)) durch Unterkühlung erstarrt werden. Dabei treten unter anderem verschiedene Konvektionsströmungen zeitgleich mit kolumnarer und äquiaxialer Kristallisation von NH₄Cl auf.

Keywords: Bild Segmentierung; dynamische Bildmaskierung; Mehrphasenströmung; Particle Image Velocimetry

  • Open Access Logo Contribution to proceedings
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland
    Spectral Random Masking für PIV in Mehrphasenströmung, 978-3-9816764-6-4, 20.1-20.7
  • Lecture (Conference)
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-29844
Publ.-Id: 29844


Comparative Study of Monosalen Complexes with Tetravalent Actinides

Radoske, T.

Two series of tetravalent actinide complexes with the salen ligand were synthesized. The coordination sphere supports two labile positions for small neutral solvent molecules, which were filled with either methanol or acetonitrile molecules. Solid state characterization reveals additional interactions of U(IV) and Np(IV) with the organic ligands.

  • Poster
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29842
Publ.-Id: 29842


Tetravalent Actinide N-Donor Affinity in Monosalen Complexes

Radoske, T.

Complexes with a range of differently substituted pyridines were synthesized using tetravalent actinides. The affinity of actinides for N-donors is discussed.

  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29841
Publ.-Id: 29841


Tetravalent Actinide Complexes with Schiff bases: Comparison with Isostructural Transition Metal and 4f Element Compounds

Radoske, T.

Isostructural complex series with tetravalent actinides were characterized and results are discussed for observable trends.

  • Lecture (others)
    FENABIUM Projekttreffen, 27.02.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29840
Publ.-Id: 29840


Amidinates as Versatile Ligands for Tetravalent Actinides

Schöne, S.; März, J.; Kaden, P.

A summary of work based on the synthesis and characterization of tetravalent actinide amidinates is given. Structural features are compared in solid and in solution phase. Comprehensive quantum chemical calculations support the findings.

  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29839
Publ.-Id: 29839


Relative Stability of Actinide(IV) Bissalen Complexes

Radoske, T.; Schöne, S.; Kloditz, R.; März, J.; Stumpf, T.; Ikeda-Ohno, A.

Schiff bases of salen-type have a wide range of applications and have proven to be a versatile ligand system for the investigation of complexation behavior. In particular, due to its hetero N/O-donor coordination properties, the salen ligands are often considered as a simplified analog of naturally-occuring organic ligands, which have potential implications for the migration behavior of radionuclides under geochemical conditions We have investigated the complexation behavior of salen ligands (L, H2salen = N,N’-bis(salicyliden)ethylenediamine) towards tetravalent metal cations and synthesized a series of complexes of tetravalent actinides (Th, U, Np, and Pu) as well as analogous tetravalent metals (Zr, Ce, and Hf). In all cases, the ligand forms bissalen ML2 complexes (M = metal). When the ML2 compound is treated with an equimolar amount of the metal tetrachloride, some metals also form M:L = 1:1 complexes with additional two Cl- in the primary coordination shell to form MLCl2. Based on this observation, we assume a trilateral equilibrium between the starting materials of metal tetrachlorides, the 1:1, and the 1:2 complex (Scheme 1), being similar to the study by Calderazzo et al.[1] This equilibrium holds even if ML2 is insoluble in the reaction medium and, therefore, we can apply the exchange reactions to determine the relative stability of the An(IV)-bissalen complexes when more than one types of metal are used. The relative stability of the complexes can then be directly compared to the results from quantum chemical calculations based on DFT. Hence, this study aims to understand the reaction mechanism and stability of salen complexes with a series of tetravalent metals, in particular tetravalent actinides (An(IV)).

  • Lecture (Conference)
    Fachtagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29838
Publ.-Id: 29838


Tetravalent Actinide and Transition Metal Amidinates – Trends and Perspectives

Schöne, S.

