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33407 Publications

Laser-Rewriteable Ferromagnetism at Thin Film Surfaces

Ehrler, J.; He, M.; Shugaev, M. V.; Polushkin, N. I.; Wintz, S.; Liersch, V.; Cornelius, S.; Hübner, R.; Potzger, K.; Lindner, J.; Fassbender, J.; Ünal, A. A.; Valencia, S.; Kronast, F.; Zhigilei, L. V.; Bali, R.
Manipulation of magnetism using laser light is considered a key to the advancement of data storage technologies. Until now, most approaches seek to optically switch the direction of magnetization rather than to reversibly manipulate the ferromagnetism itself. Here we use ~100 fs laser pulses to reversibly switch ferromagnetic ordering on and off by exploiting a chemical order-disorder phase transition in Fe60Al40, from the B2 to the A2 structure and vice versa. A single laser pulse above a threshold fluence causes non-ferromagnetic B2 Fe60Al40 to disorder and form the ferromagnetic A2 structure. Subsequent pulsing below the threshold reverses the surface to B2 Fe60Al40, erasing the laser induced ferromagnetism. Simulations reveal that the order-disorder transition is regulated by the extent of surface supercooling; above threshold the film melts-through and the consequent stability of the supercooled liquid phase suppresses vacancy diffusion, freezing the material into the disordered state. Pulsing below threshold forms a limited supercooled surface phase that solidifies at sufficiently high temperatures, enabling diffusion assisted reordering. This demonstrates that ultrafast lasers can achieve subtle atomic rearrangements in bimetallic alloys in a reversible and non-volatile fashion.
Keywords: magneto-optical devices; data storage; phase transitions; fs laser modifications; supercooling; order-disorder
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Laser schaltet Magnet an und aus (Id 27530) cites this publication

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Permalink: https://www.hzdr.de/publications/Publ-27198
Publ.-Id: 27198


Application of Gas Field Ion Source to Patterning Nanoscale Magnetic Structures

Bali, R.; Schmeink, A.; Hlawacek, G.; Lindner, J.; Faßbender, J.
Magnetic nanostructures are necessary components in a variety of sensors and devices, and in prototypes of spin-transport and spin-wave devices. In the past, broad beam ion-irradiation has been used to modify the magnetic properties via a variety of mechanisms, such as alloying, intermixing and structural disordering. In this contribution, we describe the application of the highly focused noble gas ion beam of a gas field ion source (GFIS), to the nanoscale modification of magnetic properties in alloy thin films. Materials in which the saturation magnetization (Ms) can be drastically enhanced via small changes to the atomic arrangement are ideal for the GFIS approach.
In B2 alloys such as Fe60Al40, Fe50Rh50 and Fe60V40, light noble gas ion-irradiation leads to the formation of anti-site defects, which increases the Fe – Fe nearest neighbor interactions and generates an associated increase of the Ms. The disorder induced by the GFIS beam is highly localized, with the extent of the magnetized region determined by lateral scattering of ions. These B2 alloys can be used as non-ferromagnetic templates, on to which the highly focused ion-beam acts as a magnetic writing stylus. Here we examine the conditions necessary and experimentally achievable limits for producing magnetic nanostructures using GFIS.
  • Lecture (Conference)
    2nd international HeFIB conference on Helium and emerging Focused Ion Beams, 11.-13.06.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27197
Publ.-Id: 27197


Strong neutron pairing in core+4n nuclei

Revel, A.; Marqués, F. M.; Sorlin, O.; Aumann, T.; Caesar, C.; Holl, M.; Panin, V.; Vandebrouck, M.; Wamers, F.; Alvarez-Pol, H.; Atar, L.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamano, M.; Casarejos, E.; Catford, W. N.; Cederkäll, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Datta Pramanik, U.; Diaz Fernandez, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; 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.; 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, J.; Movsesyan, A.; Nacher, E.; Naja, M.; Nikolskii, E.; Nilsson, T.; Nociforo, C.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Röder, M.; Rossi, D.; Savran, D.; Scheit, H.; Simon, H.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Velho, P.; Volkov, V.; Wagner, A.; Weick, H.; Wheldon, C.; Wilson, G.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.
The emission of neutron pairs from the neutron-rich N =12 isotones 18-C and 20-O has been studied by high-energy nucleon knockout from 19-N and 21-O secondary beams, populating unbound states of the two isotones up to 15 MeV above their two-neutron emission thresholds. The analysis of triple fragment-n-n correlations shows that the decay 19N(-1p)18C* -> 16-C+n+n is clearly dominated by direct pair emission. The two-neutron correlation strength, the largest ever observed, suggests the predominance of a 14-C core surrounded by four valence neutrons arranged in strongly correlated pairs. On the other hand, a significant competition of a sequential branch is found in the decay 21-O(-1n)20-O* -> 18-O+n+n, attributed to its formation through the knockout of a deeply-bound neutron that breaks the 16-O core and reduces the number of pairs.
Keywords: R3B radioactive beams nuclear structure neutron-rich Coulomb dissociation

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Publ.-Id: 27196


Large scale arrays of Co/Pd and Fe60Al40 nanomagnets with tunable magnetic properties for recording and magnonic applications

Krupinski, M.; Mitin, D.; Sobieszczyk, P.; Bali, R.; Zarzycki, A.; Potzger, K.; Albrecht, M.; Marszalek, M.
The fabrication and characterization of nanopatterned magnetic thin films is an important topic for magnetic recording media, sensors, information processing, and magnonic crystals. This broad spectrum of applications results from the possibility of controlling the magnetic properties of such systems in wide range by introducing artificial defects to ferromagnetic material and arranged them in ordered or disordered arrays.
This presentation will focus on the magnetic properties and switching behaviour of magnetic Co(0,3 nm)/Pd(0,9 nm) and Fe60Al40 (40 nm) films composed of arrays of dots, antidots and triangles. Such arrays of nanostructures were created by colloidal lithography complemented by RF-plasma etching and ion irradiation with 20 keV Ne+ ions, which resulted in nanomagnets with sizes down to 30 nm [1].
Using SQUID magnetometry, changes in coercive field, saturation magnetization, loop squareness, and magnetic anisotropy constant have been determined in a temperature range of 5 K – 350 K and compared with non-patterned films. The domain shapes and sizes together with the switching behaviour were studied by scanning magnetoresistive microscopy utilizing commercial reading-writing head from HDD. We have shown that the coercivity reach a maximum values for the arrays with a separation length between nanomagnets close to the domain wall width, which is caused by strong domain wall pinning. The impact of the patterning on the magnetic anisotropy is also clearly seen. The observed influence of surface morphology on magnetic properties and magnetization switching characteristics was confirmed by the micromagnetic modelling using mumax3 software. The results demonstrated that the proposed approach can be effectively used to produce large scale magnetic arrays with properties widely tuneable by temperature and patterning period.

This work was supported by Polish National Science Centre grant No 2017/01/X/ST8/01409.
  • Lecture (Conference)
    XIV International Conference on Nanostructured Materials (Nano 2018), 24.-29.06.2018, Hong Kong, Hong Kong

Permalink: https://www.hzdr.de/publications/Publ-27195
Publ.-Id: 27195


Imaging Structure and Magnetisation in New Ways Using 4D STEM

Maclaren, I.; Nord, M.; Conner, S.; Mcgrouther, D.; Allen, C. S.; Danaie, M.; Kirkland, A. I.; Bali, R.; Hlawacek, G.; Lindner, J.; Faßbender, J.
The Materials and Condensed Matter group at the University of Glasgow has long been experimenting with direct electron detectors, together with the Particle Physics Experimental group. A Medipix2 detector was integrated onto our Philips CM20FEG electron microscope in a bottom mount position in 2010 and used in initial studies [1,2]. More recently, a Medipix3 detector was installed onto our JEOL ARM200F in a fixed mount at the 35mm camera port, and together with a Merlin readout system (Quantum Detectors Ltd., Harwell, UK) it was possible to run 4D STEM imaging at >1000 frames per second, under the control of Gatan Digital Micrograph. A similar system has been installed in a bottom mount on the JEOL Grand ARM at ePSIC. Most recently, a retractable mount for the Medipix3 detector has been produced at Glasgow, and is now installed on our JEOL ARM200F in the 35mm port.

One area of use of pixelated detection is for the improved differential phase contrast (DPC) mapping of magnetization in materials. Traditional DPC-STEM uses split detectors to determine the deflection of the bright field disc but suffers from additional diffraction contrast redistributing contrast within the disc thus creating image speckle on the length-scale of the grains. This can be overcome using a pixelated detector, and processing the discs using edge detection and cross correlation to give a pure disc deflection without the diffraction contrast [3]. This has been used in studying the magnetic structures arising from the patterning of B2 Fe60Al40 – this structure is ordered and paramagnetic after deposition and annealing, but after exposure to a (suitably low dose) Ne+ beam it is disordered to a BCC structure, which is strongly ferromagnetic and has a larger the parameter. We recorded diffraction patterns (Fig 1a) at a camera length to show both the central bright field disc and the inner rings of crystal diffraction spots. Fig 1b shows the plotted magnetization in one of these stripes. Fig 1c shows the lattice parameters determined from the diffraction ring radii in the directions parallel to and perpendicular to the long stripe axis. It is clear that parallel to the length, the parameter is constrained by the surrounding film, whereas there is a larger expansion perpendicular to the interface, across the width of the patterned magnetic stripe. This suggests that strain can be used to bias the magnetization in films.

Another novel use for pixelated detectors is to use high angle scattering into higher order Laue zones to reveal ordering along the beam direction, B [4]. Datasets containing such high angle information have now been recorded at atomic resolution, such as Fig 2 from a perovskite oxide heterostructure. Fig 2a shows HAADF contrast for this dataset, and both La-containing layers are much brighter than the SrTiO3 layer, as expected. Fig 2b shows the integrated intensity in the inner Laue zone ring, which only appears for the LaFeO3 layer. This arises from the doubling of the unit cell along B, and the intensity roughly corresponds to the magnitude of atomic shuffles parallel to B, showing that these only reach a maximum at the layer midpoint. Careful inspection also shows that the signal is strongest on the La columns, demonstrating that they are the primary source of the period doubling. This allows detailed investigation of the local “crystal structure”, which differs from the bulk LaFeO3 structure. The plots in Fig 2c show these trends for lines drawn from left to right, together with the outer Laue zone radius, which reveals subtle changes in lattice parameter along the beam direction across this heterostructure.

This demonstrates two exciting areas for application of such fast pixelated detectors for 4D STEM imaging, and shows that it enables new kinds of investigations, not possible with traditional detectors.

References:

[1] A MacRaighne et al., Journal of Instrumentation 6, (2011) C01047.
[2] R Beacham et al., Journal of Instrumentation 6 (2011) C12052.
[3] M Krajnak et al., Ultramicroscopy 165 (2016) 42
[4] M Nord et al., Microscopy and Microanalysis, 22 [S3] (2016) p. 476.
[5] This work was funded by the EPSRC (Fast Pixel Detectors: a paradigm shift in STEM imaging, EP/M009963/1). We thank Diamond Light Source for access and support in use of the electron Physical Science Imaging Centre (EM16952) that contributed to the results presented here.
  • Invited lecture (Conferences)
    Microscopy & Microanalysis 2018 Meeting, 05.-09.08.2018, Baltimore MD, USA

Permalink: https://www.hzdr.de/publications/Publ-27194
Publ.-Id: 27194


Nanoscale magnetic and structural characterization of Ne+ irradiated FeAl thin films using pixelated STEM

Nord, M.; Bali, R.; Hlawacek, G.; Lindner, J.; Fassbender, J.; Maclaren, I.; Mcgrouther, D.
Recent advances in 2-dimensional pixelated direct electron detectors have enabled the development of high acquisition rate imaging of the diffraction pattern in the scanning transmission electron microscope (STEM), resulting in the acquisition of a 4D STEM dataset of a full diffraction pattern for every scan position. One use for this is STEM differential phase contrast (DPC) imaging [1], which allows for quantitative measurements of the in-plane magnetic induction when operating the microscope with the objective lens turned off. This imaging mode is essentially convergent beam low angle diffraction, allowing for structural information to also be extracted from the diffraction patterns (Fig. 1b). This novel technique enables both strain and magnetic information to be extracted from a single dataset.

In this work we have simultaneously characterized both magnetic and physical (crystal) structure of patterned ferromagnetic stripes in Fe60Al40. As-deposited Fe60Al40 has an ordered B2 structure and is paramagnetic, but irradiation with Ne+ ions causes transformation to a disordered A2 ferromagnetic BCC structure with a larger lattice parameter [2]. This allows for arbitrarily shaped ferromagnetic regions to be written using a focused ion beam (FIB) with a Ne+ source. By using a JEOL ARM200cF probe aberration corrected STEM equipped with a MERLIN 1R (Medipix3) fast pixelated detector [Quantum Detectors Ltd], we are able to acquire datasets at 1 nm spatial resolution in aberration-corrected field-free Lorentz (objective-off) mode from patterned stripe structures with lateral dimensions from 0.02 – 4 µm and lengths of 10 µm (Fig. 1a). These possess unexpected domain structures in which large fraction of the magnetization deviates away from the long-axis, against shape anisotropy. To uncover the origin of the induced magnetic anisotropy we determined the strain profile in the nanowires from the diffraction patterns, which was also found to be very anisotropic, with the lattice parameter along the long axis clamped to something close to that of the surrounding film (orange trace in Fig. 1c) whereas the lattice parameter along the short axis is significantly larger (blue trace in Fig. 1c), as expected from the irradiation. Our data shows that the resulting shape-dependent anisotropic strain fields exert a strong influence on observed magnetic domain structure.

[1] Matus Krajnak, et al., Ultramicroscopy, 165 (2016) 42–50, doi:10.1016/j.ultramic.2016.03.006

[2] Rantej Bali, et al., Nano Letters, 14 (2014) 435-441, doi:10.1021/nl404521c

The authors are indebted to the EPSRC for the funding of this work via the project “Fast Pixel Detectors: a paradigm shift in STEM imaging” (Grant reference EP/M009963/1).
  • Lecture (Conference)
    19th International Microscopy Congress (IMC19), 09.-14.09.2018, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-27193
Publ.-Id: 27193


Beryllium-7 at DREsden Accelerator Mass Spectrometry

Rugel, G.; Merchel, S.; Scharf, A.; Querfeld, R.; Steinhauser, G.; Tiessen, C.
Half-lives of routine accelerator mass spectrometry (AMS) nuclides typically range from thousands to millions of years. We measured short-lived 7Be (T1/2 = 53.2 d) at the DREsden AMS-facility (DREAMS) [1] as low as 90 mBq, which can be challenging for rapid γ-counting. Simultaneous determination of 7Be and 10 Be (T1/2= 1.387 Ma) via AMS is advantageous for improved understanding of production, transport, and deposition of atmospherically produced 7,9,10Be [2].
Data was normalized to a 7 Be sample produced via 7Li(p,n)7Be, measured by γ-counting and chemically processed to BeO after adding low-level 9Be carrier (7Be/9Be ≈ 10-12). The isobar 7Li is completely eliminated by chemistry and the degrader foil technique (at detector 7Be4+, 10.2 MeV, no 7Li4+ possible). The blank ratio of 5 × 10-16 7Be/9Be (0.8 mBq) and simple and fast chemistry allows for the measurement of rainwater samples, collected in Germany, as small as 10 mL corresponding to a few times 10-14 7Be/9Be [3,4].
Thanks to D. Bemmerer (HZDR) and G. György (ATOMKI, Hungary) for help with the 7Be normalization material.
[1] G. Rugel et al., NIMB 370 (2016) 94.
[2] A.M. Smith et al., NIMB 294 (2013) 59.
[3] R. Querfeld et al., JRNC 314 (2017) 521.
[4] C. Tiessen et al. JRNC (to be submitted).
Keywords: Be-7, AMS
  • Lecture (Conference)
    MAT Science Week (Ionenstrahlworkshop), 24.-25.04.2018, Darmstadt, Deuschland

Permalink: https://www.hzdr.de/publications/Publ-27192
Publ.-Id: 27192


Doping beyond the solid solubility limit: from bulk to nanostructured semiconductors

Berencen, Y.
Hyperdoping has recently emerged as a potential powerful technique to explore new functionalities of semiconductor materials with unique electrical and optical properties [1-3]. Hyperdoping facilitates to introduce dopants into a semiconductor material at concentrations far above those obtained at equilibrium conditions, viz. doping far beyond the solubility limit. Hyperdoped Si with chalcogens or transition metals like Au or Ti has been postulated to be a promising material for many applications, especially for Si-based infrared photodetectors and intermediate band solar cells ([3] and references therein).

Most of the relevant published papers [1-3] have been limited to the study of hyperdoped bulk Si with chalcogens. Particularly, S and Se have primarily been used for this kind of purpose since they can introduce a variety of deep donor states in the upper half of the band gap of Si, which give rise to the formation of an impurity band that allows a strong sub-band gap optical absorption at wavelengths larger than 1 µm [2]. To create such an impurity band in a semiconductor like Si, whose equilibrium solubility limit for the aforementioned dopants is around 1016 cm-3 [1], high dopant concentrations exceeding the so-called Mott limit are required [1]. Therefore, non-equilibrium thermal processing to obtain hyperdoped semiconductor materials is sound.

Chalcogens are commonly introduced by pulsed-laser irradiation of the material under study, which is simultaneously immersed in an atmosphere containing chalcogen atoms [2]. Another singular approach is to use ion implantation followed by either nanosecond (ns)-range pulsed-laser melting (PLM) [1] or millisecond (ms)-range flash lamp annealing (FLA) [3]. Both PLM and FLA are advantageous if compared with conventional annealing techniques. For instance, these techniques offer high crystal quality after recrystallization, high dopant solubility and low heating of the substrate [3]. Moreover, depending on the energy density and the timescale of annealing after implantation (typically, from few ns to dozens of ms), liquid-phase or solid-phase epitaxy can be induced on the implanted material surface, which accounts for the epitaxial recrystallization atop the crystalline substrate [3]. In particular, solid-phase epitaxy via ms-range FLA was reported to be superior to liquid-phase epitaxy through ns-range PLM in terms of less dopant redistribution and high electrical activation of dopants [3].

In the last years, semiconductor nanowires (NWs) have gained increasing importance as building blocks for nanodevices like field-effect transistors, light emitting devices, photovoltaic cells and integrated photodetectors ([4] and references therein). Indeed, their reduced sizes and the physical confinement along two directions allow the tuning of electro-optical properties such as conductivity, optical absorption and photoluminescence, among others. Recently, traditional dopants such as B and P have been introduced into Si NWs by ion implantation followed by conventional annealing [5]. Recrystallization and reactivation of dopants were successfully achieved at low doses. However, both phenomena were not successful at high doses since it resulted in the formation of polycrystals and a low ratio of dopant activation. To date, there are only theoretical examinations of the properties of Si NWs hyperdoped with chalcogens [4]. These results have shown that donor defects give rise to a strong hyperfine interaction in the hyperdoped Si NWs, which can be exploited to develop a Si-based nuclear spin quantum computer [4].

Therefore, the new approach to combine Si NWs and hyperdoping with chalcogens proposed here can provide important contributions to the state-of-the-art and will help to answer important fundamental and practical scientific issues.

