Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35836 Publications

The anomalous magnetic moment of the muon in the Standard Model

Aoyama, T.; Asmussen, N.; Benayoun, M.; Bijnens, J.; Blum, T.; Bruno, M.; Caprini, I.; Carloni Calame, C. M.; Cè, M.; Colangelo, G.; Curciarello, F.; Czyż, H.; Danilkin, I.; Davier, M.; Davies, C. T. H.; Della Morte, M.; Eidelman, S. I.; El-Khadra, A. X.; Gérardin, A.; Giusti, D.; Golterman, M.; Steven, G.; Gülpers, V.; Hagelstein, F.; Hayakawa, M.; Herdoíza, G.; Hertzog, D. W.; Hoecker, A.; Hoferichter, M.; Hoid, B.-L.; Hudspith, R. J.; Ignatov, F.; Izubuchi, T.; Jegerlehner, F.; Jin, L.; Keshavarzi, A.; Kinoshita, T.; Kubis, B.; Kupich, A.; Kupść, A.; Laub, L.; Lehner, C.; Lellouch, L.; Logashenko, I.; Malaescu, B.; Maltman, K.; Marinković, M. K.; Masjuan, P.; Meyer, A. S.; Meyer, H. B.; Mibe, T.; Miura, K.; Müller, S.; Nio, M.; Nomura, D.; Nyffeler, A.; Pascalutsa, V.; Passera, M.; Perez Del Rio, E.; Peris, S.; Portelli, A.; Procura, M.; Redmer, C. F.; Roberts, B. L.; Sánchez-Puertas, P.; Serednyakov, S.; Shwartz, B.; Simula, S.; Stöckinger, D.; Stöckinger-Kim, H.; Stoffer, P.; Teubner, T.; van de Water, R.; Vanderhaeghen, M.; Venanzoni, G.; von Hippel, G.; Wittig, H.; Zhang, Z.; Achasov, M. N.; Bashir, A.; Cardoso, N.; Chakraborty, B.; Chao, E.-H.; Charles, J.; Crivellin, A.; Deineka, O.; Denig, A.; Detar, C.; Dominguez, C. A.; Dorokhov, A. E.; Druzhinin, V. P.; Eichmann, G.; Fael, M.; Fischer, C. S.; Gámiz, E.; Gelzer, Z.; Green, J. R.; Guellati-Khelifa, S.; Hatton, D.; Hermansson-Truedsson, N.; Holz, S.; Hörz, B.; Knecht, M.; Koponen, J.; Kronfeld, A. S.; Laiho, J.; Leupold, S.; Mackenzie, P. B.; Marciano, W. J.; Mcneile, C.; Mohler, D.; Monnard, J.; Neil, E. T.; Nesterenko, A. V.; Ottnad, K.; Pauk, V.; Radzhabov, A. E.; de Rafael, E.; Raya, K.; Risch, A.; Rodríguez-Sánchez, A.; Roig, P.; San José, T.; Solodov, E. P.; Sugar, R.; Todyshev, K. Y.; Vainshtein, A.; Vaquero Avilés-Casco, A.; Weil, E.; Wilhelm, J.; Williams, R.; Zhevlakov, A. S.

We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant α and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including O(α5) with negligible numerical uncertainty. The electroweak contribution is suppressed by (m_μ/M_W)^2 and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at O(α2) and is due to hadronic vacuum polarization, whereas at O(α3) the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads a^{SM}_μ=116591810(43)×10^{−11} and is smaller than the Brookhaven measurement by 3.7σ. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future-which are also discussed here-make this quantity one of the most promising places to look for evidence of new physics.

Keywords: muon; g-2; anomalous magnetic moment

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Permalink: https://www.hzdr.de/publications/Publ-31144
Publ.-Id: 31144


Towards Geostatistical Learning for the Geosciences: A Case Study in Improving the Spatial Awareness of Spectral Clustering

Talebi, H.; Peeters, L. J. M.; Mueller, U.; Tolosana Delgado, R.; van den Boogaart, K. G.

The particularities of geosystems and geoscience data must be understood before any development or implementation of statistical learning algorithms. Without such knowledge, the predictions and inferences may not be accurate and physically consistent. Accuracy, transparency and interpretability, credibility, and physical realism are minimum criteria for statistical learning algorithms when applied to the geosciences. This study briefly reviews several characteristics of geoscience data and challenges for novel statistical learning algorithms. A novel spatial spectral clustering approach is introduced to illustrate how statistical learners can be adapted for modelling geoscience data. The spatial awareness and physical realism of the spectral clustering are improved by utilising a dissimilarity matrix based on nonparametric higher-order spatial statistics. The proposed model-free technique can identify meaningful spatial clusters (i.e. meaningful geographical subregions) from multivariate spatial data at different scales without the need to define a model of co-dependence. Several mixed (e.g. continuous and categorical) variables can be used as inputs to the proposed clustering technique. The proposed technique is illustrated using synthetic and real mining datasets. The results of the case studies confirm the usefulness of the proposed method for modelling spatial data.

Keywords: Statistical learning; Spatial data; Spatial clustering; Higher-order spatial statistics; Geoscience data

Permalink: https://www.hzdr.de/publications/Publ-31143
Publ.-Id: 31143


Combined tumor plus nontumor interim FDG‐PET parameters are prognostic for response to chemoradiation in squamous cell esophageal cancer

Zschaeck, S.; Li, Y.; Bütof, R.; Lili, C.; Hua, W.; Troost, E.; Beck, M.; Amthauer, H.; Kaul, D.; Kotzerke, J.; Baur, A.; Ghadjar, P.; Baumann, M.; Krause, M.; Hofheinz, F.

We have investigated the prognostic value of two novel interim 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) parameters in patients undergoing chemoradiation (CRT) for esophageal squamous cell carcinoma (ESCC): one tumor parameter (maximal standardized uptake ratio rSUR) and one normal tissue parameter (change of FDG uptake within irradiated nontumor‐affected esophagus ∆ SUVNTO). PET data of 134 European and Chinese patients were analyzed. Parameter establishment was based on 36 patients undergoing preoperative CRT plus surgery, validation was performed in 98 patients receiving definitive CRT. Patients received PET imaging prior and during fourth week of CRT. Clinical parameters, baseline PET parameters, and interim PET parameters (rSUR and ∆ SUVNTO) were analyzed and compared to event‐free survival (EFS), overall survival (OS), loco‐regional control (LRC) and freedom from distant metastases (FFDM). Combining rSUR and ∆ SUVNTO revealed a strong prognostic impact on EFS, OS, LRC and FFDM in patients undergoing preoperative CRT. In the definitive CRT cohort, univariate analysis with respect to EFS revealed several staging plus both previously established interim PET parameters as significant prognostic factors. Multivariate analyses revealed only rSUR and ∆ SUVNTO as independent prognostic factors (p = 0.003, p = 0.008). Combination of these parameters with the cutoff established in preoperative CRT revealed excellent discrimination of patients with a long or short EFS (73% vs . 17% at 2 years, respectively) and significantly discriminated all other endpoints (OS, p < 0.001; LRC, p < 0.001; FFDM, p = 0.02), even in subgroups. Combined use of interim FDG‐PET derived parameters ∆ SUVNTO and rSUR seems to have predictive potential, allowing to select responders for definitive CRT and omission of surgery.

Keywords: esophageal cancer; interim PET; standardized uptake ratio; normal tissue FDG uptake; chemoradiation; personalized treatment

Permalink: https://www.hzdr.de/publications/Publ-31142
Publ.-Id: 31142


Reconstructed spatial resolution and contrast recovery with Bayesian penalized likelihood reconstruction (Q.Clear) for FDG-PET compared to time-of-flight (TOF) with point spread function (PSF)

Rogasch, J.; Suleiman, S.; Hofheinz, F.; Bluemel, S.; Lukas, M.; Amthauer, H.; Furth, C.

Background

Bayesian penalized likelihood reconstruction for PET (e.g., GE Q.Clear) aims at improving convergence of lesion activity while ensuring sufficient signal-to-noise ratio (SNR). This study evaluated reconstructed spatial resolution, maximum/peak contrast recovery (CRmax/CRpeak) and SNR of Q.Clear compared to time-of-flight (TOF) OSEM with and without point spread function (PSF) modeling.

Methods

The NEMA IEC Body phantom was scanned five times (3 min scan duration, 30 min between scans, background, 1.5–3.9 kBq/ml F18) with a GE Discovery MI PET/CT (3-ring detector) with spheres filled with 8-, 4-, or 2-fold the background activity concentration (SBR 8:1, 4:1, 2:1). Reconstruction included Q.Clear (beta, 150/300/450), “PSF+TOF4/16” (iterations, 4; subsets, 16; in-plane filter, 2.0 mm), “OSEM+TOF4/16” (identical parameters), “PSF+TOF2/17” (2 it, 17 ss, 2.0 mm filter), “OSEM+TOF2/17” (identical), “PSF+TOF4/8” (4 it, 8 ss, 6.4 mm), and “OSEM+TOF2/8” (2 it, 8 ss, 6.4 mm). Spatial resolution was derived from 3D sphere activity profiles. RC as (sphere activity concentration [AC]/true AC). SNR as (background mean AC/background AC standard deviation).

Results

Spatial resolution of Q.Clear150 was significantly better than all conventional algorithms at SBR 8:1 and 4:1 (Wilcoxon, each p < 0.05). At SBR 4:1 and 2:1, the spatial resolution of Q.Clear300/450 was similar or inferior to PSF+TOF4/16 and OSEM+TOF4/16. Small sphere CRpeak generally underestimated true AC, and it was similar for Q.Clear150/300/450 as with PSF+TOF4/16 or PSF+TOF2/17 (i.e., relative differences < 10%). Q.Clear provided similar or higher CRpeak as OSEM+TOF4/16 and OSEM+TOF2/17 resulting in a consistently better tradeoff between CRpeak and SNR with Q.Clear. Compared to PSF+TOF4/8/OSEM+TOF2/8, Q.Clear150/300/450 showed lower SNR but higher CRpeak.

Conclusions

Q.Clear consistently improved reconstructed spatial resolution at high and medium SBR compared to PSF+TOF and OSEM+TOF, but only with beta = 150. However, this is at the cost of inferior SNR with Q.Clear150 compared to Q.Clear300/450 and PSF+TOF4/16/PSF+TOF2/17 while CRpeak for the small spheres did not improve considerably. This suggests that Q.Clear300/450 may be advantageous for the 3-ring detector configuration because the tradeoff between CR and SNR with Q.Clear300/450 was superior to PSF+TOF4/16, OSEM+TOF4/16, and OSEM+TOF2/17. However, it requires validation by systematic evaluation in patients at different activity and acquisition protocols.

Keywords: PET; Image reconstruction; Spatial resolution; Contrast recovery; Signal-to-noise ratio; TOF; PSF; Q.Clear; GE Discovery MI

Permalink: https://www.hzdr.de/publications/Publ-31141
Publ.-Id: 31141


Start-to-end simulations Modeling hybrid plasma accelerator experiments with PIConGPU

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

A brief summary of the evolution of LPWFA hybrid simulations and why start-to end simulations are needed to model the LPWFA setup.

Keywords: LPWFA; hybrid; PIConGPU

  • Lecture (Conference) (Online presentation)
    DMA meeting, 20.05.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31140
Publ.-Id: 31140


Electric and magnetic dipole strength in 66Zn

Schwengner, R.; Massarczyk, R.; Scheck, M.; Tornow, W.; Brown, B. A.; Battaglia, G.; Beck, T.; Bemmerer, D.; Benouaret, N.; Beyer, R.; Butterling, M.; Fiedler, F.; Finch, S. W.; Fransen, C.; Friman-Gayer, U.; Frotscher, A.; Gonzalez, R.; Grieger, M.; Hartmann, A.; Hensel, T.; Hoemann, E.; Hoffmann, H.; Isaak, J.; Janssens, R. V. F.; Johnson, S.; Jones, M. D.; Junghans, A.; Kelly, N.; Kleemann, J.; Krishichayan, F.; Little, D. R.; Ludwig, F.; Müller, S.; Odonnell, D.; Pirovano, E.; Savran, D.; Sinclair, J.; Takacs, M. P.; Turkat, S.; Urlaß, S.; Wagner, A.; Wieland, O.; Wilhelmy, J.

The dipole strength of the nuclide 66Zn was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.4 MeV at the γELBE facility as well as using quasi-monoenergetic and linearly polarized photon beams of 30 energies within the range from 4.3 to 9.9 MeV at the HIγS facility. About 140 J = 1 states were identified, out of them 9 with 1+ and 84 with 1- assignments. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. As a result, the photoabsorpton cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model. The experimental M1 strengths from resolved 1+ states are compared with results of large-scale shell-model calculations.

Keywords: Photon scattering; nuclear resonance fluorescence; dipole excitations; photoabsorption cross section; electromagnetic transitions; statistical reaction model; shell model

Permalink: https://www.hzdr.de/publications/Publ-31139
Publ.-Id: 31139


Nonlocal stimulation of three-magnon splitting in a magnetic vortex

Körber, L.; Schultheiß, K.; Hula, T.; Verba, R.; Faßbender, J.; Kakay, A.; Schultheiß, H.

We present a combined numerical, theoretical and experimental study on stimulated three-magnon splitting in a magnetic disk in the vortex equilibrium state. Our micromagnetic simulations and Brillouin-light-scattering results confirm that three-magnon splitting can be triggered even below threshold by exciting one of the secondary modes by magnons propagating in a waveguide next to the disk. The experiments show that stimulation is possible over an extended range of excitation powers and a wide range of frequencies around the eigenfrequencies of the secondary modes. Rate-equation calculations predict an instantaneous response to stimulation and the possibility to prematurely trigger three-magnon splitting even above threshold in a sustainable manner. These predictions are confirmed experimentally using time-resolved Brillouin-light-scattering measurements and are in a good qualitative agreement with the theoretical results. We believe that the controllable mechanism of stimulated three-magnon splitting could provide a possibility to utilize magnon-based nonlinear networks as hardware for reservoir or neuromorphic computing.

Here, we briefly describe how the archived data for the publication "Nonlocal stimulation of three-magnon splitting in a magnetic vortex", submitted to PRL, is structured.

"rate-equations"
- theoretical data of the temporal evolution of the spin wave modes in Fig. 4

"micromagnetic-simulation"
- MuMax3 simulation recipes (.go files) and sample-layout masks for the
simulations performed for Fig. 2(a,b,c).
- corresponding power spectra obtained with our "mumax3-pwsp" program
- mode profiles for stimulated and spontaneous splitting (Fig. 1(c) and Fig. 2(d))
- dispersion of the spin waves, calculated by micromagetnic simulation, shown in Fig. 1(b)

"experiments"
- electron beam microscopy image of the sample
- intensity spectrum of the waveguide, used to calculate the approximate
frequency/wave-vector region where the waveguide is effective (inset in Fig. 1(c))
- non-time-resolved BLS measurements, including spectra, power sweeps, etc. for
Figs 2,3 in "i3MS" folders, in more detail described by "i3MS_V1_KS_logbook.pdf"
- time-resolved BLS measurements, further explained in the corresponding subfolders
 

Keywords: spin wave; nonlinear; three-magnon splitting; stimulation; micromagnetic simulation; BLS

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-11
    DOI: 10.14278/rodare.364
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31137
Publ.-Id: 31137


Treatment of brain metastases in small cell lung cancer: Decision-making amongst a multidisciplinary panel of European experts

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

Background: Brain metastases (BM) are common in patients with small cell lung cancer (SCLC). In recent years, the role of whole brain radiotherapy (WBRT) for brain metastases in lung cancer is being reevaluated, especially in the context of new systemic treatments available for SCLC. With this analysis, we investigate decision-making in SCLC patients with BM among European experts in medical oncology and radiation oncology. Methods: We analyzed decision-making from 13 medical oncologists (selected by IASLC) and 13 radiation oncologists (selected by ESTRO) specialized in SCLC. Management strategies of individual experts were converted into decision trees and analyzed for consensus. Results and conclusion: In asymptomatic patients, chemotherapy alone is the most commonly recommended first line treatment. In asymptomatic patients with limited volume of brain metastases, a higher preference for chemotherapy without WBRT among medical oncologists compared to radiation oncologists was observed. For symptomatic patients, WBRT followed by chemotherapy was recommended most commonly. For limited extent of BM in symptomatic patients, some experts chose stereotactic radiotherapy as an alternative to WBRT. Significant variation in clinical decision-making was observed among European SCLC experts for the first line treatment of patients with SCLC and BM.

Keywords: Brain metastases; Chemotherapy; Decision-making; Small cell lung cancer; Stereotactic radiotherapy; Whole brain radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-31136
Publ.-Id: 31136


Local void fraction and pressure drop data for horizontal annular flow through orifice

Porombka, P.; Boden, S.; Lucas, D.; Hampel, U.

This dataset combines multiple measurements form air-water horizontal annular flow experiments in a pipe (case A) and a pipe with circular orifice with \(d^2 / D^2 = 0.6\)  (case B). Measurements where taken at superficial Reynolds numbers of Re=25000 for the gas phase and Re =4090 for the liquid phase. The following data are included for each case:

  • linear pressure drop between two points (case A), four points (case B) measured with split-range differential pressure transducers at 5Hz
  • time-averaged local liquid volume fraction distribution in cylindrical and Cartesian coordinates reconstructed from X-ray microtomography projections
  • reconstructed pipe axis coordinates and pipe radius
  • Python code to calculate secondary validation parameters (e.g. film thickness distribution) from primary data

The detailed 3D data is intended for validation of computational fluid dynamics codes based on phase-averaged variables such as the Euler-Euler approach.

