Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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30537 Publications
Experimental Analysis of the effect of column feed pipe configurations on the flow morphology
Döß, A.ORC; Schubert, M.; Hampel, U.
Droplets entrained by the vapor phase can drastically reduce the separation capacity of distillation columns and cause severe corrosion problems, process instabilities as well as higher emissions due to droplet carry-over into the downstream process units.
Intensive interactions between vapor and liquid phases favor droplet formation. Feed pipe and feed inlet are prone positions for such droplet formation, depending on flow rates, phase change and pipe geometry resulting in characteristic morphologies.
Several models are available to predict the flow regime for known liquid and vapor flow rates. However, these models and flow maps are often restricted to fully developed flows in straight pipes of small diameter only and do not account for the effects of various entrance lengths, larger diameters as well as bends found in industry. Thus, an experimental analysis is performed to study the effect of column feed pipe configurations on the evolving flow regime using the wire-mesh sensor technique (Fig. 1). Wire-mesh sensors visualize the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). This work is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).
Keywords: Two-phase flow morphology, Horizontal feed pipe, Wire-mesh sensor, Pipe configuration
  • Poster
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-13.09.2018, Aachen, Deutschland
    DOI: 10.1002/cite.201855425

Publ.-Id: 28181 - Permalink


Flow morphology in feed pipes: theoretical analysis and experimental investigation.
Döß, A.ORC; Schubert, M.; Hampel, U.; Schleicher, E.; Geipel, C.; Mehringer, C.; Flegiel, F.
Efficient separation in distillation columns driven by the thermodynamic non-equilibrium between vapor and liquid phase is achieved by high turbulence as well as large interfacial area. At the same time, intensive interactions between vapor and liquid phases result in the formation of droplets, whose entrainment by the vapor phase may drastically reduce the separation capacity. The feed pipe is a prone position for such droplet formation. Besides the flash evaporation, the evolving flow morphology in the feed pipe is decisive for the droplet generation.The flow morphology in pipes depends on fluid flow rates and properties as well as on the pipe geometry. Several models and flow regime maps for fully developed flows in small pipe diameters exist, relating operating conditions and flow morphology. However, industrial feed pipe configurations with larger diameters and bends are so far not studied.
Thus, an experimental study in feed pipes of 50 mm and 200 mm diameter is performed using the wire-mesh sensor technique (Fig. 1). The wire-mesh sensor visualizes the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). The obtained data are compared with the
state-of the art models to assess their applicability for feed pipes. This project is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).
Keywords: Two-phase flow morphology, Horizontal feed pipe, Wire-mesh sensor,
  • Lecture (Conference)
    ACHEMA 2018, Session: TERESA – Droplet entrainment and droplet reduction in mass transfer devices, 11.-15.06.2018, Fankfurt am Main, Deutschland

Publ.-Id: 28179 - Permalink


Ultrasonic measurements of the flow field in foam and froth
Heitkam, S.; Nauber, R.; Richter, T.; Büttner, L.; Czarske, J.; Eckert, K.
In this work, the non-invasive Ultrasound-Doppler velocimetry has been used to measure the velocity distribution inside a liquid foam bulk for the first time. The foam flows upward in a transparent channel. Optical correlation algorithms and conductivity measurement provide reference data. An array of ultrasound transducers is mounted within the channel, sending bursts along the main flow axis and receiving the echoes. The penetration depth equals up to 0.2 meters. With purposely designed flows it is demonstrated, that the velocity uncertainty is below 15 percent and the spatial resolution better than 1 cm. In static experiments, the applicability to particle laden foam and froth has been estimated. These parameters allow for monitoring of industrial processes as well as scientific investigation of three-dimensional foam and froth flow on medium scales.
Keywords: Ultrasound Doppler Velocimetry, Foam flow
  • Lecture (Conference)
    ISUD 11 - 11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 06.09.2018, Berlin, Germany

Publ.-Id: 28171 - Permalink


Neutron Imaging of Foam and Froth
Heitkam, S.; Lappan, T.; Rudolph, M.; Trtik, P.; Eckert, S.; Eckert, K.
The present contribution reports on the investigation of particle movement and drainage in unsteady foam and froth using Neutron Imaging (NI) (S. Heitkam et al. "Neutron imaging of froth structure and particle motion." Minerals Engineering, vol. 119, pp. 126-129, 2018.)

Froth flotation is one of the major separation processes in mining. Billions of tons per year of ore are treated by flotation worldwide. Despite the industrial relevance, measurement techniques for the observation of particle movement and liquid distribution inside the froth are limited.

In this situation, NI can reveal new insights on the mechanisms in froth flotation. NI is similar to radiography, but X-rays are replaced by neutrons. The neutrons pass through the measurement object, being partially attenuated. Then they hit a scintillator, generating photons that are observed by a high-speed camera. The advantage of NI in froth research is, that some materials (e.g. gadolinium) offer extremely high attenuation of neutrons. And also water attenuates neutrons about 30 times stronger than X-rays.
Keywords: Neutron Imaging, Foam, Froth
  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Publ.-Id: 28170 - Permalink


Ultrasonic measurements of the velocity distribution inside foam
Heitkam, S.; Nauber, R.; Büttner, L.; Czarske, J.; Eckert, K.
The flowing behavior of liquid foam and froth is not yet well investigated. One reason for that is, that adequate measurement techniques are scarcely available. Also, industrial foam applications could be improved by monitoring the foam flow in the process.

In this work, the ultrasound Doppler velocimetry is used to measure the velocity distribution inside liquid foam. (Nauber et al. “Ultrasonic measurements of the bulk flow field in foams.”, Physical Review E, vol. 97 (1), pp 013113, 2018). To that end, an array of five ultrasound transducers is positioned inside a foam channel. One transducer sends pulses into the foam and the others receive the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution along the beam axis. Multiplexing of the array allows for 2D-1C measurement.
Keywords: Ultrasound Doppler Velocimetry, Foam flow
  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Publ.-Id: 28169 - Permalink


Neutronen-Imaging von partikelbeladenen Schäumen
Heitkam, S.; Rudolph, M.; Lappan, T.; Sarma, M.; Eckert, S.; Trtik, P.; Lehmann, E.; Vontobel, P.; Eckert, K.
Die Flotation ist ein Trennverfahren mit großer industrieller Bedeutung, beispielsweise in der Gewinnung von Elementen aus Erzen. Dabei werden die Erze gemahlen und in Wasser suspendiert. Durch Zugabe geeigneter oberflächenaktiver Substanzen werden die gewünschten Partikel selektiv hydrophobisiert. Dadurch haften sie an eingebrachten Gasblasen an, werden an die Oberfläche transportiert und dort in sich bildenden Schaum eingelagert. Der Schaum wird abgezogen und man erhält gewünschte Partikel in hoher Konzentration.
Keywords: Neutron Imaging, Froth flotation
  • Lecture (Conference)
    Dechema Jahrestreffen, 06.03.2018, Bremen, Deutschland

Publ.-Id: 28158 - Permalink


Nematicity of correlated systems driven by anisotropic chemical phase separation
Yuan, Y.; Hübner, R.; Birowska, M.; Xu, C.; Wang, M.; Prucnal, S.; Jakiela, R.; Potzger, K.; Böttger, R.; Facsko, S.; Majewski, J. A.; Helm, M.; Sawicki, M.; Zhou, S.ORC; Dietl, T.
The origin of nematicity, i.e., in-plane rotational symmetry breaking, and in particular the relative role played by spontaneous unidirectional ordering of spin, orbital, or charge degrees of freedom, is a challenging issue of magnetism, unconventional superconductivity, and quantum Hall effect systems, discussed in the context of doped semiconductor systems such as Ga1−xMnxAs, CuxBi2Se3, and Ga(Al)As/AlxGa1−xAs quantum wells, respectively. Here, guided by our experimental and theoretical results for In1−xFexAs, we demonstrate that spinodal phase separation at the growth surface (that has a lower symmetry than the bulk) can lead to a quenched nematic order of alloy components, which then governs low-temperature magnetic and magnetotransport properties, in particular the magnetoresistance anisotropy whose theory for the C_2v symmetry group is advanced here. These findings, together with earlier data for Ga1−xMnxAs, show under which conditions anisotropic chemical phase separation accounts for the magnitude of transition temperature to a collective phase or merely breaks its rotational symmetry. We address the question to what extent the directional distribution of impurities or alloy components setting in during the growth may account for the observed nematicity in other classes of correlated systems.

Downloads:

  • Secondary publication expected

Publ.-Id: 28154 - Permalink


Towards Measuring Vacuum Birefringence
Schlenvoigt, H.-P.ORC
We will present a design study how one could detect vacuum birefringence when combining an ultra-intense optical laser and an X-ray free electron laser. By means of precision X-ray polarimetry, one may detect the polarization flip of X-ray photons induced by the ultra-strong laser fields as a signature of vacuum birefringence. We will discuss crucial experimental parameters and provide a comprehensive model to study the experimental feasibility.
Keywords: Hibef
  • Lecture (Conference)
    27th Annual International Laser Physics Workshop, 16.-20.07.2018, Nottingham, UK

Publ.-Id: 28151 - Permalink


Operating three research infrastructures at one site: electrons & photons, ions, magnetic fields
Helm, M.
Operating three research infrastructures at one site: electrons & photons, ions, magnetic fields
Keywords: research infrastructure, large-scale facility
  • Invited lecture (Conferences)
    Conference on International Cooperation of Science Centers, 19.10.2018, Huairou, China

Publ.-Id: 28147 - Permalink


Strategien zur Darstellung eines neuen 18F-markierten Adenosin-A2A-Rezeptorliganden zur PET-Bildgebung von Hirntumoren [1]
Lai, T. H.; Schröder, S.; Ludwig, F.-A.; Fischer, S.; Moldovan, R.-P.; Scheunemann, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Brust, P.
Ziel: Auf Grundlage einer Pyrazolo[2,3-d]pyrimidin-Leitverbindung[2] wurden 21 fluorierte Derivate synthetisiert. Basierend auf den dazu ermittelten Affinitäts- und Selektivitätsdaten für den humanen Adenosin-A2A-Rezeptor wurde das potente 4-Fluorbenzyl-Derivat 1 (Ki(A2A) = 5,3 nM; Ki(A1) = 220 nM) für die 18F-Markierung zur Darstellung eines neuen potentiellen A2A Radiotracers ausgewählt. Die gewünschte Position in 1 ist jedoch nicht für eine nukleophile aromatische Substitution gegen [18F]Fluorid aktiviert, sodass die Zielstellung in der Entwicklung einer geeigneten Radiosynthese von [18F]1 besteht.

Methodik: Es wurden drei Strategien zur Radiosynthese von [18F]1 verfolgt. Ausgehend vom Trimethylammonium-Präkursor 2 erfolgte die 18F-Markierung zum [18F]Fluorbenzaldehyd [18F]3. Dieser wurde entweder direkt über eine reduktive Aminierung oder nach Reduktion und anschließender Bromierung über eine Benzylierung mit dem Pyrazolo[2,3-d]pyrimidin-Baustein 4 zu [18F]1 umgesetzt. Parallel dazu wurde die direkte 18F-Markierung des Boronsäurepinacol-Präkursors 5 bearbeitet.

Ergebnisse: Ausgehend von 2 wurde [18F]1 nach der zweistufigen Radiosynthese mit nur 1,5% radiochemischer Ausbeute in der Reaktionsmischung detektiert (Radio-HPLC). Diese konnte mittels der vierstufigen Methode auf 49% gesteigert werden. In beiden Verfahren wurde eine hohe Anzahl an 18F-Nebenprodukten nachgewiesen, welche die Isolierung von [18F]1 mittels semi-präparativer HPLC erschweren. Die direkte 18F-Markierung von 5 führte zu einer radiochemischen Ausbeute von 80-90% an [18F]1 in der Reaktionsmischung (Radio-DC/-HPLC), wobei lediglich ein 18F-Nebenprodukt (< 5%) detektiert wurde.

Schlussfolgerungen: Aufgrund dieser Ergebnisse wird ausschließlich die einstufige Strategie zur Darstellung des neuen potentiellen A2A-Radiotracers [18F]1 ausgehend von 5 weiterverfolgt. Für die geplante biologische Evaluierung (in vitro und in vivo) werden derzeit geeignete Methoden zur Isolierung, Konzentration und Formulierung von [18F]1 erarbeitet.

Referenzen:
[1] Allard et al., Immunol. Cell. Biol. 2017, 95(4), 333-339
[2] Gillespie et al., Bioorg. Med. Chem. Lett. 2008, 18, 2924-2929
Keywords: Adenosin A2A Rezeptor, Radiotracer, 18F, PET, Hirntumor
  • Lecture (Conference)
    26. Jahrestagung der AGRR, 20.-22.09.2018, Aachen, Deutschland

Publ.-Id: 28145 - Permalink


1-Dimensional inorganic double helices as candidates for information storage materials
Springer, M.; Kuc, A.; Vankova, N.; Heine, T.ORC
Alkali metal monopnictides contain one-dimensional chains with a double-helical structure. In this work, we report about their possible use as information storage materials. We investigated computationally fundamental properties of hetero- and homocationic systems and ways towards the application. It was shown, that the phosphorous backbone is capable of stabilising cationic chains of different composition and thus allows encoding of information.
  • Poster
    Computational Spectroscopy: Bridging Theory and Experiment, 09.-14.09.2018, Como, Italien
  • Poster
    13th HZDR PhD seminar, Ustí, 05.-07.11.2018, Ustí nad labem, Tschechische Republik

Publ.-Id: 28143 - Permalink


Visualisation of the large scale circulation in Rayleigh-Bénard convection using contactless inductive flow tomography
Wondrak, T.; Stefani, F.; Galindo, V.; Eckert, S.
Rayleigh-Bénard (RB) convection plays an important role in geo- and astrophysics as well as in many metallurgical applications. At sufficiently high values of the Rayleigh number, a large scale circulation (LSC) is formed whose dynamics had turned out to be surprisingly rich. In this paper, the applicability of the contactless inductive flow tomography (CIFT) for the detection of the torsional mode of the LSC is investigated. CIFT enables the three-dimensional reconstruction of flow structures in liquid metals by applying one or more magnetic fields and measuring the flow induced perturbations of those fields outside the melt. Additionally, preliminary measurements of the flow induced magnetic field with a similar sensor arrangement will be presented.
Keywords: flow measurement techniques, Rayleigh-Bénard convection
  • Lecture (Conference)
    9th international symposium on electromagnetic processing of materials (EPM2018), 14.-18.10.2018, Awaji Yumebutai International Conference Center, Japan
  • Open Access LogoIOP Conference Series: Materials Science and Engineering 424(2018), 012007
    DOI: 10.1088/1757-899X/424/1/012007

Publ.-Id: 28138 - Permalink


Real-time control of the mould flow in a model of continuous casting in frame of the TOMOCON project
Wondrak, T.; Hampel, U.; Ratajczak, M.; Glavinić, I.; Stefani, F.; Eckert, S.; van der Plas, D.; Pennerstorfer, P.; Muttakin, I.; Soleimani, M.; Abouelazayem, S.; Hlava, J.; Blishchik, A.; Kenjeres, S.
In continuous casting, the flow structure of the liquid steel in the mould and the two-phase distribution in the submerged entry nozzle (SEN) are crucial for the quality of the produced steel. In order to effectively control the flow in the mould by electromagnetic brakes (EMBrs) and the injection of gas into the SEN, even a rough knowledge of the flow structure would be very helpful. In the framework of the TOMOCON project, the contactless inductive flow tomography (CIFT) and the mutual inductance tomography (MIT) will be integrated into a control loop for slab casters. This control loop will be developed and implemented at the Mini-LIMMCAST facility, which is available at the Helmholtz-Zentrum Dresden – Rossendorf. In this paper a short overview of this project will be given.
Keywords: continuous casting, electromagnetic brake, inductive measurement techniques, flow control
  • Lecture (Conference)
    9th international symposium on electromagnetic processing of materials (EPM2018), 14.-18.10.2018, Awaji Yumebutai International Conference Center, Japan
  • Open Access LogoIOP Conference Series: Materials Science and Engineering 424(2018), 012003
    DOI: 10.1088/1757-899X/424/1/012003

Publ.-Id: 28137 - Permalink


All-optical structuring of laser-driven proton beam profiles data sets
Obst-Huebl, L.ORC; Ziegler, T.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cowan, T. E.; Curry, C. B.; Fiuza, F.; Garten, M.; Gauthier, M.; Göde, S.; Glenzer, S. H.; Huebl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Pausch, R.; Prencipe, I.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

This data repository contains analyzed data files of the shown figures and simulation input files.

Please see the according README.txt files in the individual directories and the original manuscript for guidance.

