Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34121 Publications

Revealing the Formation Dynamics of the Electric Double Layer by means of in-situ Rutherford Backscattering Spectrometry

Baghban Khojasteh Mohammadi, N.; Apelt, S.; Bergmann, U.; Facsko, S.; Heller, R.

We report on a new versatile experimental setup for in-situ Rutherford backscattering spectrometry at solid- liquid interfaces that enables investigations of electric double layers directly, in-situ and in a quantitative manner. A liquid cell equipped with a three electrode arrangement is mounted in front of the beam line and a thin Si3N4 window down to a thickness of 150 nm separates the vacuum of the detector chamber from the electrolyte in the cell. Since the contribution of the window to the measured spectra is minimized, a large variety of elements at the solid-liquid interface with sensitivities far below one mono layer can be monitored. The attachment of Ba onto the Si3N4 surface as a function of contact time and pH value of the electrolyte solution was chosen as example system. From our measurement we can not only read the evolution of the double layer but also derive limits for the point of zero charge for the Si3N4 surface. Our findings of 5.7 ≤ pH_PZC ≤ 6.2 are in good accordance with values found in the literature obtained by other techniques. Despite the measurements shown in this work, the presented setup allows for a large variety of in-situ investigations at solid-liquid interfaces such as tracing electro-chemical reactions, monitoring segregation, adsorption and dissolution and corrosion processes.

Keywords: Electric Double Layer; in-situ RBS; solid-liquid interface

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Permalink: https://www.hzdr.de/publications/Publ-29106
Publ.-Id: 29106


Indium thiospinel In1-xxIn2S4 – structural characterization and thermoelectric properties

Wyżga, P.; Veremchuk, I.; Himcinshi, C.; Burkhardt, U.; Carrillo-Cabrera, W.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Kortus, J.; Gumeniuk, R.

A detailed study of polycrystalline indium-based In1-xxIn2S4 (x = 0.16, 0.22, 0.28, 0.33) thiospinel is presented. The comprehensive description of synthesis conditions, phase composition and thermoelectric properties is performed applying various diffraction, microscopic and spectroscopic methods. Single-phase α- and β-In1-xxIn2S4 were found in the samples with 0.16  x  0.22 and x = 0.33 (In2S3), respectively, while In0.720.28In2S4 is proven to contain both α- and β-polymorphic modifications. Consequently, thermoelectric characterization of well-defined α-and β-In1-xxIn2S4 is conducted for the first time. α-In1-xxIn2S4 (x = 0.16, 0.22 and 0.28) revealed n-type semiconducting behavior, large Seebeck coefficient (< - 200 μV∙K-1) and moderate charge carrier mobility on the level of ~ 20 cm2V-1s-1 at room temperature (RT). The evident decrease of charge carrier concentration (increase of electrical resistivity) and thermal conductivity (even below 0.6 W∙m-1K-1 at 760 K) for larger In-content is observed. Although β-In0.670.33In2S4 (β-In2S3) is a distinct polymorphic modification, it followed the above-mentioned trend in thermal conductivity and displayed significantly higher charge carrier mobility (~ 104 cm2V-1s-1 at RT). These findings indicate that structural disorder in α-modification affects both electronic and thermal properties in this thiospinel. The reduction of thermal conductivity counterbalances lowered power factor and thus, thermoelectric figure of merit ZTmax = 0.2 at 760 K is nearly the same for both α- and β-In1-xxIn2S4.

Keywords: In2S3; thermoelectric properties; thiospinel; Raman spectroscopy; transmission electron microscopy

Permalink: https://www.hzdr.de/publications/Publ-29105
Publ.-Id: 29105


Structural stability and thermoelectric performance of high quality synthetic and natural pyrites (FeS2)

Zuñiga-Puelles, E.; Cardoso-Gil, R.; Bobnar, M.; Veremchuk, I.; Himcinschi, C.; Hennig, C.; Kortus, J.; Heide, G.; Gumeniuk, R.

Synthetic bulk and natural pyrite from the hydrothermal mine in Schönbrunn (Saxony, Germany) are confirmed to be stoichiometric compounds with the composition FeS2 and to be stable up to ~600 K by combined chemical, spectroscopic and X-ray diffraction analyses. Natural pyrite with negligibly small amount (< 0.6 wt.%) of well-defined transition metal carbonates impurities revealed characteristics of a nondegenerate semiconductor and is considered as a model system for investigation of thermoelectric performance. In the temperature range 50-600 K both natural and synthetic high quality bulk FeS2 samples show electrical resistivity varying within (220)-(5×10-3) Ω m and Seebeck coefficients of (4)-(-450) μV K-1. The thermal conductivity is large (~40 W m-1 K-1 at 300 K) and exclusively due to phononic contribution. It reveals a well pronounced maximum centered at ~75 K for natural pyrite (grain size ≤ 5 mm), which becomes almost completely suppressed in the sintered bulk samples due to increase of the point defects concentration and additional scattering on the grain boundaries (grain size ≤ 100 μm). The thermoelectric efficiency of a pure pyrite with ZT ~ 10-6 at 600 K is indeed by a factor of ~1000 worse than those reported earlier for some minerals and synthetic samples.

Keywords: crystal structure; thermoelectric; natural mineral; pyrite

Permalink: https://www.hzdr.de/publications/Publ-29104
Publ.-Id: 29104


CeMo2B5: a new type of arrangement of puckered boron hexagonal rings

Flipo, S.; Kohut, M.; Roth, F.; Weigel, T.; Schnelle, W.; Bobnar, M.; Ormeci, A.; Burkhardt, U.; Hennig, C.; Leisegang, T.; Meyer, D.-C.; Leithe-Jasper, A.; Gumeniuk, R.

REMo2B5 (RE = Ce, Pr, Nd) and CeW2B5 have been synthesized by arc melting with further annealing at 1300 °C.
CeMo2B5 crystallizes in a new structure type with space group REMo2B5 (RE = Ce, Pr, Nd) and CeW2B5 have synthesized by arc melting with further annealing at 1300 °C. CeMo2B5 crystallizes in a new structure type with space group Pnma, a = 11.0298(2) Å, b = 3.12080(5) Å, c = 9.9594(2) Å, Z = 4. Its structural arrangement reveals puckered [B6]-hexagonal rings, trigonal-prismatic- and empty pyramidal-tetrahedralslabs.The structure can be related to the derivatives of AlB2 and CrB prototypes. The boron atoms form a two-dimensional network of corrugated ribbons, each composed of four edgelinked [B6] rings infinitely extending along the b-axis. CeMo2B5 is a Pauli paramagnet. Electrical transport measurements together with the calculated density of states at the Fermi level of 3.81 states eV–1 f.u.–1 indicate CeMo2B5 to be a typical metallic system. Electronic structure calculations reveal significant hybridization of Ce 4f5d states with Mo 4d states. The chemical bonding scenario is dominated by chains of [Ce2Mo2] clusters with multi-center bonds. These clusters are connected via metallic Mo–Mo bonds. This metal-framework, in turn, is stabilized by bonding interactions with the boron ribbons to which it donates electrons.

Keywords: intermetallic borides; crystal structure; X-ray diffraction; magnetism

Permalink: https://www.hzdr.de/publications/Publ-29103
Publ.-Id: 29103


High-Quality LWFA-Based Electron Sources

Couperus Cabadağ, J. P.

  • Invited lecture (Conferences)
    ALEGRO workshop 2019, 27.03.2019, Genève, Confédération suisse

Permalink: https://www.hzdr.de/publications/Publ-29102
Publ.-Id: 29102


Reduced diffusion in normal appearing white matter of glioma patients following radio(chemo)therapy

Raschke, F.; Wesemann, T.; Wahl, H.; Appold, S.; Krause, M.; Linn, J.; Troost, E. G. C.

Background and purpose:
Standard treatment of high grade gliomas includes gross tumour resection followed by radio(chemo)therapy. Radiotherapy inevitably leads to irradiation of normal brain tissue. The goal of this prospective, longitudinal study was to use MRI to quantify normal appearing white and grey matter changes following radiation treatment as a function of dose and time after radiotherapy.
Materials and methods:
Pre-radiotherapy MRI (proton or photon therapy) and follow-up MRIs collected in 3 monthly intervals thereafter were analysed for 22 glioma patients and included diffusion tensor imaging, quantitative T1, T2* and proton density mapping. Abnormal tissue was excluded from analysis. MR signal changes were quantified within different dose bin regions for grey and white matter and subsequently for whole brain white matter.
Results:
We found significant reductions of mean diffusivity, radial diffusivity, axial diffusivity and T2* in normal appearing white matter regions receiving a radiation dose as low as 10-20 Gy within the observational period of up to 18 months. The magnitude of these changes increased with the received radiation dose and progressed with time after radiotherapy. Whole brain white matter also showed a significant reduction in radial diffusivity as a function of radiation dose and time after radiotherapy. No significant changes were observed in grey matter.
Conclusion:
Diffusion tensor imaging and T2* imaging revealed normal appearing white matter changes following radiation treatment. The changes were dose dependant and progressed over time. Further work is needed to understand the underlying tissue changes and to correlate the observed diffusion changes with late brain malfunctions.

Keywords: White Matter; Grey Matter; Diffusion Tensor Imaging; Radiotherapy; quantitative MRI; Proton Therapy; Photon Therapy; glioma; normal tissue

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29101
Publ.-Id: 29101


Calcium binding to a disordered domain of a type III-secreted protein from a coral pathogen promotes secondary structure formation and catalytic activity

Hoyer, E.; Knöppel, J.; Liebmann, M.; Steppert, M.; Raiwa, M.; Herczynski, O.; Hanspach, E.; Zehner, S.; Göttfert, M.; Tsushima, S.; Fahmy, K.; Oertel, J.

Strains of the Gram-negative bacterium Vibrio coralliilyticus cause the bleaching of corals due to decomposition of symbiotic microalgae. The V. coralliilyticus strain ATCC BAA-450 (Vc450) encodes a type III secretion system (T3SS). The gene cluster also encodes a protein (locus tag VIC_001052) with sequence homology to the T3SS-secreted nodulation proteins NopE1 and NopE2 of Bradyrhizobium japonicum (USDA110). VIC_001052 has been shown to undergo auto-cleavage in the presence of Ca2+ similar to the NopE proteins. We have studied the hitherto unknown secondary structure, Ca2+-binding affinity and stoichiometry of the “metal ion-inducible autocleavage” (MIIA) domain of VIC_001052 which does not possess a classical Ca2+-binding motif. CD and fluorescence spectroscopy revealed that the MIIA domain is intrinsically largely disordered. Binding of Ca2+ and other di- and trivalent cations induced secondary structure and hydrophobic packing after partial neutralization of the highly negatively charged MIIA domain. Mass spectrometry and isothermal titration calorimetry showed two Ca2+-binding sites which promote structure formation with a total binding enthalpy of -110 kJ mol-1 at a low micromolar Kd. Putative binding motifs were identified by sequence similarity to EF-hand domains and their structure analyzed by molecular dynamics calculations. The stoichiometric Ca2+-dependent induction of structure correlated with catalytic activity and may provide a “host-sensing” mechanism that is shared among pathogens that use a T3SS for efficient secretion of disordered proteins.

Keywords: metal protein interactions; protein folding; rhizobium; intrinsically disordered protein

Permalink: https://www.hzdr.de/publications/Publ-29100
Publ.-Id: 29100


Frontiers of applications of Petawatt lasers, Plasma accelerator development in Dresden

Schramm, U.

Discussion on progress of PW laser applications and advanced accelerators of protons and electrons

Keywords: Petawatt laser; laser particle acceleration; LWFA; secondary sources

  • Invited lecture (Conferences)
    SPIE Optics + Optoelectronics, 02.-04.04.2019, Prag, Czech Republic
  • Invited lecture (Conferences)
    JuSPARC Kick-off Workshop, 27.-29.03.2019, Vaals, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-29099
Publ.-Id: 29099


Laser plasma proton accelerators for therapy ?

Schramm, U.

Workshop discussion on advanced accelerators for therapy.

Keywords: particle cancer therapy; laser acceleration

  • Invited lecture (Conferences)
    2nd ARIES Annual Meeting, 10.-11.04.2019, Budapest, Ungarn

Permalink: https://www.hzdr.de/publications/Publ-29098
Publ.-Id: 29098


Phonon Magnetochiral Effect

Nomura, T.; Zhang, X.-X.; Zherlitsyn, S.; Wosnitza, J.; Tokura, Y.; Nagaosa, N.; Seki, S.

The magnetochiral effect (MCE) of phonons, a nonreciprocal acoustic propagation arising due to symmetry principles, is demonstrated in the chiral-lattice ferrimagnet Cu2OSeO3. Our high-resolution ultrasound experiments reveal that the sound velocity differs for parallel and antiparallel propagation with respect to the external magnetic field. The sign of the nonreciprocity depends on the chirality of the crystal in accordance with the selection rule of the MCE. The nonreciprocity is enhanced below the magnetic ordering temperature and at higher ultrasound frequencies, which is quantitatively explained by a proposed magnon-phonon hybridization mechanism.

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Permalink: https://www.hzdr.de/publications/Publ-29097
Publ.-Id: 29097


Quantification of the metabolic uptake rate in whole body F-18 FDG PET: a comparison between dynamic and static imaging

van den Hoff, J.; Hofheinz, F.; Weise, R.; Maus, J.; Preuß, R.; Burchert, W.

Ziel/Aim:
Dynamic whole body (DWB) FDG PET has become available with the recent introduction of the "flow motion" package by Siemens which offers fully automated generation of parametric images of the metabolic uptake rate K[m]. While this approach is superior to SUV-based quantification, it requires substantially more scan time and reduces patient throughput. On the other hand, the tumor to blood standard uptake ratio (SUR) has outperformed SUV in several clinical studies, which is attributed to a very high correlation between SUR and K[m]. However, direct evidence for this correlation is scarce. Our study compares K[sur], the SUR-derived "static" estimate of K[m], with the Patlak-derived K[m].

Methodik/Methods:
Altogether, 12 oncological patients are enclosed and scheduled for DWB PET. Parametric images of K[m] and K[sur] are computed using the vendor provided Patlak procedure and in-house software, respectively. Evaluation of the voxel intensity correlation between both parametric images as well as ROI-based analysis is performed.

Ergebnisse/Results:
So far, 4 patients have been evaluated. K[m] and K[sur] are highly correlated (R^2=0.97) in areas with nonnegligible irreversible uptake (so far we investigated the range K[m]=[0.01,0.07]). K[m] and K[sur] images have very similar image contrast between such areas. Minor contrast differences exist in healthy soft tissue and regions where the Patlak approach is invalid (notably the liver). The relative scale factor between both parametric images is 0.86.

Schlussfolgerungen/Conclusions:
Our results suggest that SUR and K[sur] are proportional surrogates of true K[m]. The unquestionable potential of DWB PET might thus be more relevant for applications beyond oncological FDG PET. To test this conjecture, comprehensive studies in homogeneous patient groups are required in order to compare the prognostic value of K[m] and SUR/K[sur] in the context of survival analysis

  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29096
Publ.-Id: 29096


Quantifizierung von pulmonalen 18F-FDG-PET/CT-Untersuchungen: Vergleich von Standard Uptake Ratio (SUR) und Patlak (Ki)

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

Ziel/Aim:
Dynamische PET/CT Scans gefolgt von Patlak Modellierung der 18F-FDG-Aufnahmerate (Ki) ist eine etablierte Methode zur Quantifizierung der Lungenentzündung im tierexp. Modell des akuten Lungenversagens (ARDS), erfordert aber zeitintensive Aufnahmen und erlaubt nur ein begrenztes cranio-caudales FoV. Dyn. PET/CT Scans von Patienten mit Lebermetastasen zeigten gute Korrelationen zwischen Ki und Standard Uptake Ratio (SUR = ROI-SUV / Blut-SUV) [1]. Wir analysierten in einem tierexp. ARDS-Modell, ob stat. PET/CT Messungen und SUR-Analysen alternativ zu dyn. PET/CT und Ki für die Quantifizierung der pulmonalen Inflammation genutzt werden können.

Methodik/Methods:
In 14 Schweinen erfolgten nach Induktion eines schweren ARDS sowie nach 24h Beatmung dyn. 18F-FDG-PET/CT Scans und Patlak Ki-Analysen. Anschließende stat. PET/CT Scans (77-81min p.i.) wurden für die Bestimmung von mittleren, zeitkorrigierten SUR-Werte genutzt. SUR- und Ki-Werte wurden für 5 ventro-dorsale ROIs mittels linearer Regression verglichen (Variationskoeffizient, r2). Anhand von Blutproben wurde die Variabilität der arteriellen Inputfunktion (AIF) zwischen Tieren und Messzeitpunkten verglichen.

Ergebnisse/Results:
SUR- und Ki-Werte korrelierten vor und nach 24h Beatmung (r2=0.84 bzw. 0.97). Der zeitliche Verlauf der AIF war zwischen Tieren und Aufnahmezeitpunkten vergleichbar und konnte mittels einer inversen Potenzfunktion beschrieben werden (r2 = 0.99). Die Patlak-Zeit war Zeit-, aber nicht AIF-abhängig, und wies eine geringe Variabilität auf (t=70min: 153.6 ± 13.3min).

Schlussfolgerungen/Conclusions:
Für die Quantifizierung der pulmonalen Inflammation in exp. Studien der Anästhesie können stat. PET/CT Scans und SUR-Analysen alternativ zu dyn. 18F-FDG-PET/CT und Patlak genutzt werden. Dies ermöglicht eine schnellere Datenakquisition, die Erfassung der gesamten Lunge und eine Reduktion der erforderlichen Blutproben. Grundlage der guten Ki-SUR Korrelation bildete die geringe Variabilität des AIF.

  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29095
Publ.-Id: 29095


Validation of an independent prognostic value of the asphericity of FDG uptake in non-small cell cancer patients undergoing treatment in curative intent

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

Ziel/Aim:
In patients with non-small cell lung cancer (NSCLC) undergoing treatment with curative intent, the asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) has been demonstrated as a prognostic factor. This study aimed at validation in an independent cohort with sufficient sample size.

Methodik/Methods:
Retrospective study in 313 NSCLC patients (203 men; median age, 67 [41-87] a) undergoing FDG-PET/CT with the same scanner prior to treatment in curative intent (always including resection of the primary tumor). 137 patients had UICC stage I, 79 patients stage II and 97 patients stage III disease (adenocarcinoma [ADC], 153; squamous cell carcinoma [SCC], 143, other, 17). Delineation of primary tumor MTV with semiautomated background-adapted threshold relative to its SUVmax. Univariable Cox regression for progression-free (PFS) and overall survival (OS) for PET parameters (MTV, ASP, SUVmax, SUVmean), clinical (UICC stage I vs. II vs. III), histological (SCC vs. ADC) and treatment variables (Rx/1 vs. R0 resection, chemotherapy yes/no, radiotherapy yes/no). Multivariable Cox of parameters significant in univariate Cox.

Ergebnisse/Results:
Events (progression, relapse, death) occurred in 169/313 patients, 139 patients died (median follow-up in survivors, 37 months). In multivariable Cox for OS, ASP >33.3% (hazard ratio [HR], 1.53 [95%-confidence interval, 1.02-2.3]), Rx/1 vs. R0 resection (HR, 2.47 [1.5-4.2]) and SCC vs. ADC (HR, 1.53 [1.1-2.2]) were significant. Log-rank test for ASP was significant at any cut-off from 18% upwards. Among separate UICC stages, ASP was only prognostic for OS in stage II (optimal, >19.5%; median OS, 33 vs. 59 months; p<0.01). In multivariable Cox for PFS, ASP >21.2% (HR, 1.75 [1.2-2.5]) and Rx/1 vs. R0 (HR, 2.48 [1.5-4.1]) were significant. Log-rank test for ASP was significant at any cut-off from 10-60%.

Schlussfolgerungen/Conclusions:
ASP was validated as an independent predictor of PFS and OS in NSCLC patients with curative treatment intent. Subdividing UICC stages, ASP remained prognostic in stage II.

  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29094
Publ.-Id: 29094


Interobserver variability of image–derived arterial blood SUV in FDG–PET

Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.

Ziel/Aim:
The standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static FDG PET. However, the SUV approach has well-known shortcomings which adversely affect the reliability of the SUV as a surrogate of the metabolic rate of glucose consumption. The standard uptake ratio (SUR), i.e. the uptake time corrected ratio of tumor SUV to image-derived arterial blood SUV, has been shown to overcome most of these shortcomings and to increase the prognostic value in comparison to SUV. However, it is unclear, to what extent the SUR approach is vulnerable to observer variability of the required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.

Methodik/Methods:
FDG PET/CT scans from 83 patients were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Altogether 5 different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient.

Ergebnisse/Results:
Interobserver variability in the pooled data amounts to SD=2.8% and is much smaller than the intersubject variability of BSUV (SD=16%). Averaged over the whole patient group, deviations of individual observers from the observer average are very small and fall in the range [-0.96,1.05]%. However, interobserver variability partly differs distinctly for different patients (range: [0.7,7.4]%).

Schlussfolgerungen/Conclusions:
The present investigation proofs unambiguously that the image-based manual determination of BSUV in the aorta provides sufficient accuracy and reproducibility for the purposes of the SUR approach. This finding is in line with the already demonstrated superiority of SUR in comparison to SUV in first clinical studies.

