Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34877 Publications

Identification of beta 8 integrin as novel determinant of pancreatic cancer cell radioresistance

Lee, W.-C.; Jin, S.; Cordes, N.

Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the five most lethal malignancies in the world and has a 5-year relative overall survival rate of less than 5%. Thus, there is a great need for molecular-targeting strategies. As cell-matrix adhesion is essential for the survival, invasion and therapy resistance, we sought to identify the function of 117 focal adhesion proteins (FAP) in PDAC cell radioresistance. Intriguingly 8 integrin turned out to be one of the most potential novel targets in PDAC.
Material and methods: For FAP detection, we performed a 3D endoribonuclease-prepared siRNA (esiRNA)-based screening (3DHTesiS) in PDAC cell culture (established and primary) grown in laminin-rich extracellular matrix (IrECM). After esiRNA-mediated knockdown and X-ray irradiation (2-6 Gy single dose), clonogenic survival assay and sphere formation were determined. Beta 8 integrin expression level and distribution were detected by using Western blot and immunofluorescence staining. Beta 8 integrin staining was also combined with vesicle trafficking proteins (Caveolin-1, APPL2) and the cis-Golgi matrix protein GM130. Fiji software was used to analyze vesicle distribution after irradiation and Peason’s correlation coefficients were calculated.
Results: We identified a series of novel targets with radiosensitizing potential including beta 8 integrin. Without cytotoxicity, beta 8 integrin knockdown conferred a significant radiosensitizing effect in established patient-derived PDAC cell cultures. Moreover, beta 8 integrin depletion reduced invasion and sphere forming ability. Intriguingly, we found beta 8 integrin located in the perinuclear area colocalized with GM130 but neither in the cell membrane nor colocalized with Caveolin-1 and APPL2. Further, we observed an increased beta 8 integrin expression after irradiation associated with enhanced beta 8 integrin-positive vesicle formation in both cytoplasm and nucleus. This suggests that beta 8 integrin may contribute to intracellular vesicle trafficking under stress conditions.
Summary: We successfully designed a high-throughput radiosensitivity screening method for cell growing in a physiological 3D matrix-based environment. Interestingly, beta 8 integrin has, although not found in the cell membrane to facilitate cell adhesion, a critical role in the radiation response of pancreatic cancer cell. Ongoing work will unravel the underlying mechanisms how beta 8 integrin is controlling cytoplasmic and nuclear survival pathways.

Keywords: integrin; radiotherapy; pdac

  • Poster
    GBS, 17.-20.09.2017, Essen, Deutschland

Publ.-Id: 26043

Flüssigmetallbatterien als Option für elektrische Großspeicher

Nimtz, M.; Weber, N.; Weier, T.

Übersicht über die Forschungsaktivitäten an Flüssigmetallbatterien am HZDR.

  • Poster
    3. Wissenschaftliches SCI-Treffen "Energiesystemintegration", 11.09.2017, Karlsruhe, Deutschland

Publ.-Id: 26042

Selection of Gallium-binding peptides using Phage Display technology

Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.

Gallium is used essentially in the semiconductor compounds GaAs, GaN or GaP for high-potential future technologies. The resulting rapidly growing demand for gallium shouldn't be exclusively met by the recovery from primary raw material sources.
Biosorptive recycling of gallium from waste waters of the semiconductor industry is a promising and innovative contribution for establishing an economic and clean zero waste technology.
Peptides are excellently suitable ligands for the biosorptive complexation of gallium ions in aqueous solutions due to their variability in their amino acid sequence and their robust properties.
A well-established method for the selection of highly specific peptide ligands in medicine and biotechnology is the phage display technology. Random, short peptide sequences are presented on the surface according to genetically modified bacteriophages. In a biopanning called process, a pool of different bacteriophages is selected against a particular target, thereby enriching specific binding clone variants (figure 1). A very effective method has been established for the selection of different phage display libraries. Gallium ions immobilized on a monolithic ion exchanger are made accessible for biopanning in an FPLC system. This chromatopanning allows the selective enrichment of gallium-binding clone variants under strictly controlled process conditions.
In the present study, we report about the enrichment, identification and characterization of several gallium-binding motifs. Some promising gallium binding bacteriophage clones are chosen for further binding studies. The corresponding peptide sequences can be synthesized and used in subsequent experiments to develop biosorptive materials for selective gallium recovery from industrial waste waters.

Keywords: Phage Surface Display; biopanning; immobilized metal ions; Gallium; metal binding peptides

  • Lecture (Conference)
    6th International Symposium on biosorption and biodegradation/bioremediation, 25.-29.06.2017, Prag, Czech republic

Publ.-Id: 26041

Development of Metal Ion Binding Peptides Using Phage Surface Display Technology.

Schönberger, N.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.

Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from two commercial phage display libraries. One of them presents cyclic heptamer peptides, in which two cysteins flanke the peptide loop (C7C), and a linear dodecapeptide library (D-12).Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.

Keywords: Phage Surface Display; biopanning; immobilized metal ions; nickel; gallium; cobalt; metal binding peptides

  • Contribution to proceedings
    22nd International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland
    Solid State Phenomena 262, Schweiz: Trans Tech Publications, ISSN: 1662-9779,, 591-595
    DOI: 10.4028/

Publ.-Id: 26040

Measurements of the energy spectrum of secondary neutrons in a proton therapy environment

Dommert, M.; Reginatto, M.; Zboril, M.; Fiedler, F.; Helmbrecht, S.; Enghardt, W.; Lutz, B.

not available, to be filled in

Keywords: Neutron dosimetry; proton therapy

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 26039

Overview on Helmholtz Reactor Safety Research

Kliem, S.; Tromm, W.; Reinecke, E.-A.

The paper gives an overview on the research conducted within the topic "Reactor Safety" of the Helmholtz NUSAFE programme.

  • Lecture (Conference)
    2nd Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology, 12.-15.09.2017, Karlsruhe, Deutschland

Publ.-Id: 26038

Hierarchical thermoplastic rippled nanostructures regulate Schwann Cell adhesion, morphology and spatial organization

Masciullo, C.; Dell'Anna, R.; Tonazzini, I.; Böttger, R.; Pepponi, G.; Cecchini, M.

Periodic ripples are a variety of anisotropic nanostructures that can be realized by ion beam irradiation on a wide class of solid surfaces. Only few authors have investigated these surfaces for tuning the response of biological systems, probably because it is challenging to directly produce them in materials that well sustain long-term cellular cultures. Here, hierarchical rippled nanotopographies with lateral periodicity of ∽300 nm are produced from a gold-irradiated germanium mold in polyethylene terephthalate (PET), a biocompatible polymer approved by the US Food and Drug Administration for clinical applications, by a novel three-steps embossing process. The effects of nano-ripples on Schwann Cells (SCs) are studied in view of their possible use for nerve-repair applications. Data demonstrate that nano-ripples can enhance short-term SC adhesion and proliferation (3-24h from seeding), drive their actin cytoskeleton spatial organization and sustain long-term cell growth. Notably, SCs orient perpendicularly with respect to the nanopattern lines. These results provide information about the possible use of hierarchical nano-rippled elements for nerve-regeneration protocols.

Keywords: hierarchical nanostructures; self-organization; ion Irradiation; cell adhesion; nano-ripples

Publ.-Id: 26037

Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties

Jia, Q.; Ou, X.; Langer, M.; Schreiber, B.; Grenzer, J.; Siles, P. F.; Rodriguez, R. D.; Huang, K.; Yuan, Y.; Heidarian, A.; Hübner, R.; You, T.; Yu, W.; Lenz, K.; Lindner, J.; Wang, X.; Facsko, S.

A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, III-V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III-V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.

Keywords: self-assembly; metallic nanowire array; reverse epitaxy; magnetic anisotropy; anisotropic dielectric function


Publ.-Id: 26036

The application of atomic force microscopy in mineral flotation - A critical review

Butt, H.-J.; Xing, Y.; Gui, X.; Cao, Y.; Babel, B.; Rudolph, M.; Weber, S.; Kappl, M.

During the past years, atomic force microscopy (AFM) has matured to be an indispensable surface analytical tool in modern nanomaterials, colloid and interface science, and biological research. A sharp probe mounted near to the end of a cantilever scans along the sample surface providing a high resolution three-dimensional topographic image. On the other hand, the application of AFM used as a force sensor also becomes more and more popular after the invention of the colloidal probe AFM technique. In this review, we highlight the advances in the application of AFM in the field of mineral flotation, such as mineral morphology imaging, mineral-water interface characterization, mineral-reagent interactions, inter-particle interactions, inter-bubble interactions and bubble-particle interactions. Over the coming years, the simultaneous characterization of topography and chemical composition as an imaging tool for AFM and the synchronous measurement of the force and distance involving deformable bubble as a force sensor will become an active area.

Keywords: atomic force microscopy; mineral flotation; surface imaging; inter-particles interaction; bubble-particle interaction


Publ.-Id: 26035

Therapeutic options to overcome tumor hypoxia in radiation oncology

Troost, E.; Koi, L.; Yaromina, A.; Krause, M.

Expert review summarizing the overcome tumor cell hypoxia by treatment modification in radiation oncology.
An extensive literature search regarding various means of treatment modification was performed and key papers on those modifications were included in this review article.
Based on the identified key papers the means to overcome hypoxia in radiation oncology were summarized in this review article, e.g., increasing levels of oxygen, combining radiotherapy with agents counteracting hypoxia, or modifying radiation treatment itself.
This review summarizes the results of preclinical and clinical studies counteracting hypoxia and highlights the measures that have found their way into clinical practice.

Keywords: Hypoxia; radiotherapy; oxygenation modification; systemic agents; radiation dose-escalation

Publ.-Id: 26034

Dipole strength distribution in 206Pb for the evaluation of the neutron-capture cross section of 205Pb

Shizuma, T.; Iwamoto, N.; Schwengner, R.; Makinaga, A.; Beyer, R.; Bemmerer, D.; Dietz, M.; Junghans, A.; Kögler, T.; Ludwig, F.; Reinicke, S.; Schulz, S.; Urlaß, S.; Wagner, A.

The dipole strength distribution of 206Pb was investigated via nuclear resonance fluorescence experiment using bremsstrahlung produced with an electron beam at a kinetic energy of 10.5 MeV at the linear accelerator ELBE. We identified 88 states resonantly excited at energies from 3.7 to 8.2 MeV. The photoabsorption cross sections were extracted from the measured scattering cross sections and the branching ratios. The present (gamma,gamma') data combined with (gamma, n) data from the literature were used as an input to the statistical calculation code CCONE to evaluate the neutron capture cross section of the unstable 205 Pb nucleus.

Keywords: Photon scattering; nuclear resonance fluorescence; bremsstrahlung; photoabsorption cross section; neutron-capture cross section; statistical model

Publ.-Id: 26033

Spin-transfer driven dynamics in hybrid structures

Fowley, C.; Rode, K.; Gallardo, R.; Thiyagarajah, N.; Lau, Y.-C.; Borisov, K.; Betto, D.; Atcheson, G.; Kampert, E.; Wang, Z.; Lindner, J.; Coey, M.; Stamenov, P.; Deac, A. M.

Since the discovery of giant magnetoresistance, metal spintronics has seen unprecedented advances, from the realisation of ultra-high magnetoresistance ratios to substantial output power from both conventional spin transfer torque oscillators as well as spin-torque vortex oscillators [1]. The recently discovered of the fully compensated ferrimagnetic half-metal, manganese ruthenium gallium (MRG), due to its widely tunable magnetic properties [2], could enable spin torque oscillators which work in the range of hundreds of GHz. Being a ferrimagnet, MRG consists of two magnetic sublattices which are coupled antiferromagnetically to each other. It has been shown that in this material the magnetotransport is dominated by one magnetic sublattice whereas the overall magnetisation is determined by both sublattices [3]. This means that MRG behaves magnetically like an antiferromagnet and electrically like a highly spin polarised ferromagnet, implying that spin-transfer torque would act on one sublattice only, enabling efficient current induced excitations. Due to the different temperature dependences of the sublattice magnetisations, MRG displays a compensation temperature at which the total magnetic moment is zero and the magnetic state is impervious to external magnetic fields [4].
Here we conduct high-field magnetotransport measurements [5] on selected films of MRG with differing Ru concentration and, therefore, different compensation temperatures (Tc). Both the transverse Hall resistivity and longitudinal resistivity are recorded in magnetic fields up to 58T. MRG exhibits a large spontaneous Hall angle of ~2%, coercivity exceeding 1T at room temperature (and several Teslas close to Tc) and has very low net magnetisation of 25kA/m. Despite having a no net magnetic moment at the compensation temperature the magnitude of the Hall signal does not become zero, further indicating both the half-metallic nature of the material and that the magnetotransport is dominated by one sublattice only. An additional feature is observed in the transport data, which resembles a spin-flop transition. By comparison to analytical and mean-field calculations of the sublattice magnetisation directions we can estimate the both the sublattice anisotropy (Hk) and interlayer exchange coupling (Hex). The out-of-phase and in-phase magnetic resonance modes, therefore, lie in the range of 0.3THz and 4THz, respectively. This makes MRG a uniquely tuneable material as a free layer in spin-transfer oscillator applications [6].

[1] Baibich M.N. et al., Physical Review B, 61, 2472 (1988), Ikeda S. et al., Applied Physics Letters, 93 082508 (2008), Tsunegi S. et al., Applied Physics Letters, 109, 252402 (2016)
[2] Kurt H. et al., Physical Review Letters, 112, 027201 (2014)
[3] Borisov K. et al., Applied Physics Letters, 108, 192407 (2016)
[4] Betto D. et al., AIP Advances, 6, 055601 (2016)
[5] Fowley C. et al., Journal of Physics D : Applied Physics, 48, 164006 (2015)
[6] Awari N. et al., Applied Physics Letters, 109, 032403 (2016)

Keywords: magnetism; spin-transfer torque; wireless communication

  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Publ.-Id: 26032

Ultrahigh anisotropy Heusler alloys for THz spin-torque oscillators

Deac, A. M.

Since the discovery of giant magnetoresistance, metal spin electronics has seen unprecedented advances, from the realisation of ultra-high magnetoresistance ratios to substantial output power from spin transfer torque oscillators based on Fe/MgO/Fe-type tunnel junctions which function in the GHz range [1]. The recently discovered class of almost compensated ferrimagnetic manganese gallium pseudo-Heusler alloys, due to their widely tunable magnetic properties [2], could enable the design of spin torque oscillators which work in the range of hundreds of GHz, i.e., covering the THz gap.
To investigate the resonance modes in such compounds, we first conducted high-field magnetotransport measurements [3] on selected films with different composition and, therefore, different compensation temperatures (Tc) and effective anisotropies. In manganese ruthenium gallium (MRG), for instance, both the transverse Hall resistivity and longitudinal resistivity were recorded in magnetic fields up to 58 T, at variable temperature. MRG exhibits a large spontaneous Hall angle of ~2%, coercivity exceeding 1 T at room temperature (and several Teslas close to Tc ) and has very low net magnetisation of 25 kA/m. Despite having no net magnetic moment at Tc, the magnitude of the Hall signal does not become zero, indicating both a half-metallic nature of the material and that the magnetotransport is dominated by one sublattice only. An additional feature is observed in the transport data, which resembles a spin-flop transition. By comparison to analytical and mean-field calculations of the sublattice magnetisation directions, we can estimate both the sublattice anisotropy (Hk ) and interlayer exchange coupling (Hex). Based on these values, the out-of-phase and in-phase magnetic resonance modes are estimated to lie in the range of 0.3 THz and 2 THz, respectively. Furthermore, magnetoresistance ratios as high as 40% at 4.2 K and 12% at room temperature can be obtained when integrating MRG in magnetic tunnel junctions [4].
The out-of-phase resonance mode was also directly measured for ferrimagnetic Mn3-xGa thin films as function of anisotropy and applied magnetic fields (up to 10 T). At low applied fields, we find that the resonance frequency ranges between 200 and 350 GHz for films with different compositions (i.e. anisotropy), providing proof of concept for efficient on-chip emitters of coherent, narrow-band light pulses in the THz gap [5].