Reference
[1] Ertekin E., Winkler M. T., Recht D., Said A. J., Aziz M. J., Buonassisi T., Grossman J. C. (2012): Insulator-to-Metal Transition in Selenium-Hyperdoped Silicon: Observation and Origin. Published in: Physical Review Letters 108, 026401.
[2] Sher M. J., Mazur E. (2014): Intermediate band conduction in femtosecond-laser hyperdoped silicon. Published in: Applied Physics Letters 105, 032103.
[3] Zhou S., Liu F., Prucnal S., Gao K., Khalid M., Baehtz C., Posselt M., Skorupa W., Helm M. (2015): Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy. Published in: Scientific Reports 5, 8329.
[4] Petretto G., Massé A., Fanciulli M., Debernardi A. (2015): Analysis of hyperfine structure in chalcogen-doped silicon and germanium nanowires. Published in: Physical Review B 91, 125430.
[5] Fukata N., Takiguchi R., Ishida S., Yokono S., Hishita S., Murakami K., (2012): Recrystallization and reactivation of dopant atoms in ion-implanted silicon nanowires. Published in: ACS NANO 6, 3278.
Keywords: Chalcogens, silicon, hyperdoping, ion implantation, flash lamp annealing, insulator to metal transition, sub-band gap photoresponse, infrared plasmonics, nanowires
  • Lecture (others)
    Leibniz institute seminar, 22.02.2018, Leibniz Institute of Polymer Research Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27187
Publ.-Id: 27187


A high-efficiency gas target setup for underground experiments, and redetermination of the branching ratio of the 189.5 keV 22Ne(p,γ)23Na resonance

Ferraro, F.; Takács, M. P.; Piatti, D.; Mossa, V.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; D'Erasmo, G.; Di Leva, A.; Elekes, Z.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Marcucci, L. E.; Marigo, P.; Menegazzo, R.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Trezzi, D.; Zavatarelli, S.
The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory (INFN-LNGS), Italy, and high intensity, 250-500 μA, proton and α ion beams. In order to fully exploit these features, a high-purity, recirculating gas target system for isotopically enriched gases is coupled to a high-efficiency, six-fold optically segmented bismuth germanate (BGO) γ-ray detector. The beam intensity is measured with a beam calorimeter with constant temperature gradient. Pressure and temperature measurements have been carried out at several positions along the beam path, and the resultant gas density profile has been determined. Calibrated γ-intensity standards and the well-known Ep = 278 keV 14N(p,γ)15O resonance were used to determine the γ-ray detection efficiency and to validate the simulation of the target and detector setup. As an example, the recently measured resonance at Ep = 189.5 keV in the 22Ne(p,γ)23Na reaction has been investigated with high statistics, and the γ-decay branching ratios of the resonance have been determined.

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Publ.-Id: 27186


Experimental investigation of fluid dynamics in sandwich packings with ultrafast X-ray tomography

Sohr, J.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.
Sandwich packings consist of two layers of corrugated sheet structured packings with higher (holdup layer) and lower (de-entrainment layer) specific surface area alternatingly placed in the column. They are preferentially operated between the flooding points of both layers, which results in zones of bubbly flow, froth regime and liquid film flow in each sandwich element. Compared to conventional packed columns, sandwich packings can reach higher capacity and also higher separation efficiency as a result of intensive phase interactions. In the scope of a collaborative project, sandwich packings are experimentally and theoretically investigated. To provide detailed information on the heterogeneous flow patterns to derive reliable process models, ultrafast X-ray tomography is applied as a non-invasive measurement technique with high temporal and spatial resolution. In addition to local liquid holdup in the different layers of the packing, cross-sectional liquid distribution and axial transitions between the flow regimes are estimated. Furthermore, a method for the detection of the gas-liquid interfacial area is proposed.
  • Open Access Logo Chemical Engineering Transactions 69(2018), 727
    DOI: 10.3303/CET1869122
  • Lecture (Conference)
    11th International Conference on Distillation & Absorption, 16.-19.09.2018, Florence, Italy

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Permalink: https://www.hzdr.de/publications/Publ-27185
Publ.-Id: 27185


Rate-based modelling of CO2 absorption with sandwich packings

Flechsig, S.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.
The efficiency of fluid separation processes can be enhanced by the application of sandwich packings (SPs). They consist of two alternating layers of industrially available standard packings with different specific surface areas, one with lower (the so-called holdup layer, HL) and another with higher (the so-called de-entrainment layer, DL) capacity. SPs are typically used at operating conditions between the flooding points of HL and DL. Above the HL, a froth sub-layer is formed, which reveals high separation efficiency due to intensified phase contact. In a collaborative project, the effects of the individual flow regimes on fluid dynamics and mass transfer are being investigated, both experimentally and theoretically. In order to identify the impact of the individual flow regimes, experiments in an absorption/desorption plant are supplemented by flow imaging measurements. This paper focuses on a rate-based model, in which the heterogeneous flow patterns in SPs are considered via appropriate correlations. In order to validate this model, we measured CO2 absorption characteristics under the influence of different operating and design parameters and compared them with the simulation results.
  • Open Access Logo Chemical Engineering Transactions 69(2018), 169
    DOI: 10.3303/CET1869029
  • Poster
    11th International Conference on Distillation & Absorption, 16.-19.09.2018, Florence, Italy

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Permalink: https://www.hzdr.de/publications/Publ-27184
Publ.-Id: 27184


Peptides as Biosorbents - Promising tools for resource recovery

Braun, R.; Bachmann, S.; Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.
Despite many innovations, meeting both economic and ecological requirements remains challenging for conventional resource recovery technology. The development of highly selective peptides puts a new competitor on the market. We present an approach to identify peptides for resource recovery using Phage Surface Display. Here, we describe the development of peptides for binding of rare earth element terbium containing solids and for removal and enrichment of the heavy metal ions of cobalt and nickel out of waste waters and leaching solutions.
Keywords: phage display; biosorption; peptide; biohydrometallurgy

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Permalink: https://www.hzdr.de/publications/Publ-27183
Publ.-Id: 27183


Fluiddynamische Untersuchung von Anstaupackungen mittels ultraschneller Röntgentomographie

Sohr, J.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.
In Anstaupackungen bilden sich durch die Kombination von Packungslagen unterschiedlicher geometrischer Oberfläche abhängig von den Betriebsbedingungen Filmströmung und Sprudelschicht gleichzeitig aus. Durch die axial stark heterogene Strömungsmorphologie lassen integrale Holdup-Messungen keine Rückschlüsse auf lokale Flüssigkeitsinhalte in einzelnen Packungslagen zu.
Die ultraschnelle Röntgentomographie bietet dank einer Bildrate von bis zu 8000 Schnittbildern pro Sekunde die Möglichkeit, bei den hochdynamischen Zweiphasenströmungen relevante fluiddynamische Parameter in einzelnen Abschnitten der Anstaupackung nichtinvasiv zu bestimmen [1]. Neben der Ermittlung von Phasenanteilen und deren radialer sowie axialer Verteilung werden auch Methoden zur Ermittlung der Gas-Flüssigkeits-Grenzfläche angewandt. Ein weiterer entscheidender Parameter für die hydrodynamische Modellierung von Anstaupackungen ist die Höhe der Sprudelschicht [2]. Deren Bestimmung erfolgt zum einen mithilfe der ultraschnellen Röntgentomographie sowie ergänzend durch eine verteilte Druckverlustmessung mit einer axialen Auflösung von 10 mm. Im Rahmen dieses Beitrags werden sowohl die Messmethoden als auch Messergebnisse der experimentellen Untersuchungen vorgestellt.
Wir danken der DFG für die finanzielle Unterstützung des Kooperationsprojekts "Experimentelle und theoretische Untersuchung der Fluiddynamik und des Stofftrennverhaltens von Anstaupackungen" (KE 837/26-1, HA 3088/10-1).
[1] A. Janzen, M. Schubert, F. Barthel, U. Hampel, E.Y. Kenig, Chemical Engineering and Processing: Process Intensification 66, 20-26 (2013).
[2] U. Brinkmann, B. Kaibel, M. Jödecke, J. Maćkowiak, E.Y. Kenig, Chemie Ingenieur Technik 84: 36-45 (2012).
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrentechnik, 27.-28.02.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27182
Publ.-Id: 27182


Cluster Formation in the Superconducting Complex Intermetallic Compound Be21Pt5

Amon, A.; Ormeci, A.; Bobnar, M.; Akselrud, L. G.; Avdeev, M.; Gumeniuk, R.; Burkhardt, U.; Prots, Y.; Hennig, C.; Leithe-Jasper, A.; Grin, Y.
Materials with the crystal structure of γ-brass type (Cu5Zn8 type) are typical representatives of intermetallic compounds. From the electronic point of view, they are often interpreted using the valence electron concentration approach of Hume−Rothery, developed previously for transition metals. The γ-brass-type phases of the main-group elements are rather rare. The intermetallic compound Be21Pt5, a new member of this family, was synthesized, and its crystal structure, chemical bonding, and physical properties were characterized. Be21Pt5 crystallizes in the cubic space group F4̅3m with lattice parameter a = 15.90417(3) Å and 416 atoms per unit cell. From the crystallographic point of view, the binary substance represents a special family of intermetallic compounds called complex metallic alloys (CMA). The crystal structure was solved by a combination of synchrotron and neutron powder diffraction data. Besides the large difference in the scattering power of the components, the structure solution was hampered by the systematic presence of very weak reflections mimicking wrong symmetry. The structural motif of Be21Pt5 is described as a 2 × 2 × 2 superstructure of the γ-brass structure (Cu5Zn8 type) or 6 × 6 × 6 superstructure of the simple bcc structural pattern with distinct distribution of defects. The main building elements of the crystal structure are four types of nested polyhedral units (clusters) with the compositions Be22Pt4 and Be20Pt6. Each cluster contains four shells (4 + 4 + 6 + 12 atoms). Clusters with different compositions reveal various occupation of the shells by platinum and beryllium. Polyhedral nested units with the same composition differ by the distance of the shell atoms to the cluster center. Analysis of chemical bonding was made applying the electron localizability approach, a quantum chemical technique operating in real space that is proven to be especially efficient for intermetallic compounds. Evaluations of the calculated electron density and electron localizability indicator (ELI-D) revealed multicenter bonding, being in accordance with the low valence electron count per atom in Be21Pt5. A new type of atomic interactions in intermetallic compounds, cluster bonds involving 8 or even 14 atoms, is found in the clusters with shorter distances between the shell atoms and the cluster centers. In the remaining clusters, four- and five-center bonds characterize the atomic interactions. Multicluster interactions within the polyhedral nested units and threecenter polar intercluster bonds result in a three-dimensional framework resembling the structural pattern of NaCl. Be21Pt5 is a diamagnetic metal and one of rather rare CMA compounds revealing superconductivity (Tc = 2.06 K).

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Publ.-Id: 27181


Electronic Structure of Two-Dimensional Lead(II) Iodide Perovskites: An Experimental and Theoretical Study

Phuyala, D.; Safdari, M.; Pazoki, M.; Liu, P.; Philippe, B.; Kvashnina, K. O.; Karis, O.; Butorin, S. M.; Rensmo, H.; Edvinsson, T.; Kloob, L.; Gardner, J. M.
Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light harvesting applications due to their chemical stability, wide flexibility in composition, and recent increases in photovoltaic power conversion efficiencies. Three 2D lead iodide perovskites were studied through various X-ray spectroscopic techniques to derive detailed electronic structures and band energetics profiles at a titania interface. Core-level and valence band photoelectron spectra of HOP were analyzed to resolve the electronic structure changes due to the reduced-dimensionality of inorganic layers. The results show orbital narrowing when comparing the HOP, the layered precursor PbI2, and the conventional 3D (CH3NH3)PbI3 such that different localizations of band edge states and narrow band states are unambiguously due to the decrease in dimensionality of the layered HOPs. Support from density functional theory (DFT) calculations provide further details on the interaction and bandgap variations of the electronic structure. We observed an interlayer distance dependent dispersion in the near band edge electronic states. The results show how tuning the interlayer distance between the inorganic layers affects the electronic properties and provides important design principles for control of the interlayer charge transport properties, such as the change in effective charge masses as a function of the organic cation length. The results of these findings can aid in establishing design principles for new, layered

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Publ.-Id: 27180


Evidence for a dynamical ground state in the frustrated pyrohafnate Tb2Hf2O7

Anand, V. K.; Opherden, L.; Xu, J.; Adroja, D. T.; Hillier, A. D.; Biswas, P. K.; Herrmannsdörfer, T.; Uhlarz, M.; Hornung, J.; Wosnitza, J.
We report the physical properties of Tb2Hf2O7 based on ac magnetic susceptibility χac(T ), dc magnetic susceptibility χ(T ), isothermal magnetization M(H), and heat capacity C(T ) measurements combined with muon spin relaxation (μSR) and neutron powder diffraction measurements. No evidence for long-range magnetic order is found down to 0.1 K. However, χac(T ) data present a frequency-dependent broad peak (near 0.9 K at 16 Hz) indicating slow spin dynamics. The slow spin dynamics is further evidenced from the μSR data (characterized by a stretched exponential behavior) which show persistent spin fluctuations down to 0.3 K. The neutron powder diffraction data collected at 0.1 K show a broad peak of magnetic origin (diffuse scattering) but no magnetic Bragg peaks. The analysis of the diffuse scattering data reveals a dominant antiferromagnetic interaction in agreement with the negative Weiss temperature. The absence of long-range magnetic order and the presence of slow spin dynamics and persistent spin fluctuations together reflect a dynamical ground state in Tb2Hf2O7.

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Publ.-Id: 27179


Increasing stripe-type fluctuations in AFe2As2 (A = K, Rb, Cs) superconductors probed by 75As NMR spectroscopy

Zhang, Z. T.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Khim, S.; Gass, S.; Wolter, A. U. B.; Wurmehl, S.; Grafe, H.-J.; Kühne, H.
We report 75As nuclear magnetic resonance measurements on single crystals of RbFe2As2 and CsFe2As2. Taking previously reported results for KFe2As2 into account, we find that the anisotropic electronic correlations evolve towards a magnetic instability in the AFe2As2 series (with A = K, Rb, Cs). Upon isovalent substitution with larger alkali-metal ions, a drastic enhancement of the anisotropic nuclear spin-lattice relaxation rate and decreasing Knight shift reveal the formation of pronounced spin fluctuations with stripe-type modulation. Furthermore, a decreasing power-law exponent of the nuclear spin-lattice relaxation rate (1/T1)HIIab, probing the in-plane spin fluctuations, evidences an emergent deviation from Fermi-liquid behavior. All these findings clearly indicate that the expansion of the lattice in the AFe2As2 series tunes the electronic correlations towards a quantum critical point at the transition to a yet unobserved ordered phase.

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Publ.-Id: 27178


Defect induced magnetism in SiC

Zhou, S.ORC
Defect induced magnetism, which can be controllably generated by ion or neutron irradiation, is attracting intensive research interest. It not only challenges the traditional opinions about magnetism, but also has some potential applications in spin-electronics. SiC is a new candidate for the investigation of defect-induced ferromagnetism after graphitic materials and oxides due to its high material purity and crystalline quality [1, 2]. In this contribution, we present a comprehensive investigation on the structural and magnetic properties of ion implanted and neutron irradiated SiC samples. In combination with X-ray absorption spectroscopy, high-resolution transmission electron microscopy and first-principles calculations, we try to understand the mechanism in a microscopic picture.
For neon or xenon ion implanted SiC, we identify a multi-magnetic-phase nature [3]. The magnetization of SiC can be decomposed into paramagnetic, superparamagnetic and ferromagnetic contributions. The ferromagnetic contribution persists well above room temperature and exhibits a pronounced magnetic anisotropy. By combining X-ray magnetic circular dichroism and first-principles calculations, we clarify that p-electrons of the nearest-neighbor carbon atoms around divacancies are mainly responsible for the long-range ferromagnetic coupling [4]. Thus, we provide a correlation between the collective magnetic phenomena and the specific electrons/orbitals. Moreover, a negative magnetoresistance has been observed in ferromagnetic an conducting SiC, indicating the interplay between magnetism and free carriers [5].
With the aim to verify if a sample containing defects through its bulk volume can persist ferromagnetic coupling, we applied neutron irradiation to introduce defects into SiC [6]. Besides a weak ferromagnetic contribution, we observe a strong paramagnetism, scaling up with the neutron fluence. The ferromagnetic contribution only occurs in a narrow fluence window or after annealing. First-principles calculations hint towards a mutually exclusive role of the concentration of defects: Defects favor spin polarization at the expense of magnetic interaction. Moreover, the interaction between the nuclear spin and the paramagnetic defect can effectively tune the spin-lattice relaxation time (T1) as well as the nuclear spin coherent time (T2) [7].

[1] L. Li, et al., Appl. Phys. Lett. 98, 222508 (2011).
[2] Y. Wang, et al., Phys. Rev. B 90, 214435 (2014).
[3] Y. Wang, et al., Phys. Rev. B 89, 014417 (2014).
[4] Y. Wang, et al., Scientific Reports, 5, 8999 (2015).
[5] Y. Liu, et al., Phys. Rev. B 95, 195309 (2017).
[6] Y. Wang, et al., Phys. Rev. B 92, 174409 (2015).
[7] Z. Zhang, et al., Phys. Rev. B 95, 085203 (2017).
  • Invited lecture (Conferences)
    International Workshop: Functionality of Oxide Interfaces, 26.02.-02.03.2018, Benedictine Abbey of Frauenwörth, Germany

Permalink: https://www.hzdr.de/publications/Publ-27177
Publ.-Id: 27177


Interplay between localization and magnetism in (III,Mn)V dilute ferromagnetic semiconductors

Zhou, S.; Yuan, Y.; Sawicki, M.; Rushforth, A. W.; Zhao, J.; Dietl, T.; Helm, M.
Although the interplay between hole-mediated ferromagnetism and hole localization has long been recognized as the central issue in dilute ferromagnetic semiconductors (DFSs), its understanding remains in a nascent stage and contradicting approaches are under consideration [1, 2]. Some of the difficulties lie in the sample preparation: the dual role of Mn in III-V compounds providing local spins and holes, the poor control over donor defects (Mn interstitials and As antisites) etc. In this contribution, we examine the influence of localization on the hole-mediated ferromagnetism in (III,Mn)V DFSs by utilizing the well-developed ion-beam technology for microelectronics which can overcome the aforementioned difficulties [3].
First, we have used ion implantation of Mn combined with pulsed laser melting to prepare Ga1−xMnxAs and In1−xMnxAs with Mn concentration from 0.3% to 1.8% covering both sides of the insulator-metal transition [4-8]. The system evolves with x from a paramagnetic phase (probed down to 1.8 K), to a superparamagnetic material, to reach, via a mixed phase consisting of percolating ferromagnetic clusters and superparamagnetic grains, a global ferromagnetism without any superparamagnetism. On the insulating side of the transition, ferromagnetic signatures persist to higher temperatures in In1−xMnxAs compared to Ga1−xMnxAs with the same Mn concentration x. This substantiates theoretical suggestions that stronger p-d coupling results in an enhanced contribution to localization, which reduces hole-mediated ferromagnetism. Second, we use inert Helium ions to precisely compensate holes by donor defects, thereafter to shift the Fermi energy in DFSs while keeping the Mn concentration constant [9-12]. For a broad range of samples including (Ga,Mn)As and (Ga,Mn)(As,P) with various Mn and P concentrations, we observe a monotonous decrease of Curie temperature TC down to zero and a spin-reorientation transition with hole compensation while the conduction is changed from metallic to insulating. The previously questioned existence of TC below 10 K is also confirmed in heavily compensated samples. Our comprehensive results support strongly the heterogeneous model of electronic states at the localization boundary and point to the crucial role of weakly localized holes in mediating efficient spin-spin interactions even on the insulator side of the metal-insulator transition.