Keywords: X-ray microtomography; film thickness; circular orifice; annular flow

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-09
    DOI: 10.14278/rodare.361

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31135
Publ.-Id: 31135


Hydrodynamic forces on a clean spherical bubble translating in a wall-bounded linear shear flow

Shi, P.; Rzehak, R.; Lucas, D.; Magnaudet, J.

The three-dimensional flow around a spherical clean bubble translating steadily in a wall-bounded linear shear flow is studied numerically. The present work is concerned with the drag and lift forces experienced by the bubble over a wide range of Reynolds number (0.1 ≤ Re ≤ 10^3, Re being based on the bubble diameter and relative velocity with respect to the ambient fluid), wall distance (1.5 ≤ LR ≤ 8, LR being the distance from the bubble center to the wall normalized by the bubble radius), and relative shear rate -0.5 ≤ Sr ≤ 0.5, Sr being the ratio between the velocity difference across the bubble and the relative velocity).Based on the above range of parameters, situations where the bubble is repelled from or attracted to the wall are both covered. The flow structure and vorticity field are analyzed to obtain qualitative insight into the interaction mechanisms at work. The drag and lift forces are computed as well. Their variations agree well with theoretical predictions available in the limit of low-but-finite Reynolds number and, when the fluid is at rest, in the potential flow limit. Numerical results and analytical expressions are combined to provide accurate semi-empirical expressions for the drag and lift forces at arbitrary Reynolds number and separation distance.

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Permalink: https://www.hzdr.de/publications/Publ-31134
Publ.-Id: 31134


Olfactory dysfunction correlates with putaminal dopamine turnover in early de novo Parkinson’s disease

Löhle, M.; Wolz, M.; Beuthien-Baumann, B.; Oehme, L.; van den Hoff, J.; Kotzerke, J.; Reichmann, H.; Storch, A.

Although olfactory dysfunction is one of the most well-established prodromal symptoms in Parkinson’s disease (PD), its correlation with clinical disease progression or dopaminergic dysfunction still remains unclear. We here evaluated the association of striatal dopamine metabolism and olfactory function in a homogenous cohort of 30 patients with early untreated de novo PD. Striatal dopamine metabolism was assessed by the extended 18Fluorodopa PET scanning protocol to measure 18Fluorodopa uptake (Kocc) and the effective dopamine distribution volume ratio (EDVR) as the inverse of dopamine turnover. Olfactory function was estimated by the “Sniffin’ Sticks” test including odor threshold (T), discrimination (D) and identification (I) assessment. We detected moderate correlations of the EDVR in the posterior putamen with the TDI composite score (r = 0.412; p = 0.024; Pearson’s correlation test) and the odor identification score (r = 0.444; p = 0.014). These correlations were confirmed by multivariate regression analyses using age, sex, symptom duration and disease severity as measured by UPDRSIII motor score as candidate covariates. No other associations were observed between olfaction measures and Kocc and EDVR in all striatal regions. Together, olfactory dysfunction in early PD is not correlated with striatal 18Fluorodopa uptake as a measure for dopaminergic degeneration, but with putaminal dopamine turnover as a marker for dopaminergic presynaptic compensatory processes in early PD. These results should be treated as hypothesis generating and require confirmation by larger multicenter studies.

Permalink: https://www.hzdr.de/publications/Publ-31133
Publ.-Id: 31133


Predicting the dominating factors during heat transfer in magnetocaloric composite wires

Krautz, M.; Beyer, L.; Funk, A.; Waske, A.; Weise, B.; Freudenberger, J.; Gottschall, T.

Magnetocaloric composite wires have been studied by pulsed-field measurements up to μ0ΔH = 10 T with a typical rise time of 13 ms in order to evaluate the evolution of the adiabatic temperature change of the core, ΔTad, and to determine the effective temperature change at the surrounding steel jacket, ΔTeff, during the field pulse. An inverse thermal hysteresis is observed for ΔTad due to the delayed thermal transfer. By numerical simulations of application-relevant sinusoidal magnetic field profiles, it can be stated that for field-frequencies of up to two field cycles per second heat can be efficiently transferred from the core to the outside of the jacket. In addition, intense numerical simulations of the temperature change of the core and jacket were performed by varying different parameters, such as frequency, heat capacity, thermal conductivity and interface resistance in order to shed light on their impact on ΔTeff at the outside of the jacket in comparison to ΔTad provided by the core.

Permalink: https://www.hzdr.de/publications/Publ-31131
Publ.-Id: 31131


The influence of different artificial extracellular matrix implant coatings on the regeneration of a critical size femur defect in rats

Förster, Y.; Schulze, S.; Penk, A.; Neuber, C.; Möller, S.; Hintze, V.; Scharnweber, D.; Schnabelrauch, M.; Pietzsch, J.; Huster, D.; Rammelt, S.

Resorbable biomaterials based on artificial extracellular matrices (aECM) represent promising scaffolds for the treatment of large bone defects. Here, we investigated various glycosaminoglycan (GAG) derivatives of varying sulfation degree with respect to their influence on in vivo bone healing. The materials used in this study consisted of GAG-coated degradable polycaprolactone-co-lactide (PCL). Critical size femur defects in rats were filled with autologous bone serving as positive control or the respective coated or uncoated PCL scaffolds. After 2 and 12 weeks, progress in the healing process was investigated by analyzing the new bone matrix formation, the collagen content and hydroxyapatite formation by using micro-computed tomography (μCT), biomechanical testing, nuclear magnetic resonance spectroscopy (NMR) and histology. The sulfated GAG coating contributed substantially to bone regeneration, increased collagen synthesis and initiated mineralization of the organic matrix. Most substantial collagen production was detected in scaffolds coated with chondroitin sulfate. Scaffolds coated with hypersulfated hyaluronan induced formation of new bone volume comparable to what was observed in the positive control. GAG differing in the sugar backbone and degree of sulfation modulate the healing process at different times, eventually leading to improved bone healing.

Keywords: Artificial extracellular matrices; Glycosaminoglycans; Chondroitin sulfate; Sulfated hyaluronan; Bone healing

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-31130
Publ.-Id: 31130


Software for: Characterization of blood coagulation dynamics and oxygenation in ex-vivo retinal vessels by fluorescence hyperspectral imaging

Podlipec, R.; Iztok, U.

The Mathematica software for the analysis of blood oxygenation in the intact or damaged retinal vessel from the fluorescence hyperspectral data using optimized two-component empirical asymmetric log-normal lineshape (LN) spectral model (Urbancic et al, Opt. Express 21, 2013) modified with hemoglobin absorbance correction. 

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2020-06-03
    DOI: 10.14278/rodare.359
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31129
Publ.-Id: 31129


Compositional modelling of the impact of source lithology on the plant ionome

Pospiech, S.; van den Boogaart, K. G.; Tolosana Delgado, R.; Middleton, M.

The plant ionome is used for many applications for which it is important to understand and model how the elemental composition in the plants or plant organs evolved based on the available element sources, e.g. the effect of the soils or the underlying lithologies. Since the uptake and translocation of elements is influenced by a multitude of non-controllable parameters it is very challenging to relate a certain element pattern specifically to one parameter and quantify the effect of the parameter. Additionally, the applied modelling tools often do not take into account that both, the plant ionome and the element source, are multi-element concentrations. Concentrations are compositional data which represent the relative importance of some parts of a whole, and thus they are constrained and typically might suffer from problems of spurious correlations and negative bias, which disturbs our models of plant uptake.
In this contribution, we are presenting a statistical approach to describe the relation between geochemical composition of plants and the bedrock lithology while taking the multi-variate and constrained nature of concentrations into account. Modern compositional data analysis relies on log-ratio transforms and the Aitchison geometry. Most of the processes building the plant ionome from the element sources can be understood as linear modifications in the log-ratio space. A selective element transport would correspond to a shift of log-ratios. If this selectivity varies randomly this shift can be modelled by a multivariate normal distribution in log-ratio space. Selective element uptake by plants can thus be modelled by a downscaling of variability in the form of regression coefficients in log-ratio space. This allows to model many geochemical phenomena through a multivariate linear model in log-ratios.
To demonstrate the statistical method an exploration data set of lithologies and plant data from Northern Finland is used.

Keywords: plant geochemistry; ionome; compositional data; regression model; plant uptake; North Finland; gold mining; exploration

  • Open Access Logo Lecture (Conference) (Online presentation)
    Goldschmidt Virtual Conference 2020, 21.-26.06.2020, Online, USA

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Permalink: https://www.hzdr.de/publications/Publ-31128
Publ.-Id: 31128


Transport signatures of a junction between a quantum spin Hall System and a chiral topological superconductor

Novik, E. G.; Trauzettel, B.; Recher, P.

We investigate transport through a normal-superconductor (NS) junction made from a quantum spin Hall (QSH) system with helical edge states and a two-dimensional (2D) chiral topological superconductor (TSC) having a chiral Majorana edge mode. We employ a two-dimensional extended four-band model for HgTe-based quantum wells in a magnetic (Zeeman) field and subject to s-wave superconductivity. We show using the Bogoliubov-de Gennes scattering formalism that this structure provides a striking transport signal of a 2D TSC. As a function of the sample width (or Fermi energy) the conductance resonances go through a sequence of 2e2/h (nontrivial phase) and 4e2/h plateaux (trivial phase) which fall within the region of a nonzero Chern number (2D limit) as the sample width becomes large. These signatures are a manifestation of the topological nature of the QSH effect and the TSC.

Permalink: https://www.hzdr.de/publications/Publ-31127
Publ.-Id: 31127


Enhanced Ferromagnetism and Tunable Magnetism in Fe3GeTe2 Monolayer by Strain Engineering

Hu, X.; Zhao, Y.; Shen, X.; Krasheninnikov, A.; Chen, Z.; Sun, L.

Recent discovery of intrinsic ferromagnetism in Fe3GeTe2 (FGT) monolayer [Deng, Y.; et al. Nature 2018, 563, 94−99; Fei, Z.; et al. Nat. Mater. 2018, 17, 778−782] not only extended the family of two-dimensional (2D) magnetic materials but also stimulated further interest in the possibility to tune their magnetic properties without changing the chemical composition or introducing defects. By means of density functional theory computations, we explore strain effects on the magnetic properties of the FGT monolayer. We demonstrate that the ferromagnetism can be largely enhanced by the tensile strain in the FGT monolayer due to the competitive effects of direct exchange and superexchange interaction. The average magnetic moments of Fe atoms increase monotonically with an increase in biaxial strain from −5 to 5% in FGT monolayer. The intriguing variation of magnetic moments with strain in the FGT monolayer is related to the charge transfer induced by the changes in the bond lengths. Given the successful fabrication of the FGT monolayer, the strain-tunable ferromagnetism in the FGT monolayer can stimulate the experimental effort in this field. This work also suggests an effective route to control the magnetic properties of the FGT monolayer. The pronounced magnetic response toward the biaxial strain can be used to design the magnetomechanical coupling spintronics devices based on FGT.

Keywords: 2D materials; first-principles simulations

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Permalink: https://www.hzdr.de/publications/Publ-31126
Publ.-Id: 31126


Simulating Raman spectra by combining first-principles and empirical potential approaches with application to defective MoS2

Kou, Z.; Hashemi, A.; Puska, M.; Krasheninnikov, A.; Komsa, H.-P.

Successful application of two-dimensional transition metal dichalcogenides in optoelectronic, catalytic, or sensing devices heavily relies on the materials’ quality, that is, the thickness uniformity, presence of grain boundaries, and the types and concentrations of point defects. Raman spectroscopy is a powerful and nondestructive tool to probe these factors but the interpretation of the spectra, especially the separation of different contributions, is not straightforward. Comparison to simulated spectra is beneficial, but for defective systems first-principles simulations are often computationally too expensive due to the large sizes of the systems involved. Here, we present a combined first-principles and empirical potential method for simulating Raman spectra of defective materials and apply it to monolayer MoS2 with random distributions of Mo and S vacancies. We study to what extent the types of vacancies can be distinguished and provide insight into the origin of different evolutions of Raman spectra upon increasing defect concentration. We apply to our simulated spectra the phonon confinement model used in previous experiments to assess defect concentrations, and show that the simplest form of the model is insufficient to fully capture peak shapes, but a good match is obtained when the type of phonon confinement and the full phonon dispersion relation are accounted for.

Keywords: Raman spectra; 2D materials; simulaitons

Permalink: https://www.hzdr.de/publications/Publ-31125
Publ.-Id: 31125


Two-Pion Intensity-Interferometry in Non-Central Collisions of Au + Au @ 1.23 A GeV

Greifenhagen, R.

High-statistics π-, π- and π+, π+ HBT data for non-central Au + Au collisions at 1.23 A GeV, measured with HADES at SIS18/GSI, are presented. The three-dimensional emission source is studied in dependence on pair transverse momentum and beam energy. A tilt of the source with respect to the reaction plane is observed. The spatial extension and the tilt magnitude of the source decrease with transverse momentum. A clear charge-sign difference is observed for the spatio-temporal variances, but not for the tilt angle of the source. Derived geometrical and temporal parameters do well complement the trend over several orders of magnitude in beam-energy provided that consistent transverse momenta are selected.

Keywords: femtoscopy; HBT

Related publications

  • Contribution to proceedings
    XIV Workshop on Particle Correlations and Femtoscopy, 03.-07.06.2019, Dubna, Russian Federation
    Physics of Particles and Nuclei Volume 51, Issue 3, Berlin: Springer, 1063-7796, 288-292
    DOI: 10.1134/S1063779620030132

Permalink: https://www.hzdr.de/publications/Publ-31124
Publ.-Id: 31124


Origin of the metamagnetic transitions in Y1− xErxFe2(H,D)4.2 compounds

Paul-Boncour, V.; Isnard, O.; Shtender, V.; Scurschii, I.; Guillot, M.

The structural and magnetic properties of Y1−xErxFe2 intermetallic compounds and their hydrides and deuterides Y1−xErxFe2H(D)4.2 have been investigated using X-ray diffraction and magnetic measurements under static and pulsed magnetic field up to 60 T. The intermetallics crystallize in the C15 cubic structure (Fd-3m space group), whereas corresponding hydrides and deuterides crystallize in a monoclinic structure (Pc space group). All compounds display a linear decrease of the unit cell volume versus Er concentration; the hydrides have a 0.8% larger cell volume compared to the deuterides with same Er content. They are ferrimagnetic at low field and temperature with a compensation point at x=0.33 for the intermetallics and x=0.57 for the hydrides and deuterides. A sharp first order ferromagnetic-antiferromagnetic (FM-AFM) transition is observed upon heating at TFM−AFM for both hydrides and deuterides. These compounds show two different types of field induced transitions, which have different physical origin. At low temperature (T < 50 K), a forced ferri-ferromagnetic metamagnetic transition with Btrans1 ≈8 T, related to the change of the Er moments orientation from antiparallel to parallel Fe moment, is observed. Btrans1 is not sensitive to Er concentration, temperature and isotope effect. A second metamagnetic transition resulting from antiferromagnetic to ferrimagnetic state is also observed. The transition field Btrans2 increases linearly versus temperature and relates to the itinerant electron metamagnetic behavior of the Fe sublattice. An onset temperature TM0 is obtained by extrapolating TFM−AFM (B) at zero field. TM0 decreases linearly versus the Er content and is 45 ± 5 K higher for the hydrides compared to the corresponding deuteride. The evolution of TM0 versus cell volume shows that it cannot be attributed exclusively to a pure volume effect and that electronic effects should also be considered.

Permalink: https://www.hzdr.de/publications/Publ-31123
Publ.-Id: 31123


Germetry dependent beam dynamics of a 3.5-cell SRF Ggun cavity at ELBE

Zhou, K.; Arnold, A.; Teichert, J.; Xiang, R.; Ma, S.; Schaber, J.

In order to optimize the next generation SRF gun at HZDR ELBE radiation source, the impact on beam dynamics from the SRF cavity geometry needs to be investigated. This paper presents an analysis on the electromagnetic fields and output electron beam qualities, by changing the geometry parameters of a 3.5-cell SRF gun cavity. The simulation results show the higher electric field ratio in the first half cell to the TESLA like cell, the better beam parameters we can obtain, which, however, will also lead to a higher Emax/E0 and Bmax/E0.

Keywords: SRF gun; superconducting cavity

  • Open Access Logo Poster
    The 19th International Conference on RF Superconductivity(SRF2019), 30.06.-05.07.2019, Dresden, Germany
    DOI: 10.18429/JACoW-SRF2019-THP082
  • Open Access Logo Contribution to proceedings
    The 19th International Conference on RF Superconductivity(SRF2019), 30.06.-05.07.2019, Dresden, Germany
    Proceedings of the 19th International Conference on RF Superconductivity: JACoW, 978-3-95450-211-0
    DOI: 10.18429/JACoW-SRF2019-THP082

Permalink: https://www.hzdr.de/publications/Publ-31122
Publ.-Id: 31122


Raw data: "Quantification of peptide bound particles: A phage mimicking approach via site-selective immobilization on glass"

Schrader, M.