[1] Baibich M.N. et al., Physical Review B, 61, 2472 (1988), Ikeda S. et al., Applied Physics Letters, 93 082508 (2008), Tsunegi S. et al., Applied Physics Letters, 109, 252402 (2016)
[2] Kurt H. et al., Physical Review Letters, 112, 027201 (2014)
[3] Fowley C. et al., Journal of Physics D : Applied Physics, 48, 164006 (2015)
[4] Borisov K. et al., Applied Physics Letters, 108, 192407 (2016)
[6] Awari N. et al., Applied Physics Letters, 109, 032403 (2016)

Keywords: magnetism; spin-transfer torque; terahertz communication

  • Invited lecture (Conferences)
    62nd Annual Conference on Magnetism and Magnetic Materials, 06.-10.11.2017, Pittsburgh, USA
  • Invited lecture (Conferences)
    APS March Meeting 2018, 05.03.2018, Los Angeles, USA

Publ.-Id: 26031

Measurement of the lifetime and the proportion of 12C3+ ions in stored relativistic ion beams as a preparation for laser cooling experiments at the CSRe

Wang, H. B.; Wen, W. Q.; Huang, Z. K.; Zhang, D. C.; Hai, B.; Zhu, X. L.; Zhao, D. M.; Yang, J.; Li, J.; Li, X. N.; Mao, L. J.; Mao, R. S.; Wu, J. X.; Yang, J. C.; Yuan, Y. J.; Eidam, L.; Winters, D.; Beck, T.; Kiefer, D.; Rein, B.; Walther, T.; Loeser, M.; Schramm, U.; Siebold, M.; Bussmann, M.; Ma, X.

We report on an experiment that was conducted in preparation of laser cooling experiments at the heavy-ion storage ring CSRe. The lifetimes of ion beams made up of 12C3+ and 16O4+ ions stored at an energy of 122MeV/u in the CSRe were determined by two independent methods, firstly via a DC current transformer (DCCT) and secondly via a Schottky resonator. Using electron-cooling, the signals of the 12C3+ and 16O4+ ions could be separated and clearly observed in the Schottky spectrum. The obtained individual lifetimes of the 12C3+ and 16O4+ components were 23.6s and 17.8s, respectively. The proportion of 12C3+ ions in the stored ion beam was measured to be more than 70% at the beginning of the injection and increasing as a function of time. In addition to these measurements, the operation and remote control of a pulsed laser system placed directly next to the storage ring was tested in a setup similar to the one envisaged for future laser experiments.

Keywords: Storage ring; Laser cooling; Electron cooling; Schottky pick-up; bunched beam; dynamics


Publ.-Id: 26030

Limits on Supernova- Associated Fe-60/Al-26 Nucleosynthesis Ratios from Accelerator Mass Spectrometry Measurements of Deep-Sea Sediments

Feige, J.; Wallner, A.; Fifield, L. K.; Golser, R.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S. G.; Winkler, S. R.

We searched for presence of 26Al (t1/2=0.7 Myr) in deep-sea sediments as a signature for extraterrestrial influx. Our data show an exponential dependence of 26Al with the sample age that is fully compatible with radioactive decay of terrigenic 26Al. The same set of samples demonstrated a clear extraterrestrial 60Fe signal between 1.7 and 3.2 Myr ago. Combining our 26Al data with the recently reported 60Fe data [1] gives a lower limit for the local interstellar 60Fe/26Al isotope ratio. Our Limit of 0.24 is higher than the observed average galactic 60Fe/26Al flux ratio of (0.15 + 0.05).It favours the higher ratios deduced from nucleosynthesis models.

Publ.-Id: 26029

The structure in warm dense carbon

Vorberger, J.; Plageman, K. U.; Redmer, R.

The structure of the fluid carbon phase in the pressure region of the graphite, diamond, and BC8 solid phase is investigated. We find increasing coordination numbers with an increase in density. From zero to 30GPa, the liquid shows a decrease of packing effciency with increasing temperature. However, for higher pressures, the coordination number increases with increasing temperature. Up to 1.5 eV and independent of the pressure up to 10 Mbar, a double-peak structure in the ion structure factors exists, indicating persisting covalent bonds.

Keywords: carbon; warm dense matter; structure; XRTS

Related publications

Publ.-Id: 26027

Wissenschaftliche Software – Anspruch und Realität im Forschungsprozess

Konrad, U.

Wissenschaftliche Software ist heute unverzichtbares Werkzeug im Forschungsprozess, sie ist Voraussetzung für die Nachvollziehbarkeit der (publizierten) Ergebnisse und in vielen Fällen auch selbst ein Ergebnis, das publiziert, genutzt und langfristig bewahrt werden muss. Publikationen bestehen künftig häufig aus zitierfähigen Texten, Daten und Software und müssen entsprechend konsistent behandelt werden, dies ist eine Herausforderung auch für die Bibliotheken. Daraus ergeben sich eine Reihe von Fragestellungen und Aufgaben für die gute wissenschaftliche Praxis im Umfeld der „Offenen Wissenschaft“ (Open Science). Diese Fragen werden in dem Vortrag diskutiert.
Ausgangspunkt ist die Frage, welche Kategorien wissenschaftlicher Software es gibt und was für Rollen diese im Forschungsprozess spielen. Mit der voranschreitenden Digitalisierung von Forschung und Lehre steigt die Abhängigkeit von Software-Lösungen. Die grundlegenden Prinzipien der „guten wissenschaftliche Praxis“ wie Nachvollziehbarkeit, Reproduzierbarkeit, Transparenz und Qualitätssicherung müssen auch bei der Entwicklung und Nutzung von wissenschaftlicher Software angewandt werden. Allerdings gibt es eine Reihe von Besonderheiten für den Umgang mit Software, da diese im Vergleich zu Veröffentlichungen und Daten einem meist kontinuierlichen Entwicklungsprozess unterliegt und im Kontext spezifischer Entwicklungs- und Laufzeitumgebungen zu betrachten sind.
Darüber hinaus sind die Publikation, Nachnutzbarkeit und Verwertung von Software zentrale Herausforderungen. Die Zitation von Quellcode, die Open Source Software-Entwicklung, die Bereitstellung forschungsnaher Infrastrukturen für Entwicklung und Test sowie die Lizenzen und rechtliche Aspekte der Softwarenachnutzung sind noch nicht umfassend in der wissenschaftlichen Praxis realisiert. Darüber hinaus fehlen auch Anreizsysteme für eine nachhaltige Softwareentwicklung in der Forschung.
Für viele dieser Fragen gibt es Lösungsansätze und „best practice“ Beispiele, auf die eingegangen wird. Seit einiger Zeit gibt es dazu internationale und nationale Initiativen wie u. a. die Software Carpentry (1998, US), das Software Sustainability Institute (2008, GB) und sciforge (2014, D). Des Weiteren unterstützt die Deutsche Forschungsgemeinschaft (DFG) die Entwicklung dieses Gebietes u. a. mit dem Programm ”Research Software Sustainability”.

Keywords: Wissenschaftliche Software; Softwareentwicklung; Publikation; Repositorien; Infrastruktur; Bibliothek; Scientific software; software development; publication; repository; infrastructure

  • Lecture (Conference)
    Internationale Open Access Tage 2017, 11.-13.09.2017, Dresden, Deutschland
    DOI: 10.5281/zenodo.1040289

Publ.-Id: 26025

Two-gap superconductivity in Ag1–x Mo6S8 Chevrel phase

Feig, M.; Bobnar, M.; Veremchuk, I.; Hennig, C.; Burkhardt, U.; Starke, R.; Kundys, B.; Leithe-Jasper, A.; Gumeniuk, R.

The superconducting properties of Ag1−xMo6S8 [x = 0.08(1)] Chevrel phase [Tc = 7.9(5) K] are studied on a sample compacted by spark plasma sintering. Both lower [Bc1 = 12(1) mT] and the upper [Bc2(0) ~ 7.4(9) T] critical magnetic fields are obtained from magnetization and electrical resistivity measurements for the first time. The analysis of the low-temperature electronic specific heat indicates Ag1−xMo6S8 to be a two band superconductor with the energy gaps delta-1 = 1.6 meV (95 %) and delta-2 = 0.7 meV (5 %). Theoretical DFT calculations reveal a much stronger electron-phonon coupling in the studied Chevrel phase compared to earlier reports.

Keywords: crystal structure; x-ray diffraction methods; superconductivity; specific heat; DFT calculation

Publ.-Id: 26024

The costimulatory domain in CAR T cells determines the resistance to immunosuppression by regulatory T cells

Kegler, A.; Koristka, S.; Bergmann, R.; Feldmann, A.; Arndt, C.; Aliperta, R.; Albert, S.; Ziller-Walter, P.; Ehninger, G.; Bornhäuser, M.; Schmitz, M.; Bachmann, M.

Chimeric antigen receptor (CAR)-modified T cells are intensively studied for their application in cancer patients and already proved incredible success in clinical trials. However, the choice of the intracellular signaling domain integrated into the CAR architecture can largely influence T cell function and fate, as already shown in vitro and in vivo. Moreover, especially within solid tumors regulatory T cells (Tregs) play an important role in establishing an anti-inflammatory milieu and suppressing effector cells. Consequently, endogenous Tregs might impair CAR-engrafted T cells and thereby affect treatment outcome of cancer patients. Therefore, it is of large interest to investigate the responsiveness of T cells comprising CARs with different intracellular signaling domains on Treg suppression.
To address this question, we isolated CD4+CD25- conventional T cells (Tconv) and genetically modified them to express a universal CAR (UniCAR) construct as part of our previously developed UniCAR platform technology. In contrast to conventional CARs, UniCARs are indirectly linked to their target cells via a separate antigen-specificity providing target module (TM), which allows a flexible application of UniCAR-engrafted T cells against a wide range of tumor-associated antigens. It also enables a modulation of T cell activity between an “on” and “off” status. To compare the influence of different intracellular costimulatory signals, we designed UniCARs containing either a CD3ζ, CD28-CD3ζ or CD137-CD3ζ domain.
By using a lentiviral gene transfer system for genetic modification, transduction rates of more than 80 % were achieved. Upon TM-mediated activation via the UniCAR, Tconvs containing UniCAR28/ζ produced significantly higher amounts of the pro-inflammatory cytokine TNF and the growth-related cytokine IL 2 than UniCAR137/ζ- or UniCARζ-engrafted cells. To investigate the impact of Tregs, Tconvs containing the individual UniCAR constructs were cultured in the presence of expanded, autologous CD4+CD25+CD127lowCD45RA+ Tregs for 96h. On the one hand, Tregs were pre-stimulated with anti-CD3/CD28 beads to mimic polyclonal activation via the endogenous TCR. On the other hand, an antigen-specific stimulation was achieved by engrafting Tregs with UniCARs. In both cases, UniCAR-armed Tconvs showed a distinct responsiveness on Treg suppression in dependence on the intracellular signaling domain. We observed, that in contrast to UniCAR28/ζ-armed Tconvs, UniCAR137/ζ- and UniCARζ-engrafted cells could be substantially repressed by Tregs.
In summary, we could demonstrate that Tconvs containing UniCARs with different intracellular signaling domains display not only a distinct cytokine secretion profile but also a disparate resistance against Treg suppression. These data indicate, that the chosen costimulatory signal has an impact on both the efficacy and the safety of a cancer treatment conducted with genetically modified CAR T cells.

Keywords: tumor immunotherapy; CAR design; Treg suppression

  • Poster
    Third CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference, 06.09.2017, Mainz, Germany

Publ.-Id: 26022

Redirection of human T lymphocytes armed with on/off switchable universal chimeric antigen receptors against various malignant cells

Feldmann, A.; Bergmann, R.; Albert, S.; Metwasi, N.; Arndt, C.; Aliperta, R.; Koristka, S.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Steinbach, J.; Bachmann, M.

Recently, chimeric antigen receptor (CAR) expressing T cells have shown tremendous clinic effects in several cancer patients. However once those genetically modified T cells are adoptively transferred in a patient their reactivity cannot be controlled in case of life-threatening side effects or tumor alterations including antigen loss occur. These limitations encouraged us to develop an on/off switchable universal CAR (UniCAR) platform.
As an optimization of conventional CARs, UniCARs do not bind to a cell surface antigen. In contrast their extracellular single-chain fragment variable (scFv) is redirected to the short peptide epitope E5B9 that is physiologically not presented on the surface of living cells. Consequently the UniCAR T cells are inert. Only in the presence of a target module, that exhibits the E5B9 and binds to a tumor surface target, the UniCAR T cells can be cross-linked to tumor cells and thus get activated to kill them. Recently, we have produced a series of monospecific and bispecific target modules against a series of tumor associated antigens including PSCA, PSMA, CD33, CD123, GD2, and EGFR.
Here we demonstrate in vitro as well as in experimental mice that all these target modules are able to efficiently redirect UniCAR T cells against tumor cells in a strictly target-dependent and target-specific manner. Tumor cell killing occurred at pM target module concentrations and the killing efficacy of UniCAR T cells was comparable to conventional CAR T cells. As measured by ELISA and/or flow cytometry-based multiplex assays redirected UniCAR T cells released pro-inflammatory cytokines including for example TNF, IL-2 and IFN-γ but not IL-6. Bispecific tumor targeting mediated superior tumor cell killing effects than the usage of monospecific target modules whereas the amount of released pro-inflammatory cytokines were not increased. Finally, we have proven that redirected UniCAR T cells can kill luciferase-positive tumor cells in immunodeficient mice. In agreement with the UniCAR concept, target modules showed a very short half-life in peripheral blood, could accumulate in established tumors and were released from UniCAR-target module-complexes in a concentration-dependent manner as measured by dynamic PET analysis in mice.
In summary, we established a controllable UniCAR platform for tumor immunotherapy. The reactivity of UniCAR armed T cells can be switched on and off in the presence or absence of target modules and can be regulated in a dose-dependent manner providing an improved safety of the CAR technology. Moreover a variety of different target modules against a series of different tumor targets can be introduced in the UniCAR platform supporting its high flexibility.

Keywords: tumor immotherapy; T cell retargeting; chimeric antigen receptor

  • Poster
    Third CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference, 06.-09.09.2017, Mainz, Deutschland
  • Lecture (Conference)
    Third CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference, 06.-09.09.2017, Mainz, Deutschland

Publ.-Id: 26021

Redirection of human T cells to tumor cells via nanobody-based target modules using the universal chimeric antigen receptor system

Albert, S.; Bergmann, R.; Koristka, S.; Feldmann, A.; Arndt, C.; Aliperta, R.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Steinbach, J.; Bachmann, M.

In general, adoptive transfer of chimeric antigen receptor (CAR)-expressing T cells has an impressive immunotherapeutic potential. However, due to the time-consuming establishment of new CAR constructs, the risk of life-threatening side effects, and the lack of control mechanisms once infused into patients, we developed a switchable modular CAR platform technology termed UniCAR.
The UniCAR system is composed of two individual components, the universal signal-transducing UniCAR and an exchangeable target module (TM). In contrast to conventional CARs, the single-chain fragment variable (scFv) of the UniCAR binds to a small peptide epitope, which is physiologically not accessible on intact cells. The cross-linkage to tumor cells is mediated via TMs comprising the antigen-specifity and the epitope recognized by the UniCAR. Consequently, UniCAR-engrafted T cells are inert in the absence of redirecting TMs and only switched on in their presence. In addition to the increased safety, the modular structure enables a flexible targeting of different tissue antigens. New TMs can be easily constructed just by fusing the UniCAR epitope to a targeting entity. So far we produced a series of functional scFv-based TMs against different tumor-associated antigens like PSCA, PSMA, GD2 and CD33.
Here we demonstrate that TMs can alternatively contain a nanobody (nb) domain instead of an scFv. Nbs are derived from camelid heavy-chain antibodies, consist of a single variable domain and form the smallest known antigen binding fragments. For redirection of UniCAR T cells to epithelial tumors the frequently overexpressed EGFR is a suitable target antigen. Thus, we generated a nb-based -EGFR TM. As shown by in vitro assays with EGFR+ tumor cell lines, the novel TM efficiently activates UniCAR T cells in a strictly target-specific manner and induces the release of pro-inflammatory cytokines. Furthermore, the data reveal that the -EGFR TM triggers a highly potent tumor lysis at low pM concentrations and redirects UniCAR-engrafted T cells to tumor cells in immunodeficient mice. Using dynamic PET analysis we observed a short half-life of the TM and could confirm its release from UniCAR-TM-complexes. Thereby, it is possible to precisely dose the TM concentration and to rapidly switch the system off in case of adverse side effects. Finally, the -EGFR TM also offers the possibility to image the tumor during therapy. For an increased anti-tumor response we additionally generated a bivalent -EGFR-EGFR TM that shows improved in vitro and in vivo functionality compared to the monovalent construct.
In summary, we established a novel mono- and bivalent nb-based TM for EGFR-specific recruitment of UniCAR T cells which results in an efficient, target-specific and -dependent killing of EGFR+ tumor cells. Thus, we could prove that instead of scFvs also other binding moieties can be used and confirmed the high flexibility of the modular UniCAR platform.

