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33403 Publications

Crystal dissolution kinetics studied by a combination of Monte Carlo and Voronoi methods

Rohlfs, R. D.; Fischer, C.; Kurganskaya, I.; Luttge, A.
Kinetic Monte Carlo (kMC) methods have been used extensively for the study of crystal dissolution kinetics and surface reactivity. A current restriction of kMC simulation calculations is their limitation in spatial system size. Here we explore a new and very fast method for the calculation of the reaction kinetics of a dissolving crystal, capable of being used for much larger systems. This method includes a geometrical approach, the Voronoi distance map, to generate the surface morphology including etch pit evolution and to calculate reaction rate maps and rate spectra in an efficient way. We calculate Voronoi distance maps that are based on a distance metric corresponding to the crystal lattice, weighted additively in relation to stochastic etch pit depths.
We show the opportunity to parameterize Voronoi distance maps by kMC simulation results. As a result, the resulting temporal sequences of Voronoi maps provide kinetic information.
By comparing temporal sequences of kMC simulation and Voronoi distance maps of identical etch pit distributions, we demonstrate the opportunity of making specific predictions about the dissolution reaction kinetics, based on rate maps and rate spectra. The dissolution of an initially flat Kossel crystal surface served as an example to show that a sequence of Voronoi calculations can predict dissolution kinetics based on the information about the distribution of screw defects.
The results prove the geometrical relationship between material flux from the surface at a certain point and the distance (or, when considering anisotropy, a function of distance) to the nearest defect. In this study, for the sake of comparability, the calculations are made using input parameters directly derived from the KMC models operating at the atomic scale. We show that, using values of v(rpit) and weighting factors obtained by kMC, the resulting surface morphologies and material flux are almost identical. This implies that discrete Voronoi calculations of starting and end points of the dissolution are sufficient to calculate material flux maps, without having to simulate all-atomic time-consuming calculations in between. This opens a new promising venue to efficiently upscale full-atomic KMC models to the continuum macroscopic level where reactive transport and Lattice Boltzmann calculations can be applied.
Keywords: fluid-solid reaction kinetics, kinetic Monte Carlo simulation, Voronoi distance, rate map, rate spectra

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Permalink: https://www.hzdr.de/publications/Publ-27085
Publ.-Id: 27085


Experimental observation of Bethe strings

Wang, Z.ORC; Wu, J.; Yang, W.; Bera, A. K.; Kamenskyi, D.; Islam, A. T. M. N.; Xu, S.; Law, J. M.; Lake, B.; Wu, C.; Loidl, A.
Almost a century ago, string states—complex bound states of magnetic excitations—were predicted to exist in one-dimensional quantum magnets. However, despite many theoretical studies, the experimental realization and identification of string states in a condensed-matter system have yet to be achieved. Here we use high-resolution terahertz spectroscopy to resolve string states in the antiferromagnetic Heisenberg–Ising chain SrCo2V2O8 in strong longitudinal magnetic fields. In the field-induced quantum-critical regime, we identify strings and fractional magnetic excitations that are accurately described by the Bethe ansatz. Close to quantum criticality, the string excitations govern the quantum spin dynamics, whereas the fractional excitations, which are dominant at low energies, reflect the antiferromagnetic quantum fluctuations. Today, Bethe’s result1 is important not only in the field of quantum magnetism but also more broadly, including in the study of cold atoms and in string theory; hence, we anticipate that our work will shed light on the study of complex many-body systems in general.
Keywords: Bethe ansatz, string excitations, Heisenberg-Ising chain, THz/infrared spectroscopy, high magnetic field

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Permalink: https://www.hzdr.de/publications/Publ-27084
Publ.-Id: 27084


Origin of field-induced discontinuous phase transitions in Nd2Fe17

Diop, L. V. B.; Kuz'Min, M. D.; Skokov, K. P.; Skourski, Y.; Gutfleisch, O.
Magnetic properties of a trigonal ferromagnet Nd2Fe17 have been studied on single crystals in steady (14 T) and pulsed (32 T) magnetic fields. The easy-magnetization direction lies close to the [120] axis, deviating from the basal plane by 2.9° (at T = 5 K). Of particular interest is the low-temperature magnetization process along the high-symmetry axis [001], which is the hard direction. This process is discontinuous and involves two first-order phase transitions (FOMPs). One of them (at 20 T) is a symmetry FOMP similar to that observed in Sm2Fe17. The second transition (at 10.4 T) is unusual: as the magnetization turns abruptly toward the applied field, it also changes its azimuthal orientation (the angle ϕ) by 60°. Both transitions can be reasonably accounted for by the presence of a significant sixth-order trigonal anisotropy term.

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Permalink: https://www.hzdr.de/publications/Publ-27083
Publ.-Id: 27083


Spectroscopic and batch studies of technetium uptake by siderite

Schmeide, K.ORC; Rossberg, A.; Weiss, S.; Scheinost, A. C.
99Tc is a long-lived (t1/2 = 2.1 x 105 years) β-emitter formed during the fission of U and is of major concern for radioactive waste disposal. Its environmental mobility is primarily governed by the oxidation states VII and IV, with TcVII forming the highly mobile TcO4 aquo anion, whereas TcIV is rather immobile due to the low solubility of its hydrolysis products. Redox processes, which are able to convert TcVII into TcIV, are hence of paramount importance for the safety of radioactive waste repositories. FeII-bearing minerals, ubiquitous in nature but also forming as corrosion products of the steel canisters foreseen as a possible first enclosure of radioactive waste, play a vital role in these redox reactions due to their high redox reactivity and high sorption capacity, as has been shown not only for Tc, but also for Se, U, Np and Pu.
We studied the TcVII uptake by siderite (FeCO3), a typical FeII mineral in carbonate-rich environments, in the relevant pH range 7 – 12.6 under anoxic conditions by means of batch sorption experiments and by X-ray absorption spectroscopy. Sorption experiments showed that Tc retention by siderite is fast and efficient (log Rd ~5) across the investigated pH range and independent of ionic strength (0.1 – 1 M NaCl). Tc K-edge X-ray absorption near-edge structure (XANES) data confirmed that the Tc immobilization is due to the surface-mediated reduction of TcVII to TcIV. The local structure of TcIV in Tc siderite sorption samples and Tc siderite coprecipitates probed by extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed three different species: In the pH range 7.8 to 11.8, TcO2-dimers form inner-sphere sorption complexes at the surface of the initial siderite phase as well as on secondary magnetite or green rust formed during the redox reaction. Between pH 11.9 and 12.6, a mixed Fe/Tc hydroxocarbonate precipitate (chukanovite-like) is formed.
The results showed that siderite contributes effectively to the retention of Tc under repository conditions through formation of strong sorption complexes and precipitation of hydroxocarbonate phases with low solubility.
Keywords: Technetium, siderite, reduction, adsorption, incorporation, technetium carbonate, X-ray absorption spectroscopy
  • Contribution to proceedings
    RadChem 2018-18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
    Czech Chemical Society Symposium Series, 18th Radiochemical Conference, Mariánské Lázně, Czech Republic, 13-18 May 2018, Booklet of Abstracts, 59
  • Lecture (Conference)
    RadChem 2018-18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
  • Lecture (Conference)
    10th International Symposium on Technetium and Rhenium – Science and Utilization, 03.-06.10.2018, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-27082
Publ.-Id: 27082


Multi-Point Statistics for Tailings Deposits

Selia, S. R. R.; Tolosana-Delgado, R.; van den Boogaart, K. G.; Schaeben, H.
Technical and economic evolution of the mineral industry resulted in a new view of mining tailings. Formerly tailings are considered not valuable but now they become new resources that have promising economic values. The spatial estimation of mineral distribution is essential for optimally exploiting tailings, but this faces several issues such as non-stationarities, complex and artificial structures, and limited historic information on the feed streams and spilling points. Multi-Point Statistics methods are capable of reproducing complicated structures more appropriately as compared to two-point statistics methods. This paper proposes a new framework for performing Multi-Point Statistics on tailings deposits. Instead of using one big training image, we used several training images. In this way we can use different joint distributions at different locations to cope with the nonstationarity of tailings deposits. By providing and eventually weighting training images generated with different forward modelling parameters we can handle the uncertainty about the history of the deposit, while still exploiting available historic information. The framework is illustrated through a test on a synthetic tailings model. The synthetic truth and the training images are generated using Delft3D-Flow, an open source process-based modelling program that can also perform stratigraphic forward modeling in deltaic depositional environments. The MPS analysis is based on a new implementation with advanced capabilities.
Keywords: Multi-Point Statistics, Mining Tailings, Synthetic Training Images
  • Lecture (Conference)
    IAMG 19th Annual Conference, 02.-08.09.2018, Olomouc, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27081
Publ.-Id: 27081


Radiative neutron capture on 242Pu in the resonance region at the CERN n_TOF-EAR1 facility

Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A. R.; Krtička, M.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou33, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.
The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with uranium to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. However, an extensive use of MOX fuels, in particular in fast reactors, requires more accurate capture and fission cross sections for some Pu isotopes. In the case of 242Pu there are sizable discrepancies among the existing capture cross-section measurements included in the evaluations (all from the 1970s) resulting in an uncertainty as high as 35% in the fast energy region. Moreover, postirradiation experiments evaluated with JEFF-3.1 indicate an overestimation of 14% in the capture cross section in the fast neutron energy region. In this context, the Nuclear Energy Agency (NEA) requested an accuracy of 8% in this cross section in the energy region between 500 meV and 500 keV. This paper presents a new time-of-flight capture measurement on 242Pu carried out at n_TOF-EAR1 (CERN), focusing on the analysis and statistical properties of the resonance region, below 4 keV. The 242Pu(n,γ) reaction on a sample containing 95(4) mg enriched to 99.959% was measured with an array of four C6D6 detectors and applying the total energy detection technique. The high neutron energy resolution of n_TOF-EAR1 and the good statistics accumulated have allowed us to extend the resonance analysis up to 4 keV, obtaining new individual and average resonance parameters from a capture cross section featuring a systematic uncertainty of 5%, fulfilling the request of the NEA.
Keywords: Neutron physics, nuclear reactions, radiative capture, reactor fuel and coolants, radioactive waste

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Permalink: https://www.hzdr.de/publications/Publ-27080
Publ.-Id: 27080


Retention of Tc(VII) by pyrite nanoparticles

Rodríguez Hernández, D. M.; Mayordomo-Herranz, N.; Müller, K.
One of the major pollutants in nuclear waste is 99Tc, a redox-sensitive fission product from 235U and 239Pu with a long half-life of 2.14 X 105 years. Under environmental oxidizing conditions, 99Tc mainly exists in aqueous solution as pertechnetate, TcO4-, which is a highly water-soluble ion that does not sorb significantly on minerals or sediments 1, so that, it is considered as inert with high risk to migrate through the environment. Under reducing conditions, Tc mobility is hampered by formation of Tc(IV) with significantly lower solubility 2. Pyrite, on one hand, is a good sorbent for Tc(VII) due to the presence of the functional groups FeOH and FeSH, and on the other hand, Tc(VII) is reduced to Tc(IV) by the interaction with structural Fe2+ and possibly with sulfur atoms. Moreover, Bruggeman et al. 3 found considerably increased Tc sorption when adding pyrite to boom clay in the presence of humic substances, which also favor the Tc retention4,5.

In this work synthetized pyrite nanoparticles 6 were used to investigate Tc sorption in classical batch sorption experiments.


References

1. Lieser, K. H. & Bauscher, C. H. Technetium in the hydrosphere and in the geosphere. Radiochimica Acta 42, 205–214 (1987).
2. Meena, A. H. & Arai, Y. Environmental geochemistry of technetium. Environ. Chem. Lett. 15, 241–263 (2017).
3. Bruggeman, C., Maes, A. & Vancluysen, J. The identification of FeS2 as a sorption sink for Tc(IV). Phys. Chem. Earth 32, 573–580 (2007).
4. Maes, A., Geraedts, K., Bruggeman, C., Vancluysen, J., Rossberg, A. & Hennig, C. Evidence for the Interaction of Technetium Colloids with Humic Substances by X-ray Absorption Spectroscopy. Environ. Sci. Technol. 38, 2044–2051 (2004).
5. Geraedts, K. & Maes, A. Determination of the conditional interaction constant between colloidal technetium(IV) and Gorleben humic substances. Appl. Geochemistry 23, 1127–1139 (2008).
6. Bai, Y., Yeom, J., Yang, M., Cha, S., Sun, K. & Kotov, K. Universal synthesis of single-phase pyrite FeS2 nanoparticles, nanowires, and nanosheets. J. Phys. Chem. C 117, 2567–2573 (2013).
Keywords: Pyrite, Technetium
  • Poster
    18th Radiochemical Conference - RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27079
Publ.-Id: 27079


Electrical properties of surface and interface layers of the N- and In-polar undoped and Mg-doped InN layers grown by PA MBE

Komissarova, T. A.; Kampert, E.; Law, J.; Jmerik, V. N.; Paturi, P.; Wang, X.; Yoshikawa, A.; Ivanov, S. V.
Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

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Permalink: https://www.hzdr.de/publications/Publ-27078
Publ.-Id: 27078


U(VI) toxicity onto canola cells: Correlation of microcalorimetric data with cell viability and U(VI) speciation

Sachs, S.; Fahmy, K.; Oertel, J.; Geipel, G.; Bok, F.
The transfer of radionuclides into the food chain is of central concern for the safety assessment of both nuclear waste repositories and radioactive contaminated areas, such as legacies of the former uranium mining. The interaction of radionuclides with plants is mostly described by transfer factors without knowing the underlying processes. However, previous studies showed, for instance, a speciation-dependent influence of radionuclide uptake and translocation in plants [1]. Heavy metal stress induces the synthesis of metal-binding metabolites, storage of metal chelates in vacuoles or the secretion into the rhizosphere [2], which changes the plant cell metabolism.
We studied the interaction of U(VI) with canola cells (Brassica napus) as model system for plants focusing on the concentration-dependent impact of U(VI) on the cell metabolism. The metabolic heat flow of the cells was monitored by isothermal microcalorimetry, a highly sensitive real-time monitor that allows the detection of actinide toxicity in environmentally relevant concentrations. The calorimetric data were compared to the enzymatically determined cell viability. The U(VI) speciation in the cell culture medium was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and thermodynamic modeling to correlate the impact of U(VI) on the cell activity with its speciation [3].
Brassica napus cells showed a temporal decrease in metabolic thermal power and a general reduction of heat production with increasing U(VI) concentration. So far, metabolic calorimetry suffered from the lack of models describing metabolic decline. To overcome this, the model-independent descriptor “metabolic capacity” that allows the evaluation of calorimetric data of declining metabolic phases was introduced in our work. The obtained normalized “metabolic capacities” and the normalized enzymatically determined cell viabilities showed an almost ideal correlation and were, to a very good approximation, linearly related at U(VI) concentrations up to 200 µM U(VI). The combination with TRLFS and thermodynamic modeling indicated that the cell metabolism was affected predominantly by U(VI) hydroxo species [3].
This presentation will demonstrate the potential of life cell microcalorimetry for radioecological studies, including the discrimination between chemotoxic and radiotoxic effects of uranium at the low dose regime.

References
[1] Ebbs, S.D., Brady, J., Kochian, L.V., Role of uranium speciation in the uptake and translocation of uranium in plants. J. Exp. Bot. 49 (1998) 1183-1190.
[2] Weiler, E., Nover, L., Allgemeine und molekulare Botanik. Georg Thieme Verlag, Stuttgart, 2008.
[3] Sachs, S., Geipel, G., Bok, F., Oertel, J., Fahmy, K., Calorimetrically determined U(VI) toxicity in Brassica napus correlates with oxidoreductase activity and U(VI) speciation. Env. Sci. Technol. 51 (2017) 10843-10849.
Keywords: plants, plant cells, actinides, uranium, toxicity, metabolism, speciation, isothermal microcalorimetry, TRLFS, thermodynamic modeling
  • Contribution to proceedings
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic
    Czech Chemical Society Symposium Series, 18th Radiochemical Conference, Mariánské Lázne, Czech Republic, 13-18 May 2018, Booklet of Abstracts, 188
  • Lecture (Conference)
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27077
Publ.-Id: 27077


Investigation of the laser-plasma interaction with the method of small- angle x-ray scattering (SAXS) at an XFEL

Rödel, M.; Pelka, A.; Kluge, T.; Laso Garcia, A.; Mcbride, E.; Rödel, C.; Prencipe, I.; Hartley, N.; Kraus, D.; Gutt, C.; Schramm, U.; Cowan, T. E.
The combination of ultra-intense lasers with x-ray free-electron lasers (XFELs) opens up a variety of applications in plasma and shock physics. Many phenomena during the laser-target interaction happen on short time scales in the range from femto- to picoseconds and length scales of tens of nanometers to a few micrometers. Unlike the ultra-short, highly coherent x-ray pulse, optical methods or conventional continuous x-ray sources cannot probe the dynamics of the bulk material with sufficient temporal and spatial resolution. Here we will show the potential of SAXS in combination with short-pulse laser experiments. With this method it is possible to draw conclusions about the electron density distribution in the target by analyzing the XFEL diffraction pattern in the vicinity of the direct beam. A setup to perform such SAXS experiments was developed and optimized during a beamtime at the Matter in Extreme Conditions instrument (MEC) at the Linear Coherent Light Source (LCLS) in Stanford. We will discuss the setup and present a preliminary analysis of the data obtained during this experiment.
  • Lecture (Conference)
    DPG-Frühjahrstagung Dresden 2017, 19.-24.03.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27076
Publ.-Id: 27076


MHD of liquid metal batteries

Weber, N.; Ashour, R.; Herreman, W.; Horstmann, G.; Kelley, D.; Landgraf, S.; Nore, C.; Personnettaz, P.; Stefani, F.; Weier, T.
Liquid metal batteries (LMBs), developed originally during the 1960s in the United States, experienced a renaissance some ten years ago at MIT. Built as stable density stratification of two liquid metals, which are separated by a molten salt, they offer potentially very cheap stationary energy storage. Thus, LMBs may be the key enabler for a large scale deployment of highly fluctuating renewable energy sources. Especially their potentially long life time, the extremely high current densities and the cheap active materials make the cells an ideal candidate for stationary energy storage.
Fluid flows will naturally appear in the fully liquid cells. On the one hand, convection can be beneficial when enhancing mass transfer and improving the cell efficiency. On the other hand, strong flow must be avoided to ensure a safe operation.
The talk will give an introduction to the set-up and working principle of LMBs. The second part will be devoted to fluid dynamic
instabilities in the cells; both numerical and experimental results will be presented. The talk will focus on long wave MHD interface instabilities (as known from aluminium reduction cells), on thermal convection, and electro-vortex flow.
  • Lecture (Conference)
    Third Russian Conference on Magnetohydrodynamics, 18.06.2018, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-27075
Publ.-Id: 27075