This set contains the raw data of the fluorescence scanning experiments used in the publication of "Quantification of peptide bound particles: A phage mimicking approach via site-selective immobilization on glass" by Schrader et al.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-05
    DOI: 10.14278/rodare.357
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31121
Publ.-Id: 31121


SRF Gun and SRF Linac Driven THz at ELBE Successfully in User Operation

Xiang, R.; Arnold, A.; Evtushenko, P.; Kovalev, S.; Lehnert, U.; Lu, P.; Ma, S.; Michel, P.; Murcek, P.; Ryzhov, A.; Schaber, J.; Schneider, C.; Teichert, J.; Vennekate, H.; Will, I.

The first all-SRF accelerator driven THz source has been operated as a user facility since 2018 at ELBE radiation center. The CW electron beam is extracted from SRF gun II, accelerated to relativistic energies and compressed to sub-ps length in the ELBE SRF linac with a chicane. THz pulses are produced by passing the short electron bunches through a diffraction radiator (CDR) and an undulator. The coherent THz power increases quadratically with bunch charge. The pulse energy up to 10 μJ at 0.3 THz with 100 kHz has been generated.

Keywords: all-SRF accelerator; THz user facility; CW electron beam; SRF gun

  • Open Access Logo Poster
    The 19th International Conference on RF Superconductivity(SRF2019), 30.06.-05.07.2019, Dresden, Germany
    DOI: 10.18429/JACoW-SRF2019-THP032
  • Open Access Logo Contribution to proceedings
    The 19th International Conference on RF Superconductivity(SRF2019), 30.06.-05.07.2019, Dresden, Germany
    Proceedings of the 19th International Conference on RF Superconductivity: JACoW, 978-3-95450-211-0
    DOI: 10.18429/JACoW-SRF2019-THP032

Permalink: https://www.hzdr.de/publications/Publ-31120
Publ.-Id: 31120


Nonlinear compositional and morphological evolution of ion irradiated GaSb prior to nanostructure formation

Lively, M. A.; Holybee, B.; Toriyama, M.; Facsko, S.; Allain, J. P.

Low-energy ion irradiation of III-V semiconductor surfaces can lead to the formation of regular hexagonal dot patterns at the surface. We present experimental and computational results for ion irradiation of GaSb surfaces which elucidate the nature of the coupled compositional and morphological pattern-formation mechanisms. We demonstrate by in-situ grazing-incidence small-angle x-ray scattering (GISAXS) and angle-resolved Auger electron spectroscopy (ARAES) that the emergence of an altered compositional depth profile is essential to induce morphological changes at the surface. This morphological evolution of the surface follows nucleation-and-growth kinetics. Furthermore, we show from massive-scale molecular dynamics (MD) simulations that the compositional depth profile evolution leads to thermodynamic phase separation, providing a lateral compositional instability that drives pattern formation. Additionally, high-fluence simulations elucidate the irradiation-induced mechanisms of compositional depth profile formation. Prompt ion effects drive formation of single-element “protoclusters”, predominantly of Sb. Structural and energetic characterization of the simulation results indicate that Sb may be more mobile than Ga, providing a diffusional pathway for long-temporal-scale compositional evolution of the irradiated surface. Our findings motivate the development of new, comprehensive models which consider the total spatial and temporal complexity of multicomponent systems evolving under ion irradiation.

Keywords: nanostructures; ion beam irradiation; nanopatterning

Permalink: https://www.hzdr.de/publications/Publ-31118
Publ.-Id: 31118


Preliminary geometry optimization of a 3.5-cell SRF Gun cavity at ELBE based on beam dynamics

Zhou, K.; Li, P.; Arnold, A.; Schaber, J.; Xiang, R.; Teichert, J.; Ma, S.

At present, ELBE radiation source at HZDR is optimizing the SRF cavity for the next generation ELBE SRF GUN. This paper presents a preliminary study on the geometry optimization of a 3.5-cell SRF gun cavity based on beam dynamics. By changing the lengths of the half cell and the first TESLA like cell, two new cavity models with higher electric field in the half cell are built and their RF fields are compared with SRF GUN I and SRF GUN II. Through the scanning of the RF phases and the electric fields, the simulation results indicate that new models have smaller transverse emittance at relatively lower electric field gradients and better performance on longitudinal emittance than SRF GUN I and SRF GUN II.

Keywords: SRF cavity; SRF gun; transverse emittance

  • Open Access Logo Poster
    39th International Free-Electron Laser Conference (FEL19), 26.-30.08.2019, Hamburg, Germany
  • Open Access Logo Contribution to proceedings
    39th International Free-Electron Laser Conference (FEL19), 26.-30.08.2019, Hamburg, Germany
    Proceedings of the 39th International Free-Electron Laser Conference: JACoW, 978-3-95450-210-3
    DOI: 10.18429/JACoW-FEL2019-WEP026

Permalink: https://www.hzdr.de/publications/Publ-31117
Publ.-Id: 31117


Metal and semiconductor photocathodes in HZDR SRF gun

Xiang, R.; Arnold, A.; Murcek, P.; Teichert, J.; Schaber, J.

Quality of photocathode in a photoinjector is one of the critical issues for the stability and reliability of the whole accelerator facility. In April 2013, the IR FEL lasing was demonstrated for the first time with the electron beam from the SRF gun with Cs2Te at HZDR. Cs2Te photocathode worked in SRF gun-I for more than one year without degradation. Currently, Mg photocathodes with QE up to 0.5% are applied in SRF Gun-II, generating e- beam with bunch charge up to 300 pC in CW mode with sub-ps bunch length for the high power THz radiation. It is an excellent demonstration that SRF guns can work reliably in a high power user facility.

Keywords: photocathode; Cs2Te; Mg; photoinjector; SRF gun

  • Invited lecture (Conferences)
    ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL’19), 15.-20.09.2019, Berlin, Germany
  • Open Access Logo Contribution to proceedings
    Workshop on Energy Recovery Linacs (ERL2019), 15.-20.09.2019, Berlin, Germany
    Proceedings of workshop on Energy Recovery Linacs (ERL2019)

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Permalink: https://www.hzdr.de/publications/Publ-31116
Publ.-Id: 31116


Robust Mg cathodes in SRF gun II

Xiang, R.; Jochen, T.

we present here the status of ELBE SRF gun II and the application of Mg photocathodes in SRF gun. In order to improve the QE of Mg cathodes, we appy the ps- UV laser cleaning for bulk Mg photocathodes. Furthermore, several alternative preparation methods of Mg are also under studying.

Keywords: Mg photocathode; SRF gun; laser cleaning

  • Open Access Logo Invited lecture (Conferences)
    European Workshop on Photocathodes for Particle Accelerator Applications (EWPAA 2019), 11.-13.09.2019, Villigen PSI, Switzerland

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Permalink: https://www.hzdr.de/publications/Publ-31115
Publ.-Id: 31115


Development and Implementation of Beam-Based Feedback Algorithms for Continuous Wave Superconducting Linear Accelerators

Maalberg, A.; Zenker, K.; Schwarz, A.; Evtushenko, P.; Kuntzsch, M.

The superconducting linear accelerator ELBE at Helmholtz-Center Dresden-Rossendorf is a versatile light source operated in continuous wave mode. New experiments and beam modes have a higher demand on the beam stability and reproducibility of accelerator settings. These requirements are addressed by an upgrade of the existing digital MicroTCA.4 based LLRF control by a beam-based feedback scheme. This poster gives an overview of the current control scheme, presents the planned beam diagnostics and discusses the possible ways of incorporating the beam-based feedback at the ELBE facility and a future light source.

  • Open Access Logo Poster
    19th International Conference on RF Superconductivity, 04.07.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-31114
Publ.-Id: 31114


Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline

Brack, F.-E.; Kroll, F.; Gaus, L.; Bernert, C.; Beyreuther, E.; Cowan, T.; Karsch, L.; Kraft, S.; Kunz-Schughart, L. A.; Leßmann, E.; Metzkes-Ng, J.; Obst-Hübl, L.; Pawelke, J.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Sobiella, M.; Rita Szabó, E.; Ziegler, T.; Zeil, K.

ntense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. Here we experimentally show the successful implementation of a highly efficient (50% transmission) and tuneable dual pulsed solenoid setup to generate a homogeneous (laterally and in depth) volumetric dose distribution (cylindrical volume of 5 mm diameter and depth) at a single pulse dose of 0.7 Gy via multi-energy slice selection from the broad input spectrum. The experiments were conducted at the Petawatt beam of the Dresden Laser Acceleration Source Draco and were aided by a predictive simulation model verified by proton transport studies. With the characterised beamline we investigated manipulation and matching of lateral and depth dose profiles to various desired applications and targets. Using an adapted dose profile, we performed a first proof-of-technical-concept laser-driven proton irradiation of volumetric in-vitro tumour tissue (SAS spheroids) to demonstrate concurrent operation of laser accelerator, beam shaping, dosimetry and irradiation procedure of volumetric biological samples.

Keywords: Laser acceleration; Radiobiology; High field pulsed magnets

  • Open Access Logo Scientific Reports 10(2020), 9118
    DOI: 10.1038/s41598-020-65775-7
  • Lecture (Conference) (Online presentation)
    BLIN4: Beam Line and INstrumentation: Fourth Workshop, 29.06.2020, Dresden, Deutschland
  • Lecture (Conference) (Online presentation)
    LIGHT Collaboration Meeting, 30.06.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31113
Publ.-Id: 31113


The attempt of using GaN as a photocathode in SRF Gun II

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Murcek, P.; Zwartek, P.; Ma, S.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green). An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
GaN is a semi-conductive material that is well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required. It has also a wide wavelength range from 100 to 380 nm.

Doping elements for n-type is silicon (Si) and for p-type magnesium (Mg). Mostly p-doped GaN promises better conditions because magnesium atoms increase the minority carrier diffusion length (about 200 nm). MOVPE is the most used technique to produce p-type GaN. Low temperatures are required in comparison to undoped or n-type GaN. Afterwards an annealing process is necessary to remove magnesium-bonded hydrogen. In p-type GaN electron are the minority carriers whereas holes are the majority carriers. The doping is assumed to lower the band bending around the surface. Therefore, the vacuum level is shifted to lower energy than the conductive band minimum in the flat band region.
Activated with a thin alkali metal layer, like caesium, GaN has the ability to lower the surface work function to produce a negative electron affinity (NEA). This effect originates from the surface band bending. Electrons excite over the bandgap and can easily enter into the vacuum.

Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
Like caesium telluride cathode it is possible to recover GaN(Cs) about 50% of the original QE with a simple bake out of 200°C and doing a Cs-reactivation to recover the degraded
cathode [2].
A big advantage of visible light cathodes instead of UV cathodes is to relax the drive laser requirements.

[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.
[2] Siegmund, O. et al. 2006. “Development of GaN Photocathodes for UV Detectors.” 567:89–92

Keywords: GaN(Cs) photocathode; III-V semiconductor; NEA photocathode; thin layer deposition

  • Open Access Logo Lecture (Conference)
    ECASIA 2019-European Conference on Applications of Surface and Interface Analysis, 15.-20.09.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31112
Publ.-Id: 31112


Emittance measurements comparison of slit-scan and quadrupole scan in simulation and experiments

Ma, S.; Arnold, A.; Evtushenko, P.; Ryzhov, A.; Schaber, J.; Teichert, J.; Xiang, R.

Three quadrupoles and one screen are used for beam transverse emittance measurements at HZDR ELBE. In this paper, the emittance calculated with two different methods, one with thin-lens approximation and the other one thick-lens no approximation, are compared and analized. To analyze the measurement error, quadrupole calibration is need. Two aspects about quadrupole analysis are made. The first one is quadrupole’s effective length and strength and the second one is quadrupole’s converged or diverged ability in reality.

  • Poster
    The 19th International Conference on RF Superconductivity, SRF2019, 30.06.-05.07.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-31111
Publ.-Id: 31111


Study of using GaN(Cs) as a photocathode in SRF injector

Schaber, J.; Xiang, R.; Teichert, J.; Murcek, P.; Zwartek, P.; Arnold, A.; Ma, S.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green). An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.

Keywords: GaN photocathode; caesium activation; thin layer deposition, NEA photocathode

  • Open Access Logo Poster
    19th International Conference on RF Superconductivity, SRF2019, 30.06.-05.07.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31110
Publ.-Id: 31110


The attempt of using GaN(Cs) in SRF injector

Schaber, J.; Xiang, R.; Teichert, J.; Murcek, P.; Zwartek, P.; Arnold, A.; Ma, S.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green). An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.

Keywords: GaN; NEA activation; photocathode; thin layer deposition

  • Open Access Logo Poster
    EWPAA 2019: European workshop on photocathodes for particle accelerator applications, 11.-13.09.2019, Villingen, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-31109
Publ.-Id: 31109


Study of surface cleaning and Cs-activation on GaN photocathodes

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Murcek, P.; Zwartek, P.; Ma, S.

Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams. With such a high intensity and short wavelengths, amorphous materials and chemical reaction steps nowadays could be studied.
GaN is a semi-conductive material that is well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is only used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
It has also a wide wavelength range from 100 to 380 nm.
The equilibrium phase of GaN is wutzite, which means gallium atoms are tetrahedrically surrounded by nitride atoms in a hexagonal closed crystal structure. The tetrahedrons build alternating bilayers of Ga and N in c-direction.
Doping elements for n-type is silicon (Si) and for p-type magnesium (Mg). Mostly p-doped GaN promises better conditions because magnesium atoms increase the minority carrier diffusion length (about 200 nm). MOVPE is the most used technique to produce p-type GaN. Low temperatures are required in comparison to undoped or n-type GaN. Afterwards an annealing process is necessary to remove magnesium-bonded hydrogen. In p-type GaN electron are the minority carriers whereas holes are the majority carriers. The doping is assumed to lower the band bending around the surface. Therefore, the vacuum level is shifted to lower energy than the conductive band minimum in the flat band region.
Activated with a thin alkali metal layer, like caesium, GaN has the ability to lower the surface work function to produce a negative electron affinity (NEA). This effect originates from the surface band bending. Electrons excite over the band gap and can easily enter into the vacuum.
Generally, the stability has also a great influence on the potential application in high brightness guns. GaN shows the promise of more significant stability and robustness against vacuum contaminations than alternate photocathodes.
Like caesium telluride cathode it is possible to recover GaN(Cs) about 50% of the original QE with a simple bake out of 200°C and doing a Cs-reactivation to recover the degraded
cathode [2].
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency GaN-Based Photocathodes with Extremely High Quantum Efficiency.” 103511(2005):1–4.
[2] Siegmund, O. et al. 2006. “Development of GaN Photocathodes for UV Detectors.” 567:89–92.

Keywords: photocathode; GaN; NEA activation

  • Open Access Logo Poster
    DPG Summer school 2019- Exciting nanostructures: Characterizing advanced confined systems, 22.-27.07.2019, Bad Honnef, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31108
Publ.-Id: 31108


The attempt of using GaN (Cs) as a photocathode in SRF injector

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Murcek, P.; Zwartek, P.; Ma, S.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green).
An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.

Keywords: photocathode; semiconductor; NEA activation; surface analysis

  • Open Access Logo Poster
    DPG Frühjahrstagung, 18.-22.03.2019, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31107
Publ.-Id: 31107


The attempt of using GaN as a photocathode in SRF Gun II

Schaber, J.; Xiang, R.; Murcek, P.; Arnold, A.; Teichert, J.; Ma, S.; Zwartek, P.

The photocathodes determine the beam quality in linear accelerators and represent a key component for many accelerator projects. Free-electron lasers (FEL), synchrotron- and THz radiation sources require injector systems with high brightness electron beams.

High quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance are desirable parameters for a perfect photocathode used in accelerators. Semiconductors such as GaN and GaAs as novel materials for photocathodes are showing an enormous potential.
GaAs is a well-known material for photocathodes. After activation with caesium and oxygen, it has a high QE for visible light (red or green). An advantage of GaAs is the opportunity of the layers to emit spin-polarized electrons.
GaN is a semi-conductive material and well known for its high QE when lighted with UV light. For improving the QE only caesium for activation is required.
At the moment GaN is used for photocathode-based detectors such as photomultipliers or phototubes and for LEDs. They have characteristics of low dark current, high-speed response and high sensitivity. It is very new for application in SRF Guns. It seems to be more robust and achieves higher QE than other photocathodes [1].
Crystallinity and surface parameters define the photoemission properties. Modern analytical methods are used for identification of impurities, dislocations and characterization of the crystallinity of the semiconductors and the right cleaning treatment as well as the right caesium rating.
[1] Uchiyama, Shoichi et al. 2011. “GaN-Based Photocathodes with Extremely High Quantum Efficiency” 103511(2005):1–4.

  • Open Access Logo Lecture (Conference)
    5. Annual MT Meeting, 04.-07.03.2019, Jena, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31106
Publ.-Id: 31106


KLOE hadronic cross section data in the HepDATA repository

Müller, S.

Presentation at (remote) Kick-Off-Meeting of the PrecisionSM-Working group of the STRONG2020 EU Project.

Keywords: KLOE; HEPdata

  • Open Access Logo Lecture (Conference) (Online presentation)
    Kick-Off meeting for PrecisionSM working group of STRONG2020 project, 03.06.2020, ZOOM (Sweden), Sweden

Permalink: https://www.hzdr.de/publications/Publ-31105
Publ.-Id: 31105


Dataset for dynamic simulation of the CEFR control rod drop experiments

Fridman, E.

