Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

33407 Publications

Metal-organic complexes of tetravalent actinides with soft-donor ligands investigated by paramagnetic NMR spectroscopy

Schöne, S.ORC; Radoske, T.; Felsner, B.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
In NMR spectra of paramagnetic metal-organic complexes electronic interactions are the origin of additional NMR chemical shifts observed on resonances of nuclei of the ligand. The major two contributors to these hyperfine shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.
The paramagnetic contributions can be mathematical separated provided that a suitable diamagnetic reference is available (to subtract non-paramagnetic contributions). For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. Furthermore, all available theories behind mathematical disentangling of contributions to the paramagnetic chemical shift, even for the lanthanide series, omit the influence of spin-orbit effects that might have a sizeable contribution.[1,2]
Comparing studies of isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allow for an estimation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.
We started to study paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)). Throughout the 5f-series additional effects to the observed chemical shift are expected with increasing number of unpaired electrons. Assessing the chemical bonding situation is possible via the influences on NMR chemical shifts (via FCS) and structural properties of the complexes (via PCS) can be compared to SC-XRD structures. Herein we report the first results of investigations of N- and N,O-donor ligand complexes of the An(IV) series.

References
1 C. Adam, P. Kaden, B. B. Beele, U. Müllich, S. Trumm, A. Geist, P. J. Panak, M. A. Denecke, “Evidence for covalence in a N-donor complex of americium(III)”, Dalton Trans., 42, 14068-14074 (2013).
2. C. Adam, B. B. Beele, A. Geist, U. Müllich, P. Kaden, P. J. Panak, “NMR and TRLFS studies of Ln(III) and An(III) C5-BPP complexes”, Chemical Science, 6, 1548-1561 (2015).
Keywords: NMR, paramagnetic, Actinide, N-donor, FCS, PCS
  • Lecture (Conference)
    ISNSC - 10th International Symposium on Nano and Supramolecular Chemistry 2018, 09.-12.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27518
Publ.-Id: 27518


Paramagnetic NMR investigations in metal-organic complexes of tetravalent actinides with soft-donor ligands

Schöne, S.ORC; Radoske, T.; Felsner, B.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
Electronic interactions between metal and ligand are the origin of additional NMR chemical shifts observed on nuclei of the ligand in paramagnetic metal-organic complexes. The major two contributors to these paramagnetic chemical shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.
The mathematical separation of paramagnetic contributions in complexes relies on the availability of a suitable diamagnetic reference to subtract non-paramagnetic contributions. For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. Furthermore, all available theories behind mathematical disentangling of contributions to the paramagnetic chemical shift, even for the lanthanide series, omit the influence of spin-orbit effects that might have a sizeable contribution as well. [1,2]
Comparing isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allows for an estimation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.
To assess the chemical bonding situation via the influences on NMR chemical shifts (via FCS) we started to study paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)). With increasing number of unpaired electrons throughout the 5f-series additional effects to the observed chemical shift are expected. Structural properties of the complexes as derived from PCS contributions can be compared to single crystal X-ray diffraction structures. Herein we report the first results of investigations of N- and N,O-donor ligand complexes of the An(IV) series.

References
1 C. Adam, P. Kaden, B. B. Beele, U. Müllich, S. Trumm, A. Geist, P. J. Panak, M. A. Denecke, “Evidence for covalence in a N-donor complex of americium(III)”, Dalton Trans., 42, 14068-14074 (2013).
2. C. Adam, B. B. Beele, A. Geist, U. Müllich, P. Kaden, P. J. Panak, “NMR and TRLFS studies of Ln(III) and An(III) C5-BPP complexes”, Chemical Science, 6, 1548-1561 (2015).
Keywords: NMR, paramagnetic, Actinide, N-donor, FCS, PCS, structure determination, solution
  • Lecture (Conference)
    18th Radiochemical Conference - RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
  • Contribution to proceedings
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
    Czech Chemical Society Symposium Series 2

Permalink: https://www.hzdr.de/publications/Publ-27517
Publ.-Id: 27517


Nanohardening features in ion and neutron irradiated EUROFER97 and model alloys investigated with atom probe tomography

Gómez-Ferrer, B.; Heintze, C.; Dethloff, C.; Gaganidze, E.; Konstantinovic, M. J.; Malerba, L.; Pareige, P.; Pareige, C.
Among other effects, neutron irradiation hardens ferritic/martensitic (F/M) nuclear steels; this hardening is suspected to be due to the formation of dislocation loops, alpha' phase and solute-rich clusters (SRCs). In neutron irradiated FeCr model alloys the SRCs which are made of unavoidable impurities such as P are likely to be the main contributors to the yield strength increase, together with the presence of alpha' precipitates, if any [1,2]. Ion irradiation is an extended tool used to investigate the creation and evolution of radiation damage. Since the experiments are fast they offer the possibility to tune the parameters to design model-oriented experiments. Their use is also oriented to reproduce the effects of neutrons for nuclear applications. However, the characteristics of the nano-sized features (solute concentration, density, size and size distribution) are difficult to reproduce using ions with respect to neutrons, since the increase of the sink strength due to injecte d inters titials [3,4] and the high values of damage rate [5] influence defect production and evolution.
Atom probe tomography (APT) is used in the present work to investigate the hardening nanofeatures in irradiated materials. First, an Fe14CrNiSiP model alloy has been irradiated with both Fe+ ions and neutrons up to a dose of 0.1 dpa at 300°C. At such low doses some features, such as SRCs or Cr-rich regions, are formed, thus a direct comparison can be made to highlight differences and commonalities between the two kinds of irradiation; these results can also be used for the development of models. Second, a similar investigation has been made on neutron irradiated EUROFER97 up to 15 dpa at 300°C. The presence of radiation induced segregation (RIS) and radiation enhanced features can be correlated to the model alloy providing some insights on the nature of the hardening in F/M steels.
  • Lecture (Conference)
    E-MRS 2018 Spring Meeting, 18.-22.06.2018, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-27516
Publ.-Id: 27516


Critical heat flux as a mass flux dependent local or global phenomenon: Theoretical analysis and experimental confirmation

Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.
In this article, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity.
Keywords: boiling, critical heat flux, initiation mechanisms

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27515
Publ.-Id: 27515


Application of an Eulerian-Eulerian CFD approach to simulate the thermohydraulics of rod bundles

Ding, W.; Krepper, E.; Sarker, D.; Hampel, U.
The Eulerian-Eulerian computational fluid dynamics (CFD) approach is widely applied in the simulation of industrial scale thermal fluid dynamics problems, such as flow and heat transfer in fuel elements. However, the case dependency of sub models in the Eulerian-Eulerian CFD approach currently hampers its applicability. In order to reduce this dependency, a sub model to predict the bubble departure in both pool and flow boiling was developed in our group, which includes the impact of microlayer, thermal diffusion, condensation, mutual effect and force balance. Moreover, we also raised a new CHF- concept. It is currently based on correlations but we are continuously working on a transition to a fully physics-based model, which e.g. considers the dependency of boiling on the microlayer thickness, bubble base expansion speed and local shear stress. In order to implement the bubble dynamics model and CHF model into the Eulerian-Eulerian CFD framework, a new cavity activation and heat partitioning model was developed, which is not only used for bubble nucleation but also connects the nucleation boiling and CHF- in one CFD approach. However nucleation site density is strongly dependent on the surface properties, which is difficult to model without correlations.
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology (AMNT 2018), 29.-30.05.2018, Berlin, Germany
    49th Annual Meeting on Nuclear Technology

Permalink: https://www.hzdr.de/publications/Publ-27514
Publ.-Id: 27514


Long-term quality of life in inoperable non-small cell lung cancer patients treated with conventionally fractionated compared to hyperfractionated accelerated radiotherapy - Results of the randomized CHARTWEL trial

Hechtner, M.; Krause, M.; Konig, J.; Appold, S.; Hornemann, B.; Singer, S.; Baumann, M.
Background and purpose: To evaluate the quality of life (QoL) of patients with inoperable non-small cell lung cancer treated with conventionally fractionated radiotherapy (CF) vs. continuous hyperfractionated accelerated radiotherapy weekend-less (CHARTWEL).
Material and methods: The largest monocentric subgroup of the phase III CHARTWEL trial was analyzed up to three years after randomization. QoL was assessed with the European Organization for Research and Treatment of Cancer QoL Core Questionnaire (QLQ-C30) and lung cancer module (QLQ-LC13) and compared using linear mixed models. QoL interrelations with recurrence, metastasis, and death were explored by multi-state modeling.
Results: 160 patients (98%) provided at least one QoL assessment.
Average treatment differences of CF vs. CHARTWEL over three years were -5.4 points (95%CI [-13.6,2.8], p = 0.19) in global QoL, 11.9 ([2.8,21.0], p = 0.01) in fatigue, 13.4 ([3.5,23.3], p = 0.009) in pain, 10.5 ([1.3,19.6], p = 0.03) in dyspnea, and 5.2 ([-2.7,13.0], p = 0.19) in dysphagia. At 12 months, the probabilities of being disease-free with good, good or moderate, any global QoL, or alive were 5.1%, 20.3%, 34.2%, 54.4% under CF and 10.4%, 21.0%, 37.5%, 65.3% under CHARTWEL.
Conclusions: Over three years, QoL was similar or more favorable under CHARTWEL compared to CF. Modeling QoL together with disease states provided additional insight into treatment comparisons.
Keywords: Quality of life Non-small cell lung cancer Accelerated radiotherapy Hyperfractionation Randomized trial Multi-state model

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27513
Publ.-Id: 27513


Cognitive deficits following brain tumor radiation therapy

Buthut, M.; Haussmann, R.; Seidlitz, A.; Krause, M.; Donix, M.
Brain radiation is an important treatment option for malignant and benign brain diseases. The possible acute or chronic impact of radiation therapy on cognitive performance is important for daily functioning and quality of life. A detailed evaluation of cognitive impairment is important in the context of how to control disease progression. The susceptibility of the hippocampus to radiation-induced neuronal damage and its important role in memory highlight that therapeutic strategies require precision medicine.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27512
Publ.-Id: 27512


Magnetohydrodynamic Simulation: Liquid Metal Batteries, Crystal Growth & Steel Casting

Weber, N.; Beckstein, P.; Galindo, V.; Giesecke, A.; Liu, K.; Pal, J.; Personnettaz, P.; Stefani, F.; Timmel, K.; Weier, T.
Der Vortrag gibt einen Überblick über numerische Simulationen der Abteilung Magnetohydrodynamik am HZDR.
  • Lecture (Conference)
    OpenFOAM Stammtisch United, 24.05.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27511
Publ.-Id: 27511


Instrumentation for Liquid Metal Facilities

Gundrum, T.; Krauter, N.; Wondrak, T.; Richter, T.; Keplinger, O.; Franke, S.; Eckert, S.
Instrumentation for Liquid Metal Facilities an overview and present work
  • Invited lecture (Conferences)
    ESFR-SMART European workshop on Liquid Metal facilities; focus on sodium facilities design & safe operation, 22.-24.05.2018, Rom, Italia

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27510
Publ.-Id: 27510


Quantum Criticality of an Ising-like Spin-1/2 Antiferromagnetic Chain in a Transverse Magnetic Field

Wang, Z.; Lorenz, T.; Gorbunov, D. I.; Cong, P. T.; Kohama, Y.; Niesen, S.; Breunig, O.; Engelmayer, J.; Herman, A.; Wu, J.; Kindo, K.; Wosnitza, J.; Zherlitsyn, S.; Loidl, A.
We report on magnetization, sound velocity, and magnetocaloric-effect measurements of the Ising-like spin-1/2 quantum antiferromagnetic chain BaCo$_2$V$_2$O$_8$ as a function of temperature down to 1.3~K and applied transverse magnetic field up to 60~T. While across the Ne\'{e}l temperature of $T_N\sim5$~K anomalies in magnetization and sound velocity confirm the antiferromagnetic ordering transition, at the lowest temperature in the field-dependent measurements we find a sharp softening of sound velocity and a clear temperature minimum at $B^{c,3D}_\perp=21.4$~T, indicating suppression of the antiferromagnetic order. At higher fields, magnetocaloric-effect measurements reveal a broad temperature minimum at $B^c_\perp = 40$~T, accompanied by a broad minimum of sound velocity and a saturation-like level-off in magnetization. These features signal a quantum phase transition that is further quantified by the divergent behavior of Gr\"{u}neisen parameter $\Gamma_B \propto (B-B^{c}_\perp)^{-1}$. By contrast, at the critical field the Gr\"{u}neisen parameter converges to a constant as temperature decreases towards zero, which is a distinct characteristics of the one-dimensional transverse-field Ising quantum critical point.
Keywords: Spin chain, quantum critical point, transverse field Ising model, BaCo2V2O8, magnetization, sound velocity, magnetocaloric effects

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27509
Publ.-Id: 27509


Magnetic field dependence of antiferromagnetic resonance in NiO

Wang, Z.; Kovalev, S.; Awari, N.; Chen, M.; Germanskiy, S.; Green, B.; Deinert, J.-C.; Kampfrath, T.; Milano, J.; Gensch, M.
We report on measurements of magnetic field and temperature dependence of antiferromagnetic resonances in the prototypical antiferromagnet NiO. The frequencies of the magnetic resonances in the vicinity of 1 THz have been determined in the time-domain via time-resolved Faraday measurements after selective excitation by narrow-band superradiant terahertz (THz) pulses at temperatures down to 3 K and in magnetic fields up to 10 T. The measurements reveal two antiferromagnetic resonance modes, which can be distinguished by their characteristic magnetic field dependencies. The nature of the two modes is discussed by comparison to an eight-sublattice antiferromagnetic model, which includes superexchange between the next-nearest-neighbor Ni spins, magnetic dipolar interactions, cubic magneto-crystalline anisotropy, and Zeeman interaction with the external magnetic field. Our study indicates that a two-sublattice model is insufficient for the description of spin dynamics in NiO, while the magnetic-dipolar interactions and magneto-crystalline anisotropy play important roles.
Keywords: NiO, terahertz spectroscopy, antiferromagnetic resonance, magnetic field

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27508
Publ.-Id: 27508


Towards femtosecond-level intrinsic laser synchronization at fourth generation light sources

Chen, M.ORC; Kovalev, S.ORC; Awari, N.ORC; Wang, Z.ORC; Germanskiy, S.; Green, B.; Deinert, J.-C.ORC; Gensch, M.ORC
In this Letter, the proof of principle for a scheme providing intrinsic femtosecond-level synchronization between an external laser system and fourth generation light sources is presented. The scheme is applicable at any accelerator-based light source that is based on the generation of coherent radiation from ultrashort electron bunches such as superradiant terahertz (THz) facilities or X-FELs. It makes use of a superradiant THz pulse generated by the accelerator as an intrinsically synchronized gate signal for electro-optical slicing. We demonstrate that the scheme enables a reduction of the timing instability by more than 2 orders of magnitude. This demonstration experiment thereby proves that intrinsically synchronized time-resolved experiments utilizing laser and accelerator-based radiation pulses on few tens of femtosecond (fs) to few fs timescales are feasible.
Keywords: Synchronization, THz slicing, Spectral Decoding

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27507
Publ.-Id: 27507


SRF gun II - status as of April 2018

Arnold, A.; Teichert, J.; Xiang, R.; Murcek, P.
In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and a new cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time. With the improved parameters user experiments of the superconducting CW accelerator ELBE are to be served, that benefit from an increased average beam current at a given repetition rate of some hundred kHz. Although the cavity performance stays behind its specifications, the SRF gun has been optimized for an operation mode at 200 pC and a repetition rate of 100 kHz to generate four times more THz pulse energy then possible by ELBE's thermionic injector. Because of this significant improvement, the new gun has been recently used for first user shifts at the THz facility at ELBE. In this contribution we will report on first results and operational experiences.
Keywords: SRF gun, superconducting RF injector, ELBE, electron source
  • Lecture (others)
    HOPE II Projekttreffen im Rahmen BMBF Verbundforschungsinitiative, 16.04.2018, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27506
Publ.-Id: 27506


Structure of 13Be studied in proton knockout from 14B

Ribeiro, G.; Nacher, E.; Tengblad, O.; Diaz Fernandez, P.; Aksyutina, Y.; Alvarez-Pol, H.; Atar, L.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamano, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Datta Pramanik, U.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Holl, M.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Kurz, N.; Kröll, T.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec, J.; Movsesyan, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Rigollet, C.; Riisager, K.; Rossi, D.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Thies, R.; Velho, P.; Wagner, A.; Wamers, F.; Vandebrouck, M.; Weick, H.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J. S.; Woods, P.; Zhukov, M. V.; Zilges, A.; Zuber, K.
The neutron-unbound isotope 13Be has been studied in several experiments using different reactions, different projectile energies and different experimental setups. There is, however, no real consensus in the interpretation of the data, in particular concerning the structure of the low-lying excited states. Gathering new experimental information, which may reveal the 13Be structure, is a challenge, in particular in light of its bridging role between 12Be, where the N=8 neutron-shell breaks down, and the Borromean halo nucleus 14Be. The purpose of the present study is to investigate the role of bound excited states in the reaction product 12Be after proton knockout from 14B, by measuring coincidences between 12Be, neutrons, and rays originating from de-excitation of states fed by neutron decay of 13Be. The 13Be isotopes were produced in proton-knockout from a 400 MeV/u 14B beam impinging on a CH2 target. The 12Be-n relative-energy spectrum dsigma=dEfn was obtained from coincidences between 12Be(g.s.) and a neutron, and also as threefold coincidences by adding rays, from the de-excitation of excited states in 12Be. Neutron decay from the first 5=2+ state in 13Be to the 2+ state in 12Be at 2.11 MeV is cofirmed. An energy-independence of the proton-knockout mechanism is found from a comparison with data taken with a 35 MeV/u 14B beam. A low-lying p-wave resonance in 13Be(1/2+) is confirmed by comparing proton- and neutron-knockout data from 14B and 14Be.
Keywords: radioactive beams; nuclear structure; unbound nuclei; 13Be

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27505
Publ.-Id: 27505


Cm3+/ Eu3+ Induced Structural, Mechanistic and Functional Implications for Calmodulin

Drobot, B.ORC; Schmidt, M.ORC; Mochizuki, Y.ORC; Abe, T.; Okuwaki, K.; Brulfert, F.; Falke, S.ORC; Samsonov, S.ORC; Komeiji, Y.ORC; Betzel, C.ORC; Stumpf, T.; Raff, J.ORC; Tsushima, S.ORC
Trivalent actinides and their lanthanide holmologues are being scrutinized for their potential health risk when ingested through a range of industrial activities such as mining. Importantly, these ions are known to exhibit high affinity towards calmodulin (CaM). In case of their inadvertent uptake, the holoproteins that are occupied by these cations may block signal transduction pathways or increase the concentration of these ions in intact cells, which could lead to accumulation in human organs. Accordingly, this investigation employed spectroscopy, computational chemistry, calorimetry, and biochemistry to study the results of metal ion substitution on the protein structure, enzymatic activity and chemo- and cytotoxicity of An3+/Ln3+ ions. As will be demonstrated herein, our data confirm the higher affinity of Cm3+ and Eu3+ compared to Ca2+ to all 4 binding sites of CaM, with one site differing from the remaining three. This higher-affinity site will complex Eu3+ in an exothermic fashion; in contrast, ion binding to the three lower-affinity EF-hands was found to be endothermic. The overall endothermic binding process is ascribed to the loss of the hydration shells of the trivalent ions upon protein binding. These findings are supported by extensive quantum chemical calculations of full holo-CaM, which were performed at the MP2 level using the fragment molecular orbital method. The exceptional binding site (EF-hand 3) features fewer negatively charged residues compared to the other EF-hands, thereby allowing Eu3+ and Cm3+ to carry one or two additional waters compared to Ca2+-CaM, while also causing the structure of Cm3+ / Eu3+-CaM to become slightly disordered. Moreover, the enzymatic activity decreases somewhat in comparison to Ca2+-CaM. By utilizing a combination of techniques, we were able to generate a comprehensive picture of the CaM-actinide/lanthanide system from the molecular level to its functional impact. Such knowledge could also be applied to other metal-binding proteins.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27504
Publ.-Id: 27504