Tc immobilization on gamma alumina: a study of the reductant presence and absence

Mayordomo, N.; Müller, K.ORC
Technetium isotope 99Tc is a fission product of environmental concern, due to its high mobility and its elevated lifetime (2.13×105 years). Among their possible oxidation states, Tc(VII) and Tc(IV) are the most stable ones. On one hand, Tc(VII) occurs under oxidizing redox conditions, being pertechnetate (TcO4-) the main species, which is considered an inert and mobile anion that hardly interacts with minerals. On the other hand, Tc(IV) is present under reducing conditions and it is mainly found as solid, TcO2, since it has a very low solubility product. Studies dealing with Tc immobilization in groundwater normally consider the use of reductants or mineral containing reductant moieties to favor the transformation of Tc(VII) to Tc(IV) with the aim of decreasing its migration in water fluxes.
Nano particular gamma alumina is a well suited sorbent for anions because of the high values of surface to volume ratio, specific surface area and point of zero charge. Indeed, we have already observed the efficient sorption capacity of gamma alumina against Se(IV) anions [1]. Thus, per se, alumina is a promising candidate to sorb Tc(VII). Nevertheless, for Tc(VII) low sorption is expected. However, previous studies have reported the higher Tc retention when the mineral is in contact with a reductant [2,3]. Thus, we will study the reductiuon of Tc(VII) to Tc(IV) on nano particular gamma alumina in presence of Fe2+.
This work has been developed in the frame of VESPA II project, supported by the German Ministry of Economy and Energy (BMWi).
[1] N. Mayordomo, H. Foerstendorf, J. Lützenkirchen, K. Heim, S. Weiss, Ú. Alonso, T. Missana, K. Schmeide, N. Jordan, Selenium(IV) sorption onto γ-Al2O3: a consistent description of the surface speciation by spectroscopy and thermodynamic modeling, Environ. Sci. Technol. Accepted (2017). doi:10.1021/acs.est.7b04546.
[2] R.M. Asmussen, J.J. Neeway, A.R. Lawter, T.G. Levitskaia, W.W. Lukens, N.P. Qafoku, The function of Sn(II)-apatite as a Tc immobilizing agent, J. Nucl. Mater. 480 (2016) 393–402. doi:10.1016/j.jnucmat.2016.09.002.
[3] T. Peretyazhko, J.M. Zachara, S.M. Heald, B.H. Jeon, R.K. Kukkadapu, C. Liu, D. Moore, C.T. Resch, Heterogeneous reduction of Tc(VII) by Fe(II) at the solid-water interface, Geochim. Cosmochim. Acta. 72 (2008) 1521–1539. doi:10.1016/j.gca.2008.01.004.
Keywords: Technetium, alumina, Fe
  • Lecture (Conference)
    18th Radiochemical conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27074
Publ.-Id: 27074


Detection Systems for Range Monitoring in Proton Therapy: Needs and Challenges

Pausch, G.; Berthold, J.; Enghardt, W.; Römer, K.; Straessner, A.; Wagner, A.; Werner, T.; Kögler, T.
In-vivo range verification has been a hot topic in particle therapy for more than a decade. In spite of vast efforts made by research groups all over the world, clinical means for routinely monitoring the range of therapeutic proton or carbon ion beams in the patient’s body and to ensure their correspondence with the treatment plan are not yet available. The paper reviews recent approaches with focus on prompt-gamma based methods, and points to challenges that have not yet been fully recognized or discussed: First, the macro time structure of treatment beams in common proton therapy facilities requires detection systems with extreme load tolerance, throughput capability, and stability against load variations. Second, the test time available for verifying the range of a single pencil beam spot is of the order of milliseconds, which limits the number of prompt gamma events that can be detected and processed. Tight event selection by passive or active collimation as applied in all imaging setups sharpens the information carried by a valid event but strongly reduces their total number. It might be better to use a multitude of uncollimated detectors acquiring time and energy signatures of every gamma hit with reasonable precision, and to pick up all the pieces of information comprised in timing, energy, and coincidence patterns irrespective of their sharpness. This would maximize the number of valid events on the expense of information sharpness, and could eventually increase the total yield of information exploitable for range verification. Some aspects of such a strategy have already been realized with the Prompt Gamma-Ray Timing (PGT) and the Prompt Gamma Peak Integration (PGPI) techniques proposed recently. Data analysis schemes for a more generalized approach have not yet been developed, but the hardware to be used can already be sketched: Prompt gamma rays should be detected with scintillation detector blocks consisting of single pixels with individual light readouts and independent electronics channels, similar to those developed for applications as PET-MR. Prompt-gamma detection is, however, much more demanding with respect to dynamic range, energy resolution, load acceptance, and stability. The paper will detail and discuss corresponding requirements that represent a challenge for the detector physics community, and report on activities at HZDR and OncoRay to explore the available options.
Keywords: Partikeltherapie; Protonentherapie; Reichweitekontrolle; Prompte Gammastrahlung; Gammakamera; Gammaspektroskopie; Zeitspektroskopie; Lasteffekte; Stabilisierung; Particle therapy; proton therapy; range verification; prompt gamma; gamma detection; gamma imaging; gamma spectroscopy; timing spectroscopy; load effects; stabilization
  • Lecture (Conference)
    2018 Symposium on Radiation Measurements and Applications (SORMA XVII), 11.-14.06.2018, Ann Arbor, MI, USA
  • Open Access Logo Nuclear Instruments and Methods in Physics Research A (2020)
    Online First (2018) DOI: 10.1016/j.nima.2018.09.062

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Permalink: https://www.hzdr.de/publications/Publ-27073
Publ.-Id: 27073


ChimeraTK OPC UA Adapter for the Integration of a MicroTCA.4 based digital LLRF

Steinbrück, R.; Kuntzsch, M.; Zenker, K.; Hierholzer, M.; Killenberg, M.; Iatrou, C. P.; Rahm, J.
The superconducting linear accelerator ELBE at Helmholtz-Center Dresden-Rossendorf is a versatile light source operated in continuous wave mode. Currently there is a transition from an analogue low level radio frequency control (LLRF) to a digital MicroTCA.4 based solution developed at DESY, Hamburg. Control system integration is realized collaboratively by DESY, Technische Universität Dresden (TUD) and HZDR with ChimeraTK and the incorporated OPC UA adapter. The poster gives an overview of the variable mapping scheme used to represent LLRF data in the OPC UA server address space, the graphical user interface and first integration test results.
Keywords: ELBE MicroTCA.4 LLRF "OPC UA" ChimeraTK
  • Lecture (others)
    6th MicroTCA Workshop for Industry and Research, 04.-07.12.2017, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27072
Publ.-Id: 27072


DNA mold templated assembly of conductive gold nanowires

Bayrak, T.; Helmi, S.; Ye, J.; Kauert, D.; Kelling, J.; Schönherr, T.; Erbe, A.; Seidel, R.
We introduce a new concept for the solution-based fabrication of conductive gold nanowires using DNA templates. To this end we employ DNA nanomolds inside which electroless gold deposition is initiated by site-specifically attached seeds. Using programmable interfaces individual molds self-assemble into micrometer long mold superstructures. During the subsequent internal gold deposition, the mold walls constrain the metal growth, such that highly homogeneous nanowires with 20-30 nm diameter are obtained. Wire contacting using electron beam lithography and electrical conductance characterization at temperatures between 4.2 K and room temperature demonstrate, that metallically conducting wires can be produced, though in part of the wires the conductance is limited by boundaries between gold grains. Using different mold designs, our synthesis scheme will in the future allow the fabrication of complex metal structures with programmable shape.

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Permalink: https://www.hzdr.de/publications/Publ-27071
Publ.-Id: 27071


Control System Integration of a MicroTCA.4 Based Digital LLRF Using the ChimeraTK OPC UA Adapter

Steinbrück, R.; Kuntzsch, M.; Michel, P.; Hierholzer, M.; Killenberg, M.; Schlarb, H.; Iatrou, C. P.; Rahm, J.; Urbas, L.
The superconducting linear electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf is a versatile light source. It operates in continuous wave (CW) mode to provide a high average beam current. In order to meet the requirements for future high resolution experiments the analogue low level radio frequency control (LLRF) is currently replaced by a digital MicroTCA.4 LLRF system based on a development at DESY, Hamburg.
Operation and parametrization is realized by a server application implemented by DESY using the ChimeraTK software framework. To interface the WinCC 7.3 based ELBE control system an OPC UA adapter for ChimeraTK has been developed in cooperation of DESY, Technische Universität Dresden (TUD) and HZDR. The contribution gives an overview of the collaborating parties, the variable
mapping scheme used to represent LLRF data in the OPC UA server address space and integration experiences with different industrial OPC UA Clients like WinCC 7.3 and LabVIEW.
Keywords: MicroTCA.4 LLRF "OPC UA" ChimeraTK
  • Poster
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 03.-13.10.2017, Barcelona, Spain
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166
  • Contribution to proceedings
    ICALEPCS2017 - 16th International Conference on Accelerator and Large Experimental Physics Control Systems, 08.-13.10.2017, Barcelona, Spain
    Proceedings of ICALEPCS2017
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA166

Permalink: https://www.hzdr.de/publications/Publ-27070
Publ.-Id: 27070


Stability investigations of actinide doped calcium silicate hydrate phases in highly saline electrolytes

Wolter, J.-M.; Schmeide, K.; Huittinen, N. M.; Stumpf, T.
To evaluate the retention potential of the concrete barrier in a nuclear waste repository towards actinides in the presence of high saline water, leaching experiments with actinide-doped calcium silicate hydrate (CSH) phases were performed in highly saline electrolytes. Therefore, U(VI)- and Cm(III)-doped CSH phases with different C/S ratios (1.0-2.0) were synthesized directly in presence of either U(VI) or Cm(III) and characterized by time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The time-dependent release of Ca, Si, U, and Cm from CSH phases into brines containing either 2.5 M NaCl, 2.5 M NaCl/0.02 M Na2SO4, 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 for U(VI)-doped CSH phases or 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 for Cm(III)-doped CSH phases was monitored in batch leaching experiments for 30 or 60 days, respectively. Subsequently, leaching induced changes of the CSH structure and of the U(VI) or Cm(III) coordination environment were investigated with TRLFS, IR spectroscopy and XRD.

Site-selective TRLFS studies of the Cm(III)/CSH binding at 8 K revealed a luminescence line-narrowing effect, which could be ascribed to the presence of a continuum of similar curium species on two different sorption sites in the CSH interlayer. The leached CSH phases showed pronounced differences in terms of decomposition behavior and actinide release depending on their C/S ratio, leaching electrolyte, and incorporated actinide. U(VI)-doped CSH phases leached in 2.5 M NaCl showed an increased release of Ca and a U(VI) precipitation as uranophane while the leaching in 0.02 M NaHCO3 led to a mobilization of U(VI) as an aqueous Ca2UO2(CO3)3 species.

In contrast, Cm(III) was not mobilized by NaHCO3 but incorporated into newly formed secondary phases like calcite and vaterite as detected by site-selective TRLFS. The comparison between leaching experiments performed in 0.02 M NaHCO3 and 2.5 M NaCl/0.02 M NaHCO3 revealed that the presence of 2.5 M NaCl increases the carbonate-induced U(VI) mobilization from CSH phases with higher C/S ratios while no influence on the Cm(III) retention was detectable.
Keywords: CSH, Cm(III), U(VI), highly saline, electrolytes, leaching, TRLFS, IR, XRD
  • Contribution to proceedings
    RadChem 2018 – 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Česká republika
  • Poster
    18th Radiochemical Conference, 13.-18.05.2018, 13.-18.05.2018, Mariánské Lázně, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-27069
Publ.-Id: 27069


Vertical Nanowire Based Single Electron Transistor Self-Assembled by Ion Beam Mixing and Phase Separation

Heinig, K.-H.; von Borany, J.; Hlawacek, G.; Hübner, R.; Wolf, D.; Engelmann, H.-J.; Bischoff, L.; Xu, X.; Prüfer, T.; Möller, W.; Facsko, S.
Electronics has been dominated by silicon since half a century. Si will dominate electronics another decade, however its functionality might change from classical field-controlled currents through channels (the Field Effect Transistor FET) to quantum mechanical effects like field-controlled hopping of single electrons to a quantum dot (Single Electron Transistor SET). The SET is the champion of low-power consumption. This is attractive for the Internet of Things: more and more devices need batteries and plugs. Together with improved batteries, advanced computation must be delivered at extremely low-power consumption. At low temperatures, the functionality of SETs has been proven. Large-scale use of SETs requires room temperature operation, which can be achieved with tiny Si dots (<4 nm) in SiO2, exactly located between source and drain with distances of ~1…2 nm. Manufacturability of such nanostructures is the roadblock for large-scale use of SETs. Lithography cannot deliver such feature sizes. Therefore, there are currently intense studies to fulfill these requirements by self-organization processes. The ion beam technique is a well-established technology in microelectronics used for doping and amorphization, and even for ion beam mixing [1]. The parameters of ion beam processing are very well controllable. We searched for a self-organization process in a vertical silicon nanowire with an embedded, very thin (~6nm) SiO2 layer. Ion beam mixing transforms this layer to metastable SiOx. If the nanowire is thin enough, a subsequent thermal treatment leads by phase separation to a single Si nanodot (~3nm) self-aligned to the lower and upper Si at distances of <2nm. Here, we present 3D computer simulations on ion beam mixing (TRI3DYN code [2]) and Si nanodot formation (3D kinetic Monte Carlo code [3]). Such simulations predicted successfully the fabrication of non-volatile memories using ion beam mixing [4]. Experimentally, single Si nanodot formation has been proven by local mixing in a c-Si/SiO2/a-Si layer stack. The nanoscale mixing has been performed with a Helium Ion Microscope using an Argon beam of ~2nm diameter. After Rapid Thermal Annealing, the self-organized single Si nanodot has been imaged by cross-section energy-filtered transmission electron microscopy EFTEM. In a vertical nanowire the very small volume of mixed SiO2 is not due to nanoscale ion beams but due to the small diameter of the wire. It will be shown, how a vertical nanowire gate-all-around SETs operating at room temperature can be CMOS-compatibly fabricated by this method.
This work has been funded by the European Union’s Horizon 2020 research and innovation program under grant
agreement No 688072.
[1] K.H. Heinig, T. Müller, B. Schmidt, M. Strobel, W. Möller, Appl. Phys. A77 (2003) 17.
[2] W. Möller, NIM B322 (2014) 23.
[3] M. Strobel, K.-H. Heinig, W. Möller, Phys. Rev. B64 (2001) 245422.
[4] T. Mueller et al., Appl .Phys. Lett. 81 (2002) 3049; ibid 85 (2004) 2373.
Keywords: ion beam mixing, phase separation, computer simulations, manufacturing, single electron transistor
  • Lecture (Conference)
    Symposium “Progress in Developing and Applications of Functional 1D Nanostructiures”, 2017 Fall Meeting of the Materials Research Society, 26.11.-01.12.2017, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-27068
Publ.-Id: 27068


Ion-Beam-Induced Self-Organisation of Nanostructures at Interfaces

Heinig, K.-H.; Prüfer, T.; Möller, W.; Hlawacek, G.; Xu, X.; Bischoff, L.; Hübner, R.; Wolf, D.; Facsko, S.; von Borany, J.
Ion irradiation through an interface between the phases A and B causes atomic displacements which results at low temperatures in a diffusion-like concentration profile. Even if phases A and B are immiscible, a metastable layer of an A/B mixture forms at high ion fluence. A subsequent thermal treatment will activate phase separation in this A/B mixture via nucleation and coarsening. This phase separation process has the potential of self-organisation of nanostructures, where the resulting nanostructure can be tailored by understanding and controlling the reaction pathway.
(i) At first, in this presentation it will be shown how the ion beam mixing of a flat infinite interface can be simulated with the SRIM and TRIDYN programs.
(ii) Then, by means of 3D kinetic lattice Monte-Carlo simulations it will be demonstrated how a thermally activated phase separation of the A/B mixture starts either by formation of nuclei of the minority phase or by spinodal decomposition.
(iii) Simulations for long times show that the subsequent nanostructure evolution is driven by interface minimization, i.e. Ostwald ripening of nanocluster ensembles or coarsening of spinodal structures.
At this stage, a self-organisation process governed by Brailsford's diffusional screening length can evolve, which can be eventually controlled. The A/B interface which re-forms during phase separation plays a central role for self-organisation and self-alignment of nanostructures.
These general mechanisms are effective in ion beam mixing of a thin SiO2 layer buried in Si with the following observations: (i) Zones denuded of Si form during annealing at the upper and lower interface. (ii) Additionally, three, two or one layer of Si nanoclusters form and align with the interface. (iii) If only a tiny volume ~(10nm)^3 of metastable SiOx (such as in an ion beam mixed nanopillar of a Si/SiO2/Si stack) becomes phase separated, the reaction pathway leads always to the existence of a single Si dot for a rather long time period.
This single Si nanodot fabrication becomes even more stable if all boundaries of the tiny SiOx volume are sinks for Si diffusing in SiO2, which can be realized by sideways in-diffusion of oxygen into the nanopillar.
Finally it will be shown, how such a single Si nanodot fabrication process can be used for manufactoring of single electron transisrors working at room temperature.
Keywords: Nanostructure fabrication, ion-beam-mixing, phase separation, silicon nanodot, single electron transistor
  • Invited lecture (Conferences)
    FOR3NANO: Formation of 3D Nanostructures by Ion Beams, 28.-30.06.2017, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-27067
Publ.-Id: 27067


Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for ¹⁰Be and ²⁶Al analysis

Merchel, S.ORC; Gärtner, A.; Beutner, S.; Bookhagen, B.; Chabilan, A.
The purity of the analysed samples (e.g. quartz) with respect to chemical composition and radionuclide contamination is essential for geomorphologic applications using so-called terrestrial cosmogenic nuclides (TCNs). To guarantee this, numerous cleaning and dissolution procedures have been developed. At the DREsden Accelerator Mass Spectrometry (DREAMS) facility, we also work on enhancing the chemical quartz-enrichment methodology from bulk rock and dissolution of quartz. Repeated exposure of the bulk material to acid mixtures (HCl/H2SiF6) at room temperature for cleaning and its monitoring by optical microscopy works for most quartz-rich samples. The quartz dissolution in HF under rather mild conditions (at room temperature on a shaker-table) has the advantage to leave difficult-to-dissolve minerals (e.g., tourmaline, zircon, rutile, sillimanite, kyanite, chromite, corundum), not separated by other physical methods before, as residue. Our comparison with a high-temperature dissolution method (in a microwave) indicates that an additional amount of interfering elements, such as in average about 3 mg of Ti, more than 7 mg of Al, and about 22 μg of Be to the sample (for 50 g SiO2), shows the superiority of our mild method. This way, we reduce problems for chemistry and AMS, but also ensure better comparability to production rates of cleaner stoichiometric quartz from calibration sites
Keywords: accelerator mass spectrometry, in-situ, terrestrial cosmogenic nuclide, residue, quartz