  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29093
Publ.-Id: 29093


Die Asphärizität neuroendokriner Tumore in der prätherapeutischen Somatostatinrezeptor-Bildgebung: Ein innovativer Prädiktor für das progressionsfreie Überleben unter Everolimus?

Wetz, C.; Genseke, P.; Pape, U.; Jann, H.; Furth, C.; Kreißl, M.; Hofheinz, F.; Venrito, M.; Stüven, A.; Amthauer, H.

Ziel/Aim:
Bei Patienten mit pulmonalen oder gastrointestinalen neuroendokrinen Tumoren (NET) kann der teils nebenwirkungsreiche mTOR-Inhibitor Everolimus das progressionsfreie Überleben (PFS) verlängern. Ziel dieser Studie war die Evaluation der läsionalen Asphärizität (ASP) in der prätherapeutischen Somatostatinrezeptor (SSR)-Bildgebung hinsichtlich einer weiteren Spezifizierung von Patientensubgruppen die von der Therapie im Besonderen profitieren.

Methodik/Methods:
Retrospektive, bizentrische Analyse von 30 Patienten (m=17; w=13; medianes Alter, 59 [38-75] Jahre) mit einer prätherapeutischen [111In-DTPA0]octreotid Szintigraphie. Die funktionellen Volumina von bis zu 3 führenden Läsionen je Patient (n=74) wurden mittels halbautomatischer, hintergrundadaptierter Segmentierung erhoben (ROVER, Version 2.1.20) und jeweils die sphärische Heterogenität des SSR-Besatzes - die ASP - berechnet. Für die maximal gemessene ASP je Patient erfolgten Kaplan-Meier-Analysen inklusive log-rank-Tests sowie eine univariate Cox Regression bzgl. des PFS.

Ergebnisse/Results:
Alle 30 Patienten waren unter Everolimus progredient oder entwickelten ein Rezidiv. In der univariaten Analyse erwies sich die ASP [Median, 12,7%; Spannweite, 1,1–43,5] als Prädiktor des PFS (p=0,033; Hazard Ratio [HR], 2,391 je eine Einheit). Patienten mit einer hohen ASP (>14%) zeigten ein medianes PFS von 6,7 Monaten (95%-Konfidenzintervall [CI], 2,1-11,4 Monate) gegenüber 14,4 Monaten (95%-CI, 12,5-16,3 Monate; p=0,028) für eine ASP ≤14%.

Schlussfolgerungen/Conclusions:
Mittels ASP kann im untersuchten Patientenkollektiv eine Prädiktion des PFS erreicht werden. In Bezug auf eine Nutzen-/Risiko-Abwägung zur Indikationsstellung der Everolimusgabe erscheint der Einsatz der prätherapeutischen ASP bzgl. einer optimalen Patientenauswahl bedeutsam; Patienten mit einer ASP >14% hatten ein signifikant kürzeres PFS.

  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29092
Publ.-Id: 29092


Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice

Njemanze, P. C.; Kranz, M.; Brust, P.

Fourier time series analysis could be used to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. Color memory processes of long-term potentiation and long-term depression could be identified through spectral analysis. We used small animal positron emission tomography and magnetic resonance imaging (PET/MRI) to measure the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain during light stimulation with blue and yellow filters compared to darkness condition. The mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition was analyzed using standard Fourier analysis software to derive spectral density estimates for each condition. Spectral peaks were identified as originating from the subcortical region (S-peak) by subcortical long-term potentiation (SLTP) or depression (SLTD), and originating from the cortical region (C-peak) by cortical long-term potentiation (CLTP) or depression (CLTD). Luminance opponency occurred at S-peak by SLTP in the dorsal stream in the left visual cortex in male mice. On the other hand, chromatic opponency occurred by wavelength-differencing at C-peak by CLTP in the cortico-subcortical pathways in the ventral stream of the left visual cortex in male mice. In contrast in female mice, during luminance processing, there was resonance phenomenon at C-peak in the ventral stream in the right visual cortex. Chromatic opponency occurred at S-peak by SLTP in the dorsal stream in the right visual cortex in female mice. Application of Fourier analysis improved spatial and temporal resolutions of conventional fPET/MRI methods. Computation of colour processing as a conscious experience has wide range applications in neuroscience and artificial intelligence.

Keywords: Chromatic Opponency; Brain; Light Stimulation; Sex; Asymmetry; Spectroscopy; Memory

  • Open Access Logo Book chapter
    Dr. Goran S. Nikolić, Dr. Dragana Marković-Nikolić: Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice / Fourier Transforms - Century of Digitalization and Increasing Expectations, London: IntechOpen, 2019, 1-23-1
    DOI: 10.5772/intechopen.85641

Permalink: https://www.hzdr.de/publications/Publ-29091
Publ.-Id: 29091


Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets

Appel, P.; Shields, B. J.; Kosub, T.; Hedrich, N.; Hübner, R.; Fassbender, J.; Makarov, D.; Maletinsky, P.

Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared with their ferromagnetic counterparts. Whereas nanoscale thin-film materials are key to the development of future antiferromagnetic spintronic technologies, existing experimental tools tend to suffer from low resolution or expensive and complex equipment requirements. We offer a simple, high-resolution alternative by addressing the ubiquitous surface magnetization of magnetoelectric antiferromagnets in a granular thin-film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200 nm thin films of Cr2O3 in real space and across the paramagnet-to-antiferromagnet phase transition, finding an average domain size of 230 nm, several times larger than the average grain size in the film. These experiments allow us to discern key properties of the Cr2O3 thin film, including the boundary magnetic moment density, the variation of critical temperature throughout the film, the mechanism of domain formation, and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into the magnetic ordering mechanism of Cr2O3 and firmly establishes single-spin magnetometry as a versatile and widely applicable tool for addressing antiferromagnetic thin films on the nanoscale.

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Permalink: https://www.hzdr.de/publications/Publ-29090
Publ.-Id: 29090


Modelling high resolution XANES for nuclear materials

Amidani, L.; Pidchenko, I.; Kvashnina, K.

X-ray Absorption Spectroscopy (XAS) is an invaluable tool in nuclear material research, allowing to probe the oxidation state and the local coordination of a selected atomic species. The first part of the spectrum, the X-ray Near Edge Structure (XANES), is less exploited than the Extended X-ray Absorption Fine Structure (EXAFS). However XANES conceals a wealth of information on the electronic structure and the local geometry around the absorber. Nowadays important progresses in the interpretation of XANES have been made thanks to i) the development of dedicated ab-initio codes using powerful computational resources and ii) the use of high resolution XANES, which is especially advantageous for actinides.
We present here an example of how to extracted valuable information from XANES. We performed a systematic study of U L₃ edge XANES for U⁵⁺ and U⁶⁺ in different local coordination. It is well known that the presence uranyl bonds gives a characteristic feature in the post-edge of U L₃ XANES and it has been observed experimentally that this feature shifts to lower energy when going from the uranyl to the uranate coordination. We found that in U⁶⁺ and U⁵⁺ mixed systems the U⁵⁺ in octahedral coordination gives a characteristic shoulder just before the uranyl feature due to the splitting of the 6d DOS from the octahedral crystal field. We think that the shift of the uranyl feature going to uranate configuration indeed points to the presence of U⁵⁺.

  • Lecture (Conference)
    E-MRS spring meeting, 27.-31.05.2019, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-29089
Publ.-Id: 29089


Modeling XANES of U⁵⁺ and U⁶⁺ in different local coordination geometries

Amidani, L.; Pidchenko, I.; Kvashnina, K.

X-ray Absorption Spectroscopy (XAS) is an invaluable tool in nuclear material research, allowing to probe the oxidation state and the local coordination of selected atomic species. The first part of the spectrum, the X-ray Near Edge Structure (XANES), is less exploited than the Extended X-ray Absorption Fine Structure (EXAFS). However XANES conceals a wealth of information on the electronic structure and on the local geometry around the absorber. What prevents XANES to become a more common technique is the complexity of its analysis, which still gives more qualitative than quantitative information. Nowadays important progresses in the interpretation of XANES have been made thanks to i) the development of dedicated ab-initio codes using powerful computational resources and ii) the use of High Energy Fluorescence Detected (HERFD) XANES, which boosted spectral resolution especially in the case of actinides. These recent developments make the systematic studies based on XANES simulations an invaluable tool to strengthen our understanding of XANES.
In this regards we present a detailed investigation on how the local coordination of U⁵⁺ and U⁶⁺ affects the U L₃ edge HERFD XANES. By simulating a large number of structures containing U⁵⁺ and/or U⁶⁺ in different local coordination geometries we found systematic trends, especially correlated with the presence of longer or shorter U – O bonds. It is well established that the presence of the short uranyl bond shows up in U L₃ edge XANES by the presence of a characteristic post-edge feature [1]. Interestingly, some experimental investigations reported that the uranyl post-edge feature shifts to lower energy when going from the uranyl to the uranate coordination, i.e. identical U – O distances [2,3]. Our systematic investigation confirms that this behavior correlates with the presence of U coordinated with 6 oxygen atoms in a regular octahedron and it is a consequence of the splitting of U 6d Density of States (DOS) induced by the crystal field. The possibility to detect the presence of U⁵⁺ in systems with both U⁵⁺ and U⁶⁺ by HERFD XANES will be discussed on the bases of our systematic investigation.

  • Lecture (Conference)
    49èmes Journées des Actinides, 14.-18.04.2019, Erice, Italy

Permalink: https://www.hzdr.de/publications/Publ-29088
Publ.-Id: 29088


Plant cell (Brassica napus) response on europium(III) and uranium(VI) exposure

Moll, H.; Sachs, S.; Geipel, G.

Experiments conducted over a period of 6 weeks using Brassica napus callus cells grown in vitro under Eu(III) or U(VI) stress showed that B. napus cells were able to bioassociate both potentially toxic metals (PTM), 762 nmol Eu/gfresh cells and 995 nmol U/gfresh cells. Most of the Eu(III) and U(VI) was found to be enriched in the cell wall fraction. Under high metal stress (200 µM), cells responded with reduced cell viability and growth. Subsequent speciation analyses using both metals as luminescence probes confirmed that B. napus callus cells provided multiple-binding environments for Eu(III) and U(VI). Moreover, two different inner-sphere Eu3+ species could be distinguished. For U(VI), a dominant binding by organic and/or inorganic phosphate groups of the plant biomass can be concluded.

Keywords: uranium; europium; plant cells; luminescence spectroscopy; viability

Permalink: https://www.hzdr.de/publications/Publ-29087
Publ.-Id: 29087


Numerical investigation on the effects of vortex generators on sub-channel flow in a rod bundle

Tas, S.; Krepper, E.; Unger, S.; Hampel, U.

Spacer grids of fuel assemblies are equipped with vanes, which promote mixing and turbulence within and across the sub-channels and thereby enhance the heat transfer. In this study, we investigated the impact of vortex generating vanes on the downstream flow evolution and heat transfer from the fuel rods by numerical analyses. Simulations were performed with ANSYS CFX. We investigated the turbulence change along the channel in the presence of the vanes depending on vorticity. The use of vanes results in a vortex, in which the vorticity enhances with increasing vane angle. These change induce turbulence kinetic energy variations. Physical conditions for optimum heat transfer along the sub-channel were determined in terms of Nusselt number. The Nusselt numbers of the present simulation were compared with experimental results from literature and a slight over prediction of the simulation compare to the experiment was found.

Keywords: Turbulent flow; Heat transfer; Numerical analysis

  • Lecture (Conference)
    50th Annual Meeting on Nuclear Technology, 07.-08.05.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29086
Publ.-Id: 29086


Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo2F7

Zeisner, J.; Bräuninger, S. A.; Opherden, L.; Sarkar, R.; Gorbunov, D. I.; Krizan, J. W.; Herrmannsdörfer, T.; Cava, R. J.; Wosnitza, J.; Büchner, B.; Klauss, H. H.; Kataev, V.

We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo2F7. Frequency- and temperature-dependent ESR investigations above the freezing temperature Tf ∼ 2.4 K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found along with a spin-glass phase developing below 20 K which is associated with a gapped low-energy excitation. Effective g factors close to 2 are obtained for both modes, in line with pulsed high-field magnetization measurements which show an unsaturated isotropic behavior up to 58 T at 2 K. In order to describe the field-dependent magnetization in high magnetic fields, we propose an empirical model accounting for highly anisotropic ionic g tensors expected for this material and taking into account the strongly competing interactions between the spins which lead to a frustrated ground state. As a detailed quantitative relation between effective g factors as determined from ESR and the local g tensors obtained by neutron scattering [Ross et al., Phys. Rev. B 93, 014433 (2016)] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores.

Permalink: https://www.hzdr.de/publications/Publ-29085
Publ.-Id: 29085


Reference Database for Photon Strength Functions

Goriely, S.; Dimitriou, P.; Wiedeking, M.; Belgya, T.; Firestone, R.; Kopecky, J.; Krticka, M.; Plujko, V.; Schwengner, R.; Siem, S.; Utsunomiya, H.; Hilaire, S.; Peru, S.; Cho, Y. S.; Filipescu, S. M.; Iwamoto, N.; Kawano, T.; Oblozinsky, P.; Tao, X.; Varlamov, V.; Xu, R.

Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of nuclear reactions and consequently they are highly relevant to a wide range of fields in basic sciences and applications such as nuclear structure, nuclear astrophysics, medical isotope production, fission and fusion reactor technologies, activation analyses and safeguards. They are also sources of information for widely used databases such as the IAEA Reference Input Parameter Library, the evaluated data files, such as ENSDF, EGAF, and the astrophysical reaction databases (e.g. BRUSLIB, STARLIB, REACLIB). In the past two decades, there has been considerable growth in the amount of reaction gamma-ray data measured to determine photon strength functions. Quite often the different experimental techniques lead to discrepant results and users are faced with the dilemma of deciding which (if any) amongst the divergent data they should adopt.

Keywords: Photon strength functions; gamma-ray strength; data base

Permalink: https://www.hzdr.de/publications/Publ-29084
Publ.-Id: 29084


Flexible magnetoelectronics

Makarov, D.

I will review our activities on shapeable magnetoelectronics. Fabrication and application potential of flexible magnetic field sensors will be in the focus of the talk.

Keywords: flexible electronics; magnetoelectronics

  • Invited lecture (Conferences)
    Nanoforum 2019, 17.05.2019, Linz, Austria

Permalink: https://www.hzdr.de/publications/Publ-29083
Publ.-Id: 29083


Current status of the PEnELOPE laser system

Albach, D.; Emmanuello, C.; Löser, M.; Siebold, M.; Schramm, U.

We present an update on the development of the PENELOPE laser system currently under construction at the Helmholtz-Zentrum Dresden-Rossendorf, Germany. Pulses from an oscillator are stretched to the nanosecond scale before several amplification stages will boost the energy up to the 150 J level on target. About 150 fs are foreseen at repetition rates of up to 1 Hz, ultimately yielding a peak power of 1 PW.
Our primary objective lies currently on the compression of the amplified pulses on the Joule scale. First tests used a direct compression of the stretched oscillator output (hence a small beam size), while the amplified compression will be performed with the full sized beam. Compressibility of the full scale beam is therefore of major interest. The second target is the improvement of the average power capacity of especially the second to the last amplifiers section. Room temperature operation is the main aim for the close future with lower temperature operation envisioned.

Keywords: laser; diode pumping; ytterbium; CaF2

  • Lecture (others)
    The 11th International Workshop of High Energy Class Diode Pumped Solid State Lasers (HEC-DPSSL), 13.-16.01.2019, Daejeon, Süd-Korea

Permalink: https://www.hzdr.de/publications/Publ-29082
Publ.-Id: 29082


Microscopic Nature of the First-Order Field-Induced Phase Transition in the Strongly Anisotropic Ferrimagnet HoFe5Al7

Gorbunov, D. I.; Strohm, C.; Henriques, M. S.; van der Linden, P.; Pedersen, B.; Mushnikov, N. V.; Rosenfeld, E. V.; Petricek, V.; Mathon, O.; Wosnitza, J.

We report on x-ray magnetic circular dichroism experiments in pulsed fields up to 30 T to follow the rotations of individual magnetic moments through the field-induced phase transition in the ferrimagnet HoFe5Al7. Near the ground state, we observe simultaneous stepwise rotations of the Ho and Fe moments and explain them using a two-sublattice model for an anisotropic ferrimagnet with weak intersublattice exchange interactions. Near the compensation point, we find two phase transitions. The additional magnetization jump reflects the fact that the Ho moment is no longer rigid as the applied field acts against the intersublattice exchange field.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29081
Publ.-Id: 29081


Inductive Heating Using a High-Magnetic-Field Pulse to Initiate Chemical Reactions to Generate Composite Materials

Zimmerer, C.; Salazar Mejia, C.; Utech, T.; Arnhold, K.; Janke, A.; Wosnitza, J.

Induction heating is efficient, precise, cost-effective, and clean. The heating process is coupled to an electrically conducting material, usually a metal. As most polymers are dielectric and non-conducting, induction heating is not applicable. In order to transfer energy from an electromagnetic field into polymer induction structures, conducting materials or materials that absorb the radiation are required. This report gives a brief overview of induction heating processes used in polymer technology. In contrast to metals, most polymer materials are not affected by electromagnetic fields. However, an unwanted temperature rise of the polymer can occur when a radio frequency field is applied. The now available high-field magnetic sources provide a new platform for induction heating at very low frequencies, avoiding unwanted thermal effects within the material. Using polycarbonate and octadecylamine as an example, it is demonstrated that induction heating performed by a magnetic-field pulse with a maximum flux density of 59 T can be used to initiate chemical reactions. A 50 nm thick Ag loop, with a mean diameter of 7 mm, placed in the polymer-polymer interface acts as susceptor and a resistive heating element. The formation of urethane as a linker compound was examined by infrared spectroscopic imaging and differential scanning calorimetry.

Permalink: https://www.hzdr.de/publications/Publ-29080
Publ.-Id: 29080


Upgrade of the ERDA setup at the HZDR 6 MV tandem accelerator

Julin, J.; Aniol, R.; Munnik, F.; Heller, R.

During 2019 the elastic recoil detection (ERD) beamline attached to the 6 MV tandem accelerator at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has been modernized completely. Since many of the vacuum and electrical components of the previous setup had been showing signs of aging or failing, the decision was made to replace these and rebuild the setup. Additionally, during 2018 the construction of a new time-of-flight spectrometer for ERD was also completed, and it was seen that the ERD setup as a whole would benefit from a combination of a new chamber, mechanical supports and a control system.

The new setup incorporates the previously used Z-separating Bragg ionization chamber (BIC), which is typically used with 43 MeV 35Cl beam. It is connected to a port on the chamber giving 30 degree scattering angle. The time-of-flight branch is attached to the other side of the chamber at a 40 degree scattering angle. Various beams up to an energy of 20 MeV for 35Cl or 30 MeV for 63Cu can be used, or even higher if hydrogen depth profiling is not necessary. The detector branches can be operated independently of each other, minimizing downtime due to breakdowns of detectors or maintenance. This is exceedingly important since the ion beam center (IBC) is a user facility and the beam time for the 6 MV accelerator is allocated based on proposals and scheduled long in advance to the actual measurement.

This presentation will give an overview of the new ERD setup, including specifics on the design of the new chamber, control and vacuum systems, detectors and data acquisition as well as some experimental data, performance figures and experiences gained during the construction of the setup.

Keywords: IBA; ERDA

  • Poster
    ECAART13 - 13th European Conference on Accelerators in Applied Research and Technology, 05.-10.05.2019, Split, Croatia

Permalink: https://www.hzdr.de/publications/Publ-29078
Publ.-Id: 29078


The influence of orifice types on the flow structure of a bubble-driven liquid-metal flow in a horizontal magnetic field

Richter, T.; Wondrak, T.; Eckert, K.; Eckert, S.; Odenbach, S.

Bubble plumes play an important role in metallurgical applications in order to stir and refine melts. Static electromagnetic fields allow a contactless control of those bubble plumes. However, for a tailored control the effects of the magnetic field to the bubble motion are important.
It is well known, that a bubble plume rising in a bulk of liquid metal has an axially symmetric shape. But the motion becomes asymmetric, when a static magnetic field (B) is applied in horizontal direction to the liquid metal. The direction of the flow parallel to B is upward, while the direction of the flow perpendicular to B is downward close to the plume.
Measurements of Zhang et al. of a bubble plume in the liquid metal GaInSn, emerging from a single orifice in a cylindrical vessel by the usage of the ultrasound Doppler velocimetry (UDV), confirmed this asymmetric motion. They observed traveling vortex structures in the direction perpendicular to B for moderate Hartmann numbers (Ha). This vortex structure became frozen, when high Ha were reached.
The focal point of this paper is the measurement of the bubble features in a similar container instead of measuring the flow of the liquid metal. The ultrasound transit time technique (UTTT) is employed, which was previously utilized to detect and analyze the motion of single bubbles rising in GaInSn. In comparison to the previous setup, a square vessel instead of round one is used and a sharp injection needle instead of a polished one was placed at the bottom of the vessel. During these new measurements, almost contradictory results are obtained: for small Ha numbers static vortex structures, which were deduced from the bubble motion, were observed, while traveling vortices were measured, when higher Ha were reached. The cause of this discrepancy is presumably the sharp orifice in the new setup, because the different cross section of the tank would rarely influence the motion.
We want to analyze the influence of the orifice type, by the comparison of two different shaped orifices, on the flow behavior in a new measurement campaign, where the bubble motion and the flow structure are detected by UTTT and UDV.

