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31735 Publications
Aufklärung der Rolle von CeO2-Nanopartikel-Auflösung bei der Aufnahme in die Pflanze mittels intelligenter Radiomarkierung
Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.;
Die Identifizierung der Hauptaufnahmepfade von technischen Nanopartikeln in Pflanzen ist ein wichtiger Faktor bei der Einschätzung ihres Verbleibs in der Umwelt und der damit verbundenen Risiken. Durch den Einsatz unterschiedlicher Radiomarkierungsmethoden gelang es eine hauptsächlich partikulär stattfindende Aufnahme von CeO2-Nanopartikeln zu zeigen, im Gegensatz zu einer Aufnahme in Form ionischen Cers.
Keywords: Cerdioxid, cerium dioxide Nanopartikel, nanoparticle Pflanzenaufnahme, plant uptake Radiochemie, radiochemistry

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Publ.-Id: 25471 - Permalink


Aufnahme von radiomarkierten CeO2 Nanopartikeln durch Pflanzen
Fricke, T.; Schymura, S.; Hildebrand, H.; Franke, K.;
Untersuchungen zum Verbleib von Nanopartikeln (NP) entlang des Wirkungspfades „Klärschlamm – Boden – Pflanze“ sollen die Umweltgefährdung von NP aufzeigen. Dabei steht die Aufnahme von NP durch Pflanzen im Fokus der Untersuchungen.
Durch Versuche mit Hydrokulturen zur Aufnahme von radiomarkierten [48V]TiO2 und [139Ce]CeO2 durch Pflanzen (Sonnenblume, Radieschen, Feldsalat, Weidelgras) sollte das Aufnahmepotential von verschiedenen Pflanzenspezies ermittelt werden. Dazu erfolgte eine Exposition der Versuchspflanzen mit NP im umweltrelvanten Konzentrationsbereich in Leitungswasser (+Fulvinsäure), synthetischem und gereinigtem Abwasser für 96 h. Die Ergebnisse zeigen, dass eine Aufnahme in Pflanzen durchweg erfolgt. Dabei werden nur geringe Mengen im ng-Bereich in die Sprosse der Pflanzen transloziert. Anhand von Messungen mit Energiedispersiver Röntgenspektroskopie (REM-EDX) kann gezeigt werden, dass die NP gößtenteils mit den Zellwänden der Wurzeloberfläche und dem Wurzelapoplasten assoziert sind (Abbildung 1). Durch autoradiographische Aufnahmender radiomarkierten NP konnten außerdem die Verteilungen der NP innerhalb der Pflanze visualisiert werden. Daraus lässt sich ableiten, dass die NP nicht über aktive Transportmechanismen in die Pflanze aufgenommen werden. Maßgeblich für die Verlagerung von NP in die Sprosse ist dabei der transpirationsgetriebene Wasserstrom in die Pflanze. Es kommt zu Ablagerungen der NP entlang der Blattadern und der Blattränder. Weiterhin lässt sich vermuten, dass NP innerhalb der Pflanze Lösungsprozessen unterliegen. Für Sonnenblume konnte beobachtet werde, dass sich CeO2 nach nur einer Woche zum größten Teil aufgelöst hat und das freie ionische 139Ce sich in der kompletten Pflanze verteilt hat.
In Versuchen mit Erdkulturen wurde die Aufnahme von NP in die Pflanze aus mit Erde dotiertem Klärschlamm mit [48V]TiO2 und [139Ce]CeO2 untersucht. Erste Ergebnisse zeigen, dass eine Aufnahme von NP nicht für alle Pflanze nachweisbar ist. Für Weidelgras konnte als einzige der untersuchten Pflanzen, eine Verlagerung von CeO2 aus der Erde in die Pflanze belegt werden. Dabei können nur geringste Konzentrationen von 1 - 4 ng kg-1 nach 14 Tage in der Pflanze nachgewiesen werden. Die Ergebnisse für vergleichbare Untersuchungen mit TiO2 stehen noch aus. Darüber hinaus sind Versuche geplant, die die Bindung der NP an der Bodenpartikeln genauer darstellen sollen.
Abschließend wird eine Risikobewertung erarbeitet, welche regulatorische Maßnahmen erachten soll, um zukünftig die Exposition von NP in die Umwelt zu vermeiden.
Keywords: Nanopartikel, nanoparticle Cerdioxid, cerium dioxide Radiomarkierung, radiolabeling Pflanzenaufnahme, plant uptake
  • Poster
    NanoCare Clustertreffen 2017, 04.-05.05.2017, Karlsruhe, Deutschland

Publ.-Id: 25469 - Permalink


Simultaneous loss of interlayer coherence and long-range magnetism in quasi-two-dimensional PdCrO2
Ghannadzadeh, S.; Licciardello, S.; Arsenijevic, S.; Robinson, P.; Takatsu, H.; Katsnelson, M. I.; Hussey, N. E.;
In many layered metals, coherent propagation of electronic excitations is often confined to the highly conducting planes. While strong electron correlations and/or proximity to an ordered phase are believed to be the drivers of this electron confinement, it is still not known what triggers the loss of interlayer coherence in a number of layered systems with strong magnetic fluctuations, such as cuprates. Here, we show that a definitive signature of interlayer coherence in the metallic-layered triangular antiferromagnet PdCrO2 vanishes at the Néel transition temperature. Comparison with the relevant energy scales and with the isostructural non-magnetic PdCoO2 reveals that the interlayer incoherence is driven by the growth of short-range magnetic fluctuations. This establishes a connection between long-range order and interlayer coherence in PdCrO2 and suggests that in many other low-dimensional conductors, incoherent interlayer transport also arises from the strong interaction between the (tunnelling) electrons and fluctuations of some underlying order.

Publ.-Id: 25468 - Permalink


Drastic change of the Fermi surface across the metamagnetic transition in CeRh2Si2
Götze, K.; Aoki, D.; Lévy-Bertrand, F.; Harima, H.; Sheikin, I.;
We report high field de Haas–van Alphen (dHvA) effect measurements in CeRh2Si2 both below and above the first-order 26 T metamagnetic transition from an antiferromagnetic to a polarized paramagnetic state. The dHvA frequencies observed above the transition are much higher than those observed below, implying a drastic change of the Fermi-surface size. The dHvA frequencies above the transition and their angular dependence are in good agreement with band-structure calculations for LaRh2Si2, which correspond to CeRh2Si2 with localized f electrons. Given that the f electrons are also localized at low fields in CeRh2Si2, the Fermi-surface reconstruction is due to the suppression of antiferromagnetism and the restoration of the crystallographic Brillouin zone rather than the delocalization of the f electrons. This example suggests that the intuitive notation of “small” and “large” Fermi surfaces commonly used for localized and itinerant f electrons, respectively, requires careful consideration, taking into account the modification of the Brillouin zone in the antiferromagnetic state, when interpreting experimental results.

Publ.-Id: 25467 - Permalink


Low-temperature magnetic structure and EPR properties of the quasi-1D S = 1/2 Heisenberg helimagnet CuCl2·2NC5H5
Ponomaryov, A. N.; Zviagina, L.; Wosnitza, J.; Thede, M.; Ressouche, E.; Povarov, K. Y.; Zheludev, A.; Landee, C. P.; Zvyagin, S. A.;
We present results of electron paramagnetic resonance (EPR) and neutron diffraction studies of CuCl2·2NC5H, which is regarded as one of the best known uniform spin-1/2 Heisenberg antiferro-magnet chain systems. We revealed that at TN = 1.12 K CuCl2·2NC5H5 undergoes the transition into the magnetically ordered spiral state with Q = (0.5, 0.4, 0.5) r.l.u.. It was shown that the zig-zag interchain interactions result in a noticeable geometrical frustration, also affecting the ordered moment per Cu2+ and EPR properties, including the angular dependence of the linewidth. The temperature dependencies of the EPR parameters are discussed.

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Publ.-Id: 25466 - Permalink


Mass-separated Focused Ion Beams for Self-Organized Surface Patterning
Bischoff, L.; Böttger, R.; Pilz, W.; Facsko, S.; Heinig, K.-H.;
Heavy mon- and polyatomic ions (Au or Bi) from mass-separated FIB working with LMAIS can cause localized melting at the ion impact point due to the enhanced energy density in the collision cascade [1,2]. The formation of high aspect ratio, hexagonal dot patterns on Ge, Si or GaAs after high fluence, normal incidence irradiation choosing a suited combination of energy density deposition and substrate temperature, which facilitated transient melting of the ion collision cascade volume could be demonstrated [2-5]. In this study the universality of this ion impact-melting-induced, self-organized pattern formation is expanded to the compound semiconductor GaSb under Aunm+ ion irradiation with various conditions in particular, ion species, fluence, energy/atom, temperature and angle of incidence. Calculations of the needed melting energies per atom (Emelt) for different materials show, that GaSb is a preferring candidate for a successful surface patterning by mon- and polyatomic heavy ions whereas i.e. the surface of SiC remains stable under the given conditions. Furthermore the surface modification behavior under Au and Bi heavy ion impact should be compared. HR-SEM, AFM and EDX analysis of irradiated surfaces reveal that for compound semiconductors, additional superstructures are evolving on top of the regular semiconductor dot patterns, indicating superposition of a second dominant driving force for pattern self-organization.

[1] C. Anders, K.-H. Heinig and H. M. Urbassek, Polyatomic bismuth impacts into germanium: Molecular dynamics study, Phys. Rev. B 87 (2013) 245434.
[2] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko, and W. Pilz, Self-organization of Ge nanopattern under erosion with heavy Bi monomer and cluster ions, Nucl. Instr. and Meth. B 272 (2012) 198.
[3] R. Böttger, L. Bischoff, K.-H. Heinig, W. Pilz and B. Schmidt, From sponge to dot arrays on (100)Ge by increasing the energy of ion impacts, Journal of Vacuum Science and Technology B 30 (2012) 06FF12.
[4] R. Böttger, K-.H Heinig, L. Bischoff, B. Liedke, R. Hübner, and W. Pilz,
Silicon nanodot formation and self-ordering under bombardment with heavy Bi3 ions, physica status solidi – Rapid Research Letters 7 (2013) 501.
[5] L. Bischoff, R. Böttger, K.-H. Heinig, S. Facsko, and W. Pilz, Surface patterning of GaAs under irradiation with very heavy polyatomic Au ions, Applied Surface Science 310 (2014) 154.
Keywords: Heavy mon- and polyatomic ions Au or Bi; LMAIS; patterns on Ge, Si, GaAs, SiC, GaSb
  • Lecture (Conference)
    1st EUFN Workshop, 04.-05.07.2017, Graz, Austria

Publ.-Id: 25465 - Permalink


Polyatomic Ions from Liquid Metal Alloy Ion Sources for Broad Beam Ion Irradiation
Pilz, W.; Bischoff, L.; Böttger, R.; Laufer, P.; Tajmar, M.;
Surface patterning based on self-organized nano-structures on i.e. semiconductor materials formed by heavy mono - and polyatomic ion irradiation from Liquid Metal (Alloy) Ion Sources (LMAIS) is a very promising technique [1,2]. To overcome the lack of only very small treated areas by applying a Focused Ion Beam (FIB) instrument this technology was transferred into larger single-end ion beam systems like an ion implanter. Main component is an ion beam injector based on high current LMAIS, developed for space propulsion systems [3] combined with suited ion optics allocating ion currents in the µA range in a nearly parallel beam of a few mm in diameter. The mass selection of the needed ion species can be performed either by an introduced ExB mass separator (Wien filter) and/or the existing magnet of the ion implanter itself which also can define the final ion energy up to 200 keV.
Different types of LMAIS [4] (needle, porous emitter, capillary) are presented and characterized. The ion beam injector design is specified as well as the implementation of this module into a high current ion implanter (Danfysik Series 1090) operating at the HZDR Ion Beam Center (IBC). The obtained results of a large area surface modification (mm²) of Ge at room temperature using Bi2+ polyatomic ions from a GaBi capillary LMAIS is presented and compared with the small area dot structures (µm²) made by mass separated FIB.

[1] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko and W. Pilz, Self-organization of Ge nanopattern under erosion with heavy Bi monomer and cluster ions, Nucl. Instrum. Methods B 272 (2012), 198.
[2] R. Böttger, L. Bischoff, K.-H. Heinig, W. Pilz and B. Schmidt, From sponge to dot arrays on (100)Ge by increasing the energy of ion impacts, J. Vac. Sci. Technol. B 30 (2012), 06FF12.
[3] M. Tajmar and B. Jang, New materials and processes for field emission ion and electron Emitters, CEAS Space J. 4 (2013), 47.
[4] L. Bischoff, P. Mazarov, L. Bruchhaus and J. Gierak, Liquid metal alloy ion sources - An alternative for focused ion beam technology, Appl. Phys. Rev. 3 (2016), 021101.
Keywords: Liquid Metal Alloy Ion Source; Surface pattern, Broad beam implantation
  • Lecture (Conference)
    1st EUFN Workshop, 04.-05.07.2017, Graz, Austria

Publ.-Id: 25464 - Permalink


Continuous-Wave and Q-Switched Yb:YSGG Waveguide Laser
Ma, L.; Tan, Y.; Wang, S.; Akhmadaliev, S.; Zhou, S.; Yu, H.; Zhang, H.; Chen, F.;
We report on the continuous-wave and passively Q-switched waveguide laser at the wavelength of ~1024 nm, based on the (Yb0.1Y0.9)3(Sc1.5Ga0.5)Ga3O12 (Yb:YSGG) crystal. The ridged waveguide was fabricated on the surface of 100 at. % Yb:YSGG crystal by the swift ion irradiation and the precise diamond blade dicing. Utilizing this waveguide as the gain medium and resonant cavity, the laser emission at ~1024 nm was realized. Coating the Tungsten Disulfide onto the waveguide surface as the saturable absorber, the Q-switched laser emission was also obtained with the pulse duration of 125 ns.

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Publ.-Id: 25463 - Permalink


Ridge Waveguides and Y-Branch Beam Splitters in KTiOAsO4 Crystal by 15 MeV Oxygen Ion Implantation and Femtosecond Laser Ablation
Chen, C.; Akhmadaliev, S.; Romero, C.; de Aldana, J.; Zhou, S.; Chen, F.;
We report on the fabrication of ridge waveguides and Y-branch beam splitters in KTiOAsO4 nonlinear optical crystal by the combination of 15 MeV oxygen (O5+) ion implantation and femtosecond laser ablation. Guiding properties were investigated at the wavelengths of 633 and 808 nm, respectively, showing high polarization sensitivity of light propagation. Splitting ratios of these beam splitters are dependent on in-coupling alignment. The simulated guiding modal distributions of splitted guided beams, which was based on a reconstructed refractive index profile, shows reasonable consistence with the measured ones. After the stepwise annealing treatment at 473 and 573 K for 1 h each, the propagation losses for these guiding structures have been reduced considerably.

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Publ.-Id: 25462 - Permalink


Microstructure evolution of predefined catalysts for diameter-controlled growth of single-walled carbon nanotubes
Melkhanova, S.; Haluska, M.; Hübner, R.; Gemming, S.; Krause, M.;
Predefined catalysts have been recently successfully employed for diameter- and chirality-selective CVD growth of single-walled carbon nanotubes (SWCNTs).[1-3] They simplify the exhausting optimization of parameters for in situ catalyst formation and ensure a very good control of catalyst properties. Using C:Ni nanocomposite templates (NCTs) as catalyst precursors, SWCNTs with a selective, monomodal diameter distribution were obtained. More than the half of the SWCNTs had a diameter of (1.36±0.10) nm.[3]

While the preparation of NCTs is well defined and controlled, the activation of the NPs for nanotube synthesis by CVD is a critical step that is still not fully understood. Element-resolved scanning and high-resolution transmission electron microscopy and Raman spectroscopy were used to clarify the microstructure of C:Ni NCTs in the different stages of the SWCNT growth. These studies reveal a distinct change of the NCT microstructure by conserving the initial nanocomposite morphology to a very large extend.

[1] F. Yang et al., Nature 510, 522 (2014);
[2] H. An et al., Nanoscale 8, 14523 (2016);
[3] S. Melkhanova et al., Nanoscale 8, 14888 (2016)
Keywords: Single-walled carbon nanotubes, nanocomposites, catalysis, Raman spectroscopy, transmission electron microscopy
  • Poster
    XXXIstInternational Winterschool on Electronic Properties of Novel Materials, 04.-11.03.2017, Kirchberg, Österreich

Publ.-Id: 25461 - Permalink


NanoSuppe – Verhalten von synthetischen Nanopartikeln im Wirkungspfad Abwasser- Klärschlamm – Pflanze am Beispiel TiO2, CeO2, MWCNT und Quantum Dots
Fricke, T.; Schymura, S.; Neugebauer, M.; Hildebrand, H.; Franke, K.;
Ziel des Vorhabens „NanoSuppe“ ist es den Verbleib von Nanopartikeln (NP) entlang des Wirkpfades „Abwasser-Klärschlamm-Pflanze“, unter Berücksichtung von typischen Prozesssabläufen in kommunalen Kläranlagen, zu untersuchen. Dafür finden Experimente zum Verbleib von NP in Laborkläranlagen statt und der Eintrag von NP in die Umwelt durch Kläranlagen-Effluenten, z.B. Klärschlamm als Dünger, wird erforscht. In Batch und Säulenversuchen werden Erkenntnisse zur Umweltmobilität der NP gewonnen und durch Versuchsreihen in Hydrokultur und Erdkultur die mögliche Aufnahme von NP in Pflanzen untersucht.
Das Projekt zeichnet sich hierbei durch die Verwendung radiomarkierter Nanopartikel aus. Dies ermöglicht eine genaue Quantifizierung und Ermittlung der Verteilung der NP in den untersuchten komplexen Matrizes bei Einsatz umweltrelevanter Konzentrationen. Der Einsatz der Radiotracertechnik erfolgt dabei ausschließlich an Boden-, Pflanzen- und Klärschlammproben im Labor und unter kontrollierten Bedingungen. Es wird ein Prozessmonitoring erzielt und Aussagen zum Verhalten und Verbleib von Nanopartikeln entlang des Wirkungspfades möglich.
Keywords: Nanopartikel, nanoparticle Kläranlage, waste water treatment plant Pflanzenaufnahme, plant uptake
  • Lecture (Conference)
    NanoCare Clustertreffen 2017, 04.-05.05.2017, Karlsruhe, Deutschland