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Permalink: https://www.hzdr.de/publications/Publ-27065
Publ.-Id: 27065


Current Status and Perspectives of the OECD/NEA sub-group on Uncertainty Analysis in Modelling (UAM) for Design, Operation and Safety Analysis of SFRs (SFR-UAM)

Rimpault, G.; Buiron, L.; Stauff, N. E.; Kim, T. K.; Taiwo, T. A.; Lee, Y.-K.; Zwermann, W.; Bostelmann, F.; Velkov, K.; Guilliard, N.; Fridman, E.; Kereszturi, A.; Batki, B.; Kodeli, I.-A.; Mikityuk, K.; Lopez, R.; Gomez, A.; Puente-Espel, F.; Del Valle, E.; Peregudov, A.; Semenov, M.; Manturov, G.; Abramova, M.; Trivedi, I.; Ivanov, K.; Pautz, A.; Yamaji, A.; Hill, I.; Ivanova, T.
An OECD/NEA sub-group on Uncertainty Analysis in Modelling (UAM) for Design, Operation and Safety Analysis of Sodium-cooled Fast Reactors (SFR-UAM) has been formed under the NSC/WPRS/EGUAM to check the use of best-estimate codes and data. This work comes from the desire to design reactors with improved safety performance while preserving a sustainable source of energy at a rather low cost.
Two SFR cores are being studied: a large 3600MWth oxide core and a medium 1000MWth metallic core. In order to assess tools being used for studying these cores, various sub-exercises have been set up for what concerns neutronics with cell, sub-assembly, super-cell and core benchmarks under steady state conditions either at BOL conditions or at EOEC. A sub-assembly depletion benchmark is being set up before going into full core calculations with depletion.
Since the objective is to define the grace period or the margin to melting available in the different accident scenarios and this within uncertainty margins, uncertainties of different origins (methods, neutronics, thermal-hydraulic, fuel behavior) once identified and evaluated will be propagated through.
In order to ensure validity to these exercises, the sub-group incorporates some experimental validations on neutronics, thermal hydraulics, fuels and systems. This will be done with experiments from IRPhE & ICSBEP, SEFOR, THORS and the SUPER-PHENIX start-up transient programme.
  • Contribution to proceedings
    ANS Best Estimate Plus Uncertainty International Conference (BEPU 2018), 13.-19.05.2018, Lucca, Italy
    BEPU2018-253

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Permalink: https://www.hzdr.de/publications/Publ-27064
Publ.-Id: 27064


Von Mäusen und Menschen - Abschätzung der internen Strahlenexposition neuartiger Radiotracer unter Nutzung eines Kleintier-PET/MRT

Kranz, M.; Sattler, B.; Deuther-Conrad, W.; Patt, M.; Schildan, A.; Patt, J.; Tiepolt, S.; Wilke, S.; Smits, R.; Hoepping, A.; Fischer, S.; Wünsch, B.; Steinbach, J.; Brust, P.; Sabri, O.
Ziel: Bei der Translation neuartiger Radiotracer in die klinische Phase ist eine Abschätzung der Strahlenexposition vor Erstanwendung am Menschen notwendig. Hierbei werden die Organdosen (OD) sowie die effektive Dosis (ED) am Tiermodell abgeschätzt, welche nach i.v. Injektion eines Radiotracers entstehen. Erstmalig wurde Kleintier-PET/MRT zur rein bildgebungsbasierten Inkorporationsdosimetrie mit CD-1 Mäusen eingesetzt. Um den Einfluss von Speziesunterschieden zu untersuchen wurden PET/CT-Studien an Ferkeln durchgeführt und die Ergebnisse mit am Menschen erhobenen Ergebnissen (PET/CT) verglichen.
Methodik: Nach i.v. Injektion von (-)- oder (+)-[18F]Flubatine (a, b) bzw. (S)- oder (R)-[18F]Fluspidine (c,d) wurden (i) In-vivo-PET/MRT- (MEDISO nanoScan, Budapest) und PET/CT-Scans (SIEMENS Biograph 16) bis zu 7 h p.i. durchgeführt, die List-Mode Daten unter Nutzung der Standardkorrekturen rekonstruiert und die Organaktivitäten (OA) mit ROVER (ABX, Radeberg) bestimmt; (ii) (a, c, d) Ex-vivo-Organentnahme an Mäusen und Messung der OA in einem Gammacounter durchgeführt (Goldstandard). Nach Extrapolation der Tierdaten auf menschliche Verhältnisse, wurden die OD und die ED mit OLINDA für 3 Spezies berechnet.
Ergebnisse: Die Dosimetrie für a/b ergab eine ED (µSv/MBq) von 12,5/12,1 (30 Mäuse), 13,4/14,3 (8 Ferkel), 22,3/23,0 (n=6 Menschen) und für (c/d) 12,9/14,0 (6 Mäuse), 21,0/n.a. (4 Menschen). Während a und b eine vergleichbare Biokinetik sowie ED zeigen, ist die ED von c und d signifikant (p=0,025) verschieden basierend auf Enantiomeren Unterschieden. Weiterhin zeigt sich eine Unterschätzung der ED erhoben mit Tierdaten im Vergleich zum Menschen von 38% (Ferkel) bis 47% (Mäuse).
Schlussfolgerung: Die Strahlenexposition nach i.v. Applikation von a,b,c,d liegt im Bereich der durch andere F-18-markierter Radiotracer. Die Abschätzung der ED unter Nutzung von Tiermodellen mit Hilfe eines Kleintier-PET/MRT ist unter Berücksichtigung der genannten Limitationen möglich und liefert mit dem Ex-vivo-Goldstandard vergleichbare Ergebnisse.
  • Lecture (Conference)
    56. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 18.-21.04.2018, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2018), V161

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Permalink: https://www.hzdr.de/publications/Publ-27063
Publ.-Id: 27063


Underground Nuclear Astrophysics in 2017 at LUNA, LUNA-MV, and Felsenkeller

Bemmerer, D.
The state of the art of underground nuclear astrophysics is reviewed. Starting from recent progress on hydrogen burning and Big Bang nucleosynthesis at LUNA, the upcoming new underground accelerators LUNA-MV and Felsenkeller are discussed.
Keywords: Nuclear Astrophysics underground; LUNA; Felsenkeller
  • Invited lecture (Conferences)
    Strategietreffen "Astroteilchenphysik in Deutschland", 07.-08.12.2017, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27062
Publ.-Id: 27062


Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller

Bemmerer, D.
Strahlenschutzaspekte beim neuen Beschleunigerlabor im Dresdner Felsenkeller. Zusätzlich zum klassischen Strahlenschutz am 5 MV Ionenbeschleuniger im Felsenkeller wird auch die Low-Background-Problematik unter Tage diskutiert.
  • Invited lecture (Conferences)
    TÜV Süd Akademie "Strahlenschutz in Medizin, Forschung und Industrie", 06.-07.12.2017, Marburg/Lahn, Deutschland
  • Invited lecture (Conferences)
    Webinar Deutsche Gesellschaft für Medizinische Physik, 24.05.2018, Gießen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27061
Publ.-Id: 27061


Nuclear Astrophysics Basics II

Bemmerer, D.
Carbon-nitrogen-oxygen cycle, nuclear cosmology, Felsenkeller underground accelerator
  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27060
Publ.-Id: 27060


Nuclear Astrophysics Basics I

Bemmerer, D.
Nuclear Astrophysics Basics I: Cross Section, Gamow Peak, Thermonuclear Reaction Rate, and the Sun.
  • Invited lecture (Conferences)
    Lecture Week on Nuclear Structure and Nuclear Astrophysics, 04.-05.12.2017, Zell / Mosel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27059
Publ.-Id: 27059


Attempts to understand potential deficiencies in chemical procedures for AMS

Merchel, S.ORC; Gurlit, S.; Opel, T.; Rugel, G.; Scharf, A.; Tiessen, C.; Weiß, S.; Wetterich, S.
A major research focus of the DREsden Accelerator Mass Spectrometry (DREAMS) facility is sample preparation: in-house and at cooperating laboratories. Besides routine applications, developments are mainly driven by the users' demands such as "new" radionuclides (e.g. short-lived 7Be), radionuclides from new matrices or in larger sample amounts and at lower concentrations. Within the chemical preparation of BeO for 7,10Be, Al2O3 for 26Al, AgCl for 36Cl, and Fe2O3 for 60Fe and actinide AMS targets, we investigated and improved mostly particular steps: For oxide preparation alteration for several hours and two-times rinsing of hydroxides is recommended, especially for Be(OH)2 and Al(OH)3, to prevent losses in the final preparation steps. Rinsing of freshly precipitated hydroxides can yield to losses as high as 31%. For Al(OH)3 rinsing with H2O (pH5) instead of pH8-9 is recommended for further reducing redissolving. For 60Fe and coprecipitated actinides (the latter tested by U6+ and Er3+), rinsing of overnight-altered Fe(OH)3, yield to 2.6-3.5% losses. The depletion of the isobar 7Li for (7)BeO is easily gained by hydroxide precipitation and rinsing. The quality of BeO and Al2O3 AMS targets can be monitored and improved (e.g. by using larger ion exchanger columns) by using the so-called "quality factor", which is the current of the stable nuclide (9Be or 27Al), normalised to the current of the standard of the same batch. Finally, there is a high potential for ion exchange as a pre-enrichment tool for Cl for large ice samples containing low natCl concentrations and low absolute amounts of natCl.
Keywords: accelerator mass spectrometry, 10Be, 26Al, 36Cl, 60Fe, cosmogenic nuclides

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Permalink: https://www.hzdr.de/publications/Publ-27058
Publ.-Id: 27058


Invenio-Uploadbyurl - background uploads via SFTP and HTTP protocol for Invenio

Frust, T.
A lot of HZDR research data is already located on one of the storage systems in a data center. For those data there are better ways transfering them to Rodare than using an HTTP web upload. This module for Invenio allows you to browse all the files that reside on registered storage systems accessible via the SFTP protocol. They are transferred to the Invenio using SFTP in a background job.
Keywords: SFTP; Invenio; RODARE; Background upload
  • Software in external data repository
    Publication year 2018
    Programming language: Python 3
    System requirements: Python 3, SFTP, Paramiko, Celery, Invenio
    License: GPLv3 (Link to license text)
    Hosted on HZDR GitLab: Link to location

Permalink: https://www.hzdr.de/publications/Publ-27057
Publ.-Id: 27057


Gold transport in hydrothermal chloride-bearing fluids: Insights from in situ x-ray absorption spectroscopy and ab initio molecular dynamics

Tagirov, B. R.; Trigub, A. L.; Filimonova, O. N.; Kvashnina, K. O.; Nickolsky, M. S.; Lafuerza, S.; Chareev, D. A.
Chloride-bearing fluids are widespread in the Earth's interior from low-temperature subsurface conditions to deep lithosphere. The concentration of chloride salts varies from diluted aqueous solutions to concentrated brines and anhydrous (dry) chloride melts beneath volcanoes. Here we report an investigation of the state of Au in hydrothermal chloride fluids and anhydrous melts by means of in situ X-ray absorption spectroscopy combined with ab initio molecular dynamics simulations and thermodynamic modeling. The experiments included registration of Au L 3 -edge X-ray absorption near edge structure/extended X-ray absorption fine structure spectra of Au-bearing fluids in the temperature range from 350 to 575 °C at pressures of 150-4500 bar. Spectra of Au dissolved in dry CsCl/NaCl/KCl + K 2 S 2 O 8 melt were recorded at 650 °C. It was found that Au is coordinated by two Cl atoms (R Au-Cl = 2.25-2.28 Å). The alkali metal atoms (Me) were detected in the distant coordination sphere of Au at R Au-Me = 3.3-4.1 Å. The alkali metal cations in the vicinity of Au-Cl complex partly compensate the positive charge located on Au and, by this way, affect the Au-Cl distance. An increase of the fluid pressure causes expansion of the second coordination sphere composed of the alkali metal cations, which leads to the increase of the positive Au charge and results in slight contraction of the first coordination sphere of Au. Accordingly, the transport of Au in high-temperature chloride-bearing natural ore-forming fluids of moderate to high densities (>0.3 g·cm -3 ) can be explicitly described by the formation of the AuCl 2 - at any salt concentration from low-salinity fluids to hydrosaline liquids and anhydrous melts. In general, this means that the hydrothermal fluid chemistry simplifies with increasing temperature.

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Permalink: https://www.hzdr.de/publications/Publ-27056
Publ.-Id: 27056


Using XFELs to Probe Kilotesla Magnetic Fields inside Solid Density Plasmas Driven by Optical High Power Lasers

Huang, L. G.; Schlenvoigt, H.-P.; Takebe, H.; Cowan, T. E.
The relativistic laser matter interaction is a complex interplay of ionization, extreme current densities, rapidly evolving strong fields and acceleration processes. Understanding the interaction physics is a challenging but highly rewarding endeavor. The unprecedented brightness of XFELs opens a new window for discovering the interior of solid-density plasmas created by relativistic laser interactions with matter, resolving the relevant femtosecond and sub-micrometer scales experimentally.
Here, we focus on discussing the feasibility of probing the magnetic fields by X-Ray polarimetry via Faraday rotation using XFEls.
Keywords: laser,plasmas, magnetic fields,faraday rotation,xfel
  • Poster
    European XFEL Users' Meeting 2018, 23.-26.01.2018, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-27055
Publ.-Id: 27055


Quasifree (p,2p) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

Atar, L.; Paschalis, S.; Barbieri, C.; Bertulani, C. A.; Díaz Fernández, P.; Holl, M.; Najafi, M. A.; Panin, V.; Alvarez-Pol, H.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Galaviz Redondo, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Kahlbow, J.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec-Gałązka, J.; Movsesyan, A.; Nacher, E.; Nikolskii, E. Y.; Nilsson, T.; Nociforo, C.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D. M.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G. L.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.
Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the
R3B/LAND setup with incident beam energies in the range of 300–450 MeV/u. The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type AO(p,2p)A−1N have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry

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Publ.-Id: 27054


Femtosecond laser-generated high-energydensity states studied by x-ray FELs

Nakatsutsumi, M.; Appel, K.; Baehtz, C.; Chen, B.; Cowan, T. E.; Göde, S.; Konopkova, Z.; Pelka, A.; Priebe, G.; Schmidt, A.; Sukharnikov, K.; Thorpe, I.; Tschentscher, T.; Zastrau, U.
The combination of powerful optical lasers and an x-ray free-electron laser (XFEL) provides unique capabilities to study the transient behaviour of matter in extreme conditions. The high energy density science instrument (HED instrument) at the European XFEL will provide the experimental platform on which an unique x-ray source can be combined with various types of high-power optical lasers. In this paper, we highlight selected scientific examples together with the associated x-ray techniques, with particular emphasis on femtosecond (fs)-timescale pump–probe experiments. Subsequently, we present the current design status of the HED instrument, outlining how the experiments could be performed. First user experiments will start at the beginning of 2018, after which various optical lasers will be commissioned and made available to the international scientific community.
Keywords: x-ray free-electron laser, femtosecond dynamics, relativistic plasma, high-energydensity state

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Publ.-Id: 27053


Isothermal differential dilatometry based on X-ray analysis applied to stress relaxation in thin ion-beam-sputtered Pt films

Gruber, W.; Baehtz, C.; Geue, T.; Stahn, J.; Schmidt, H.
Relaxation of stress and point defects in ion-beam-sputtered Pt films with a thickness of 20 and 40 nm during isothermal annealing was investigated. First, isothermal differential dilatometry measurements based on X-ray analysis were carried out between 130 and 400 °C. They show that the relaxation of compressive stress is associated with the formation of vacancies at the surface. From the measurements, an activation enthalpy of 0.14 eV was estimated for the stress relaxation process. In addition, self-diffusion experiments of Pt were carried out on the same type of films using stable 194Pt tracer. From secondary ion mass spectrometry on samples annealed for longer times, an activation enthalpy of 0.5 eV for Pt diffusion in grain boundaries was estimated. The influence of vacancy creation at the surface, vacancy transport, and the annihilation of nonequilibrium
bulk interstitials and thermally created vacancies on stress relaxation is discussed.
Keywords: Thin films, Synchrotron, X-ray diffraction, ion-beam-sputtering

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Publ.-Id: 27052


Non-Reciprocal Spin-Wave Emission from Topological Spin Textures

Schneider, T.; Sluka, V.; Kakay, A.; Weigand, M.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.; Wintz, S.
Investigations of spin waves are of great interest for both fundamental science and applications. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths or to generate such spin waves parametrically.
Here, we will show a combined experimental and theoretical study of spin waves in a stacked vortex pair system formed in a NiFe/Ru/CoFeB trilayer. The magnetization dynamics was imaged by means of time-resolved scanning transmission x-ray microscopy (STXM). Thereby, two different spin wave regimes were identified. For excitation frequencies above 500 MHz, mainly 2D plane waves within the magnetic domains were observed. However, a transition from 2D to 1D wave transport occurs for excitation frequencies below 500 MHz. In this case almost no spin waves were detected within the domains but high amplitudes were found within the 180° domain walls. An analytic and numerical analysis was done for both regimes, resulting in both a qualitative and quantitative understanding of the finite frequency gap in the spin wave dispersion relation for the ferromagnetic domains. Moreover, the dispersion relation was found to exhibit a strong non-reciprocity.
Keywords: Spin-wave, non-reciprocity, spin textures
  • Lecture (Conference)
    APS March Meeting 2018, 05.-09.03.2018, Los Angeles, USA

Permalink: https://www.hzdr.de/publications/Publ-27051
Publ.-Id: 27051


Chiral-partner D mesons in a heat bath within QCD sum rules

Buchheim, T.; Hilger, T.; Kämpfer, B.; Leupold, S.
Utilizing QCD sum rules, we extract the temperature dependences of the spectral properties of the pseudo-scalar and scalar D mesons regarded as chiral partners. Besides the masses also decay constants are analyzed as the D meson yields in heavy-ion collisions may be sensitive to their altered decay properties in an ambient strongly interacting medium. Our findings are (i) a decreasing scalar D meson mass for growing temperatures while its pseudo-scalar partner meson seems hardly affected, which is in qualitative agreement with hadronic model calculations; (ii) inferring an equally weak temperature dependence of the pseudo-scalar D meson decay properties the decreasing residua and decay constants of the scalar particle point towards partial chiral restoration. As a bonus of our analysis in the pseudo-scalar sector we determine the pseudo-scalar decay constant at vanishing temperature. Due to the connection to particular leptonic branching fractions this decay constant is of great interest allowing for the determination of the off-diagonal CKM matrix element |Vcd| at zero temperature.