A series of tetravalent actinide amidinates with chiral (S)-HPEBA ligands is presented. The complexes are structurally characterized in solid state and in solution. Further reactivity is proved by reduction to trivalent homoleptic complexes.

  • Lecture (others)
    Challenges in f-element chemistry - Bilaterales Meeting HZDR/KIT, 10.01.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29837
Publ.-Id: 29837


Amidinates – Versatile Ligands for Tetravalent Actinides

Schöne, S.; Kloditz, R.; März, J.; Kaden, P.; Patzschke, M.; Roesky, P. W.; Stumpf, T.

Amidinates, a group of heteroallylic nitrogen donor ligands of type [RC(NR‘)2]–, have been used in a widespread manner in coordination chemistry and organometallics. They usually coordinate in a N,N’-bidendate mode to almost all metals in the periodic table including lanthanides and early actinides. The steric and electronic properties can be easily tuned by varying the substituents R and R’ to make them a valuable class of spectator ligands.
We have expanded the rich chemistry of amidinates to the tetravalent transuranic elements Np and Pu and compared the results to the earlier actinides Th and U and other tetravalent analogues. The focus of our investigations lies in the comprehensive characterization of An(IV) complexes with amidinates, both in the solid state and in solution. A comparison within the series enables us to perform a detailed structural analysis, which is complemented by high-level quantum chemical calculations to gain deeper insight into the bonding properties of tetravalent actinides (An(IV)).
Several An(IV) amidinate complexes have been synthesized including a series of chiral complexes using the chiral benzamidine, (S,S)-N,N‘-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA) [1]. We obtained the first enantiopure amidinate complexes [AnIVCl((S)-PEBA)3] (An = Th, U, and Np) as well as the analogous Ce(IV) compound, a chemical analog of An(IV). The tris-amidinate complexes have been structurally characterized in solid state and in solution showing a comparable complex geometry.
The presence of one chloro ligand in addition to three stabilizing amidinate ligands in the An coordination sphere points to complex reactivity. This could indeed be demonstrated by reduction to homoleptic trivalent actinide amidinates [An((S)-PEBA)3] (An = U, Np) as well as halogen exchange with pseudo-halogenides (i.e. N3–).

  • Lecture (Conference)
    GdCh Fachgruppentagung Nuklearchemie, 25.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29836
Publ.-Id: 29836


La–Sr–Mn–Co–O Films for High Pulsed Magnetic Field Measurements at Cryogenic Temperatures

Rudokas, V.; Zurauskiene, N.; Lukose, R.; Kersulis, S.; Stankevic, V.; Pavilonis, D.; Balevicius, S.; Plausinaitiene, V.; Vagner, M.; Skapas, M.; Arsenijevic, S.

The magnetoresistance of nanostructured La1−xSrx(Mn1−yCoy)zO3±δ (La–Sr–Mn–Co–O) films with substitution of Co for Mn with amount of Co/(La + Sr) = 0.12 and different Mn excess Mn/(La + Sr) = 1.05, 1.07, nd 1.11 was investigated at temperatures of 4–230 K in pulsed magnetic fields up to 60 T. It was found that the manganite–cobaltite films exhibit larger magnetoresistance in comparison with manganite films without Co doping. The largest magnetoresistance values and sensitivity to the magnetic field are obtained for La–Sr–Mn–Co–O films having Mn Content close to the stoichiometric ratio for manganites: Mn/(La + Sr) = 1.05. It was found that magnetoresistance at high fields (20–60 T) has a minimum at (50–80 K) and increases with the decrease of temperature. The possibility to use these films for magnetic field measurements at cryogenic temperatures is demonstrated.

Permalink: https://www.hzdr.de/publications/Publ-29835
Publ.-Id: 29835


Microorganisms for biological remediation of uranium contaminated sites – a microscopic and spectroscopic approach

Krawczyk-Bärsch, E.; Gerber, U.; Müller, K.; Rossberg, A.; Merroun, M. L.