Publ.-Id: 25460 - Permalink


PET imaging reveals hindrance effects in MWCNT nanofluid flow
Schymura, S.; Kulenkampff, J.; Franke, K.; Lippmann-Pipke, J.;
The retention of particles in porous media is typically attributed to filtrtation effects such as straning, adsorption, or sedimentation. However, using positron emission tomography (PET) as imaging modality we were able to show the effect of hindrance in concentrated nanofluids due to particle-particle interactions. A flow-through column experiment with a MWCNT nanofluid was devised for optimal particle mobility: strong repulsive interactions between particles and between particles and the matrix (glass beads), inhibiting aggregation and adsorption and a large pore size rendering straining unlikely. Using the PET technique we could observe the transport of the MWCNT nanofluid through the glass bead packing in situ. During pulse injection of the suspension into the porous media the suspension spread out as a horizontal plume at the bottom of the column by “flooding” the respective pore volume. After this pulse injection the subsequently injected water seemed to penetrate the suspension only mobilizing MWCNTs from the top of the suspension plume rather than displacing the bulk of injected nanofluid. This mobilization from the top of the plume is most effective in the central parts of the column where the flow velocity is highest while most of the nanofluid is trapped in more stagnant zones of the pore space at the bottom edges of the column with minimal MWCNT displacement. The mobilized MWCNTs are higly diluted and only visible via the continuous diminishing of the plume from its central top boundry.
These observations can be explained by a pronounced hindrance of the particle transport due to particle-particle interactions in the concentrated suspension (Lamas et al, 2012) which is only overcome at the edges of the nanofluid plume, primarily in the central zones of highest flow velocity. Controlled sedimentation experiments reveal the absence of settling for high MWCNT concentrations due to hindrance. This hindrance which inhibits gravitational settling in turn also inhibits transport, in particular at low flow velocities.
In order to achieve the PET measurements the MWCNTs used in this experiment were oxidzed by oxidative acid treatment and radiolabeled with the positron emitter I-125. In an uncomplicated one-pot synthesis the CNTs were labeled by an electrophilic attack of I+ on the electron-rich CNT side-wall catalyzed by the so-called iodogen 1,3,4,6-Tetrachloro-3α-6α-diphenylglucoluril.
Keywords: Kohlenstoffnanoröhrchen/ carbon nanotubes Positronen Emissions Tomographie/ positron emission tomography Transport/ transport poröses Medium/ porous media
  • Poster
    Interpore 2017, 08.-11.05.2017, Rotterdam, Netherlands

Publ.-Id: 25459 - Permalink


Dissolution of CeO2 NPs and its role in plant uptake elucidated by smart radiolabeling
Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.;
Environmental transformations of nanoparticles (NPs) play a major role in determining their likely fate in the environment and the implications for toxicity, mobility and general risk assessment. A main question in this context is the dissolution of nanoparticles. If a nanoparticle dissolves quickly it may be treated as ionic species in terms of risk assessment, while particulate species can show different tendencies of transport, uptake by organisms and consequently toxicity. Slowly dissolving NPs can exhibit a so-called Trojan-horse effect, transporting and releasing ions at places where said ions would not have been transported – at least not at the same concentrations - without traveling on horseback, i.e. in particulate forms.
Using different radiolabeling techniques we have investigated the dissolution of CeO2 NPs. Through activation by proton bombardment using a cyclotron we have radiolabeled CeO2 NPs with radioactive Ce-139 via a (p,2n) nuclear reaction from Ce-140 to Pr-139 followed by the decay of Pr-139 to Ce-139. Here the radiolabel can be assumed to be uniformly distributed in the resulting [Ce-139]CeO2 NPs. In contrast to this we also have produced [Ce-139]CeO2 NP using an in-diffusion technique where ionic radioactive Ce-139 diffuses into the NPs at elevated temperatures. Here the radiolabel is located close to the surface of the NPs. This results in different leaching kinetics of Ce-139 for the two batches of [Ce-139]CeO2 NPs (Fig. 1). The comparison of the different rates allows us to calculate that about 47 % of the 139Ce introduced by in-diffusion is located in the first atomic layer of the CeO2 NPs. We can show that dissolution plays an insignificant role under environmentally relevant conditions with leaching rates well below 1 % of Ce. However, this still reflects significant changes of the surface of the CeO2, as a dissolution of only 1.5 % corresponds to a complete removal of the first atomic layer.
Furthermore, using the differently labeled [Ce-139]CeO2 NPs we can show that the uptake of Ce into plants when exposed to CeO2 NP is mainly an uptake of particulate CeO2 rather than dissolved ionic Ce.
Keywords: Nanopartikel, nanoparticle Cerdioxid, cerium dioxide Radiomarkierung, radiolabeling Pflanzenaufnahme, plant uptake
  • Poster
    NanoCare Clustertreffen 2017, 04.-05.05.2017, Karlsruhe, Deutschland

Publ.-Id: 25458 - Permalink


Magnetic anisotropy of polycrystalline high-temperature ferromagnetic MnxSi1-x (x≈0.5) alloy films
Drovosekova, A. B.; Kreines, N. M.; Savitsky, A. O.; Kapelnitsky, S. V.; Rylkov, V. V.; Tugushev, V. V.; Prutskov, G. V.; Novodvorskii, O. A.; Shorokhova, A. V.; Wang, Y.; Zhou, S.;
A set of thin film MnxSi1-x alloy samples with different manganese concentration x≈0.44−0.63 grown by the pulsed laser deposition (PLD) method onto the Al2O3 (0001) substrate was investigated in the temperature range 4–300 K using ferromagnetic resonance (FMR) measurements in the wide range of frequencies (View the MathML source) and magnetic fields (View the MathML source). For samples with x≈0.52−0.55, FMR data show clear evidence of ferromagnetism with high Curie temperatures View the MathML source. These samples demonstrate a complex magnetic anisotropy described phenomenologically as a combination of the essential second order easy plane anisotropy contribution and the additional fourth order uniaxial anisotropy contribution with easy direction normal to the film plane. The observed anisotropy is attributed to a polycrystalline (mosaic) structure of the films caused by the film-substrate lattice mismatch. The existence of extra strains at the crystallite boundaries initiates a random distribution of local in-plane anisotropy axes in the samples. As a result, the symmetry of the net magnetic anisotropy is axial with the symmetry axis normal to the film plane. The principal features of the observed anisotropy are explained qualitatively within the proposed microscopic model.
Keywords: Magnetic MnxSi1-x alloy films; Magnetic anisotropy; Ferromagnetic resonance

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Publ.-Id: 25457 - Permalink


Giant Enhancement of Nonlinear Optical Response in Nd:YAG Single Crystals by Embedded Silver Nanoparticles
Li, R.; Dong, N.; Cheng, C.; Ren, F.; Hübner, R.; Wang, J.; Zhou, S.; Chen, F.;
We report on the enhancement and modulation of nonlinear optical response in an Nd:Y3Al5O12 (Nd:YAG) laser crystal through embedded silver nanoparticles (NPs) fabricated by Ag+ ion implantation. The linear absorption spectrum of the sample clearly reveals a localized surface plasmon resonance (SPR) band from 350 to 700 nm correlated to the Ag NPs. By using the Z-scan technique with femtosecond pulses at a wavelength of 515 nm, which is considered as an optical excitation within the SPR band, the nonlinear refraction index reaches values as high as ∼10–12 cm2/W, enhanced by ∼4 orders of magnitude in comparison to that of unimplanted Nd:YAG (without Ag NPs). In addition, it has been shown that embedded Ag NPs in the Nd:YAG host reveal saturable absorption signifying the nonlinear responses. We have also observed that the nonlinear absorption coefficients depend significantly on the excitation energy and can be modulated by varying the fluence of Ag+ ions.

Publ.-Id: 25456 - Permalink


Effect of microstructural anisotropy on fracture toughness of hot rolled 13Cr ODS steel – the role of primary and secondary cracking
Das, A.; Viehrig, H. W.; Bergner, F.; Heintze, C.; Altstadt, E.; Hoffmann, J.;
ODS steels have been known to exhibit anisotropic fracture behaviour and form secondary cracks. In this work, the factors responsible for the anisotropic fracture behaviour have been investigated using scanning electron microscopy and electron backscatter microscopy. Fracture toughness of hot rolled 13Cr ODS steel was determined using unloading compliance method for L-T and T-L orientations at various temperatures. L-T orientation had higher fracture toughness than T-L orientation and also contained more pronounced secondary cracking. Secondary cracks appeared at lower loads than primary cracks in both orientations. Primary crack propagation was found to be preferentially through fine grains in a bimodal microstructure. Grains were aligned and elongated the most towards rolling direction followed by T and S directions resulting in fracture anisotropy. Crystallographic texture and preferential alignment of Ti enriched particles parallel to rolling direction also contributed towards fracture anisotropy.
Keywords: ODS-steel, fracture behaviour, anisotropy, secondary cracking, bimodal microstructure, delamination, fractography

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Publ.-Id: 25455 - Permalink


Transition between quasi 2D and 3D Rayleigh-Bénard convection in a horizontal magnetic field
Vogt, T.; Ishimi, W.; Yanagisawa, T.; Tasaka, Y.; Sakuraba, A.; Eckert, S.;
MHD Rayleigh-Bénard convection was studied experimentally and numerically using a liquid metal inside a box with square horizontal cross section and aspect ratio five. Applying a sufficiently strong horizontal magnetic field converts the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field. The aim of this paper is to provide a detailed description of the flow field, which is often considered as quasi 2D. In this paper we focus on the transition from a quasi-two-dimensional state towards a three-dimensional flow occurring with decreasing magnetic field strength. We present systematic flow measurements that were performed by means of ultrasound Doppler velocimetry. The measured data give an insight into the dynamics of the primary convection rolls, the secondary flow induced by Ekman pumping and reveal the existence of small vortices that develop around the convection rolls. The flow measurements are completed by direct numerical simulations. Numerical results and experimental findings show an excellent agreement with respect to the qualitative flow features.
Keywords: Rayleigh-Bénard convection, Magnetohydrodynamic, Magnetoconvection

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Publ.-Id: 25454 - Permalink


4-Phosphorylpyrazolones as receptor molecules for f-block elements
Schnaars, K.; März, J.; Hennersdorf, F.; Harting, D.; Acker, M.; Wenzel, M.; Ikeda-Ohno, A.ORC; Stumpf, T.; Gloe, K.; Weigand, J. J.
The similar chemical properties of f-block elements are still a challenging task in the separation of nuclear fuel waste material by hydrometallurgical methods. Extractants based on phosphorus (e.g. D2EHPA, PC88A, TBP) are typically used in industrial recovery processes.1, 2 Chelating agents, such as 4-acylpyrazolones received remarkable attention as extractants for rare earth elements.3 Our approach is to achieve suitable reagents for selective separation of lanthanides and actinides by implementing the phosphoryl group in the backbone of pyrazolones. This is the first publication on 4-phosphorylpyrazolones4, 5 with respect to their coordination behaviour towards f-block elements.
Keywords: f-elements, actinides, lanthanides, phosphoryl, ligand, complexation, coordination
  • Lecture (Conference)
    Actinides 2017, 13.-14.07.2017, Seidai, Japan

Publ.-Id: 25453 - Permalink


Radioecological research for NORM sites - Development of a roadmap
Arnold, T.; Sachs, S.;
This poster presents the main objectives tasks and milestones of a roadmap, which was developed by the COMET/ALLIANCE working group NORM with focus on important priorities within NORM related research.
Keywords: NORM, roadmap, COMET, ALLIANCE
  • Poster
    COMET Final Event, 25.-27.04.2017, Bruges, Belgium

Publ.-Id: 25452 - Permalink


Swift heavy ion track formation in SrTiO3 and TiO2 under random, channeling and near-channeling conditions
Karlušić, M.; Jakšić, M.; Lebius, H.; Ban-D'Etat, B.; Wilhelm, R. A.ORC; Heller, R.; Schleberger, M.
Conditions for ion track formation in single crystal SrTiO3 and TiO2 (rutile) after irradiations using swift heavy ion beams with specific energies below 1 MeV/amu were investigated in this work. Rutherford backscattering spectroscopy in channeling was used to measure ion tracks in the bulk, while atomic force microscopy was used for observation of ion tracks on the surfaces. Variations in the ion track sizes and respective thresholds were observed after irradiations under random, channeling and near-channeling conditions close to normal incidence. These variations are attributed to the specifics of the electronic stopping power of swift heavy ions under the investigated conditions. In the case of ion channeling, electronic stopping power is reduced and observed ion tracks are smaller. The opposite was found under the near-channeling conditions when lowering of the ion track formation threshold was observed. We attribute this finding to the oscillating electronic stopping power with large peak values. For both materials, thresholds for bulk and surface ion track formation were found to be surprisingly close, around 10 keV nm−1. Obtained results are compared with predictions of the analytical thermal spike model.
Keywords: SrTiO3, TiO2, swift heavy ion, ion track, thermal spike, RBS/c, AFM

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Publ.-Id: 25451 - Permalink


Modeling and Simulation of Turbulent Bubbly Flows
Parekh, J.;
The application of multiphase computational fluid dynamics (CFD) simulation for scale-up and intensification of chemical engineering processes bears the potential to identify energy- and resource- efficient solutions. This avoids the need to employ the conventional semi-empirical methods which are expensive and time-consuming.
Such simulations are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, for practical applications, suitable closure relations are needed which describe the physics on the scale of individual bubbles or groups thereof. A suitable closure model for the fluid dynamics of bubbly flows is developed at HZDR. The goal of this development is to establish a predictive model which is validated for a broad range of applications. For this purpose, simulations results are compared with experimental data.
Within the present project, a full Reynolds-stress turbulence model is introduced into the mathematical framework and compared with the two-equation model used so far. In particular, new anisotropic source terms for the bubble-induced turbulence are investigated. Bubbly pipe flows, in which individual components of the Reynolds-stress tensor have been measured, are considered as applications. The simulations are run in OpenFOAM.
Simulation results for the gas fraction, liquid velocity and turbulent kinetic energy are largely found to be in accordance with the experimental measurements. Deviations occur mostly for some cases with larger superficial gas velocity. Reynolds-stress models (RSMs) when extended to include the bubble-induced turbulence demonstrate the potential to predict the Reynolds stresses. The RSMs thereby are able to account for the deficiencies of the two-equation turbulence model.
Keywords: dispersed gas liquid multiphase flow, Euler-Euler two-fluid model, Reynolds stress turbulence model, bubble-induced turbulence, CFD simulation, model validation
  • Master thesis
    RWTH Aachen, 2017
    Mentor: Prof. Dr.-Ing. Heinz Pitsch

Publ.-Id: 25450 - Permalink


On the equivalence of image-based dual-energy CT methods for the determination of electron density and effective atomic number in radiotherapy
Möhler, C.ORC; Wohlfahrt, P.ORC; Richter, C.; Greilich, S.
Dual-energy computed tomography enables the determination of relative electron density and effective atomic number. As this can increase accuracy in radiotherapy treatment planning, a substantial number of algorithms for the determination of the two quantities has been suggested – most of them based on reconstructed CT images. We show that many of these methods share a common theoretical framework. Equations can be transformed from one method to the other by re-definition of the calibration parameters. We suggest that further work should be spent on practical calibration and the reliability of CT numbers rather than on the theoretical framework.
Keywords: Material Characterization; Radiotherapy; Treatment planning; Dose calculation; Proton and Ion Beam Therapy

Publ.-Id: 25448 - Permalink


Simulation von reaktivem Stofftransport in Blasensäulen
Krauß, M.;
Die Anwendung von Methoden der CFD („Computational fluid dynamics“) für Scale-up und Intensivierung verfahrenstechnischer Prozesse bietet die Möglichkeit, energie- und ressourceneffiziente Lösungen zu identifizieren, deren Untersuchung mit konventionellen halb-empirischen Methoden kostspielig und langwierig wäre.
Eine solche Simulation im großtechnischen Maßstab ist im Rahmen der Euler-Euler Beschreibung möglich, in der Prozesse auf der Skala einzelner Blasen modelliert werden. Ein geeignetes Schließungsmodell für Hydrodynamik und Stofftransport in Blasenströmungen wird am HZDR entwickelt. Ziel dieser Entwicklung ist, ein vorhersagetaugliches Modell zu etablieren, das für einen breiten Bereich von Anwendungsbedingungen validiert ist.
Zu diesem Zweck werden Simulationsrechnungen mit experimentellen Daten verglichen, die zunehmend komplexere Geometrien und Effekte einbeziehen. Auf Basis der jeweils erzielten Übereinstimmung werden Modellerweiterungen und -verbesserungen vorgenommen. Im Rahmen der Diplomarbeit soll die reaktive Absorption von Kohlenstoffdioxid in Natronlauge in Blasensäulen untersucht werden.
Keywords: disperse Gas-Flüssigkeits Mehrphasen Strömungen, Euler-Euler Zwei-Fluid Modell, CFD Simulation, Strömungsmechnaik, Stofftransport, chemische Reaktion, Absorption
  • Diploma thesis
    TU Dresden, 2017
    Mentor: Prof. Dr.-Ing. habil. R. Lange

Publ.-Id: 25447 - Permalink


Modeling of Fluid Dynamics, Mass Transfer, and Chemical Reaction in Bubbly Flows
Rzehak, R.; Krauß, M.;
Mass transfer from gas bubbles to the surrounding liquid or vice versa is an important consideration in chemical engineering. Frequently such absorption or desorption processes are accompanied by a chemical reaction in the liquid phase. Compared with the fluid dynamics of bubbly flows, modeling and simulation of these processes is much less developed. The present work shows some recent advances made in validating closures for the Eulerian two-fluid framework of interpenetrating continua.
Keywords: dispersed gas liquid multiphase flow, Euler-Euler two-fluid model, CFD simulation, fluid dynamics, mass transfer, chemical reaction, absorption
  • Contribution to proceedings
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 30.05.-01.06.2017, Trondheim, Norway
    Proceedings of the 12th International Conference on Computational Fluid Dynamics in the Oil & Gas, Metallurgical and Process Industries, Oslo: SINTEF Academic Press, 978-82-536-1544-8, 383-390
  • Lecture (Conference)
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 30.05.-01.06.2017, Trondheim, Norway

Publ.-Id: 25446 - Permalink


Reactive absorption of CO2 in NaOH: An Euler-Euler simulation study
Krauß, M.; Rzehak, R.;
Recently, a new model for the reactive mass transfer during absorption of CO2 in aqueous NaOH was developed, based on using a rather generally applicable expression for the enhancement factor and taking into account the reaction of CO2 with water in addition to that with hydroxide ions [Krauß and Rzehak, Chemical Engineering Science 166 (2017) 193–209]. By substituting the interfacial area concentration estimated from experimental data, good agreement was found for the pointwise measurement of time-dependent pH-value in a bubble column taken from the literature [Darmana et al., Chemical Engineering Science 62 (2007), 2556–2575]. In the present contribution, this mass transfer model is implemented in an Euler-Euler / RANS framework including also the hydrodynamic part of the problem. Hydrodynamic closures were taken the same as applied successfully for a range of different conditions in previous work. However, the accuracy of the coupled model in predicting the measured pH-value is seen to fall behind that of the simple pointwise approximation. This suggests that for the present application, the hydrodynamic part of the model requires further improvement. Possible directions to this end are discussed.
Keywords: mass transfer, chemical reaction, chemisorption, enhancement factor, dispersed gas-liquid multiphase flow, Euler-Euler two-fluid model, CFD simulation

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  • Secondary publication expected

Publ.-Id: 25445 - Permalink


The fate of Pu released from nuclear test events into the environment
Ikeda-Ohno, A.ORC
Nuclear weapons tests conducted worldwide have dispersed long-lived and radioactive nuclear debris including plutonium (Pu). A reliable assessment of the environmental impact of these radioactive contaminants and their potential implications for human health requires an understanding of their physical/chemical characteristics at the molecular scale. This lecture focuses particularly on the physical/chemical characterisation of the Pu contaminant, one of the most problematic radioactive contaminants released from nuclear tests, by synchrotron-based X-ray microscopy / spectroscopy. The study reveals direct experimental evidence that the Pu legacy remaining at one of the former testing sites in Australia (Taranaki, Maralinga) exists as particulates of Pu(IV) oxyhydroxide compounds, a very concentrated and low-soluble form of Pu, which will serve as ongoing radioactive sources far into the future. Based on the obtained results, a possible scenario of the physical/chemical transformation of the original Pu materials dispersed in the semi-arid environment at Maralinga can be also deduced. The lecture also highlights the importance of the comprehensive characterization of radioactive contaminants for reliable environmental- and radiotoxicological assessment.
Keywords: Actinides, plutonium, environmental science, chemical transformation, synchrotron, X-ray microscopy, X-ray spectroscopy
  • Invited lecture (Conferences)
    Guest lecture at the lecture series "Radioecology", 18.05.2017, TU Dresden, Germany