Dataset for dynamic simulation of the CEFR control rod drop experiments 

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-03
    DOI: 10.14278/rodare.353

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Permalink: https://www.hzdr.de/publications/Publ-31104
Publ.-Id: 31104


Biomineralization of uranium-phosphates fueled by microbial 1 degradation of isosaccharinic acid (ISA)

Kuippers, G.; Morris, K.; Townsend, L. T.; Bots, P.; Kvashnina, K.; Bryan, N.; Lloyd, J. R.

Geological disposal is the preferred long-term solution for higher activity radioactive wastes (HAW) including Intermediate Level Waste (ILW). In a cementitious disposal system, cellulosic waste items present in ILW could undergo alkaline hydrolysis, producing significant quantities of isosaccharinic acid (ISA), a chelating agent for radionuclides. Although microbial degradation of ISA has been demonstrated, its impact upon the fate of radionuclides in a GDF is a topic of ongoing research. This study investigates the fate of U(VI) in pH neutral, anoxic, microbial enrichment cultures, approaching conditions similar to the far field of a GDF, containing ISA as the sole carbon source, and elevated phosphate concentrations, incubated both (i) under fermentation and (ii) Fe(III)-reducing conditions. In the fermentation experiment, U(VI) was precipitated as insoluble U(VI)-phosphates, whereas under Fe(III)-reducing conditions, the majority of the uranium was precipitated as reduced U(IV)-phosphates, potentially via enzymatic reduction (mediated by metal-reducing bacteria including Geobacter species detected by 16S rRNA gene sequencing). Overall, this suggests the potential for the establishment of a microbially-mediated “bio-barrier” extending into the far field geosphere surrounding a GDF which has the potential to evolve in response to aspects of a GDF and can have a controlling impact on the fate of radionuclides.

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  • Secondary publication expected from 23.03.2022

Permalink: https://www.hzdr.de/publications/Publ-31103
Publ.-Id: 31103


ESFR-SMART WP1.2.1 dataset

Fridman, E.

ESFR-SMART WP1.2.1 dataset

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-03
    DOI: 10.14278/rodare.351

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Permalink: https://www.hzdr.de/publications/Publ-31102
Publ.-Id: 31102


Helmholtz AI For Matter at Helmholtz-Zentrum Dresden-Rossendorf

Steinbach, P.; Hoffmann, N.

This poster summarizes the Helmholtz AI local unit for Matter Research installed at HZDR. The poster was presented at the Helmholtz AI Kick-Off Meeting on March 5th, 2020, in Munich, Germany.

Keywords: Helmholtz AI; FWCC; Deep Learning; Machine Learning; Data Science; Kick-Off

  • Open Access Logo Poster (Online presentation)
    Helmholtz AI Kick-Off Meeting, 05.03.2020, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31099
Publ.-Id: 31099


Neutronic analysis of the European Sodium Fast Reactor: Part II - burnup results

Fridman, E.; Álvarez-Velarde, F.; Romojaro-Otero, P.; Tsige-Tamirat, H.; Jiménez-Carrascosa, A.; García-Herranz, N.; Bernard, F.; Gregg, R.; Krepel, J.; Massara, S.; Poumerouly, S.; Girardi, E.; Mikityuk, K.

In the framework of the Horizon 2020 project ESFR-SMART, the European Sodium Fast Reactor (ESFR) core was updated through a safety-related modification and optimization of the core design from the earlier FP7 CP-ESFR project.

This study is dedicated to neutronic analysis of the new SFR core. The conducted work is reported in two parts. Part I dealt with the evaluation of the safety-related neutronic parameters of the fresh core carried out by 8 organizations using both continuous energy Monte Carlo and deterministic computer codes. A special emphasis was put on the calibration and verification of the computational tools involved in the analyses.

Part II is devoted to once-through and realistic batch-wise burnup calculations aiming at the establishing of the equilibrium core state, which will later serve as a basis for detailed safety analyses.

Keywords: ESFR; safety; Horizon 2020

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  • Open Access Logo Journal of Nuclear Engineering and Radiation Science 8(2022)1, 011302
    Online First (2020) DOI: 10.1115/1.4048765

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Permalink: https://www.hzdr.de/publications/Publ-31098
Publ.-Id: 31098


Neutronic analysis of the European Sodium Fast Reactor: Part I - fresh core results

Fridman, E.; Álvarez-Velarde, F.; Romojaro-Otero, P.; Tsige-Tamirat, H.; Jiménez-Carrascosa, A.; García-Herranz, N.; Bernard, F.; Gregg, R.; Krepel, J.; Massara, S.; Poumerouly, S.; Girardi, E.; Mikityuk, K.

In the framework of the Horizon 2020 project ESFR-SMART (2017-2021), the European Sodium Fast Reactor (ESFR) core was updated through a safety-related modification and optimization of the core design from the earlier FP7 CP-ESFR project (2009-2013).

This study is dedicated to neutronic analyses of the improved ESFR core design. The conducted work is reported in two parts. Part I deals with the evaluation of the safety-related neutronic parameters of the fresh Beginning-of-Life (BOL) core carried out by 8 organizations using both continuous energy Monte Carlo and deterministic computer codes. In addition to the neutronics characterization of the core, a special emphasis was put on the calibration and verification of the computational tools involved in the analyses.

Part II is devoted to once-through and realistic batch-wise burnup calculations aiming at the establishing of the equilibrium core state, which will later serve as a basis for detailed safety analyses.

Keywords: ESFR; Safety; Horizon 2020

Related publications

  • Journal of Nuclear Engineering and Radiation Science 8(2022)1, 011301
    Online First (2020) DOI: 10.1115/1.4048905

Permalink: https://www.hzdr.de/publications/Publ-31097
Publ.-Id: 31097


Dynamic simulation of the CEFR control rod drop experiments with the Monte Carlo code Serpent

Fridman, E.; Huo, X.

The China Experimental Fast Reactor (CEFR) is the first SFR operated in China. The CEFR physical start-up tests, conducted in 2010, included control rod (CR) worth (CRW) measurements by the rod drop method.
In this study, the transient simulations of the actual course of the CR drop experiments have been performed with the Monte Carlo code Serpent using a detailed 3D heterogeneous model of the CEFR core. The estimated time-depended neutron population, dynamic reactivity, and CRWs have been compared to the measurements. The experimental and calculated reactivity curves have shown a very close behavior for the entire simulated time interval. With regard to the CRW results, a very good compliance between the experiment and simulations as well as among the applied computational approaches has been observed. The obtained results indicate that Serpent can be routinely applied to transient simulations, the area which until recently was limited to deterministic methods.

Keywords: CEFR; Serpent; dynamic Monte Carlo; rod drop experiments

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-31096
Publ.-Id: 31096


An improved contact method for quantifying the mixing of a binary granular mixture

Papapetrou, T. N.; Lecrivain, G.; Bieberle, M.; Boudouvis, A.; Hampel, U.

When two granular phases are brought into motion in a rotating drum, a competition of mixing and segregation occurs. Several image analysis methods have been used to quantify the mixing. In this work, a modification of the contact method, originally proposed by Van Puyvelde (1999), is suggested to allow evaluation of the mixing index for each separate image. A strength of this modified method lies in the removal of the case-dependent normalization of the mixing index, which has so far impaired a direct comparison to other studies. This modified method is tested on artificial and experimental images of a granular bed composed of spherical glass and polypropylene beads of equal size. The bed evolves in a rotating drum under the rolling regime. The temporal evolution of the mixing index is in excellent agreement with the commonly used variance method.

Keywords: binary particle mixing; rotating drum; image analysis; mixing index; contact method; variance method

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Permalink: https://www.hzdr.de/publications/Publ-31095
Publ.-Id: 31095


Laboratory study of stationary accretion shock relevant to astrophysical systems

Mabey, P.; Albertazzi, B.; Falize, E.; Michel, T.; Rigon, G.; van Box Som, L.; Pelka, A.; Brack, F.-E.; Kroll, F.; Filippov, E.; Gregori, G.; Kuramitsu, Y.; Lamb, D. Q.; Li, C.; Ozaki, N.; Pikuz, S.; Sakawa, Y.; Tzeferacos, P.; Koenig, M.

Accretion processes play a crucial role in a wide variety of astrophysical systems. Of particular interest are magnetic cataclysmic variables, where, plasma flow is directed along the star’s magnetic field lines onto its poles. A stationary shock is formed, several hundred kilometres above the stellar surface; a distance far too small to be resolved with today’s telescopes. Here, we report the results of an analogous laboratory experiment which recreates this astrophysical system. The dynamics of the laboratory system are strongly influenced by the interplay of material, thermal, magnetic and radiative effects, allowing a steady shock to form at a constant distance from a stationary obstacle. Our results demonstrate that a significant amount of plasma is ejected in the lateral direction; a phenomenon that is under-estimated in typical magnetohydrodynamic simulations and often neglected in astrophysical models. This changes the properties of the post-shock region considerably and has important implications for many astrophysical studies.

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Permalink: https://www.hzdr.de/publications/Publ-31094
Publ.-Id: 31094


Helmholtz AI Consultants at Helmholtz-Zentrum Dresden-Rossendorf

Steinbach, P.

This poster summarizes the dedicated Helmholtz AI consultant team installed at HZDR. The poster was presented at the Helmholtz AI Kick-Off Meeting on March 5th, 2020, in Munich, Germany.

Keywords: Helmholtz AI; consultants; Local Unit; Matter; Kick-Off

  • Open Access Logo Poster
    Helmholtz AI Kickoff, 05.03.2020, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-31093
Publ.-Id: 31093


Directed, elliptic and higher order flow harmonics of protons, deuterons and tritons in Au+Au collisions at sqrt(s_NN)=2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Ciepal, I.; Deveaux, C.; Dreyer, J.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Mamaev, M.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Rathod, N.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Singh, U.; Smyrski, J.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wójcik, D.; Zanevsky, Y.; Zumbruch, P.

Flow coefficients vn of the orders n=1−6 are measured with the High-Acceptance DiElectron Spectrometer (HADES) at GSI for protons, deuterons and tritons as a function of centrality, transverse momentum and rapidity in Au+Au collisions at sqrt(s_NN)=2.4 GeV. Combining the information from the flow coefficients of all orders allows to construct for the first time, at collision energies of a few GeV, a complete, multi-differential picture of the emission pattern of these particles. The ratio v4/v22 at mid-rapidity is found to be remarkably close to the value 0.5, as might be indicative for an ideal fluid scenario.

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Permalink: https://www.hzdr.de/publications/Publ-31092
Publ.-Id: 31092


Recent insights in barium-131 as a diagnostic match for radium-223: cyclotron production, separation, labeling and imaging

Reissig, F.; Bauer, D.; Ullrich, M.; Kreller, M.; Pietzsch, J.; Mamat, C.; Kopka, K.; Pietzsch, H.-J.; Walther, M.

Barium-131 is a promising SPECT-compatible radionuclide for nuclear medicine and a promising diagnostic match for the alpha emitters radium-223/-224 by providing similar chemical properties as well as physical half-lives. Methods: Herein, we report on the sufficient production route 133Cs(p,3n)131Ba by using 28 MeV proton beams. Moreover, a sufficient purification process, based on SR Resin, was applied. For the first time, radiolabeling of macropa (literature-known chelator) with barium-131 was performed. Biodistribution studies and small animal SPECT/CT measurements were carried out with [131Ba]Ba(NO3)2 as reference and 131Ba-labeled macropa. Results: An average of 190 MBq barium-131 per irradiation was obtained. The purification process led to barium-131 in high radiochemical purity. Only an isotopic impurity of 0.01% barium-133 was detectable. Radiolabeling methods under mild conditions and reaction controls based on TLC systems were successfully applied for the labeling of the chelator macropa. For the first time, small animal SPECT imaging was performed using [131Ba]Ba(NO3)2 and 131Ba-labeled macropa in healthy mice. Biodistribution studies revealed the expected rapid bone uptake of [131Ba]Ba2+ ions, whereas 131Ba-labeled macropa showed a fast clearance from the blood, thereby showing a significantly (P < 0.001) lower accumulation in the bone. Conclusion: Barium-131 is a promising SPECT radionuclide and delivers appropriate imaging qualities in small animals. Furthermore, the relative stability of the 131Ba-labeled macropa complex in vivo forms the basis for the development of sufficient new chelators for heavy alkaline earth metal ions, especially for radium isotopes. Those radionuclides and the necessary stable chelation are of great interest in the research field of targeted alpha therapy. Thereby, barium-131 will reveal its meaning as diagnostic match to the alpha emitters radium-223 and radium-224.

Keywords: barium-131; cyclotron production; radionuclide separation; macropa; small animal SPECT

Permalink: https://www.hzdr.de/publications/Publ-31091
Publ.-Id: 31091


Corrigendum to “Controls on strath terrace formation and evolution: The lower Guadiana River, Pulo do Lobo, Portugal”

Ortega-Becerril, J. A.; Garzón, G.; Tejero, R.; Meriaux, A.-S.; Delunel, R.; Merchel, S.; Rugel, G.

The authors regret publishing the original article while omitting four authors. The correct author list and affiliations have now been corrected.
We would also like to make the clarifications and corrections listed below on the cosmogenic radionuclide (CRN) analysis.
1) All ¹⁰Be samples were collected in 2010 and prepared at the Newcastle Cosmogenic Isotope Laboratory. Accelerator mass spectrometry (AMS) of ¹⁰Be was performed in 2011 at the DREAMS-facility at the Helmholtz-ZentrumDresden-Rossendorf (HZDR) (Akhmadaliev et al., 2013).
2) All the ¹⁰Be model ages were calculated similarly to Mériaux et al. (2012). Spallation and muon production rate schemes are compatible with the CRONUS-Earth calculator v2.2 using the mid-latitude attenuation length of Farber et al. (2008). Ζero erosion model ages were calculated similarly than the Stone/Lal scaling scheme of Balco et al. (2008) with a constant production rate “St” for ¹⁰Be of 4.49 ± 0.39 atoms/g·year instead of the updated 4.01 ± 0.32 atoms/g·year for that scheme by Phillips et al. (2016). The “St” model ages are corrected for the production rate update. Thickness corrections assume a density of ρ = 2.65 g/cm³ for each sample.
The topographic shielding is derived from topographic data collected in the field. The propagated analytical uncertainties include
error blank, carrier, counting statistics and the uncertainty of the standard-like material SMD-Be-12 (Akhmadaliev et al., 2013). The propagated uncertainties include statistical uncertainties from the AMS, 8% uncertainty on the production rate, 0.87% for the decay constants of ¹⁰Be (Korschinek et al., 2010), as well as uncertainty of 5% on the density and 2.25% on the attenuation length of 177 ± 4 g/cm² (Farber et al., 2008). The ages are given in ka. Table 2 has been corrected and completed with the time-dependent model ages calculated using the “LSDn” scaling model (Lifton et al., 2014).
These “LSDn” model ages integrate the variation of the magnetic field over time together with the non-dipole field components and up-to-date spallation and muon scaling schemes with elevation, latitude and longitude, and production rate of 3.92 ± 0.31 atoms/g·year for this LSDn scaling (see Borchers et al., 2016, Marrero et al., 2016 and Phillips et al., 2016 for details). In both cases, all the CRN model ages are calculated assuming no erosion, therefore all these models are minimum ages for that of the strath terraces.
The authors would like to apologise for any inconvenience caused.

Keywords: AMS; geomorphology

Permalink: https://www.hzdr.de/publications/Publ-31090
Publ.-Id: 31090


Effects of pillar size modulation on the magneto-structural coupling in self-assembled BiFeO3–CoFe2O4 heteroepitaxy

Amrillah, T.; Chen, Y.-X.; Ngoc Duong, M.; Abdussalam, W.; Mangasa Simanjuntak, F.; Chia-Hao, C.; Ying-Hao, C.; Jenh-Yih, J.

The magneto-structural coupling of BiFeO3 (BFO)–CoFe2O4 (CFO)/LaAlO3 (LAO) heteroepitaxy with various lateral sizes of CFO pillars embedded in a BFO matrix was investigated. A struc- tural phase transformation of the BFO matrix was observed when the pillar size of CFO was increased to exceed 200 nm. Such structural transformation led to modification of magneto-elastic coupling behavior and magnetic anisotropy in the BFO–CFO/LAO system. The flexibility of tuning the pillar size of CFO, and hence, the strain and interfacial effect on the multiferroic system have significant application implications in these functional oxide nanocomposites.

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Permalink: https://www.hzdr.de/publications/Publ-31089
Publ.-Id: 31089


Simulation of RF Noise Propagation to Relativistic Electron Beam Properties in a Linear Accelerator

Maalberg, A.; Kuntzsch, M.; Petlenkov, E.

The control system of the superconducting electron linear accelerator ELBE is planned to be upgraded by a beam-based feedback. As the design of the feedback algorithm enters its preliminary stage, the problem of analyzing the contribution of various disturbances to the development of the electron beam instabilities becomes highly relevant. In this paper we exploit the radio frequency (RF) phase and amplitude noise data measured at ELBE to create a behavioral model in Simulink. By modeling the interaction between a RF electromagnetic field and an electron bunch traversing a bunch compressor we analyze how the addition of RF noise impacts the electron beam properties, such as energy, duration and arrival time.

Keywords: Electron Linear Accelerator; Bunch Compression; RF Noise; Simulink Model

Permalink: https://www.hzdr.de/publications/Publ-31088
Publ.-Id: 31088


Revealing the Role of Epithelial Mechanics and Macrophage Clearance during Pulmonary Epithelial Injury Recovery in the Presence of Carbon Nanotubes

Septiadi, D.; Abdussalam, W.; Rodriguez-Lorenzo, L.; Spuch-Calvar, M.; Bourquin, J.; Petri-Fink, A.; Rothen-Rutishauser, B.