Manuscript title:
  All-optical structuring of laser-driven proton beam profiles

Authors:
  Lieselotte Obst, Tim Ziegler, Florian-Emanuel Brack, Joao Branco, Michael Bussmann, Thomas E. Cowan, Chandra B. Curry, Frederico Fiuza, Marco Garten, Maxence Gauthier, Sebastian Göde, Siegfried H. Glenzer, Axel Huebl, Arie Irman, Siegfried H. Glenzer, Axel Huebl, Arie Irman, Jongjin B. Kim, Thomas Kluge, Stephan Kraft, Florian Kroll, Josefine Metzkes-Ng, Richard Pausch, Irene Prencipe, Martin Rehwald, Christian Rödel, Hans-Peter Schlenvoigt, Ulrich Schramm, Karl Zeil

Submitted to:
  Nature Communications (2018)


Responsible for the data repository:
  Lieselotte Obst-Huebl, TU Dresden and HZDR
  Axel Huebl, TU Dresden and HZDR
  Tim Ziegler, TU Dresden and HZDR
  Thomas Kluge, HZDR

 


Related publications
All-optical structuring of laser-driven proton beam profiles (Id 28155) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-10-30
    DOI: 10.14278/rodare.65
    License: CC-BY-4.0

Downloads:

Publ.-Id: 28136 - Permalink


Contactless inductive flow tomography for models of continuous casting and crystal growth
Ratajczak, M.; Wondrak, T.ORC; Glavinić, I.; Stefani, F.
Contactless inductive flow tomography (CIFT) enables the reconstruction of the major flow structure in electrically conducting liquids, like molten steel or silicon. It is based on the permeation of the melt by an external primary magnetic field and the subsequent induction of currents, which generate a flow-induced secondary magnetic field. The measured secondary field allows for reconstruction of the flow by solving the underlying linear inverse problem. We present results for the application of CIFT for two lab-scale model experiments of (a) continuous steel casting in the presence of an electromagnetic brake and (b) Czochalski crystal growth with a thermally driven convection. In the first scenario (a), the electromagnetic brake poses the biggest challenge, since its strong static magnetic field of about 300 mT superimposes the flow-induced field of about 100 nT, and the brake’s ferromagnetic parts distort the CIFT excitation field. We show how this can be overcome by simulations and adequate instrumentation using gradiometric induction coil sensors, which enables correct flow reconstructions in this scenario. In the second setup (b) the biggest challenges arise from the long measurement times of up to 12 hours together with thermal expansion and contraction of the setup mounting due to the intrinsic temperature gradient of the melt. Here an optimized experimental construction is necessary to enable successful measurements magnetic field measurements with Fluxgate sensors. The experimental data reveal plausible stationary and transient phenomena in accordance with numerical
flow simulations.
Keywords: metallurgy, contactless inductive flow tomography, magnetic field measurement, flow measurement
  • Contribution to proceedings
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK
    Proceedings of the 9th world congress on industrial process tomography, 978 0 85316 3497, 839-845
  • Lecture (Conference)
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK

Publ.-Id: 28135 - Permalink


Numerical aspects of contactless inductive flow tomography for crystal growth
Wondrak, T.ORC; Jacobs, R. T.; Galindo, V.; Stefani, F.
The flow structure of liquid silicon in the crucible for Czochralski (Cz) crystal growth is important for the quality of the silicon crystal. However, the high temperature and the required cleanliness of the melt represent a challenge for any flow measurement device. A promising technique to reconstruct the flow of a conducting liquid is contactless inductive flow tomography (CIFT). The procedure relies on the measurement of the flow induced perturbation of a primary magnetic field and the inversion of the corresponding integral equation system. In this paper, the numerical challenges for the application of CIFT to Cz crystal growth will be investigated. This includes the treatment of the singularities of the integral equation system as well as the selection of appropriate integration techniques. The paper concludes with numerical investigation of the expected flow induced magnetic field for a reversal of the rotation in simple model of a typical crucible.
Keywords: contactless inductive flow tomography, Czochralski crystal growth, flow measurement, liquid metal
  • Contribution to proceedings
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK
    Proceedings of the 9th world congress on industrial process tomography, 978 0 85316 3497, 451-456
  • Lecture (Conference)
    9th world congress on industrial process tomography, 02.-6.9.2018, Bath, UK

Publ.-Id: 28134 - Permalink


Surface nanobubbles on the carbonate mineral dolomite
Owens, C. L.ORC; Schach, E.; Rudolph, M.ORC; Nash, G. R.
Surface nanobubbles are of wide interest to a number of research fields, ranging from mineral processing to metamaterials. Their formation on hydrophobic surfaces has long been confirmed but the factors controlling their size and location are less well understood. In this work we investigate, using non-contact atomic force microscopy, the properties of surface nanobubbles on the mineral dolomite under three aqueous solutions; water, depressant and collector. Nanobubbles were observed under all three conditions, but with the highest density observed under collector conditions. Analysis of the critical angle of the bubbles suggests that the collector does not affect the surface tension of the bubbles, but instead does affect their pinning, consistent with the observed increased density.
Keywords: nanobubbles, flotation, atomic force microscopy

Publ.-Id: 28133 - Permalink


Magnon Transport in Spin Textures
Schultheiss, H.
One of the grand challenges in cutting edge quantum and condensed matter physics is to harness the spin degree of electrons for information technologies. While spintronics, based on charge transport by spin polarized electrons, made its leap in data storage by providing extremely sensitive detectors in magnetic hard-drives, it turned out to be challenging to transport spin information without great losses. With magnonics a visionary concept inspired researchers worldwide: Utilize magnons - the collective excitation quanta of the spin system in magnetically ordered materials - as carriers for information. Magnons are waves of the electrons’ spin precessional motion. They propagate without charge transport and its associated Ohmic losses, paving the way for a substantial reduction of energy consumption in computers.
While macroscopic prototypes of magnonic logic gates have been demonstrated, the full potential of magnonics lies in the combination of magnons with nano-sized spin textures. Both magnons and spin textures share a common ground set by the interplay of dipolar, spin-orbit and exchange energies rendering them perfect interaction partners. Magnons are fast, sensitive to the spins’ directions and easily driven far from equilibrium. Spin textures are robust, non-volatile and still reprogrammable on ultrashort timescales. The vast possibilities offered by combining this toolset of magnetic phenomena, add value to both magnonics and the fundamental understanding of complex spin textures.
I will give an introduction about magnon propagation and manipulation in microstructures with non-collinear spin textures, in particular magnons propagating in nano channels formed by magnetic domain walls. Furthermore, I will address how magnons can be excited in domain wall channels by pure spin currents originating from the spin Hall effect.
References:
[1] K. Wagner, A. Kákay, K. Schultheiss, A. Henschke, T. Sebastian, and H. Schultheiss, Nature Nanotech 11, 432 (2016).
[2] K. Vogt, F. Y. Fradin, J. E. Pearson, T. Sebastian, S. D. Bader, B. Hillebrands, A. Hoffmann, and H. Schultheiss, Nat Comms 5, 3727 (2014).
Keywords: magnonics, spin waves, spin textures, domain walls, auto-oscillations
  • Invited lecture (Conferences)
    Lüscher Seminar, 08.02.2018, Klosters, Schweiz
  • Invited lecture (Conferences)
    Spin Mechanics 5 and Nano MRI 6 workshop, 16.02.2018, Chamonix, Schweiz
  • Invited lecture (Conferences)
    Nano-Magnonics Workshop, 20.02.2018, Kaiserslautern, Deutschland
  • Invited lecture (Conferences)
    International Conference on Microwave Magnetics, 25.06.2018, Exeter, England
  • Invited lecture (Conferences)
    Workshop on Advances in Brillouin Light Scattering, 13.09.2018, Perugia, Italien
  • Invited lecture (Conferences)
    International Advanced School on Magnonics, 20.09.2018, Kyiv, Ukraine

Publ.-Id: 28132 - Permalink


Ultrasmall Nanomaterials for Multimodal Cancer Imaging
Stephan, H.
Ultrasmall nanomaterials (NMs) offer excellent prospects for the development of new non-invasive strategies of early diagnosis and efficient monitoring of therapeutic treatments. Provided with special functionalities, NMs allow the simultaneous application of different molecular imaging methods. In the field of cancer medicine, the combination of different imaging techniques such as nuclear (PET: positron emission tomography and SPECT: single-photon emission computed tomography) and near-infrared fluorescence (NIRF) imaging for tracking down tumors and metastases is particularly attractive.
This lecture will focus on the development and application of very small radiolabeled NMs, embracing inorganic particles and soft polymeric structures. Novel strategies will be discussed to develop stealth NMs capable of avoiding biomolecular corona formation and thus evading scavenging of NMs by the mononuclear phagocyte system, leading to eventual accumulation in the liver and spleen.
  • Invited lecture (Conferences)
    Kolloquium, 25.10.2018, Hamburg, Deutschland

Publ.-Id: 28130 - Permalink


Magnon auto-oscillation under zero magnetic field
Nishida, N.; Hache, T.; Arekapudi, S. S. P. K.; Awad, A. A.; Hellwig, O.; Fassbender, J.; Schultheiss, H.
Magnons are attractive for application in energy efficient information technology, because they propagate without any actual charge currents and they offer high frequencies up to THz range. Here we present a novel scheme for magnon generation using spin currents and domain walls.
When a charge current is applied to a heavy metallic/ferromagnetic bilayer, the spin currents originating from a spin Hall effect in the heavy metal apply a spin transfer torque on the magnetization. This allows driving efficiently auto-oscillations of magnetization [1]. We focused on domain walls as local magnon nano channels [2]. Since domain walls can be moved by electrical currents [3], they are attractive for reprogrammable nano circuits.
A 370 nm wide zigzag structure was fabricated from a Pt/CoFeB bilayer. A domain wall was generated at the apex by magnetic saturation. The magnon intensity on the remanent state was measured by Brillouin light scattering microscopy [4] with applying a dc current. The magnon excitation showed the dc current dependency. Magnons were detected only for positive dc currents. We succeeded to drive magnon auto-oscillation in the domain wall under zero magnetic field by spin transfer torque.

Reference
[1] A. N. Slavin and V. Tiberkevich, IEEE Trans. Magn. 45, 1875 (2009).
[2] K. Wagner et. al., Nat. Nanotech. 11, 432 (2016).
[3] S. S. P. Parkin et. al., Science 320, 190 (2008).
[4] T. Sebastian et. al., Front. Phys. 3, 35 (2015).
  • Lecture (Conference)
    9th Joint European Magnetic Conference, 03.-07.09.2018, Mainz, Germany

Publ.-Id: 28122 - Permalink


Magnon auto-oscillation in domain walls
Nishida, N.; Hache, T.; Arekapudi, S. S. P. K.; Awad, A. A.; Hellwig, O.; Fassbender, J.; Schultheiss, H.
Magnons are the fundamental excitations in magnetic materials, and they can transport angular momentum without actual charge currents. Therefore, they are attractive for applications in energy efficient information technology, offering high operating frequencies up to the THz range. Here we present a novel scheme for magnon generation using spin currents and domain walls.
When a charge current is applied to a bilayer consisting of a heavy metal and a ferromagnetic metal, the spin currents originating from the spin Hall effect in the heavy metal apply a spin transfer torque on the magnetization of the ferromagnetic layer. This allows driving efficiently auto-oscillations of magnetization [1]. We focused on domain walls as local nano magnon channels [2]. Since it is possible to move domain walls by electrical currents [3], domain walls are attractive for nano-sized reprogrammable circuits.
A 370 nm wide boomerang structure was fabricated from a Pt/CoFeB bilayer (Fig.1). The sample was magnetized by applying an external magnetic field H. After the saturation, the external magnetic field was set to 0 Oe, and a dc current was applied to the sample. The magnon intensity at the apex of the boomerang structure was measured by Brillouin light scattering microscopy [4]. Figure 2 shows the dc current dependency of the magnon spectrum on the remanent state. Magnons were detected for currents between 3.6 mA and 4.5 mA, while no magnons were observed
for any negative dc currents. A domain wall is generated at the apex for the remanent state because of the shape anisotropy of the boomerang structure. We succeeded to excite magnons under zero magnetic field due to the autooscillation of the magnetization by spin transfer torque.

Reference
[1] A. N. Slavin and V. Tiberkevich, IEEE Trans. Magn. 45, 1875 (2009).
[2] K. Wagner et. al., Nat. Nanotech. 11, 432 (2016).
[3] S. S. P. Parkin et. al., Science 320, 190 (2008).
[4] T. Sebastian et. al., Front. Phys. 3, 35 (2015).
  • Lecture (Conference)
    International Conference on Magnetism, 15.-20.07.2018, San Francisco, USA

Publ.-Id: 28121 - Permalink


A simple route to synchronized nucleation of self-catalyzed GaAs nanowires on silicon for sub-Poissonian length distributions
Tauchnitz, T.ORC; Berdnikov, Y.; Dubrovskii, V. G.ORC; Schneider, H.; Helm, M.; Dimakis, E.ORC
We demonstrate a simple route to grow ensembles of self-catalyzed GaAs nanowires with a remarkably narrow statistical distribution of lengths on natively oxidized Si(111) substrates. The fitting of the nanowire length distribution with a theoretical model reveals that the key requirements for narrow length distributions are the synchronized nucleation of all nanowires on the substrate and the absence of beam shadowing from adjacent nanowires. Both requirements are fulfilled by controlling the size and number density of the openings in SiOx, where the nanowires nucleate. This is achieved by using a pre-growth treatment of the substrate with Ga droplets and two annealing cycles. The narrowest nanowire length distributions are markedly sub-Poissonian, which validates the theoretical predictions about temporally anti-correlated nucleation events in individual nanowires, the so-called nucleation antibunching. Finally, the reproducibility of sub-Poissonian length distributions attests the reliability of our growth method.
Keywords: substrate for nanowires, nucleation antibunching, nucleation delay, nanowire nucleation

Publ.-Id: 28118 - Permalink


Excitation of whispering gallery magnons in a magnetic vortex
Schultheiss, K.; Verba, R.; Wehrmann, F.; Wagner, K.; Körber, L.; Hula, T.; Hache, T.; Kákay, A.; Awad, A. A.; Tiberkevich, V.; Slavin, A. N.; Fassbender, J.; Schultheiss, H.
We present the generation of whispering gallery magnons with unprecedented high wave vectors via nonlinear 3-magnon scattering in a μm-sized magnetic vortex state disc. These modes exhibit a strong localisation at the perimeter of the disc and practically zero amplitude in an extended area around the vortex core. They originate from the splitting of the fundamental radial magnon modes, which can be resonantly excited in a vortex texture by an out-of-plane microwave field. We shed light on the basics of this non-linear scattering mechanism from experimental and theoretical point of view. Using Brillouin light scattering (BLS) microscopy, we investigated the frequency and power dependence of the 3-magnon splitting. The spatially resolved mode
profiles give evidence for the localisation at the boundaries of the disc and allow for a direct determination of the modes wavenumber.
Keywords: magnons, spin wave, nonlinear magnetization dynamics, magnetic vortex, Brillouin light scattering
  • Invited lecture (Conferences)
    International Conference on Magnetism, 19.07.2018, San Francisco, USA
  • Lecture (Conference)
    Joint European Magnetic Symposia (JEMS), 04.09.2018, Mainz, Deutschland

Publ.-Id: 28116 - Permalink


Electrochemical studies on zinc in boric acid containing electrolytes
Harm, U.; Kryk, H.; Hampel, U.
During the sump recirculation phase after a leak in the primary cooling circuit of a pressurized water reactor (PWR), corrosion of hot-dip galvanized containment internals (e.g. grating treads, supporting grids of sump strainers) in the boric acid containing coolant may occur, which could later cause problems due to the possible precipitation of formed zinc borates (fouling) at hot regions of the reactor core [1, 2].
Beside other safety related investigations, generic zinc corrosion studies in boric acid electrolytes were conducted to investigate the dependency of the zinc corrosion rates in PWR coolants on different boundary conditions (fluid temperatures, pH, boric acid concentration, flow conditions nearby the zinc surface).
Corrosion experiments with dipped zinc sheets in stirred boric acid solutions already had shown that moderate variations of the fluid temperatures or the boric acid content only caused small changes in resulting zinc corrosion rates, but an increase of flow rates or turbulences often led to significantly increased corrosion rates [2].
For a better understanding of these results, additionally, some series of electrochemical measurements were carried out using a rotating disc electrode (zinc) as working electrode, a platinum counter electrode and tempered aqueous boric acid solutions (plus 0.1 M Na2SO4 as conducting salt) as electrolyte. Linear anodic and cathodic polarization was realized (up to potentials of 200 mV different from the free corrosion potential) under variation of fluid temperature (20 to 60 °C), boric acid content (1000 to 3000 ppm boron), pH (4.7 to 7) and the rotation speed.
First results of these experiments (e.g. comparing tafel plots) showed similar dependencies of the zinc corrosion rates than described above for the zinc dissolution experiments. The cathodic polarization curves mostly showed a plateau of the current densities with increasing cathodic polarization (overvoltage) indicating a strong control of the cathodic reaction (and thus the corrosion process as a whole) by the transport limitation of the dissolved oxygen to the zinc surface. Comparison of the tafel plots resulting from measurements at different rotation speeds (similar otherwise conditions) also demonstrated a strong increase of the zinc corrosion rates with increasing flow rates. For example, calculated zinc corrosion rates for infinite high rotation speeds (Levich extrapolation) usually are more than ten times higher compared to those of similar experiments without rotation. Therefore, also these results of the electrochemical investigations confirm the earlier results of a transport controlled corrosion process (see above) and may help to quantify the possible ranges of resulting corrosion rates at different boundary conditions.
This work is funded by the German Federal Ministry of Economic Affairs and Energy (BMWi) with the grant number 1501496 on the basis of a decision by the German Bundestag.

