Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35819 Publications

Shape change of biogenic elemental selenium nanomaterials decreases their colloidal stability

Jain, R.; Jordan, N.; Tsushima, S.; Hübner, R.; Weiss, S.; Lens, P.

Selenium is an important element for technology and dietary supplements but it is toxic at slightly higher concentration. Thus, its removal from the wastewaters is important. Microbial reduction of selenium oxyanions in thermophilic bioreactor (55 oC) removed higher selenium when compared to the control mesophilic bioreactor (30 oC). This study demonstrated that the better performance of the thermophilic bioreactor was due to the better settling properties of biogenic elemental selenium nanorods (BioSe-Nanorods) produced in thermophilic conditions compared to biogenic elemental selenium nanospheres (BioSe-Nanospheres) produced in mesophilic conditions. The BioSe-Nanorods were less colloidally stable than the extracellular polymeric substances (EPS) capped BioSe-Nanospheres as demonstrated by the former's lesser negative zeta potential values when exposed to elevated concentrations of NaCl and CaCl2 as well as better settling in different lake waters. The lower colloidal stability was due to a lesser negative surface charge density of BioSe-Nanorods compared to BioSe-Nanospheres. This study also argued that the EPS were the corona of BioSe-Nanorods as well. Further, this study observed that the formation of BioSe-Nanorods proceeds via BioSe-Nanospheres. This study demonstrates the importance of the shape of nanoparticles in determining their bioremediation effectiveness and the fate in the environment.

Keywords: Surface charge density; ζ-potential; microbial reduction; selenium nanorods; DFT


Publ.-Id: 24406

Interatomic potential to study the formation of NiCr clusters in high Cr ferritic steels

Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.

Under irradiation NiSiPCr clusters are formed in high-Cr ferritic martensitic steels as well as in FeCr model alloys. In the literature little is known about the origin and contribution to the hardening of these clusters. In this work we performed density functional theory (DFT) calculations to study the stability of small substitutional NiCr-vacancy clusters and interstitial configurations in bcc Fe. Based on DFT data and experimental considerations a ternary potential for the ferritic FeNiCr system was developed. The potential was applied to study the thermodynamic stability of NiCr clusters by means of Metropolis Monte Carlo (MMC) simulations. The results of our simulations show that Cr and Ni precipitate as separate fractions and suggest only a limited synergetic effect between Ni and Cr. Therefore our results suggest that the NiCrSiP clusters observed in experiments must be the result of other mechanisms than the synergy of Cr and Ni at thermal equilibrium.

Keywords: interatomic potential; Fe-Cr-Ni alloys; precipitates; clusters

Publ.-Id: 24405

Terahertz free-electron laser spectroscopy of excitons in III-V semiconductor quantum wells and single quantum dots

Schneider, H.; Stephan, D. R.; Zybell, S.; Winnerl, S.; Bhattacharyya, J.; Eßer, F.; Helm, M.

Using intense, spectrally narrow terahertz pulses from the free-electron laser facility FELBE in Dresden, Germany, we have investigated exciton population dynamics in III-V QWs and single quantum dots. To this end, carriers are optically injected by picosecond near-infrared pulses to populate the lowest excitonic level. Using narrowband terahertz pulses, excitons are resonantly excited into higher levels. Time-dependent photoluminescence measurements based on a streak camera system and on time-correlated photon counting, respectively, then allow us to study the transient population of dipole-allowed higher exciton levels and to access the relaxation dynamics.

Keywords: excitons; GaAs; quantum well; quantum dot; terahertz; free-electron laser; time-resolved photoluminescence

  • Invited lecture (Conferences)
    SPIE Photonics Asia, Symposium on "Infrared, Millimeter Wave, and Terahertz Technologies", 12.-14.10.2016, Beijing, China

Publ.-Id: 24404

Terahertz free-electron laser spectroscopy of semiconductor nanostructures

Schneider, H.

This talk reviews recent spectroscopic studies on semiconductor nanostructures using the THz free-electron laser FELBE. Its intense, quasi-continuous, nearly transform-limited ps pulses provide unique research opportunities to advance THz science.

Keywords: spectroscopy; terahertz; free-electron laser

  • Invited lecture (Conferences)
    The 8th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2016), 10.-12.10.2016, Chongqing, China

Publ.-Id: 24403

MHD sloshing instability in liquid metal batteries

Horstmann, G. M.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) are discussed today as a cheap grid scale energy storage, as required for the deployment of fluctuating renewable energies. LMBs incorporate stratified three-layer fluid systems consisting of two liquid metal electrodes separated by a thin molten salt electrolyte. Due to the high electrical conductivities of the liquid metals, LMBs are highly susceptible for becoming unstable by MHD interactions of magnetic fields induced by internal and external currents. Besides the Tayler instability and the electrovortex instability, the so-called sloshing instability, also known as the metal pad roll instability in aluminum reduction cells, was identified as a key instability mechanism capable to cause short-circuits. Dimensionless stability parameters derived from inviscid two-layer systems can predict the onsets for sloshing and short-circuits with some success for a limited parameter range, but the two-layer description is far from perfect. To quantify the two-layer limitations, a three-layer dispersion relation was derived and deviations from the two-layer system were discussed. On this basis it is planned to extract three-layer stability criteria additionally including viscous damping to predict instability onsets in direct dependence of the geometrical parameters and material properties of LMBs. Further to this, three-layer experiments are under development aiming to measure the interaction and stability of interfacial waves using Doppler Ultrasound Velocimetry (DOP) and Magnetic Field Tomography (MFT) for checking the validity of different stability criteria.

Keywords: MHD; Sloshing; Liquid Metal Battery

  • Poster
    MHD Days 2016, 30.11.-02.12.2016, Göttingen, Deutschland

Publ.-Id: 24402

Long-range interactions in the effective low energy Hamiltonian of Sr2IrO4: a core level resonant inelastic x-ray scattering study

Agrestini, S.; Kuo, C.-Y.; Moretti Sala, M.; Hu, Z.; Kasinathan, D.; Ko, K.-T.; Glatzel, P.; Rossi, M.; Cafun, J.-D.; Kvashnina, K. O.; Matsumoto, A.; Takayama, T.; Takagi, H.; Tjeng, L. H.; Haverkort, M. W.

We have investigated the electronic structure of Sr2IrO4 using core level resonant inelastic x-ray scattering. The experimental spectra can be well reproduced using ab initio density functional theory based multiplet ligand field theory calculations, thereby validating these calculations. We found that the low-energy, effective Ir t2g orbitals are practically degenerate in energy. We uncovered that covalency in Sr2IrO4, and generally in iridates, is very large with substantial oxygen ligand hole character in the Ir t2g Wannier orbitals. This has far reaching consequences, not only are onsite crystal-field energies determined by the long range crystal-structure, more significantly, magnetic exchange interactions will have long range distance dependent anisotropies in the spin direction. These findings set constraints and show pathways for the design of d5 materials that can host compass like magnetic interactions.

Publ.-Id: 24401

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Ablyazimov, T.; Abuhoza, A.; Adak, R. P.; Adamczyk, M.; Agarwal, K.; Aggarwal, M. M.; Ahammed, Z.; Ahmad, F.; Ahmad, N.; Ahmad, S.; Akindinov, A.; Akishin, P.; Akishina, E.; Akishina, T.; Akishina, V.; Akram, A.; Al-Turany, M.; Alekseev, I.; Alexandrov, E.; Alexandrov, I.; Amar-Youcef, S.; Anđelić, M.; Andreeva, O.; Andrei, C.; Andronic, A.; Anisimov, Y.; Appelshäuser, H.; Argintaru, D.; Atkin, E.; Avdeev, S.; Averbeck, R.; Azmi, M. D.; Baban, V.; Bach, M.; Badura, E.; Bähr, S.; Balog, T.; Balzer, M.; Bao, E.; Baranova, N.; Barczyk, T.; Bartoş, D.; Bashir, S.; Baszczyk, M.; Batenkov, O.; Baublis, V.; Baznat, M.; Becker, J.; Becker, K.-H.; Belogurov, S.; Belyakov, D.; Bendarouach, J.; Berceanu, I.; Bercuci, A.; Berdnikov, A.; Berdnikov, Y.; Berendes, R.; Berezin, G.; Bergmann, C.; Bertini, D.; Bertini, O.; Beşliu, C.; Bezshyyko, O.; Bhaduri, P. P.; Bhasin, A.; Bhati, A. K.; Bhattacharjee, B.; Bhattacharyya, A.; Bhattacharyya, T. K.; Biswas, S.; Blank, T.; Blau, D.; Blinov, V.; Blume, C.; Bocharov, Y.; Book, J.; Breitner, T.; Brüning, U.; Brzychczyk, J.; Bubak, A.; Büsching, H.; Bus, T.; Butuzov, V.; Bychkov, A.; Byszuk, A.; Cai, X.; Cálin, M.; Cao, P.; Caragheorgheopol, G.; Carević, I.; Cătănescu, V.; Chakrabarti, A.; Chattopadhyay, S.; Chaus, A.; Chen, H.; Chen, L.; Chen, J.; Chepurnov, V.; Cherif, H.; Chernogorov, A.; Ciobanu, M. I.; Claus, G.; Constantin, F.; Csanád, M.; D'Ascenzo, N.; Das, S.; Das, S.; de Cuveland, J.; Debnath, B.; Dementiev, D.; Deng, W.; Deng, C.; Deppe, H.; Deppner, I.; Derenovskaya, O.; Deveaux, C. A.; Deveaux, M.; Dey, K.; Dey, M.; Dillenseger, P.; Dobyrn, V.; Doering, D.; Dong, S.; Dorokhov, A.; Dreschmann, M.; Drozd, A.; Dubey, A. K.; Dubnichka, S.; Dubnichkova, Z.; Dürr, M.; Dutka, L.; Dželalija, M.; Elsha, V. V.; Emschermann, D.; Engel, H.; Eremin, V.; Eşanu, T.; Eschke, J.; Eschweiler, D.; Fan, H.; Fan, X.; Farooq, M.; Fateev, O.; Feng, S.; Figuli, S. P. D.; Filozova, I.; Finogeev, D.; Fischer, P.; Flemming, H.; Förtsch, J.; Frankenfeld, U.; Friese, V.; Friske, E.; Fröhlich, I.; Frühauf, J.; Gajda, J.; Galatyuk, T.; Gangopadhyay, G.; García Chávez, C.; Gebelein, J.; Ghosh, P.; Ghosh, S. K.; Gläßel, S.; Goffe, M.; Golinka-Bezshyyko, L.; Golovatyuk, V.; Golovnya, S.; Golovtsov, V.; Golubeva, M.; Golubkov, D.; Gómez Ramírez, A.; Gorbunov, S.; Gorokhov, S.; Gottschalk, D.; Gryboś, P.; Grzeszczuk, A.; Guber, F.; Gudima, K.; Gumiński, M.; Gupta, A.; Gusakov, Y.; Han, D.; Hartmann, H.; He, S.; Hehner, J.; Heine, N.; Herghelegiu, A.; Herrmann, N.; Heß, B.; Heuser, J. M.; Himmi, A.; Höhne, C.; Holzmann, R.; Hu, D.; Huang, G.; Huang, X.; Hutter, D.; Ierusalimov, A.; Ilgenfritz, E.-M.; Irfan, M.; Ivanischev, D.; Ivanov, M.; Ivanov, P.; Ivanov, V.; Ivanov, V.; Ivanov, V.; Ivashkin, A.; Jaaskelainen, K.; Jahan, H.; Jain, V.; Jakovlev, V.; Janson, T.; Jiang, D.; Jipa, A.; Kadenko, I.; Kähler, P.; Kämpfer, B.; Kalinin, V.; Kallunkathariyil, J.; Kampert, K.-H.; Kaptur, E.; Karabowicz, R.; Karavichev, O.; Karavicheva, T.; Karmanov, D.; Karnaukhov, V.; Karpechev, E.; Kasiński, K.; Kasprowicz, G.; Kaur, M.; Kazantsev, A.; Kebschull, U.; Kekelidze, G.; Khan, M. M.; Khan, S. A.; Khanzadeev, A.; Khasanov, F.; Khvorostukhin, A.; Kirakosyan, V.; Kirejczyk, M.; Kiryakov, A.; Kiš, M.; Kisel, I.; Kisel, P.; Kiselev, S.; Kiss, T.; Klaus, P.; Kłeczek, R.; Klein-Bösing, C.; Kleipa, V.; Klochkov, V.; Kmon, P.; Koch, K.; Kochenda, L.; Koczoń, P.; Koenig, W.; Kohn, M.; Kolb, B. W.; Kolosova, A.; Komkov, B.; Korolev, M.; Korolko, I.; Kotte, R.; Kovalchuk, A.; Kowalski, S.; Koziel, M.; Kozlov, G.; Kozlov, V.; Kramarenko, V.; Kravtsov, P.; Krebs, E.; Kreidl, C.; Kres, I.; Kresan, D.; Kretschmar, G.; Krieger, M.; Kryanev, A. V.; Kryshen, E.; Kuc, M.; Kucewicz, W.; Kucher, V.; Kudin, L.; Kugler, A.; Kumar, A.; Kumar, A.; Kumar, L.; Kunkel, J.; Kurepin, A.; Kurepin, N.; Kurilkin, A.; Kurilkin, P.; Kushpil, V.; Kuznetsov, S.; Kyva, V.; Ladygin, V.; Lara, C.; Larionov, P.; Laso García, A.; Lavrik, E.; Lazanu, I.; Lebedev, A.; Lebedev, S.; Lebedeva, E.; Lehnert, J.; Lehrbach, J.; Leifels, Y.; Lemke, F.; Li, C.; Li, Q.; Li, X.; Li, Y.; Lindenstruth, V.; Linnik, B.; Liu, F.; Lobanov, I.; Lobanova, E.; Löchner, S.; Loizeau, P.-A.; Lone, S. A.; Lucio Martínez, J. A.; Luo, X.; Lymanets, A.; Lyu, P.; Maevskaya, A.; Mahajan, S.; Mahapatra, D. P.; Mahmoud, T.; Maj, P.; Majka, Z.; Malakhov, A.; Malankin, E.; Malkevich, D.; Malyatina, O.; Malygina, H.; Mandal, M. M.; Mandal, S.; Manko, V.; Manz, S.; Marin Garcia, A. M.; Markert, J.; Masciocchi, S.; Matulewicz, T.; Meder, L.; Merkin, M.; Mialkovski, V.; Michel, J.; Miftakhov, N.; Mik, L.; Mikhailov, K.; Mikhaylov, V.; Milanović, B.; Militsija, V.; Miskowiec, D.; Momot, I.; Morhardt, T.; Morozov, S.; Müller, W. F. J.; Müntz, C.; Mukherjee, S.; Muńoz Castillo, C. E.; Murin, Y.; Najman, R.; Nandi, C.; Nandy, E.; Naumann, L.; Nayak, T.; Nedosekin, A.; Negi, V. S.; Niebur, W.; Nikulin, V.; Normanov, D.; Oancea, A.; Oh, K.; Onishchuk, Y.; Ososkov, G.; Otfinowski, P.; Ovcharenko, E.; Pal, S.; Panasenko, I.; Panda, N. R.; Parzhitskiy, S.; Patel, V.; Pauly, C.; Penschuck, M.; Peshekhonov, D.; Peshekhonov, V.; Petráček, V.; Petri, M.; Petriş, M.; Petrovici, A.; Petrovici, M.; Petrovskiy, A.; Petukhov, O.; Pfeifer, D.; Piasecki, K.; Pieper, J.; Pietraszko, J.; Płaneta, R.; Plotnikov, V.; Plujko, V.; Pluta, J.; Pop, A.; Pospisil, V.; Poźniak, K.; Prakash, A.; Prasad, S. K.; Prokudin, M.; Pshenichnov, I.; Pugach, M.; Pugatch, V.; Querchfeld, S.; Rabtsun, S.; Radulescu, L.; Raha, S.; Rami, F.; Raniwala, R.; Raniwala, S.; Raportirenko, A.; Rautenberg, J.; Rauza, J.; Ray, R.; Razin, S.; Reichelt, P.; Reinecke, S.; Reinefeld, A.; Reshetin, A.; Ristea, C.; Ristea, O.; Rodriguez Rodriguez, A.; Roether, F.; Romaniuk, R.; Rost, A.; Rostchin, E.; Rostovtseva, I.; Roy, A.; Roy, A.; Rożynek, J.; Ryabov, Y.; Sadovsky, A.; Sahoo, R.; Sahu, P. K.; Sahu, S. K.; Saini, J.; Samanta, S.; Sambyal, S. S.; Samsonov, V.; Sánchez Rosado, J.; Sander, O.; Sarangi, S.; Satława, T.; Sau, S.; Saveliev, V.; Schatral, S.; Schiaua, C.; Schintke, F.; Schmidt, C. J.; Schmidt, H. R.; Schmidt, K.; Scholten, J.; Schweda, K.; Seck, F.; Seddiki, S.; Selyuzhenkov, I.; Semennikov, A.; Senger, A.; Senger, P.; Shabanov, A.; Shabunov, A.; Shao, M.; Sheremetiev, A. D.; Shi, S.; Shumeiko, N.; Shumikhin, V.; Sibiryak, I.; Sikora, B.; Simakov, A.; Simon, C.; Simons, C.; Singaraju, R. N.; Singh, A. K.; Singh, B. K.; Singh, C. P.; Singhal, V.; Singla, M.; Sitzmann, P.; Siwek-Wilczyńska, K.; Skwira-Chalot, I.; Som, I.; Song, G.; Song, J.; Sosin, Z.; Soyk, D.; Staszel, P.; Strikhanov, M.; Strohauer, S.; Stroth, J.; Sturm, C.; Sultanov, R.; Sun, Y.; Svirida, D.; Svoboda, O.; Szabó, A.; Szczygieł, R.; Talukdar, R.; Tang, Z.; Tanha, M.; Tarasiuk, J.; Tarassenkova, O.; Târzilă, M.-G.; Teklishyn, M.; Tischler, T.; Tlustý, P.; Tölyhi, T.; Toia, A.; Topil'Skaya, N.; Träger, M.; Tripathy, S.; Tsakov, I.; Tsyupa, Y.; Turowiecki, A.; Tuturas, N. G.; Uhlig, F.; Usenko, E.; Valin, I.; Varga, D.; Vassiliev, I.; Vasylyev, O.; Verbitskaya, E.; Verhoeven, W.; Veshikov, A.; Visinka, R.; Viyogi, Y. P.; Volkov, S.; Volochniuk, A.; Vorobiev, A.; Voronin, A.; Voronin, A.; Vovchenko, V.; Vznuzdaev, M.; Wang, D.; Wang, X.-W.; Wang, Y.; Wang, Y.; Weber, M.; Wendisch, C.; Wessels, J. P.; Wiebusch, M.; Wiechula, J.; Wielanek, D.; Wieloch, A.; Wilms, A.; Winckler, N.; Winter, M.; Wiśniewski, K.; Wolf, G.; Won, S.; Wu, K.-J.; Wüstenfeld, J.; Xiang, C.; Xu, N.; Yang, J.; Yang, R.; Yin, Z.; Yoo, I.-K.; Yuldashev, B.; Yushmanov, I.; Zabołotny, W.; Zaitsev, Y.; Zamiatin, N. I.; Zanevsky, Y.; Zhalov, M.; Zhang, Y.; Zhang, Y.; Zhao, L.; Zheng, J.; Zheng, S.; Zhou, D.; Zhou, J.; Zhu, X.; Zinchenko, A.; Zipper, W.; Zrelov, M.; Zryuev, V.; Zumbruch, P.; Zyzak, M.

