Publication database - Helmholtz-Zentrum Dresden-Rossendorf

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24624 Publications
Immobilisierung von Tc(VII)/Tc(IV) an Eisenphasen
Spranger, F.
Abstract: Die Immobilisierung von Tc(VII)/Tc(IV) an den Eisenphasen Magnetit und Siderit wurde mittels Batch-Sorptionsversuchen, ATR FT-IR-Spektroskopie und Röntgenabsorptionsspektroskopie untersucht.
Keywords: Technetium, Magnetite, Siderite
  • Bachelor thesis
    TU Dresden, 2015
    Mentor: Dr. Katja Schmeide / Prof. Dr. Thorsten Stumpf
    43 Seiten
Registration No. 22522

Radiation-induced lung damage - Clinical risk profiles and predictive imaging on their way to risk-adapted individualized treatment planning?
Ebert, N.; Baumann, M.; Troost, E. G.
Abstract: there ist no abstract Registration No. 22517

Targeting of β1 integrins impairs DNA repair for radiosensitization of head and neck cancer cells.
Dickreuter, E.; Eke, I.; Krause, M.; Borgmann, K.; van Vugt, M. A.; Cordes, N.
Abstract: β1 Integrin-mediated cell-extracellular matrix interactions allow cancer cell survival and confer therapy resistance. It was shown that inhibition of β1 integrins sensitizes cells to radiotherapy. Here, we examined the impact of β1 integrin targeting on the repair of radiation-induced DNA double-strand breaks (DSBs). β1 Integrin inhibition was accomplished using the monoclonal antibody AIIB2 and experiments were performed in three-dimensional cell cultures and tumor xenografts of human head and neck squamous cell carcinoma (HNSCC) cell lines. AIIB2, X-ray irradiation, small interfering RNA-mediated knockdown and Olaparib treatment were performed and residual DSB number, protein and gene expression, non-homologous end joining (NHEJ) activity as well as clonogenic survival were determined. β1 Integrin targeting impaired repair of radiogenic DSB (γH2AX/53BP1, pDNA-PKcs T2609 foci) in vitro and in vivo and reduced the protein expression of Ku70, Rad50 and Nbs1. Further, we identified Ku70, Ku80 and DNA-PKcs but not poly(ADP-ribose) polymerase (PARP)-1 to reside in the β1 integrin pathway. Intriguingly, combined inhibition of β1 integrin and PARP using Olaparib was significantly more effective than either treatment alone in non-irradiated and irradiated HNSCC cells. Here, we support β1 integrins as potential cancer targets and highlight a regulatory role for β1 integrins in the repair of radiogenic DNA damage via classical NHEJ. Further, the data suggest combined targeting of β1 integrin and PARP as promising approach for radiosensitization of HNSCC.Oncogene advance online publication, 15 June 2015; doi:10.1038/onc.2015.212. Registration No. 22516

SABR in NSCLC--the beginning of the end or the end of the beginning?
Brada, M.; Pope, A.; Baumann, M.
Abstract: there is no Abstract Registration No. 22514

Physical modelling of temperature fluctuations in a high aspect ratio model of the Czochralski crystal growth
Pal, J.; Cramer, A.; Grants, I.; Eckert, S.; Gerbeth, G.
Abstract: A low temperature liquid metal model of the Czochralski (CZ) crystal growth process is considered experimentally for a high aspect ratio. Temperature fluctuations close to the edge of the model crystal are studied under the action of a rotating magnetic field (RMF) and/or rotation of the model crystal. A rotation of thermal structures is observed which loses its periodicity at sufficiently high strengths of the RMF. This finding is in qualitative agreement with previous findings in Rayleigh-Bénard (RB) cells. Opposing to that more generic case, the remaining amplitude of the temperature fluctuations stays significantly higher. I.e., the suppression of the fluctuations, which are detrimental to the growth of a mono-crystal, is weaker in the model under investigation.
Keywords: Rayleigh-Bénard convection, Large-scale temperature oscillation, Magnetohydrodynamics, Electromagnetic stirring, Czochralski crystal growth, Model Experiment Registration No. 22511

Radiosensitization of NSCLC cells by EGFR inhibition is the result of an enhanced p53-dependent G1 arrest.
Kriegs, M.; Gurtner, K.; Can, Y.; Brammer, I.; Rieckmann, T.; Oertel, R.; Wysocki, M.; Dorniok, F.; Gal, A.; Grob, T. J.; Laban, S.; Kasten-Pisula, U.; Petersen, C.; Baumann, M.; Krause, M.; Dikomey, E.
Abstract: PURPOSE:

How EGF receptor (EGFR) inhibition induces cellular radiosensitization and with that increase in tumor control is still a matter of discussion. Since EGFR predominantly regulates cell cycle and proliferation, we studied whether a G1-arrest caused by EGFR inhibition may contribute to these effects.

We analyzed human non-small cell lung cancer (NSCLC) cell lines either wild type (wt) or mutated in p53 (A549, H460, vs. H1299, H3122) and HCT116 cells (p21 wt and negative). EGFR was inhibited by BIBX1382BS, erlotinib or cetuximab; p21 was knocked down by siRNA. Functional endpoints analyzed were cell signaling, proliferation, G1-arrest, cell survival as well as tumor control using an A549 tumor model.

When combined with IR, EGFR inhibition enhances the radiation-induced permanent G1 arrest, though solely in cells with intact p53/p21 signaling. This increase in G1-arrest was always associated with enhanced cellular radiosensitivity. Strikingly, this effect was abrogated when cells were re-stimulated, suggesting the initiation of dormancy. In line with this, only a small non-significant increase in tumor control was observed for A549 tumors treated with fractionated RT and EGFR inhibition.

For NSCLC cells increase in radiosensitivity by EGFR inhibition results from enhanced G1-arrest. However, this effect does not lead to improved tumor control because cells can be released from this arrest by re-stimulation.

Keywords: Cell cycle; EGFR inhibition; G1 arrest; NSCLC; Radiosensitization; p53 Registration No. 22505

Materialien für morgen: Energieeffiziente Prozesse in der Informationstechnologie
Gemming, S.
Abstract: Kurzer Festvortrag bei der Feier 20 Jahre Helmholtz - 20 Highlights
Keywords: energy, resistive, memristor, self-organization, self-assembly, simulation
  • Invited lecture (Conferences)
    20 Jahre Helmholtz, 25.06.2015, Berlin Adlershof, WISTA, Deutschland
Registration No. 22501

Dynamic processes in materials for energy conversion and storage
Gemming, S.
Abstract: Modern material combinations, which we use for converting, storing and saving energy, exploit the synergistic effects of multi-component systems to achieve functionalities beyond those of the single constituents alone. Steps towards a rational design of such material systems have increasingly inspired research activities both from experiment and theory. With the considerable increase of computational resources, simulations have successfully started to bridge the gap between idealized, rather specific theoretical concepts and experimental realization for system length and time scales, which reflect specific physical processes involved in energy saving, conversion, and storage. I will present examples from recent work which span the range the range from nano-scale battery effects in thin multifunctional oxide films of spongy structures by spinodal decomposition of silicon monoxide for storage and conversion to formation and stability of anti-wear coatings for energy efficient applications. Those studies illustrate recent developments to arrive at a truly scale- adapted modeling of energy materials.
Keywords: energy, density functional theory, energy conversion, energy storage
  • Invited lecture (Conferences)
    International Colloquium on the Simulation of Energy Materials, 12.06.2015, Jülich, Deutschland
Registration No. 22500

Microscopic processes in data and energy storage - considerations based on multiscale modeling
Gemming, S.
Abstract: There is no abstract available.
Keywords: density functional theory, memristive, resistive, strontium titanate, tintaniom oxide
  • Invited lecture (Conferences)
    Seminarreihe der FSU Jena, 23.01.2015, Jena, Deutschland
Registration No. 22499

Theoretical investigation of an in situ k-restore process for damaged ultra-low-k materials based on plasma enhanced fragmentation
Förster, A.; Wagner, C.; Gemming, S.; Schuster, J.
Abstract: The authors present theoretical investigations of a k-restore process for damaged porous ultra-low-k (ULK) materials. The process is based on plasma enhanced fragmented silylation precursors to replace k-value damaging, polar Si-OH and Si-H bonds by k-value lowering Si-CH3 bonds. The authors employ density functional theory to determine the favored fragments of silylation precursors and show the successful repair of damaged bonds on our model system.
Keywords: density-functional theory, molecules, adsorption, passivation, molecular dynamics Registration No. 22498

Near-surface hydrogen depletion of diamond-like carbon films produced by direct ion deposition
Markwitz, A.; Gupta, P.; Mohr, B.; Hübner, R.; Leveneur, J.; Zondervan, A.; Becker, H.-W.
Abstract: Amorphous atomically flat diamond-like carbon (DLC) coatings were produced by direct ion deposition using a system based on a Penning ion source, butane precursor gas and post acceleration. Hydrogen depth profiles of the DLC coatings were measured with the 15N R-NRA method using the resonant nuclear reaction 1H(15N,alpha gamma)12C (Eres = 6.385 MeV). The films produced at 3.0-10.5 kV acceleration voltage show two main effects. First, compared to average elemental composition of the film, the near-surface region is hydrogen depleted. The increase of the hydrogen concentration by 3% from the near-surface region towards the bulk is attributed to a growth model which favours the formation of sp2 hybridised carbon rich films in the film formation zone. Secondly, the depth at which the maximum hydrogen concentration is measured increases with acceleration voltage and is proportional to the penetration depth of protons produced by the ion source from the precursor gas. The observed effects are explained by a deposition process that takes into account the contributions of ion species, hydrogen effusion and preferential displacement of atoms during direct ion deposition.
Keywords: Diamond-like carbon, Hydrogen depletion, Depth profile, Nuclear reaction analysis, Growth process Registration No. 22497

High Energy Radial Deposition of Diamond-Like Carbon Coatings
Suschke, K.; Hübner, R.; Murmu, P. P.; Gupta, P.; Futter, J.; Markwitz, A.
Abstract: Diamond-like carbon (DLC) coatings were deposited with a new direct ion deposition system using a novel 360 degree ion source operating at acceleration voltage between 4 and 8 kV. Cross-sectional TEM images show that the coatings have a three layered structure which originates from changes in the deposition parameters taking into account ion source condition, ion current density, deposition angles, ion sputtering and ion source movement. Varying structural growth conditions can be achieved by tailoring the deposition parameters. The coatings show good promise for industrial use due to their high hardness, low friction and excellent adhesion to the surface of the samples.
Keywords: diamond-like carbon; direct ion deposition; anode layer ion source; amorphous carbon; TEM Registration No. 22496

High-field terahertz spectroscopy at HZDR
Schneider, H.
Abstract: There is no abstract.
Keywords: terahertz spectroscopy, free-electron laser
  • Lecture (others)
    Seminar, Institut Saint-Louis, 18.09.2015, Saint-Louis, Frankreich
Registration No. 22493