Pushing the limits of applicability of REBCO coated conductor films through fine chemical tuning and nanoengineering of inclusions

Rizzo, F.; Augieri, A.; Kursumovic, A.; Bianchetti, M.; Opherden, L.; Sieger, M.; Hühne, R.; Hänisch, J.; Meledin, A.; van Tendeloo, G.; Macmanus-Driscol, J. L.; Celentano, G.
An outstanding current carrying performance (namely critical current density, Jc) over a broad temperature range of 10–77 K for magnetic fields up to 12 T is reported for films of YBa2Cu3O7−x with Ba2Y(Nb,Ta)O6 inclusion pinning centres (YBCO-BYNTO) and thicknesses in the range of 220–500 nm. Jc values of 10 MA cm−2 were measured at 30 K – 5 T and 10 K – 9 T with a corresponding maximum of the pinning force density at 10 K close to 1 TN m−3. The system is very flexible regarding properties and microstructure tuning, and the growth window for achieving a particular microstructure is wide, which is very important for industrial processing. Hence, the dependence of Jc on the magnetic field angle was readily controlled by fine tuning the pinning microstructure. Transmission electron microscopy (TEM) analysis highlighted that higher growth rates induce more splayed and denser BYNTO nanocolumns with a matching field as high as 5.2 T. Correspondingly, a strong peak at the B||c-axis is noticed when the density of vortices is lower than the nanocolumn density. YBCO-BYNTO is a very robust and reproducible composite system for high-current coated conductors over an extended range of magnetic fields and temperatures.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27503
Publ.-Id: 27503


Anomalous Hall effect in fully compensated half-metallic Mn₂RuₓGa thin films

Fowley, C.; Rode, K.; Lau, Y. C.; Thiyagarajah, N.; Betto, D.; Borisov, K.; Atcheson, G.; Kampert, E.; Wang, Z.; Yuan, Y.; Zhou, S.; Lindner, J.; Stamenov, P.; Coey, J. M. D.; Deac, A. M.
High-field magnetotransport is investigated in thin films of half-metallic ferrimagnet Mn₂RuₓGa. A non-vanishing Hall signal is observed over a broad temperature range, spanning the compensation temperature (155K), where the net magnetic moment is strictly zero, the Hall conductivity is 6673 Ohm⁻¹ m⁻¹ and the coercivity exceeds 9T. Molecular field modelling is used to determine the intra- and inter-sublattice exchange constants and from the spin-flop transition we infer the anisotropy of the electrically active sublattice to be 216 kJm⁻³ and predict the magnetic resonances frequencies. Exchange and anisotropy are comparable and hard-axis applied magnetic fields result in a tilting of the magnetic moments from their collinear ground state. Our analysis is applicable to collinear ferrimagnetic half-metal systems.
Keywords: Ferrimagnetism, Magnetotransport, Half-metals, Anomalous Hall effect, Magnetic anisotropy, Exchange interaction
  • Invited lecture (Conferences)
    Intermag 2018, 23.-27.04.2018, Singapore, Singapore
  • Open Access Logo Physical Review B 98(2018), 220406(R)
    DOI: 10.1103/PhysRevB.98.220406

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27502
Publ.-Id: 27502


Features of magnetization behavior in the rare-earth intermetallic compound (Nd0.5Ho0.5)2Fe14B

Kostyuchenko, N. V.; Tereshina, I. S.; Gorbunov, D. I.; Tereshina-Chitrova, E. A.; Andreev, A. V.; Doerr, M.; Politova, G. A.; Zvezdin, A. K.
The crystal-electric field parameters are determined for the (Nd0.5Ho0.5)2Fe14B compound by analyzing experimental magnetization curves obtained in magnetic fields up to 60 T. The values of the crystal-field parameters B20, B40, B60, B44, B64 are 56.3, −73.2, −10.74, −8.9, 0 cm−1 for Nd3+ ion and 312.38, −176.78, 89.2, −88.43, 0 cm−1 for Ho3+ ion. The transition from the ferri- to the field-induced ferromagnetic state has been studied in detail.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27501
Publ.-Id: 27501


Magnetic and magnetocaloric properties of single Crystal (Nd0.5Pr0.5)2Fe14B

Politova, G. A.; Tereshina, I. S.; Gorbunov, D. I.; Paukov, M. A.; Andreev, A. V.; Grechishkin, R. M.; Rogacki, K.
In this work the magnetic and magnetocaloric properties of a (Nd0.5Pr0.5)2Fe14B single crystal have been investigated in a wide range of temperatures and magnetic fields. Magnetic phase transition temperatures (spin-reorientation transition (SRT) at TSR = 73 K and Curie point at Tc = 570 K) were determined together with the values of saturation magnetization Ms and magnetocrystalline anisotropy constants K1 and K2. In the vicinity of a spin-reorientation magnetic phase transition, the value of the magnetocaloric effect was determined as an isothermal magnetic entropy change (DSM). The universal curve of ΔS´(ʘ) around TSR under various magnetic field changes has been constructed by using a phenomenological procedure. It is found that this approach is applicable to materials with a second-order spin-reorientation phase transition.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27500
Publ.-Id: 27500


Complex magnetic order in the kagome ferromagnet Pr3Ru4Al12

Henriques, M. S.; Gorbunov, D. I.; Andreev, A. V.; Fabrèges, X.; Gukasov, A.; Uhlarz, M.; Petricek, V.; Ouladdiaf, B.; Wosnitza, J.
In the hexagonal crystal structure of Pr3Ru4Al12, the Pr atoms form a distorted kagome lattice, and their magnetic moments, are subject to competing exchange and anisotropy interactions.We performed magnetization, magnetic-susceptibility, specific-heat, electrical-resistivity, and neutron-scattering measurements. Pr3Ru4Al12 is a uniaxial ferromagnet with TC = 39 K that displays a collinear magnetic structure (in the high-temperature range of the magnetically ordered state) for which the only crystallographic position of Pr is split into two sites carrying different magnetic moments. A spin-reorientation phase transition is found at 7 K. Below this temperature, part of the Pr moments rotate towards the basal plane, resulting in a noncollinear magnetic state with a lower magnetic symmetry. We argue that unequal RKKY exchange interactions competing with the crystal electric field lead to a moment instability and qualitatively explain the observed magnetic phases in Pr3Ru4Al12.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27499
Publ.-Id: 27499


CFD Modeling and Simulation of Heat and Mass Transfer in Passive Heat Removal Systems

Moonesi Shabestary, A.; Krepper, E.; Lucas, D.
This paper is presenting the CFD-modelling and simulation of condensation inside passive heat removal systems. Designs of future nuclear boiling water reactor concepts are equipped with emergency cooling systems which are passive systems for heat removal. The emergency cooling system consists of slightly inclined horizontal pipes which are immersed in a tank of subcooled water. At normal operation conditions, the pipes are filled with water and no heat transfer to the secondary side of the condenser occurs. In the case of some accident scenarios the water level may decrease in the core, steam enters the emergency pipes and due to the subcooled water around the pipe, this steam condenses. The emergency condenser acts as a strong heat sink which is responsible for a quick depressurization of the reactor core.
This procedure acts passive i.e. without any additional external measures. The actual project is defined to model the phenomena which are occurring inside the emergency condensers. The focus of the project is on detection of different morphologies such as annular flow, stratified flow, slug flow and plug flow and also modeling of the laminar film which is occurring during the condensation near the wall.
  • atw - International Journal for Nuclear Power 63(2018)4

Downloads:

  • available with HZDR-Login
  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-27498
Publ.-Id: 27498


Bethe‐Strings: Exotische Anregungen in Spinsystemen

Wang, Z.; Loidl, A.
Hans Bethe sagte 1931 in einer fundamentalen Arbeit die Existenz von stark gebundenen Zuständen von Quasiteilchen voraus. Nun konnte eine internationale Kooperation erstmals derartige Bethe‐Strings in einem Kristall nachweisen.
Keywords: Spin Kette, Quasiteilchen, String Erregungen, Hans Bethe

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27497
Publ.-Id: 27497


Stability and instability of hydromagnetic Taylor–Couette flows

Rüdiger, G.; Gellert, M.; Hollerbach, R.; Schultz, M.; Stefani, F.
Decades ago S. Lundquist, S. Chandrasekhar, P. H. Roberts and R. J. Tayler first posed questions about the stability of Taylor–Couette flows of conducting material under the influence of large-scale magnetic fields. These and many new questions can now be answered numerically where the nonlinear simulations even provide the instability-induced values of several transport coefficients. The cylindrical containers are axially unbounded and penetrated by magnetic background fields with axial and/or azimuthal components. The influence of the magnetic Prandtl number Pm on the onset of the instabilities is shown to be substantial. The potential flow subject to axial fields becomes unstable against axisymmetric perturbations for a certain supercritical value of the averaged Reynolds number (with Re the Reynolds number of rotation, Rm its magnetic Reynolds number). Rotation profiles as flat as the quasi-Keplerian rotation law scale similarly but only for Pm >> 1 while for the instability instead sets in for supercritical Rm at an optimal value of the magnetic field. Among the considered instabilities of azimuthal fields, those of the Chandrasekhar-type, where the background field and the background flow have identical radial profiles, are particularly interesting. They are unstable against nonaxisymmetric perturbations if at least one of the diffusivities is non-zero. For Pm << 1the onset of the instability scales with Re while it scales with Rm for Pm >> 1. Even superrotation can be destabilized by azimuthal and current-free magnetic fields; this recently discovered nonaxisymmetric instability is of a double-diffusive character, thus excluding Pm=1 . It scales with Re for Pm -> 0 and with Rm for Pm -> infinity.
The presented results allow the construction of several new experiments with liquid metals as the conducting fluid. Some of them are described here and their results will be discussed together with relevant diversifications of the magnetic instability theory including nonlinear numerical studies of the kinetic and magnetic energies, the azimuthal spectra and the influence of the Hall effect.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27496
Publ.-Id: 27496


Experiences with the SRF Gun II for User Operation at the ELBE Radiation Source

Teichert, J.; Arnold, A.; Bawatna, M.; Evtushenko, P. E.; Gensch, M.; Green, B. W.; Kovalev, S.; Lehnert, U.; Lu, P. N.; Michel, P.; Murcek, P.; Vennekate, H.; Xiang, R.
The second version of the superconducting RF photoinjector (SRF Gun II) was successfully commissioned at the ELBE radiation source in 2014. The gun features an improved 3.5-cell niobium cavity combined with a superconducting solenoid integrated in the cryostat. With a Mg photocathode the SRF Gun II is able to generate bunches with up to 200 pC and with sub-ps length in CW mode with 100 kHz pulse frequency for the THz radiation facility at ELBE. In the ELBE linac, the beam is accelerated, gets a proper correlated energy spread, and is compressed in a magnetic chicane. Sub-ps pulses are obtained producing coherent diffraction radiation and superradiant undulator radiation.
Keywords: electron source, SRF gun, superconducting RF, THz radiation, coherent diffration radiation, superradiant radiation, ELBE
  • Poster
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
  • Open Access Logo Contribution to proceedings
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
    Proceedings of the 9th International Particle Accelerator Conference IPAC´18, Genf: JACoW, 1247-1250
    DOI: 10.18429/JACoW-IPAC2018-THPMF040

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27495
Publ.-Id: 27495


Study of Magnesium Photocathodes for Superconducting RF Photoinjectors

Xiang, R.; Arnold, A.; Lu, P. N.; Murcek, P.; Teichert, J.; Vennekate, H.
The superconducting RF photoinjector (SRF Gun II) has successfully served for the ELBE user facility at HZDR. The quality of photocathodes is one of the most critical issues in improving the stability and reliability for its application. Mg has a comparably low work function and shows quantum efficiency up to 0.3% after laser cleaning. But the present cleaning with a high intensity laser beam is time consuming and produces unwanted surface roughness. Thermal treatment and excimer laser cleaning are being investigated as alternative methods.
Keywords: electron source, photocathode, Mg, SRF gun, superconducting RF, laser cleaning
  • Poster
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
  • Open Access Logo Contribution to proceedings
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
    Proceedings of the 9th International Particle Accelerator Conference IPAC´18, Genf: JACoW, 4142-4144
    DOI: 10.18429/JACoW-IPAC2018-THPMF039

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27494
Publ.-Id: 27494


A Cu Photocathode for the Superconducting RF Photoinjector of BERLinPro

Kühn, J.; Bürger, M.; Frahm, A.; Jankowiak, A.; Kamps, T.; Klemz, G.; Kourkafas, G.; Neumann, A.; Ohm, N.; Schmeißer, M.; Schuster, M.; Völker, J.; Murcek, P.; Teichert, J.
The initial commissioning of the Superconducting RF (SRF) photoinjector is achieved with a Cu photocathode due to its robustness with respect to interactions with the SRF cavity of the injector. Here we present the preparation and characterization of a Cu photocathode plug and the diagnostics to insert the photocathode in the back wall of the SRF cavity. A polycrystalline bulk Cu plug was polished, particle free cleaned and characterized by x-ray photoelectron spectroscopy. During the transfer of the photocathode insert into the gun module the whole process was controlled by several diagnostic tools monitoring the insert position as well as RF, vacuum and cryogenic signals. We discuss the challenges of the photocathode transfer into an SRF cavity and how they can be tackled.
Keywords: electron source, photocathode, Cu, SRF gun, superconducting RF
  • Poster
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
  • Open Access Logo Contribution to proceedings
    9th International Particle Accelerator Conference IPAC´18, 29.04.-04.05.2018, Vancouver, Canada
    Proceedings of the 9th International Particle Accelerator Conference IPAC´18, Genf: JACoW, 1247-1250
    DOI: 10.18429/JACoW-IPAC2018-TUPMF002

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27493
Publ.-Id: 27493


Reply to “Comment on Methodological accuracy of image-based electron density assessment using dual-energy computed tomography” [Med. Phys. 44, 2429-2437 (2017)]

Möhler, C.ORC; Wohlfahrt, P.ORC; Richter, C.; Greilich, S.ORC
To the editor,
In his recent letter, Dr. Bouchard expressed his concern that our article on electron density (ED) assessment with dual-energy computed tomography (DECT) contained “some errors and speculative arguments”. We are aware that any study — no matter how carefully conducted — can exhibit erroneous aspects. In this case, however, we concluded that most of the statements and additional data provided by Dr. Bouchard in fact support the key findings of our paper, while other points raised can be attributed to a different use of concepts and to occasional overinterpretation. We therefore firmly reject his assertion. In this reply we provide our response to the criticism
raised:
Keywords: dual-energy CT, electron density, proton therapy

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27492
Publ.-Id: 27492


EOS at cw beam operation at Elbe

Schneider, C.; Gensch, M.; Kuntzsch, M.; Michel, P.; Seidel, W.; Kaya, K.; Al Shemmary, A.; Stojanovic, N.; Evtushenko, P.
The ELBE accelerator is a super conduction electron cw machine located at the Helmholtz Center Dresden Rossendorf Germany with 1 mA current, now tested for up to 2 mA. Besides other important diagnostics for setting up the machine for user beam time and further improvement of the machine – a THz source is momentary under commissioning – a EOS measuring station for bunch length measurements is locate right behind the second super conducting Linac. Measuring with a crystal in the vicinity of an up to 2 mA cw beam implies higher beam loss and also higher radiation exposure of the crystal and hence also a safety risk for the UHV conditions of the super conducting cavities in the case of crystal damage. Therefore the EOS measuring principle is adapted to larger measuring distances and also for beam requirements with lower bunch charge at ELBE. A description of the setup, considerations of special boundary conditions and as well results for 13 MHz cw beam operation are presented.
  • Open Access Logo Contribution to proceedings
    IPAC2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27491
Publ.-Id: 27491


Microresonator-ferromagnetic resonance investigation of thermal spin-transfer torque in Co2FeAl/MgO/CoFeB magnetic tunnel junctions

Cansever, H.ORC; Narkowicz, R.; Lenz, K.; Fowley, C.; Ramasubramanian, L.; Yildirim, O.; Niesen, A.; Huebner, T.ORC; Reiss, G.; Lindner, J.; Fassbender, J.; Deac, A. M.
Similar to electrical currents flowing through magnetic multilayers [1,2], thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin currents and generate ‘thermal’ spin-transfer torques large enough to induce magnetization dynamics on the free layer [3, 4]. The relation of spin current, charge current and heat current was theoretically described by Bauer et al. using Onsager’s reciprocity rule [5]. According to Onsager’s law, spin currents can be produced by bias voltages or thermal gradients and investigated in terms of spin-Seebeck effect in magnetic multilayers.
First, Hatami et al. theoretically studied the spin-Seebeck effect in spin-valves and introduced the concept of thermal spin-transfer torques. They predicted that the thermally induced spin current creates an imbalance on the interface between non-magnetic and ferromagnetic layers due to collisions (electron-electron and electron-phonon interactions) [3]. Thermal spin-transfer torques were studied experimentally within asymmetric Co/Cu/Co nanowire spin-valves which exhibit switching field changes under varying a.c. currents causing Joule heating [6]. In magnetic tunnel junctions, it was theoretically predicted that temperature differences of around 10 K over an ultrathin barrier (1 nm) can create magnetization dynamics in Fe/MgO/Fe magnetic tunnel junctions [4]. The spin-Seebeck effect has been studied on CoFeB/MgO/CoFeB magnetic tunnel junctions using different heating methods such as Joule heating, heating with Peltier elements, as well as laser heating [8-14]. Recently, it was shown that using Co2FeAl as a reference layer improves tunneling magneto-Seebeck (TMS) in magnetic tunnel junctions [7].
Here, we describe a novel experimental approach and setup to observe effects of thermal gradients within magnetic tunnel junctions with Heusler compounds by using the microresonator ferromagnetic resonance (µR-FMR) method under laser heating. Initially, microresonators (shown in figure 1) were introduced by Narkowicz et al. for electron paramagnetic resonance (EPR) experiments to achieve optimal sensitivity for small objects [8]. Detecting the FMR signal of nano- to micron-sized samples in conventional cavities (cm3) is not possible, due to the too small ferromagnetic volume, and therefore low filling factor. A planar microresonator, by definition, is a two-dimensional structure, its diameter can be tailored to match the order of the sample’s size (shown as a black ellipse in the microresonator loop in figure 1). Two stubs are attached to the inductive loop. The capacitive radial stub in first approximation may be viewed as an element to tune the loop to the operation frequency, while the rectangular stub matches the structure to the 50 Ω impedance of the microstrip feedline.