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Permalink: https://www.hzdr.de/publications/Publ-27050
Publ.-Id: 27050


Assisted Vacuum Decay by Time Dependent Electric Fields

Otto, A.; Oppitz, H.; Kämpfer, B.
We consider the vacuum decay by electron-positron pair production in spatially homogeneous, time dependent electric fields by means of quantum kinetic equations. Our focus is on the impact of various pulse shapes as envelopes of oscillating fields and the assistance effects in multi-scale fields, which are also seen in photons accompanying the creation and motion of pairs.

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Permalink: https://www.hzdr.de/publications/Publ-27049
Publ.-Id: 27049


Characteristics of large-scale structures in turbulent Rayleigh-Benard convection in a liquid metal layer

Yanagisawa, T.; Akashi, M.; Tasaka, Y.; Murai, Y.; Vogt, T.; Eckert, S.
We performed laboratory experiments on Rayleigh-Benard convection with a liquid metal in a square box geometry having an aspect ratio five. Horizontal velocity profiles of convective flow were measured at several lines by using ultrasonic velocity profiling. By combining the information from profiles, we can reconstruct organized large-scale flow structures with turbulent fluctuations. Systematic variation of the structure was detected with increasing the Rayleigh number (Ra) from 10^4 to 10^5; a quasi-two-dimensional roll changes to a cell having a relatively larger horizontal scale. In addition, we found that the large-scale structure, whether it is roll or cell, show quasi-periodic oscillation whose representative period is approximately same as the circulation time of the large-scale flow. We also performed numerical simulations of convection with the same geometry as our experiments by setting a small Prandtl number (Pr=0.025) like a liquid metal. Quantitative comparison on the velocity profiles between experiments and simulations provided quite satisfactory agreement, and we analyzed the whole structure of the flow and the style of oscillation in detail based on the result of simulation. By integrating results from experiments and simulations, we propose a scaling low on the Ra dependence of horizontal size of large-scale flow structure, and estimate an enlarged value of effective momentum diffusivity by turbulence in a low Pr convection.
  • Lecture (Conference)
    11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD 11), 05.-07.09.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27047
Publ.-Id: 27047


Large scale structures of a turbulent Rayleigh-Bénard convection in a liquid metal layer confined by a moderate aspect ratio box

Akashi, M.; Tasaka, Y.; Yanagisawa, T.; Murai, Y.; Vogt, T.; Eckert, S.
We report laboratory experiments of Rayleigh-Bénard convection with a liquid metal, Prandtl number Pr = 0.03, in a rectangular cell with a moderate aspect ratio. Rayleigh number, Ra, was set at a range from 7.9 × 10^3 to 3.5 × 10^5 at which the thermal turbulence regime is expected. Multiple horizontal velocity profiles in the fluid layer by ultrasonic velocity profiling elucidated formations of several large scale flow structures with periodic oscillations. The flow structure has transitions as increasing Ra from a quasi-two-dimensional roll-like structure to a three-dimensional cell-like structure via unstable intermediate regimes with stepwise increase of its horizontal scale. By using observed Ra dependences of the frequency of oscillation and the velocity of large scale flow, we made up a model to explain the increase of horizontal scale. We evaluated effective viscosities and diffusivities based on the turbulent fluctuations, and found that the morphology of roll-like structure can be understood by using these effective values.
  • Lecture (Conference)
    The 70th Annual Meeting of the American Physical Society Division of Fluid Dynamics, 20.11.2017, Denver, USA

Permalink: https://www.hzdr.de/publications/Publ-27046
Publ.-Id: 27046


High-resolution patterning of germanium for nanoelectronics applications

Gangnaik, A. S.; Khan, M. B.; Ghamsari, S. J.; Rebohle, L.; Erbe, A.; Holmes, J. D.; Georgiev, Y. M.ORC
Ge is among the most attractive alternative channel materials for the next-generation nanoelectronics. However, Ge patterning with electron beam lithography (EBL) using the negative resist HSQ is challenging. The complex native oxide GeOx is soluble in the HSQ aqueous developers. As a result, lift-off of sub-20 nm features written by EBL occurs during development. In the presentation, it will be shown that this issue can be solved by: (i) removal of GeOx and passivation of Ge surface prior to HSQ deposition or (ii) application of a buffer layer between GeOx and HSQ. Arrays of sub-20 nm HSQ lines were successfully fabricated on Ge with both approaches. Moreover, a significantly simplified process for removal of GeOx and passivation of Ge surface will also be presented, which allows patterning of 6-7 nm Ge NWs, the smallest Ge nanostructures reported to date.

Finally, different applications of the above mentioned patterning processes will be discussed.
Keywords: Germanium, nanowires, nanoelectronics, electron beam lithography
  • Lecture (Conference)
    DPG Spring Meeting 2018 in Berlin, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27045
Publ.-Id: 27045


Technology for fabrication of suspended sub-5 nm silicon nanowires and applications thereafter

Petkov, N.; Georgiev, Y. M.ORC
Si nanowires (Si NWs) are very promising as channels for field effect transistors (FETs) and also as sensing devices. When the NW diameter is in the sub-10 nm range, quantum confinement of carriers is observed at room temperature, which is very appealing from scientific and application point of view.

This paper will present a technology for fabrication of sub-5 nm suspended Si NWs on silicon-on-insulator wafers. News of 20 nm width are first defined in the top Si layer by electron beam lithography and reactive ion etching. Then the NWs are subjected to three consecutive cycles of rapid thermal oxidation in oxygen atmosphere and wet etching in hydrofluoric acid. The resulting suspended Si NWs have high-quality crystalline structure and sub-5 nm size.

The possible applications of such NWs will be discussed, including FET-based Si NW chemo-/biosensors as well as gate all around (GAA) FETs. Additionally, the development of self-aligned nickel silicide NW contacts will be presented. The formation mechanism was examined by in-situ electron microscopy as a function of NW diameter and surface oxide.
Keywords: Silicon nanowires, field effect transistors (FETs), nanowire sensors, silicon-on-insulator, nickel silicide, electron beam lithography
  • Lecture (Conference)
    DPG Spring Meeting 2018 in Berlin, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27044
Publ.-Id: 27044


New Heterodinuclear Zn/Ln (Ln = Gd, Tb, Er, Yb) Complexes of Hexadentate N,N'-Bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamines: Synthesis and Structure

Kelly, N.; Schnaars, K.; Gloe, K.; Doert, T.; Weigand, J. J.; Gloe, K.
Two N,N′-bis(3-alkoxy-2-hydroxybenzyl)cyclohexane-1,2-diamine proligands, H₂L¹ (R = OCH₃) and H₂L² (R = OC₂H₅), and five heterodinuclear Znᴵᴵ/Lnᴵᴵᴵ complexes, [Zn(L)(µ-CH₃COO)Ln(NO₃)₂], containing [L¹]²⁻ and Gd³⁺, Tb³⁺, Er³⁺, or Yb³⁺ and [L²]²⁻ and Yb³⁺ have been synthesised and structurally characterised. The complexes are isostructural and crystallise in the P2₁/n monoclinic space group. Zinc(II) is coordinated by the inner N₂O₂ donor set of the ligand and an oxygen of the bridging acetate anion; the lanthanide(III) ions possess an O₉ coordination environment involving the interaction with the ligand’s outer O₄ donor set, two bidentate nitrate ions, and the bridging acetate.

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Permalink: https://www.hzdr.de/publications/Publ-27043
Publ.-Id: 27043


Investigation of heavy metal release at a municipal solid waste incineration facility - an excellent example for the unique potential of intrinsic radiotracer application to the investigation of industrial processes in chemical engineering

Jentsch, T. B. O.
Radiotracers are widespread in use for investigation of material transport processes in industry and environment. Often they are used for the measurement of the residence time distribution in continuously operating chemical engineering facilities and reactors. Mostly intrinsic or physical tracers are used for these purposes.

In case of phase transformation processes are in the focus of interest physical or extrinsic tracers are not the labelling material of choice. Intrinsic or chemical tracers are required in that case.

At example of the heavy metal release investigation at a municipal solid waste incineration facility the unique potential of intrinsic radiotracers will be demonstrated in the given paper.

Goal of the investigation at the municipal solid waste incineration facility reported in this paper was the behaviour study of different heavy metal species at various incineration conditions. With the help of short lived radioisotopes of copper (Cu-64) and zinc (Zn-69m) could be shown at which position of the incinerator and in which amount the heavy metal under investigation was released.

The experimental results of this investigation were an essential contribution for better understanding the processes inside the incinerator and to optimize the processing conditions.
Keywords: heavy metal release, radiotracer, municipal solid waste incineration, copper-64, zinc-69m
  • Lecture (Conference)
    ICARST 2017 - International Conference on Applications of Radiation Science and Technology, 24.-28.04.2017, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-27039
Publ.-Id: 27039


PO-0619: Comparison of a nanoString and RNA microarray gene signature predicting LRC after PORT-C in HNSCC

Schmidt, S.; Linge, A.; Zwanenburg, A.; Leger, S.; Lohaus, F.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Belka, C.; Combs, S. E.; Mönnich, D.; Zips, D.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.; Löck, S.
A gene signature predicting loco-regional control (LRC) of locally advanced head and neck squamous cell carcinoma (HNSCC) after postoperative radiochemotherapy (PORTC) will be evaluated using nanoString and RNA microarray data. The prognostic power of the signature as well as the correlation between both methods is evaluated to underline the robustness of the proposed signature.

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Permalink: https://www.hzdr.de/publications/Publ-27038
Publ.-Id: 27038


Pencil beam scanning treatments in free-breathing lung cancer patients–is 5 mm motion a limit?

Jakobi, A.; Perrin, R.; Knopf, A.; Richter, C.
To evaluate the dose degradation when treating lung cancer patie nts with proton pencil beam scanning during free-breathing. We assess if treatments without rescanning are feasible in order to avoid prolonged treatment time, especially for slow scanning facilities.

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Permalink: https://www.hzdr.de/publications/Publ-27034
Publ.-Id: 27034


High-precision radiotherapy–Do we need better pre-treatment CT imaging?

Greilich, S.; Richter, C.
Computed tomography (CT) images from fan-beam medical grade scanners are the current gold standard for treatment planning in radiation oncology: they provide geometrically correct, reliable, and quantitative measures of photon attenuation in the patient. However, this information is not fully identical with the physical quantities needed for dose calculation and optimization and additional uncertainty is introduced by inferring them from the kV images. Also, the low soft tissue contrast in CT impacts delineation accuracy. While additional Imaging modalities are advocated as complementary – sometimes alternative – techniques to CT imaging, uncertainties in image registration can even deteriorate the quality of treatment planning. Dual-energy CT – i.e. using scans from two X-ray spectra or detection in two separate energy ranges – retains the virtues of computed tomography while it opens at the same time the possibility to overcome the restrictions mentioned. It can improve the accuracy of dose calculation and delineation and enables to abandon the use of a general translation rule (“Hounsfield look-up table”) for the photon attenuation (CT numbers) - replacing it by a patient-specific determination of radiological tissue quantities. DECT-derived quantities might additionally provide opportunities in advanced image analysis methods such as radiomics, i.e. the machine-learning-based approach for the prediction of patient outcome and treatment personalization. CT-based radiomics analyses might even be able to uncover information that can so far only be derived from additional multi-modal imaging. Currently, many applications based on innovations in pre-treatment CT imaging and image analysis are investigated that could have the potential to change clinical practice in future. This presentation is intended to set the stage for the focus session which tries to look into the question, which of These applications can find its way into routine clinical application.
  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017), S292-S297
    DOI: 10.1515/bmt-2017-5057

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Permalink: https://www.hzdr.de/publications/Publ-27032
Publ.-Id: 27032


PO-0819: Robustness evaluation of single-and multifield optimized proton plans for unilateral head and neck.

Cubillos-Mesías, M.; Baumann, M.; Troost, E. G. C.; Appold, S.; Krause, M.; Richter, C.; Stützer, K.
To compare 4 different proton pencil beam scanning (PBS) treatment approaches for unilateral head and neck cancer (HNC) targets in terms of robustness, including anatomical changes during the treatment course.

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Permalink: https://www.hzdr.de/publications/Publ-27030
Publ.-Id: 27030


Modeling patterns of anatomical deformations in prostate patients undergoing radiation therapy with an endorectal ballon

Brion, E.; Richter, C.; Macq, B.; Stützer, K.; Exner, F.; Troost, E.; Hölscher, T.; Bondar, L.
External beam radiation therapy (EBRT) treats cancer by delivering daily fractions of radiation to a target volume. For prostate cancer, the target undergoes day-to-day variations in position, volume, and shape. For stereotactic photon and for proton EBRT, endorectal balloons (ERBs) can be used to limit variations. To date, patterns of non-rigid variations for patients with ERB have not been modeled. We extracted and modeled the patient-specific patterns of variations, using regularly acquired CT-images, non-rigid point cloud registration, and principal component analysis (PCA). For each patient, a non-rigid point-set registration method, called Coherent Point Drift, (CPD) was used to automatically generate landmark correspondences between all target shapes. To ensure accurate registrations, we tested and validated CPD by identifying parameter values leading to the smallest registration errors (surface matching error 0.13±0.09 mm). PCA demonstrated that 88±3.2% of the target motion could be explained using only 4 principal modes. The most dominant component of target motion is a squeezing and stretching in the anterior-posterior and superior-inferior directions. A PCA model of daily landmark displacements, generated using 6 to 10 CT-scans, could explain well the target motion for the CT-scans not included in the model (modeling error decreased from 1.83±0.8 mm for 6 CT-scans to 1.6±0.7 mm for 10 CT-scans). PCA modeling error was smaller than the naive approximation by the mean shape (approximation error 2.66±0.59 mm). Future work will investigate the use of the PCA-model to improve the accuracy of EBRT techniques that are highly susceptible to anatomical variations such as, proton therapy.
  • Abstract in refereed journal
    Proceedings of SPIE 10135(2017), 1013506
    DOI: 10.1117/12.2251933

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Permalink: https://www.hzdr.de/publications/Publ-27028
Publ.-Id: 27028


Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen,

Bailey, D. L.; Pichler, B. J.; Gückel, B.; Antoch, G.; Barthel, H.; Bhujwalla, Z. M.; Biskup, S.; Biswal, S.; Bitzer, M.; Boellaard, R.; Braren, R. F.; Brendle, C.; Brindle, K.; Chiti, A.; La Fougère, C.; Gillies, R.; Goh, V.; Goyen, M.; Hacker, M.; Heukamp, L.; Knudsen, G. M.; Krackhardt, A. M.; Law, I.; Morris, J. C.; Nikolaou, K.; Nuyts, J.; Ordonez, A. A.; Pantel, K.; Quick, H. H.; Riklund, K.; Sabri, O.; Sattler, B.; Troost, E.; Zaiss, M.; Zender, L.; Beyer, T.
The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

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Permalink: https://www.hzdr.de/publications/Publ-27024
Publ.-Id: 27024


Atomistic Simulation of Interface-Driven Self-Alignment of Si-SiO2 Nanostructures

Prüfer, T.; Heinig, K. H.; Möller, W.; von Borany, J.
Si nanostructures are very promising candidates for optical and electrical applications. Charged nanocluster can be used for data storage [2]; their discrete energy levels can be used for logic operations; sponge nanostructures can be used as the ion conductor in fuel cells. The size-dependency of their energy levels makes them interesting for application in colour displays.
Among a lot of other methods to synthesize nanoclusters or sponges we present an approach which allows a selfalignment of nanostructures at an interface. The basic idea is to bring together Si, SiO2 and SiOx and anneal it to cause phase separation of SiOx. The interfaces between Si/SiOx and SiOx/SiO2 act as driving forces for the selfalignment of the separated Si and SiO2. To create SiOx we consider 2 processes: (i) Deposition of SiOx films by PVD or CVD and (ii) Ion beam Mixing of Si/SiO2 interfaces.
By PVD it’s possible to create arbitrary shapes of Si/SiO2/SiOx layerstacks. The subsequent annealing causes different effects at the interface. Mainly depending on the structure of the layerstack, but also on the annealing time, different reaction pathways can be observed. The system can end up with different numbers of cluster layers or sponge structures, aligned parallel to the interface. Here we show how and why it is possible to control the sizes, densities and distances of these structures.
The ion irradiation through a Si/SiO2 interface causes mixing of both phases and transforms the interface into SiOx.
This method is not that flexible as PVD, but it’s easier to be implemented into common industrial technologies, like the production of CMOS compatible devices. The reformation of the Si/SiO2 interface during heat treatment is again acting as a driving force for the self-alignment and forms a zone between the interface and the resulting nanostructures which is denuded of excess Si. In this case, sizes and density can be controlled by irradiation and annealing parameters.
Earlier studies [1] have proven the reliability of dot formations using ion beam mixing technologies for application as memories [2]. Here, we show simulation results for the formation of Si nanostructures at interfaces in layerstacks of Si, SiOx, SiO2 and basic principles of the driving forces for this kind of self-alignment. Computer simulations using the binary collision approximation (TRIDYN [3]) and the kinetic monte carlo method [4] are employed to subsequently describe the ion irradiation and annealing processes, respectively.
This part of the work is being funded by the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 688072 (Project IONS4SET).
[1] T. Müller et al., Appl. Phys. Lett. 81 (2002) 3049; ibid. 85 (2004) 2373.
[2] K.H. Heinig et al., Appl. Phys. A77 (2003)17.
[3] W. Möller, W. Eckstein, Nucl. Instr. and Meth. in Phys. Res. B2 (1984) 814
[4] M. Strobel et al., Phys. Rev. B64 (2001)245422.
  • Lecture (Conference)
    Material Research Society Fall Meeting 2017, 26.11.-01.12.2017, Boston, United States of America