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.

Publ.-Id: 24400

Nukleare Transmutation: Moderne Alchemie oder Chance für die Kernenergie?

Kögler, T.

Mit Beschluss des Bundestages vom 30. Juni 2011 wird Deutschland bis 2022 seine Kernkraftwerke schrittweise stilllegen. Mit der Energiewende soll bis 2050 ein Großteil der benötigten Energie aus regenerativen Trägern bereitgestellt werden. Bis dahin ist es ein langer und schwieriger Weg, auf welchem noch zahlreiche technologische Probleme gelöst werden müssen.
Im Gegensatz zur Bundesrepublik setzen viele Länder (z.B.: China) weiterhin auf die Kernenergie. Ein Grund dafür: neuartige Reaktorkonzepte (Gen IV) machen diese sicherer und effizienter, vor allem stellen sie Lösungen zur Beseitigung des nuklearen Abfalls vor.
Dieser Vortrag beschäftigt sich mit ausgewählten Aspekten der Energiewende, erläutert die physikalischen Prozesse die zur Erzeugung oder Vernichtung des hochradioaktiven Kernabfalls führen und gibt einen Überblick über zukünftige Reaktortechnologien und Transmutationsanlagen.

Keywords: Nukleare Transmutation; Generation IV Reaktoren; Energiewende; Beschleunigergetriebene Systeme

  • Lecture (others)
    Energie, Resourcen, Umwelt, 06.03.2017, Löbau, Deutschland
  • Lecture (others)
    Löbauer Umweltforum, 18.02.2017, Löbau, Deutschland

Publ.-Id: 24399

Terahertz spectroscopy of semiconductor nanostructures with a free-electron laser

Schneider, H.

In this talk I will present recent experimental investigations on carrier dynamics in graphene studied via pump-probe spectroscopy, on time-resolved photoluminescence dynamics of single InAs/GaAs quantum dots under pulsed inter-sublevel excitation, and on sub-diffraction limited terahertz imaging by a GaAs-based superlens studied by scattering near-field optical microscopy. The experiments have been carried out using the mid-infrared/terahertz free-electron laser facility FELBE in Dresden, Germany.

Keywords: free-electron laser; terahertz; semiconductor nanostructures

  • Lecture (others)
    Seminar, Ecole Normale Superieure, Laboratoire Pierre Aigrain, 23.09.2016, Paris, France
  • Lecture (others)
    Seminar, Chinese Academy of Engineering Physics, 18.10.2016, Chengdu, China

Publ.-Id: 24398

Terahertz-induced inter-sublevel dynamics of single InAs/GaAs quantum dots studied by micro-photoluminescence

Stephan, D.; Bhattacharyya, J.; Huo, Y. H.; Schmidt, O. G.; Rastelli, A.; Helm, M.; Schneider, H.

We explore the transient response of single self-assembled InAs/GaAs quantum dots (QD) to narrow-band terahertz (THz) pulses produced by the free-electron laser FELBE at HZDR. The THz excitation is tuned to the electron inter-sublevel s-to-p transition. For the QDs under study, this transition occurs in the range 13-20 meV because of in-situ intermixing. The THz pulse is applied at a time delay of about 0.7 ns after interband excitation. The dynamics of electron excitation and relaxation between QD sublevels is revealed by time-resolved micro-photoluminescence (PL) measurements performed on individual QDs.

Keywords: quantum dot; photoluminescence; terahertz; free-electron laser

  • Lecture (Conference)
    33rd International Conference on the Physics of Semiconductors (ICPS 2016), 31.07.-05.08.2016, Beijing, China

Publ.-Id: 24397

Terahertz pump-terahertz probe system at Novosibirsk free electron laser: commissioning and results of first experiments

Choporova, Y. Y.; Gerasimov, V. V.; Hübers, H.-W.; Knyazev, B. A.; Kulipanov, G. N.; Ovchar, V. K.; Pavelyev, V. S.; Zhukavin, R. K.; Schneider, H.; Vinokurov, N. A.; Volodkin, B. O.; Shastin, V. N.

A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser facility. Monochromatic laser radiation with a bandwidth of about 1% can be tuned within the spectral ranges of 90 - 240 and 30 - 90 μm. The laser emits radiation as a continuous stream of 100-ps pulses with a repetition rate of 5.6 MHz. The average radiation power can reach 100 W. The temperature of samples located in a helium cryostat can be varied from 2 up to 325 K. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in a germanium crystal will be presented.

Keywords: free-electron laser; pump-probe

  • Lecture (Conference)
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark
  • Contribution to proceedings
    41st International Conference on Infrared, Millimeter and Terahertz Waves, 25.-30.09.2016, Kopenhagen, Denmark, 1-2
    DOI: 10.1109/IRMMW-THz.2016.7758465

Publ.-Id: 24396

First terahertz-range experiments on pump-probe setup at Novosibirsk free electron laser

Choporova, Y. Y.; Gerasimov, V. V.; Knyazev, B. A.; Sergeev, S. M.; Shevchenko, O. A.; Zhukavin, R. K.; Abrosimov, N. V.; Kovalevsky, K. A.; Ovchar, V. K.; Hübers, H.-W.; Kulipanov, G. N.; Shastin, V. N.; Schneider, H.; Vinokurov, N. A.

A single-color pump-probe system has been commissioned at the Novosibirsk free electron laser. The laser emits a tunable monochromatic terahertz radiation. To prove the proper system operation, we investigated the time-resolved absorption of a sample of n-type germanium doped with antimony, which was previously investigated at the FELBE facility, in the temperature range from 5 to 50 K. The measured relaxation time amounted to about 1.7 ns, which agreed with the results obtained at FELBE. The results of pump-probe measurements of non-equilibrium dynamics of hot electrons in a germanium crystal at cryogenic temperatures are presented for wavelengths of 105, 146 and 150 μm.

Keywords: free-electron laser; pump-probe

  • Lecture (Conference)
    2016 International Conference "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2016), 04.-07.07.2016, Novosibirsk, Russia
  • Open Access Logo Contribution to proceedings
    2016 International Conference "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2016), 04.-07.07.2016, Novosibirsk, Russia
    Physics Procedia, Volume 84, Pages 1-434 (2016) Proceedings of the Int. Conf. "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2016) Edited by N. A. Vinokurov and B. A. Knyazev: Elsevier, 1875-3892, 152
    DOI: 10.1016/j.phpro.2016.11.027

Publ.-Id: 24395

A light-weight compact proton gantry design with a novel dose delivery system for broad-energetic laser-accelerated beams

Masood, U.; Cowan, T. E.; Enghardt, W.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Wilkens, J. J.; Pawelke, J.

Proton beams provide superior dose-conformity in radiation therapy. However, the large sizes and costs limit the widespread use of proton therapy (PT). The recent progress in proton acceleration via high-power laser systems has made it a compelling alternative to conventional accelerators, as it could potentially reduce the overall size and cost of the PT facilities. However, the laser-accelerated beams exhibit different characteristics than conventionally accelerated beams, i.e. very intense proton bunches with large divergences and broad-energy spectra. For the application of laser-driven beams in PT, new solutions for beam transport, such as beam capture, integrated energy selection, beam shaping and delivery system are required due to due to the specific beam parameters. The generation of these beams are limited by the low repetition rate of high-power lasers and this limitation would require alternative solutions for tumour irradiation which can efficiently utilize the available high proton fluence and broad-energy spectra per proton bunch to keep treatment times short. This demands new dose delivery system and irradiation field formation schemes. In this paper, we present a multi-functional light-weight and compact proton gantry design based on ironless pulsed high-field magnets for laser-driven sources. This achromatic design includes an improved beam capturing and energy selection system, with a novel beam shaping and dose delivery system, so-called ELPIS. ELPIS system utilizes magnetic fields, instead of physical scatterers, for broadening the spot-size of broadenergetic beams while capable of simultaneously scanning them in lateral directions. To investigate the clinical feasibility of this gantry design, we conducted a treatment planning study with a 3D treatment planning system augmented for the pulsed beams with optimizable broad-energetic widths and selectable beam spot sizes. High quality treatment plans could be achieved with such unconventional beam parameters, deliverable via the presented gantry and ELPIS dose delivery system. The conventional PT gantries are huge and require large space for the gantry to rotate the beam around the patient, which could be reduced up to 4 times with the presented pulse powered gantry system. With the development of next generation high-power laser systems, with petawatt laser power, necessary to reach proton energies required for therapy application, it could be possible to reduce the footprint of the PT facilities, without compromising on clinical standards.


Publ.-Id: 24394

Characterization of anisotropically shaped silver nanoparticle arrays via spectroscopic ellipsometry supported by numerical optical modeling

Gkogkou, D.; Shaykhutdinov, T.; Oates, T. W. H.; Gernert, U.; Schreiber, B.; Facsko, S.; Hildebrandt, P.; Weidinger, I. M.; Esser, N.; Hinrichs, K.

The present investigation aims to study the optical response of anisotropic Ag nanoparticle arrays deposited on rippled silicon substrates by performing a qualitative comparison between experimental and theoretical results. Spectroscopic ellipsometry was used along with numerical calculations using finite-difference time-domain (FDTD) method and rigorous coupled wave analysis (RCWA) to reveal trends in the optical and geometrical properties of the nanoparticle array. Ellipsometric data show two resonances, in the orthogonal x and y directions, that originate from localized plasmon resonances as demonstrated by the calculated near-fields from FDTD calculations. The far-field calculations by RCWA point to decoupled resonances in x direction and possible coupling effects in y direction, corresponding to the short and long axis of the anisotropic nanoparticles, respectively.

Keywords: Anisotropy; FDTD; Nanostructure characterization; Optical modeling; RCWA; Spectroscopic ellipsometry

Publ.-Id: 24393

Retention of selenium by calcium aluminate hydrate (AFm) phases under strongly reducing radioactive waste repository conditions

Rojo, H.; Scheinost, A. C.; Lothenbach, B.; Laube, A.; Wieland, E.; Tits, J.

Safety assessment studies of future nuclear waste repositories carried out in many countries predict selenium-79 to be a critical radionuclide due to its presence in the anionic form resulting in weak retardation by most common rock minerals. This assumption, however, ignores its potential uptake by AFm phases, positively charged anion exchangers which are present in significant quantities in the cementitious materials used in artificial barriers. Here we report for the first time wet chemistry and spectroscopic data on the interaction of the most reduced selenium anion species, i.e. HSe-, with two AFm phases commonly found in cement, monocarbonate (AFm-CO3) and hemicarbonate (AFm-OHCO3). Batch sorption experiments show that Se(-II) is retained much more strongly (Rd = 100±50 L kg-1) by the hemicarbonate than by the monocarbonate (Rd = 4±2 L kg-1). The cause of this different sorption behavior was elucidated by extended X-ray absorption fine-structure (EXAFS) spectroscopy, showing that Se(-II) is mainly intercalated in the larger and hence more accessible interlayer of the hemicarbonate (d-spacing = 0.82 nm), whereas most Se(-II) is sorbed by the anion exchange sites on the outer surfaces of the AFm platelets in the case of monocarbonate, where the interlayer space is less accessible due to the smaller d-spacing of 0.75 nm. EXAFS spectra of oxidation experiments further show that Se(-II) in the interlayers is better protected from oxidation than Se(-II) sorbed to the outer surfaces. The quantitative sorption data along with the molecular-scale processes obtained from this study provide crucial insight into the Se mobility in the cementitious near-field of a radioactive waste repository under reducing conditions.

Keywords: AFm phases; layered double hydroxides; selenide sorption; reducing conditions; x-ray absorption spectroscopy


Publ.-Id: 24392

A new convenient route to radiofluorinated or radioiodinated aromatic amino acid analogues

Serre, A.; Chezal, J.-M.; Canitrot, D.; Witkowski, T.; Degoul, F.; Debiton, E.; Miot-Noirault, E.; Wenzel, B.; Maisonial-Besset, A.

Aim: Amino acid transporters (AATs) are proteins that supply cells with amino acids (AAs). Cancer cells, compared to normal ones, often present a rapid growth and a high proliferation rate, supported by increased expression and/or activity of AATs. Radiolabeled AAs that intensively accumulate in tumour cells can provide high contrast SPECT or PET imaging of primary lesions and distant metastases. One of the most upregulated AAT in cancers is the LAT1 system which transports large neutral AAs as branched and aromatic ones. Therefore, a lot of radiolabelled tyrosine analogues have been developed (i.e. O-2-[18F]fluoroethyl-L-tyrosine, [18F]DOPA, [123I]ITIC(OH)). While radioiodinated derivatives of some of these electron-rich arenes are easily available, fluoroaryl analogues are particularly complicated to access by classical nucleophilic substitution with [18F]F-. Based on the ITIC(OH) scaffold, we developed a new synthetic pathway to easily produce radioiodinated or radiofluorinated tyrosine analogues.
Material and methods: A convergent synthetic pathway (Fig. 1) was designed to produce the radioiodinated tracers, reference fluorinated derivatives, and radiofluorinated compounds from common organotin intermediates. The latter were synthesized from iodinated analogues and labelled with [125I]iodide using electrophilic demetallation reaction or converted into iodonium salts for 18F-labelling. The reference fluorinated derivatives were obtained by treatment of the organotin compounds by F-TEDA-PF6. The enantiomeric excess of all produced compounds was assessed by chiral analytic HPLC analyses. For comparison, the corresponding derivatives from the series D were also synthesized.
Results: Our synthetic approach allowed the successful production of non-radioactive iodinated or fluorinated derivatives with high ee (>99%) and with a controlled position of halogenation. While, corresponding radioiodinated structures were easily synthesized using classical electrophilic substitution from organotin intermediates, the access to iodonium salt precursors and radiofluorinated derivatives warranted a lot of investigations to achieve acceptable (radio)chemical yields. Chiral analytical HPLC analyses revealed that no racemisation occurred during radiolabelling with [125I]iodide or [18F]fluoride.
Conclusion: We developed an efficient method to access to radioiodinated or radiofluorinated cyclic tyrosine analogues via organotin and iodonium salt intermediates. This strategy could be extended to a broad range of electron-rich aromatic derivatives.

Fig. 1. Convergent synthetic approach to access to radioiodinated and radiofluorinated cyclic tyrosine analogues via organotin intermediates

  • Poster
    ISRS2017 - 22nd International Symposium on Radiopharmaceutical Sciences, 14.05.2017, Dresden, Deutschland
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, 184
    DOI: 10.1002/jlcr.3508

Publ.-Id: 24391

Understanding the temperature-dependent evolution of solution processed metal oxide transistor characteristics based on molecular precursor derived amorphous indium zinc oxide

Sanctis, S.; Hoffmann, R. C.; Precht, R.; Anwand, W.; Schneider, J. J.

Amorphous indium zinc oxide (IZO) thin films are accessible by solution-deposition of mixtures of molecular single-source precursors with dimethyl 2-hydroxyimino- and 2-nitromalonato ligands (dmm-NOH and Hdmm-NO2, respectively). Thermal combustion of the precursor molecules In3O3(dmm-NO2)3.(toluene) and [Zn4O(dmm-NO)6] leads to a highly exothermic decomposition reaction yielding amorphous indium zinc oxide (IZO) even at a temperature of 150 °C. The main aim of the present investigation is to correlate the electronic performance in such solution processed field-effect transistors (FET) with the presence of surface groups and bulk defects depending on the processing temperatures of the resulting IZO films (250 to 400 °C). In depth electronic characterization using X-Ray- and Photoelectron Emission Spectroscopy (XPS and UPS) reveals major electronic changes during thin film formation in the temperature range between 275 and 300 °C. These findings are confirmed by Positron Annihilation Spectroscopy (PAS) which allows the monitoring of defects in a picometer range in the resulting functional IZO thin films. Resulting transistor mobilities (m) of the semiconducting IZO films are in the range of those of amorphous silicon even at a processing temperature of 250 °C and increase up to 6 and 9.5 cm2 (V s)-1 at 350 and 400 °C with on/off ratios of 105 up to 107, respectively.

Keywords: indium zinc oxide; XPS; UPS; PAS; electronic properties

Publ.-Id: 24390

Bi(III) immobilization inside MIL-101: enhanced photocatalytic performance

Kovalenko, K. A.; Ruban, N. V.; Adonin, S. A.; Korneev, D. V.; Erenburg, S. B.; Trubina, S. V.; Kvashnina, K.; Sokolov, M. N.; Fedin, V. P.

A novel hybrid material Bi(III)@MIL-101 (Bi(III) = Bi-containing oxoclusters, MIL-101 = chromium(III) oxoterephthalate) has been obtained by the intra-pore hydrolysis of guest bismuth(III) chloride in ammonia solution. The compound was fully characterized by chemical analysis, PXRD, nitrogen sorption and TEM techniques. According to characterization techniques all Bi species are only inside matrix and elemental analysis reveals ca. 1 Bi atom per mesocage. The chemical structure of Bi(III)-containing clusters inside MIL-101 matrix has been suggested according to EXAFS study. The catalytic activity of Bi(III)@MIL-101 has been tested in photodegradation of methyl red (MR). An introduction of Bi(III)-species inside MIL-101 has significantly increased the photocatalytic performance in comparison with layered BiOCl which has been obtained in the same synthetic conditions without MIL-101.

  • Open Access Logo New Journal of Chemistry 41(2017)6, 2255-2260
    Online First (2017) DOI: 10.1039/C6NJ03482A


Publ.-Id: 24389

The State of Platinum in Pyrite Studied by X-Ray Absorption Spectroscopy of Synthetic Crystals

Filimonova, O. N.; Nickolsky, M. S.; Trigub, A. L.; Chareev, P. V.; Kvashnina, K. O.; Kovalchuk, E. V.; Vikentyev, I. V.; Tagirov, B. R.

Pyrite (FeS2) is a typical container of Pt in ores of magmatic and hydrothermal origin and in some carbonrich ores of sedimentary-diagenetic origin. Knowledge of the state of Pt disseminated in the matrix of pyrite, including local atomic environment (type of atoms in the nearest and distant coordination shells, coordination numbers, interatomic distances) and oxidation state, is necessary for physical-chemical modeling of platinum group element mineralization and for the improvement of Pt ore extraction and processing technologies. Here we report results of an investigation of local atomic structure of synthetic Pt-bearing pyrites by means of X-ray absorption spectroscopy (XAS). Synthesis experiments, performed at 580° and 590°C in a Pt-saturated system by means of salt-flux method, yielded crystals of pyrite with concentrations of Pt up to 4 wt %. Scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) showed that the distribution of Pt within the pyrite grains is of zonal character, but within the distinct zones Pt is distributed homogeneously. Negative correlation between the concentrations of Pt and Fe was observed in the synthesized pyrite grains. The slope of the correlation line corresponds to the formation of the solid solution in the Pt-Fe-S system and/or to the formation of PtS2. The XAS experiments revealed the existence of two forms of Pt in pyrite. The main form is the solid solution Pt(IV), which isomorphically substitutes for Fe. The Pt-S distance in pyrite is ~0.1 Å longer than that of Fe-S in pure pyrite. The distortion of the pyrite crystal structure disappears at R >2.5 Å. The second Ptrich form was identified by means of high-resolution transmission electron microscopy (HRTEM) as nanosized inclusions of PtS2. Heating experiments with in situ registration of X-ray absorption spectra resulted in partial decomposition (dissolution) of PtS2 nanosized inclusions with the formation of the solid solution (Fe1–xPtx)S2. Therefore, the PtS2 nanosized particles can be considered as a quench product. Our data demonstrate that both Pt solid solution and PtS2 nanosized inclusions (at high Pt content) can exist in natural Pt-bearing pyrites.