Two-photon quantum well photodetectors for the THz regime
Franke, C.; Walther, M.; Helm, M.; Schneider, H.
Abstract: Two-photon quantum-well photodetector devices designed for transition energies corresponding to 3 – 6 THz have been realized and intersubband energies were verified by photocurrent spectroscopy. Super-linear but not ideally quadratic behavior has been demonstrated by interferometric autocorrelation experiments using narrow-band terahertz pulses from the free-electron laser FELBE. With decreasing operation frequency, detector operation is progressively limited to low applied fields because of pronounced breakdown phenomena of the conductivity. This work has been supported by the Deutsche Forschungsgemeinschaft, project number SCHN 1127/2-1.
Keywords: terahertz two-photon intersubband absorption, quadratic detection, autocorrelation, GaAs/AlGaAs quantum well
  • Lecture (Conference)
    The 13th International Conference on Intersubband Transitions in Quantum Wells (ITQW'2015), 06.-11.09.2015, Wien, Österreich
Registration No. 22492

Strong electroluminescence from terbium-doped metal-insulator-semiconductor structures
Berencen, Y.; Braun, M.; Garrido, B.; Hiller, D.; Liu, B.; Ramirez, J. R.; Sun, J.; Wutzler, R.; Helm, M.; Skorupa, W.
Abstract: Integrated photonics is a key technology of the 21st century, and the electrically driven, integrated light emitter is an important building block, but difficult to realize. Thus, an enormous variety of different materials and material systems have been investigated in the past, ranging from the various approaches to integrate III-V semiconductors to the different types of Si-based light emission. Within the latter group rare earth (RE) implanted MOS structures feature a high conformity with standard CMOS processes combined with the excellent optical properties of RE elements. The present contribution discusses the problems of Si-based light emitters at the example of RE-doped MOS structures, and compares various light emitter designs and their potential to overcome these problems.
In detail, the power efficiency, the operation lifetime and the operation voltage of Tb- MOS structures are investigated. The main electroluminescence excitation mechanism is impact excitation of hot electron which plays an ambivalent role: efficient excitation is often related with efficient defect creation. In addition, a dark zone close to the injecting interface limits the scalability towards low voltages. The excitation mechanism und thus the performance of the light emitter is affected by the structure and composition of the dielectric stack of the MOS structure. Within this study, several host materials for the RE ions, namely stoichiometric and Si-rich silicon oxide or silicon nitride; different fabrication methods, namely plasma enhanced chemical vapour deposition, ion implantation and atomic layer deposition; and the use of additional buffer or injection layers are investigated.

Keywords: terbium, Si-based light emitters, electroluminescence, atomic layer deposition
  • Invited lecture (Conferences)
    Freiberg Silicon Days 2015, 18.-19.06.2015, Freiberg, Deutschland
Registration No. 22491

Temperature distribution during flash lamp annealing of thin film multilayer systems
Schumann, T.; Prucnal, S.; Skorupa, W.; Henke, T.
Abstract: Flash lamp annealing (FLA) is a modern annealing technique which takes advantage of the millisecond- and microsecond time scale. However, in many cases a direct temperature determination is sophisticated and complex, and sometimes an a priori guess of the temperature is desirable. In this work we simulate the space and time dependent temperature distribution during FLA and compare it with experimental results, e.g. with observable phase changes during the crystallization of amorphous Si layers on insulator for thin film transistor applications. In detail, we will address the following items: (i) the influence of multiple reflections within the layer system as well as between sample and chamber walls, (ii) the influence of lateral and transversal temperature gradients, and (iii) the edge overheating problem. Simulations were performed with the help of both in-house and commercial software tools.
Keywords: flash lamp annealing, temperature distribution, crystallization, amorphous silicon
  • Lecture (Conference)
    European Material Research Society, Fall Meeting 2015, 15.-18.09.2015, Warsaw, Poland
Registration No. 22490

ESTRO consensus guideline on target volume delineation for elective radiation therapy of early stage breast cancer.
Offersen, B. V.; Boersma, L. J.; Kirkove, C.; Hol, S.; Aznar, M. C.; Biete Sola, A.; Kirova, Y. M.; Pignol, J. P.; Remouchamps, V.; Verhoeven, K.; Weltens, C.; Arenas, M.; Gabrys, D.; Kopek, N.; Krause, M.; Lundstedt, D.; Marinko, T.; Montero, A.; Yarnold, J.; Poortmans, P.

Delineation of clinical target volumes (CTVs) is a weak link in radiation therapy (RT), and large inter-observer variation is seen in breast cancer patients. Several guidelines have been proposed, but most result in larger CTVs than based on conventional simulator-based RT. The aim was to develop a delineation guideline obtained by consensus between a broad European group of radiation oncologists.

During ESTRO teaching courses on breast cancer, teachers sought consensus on delineation of CTV through dialogue based on cases. One teacher delineated CTV on CT scans of 2 patients, followed by discussion and adaptation of the delineation. The consensus established between teachers was sent to other teams working in the same field, both locally and on a national level, for their input. This was followed by developing a broad consensus based on discussions.

Borders of the CTV encompassing a 5mm margin around the large veins, running through the regional lymph node levels were agreed, and for the breast/thoracic wall other vessels were pointed out to guide delineation, with comments on margins for patients with advanced breast cancer.

The ESTRO consensus on CTV for elective RT of breast cancer, endorsed by a broad base of the radiation oncology community, is presented to improve consistency.
Registration No. 22489

Package Labelling with Printed Metal-Particle Suspensions using Millisecond Thermal Processing
Wiesenhütter, K.; Schumann, T.; Zichner, R.; Gebel, T.; Wiesenhütter, U.; Richter, H. U.; Skorupa, W.
Abstract: The need for novel, flexible and low-cost electronic products with functionality far beyond that offered by conventional size-restricted and rigid semiconductor devices requires a rapid development of advanced material and deposition technology concepts. One of the most promising pathways to realize this ambitious goal is printed flexible electronics (PFE). Recently, printing has successfully demonstrated its potential for manufacture of advanced low-cost electronic products such as flexible displays, thin-film solar cells, large-area sensors etc. Importantly, by using bendable, inexpensive media (e.g.: paper-like substrates, polymer films) and high-throughput roll-to-roll (R2R) processing, a significant reduction of the overall costs associated with electronic device fabrication has been achieved.
Here, we report on a successful application of millisecond thermal processing by flash lamp annealing (FLA) as a highly-attractive technique for the functionalization of copper paste screen printed on low-thermal budget paper-like media for package labelling. The effect of the FLA parameters (i.e. pulse duration and energy density), on the substrate behavior as well as on the microstructure and electrical response of the as-flashed films was studied. A significant drop of the sheet resistance of the FL-treated layers as compared to the as-printed layers was observed. As ms-FLA permits selective, near-surface heating, a damage of the sensitive substrates was avoided. The microstructure of the copper paste before and after FLA was also investigated. Being highly-efficient, “non-destructive, and compatible with R2R processing, FLA offers the realization of advanced PFE products.

Keywords: package labeling, flash lamp annealing, millisecond thermal processeing, metal-particle suspension,
  • Lecture (Conference)
    Paper electronics: a new challenge for materials a new opportunity for devices II, Symposium BB at the E-MRS Spring Meeting, 11.-15.05.2015, Lille, France
Registration No. 22488

Aldehyde Dehydrogenase Is Regulated by β-Catenin/TCF and Promotes Radioresistance in Prostate Cancer Progenitor Cells.
Cojoc, M.; Peitzsch, C.; Kurth, I.; Trautmann, F.; Kunz-Schughart, L. A.; Telegeev, G. D.; Stakhovsky, E. A.; Walker, J. R.; Simin, K.; Lyle, S.; Fuessel, S.; Erdmann, K.; Wirth, M. P.; Krause, M.; Baumann, M.; Dubrovska, A.
Abstract: Radiotherapy is a curative treatment option in prostate cancer. Nevertheless, patients with high-risk prostate cancer are prone to relapse. Identification of the predictive biomarkers and molecular mechanisms of radioresistance bears promise to improve cancer therapies. In this study, we show that aldehyde dehydrogenase (ALDH) activity is indicative of radioresistant prostate progenitor cells with an enhanced DNA repair capacity and activation of epithelial-mesenchymal transition (EMT). Gene expression profiling of prostate cancer cells, their radioresistant derivatives, ALDH(+) and ALDH(-) cell populations revealed the mechanisms, which link tumor progenitors to radioresistance, including activation of the WNT/β-catenin signaling pathway. We found that expression of the ALDH1A1 gene is regulated by the WNT signaling pathway and co-occurs with expression of β-catenin in prostate tumor specimens. Inhibition of the WNT pathway led to a decrease in ALDH(+) tumor progenitor population and to radiosensitization of cancer cells. Taken together, our results indicate that ALDH(+) cells contribute to tumor radioresistance and their molecular targeting may enhance the effectiveness of radiotherapy. Registration No. 22487

Demands of radiotherapy on modern radiological imaging
Anforderungen der Strahlentherapie an die moderne radiologische Bildgebung

Buetof, R.; Krause, M.
Abstract: Background

The aim of radiotherapy as a local treatment method is the eradication of all vital tumor cells in order to achieve permanent local tumor control. From a clinical point of view this means that a patient suffering from cancer can only be cured if all cancer stem cells as a specific subpopulation within a tumor are eliminated by the treatment.

New radiation techniques often employ lower normal tissue doses with less toxicity and/or the possibility to apply higher radiation doses to the target volume. High-resolution imaging is hereby mandatory for precise tumor volume definition as a basis of local tumor control. New developments in the field of bioimaging lead to further perspectives in radiotherapy.

By combining anatomical information with biological characteristics of the tumor, additional benefits for treatment planning and outcome can be achieved. Thus, the use of these modern imaging methods to define irradiation target volumes more clearly forms the basis for the application of modern radiation techniques.

Keywords: Cancer stem cells Tumor volume Local tumor control Bioimaging Radiation oncology Registration No. 22486

Thermal processing within milliseconds: semiconductors and beyond
Skorupa, W.
Abstract: In this talk I will review the advances that subsecond thermal processing in the millisecond range using xenon-filled flash lamps (FLA) brings to the processing of advanced semiconductor materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications via doping and/or defect engineering. A recent state-of-the-art is published in Ref./1/. An important issue of our present work is the liquid phase processing in the millisecond range at the surface of solid substrates. A recent example is the controlled formation of III-V nanocrystals (InAs, GaAs) in silicon nanowires after ion beam synthesis /2/. We prepared coarse grained dendritic crystal structures in thin silicon films on silicon dioxide to show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process /3/. We could demonstrate that germanium and silicon exhibit superconductivity at ambient pressure and temperatures in the range of 1-2 K by avoiding Ga clusters /4/. Regarding photovoltaic applications, we dealt with the ion beam doping and thermal processing of PV silicon demonstrating a distinct improvement of the minority carrier diffusion length compared to rapid thermal processing and furnace treatments /5/. Moreover, we engineered the hydrogen content in photovoltaic silicon in correlation to the phosphorus doping using plasma immersion ion implantation and FLA /6/. Also, we demonstrated FLA driven phosphorus in-diffusion from a surface source /7/.