Permalink: https://www.hzdr.de/publications/Publ-27018
Publ.-Id: 27018


WTZ Russland - Transientenanalysen für schnelle Reaktoren

Kliem, S.ORC; Nikitin, E.; Rachamin, R.; Glivici-Cotruta, V.
Der Reaktordynamikcode DYN3D wird für Kernanalysen von Natrium-gekühlten schnellen Reaktoren (SFR) erweitert. In diesem Bericht werden neu implementierte thermomechanische Modelle für die adäquate Simulation von SFR-Transienten beschrieben, die die Simulation der axialen Wärmeausdehnung von Brennstäben und die radiale Ausdehnung des Reaktorkerns umfassen. Darüber hinaus wurde das Verfahren zur Erstellung von Querschnittsbibliotheken für DYN3D für SFR-Analysen erweitert. Die Verifizierung der neuen Modelle und der Querschnittserstellung erfolgte auf Vollkern-Ebene mit stationären Experimenten von der BFS-Testanlage des IPPE Obninsk und Daten des großen oxidischen Kerns des OECD/NEA-Benchmark und den Experimenten zum Zyklusende des Phenix-Kerns. Die DYN3D-Ergebnisse wurden mit der Monte-Carlo-Referenzlösung verglichen, die durch den SERPENT-Code berechnet wurde. Die Testergebnisse zeigen, dass die neu entwickelten Modelle die Wärmeausdeh-nungseffekte der Kernstruktur genau berücksichtigen können. Das neu entwickelte Verfahren zur Erstellung von Querschnittsbibliotheken wurde ebenfalls auf der Basis von SERPENT-Ergebnissen erfolgreich verifiziert. Zur Validierung wurden mehrere Tests, die sowohl stationäre als auch transiente Fälle aus den Phenix-Experimenten enthalten, mit DYN3D berechnet. Die DYN3D-Lösungen weisen eine gute Übereinstimmung mit den experimentellen Daten auf, was die Anwendbarkeit der Codes für Kernanalysen von Natrium-gekühlten schnellen Reaktoren bestätigt.
Keywords: DYN3D, SERPENT, Natrium gekühlter Reaktor, thermomechanische Modelle, Validierung
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-086 2018
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-27016
Publ.-Id: 27016


Process Simulation of Single Si Quantum Dot Formation for Single Electron Transistors

Prüfer, T.; Heinig, K. H.; Möller, W.; Hlawacek, G.; Xu, X.; Friedlund, C.; Djurabekova, F.; von Borany, J.
Conventional Lithography allows the fabrication of structures down to ~10 nm, being still too large for single electron transistors (SET) operating at room temperature (RT), which requires a tiny quantum dot (<5nm) embedded in SiO2, with tunnel distances to the source and drain <2nm. Here, we predict a fully CMOS-compatible method of self-assembly of a single Si quantum dot. We assume that 10…20nm thin nanopillars of a layer stack c-Si/6nm SiO2/30nm a-Si are made by conventional lithography. We predict that such a single dot is self-organized and self-assembled between the top and bottom silicon layer by phase separation of metastable SiOx. The SiOx is made by collisional mixing in the layer stack, which is simulated by TRI3DYN [1]. The phase separation of SiOx is described by 3D kinetic lattice Monte Carlo simulations [2]. Our results predict that a single Si nanodot forms if the volume of SiOx is smaller than (10nm)^3. This work has been funded by the European Union's Horizon 2020 research and innovation program under grant agreement No 688072.
[1] W. Möller; NIM B, 322, 23–33
[2] M. Strobel, K.H. Heinig, W. Möller, PRB 64, 245422
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27014
Publ.-Id: 27014


Influence of resistance and spin-torque bias dependence on the output power of MgO-based nano oscillators

Kowalska, E.; Fukushima, A.; Sluka, V.; Fowley, C.; Kákay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Yuasa, S.; Deac, A. M.
Spin-transfer torques (STTs) can be exploited in order to manipulate magnetic moments of nanomagnets, allowing for new consumer-oriented devices to be designed, such as tuneable radio-frequency spin-torque nano oscillators (STNOs) for wireless communication. Currently, the structure involving an MgO-based magnetic tunnel junction (MTJ) with hybrid geometry combining an IP reference layer and an out-of-plane free layer is the system of choice [1,2]. This configuration, Fig. 1a, maximizes the output power, reduces the critical current [3], and can allow for stable precession regardless of magnetic or applied current history [1,4,5].

Here, we experimentally observe an unusual curvature of the critical lines on the current-field phase diagram enclosing the region of steady-state dynamics (Fig. 2a) which has never been reported in similar metallic- or MTJ-based devices. Theoretically, we incorporate the angular dependence of the TMR (dRAP/dV) [6-8] and bias dependent spin-transfer torques [9-11] into the in-plane and the perpendicular STT and solve LLGS equation [12]. We find that the angular dependence of TMR introduces an asymmetry in the in-plane STT and gives rise to stable precession. Moreover, including the bias dependence of TMR (Fig. 1b) correctly reproduces the curvature of the dynamical region in the experimental phase diagram (Fig. 2b), gradually suppressing the induced asymmetry, and with it the output power. Therefore, the TMR ratio and its bias dependence are both equally crucial factors governing the performance of MTJ-based STNOs.
Keywords: STNO,MTJ,STT
  • Lecture (Conference)
    MMM 2017 - 62nd Annual Conference on Magnetism and Magnetic Materials, 06.-10.11.2017, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-27010
Publ.-Id: 27010


15 years of CW SRF operation at ELBE

Arnold, A.; Büchner, A.; Büttig, H.; Freitag, M.; Lehnert, U.; Michel, P.; Schneider, C.; Teichert, J.
ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. Although these cavities performed well in the vertical test, they were limited by field emission from the very beginning to about 10 MV/m each. The reason is still unknown, but several candidates are being discussed. The prime suspect is particle contamination during cleanroom and beamline assembly but also a mechanism that allows particles to migrate from far away towards the cavity over an extended period of time might be possible. And also outgassing EPDM gaskets that are installed in the entire accelerator are a candidate for deterioration. Nevertheless, to ensure a reliable user operation, the performance of the cavities is determined in regular intervals by Q vs. E measurements and by means of high power RF processing and complete thermal cycling the performance could be partially returned to an earlier state. With the contribution we try to summarize our experiences in operating a superconducting CW LINAC over the last 15 years in an unclassified and probably dirty environment.
Keywords: CW, SRF, operation, ELBE, cryomodule
  • Invited lecture (Conferences)
    Operating SRF systems reliably in a "dirty" accelerator, 14.-15.09.2017, Berlin, Deutschland
  • Invited lecture (Conferences)
    TESLA Technology Collaboration Meeting, 06.-09.02.2018, Mailand, Italien

Permalink: https://www.hzdr.de/publications/Publ-27009
Publ.-Id: 27009


Cancer stem cells: Radioresistance, prediction of radiotherapy outcome and specific targets for combined treatments.

Krause, M.; Dubrovska, A.; Linge, A.; Baumann, M.
Inactivation of cancer stem cells (CSCs) is of utmost importance for tumor cure after radiotherapy. An increasing body of evidence complies with a higher radioresistance of CSCs compared to the mass of tumor cells, supporting the use of CSC related biomarkers for prediction of radiotherapy outcome. Treatment individualization strategies for patient groups with vastly different risk of recurrence will most likely require application of more than one biomarker. Specifically, inclusion of established biomarkers like tumor size for primary radio(chemo)therapy or human papilloma virus (HPV) infection status in head and neck squamous cell carcinoma seems to be of very high relevance. The high heterogeneity of CSC subclones along with changes of the functional behavior of individual tumors under treatment underlines the importance of the selection of the optimal timepoint(s) of biomarker evaluation, but also provides a potential therapeutic target for combined treatment approaches with irradiation.

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Publ.-Id: 27005


PORTAF–postoperative radiotherapy of non-small cell lung cancer: accelerated versus conventional fractionation–study protocol for a randomized controlled trial

Bütof, R.; Simon, M.; Löck, S.; Troost, E.; Appold, S.; Krause, M.; Baumann, M.
BACKGROUND:

In early-stage non-small cell lung cancer (NSCLC) without affected lymph nodes detected at staging, surgical resection is still the mainstay of treatment. However, in patients with metastatic mediastinal lymph nodes (pN2) or non-radically resected primary tumors (R1/R2), postoperative radiotherapy (possibly combined with chemotherapy) is indicated. So far, investigations about time factors affecting postoperative radiotherapy have only examined the waiting time defined as interval between surgery and start of radiotherapy, but not the overall treatment time (OTT) itself. Conversely, results from trials on primary radio(chemo)therapy in NSCLC show that longer OTT correlates with significantly worse local tumor control and overall survival rates. This time factor of primary radio(chemo)therapy is thought to mainly be based on repopulation of surviving tumor cells between irradiation fractions. It remains to be elucidated if such an effect also occurs when patients with NSCLC are treated with postoperative radiotherapy after surgery (and chemotherapy). Our own retrospective data suggest an advantage of shorter OTT also for postoperative radiotherapy in this patient group.
METHODS/DESIGN:

This is a multicenter, prospective randomized trial investigating whether an accelerated course of postoperative radiotherapy with photons or protons (7 fractions per week, 2 Gy fractions) improves locoregional tumor control in NSCLC patients in comparison to conventional fractionation (5 fractions per week, 2 Gy fractions). Target volumes and total radiation doses will be stratified in both treatment arms based on individual risk factors.
DISCUSSION:

For the primary endpoint of the study we postulate an increase in local tumor control from 70% to 85% after 36 months. Secondary endpoints are overall survival of patients; local recurrence-free and distant metastases-free survival after 36 months; acute and late toxicity and quality of life for both treatment methods.

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Permalink: https://www.hzdr.de/publications/Publ-26999
Publ.-Id: 26999


PO-0616: HPV, CSC marker expression and tumor hypoxia as prognosticators for LRC in patients with HNSCC

Linge, A.; Löck, S.; Krenn, C.; Appold, S.; Lohaus, F.; Schneider, M.; Nowak, A.; Gudziol, V.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.
PO-0616: HPV, CSC marker expression and tumor hypoxia as prognosticators for LRC in patients with HNSCC

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Permalink: https://www.hzdr.de/publications/Publ-26997
Publ.-Id: 26997


PO-0968: The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC

Kurth, I.; Digomann, M.; Hein, L.; Linge, A.; Koi, L.; Loeck, S.; Maebert, K.; Stephan, H.; Peitzsch, C.; Krause, M.; Baumann, M.; Dubrovska, A.
PO-0968: The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC

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Publ.-Id: 26996


Optimisation and stabilisation of cathepsin B-endopeptidase substrates: Towards a Cathepsin B-activated cell-penetrating peptide

Kuhne, K.; Behring, L.; Belter, B.; Neuber, C.; Wodtke, R.; Pietzsch, J.; Löser, R.
Cathepsin B (CTB), whose expression in tumours correlates with increased metastasis, therapy resistance, and generally poor prognosis, represents an excellent target for molecular imaging using radiotracers [1]. It is our aim to develop a CTB-specifc, substrate-based radiotracer based on activatable, poly-D-arginine-derived cell pentrating peptides [2]. Central prerequisite for such a probe is an endopeptidase substrate for CTB used as an activator sequence that shows efficient cleavage kinetics towards CTB and is stable in circulation and against other relevant cathepsins. After newly identifying the P4' position as major determinant of CTB endopeptidase specificity, we determined Val (kcat/KM=245 mM-1s-1, 16xGly) as the ideal amino acid at this position. In terms of stabilisation, we were able to increase serum half-life from 3.6 min to >1440 min by amino acid exchange at P1 and N2-methylation of a secondary cleavage site, while still retaining good cleavability by CTB. Analysis of cleavage by other relevant ctahepsins is currently ongoing.

Literature
[1] Löser & Pietzsch Front. Chem. 2015, 3, 37
[2] Jang et al. PNAS 2004, 101, 17867
  • Poster
    International Sympsosium on Bioorganic Chemistry (ISBOC-11), 27.-29.09.2017, Konstanz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26995
Publ.-Id: 26995


Neutron imaging of particle laden Foam

Heitkam, S.; Lappan, T.; Eckert, S.; Eckert, K.
This presentation reports on the simultaneous measurement of foam structure and attached particles employing neutron imaging. An aqueous foam sample is placed in the NEUTRA beamline at PSI, enables for achieving a spatial resolution of less than 200 μm at a frame rate of more than 1 Hz. A forced drainage setup allows to control the liquid content of the foam. The averaged attenuation of the neutrons is demonstrated to yield the liquid fraction of the foam. Hydrophobized gadolinium particles of 200 μm diameter are added to the foam. Using two surfactants different levels of hydrophobicity are achieved. Depending on the drainage flow and the hydrophobicity, the particles are washed out of the foam with different rates. An avalanche-like motion of particle clusters is observed. The neutron radiography is demonstrated to yield unique insights into the unsteady froth flotation process.
Keywords: Neutron Imaging, Froth, Foam
  • Lecture (others)
    Seminarvortrag, 24.10.2017, Strasbourg, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-26994
Publ.-Id: 26994


Using Lorentz forces to control the distribution of bubbles in a vertical tube filled with liquid metal

Heitkam, S.; Tschisgale, S.; Krull, B.; Wetzel, T.; Baake, E.; Fröhlich, J.
In this work, a method to increase the residence time of bubbles in tubes or pipes filled with liquid metal is investigated. Imposing a horizontal electric current and a perpendicular horizontal magnetic field generates an upward-directed Lorentz force. This force can counteract gravity and cause floating of bubbles. Even with homogeneous electric fields these float in the mean but fluctuate randomly within the swarm due to mutual interactions.
In the present case the cylindrical shape of the container furthermore creates inhomogeneous electric currents and an inhomogeneous force distribution resulting in a macroscopic convection pattern stirring the bubbles and further homogenising the spatial distribution of the bubbles.
Keywords: Magnetohydrodynamics, Bubbles, Flow

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Permalink: https://www.hzdr.de/publications/Publ-26993
Publ.-Id: 26993


The Role of epithelial to mesenchymal transition (EMT) as Biomarker for Radioresistance in HNSCC

Kurth, I.; Digomann, D.; Hein, L.; Linge, A.; Koi, L.; Loeck, S.; Maebert, K.; Stephan, H.; Peitzsch, C.; Krause, M.; Baumann, M.; Dubrovska, A.
Purpose or Objective
It is described that epithelial – to -mesenchymal transition (EMT) plays an important role in head and neck squamous carcinomas (HNSCC) progression and resistance to therapy. Recent studies suggest that for instance the expression of EMT related microRNAs may cause intrinsic radioresistance in HNSCC. During the process of EMT epithelial cancer cells obtain a more mesenchymal –like motile and invasive phenotype, which has been argued to sustain survival and therapy resistance of those tumor cells and facilitate cancer progression. Radiotherapy is one of the main approaches to treat HNSCC. However, tumor radioresistance often impedes the success of radiotherapy and has been found to drive tumor aggressiveness and expansion. In this study we asked the question, if radioresistant HNSCC populations display EMT features on a molecular as well as on a functional level and whether we can correlate those characteristics to treatment outcome.
Material and Methods
We used multiple irradiated HNSCC lines (IR) as an established model to investigate the traits of radioresistance. Global gene expression analysis in vitro and on xenograft models and functional radiobiological analyis was applied.
Results
Interestingly, global gene expression analysis revealed a negative correlation of genes associated with cell motility and migration in the IR derivatives of two HNSCC cell lines, namely Cal33, FaDu. We functionally validated those findings and screened for known EMT marks from literature by functional migration assays and EMT-related protein expression in several HNSCC model cell lines and established xenografts as well as in their IR derivatives in order to correlate the acquired findings to radiotherapy outcome. The only positive correlation was found for the initial before therapy protein expression in vitro and in vivo for Slug, a zinc - finger protein encoded by the SNAI2 gene and c-Met, a receptor tyrosine kinase encoded by the MET gene. Functional knockdown of Slug or c-Met expression let to radiosensitization in 3-D clonogenic survival assays of several HNSCC cell lines.
Conclusion
Currently the expression of these molecules is scored for clinical outcome to better understand the context of EMT biomarkers for HNSCC progression and the development of a potential well-directed combinational radiochemotherapy.
Keywords: EMT, radiotherapy, HNSCC, migration

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Permalink: https://www.hzdr.de/publications/Publ-26992
Publ.-Id: 26992


Cytokine-dependent regulation of prostate cancer stem cells maintenance in response to radiotherapy

Peitzsch, C.; Baumbach, M.; Cojoc, M.; Hein, L.; Kurth, I.; Baumann, M.; Krause, M.; Dubrovska, A.
Purpose: According to the cancer stem cell hypothesis prostate cancer is driven by a malignant subpopulation with stem-like properties. These cancer stem cells (CSC) contribute to tumor-initiation, metastasis, therapy-resistance and tumor relapse. In parallel, genetic mutations accumulate over time and CSC subclones evolve. Therapeutic interventions like radiotherapy provide selective pressure for the expansion of resistant subclones with genetic diversification. We hypothesize that the determination of CSC-related biomarker in prostate cancer biopsies is correlating with clinical parameter and can be used for patient stratification and treatment selection to improve personalized radiotherapy.
Methodology: We generated isogenic radioresistant prostate cancer cell lines with a high expression of CSC marker, a epithelial-to-mesenchymal transition (EMT) phenotype, higher self-renewal properties, higher tumorigenicity and enhanced DNA repair capacity. We applied comparative genomic, proteomic, metabolomic, epigenomic and secretome analysis to identify novel biomarker for prostate cancer radioresistance and to unravel contributing molecular mechanisms.
Results: Within our first proof-of-principle study, we could show that ALDH-positive CSCs are radioresistant and maintained directly by the Wnt/β-catenin signaling pathway (1). In addition, we found that irradiation is inducing CSC marker and CSC properties in a dose- and time-dependent manner. This irradiation-induced CSC-plasticity was attributed to the modulation of the histone methylation code (2). Within the present study we analyzed a panel of secreted cytokines and their corresponding cytokine receptors in the radioresistant prostate cancer sublines, in a s.c. xenotransplantation model, in ex vivo irradiated primary prostate cancer biopsies and in blood samples of prostate cancer patients during the course of radiotherapy and found, for example, the CXCR4-CXCL12 signaling to be involved in the CSC maintenance and the induction of prostate cancer radioresistance.

References:

(1) Peitzsch C, Cojoc M, Hein L, Kurth I, Mäbert K, Trautmann F, Klink B, Schrock E, Wirth MP, Krause M et al: An epigenetic reprogramming strategy to re-sensitize radioresistant prostate cancer cells. Cancer research 2016, 76; 2637.

(2) Cojoc M*, Peitzsch C*, Kurth I, Trautmann F, Kunz-Schughart LA, Telegeev GD, Stakhovsky EA, Walker JR, Simin K, Lyle S et al: Aldehyde Dehydrogenase Is Regulated by beta-Catenin/TCF and Promotes Radioresistance in Prostate Cancer Progenitor Cells. Cancer research 2015, 75(7):1482-1494.
Keywords: Cytokines, prostate cancer, radioresistance

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Publ.-Id: 26991


Synthesis and 18F-Radiolabelling of Novel Benzoimidazotriazines for Imaging of Phosphodiesterase 2A (PDE2A)

Ritawidya, R.; Wenzel, B.; Teodoro, R.; Scheunemann, M.; Deuther-Conrad, W.; Brust, P.
1. Introduction
Cyclic nucleotide phosphodiesterases (PDEs) are a class of intracellular enzymes that inactivate the secondary messenger molecules cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Thus, PDEs regulate the signaling cascades mediated by these cyclic nucleotides and affect fundamental cellular processes, such as proliferation, differentiation, migration, survival, and apoptosis. Accordingly, they are promising therapeutic targets. Since PDE2A was found to be related to a variety of tumors, it is our aim to synthesize novel PDE2A inhibitors based on the benzoimidazotriazine (BIT) moiety that might be a prospective lead compound for the development of an F-18 labelled ligand for PDE2A imaging with PET.