  • Secondary publication expected

Publ.-Id: 24388

Impact of Synthetic Route on Structural and Physical Properties of Butyl-1,4-Diammonium Lead Iodide Semiconductors

Safdari, M.; Phuyal, D.; Philippe, B.; Svensson, P. H.; Butorin, S. M.; Kvashnina, K. O.; Rensmo, H.; Gardner, L. K. J. M.

We report on the significant role of the synthetic route and importance of solvent for synthesis of organic-inorganic lead iodide materials. Through one route, intercalation of dimethylformamide in the crystal structure was observed leading to one dimensional (1D) [NH3(CH2)4NH3]Pb2I6 structure of the product. This product was compared with the two dimensional (2D) [NH3(CH2)4NH3]PbI4 recovered from aqueous solvent based synthesis with the same precursors. UV-visible absorption spectroscopy showed a red-shift of 0.1 eV for the band gap of the 1D network in relation to the 2D system. This shift primarily originates from a shift in the valence band edge as determined from photoelectron- and X-ray spectroscopy results. These findings also suggest iodide 5p orbital as the principle component in the density of states in the valence band edge. Single crystal data shows change in the local coordination around iodide, while in both materials, lead atoms are surrounded by iodide atoms in octahedral units. The conductivity of the one dimensional material ([NH3(CH2)4NH3]Pb2I6) was 50% of the two dimensional material ([NH3(CH2)4NH3]PbI4). The fabricated solar cells reflect these changes in the chemical and electronic structure of both materials, although the total light conversion efficiency of solar cells based on both products were similar.

Publ.-Id: 24387

Modelling free-surface dynamics in the Ribbon Growth on Substrate process (RGS)

Beckstein, P.; Galindo, V.; Gerbeth, G.

The Ribbon Growth on Substrate (RGS) technology is a promising technology that allows the controlled, high crystallization rate production of silicon wafers and advanced metal-silicide alloys. In order to optimize this process, insights from modelling the
liquid metal flow are very desirable. The RGS process is dominated by a time-dependent, three-dimensional free-surface flow of the processed melt under the influence of electromagnetic forces. Thereby, main flow structures and possible instabilities strongly depend
on the melt shape. We have developed a new numerical multiphysics-software within the OpenFOAM (extensions) framework, which allows us to efficiently simulate hydrodynamic and electrodynamic effects and their interaction.

Keywords: RGS; Multiphysics; Free-surface; Eddy-currents; OpenFOAM

  • Contribution to proceedings
    10th PAMIR International Conference - Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, Cagliari: Arti Grafiche Pisano, 978-88-90551-93-2, 257-261
  • Lecture (Conference)
    10th PAMIR International Conference - Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy, 20.-24.06.2016, Cagliari, Italy

Publ.-Id: 24386

Observations on bubble shapes in bubble columns under different flow conditions

Ziegenhein, T.; Lucas, D.

The bubble shape is fundamental for every aspect of modelling bubbly flows. The interface is usually highly deformable so that the bubble shape is in general dependent on the surrounding flow field. Since recent work on this topic addressed almost entirely single-bubbles rising in quiescent flow, the extent of such flow field dependencies is rather unknown. This study examines the effect on the bubble shape when flow properties, i.e. the gas flow rate, sparger setup, and column geometry, are changed by evaluating six different bubble column experiments. The results of this integral approach reveal that the bubble shape of small bubbles is distinctly influenced whereas the shape of large bubbles is unchanged. Averaged over all flow rates, we find that the size-dependent bubble shapes are quite similar for all six experiments.
Further studies focusing on single local effects like the shear rate or wake effects are highly desirable to obtain a deeper understanding of the underlying processes; for this purpose, the given results can help to assess the most important effect and in which extend it should be studied.

Keywords: Bubble shape; Bubbly flows; Bubble column; Turbulent flow; Swarm effects


Publ.-Id: 24384

Airlift Reactor – Experiment and CFD Simulation

Ziegenhein, T.

It is more and more possible to design bubbly flow reactors with methods of the computational fluid dynamics (CFD). Measurements that can be used for model validation, however, are often missing, especially for complex setups like airlift reactors. Such measurements include locally resolved information about the dispersed and continuous phase, particularly the information about the flow field and interface structures are important. In the present work Reynolds stresses, liquid velocity and gas void fraction profiles as well as bubble size distributions are provided at several positions in the riser and the downcomer in a rectangular airlift reactor for this purpose. In addition, the hydrodynamics inside this airlift reactor are described in detail by the measured values.

Keywords: dispersed gas-liquid multiphase flow; airlift reactor; model validation; particle tracking velocimetry; turbulence; videography

  • Poster
    14th Multiphase Flow Conference & Short Course, 08.-10.11.2016, Dresden, Deutschland

Publ.-Id: 24383

Lattice vibrations and electrical transport in (Bi1-xInx)2Se3 films

Zhu, J.; Liu, F.; Zhou, S.; Franke, C.; Wimmer, S.; Volobuev, V. V.; Springholz, G.; Pashkin, A.; Schneider, H.; Helm, M.

We present Raman, terahertz transmission, and transport measurements on (BiIn)2Se3 films to study the evolution of phonon modes and resistivity with an increasing indium content across the metal-insulator phase transition. The frequencies of two Raman-active modes E2g and A21g as well as an infrared-active mode Eu increase with an increasing indium content due to the smaller atomic weight of indium compared to bismuth. Terahertz data are fitted by a Drude Lorentz model. Drude scattering rates increase from 47 to 75 cm -1 with an increasing indium content from 0% to 16% due to stronger impurity scattering. The carrier concentration drops significantly for x=24%. The temperature dependence of the resistivity switches from metallic at x=16% to insulating at x =24%, indicating a metal-insulator transition in between.

Keywords: lattice vibrations; Raman spectra; topological insulators; electrical transport; Bi2Se3

Publ.-Id: 24382

Experimental investigations on the lift force for turbulent flows with low Morton number

Ziegenhein, T.; Lucas, D.

The lateral lift force has an important influence on the gas distribution in bubbly flows. For this reason reliable closure models reflecting this force are required for CFD-simulations of bubbly flows. In Direct Numerical Simulations as well in experimental investigation it was shown that the lift force strongly depends on the bubble size and even changes its sign depending on the bubble size. Tomiyama et al. (2002) obtained a correlation from experiments with single bubbles in a linear laminar shear flow for high Morton number systems, which is frequently used in CFD-simulations. In this work the lift force is determined experimentally in low Morton number systems with a turbulent background flow. Single bubbles move through a linear shear field generated in a flat column by asymmetric aerating. An averaged bubble trajectory is obtained from a long-term averaged gas volume fraction field along which the force balance including buoyancy, drag, virtual mass and lift is solved to determine the lift force coefficient. The additional parameters required, as relative velocity are obtained from the experiments. The dependency of the lift force coefficient on the horizontal bubble diameter is in good agreement with the data obtained by Tomiyama et al., however the Wellek correlation for the aspect ratio seems to be not valid for the pure system considered.

Keywords: Lift Force; Bubbly flows; Turbulence

  • Lecture (Conference)
    ICMF 2016 International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy

Publ.-Id: 24381

Computational Fluid-Dynamic modeling of the pseudo-homogeneous flow regime in large-scale bubble columns

Besagni, G.; Inzolia, F.; Ziegenhein, T.; Lucas, D.

An understanding of the fluid dynamics and the transport phenomena in bubble columns (in the homogeneous and heterogeneous flow regimes) is of fundamental importance to support the design and scale-up methods. In this respect, multiphase Computational Fluid-Dynamics (CFD) simulations in the Eulerian multi-fluid framework are particularly useful to study the fluid dynamics in large-scale reactors; in particular, this study concerns the modeling of the fluid dynamics in bubble columns within the boundaries of the homogeneous flow regime. Reliable predictions of the homogeneous flow regime with this approach are, however, limited up to now. One important drawback is that usually the needed closure models for the interphase forces, turbulence and coalescence and break-up are selected case-by-case, which hinder improvement of the predictive value. A set of closure relations has been collected at the Helmholtz-Zentrum Dresden-Rossendorf that represents the best available knowledge and may serve as a baseline model for further investigations. In this paper, the validation of this set of closure relations has been extended to the pseudo-homogeneous flow regime—characterized by a wide spectrum of bubble sizes and typically associated with the large sparger openings used in industrial applications—in large-scale bubble columns, thus establishing a first step towards the simulation of industrial-scale reactors. To this end, the benchmark considered is a comprehensive dataset obtained for a large-scale bubble column, which has been built accordingly with the well-known scale up criteria (large-diameter, high aspect ratio and large sparger openings). The numerical approach has been tested in its fixed-poly-dispersed formulation (considering the two- and four-classes approaches to represent the dispersed phase) and considering the coalescence and break-up closures. The results suggest that the correct simulation of the fluid dynamics in the bubble column requires the definition of coalescence and break-up closures. The results have been critically analyzed and the reasons for the discrepancies between the numerical results and the experimental data have been identified and may serve as basis for future studies.

Keywords: CFD; Bubble column; Large-scale; Bubble size distribution; Coalescence and break-up; Validation

Publ.-Id: 24380

Synthesis of coordination polymers of tetravalent actinides (U and Np) with phthalate or mellitate ligand in aqueous medium

Martin, N. P.; März, J.; Volkringer, C.; Henry, N.; Hennig, C.; Ikeda-Ohno, A.; Loiseau, T.

Four coordination polymers bearing uranium or neptunium have been hydrothermally synthesized at 130°C, from a tetravalent actinide chloride (AnCl4) source in association with phthalic (noted 1,2-H2bdc hereafter) or mellitic (noted H6mel hereafter) acid in aqueous mediua. With the phthalate ligand, two analogous assemblies ([An2O2(H2O)2(1,2-bdc)2]·H2O ; An = U4+ (1) or Np4+ (2)) have been isolated and are built up from the connection of square anti-prismatic polyhedra (AnO8) linked to each other via μ3-oxo groups (edge-sharing mode) in order to construct infinite zig-zag ribbons. The phthalate molecules connect adjacent chains to each other to generate a 2D network. Water molecules are bonded to the actinide center or found intercalated between the layers. With the mellitate ligand, two distinct structures have been identified. The uranium-based compound (U2(OH)2(H2O)2(mel) (3)) exhibits a 3D structure composed of dinuclear units of UO8 polyhedra (square anti-prism) linked via common edge (μ2-hydroxo). The 3D framework consists of the connection of the mellitate linker with the dinuclear brick with its six carboxylate arms. The structure of the neptunium mellitate ([(NpO2)10(H2O)14(Hmel)2]·12H2O (4)) reveals the oxidation of the initial Np(IV) toward Np(V) in our synthetic hydrothermal conditions, and this generates typical neptunyl entities with pentagonal bipyramidal environment (NpO7 unit). The resulting network is a layered assembly, composed of sheets of NpO7 linked in a square net, with cation-cation interactions between neptunyl bond (Np=O) and Np-O bonds from the pentagonal plane. The cohesion of the 3D structure is ensured by the mellitate molecules acting as bridging linkers between the NpO7 sub-network. For the mellitate, only four carboxylate groups are engaged with the connection of the NpO7-based layer.

Keywords: actinides; uranium; neptunium; coordination; polymers; carboxylate; complexation


Publ.-Id: 24379

Dissociation between brown adipose tissue 18F-FDG uptake and thermogenesis in uncoupling protein deficient mice

Hankir, M. K.; Kranz, M.; Keipert, S.; Andreasen, S.; Kern, M.; Patt, M.; Klöting, N.; Hesse, S.; Brust, P.; Jastroch, M.; Fenske, W. K.

18F-FDG PET imaging is routinely used to assess recruitment of BAT thermogenesis which requires mitochondrial uncoupling protein 1 (UCP1). It remains unsettled whether 18F-FDG uptake by BAT is altered in the absence of UCP1-mediated heat production.
METHODS: UCP1 knockout (UCP1 KO) and wild-type (WT) mice received single intraperitoneal injections of the selective β3 adrenergic receptor agonist CL 316, 243 (1mg/kg) and underwent metabolic cage, infrared thermal imaging and static 18F-FDG PET/MRI experiments. Bioenergetics of isolated brown adipocytes were examined by extracellular flux analysis.
RESULTS: In response to CL 316, 243 treatment, oxygen consumption and BAT thermogenesis were diminished in UCP1 KO mice; however the stimulation of 18F-FDG uptake by BAT was fully retained. Brown adipocytes derived from UCP1 KO mice exhibited defective induction of uncoupled respiration when glycolytic flux appeared normal.
CONCLUSION: Increased glucose metabolism in BAT can occur independently of UCP1-mediated thermogenesis.

Keywords: PET; thermogenesis

Publ.-Id: 24378

Sorption competition of trivalent metals on corundum (α-Al2O3) studied on the macro- and microscopic scale

Virtanen, S.; Eibl, M.; Meriläinen, S.; Rossberg, A.; Lehto, J.; Rabung, T.; Huittinen, N.

Sorption of trivalent actinides and lanthanides onto the surface of geological materials relevant for nuclear waste disposal is a topic that has been widely studied in recent years. However, the sorption properties of metals are often investigated by studying the sorption behaviour of a single metal at a time, thus, these experiments do not account for potential effects of sorption competition in the presence of multiple dissolved elements or compounds. Bradbury and Baeyens (2005) performed extensive investigations of the sorption competition between various metal cations on the clay mineral montmorillonite. By investigating the competition of metals with similar and dissimilar chemical behaviour (e.g. tendency to hydrolysis and valence state), the authors concluded that metal cations with dissimilar chemical properties do not affect the uptake of one another by the clay mineral, whereas metals with similar chemistries do. Thus, if the data obtained in single metal sorption experiments are used in the safety assessment of nuclear disposal, careful considerations of the chemical environment in the near- or far-field of nuclear waste repository is needed to avoid the possible overestimation of radionuclide sorption.
In this study, we have combined batch sorption and spectroscopic experiments that were performed with Eu(III), Cm(III) and Am(III) in in the absence and presence of Y(III) as competing cation. The objective was to investigate how the sorption behaviour of trivalent actinides and lanthanides is affected by the presence of another trivalent metal. Following the findings of Bradbury and Baeyens (2005) our hypothesis is that the addition of higher concentrations of trivalent Y(III) together with a chemically similar trivalent metal, Eu(III), Cm(III) or Am(III), would affect the sorption behaviour of that metal.
Batch sorption experiments were performed with Eu(III) at different pH (pH-edges) and concentrations (isotherms). The competing metal Y(III) was added before Eu(III) to the mineral suspension in concentrations ranging from 1×10-6 M to 1×10-4 M. In the Eu(III) pH-edge experiments, the sorption of 1×10-5 M Eu(III) was investigated on 0.5 g/l corundum at varying pH, with and without Y(III). In the Eu(III) isotherm experiments, the initial Eu(III) concentration was varied between 1×10-9 M – 1×10-4 M and Y(III) was used in the competing isotherm samples at a constant pH of 7. Batch experiments showed that the addition of Y(III) did decrease the sorption of Eu(III) (Figure 1) on a macroscopic scale. However, as the main emphasis of this study was the possible changes happening at the molecular level as a results of sorption competition, spectroscopic methods were also employed. Time-resolved laser fluorescence spectroscopy (TRLFS) enables the investigations of Cm(III) sorption speciation directly on the mineral surface. We investigated the changes in the speciation of 1×10-7 M Cm(III) in 0.5 g/l corundum suspensions at varying pH under non-competing and competing conditions using 1×10-4 M Y(III). The results indicate changes in the Cm(III) sorption species distribution, thus, confirming our findings in the batch sorption experiments showing that 1×10-4 M Y(III) suppresses Cm sorption complex formation on the mineral surface depending on the solution pH (Figure 2). Cm(III) luminescence spectra of only Cm(III) and of Cm(III) together with Y(III), show that the fraction of aqueous Cm species is substantially greater with high concentrations of Y(III) present. Only when the pH is increased above 7, the first Cm sorption species appears, resulting in a shift of the observed emission peak maximum. X-ray absorption spectroscopy (XAS) was applied to identify the formed trivalent actinide sorption complexes. We investigated the sorption of 6×10-6 M or 2×10-5 M Am(III) on the corundum surface at pH 8.5 in the absence and presence of 2×10-5 or 2×10-4 M Y(III). The treatment of the XAS-data is still ongoing and results will be discussed more closely in the conference presentation.

  • Lecture (Conference)
    Ninth international conference on nuclear and radiochemistry (NRC9), 29.08.-02.09.2016, Helsinki, Finland

Publ.-Id: 24377

Molecular interactions of two fungi with uranium and europium

Wollenberg, A.; Günther, A.; Merroun, M. L.; Raff, J.; Stumpf, T.

If radionuclides are released in the environment their mobility and behavior is influenced by interactions with abiotic and biotic matter. As fungi are ubiquitous in nature they have to be taken into consideration in particular. For example, fungi can bind radionuclides in different ways, with the result that the radionuclides are immobilized and preventing further migration through the soil. The aim of this study was to investigate the binding of uranium and europium, the latter as surrogate for trivalent actinides, by fungi Schizophyllum commune and Leucoagaricus naucinus.
First batch experiments showed the binding of U(VI) and Eu(III) by fungi depends on the initial conditions. Both fungi showed increasing sorption capacities with higher initial metal concentrations and lower initial biomass. In contrast, the fungi showed different metal binding behavior in dependence on pH. Scanning transmission electron microscopy in combination with high angle annular dark-field analysis (HAADF-STEM) revealed location of U(VI) on the surface and inside of cells of Schizophyllum commune.
Furthermore the U(VI)-binding of the fungi was investigate with time-resolved laser-induced fluorescence spectroscopy (TRLFS) depending on metal concentration. The results showed the speciation of U(VI) is changed in the initial solution during binding process. In addition, it was demonstrated that mainly phosphate groups are responsible for the binding on the surface of the biomass.

Keywords: fungi; uranium; europium

  • Poster
    15. Symposium on Remediation, 13.-14.10.2016, Jena, BRD

Publ.-Id: 24376

Studies of activation monitors at the HZDR medical cyclotron: Simulation and Experiment

Konheiser, J.; Müller, S. E.

The neutron source terms for a proton beam hitting an O-18 enriched water target were calculated with MCNP6 and FLUKA. First comparisons of simulation and experiments for activation studies at the IBA CYCLONE 18/9 cyclotron.

  • Lecture (others)
    16. AAA Workshop, 05.12.2016, Garching, Germany

Publ.-Id: 24375

22Ne and 23Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for 22Ne(p,γ)23Na

Slemer, A.; Marigo, P.; Piatti, D.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Bressan, A.; Broggini, C.; Bruno, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F.; Prati, P.; Straniero, O.; Szücs, T.; Takács, M. P.; Trezzi, D.