Keywords: ultrasound transit time technique; liquid metal; bubble plume

  • Lecture (Conference)
    11th PAMIR international conference fundamental and applied MHD, 01.-05.07.2019, Reims, France
  • Contribution to proceedings
    11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
    The influence of orifice types on the flow structure of a bubble-driven liquid-metal flow in a horizontal magnetic field

Permalink: https://www.hzdr.de/publications/Publ-29077
Publ.-Id: 29077


Radiopharmakologische Charakterisierung eines neuen Chelators konjugiert an das PSMA-Bindungsmotiv Glutamat-Urea-Lysin

Sihver, W.; Böhme, J.; Wodtke, R.; Walther, M.; Steinbach, J.; Pietzsch, J.; Pietzsch, H.-J.

Molekulare Bildgebung mittels PET bzw. SPECT ist in der Krebsforschung ein unverzichtbares Werkzeug geworden, da diese genaue Informationen zu molekularen Eigenschaften von Tumoren liefern kann. Auf der Suche nach vielseitig einsetzbaren Chelatoren wurde für die Radionuklidmarkierung zielgerichteter PET/SPECT-Liganden ein Cyclohexandiamin-Triazol-Chelator entwickelt und an das Bindungsmotiv des prostata-spezifischen Antigens (PSMA) Glutamat-Urea-Lysin gekoppelt (Ligand in Abb. 1 = L). Dieses Motiv ist bekannt für seine gute Affinität an PSMA [1], welches bei verschiedenen Tumorentitäten stark exprimiert wird [2–4].
Ziel der Untersuchung war es, das radiopharmakologische Potential von L nach Radiomarkierung mit 68Ga, 111In und 18F bezüglich der Bindungseigenschaften und Zell-Internalisierung abzuschätzen und mit dem ‚Gold-Standard‘ PSMA-617 (177Lu- oder 64Cu-markiert) zu vergleichen.
Für den nichtmarkierten Liganden L wurde in Kompetitionsassays versus [177Lu]Lu-PSMA-617 eine etwas geringere Affinität als für PSMA-617 ermittelt. Sättigungsanalysen von [68Ga]Ga-L, [111In]In-L und [18F]F-L an LNCaP-Zellhomogenaten ergaben ähnliche Affinitäten (Kd 18–30 nM), die wiederum etwas niedriger waren als die von [177Lu]Lu-PSMA-617 (11 nM). Die Ergebnisse der Internalisierungsversuche zeigten eine stärkere Aufnahme von [64Cu]Cu-PSMA-617 in LNCaP-Zellen als vom verschieden radiomarkierten L.
Mit dem Konjugat L konnten nach erfolgreicher Radiomarkierung mit 68Ga, 111In und 18F vielversprechende Bindungseigenschaften gegenüber PSMA bestimmt werden. Die Vielseitigkeit dieses Chelators bietet die Möglichkeit mit entsprechendem Radionuklid sowohl für PET (68Ga, 18F) als auch für SPECT (111In) einsetzbar zu sein.

Literatur:

[1] K. Kopka, J. Nucl. Med. 2017, 58,17S. [2] H.R. Kulkarni, Br. J. Radiol. 2018, 91,20180308. [3] Y. Tolkach, Breast Cancer Res.Treat. 2018, 169,447. [4] M.C. Haffner, Hum.Pathol. 2009, 40,1754.

  • Lecture (Conference)
    Radiopharmakologische Charakterisierung eines neuen Chelators konjugiert an das PSMA-Bindungsmotiv Glutamat-Urea-Lysin /GDCh Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29076
Publ.-Id: 29076


Nature and Surface Interactions of Sulfur-Containing Deposits on V2O5-WO3/TiO2- Catalysts for SCR-DeNOx

Rammelt, T.; Kuc, A.; Böhm, J.; Heine, T.; Gläser, R.

Sulfur-containing deposits form on a monolithic V2O5-WO3/TiO2 (VWT) catalyst during SCR-DeNOx with NH3 at 473 and 523 K and pressures up to 500 kPa in the presence of SO2 with sulfate contents of 1.7 to 13.0 wt.-%. Using TGA and DRIFTS, these deposits are determined to be mainly NH4HSO4 for SCR temperatures > 523 K. At lower temperatures, (NH4)2SO4 is formed. The thermal stability of NH4HSO4 supported on different transition metal oxides including V2O5, WO3, TiO2, MoO3 and Al2O3 varies with decomposition temperatures from 620 to 820 K. Using DFT calculations, it is show that the thermal stability of supported NH4HSO4 is mainly determined by hydrogen bonding of the HSO4- anions with the metal oxide surface. Increasing electronegativity of the metal atoms of the support oxide leads to weakening of the S-O bonds in the HSO4- anions and to lower decomposition temperatures of the supported NH4HSO4.

Downloads:

  • Secondary publication expected from 21.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29075
Publ.-Id: 29075


Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte-Driven Nanostructuring

Gao, D.; Sinev, I.; Scholten, F.; Arán-Ais, R. M.; Divins, N. J.; Kvashnina, K.; Timoshenko, J.; Roldan Cuenya, B.

The production of multicarbon products (C2+) from CO2 electroreduction reaction (CO2RR) is highly desirable for storing renewable energy and reducing carbon emission. Here we report the electrochemical synthesis of CO2RR catalysts that are highly selective for C2+ products via electrolyte-driven nanostructuring. Nanostructured Cu catalysts synthesized in the presence of specific anions can selectively convert CO2 to ethylene and multicarbon alcohols in aqueous 0.1 M KHCO3 solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of ~80% and partial current density of ~34 mA cm−2 for C2+ products at −0.9 V vs RHE. Operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy measurements revealed that the high C2+ selectivity of these nanostructured Cu catalysts can be mainly attributed to their nanoporous structure, presence of subsurface oxygen and Cu+ species, and the adsorbed halides. This work provides new insight into the parameters that should be tuned in order to rationally design C2+-selective CO2RR catalysts.

Permalink: https://www.hzdr.de/publications/Publ-29074
Publ.-Id: 29074


Predicting late magnetic resonance image changes in glioma patients after proton therapy

Eulitz, J.; Troost, E. G. C.; Raschk, F.; Schulz, E.; Lutz, B.; Dutz, A.; Löck, S.; Wohlfahrt, P.; Enghardt, W.; Karpowitz, C.; Krause, M.; Lühr, A.

Introduction:

Proton radiation therapy is an effective treatment for glioma patients. To exploit its full potential, a better description of regional differences in radiation response within the brain is required. In this study, we present a model for predicting magnetic resonance (MR) image changes in glioma patients that considers the variability in proton relative biological effectiveness (RBE) as well as the regional susceptibility of brain tissue to radiation damage.

Material and methods:

Six glioma patients treated with adjuvant proton radio(chemo)therapy showed contrast enhancement on follow-up T1-weighted MR imaging corresponding to treatment-related changes. Physical dose and linear energy transfer (LET) were obtained from high-precision Monte-Carlo simulations. The periventricular region (PVR) was contoured as a 4 mm expansion around the ventricles. Correlations between the image changes and dose, LET, and the PVR were evaluated voxel-wise in univariable and multivariable logistic regression analyses. Model performance was assessed by the area under the curve (AUC) using leave-one-out cross validation. The tolerance dose TD50, at which 50% of the tissue voxels show toxicity was interpolated from the model and used for RBE estimation.

Results:

The spatial distribution of MR image changes in the brain was highly non-uniform and correlated poorly with the considered predictors in univariable analysis. Multivariable modelling with either only dose and LET or PVR as third predictor revealed AUC values of 0.89 and 0.92, respectively. TD50 decreased with increasing LET and the modelled RBE was found to vary between 0.9 and 2.3. No relevant difference in model performance was found for track- or dose-averaged LET.

Conclusion:

The strong correlation of MR image changes with dose, LET, and the PVR demonstrates the relevance of non-uniform dose response models. A larger patient cohort including patients without image changes will be used to validate the clinically observed indication of a variable proton RBE.

Keywords: Proton Therapy; Glioma; Variable RBE; MR image changes

Permalink: https://www.hzdr.de/publications/Publ-29073
Publ.-Id: 29073


Performance Analysis for Large Scale GPU Applications and DL Frameworks

Juckeland, G.; Henschel, R.

Get your hands on the latest versions of Score-P and Vampir to profile the execution behavior of your large-scale GPU-Accelerated applications. See how these HPC community tools pick up as other tools (such as NVVP) drop off when your application spans multiple compute nodes. Regardless of whether your application uses CUDA, OpenACC, OpenMP or OpenCL for acceleration, or whether it is written in C, C++, Fortran or Python, you will receive a high-resolution timeline view of all program activity alongside the standard profiles to identify hot spots and avenues for optimization. The novel Python support now also enables performance studies for optimizing the inner workings of deep learning frameworks.

  • Lecture (Conference)
    GPU Technology Conference 2019, 17.-21.03.2019, San Jose, CA, USA

Permalink: https://www.hzdr.de/publications/Publ-29070
Publ.-Id: 29070


The dominating mechanisms for the formation of solute-rich clusters in steels under irradiation

Castin, N.; Bonny, G.; Bakaev, A.; Bergner, F.; Domain, C.; Hyde, J. M.; Messina, L.; Radiguet, B.; Riddle, N.; Malerba, L.

The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor causing the degradation of the macroscopic properties of steels under irradiation. The mechanisms driving their formation are still debated. This work focuses on low-Cu reactor pressure vessel (RPV) steels, where solute species are generally not expected to precipitate. We rationalize the processes that take place at the nanometer scale under irradiation, relying on the latest theoretical and experimental evidence on atomic-level diffusion and transport processes. These are compiled in a new model, based on the object kinetic Monte Carlo (OKMC) technique. We evaluate the relevance of the underlying physical assumptions by applying the model to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography and small angle neutron scattering, complemented with information from the literature. The results of this study reveal that the role of immobilized self-interstitial atoms (SIA) loops dominates the nucleation process of NSRC.

Keywords: Hardening; Embrittlement; Steel; Modelling

Permalink: https://www.hzdr.de/publications/Publ-29069
Publ.-Id: 29069


Inter-observer variability in target delineation increases during adaptive treatment of head-and-neck and lung cancer

Apolle, R.; Appold, S.; Bijl, H. P.; Blanchard, P.; Bussink, J.; Faivre-Finn, C.; Khalifa, J.; Laprie, A.; Lievens, Y.; Madani, I.; Ruffier, A.; de Ruysscher, D.; van Elmpt, W.; Troost, E. G. C.

Introduction
Inter-observer variability (IOV) in target volume delineation is a well-documented source of geometric uncertainty in radiotherapy. Such variability has not yet been explored in the context of adaptive re-delineation based on imaging data acquired during treatment. We compared IOV in the pre- and mid-treatment setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locoregionally advanced head-and-neck squamous cell carcinoma (HNSCC) and (non-)small cell lung cancer [(N)SCLC].

Materials and Methods
Five and six observers participated in the HNSCC and (N)SCLC arm, respectively, and provided delineations for five cases each. Imaging data consisted of CT studies partly complemented by FDG-PET and was provided in two separate phases for pre- and mid-treatment. Global delineation compatibility was assessed with a volume overlap metric (the Generalised Conformity Index), while local extremes of IOV were identified through the standard deviation of surface distances from observer delineations to a median consensus delineation. Details of delineation procedures, in particular GTV to CTV expansion and adaptation strategies, were collected through a questionnaire.

Results
Volume overlap analysis revealed a worsening of IOV in all but one case per disease site, which failed to reach significance in this small sample (p-value range 0.063- 0.125). Changes in agreement were propagated from GTV to CTV delineations, but correlation could not be formally demonstrated. Surface distance based analysis identified longitudinal target extent as a pervasive source of disagreement for HNSCC. High variability in (N)SCLC was often associated with tumours abutting consolidated lung tissue or potentially invading the mediastinum. Adaptation practices were variable between observers with fewer than half stating that they consistently adapted pre-treatment delineations during treatment.

Conclusion
IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the conventional causes of IOV. Consensus guidelines are urgently needed.

Keywords: Target volume delineation; Inter-observer variability; Adaptive radiotherapy; Head-and-neck squamous cell carcinoma; (Non-)small cell lung cancer

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Permalink: https://www.hzdr.de/publications/Publ-29068
Publ.-Id: 29068


Einfluss von Protonen-Reichweiteunsicherheiten auf LET-Verteilungen am Beispiel von Hirntumor-Patienten

Hahn, C.; Peters, N.; Wohlfahrt, P.; Richter, C.; Eulitz, J.; Enghardt, W.; Lühr, A.

Einleitung
Erste klinische Evidenz zeigt, dass die relative biologische Wirksamkeit (RBW) von Protonen auch vom linearen Energietransfer (LET) bestimmt wird. Die patientenspezifische LET-Verteilung folgt aus der Eindringtiefe der Protonenstrahlen und wird daher unmittelbar von Reichweiteunsicherheiten beeinflusst. Diese Studie quantifiziert den Einfluss von Reichweiteunsicherheiten auf LET-Verteilungen im klinischen Zielvolumen (CTV) und angrenzenden Risikoorganen am Beispiel von Hirntumor-Patienten.

Material & Methoden
Für jeden Patienten wurden zwei nominelle, robust-optimierte Bestrahlungspläne mit Pencil-Beam-Scanning unter Verwendung von Single-Field-Uniform-Dose und Multi-Field-Optimization erstellt. Dabei wurde jeweils ein Simultan-Integrierter-Boost mit zwei Einstrahlrichtungen geplant. Das Protonenbremsvermögen jedes Voxels folgte direkt aus dem Dual-Energy-CT-Scan für die Therapieplanung. Systematische Reichweiteunterschiede wurden durch Skalierung des Bremsvermögens erzeugt. Die Bestrahlungspläne wurden mittels Monte-Carlo-Methode für drei Reichweiteszenarien (nominell, ±3.5%) simuliert und der dosisgemittelte LET voxelweise bestimmt (RayStation, Forschungsversion 5.99.50). Die Auswertungen der LET-Differenzen erfolgte voxelweise, organspezifisch und auf einem Signifikanzniveau von 5% (zweiseitiger t-Test).

Ergebnisse
Der mittlere LET im Zielvolumen änderte sich weder signifikant durch die simulierten Reichweiteunsicherheiten noch durch die verwendete Planungsstrategie. Gemittelt über Patienten, Planungsstrategie und Reichweiteszenarien betrug der mittlere LET (±Standardabweichung) im CTV 2.78 (±0.07) keV/µm. Im Vergleich zum CTV war der mittlere LET in Risikoorganen signifikant erhöht. Reichweiteunsicherheiten führten innerhalb einer Planungsstrategie patientenspezifisch zu einer Veränderung des mittleren LET um bis zu 0.70 keV/µm (rechter Sehnerv) bzw. 0.38 keV/µm (Hirnstamm). Die Reichweiteunsicherheiten führten zu relevanten Änderungen der LET-Varianz in angrenzenden Risikoorganen mit LET-Maxima bei einzelnen Patienten, z.B. im Hirnstamm (maximale Dosis von 51.8 Gy(RBW)) oder im rechten Sehnerv (53.6 Gy(RBW)).

Zusammenfassung
Die Reichweiteunsicherheit der Protonentherapie bei Hirn-Tumor-Patienten beeinflusste die LET-Verteilungen in Risikoorganen, aber nicht im Zielvolumen. Beobachtete hohe, lokale LET-Varianzen sowie LET-Maxima in Risikoorganen könnten zu einer erhöhten biologischen Wirksamkeit führen und bei Dosen nahe dem Grenzwert unerwartete Normalgewebskomplikationen hervorrufen.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29067
Publ.-Id: 29067


Degradation of Cu-bearing uranyl As-P micromineral phases from Krunkelbach uranium deposit, Southern Germany

Pidchenko, I.; Bauterns, S.; Amidani, L.; Kvashnina, K. O.

The abandoned Krunkelbach uranium (U) mine, Southern Germany, with 2-3 km surrounding area represents a unique natural analogue site with accumulation of U minerals suitable for investigations of potential mobilization-immobilization processes expected in a real spent nuclear fuel repository. A specific feature of the site is the occurrence of more than forty secondary U minerals, from mixed redox U oxy-hydroxides to alkaline metal uranyl silicates, thus representing a wide scale of U ore weathering events. In this work the combination of synchrotron and laboratory techniques is used to unveil U speciation and micro heterogeneities in U phases accumulated on granitic rock outcrop from U deposit area. Available data on the age of the secondary U mineralization indicates that oxidizing processes at the site started some 340,000 years ago and continues up to date. Several phases close to Cu(UO2)2(PO4)2-x(AsO4)x·8H2O are identified on 1×2 mm2 area with presumably older, more evenly distributed Cu(UO2)2(SiO3OH)2·6H2O and (Fe, Ba, Pb)(UO2)2(WO4) (OH)4·12H2O, mineralization. Based on a multi-technique investigation 10-200 µm Cu(UO2)2(PO4)2-x(AsO4)x·8H2O particles with widely varying As-P content are analyzed. The evidences of a degradation occurred on some zones on the selected crystals are found associated with higher As and decreased P content. This observation can be apparently attributed to different degradation properties of the mixed As-P phases depending on As-P ratio and originate from different solubility properties of Cu(UO2)2(PO4)2·8H2O and Cu(UO2)2(AsO4)2·8H2O species. The conditions for preferential formation of As rich Cu(UO2)2(XO4)2·8H2O [X=As, P] phases and its possible role on U transport in environment under oxidizing conditions are discussed.

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

Permalink: https://www.hzdr.de/publications/Publ-29066
Publ.-Id: 29066


Kuramoto Model on KKI18 connectome

Ódor, G.; Kelling, J.

Results of fourth-order Runge--Kutta integration of the first-order Kuramoto model in brain connectome graph.

  • Awr.dat.gz : connectome graph
  • Awri.dat.gz : connectome graph with 5% inhibitory links
  • ccdata.tgz , sredata.tgz : simulations data for different configurations
    (averages at top-level, single runs in folders)
    • eERll*.dat: cube graph with random long-range links
    • o.ocp-kur_{lambda}_*.dat: connectome with coupling lambda
    • o.ocp-kur_{lambda}I_*.dat: connectome with inhibitory links, coupling lambda
    • elo-Thr: smoothed probability distributions of avalance times
  • awr.tgz : simulation data for connectome graphs sorted by parameters
    • structure: [connectome]/norm_[norm]/dt_[dt]/lam_[lam]/
    • connectomes:
      • Awr: see above
      • AwrC: AwrC.dat.gz (Awr withough disconnected components)
      • Awri10: Awri10.dat.gz (10% inhbibitory)
      • Awri20: Awri20.dat.gz
      • Awri5: see Awri above
      • AwriL5_s23: AwriL5_s23.dat.gz (Awri5 with different random sites flipped)
      • AwriN5_s23_max2000: AwriN5_s23_max2000.dat.gz (Awri5 with different random sites flipped, only site with <=2000 connections flipped)

Keywords: Kuramoto Model; Graph; Synchronization

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-03-14
    DOI: 10.14278/rodare.120
    License: CC-BY-SA-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29065
Publ.-Id: 29065


Liquid Metal Model Experiments for Continuous Casting of Steel Under the Influence of Magnetic Fields

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

Magnetic fields are widely applied in the continuous casting process to modify the flow pattern in the mold and thereby improve the quality of the semi-finished product. While the use of Electromagnetic Brakes (EMBr) is common in slab casting, Electromagnetic Stirring (EMS) is mainly applied in bloom and billet casting and recently also in slab casting. Due to the harsh conditions in the real casting process, model experiments in cold liquid metals enable accurate measurements of velocity fields, surface oscillations, gas bubble characteristics, etc. These models improve understanding the effects of electromagnetic actuators and provide data to validate numerical models.

We present experimental results obtained in a model of a continuous caster, the Mini-LIMMCAST facility, where the velocity field is measured by Ultrasound Doppler Velocimetry (UDV). Results of experiments conducted with EMS in a round bloom geometry as well as experiments with EMBr in slab geometries are presented.

Keywords: Model Experiments; Ultrasound Doppler Velocimetry; Continuous Casting; Electromagnetic Brake; Electromagnetic Stirring

  • Contribution to proceedings
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Canada, 620-627
    DOI: 10.33313/503/065
  • Lecture (Conference)
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Kanada

Permalink: https://www.hzdr.de/publications/Publ-29064
Publ.-Id: 29064


A spectroscopic investigation of Eu3+ incorporation in LnPO4 (Ln = Tb, Gd1–xLux, x = 0.3, 0.5, 0.7, 1) ceramics

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

Introduction
In recent years, rare-earth orthophosphates LnPO4 have attracted attention as potential hosts for the immobilization of specific radioactive waste streams.
Objectives
In the present work, the incorporation of Eu3+ in LnPO4 host materials predominantly having the xenotime structure has been investigated on the molecular level. As host cations we used Tb and Lu as well as a solid solution series of Gd1–xLuxPO4 (x = 0.3, 0.5, 0.7). The site selective laser luminescence spectroscopy (TRLFS) technique was applied to study the distribution of Eu3+ in the synthetic xenotime phases, while PXRD and Raman spectroscopy were used for bulk structural investigations direct after synthesis and after one year of storage at ambient conditions.
Results
The PXRD patterns of the solid solution series show the formation of a single xenotime phase up to a substitution of x = 0.5 both before and after aging. The TRLFS emission spectra also show that Eu3+ is substituted for the host cation site in the xenotime hosts. After one year, the emission spectra show a broad dominant signal between the transitions regions of the 7F1‒ and 7F2‒bands, and the luminescence signal no longer corresponds to Eu3+‒incorporation in a xenotime environment, only. These changes indicate a time-dependent change in the local structure of the europium dopant. Based on these observations we suggest an exclusion of Eu3+ from the crystal structure and subsequent migration of the cation to the grain boundaries during aging. The migration of Eu3+ in void spaces through the crystal structure could be responsible for the additional signals in the emission spectra, while the narrow void space forces an overlap between Eu3+ and oxygen atomic orbitals, resulting in the broad signal between the 7F1‒ and 7F2‒bands.
Conclusions
The segregation of Eu3+ to grain boundaries after a relatively short aging in the xenotime materials, indicates that xenotime ceramics will not serve as a suitable waste form for trivalent actinides from high–level nuclear waste.