[1] M. Sawicki et al., Nat. Phys. 6, 22 (2010).
[2] M. Kobayashi et al., Phys. Rev. B 89, 205204 (2014).
[3] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001 (2015).
[4] S. Zhou et al., Appl. Phys. Express 5, 093007 (2012).
[5] Y. Yuan…, S. Zhou, J. Phys. D: Appl. Phys. 48, 235002 (2015).
[6] S. Prucnal…, S. Zhou, Phys. Rev. B 92, 224407 (2015).
[7] Y. Yuan…, S. Zhou, Phys. Rev. Mater. 1, 054401 (2017).
[8] Y. Yuan…, S. Zhou, J. Phys.: Condens. Matter 30, 095801 (2018).
[9] L. Li…, S. Zhou, J. Phys. D: Appl. Phys. 44 099501 (2011).
[10] S. Zhou et al., Phys. Rev. B 95, 075205 (2016).
[11] M. Lonsky…, S. Zhou, J. Müller, Phys. Rev. B 97, 054413 (2018).
[12] Y. Yuan..., S. Zhou, J. Phys. D: Appl. Phys., in press (2018).
  • Poster
    34th International conference on the physics of semiconductors, 29.07.-03.08.2018, Montpellier, France

Permalink: https://www.hzdr.de/publications/Publ-27176
Publ.-Id: 27176


Hydrogen-assisted Post-growth Doping of Tellurium into Molybdenum Disulfide Monolayers with Tunable Compositions

Yin, G.; Zhu, D.; Lv, D.; Zhang, Z.; Hashemi, A.; Krasheninnikov, A. V.ORC; Komsa, H.-P.; Jin, C.
Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS2) monolayers to form MoS2xTe2(1−x) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H2 plays an indispensable role in the Te substitution into as-grown MoS2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS2(1−x)Te2x alloy, while with increasing Te concentration (up to ∼27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density functional theory calculations are used to investigate the stability of the alloy structures and their electronic properties. Comparison with experimental results indicate that the samples are unstrained and the Te atoms are predominantly substituted in the top S sublattice. Importantly, such ultimately thin Janus structure of MoS2(1−x)Te2x exhibits properties that are distinct from their constituents. We believe our results will inspire further exploration of the versatile properties of asymmetric 2D TMD alloys.
Keywords: 2D materials, post-growth, tellurium, TMDC, MoS2

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Publ.-Id: 27175


Big Bang Cosmology in the Lab: The 2H(p,γ)3He reaction studied at LUNA

Stöckel, K. For The Luna Collaboration
Recent high-precision measurements of the primordial 2H abundance have opened the path to use Big Bang nucleosynthesis to constrain the primordial baryon to photon ratio with similar precision as the cosmic microwave background. This would provide an independent cross-check on current Big Bang models. However, the interpretation of the abundance is limited by the lack of precise nuclear data, in particular on the main 2H destruction channel, the 2H(p,γ)3He reaction. A new experiment to study the 2H(p,γ)3He cross section directly in the Big Bang energy window is underway at the LUNA 400 kV accelerator, deep underground in the Gran Sasso laboratory, Italy. The progress of experiment and analysis will be summarized. – Supported by DFG (BE 4100/4-1).
  • Lecture (Conference)
    DPG-Frühjahrstagung Bochum 2018, 26.02.-02.03.2018, Bochum, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27174
Publ.-Id: 27174


Monothioarsenate transformation kinetics determines arsenic sequestration by sulfhydryl groups of peat

Besold, J.; Biswas, A.; Suess, E.; Scheinost, A. C.; Rossberg, A.; Mikutta, C.; Kretzschmar, R.; Gustafsson, J. P.; Planer-Friedrich, B.
In peatlands, arsenite was reported to be effectively sequestered by sulfhydryl groups of organic matter. To which extent porewater arsenite can react with reduced sulfur to form thioarsenates and how this affects arsenic sequestration in peatlands, is unknown. Here, we show that in the arsenic-rich peatland Gola di Lago, Switzerland, up to 93% of all arsenic species in surface and porewaters were thioarsenates. The dominant species, monothioarsenate, likely formed from arsenite and surface-associated zero-valent sulfur (S(0)). Laboratory incubations with sulfide-reacted peat showed for both, monothioarsenate and arsenite, increasing total arsenic sorption with decreasing pH from 8.5 to 4.5. However, X-ray absorption spectroscopy revealed no binding of monothioarsenate via sulfhydryl groups. The sorption observed at pH 4.5 was acid-catalyzed dissociation of monothioarsenate, forming arsenite. The lower the pH and the more sulfhydryl sites, the more arsenite sorbed which in turn shifted equilibrium towards further dissociation of monothioarsenate. At pH 8.5, monothioarsenate was stable over 41 days. In conclusion, arsenic is effectively sequestered in anoxic, acidic environments where arsenite is the only arsenic species. Where fluctuating redox conditions enable sulfide oxidation to S(0), monothioarsenate forms and at neutral to alkaline pH, slow transformation kinetics make this species highly mobile.
Keywords: arsenic speciation wetland ground water xafs

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Publ.-Id: 27173


Analysis of the Electric-Double-Layer formation by in-situ Rutherford Backscattering Spectrometry

Baghban Khojasteh Mohammadi, N.; Heller, R.; Bergmann, U.; Apelt, S.
A setup for in-situ Rutherford Backscattering Spectrometry (RBS) has been installed at the 2 MV Van-de-Graaff accelerator at the Ion Beam Center (IBC) of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Online analysis of solid-liquid interfaces as well as electro-chemistry experiments are conducted by this technique. A Si3N4 window separates the liquid from the vacuum in the RBS chamber. A He+ beam (E = 1.7 MeV) is utilized for the RBS measurements. RBS as well as Particle Induced X-Ray Emission Spectroscopy (PIXE) spectra are recorded simultaneously to increase the sensitivity for trace elements. The technique was employed for direct measurements of the Electric-Double-Layer (EDL) formation on Si3N4. Investigations of the EDL formation at solid-liquid interfaces are of great significance due to the various valuable applications such as super-capacitors that can be utilized to provide a backup power supply or applied in various other fields [1-3]. In our preliminary experiments, the specific adsorption of Barium ions from a 1mM BaCl2 solution with various pH values was observed in a direct and quantitative manner. Sensitivity of the technique reaches the ppm range and areal densities can be measured down to 0.1 atomic monolayer.
[1]Kötz et al., (2002). The 12th International Seminar on Double Layer Capacitors and Similar Energy Storage Devices, Dec, USA.
[2]Faggioli et al., (1999). J. Power Sources, 84(2): 261.
[3]Simon et al., (2008). Nature materials, 7(11): 845.
Keywords: in-situ RBS, Electric-Double-Layer
  • Lecture (Conference)
    Workshop on Ion and Particle Beams (Ionenstrahl Workshop), 24.-25.04.2018, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-27172
Publ.-Id: 27172


An experimental approach to reactive transport in geomaterials: GeoPET

Kulenkampff, J.; Franke, K.; Gründig, M.; Hildebrand, H.; Karimzadeh, L.; Schymura, S.; Fischer, C.
Detailed understanding of reactive transport in geomaterials of chemical species, including radionuclides, is required for the utilization of the subsoil, e.g. for designing ore production by in-situ leaching, or for radioactive waste disposal. To complement the well-established conventional approach, i.e. computer model simulations based upon bulk material parameters and geochemical data bases, we apply process tomography with positron emission tomography (GeoPET) for direct observation and parameterization of the reactive transport processes. This enables to consider heterogeneity as pervasive feature of processes in complex media. One example is localized flow meandering along fractures, where preferential flow may jeopardize leaching efficiency. On the other hand, fissure networks through otherwise tight material could provide fast transport pathways through geological barriers.
Our workflow consist of 1) production of appropriate PET-nuclides and labelling, 2) transport experiment on samples of drill core size with the labelled species, 3) recording of PET-data (list-mode-files) during the course of tracer propagation, 4) computation of PET-frames with appropriate frame rate and correction for material effects, 5) parameterization of the spatiotemporal data set with the target parameters effective volume distribution and velocity distribution.
The choice of PET-nuclides is broader than in common biomedical PET applications, because longevity and toxicity of the tracers are inconsiderable, but spatial resolution and efficient corrections for attenuation and scatter require attention. The development of the GeoPET method during the past decade is described in Kulenkampff et al. (2016).
As illustration, we present an example from ore leaching, where the leaching solution is flown through an artificial fracture. During leaching we experimentally determined the macroscopic flow field with GeoPET. With these hydrodynamic data we are able to establish a realistic and light-weight reactive transport model which can directly serve for efficient design of leaching.
The procedure is one good example for the benefit of radiotracers for unravelling complex processes by non-destructive molecular imaging. We strongly suggest utilizing this distinguished tool, in particular for .parameterization and upscaling of heterogeneous reactive transport models.

Kulenkampff, J., Gründig, M., Zakhnini, A., Lippmann-Pipke, J. 2016. Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217-1231, 10.5194/se-7-1217-2016.
  • Lecture (Conference)
    RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27171
Publ.-Id: 27171


Comparison of different treatment planning approaches for intensity-modulated proton therapy with simultaneous integrated boost for pancreatic cancer

Stefanowicz, S.; Stützer, K.; Zschaeck, S.; Jakobi, A.; Troost, E. G. C.ORC
Background
Neoadjuvant radio(chemo)therapy of non-metastasized, borderline resectable or unresectable locally advanced pancreatic cancer is complex and prone to cause side-effects, e.g., in gastrointestinal organs. Intensity-modulated proton therapy (IMPT) enables a high conformity to the targets while simultaneously sparing the normal tissue such that dose-escalation strategies come within reach. In this in silico study, we compared four IMPT planning strategies including robust multi-field optimization (rMFO) and a simultaneous integrated boost (SIB) for dose-escalation in pancreatic cancer patients.

Methods
For six pancreatic cancer patients referred for adjuvant or primary radiochemotherapy four rMFO-IMPT-SIB treatment strategies of two or three (non-)coplanar beam arrangements were calculated. Dose values for both targets, the elective clinical target volume (CTV) and the SIB, and the organs at risk as well as target conformity and homogeneity indexes, derived from the dose volume histograms, were statistically compared.

Results
All treatment plans of each strategy fulfilled the prescribed doses to the targets (D95%≥95%, D2%≤107%). No significant differences for the conformity index were found (p>0.05), however, treatment plans with a three non-coplanar beam approach were most homogenous to both targets (p<0.045). Dose constraints for large and small bowel as well as for the liver and the spinal cord were met with all beam arrangements. Irrespective of the planning strategies, the dose constraint for the duodenum and stomach were not met. Using the three-beam arrangements, the dose to the left kidney could be significant decreased when compared to a two-beam strategy (p<0.045).

Conclusion
Based on our findings we recommend a three-beam configuration with at least one non-coplanar beam for rMFO-IMPT-SIB in advanced pancreatic cancer patients achieving a homogeneous dose distribution in the target while simultaneously minimizing the dose to the organs at risk.
Keywords: pancreatic cancer; intensity modulated proton therapy; simultaneous integrated boost; dose escalation

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Publ.-Id: 27170


High-Yield Optical Undulators Scalable to Optical Free-Electron Laser Operation by Traveling-Wave Thomson-Scattering

Steiniger, K.ORC
All across physics research, incoherent and coherent light sources are extensively utilized.
Especially highly brilliant X-ray sources such as third generation synchrotrons or free-electron lasers have become an invaluable tool enabling experimental techniques that are unique to these kinds of light sources.
But these sources have developed to large scale facilities and a demand in compact laboratory scale sources providing radiation of similar quality arises nowadays.

This thesis focuses on Traveling-Wave Thomson-Scattering (TWTS) which allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources.
The TWTS geometry provides optical undulators, through which electrons pass and thereby emit radiation, with hundreds to thousands of undulator periods by utilizing pulse-front tilted lasers pulses from high peak-power laser systems.

TWTS can realize incoherent radiation sources with orders of magnitude higher photon yield than established head-on Thomson sources.
Moreover, optical free-electron lasers (OFELs) can be realized with TWTS if state-of-the-art technology in electron accelerators and laser systems is utilized.

Tilting the laser pulse front with respect to the wavefront by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows realizing thousands of optical undulator periods.

This thesis will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems.
The requirements on electron bunch and laser pulse quality of these ultraviolet TWTS OFELs are discussed in detail as well as the corresponding requirements of TWTS OFELs emitting in the soft and hard X-ray range.
These requirements are derived from scaling laws which stem from a self-consistent analytic description of the electron bunch and radiation field dynamics in TWTS OFELs presented within this thesis.
It is shown that these dynamics in TWTS OFELs are qualitatively equivalent to the electron bunch and radiation field dynamics of standard free-electron lasers which analytically proves the applicability of TWTS for the realization of an optical free-electron laser.

Furthermore, experimental setup strategies to generate the pulse-front tilted TWTS laser pulses are presented and designs of experimental setups for the above examples are discussed.
The presented setup strategies provide dispersion compensation, required due to angular dispersion of the laser pulse, which is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.
An example of such an enhanced Thomson source by TWTS, which provides orders of magnitude higher spectral photon density than a comparable head-on interaction geometry, is presented, too.
Keywords: Traveling-Wave, Thomson scattering, X-ray, free-electron laser, pulse-front tilt
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-089 2018

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Publ.-Id: 27169


Thick Permalloy films for the imaging of spin texture dynamics in perpendicularly magnetized systems

Finizio, S.; Wintz, S.; Bracher, D.; Kirk, E.; Semisalova, A. S.; Förster, J.; Zeissler, K.; Weßels, T.; Weigand, M.; Lenz, K.; Kleibert, A.; Raabe, J.
Performance combined with simplicity: we demonstrate that thick Permalloy films exhibiting a weak growth-induced perpendicular magnetic anisotropy can be employed as an ideal test system for the study of magnetodynamical processes in perpendicularly magnetized systems exhibiting magnetic textures ranging from isolated magnetic bubbles to more complex n"pi" states.
Keywords: Skyrmion, STXM, PMA

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Publ.-Id: 27168


Magnetic small-angle neutron scattering

Mühlbauer, S.; Honecker, D.; Perigo, E. A.; Bergner, F.ORC; Disch, S.; Heinemann, A.; Erokhin, S.; Berkov, D.; Leighton, C.; Eskildsen, M. R.; Michels, A.
Small-angle neutron scattering (SANS) is one of the most important techniques for microstructure determination, being utilized in a wide range of scientific disciplines, such as materials science, physics, chemistry, and biology. The reason for its great significance is that conventional SANS is probably the only method capable of probing structural inhomogeneities in the bulk of materials on a mesoscopic real-space length scale, from roughly 1 − 300 nm. Moreover, the exploitation of the spin degree of freedom of the neutron provides SANS with a unique sensitivity to study magnetism and magnetic materials at the nanoscale. As such, magnetic SANS ideally complements more real-space and surface-sensitive magnetic imaging techniques, e.g., Lorentz transmission electron microscopy, electron holography, magnetic force microscopy, Kerr microscopy, or spin-polarized scanning tunneling microscopy. In this review article we summarize the recent applications of the SANS method to study magnetism and magnetic materials. This includes a wide range of materials classes, from nanomagnetic systems such as soft magnetic Fe-based nanocomposites, hard magnetic Nd−Fe−B-based permanent magnets, magnetic steels, ferrofluids, nanoparticles, and magnetic oxides, to more fundamental open issues in contemporary condensed matter physics such as skyrmion crystals, noncollinar magnetic structures in noncentrosymmetric compounds, magnetic/electronic phase separation, and vortex lattices in type-II superconductors. Special attention is paid not only to the vast variety of magnetic materials and problems where SANS has provided direct insight, but also to the enormous progress made regarding the micromagnetic simulation of magnetic neutron scattering.

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Permalink: https://www.hzdr.de/publications/Publ-27167
Publ.-Id: 27167


Detecting Beryllium-10 from exotic decays by Accelerator Mass Spectrometry (AMS)

Forstner, O.; Merchel, S.ORC; Lachner, J.; Rugel, G.; Is541 Kollaboration
The one-neutron halo-nucleus 11Be decays via beta-minus to the stable nucleus 11B (t1/2=13.76 s). In rare cases a subsequent emission of a proton leads to the unstable nucleus 10Be. Theoretical calculations predict a branching ratio of this rare decay channel of below 10-7. With the capability of AMS in measuring ultra-low isotopic ratios (10Be/9Be < 10-15) the branching ratio of beta-delayed proton decay to 10Be could be measured for the first time.
A beam of 11Be ions was produced at the radioactive ion beam facility ISOLDE at CERN. After mass separation the ions were implanted in Cu targets. These targets containing the produced 10Be were spiked with low-level 9Be and in the form of BeO chemically prepared as AMS targets at HZDR. The resulting 10Be/9Be ratios were determined via AMS at the VERA laboratory of the University of Vienna. With the known quantity of added 9Be the amount of implanted 10Be was calculated. Due to the low expected branching ratio and the resulting low number of implanted 10Be atoms a high efficiency paired with a low background of the 9Be carrier material was necessary.
To further widen the spectrum of radionuclides measureable by AMS and lowering the detection limits for similar nuclear physics research, we are planning to implement an optical filtering method for selective suppression of isobars by laser photodetachment (LISEL) at the 6 MV tandem accelerator at HZDR.
Keywords: AMS
  • Lecture (Conference)
    Workshop on Ion and Particle Beams (Ionenstrahl Workshop), 24.-25.03.2018, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27166
Publ.-Id: 27166


Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing

Nie, W. J.; Zhang, Y. X.; Yu, H. H.; Li, R.; He, R. Y.; Dong, N. N.; Wang, J.; Hübner, R.; Böttger, R.; Zhou, S. Q.; Amekura, H.; Chen, F.
We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au+ ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF4 crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS2 saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

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Permalink: https://www.hzdr.de/publications/Publ-27165
Publ.-Id: 27165


OpenFOAM – a contributer‘s point of view

Schlegel, F.; Liao, Y.; Oertel, R.; Meller, R.
Der Vortrag behinhaltet einen Überblick über die Arbeiten im Bereich Mehrphasen-Simulation der Abteilung FWDC mit Hilfe der C++-Bibliothek OpenFOAM.
  • Lecture (Conference)
    German CFD Meeting, 06.03.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27164
Publ.-Id: 27164


Magnetic Properties of Coupled Co/Mo/Co Structures Tailored by Ion Irradiation

Wawro, A.; Kurant, Z.; Jakubowski, M.; Tekielak, M.; Pietruczik, A.; Böttger, R.; Maziewski, A.
Modifications of the magnetic properties of Co=Mo=Co films activated by irradiation with 30-keV Ar and 17-keV Ne ion beams are investigated and compared with the influence of 35-keV Ga ions. This system is magnetized in the sample plane and exhibits a twofold anisotropy. The interlayer coupling of magnetization in as-deposited structures is parallel except for the Mo spacer thickness range between 0.5 and 1.0 nm, where the magnetization of the Co layers is antiparallel oriented. The coupling changes and gradually reduced strength of the ferromagnetic properties are compared for all ion types and discussed as a function of the Mo spacer thickness and the ion fluence. The structural evolution of the studied films with increasing fluence determined from TRIDYN simulations is discussed in relation to the observed magnetic changes.We also propose various types of magnonic crystals that can be fabricated by exploiting the results presented in this work.
Keywords: Ion Irradiation, layered magnetic structures, interlayer coupling, magnetism