Keywords: CAR T cell therapy; nanobodies; EGFR-targeting

  • Poster
    Third CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference, 06.09.2017, Mainz, Deutschland

Publ.-Id: 26020

Selenium(IV) sorption onto γ-Al2O3: a consistent description of the surface speciation by spectroscopy and thermodynamic modeling

Mayordomo, N.; Foerstendorf, H.; Lützenkirchen, J.; Heim, K.; Weiss, S.; Alonso, U.; Missana, T.; Schmeide, K.; Jordan, N.

The sorption processes of selenium(IV) onto γ-Al2O3 were studied by in situ vibrational spectroscopy, batch sorption studies, zeta potential measurements and Surface Complexation Modeling (SCM). In the pD range from 5 to 9, in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy revealed the predominant formation of a single inner-sphere surface species at the alumina surface irrespective of the presence or absence of atmospherically derived carbonate. The adsorption of Se(IV) decreased with increasing pH, and no impact of the ionic strength was observed in the range from 0.01 to 0.1 mol L−1 NaCl. The formation of inner-sphere surface complexes was also suggested from the shift of pHIEP of γ-Al2O3 observed during zeta potential measurements at the highest Se(IV) concentration applied (10−4 mol L−1). Based on these qualitative findings, the acid-base surface properties of γ Al2O3 and the Se(IV) adsorption edges were successfully described using a 1-pK CD-MUSIC model, using one inner-sphere bidentate surface complex. The results of competitive sorption experiments strongly suggested that the surface affinity of Se(IV) towards γ-Al2O3 is higher than that of dissolved inorganic carbon (DIC). Nevertheless, the competing effect might impact the migration of selenium(IV) by reducing the number of available sorption sites on mineral surfaces. Consequently, this should be taken into account in predicting the environmental fate of selenium(IV).

Keywords: Selenium(IV); Sorption; ATR FT-IR spectroscopy; CD-MUSIC; Alumina, Carbonate; Competition

Publ.-Id: 26019

Development of novel target modules for retargeting of UniCAR T cells to GD2 positive tumor cells

Mitwasi, N.; Feldmann, A.; Bergmann, R.; Berndt, N.; Arndt, C.; Koristka, S.; Kegler, A.; Jureczek, J.; Hoffmann, A.; Ehninger, A.; Cartellieri, M.; Albert, S.; Rössig, C.; Ehninger, G.; Pietzsch, J.; Steinbach, J.; Bachmann, M.

As the expression of a tumor associated antigen (TAA) is commonly not restricted to tumor cells adoptively transferred T cells modified to express a conventional chimeric antigen receptor (CAR) might not only destroy the tumor cells but also attack target-positive healthy tissues. Furthermore, CAR T cells in patients with large tumor bulks will unpredictably proliferate and put the patients at high risk of adverse side effects including cytokine storms and tumor lysis syndrome. To overcome these problems, we previously established a modular CAR technology termed UniCAR: UniCAR T cells can repeatedly be turned on and off via dosing of a target module (TM). TMs are bispecific molecules which cross-link UniCAR T cells with target cells.
After elimination of the respective TM, UniCAR T cells automatically turn off. Here we describe novel TMs against the disialoganglioside GD2 which is overexpressed in neuroectodermal but also many other tumors. In the presence of GD2-specific TMs, we see a highly efficient target-specific and -dependent activation of UniCAR T cells, secretion of pro-inflammatory cytokines, and tumor cell lysis both in vitro and experimental mice. According to PET-imaging anti-GD2 TM enrich at the tumor site and are rapidly eliminated thus fulfilling all prerequisites of a UniCAR TM.

Keywords: immunotherapy; CAR T cells

Publ.-Id: 26018

Qualification tests of optical coatings in space environment

Pelizzo, M. G.; Corso, A. J.; Tessarolo, E.; Martucci, A.; Donazzan, A.; Böttger, R.; Hübner, R.; Napolitani, E.

Optical components such as mirrors, filters and windows need to be tested and qualified to verify their resistance in space environments. Future space missions, such as ESA JUICE and SOLO, will operate in harsh environments, rich of ions and electrons. Experiments and development of appropriate protocols are needed to develop proper radiation-hard components and to qualify them.

Keywords: Ions; Coatings; Radiation effects; Nonhomogeneous media; Reflectivity; Optical filters; Protons

  • Contribution to proceedings
    2017 IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace), 21.-23.07.2017, Padua, Italy: IEEE, 978-1-5090-4234-0
    DOI: 10.1109/MetroAeroSpace.2017.7999570
  • Lecture (Conference)
    IEEE International Workshop on Metrology for AeroSpace (MetroAeroSpace), 21.-23.07.2017, Padua, Italy

Publ.-Id: 26017

Structural and optical studies of Pr implanted ZnO films subjected to a long-time or ultra-fast thermal annealing

Ratajczak, R.; Mieszczynski, C.; Prucnal, S.; Guziewicz, E.; Stachowicz, M.; Snigurenko, D.; Gaca, J.; Böttger, R.; Wojcik, M.; Heller, R.; Skorupa, W.; Borany, J. V.; Turos, A.

Epitaxial thin ZnO films grown by Atomic Layer Depositionwere implanted with 150 keV Pr ions to a fluence of 1 × 1015 at/cm2. Implanted samples were subjected to two different kinds of annealing: rapid thermal annealing (RTA) and millisecond-range flash lamp annealing (FLA). Structural properties of implanted and annealed ZnO and the optical response were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c), High-resolution X-ray diffraction and Photoluminescence Spectroscopy (PL), respectively. The results shown, that both annealing techniques lead to recrystallization of the ZnO lattice, that was damaged during the ion implantation. Upon RTA performed at 800 °C a return of Zn atoms from interstitial to their regular site positions is accompanied by rejection of primarily substitutional Pr atoms to the interstitial sites. Consequently, it leads to the out-diffusion and precipitation of Pr atoms on the surface. In contrast to RTA, the diffusion of implanted Pr during a millisecond range FLA treatment is completely suppressed. Despite differences in location of Pr inside the ZnO matrix after FLA and RTA, both annealing techniques lead to the optical activation of Pr3+. Interestingly, our RBS/c study for as implanted layers also revealed the anomalous damage peak, called intermediate peak (IP) located between the expected surface and the bulk damage peak. The PL spectra clearly suggest, that the defect which forms the IP, can be assigned to Zn interstitials. The long-time annealing at 800 °C in oxygen atmosphere causes the complete removal of the IP.

Keywords: Zinc oxide; Atomic layer deposition; Rare-earth; Ion implantation; Praseodymium; Rapid thermal annealing; Flash lamp annealing; Channeling Rutherford backscattering spectrometry; High-resolution X-ray diffraction; Photoluminescence

Publ.-Id: 26016

Dosimetric evidence confirms computational model of magnetic field induced dose distortions of therapeutic proton beams

Schellhammer, S. M.; Gantz, S.; Lühr, A.; Oborn, B. M.; Bussmann, M.; Hoffmann, A. L.

Given the sensitivity of proton therapy to anatomical variations, this cancer treatment modality is expected to benefit greatly from integration with magnetic resonance (MR) imaging. One of the obstacles hindering such an integration are strong magnetic field induced dose distortions. These have been predicted in simulation studies, but no experimental validation has been performed so far. Here we show the first measurement of planar distributions of dose deposited by therapeutic proton pencil beams traversing a one-Tesla transversal magnetic field while depositing energy in a tissue-like phantom using film dosimetry. The lateral beam deflection ranges from one millimeter to one centimeter for 80 to 180 MeV beams. Simulated and measured deflection agree within one millimeter for all studied energies. These results proof that the magnetic field induced proton beam deflection is both measurable and accurately predictable. This demonstrates the feasibility of accurate dose calculation as well as measurement within the framework of MR-integrated proton therapy.

Publ.-Id: 26015

Electrical behaviour of carbon nanotubes under low-energy proton irradiation

Abbe, E.; Schüler, T.; Klosz, S.; Starruß, E.; Pilz, W.; Böttger, R.; Kluge, O.; Schmiel, T.; Tajmar, M.

Several applications for carbon nanotubes (CNT) have been proposed for space applications in the last years. However, their behaviour in the harsh space environment is mostly unknown. Energetic particles such as protons can influence the material degradation in space. This material damage could result in a system failure of space systems. Therefore it is necessary to investigate the performance of new materials under proton irradiation.

Screen and jet printed disordered single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) and multi-walled carbon nanotubes/resin composites (ME) were exposed to 1 keV, 15 keV and 100 keV protons. The electrical behaviour of the CNT conductor paths was measured during the experiment. After this exposure, the CNTs were analyzed using Raman scattering and a scanning electron microscope (SEM).

Their is a clear evidence that proton radiation can destroy carbon nanotubes and influence their electrical performance.

Keywords: Mulltiwalled carbon nanotubes; Single walled carbon nanotubes; Irradation; Protons; Enviromental behaviour

Publ.-Id: 26014

Beam loading limited high peak current laser wakefield accelerators

Köhler, A.; Couperus, J. P.; Krämer, J. M.; Kurz, T.; Zarini, O.; Pausch, R.; Debus, A.; Garten, M.; Hübl, A.; Bussmann, M.; Schramm, U.; Irman, A.

Laser wakefield accelerators (LWFA) can potentially generate high-peak current electron beams at the order of a few tens of kiloAmperes which are very attractive as drivers for compact secondary radiation sources ranging from THz up togamma-ray or as drivers for beam driven wakefield accelerators (PWFA).
The phenomenon of beam loading affects the amount of trapped charge inside the plasma cavity while influencing the final beam parameters, i.e., transverse emittance and maximum attainable energy and spread.
We experimentally investigate these effects in the self-truncated ionization injection scheme (STII) by loading several hundreds of pC of charge into the wakefield within a monoenergetic bunch. We explore the influence of beam loading on electron energy, energy spread and beam divergence. We show that beam quality is maintained up to an estimated peak-current of 30 kA, which is an order of magnitude higher than can be reached in current state-of-the-art conventional electron accelerators.

  • Poster
    8th International Particle Accelerator Conference, 14.05.2017, Copenhagen, Denmark

Publ.-Id: 26013

Investigation of electron dynamics in a ionization-injection laser-wakefield accelerator via betatron radiation

Koehler, A.; Couperus, J. P.; Zarini, O.; Pausch, R.; Krämer, J. M.; Debus, A.; Irman, A.; Bussmann, M.; Schramm, U.

The features of betatron radiation emitted from accelerated electrons in a laser-wakefield accelerator can help as a diagnostic tool to investigate their dynamics during the acceleration. Here we describe our recent LWFA experiments deploying the ionization induced injection technique carried out with the Draco Ti:Sapphire laser. Equipped with an 2D spectroscopy technique based on single pixel absorption events, we analyze the spectral features of the emitted betatron radiation for a set of different plasma densities. Combined with electron spectra acquired at the same time, the betatron source size for a set of different electron bunches is deduced.

  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.04.2017, Prague, Czech Republic

Publ.-Id: 26012

Singularity consideration in the integral equations for contactless inductive flow tomography

Jacobs, R. T.; Wondrak, T.; Stefani, F.

The Contactless Inductive Flow Tomography is a procedure that enables the reconstruction of the global three-dimensional flow structure of an electrically conducting fluid by measuring the flow induced magnetic flux density outside the melt and by subsequently solving the associated linear inverse problem. The accurate computation of the forward problem which is essential for the inversion represents the focal point of this investigation. The tomography procedure is described by a system of coupled integral equations where the integrals contain a singularity when a source point coincides with a field point. The contribution of a singular point to the value of the surface and volume integrals in the system is considered in detail. A significant improvement of the accuracy is achieved by applying higher order elements and by attributing special attention to the singularities inherent in the integral equations. The treatment of the singularities described in this investigation is similar to the procedure applied in the boundary element method. It represents a novelty in the Contactless Inductive Flow Tomography.

Keywords: Contactless inductive flow tomography; magnetohydrodynamics; integral equations; inverse problems

  • The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 37(2018)4, 1366-1375
    DOI: 10.1108/COMPEL-08-2017-0361

Publ.-Id: 26010

Inclusion of Incidental Radiation Dose to the Cardiac Atria and Ventricles Does Not Improve the Prediction of Radiation Pneumonitis in Advanced-Stage Non-Small Cell Lung Cancer Patients Treated With Intensity Modulated Radiation Therapy

Wijsman, R.; Dankers, F. J. W. M.; Troost, E. G. C.; Hoffmann, A. L.; van der Heijden, E. H. F. M.; de Geus-Oei, L.-F.; Bussink, J.

Purpose: To evaluate if inclusion of incidental radiation dose to the cardiac atria and ventricles improves the prediction of Grade ≥3 radiation pneumonitis (RP) in advanced stage non-small cell lung cancer (AS-NSCLC) patients treated with intensity-modulated radiation therapy or volumetric-modulated arc therapy.
Material and methods: Using a bootstrap modelling approach, clinical parameters and dose-volume histogram (DVH) parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction in 188 AS-NSCLC patients.
Results: After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; p=0.004). The MLD showed the highest Spearman correlation coefficient (Rs) for RP (Rs=0.21; p<0.01). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters. After bootstrap modelling, the heart DVH parameters were seldom included in the model predicting Grade ≥3 RP. The optimal model for RP consisted of the parameters: MLD and cardiac comorbidity (area under the curve: 0.71).
Conclusion: Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of AS-NSCLC patients.

Keywords: Non-small cell lung cancer; Intensity-modulated radiation therapy; Volumetric-modulated arc therapy; radiation pneumonitis; cardiac exposure

Publ.-Id: 26009

Use of small animal PET/MRI for internal radiation dose assessment

Kranz, M.

The thesis is based on three publications investigating newly developed radiotracers in different animal models. The radiation safety and biodistribution has to be proven prior to the application of first-in-man studies. Resultantly, based on the preclinical dosimetry presented herein, a clinical trial was approved by the competent authorities of Germany for (-)-[18F]flubatine, (+)-[18F]flubatine and (S)-(-)-[18F]fluspidine. Although the radiation safety was proven for (R)-(+)-[18F]fluspidine too, so far it is used in preclinical studies only.

  • Doctoral thesis
    Universität Leipzig, 2017
    Mentor: Prof. Brust, Prof. Sattler

Publ.-Id: 26008

Laser-driven proton acceleration from a solid hydrogen ribbon

Kraft, S.

In the last years, more and more high repetition rate ultrahigh power lasers are build. In order to use the novel capabilities in applications with laser accelerated ion beams, new target types have to be developed. These targets have to fulfil two conditions: they have to stand several hundreds or even thousands of shots and produce as less debris as possible in order to spare the expensive optics. Promising candidates are pure hydrogen targets.
Here we report on experiments with a solid hydrogen ribbon performed at the ELFIE facility in France and compare the results to shots on normal metal and plastic foils.

  • Invited lecture (Conferences)
    Laserlab User Meeting, 27.-29.08.2017, Vilnius, Litauen

Publ.-Id: 26007

Helmholtz International Beamline for Extreme Fields: A stroke of luck for High-Intensity Lasers at the European XFEL

Schlenvoigt, H.-P.; Cowan, T.

We will present the status of HiBEF, a UserConsortium driving HED science at the European X-ray Free Electron Laser, and discuss a possible route towards the detection of Vacuum Birefringence.