We investigate the impact of the new LUNA rate for the nuclear reaction 22Ne(p,γ)23Na on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally- pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre- main sequence up to the termination of the TP-AGB phase, for a few sets of stellar models with initial masses in the range 3.0 M⊙ − 6.0 M⊙ and three values of metallicity, Zi = 0.0005, Zi = 0.006, and Zi = 0.014. We compare the results of the Ne-Na nucleosynthesis obtained with the new LUNA rate and others available in the literature. We find that the improvement in the astrophysical S-factor obtained with LUNA has remarkably reduced the corresponding nuclear uncertainties in the 22Ne and 23Na AGB yields, which drop from factors of ≃ 10 to just a few for the lowest metallicity models. The uncertainties that still affect the 22Ne and 23Na AGB ejecta are mainly dominated by evolutionary aspects (efficiency of mass-loss, dredge-up events, convection). With the new LUNA data AGB stars with hot-bottom burning produce amounts of 23Na that are in between those predicted with NACRE and Iliadis et al. rates. Finally, we discuss how the LUNA results impact on the hypothesis that invokes primordial massive AGB and super-AGB stars as the main agents of the observed O-Na anticorrelation in Galactic globular clusters. In this context, we derive quantitative constraints on the efficiencies that should characterize other key physical processes (mass loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anticorrelation and the observational constraints on the CNO abundance. While best-fitting AGB models can be actually singled out, yet they cannot be taken as a theoretical piece in full support to the AGB hypothesis, as various issues still remain.

Keywords: stars: evolution; stars: AGB and post-AGB; stars: carbon; stars: abundances; stars: mass loss; Physical Data and Processes: nuclear reactions; abundances; nucleosynthesis


Publ.-Id: 24374

FENABIUM: Research at HZDR

März, J.; Schöne, S.; Radoske, T.; Kaden, P.

Vortrag zum Kick-off Meeting des FENABIUM Verbundprojekts (BMBF) mit der TU Dresden und Universität Leipzig.
Die Ergebnisse zeigen die Synthese und Charakterisierung vierwertiger Actinidkomplexe mit Amidinen und Schiffschen Basen unter Schutzgasbedingungen, die in der Gruppe "Chemie der f-Elemente" des Instituts für Ressourcenökologie durchgeführt wurden.

Keywords: Actinide complex; Chemistry of the f-elements

  • Lecture (Conference)
    FENABIUM Kick-off Meeting, 14.11.2016, Dresden, Deutschland

Publ.-Id: 24373

Bentonite-geotechnical barrier and source for microbial life

Matschiavelli, N.; Steglich, J.; Kluge, S.; Cherkouk, A.

The storage of highly radioactive waste is a challenging task for many scientists. For a deep geological deposition of the waste a multi-barrier concept is favoured, which combines a technical barrier (canister including the highly radioactive waste), a geotechnical barrier (e.g. Bentonite) and the geological barrier (host rock). Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, Bentonites fulfil in this system a sealing and buffering function. Depending on the mineral composition Bentonites contain many suitable electron-donors and –acceptors, enabling potential microbial life. For the potential repository of nuclear waste the microbial mediated transformation of Bentonite could influence its properties as a barrier material. To elucidate the microbial potential within selected Bentonites, microcosms were set up containing a certain amount of Bentonite (20 g) and 40 ml anaerobic synthetic Opalinus-clay-pore water solution under an N2/CO2-gas-atmosphere. Substrates like acetate and lactate were supplemented to stimulate potential microbial activity. Microcosms were incubated in the dark, without shaking at 30°C. Within an indefinite time scale samples were taken at different time-points of incubation and were analysed regarding geochemical parameters like pH, O2-concentration, redox potential, iron-concentration and sulphate-concentration as well as biological parameters like the consumption and formation of metabolites. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate. Furthermore, microbial iron-reduction was determined. The results reveal the importance of the selection of the best suitable Bentonite in order to avoid transformation by indigenous microbes.

  • Poster
    Microbiology and Infection 2017 - 5th Joint Conference of the DGHM & VAAM, 05.-08.03.2017, Würzburg, Deutschland

Publ.-Id: 24372

The upper critical field and its anisotropy in (Li1−xFex)OHFe1−ySe

Wang, Z.; Yuan, J.; Wosnitza, J.; Zhou, H.; Huang, Y.; Jin, K.; Zhou, F.; Dong, X.; Zhao, Z.

The temperature dependence of the upper critical field (Hc2) in a (Li1−xFex)OHFe1−ySe single crystal (Tc ≈ 40 K) has been determined by means of magnetotransport measurements down to 1.4 K both for inter-plane (H‖c, H‖c c2) and in-plane (H‖ab, H‖ab c2) field directions in static magnetic fields up to 14 T and pulsed magnetic fields up to 70 T. H‖c c2 exhibits a quasilinear increase with decreasing temperature below the superconducting transition and can be described well by an effective two-band model with unbalanced diffusivity, while H‖ab c2 shows a flattening below 35 K and follows the Werthamer–Helfand–Hohenberg (WHH) model incorporating orbital pair-breaking and spin-paramagnetic effects, yielding zero-temperature critical fields of H‖c c2(0) ≈ 67 T and H‖ab c2(0) ≈ 98 T. The anisotropy of the upper critical fields, γ(T)= H‖ab c2/ H‖c c2 monotonically decreases with decreasing temperature from about 7 near Tc to 1.5 at 0 K. This reduced anisotropy, observed in most Fe-based superconductors, is caused by the Pauli limitation of H‖ab c2.

Publ.-Id: 24371

Afterglow of the dynamical Schwinger process: soft photons amass

Otto, A.; Kämpfer, B.

We consider the conversion of an electric field into photons as a secondary probe of the dynamical Schwinger process. In spatially homogeneous electric fields, quantum fluctuations of electron-positron (e+e−) pairs are lifted on the mass shell leaving asymptotically a small finite pair density. The e+e− dynamics in turn couples to the quantized photon field and drives its on-shell mode occupation. The spectral properties of the emerging asymptotic photons accompanying the Schwinger process are calculated in lowest-order perturbation theory. Soft photons in the optical range are produced amass in the sub critical region, thus providing a promising discovery avenue, e.g.\ for laser parameters of the Extreme Light Initiative (ELI-NP) to be put in operation soon.


Publ.-Id: 24370

Extended soft-wall model for the QCD phase diagram

Zöllner, R.; Wunderlich, F.; Kämpfer, B.

The soft-wall model, emerging as bottom-up holographic scenario anchored in the AdS/CFT correspondence, displays the disappearance of normalisable modes referring to vector mesons at a temperature $T_{\dis}$ depending on the chemical potential μ, $T_{\dis}(\mu)$. We explore options for making $T_{\dis}(\mu)$ consistent with the freeze-out curve Tf.o.(μ) from relativistic heavy-ion collisions and the cross-over curve Tc(μ) from QCD at small values of μ.

Publ.-Id: 24369

Study of magnetic, structural and magnetocaloric properties of La0.6Pr0.4Mn2Si2 under high pressures and magnetic field

Kastil, J.; Arnold, Z.; Isnard, O.; Skourski, Y.; Kamarad, J.; Itié, J. P.

The structural, magnetic and magnetocaloric properties of La0.6Pr0.4Mn2Si2 compound were measured in wide range of temperature, magnetic field and hydrostatic pressure. The structural study up to 10 GPa confirmed the existence of critical Mn-Mn distance 0.2883 nm for the ferromagnetic to antiferromagnetic transition at room temperature. The results demonstrated the crucial role of the volume in the suppression of the ferromagnetic phase above the transition temperature T1 = 168 K under pressure. The huge pressure shift of the transition temperature T1, dT1 /dp = 230 K/GPa, was observed. Based on our magnetization measurement the low temperature transition at T2 = 30 K is connected with reorientation of Mn moment and the rare-earth sublattice is not ordered in this case. The direct magnetocaloric measurement showed moderate values of the adiabatic temperature change connected with the magnetic transition at Tc and T1 and confirmed the first order character of the transition at T1 and second order character of the transition at Tc.

Publ.-Id: 24368

Uranium(VI) retention by Ca-bentonite under (hyper)alkaline conditions

Philipp, T.; Schmeide, K.

The presentation summerizes the results of batch experiments on the uranium(VI) sorption on Ca-bentonite under (hyper)alkaline conditions combined with Time-resolved laser-induced fluorescence spectroscopy (TRLFS).

Keywords: sorption; clay; Ca-bentonite; uranium(VI); hyperalkaline; high ionic strengths; TRLFS

  • Lecture (others)
    3. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, Heidelberg, 25.-26.10.2016, Heidelberg, Deutschland

Publ.-Id: 24367

New possibilities of plasma immersion ion implantation (PIII) and deposition (PIII&D) in industrial components using metal tube fixtures

Ueda, M.; Silva, A. R.; Pillaca, E. J. D. M.; Mariano, S. F. M.; Rossi, J. O.; Oliveira, R. M.; Pichon, L.; Reuther, H.

New possibilities of Plasma Immersion Ion Implantation (PIII) and deposition (PIII&D) for treating industrial components in the batch mode have been explored. A metal tubular fixture is used to allocate the components inside around and along the tube, exposing to the plasma only the parts of each component that will be implanted. Hollow cathode- like plasma is generated only inside the tube filled with the desired gas, by applying high negative voltage pulses to the hollow cylindrical metal fixture which is insulated from the vacuum chamber walls. The metal tube (Me-tube) loaded with workpieces can be set-up inside the vacuum chamber in the standing-up, upside down or lying down arrangements. PIII tests were also run with and without metal sheet lids on the tube as well as with and without the components. Sputtering deposition and carbonitriding are also possible in this scheme by placing carbon tapes inside the tube and running the process with nitrogen PIII. Relatively clean DLC (Diamond Like Carbon) PIII&D deposition is possible by this method also since the plasma occupies mainly the Me-tube interior and not the whole chamber. Furthermore, operating high density PIII and PIII&D systems without additional plasma source, using only the high voltage pulser, is now possible to treat three dimensional parts. These methods are very convenient for batch processing of industrial parts by ion implantation and by ion implantation and deposition, in which a large number of small to medium size components can be treated by PIII and PIII&D, very quickly, efficiently and also at low cost.

Publ.-Id: 24366

Visualizing concentration distributions in macroscopic samples in the course of geochemical processes

Kulenkampff, J.; Karimzadeh, L.; Schymura, S.; Barthen, R.; Gründig, M.; Lippold, H.; Lippman-Pipke, J.

Geochemical processes, although generally well characterized on the molecular scale, are complicated by structural effects and process-inherent pattern formation. These effects cause variable scaling behaviour of the processes. This can be investigated through a significant process variable, the concentration of a geochemical species. As experimental method, therefore, we established positron emission tomography (PET) for high-resolving, sensitive, and quantitative tomographic imaging of tracer distributions in representative samples on the scale of drill cores (Kulenkampff et al. 2016). In contrast to other groups, we utilize a high-resolution PET-scanner and specially designed reconstruction software („GeoPET“) with about four times higher spatial resolution (about 1 mm) than standard medical PET scanners. This resolution is adequate for drill core sizes, and enables to visualize and analyze preferential pathway effects and local accumulations of tracers in detail, with an integration volume just above the typical pore scale. Thus, the method is ideally suited for parameterizing and verifying reactive transport simulations on the relevant macro-scale.
We applied the method on a variety of reactive transport processes, including leaching of copper minerals, injection of water glass for barrier improvement, transport of plant protectants in the soil, and transport of nano-particles in soils, rocks and technical devices.
Generally, both with conservative and reactive tracers, we observe strong localization of the transport pathways. This formation of preferential transport pathways implies that simulation models should consider a decrease of the effective volume and effective internal surface area, as well as high concentration gradients and non-uniform concentration distributions. PET is the potential method for parameterizing such models without prior flow simulations based on tomographic modalities for structural imaging, like µCT.

Kulenkampff, J., Gründig, M., Zakhnini, A., and Lippmann-Pipke, J.: Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217-1231, 2016.

Keywords: process tomography; PET; leaching; reactive transport

  • Lecture (Conference)
    9th International Conference on Porous Media & Annual Meeting, 08.-11.05.2017, Rotterdam, Niederlande

Publ.-Id: 24365

Non-destructive tomographic monitoring of transport processes in barrier material (Opalinus clay) with PET

Kulenkampff, J.; Gründig, M.; Lippmann-Pipke, J.

Parameterizing transport in barrier materials is a challenge, because the processes are extremely slow, limited to smallest quantities, and frequently strongly localized, e.g. to fractures. These processes are generally well characterized on the molecular scale, but strongly affected by structural effects on the larger scales. Due to the intricate derivation of experimentally substantiated parameters, the impact of these scaling effects is often unduly neglected in process simulations for safety assessment.
As most sensitive tomographical modality, which is capable to monitor traces with molecular concentrations on macroscopic samples, we apply positron-emission-tomography (PET) with a high-resolution scanner („GeoPET“) for parameterizing transport in barrier materials (Kulenkampff et al. 2016a).
We focus here on diffusion in Opalinus clay as potential barrier rock for nuclear waste deposits (Kulenkampff et al. 2016b, 2016c). Our method is complementary to diffusion experiments in small diffusion cells and additionally provides information on heterogeneity and anisotropy of the process.
We derived anisotropic diffusion coefficients from the measured spatiotemporal tracer distribution which are in accordance with results from diffusion cells (Lippmann-Pipke et al., 2016). The spatial characteristic of the tracer distribution suggests that this anisotropy is caused by preferential transport along fine layers on the millimetre to centimetre scale. This finding should be considered in process simulations, because it means a reduction of the volume that effectively is affected by the process and thus faster progress of the tracer and a reduction of the reactive internal surface area, when adsorption is considered.
Other examples, where we take advantage from the favourable features of the GeoPET-method, are advective fluid transport in fractured salt and crystalline rocks, as well as reactive injection of water glass into salt rock.
In all these cases we monitor tracer concentrations and thus the key parameter for reactive transport modelling. We recommend GeoPET as unique experimental method to verify transport simulations on the macroscopic scale of drill cores.

Kulenkampff, J., Gründig, M., Zakhnini, A., and Lippmann-Pipke, J.: Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217-1231, 2016a.
Kulenkampff, J., Zakhnini, A., Gründig, M., and Lippmann-Pipke, J.: Quantitative experimental monitoring of molecular diffusion in clay with positron emission tomography, Solid Earth, 7, 1207-1215, 2016b.
Kulenkampff, J., Gründig, M., Zakhnini, A., Lippmann-Pipke, J.: Observation of 22Na+ - Diffusion in Opalinus Clay using Positron Emission Tomography (GeoPET) (mpeg-movie),, 2016c.
Lippmann-Pipke, J., Gerasch, R., Schikora, J., and Kulenkampff, J.: Benchmarking PET for geoscientific applications: 3D quantitative diffusion coefficient estimation in clay rock, Comput. Geosci., in review, 2016.

Keywords: diffusion; clay; anisotropy; heterogeneity; tomography; PET

  • Lecture (Conference)
    9th International Conference on Porous Media & Annual Meeting, 08.-11.05.2017, Rotterdam, Niederlande

Publ.-Id: 24364

New insights into the pretargeting approach to image and treat tumours

Patra, M.; Zarschler, K.; Pietzsch, H.-J.; Stephan, H.; Gasser, G.

Tumour pretargeting is a promising strategy for cancer diagnosis and therapy allowing for the rational use of long circulating, highly specific monoclonal antibodies (mAbs) for both non-invasive cancer radioimmunodetection (RID) and radioimmunotherapy (RIT). In contrast to conventional RID/RIT where the radionuclides and oncotropic vector molecules are delivered as presynthesised radioimmunoconjugates, the pretargeting approach is a multistep procedure that temporarily separates targeting of certain tumour-associated antigens from delivery of diagnostic or therapeutic radionuclides. In principle, unlabelled, highly tumour antigen specific mAb conjugates are, in a first step, administered into a patient. After injection, sufficient time is allowed for blood circulation, accumulation at the tumour site and subsequent elimination of excess mAb conjugates from the body. The small fast-clearing radiolabelled effector molecules with a complementary functionality directed to the prelocalised mAb conjugates are then administered in a second step. Due to its fast pharmacokinetics, the small effector molecules reach the malignant tissue quickly and bind the local mAb conjugates. Thereby, corresponding radioimmunoconjugates are formed in vivo and, consequently, radiation doses are deposited mainly locally. This procedure results in a much higher tumour/non-tumour (T/NT) ratio and is favourable for cancer diagnosis and therapy as it substantially minimises the radiation damage to non-tumour cells of healthy tissues. The pretargeting approach utilises specific noncovalent interactions (e.g. strept(avidin)/biotin) or covalent bond formations (e.g. inverse electron demand Diels–Alder reaction) between the tumour bound antibody and radiolabelled small molecules. This tutorial review descriptively presents this complex strategy, addresses the historical as well as recent preclinical and clinical advances and discusses the advantages and disadvantages of different available variations.

Publ.-Id: 24362

Erste Untersuchungen zur Uranrückhaltung an C-S-H-Phasen und Ca-Bentonit

Philipp, T.; Wolter, J.-M.

Im Rahmen des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“ wird unter Anderem die Radionuklidrückhaltung an Tongestein und Tonmineralen unter hyperalkalinen Bedingungen und bei hohen Ionenstärken untersucht. Der Vortrag fasst die ersten Ergebnisse zur Sorption von Uran(VI) an Ca-Bentonit unter Variation verschiedener Umgebungsparameter (S/L-Verhältnis, U(VI)-Konzentration, pH, An-/Abwesenheit von CO2) zusammen.

Keywords: Ca-Bentonit; Ton; Montmorillonit; Uran(VI); Sorption; hyperalkalin; hohe Ionenstärke

  • Lecture (others)
    2. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 22.03.-23.11.2016, München, Deutschland

Publ.-Id: 24361

Leaching of uranium(VI) doped CSH phases in high saline water

Wolter, J.-M.

Leaching experiments of uranium(VI) doped calcium-silicate-hydrate (CSH) phases were carried out in a 2.5 M sodium chloride solution and different additions like sodium bicarbonate or sodium sulfate to determine the CSH stability in high saline water. The results were backed up with several spectroscopic techniques like time resolved laser fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR) and powder x-ray diffraction (PXRD) to structural changes of the CSH phases through the leaching.

Keywords: Uranium; CSH; TRLFS; IR; PXRD; sodium chloride; sodium sulfate; sodium carbonate

  • Lecture (others)
    3. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 24.10.2016, Heidelberg, Deutschland

Publ.-Id: 24360

Radioactive particles as concentrated sources related to uptake and dose in mammals

Johansen, M. P.; Child, D.; Ikeda-Ohno, A.; Payne, T. E.; Howell, N.; Caffrey, E.; Collins, R. N.