  • Lecture (Conference)
    27th Annual Meeting of the German Crystallographic Society (DGK), 25.-28.03.2019, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-29063
Publ.-Id: 29063


Protonentherapie von Lungentumoren: Logfile-basierte Dosisrekonstruktion zur klinischen Implementierung des Pencil-Beam-Scanning-Verfahrens

Spautz, S.; Meijers, A.; Jakobi, A.; Thiele, J.; Knopf, A.; Troost, E. G. C.; Richter, C.; Stützer, K.

Einleitung
Bei der Protonentherapie von Lungentumoren mittels Pencil-Beam-Scanning (PBS) kann der Interplay-Effekt aus Protonenstrahl- und Zielvolumenbewegung zu Dosisabweichungen führen. Ob klinisch relevante Dosisparameter eingehalten werden, ist nicht vorhersehbar, weshalb PBS für Lungentumore in unserem Institut noch nicht klinische angewendet wird. Mit dieser Arbeit kann im Rahmen der Qualitätssicherung die tatsächlich applizierte Dosis nach jeder Fraktion rekonstruiert werden. Dies soll zunächst für die PBS-Bestrahlung von Patienten in freier Atmung, ohne Bewegungskompensation und mit Tumorbewegungen unter 5mm angewendet werden, da der Interplay-Effekt-Einfluss bei diesen Amplituden gering ist.
Material und Methoden
Die Dosisrekonstruktion erfolgt skript-basiert im Planungssystem Raystation (RaySearch Laboratories AB, Schweden). Durch Kombination der Maschinen-Logfiles der Protonen-Bestrahlungsanlage (IBA, Belgien), welche die Spotpositionen und applizierten Monitoreinheiten während der Bestrahlung mit einer zeitlichen Auflösung von 250 μs enthalten, der simultan gemessenen Atemkurve des Patienten (ANZAI, Japan) und den wöchentlichen 4D-CTs (Siemens Somatom Definition AS, Deutschland) werden alle Spots zeitlich den entsprechenden 4D-CT Atemphasen zugeordnet. Die daraus errechneten Dosisverteilungen pro Atemphase werden auf ein Referenz-CT deformiert, auf welchem die akkumulierte Dosis nach jeder Fraktion bewertet werden kann. (Abb.1)
Ergebnisse
Das Verfahren wurde an der Universitätsprotonentherapie Dresden (UPTD) implementiert und an klinischen Datensätzen eines ausgewählten Patienten getestet. Die Phasenaufteilung der Atemkurve erfolgt, konform zum Algorithmus des 4D-CTs, amplitudenbasiert (Abb.2). Pro Fraktion benötigt die Dosisnachberechnung etwa 10 min und ist somit praktikabel im klinischen Arbeitsablauf einsetzbar.
Derzeit wird die Methode experimentell an einem dynamischen Thorax-Phantom (CIRS, USA) validiert und die zeitliche Synchronisierung von Maschinen-Logfiles und Atemkurve überprüft. Die Behandlung erster Patienten mit diesem Verfahren ist für die zweite Hälfte dieses Jahres geplant.
Zusammenfassung
Mit der vorgestellten Methode ist es möglich, die applizierte Dosis nach jeder Fraktion zu rekonstruieren und die akkumulierte Dosis über die gesamte Behandlungsdauer zu kontrollieren. Somit können durch anatomische Änderungen und den Interplay-Effekt bedingte Dosisabweichungen erkannt und benötigte Schritte wie Planadaptionen eingeleitet werden.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29062
Publ.-Id: 29062


Exploration of Proton Bunch Monitoring for In-vivo Range Verification in Proton Therapy

Permatasari, F.; Römer, K.; Werner, T.; Wagner, A.; Pausch, G.; Kögler, T.

Introduction
The accuracy of proton therapy is basically delimited by range uncertainties. In order to fully exploit the benefit of proton therapy, real-time range verification is needed. Prompt gamma rays, produced during the deceleration of protons in tissue, allow assessing the proton range indirectly. Prompt gamma-ray timing (PGT) utilizes measured time distributions of prompt gamma rays for estimating the beam range [1-4]. At the given therapy facility, however, the accuracy of range determination is affected by drifts of the proton bunch timing (or phase) with respect to the cyclotron radiofrequency, and by the proton bunch width. To counter this limitation, a proton bunch monitor (PBM) has to be introduced.

Materials & Methods
The coincident detection of protons elastically scattered out of a thin target allows measuring phase and width of the proton micro-bunches [3]. Two CeBr3 scintillation detectors coupled with PGT electronics [4] were employed for these measurements. Alternatively, scintillating fibers placed in the beam halo have also been studied.

Results
The applicability of standard PGT detectors and electronics [4] for accurate bunch phase and width measurements has been demonstrated. The detection of beam-halo protons with scintillating fibers seems to be a feasible alternative for bunch phase monitoring at higher sampling rates. Quantitative analysis are still ongoing.

Summary
Alternative proton bunch monitoring approaches have been investigated to assess beam parameters necessary for range verification by means of the PGT method. An appropriate PBM would complete the current PGT detection system.

Acknowledgement
This work has been supported by StrahlenSchutzSeminar in Thüringen e.V.

Literature
[1] C. Golnik et al., Phys. Med. Biol. 59 (2014) 5399
[2] F. Hueso-González et al., Phys. Med. Biol. 60 (2015) 6247
[3] J. Petzoldt et al., Phys. Med. Biol. 61 (2016) 2432
[4] T. Werner et al., Phys. Med. Biol. accepted (2019)

Keywords: proton therapy; range verification; prompt gamma-ray; PGT

  • Lecture (Conference)
    50. Jahrestagung der DGMP, 19.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29061
Publ.-Id: 29061


First-in-man validation of CT-based stopping-power prediction using prompt-gamma-based range verification

Berthold, J.; Khamfongkhruea, C.; Petzoldt, J.; Thiele, J.; Hölscher, T.; Wohlfahrt, P.; Pausch, G.; Janssens, G.; Smeets, J.; Richter, C.

Introduction
Currently, the uncertainty in CT-based range prediction is substantially impairing the accuracy of particle therapy. Improvements like a determination of stopping-power ratio (SPR) from dual-energy CT (DECT) have been proposed. However, a validation of range prediction in patients has not been achieved by any means. Here, we present the first verification of proton range prediction in patients, using Prompt-Gamma-Imaging (PGI).

Materials & Methods
A PGI-slit-camera system was modified to enhance its positioning accuracy using a floor-based docking station. Its accuracy and positioning reproducibility were determined with x-ray and PGI measurements. The PGI system was clinically applied to monitor absolute proton ranges for a 1.5Gy field during eight fractions of hypo-fractionated treatment of two prostate-cancer patients using pencil beam scanning (Fig.1). For all monitored fractions, in-room control-CT scans were acquired in treatment position enabling PGI-based spot-by-spot range analysis for the actual patient anatomy. The PG measurements were compared to simulations of the expected PGI signal using either a standard CT-number-to-SPR conversion (HLUT) or a HLUT optimized with patient-specific DECT-derived SPR information (DECT-HLUT), respectively.

Results
The accuracy and precision for global range verification (averaging over multiple spots) was determined to be 0.6mm and 1.3mm (both 2σ-level), respectively. The precision is limited by remaining uncertainties in image registration and positioning reproducibility (1mm,2σ). To verify range prediction in patients, the histogram of range shifts was analyzed concerning its Gaussian mean (Fig. 2) as surrogate for the accuracy of the respective range prediction method, independent from random uncertainty contributions (e.g. positioning, statistical uncertainty in shift determination). The mean deviation for the DECT-HLUT and standard HLUT were -0.6mm and 1.3mm, respectively.

Conclusion
The accuracy of PGI-based range verification was improved to enable the verification of CT-based stopping-power prediction in patients for the first time. First data evaluation suggests a slight superiority of DECT-based range prediction.

  • Lecture (Conference)
    50. Jahrestagung DGMP, 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29060
Publ.-Id: 29060


Combined measurement of velocity and temperature in liquid metal convection

Zürner, T.; Schindler, F.; Vogt, T.; Eckert, S.; Schumacher, J.

Combined measurements of velocity components and temperature in a turbulent Rayleigh-Benard convection flow at a low Prandtl number and for large Rayleigh numbers are conducted in a series of experiments with durations of more than a thousand free fall time units. Multiple crossing ultrasound beam lines and an array of thermocouples at mid-height allow for a detailed analysis and characterization of the complex three-dimensional dynamics of the single large-scale circulation (LSC) roll in the cylindrical convection cell of unit aspect ratio which is filled with the liquid metal alloy GaInSn. We extract the superposition of short-term oscillations of the LSC with different orientation angles close to the top/bottom plates and the related sloshing motion in the mid-plane with the slow azimuthal drift of the mean roll orientation as a whole that proceeds on a hundred times slower time scale, and measure the internal temporal correlations of this complex large-scale flow. The coherent LSC drives a vigorous turbulence in the whole cell that is quantified by direct Reynolds number measurements at different locations in the cell. The velocity increment statistics in the bulk of the cell displays characteristic properties of intermittent small-scale fluid turbulence. We also show that the impact of the symmetry-breaking large-scale flow persists to small-scale velocity fluctuations thus preventing the establishment of isotropic turbulence in the cell center. Reynolds number amplitudes depend sensitively on beam line position in the cell such that different definitions have to be compared. The global momentum and heat transfer scalings with Rayleigh number are found to agree with those of direct numerical simulations and other laboratory experiments.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29059
Publ.-Id: 29059


Microorganisms present in bentonites from a deep underground experiment

Lopez-Fernandez, M.; Drozdowski, J.; Kluge, S.; Cherkouk, A.

The deep geological repository is one of the internationally accepted options to dispose highly radioactive waste. For this, a multi-barrier system where the radioactive waste will be encapsulated in a technical barrier (metal containers) surrounded by a geotechnical barrier (e.g. compacted bentonite) deep underground in a stable geological formation (host rock) can be used. Bentonites might be used as sealing and backfilling material due to their good properties such as high swelling capacity and low hydraulic conductivity. However, indigenous microorganisms and those introduce during the repository construction and operation can affect these properties.
Bentonite core samples were collected from the Full-scale Engineered Barrier Experiment (FEBEX) in the frame of the FEBEX-Dismantling Project [1] at the Grimsel Test Site (Switzerland) to study their microbial diversity. For that, total DNA was extracted directly from the cores. In addition, sulfate- and iron-reducing microorganisms were enriched from the bentonite samples using specific media. From those enrichments total DNA was extracted and sulfate- and iron-reducing microorganisms were isolated. The microbial communities of the cores, the enrichments, as well as the isolates were analyzed by 16S rRNA gene sequencing. The results showed that the FEBEX bentonite microbial population was directly affected by the continuous high temperature. The dominant phylum in both enrichments was Firmicutes. Desulfosporosinus, Clostridium and Bacillus spp. were identified from the medium for sulfate-reducers, while Desulfitobacterium and Bacillus spp. were detected in the iron-reducing enrichment. Pure cultures were isolated from both enrichments, identifying spore-forming bacteria.
This study revealed that microorganisms were detected on the FEBEX bentonite after almost twenty years of continuous heating. Sulfate- and iron-reducing microbes were enriched by using favorable conditions in specific media. Therefore, it is important to characterize the microbial population of the bentonite used as geotechnical barrier, because microbes might compromise the safety of the deep geological repository of highly radioactive waste.

[1] http://www.grimsel.com/gts-phase-vi/febex-dp/febex-dp-introduction

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

Permalink: https://www.hzdr.de/publications/Publ-29058
Publ.-Id: 29058


Combined Magnetron Sputtering- and Flash Lamp Annealing- Tool for Thin Film Processing under Vacuum Conditions

Begeza, V.; Rebohle, L.; Neubert, M.; Zhou, S.

Unintentional contaminations during the thin film processing can occur, wich can lead to serious quality and performance degradations. In this work a new tool is presented wich combines DC Magnetron Sputtering and the Flash Lamp Annealing technology. Both processes are performed under vacuum conditions, to keep the Oxygen and Hydrogen contamination of the film low.

Keywords: Flash Lamp Annealing; Magnetron Sputtering; thin film processing; vacuum

  • Lecture (Conference)
    44. Treffen der Nutzergruppe Heißprozesse und RTP, 03.-04.04.2019, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29057
Publ.-Id: 29057


Effect of Anions on the Changes in the Structure and Adsorption Mechanism of Zirconium Species at the Muscovite (001) – Water Interface

Yuan, K.; Bracco, J. N.; Schmidt, M.; Soderholm, L.; Fenter, P.; Lee, S. S.

Multivalent cations primarily exist as polynuclear hydroxo and oxyhydroxo clusters and/or nanoparticles (NPs) in aqueous environments, where their interactions with mineral surfaces can be influenced by complexing anions. Here, we investigated the effect of background electrolyte anions (specifically ClO4-, Cl-, SO42-, and HPO42-) on the distribution of tetravalent Zr adsorbed on the negatively charged basal surface of muscovite mica. The experiments were conducted at constant pH (= 3), total Zr(IV) concentration (= 0.1 mM), and ionic strength (= 0.1 M). The Zr coverages measured by X-ray fluorescence (XRF) in ClO4- and Cl- systems were 1.3 and 2.1 Zr/AUC (where AUC = 46.72 Å2 is the area of the unit cell of the mica (001) surface), respectively, and mostly remained unchanged during the reaction time from 6 to 50 h. In these conditions, Zr adsorption occurred both as small NPs (with an average height of ~4 nm observed by ex situ atomic force microscopy, AFM) and in a ~2 nm-thick molecular layer (observed by in situ resonant anomalous X-ray reflectivity, RAXR). In comparison, higher Zr coverages that increased with reaction time (i.e., from ~4 to ~7 Zr/AUC from 6 to 50 h reactions) were observed in the SO42- system. Ex situ AFM revealed that the Zr uptake in this system occurred predominantly as NPs that were ca. 5 to 15 nm tall and 20 to 40 nm wide, but no evidence of the interfacial molecular-layer formation was observed by RAXR. In the HPO42– solution, all measurements unequivocally showed no significant Zr sorption, in stark contrast to the observations in the other solutions. Details of the Zr surface coverage and sorption modes are consistent with the known clustering of tetravalent Zr in solutions in the presence of these anions. These results demonstrate the significant impact of anions on the adsorption affinity and mechanism of Zr on the negatively charged mica surface.

Keywords: CTF/RAXR; Sorption; Zirconium; Nanoparticles; XRF; AFM

Permalink: https://www.hzdr.de/publications/Publ-29056
Publ.-Id: 29056


Towards the electronic structure of actinide oxides nanoparticles

Kvashnina, K.

Understanding the mechanisms of different chemical reactions with actinides at the atomic level is a key step towards safe disposal of nuclear wastes and towards the identification of physical-chemical processes of radionuclides in the environment. This contribution will provide an overview of the recently performed studies on Uranium, Thorium, Plutonium and Cerium oxide nanoparticles at the Rossendorf Beamline (ROBL)[1] of the European Synchrotron (ESRF) in Grenoble (France). This innovative, recently upgraded, world-wide unique experimental station, funded and operated by HZDR in Dresden (Germany) was used to study actinide systems by several experimental methods, mainely by X-ray absorption spectroscopy in high energy resolution fluorescence detection (HERFD) mode and resonant inelastic X-ray scattering (RIXS) at the An/Ln L3 and An M4,5 edge [2–5]. The experimental results have been analysed using a number of theoretical methods based on density functional theory and atomic multiplet theory. This research has received funding from European Research Council (ERC) under grant agreement 759696

  • Lecture (Conference)
    Goldschmidt2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29055
Publ.-Id: 29055


Reduction of NpO2+ and TcO4- at the FeII-montmorillonite-water interface

Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.

The fate of the long-lived, redox-sensitive radionuclides neptunium (237Np) and technetium (99Tc) in deep geological radioactive waste repositories is a major environmental issue. Both elements are highly soluble in their oxidized redox state, and are not (TcO4-) or only weakly sorbed (NpO2+) by negatively charged clay minerals. In the presence of adsorbed and/or structural FeII, however, clay minerals have been shown to reduce (co-)adsorbed contaminants such as U and Se [1, 2], thereby increasing the solid-water distribution coefficient (retention) by several orders of magnitude. In order to investigate if, to which extent, and under which conditions NpV and TcVII are reduced to their tetravalent oxidation states, we conducted Np and Tc batch adsorption experiments with iron-free montmorillonite and with DCB-reduced Wyoming (2.9 wt. % Fe) montmorillonite under different experimental conditions (i.e. anoxic, electrochemical reduction, in the absence and presence of dissolved FeII). The final oxidation state and the type of surface complex formed was elucidated by X-ray absorption spectroscopy at Np-L3, Tc-K and Fe-K edges. We show that both adsorbed and structural FeII are able to reduce NpV and TcVII to NpIV and TcIV, respectively, but the extent strongly depends on the available amount of FeII and on the experimental conditions. The reduced Np strongly complexes towards co-adsorbed Fe and no NpO2 formation is observed. In the case of Tc, mainly TcO2-like nanoparticles form. Surface complexation via Fe is only observed at low Tc surface loadings.

Keywords: Technetium; Neptunium; ROBL; EXAFS; redox; clay; iron

  • Invited lecture (Conferences)
    Goldschmidt Conference, 18.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29054
Publ.-Id: 29054


REMOO-2019 Blind Test Calculation Workshop (BTW)

Höhne, T.

A blind test benchmark of transient 2-phase flow simulation codes will be organized.
The purpose is to give participants an opportunity to test their code capability to predict onset of dryout, post-dryout heat transfer phenomena as well as subsequent rewetting in a boiling water rod bundle geometry under realistic operational conditions. Experimental data that will be used in the blind test have been obtained in a 4 by 4 rod bundle and include pressure drops along the bundle divided into six sub-sections, rod clad temperatures at fourteen elevations and coolant temperatures at six elevations.
For analyzed experimental case, steady-state initial and boundary conditions as well as transient forcing functions have been recorded together with above-mentioned parameters.

Keywords: CFD; Subchannel codes; dryout; post dryout; rod bundle

  • Lecture (Conference)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Permalink: https://www.hzdr.de/publications/Publ-29053
Publ.-Id: 29053


Adsorption of UVI and EuIII on illite: The important role of accessory minerals

Marques Fernandes, M.; Scheinost, A. C.; Huittinen, N.; Baeyens, B.

Adsorption models able to predict the fate of (radio-)contaminants at water-mineral interfaces are important tools to assess the risk related to their migration in natural environments. In general, adsorption in a multimineralic environment is assumed to be governed by the major reactive mineral constituents. A common procedure to predict the adsorption by a soil/rock entity is to combine in an additive way the adsorption models for each single mineral composing the mineral assemblage, i.e. based on the relative reactive amounts of each mineral.
Ideally, robust and reliable adsorption models should be developed for each environmentally relevant mineral based on experimental data obtained under a wide range of conditions to guarantee their predictive capability. For this it is of utmost importance to study the retention of contaminants on well-characterized minerals, under well-defined and controlled conditions.
Diocthahedral alumina-silicates such as illite and montmorillonite are common mineralogical components of soils and sedimentary rocks which control the migration of (radio-)contaminants in natural systems through their exceptional bulk physical and chemical properties.
In the present study we will illustrate how the adsorption properties of a presumably pure clay mineral, illite du Puy (IdP), can be strongly altered by an accessory mineral (< 0.5 wt.%). The adsorption of UVI as well EuIII on purified IdP (<0.5 µm) under certain conditions (i.e., pH, concentration, presence/absence of dissolved carbonate) showed an unexpected enhancement of the retention of UVI and trivalent actinides and lanthanides (Cm/Am/Eu). The application of extended X-ray absorption fine structure spectroscopy and time resolved laser fluorescence spectroscopy on IdP samples loaded with UVI and EuIII, respectively, clearly suggest complexation by phosphate groups not expected in IdP. For U, the formed surface complex could be identified as an autunite-like phase. In the case of Eu, the formation of a ternary apatite-like Eu-Ca-PO4 solid phase was observed. Furthermore, leached phosphate from the clay mineral resulted in the precipitation of non-sorbed EuIII as rhabdophane (EuPO4×nH2O). The accessory mineral phase itself responsible for this anomalous behaviour is difficult to identify with common analytical methods such as TEM or XRD due to e.g. the low concentration and/or amorphous nature of the accessory phase or the low electron density of its constituent elements. Repeated acid-pre-treatment of IdP released P and Ca, pointing towards an apatite-like accessory phase as source of phosphate for the formation of the UVI and EuIII solid phases. In the pre-treated solid phosphate complexation was greatly reduced. In the case of UVI, an inner-sphere surface complex on IdP edge sites could be identified in the XAFS investigations. Our results demonstrate that adsorption models calibrated over a wide range of experimental conditions, complemented by a molecular-level control and a true mechanistic understanding, is of paramount importance for reliable modelling of adsorption processes at the solid-liquid interface.