Environmental pollution by metals and radionuclides is one of the biggest challenges. For remediation of contaminated environments after activities such as uranium mining and uranium processing, microorganisms could be important due to their ability to immobilize radionuclides and heavy metals. Bioremediation strategies can be improved by a better understanding of binding mechanisms on the molecular level. Therefore, we applied uranium interaction experiments with Acidovorax facilis, an aerobic, Gram-negative Betaproteobacteria, which is commonly found in soils but also in the mine water of uranium mines. For spectroscopic and microscopic studies, kinetic uranium(VI) sorption experiments were performed under aerobic conditions with an Acidovorax facilis strain by adjusting an initial uranium(VI) concentration to 0.1 mM to the batch culture at a neutral pH range. A high-resolution image of the cellular localization of uranium by A. facilis was achieved by using electron microscopy (STEM/HAADF). The elemental distribution analysis of phosphorus and uranium clearly indicates that uranium is entirely present in the cell membrane and only with minor amounts in the poly-phosphate granules (PPGs) during the first hour of incubation (s. Fig.1). By cryo-Time-resolved laser-induced fluorescence spectroscopy (cryo-TRLFS) studies it was shown that the local coordination of uranium species associated with the cells depends upon time contact. Uranium is bound mainly to phosphate groups of lipopolysaccharide [1] at the outer membrane within the first hour. And, that both, phosphoryl and carboxyl functionality groups of LPS and peptidoglycan of A. facilis cells may effectuate the removal of high uranium amounts from solution at 24–48 h of incubation. These results support those obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS), where a relative short average U-Oeq bond length of 2.35 Å was observed for the uranium(VI) interaction with lipopolysaccharide indicating a binding of the uranium(VI) via organic phosphate groups in a monodentate fashion. Our results clearly demonstrate that A. facilis may play an important role in predicting the transport behaviour of uranium in the environment and that the results will contribute to the improvement of bioremediation methods of uranium-contaminated sites.

Keywords: uranium; sorption; Acidovorax facilis; STEM; EXAFS

  • Lecture (Conference)
    3rd International Caparica Conference on Polutant Toxic Ions and Molecules, 04.-07.11.2019, Costa da Caparica, Portugal

Permalink: https://www.hzdr.de/publications/Publ-29833
Publ.-Id: 29833


Imaging artefacts during simultaneous in-beam MR imaging and proton pencil beam irradiation

Gantz, S.; Hietschold, V.; Schneider, S.; Hoffmann, A. L.

The targeting precision of proton therapy is expected to benefit from real-time MRI guidance. We developed a setup of a first prototype in-beam MRI scanner with a proton pencil beam scanning nozzle. Dipole magnets in the nozzle used for beam steering produce time-dependent magnetic fringe fields that may interfere with the MR image acquisition. In this study, we show that vertical beam steering shows no degradation of the MR image quality, whereas horizontal beam steering introduces severe ghosting artefacts in phase encoding direction. The origin of these artefacts is unraveled and strategies to eliminate or correct these artefacts are proposed.

  • Contribution to proceedings
    ISMRM 2020, 18.04.2020, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-29832
Publ.-Id: 29832


Superconductivity of Organic Charge-Transfer Salts

Wosnitza, J.

Forty years after the discovery of the first organic superconductor, the nature of the superconducting state in these materials is still not fully understood. Here, I present an overview on the historical developments and current knowledge on this topic for the quasi-one- and quasi-two-dimensional (2D) organic charge-transfer salts. Thereby, I focus on the prototype materials based on the donor molecules tetramethyltetraselenafulvalene (TMTSF) and bisethylenedithio-tetrathiafulvalene (BEDT-TTF or ET for short). 2D organic superconductors based on the latter molecule are found to show Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states at high magnetic fields and low temperatures. Thermodynamic and nuclear magnetic resonance data give robust evidence for the existence of this FFLO state with modulated order parameter.