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Permalink: https://www.hzdr.de/publications/Publ-27163
Publ.-Id: 27163


Localized ion beam mixing using a focused Neon beam for future SET applicatons

Xu, X.; Hlawacek, G.; Wolf, D.; Engelmann, H.-J.; Prüfer, T.; Hübner, R.; Bischof, L.; von Borany, J.; Facsko, S.; Heinig, K.-H.
The increased use of personal computing devices and the Internet of Things (IoT) is accompanied by a demand for a computation unit with extra low energy dissipation. The Single Electron Transistor (SET), which uses a Coulomb island to manipulate the movement of single electrons, is a candidate device for future low-power electronics. However, so far its development is hindered by low-temperature requirements and the absence of CMOS compatibility. By combining advanced top-down lithography with botom-up self-assembly of Si nano dots (NDs) we will overcome this barrier.
In this work, Si NDs—suitable as RT Coulomb islands—are formed via ion beam mixing followed by thermally stimulated phase separation. Spatial control over the ND formation is achieved by using the highly focused Neon beam with a diameter of only 2 nm available in the helium ion microscope (HIM).
The impinging energetic ions will locally mix excess Si from a top Si-layer and into a buried SiO 2 layer which is grown on a Si wafer. This results in a mixing volume small enough for restricted Ostwald ripening and successful single ND formation. The formation of spatially controlled single NDs with a diameter of only 2.2 nm is confrmed by comparing the energy fltered transmission electron microscopy (EFTEM) Si plasmon-loss intensity with simulated plasmon loss images. The conditions for ND formation, namely the dependence on primary energy, irradiation fuence, layer thickness and thermal budget during rapid thermal annealing (RTA), are optimized based on an extensive survey of this multidimensional parameter space. The investigation is guided by TRIDYN simulations of the Si excess in an SiO 2 layer due to ion beam mixing and 3D Kinetic Monte-Carlo (3DkMC) simulation for the phase separation during the thermal treatment. To achieve a CMOS compatible mass fabrication of individual NDs the results are than transferred to Si + broad beam irradiation and cross checked by EFTEM. In this case localization will be achieved by pre-structuring the sample into narrow pillars using lithography.
This work has been funded by the European Union’s Horizon 2020 Research and Innovation Program under grant agreement No. 688072 “IONS SET”.
Keywords: HIM
  • Lecture (Conference)
    picoFIB, 31.01.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27162
Publ.-Id: 27162


External validation of an NTCP model for acute esophageal toxicity in locally advanced NSCLC patients treated with intensity-modulated 5 (chemo-)radiotherapy

Dankers, F.; Wijsman, R.; Troost, E.; Tissing-Tan, C.; Kwint, M.; Belderbos, J.; de Ruysscher, D.; Hendriks, L.; de S.-Oei, L.-F.; Rodwell, L.; Dekker, A.; Monshouwer, R.; Hoffmann, A.; Bussink, J.
Purpose: We externally validated a previously established multivariable normal-tissue complication probability (NTCP) model for Grade ≥2 acute esophageal toxicity (AET) after intensity-modulated (chemo-)radiotherapy or volumetric-modulated arc therapy for locally advanced non-small cell lung cancer.
Experimental design: A total of 603 patients from five cohorts within four different Dutch institutes were included. Using the NTCP model, containing predictors concurrent chemoradiotherapy, mean esophageal dose, gender and clinical tumor stage, the risk of Grade ≥2 AET was estimated per patient and model discrimination and (re)calibration performance was evaluated for all cohorts.
Results: Five validation cohorts experienced higher incidence of Grade ≥2 AET compared to the training cohort (49.3%-70.2% vs 35.6%; borderline significant for one cohort, highly significant for four cohorts). For three cohorts, discriminative performance was similar to the training cohort (area under the curve (AUC) 0.81-0.89 vs 0.84). In the two remaining cohorts the model showed poor discriminative power (AUC 0.64 and 0.63). Reasonable calibration performance was observed in two cohorts, and recalibration further improved performance in all three cohorts with good discrimination. Recalibration for the two poorly discriminating cohorts did not improve performance.
Conclusions: The NTCP model for AET prediction was successfully validated in three out of five patient cohorts. The model did not perform well in two cohorts, which included patients receiving substantially 105 different treatment.
Before applying the model in clinical practice validation of discrimination and calibration performance on a local cohort is recommended. Recalibration of the model is advised to match predicted probabilities to locally observed frequencies of AET.

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Permalink: https://www.hzdr.de/publications/Publ-27161
Publ.-Id: 27161


Charge exchange and energy loss of slow highly charged ions transmitted through 2D materials

Wilhelm, R. A.ORC; Creutzburg, S.; Schwestka, J.; Gruber, E.; Kozubek, R.; Lehnert, T.; Leiter, R.; Heller, R.; Krasheninnikov, A.; Facsko, S.; Kaiser, U.; Kotakoski, J.; Schleberger, M.; Aumayr, F.
Slow highly charged ions carry a large amount (several 10 keV) of potential energy, which gets released by target excitation and secondary particle emission upon impact on a solid surface. The energy release can trigger permanent material modifications on semi-conducting and insulating materials [1]. To understand the energy release mechanism and get information on it’s time scale, we use freestanding 2D materials, limiting the interaction time of the ions upon transmission to a few femtoseconds. We detect the ions after the interaction by means of charge state, energy, and angle resolved detection techniques. Further, we detect emitted secondary electrons in coincidence with a particular charge exchange.
Using freestanding single layer graphene, our experimental findings revealed an ultrafast charge exchange and projectile de-excitation mechanism [2,3]. We also determined the in-plane current density in the material, which is transiently active to supply electrons to the ion, to be in the order of 1012A/cm2. Still, graphene is able to sustain these large current densities for a fs-time-scale without rupture. Here we go one step further and present results of ion transmission spectroscopy of single layer hBN and MoS2, which are insulating and semi-conducting, respectively.
  • Invited lecture (Conferences)
    IBMM 2018 - International Conference on Ion Beam Modification of Materials, 24.-29.06.2018, San Antonio, TX, USA

Permalink: https://www.hzdr.de/publications/Publ-27160
Publ.-Id: 27160


From the creation of carbon nanomembranes in a low energy electron microscope to perforation with highly charged ions

Wilhelm, R. A.ORC; Neumann, C.; Küllmer, M.; Winter, A.; Turchanin, A.
Carbon nanomembranes are materials with only nm thickness, which can be used as freestanding membranes in filtration applications. They exhibit interesting properties as they can be e.g. transformed into (semi-)metallic graphene, but are insulating in their pristine phase. Using a Low Energy Electron Microscope allowed us to follow the formation of a carbon nanomembrane by electron-induced cross-linking of a self-assembled monolayer in-situ and in real-time. Releasing the membrane from the substrate and irradiating it with highly chared ions leads finally to regularely sized nanopores.
  • Lecture (others)
    Seminar AG Turchanin, 11.01.2018, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27159
Publ.-Id: 27159


Synemin is a novel co-regulator of non-homologous end joining in head and neck cancer cells

Deville, S. S.; Förster, S.; Cordes, N.
Introduction:
Cancer therapy resistance is one of the major obstacles for higher cure rates. Novel key players of the resistome are focal adhesion proteins (FAPs). As FAPs are critically involved in DNA repair, we here characterize the yet unknown function of the FAP and intermediate filament protein Synemin (SYN) as a novel DNA repair regulator and potential cancer drug target in head and neck squamous cell carcinoma (HNSCC).

Methods and materials:
Our novel 3D High Throughput esiRNA Screen (3DHTesiRNAs) using laminin-rich extracellular matrix (lrECM) was conducted to measure radiation-induced residual DNA double strand breaks (DSBs; foci assay) and clonogenic radiation survival in UTSCC15-pEGFP-53BP1 cells. Validations were performed in 10 additional HNSCC cell lines in 3D lrECM. Upon SYN depletion, DSB repair reporter assays for non-homologous end joining (NHEJ) and homologous recombination (HR) as well as Western Blotting for protein expression and phosphorylation were carried out. SYN depleted cells with and without irradiation were analyzed for kinase activity profiling (PamGene) and protein interactome determination using a sequential immunoprecipitation/mass spectrometry approach.

Results and Discussion:
Among the targets found in the 3DHTesiRNAs, SYN turned out as one of the top FAP candidate determinants of HNSCC cell survival. SYN silencing radiosensitized HNSCC cells, while its exogenous overexpression induced radioprotection. We found an increased SYN/chromatin interaction and a marked perinuclear SYN accumulation post irradiation. Intriguingly, SYN depletion elicited a 40% reduction in NHEJ activity without affecting HR or alt-EJ. In line, ATM, DNA-PKcs and c-Abl phosphorylation as well as Ku70 expression strongly declined in SYN depleted and irradiated cells relative to controls and, in contrast, to the rescue of these protein modifications by SYN overexpression. Single, double and triple depletion of SYN, DNA-PKcs and c-Abl resulted in similar radiosensitization and DSB levels as observed for SYN only, suggesting its upstream role. In the kinome analysis we observed variable changes in the serine/threonine kinases, in contrast to the tyrosine kinases with a pronounce reduced kinase activity after SYN silencing.

Conclusion:
Our data suggest the intermediate filament SYN as a new important determinant of DNA repair, tyrosine kinome and radioresistance of HNSCC cells. These observations further support the notion that DNA repair is controlled by cooperative interactions between nuclear and cytoplasmic proteins.
Keywords: synemin, radiobiology
  • Poster
    EACR 2018 - 25th Biennial Congress of the European Association for Cancer Research, 30.06.-03.07.2018, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-27158
Publ.-Id: 27158


beta8 integrin critically contributes to pancreatic cancer cell radiochemoresistance and intracellular vesicle trafficking under stress conditions

Lee, W.-C.; Jin, S.; Cordes, N.
Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies in the world and has a 5-year relative overall survival rate of less than 5%. Thus, there is a great need for functional targeting d strategies. As cell-matrix adhesion is essential for the survival, invasion and therapy resistance, we sought to identify the function of 117 focal adhesion proteins (FAP) in PDAC cell radiochemoresistance. Intriguingly, 8 integrin turned out to be one of the most potential novel targets in PDAC.
Material and methods: We performed a 3D endoribonuclease-prepared siRNA (esiRNA)-based high throughput screening (3DHTesiS) in PDAC cell cultures (established and patient-derived (PDC)) grown in laminin-rich extracellular matrix (IrECM). In addition to characterizing 8 integrin expression, distribution and co-localization with other cellular organelles such as golgi apparatus, clonogenic survival assays were performed upon esiRNA-mediated knockdown, X-ray irradiation (6 Gy single dose) and gemcitabine. Fiji software was used to determine Peason’s correlation coefficient, vesicle distribution and expression patterns upon irradiation or gemcitabine. An inhibitor screen was conducted to identify pathway involved in changes of 8 integrin localization upon treatment.
Results: We identified a series of novel targets including 8 integrin. Without cytotoxicity, 8 integrin depletion elicited radiochemosensitization in PDAC, PDCs cell lines and reduced sphere formation and 3D invasion into collagen-I. Intriguingly, we found 8 integrin located in perinuclear area where it colocalized with the cis-Golgi matrix protein GM130. Upon irradiation and gemcitabine, 8 integrin dissociated from the perinuclear region and spread throughput the cytosol without enhanced localization to exosomes; a process abrogated by antimycin A or oligomycin pre-treatment.
Summary: Our findings, generated in 3D lrECM PDAC cell ccultures, suggest 8 integrin as a novel determinant of PDAC radiochemoresistance. Moreover, 8 integrin may, although not found in the cell membrane to facilitate cell adhesion, a critical role in intracellular vesicle trafficking under stress conditions. Ongoing work will unravel the underlying mechanisms how 8 integrin is controlling cytoplasmic and nuclear survival pathways.
Keywords: beta8 integrin, radiotherapy
  • Poster
    EACR 2018 - European Association for Cancer Research, 30.06.-03.07.2018, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-27157
Publ.-Id: 27157


Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation

Yuan, Y.; Amarouche, T.; Xu, C.; Rushforth, A.; Boettger, R.; Edmonds, K.; Campion, R.; Gallagher, B.; Helm, M.; von Bardeleben, H.; Zhou, S. Q.
In the present work, the uniaxial magnetic anisotropy of GaMnAsP is modified by helium ion irradiation. According to the micro-magnetic parameters, e.g. resonance fields and anisotropy constants deduced from ferromagnetic resonance measurements, a rotation of the magnetic easy axis from out-of-plane [001] to in-plane [100] direction is achieved. From the application point of view, our work presents a novel avenue in modifying the uniaxial magnetic anisotropy in GaMnAsP with the possibility of lateral patterning by using lithography or focused ion beam.

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Permalink: https://www.hzdr.de/publications/Publ-27156
Publ.-Id: 27156


Electronic phase separation in insulating (Ga, Mn) As with low compensation: super-paramagnetism and hopping conduction

Yuan, Y.; Wang, M.; Xu, C.; Hübner, R.; Böttger, R.; Jakiela, R.; Helm, M.; Sawicki, M.; Zhou, S.
In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator–metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.

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Permalink: https://www.hzdr.de/publications/Publ-27155
Publ.-Id: 27155


Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1−xMnxAs and Ga1−xMnxP by means of fluctuation spectroscopy

Lonsky, M.; Teschabai-Oglu, J.; Pierz, K.; Sievers, S.; Schumacher, H. W.; Yuan, Y.; Böttger, B.; Zhou, S.; Müller, J.
We present systematic temperature-dependent resistance noise measurements on a series of ferromagnetic Ga1−xMnxAs epitaxial thin films covering a large parameter space in terms of the Mn content x and other variations regarding sample fabrication. We infer that the electronic noise is dominated by switching processes related to impurities in the entire temperature range. While metallic compounds with x>2% do not exhibit any significant change in the low-frequency resistance noise around the Curie temperature TC, we find indications for an electronic phase separation in films with x<2% in the vicinity of TC, manifesting itself in a maximum in the noise power spectral density. These results are compared with noise measurements on an insulating Ga1−xMnxP reference sample, for which the evidence for an electronic phase separation is even stronger and a possible percolation of bound magnetic polarons is discussed. Another aspect addressed in this work is the effect of ion-irradiation-induced disorder on the electronic properties of Ga1−xMnxAs films and, in particular, whether any electronic inhomogeneities can be observed in this case. Finally, we put our findings into the context of the ongoing debate on the electronic structure and the development of spontaneous magnetization in these materials.

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Permalink: https://www.hzdr.de/publications/Publ-27154
Publ.-Id: 27154


Time of Flight Backscatter and Secondary Ion Spectrometry in a Helium Ion Microscope

Klingner, N.; Hlawacek, G.; Heller, R.; von Borany, J.; Facsko, S.
Helium Ion Microscopy (HIM) utilizes a Gas Field Ion Source (GFIS) to create a Helium or Neon ion beam with a diameter better than 0.5 nm and 1.8 nm, respectively. The method is well known for its high resolution imaging and nano-fabrication capabilities which it is able to provide not only for conducting but also insulating samples without the need for a conductive coating. The latter specimens are typically found in the fields of biosciences, MEMS/NEMS technology, catalyst research and many others. The availability of He and Ne ions with either low or moderate sputter yields, allow direct write nano-structuring with a precision below 10 nm in the HIM [1, 2].
However, the existing GFIS based focused ion beam (FIB) tools suffer from the lack of a well integrated analytic method that can enrich the highly detailed morphological images with materials contrast. While HIM technology is relatively young several efforts have been made to add such an analytic capability to the technique. So far, ionoluminescence [1, 3], backscattering spectrometry (BS) [1, 4, 5], and secondary ion mass spectrometry (SIMS) using a magnetic sector [6] or time of flight (TOF) setup have been demonstrated [4].
After a brief introduction to HIM itself and a summary of the existing approaches I will focus on our own time of flight based analytic approaches. TOF-HIM is enabled by using a fast blanking electronics to chop the primary beam into pulses with a minimal length of only 20 ns. In combination with an multichannel-plate based stop detector this enables TOF backscatter spectrometry (TOF-BS) using He ions at an energy of only 30 keV. The achieved lateral resolution is 54 nm and represents a world record for spatially resolved backscattering spectrometry. The energy resolution has been measured to be 1.5 keV (5%). This is sufficient to separate most of the elements (see fig. 1) and allows the detection of thin surface layers formed from heavy elements. The results will be compared to the theoretical reachable lateral and energy resolution and the limiting experimental and physical constraints of this approach will be reviewed.
Finally first TOF-SIMS results obtained with a very simple experimental configuration will be presented. Based on the findings obtained with this poor man’s version of TOF-SIMS setup a dedicated extraction optics for secondary ions has been designed and tested. This revised setup can be operated in point and shoot mode to obtain high resolution SIMS data or in imaging mode to obtain element maps of the specimen surface. First experiments revealed a very high relative transmission of up to 76% which is crucial to collect enough signal from nanoparticles prior to their complete removal by ion sputtering. For m/q ≤ 80 u a Dm ≤ 0.3 u has been achieved. This is sufficient for many life science applications that rely on the isotope identification of light elements (e.g.: C, N). The lateral resolution of 8 nm has been evaluated using the knife edge method and a 75%/25% criterion which represents a world record for spatially resolved secondary ion mass spectrometry.
Keywords: HIM
  • Invited lecture (Conferences)
    Microscopy and Microanalysis, 05.-09.08.2018, Baltimore, USA
    DOI: 10.1017/S1431927618004506
  • Lecture (Conference)
    CAARI - 25th Conference on Application of Accelerators in Research and Industry, 13.-17.08.2018, Fort Worth, USA
  • Lecture (Conference)
    AVS International Symposium & Exhibition, 21.-26.10.2018, Long Beach, USA

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Permalink: https://www.hzdr.de/publications/Publ-27153
Publ.-Id: 27153


Harnessing the Coordination Chemistry of 1,4,7-Triazacyclononane for Biomimicry and Radiopharmaceutical Applications

Joshi, T.; Kubeil, M.ORC; Nsubuga, A.; Singh, G.ORC; Gasser, G.ORC; Stephan, H.ORC
TACN-based mono- and poly-nuclear metal complexes have found extensive use as biological mimics for understanding the structural and operational aspects of complex natural systems. Their coordination flexibility has also provided researchers access to a vast library of radiometal binding motifs that display excellent thermodynamic stability and kinetic inertness upon metal complexation. Synthetic modification on the TACN backbone has yielded ligands that can form metal complexes with coordination geometries well-suited for these applications. In particular, Leone Spiccia’s research has played a significant role in accelerating the progress in these two fields. With a focus on providing an overview of his contributions to the biomimicry and radiopharmaceutical disciplines, this minireview uses relevant examples to put in perspective the utility of macrocyclic coordination chemistry for biological inorganic chemistry applications.
Keywords: 1,4,7-Triazacyclononane, Coordination Chemistry, Metal complexes, Metallobiosites, Radiopharmaceuticals

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Permalink: https://www.hzdr.de/publications/Publ-27152
Publ.-Id: 27152


RODARE Logos

Frust, T.ORC

RODARE (Rossendorf Data Repository) is the institutional data repository at Helmholtz-Zentrum Dresden-Rossendorf. The initial logos of the platform are collected in this upload and are available as Open Access.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-02-28
    DOI: 10.14278/rodare.1
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-27151
Publ.-Id: 27151


Exploration targeting by multivariate compositional extrema

van den Boogaart, K. G.; Tolosana Delgado, R.; Mckinley, J.
Many different exploration targeting methods exist, like weights of evidence; inferring the probability of a deposit based on a local geology; genetic models identifying favourable conditions; and fractal based methods trying to identify regions of high value of certain fractal measures. This contribution proposes an approach potentially useful for deposits under cover: to find locations which are locally extrema on a certain spatial scale.