Keywords: HiBEF; XFEL; HED; Vacuum Birefringence

  • Invited lecture (Conferences)
    2nd Conference on Extremely High Intensity Laser Physics, 05.09.2017, Lisbon, Portugal

Publ.-Id: 26006

X-ray polarimetry of high-intensity laser-driven phenomena

Schlenvoigt, H.-P.

The talk will present two prominent examples of X-ray polarimetry, namely Faraday rotation and vacuum birefringence. A general model for polarimetry will be presented. Detailed technical requirements from both XFEL and optical laser will be discussed.

Keywords: HiBEF; XFEL; Faraday Rotation; Polarimetry

  • Lecture (Conference)
    High Intensity Laser Matter Science at The HED Instrument at The European XFEL, 06.04.2017, Schenefeld, Deutschland

Publ.-Id: 26005

Novel insights into the covalent bonding character of tetravalent actinide complexes with N-donor ligands

Kloditz, R.; Radoske, T.; Schöne, S.; Patzschke, M.; Stumpf, T.

The electronical properties of f-elements, especially of the actinides, are a very puzzling topic to investigate. The frontier orbitals (5f, 6d, 7s) all lying in a similar energy regime along with open shells and relativistic effects contribute to a very complex situation, where single-reference methods like DFT and Hartree-Fock may be not suitable any more. In recent years, the investigation of actinides in combination with organic ligands revealed a very rich chemistry with many forms of coordination and chemical bonding. Besides that, many visually appealing and intuitive tools have been developed, with which the chemical bond can be analysed. These tools for bond analysis include natural-bonding orbitals (NBO) and density-difference plots. The aim of this study is therefore to apply these bond analysis tools to a range of tetravalent actinide complexes with N- donor ligands, like Schiff bases and amidinates, to elucidate their complicated electronic properties. Thermodynamic computations on the stability of the complexes will also be presented to understand the chemical properties of the actinides and predict yet unknown complexes.

Keywords: Actinides; theoretical chemistry; real-space bonding analysis; non-covalent interactions

  • Poster
    Relativistic Effects on heavy Element Chemistry and Physics, 02.-06.09.2017, Marburg, Deutschland

Publ.-Id: 26004

GMaps – eine dreidimensinale Datenstruktur zur Modellierung und Simulation von realen Erz-Mikrostrukturen

Menzel, P.

Zur Bestimmung der optimalen Prozessketten zur Verarbeitung von Komplexerzen muss der gesamte Prozess simuliert und auf spezifisches Eingabematerial optimiert werden. Für diese Simulation ist die genaue Kenntnis der Mikrostruktur im Erzkörper notwendig.
Diese Erz-Mikrostruktur ist sehr komplex und kann nur mit sehr allgemeinen Datenstrukturen digital abgebildet und verarbeitet werden. Wir verwenden dafür ein Konzept genannt „Generalized Map“, dass es erlaubt, nahezu beliebige Vermaschungen innerhalb von natürlichen Körpern abzubilden und dennoch sehr effizient auf die einzelnen Bestandteile zugreifen zu können.

In dieser Arbeit werden die Verwendung von Generalized Maps zur Modellierung und Simulation von Erz-Mikrostrukturen und verschiedenen Anwendungen vorgestellt.

Keywords: GMaps; Mikrostrukturen/Microstruccures

  • Lecture (others)
    Geophysikalisches Barbara-Kolloquium, 02.12.2017, Freiberg, Deutschland

Publ.-Id: 26003

Thermally induced magnetic switching in bit-patterned media

Pfau, B.; Günther, C. M.; Hauet, T.; Eisebitt, S.; Hellwig, O.

We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an analytical model for the thermally activated switching of the islands, we are able to determine the intrinsic magnetic anisotropy of each island and, consequentially, a distribution of anisotropies for the island ensemble investigated. In the distribution, we identify a separated group of islands with a particularly small anisotropy. We attribute this group to islands containing misaligned grains triggering the magnetic reversal. At room temperature and slow field sweep rates, the observed thermal broadening of the switching-field distribution is small compared to the intrinsic broadening. However, we illustrate that thermal fluctuations play a crucial role at high sweep rates by extrapolating our results to technological relevant regimes.


Publ.-Id: 26002

Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations

Banerjee, C.; Gruszecki, P.; Klos, J. W.; Hellwig, O.; Krawczyk, M.; Barman, A.

By combining Brillouin light scattering and micromagnetic simulations, we studied the spin-wave (SW) dynamics of a Co/Pd thin film multilayer, which features a stripe domain structure at remanence. The periodic up and down domains are separated by corkscrew type domain walls. The existence of these domains causes a scattering of the otherwise bulk and surface SW modes, which form mode families, similar to a one-dimensional magnonic crystal. The dispersion relation and mode profiles of SWs are measured for the transferred wave vector parallel and perpendicular to the domain axis.


Publ.-Id: 26001

Core degradation analysis for a generic German PWR with the severe accident code ATHLET-CD

Wilhelm, P.; Jobst, M.

The progress of core degradation as well as evaluation of time spans for key events during the accident evolvement provides essential information related to the safety assessment of nuclear power plants. Knowledge is gained from performed experimental programmes which support the development of computer models incorporated in computer codes for analysis of severe accidents. Severe accident codes are applied since decades and constantly improved on the basis of gained new knowledge. Code-to-experiment comparison as well as code-to-code comparison is of paramount importance for the verification and validation of the codes.
For assessment of the core degradation progression in a generic German pressurized water reactor of type KONVOI a computer model based on the severe accident code ATHLET-CD was applied. The model was primarily developed within the frames of the joint research project WASA-BOSS (Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen) funded by the German Federal Ministry of Education and Research. The model was applied for simulation and analysis of accidents with core degradation from two main groups of accidents – station blackout and small-break loss-of-coolant-accident. For the current paper we have focused on analysis of core degradation during a hypothetical station blackout severe accident scenario. Analysed is the severe accident progression with failure of the safety barriers providing insights into the main phenomena which could arise in such an accident like core heat-up, cladding failure, release of fission products, hydrogen production, core degradation and reactor pressure vessel failure.
The analysis of the simulation results showed the applicability of the developed model for simulation of accidents with core degradation from the initiating event until failure of the reactor pressure vessel. The model was tested for simulations with varying the fuel burnup, with main focus on the release of the fission products from the core.

Keywords: Core Degradation; Severe Accident; Generic German PWR; ATHLET-CD; Fission Product Release; Burnup

  • Contribution to proceedings
    IAEA Technical Meeting on the Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors (I3-TM-54660), 09.-12.10.2017, Vienna, Austria
    Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors, Wien: IAEA, 9789201029195
  • Lecture (Conference)
    IAEA Technical Meeting on the Status and Evaluation of Severe Accident Simulation Codes for Water Cooled Reactors (I3-TM-54660), 09.-12.10.2017, Vienna, Austria

Publ.-Id: 26000

Synthesis and X-ray Crystal Structure of N’-Cyano-N,N’-dimethyl-4-nitrobenzohydrazide

Löser, R.; Pitzschler, R.; Köckerling, M.

Using a two-step procedure N’-Cyano-N,N’-dimethyl-4-nitrobenzohydrazide was synthesized. The structure was established using single crystal X-ray diffraction. It crystalized in the orthorhombic space group P212121 with a = 8.1974(6), b = 10.6696(7), and c = 12.9766(8) Å. The first reported crystal structure of an acyclic cyanohydrazide is discussed with the focus on the geometry of the hydrazide moiety but also intermolecular contacts in the crystal are considered. Implications of the structural findings towards the enzyme inhibitory activity of related azapeptide nitriles are indicated.

Publ.-Id: 25999

Time-lapse 3D imaging by positron emission tomography of Cu mobilized in a soil column by the herbicide MCPA

Kulenkampff, J.; Stoll, M.; Gründig, M.; Mansel, A.; Lippmann-Pipke, J.; Kersten, M.

Phenoxyalkanoic acids like the 4-chloro-2-methylphenoxyacetic acid (MCPA) are the second highest used xenobiotic herbicides worldwide after glyphosate because of their apparently favorable environmental properties. Experimental batch equilibration data suggested a reduced Cu adsorption efficiency with the soil mineral goethite below pH 6 in presence of MCPA. This has been verified by advanced surface complexation adsorption modelling involving dissolved Cu-MCPA complexation constants. Positron emission tomography is a non-invasive molecular imaging method for time-resolved three-dimensional information commonly applied on non-retarded tracers in soil core scale experiments. Mineral surface reactive tracers like Cu-64 are too immobile for the relatively short observation times available with this advanced imaging technique. However, Cu-64 radiolabeled Cu-MCPA complex migration could be observed in as long as 10-cm artificial soil test columns where break-through occurred within a few days. For the first time, time-lapse movies of Cu migration in the opaque soil columns were recorded using this novel reactive transport process tomography approach.

Keywords: PET; reactive transport; soil; process tomography


Publ.-Id: 25998

Radiative and non-radiative de-excitation of slow highly charged ions transmitted through freestanding single layer graphene

Wilhelm, R. A.; Schwestka, J.; Gruber, E.; Heller, R.; Kozubek, R.; Schleberger, M.; Facsko, S.; Aumayr, F.

Slow highly charged ions interacting with a solid surface undergo an ultrafast charge exchange combined with a rapid electronic de-excitation within less than 10 fs. These processes involve capture of some 10 electrons, emission of at least some 10 additional electrons from the surface and radiative as well as non-radiative de-excitation of the ion. To investigate the branching ratio of radiative vs. non-radiative de-excitation we measured x-ray emission of highly charged Ar ions with two, one or no K-shell hole(s) when they are transmitted through a freestanding single layer of graphene.

  • Lecture (Conference)
    Conference on Ion-Surface Interactions 2017 (ISI2017), 20.-25.08.2017, Moskau, Russland

Publ.-Id: 25997

Oncoidal granular iron formation in the Mesoarchaean Pongola Supergroup, southern Africa: Textural and geochemical evidence for biological activity during iron deposition

Smith, A. J. B.; Beukes, N. J.; Gutzmer, J.; Czaja, A. D.; Johnson, C. M.; Nhleko, N.

We document the discovery of the first granular iron formation (GIF) of Archaean age and present textural and geochemical results that suggest these formed through microbial iron oxidation. The GIF occurs in the Nconga Formation of the ca. 3.0–2.8 GacPongola Supergroup in South Africa and Swaziland. It is interbedded with oxide and silicate facies micritic iron formation (MIF). There is a strong textural control on iron mineralization in the GIF not observed in the associated MIF. The GIF is marked by oncoids with chert cores surrounded by magnetite and calcite rims. These rims show laminated domal textures, similar in appearance to microstromatolites. The GIF is enriched in silica and depleted in Fe relative to the interbedded MIF. Very low Al and trace element contents in the GIF indicate that chemically precipitated chert was reworked above wave base into granules in an environment devoid of siliciclastic input. Microbially mediated iron precipitation resulted in the formation of irregular, domal rims around the chert granules. During storm surges, oncoids were transported and deposited in deeper water environments. Textural features, along with positive δ56Fe values in magnetite, suggest that iron precipitation occurred through incomplete oxidation of hydrothermal Fe2+ by iron-oxidizing bacteria. The initial Fe3+-oxyhydroxide precipitates were then post-depositionally transformed to magnetite. Comparison of the Fe isotope compositions of the oncoidal GIF with those reported for the interbedded deeper water iron formation (IF) illustrates that the Fe2+ pathways and sources for these units were distinct. It is suggested that the deeper water IF was deposited from the evolved margin of a buoyant Fe2+aq-rich hydrothermal plume distal to its source. In contrast, oncolitic magnetite rims of chert granules were sourced from ambient Fe2+aq-depleted shallow ocean water beyond the plume.

Publ.-Id: 25996

Incorporation of Europium(III) into Scheelite-Related Host Matrices ABO4 (A = Ca2+, Sr2+, Ba2+; B = W6+, Mo6+): Role of A- and B- Sites on the Dopant Site-Distribution and Photoluminescence

Xiao, B.; Schmidt, M.

Scheelite and powellite related materials doped with trivalent lanthanides or actinides have been the subject of extensive research due to their important role in mineralogical, technological and environmental implications. Detailed structural knowledge of these solid solutions is essential for understanding their physicochemical properties and predicting material properties. In this work, we conduct a comprehensive spectroscopic analysis by means of polarization-dependent site-selective time resolved laser-induced fluorescence spectroscopy (p-TRLFS), to delineate the influence of the host phase cations for a series of scheelite-type matrices based on a general formulae of ABO4 (A = Ca2+, Sr2+, Ba2+; B = W6+, Mo6+) on the local environment of the Eu3+ dopant. Eu3+ has been used as a luminescent probe to access the local structural environment of crystalline substitutional sites suitable for trivalent lanthanides or actinides occupation. Our results show that the lattice distortion is overall minor, but increases with increasing mismatch of host and guest cation size. We observe a linear dependence of Eu3+’s excitation energy on the host cation size and the A – O bond distance, which can be used to determine the hitherto unknown Eu – O bond distance in NaEu(WO4)2. A value of 2.510 Å was determined, somewhat larger than a previously reported number for NaEu(MoO4)2. The results also show clear evidence that the local coordination environment of Eu in WO42- materials is more symmetrical than in their isostructural MoO42- counterparts. The detailed spectroscopic interpretation conducted in this study resolves the relation between local distortion around a dopant and the host phase cations in structural disordered materials and may give novel insights with respect to rational design and tailoring of functional materials.

Keywords: scheelite; laser spectrum; TRLFS; site symmetry


Publ.-Id: 25995

Time-resolved imaging of the gyration dynamics of magnetic bubbles and magnetic skyrmioniums

Finizio, S.; Wintz, S.; Kirk, E.; Weigand, M.; Raabe, J.

Time-resolved imaging of the gyration dynamics of magnetic bubbles and magnetic skyrmioniums

Keywords: magnetism; spin dynamics; skyrmionium; x-ray microscopy

  • Poster
    62nd Annual Magnetism & Magnetic Materials Conference, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 25994

Imaging of magnetic materials at sub-µm and sub-ns resolutions at the Pollux endstation of the Swiss Light Source

Finizio, S.; Wintz, S.; Watts, B.; Raabe, J.

Keywords: magnetism; x-ray microscopy

  • Poster
    62nd Annual Magnetism & Magnetic Materials Conference, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 25993

Imaging of magnetic skyrmions with the PolLux endstation of the Swiss Light Source

Finizio, S.; Wintz, S.; Watts, B.; Raabe, J.

Keywords: magnetism; x-ray microscopy; skyrmions

  • Poster
    Skymag 2017, 02.-05.05.2017, Paris, Frankreich

Publ.-Id: 25992

Frequency- and Amplitude Modulation of Spin-Wave Signals generated in Topological Spin Textures

Wintz, S.; Finizio, S.; Schultheiss, K.; Liersch, V.; Kilibarda, F.; Warnatz, T.; Suszka, A. K.; Warnicke, P.; Wohlhüter, P.; Erbe, A.; Lindner, J.; Raabe, J.; Fassbender, J.

Keywords: magnetism; spin waves; x-ray microscopy

  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Publ.-Id: 25991

In-situ membrane bending setup for the investigation of magnetostrictive materials with XMCD-STXM imaging

Finizio, S.; Wintz, S.; Kirk, E.; Raabe, J.

Keywords: magnetism; magnetostriction; spin dynamics

  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Publ.-Id: 25990

Spin textures as local and tunable spin-wave emitters

Wintz, S.; Sluka, V.; Dieterle, G.; Weigand, M.; Tiberkevich, V.; Schneider, T.; Gallardo, R. A.; Finizio, S.; Erbe, A.; Lindner, J.; Schütz, G. A.; Slavin, A. N.; Raabe, J.; Fassbender, J.

Keywords: magnetism; spin waves; x-ray microscopy

  • Invited lecture (Conferences)
    62nd Annual Magnetism & Magnetic Materials Conference, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 25989

Spin Wave Emission from Topological Spin Textures

Wintz, S.; Sluka, V.; Schneider, T.; Kakay, A.; Weigand, M.; Schultheiss, K.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.