/1/ W. Skorupa and H. Schmidt: “Subsecond annealing of advanced materials”, Springer Series in Materials Science 192 (2014), ISBN 978-3-319-03131-6.
/2/ S.Prucnal,…,W.Skorupa et al.: “III–V semiconductor nanocrystal formation in silicon nanowires via liquid-phase epitaxy”, Nano Research 7, 1769 (2014); (see also Nano Lett. 11, 2814 (2011)).
/3/ M.Voelskow,…,W.Skorupa et al.: “Formation of dendritic crystal structures in thin silicon films on silicon dioxide by carbon ion implantation and high intensity large area flash lamp irradiation”, J. Cryst. Growth, 388, 70 (2014)
/4/ V.Heera,…,W.Skorupa et al.: “Depth-resolved transport measurements and atom-probe tomography of heterogeneous, superconducting Ge:Ga films”, Supercond.Sc.&Technol. 27, 055025 (2014).
/5/ S.Prucnal,…,W.Skorupa et al.: “Millisecond annealing for advanced doping of dirty-silicon solar cells”, J. Appl. Phys. 111, 123104 (2012).
/6/ F.L. Bregolin,…,W.Skorupa et al.:“Hydrogen engineering via plasma immersion ion implantation and flash lamp annealing in silicon-based solar cell substrates”, J. Appl. Phys. 115, 064505 (2014).
/7/ H.B. Normann,…,W.Skorupa et al.: “Phosphorus in-diffusion from a surface source by millisecond flash lamp annealing for shallow emitter solar cells”, Appl.Phys.Lett. 102, 132108 (2014).

Keywords: flash lamp annealing, subsecond thermal processing, ion implantation, semiconductors, doping, nanowires
  • Invited lecture (Conferences)
    Gettering and Defect Engineering in Semiconductor Technology 2015 — 30 Years of GADEST, 20.-25.09.2015, Erlangen, Germany
Registration No. 22485

Subsecond thermal processing for nanostructured semiconductors
Skorupa, W.
Abstract: This talk reviews the advances that subsecond thermal processing in the millisecond range using xenon-filled flash lamps (FLA) brings to the processing of advanced semiconductor materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications via doping and/or defect engineering. A recent state-of-the-art is published in Ref./1/.
An important issue of our present work is the liquid phase processing in the millisecond range at the surface of solid substrates. A recent example is the controlled formation of III-V nanocrystals (InAs, GaAs) in silicon nanowires after ion beam synthesis /2/. We prepared coarse grained dendritic crystal structures in thin silicon films on silicon dioxide to show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process /3/. We could demonstrate that germanium and silicon exhibit superconductivity at ambient pressure and temperatures in the range of 1-2 K by avoiding Ga clusters after ion implantation and FLA /4/. Regarding photovoltaic applications, we dealt with the ion beam doping and thermal processing of PV silicon demonstrating a distinct improvement of the minority carrier diffusion length compared to rapid thermal processing and furnace treatments /5/. Moreover, we engineered the hydrogen content in photovoltaic silicon in correlation to the phosphorus doping using plasma immersion ion implantation and FLA /6/. Also, we demonstrated FLA driven phosphorus in-diffusion from a surface source /7/.

/1/ W. Skorupa and H. Schmidt: “Subsecond annealing of advanced materials”, Springer Series in Materials Science 192 (2014), ISBN 978-3-319-03131-6.
/2/ S.Prucnal,…,W.Skorupa et al.: “III–V semiconductor nanocrystal formation in silicon nanowires via liquid-phase epitaxy”, Nano Research 7, 1769 (2014); (see also Nano Lett. 11, 2814 (2011)).
/3/ M.Voelskow,…,W.Skorupa et al.: “Formation of dendritic crystal structures in thin silicon films on silicon dioxide by carbon ion implantation and high intensity large area flash lamp irradiation”, J. Cryst. Growth, 388, 70 (2014)
/4/ V.Heera,…,W.Skorupa et al.: “Depth-resolved transport measurements and atom-probe tomography of heterogeneous, superconducting Ge:Ga films”, Supercond.Sc.&Technol. 27, 055025 (2014).
/5/ S.Prucnal,…,W.Skorupa et al.: “Millisecond annealing for advanced doping of dirty-silicon solar cells”, J. Appl. Phys. 111, 123104 (2012).
/6/ F.L. Bregolin,…,W.Skorupa et al.:“Hydrogen engineering via plasma immersion ion implantation and flash lamp annealing in silicon-based solar cell substrates”, J. Appl. Phys. 115, 064505 (2014).
/7/ H.B. Normann,…,W.Skorupa et al.: “Phosphorus in-diffusion from a surface source by millisecond flash lamp annealing for shallow emitter solar cells”, Appl.Phys.Lett. 102, 132108 (2014).

Keywords: flash lamp annealing, subsecond thermal processing, ion implantation, semiconductors, doping, nanowires
  • Invited lecture (Conferences)
    28th International Conference on Defects in Semiconductors (ICDS 2015), 27.-31.07.2015, Aalto, Finland
Registration No. 22484

Nanotechnologie für die Korrosionsunterdrückung an Metall-Legierungen
Skorupa, W.
Abstract: Im Rahmen eines vom Freistaat Sachsen über die Sächsische Aufbaubank geförderten Projektes haben wir uns mit der Anwendung der Nanotechnologie für den Korrosionsschutz von Blei-Zinn-Legierungen und Messing (Cu-Zn-Legierung) beschäftigt. Es wurde Dünnschichtabscheidung mittels gepulstem Laser bzw. Magnetronsputtern in Kombination zur Plasmaimmersions-Implantation verwendet. Es werden Ergebnisse von Laborstudien und Feldexperimenten in Kirchen für die beiden o.g. Legierungen berichtet, die effiziente Korrosionshemmung mit Dünnschichten im Dickenbereich <50 nm demonstrieren.
Keywords: Corrosion, plasma immersion ion implantation, lead-tin alloy, copper-zinc-alloy, nanotechnology
  • Lecture (Conference)
    37. Treffen der Nutzergruppe Heißprozesse und RTP, 25.03.2015, Erlangen, Germany
Registration No. 22483

Plasmaimmersions-Implantation gegen Korrosion an Metall-Legierungen
Skorupa, W.
Abstract: Im Rahmen eines vom Freistaat Sachsen über die Sächsische Aufbaubank geförderten Projektes haben wir uns mit der Anwendung der Nanotechnologie für den Korrosionsschutz von Blei-Zinn-Legierungen und Messing (Cu-Zn-Legierung) beschäftigt. Es wurde Dünnschichtabscheidung mittels gepulstem Laser bzw. Magnetronsputtern in Kombination zur Plasmaimmersions-Implantation verwendet. Es werden Ergebnisse von Laborstudien und Feldexperimenten in Kirchen für die beiden o.g. Legierungen berichtet, die effiziente Korrosionshemmung mit Dünnschichten im Dickenbereich <50 nm demonstrieren.
Keywords: Corrosion, plasma immersion ion implantation, lead-tin alloy, copper-zinc-alloy
  • Lecture (Conference)
    53. Treffen der Nutzergruppe Ionenimplantation, 26.03.2015, Erlangen, Germany
Registration No. 22482

Adapting Scott and Bruce's General Decision-Making Style Inventory to Patient Decision Making in Provider Choice.
Fischer, S.; Soyez, K.; Gurtner, S.
Abstract: OBJECTIVE:

Research testing the concept of decision-making styles in specific contexts such as health care-related choices is missing. Therefore, we examine the contextuality of Scott and Bruce's (1995) General Decision-Making Style Inventory with respect to patient choice situations.

Scott and Bruce's scale was adapted for use as a patient decision-making style inventory. In total, 388 German patients who underwent elective joint surgery responded to a questionnaire about their provider choice. Confirmatory factor analyses within 2 independent samples assessed factorial structure, reliability, and validity of the scale.

The final 4-dimensional, 13-item patient decision-making style inventory showed satisfactory psychometric properties. Data analyses supported reliability and construct validity. Besides the intuitive, dependent, and avoidant style, a new subdimension, called "comparative" decision-making style, emerged that originated from the rational dimension of the general model.

This research provides evidence for the contextuality of decision-making style to specific choice situations. Using a limited set of indicators, this report proposes the patient decision-making style inventory as valid and feasible tool to assess patients' decision propensities.

Keywords: decision-making style; patient choice; scale development and adaption Registration No. 22481

Nanotechnologie mittels Dünnschichtabscheidung und Plasmaimmersions-Implantation für die Korrosionsunterdrückung an Metall-Orgelpfeifen
Skorupa, W.; Pelic, B.; Eule, A.-C.; Werner, H.
Abstract: Die klassische Orgel ist die wahrscheinlich komplexeste Errungenschaft des Abendlandes, da ihre Herstellung und Nutzung neben handwerklich-produktionstechnischen und wissenschaftlichen auch künstlerisch-ästhetische und religiöse Komponenten aufweist. Trotzdem unterliegt auch sie dem allbekannten Verfallsmechanismus der menschlichen Schöpfungen, in diesem Fall infolge Korrosion, die sich vor allem bei den metallischen Werkstoffen bemerkbar macht. Dies sind hauptsächlich Blei-Zinn-Legierungen und Messing (Cu-Zn-Legierung). Während die Bleikorrosion infolge von organischen Säuredämpfen (Essigsäure, Ameisensäure) schon Jahrhunderte bekannt ist, wurde die Korrosion von Messing im Orgelbau eher marginal berichtet. Eine der wesentlichen Ursachen für die Säuredämpfe liegt in der Verwendung von Holzkonstruktionen im Orgelbau, wobei vor allem Eichenholz aufgrund seines Essigsäuregehaltes kritisch ist.
Im Rahmen eines vom Freistaat Sachsen über die Sächsische Aufbaubank geförderten Projektes haben wir uns, nach unserem Wissen weltweit erstmals, mit der Anwendung der Nanotechnologie für den Korrosionsschutz der genannten metallischen Materialien beschäftigt. Es wurde Dünnschichtabscheidung mittels gepulstem Laser bzw. Magnetronsputtern in Kombination zur Plasmaimmersions-Implantation verwendet. Problematisch ist dabei auch, dass beide Legierungen wenig vakuumverträglich sind. Es werden Ergebnisse von Laborstudien und Feldexperimenten in Kirchen für die beiden o.g. Legierungen berichtet, die effiziente Korrosionshemmung mit Dünnschichten im Dickenbereich <50 nm demonstrieren.

Keywords: corrosion, plasma immersion ion implantation, lead-tin alloy, brass, Cu-Zn alloy
  • Lecture (Conference)
    Workshop "Oberflächentechnologie mit Plasma- und Ionenstrahlprozessen", 10.-12.03.2015, Mühlleithen, Vogtland, Sachsen, Germany
Registration No. 22480

Subsecond thermal processing for nanomaterials and beyond
Skorupa, W.
Abstract: This talk reviews the advances that subsecond thermal processing in the millisecond range using xenon-filled flash lamps (FLA) brings to the processing of advanced semiconductor materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications via doping and/or defect engineering. A recent state-of-the-art is published in Ref./1/.
An important issue of our present work is the liquid phase processing in the millisecond range at the surface of solid substrates. A recent example is the controlled formation of III-V nanocrystals (InAs, GaAs) in silicon nanowires after ion beam synthesis /2/, see the contribution of S.Prucnal at this workshop. Further, we prepared coarse grained dendritic crystal structures in thin silicon films on silicon dioxide to show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process /3/. We could demonstrate that germanium and silicon exhibit superconductivity at ambient pressure and temperatures in the range of 1-2 K by avoiding Ga clusters after ion implantation and FLA /4/. Regarding photovoltaic applications, we dealt with the ion beam doping and thermal processing of PV silicon demonstrating a distinct improvement of the minority carrier diffusion length compared to rapid thermal processing and furnace treatments /5/. Moreover, we engineered the hydrogen content in photovoltaic silicon in correlation to the phosphorus doping using plasma immersion ion implantation and FLA /6/. Also, we demonstrated FLA driven phosphorus in-diffusion from a surface source /7/.