Fig A. BIT key intermediates, B. Radiosynthesis of [18F]BIT1

2. Materials & Methods
Based on BIT key intermediates (Fig. A), a small series of novel fluorinated BIT derivatives was successfully prepared (overall in 7-10 steps) and the affinities towards PDE2A and other PDE subtypes were estimated. The most promising compound, BIT1, was radiolabelled by using the corresponding nitro precursor. The reaction was optimized by choosing different solvents, amounts of precursor, modes of heating (conventional or microwave), temperatures, and reaction times. Afterwards, best conditions (Fig. B) were transferred to an automated synthesis module (TracerLab FX2 N, GE Healthcare). The radiotracer was isolated by semi-preparative HPLC (Reprosil-Pur AQ column, 25010mm, 46 % ACN/aqu. 20 mM NH4OAc, flow 5.5 ml/min) followed by purification with a Sep-Pak C18 Plus light cartridge and formulation in isotonic saline containing 10% ethanol.

3. Results
BIT1 showed a high affinity towards PDE2A (IC50 PDE2A3 = 3.33 nM) and selectivity over other PDE subtypes. [18F]BIT1 was successfully synthesized with a radiochemical yield of 51.9 ± 1.3 % (n=3), molar activities between 46 – 100 GBq/µmol and radiochemical purities of ≥ 99%.


4. Discussion & Conclusion
Radiofluorination of a novel PDE2A ligand [18F]BIT1 was obtained with appropriate radiochemical yield and molar activity. First biological investigations are planned to estimate the potential of [18F]BIT1 as imaging agent for PDE2A.

Acknowledgement
1. Deutsche Forschungsgemeinschaft (German Research Foundation, Project Number: SCHE 1825/3-1).
2. Scholarship Program for Research and Innovation in Science and Technology Project (RISET-PRO)-Indonesia Ministry of Research, Technology and Higher Education.
Keywords: benzoimidazotriazines, PDE2A, radiolabelling, imaging
  • Lecture (Conference)
    European Symposium on Radiopharmacy and Radiopharmaceuticals, 05.-08.04.2018, Groningen, Netherlands

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Permalink: https://www.hzdr.de/publications/Publ-26990
Publ.-Id: 26990


High temperature reactions of UO2, ZrO2, B4C, CaO, and SiO2 under reducing and oxidizing atmospheres

Uehara, A.; Akiyama, D.; Numako, C.; Takeda-Homma, S.; Ikeda-Ohno, A.ORC; Terada, Y.; Ina, T.; Nitta, K.; Kirishima, A.; Sato, N.
Uranium and several other radioactive materials reacted with zircaloy (Zry) and/or its oxide, ZrO2, presented in the fuel cladding, to form fuel debris at the Fukushima Daiichi Nuclear Power Station in 2011. Under very high temperature conditions, the melt core, mainly consisting of the control rods (stainless steel rod filled with B4C) and fuel assembly (UO2 and Zry) materials, was solidified at the lower head of the pressure vessel. In addition, the melt core was also solidified at the lower head of the pedestal reacted with cement materials (CaO and SiO2). In order to forward a safe and controlled decommissioning process, structural and thermodynamic estimations of the fuel debris under various atmospheric conditions such as reducing and oxidizing atmospheres have been conducted. In the present study, the local structure of basic uranium/zirconium compounds has been characterized under different treatment conditions in the presence of B4C, CaO and SiO2 in atmospheric conditions with different temperatures ranging from 1473 to 1873 K. These reactions are of specific interest to the interaction between nuclear fuel and cladding tube materials.
Keywords: Nuclear debris, uranium, zirconium, solid-solution, synchrotron, X-ray absorption spectroscopy, powder X-ray diffraction
  • Lecture (Conference)
    17th international conference on X-ray absorption fine structure (XAFS 2018), 22.-27.07.2018, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-26989
Publ.-Id: 26989


Epigenetic and metabolic reprogramming as a target for prostate tumor radiosensitization

Dubrovska, A.; Peitzsch, C.; Tyutyunnykova, A.; Cojoc, M.
Purpose or Objective
Radiotherapy remains one of the main modalities to treat solid cancers and is one of the mainstays of curative prostate cancer treatment. Nevertheless, the risk of recurrence after radiotherapy still remains substantial in locally advanced disease. Tumor relapse after radiotherapy is attributed to the population of cancer stem cells (CSCs) which survived the treatment. Therefore, analysis of the CSC populations might be an important predictive tool of radiotherapy outcome and individualized treatment selection. However, compelling evidence suggests a high plasticity of CSCs imposed by tumor treatment. This study is aiming to investigate the interconnection of the glutamine metabolism and cancer cell plasticity in the development of tumor radioresistance for the development of new biomarkers to predict radiation treatment outcome.
Material and Methods
The employed methodological approaches include gene expression analysis, comparative genomic hybridization array, proteomic analysis, metabolic profiling, in vitro radiobiological clonogenic survival assays, assessment of the histone methylation marks and CSC marker expression, analysis of DNA damage repair and oxidative stress response. This study is based on the different models including tumor cell lines and their radioresistant derivatives, prostate cancer xenografts, ex vivo treated tissues and analysis of the publicly available TCGA prostate cancer datasets.
Results
Our study revealed that irradiation causes long-term upregulation in the expression of stem cell markers and induces tumor cell reprogramming. Furthermore, radioresistant and tumorigenic cell populations undergo a phenotypic switch during the course of radiotherapy. This phenotypic plasticity is associated with genetic, epigenetic and metabolic changes induced by irradiation. Expression of CSC markers and proteins involved in glutamine metabolism can be used to predict clinical outcome of prostate cancer patients.
Conclusion
Our studies suggest that radioresistant properties of prostate cancer cells are dynamic in nature and that combination of irradiation with therapeutic agents which prevent tumor cell reprogramming and metabolic switch may restore the cytotoxic effects of irradiation in radioresistant CSC populations.
References:
Cojoc M et al. Cancer Res. 2015; 75(7):1482-94;
Peitzsch C et al. Cancer Res. 2016; 76(9):2637-51;
Kurth I et al. Oncotarget 2015; 6(33):34494-509;
Krause M et al. Advanced Drug Delivery Reviews, 2016, pii: S0169-409X(16)30052-7.
Keywords: Metabolism, radioresistance, prostate cancer
  • Contribution to proceedings
    ESTRO36, 05.-09.05.2017, Vienna, Austria
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 123(2017), S201
    DOI: 10.1016/S0167-8140(17)30815-0

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Permalink: https://www.hzdr.de/publications/Publ-26986
Publ.-Id: 26986


Measurement of foam flow using Ultrasound Doppler Velocimetry + Froth dynamics by Neutron Imaging

Heitkam, S.; Nauber, R.; Büttner, L.; Czarske, J.; Eckert, K.
The flowing behavior of liquid foam and froth is only scarcely investigated. One reason for that is, that no adequate measurement technique exists. Also, industrial flotation applications could be improved by monitoring the froth flow in the process.

In this work, the Ultrasound Doppler Velocimetry has been used to measure the velocity distribution inside liquid foam. To that end, an array of ultrasound transducers sends pulses into the foam and receiving the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution on the beam axis. Multiplexing of the array allows for 2D-1C measurement.

Comparing with optical measurement it is demonstrated, that the velocity uncertainty at 2.5 Hz frame rate is below 15 percent and the spatial resolution better than 10 mm. These parameters allow for on-line monitoring of industrial processes as well as scientific investigation of three-dimensional froth and foam flows.
Keywords: Foam, Froth, Flotation, Ultrasound Dopller Velocimetry, Neutron Imaging
  • Lecture (Conference)
    Flotation17, 12.-16.11.2017, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-26982
Publ.-Id: 26982


Profile of European proton and carbon ion therapy centers assessed by the EORTC facility questionnaire.

Weber, D. C.; Abrunhosa-Branquinho, A.; Bolsi, A.; Kacperek, A.; Dendale, R.; Geismar, D.; Bachtiary, B.; Hall, A.; Heufelder, J.; Herfarth, K.; Debus, J.; Amichetti, M.; Krause, M.; Orecchia, R.; Vondracek, V.; Thariat, J.; Kajdrowicz, T.; Nilsson, K.; Grau, C.
BACKGROUND:

We performed a survey using the modified EORTC Facility questionnaire (pFQ) to evaluate the human, technical and organizational resources of particle centers in Europe.
MATERIAL AND METHODS:

The modified pFQ consisted of 235 questions distributed in 11 sections accessible on line on an EORTC server. Fifteen centers from 8 countries completed the pFQ between May 2015 and December 2015.
RESULTS:

The average number of patients treated per year and per particle center was 221 (range, 40-557). The majority (66.7%) of centers had pencil beam or raster scanning capability. Four (27%) centers were dedicated to eye treatment only. An increase in the patients-health professional FTE ratio was observed for eye tumor only centers when compared to other centers. All centers treated routinely chordomas/chondrosarcomas, brain tumors and sarcomas but rarely breast cancer. The majority of centers treated pediatric cases with particles. Only a minority of the queried institutions treated non-static targets.
CONCLUSIONS:

As the number of particle centers coming online will increase, the experience with this treatment modality will rise in Europe. Children can currently be treated in these facilities in a majority of cases. The majority of these centers provide state of the art particle beam therapy.

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Publ.-Id: 26981


Radiation Resistance in KRAS-Mutated Lung Cancer Is Enabled by Stem-like Properties Mediated by an Osteopontin-EGFR Pathway.

Wang, M.; Han, J.; Marcar, L.; Black, J.; Liu, Q.; Li, X.; Nagulapalli, K.; Sequist, L. V.; Mak, R. H.; Benes, C. H.; Hong, T. S.; Gurtner, K.; Krause, M.; Baumann, M.; Kang, J. X.; Whetstine, J. R.; Willers, H.
Lung cancers with activating KRAS mutations are characterized by treatment resistance and poor prognosis. In particular, the basis for their resistance to radiation therapy is poorly understood. Here, we describe a radiation resistance phenotype conferred by a stem-like subpopulation characterized by mitosis-like condensed chromatin (MLCC), high CD133 expression, invasive potential, and tumor-initiating properties. Mechanistic investigations defined a pathway involving osteopontin and the EGFR in promoting this phenotype. Osteopontin/EGFR-dependent MLCC protected cells against radiation-induced DNA double-strand breaks and repressed putative negative regulators of stem-like properties, such as CRMP1 and BIM. The MLCC-positive phenotype defined a subset of KRAS-mutated lung cancers that were enriched for co-occurring genomic alterations in TP53 and CDKN2A. Our results illuminate the basis for the radiation resistance of KRAS-mutated lung cancers, with possible implications for prognostic and therapeutic strategies. Cancer Res; 77(8); 2018-28. ©2017 AACR.

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Publ.-Id: 26980


Heat shock protein 70 and tumor-infiltrating NK cells as prognostic indicators for patients with squamous cell carcinoma of the head and neck after radiochemotherapy: A multicentre retrospective study of the German Cancer Consortium

Stangl, S.; Tontcheva, N.; Sievert, W.; Shevtsov, M.; Niu, M.; Schmid, T.; Pigorsch, S.; Combs, S.; Haller, B.; Balermpas, P.; Rödel, F.; Rödel, C.; Fokas, E.; Krause, M.; Linge, A.; Lohaus, F.; Baumann, M.; Tinhofer, I.; Budach, V.; Stuschke, M.; Grosu, A.; Abdollahi, A.; Debus, J.; Belka, C.; Maihöfer, C.; Mönnich, D.; Zips, D.; Multhoff, G.
Tumor cells frequently overexpress heat shock protein 70 (Hsp70) and present it on their cell surface, where it can be recognized by pre-activated NK cells. In our retrospective study the expression of Hsp70 was determined in relation to tumor-infiltrating CD56+ NK cells in formalin-fixed paraffin embedded (FFPE) tumor specimens of patients with SCCHN (N = 145) as potential indicators for survival and disease recurrence. All patients received radical surgery and postoperative cisplatin-based radiochemotherapy (RCT). In general, Hsp70 expression was stronger, but with variable intensities, in tumor compared to normal tissues. Patients with high Hsp70 expressing tumors (scores 3-4) showed significantly decreased overall survival (OS; p = 0.008), local progression-free survival (LPFS; p = 0.034) and distant metastases-free survival (DMFS; p = 0.044), compared to those with low Hsp70 expression (scores 0-2), which remained significant after adjustment for relevant prognostic variables. The adverse prognostic value of a high Hsp70 expression for OS was also observed in patient cohorts with p16- (p = 0.001), p53- (p = 0.0003) and HPV16 DNA-negative (p = 0.001) tumors. The absence or low numbers of tumor-infiltrating CD56+ NK cells also correlated with significantly decreased OS (p = 0.0001), LPFS (p = 0.0009) and DMFS (p = 0.0001). A high Hsp70 expression and low numbers of tumor-infiltrating NK cells have the highest negative predictive value (p = 0.00004). In summary, a strong Hsp70 expression and low numbers of tumor-infiltrating NK cells correlate with unfavorable outcome following surgery and RCT in patients with SCCHN, and thus serve as negative prognostic markers.
Keywords: Hsp70; IHC; NK cells; SCCHN; prognostic biomarker; retrospective trial

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Publ.-Id: 26978


Tumor heterogeneity determined with a γH2AX foci assay: A study in human head and neck squamous cell carcinoma (hHNSCC) models

Rassamegevanon, T.; Löck, S.; Range, U.; Krause, M.; Baumann, M.; von Neubeck, C.
PURPOSE:

This study aimed to analyze the intra-tumoral heterogeneity of γH2AX foci in tumor specimens following ex vivo radiation to evaluate the potential of γH2AX foci as predictors for radiosensitivity.
MATERIAL AND METHODS:

γH2AX foci were quantified in tumor specimens of 3hHNSCC tumor models with known differences in radiosensitivity after reoxygenation in culture medium (10h, 24h), single dose exposure (0Gy, 4Gy), and fixation 24h post-irradiation. Multiple, equally treated samples of the same tumor were analyzed for foci, normalized and fitted in a linear mixed-effects model.
RESULTS:

The ex vivo reoxygenation time had no significant effect on γH2AX foci counts. A significant intra model heterogeneity could be shown for FaDu (p=0.033) but not for SKX (p=0.167) and UT-SCC-5 (p=0.082) tumors, respectively. All tumor models showed a significant intra-tumoral heterogeneity between specimens of the same tumor (p<0.01) or among microscopic fields of a particular tumor specimen (p<0.0001).
CONCLUSION:

Similar results for ex vivo γH2AX foci between 10h and 24h reoxygenation time support the applicability of the assay in a clinical setting. The high intra-tumoral heterogeneity underlines the necessity of multiple analyzable samples per patient and therewith the need for an automated foci analysis.

Copyright © 2017 Elsevier B.V. All rights reserved.
Keywords: Biomarker; Radiosensitivity; Tumor heterogeneity; γH2AX foci

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Permalink: https://www.hzdr.de/publications/Publ-26977
Publ.-Id: 26977


Development of a genetic sensor that eliminates p53 deficient cells

Mircetic, J.; Dietrich, A.; Paszkowski-Rogacz, M.; Krause, M.; Buchholz, F.
The TP53 gene fulfills a central role in protecting cells from genetic insult. Given this crucial role it might be surprising that p53 itself is not essential for cell survival. Indeed, TP53 is the single most mutated gene across different cancer types. Thus, both a theoretical and a question of significant practical applicability arise: can cells be programmed to make TP53 an essential gene? Here we present a genetic p53 sensor, in which the loss of p53 is coupled to the rise of HSV-TK expression. We show that the sensor can distinguish both p53 knockout and cells expressing a common TP53 cancer mutation from otherwise isogenic TP53 wild-type cells. Importantly, the system is sensitive enough to specifically target TP53 loss-of-function cells with the HSV-TK pro-drug Ganciclovir both in vitro and in vivo. Our work opens new ways to programming cell intrinsic transformation protection systems that rely on endogenous components.

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Permalink: https://www.hzdr.de/publications/Publ-26974
Publ.-Id: 26974


Comparison of detection methods for HPV status as a prognostic marker for loco-regional control after radiochemotherapy in patients with HNSCC.

Linge, A.; Schötz, U.; Löck, S.; Lohaus, F.; von Neubeck, C.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Bunea, H.; Grosu, A.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Lauber, K.; Pigorsch, S.; Combs, S.; Mönnich, D.; Zips, D.; Baretton, G.; Buchholz, F.; Krause, M.; Belka, C.; Baumann, M.
OBJECTIVE:

To compare six HPV detection methods in pre-treatment FFPE tumour samples from patients with locally advanced head and neck squamous cell carcinoma (HNSCC) who received postoperative (N = 175) or primary (N = 90) radiochemotherapy.
MATERIALS AND METHODS:

HPV analyses included detection of (i) HPV16 E6/E7 RNA, (ii) HPV16 DNA (PCR-based arrays, A-PCR), (iii) HPV DNA (GP5+/GP6+ qPCR, (GP-PCR)), (iv) p16 (immunohistochemistry, p16 IHC), (v) combining p16 IHC and the A-PCR result and (vi) combining p16 IHC and the GP-PCR result. Differences between HPV positive and negative subgroups were evaluated for the primary endpoint loco-regional control (LRC) using Cox regression.
RESULTS:

Correlation between the HPV detection methods was high (chi-squared test, p < 0.001). While p16 IHC analysis resulted in several false positive classifications, A-PCR, GP-PCR and the combination of p16 IHC and A-PCR or GP-PCR led to results comparable to RNA analysis. In both cohorts, Cox regression analyses revealed significantly prolonged LRC for patients with HPV positive tumours irrespective of the detection method.
CONCLUSIONS:

The most stringent classification was obtained by detection of HPV16 RNA, or combining p16 IHC with A-PCR or GP-PCR. This approach revealed the lowest rate of recurrence in patients with tumours classified as HPV positive and therefore appears most suited for patient stratification in HPV-based clinical studies.
Keywords: DKTK-ROG; HNSCC; HPV; Loco-regional control; Radiochemotherapy; p16

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Permalink: https://www.hzdr.de/publications/Publ-26970
Publ.-Id: 26970


Thionine-graphene oxide covalent hybrid and its interaction with light.