Keywords: magnetism; spin waves; x-ray microscopy

  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moskau, Russische Föderation

Publ.-Id: 25988

Tailoring the gyrotropic resonance of magnetic vortices by strain

Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Wohlhüter, P.; Zeissler, K.; Raabe, J.

Keywords: magnetism; vortex; magnetostriction; spin dynamics

  • Lecture (Conference)
    62nd Annual Magnetism & Magnetic Materials Conference, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 25987

Control of the magnetic vortex core dynamics in magnetostrictive microstructured elements through the Magneto-Elastic coupling

Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Raabe, J.

Keywords: magnetism; vortex; magneto elastic; spin dynamics

  • Lecture (Conference)
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Ireland

Publ.-Id: 25986

Software commissioning of a Monte-Carlo model for the double-scattering treatment head at University Proton Therapy Dresden

Eulitz, J.; Lühr, A.; Enghardt, W.; Lutz, B.

Compared to treatment planning systems (TPS) in proton therapy, Monte-Carlo simulations have the potential to describe radiation fields in patients more precisely. However, next to an accurate Monte-Carlo model of the treatment head a benchmarking with respect to dose measurements is required. The purpose of this work was to set up and validate a Monte-Carlo simulation model of the clinical proton treatment fields at the University Proton Therapy Dresden (UPTD).
A detailed model of the treatment head geometry of the UPTD in double-scattering mode was implemented using the Monte-Carlo simulation environment TOPAS. The proton beam source was optimized to match measured reference depth-dose distributions for all clinically available treatment field options. The commissioned software model was validated against an independent set of depth-dose and lateral dose validation data measured in a water phantom. A setup for the direct simulation of so-called monitor units (MU), relating dosimeter readings in the treatment head to absolute dose in a water phantom, was implemented.
Validation data on depth-dose distributions were reproduced within range differences of 0.26 mm and a relative dose uncertainty of 1% for all treatment options (i.e., comparable to measurement uncertainties). Simulated lateral dose profiles differed from validation data in lateral width and penumbra less than 0.95 mm and 0.56 mm, respectively. Measured MU values were predicted within 2% accuracy for several reference and patient treatment fields.
The commissioned Monte-Carlo model reproduced the dose validation data measured during the clinical validation of the UPTD within clinical tolerances. This enables high-precision simulations of clinical proton beams. Furthermore, it has the potential to predict absolute doses and to use patient-specific MU values, which might decrease the patient-specific measurement effort at UPTD.
This, however, requires further validation.

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 25985

Control of the gyration of magnetic vortices by the magneto-elastic effect

Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Wohlhüter, P.; Zeissler, K.; Raabe, J.

The influence of a strain-induced uniaxial magnetoelastic anisotropy on the magnetic vortex core dynamics microstructured magnetostrictive Co40 Fe40 B20 elements was investigated with time-resolved scanning transmission x-ray microscopy. The measurements revealed a monotonically decreasing eigenfrequency of the vortex core gyration with the increasing magnetoelastic anisotropy, which follows closely the predictions from in micromagnetic modeling.

Keywords: magnetism; x-ray microscopy; vortex; spin dynamics


Publ.-Id: 25984

Investigation of the LET-dependency from BeO using single photon detection for dosimetry in proton beams

Radtke, J.; Kormoll, T.; Grabs, L.; Lutz, B.; Lühr, A.; Ullrich, W.; Sponner, J.; Henniger, J.

Optically stimulated luminescence (OSL) is gaining greater importance in the field of personal dosimetry in the last few years. Its principle is based on the release of small amounts of light induced by the prior absorption of ionizing radiation. One suitable luminophore for OSL is beryllium oxide (BeO). Because of its near tissue equivalent effective atomic number of 7, it is excellent for personal dosimetry. Furthermore, the luminescence signal has a wide dose linearity ranging from the µGy region up to few Gy. For this reason, this ceramic can be used for several different areas of application. A new generation of measurement systems based on the OSL of BeO, which has a very low OSL light intensity, was developed by the radiation physics group at TU Dresden. This property allows single photon detection which is superior in contrast to other detection methods. Therefore, a single photon sensor was used as a detector. The single photon mode of the detector in combination with the so called timestamp detection method allows accessing the greatest possible information of the OSL light. This work applies the new system to dosimetry of a proton beam. Because of the LET-dependencies of the luminescence light, this presents a challenge. Common problems of solid state dosimetry are local saturation effects, which were investigated for BeO. Opportunities for correction in terms of the LET-dependency of the luminophore are being discussed. For the empirical determination of the behavior of BeO in proton beams, measurements at the medical proton therapy facility at the University Proton Therapy Dresden (UPTD) were carried out. All collected data were analyzed for LET-dependency on the response signal. For the measurements, BeO ceramics were placed at different depth infront and inside the spread out Bragg peak (SOBP). The dose read from dosimeters was analyzed with respect to the applied dose and the LET. All measurements infront of the SOBP shows no deviation of the estimated dose. The dose determination in the SOBP yielded an underestimation by 15%. This is object of current investigation.

  • Poster
    Jahrestagung der biomedizinischen Technik und Dreiländertagung der medizinischen Physik, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 25983

Monte-Carlo simulation of proton treatment fields in patients to support treatment planning

Eulitz, J.; Lutz, B.; Oesten, H.; Wohlfahrt, P.; Enghardt, W.; Lühr, A.

Monte-Carlo (MC) simulations may allow for reducing range margins and applying variable relative-biological-effectiveness (RBE) models in proton therapy. Here, an approach is presented to support treatment planning of patients by highlighting regions with increased dose uncertainties originating from dose calculation and the assumption of a constant RBE of 1.1.
A software framework was developed and experimentally validated, which simulates proton plans at the University Proton Therapy Dresden (UPTD) using the MC tool TOPAS. It is based on a commissioned model of the UPTD treatment head in double-scattering mode. Clinical treatment plans and computed tomography datasets were imported in DICOM format. MC-based dose distributions were compared with dose distributions received from the clinically applied treatment planning system (TPS) XIO, Elekta. Obtained dose, linear-energy-transfer (LET), and modelled RBE maps (using experimental in vitro data) were imported into the TPS RayStation, RaySearch for plan evaluation.
TPS doses above the 95% iso dose level are reproduced within gamma pass rates GPR ≥ 98%, when applying 1 mm local and 2 % dose gamma criterion. Dose differences reached values up to 8 Gy for field volumes up to 4 cm 3 , particularly at regions with high-density gradients (e.g. bone and air cavities) and at the field edges. LET and variable RBE hot spots were obtained at (distal) field edges while at the field center RBE values below 1.1 were predicted. Clinical dose values differed by up to 10 Gy using either the assumption of a constant or a variable RBE.
The treatment planning and delivery workflow at UPTD was mapped in a MC simulation. In general, good agreement between TPS and MC clinical dose values was found. However, relevant clinical dose differences were obtained and emphasise the necessity of using MC to enhance the physical and biological dose prediction in patients.

  • Lecture (Conference)
    Jahrestagung der biomedizinischen Technik und Dreiländertagung der medizinischen Physik, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 25982

Experimental verification of particle-range prediction in biological tissue by single- and dual-energy computed tomography

Möhler, C.; Russ, T.; Wohlfahrt, P.; Elter, A.; Runz, A.; Richter, C.; Greilich, S.

We introduce a hybrid experimental setup to accurately measure x-ray and ion absorption in tissue or other materials. With this setup using a 3D-printed sample container, the stopping-power ratio (SPR) of homogeneous materials can be measured with an uncertainty of below 0.1%. A total of 40 homogeneous porcine and bovine soft-tissue samples were prepared for measurement, comprising five samples each of eight tissue types (three different muscle and fatty tissues, liver, lung). Using a standard stoichiometric calibration for single-energy CT (SECT) as well as a state-of-the-art dual-energy CT (DECT) approach, SPR was predicted for all tissues and then compared to the measured reference. With the SECT approach, the SPR of all tissues, excluding lung due to its large heterogeneity, was underestimated by up to -3% with a mean (absolute) error of -1.5% (1.5%). In contrast, the DECT-based SPR prediction showed no significant bias with a mean error below the measurement uncertainty of 0.1% and a mean absolute error of 0.2%. In this study, the potential of DECT to decrease range uncertainty could thus be confirmed in biological tissue.

Keywords: proton and ion radiation therapy; treatment planning; stopping-power ratio; range verification

Publ.-Id: 25981

Die Energiewende braucht verlässliche Rahmenbedingungen für den Metallerzbergbau - The energy transition needs a reliable framework for metal ore mining

Wellmer, F. W.; Gutzmer, J.; Kullik, J.; Erlach, B.

Mit dem Projekt Energiesysteme der Zukunft (ESYS) wollen acatech – Deutsche Akademie der Technikwissenschaften, die Nationale Akademie der Wissenschaften Leopoldina und die Union der deutschen Akademien der Wissenschaften Impulse für die mittel- bis langfristige Umsetzung der Energiewende in Deutschland setzen. Im Rahmen des Projekts haben Wissenschaftler(innen) unterschiedlicher Fachrichtungen auch die Stellungnahme Rohstoffe für die Energiewende – Wege zu einer sicheren und nachhaltigen Versorgung (acatech et al. 2017) verfasst. Sie zeigt Handlungsoptionen für eine langfristige und nachhaltige Versorgung mit den für die Energiewende erforderlichen Rohstoffen auf. Die wissenschaftlichen Grundlagen der Handlungsoptionen sind in der Publikation Rohstoffe für die Energieversorgung der Zukunft: Geologie – Märkte – Umwelteinflüsse (Angerer et. al. 2016) dargestellt.
Martin David, Magdalena Wallkamm und Alena Bleicher haben sich in GAIA mit beiden Publikationen auseinandergesetzt (David et al. 2017). Ihre wesentliche Kritik lautet: ESYS habe eine überwiegend technologische (Umwelt-)Perspektive, während andere gesellschaftliche Fragen zu kurz kämen. Wir gehen im Folgenden auf die Kritikpunkte ein.

Keywords: energy transition; metals; mining; rare earths; social-license to operate

  • GAIA - Ökologische Perspektiven für Wissenschaft und Gesellschaft 26(2017)3, 233-236
    DOI: 10.14512/gaia.26.3.4

Publ.-Id: 25980

Cues to greater recycling efficiency-characterization of a crushed mobile phone by mineral liberation analysis

Sandmann, D.; Jäckel, H.-G.; Gutzmer, J.

In 2016 more than 1.35 billion smartphones have been manufactured (TrendForce Corp. 2017). Smartphones can contain up to 60 different elements and the summarized metal weight of the 2016 production is very likely more than 50,000 tons (The Royal Society of Chemistry 2017, 911Metallurgist 2013). However, at present, very few of the elements contained in these devices are recycled at recycling rates of more than 50%. For most elements, the recycling rates are significantly lower than 50%, and the recycling rates of rare earths, indium, tantalum or gallium are even below 1% (Compound Interest 2015)! The major challenge of mobile phone recycling is the complex composition of the devices made of many individual components. This is aggravated by the fact that many elements occur in traces only and / or are located in highly complex material composites.
To enable more effective recycling of mobile phones, it is imperative to characterise their components, the presence of elements in it, as well as the crushing behaviour as detailed as possible.
In a pilot study, a Nokia mobile phone Model 5228 Type RM-625, crushed with a Universal Granulator UG300 by colleagues of the Professorship of recycling machines of the TU Bergakademie Freiberg, was examined by Mineral Liberation Analysis (MLA). The analysis on three sieve fractions of the comminuted material was carried out with an MLA 650F at the Helmholtz Institute Freiberg for Resource Technology. The samples were scanned in an automated MLA measurement with a grid of EDX spectra (GXMAP mode). A total of 130 different phases were detected during the analysis. More than 100 of these phases occur at levels <1 % by weight. This strongly illustrates the very complex composition of mobile phones and the need for detailed analytical characterisation. A comparison of the modal content of the three sieve fractions showed an enrichment of certain components in specific fractions.

911Metallurgist (2013) - Mining & iPhone Recycling, [accessed 2017 Aug 15].
Compound Interest (2015) - The Recycling Rates of Smartphone Metals, [accessed 2017 Aug 15].
The Royal Society of Chemistry (2017) - Getting the metals out of old phones, [accessed 2017 Aug 15].
TrendForce Corp. (2017) - Press Release. TrendForce Reports Global Smartphone Production Volume Totaled 1.36 Billion Units; Samsung Held On as Leader While OPPO and Vivo Burst into Global Top Five, [accessed 2017 Aug 15].

  • Contribution to proceedings
    69. BHT - FREIBERGER UNIVERSITÄTSFORUM 2018, Fachkolloquium 8: E-Mobility & Circular Economy, 06.-07.06.2018, Freiberg, Germany
    Materials Science Forum, Vol. 959, 134-141
    DOI: 10.4028/


Publ.-Id: 25979

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Jang, J.; Friedrich, D.; Müller, S.; Lamers, M.; Hempel, H.; Lardhi, S.; Cao, Z.; Harb, M.; Cavallo, L.; Heller, R.; Eichberger, R.; van de Krol, R.; Abdi, F. F.

Widespread application of solar water splitting for energy conversion is largely dependent on the progress in developing not only efficient but also cheap and scalable photoelectrodes. Metal oxides, which can be deposited with scalable techniques and are relatively cheap, are particularly interesting, but high efficiency is still hindered by the poor carrier transport properties (i.e., carrier mobility and lifetime). In this paper, a mild hydrogen treatment is introduced to bismuth vanadate (BiVO4), which is one of the most promising metal oxide photoelectrodes, as a method to overcome the carrier transport limitations. Time-resolved microwave and terahertz conductivity measurements reveal more than twofold enhancement of the carrier lifetime for the hydrogen-treated BiVO4, without significantly affecting the carrier mobility. This is in contrast to the case of tungsten-doped BiVO4, although hydrogen is also shown to be a donor type dopant in BiVO4. The enhancement in carrier lifetime is found to be caused by significant reduction of trap-assisted recombination, either via passivation of deep trap states or reduction of trap state density, which can be related to vanadium antisite on bismuth or vanadium interstitials according to density functional theory calculations. Overall, these findings provide further insights on the interplay between defect modulation and carrier transport in metal oxide photoelectrodes, which will benefit the development of low-cost, highly efficient solar energy conversion devices.

Publ.-Id: 25977

Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy

Mikhaylov, A. A.; Priamushko, T. S.; Babikhina, M. N.; Kudiiarov, V. N.; Heller, R.; Laptev, R. S.; Lider, A. M.

To study the hydrogen distribution in Zr-1Nb alloy (E(cyrillic)110 alloy) GD-OES was applied in this work. Qualitative analysis needs the standard samples with hydrogen. However, the standard samples with high concentrations of hydrogen in the zirconium alloy which would meet the requirements of the shape, size are absent. In this work method of Zr + H calibration samples production was performed at the first time. Automated Complex Gas Reaction Controller was used for samples hydrogenation. To calculate the parameters of post-hydrogenation incubation of the samples in an inert gas atmosphere the diffusion equations were used. Absolute hydrogen concentrations in the samples were determined by melting in the inert gas atmosphere using RHEN602 analyzer (LECO Company). Hydrogen distribution was studied using nuclear reaction analysis (HZDR, Dresden, Germany). RF GD-OES was used for calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik, Germany. © 2017.

Keywords: Calibration; Glow discharge optical emission spectroscopy (GD-OES); Hydrogen; Standard samples; Zirconium alloy

Publ.-Id: 25976

Zur Ligandenentwicklung für den vesikulären Acetylcholintransporter im Gehirn

Barthel, C.

Es ist kein Abstract vorhanden.

  • Doctoral thesis
    Universität Leipzig, 2017
    Mentor: Dr. Barbara Wenzel
    203 Seiten

Publ.-Id: 25975

Holographic vector mesons in a dilaton background

Zöllner, R.; Kämpfer, B.

Within a holographic framework, we consider vector mesons riding on a gravity-dilaton background. The latter one is determined directly from a Schr\"odinger equivalent potential which delivers a proper ρ meson Regge trajectory. The mapping on the dilaton potential yields a thermodynamic phase structure with a first-order transition.

Publ.-Id: 25974

Improvements of the ELBE Control System Infrastructure and SCADA Environment

Justus, M.; Steinbrück, R.; Leege, K. W.; Schamlott, A.; Michel, P.