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Permalink: https://www.hzdr.de/publications/Publ-29831
Publ.-Id: 29831


A numerical simulator for modeling the coupling processes of subsurface fluid flow and reactive transport processes in fractured carbonate rocks

Yuan, T.; Wei, C.; Zhang, C.-S.; Qin, G.

Water–rock interactions can alter rock properties through chemical reactions during subsurface transport processes like geological CO2 sequestration (GCS), matrix acidizing, and waterflooding in carbonate formations. Dynamic changes in rock properties cause a failure of waterflooding and GCS and could also dramatically affect the efficiency of the acidizing. Efficient numerical simulations are thus essential to the optimized design of those subsurface processes. In this paper, we develop a three-dimensional (3D) numerical model for simulating the coupled processes of fluid flow and chemical reactions in fractured carbonate formations. In the proposed model, we employ the Stokes–Brinkman equation for momentum balance, which is a single-domain formulation for modeling fluid flow in fractured porous media. We then couple the Stokes–Brinkman equation with reactive-transport equations. The model can be formulated to describe linear as well as radial flow. We employ a decoupling procedure that sequentially solves the Stokes–Brinkman equation and the reactive transport equations. Numerical experiments show that the proposed method can model the coupled processes of fluid flow, solute transport, chemical reactions, and alterations of rock properties in both linear and radial flow scenarios. The rock heterogeneity and the mineral volume fractions are two important factors that significantly affect the structure of conductive channels.

Keywords: reactive-transport; fracture evolution; mineral dissolution; fractured carbonate formations

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Permalink: https://www.hzdr.de/publications/Publ-29830
Publ.-Id: 29830


Novel 2-fluoropyridinyl analogs of FACH and biological evaluation of one potential radioligand for imaging of monocarboxylate transporters (MCTs) with PET

Sadeghzadeh, M.; Wenzel, B.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Teodoro, R.; Jonnalagadda, S.; Jonnalagadda, S. K.; Mereddy, V. R.; Drewes, L. R.; Brust, P.

Objective: MCT1-4 are involved in several diseases, particularly in cancer. [18F]FACH has recently been developed as a novel MCT-targeting imaging agent (1), which could be used for monitoring MCT-based treatment approaches. With the aim to develop a similar potent radiotracer with higher brain permeability for future brain tumor studies, we designed structurally modified analogs of FACH possessing increased lipophilicity.

Methods: Two analogs of FACH (I and II) were synthesized by introduction of a 2-fluoropyridinyl moiety via Buchwald-Hartwig cross coupling reaction. Inhibition of MCT1 was measured by [14C]lactate uptake assay using rat brain endothelial cells and analog I with higher inhibition was selected to synthesize corresponding precursor used for radiofluorination by aromatic nucleophilic substitution. LogD7.4 of [18F]I was experimentally determined in the n-octanol-PBS system. In vitro autoradiography and dynamic PET studies of [18F]I were performed in CD-1 mice.

Results: The analogs I and II showed a moderate MCT1 inhibition with IC50 values of 118 and 274 nM, respectively. [18F]I was obtained with radiochemical yields of 73±12% (n=4, non-isolated) and a high radiochemical purity of > 98%. A logD7.4 value of 0.816 was achieved for [18F]I, which was 2-fold higher than that for [18F]FACH. By in vitro autoradiography in cryosections of the mouse kidney, nearly complete displacement of [18F]I by 10-5 M CHC-Na was observed. In vivo, similar to [18F]FACH, a low uptake of [18F]I in the brain without significant washout was found with an almost constant SUV of 0.15 between 15 and 60 min p.i.

Conclusion: Despite a higher lipophilicity of [18F]I compared to [18F]FACH, the brain uptake of [18F]I was in a similar low range. However, the high and specific uptake of the new radiotracer in the kidneys suggests suitability of [18F]I for detecting MCTs’ expression in vivo.

References: (1) Sadeghzadeh M, et al. J Label Compd Radiopharm.2019; 62: 411-424.