[1] Seeliger, A.; Alt, S.; Kästner, W.; Renger, S.; Kryk, H.; Harm, U.: Zinc corro¬sion after loss-of-coolant accidents in pressurized water reactors - thermo- and fluid-dynamic effects. Nuclear Engine-ering and Design, 2016, 305, 489-502
[2] Harm, U.; Kryk, H.; Hampel, U.: Generic Zinc Corrosion Studies at PWR LOCA Conditions. Annual Meeting on Nuclear Technology (AMNT 2017), 2017
Keywords: Nuclear energy; corrosion; zinc release; electrochemistry; experiments
  • Poster
    Electrochemistry 2018, 24.-26.09.2018, Ulm (Universität Ulm), Deutschland

Publ.-Id: 28112 - Permalink


Investigations on the effects of heater surface characteristics on the bubble waiting period during nucleate boiling at low subcooling
Sarker, D.; Ding, W.; Franz, R.; Varlamova, O.; Kovats, P.; Zähringer, K.; Hampel, U.
In nucleate boiling the ‘bubble waiting period’, that is, the time duration between the departure of a grown bubble and the start of the formation of a new bubble from a cavity, plays a crucial role for the total heat transfer. Experiments were performed to study the influence of the heater surface characteristics on this parameter. A femtosecond pulsed laser was used to produce nano- and micro-patterned surfaces with roughness in the range of micrometers on stainless steel heater surfaces. Boiling experiments were conducted on a vertically oriented heater at atmospheric pressure and with degassed deionized water. Bubble generation, departure, sliding, detachment and inception of the next bubble have been recorded by high-resolution optical shadowgraphy. Bubble waiting periods were found to be longer for low-wettability smooth and rough surfaces. High-wettability rough surfaces showed a shorter bubble waiting period. The shortest (approximately 3 ms) and the longest (approximately 30 ms) bubble waiting periods were found for well-wetting surfaces with Sq = 0.18 µm and for low-wetting surfaces with 0.12 µm, respectively. These corresponding roughness heights are denoted as ‘optimal roughness heights’.
Keywords: Bubble waiting periodSurface wettabilityRoughnessVertical heaterNucleate boiling

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  • Secondary publication expected from 06.10.2019

Publ.-Id: 28109 - Permalink


Molekulare Geochemie für das nukleare Endlager
Schmidt, M.ORC
In diesem Überblicksvortrag werden wissenschaftliche Fragestellungen zur Endlagerung hochradioaktiver Abfälle diskutiert. Die Komplexität des geotechnischen und -chemischen Systems inbesondere im Bezug zur Rückhaltung der minoren Actiniden und Plutonium wird dargestellt, um die Notwendigkeit für ein molekulares Prozessverständnis darzulegen. Letztlich wird an Beispielen diskutiert wie dieses Prozessverständnis erhalten werden kann und wie es zur Langzeitsicherheitsanalyse beiträgt.
Keywords: Endlager, Geochemie, Actiniden, molekulares Prozessverständnis
  • Invited lecture (Conferences)
    50. Kraftwerkstechnisches Kolloquium, 23.-24.10.2018, Dresden, Deutschland

Publ.-Id: 28107 - Permalink


Industrial flowsheeting and thermo-economic assessment
Reuter, M. A.; Llamasa, A. A.
Session 2 was organised by the SOCRATES project. SOCRATES studies the development of near-zero waste processes for the recycling of low-grade metal containing industrial waste streams, such as bottom ashes, copper tailings and slags and sludges from the non-ferrous industry, commonly deposited in industrial landfills and tailing ponds. Markus Reuter and Alejandro Abadias (Helmholtz-Zentrum Dresden-Rossendorf, Germany) illustrated how novel near-zero waste flowsheets for the treatment of these residues are assessed within the SOCRATES project. Focus of the session was on the primary copper production flowsheet (from rock to metal), in which two scenarios were compared, being production of copper without treatment of wastes and with additional metal recovery from wastes (slags and drosses). The analysis was performed through composing a mass and energy balance of the flowsheet and performing an exergy analysis and life cycle assessment.
Keywords: near-zero waste, recycling, SOCRATES,
  • Lecture (others)
    Summer school 2018: “To mine or not to mine”, 10.-12.09.2018, Leuven, Belgien

Publ.-Id: 28105 - Permalink


The limits of the Circular Economy
Reuter, M. A.
-> Circular Economy (CE) - The origins
-> Circular Economy Engineering (CEE)
-> Metallurgical Internet-of-Things (m-IoT) - Comprehensive flowsheets that integrate product design with physical separation and process metallurgy
-> informing Resource Efficiency (iRE)
Fairphone / Plasma furnace for battery smelting
Keywords: Circular Economy, Circular Economy Engineering, Metallurgical Internet-of-Things, Resource Efficiency, Fairphone
  • Lecture (others)
    Circular Economy of EV Batteries - Workshop, 24.-25.05.2018, Espoo, Finnland

Publ.-Id: 28104 - Permalink


Process Model Based LCA Using HSC Chemnistry Software
Reuter, M. A.; Roine, A.
The process industry defines the initial LCA values that are used for raw materials in the manufacturing industry. Plant vs Factory!
If we are talking about the circular economy and the whole value chain, then we must also take into account the effect of the process industry and recycling. This is the only way to minimize total environmental footprints.
Keywords: circular economy, recycling, environmental footprints
  • Lecture (others)
    LCA Course SusCriMat - Winterschool, 15.-19.01.2018, Les Diablerets, Schweiz

Publ.-Id: 28103 - Permalink


Urban Mining: Dream or Reality – The Limits and opportunities of the Circular Economy
Reuter, M. A.
The circular economy will play an important role in shaping a resource-efficient society. Enabling this transformation from a linear to a circular economy requires precise quantification of resource efficiency and thus the economic viability of the system.

Based on the development of simulation tools of classical minerals processing and process metallurgy, the HSC Sim (www.outotec.com) simulation platform could be further developed, gleaning from many academically published works of the authors. This permits the simulation of the circular economy system and to subsequently calculate its resource efficiency. It for example also enables the estimation of a simulation-based recycling index of a product from the "Bill of Material" and "Full Material Declaration". It is a unique methodology for "Design for Recycling".

Figure 1 shows that a key to this simulation is a detailed understanding of the mineralogy as well as the limits of the circular economy system and its many products, materials and systems. In addition, a detailed understanding and quantification of the thermodynamic properties of the system is key to understanding its economics. With this approach, we will show the actual losses of the "circular economy" system and thus illuminate the limits and hence explore in detail if Urban Mining is a dream or economic reality.
Keywords: Fairphone, recycling, circular economy
  • Invited lecture (Conferences)
    EuroScience Open Forum, 09.-14.07.2018, Toulouse, Frankreich

Publ.-Id: 28102 - Permalink


ASTEC model of the THS-15 test facility and first simulation results
Jobst, M.
In the framework of the NuWaMa project (Expansion of a German-Czech Collaboration in the Field of Nuclear Waste Management), a research stay at ÚJV Řež (Czech Republic) took place during May 2018 (from 1st of May till 31st of May). The objective of the research stay was the development of a numerical model of the thermal-hydraulic test facility THS-15, which had been put in operation at the ÚJV site in Řež recently in order to investigate phenomena related to ex-vessel cooling for in-vessel retention of molten corium. Assessing the performed experiments with the help of the numerical model is an important contribution to a comprehensive under-standing of the observed phenomena. The current state of the ASTEC model and the first calculation results are presented.
Keywords: VVER; in-vessel melt retention; THS-15 test facility; ASTEC; numerical simulation; critical heat flux
  • Lecture (Conference)
    ASTEC Users' Club Meeting, 09.-11.10.2018, Aix-en-Provence, République française

Publ.-Id: 28099 - Permalink


Microstructure, strengthening mechanisms & properties of ODS alloys developed under MatISSE project
Chauhan, C.; Bergner, F.; Etienne, A.; Aktaa, J.; de Carlan, Y.; Heintze, C.; Litvinov, D.; Hernandez-Mayoral, M.; Oñorbe, E.; Radiguet, B.; Ulbricht, A.
The invited talk aims at summarizing results from a publication that received the best paper award 2017 of the Journal of Nuclear Materials. Microstructure, strengthening mechanisms and properties of ODS alloys are addressed.
Keywords: ODS alloys, microstructure characterization, strengthening mechanisms
  • Invited lecture (Conferences)
    NuMat2018: The Nuclear Materials Conference, 14.-18.10.2018, Seattle, USA

Publ.-Id: 28091 - Permalink


High Energy Fast X-ray Tomography
Barthel, F.; Windisch, D.; Hampel, U.
Ultrafast X-ray computed tomography with ROFEX scanners has become a common tool for investigations of multiphase phenomena in science and industrial application within recent years. Though being very successful in giving unprecedented insights into dynamic processes, ROFEX scanners yet have some limitations in terms of permissible sizes and density of the investigated objects. Due to the limited penetration capability of X-rays at photon energy of up to 150 keV experimental mock-ups need to be made out of light construction materials and many experimental setups had to be scaled down from their real size to fit into the scanner. Often this limits the transferability of results to larger industrial facilities.
This contribution introduces the new High-Energy Computed Tomography scanner of Rossendorf (HECToR) as the next step towards improved industrial applicability. The facility utilizes a 1 MeV electron accelerator with a continuous beam power of up to 100 kW. The functional principle has been adapted from the ROFEX scanners. HECToR is able to scan objects with a maximum diameter of 400 mm at a temporal resolution of up to 5000 frames per second and with a spatial resolution of 3 mm at best conditions. The paper introduces the scanner concept, its components and presents first dynamic studies on generic two-phase flows in steel vessels. Furthermore, the imaging characteristics are discussed in detail.
Keywords: ROFEX, ultrafast X-ray CT, high energy, HECToR
  • Contribution to proceedings
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
    Proceedings of the 9th world cogress on industrial process tomography
  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK

Publ.-Id: 28090 - Permalink


Review Article: Review of electrohydrodynamical ion sources and their applications to focused ion beam technology
Gierak, J.; Mazarov, P.; Bruchhaus, L.; Jede, R.; Bischoff, L.
In this article, the authors review, compare, and discuss the characteristics and applicative potential of a variety of nongallium ion liquid metal ion sources they have developed and successfully applied to nanopatterning. These sources allow generating on-demand ion beams and are promising for extending focused ion beams applications. They detail the operating characteristics of such sources capable to emit metal projectiles ranging from atomic ions with different charge states to polyatomic ions and to large metal clusters having sizes up to a few nanometers. They highlight their interest and relevance to current nanoscience challenges in terms of ultimate patterning or bottom-up nanofabrication capabilities.
Keywords: Liquid Metal Ion Source, nongallium, nanoscience
  • Journal of Vacuum Science & Technology B 36(2018)6, 06J101-1-06J101-6
    DOI: 10.1116/1.5047150

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  • Secondary publication expected

Publ.-Id: 28088 - Permalink


Forschungsdatenmanagement am Helmholtz-Zentrum Dresden-Rossendorf und am Helmholtz-Zentrum Berlin (RDM@DB)
Konrad, U.ORC; Görzig, H.; Juckeland, G.
Das BMBF Verbundprojekt RDMatDB wird im Rahmen der Förderrichtlinie "Erforschung des Managements von Forschungsdaten in ihrem Lebenszyklus“ realisiert. Ziel des Projektes ist es, Forschungsdaten-Management-Lösungen zu entwickeln, die das HZDR und HZB als Betreiber von Infrastrukturen in die Lage versetzen, die sich aus den FAIR-Prinzipien des Datenmanagements ergebenden Anforderungen zu erfüllen. Im dem Vortrag auf der BMBF-Veranstaltung "Forschungsdatenmanagement - künftige Entwicklungen und aktuelle Fragen der Wissenschaft" wird das Projekt und die Perspektiven vorgestellt.
Keywords: The BMBF joint project RDMatDB of the HZDR and HZB is implemented within the scope of the funding program "Research on the management of research data in its life cycle ". The goal of the project is to develop research data management solutions which the HZDR and HZB consider to meet the requirements of the FAIR data management principles. The project and perspectives are presented at the BMBF event "Research Data Management - Future Developments and Current Issues of Science".
  • Invited lecture (Conferences)
    Forschungsdatenmanagement - künftige Entwicklungen und aktuelle Fragen der Wissenschaft, 17.-18.10.2018, Berlin, Deutschland
    DOI: 10.14278/rodare.62

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Publ.-Id: 28087 - Permalink


Influence of the magnetic field on the stability of the multiferroic conical spin arrangement of Mn0.80Co0.20WO4
Urcelay-Olabarria, I.; Ressouche, E.; Ivanov, V. Y.; Skumryev, V.; Wang, Z.; Skourski, Y.; Balbashov, A. M.; Popov, Y. F.; Vorob'En, G. P.; Qureshi, N.; Garcia-Munoz, J. L.; Mukhin, A. A.
The evolution of the low temperature antiferromagnetic conical (characterized by two, commensurate and incommensurate propagation vectors), and the high temperature collinear spin arrangements of the 20% Co-doped MnWO4 multiferroic has been studied in the presence of magnetic field up to 60 T by means of macroscopicmagnetic and pyroelectricmeasurements, and by neutron diffraction experiments in fields up to 12 T on a single crystal. The complete magnetoelectric phase diagrams for magnetic fields along distinct magnetic directions with respect to the spin structure have been constructed up to magnetic field values exceeding those necessary to induce a spin-flip transition into the paramagnetic state. The differences in the topology of the diagrams are discussed. The obtained results might be common for other magnetic materials possessing conical antiferromagnetic structures.

Publ.-Id: 28085 - Permalink


Anomalous Hall effect in Weyl semimetal half-Heusler compounds RPtBi (R = Gd and Nd)
Shekhar, C.; Kumar, N.; Grinenko, V.; Singh, S.; Sarkar, R.; Luetkens, H.; Wu, S.-C.; Zhang, Y.; Komarek, A.; Kampert, E.; Skourski, Y.; Wosnitza, J.; Schnelle, W.; Mccollam, A.; Zeitler, U.; Kübler, J.; Yan, B.; Klauss, H.-H.; Parkin, S. P.; Felser, C.
Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω−1·cm−1 and an anomalous Hall angle as large as 23%.Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition (TN) at 9 K without any noticeable magnetic correlations above TN. Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE.
  • Proceedings of the National Academy of Sciences of the United States of America 115(2018)37, 9140-9144
    DOI: 10.1073/pnas.1810842115

Publ.-Id: 28084 - Permalink


Low-Temperature Magnetic Hysteresis in Nd(Pr)-Fe-B Nanostructured Alloys with Nd2Fe14B Type Main Phase Composition
Neznakhin, D. S.; Politova, G. A.; Ivanov, L. A.; Volegov, A. S.; Gorbunov, D. I.; Tereshina, I. S.; Kudrevatykh, N. V.
Magnetic hysteresis properties of nanostructured industrially manufactured Nd-Fe-B and Pr-Fe-B alloys on the base of a tetragonal Nd2Fe14B (2-14-1) hard magnetic phase (MQP-B, MQP-B+ and MQP-16-7 brands) have been investigated at 4.2 K in magnetic fields up to 58 T. The chemical composition of the alloys given in the certificates was defined more precisely. The grain sizes of the main 2-14-1 phase were determined. The average grain size is much smaller than a critical single domain diameter. Coercivity, remanence magnetization, saturation magnetization and maximal magnetic energy product were determined at 4.2 K and compared with those obtained at room temperature.

Publ.-Id: 28083 - Permalink


Millisecond Dynamics of the Magnetocaloric Effect in a First- and Second-Order Phase Transition Material
Döntgen, J.; Rudolph, J.; Gottschall, T.; Gutfleisch, O.; Hägele, D.
The millisecond-dynamics of the magnetocaloric effect in Gd and La-Fe-Si-Mn, which exhibit first- and second-order phase-transitions, respectively, are investigated. Direct measurements of the adiabatic temperature change ΔT are obtained from modulation infrared thermometry with field-cycling frequencies exceeding 1 kHz at amplitudes of up to 45 mT. The peak amplitude of ΔT(T) shows a dependence on sample thickness and decreases with increasing modulation frequency for both materials despite a frequency independent susceptibility of Gd. The adiabatic DT depends quadratically on the external field for Gd while La-Fe-Si-Mn shows a peculiar bucket-shaped curve for temperatures below the peak maximum. A comparative study of non-caloric samples shows that dissipative heating by eddy currents or magnetic hysteresis does not explain the observed behavior. The transient ΔT(t) instead suggests a mechanism involving strong temperature gradients at the ferromagnetic–paramagnetic boundaries and underlines the importance of further dynamical studies for a fundamental understanding of the magnetocaloric effect in first-order materials.

Publ.-Id: 28082 - Permalink


Improving landslide susceptibility mapping using morphometric features in the Mawat area, Kurdistan Region, NE Iraq: Comparison of different statistical models
Othman, A. A.; Gloaguen, R.; Andreani, L.ORC; Rahnama, M.
Susceptibility mapping provides information about vulnerable locations and thus helps to potentially decrease infrastructure damage due to mass wasting. During the past decades, expansion of settlements into areas prone to landslides in Iraq has highlighted the importance of accurate landslide susceptibility studies. The main goal of this research is to implement selected morphometric parameters to improve prediction of landslide susceptibility in the Zagros Mountain region. We used the Mawat area, in the Kurdistan Region (NE Iraq) to test the added value of morphometric indicators. Sixteen morphometric factors, mainly derived from a Digital Elevation Model (DEM), extracted using the stereo-ability of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite, as well as geological and environmental predictive factors, were appraised. We evaluated and compared Frequency Ratio (FR), Weight of Evidence (WOE), Logistic Regression (LR) and Probit Regression (PR) approaches in combination with morphometric indices to determine the Landslide Susceptibility (LS). The areas under the curve (AUC) of the Prediction Rate Curve (PRC), Relative landslide density Index (R index), and True Positive Percentage (TPP) for the four models show that all models perform similarly, and the focus should be on careful selection of the predictive factors, which is far more important than the methods used. Results indicate that lithology and slope aspects are the more dominant factors that lead to detect possible occurrence of landslides. Furthermore, this work demonstrates that the hypsometric integral performs better than the commonly used slope curvature as a predictor and thus increases the prediction accuracy of the susceptibility map. We argue that the use of adequate morphometric parameters can increase the efficiency of the LS mapping in other regions of the world.
Keywords: Frequency ratio, Weight of evidence, Logistic regression, Probit regression, Landslide susceptibility (LS), Iraq

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Publ.-Id: 28073 - Permalink


Beyond a phenomenological description of magnetostriction
Reid, A. H.; Shen, X.; Maldonado, P.; Chase, T.; Jal, E.; Granitzka, P. W.; Carva, K.; Li, R. K.; Li, J.; Wu, L.; Vecchione, T.; Liu, T.; Chen, Z.; Higley, D. J.; Hartmann, N.; Coffee, R.; Wu, J.; Dakovski, G. L.; Schlotter, W. F.; Ohldag, H.; Takahashi, Y. K.; Mehta, V.; Hellwig, O.; Fry, A.; Zhu, Y.; Cao, J.; Fullerton, E. E.; Stöhr, J.; Oppeneer, P. M.; Wang, X. J.; Dürr, H. A.
Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction—the underlying magnetoelastic stress—can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.