The ELBE Center for High-Power Radiation Sources comprises a 40 MeV c.w. electron linear accelerator, driving diverse secondary beams, both electromagnetic radiation and particles. Its control system is based on PLCs, fast data acquisition systems and the industrial SCADA system WinCC. In the past three years, requirements for availability and reliability increased, while at the same time changes of the machine configuration and instrumentation need to be handled permanently. Improvements of the control system infrastructure concerning power supply, IT and systems monitoring have been realized and are still under way. Second, along with the last major SCADA system upgrade, we implemented a more redundant SCADA infrastructure, improved long term data storage and continuously improved our standards for software development.

Keywords: ELBE; Control System

  • Poster
    ICALEPCS 2017 - 16th International Conference on Accelerator and Large Experimental Control Systems, 08.-13.10.2017, Barcelona, Espana
  • Open Access Logo Contribution to proceedings
    ICALEPCS 2017 - 16th International Conference on Accelerator and Large Experimental Control Systems, 08.-13.10.2017, Barcelona, Espana
    16th International Conference on Accelerator and Large Experimental Physics Control Systems: JACoW Publishing, 978-3-95450-193-9, 1405-1408
    DOI: 10.18429/JACoW-ICALEPCS2017-THPHA027

Publ.-Id: 25973

Synthese und Entwicklung eines fluorierten Pyrimidingrundkörpers für weitere Radiotracerentwicklungen

Milewski, M.

Es ist kein Abstract vorhanden.

  • Bachelor thesis
    Universität Leipzig, 2017
    Mentor: Lindemann, Marcel
    52 Seiten

Publ.-Id: 25971

High-Mobility, Band-Like Charge Transport in a Semiconducting Two-Dimensional Metal-Organic Framework

Dong, R.; Han, P.; Arora, H.; Ballabio, M.; Karakus, M.; Zhang, Z.; Shekhar, C.; Adler, P.; St. Petkov, P.; Erbe, A.; Mannsfeld, S. C. B.; Felser, C.; Heine, T.; Bonn, M.; Feng, X.; Canovas, E.

Metal–organic frameworks (MOFs) are hybrid materials based on crystalline coordination polymers that consist of metal ions connected by organic ligands. In addition to the traditional applications in gas storage and separation or catalysis, the long-range crystalline order in MOFs, as well as the tunable coupling between the organic and inorganic constituents, has led to the recent development of electrically conductive MOFs as a new generation of electronic materials. However, to date, the nature of charge transport in the MOFs has remained elusive. Here we demonstrate, using high-frequency terahertz photoconductivity and Hall effect measurements, Drude-type band-like transport in a semiconducting, π–d conjugated porous Fe3(THT)2(NH4)3 (THT, 2,3,6,7,10,11-triphenylenehexathiol) two-dimensional MOF, with a room-temperature mobility up to ~ 220 cm2 V–1 s–1. The temperature-dependent conductivity reveals that this mobility represents a lower limit for the material, as mobility is limited by impurity scattering. These results illustrate the potential for high-mobility semiconducting MOFs as active materials in thin-film optoelectronic devices.

Keywords: conductive metal-organic frameworks; polymers; microelectronics


  • Secondary publication expected

Publ.-Id: 25970

Individualized risk assessment in neuroblastoma: does the tumoral metabolic activity on 123I-MIBG SPECT predict the outcome?

Rogasch, J.; Hundsdoerfer, P.; Furth, C.; Wedel, F.; Hofheinz, F.; Krüger, P.; Lode, H.; Brenner, W.; Eggert, A.; Amthauer, H.; Schatka, I.


Risk-adapted treatment in children with neuroblastoma (NB) is based on clinical and genetic factors. This study evaluated the metabolic tumour volume (MTV) and its asphericity (ASP) in pretherapeutic 123I-MIBG SPECT for individualized image-based prediction of outcome.


This retrospective study included 23 children (11 girls, 12 boys; median age 1.8 years, range 0.3–6.8 years) with newly diagnosed NB consecutively examined with pretherapeutic 123I-MIBG SPECT. Primary tumour MTV and ASP were defined using semiautomatic thresholds. Cox regression analysis, receiver operating characteristic analysis (cut-off determination) and Kaplan-Meier analysis with the log-rank test for event-free survival (EFS) were performed for ASP, MTV, laboratory parameters (including urinary homovanillic acid-to-creatinine ratio, HVA/C), and clinical (age, stage) and genetic factors. Predictive accuracy of the optimal multifactorial model was determined in terms of Harrell’s C and likelihood ratio χ2.


Median follow-up was 36 months (range 7–107 months; eight patients showed disease progression/relapse, four patients died). The only significant predictors of EFS in the univariate Cox regression analysis were ASP (p = 0.029; hazard ratio, HR, 1.032 for a one unit increase), MTV (p = 0.038; HR 1.012) and MYCN amplification status (p = 0.047; HR 4.67). The mean EFS in patients with high ASP (>32.0%) and low ASP were 21 and 88 months, respectively (p = 0.013), and in those with high MTV (>46.7 ml) and low MTV were 22 and 87 months, respectively (p = 0.023). A combined risk model of either high ASP and high HVA/C or high MTV and high HVA/C best predicted EFS.


In this exploratory study, pretherapeutic image-derived and laboratory markers of tumoral metabolic activity in NB (ASP, MTV, urinary HVA/C) allowed the identification of children with a high and low risk of progression/relapse under current therapy.

Keywords: Neuroblastoma; Prognosis; 123I-MIBG; Asphericity; Metabolic tumour volume

Publ.-Id: 25969

Specific Features of the Ion-Beam Synthesis of Ge Nanocrystals in SiO2 Thin Films

Tyschenko, I. E.; Cherkov, V. A.; Volodin, V. A.; Voelskow, M.

The systematic features of the formation of Ge nanocrystals in SiO2 thin films implanted with Ge ions and then subjected to high-temperature annealing (1130°C) are studied in relation to hydrostatic pressure. It is established that annealing at atmospheric pressure is accompanied by the diffusion of Ge atoms from the implantation region to the Si substrate and does not induce the formation of Ge nanocrystals. An increase in pressure during annealing yields a deceleration in the diffusion of germanium into silicon and is accompanied by the formation of twinned lamellae at the Si/SiO2 interface (at pressures of ~103 bar) or by the nucleation and growth of Ge nanocrystals (at pressures of ~104 bar) in the SiO2 film. The results are discussed on the basis of the concept of a change in the activation volume of the formation and migration of point defects under conditions of compression.

Keywords: Ion Beam Synthesis; nanocrystals; SiO2

Publ.-Id: 25968

The precession dynamo at HZDR -- Preliminary flow measurements and simulations

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.

No abstract required

Keywords: Dynamo; Dresdyn

  • Invited lecture (Conferences)
    Max Planck Princeton Research Center for Plasma Physics Greifswald Meeting — September 2017, 19.-22.09.2017, Greifswald, Deutschland

Publ.-Id: 25967

Dynamo action from a laminar non-linear flow in a precessing cylinder

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.

Within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a dynamo experiment is under development in which a precession driven flow of liquid sodium will be used to excite dynamo action. In my presentation I will address preparative numerical simulations and flow measurements conducted at a small model experiment filled with water. The results provide typical flow pattern and flow amplitudes in dependence of precession ratio and Reynolds number and are used for the setup of kinematic dynamo models in order to estimate whether the particular flow is able to drive a dynamo.

In the strongly non-linear regime the flow essentially consists of the directly forced Kelvin mode superimposed by standing inertial waves caused by non-linear self-interaction of the forced mode whereas time-dependent contributions in terms of randomly distributed small-scale noise remain negligible. Most remarkable feature is the occurrence of a resonant-like axisymmetric mode around a precession ratio of Omega_prec/Omega_cyl = 0.1. Only the combination of this axisymmetric mode and the forced m=1 Kelvin mode is capable of driving a dynamo. Our simulations yield a critical magnetic Reynolds number of Rm_c=430 which is well within the regime that will be achieved in the experiment. However, the occurrence of the axisymmetric mode slightly depends on the absolute rotation rate of the cylinder and future experiments are required to indicate whether this instability will persist at the extremely large Re that will be obtained in the large scale experiment.

Keywords: Dynamo; Dresdyn

  • Poster
    MREP 2017, 11.-12.09.2017, Cambridge, Great Britain

Publ.-Id: 25966

Horizon 2020 EuPRAXIA design study

Walker, P. A.; Alesini, P. D.; Alexandrova, A. S.; Anania, M. P.; Andreev, N. E.; Andriyash, I.; Aschikhin, A.; Assmann, R. W.; Audet, T.; Bacci, A.; Barna, I. F.; Beaton, A.; Beck, A.; Beluze, A.; Bernhard, A.; Bielawski, S.; Bisesto, F. G.; Boedewadt, J.; Brandi, F.; Bringer, O.; Brinkmann, R.; Bründermann, E.; Büscher, M.; Bussmann, M.; Bussolino, G. C.; Chance, A.; Chanteloup, J. C.; Chen, M.; Chiadroni, E.; Cianchi, A.; Clarke, J.; Cole, J.; Couprie, M. E.; Croia, M.; Cros, B.; Dale, J.; Dattoli, G.; Delerue, N.; Delferriere, O.; Delinikolas, P.; Dias, J.; Dorda, U.; Ertel, K.; Pousa, A. F.; Ferrario, M.; Filippi, F.; Fils, J.; Fiorito, R.; Fonseca, R. A.; Galimberti, M.; Gallo, A.; Garzella, D.; Gastinel, P.; Giove, D.; Giribono, A.; Gizzi, L. A.; Grüner, F. J.; Habib, A. F.; Haefner, L. C.; Heinemann, T.; Hidding, B.; Holzer, B. J.; Hooker, S. M.; Hosokai, T.; Irman, A.; Jaroszynski, D. A.; Jaster-Merz, S.; Joshi, C.; Kaluza, M. C.; Kando, M.; Karger, O. S.; Karsch, S.; Khazanov, E.; Khikhlukha, D.; Knetsch, A.; Kocon, D.; Koester, P.; Kononenko, O.; Korn, G.; Kostyukov, I.; Labate, L.; Lechner, C.; Leemans, W. P.; Lehrach, A.; Li, F. Y.; Li, X.; Libov, V.; Lifschitz, A.; Litvinenko, V.; Lu, W.; Maier, A. R.; Malka, V.; Manahan, G. G.; Mangles, S. P. D.; Marchetti, B.; Marocchino, A.; Ossa, A. M. D. L.; Martins, J. L.; Massimo, F.; Mathieu, F.; Maynard, G.; Mehrling, T. J.; Molodozhentsev, A. Y.; Mosnier, A.; Mostacci, A.; Mueller, A. S.; Najmudin, Z.; Nghiem, P. A. P.; Nguyen, F.; Niknejadi, P.; Osterhoff, J.; Papadopoulos, D.; Patrizi, B.; Pattathil, R.; Petrillo, V.; Pocsai, M. A.; Poder, K.; Pompili, R.; Pribyl, L.; Pugacheva, D.; Romeo, S.; Rossi, A. R.; Roussel, E.; Sahai, A. A.; Scherkl, P.; Schramm, U.; Schroeder, C. B.; Schwindling, J.; Scifo, J.; Serafini, L.; Sheng, Z. M.; Silva, L. O.; Silva, T.; Simon, C.; Sinha, U.; Specka, A.; Streeter, M. J. V.; Svystun, E. N.; Symes, D.; Szwaj, C.; Tauscher, G.; Thomas, A. G. R.; Thompson, N.; Toci, G.; Tomassini, P.; Vaccarezza, C.; Vannini, M.; Vieira, J. M.; Villa, F.; Wahlström, C.-G.; Walczak, R.; Weikum, M. K.; Welsch, C. P.; Wiemann, C.; Wolfenden, J.; Xia, G.; Yabashi, M.; Yu, L.; Zigler, J. Z. A.

The Horizon 2020 Project EuPRAXIA ("European Plasma Research Accelerator with eXcellence In Applications") is preparing a conceptual design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics (HEP) detector tests, and other applications such as compact X-ray sources for medical imaging or material processing. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. EuPRAXIA aims to be included on the ESFRI roadmap in 2020.

Keywords: Plasma accelerator


Publ.-Id: 25965

Engineering of optical and electrical properties of ZnO by non-equilibrium thermal processing: The role of zinc interstitials and zinc vacancies

Prucnal, S.; Wu, J.; Berencen, Y.; Liedke, M. O.; Wagner, A.; Liu, F.; Wang, M.; Rebohle, L.; Zhou, S.; Cai, H.; Skorupa, W.

A controlled manipulation of defects in zinc oxide (ZnO) and the understanding of their electronic structure can be a key issue towards the fabrication of p-type ZnO. Zn vacancy (V-Zn), Zn interstitials (I-Zn), and O vacancy (V-O) are mainly native point defects, determining the optoelectronic properties of ZnO. The electronic structure of these defects still remains controversial. Here, we experimentally demonstrate that the green emission in ZnO comes from V-Zn-related deep acceptor and V-Zn-V-O clusters, which is accompanied by the radiative transition between the triplet and the ground singlet state with the excited singlet state located above the CB minimum. Moreover, the I-Zn is identified to be a shallow donor in ZnO, being mainly responsible for the n-type conductivity of non-intentionally doped ZnO.

Keywords: ZnO; flash lamp annealing; defects; photoluminescence; positron annihilation spectroscopy


Publ.-Id: 25964

FEL-Based Near-Field Infrared to THz Nanoscopy

Kehr, S.; Doering, J.; Gensch, M.; Helm, M.; Eng, L. M.


  • Secondary publication expected

Publ.-Id: 25963

Detecting Threatening States in Laser Beams

Kelling, J.; Juckeland, G.

This poster presents our approach to automatic detection of critical failure states in the pulsed Petawatt laser systems DRACO and PENELOPE, used for investigations of exotic states of matter and medical applications. The beam shape is controlled to avoid high destructive energy densities. However, randomly occurring states threatening the device must be detected between pulses and trigger an interlock in the device firing at 10Hz.

The states we are aiming to detect are rare; thus, training data for this category is scarce. To address this, we present two approaches: First, to identify regions of interest based on physical properties of the system and apply a convolutional neural network (CNN) to to identify true positives. Secondly, using CNN-based image segmentation to localize and classify regions of interest.

Keywords: image classification; deep learning; smart laser operation

  • Poster
    Deep Learning Bootcamp 2017, 21.-25.08.2017, Dresden, Deutschland

Publ.-Id: 25962

Efficient Parallel Monte-Carlo Simulations for Large-Scale Studies of Surface Growth Processes

Kelling, J.; Ódor, G.; Weigel, M.; Gemming, G.

Lattice Monte Carlo methods are used to investigate far from and out-of-equilibrium systems, including surface growth, spin systems and solid mixtures. Such studies require observations of large systems over long times scales, to allow structures to grow over orders of magnitude, which necessitates massively parallel simulations. This talk presents work done to address the problem of parallel processing introducing correlations in Monte Carlo updates. Studies of the effect of correlations on scaling and dynamical properties of surface growth systems and related lattice gases is investigated further by comparing results obtained by correlation-free and intrinsically correlated simulations. Where the latter, based on a stochastic cellular automaton approach, are of interest because of their high efficiency. The primary subject of study is the Kardar–Parisi–Zhang surface growth in (2+1) dimensions. Key physical insights about this universality class, like precise universal exponent values and exponent relations, obtained from large-scale simulations are presented.
At the end of the talk, I will also speak about my current work at the computational science group at HZDR, which includes problems like frameworkdevelopment, image analysis and related machine learning applications.

Keywords: Lattice Monte Carlo; GPU; Surface Growth; Kardar-Parisi-Zhang

  • Lecture (Conference)
    IHRS NanoNet Annual Workshop 2017, 16.-18.08.2017, Neuklingenberg, Deutschland

Publ.-Id: 25961

Direct Measurement of the Magnetocaloric Effect in La(Fe,Si,Co)13 Compounds in Pulsed Magnetic Fields

Ghorbani Zavareh, M.; Skourski, Y.; Skokov, K. P.; Karpenkov, D. Y.; Zvyagina, L.; Waske, A.; Haskel, D.; Zhernenkov, M.; Wosnitza, J.; Gutfleisch, O.