Figure 1: Layout of a planar microresonator with simulated electric field distribution at the resonance frequency. The inset shows the current and magnetic field distribution (out-of-plane direction) in the loop containing a sample (black ellipse).
We investigated magnetic tunnel junctions (MTJs) fabricated out of Co2FeAl/MgO/CoFeB stacks. The sample and microresonator fabrication consist of multiple steps of lithography, ion etching and lift-off processes. The sample is finally patterned into a 6x9 µm2 elliptical shape using electron beam lithography (EBL) and ion beam etching is used to etch down the sample to the substrate. Microresonators are then fabricated around the sample using UV lithography. For laser heating, a continuous-wave (CW) laser at 532 nm wavelength and with tunable power up to 33 mW is focused on the sample.
“Hot-FMR” measurements were performed on unpatterned multilayers between 300 K and 450 K (figure 2) to understand the effect of global heating. It is clearly seen that the FMR signal of Co2FeAl exhibits a shift with increasing temperature. As seen in the inset graph, it is difficult to quantify the changes for the CoFeB signal, due to its small intensity. Subsequent, measurements in the presence of a thermal gradient were performed on 6x9 µm2 MTJs, integrated into microresonator loops with an inner diameter of 20 µm. The MTJs were submitted to laser irradiation, up to a maximum power of 33 mW. Unlike the Hot-FMR measurements, the resonance field and linewidth did not show clear changes with increasing laser power. The results suggest that the laser power is neither sufficient to induce magnetization dynamics via thermal gradients across the barrier, nor lead to significant changes of the magnetic parameters due to global heating of the sample.
Figure 2: FMR spectra of the extended films of Co2FeAl / MgO / CoFeB measured in the in-plane direction at different temperatures
As a conclusion, the effect of a global temperature change on the resonance frequency and linewidth of Co2FeAl was analyzed. With regards to the µR-FMR results, higher laser power is needed to induce magnetization dynamics. Moreover, the lateral heat transport might reduce the vertical thermal gradients, thus similar measurements on smaller structures are required.
This study was funded by the German Research Foundation (DFG) via priority program SpinCaT (SPP 1538). We thank H. Schultheiss for helping with the optical part of the experimental setup and S. Zhou for giving the access to the VSM setup.
[1] J.C. Slonczewski, J. Magn. Magn. Mater. 159, L1, (1996).
[2] L. Berger, Phys. Rev. B 54, 9353, (1996).
[3] M. Hatami, G.E.W. Bauer, Q. Zhang and P.J. Kelly, Phys. Rev. Lett. 99, 066603 (2007).
[4] X. Jia, K. Xia and G.E.W. Bauer, Phys. Rev. Lett. 107, 176603 (2011).
[5] G.E.W. Bauer, E. Saitoh and B.J. van Wees, Nature Mater. 11, 391, (2012).
[6] H. Yu, S. Granville, D.P. Yu and J.-Ph. Ansermet, Phys. Rev. Lett. 104, 146601 (2010).
[7] A. Boehnke, U. Martens, C. Sterwerf, A. Niesen, T. Huebner, M. von der Ehe, M. Meinert, T. Kuschel, A. Thomas, C. Heiliger, M. Münzenberg M, Nature Communications 8,(1),1626, (2017).
[8] R. Narkowicz, D. Suter and R. Stonies, J. Magn. Reson.175, 275 (2005).
Keywords: thermal spin transfer torque, ferromagnetic resonance, microresonator, magnetic tunnel junctions
  • Lecture (Conference)
    INTERMAG 2018 Singapore, 23.-27.04.2018, Singapore, Singapore

Permalink: https://www.hzdr.de/publications/Publ-27490
Publ.-Id: 27490


Radiation Tests Of Aerospace Components At Elbe

Schneider, C.; Bemmerer, D.; Michel, P.; Stach, D.
The cw electron accelerator ELBE operates mainly in the beam energy range 6 to 32 MeV and beam current range 1μA to 1mA. For most experiments a thermionic gun is used as electron source. The cw electron pulse structure so as the pulse charge is realized by applying electrical pulses with specific amplitudes and frequencies on the grid of the gun. The standard cw operation frequency is 13 MHz but can be divided sequentially by the factor 2 down to 101 kHz. For very special pulse structures a so called single pulser module exist performing different patterns also with dark current suppression via a macro pulser gate. For evaluating the performance and hardness under irradiation of e.g. aerospace components much lower doses resp. currents lower than the μA range are required. Furthermore reproducible and stable doses in a specific area for consecutively radiation of samples are necessary. In the presentation the investigations and concepts used at ELBE for the irradiation of different aerospace components are described.
  • Open Access Logo Contribution to proceedings
    IPAC2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27489
Publ.-Id: 27489


Unmixing-based feature extraction for mineral mapping

Contreras, C.; Khodadadzadeh, M.; Tusa, L.; Gloaguen, R.
Hyperspectral imaging is a well-accepted technology for mineral mapping. However, the advantage of using hyperspectral data for this purpose depends on the applied techniques. Spectral unmixing and classification algorithms have been widely applied in the literature to map and determine different minerals composition.
Generally, these two algorithms are used independently, however, in the scientific community dedicated to the field of land cover classification, new techniques have been developed in which, both classification and spectral unmixing are used complementarily. For example, spectral unmixing techniques have been used for feature extraction prior to a supervised classification. This strategy has been explored to address the problem of mixed pixels, which are dominant in hyperspectral images. Previous studies concluded that using unmixing-based features do not particularly improve classification accuracies in comparison to applying the extracted features by a classic algorithm such as the Minimum Noise Fraction (MNF). However, the advantage over this is that features extracted from spectral unmixing techniques have physical meaning since they can be interpreted as the abundances of the materials present in the scene, and they do not relegate variations of features with less significant signal-to-noise ratio, therefore, small classes are better characterized. Nevertheless, in geological remote sensing applications, the use of spectral unmixing as a feature extraction technique prior to a supervised classification has not been previously applied.
In this context, this work proposes the use of an automatic endmember extraction algorithm (e.g., Vertex Component Analysis – VCA) to further obtain the mineral abundances at a sub-pixel scale with a linear unmixing process. These features are subsequently used as inputs to a standard supervised classification technique (e.g., Support Vector Machine – SVM). The experiments are carried out on a hyperspectral VNIR/SWIR dataset of core samples. With this technique, we introduce a novel supervised approach, which, based on preliminary attempts, is expected to deliver both qualitative and quantitative improvements in the final classification accuracies.
  • Poster
    European Geosciences Union General Assembly 2018 (EGU), 08.-13.04.2018, Vienna, Austria

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27488
Publ.-Id: 27488


Design Of A Stripline Kicker For The Elbe Accelerator

Schneider, C.; Arnold, A.; Hauser, J.; Michel, P.; Staats, G.
ELBE is a linac based cw electron accelerator serving different secondary beams one at a time. Depending on the user demand the bunch repetition rate may vary from single pulse up to 13 MHz. For the future different end stations should be served simultaneously, hence specific bunch patterns have to be kicked into different beam-lines. To use e.g. one bunch out of the bunch train very short kicking durations have to be realized. The variabil-ity of the bunch pattern and the frequency resp. switching time are one of the main arguments for a stripline-kicker combined with high voltage (HV)-switches as basic con-cept. A nearly homogenous field in the kicker has to be realized for uniform deflection of the electron bunch and keep the emittance growth of the bunch as low as possi-ble. Furthermore the fast switching ability of the kicker demands for a fast decay of the HV-pulse resp. its reflec-tions in the structure implying a specific design of the kicker elements. For this reason a design with two tapered active electrodes and two ground fenders was optimized in time and frequency domain with the software package CST. Additionally a first prototype was manufactured for laboratory and first beam-line tests.
  • Open Access Logo Contribution to proceedings
    IPAC2017 - 8th International Particle Accelerator Conference, 14.-19.05.2017, Copenhagen, Denmark

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27487
Publ.-Id: 27487


Effect of DTPA on adsorption of Eu(III) onto quartz sand as a function of pH

Karimzadeh, L.; Lippold, H.
Organic ligands are known to affect radionuclide adsorption onto mineral surfaces. Quantitative description of these ternary systems requires appropriate modelling of the constituent interaction processes, which are not yet fully understood. In this study, the effect of the decontamination agent DTPA on adsorption of Eu(III) (as an analogue of trivalent actinides) onto quartz sand was investigated in radiotracer studies with 152Eu, at a pH range from 3 to 9. The experimental results show that DTPA strongly reduces adsorption of Eu(III) and thus promotes its mobility by formation of aqueous Eu-DTPA complexes over the whole studied pH range. This behavior was successfully described by generalized two-layer surface complexation model based on the aqueous speciation of Eu(III) / DTPA as a function of pH.
Keywords: DTPA, Surface complexation modeling, Europium, Quartz sand
  • Poster
    10th International Symposium on Nano and Supramolecular chemistry, 09.-12.07.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27486
Publ.-Id: 27486


Recent Developments of the Liquid Metal Taylor Couette Experiment PROMISE

Seilmayer, M.; Stefani, F.; Gundrum, T.
In the beginning of the 20th century Taylor-Couette (TC) experiments were carried out with transparent liquids like water or air, which are electrical no-conducting. With the first experiments of Donnelly [1] in the sixties, a more general approach with liquid metal experiments started to investigate the interaction between magnetic fields and the TC flows of electrically conducting fluids. Two challenges of opaque liquid metal experiments are the measurement technique to investigate the flow structure inside the liquid and the precision and strength of the magnetic field.
We like to report recent results carried out with a quasi coaxial return path, which was introduced to the PROMIS experiment in the last years. Instead of the former frame coil an axial-symmetric return path closes the electrical circuit, which improves the field symmetry inside the experiment and minimizes the stray field outside the setup. Since this arrangement consists of an electrical parallel connection of the return conductors and the parallel connection of the hydraulic cooling circuit, it must be checked whether stability problems can occur in the current distribution in the return conductors. It turned out that the current return design can be controlled by simple and cheap proportional heater valves [2].

[1] R. J. Donnelly and M. Ozima, Phys. Rev. Lett., 4(10), 497--498, 1960
[2] M. Seilmayer and N. Krauter, IEEE Sensors Journal, 18(3), 1256--1264, 201
Keywords: DRESDYN, PROMISE, MRI, AMRI, Taylor Couette, Liquid Metal
  • Lecture (Conference)
    ICTW 20: 20th International Couette-Taylor Workshop, 11.-13.07.2018, Marseille, France

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27485
Publ.-Id: 27485


Successfully estimating tensile strength by small punch testing

Holmström, S.; Simonovski, I.; Baraldi, D.; Bruchhausen, M.; Altstadt, E.; Delville, R.
The Small Punch (SP) test is a relatively simple test well suited for material ranking and material property estimation in situations where standard testing is not possible or considered too material consuming. The material tensile properties, e.g. the ultimate tensile strength (UTS) and the proof strength are usually linearly correlated to the force-deflection behaviour of a SP test. However, if the test samples and test set-up dimensions are not according to standardized dimensions or the material ductility does not allow the SP sample to deform to the pre-defined displacements used in these correlations the standard formulations can naturally not be used. Also, in cases where no supporting UTS data is available the applied correlation factors cannot be verified. In this paper a formulation is proposed that enables estimation of UTS without supporting uniaxial tensile strength data for a range of materials, both for standard type and for curved (tube section) samples. The proposed equation was originally developed for estimating the equivalent stress in small punch creep but is now shown to also found to robustly estimate the UTS of several ductile ferritic, ferritic/martensitic and austenitic steels. It is also shown that the methodology can be further applied on non-standard test samples and test set-ups and to estimate the properties of less ductile materials such as 46% cold worked 1515Ti cladding steel tubes. In the case of curved samples the UTS estimates have to be corrected for curvature to equal the corresponding flat specimen behaviour. The geometrical correction factors are dependent on tube diameters and wall thicknesses and were solved by finite element simulations. The outcome of the testing and simulation work shows that the UTS can be robustly estimated both for flat samples as well as on thin walled tube samples. The usability of the SP testing and assessment method for estimating tensile strength of engineering steels in general and for nuclear claddings in specific has been verified.
Keywords: small punch test, tensile strength
  • Contribution to proceedings
    5th International Small Sample Test Techniques (SSTT) Conference 2018, 10.-12.07.2018, Swansea, United Kingdom
    Conference Proceedings of 5th International Small Sample Test Techniques Conference SSTT 2018, Swansea

Permalink: https://www.hzdr.de/publications/Publ-27484
Publ.-Id: 27484


European standard on small punch testing of metallic materials

Bruchhausen, M.; Altstadt, E.; Austin, T.; Dymacek, P.; Holmström, S.; Jeffs, S.; Lacalle, R.; Lancaster, R.; Matocha, K.; Petzova, J.
In the 1980s, studying the effect of neutron irradiation and temper embrittlement on structural materials for the fusion and fission programmes was a major challenge. In this context the development of small specimen test techniques began, allowing the characterization of structural materials for nuclear applications with small amounts of material. The small punch technique is of one these small specimen test approaches. It is widely used for the development and monitoring of structural materials, however there is currently no comprehensive international standard for small punch testing.
An EN standard on small punch testing is currently being developed under the auspices of ECISS/TC101/WG1. Besides describing the apparatus, procedures, and specimens, it will include recommendations for the estimation of tensile, fracture and creep properties from small punch testing as well as machine readable formats for representing and transferring test data.
This paper describes the current status of the standard and highlights some of the changes with regard to the current CWA 15672 (2007).
Keywords: small punch test, standard
  • Contribution to proceedings
    5th International Small Sample Test Techniques (SSTT) Conference 2018, 10.-12.07.2018, Swansea, United Kingdom
    Conference Proceedings of 5th International Small Sample Test Techniques Conference SSTT 2018, Swansea

Permalink: https://www.hzdr.de/publications/Publ-27483
Publ.-Id: 27483


Effect of anisotropic microstructure of ODS steels on small punch test results

Altstadt, E.; Houska, M.; Das, A.
Oxide dispersed strengthened (ODS) steels can exhibit a strongly anisotropic microstructure leading to anisotropic mechanical properties. The ductile to brittle transition temperature in the small punch (SP) test is therefore dependent on the specimen orientation. Three ODS steels with 13-14 mass percent Cr, manufactured through hot extrusion and hot rolling respectively, were investigated by means of SPT in different orientations. Existing microstructural data (EBSD) are used to discuss the anisotropic fracture behavior observed in the SPT. In addition, the SPT results are compared with those from existing fracture mechanics tests based on sub-sized C(T) samples. The applicability of the empirical conversion of SPT based transition temperatures into Charpy transition temperatures – well established for isotropic homogeneous metals – is investigated for materials with anisotropic microstructure.
Keywords: small punch test, ductile-to-brittle transition temperature, oxide dispersion strengthened steel
  • Contribution to proceedings
    5th International Small Sample Test Techniques (SSTT) Conference 2018, 10.-12.07.2018, Swansea, United Kingdom
    Conference Proceedings of 5th International Small Sample Test Techniques Conference SSTT 2018, Swansea

Permalink: https://www.hzdr.de/publications/Publ-27482
Publ.-Id: 27482


Two-scale CFD analysis of a spent fuel pool involving partially uncovered fuel storage racks

Oertel, R.; Hanisch, T.; Krepper, E.; Lucas, D.; Rüdiger, F.; Fröhlich, J.
The thermal-hydraulic conditions in a storage pool for spent nuclear fuel were studied for a loss of cooling accident leading to partially uncovered fuel racks. While under normal operating conditions, the fuel is cooled by means of single-phase natural convection in liquid water, the heat transfer rate into the gaseous pool atmosphere for the above scenario is comprised of comparably relevant portions of heat convection, thermal radiation and heat conduction. These mechanisms were analyzed with the aid of computational Fluid Dynamics using two complementary models that address different length scales. The models emulate the conditions at reactor unit 4 of the former Fukushima Daiichi nuclear power plant at the time of the accident, as it is a case example for a loss of cooling scenario and sufficient material for adequate modeling is available in the literature. A large-scale model served for the purpose of analyzing the developing flow patterns. It includes the fuel represented as porous medium as well as the pool and reactor building atmosphere. It was found that a characteristic flow field forms in the pool atmosphere that prevails for all studied water levels and decay heat rate distributions, while the temperature of the fuel can be reduced significantly by means of a checkerboard storage. However, the boundary conditions in the head region of a fuel assembly are clearly a function of its storage location in the pool. Representative conditions were extracted and applied to a second model that represents a single geometry-resolved fuel assembly with a portion of the atmosphere above it. With the corresponding simulations it was determined that, in terms of cooling efficiency, the conditions near the pool wall are favorable compared to a location close to the pool center. In conclusion, the study indicates that a beneficial storage solution combines checkerboarding with a tendency of storing fuel that exhibits a higher decay heat rate near the wall.
Keywords: Spent Fuel Pool Accidents, Flow Patterns, Fukushima, CFD Simulation, Partially Uncovered Fuel
  • Nuclear Engineering and Design 341(2019), 432-450
    DOI: 10.1016/j.nucengdes.2018.10.014
  • Lecture (others)
    KompOst Doktorandenseminar 2018, 13.12.2018, Hochschule Zittau/Görlitz, Deutschland

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27481
Publ.-Id: 27481


The response of a halophilic microbial isolate from rock salt to repository relevant conditions

Bachran, M.; Hilpmann, S.; Kluge, S.; Cherkouk, A.
Next to crystalline rock and clay, rock salt formations are considered as potential host rock systems for the long-term storage of highly radioactive waste in a deep geological repository in Germany. To date, little is known about the habitat rock salt and the way of life of the microorganisms occurring there. Due to the high salinity and lack of nutrients, only adapted microorganisms such as extremely halophilic archaea can survive under these extreme conditions.[1] It is of interest to know what kind of extreme halophilic archaea are living there, how active they are under repository relevant conditions, and how these microorganisms can influence the safe storage of the waste. In this study an Halobacterium isolate was retrieved from a German rock salt sample. This Halobacterium sp. GP5 1-1 was investigated in detail with regard to its interaction with uranium, one of the major radionuclides in highly radioactive wastes. In comparison to Halobacterium noricense DSM 15987T the studied species showed only the involvement of carboxylate groups in the interaction with uranium by in situ attenuated total reflection fourier-transform infrared spectroscopy.[2] In addition, information about the activity and possible metabolism under repository relevant conditions of Halobacterium sp. GP5 1-1 were gain via proteomic analysis. Finally, microbial diversity studies based on the isolation of high-molecular weight genomic DNA from German rock salt samples and the subsequent high-throughput sequencing of the V4 region of the 16S rRNA gene were performed.
  • Poster
    12th Edition of the International Congress on Extremophiles, 16.-20.09.2018, Ischia, Italien

Permalink: https://www.hzdr.de/publications/Publ-27480
Publ.-Id: 27480


Increasing apparent affinity of EGFR-directed target modules results in enhanced anti-tumor and diagnostic properties of the UniCAR system

Albert, S.; Arndt, C.; Koristka, S.; Berndt, N.; Bergmann, R.; Feldmann, A.; Schmitz, M.; Pietzsch, J.; Steinbach, J.; Bachmann, M.
Immunotherapy with CAR-modified T cells has recently entered into the clinical routine. Nonetheless, until now most concerning side effects associated with CAR T cell therapies are cytokine release syndrome and “on-target, off-tumor” reactions. In order to improve CAR technology regarding safety, we developed a novel switchable platform termed UniCAR. It relies on the separation of the functional domains of conventional CARs. Thus, the UniCAR system is composed of (I) T cells modified to express an universal CAR (UniCAR) and (II) tumor-specific target modules (TM). UniCAR T cell activity can be easily controlled: While they are inert in the absence of TMs, their anti-tumor reactivity can be only switched on in the presence of TMs.
For redirection of UniCAR T cells to EGFR+ epithelial tumors, we recently established a monovalent nanobody-based α-EGFR TM, either expressed in bacterial or eukaryotic cells. In spite of the identical primary sequence the eukaryotic α-EGFR TM showed a reduced killing capability and affinity. This observation encouraged us, to elucidate whether TM functionality can be further improved by an increase in affinity. Consequently, we here constructed a novel bivalent α-EGFR-EGFR TM, expressed it in eukaryotic cells and compared its anti-tumor reactivity and pharmacokinetic properties with the monovalent α-EGFR TM. As expected, the avidity of the bivalent TM is higher than that of its monovalent counterpart. By raising the number of binding sites, the resulting bivalent α-EGFR-EGFR TM shows also an improved killing efficacy and capability in vitro and in vivo. While the monovalent α-EGFR TM could only mediate the killing of tumor cells expressing high levels of EGFR, the bivalent α-EGFR-EGFR TM could also redirect UniCAR T cells to tumor cells expressing lower levels of EGFR. According to in vivo PET experiments, the increased molecular weight of the bivalent α-EGFR-EGFR TM delays its elimination and thereby improves the enrichment at the tumor site. Consequently, the bivalent TM seems to be more suitable for PET imaging approaches and tumor eradication.
  • Poster
    Tumorimmunology meets Oncology TIMO XIV (Workshop), 24.05.2018, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27479
Publ.-Id: 27479