  • Lecture (Conference) (Online presentation)
    58. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN2020), 22.-25.04.2020, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-29829
Publ.-Id: 29829


Preclinical in vivo evaluation of [18]FACH in piglets: A new radiotracer for imaging of monocarboxylate transporters (MCTs)

Gündel, D.; Sadeghzadeh, M.; Wenzel, B.; Sattler, B.; Deuther-Conrad, W.; Kranz, M.; Toussaint, M.; Ludwig, F.-A.; Moldovan, R.-P.; Teodoro, R.; Sabri, O.; Brust, P.

Objective: Recently, we developed [18F]FACH as the first radiolabeled inhibitor of MCTs for potential tumor imaging (1). Encouraged by the very promising results in mice, showing the specific binding/transport of [18F]FACH in kidneys combined with high in vivo stability, herein we report on the biological evaluation of this radiotracer in piglets.

Methods: Biological evaluation was performed in 6 piglets (Landrace, 19.9±3.0 kg). The blocking experiments (n=3) were conducted using sodium α-cyano-4-hydroxycinnamate (α-CHC-Na, 25 mg/kg) administered i.v. 10 min prior to tracer application. The animals were anesthesized (ketamin/midazolam) and scanned by a SIEMENS Biograph mMR PET/MRI-system up to 60 min p.i. of 295±28 MBq [18]FACH via ear vein. The reconstructed list-mode PET-data were analyzed utilizing the PMOD Software. In vivo metabolite analysis was performed using plasma isolated from arterial blood samples (5, 15, 30, 45 and 60 min) and samples of homogenized kidney by semi-preparative radio-HPLC after deproteinization by ACN/H2O (9:1).

Results: In contrast to mouse, a rather fast metabolism of the radiotracer was observed in piglet. Five and 30 minutes after injection, the intact tracer was found to represent 50±13% and 12±6% of total plasma activity, respectively. Metabolite analysis revealed 48% of intact tracer in kidney cortex at 60 min p.i. Despite the fast metabolism, the PET scan results showed comparable selective kidney uptake of [18F]FACH in piglets as in mice. The blocking experiments revealed a reduction of this uptake to about 72% after pre-injection of α-CHC-Na.

Conclusion: The high kidney uptake of [18F]FACH obtained in both mice and piglets together with high inhibition by α-CHC-Na, specific inhibitor of MCT, provide evidence that the new MCT-targeting radiotracer could be proven in ongoing studies to be useful for imaging of MCTs expression with PET.

  • Lecture (Conference) (Online presentation)
    58. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN2020), 22.-25.04.2020, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-29827
Publ.-Id: 29827


X-ray spectrometer simulation code with a detailed support of mosaic crystals

Smid, M.; Pan, X.; Falk, K.

We present a newly developed ray tracing code called mmpxrt, dedicated to study and design x-ray crystal optics, with a special focus on mosaic crystal spectrometers. Its main advantage over other currently available ray tracing codes is that it includes detailed and benchmarked algorithm to treat mosaic crystals, especially HOPG and HAPG (Highly Oriented / Annealed Pyrolitic Graphite). The code is dedicated primarily to study crystal spectrometers, therefore their implementation is very straightforward, and the code has mostly automatic evaluation of their performance. It can, however, be used universally to study other crystal instruments, like monochromators, mirrors, and analyzers.
The code is publicly available, written in Python3 and is distributed as a Python library with test cases included.

Keywords: mossaic crystal; x-ray spectroscopy; raytracing; python

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  • Secondary publication expected from 31.12.2021

Permalink: https://www.hzdr.de/publications/Publ-29826
Publ.-Id: 29826


Population balance modelling of isothermal and non-isothermal bubbly flows

Liao, Y.