We report on magnetization, magnetostriction, and magnetocaloric-effect measurements of polycrystalline LaFe11.74Co0.13Si1.13 and LaFe11.21Co0.65Si1.11 performed in both pulsed and static magnetic fields. Although the two compounds behave rather differently at low fields (∼5 T), they show quite similar values of the magnetocaloric effect, namely a temperature increases of about 20 K at high fields (50–60 T). The magnetostriction and magnetization also reach very similar values here. We are able to quantify the magnetoelastic coupling and, based on that, apply the Bean-Rodbell criterion distinguishing first- and second-order transitions.

Publ.-Id: 25960

Doubly dressed bosons: Exciton polaritons in a strong terahertz field

Piętka, B.; Bobrovska, N.; Stephan, D.; Teich, M.; Król, M.; Winnerl, S.; Pashkin, A.; Mirek, R.; Lekenta, K.; Morier-Genoud, F.; Schneider, H.; Deveaud, B.; Helm, M.; Matuszewski, M.; Szczytko, J.

We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.

Keywords: ultrastrong coupling regime; dressed states; exciton polaritons


Publ.-Id: 25959

Observation of Reactive Transport in Soil Columns with Positron Emission Tomography (GeoPET)

Kulenkampf, J.; Stoll, M.; Gründig, M.; Mansel, A.; Lippmann-Pipke, J.

Here we investigate reactive transport in soils with GeoPET as quantitative spatiotemporal molecular imaging method. As PET directly yields tracer concentrations, the data can be utilised for parameterization and validation of reactive transport computer models.
Artificial soil columns (sand/silt/clay/Goethit, length 90 mm, diameter 40 mm) have been prepared under CO2-atmosphere. Four different experiments on one and the same soil column are shown as motion pictures from the GeoPET-observations:
1) Injection of water, labelled with [18F]KF, into the CO2-saturated column
2) Conservative transport of [18F]KF solution through the water-saturated column
3) Injection of the reactive tracer [64Cu]Cu(MCPA)2 into the unconditioned water-saturated column
4) Injection of the reactive tracer [64Cu]Cu(MCPA)2 into the preconditioned column.

The study was supported within the framework of the priority program “Biogeochemical Interfaces in Soil” by the German Science Foundation (DFG SPP 1315: KE508/19 and LI872/5).

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, 2016.
Kulenkampff, J., Gründig, M., Zakhnini, A., Gerasch, R., and Lippmann-Pipke, J.: Process tomography of diffusion, using PET, to evaluate anisotropy and heterogeneity, Clay Miner., 50, 369–375, 2015.
Kulenkampff, J., Gründig, M., Zakhnini, A., and Lippmann-Pipke, J.: Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217–1231, 2016.
Zakhnini, A., Kulenkampff, J., Sauerzapf, S., Pietrzyk, U., and Lippmann-Pipke, J.: Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (18F, 124I and 58Co) in Opalinus Clay, anhydrite and quartz, Comput. Geosci., 57, 183–196, 2013.
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. 101, 21-27, 2017.
Stoll, M., Kulenkampff, J., Gründig, M., Lippmann-Pipke, J., and Kersten, M.: Molecular positron emission tomography imaging of Cu mobility enhanced by the herbicide 4-chloro-2-methylphenoxy-acetic acid in a soil column, submitted
Lippold, H., Karimzadeh L., Kulenkampff, J. Wissmeier, L., Stuhlfauth, C., Stoll, M., Lippmann-Pipke, L.: Effect of pH on the mobility of the herbicide MCPA in a goethite-sand matrix: 1D and 2D reactive transport modelling, to be submitted

Keywords: PET; reactive transport; soil; tomography


Publ.-Id: 25957

Origin of perpendicular magnetic anisotropy in Co/Ni multilayers

Arora, M.; Hübner, R.; Suess, D.; Heinrich, B.; Girt, E.

We studied the variation in perpendicular magnetic anisotropy of (111) textured Au/N×[Co/Ni]/Au films as a function of the number of bilayer repeats N. The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N≤10 and then moderately decreases for N>10. The model we propose reveals that the decrease of the anisotropy for N<10 is predominantly due to the reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N>10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N.

Publ.-Id: 25956

Combining Absorption and Emission Spectroscopy for the Detection and Characterization of Rare Earth Elements

Jakob, S.; Fuchs, M.; Gloaguen, R.

In the last decade, the fast development of technology and high-tech industry distinctly increased the demand of Rare Earth Elements (REEs). The combination with the globally strongly concentrated distribution of production sites classifies REEs as critical raw materials and raises the need for the exploration of complex deposits with lower concentrations or remote locations. Spectroscopic methods are the key for an advanced, fast and non-invasive approach to reduce the economic and ecologic costs of REE characterization, not only within exploration, but along the whole raw material value chain. 
Currently, the research of spectral detection and characterization of REEs is concentrated on absorption spectroscopy. Although a considerable amount of REEs can be detected by their characteristic reflectance spectrum, the commonly low intensity of characteristic absorption limits its applicability for robust detection and characterization to a few REEs, such as Neodymium and Samarium.
In the past decades, studies were conducted to characterize REE crystals by their fluorescence properties. In contrast to absorption spectroscopy, an emission is induced in the sample using a laser with a defined excitation wavelength to maximize the response that depends on the investigated material. With emission spectroscopy, a broad set of REEs can be characterized, but still, the attribution of emission features is challenging, as it depends on crystal structure and experimental parameters.
Hereby, we propose a new approach for combining absorption and emission spectroscopy to characterize REEs and overcome the limitations of the single method. For that, we first investigated single REE crystal standards with different bindings using absorption as well as emission spectroscopy. The results can be used to create a library or decision routine for the detection of REE using combined absorption and emission spectroscopy. We will then test the proposed method on natural REE bearing samples, which are additionally characterized chemically and mineralogically to provide a proper validation. Hereby, the influence of the mineral matrix, natural crystal structure and mixed REE composition can be estimated and overcome by using lasers with different stimulation wavelengths in the UV and visible range of the spectrum. Absorption spectroscopy is conducted by point measurements with a reflectance spectrometer as well as with hyperspectral cameras. We developed the tools for processing and the analysis of the spectral data to ensure a fast and robust interpretation of the spectral features.
First results show the detectability of Dy, Er, Ho, Nd, Pr, Sm, and Tm with absorption and the detection of Er, Eu, Ho, Nd, Pr, Tb, and Yb with emission spectroscopy. Additionally, for REEs having spectral signatures in both cases, absorption features overprint the emission spectra within the broad fluorescence signal of the mineral matrix. They coincide with known and measured absorption features of the specific REEs. This, the integration of both features remarkably increases the detectability and the robustness of detection for those elements.

  • Lecture (Conference)
    10th EARSeL SIG Imaging Spectroscopy Workshop, 19.-21.04.2017, Zürich, Switzerland

Publ.-Id: 25955

Nanorattles with tailored electric field enhancement

Schnepf, M. J.; Mayer, M.; Kuttner, C.; Tebbe, M.; Wolf, D.; Dulle, M.; Altantzis, T.; Formanek, P.; Förster, S.; Bals, S.; König, T. A. F.; Fery, A.

Nanorattles are metallic core-shell particles with core and shell separated by a dielectric spacer. These nanorattles have been identified as a promising class of nanoparticles, due to their extraordinary high electric-field enhancement inside the cavity. Limiting factors are reproducibility and loss of axial symmetry owing to the movable metal core; movement of the core results in fluctuation of the nanocavity dimensions and commensurate variations in enhancement factor. We present a novel synthetic approach for the robust fixation of the central gold rod within a well-defined box, which results in an axisymmetric nanorattle. We determine the structure of the resulting axisymmetric nanorattles by advanced transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Optical absorption and scattering cross-sections obtained from UV-vis-NIR spectroscopy quantitatively agree with finite-difference time-domain (FDTD) simulations based on the structural model derived from SAXS. The predictions of high and homogenous field enhancement are evidenced by scanning TEM electron energy loss spectroscopy (STEM-EELS) measurement on single-particle level. Thus, comprehensive understanding of structural and optical properties is achieved for this class of nanoparticles, paving the way for photonic applications where a defined and robust unit cell is crucial.

Publ.-Id: 25954

Ultrafast carrier dynamics in VO₂ across the pressure-induced insulator-to-metal transition

Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.

We utilize near-infrared pump ‒ mid-infrared probe spectroscopy to investigate the ultrafast electronic response of pressurized VO₂. Distinct pump‒probe signals and a pumping threshold behavior are observed even in the pressure-induced metallic state showing a noticeable amount of localized electronic states. Our results are consistent with a scenario of a bandwidth-controlled Mott-Hubbard transition.

Keywords: pressure-induced metallization; bandwidth-controlled Mott-Hubbard transition; insulator-to-metal transition; high pressure; diamond anvil cell; vanadium dioxide; VO₂; pump - probe spectroscopy

Related publications

Publ.-Id: 25953

Local Lorentz force and ultrasound Doppler velocimetry in a vertical convection liquid metal flow

Zürner, T.; Vogt, T.; Resagk, C.; Eckert, S.; Schumacher, J.

We report velocitymeasurements in a vertical turbulent convection flow cell that is filled with the eutectic liquid metal alloy gallium-indium-tin by a combined use of local Lorentz force velocimetry (LLFV) and ultrasound Doppler velocimetry (UDV). We demonstrate the applicability of LLFV for a thermal convection flow and reproduce a linear dependence of the measured force in the range of micronewtons on the local flow velocitymagnitude. Furthermore, the presented experiment is used to explore scaling laws of the global turbulent transport of heat and momentum in this low-Prandtl-number convection flow. Our results are found to be consistent with theoretical predictions and recent direct numerical simulations.

  • Open Access Logo Experiments in Fluids 59(2018)1, 3
    DOI: 10.1007/s00348-017-2457-0
  • Lecture (Conference)


Publ.-Id: 25952

Magnetic flow control in growth and casting of photovoltaic silicon: Numerical and experimental results

Poklad, A.; Pal, J.; Galindo, V.; Grants, I.; Heinze, V.; Meier, D.; Pätzold, O.; Stelter, M.; Gerbeth, G.

A novel, vertical Bridgman-type technique for growing multi-crystalline silicon ingots in an induction furnace is described. In contrast to conventional growth, a modified setup with a cone-shaped crucible and susceptor is used. A detailed numerical simulation of the setup is presented. It includes a global thermal simulation of the furnace and a local simulation of the melt, which aims at the influence of the melt flow on the temperature and concentration fields. Furthermore, seeded growth of cone-shaped Si ingots using either a monocrystalline seed or a seed layer formed by pieces of poly-Si is demonstrated and compared to growth without seeds. The influences of the seed material on the grain structure and the dislocation density of the ingots are discussed. The second part addresses model experiments for the Czochralski technique using the room temperature liquid metal GaInSn. The studies were focused on the influence of a rotating and a horizontally static magnetic field on the melt flow and the related heat transport in crucibles being heated from bottom and/or side, and cooled by a crystal model covering about 1/3 of the upper melt surface.

Keywords: Magnetic flow control; Crystall-Growth; Photovoltaic Silicon; Numerical Simulation

Publ.-Id: 25951

The effect of the initial microstructure in terms of sink strength on the ion-irradiation-induced hardening of ODS alloys studied by nanoindentation

Duan, B.; Heintze, C.; Bergner, F.; Ulbricht, A.; Akhmadaliev, S.; Oñorbe, E.; de Carlan, Y.; Wang, T.

Oxide dispersion strengthened (ODS) Fe-Cr alloys are promising candidates for structural components in nuclear energy production. The small grain size, high dislocation density and the presence of particle matrix interfaces may contribute to the improved irradiation resistance of this class of alloys by providing sinks and/or traps for irradiation-induced point defects. The extent to which these effects impede hardening is still a matter of debate. To address this problem, a set of alloys of different grain size, dislocation density and oxide particle distribution were selected. In this study, three-step Fe-ion irradiation at both 300 C and 500 C up to 10 dpa was used to introduce damage in five different materials including three 9Cr-ODS alloys, one 14Cr-ODS alloy and one 14Cr-non-ODS alloy. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), small angle neutron scattering (SANS), and nanoindentation testing were applied, the latter before and after irradiation. Significant hardening occurred for all materials and temperatures, but it is distinctly lower in the 14Cr alloys and also tends to be lower at the higher temperature. The possible contribution of Cr-rich alpha’-phase particles is addressed. The impact of grain size, dislocation density and particle distribution is demonstrated in terms of an empirical trend between total sink strength and hardening.

Keywords: Oxide dispersion strengthened alloys; Ion irradiation; Nanoindentation; Hardening; Sink strength


Publ.-Id: 25950

Microstructure characterization and strengthening mechanisms of oxide dispersion strengthened (ODS) Fe-9%Cr and Fe-14%Cr extruded bars

Chauhan, A.; Bergner, F.; Etienne, A.; Aktaa, J.; de Carlan, Y.; Heintze, C.; Litvinov, D.; Hernandez-Mayoral, M.; Oñorbe, E.; Radiguet, B.; Ulbricht, A.

The collaborative study is focused on the relationship between microstructure and yield stress for an ODS Fe-9%Cr-based transformable alloy and an ODS Fe-14%Cr-based ferritic alloy. The contributions to the total room temperature yield stress arising from various strengthening mechanisms are addressed on the basis of a comprehensive description of the microstructures uncovered by means of transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), small-angle neutron scattering (SANS) and atom probe tomography (APT). While these methods provide a high degree of complementarity, a reasonable agreement was found in cases of overlap of information. The derived set of microstructure parameters along with reported strengthening equations was used to calculate the room temperature yield stress. The estimates were critically compared with the measured yield stress for an extended set of alloys including data reported for Fe-Cr model alloys and steels thus covering one order of magnitude or more in grain size, dislocation density, particle density and yield stress. The comparison shows that particle strengthening, dislocation forest strengthening, and Hall-Petch strengthening are the major contributions and that a mixed superposition rule reproduces the measured yield stress within experimental scatter for the whole extended set of alloys. The wide variation of microstructures additionally underpins the conclusions and goes beyond previous work, in which one or few ODS steels and narrow microstructure variations were typically covered.

Keywords: ODS steel; Strengthening mechanisms; TEM; APT; SANS


Publ.-Id: 25949

Modeling electromagnetically driven free-surface flows motivated by the Ribbon Growth on Substrate (RGS) process

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

The Ribbon Growth on Substrate (RGS) technology is a crystallization technique that allows direct casting of silicon wafers and sheets of advanced metal-silicide compounds. With the potential of reaching high crystallization rates, it promises a very efficient approach for future photo-voltaic silicon wafer production compared to well-established processes in industry. However, a number of remaining problems, like process stability and controllability, need to be addressed for the RGS technology to eventually become a competitor in the near future. In this regard, it is very desirable to gain detailed insights into the characteristic process dynamics. To comply with this demand, we have developed a new numerical tool based on OpenFOAM (foam-extend), capable of simulating the free-surface dynamics of the melt flow under the influence of an applied alternating magnetic field. Our corresponding model thereby resolves the interaction of hydrodynamic and magnetodynamic effects in three-dimensional space. Although we currently focus on the RGS process, the modeling itself has been formulated in a more general form, which may be used for the investigation of similar problems, too. Here we provide a brief overview of these developments.

Keywords: RGS process; OpenFOAM; electromagnetic driven flow; foam-extend; free-surface

Publ.-Id: 25948

Charakterisierung eines zerkleinerten Mobiltelefons mittels Mineral Liberation Analysis (MLA)

Sandmann, D.