Strain and order-parameter coupling in Ni-Mn-Ga Heusler alloys from resonant ultrasound spectroscopy

Salazar Mejia, C.; Born, N.-O.; Schiemer, J. A.; Felser, C.; Carpenter, M. A.; Nicklas, M.
Resonant ultrasound spectroscopy and magnetic susceptibility experiments have been used to characterize strain coupling phenomena associated with structural and magnetic properties of the shape-memory Heusler alloy series Ni50+xMn25−xGa25 (x=0, 2.5, 5.0, and 7.5). All samples exhibit a martensitic transformation at temperature TM and ferromagnetic ordering at temperature TC, while the pure end member (x=0) also has a premartensitic transition at TPM, giving four different scenarios:
Tc > TPM > TM, TC > TM without premartensitic transition, TC ≈ TM, and TC < TM. Fundamental differences in elastic properties, i.e., stiffening versus softening, are explained in terms of coupling of shear strains with three discrete order parameters relating to magnetic ordering, a soft mode, and the electronic instability responsible for the large strains typical of martensitic transitions. Linear-quadratic or biquadratic coupling between these order parameters, either directly or indirectly via the common strains, is then used to explain the stabilities of the different structures. Acoustic losses are attributed to critical slowing down at the premartensite transition, to the mobility of interphases between coexisting phases at the martensitic transition, and to mobility of some aspect of the twin walls under applied stress down to the lowest temperatures at which measurements were made.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27478
Publ.-Id: 27478


Investigating spin-transfer torques induced by thermal gradients in magnetic tunnel junctions by using micro-cavity ferromagnetic resonance

Cansever, H.; Narkowicz, R.; Lenz, K.; Fowley, C.; Ramasubramanian, L.; Yildirim, O.; Niesen, A.; Huebner, T.; Reiss, G.; Lindner, J.; Fassbender, J.; Deac, A. M.
Similar to electrical currents flowing through magnetic multilayers, thermal gradients applied across the barrier of a magnetic tunnel junction may induce pure spin-currents and generate ‘ thermal’ spin-transfer torques large enough to induce magnetization dynamics in the free layer. In this study, we describe a novel experimental approach to observe spin-transfer torques induced by thermal gradients in magnetic multilayers by studying their ferromagnetic resonance response in microwave cavities. Utilizing this approach allows for measuring the magnetization dynamics on micron/nano-sized samples in open-circuit conditions, i.e. without the need of electrical contacts. We performed first experiments on magnetic tunnel junctions patterned into 6×9μm2 ellipses from Co2FeAl/MgO/CoFeB stacks. We conducted microresonator ferromagnetic resonance (FMR) under focused laser illumination to induce thermal gradients in the layer stack and compared them to measurements in which the sample was globally heated from the backside of the substrate. Moreover, we carried out broadband FMR measurements under global heating conditions on the same extended films the microstructures were later on prepared from. The results clearly demonstrate the effect of thermal spin-torque on the FMR response and thus show that the microresonator approach is well suited to investigate thermal spin-transfer-driven processes for small temperatures gradients, far below the gradients required for magnetic switching.
Keywords: thermal spin transfer torque, microresonator, ferromagnetic resonance, magnetic tunnel junction

Downloads:

  • available with HZDR-Login
  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-27477
Publ.-Id: 27477


Magnetocaloric materials for refrigeration near room temperature

Waske, A.; Gruner, M. E.; Gottschall, T.; Gutfleisch, O.
This article overviews the current status of magnetocaloric materials for room-temperature refrigeration. We discuss the underlying mechanism of the magnetocaloric effect and illustrate differences between fi rst- and second-order type materials starting with gadolinium as a reference system. Beyond the key functional properties of magnetocaloric materials, the adiabatic temperature, and entropy change, we briefl y address the criticality of the most promising materials in terms of their supply risk. Looking at practical applications, suitable geometries and processing routes for magnetocaloric heat exchangers for device implementation are introduced.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27476
Publ.-Id: 27476


Spatially Nonuniform Superconductivity in Quasi-Two-Dimensional Organic Charge-Transfer Salts

Wosnitza, J.
In the following, a brief overview on the recently found robust experimental evidence for the existence of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state in layered organic superconductors is given. These electronically quasi-two-dimensional (2D) clean-limit superconductors are ideally suited for observing FFLO states. Applying a magnetic field parallel to the layers suppresses orbital effects and superconductivity is observed beyond the Pauli paramagnetic limit. Both, thermodynamic as well as microscopic experimental data show the existence of an additional high-field low-temperature superconducting state having a one-dimensionally modulated order parameter.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27475
Publ.-Id: 27475


Fermi-surface topology of the heavy-fermion system Ce2PtIn8

Klotz, J.; Götze, K.; Green, E. L.; Demuer, A.; Shishido, H.; Ishida, T.; Harima, H.; Wosnitza, J.; Sheikin, I.
Ce2PtIn8 is a recently discovered heavy-fermion system structurally related to the well-studied superconductor CeCoIn. Here we report on low-temperature de Haas–van Alphen-effect measurements in high magnetic fields in Ce2PtIn8 and Pr2PtIn8. In addition, we performed band-structure calculations for localized and itinerant Ce-4f electrons in Ce2PtIn8. Comparison with the experimental data of Ce2PtIn8 and of the 4f -localized Pr2PtIn8 suggests the itinerant character of the Ce-4f electrons. This conclusion is further supported by the observation of effective masses in CePtIn8, which are strongly enhanced with up to 26 bare electron masses.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27474
Publ.-Id: 27474


Crystal-field effects in the kagome antiferromagnet Ho3Ru4Al12

Gorbunov, D. I.; Nomura, T.; Ishii, I.; Henriques, M. S.; Andreev, A. V.; Doerr, M.; Stöter, T.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.
In Ho3Ru4Al12, the Ho atoms form a distorted kagome lattice. We performed magnetization, magnetic-susceptibility, specific-heat, and ultrasound measurements on a single crystal. We find that the magnetic and magnetoelastic properties of Ho3Ru4Al12 result from an interplay between geometric frustration and crystalelectric-field (CEF) effects. The Ho atoms order antiferromagnetically at TN = 4.5 K with reduced magnetic moments. In applied field, the magnetization shows anomalies that can be explained by CEF level crossings. We propose a CEF level scheme for which the ground-state doublet and the first two excited singlets at about 2.7 K form a quasiquartet. Indirect interlevel transitions allow for a quadrupolar interaction. This interaction explains well changes in the elastic shear modulus C44 as a function of temperature and magnetic field.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27473
Publ.-Id: 27473


Search for multipolar instability in URu2Si2 studied by ultrasonic measurements under pulsed magnetic field

Yanagisawa, T.; Mombetsu, S.; Hidaka, H.; Amitsuka, H.; Cong, P. T.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.; Huang, K.; Kanchanavatee, N.; Janoschek, M.; Maple, M. B.; Aoki, D.
The elastic properties of URu2Si2 in the high magnetic field region above 40 T, over a wide temperature range from 1.5 to 120 K, were systematically investigated by means of high-frequency ultrasonic measurements. The investigation was performed at high magnetic fields to better investigate the innate bare 5f -electron properties, since the unidentified electronic thermodynamic phase of unknown origin, the so-called “hidden order” (HO), and associated hybridization of conduction and f electrons (c-f hybridization) are suppressed at high magnetic fields. From the three different transverse modes we find contrasting results; both the Γ4(B2g) and Γ5(Eg) symmetry modes C66 and C44 show elastic softening that is enhanced above 30 T, while the characteristic softening of the Γ3/B1g) symmetry mode (C11 - C12)/2 is suppressed in high magnetic fields. These results underscore the presence of a hybridization-driven Γ3(B1g) lattice instability in URu2Si2. However, the results from this work cannot be explained by using existing crystalline electric field schemes applied to the quadrupolar susceptibility in a local 5f2 configuration. Instead, we present an analysis based on a band Jahn-Teller effect.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27472
Publ.-Id: 27472


Feldspar flotation as a quartz-purification method in cosmogenic nuclide dating: A case study of fluvial sediments from the Pamir

Sulaymonova, V. A.ORC; Fuchs, M. C.ORC; Gloaguen, R.ORC; Möckel, R.; Merchel, S.ORC; Rudolph, M.ORC; Krbetschek, M. R.
Cosmogenic nuclide (CN) dating relies on specific target minerals such as quartz as markers to identify various geological events including the timing of landscape evolution. The presence of feldspar in the analysed sediment samples poses a challenge to the separation of quartz and affects the chemical procedures for extracting the radioactive CNs ¹⁰Be and ²⁶Al. Additionally, feldspar contaminations also reduce the ²⁶Al/²⁷Al ratio, thus, hindering the accurate determination of ²⁶Al by accelerator mass spectrometry (AMS). Using our samples from Central Asia, the standard physical separation and chemical cleaning-up procedure for quartz-enrichment was not sufficient to quantitatively remove the feldspar. A modified froth flotation mineral-separation technique is presented that overcomes previous global challenges and enables sufficient quartz-enrichment before CN chemistry. We exemplify the need for feldspar flotation as part of the sample preparation procedure using fluvial sediment samples, which contain 16-50 weight percent (wt.%) of feldspar and which still show 9-47 wt.% of feldspar after chemical cleaning without flotation.
Keywords: mineral separation; quartz; feldspar; accelerator mass spectrometry; cosmogenic nuclide dating

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27471
Publ.-Id: 27471


LISEL@DREAMS – The future of Accelerator Mass Spectrometry

Forstner, O.; von Borany, J.; Merchel, S.ORC; Rugel, G.; Wendt, K.
LISEL (Low-energy Isobar SEparation by Lasers) is a future project at the DREAMS (DREsden Accelerator Mass Spectrometry) facility to widen the applications of AMS by extending the range of measurable (radio-)nuclides.

AMS has proven to be a versatile tool capable of detecting a large number of long-lived radionuclides at the ultra-trace level – i.e. isotope ratios down to 10-16. However, being a mass spectrometric method, it is limited by the presence of strong isobaric background. To overcome this limitation, we propose to remove the isobars already at the low-energy side by laser photodetachment. This method allows to selectively neutralize isobars by laser radiation, leaving the ions of interest intact. First studies were performed at the University of Vienna and gave promising results [1,2] for the easier to be measured low-mass AMS isotopes Al-26 and Cl-36.

Within the LISEL project this method will be for the first time applied to an AMS facility based on a 6 MV tandem accelerator. The first isotopes to be addressed with the new method will be Mn-53 and Fe-60. Both are currently only measurable at AMS facilities with more than 10 MV terminal voltage (currently available only at the ANU in Canberra or the LMU/TU Munich in Garching). Further on, we foresee to apply this method to other rare isotopes, making LISEL@DREAMS a versatile machine for “all” isotopes. This will subsequently widen the applications and also the user community.

[1] Forstner, O. et al., Nucl. Instr. Meth. B 361 (2015) 217-221.
[2] Martschini, M. et al., Int. J. Mass Spectrom. 415 (2017) 9-17.
Keywords: AMS, laser, photodetachment
  • Lecture (Conference)
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten (SNI2018), 17.-19.09.2018, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27470
Publ.-Id: 27470


Neutron activation analysis (NAA) reveals “fingerprint” of materials: From microchips to meteorites

Li, X.; Lierse Von Gostomski, C.; Merchel, S.ORC; Rugel, G.
With its very pure thermal neutron flux, the reactor FRM II at Garching offers very good opportunities for studies of chemical composition in samples. The advantages of the instrumental NAA (INAA) are simple sample preparation without chemical handlings, high sensitivity, multi-element capability at all concentration levels (main, minor & trace) and almost non-destructiveness. The so-called “fingerprint” method, especially analysing rare earth elements (REEs), can give us e.g. more details of the provenance of the samples.
INAA is applied in material science e.g. quality assurance of semi-conductor materials. Impurities in the sub-ppb-level (1:10⁹) can be detected after long-time irradiation with high neutron flux (> 1014 cm-2 s-1).
One of the interesting interdisciplinary projects is the bulk analysis of meteorites. Among them is the stony meteorite “Cloppenburg”, which was found in 2017 as the 49th German meteorite [1]. More than 45 elements could be determined by INAA [2]. The INAA data is mandatory for the interpretation of cosmogenic radionuclide data determined by accelerator mass spectrometry (AMS) [3] to reconstruct the history of the meteorite(s) such as irradiation and terrestrial age, and preatmospheric size.
Ref.:
[1] Meteoritical Bulletin, no. 106, in prep. (2018).
[2] X. Li et al., Proc. of Paneth-Kolloquium (2017).
[3] S. Merchel et al., this meeting.
Keywords: INAA, neutron activation analysis, AMS, REE
  • Lecture (Conference)
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten (SNI2018), 17.-19.09.2018, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27469
Publ.-Id: 27469


Description of Ore Particles from X-Ray Microtomography (XMT) Images, Supported by Scanning Electron Microscope (SEM)-Based Image Analysis

Furat, O.; Leißner, T.; Ditscherlein, R.; Šedivý, O.; Weber, M.; Bachmann, K.; Gutzmer, J.; Peuker, U.; Schmidt, V.
In this paper, 3D image data of ore particle systems is investigated. By combining X-ray micro tomography (XMT) with scanning electron microscope (SEM) based image analysis additional information about the mineralogical composition from certain planar sections can be gained. For the analysis of tomographic images of particle systems the extraction of single particles is essential. This is performed with a marker-based watershed algorithm and a post-processing step utilizing a neural network to reduce oversegmentation. The results are validated by comparing the 3D particle-wise segmentation empirically with 2D SEM images which have been obtained with a different imaging process and segmentation algorithm. Finally, a stereological application is shown, in which planar SEM images are embedded into the tomographic 3D image. This allows the estimation of local X-ray attenuation coefficients, which are material-specific quantities, in the entire tomographic image.
Keywords: X-ray micro tomography (XMT), mineral liberation analyzer (MLA), segmentation, stereology, attenuation coefficient

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27468
Publ.-Id: 27468


Running out of patience for radionuclide decay: Accelerator mass spectrometry (AMS) counts faster

Rugel, G.; Merchel, S.ORC; Llovera, R.; Scharf, A.; Dreams-Users
Accelerator mass spectrometry (AMS) is the most sensitive analytical method to measure long-lived radionuclides. Several AMS system has been recently established in Europe, however, most of them exclusively detecting carbon-14. At Dresden a 6 MV tandem accelerator is used for AMS since 2011: The DREAMS (DREsden AMS) facility [1-3] is part of the Ion Beam Center, a large-scale user facility, where users apply for measurements via a proposal system.
Radionuclides, which are routinely measured at DREAMS, are ¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca, and ¹²⁹I. We recently also focussed on nuclides with shorter half-lives such as ⁷Be or ⁴⁴Ti. The detection limits are generally several orders of magnitude better than any other mass spectrometry or decay counting method. AMS needs smaller sample sizes and measurements are finished within a few minutes to hours; though after performing chemical separation of the radionuclide from the sample matrix (ice, snow, rain, ground water, marine sediments, soil, meteorites, deep-sea nodules, lava, rocks).
DREAMS users apply AMS to most diverse interdisciplinary projects. Prominent examples are the proof and dating of multiple supernovae during the last 10 Ma [4] and dating of a boulder from a rock fall triggered by a medieval Earthquake in in the Nepal Himalaya [5].
Ref.: [1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Rugel et al., NIMB 370 (2016) 94. [3] www.dresden-ams.de. [4] Wallner et al., Nature 532 (2016) 69. [5] Schwanghart et al., Science 351 (2016) 147.
Keywords: AMS, radionuclide
  • Lecture (Conference)
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten (SNI2018), 17.-19.09.2018, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27467
Publ.-Id: 27467


Short-Lived DREAMS of Be-7

Rugel, G.; Merchel, S.ORC; Scharf, A.; Querfeld, R.; Steinhauser, G.; Tiessen, C.
Routine AMS (Accelerator Mass Spectrometry) nuclide half-lives range from a few thousand to a few million years. In contrast to this, we measured short-lived ⁷Be (T1/2 = 53.2 d) at the DREsden AMS-facility (DREAMS) [1]. The possibly troublesome isobar ⁷Li in mass spectrometry is easily separated by passing an additional silicon nitride foil as it does not exist in charge state 4+. The ⁷Be-sample data has been normalized to a proton-activated normalization material (produced by ⁷Li(p,n)⁷Be) that was measured by 𝛾-counting and chemically processed by adding stable ⁹Be carrier to BeO (⁷Be/⁹Be ≈ 10¹²).

This way, at DREAMS ⁷Be could be quantified as low as of 90 mBq, which is a challenge for conventional 𝛾-counting in a timely manner. Additionally, the measurement of ⁷Be and ¹⁰Be (T1/2 = 1.387 Ma) within the same sample is advantageous for investigating the production, transport, and deposition of atmospherically produced ⁷¹⁰Be [2]. Combined with a very good blank ratio of 5 × 10¹⁶ ⁷Be/⁹Be (corresponding to 0.8 mBq), it allows rainwater samples as small as 10 ml to be prepared with simple and fast chemistry (< 7 h for a batch of ten samples) and measured with AMS (< 11 h for a batch of ten samples) [3,4].

DREAMS [1,5] is part of the HZDR Ion Beam Center, a large-scale user facility, where external users apply for free AMS measurements of ⁷Be and other radionuclides (¹⁰Be, ²⁶Al, ³⁶Cl, ⁴¹Ca, ¹²⁹I,…) via a proposal system.

Acknow.: Thanks to D. Bemmerer (HZDR) and G. György (ATOMKI, Hungary) for help with the production and 𝛾-counting of the ⁷Be normalization material. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association. We would like to thank the DREAMS operator team for their assistance with AMS measurements. Funding by a DAAD RISE-Pro Grant (HZDR-PH-456) is highly appreciated.

Literature:
[1] Rugel, G., et al.: The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data. Nucl. Instr. Meth. Phys. Res. B (2016) Issue 370, pp. 94-100. [2] Smith, A.M., et al.: A new capability for ANTARES: ⁷Be by AMS for ice samples. Nucl. Instr. Meth. Phys. Res. B (2013) Issue 294, pp. 59-66. [3] Querfeld, R., et al.: Low-cost production of a beryllium-7 tracer from rainwater and purification: preliminary results. J. Radioanal. Nucl. Chem. (2017) Issue 314, pp. 521-527. [4] Tiessen, C., et al.: Optimising accelerator mass spectrometry (AMS) for beryllium-7 measurements in smallest rain samples. J. Radioanal. Nucl. Chem. (in preparation). [5] www.hzdr.de/ibc.
Keywords: AMS, radionuclide
  • Lecture (Conference)
    8. RCA-Workshop, 12.-14.06.2018, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27466
Publ.-Id: 27466


Data for publication

Kluge, T.ORC; Rödel, M.; Metzkes, J.; Pelka, A.; Garcia, A. L.; Prencipe, I.; Rehwald, M.; Nakatsutsumi, M.; Mcbride, E. E.; Schönherr, T.; Garten, M.; Hartley, N. J.; Zacharias, M.; Erbe, A.; Georgiev, Y. M.; Galtier, E.; Nam, I.; Lee, H. J.; Glenzer, S.; Bussmann, M.; Gutt, C.; Zeil, K.; Rödel, C.; Hübner, U.; Schramm, U.; Cowan, T. E.