Publ.-Id: 25444 - Permalink


Status of routine operation and developments at DREAMS
Rugel, G.; Merchel, S.; Scharf, A.; Ziegenrücker, R.; DREAMS-Users;
Since fall 2011, the DREsden AMS-facility (DREAMS), has performed routine AMS at the Ion Beam Centre’s (IBC) 6 MV tandem accelerator located at the Helmholtz-Zentrum Dresden-Rossendorf [1, 2]. The accelerator is shared with others for purposes such as ion beam analysis and high-energy ion implantation. Measurements of 10Be, 26Al, 36Cl, 41Ca, and 129I are routinely performed for a wide range of applications. Samples are prepared in close cooperation with DREAMS’s users, mostly in our two dedicated, high quality laboratories on-site [3]. One particular ion source with a very low long-term memory is used exclusively for measuring the halogens (36Cl and 129I) [4]. For measurements of 26Al/27Al ratios we have reduced the background to 6×10-16. Additionally, we started to investigate the potential for non-routine AMS-nuclide determination (stable and short-lived) for e.g. astrophysical applications.
[1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Rugel et al. NIMB 370 (2016) 94. [3] Merchel et al. these proceedings [4] S. Pavetich et al., NIMB 329 (2014) 22.
Keywords: AMS, Be-10, Al-26, Cl-36, Ca-41, I-129
  • Poster
    The Fourteenth International AMS Conference, 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25443 - Permalink


Radiobiology with laser accelerated ion beams
Kraft, S.;
Radiobiology with laser accelerated ion beams
  • Invited lecture (Conferences)
    WHELMI Inauguration, 25.04.2017, Rehovot, Israel

Publ.-Id: 25442 - Permalink


Status of the progress at the Dresden Super-SIMS
Rugel, G.; Akhmadaliev, S.; Belokonov, G.; Böttger, R.; von Borany, J.; Gutzmer, J.; Kaever, P.; Meyer, M.; Noga, P.; Renno, A. D.; Scharf, A.; Tiessen, C. J.; Voigtländer, J.; Wagner, N.; Wiedenbeck, M.; Winter, A.; Wu, H. S.; Ziegenrücker, R.;
The DREAMS (DREsden AMS) facility [1,2] has been proven to be very suitable for a number of applications. We are broadening our application scope by the implementation of a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry) device [3]. Our system combines the spatial resolution capability of a SIMS (CAMECA IMS 7f-auto) with the pre-existing DREAMS’s capability to remove isobaric molecular signatures in the ion beam. An improvement down to isotopic ratios of ~ 10-9 -10-12 is expected, i.e. an order of magnitude better than traditional dynamic SIMS (e.g. [4,5]).
To match the acceptance conditions of our 6 MV Tandetron accelerator, the SIMS device (providing an ion beam with 5 to 10 keV energy) can be raised to a potential of up to -30 kV. The connection between the SIMS device and the accelerator has been realized with a transition lens, which focusses the ion beam to the accelerator entrance. SIMS-extracted ion beams have already been successfully measured on the high-energy accelerator side detector.
First measurements were done with two matrices: a P-doped Si-wafer and a natural galena crystal (PbS). The wafer was analysed for all naturally occurring Si isotopes (28Si, 29Si, 30Si) as well as for 31P. Count rates for all of the aforementioned isotopes were measured. Galena was analysed for S isotopes (32S, 33S, 34S, 36S). We present ongoing developments, results, as well as plans to extend to other matrices and isotope systems. With more development this ultrasensitive analytical method could be best-suited for analysing geological samples within our resource technology focus.

[1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Rugel et al. NIMB 370 (2016) 94. [3] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316. [4] Maden, PhD thesis, ETH Zurich 2003. [5] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470.
Keywords: SIMS, Super-SIMS, Trace element AMS, galena
  • Poster
    The Fourteenth International AMS Conference (AMS 14), 14.-18.08.2017, Ottawa, Canada

Publ.-Id: 25441 - Permalink


Investigation of a bioflotation interface with infrared spectroscopy
Firkala, T.; Lederer, F.; Pollmann, K.; Rudolph, M.;
In this paper we report an approach for the structural analysis of mineral-collector interfaces of (bio)flotation systems by means of attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR). The extraction of rare earth metals from electronic waste materials is an important challenge for the recycling industry. In a current project bacteriophage are used as biocollectors to develop a bioflotation model system for the separation of lanthanum phosphate doped with cerium and terbium (LaPO4:Ce3+,Tb3+) from mixed fluorescent phosphors. As an initial analytical concept fluorescence microscopy was successfully applied to investigate particles of spent fluorescent lamp powders and to visualize the bacteriophage on the surface of the waste material. However, due to the restrictions of this technique we are not able to identify the molecular interactions of the bacteriophage with the recycled material. ATR FT-IR was found to be an effective tool to detect the major coat protein of the bacteriophage biocollectors on the surface of the LaPO4:Ce3+,Tb3+ and sense their specific bonding interaction opening the gates for the high level chemical characterization of the interface.
Keywords: flotation, interface, surface analysis, biorecycling, infrared spectroscopy

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Publ.-Id: 25440 - Permalink


Evolution of the Uranium Chemical State in Mixed-Valence Oxides
Leinders, G.; Bes, R.; Pakarinen, J.; Kvashnina, K.; Verwerft, M.;
A fundamental question concerning the chemical state of uranium in the binary oxides UO2, U4O9, U3O7, U3O8 and UO3 is addressed. By utilizing high energy resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES) at the uranium M4 edge, a novel technique in the tender X-ray region, we obtain the distribution of formal oxidation states in the mixed valence oxides U4O9, U3O7 and U3O8. Moreover, we clearly identify a pivot from U(IV)-U(V) to U(V)-U(VI) charge compensation, corresponding with transition from a fluorite-type structure (U3O7) to a layered structure (U3O8). Such physicochemical properties are of interest to a broad audience of researchers and engineers active in domains ranging from fundamental physics, to nuclear industry and environmental science.

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Publ.-Id: 25439 - Permalink


Pencil beam scanning treatments in free-breathing lung cancer patients - is 5 mm motion a limit?
Jakobi, A.; Knopf, A.; Perrin, R.; Richter, C.ORC
Purpose
To evaluate the dose degradation when treating lung cancer patients with proton pencil beam scanning during free-breathing. We assess if treatments without rescanning are feasible in order to avoid prolonged treatment time, especially for slow scanning facilities.
Material and Methods
For 40 lung cancer patients, 4DCT imaging was used to generate 4D dynamic dose distributions of 3D treatment plans with 3 pencil beam scanning fields optimised with the single field uniform dose technique. Simulations included the use of random breathing states of the patient at start of irradiation resulting in multiple possible 4D dynamic dose distributions per fraction. Complete treatment was assumed to consist of 33 fractions of probabilistically chosen single fractions. Treatments were assumed to be delivered with an IBA universal nozzle without rescanning (1.5ms between spots, 2s between energy layers, spot sigma 4mm at highest energy). Tumour motion amplitude was the maximum displacement in tumour centre-of-mass assessed by the 4DCT. Evaluation was done by looking at under- and overdosage in the target structure. In addition, changes in the dose distribution due to changes in motion and anatomy during treatment were analysed using a repeated 4DCT for 4D dynamic dose calculation in one patient case.
Results
Almost 50% of the patients had tumour motion amplitudes of less than 5mm. For these patients, the simulated dose degradation per fraction was much smaller than for patients with larger motion amplitudes, with 2% versus 12 % average absolute reduction of the V95 (p<0.01), and an average increase in absolute V107 of 2% vs 9% (p<0,01). In no patient case studied was the minimum dose in the target degraded to below 80% of the prescribed dose, and rarely increased above 120%. Simulating a 33-fraction treatment, the mean reduction of the V95 was below 1% for patients with motion amplitudes below 5mm, while for patients with larger motion, V95 was degraded on average by 4% with worst case scenarios of 4% versus 19% (p<0.01), cf. Fig. 1. V107 had an average increase of about 0% and 1% (n.s.), with worst case values of 5% and 15%. The additional analysis of one patient case with a repeated CT revealed a large increase of tumour motion by about 5mm during treatment, resulting in a large dose degradation and partial miss of the target (V95<70%), cf. Fig. 2.
Conclusion
Motion amplitude is an indicator of dose degradation caused by the interplay effect. Fractionation reduces the dose degradation to such an amount that rescanning might be unnecessary for patients with a small tumour motion less than 5mm. Patients with larger tumour motion should not be treated without any kind of motion mitigation technique (e.g. rescanning , gating or breath hold) to prevent tumour underdosage persisting through to the end of fractionated treatment. Furthermore, the tumour motion needs to be assessed during treatment for all patients to quickly react to possible changes in motion which might require a treatment adaptation.
Keywords: non-small cell lung cancer, proton therapy, pencil beam scanning, tumour motion, interplay, treatment planning study
  • Poster
    ESTRO 36 - Poster, 05.-09.05.2017, Wien, Österreich

Publ.-Id: 25438 - Permalink


Development of a Super-SIMS for geological applications
Ziegenrücker, R.; Akhmadaliev, S.; Belokonov, G.; von Borany, J.; Böttger, R.; Gutzmer, J.; Kaever, P.; Meyer, M.; Noga, P.; Renno, A. D.; Rugel, G.; Scharf, A.; Tiessen, C. J.; Voigtländer, J.; Wagner, N.; Wiedenbeck, M.; Winter, A.; Wu, H. S.;
The DREAMS (DREsden Accelerator Mass Spectrometry) facility [1, 2] has been proven to be very suitable for a number of applications. We are broadening our application scope by the implementation of a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry) device [3]. Our system combines the spatial resolution capability of a SIMS (CAMECA IMS 7f-Auto) with the pre-existing DREAMS’s capacity to remove isobaric molecular signatures in the ion beam. An improvement down to ultra-trace element concentrations of 1 µg/g to 100 ng/g is expected, i.e. an order of magnitude better than traditional dynamic SIMS (see e.g. [4, 5]).
To match the acceptance conditions of our 6 MV Tandetron accelerator for all masses from 1 to 300 amu, the SIMS device (providing an ion beam with 5 to 10 keV energy) can be raised to a potential of up to -30 kV. The connection between the SIMS device and the accelerator has been realized with a transition lens, which focusses the ion beam to the accelerator entrance. SIMS-extracted ion beams have already been successfully measured on the high-energy accelerator side detector.
First measurements were done with two matrices: a P-doped Si-wafer and a natural galena crystal (PbS). The wafer was analysed for all naturally occurring Si isotopes (28Si, 29Si, 30Si) as well as 31P. Count rates for all of the aforementioned isotopes were measured. Galena was analysed for S isotopes (32S, 33S, 34S, 36S). We present ongoing developments, results, as well as plans to extend to other matrices and isotope systems. With more development this ultrasensitive analytical method could be best-suited for analysing geological samples within our resource technology focus.

[1] S. Akhmadaliev, et al., Nucl. Instrum. Meth. B 294, 2013, 5-10.
[2] G. Rugel, et al. Nucl. Instrum. Meth. B 370, 2016, 94-100.
[3] J. M. Anthony, D. J. Donahue, A. J. T. Jull, Mat. Res. Soc. Symp. Proc. 69, 1986, 311-316.
[4] C. Maden, PhD thesis, ETH Zurich, 2003.
[5] S. Matteson, Mass Spectrom. Rev. 27 (5), 2008, 470-484.
Keywords: SIMS, Super-SIMS, Trace element AMS, galena
  • Poster
    21st International Conference on Secondary Ion Mass Spectrometry - SIMS21, 10.-15.09.2017, Kraków, Poland

Publ.-Id: 25437 - Permalink


Assessment of separation efficiency modeling and visualization approaches pertaining to flow and mixing patterns on distillation trays
Vishwakarma, V.; Schubert, M.; Hampel, U.;
Distillation columns are essential to chemical process industries, and most of them are fitted with crossflow trays due to their versatility. Since these columns are expensive in terms of cost and energy consumption, an accurate determination of their separation efficiency is a prerequisite to optimization of their performance by design modification and revamping. This would further reduce the extra trays, added to account for the uncertainties, during the column design. There have been several attempts in the past to understand the nature of liquid mixing and flow patterns on the trays through experiments and CFD simulations, and to relate them with their separation efficiency through CFD, empirical and theoretical models. The present work aims at reviewing the experimental and the simulational studies accomplished to characterize the flow and the mixing patterns on column trays. In particular, a comprehensive review of the existing theoretical efficiency prediction models along with the critical analysis of their strengths and weaknesses is presented. The dependence of the tray efficiency on system and flow properties is also discussed. In addition, a concise strategy on how to process and utilize the experimental data in tandem with mathematical models is proposed. The future of the tray efficiency modeling is anticipated to feature hybrid approaches, i.e. using theoretical models supplemented with fluid dynamics information from experimentally validated CFD models. Thus, knowledge of the existing theoretical approaches is imperative for their improvement and development of the new ones for better tray efficiency predictions.
Keywords: Distillation tray, tray efficiency, flow and mixing patterns, CFD, experiments, flow maldistribution

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  • Secondary publication expected

Publ.-Id: 25436 - Permalink


Effect of flow non-idealities on tray efficiency
Vishwakarma, V.; Schubert, M.; Hampel, U.;
Cross-flow trays are highly reputed among vapour-liquid contacting devices in distillation columns. Their ability to perform in various operating conditions, low fouling sensitivity, low cost and access for inspections make them potential nominee for column internals. Tray separation efficiency as well as overall performance of the column is strongly dictated by evolving flow patterns on the tray. Liquid plug flow is considered ‘ideal’ at which the maximum tray efficiency can be expected. On the other hand, liquid channelling, bypassing, retrograde flow and stagnant zones are known to be detrimental to tray efficiency. Schubert et. al. (2016) established the wire-mesh sensor as a novel technique to extract liquid flow patterns on trays and presented the effect of variable liquid load and weir design on the flow patterns.
As a follow up, the most common mathematical models, which were recently revisited by Vishwakarma et al. (2016), are applied to associate flow and mixing patterns with tray efficiency. They indicate serious loss in efficiency for the tray with largest stagnant regions. The location of dead zones is also important as most of the mass transfer on large trays happens in their first half. Any stagnant liquid in these areas is highly disadvantageous for the tray to fractionate as per expectations. This contribution will stimulate to develop a new practicable model that can account for the effect of location and type of non-ideality on the tray efficiency.

(1) M. Schubert, M. Piechotta, M. Beyer, E. Schleicher, U. Hampel and J. Paschold, ‘An imaging technique for characterization of fluid flow pattern on industrial-scale column sieve trays’, Chemical Engineering Research and Design, vol. 111, pp.138–146, 2016.
(2) V. Vishwakarma, M. Schubert and U. Hampel, ‘Distillation tray efficiency modelling: a forgotten chapter’, Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 16-17 March 2016, Garmisch-Partenkirchen.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 08.-10.03.2017, Cologne, Germany

Publ.-Id: 25435 - Permalink


Three Dimensional Computational Fluid Dynamics Simulation of Condensation Inside Inclined Tubes
Moonesi Shabestary, A.; Krepper, E.; Lucas, D.; Höhne, T.;
The current paper comprises CFD- modelling and simulation of condensation and heat transfer inside horizontal pipes. Designs of future nuclear boiling water reactor concepts are equipped with emergency cooling systems which are passive systems for heat removal. The emergency cooling system consists of slightly inclined horizontal pipes which are immersed in a tank of subcooled water. At normal operation conditions, the pipes are filled with water and no heat transfer to the secondary side of the condenser occurs. In the case of an accident the water level in the core is decreasing, steam comes in the emergency pipes and due to the subcooled water around the pipe, this steam will condense. The emergency condenser acts as a strong heat sink which is responsible for a quick depressurization of the reactor core when any accident happens. The actual project is defined in order to model all these processes which happen in the emergency cooling systems. The most focus of the project is on detection of different morphologies such as annular flow, stratified flow, slug flow and plug flow. The first step is the investigation of condensation inside a horizontal tube by considering the direct contact condensation (DCC). Therefore, at the inlet of the pipe an annular flow is assumed. In this step, the Algebraic Interfacial Area Density (AIAD) model is used in order to simulate the interface. The second step is the extension of the model to consider wall condensation effect as well which is closer to the reality. In this step, the inlet is pure steam and due to the wall condensation, a liquid film occurs near the wall which leads to annular flow. The last step will be modelling of different morphologies which are occurring inside the tube during the condensation via using the Generalized Two-Phase Flow (GENTOP) model extended by heat and mass transfer. By using GENTOP the dispersed phase is able to be considered and simulated. Finally, the results of the simulations will be validated by experimental data which will be available in HZDR. In this paper the results of the first part has been presented.
Keywords: CFD modeling, AIAD, condensation, heat Transfer, mass transfer, phase change
  • Contribution to proceedings
    25th International Conference on Nuclear Engineering - ICONE 2017, 02.-06.07.2017, Shanghai, China
    Proceedings of ICONE 2017, Vol. 8, 131175
    DOI: 10.1115/ICONE25-66167
  • Lecture (Conference)
    25th International Conference on Nuclear Engineering - ICONE 2017, 04.07.2017, Shanghai, China

Publ.-Id: 25433 - Permalink


Experimentelle Untersuchungen zur Speziesumwandlung bei Absorption von CO2 in einer Blasensäule
Kipping, R.; Kryk, H.; Hampel, U.;
Blasensäulenreaktoren zählen aufgrund ihrer einfachen Bauweise und ihres ausgezeichneten Wärme-und Stofftransportverhaltens zu einem der häufig genutzten Reaktortypen in der chemischen Industrie. Gegenstand aktueller Forschungsarbeiten innerhalb des DFG Schwerpunktprogramms 1740 „Reaktive Blasenströmungen“ ist die Untersuchung lokaler Transportprozesse, um das Verständnis über die Kopplung von Hydrodynamik und Stofftransport bei reaktiven 2-Phasenströmungen in Blasensäulen zu verbessern. Aufgrund limitierter Messtechnik stellt die Ermittlung von lokalen Konzentrationsfeldern und Stofftransportraten in dichten Blasenströmungen eine besondere Herausforderung dar. In diesem Beitrag werden experimentelle Untersuchungen zum Stofftransport am Beispiel der chemischen Absorption von CO2 vorgestellt, bei der die am HZDR entwickelte Gittersensormesstechnik zur Ermittlung der Konzentration und der Umwandlung ionischer Spezies eingesetzt wird. Für diesen Zweck konnte der Gittersensor anhand eines theoretischen Modells und Validierungsexperimente erfolgreich qualifiziert werden. Die experimentellen Ergebnisse der Stofftransportuntersuchungen in einem Blasensäulenreaktor zeigen die Stofftransportraten für verschiedene Eingangsparameter (z.B. Eingangskonzentration der Natronlauge und Gasdurchsatz des CO2) sowohl in Abhängigkeit des Radius als auch in verschiedenen Höhen des Reaktors.
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen, Partikelmesstechnik, Zerkleinern und Klassieren, Computational Fluid Dynamics, Mischvorgänge und dem TAK Aerosoltechnologie, 14.-15.03.2017, Dresden, Deutschland