Krzyszkowska, E.; Walkowiak-Kulikowska, J.; Stienen, S.; Wojcik, A.
Graphene oxide sheets (GO) were covalently functionalized with thionine molecules. The obtained hybrid material, Th-GO, was characterized by means of scanning electron microscopy (SEM), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Subsequently, the interaction of light with the free dye molecules and with dye molecules bound to the graphene oxide sheets was probed via UV-Vis spectroscopy, fluorescence spectroscopy and femtosecond pump-probe spectroscopy. The experimental results proved that thionine was successfully grafted onto the GO sheets, however, only one of the two amino groups of thionine was always involved in the amide bond formation. The Th-GO hybrid suspended in N,N-dimethylformamide (DMF) exhibited suppressed fluorescence as compared to the free dye in the same solvent, pointing to an efficient interaction between the photoexcited dye and the graphene sheets. Yet, no electron transfer products were detected by transient absorption measurements, even though there was a shortening of the singlet excited state lifetime of thionine (from the 567 ps for the free dye to the 313 ps for the dye in Th-GO). These results can be rationalized in terms of a fast back electron transfer process or possibly an energy transfer process.

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Publ.-Id: 26965


Synchrotron X-ray Imaging and Numerical Modelling of Dendritic Sidebranch Evolution during Coarsening

Neumann-Heyme, H.; Shevchenko, N.; Eckert, K.; Grenzer, J.; Beckermann, C.; Eckert, S.
We study the local dynamics of dendritic side arms during coarsening by combining in-situ radiography observations with numerical and analytical models. A flat sample of a Ga-In alloy is partially solidified and then held isothermally in a vertical temperature gradient. The evolving dendritic microstructure is visualized by synchrotron X-ray imaging at the BM20 beamline (ESRF, France). The resulting 2D images provide a high resolution in space and time at low noise levels, enabling accurate dynamical measurements. Throughout the initial growth stage there is evidence of solutal natural convection, which however vanishes towards the subsequent coarsening processes. During the coarsening stage, the time evolution of essential geometrical features of side branches was captured by automated image processing. This data is used to quantify the dynamics of three basic evolution scenarios for side branches: retraction, pinch-off and coalescence. We exploit the universal dynamics of sidearm necks during pinch-off to determine the product of liquid diffusivity and capillarity length, 𝐷𝑑0, as a parameter that is crucial in the calibration of quantitative reference models. By employing an idealized phase-field model for the evolution of a single side branch, we are able to predict the behaviour of selected side branches from the experiment in a consistent way.
Keywords: Dendritic Solidification, Coarsening Dynamics, Material Properties
  • Contribution to proceedings
    International Conference on Solidification Processing, SP17, 25.-28.07.2017, Old Windsor, UK, 978-1-908549-29-7, 214-217
  • Lecture (Conference)
    International Conference on Solidification Processing, SP17, 25.-28.07.2017, Old Windsor, UK

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Permalink: https://www.hzdr.de/publications/Publ-26964
Publ.-Id: 26964


Neoadjuvant radiochemotherapy decreases the total amount of tumor infiltrating lymphocytes, but increases the number of CD8+/Granzyme B plus (GrzB) cytotoxic T-cells in rectal cancer

Jarosch, A.; Sommer, U.; Bogner, A.; Reißfelder, C.; Weitz, J.; Krause, M.; Folprecht, G.; Baretton, G. B.; Aust, D. E.
Although neoadjuvant radiochemotherapy (nRCTx) is an established oncological treatment in patients with advanced rectal cancer, little is known about its effects on the tumor microenvironment. Quantity and composition of tumor infiltrating lymphocytes (TILs) are known to influence patients’ prognosis but nRCTx-induced modifications are still unclear. We determined the composition of the immune cell infiltrate in rectal cancer after nRCTx and its influence on tumor regression, local recurrence rate and survival. We investigated density and composition of tumor infiltrating CD3C and CD8C T-cells and the quantity and ratio of CD8C/GrzBC T-cells to CD8C T-cells in 130 rectal cancers after nRCTx compared to a cohort of 30 primarily resected rectal cancers. Furthermore, we analyzed 22 pretherapeutic rectal cancer biopsies, later
treated with nRCTx and surgery to evaluate nRCTx-inducedmodifications of the tumor microenvironment.
The total numbers of CD3C and CD8C T-cells in tumor stroma (p < 0.001) and tumor Epithelium (p < 0.001 CD3; 0.002 CD8) were significantly lower in rectal cancers after nRCTx compared to primarily resected cases, while the ratio of CD8C/GrzBC T-cells to CD8C T-cells was significantly increased in the nRCTx cohort (p < 0.001). In multivariate analyses, CD8C/GrzBC T-cells in the tumor stroma were significantly associated with high regression grade and a lower likelihood of local recurrence (p D 0.029).
nRCTx modifies the tumor microenvironment of rectal cancer leading to a total decrease of TILs, but a relative increase in CD8C/GrzBC T-cells in the tumor stroma. CD8C/GrzBC T-cells may contribute to local tumor control and the better outcome.
Keywords: rectal cancer; histological tumor regression; granzyme B (GrzB); neoadjuvant radiochemotherapy; Tumor microenvironment

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Permalink: https://www.hzdr.de/publications/Publ-26963
Publ.-Id: 26963


Laboratory experiments on dynamo action and magnetorotational instability

Stefani, F.
Magnetic fields of planets, stars and galaxies are produced by the homogeneous dynamo effect in moving electrically conducting fluids, such as liquid metals or plasmas. Once generated, magnetic fields can foster cosmic structure formation by destabilizing, via the magnetorotational instability (MRI), Keplerian flows that would be otherwise hydrodynamically stable.
For a long time, both effects had been the subject of purely theoretical and numerical research. This changed in 1999 when the threshold of magnetic-field self-excitation was crossed in the two liquid sodium experiments in Riga and Karlsruhe [1]. Since 2006, the VKS dynamo experiment in Cadarache has successfully reproduced many features of geophysical interest, such as field reversals and excursions. Liquid metal experiments in Grenoble, Madison, Maryland, Perm, Princeton, Perm, and Socorro have contributed further important findings. MRI-related research was partly successful with the observation of the helical MRI [2] and the azimuthal MRI [3] at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). First evidence of the current-driven Tayler instability (TI) in a liquid metal was obtained here, too [4].
The lecture gives a cursory account of the recent laboratory experiments on dynamo action and magnetically triggered flow instabilities. It concludes with an overview about future experiments, with special focus on the precession-driven liquid sodium experiment and the large-scale MRI experiment that are under construction in the framework of the DRESDYN project at HZDR [5].

[1] Gailitis, A. et al., Rev. Mod. Phys. 74 (2002), 973-990
[2] Stefani, F. et al., Phys. Rev. Lett. 97 (2006), 184502
[3] Seilmayer, M. et al., Phys. Rev. Lett. 113 (2014), 024505
[4] Seilmayer, M. et al., Phys. Rev. Lett. 108 (2012), 244501
[5] Stefani, F. et al., IOP Conf. Ser.: Mater. Sci. Eng. 228 (2017), 012002
  • Invited lecture (Conferences)
    Séminaires de l'IRAP, 18.01.2018, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-26962
Publ.-Id: 26962


Tidally synchronized Tayler-Spruit and Babcock-Leighton type dynamos

Stefani, F.; Giesecke, A.; Weber, N.; Weier, T.
The usual explanation of the Hale cycle of the solar magnetic field builds on intrinsic features of the solar dynamo, comprising the turbulent resistivity and the intensities of the alpha effect, the Omega effect and the meridional circulation. However, the dissimilarity of the sequence of solar cycles with a random walk in phase, and their remarkable synchronization with the 11.07 years period of the alignment of the tidally dominant planets Venus, Earth and Jupiter has not remained unobserved.
Asking for a viable physical mechanism that could link the very weak planetary forces with solar dynamo action, we focus on the helicity oscillations that were recently found in simulations of the current-driven, kink-type Tayler instability that is characterized by an m=1 azimuthal dependence. We show how these helicity oscillations can be resonantly excited by m=2 perturbations that reflect tidal oscillations. Specifically, we speculate that the 11.07 years tidal oscillation may lead to a 1:1 resonant excitation of the oscillation of the associated alpha effect. In the framework of simple dynamo model of the Tayler-Spruit type, we recover the 22.14-year cycle of the solar dynamo. Interestingly, slight parameter changes of this model lead to transitions between oscillatory and pulsatory behaviour with maintained phase coherence, which might serve as an analogue of the behaviour during grand minima.
We have also tested similar dynamo models of the Babcock-Leighton type, for which we have pursued two ideas on how such a synchronization could work. The first one bears on the concept of a sensitive flux storage capacity of the tachocline, which might be easily influenced by minor perturbations as provoked by tidal forces, the second one on periodic changes of the Omega effect. In either case, and in contrast to this easy and robust synchronizability of Tayler-Spruit type dynamos, the model proved rather rather stubborn to synchronization.
  • Lecture (others)
    GDRI Dynamo Meeting, 27.-29.11.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-26961
Publ.-Id: 26961


Dynamos, instabilities, inverse problems: Paul Roberts' legacy for experimental MHD

Stefani, F.
Retracing Paul Roberts' footsteps, I survey the recent experimental activities related to dynamo action, magnetically triggered flow instabilities, Alfvén waves, and magnetic flow tomography. I'm certain he will be most pleased by those developments that have superseded some of the pessimistic prognoses made in his seminal 1967 book: "Since processes of self-excitation are out of the question..." (p. 172), is just a case in point.
  • Invited lecture (Conferences)
    Fifty years after Roberts’ MHD: Dynamos and planetary flows today (PHR2017), 16.-17.11.2017, London, UK

Permalink: https://www.hzdr.de/publications/Publ-26960
Publ.-Id: 26960


Of Mikes and butterflies

Stefani, F.
More often than not, after having worked for some time on a problem related to dynamos or magnetic instabilities, I said to myself: "I should have read Michael Proctor before!" Actually, not many scientists have influenced magnetohydrodynamics so profoundly as he did. In a personally biased selection, I discuss some experimental and theoretical MHD topics which were strongly influenced by Michael Proctor's ideas. Those include: 1) The distinction between convective and absolute instabilities, which turned out to be essential for the experimental demonstration of the dynamo effect in Riga and the helical magnetorotational instability (MRI) in Dresden, 2) the Malkus-Proctor effect, as nicely illustrated by the saturation mechanism of the Riga dynamo, 3) double-diffusive magnetic instabilities, such as buoyancy instabilities, but also helical and azimuthal MRI and Super-AMRI, 3) spectral degeneracies of dynamo operators in diabolic or exceptional points, and their (putative) role for reversals of the geodynamo, 4) highly nonlinear dynamo mechanisms, such as MRI dynamos and Tayler-Spruit dynamos.
  • Lecture (others)
    MREP 2017, 11.-12.09.2017, Cambridge, UK

Permalink: https://www.hzdr.de/publications/Publ-26959
Publ.-Id: 26959


Laboratory experiments and numerical simulations on magnetic instabilities.

Stefani, F.; Gellert, M.; Kasprzyk, C.; Paredes, A.; Rüdiger, G.; Seilmayer, M.
Magnetic fields of planets, stars, and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both hydromagnetic dynamo action and magnetically triggered flow instabilities had been the subject of purely theoretical research. Meanwhile, however, the dynamo effect has been observed in large-scale liquid sodium experiments in Riga, Karlsruhe, and Cadarache. In this chapter, we summarize the results of some smaller liquid metal experiments devoted to various magnetic instabilities, such as the helical and the azimuthal magnetorotational instability, the Tayler instability, and the different instabilities that appear in a magnetized spherical Couette flow. We conclude with an outlook on a large scale Tayler-Couette experiment using liquid sodium, and on the prospects to observe magnetically triggered instabilities of flows with positive shear.
Keywords: Dynamo, Magnetorotational instability
  • Book chapter
    Lühr H., Wicht J., Gilder S., Holschneider M.: Magnetic fields in the solar system. Astrophysics and Space Science Library, vol. 448, Cham: Springer, 2018, 978-3-319-64291-8, 125-152
    DOI: 10.1007/978-3-319-64292-5_5

Permalink: https://www.hzdr.de/publications/Publ-26958
Publ.-Id: 26958


Evaporation-assisted magnetic separation of rare earth ions in aqueous solutions

Lei, Z.; Fritzsche, B.; Eckert, K.ORC
This work aims to answer the question of why an enrichment of paramagnetic ions can be observed in a magnetic field gradient [1] despite the presence of a counteracting Brownian motion. For that purpose, we study a rare earth chloride (DyCl3) solution in which weak evaporation is adjusted by means of small differences in the vapor pressure in a specially developed cell, see Fig. 1.
The temporal evolution of the refractive index field of this solution, as a result of heat and mass transfer, is measured by means of a Mach-Zehnder interferometer. We develop a numerical algorithm which splits the refractive index field into two parts, one space-dependent and conservative and the other time-dependent and transient. By using this algorithm in conjunction with a numerical simulation of the temperature and concentration field, we are able to show that 90% of the refractive index in the evaporation-driven boundary layer is caused by an increase in the concentration of Dy(III) ions. A simplified analysis of the gravitational and magnetic forces, entering the Rayleigh number, leads to a diagram of the system's instability. Accordingly, the enrichment layer of elevated Dy(III) concentration is placed in a spatial zone dominated by a field gradient force. This leads to the unconditional stability of this layer in the present field. The underlying mechanism is the levitation and reshaping of the evaporation-driven boundary layer by the magnetic field gradient [2].

[1] X. Yang, K. Tschulik, M. Uhlemann, S. Odenbach, K. Eckert, J. Phys. Chem. Lett. 3 (2012), 3559–3564.
[2] Z. Lei, B. Fritzsche, K. Eckert, submitted to J. Phys. Chem. C (2017).
Keywords: magnetic separation, rare earth, interferometry
  • Lecture (Conference)
    International Conference on Magneto-Science 2017 (ICMS 2017), 23.-27.10.2017, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-26957
Publ.-Id: 26957


Laser ion acceleration using the Draco Petawatt facility at HZDR

Zeil, K.; Obst, L.; Rehwald, M.; Brack, F.; Metzkes, J.; Kraft, S.; Schlenvoigt, H.-P.; Ziegler, T.; Jahn, A.; Kroll, F.; Kluge, T.; Schramm, U.
Demanding applications like radiation therapy of cancer are pushing the frontier of laser driven proton accelerators with controlled and well-defined proton beam properties. This talk will give an overview of recent achievements at the high-contrast high power laser source DRACO at the HZDR in Dresden (Germany). The laser system was recently upgraded by an additional Petawatt (PW) amplifier stage and new front end components finally providing high contrast pulses of >500 TW on target at 1 Hz pulse repetition rate. In first experiments the delivery of these pulses on target was demonstrated and the feasibility of worldwide first controlled volumetric irradiation of a specifically developed tumor model, grown on the ears of nude mice with laser-accelerated protons was investigated. In order to efficiently capture and shape the divergent TNSA proton beam, a setup of two pulsed high-field solenoid magnets will be presented to reliably generate homogeneous dose distributions in lateral direction and in depth.
The performance of laser based proton and ion acceleration and the scaling of the laser energy to achieve increased ion energies strongly depend on the laser temporal contrast and its effect on the target plasma scale length. Plasma mirror setups have proven to be a valuable tool to significantly improve the temporal contrast by reducing pre-pulse intensity and steepening the rising edge of the main laser pulse. Re-collimating single plasma mirror devices have been implemented into the Draco laser beam lines and the talk will summarize on measurements of the resulting contrast enhancement comparing different techniques. With the achieved contrast enhancement, laser proton acceleration and proton energy scaling were investigated within the TNSA regime using ultra-thin foil targets and implications for the radiobiological experiments will be discussed.
  • Lecture (Conference)
    Laser and Plasma Acceleration Workshop, 28.08.2017, Jeju Island, South Korea

Permalink: https://www.hzdr.de/publications/Publ-26956
Publ.-Id: 26956


Laser ion acceleration using the Draco Petawatt facility at HZDR - experiments and radio-biological application

Zeil, K.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Brack, F.; Kroll, F.; Metzkes, J.; Prencipe, I.; Huebl, A.; Kluge, T.; Bussmann, M.; Kraft, S.; Ziegler, T.; Bernert, C.; Jahn, A.; Gaus, L.; Schramm, U.
Demanding applications like radiation therapy of cancer are pushing the frontier of laser driven proton accelerators with controlled and well-defined proton beam properties. This talk will give an overview of recent achievements at the high-contrast high power laser source DRACO at HZDR. The laser system was recently upgraded by an additional Petawatt (PW) amplifier stage and new front end components finally providing high contrast pulses of >500 TW on target at 1 Hz pulse repetition rate. In first experiments with the new PW beam line of Draco the feasibility of worldwide first controlled volumetric irradiation of a specifically developed tumor model, grown on the ears of nude mice with laser-accelerated protons was investigated. In order to efficiently capture and shape the divergent TNSA proton beam, a setup of two pulsed high-field solenoid magnets was used. In the talk the reliable generation of homogeneous dose distributions lateral and in depth will be discussed.

The performance of laser based ion acceleration and the scaling of the laser energy to achieve increased ion energies strongly depend on the laser temporal contrast and its effect on the target plasma scale length. Plasma mirror setups have proven to be a valuable tool to significantly improve the temporal contrast by reducing pre-pulse intensity and steepening the rising edge of the main laser pulse. With such contrast enhancement techniques laser proton acceleration using ultra-thin foil targets as well as a renewable debris-free hydrogen jet (in collaboration with SLAC and European XFEL) target was investigated with a laser pulse energy of 3 J and duration of 30 fs and show robust TNSA proton pulses with energies of up to 25 MeV. An important implication of this is the demonstration of a credible path toward high repetition rate laser-based ion acceleration applications.
  • Invited lecture (Conferences)
    International Conference on High Energy Density Sciences, 21.4.2017, Tokio-Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-26955
Publ.-Id: 26955


Evolution of the Interfacial Area in Dendritic Solidification

Neumann-Heyme, H.; Eckert, K.; Beckermann, C.
The specific area of the solid-liquid interface is an important integral measure for the morphological evolution during solidification. It represents not only the inverse of a characteristic length scale of the microstructure, but it is also a key ingredient in volume-averaged models of alloy solidification. Analytical descriptions exist for either pure coarsening or pure growth processes. However, all alloy solidification processes involve concurrent growth and coarsening. In the present study, the kinetics of the solid-liquid interface of a dendrite are studied using a 3D phase-field model. The simulation results are combined with data from recent synchrotron tomography experiments to study the influence of the cooling rate and alloy composition on the evolution of the interfacial area. A general relation for the specific interfacial area of dendrites is presented that is valid over the entire range of cooling rates, including isothermal coarsening.
Keywords: Dendritic Solidification, Interfacial Area, Phase-Field Simulation
  • Contribution to proceedings
    International Conference on Solidification Processing, SP17, 25.-28.07.2017, Old Windsor, UK
    Evolution of the Interfacial Area in Dendritic Solidification, 978-1-908549-29-7, 193-196
  • Lecture (Conference)
    International Conference on Solidification Processing, SP17, 25.-28.07.2017, Old Windsor, UK

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Permalink: https://www.hzdr.de/publications/Publ-26954
Publ.-Id: 26954


Research at the Dresden High Magnetic Field Laboratory

Wosnitza, J.
  • Invited lecture (Conferences)
    Seminar at the Department of Chemistry, Graduate School of Science, Osaka University, 22.09.2017, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-26953
Publ.-Id: 26953


Therapie des kleinzelligen Lungenkarzinoms im Stadium „limited disease“. RCT normo- oder hyperfraktioniert?