Wound healing assays are extensively used to study tissue repair mechanisms; they are typically performed by means of physical (i.e., mechanical, electrical, or optical) detachment of the cells in order to create an open space in which live cells can lodge. Herein, an advanced system based on extensive photobleaching-induced apoptosis; providing a powerful tool to understand the repair response of lung epithelial tissue, consisting of a small injury area where apoptotic cells are still intact, is developed. Notably, the importance of epithelial mechanics and the presence of macrophages during the repair can be understood. The findings reveal that individual epithelial cells are able to clear the apoptotic cells by applying a pushing force, whilst macrophages actively phagocytose the dead cells to create an empty space. It is further shown that this repair mechanism is hampered when carbon nanotubes (CNTs) are introduced: formation of aberrant (i.e., thickening) F-actins, maturation of focal adhesion, and increase in traction force leading to retardation in cell migration are observed. The results provide a mechanistic view of how CNTs can interfere with lung repair.

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Permalink: https://www.hzdr.de/publications/Publ-31087
Publ.-Id: 31087


Two-photon retinal theranostics by adaptive compact laser source

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

To avoid a devastating effect of eye vision impairment on the information flow from the eye to our brain, enormous effort is being put during the last decades into the development of more sensitive diagnostics and more efficient therapies of retinal tissue. While morphology can be impressively imaged by optical coherence tomography, molecular-associated pathology information can be provided almost exclusively by auto-fluorescence-based methods. Among the latter, the recently developed fluorescence lifetime imaging ophthalmoscopy (FLIO) has the potential to provide both structural information and interacting pictures at the same time. The requirements for FLIO laser sources are almost orthogonal to the laser sources used in phototherapy that is expected to follow up the FLIO diagnostics. To make theranostics more effective and cheaper, the complete system would need to couple at least the modalities of low-power high-repetition-rate FLIO and precision high-pulse energy-adjustable repetition rate phototherapy. In addition, the intermediate-power high repetition rate for two-photon excitation would also be desired to increase the depth resolution. In our work, compact fiber-laser based on high-speed gain-switched laser diode has been shown to achieve adaptable/independently tunable repetition rate and energy per pulse allowing coupled fluorescence lifetime diagnostics via two-photon excitation and phototherapy via laser-induced photodisruption on a local molecular environment in a complex ex vivo retinal tissue.

Keywords: adaptable fiber laser; retinal tissue; theranostics; multimodal imaging; fluorescence lifetime imaging

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Permalink: https://www.hzdr.de/publications/Publ-31086
Publ.-Id: 31086


Material assignment for proton range prediction in Monte Carlo patient simulations using stopping-power datasets

Fibiani-Permatasari, F.; Eulitz, J.; Richter, C.; Wohlfahrt, P.; Lühr, A.

Motivation and objective: For each institute, the selection and calibration of the most suitable approach to assign material properties for Monte Carlo (MC) patient simulation in proton therapy is a major challenge. Current conventional approaches based on computed tomography (CT) depend on CT acquisition and reconstruction settings. This study proposes a material assignment approach, referred to as MATA (MATerial Assignment), which is independent of CT scanner properties and, therefore, universally applicable by any institute. Materials and methods: The MATA approach assigns material properties to the physical quantity stopping-power ratio (SPR) using a set of 40 material compositions specified for human tissues and linearly determined mass density. The application of clinically available CT-number-to-SPR conversion avoids the need for any further calibration. The MATA approach was validated with homogeneous and heterogeneous SPR datasets by assessing the SPR accuracy after material assignment obtained either based on dose scoring or determination of water-equivalent thickness. Finally, MATA was applied on patient datasets to evaluate dose differences induced by different approaches for material assignment and SPR prediction. Results: The deviation between the SPR after material assignment and the input SPR was close to zero in homogeneous datasets and below 0.002 (0.2% relative to water) in heterogeneous datasets, which was within the systematic uncertainty in SPR estimation. The comparison of different material assignment approaches revealed relevant differences in dose distribution and SPR. The comparison between two SPR prediction approaches, a standard look-up table and direct SPR determination from dual-energy CT, resulted in patient-specific mean proton range shifts between 1.3 mm and 4.8 mm. Conclusion: MATA eliminates the need for institution-specific adaptations of the material assignment. It allows for using any SPR dataset and thus facilitates the implementation of more accurate SPR prediction approaches. Hence, MATA provides a universal solution for patient modeling in MC-based proton treatment planning.

Keywords: Monte Carlo simulation; TOPAS; stopping-power ratio; dual-energy CT; proton radiotherapy

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Permalink: https://www.hzdr.de/publications/Publ-31085
Publ.-Id: 31085


Thermal neutron radiography of a passive proton exchange membrane fuel cell for portable hydrogen energy systems

M. Chaparro, A.; Ferreira-Aparicio, P.; Folgado, M. A.; Hübscher, R.; Lange, C.; Weber, N.

A proton exchange membrane fuel cell (PEMFC) for portable applications is studied with thermal neutron radiography. The PEMFC operates under passive conditions, with air-breathing cathode and dead-end anode supplied with static ambient air and dry hydrogen, respectively. A columnar cathodic plate favors the mobility of water drops over the cathode surface and their elimination. Thermal neutron images show liquid water build-up during operation of the cell in vertical and horizontal position, i.e. aligned parallel and perpendicular to the gravity field, respectively. Polarization curves and impedance spectroscopy show orientation dependent cell response that can be related with the water profiles. In vertical position, the elimination of drops sliding over the cathode surface as well as natural convection favor lower water contents in the cathode and improve oxygen transport. The vertical cell can be operated for hours in ambient conditions, providing steady power densities above 100 mW cm-² . In horizontal position, natural forces are less effective for water removal leading to 17% decrease in peak power density. The horizontal position is especially adverse if the upper electrode is the cathode, because anode flooding causes cell failure after production of a small amount of water (5 mg cm-²).

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Permalink: https://www.hzdr.de/publications/Publ-31084
Publ.-Id: 31084


Element- and orbital-selective magnetic coherent rotation at the first-order phase transition of a hard uniaxial ferrimagnet

Yamamoto, S.; Gorbunov, D.; Akai, H.; Yasumura, H.; Kotani, Y.; Nakamura, T.; Kato, T.; Mushnikov, N. V.; Andreev, A. V.; Nojiri, H.; Wosnitza, J.

3d-4 f intermetalic compounds with heavy rare-earth elements show first-order phase transitions in high magnetic fields due to the competition between the exchange interaction and the magnetocrystalline anisotropy. However, the microscopic picture of the field-induced noncollinear magnetic structures remains elusive. Here we report the direct experimental observation of the coherent stepwise rotation of the 3d and 4 f magnetic moments of the uniaxial hard ferrimagnet TmFe5Al7 by using soft x-ray magnetic circular dichroism in pulsed magnetic fields up to 25 T. The element- and shell-selective moments show a transition from the collinear ferrimagnet toward the forced ferromagnetic state via a canted phase, which is explained by a two-sublattice model.

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Permalink: https://www.hzdr.de/publications/Publ-31083
Publ.-Id: 31083


Advanced characterization of multicaloric materials in pulsed magnetic fields

Gottschall, T.; Bykov, E.; Gràcia-Condal, A.; Beckmann, B.; Taubel, A.; Pfeuffer, L.; Gutfleisch, O.; Manosa, L.; Planes, A.; Scurschii, I.; Wosnitza, J.

The multicaloric effect is described by a temperature or entropy change of a material triggered by external stimuli applied or removed simultaneously or sequentially. The prerequisite for this is a material exhibiting multiple ferroic states. However, direct measurements of the effect are rarely reported. Now, for this reason, we built a measurement device allowing to determine the adiabatic temperature change in pulsed magnetic fields and, simultaneously, under the influence of a uniaxial load. We selected the all-d-metal Heusler alloy Ni–Mn–Ti–Co for our first test because of its enhanced mechanical properties and enormous magneto- and elastocaloric effects. Ni–Mn–Ti–Co was exposed to pulsed magnetic fields up to 10 T and uniaxial stresses up to 80 MPa, and the corresponding adiabatic temperature changes were measured. With our new experimental tool, we are able to better understand multicaloric materials and determine their cross-coupling responses to different stimuli.

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Permalink: https://www.hzdr.de/publications/Publ-31082
Publ.-Id: 31082


Unexpected magnetic phase in the weakly ordered spin-1/2 chain cuprate Sr2CuO3

Sergeicheva, E. G.; Sosin, S. S.; Gorbunov, D.; Zherlitsyn, S.; Gu, G. D.; Zaliznyak, I. A.

The magnetic phase diagram of a spin- 1/2 chain antiferromagnet Sr2CuO3 is studied by an ultrasound phase-sensitive detection technique. The system is in the extreme proximity of the Luttinger-liquid quantum-critical point and we observe an unusually strong effect of magnetic field, which is very weak compared to the in-chain interaction, on the Néel ordering temperature. Inside the ordered phase, we detect an unexpected, field-induced continuous phase transition. The transition is accompanied by softening of magnetic excitation observed by electron-spin resonance, which in previous work [E. G. Sergeicheva et al., Phys. Rev. B 95, 020411(R) (2017)] was associated with a longitudinal (amplitude) mode of the order parameter. These results suggest a transition from a transverse collinear antiferromagnet to an amplitude-modulated spin-density-wave phase in a very weak magnetic field, which is unexpected for a system of weakly coupled Heisenberg spin- 1/2 chains.

Permalink: https://www.hzdr.de/publications/Publ-31081
Publ.-Id: 31081


Effect of curvature on the eigenstates of magnetic skyrmions

Korniienko, A.; Kakay, A.; Sheka, D. D.; Kravchuk, V. P.

Spectrum of spin eigenmodes localized on a ferromagnetic skyrmion pinned by a geometrical defect (bump) of magnetic films is studied theoretically. By means of direct numerical solution of the corresponding eigenvalue problem and finite element micromagnetic simulations we demonstrate, that the curvature can induce localized modes with higher azimuthal and radial quantum numbers, which are absent for planar skyrmions (for the same parameters). The eigenfrequencies of all modes, except the breathing and gyromodes decreases with increasing curvature. Due to the translational symmetry break, the zero translational mode of the skyrmion gains a finite frequency and forms the gyromode, which describes the uniform rotation of skyrmions around the equilibrium position. In order to treat the gyromotion analytically we developed a Thiele-like collective variable approach. We show that Neel skyrmions in curvilinear films experience a driving force originating from the gradient of the mean curvature. The gyrofrequency of the pinned skyrmion is proportional to the second derivative of the mean curvature at the point of equilibrium.

Keywords: skyrmions; curvature; eigenmodes; Thiele equation

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Permalink: https://www.hzdr.de/publications/Publ-31080
Publ.-Id: 31080


Multidimensional characterization of separation processes – Part 2: Comparability of separation efficiency

Buchmann, M.; Schach, E.; Leißner, T.; Kern, M.; Mütze, T.; Rudolph, M.; Peuker, U.; Tolosana Delgado, R.

Following the proposal of deriving statistical entropy maps from multidimensional separation curves, an extension is proposed to allow to compare the separation efficiency of various separation processes. This is achieved by integrating the entropy map weighted by the mass distribution of the particles in the feed. This proposal has several advantages: its straightforward extension to multidimensional partition curves, its scalar value (which allows for a natural ranking of processes), its flexibility to adapt to each and every feed, and its non-parametric character. A typical dynamic air classification process of an iron ore is presented as an example.

Keywords: Multidimensional partition curves; Weighted entropy; Particle tracking; Kernel density estimates; Mineral processing

Permalink: https://www.hzdr.de/publications/Publ-31079
Publ.-Id: 31079


Generating a tide-like flow in a cylindrical vessel by electromagnetic forcing

Jüstel, P.; Röhrborn, S.; Frick, P.; Galindo, V.; Gundrum, T.; Schindler, F.; Stefani, F.; Stepanov, R.; Vogt, T.

We show and compare numerical and experimental results on the electromagnetic generation of a tide-like flow structure in a cylindrical vessel which is filled with the eutectic liquid metal alloy GaInSn. Fields of various strengths and frequencies are applied to drive liquid metal flows. The impact of the field variations on amplitude and structure of the flows are investigated. The results represent the basis for a future Rayleigh-Bénard experiment, in which a modulated tide-like flow perturbation is expected to synchronize the typical sloshing mode of the large-scale circulation. A similar entrainment mechanism for the helicity in the Sun may be responsible for the synchronization of the solar dynamo with the alignment cycle of the tidally dominant planets Venus, Earth and Jupiter.

Keywords: electromagnetic forcing; impinging jets; magnetohydrodynamics; helicity synchronization

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Permalink: https://www.hzdr.de/publications/Publ-31078
Publ.-Id: 31078


Magnetic Effects on Microstructure and Solute Plume Dynamics of Directionally Solidifying Ga-In Alloy

Kao, A.; Shevchenko, N.; He, S.; Lee, P. D.; Eckert, S.; Pericleous, K.

The effects of applying a 0.2 T transverse magnetic field to a solidifying Ga-25%wt.In alloy were investigated through a joint experimental and numerical study. The magnetic field introduced significant changes to both the microstructure and the dynamics of escaping high concentration Ga plumes. Plume migration across the interface was quantified and correlated to simulations to demonstrate that Thermoelectric Magnetohydrodynamics (TEMHD) is the underlying mechanism. TEMHD introduced macro segregation within the dendritic structure leading to the formation of a stable ‘chimney’ channel by increasing solutal buoyancy in the flow direction. The resulting pressure difference across the solidification front, introduced a secondary hydrodynamic phenomenon that subsequently causes solute plume migration.

Keywords: Microstructure; Solidification; Magnetic Field; Freckle Defects; X-ray imaging; In situ observations

  • Open Access Logo JOM: The Journal of the Minerals, Metals & Materials Society 72(2020), 3645-3651
    Online First (2020) DOI: 10.1007/s11837-020-04305-2

Permalink: https://www.hzdr.de/publications/Publ-31077
Publ.-Id: 31077


Silicon Surface Passivation by ALD-Ga₂O₃: Thermal vs. Plasma-Enhanced Atomic Layer Deposition

Hiller, D.; Julin, J. A.; Chnani, A.; Strehle, S.

Silicon surface passivation by gallium oxide (Ga2O3) thin films deposited by thermal- and plasma-enhanced atomic layer deposition (ALD) over a broad temperature range from 75 °C to 350 °C is investigated. In addition, the role of oxidant (O3 or O-plasma) pulse lengths insufficient for saturated ALD-growth is studied. The material properties are analyzed including the quantification of the incorporated hydrogen. We find that oxidant dose pulses insufficient for saturation provide for both ALD methods generally better surface passivation. Furthermore, different Si surface pretreatments are compared (HF-last, chemically grown oxide, and thermal tunnel oxide). In contrast to previous reports, the annealing time to activate the surface passivation is found to be significantly shorter. The best surface saturation current densities (JOs) or surface recombination velocities (Seff) are 6 and 9 fA/cm² or 0.6 and 1.5 cm/s for n- and p-type Si, respectively. We correlate the surface passivation with the negative fixed charge density (Qfix; field-effect passivation) and the interface defect density (Dit; chemical passivation). It turns out that a high Qfix is present, irrespective of the utilized ALD-method, deposition temperature, or postannealing, whereas low Dit is only achieved fo rplasma-enhanced ALD at low temperatures. A critical H-density of∼10¹⁶ cm−2 is identified as a necessary but not sufficient condition for excellent surface passivation. Finally, contact resistivities are measured to investigate the possibility of using ALD-Ga2O3 as passivating contact material. In order to understand the current-voltage measurements, the energetic positions of the band edges and the Fermi level are determined by ultraviolet photoelectron spectroscopy and Kelvin probe.

Keywords: Atomic layer deposition (ALD); gallium oxide(Ga2O3); hydrogen; silicon surface passivation

Permalink: https://www.hzdr.de/publications/Publ-31076
Publ.-Id: 31076


The integration of structural mechanics into microstructure solidification modelling

Soar, P.; Kao, A.; Djambazov, G.; Shevchenko, N.; Eckert, S.; Pericleous, K.

In situ structural mechanics are an often neglected area when modelling alloy microstructure during solidification, despite the existence of practical examples and studies which seem to indicate that the interaction between thermal or mechanical stresses and microstructure can have a significant impact on its evolution and hence the final properties at a macroscopic level. A bespoke structural mechanics solver using the finite volume method has been developed to solve the linear elasticity equations, with design choices being made to facilitate the coupling of this solver to run in situ with an existing solidification model. The accuracy of the structural mechanics solver is verified against an analytic solution and initial results from a fully coupled system are presented which demonstrate in a fundamental example that the interaction between structural mechanics and a solidifying dendrite can lead to a significant change in growth behaviour.

Keywords: Structural Mechanics; Microstrcture Solidification; Multi-Physics

  • Lecture (Conference) (Online presentation)
    MCWASP XV: Modelling of Casting, Welding and Advanced Solidification Processes, 22.-23.06.2020, Jönköping, Sweden
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 861(2020)1, 012054
    DOI: 10.1088/1757-899X/861/1/012054

Permalink: https://www.hzdr.de/publications/Publ-31075
Publ.-Id: 31075


Controlling Freckle Defect Formation with Magnetic Fields During Directional Solidification of GaIn Alloy

Kao, A.; Krastins, I.; Shevchenko, N.; Eckert, S.; Pericleous, K.