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Publ.-Id: 28072 - Permalink


Measuring the thermal properties of anisotropic materials using beam-offset frequency domain thermoreflectance
Rahman, M.; Shahzadeh, M.; Braeuninger-Weimer, P.; Hofmann, S.; Hellwig, O.; Pisana, S.
Thermoreflectance techniques have become popular to measure the thermal properties of thin films such as thermal conductivity and thermal boundary conductance (TBC). Varying the focused spot sizes of the beams increases the sensitivity to in-plane heat transport, enabling the characterization of thermally anisotropic materials. However, this requires realignment of the optics after each spot size adjustment. Offsetting the probe beam with respect to the pump beam and modulating over a wide range of frequencies (5 kHz to 50 MHz) yield better sensitivity to the thermophysical properties of anisotropic materials without varying the spot sizes. We demonstrate how beam-offset frequency domain thermoreflectance can be used to measure the in- and out-of-plane thermal conductivity as well as the TBC simultaneously from a single data set by working at reduced spot sizes. Lowering the laser spot size allows us to detect signals over a wide range of frequencies and use larger beam offsets, thanks to the increase in the thermoreflectance signal. We measure the anisotropic thermal properties of a range of materials, including single layer Graphene on SiO2, which is of interest for novel electronic devices.
Keywords: Graphene, Thermal conductivity, Optical metrology, Metal oxides, Frequency domain thermoreflectance

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Publ.-Id: 28071 - Permalink


Chemical-vapor deposited ultra-fast diamond detectors for temporal measurements of ion bunches
Jahn, D.; Träger, M.; Kis, M.; Brabetz, C.; Schumacher, D.; Blaević, A.; Ciobanu, M.; Pomorski, M.; Bonnes, U.; Busold, S.; Kroll, F.; Brack, F.-E.; Schramm, U.; Roth, M.
This article reports on the development of thin diamond detectors and their characterization for their application in temporal profile measurements of subnanosecond ion bunches. Two types of diamonds were used: a 20 μm thin polycrystalline chemical vapor deposited (CVD) diamond and a membrane with a thickness of (5 ± 1) μm etched out of a single crystal (sc) CVD diamond. The combination of a small detector electrode and an impedance matched signal outlet leads to excellent time response properties with a signal pulse resolution (FWHM) of τ = (113 ± 11) ps. Such a fast diamond detector is a perfect device for the time of flight measurements of MeV ions with bunch durations in the subnanosecond regime. The scCVD diamond membrane detector was successfully implemented within the framework of the laser ion generation handling and transport project, in which ion beams are accelerated via a laser-driven source and shaped with conventional accelerator technology. The detector was used to measure subnanosecond proton bunches with an intensity of 10^8 protons per bunch

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Publ.-Id: 28070 - Permalink


A multicaloric cooling cycle that exploits thermal hysteresis
Gottschall, T.; Gràcia-Condal, A.; Fries, M.; Taubel, A.; Pfeuffer, L.; Manosa, L.; Planes, A.; Skokov, K. P.; Gutfleisch, O.
The giant magnetocaloric effect, in which large thermal changes are induced in a material on the application of a magnetic field, can be used for refrigeration applications, such as the cooling of systems from a small to a relatively large scale. However, commercial uptake is limited. We propose an approach to magnetic cooling that rejects the conventional idea that the hysteresis inherent in magnetostructural phase-change materials must be minimized to maximize the reversible magnetocaloric effect. Instead, we introduce a second stimulus, uniaxial stress, so that we can exploit the hysteresis. This allows us to lock-in the ferromagnetic phase as the magnetizing field is removed, which drastically removes the volume of the magnetic field source and so reduces the amount of expensive Nd–Fe–B permanent magnets needed for a magnetic refrigerator. In addition, the mass ratio between the magnetocaloric material and the permanent magnet can be increased, which allows scaling of the cooling power of a device simply by increasing the refrigerant body. The technical feasibility of this hysteresis-positive approach is demonstrated using Ni–Mn–In Heusler alloys. Our study could lead to an enhanced usage of the giant magnetocaloric effect in commercial applications.

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  • Secondary publication expected from 05.04.2019

Publ.-Id: 28069 - Permalink


High-frequency measurements of thermophysical properties of thin films using a modified broad-band frequency domain thermoreflectance approach
Shahzadeh, M.; Rahman, M.; Hellwig, O.; Pisana, S.
In this work, we present the implementation of a new method to perform high-frequency thermoreflectance measurements on thin films. The so-called differential broad-band frequency domain thermoreflectance method follows broad-band frequency domain thermoreflectance developed previously [Regner et al., Rev. Sci. Instrum. 84 (6), 064901 (2013)], without the use of expensive electro-optic modulators. Two techniques are introduced to recover the thermal phase of interestand to separate it from the unwanted instrumental contributions to the recorded phase. Measuring a differential thermal phase by either varying the spot size or offsetting the pump and probe beams, the thermophysical properties of materials can be extracted. This approach enables the study of nanoscale heat transport where non-equilibrium phenomena are dominating.
Keywords: Thin films, Materials properties, Thermal conductivity, Optical metrology, Frequency domain thermoreflectance

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Publ.-Id: 28068 - Permalink


Single-crystal neutron diffraction study of hexagonal multiferroic YbMnO3 under a magnetic field
Chattopadhyay, S.; Simonet, V.; Skumryev, V.; Mukhin, A. A.; Ivanov, V. Y.; Aroyo, M. I.; Dimitrov, D. Z.; Gospodinov, M.; Ressouche, E.
We report a single-crystal neutron diffraction study of the magnetic structure of the multiferroic compound YbMnO3, a member of the hexagonal manganite family, in zero field and under a magnetic field applied along the c axis. We propose a scenario for the zero-field magnetic ordering and for the field-induced magnetic reorientation of the Mn atom and of the two Yb atoms on distinct crystallographic sites, compatible with the macroscopic measurements, as well as with previous powder neutron diffraction experiments and results from other techniques (optical second-harmonic generation and Mössbauer spectroscopy). Our study should contribute to settling some debated issues regarding the magnetic properties of thismaterial as part of a broader investigation of the entire hexagonal RMnO3 (R = Dy, Ho, Er, Tm, Yb, Lu, Y) family.

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Publ.-Id: 28067 - Permalink


Ultrafast laser generated strain in granular and continuous FePt thin films
von Reppert, A.; Willig, L.; Pudell, J.-E.; Rössle, M.; Leitenberger, W.; Herzog, M.; Ganss, F.; Hellwig, O.; Bargheer, M.
We employ ultrafast X-ray diffraction to compare the lattice dynamics of laser-excited continuous and granular FePt films on MgO (100) substrates. Contrary to recent results on free-standing granular films, we observe in both cases a pronounced and long-lasting out-of-plane expansion. We attribute this discrepancy to the in-plane expansion, which is suppressed by symmetry in continuous films. Granular films on substrates are less constrained and already show a reduced out-of-plane contraction. Via the Poisson effect, out-of-plane contractions drive in-plane expansion and vice versa. Consistently, the granular film exhibits a short-lived out-of-plane contraction driven by ultrafast demagnetization which is followed by a reduced and delayed expansion. From the acoustic reflections of the observed strain waves at the film-substrate interface, we extract a 13% reduction of the elastic constants in thin 10 nm FePt films compared to bulk-like samples.
Keywords: Epitaxy, Poisson's ratio, Magnetic devices, Magnetic materials, Stress strain relations, Thin films, Ultrafast X-ray diffraction, Lattice dynamics, Phonons, Elastic modulus

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Publ.-Id: 28066 - Permalink


Ultrafast Self-Induced X-Ray Transparency and Loss of Magnetic Diffraction
Chen, Z.; Higley, D.  J.; Beye, M.; Hantschmann, M.; Mehta, V.; Hellwig, O.; Mitra, A.; Bonetti, S.; Bucher, M.; Carron, S.; Chase, T.; Jal, E.; Kukreja, R.; Liu, T.; Reid, A.  H.; Dakovski, G.  L.; Föhlisch, A.; Schlotter, W.  F.; Dürr, H.  A.; Stöhr, J.
Using ultrafast ≃2.5  fs and ≃25  fs self-amplified spontaneous emission pulses of increasing intensity and a novel experimental scheme, we report the concurrent increase of stimulated emission in the forward direction and loss of out-of-beam diffraction contrast for a Co/Pd multilayer sample. The experimental results are quantitatively accounted for by a statistical description of the pulses in conjunction with the optical Bloch equations. The dependence of the stimulated sample response on the incident intensity, coherence time, and energy jitter of the employed pulses reveals the importance of increased control of x-ray free electron laser radiation.

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Publ.-Id: 28063 - Permalink


Irradiation effects in monazite-(Ce) and zircon: Raman and photoluminescence study of Au-irradiated FIB foils
Nasdala, L.; Akhmadaliev, S.; Artac, A.; Chanmuang, N. C.; Habler, G.; Lenz, C.
Lamellae of 1.5 µm thickness, prepared from well-crystallised monazite-(Ce) and zircon samples using the focused-ion-beam technique, were subjected to triple irradiation with 1 MeV Au+ ions (15.6% of the respective total fluence), 4 MeV Au2+ ions (21.9%) and 10 MeV Au3+ ions (62.5%). Total irradiation fluences were varied in the range 4.5E12 -1.2E14 ions/cm2. The highest fluence resulted in amorphisation of both minerals; all other irradiations (i.e. up to 4.5E13 ions/cm2) resulted in moderate to severe damage. Lamellae were subjected to Raman and laser-induced photoluminescence analysis, in order to provide a means of quantifying irradiation effects using these two micro-spectroscopy techniques. Based on extensive Monte Carlo calculations and subsequent defect-density estimates, irradiation-induced spectroscopic changes are compared with those of naturally self-irradiated samples. The finding that ion irradiation of monazite-(Ce) may cause severe damage or even amorphisation, is in apparent contrast to the general observation that naturally self-irradiated monazite-(Ce) does not become metamict (i.e. irradiation-amorphised), in spite of high self-irradiation doses. This is predominantly assigned to the continuous low-temperature damage annealing undergone by this mineral; other possible causes are discussed. According to cautious estimates, monazite-(Ce) samples of Mesoproterozoic to Cretaceous ages have stored only about 1% of the total damage experienced. In contrast, damage in ion-irradiated and naturally self-irradiated zircon is on the same order; reasons for the observed slight differences are discussed. We may assess that in zircon, alpha decays create significantly less than 1000 Frenkel-type defect pairs per event, which is much lower than previous estimates. Amorphisation occurs at defect densities of about 0.10 dpa (displacements per lattice atom).
Keywords: Radiation damage, Heavy-ion irradiation, Focused ion beam, Raman spectroscopy, Photoluminescence

Publ.-Id: 28059 - Permalink


Smart Tomographic Sensors for Advanced Industrial Process Control - TOMOCON
Hampel, U.; Wondrak, T.; Bieberle, M.; Lecrivain, G.; Schubert, M.; Eckert, K.; Reinecke, S.
With the recent developments in high-power massive parallel computing, process tomography has gained the required real-time capability of being employed as sensors in advanced control systems. Process tomography techniques are of great value as they provide distributed process parameters for opaque processes.
The European Training Network TOMOCON joins 27 international academic and industry partners working together in the emerging field of industrial process control using smart tomographic sensors to lay the scientific and technological fundamentals of integrating imaging sensors into industrial processes and to demonstrate its functional feasibility on lab and pilot-scale applications. Particular focus is on the training of the doctoral researchers in the fields of process tomography hardware, control systems design, industrial process design, multi-physics modelling, and human-computer interaction.
The teams are engaged in multi-disciplinary research on various tomographic imaging modalities, tomographic image processing as well as advanced multi-physics modelling of processes, sensors and actuators. Proof-of-principle demonstrations of tomography-based processes focus on important industrial processes, such as inline fluid separation, microwave drying of porous materials, continuous steel casting and ultrasound-controlled crystallization.
  • Poster
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-15.09.2018, Aachen, Deutschland
  • Open Access LogoAbstract in refereed journal
    Chemie Ingenieur Technik 90(2018)9, 1238-1239
    DOI: 10.1002/cite.201855235

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  • Secondary publication expected from 24.08.2019

Publ.-Id: 28057 - Permalink


Investigation of bioreactors by smart sensor particles
Reinecke, S. F.; Hampel, U.
Advanced monitoring of the spatio-temporal distribution of process parameters in the large-scale vessels of chemical or bioreactors, such as industrial fermenters, biogas digesters and activated sludge basins, offers a high potential for the investigation and further optimization of plants and embedded processes. However, in most industrial scale applications the acquisition of these parameters and their spatial distributions in the large-scale vessels is hampered by the limited access to the process itself, because sensor mounting or cable connections are not feasible or desired. Therefore, state of the art instrumentation of such reactors is commonly limited to few spatial positions where it is doubtfully assumed that the measured parameters are representative for the whole reaction mixture.
Instrumented sensor particles have been developed by Thiele et al. [1] for investigation of hydrodynamic and biochemical processes chemical reactors and bioreactors. The sensor particles allow autonomous long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of agitated industrial vessels. Each sensor particle comprises of an on-board measurement electronics that logs the signals of the embedded sensors. A buoyancy control unit enables automated taring to achieve neutral buoyancy and thus flow-following capabilities of the sensor particles [2]. Moreover, controlled floating of the sensor particles is possible to expose them for recovery from the fluid surface. The paper presents results of the sensor system validation and tests in an air-water column reactor, a pilot biogas digester and a waste water treatment plant. Moreover, ongoing developments of smart sensor particles features, i.e. magnetic position detection and inertial position tracking, are presented.
  • Lecture (Conference)
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-15.09.2018, Aachen, Deutschland
  • Open Access LogoAbstract in refereed journal
    Chemie Ingenieur Technik 90(2018)9, 1268-1268
    DOI: 10.1002/cite.201855298

Publ.-Id: 28056 - Permalink


Inertial position tracking of flow following sensor particles
Reinecke, S. F.; Hampel, U.
In this paper, a concept for inertial position tracking of flow following sensor particles based on data fusion of inertial sensors is presented. The employed data fusion technique is quaternion based and uses an extended Kalman filter algo-rithm. A generalized sensor system kinematics has been developed to test the filter algorithm where two data conditions have been considered. Eventually, first simulation results are compared which shows the performance of the filter re-garding sensor drift and noise.
  • Contribution to proceedings
    Sensoren und Messsysteme 2018 ∙ 26. – 27.06.2018 in Nürnberg, 26.-27.06.2018, Nürnberg, Deutschland
    Beiträge der 19. ITG/GMA-Fachtagung 26. – 27. Juni 2018 in Nürnberg, 978-3-8007-4683-5
  • Lecture (Conference)
    Sensoren und Messsysteme 19. ITG/GMA-Fachtagung 26. – 27. Juni 2018 in Nürnberg, 26.-27.06.2018, Nürnberg, Deutschland

Publ.-Id: 28055 - Permalink


Visible Light Actuated Efficient Exclusion Between Plasmonic Ag/AgCl Micromotors and Passive Beads
Wang, X.; Baraban, L.; R. Misko, V.; Nori, F.; Huang, T.; Cuniberti, G.; Fassbender, J.; Makarov, D.
Insight is provided into the collective behavior of visible‐light photochemically driven plasmonic Ag/AgCl Janus particles surrounded by passive polystyrene (PS) beads. The active diffusion of single Janus particles and their clusters (small: consisting of two or three Janus particles and large: consisting of more than ten Janus particles), and their interaction with passive PS beads, are analyzed experimentally and in simulations. The diffusivity of active Janus particles, and thus the exclusive effect to passive PS beads, can be regulated by the number of single Janus particles in the cluster. On the simulation side, the Langevin equations of motion for self‐propelled Janus particles and diffusing passive PS beads are numerically solved using Molecular‐Dynamics simulations. The complex interactions of both subsystems, including elastic core‐to‐core interactions, short‐range attraction, and effective repulsion due to light‐induced chemical reactions are considered. This complex mixed system not only provides insight to the interactive effect between active visible light‐driven self‐propelled micromotors and passive beads, but also offers promise for implications in light‐controlled propulsion transport and chemical sensing.