Keywords: uranium; autunite; apatite; XAFS; illite; sorption

  • Invited lecture (Conferences)
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29052
Publ.-Id: 29052


A 224Ra-labeled polyoxopalladate as putative radiopharmaceutical

Gott, M.; Yang, P.; Kortz, U.; Stephan, H.; Pietzsch, H.-J.; Mamat, C.

Despite its attractive properties, internal targeted alpha therapies using 223/224Ra are limited to bone-seeking applications. As there is no suitable chelator available, the search for new carriers to stably bind Ra2+ and to connect it to biological target molecules is necessary. Polyoxopalladates represent a class of compounds where Ra2+ can be easily introduced into the Pd-POM core during a facile one-pot preparation. Due to the formation of a protein corona the connection to other targeting (bio)macromolecules is possible.

Keywords: Radium; Barium; POM; alpha-therapy

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29051
Publ.-Id: 29051


A Monte Carlo based radiation response model to assess variability of clinical RBE in proton therapy

Eulitz, J.; Lutz, B.; Wohlfahrt, P.; Dutz, A.; Enghardt, W.; Karpowitz, C.; Krause, M.; Troost, E. G. C.; Lühr, A.

The clinical implementation of a variable relative biological effectiveness (RBE) in proton therapy is currently controversially discussed. First clinical evidence indicates a variable proton RBE, which needs to be verified. In this study, a radiation response model for assessing clinical RBE variability is established. The model was applied to four selected glioma patients (grade III) treated with adjuvant radio(chemo)therapy and who developed late morphological image changes on T1-weighted contrast-enhanced (T1w-CE) magnetic resonance (MR) images within approximately two years of recurrence-free follow-up. The image changes were correlated voxelwise with dose and linear energy transfer (LET) values using univariable and multivariable logit functions. The model performance was assessed by the area-under-the-curve (AUC) performing a leave-one-out cross validation. The tolerance dose TD50 at which 50% of patient voxel experienced toxicity was interpolated from the model. A Monte Carlo (MC) framework was developed to simulate dose and LET distributions, which includes variance reduction (VR) techniques to decrease computation time. Its reliability and accuracy was evaluated based on dose calculations of the clinical treatment planning system (TPS) as well as absolute dose measurements performed in the patient specific quality assurance.
Morphological image changes were related to a combination of dose and LET. The multivariable model revealed a cross-validated AUC of 0.88 (95% confidence interval 0.80 – 0.95). The TD50 decreased linearly with increasing LET indicating an increase in biological effectiveness. The MC framework reliably predicted average TPS dose within the clinical target volume as well as absolute water phantom dose measurements within 2% accuracy using dedicated VR settings.
The observed correlation of dose and LET with late brain tissue damage suggests considering RBE variability for predicting chronic radiation-induced brain toxicities. The MC framework simulates precisely and time-efficiently radiation fields in patients. Hence, this study encourages and enables in-depth patient evaluation to assess the variability of clinical proton RBE.

Keywords: Proton Therapy; Clinical RBE; Monte Carlo; Passive Scattering

Permalink: https://www.hzdr.de/publications/Publ-29049
Publ.-Id: 29049


Improved electrode design for interdigitated large-area photoconductive terahertz emitters

Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.

We study here the effect of the electrode parameters on the terahertz emission efficiency of large-area emitters based on interdigitated electrodes. Electrode parameters are optimized to get maximum terahertz emission by optimizing the balance condition among the emission efficiency of individual electrode pairs, number of emitters per unit area, and fraction of semiconductor exposed for optical pumping. A maximum enhancement by about 50 % in the peak to peak electric field is observed as compared to the previous state of the art design.

Keywords: Terahertz emitters; photoconductive switch; interdigitated electrode

Permalink: https://www.hzdr.de/publications/Publ-29048
Publ.-Id: 29048


Implementation of HZDR baseline model for poly-dispersed bubbly flow in OpenFOAM

Liao, Y.

The predictability of TFM-CFD is largely restricted by the reliability of closures that should reconstruct the information about the phenomena and processes occuring at the interface. The development of physically based models is severely obstructed by insufficient knowledge on the physics and numerous misleading work based on case-by-case tuning. A strategy towards general closures is necessary. A few years ago HZDR proposed a baseline model for TFM-CFD simulation of poly-dispersed bubbly flow with a fixed set of closures. It aims to identify the missing physics in the existing models and improve them step by step. In this work the baseline model is implemented and tested in the open source CFD code OpenFOAM for a large number of bubbly flow cases including vertical pipe flow and bubble column.

  • Lecture (Conference)
    CFD-Verbund, 11.-12.03.2019, Garching bei München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29047
Publ.-Id: 29047


Application of computational fluid dynamics codes for nuclear power plant design

Krause, M.; Smith, B.; Höhne, T.; In, W. K.

Computational Fluid Dynamics (CFD) codes have reached a level of maturity, at least for single-phase applications, to be utilized in the design process of Nuclear Power Plant (NPP) components, such that advanced NPPs over the past years have increasingly utilized CFD codes in their design. A recently completed Cooperative Research Project (CRP) addressed the application of CFD codes to the process of optimizing the design of components in Pressurized Water-cooled Reactors (PWRs). Following several initiatives within the IAEA where CFD codes have been applied to situations of interest in nuclear reactor technology, this CRP aimed to contribute to a consistent application of CFD codes by establishing a common platform to assess their capabilities and level of qualification.

Eleven participant organizations from nine Member States performed simulations against four “CFD-grade” experiments performed to investigate key phenomena for CFD simulations. Two are based on test data from the ROCOM (ROssendorf COolant Mixing) facility at HZDR in Germany, and another two are based on rod-bundle experiments in the OFEL (Omni Flow Experimental Loop) facility at KAERI in Korea.

This paper outlines the objectives of the CRP, provides a description of the test facilities and experiments, and discusses selected results obtained for the four above benchmark exercises.

Keywords: Computational Fluid Dynamics; Reactor Design; CFD Benchmark

  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Permalink: https://www.hzdr.de/publications/Publ-29046
Publ.-Id: 29046


Perfluorinated Calixarene Shuttles for Radium and Barium

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

Alpha therapy is continually discussed in radiopharmaceutical research. [223Ra]RaCl2 is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical so far. Since the use of 223Ra is only based on its calcimimetic behavior. It is directly bond to bone structures in the body. To enhance the therapeutic potential of radium isotopes, it is necessary to develop novel carrier systems for radium ions as a base of biological targeting units. By the combination of 223Ra or 224Ra, which both have suitable physical half-lives for therapeutic applications, and 131Ba which has a similar half-life but diagnostic radiation properties, a theragnostic idea can also be followed. Our project aims at the synthesis of calixarene-based ligands for the stable complexation of barium and radium ions. Recent studies in our group have already shown the high potential of such ligands.

Keywords: Radium-223; Barium-131; Calixarene

  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S261

Permalink: https://www.hzdr.de/publications/Publ-29045
Publ.-Id: 29045


A multi-scale approach simulating generic pool boiling

Höhne, T.; Lucas, D.

The paper presents an application of the GENTOP model for phase transfer and discusses the sub-models used. Boiling of a heated surface under atmospheric conditions is simulated by the multi-field CFD approach. Sub-cooled water in a generic pool is heated up first in the near wall region leading to the generation of small bubbles. Further away from the bottom wall larger bubbles are generated by coalescence and evaporation. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach and it allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models need a constant improvement and separate, intensive validation effort using CFD grade experiments. Recently, a bubble dynamics model inside the heat partitioning approach has been developed and will be applied in GENTOP in future.

Keywords: multi-phase; boiling; GENTOP; multi-scale; CFD

  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Nuclear Science and Engineering (2020)
    DOI: 10.1080/00295639.2020.1764265

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  • Secondary publication expected from 29.05.2021

Permalink: https://www.hzdr.de/publications/Publ-29043
Publ.-Id: 29043


Energy relaxation and electron phonon coupling in laser heated solids

Vorberger, J.; Butcher, T. A.

density functional theory based description of electron phonon coupling for energy relaxation in laser heated solids

Keywords: warm dense matter; energy relaxation; temperature relaxation; electron-phonon coupling; laser heating

  • Open Access Logo Contribution to proceedings
    39th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 27.01.-01.02.2019, Hirschegg, Austria

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29042
Publ.-Id: 29042


Multiphase CFD Modelling: State-of-the-art applications in Energy related Industrial Applications

Höhne, T.

Two-phase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a clear requirement for numerical tools. Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive. Since large scale applications are considered such as chemical reactors or components of the cooling system of a nuclear power plant the Euler-Euler two- or multi fluid model is the base for the development. Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our multiphase flow research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered. A second focus is to establish modelling frameworks as iMUSIG, AIAD and GENTOP to allow a proper consideration of the local physical phenomena. These activities will help to improve the CFD code capabilities in energy related industrial applications.

Keywords: CFD; Multiphase; Fluid Dynamics; HZDR; AIAD; GENTOP

  • Invited lecture (Conferences)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China
  • Contribution to proceedings
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Permalink: https://www.hzdr.de/publications/Publ-29041
Publ.-Id: 29041


Radium-doped BaSO4 Nanoparticles for Future Targeted Alpha Therapy

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

Targeted alpha therapy (TAT) is continually focused and discussed in radiopharmaceutical research [1]. By the combination of an alpha emitting radionuclide with a biological targeting unit, tumor cells can be affected very efficiently by inducing a high number of double strand breaks to the DNA. 223Ra and 224Ra are two alpha-emitting radionuclides with suitable half-lives for TAT. 223Ra in form of [223Ra]RaCl2 (Xofigo®) is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical as well as the prime example for the working principle of TAT. Based on its calcimimetic behavior, radium is built into the bone structure. To exploit the therapeutic potential of alpha emitters like 223Ra and 224Ra, novel targeting strategies and carrier systems have to be developed. Therefore, it is worth to examine alternative carriers like nanoparticles, using the principle of co-precipitation of Ra/BaSO4. By the combination of a therapeutic alpha-emitting radionuclide like 223Ra on the one hand and the diagnostically applicable barium radioisotope 131Ba on the other hand with nearly identical physical half-lives it is also possible pursue theragnostic approaches. Thus, our research aims at developing a simple method for the synthesis of small radiolabeled Ra/BaSO4 nanoparticles and testing further surface functionalization regarding the ability of constructing biological targeting moieties.

Keywords: Radium-224; Barium-131; Nanoparticle

  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S265

Permalink: https://www.hzdr.de/publications/Publ-29040
Publ.-Id: 29040


Calixarene-based ligands for Radium and Barium

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

Due to their high biological effectiveness and suitable half-lives, there is increased interest in using the radionuclides radium-223 and radium-224 for radiopharmaceutical applications. Xofigo ([223Ra]radium chloride) is a bone-seeking, alpha-emitting radiopharmaceutical with EMA and FDA approval. It is used to treat bone metastasis of castrate-resistant prostate cancer. To expand the possible applications for these promising radionuclides, it is necessary to stably bind the radionuclide within a chelator. Therefore, calixarene-based ligands have been synthesized, which show encouraging affinities to radium ions. In our recent studies, we have already presented the high potential of these ligands. Since radium and barium have similar chemistry, and therefore comparable affinities to our ligands, it is possible to create a matched pair for theragnostic approaches. The radionuclide barium-131 has a suitable physical half-life for therapeutic applications and the potential of being a SPECT nuclide.

Keywords: Radium-224; Barium-131; Calixarene

  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access Logo Abstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S39
    DOI: 10.1016/j.jmir.2019.03.118

Permalink: https://www.hzdr.de/publications/Publ-29039
Publ.-Id: 29039


Interobserver variability of image-derived arterial blood SUV in whole-body FDG PET

Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.

Background: Today, the standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static [18 F-]fluorodeoxyglucose (FDG) positron emission tomography (PET) investigations. However, the SUV approach has several well-known shortcomings which adversely affect the reliability of the SUV as a surrogate of the metabolic rate of glucose consumption. The standard uptake ratio (SUR), i.e., the uptake time-corrected ratio of tumor SUV to image-derived arterial blood SUV, has been shown in the first clinical studies to overcome most of these shortcomings, to decrease test-retest variability, and to increase the prognostic value in comparison to SUV. However, it is unclear, to what extent the SUR approach is vulnerable to observer variability of the additionally required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.

Methods: FDG PET/CT scans from 83 patients (72 male, 11 female) with non-small cell lung cancer (N = 46) or head and neck cancer (N = 37) were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Two of the observers applied two further tools. Altogether, five different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Intersubject variability of BSUV determination was assessed using the fractional deviations for the individual patients from the patient group average and was quantified as standard deviation (SDis ), 95% confidence interval, and range. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient and quantified as standard deviations (SDp , SDd ) or root mean square (RMS), 95% confidence interval, and range in each patient, each observer, and the pooled data respectively.

Results: Interobserver variability in the pooled data amounts to RMS = 2.8% and is much smaller than the intersubject variability of BSUV (SDis = 16%). Averaged over the whole patient group, deviations of individual observers from the observer average are very small and fall in the range [− 0.96, 1.05]%. However, interobserver variability partly differs distinctly for different patients, covering a range of [0.7, 7.4]% in the investigated patient group.

Conclusion: The present investigation demonstrates that the image-based manual determination of BSUV in the aorta is sufficiently reproducible across different observers and delineation tools which is a prerequisite for accurate SUR determination. This finding is in line with the already demonstrated superior prognostic value of SUR in comparison to SUV in the first clinical studies.

Keywords: PET; FDG; Quantification; SUV; SUR; Blood SUV

Permalink: https://www.hzdr.de/publications/Publ-29038
Publ.-Id: 29038


Flexible IGZO TFTs and their Suitability for Space Applications

Costa, J. C.; Pouryazdan, A.; Panidi, J.; Spina, F.; Anthopoulos, T.; Liedke, M. O.; Schneider, C.; Wagner, A.; Münzenrieder, N.

In this paper, Low Earth Orbit radiation, temperature and magnetic field conditions are mimicked to investigate the suitability of flexible Indium Gallium Zinc Oxide transistors for lightweight space wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive radiation detectors or physiological monitors. Due to the harsh environment to which these space wearables would be exposed, they have to be able to withstand high radiation doses, low temperatures and magnetic fields. For this reason, the impacts of high energetic electron irradiation with fluences up to 1E12 e−/cm2, low operating temperatures down to 78K and magnetic fields up to 11mT are investigated. This simulates 278 h in Low Earth Orbit. The threshold voltage and mobility of transistors that were exposed to e- irradiation are found to shift by +(0.09 +- 0.05)V and (0.6 +- 0.5) cm 2 V−1 s−1. Subsequent low temperature exposure resulted in additional shifts of +0.38V and -5.95 cm2 V−1 s−1 for the same parameters. These values are larger than the ones obtained from non irradiated reference samples. In addition, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiate, cooled down and exposed to the magnetic fields. If these notions are considered during the systems’ design, these devices can be used to unobtrusively integrate sensor systems into space suits.

Keywords: Flexible electronics, Space applications, Amorphousnoxides; Wearables, Thin film transistors

Permalink: https://www.hzdr.de/publications/Publ-29037
Publ.-Id: 29037


Fifteen Years of Radionuclide Research at the KIT Synchrotron Source in the Context of the Nuclear Waste Disposal Safety Case

Rothe, J.; Altmaier, M.; Dagan, R.; Dardenne, K.; Fellhauer, D.; Gaona, X.; González-Robles Corrales, E.; Herm, M.; Kvashnina, K.; Metz, V.; Pidchenko, I.; Schild, D.; Vitova, T.; Geckeis, H.

For more than 120 years, systematic studies of X-ray interaction with matter have been the basis for our understanding of materials—both of natural or man-made origin—and their structure-function relationships. Beginning with simple radiographic imaging at the end of the 19th century, X-ray based analytical tools such as X-ray diffraction, X-ray fluorescence and photoemission or X-ray absorption techniques are indispensable in almost any field of chemical and material sciences—including basic and applied actinide and radionuclide studies. The advent of dedicated synchrotron radiation (SR) sources in the second half of the last century has revolutionized the analytical power of X-ray probes, while—with increasing number of SR facilities—beamline instrumentation followed a trend towards increasing specialization and adaption to a major research topic. The INE-Beamline and ACT station at the KIT synchrotron source belong to the exclusive club of a few synchrotron beamline facilities—mostly located in Europe—dedicated to the investigation of highly radioactive materials. Since commissioning of the INE-Beamline in 2005, capabilities for synchrotron-based radionuclide and actinide sciences at KIT have been continuously expanded, driven by in-house research programs and external user needs.

Permalink: https://www.hzdr.de/publications/Publ-29035
Publ.-Id: 29035


Metallgewinnung durch Mikrobiologie – Biologisch assistierte Prozesse in der Rohstofftechnologie

Lederer, F.

Der Rohstoffsektor ist geprägt von enormem Materialbedarf für die Entwicklung und Produktion neuer High-Tech Produkte. Neben der Optimierung von Bergbauprozessen zur Gewinnung von primären Rohstoffen fokussiert das Helmholtz-Institut Freiberg für Ressourcentechnologie die Vision der Kreislaufwirtschaft. Diese setzte neben dem Schwerpunkt Nachhaltigkeit im Hinblick auf Produktdesign, Produktion, Verteilung, Konsum, Verwendung, Reparatur und Sammlung vor allem auf das Recycling von Wertstoffen.
Mikrobiologisch assistierte Recyclingprozesse zur Rückgewinnung von Wertstoffen aus Elektronikschrott und Bergbauresthalden sowie innovative und umweltfreundliche Lösungen für die Ressourcensicherung standen im Fokus der 29. Jenaer Industriegespräche der DPG.
Themenschwerpunkte des Vortrages waren Interaktionen von Mikroorganismen mit Metallen, das biotechnologische Potential neuer Ressourcentechnologien, Grenzen überwindende Bioflotation, die Metallgewinnung mittels Siderophoren, Evolution im Reagenzglas sowie Biokollektoren für das Recycling von Wertstoffen aus Elektroschrott.

  • Invited lecture (Conferences)
    29. Jenaer Industriegespräche der DPG, 20.03.2019, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29034
Publ.-Id: 29034


Consolidative thoracic radiotherapy in stage IV small cell lung cancer: Selection of patients amongst European IASLC and ESTRO experts

Putora, P. M.; Glatzer, M.; de Ruysscher, D.; Faivre-Finn, C.; Belderbos, J.; Besse, B.; Blackhall, F.; Califano, R.; Cappuzzo, F.; de Marinis, F.; Dziadiuszko, R.; Felip, E.; Früh, M.; Garrido, P.; Le Pechoux, C.; Mcdonald, F.; Nestle, U.; Novello, S.; Brien, M. O.; Paz Ares, L.; Peeters, S.; Pöttgen, S.; Ramella, S.; Reck, M.; Troost, E. G. C.; van Houtte, P.; Westeel, V.; Widder, J.; Mornex, F.; Slotman, B. J.

Background: The role of consolidative thoracic radiotherapy (TRT) in stage IV small cell lung cancer (SCLC) is not uniformly accepted. Methods: We obtained a list of 13 European medical oncologists from the International Association for the Study of Lung Cancer (IASLC) and 13 European radiation oncologists from the European Society for Therapeutic Radiation Oncology (ESTRO). The strategies in decision making for TRT in stage IV SCLC were collected. Decision trees were created representing these strategies. Frequencies of recommending TRT were analysed for various parameter combinations based on the objective consensus methodology. Results: The factors associated with the recommendation for TRT included fitness of the patient, limited extrathoracic tumour burden, initial bulky thoracic disease and response to chemotherapy. The highest consensus for TRT was in fit patients with limited extrathoracic tumour burden and initial bulky disease with either a complete extrathoracic response or partial thoracic response (92% recommend TRT). For these patients the recommendations were the same for medical and radiation oncologists. In the setting of partial response (intra- and extra-thoracically) without initial bulky thoracic disease radiation oncologists were more likely to recommend TRT than medical oncologists. For unfit patients or for patients with poor overall response to chemotherapy, the majority did not recommend TRT. Conclusion: European radiation and medical oncologists specializing in lung cancer recommend TRT in selected patients with stage IV SCLC and restrict its use primarily to fit patients who responded to chemotherapy with limited extrathoracic tumour burden.

Keywords: ESTRO; Expert opinion; IASLC; Small cell lung cancer; Stage IV; Thoracic radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-29033
Publ.-Id: 29033


Repeat FMISO-PET imaging weakly correlates with hypoxia-associated gene expressions for locally advanced HNSCC treated by primary radiochemotherapy

Löck, S.; Linge, A.; Seidlitz, A.; Bandurska-Luque, A.; Nowak, A.; Gudziol, V.; Buchholz, F.; Aust, D. E.; Baretton, G. B.; Zöphel, K.; Steinbach, J.; Kotzerke, J.; Overgaard, J.; Zips, D.; Krause, M.; Baumann, M.; Troost, E. G. C.