Segregation of alloying components during solidification leads to stable solute channels, that solidify into defects called freckles. Freckles are caused by buoyancy driving lighter liquid elements, forming a macroscale channel that is fed by inter-dendritic flow. When fully solidified this channel represents a discontinuity in material properties and can lead to the failure of components. The application of a magnetic field, B, adds two physical phenomena to the process: the first is Electromagnetic Damping (EMD) of the liquid metal motion, the second is interstitial flow due to Thermoelectric (TE) Magnetohydrodynamics (MHD). TE effects translate temperature variations at the junction of two conductive materials into electric current, in this case between the solid and liquid.
The current, j¸ interacts with the magnetic field producing a Lorentz force F=j×B. Both the orientation and magnitude of the magnetic field determine the direction and strength of EMD and TEMHD effects.
Consider directional solidification of a solutal unstable buoyant alloy, namely Ga-25wt. %In. Both high velocity plumes of solute and the TE currents will be predominantly aligned to the thermal gradient (∇T), while the feeding inter-dendritic flow is primarily perpendicular to ∇T. A magnetic field orientated perpendicular to ∇T introduces EMD effects on the channel and also interacts with TE currents driving TEMHD flow. To capture these phenomena a parallel Cellular Automata Lattice Boltzmann Method that solves for microstructure solidification, fluid dynamics and electromagnetism using 100s millions of computational cells is used to simulate the freckle formation process at the sample scale. The results indicate that the channel formation can be significantly altered, showing the magnetic field as a potential technique for defect mitigation.

Keywords: Microstructure Solidification; Magnetic Field; Freckle Defects

  • Poster (Online presentation)
    MCWASP XV: Modelling of Casting, Welding and Advanced Solidification Processes, 22.-23.06.2020, Jönköping, Sweden

Permalink: https://www.hzdr.de/publications/Publ-31074
Publ.-Id: 31074


Volt-per-Ångstrom terahertz fields from X-ray free-electron lasers

Tanikawa, T.; Karabekyan, S.; Kovalev, S.; Casalbuoni, S.; Askegar, V.; Bonetti, S.; Wall, S.; Laarmann, T.; Turchinovich, D.; Zalden, P.; Kampfrath, T.; Fisher, A. S.; Stojanovic, N.; Gensch, M.; Geloni, G.

The electron linear accelerators driving modern X-ray free-electron lasers can emit intense, tunable, quasi-monochromatic terahertz (THz) transients with peak electric fields of V Å−1 and peak magnetic fields in excess of 10 T when a purpose-built, compact, superconducting THz undulator is implemented. New research avenues such as X-ray movies of THz-driven mode-selective chemistry come into reach by making dual use of the ultra-short GeV electron bunches, possible by a rather minor extension of the infrastructure.

Keywords: superradiant emission; terahertz control; terahertz radiation; ultrafast phenomena; X-ray free-electron laser

Permalink: https://www.hzdr.de/publications/Publ-31073
Publ.-Id: 31073


In situ observation of directional solidification in Ga-In alloy under a transverse DC magnetic field

He, S.; Shevchenko, N.; Eckert, S.

The directional solidification of a Ga-25wt.%In alloy under the effect of a transverse DC magnetic field is investigated by X-ray radiography. The magnetic field pointing parallel to the X-ray beam is generated by two ring-shaped permanent magnets. The magnetic field reaches values up to ~0.19 T in the field of view. The dendritic growth and the flow patterns of Ga-rich plumes migrating along the solidification front are captured and analyzed. It shows that the local fluctuations of solute concentration are partially damped by the magnetic field. At the temperature gradient of 1 K/mm, the growth velocities of solidification front and plumes are not affected. In the case of higher temperature gradient (~2 K/mm), the magnetic field causes an increase of the plume velocity in the horizontal direction and a decrease in the vertical direction while the velocity of the solidification front remains constant. Additionally, it is found that the magnetic field damps the fluctuations of tip velocity and refines the primary arm spacing. Above phenomena are discussed based on the thermoelectric magnetic and electromagnetic braking effects. The in situ experimental data are important for verification and improvement of the existing numerical simulations of solidification under the magnetic field.

Keywords: X-ray radiography; directional solidification; transverse magnetic field; dendritic growth; Ga-rich plumes

  • Poster (Online presentation)
    MCWASP XV: Modelling of Casting, Welding and Advanced Solidification Processes, 22.-23.06.2020, Jönköping, Sweden
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 861(2020)1, 012025
    DOI: 10.1088/1757-899X/861/1/012025

Permalink: https://www.hzdr.de/publications/Publ-31072
Publ.-Id: 31072


Evolution of dendritic morphology in a solidifying Ga-In alloy studied by in-situ synchrotron radiography

Shevchenko, N.; Neumann-Heyme, H.; Grenzer, J.; Keplinger, O.; Rack, A.; Eckert, K.; Eckert, S.

The local dynamics of dendritic tips and side arms during the growth and coarsening stages are studied by X-ray synchrotron radiography and by numerical simulation. The direct investigation of dendritic side arm evolution appears to be rather complex and impose high requirements with respect to the spatial and temporal resolution and sensitivity of the detector. The synchrotron imaging experiments were performed at the ID19 beamline (ESRF, France) at a spatial resolution of < 1 µm. A flat sample of a Ga-In alloy is solidified from top to down applying a vertical temperature gradient. The present measurements provide real-time in-situ data on three phenomena that are of major importance in dendrite morphology evolution: side arm coarsening, side arm-splitting and dendrite tip evolution. The combination of numerical modeling and synchrotron experiments has allowed to improve the understanding of coarsening of dendritic side arms and to obtain material information that is relevant for quantitative modeling. Another interesting effect can be observed during in situ solidification experiments: a transition from a four-fold symmetry to a hyperbranched dendritic morphology. This morphological transition originating from the splitting of dendrite side arms has been detected.

Keywords: X-ray radiography; synchrotron experiments; side arms; dendrite tip; coarsening

  • Poster (Online presentation)
    MCWASP XV: Modelling of Casting, Welding and Advanced Solidification Processes, 22.-23.06.2020, Jönköping, Sweden

Permalink: https://www.hzdr.de/publications/Publ-31071
Publ.-Id: 31071


Para-ferroelectric phase transition driven by swift heavy-ion irradiation in KTN crystal

He, S.; Yang, Q.; Li, X.; Liu, H.; Cao, L.; Akhmadaliev, S.; Wang, X.; Ren, Y.; Zhou, S.; Wu, P.

We report a novel approach of using swift O5+ ion irradiation to implement para-ferroelectric phase transition in a relaxor ferroelectric KTa0.62Nb0.38O3 (KTN) single crystal. With 15-MeV swift O5+ ion irradiation, a well-defined two-layer structure has been formed in the KTN sample due to the interaction between the O ions and KTN via electronic stopping and the nuclear stopping, respectively. The microstructures in these two layers are characterized by using a micro-Raman (μ-Raman) spectral technique. The significant changes of both spectral intensities and locations in three characteristic Raman peaks suggest that the top layer of the KTN sample due to electronic stopping exists a single-domain-ferroelectric state with a uniform and enhanced polarization orientation along [0 0 1]c direction. More importantly, we observe the irradiated region can effectively confine the light propagation in the ferroelectric layer, which can be further controlled by external fields. The results are promising for designing new integrated photonic devices.

Keywords: Phase transition; Swift heavy ion irradiation; Relaxor ferroeletrics

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Permalink: https://www.hzdr.de/publications/Publ-31070
Publ.-Id: 31070


Unravelling the Pleistocene glacial history of the Pamir Mountains, Central Asia

Stübner, K.; Bookhagen, B.; Merchel, S.; Lachner, J.; Gadoev, M.

Several hundred thousand year old moraines preserved in the semi-arid environment of High Mountain Asia attest to Middle Pleistocene glaciations, but the regional correlation of glacial stages and the spatial extent of the glacial advances remain poorly constrained.We examined glacial landforms and quaternary sediments in the Bartang valley, northwestern Pamir, a region with no previous quantitative glacial chronology. Using cosmogenic ¹⁰Be exposure ages, we dated glacially polished bedrock, moraines, and mass wasting deposits. Our data show that the northwestern Pamir was heavily glaciated in the Middle Pleistocene (> 220 ky) with large valley glaciers occupying some of the major valleys in the western Pamir. During the penultimate glacial cycle (191-130 ky) these valleys may have been largely ice free. Catastrophic mega debris flows with volumes > 0.05 km3 occurred after the ice retreat and reflect paraglacial destabilization of glacial sediments. The age of the best-dated mega debris flow (81 ± 4 ky) is similar to moraine ages ~70-80 ky documented throughout the Pamir, demonstrating that remobilized sediments may provide valuable age constraints on glacial histories. In order to facilitate regional comparison of glacial chronologies, we developed a Gaussian separation algorithm, which determines a moraine age from a distribution of boulder exposure ages based on the assumption that postdepositional processes prevail over inheritance, and that the oldest boulder ages best represent the timing of moraine formation. We compiled moraine boulder exposure ages from the Pamir and adjacent regions and provide a summary of Middle and early Late Pleistocene glacial cycles of western High-Mountain Asia.

Keywords: AMS; Pamir; glacial history

Permalink: https://www.hzdr.de/publications/Publ-31069
Publ.-Id: 31069


Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Ajayakumar, M.; Fu, Y.; Liu, F.; Komber, H.; Tkachova, V.; Xu, C.; Zhou, S.; Popov, A.; Liu, J.; Feng, X.

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

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Permalink: https://www.hzdr.de/publications/Publ-31068
Publ.-Id: 31068


Separation of aluminium and iron from lanthanum - a comparative study of solvent extraction and hydrolysis-precipitation

Balinski, A.; Kelly, N.; Helbig, T.; Meskers, C. E. M.; Reuter, M.

This study investigates the removal of aluminium and iron from REE containing solutions by solvent extraction with saponified naphthenic acid and by hydrolysis-precipitation. The results emphasize both, the preferential application as well as limitations of every method. We find that emulsification occurring during solvent extraction of aluminium is caused by its slow extraction rate in comparison to the neutralization reaction and by the proximity of the pH value required for aluminium extraction and the pH value at which hydrolysis of aluminium occurs. However, by choosing long shaking time of at least 4 h the emulsion recedes. The formation of emulsion can be avoided by strict control of pH value during the extraction. Moreover, the loading capacity of the organic phase with aluminium is limited due to the strong increase in viscosity of the organic phase with increasing aluminium concentration and due to the gel formation. Regarding the extraction of iron, the amount of extracted ions is limited due to the overlap of the pH range required for the extraction with pH range in which sparingly soluble iron oxides/hydroxides are formed. In summary, aluminium and iron can be simultaneously removed from REE containing solution by solvent extraction with saponified naphthenic acid in one extraction stage only from diluted solutions. However, in comparison to the hydrolysis-precipitation method a higher purity of the solution is achieved. A complete removal of aluminium and iron from concentrated solutions can be achieved in two stages. First, the content of aluminium and iron should be reduced by hydrolysis-precipitation. After that, a high-purity solution can be obtained by subsequent solvent extraction by saponified naphthenic acid.

Keywords: rare earth elements; aluminium; iron; impurity removal; solvent extraction; naphthenic acid; saponification; hydrolysis-precipitation

Permalink: https://www.hzdr.de/publications/Publ-31067
Publ.-Id: 31067


openTIV

Ziegenhein, T.; Heßenkemper, H.; Lucas, D.

openTIV is a computer vision library mainly developed to evaluate pictures taken from multiphase flows. Specifically, the application of identifying phase interfaces and tracking particles (PTV and PIV) was intended by the authors. Besides that, post-processing libraries to calculate, for example, the standard dimensionless numbers (Reynolds, Morton, Eoetvoes (Bond), etc.) and void fraction profiles are provided as well. All libraries are based on the standard mathematical and physical library, which consists of essential solvers and mathematical structures, inside the package. The library includes the tools to help develop new methods for evaluating images from multiphase flows. It is not intended to provide a complete package of image processing methods, as can be found in the OpenCV package (which can be used with the openTIV libraries).

Keywords: Computer Vision; Multiphase Flow; PIV; PTV; Boundary Tracking; Image Processing

Permalink: https://www.hzdr.de/publications/Publ-31066
Publ.-Id: 31066


Structural Evolution of Ag-LEV Zeolite upon Heating: an in situ Single-Crystal X-ray Diffraction (SC-XRD) and X-ray Absorption Spectroscopy (XAS) Study

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

Ag-modified zeolites are of great interest because of their improved catalytic, photocatalytic, sorption, and antibacterial properties []. To properly tune these properties, a deeper understanding of several structural factors is necessary. In particular, the following aspects have been proved to play a key role[]: i) the position of silver atoms with respect to the tetrahedral framework, ii) the possible formation of Ag-clusters within the zeolitic pores, and iii) the structural changes occurring upon dehydration, since most of these materials are employed after thermal treatment.

Keywords: zeolite; silver; XAFS; XRD; atomistic simulations; DFT

Permalink: https://www.hzdr.de/publications/Publ-31065
Publ.-Id: 31065


Stereotactic ablative body radiotherapy (SABR) combined with Immunotherapy (L19-IL2) in stage IV NSCLC patients, ImmunoSABR: a multicentre, randomised controlled open-label phase II trial

Lieverse, R.; Van, L. E.; Oberije, C.; Troost, E. G. C.; Hadrup, S.; Dingemans, A.; Hendriks, L.; Eckert, F.; Hiley, C.; Dooms, C.; Lievens, Y.; De, J. M.; Hendriks, L.; Bussink, J.; Geets, X.; Valentini, V.; Elia, G.; Nerio, D.; Billiet, C.; Abdollahi, A.; Pasquier, D.; Boisselier, P.; Yaromina, A.; De, R. D.; Dubois, L.; Lambin, P.

About 50% of non-small cell lung cancer (NSCLC) patients have metastatic disease at initial diagnosis, which limits their treatment options and, consequently, the 5-year survival rate (15%). Immune checkpoint inhibitors (ICI), either alone or in combination with chemotherapy, have become standard of care (SOC) for most good performance status patients. However, most patients will not obtain long-term benefit, and new treatment strategies are therefore still needed. We previously demonstrated clinical safety of the tumour-selective immunocytokine L19-IL2, consisting of the anti-EDB scFv L19 antibody coupled to IL2, combined with stereotactic ablative radiotherapy (SABR). Within this phase II ImmunoSABR trial, the combination of SABR with or without ICI and the immunocytokine L19-IL2 will be tested as 1st, 2nd or 3rd line treatment in stage IV NSCLC patients. This bi-modal and triple treatment approach is based on the direct cytotoxic effect of radiotherapy, the tumour selective immunocytokine L19-IL2, the abscopal effect observed distant from the irradiated metastatic site(s), and the memory effect.
This investigator initiated, multicentric, randomised controlled open-label phase II clinical trial (NCT03705403) will test the hypothesis that the combination of SABR and L19-IL2 increases the progression free survival (PFS) in patients with limited metastatic NSCLC. Patients will be stratified according to their metastatic load (oligo-metastatic: up to 5, or poly-metastatic: 6 to 10 metastases). Patients will be randomised by minimisation to the experimental (E-arm) or the control arm (C-arm). The C-arm will receive SOC, according to the local protocol. E-arm oligo-metastatic patients will receive SABR to all lesions followed by L19-IL2 therapy; radiotherapy for poly-metastatic patients consists of irradiation of at least one (symptomatic) to a maximum of 5 lesions (including ICI in both arms if this is the SOC). ImmunoSABR consists of 14 participating centres located in 6 countries. The accrual period will be 2.5 years, starting after the first centre is initiated and active. Primary endpoint is PFS at 1.5 years based on blinded radiological review, and secondary endpoints are overall survival, toxicity, quality of life and abscopal response. Associative biomarker studies, blood and tumour cell immune monitoring, CT-based radiomics, stool collection, iRECIST, and tumour growth rate will be performed. The first results are expected end 2023.

Keywords: Immunotherapy; L19-IL2; anti-PDL1; anti-PD1; radiotherapy; SABR; phase 2; NSCLC; stage IV; multicentre

  • Open Access Logo BMC Cancer 20(2020), 557

Permalink: https://www.hzdr.de/publications/Publ-31064
Publ.-Id: 31064


National societies' needs as assessed by the ESTRO National Society Committee survey: a European perspective

Garibaldi, C.; Jornet, N.; Tan, L.; Bojen, A.; Franco, P.; Bussink, J.; Troost, E. G. C.; Bak, B.; Bibault, J.; Dzhugashvili, M.; Van, D. B. L.; Fizaine, L.; Leci, A.; Ricardi, U.; Jereczek-Fossa, B.

Purpose: to determine how ESTRO can collaborate with Radiation Oncology National Societies (NS) according to its mission and values, and to define the new roadmap to strengthen the NS network role in the forthcoming years.

Materials and methods: the ESTRO NS committee launched a survey addressed to all European National Societies, available online from June 5th to October 30th 2018. Questions were divided into three main sections: 1. general information about NS; 2. relevant activities (to understand the landscape of each NS context of action); 3. relevant needs (to understand how ESTRO can support the NS). Eighty-nine European NS were invited to participate. Respondents were asked to rank ESTRO milestones in order of importance, indicating the level of priority to their society.