Publ.-Id: 25431 - Permalink


Assessment of solid/liquid equilibria in the (U, Zr)O2+x system
Mastromarino, S.; Seibert, A.; Hashem, E.; Ciccioli, A.; Prieur, D.; Scheinost, A.; Stohr, S.; Lajarge, P.; Boshoven, J.; Robba, D.; Ernstberger, M.; Bottomley, D.; Manara, D.;
Solid/liquid equilibria in the system UO2 – ZrO2 are revisited in this work by laser heating coupled with fast optical thermometry. Phase transition points newly measured under inert gas are in fair agreement with the early measurements performed by Wisnyi et al. in 1957, the only study available in the literature on the whole pseudo-binary system. However, a minimum melting point is identified here for compositions near (U0.6Zr0.4)O2, around 2800 K. The solidus line is rather flat on a broad range of compositions around the minimum. It increases for compositions closer to the pure end members, up to the melting point of pure UO2 (3130 K) on one side and pure ZrO2 (2970 K) on the other. Solid state phase transitions (cubic-tetragonal-monoclinic) have also been observed in the ZrO2-rich compositions by Raman spectroscopy and x-ray diffraction. Investigations under compressed air revealed a significant decrease in the melting points down to 2500 K – 2600 K for increasing uranium content (x(UO2)> 0.2). This was found to be related to further oxidation of uranium dioxide, confirmed by x-ray absorption spectroscopy. For example, a typical oxidised corium composition U0.6Zr0.4O2.13 was observed to solidify at a temperature as low as 2523 K.
The current results are important for assessing the thermal stability of the system fuel – cladding in an oxide based nuclear reactor, and for simulating the system behaviour during a hypothetical severe accident.
Keywords: Corium, Core Meltdown, Laser heating, Nuclear Fuel, Uranium dioxide, Zirconium dioxide

Publ.-Id: 25430 - Permalink


Retrospective assessment of MRI-based volumetric changes of normal tissues in glioma patients following radio(chemo)therapy
Gommlich, A.; Raschke, F.; Wahl, H.; Troost, E.ORC
In glioma patients, linac-based photon beam irradiation is a widely applied therapy, which achieves highly conformal target volume coverage, but is also known to cause side-effects to adjacent areas of healthy tissue. Apart from subjective measures, such as quality of life assessment and neurocognitive function tests, objective methods to quantify tissue damage are needed to assess this impact. Magnetic resonance imaging (MRI) is a well-established method for brain tumor diagnoses as well as assessing treatment response. In this study, we retrospectively assessed volumetric changes of gray matter (GM) and white matter (WM) in glioma patients following photon irradiation using a heterogeneous MRI-dataset obtained in routine clinical practice at different sites with imaging parameters and magnetic field strengths. We found a significant reduction in WM volume at one year (p = 0.01) and two years (p = 0.008) post radio(chemo)therapy whereas corresponding GM volumes did not change significantly (p = 0.05 and p = 0.11, respectively). More importantly, we also found large variations in the segmented tissue volumes caused by the heterogeneous MR data, thus potentially masking more subtle tissue changes over time. On the basis of these observations, we present suggestions regarding data acquisitions in future prospective MR studies to assess such volumetric changes.
Keywords: MRI; glioma; normal tissue changes

Publ.-Id: 25429 - Permalink


Dynamics of a particle attachment to an immersed bubble
Lecrivain, G.; Yamamoto, R.; Hampel, U.; Taniguchi, T.;
We propose an extended smooth profile method which can deal with particle-dynamics dispersed in a binary fluid. The smooth profile method, originally developed for the simulation of particle transport in a homogeneous fluid, has been successfully combined with a binary fluid model based on Ginzburg-Landau free energy functional. In this approach, the three types of interfaces among particles and two fluids are treated as diffuse interfaces. By using the method, we simulated the attachment and detachment dynamics of a colloidal particle to the surface of a position fixed bubble in a Newtonian fluid under various capillary numbers. It is found that the method can reproduce the three micro-processes associated with the particle attachment ((i) particle approach, (ii) collision, (iii) sliding down on the bubble surface) (Gregory et al, 2016). The present method will make it possible to simulate a froth flotation process, where the capture of hydrophobic particles by rising bubbles is of primary importance.
Keywords: Flotation; Direct Numerical Simulation; Smoothed Profile Method; Immersed Boundary Method
  • Contribution to proceedings
    3rd International Symposium on Multiscale Multiphase Process Engineering (MMPE), 08.-11.05.2017, Toyama, Japan

Publ.-Id: 25428 - Permalink


Dynamic liquid-solid mass transfer in solid foam packed reactors at trickle and pulse flow
Zalucky, J.; Schubert, M.; Lange, R.; Hampel, U.;
The effective liquid-solid mass transfer (LSMT) has been investigated in solid foam packed reactor under cocurrent gas-liquid downflow. Based on a comprehensive literature analysis, the limiting current technique was adapted successfully to solid foam packings enabling measurements of dynamic mass transfer coefficients at different axial packing positions. The flexible reactor setup was used to analyze the appropriateness of various setup configurations. The LSMT coefficients are presented for two different solid foam pore densities for a wide range of gas and liquid velocities covering trickling and pulsing flow regime. To illustrate the difference in the LSMT dynamic in terms of electric current compared to the liquid holdup at pulse flow, a compartment model is developed. Excellent agreement is achieved between simulations and measurement data. Eventually, the effective mass transfer data are compared with conventional random and structured packings.
Keywords: Liquid-solid mass transfer; Limiting current technique; Pulse flow dynamics; Solid foam; Compartment model

Publ.-Id: 25426 - Permalink


Discrete Single Crystalline Titanium Oxide Nanoparticle Formation from a Two-Dimensional Nanowelded Network
Dhal, S.; Chatterjee, S.; Facsko, S.; Möller, W.; Böttger, R.; Satpati, B.; Ratha, S.; Hübner, R.;
Nanostructured materials are gaining increasing importance due to their unique properties resulting from the high surface to volume ratio and the altered characteristics of the nanoscaled building blocks. The properties of these materials depend strongly on their microstructure and thus can be controlled by inducing transformation on the nanoscale. In this work, a simple low energy ion beam irradiation technique is presented that can be used to effectively weld the hydrogen titanate nanotubes into a large-scale network of nanowires. By varying the ion fluence, we are able to fragment the entire nanowire network into uniformly distributed nanocrystalline particles with an average size of 5 ± 2 nm. Three-dimensional computer simulations of the ion irradiation effects on the nanotubes reproduce most of the experimental findings and thus confirm that the early development of the system is governed by atomic collision processes. Our study demonstrates that the selective use of ion irradiation can transform metal-oxide nanotubes into large-scale welded networks of nanowires and further into nanocrystalline particles through nucleation and growth.
Keywords: ion irradiation, titanium oxide, nanowelding, nanoparticle

Publ.-Id: 25425 - Permalink


A study of the behaviour of copper in different types of silicate glasses implanted with Cu+ and O+ ions
Švecová, B.; Vařák, P.; Vytykáčová, S.; Nekvindová, P.; Macková, A.; Malinský, P.; Böttger, R.;
Glasses containing copper are promising photonic materials for lasing devices and all-optical components. It has already been shown that the oxidation state of the implants depends on many factors. This paper is going to report on one of them, i.e. the influence of the composition of a silicate glass matrix on the behaviour of the implanted Cu ions before and after a subsequent implantation of oxygen ions.
Three types of silicate glasses having a different extent of cross-linking were implanted with copper ions with an energy of 330 keV and a fluence 1 × 1016 ions cm−2. Then the glasses were implanted with oxygen ions with an energy of 110 keV into the same depth as the already implanted Cu ions. The concentration depth profiles of Cu in the glasses were studied by Rutherford Backscattering Spectrometry. After the implantation, the samples were characterised by optical absorption and photoluminescence spectroscopy. The samples were annealed in ambient atmosphere for 1 h at 600 °C, which is near the transformation temperature of those glasses. The effect of annealing on the distribution of the implants and on the absorption and emission spectra of the as-implanted glasses will be discussed as well
Keywords: Silicate glasses; Ion implantation; Copper; Oxygen

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Publ.-Id: 25424 - Permalink


Studies of carbon monoxide release from ruthenium(II) bipyridine carbonyl complexes upon UV light exposure
Kubeil, M.ORC; Vernooij, R. R.; Kubeil, C.; Wood, B. R.; Graham, B.; Stephan, H.; Spiccia, L.
The UV light-induced CO release characteristics of a series of ruthenium(II) carbonyl complexes of the form trans-(Cl) [RuLCl2(CO)2] (L = 4,4’-dimethyl-2,2’-bipyridine, 4’-methyl-2,2’-bipyridine-4-carboxylic acid or 4,4’-dicarboxylic acid-2,2’-bipyridine) have been elucidated using a combination of UV-Vis absorbance and Fourier transform infrared (FTIR) spectroscopies, multivariate curve resolution-alternating least squares (MCR-ALS) analysis, and density functional theory calculations. In acetonitrile, photolysis appears to proceed via a serial three-step mechanism involving sequential formation of [RuL(CO)(CH3CN)Cl2], [RuL(CH3CN)2Cl2], and [RuL(CH3CN)3Cl]+. Release of the first CO molecule occurs quickly (k1 >> 3 min-1), while release of the second CO proceeds at a much more modest rate (k2 = 0.099–0.17 min-1) and is slowed by the presence of electron-withdrawing carboxyl substituents on the bipyridine ligand. In aqueous media (1% DMSO in H2O), the two photo-decarbonylation steps proceed much more slowly (k1 = 0.46–1.3 min-1 and k2 = 0.026–0.035 min-1, respectively) and the influence of the carboxyl groups is less pronounced. These results have implications for the design of new light-responsive CO-releasing molecules (“photoCORMs”) intended for future medical use.
Keywords: photoCORMs, ruthenium bipyridine carbonyl complexes, mechanism, TD-DFT, MCR-ALS

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Publ.-Id: 25423 - Permalink


XFEL Probing of Relativistic Plasmas Generated by fs Laser Pulses - Laser & Target Requirements
Metzkes, J.;
  • Lecture (Conference)
    High Intensity Laser Matter Science at the HED instrument at the European XFEL, 05.-06.04.2017, Schenefeld, Deutschland
  • Poster
    High Intensity Laser Matter Science at the HED instrument at the European XFEL, 05.-06.04.2017, Schenefeld, Deutschland

Publ.-Id: 25422 - Permalink


Ion acceleration in laser-driven plasmas
Metzkes, J.;
  • Invited lecture (Conferences)
    Arbeitstreffen Kernphysik 2017, 02.-09.03.2017, Schleching, Deutschland

Publ.-Id: 25421 - Permalink


Isolation of specific binding peptides for ionic species of nickel and cobalt using the phage surface display technique
Matys, S.; Schönberger, N.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.;
Since several years, the phage surface display technique has been successfully applied for the development of new receptor-ligand pairs for medical purposes, new pharmaceuticals or the elucidation of protein-protein interactions. A comparatively new methodological approach is the use of this technique for bioremediation. In the BMBF-funded German-French project "EcoMetals" we focused on novel innovative biological methods for the extraction of copper and accompanying elements from complex copper-containing ores or tailings. The selective separation of individual industrially relevant chemical elements from complex copper-containing leaching solutions represents a particular challenge. Where established chemical methods do not work due to low concentrations or complex composition of these solutions, selectively binding biological structures could become attractive. Up to now, metal-binding peptides are regarded as particularly promising candidates. We used for the isolation and characterization of nickel- and cobalt-specific peptides a bacteriophage library (Ph.D.C7C Phage Display Peptide Library Kit, New England Biolabs, Inc.) for targeted removal and enrichment of these elements from a complex leaching solution. In this library the minor coat protein pIII is genetically modified leading to the expression of 5 copies phage tail protein containing a foreign heptapeptide loop flanked by a disulfide bridge. From a pool of 109 different peptide motifs, 24 peptides for nickel and 19 peptides for cobalt were isolated in an iterative process, the so-called bio-panning. The binding strength of these phages was compared with the wildtype. Cross binding tests revealed for most of the nickel binding phages also binding capacities for cobalt and vice versa.
Keywords: phage surface display technique, bacteriophage, biosorption, Co- and Ni-ions, peptides
  • Poster
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Germany

Publ.-Id: 25420 - Permalink


Concepts for the development of new materials for biosorption processes
Matys, S.; Lederer, F.; Schönberger, N.; Braun, R.; Vogel, M.; Raff, J.; Jain, R.; Schrader, S.; Pollmann, K.;
Biosorption describes the capability of biomass or biomolecules to bind and concentrate metals via several functional groups. Different organisms and many biopolymers are already known for their potential to capture valuable or toxic metal ions from water streams. The directed engineering of microorganisms or biomolecules in order to modify their specificity and affinity provides a smart tool towards the development of new technologies for metal recovery in an energy and chemical-saving while environmentally friendly way. Biosorptive materials are not only attractive for bioremediation purposes, but also for the concentration and recovery of elements from recycling processes or mining waters. Currently, we are focusing on the development of new bio-sorbents based on self-assembling surface proteins (S-layers), siderophores or short peptides for the selective recovery of accompanying elements in complex copper leaching solutions, industry relevant or toxic metal ions from process water streams such as Ga or As and microparticles containing rare earth elements from compact fluorescent lamp powder. Thereby, specifically and selectively metal binding peptides for particulate materials as well as for ionic species could be identified from commercially available phage libraries using the phage surface display technique. Dependent on the length of the metal binding peptides these libraries contain a pool of phage with nearly 10^7 to 10^9 different genetically engineered peptide motifs presented at their surface. Within the French-German bilateral project “EcoMetals” with the aim of the development of innovative eco-efficient biohydrometallurgy processes for the recovery of strategic and rare metals from primary and secondary resources a phage library containing engineered heptamer peptides was used for screening of specific cobalt and nickel binding peptide motifs. In an iterative biopanning process 22 cobalt and 29 nickel binding peptide motifs could be identified. Comparative single clone binding tests were conducted to identify the strongest binding peptides. These peptides will be used as biological compounds in biosorptive composites for the specific recovery of metal ions from complex aqueous solutions. Cross binding tests revealed for most of the nickel binding phages also binding capacities for cobalt and vice versa. One which has been identified originally as the best cobalt binding phage clone showed a six times enhanced nickel binding capacity in comparison to the wild type phage, whereas the best nickel binding phage clone was able to bind eleven times more cobalt than the wild type.This contribution will give an insight into current research activities in our group focusing on the recently established phage surface display technique and discuss strategies for application directed upscaling.
Keywords: biosorption, metal recovery, phage display
  • Lecture (Conference)
    16ème édition du congrès de la Société Française de Génie des Procédés, 11.-13.07.2017, Nancy, Frankreich

Publ.-Id: 25419 - Permalink


S-layer proteins for optical bio-sensing purposes
Matys, S.; Lakatos, M.; Raff, J.; Vogel, M.; Pollmann, K.;
S-layer proteins appear to be suitable for wide variety of different technical applications due to their distinctive physico-chemical properties and their multifunctional importance.
Since several years the focus has been placed especially on their potential use for biosensor applications. There are many approaches under investigation to develop sensors that are highly specific and sensitive as well as robust, reliable and not expensive. Optical methods currently appear an attractive solution. Colloidal gold nanoparticle suspensions as sensory active systems, for instance, have been the subject of intensive investigations for many years. For the development of potential metal-selective biosensors two different approaches of gold nanoparticles based systems in combination with S-layer proteins are presented. Chemically pre-fabricated gold nanoparticles can be stabilized by various simple or more complex organic molecules such as S-layer proteins. Additionally to the stabilization, the S-layer can serve as capture structure for respective ionic analytes. The interaction of the analyte with the S-layer results in the agglomeration of the gold nanoparticles. Due to the plasmonic activities of the metal nanoparticles this can cause a color change of the solution, which can be detected colorimetrically. This sensor principle has been applied successfully for the detection of arsenic (V). Another promising approach is the use of S-layers as template structures for the production of highly fluorescent, size-controlled gold nanoclusters. These gold nanoclusters can be synthesized directly at the protein by a simple chemical reaction. In combination with the known S-layer-mediated selective and specific binding of ionic analytes, e.g. rare earth elements as surrogates/analogues for intrinsic protein bound Ca2+, a subsequent analyte-induced change in the fluorescence intensity of the gold nanoclusters might be used as sensory system for the detection of such strategic relevant elements.
Keywords: S-layer proteins, gold nanoparticles, bio-sensing
  • Lecture (Conference)
    XXVI International Materials Research Congress, 20.-25.08.2017, Cancun, Mexiko
  • Lecture (others)
    Workshop DNA Mitteldeutschland, 14.09.2017, Dresden, Deutschland

Publ.-Id: 25418 - Permalink


Application of the Mineral Liberation Analyzer in mineral processing
Hoang, D. H.; Leißner, T.; Sterbik, N.; Haser, S.; Rudolph, M.ORC; Peuker, U. A.
The Mineral Liberation Analyzer combines an Scanning Electron Microscope (SEM) and multiple Energy Dispersive X-ray detectors with automated quantitative mineralogy software. SEM-based automated mineralogy tools are essential in measuring parameters, such as modal mineralogy, mineral locking, mineral association, theoretical grade - recovery and mineral liberation. Such quantitative information are fundamental to investigate the mineralogical characteristics of an ore and evaluate its mineral processing.
A carbonaceous apatite ore sample from Lao Cai deposit, Vietnam was used in this study. The petrographic, mineralogical and mineral liberation observations showed that the ore sample is quite complex, containing carbonate impurities (dolomite and calcite) and having very fine intergrowth texture. The fine intergrowth in complex apatite ores requires very fine grinding for liberation in flotation.
Keywords: MLA, Flotation, Apatite, sedimentary ore, Calcite, Dolomite
  • Contribution to proceedings
    International Forum - Contest of Young Researches, Topical Issue of Rational Use of Natural Resources, 19.-21.04.2017, St. Petersburg, Russia
    International Forum - Contest of Young Researches, Topical Issue of Rational Use of Natural Resources, St. Petersburg, Russia: Gorny Institute, 978-5-94211-780-1, 170-173

Publ.-Id: 25417 - Permalink


Building a reference database for thermodynamic sorption modelling
Bok, F.; Richter, A.; Brendler, V.;
Any safety assessment of waste disposal concepts requires comprehensive and consistent thermodynamic data for the respective reactive transport modelling. This includes sorption, ion exchange or surface precipitation as major retardation processes. The current lack of respective quality-assured databases for these interface phenomena (invalid reaction formulation, missing consistency, restricted application ranges, and contradictory data) severely hampers a reliable modelling.
This work aims on a re-evaluation of already published sorption raw data based on spectroscopically verified surface complexes and their formation reactions. This shall help to transform the free-for-use digitized sorption data collection RES³T (http://www.hzdr.de/res3t) into a true thermodynamic reference database be used for complex real systems such as rocks or soils following the “Component Additivity” approach. Coupled to this is an extension of RES³T allowing also for the storage of sorption raw data sets. Eventually, a full integration with the thermodynamic reference database THEREDA (http://www.thereda.de) is envisaged to provide a comprehensive database for a holistic geochemical modeling.
Sorption speciation calculations of radionuclides on various mineral surfaces will be presented, showing the actual consequences of inconsistent sorption data that can be found in literature, as well as the possibilities using a validated surface speciation. The latter is mainly based on a combination of ATR FT-IR, TRLFS, and EXAFS which allows to create chemically realistic surface complexing models. In combination with the site-density data (including ones from crystallographic measurements), surface complexation models are deduced that describe the sorption of radionuclides accurately and with less surface species then assumed in a vast number of literature references published in the past. Due to the correct description of the realistic surface chemistry and the internal consistency, these models are more robust to other chemical and environmental conditions (pH, pe, composition of the aqueous phase).
As examples, the sorption of uranium(VI) onto various mineral phases (Al-, Fe- and Si-phases), ubiquitous in nature will be presented.
Keywords: THEREDA, Reference database, Sorption
  • Lecture (Conference)
    254th ACS National Meeting, 20.-24.08.2017, Washington, DC, USA