Mobiltelefone, von denen im Jahr 2016 weltweit über 1,4 Milliarden Geräte hergestellt wurden, können bis zu 60 verschiedene Elemente enthalten (TrendForce Corp., The Royal Society of Chemistry). Gegenwärtig werden allerdings nur sehr wenige der in den Mobiltelefonen enthaltenen Elemente mit Recycling-Raten von mehr als 50 % recycelt (Compound Interest). Bei den meisten Elementen liegt die Recycling-Rate bei deutlich unter 50 % und bei den Seltenen Erden, Indium, Tantal oder Gallium sogar bei unter 1 %! Ein Hauptproblem beim Recycling von Mobiltelefonen ist ihre komplexe Zusammensetzung aus vielen Einzelbauteilen. Erschwerend kommt hinzu, dass viele Elemente kommen nur in Spuren vorhanden sind und / oder sich in hoch-komplexen Materialverbunden befinden.
Um ein effektiveres Recycling der Mobiltelefone zu ermöglichen, ist es unumgänglich ihre Bauteile, das Vorkommen der Elemente darin, sowie das Zerkleinerungsverhalten möglichst detailliert zu charakterisieren.
In einer Pilotstudie wurde ein, vom Lehrstuhl für Recyclingmaschinen der TU Bergakademie Freiberg, mit einem Universal-Granulator UG300 zerkleinertes Nokia-Mobiltelefon Modell 5228 Typ RM-625 mit Hilfe von Mineral Liberation Analysis (MLA) untersucht. Die Analyse an drei Siebfraktionen des zerkleinerten Materials erfolgte mit einer MLA 650F am Helmholtz-Institut Freiberg für Ressourcentechnologie.
Eine erste manuelle Aufnahme von Rückstreuelektronenbildern zeigt unter anderem Metallphasen mit einer Kleinheit von < 0,5 µm. Nachfolgend wurden die Proben in einer automatisierten MLA-Messung mit einem Gitternetz von EDX-Spektren abgerastert (GXMAP-Modus). Insgesamt wurden bei der Analyse ca. 130 verschiedene Phasen detektiert. Mehr als 100 davon treten mit Anteilen von < 1 Gewichtsprozent auf. Ein Vergleich des Modalbestandes der drei Siebfraktionen zeigte eine Anreicherung bestimmter Bauteile in speziellen Fraktionen.

Compound Interest -
The Royal Society of Chemistry 20.03.2017 -
TrendForce Corp. Press Release 25.01.2017 -

  • Lecture (Conference)
    Tagung 2017 „Aufbereitung und Recycling“, 08.-09.11.2017, Freiberg, Deutschland


Publ.-Id: 25947

Validation of X-ray radiography for characterization of gas bubbles in liquid metals

Keplinger, O.; Shevchenko, N.; Eckert, S.

X-ray radiography has proved to be an efficient and powerful tool for the visualization of two-phase flows in non-transparent fluids, in particular in liquid metals. This paper presents a validation of the X-ray radiography by comparing measurements in water with corresponding results obtained by optical methods. For that purpose Ar bubbles were injected through a single orifice. The measurements results are compared in terms of bubble size, bubble shape and velocity. Furthermore, visualization experiments were performed in the eutectic alloy GaInSn where the image contrast between the liquid phase and the gas bubble is much stronger. Some obvious differences of the bubble dynamics in water and GaInSn are discussed.

Keywords: X-ray radiography; two-phase flows; GaInSn; water

Publ.-Id: 25946

Spins in Formation

Schultheiss, H.

Spinwellen sind kollektive Anregungen magnetischer Momente eines Festkörpers. Lokal lassen sie sich auf sehr kleinen Längenskalen lenken durch ein Drehen der Magnetisierung. Damit ist es möglich, den Fluss von Spinwellen gezielt zu steuern. Dieser Vorgang könnte in der Informationstechnologie als Logik- baustein Anwendung finden.

Keywords: Spintronic; Magnonic

  • Physik Journal 09(2017), 59
  • Lecture (others)
    Physikalisches Kolloquium Universität Augsburg, 27.11.2017, Augsburg, Deutschland
  • Lecture (others)
    Physikalisches Kolloquium TU Chemnitz, 15.11.2017, Chemnitz, Deutschland
  • Lecture (others)
    Kolloquium Walther Meissner Institut, 27.1.2017, Garching, Deutschland
  • Lecture (others)
    SFB Seminar Uni Regensburg, 26.1.2017, Regensburg, Deutschland
  • Lecture (others)
    Physikalisches Kolloquium TU Dresden, 13.6.2017, Dresden, Deutschland
  • Invited lecture (Conferences)
    DPG Frühjahrstagung, 22.3.2017, Dresden, Deutschland
  • Lecture (Conference)
    633tes Wilhelm und Else Heraeus Seminar, 5.1.2017, Bad Honnef, Deutschland

Publ.-Id: 25945

Magnonics: Spin waves connecting charges, spins and photons

Chumak, A. V.; Schultheiss, H.

Spin waves (SW) are the excitation of the spin system in a ferromagnetic condensed matter body. They are collective excitations of the electron system and, from a quasi-classical point of view, can be understood as a coherent precession of the electrons' spins. Analogous to photons, they are also referred to as magnons indicating their quasi-particle character. The collective nature of SWs is established by the short-range exchange interaction as well as the non-local magnetic dipolar interaction, resulting in coherence of SWs from mesoscopic to even macroscopic length scales. As one consequence of this collective interaction, SWs are 'charge current free' and, therefore, less subject to dissipation caused by scattering with impurities on the atomic level. This is a clear advantage over diffusive transport in spintronics that not only uses the charge of an electron but also its spin degree of freedom. Any (spin) current naturally involves motion and, thus, scattering of electrons leading to excessive heating as well as losses. This renders SWs a promising alternative to electric (spin) currents for the transport of spin information—one of the grand challenges of condensed matter physics.

Keywords: Magnonics; Spintronics; Photonics; Spin Waves

Publ.-Id: 25944

Towards ion beam therapy based on laser plasma accelerators

Karsch, L.; Beyreuther, E.; Enghardt, W.; Gotz, M.; Masood, U.; Schramm, U.; Zeil, K.; Pawelke, J.

Only few ten radiotherapy facilities worldwide provide ion beams, in spite of their physical advantage of better achievable tumor conformity of the dose compared to conventional photon beams. Since, mainly the large size and high costs hinder their wider spread, great efforts are ongoing to develop more compact ion therapy facilities.
One promising approach for smaller facilities is the acceleration of ions on micrometre scale by high intensity lasers. Laser accelerators deliver pulsed beams with a low pulse repetition rate, but a high number of ions per pulse, broad energy spectra and high divergences. A clinical use of a laser based ion beam facility requires not only a laser accelerator providing beams of therapeutic quality, but also new approaches for beam transport, dosimetric control and tumor conformal dose delivery procedure together with the knowledge of the radiobiological effectiveness of laser-driven beams.
Over the last decade research was mainly focused on protons and progress was achieved in all important challenges. Although currently the maximum proton energy is not yet high enough for patient irradiation, suggestions and solutions have been reported for compact beam transport and dose delivery procedures, respectively, as well as for precise dosimetric control. Radiobiological in vitro and in vivo studies show no indications of an altered biological effectiveness of laser-driven beams.
Laser based facilities will hardly improve the availability of ion beams for patient treatment in the next decade. Nevertheless, there are possibilities for a need of laser based therapy facilities in future.


Publ.-Id: 25943

Tunable nonlinear optical resonances in Landau-quantized graphene

König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Venanzi, T.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

Graphene has been in discussion as a candidate as a strong THz nonlinear material for a long time, because of its linear band structure [1,2]. However, an experimental demonstration of strong nonlinearities in Graphene in this spectral range is still missing. For Landau-quantized Graphene, in which the absorption is resonantly enhanced for allowed transitions between the Landau-levels, theory predicts a strongly enhanced nonlinearity, too [3]. In our joint experimental and theoretical work we study the third order nonlinearity in Landau-quantized graphene by employing a degenerate timeintegrated four-wave mixing experiment (FWM) in the mid-infrared spectral range. The free-electron laser FELBE was tuned to a photon energy of 78meV and the graphene sample was kept at 10K in a thin helium gas atmosphere. The magnetic field was set to 4.5T bringing the LL-1→LL0 and LL0→LL1 transition into resonance with the linearly polarized beams (see Fig.1a). The measured FWM signal (see Fig.1c) features a faster dynamics than the pump-probe signal (see Fig.1b) and is beyond the time resolution of our experiment. Nevertheless, we can recover the expected field dependencies of the studied third order nonlinearity in the experiment. The resonance behavior is measured by sweeping the magnetic field and is in agreement with our theoretical calculation. Furthermore, we derive a value of χ(3) from our experimental data that confirms the predicted strongly enhanced nonlinearity [4].
[1] S. A. Mikhailov and K. Ziegler, J. Phys.: Condens. Matter, 20, 384204, (2008)
[2] Z. Zhang and P. L. Voss, Opt. Lett., 36, 4569, (2011)
[3] X. Yao and A. Belyanin, Phys. Rev. Lett., 108, 255503, (2012)
[4] J. C. König-Otto, Y. Wang, A. Belyanin, C. Berger, W. A. de Heer, M. Orlita, A. Pashkin, H.
Schneider, M. Helm, and S. Winnerl, Nano Lett., 17, 2184, (2017)

Keywords: graphene; Landau-quantized graphene; nonlinear optics; carrier dynamics; spectroscopy

  • Lecture (Conference)
    Graphene Week 2017, 25.-29.09.2017, Athena, Hellas

Publ.-Id: 25942

THz Nonlinear Response of Landau-Quantized Graphene

König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

The third-order nonlinear susceptibility of Landau-quantized graphene is studied by degenerate time-integrated four-wave mixing in the THz regime. The revealed resonance behavior and the observed field dependencies are in agreement with our theoretical calculations.

Keywords: graphene; Landau-quantized graphene; nonlinear optics; carrier dynamics; spectroscopy

  • Lecture (Conference)
    CLEO, 14.-19.05.2017, San Jose, USA

Publ.-Id: 25941

Influence of structural quality on the carrier dynamics in graphene

König-Otto, J. C.; Schneider, H.; Helm, M.; Winnerl, S.

Production of large-scale high quality graphene is a challenging task. Therefore understanding how quality will influence the properties of graphene is crucial for industrial applications. In this work we focus on the influence of defects on the carrier dynamics. To this end areas of a multilayer epitaxial graphene sample with high structural quality [1] are irradiated with different doses of low energy carbon ions. The different areas with now varying graphene quality (see D-Peaks in Raman spectra in Figure 1) are studied by a pump-probe experiment utilizing low energetic photons from a free-electron laser (photon energy 75meV). In this regime carrier relaxation is particularly slow as compared to excitation with visible light since scattering with optical phonons (energy 200meV) is efficiently suppressed [2]. The change in transmission is depicted in Figure 2 for three different structural qualities. One can directly see that the relaxation in the damaged areas is significantly faster than in the pristine graphene. This might be an indication for the presence of the intensively discussed supercollisions in graphene [3].
[1] C. Berger et al., Science 312, 1191 (2006).
[2] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[3] J. C. W. Song et al., Phys. Rev. Lett. 109, 106602 (2012).

Keywords: graphene; defects; carrier dynamics

  • Poster
    Graphene2017, 28.-31.03.2017, Barcelona, Espana

Publ.-Id: 25940

Landau-Quantized Graphene: A Tunable Nonlinear Optical Material in the THz Range

König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.

Finding nonlinear optical materials for the THz and mid-infrared regimes is not straightforward. State-of-the-art devices with a high third-order optical susceptibility are often processed as complex multiquantum-well structures designed to feature one specific resonance frequency. In our work we study Landau-quantized graphene as a tunable and simple to produce nonlinear material. To this end we perform time-integrated degenerate four-wave mixing (FWM) experiments at a photon energy of 78 meV resonant to the transitions between the Landau levels LL−1, LL0 and LL1 at a magnetic field of roughly 4 T. We can recover expected scaling of the FWM-signal with the incident fields and the resonance behavior. The value of the third-order surface susceptibility in this material is in agreement with our calculations based on the density matrix formalism. We find the order of 𝜒(3) of Landau-quantized graphene to be competitive with more complex and elaborated solutions.

Keywords: graphene; Landau-quantized graphene; nonlinear optics; carrier dynamics; spectroscopy

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 25939

Carrier Dynamics in Graphene: Ultrafast Many-Particle Phenomena

Malic, E.; Winzer, T.; Wendler, F.; Brem, S.; Jago, R.; Knorr, A.; Mittendorff, M.; König-Otto, J. C.; Plötzing, T.; Neumaier, D.; Schneider, H.; Helm, M.; Winnerl, S.

Graphene is an ideal material to study fundamental Coulomb- and phonon-induced carrier scattering processes. Its remarkable gapless and linear band structure opens up new carrier relaxation channels. In particular, Auger scattering bridging the valence and the conduction band changes the number of charge carriers and gives rise to a significant carrier multiplication - an ultrafast many-particle phenomenon that is promising for the design of highly efficient photodetectors. Furthermore, the vanishing density of states at the Dirac point combined with ultrafast phonon-induced intraband scattering results in an accumulation of carriers and a population inversion suggesting the design of graphene-based terahertz lasers. Here, we review our work on the ultrafast carrier dynamics in graphene and Landau-quantized graphene is presented providing a microscopic view on the appearance of carrier multiplication and population inversion.

Keywords: graphene; carrier dynamics; spectroscopy


Publ.-Id: 25938

“Brothers in Arms” – HIF High-Speed PIXE and MEGA Spectrometer

Renno, A.; Buchriegler, J.; Dreßler, S.; Hanf, D.; Munnik, F.; Scharf, O.; Ziegenrücker, R.

In a fast growing world with increasing demand on resources like high-tech metals as In, Ga, Ge, or rare earth elements (REE), mineralogists and economic geologists need faster and automated analytical tools to explore mineral deposits, make them accessible and define necessary initial data for all subsequent processing steps. Next to the necessary knowledge in which phases the elements of interest, ecotoxical as well as deleterious elements are concentrated, it is important to determine structural parameters like grain sizes and possible intergrowths relations of these minerals. These are typical geometallurgical analytical tasks, which are so far routinely performed by electron beam based methods of automated mineralogy, like MLA (mineral liberation analysis) or QEMSCAN, with their advantages and disadvantages. The methodological problems of these type of methods are, for example, the necessary measurement time, insufficient limits of detection (no trace element detection) and high background (electron Bremsstrahlung).

Some of these hurdles can be overcome by using alternative excitation radiation, like ions, known as particle-induced X-ray emission (PIXE) or X-rays, known as X-ray fluorescence (XRF). Combining these with a full-field detection system, such as the so-called SLcam®[1], allows the determination of trace element distributions in reasonable time over a large field of view.

The SLcam® consists of a 12 x 12 mm², X-ray sensitive pnCCD chip with 69696 pixels. A high read-out speed of up to 1000 Hz, allows the acquisition of complete X-ray spectra (2-20 keV) on each pixel simultaneously, with an energy resolution of around 160 eV (@ Mn-K even for high photon fluxes. A poly-capillary lens is used to guide the X-rays from their point of origin on the sample to the corresponding pixel on the detector-chip. Usage of a straight 1:1 lens results in a lateral resolution better than 100 µm.

The MEGA spectrometer is equipped with a laboratory-scale X-ray tube. XRF is used for the determination of major and trace element data. It’s “small”, table-top like size would in principle allow to use the set-up directly at the mining site. The so called High-Speed PIXE[2] uses a broad proton beam to excite the fluorescence radiation. Samples with a total weight of up to 10 kg and a maximum size 25 x 25 x 2.5 cm³ can be mounted in a dedicated vacuum sample chamber. The instrument is installed at the Ion Beam Center at the Helmholtz-Zentrum Dresden-Rossendorf. The advantages and disadvantages of both instruments will be presented, as well as first results of combined qualitative studies of the distribution of trace elements in representative samples to demonstrate the importance of these innovative concepts for geometallurgical research.

[1] Scharf, O., et al. (2011). Compact pnCCD-Based X-ray Camera with High Spatial and Energy Resolution: A Color X-ray Camera. Analytical Chemistry, 83(7), 2532–2538.
[2] Hanf, D., et al. (2016). A new particle-induced X-ray emission set-up for laterally resolved analysis over wide areas. Nuclear Instruments and Methods in Physics Research B, 377, 7-24.

Keywords: PIXE; High-Speed PIXE; XRF; Trace Elemenet Analysis

  • Poster
    2nd International Conference on Applied Mineralogy & Advanced Materials and 13th International Conference on Applied Mineralogy, 05.-09.06.2017, Castellaneta Marina- Taranto, Italy

Publ.-Id: 25937

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