The radiological residues at the former weapons testing sites in Australia, at Maralinga, Emu and the Monte Bello Islands, often occur in particulate form (“hot particles”). Large numbers of these particles were emitted from nuclear test detonations and non-nuclear tests. For example, more than 3000 readily identifiable particles can occur in the soil of a single square meter, in a plume that extends for tens of kilometres at the Taranaki site (Maralinga). The physical and chemical characteristics of these particles affect their mobility and availability for uptake into living organisms. These particles, which are weathering slowly, may contain long-lived radionuclides (e.g. 239Pu) and thus will provide persistent sources of smaller, more readily respirable hot-particles, as well as ionic forms of radionuclides, for many thousands of years. From these Australian sites, we have gathered a series of particles that have weathered and interacted with the environment for 50+ years since their initial formation and release events. The particles are being evaluated using a range of methods including gamma spectrometry, PSL autoradiography, Accelerator Mass Spectrometry analysis (AMS), leaching studies, and X-ray fluorescence microscopy (XFM) at the Australian Synchrotron. Significant findings include the clustering of 137Cs on the exterior of a glassy fission fragment, with 90Sr occurring in the nearby interior, suggesting the 137Cs may be more available for weathering processes, and the beta emissions from the 90Sr may be largely self-shielded within the particle. In contrast, a different particle from a nearby site lacked any fission products, but contained Pu(IV) oxyhydroxides, consistent with weathering in a semi-arid environment. The 239Pu would impart significant dose to nearby tissue. However, XFM data, including X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) indicate particles with a “core-shell” structure, with most Pu(IV) oxyhydroxide clustered in the core surrounded by an external layer containing Ca, Fe, and U. Detailed dose modelling suggests most of the alpha emissions from particles > 5μm are self-shielded within the particles themselves, and therefore impart lower dose than the equivalent dissolved Pu. However, when Pu exists on exterior surfaces, a hot particle that has been internalised (e.g. lodged in a mammalian lung) may produce relatively intense dose rates to adjacent tissues.

Keywords: actinides; plutonium; mammal; uptake; particulates; bioavailability; radio ecology

  • Poster
    Australian Synchrotron User Meeting 2016, 24.-25.11.2016, National Centre for Synchrotron Science, AS, Australia

Publ.-Id: 24359

A laser-based hadrontherapy facility: current status at HZDR

Kraft, S.

Laser based ion acceleration has the potential to serve as a more flexible solution as compared to conventional ion beam therapies. In order to explore these potentials, several groups from physics, biology and medicine have joint forces in Dresden.
This talk will give an overview over the activities focusing especially on the proton source and the beam transport. The Ti:Sapph laser system was upgraded to 500TW in order to produce higher energies and starts operation this summer. Additionally, new target types such as solid hydrogen and liquid crystals where tested. For beam transport novel techniques with pulsed power magnets producing field of up to 20 Tesla are implemented.

  • Invited lecture (Conferences)
    3rd ELImed workshop, 07.-09.09.2016, Catania, Italien

Publ.-Id: 24358

Methodological accuracy of image-based electron-density assessment using dual-energy computed tomography

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

Purpose: Electron density is the most important tissue property influencing photon and ion dose distributions in radiotherapy patients. Dual-energy computed tomography (DECT) enables the determination of electron density by combining the information on photon attenuation obtained at two different effective x-ray energy spectra. Most algorithms suggested so far use the CT numbers provided after image reconstruction as input parameters, i.e. are imaged-based. To explore the accuracy that can be achieved with these approaches, we quantify the intrinsic methodological and calibration uncertainty of the seemingly simplest approach.
Methods: In the studied approach, electron density is calculated with a one-parametric linear superposition (‘alpha blending’) of the two DECT images, which is shown to be equivalent to an affine relation between the photon attenuation cross sections of the two x-ray energy spectra. We propose to use the latter relation for empirical calibration of the spectrum-dependent blending parameter. For a conclusive assessment of the electron-density uncertainty, we chose to isolate the purely methodological uncertainty component from CT-related effects such as noise and beam hardening.
Results: Analyzing calculated spectrally weighted attenuation coefficients, we find universal applicability of the investigated approach to arbitrary mixtures of human tissue with an upper limit of the methodological uncertainty component of 0.2%, excluding high-Z elements such as iodine. The proposed calibration procedure is bias-free and straightforward to perform using standard equipment. Testing the calibration on five published data sets, we obtain very small differences in the calibration result in spite of different experimental setups and CT protocols used. Employing a general calibration per scanner type and voltage combination is thus conceivable.
Conclusion: Given the high suitability for clinical application of the alpha-blending approach in combination with a very small methodological uncertainty, we conclude that further refinement of image-based DECT-algorithms for electron-density assessment is not advisable.

Keywords: proton and ion beam therapy; electron density; effective atomic number; range uncertainty; treatment planning

  • Medical Physics 44(2017)6, 2429-2437
    Online First (2017) DOI: 10.1002/mp.12265

Publ.-Id: 24357

The prospect of laser plasma accelerators for ion beam therapy of cancer

Schramm, U.

Talk and podium discussion on prospect of laser accelerated ions for therapy applications

Keywords: ion beam cancer therapy

  • Invited lecture (Conferences)
    International Symposium on Ultrafast Intene Laser Science ISUILS, 02.-05.10.2016, Cassis, Frankreich

Publ.-Id: 24356

ELI related activities, potential partners and status in Germany

Schramm, U.; Schramm, B.; Sauerbrey, R.

Presentation of the German position to ELI DC and ELI ERIC

Keywords: ELI

  • Invited lecture (Conferences)
    ELI DC 2nd partners meeting, 16.-17.11.2016, Bukarest, Rumänien

Publ.-Id: 24355

Development of the first fluorine-18 labelled radioligand for imaging of the adenosine A2B receptor

Lindemann, M.; Wenzel, B.; Hinz, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Teodoro, R.; Juhl, C.; Müller, C.; Brust, P.; Steinbach, J.

The G protein-coupled A2B receptor differs from other adenosine receptor subtypes (A1, A2A, A3) by its low affinity towards the endogenous ligand adenosine. It is suggested to be involved in various pathological processes accompanied by increased levels of adenosine, e.g. inflammation, hypoxia, and cancer. To enable the investigation of the function and expression of A2B-receptor in living organisms, we developed a fluorine-18 labelled radioligand with the particular aim of imaging of neurooncological and neuroinflammatory processes by PET.
Based on the pyrazine compound 1 [1] (Fig. A) several novel fluorine-containing derivatives were synthesized in four steps and their affinities and selectivities toward all four adenosine receptor subtypes were determined. The most promising candidate PA51 was radiolabelled by using the corresponding nitro precursor in DMSO with thermal as well as microwave heating (Fig. B). To study the in vivo metabolism of [18F]PA51 plasma and brain samples obtained from mouse at 30 min p.i. were investigated by using (a) conventional extraction procedures and (b) a micellar HPLC approach.
[18F]PA51 (binding affinities in Fig. B) was successfully synthesized with radiochemical yields of 36.1±4.6% (dec. corr., formulated product), molar activities of 10-30 GBq/µmol, and radiochemical purities of =99% (determined by analytical HPLC by UV absorption at ? = 254 nm). In vivo studies in mice revealed high initial brain uptake (5 min p.i.). Fast metabolism was found with formation of a single major radiometabolite able to cross the blood-brain barrier.
[18F]PA51 is unsuitable for imaging of A2B receptors in brain in vivo due to the presence of a radiometabolite. However, the initially high uptake of activity in the brain encourages further structural modifications to improve the selectivity and the metabolic stability.
[1] P. Eastwood, et al. ACS Med. Chem. Lett. 2011, 2, 213-218.

Keywords: A2B receptor; fluorine-18; PET

  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, 411
    DOI: 10.1002/jlcr.3508

Publ.-Id: 24354

Entwicklung des ersten F-18-markierten Radioliganden zur molekularen Bildgebung des Adenosinrezeptors A2B im Gehirn

Lindemann, M.; Wenzel, B.; Hinz, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Teodoro, R.; Juhl, C.; Müller, C.; Brust, P.; Steinbach, J.

Ziel: Der G-Protein-gekoppelte A2B-Rezeptor wird, im Gegensatz zu den anderen drei Rezeptorsubtypen (A1, A2A, A3) nur bei hohen Adenosinkonzentrationen aktiviert (Entzündungen, Hypoxie, Tumore). Bisher gibt es noch keinen hochaffinen und selektiven PET-Radioliganden für diesen Rezeptor. Daher wollen wir einen F-18-markierten Radioliganden für den A2B-Rezeptor zur Darstellung von neuroonkologischen und neuroinflammatorischen Prozessen mittels PET entwickeln.

Methodik: Basierend auf einer Pyrazinstruktur [1] wurden neuartige fluorierte Derivate synthetisiert und deren Affinität und Selektivität gegenüber den Rezeptorsubtypen bestimmt. Ausgehend von einem Nitropräkursor wurde die geeignetste Verbindung, PA51, in DMSO bei 150°C mit F-18 markiert. Nach Isolierung mittels semipräparativer HPLC wurde [18F]PA51 in Mäuse injiziert, um Hirnaufnahme (5 und 30 min p.i.) und Metabolismus (30 min p.i.) zu untersuchen. Die Radiometabolite wurden in Plasma- und Hirnproben mit mizellarer HPLC bestimmt.

Ergebnisse: Die Radiomarkierung von [18F]PA51 (A2B Ki=4.24±0.04 nM; A1 Ki=20.9±5.22 nM; A2A Ki=55.0±6.10 nM; A3 Ki=796 nM) konnte mit einer radiochemischen Ausbeute von 36.1±4.6% (zerfallskorrigiert), molaren Aktivitäten im Bereich von 10-30 GBq/µmol und einer radiochemischen Reinheit von = 99% durchgeführt werden. Die Mausstudien zeigten eine initial hohe Aktivitätsanreicherung im Gehirn (SUV5 min p.i. = 4). Allerdings wurde 30 min p.i. eine schnelle Metabolisierung im Plasma beobachtet und im Gehirn ein Radiometabolit mit 30% der Gesamtaktivität nachgewiesen.

Schlussfolgerungen: [18F]PA51 ist für einen Einsatz als PET-Radioligand zur molekularen Bildgebung des A2B-Rezeptors im Gehirn nicht geeignet. Deshalb sind weitere strukturelle Modifikationen geplant, um die metabolische Stabilität und die Selektivität der Verbindung zu erhöhen.


[1] Eastwood et al. ACS Med. Chem. Lett. 2011, 2, 213.

Keywords: A2B Rezeptor; F-18

  • Lecture (Conference)
    Nuklearmedizin 2017, 26.-29.04.2017, Dresden, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2017)2, A45

Publ.-Id: 24353

Spatial variability of source composition and petrogenesis in rift and rift flank alkaline lavas from the Eger Rift, Central Europe

Haase, K. M.; Beier, C.; Regelous, M.; Rapprich, V.; Renno, A. D.

Geochemical data on Oligocene melilititic and nephelinitic rocks from the northern Eger Rift flank in Central Europe reveal significant differences to nephelinites and basanites of volcanic complexes in the rift axis. The mafic rift flank lavas are more enriched in TiO2, P2O5 and CaO but have lower SiO2 compared to the alkaline volcanic rocks in the Eger Rift. The differences inmajor element compositions imply (1) lower degrees of partial melting beneath the rift flank than beneath the rift axis evident fromlower SiO2 and higher (Ce/Yb)N ratios in the off-axis basalts and (2) different assemblages of fractional crystallization. The mafic rift flankmagmas experienced crystal fractionation of olivine followed by clinopyroxene fractionation in contrast to early simultaneous olivine and clinopyroxene fractionation in the magmas below the rift basin. In addition, assimilation of continental crustal rocks is associated with crystal fractionation and changes the composition of the lavas. The rift axis lavas are enriched in Nb and Ba relative to La and have higher Sr and lower Nd isotope ratios than the rift flank magmas indicating differentmantle sources. The melting zones beneath the rift axis and the rift flank region are separated although they are only some 20 km apart and no melt exchange between the magma systems is observed. All magmas probably experienced mixing between a deep carbonatitic and a shallower low-degree silicate melt.

Keywords: Continental rifting; Intraplate volcanism; Magma formation; Fractional crystallization; Crustal assimilation

Publ.-Id: 24352

The controversial role of phospholipase C epsilon (PLCε) in cancer development and progression

Tyutyunnykova, A.; Telegeev, G.; Dubrovska, A.

The phospholipase C (PLC) enzymes are important regulators of membrane phospholipid metabolism. PLC proteins can be activated by the receptor tyrosine kinases (RTK) or G-protein coupled receptors (GPCR) in response to the different extracellular stimuli including hormones and growth factors. Activated PLC enzymes hydrolyze phosphoinositides to produce Ca2+ and diacylglycerol which are important mediators of the intracellular signaling transduction. PLC family includes 13 isozymes belonging to 6 subfamilies according to their domain structures and functions. Although importance of PLC enzymes for key cellular functions is well established, the PLC proteins belonging to the ε, ζ and η subfamilies were identified and characterized only during the last decade. As a largest known PLC protein, PLCε is involved in a variety of signaling pathways and controls different cellular properties. Nevertheless, its role in carcinogenesis remains elusive.
The aim of this review is to provide a comprehensive and up-to-date overview of the experimental and clinical data about the role of PLCε in the development and progression of the different types of human and experimental tumors.

Keywords: Phospholipase Cε; cancer development; intracellular signaling; oncogene; tumor suppressor

Publ.-Id: 24350

Cancer stem cells: the root of tumor recurrence and metastases

Peitzsch, C.; Tyutyunnykova, A.; Pantel, K.; Dubrovska, A.

Despite the progress in the prevention, diagnostics and treatment, cancer remains a major cause of morbidity and mortality around the world. According to the world health organization (WHO), more than 14 million newly diagnosed cases and more than 8 million deaths were reported in 2012, and increase in new cases of cancer by 70% and cancer related deaths by 45% is expected over the next 2 decades. Metastatic tumors are the cause of more than 90% of cancer related deaths due to the fact that current therapies frequently fail to provide durable curative response if tumor is spread. In this review, we summarize the main common hallmarks and evolving concept of cancer stem cells and metastasis initiating cells, their dynamic interaction with microenvironmental factors, discuss perspectives of using cancer stem cells and circulating tumor cells as prognostic and predictive tumor biomarkers as well as possible strategies for their targeting in the clinical setting.

Keywords: Cancer stem cells; Circulating tumor cells; Epithelial-mesenchymal transition; Metastatic niche; Metastasis-initiating cells; Liquid biopsy; Biomarkers


Publ.-Id: 24349

Microbial Transformations of Selenite by Methane-Oxidizing Bacteria

Eswayah, A.; Hondow, N.; Scheinost, A. C.; Smith, T.; Gardiner, P.

Methane oxidizing bacteria are well known for their role in the global methane cycle and their potential for microbial transformation of wide range of hydrocarbon and chlorinated hydrocarbon pollution. In recent years it has also emerged that methane-oxidizing bacteria interact with inorganic pollutants in the environment, including heavy metals. Here we report what we believe to be the first study of the interaction of methane-oxidizing bacteria with selenite. Results indicate that the commonly used laboratory model strains of methane oxidizing bacteria, Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b are both able to reduce the toxic selenite (SeO32-) form to nanoparticulate elemental selenium (Se0). Subsequently, volatile selenium-containing species were detected from the Mc. capulatus and Ms. trichosporium cultures, concomitant with the loss of red colour due to Se0 from both cultures. This suggests that both strains may have an additional activity that can either transform Se0 or selenite into volatile methylated forms of selenium. Collectively these results are promising for the use of methane-oxidising bacteria for bioremediation or suggest possible uses in the production of selenium nanoparticles for biotechnology.

Keywords: selenium; Methylosinus trichosporium; Methylococcus capsulatus; EXAFS; XANES

Publ.-Id: 24348

Superiority in robustness of multi-field optimization over single-field optimization for pencil-beam proton therapy for oropharynx carcinoma: an enhanced robustness analysis

Stützer, K.; Lin, A.; Kirk, M.; Lin, L.

Purpose: To compare the difference in robustness of single-field (SFO) and robust multi-field optimized (rMFO) proton plans for oropharynx carcinoma patients by improved robustness analysis.
Methods: rMFO proton plans were generated for 11 oropharynx patients treated with SFO intensity modulated proton therapy (IMPT) with simultaneous integrated boost prescription. Doses from both planning approaches are compared for the initial plans and the worst cases from 20 optimization scenarios of setup errors (SE) and range uncertainties (RU). Expected average dose distributions per RU are obtained by adding the contributions from the respective scenarios with a weight according to their expected SE probability, and thus allowing quantification of the RU-related spread of dose parameters. Boundary dose distributions created from 56 combined SE and RU scenarios and considering the vanishing influence of SE after 30 fractions are used to approximate realistic worst case values for the total treatment course. Error bar distributions are derived from these boundary doses and error bar metrics are reported for the clinical target volumes (CTV) and organs at risk (OAR).
Results: rMFO-plans show improved CTV coverage and homogeneity while simultaneously reducing the average mean dose to the constrictor muscles, larynx and ipsilateral middle ear by 5.6Gy(RBE), 2.0Gy(RBE) and 3.9Gy(RBE), respectively. This is also observed by the different robustness evaluation methods, where additionally the average maximum brainstem and mean ipsilateral parotid dose significantly lower. For rMFO-plans, the RU-related spread in OAR dose parameters is smaller and many error bar metrics are found to be superior. SFO-plans show lower global maximum dose for single-scenario worst cases and slightly lower mean oral cavity dose throughout.
Conclusion: The benefit of better CTV coverage and OAR dose sparing by rMFO compared to SFO proton plans is preserved under considerations of SE and RU.

Keywords: Proton therapy; Robustness; Oropharynx

Publ.-Id: 24347

Polarization- and Wavelength-Dependent Surface-Enhanced Raman Spectroscopy Using Optically Anisotropic Rippled Substrates for Sensing

Gkogkou, D.; Schreiber, B.; Shaykhutdinov, T.; Ly, H.; Kuhlmann, U.; Gernert, U.; Facsko, S.; Hildebrandt, P.; Esser, N.; Hinrichs, K.; Weidinger, I.; Oates, T.

Anisotropic Ag nanoparticle arrays were created by metal evaporation on rippled silicon templates for sensing of molecules with surface-enhanced Raman spectroscopy. Our results show that these substrates can be used for analysis of complex molecular mixtures and discrimination of solvent molecules. These properties are due to their polarization and wavelength dependency that provide enhancement in a wide spectral range. The dielectric function parallel and perpendicular to the long axis of the nanostructures was determined via ellipsometry yielding two different plasmonic resonances. Polarized surface-enhanced raman scattering (SERS) was subsequently measured as a function of the polarization angle θ for a 4-mercaptobenzonitrile self-assembled monolayer covalently attached to the Ag surface. For 514 nm excitation a cos2 θ-dependence and for 647 nm excitation a sin2 θ-dependency were found, with the maxima expressing the resonances perpendicular and parallel to the ripples, respectively. Those results open the path for using such a substrate as a chemical sensor providing strong enhancement in a broad range of laser wavelengths on only one sensing surface and increasing the specificity by matching resonant Raman conditions.

Keywords: chemical sensors; anisotropic sensor substrates; polarized SERS; silver nanoparticle arrays; 4-mercaptobenzonitrile; enhancement substrate

Publ.-Id: 24346

Combination of 90Y-labelled-Cetuximab with fractionated radiotherapy: report on therapy scheduling and curative potential

Dietrich, A.; Andreeff, M.; Koi, L.; Schubert, M.; Sihver, W.; Faulhaber, D.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.