Raw data, lineouts and fits for the publication

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-05-09
    DOI: 10.14278/rodare.23
    License: CC-BY-SA-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27465
Publ.-Id: 27465


Die Potentialsonde, Entwicklung am HZDR im ersten Jahrzehnt dieses Jahrtausends

Cramer, A.ORC
Die Idee, die durch ein in einem Magnetfeld strömendes elektrisch leitfähiges Medium zwischen zwei eingetauchten Elektroden induzierte Spannung als Repräsentant der Strömungsgeschwindigkeit zu messen, ist Michael Faraday, der als Begründer des Elektromagnetismus angesehen werden kann, zuzusprechen. Der Abstand der Elektroden war riesig, dafür war das Magnetfeld, Faraday benutzte das Erdfeld, klein.

Als die Potentialsonde miniaturisiert wurde, hat sich an dem Verhältnis Spannung pro Geschwindigkeitseinheit nichts wesentlich geändert. Th. von Weissenfluh konnte in den 90er Jahren die Sensitivität merklich verbessern. Er sagte eine Nichtlinearität von Spannnung und Geschwindigkeit voraus wenn die lokale Reynoldszahl, gebildet mit dem Elektrodenabstand, gegen 1 oder darunter geht, konnte dies aber nicht messen.

Eine grobe Abschätzung der auflösbaren mittleren Geschwindigkeit liegt bei etwa einem mm/s. Sind Turbulenzmessungen gefragt, kommen zwei Erschwernisse hinzu. Die Fluktuationen sind oft noch einmal deutlich kleiner als die mittlere Geschwindigkeit, und damit die Sonde nicht als Tiefpassfilter arbeitet sind nur vergleichsweise kleine Elektrodenabstände erlaubt.

Dies ist als Grund dafür anzusehen, dass in der Literatur mit der Potentialsonde durchgeführte Turbulenzmessungen nur für relativ schnelle Strömungen vorliegen. Für viele Anwendungen aus der Metallurgie ist das ausreichend, nicht jedoch für Problemstellungen aus der Kristallzucht. Das war die Motivation dafür, sich mit der Auflösung, möglichst für schnelle transiente Messungen, zu beschäftigen.

Im Seminar wird ein System vorgestellt, mit dem die von von Weissenfluh erwartete Nichtlinearität mit guter Reproduzierbarkeit und Genauigkeit vermessen wurde. Die induzierten Spannungen lagen im Falle einer stationären Strömung bis deutlich unter 1 nV.

Das zweite Beispiel wird sich mit Turbulenzmessungen beschäftigen, speziell mit dem Kompromiss zwischen Geschwindigkeitsauflösung und Messfrequenz.
  • Invited lecture (Conferences)
    Seminar über Nukleare Energieerzeugung, 07.05.2018, Eggenstein-Leopoldshafen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27464
Publ.-Id: 27464


Radiumdotierte Bariumsulfat-Nanopartikel für die radiotherapeutische Anwendung

Reissig, F.ORC; Pietzsch, H.-J.ORC; Steinbach, J.ORC; Mamat, C.ORC
Durch fortschreitende Alterung der Bevölkerung ist eine kontinuierliche Zunahme von Tumorerkrankungen zu verzeichnen. Die Optimierung bestehender sowie die Entwicklung neuer Therapiekonzepte ist daher unabdingbar. Ein aktuell intensiv diskutierter Ansatz ist die nuklearmedizinische Therapie mit Alphastrahler-markierten Radiopharmaka. Radionuklide wie 223/224Ra oder 225Ac sind in der Lage, Tumorgewebe aufgrund ihres vergleichsweise hohen, linearen Energietransfers infolge einer Kaskade von Alpha-Zerfällen effizient zu zerstören. Ein theragnostischer Ansatz könnte mit dem „Matched Pair“ 131Ba/223/224Ra verfolgt werden. Die Herausforderung der stabilen Fixierung von Barium- und Radiumionen könnte durch Kofällung radiomarkierter [131/133Ba/223/224Ra]Ba(Ra)SO4-Nanopartikel (NP) erfolgen.
  • Lecture (Conference)
    8. RCA Workshop, 12.-14.06.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27463
Publ.-Id: 27463


Sulfonated calix-baskets for complexation of Barium and Radium

Mamat, C.ORC; Reissig, F.ORC; Bauer, D.ORC; Pietzsch, H.-J.ORC; Steinbach, J.ORC
Understanding the coordination chemistry of heavy group 2 metals, especially of barium as surrogate for radium, is mandatory not only for radiopharmaceutical applications of radium. This is from high importance since radium-223 is the only approved therapeutic alpha-emitter (by EMA and FDA). Unfortunately, the applications are limited. To date, radium-223 is only in use as RaCl2 for the treatment of bone cancer metastases. To overcome this limitation, which is also true for other group 2 metals, special cage-like compounds have to be developed as ligands like sulfonated calix[4]crowns to stably bind the Ba2+ and Ra2+ to avoid a release in vivo. This will be the basis for a future application of heavy group 2 metals and not only of radium to treat other cancer entities than bone metastases. Ra2+ can then be included in radiopharmaceuticals which contain a chelator and a biologically active molecule part to find the tumor cell.
For this purpose, a series of modified calix[4]crown-6 derivatives was synthesized to chelate barium, which serves as non-radioactive surrogate for radium-223/-224. These calixcrowns were functionalized sulfonate moieties including deprotonable groups and the corresponding barium complexes were synthesized. Stability constants of these complexes were measured using UV/Vis titration experiments to determine logK values. Further extraction studies were performed with [133Ba]Ba2+ and [224Ra]Ra2+ to further characterize the binding affinity of calixcrowns.
  • Lecture (Conference)
    RadChem - 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czech Republic
  • Open Access Logo Contribution to proceedings
    RadChem - 18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázne, Czech Republic
    Czech Chemical Society Symposium Series, Praha: Czech Chemical Society (CCS), 228-229

Permalink: https://www.hzdr.de/publications/Publ-27462
Publ.-Id: 27462


Super-SIMS at HZDR - first steps

Rugel, G.; Renno, A. D.ORC; Akhmadaliev, S.; Belokonov, G.; Böttger, R.; von Borany, J.; Gutzmer, J.; Kaever, P.; Meyer, M.; Noga, P.; Tiessen, C. J.; Voigtländer, J.; Wagner, N.; Wiedenbeck, M.; Winter, A.; Wu, H.; Ziegenrücker, R.
The integration of an ion source with very high spatial resolution with a tandem accelerator is a long-standing concept for improving analytical selectivity and sensitivity by orders of magnitude [1-3]. Translating this design concept to reality has its challenges [e.g. 4-6]. Supporting a strong focus on natural, metallic and mineral resources the, Helmholtz Institute Freiberg for Resource Technology installed such a system at the Ion Beam Centre at HZDR. This so-called Super-SIMS will be at the core of a comprehensive pallet of micro-analytical methods devoted to the characterization of minerals and ores. Secondary ion beam from a CAMECA IMS 7f-auto are injected into the pre-existing 6MV Dresden Accelerator Mass Spectrometry facility [7,8], which quantitatively eliminates isobaric molecular species from the ion beam. Our SIMS component can function as either a stand-alone device or can be used to inject the negatively charged secondary ions at energies of up to 40 keV (to match the acceptance conditions) into the accelerator. A dedicated ion optical unit has been constructed and installed to match the SIMS ion beam to the maximum acceptance of the accelerator.
We will present measurements of the performance parameters of the instrument as well as first results of halogen (F, Cl, Br, and I) determinations in galena, sphalerite and pyrrhotite.
[1] Purser et al. Surface and Interface Analysis 1(1), 1979, 12. [2] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316. [3] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470. [4] Ender et al. NIMB 123 (1997) 575. [5] Maden, PhD thesis, ETH Zurich 2003. [6] Fahey et al. Analytical Chemistry 88(14), 2016, 7145. [7] Akhmadaliev et al., NIMB 294 (2013) 5. [8] Rugel et al. NIMB 370 (2016) 94.
Keywords: Super-SIMS, SIMS
  • Poster
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten (SNI2018), 17.-19.09.2018, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27461
Publ.-Id: 27461


Nano-particulate pressed powder pellets: multi-method homogenous MRMs for in situ analysis with high spatial resolution

Müller, S.; Garbe-Schönberg, D.; Nordstad, S.; Schönberg, L.; Savard, D.; Wiedenbeck, M.; Renno, A. D.ORC
The quality of in-situ micro-analytical data relies on the availability and use of sufficiently matrix-matched reference materials. Their physical and chemical properties have to meet the requirements of analytical instrumentation, e.g., withstand high-vacuum and impact of high-energy laser, electron, and ion beams, they have to be stable over time and under various environmental conditions, certified following ISO guidelines, and available for a wide variety of compositions matching the unknown samples. Homogeneity of pulverized pressed materials is a function of both sampled volume and grain size and must allow elemental and isotope analysis with high spatial resolution <10-32μm as required in imaging applications or mineral analysis. We developed a method for manufacturing undiluted, binder-free pressed powder pellets[1] with particle grain size down to the nanometer range (D50 <170 nm) that meet the above requirements, have extremely low roughness RA < 50 nm of pellet surface, and excellent within and between pellet homogeneity.
This technique has been applied so far to a wide range of very different sample types: biogenic carbonates (foraminifera, clam shells, algae, coral), speleothem, silicate rocks, iron ores and banded iron formation, manganese nodules, sulphides UQAC-FeS, refractory minerals, plutonic and volcanic rocks, fly ash, bone-apatite, minerals for Rb/Sr age-dating[2] etc.
We successfully tested blending of different materials opening new ways for producing e.g., series of elemental and isotopic calibration standards. These “nanopellets” have been used with LA-ICP-MS, LIBS, µ-XRF, handheld-XRF instruments, and also with EPMA, PIXE, SIMS making them a new and, possibly, universal matrix-matched MRM. They have the potential of replacing time-consuming, hazardous and tedious acid digestion procedures. Here we give an overview of the present state of development of new MRM[3] and their characterization in terms of grain size distribution, surface topography, porosity, homogeneity, and accuracy of analytical results for both elemental (major, minor, trace and ultra-trace elements) and isotopic (Sr, Li, B, O) composition.
Keywords: Reference Materials, Nanopowder, LA-ICP-MS, SIMS, PIXE
  • Lecture (Conference)
    14th European Workshop on Laser Ablation, 26.-29.06.2018, Pau, France

Permalink: https://www.hzdr.de/publications/Publ-27460
Publ.-Id: 27460


Core reflooding analyses for a generic German PWR

Wilhelm, P.; Jobst, M.
  • Lecture (Conference)
    NUGENIA Meeting TA2 Severe Accidents, 16.-19.04.2018, Puerto de La Cruz, Spain

Permalink: https://www.hzdr.de/publications/Publ-27459
Publ.-Id: 27459


Modelling and Simulation of Severe Accidents in Pressurized Water Reactors

Wilhelm, P.; Schäfer, F.; Jobst, M.; Kozmenkov, Y.; Kosowski, K.
Modelling and Simulation of Severe Accidents in Pressurized Water Reactors
  • Lecture (Conference)
    NUGENIA Annual Forum 2018/Nuclear Days 2018, 10.-12.04.2018, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-27458
Publ.-Id: 27458


Characterization of the Secondary Neutron Radiation at the University Proton Therapy Dresden

Lutz, B.ORC; Zboril, M.; Dommert, M.; Swanson, R.; Enghardt, W.; Fiedler, F.; Reginatto, M.
Radiation therapy is one of the most used treatment modalities of cancer. While most patients receive photon-therapy, a growing number of patients are treated with particles, mainly protons. Protons offers a more localized dose deposition compared to photon-therapy. This allows to reduce the dose that is applied by the primary beam to the healthy tissue outside the target volume. At the same time, the use of protons leads to a change in the composition of the secondary radiation field, when compared to photons. In most locations, the out-of-field dose is dominated by secondary neutrons. The out-of-field dose varies significantly in shape and size. Currently, there is no established procedure to monitor the secondary neutron dose to the patients.
This paper describes the simulation and measurement of the secondary neutron radiation field at the University Dresden Proton Therapy. The simulation uses a detailed model of the beam delivery system, an IBA universal nozzle. The simulations have been validated by a comprehensive set of extended range Bonner sphere spectrometer measurements, with the NEMUS spectrometer operated by the Physikalisch-Technische Bundesanstalt. The set of measurements covers all possible machine configurations for the double scattering mode. An excellent agreement between unfolded measurements and simulation predictions is achieved.
The data shows that the neutron field is varying strongly on the scale of a human body. This indicates that the use of fluence to dose conversion tables is not justified for neutron dose calculation in patients. Therefore, the presented data is of high importance for future studies of the organ doses in different treatment scenarios.
Keywords: neutron, Bonner sphere spectrometer, proton therapy, double scattering
  • Lecture (Conference)
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, 10.-17.11.2018, Sydney, Australia
  • Contribution to proceedings
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, 10.-17.11.2018, Sydney, Australia
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC): IEEE, 978-1-5386-8494-8, 1-6
    DOI: 10.1109/NSSMIC.2018.8824583

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27457
Publ.-Id: 27457


Tests of MACACO Compton telescope with 4.44MeV gamma rays

Muñoz, E.; Barrio, J.; Bemmerer, D.; Etxebeste, A.; Fiedler, F.; Hueso-González, F.; Lacasta, C.; Oliver, J. F.; Römer, K.; Solaz, C.; Wagner, L.; Llosá, G.
Hadron therapy offers the possibility of delivering a large amount of radiation dose to tumors with minimal absorption by the surrounding healthy tissue. In order to fully exploit the advantages of this technique, the use of real-time beam monitoring devices becomes mandatory.
Compton imaging devices can be employed to map the distribution of prompt gamma emission during the treatment and thus assess its correct delivery. The Compton telescope prototype developed at IFIC-Valencia for this purpose is made of three layers of LaBr3 crystals coupled to silicon photomultipliers. The system has been tested in a 4.44 MeV gamma field at the 3 MV Tandetron accelerator at HZDR, Dresden. Images of the target with the system in three different positions separated by 10 mm were successfully reconstructed. This indicates the ability of MACACO for imaging the prompt gamma rays emitted at such energies.
Keywords: Compton imaging; Instrumentation for hadron therapy; Gamma detectors (scintillators, CZT, HPG, HgI etc); Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27456
Publ.-Id: 27456


Modelling of focused ion beam induced increases in sample temperature: a case study of heat damage in biological samples

Wolff, A.ORC; Klingner, N.ORC; Thompson, W.; Zhou, Y.; Lin, J.; Peng, Y. Y.; Ramshaw, J. A. M.; Xiao, Y.
Ion beam induced heat damage in soft materials and biological samples is not yet well understood in Focused Ion Beam systems (FIBs). The work presented here discusses the physics behind the ion beam – sample interactions and the effects which lead to increases in sample temperature and potential heat damage. A model by which heat damage can be estimated and which allows parameters to be determined that reduce/prevent heat damage was derived from Fourier’s law of heat transfer and compared to finite element simulations, numerical modeling results and experiments. The results suggests that ion beam induced heat damage can be prevented/minimized by reducing the ion beam current (local dose rate), decreasing the beam overlap (reduced local ion dose) and by introducing a blur (increased surface cross-section area, reduced local dose) while sputtering, patterning or imaging soft material and non-resin-embedded biological samples using FIBs.
Keywords: Focused Ion Beam, Heat Damage, Biological Sample, SRIM, COMSOL, FTCS

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27455
Publ.-Id: 27455


Time-of-flight secondary ion mass spectrometry in the helium ion microscope

Klingner, N.ORC; Heller, R.; Hlawacek, G.ORC; Facsko, S.ORC; von Borany, J.
A helium ion microscope, known for high resolution imaging and machining with helium or neon ions, has been equipped with a time-of-flight spectrometer for in-situ compositional analysis.
Here we report on its design, implementation and show first results of this powerful add-on.
Our design considerations were strongly based on detailed simulations of the ion collision cascade with a focus on the physically achievable resolution for the various detection limits.
Based on these simulations different secondary ion extraction systems and spectrometer types are considered and compared with respect to the demands and limitations of the microscope.
As a result the development and examination of a straight secondary ion extraction and a time-of-flight spectrometer is reported that allows the simultaneous measurement of all secondary ion masses.
First experimental results demonstrate an excellent mass resolution as well as high-resolution secondary ion imaging capabilities with sub-8 nm lateral resolution.
High resolution secondary electron images correlated with in-situ mass-separated sputtered ion distributions have a high potential to answer open questions in different fields of materials science.
Keywords: Helium Ion Microscope; Time-Of-Flight; SIMS

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27454
Publ.-Id: 27454


Reaction of uranium- and zirconium oxides under reducing and oxidizing atmospheres: X-ray absorption and X-ray diffraction studies

Uehara, A.; Akiyama, D.; Numako, C.; Terada, Y.; Nitta, K.; Ina, T.; Takeda-Homma, S.; Ikeda-Ohno, A.ORC; Kirishima, A.; Sato, N.
Chemical and redox reaction between uranium (U) and zirconium (Zr) at high temperature under a reducing or oxidizing atmosphere were investigated to simulate fuel debris formed by Fukushima nuclear power plant accident. X-ray absorption spectroscopy (XAS) at U LIII-edge and Zr K edge and powder X-ray diffraction (XRD) of the mixed UO2/ZrO2 materials treated at high temperature from 1473 to 1873 K under reducing or oxidizing atmosphere were performed. For UO2-ZrO2 samples from1473 to 1873 K under the oxidizing atmosphere (Ar + 2% O2, 1h), it was found that the compounds were primarily consisted of five species including U3O8, UO2, U2Zr5O15, monoclinic-ZrO2, and tetragonal-ZrO2, whose fractions were calculated by principal component analysis (PCA) on both the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) collected at both U LIII edge and Zr K edge. Here, the formation of U2Zr5O15, a pentavalent uranium compound, was confirmed by the U LIII edge-XANES between the temperature range from 1473 to 1573 K. These results were also supported by powder-XRD analysis. Under the reducing atmosphere (Ar + 10% H2, 1h), UO2 remained at the whole temperature range without reacting with ZrO2, whereas monoclinic- and tetragonal ZrO2 were formed at 1573 K (60- and 40%, respectively). This study can pave the way for understanding the interaction between nuclear fuels and cladding materials in damaged reactors, enabling to simulate possible decontamination procedures.
Keywords: Nuclear fuel debris, Fukushima Dai-ichi Nuclear Power Plants, accidents, environmental science, mixed oxides, solid-state chemistry, X-ray absorption spectroscopy, powder X-ray diffraction
  • Lecture (Conference)
    NuMat2018: The Nuclear Materials Conference, 15.10.2018, Seattle, WA, USA

Permalink: https://www.hzdr.de/publications/Publ-27453
Publ.-Id: 27453


Ion Sources for Focused Ion Beam Applications

Bischoff, L.; Mazarov, P.; Pilz, W.; Gierak, J.
One of the most important elements of a Focused Ion Beam (FIB) system is the ion source which has to guarantee a stable, long life working in the needed application field with the required properties. Main points are the achievable focus of the spot, the ion current, the energy and also the ion species itself. At present nearly half of elements of the periodic table can be used in FIB equipment to modify or tune locally electrical, optical, mechanic or magnetic properties. Depending on the special task very different types of ion sources can be found. Among them the Liquid Metal Ion Sources (LMIS) mostly used for Ga and derived from that the Liquid Metal Alloy Ion Sources (LMAIS) [1] are most popular ones having a brightness of 106 A/cm² sr. The obtainable resolution is a few nm with ion currents of some pA. In a similar manner Ionic Liquid Ion Sources (ILIS) work using salts or certain compounds from which positive and negative mono- and polyatomic ions can be emitted [1,2]. Due to the limited ion current in such sources to lower than 100 nA and so applications like larger volume removing are restricted. ECR or RF plasma sources can fill the gap working with heavy Xe ions and currents up to 2 µA [3,4]. In the last decade a long known source was rediscovered – the Gas Field Ion Source (GFIS) and generate the initial point for the successful development of the Helium Ion Microscope (HIM) [5]. A final lateral spot size of about half nm opens new prospects in the field of ion microscopy and nano-engineering. Another modern and interesting approach is the magneto-optical trap ion source (MOTIS) successful demonstrated for Cr and Li ions [6].
All ion sources used in FIB systems will be compared, characterized, discussed and described with a typical application.