While surface features typically dominate the absolute values of measurements, covered objects can still produce large halos of much smaller absolute value. Our method thus looks for halos at a certain spatial scale. It does so by estimating a band filtered negative of the second derivative of the random field from spatial data, either from regular data or from a geostatistical analysis. In a certain sense this is looking for local peakiness, but filters the high frequency noise from surface effects by means of signal processing methods. The local maxima and their surrounding are then taken as the potential targets.

In a multivariate surface dataset, as provided by a geochemical exploration campaign, such a filter can be applied to the complete vector (i.e. the clr or ilr transformed compositions). This results is a nought mean compositional random field. Furthermore the bandwidth of the filter can be varied and considered as a third dimension. In this 3D map, we can again find various types of extremal points. The location on the 2D geographic space of the extreme value of the signal depends on the location of the deposit. Furthermore, the location on the third dimension relates to the deposit size or depth, and its compositional value describes its geochemical properties.

We demonstrate the effects of the method with a regional geochemical exploration dataset.
Keywords: Potential Mapping, Geostatistics, Signal Analysis
  • Lecture (Conference)
    IAMG 2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-09.09.2018, Olomouc, Česká republika
  • Contribution to proceedings
    IAMG 2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-09.09.2018, Oulomoc, Česká republika
    Short Abstracts of IAMG2018 – The 19th Annual Conference of the International Association for Mathematical Geosciences, Olomouc, Czech Republic: IAMG, 978-80-270-4612-6

Permalink: https://www.hzdr.de/publications/Publ-27150
Publ.-Id: 27150


Analyse der Bildrekonstruktion auf Basis von irregulären Gittern für die Untersuchung von Mehrphasenströmungen mittels ultraschneller Röntgen-Computertomographie

Pfahl, A.
Hauptbestandteil dieser Arbeit ist die ausführliche Evaluation der computertomographischen Bildgebung auf diversen irregulären Gitterstrukturen. Obwohl das derzeitige Standardverfahren der Bildrekonstruktion, die gefilterte Rückprojektion auf regulären Pixelgittern, sich im Besonderen für einen schnellen Bildgebungsprozess und die Verarbeitung großer Datenmengen eignet, so verfügen die resultierenden Bilder aufgrund der dabei notwendigen Interpolationsschritte über eine Bildqualität, die den Anforderungen in einigen Anwendungsgebieten nicht genügt. Aus diesem Grund rückt zur Vermeidung bzw. Reduzierung der Interpolationsfehler ein alternativer Lösungsansatz, basierend auf algebraischen Rekonstruktionstechniken, unter Einbezug der realen Geometrie des bildgebenden Systems, der dadurch bedingten maximal erreichbaren
Ortsauflösung sowie Vorwissen über das Untersuchungsobjekt mithilfe irregulärer Rekonstruktionsgitter in den Fokus.
Da die Erzeugung irregulärer Gitterstrukturen zumeist mit einem hohen Rechen- und Speicheraufwand verbunden ist, müssen effiziente Algorithmen erarbeitet und implementiert werden. Auch die aus den Gittern resultierenden stark unterbestimmten Gleichungssysteme, für die die üblicherweise zum Einsatz kommenden algebraischen Verfahren keine respektablen Lösungen hervorbringen, stellen eine Herausforderung dar. Daher müssen alternative Algorithmen betrachtet werden. Die Beurteilung der irregulären Gitter und somit des vom Standard abweichenden Konzeptes erfolgt schließlich anhand globaler und lokaler Bildgütekriterien und stets im Vergleich zur Rekonstruktion auf regulären Pixelgittern in der Hoffnung, eine signifikante Qualitätssteigerung in den rekonstruierten Bildern verzeichnen zu können.
Keywords: ultraschnell, Röntgen, Computertomographie, Bildrekonstruktion
  • Master thesis
    Universität zu Lübeck, 2018
    Mentor: Martina Bieberle, Thorsten M. Buzug
    73 Seiten

Permalink: https://www.hzdr.de/publications/Publ-27149
Publ.-Id: 27149


Virtual mineral processing simulation in software MLALookUP

Krupko, N.; Kern, M.; van den Boogaart, K. G.
Designing a more effective and productive mineral processing plant is a major objective for engineers and researchers. An optimized flowsheet produces one or more concentrates with high recovery and grade of the target mineral(s) and low impurities of minerals that reduce the value of the concentrate. In the initial stages of flowsheet development, lab-scale experiments are prepared and meticulously reviewed. This process is very time-consuming and cost-intensive. Furthermore, the results of these experiments can be inconclusive.
To overcome these problems, a virtual mineral processing simulation software called MLALookUP was developed. The simulation model helps to predict the performance of a processing plant and to find the optimal order of processing techniques to reach the targeted concentrate composition. MLALookUP uses data from mineral liberation analysis (MLA), a tool that generates and analyses high-resolution images with compositional particle information by combining scanning electron microscopy and energy-dispersive X-ray spectroscopy.
The software uses geometallurgical properties of the material that was analyzed with MLA. Depending on these properties, MLALookUP runs virtual separation machines, which are prepared and analyzed by the user on the basis of threshold parameters. Starting with the feed material, a sequence of virtual separation machines simulates all processing steps until the final concentrate. In this way, the values of grade, recovery and mass proportion are predicted in each stream. The software gives the possibility to vary processing threshold parameters and to define the optimal order of processing experiments in a flowsheet.
  • Contribution to proceedings
    IAMG2018 - 19th Annual Conference of the International Association for Mathematical Geosciences, 02.-08.09.2018, Olomouc, Česká republika
    Short Abstracts of IAMG2018 – The 19th Annual Conference of the International Association for Mathematical Geosciences, Olomouc, Czech Republic: IAMG, 978-80-270-4612-6

Permalink: https://www.hzdr.de/publications/Publ-27147
Publ.-Id: 27147


The metrics of calorimetry in radionuclide-dependent plant metabolism

Fahmy, K.; Sachs, S.; Bok, F.; Geipel, G.; Oertel, J.
Radioecological studies depend on the quantitative toxicity assessment of environmental radionuclides. At low dose exposure, the life span of affected organisms is barely shortened enabling the transfer of radionuclides through an almost intact food chain. Lethality-based toxicity estimates are not adequate in this regime because they require higher concentrations. However, increased radionuclide concentration alters its speciation, rendering the extrapolation to the low dose exposure chemically inconsistent. Here, we demonstrate that microcalorimetry provides a sensitive real-time monitor of toxicity of uranium (in the U(VI) oxidation state) in a plant cell model of Brassica napus. We introduce the calorimetric descriptor “metabolic capacity” and show that it correlates with enzymatically determined cell viability. It is independent of physiological models and robust against the naturally occurring fluctuations in the metabolic response to U(VI) of plant cell cultures. In combination with time-resolved laser-induced fluorescence spectroscopy and thermodynamic modeling, we show that the plant cell metabolism is affected predominantly by hydroxo-species of U(VI) with an IC50 threshold of ~90 µM. The data emphasize the yet little exploited potential of microcalorimetry for the speciation-sensitive ecotoxicology of radionuclides.
Keywords: microcalorimetry time-resolved laser fluorescence metabolism uranium ecology
  • Lecture (Conference)
    XX Conference of International Society for Biological Calorimetry (ISBC 2018), 13.-15.06.2018, Krakow, Polen

Permalink: https://www.hzdr.de/publications/Publ-27146
Publ.-Id: 27146


Probing charged lepton flavor violation with the Mu2e experiment

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

The design and status of the Mu2e experiment will be presented. In addition, I will highlight the results from several test runs carried out at HZDR's ELBE facility to study the radiation hardness and performance of components for the Mu2e calorimeter and for the detector that monitors the rate of stopped muons in the aluminum target.
Keywords: charged lepton flavor violation muon to electron conversion MU2E ELBE
  • Lecture (Conference)
    DPG Spring Meeting 2018, 26.02.-02.03.2018, Bochum, Germany

Permalink: https://www.hzdr.de/publications/Publ-27145
Publ.-Id: 27145


Cost-competitiveness of siderophores in recovering of critical metals from waste streams

Jain, R.; Pollmann, K.
Siderophores are known for their specificity and sensitivity towards the critical metals whose supply is at risk in future. Thus, the use of these siderophores for the recovery of these critical metals from their low concentrated wastewater is very attractive options. However, there is no detailed cost estimation for their application in wastewater. This study detailed the economic feasibility of application of desferrioxamines for the recovery of gallium from industrial wastewater. The study looked into the factors such as regeneration recycles, downstream processing, cost of gallium, operational cost of the technology and cost & grade of desferrioxamine production. The calculations showed that minimum 10 regeneration cycles are required for the cost-effectiveness of the technology. Further, siderophores, at the present level of technology, are easily economically feasible for metals costing 300 € per Kg (indium and dysprosium).
  • Lecture (Conference)
    Sustainable mineral 2018, 14.-15.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-27144
Publ.-Id: 27144


Formation and Aggregation of ZrO2 Nanoparticles on Muscovite (001)

Qiu, C.; Eng, P. J.; Hennig, C.ORC; Schmidt, M.ORC
The aggregation of nanoparticles is a key step in the formation of solid phases and a controlling factor for the behavior of suspended nanoparticles in solution. Using a charged mineral surface [muscovite (001)] we apply the surface X-ray diffraction techniques Crystal Truncation Rod (CTR) measurements and Resonant Anomalous X-ray reflectivity (RAXR) to investigate the aggregation process of Zr nanoparticles at the sub-nm scale. The aggregation process was studied as a function of ionic strength (0, 1, 10, and 100 mM NaCl), and the interfacial particles were characterized by CTR/RAXR and AFM. The observations are consistent with an aggregation process that follows a multi-step mechanism, which starts with the 3D aggregation of primary building units to form nanosheets. These sheets continue to grow through addition of building units to their reactive edges at higher ionic strength. Once the size and concentration of aggregates is sufficient, “face-to-face” stacking of nanosheets becomes the preferred aggregation mechanism as this minimizes the electrostatic repulsion of the charge that accumulates along nanosheet edges.
Keywords: Zr, muscovite, X-ray surface diffraction

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Permalink: https://www.hzdr.de/publications/Publ-27143
Publ.-Id: 27143


Experimental Investigation on the Heat Transfer of Innovative Finned Tubes for Passive Cooling of Nuclear Spent Fuel Pools

Unger, S.; Beyer, M.; Arlit, M.; Hampel, U.
In beyond-design-basis accidents active spent fuel pool cooling by pumps may not be possible. Promising concepts to enhance the reliability of nuclear power plants are passive heat removal systems using air as an unlimited heat sink. However the major drawbacks of such systems are small heat transfer coefficients, particularly on air side. Thus finned tube bundle heat exchangers are used to extend the heat transfer surface. However, conventional heat exchangers are limited in heat transfer capacity. For this purpose an innovative fin design was developed and experimentally investigated. A significant heat transfer enhancement was found for a moderate flow disturbance.
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the 49th Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-27142
Publ.-Id: 27142


High-field magnetoelasticity of Tm2Co17 and comparison with Er2Co17

Andreev, A. V.; Zvyagin, A. A.; Skourski, Y.; Yasin, S.; Zherlitsyn, S.
Acoustic properties (ultrasound velocity and attenuation) and magnetostriction were measured in pulsed fields up to 60 T applied along the c axis of Tm2Co17 single crystal. Similar to Er2Co17, the transition in Tm2Co17 is accompanied by clear anomalies in the sound velocity. The observed 0.3% jump of the sound velocity at the transition is negative in Tm2Co17, whereas it is positive in Er2Co17. The magnetostriction at the transition also differs very much from that in Er2Co17. In Tm2Co17, the transition is accompanied by a smooth minimum of 0.15×10-4 in longitudinal magnetostriction whereas in Er2Co17 by a very sharp expansion of much larger magnitude (1.2×10-4). In the transverse mode, the effect in Tm2Co17 looks as very broad minimum of low amplitude (<0.1×10-4) whereas in Er2Co17 as very sharp and large shrinkage (2.6×10-4). Thus, both the magnetoacoustics and magnetostriction are rather different in Tm2Co17 and Er2Co17. This supports different nature of the field-induced transitions in these compounds.

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Permalink: https://www.hzdr.de/publications/Publ-27141
Publ.-Id: 27141


Unconventional field induced phases in a quantum magnet formed by free radical tetramers

Saúl, A.; Gauthier, N.; Askari, R. M.; Coté, M.; Maris, T.; Reber, C.; Lannes, A.; Luneau, D.; Nicklas, M.; Law, J. M.; Green, E. L.; Wosnitza, J.; Bianchi, A. D.; Feiguin, A.
We report experimental and theoretical studies on themagnetic and thermodynamic properties ofNIT-2Py, a free radical based organic magnet. From magnetization and specific-heat measurements we establish the temperature versus magnetic field phase diagram which includes two Bose-Einstein condensates (BEC) and an infrequent half-magnetization plateau. Calculations based on density functional theory demonstrate that magnetically this system can be mapped to a quasi-two-dimensional structure of weakly coupled tetramers. Density matrix renormalization group calculations show the unusual characteristics of the BECs where the spins forming the low-field condensate are different than those participating in the high-field one.

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Permalink: https://www.hzdr.de/publications/Publ-27140
Publ.-Id: 27140


Multiplet of skyrmion states on a curvilinear defect: Reconfigurable skyrmion lattices

Kravchuk, V. P.; Sheka, D. D.; Kákay, A.; Volkov, O. M.; Rößler, U. K.; van den Brink, J.; Makarov, D.; Gaididei, Y.
Typically, the chiral magnetic Skyrmion is a single-state excitation. Here we propose a system, where multiplet of Skyrmion states appears and one of these states can be the ground one. We show that the presence of a localized curvilinear defect drastically changes the magnetic properties of a thin perpendicularly magnetized ferromagnetic film. For a large enough defect amplitude a discrete set of equilibrium magnetization states appears forming a ladder of energy levels. Each equilibrium state has either a zero or a unit topological charge; i.e., topologically trivial and Skyrmion multiplets generally appear. Transitions between the levels with the same topological charge are allowed and can be utilized to encode and switch a bit of information. There is a wide range of geometrical and material parameters, where the Skyrmion level has the lowest energy. Thus, periodically arranged curvilinear defects can result in a Skyrmion lattice as the ground state.
Keywords: Skyrmions, curvilinear defects

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Permalink: https://www.hzdr.de/publications/Publ-27139
Publ.-Id: 27139


Clinical translation and regulatory aspects of CAR/TCR-based adoptive cell therapies-the German Cancer Consortium approach.

Krackhardt, A. M.; Anliker, B.; Hildebrandt, M.; Bachmann, M.; Eichmüller, S. B.; Nettelbeck, D. M.; Renner, M.; Uharek, L.; Willimsky, G.; Schmitt, M.; Wels, W. S.; Schüssler-Lenz, M.
Adoptive transfer of T cells genetically modified by TCRs or CARs represents a highly attractive novel therapeutic strategy to treat malignant diseases. Various approaches for the development of such gene therapy medicinal products (GTMPs) have been initiated by scientists in recent years. To date, however, the number of clinical trials commenced in Germany and Europe is still low. Several hurdles may contribute to the delay in clinical translation of these therapeutic innovations including the significant complexity of manufacture and non-clinical testing of these novel medicinal products, the limited knowledge about the intricate regulatory requirements of the academic developers as well as limitations of funds for clinical testing. A suitable good manufacturing practice (GMP) environment is a key prerequisite and platform for the development, validation, and manufacture of such cell-based therapies, but may also represent a bottleneck for clinical translation. The German Cancer Consortium (DKTK) and the Paul-Ehrlich-Institut (PEI) have initiated joint efforts of researchers and regulators to facilitate and advance early phase, academia-driven clinical trials. Starting with a workshop held in 2016, stakeholders from academia and regulatory authorities in Germany have entered into continuing discussions on a diversity of scientific, manufacturing, and regulatory aspects, as well as the benefits and risks of clinical application of CAR/TCR-based cell therapies. This review summarizes the current state of discussions of this cooperative approach providing a basis for further policy-making and suitable modification of processes.
Keywords: CAR/TCR-transgenic T cells; Cellular therapy; Clinical translation; Regulatory aspects

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Permalink: https://www.hzdr.de/publications/Publ-27138
Publ.-Id: 27138


On the insulator-to-metal transition in titanium-implanted silicon

Liu, F.; Wang, M.ORC; Berencén, Y.; Prucnal, S.; Engler, M.; Hübner, R.; Yuan, Y.; Heller, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.
Hyperdoped silicon with deep level impurities has attracted much research interest due to its promising optical and electrical properties. In this work, single crystalline silicon supersaturated with titanium is fabricated by ion implantation followed by both pulsed laser melting and flash lamp annealing. The decrease of sheet resistance with increasing Ti concentration is attributed to a surface morphology effect due to the formation of cellular breakdown at the surface and the percolation conduction at high Ti concentration is responsible for the metallic-like conductivity. The insulator-to-metal transition does not happen. However, the doping effect of Ti incorporation at low concentration is not excluded, which might be responsible for the sub-bandgap optical absorption reported in literature.
Keywords: Hyperdoped silicon; deep level impurities;flash lamp annealing; insulator-to-metal transition

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Permalink: https://www.hzdr.de/publications/Publ-27136
Publ.-Id: 27136


Intensity-modulated proton therapy decreases dose to organs at risk in low-grade glioma patients: results of a multicentric in silico ROCOCO trial

Eekers, D.; Roelofs, E.; Cubillos-Mesias, M.; Niel, C.; Smeenk, R.; Minken, A.; Granzier, M.; Janssens, G.; Kaanders, J.; Lambin, P.; Troost, E. G. C.
Background and Purpose
Patients with low-grade glioma (LGG) have a prolonged survival expectancy due to better discriminative tumor classification and multimodal treatment. Consequently, longterm treatment toxicity, e.g., neurocognitive function, gains importance. Contemporary radiotherapy techniques such as intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), Tomotherapy (TOMO) and intensity-modulated proton therapy (IMPT) enable high-dose irradiation of the target but they differ regarding delivered dose to organs at risk (OARs). The aim of this comparative in silico study was to determine the dosimetric differences in delivered doses to the OARs.
Material and Methods
Imaging datasets of twenty-five LGG patients having undergone postoperative radiotherapy were included. For each of these patients, in silico treatment plans to a total dose of 50.4Gy to the target volume were generated for the four treatment modalities investigated (i.e., IMRT, VMAT, TOMO, IMPT). Resulting treatment plans were analyzed regarding dose to target and surrounding OARs comparing IMRT, TOMO and IMPT to VMAT (reference technique).
Results
In total, 100 treatment plans for the twenty-five patients were analyzed. Compared to VMAT the IMPT mean dose (Dmean) for 9 out of 10 (90%) OARs was statistically significantly (p<0.02) reduced, for TOMO 3/10 (30%) and 1/10 (10%) for IMRT. IMPT was the prime modality reducing dose to the OARs followed by TOMO. The pituitary gland was best spared by TOMO (Table 2).
Conclusions
The low dose volume to the majority of OARs was significantly reduced when using IMPT compared to VMAT. Whether this will lead to a significant reduction in neurocognitive decline is to be determined in carefully designed future clinical trials.
Keywords: In silico planning study, Low Grade Glioma, Photon and proton irradiation, IMPT, VMAT, IMRT, TOMO

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Permalink: https://www.hzdr.de/publications/Publ-27134
Publ.-Id: 27134


Probe of plutonium oxide nanoparticles at the large-scale facility

Gerber, E.; Romanchuk, A.; Pidchenko, I.; Hennig, C.; Trigub, A.; Weiss, S.; Scheinost, A.; Kalmykov, S.; Kvashnina, K.
Plutonium is a chemical element of a most significant concern at the nuclear legacy sites. The problem of the plutonium migration plays an important role in the environmental radioactivity because of its high radiological toxicity. It was shown previously that plutonium migrates in the subsurface environment on the kilometer scale at some previously contaminated sites [1-2]. During the last few years due to the evolution of spectroscopic and microscopic techniques it was found that so called “colloidal Pu(IV) polymers” actually represents as aggregates of PuO2 nanoparticles with size ~ 2 nm. [3-4]. Investigation of plutonium oxides nanoparticles is complicated, as plutonium can exist in four partially unstable oxidation states in aqueous solution: III, IV, V, VI under environmental conditions. At the same time, presence of Pu in different oxidation states in PuO2 structure is still an open question.