/1/ W. Skorupa and H. Schmidt: “Subsecond annealing of advanced materials”, Springer Series in Materials Science 192 (2014), ISBN 978-3-319-03131-6.
/2/ S.Prucnal,…,W.Skorupa et al.: “III–V semiconductor nanocrystal formation in silicon nanowires via liquid-phase epitaxy”, Nano Research 7, 1769 (2014); (see also Nano Lett. 11, 2814 (2011)).
/3/ M.Voelskow,…,W.Skorupa et al.: “Formation of dendritic crystal structures in thin silicon films on silicon dioxide by carbon ion implantation and high intensity large area flash lamp irradiation”, J. Cryst. Growth, 388, 70 (2014)
/4/ V.Heera,…,W.Skorupa et al.: “Depth-resolved transport measurements and atom-probe tomography of heterogeneous, superconducting Ge:Ga films”, Supercond.Sc.&Technol. 27, 055025 (2014).
/5/ S.Prucnal,…,W.Skorupa et al.: “Millisecond annealing for advanced doping of dirty-silicon solar cells”, J. Appl. Phys. 111, 123104 (2012).
/6/ F.L. Bregolin,…,W.Skorupa et al.:“Hydrogen engineering via plasma immersion ion implantation and flash lamp annealing in silicon-based solar cell substrates”, J. Appl. Phys. 115, 064505 (2014).
/7/ H.B. Normann,…,W.Skorupa et al.: “Phosphorus in-diffusion from a surface source by millisecond flash lamp annealing for shallow emitter solar cells”, Appl.Phys.Lett. 102, 132108 (2014).

Keywords: flash lamp annealing, thermal processing, ion implantation, semiconductors,
  • Invited lecture (Conferences)
    NATO Advanced Research Workshop: "Functional Nanomaterials and Devices for Electronics, Sensors, Energy Harvesting", 13.-16.04.2015, Lviv, Ukraine
Registration No. 22479

Comparative study of defect evolution in carbon implanted strained SiGe and SiSn layers
Gaiduk, Peter I.; Hansen, J. L.; Larsen, A. N.; Skorupa, W.
Abstract: By combining secondary ion-mass spectrometry, transmission-electron microscopy (TEM) and Rutherford-backscattering spectrometry we show that the redistribution of implanted carbon atoms around epitaxially strained Si/SiGe layers results in their accumulation on the Si side and depletion on the SiGe side. On the contrary, uphill diffusion of carbon into SiSn layers takes place in the case of Si/SiSn structures. The TEM study demonstrates formation of dislocation loops, stacking faults and interstitial clusters in the Si/SiGe layers, but elimination of interstitial dislocation loops and suppression of tin precipitates in the Si/SiSn layers. We deduced different evolution of dislocation loops and a precipitate is due to dopant-defect complexes. The complex formation is enhanced by separation of implanted point defects in strain-fields of Si/SiSn and Si/SiGe layers.
Keywords: epitaxially strained Si/SiGe layers, carbon, diffusion, ion implantation Registration No. 22478

Prognostic Value of Pretherapeutic Tumor-to-Blood Standardized Uptake Ratio in Patients with Esophageal Carcinoma.
Bütof, R.; Hofheinz, F.; Zöphel, K.; Stadelmann, T.; Schmollack, J.; Jentsch, C.; Löck, S.; Kotzerke, J.; Baumann, M.; van den Hoff, J.
Abstract: Despite ongoing efforts to develop new treatment options, the prognosis for patients with inoperable esophageal carcinoma is still poor and the reliability of individual therapy outcome prediction based on clinical parameters is not convincing. The aim of this work was to investigate whether PET can provide independent prognostic information in such a patient group and whether the tumor-to-blood standardized uptake ratio (SUR) can improve the prognostic value of tracer uptake values.

(18)F-FDG PET/CT was performed in 130 consecutive patients (mean age ± SD, 63 ± 11 y; 113 men, 17 women) with newly diagnosed esophageal cancer before definitive radiochemotherapy. In the PET images, the metabolically active tumor volume (MTV) of the primary tumor was delineated with an adaptive threshold method. The blood standardized uptake value (SUV) was determined by manually delineating the aorta in the low-dose CT. SUR values were computed as the ratio of tumor SUV and blood SUV. Uptake values were scan-time-corrected to 60 min after injection. Univariate Cox regression and Kaplan-Meier analysis with respect to overall survival (OS), distant metastases-free survival (DM), and locoregional tumor control (LRC) was performed. Additionally, a multivariate Cox regression including clinically relevant parameters was performed.

In multivariate Cox regression with respect to OS, including T stage, N stage, and smoking state, MTV- and SUR-based parameters were significant prognostic factors for OS with similar effect size. Multivariate analysis with respect to DM revealed smoking state, MTV, and all SUR-based parameters as significant prognostic factors. The highest hazard ratios (HRs) were found for scan-time-corrected maximum SUR (HR = 3.9) and mean SUR (HR = 4.4). None of the PET parameters was associated with LRC. Univariate Cox regression with respect to LRC revealed a significant effect only for N stage greater than 0 (P = 0.048).

PET provides independent prognostic information for OS and DM but not for LRC in patients with locally advanced esophageal carcinoma treated with definitive radiochemotherapy in addition to clinical parameters. Among the investigated uptake-based parameters, only SUR was an independent prognostic factor for OS and DM. These results suggest that the prognostic value of tracer uptake can be improved when characterized by SUR instead of SUV. Further investigations are required to confirm these preliminary results.

Keywords: PET; SUR; SUV; definitive radiochemotherapy; esophageal cancer Registration No. 22475

Ion beam technology
Fassbender, J.
Abstract: Overview over ion beam technology at HZDR
  • Invited lecture (Conferences)
    High resolution diagnostics and ion beam technology, 01.-02.10.2015, Bratislava, Slovakei
Registration No. 22474

High-field magnetic behavior and forced-ferromagnetic state in an ErFe11TiH single crystal
Kostyuchenko, N. V.; Zvezdin, A. K.; Tereshina, E. A.; Skourski, Y.; Doerr, M.; Drulis, H.; Pelevin, I. A.; Tereshina, I. S.
Abstract: The crystal-field and exchange parameters are determined for the single-crystalline hydride ErFe11TiH compound by analyzing the experimental magnetization curves obtained in magnetic fields of up to 60 T. By using the calculated parameters we succeeded in modeling theoretical magnetization curves for ErFe11TiH up to 200 Т and to study in detail the transition from ferrimagnetic to a ferromagnetic state in the appliedmagnetic field. Registration No. 22473

RF performance results of the 2nd ELBE SRF gun
Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.
Abstract: An improved SRF gun (ELBE SRF gun II) has been installed and commissioned at HZDR. This new gun replaced the first SRF gun of the ELBE accelerator which had been in operation since 2007. The new gun has an improved 3.5-cell niobium cavity those SRF performances have been studied first with a copper cathode. After the replacement by our standard Cs2Tecathode we observed a tremendous degradation of the cavity gradient paired with an increase of field emission. In this contribution we will report on our in-situ investigations to find the origin and the reason for the particle contamination that happened during the first cathode transfer.
Keywords: SRF gun, photo electron source, injector, ELBE, superconducting RF
  • Poster
    7th International Conference on RF Superconductivity, SRF 2015, 13.-18.09.2015, Whistler, British Columbia, Canada
Registration No. 22470

Impact of waiting time after surgery and overall time of postoperative radiochemotherapy on treatment outcome in glioblastoma multiforme.
Seidlitz, A.; Siepmann, T.; Löck, S.; Juratli, T.; Baumann, M.; Krause, M.

A time factor of radiooncological treatment has been demonstrated for several tumours, most prominently for head and neck squamous cell carcinoma and lung cancer. In glioblastoma multiforme studies of the impact of postoperative waiting times before initiation of radio- or radiochemotherapy were inconclusive. Moreover analysis of the impact of overall treatment time of radiochemotherapy as well as overall duration of local treatment from surgery to the end of radiochemotherapy is lacking to date.

In this retrospective cohort study, we included 369 consecutive patients treated at our institution between 2001 and 2014. Inclusion criteria were histologically proven glioblastoma multiforme, age ≥ 18 years, ECOG performance status 0-2 before radiotherapy, radiotherapy or radiochemotherapy with 33 × 1.8 Gy to 59.4 Gy or with 30 × 2.0 Gy to 60 Gy. The impact of postoperative waiting time, radiation treatment time and overall duration of local treatment from surgery to the end of radiotherapy on overall (OS) and progression-free (PFS) survival were evaluated under consideration of known prognostic factors by univariate Log-rank tests and multivariate Cox-regression analysis.

The majority of patients had received simultaneous and further adjuvant chemotherapy, mainly with temozolomide. Median survival time and 2-year OS were 18.0 months and 38.9% after radiochemotherapy compared to 12.7 months and 12.6% after radiotherapy alone. Median progression-free survival time was 7.5 months and PFS at 2 years was 14.3% compared to 6.0 months and 3.3%, respectively. Significant prognostic factors in multivariate analysis were age, resection status and application of simultaneous chemotherapy. No effect of the interval between surgery and adjuvant radiotherapy (median 27, range 11-112 days), radiation treatment time (median 45, range 40-71 days) and of overall time from surgery until the end of radiotherapy (median 54, range 71-154 days) on overall and progression-free survival was evident.

Our data do not indicate a relevant time factor in the treatment of glioblastoma multiforme in a large contemporary single-centre cohort. Although this study was limited by its retrospective nature, its results indicate that short delays of postoperative radiochemotherapy, e.g. for screening of a patient for a clinical trial, may be uncritical.
Registration No. 22467

Multiphoton-induced luminescence and its domain contrast in Mg-doped LiNbO3 and LiTaO3
Reichenbach, P.; Kämpfe, T.; Haußmann, A.; Steudtner, R.; Woike, T.; Eng, L. M.
Abstract: We investigate the luminescence in a wide bandgap oxide, Mg-doped LiNbO3 and LiTaO3 , with both spectral and temporal resolution, enhancing the insight into the relaxation properties relevant in these materials.
  • Lecture (Conference)
    DPG Frühjahrstagung, 15.-20.03.2015, Berlin, Deutschland
Registration No. 22465

Superparamagnetic behavior of Fe doped InAs prepared by ion implantation and pulsed laser annealing
Yuan, Ye; Sawicki, M.; Cai, H.; Helm, M.; Zhou, S.
Abstract: Dilute magnetic semiconductors (DMSs) attracted great interests in the last several decades because of their potential for spintronic device [1]. III-V compounds especially GaAs based DMS has recently emerged as the most popular material for this new technology. However, that the low mobility of holes in p-type DMS limits the potential application in semiconductor spintronic devices. Therefore, the searching for n-type DMS is of interest.

The doping of Fe in InAs is attracting research attentions due to the possibility to fabricate n-type diluted magnetic semiconductors [2, 3]. However, the low solubility of Fe in InAs is the most difficulty to achieve InFeAs DMS. In this work, we obtain Fe doped InAs layers by ion implantation and pulsed laser annealing. This approach has shown success for preparing other III-V based DMSs [4, 5]. The formed InFeAs layers are proved to be epitaxial-like on InAs substrates. The prepared InFeAs layers reveal similar magnetic properties independent of their conductivity types. While the samples are lacking of charactersistics of DMS, they appear to be superparamagnetic behavior, revealing such as time-dependent magnetiszation measurements reveal aging and memory effects.