[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[2] A. N. Zorzos and P. Lozano, The use of ionic liquid ion sources in focused ion beam applications, J. Vac. Sci. Technol. B 26 (2008) 2097.
[3] A. Delobbe, O. Salord, T. Hrncir, A. David, P. Sudraud and F. Lopour, High Speed TEM Sample Preparation by Xe FIB, Microsc. Microanal. 20 (2014) 298.
[4] T.L. Burnetta, R. Kelley, B. Winiarski, L. Contreras, M. Daly, A. Gholinia, M.G. Burke, and P.J. Withers, Large volume serial section tomography by Xe Plasma FIB dual beam Microscopy, Ultramicroscopy 161 (2016) 119.
[5] G. Hlawacek, V. Veligura, R. van Gastel, and B. Poelsema, Helium ion microscopy, J. Vac. Sci. Technol. B 32 (2014) 020801.
[6] B. Knuffman, A. V. Steele, J. Orloff, M. Maazouz, and J. J. McClelland, A Focused Ion Beam Source Based On Laser-Cooled Atoms, AIP Conference Proceedings 1395 (2011) 85.
Keywords: Focused Ion Beam, Plasma Ion Sources, LMAIS, MOTIS
  • Lecture (Conference)
    MAT Science Week, 24.-27.04.2018, Darmstadt, Germany
  • Lecture (Conference)
    Helium and emerging Focused Ion Beams HeFIB2018, 11.-13.06.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27452
Publ.-Id: 27452


Comparison of mechanical properties and composition of magnetron sputter and plasma enhanced atomic layer deposition aluminum nitride films

Sippola, P.; Pyymaki Perros, A.; Ylivaara, O. M. E.; Ronkainen, H.; Julin, J.ORC; Liu, X.; Sajavaara, T.; Etula, J.; Lipsanen, H.; Puurunen, R. L.
Comparative study of mechanical properties and elemental and structural composition was made for aluminum nitride thin films deposited with reactive magnetron sputtering and plasma enhanced atomic layer deposition (PEALD). The sputtered films were deposited on Si (100), Mo (110) and Al (111) oriented substrates to study the effect of substrate texture to the film properties. For the PEALD trimethylaluminum-ammonia (TMA/NH3) films, the effects of process parameters such as temperature, bias voltage, and plasma gas (NH3 vs. N2/H2) on the AlN properties were studied. All the AlN films had a nominal thickness of 100 nm. Time-of-flight elastic recoil detection analysis (ToF-ERDA) showed the sputtered films to have lower impurity concentration with an Al/N ratio of 0.95, while the Al/N ratio for the PEALD films was 0.81-0.90. The mass densities were ~3.10 g/cm3 and ~2.70 g/cm3 for sputtered and PEALD AlN, respectively. Only the sputtered films were crystalline, as determined by x-ray diffraction (XRD). Nanoindentation experiments showed the elastic modulus and hardness to be 250 GPa and 22 GPa, respectively, for sputtered AlN on (110) substrate, whereas with PEALD AlN, values of 180 GPa and 19 GPa, respectively, were obtained. The sputtered films were under tensile residual stress (61 to 421 MPa) whereas PEALD films had a residual stress ranging from tensile to compressive (846 to -47 MPa) and high plasma bias resulted in compressive films. The adhesion of both films was good on Si, although sputtered films showed more inconsistent critical load behaviour. Also, the substrate underneath the sputtered AlN did not withstand as high wear forces as with the PEALD AlN. The coefficient of friction was determined to be ~0.2 for both AlN types and their wear characteristics were almost identical.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27451
Publ.-Id: 27451


Kopplung von Energiesystem und Rohstoffsystem

van den Boogaart, K. G.
Energiesystem und Rohstoffsystem sind eng verknüpft. Unser Beitrag in ES2050 beschäftigt sich mit dieser Verknüpfung. Zur Erzeugung, "Ubertragung und Speicherung werden Stoffliche Resourcen benötigt. Der Bedarf stofflicher Resourcen ist bei der Verwendung erneuerbare Energien typischerweise höher als bei fossilen Energieträgern. Stoffliche Resourcen sind aber nur teilweise erneuerbar. Ihre Bereistellung aus Primärem Quellen oder Recycling erfordert selbst Energie und weitere Rohstoffe. Daraus ergibt sich ein Netzwerk aus gegenseitigen Anforderungen, dessen Eigenschaften wir untersuchen. Da viele Quellen begrenzt sind, ändert sich dabei je nach benötigter Menge der indirekte Bedarf an weiteren Quellen.

Die wichtigsten Erkenntnisse bisher sind:

1) Für mache Arten erneuerbarer Energien würden die heute bekannten Rohstoffquellen nicht ausreichen. Auch aus Rohstoffsicht ist daher immer ein Energiemix erforderlich.

2) Betrachtet man Energiesystem und Rohstoffsystem gemeinsam können Rückkopplungen auftreten, die den Aufwand für bottleneck-Rohstoffe explodieren lassen.

3) Erneuerbare Energien sind aus Rohstoff-Sicht noch unbedingt erneuerbar. Sie verbrauchen Rohstoffe. Ein energetisch ökonomisches Recycling ist nicht immer möglich.

4) Ein kostenoptimiertes System neigt zu hohen Rohstoffverbräuchen.

5) Verbote im Systeme verringern die Effizienz.
  • Lecture (Conference)
    ES2050 Statustagung, 08.-09.05.2018, Frankfurt(Main), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27450
Publ.-Id: 27450


Metallic twin boundaries boost the hydrogen evolution reaction on the basal plane of molybdenum selenotellurides

Kosmala, T.; Diaz, H. C.; Komsa, H.-P.; Ma, Y.; Krasheninnikov, A. V.ORC; Batzill, M.; Agnoli, S.
The hydrogen evolution reaction (HER) is a fundamental process that impacts several important clean energy technologies. Great efforts have been taken to identify alternative materials that could replace Pt for this reaction or that may present additional functional properties such as optical activity and advanced electronic properties. Herein, a comparative study of the HER activity for ultrathin films of MoTe2, MoSe2, and their solid solutions on highly oriented pyrolytic graphite is reported. Combining advanced characterization techniques and density functional theory calculations with electrochemical measurements, it is shown that the chemical activity of the scarcely reactive 2H phases can be boosted by the presence of metallic twin boundaries. These defects, which are thermodynamically stable and naturally present in Mo-enriched MoTe2 and MoSe2, endow the basal plane of the 2H phase with a high chemical activity, which is comparable to the metastable 1T polymorph.
Keywords: 2D materials, hydrogen evolution reaction, first-principles calculations

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27449
Publ.-Id: 27449


Post-synthesis modifications of two-dimensional MoSe2 or MoTe2 by incorporation of excess metal atoms into the crystal structure

Coelho, P. M.; Komsa, H.-P.; Diaz, H. C.; Ma, Y.; Krasheninnikov, A. V.ORC; Batzill, M.
Phase engineering has extensively been used to achieve metallization of two-dimensional (2D) semiconducting materials, as it should boost their catalytic properties or improve electrical contacts. In contrast, here we demonstrate compositional phase change by incorporation of excess metals into the crystal structure. We demonstrate post-synthesis restructuring of the semiconducting MoTe2 or MoSe2 host material by unexpected easy incorporation of excess Mo into their crystal planes, which causes local metallization. The amount of excess Mo can reach values as high as 10% in MoTe2 thus creating a significantly altered material compared to its parent structure. The incorporation mechanism is explained by density functional theory in terms of the energy difference of Mo atoms incorporated in the line phases as compared to Mo ad-clusters. Angle resolved photoemission spectroscopy reveals that the incorporated excess Mo induces band gap states up to the Fermi level causing its pinning at these electronic states. The incorporation of excess transition metals in MoTe2 and MoSe2 is not limited to molybdenum, but other transition metals can also diffuse into the lattice, as demonstrated experimentally by Ti deposition. The mechanism of incorporation of transition metals in MoSe2 and MoTe2 is revealed, which should help to address the challenges in synthesizing defect-free single layer materials by, for example, molecular beam epitaxy. The easy incorporation of metal atoms into the crystal also indicates that the previously assumed picture of a sharp metal/2D- material interface may not be correct, and at least for MoSe2 and MoTe2, in-diffusion of metals from metal-contacts into the 2D material has to be considered. Most importantly though, the process of incorporation of transition metals with high concentrations into pristine 2D transition-metal dichalcogenides enables a pathway for their post-synthesis modifications and adding functionalities.
Keywords: 2D materials, defects, first-principles simulaitons

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27448
Publ.-Id: 27448


Supported Two-Dimensional Materials under Ion Irradiation: the Substrate Governs Defect Production

Kretschmer, S.; Maslov, M.; Ghaderzadeh, S.; Ghorbani-Asl, M.; Hlawacek, G.; Krasheninnikov, A. V.
Focused ion beams perfectly suit for patterning two-dimensional (2D) materials, but the optimization of irradiation parameters requires full microscopic understanding of defect production mechanisms. Contrary to free-standing 2D systems, the details of damage creation in supported 2D materials are not fully understood, while the majority of experiments have been carried out for 2D targets deposited on substrates. Here we suggest a universal and computationally efficient scheme to model the irradiation of supported 2D materials, which combines analytical potential molecular dynamics with Monte Carlo (MC) simulations, which makes it possible to assess independently the contributions to the damage from backscattered ions and atoms sputtered from the substrate. Using the scheme, we study defect production in graphene and MoS₂ sheets, which are the two most important and wide-spread 2D materials, deposited on a SiO₂ substrate. For helium and neon ions with a wide range of initial ion energies including those used in commercial helium ion microscope (HIM), we demonstrate that depending on ion energy and mass, defect production in 2D systems can be dominated by backscattered ions and sputtered substrate atoms rather than by the direct ion impacts, and that the amount of damage in 2D materials heavily depends on whether a substrate is present or not. We also study the factors which limit the spatial resolution of the patterning process. Our results, which agree well with the available experimental data, provide not only insights into defect production, but also quantitative information, which can be used for the minimization of damage during imaging in HIM or optimization of the patterning process.
Keywords: Ion Irradiation, Helium Ion Microscope, Substrate, Defect Production

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27447
Publ.-Id: 27447


Redirection of switchable UniCAR T cells against radioresistant cancer cells

Feldmann, A.; Arndt, C.; Bergmann, R.; Berndt, N.; Jureczek, J.; Albert, S.; Lindner, D.; Koristka, S.; Steinbach, J.; Ehninger, G.; Krause, M.; Kurth, I.; Dubrovska, A.; Bachmann, M.
Introduction: Radiation is a common therapy for solid tumors. Unfortunately there is a high risk for the outgrowth of radioresistant tumor cells against which only limited treatment options exist. We challenged the idea whether or not chimeric antigen receptor (CAR) engineered T lymphocytes could be used as an adjuvant immunotherapy in combination with radiotherapy. Recently, we have established switchable universal CARs (UniCARs) that bind to a short peptide epitope (E5B9) which does not exist on the surface of living cells. UniCAR T cells are exclusively redirected to tumor cells in the presence of a target module (TM) that exhibits the E5B9 epitope and binds to a tumor associated antigen (TAA) on the tumor cell surface.
Materials and Methods: We used different radioresistant sublines of the head and neck cancer cell line Cal33. Gene expression data for certain TAAs were confirmed by flow cytometry. TMs against potential targets were created from the variable domains of monoclonal antibodies, cloned in lentiviral vectors and purified from supernatants of permanently TM producing 3T3 cells. UniCAR T cells were generated by lentiviral transduction.
Results: Radioresistant Cal33 cell lines expressed PSCA, EGFR and CD98. UniCAR TMs were created against these TAAs. Armed with these TMs UniCAR T cells efficiently killed radioresistant Cal33 cells in vitro and in vivo.
Conclusions: Radioresistant tumor cells can efficiently be killed by redirecting UniCAR T cells against PSCA, CD98 and EGFR and thus resistance to radiotherapy can be overcome by immunotherapy based on the UniCAR technology to these targets.
Keywords: Antibodies, Engineering of antibodies and nanobodies, Immunotherapy
  • Poster
    5th European Congress of Immunology, 02.-05.09.2018, Amsterdam, Niederlande

Permalink: https://www.hzdr.de/publications/Publ-27446
Publ.-Id: 27446


Fundamental Principles of Spectral Methods related to Discrete Data

Seilmayer, M.; Ratajczak, M.
Until the mid 20th century, the groundbreaking works of Claude Shannon regarding infor- mation theory laid the foundation for the vast field of digital signal processing and spectral data analysis, and thereby enabled almost all modern daily life information technologies we are now used to. Digital telecommunication, audio and video compression are just some ex- amples of advanced signal processing which are not possible without a theory about discrete data and its spectral representation. Signal processing starts with the process of sampling by means of a mathematical model, which results in a mapping between the continuous physical measure – like temperature, voltage fluctuations of a microphone or a camera picture – and its time and value discrete representation. According to that, information about the signal can be gained by filtering, data manipulation, pattern extraction and related procedures. Because of the vast variety of applications, many different spectral methods were developed which utilize different mathematical transforms, for example the Fourier transform or the Hilbert transform. Utilizing the appropriate transform for a problem also opens up shortcuts in calculations, or makes signal features visible by decomposing the signal into the associated spectral domain.
Keywords: Fourier Transform, Hilbert Transform, Spectral Analysis, Discrete Data, R
  • Open Access Logo Book chapter
    Prof. Sergey Y. Yurish: Advances in Measurements and Instrumentation: Reviews' Book Series, Vol. 1, Barcelona: International Frequency Sensor Association (IFSA), 2018, 978-84-09-07321-4, 53-120

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27445
Publ.-Id: 27445


Influence of Histidine-tag on immunotherapeutic and diagnostic properties of anti-PSCA target modules

Jureczek, J.; Bergmann, R.; Berndt, N.; Albert, S.; Koristka, S.; Arndt, C.; Steinbach, J.; Bachmann, M.; Feldmann, A.
Antibodies (Abs) and their recombinant derivatives play an increasing role in tumor therapy and diagnostic imaging. The theranostic target modules (TMs) recently developed by us can be used for individualized and precise cancer immunotherapy and at the same time as radiotracers for tumor imaging. The TMs consist of an antigen binding moiety that binds to the prostate stem cell antigen (PSCA) on the tumor cell surface and present the peptide epitope E5B9. Via E5B9 the TMs can retarget human T cells that are genetically modified with universal anti-E5B9 chimeric antigen receptors (UniCARs) towards the tumor cells. The cross-linkage of UniCAR T cells and tumor cells via the TM results in T cell activation and tumor cell killing. This immunotherapeutic approach was shown as an inducible CAR platform technology that can be used for the treatment of leukemic as well as solid cancers. This technic has an intrinsic emergency brake: The short half-life of the TMs in vivo allows a fast switch off of the UniCAR system. In detail, UniCAR T cells per se are inactive because their UniCARs do not recognize an antigen on the cell surface. Only in the presence of tumor-bound TMs UniCAR T cells can be redirected to tumor cells and turned on. But they are switched off when the application of TMs is stopped and their concentration is too low to activate UniCAR T cells what also becomes particularly relevant in case of side effects occur in the patients. TMs cannot only be used as a therapeutic drug but also as a diagnostic tool for tumor imaging. For this purpose TMs can be modified with a bifunctional chelator. After conjugation they can be labeled with radiometals like 64Cu2+ or 68Ga3+ and used as an imaging tracer for PET analysis.
Usually our TMs contain a tag of six histidine residues (His6-tag) at the C-terminus. The His6-tag is used for convenient purification by immobilized metal ion affinity chromatography and detection of the TMs. However the His6-tag may affect PK and biodistribution of the TMs. In particular with respect to clinical application of the TMs the His6-tag may induce immunologic reactions. Furthermore the purification of His6-tagged TMs by immobilized metal ion affinity chromatography might cause metal ions in the TMs which have influence on their radiolabeling and can be critical for patients’ health. To address these concerns we have generated an anti-PSCA TM without His6-tag (PSCA TM) and compared its theranostic properties to the corresponding TM with the His6-tag (PSCA-His TM). The PSCA TMs were successfully prepared by digestion with TEV protease recognizing a strict seven amino acid cleavage recognition site which was introduced upstream from the His6-tag in the PSCA-TEV-His TM construct. Both TMs with or without His6-tag showed similar high binding affinities to PSCA on PC3-PSCA prostate cancer cells whereas the Kd values were in the nM range. As shown by chromium release assays both target modules were able to redirect UniCAR T cells to efficiently kill PSCA-presenting tumor cells in a strictly target-dependent and target-specific manner. In vitro tumor cell killing of PSCA TM was less efficient than PSCA-His TM but still in pM range. Most importantly in NMRI-FOX1nu/nu mice the PSCA TM redirected UniCAR T cells to eliminate luciferase/PSCA-double positive tumor cells as efficient as the PSCA-His TM. PET analysis of the 64Cu-labeled TMs in these mice showed higher accumulation of the PSCA TM in the PSCA-positive tumors and less nonspecific binding in normal tissues (like blood and heart) after 2 h. At the same time the blood clearance of PSCA TM was distinctly faster than of the PSCA-His TM resulting in better contrast of the tumor for the PSCA TM in the PET images after 2 h. On the other hand, the PSCA-His TMs was slower cleared from the blood resulting in a higher PSCA-His TM concentration in the tumor later on after one day.
To summarize we have established two PSCA TMs one with and the other without a C-terminal His6-tag which differ in their theranostic properties. Both TMs efficiently redirect UniCAR T cells to kill tumor cells. The PSCA TMs have a higher tumor accumulation and lower nonspecific binding in the normal tissues and blood resulting in a very short half-life that may allow an even faster emergency shut down of the UniCAR system if necessary and excellent short time imaging. The PSCA-His TMs are characterized by a larger nonspecific binding, slower blood-clearance and are apparently better suited for long-term imaging. Both TMs are applicable for the UniCAR based immunotherapy and imaging, complement each other and so they are suitable for the individualized, precise human theranostic.
Keywords: Radioimmunology, UniCAR, Tumor Immunotherapy
  • Poster
    Workshop und Symposium Tumor Immunology meets Oncology XIV, 24.05.2018, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27444
Publ.-Id: 27444


The {Np38} clusters: The missing link in the largest poly-oxo cluster series of tetravalent actinides

Martin, N. P.ORC; Volkringer, C.ORC; Roussel, P.; März, J.; Hennig, C.ORC; Loiseau, T.ORC; Ikeda-Ohno, A.ORC
Two poly-oxo cluster complexes of tetravalent neptunium (Np(IV)), Np38O56Cl18(bz)24(THF)8·nTHF and Np38O56Cl42(ipa)20·mipa (bz = benzoate, THF = tetrahydrofuran, and ipa = isopropanol) were obtained via solvothermal synthesis and structurally characterised by single-crystal X-ray diffraction. The {Np38} clusters are comparable to the analogous {U38} and {Pu38} motifs, filling the gap in this largest poly-oxo cluster series of tetravalent actinides.
Keywords: actinides, neptunium, clusters, polymers, structure, X-ray diffraction, hydrolysis, solid state, coordination

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27443
Publ.-Id: 27443


Synthesis and structural characterization of the first neptunium based metal-organic frameworks incorporating {Np6O8} hexanuclear cluster