This contribution will show first results of plutonium oxide nanoparticles studies at the large-scale facility – The European Synchrotron (ESRF) by X-ray spectroscopy and X-ray diffraction methods. Plutonium nanoparticles were prepared by rapid chemical precipitation using precursors in the different oxidation states. These precursors were obtained by chemical reduction or oxidation of Pu stock solution. The obtained nanoparticles were characterized by high energy resolution fluorescence detection (HERFD) [5] X-ray absorption spectroscopy, extended X-ray absorption fine structure (EXAFS) and X-ray diffraction (XRD) techniques. The experiments were performed at the Rossendorf Beamline (ROBL) at the ESRF, dedicated to actinide science, where we recently installed a novel X-ray emission spectrometer with ground-breaking detection limits. The recently upgraded ROBL beamline at the ESRF provides now a unique opportunity to study actinide materials by several experimental techniques - HERFD, XES, RIXS [6], EXAFS and XRD simultaneously. We will show how the detailed information about local and electronic structure and plutonium oxidation state in different nanoparticles can be obtained using the variety of methods at large scale facilities.


References
[1] A.B. Kersting et al., Nature 397, 56, (1999).
[2] A.P. Novikov et al., Science 314, 638 (2006).
[3] B.A. Powell et al., Environ. Sci. Technol. 45, 2698 (2011).
[4] A.R. Romanchuk et al., Geochim. Cosmochim. Acta. 121, 29 (2013).
[5] K.O. Kvashnina et al., Phys. Rev. Lett. 111, 253002 (2013).
[6] K.O. Kvashnina et al., J. Electron. Spectrosc. Relat. Phenom. 194, 27 (2013).
Keywords: nanoparticles, plutonium, HERFD, EXAFS, XRD
  • Lecture (Conference)
    48èmes Journées des Actinides (JdA2018), 21.-24.03.2018, Praia de Porto Novo, Portugal

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Permalink: https://www.hzdr.de/publications/Publ-27133
Publ.-Id: 27133


Metabolism Studies - experiences, pitfalls and results

Ludwig, F.-A.
Experiences, pifalls and results of latest metabolism studies are presented and demonstrated by examples from own research.
Keywords: metabolism, PET, fluorine-18, [18F]flubatine, [18F]fluspidine, liver microsomes, clinical studie, LC-MS
  • Lecture (others)
    Doctoral Colloquium, 22.02.2018, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27131
Publ.-Id: 27131


Investigation of decommissioned reactor pressure vessels of the nuclear power plant Greifswald

Viehrig, H.-W.ORC; Altstadt, E.ORC; Houska, M.ORC; Müller, G.; Ulbricht, A.; Konheiser, J.; Valo, M.
The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows:
• Irradiated (Unit 4),
• irradiated and recovery annealed (Units 2 and 3), and
• irradiated, recovery annealed and re-irradiated (Unit1).
The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam.
Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined:
• The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed.
• KJc values of the weld metals generally followed the course of the MC though with a large scatter.
• There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams.
• The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front.
• The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals.
• A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner.
• It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal.
• The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.
Keywords: reactor pressure vessel, decommissione, base metal, welding seam, cladding, fracture toughness, integrity assessment
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-088 2018

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Permalink: https://www.hzdr.de/publications/Publ-27130
Publ.-Id: 27130


Investigation of Heat Transfer from Dried Rod Surfaces in a Spent Fuel Mock-up with a Thermal Anemometry Grid Sensor

Arlit, M.; Schleicher, E.; Hampel, U.
Within the paper we will give a brief description of the TAGS and the test facility ALADIN. Furthermore, we will discuss the role of convective cooling by steam of heated rods during boil-off experiments by parameters measured with the TAGS.
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the 48th Annual Meeting on Nuclear Technology, 978-3-926956-95-8

Permalink: https://www.hzdr.de/publications/Publ-27129
Publ.-Id: 27129


Gyro Nozzle – An innovative Submerged Entry Nozzle Design for Billet and Bloom casting

Hackl, G.; Tang, Y.; Nitzl, G.; Schurmann, D.ORC; Willers, B.; Eckert, S.
Mathematical simulations by means of CFD and physical models operated with liquid metal were utilized to investigate the flow characteristics obtained by the use of RHI-Magnesita’s Gyro nozzle in the mould region with a round cross section. The focus of this work was to characterize the interaction with a mold electro-magnetic stirrer (M-EMS) and compare the results with a conventional straight through SEN design. Even without the use of an electromagnetic stirrer the Gyro nozzle establishes a rotational flow in the mold. When a rotational magnetic field is applied the velocity profile at the meniscus is not severely affected. Strong fluctuations and the formation of vortices, as detected with a standard SEN, were not observed. In contrast, with increasing distance to the meniscus the rotational flow is stronger established when compared to the standard SEN, which should be beneficial in terms of the crystallization pattern of the solidified steel. The flow in general is more stable, independent of the operating conditions. Both modeling approaches show the same trend. Based on the obtained results it can be stated, that the Gyro nozzle shows a superior behavior over conventional straight through SEN designs for both the stirred and non-stirred case.
Keywords: CFD, liquid metal modeling, M-EMS, SEN, isostatically pressed products
Related publications
Flow Measurements in a Liquid Metal Model for Continuous … (Id 27436) is a supplement to this publication
  • Contribution to proceedings
    AISTech 2018, 07.-10.05.2018, Philadelphia, USA
    AISTech 2018 Proceedings, Warrendale, PA, USA: Association for Iron & Steel Technology (AIST), 978-1-935117-72-8, 1655-1662
  • Iron & Steel Technology 16(2019)7, 84-90
  • Bulletin - The Journal of Refractory Innovations (2019), 52-57

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Permalink: https://www.hzdr.de/publications/Publ-27128
Publ.-Id: 27128


Nε-Acryloyllysine piperazides as irreversible inhibitors of transglutaminase 2 – synthesis, structure-activity relationships and pharmacokinetic profiling

Wodtke, R.; Hauser, C.; Ruiz-Gómez, G.; Jäckel, E.; Bauer, D.; Lohse, M.; Wong, A.; Pufe, J.; Ludwig, F.-A.; Fischer, S.; Hauser, S.; Greif, D.; Pisabarro, M. T.; Pietzsch, J.; Pietsch, M.; Löser, R.
Transglutaminase 2 (TGase 2)-catalysed transamidation represents an important posttranslational mechanism for protein modification with implications in physiological and pathophysiological conditions including fibrotic and neoplastic processes. Consequently, this enzyme is considered a promising target for the diagnosis and therapy of these diseases. In this study, we report on the synthesis and kinetic characterisation of Nε-acryloyllysine piperazides as irreversible inhibitors of TGase 2. Systematic structural modifications on 54 new compounds were performed with a major focus on fluorine-bearing substituents due to the potential of such compounds to serve as radiotracer candidates for positron emission tomography. The determined inhibitory activities ranged from 100-10000 M-1s-1, which resulted in comprehensive structure-activity relationships. Structure-activity correlations using various substituent parameters accompanied by covalent docking studies provide an advanced understanding of the molecular recognition for this inhibitor class within the active site of TGase 2. Selectivity profiling of selected compounds for other transglutaminases demonstrated an excellent selectivity towards transglutaminase 2. Furthermore, an initial pharmacokinetic profiling of selected inhibitors was performed including the assessment of potential membrane permeability and liver microsomal stability.

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Publ.-Id: 27127


Introduction into CMFD: Basic equations of multiphase flows and the Euler-Euler approach

Hoehne, T.
Computational fluid dynamics (CFD) is one of the branches of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows.
Computers are used to perform the millions of calculations required to simulate the interaction of liquids and gases with surfaces defined by boundary conditions.
Even with high-speed supercomputers only approximate solutions can be achieved in many cases.
Ongoing research, however, may yield software that improves the accuracy and speed of complex simulation scenarios such as transonic or turbulent flows.
Validation and verification of such software is necessary using high resolution experiments.
Keywords: multiphase flow, CFD, super computing, Euler-Euler
  • Invited lecture (Conferences)
    Multiphase flow CFD workshop, 05.-07.06.2018, Changsha, China
  • Contribution to proceedings
    Multiphase flow CFD workshop, 05.-07.06.2018, Changsha, China

Permalink: https://www.hzdr.de/publications/Publ-27126
Publ.-Id: 27126


Stratified & Segregated Flow Modelling - AIAD

Hoehne, T.
Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation
Keywords: AIAD, CFD, SWT, Drag
  • Invited lecture (Conferences)
    Multiphase Flow Workshop, 05.-07.06.2018, Changsha, China
  • Contribution to proceedings
    Multiphase flow CFD Workshop, 05.-07.06.2018, Changsha, China

Permalink: https://www.hzdr.de/publications/Publ-27125
Publ.-Id: 27125


Numerical simulation of the IAEA benchmark regarding ROCOM PTS test cases

Hoehne, T.; Kliem, S.
The development, verification and validation of CFD codes in respect to Nuclear Power Plant (NPP) safety and design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. Therefore, a set of ROCOM CFD-grade test data were made available to set up an International Atomic Energy Agency (IAEA) benchmark, relating to PTS scenarios. The benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification. Data obtained from the PTS experiment were compared in the study presented here with predictions obtained from CFD software. In addition a test case without buoyancy forces was selected to show the influence of density differences. Compared to the earlier study, significant progress was made in the development of CFD codes concerning both numerical aspects and physical modelling; here especially the treatment of turbulence. The CFX code (and turbulence modelling approaches) shows a respectable qualitative agreement with the experimental data. The dominant mixing phenomena have been treated correctly. Further, experimental and numerical analysis together seems necessary to better understand the flow behaviour under momentum driven flow conditions at low velocities.
Keywords: ROCOM, PTS, CFX, ECC
  • Contribution to proceedings
    CFD4NRS-7 OECD-NEA & IAEA Workshop "Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation", 04.-06.09.2018, Shanghai, China
  • Lecture (Conference)
    CFD4NRS-7 OECD-NEA & IAEA Workshop "Application of CFD/CMFD Codes to Nuclear Reactor Safety and Design and their Experimental Validation", 04.-06.09.2018, Shanghai, China

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Permalink: https://www.hzdr.de/publications/Publ-27124
Publ.-Id: 27124


A novel CFD multi-field concept of boiling including flow pattern transitions in a vertical pipe

Hoehne, T.; Krepper, E.; Lucas, D.
The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models and the Wall Boiling Model need a constant improvement and separate, intensive validation effort using CFD grade experiments.
Keywords: multi-phase, boiling, GENTOP, multi-scale, CFD
  • Contribution to proceedings
    XI International Conference on Computational Heat and Mass Transfer - ICCHMT 2018, 21.-24.05.2018, Krakau, Polen
  • Lecture (Conference)
    XI International Conference on Computational Heat and Mass Transfer - ICCHMT 2018, 21.-24.05.2018, Krakau, Polen

Permalink: https://www.hzdr.de/publications/Publ-27123
Publ.-Id: 27123


Current status of CFD codes - possibilities, limitations, current developments and future trends

Hoehne, T.
Single and multiphase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a strong requirement for numerical tools. With the use of modern multiprocessor machines, application areas are expected to broaden, and progress to accelerate. Accompanying this drive forwards is a need to establish quality and trust in the predictive capabilities of the codes, and, as a consequence of open public awareness.

Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which single/multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive.

Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our fluid dynamics research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered.

The current status of commercial (like ANSYS CFX, Fluent) and open source (like OpenFoam) CFD tools and available models will be discussed. Code comparisons of similar problems will show the possibilities and limitations of each CFD code system.

These activities will help to improve the CFD codes capabilities in energy related industrial applications.
Keywords: CFD
  • Invited lecture (Conferences)
    REMOO-2018 Conference, 29.-31.05.2018, Venedig, Italien
  • Contribution to proceedings
    REMOO-2018 Conference, 29.-31.05.2018, Venedig, Italien

Permalink: https://www.hzdr.de/publications/Publ-27122
Publ.-Id: 27122


Numerical simulation of a counter-current flow experiment at the WENKA channel using a droplet entrainment model

Hoehne, T.; Gabriel, S.
One drawback today in simulating horizontal wavy two-phase flows is that there is no treatment of droplet formation mechanisms at the liquid surface. For self-generating waves and slugs, the interfacial momentum exchange and the turbulence parameters have to be modelled correctly. Furthermore, understanding and considering the mechanism of droplet entrainment for heat and mass transfer processes is of great importance in the nuclear industry.
Therefore a step of improvement of modelling liquid/gas interfaces is the consideration of droplet entrainment mechanisms. The proposed entrainment model assumes that due to liquid turbulence the interface gets rough and wavy leading to the formation of droplets. The new approach is validated against existing horizontal two-phase flow data from the WENKA (Water ENtraninment Channel KArlsruhe) channel.
Tests were carried out for water and air at ambient pressure and temperature. High speed videometry was applied to obtain velocities from flow pattern maps of the rising and falling fluid. In the horizontal part of the channel with partially reversed flow the fluid velocities were measured by planar particle image velocimetry. The test MP 28 with droplet generation at the reversed flow conditions was utilized to compare it with the simulation data. The agreement of the experimental findings and CFD results is acceptable. Also the droplet mass flow was compared and showed the applicability of the droplet entrainment model. Further work is necessary to validate the model for different flow conditions.
Keywords: CFD, Two-phase flow, WENKA, AIAD
  • Lecture (others)
    CFD-Verbundtreffen, 06.03.2018, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27121
Publ.-Id: 27121


A multiscale approach simulating boiling in a heated pipe including flow pattern transition

Hoehne, T.; Krepper, E.; Lucas, D.; Montoya, G.
The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models and the Wall Boiling Model need a constant improvement and separate, intensive validation effort using CFD grade experiments.
Keywords: multi-phase, boiling, GENTOP, multi-scale, CFD

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Permalink: https://www.hzdr.de/publications/Publ-27120
Publ.-Id: 27120


EASY – Evidence of design basis accidents mitigation solely with passive safety systems

Buchholz, S.; Schaffrath, A.; Bonfigli, G.; Kaczmarkiewicz, N.; Sporn, M.; Schäfer, F.; Wagner, T.
Current advanced reactor designs of generation III and III+ as well as SMR are extensively providing passive safety systems in order to control design basis accidents. Assessment of these systems is needed to verify their functionality. This can be done by experiments and computer calculations. For the latter, well validated computer codes are needed, which are able to simulate the behaviour of these systems reliably. On the basis of the KERENA reactor concept (AREVA) the currently running EASY project is performed to validate and enhance the code system AC2 for such applications. Experimental data of the large scaled INKA test facility in Karlstein (Main) is used for the validation process. During EASY, model improvement of AC2 as well as validation calculations are performed. Beside the enhancement of the coupling between the two codes ATHLET and COCOSYS, a model for the simulation of the behaviour of the passive flooding valve has been created. Additionally the 3D model of ATHLET has been enhanced in order to simulate a water surface within the 3D domain of a large water pool (e.g. for the core flooding pool in KERENA). Validation of AC2 is performed in two steps: At first single component tests with fixed boundary conditions performed at INKA in the past are used. The second step is the validation of AC2 against in EASY performed new experiments regarding design basis accidents of KERENA (SB-LOCA, LB-LOCA and SBO).
Keywords: ATHLET, KERENA, INKA, EASY
  • Contribution to proceedings
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    EASY – Evidence of design basis accidents mitigation solely with passive safety systems
  • Lecture (Conference)
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27119
Publ.-Id: 27119


Post-test analysis of the RPV lower head leak experiment at the INKA test facility using ATHLET

Sporn, M.; Schuster, C.; Hurtado, A.; Hampel, U.; Schäfer, F.
The KERENA reactor with 1,250 MW electrical power is an evolutionary boiling-water reactor (BWR) concept jointly developed by AREVA GmbH and PreussenElektra GmbH. It is a Generation III+ reactor with innovative passive safety systems such as emergency and containment cooling condenser, core flooding system and pressure pulse transmitter (PPPT) to complement the safety concept of a BWR. One design goal of the KERENA reactor concept is, that in case of an accident the core can be cooled for at least 72 hours by passive safety systems only. The INKA test facility at AREVA in Karlstein was built to investigate the heat removal capabilities and the interaction of the passive safety systems and components of the KERENA concept during different accidental scenarios. This test facility represents the KERENA main components like RPV, flooding and pressure suppression pool, drywell and shielding/storage pool, emergency condenser and containment cooling condenser at a sophisticated geometrical and power scaling. In summer 2017 at the INKA test facility a feed water line break, a leak at the lower head of the RPV and a station blackout were experimentally simulated to investigate the integral plant behaviour and the designated safety functions of each single passive component. An existing ATHLET input deck of the INKA test facility, which was already validated against the INKA experiment of a main steam line break, was extended by a PPPT model and the break lines for the loss of coolant experiments. Pre- and post-test calculations for the “leak at the lower head of the RPV” experiment were conducted to assess and validate the input deck. The experiment has shown that the passive safety systems are capable to remove the decay heat and the core flooding system was also triggered in this accident sequence. Comparing the ATHLET simulations with the experimental data, some deviations were found, which are currently being investigated and treated by ATHLET input data adjustments.
Keywords: ATHLET, KERENA, INKA, EASY
  • Contribution to proceedings
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland
    Proceedings of the Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    Jahrestagung Kerntechnik, Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27118
Publ.-Id: 27118


Overview of research and therapy facilities for radiobiological experimental work in particle therapy. Report from the European Particle Therapy Network radiobiology group