Results: a total of 64 out of 89 NS (72%) from 32 European countries completed the questionnaire. The majority of NS ranked “Optimal patient care to cure cancer and to reduce treatment-related toxicity” as the highest level of priority. This aligns well with the ESTRO vision 2030 “Optimal health for all together.” NS also indicated a high need for more consensus guidelines and exchange of best practices, access to high quality accredited education, implementation of the ESTRO School Core Curriculum at the national level, and defining quality indicators and standard in Radiation Oncology, improved communication and increased channelling of information.

Conclusion: The results of this survey will be used to strengthen the relations between ESTRO and European NS to promote and develop initiatives to improve cancer care.

Permalink: https://www.hzdr.de/publications/Publ-31063
Publ.-Id: 31063


Molecular imaging of monocarboxylate transporters with PET – development and biological evaluation of novel 2-fluoropyridinyl analogs of FACH

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

Introduction
Monocarboxylate transporters 1-4 (MCT1-4) are involved in several metabolism-related diseases, especially cancer, providing the chance to be considered as relevant targets for diagnosis and therapy. Recently, we reported on [18F]FACH as a novel MCT-targeting imaging agent (1), whose limited blood-brain barrier permeability, however, excludes application in brain diseases. Accordingly, we aimed to develop a more lipophilic FACH-derived radiotracer possessing higher brain uptake.
Materials and Methods
Two 2-fluoropyridinyl-substituted analogs of FACH (1 and 2) were obtained by Buchwald-Hartwig cross coupling reaction.
The potency of 1 and 2 to inhibit MCT1 was measured by [14C]lactate uptake assay using rat brain endothelial-4 cells. Radiolabeling of [18F]1 was proceeded using 1 mg nitro precursor and [18F]fluoride in the presence of Kryptofix and K2CO3 in dimethyl sulfoxide at 130 °C within 15 min. The logD7.4 value of [18F]1 was experimentally determined in the n-octanol-PBS system. For biological evaluation of [18F]1, in vitro autoradiography on cryosections of mouse kidney and small animal PET-MRI studies in female CD-1 mice were performed. Target specificity was proven by using the sodium salt of the MCT inhibitor α-cyano-4-hydroxycinnamic acid (α-CCA-Na).

Results
The analogs 1 and 2 inhibited MCT1 with IC50 values of 118 and 274 nM, respectively. [18F]1 was obtained by radiofluorination of the nitro precursor via nucleophilic aromatic substitution reaction with radiochemical yields of 73 ± 12% (n = 4, non-isolated, radio-HPLC), a high radiochemical purity of ˃ 98% and molar activities in the range of 180-200 GBq/µmol (n = 3, end of synthesis) using starting activities of 2-3 GBq. The logD7.4 value of 0.82 achieved for [18F]1 indicated 2-fold higher lipophilicity in comparison to [18F]FACH (2). In vivo and in vitro studies revealed high uptake of the new radiotracer in kidney and other peripheral MCT-expressing organs together with significant reduction by using α-CCA-Na (10 µM). The brain uptake of [18F]1 was similar to [18F]FACH without significant washout and an almost unchanged SUV of 0.15 between 15 and 60 min p.i.
Conclusion
Despite a higher lipophilicity of [18F]1 compared to [18F]FACH, the brain uptake of [18F]1 was in a similar low range, revealing the need for further structural modification. However, a high and specific uptake of the new radiotracer in the kidneys suggests suitability of [18F]1 for investigations on the expression of MCT in vivo.
References
(1) Sadeghzadeh M, et al. J Label Compd Radiopharm.2019; 62: 411-424.
(2) Sadeghzadeh M, et al. Sci Rep. 2019; 9: 18890-18897.

  • Contribution to proceedings
    33rd Annual Congress of the European Association of Nuclear Medicine (EANM-2020), 17.-21.10.2020, Vienna, Austria
    European Journal of Nuclear Medicine and Molecular Imaging 47(2020), S11-S12

Permalink: https://www.hzdr.de/publications/Publ-31062
Publ.-Id: 31062


OpenFOAM activities at HZDR

Schlegel, F.

Introcution into the OpenFOAM activties at HZDR

  • Lecture (Conference)
    German CFD Network of Competence, 10.-11.03.2020, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31061
Publ.-Id: 31061


Identification of Dy³⁺ /Dy²⁺ as electron trap in persistent phosphors

Joos, J. J.; Korthout, K.; Amidani, L.; Glatzel, P.; Poelman, D.; Smet, P. F.

A long-standing issue in persistent luminescence is settled by providing direct evidence that Dy³⁺ is the main electron trap in Sr₄Al₁₄O₂₅:Eu,Dy by combining laser excitation with X-ray spectroscopy. A reversible electron transfer is demonstrated, controlled by light and showing the same kinetics as the persistent luminescence. Exposure to violet light induces charging by oxidation of the excited Eu²⁺ while Dy³⁺ is simultaneously reduced. Oppositely, detrapping of Dy²⁺ occurs at ambient temperature or by infrared illumination, yielding afterglow or optically stimulated luminescence, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-31060
Publ.-Id: 31060


Visualization of Liquid Reaction in Submerged Top-blow Agitation Process

Zhang, X.; Wu, J.; Zhang, H.; Ding, W.; Zhang, J.

The liquid reaction in a submerged top-blow agitation process was studied using planar laser-induced fluorescence (PLIF) technology based on the principle of fluorescence quenching. The liquid reaction effects were analyzed using the reaction degree θ(t) and reaction time t95 under different conditions. The results show that the liquid reaction time decreases obviously for an increase in the air flow rate and submerged depth of the spray gun. The injection position of Fe3+ has a great influence on the reaction process; the reaction process is also different under other blowing conditions when Fe3+ is injected at the bottom. The reaction time of Fe3+ at the bottom injection position is higher than that at the top injection position; increasing the air flow rate and submerged depth of the spray gun can effectively reduce the difference in the reaction times at the two injection points. The effect of the injection position on the reaction time is eliminated when the spray gun submerged depth is close to the reactor bottom. The initial volume of Fe3+ has no obvious effect on the reaction time; however, an increase in the initial molarity of Fe3+ can decrease the reaction time.

Keywords: Fluorescence quenching reaction; Liquid reaction process; Planar laser-induced fluorescence; Reaction degree; Submerged top blow

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Permalink: https://www.hzdr.de/publications/Publ-31059
Publ.-Id: 31059


Nonlocal stimulation of three-magnon splitting in a magnetic vortex

Körber, L.; Schultheiß, K.; Hula, T.; Verba, R.; Faßbender, J.; Kakay, A.; Schultheiß, H.

We present a combined numerical, theoretical and experimental study on stimulated three-magnon splitting in a magnetic disk in the vortex equilibrium state. Our micromagnetic simulations and Brillouin-light-scattering results confirm that three-magnon splitting can be triggered even below threshold by exciting one of the secondary modes by magnons propagating in a waveguide next to the disk. The experiments show that stimulation is possible over an extended range of excitation powers and a wide range of frequencies around the eigenfrequencies of the secondary modes. Rate-equation calculations predict an instantaneous response to stimulation and the possibility to prematurely trigger three-magnon splitting even above threshold in a sustainable manner. These predictions are confirmed experimentally using time-resolved Brillouin-light-scattering measurements and are in a good qualitative agreement with the theoretical results. We believe that the controllable mechanism of stimulated three-magnon splitting could provide a possibility to utilize magnon-based nonlinear networks as hardware for reservoir or neuromorphic computing.

Keywords: spin wave; nonlinear; three-magnon splitting; stimulation; micromagnetic simulation; BLS

Related publications

  • Open Access Logo Physical Review Letters 125(2020)20, 207203
    DOI: 10.1103/PhysRevLett.125.207203
  • Lecture (Conference) (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, online, online

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Permalink: https://www.hzdr.de/publications/Publ-31058
Publ.-Id: 31058


Metabolomics, machine learning and immunohistochemistry to predict succinate dehydrogenase mutational status in phaeochromocytomas and paragangliomas

Wallace, P. W.; Conrad, C.; Brückmann, S.; Pang, Y.; Caleiras, E.; Murakami, M.; Korpershoek, E.; Zhuang, Z.; Rapizzi, E.; Kroiss, M.; Gudziol, V.; Timmers, H. J. L. M.; Mannelli, M.; Pietzsch, J.; Beuschlein, F.; Pacak, K.; Robledo, M.; Klink, B.; Peitzsch, M.; Gill, A. J.; Tischler, A. S.; de Krijger, R. R.; Papathomas, T.; Aust, D.; Eisenhofer, G.; Richter, S.

Phaeochromocytomas and paragangliomas (PPGL) are rare neuroendocrine tumours with a hereditary background in over one third of patients. Mutations in succinate dehydrogenase (SDH) genes increase the risk for PPGLs and several other tumours. Mutations in subunit B (SDHB) in particular are a risk factor for metastatic disease, further highlighting the importance of identifying SDH mutations for patient management. Genetic variants of unknown significance, where implications for the patient and family members are unclear, are a problem for interpretation. For such cases, reliable methods for evaluating protein functionality are required. Immunohistochemistry for SDHB (SDHB-IHC) is the method of choice, but does not assess functionality at the enzymatic level. Liquid chromatography mass spectrometry-based measurements of metabolite precursors and products of enzymatic reactions provides an alternative method. Here, we compare SDHB-IHC with metabolite profiling in 189 tumours from 187 PPGL patients. Besides evaluating succinate:fumarate ratios (SFR), machine learning algorithms were developed to establish predictive models for interpreting metabolite data. Metabolite profiling showed higher diagnostic specificity compared to SDHB-IHC (99.2% vs 92.5%, p=0.021), whereas sensitivity was comparable. Application of machine learning algorithms to metabolite profiles improved predictive ability over that of the SFR, in particular for hard-to-interpret cases of head and neck paragangliomas (AUC 0.9821 vs. 0.9613, p=0.044). Importantly, the combination of metabolite profiling with SDHB-IHC has complementary utility, as SDHB-IHC correctly classified all but one of the false-negatives from metabolite profiling strategies while metabolite profiling correctly classified all but one of the false-negatives/positives from SDHB-IHC. From 186 tumours with confirmed status of SDHx variant pathogenicity, the combination of the two methods resulted in 185 correct predictions, highlighting the benefits of both strategies for patient management.

Keywords: mass spectrometry; succinate to fumarate ratio; multi-observer; Krebs cycle metabolites; linear discriminant analysis; LC-MS/MS; diagnostics; variants of unknown significance; metabolite profiling; prediction models

  • The Journal of Pathology 251(2020), 378-387
    Online First (2020) DOI: 10.1002/path.5472

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-31057
Publ.-Id: 31057


Deuteration versus ethylation – strategies to improve the metabolic fate of a 18F-labeled celecoxib derivative

Laube, M.; Gassner, C.; Neuber, C.; Wodtke, R.; Ullrich, M.; Haase-Kohn, C.; Löser, R.; Köckerling, M.; Kopka, K.; Knieß, T.; Hey-Hawkins, E.; Pietzsch, J.

The inducible isoenzyme cyclooxygenase-2 (COX-2) is closely associated with chemo-/radioresistance and poor prognosis of solid tumors. Therefore, COX-2 represents an attractive target for functional characterization of tumors by positron emission tomography (PET). In this study, the celecoxib derivative 3-([18F]fluoromethyl)-1-[4-(methylsulfonyl)phenyl]-5-(p-tolyl)-1H-pyrazole ([18F]5a) was chosen as a lead compound having a reported high COX-2 inhibitory potency and a potentially low carbonic anhydrase binding tendency. The respective deuterated analog [D2,18F]5a and the fluoroethyl-substituted derivative [18F]5b were selected to study the influence of these modifications with respect to COX inhibition potency in vitro and metabolic stability of the radiolabeled tracers in vivo. COX-2 inhibitory potency was found to be influenced by elongation of the side chain but, as expected, not by deuteration. An automated radiosynthesis comprising 18F-fluorination and purification under comparable conditions provided the radiotracers [18F]5a,b and [D2,18F]5a in good radiochemical yields (RCY) and high radiochemical purity (RCP). Biodistribution and PET studies comparing all three compounds revealed bone accumulation of 18F-activity to be lowest for the ethyl derivative [18F]5b. However, the deuterated analog [D2,18F]5a turned out to be the most stable compound of the three derivatives studied here. Time-dependent degradation of [18F]5a,b and [D2,18F]5a after incubation in murine liver microsomes was in accordance with the data on metabolism in vivo. Furthermore, metabolites were identified based on UPLC-MS/MS.

Keywords: Deuteration; fluorine-18; metabolism; murine liver microsomes; positron emission tomography; radiometabolite; radiotracer; selective COX-2 inhibitors (Coxibs); side chain elongation

Permalink: https://www.hzdr.de/publications/Publ-31056
Publ.-Id: 31056


Figure and data from 'Surface Modification of Silicon Nanowire Based Field Effect Transistors with Stimuli Responsive Polymer Brushes for Biosensing Applications'

Baraban, L.; Klinghammer, S.; Rauch, S.; Uhlmann, P.; Pregl, S.; Cuniberti, G.

Figure compilations with the access to the origin files of the graphs. Created by Stephanie Klinghammer and Larysa Baraban: fabrication of SiNQ, measurements)

Keywords: polymer brushes functionalization; iv curves

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-20
    DOI: 10.14278/rodare.339

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Permalink: https://www.hzdr.de/publications/Publ-31055
Publ.-Id: 31055


Tales from the Trenches: Developing sciview, a new 3D viewer for the ImageJ community

Günther, U.; Harrington, K. I. S.

ImageJ/Fiji is a widely-used tool in the biomedical community for performing everyday image analysis tasks. However, its 3D viewer component (aptly named 3D Viewer) has become dated and is no longer actively maintained. We set out to create an alternative tool that not only brings modern concepts and APIs from computer graphics to ImageJ, but is designed to be robust to long-term, open-source development. To achieve this we divided the visualization logic into two parts: the rendering framework, scenery, and the user-facing application, sciview. In this paper we describe the development process and design decisions made, putting an emphasis on sustainable development, community building, and software engineering best practises. We highlight the motivation for the Java Virtual Machine (JVM) as a target platform for visualisation applications. We conclude by discussing the remaining milestones and strategy for long-term sustainability.

Keywords: Software development techniques; rendering; graphics

Permalink: https://www.hzdr.de/publications/Publ-31054
Publ.-Id: 31054


Particle dataset for constructing mineral processing case studies

Pereira, L.; Frenzel, M.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gutzmer, J.

This file contains a train and a test datasets that can be used to construct fictional mineral processing studies, on a particle level, using known equations for different separation techniques. This data was collected with a mineral liberation analyzer at the Helmholtz Institute Freiberg for Resource Technology. The probabilities, and classes present together with the data are part of a publication in the journal of cleaner production. These could be simply removed in order to construct new cases.

Keywords: particle-tracking; geometallurgy; mineral processing modelling; flotation; automated mineralogy; resource efficiency

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-19
    DOI: 10.14278/rodare.335
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31053
Publ.-Id: 31053


Charged pion production in Au+Au collisions at sqrt(s_NN) = 2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Ciepal, I.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Glaessel, S.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Muentz, C.; Muenzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rathod, N.; Rosier, P.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Singh, U.; Smyrski, J.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Stroebele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wojcik, D.; Zanevsky, Y.; Zumbruch, P.

We present high-statistic data on charged pion emission from Au+Au collisions at sqrt(s_NN) = 2.4 GeV (corresponding to E_beam = 1.23 A GeV) in four centrality classes in the range 0 - 40% of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the world data, but undershoot by 2.5σ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations.

Permalink: https://www.hzdr.de/publications/Publ-31052
Publ.-Id: 31052


Nonlinear losses in magnon transport due to four-magnon scattering

Hula, T.; Schultheiß, K.; Buzdakov, A.; Körber, L.; Bejarano, M.; Flacke, L.; Liensberger, L.; Weiler, M.; Shaw, J. M.; Nembach, H. T.; Faßbender, J.; Schultheiß, H.

We report on the impact of nonlinear four-magnon scattering on magnon transport in microstructured waveguides with low magnetic damping. Using microfocused Brillouin light scattering, we analyze magnon propagation lengths in a broad range of excitation powers and observe a decrease of the attenuation length at high powers, which is consistent with the onset of nonlinear four-magnon scattering. Hence, when measuring magnon propagation lengths and deriving damping parameters from those results, one needs to be careful to stay in the linear regime. Otherwise, the intrinsic nonlinearity of magnetization dynamics may lead to a misinterpretation of magnon propagation lengths and, thus, to wrong values of the magnetic damping of the system.

Related publications

  • Open Access Logo Applied Physics Letters 117(2020)4, 042404
    Online First (2020) DOI: 10.1063/5.0015269

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Permalink: https://www.hzdr.de/publications/Publ-31050
Publ.-Id: 31050


Classification of the source of treatment deviation in proton therapy using prompt-gamma imaging information

Khamfongkhruea, C.; Berthold, J.; Janssens, G.; Petzoldt, J.; Smeets, J.; Pausch, G.; Richter, C.