Martin, N. P.ORC; März, J.; Feuchter, H.; Duval, S.; Roussel, P.; Henry, N.; Petricek, V.; Ikeda-Ohno, A.ORC; Loiseau, T.ORC; Volkringer, C.ORC
Successful synthesis of the first transuranium Metal-Organic Frameworks (MOFs) involving neptunium(IV) (Np(IV) is reported. These compounds were obtained from the controlled hydrolysis of Np(IV) in the presence of dicarboxylate ligands. The final structures contain the [Np6O4(OH)4(H2O)6]12+ unit, which were never cristallized before with tetravalent neptunium, associated with ditopic ligands.
Keywords: actinides, neptunium, metal-organic frameworks, carboxylate, coordination chemistry, structure, X-ray diffraction

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27442
Publ.-Id: 27442


Influence of substitutional atoms on the diffusion of oxygen in dilute iron alloys

Wang, X.; Posselt, M.; Faßbender, J.
A multiscale approach including Density Functional Theory (DFT) and Atomistic Kinetic Monte Carlo (AKMC) simulations is applied to investigate the diffusion of interstitial oxygen atoms in bcc Fe under the influence of substitutional foreign atoms (Al, Si, P, S, Ti, Cr, Mn, Ni, Y, Mo, W). The substitutional atoms can be assumed to be immobile since their diffusion coefficient is much smaller than that of oxygen. At first jumps of oxygen in pure bcc Fe, between first-, second-, and third-neighbor octahedral interstitial sites are investigated. It is found that the first-neighbor jump is most relevant, with the tetrahedral site as the saddle point. The second-neighbor jump consists of two consecutive first-neighbor jumps. The barrier for a direct third-neighbor jump is too high to be significant for the diffusion process. In the presence of substitutional atoms the most important migration paths are first-neighbor jumps between modified octahedral sites with modified tetrahedral sites as saddle points. Calculations show that Si, P, Ni, Mo and W cause some modifications of the migration barriers of oxygen and their interaction with O is mainly repulsive. Al, Cr and Mn have a significant influence on the barriers and they exhibit strong attractive interactions with O. The most important modification of the barriers is found for S, Ti, and Y where deep attractive states exist. Based on the migration energies obtained by DFT, AKMC simulations on a rigid lattice are employed to determine the diffusion coefficient of oxygen in a dilute iron alloy containing the different substitutional atoms. It is found that Si, P, Ni, Mo, and W have almost no influence on the diffusivity of O, i.e. it is nearly identical to that in pure bcc Fe. The presence of Al, Cr, Mn, S, Ti, and Y causes a significant reduction of the mobility of oxygen. In these cases the temperature dependence of the oxygen diffusion coefficient shows considerable deviations from an Arrhenius law and other peculiarities. These phenomena are discussed in detail by considering the occupation time for the different states and the frequency of jumps between the states. The present findings on the strong dependence on the kind of substitutional atoms change the picture of oxgygen diffusion in dilute iron alloys substantially.
Keywords: First-principle calculations; Atomistic kinetic Monte Carlo simulations; Diffusion; Oxygen; Influence of substitutional solutes; bcc-Fe

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27441
Publ.-Id: 27441


Protecting Pulsed High-Power Lasers with Real-Time Object Detection

Kelling, J.; Gebhardt, R.; Helbig, U.; Bock, S.; Schramm, U.; Juckeland, G.
Learn how to train and employ state-of-the-art object localization in a real-time safety application. In Petawatt laser systems, firing at 10Hz, suddenly appearing scatterers can damage components. Damage(-spreading) can be avoided by suspending operation immediately on occurrence of such an event.

We present our approach for the automatic detection of critical failure states from intensity profiles of the laser beam. In order to minimize the rate of false alarms, which would reduce productivity or even render our system useless, we refrain from general anomaly detection and go for detecting known error patterns. In this talk we present how we fitted the You Look Only Once (YOLO) approach, which is suited to low-latency object detection, to our problem and how we adapted the required multi-step training protocol to the available experimental data.

# extended abstract:
High-power lasers are operated at our research center for investigations of exotic states of matter and medical applications, among others. This project to improve the automatic shutdown/interlock system of two lasers (one in operation, one currently under construction) has the goal of reducing the probability of, potentially expensive, damage-spreading scenarios, while at the same time avoiding false alarms. In order to achieve high precision, we train for high recall only for known indicators, instead of using anomaly detection.

After we presented a proof-of-concept for this type of failure-state-detection at GTC 2018, where the main challenge was in dealing with a far too small dataset, we are now working on a pure deep-learning approach driven by systematic experimental data. In the new design, intended for production use, the classification takes place on differences between a running average of non-signaling images and the current shot. This is required, because no images can be obtained which can be classified as "good" without context. In order to achieve fast object-detection, to highlight potential problems for the operator, the you look only once (YOLO) approach[1], which we modify by removing the final layers for bounding-box prediction and train the network to directly produce an expressive feature map (lazy YOLO).

From this talk, the audience can learn how we adapted the well-known YOLO approach to our real-world application, from the employed network to the multi-step training protocol. Another topic is the design for short response times, to which end we employ Caffe, OpenCV on GPU and use C++ as main programming language instead of python.
Keywords: Image Classification, Caffe, automatic Laser-safety shutdown, Object Detection
  • Lecture (Conference)
    GTC Europe, 09.-11.10.2018, München, Deutschland

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27440
Publ.-Id: 27440


Effect of Strong Load Variations on Gain and Timing of CeBr3 Scintillation Detectors Used for Range Monitoring in Proton Radiotherapy

Pausch, G.; Mueller, C.; Berthold, J.; Enghardt, W.; Kuechler, M.; Roemer, K.; Stein, J.; Straessner, A.; Wagner, A.; Werner, T.; Wolf, A.; Koegler, T.
CeBr3 scintillation detectors with light readout by photomultiplier tubes (PMT) have been used for prompt-gamma measurements in proton radiotherapy aiming at treatment verification by Prompt Gamma Timing (PGT) or Prompt Gamma Spectroscopy (PGS). Such treatments are usually structured in distinct beam spots grouped in several mono-energy layers, separated by breaks of few-seconds duration for beam energy switching. This causes a multitude of extreme load steps during delivery of a single treatment field. The paper presents preliminary results of two experiments exploring effects of such load steps on gain and timing of PGT detection units as developed for use in clinical treatments. Multiple units, consisting of scintillation detector (2”×1…2” CeBr3 crystal coupled to Hamamatsu R13089 or R13089-100 photomultiplier) and a plugged-on high-throughput digital spectrometer (U100 by Target Systemelektronik) that also provides well stabilized dynode voltages for the PMT, were exposed to prompt gamma radiation produced by 225 MeV protons in a plexiglass (PMMA) layer, or to bremsstrahlung produced by 13 MeV electrons. Beam shots of 3-5 s duration and varied intensity provoked load steps from background up to the Mcps region and back, and allowed analyzing the immediate and the retarded response of PMT gain and timing. Indeed we observed a noticeable change of the PMT transit time with the detector load, indicating that space charge effects are involved. The scaling of gain turns with the mean anode current supports this hypothesis. As long as the mean anode current is in a ‘reasonable’ operating range, gain and timing drifts of given detectors are well correlated, at least in the stationary case. The observed load-induced timing shifts are as large as 100 ps and would seriously disturb PGT measurements in a treatment, but could eventually be corrected for by tracking the PMT gain. In treatments, this could be done by tracking the ubiquitous 511 keV annihilation peak.
Keywords: Scintillation detector; gamma spectroscopy; photomultiplier; load effect; count rate; gain; timing; stabilization; particle therapy; proton therapy; treatment verification; range verification; prompt gamma
  • Lecture (Conference)
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, 10.-14.11.2018, Sydney, Australia

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27439
Publ.-Id: 27439


Alles Test Kursiv

Rücker, C.ORC
Hier steht der Abstract
  • Erstens
  • Zweitens

Keywords: Keyword1, Keyword2, Keyword3, Keyword4
Related publications
HIM and AFM Data set from first AFM in the HIM test (Id 30718) is previous version of this publication

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27438
Publ.-Id: 27438


Unexpected field-induced dynamics in magnetostrictive microstructured elements under isotropic strain

Finizio, S.; Wintz, S.; Gliga, S.; Kirk, E.; Suszka, A. K.; Wohlhüter, P.; Zeissler, K.; Raabe, J.
We investigated the influence of an isotropic strain on the magnetization dynamics of microstructured magnetostrictive Co40Fe40B20 (CoFeB) elements with time-resolved scanning transmission x-ray microscopy. We observed that the application of isotropic strain leads to changes in the behavior of the microstructured magnetostrictive elements that cannot be fully explained by the volume magnetostriction term, requiring an alternative explanation to the current models used for the interpretation of the influence of mechanical strain on the dynamical processes of magnetostrictive materials.
Keywords: magnetostriction, magnetization dynamics, magnetoelastics

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27437
Publ.-Id: 27437


Flow Measurements in a Liquid Metal Model for Continuous Casting of Steel

Schurmann, D.; Willers, B.; Eckert, S.; Hackl, G.; Nitzl, G.
Poster for the Graduate Student Poster Contest of the AISTech 2018 Conference in Philadelphia, USA.
Related publications
Gyro Nozzle – An innovative Submerged Entry Nozzle Design … (Id 27128) is supplemented by this publication
  • Poster
    AISTech 2018, 07.-10.05.2018, Philadelphia, USA

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27436
Publ.-Id: 27436


Origin and Manipulation of Stable Vortex Ground States in Permalloy Nanotubes

Zimmermann, M.; Gerhard-Meier, T. N.; Dirnberger, F.; Kákay, A.; Decker, M.; Wintz, S.; Finizio, S.; Josten, E.; Raabe, J.; Kronseder, M.; Bougeard, D.; Lindner, J.; Back, C. H.
We present a detailed study on the static magnetic properties of individual permalloy nanotubes (NTs) with hexagonal cross-sections. Anisotropic magnetoresistance (AMR) measurements and scanning transmission X-ray microscopy (STXM) are used to investigate their magnetic ground states and its stability. We find that the magnetization in zero applied magnetic field is in a very stable vortex state. Its origin is attributed to a strong growth-induced anisotropy with easy axis perpendicular to the long axis of the tubes. AMR measurements of individual NTs in combination with micromagnetic simulations allow the determination of the magnitude of the growth-induced anisotropy for different types of NT coatings. We show that the strength of the anisotropy can be controlled by introducing a buffer layer underneath the magnetic layer. The magnetic ground states depend on the external magnetic field history and are directly imaged using STXM. Stable vortex domains can be introduced by external magnetic fields and can be erased by radio-frequency magnetic fields applied at the center of the tubes via a strip line antenna.
Keywords: Nanotube, anisotropic magnetoresistance, permalloy, vortex, ground state

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27435
Publ.-Id: 27435


Electrical Induced Annealing technique for neutron radiation damage on SiPMs

Cordelli, M.; Diociaiuti, E.; Donghia, R.; Ferrari, A.ORC; Miscetti, S.; Muller, S.ORC; Pezzullo, G.; Sarra, I.
The use of Silicon Photo-Multipliers (SiPMs) has become popular in the design of High Energy Physics experimental apparatus with a growing interest for their application in detector area where a significant amount of non-ionising dose is delivered. For these devices, the main effect caused by the neutron flux is a linear increase of the leakage current. In this paper, we present a technique that provides a partial recovery of the neutron damage on SiPMs by means of an Electrical Induced Annealing. Tests were performed on a sample of three SiPM arrays (2 × 3) of 6 mm^2 cells with 50 {\mu}m pixel sizes: two from Hamamatsu and one from SensL. These SiPMs were irradiated up to an integrated neutron flux up to 8 × 10^11 n_{1MeV−eq}/cm2. Our techniques allowed to reduced the leakage current of a factor ranging between 15-20 depending on the overbias used and the SiPM vendor.
Keywords: SiPM, radiation damage, induced recovery

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27434
Publ.-Id: 27434


From mono- to bivalent: improving theranostic properties of target modules for redirection of UniCAR T cells against EGFR-expressing tumor cells in vitro and in vivo

Albert, S.; Arndt, C.; Koristka, S.; Berndt, N.; Bergmann, R.; Feldmann, A.; Schmitz, M.; Pietzsch, J.; Steinbach, J.; Bachmann, M.
CAR-modified T cells show impressive results in clinical trials. However, cytokine release syndrome and “on-target, off-tumor” reactions represent most concerning side effects. To improve the safety of CAR-T cell therapy, we established a switchable CAR platform termed UniCAR system consisting of two components: UniCAR-modified T cells and tumor-specific target modules (TM). For treatment of EGFR+ epithelial tumors, we recently described a monovalent nanobody-based α-EGFR TM, either expressed in bacteria or eukaryotic cells. In spite of the identical primary sequence the eukaryotic showed a reduced killing capability and affinity. Here we describe a novel bivalent α-EGFR-EGFR TM. As expected, the avidity of the bivalent TM is higher than that of its monovalent counterpart. Binding of neither the monovalent α-EGFR TM nor the bivalent α-EGFR-EGFR TM to EGFR effected the EGF-mediated signaling. While the monovalent α-EGFR TM could only mediate the killing of tumor cells expressing high levels of EGFR, the bivalent α-EGFR-EGFR TM could redirect UniCAR T cells to tumor cells expressing low levels of EGFR. According to PET experiments in vivo, the increased avidity of the bivalent α-EGFR-EGFR TM improves the enrichment at the tumor site and its use for PET imaging.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27433
Publ.-Id: 27433


Functional thiols as repair and doping agents of defective MoS2 monolayers

Förster, A.; Gemming, S.; Seifert, G.
Recent experimental and theoretical studies indicate that thiols (R-SH) can be used to repair sulfur vacancy defects in MoS2 monolayers (MLs). This density functional theory (DFT) study investigates how the thiol repair mechanism process can be used to dope MoS2 MLs. Fluorinated thiols as well as amine-containing ones are used to p- and n-dope the MoS2 ML, respectively. It is shown that functional groups are only physisorbed on the repaired MoSS2 surface. This explains the reversible doping with fluorinated thiols.
Keywords: 2D materials, desnsity functional theory, DFT, defects, thiols, repair, doping, tuning

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27430
Publ.-Id: 27430


Absolute Equation-of-State Measurement for Polystyrene from 25 - 60 Mbar Using a Spherically Converging Shock Wave

Döppner, T.; Swift, D. C.; Kritcher, A. L.; Bachmann, B.; Collins, G. W.; Chapman, D. A.; Hawreliak, J.; Kraus, D.; Nilsen, J.; Rothman, S.; Benedict, L. X.; Dewald, E.; Fratanduono, D. E.; Gaffney, J. A.; Glenzer, S. H.; Hamel, S.; Landen, O. L.; Lee, H. J.; Lepape, S.; Ma, T.; Macdonald, M. J.; Macphee, A.; Milathianaki, D.; Millot, M.; Neumayer, P.; Sterne, P. A.; Tommasini, R.; Falcone, R. W.
We have developed an experimental platform for the National Ignition Facility (NIF) that uses spherically converging shock waves for absolute equation of state (EOS) measurements along the principal Hugoniot. In this Letter we present radiographic compression measurements for polystyrene that were taken at shock pressures reaching 60 Mbar (6 TPa). This significantly exceeds previously published results obtained on the Nova laser [Cauble et al., Phys. Rev. Lett. 80, 1248 (1998)] at strongly improved precision, allowing to discriminate between different EOS models. We find excellent agreement with Kohn-Sham Density Functional Theory based molecular dynamics simulations.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27429
Publ.-Id: 27429


Application of the Nirta® Solid irradiation system at the cyclotron Cyclone 18/9® at the HZDR in Leipzig

Franke, K.; Mansel, A.
The cyclotron Cyclone 18/9® (IBA RadioPharma Solutions) at the HZDR in Leipzig serves different research prurposes within the fields of neuroradiopharamceutical research and resource ecology. The latter is utilizing mainly solid targets with two installed Nirta® Solid irradiation systems (IBA RadioPharma Solutions). The wide variety of research projects implies a broad spectrum of required non-conventional radionuclides (Ti-45, V-48, Cr-51, Co-56, Cu-64, Sr-85, Y-86, Y-88, Zr-89, Ag-105, La-135, Ce-139, Au-194). Here we give an overview about the used target designs, irradiation parameters and target processing.
One Nirta® Solid irradiation system (SIS1) is mounted at a 2 m beam transfer line at port 3. Another irradiation system (SIS2) is directly attached to yoke of the cyclotron via a short tube at port 4. In both cases the proton energy is adjusted by the vacuum window and the entrance window of the target. SIS2 is the standard setup. It can hold coin like target disks (Ø 24 mm x 2mm). The maximal effective target size is Ø 12 mm x 1 mm. The SIS2 is used for the irradiation of metal foils, which are crimped inside the disk in between a cover and a backing plate. SIS1 has been modified to operate target capsules with a maximal effective target size of Ø 12 mm x 4 mm. This enables the irradiation of powders and pellets aside its use for metal foils. Both irradiation systems can be pre-loaded with 3 targets for consecutive irradiations. Different target materials are used for irradiation, like metal foils (Sc-45(p,n)Ti-45, Ti-48(p,n)V-48, V-nat(p,n)Cr-51, Ni-64(p,n)Cu-64, Y 89(p,n)Zr-89, Pd-nat(p,n)Ag-105), metal powders (Ti-48(p,n)V-48, Fe-nat(p,n)Co-56, Pt-nat(p,n)Au-194), oxides (La-nat(p,n)Ce-139), carbonates (Sr 86(p,n)Y-86, Sr 88(p,n)Y-88, Ba-135(p,n)La-135) and chlorides (Rb-85(p,n)Sr-85). If required electroplating or pellet pressing is applied for target preparation. After irradiation the targets are transferred out of the vault by a conveyer system. For target processing different techniques, like liquid/liquid extraction, liquid/solid extraction and chromatography are used. Radionuclidical purity is shown by gamma-ray spectrometry.
The presented methods allow us a straightforward and reliable production of n.c.a. radionuclides for our research purposes and an effective recovery of the enriched target materials. Target irradiation, preparation and processing are easily adapted in accordance to the experimental needs.
Keywords: solid target cyclotron
  • Poster
    17th International Workshop on Targetry and Target Chemistry (WTTC17), 27.-31.08.2018, Coimbra, Portugal

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27428
Publ.-Id: 27428


Freisetzung und Rückhaltung von Radionukliden in Systemen mit Zementphasen, Zuschlagstoffen und Tongestein.