External beam irradiation (EBRT) can precisely target solid tumors but is limited by the surrounding normal tissue. Radioimmunotherapy mediates additional internal irradiation with the potential to strike also (micro-)metastases. The combination of internal and external radiotherapy (CIERT) is a promising treatment strategy as it potentially combines advantages of both modalities without increasing toxicity. We previously showed that CIERT using 90Y-labelled-Cetuximab ([90Y]Y-Cet) massively increased tumor control probability (TCP) of FaDu xenografts compared to single dose EBRT alone. In the presented project, we investigated CIERT using clinical relevant fractionated EBRT with 30 fractions (fx) over 6 weeks. To model [90Y]Y-Cet uptake and study the best application timing, FaDu-bearing mice were injected with near-infrared-labeled-Cetuximab (NIR-Cet) at different time points during fxEBRT with differing doses. NIR-Cet uptake was longitudinally followed by in vivo optical imaging. From the results we concluded, that low to moderate doses of fxEBRT can enhance Cetuximab uptake. Based on the data, we injected [90Y]Y-Cet after 10 fx of EBRT in ongoing TCP-experiments for testing curative potential of CIERT. First analysis after 90 d observation period show that CIERT massively increase TCP compared to fxEBRT alone or in combination with unlabeled Cetuximab. Even in the group with the lowest external dose (1 Gy/fx, total dose = 30 Gy) plus [90Y]Y-Cet all tumors were permanently controlled. In contrast, the total fxEBRT dose to cure 50% of the tumors without [90Y]Y-Cet injection was 62.8 Gy [57.5, 69.5]. Our results indicate that the combination of radiolabeled therapeutics with fractionated external radiotherapy in a clinical relevant setting has a remarkably potential to improve treatment outcome. An efficient uptake of the drug is a prerequisite for the success of CIERT and may be improved by application of some EBRT dose prior to injection. This scheduling would enable patient stratification via a corresponding PET-tracer during ongoing therapy.

Keywords: internal and external radiotherapy (CIERT); HNSCC xenograft

  • Open Access Logo Contribution to proceedings
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland
    Journal of Labelled Compounds and Radiopharmaceuticals

Publ.-Id: 24345

Magnetism of Rare Earth Tetraborides

Mat'As, S.; Siemensmeyer, K.; Wheeler, E.; Wulf, E.; Beyer, R.; Herrmannsdörfer, T.; Ignatchik, O.; Uhlarz, M.; Flachbart, K.; Gabani, S.; Priputen, P.; Efdokimova, A.; Shitsevalova, N.

The rare earth tetraborides REB4 with RE = Ho, Er, Tm, crystallize in a tetragonal lattice where the positions of the RE ions can be mapped to a Shastry-Sutherland lattice. We have investigated the magnetic properties by means of magnetisation and specific heat experiments in a magnetic field. All compounds are anisotropic, with RE = Er, Tm they are strong Ising magnets, for RE = Ho we find xy anisotropy. In magnetic field we find complex behaviour with a number of different phases as a function of applied field, field direction and temperature. Remarkable is the observation of fractional magnetisation plateaux for magnetic field || (001) in HoB4 and TmB4.

Publ.-Id: 24344

Bimetallic MOFs (H3O)x[Cu(MF6)(pyrazine)2] (4-x)H2O (M = V4+, x = 0; M = Ga3+, x = 1): co-existence of ordered and disordered quantum spins in the V4+ system

Manson, J. L.; Schlueter, J. A.; Garrett, K. E.; Goddard, P. A.; Lancaster, T.; Möller, J. S.; Blundell, S. J.; Steele, A. J.; Franke, I.; Pratt, F. L.; Singleton, J.; Bendix, J.; Lapidus, S. H.; Uhlarz, M.; Ayala-Valenzuela, O.; Mcdonald, R. D.; Gurak, M.; Baines, C.

The title compounds are bimetallic MOFs containing [Cu(pyz)2]2+ square lattices linked by MF6 n- octahedra. In each, only the Cu2+ spins exhibit long-range magnetic order below 3.5 K (M = V4+) and 2.6 K (M = Ga3+). The V4+ spins remain disordered down to 0.5 K.

Publ.-Id: 24343

PENELOPE – a high energy 150 fs diode-pumped laser system

Albach, D.; Loeser, M.; Röser, F.; Siebold, M.; Schramm, U.

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is currently constructing a fully diode-pumped Petawatt laser ‒ PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system relying on Yb:CaF2 as gain medium designed for pulse energies of 150 J and a pulse duration of 150 fs operating at a repetition rate of 1 Hz...

  • Invited lecture (Conferences)
    7th International Conference on Ultrahigh Intensity Lasers (ICUIL), 11.-16.09.2016, Montebello, Canada

Publ.-Id: 24342

Magnetotransport and de Haas–van Alphen measurements in the type-II Weyl semimetal TaIrTe4

Khim, S.; Koepernik, K.; Efremov, D. V.; Klotz, J.; Förster, T.; Wosnitza, J.; Sturza, M. I.; Wurmehl, S.; Hess, C.; van den Brink, J.; Büchner, B.

The layered ternary compound TaIrTe4 has been predicted to be a type-II Weyl semimetal with only four Weyl points just above the Fermi energy. Performing magnetotransport measurements on this material we find that the resistivity does not saturate for fields up to 70 T and follows a ρ ∼ B1.5 dependence. Angular-dependent de Haas–van Alphen measurements reveal four distinct frequencies. Analyzing these magnetic quantum oscillations by use of density functional theory calculations we establish that in TaIrTe4 the Weyl points are located merely ∼40–50 meV above the chemical potential.

Publ.-Id: 24341

Identification of mineral-binding peptides that discriminate between chalcopyrite and enargite.

Curtis, S.; Lederer, F. L.; Dunbar, S. W.; Macgillivray, R. T. A.

Innovative approaches to the separation of minerals and subsequent extraction of metals are imperative owing to the increasing mineralogical complexity of ore deposits that are difficult or even impossible to separate into slurries or solutions containing only the minerals or metals of interest. Low recovery of metal is typical for these complex deposits leading to significant losses to tailings. In addition, the minerals often contain impurities, some toxic, which are difficult and costly to control or manage during the processing of a concentrate or other mineral product. One example of this complex situation is the significant economic and environmental costs associated with diluting and processing copper concentrates containing arsenic (in the form of the mineral enargite, Cu3AsS4) in the production of pure copper. To overcome these separation problems, we have utilized phage display to identify peptides that demonstrate selective recognition of enargite and the arsenic-free copper sulfide, chalcopyrite. Screening of two random peptide phage display libraries resulted in the identification of an enargite-selective peptide with the sequence MHKPTVHIKGPT and a chalcopyrite-selective peptide with the sequence RKKKCKGNCCYTPQ. Mineral-binding selectivity was demonstrated by binding studies, zeta potential determination and immunochemistry. Peptides that have the ability to discriminate between enargite and chalcopyrite provide a greener option for the separation of arsenic containing contaminants from copper concentrates. This represents the first step towards a major advance in the replacement or reduction of toxic collectors as well as reducing the level of arsenic-bearing minerals in the early stages of mineral processing.

Keywords: Phage display; mineral binding peptides; enargite; chalcopyrite

  • Biotechnology and Bioengineering 114(2017)5, 998-1005
    Online First (2016) DOI: 10.1002/bit.26218

Publ.-Id: 24340

Neue Wege zum Recycling von Seltenen Erden

Lederer, F. L.; Curtis, S.; Dunbar, S. W.; Macgillivray, R. T. A.

Geeignete Methoden zur wirtschaftlichen Aufbereitung der Seltenen Erden im Leuchtpulver von Kompaktleuchtstofflampen (KLL) sind aufgrund fehlender Spezifität Mangelware. Phage Surface Display spielte bisher vor allem in der Medizin eine wichtige Rolle. Forscher der Universität von British Columbia in Kanada setzen es allerdings schon seit einigen Jahren erfolgreich ein, um Antikörper gegen anorganisches Material zu identifizieren. In der kanadischen Forschergruppe erlernte Methoden verhalfen zur Identifizierung von Peptiden mit einer hohen Spezifität für LaPO4:Ce,Tb, dem grünen Leuchtstoff der KLL. Gefundene Bakteriophagen mit Peptiden, die höchste Spezifität für ein Zielmaterial zeigen, sollen in Flotationsexperimenten auf ihre Bindungseigenschaften bei der Separation von Zielmaterial aus einem Materialgemisch untersucht werden. Bakteriophagen oder die Peptide selbst sollen zukünftig dabei helfen, Seltene Erden aus Elektroschrott gewinnbringend zu trennen.

This project has received funding by a Marie Curie International Outgoing Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 623744.

Keywords: Seltene Erden; Kompaktleuchtstofflampen; Phage Surface Display

  • Lecture (Conference)
    ProcessNet-Jahrestagung und 32. DECHEMA-Jahrestagung der Biotechnologen 2016, 12.-15.09.2016, Aachen, Deutschland
  • Abstract in refereed journal
    Chemie Ingenieur Technik 88(2016)9, 1347-1347
    DOI: 10.1002/cite.201650149

Publ.-Id: 24339

Enhancement of carrier mobility in thin Ge layer by Sn co-doping

Prucnal, S.; Liu, F.; Berencén, Y.; Vines, L.; Bischoff, L.; Grenzer, J.; Andric, S.; Tiagulskyi, S.; Pyszniak, K.; Turek, M.; Drozdziel, A.; Helm, M.; Zhou, S.; Skorupa, W.

We present the development, optimization and fabrication of high carrier mobility materials based on GeOI wafers co-doped with Sn and P. The Ge thin films were fabricated using plasmaenhanced chemical vapour deposition followed by ion implantation and explosive solid phase epitaxy, which is induced by millisecond flash lamp annealing. The influence of the recrystallization mechanism and co-doping of Sn on the carrier distribution and carrier mobility both in n-type and p-type GeOI wafers is discussed in detail. This finding significantly contributes to the state-of-the-art of high carrier mobility-GeOI wafers since the results are comparable with GeOI commercial wafers fabricated by epitaxial layer transfer or SmartCut technology.

Keywords: GeOI; flash lamp annealing; ion implantation; explosive recrystallization


Publ.-Id: 24338

Case report of the first lung cancer patient treated with passive scatter proton therapy at the University Proton Therapy Dresden

Stützer, K.; Jakobi, A.; Thiele, J.; Wohlfahrt, P.; Troost, E.; Richter, C.

Purpose: We present the data of the first lung cancer patient treated at the University Proton Therapy Dresden with double scattering with respect to dosimetric stability throughout the treatment course.
Material and Methods: In August 2016, the first lung cancer patient was enrolled in the proton therapy arm of the clinical trial PRONTOX (NCT02731001). The patient with a stage III disease underwent multiple CT imaging: a pre-treatment 4DCT which was used for treatment planning and sequential 4DCT imaging in treatment position once a week (5 in total) for evaluation of motion and anatomical changes. The tumour GTV was contoured on all 4DCT phases and its centre of mass was used for motion assessment. A double scattering proton treatment plan with 3 beams was generated on the average CT using the iCTV (iGTV+involved lymph node stations+8mm) as target. The iGTV was overwritten with an average density. Margins and smearing were applied following Moyers et al. 2001. A robustness assessment was undertaken before treatment by evaluating the dose on all 4DCT phases, and recalculating the doses with uncertainties of ±3.5% HU and 8 set-up shifts of x,y,z=±3 mm. A re-evaluation of the dose distribution was performed weekly on the sequential average CT. For this purpose, the delineated contours were transformed with deformable image registration to match the new CT data.
Results: Pre-treatment motion of the GTV was below 1.5 mm in all directions and did not change during treatment. The pre-treatment robustness evaluation showed median changes below 5% for all evaluated OAR parameters, not exceeding the dose constraints, and a median dose coverage drop of iCTV from V95=99.8 % to V95=97.7%, which was deemed acceptable. OAR parameters evaluated on the sequential CT scans increased throughout the treatment by maximum 8% in the worst case, but not exceeding any constraints, while iCTV coverage was only slightly decreased (worst case drop of 0.1% in V95). An anatomical and dosimetric comparison of the planning CT and the sequential CT which had the worst iCTV coverage is shown in Figure 1.
Conclusion: The first lung cancer patient double scattering proton treatment at the University Proton Therapy Dresden was safely implemented. Within the framework of the trial, follow-up data regarding side effects and outcome will be collected and analysed. The collected data will also be used for evaluations of interplay and motion mitigation for pencil beam scanning treatment, including daily recorded breathing patterns and irradiation log files to enable the implementation of this technique in future.

  • Poster
    4D Workshop 2016, 08.-09.12.2016, Groningen, Netherlands

Publ.-Id: 24337

PEnELOPE - a high energy 150 fs hybrid thin disk and gas-cooled multi-slab laser system

Siebold, M.; Albach, D.; Loeser, M.; Schramm, U.

The Helmholtz-Centre Dresden-Rossendorf (HZDR) is currently launching the fully diode-pumped Petawatt laser PEnELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments). A five stage amplifier system using Yb:CaF2 as gain medium...

  • Lecture (Conference)
    Stuttgarter Lasertage, 31.05.-01.06.2016, Stuttgart, Germany

Publ.-Id: 24336

Enhanced Laser Proton Acceleration with Ultra-High Laser Contrast

Obst, L.; Poole, P.; Metzkes, J.; Zeil, K.; Cochran, G.; Kluge, T.; Schlenvoigt, H.-P.; Kraft, S.; Brack, F.; Kroll, F.; Prencipe, I.; Rehwald, M.; Schumacher, D.; Schramm, U.; Cowan, T.

We present results of our experimental campaign on laser proton acceleration, in which liquid crystal film targets of tunable thickness were irradiated with plasma mirror cleaned laser pulses. The data show a significant increase in proton cut-off energy up to 25 MeV for a target thickness of 10 nm as compared to the few- micron scale reference for this target configuration yielding roughly 12 MeV.

Keywords: Laser; Plasma; Particle Acceleration

  • Lecture (others)
    HZDR PhD Seminar, 17.10.2016, Oberwiesenthal, Deutschland

Publ.-Id: 24335

High-repetition-rate laser-proton acceleration from a condensed hydrogen jet

Obst, L.; Rehwald, M.; Göde, S.; Sommer, P.; Brack, F.; Schramm, U.; Gauthier, M.; Macdonald, M.; Roedel, C.; Glenzer, S.; Zeil, K.; Metzkes, J.; Schumaker, W.; Schlenvoigt, H.-P.

Applications of laser-accelerated protons demand a stable source of energetic particles at high repetition rates. We present the results of our experimental campaign in cooperation with MEC/SLAC at the 10Hz Ti:Sa laser Draco of Helmholtz-Zentrum Dresden-Rossendorf (HZDR), employing a pure condensed hydrogen jet as a renewable target. Draco delivers pulses of 30fs and 5J at 800nm, focused to a 3µm spot by an F/2.5 off-axis parabolic mirror. The jet's nominal electron density is approximately 30 times the critical density and its thickness is 2µm, 5µm or 10µm, depending on the applied aperture on the source. Ion diagnostics reveal mono-species proton acceleration in a solid angle of at least +/-45 ° with respect to the incoming laser beam, with maximum energies of around 5 MeV. The expanding jet could be monitored on-shot with a temporally synchronized probe beam perpendicular to the pump laser axis. Recorded probe images resemble those of z-pinch experiments with metal wires and indicate an m=0 instability in the plasma.

Keywords: Laser; Plasma; Targets; Particle Acceleration

  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft Frühjahrstagung 2016, 17.03.2016, Darmstadt, Deutschland

Publ.-Id: 24334

Ultra-fast Thermal Processing for thin metallic films

Rebohle, L.; Schumann, T.; Prucnal, S.; Skorupa, W.

Thermal processing in the ms range comprises modern, non-equilibrium annealing techniques which allow various material modifications at the surface without affecting the bulk. Flash lamp annealing (FLA) is one of the most diverse methods of short time annealing with applications ranging from the classical field of semiconductor doping to the treatment of polymers and flexible substrates. The presentation focuses on several FLA aspects which are important for thin film applications, especially for thin metallic films.

Keywords: flash lamp annealing; thin film applications

  • Lecture (others)
    FLA Seminar, CERN, 19.10.2016, Genf, Schweiz

Publ.-Id: 24333

Structural clarification of a tert-butyl-calix[4]arene-based 8-hydroxyquinoline complex with uranium(VI) in non-aqueous solution

Bauer, A.; März, J.; Barthen, R.; Jäschke, A.; Glasneck, F.; Schmeide, K.; Brendler, V.; Kersting, B.; Stumpf, T.

The actinides uranium and thorium are considered disturbing constituents in rare earth production. Thus they have to be removed, e.g. by extraction.[1] Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of uranium(VI).[2]
A new chalice-like tert-butyl-calix[4]arene-based 8-hydroxyquinoline ligand consisting of four phenolic units was synthesized. Tert-butyl substituents provide a hydrophobic character. Functionalizing of the phenolic hydroxyl groups by 8-hydroxyquinoline ensures the affinity to uranyl ions.[2]
For better process understanding we examined the mechanisms of uranyl complexation by the calix[4]arene derivative. The structure of the tert-butyl-calix[4]arene-based 8-hydroxyquinoline uranyl complex was unveiled by spectroscopy and microcalorimetry.
The complexation studies were performed in acetonitrile. Luminescence spectroscopic studies indicated the interaction of uranyl ions with the ligand. UV visible investigations evidenced the presence of a 1:1 and a 1:2 ligand uranyl complex with stability constants of log ß1:1 = 5.94 ± 0.016 and log ß1:2 = 6.33 ± 0.013.
Microcalorimetry provided the thermodynamic characterization of the complexation.
Single crystal X-ray analysis of the 1:1 complex revealed the coordination of the uranyl ion via a N2O2 donor set (Fig. 1). The charge is compensated by an additional coordinated nitrate ion. Due to the chelation reddish uranyl calix[4]arene complexes were formed as indicated by the absorption band at 525 nm. An increase of the peak up to the addition of two equivalents of uranyl ions suggested a complexation of both uranyl ions through chelation in acetonitrile.
The application of electrospray ionization time-of-flight mass spectrometry affirmed the coordination of two hexavalent uranyl nitrate ions in acetonitrile.
In addition, to improve the understanding of the ligand complexation properties the interaction with thorium is studied.

[1] Z. W. Zhu, Y. Pranolo, C.Y. Cheng, Miner Eng 2015, 77, 185-196.
[2] A. Jäschke, M. Kischel, A. Mansel, B. Kersting, 2016, in prep.

Keywords: SE-FLECX; rare earth production; calix[4]arene; uranium; complexation studies

  • Poster
    ANAKON 2017, 03.-06.04.2017, Tübingen, Deutschland

Publ.-Id: 24332

Structural investigations of (La,Pu)PO4 monazite solid solutions: XRD and XAFS study

Arinicheva, Y.; Popa, K.; Scheinost, A. C.; Rossberg, A.; Dieste-Blanco, O.; Raison, P.; Cambriani, A.; Neumeier, S.; Somers, J.; Bosbach, D.

A fundamental understanding of actinide incorporation processes in envisioned nuclear waste forms, such as monazite ceramics, is required for a reliable prediction of the long-term stability of such ceramic materials for safe nuclear disposal. The present study provides structural insights into the formation of monazite solid solutions by incorporation of PuIII and verifies previous results on surrogate materials, where Eu and Gd served as inactive analogues for trivalent actinides.
A solid state method was used to synthesize La1-xPuxPO4 (x = 0.01, 0.05, 0.10, 0.15, 0.5) solid solutions with monazite structure. XRD measurements of the compounds with x = 0.50 revealed the formation of two phases: (La,Pu)PO4-monazite and a cubic phase (PuO2). Pure-phase La1-xPuxPO4-monazite solid solutions were obtained for materials with x = 0.00-0.15 and confirmed by a linear dependence of the lattice parameters on composition according to Vegard’s law. X-ray absorption spectroscopy (XAS) analysis at the Pu-LIII and La-LIII edges verified the +III valence state of plutonium in the monazite solid solutions. The local environment of Pu is similar as in PuPO4-like along the solid solution series, except for the longest fitted cation-cation distance, which may be an indication of cluster formation consisting of a few Pu-atoms in the La-Pu-monazite lattice.