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Publ.-Id: 28051 - Permalink


High-Motility Visible Light-Driven Ag/AgCl Janus Micromotors
Wang, X.; Baraban, L.; Nguyen, A.; Ge, J.; R. Misko, V.; Tempere, J.; Nori, F.; Formanek, P.; Huang, T.; Cuniberti, G.; Fassbender, J.; Makarov, D.
Visible light‐driven nano/micromotors are promising candidates for biomedical and environmental applications. This study demonstrates blue light‐driven Ag/AgCl‐based spherical Janus micromotors, which couple plasmonic light absorption with the photochemical decomposition of AgCl. These micromotors reveal high motility in pure water, i.e., mean squared displacements (MSD) reaching 800 µm2 within 8 s, which is 100× higher compared to previous visible light‐driven Janus micromotors and 7× higher than reported ultraviolet (UV) light‐driven AgCl micromotors. In addition to providing design rules to realize efficient Janus micromotors, the complex dynamics revealed by individual and assemblies of Janus motors is investigated experimentally and in simulations. The effect of suppressed rotational diffusion is focused on, compared to UV light‐driven AgCl micromotors, as a reason for this remarkable increase of the MSD. Moreover, this study demonstrates the potential of using visible light‐driven plasmonic Ag/AgCl‐based Janus micromotors in human saliva, phosphate‐buffered saline solution, the most common isotonic buffer that mimics the environment of human body fluids, and Rhodamine B solution, which is a typical polluted dye for demonstrations of photocatalytic environmental remediation. This new knowledge is useful for designing visible light driven nano/micromotors based on the surface plasmon resonance effect and their applications in assays relevant for biomedical and ecological sciences.

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Publ.-Id: 28050 - Permalink


Injection locking of multiple auto-oscillation modes in a tapered nanowire spin Hall oscillator
Wagner, K.ORC; Smith, A.; Hache, T.; Chen, J.-R.; Yang, L.; Montoya, E.; Schultheiss, K.; Lindner, J.; Fassbender, J.; Krivorotov, I.; Schultheiss, H.
Spin Hall oscillators (SHO) are promising candidates for the generation, detection and amplification of high frequency signals, that are tunable through a wide range of operating frequencies. They offer to be read out electrically, magnetically and optically in combination with a simple bilayer design. Here, we experimentally study the spatial dependence and spectral properties of auto-oscillations in SHO devices based on Pt(7 nm)/ Ni80Fe20(5nm) tapered nanowires. Using Brillouin light scattering microscopy, we observe two individual self- localized spin-wave bullets that oscillate at two distinct frequencies (5.2 GHz and 5.45 GHz) and are localized at different positions separated by about 750 nm within the SHO. This state of a tapered SHO has been predicted by a Ginzburg-Landau auto-oscillator model, but not yet been directly confirmed experimentally. We demonstrate that the observed bullets can be individually synchronized to external microwave signals, leading to a frequency entrainment, linewidth reduction and increase in oscillation amplitude for the bullet that is selected by the microwave frequency. At the same time, the amplitude of other parasitic modes decreases, which promotes the single-mode operation of the SHO. Finally, the synchronization of the spin-wave bullets is studied as a function of the microwave power. We believe that our findings promote the realization of extended spin Hall oscillators accomodating several distinct spin-wave bullets, that jointly cover an extended range of tunability.
Keywords: Magnonik, auto-oscillation, magnetic auto-oscillator, spin Hall oscillator, magnetization dynamic, Brillouin-Light-Scattering

Publ.-Id: 28043 - Permalink


Giant impact of self-photothermal on light-induced ultrafast insulator-to-metal transition in VO₂ nanofilms at terahertz frequency
Zhai, Z.-H.; Chen, S.-C.; Du, L.-H.; Zhong, S.-C.; Huang, W.; Li, Z.-R.; Schneider, H.; Shi, Q.; Zhu, L.-G.
Ultrafast detection and switching of light are key processes in high-speed optoelectronic devices. However, the performances of VO₂-based optoelectronics are strongly degraded by photothermal. The mechanism of the latter is still unclear. Here, by using femtosecond-laser (fs-laser) driven kinetic terahertz wave absorption, we quantitatively separate slow photothermal response and ultrafast photodoping response (e.g. light-induced insulator-to-metal transition) from second- to picosecond-timescales, and discover the competing interplay between them. With self-photothermal (mainly determined by fs-laser pulse repetition rate and pump fluence), the ultrafast transition time was degraded by 190% from 50 ps to 95 ps, the ultrafast transition threshold was decreased to 82% from 11mJ/cm² to 9mJ/cm², while the amplitudes of the two photoresponse are competing. Percolation theory, along with the macroscopic conductivity response, is used to explain the competing interplay. Our findings are relevant for designing and optimizing VO₂-based ultrafast optoelectronic devices.
Keywords: vanadium-dioxide, insulator-to-metal transition, photo-thermal effect

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Publ.-Id: 28042 - Permalink


Detailed characterization of uranyl complexes with small organic ligands on a molecular level: a spectroscopic approach
Brinkmann, H.; Heim, K.; Kaden, P.; Kloditz, R.; Moll, H.; Patzschke, M.
The fundamental aspects of uranyl-spectroscopy (absorption, luminescence, IR), data interpretation and subsequent conclusions to interpret the U(VI)-speciation will be discussed. Furthermore, it will be explained how spectroscopy (NMR and IR) can be used to identify the binding properties of organic molecules, exemplarily explained for a polyhydroxy-carboxylic acid.
Keywords: uranium, spectroscopy, isosaccharinic acid
  • Lecture (others)
    MIND Advanced training course | Geomicrobiology in radioactive waste disposal, 08.-11.10.2018, Mol, Belgien

Publ.-Id: 28040 - Permalink


Morphological and Functional Modifications of Optical Thin Films for Space Applications Irradiated with Low-Energy Helium Ions
Pelizzo, M. G.; Corso, A. J.; Tessarolo, E.; Böttger, R.; Hübner, R.; Napolitani, E.; Bazzan, M.; Rancan, M.; Armelao, L.; Jark, W.; Eichert, D.; Martucci, A.
Future space missions will operate in increasingly hostile environments, such as those in low-perihelion solar orbits and Jovian magnetosphere. This exploration involves the selection of optical materials and components resistant to the environmental agents. The conditions in space are reproduced on ground through the use of ion accelerators. The effects of He particles coming from the solar wind impinging on a gold thin film have been systematically investigated, considering absorbed doses compatible with the duration of the European Space Agency Solar Orbiter mission. Structural and morphological changes have been proved to be dependent not only on the dose but also on the irradiation flux. A predictive model of the variation of thin film reflectance has been developed for the case of lower flux irradiation. The results are discussed regarding reliability and limitations of laboratory testing. The outcomes are important to address the procedures for the space qualification tests of optical coatings.
Keywords: optical thin films, gold coatings, ion irradiation, helium ions, space weather

Publ.-Id: 28038 - Permalink


Competing risks in survival data analysis
Dutz, A.; Löck, S.
Clinical trials and retrospective studies in the field of radiation oncology often consider time-to-event data as their primary endpoint. Such studies are susceptible to competing risks, i.e. competing events may preclude the occurrence of the event of interest or modify the chance that the primary endpoint occurs. Competing risks are frequently neglected and the event of interest is analysed with standard statistical methods. Here, we would like to create awareness of the problem and demonstrate different methods for survival data analysis in the presence of competing risks.
Keywords: Competing risk, Survival data, Time-to-event data, Cox regression

Publ.-Id: 28036 - Permalink


Alkyl Branching Position in Diketopyrrolopyrrole Polymers: Interplay between Fibrillar Morphology and Crystallinity and Their Effect on Photogeneration and Recombination in Bulk-Heterojunction Solar Cells
Shivhare, R.; Erdmann, T.; Hörmann, U.; Collado-Fregoso, E.; Zeiske, S.; Benduhn, J.; Ullbrich, S.; Hübner, R.; Hambsch, M.; Kiriy, A.; Voit, B.; Neher, D.; Vandewal, K.; Mannsfeld, S. C. B.
Diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP-based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (ECT) of the blend films lies exceptionally close to the singlet energy of the donor (ED*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (VOC) is therefore determined to be due to rather high nonradiative (≈ 418 ± 13 mV) and unavoidable radiative voltage losses (≈ 255 ± 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (JSC) covers a vast span from 7 to 18 mA cm-2 for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.

Publ.-Id: 28035 - Permalink


Dezentrale Produktion werthaltiger Kohlenwasserstoffe mit Hilfe lastflexibler, integrierter Elektrolyse-Synthese-Apparate
Schwarze, L.; Fogel, S.; Schwabe, F.; Partmann, C.; Lippmann, W.; Kryk, H.; Hurtado, A.; Hampel, U.
Der stetige Ausbau von Wind- und Solarenergie in Deutschland erfordert effiziente Technologien zur räumlich-zeitlichen Flexibilisierung des Energieversorgungssystems. Infolge der Netzeinbindung fluktuierender Energien ergeben sich grundlegend neue Anforderungen an die bestehende, grundlastbasierte Energiewirtschaft und deren Infrastruktur. Technologien zur direkten Speicherung von Elektroenergie in relevanten Größenordnungen scheitern derzeit aus verschiedenen Gründen, bspw. der Standort-Limitierung von Pumpspeicherkraftwerken oder der Kostenineffizienz von Batterien. Im Rahmen des Verbundforschungsvorhabens „DELTA“ (EF-RE-Förderkennzeichen: 100240618) wird ein frei skalierbarer, dezentral einsetzbarer, modular aufgebauter, wirtschaftlich attraktiver und technisch flexibler Demonstrator zur chemischen Langzeitspeicherung von Elektroenergie (Power-to-Liquid) entwickelt und erprobt. Strom wird einem tubularen, protonenleitenden Dampf-Elektrolyseur zur Erzeugung von hochreinem Wasserstoff zugeführt. Dieser wird direkt unter stofflicher Verwertung von CO2 einer integrierten, heterogen katalysierten Methanolsynthese unterzogen. Durch die Kopplung stationärer CO2-Emittenten und -Verbraucher wird CO2 in einem geschlossenen Kreislauf nutzbar. Flüssige Kohlenwasserstoffe finden sektorübergreifend sowohl als synthetische Kraftstoffe als auch als Grundstoffe für weitere chemische Produkte oder zur Rückverstromung Verwendung und stellen somit eine interessante Wertschöpfungsalternative innerhalb der Chemie- und Energiewirtschaft dar. Die hohe Systemintegration innerhalb des Demonstrators ermöglicht eine energetisch optimierte Prozessführung sowie ein effizientes Energie- und Stoffstrom-Management, weshalb sich das Reaktorsystem durch geringe Energieverluste, hohe Systemwirkungsgrade, Kosteneffizienz und eine hohe Zuverlässigkeit sowie Lastwechselfähigkeit auszeichnet. Der Demonstrator stellt in einer späteren technischen Anwendung ein Basismodul dar, welches mit weiteren Modulen zu einer flexiblen Gesamtanlage verschaltet werden kann. Im Rahmen der Präsentation soll das grundlegende Anlagenkonzept sowie die ersten Ergebnisse des Basic Engineerings und der rechnergestützten Modellierung und Simulation vorgestellt werden.
Keywords: Elektrolyse, Methanolsynthese, Power-to-X, Lastflexibel, Energiespeicher
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 07.-08.03.2018, Frankfurt am Main, Deutschland

Publ.-Id: 28034 - Permalink


Development and evaluation of a 99mTc(III) ‘4 + 1’ complex derived from estradiol for imaging breast cancer
Tejería, E.; Pietzsch, H.-J.; Giglio, J.; Rey, A.
Estrogen receptors are overexpressed in about 70% of breast cancer and identification of their presence is important to select the appropriate treatment and evaluate the response.
With this objective, an estradiol derivative (L) 5-((1-carboxy-2-(4-((13S,17S)-3,17-dihydroxy-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthren-17-yl)-1H-1,2,3-triazol-1-yl)ethyl)amino)-N-methylidyne-5-oxopentan-1-aminium, was used to develop a ‘4+1’ complex of Tc(III) for estrogen receptor imaging.
The synthesis of L involved the coupling of the amino group of 3-azido-L-alanine with an activated isonitrile, to then perform a "click chemistry" reaction with the ethinyl group of ethinylestradiol.
Labelling was carried out in two stages, preparation of the precursor [99mTc]Tc-EDTA, using mannitol, EDTA and SnCl2 as reducing agent and simultaneous substitution (30 min at 75°C) with L (20 mg) and the tetradentate coligand 2-[Bis(2-mercaptoethyl)amino]ethanethiol (NS3) (2 mg). The HPLC analysis showed a major peak (tr=13 min). The radiochemical purity of the HPLC purified complex was greater than 95%.
The lipophilicity expressed as logP (partition coefficient between octanol and phosphate buffer 0.1M, pH = 7.4) was 0.48±0.06. The plasma protein binding was (46 ± 6) % at 60 minutes. The complex was stable in the labelling milieu and in human serum for at least 4 hours. Cell uptake in MCF7 cells are in progress.
A potential radiopharmaceutical derived from estradiol was obtained with high radiochemical purity. The complex presents adequate stability and physicochemical properties. In vitro and in vivo studies including nude mice bearing xenografted breast tumors will be used to validate the clinical potentiality.
  • Lecture (Conference)
    TeraChen 2018, 26.-29.09.2018, Brixen, Italien

Publ.-Id: 28031 - Permalink


Cross-bridged cyclams with bis(phosphinic acid) pendants for a fast Cu(II) complexation: towards efficient 64-Cu labeling
Kubíček, V.; David, T.; Lubal, P.; Pietzsch, H.-J.; Hermanna, P.
Copper radioisotopes chelators are commonly based on macrocycles but they mostly suffer from in vivo instability, slow (not efficient) radiolabeling and low selectivity over competing ions. Cyclam derivatives offer high selectivity for Cu(II). Complexes of cross-bridged (CB-) cyclams are very stable in-vivo, however, their radiolabelling is not efficient.
We have found that bis(phosphinic acid) pendant arm (BPi) highly accelerate Cu(II) complexation.[1] It was also found, on Me3cyclam derivatives as model ligands, that phosphonic acid (Po) and bis(phosphorus acid) pendant arms are the most suitable ones for fast chelation.[2]
Chelators with BPi-like pendants on CB-cyclam (cb-BPC) were synthesized. Their complexation properties (structure, thermodynamics, formation/decomplexation kinetics) were investigated and analogous data were also obtained for known phosphorus chelators as cb-TE2P. All ligands are basic (last pKa>13.5) and form thermodynamically stable copper complexes. Other metal ion complexes are hardly formed in water. The Cu(II) complexes are formed quickly with some dependence on a kind of the pendant arms. Complexes of BPi containing chelators are significantly less kinetically inert than those of cb-TE2P but still much more inert than complexes of most of common chelators as DOTA. The phosphonic acid and BPi on CB-cyclams exhibit fast radiolabeling with 64-Cu even at room temperature and the labelled chelators are obtained with a high specific activity. These radiolabelling properties are not altered after conjugations.[3] The ligands can be suggested as a new chelator family for copper radioisotopes.
  • Poster
    TeraChem 2018, 26.-29.09.2018, Brixen, Italien

Publ.-Id: 28030 - Permalink


Bifunctional cyclam derivatives with a bis(phosphinate) pendant arm as efficient chelators for copper radionuclides
David, T.; Hlinová, V.; Kubíček, V.; Bergmann, R.; Pietzsch, H.-J.; Hermann, P.
Bifunctional cyclam derivatives with one bis(phosphinic acid) pendant arm bearing carboxylate, amine, isothiocyanate, azide or cyclooctyne functions in the pendant arm side chain were synthesized (Figure). The bifunctional groups were introduced far from the metal-binding site, either by using newly synthesized bis(phosphinic acid) precursors or by modifying the reactive groups. Direct coupling without protecting the pendant phosphinate or ring secondary amine groups was feasible. The ligands were successfully conjugated to model compounds including oligopeptides, biotin or fluorescent dye.
Labeling of the bifunctional ligands with 64Cu showed very high radiolabeling efficiency, leading to a significantly higher molar activity than that described for other commonly used macrocyclic chelators. It confirms that using properly designed phosphinic acid pendant arm(s) is a good strategy to achieve conjugation flexibility (due to the distant bifunctional site) without compromising the radiolabeling efficiency or the high specific activity of radiopharmaceuticals.
A prototypic representative was evaluated in-vivo by metabolite analysis, biodistribution studies and PET scans. The data clearly showed the very high metabolic stability of the 64Cu chelate unit as no decomplexation was detected. Except for the excretory organs, no prominent uptake and retention was observed.
Thus, bis(phosphinate)-bearing cyclam-based ligands are highly promising radiocopper chelators for conjugation to targeting units, such as peptides, oligonucleotides or antibodies and their fragments.
  • Poster
    TeraChem 2018, 26.-29.09.2018, Brixen, Italien

Publ.-Id: 28029 - Permalink


Ligand development for the Radiometal Hg-197(m)
Gilpin, M.; Walther, M.; Pietzsch, H.-J.; Steinbach, J.
Reactor-produced Hg-197 had previous medical use for imaging[1] but was discontinued due to low stability and low specific-activity. Cyclotron-produced Hg-197(m) can overcome the toxicity problem, due to much higher molar activity[2], allowing access to the radiometal’s useful decay modes (γ for SPECT-imaging. Conversion & auger electrons for therapy) at sub-toxic Hg-concentrations.
Development in Hg ligands for medicinal applications necessitates stability in vivo but the poor long-term stability of Mercury compounds in solution is an ongoing issue[3]. Hg-organometallics show good water-stability and bypass the issue of Hg-S bonds suffering from competition by common biomolecules, e.g. cysteine. Therefore, our focus is on Hg-C chemistry, specifically the strongest bond kind: the mercury-phenyl bond[4].
As prior research has shown that the synthetically simpler route of monodentate ligands (κ1-L2Hg) suffers from significant cleavage[5], this research is centred on the syntheses of bidentate chelators benefitting from entropic stability. Purification of the Hg-197(m) leaves it in an acidic aqueous medium as the chloride salt, thus transmetallation, via stannyl or boronic acid derivatives, was chosen as a viable option for mercury attachment. Chelator designs began with a dibenzylisophthalamide template but low selectivity for the 1:1-compound encouraged a better fitting structure. Recent radio-labelling experiments show promise for specific binding with a design based on the bispidine backbone (attractive for being known in co-ordination chemistry for a variety of metals[6] and possessing bridge linking-functionalisation).
Analyses are performed through radio-TLC and HPLC, whilst stable mercury compound analysis includes Hg-199 NMR.