Wolter, J.-M.; Philipp, T.; Schmeide, K.; Schymura, S.; Huittinen, N.; Stumpf, T.
Leaching experiments of uranium(VI) and Cm(III) doped calcium-silicate-hydrate (CSH) phases with various calcium to silicon ratios were carried out in NaCl, NaCl/Na2SO4, NaCl/NaHCO3 and NaHCO3 containing solutions to study the time-dependent release of Ca, Si, U and Cm. Potential changes of the U(VI) and Cm(III)-CSH binding induced by leaching were monitored with time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD).
Furthermore, investigations of the Eu(III) sorption on Ca-bentonite in the presence of high ionic strengths and superplasticizer were carried out.
Additionally, the U(VI) binding to the Ca-bentonite surface in the hyper-alkaline pH region was studdied with EXAFS.
Keywords: Cm(III), U(VI), Eu(III), TRLFS, IR, EXAFS, PXRD, CSH, Ca-bentonite, NaCl, Na2SO4, NaHCO3, CaCl2
  • Lecture (others)
    6. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 25.-26.04.2018, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27425
Publ.-Id: 27425


Determination of the thermal cycle during flash lamp annealing without a direct temperature measurement

Rebohle, L.; Neubert, M.; Schumann, T.; Skorupa, W.
Flash lamp annealing (FLA) is a modern annealing technique which, starting from microelectronics, has spread over new application areas like flexible electronics, photovoltaics or thin film deposition. Because of the short annealing time in the range of milliseconds and below, FLA allows the suppression of unwanted processes like diffusion, the annealing of temperature-sensible substrates, and the saving of process time and energy. In addition, it is predestined for roll-to-roll applications. However, the determination of the thermal cycle during FLA is challenging. The existing methods for a direct temperature measurement, mostly based on pyrometry, are elaborate and have to solve the problem to detect thermal radiation against the background of the intense flash light. An alternative way is simulation, but now an extended knowledge about the flash and the material system to be flashed is needed. In this work we describe a methodology to determine the thermal cycle during FLA without the need for a direct temperature measurement. This methodology is based on an optical-thermodynamic simulation and calibration experiments which can be implemented with reasonable effort under certain assumptions. The simulation considers not only the properties of the flash and the sample, but also the reflectivity of the chamber walls. Finally, the pros and cons of this methodology are shortly discussed.
Keywords: flash lamp annealing, intense pulsed light, photonic sintering, temperature simulation

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27424
Publ.-Id: 27424


Genesis of hydrothermal silver-antimony-sulfide veins of the Braunsdorf sector as part of the classic Freiberg silver mining district, Germany

Burisch, M.; Hartmann, A.; Bach, W.; Krolop, P.; Gutzmer, J.
The peripheral regions of the Freiberg vein-type silver mining district comprise several sub districts of which Bräunsdorf was among the richest in terms of Ag grade. 114 t (ca. 3.9 million ounces) of Ag were historically produced from the Neue Hoffnung Gottes Mine near Bräunsdorf. Mining there exploited basically just one single hydrothermal vein, the Neuer Segen Gottes Stehender. The vein infill is marked by a polymetallic sulphide-quartz assemblage (known as kb stage across the Freiberg District) and abundant Ag-Sb-sulphide-carbonate-quartz mineralization, which is limited to the peripheral areas of the Freiberg District. Although Ag-Sb- and Sb-sulphides seem to be spatially and paragenetically closely related to each other, they typically do not occur together in the veins on the scale of meters. Instead, specific zones are dominated by Sb-sulphides without Ag or vice versa. Generally, the abundance of Ag-Sb-sulphides increases with depth.
To develop a sound genetic understanding of polymetallic sulphide-quartz and Ag-Sb-sulphide-carbonate-quartz mineralization in the Bräunsdorf sub district we conducted detailed textural analyses of ore and gangue minerals, fluid inclusion analyses, electron microprobe analyses and thermodynamic computations in order to characterize the ore fluids and ore-forming processes related to the Ag-Sb mineralization. The early-stage polymetallic-sulphide mineralization (stage 1) is related to fluids with low salinities (0.5 - 4 % eq. wt(NaCl)) and formed at temperatures ≥ 300 °C. Microthermometric data related to minerals of the slightly younger Ag-Sb-sulphide assemblage (stage 2) show a range in salinity similar to ore stage 1, but have significantly lower homogenisation temperatures of 280-180 °C. Dissolution textures of previous ore stage 1 minerals and qualitative fluid constraints based on mineral chemistry imply that the composition of the ore fluid changed significantly from Cu-, Pb-, Zn- and As -rich fluids present during ore stage 1 to Ag-Sb-rich fluids prevailing during ore stage 2. Based on fluid inclusion data cooling can be regarded as the major ore-forming process. Reaction path model calculations for cooling of fluids with different initial pH values (5, 6 and 7) reproduce the observed mineral assemblages very well and predict spatial zonation of the Ag-Sb- and Sb-sulphide minerals that are in excellent agreement with field observations. We conclude that Ag-rich zones may well occur below Sb-rich zones in hydrothermal vein-type systems similar to those of the Freiberg District. This relationship may be of potential use for exploration targeting.
Keywords: Freiberg District, stibnite, berthierite, tennantite-terahedrite group minerals, fluid inclusions, reaction path modelling
  • Contribution to proceedings
    GeoBonn, 02.-06.09.2018, Bonn, Deutschland
    Proceedings to GeoBonn
  • Lecture (Conference)
    GeoBonn, 02.-06.09.2018, Bonn, Deutschland
  • Mineralium Deposita 54(2019)2, 263-280
    DOI: 10.1007/s00126-018-0842-0

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27423
Publ.-Id: 27423


RawMatCop: developing skills at the intersection between earth observation and the raw materials community

Andreani, L.; Ibrahim, E.; Marzan, I.; Gloaguen, R.; Pirard, E.; Fernández, J.
The RawMatCop programme was launched in 2017 and aims to develop skills, expertise, demonstrations, and applications of Copernicus data to the raw materials sector. It is co-funded by the European Commission (DG for Internal Market, Industry, Entrepreneurship and SMEs) and the EIT RawMaterials (RawMaterials Academy).
Raw materials have become increasingly important to the European Union's economy, growth, and competitiveness. In this context, the EU aims to facilitate the exchange of best practices among its member states to improve the sustainable and safe supply of raw materials to the EU economy and society. Thus, monitoring of mining activities and environmental impact of waste and residue management are key issues of that strategy. With state-of-the-art spaceborne imagery, Copernicus has a strong potential in contributing to EU’s requirements and expectations.
The aim of RawMatCop is to illustrate the usefulness of Copernicus data through three 'Research & Application Areas’ relevant for the raw materials sector: (1) multi-scale and multi-source exploration, (2) spatiotemporal mapping of dust dispersion around mining sites, (3) monitoring of surface/subsurface deformation.
Multispectral data proves to be an incredible tool for regional scale mapping of surface alterations associated to mineralization or mining activities. One clear advantage of Sentinel-2 data over other sensors is that it has a good coverage of the visible and near infrared portion of the electromagnetic spectrum, which makes it an ideal tool for mapping iron-oxides. The current activities of RawMatCop include mapping alterations and iron features associated to Volcanic Hosted Massive Sulfides (Iberian Pyrite Belt, Spain) as well as mapping the weathering of lateritic profiles and iron-oxide associated to active mining in New Caledonia. For this purpose, several workflow based on downscaling from satellite based to in-situ observations are being tested. Furthermore, RawMatCorp is also contributing to the consistency assessment of mostly open-source atmospheric correction approaches used for Sentinel-2 processing (iCOR, Sen2Cor, MAJA) and the influence of the mining setting on their performance. Moreover, ground deformation is one of the most important hazards related to mining activities, and RawMatCorp is also addressing this topic through monitoring the Riotinto mine (SW Spain). This monitoring utilizes SAR and passive seismic techniques to develop a joint Early Warning System aiming to reduce risks on ground mechanical integrity.
Keywords: Raw materials, Copernicus, Sentinel, multispectral, SAR, exploration, mining
  • Poster
    Luxembourg Earth Observation Day, 19.04.2018, Mondorf-les-Bains, Luxembourg

Permalink: https://www.hzdr.de/publications/Publ-27422
Publ.-Id: 27422


Cognitive correlates of α4β2 nicotinic acetylcholine receptors in mild Alzheimer's dementia

Sabri, O.; Meyer, P. M.; Gräf, S.; Hesse, S.; Wilke, S.; Becker, G.-A.; Rullmann, M.; Patt, M.; Luthardt, J.; Wagenknecht, G.; Hoepping, A.; Smits, R.; Franke, A.; Sattler, B.; Tiepolt, S.; Fischer, S.; Deuther-Conrad, W.; Hegerl, U.; Barthel, H.; Schönknecht, P.; Brust, P.
In early Alzheimer's dementia, there is a need for PET biomarkers of disease progression with close associations to cognitive dysfunction that may aid to predict further cognitive decline and neurodegeneration. Amyloid biomarkers are not suitable for that purpose. The α4β2 nicotinic acetylcholine receptors (α4β2-nAChRs) are widely abundant in the human brain. As neuromodulators they play an important role in cognitive functions such as attention, learning and memory. Post-mortem studies reported lower expression of α4β2-nAChRs in more advanced Alzheimer's dementia. However, there is ongoing controversy whether α4β2-nAChRs are reduced in early Alzheimer's dementia. Therefore, using the recently developed α4β2-nAChR-specific radioligand (-)-18F-flubatine and PET, we aimed to quantify the α4β2-nAChR availability and its relationship to specific cognitive dysfunction in mild Alzheimer's dementia. Fourteen non-smoking patients with mild Alzheimer's dementia, drug-naïve for cholinesterase therapy, were compared with 15 non-smoking healthy controls matched for age, sex and education by applying (-)-18F-flubatine PET together with a neuropsychological test battery. The one-tissue compartment model and Logan plot method with arterial input function were used for kinetic analysis to obtain the total distribution volume (VT) as the primary, and the specific binding part of the distribution volume (VS) as the secondary quantitative outcome measure of α4β2-nAChR availability. VS was determined by using a pseudo-reference region. Correlations between VT within relevant brain regions and Z-scores of five cognitive functions (episodic memory, executive function/working memory, attention, language, visuospatial function) were calculated. VT (and VS) were applied for between-group comparisons. Volume of interest and statistical parametric mapping analyses were carried out. Analyses revealed that in patients with mild Alzheimer's dementia compared to healthy controls, there was significantly lower VT, especially within the hippocampus, fronto-temporal cortices, and basal forebrain, which was similar to comparisons of VS. VT decline in Alzheimer's dementia was associated with distinct domains of impaired cognitive functioning, especially episodic memory and executive function/working memory. Using (-)-18F-flubatine PET in patients with mild Alzheimer's dementia, we show for the first time a cholinergic α4β2-nAChR deficiency mainly present within the basal forebrain-cortical and septohippocampal cholinergic projections and a relationship between lower α4β2-nAChR availability and impairment of distinct cognitive domains, notably episodic memory and executive function/working memory. This shows the potential of (-)-18F-flubatine as PET biomarker of cholinergic α4β2-nAChR dysfunction and specific cognitive decline. Thus, if validated by longitudinal PET studies, (-)-18F-flubatine might become a PET biomarker of progression of neurodegeneration in Alzheimer's dementia.

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27421
Publ.-Id: 27421


Phytotoxicity of tin mine waste and accumulation of involved heavy metals in common buckwheat (Fagopyrum esculentum Moench)

Franzaring, J.; Damsohn, W.; Fangmeier, A.; Schlosser, S.; Kurz, H.; Büttner, P.
Extraction and processing of cassiterite (SnO2) left large tailings with high concentrations of tin, tungsten, molybdenum and lithium. Information on the phytotoxicity of mine waste is important with regard to ecological hazards. Exposure studies help to identify plants useful for the stabilization of waste tips and the phytomining of metals. A greenhouse study was performed using a dilution series of mine waste and four crops, a halophytic and a metallophytic species to derive dose response curves. Based on effective doses for growth reductions, sensitivity increased in the following order: maize > common buckwheat > quinoa > garden bean. Element analyses in different species and compartments of common buckwheat grown in a mixture of standard soil and 25% of the mine waste showed that only low levels of the metals were taken up and that transfer to seed tissues was negligible. As indicated by soil metal levels prior to and after the experiment, only lithium and arsenic proved to be plant available and reached high levels in green tissues while seed levels were low. The experiment confirmed differences in the uptake of metals with regard to elements and species. Common buckwheat is a suited candidate for cultivation on metal polluted soils. © 2018 Taylor & Francis Group, LLC.
Keywords: bioaccumulationdose-response, curvessoil, contaminationsoil, reclamation

Downloads:

  • available with HZDR-Login

Permalink: https://www.hzdr.de/publications/Publ-27420
Publ.-Id: 27420


A wired-AND transistor: Polarity controllable FET with multiple inputs

Simon, M.; Trommer, J.; Liang, B.; Fischer, D.; Baldauf, T.; Khan, M. B.; Heinzig, A.; Knaut, M.; Georgiev, Y. M.; Erbe, A.; Bartha, J. W.; Mikolajick, T.; Weber, W. M.
Introduction: Reconfigurable field effect transistors (RFET) have the ability to toggle polarity between n- and pconductance at runtime [1], [2]. The here presented multiple independent gate (MIG) RFET expands the device functionality by offering additional logical inputs, valuable for e.g. efficient XOR or majority gate implementations [3], [4] or the here originally presented multiplexer circuit. Moreover, for the first time with a top-down RFET approach equal ON-currents are obtained for every configuration while requiring only one supply voltage (VDD).
Working principle: The presented RFET consists of an intrinsic silicon nanowire channel (Fig. 1a). At both ends NiSi₂ is intruded, which has a work function aligned near to the middle of the Si band gap. Each of the resulting Schottky junctions is gated individually (CG1, PG) and additional gates are introduced along the channel (CG2, CG3). The program gate (PG) determines the device’s polarity and has the same potential as the corresponding drain (0 V for hole or VDD for electron conductance). If all control gates (CG1-3) are biased equally, the RFET turns ON Fig. 3a, b, f, g). Whenever any or all CGs are biased equally to the source’s potential, a potential barrier is formed, switching the RFET OFF (Fig. 3c-e, h-j). Hence, the FET works as wired-AND logic gate (Fig. 6a).
The fabrication with CMOS compatible processes and materials is based on a 20 nm silicon-on-insulator (SOI) wafer and requires no doping. The nanowire is formed by a reactive ion etch process [5]. By repeated oxidation and HF etching the wire is further rounded and thinned to ca. 60 nm width and 4 nm height. An omega-shaped gate stack of 5 nm SiO₂, and conductive TiN, Ti and Pt surrounds and radially compresses the wire (Fig. 1b). Finally, nickel is deposited at both ends of the wire and atomically abrupt and flat NiSi₂ Schottky junctions are formed (Fig. 1c).
Performance: The transfer characteristics in Fig. 4 reveal an ON/OFF ratio of five orders of magnitudes and ONcurrents which are equal regardless of the programmed configuration. Additionally, only one supply voltage is needed for gates and drain. Despite its necessity for the use in complementary logic circuits, this symmetry was never achieved before for top-down fabricated RFETs. For NiSi₂ and Si, the Schottky barrier height is slightly lower for holes than for electrons leading to initially asymmetric ON-currents. However, by the influence of the omega gate stressor on the band structure the electron and hole injection through the Schottky barrier can be equalized as demonstrated in Fig. 2 [6]. Fig. 4 further shows that the minimum subthreshold swing SS and threshold voltage are lower for the switching with CG2 and CG3 than for all combinations including CG1. This is because CG1 directly controls the inlet at the Schottky junction whereas the other gates only build a conventional channel barrier. Having two efficiently switching gates (CG2+3), as demonstrated for the first time, thus improves the efficiency of RFETs.
From Fig. 5 it can be seen that the gates’ voltage determines the shape of the output characteristics. Hole dominated currents rise with retard because the injecting Schottky barrier is still non-transparent for tunneling at VD = 0 V.
Applications of the device reach from camouflage circuits for hardware secure authentication [7] and fine-grained FPGAs [8] over area and power-delay optimized circuits [3], [4] to novel logic synthesis based on majority-inverter graphs [9]. As a graspable and novel example, the presented device can serve as transmission gate (Fig. 6b) in a multiplexer (MUX) (Fig. 6c, d), which requires program gates at both in- and output. An n-bit MUX can be reduced by every second stage, thus only (2^[n+1]− 2^i)/3 transmission gates are required, with i=1 for odd and i=2 for even numbers of n (with classical CMOS: 2^[n+1] − 2). For a 4-bit MUX this results in altogether 30% less transistors when considering also the select and program signal inverters and the reduced buffer needs (Fig. 6e). Eventually, more gates per transistor can further reduce the transistor count, e.g. for a 5-gate RFET in a 6-bit MUX by even 42%.
[1] A. Heinzig et al., Nano Lett., vol. 12, no. 1, pp. 119–124, (2012).
[2] M. D. Marchi et al., in Electron Devices Meeting (IEDM), 2012 IEEE International, pp. 8.4.1–8.4.4, (2012).
[3] P.-E. Gaillardon et al., in Test Symposium (LATS), 2016 17th Latin-American, pp. 195–200, (2016).
[4] J. Trommer et al., in 2016 Design, Automation Test in Europe Conference Exhibition (DATE), pp. 169–174, (2016).
[5] M. Simon et al., IEEE Trans. Nanotechnol., vol. 16, no. 5, pp. 812–819, (2017).
[6] T. Baldauf et al., Solid-State Electron., vol. 128, pp. 148–154, (2017).
[7] Y. Bi et al., in 2014 IEEE 23rd Asian Test Symposium, pp. 342–347, (2014).
[8] P. E. Gaillardon et al., IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 23, no. 10, pp. 2187–2197, (2015).
[9] L. Amaru et al., Proc. IEEE, vol. 103, no. 11, pp. 2168–2195, (2015).
  • Contribution to proceedings
    76th Device Research Conference (DRC), 2018, 24.-27.06.2018, Santa Barbara, USA
    Conference Digest, DRC, 8442159

Permalink: https://www.hzdr.de/publications/Publ-27419
Publ.-Id: 27419


Controlled Nickel Silicidation of Silicon Nanowires for Fabrication of Reconfigurable Field Effect Transistors

Khan, M. B.; Deb, D.; Georgiev, Y. M.; Prucnal, S.; Voelskow, M.; Erbe, A.
Physical scaling down of field effect transistors (FET) is reaching its end. To meet the consistent demand for faster, smaller and energy efficient transistors, new concepts which include new materials, new architectures, new computation principles and enhanced functionality are under research. Focus of this work is to fabricate devices with enhanced functionality, the so called reconfigurable FET (RFET) which can be configured as p- or n-channel FET. These FETs are realized by fabricating silicon nanowires (SiNWs) on Si on insulator (SOI) substrates. These NWs are subsequently nickel silicided at both ends to form Si-NiSi2-Si Schottky junctions. Control over silicide length is important to scale Si channel and to have symmetric contacts on both sides of nanowires. Focus of our recent work is achieve this control over silicidation by using flash lamp annealing (FLA). Comparison between silicidation using flash lamp annealing (FLA) and rapid thermal annealing (FLA) along with the resulting electrical characteristics of these devices will be presented at the conference.
  • Poster
    DPG-Frühjahrstagung 2018, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27418
Publ.-Id: 27418


Profiling of RT-PICLS Code

Kelling, J.; Juckeland, G.ORC

It was observed, that the RT-PICLS code ran by FWKT on the hypnos cluster was producing an unusual amount of system load, according to Ganglia metrics. Since this may point to an IO-problem in the code, this code was analyzed more closely.

RT-PICLS was run with additionally provided input data on 64 CPU cores (AMD Opteron) in a single node of the hypnos cluster. Score-P 4.0 with IO-tracing support was used for profiling and tracing of the application. A developer version of Vampir 9.2 [3] enabled graphical analysis of the traces.

Different file systems were evaluated for storing the output:

  • bigdata: the high-performance file system of the cluster based on GPFS.
  • nfs: a loop-mounted EXT4 image mounted to the current compute node via NFS.
  • scr: the local scratch file-system of the compute node.
  • tmpfs: a virtual filesystem, physically located in the main memory of the compute node.

The trace files that were used to compile the referenced report are collected in this upload.

Keywords: Scorep; Vampir; Tracing; Profiling
Related publications
Profiling of RT-PICLS Code (Id 25474) is a supplement to this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-04-25
    DOI: 10.14278/rodare.15
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-27417
Publ.-Id: 27417


Time-delayed multiple shocks

Kraus, D.
Time-delayed multiple shocks
  • Invited lecture (Conferences)
    Workshop on Dynamic Laser Compression Experiments at the HED instrument at European XFEL, 12.-14.09.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27416
Publ.-Id: 27416


Structural transitions in shock-compressed (hydro) carbon(s)

Kraus, D.
Structural transitions in shock-compressed (hydro) carbon(s)
  • Invited lecture (Conferences)
    Workshop on High Pressure, Planetary and Plasma Physics, 14.-16.09.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27415
Publ.-Id: 27415


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266] [267] [268] [269] [270] [271] [272] [273] [274] [275] [276] [277]