Keywords: Plutonium; monazite; waste form; solid state synthesis; solid solutions; XRD; EXAFS

Publ.-Id: 24331

Highly doped zinc oxide films produced by advanced thermal processing in the millisecond range

Rebohle, L.; Braun, M.; Prucnal, S.; Skorupa, W.; Guziewicz, E.; Snigurenko, D.

Zinc oxide (ZnO) is an attractive candidate to replace indium tin oxide in microelectronic and photovoltaic applications. Furthermore, ZnO nanostructures hold great promise for sensor applications. Whereas n-type doping can be easily achieved, p-type doping is a more challenging issue as most defects like Zn interstitials act as n-type dopants.
In this work 100 nm thick ZnO layers were grown by atomic layer deposition on a thermal SiO2 layer on top of a Si wafer. Subsequently, the layers were implanted by phosphorus or antimony, followed by flash lamp annealing (FLA). The ZnO layers were investigated by means of Raman, photoluminescence, sheet resistance and Hall measurements. Depending on the FLA conditions, the doping type shifts from n-type dominated by defects to p-type caused by the implanted group V elements.

Keywords: flash lamp annealing; ion implantation; zinc oxide

  • Lecture (Conference)
    Material Science and Engineering, 27.-29.09.2016, Darmstadt, Deutschland

Publ.-Id: 24330

A Bayesian Approach for Measurements of Stray Neutrons at Proton Therapy Facilities: Quantifying Neutron Dose Uncertainty

Dommert, M.; Lutz, B.; Reginatto, M.; Zbořil, M.

The use of proton beams in radiation therapy allows for the deposition of high doses at the tumor position while minimizing the dose to the surrounding healthy tissue. However, in addition to proton radiation, the patient is also exposed to secondary radiation, which produces an unwanted out-of-field dose. As neutron radiation can provide the largest contribution to this out-of-field dose for proton therapy, it is important to characterize the stray neutron field in the therapy room.
As part of a collaboration with HZDR, PTB has carried out measurements with the Bonner sphere spectrometer NEMUS at the OncoRay Proton Therapy Facility in Dresden. The analysis of Bonner sphere measurements is typically done using unfolding codes. However, it is very difficult to implement reliable uncertainty propagation in standard unfolding codes. An alternative approach, which does provide reliable estimates of uncertainties of neutron spectra which lead to rigorous estimates of uncertainties of the dose, is to analyze the Bonner sphere data using Bayesian parameter estimation [1][2]. In this work, we extend previous approaches and apply this method to secondary neutrons from radiation therapy proton beams. This requires introducing a parameterized model which can describe the main features of the neutron spectra. We choose the parameterization based on information that is available from measurements and detailed Monte Carlo simulations.
To demonstrate the validity of this approach, we consider the results of an experiment carried out at the experimental hall of the OncoRay facility. Measurements were done with the following experimental set-up: a brass target was placed in the proton beam and the proton beam was pulsed with 10 Hz to mimic the operation of a range modulator wheel. Bonner spheres were placed at different angles with respect to the incoming proton beam. We selected a set of 7 polyethylene spheres and 3 extended spheres with lead or copper inserts. The results of the analysis are the spectra of secondary neutrons with their corresponding doses with uncertainties. The approach that we describe here provides a basic method to assess neutron spectra and their uncertainties and will be extended in future applications to include additional parameters; e.g., those describing the settings of the proton beam.
[1] M. Reginatto, Radiat. Prot. Dosim 120, 64-69 (2006).
[2] M. Reginatto, Rad. Meas. 44, 692-699 (2009).

Keywords: unfolding; Bayesian parameter estimation; neutron dose; proton therapy

  • Poster
    Neutron and Ion Dosimetry Symposium, 14.-19.05.2017, Kraków, Polska

Publ.-Id: 24329

Flow Structures Analysis Downstream Gas Spargers of Different Orifice Pattern in Bubble Columns

Möller, F.; Bieberle, A.; Barthel, F.; Schubert, M.; Hampel, U.; Weber, M.; Weber, M.

Bubble column reactors are widely employed for gas-liquid reactions due to their superior mass and heat transfer accompanied by being geometrically simple and free from any moving part. However, the gas sparger is a crucial device, which directly determines the process performance. The bubbles released from the orifices of the gas sparger start rising up and buoyancy and drag forces etc., in turn, depending on bubble size, control the traveling velocity of the bubbles, and eventually the overall hydrodynamic behavior, such as mixing and gas holdup. Hence, to get an insight into the impact of orifice patterns and holes’ diameter of a gas sparger on the axially evolving gas-liquid dispersion, an ultrafast X-ray tomography study is performed in a 2 m height bubble column of 100 mm diameter. Two different perforated plate-type spargers are used, namely a single orifice sparger with a 2.9 mm center hole and a plate with 13 orifices arranged in a triangular pitch with a hole diameter of 0.8 mm, respectively. The experiments were performed in a non-coalescing system for superficial gas velocities up to 2.5 cm/s. From the X-ray measurements, the evolving gas structures, the bubble size distributions as well as the cross-sectional gas holdup distributions are extracted along the column height and the benefit of a fine initial distribution is evaluated.

  • Lecture (Conference)
    International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Contribution to proceedings
    International Conference on Multiphase Flows, 22.-27.05.2016, Firenze, Italy

Publ.-Id: 24328

Liquid Circulation and Swarm Dynamics in Bubble Columns with Internals

Möller, F.; Hampel, U.; Schubert, M.

Bubble column reactors are apparatuses of choice for many gas-liquid and gas-liquid-solid reactions due to their superior mixing, heat and mass transfer behavior as well as their simple design without any moving part. In particular, they are often used for exothermic reaction processes such as methanol synthesis, Fischer-Tropsch synthesis etc. Hence, the heat has to be removed out of the system in order to guarantee safe operation at optimal reaction conditions. For this purpose a variety of heat exchangers e.g. internal heat exchanging tube bundles, which can also be used to generate steam, are applied. However, the effects of heat exchanger installation in bubble columns on the gas-liquid flow are still fragmentary.
This contribution focusses on the effect of internals on liquid circulation and swarm dynamics. Internal longitudinal flow heat exchanging bundles with various tube pattern configurations (triangular, and square pitch) and tube diameters between 8 and 13 mm while covering a cross sectional area of ~25% are subject to hydrodynamic and mixing studies in a column of 100 mm diameter.
Wire-mesh sensors with measurement points suitably distributed in the cross-section between the internals’ tubes were installed at different axial positions to study liquid mixing and dispersion in the bubble column as well as lateral fluid exchange between sub-channels. Tracer studies were performed and suitable transfer functions were applied for the determination of the liquid dispersion coefficient. It was found that bubble columns with tube bundle internals show similar behavior as airlift reactors. In addition, ultrafast X-ray tomography is applied to study the effect of the internal configurations on the axial bubble size distribution and gas fraction evolution as well as on the prevailing flow regimes.

  • Poster
    Jahrestreffen Bingen 2016 - Fachgruppen Agglomerations- und Schüttguttechnik, Mehrphasenströmungen und Computational Fluid Dynamics (AGG, MPH, CFD), 29.02.-02.03.2016, Bingen, Deutschland

Publ.-Id: 24327

Electrical conduction and negative magnetoresistance in tellurium-hyperdoped silicon

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

Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped Si layers have been fabricated by ion implantation followed by either millisecond flash lamp annealing (FLA) or nanosecond pulsed-laser melting (PLM). The electrical conduction and magnetoresistance of Te-hyperdoped Si are investigated at magnetic fields up to 5 T and temperatures ranging from 2 K to 300 K. With increasing Te concentration, an insulator-to-metal transition is observed although Te introduces a deep donor level (around 300–400 meV) below the Si conduction band. Moreover, the temperature-dependent conductivity measured at zero magnetic field shows that the charge transport is associated with variable-range hopping (VRH) at low temperatures, which scales as δ(T)=δ0 exp[-(T0/T)s] (S=1/4 or 1/2). In addition negative magnetoresistance is observed at low magnetic field, turning positive at B around 0.9 T.

Keywords: hyperdoped silicon; Tellurium; hopping conductivity; negative magnetoresistance

  • Poster
    33rd International Conference on the Physics of Semiconductors, 31.07.-05.08.2016, Beijing, China

Publ.-Id: 24326

An optimized small animal tumour model for experimentation with low energy protons

Beyreuther, E.; Brüchner, K.; Krause, M.; Schmidt, M.; Szabo, R.; Pawelke, J.

Background: The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also the radiobiological characterization of the resulting ultra-short and ultra-intensive particle beam pulses. Subsequent to comprehensive cell studies a mouse ear tumour model was established allowing for the penetration of low energy protons (~20 MeV) currently available at laser driven accelerators. The model was successfully applied for a first tumour growth delay study with laser driven electrons, whereby the need of improvements crop out .
Methods: To optimise the mouse ear tumour model with respect to a stable, high take rate and a lower number of secondary tumours MatrigelTM was introduced for tumour cell injection. Different concentrations of two human tumour cell lines (FaDu, LN229) and Matrigel were evaluated for stable tumour growth and fulfilling the allocation criteria for irradiation experiments. The originally applied cell injection with PBS was performed for comparison and to assess the long-term stability of the model. Finally, the optimum suspension of cells and Matrigel was applied to determine applicable dose ranges for tumour growth delay studies by 200 kV X-ray irradiation.
Results: Both human tumour models showed a high take rate and exponential tumour growth starting at a volume of ~10 mm3. As disclosed by immunofluorescence analysis these small tumours already interact with the surrounding tissue and activate endothelial cells to form vessels. The formation of delimited, solid tumours at irradiation size was shown by standard H&E staining and a realistic dose range for inducing tumour growth delay, but not tumour control, was obtained for both tumour entities.
Conclusion: The already established mouse ear tumour model was successfully upgraded now providing stable tumour growth with high take rate for two tumour entities (HNSCC, glioblastoma) that are of interest for future irradiation experiments at experimental accelerators.

Keywords: mouse tumour model; low energy protons; laser particle acceleration; low penetrating radiation; proton therapy

Publ.-Id: 24324

Helium-ion microscopy, helium-ion irradiation and nanoindentation of Eurofer 97 and ODS Eurofer

Bergner, F.; Hlawacek, G.; Heintze, C.

Understanding of unsolved details of helium embrittlement requires experimental evidence for dedicated sets of materials and over a wide range of irradiation conditions. The study is focussed on the comparison of the reduced-activation ferritic-martensitic 9%Cr steel with its oxide dispersion strengthened (ODS) counterpart with respect to irradiation-induced hardening. Imaging and He-ion irradiation in the He-ion microscope at 30 ºC in a wide range of appm He (from 0.9 x 1E2 to 1.8 x 1E6) and displacements per atom (from 3 x 1E-3 to 65) were combined with post-irradiation nanoindentation in order to detect blistering and irradiation-induced hardness changes. The applicability of this combination of techniques is demonstrated and pros and cons are discussed. We have found that the irradiation-induced hardness increase is higher and the onset of significant hardening tends to occur at lower fluence for Eurofer 97 than for ODS Eurofer, indicating that the presence of oxide nanoparticles is efficient to reduce the detrimental effect of He under the applied irradiation conditions.

Keywords: Ferritic-martensitic chromium steel; Oxide dispersion strengthened steel; He-ion microscopy; Ion irradiation; Nanoindentation


Publ.-Id: 24323

Mechanical properties and plasticity size effect of Fe-6%Cr irradiated by Fe ions and by neutrons

Hardie, C. D.; Odette, G. R.; Wu, Y.; Akhmadaliev, S.; Roberts, S. G.

The mechanical behaviour of Fe6%Cr in the un-irradiated, self-ion irradiated and neutron irradiated conditions was measured and compared. Irradiations were performed to the same dose and at the same temperature but to very different damage rates for both methods. The materials were tested using nanoindentation and micromechanical testing, and compared with microstructural observations from Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT) reported elsewhere. Irradiated and un-irradiated micro-cantilevers with a wide range of dimensions were used to study the interrelationships between irradiation hardening and size effects in small-scale plasticity. TEM and APT results identified that the dislocation loop densities were ~2.9 E22 m-3 for the neutron irradiated material and only 1.4E22 m-3 for the ion irradiated material. Cr segregation to loops was only found for the neutron-irradiated material. The nanoindentation hardness increase due to neutron irradiation was 3 GPa and that due to ion irradiation 1 GPa. The differences between the effects of the two irradiation types are discussed, taking into account inconsistencies in damage calculations, and the differences in PKA spectra, dose rate and transmutation products for the two irradiation types.

Publ.-Id: 24322

Ion-beam induced atomic mixing in isotopically controlled silicon multilayers

Radek, M.; Bracht, H.; Liedke, B.; Böttger, R.; Posselt, M.

Implantation of germanium (Ge), gallium (Ga), and arsenic (As) into crystalline and preamorphized isotopically controlled silicon (Si) multilayer structures at temperatures between 153 K and 973K was performed to study the mechanisms mediating ion-beam induced atomic mixing. Secondary-ion-mass-spectrometry (SIMS) was applied to determine concentration-depth profiles of the stable isotopes before and after ion implantation. The intermixing is analytically described by a depth-dependent displacement function. The maximum displacement is found to depend not only on temperature and microstructure but also on the doping type of the implanted ion. Molecular dynamics calculations evaluate the contribution of cascade mixing, i.e., thermal-spike mixing, to the overall observed atomic mixing. Calculated and experimental results on the temperature dependence of ion-beam mixing in the amorphous and crystalline structures provide strong evidence for ion-beam induced enhanced crystallization (IBIEC) and enhanced self-diffusion (IBIESD), respectively. Whereas the former process is confirmed by channeling Rutherford backscattering analyses of the amorphous layer thickness remaining after implantation, the latter process is consistently attributed to the formation of highly mobile Si di-interstitials formed under irradiation and in the course of damage annealing. The observed ion-beam mixing in Si is compared to recent results on ion-beam mixing of Ge isotope multilayers that, in contrast to Si, are fully described by thermal-spike mixing only.

Keywords: ion beam mixing; silicon isotope multilayers

Publ.-Id: 24321

Selektive Phasengeschwindigkeitsmessung in Blasenströmungen durch den kombinierten Einsatz einer Heißfilmsonde und der ultraschnellen Röntgentomographie

Kipping, R.; Kryk, H.; Hampel, U.

Blasensäulenreaktoren bieten aufgrund ihrer einfachen Bauweise und ihres ausgezeichneten Wärme- und Stofftransportverhaltens einen häufig genutzten Reaktortyp in der chemischen Industrie. Besonders die Beschreibung der Hydrodynamik und der Geschwindigkeitsprofile der unterschiedlichen Phasen, sowie deren radiale Verteilung haben einen erheblichen Einfluss auf den Stofftransport und chemische Reaktion. In diesem Beitrag sollen die Ergebnisse der Untersuchung zur Flüssigphasengeschwindigkeit in Blasenströmungen vorgestellt werden. Die Anwendbarkeit von Heißfilmsonden ist bei Vorliegen einer Mehrphasenströmung stark begrenzt. In Blasensäulen beinhaltet das gemessene Geschwindigkeitssignal Anteile der Gas- und Flüssigphase. Zur Untersuchung der Umströmung von Blasen und zur Bestimmung von Turbulenzparametern ist es notwendig diese Anteile voneinander zu trennen. Ausschließlich bei geringen Gasgehalten bietet der charakteristische Signalverlauf bei der Interaktion von Blase und Sonde eine Möglichkeit dazu. In dieser Arbeit kann mit Hilfe der Zwei-Ebenen Tomographie, die genaue Position der Heißfilmsonde und die vorliegende Phase an dieser Stelle in der Blasensäule bestimmt werden. Weiterhin können neben der Flüssigphasengeschwindigkeit auch Parameter der Hydrodynamik der Gasphase, wie Blasenform, Blasengröße bestimmt werden und in Abhängigkeit zur Flüssigphasengeschwindigkeit gestellt werden.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations-und Schüttguttechnik, Computational Fluid Dynamics und Mehrphasenströmungen, 29.02.-02.03.2016, Bingen, Deutschland

Publ.-Id: 24320

Experimental investigation of mass transfer of CO2 bubbles with ultrafast electron beam X-rax tomography

Kipping, R.; Kryk, H.; Hampel, U.

Bubble columns are a favored reactor type for the operation of gas-liquid reactions (e.g. oxidation and hydrogenation processes) in chemical industries. The improved design and operation of bubble column reactors requires a detailed understanding of the flow phenomena as well as mass transfer processes within these reactors. This study presents the experimental investigation the gas liquid mass transfer in a bubble column on the basis of the chemical absorption of CO2. This contribution presents ultrafast X-ray CT measurements within a bubble column. The mass transfer has been determined by the analysis of the decrease of gas the gas phase, especially the shrinkage of the CO2 bubbles.

Keywords: reactive two-phase flow; ultrafast X-ray tomography; chemical absorption; mass transfer

  • Lecture (Conference)
    FERMaT-SPP1740-Symposium, 06.-08.06.2016, Toulouse, Frankreich

Publ.-Id: 24319

How gangue particle size can affect the recovery of ultrafine and fine particles during froth flotation

Leistner, T.; Peuker, U. A.; Rudolph, M.

In general, the poor flotation behavior of ultrafine (< 10 µm) particles is mainly associated with a low particle/bubble collision efficiency within the flotation process due to an unfavorable particle/bubble size ratio. In those considerations the size of the gangue particle system does not play a significant role. This study investigates the effect of gangue particle size on the recovery of ultrafine and fine (10…50 µm) particles. Artificial, binary model particle system, using magnetite as the target and quartz as the gangue mineral, are used for the investigation in order to considerably eliminate reported problems associated with ultrafine gangue particles. Results indicate that ultrafine magnetite can be recovered like fine magnetite when the gangue particles are fine as well. In contrast, fine magnetite recovery drops significantly when ultrafine quartz is used as the gangue mineral system.

Keywords: Flotation; ultrafines; gangue; hydrodynamics

Publ.-Id: 24318

Characterization of a chemical reaction in a bubble column using Wire-Mesh Sensor and ultrafast X-ray CT

Kipping, R.; Kryk, H.; Schleicher, E.; Hampel, U.

Design and operation of bubble columns are of main importance, since they strongly influence yield and selectivity of chemical reactions. In order to improve the process efficiency, a fundamental understanding of flow phenomena in bubble columns is necessary. A lot of research has been carried out for the investigation of hydrodynamics of bubble columns. Nonetheless, hydrodynamics is changing in the presence of a chemical reaction (e.g. shrinkage of bubbles due to mass-transfer processes). Hence, there is a strong interaction of hydrodynamics, mass-transfer and chemical reaction within bubble columns, which has been investigated in the past, amongst others, using the reaction of sodium hydroxide and carbon dioxide. However, most works are restricted to low gas holdups or provide only single point information due to the use of local probes (e.g. pH measurement). This contribution comprises the experimental investigation of the reaction of sodium hydroxide and carbon dioxide, applying Wire-Mesh Sensors for determining the locally occurring reaction steps at different operating conditions (e.g. gas flow rate of carbon dioxide, initial concentrations of sodium hydroxide). In turn, experimental results are compared with concentration profiles derived from known reaction kinetics. The application of Wire-Mesh Sensors for this purpose allows the visualization of the concentration distribution within the cross-section of the bubble column. Additionally, ultrafast X-ray computer tomography is used simultaneously to study the change of hydrodynamics during the reaction.