Dosanjh, M.; Jones, B.; Pawelke, J.ORC; Pruschy, M.; Singers Sørensen, B.
Particle therapy (PT) as cancer treatment, using protons or heavier ions, can provide a more favourable dose distribution compared to x-rays. While the physical characteristics of particle radiation have been the aim of intense research, less focus has been placed on the actual biological responses arising from particle irradiation.
One of the biggest challenges for proton radiobiology is the RBE, with an increasing concern that the clinically-applied generic RBE-value of 1.1 is an approximation, as RBE is a complex quantity, depending on both biological and physical parameters, such as dose, LET, cellular and tissue radiobiological characteristics, as well as the endpoints being studied. Most of the available RBE data derive from in vitro experiments, with very limited in vivo data available, especially in late-reacting tissues, which provide the main constraints and influence the quality of life endpoints in radiotherapy. There is a need for systematic, large-scale studies to thoroughly establish the biology of particle radiation in a number of different experimental models in order to refine biophysical mathematical models that can potentially be used to guide PT.
The overall objective of the European Particle Therapy Network (EPTN) WP6 is to form a network of research and therapy facilities in order to coordinate and standardise the radiobiological experiments, to obtain more accurate predictive parameters than in the past. Coordinated research is required in order to obtain the most appropriate experimental data. The aim in this paper is to describe the available radiobiology infrastructure of the centers involved in EPTN WP6.
Keywords: particle therapy, radiobiology, RBE, EPTN

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Permalink: https://www.hzdr.de/publications/Publ-27117
Publ.-Id: 27117


Study on optimal scintillation detectors for ultrafast electron beam X-ray CT scanners

Iskander, K. N. A.
Currently, ROFEX systems rely on CZT detectors to convert X-rays directly into electric signals. Despite simplicity and high X-ray detection efficiency, the performance of the CZT detectors is limited as a consequence of polarization effects that saturate the detector output, and hence degrades the quality of the reconstructed image. Furthermore, CZT detectors require high bias voltage (1-2 KV) to operate besides manufacturing challenges due to the limited crystal growth of the CZT material. With the intention to overcome the above-stated problems, scintillation-based detectors have been suggested to replace the CZT detectors in ROFEX scanners. For the design of an optimal scintillation-based detector system, suitable scintillators, photodetectors as well as a suitable front-end have to be selected, analyzed and tested.
Keywords: radiation detectors, scintillation detectors, ultrafast electron beam X-ray CT
  • Diploma thesis
    Anhalt University of Applied Science, 2018
    Mentor: Dr. André Bieberle
    66 Seiten
  • Lecture (others)
    Verteidigung der Masterarbeit, 22.02.2018, Köthen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-27116
Publ.-Id: 27116


PANAS – Experimental and theoretical investigations of generic thermal hydraulic issues of passive safety systems

Schuster, C.; Lippmann, W.; Hampel, U.; Walther, M.; Leyer, S.
To guarantee the nuclear safety which means keeping the radioactivity inside the fuel rods it is necessary to remove the decay heat in all circumstances of normal and abnormal operation situations. Decay heat removal systems of the present reactor fleet are based on active components like pumps, motor driven valves, electrically I&C etc. They depend on the supply of additional energy which could fail how it was imposingly demonstrated in Fukushima. Virtually all new reactor designs of generation 3+ are characterized by the implementation of various passive safety components.
Passive Residual Heat Removal (PRHR) systems use heat transfer induced density differences to provide sufficient driving forces to establish a system mass flow in natural circulation loops of various configurations. Thus in order to design and model the system performance the determination of the heat transfer resistances is a crucial part since it influences the quality of calculation results on two sides: the heat transferred to the coolant as well as the mass flow of the coolant. Today’s state-ofthe-art PRHR systems use mostly the phase transition between the liquid and the vapor phase of the coolant to maximize the system mass flow and thus the performance. Precondition for the adoption of PRHR systems in nuclear reactors is the verification of the functional capability in all operation modes of the power plant. Therefore a comprehensive experimental work at different mockup scales combined with theoretical investigations (e. g. CFD and system codes) has to be undertaken.
Keywords: Passive safety systems, heat transfer, CFD
  • Lecture (Conference)
    49th Annual Meeting on Nuclear Technology (AMNT 2018), 29.-30.05.2018, Berlin, Deutschland
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology (AMNT 2018), 29.-30.05.2018, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27115
Publ.-Id: 27115


Role of sodium carbonate in scheelite flotation – a multi-faceted reagent

Kupka, N.; Rudolph, M.
Even though sodium carbonate is a reagent frequently used in flotation, its role is mostly described as a buffering pH modifier and a pulp dispersant. In the case of scheelite flotation, it has been hinted that sodium carbonate improves both grade and/or recovery but the mechanism itself is ambiguous at best or at least has not been distinctly reported in the literature. Furthermore, the addition of depressants such as sodium silicate or quebracho could be triggering additional mechanisms. Through batch flotation testwork on a skarn scheelite ore with high calcite content, single mineral flotation and contact angle measurements, this article aims at demonstrating that sodium carbonate is a multi-faceted reagent, which serves as a buffering pH modifier, a pulp dispersant precipitating calcium and magnesium ions in suspension, a depressant for calcite and calcium silicates and also a promoter for scheelite. It acts mostly synergistically and partially antagonistically with other depressants, notably sodium silicate and quebracho.
Keywords: sodium carbonate, scheelite flotation, mechanism

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Permalink: https://www.hzdr.de/publications/Publ-27114
Publ.-Id: 27114


Analysis of Flow Patterns in High Gravity Equipment Using Gamma‑ray Computed Tomography

Groß, K.; Bieberle, A.; Gladyszewski, K.; Schubert, M.; Skiborowski, M.; Górak, A.
Fluctuating and fast changing markets create a need for flexible equipment to adjust the production capacity to the actual demand. Application of Rotating Packed Beds (RPBs) in chemical production may meet these needs because of their modularity and flexibility. In this equipment the liquid traffic in the apparatus is caused by the centrifugal force and the mass transfer occurs mainly in a ring shaped rotating packing. Changing rotational speed offers an additional degree of freedom in equipment operation, as compared to standard columns. The advantages are an increasing capacity in a compact machine size, while providing enhanced mass transfer.
One of the reasons why RPBs are seldomly applied in Europe is the yet limited knowledge about the occurring flow mechanisms. Early studies by Burns et al. [1] mostly rely on visual observations and photographs. More recently Yang et al. [2] presented first results derived by the application of x-ray computed tomography. However, the results of their study are limited, because no gas flow was present in the experiments and their radial packing length was restricted to several centimeters.
In the present study we present observations of flow patterns within RPB, gained by using high energy intensity of the gamma radiation source. We investigated the flow behavior within an RPB with packing diameters of up to 480 mm. In addition to the classical computed tomography, angular resolved analysis is presented which allows for the observation of flow patterns relative to the motion of the rotor. Therefore they give insight about lateral movement of the liquid and first guidelines for the design of packings specific to RPBs can be made.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrentechnik, Membrantechnik und Mischvorgänge, 27.-28.02.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27113
Publ.-Id: 27113


Biodistribution studies of ultrasmall silicon nanoparticles and carbon dots in experimental rats and tumor mice

Licciardello, N.; Hunoldt, S.; Bergmann, R.; Singh, G.; Mamat, C.; Faramus, A.; Ddungu, J. L. Z.; Silvestrini, S.; Maggini, M.; de Cola, L.; Stephan, H.
Ultrasmall clearable nanoparticles possess enormous potential as cancer imaging agents. In particular, biocompatible silicon nanoparticles (Si NPs) and carbon quantum dots (CQDs) hold great potential in this regard. Their facile surface functionalization easily allows the introduction of different labels for in vivo imaging. However, to date, a thorough biodistribution study by in vivo positron emission tomography (PET) as well as a comparative study of Si vs C particles of similar size are missing. In this contribution, ultrasmall (size < 5 nm) Si NPs and CQDs were synthesized and characterized by high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared (FTIR), absorption and steady-state emission spectroscopy. Subsequent functionalization of NPs with a near-infrared dye (Kodak-XS-670) or a radiolabel (64Cu) enabled a detailed in vitro and in vivo study of the particles. For radiolabeling experiments, the bifunctional chelating agent S-2-(4-Isothiocyanatobenzyl)-1,4,7-triaazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) was conjugated to the amino surface groups of the respective NPs. Efficient radiolabeling of NOTA-functionalized NPs with the positron emitter 64Cu was found. The biodistribution and PET studies showed a rapid renal clearance from the in vivo systems for both variants of the nanoparticles. Interestingly, the different derivatives investigated exhibited significant differences in the biodistribution and pharmacokinetic properties. This can mostly be attributed to different surface charge and hydrophilicity of the NPs, arising from the synthetic strategy used to prepare the particles.
Keywords: silicon nanoparticles, carbon quantum dots, copper-64, biodistribution, small animal positron emission tomography

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-27112
Publ.-Id: 27112


Thermal Conductivity Survey of Different Manufactured Insulation Systems of Rectangular Copper Wires

Seilmayer, M.ORC; Katepally, V. K.ORC
Especially in high power applications, thermal design of magnetic field coils is a critical part of efficient electromagnetic system design. Since thermal expansion of the coil effects magnetic field geometry, temperature drop across the windings should be kept as low as possible. Here the insulation system between wires guides ohmic heat to the surface of the coil and influences the total thermal performance. Because of very less information about the general thermal performance and quality of manufactured multilayer insulation systems, the present survey investigates several variants made of enameled wires and Polyimide film wrapped wires. Hereby, different joining technologies like bonding or backfilling determine the thermal conductivity, which obviously differs from values of individual raw materials. Best performance could be gained with a Kapton– CR film wrapped wire, backfilled with high thermal conductivity resin. Finally, the survey concludes that manufactured insulation systems drop approximately ten to twenty percent of the thermal conductivity, which could be theoretically achieved by an optimal layer composition of individual raw materials.
Keywords: Power cable thermal factors, Insulation thermal factors, Coil design, DRESDYN, High Power

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Permalink: https://www.hzdr.de/publications/Publ-27111
Publ.-Id: 27111


Hydrogen burning: Study of the 22Ne(p,gamma)23Na, 3He(alpha,gamma)7Be and 7Be(p, gamma)8B reactions at ultra-low energies

Takács, M. P.
The neon-sodium cycle (NeNa cycle) of hydrogen burning is active in stars of the Asymptotic Giant Branch, in classical novae, and in supernovae of type Ia. The thermonuclear reaction rate of the 22Ne(p,γ)23Na reaction is determined by a large number of resonances, and it represents the most uncertain rate in the NeNa cycle. This PhD thesis reports on an experiment to study tentative 22Ne(p,γ)23Na resonances at Elab = 71 and 105 keV, as well as the direct capture component of the reaction rate for Elab ≤ 400 keV. The measurements were performed deep underground at the Laboratory for Un- derground Nuclear Astrophysics - LUNA (Gran Sasso, Italy), taking advantage of the strong reduction in the cosmic ray induced background. The LUNA-400-kV electrostatic accelerator and a differentially pumped, windowless gas target of iso- topically enriched 22Ne gas were used. The γ-rays from the reaction were detected with a 4π bismuth germanate scintillator. The data show upper limits on the strengths of the resonances at Elab = 71 and 105 keV of 5.8 × 10−11 and 7.0 × 10−11 eV respectively. The resonances at Elab = 156.2, 189.5 and 259.7 keV have been re-studied and show 20% higher strength than the literature. The present experiment did not show any evidence for the direct capture process at the low energies studied. In addition to the experimental work at LUNA, the 3He(α, γ)7Be and 7Be(p, γ)8B reactions were studied using the most recent solar neutrino data available. Based on the standard solar model and the experimentally measured fluxes of solar 7Be and 8B neutrinos, the astrophysical S-factors of both reactions were evaluated directly in the solar Gamow peak.
Keywords: Nuclear Astrophysics Solar Neutrinos LUNA Neon-sodium cycle
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-087 2018

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Permalink: https://www.hzdr.de/publications/Publ-27110
Publ.-Id: 27110


Sorption of iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy

Köhler, F.; Riebe, B.; Scheinost, A. C.; König, C.; Hölzer, A.; Walther, C.
The environmental fate of iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11–41% to 62–85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.
Keywords: iodine iodate iodite soils XAFS sequential extraction sorption

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  • Secondary publication expected from 18.06.2020

Permalink: https://www.hzdr.de/publications/Publ-27109
Publ.-Id: 27109


Overexpression of receptor tyrosine kinase EphB4 triggers tumor growth and hypoxia in A375 melanoma xenografts: insights from multitracer small animal imaging experiments

Neuber, C.; Belter, B.; Meister, S.; Hofheinz, F.; Bergmann, R.; Pietzsch, H.-J.; Pietzsch, J.ORC
Experimental evidence has associated receptor tyrosine kinase EphB4 with tumor angiogenesis also in malignant melanoma. Considering the limited in vivo data available, we have conducted a systematic multitracer and multimodal imaging investigation in EphB4-overexpressing and mock-transfected A375 melanoma xenografts. Tumor growth, perfusion, and hypoxia were investigated by positron emission tomography. Vascularization was investigated by fluorescence imaging in vivo and ex vivo. The approach was completed by magnetic resonance imaging, radioluminography ex vivo, and immunohistochemical staining for blood and lymph vessel markers. Results revealed EphB4 to be a positive regulator of A375 melanoma growth, but a negative regulator of tumor vascularization. Resulting in increased hypoxia, this physiological characteristic is considered as highly unfavorable for melanoma prognosis and therapy outcome. Lymphangiogenesis, by contrast, was not influenced by EphB4 overexpression. In order to distinguish between EphB4 forward and EphrinB2, the natural EphB4 ligand, reverse signaling a specific EphB4 kinase inhibitor was applied. Blocking experiments show EphrinB2 reverse signaling rather than EphB4 forward signaling to be responsible for the observed effects. In conclusion, functional expression of EphB4 is considered a promising differentiating characteristic, preferentially determined by non-invasive in vivo imaging, which may improve personalized theranostics of malignant melanoma.
Keywords: Eph receptor tyrosine kinase family; Ephrin ligands; tumor microenvironment; malignant melanoma; small animal positron emission tomography; tumor angiogenesis; tumor hypoxia

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Permalink: https://www.hzdr.de/publications/Publ-27108
Publ.-Id: 27108


Experimentelle Untersuchung der Wärmeübertragung, des Druckverlustes und des Strömungsfeldes an ovalen Rippenrohren unter Variation des Anströmwinkels

Unger, S.; Beyer, M.; Arlit, M.; Hampel, U.
Einleitung
Rippenrohrwärmeübertrager finden in vielen Bereichen der Industrie Anwendung, wie beispielsweise in der Klimatechnik, Kältetechnik, Kraftwerkstechnik und in chemischen Anlagen. Da ca. 90% des gesamten thermischen Widerstandes gasseitig auftreten, werden hier Oberflächenerweiterungen in Form von Rippen genutzt. Bei vielen Anwendungsfällen werden die Rippenrohrwärmeübertrager geneigt installiert, um den benötigten Bauraum zu reduzieren oder um ein Abfließen von Kondensat auf der Rohrinnenseite zu gewährleisten. Daher soll der Einfluss des Anströmwinkels auf die Wärmeübertragungsleistung und Strömungscharakteristik untersucht und beschrieben werden.

Messtechnik, experimenteller Aufbau und Durchführung
Die stationären Messungen wurden in einem ca. 6.5 m langen, senkrechten und transparenten Strömungskanal mit rechteckigem Querschnitt durchgeführt. Im Einströmbereich des Kanals befinden sich drei Sieb- sowie ein Wabengleichrichter zur Strömungsformierung an die sich eine Testsektion mit den zu untersuchenden Rippenrohren anschließt. Es wurden 3 Rippenrohre mit Rippenabständen von 6 mm,11 mm und 16 mm jeweils unter vier Anströmwinkeln (0°,20°,30° und 40°) untersucht. Die Strömung wurde durch einen Kompressor aufgeprägt und die mittlere Strömungsgeschwindigkeit zwischen 0,5 m/s und 3 m/s variiert. Die ovalen Rippenrohre wurden additiv aus 316L Edelstahl (Wärmeleitfähigkeit: 16.2 W/mK) gefertigt und sind durch Haltebuchsen an den Kanalwänden fixiert. Der Austausch von Haltebuchsen und dazugehörigen Kanalwänden ermöglichte die Positionierung der Rippenrohre mit den erforderlichen Winkeln. Im Inneren der Rippenrohre befinden sich drei elektrisch beheizte Heizpatronen. Um eine gute Wärmeleitung zum Rippenrohr zu gewährleisten, sind die Zwischenräume mit Kupferpulver ausgefüllt. Aus jeweils drei stromaufwärts und –abwärts angeordneten Thermoelementen wurde die mittlere Lufttemperatur bestimmt. Das radiale Temperaturprofil der Rippen wurde mithilfe von 12 Thermoelementen entlang der Rippenoberfläche vermessen, um den Rippenwirkungsgrad zu bestimmen. An senkrechten Bohrungen der Kanalwand unter- und oberhalb der Testsektion befinden sich die Anschlüsse der Differenzdruckmessung.
Zur Einstellung der stationären Versuchsrandbedingungen wurde die mittlere Oberflächentemperatur des Rippenrohres, durch Anpassung der elektrischen Leistung in Abhängigkeit von der Anströmgeschwindigkeit konstant bei 60° C gehalten. Die Aufzeichnung der Messdaten erfolgte mit einer zeitlichen Auflösung von 1Hz. Ein Temperaturgittersensor wurde verwendet um in 16 Messstellen stromabwärts der Versuchsstrecke das Temperatur- und Geschwindigkeitsfeld mithilfe von Widerstandstemperaturmessung und thermischer Anemometrie zu bestimmen.