1. T. Dietl et al., Science 287, 1019-1022 (2000)
2. M. Kobayashi et al., Appl. Phys. Lett., 105, 032403(2014)
3. P. Nam Hai et al., Appl. Phys. Lett., 101, 182403 (2012)
4. D. Bürger et al., Phys. Rev. B, 81, 115202 (2010)
5. M. Khalid et al., Phys. Rev. B, 89, 121301(R) (2014)
  • Lecture (Conference)
    EMRS 2015 Fall meeting, 15.-18.09.2015, Warsaw, Poland
Registration No. 22464

Thermal annealing behavior of α-Al2O3 scintillation screens
Lederer, S.; Akhmadaliev, S.; Forck, P.; Gütlich, E.; Lieberwirth, A.; Ensinger, W.
Abstract: Polycrystalline alumina samples (α-Al2O3, purity: 99.8%) were irradiated by 63Cu heavy ions (E = 0.5 MeV/u) at various fluences. After irradiation, absorption measurements were performed within the wavelength range from 200 to 1000 nm to evaluate color center evolution. Thermal annealing behavior of the created defects was investigated with respect to annealing temperature and duration. Complex color center formation processes depending on particle fluence and temperature could be observed. Calculated activation energies necessary for F- and F+-center migration are ∼0.3 eV for temperatures ranging from RT to ∼673 K.
Keywords: Alumina; Heavy-ion irradiation; Color center; Thermal annealing; Scintillation screens Registration No. 22460

Exceptional points, spectral singularities, vector field singularities and discriminant varieties
Günther, U.
Abstract: Many physically realistic problems can be described in terms of parameter-dependent eigenvalue problems of some non-Hermitian operators, as scattering problems or as dynamical flow problems. A common feature of such problems is the existence of degenerate configurations which can be associated to dynamical bifurcation behavior, spectral branch points or special types of singularities in the scattering matrix. Mathematically, such problems are related to non-diagonalizable spectral operator decompositions (the existence of non-trivial Jordan blocks), multiple eigenvalues and the coalescence of singularities in vector flow fields. In parameter spaces these configurations show up as so called discriminant varieties well known from algebraic geometry and singularity theory. In the talk, the structural interrelation of these effects is demonstrated and illustrated on concrete problems from PT quantum mechanics, optical lasing systems and the Bloch-sphere representation of simple time-dependent quantum mechanical problems.
Keywords: non-Hermitian operators, degenerate configurations, dynamical bifurcation behavior, spectral branch points, spectral singularities, Jordan blocks, multiple eigenvalues, singularity coalescence, discriminant varieties
  • Invited lecture (Conferences)
    Mathematics in Technical and Natural Sciences, 18.-24.09.2015, Koscielisko, Poland
Registration No. 22456

Hamiltonian and dissipative second-order polynomial flows on spheres S^2
Günther, U.; Graefe, E.-M.; Korsch, H.-J.
Abstract: The dynamics of nondissipative and dissipative autonomous Bose-Hubbard dimers is considered in second-order polynomial approximation as flow dynamics on the Bloch sphere. Special emphasis is laid on the stationary-point and singularity structure of the flows, related underlying algebraic stability features encoded in 10th-order homogeneous polynomials describing algebraic discriminant varieties over 3-dimensional projective parameter spaces. Reduced resolvent techniques, hidden Jordan block structures and relations to singularity theory provide further insights into the dynamics and possibly existing limit cycles.
Keywords: Bose-Hubbard model, dimer, autonomous dynamical system, Bloch Sphere, stationary points, discriminant varieties, reduced resolvent, Jordan blocks, limit cycles
  • Invited lecture (Conferences)
    Quantum (and Classical) Physics with Non-Hermitian Operators (PHHQP13), 12.-16.07.2015, Jerusalem, Israel
Registration No. 22455

Application of ion beams to fabricate and tune ferromagnetic semiconductors
Zhou, S.
Abstract: Combining semiconducting and ferromagnetic properties, ferromagnetic semiconductors have been under intensive investigation for more than two decades. Mn doped III-V compound semiconductors have been regarded as the prototype of ferromagnetic semiconductors from both experimental and theoretic investigations. The magnetic properties of III-V:Mn can be controlled by manipulating free carriers via electrical gating, as for controlling the electrical properties in conventional semiconductors. However, the preparation of ferromagnetic semiconductors presents a big challenge due to the low solubility of Mn in semiconductors. Ion implantation has been developed as a standard method for doping Si in microelectronic industry. In this talk, I will show how ion beams can be used in fabricating and understanding ferromagnetic semiconductors. First, ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LTMBE) approach [1-6]. Both ion implantation and pulsed-laser melting occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants and the subsequent laser pulse deposit energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III-V:Mn. Both GaMnP and InMnP films show the signature of ferromagnetic semiconductors and an insulating behavior. Second, we use helium ion to precisely compensate hole in ferromagnetic semiconductors while keeping the Mn concentration constant [7-9]. By this approach, one can tune the magnetic properties of ferromagnetic semiconductor as well as pattern a lateral structure. It also provides a route to understand how carrier-mediated ferromagnetism is influenced by localization.

[1] M. Scarpula, et al. Phys. Rev. Lett. 95, 207204 (2005).
[2] D. Bürger, S. Zhou, et al., Phys. Rev. B 81, 115202 (2010).
[3] S. Zhou, et al., Appl. Phys. Express 5, 093007 (2012).
[4] M. Khalid et al., Phys. Rev. B 89, 121301(R) (2014).
[5] Y. Yuan, et al, IEEE Trans. Magn. 50, 2401304 (2014).
[6] Y. Yuan, et al. J. Phys. D: Appl. Phys. in press (2015).
[7] Lin Li, et al., J. Phys. D: Appl. Phys. 44 099501 (2011).
[8] Lin Li, et al., Nucl. Instr. Meth. B, 269, 2469-2473 (2011).
[9] S. Zhou, et al. Phys. Rev. B, in revision (2015).

Keywords: Ferromagnetic semiconductors, Ion implantation
  • Invited lecture (Conferences)
    The 2015 E-MRS Fall Meeting, 14.-18.09.2015, Warsaw, Poland
Registration No. 22453

Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium-americium mixed oxides
Prieur, D.; Lebreton, F.; Martin, P. M.; Caisso, M.; Butzbach, R.; Somers, J.; Delahaye, T.
Abstract: Uranium-americium mixed oxides are potential compounds to reduce americium inventory in nuclear waste via a partitioning and transmutation strategy. A thorough assessment of the oxygen-to-metal ratio is paramount in such materials as it determines the important underlying electronic structure and phase relations, affecting both thermal conductivity of the material and its interaction with the cladding and coolant. In 2011, various XAS experiments on U1(-x)Am(x)O(2 +/-delta) a samples prepared by different synthesis methods have reported contradictory results on the charge distribution of U and Am. This work alleviates this discrepancy. The XAS results confirm that, independently of the synthesis process, the reductive sintering of U1-xAmxO2 +/-delta leads to the formation of similar fluorite solid solution indicating the presence of Am+III and U+V in equimolar proportions.
Keywords: EXFAS Uranium Americium nuclear fuel transmutation Registration No. 22451

Quasi-two-dimensional Fermi surfaces of the heavy-fermion superconductor Ce2PdIn8
Götze, K.; Klotz, J.; Gnida, D.; Harima, H.; Aoki, D.; Demuer, A.; Elgazzar, S.; Wosnitza, J.; Kaczorowski, D.; Sheikin, I.
Abstract: We report low-temperature de Haas–van Alphen (dHvA) effect measurements in magnetic fields up to 35 T of the heavy-fermion superconductor Ce2PdIn8. The comparison of the experimental results with band-structure calculations implies that the 4f electrons are itinerant rather than localized. The cyclotron masses estimated at high field are only moderately enhanced, 8m0 and 14m0, but are substantially larger than the corresponding band masses. The observed angular dependence of the dHvA frequencies suggests quasi-two-dimensional Fermi surfaces in agreement with band-structure calculations. However, the deviation from ideal two-dimensionality is larger than in CeCoIn5, to which Ce2PdIn8 bears a lot of similarities. This subtle distinction accounts for the different superconducting critical temperatures of the two compounds. Registration No. 22449

Tumor volume determination: Demands of radiotherapy on modern radiological imaging
Buetof, R.; Krause, M.
Abstract: Background: The aim of radiotherapy as a local treatment method is the eradication of all vital tumor cells in order to achieve permanent local tumor control. From a clinical point of view this means that a patient suffering from cancer can only be cured if all cancer stem cells as a specific subpopulation within a tumor are eliminated by the treatment. Results: New radiation techniques often employ lower normal tissue doses with less toxicity and/or the possibility to apply higher radiation doses to the target volume. High-resolution imaging is hereby mandatory for precise tumor volume definition as a basis of local tumor control. New developments in the field of bioimaging lead to further perspectives in radiotherapy. Conclusion: By combining anatomical information with biological characteristics of the tumor, additional benefits for treatment planning and outcome can be achieved. Thus, the use of these modern imaging methods to define irradiation target volumes more clearly forms the basis for the application of modern radiation techniques.
Keywords: Bioimaging; Cancer stem cells; Local tumor control; Radiation oncology; Tumor volume Registration No. 22446

Identification of Patient Benefit From Proton Therapy for Advanced Head and Neck Cancer Patients Based on Individual and Subgroup Normal Tissue Complication Probability Analysis.
Jakobi, A.; Bandurska-Luque, A.; Stützer, K.; Haase, R.; Löck, S.; Wack, L. J.; Mönnich, D.; Thorwarth, D.; Perez, D.; Lühr, A.; Zips, D.; Krause, M.; Baumann, M.; Perrin, R.; Richter, C.
Abstract: PURPOSE:

The purpose of this study was to determine, by treatment plan comparison along with normal tissue complication probability (NTCP) modeling, whether a subpopulation of patients with head and neck squamous cell carcinoma (HNSCC) could be identified that would gain substantial benefit from proton therapy in terms of NTCP.

For 45 HNSCC patients, intensity modulated radiation therapy (IMRT) was compared to intensity modulated proton therapy (IMPT). Physical dose distributions were evaluated as well as the resulting NTCP values, using modern models for acute mucositis, xerostomia, aspiration, dysphagia, laryngeal edema, and trismus. Patient subgroups were defined based on primary tumor location.

Generally, IMPT reduced the NTCP values while keeping similar target coverage for all patients. Subgroup analyses revealed a higher individual reduction of swallowing-related side effects by IMPT for patients with tumors in the upper head and neck area, whereas the risk reduction of acute mucositis was more pronounced in patients with tumors in the larynx region. More patients with tumors in the upper head and neck area had a reduction in NTCP of more than 10%.