Background: Hypoxia is an important factor of tumour resistance to radiotherapy, chemotherapy and potentially immunotherapy. It can be measured e.g. by positron emission tomography (PET) imaging or hypoxia-associated gene expressions from tumour biopsies. Here we correlate [ 18 F]fluoromisonidazole (FMISO)-PET/CT imaging with hypoxia-associated gene expressions on a cohort of 50 head and neck squamous cell carcinoma (HNSCC) patients and compare their prognostic value for response to radiochemotherapy (RCTx). Methods: FMISO-PET/CT images of 50 HNSCC patients were acquired at four time-points before and during RCTx. For 42 of these patients, hypoxia-associated gene expressions were evaluated by nanoString technology based on a biopsy obtained before any treatment. The FMISO-PET parameters tumour-to-background ratio and hypoxic volume were correlated to the expressions of 58 hypoxia-associated genes using the Spearman correlation coefficient ρ. Three hypoxia-associated gene signatures were compared regarding their correlation with the FMISO-PET parameters using their median expression. In addition, the correlation with tumour volume was analysed. The impact of both hypoxia measurement methods on loco-regional tumour control (LRC) and overall survival (OS) was assessed by Cox regression. Results: The median expression of hypoxia-associated genes was weakly correlated to hypoxia measured by FMISO-PET imaging (ρ ≤ 0.43), with higher correlations to imaging after weeks 1 and 2 of treatment (p < 0.001). Moderate correlations were obtained between FMISO-PET imaging and tumour volume (ρ ≤ 0.69). Prognostic models for LRC and OS based on the FMISO-PET parameters could not be improved by including hypoxia classifiers. Conclusion: We observed low correlations between hypoxia FMISO-PET parameters and expressions of hypoxia-associated genes. Since FMISO-PET showed a superior patient stratification, it may be the preferred biomarker over hypoxia-associated genes for stratifying patients with locally advanced HNSCC treated by primary RCTx.

Keywords: FMISO-PET; Gene signature; Hypoxia; Locally advanced HNSCC; Radiochemotherapy

Permalink: https://www.hzdr.de/publications/Publ-29032
Publ.-Id: 29032


Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems

Hähnel, V.; Khan, F. Z.; Mutschke, G.; Cierpka, C.; Uhlemann, M.; Fritsch, I.

A novel method to drive and manipulate fluid in a contactless way in a microelectrode-microfluidic system is demonstrated by combining the Lorentz and magnetic field gradient forces. The method is based on the redox-reaction [Fe(CN)6]3−/[Fe(CN)6]4− performed in a magnetic field oriented perpendicular to the ionic current that crosses the gap between two arrays of oppositely polarized microelectrodes, generating a magnetohydrodynamic flow. Additionally, a movable magnetized CoFe micro-strip is placed at different positions beneath the gap. In this region, the magnetic flux density is changed locally and a strong magnetic field gradient is formed. The redox-reaction changes the magnetic susceptibility of the electrolyte near the electrodes, and the resulting magnetic field gradient exerts a force on the fluid, which leads to a deflection of the Lorentz force-driven main flow.
Particle Image Velocity measurements and numerical simulations demonstrate that by combining the two magnetic forces, the flow is not only redirected, but also a local change of concentration of paramagnetic species is realized.

Keywords: microfluidics; electrochemistry; redox-reaction; magnetic field; Lorentz force; magnetic gradient force; flow control

  • Open Access Logo Scientific Reports 9(2019), 5103
    DOI: 10.1038/s41598-019-41284-0
  • Lecture (Conference)
    11th International PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-29031
Publ.-Id: 29031


Avoided energy cost of producing minerals: The case of iron ore

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

There is growing concern about the decline of the ore grade in mines and the increased energy usage for processing and refining metals. In the limit, where no concentrated deposits exist, minerals must be obtained from bare rock. A method for quantitatively assessing the “free bonus” granted by nature in providing concentrated minerals in mines and thus assessing the quality of the different resources is estimating how much energy is needed to concentrate the minerals, as they are already in mines, from bare rock. This bonus granted by nature reduces the costs of human mining and metallurgical processes, as well as the mining effort required of future generations. In this study, the concentration of high-iron-content minerals in common rocks was investigated via a computational model developed using the HSC software. As expected, the range of results for the specific energy for the concentration of iron from common rocks was considerably higher than the energy required by modern processes. This reveals the need to value current iron deposits and the challenge of developing sustainable methods of metal production to satisfy the needs of the present and future generations.

Keywords: Energy consumption; Exergy replacement cost; Iron; Metallurgy; Mining; Thanatia

Permalink: https://www.hzdr.de/publications/Publ-29030
Publ.-Id: 29030


Einfluss polymerer Zementadditive auf die Mobilität von Radionukliden unter Nahfeldbedingungen eines Endlagers

Lippold, H.; Becker, M.; Schymura, S.

Zementmaterialien, die im Endlagersystem als Bau- und Versatzstoff verwendet werden, enthalten polymere Fließmittel (Superplasticizer) mit komplexierenden Eigenschaften. Insbesondere in Niedrig-pH-Zement kann eine teilweise Persistenz nicht ausgeschlossen werden [1]. Bei Freisetzung durch Laugungsprozesse nach Wasserzutritt besteht die Möglichkeit, dass Adsorptionsbarrieren für Radiometalle durch Komplexbildung unterwandert werden [2, 3]. Die entsprechenden Randbedingungen (pH-Wert, Elektrolytgehalt) sind zu identifizieren.

Die Komplexbildung von Eu(III) (Actinid-Analogon) mit einem kommerziellen Superplasticizer auf Polycarboxylatether-Basis (MasterGlenium® 51, BASF) wurde mittels Ultrafiltration und 152Eu als Radiotracer konzentrationsabhängig vermessen und auf der Grundlage des Ladungsneutralisationsmodells [4] mit Bezug auf den Carboxylgruppengehalt parametrisiert. Bei geringer Ionenstärke besteht demnach ein hohes Mobilisierungspotential. Die für Zementsysteme typischen hohen Elektrolytgehalte schränken den Effekt allerdings stark ein. Die Auswirkung des Plasticizers auf das Adsorptionsverhalten von Eu(III) an Ca-Bentonit als Puffermaterial wurde in Gegenwart von NaCl und CaCl2 (bis 4 mol/L) unter CO2-Ausschluss im pH-Bereich 9 - 13 untersucht. Die Mobilität des Metalls wird bereits bei moderaten Ionenstärken ausschließlich durch den Elektrolyteffekt bestimmt, eine Komplexbildung also völlig unterbunden. Somit ist aufgrund des chemischen Milieus im Endlagernahfeld selbst im Falle einer Freisetzung der intakten Polymere nicht von Carrier-Effekten auszugehen.

[1] M. A. Glaus, L. R. Van Loon, Nagra Technical Report 03-09, 2004.
[2] M. Dario et al., SKB Technical Report TR-04-04, 2004.
[3] A. J. Young, Dissertation, Loughborough University, 2012.
[4] J. I. Kim, K. R. Czerwinski, Radiochim. Acta 1996, 73, 5.

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

Permalink: https://www.hzdr.de/publications/Publ-29029
Publ.-Id: 29029


Doping of silicon nanowires by ion implantation and flash lamp annealing

Berencen, Y.; Prucnal, S.; Wang, M.; Rebohle, L.; Helm, M.; Zhou, S.; Skorupa, W.

In this work, we report on non-equilibrium processing for controlled doping of Si/SiO2 core/shell nanowires with shallow- and deep-level dopants below and above their equilibrium solid solubility. In detail, the shallow-level dopants B and P as well as the deep-level dopant Se was implanted, followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to the formation of an intermediate band in Si which in turn causes a room-temperature sub-band gap photoresponse of the nanowire when configured as a photoconductor device [1]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual nanowires at different depth along the NW core.
[1] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 1800101

Keywords: doping; nanowires; semiconductor; silicon; ion implantation; flash lamp annealing

  • Lecture (Conference)
    44. Treffen der Nutzergruppe Heißprozesse und RTP, 03.04.2019, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29028
Publ.-Id: 29028


Evaluierung der Tracking Genauigkeit eines Niedrigfeld MR-LINACs mittels eines 4D MRT Bewegungsphantoms

Schneider, S.; Dolde, K.; Rothlübbers, S.; Jenne, J.; Spindeldreier, K.; Pfaffenberger, A.; Hoffmann, A.; Klüter, S.

Einleitung
Mit der Entwicklung von hybriden Magnetresonanz-geführten Linearbeschleunigern (MR-LINAC) wurde die Möglichkeit der MR-Echtzeitbildgebung während der Strahlentherapie klinische Realität. Gerade Patienten mit bewegten Tumoren könnten davon profitieren, da die Tumorbewegung durch Gating oder Tracking Verfahren kompensiert werden kann. Ziel dieser Studie war die Evaluierung der Genauigkeit der implementierten online Echtzeit Tracking-Verfahren eines 0.35 T MR-LINAC, sowie der Vergleich zu alternativen offline Tracking-Algorithmen Verfahren.

Material & Methoden
Ein MRT-Bewegungsphantom wurde mit klinisch verwendeter sagittaler cine-MR Bildgebung gescannt. Das bewegbare Hoch-Kontrast Target des Phantoms vollführte dabei verschiedene sinusförmige 1D, 2D, und 3D Trajektorien unterschiedlicher Amplituden (4.5-40 mm) bei einer Frequenz von 0.2 Hz. Die Genauigkeit der im MR-Scanner implementierten, auf deformierbarer Registrierung basierenden, online Tracking Verfahren (TM-1, TM-2) wurde evaluiert. Diese wurde mit einer offline Schwellenwert-basierten Tracking Analyse (TM-3) und einem Echtzeit-fähigen Particle Filter Algorithmus basierenden Tracking Verfahren verglichen. Damit wurde die erreichbare Genauigkeit der Tracking Verfahren untersucht, die die 2D cine MR-Bildgebung prinzipiell ermöglicht.

Ergebnisse
Die online Tracking Methoden TM-1 und TM-2 beschrieben die vorgegebene Bewegung mit einer durchschnittlichen Abweichung der Schwerpunktsbewegung von der vorgegebenen Trajektorie von Δ_mittelTM-1 ≤ 1.5 mm und Δ_mittelTM-2 ≤ 2.7 mm und einer maximalen Abweichung von Δ_maxTM-1 ≤ 5.1 mm und Δ_maxTM-2 ≤ 5.4 mm. TM-3 resultierte in Δ_mittelTM-3 ≤ 0.4 mm und Δ_maxTM-3 ≤ 3.1 mm, während TM-4 die Bewegung teilweise präziser akkurater beschrieb mit Δ_meanTM-4 ≤ 0.4 mm und Δ_maxTM-4 ≤ 2.4 mm.

Zusammenfassung
Wenn auch das klinisch verwendete Tracking Verfahren TM-1 für Gating zufriedenstellende Genauigkeiten erreicht, erlaubt die Bildgebung des Hoch-Kontrast Targets des Phantoms am MR-LINACs höhere Genauigkeiten. Mit entsprechend entwickelten Tracking-Algorithmen lässt sich diese Genauigkeit prinzipiell auch in Echtzeit erreichen.

Keywords: MR-Linac; 4D MRI Phantom; Tracking

  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V., 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29027
Publ.-Id: 29027


Ultrasonic flow measurements in liquid metal flows with partial solidification

Franke, S.; Räbiger, D.; Eckert, S.

The monitoring of the flow rate is an inherent part of process control in all technical large-scale plants to guarantee process stability and safety. It is particularly important for nuclear applications. In the case of a liquid metal coolant in addition, the control of the aggregate state is important.
The use of ultrasound techniques opens an attractive opportunity to measure both the fluid velocity by evaluating the Doppler phase shift and the phase boundary by the detection of the reflection signal from the interface. In addition, the measuring principle enables a noninvasive implementation of the measuring technique. A test facility is necessary to qualify the measuring technique for real applications.
In this study a new LBE experimental facility has been designed and constructed. The setup enables to control the temperature and the fluid flow in the liquid. Further a partial solidification can be induced. The liquid metal vessel is equipped with ten ports for ultrasonic probes. These ports allow for testing the ultrasound measuring principle for different conditions. It was demonstrated that the ultrasonic sensors can be operated up to 200°C at the piezo element. First measuring results demonstrate the potential of ultrasound measuring techniques for monitoring liquid metal applications.

  • Lecture (Conference)
    SESAME International Workshop, 19.-21.03.2019, Petten, Netherlands
  • Contribution to proceedings
    SESAME International Workshop, 19.-21.03.2019, Petten, Netherlands
    SESAME International Workshop

Permalink: https://www.hzdr.de/publications/Publ-29026
Publ.-Id: 29026


Probing charged lepton flavor violation with the Mu2e experiment

Mueller, S. E.; Ferrari, A.

The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless conversion of muons to electrons in the field of an aluminum nucleus. In the Standard Model, this process, which violates charged lepton flavor, is highly suppressed and therefore undetectable. However, scenarios for physics beyond the Standard Model predict small but observable rates. The Mu2e experiment aims at a sensitivity four orders of magnitude better than existing experiments. This is achieved by a rigorous control of all backgrounds that could mimic the monoenergetic conversion electron.

At HZDR, we use the ELBE radiation facility to study radiation hardness and performance of components for the Mu2e calorimeter and contribute with Monte Carlo simulations to the understanding of the optimal configuration for the detector that will monitor the rate of stopped muons in the aluminum target. Additional simulations are performed for both the pion production target and the muon stopping target.

In the presentation, the design and status of the Mu2e experiment will be presented, and results from the ELBE beamtimes and the simulation studies will be given.

Keywords: Mu2e; CLFV; ELBE

  • Lecture (Conference)
    Spring Meeting DPG, 22.03.2019, Muenchen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29025
Publ.-Id: 29025


Composition and Structure of Surface Oxides on Press-Hardened Hot-Dip Galvanized Steel

Gaderbauer, W.; Arndt, M.; Steck, T.; Klingner, N.; Faderl, J.; Groiß, H.

Zink-coated press hardened steel (PHS) is due to its extremely high tensile strength and its excellent corrosive protection indispensable for structural elements in modern automotive applications. Different studies clarify the resulting microstructure of the Zn-coating after press hardening [1] of such steel parts. Also, the uppermost surface oxide layer, which can be influenced by steel matrix alloy elements, has a significant impact on the processing properties like coating or welding.
In this study, we investigated these surface oxide layers for alloy compositions of four different PHS systems with scanning and conventional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and helium ion microscopy (HIM). The complex and porous oxide-layers were stabilized by epoxy before the preparation of cross-sections and TEM-lamellae by focused ion beam milling.
The main oxides on top of the original thin Al2O3 layer, originating from the primary galvanizing process, could be determined with energy dispersive X-ray spectroscopy (EDX), selected area diffraction and AES as Zn-oxides and (Mn,Zn)Mn2O4 spinel (Fig. 1a). Also noticeable was a varying, nanometre thick Cr enrichment at this Al2O3 layer (Fig. 1b), which depends strongly on the steel alloy. Further experiments with secondary mass spectrometry (ToF-SIMS) attached to a HIM [2] allowed reliable distinguishing between ZnO and Zn(OH)2 (Fig. 2c), which are both present in our oxide layers.
Thus, we could show an influence of different steel alloy elements on the final oxide structure after press hardening. The formation of spinel is triggered by Mn, which is transported with the Zn above the Al2O3 layer, which itself is a trap for Cr, leading to a coverage of it with Cr-oxides.

Figure 1. a) AES Mapping. b) STEM-EDX Mapping c) ToF-SIMS Mapping

References:
[1] H. Järvinen et al, Surface and Coatings Technology 352 (2018), 378-391.
[2] N. Klingner et al, Ultramicroscopy 198 (2019), 10-17.

The financial support by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development in the frame of the CDL for nanoscale phase transformations is gratefully acknowledged.

  • Lecture (Conference)
    9th Austrian Society for Electron Microscopy workshop, 25.-26.04.2019, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29024
Publ.-Id: 29024


Entwicklung einer Positionierhilfe für die Bestrahlung von Weichgewebssarkomen des Unterarms in einem ersten klinischen Prototyp der MR-integrierten Protonentherapie

Anders, P.; Karsch, L.; Hoffmann, A.

Einleitung
Die Machbarkeit von gleichzeitiger Protonentherapie und MR-Bildgebung wurde bereits durch die experimentelle Integration eines Niederfeld-MRTs in eine statische Protonenstrahlführung gezeigt[1].
Als nächster Schritt wurde der MR-Scanner in eine Pencil-Beam-Scanning Strahlführung integriert. Dieser Aufbau soll perspektivisch für eine erste Patientenbestrahlung an Weichgewebssarkomen des Unterarms genutzt werden. Da die geometrischen Randbedingungen im in-beam-MRT lediglich eine Bestrahlung im Sitzen mit seitlich ausgestrecktem Arm zulassen (Abb. 1), das Planungs-CT aber liegend mit über dem Kopf ausgestreckten Armen durchgeführt wird, ist eine neuartige Arm-Positionierhilfe notwendig. Der Beitrag zeigt deren Entwicklung anhand erster Ergebnisse.

Material & Methoden
Die Komponenten der Positionierhilfe (Armschiene, Griffe, Anschlagbolzen) wurden in der hauseigenen Werkstatt aus Polyurethan gefertigt. Diese können je nach Patientenanatomie ausgewechselt werden. Zur Evaluierung der Positioniergenauigkeit wurden wiederholt MRT-Bildserien eines Probanden einerseits in Bestrahlungsposition am 0,22T in-beam-MRT aufgenommen, andererseits an einem 3T-MRT aufgezeichnet (Abb. 2), um die Patientenposition während des Planungs-CTs zu simulieren. Mittels einer selbst programmierten Bildregistrierungssoftware wurden Positionsabweichungen bestimmt.

Ergebnisse
Die Positionierung des Arms konnte am 3T-MRT mit einer Unsicherheit von coronal sowie sagittal durchgeführt werden. Am 0,22T-MRT betrug die Unsicherheit coronal sowie transversal. Außerdem zeigte sich, dass die Armschiene für den Übergang aus der liegenden in die sitzende Position geeignet ist.

Zusammenfassung
Eine Arm-Positionierhilfe für die erste Patientenbestrahlung von Weichgewebssarkomen des Unterarms an einem klinischen Prototyp für MR-integrierte Protonentherapie wurde entwickelt und evaluiert. Sie ermöglicht die Immobilisierung des Patientenarms sowohl in der üblichen Liegeposition des Planungs-CTs als auch in der aufgrund geometrischer Randbedingungen während der Bestrahlung nötigen Sitzposition im in-beam-MRT.

Keywords: Protonentherapie; MRT

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V., 18.-21.09.2019, Stuttgart, Deutschland
  • Poster
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V, 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29022
Publ.-Id: 29022


Experimentelle Untersuchung der Strahlqualität für MR integrierten Protonentherapie

Gantz, S.; Schellhammer, S.; Smeets, J.; Hoffmann, A.

Einleitung
In ersten Untersuchungen zur Integration von MR-Bildgebung und Protonentherapie (MRiPT) konnte deren prinzipielle Machbarkeit an einer statischen Strahlführung gezeigt werden. Als weiterer Schritt zu einem klinischen Prototyp wurde nun der MR-Scanner mit einer Pencil-Beam-Scanning (PBS) Strahlführung integriert. Ziel dieser Arbeit ist die Charakterisierung der Strahlqualität im magnetischen Isozentrum des in-beam MR-Scanners.

Material & Methoden
Ein offener 0.22 T MR-Scanner (MrJ2200, ASG Superconductors) wurde nächstmöglich an eine horizontale PBS Protonenstrahlführung installiert. Strahlprofilmessungen wurden sowohl mit als auch ohne den MR-Scanner an der Position des magnetisches Isozentrums des MR-Scanners (39 cm strahlabwärts des nominalen PBS Isozentrums) durchgeführt. Strahlprofile wurden ohne MRT mithilfe eines Szintillatordetektors (Lynx, IBA Dosimetry) sowie im Untersuchungsfeld des MRT mittels radiochromen Filmen (GAFchromic EBT3, Ashland) vermessen (Abb. 1). Für beide Konfigurationen wurden für 3 verschiedene Protonenenergien(70, 125 und 220 MeV) Punktraster bis zur maximalen nominalen Feldgröße von 400x200 mm2 vermessen. Aus diesen Messungen wurden Spotgrößen, -position und -symmetrie sowie durch das Magnetfeld verursachte Strahlablenkungen und Feldverzerrungen ermittelt.

Ergebnisse
Spotgrößen mit und ohne Magnetfeld sind in Tabelle 1 zusammengefasst. Spotgrößen im Magnetfeld stimmen auf ±0.3 mm mit Ergebnissen ohne Magnetfeld überein. Die horizontale Strahlablenkung des Zentralspots beträgt 26, 19 und 15 mm für 70, 125 und 220 MeV. Durch das Magnetfeld tritt eine energieabhängige, trapezoidale Verzerrung des Bestrahlungsfeldes auf, mit vertikalen Höhenunterscheiden zwischen 10 und 16 mm, sowie einer energieabhängigen Rotation der achsfernen Punkte bis zu 45°.