Publ.-Id: 25416 - Permalink


Parametric instability in periodically perturbed dynamos
Giesecke, A.; Stefani, F.; Herault, J.;
We examine kinematic dynamo action driven by an axisymmetric large scale flow that is superimposed with an azimuthally propagating non-axisymmetric perturbation with a frequency ω. Although we apply a rather simple large scale velocity field, our simulations exhibit a complex behavior with oscillating and azimuthally drifting eigenmodes as well as stationary regimes. Within these non-oscillating regimes we find parametric resonances characterized by a considerable enhancement of dynamo action and by a locking of the phase of the magnetic field to the pattern of the perturbation. We find an approximate fulfillment of the relationship between the resonant frequency ωres of the disturbed system and the eigenfrequency ω0 of the undisturbed system given by ωres = 2 ω0 which is known from paradigmatic rotating mechanical systems and our prior study [Giesecke et al., Phys. Rev. E, 86, 066303 (2012)]. We find further -- broader -- regimes with weaker enhancement of the growth rates but without phase locking. However, this amplification regime arises only in case of a basic (i.e. unperturbed) state consisting of several different eigenmodes with rather close growth rates. Qualitatively, these observations can be explained in terms of a simple low dimensional model for the magnetic field amplitude that is derived using Floquet theory.
Keywords: Dynamo Instability Parametric Resonance

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Publ.-Id: 25414 - Permalink


Molecular Doping of a High Mobility Diketopyrrolopyrrole- Dithienylthieno[3,2-b]thiophene Donor-Acceptor Copolymer with F6TCNNQ
Karpov, Y.; Erdmann, T.; Stamm, M.; Lappan, U.; Guskova, O.; Malanin, M.; Raguzin, I.; Beryozkina, T.; Bakulev, V.; Günther, F.; Gemming, S.; Seifert, G.; Hambsch, M.; Mannsfeld, S.; Voit, B.; Kiriy, A.;
Herein we present a molecular doping of a high mobility diketopyrrolopyrrole–dithienylthieno[3,2-b]thiophene donor–acceptor copolymer poly[3,6-(dithiophene-2-yl)-2,5-di(6-dodecyloctadecyl)pyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene], PDPP(6-DO)2TT, with the electron-deficient compound hexafluorotetracyanonaphthoquinodimethane (F6TCNNQ). Despite a slightly negative HOMO(donor)–LUMO(acceptor) offset of −0.12 eV which may suggest a reduced driving force for the charge transfer (CT), a partial charge CT was experimentally observed in PDPP(6-DO)2TT:F6TCNNQ by absorption, vibrational, and electron paramagnetic resonance spectroscopies and predicted by density functional theory calculations. Despite the modest CT, PDPP(6-DO)2TT:F6TCNNQ films possess unexpectedly high conductivities up to 2 S/cm (comparable with the conductivities of the benchmark doped polymer system P3HT:F4TCNQ having a large positive offset). The observation of the high conductivity in doped PDPP(6-DO)2TT films can be explained by a high hole mobility in PDPP(6-DO)2TT blends which compensates a lowered (relatively to P3HT:F4TCNQ) concentration of free charge carriers. We also show that F6TCNNQ-doped P3HT, the system which has not been reported so far to the best of our knowledge, exhibits a conductivity up to 7 S/cm, which exceeds the conductivity of the benchmark P3HT:F4TCNQ system.
Keywords: organic electronics, molecular doping, p-dopant, conjugated polymer, electrical conductivity, charge transfer complex

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Publ.-Id: 25413 - Permalink


Effect of Acid Washing on the Oxygen Reduction Reaction Activity of Pt-Cu Aerogel Catalysts
Henning, S.; Kühn, L.; Herranz, J.; Nachtegaal, M.; Hübner, R.; Werheid, M.; Eychmüller, A.; Schmidt, T. J.;
Developing highly active and durable oxygen reduction reaction (ORR) catalysts is crucial to reduce the cost of polymer electrolyte fuel cells (PEFCs). To meet those requirements, unsupported Pt-Cu alloy nanochains (aerogels) were synthesized by a simple co-reduction route in aqueous solution and their structure was characterized by X-ray absorption spectroscopy and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. These catalysts exceeded the ORR activity of commercial Pt/C catalysts by more than 100% in rotating disk electrode (RDE) experiments and met the corresponding US DOE target for automotive PEFC implementation, thereby qualifying as very promising materials. The behavior of Pt-Cu aerogels under PEFC operation conditions was mimicked by acid washing experiments which showed that the Cu content in the alloy phase and ORR activity decrease through this step. Comparing composition, structure and ORR activity for various specimens, the Cu content in the alloy phase was identified as the main descriptor of ORR activity. An almost linear correlation was found between those two parameters and complemented by supporting data from the literature.
Keywords: Aerogels; Dealloying; ORR; PEFC; X-ray absorption

Publ.-Id: 25412 - Permalink


Point defects in ZnO crystals grown by various techniques
Čížek, J.; Vlček, M.; Hruška, P.; Lukáč, F.; Melikhova, O.; Anwand, W.; Selim, F.; Hugenschmidt, C.; Egger, W.;
In the present work point defects in ZnO crystals were characterized by positron lifetime spectroscopy combined with back-diffusion measurement of slow positrons. Defects in ZnO crystals grown by various techniques were compared. Hydrothermally grown ZnO crystals contain defects characterized by lifetime of ≈181 ps. These defects were attributed to Zn vacancies associated with hydrogen. ZnO crystals prepared by other techniques (Bridgman, pressurized melt growth, and seeded chemical vapour transport) exhibit shorter lifetime of ≈165 ps. Positron back-diffusion studies revealed that hydrothermally grown ZnO crystals contain higher density of defects than the crystals grown by other techniques. The lowest concentration of defects was detected in the crystal grown by seeded chemical vapor transport.

Publ.-Id: 25411 - Permalink


Correlation of CT-based Imaging Features with Radiochemotherapy-induced Dysphagia and Xerostomia in Head and Neck Patients
Pilz, K.; Leger, S.; Zwanenburg, A.; Richter, C.; Krause, M.; Baumann, M.; Löck, S.; Troost, E.;
Purpose/Objective: Radiochemotherapy (RCT) for patients with head and neck squamous cell carcinoma (HNSCC) frequently causes xerostomia and dysphagia, which may be alleviated by treatment adaption, e.g., modulation of dose distribution to the salivary glands. Current clinical models, which are based on dosimetric parameters, mostly achieve moderate prediction accuracy. Therefore, we aimed to improve the prediction of xerostomia and dysphagia by using additional imaging biomarkers based on computed tomography (CT) scans.

Material/Methods: In this study 46 patients with UICC stage III/IV advanced head and neck squamous cell carcinoma (HNSCC) were considered (NCT00180180, [1]). All patients received primary RCT and underwent a pre-treatment CT scan without intravenous contrast agent. Patient-reported xerostomia and dysphagia were evaluated at baseline, every week during RCT, four weeks after treatment and three monthly thereafter. 5040 imaging features were extracted from the parotid and submandibular glands. Feature reproducibility tests based on the RIDER re-test data set [2] were performed leading to 1513 imaging features in total. The most informative features were selected by a univariate logistic regression analysis. The developed radiomic signature was used to train and validate multivariate logistic regression and random forest models using repeated 5-fold cross validation. The predication accuracy was assessed by the area under the curve (AUC).

Results: The logistic regression and the random forest model achieved similar performance in predicting xerostomia (AUC=0.71). The developed signature consisted of one dosimetric parameter and one imaging feature. For the prediction of dysphagia both models achieved only a moderate prediction accuracy (AUC=0.55).

Conclusions: For prediction of xerostomia, a signature was developed and showed a good performance. For dysphagia only moderately performing models could be obtained in this cohort. Based on our results, subgroups of patients at a high risk of xerostomia may be identified and offered treatment adaption. However, further investigations are currently ongoing, i.e., externally validating the developed signature, which is an important step in developing clinically relevant prediction models.
  • Poster
    ESTRO 36, 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 123(2017), S585-S586
    DOI: 10.1016/S0167-8140(17)31501-3

Publ.-Id: 25410 - Permalink


Magnetic properties of a Ho2Fe14Si3 single crystal
Andreev, A. V.; Gorbunov, D. I.; Skourski, Y.; Kuz'Min, M. D.; Tereshina, E. A.; Henriques, M. S.;
Magnetization of a Ho2Fe14Si3 single crystal was measured in a steady magnetic field of up to 9 T and in pulsed fields of up to 60 T applied along the principal axes. Ho2Fe14Si3 is a ferrimagnet below TC = 480 K, has a spontaneous magnetic moment of about 8 µB/f.u. (at T = 4.2 K) and exhibits a large easy-plane magnetic anisotropy. There is also a certain anisotropy within the basal plane, the b axis [120] being the easy-magnetization direction. In fields applied along the a and b axes field-induced first-order phase transitions are observed at 29 T and at 22 T, respectively. Along the easy axis b we observe also an S-shaped anomaly at about 47 T, which does not correspond to a phase transition. A simple model predicts that the two observed first-order transitions are the only ones taking place in Ho2Fe14Si3; the magnetization should subsequently grow continuously and arrive at saturation at ~100 T. This is in stark contrast to the behavior of the parent compound Ho2Fe17, where as many as three sequential first-order transitions are expected for H‖b. The reason for the disparity is that the basal-plane anisotropy constant KHo is at least one order of magnitude smaller in Ho2Fe14Si3 than it is in Ho2Fe17.

Publ.-Id: 25409 - Permalink


Deep sub-threshold φ production and implications for the K+/K- freeze-out in Au+Au collisions
Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcy, G.; Kornakov, G.; Kotte, R.; Kühn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K. N.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.;
We present first data on charged kaons and phi mesons in Au+Au collisions at a kinetic beam energy of 1.23A GeV. As observed already at slightly higher beam energies, we find significantly different slopes for the K+ and K- transverse-mass spectra, and no significant increase of the the K-/K+ multiplicity ratio with increasing centrality of the collision. The {\phi}/K- multiplicity ratio is found to be surprisingly high with a value of 0.52 ± 0.16 and shows no dependence on the centrality, either. The different slopes of the K+ and K- spectra can be explained by feed-down from phi mesons, which substantially softens the spectra of K- mesons.

Publ.-Id: 25408 - Permalink


Thoracic tumor treatment course assessment based on 4D dose accumulation for scanned proton therapy
Meijers, A.; Richter, C.; Dessy, F.; Widder, J.; Korevaar, E.; Jakobi, A.; Ribeiro, C.; Langendijk, J.; Knopf, A.;
Purpose or Objective
With the increase of proton therapy facilities worldwide featuring Pencil Beam Scanning (PBS) as their only treatment modality, PBS is on the way of becoming the standard for proton therapy. However, for some indications in the thoracic region PBS is not widely used due to uncertainties in the planned dose, which can be caused by combined effects of setup errors, range uncertainty, interplay effect, breathing irregularity, anatomical variations, delivery machine uncertainties, etc. By performing pre-treatment plan robustness evaluation that includes these effects, it is evident that actual delivered fractional dose at any instance is highly uncertain to predict. 4D dose accumulation is able to control some of the uncertainties that are affecting pretreatment evaluation of the plan quality. Therefore, the purpose of this proof-of-concept study is to investigate the
feasibility of monitoring and assessing the quality of delivered treatment fractions throughout the treatment course.

Material and Methods
4D dose accumulation is performed by utilizing (1) delivery machine log files (IBA, Belgium), (2) breathing pattern records (ANZAI, Japan) and (3) planning 4DCT scans or repeated 4D control CT scans (Siemens, Germany). Dose computation is performed in the RayStation (RaySearch, Sweden) treatment planning system (TPS). For every spot that is delivered during a particular fraction, the spot energy, position, dose (as charge) and absolute time of delivery is retrieved from the machine
log file using a dedicated script. Patient’s breathing pattern is analyzed and inhale peaks are determined. Subsequently, all breathing cycles are divided in 10 phases and each phase is associated with absolute time. PBS spots are split in 10 groups according to their corresponding phase and written to 10 treatment sub-plans (DICOM), where every sub-plan corresponds to a particular phase of the 4DCT. Using scripting capabilities of the TPS, sub-plans are imported for dose computation. Eventually dose warping to the reference phase is performed to estimate the delivered fractional dose. Data sets used for the proof-of-concept were not collected during the same treatment fraction.

Results
By using the described method the timeline of a PBS delivery can be correlated with patient’s breathing pattern as shown in Figure 1. Computation of log based sub-plans on 4DCT results in an accumulated fractional 4D dose distribution as shown in Figure 2. Based on the exemplary case, the method allows to assess the conformity between planned and delivered doses (i.e.,
CTV V95 has dropped to 96.7% from nominal 100%).

Conclusion
The availability of a real-time 4D dose accumulation based treatment assessment tool allows to assess the quality of the delivered dose during progress of the treatment course and to take appropriate actions, as for example, plan adaptation, in cases of significant deviations. It is foreseen to extend this study for a full treatment course of a broader population of patients.
  • Lecture (Conference)
    ESTRO 36, 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 123(2017)Suppl 1, S259-S259
    DOI: 10.1016/S0167-8140(17)30928-3

Publ.-Id: 25407 - Permalink


Sensitivity evaluation of prompt γ-ray based range verification with a slit camera
Nenoff, L.; Priegnitz, M.; Trezza, A.; Smeets, J.; Janssens, G.; Vander Stappen, F.; Hotoiu, L.; Prieels, D.; Enghardt, W.; Pausch, G.; Richter, C.;
Purpose
The dose distribution and range of proton beams are exceedingly prone to uncertainties and anatomical changes, demanding for an in-vivo range verification. A promising approach is prompt γ-ray imaging (PGI), which was recently implemented clinically in Dresden using a so-called PGI slit camera [1,2] in double scattering (DS). However, the detectability of local range shifts, affecting only part of the lateral field in DS, is limited. The spot-wise dose deposition in pencil beam scanning (PBS) promises a finer spatial resolution of range shifts. The purpose of this study is to comprehensively investigate the sensitivity to detect range shifts in DS and PBS using a head phantom in a clinical setup.

Materials and Methods
For a realistic brain tumor treatment, treatment plans in DS and PBS (2 beams, 60 GyE,
2 GyE/fx), were created. One beam (1 GyE) was applied to a CIRS head phantom and monitored with the PGI slit camera. To investigate the influence of the spot dose, the same beam with 5 GyE was also delivered and measured. Global and local (5 cm in diameter) range shifts were introduced and the PGI profiles (prompt-γ counts over depth) with and without shifts were compared. Sum profiles containing prompt-γ counts over the entire fraction were used for the comparison of DS and PBS. Moreover, PGI profiles measured in PBS were analyzed spot-wise and will also be compared with simulated profiles for absolute range determination.

Results
A good agreement between introduced and measured global shifts was found in the sum profile evaluation for both modalities, PBS and DS (Table 1). Relative differences were below 2, 7 and 12 % for the 10, 7 and 4 mm shifts, respectively. Local shifts are not detectable using sum profiles. For the applied local shifts, a spot-wise comparison of PGI profiles in PBS allows the detection and localization of global and local shifts (Figure 1). For interpretation, neighboured spots should be clustered, as shifts detected for single spots are less reliable due to low statistics. Higher doses (5 vs. 1 GyE) allow the detection of smaller shifts as shown in Figure 1 for the 4 mm local shift.

Conclusion
The systematic sensitivity study revealed the capability of the PGI slit camera to detect range shifts under clinical conditions. In both treatment modalities, global range shifts can be detected. Additionally, in PBS a spot-wise comparison allows also the determination of interfractional local range shifts. Moreover, a still ongoing evaluation of PBS measured and simulated spot-wise profiles for absolute range verification will be presented.
  • Lecture (Conference)
    ESTRO 36, 05.-09.05.2017, Wien, Österreich
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 123(2017)Suppl 1, S76-S77
    DOI: 10.1016/S0167-8140(17)30596-0

Publ.-Id: 25406 - Permalink


Experiments on counter-current flow limitation in a PWR hot leg model
Lucas, D.; Beyer, M.; Pietruske, H.; Szalinski, L.;
Counter-Current Flow Limitation (CCFL) is of importance for PWR safety analyses in several accident scenarios connected with loss of coolant events. To investigate the characteristics of this phenomenon and to establish a database suitable for CFD-model development and validation a 1:3 scaled flat model of a German Konvoi reactor hot leg including a part of the steam generator inlet chamber was built up. The test section was operated in the TOPFLOW pressure chamber to allow optical observation of steam-water flows at pressure levels up to 50 bars. The test series comprises air-water tests at 1 and 2 bar as well as steam-water tests at 10, 25 and 50 bar. The gas was injected from the tank simulating the reactor vessel while the water enters into the steam generator (SG) separator tank. A steel sheet divides the SG separator tank in two parts. The first one serves as completion of the SG inlet chamber from the water side and the second is necessary to keep the level in the first part constant, using the steel sheet as level drain. This allows to investigate CCFL under steady state conditions. During the experiments the flow structure was observed along the hot leg model using a high-speed camera and web-cams. In addition pressure was measured at several positions along the horizontal part and the water levels in the reactor simulator and steam generator simulator tanks were determined. From the measurements flooding curves basing on the Wallis parameters for gas and liquid were obtained. The results show a slight shift of the curves in dependency on pressure. In addition a slight decrease of the slope was found with increasing pressure. Additional investigations on the frequencies of liquid slugs were done.
Keywords: two-phase flow, counter-current flow limitation, flooding, experiment, hot leg
  • Contribution to proceedings
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China
  • Lecture (Conference)
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi'an, China

Publ.-Id: 25405 - Permalink


Counter-current flow limitation for air-water and steam-water flows in a PWR-relevant geometry
Lucas, D.; Beyer, M.; Pietruske, H.; Szalinski, L.;
Steady state counter-current flow limitation (CCFL) experiments were conducted in a 1:3 scaled flat model of the hot leg and part of the steam generator inlet chamber of a German Konvoi pressurized water reactor. The experiments include air-water tests at 1 and 2 bar as well as steam-water tests at 10, 25 and 50 bar. Flooding characteristics are obtained in dependency on the dimensionless gas and liquid flow rates (Wallis-parameter). They should a slight, but clear dependency on pressure – with increasing pressure more liquid can flow in counter-current to the gas in case of partial CCFL. Also the dimensionless gas flow rate for zero penetration slightly increases with pressure. Beside the flooding characteristics also slug frequencies were analyses basing on pressure measurements along the horizontal part of the test section. Finally, comprehensive video material was obtained which is suited for extracting quantitative data on the local flow structure. This can contribute to the further CFD-code development and validation.
Keywords: two-phase flow, counter-current flow limitation, flooding, experiment, PWR hot leg