Keywords: Wire-Mesh Sensor; ultrafast X-ray tomography; two-phase flow; chemical reaction

  • Lecture (Conference)
    WCIPT8 - 8th World Congress on Insutrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien
  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Insutrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien

Publ.-Id: 24317

Different oxidation states of Tc in solid state compounds and surface complexes – an XAS study

Schmeide, K.; Scheinost, A.

Results of XAS measurements of Tc siderite sorption samples as well as of solid state model compounds containing Tc in different oxidation states were presented.

Keywords: technetium; siderite; reduction; coordination; structure

  • Invited lecture (Conferences)
    8th International Workshop on “Coordination Chemistry of Metals with Medical Relevance and Supramolecular Building Blocks“, 26.-27.05.2016, Berlin, Deutschland

Publ.-Id: 24316

Targetting microglia activation in schizophrenia by minocycline treatment

Mattei, D.; Ivanov, A.; Ferrai, G.; Jordan, P.; Guneykaya, D.; Schaafsma, W.; Przanowski, P.; Deuther-Conrad, W.; Brust, P.; Hesse, S.; Eggen, B.; Bodekke, E.; Kaminska, B.; Pombo, A.; Kettenmann, H.; Wolf, S. A.

The importance of the brain's phagocyte – the microglia – came recently into focus as a novel therapeutic target in psychiatric disorders. Dysregulations of microglia have been reported in post mortem tissue and also in vivo by increased radio ligand binding to the (phagocyte-specific) TSPO receptor in brains of schizophrenic patients. The tetracycline minocycline that partially acts on microglia has been shown to improve mainly negative symptoms in a few clinical studies. We here use an animal model of maternal immune activation to test its validity for clinical translation and investigate the pathways that are targeted by minocycline specific in microglia. Pregnant dams were injected intraperitoneally with the viral mimic PolyI:C or saline at gestational day 15 and the offspring was tested for behavioral deficits at postnatal day 60. Indeed, the offspring showed behavioral correlates of schizophrenia like decreased pre-pulse inhibition, sociability and cognitive performance along with an increased binding potential to the TSPO shown by autoradiography using [18F]GE-180 on hippocampal slices. This was accompanied by a profoundly altered transcriptome signature in hippocampal microglia and decreased phagocytic activity. Thereafter, mice were treated for five weeks with minocycline (3 mg/kg/day). This treatment normalized the behavioral deficits, TSPO binding and phagocytic activity and restored the transcriptome signature towards control levels. Our findings indicate that minocycline is a potent drug to affect specific microglial functions and thereby attenuate symptoms of schizophrenia in an animal model.

Keywords: Neuroimmunology; Schizophrenia: basic; Glia

  • Lecture (Conference)
    29th ECNP Congress, 17.-20.09.2016, Vienna, Österreich
  • European Neuropsychopharmacology 26(2016), 134


Publ.-Id: 24315

Reactive absorption of CO2 in NaOH: Detailed study of enhancement factor models

Krauss, M.; Rzehak, R.

In a pioneering study, Darmana et al. [Chemical Engineering Science 62 (2007), 2556 - 2575], considered the reactive absorption of CO2 in aqueous NaOH in a bubble column. Although quite good agreement was obtained between an Euler-Lagrange simulation and measured pH-values at a single point, a number of aspects of the model deserve further discussion. This will be provided in the present work by using a simplified treatment that applies at the measurement location. Particularly relevant is the enhancement factor, which describes the effect of the chemical reaction on the mass transfer. An investigation of alternative expressions for this quantity is given, based on which an improved match with the data can be obtained. Furthermore, the complete network of possible reactions in this system has to be considered.

Keywords: mass transfer; chemical reaction; chemisorption; enhancement factor; dispersed gas liquid multiphase flow; modeling and simulation


Publ.-Id: 24314

Euler-Euler Simulation und Modellvalidierung für Blasenströmungen

Guo, J.

Die Anwendung von Methoden der CFD („Computational fluid dynamics“) für Scale-up und Intensivierung verfahrenstechnischer Prozesse bietet die Möglichkeit, energie- und ressourceneffiziente Lösungen zu identifizieren, deren Untersuchung mit konventionellen halb-empirischen Methoden kostspielig und langwierig wäre.
Eine solche Simulation im großtechnischen Maßstab ist im Rahmen der Euler-Euler Beschreibung möglich, in der Prozesse auf der Skala einzelner Blasen modelliert werden. Ein solches Schließungsmodell für Hydrodynamik und Stofftransport in Blasenströmungen wird am HZDR entwickelt. Ziel dieser Entwicklung ist, ein vorhersagetaugliches Modell zu etablieren, das für einen breiten Bereich von Anwendungsbedingungen validiert ist.
Zu diesem Zweck werden Simulationsrechnungen mit experimentellen Daten verglichen, die zunehmend komplexere Geometrien und Effekte einbeziehen. Auf Basis der jeweils erzielten Übereinstimmung werden Modellerweiterungen und -verbesserungen vorgenommen. Im Rahmen der Diplomarbeit sollen hierzu Strömungen in Blasensäulen und Blasenströmungen in Rohren untersucht werden.

Keywords: Blasenströmung; Euler-Euler zwei-Fluid-Modell; CFD-Simulation

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Dr. Roland Rzehak (HZDR), Prof. Rüdiger Lange (TU-Dresden)
    57 Seiten

Publ.-Id: 24313

Analysis of SAM Coatings for Dropwise Condensation in Passive Safety Systems

Unger, S.; Sarker, D.; Harm, U.; Hampel, U.

Passive safety systems of spent fuel pools are one key technology for further improvement of the reliability of nuclear power plants. These systems transfer high amount of heat, while using air as a heat sink. For that reason the overall temperature differences are small. Since the heat transfer is based on natural convection and gravitational force, the heat transfer resistance of the heat exchangers are high compare to active systems. A Self-Assembled Monolayer (SAM) coating can address both challenges by enable a high compact condensation heat exchanger and by reducing the heat transfer resistance during condensation. Therefore different coating chemicals and surface roughness were analysed, to create the most beneficial heat transfer surface.

Keywords: Passive safety; dropwise condensation; condensation; heat transfer

  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
    Proceedings of the 47th Annual Meeting on Nuclear Technology

Publ.-Id: 24312

Surprising effects of electron-electron scattering in graphene

Helm, M.; König-Otto, J.; Mittendorff, M.; Pashkin, A.; Schneider, H.; Wendler, F.; Winzer, T.; Malic, E.; Knorr, A.; Winnerl, S.

Two surprising effects related to electron-electron scattering in graphene are demonstrated: One is a long-lived anisotropic carrier distribution after THz excitation, and the other one is an unexpected sign reversal of the pump-probe signal in a magnetic field. The latter reflects an Auger scattering so strong that it overcomes the effect of optical pumping.

Keywords: graphene; pump-probe; terahertz; free-electron laser

  • Invited lecture (Conferences)
    5th Russia-Japan-USA-Europe Symposium on Fundamental & Applied Problems of Terahertz Devices & Technologies (RJUSE TeraTech-2016), 31.10.-04.11.2016, Sendai, Japan

Publ.-Id: 24311

Glacial chronology and production rate cross-calibration of five cosmogenic nuclide and mineral systems from the southern Central Andean Plateau

Luna, L. V.; Bookhagen, B.; Niedermann, S.; Rugel, G.; Scharf, A.; Merchel, S.

Glacial deposits on the high-altitude, arid southern Central Andean Plateau (CAP), the Puna in northwestern Argentina, document past changes in climate, but the associated geomorphic features have rarely been directly dated. This study provides direct age control of glacial moraine deposits from the central Puna (24°S) at elevations of 3900–5000 m through surface exposure dating with cosmogenic nuclides.
Our results show that the most extensive glaciations occurred before 95 ka and an additional major advance occurred between 46 and 39 ka. The latter period is synchronous with the highest lake levels in the nearby Pozuelos basin and the Minchin (Inca Huasi) wet phase on the Altiplano in the northern CAP. None of the dated moraines produced boulder ages corresponding to the Tauca wet phase (24–15ka).
Additionally, the volcanic lithologies of the deposits allow us to establish production ratios at low latitude and high elevation for five different nuclide and mineral systems: 10Be, 21Ne, and 26Al from quartz (11 or 12 samples) and 3He and 21Ne from pyroxene (10 samples). We present production ratios for all combinations of the measured nuclides and cross-calibrated production rates for 21Ne in pyroxene and quartz for the high, (sub-)tropical Andes. The production rates are based on our 10Be-normalized production ratios and a weighted mean of reference 10Be production rates calibrated in the high, tropical Andes (4.02 ±0.12 at g-1yr-1). These are, 21Neqtz: 18.1 ±1.2 and 21Nepx: 36.6 ±1.8 (En88–94) scaled to sea level and high latitude using the Lal/Stone scheme, with 1σuncertainties. As 3He and 26Al have been directly calibrated in the tropical Andes, we recommend using those rates.
Finally, we compare exposure ages calculated using all measured cosmogenic nuclides from each sample, including 11 feldspar samples measured for 36Cl, and a suite of previously published production rates.

Keywords: cosmogenic nuclides; production rate; cross-calibration; South American Monsoon; Quaternary climate change; moraine

Publ.-Id: 24310

10Be surface exposure dating of the last deglaciation in the Aare Valley, Switzerland

Wüthrich, L.; Garcia Morabito, E.; Zech, J.; Trauerstein, M.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Christl, M.; Zech, R.

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied 10Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.

Keywords: Pleistocene; Cosmogenic nuclides; Exposure Dating; Alpine foreland; accelerator mass spectrometry

Publ.-Id: 24309

Simulation of Liquid Metal Batteries by Continuum Mechanics

Weber, N.; Beckstein, P.; Galindo, V.; Landgraf, S.; Stefani, F.; Weier, T.

Liquid metal batteries (LMB) are built as a stable density stratification of two liquid metals, separated by a likewise liquid salt. If the materials are correctly chosen, all three phases self-assemble (figure 1). During discharge, the anode metal will donate electrons, the ion will diffuse through the electrolyte layer and alloy there with the cathode metal.
The main advantage of LMBs is the very low price: low-cost raw materials together with a simple set-up and scalability make such cells an ideal stationary storage, which is highly needed for buffering fluctuating renewable energies. The liquid-liquid interfaces allow for optimal kinetics, i.e. for a fast response time and current densities up to 10 A/cm2. Furthermore, they avoid micro-degradation - as known from solid cells - and allow for potentially very high life-times.
Safety will play a major role in the construction of such cells – especially due to the high amount of liquid and reactive metals. In that context, a short circuit of the thin electrolyte layer should be avoided. In large liquid metal batteries with diameters in the order of several decimetres, even the discharging current itself may lead to a fluid flow, able to short-circuit the battery.

We will present numerical simulations of the fluid flow in LMBs and estimate their relevance for real cells. The numerical solvers combining heat transfer, fluid- and electrodynamics with the volume of fluid method are implemented in the open source library OpenFOAM. Reviewed phenomena include thermal convection, electro-vortex flow, the Tayler-instability as well as metal pad rolling, which is well known from aluminium reduction cells.

Keywords: OpenFOAM; liquid metal battery

  • Lecture (Conference)
    Helmholtz-Workshop "Multiscale Modeling of Energy Storage Materials", 10.-11.11.2016, Berlin, Deutschland

Publ.-Id: 24308

Particles as concentrated sources related to uptake and radiological dose in mammals

Johansen, M. P.; Caffrey, E.; Child, D. P.; Collins, R.; Hotchkis, M. A. C.; Howell, N. A.; Payne, T. E.; Mokhber-Shahin, L.; Ikeda-Ohno, A.

The radiological residues at the former weapons testing sites at Maralinga, Emu and the Monte Bello Islands often occur in particulate form (so called hot particles). Large numbers of these particles were emitted from nuclear and non-nuclear tests. For example each square meter in a plume which extends for tens of kilometres at the Taranaki site (Maralinga) can contain more than 3000 readily identifiable particles. The physical and chemical characteristics of these particles affect their mobility and availability for uptake into living organisms. When they contain long-lived radionuclides (e.g. 239Pu) these particles may slowly weather, and thus provide a persistent source of ionic forms, or smaller particles, for many thousands of years.
From these Australian sites, we have gathered a series of particles that have weathered and interacted with the environment for 50+ years since their initial formation and release events. The particles are being evaluated using a range of methods including gamma spectrometry, autoradiography, high sensitivity Accelerator Mass Spectrometry analysis (AMS), leaching studies, and synchrotron X-ray fluorescence microscopy.
Significant findings include the clustering of Cs on the exterior of a glassy fission fragment, with Sr occurring in the nearby interior, suggesting the 137Cs may be more available for weathering processes, and the beta emissions from the 90Sr may be largely self-shielded within the particle. In contrast, a different particle from a nearby site lacked any fission products, but contained Pu(IV) oxyhydroxides consistent with weathering in a semi-arid environment. Although the 239Pu is very active, detailed dose modelling suggests most of the alpha emissions from particles > 5µm are shelf-shielded within the particles themselves, and therefore impart lower dose than the equivalent Pu dissolved and distributed throughout an organ. However, when Pu exists on exterior surfaces, a hot particle that has been internalised (e.g. lodged in a mammalian lung) may produce relatively highly concentrated dose rates to adjacent tissues.

Keywords: Plutonium; actinides; particulates; update; nuclear tests; dose; mammals; radio ecology

  • Lecture (Conference)
    2nd International Conference on Radioecological concentration processes (50 years later), 09.11.2016, Seville, Spain

Publ.-Id: 24307

The cosmic-ray exposure history of the Twannberg iron meteorite (IIG)

Smith, T.; Hofmann, B. A.; Leya, I.; Merchel, S.; Pavetich, S.; Rugel, G.; Scharf, A.

The Twannberg iron meteorite is one out of only six members of the group IIG. The numerous finds of Twannberg meteorites in recent years have challenged our knowledge about its cosmic-ray exposure history and especially on the time of fall with respect to glacial events. The combined noble gas and radionuclide data obtained in this new systematic study indicate that Twannberg was a large object with a pre-atmospheric radius in the range of 2-4 meters, which corresponds to ~1000 tons. The cosmic-ray exposure age for Twannberg is 66.0±7.8 Ma. The most surprising result is the long terrestrial age of Tterr = 202 +19 -20 ka, which is unexpected considering the humid conditions in Switzerland. However, this age is in accord with glaciation events, indicating that the less shielded samples from Mt. Sujet still represent the original strewnfield but that the samples from Gruebmatt and Twannbach, which are from more shielded positions, have been glacially transported during the second last ice age from an original position west of Mt. Sujet towards east-north-east.

Keywords: AMS; cosmic rays; accelerator mass spectrometry; exposure age; terrestrial age; meteorite

  • Meteoritics & Planetary Science 52(2017), 2241-2257
    Online First (2017) DOI: 10.1111/maps.12928

Publ.-Id: 24306

Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering

Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.

Traveling-Wave Thomson-Scattering (TWTS) allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources by providing optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses.

With TWTS the realization of optical free-electron lasers (OFELs) as well as incoherent radiation sources with orders of magnitude higher photon yields than classic head-on Thomson sources becomes possible with state-of-the-art technology in electron accelerators and laser systems.

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

The talk will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. Especially the ultra-low emittance of laser wakefield accelerated electron beams can be exploited to compensate for their one percent level energy spreads. We discuss an experimental setup to generate the tilted TWTS laser pulses. The method presented provides dispersion compensation, required due to angular dispersion, and is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups.

Keywords: Traveling-Wave; Thomson scattering; FEL; X-ray; Laser dispersion compensation

  • Lecture (others)
    Invited Seminar talk at Helmholtz Institut Jena, 30.09.2016, Jena, Deutschland

Publ.-Id: 24305

Scaling EUV and X-ray Thomson Sources to Optical Free-Electron Laser Operation with Traveling-Wave Thomson-Scattering

Steiniger, K.; Albach, D.; Debus, A.; Loeser, M.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.

Traveling-Wave Thomson-Scattering (TWTS) is a novel Thomson scattering geometry which allows for orders of magnitude higher photon yields than classic head-on Thomson sources. TWTS thereby remains compact and provides narrowband and ultra-short ultraviolet to γ-ray radiation pulses just as classic Thomson sources. Even the realization of optical free-electron lasers is possible with the TWTS geometry since it provides both optical undulators with thousands of periods needed to microbunch the electron beam and a reduction of electron beam quality requirements compared to classic Thomson scattering to a level technically feasible today.
TWTS employs a side-scattering geometry depicted in fig. 1. Laser and electron propagation direction of motion enclose the interaction angle ϕ. Tilting the laser pulse front with respect to the wave front by half the interaction angle ensures continuous overlap of electrons and laser pulse over the whole laser pulse width while the laser pulse crosses the electron beam trajectory. In this way the interaction length becomes controllable by the laser pulse width and independent of the laser pulse duration. Utilizing wide, petawatt class laser pulses for TWTS allows to realize thousands of optical undulator periods.
The variability of TWTS with respect to the interaction angle can be used to control the radiation wavelength even for electron sources with fixed energy. For a fixed target wavelength on the other hand, the free choice of interaction angle enables control over electron beam quality requirements. Small interaction angle scenarios (ϕ∼10°) typically yield the best trade-off between requirements on electron beam quality, laser power and laser intensity stability.
In the talk we will show that TWTS OFELs emitting extreme ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. We detail an experimental setup to generate the tilted TWTS laser pulses which aims at compactness and provides focusing of these high-power pulses and compensation of dispersion accompanying pulse-front tilts. The method presented for dispersion compensation is especially relevant when building high yield X- and γ-ray sources in large interaction angle setups of TWTS.

Keywords: Traveling-Wave; Thomson scattering; FEL; X-ray; Laser dispersion compensation

  • Poster
    The 15th International Conference on X-Ray Lasers, 22.-27.05.2016, Nara, Japan

Publ.-Id: 24304

Inclusive Λ production in proton-proton collisions at 3.5 GeV

Adamczewski-Musch, J.; Agakishiev, G.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataroe, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

The inclusive production of {\Lambda} hyperons in proton-proton collisions at s√ = 3.18 GeV was measured with HADES at the GSI Helmholtzzentrum f\"ur Schwerionenforschung in Darmstadt. The experimental data are compared to a data-based model for individual exclusive {\Lambda} production channels in the same reaction. The contributions of intermediate resonances such as {\Sigma}(1385), {\Delta}++ or N* are considered in detail. In particular, the result of a partial wave analysis is accounted for the abundant pK+{\Lambda} final state. Model and data show a reasonable agreement at mid rapidities, while a difference is found for larger rapidities. A total {\Lambda} production cross section in p+p collisions at s√ = 3.18 GeV of {\sigma}(pp → {\Lambda} + X) = 207.3 ± 1.3 +6.0 -7.3 (stat.) ± 8.4 (syst.) +0.4 -0.5 (model) {\mu}b is found.


Publ.-Id: 24303

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