Purpose: Prompt-gamma imaging (PGI) based range verification has been successfully implemented in clinical proton therapy recently and its sensitivity to detect treatment deviations is currently investigated. The cause of treatment deviations can be multiple - e.g. CT-based range prediction, patient setup, and anatomical changes. Hence, it would be beneficial, if PGI-based verification would not only detect a treatment deviation but would also be able to directly identify its most probable source. Here, we propose a heuristically derived decision tree approach to automatically classify the sources of range deviation in proton pencil-beam scanning (PBS) treatments of head and neck tumors based on range information obtained with a PGI slit camera.
Materials and Methods: The decision tree model was iteratively generated on a training dataset of different anatomical complexities, for an anthropomorphic head phantom and patient CT data (planning and control CTs) from 5 patients. Different range prediction errors, setup changes and relevant and non-relevant anatomical changes were introduced or derived from control CTs, summing up to a total of 98 training scenarios. Independent validation was performed for another 98 scenarios, derived solely from patient CT data of another 7 patients. PBS head and neck treatment plans were generated for the nominal scenario. For all PBS spots in the investigated field, PGI profiles were simulated using a dedicated analytical model of the slit camera for the nominal as well as the different error scenarios. From comparison of PGI profiles for nominal and error scenarios, a spot-wise range shift was determined for each error scenario. The heuristic approach includes a pre-filtering of the most suitable PBS spots for PGI treatment verification. From the validation, the accuracy, sensitivity and specificity of the model were determined.
Results: A five-step consecutive filter was developed to pre-select PBS spots. On average, 31% of spots (1044 spots) remained as input for the classification model. The derived heuristic decision tree model is based on five parameters: The coefficient of determination (R2), the slope and intercept of the linear regression between PGI-derived range shifts and the respectively predicted proton ranges for the investigated PBS spots, as well as the average and standard deviation of the PGI-derived shifts. With this approach, 94 of 98 error scenarios could be classified correctly in validation (accuracy of 96%). A sensitivity and specificity of 100% and 86% was reached.
Conclusions: In this simulation study it was demontrated that the source of a treatment deviation can be identified from simulated PGI information in head and neck tumor treatments with high sensitivity and specificity. The application, refinement and evaluation of the approach on measured PGI data will be the next step to show the clinical feasibility of PGI-based error source classification.

  • Open Access Logo Medical Physics 47(2020)10, 5102-5111
    Online First (2020) DOI: 10.1002/mp.14393

Permalink: https://www.hzdr.de/publications/Publ-31049
Publ.-Id: 31049


Antihypertensive use differentially associated with lower cerebral blood flow in older people with hypertension

van Dalen, J. W.; Mutsaerts, H. J.; Petr, J.; Caan, M. W.; Moll Van Charante, E. P.; Macintosh, B. J.; van Gool, W. A.; Nederveen, A. J.; Richard, E.

Consistent cerebral blood flow (CBF) is fundamental to brain function. Cerebral autoregulation ensures CBF stability. Chronic hypertension can lead to disrupted cerebral autoregulation in older people, potentially leading to blood pressure levels interfering with CBF. We investigated the associations of CBF with blood pressure and antihypertensive treatment, using arterial spin labelling MRI, in a prospective longitudinal cohort of 186 community-dwelling older individuals (77±3 years, 53% female) with hypertension, 125 (67%) of whom with 3-year follow-up. We assessed concurrent and longitudinal associations of diastolic blood pressure, systolic blood pressure, mean arterial pressure, pulse pressure, and antihypertensive drug use, with grey matter and white matter CBF (mL/100g/min), and the CBF spatial coefficient of variation (SCoV): a measure of CBF heterogeneity which may be more sensitive to cerebrovascular damage. We found no associations between blood pressure and concurrent CBF, nor between changes in blood pressure and CBF over 3-year follow-up. Antihypertensive use was associated with lower CBF and higher SCoV. Within antihypertensive types, calcium channel blockers and angiotensin receptor blockers were not associated with lower CBF. This aligns with previous evidence suggesting a protective effect of these antihypertensive classes on dementia, and may provide an important lead for future research.

Permalink: https://www.hzdr.de/publications/Publ-31048
Publ.-Id: 31048


A radiopharmacologist's and radiochemist's view on targeting the Eph/ephrin receptor tyrosine kinase system

Neuber, C.; Belter, B.; Mamat, C.; Pietzsch, J.

In the last decade, there have been extensive efforts to open up the Eph/ephrin subfamily of the receptor tyrosine kinase family for diagnostic and therapeutic applications. Besides classical pharmaceutical developments, which focus either on drugs targeting the extracellular ligand binding domains or the intracellular tyrosine kinase domains of these receptors, there also have been first radiopharmaceutical approaches. Here the focus is on the development of specific and selective probes for molecular imaging, particularly, by means of positron emission tomography, and the functional characterization of the Eph/ephrin subfamily in certain target tissues. The aim of this mini-review is to summarize the different approaches towards Eph-targeting radiotracers by using antibodies, peptides, and small molecules, and to discuss their radiopharmacological characterization. With regard to the small molecules, further considerations will focus on the design and synthesis of non-radioactive reference compounds and precursors as well as on radiolabeling strategies.

Keywords: Antibodies; cancer theranostics; extracellular ligand; fluorine-18; peptides; positron emission tomography; radiotracer; receptor tyrosine kinases; tyrosine kinase inhibitors; small molecule

Permalink: https://www.hzdr.de/publications/Publ-31047
Publ.-Id: 31047


Anisotropic exclusion effect between photocatalytic Ag/AgCl Janus particles and passive beads in a dense colloidal matrix

Huang, T.; Gobeil, S.; Wang, X.; Misko, V.; Nori, F.; de Malsche, W.; Faßbender, J.; Makarov, D.; Cuniberti, G.; Baraban, L.

Synthetic nano- and micromotors interact with each other and their surroundings in a complex manner. Here, we report on the anisotropy of active-passive particle interaction in a soft matter system containing an immobile yet photochemical Ag/AgCl-based Janus particle embedded in a dense matrix of passive beads in pure water. The asymmetry in the chemical gradient around the Janus particle, triggered upon visible light illumination, distorts the isotropy of the surrounding electric potential and results in the repulsion of adjacent passive beads to a certain distance away from the Janus particle. This exclusion effect is found to be anisotropic with larger distances to passive beads in front of the Ag/AgCl cap of the Janus particle. We provide insight into this phenomenon by performing the angular analysis of the radii of exclusion and tracking their time evolution at the level of a single bead. Our study provides a novel fundamental insight into the collective behavior of a complex mixture of active and passive particles and is relevant for various application scenarios, e.g., particle transport at micro- and nanoscale and local chemical sensing.

Keywords: photocatalytic reaction; micro and nanomotors; visible light; active Janus particles; spherical colloidal particles; exclusion phenomena

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-18
    DOI: 10.14278/rodare.329
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31046
Publ.-Id: 31046


Annual Report 2019 - Institute of Ion Beam Physics and Materials Research

Faßbender, J.; Helm, M.; Zahn, P.

The Institute of Ion Beam Physics and Materials Research conducts materials research for future applications in, e.g., information technology. To this end, we make use of the various possibilities offered by our Ion Beam Center (IBC) for synthesis, modification, and analysis of thin films and nanostructures, as well as of the free-electron laser FELBE at HZDR for THz spectroscopy. The analyzed materials range from semiconductors and oxides to metals and magnetic materials. They are investigated with the goal to optimize their electronic, magnetic, optical as well as structural functionality. This research is embedded in the Helmholtz Association’s programme “From Matter to Materials and Life”. Seven publications from last year are highlighted in this Annual Report to illustrate the wide scientific spectrum of our institute.
After the scientific evaluation in the framework of the Helmholtz Programme-Oriented Funding (POF) in 2018 we had some time to concentrate on science again before end of the year a few of us again had to prepare for the strategic evaluation which took place in January 2020, which finally was also successful for the Institute.
In 2019, there have been a number of organizational changes. First, and most prominently, we were able to hire Prof. Dr. Anton Wallner as new head of our department Accelerator Mass Spectrometry (AMS) and Isotope Research. This appointment is jointly with the TU Dresden where Toni has recei¬ved a chair in the Institute of Nuclear and Particle Physics. Along with this employment, our scientific advisory board and board of trustees approved the acquisition of a dedicated 1 MV accele¬rator for AMS including a laser detachment system. With this move, we hope to widen the scope of the user facility Ion Beam Center to new user communities in the field of nuclear astrophysics, environmental and geosciences. Second, the department Ion Beam Center is now headed by Dr. Stefan Facsko, who took over the responsibility from Dr. Johannes von Borany who stepped down for partial retirement. Stefan has been working in the Ion Beam Center since 2003 in various functions and is one of our most established researchers. We wish him all the best for this responsible position. Third, after the successful evaluation of Dr. Denys Makarov we created a new department Intelligent Materials and Devices, which is now headed by Denys. For his outstanding work in the field of mag¬netic sensor technology he also received the HZDR Research Award 2019. In the same ceremony, Dr. Jacob König-Otto received the HZDR Doctoral Prize 2019 for his dissertation at our Institute. Fourth, in fall we struck a new path and created a young researcher group on “Immuno-oncology on a chip: nano-assisted screening for cancer therapy” across disciplines and Institutes headed by Dr. Larysa Baraban. Larysa heads a group in the Institute of Radiopharmaceutical Cancer Research and collabo¬rates closely with our colleagues Dr. Artur Erbe on nanodevices and Dr. Denys Makarov on sensorics. We believe that this synergetic approach will pave the way to a fast and cost-efficient screening technology for personalized health care.
Again, in 2019, the level of newly received third-party funding was very good. In particular, we received the funding for two Helmholtz Innovation Laboratories (HIL); one on thermal treatment technology for defect engineering (UltraTherm) headed by Dr. Lars Rebohle and one on flexible sensors (FlexiSens) headed by Dr. Denys Makarov. The main emphasis of both HILs is to provide support of and technology transfer to small and medium enterprises in the respective technological areas. We are sure that in addition to our ion technology service provided via the HZDR Innovation GmbH both Innovation Labs will boost our technology transfer activities.
Several conferences and workshops were organized by scientists from our institute: the “Ion Beam Physics Workshop” as the annual meeting of the German Ion Beam Community was organized by Dr. Stefan Facsko and attracted around 50 participants to discuss the newest national developments and research in the field of ion beam physics. In addition, the “3rd European Focused Ion Beam Network Workshop” was organized by Dr. Hans-Jürgen Engelmann and co-workers; 135 participants from 17 countries found their way to HZDR to discuss current research topics and exchange experience in Focused-Ion-Beam (FIB) and Scanning-Electron-Microscopy (SEM) work.
Finally, we would like to cordially thank all partners, friends, and organizations who supported our progress in 2019. Special thanks are due to the Executive Board of the Helmholtz-Zentrum Dresden-Rossendorf, the Minister of Science and Arts of the Free State of Saxony, and the Ministers of Education and Research, and of Economic Affairs and Energy of the Federal Government of Germany. Numerous partners from universities, industry and research institutes all around the world contributed essentially, and play a crucial role for the further development of the institute. Last but not least, the directors would like to thank again all members of our institute for their efforts and excellent contributions in 2019.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-109 2020
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-31045
Publ.-Id: 31045


"Materials" - Special Issue "First-Principle and Atomistic Modelling in Materials Science"

Posselt, M.

Dear Colleagues,

Theoretical calculations and computer simulations are very important methods to improve our understanding of atomic-level processes in materials and to extend our knowledge on their static, dynamic, kinetic, and thermodynamic properties. Furthermore, the response of the material to external pertubations, in particular mechanical or thermal load and irradiation, can be studied using such computational techniques. This Special Issue of Materials shall include articles dealing with applications of first-principle density functional theory (DFT) and atomistic modelling based on interatomic potentials (AM). Both techniques are widely used to investigate ground state properties, finite-temperature effects, and dynamic processes. Based on the fundamental data delivered by DFT or AM, Monte Carlo simulations are employed to study the thermodynamics and kinetics of the respective materials. The present issue shall also include publications in which such a combination of the different computational methods is presented and be focused on solid inorganic materials with a crystalline or amorphous structure. Short communications on recent results, original research articles, as well as reviews may be submitted. This issue provides the opportunity for a detailed explanation of new computational techniques and for the publication of results obtained by the application of known theoretical methods to nonconventional classes of materials.

Dr. Matthias Posselt
Guest Editor

Contributions were submitted continuously from 2019 to 2021 and published after peer review.
Final Status (March 2021): 10 Articles, 1 Letter, 1 Editorial
https://www.mdpi.com/journal/materials/special_issues/Princ_Model

Keywords: First-Principle Calculations; Atomistic Modelling

  • Open Access Logo Book (Editorship)
    Basel, Switzerland: MDPI, 2021

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Permalink: https://www.hzdr.de/publications/Publ-31044
Publ.-Id: 31044


Soft Hydrothermal Synthesis of Hafnon, HfSiO4

Estevenon, P.; Kaczmarek, T.; Rafiuddin, M. R.; Welcomme, E.; Szenknect, S.; Mesbah, A.; Moisy, P.; Poinssot, C.; Dacheux, N.

The conditions allowing the preparation of single phase HfSiO4 has been determined through a multiparametric study by varying the concentrations of the reactants, the pH of the reactive media or the temperature and duration of the hydrothermal treatment. HfSiO4 was prepared through relatively soft conditions (pH ≤ 1.6, CSi ≈ CHf 0.21 mol·L‑1, T ≥ 150°C for t ≥ 24 hours).

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-29
    DOI: 10.14278/rodare.327

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Permalink: https://www.hzdr.de/publications/Publ-31043
Publ.-Id: 31043


Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond

Zhang, G.; Samuely, T.; Iwahara, N.; Kačmarčík, J.; Wang, C.; May, P. W.; Jochum, J. K.; Onufriienko, O.; Szabó, P.; Zhou, S.; Samuely, P.; Moshchalkov, V. V.; Chibotaru, L. F.; Rubahn, H.-G.

The combination of different exotic properties in materials paves the way for the emergence of their new potential applications. An example is the recently found coexistence of the mutually antagonistic ferromagnetism and superconductivity in hydrogenated boron-doped diamond, which promises to be an attractive system with which to explore unconventional physics. Here, we show the emergence of Yu-Shiba-Rusinov (YSR) bands with a spatial extent of tens of nanometers in ferromagnetic superconducting diamond using scanning tunneling spectroscopy. We demonstrate theoretically how a two-dimensional (2D) spin lattice at the surface of a three-dimensional (3D) superconductor gives rise to the YSR bands and how their density-of-states profile correlates with the spin lattice structure. The established strategy to realize new forms of the coexistence of ferromagnetism and superconductivity opens a way to engineer the unusual electronic states and also to design better-performing superconducting devices.

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Permalink: https://www.hzdr.de/publications/Publ-31042
Publ.-Id: 31042


In situ study of the synthesis of thorite (ThSiO4) under environmental representative conditions

Estevenon, P.; Causse, J.; Szenknect, S.; Welcomme, E.; Mesbah, A.; Moisy, P.; Poinssot, C.; Dacheux, N.

Thorite, ThSiO4 with Zircon structure type, is one of the most abundant natural source of thorium on earth. While actinides are known to form nanoparticles in silicate medium, no direct link between those colloids and crystalline form of thorite was evidenced until now. Here we show that thorite can be produced in experimental conditions close to environmental pH and temperature. Thanks to in-situ Small and Wide Angle X-rays Scattering (SWAXS) measurements, colloids of a few nanometers are first evidenced for low reaction time. These colloids exhibit elongated shapes and finally tend to aggregate after the size has reached 10 nm. Once aggregated, the system goes through a maturation step finishing with the emergence of nanocrystallites presenting thorite zircon structure. This maturation step is longer when the reaction temperature is decreased highlighting kinetic considerations. The conclusions of this article have potential implications in the paragenesis of Th minerals deposits, but also in the behaviour of Th and, by analogy, tetravalent actinides in the environment. The Th-silicate colloids evidenced in this work have, at low temperature and at near neutral pH, a long-term stability and a morphology in favor of a high mobility in groundwaters. If these species are formed in more diluted media, this could be problematic regarding to the spreading of Th and, by analogy of others tetravalent actinides in the environment.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-12
    DOI: 10.14278/rodare.325

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Permalink: https://www.hzdr.de/publications/Publ-31041
Publ.-Id: 31041


Formation of PuSiO4 under hydrothermal conditions

Estevenon, P.; Welcomme, E.; Tamain, C.; Jouan, G.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Moisy, P.; Dacheux, N.

Attempts to synthesize plutonium (IV) silicate, PuSiO4, have been performed on the basis of the results recently reported in the literature for CeSiO4, ThSiO4 and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4 by applying the conditions reported for thorium and uranium, an efficient way of PuSiO4 synthesis was established following those optimized for CeSiO4 system. This method was based on the slow oxidation of plutonium (III) silicate reactants under hydrothermal conditions at 150°C in hydrochloric acid (pH = 3 – 4). This result shed a new light on the potential behavior of plutonium in reductive environment, highlighted the representativeness of cerium surrogates to study plutonium in such conditions and brought some important pieces of information on plutonium chemistry in silicate solutions.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-20
    DOI: 10.14278/rodare.295

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Permalink: https://www.hzdr.de/publications/Publ-31040
Publ.-Id: 31040


The Serial Interface Package -- v3.0

Seilmayer, M.

The package enables reading and writing binary and ASCII data to RS232/RS422/RS485 or any other virtual serial interface of the computer. The major extensions are made with new functions and an improved robustness.

Keywords: RS232; RS485; serial interface; R

  • Software in external data repository
    Publication year 2020
    Programming language: R, Tcl/TK
    System requirements: Windows, Linux, MacOS
    License: GPL-2Link to location

Permalink: https://www.hzdr.de/publications/Publ-31039
Publ.-Id: 31039


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