Ergebnisse
Die Messergebnisse zeigen einen deutlichen Anstieg des Wärmeübergangskoeffizienten mit größerem Rippenabstand. Hintergrund sind die Strömungsgrenzschichten, welche bei niedrigerem Abstand der Rippen schon früher stromabwärts zusammenwachsen und den Wärmeübergangskoeffizient reduzieren. Des Weiteren wurde festgestellt, dass bei einem Rippenabstand von 6 mm der Rippenwirkungsgrad am höchsten und bei 16 mm am kleinsten ist. Generell wurden höhere Temperaturen der Rippe im thermischen Nachlaufgebiet hinter dem Rohr sowie niedrigere Rippentemperaturen im Anströmbereich des Rippenrohres gemessen. Aufgrund der erhöhten Oberfläche ist bei 6 mm Rippenabstand der Druckverlust am höchsten, gefolgt von den Abständen 11 mm und 16 mm.
Durch einen erhöhten Anströmwinkel von 40° nimmt die Turbulenz entlang der Rippenoberfläche zu und der Wärmeübergangskoeffizient erhöht sich um 38 % bei 6 mm Rippenabstand gegenüber der senkrechten Anströmung. Der Druckverlust nimmt mit dem Anströmwinkel stark zu. Somit ist der Druckverlust in der 40° Position gegenüber der senkrechten Anströmung für 6 mm um den Faktor 3.23 größer.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mehrphasenströmungen (MPH), Wärme- und Stoffübertragung (WSUE) und Computional Fluid Dynamics (CFD), 06.-07.03.2018, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27107
Publ.-Id: 27107


Projektidee KESS Kreislaufwirtschaftliches EntscheidungsSimulationsSystem

van den Boogaart, K. G.
Das Projekt KESS - Kreislaufwirtschaftliches EntscheidungsSimulationsSystem beschäftigt sich mit der Vorhersage von Entscheidungen, Wert- und Stoffströmen einer zukünfigen Kreislaufwirtschaft. Gesucht werden Kooperationspartner aus den Bereichen Psychologie, Wirtschaftsrecht, Wirtschaft, Reuse, Repair, und Recyclingmodellierung, sowie Mathematik und Informatik. Besonders Willkommen sind Wirtschaftsunternehmen mit Fragestellungen zu zukünftigen Geschäftsmodellen im Rahmen der Kreislaufwirtschaft.
Keywords: Kreislaufwirtschaft, Spieltheorie, Entscheidungstheorie, Stoffstrommodellierung
  • Lecture (others)
    Vernetzungs- und Informationsveranstaltung, 22.02.2018, Berlin, Deutschlad

Permalink: https://www.hzdr.de/publications/Publ-27106
Publ.-Id: 27106


Effect of background electrolyte composition on the sorption behavior of Th(IV) and Zr(IV) on the muscovite (001) basal plane

Schmidt, M.ORC; Qiu, C.; Hellebrandt, S.; Hennig, C.; Eng, P. J.; Skanthakumar, S.; Soderholm, L.
Reliable long-term predictions about the safety of a potential nuclear waste repository must be based on a sound, molecular-level comprehension of the geochemical behavior of the radionuclides. Especially, their reactivity at the water/mineral interface will control their mobility and thus hazard potential.[1] A recent study has found a surprising dependency of the uptake of Th(IV) on the muscovite (001) basal plane on the composition of the background electrolyte.[2]
Two effects were observed a sorption reducing effect of ClO4- relative to Cl- and a sorption increasing effect of Li+ relative to Na+. Thus, a simple change from NaClO4 medium to LiClO4 led to an increase in surface occupancy by more than two orders of magnitude, which subsequently leads to the formation of Th(IV)-(hydr)oxo-nanoparticles. A mechanistic interpretation is hitherto not available, so it remains unknown whether cation and anion effects occur independently and whether the background electrolyte’s cation affects the formation of nanoparticles in solution or increases sorption at the water/mineral interface.
To probe whether anion and cation effects occur independently, Th(IV) sorption was studied in the presence of LiCl and KCl ([Th] = 0.1 mM, pH = 3.3, I = 0.1 M) using the surface X-ray diffraction techniques crystal truncation rod (CTR) diffraction and resonant anomalous X-ray reflectivity (RAXR). The finding show strong uptake at the muscovite basal plane in both cases, exceeding the surface occupancy previously described in NaCl media,[3] thus confirming that the cation effect is indeed independent of the background electrolyte’s anion.
To elucidate whether the observed differences occur, when oligomers are present before introduction of the mineral surface, we studied the uptake behavior of Zr(IV). Zr(IV) has a much more pronounced hydrolysis, and similar subsequent formation of oligomers and nanoparticles compared to Th(IV). The interfacial structure of muscovite was characterized in contact with Zr(IV) in solutions of various background electrolytes MCl (M = Li – Cs, [Zr] = 0.1 mM; pH 2.5, I = 0.1 M). In parallel, we performed AFM to characterize the morphology of any particles found on the mineral surface. The results clearly show that only small differences are induced by the electrolyte composition, which are generally well explained by the alkali cations sorption affinity and speciation at the muscovite (001) basal plane. Apparently, the background electrolyte effect is suppressed (or not effective at all) when the initial speciation of the metal is as small oligomers, indicating that the effects observed for Th(IV) occur at the water/mineral interface, and not in solution.

(1) Geckeis, H.; Lützenkirchen, J.; Polly, R.; Rabung, T.; Schmidt, M., Chem. Rev. 2013, 113, 1016-1062.
(2) Schmidt, M.; Hellebrandt, S.; Knope, K. E.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P., Geochim. Cosmochim. Acta 2015, 165, 280-293.
(3) Schmidt, M.; Lee, S. S.; Wilson, R. E.; Soderholm, L.; Fenter, P., Geochim. Cosmochim. Acta 2012, 88, 66-76.
Keywords: Actinides, thorium, zirconium, CTR, RAXR, surface diffraction, sorption, interfacial processes, background electrolyte
  • Lecture (Conference)
    RadChem 2018, 13.-18.05.2018, Marianske Lazne, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-27105
Publ.-Id: 27105


Near-field optical examination of potassium n-butyl 2 xanthate / chalcopyrite flotation products

Firkala, T.; Kuschewski, F.; Nörenberg, T.; Klopf, J. M.; Pashkin, A.; Foerstendorf, H.; Rudolph, M.; Kehr, S. C.; Eng, L. M.
The present study introduces scattering-type scanning near-field infrared optical nanospectroscopy (s-SNIM) as a valuable and well-suited tool for spectrally fingerprinting n-butyl xanthate (KBX) molecules adsorbed to chalcopyrite (CCP) sample surfaces. The collector KBX is well known to float CCP and is used in beneficiation. We thus identify KBX molecules both by IR optical far and near field techniques, applying attenuated total internal reflection Fourier-transform infrared spectroscopy (ATR FT-IR) in comparison to s-SNIM, respectively. The major KBX band around 880 cm−1 is probed in s-SNIM using both the tunable free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf, Germany and CO2 table-top laser illumination. We then are able to monitor the KBX agglomeration in patches of < 500 nm in diameter at the CCP surface, but equally to nanospectroscopically identify the presence of KBX molecules down to the 10−4 M concentration.
Keywords: potassium n-butyl xanthate; chalcopyrite; flotation; near-field nanoscopy; IR spectroscopy; scanning probe microscopy; fingerprint region; ultra-low concentration.

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Permalink: https://www.hzdr.de/publications/Publ-27104
Publ.-Id: 27104


Magnetic stirring and sonication of metal melts

Gerbeth, G.
  • Invited lecture (Conferences)
    XVIII International UIE-Congress, 06.-09.06.2017, Hannover, Germany

Permalink: https://www.hzdr.de/publications/Publ-27103
Publ.-Id: 27103


Experimental Modelling of Metallurgical Processes

Eckert, G.; Gerbeth, S.
  • Invited lecture (Conferences)
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries - SINTEF, 30.05.-01.06.2017, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-27102
Publ.-Id: 27102


High energy resolution X-ray spectroscopy and diffraction studies of plutonium oxide nanoparticles

Gerber, E.; Romanchuk, A.; Pidchenko, I.; Hennig, C.; Trigub, A.; Weiss, S.; Scheinost, A.; Kalmykov, S.; Kvashnina, K.
The release of radioactive plutonium (Pu) into the environment is of general concern due to the high radiotoxicity and long half-life of its main isotopes. Previous research has shown that plutonium migrates in the subsurface environment on the kilometer scale at some previously contaminated sites [1-4]. Additionally, previous research demonstrated the spontaneous formation of Pu oxide nanoparticles under certain environmental conditions [5]. However, fundamental properties of such Pu oxide nanoparticles, including their local, crystal and electronic structure, remain largely unexplored, hence it is difficult to understand their formation or to predict their transport in the environment.

Plutonium may exist in four oxidation states, III, IV, V, VI, in aqueous solution under environmental conditions, which can change relatively easily. While Pu(IV) is the dominant oxidation state in such PuO2-like nanoparticles, their exact composition in terms of oxidation states and local structure remains an open question. Therefore, it is necessary to advance the fundamental understanding of the Pu oxide nanoparticles and to review the processes, through which the formation of Pu oxide nanoparticles takes place.

This contribution will give an overview on the results of Pu oxide nanoparticle research conducted at the Rossendorf Beamline at The European Synchrotron (ESRF) [6]. Pu oxide nanoparticles were prepared by rapid chemical precipitation using precursors in the different oxidation states (Pu(III), Pu(IV), Pu(V) and Pu(VI)). These precursors were obtained by chemical reduction or oxidation of Pu stock solution.

The recently upgraded ROBL beamline at the ESRF, dedicated to actinide science, provides now a unique opportunity to characterize actinide materials by several experimental techniques simultaneously. We will show how the detailed information about local and electronic structure and Pu oxidation state in different nanoparticles can be obtained using the variety of methods: Extended X-ray absorption fine structure (EXAFS [7]), X-ray absorption near edge structure (XANES), high-energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy [8-10], resonant inelastic X-ray scattering (RIXS [11]), and X-ray diffraction techniques.
  • Lecture (Conference)
    17th International Conference on X-ray Absorption Fine Structure, 22.-27.07.2018, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-27101
Publ.-Id: 27101


Interaction of Stem Cell Properties and DNA Repair determine the Radiosensitizing Effect after Inhibition of CHK1, RAD51 and PARP1 in TNBCs

Meyer, F.; Becker, S.; Niecke, A.; Werner, S.; Peitzsch, C.; Hein, L.; Dubrovska, A.; Goy, Y.; Parplys, A.; Petersen, C.; Riepen, B.; Zielinski, A.; Rothkamm, K.; Borgmann, K.

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Permalink: https://www.hzdr.de/publications/Publ-27100
Publ.-Id: 27100


Discrimination of ceramic surface finishing by vertical scanning interferometry

Ionescu, C.; Fischer, C.; Hoeck, V.; Luttge, A.
Finishing techniques are significant markers of the technological “knowhow” involved in the production of the clay-based traditional ceramic ware.
In order to provide a reliable tool to discriminate among two main surface processing techniques, i.e. smoothing and burnishing, vertical scanning interferometry (VSI) – a recently developed non-destructive technique for analyzing the surface roughness and topography, is applied. The smoothed areas have an obvious roughness expressed by linear structures. The latter are made of parallel ridges and trenches with an average depth of 15–20 μm. Burnishing leads to a lower topography and a lower roughness compared to the smoothed surface section. The VSI quantifies the spatial distribution of the surface building blocks, which consist of phyllosilicate aggregates of variable size. The statistical treatment of the roughness data obtained by VSI shows that the surface topography provides significant information on the pottery processing and a clear qualitative and quantitative discrimination between different surfaces. VSI supports the reconstitution of the chaȋne opératoire for traditional ceramic pottery and the recognition of the surface finishing techniques.

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Permalink: https://www.hzdr.de/publications/Publ-27098
Publ.-Id: 27098


Recent update on the KLOE ISR-measurements

Keshavarzi, A.; Müller, S. E.ORC; Teubner, T.; Venanzoni, G.
Recent updates on KLOE ISR measurements
  • Invited lecture (Conferences)
    Workshop on hadronic vacuum polarization contributions to muon g-2, 12.-14.02.2018, KEK Tsukuba, Japan

Permalink: https://www.hzdr.de/publications/Publ-27097
Publ.-Id: 27097


Intratumoral heterogeneity and TERT promoter mutations in progressive/higher-grade meningiomas

Juratli, T. A.; Thiede, C.; Koerner, M. V. A.; Tummala, S. S.; Daubner, D.; Shankar, G. M.; Williams, E. A.; Martinez-Lage, M.; Soucek, S.; Robel, K.; Penson, T.; Krause, M.; Appold, S.; Meinhardt, M.; Pinzer, T.; Miller, J. J.; Krex, D.; Ely, H. A.; Silverman, I. M.; Christiansen, J.; Schackert, G.; Wakimoto, H.; Kirsch, M.; Brastianos, P. K.; Cahill, D. P.
Background: Recent studies have reported mutations in the telomerase reverse transcriptase promoter (TERTp) in meningiomas. We sought to determine the frequency, clonality and clinical significance of telomere gene alterations in a cohort of patients with progressive/higher-grade meningiomas.

Methods: We characterized 64 temporally- and regionally-distinct specimens from 26 WHO grade III meningioma patients. On initial diagnoses, the meningiomas spanned all WHO grades (3 grade I, 13 grade II and 10 grade III). The tumor samples were screened for TERTp and ATRX/DAXX mutations, and TERT rearrangements. Additionally, TERTp was sequenced in a separate cohort of 19 patients with radiation-associated meningiomas. We examined the impact of mutational status on patients’ progression and overall survival.

Results: Somatic TERTp mutations were detected in six patients (6/26 = 23%). Regional intratumoral heterogeneity in TERTp mutation status was noted. In 4 patients, TERTp mutations were detected in recurrent specimens but not in the available specimens of the first surgery. Additionally, a TERT gene fusion (LPCAT1-TERT) was found in one sample. In contrary, none of the investigated samples harbored an ATRX or DAXX mutation. In the cohort of radiation-induced meningiomas, TERTp mutation was detected in two patients (10.5%). Importantly, we found that patients with emergence of TERTp mutations had a substantially shorter OS than their TERTp wild-type counterparts (2.7 years, 95% CI 0.9 – 4.5 years versus 10.8 years, 95% CI 7.8 -12.8 years, p=0.003).

Conclusions: In progressive/higher-grade meningiomas,TERTp mutations are associated with poor survival, supporting a model in which selection of this alteration is a harbinger of aggressive tumor development. In addition, we observe spatial intratumoral heterogeneity of TERTp mutation status, consistent with this model of late emergence in tumor evolution. Thus, early detection of TERTp mutations may define patients with more aggressive meningiomas. Stratification for TERT alterations should be adopted in future clinical trials of progressive/higher-grade meningiomas.

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Permalink: https://www.hzdr.de/publications/Publ-27096
Publ.-Id: 27096


An Image Reconstruction Framework and Camera Prototype Aimed for Compton Imaging for In-vivo Dosimetry of Therapeutic Ion Beams

Schoene, S.; Enghardt, W.; Fiedler, F.; Golnik, C.; Pausch, G.; Rohling, H.; Kormoll, T.
Prompt γ-ray imaging in hadron therapy is a novel approach for range verification. Due to the high energy of prompt γ-rays emitted during therapeutic irradiation in the order of MeV, Compton imaging is a feasible method. In this work, an imaging prototype together with the corresponding data handling and an image reconstruction framework are presented. Data and reconstructed images from laboratory measurements are shown and evaluated. A spatial resolution of 7 mm full width at half maximum in a distance of 7 cm has been achieved. More importantly, current limitations were identified for further work. It has been shown that an assumption on the unknown initial photon energy can considerably improve the imaging result.

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Permalink: https://www.hzdr.de/publications/Publ-27095
Publ.-Id: 27095


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.

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Permalink: https://www.hzdr.de/publications/Publ-27094
Publ.-Id: 27094


Adhesion- and stress-related adaptation mechanisms eliciting glioblastoma radiochemoresistance can be effectively circumvented by beta1 integrin/JNK co-targeting

Vehlow, A.; Klapproth, E.; Storch, K.; Dickreuter, E.; Seifert, M.; Dietrich, A.; Bütof, R.; Temme, A.; Cordes, N.
Glioblastoma multiforme (GBM) is the most common brain tumor in adults and characterized by poor clinical outcome due to genetic and epigenetic alterations in resistance-mediating genes and destructive infiltration into the normal brain. Upon therapy, malignant tumors show adaptation to maintain their homeostasis. Two critical determinants of this adaptation process are cell adhesion by beta1 integrins and stress signaling via c-Jun N-terminal kinases (JNK). Here, we evaluated the potential of simultaneous beta1 integrin/JNK targeting to overcome GBM adaptation controlling radiochemoresistance and invasion.

Comparative Oncomine data base analysis was performed on the expression of JNK1/2/3 isoforms, beta1 integrin and its ligands in GBM with normal brain. Different human GBM cell populations (patient-derived, stem-like, established) were analyzed for sphere formation, clonogenicity, 3D collagen type-1 invasion, cell cycling, chromatin organization, DNA double strand break (DSB) repair (γH2AX foci assay), broad-spectrum phosphoproteome analysis, FACS analysis and protein expression/phosphorylation upon irradiation (0-6 Gy X-rays) and chemotherapy (Temozolomide) with and without single and simultaneous inhibition of beta1 integrin (AIIB2) and JNK (SP600125, JNKi). The radiochemosensitizing potential of AIIB2/JNKi was also investigated in an orthotopic GBM mouse model using stem-like cells.

In contrast to JNK isoforms, beta1 integrin and col1 showed significant overexpression in GBM compared with normal brain. While single inhibition of beta1 integrin and JNK mediated cytotoxicity, only combined targeting resulted in radiochemosensitization. Intriguingly, double AIIB2/JNKi treatment abrogated GBM cell invasion. Importantly, dual beta1 integrin/JNK inhibition elicited a significant reduction in tumor growth and longer survival of mice concomitantly treated with radiotherapy/Temozolomide. Mechanistically, JNK blocking induced beta1 integrin expression for stimulating diverse signaling pathways controlling cell cycling, invasion and radiochemosensitivity. Radiosensitization by AIIB2/JNKi is caused by enhanced ATM phosphorylation and prolonged G2/M cell cycle arrest as well as impaired DNA double strand break repair in the context of elevated levels of euchromatin.

In summary, our data reveal that dual beta1 integrin/JNK targeting efficiently impairs adhesion and stress-related adaptation mechanisms involved in radiochemoresistance and invasion. More in-depth evaluation is warranted to clarify the potential of this kind of beta1 integrin/JNK multi-targeting strategy administrated concomitantly to standard radiochemotherapy in patients suffering from GBM.

Permalink: https://www.hzdr.de/publications/Publ-27093
Publ.-Id: 27093


Annual Report 2017 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.ORC; Bok, F.; Richter, A.
THE INSTITUTE OF RESOURCE ECOLOGY (IRE) IS ONE of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-085 2018
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-27092
Publ.-Id: 27092


Extension of the reactor dynamics code DYN3D to SFR applications – Part III: validation against the initial phase of the Phenix EOL natural convection test

Nikitin, E.; Fridman, E.
The reactor dynamics code DYN3D, initially developed for LWR applications, is being extended for steady state and transient analyses of Sodium cooled Fast Reactor (SFR) cores. The extension includes the development of the few-group cross section generation methodology, updating of the thermal-hydraulic database with thermal-physical properties of sodium, and development of the thermal-mechanical model to account for thermal expansion effects of the core components.
Part I of the paper provided a detailed description of the recently implemented thermal expansion models able to treat axial expansion of fuel rod and radial expansion of diagrid. The results of the initial verification test were also presented in Part I of the paper.
The capability of the extended version of DYN3D to perform steady state and transient analyses of SFR cores was validated using selected tests from the end-of-life experiments conducted at the Phenix reactor. Steady state analysis of the control rod withdrawal tests is covered in Part II of the paper.
Part III of the paper reports on the results of the transient analysis of the initial stage of the natural circulation test from the Phenix end-of-life experiments.
Keywords: SFR, Phenix EOL tests, thermal expansion, nodal diffusion, transient analysis, DYN3D, Serpent

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Permalink: https://www.hzdr.de/publications/Publ-27091
Publ.-Id: 27091


Ein möglicher prognostischer Biomarker für das Therapieansprechen und therapeutisches Zielmolekül zur Strahlensensitivierung in Kopf-Hals-Plattenepithelkarzinomen

Digomann, D.; Kurth, I.; Linge, A.; Hein, L.; Baumann, M.; Dubrovska, A.
  • Abstract in refereed journal
    Strahlentherapie und Onkologie 193(2017), S25-S26

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Permalink: https://www.hzdr.de/publications/Publ-27090
Publ.-Id: 27090


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