References :
(1) Sodee. J. Nucl. Med. 1968; 9: 645.
(2) Walther et al. Appl. Radiat. Isot. 2015; 97: 177–181.
(3) Henke et al. Wat. Res. 2000; 34: 3005-3013.
(4) Dean. Lange’s Handbook of Chemistry, 15th ed.; McGraw-Hill Inc, 1998; 606.
(5) Wilhelm. et al. Z. Naturforsch. 2000; 55b: 35–38.
(6) Comba et al. Inorg. Chem. 2009; 48: 6604–6614.
Keywords: Mercury 197, Chelator, Ligand, Radiometal, Bispidine, Cancer, Theragnostics
  • Poster
    TERACHEM 2018, 24.-29.09.2018, Bressanone, Italy

Publ.-Id: 28026 - Permalink


1,4,7-Triazacyclononane: An effective chelator for copper-64
Kubeil, M.ORC; Pant, K.; Joshi, T.; Stephan, H.
1,4,7-Triazacyclononane (TACN) is a versatile platform from which various ligands can be derived to form effective chelators for (radio)copper(II) complexation. [1] The ability of TACN-derivatives to form highly stable complexes with copper(II) is greatly influenced by the number and type of substituents on the macrocyclic ring. The formed copper(II) complexes show a broad variability in their thermodynamic stability and kinetic inertness, varying in structure from square-pyramidal to distorted octahedral. TACN-based BFCAs have also been used for indirect radiolabelling of biomolecules, rendering them suitable for imaging and therapy.
Herein, examples of various copper-64 TACN complexes will be presented which provide a picture of how different substituents influence the coordination mode, electronic properties and in vivo stability of. By applying principles of coordination chemistry, it is possible to tune the affinity of TACN-based ligands for copper ligation, as well as their availability for subsequent biomolecular functionalisation. Target-specific TACN based conjugates (peptides, antibody fragments) and bio(nano)materials labelled with copper-64 enabling tumour imaging and biodistribution studies via positron emission tomography will be discussed as well. [2, 3, 4]

[1] T. Joshi et al. ChemPlusChem 2018; DOI: 10.100 2/cplu.201800103.
[2] K. Pant et al. Bioconjugate Chem. 2015; 26: 906-918.
[3] K. Viehweger et al. Bioconjugate Chem. 2014; 25: 1011-1022.
[4] R. Bergmann et al. Sci. Rep. 2017; 7.
Keywords: TACN, copper-64, chelator
  • Poster
    The third International Symposium on Technetium and Other Radiometals in Chemistry and Medicine, 26.-29.09.2018, Brixen, Bressanone, Italia

Publ.-Id: 28020 - Permalink


“Click to ligand/conjugate” for facile labeling with AlF-18, Ga-68, In-111 or Cu-64
Walther, M.; Wodtke, R.; Bergmann, R.; Zarschler, K.; Sihver, W.; Pietzsch, H.-J.
During the last 10 years an increasing number of ligands were developed and tested for their suitability for AlF-18 labeling. Initially, the well-known macrocyclic ligands NOTA and NODA with low yielding-high temperature reactions were used. In contrast, open chain ligands derived from ethylenediamine provide a fast complex formation at lower temperatures (<40°C). The use of a terminal alkyne linker enables the conjugation to target molecules via copper catalysed azide-alkyne cycloaddition as final step in ligand synthesis. Furthermore, the new triazole containing ligand offers interesting additional applications, besides AlF 18 labeling. In this context, one of the triazole nitrogen atoms could act as an additional soft donor atom to allow the stable fixation of other radiometal ions preferring a six-fold coordination, like Ga-68, In-111 or Cu-64. Examples for the ligand synthesis, radiolabeling experiments, stability studies and initial in vitro and in vivo studies will be presented in this work.
Keywords: CuAAC, [18F]Aluminumfluorid, Cu-64, Ga-68
  • Poster
    TERACHEM2018, 26.-29.09.2018, Bressanone, Italy

Publ.-Id: 28019 - Permalink


Carbon doping controlled thermoluminescent defect centers in nanoporous alumina for ion beam dosimetry
Bhowmick, S.; Pal, S.; Das, D.; Singh, V. K.; Khan, S. A.; Hübner, R.; Barman, S. R.; Kanjilal, D.; Kanjilal, A.
The flexibility of amorphous anodized alumina (AAO) in developing radiation dosimeter for hadron therapy is reported by controlled carbon ion implantation, followed by thermoluminescence (TL) measurements. The efficacy of amorphous AAO in controlling TL sensitivity is found to be governed by an increase in F+ defect centers as a function of carbon concentration, as revealed from the close resemblance of the trend in photoluminescence intensity. Moreover, its nanoporous structure is demonstrated to be advantageous for defect engineering due to the increase in the surface-to-volume ratio. Detailed X-ray photoelectron spectroscopy analysis suggests the formation of F+ centers by substituting Al3+ ions with C2+ in the vicinity of oxygen vacancies, where depth-dependent study showed the evolution of conducting channels owing to sp2 hybridized C–C bonding, leading to a differential charging effect. This work provides a direction to tune nanoporous AAO in its amorphous form for future ion beam dosimetry.

Publ.-Id: 28018 - Permalink


GitLab-Runner fork
Frust, T.
This is a fork of the official gitlab-runner repository at https://gitlab.com/gitlab-org/gitlab-runner and is used to generate binaries and the helper image for the Power architecture (ppc64le), since this architecture is not officially supported by GitLab itself.
  • Software in external data repository
    Publication year 2018
    Programming language: Go
    System requirements: Power architecture (ppc64le)
    License: MIT (Link to license text)
    Hosted on HZDR GitLab: Link to location

Publ.-Id: 28017 - Permalink


Improved Conjugation, 64-Cu Radiolabeling, in Vivo Stability, and Imaging Using Nonprotected Bifunctional Macrocyclic Ligands: Bis(Phosphinate) Cyclam (BPC) Chelators
David, T.; Hlinová, V.; Kubíček, V.; Bergmann, R.; Striese, F.; Berndt, N.; Szöllösi, D.; Hegedus, N.; Mathe, D.; Bachmann, M.; Pietzsch, H.-J.; Hermann, P.
Bifunctional derivatives of bis(phosphinate)-bearing cyclam (BPC) chelators bearing a carboxylate, amine, isothiocyanate, azide, or cyclooctyne in the BP side chain were synthesized. Conjugations required no protection of phosphinate or ring secondary amine groups. The ring amines were not reactive (proton protected) at pH < ∼8. For isothiocyanate coupling, oligopeptide N-terminal α-amines were more suitable than alkyl amines, e.g., Lys ω-amine (pKa ∼7.5−8.5 and ∼10−11, respectively) due to lower basicity.
The Cu-64 labeling was efficient at room temperature (specific activity ∼100 GBq/μmol; 25 °C, pH 6.2, ∼100 ligand equiv, 10 min). A representative Cu-64-BPC was tested in vivo showing fast clearance and no nonspecific radioactivity deposition. The monoclonal anti-PSCA antibody 7F5 conjugates with thiocyanate BPC derivative or NODAGA were radiolabeled and studied in PC3-PSCA tumor bearing mice by PET. The radiolabeled BPC conjugate was accumulated in the prostate tumor with a low off-target uptake, unlike Cu-64-labeled NODAGA−antibody conjugate. The BPC chelators have a great potential for theranostic applications of the Cu-64/Cu-67 matched pair.

Publ.-Id: 28015 - Permalink


Progress on High Peak Current Laser Wakefield Electron Acceleration
Schramm, U.ORC
Report on the generation of multi 10 kA electron bunches with LWFA and related applications.
  • Invited lecture (Conferences)
    60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources (FLS2018), 05.-09.03.2018, Shanghai, China

Publ.-Id: 28014 - Permalink


From plasma acceleration to accelerators ?
Schramm, U.ORC
Status of PW laser experiments
  • Invited lecture (Conferences)
    OPIC OPTICS & PHOTONICS International Congress, 23.-26.04.2018, Pacifico Yokohama, Japan
  • Invited lecture (Conferences)
    Freitagsseminar IAP-Frankfurt, 22.06.2018, Frankfurt, Deutschland
  • Invited lecture (Conferences)
    HICforFAIR-Kolloquium Giessen, 21.06.2018, Giessen, Deutschland

Publ.-Id: 28013 - Permalink


Stability and Electronic Properties of Palladium Dichalcogenide Polytypes as Nanomaterials
Kempt, R.; Kuc, A.; Heine, T.
We present a detailed computational investigation of the stability and electronic properties of three different polytypes of the palladium dichalcogenides PdX2. These are intriguing for electronic and optical applications as nanomaterials, including logical junctions because of a potential metal-semiconductor transition in the 1T polytype when going from bulk to monolayers.[1,2]
Both PdS2 and PdSe2 crystallize in a layered pyrite-type structure or 2O (see Fig. 1) as bulk materials.[3] Only for high pressures, they adopt the cubic pyrite-type structure.[4] Recently, monolayers of PdSe2 have been exfoliated and shown to maintain their pentagonal structure found in the bulk material.[5] In contrast to PdS2 and PdSe2, bulk PdTe2 occurs naturally in 1T.[6]
We evaluate the differences in chemical bonding between the possible polytypes by density functional theory and show that it requires a hybrid approach in order to properly account for the electron correlation effects in these systems. From there, we estimate their electronic properties and stabilities as nanomaterials.
  • Lecture (Conference)
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Publ.-Id: 28011 - Permalink


On the chemistry and mobility of hydrogen in the interstitial space of layered crystals h-BN, MoS2, and graphite
An, Y.; Kuc, A.; Petkov, P.; Lozada-Hidalgo, M.; Heine, T.
Recently, transport and separation of hydrogen isotopes in the layered materials hexagonal boron nitride and molybdenum disulphide have been reported.[1] Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H) atoms in the interstitial space of these layered materials. We show that both H as well as H+ can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in a good agreement with experiments. In h-BN and MoS2 the transport mechanism involves a hopping process between the nearby layers, which is assisted by the low-energy phonon shear modes of layers.
  • Poster
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Publ.-Id: 28010 - Permalink


Electronic Properties of 2D van der Waals TMDCs Heterostructures from First Principles Calculations
Ramzan, M. S.; Kuc., A.
Two-dimensional (2D) transition metal dichalcogenides (TMDCs) MX2 (M = Mo, W; X = S, Se) have attracted considerable attention in electronics and optoelectronic due to their intrinsic band gap[1]. Moreover, weak van der Waals interaction between layers make it possible to stack different TMDCs layers to form heterostructures with new electronic properties. In this work we have studies effect of interfacing TMDCs with different chalcogen atoms and/or different transition atoms to study effect of interface and dielectric constant on electronics. We will show that by controlling ratio of layers and hero-interfaces, direct gap can be achieved in more than four layers which might be ideal for solar energy harvesting.
  • Poster
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Publ.-Id: 28009 - Permalink


Non equilibrium anisotropic excitons in atomically thin ReS2
Urban, J. M.; Baranowski, M.; Kuc, A.; Klopotowski, L.; Surrente, A.; Ma, Y.; Wlodarczyk, D.; Suchocki, A.; Ovchinnikov, D.; Heine, T.; Maude, D. K.; Kis, A.; Plochocka, P.
We present a systematic investigation of the electronic properties of bulk and few layer ReS2 van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by ∼ 20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calcu- lations predict bilayer ReS2 to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases.

Publ.-Id: 28007 - Permalink


Two dimensional crystals in three dimensions
Kempt, R.; Kuc, A.; Han, J. H.; Cheon, J.; Heine, T.
Two-dimensional crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley- and spin-orbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, we propose the formation of stacks of two-dimensional crystals intercalated with small surfactant molecules. We show, using first principles calculations, that already very short surfactant methyl amine electronically decouples the layers. We demonstrate the indirect-direct band gap transition characteristic for Group 6 transition metal dichalcogenides experimentally by observing the emergence of a strong photoluminescence signal for ethoxide-intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the two-dimensional crystals with electronic properties typical for monolayers. Variation of the surfactant’s chemical potential allows fine-tuning of electronic properties and potentially elimination of trap states caused by defects.

Publ.-Id: 28006 - Permalink


Electronic properties of 2D and 1D inorganic materials for applications in nano(opto)electronics
Kuc, A.
The nanoelectronic industry is rapidly approaching limits of the silicon-technology, what leads to a necessity of developing new technologies, which would replace silicon in the future. Therefore, searching for materials that perform better than silicon at the atomic scale became a very important topic in the electronic and materials sciences in the past decades. Recently, two-dimensional (2D) layered materials, such as graphene, black phosphorous, silicene, or transition-metal dichalcogenides (TMCs), have attracted great attention, because of their extraordinary electronic properties and, at the same time, very good mechanical stability, which are desired features for nanoelectornic applications. The progress in the production of such 2D crystals grows rapidly every year, therefore, it is very important to estimate, understand, and explore the fundamental physics of these materials, in order to boost breakthrough technologies.
Layered transition-metal dichalcogenides have gained increasing attention ever since the seminal works published in 2010 and 2011, showing phenomenal electronic properties of monolayered systems, their easy exfoliation from bulk materials, due to the weak interlayer interactions, as well as, their applications as building blocks in the nanoelectronic logical devices. In this thesis, we present selected research based of density-functional theory, which has been carried out on the subject of electronic structure of TMC and other 2D crystals. These materials exhibit electronic properties, which are easily tuned by external modulators, such as tensile strain, doping, electric or magnetic fields, formation of different polytypes. The change in the electronic properties of semiconducting TMCs due to these external modulators vary in a wide range, e.g., semiconductor-metal transition, Rashba, Zeeman and Stark effects, induced spin-orbit coupling in centrosymmetric bilayered forms by breaking of inversion symmetry, topologically protected states in topological insulators. We also present the coherent transport properties of these 2D materials using calculations based on the density functional based tight-binding method in combination with the non-equilibrium Green’s function technique and the Landauer-Büttiker formula.
We show that the intrinsic electronic structure of MoS2 and other semiconducting TMCs change with the number of layers in the film. The indirect-band gap in the bulks changes to a direct-band gap in the monolayers and the size of the band gap is nearly 1 eV larger for the latter forms. On top of the electronic band gaps, which are mainly discussed in this thesis, TMC exhibit also very large exciton binding energies, which need to be taken into account, when discussing overall electronic properties. TMC monolayers exhibit very large spin-orbit splitting in the valence bands, which varies between 150 and almost 500 meV, depending on the stoichiometry. Stacking different monolayers of TMC materials results in reduced direct-band gaps with much smaller values than the respective pure materials, which comes from the formation of the type II heterostructures. In such heterostructures, the valence band maximum is formed from the states of different layers. This results in materials with excitons localized in such a way that the electron is located in one layer and the hole in the other.
We believe that the knowledge gained from the research presented in this thesis can provide new perspectives for the applications of TMC materials in the next generation of nano(opto)electronic devices.
  • Other
    Jacobs University Bremen, 2018
    Mentor: Prof. Thomas Heine

Publ.-Id: 28005 - Permalink


Photochemical creation of covalent organic 2D monolayer objects in defined shapes via a lithographic 2D-polymerization
Servalli, M.; Celebi, K.; Payamyar, P.; Zheng, L.; Polozij, M.; Lowe∥, B.; Kuc, A.; Schwarz, T.; Thorwarth, K.; Borgschulte○, A.; Heine, T.; Zenobi, R.; Schlüter, A. D.
In this work, we prepare Langmuir-Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by naked eye upon excitation. In-situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4+4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confo-cal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving two-dimensional macromolecular monolayer objects of the desired shape. This is the first photolithographic process that employs 2D-polymerizations and affords 1 nm-thin coatings.

Publ.-Id: 28004 - Permalink


Probing charge transfer characteristics in a donor–acceptor metal–organic framework by Raman spectroelectrochemistry and pressure-dependence studies
Usov, P. M.; Leong, C. F.; Chan, B.; Hayashi, M.; Kitagawa, H.; Sutton, J. J.; Gordon, K. C.; Hod, I.; Farha, O. K.; Hupp, J. T.; Addicoat, M.; Kuc, A. B.; Heine, T.; D’Alessandro, D. M.
The stimuli responsive behaviour of charge transfer donor–acceptor metal–organic frameworks (MOFs) remains an understudied phenomenon which may have applications in tuneable electronic materials. We now report the modification of donor–acceptor charge transfer characteristics in a semiconducting tet- rathiafulvalene–naphthalene diimide-based MOF under applied electrochemical bias and pressure. We employ a facile solid state in situ Raman spectroelectrochemical technique, applied for the first time in the characterisation of electroactive MOFs, to monitor the formation of a new complex TTFTC􏰀+–DPNI from a largely neutral system, upon electrochemical oxidation of the framework. In situ pressure- dependent Raman spectroscopy and powder X-ray diffraction experiments performed in a diamond anvil cell revealed blue shifts in the donor and acceptor vibrational modes in addition to contractions in the unit cell which are indicative of bond shortening. This study demonstrates the utility of in situ Raman spectroscopic techniques in the characterisation of redox-active MOFs and the elucidation of their electronic behaviours.