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Publ.-Id: 25404 - Permalink


On the Scalability of Data Reduction Techniques in Current and Upcoming HPC Systems from an Application Perspective
Huebl, A.ORC; Widera, R.ORC; Schmitt, F.; Matthes, A.ORC; Podhorszki, N.ORC; Choi, J. Y.; Klasky, S.; Bussmann, M.ORC
We implement and benchmark parallel I/O methods for the fully-manycore driven particle-in-cell code PIConGPU. Identifying throughput and overall I/O size as a major challenge for applications on today's and future HPC systems, we present a scaling law characterizing performance bottlenecks in state-of-the-art approaches for data reduction. Consequently, we propose, implement and verify multi-threaded data-transformations for the I/O library ADIOS as a feasible way to trade underutilized host-side compute potential on heterogeneous systems for reduced I/O latency.
Keywords: I/O HPC data reduction compression scalability PIConGPU manycore
  • Contribution to proceedings
    The 1st International Workshop on Data Reduction for Big Scientific Data (DRBSD-1) co-located with ISC High Performance, 18.-22.06.2017, Frankfurt, Deutschland
    High Performance Computing, Vol. 10524, 15-19
    DOI: 10.1007/978-3-319-67630-2_2
  • Lecture (Conference)
    The 1st International Workshop on Data Reduction for Big Scientific Data (DRBSD-1) co-located with ISC High Performance, 18.-22.06.2017, Frankfurt, Deutschland

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Publ.-Id: 25403 - Permalink


Digitalizing the Circular Economy: Opportunities and Limits
Reuter, M. A.;
With own practical examples e.g. linking the product design of LED lamps and screens, mobile phones to metallurgy Markus Reuter will illustrate the opportunities and limitations of reaching a CE. The keynote will show simulation based design for recycling tools, developed by the author and colleague through his many years of industry and academia experience.
  • Invited lecture (Conferences)
    REthink / AVP Circular Economy Startup Week, 08.03.2017, Aalto, Finnland
  • Invited lecture (Conferences)
    Stakeholder Meeting #2, 27.03.2017, Aalto, Finnland

Publ.-Id: 25402 - Permalink


Source term and activation analysis for the new cyclotron for medical applications at HZDR with MCNP6 and FLUKA
Müller, S. E.ORC; Konheiser, J.; Naumann, B.; Ferrari, A.; Magin, A.
A new cyclotron is currently being commissioned at the Center of Radiopharmaceutical Cancer Research of the HZDR. The energy range of up to 28 MeV protons for the 18O(p,n)18F reaction required a recalculation of the neutron source terms needed in the shielding calculations, since the manufacturer supplied data was based on a 24 MeV proton beam. The radiation transport programs MCNP6 and FLUKA were used to calculate the neutron fluence emerging from the 18O-enriched water target during operation. Both Monte Carlo programs agree within 20 % on the neutron yield per incident proton for 24 and 28 MeV proton beams, while at 24 MeV, the manufacturer supplied data is considerably lower than the simulation results. To validate the radiation fields obtained in the simulations, an experimental program has been started using activation samples which are placed close to the water target of the cyclotron which is currently used to produce 18F. After irradiation, the samples are analyzed, and the resulting activation is compared to Monte Carlo calculations of the expected sample activation.
  • Lecture (Conference)
    DPG Spring Meeting 2017, 27.-31.03.2017, Münster, Germany

Publ.-Id: 25401 - Permalink


Systeminnovationen für die Zukunft der Kreislaufwirtschaft
Reuter, M. A.;
Mitteldeutscher Kreislaufwirtschaftstag
Der „Mitteldeutsche Kreislaufwirtschaftstag“ wird erstmals Elemente des Sächsischen Kreislaufwirtschaftstages und des Mitteldeutschen Entsorgungsforums zu einem neuen Fachforum vereinen. Während der eintägigen Veranstaltung wird der Status Quo der Branche in acht Vorträgen beleuchtet. Einige der Schwerpunkte sind aktuelle Entwicklungen in der europäischen und deutschen Kreislaufwirtschaftspolitik, Perspektiven für die private Entsorgungswirtschaft, Systeminnovationen, praktische Fragen zur effektiven Verwertung biogener oder mineralischer Abfälle sowie Best-Practice-Beispiele für ein abfallwirtschaftliches Behördenengineering. Zu den Referenten gehören Dr. Helge Wendenburg vom Bundesministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit, Peter Kurth vom BDE Bundesverband der Deutschen Entsorgungs-, Wasser- und Rohstoffwirtschaft, Prof. Markus Reuter vom Helmholtz-Institut für Ressourcentechnologie in Freiberg, Michael Heide von der Bundesgütegemeinschaft Recycling-Baustoffe und Dr. Hubert Seier von der DSC GmbH.
Keywords: Circular Economy, Fairphone Recyclability
  • Invited lecture (Conferences)
    Mitteldeutscher Kreislaufwirtschaftstag / terratec (Fachmesse für Entsorgung, Kreislauf- und Ressourcenwirtschaft), 05.-07.04.2017, Leipzig, Deutschland

Publ.-Id: 25400 - Permalink


Rückhaltung von U(VI) und Eu(III) an Ca-Bentonit und CSH-Phasen unter hoch salinaren und alkalischen Bedingungen
Wolter, J.-M.; Philipp, T.; Lippold, H.; Schmeide, K.; Stumpf, T.;
Leaching experiments of uranium(VI) doped calcium-silicate-hydrate (CSH) phases with various calcium to silicon ratios were carried out in NaCl, NaCl/Na2SO4, NaCl/NaHCO3 and NaHCO3 containing solutions to study the time-dependent release of Ca, Si and U. Potential changes of the U(VI)-CSH binding induced by leaching were monitored with time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD).
  • Lecture (others)
    4. Workshop des BMWi-Verbundvorhabens “Geochemische Radionuklidrückhaltung an Zementalterationsphasen (GRaZ)“, 05.-06.04.2017, Mainz, Deutschland

Publ.-Id: 25399 - Permalink


Expression of ecto-nucleoside triphosphate diphosphohydrolases-2 and -3 by the enteric nervous system impacts inflammation in experimental colitis and Crohn’s disease
Feldbrügge, L.; Moss, A. C.; Yee, E. U.; Csizmadia, E.; Mitsuhashi, S.; Longhi, M. S.; Stephan, H.ORC; Wu, Y.; Cheifetz, A. S.; Müller, C. E.; Sevigny, J.; Robson, S. C.; Jiang, Z. G.
Abstract
Background & Aims: Recent studies have suggested that the enteric nervous system can modulate gut immunity. Ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) of the CD39 family regulate purinergic signaling by sequential phosphohydrolysis of extracellular ATP, a pro-inflammatory signaling molecule. Herein, we test the hypothesis that E-NTPDases modulate neuro-immune crosstalk in gut inflammation.
Methods: We determined expression patterns of NTPDase-2 and NTPDase-3 in murine and human colon. Experimental colitis was induced by dextran sodium sulfate (DSS) in mice deficient in NTPDase-2 or NTPDase-3. We compared plasma ADPase activity from Crohn’s patients to healthy controls, and correlated levels of ADPase activity with Crohn’s disease activity.
Results: NTPDase-2 and 3 were mainly expressed in cells of the enteric nervous system in both murine and human colon. When compared to wild type, DSS-induced colitis was exacerbated in NTPDase-2 null mice, as measured by both clinical disease activity and histology, while NTPDase-3 null mice merely developed more severe anemia. Colonic macrophages isolated from NTPDase-2 null mice displayed a more pro-inflammatory phenotype compared to wild type. Crohn’s patients had decreased plasma ADPase activity when compared to healthy controls. The enzyme activity sensitive to an inhibitor against NTPDase-2 and NTPDase-3 showed the most striking difference and was inversely correlated with Crohn’s disease activity.
Conclusions: NTPDase-2 and 3 are ecto-enzymes expressed in the enteric nervous system in both murine and human colon, and are protective against gut inflammation in experimental colitis and exhibit alterations in human Crohn’s disease. These observations suggest that purinergic signaling modulated by non-CD39 NTPDases governs neuro-immune interactions that are relevant in Crohn’s disease.
Keywords: Crohn’s disease, ectonucleotidase, CD39, NTPDase-2 (CD39L1), NTPDase-3 (CD39L3)

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Publ.-Id: 25398 - Permalink


Speciation of uranium(VI) in the presence of cellulose degradation products
Brinkmann, H.; Moll, H.;
Low and intermediate level waste contain cellulosic material in considerable amounts. In a repository nuclear waste is often surrounded by cementitious backfill material. If water ingresses a hyperalkaline environment will be established. Since cellulose will be relatively fast degraded under alkaline conditions, there is a high risk that small organic, water soluble molecules will be formed. These molecules can act as complexing agents for radionuclides and thereby affecting their sorption behavior and solubility adversely. Therefore the focus of current investigations is on the interaction of uranium (VI) with Isosaccharinic acid (ISA) as main degradation product of cellulose first in the acidic pH range. The progress and results of these studies within the MIND project (work package 1) will be presented.
Keywords: Cellulose, Isosaccharinic acid, Uranium, Speciation
  • Lecture (others)
    MIND Project Annual Meeting 2017, 03.-05.05.2017, Prague, Czech Republic

Publ.-Id: 25397 - Permalink


The redistribution of platinum-group elements and platinum-group minerals in the weathered chromitites of the Lower and Middle Group chromitites of the Bushveld Complex and the mineralogical siting of Ru
Junge, M.; Bachmann, K.; Kotzé, E.; Oeser-Rabe, M.;
The chromitite seams of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa contain elevated Pt and Pd concentrations. So far, only limited work has been done on the distribution of platinum-group elements (PGE) and platinum-group minerals (PGM) in these ores. In particular, the knowledge about the effects of weathering of PGM and the redistribution of PGE in these ores are rare. Previous studies showed that the main PGM are PGE-sulfides (cooperite-braggite, malanite, laurite), followed by PGE-sulfarsenides, sperrylite and Pt-Fe alloys. During weathering PGM are largely destroyed and only relict PGM are observed. Platinum-group minerals are weathered along small cracks and neo-formation of PGM may take place. Additionally, the mineralogical siting of Ru within chromitites is studied here. It was shown by LA-ICP-MS work that chromite can host some 100s-ppb of Ru.
  • Contribution to proceedings
    14th Biennial SGA Meeting, 20.-23.08.2017, Québec City, Canada
    SGA Québec 2017 Mineral Resources to Discover

Publ.-Id: 25396 - Permalink


Synthesis and in vitro evaluation of 5-substituted benzovesamicol analogs containing N-substituted amides as potential positron emission tomography tracers for the vesicular acetylcholine transporter
Roslin, S.; de Rosa, M.; Deuther-Conrad, W.; Eriksson, J.; Odell, L. R.; Antoni, G.; Brust, P.; Larhed, M.;
Herein, new ligands for the vesicular acetylcholine transporter (VAChT), based on a benzovesamicol scaffold, are presented. VAChT is acknowledged as a marker for cholinergic neurons and a positron emission tomography tracer for VAChT could serve as a tool for quantitative analysis of cholinergic neuronal density. With an easily accessible triflate precursor, aminocarbonylations were utilized to evaluate the chemical space around the C5 position on the tetrahydronaphthol ring. Synthesized ligands were evaluated for their affinity and selectivity for VAChT. Small, preferably aromatic, N-substituents proved to be more potent than larger substituents. Of the fifteen compounds synthesized, benzyl derivatives (±)-7i and (±)-7l had the highest affinities for VAChT. Compound (±)-7i was chosen to investigate the importance of stereochemistry for binding to VAChT and selectivity toward the σ1 and σ2 receptors. Enantiomeric resolution gave (+)-7i and (-)-7i, and the eutomer showed seven times better affinity. Although racemate (±)-7i was initially promising, the affinity of (-)-7i for VAChT was not better than 56.7nM which precludes further preclinical evaluation. However, the nanomolar binding together with the ready synthesis of [11C]-(±)-7i shows that (-)-7i can serve as a scaffold for future optimizations to provide improved 11C-labelled VAChT PET tracers.
Keywords: Vesicular acetylcholine transporter VAChT PET tracer Aminocarbonylation 11C-labeling

Publ.-Id: 25395 - Permalink


Evaluation of hemodynamic impairments in unilateral high-grade carotid artery stenosis patients and healthy age-matched participants
Kaczmarz, S.; Göttler, J.; Griese, V.; Petr, J.ORC; Zimmer, C.; Sorg, C.; Preibisch, C.
Objectives:
Internal carotid-artery stenosis (ICAS) is a major public health issue, as it accounts for approximately 20% of all strokes1. However, related complex hemodynamic impairments are not well understood2. We therefore propose a multimodal MRI-protocol. The major aims were to evaluate its reliability and investigate physiological changes.
Methods:
In the ongoing clinical study, 52 subjects (29 healthy controls: 70.3±4.7y, 13 males; 23 patients with asymptomatic unilateral ICAS, NASCET>70%: 70.5±6.8y, 15 males) underwent MRI on a Philips 3T-Ingenia. We propose a combination of three different MR-based methods, accounting for cerebrovascular reactivity (CVR) by breathhold-fMRI (voxelsize 3x3x3mm3, 38 slices, TE/TR=30ms/1200ms, acq.time=5:48min), CBF by pCASL (3D-readout, voxelsize 2.7x2.8x6mm3, 16 slices, TE/TR=7.4ms/4403ms, label duration=1800ms, PLD=2000ms, acq.time 5:43min) and relative oxygen extraction fraction (rOEF) by a multi-parametric quantitative-BOLD approach3 (voxelsize 2x2x3mm3, 30 slices). For each participant, individual masks of watershed areas were defined for both hemispheres in grey-matter and mean values of all three modalities were compared.
Results:
In healthy participants, our results show no significant lateralization of all three modalities on a group level. For ICAS-patients, regionally reduced CVR (p=0.003) as well as hypoperfusion (p< 0.001) were found ipsilateral to the stenosis (figure). In accordance with the literature, we did not find ICAS-induced changes in oxygen extraction on a group level (p=0.310).4 Even though focal rOEF increases could be suspected in single patients.
Conclusions:
The presented preliminary results thus imply successful application of our multimodal-MRI approach and are highly promising with respect to gaining a deeper insight into ICAS-related physiological changes. Further investigations of the relations between the parameters are currently in progress.
  • Open Access LogoContribution to proceedings
    28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 01.04.2017, Berlin, Germany
    Proceedings of the 28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 498
  • Poster
    28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 01.04.2017, Berlin, Germany

Publ.-Id: 25394 - Permalink


The Common Data Acquisition Platform in the Helmholtz Association
Kaever, P.; Balzer, M.; Kopmann, A.; Zimmer, M.; Rongen, H.;
Various centres of the German Helmholtz Association (HGF) started in 2012 to develop a modular data acquisition (DAQ) platform, covering the entire range from detector readout to data transfer into parallel computing environments. This platform integrates generic hardware components like the multi-purpose HGF-Advanced Mezzanine Card or a smart scientific camera framework, adding user value with Linux drivers and board support packages. Technically the scope comprises the DAQ-chain from FPGA-modules to computing servers, notably frontend-electronics-interfaces, microcontrollers and GPUs with their software plus high-performance data transmission links. The core idea is a generic and component-based approach, enabling the implementation of specific experiment requirements with low effort. This so called DTS-platform will support standards like MTCA.4 in hard- and software to ensure compatibility with commercial components. Its capability to deploy on other crate standards or FPGA-boards with PCI express or Ethernet interfaces remains an essential feature. Competences of the participating centres are coordinated in order to provide a solid technological basis for both research topics in the Helmholtz Programme "Matter and Technology", "Detector Technology and Systems" and "Accelerator Research and Development". The DTS-platform aims at reducing costs and development time and will ensure access to latest technologies for the collaboration. Due to its flexible approach, it has the potential to be applied in other scientific programs.
Keywords: Data acquisition concepts; Software architectures (event data models, frameworks and databases); Detector control systems (detector and experiment monitoring and slow-control systems, architecture, hardware, algorithms, databases); Image reconstruction in medical imaging
  • Contribution to proceedings
    Topical Workshop on Electronics for Particle Physics (TWEPP2016), 26.-30.09.2016, Karlsruhe, Deutschland
    Journal of Instrumentation 12(2017),C04004: IOPscience
    DOI: 10.1088/1748-0221/12/04/C04004

Publ.-Id: 25393 - Permalink


Electronic Structure Simulation of Thin Silicon Layers: Impact of Orientation, Confinement, and Strain
Joseph, T.; Fuchs, F.; Schuster, J.; Schulz, S. E.;
Fully Depleted Silicon on Insulator transistors (FDSOI) are a promising approach for further scaling. The device features a fully depleted body which is isolated by an insulator box. This introduces better electrostatics, lower leakage current and thus better channel control. The device performance is heavily influenced by the orientation, confinement and strain in the ultra-thin body. In this work the electronic structure of ultra-thin silicon layers is investigated using Density Functional Theory (DFT). The simulation parameters for the model system were calibrated to reproduce the experimental band gap of bulk silicon. This ensures that the model describes the electronic structure of ultra-thin silicon layers accurately. Our study demonstrates the impact of confinement, orientation and strain on material dependent transport properties and their influence on the device performance. For this purpose our results will be used as an input for device simulations using Synopsys Sentaurus TCAD.
We find that the band gap of the silicon layer increases with decreasing slab thickness which is a clear indication of quantum confinement. From the simulation, the band gap for the {100} confinement is found to be higher than {110} and {111} scenarios. Band gap is one of the factors which influence the intrinsic carrier in the semiconductor and thereby the transport. Another important factor for the transport is lattice strain. Strain is a useful method for modulating band structures. One good example is the transformation of direct band gap in {100} confined silicon slab to indirect band gap with 2 % biaxial compression. In our presentation we will discuss the influence of the effective mass as well. Furthermore, the strain dependence of the electronic structure and its impact on device properties is analyzed systematically.
Keywords: silicon, confinement, density functional theory, FDSOI, strain engineering
  • Poster
    Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland

Publ.-Id: 25392 - Permalink


Simulation of Reconfigurable Field-effect Transistors: Impact of the NiSi2-Si Interfaces, Crystal Orientation, and Strain
Fuchs, F.; Schuster, J.; Gemming, S.;
Reconfigurable transistors (RFETs) can be switched between electron and hole current by changing the polarity of the gate potential. This allows a much higher functionality and hence, logic operations can be realized with fewer transistors. The device performance of such a transistor is strongly dominated by the contact physics.
In this work, the electron transport across the NiSi 2 -Si interface is studied using the NEGF formalism and density functional theory, which allows us to consider the atomic structure of the interface. A new model is then presented which relates the electron transport through the interface to the transfer characteristic of an RFET. The model is compared to experimental data, which shows very good agreement, especially with respect to the ratio between electron and hole current (left figure).
Based on the model, different structure variations at the interface and their consequences on the device performance are discussed. It is demonstrated that best symmetry between electron and hole current is achieved for the <110> crystal orientation, which is much worse for <100> orientation (right figure). This makes the <110> orientation advantageous for RFETs. Also the influence of strain generated parallel to the interface plane is investigated (right figure). It is shown that strain can be used to tune the symmetry in case of <110> crystal orientation even further. This is entirely different for the <100> crystal orientation, where the highest electron currents are observed for all strain states. In this state, the electron currents are about three orders of magnitude higher than the hole currents. A detailed discussion of these differences based on work function and band structure analysis will be given in our contribution.
Keywords: reconfigurable transistor, RFET, density functional theory, metal-semiconductor interface
  • Lecture (Conference)
    Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland

Publ.-Id: 25391 - Permalink


NiSi2-Si interfaces as building blocks for reconfigurable field-effect transistors: from the atomic structure to device characteristics
Fuchs, F.; Schuster, J.; Gemming, S.;
The electron transport across metal-semiconductor interfaces is crucial for the functionality of reconfigurable field-effect transistors, which can be switched between electron and hole current. Devices were already fabricated experimentally, however, a profound understanding of the underlaying mechanism is not yet available.
This study focuses on the NiSi2-Si interface, which is studied using the NEGF formalism. Based on the calculated transmission spectra, the transfer characteristic of a reconfigurable transistor is obtained using a simplified approach. Even though this model strongly simplifies the electrostatic environment in a transistor, very good agreement with experimental devices is demonstrated. The impact of strain on the device characteristic is studied as well. It is shown that the magnitude of electron and hole current can be altered successfully. They can also be tuned to be symmetric, which fits to experimental observations. Finally, new insight into the device functionality is gained based on our calculations of the work functions and effective masses of the isolated NiSi 2 and Si.
Keywords: reconfigurable transistor, RFET, density functional theory, metal-semiconductor interface
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Publ.-Id: 25390 - Permalink


Phage display – a new tool for the recovery of valuable metals from primary and secondary resources
Matys, S.; Lederer, F.; Schönberger, N.; Braun, R.; Lehmann, F.; Flemming, K.; Bachmann, S.; Curtis, S.; Macgillivray, R.; Pollmann, K.;
The development of effective and ecofriendly processes for the recovery of critical elements poses a challenge for scientists all over the world. A novel approach is the generation of highly specific peptides that bind with high affinity to individual elements of interest. The peptides are selected by phage surface display (PSD) technology. In this study PSD technology has been applied in two different approaches. The focus of the first approach was the identification of peptides that bind specifically to special particles of interest that are part of electronic scrap aiming towards the development of new recycling processes. In the second approach metal ion binding peptides were isolated via PSD to use them for the targeted removal and enrichment of these elements from complex leaching solutions or from industrial waters. To address the economic production of peptides, the development of a new expression system is also part of this study.
Keywords: bacteriophage, biosorption, bioflotation, fluorescent phosphors, Ga-, Co-, Ni-ions, heterologous peptide expression
  • Open Access LogoSolid State Phenomena 262(2017), 443-446
    DOI: 10.4028/www.scientific.net/SSP.262.443
  • Lecture (Conference)
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland

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Publ.-Id: 25389 - Permalink


PET imaging of α7 nicotinic acetylcholine receptors in a heterotopic xenograft model of brain cancer
Deuther-Conrad, W.; Neuber, C.; Teodoro, R.; Kranz, M.; Belter, B.; Peters, D.; Pietzsch, J.; Brust, P.;
Objectives
Molecular imaging by means of PET supports both the molecular profiling of tumors and the validation of corresponding targeted therapies in cancer treatment. The intracellular pathways triggered by nicotinic acetylcholine receptors (nAChR) mediate carcinogenic effects related to tobacco-derived compounds as well as autocrine and paracrine stimulation. In particular the α7 nAChR is of significance for the pathogenesis of cancers and may have potential for novel therapeutic concepts. Accordingly, we investigated with the in-house developed α7 nAChR-specific radioligand [18F]NS10743 the expression of α7 nAChR in the heterotopic U87-MG xenograft mouse model of glioblastoma.
Methods
Subcutaneous U87-MG tumor xenografts were generated in female NMRI nu/nu mice. [18F]NS10743 was obtained by automated radiosynthesis [1]. All animals were scanned in a nanoScan® PET/MRI system for 60 min post injection of [18F]NS10743 under control (n=5) and blocking (n=4) conditions (2 mg/kg NS6740 i.p. 15 min before the radioligand) on two consecutive days. Volumes of interest (VOI) were identified from the co-registered MR images (brain, tumor, and muscle) or from the first frame of the PET images (vena cava). Data analysis was based on the calculation of standardized uptake values (SUVs) and the shape of the time-activity curves (TACs). Intratumoral heterogeneity has been addressed by an additional VOI using a 75%-SUVmax isocontour in the control scans. Perfusion was assessed by Hoechst 33342, and autoradiography, fluorescence microscopy, and immunohistochemistry studies were performed ex vivo.
Results
Within 3-4 weeks after implantation of U87-MG cells, the longest axis of the tumor xenograft reached 5-10 mm. Dynamic PET scans, performed after i.v. administration of 6-12 MBq [18F]NS10743 (7-65 GBq/µmol at time of injection), revealed moderate uptake in the tumor with SUVmax of 0.91±0.16 at 40 min p.i. and tumor-to-muscle ratios of 0.93±0.08 at 60 min p.i. The individual tumor TACs are consistent regarding shape with relatively slow increase in the uptake of activity. NS6740 pre-blocking significantly reduced the activity uptake in the tumor (SUVmax=0.65±0.10; p<0.05).
Conclusions
Dynamic PET with [18F]NS10743 was able to detect α7 nAChR in the subcutaneous U87-MG mouse xenograft model of glioblastoma. The suitability of this approach for detection of α7 nAChR-expressing tumors in the brain remains to be investigated.
References
[1] R. Teodoro et al., Appl Radiat Isot, 2014, 95c,76-84
Keywords: molecular characterisation; glioblastoma; xenograft; U87; alpha7 nicotinic acetylcholine receptor; molecular imaging; PET; [18F]NS10743; microPET; sequential PET/MRI
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)1, 165
    DOI: 10.1002/jlcr.3508

Publ.-Id: 25388 - Permalink


Engineering the Electronic Properties of Two-Dimensional Transition Metal Dichalcogenides by Introducing Mirror Twin Boundaries
Komsa, H.-P.; Krasheninnikov, A. V.ORC
Grain boundaries in 2D materials can have marked influence on the material properties. The effects can be not only detrimental, but also beneficial in transition metal dichalcogenides (TMDs), so that controlling the density and type of the boundaries in these systems should be important for engineering their properties. However, this is often possibly only during the growth stage. Molybdenum and tungsten dichalcogenides feature a particular set of 60° mirror twin boundaries, which are reported to occur upon merging of the growing flakes, to appear during growth to accommodate for the nonstoichiometry of the sample, or to be produced a posteriori by electron irradiation or thermal annealing. Furthermore, different preparation conditions lead to different atomic structure of the boundary, which consequently exhibit different electronic properties. This has obviously garnered interest for the ability to control grain boundary types and densities. In this progress report, the recent experimental and theoretical work related to the characterization of mirror twin boundaries is reviewed. A consistent set of formation energies for the mirror twin boundaries is provided, which then allows a coherent picture on the formation mechanisms under different conditions to be drawn. Finally, the electronic structure of these boundaries is analyzed and their potential applications are discussed.
Keywords: 2D materials, first principles calculations

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Publ.-Id: 25387 - Permalink


Atomic defects and doping of monolayer NbSe2
Nguyen, L.; Komsa, H.-P.; Khestanova, E.; Kashtiban, R.; Peters, J. P.; Lawlor1, S.; Sanchez, A. M.; Sloan, J.; Gorbachev, R.; Grigorieva, I.; Krasheninnikov, A. V.ORC; Haigh, S. J.
We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.
Keywords: graphene, 2D materials, TEM, first-principles calculations

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Publ.-Id: 25386 - Permalink


EDTA and DTPA as scaffolds for successful Ln3+/An3+ separations from spent nuclear fuel
Langford-Paden, M. H.; Andrews, M. B.; Swinburn, A. N.; Alker, A.; Beal, K.; Anuar, N. S. B. K.; Knight, M. E.; Jones, J. E.; Beele, B.; Adam, C.; Panak, P.; Geist, A.; Kaden, P.; Natrajan, L. S.;
Multi-dentate ligands are instrumental to extraction and separations chemistry associated with nuclear fuel reprocessing. Specifically, the TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexations) process utilises DTPA to facilitate the separation of minor actinides, MA3+ (Am3+ and Cm3+), from Ln3+ and Y3+, allowing the MA3+ to be reprocessed further by transmutation. The TALSPEAK process involves the preferential extraction of the major component (Ln3+) into the organic phase using HDEHP, while the DTPA-derived ligands remain in the aqueous phase coordinating MA3+ which favour soft donor interactions. The process requires the use of lactic acid as a buffer to maintain pH 3.6 in order to prevent the precipitation of DTPA complexes at low pH, commonly experienced during the processing cycle. Amino acid conjugates derived from EDTA and DTPA present ideal candidates as self-buffering DTPA/EDTA ligands, therefore removing the need for lactic acid in the TALSPEAK process. The ligands (right) produce an internal buffer pH 1.5-2.5 at μM to mM concentrations. The synthesis, coordination chemistry, photophysical properties and separation behaviour of these new ligands and stability towards ionising radiation is presented.
Keywords: Lanthanide(III), Actinide(III), amino acids, DTPA
  • Poster
    ThUL School in Actinide chemistry 2016, 19.-23.09.2016, Dresden, Deutschland

Publ.-Id: 25385 - Permalink


Two-dimensional MoS2 under ion irradiation: from controlled defect production to electronic structure engineering
Ghorbani-Asl, M.; Kretschmer, S.; Spearot, D. E.; Krasheninnikov, A. V.ORC
Two-dimensional (2D) transition metal dichalcogenides (TMDs), like MoS2, have unique electronic and optical properties, which can further be tuned using ion bombardment and post-synthesis ion-beam mediated methods combined with exposure of the irradiated sample to precursor gases. The optimization of these techniques requires a complete understanding of the response of 2D TMDs to ion irradiation, which is affected by the reduced dimensionality of the system. By combining analytical potential molecular dynamics with first-principles calculations, we study the production of defects in free-standing MoS2 sheets under noble gas ion irradiation for a wide range of ion energies when nuclear stopping dominates, and assess the probabilities for different defects to appear. We show that depending on the incident angle, ion type and energy, sulfur atoms can be sputtered away predominantly from the top or bottom layers, creating unique opportunities for engineering mixed MoSX compounds where X are chemical elements from group V or VII. We study the electronic structure of such systems, demonstrate that they can be metals, and finally discuss how metal/semiconductor/metal junctions, which exhibit negative differential resistance, can be designed using focused ion beams combined with the exposure of the system to fluorine.
Keywords: Two-dimensional materials, ion irradiation, atomistic simulations, defects

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Publ.-Id: 25384 - Permalink


Radiosynthesis of (S)-[18F]T1: The first PET radioligand for molecular imaging of α3β4 nicotinic acetylcholine receptors
Sarasamkan, J.; Fischer, S.; Deuther-Conrad, W.; Ludwig, F.-A.; Scheunemann, M.; Arunrungvichian, K.; Vajragupta, O.; Brust, P.;
Recent pharmacologic data revealed the implication of α3β4 nicotinic acetylcholine receptors (nAChRs) in nicotine and drug addiction. To image α3β4 nAChRs in vivo, we aimed to establish the synthesis of a [18F]-labelled analog of the highly affine and selective α3β4 ligand (S)-3-(4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl)quinuclidine ((S)-T1). (S)-[18F]T1 was synthesized from ethynyl-4-[18F]fluorobenzene ([18F]5) and (S)-azidoquinuclidine by click reaction.
After a synthesis time of 130 min (S)-[18F]T1 was obtained with a radiochemical yield (non-decay corrected) of 4.3 ± 1.3%, a radiochemical purity of > 99% and a molar activity of > 158 GBq/µmol. The brain uptake and the brain-to-blood ratio of (S)-[18F]T1 in mice at 30 min post injection were 2.02 (SUV) and 6.1, respectively.
According to an ex-vivo analysis, the tracer remained intact (> 99%) in brain. Only one major radiometabolite was detected in plasma and urine samples. In-vitro autoradiography on pig brain slices revealed binding of (S)-[18F]T1 to brain regions associated with the expression of α3β4 nAChRs, which could be reduced by the α3β4 nAChR selective drug AT-1001. These findings make (S)-[18F]T1 a potential tool for the non-invasive imaging of α3β4 nAChRs in the brain by PET.
Keywords: α3β4 Nicotinic acetylcholine receptor Click reaction Drug addiction Positron emission tomography [18F]-Radioligand (S)-[18F]T1 Radiofluorination

Publ.-Id: 25383 - Permalink


Heating, Ionization and Magnetic Instability in Short Pulse High Power Laser-Solid Target Interactions
Huang, L. G.; Kluge, T.; Schlenvoigt, H.-P.; Metzkes, J.; Cowan, T.;
During short pulse high power laser solid matter interactions, a significant fraction of laser pulse energy is absorbed to generate an intense beam of fast electrons with relativistic kinetic energies near the critical density surface. The transport of the intense fast beam into the solid target is of fundamental importance to many complex dynamics such as plasma oscillation, heating, ionization, instability, electric field and magnetic field generation, photon emission and so on. In the talk, we will present the ultrafast plasma dynamics for ion heating in buried layer targets[1], bulk electron heating [2], collisional ionization [2,3], transport instability and quasistatic magnetic generation from PIC simulations.
In order to connect the complex plasma dynamics seen in PIC simulations with experiments, we will discuss the role of insitu synthetic diagnostics that mimic experimental diagnostics. As one key example we propose to use XRay Free Electron Lasers for probing the density modulations in the bulk target by small angle Xray scattering which allows for femtosecond and nanometer resolution of transient plasma processes. We will also discuss the feasibility to probe selfgenerated MegaGauss magnetic fields associated with the transport instability of the laser accelerated hot electrons using Faraday rotation method. With these techniques, probing fundamental plasma properties will allow for direct comparison to simulations, challenging state of the art theoretical modeling of collisions, ionizations and so on.
[1] L. G. Huang, M. Bussmann, T. Kluge, A. L. Lei, W. Yu, and T. E. Cowan, Phys. Plasmas 20, 093109 (2013).
[2] L. G. Huang, T. Kluge, and T. E. Cowan, Phys. Plasmas 23, 063112 (2016).
[3] T. Kluge, M. Bussmann, H.K.Chung, C. Gutt, L. G. Huang, M. Zacharias, U. Schramm, and T. E. Cowan, Phys.Plasmas 23, 033103 (2016).
Keywords: high power laser,XFEL,solid target, heating,ionization,magnetic instability
  • Lecture (Conference)
    Workshop: High Intensity Laser Matter Science at the HED Instrument at the European XFEL, 05.-06.04.2017, Hamburg, Germany

Publ.-Id: 25382 - Permalink


Coordination Chemistry of Uranium (U(IV) and -(VI)) with Bidentate N-donor Ligands, 2,2’-Bipyridine and 1,10-Phenanthroline
März, J.; Schöne, S.; Radoske, T.; Patzschke, M.; Stumpf, T.; Ikeda-Ohno, A.ORC
Because of their remarkable stability towards a wide variety of transition metals1, the bidentate N-donor ligands 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) have attracted considerable attention in the field of coordination chemistry over the last decades. The coordination chemistry of uranium (U) with these N-donor ligands has been also explored primarily for its hexavalent state (U(VI) as UO22+), whilst much less attention has been paid for the lower oxidation states, such as tetravalent (U(IV)). Here we present a systematic study on the coordination chemistry of U(IV) and -(VI) with bipy and phen under different chemical conditions, such as different solvents and changing the metal / ligand ratio.
We succeeded to obtain a series of U(IV) complexes with the U:ligand ratio of 1:1 and 1:2, all showing the eight-fold coordination geometry of the uranium centre. In addition to the ligand, chloro and methanolato ligands are also coordinating to the metal centre for charge compensation. Interestingly, the complexation between U(IV) and the ligand does occur even in protic solvents, in which the ligand is expected to be protonated. We also obtained another series of U(VI) complexes with both bipy and phen, underlining the versatile coordination chemistry of uranyl (UO22+). That is, the coordination between uranyl and the ligand depends strongly on the pH of the solvent used. For instance, as shown in the right of Fig. 1, dinuclear uranyl arrangements with hydroxo-brinding are dominated in the media with higher pH. As illustrated in Fig. 1, bipy and phen are forming isostructural complexes both with U(IV) and- (VI). The electronic structure of the complexes is further studied by quantum chemical calculations.
Keywords: Coordination chemistry Actinides Uranium N-donor ligands
  • Lecture (Conference)
    Actinides, 09.-14.07.2017, Sendai, Japan

Publ.-Id: 25381 - Permalink


Interaction of Tetravalent Actinides (An(IV)) with Mixed N/O-Donor Imine Type Ligands
Radoske, T.; März, J.; Kaden, P.; Walter, O.; Weigand, J. J.; Stumpf, T.; Ikeda-Ohno, A.ORC
Because of their unique electronic properties originating from 5f-orbitals, the coordination chemistry of actinides (An) is still an attractive research field in terms not only of nuclear engineering but also of basic chemistry. In particular, the early An show profound complex chemistry due to a wide variety of possible oxidation states ranging from +II to +VII, which is in contrast to the dominant trivalent state for their chemical analog of lanthanides. The aim of our research activities is to gain knowledge about the interaction of An with a variety of hard- and soft-donor ligands, eventually providing a comprehensive understanding of the electronic nature of actinide compounds. To this end, the focus of this study lies on the characterization of Th(IV) and U(IV) complexes with the imine ligand salen and its derivative (Figure 1). The ligands possess both O- (i.e. hard) and N-donor (soft) groups in the structure, which could be also considered as a simplified model of naturally relevant organic O-/N-donor ligands.