Frosch, S.; Troost, E. G. C.
Die simultane Radiochemotherapie (RCT) ist beim kleinzelligen Lungenkarzinom der Therapiestandard im Stadium „limited disease“. Aktuell besteht allerdings noch eine Kontroverse über den Bestrahlungsablauf und die optimale Bestrahlungsdosis. Bisherige Daten zeigten die Überlegenheit einer akzeleriert-hyperfraktionierten Bestrahlung mit täglich zwei Fraktionen im Vergleich zur konventionell fraktionierten Bestrahlung mit täglich einer Fraktion, jedoch auf Kosten von mehr Toxizität [1]. Allerdings war in dieser Studie die Gesamtdosis in beiden Gruppen gleich; Kritiker postulieren, dass eine höhere Gesamtdosis – einmal pro Tag appliziert – im konventionellen Therapiearm die Ergebnisse hätte verbessern können.
  • InFo Onkologie 21(2018)1, 27-28

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Permalink: https://www.hzdr.de/publications/Publ-26952
Publ.-Id: 26952


The FFLO state in layered organic superconductors

Wosnitza, J.
  • Invited lecture (Conferences)
    International Conference on Electron Correlation in Superconductors and Nanostructures, 17.-20.08.2017, Odessa, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-26951
Publ.-Id: 26951


FFLO states in layered organic superconductors

Wosnitza, J.
  • Invited lecture (Conferences)
    QCNP 2017 Quantum Criticality & Novel Phases, 26.02.-01.03.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26950
Publ.-Id: 26950


Stereotactic radiosurgery for brainstem metastases : In experienced hands a good treatment option with excellent risk-benefit ratio

Khademalhosseini, Z.; Khademolhosseini, M.; Kummer, B.; Krause, M.

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Permalink: https://www.hzdr.de/publications/Publ-26949
Publ.-Id: 26949


SDF-1/CXCR4 expression in head and neck cancer and outcome after postoperative radiochemotherapy

De-Colle, C.; Mönnich, D.; Welz, S.; Boeke, S.; Sipos, B.; Fend, F.; Mauz, P.-S.; Tinhofer, I.; Budach, V.; Jawad, J. A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Bayer, C.; Belka, C.; Pigorsch, S.; Combs, S. E.; Lohaus, F.; Linge, A.; Krause, M.; Baumann, M.; Zips, D.; Menegakis, A.
Introduction

Outcome after postoperative radiochemotherapy (RT-CT) for patients with advanced head and neck squamous cell carcinomas (HNSCC) remains unsatisfactory, especially among those with HPV negative tumours. Therefore, new biomarkers are needed to further define subgroups for individualised therapeutic approaches. Preclinical and first clinical observations showed that the chemokine receptor CXCR4 and its ligand SDF-1 (CXCL12) play an important role in tumour cell proliferation, survival, cancer progression, metastasis and treatment resistance. However, the data on the prognostic value of SDF-1/CXCR4 expression for HNSCC are conflicting. The aim of our hypothesis-generating study was to retrospectively explore the prognostic potential of SDF-1/CXCR4 in a well-defined cohort of HNSCC patients collected within the multicenter biomarker study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG).
Material and methods

Patients with stage III and IVA HNSCC of the oral cavity, oropharynx and hypopharynx were treated with resection and adjuvant radiotherapy (RT) with ≥60 Gy and concurrent cisplatin-based chemotherapy (CT). Tissue micro-arrays (TMAs) from a total of 221 patients were generated from surgical specimens, 201 evaluated for the SDF-1 and CXCR4 expression by immunofluorescence and correlated with clinico-pathological and outcome data.
Results

In univariate and multivariate analyses intracellular SDF-1 expression was associated with lower loco-regional control (LRC) in the entire patient group as well as in the HPV16 DNA negative subgroup. CXCR4 expression showed a trend for lower LRC in the univariate analysis which was not confirmed in the multivariate analysis. Neither for SDF-1 nor CXCR4 expression associations with distant metastasis free or overall survival were found.
Conclusions

Our exploratory data support the hypothesis that overexpression of intracellular SDF-1 is an independent negative prognostic biomarker for LRC after postoperative RT-CT in high-risk HNSCC. Prospective validation is warranted and further exploration of SDF-1/CXCR4 as a potential therapeutic target to overcome treatment resistance in HNSCC appears promising.

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Permalink: https://www.hzdr.de/publications/Publ-26947
Publ.-Id: 26947


The PD-1/PD-L1 axis and human papilloma virus in patients with head and neck cancer after adjuvant chemoradiotherapy: A multicentre study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG).

Balermpas, P.; Rödel, F.; Krause, M.; Linge, A.; Lohaus, F.; Baumann, M.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Gkika, E.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Stangl, S.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Multhoff, G.; Combs, S. E.; Welz, S.; Zips, D.; Lim, S. Y.; Rödel, C.; Fokas, E.
We examined the prognostic role of PD-1+ and CD8+ tumor infiltrating lymphocytes (TILs), and PD-L1+ cells in patients with squamous cell carcinoma of the head and neck (SCCHN) treated with surgery and postoperative chemoradiotherapy (CRT). FFPE samples from 161 patients were immunohistochemically stained for PD-1, CD8 and PD-L1. The immune marker expression was correlated with clinicopathologic characteristics, and overall survival (OS), local progression-free survival (LPFS) and distant metastases free-survival (DMFS), also in the context of HPV16 DNA/p16 status. The median follow-up was 48 months (range: 4-100). The 2-year-OS was 84.1% for the entire cohort. High PD-1 and PD-L1 expression were more common in patients with positive HPV16 DNA (p < 0.001 and p = 0.008, respectively) and high infiltration by CD8+ TILs (p < 0.001 for both markers). High PD-L1 expression correlated with superior OS (p = 0.025), LPFS (p = 0.047) and DMFS (p = 0.048) in multivariable analysis, whereas no significance could be demonstrated for PD-1. Patients with CD8high /PD-L1high expression had favorable outcome (p < 0.001 for all endpoints) compared to other groups. We validated the superior OS data on CD8high /PD-L1high using the Cancer Genome Atlas TCGA dataset (n = 518; p = 0.032). High PD-L1 expression was a favorable prognostic marker in HPV16-negative but not HPV16-positive patients. In conclusion, HPV-positive tumors showed higher expression of immune markers. PD-L1 expression constitutes an independent prognostic marker in SCCHN patients post-adjuvant CRT. In conjunction with CD8 status, these data provide an important insight on the immune contexture of SCCHN and are directly relevant for future treatment stratification with PD-1/PD-L1 immune checkpoint inhibitors to complement CRT.
Keywords: CD8; HPV; PD-1/PD-L1; SCCHN; chemoradiotherapy; prognostic

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Publ.-Id: 26945


Prompt gamma spectroscopy for range control with CeBr3.

Martins, P. M.; Bello, R. D.; Rinscheid, A.; Roemer, K.; Werner, T.; Enghardt, W.; Pausch, G.; Seco, J.
Prompt gamma spectroscopy for range control with CeBr3.

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Publ.-Id: 26944


Magnetically induced cavitation for the dispersion of nanoparticles in liquid metals

Sarma, M.; Gerbeth, G.; Grants, I.; Kaldre, I.; Bojarevics, A.
Dispersion of particles to produce metal matrix nanocomposites (MMNC) can be achieved by means of ultrasonic vibration of the melt using ultrasound transducers. However direct transfer of this method to produce steel composites is not feasible because of the much higher working temperature. Therefore, an inductive technology for contactless treatment by acoustic cavitation was developed. This report describes the samples produced to assess the feasibility of the proposed method for nano-particle separation in steel. Stainless steel samples with inclusions of TiB2, TiO2, Y2O3, CeO2, Al2O3 and TiN have been created and analyzed. Additional experiments have been performed using light metals with an increased value of the steady magnetic field using a superconducting magnet with a field strength up to 5 T.
Keywords: MMC production, Steel composites, Cavitation treatment
  • Contribution to proceedings
    XVIII International UIE-Congress Electrotechnologies for Material Processing, 06.-09.06.2017, Hannover, Deutschland: Vulkan-Verlag GmbH, 978-3-8027-3095-5

Permalink: https://www.hzdr.de/publications/Publ-26938
Publ.-Id: 26938


Prospective data registration and clinical trials for particle therapy in Europe

Langendijk, J.; Orrechhia, R.; Haustermans, K.; Zips, D.; Balosso, J.; Lievens, Y.; Weber, D.; Grau, C.; Troost, E.
To enhance evidence-based introduction of particle therapy in Europe, one of the work packages within the European Proton Therapy network (EPTN) will focus on uniform data registration and defining methodological criteria for phase I, II and III clinical trials. The main objective of EPTN WP1 is to establish a uniform prospective data registration program for all patients treated with particle therapy in Europe. This will be supported by EORTC through existing and new additional QA-platforms and IT-infrastructures for data collection with different formats. In addition, EPTN WP1, to enhance high quality clinical trials, EPTN-WP1 will define the requirements for high quality clinical trials and set up an infrastructure for methodological support.
Keywords: Particle therapy, PROMs, registry

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Permalink: https://www.hzdr.de/publications/Publ-26937
Publ.-Id: 26937


Azimuthal magnetorotational instability with super-rotation

Rüdiger, G.; Schultz, M.; Gellert, M.; Stefani, F.
It is demonstrated that the azimuthal magnetorotational instability (AMRI) also works with radially increasing rotation rates contrary to the standard magnetorotational instability for axial fields which requires negative shear. The stability against non-axisymmetric perturbations of a conducting Taylor–Couette flow with positive shear under the influence of a toroidal magnetic field is considered if the background field between the cylinders is current free. For small magnetic Prandtl number Pm->0 the curves of neutral stability converge in the (Hartmann number, Reynolds number) plane approximating the stability curve obtained in the inductionless limit Pm=0. The numerical solutions for Pm=0 indicate the existence of a lower limit of the shear rate. For large Pm the curves scale with the magnetic Reynolds number of the outer cylinder but the flow is always stable for magnetic Prandtl number unity as is typical for double-diffusive instabilities. We are particularly interested to know the minimum Hartmann number for neutral stability. For models with resting or almost resting inner cylinder and with perfectly conducting cylinder material the minimum Hartmann number occurs for a radius ratio of 0.9. The corresponding critical Reynolds numbers are smaller than 10000.

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Publ.-Id: 26936


Quasi-free (p,pN) scattering of light neutron-rich nuclei around N = 14

Diaz Fernandez, P.; Alvarez-Pol, H.; Crespo, R.; Cravo, E.; Atar, L.; Deltuva, A.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamano, M.; Cabanelas, P.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Datta Pramanik, U.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fernandez-Dominguez, B.; Fraile, L. M.; Freer, M.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Jurciukonis, D.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec, J.; Moro, A. M.; Movsesyan, A.; Nacher, E.; Najafi, A.; Nikolskii, E.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietras, B.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.
In this work we investigate for the first time the quasi-free scattering reactions (p,pn) and (p,2p) simultaneously for the same projectile in inverse and complete kinematics for radioactive beams with the aim to study the evolution of single-particle properties from N = 14 to N = 15.
Keywords: quasi-free scattering reactions radioactive beams single-particle

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Publ.-Id: 26935


Comparing the outcome of proton beam irradiation with experimental x-ray and clinical photons in a sophisticated 3-D assay setup

Sorour, N.; Hussein, R.; von Neubeck, C.; Lühr, A.; Schölch, S.; Beyreuther, E.; Pawelke, J.; Kunz-Schughart, L. A.
Background and Aim:
Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer with a median survival of <6 months. The role of radiotherapy in PDAC treatment is consistently under debate. Recent studies imply the superiority of proton versus photon irradiation and propose a benefit for pancreatic cancer patients. We therefore aimed at a systematical comparison of the treatment outcome of PDAC cells when exposed to different beams (photons, protons). Our study included the technical setup, establishment, and application of a multicellular 3-D assay to assess the putatively „curative“ biological endpoint of spheroid control probabilities (SCP).

Materials and Methods:
Four PDAC cell line models were applied in 96-well liquid-overlay spheroid culture. A clinical LINAC (6 MV) at a dose rate of 3 Gy/min and an experimental X-ray tube (220 kV) at a dose rate of 1.3 Gy/min were used for photon irradiation. For proton exposure, spheroids were placed within a spread-out Bragg peak (SOBP) of a double scattered proton beam (150 MeV) and irradiated with a dose rate of 3, 6 and 10 Gy/min. After single-dose irradiation (0-30 Gy), radioresponse was evaluated by a 60-day post-treatment monitoring of spheroid integrity, recovery, and volume growth.

Results and Conclusions:
For proton irradiation, variations in the dose rate were proven to neither alter the SCP nor the spheroid volume growth behavior. SCP and SCD50 (spheroid control dose 50%) turned out to be reproducible read-outs for 3-D culture treatment outcome. Experimental and clinical photon beams led to similar response of PDAC 3-D models. However, all spheroids showed a higher sensitivity to protons reflected by a significant reduction in the SCD50 values and an RBE of 1.2-1.5. New combinatorial treatment strategies with protons are now under evaluation.
  • Lecture (Conference)
    DEGRO 2018, 21.06.2018, Leipzig, Deutschland
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 194(2018), S29-S30

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Publ.-Id: 26934


Sensitization of pancreatic cancer cells to photons and protons via enzymotherapeutic metabolic targeting of arginine

Sorour, N.; Hussein, R.; von Neubeck, C.; Lühr, A.; Stasyk, O.; Kunz-Schughart, L. A.
Background and Aim:
The abnormal metabolism of pancreatic ductal adenocarcinoma (PDAC) cells offers some interesting points of attack. About 20-30% of PDACs are described to be auxotrophic for arginine because of a reduced or complete loss of anabolic protein expression and/or activity. New strategies for the treatment of this deadly disease should consider the combination of radiotherapy with novel metabolic targeting modalities. We found various arginine deprivation therapy (ADT) approaches to radiosensitize several non-auxotrophic cancer cell types. Hence, we hypothesized that enzymotherapeutic ADT should be particularly efficient in radiosensitizing auxotrophic PDACs to both photons and protons.

Materials and Methods:
Human and murine cell lines reflecting auxotrophic PDACs in patients were studied. ADT was achieved with 2 U/ml of recombinant human arginase in the presence and absence of citrulline. Single dose irradiation of 0-30 Gy was applied with a 200kV X-ray tube and a 150 MeV double-scattered proton beam. Treatment response was assessed by 2-D clonogenic survival and/or 3-D spheroid control probability (SCP) assays. Our specifically designed setup allowed the testing of innovative treatment regimens including proton therapy with/without ADT and Gemcitabine (Gem).

Results and Conclusions:
ADT led to a massive sensitization to X-ray in all PDAC models. Sensitization in 3-D culture was reflected by a significantly reduced SCP and spheroid control dose 50% (SCD50) with an RBE of 2.0. Cells showed a higher sensitivity in the 3-D assay to protons than photons but ADT still further improved the radioresponse. As an example, the RBE of protons plus ADT versus photons alone in one human PDAC spheroid typel was 3.9. In the same model, proton therapy outcome was hardly affected by Gem; however, the combination of ADT with Gem and proton therapy was particularly effective with an exceptional RBE compared to photons of 5.0. Extended mechanistic studies are ongoing; transfer in vivo is envisioned.
  • Lecture (Conference)
    DEGRO 2018, 21.06.2018, Leipzig, Deutschland
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 194(2018), S96

Permalink: https://www.hzdr.de/publications/Publ-26933
Publ.-Id: 26933


Single molecule level measurements: salen molecule

Kilibarda, F.; Sendler, T.; Mortensen, M.; Gothelf, K.; Erbe, A.
The research presents novel ideas and directions which are supposed to overcome the obstacles conditioned by larger and larger deviations from the Moor's law. One of the possible solutions of the problem lies in the field of Molecular Electronics. We attempt to reduce the size and power needed to operate the device by using single molecules as building blocks in our circuits. This not only offers new features but also self-organizing properties. In order to choose the correct building blocks for our future circuits, we first characterize them. One of the prominent techniques is the Mechanically Controllable Break Junction (MCBJ). With this method we can examine properties of electron transport through single molecules, and determine parameters such as molecular energy level and metal-molecule coupling strength. The technique is demonstrated on salen and salen derivatives. The research shows that we can successfully tune molecular energy levels by the use of chemical doping.
Keywords: Scaling, molecular electronics, single molecule, self-organizing, MCBJ, break junction, characterization, electron transport, energy level, salen, energy level tuning, chemical doping
  • Poster
    Trends in Nanoscience 2017, 27.-30.03.2017, Kloster Irsee, Bavaria, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26932
Publ.-Id: 26932


Molecular characterization in liquid and cryogenic environments

Kilibarda, F.; Strobel, A.; Lokamani, M.; Sendler, T.; Mortensen, M.; Gothelf, K.; Erbe, A.
Current industrial scaling processes are reaching limits. We see not only diminishing returns with further scaling attempts, but also physical limitations that come more and more into play. In our research we offer a novel approach, to use single molecules as electronic components.
This approach offers not only size improvements, but also a reduction in power consumption and costs. Our research focuses on classifying different molecules with the help of Mechanically Controlled Break Junction (MCBJ). Here we present two different kinds of measurements.
One is performed in liquid solution and under ambient conditions, and the other one in a cryogenic environment, under vacuum.
As a test bed for these measurements we use salen and 𝐶₆₀ molecules, respectively. In the case of salen molecules, we show, how chemical doping influences energy levels and affects electron transport through the molecule. The experimental results are supported by quantum chemical calculations. The 𝐶₆₀ measurements demonstrate that we can remove the influence of the solvent by in situ molecular evaporation into the nanoscopic junction. Additionally, operation under vacuum allows us to use more reactive metals for the nano-junction, and thus vary metal-molecule orbital overlap, where in traditional approach contacts are made out of noble metals like gold.
Keywords: Scaling, single molecule, molecular electronics, MCBJ, break junction, electron transport, energy level, quantum chemical calculation, cryogenic, solvent, chemical doping, salen, 𝐶₆₀
  • Poster
    DPG-Frühjahrstagung, 11.-16.03.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-26931
Publ.-Id: 26931


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