Publ.-Id: 28003 - Permalink


Electronic structure of defective transition-metal dichalcogenides: theoretical investigations
Kuc, A.
We have investigated the electronic structure changes of transition-metal dichalcogenides (TMCs), when various structural defects are present [1]. Healing of the defects by formation of sandwich materials will be also discussed [2]. Moreover, adsorption of small molecules on the defect sites were investigeted and the resulting the band structures will be presented [3].
Defects have very strong influence on the electronic properties of TMC materials, especially on their electronic transport, which could be strongly suppressed in the presence of large defect concentration. Defects can be healed by donation of, e.g. chalcogen atoms, from other TMC layers in a sandwich materials. Moreover, in experiments, the defect sites are not free and different molecules could be adsorbed, depending on the conditions in which the defects are formed.
Keywords: Electronic properties of TMDCs
  • Lecture (Conference)
    Hengstberger Symposium, 22.-24.10.2018, Heidelberg, Germany

Publ.-Id: 28002 - Permalink


Application of amphiphilic siderophores in froth flotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process. The hydrophilic part, carrying hydroxamate groups is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested, that siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubbles and avoid additional chemicals and further working steps for making the target mineral particles hydrophobic. The aim of this study is to show the usage of amphiphilic siderophores in froth flotation process in different scales and with different minerals.
Keywords: Siderophore, Marinobactin, Marinobacter, Flotation, Bioflotation
  • Lecture (Conference)
    Sustainable Minerals 2018, 14.-15.06.2018, Windhoek, Namibia

Publ.-Id: 27996 - Permalink


Production of amphiphilic siderophores for bioflotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment.
A lot of microorganisms and their produced siderophores have already been identified and analyzed in detail. Until now, siderophores are only used as medicine against iron or heavy metal poisoning. The biotechnological production offers the application in very different fields, like extraction, recovery and treating of different metals. Especially the group of amphiphilic siderophores are very interesting for the classical froth flotation process. The aim of this study is the optimized and efficient biotechnological production of the amphiphilic siderophore Marinobactin by the marine bacterium Marinobacter sp. DS40M6 and to show for the first time that it is possible to use these biomolecules in froth flotation process.
Keywords: Siderophore, Marinobactin, Marinobacter, Flotation, Bioflotation
  • Poster
    Biohydrometallurgy 2018, 11.-13.06.2018, Windhoek, Namibia

Publ.-Id: 27995 - Permalink


Cognitive correlates of a4b2 nicotinic acetylcholine receptors in mild Alzheimer’s dementia
Sabri, O.; Meyer, P. M.; Graef, S.; Hesse, S.; Wilke, S.; Becker, G.-A.; Rullmann, M.; Patt, M.; Luthardt, J.; Gudrun Wagenknecht, G.; Hoepping, A.; Smits, R.; Franke, A.; Sattler, B.; Tiepolt, S.; Fischer, S.; Deuther-Conrad, W.; Hegerl, U.; Barthel, H.; Schoenknecht, P.; Brust, P.
In early Alzheimer’s dementia, there is a need for PET biomarkers of disease progression with close associations to cognitive dysfunction that may aid to predict further cognitive decline and neurodegeneration. Amyloid biomarkers are not suitable for that purpose. The a4b2 nicotinic acetylcholine receptors (a4b2-nAChRs) are widely abundant in the human brain. As neuromodulators they play an important role in cognitive functions such as attention, learning and memory. Post-mortem studies reported lower expression of a4b2-nAChRs in more advanced Alzheimer’s dementia. However, there is ongoing controversy whether a4b2-nAChRs are reduced in early Alzheimer’s dementia. Therefore, using the recently developed a4b2-nAChR-specific radioligand (-)-18F-flubatine and PET, we aimed to quantify the a4b2-nAChR availability and its relationship to specific cognitive dysfunction in mild Alzheimer’s dementia. Fourteen non-smoking patients with mild Alzheimer’s dementia, drug-naı¨ve for cholinesterase therapy, were compared with 15 non-smoking healthy controls matched for age, sex and education by applying (-)-18F-flubatine PET together with a neuropsychological test battery. The one-tissue compartment model and Logan plot method with arterial input function were used for kinetic analysis to obtain the total distribution volume (VT) as the primary, and the specific binding part of the distribution volume (VS) as the secondary quantitative outcome measure of a4b2-nAChR availability. VS was determined by using a pseudo-reference region. Correlations between VT within relevant brain regions and Z-scores of five cognitive functions (episodic memory, executive function/working memory, attention, language, visuospatial function) were calculated. VT (and VS) were applied for between-group comparisons. Volume of interest and statistical parametric mapping analyses were carried out.
Analyses revealed that in patients with mild Alzheimer’s dementia compared to healthy controls, there was significantly lower VT, especially within the hippocampus, fronto-temporal cortices, and basal forebrain, which was similar to comparisons of VS. VT decline in Alzheimer’s dementia was associated with distinct domains of impaired cognitive functioning, especially episodic memory and executive function/working memory. Using (-)-18F-flubatine PET in patients with mild Alzheimer’s dementia, we show for the first time a cholinergic a4b2-nAChR deficiency mainly present within the basal forebrain-cortical and septohippocampal cholinergic projections and a relationship between lower a4b2-nAChR availability and impairment of distinct cognitive domains, notably episodic memory and executive function/working memory. This shows the potential of (-)-18F-flubatine as PET biomarker of cholinergic a4b2-nAChR dysfunction and specific cognitive decline. Thus, if validated by longitudinal PET studies, (-)-18F-flubatine might become a PET biomarker of progression of neurodegeneration in Alzheimer’s dementia.
Keywords: (-)-18F-flubatine; PET; cognitive dysfunction; a4b2-nAChRs; Alzheimer’s dementia Abbreviations: a4b2-nAChR = a4b2 nicotinic acetylcholine receptor; GMD = grey-matter density; PVEC = partial volume effect correction; VND = non-displaceable distribution volume; VS = specific binding part of the distribution volume; VT = distribution volume

Publ.-Id: 27993 - Permalink


Fourier Analysis of Cerebral Metabolism of Glucose: Gender Differences in Mechanisms of Color Processing in the Ventral and Dorsal Streams in Mice
Njemanze, P. C.; Kranz, M.; Brust, P.
Conventional imaging methods could not distinguish processes within the ventral and dorsal streams. The application of Fourier time series analysis was helpful to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. The present study measured the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain using small animal positron emission tomography and magnetic resonance imaging (PET/MRI) during light stimulation with blue and yellow filters compared to darkness condition. Fourier analysis was performed using mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition to derive spectral density estimates for each condition. In male mice, luminance opponency occurred by S-peak changes in the sub-cortical retino-geniculate pathways in the dorsal stream supplied by ganglionic arteries in the left visual cortex, while chromatic opponency involved C-peak changes in the cortico-subcortical pathways in the ventral stream perfused by cortical arteries in the left visual cortex. In female mice, there was resonance phenomenon at C-peak in the ventral stream perfused by the cortical arteries in the right visual cortex in female mice during luminance processing. Conversely, chromatic opponency occurred by S-peak changes in the subcortical retino-geniculate pathways in the dorsal stream supplied by the ganglionic arteries in the right visual cortex. In conclusion, Fourier time series analysis uncovered distinct mechanisms of color processing in the ventral stream in male, while in female mice color processing was in the dorsal stream. It demonstrated that computation of colour processing as a conscious experience could have a wide range of applications neuroscience, artificial intelligence and quantum mechanics.
Keywords: chromatic opponency, sex differences, light wave, light particle, blood flow, frequency, resonance

Publ.-Id: 27992 - Permalink


Highly Sensitive Electromechanical Piezoresistive Pressure Sensors Based on Large-Area Layered PtSe2 Films
Wagner, S.; Yim, C.; Mcevoy, N.; Kataria, S.; Yokaribas, V.; Kuc, A.; Pindl, S.; Fritzen, C.-P.; Heine, T.; Duesberg, G. S.; Lemme, M. C.
Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe2), an exciting and unexplored 2D transition metal dichalcogenide material, is particularly interesting because its low temperature growth process is scalable and compatible with silicon technology. Here, we report the potential of thin PtSe2 films as electromechanical piezoresistive sensors. All experiments have been conducted with semimetallic PtSe2 films grown by thermally assisted conversion of platinum at a complementary metal−oxide−semiconductor (CMOS)-compatible temperature of 400 °C. We report high negative gauge factors of up to −85 obtained experimentally from PtSe2 strain gauges in a bending cantilever beam setup. Integrated NEMS piezoresistive pressure sensors with freestanding PMMA/PtSe2 membranes confirm the negative gauge factor and exhibit very high sensitivity, outperforming previously reported values by orders of magnitude. We employ density functional theory calculations to understand the origin of the measured negative gauge factor. Our results suggest PtSe2 as a very promising candidate for future NEMS applications, including integration into CMOS production lines.
Keywords: Pressure sensors, platinum diselenide, two-dimensional, gauge factors, strain sensors

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Publ.-Id: 27990 - Permalink


Calix[4]crown-6 scaffold for the complexation of barium and radium
Bauer, D.; Reissig, F.; Steinberg, J.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Radium is the heaviest known member of the alkaline earth metals and all 33 of its isotopes are radioactive. Two of these, radium-223 and radium-224, have suitable half-lives with 11.4 d and 3.6 d, respectively, and nuclear decay properties that make them useful tools for alpha particle therapy. Unfortunately, no suitable chelating agents are available for a stable complexation. Thus, radium-223 is only in use as radium chloride to treat bone metastases. For this purpose, a series of modified calix[4]crown-6 derivatives was synthesized to chelate heavy group 2 metal ions like barium, which serves as a non-radioactive surrogate for radium-223/-224.
The calix[4]arene framework can be seen as an ideal platform to build an optimized chelator. Two of the four hydroxy groups of the lower rim can be functionalized as deprotonizable groups to form a neutral complex with barium or radium; the remaining two are bridged by a crown ether moiety. With this concept, the advantages of the electrostatic, macrocyclic, and cryptate effect are combined. Another benefit of the calixcrowns is their easy access.
As a result, our calix[4]crowns were functionalized with either cyclic amide moieties or with deprotonizable groups like carboxylic acids or hydroxyl amines, and the corresponding barium complexes were synthesized.
To prove the ability of these chelators for a further usage in radiopharmacy, stability constants of the corresponding barium complexes were determined by using NMR and UV/Vis titration to determine logK values. Further extraction studies were performed to characterize the binding affinity of calixcrowns to barium-133 and radium-224.
Keywords: calixarene, alkaline earth metals, barium, radium
  • Poster
    The Third International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 26.-29.09.2018, Bressanone, Italien

Publ.-Id: 27987 - Permalink


Chelatoren für die Komplexierung schwerer Erdalkalimetallionen
Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Ziel:
Nach dem heutigen Stand sind keine geeigneten Chelatoren zur stabilen Komplexierung von schweren Erdalkalimetallen Barium und Radium bekannt. Da die Alphaemitter Radium-223 Radium-224 jedoch hohes therapeutisches Potential besitzen, ist die Entwicklung von multimodalen Liganden von großem Interesse. Ein solcher Ligand könnte eine Matched-Pair-Strategie eröffnen. Während Radium-223 und Radium-224 therapeutisch einsetzbar sind, besitzt Barium-131, welches analoge chemische Eigenschaften aufzeigt, gute diagnostische Eigenschaften. Bis jetzt ist die klinische Nutzung von Radium auf die Behandlung von Knochenmetastasen durch das calcimimetische Radiopharmakon [223Ra]RaCl2 (Xofigo®) beschränkt. Diese Anwendung gilt es zu erweitern.

Methodik:
Radium-224 wurde in Form seines Nitrats mittels Ionenaustauschchromatographie aus einem Thorium-228-Generator gewonnen. Als Bariumisotop für Extraktionsstudien wurde das langlebige und kommerziell erhältliche Radionuklid Barium-133 genutzt. Die Radiomarkierungen wurden mittels HPLC und Extraktionsstudien charakterisiert.
Stabilitätskonstanten wurden mit stabilem Barium mittels UV/Vis und Kalorimetrie berechnet. Mit den Radiometallen Barium-133 und Radium-224 konnten vergleichbare Konstanten mittels Zwei-Phasen-Extraktion (Wasser/Chloroform) bestimmt werden.
Als Liganden dienten unter anderem verschieden funktionalisierte, 18-Krone-6-überbrückte Calix[4]-arene.

Ergebnisse:
Es wurden vier Liganden auf Calix[4]-aren-Basis dargestellt und deren Interaktion mit Bariumionen untersucht. Ein relativ hohe Stabilitätskonstante konnte vor allem für ein Sulfonamid-Derivat ermittelt werden. Angeschlossene Extraktionsstudien zeigten für diesen Liganden eine nahezu vollständige Extraktion von [133Ba]Ba2+ aus der wässrigen Phase unter physiologischen Bedingungen.
Analoge Versuche wurden mit [224Ra]Ra2+ durchgeführt. Der Komplex zeigte dabei eine ähnliche Stabilität.
Schlussfolgerungen:
Der Sulfonamid-Ligand wurde als potenter Chelator für Radium/Barium identifiziert. Weitere Modifikationen werden erfolgen, um die Stabilität weiter zu erhöhen und eine Biokompatibilität zu ermöglichen. In-vitro- und in-vivo-Studien müssen vorbereitet werden.
Keywords: Calixarene, Erdalkalimetalle, Komplexierung, Barium, Radium
  • Lecture (Conference)
    23. Jahrestagung der Arbeitsgemeinschaft Radiochemie & Radiopharmazie, 20.-22.09.2018, Aachen, Deutschland

Publ.-Id: 27986 - Permalink


An Introduction to the SPEC High Performance Group and their HPC Benchmark Suites
Juckeland, G.ORC
The SPEC High-Performance Group (HPG) develops benchmarks that:
- represent large, real applications, in scientific and technical computing,
- use industry standard parallel application programming interfaces (APIs), OpenMP and MPI
- support shared-memory and message passing programming paradigms,
- can evaluate shared-memory computers, distributed-memory computers and workstation clusters as well as traditional massively parallel processor computers,
- come in several data sets sizes (from a few minutes to days of execution time),
- allow for certain hand optimizations of the codes (as opposed to compiler-only optimizations)
  • Invited lecture (Conferences)
    ZKI Arbeitskreis Supercomputing Herbstreffen, 25.-26.09.2018, Freiburg, Deutschland

Publ.-Id: 27985 - Permalink


Is It Here/There Yet? - Real Life Experiences of Generating/Evaluating Extreme Data Sets Around the World
Juckeland, G.ORC; Huebl, A.ORC; Bussmann, M.ORC
Large scale simulations easily produce vast amounts of data that cannot always be evaluated in-situ. At that point parallel file systems come into play, but their per node performance is essentially limited to about the speed of a USB 2.0 thumb drive (e.g. the Spider file system at OLCF provides over 1 TB/s write bandwidth, but with 18000+ nodes of Titan writing simultaneously, this number is reduced to about 50 MB/s per node). Making the most out of such a limited resource requires I/O libraries that actually scale. In addition such libraries also offer on the fly data transformations (e.g. compression) to better utilize the raw I/O bandwidth, albeit, opening a new can of worms by trading compression throughput with compression ratios for performance. We will present a detailed study of I/O performance and various compression techniques at OLCF and compare them against smaller local I/O installations, demonstrating the highest achieved I/O performance for real world applications at OLCF. Furthermore, we demonstrate that the best performing I/O setup can be determined prior to starting the job based on hardware characteristics.
Now that you have your data on disk the clock starts ticking and you are fighting against the deadline until your data will be purged, since most centers only offer the high performing storage spaces on a temporary basis. Extracting all valuable information out of a petabyte sized data set requires parallel processing as well and induces wait times until the resources are available and quite naturally a lot of trial-and-error for the evaluation. The time constraint for keeping the temporary data becomes even more troublesome when trying to compare multiple large simulations that naturally have a delay of multiple days until they are scheduled and write their results. And ideally analysis could embrace the data of multiple simulations of a quarterly accounted, yet year-long computing campaign. Another challenge for actually conducting scientific discoveries comes when utilizing multiple compute sites. This seems to be rather usual for research groups as they will use all the compute clock cycles they
can get wherever that may be. For comparative studies the data sets now need to be available at the same time for analysis, e.g. via archiving solutions or transfer to one location. The achievable transfer bandwidth between data centers is in our experience still much lower than expected. The talk will also present on the experiences of evaluating petabyte sized data sets in such a diverse environment.
  • Lecture (Conference)
    Extreme Data Workshop 2018, 18.-19.09.2018, Jülich, Deutschland