Zusammenfassung
Erstmals konnte die experimentelle Charakterisierung eines PBS-Strahls im Isozentrum des in-beam MR-Scanner erfolgen. Die Ergebnisse zeigen die Notwendigkeit weiterer präziser Messungen im Untersuchungsfeld des MR-Scanners, sowie für die Bestrahlungsplanung den Bedarf der Entwicklung eines dedizierten Strahlmodells unter Berücksichtigung des gesamten Magnetfeldes.

  • Lecture (Conference)
    50. DGMP Jahrestagung, 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29021
Publ.-Id: 29021


Flüssigmetallbatterien als Option für elektrische Großspeicher

Nimtz, M.; Landgraf, S.; Personnettaz, P.; Weber, N.; Weier, T.

Der Bedarf an kostengünstigen Großspeichern für elektrische Energie wird zukünftig, bei zunehmendem Ausbau der erneuerbaren Energien, wachsen. Derzeit vorhandene Technologien (im wesentlichen Lithium-Ionen bzw. Blei-Säure Batterien) bieten bis in den Bereich von etwa 10 bis 30 MW bzw. MWh eine anwendungsbereite Speicherform.
Hauptanwendungsfeld ist hierbei zurzeit die Primärregelenergie, da dort vergleichsweise kleine Entladetiefen und nur wenige Vollzyklen auftreten. Ein Einsatz als Speicher im Stunden- oder gar Mehrtagesbetrieb kann von diesen Technologien jedoch meist nicht erbracht werden, da die Alterung der Zellen bei hohen Entladetiefen (ΔSOC > 50%) stark zunimmt und dementsprechend die Kapazität der Zellen bereits nach wenigen Jahren stark abnimmt.
Flüssigmetallbatterien [1] bieten eine Alternative zu den vorgenannten Technologien, wobei der Fokus hier auf dem Einsatz als Großspeicher (>>1 MWh) liegt. In Flüssigmetallbatterien liegen alle Aktivmaterialien in flüssiger Form vor. Alterungseffekte, die auf einer Schädigung oder auf der Degeneration der Elektrodenmaterialien beruhen, werden hier nicht erwartet. Prognostizierte Vollzyklenzahlen liegen im Bereich von 105 Vollzyklen, was die Flüssigmetallbatterien auch für den Einsatz abseits der Primärregelung interessant macht. Weitere Vorteile sind der einfache Aufbau, gute Skalierbarkeit und die leichte Wiederaufbereitung der verwendeten Materialien.
Der Beitrag stellt die Technologie, die Einsatzmöglichkeiten und Parameter sowie die Forschungsaktivitäten am Helmholtz-Zentrum Dresden-Rossendorf [2] vor. Schwerpunkt ist die Darstellung der neu entwickelten Software „LMB-System-Calculator“, welche eine integrierte Auslegung, Modellierung und Simulation von Flüssigmetallbatterien in Hinblick auf geometrische (siehe Abb. 1), elektrische und thermische Größen erlaubt.

Keywords: Flüssigmetallbatterie; Energiespeicher; Modellierung; Simulation; Liquid metal battery; energy storage; modelling; simulation

  • Lecture (Conference)
    51. Kraftwerkstechnisches Kolloquium, 22.-23.10.2019, Dresden, Deutschland
  • Contribution to proceedings
    51. Kraftwerkstechnisches Kolloquium, 22.-23.10.2019, Dresden, Deutschland
    Kraftwerkstechnik 2019 - Power PLant Technology, Freiberg: Saxonia, 978-3-934409-93-4, 677-686

Permalink: https://www.hzdr.de/publications/Publ-29019
Publ.-Id: 29019


An eurlerian-eulerian CFD approach to simulate the thermaohydrulics of piipes, channel or rod bundles: from onset of nucleate boiling to CHF

Ding, W.; Krepper, E.; Hampel, U.

The Eulerian-Eulerian computational fluid dynamics (CFD) approach is widely applied in the simulation of industrial scale thermal fluid dynamics problems, such as flow and heat transfer in fuel elements. However, the case dependency of submodels in the Eulerian-Eulerian CFD approach currently hampers its applicability. In order to reduce this dependency, a submodel to predict the bubble departure in both pool and flow boiling was developed in our group, which includes the impact of microlayer, thermal diffusion, condensation and force balance. Moreover, we also developed a new CHF- concept. It is currently based on correlations but we are continuously working on a transition to a fully physics-based model, which e.g. considers the dependency of boiling on the microlayer thickness, bubble base expansion speed and local shear stress. In order to implement the bubble dynamics model and CHF- model into the Eulerian-Eulerian CFD framework, a new cavity activation and heat partitioning model was developed, which is not only used for bubble nucleation but also connects the nucleate boiling and CHF- in one CFD approach. However, nucleation site density is strongly dependent on the surface properties, which is difficult to model without correlations.

Keywords: CFD; Wall boiling; CHF

  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-22.08.2019, Portland, USA

Permalink: https://www.hzdr.de/publications/Publ-29018
Publ.-Id: 29018


Critical heat flux as a mass flux dependent phenomenon: Theoretical analysis, experimental confirmation and further CFD application

Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.

In this work, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling firstly. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity. Further we applied this concept into an Euler-Euler computational multiphase fluid dynamics (CMFD) approach with wall boiling model which successfully predict the critical volume fraction under different conditions. The simulation results also had a good agreement with the corresponding experimental results.

Keywords: Critical heat flux; Boiling; CMFD

  • Invited lecture (Conferences)
    9th China-Korea Workshop on Nuclear Reactor Thermal-Hydraulics (WORTH-9), 15.-18.05.2019, Chongqing, China
  • Lecture (Conference)
    10th International Conference on Multiphase Flow, 19.-24.05.2019, Rio de Janeiro, Brazil

Permalink: https://www.hzdr.de/publications/Publ-29017
Publ.-Id: 29017


Pulse-front tilt in laser-plasma accelerators with short focal lengths

Steiniger, K.; Albach, D.; Bussmann, M.; Debus, A.; Kluge, T.; Loeser, M.; Pausch, R.; Siebold, M.; Zeil, K.; Schramm, U.

Laser ion accelerators utilize high-power laser pulses in tight-focusing geometries to provide pulsed, high-intensity ion beams. Efficient capturing, transport and application of these beams is an ongoing effort which depends on precise knowledge of the accelerated ion distribution's properties and how to control these. For example, it is known that the propagation direction of the accelerated ions can be controlled by tilting the driving laser pulse-front. Since laser pulse-front tilts can be present accidentally, for example by a small misalignment of the compressor gratings in a chirped-pulse amplification system, knowledge of the scaling of the pulse-front tilt at a target position is desired. The talk gives relations for pulse-front orientation dependent on setup parameters and identifies regimes were pulse-front tilt has a sizable impact.

Keywords: Pulse-front tilt; high-power laser

  • Lecture (Conference)
    DPG-Frühjahrstagung, 17.-22.03.2019, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29015
Publ.-Id: 29015


Flüssigmetallbatterien als Großspeicher - Technologie, Scale-Up und Optionen zur Sektorkopplung

Nimtz, M.

Es werden die grundsätzlichen Eigenschaften von Flüssigmetallbatterien beschrieben sowie Methoden und Ergebnisse zum Scale-Up vorgestellt. Des weiteren werden Funktionsweise und Anwendung der LMB-System-Calculator Software erläutert sowie Anwendungsoptionen für Flüssigmetallbbatterien, insbesondere bei der Sektorkoppelung vorgestellt.

Basic properties of Liquid Metal Batteries are described and methods and results for scale-up calculations are presented.
Also, functioning and usage of the LMB-System-Calculator software are discussed and options for the operation of Liquid Metal Batteries, especially for the sector-coupling are presented.

Keywords: LMB; Flüssigmetallbatterien; Scale-Up; Speicher; Sektorkoppelung; LMB; liquid metal battery; scale-up; storage; sectro-coupling

  • Lecture (others)
    Energie System 2050 Forschungsthema 1, 1. Workshop 2019, 19.-20.03.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29014
Publ.-Id: 29014


Chemistry and accelerator mass spectrometry – A life happily ever after?

Merchel, S.

Accelerator mass spectrometry (AMS) is the most sensitive analytical method to measure long-lived radionuclides. The detection limits are generally several orders of magnitude better, i.e. as low as 10-16 (radionuclide/stable nuclide), than any other mass spectrometry or decay counting method. AMS needs smaller sample sizes and measurements are finished within a few minutes to hours.

However, it is often forgotten that research projects applying AMS start with taking appropriate samples, followed by labour- and cost-intensive sample preparation. The goal can easily be described as “making the big samples (up to several kg’s) to fit in an AMS target holder (< 10 mg)”. This includes getting rid of the matrix and the troublesome isobars. By technical improvements of AMS leading to lower detection limits or better mass-and-element discrimination, sample masses can be reduced to gram-quantities instead of kg’s allowing easier, faster, and cheaper chemistry. Recent AMS developments also address very efficiently isobar elimination.

Nevertheless, some samples can contain different sources of the radionuclide-of-interest such as ¹⁰Be produced in the Earth’s atmosphere polluting the ¹⁰Be of interest produced in-situ in quartz. Hence, in this case chemistry is inevitable for cleaning the samples from the contamination. Another “mission” of chemistry might be the reduction of corresponding stable nuclides, e.g. 35,37Cl, ²⁷Al, natFe by preceding cleaning or by gentle leaching to enhance the radionuclide/stable nuclide ratio or to minimize interfering nuclear reactions such as thermal-neutron capture on ³⁵Cl. When applying isotope-dilution AMS to simultaneously determine the natCl content of a sample, which is an absolute requirement for surface exposure dating of Ca- or K-rich minerals, chemical sample preparation is also mandatory.

As the majority of research projects involving AMS is of true interdisciplinary character, knowledge of sample preparation is usually passed-on to (young) non-chemists. These are trained learning-by-doing to perform the chemical preparation of their own samples. Therefore, the development of “routine” AMS sample preparation needs to have a strong focus on safety and easy-to-be-trained aspects with the least opportunity for failure.

In conclusion, although new AMS technical developments for isobar suppression like the laser-negative ion interaction system at VERA promise to reduce elaborate chemistry in some cases, we should keep in mind that chemical knowledge will always be needed for a lot of interdisciplinary research projects.

Keywords: AMS

  • Lecture (others)
    VERA-Seminar, Institut für Isotopenphysik, Universität Wien, 28.03.2019, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29013
Publ.-Id: 29013


Li-containing liquid metal alloy ion sources for focused-ion beam instrumentation

Mazarov, P.; Nadzeyka, A.; Richter, T.; Yu, Y.; Sanabia, J. E.; Bischoff, L.; Hlawacek, G.; Pilz, W.; Klingner, N.

Focused Ion Beams (FIB) gain an increasing interest in the field of nanotechnology particular for prototyping of microelectronic devices, patterning of 2D materials, high resolution imaging or high resolution ion lithography1. Concerning ion beam resolution and minimization of unwanted damage, light ions like He or Li are preferred candidates. Liquid metal alloy ion sources (LMAIS) with a life time of more than 1000 µAh on the basis of Ga35Bi60Li5 and Sn95Li5 alloys were developed, characterized and finally applied in a commercial mass-separated VELION FIB-SEM system (Raith GmbH). The resolution for imaging and also for the formation of nanostructures using a thin gold film was determined.
In the case of Li ions from the mass separated FIB a lateral resolution of 5.6 nm could be obtained in first experiments2 and the sputter yield was determined to 0.4 for 35 keV Li ions on Au. For reference, the helium ion microscope (HIM) has a lateral resolution of about 0.5 nm and 1.8 nm, for He and Ne respectively, He has a sputter yield of 0.13. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the SnLi-FIB could therefore be considered alternatives to the HIM with the benefit of providing additional ion species in a mass separated FIB without changing the ion source.

1 L. Bischoff et al. Appl. Phys. Rev. 3, 021 101 (2016).
2 W. Pilz et al. J. Vac. Sci. Technol. B A-18-399 (submitted, 2018).
3 G. Hlawacek et al. J. Vac. Sci. Technol. B 32, 020 801 (2014).

  • Lecture (Conference)
    The 63rd International Conference On ELECTRON, ION, AND PHOTON BEAM TECHNOLOGY AND NANOFABRICATION, 28.-31.05.2019, Minneapolis, United States of America

Permalink: https://www.hzdr.de/publications/Publ-29012
Publ.-Id: 29012


SiCxNy:Fe films as a tunable ferromagnetic material with tailored conductivity

Pushkarev, R.; Fainer, N.; Kirienko, V.; Matsynin, A.; Nadolinnyy, V.; Merenkov, I.; Trubina, S.; Ehrenburg, S.; Kvashnina, K.

Amorphous ferromagnetic materials with the variable composition are promising candidates for application in rapidlygrowing technological fields, such as spintronics. However, the significant downside of current state-of-art materials is a conductivity mismatch between injector and semiconductor which often is associated with the unavailability to control and precisely tailor magnetic properties and conductivity. We report on the synthesis of soft-magnetic SiCxNy:Fe films with the saturation magnetization of 20 e.m.u./cm3 and conductivity similar to the one of Si, which is crucial for possible applications.
XRD with synchrotron radiation and EXAFS revealed the complex composite structure of the films: crystals of Fe3Si, Fe5Si3, SiC and graphite are embedded into the amorphous matrix of SiCxNy. The variation of deposition conditions allowed us to separately control the magnetic properties through the iron concentration and the conductivity of the material through the amorphous SiCxNy matrix composition. The reported results revealed a significant potential of SiCxNy:Fe films as a prospective object for analysis of spin-polarized transport in amorphous semiconductors and for application in field of spintronics.

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Permalink: https://www.hzdr.de/publications/Publ-29011
Publ.-Id: 29011


Bridging the Green Gap: Metal–Organic Framework Heteromultilayers Assembled from Porphyrinic Linkers Identified by Using Computational Screening

Haldar, R.; Batra, K.; Marschner, S. M.; Kuc, A. B.; Zahn, S.; Fischer, R. A.; Bräse, S.; Heine, T.; Wöll, C.

In organic photovoltaics, porphyrins (PPs) are among the most promising compounds owing to their large absorption cross section, wide spectral range, and stability. Nevertheless, a precise adjustment of absorption band positions to reach a full coverage of the so-called green gap has not been achieved yet. We demonstrate that a tuning of the PP Q- and the Soret bands can be done using a computational approach where substitution patterns are optimized in silico. The Most promising candidate structures were then synthesized. The experimental UV/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow using the PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we were additionally able to exploit packing effects resulting in pronounced red shifts, which allowed to further optimizing the photophysical properties of PP assemblies. Finally, we use a layer-by-layer method to assemble the PP linkers into surface-mounted MOFs (SURMOFs), thus obtaining high optical quality, homogeneous and crystalline multilayer films. Experimental results are in full accord with the calculations, demonstrating a huge potential of computational screening methods in the tailoring of MOF and SURMOF photophysical properties.

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Permalink: https://www.hzdr.de/publications/Publ-29010
Publ.-Id: 29010


Synthesis and Functionalization of Radium-doped Barium Sulfate Nanoparticles

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

The radionuclides radium-223 and radium-224 are two alpha-emitting radionuclides with suitable properties for the TAT. To this date, radium-223 in form of [223Ra]radium chloride (Xofigo) is the only EMA and FDA approved alpha-emitting radiopharmaceutical. Due to its calcimimetic behavior, the radium ion is a bone-seeking therapeutic. To extend the radiopharmaceutical potential of both radionuclides, novel carrier systems have to be developed. Therefore, it is appropriate to investigate different kinds of nanoparticles for their ability to transport radium. Especially, a barium sulfate matrix seems to be sufficient since the principle of co-precipitating the sulfates of radium and barium allows an easy and fast synthesis of radium-doped nanoparticles. Beyond the incorporation of alpha-emitting radionuclides like radium-223 and radium-224, the homologue radionuclide barium-131 can be incorporated as well. Barium 131 decays by electron capture and provides suitable properties for diagnostic applications in nuclear medicine. Radium-223/-224 and barium-131 form a matched pair for new theragnostic approaches. In our research group, we are developing simple methods for the synthesis of small radiolabeled radium/barium sulfate nanoparticles. Furthermore, we are investigating suitable surface functionalizations to attach biological targeting moieties.

Keywords: Bariumsulfat; Radium-224; Nanopartikel

  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access Logo Abstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S38-S38
    DOI: 10.1016/j.jmir.2019.03.117

Permalink: https://www.hzdr.de/publications/Publ-29009
Publ.-Id: 29009


Synthese neuartiger Calix[4]arenkäfige für die stabile Bindung von Ba2+ und Ra2+

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

Therapieansätze in der Nuklearmedizin mit Radium-223 beschränken sich zurzeit auf die Behandlung von Knochenmetastasen. Ziel ist es, das Anwendungsfeld für Radium-223 zu erweitern. Dafür werden Liganden entwickelt, die Radium-223 stabil binden und gleichzeitig eine spezifische Erkennungssequenz für diverse Krebsentitäten besitzen. Calixkronen mit funktionalisierten Seitenketten sind dafür vielversprechend.

Calix[4]krone-6-derivate mit Trifluormethylsulfonyl- [1] und 4-Nitrophenylsulfonyl-Seitenketten wurden synthetisiert und mittels NMR und UV/Vis auf ihre Komplexierungseigenschaften für Ba2+ untersucht. Anschließend wurden mittels eines Extraktionsassays Komplexierungen durchgeführt und die resultierenden Komplexe auf ihre Stabilität in Gegenwart anderer Ionen wie Ca2+ untersucht. Die Extraktionsversuche wurden im Chloroform/Wasser-Zweiphasensystem durchgeführt. Dabei wurde eine wässrige Metallsalzlösung ([133Ba]Ba2+ c.a. bzw. [224Ra]Ra2+ n.c.a.) definierter Konzentration vorgelegt und mit einer definierten Stoffmenge des jeweiligen Liganden in Chloroform für 1 h bei RT extrahiert.
Die beiden Calixarenderivate wurden in einer vierstufigen Synthese hergestellt. Anschließende Komplexierungsversuche mit Ba(ClO4)2 verliefen erfolgreich und die Komplexe wurden mittels NMR-Spektroskopie nachgewiesen. Für beide Liganden wurden Stabilitätskonstanten von 5,3-6,3 (Ba2+) bzw. 5,8 (Ra2+) berechnet. Die Radiumkomplexe beider Liganden waren gegenüber Ca2+-Ionen stabil (Release <5%), der Bariumkomplex des Nitrophenylsulfonylliganden war ebenfalls stabil (Release <5%), der des Trifluormethylsulfonylliganden zeigte 30% Release.
Die Wahl der sterisch anspruchsvollen und elektronenziehenden Sulfonylgruppen hatte positive Auswirkungen sowohl auf das Komplexierungsverhalten mit Ba2+ und Ra2+ als auch auf die Stabilität der resultierenden Komplexe in Gegenwart von zweiwertigen Fremdionen.

Keywords: Barium-133; Radium-224; Calixaren

  • Lecture (Conference)
    57. Jahrestagung der DGN 2019, 03.-06.04.2019, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 58(2019), 136
    DOI: 10.1055/s-0039-1683562

Downloads:

  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29008
Publ.-Id: 29008


Synthesis and Biological Investigation of A Novel Fluorine-18 Labeled Benzoimidazotriazine: A Potential Radioligand for In Vivo Phosphodiesterase 2A (PDE2A) PET imaging

Ritawidya, R.; Teodoro, R.; Wenzel, B.; Kranz, M.; Toussaint, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Scheunemann, M.; Brust, P.

Objectives: Cyclic nucleotide phosphodiesterase 2A (PDE2A), an enzyme which hydrolyzes the second messengers cAMP and cGMP, is highly enriched in distinct areas of the brain. Accordingly, PDE2A is involved in important signaling pathways related to normal brain function but also to
neurodegeneration and neuro-oncology [1]. To enable the visualization of this protein in the brainwith PET, we developed a novel fluorine-18 radioligand for PDE2A.
Methods: Based on the benzoimidazotriazine (BIT) tricyclic scaffold, several fluorine-containing derivatives were synthesized via a multi-step synthesis route, and their inhibitory profiles were assessed by PDE isoenzyme-specific activity assays. The most potent and selective PDE2A ligand
BIT1 was radiolabeled via nucleophilic aromatic substitution of the corresponding 2-nitro pyridine precursor by [18F]fluoride in DMSO with thermal heating (Figure 1). [18F]BIT1 was isolated using semi-preparative HPLC (Reprosil-Pur C18-AQ column, 250 x 10 mm, 46% ACN/aqu. 20 mM
NH4OAc, flow 5.5 mL/min) followed by final purification with solid-phase extraction and formulation in isotonic saline containing 10% ethanol. Preliminary in vitro autoradiography and in vivo PET studies (60 min dynamic PET imaging, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) of [18F]BIT1 were performed using pig brain slices and female CD-1 mice, respectively. The in vivo metabolism of [18F]BIT1 was investigated by radio-HPLC analysis of mouse plasma and brain samples at 30 min p.i.
Results: From the series of BIT derivatives, BIT1 was selected as candidate for PET imaging of PDE2A based on the most suitable inhibitory potential and profile (IC50 PDE2A3 = 3.3 nM;16-fold selectivity over PDE10A). [18F]BIT1 was successfully synthesized with a radiochemical yield of 54 ± 2% (n = 3, EOB), molar activities of 155 – 175 GBq/μmol (EOS) and radiochemical purities of ≥99%. [18F]BIT1 was stable in saline, pig plasma, and n-octanol up to 60 min at 37 °C. The distribution pattern of [ 18F]BIT1 in pig brain cryosections corresponds to the spatial distribution of PDE2A with accumulation in the striatal regions caudate nucleus and nucleus accumbens. Additionally, the displacement of [18F]BIT1 with BIT1 as well as TA1 (a potent PDE2A ligand) indicated saturability and selectivity of these binding sites. Uptake of [18F]BIT1 in the brain was shown by subsequent imaging studies in mice (SUVwhole brain = 0.7 at 5 min p.i.); however, more detailed analyses revealed nonspecific distribution of the tracer in the brain (78% parent compound at 30 min p.i.).
Conclusions: The potent and selective PDE2A inhibitor [18F]BIT1 binds in vitro in brain regions known to express PDE2A. Further structural modifications will be performed to develop radiotracers with improved brain uptake and target-selective accumulation in vivo.
Acknowledgement
1. Deutsche Forschungsgemeinschaft (German Research Foundation, SCHE 1825/3-1).
2. Scholarship Program for Research and Innovation in Science and Technology Project
(RISET-PRO)-Indonesia Ministry of Research, Technology and Higher Education (World
Bank Loan No: 8245-ID)

References
[1] S. Schröder, B. Wenzel, W. Deuther-Conrad, M. Scheunemann, P. Brust, Novel Radioligands
for Cyclic Nucleotide Phosphodiesterase Imaging with Positron Emission Tomography: An Update
on Developments Since 2012, Molecules 21 (2016) 650–685.