Subgrouping can help to identify patients who may benefit more than others from the use of IMPT and, thus, can be a useful tool for a preselection of patients in the clinic where there are limited PT resources. Because the individual benefit differs within a subgroup, the relative merits should additionally be evaluated by individual treatment plan comparisons.
Registration No. 22444

Regional radiotherapy in high-risk breast cancer: is the issue solved?
Krause, M.; Petersen, C.; Offersen, B. V.; Baumann, M.
Abstract: Adjuvant radiotherapy is the treatment standard for breast cancer with lymph node metastases after breast-conserving surgery or mastectomy. The inclusion of regional lymph nodes into the treatment volumes has been a question in recent clinical trials. Their impact on treatment standards and open questions is discussed. Registration No. 22443

ThermAc: A Joint Project on Aquatic Actinide Chemistry and Thermodynamics at Elevated Temperature Conditions
Altmaier, M.; Gaona, X.; Endrizzi, F.; Brendler, V.; Steudtner, R.; Franzen, C.; Tsushima, S.; Panak, P. J.; Skerencak-Frech, A.; Hagemann, S.; Brandt, F.; Krüger, S.; Colàs, E.; Grivé, M.; Thoenen, T.; Kulik, D. A.
Abstract: The ThermAc project aims at extending the chemical understanding and available thermodynamic database for actinides, long-lived fission products and relevant matrix elements in aquatic systems at elevated temperatures.
  • Poster
    Migration 2015, 13.-18.09.2015, Santa Fe, NM, USA
Registration No. 22440

Evaluation of in vivo quantification accuracy of the Ingenuity-TF PET/MR
Maus, J.; Schramm, G.; Hofheinz, F.; Oehme, L.; Lougovski, A.; Petr, J.; Platzek, I.; Beuthien-Baumann, B.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.
Abstract: Purpose: The quantitative accuracy of standardized uptake values (SUVs) and tracer kinetic uptake parameters in patient investigations strongly depends on accurate determination of regional activity concentrations in positron emission tomography (PET) data. This determination rests on the assumption that the given scanner calibration is valid in vivo. In a previous study, we introduced a method to test this assumption. This method allows to identify discrepancies in quantitative accuracy in vivo by comparison of activity concentrations of urine samples measured in a well-counter with activity concentrations extracted from PET images of the bladder. In the present study, we have applied this method to the Philips Ingenuity-TF PET/MR since at the present stage, absolute quantitative accuracy of combined PET/MR systems is still under investigation.
Methods: Twenty one clinical whole-body F18-FDG scans were included in this study. The bladder region was imaged as the last bed position and urine samples were collected afterward. PET images were reconstructed including MR-based attenuation correction with and without truncation compensation and 3D regions-of-interest (ROIs) of the bladder were delineated by three observers. To exclude partial volume effects, ROIs were concentrically shrunk by 8–10 mm. Then, activity concentrations were determined in the PET images for the bladder and for the urine by measuring the samples in a calibrated well-counter. In addition, linearity measurements of SUV vs singles rate and
measurements of the stability of the coincidence rate of “true” events of the PET/MR system were performed over a period of 4 months.
Results: The measured in vivo activity concentrations were significantly lower in PET/MR than in the well-counter with a ratio of the former to the latter of 0.756±0.060 (mean ± std. dev.), a range of 0.604–0.858, and a P value of 3.9·10−14. While the stability measurements of the coincidence rate of “true” events showed no relevant deviation over time, the linearity scans revealed a systematic error of 8%–11% (avg. 9%) for the range of singles rates present in the bladder scans. After correcting for this systematic bias caused by shortcomings of the manufacturers calibration procedure, the PET to well-counter ratio increased to 0.832±0.064 (0.668–0.941), P = 1.1·10−10. After compensating for truncation of the upper extremities in the MR-based attenuation maps, the ratio further improved to 0.871±0.069 (0.693–0.992), P = 3.9·10−8.
Conclusions: Our results show that the Philips PET/MR underestimates activity concentrations in the bladder by 17%, which is 7 percentage points (pp.) larger than in the previously investigated PET and PET/CT systems. We attribute this increased underestimation to remaining limitations of the MRbased attenuation correction. Our results suggest that only a 2 pp. larger underestimation of activity concentrations compared to PET/CT can be observed if compensation of attenuation truncation of the upper extremities is applied. Thus, quantification accuracy of the Philips Ingenuity-TF PET/MR can be considered acceptable for clinical purposes given the ±10% error margin in the EANM guidelines. The comparison of PET images from the bladder region with urine samples has proven a useful method. It might be interesting for evaluation and comparison of the in vivo quantitative accuracy of
PET, PET/CT, and especially PET/MR systems from different manufacturers or in multicenter trials.

Keywords: PET/MR, quantitative evaluation, in vivo, quantification accuracy, truncation compensation Registration No. 22419

Correlation between Fermi surface transformations and superconductivity in the electron-doped high-Tc superconductor Nd2−xCexCuO4
Helm, T.; Kartsovnik, M. V.; Proust, C.; Vignolle, B.; Putzke, C.; Kampert, E.; Sheikin, I.; Choi, E.-S.; Brooks, J. S.; Bittner, N.; Biberacher, W.; Erb, A.; Wosnitza, J.; Gross, R.
Abstract: Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd2−xCexCuO4 by exploring the Fermi surface properties of high-quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level xc = 0.175 corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping xopt = 0.145 where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus the superconducting dome appears to be pinned by two critical points to the normal state phase diagram. Registration No. 22418

Precise nuclear reaction data for solar fusion ...and the Felsenkeller laboratory in Dresden
Bemmerer, D.
Abstract: Precise data for the solar neutrino fluxes from the decays of beryllium-7 (5% error) and boron-8 (3% error) have opened a new era for the study of solar fusion. In a stunning reversal, solar neutrino fluxes now have lower uncertainties than solar model inputs. Thus, the logical next step is to bring the relevant laboratory nuclear data to a level of precision matching the neutrino data. The relevant energies are far below the repulsive Coulomb barrier of the interacting nuclei for the case of solar fusion reaction. This leads to very low nuclear reaction cross sections, so that relevant data can only be taken in a low-background environment underground, shielded from cosmic ray background. The talk will review recent progress in the field of solar fusion reactions and give an outlook on future work at the upcoming Felsenkeller underground accelerator lab in Dresden, Germany. At Felsenkeller, in spring 2016 a high-current 5 MV accelerator will be placed in an underground laboratory, where the cosmic ray muon flux is suppressed by a factor of 40. This new laboratory will enable uniquely sensitive experiments to study solar fusion and other astrophysically relevant nuclear reactions.
Keywords: Underground nuclear astrophysics solar fusion solar neutrinos Felsenkeller
  • Invited lecture (Conferences)
    Kolloquium KIS, 25.06.2015, Freiburg, Deutschland
Registration No. 22416

Progress of the Felsenkeller shallow-underground 5 MV accelerator for nuclear astrophysics
Bemmerer, D.; Zuber, K.
Abstract: In the case of astrophysically important reactions, cross section measurements at or near the Gamow energy require high-intensity accelerators, long running times of typically one year per experiment, and ultra low background [1]. The highly successful LUNA 0.4MV accelerator in Gran Sasso, Italy, has pioneered this field with data on several nuclear reactions of stellar hydrogen burning and of Big Bang nucleosynthesis. As a result, there is a call for one or more new underground accelerators with higher beam energy, able to address also helium and carbon burning and the neutron sources for the astrophysical s-process [2].
Such an accelerator is being installed at the Felsenkeller underground site in Dresden, Ger- many. It is shielded from cosmic radiation by 45 m of rock, reducing the muon flux by a factor of 40. An intercomparison exercise has shown that at Felsenkeller, the background in a typical nuclear astrophysics γ-ray detector is competitive to the deep-underground case in the crucial 6-8 MeV γ-ray energy range, if an additional muon veto is used.
A high-current 5MV Pelletron accelerator that was previously used in York, UK, has been bought for this purpose. It is being fitted with an internal ion source to provide intensive H+ and He+ beams in addition to the existing external sputter ion source. The site construction progress will be shown. The laboratory will be open to outside users, who are invited to form a user consortium.

Keywords: Nuclear Astrophysics Felsenkeller Underground physics Big Bang nucleosynthesis Solar fusion
  • Lecture (Conference)
    Nuclear Physics in Astrophysics VII, 18.-22.05.2015, York, United Kingdom
Registration No. 22415

Underground nuclear astrophysics at the Dresden Felsenkeller
Bemmerer, D.
Abstract: Favored by the low background underground, accelerator-based exper- iments are an important tool to study nuclear astrophysics reactions involving stable charged particles. This technique has been used with great success at the 0.4 MV LUNA accelerator in the Gran Sasso lab- oratory in Italy. However, the nuclear reactions of helium and car- bon burning and the neutron source reactions for the astrophysical s-process require higher beam energies, as well as the continuation of solar fusion studies. As a result, NuPECC strongly recommended the installation of one or more higher-energy underground accelerators. Such a project is underway in Dresden. A 5MV Pelletron accelerator is currently being refurbished by installing an ion source on the high voltage terminal, enabling intensive helium beams. The preparation of the underground site is funded, and the civil engineering project is being updated. The science case, operational strategy and project status will be reported.
Keywords: Felsenkeller Nuclear Astrophysics
  • Lecture (Conference)
    DPG-Frühjahrstagung, 24.03.2015, Heidelberg, Deutschland
Registration No. 22414

Underground nuclear astrophysics from the Big Bang to astrophysical novae
Bemmerer, D.
Abstract: New astronomical observations on the Sun and other astronomical objects require for their interpretation new, precise nuclear cross section data. However, in stable-beam experiments for nuclear astrophysics, in many cases the cross section is so low that the laboratory background in a detector forms an insurmountable obstacle to experiments at astrophysical energies. By placing the experimental setup in an underground laboratory, the cosmic ray induced background can be reduced so far that highly sensitive experiments are feasible. Data on Big Bang nucleosynthesis and a number of hydrogen burning reactions in the Sun, asymptotic-giant branch stars and astrophysical novae are reviewed here.
Keywords: Nuclear Astrophysics Big Bang Nova explosions LUNA Felsenkeller
  • Invited lecture (Conferences)
    International Workshop XLIII on Gross Properties of Nuclei and Nuclear Excitations „Nuclear Structure and Reactions: Weak, Strange and Exotic“, 13.01.2015, Hirschegg, Österreich
  • Invited lecture (Conferences)
    Seminar INFN Genova, 05.03.2015, Genova, Italia
Registration No. 22413

Work on the NeuLAND time of flight detector for 0.2-1.0 GeV neutrons at HZDR and TU Dresden
Bemmerer, D.
Abstract: A new setup for kinematically complete reaction experiments for beams of radioactive nuclei far from the valley of stability is under construction at FAIR Darmstadt, Germany. NeuLAND, a highly efficient (>90%) neutron time of flight detector made of fast plastic scintillators is included in the setup. In order to reach proper resolution in the reconstructed energy spectrum, a time resolution of sigma < 150 ps is required. Using the ELBE picosecond electron beam as a time reference, it is currently being studied whether semiconductor-based photosensors (SiPMs) can be used for the readout of the NeuLAND scintillator bars.
Keywords: Nuclear Astrophysics Time-of-flight detector FAIR Radioactive ion beam
  • Lecture (Conference)
    Kolloquium Institut für Kern- und Teilchenphysik, 29.01.2015, Dresden, Deutschland
Registration No. 22412