Results and Discussion
A series of single crystals of the U(IV)-salen complexes were obtained as a function of M:L ratio and pH by liquid-liquid diffusion methods. SC-XRD measurements on the obtained crystals revealed the new crystal structures, all showing the eight-fold coordination of the U centre with a trigonal dodecahedral geometry with the ligands on the primary coordination sphere of U.
UV-visible absorption measurements of U(IV)-salen solution as a function of M:L ratio indicate the existence of two independent solution species in the system, assigning as the U(IV)-salen complexes with the M:L ratios of 1:1 and 1:2. 1H-NMR spectra of the dissolved complex [UIV(Le)2] and the pure ligand in solution were recorded. All expected multiplets of the complex can be clearly identified and confirm complexation. The spectra also showed a significant high-field shift due to proximity of the paramagnetic uranium(IV) centre, indicating that the metal is positioned at the centre of the coordination polyhedron formed by the two ligand molecules.
Keywords: Actinides, Uraniun, Thorium, Salen, Imine, Ligand, Complex
  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan

Publ.-Id: 25380 - Permalink


Uranium(V) incorporation mechanisms and stability in Fe(II)/Fe(III) iron (oxyhydr)oxides
Roberts, H. E.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Kvashnina, K.; Shaw, S.;
Understanding the interactions between radionuclides and mineral phases underpins site environmental clean-up and waste management in the nuclear industry. The transport and fate of radionuclides in many subsurface environmental systems are controlled by adsorption, redox and mineral incorporation processes. Interactions of iron (oxyhydr)oxides with uranium have been extensively studied due to both the abundance of uranium as an environmental contaminant and the ubiquity of iron (oxyhydr)oxides in engineered and natural environments. Despite this, detailed mechanistic information regarding the incorporation of uranium into Fe(II) bearing magnetite and green rust is sparse. Here, we present a co-precipitation study where U(VI) was reacted with environmentally relevant iron(II/III) (oxyhydr)oxide mineral phases. Based on diffraction, microscopic and spectroscopic evidence, we propose the reduction of U(VI) via a one electron transfer to U(V) and stabilisation of the U(V) by incorporation during co-precipitation with iron (oxyhydr)oxides. U(V) was stable in both magnetite and green rust structures and incorporated via substitution for octahedrally coordinated Fe in a uranate-like coordination environment. As the Fe(II)/Fe(III) ratio increased, a proportion of U(IV) was also precipitated as surface associated UO2. These novel observations have significant implications for the behaviour of uranium within engineered and natural environments.
Keywords: Uranium | Magnetite | Green Rust | Incorporation | Environmental fate

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Publ.-Id: 25379 - Permalink


Vortex dynamics in disks with tailored magnetisations: from single frequency to multiple frequencies
Ramasubramanian, L.; Fowley, C.; Kákay, A.; Yildirim, O.; Matthes, P.; Lindner, J.; Fassbender, J.ORC; Gemming, S.; Schulz, S. E.; Deac, A. M.
The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation e.g. the diameter and height of a magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Ion implantation is a promising method to fabricate such devices [5].
To study the formation of magnetic vortices with respect to size and thickness, disks with different radii- 0.5 µm to 4 µm and thicknesses- 25 nm and 30 nm were prepared using electron beam lithography followed by electron beam evaporation. Moreover, to allow for electrical measurements, the single disks were contacted by gold leads to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements.
The magnetic field dependence can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters whereas larger field sensitivity is present in larger disks (Figure 1 (b)).
Magnetotransport measurements on electrically contacted disks (Figure 2 (a)) show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 2 (b)). Additionally, to the shown static DC measurements, AC measurements are accessible by a lock-in technique and the resonance frequencies measured for 3 µm and 4 µm radii disks with 25 nm permalloy are 40.9 MHz and 29.5 MHz respectively. In order to alter the saturation magnetisation within defined volumes and to achieve two different oscillation frequencies, a concentric region is irradiated within the actual disk (Figure 2 (c)). After ion irradiation, modified magnetic vortex dynamics are investigated by ac-magnetotransport measurements and the results are supported by micromagnetic simulations.
Acknowledgements:
This work is supported by the Helmholtz Young Investigator Initiative Grant No. VH-N6-1048. Support of the Nanofabrication Facilities of Rossendorf at the Ion Beam Centre is gratefully acknowledged (Dr. Artur Erbe, Bernd Scheumann).
Keywords: magnetic vortex, electrical detection, dynamics
  • Lecture (Conference)
    INTERMAG, 24.-28.04.2017, Dublin, Ireland

Publ.-Id: 25378 - Permalink


Electrically detected magnetic vortex dynamics in Permalloy disks
Ramasubramanian, L.; Fowley, C.; Kákay, A.; Yildirim, O.; Matthes, P.; Lindner, J.; Fassbender, J.ORC; Gemming, S.; Schulz, S. E.; Deac, A. M.
The magnetic “vortex” is a potential candidate for future spintronic devices, like frequency sensors [S. Kasai, et al. PRL 97, 107204 (2006)] [R. Moriya, et al. Nat. Phys. 4:368 (2008)], spin torque oscillators [V. S. Pribiag, et al. Nat. Phys. 3:498 (2007)], and tunable magnonic crystals [J. Shibata, et al. PRB 67, 224404 (2003)]. The fundamental frequency is determined by the saturation magnetisation, as well as the geometrical confinement of the magnetisation i.e. the diameter and height of a magnetic disk. In this study, Permalloy disks (with diameters ranging from 1µm to 8µm) are patterned and contacted to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect, X-ray photoemission electron microscopy and magnetotransport measurements. The resonance frequency is measured using a lock-in technique based on the anisotropic magnetoresistance effect. Modification of the resonance frequency by ion irradiation will be presented.
Keywords: magnetic vortex, dynamics, electrical detection
  • Lecture (Conference)
    DPG-Frühjahrstagung 2017, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 25377 - Permalink


Thermally Induced Spin Transfer Torque on MgO-based magnetic tunnel junctions using microstrip based resonator
Cansever, H.; Fowley, C.; Narkowicz, R.; Kowalska, E.; Aleksandrov, Y.; Yildirim, O.; Titova, A.; Lenz, K.; Lindner, J.; Fassbender, J.ORC; Deac, A. M.
Magnetic tunnel junctions have been commonly used in spintronics applications, such as magnetic random access memory (M-RAM), spin transfer torque RAM (STT-RAM) and hard disc drive (HDD) because of high storage capacity. A spin polarized current flowing through a ferromagnetic layer can exert spin-transfer-torque (STT) on the local magnetization. When we apply thermal gradient across the junction we can induce what is called thermal spin transfer torque (T-STT). In this study, the microresonator FMR technique is used in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradients across the barrier. Details of resonator fabrication and preliminary measurements are presented. This work is supported by DFG-SPP1538.
Keywords: spin transfer torque, microresonator, thermal gradient
  • Lecture (Conference)
    DPG-Frühjahrstagung 2017, 19.-24.03.2017, Dresden, Germany

Publ.-Id: 25376 - Permalink


Synthesis and characterization of the first chiral benzamidinate complexes of tetravalent actinides (An(IV))
Schöne, S.ORC; März, J.; Kaden, P.; Weigand, J. J.; Roesky, P. W.; Stumpf, T.; Ikeda-Ohno, A.ORC
In contrast to the dominant trivalent state for the lanthanides (Ln(III)), a wide variety of oxidation states (from +II to +VII) of actinides (An) makes their chemistry intricate but attractive. Especially the early An of thorium (Th), uranium (U), neptunium (Np) and plutonium (Pu) form highly charged cations with the oxidation state four (An4+), which are of particularly interest for the coordination chemistry due to their strong interaction with organic ligands. The focus of our investigations lies in the comprehensive characterization of tetravalent An (An(IV)) complexes with soft ligand donor atoms, such as nitrogen. The present study focuses particularly on the interaction of An(IV) with benzamidinate ligands, which could be considered as a simplified model of naturally occurring N-donor organic compounds.
Recently, the lanthanide complexes with the chiral benzamidine, (S,S)-N,N-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA), have been successfully synthesized by the group of Prof. Roesky1,2. The present study is inspired by these precedent studies to synthesize a new series of benzamidine compounds with An(IV).
  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan
  • Lecture (Conference)
    10th International Symposium on Nano and Supramolecular Chemistry, 10.07.2018, Dresden, Deutschland

Publ.-Id: 25375 - Permalink


Magnetic properties of HoFe₆Al₆ with a compensation point near absolute zero: A theoretical and experimental study
Sabdenov, C. K.; Davydova, M. D.; Zvezdin, K. A.; Zvezdin, A. K.; Andreev, A. V.; Gorbunov, D. I.; Tereshina, E. A.; Skourski, Y.; Sebek, J.; Tereshina, I. S.;
Ferrimagnet HoFe6Al6 (tetragonal ThMn12-type crystal structure) has a compensation point for the Ho and Fe magnetic sublattices at a temperature close to absolute zero. The experimental study was carried out in fields up to 60 T. H-T phase diagrams and a full magnetization process along the principal crystallographic directions of a single-crystalline sample are obtained theoretically by using a model of a f-d ferrimagnet with two anisotropic sublattices, coupled by weak exchange interaction. The two first-order phase transitions, found experimentally along the [110] and [100] axes, were explained theoretically. The transition along the [110] direction occurs between noncollinear and collinear phases, it starts at the compensation point and ends at a tricritical point around 60 T. The transition along the [100] direction goes also from the point of compensation to the point of the liquid-vapor type at 40 T. This transition was shown to occur between two distinct noncollinear phases. The crucial role of the strong rare-earth anisotropy for the positions of the obtained critical points was revealed.

Publ.-Id: 25374 - Permalink


Uniaxial-stress tuned large magnetic-shape-memory effect in Ni-Co-Mn-Sb Heusler alloys
Salazar Mejia, C.; Küchler, R.; Nayak, A. K.; Felser, C.; Nicklas, M.;
Combined strain and magnetization measurements on the Heusler shape-memory alloys Ni45Co5Mn38Sb12 and Ni44Co6Mn38Sb12 give evidence for strong magneto-structural coupling. The sample length changes up to 1% at the martensitic transformation, between a ferromagnetic, austenitic phase at high temperatures and a weakly magnetic, low-symmetry martensitic phase at lower temperatures. Under moderate uniaxial stress, the change in the sample length increases to and saturates at about 3%, pointing to stabilization of a single martensitic variant. A reverse martensitic transformation can also be induced by applying magnetic field: we find that within the temperature range of thermal hysteresis of the martensitic transformation, applying a field can induce a metastable expansion of the sample, while at slightly lower temperatures, the field response is reversible. These findings provide key information for future use of Ni(Co)-Mn-Sb-based Heusler compounds in, e.g., actuators and mechanical switches.

Publ.-Id: 25373 - Permalink


Analysis of the exclusive final state npe+e in quasi-free np reaction
Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.;
We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25 GeV/u inpinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of e+e− pairs above the π0 mass in the exclusive channel dp→npe+e−(pspect) as compared to the exclusive channel ppe+e− measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double-Δ excitation combined with intermediate ρ-meson production. Differential cross sections as a function of the e+e− invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical side.

Publ.-Id: 25372 - Permalink


Thermal anemometry grid sensor for spatially-resolved measurement of gas phase temperature and velocity in fuel element subchannels
Arlit, M.; Schleicher, E.; Hampel, U.;
Since the Fukushima accident the spent fuel pool has gained some special focus in nuclear safety research, since it is potentially endangered by a longer persisting station black-out or a loss of the coolant due to a leakage in the pool liner. Behind this background the German national joint project SINABEL (SIcherheit NAsslager BrennElement Lagerbecken) has been launched, which targets an experimental investigation and an improved modelling of the thermal hydraulics in fuel element mock-up in the spent fuel pool under accident scenario conditions. The goal is to develop validated simulation tools for the prediction of temperature courses and the support of the emergency management.
Experimental investigations within the project are performed in a mock-up of a 10 x 10 boiling water reactor fuel element. Surface temperatures of the electrical heated rods are measured by means of 134 thermocouples at different locations. Another parameter of interest is the steam flow velocity in the sub-channels. For this purpose no commercial measurement technique is applicable due to limited accessibility and high temperatures. For this reasons a special thermal anemometry grid sensor has been developed. It consists of a grid of thermal resistors in the bundle cross-section with one resistor in each sub-channel. Via the resistors fluid temperature as well as flow velocity can be obtained. Applied measurement techniques are resistance thermometry and thermal anemometry respectively. The measurements are obtained simultaneously by sampling the data with a special multiplexed excitation scheme. Our contribution gives a brief description of the thermal anemometry grid sensor along with first results from studies on a potential natural circulation in the completely dried state.
Keywords: Thermal anemometry grid sensor, Temperature grid sensor, Spent fuel pool, Thermal hydraulics
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi´an, China

Publ.-Id: 25371 - Permalink


Neutron Noise Observations in German KWU Built PWR and Analyses with the Reactor Dynamics Code DYN3D
Rohde, U.; Seidl, M.; Kliem, S.ORC; Bilodid, Y.
Low-frequency neutronic noise with a bandwidth of up to ten percent of the reactor power has been observed in Konvoi-type PWRs in Germany in the last years. Several attempts were made to identify the reasons for increased magnitudes of the neutronic fluctuations in comparison with pre-Konvoi reactors, and various hypotheses have been created to explain this effect.
In this paper, results of noise simulations performed with use of the reactor dynamics code DYN3D are presented. Both fluctuations of the coolant inlet temperature and mass flow rate were considered. Besides of un-correlated fluctuations, correlated temperature fluctuations were simulated. The correlations between fluctuations in the individual fuel assemblies were obtained based on an experimentally validated coolant mixing model. However, the features of the neutronic noise found in the simulations do not correspond to the measurements.
Obviously, more complex mechanisms than only temperature and/or mass flow fluctuations have to be considered. Simulated fluctuations of the local moderator density, independently from thermal hydraulics, indicate that potentially deformations or vibrations of the fuel rod lattice leading to variations of the local moderator content might be responsible for the observed neutronic noise. Advanced models coupling neutronics, thermal hydraulics, turbulence and mechanical modelling have to be developed.
Keywords: PWR, KWU, Neutron noise, DYN3D

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  • Secondary publication expected

Publ.-Id: 25370 - Permalink


Field induced phase transition in the few photon regime
Panferov, A. D.; Smolyansky, S. A.; Titov, A. I.; Kämpfer, B.; Otto, A.; Blaschke, D. B.; Juchnowski, L.;
Some features of the field induced phase transition accompanied by the vacuum creation of an electron-positron plasma (EPP) in strong time-dependent electric fields have been discussed in the work [1] in the domain of the tunneling mechanism (ω ≪ m, where ω is the characteristic frequency of the external field and m is the electron mass). In the present contribution the features of this process will be considered in the few photon domain where ω ~ m. We observe a narrowing of the transient domain of the quickly oscillations and, mainly, a considerable growth of the effectiveness of the EPP production. Under these circumstances, we see an increase of the effectiveness of the EPP creation in the particular case of a bifrequent excitation, where both mechanisms (tunneling and few photon) act simultaneously [2, 3].

Publ.-Id: 25369 - Permalink


Proton radiography for integrating positioning and treatment planning of small animals at an experimental proton beam
Müller, J.; Neubert, C.; von Neubeck, C.; Krause, M.; Enghardt, W.; Bütof, R.; Dietrich, A.; Lühr, A.;
Integrated small animal X-ray imaging and irradiation devices have facilitated image-guided pre-clinical radiooncological experiments. Here, a proton-based radiography method is proposed for in-line small animal treatment planning and positioning verification at an experimental proton beamline.
A double-scattered 125 MeV proton beam (10 x 10 cm² field size) and a flat-panel, scintillation-based dose detector (Lynx, IBA Dosimetry) were used to obtain planar scans of deceased mice positioned in a closed multi-modality bed. Two modes of image acquisition were used: absorption and scattering. In absorption mode, slabs of plastic with a water equivalent path length (WEPL) of 7.08 g/cm² were placed between object and Lynx detector. In scattering mode, all plastic slabs were removed. Digital, pixel-wise image processing was applied to combine the information. A WEPL calibration curve was obtained using plastic slices of known WEPL as objects. For verification, planar X-ray images of the same objects were acquired.
The proposed radiography technique allowed for detection of contours (e.g., mouse body, bed and background) and reliable automated (rigid) registration of proton radiography images to planar X-ray scans. Planar 2D radiological thickness maps of mice were obtained. Specific structures could be visualized with a spatial resolution of less than 1 mm, especially regions with high local density differences including lung, hind leg, jaws and skull.
The method appears suitable to position small animals for precise irradiation of subcutaneous (hind leg) and orthotopic (lung, brain) tumor models. Currently extended image analysis may enhance visualization of the animal’s internal structure to facilitate in-line treatment planning.
Keywords: Radiography, Imaging, proton therapy, Preclinical research, Cancer
  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Publ.-Id: 25368 - Permalink


Year-round record of bulk and size-segregated aerosol composition in central Antarctica (Concordia site) Part 2: Biogenic sulfur (sulfate and methanesulfonate) aerosol
Legrand, M.; Preunkert, S.; Weller, R.; Zipf, L.; Elsässer, C.; Merchel, S.; Rugel, G.; Wagenbach, D.;
Multiple year-round (2006-2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (84 ± 25 ng m-3 against 4.4 ± 2.3 ng m-3 in July) is consistent with observations made at the coast (280 ± 78 ng m-3 in January against 16 ± 9 ng m-3 in July at Dumont d’Urville, for instance). In contrast, the well-marked maximum of MSA at the coast in January (60 ± 23 ng m-3 at Dumont d’Urville) is not observed at Concordia (4.6 ± 2.4 ng m-3 in January). Instead, the MSA level at Concordia peaks in October (5.6 ± 1.9 ng m-3) and March (13.2 ± 6.1 ng m-3).
As a result, a surprisingly low MSA to nssSO4 ratio (RMSA) is observed at Concordia in midsummer (0.05 ± 0.02 in January against 0.25 ± 0.09 in March). We find that the low value of RMSA in mid-summer at Concordia is mainly driven by a drop of MSA levels that takes place in submicron aerosol (0.3 μm diameter). The drop of MSA coincides with periods of high photochemical activity as indicated by high ozone levels, strongly suggesting the occurrence of an efficient chemical destruction of MSA over the Antarctic plateau in mid-summer. The relationship between MSA and nssSO4 levels is examined separately for each season and indicates that concentration of non-biogenic sulfate over the Antarctic plateau does not exceed 1 ng m-3 in fall and winter and remains below 5 ng m-3 in spring. This weak non-biogenic sulfate level is discussed in the light of radionuclides (210Pb, 10Be, and 7Be) also measured on bulk aerosol samples collected at Concordia. The findings highlight the complexity in using MSA in deep ice cores extracted from inland Antarctica as a proxy of past DMS emissions from the southern ocean.
Keywords: Methanesulfonate, MSA to non-sea-salt sulfate ratio, DMS emissions, sea-salt aerosol, 210Pb, 10Be and 7Be, Chemistry(chemical composition and reactions)

Publ.-Id: 25367 - Permalink


Influence of FeII on the retention mechanisms of NpO2+ by montmorillonite
Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.;
For the safety case for high-level radioactive waste repositories, redox phenomena play an important role for radionuclide retention. In the near field, the corrosion of steel canisters will release large amounts of ferrous iron and in addition produce H2 with a strong influence on the “in situ” redox potential (Eh). This combination of high {FeII} and low (Eh) in the interstitial waters of the engineered barrier system (bentonite, consisting predominantly of the phyllosilicate montmorillonite) is expected to have a strong impact on the retention of redox sensitive radionuclides like Tc, Se and the early actinides U, Np, and Pu, all of high relevance for safety of radioactive waste repositories.
In the present work we investigated by X-ray absorption spectroscopy (XAS) the influence of FeII on the retention of the redox sensitive NpV by montmorillonite. Since natural montmorillonite always contains structural Fe, we made use of a synthetic iron-free montmorillonite (IFM) [1] to discriminate the influence of sorbed FeII from that of structural iron. For FeII loadings below 40 mmol·kg-1, sorbed Fe had no effect, with Np showing the typical sorption behaviour of the pentavalent aquo-ion by forming comparatively weak inner-sphere sorption complexes at the edge sites of montmorillonite. For FeIIsorb above 40 mmol·kg-1, however, we observed an increasing reduction of NpV to NpIV, with a complete reduction for FeIIsorb  80 mmol·kg-1. In spite of the low solubility of NpO2, we did not observe precipitation of this phase, but formation of mononuclear innersphere sorption complexes (Fig. 1-A). The influence of structural FeII was investigated using citrate-dithionite–bicarbonate (CDB) reduced SWy montmorillonite (i.e. structural FeIII fully reduced to FeII). XAS showed that Np is present only as NpIV on the clay surface (Fig. 1-B).
Our study demonstrates that both structural and adsorbed FeII on montmorillonite lead to a surface mediated reduction of NpV, thereby increasing the retention by more than two orders of magnitude.
Keywords: montmorillonite iron neptunium EXAFS XANES sorption modeling
  • Lecture (Conference)
    AnXAS 2017: 8th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, 11.-13.04.2017, Oxford, United Kingdom

Publ.-Id: 25366 - Permalink


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