Keywords: Phosphodiesterases; positron emission tomography; molecular imaging; benzoimidazotriazines

  • Poster
    International Symposium in Radiopharmaceutical Sciences, 26.-31.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-29007
Publ.-Id: 29007


The effect of tumor volume changes on the boost-volume coverage in glioblastoma patients

Hessen, E.; Nijkamp, J.; Troost, E.; Makocki, S.; de Jong, M.; Dewit, L. H. G.; Jasperse, B.; van der Heide, U.; Borst, G.

Purpose/Objective: Radiotherapy is one of the main treatment modalities in the multimodal therapy of glioblastoma patients. The ongoing NRG-BN001 trial (NCT02179086) is evaluating whether boosting a sub-volume with photons or protons improves overall survival as compared to standard-dose photon irradiation. We hypothesize that anatomical changes during irradiation may affect the dose coverage and that these changes may have a greater impact on proton treatment plans compared to photon treatment plans.
Material & Methods: For 24 glioblastoma patients, the MRI was repeated half way during radiation treatment. Three patients had a gross total resection (GTR), four patients underwent a biopsy and 17 patients had a subtotal resection (STR). These patients were treated according to the EORTC-ACROP guideline. A simulated photon and proton treatment plan (intensity modulated proton therapy; IMPT) according to the NRG-BN001 trial were made retrospectively. In this trial, patients in the experimental arm receive a dose of 46Gy/30fr on the T2w/FLAIR abnormalities and 75Gy/30fr on the planning target boost volume (PTV-7500). The PTV-7500 was defined as the resection cavity and/or contrast enhancing lesion on the T1w post gadolinium sequence of the MRI plus a margin of 5 mm (CTV) plus a 4 mm expansion in all dimensions. The trial constraints states that at least 95% of the PTV-7500 should receive 75Gy. To analyze the effect of anatomical changes during treatment on the dose coverage, we evaluated the planned dose distribution (based on the planning MRI) on the delineated PTV-7500 of the repeated MRI.
Results: The median time interval between the two MRIs was 25.5 days (range 15 – 36 days). Between the two scans, the PTV-7500 volume changed with a median of -0.1cc. However, we observed a wide range of -52.8 to +52.2cc. For the photon treatment plans we observed that 83% (n=20) of the patients showed a decline in PTV-7500 coverage (corresponding with a median decline of 6.5% and 8.3cc). The quartile of patients (n=6) with the largest PTV-7500 increase showed a 10% reduction in dose coverage (corresponding with a median volume of 33.2cc). There was no significant difference in coverage changes of the boost volume between the GTR, biopsy only and STR patients (p=0.632). The evaluation of the IMPT plans is ongoing and will be presented during the conference.
Conclusion: During fractionated radiation treatment for glioblastoma patients we observed large target volumetric changes in the boost volume half way during treatment. These target volume changes may lead to substantial declines in dose coverage when patients are treated according to dose-escalation protocol boosting specific sub-volumes. Thus, an important subset of glioblastoma patients may benefit from an MRI guided dose escalation strategy.

  • Lecture (Conference)
    ASTRO, 15.-18.09.2019, Chicago, USA
  • Open Access Logo Abstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 105(2019)1, E99-E100
    DOI: 10.1016/j.ijrobp.2019.06.2290

Permalink: https://www.hzdr.de/publications/Publ-29006
Publ.-Id: 29006


Robust optimization of dose-volume metrics for prostate HDR-brachytherapy incorporating target and oar volume delineation uncertainties

Balvert, M.; Den Hertog, D.; Hoffmann, A. L.

In radiation therapy planning, uncertainties in the definition of the target volume yield a risk of underdosing the tumor. The traditional corrective action in the context of external beam radiotherapy (EBRT) expands the clinical target volume (CTV) with an isotropic margin to obtain the planning target volume (PTV). However, the EBRT-based PTV concept is not directly applicable to brachytherapy (BT) since it can lead to undesirable dose escalation. Here, we present a treatment plan optimization model that uses worst-case robust optimization to account for delineation uncertainties in interstitial high-dose-rate BT of the prostate. A scenario-based method was developed that handles uncertainties in index sets. Heuristics were included to reduce the calculation times to acceptable proportions. The approach was extended to account for delineation uncertainties of an organ at risk (OAR) as well. The method was applied on data from prostate cancer patients and evaluated in terms of commonly used dosimetric performance criteria for the CTV and relevant OARs. The robust optimization approach was compared against the classical PTV margin concept and against a scenario-based CTV margin approach. The results show that the scenario-based margin and the robust optimization method are capable of reducing the risk of underdosage to the tumor. As expected, the scenario-based CTV margin approach leads to dose escalation within the target, whereas this can be prevented with the robust model. For cases where rectum sparing was a binding restriction, including uncertainties in rectum delineation in the planning model led to a reduced risk of a rectum overdose, and in some cases, to reduced target coverage.© 2019 INFORMS

Keywords: Brachytherapy; Delineation uncertainties; Mixed-integer linear optimization; Robust optimization; Treatment planning

Permalink: https://www.hzdr.de/publications/Publ-29005
Publ.-Id: 29005


Solving the Kuramoto Oscillator Model on Random Graphs

Kelling, J.; Ódor, G.; Gemming, G.

The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions. The Kuramoto model describes systems of coupled oscillators which, which exhibit non-trivial behavior on complex graphs, making it a suitable tool to study the synchronization dynamics of brains an other systems.

Numerical solution of Kuramoto type ordinary differential equations for long times and large systems requires strong computation power, due to the inherent chaoticity of this nonlinear system.

This poster presents a GPU implementation of a solver achieving large speedups over CPU on sparse random graphs. The key to performance here, is the presented memory layout which supplements the SIMT usage of our design.

# extended abstract
The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions.

Using the Kuramoto model[1], we are studying a range of problems, from basinc questions about synnchronisation transitions on disordered lattices and random graphs to problems mentioned in the short abstract. The model shows komplex behavior on human connectome graph, which allow the study of synchronization in the human brain[2]. An extension of the model allows modeling power grid networks[3,4].

Very intensive Simulations are required to obtain precise result especiall near criticality, which these systems show at synchronization transitons. To enable the study of these systems at sufficent precision, we implemented a GPU code, which we are presenting in this poster. To this end we used boost::odeint to get the standart numerical integartion out of the way an focus on the most performance critical aspect: the evaluation of the model itself. The key to our implementation is the choice of SIMT vectorization and a suitable memory layout, which are presented in the poster. The aspects also remain the same, when we add the extension to the second-order Kuramoto Model[2], which is required to model powergrids.

[1] Kuramoto, Y. In Araki, H. (ed.) Mathematical Problems in Theoretical Physics, vol. 39 of Lecture Notes in Physics, Berlin, 420
[2] Villegas, P., Moretti, P. & Muñoz, M. A. Scientific Reports 4, 5990 (2014).
[3] Filatrella, G., Nielsen, A. H. & Pedersen, N. F. Eur. Phys. J. B 61, 485–491 (2008)
[4] Ódor, G. & Hartmann, B. Phys. Rev. E 98, 022305 (2018).

Keywords: GPGPU; random graph; Kuramoto model

Permalink: https://www.hzdr.de/publications/Publ-29004
Publ.-Id: 29004


Beneficiation of parisite-rich rare earth ore from the Nam Xe South deposit, Vietnam

Möckel, R.; Heinig, T.; Cardenas Vera, A. F.; Gutzmer, J.; Merker, G.; van Phan Quang, .

Parisite-rich rare earth element (REE) ores from the Nam Xe deposit in northern Vietnam were beneficiated on a lab scale. Beneficiation experiments included, amongst others, sensor-based sorting, magnetic separation and flotation. Particular analytical focus during all experiments was set on the grain size, association and intergrowth of of the main REE carrier mineral parisite, which is finely intergrown with minerals of the barite-celestine solid solution series. All experiments were accompanied by mineral liberation analysis and chemical assays in order to be able to provide direction towards an optimal beneficiation strategy for this REE ore with its rather unique mineralogy. Special focus was set on the grain characteristics of the main REE carrier mineral parisite, which is finely intergrown above all with minerals from the barite-celestine solid solution series.
A multi-stage flotation technique was developed that uses an ambient rougher and a hot cleaner stage. Concentrates with 40% TREO grade with a total recovery of about 80% were achieved. It was shown that a combination with a sensor-based pre-sorting prior to the flotation can increase the input grade for flotation considerably by a nearly loss-free rejecting of virtually barren bed rock. The process combination developed holds good potential for further improvements.

  • Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Scotland

Permalink: https://www.hzdr.de/publications/Publ-29003
Publ.-Id: 29003


Fragment molecular orbital (FMO) method for studying actinide/lanthanide interaction with DNA/protein

Tsushima, S.; Mochizuki, Y.; Fahmy, K.

Due to its potential health and environmental impacts, actinide binding to biomolecules has been a subject of intensive investigations. A large number of experimental works have been carried out but our understanding remains mostly in a macroscopic scale. Modeling actinide interaction with large biomolecules using ab initio quantum chemical calculations may drastically expand our molecular level knowledge but is challenged by a demand for huge computational resources.
Our strategy to overcome this difficulty is to apply fragment molecular orbital (FMO) method. In FMO, the molecular system of interest is partitioned into small fragments. Each fragment and fragment pair is subject to self-consistent field calculations under environmental electrostatic potentials and the electronic structure of the whole system is reconstituted [1]. This procedure drastically reduces computational cost of Hartree Fock calculations from N3 to N2 (or less) and is readily parallelizable. FMO has been extended to MP2 and to DFT to include electron correlation and was successfully applied to the systems such as hydrated DNA [2].
Currently we are upgrading the FMO program Abinit-MP [3] to implement 5f elements into the program. We first choose uranyl-bound DNA for a case study. Calculations are performed as follows. UO22+-bound d(CGCGAATTCGCG)2 (Dickerson-Drew dodecamer) with 20 Na+ ions and SPC/E water shell with 10 Å thickness is first thermally equilibrated and subsequently submitted to MD simulation at 300 K for 100 ns interval using AMBER 14 program. Force field parameters for UO22+ and coordinating water are those developed by Pomogaev et al. [4]. At each 1 ns time step of MD simulation, the structure is extracted and submitted to FMO single point energy calculation at the MP2 level. In FMO, nucleic unit is appropriately divided into sugar, base, and phosphate fragments. Inter-fragment interaction energy analysis is performed to explore the binding affinity of uranyl to DNA and its influence on base pairing.
[1] K.Kitaura et al. (1999) Chem. Phys. Lett. 313, 701–706.
[2] K.Fukuzawa et al. (2015) Comput.Theor.Chem. 1054, 29–37.
[3] S.Tanaka et al. (2014) Phys. Chem. Chem. Phys. 16, 10310–10344.
[4] V.Pomogaev et al. (2013) Phys. Chem. Chem. Phys. 15, 15954–15963.

  • Poster
    Joint 12th EBSA and 10th ICBP-IUPAP Biophysics Congress, 20.-24.07.2019, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29002
Publ.-Id: 29002


Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets

Lumpkin, A.; Laberge, M.; Rule, D.; Zgadzaj, R.; Hannasch, A.; Downer, M.; Zarini, O.; Bowers, B.; Irman, A.; Couperus, J.; Debus, A.; Kohler, A.; Schramm, U.

We report initial observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched electrons from laser-driven plasma accelerators (LPAs). These are revealed in the angular distribution patterns obtained by a CCD camera with the optics focused at infinity, or the far-field, viewing a Wartski two-foil interferometer. The beam divergences deduced by comparison to results from an analytical model are sub-mrad, and they are smaller than the ensemble vertical beam divergences measured at the downstream screen of the electron spectrometer. The transverse sizes of the beamlet images were obtained with focus at the object, or near field, and were in the few-micron regime as reported by LaBerge et al. [8]. The enhancements in intensity are significant relative to incoherent optical transition radiation (OTR) enabling multiple cameras to view each shot. We present two-foil interferometry effects coherently enhanced in both the 100-TW LPA at 215 MeV energy at Helmholtz-Zentrum Dresden-Rossendorf and the PW LPA at 1.0-GeV energy at the University of Texas-Austin. A transverse emittance estimate is reported for a microbunched beamlet example generated within the plasma bubble.

Keywords: LPA; microbunching; COTR; beam size; divergence

  • Contribution to proceedings
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge, CO, USA
    2018 IEEE Advanced Accelerator Concepts Workshop (AAC): IEEE, 978-1-5386-7721-6
    DOI: 10.1109/AAC.2018.8659381

Permalink: https://www.hzdr.de/publications/Publ-29001
Publ.-Id: 29001


Bacillus safensis JG-B5T affects the fate of selenium by extracellular production of colloidally less stable nanoparticles

Fischer, S.; Krause, T.; Lederer, F.; Merroun, M. L.; Shevchenko, A.; Hübner, R.; Stumpf, T.; Jordan, N.; Jain, R.

Bacteria strain Bacillus safensis JG-B5T is an obligate aerobic microorganism isolated from uranium mining waste pile. The role played by this microorganism in the transport of selenium is poorly understood. This study demonstrated that B. safensis JG-B5T can reduce 70 % of 2.5 mM selenite whereas selenate reduction was not observed. Formation of the resulting biogenic elemental selenium nanoparticles (BioSeNPs) occurred exclusively extracellularly. The ζ-potential of the produced BioSeNPs varied from −44.2 (±0.2) mV to −10.6 (±3.3) mV when Na+:Se ratio was varied from 0 to 0.8 (mM:mM), suggesting a lower colloidal stability. Further experiments in two-chamber reactors and transmission electron microscopy revealed that direct cell contact is essential for selenite reduction by B. safensis JG-B5T. The selenite reduction is likely primarily mediated through membrane-associated proteins, like succinate dehydrogenase as revealed by genome and proteomics analysis. Altogether, this study showed that aerobic bacteria B. safensis JG-B5T is involved in decreasing the environmental bioavailability and toxicity of selenium by membrane protein-mediated reduction of selenite oxyanions and formation of extracellular BioSeNPs with low colloidal stability.

Keywords: Obligate aerobic; two-chamber reactor; proteomics; membrane-associated proteins; selenite

Permalink: https://www.hzdr.de/publications/Publ-29000
Publ.-Id: 29000


Photocatalytic Oxygenation of Cyclohexene Initiated by Excitation of [UO2(OPCyPh2)4]2+ under Visible Light

Mashita, T.; Tsushima, S.; Takao, K.

Oxygenation reaction of cyclohexene was studied under presence of a 4-fold UO22+ complex with cyclohexyldiphenylphosphine oxide, [UO2(OPCyPh2)4]2+, and blue light irradiation at 436 nm in acetonitrile. As a result, 1,6-hexanedial, cyclohexene oxide, 2-cyclohexen-1-one, and 2-cyclohexen-1-ol were photocatalytically generated as oxygenated products with TOF = 6.7 h−1. In contrast, dimerization of cyclohexene was observed under Ar atmosphere. This implies that a hydrogen atom at the allyl position is abstracted by photoexcited *[UO2(OPCyPh2)4]2+ to give a cyclohexene radical and a U(V) intermediate [UVO2(OPCyPh3)4]+, being well supported by DFT calculation. Under O2 atmosphere, the former reacts with dissolved O2 to give 2-cyclohexen-1-one and 2-cyclohexen-1-ol. Dissolved O2 would be activated by the U(V) intermediate to afford O22− in the end, which drives oxygenation of C=C bond of unreacted cyclohexene.

Permalink: https://www.hzdr.de/publications/Publ-28999
Publ.-Id: 28999


Sensitivity and uncertainty analysis for geochemical models for repository safety assessment

Stockmann, M.; Becker, D.-A.; Noseck, U.; Brendler, V.

A key component of safety assessment for radioactive waste repositories in deep geological formations is the simulation of potential radionuclide release scenarios and the transport of radionuclides through the repository system. The realistic modelling of (hydro-)geochemical processes is of high relevance for assessing the migration of radionuclides in groundwater systems. One important retardation process for radionuclides to be considered is sorption onto mineral surfaces of the host rock / sediments. Due to the heterogeneities of the natural system and the high complexity of the geochemical models with uncertain or varying input parameters, it is important to understand which of the input parameter uncertainties have considerable influences on the model output uncertainty. This in turn allows model reduction required to upscale from the molecular to the plug scale. Consequently, we performed sensitivity and uncertainty analysis (SA/UA) to investigate and understand our geochemical model.
For the quantification of the contaminant retention in groundwater, the solid/liquid distribution coefficients (Kd-values) calculated for a given groundwater/rock system are traditionally used. Most often conventional concepts with constant Kd values are applied in reactive transport simulations. Such an approach has the advantage to be simple and computationally fast but cannot reflect changes in geochemical conditions that will occur during the evolution of the repository system, e.g. due to climatic changes. Due to the German safety criteria with an assessment period of about 1 million years it is necessary to consider the impact of such geochemical changes on the radionuclide transport and retardation. For this, we developed a new approach, where the smart Kd concept (www.smartkd-concept.de) [1] is modified in complex geochemical models including mechanistic sorption models, and implemented it in reactive transport calculations [2, 3]. Possible migration scenarios for repository-relevant radionuclides (isotopes of Am, Cm, Cs, Ni, Np, Pu, Ra, Se, Th and U) through a typical sedimentary rock system covering potential repository host rocks, namely salt and clay formations in Northern Germany as natural geological barrier, were developed in the first stage.
Smart Kd-values and their associated sensitivities and uncertainties were computed for a wide range of important geochemical input parameters / boundary conditions such as pH value, ionic strength, concentration of competing cations and complexing ligands, e.g. dissolved inorganic carbon (DIC) and calcium (Ca2+). Our toolbox coupled the geochemical speciation code PHREEQC [4] with the numeric tool UCODE [5] and SimLab2.2/4 [6]. SimLab has the advantage to permit a simultaneous variation of all input parameters according to their probability density functions and mutual correlations. It provides (in contrast to UCODE, which also incorporates some simple SA/UA algorithms) methods for Global SA. Comparable SA/UA have been done with a new software package RepoSUN, which is based on SimLab4 [7]. For the varying parameters uncertainty intervals were defined from field investigations and log-uniform distributions were assumed for all parameters, except for the pH value, which was assumed to be uniformly distributed. The results, i. e. the smart Kd values, were analyzed in the following way:
o As the output distribution covers several orders of magnitude, a log-transformation was performed on the output data. Then the computed a-priory multidimensional smart Kd matrices (see for U(VI) in Fig. 1, left) are accessible for interpolations during subsequent transport simulations.
o A histogram of the model output visualizes the distribution (see for U(VI) in Fig. 1, right).
o Some statistical measures were calculated to characterize the distribution (minimum, maximum, mean, standard deviation).
o Sensitivity measures were calculated for each of the input parameters: the standardized regression coefficient (SRC), the standardized rank regression coefficient (SRRC) and the variance-based first-order sensitivity index (SI1).
On the basis of the results it could be shown that the smart Kd approach goes considerably beyond the conventional concepts. We could illustrate that constant Kd values (see for U(VI) in Fig. 1, right, green line) used in previous transport simulations [8] are a crude assumption, as in reality they rather range over several orders of magnitude. Moreover, with the results from the SA, the most important input parameters influencing the radionuclide retardation can be identified (key parameters of the model). The calculated sensitivity indices allowed us to assess the most and less sensitive parameters. From the visualized smart Kd matrix for U(VI) (Fig. 1, left) it is obvious that mainly the pH value and the DIC influences the sorption of U(VI) under the given conditions. SA is a useful means for reducing the complexity of a geochemical model by focusing on the most important input parameters.

  • Poster
    Ninth International Conference on Sensitivity Analysis of Model Output (SAMO'19), 28.-30.10.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-28998
Publ.-Id: 28998


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