γ ray spectroscopy of 19C via single neutron knock-out reaction
Vajta, Zs.; Dombrádi, Zs.; Elekes, Z.; Aiba, T.; Aoi, N.; Baba, H.; Bemmerer, D.; Fülöp, Zs.; Iwasa, N.; Kobayashi, Á. Kiss T.; Kondo, Y.; Motobayashi, T.; Nakabayashi, T.; Nannichi, T.; Sakurai, H.; Sohler, D.; Takeuchi, S.; Tanaka, K.; Togano, Y.; Yamada, K.; Yamaguchi, M.; Yoneda, K.
Abstract: The one-neutron knock-out reaction H1(C20,C19γ) was studied at RIKEN using the DALI2 array. A γ-ray transition was observed at 198(10) keV. Based on the comparison between the experimental production cross section and theoretical predictions, the transition was assigned to the de-excitation of the 3/21+ state to the ground state.
Keywords: Nuclear Physics Radioactive ion beam Nuclear Structure Registration No. 22411

Resonance strengths in the 17,18O(p, α)14,15N reactions and background suppression underground
Bruno, C. G.; Scott, D. A.; Formicola, A.; Aliotta, M.; Davinson, T.; Anders, M.; Best, A.; Bemmerer, D.; Broggini, C.; Cavanna, A. Caciolli F.; Corvisiero, P.; Depalo, R.; Di Leva, A.; Elekes, Z.; Fülöp, Zs.; Gervino, G.; Griffin, C. J.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Imbriani, G.; Junker, M.; Menegazzo, R.; Napolitani, E.; Prati, P.; Somorjai, E.; Straniero, O.; Strieder, F.; Szücs, T.; Trezzi, D.
Abstract: We report on measurements of resonance strengths and energies for the Ep=151 and 193 keV resonances in the18O(p, α )15N and17O(p, α )14N reactions, respectively, obtained during commissioning of a new setup for alpha-particle detection studies at the LUNA underground laboratory. Our values, ωγ(151)=164.2±0.9stat+12.1−11.7syst meV and ωγ(193)=1.68±0.03stat±0.12syst meV, are in excellent agreement with those reported in the literature. New values of resonance energies are Ep=151.2±0.3 keV and Ep=194.8±0.3 keV, respectively, this latter with the highest precision to date. Comparative background measurements in silicon detectors overground and underground were also carried out, yielding up to a factor of 15 in background suppression at LUNA at energies around 200keV. This clearly demonstrates the usefulness of underground measurements in charged-particles experiments, especially at low detection energies.
Keywords: Nuclear Astrophysics Registration No. 22410

Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Tri-n-butyl phosphate
Gaillard, C.; Boltoeva, M.; Billard, I.; Georg, S.; Mazan, V.; Ouadi, A.; Ternova, D.; Hennig, C.
Abstract: We present new results on the liquid–liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri-n-butyl phosphate/1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (TBP/[C4mim][Tf2N]) phase. The individual solubilities of the ionic-liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio DU. In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO2(TBP)2]2+, by an exchange with one proton and one C4mim+. At high acid concentrations, the extraction proceeds through a cationic exchange between [UO2(NO3)(HNO3)(TBP)2]+ and one C4mim+. As a consequence of this mechanism, the variation of DU as a function of TBP concentration depends on the C4mim+ concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of DU versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic-liquid phase.
Keywords: ionic liquid uranium exafs Registration No. 22409

Single-crystal X-ray diffraction and resonant X-ray magnetic scattering at helium-3 temperatures in high magnetic fields at beamline P09 at PETRA III
Francoual, S.; Strempfer, J.; Warren, J.; Liu, Y.; Skaugen, A.; Poli, S.; Blume, J.; Wolff-Fabris, F.; Canfield, P. C.; Lograsso, T.
Abstract: The resonant scattering and diffraction beamline P09 at PETRA III at DESY is equipped with a 14 T vertical field split-pair magnet. A helium-3 refrigerator is available that can be fitted inside the magnet's variable-temperature insert. Here the results of a series of experiments aimed at determining the beam conditions permitting operations with the He-3 insert are presented. By measuring the tetragonal-to-orthorhombic phase transition occurring at 2.1 K in the Jahn-Teller compound TmVO4, it is found that the photon flux at P09 must be attenuated down to 1.5 x 109 photons s-1 for the sample to remain at temperatures below 800 mK. Despite such a reduction of the incident flux and the subsequent use of a Cu(111) analyzer, the resonant X-ray magnetic scattering signal at the Tm LIII absorption edge associated with the spin-density wave in TmNi2B2C below 1.5 K is intense enough to permit a complete study in magnetic field and at sub-Kelvin temperatures to be carried out. Registration No. 22404

Epitaxial Post-Implant Recrystallization in Germanium Nanowires
Kelly, R. A.; Liedke, B.; Baldauf, S.; Gangnaik, A.; Biswas, S.; Georgiev, Y.; Holmes, J. D.; Posselt, M.; Petkov, N.
Abstract: As transistor dimensions continue to diminish, techniques for fabrication need to be adapted. In particular, crystal recovery post ion implantation is required due to destructive ion bombardment inducing crystal damage including amorphization. Here, we report a study on the post-implant recrystallization in germanium (Ge) nanowires (NWs) following gallium (Ga) ion doping. In this work a variation of NW diameters and orientations were irradiated and annealed in situ to investigate the mechanism of recrystallization. An added complication of misorientation of crystal grains increases the complexity of crystal recovery for suspended NWs. We show that when the misorientation is prevented, by leaving a crystal link between two seeds and providing a rigid support, recrystallization occurs primarily via solid phase epitaxial growth (SPEG). Finally, we demonstrate that topdown fabricated Ge NWs on insulator can be recovered with no extended defects. This work highlights both experimentally and through molecular dynamic simulations the importance of engineering crystal recovery in Ge NWs which may have potential for next-generation complementary metal-oxide semiconductor (CMOS) devices.
Keywords: Ge nanowires, post-implant recrystallization Registration No. 22399

Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium
Radek, M.; Bracht, H.; Johnson, B. C.; McCallum, J. C.; Posselt, M.; Liedke, B.
Abstract: The atomic mixing of matrix atoms during solid-phase epitaxy (SPE) is studied by means of isotopically enriched germanium (Ge) multilayer structures that were amorphized by Ge ion implantation up to a depth of 1.5 micrometer. Recrystallization of the amorphous structure is performed at temperatures between 350 °C and 450 °C. Secondary-ion-mass-spectrometry is used to determine the concentration-depth profiles of the Ge isotope before and after SPE. An upper limit of 0.5 nm is deduced for the displacement length of the Ge matrix atoms by the SPE process. This small displacement length is consistent with theoretical models and atomistic simulations of SPE, indicating that the SPE mechanism consists of bond-switching with nearest-neighbours across the amorphous-crystalline (a/c) interface.
Keywords: solid-phase epitaxial recrystallization, Ge, atomic transport Registration No. 22398

Assisted dynamical Schwinger effect: pair production in a pulsed bifrequent field
Panferov, A. D.; Smolyansky, S. A.; Otto, A.; Kämpfer, B.; Blaschke, D.; Juchnowski, L.
Abstract: Electron-positron pair production by the superposition of two laser pulses with different frequencies and amplitudes is analyzed as a particular realization of the assisted dynamic Schwinger effect. It is demonstrated that, within a non-perturbative kinetic equation framework, an amplification effect is conceivable for certain parameters. When both pulses have wavelengths longer than the Compton wavelength, the residual net density of produced pairs is determined by the resultant field strength. The number of pairs starts to grow rapidly if the wavelength of the high-frequency laser component gets close to the Compton wavelength. Registration No. 22394

Spectral caustics in laser assisted Breit-Wheeler process
Nousch, T.; Seipt, D.; Kämpfer, B.; Titov, A. I.
Abstract: Electron-positron pair production by the Breit-Wheeler process embedded in a strong laser pulse is analyzed. The transverse momentum spectrum displays prominent peaks which are interpreted as caustics, the positions of which are accessible by the stationary phases. Examples are given for the superposition of an XFEL beam with an optical high-intensity laser beam. Such a configuration is available, e.g., at LCLS at present and at European XFEL in near future. It requires a counter propagating probe photon beam with high energy which can be generated by synchronized inverse Compton backscattering. Registration No. 22393

Gamma background studies in 45 m and 150 m deep mines
Szücs, T.
Abstract: A very low background level is a key requirement for low-energy nuclear astrophysics experiments. A detailed high energy (E_gamma > 3 MeV) gamma-background study with two escape-suppressed HPGe detectors has been performed at a medium deep underground site, in the Reiche Zeche mine (150 m) in Freiberg, Germany [1]. The new data complement a data set with the same detector at the Earth's surface, shallow underground (45 m) in the Felsenkeller laboratory in Dresden, Germany [2], and deep underground (1400 m) in LNGS in Gran Sasso, Italy [3]. The detailed background data from one and the same escape-suppressed HPGe detector at different underground depths allows the investigation of the effect of the active and passive shielding on the high energy (E_gamma > 3 MeV) laboratory background. A detailed interpretation of the behaviour of different background components as a function of the underground depth will be presented. The data show that already a shallow underground site has sufficiently low gamma-background for many nuclear astrophysics studies when an additional active shield is used to veto the remaining muon flux. Benefiting from these low background conditions, a used 5MV Pelletron tandem accelerator is currently being refurbished for installation at the Dresden Felsenkeller [4].
[1] T. Szücs et al., Eur. Phys. J. A 51, 33 (2015).
[2] T. Szücs et al., Eur. Phys. J. A 48, 8 (2012).
[3] T. Szücs et al., Eur. Phys. J. A 44, 513 (2010).
[4] D. Bemmerer et al., Proc. of Sciences NIC XIII, 044 (2015).

Keywords: background, underground, active shielding
  • Lecture (Conference)
    European Nuclear Physics Conference (EuNPC2015), 31.08.-04.09.2015, Groningen, The Netherlands
Registration No. 22391

High-temperature scintillation of alumina under 32 MeV 63Cu5+ heavy-ion irradiation
Lederer, S.; Akhmadaliev, S.; von Borany, J.; Gütlich, E.; Lieberwirth, A.; Zimmermann, J.; Ensinger, W.
Abstract: Polycrystalline alumina samples (α-Al2O3, purity: 99.8%) were irradiated with 63Cu5+63Cu5+ ions of 32 MeV kinetic energy (≈0.5 MeV/u) up to fluences of 1E14 ions/cm2 at various temperatures ranging from 295 to 973 K. Ion beam induced luminescence and emission spectra were monitored at wavelengths from 320 to 800 nm. Optical absorption measurements were performed to deduce color center formation. Results were evaluated by the Birks model to determine the material’s radiation hardness. The applicability of alumina as scintillation screens for ion beam diagnostics could be extended by enhanced temperature operation. Analysis of the emission spectra shows a complex color center formation behavior as a function of fluence and temperature.
Keywords: Alumina; Heavy-ion irradiation; Scintillation yield decrease; High-temperature scintillation; Thermal annealing Registration No. 22384