In bubbly flows, bubble size may vary with time and space as the result of coalescence and breakage, shrinkage and growth due to mass and/or heat transfer as well as other dynamic and transport processes occurring at the interface. One major task and challenge in modelling of bubbly flows is to reconstruct these processes and trace the change of local bubble size, since it is crucial in affecting the rate of all interfacial transfers. The population balance equation provides the basis for the description of the dynamics of particulate systems. It has become of great interest in a number of scientific disciplines or application fields. Different forms of the population balance models have been presented, and they all allow one to take into account above bubble size change mechanisms through so-called kernels. Nevertheless, continuous efforts are needed in developing, calibrating and validating the kernels. In addition, reliable and efficient solution of the population balance equation is not trivial. The presentation will focus on the class method of population balance modelling, its coupling with the two-fluid-model and application to adiabatic air-water, condensing and evaporating steam-water bubbly flows as well as recent progresses in developing coalescence and breakup kernels.

Keywords: Bubbly flow; Coalescence and breakup; CFD-PBM coupled method; Phase change; Population balance model

  • Invited lecture (Conferences)
    NSFC-DEG International Workshop on Three-Phase Flow Modelling and Simulation, 23.-25.10.2019, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-29825
Publ.-Id: 29825


The intensive DT neutron generator of TU Dresden

Klix, A.; Döring, T.; Domula, A.; Zuber, K.

TU Dresden operates an accelerator-based intensive DT neutron generator. Experimental activities comprise investigation into material activation and decay, neutron and photon transport in matter and R&D work on radiation detectors for harsh environments. The intense DT neutron generator is capable to produce a maximum of 1012 n/s. The neutron source is a solid-type water-cooled tritium target based on a titanium matrix on a copper carrier. The neutron yield at a typical deuteron beam current of 1 mA is of the order of 1011 n/s in 4Π. A pneumatic sample transport system is available for short-time irradiations and connected to wo high-purity germanium detector spectrometers for the measurement of induced activities. The overall design of the experimental hall with the neutron generator allows a flexible setup of experiments including the possibility of investigating larger structures and cooled samples or samples at high temperatures.

Permalink: https://www.hzdr.de/publications/Publ-29823
Publ.-Id: 29823


ATM controls DNA repair and mitochondria transfer between neighboring cells

Jin, S.; Cordes, N.

Intercellular communication is essential for multicellular tissue vitality and homeostasis. We show that healthy cells message protective signals through direct cell–cell connections to adjacent DNA–damaged cells in a microtubule–dependent manner. In DNA–damaged cells, mitochondria restoration is facilitated by fusion with undamaged mitochondria from healthy cells and their DNA damage repair is optimized in presence of healthy cells. Both, mitochondria transfer and intercellular signaling for an enhanced DNA damage response are critically regulated by the activity of the DNA repair protein ataxia telangiectasia mutated (ATM). These healthy–to–damaged prosurvival processes sustain normal tissue integrity and may be exploitable for overcoming resistance to therapy in diseases such as cancer.

Keywords: Cell–cell communication; genotoxic stress; mitochondria exchange; DNA damage repair; ataxia telangiectasia mutated (ATM)

Permalink: https://www.hzdr.de/publications/Publ-29822
Publ.-Id: 29822


Studies on Flat Sandwich-type Self-Powered Detectors for Flux Measurements in ITER Test Blanket Modules

Raj, P.; Angelone, M.; Döring, T.; Eberhardt, K.; Fischer, U.; Klix, A.; Schwengner, R.

Neutron and gamma flux measurements in designated positions in the test blanket modules (TBM) of ITER will be important tasks during ITER's campaigns. As part of the ongoing task on development of nuclear instrumentation for application in European ITER TBMs, experimental investigations on self-powered detectors (SPD) are undertaken. This paper reports the findings of neutron and photon irradiation tests performed with a test SPD in flat sandwich-like geometry. Whereas both neutrons and gammas can be detected with appropriate optimization of geometries, materials and sizes of the components, the present sandwich-like design is more sensitive to gammas than 14 MeV neutrons. Range of SPD current signals achievable under TBM conditions are predicted based on the SPD sensitivities measured in this work.

Permalink: https://www.hzdr.de/publications/Publ-29821
Publ.-Id: 29821


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