Publ.-Id: 27984 - Permalink


Advanced proxies for provenance, erosion and transport mechanisms of modern stream sediments – An application of SEM-based quantitative mineralogical analysis
Rütters, S.; Tolosana-Delgado, R.; Gutzmer, J.
In order to analyse stream sediments for provenance with respect to erosion and transport mechanisms, several methods are established (e.g. bulk sediment geochemistry, mineralogy (provided by XRD) and indicator mineral analysis). In this study, we make use of automated mineralogy by Mineral Liberation Analyser (MLA) as a potentially tool to advance sediment provenance studies.
The MLA combines backscattered electron (BSE) imaging with energy dispersive X‐ray spectrometry (EDS) generating compositional data each sediment particles of the sample. The provided data include particle as well as mineral grain parameters (i.e. size and shape) as well as the mineralogical composition and properties (e.g. elemental composition, density) of each particle (including individual constituting mineral grains). The aim is to join the provided parameters in a holistic model including statistical automatisms. In order to ensure a valid combination of the heterogenic and voluminous set of data provided by MLA, robust statistical analyses are needed. These statistical analyses unveil trends and dependencies in suites of related samples. Furthermore, in this study bulk geochemistry and XRD measurements are integrated to guaranty the quality of the introduced method and subsequently to critically assess the benefit of the measurement.
The study area is located in the Vogtland region of the Free State of Saxony (Germany). The variscan bedrocks comprise plutonic (i.e. different types of granite) and metamorphic units (mica schists, phyllites and quartzites), which are very well studied. Especially since, the Vogtland and the neighbouring Erzgebirge are well known for the occurrence of granite‐related mineral systems, represented as polymetallic deposits (skarn‐, vein‐, stockwork‐, and greisen‐type). In addition, this area is menial populated, suggesting a restricted anthropogenic contaminations of the stream sediment.
First results of this study, give rise for a clear improvement in the detection of lithological changes of the source rock composition and transport features of the unconsolidated sediments. This can be easily identified, based on the modal mineralogy, geochemical changes and grain‐parameter patterns. In addition, mixing of the material can be calculated with respect lithological changes along the river path. Another issue, is to detect the anthropogenic contamination of the sampled material and to balance the impact to the chemical composition.
  • Open Access LogoContribution to proceedings
    WGSG Dublin IV, 27.-29.06.2018, Dublin, Ireland

Publ.-Id: 27979 - Permalink


Formation of n- and p-type regions in individual Si/SiO2 core/shell nanowires by ion beam doping
Berencén, Y.ORC; Prucnal, S.; Möller, W.; Hübner, R.; Rebohle, L.; Schönherr, T.; Bilal Khan, M.; Wang, M.; Glaser, M.; Georgiev, Y. M.; Erbe, A.; Lugstein, A.; Helm, M.; Zhou, S.ORC
A method for cross-sectional doping of individual Si/SiO2 core/shell nanowires (NWs) is presented. P and B atoms are laterally implanted at different depths in the Si core. The healing of the implantation-related damage together with the electrical activation of the dopants takes place via solid phase epitaxy driven by millisecond-range flash lamp annealing. Electrical measurements through a bevel formed along the NW enabled us to demonstrate the concurrent formation of n- and p-type regions in individual Si/SiO2 core/shell NWs. These results might pave the way for ion beam doping of nanostructured semiconductors produced by using either top-down or bottom-up approaches.
Keywords: nanowires, ion beam doping, flash lamp annealing

Downloads:

  • Secondary publication expected from 25.09.2019

Publ.-Id: 27975 - Permalink


First time in vivo assessment of sigma-1 receptor binding (Sig-1R) in the brain of unmedicated acute major depressive disorder (MDD) using the novel Sig-1R-specific radioligand (-)-[F-18]Fluspidine and PET
Meyer, P. M.; Strauß, M.; Becker, G. A.; Hesse, S.; Bednasch, K.; Ettrich, B.; Zientek, F.; Rullmann, M.; Luthardt, J.; Fischer, S.; Patt, M.; Wünsch, B.; Brust, P.; Sabri, O.
Ziel/Aim:
The Sig-1R is a chaperone protein localized at the endoplasmatic reticulum (ER) that can translocate under ER stress, a mechanism which is critically involved in the pathophysiology of MDD. In order to investigate the pathophysiology of Sig-1R regulation in MDD, for the first time we quantitatively assessed Sig-1R binding in the brain of unmedicated, acute MDD and compared it with healthy controls (HC) using the novel radioligand (-)-[F-18]Fluspidine and PET.
Methodik/Methods:
Unmedicated, moderate to severe, acute MDD (n=12; 33±13ys; 6 males: HAMD: 19.0±4.3; MDD+ with family histora [n=6] and MDD- without family history of depression [n=6]), were investigated using(-)-[F-18]Fluspidine PET (300 MBq, ECAT Exact HR+) and compared with age-/sex-matched healthy controls (HC; n=9; 37±16ys [n.s.]; 4 males [n.s]). Distribution volume parameters (VT) were determined using full pharmacokinetic modelling (2TCM, metabolite correction). Regional VOI-analyses were carried out.
Ergebnisse/Results:
Compared with HC, in MDD, VT was significantly higher within the ncl. caudatus, ncl. accumbens, fronto-temporo-parieto-occipital and cingulate cortices, insula, amygdala, thalamus and midbrain/raphe (+15 to +24%, P<0.05). Compared with MDD-, in MDD+, VT was higher in the fronto -temporo and cingulate cortices, insula, hippocampus, putamen, thalamus (P<0.05). There was an inverted U-relationship between the severity of MDD (HAMD) and VT in the fronto-temporo-parietal and posterior cingulate cortices and thalamus (P<0.05).
Schlussfolgerungen/Conclusions:
Using (-)-[F-18]Fluspidine PET, we demonstrate for the first time higher Sig-1R binding in meso-striato-cortico-limbic and paralimbic brain regions of unmedicated, acute MDD. Higher Sig-1R binding in MDD+, compared with MDD-, may express different subtypes of depression. Increased Sig-1Rs in acute MDD and the inverted U-relationship between severity and Sig-1R may reflect neuroadaptive uptregulation of Sig-1R counteracting ER stress that is exhausted in the severest stages of MDD leading to apoptosis.
  • Lecture (Conference)
    56. Jahrestagung der DGN, 18.-21.04.2018, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2018), V65

Publ.-Id: 27974 - Permalink


Ion acceleration with on-shot monitored ultra-high contrast using the DRACO Petawatt laser facility
Ziegler, T.ORC; Bernert, C.; Bock, S.; Brack, F.-E.; Bussmann, M.ORC; Garten, M.ORC; Kraft, S.ORC; Kroll, F.ORC; Metzkes-Ng, J.ORC; Obst, L.ORC; Oksenhendler, T.; Rehwald, M.ORC; Schlenvoigt, H.-P.ORC; Schramm, U.ORC; Zeil, K.
Laser-driven ion acceleration promises to provide a compact solution for demanding applications like particle therapy, proton radiography or inertial confinement research. Controlling the beam parameters to achieve these goals is currently pushing the frontier of laser driven particle accelerators.
We present an overview of recent achievements at the high power ultra-short pulse laser source DRACO at the HZDR in Dresden (Germany). The laser system was recently upgraded by new front end components and an additional Petawatt (PW) amplifier stage, finally providing high contrast pulses of 30J within 30fs at 1 Hz pulse repetition rate.
The performance of the plasma acceleration is strongly dependent on the complex pre-plasma formation process at the target front surface which is determined by the temporal intensity contrast. Plasma mirror setups have proven to be a valuable tool to significantly improve the temporal contrast by reducing pre-pulse intensity and steepening the rising edge of the main laser pulse. Re-collimating single plasma mirror devices have therefore been implemented into the Draco laser beam lines, enabling investigation of laser proton acceleration and proton energy scaling within the TNSA regime using ultra-thin foil targets.
The results of the simultaneously measured proton emission energies in laser forward direction, laser backward direction and the temporal contrast, measured on a single-shot base by means of self-referenced spectral interferometry with extended time excursion (SRSI-ETE) at unprecedented dynamic and temporal range, will be presented.
  • Poster
    45th Conference on Plasma Physics, 02.-06.07.2018, Prague, Czech Republic

Publ.-Id: 27973 - Permalink


All-optical shaping of laser-driven proton beam profiles
Ziegler, T.ORC; Obst-Huebl, L.ORC; Brack, F.-E.; Branco, J.; Bussmann, M.ORC; Cowan, T. E.ORC; Curry, C. B.ORC; Fiuza, F.ORC; Garten, M.ORC; Gauthier, M.ORC; Göde, S.; Glenzer, S. H.; Huebl, A.ORC; Irman, A.; Kim, J. B.; Kluge, T.ORC; Kraft, S.ORC; Kroll, F.ORC; Metzkes-Ng, J.ORC; Pausch, R.ORC; Prencipe, I.; Rehwald, M.ORC; Rödel, C.; Schlenvoigt, H.-P.ORC; Schramm, U.ORC; Zeil, K.
Extreme field gradients intrinsic to relativistic laser plasma interactions enable compact MeV proton accelerators with unique bunch characteristics, yet complicate direct proton beam control. Only complex micro-engineering of the plasma accelerator itself and limited adoption of conventional beam optics, so far provided access to global beam parameters as direction and divergence. Here we present a novel, counter-intuitive, yet readily applicable all-optical approach to imprint detailed spatial information from the driving laser pulse to the proton bunch. In a series of experiments, the spatial profile of the energetic proton bunch was found to exhibit identical features as the fraction of the laser pulse passing around a target of limited size. The formation of quasi-static electric fields in the beam path by ionization of residual gas in the experimental chamber results in asynchronous information transfer between the laser pulse and the naturally delayed proton bunch. Essentially acting as a programmable memory, these fields provide access to a new level of proton beam manipulation.
  • Poster
    8th Conference of the International Committee on Ultrahigh Intensity Lasers, 09.-14.09.2018, Lindau, Germany

Publ.-Id: 27972 - Permalink


A fine future - Flotation in times of circular economy and energy transition
Rudolph, M.ORC
The invention of flotation about 140 years ago was one of the great achievements of modern processing technology. For many metallic/mineral raw materials, processing without a flotation stage would be unthinkable. This article presents the especially important topics in the field of basic research and technological development of flotation in times of the circular economy and energy transition.
Keywords: Flotation, Circular Economy, Energiewende
  • Open Access LogoAT Mineral Processing 59(2018), 56-64

Publ.-Id: 27971 - Permalink


Heterogeneity of γH2AX foci increases in ex vivo biopsies relative to in vivo tumors
Rassamegevanon, T.; Löck, S.; Baumann, M.; Krause, M.; von Neubeck, C.
The biomarker for DNA double stand breaks, gammaH2AX (γH2AX), holds a high potential as an intrinsic radiosensitivity predictor of tumors in clinical practice. Here, two published γH2AX foci datasets from in and ex vivo exposed human head and neck squamous cell carcinoma (hHNSCC) xenografts were statistically re-evaluated for the effect of the assay setting (in or ex vivo) on cellular geometry and the degree of heterogeneity in γH2AX foci. Significant differences between the nucleus areas of in- and ex vivo exposed samples were found. However, the number of foci increased linearly with nucleus area in irradiated samples of both settings. Moreover, irradiated tumor cells showed changes of nucleus area distributions towards larger areas compared to unexposed samples, implying cell cycle alteration after radiation exposure. The number of residual γH2AX foci showed a higher degree of intra-tumoral heterogeneity in the ex vivo exposed samples relative to the in vivo exposed samples. In the in vivo setting, the highest intra-tumoral heterogeneity was observed in initial γH2AX foci numbers (foci detected 30 min following irradiation). These results suggest that the tumor microenvironment and the culture condition considerably influence cellular adaptation and DNA damage repair.
Keywords: radiation; predictive biomarker; DNA damage response; mixed model statistics

Publ.-Id: 27970 - Permalink


An endorectal balloon reduces patient-reported GI toxicity in postop radiotherapy of prostate cancer
Holscher, T.; Rentsch, A.; Zastrow, S.; Wirth, M.; Ahmad, A.; Krause, M.; Troost, E.
Purpose or Objective
In dose-escalated radiotherapy (RT) of prostate cancer late rectal toxicity is one of the dose limiting factors. In primary RT, an endorectal balloon (RB) has been shown to reduce the dose to parts of rectum and anus, stabilize prostate position and may therefore be a means to improve therapeutic ratio. In postoperative radiotherapy the effect of RB is less well-known, in general a dose of <70 Gy is applied and therefore no clinical outcome data regarding the benefit of a RB is available.
The aim of this retrospective study was to assess the patient-reported late rectal toxicity (GItox) 3, 12, and 24 months after RT in postoperative prostate cancer patients receiving a daily RB, compared to an earlier cohort, which was treated without RB.
Material and Methods
We identified all patients who received postoperative radiotherapy (66 Gy in 33 fractions) after radical prostatectomy, had no nodal or distant metastases and at least one follow-up visit. In those treated between 2008 and 2013, no RB was applied whereas between 2014 and 2016, a RB was routinely applied. All patients were followed with the same set of questionnaires and outpatient visits. Results where compared and analysed by Chi²-Test (SPSS 23.0).
Results
In total, 433 patients were retrieved, of whom 194 were treated with and 239 patients without RB. The patients were well balanced according initial NCCN risk and other confounding factors. The maximum patient reported GItox in the first 2 years after RT was low: 75,5%, 20,8%, 3,7 %, 0 % reported no, grade 1 (G1), G2 and G3 GItox, respectively. The prevalence of rate of G1+ GItox was 16,5%, 15,1% and 18,0% at 3, 12, and 24 months, respectively. No GItox within 2 years occurred in 71,1% patients without RB versus 80,9% with RB. G1+ GItox was reported in 28,5% without RB and in 19,1% with RB. G2 GITox was reported by 13 (5,4%) patients without and by 3 (1,5%) with RB. These results are statistically significant at p<0,025.
Conclusion
This retrospective data show a significant and clinically relevant reduction of GItox after postoperative RT for prostate cancer using an endorectal balloon. A prospective randomized trial is currently being prepared.

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Publ.-Id: 27969 - Permalink


A concept to personalize radiation oncology: Predicting cell-specific survival prior to treatment
Oesten, H.; von Neubeck, C.; Löck, S.; Enghardt, W.; Krause, M.; Mcmahon, S.; Grassberger, C.; Paganetti, H.; Lühr, A.
Material and Methods
Based on a previously developed mechanistic radiation response model of DNA repair and cell survival (CS) prediction for normal tissue cells, we simulated measured radiobiological parameters (α and β) of 19 in vitro cancer cell lines (skin, lung, brain). The radiation model incorporated four cell-specific parameters: number of chromosomes, p53 mutation status, cell-cycle distribution and the effective genome size (GS). Only the first three input parameters were experimentally available; the latter was obtained by minimizing the difference between the simulated and measured α and β values. A parametrization of the GS as a function of the cells’ chromosome number and nucleus volume was proposed. The use of these input parameters was validated by comparing the simulated outcome of time-dependent γH2AX data over 24h with independent experimental datasets.
Results
Overall good agreement between simulated and measured in vitro cancer CS curves was achieved (Fig. 1). The measured β values increased quadratically with the obtained GS (R2=0.81) irrespective of other cell-specific parameters (Fig. 2b). The measured α values increased linearly with GS manifesting different slopes distinguishable into the cells’ p53 mutation status (Fig. 2a). Measured α and β values were predictable based on GS with a one-sigma uncertainty: σ=0.04Gy-1 for α and σ=0.01Gy-2 for β. The GS correlated (R2=0.70) with the number of chromosomes for all but four cell lines. The detailed cell-specific cell cycle distribution had a negligible impact on α and β. Measured time-dependent γH2AX data were consistent with the repair kinetics simulations (R2=0.95).
Conclusion
A mechanistic model for radiation response of normal human cells was successfully modified to simulate measured in vitro CS of 19 cancer cell lines. Independent of cancer entity, the radiobiological value β was predictable only with known GS while the prediction of α additionally required at least knowledge of the p53 mutation status. An observed correlation of GS with the number of chromosomes and nucleus size, both clinically accessible from a biopsy prior to treatment, may facilitate individualized radiotherapy based on cell-specific survival prediction.

Publ.-Id: 27968 - Permalink


Scalable Multi-Platform PIC Simulations as an Open Science Service
Huebl, A.ORC; Pausch, R.; Widera, R.; Garten, M.; Debus, A.; Goethel, I.; Matthes, A.; Worpitz, B.; Starke, S.; Kelling, J.; Kossagk, S.; Bastrakov, S.; Kluge, T.; Juckeland, G.; Schramm, U.; Cowan, T. E.; Bussmann, M.
PIConGPU is a fully open, community-driven, 3D and 2D3V particle-in-cell code for the age of heterogeneous, many-core driven supercomputing. Developed in a single source C++ code base, PIConGPU supports both "traditional" CPU architectures as well as modern and highly parallel architectures such as OpenPOWER, Xeon Phi, and Nvidia GPUs.

PIConGPU has shown to be suitable for production runs on the full system size of TOP5 clusters such as Titan (ORNL) and Piz Daint (CSCS). Machines like those enable few-hour turnarounds for full 3D3V simulations on complex studies such as laser-ion acceleration from mass-limited targets, long-scale laser-wakefield acceleration with high bunch charges, and hybrid acceleration schemes. The resulting output of systematic parameter scans (PBytes+) raises a severe challenge for data centers. We address these issues with modern IO frameworks, performance modeling, and in situ data reduction techniques. Using such online methods we can investigate a wide range of observables relevant for experiments and run dozens of simulations at the same time frame as an experimental beam time.

PIConGPU is further complemented by modern methods for photon generation, transport, as well as X-ray interaction. This simulation framework aims to provide documented, installable, and re-usable software components for the community, well-suited for open data (openPMD) and open science workflows without restrictions. Latest developments include a python-centric, extensive framework for specific experiments, which provides all of the above in an intuitive, non-expert user interface.
Keywords: PIConGPU, Scalability, performance-portability, Open Source, Open Science, FOSS, Open Data, In Situ processing, SaaS, GPU, Big Data
  • Lecture (Conference)
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge (CO), United States of America
    DOI: 10.5281/zenodo.1345080
  • Poster
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge (CO), United States of America

Publ.-Id: 27965 - Permalink


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