Solidification characteristics of Fe-Ni peritectic alloy thin strips under a near-rapid solidification condition
Song, C.-J.; Yang, Y.; Guo, Y.-Y.; Zhang, Y.-H.; Lu, W.; Zhai, Q.-J.
Abstract: This paper is an experimental investigation of the structure evolution and the solute distribution of 2 mm thick strips of Fe-(2.6, 4.2, 4.7, 7.9wt.%)Ni peritectic alloy under a near-rapid solidification condition, which were in the regions of d-ferrite single-phase, hypo-peritectic, hyper-peritectic and γ-austenite single-phase, respectively. The highest area ratio of equiaxed grain zone in the hyper-peritectic of Fe-4.7wt.%Ni alloy strip was observed, while other strips were mainly columnar grains. The lowest micro-segregation was obtained in the Fe7.9wt.%Ni alloy strip, while micro-segregation in the Fe-4.7wt.%Ni alloy was the highest. As opposed to the microsegregation, the macro-segregation of all the Fe-Ni strips was suppressed due to the rapid solidification rate. Finally, the structure formation mechanism of Fe-Ni alloy strips was analyzed.
Keywords: Fe-Ni peritectic alloy; Near-rapid solidification; Solidification characteristics
  • China Foundry 12(2015)3, 189-195
    Button zum Volltext


Registration No. 22381

Ion implantation of the 4H SiC epitaxial layers and substrates with 2MeV Se+ and 1MeV Al+ ions
Wierzchowski, W.; Turos, A.; Wieteska, K.; Stonert, A.; Ratajczak, R.; Jóźwik, P.; Wilhelm, R.; Akhamadaliev, S.; Mazur, K.; Paulmann, C.
Abstract: The implantations were performed in 4H silicon carbide homoepitaxial layers deposited on (00.1) substrates with 8° offcut, and reference 4H-SiC substrates. The 2MeV Se+ ions and 1MeV Al+ ions were implanted with four fluences subsequently increased by the factor of 4-5×. The samples were studied by means of X-ray diffraction topography, high-resolution diffractometry, specular X-ray reflectometry, and Rutherford backscattering spectrometry\channeling method. The dislocation density in the samples evaluated from the diffraction topographs did not exceed 5×103cm-2. The representative roughness values evaluated from the reflectometric measurements was 2.3±0.1nm for the substrates and less than 1.4±0.1nm for the epitaxial layers. A significantly higher damage level in the case of 2MeV Se+ ions in comparison with 1MeV Al+ ion and a linear increase of the strain with the fluence was indicated, but the highest doses of selenium ions caused the amorphization of the implanted layer. It was also possible to obtain a good fitting of the theoretical and experimental diffraction curves approximating the strain profiles by the distribution of the point defects calculated with the SRIM 2008 code. It was confirmed that the maximum coming from surface damages observed in channeling spectra of the virgin substrate wafers was significantly higher than in the case of epitaxial layers. Registration No. 22379

Effect of pressure and high magnetic field on phase transitions and magnetic properties of Ni1.92Mn1.56Sn0.52 and Ni2MnSn Heusler compounds
Kastil, J.; Kamarad, J.; Isnard, O.; Skourski, Y.; Misek, M.; Arnold, Z.
Abstract: Complex study of magnetic, magnetocaloric and structural properties of the Ni2MnSn and Ni1.92Mn1.56Sn0.52 compounds was performed. The stoichiometric single-crystal of Ni2MnSn was prepared by Czochralski method. The remarkable pressure effect on the martensitic magnetization and the martensite-austenite transition temperature TM–A was observed in the Ni1.92Mn1.56Sn0.52 compound. The coefficient dTM–A/dp reached value of 18 K/GPa. The already low value of martensite magnetization of Ni1.92Mn1.56Sn0.52 was further substantially decreased by external pressure, in contrast with pressure almost insensitive magnetization of the stoichiometric Ni2MnSn single-crystal. The pulse magnetic field of 58 T invoked the structural transition at temperature 180 K that is of about 100 K below TM–A of Ni1.92Mn1.56Sn0.52 at zero field. An anomalous increase of resistivity of the compound has been observed at temperature range below TM–A, however, it does not copy the sharp change of magnetization at TM–A. The obtained results indicate the important role of interatomic distances on the magnetic ordering and electronic structure of the studied Heusler alloys and are in agreement with the Jahn-Teller mechanism of the martensitic transition in these compounds. Registration No. 22378

Investigation into the Formation of Nanoparticles of Tetravalent Neptunium in Slightly Alkaline Aqueous Solution
Husar, R.
Abstract: Considering the worldwide growing discharge of minor actinides and the current need for geological disposal facilities for radioactive waste, this work provides a contribution to the safety case concerning Np transport if it would be released from deep repository sites and moving from alkaline cement conditions (near-field) to more neutral environmental conditions (far-field). The reducing conditions in a nuclear waste repository render neptunium tetravalent, which is assumed to be immobile in aqueous environment due to the low solubility solution of Np(IV). For tetravalent actinide nuclides, the most significant transport should occur via colloidal particles. This work demonstrates the formation of intrinsic neptunium dioxide nanocrystals and amorphous Np(IV) silica colloids under environmentally relevant conditions.

The dissociation of the initial soluble Np(IV) complex (i.e. [Np(IV)(CO3)5]6-) induces the intrinsic formation of nanocrystalline NpO2 in the solution phase. The resulting irregularly shaped nanocrystals with an average size of 4 nm exhibit a face-centered cubic (fcc), fluorite-type structure (space group ). The NCs tend to agglomerate under ambient conditions due to the weakly charged hydrodynamic surface at neutral pH (zetapotential ~0 mV). The formation of micron-sized agglomerates, composed of nanocrystals of 2-5 nm in size, and the subsequent precipitation cause immobilization of the major amount of Np(IV) in the Np carbonate system. Agglomeration of NpO2 nanocrystals in dependence on time was indicated by PCS and UV-vis absorption spectroscopy with the changes of baseline characteristics and absorption maximum at 742 nm.

Hitherto, unknown polynuclear species as intermediate species of NpO2 nanocrystal formation were isolated from solution and observed by HR-TEM. These polynuclear Np species appear as dimers, trimers and hexanuclear compounds in analogy with those reported for other actinides.

Intrinsic formation of NpO2 (fcc) nanocrystals under ambient environmental conditions is prevented by admixing silicic acid: amorphous Np(IV) silica colloids are formed when silicate is present in carbonate solution.

Herein, the initial molar ratio of Si to Np in solution lead to the formation of Np(IV) silica particles of different composition and size where Si content determines the structure and stability of resulting colloids. Implications for different electronic structures of Np(IV) in dependence on Si content in the solid phase are given by the shift of the absorption maximum at 742 nm characteristic for Np(IV) colloids, silica excess of 5 times the magnitude of Si to Np reveal a redshift up to 6 nm in the colloidal UV-vis spectrum. Precipitation of Np(IV) particles in the ternary system results in a different coordination sphere of Np(IV) compared to the binary system, and the incorporation of Si into internal structure of Np(IV) silica colloids in coffinite-like structure is confirmed by EXAFS. TEM confirms different kinds of particle morphologies in dependence on the silica content. Silica-poor systems reveal porous particles in the micron-range which consist of irregular cross-linked hydrolyzed Np(IV) silica compartments with pores <15 nm.

In contrast, long-term stabilized and silica-enriched systems are characterized by isolated particles with an average particle size of 45 nm. Agglomerates of such isolated Np(IV) silica particles appear as consolidated amorphous solids with a densely closed surface and exhibit no internal fractures. The latter mentioned morphology of Np(IV) silica particles might facilitate the migration behavior of Np(IV) in a stabilized colloidal form under environmental conditions. The silica-enriched particles with densely closed surface are long-term stabilized as colloidal dispersion (>1 year) due to repulsion effects caused by significant surface charge. Particles synthesized from Si/Np = 9/1 carry exclusively negative surface charge in nearly the whole pH range from pH 3 to pH 10 with zetapotential = (-) 5 to (-) 30 mV. The zeta potentials of all particle systems containing silica are significantly shifted to more negative values below pH 7 where the isoelectrical point shifts from pH = 8.0 to 2.6 effecting negative charge under ambient conditions which supports electrostatic stabilization of Np(IV) particles. Particle surface charge at the slipping plane, particle size and shape necessarily depend on the initial magnitude of Si content in solution during particle formation. Particular changes of the morphology and internal structure of different Np(IV) silica colloids by aging are indicated by TEM and XPS. The composition and the crystallinity state of the initially formed amorphous phases partially changed into well-ordered nanocrystalline units characterized with fcc structure.

The presence of silicate under conditions expected in a nuclear waste repository significantly influences the solubility of Np(IV) and provoke the stabilization of waterborne Np(IV) up to concentrations of 10-3 M, exceeding Np´s solubility limit by a factor of up 10.000.

Neptunium and silicate significantly interact with each other, and thereby changing their individual hydrolysis and polymerization behavior. Silicate prevents the intrinsic formation of NpO2 NCs in fcc-structure, and at the same time, Np(IV) prevents the polymerization of silicate. Both processes result in the formation of Np(IV) silica colloids which possibly influence the migration behavior and fate of Np in the waste repositories and surrounding environments. For tetravalent actinides in general, the most significant transport in the environment would occur by colloidal particles. Therefore, Np(IV) silica colloids could have a significant implication in the migration of Np, the important minor actinide in the waste repositories, via colloidal transport.

Keywords: Actinides, neptunium, nanoparticles, nanocrystals, environmental chemistry
  • Doctoral thesis
    TU Dresden, 2015
    Mentor: Prof. Dr. Thorsten Stumpf
    113 Seiten


Registration No. 22375

Remote sensing based improvement of the geological map of the Neoproterozoic Ras Gharib segment in the Eastern Desert (NE-Egypt) using texture features
Jakob, S.; Bühler, B.; Gloaguen, R.; Breitkreuz, C.; Eliwa, H. A.; El Gameel, K.
Abstract: Geological mapping in the Eastern Desert is impeded by difficult accessibility. We improve the existing geological maps by including texture features in a classification scheme of ASTER and Landsat 8 data. We tested the improvement of support vector machine classification using band ratios, principal component analysis (PCA) and texture analysis in the Ras Gharib segment (NE Egypt). A very high classification overall accuracy of 99.85% was achieved. We demonstrate that the input of textures provide valuable additional data for lithological mapping. With the gained information, the existing geological map of the study area was improved distinctly in precision and resolution, but also in terms of correction of yet wrong or inaccurate locations and of lithological unit extents.
Keywords: Remote sensing; North Eastern Desert of Egypt; Texture analysis; Lithological mapping; ASTER and Landsat 8 image analysis; Support vector machine classification Registration No. 22374

Large Eddy Simulation of a rectangular bubble column
Ma, T.; Lucas, D.
Abstract: Prediction of mean flow and turbulent parameter with Euler-Euler-LES
Keywords: Two-fluid model; LES
  • Poster
    Dynamics of bubbly flow, 08.-12.06.2015, Udine, Italy
Registration No. 22367

lll-V integration in Si and Ge by ion beam synthesis and flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Hübner, R.; Skorupa, M. Helm W.
Abstract: In order to follow Moore’s law on the path to smaller and smaller devices, more and more materials have to be integrated into Si technology. Current research activities focus on the integration of Ge and binary III-V compounds into Si, as these materials promise a further transistor performance increase due to their high hole and electron mobility, respectively. In addition, the direct band gap of most of the compound semiconductors is of great interest for optoelectronic applications. However, the integration into Si generates a lot of challenges regarding both the quality of the III-V material itself and the quality of its interfaces. At present, most integration technologies rely on molecular beam epitaxy or similar growth mechanisms. Recently, we showed that III-V nanocrystals (NC) in Si can also be fabricated by sequential ion implantation followed by flash lamp annealing (FLA) [1]. Moreover, the use of a patterned implantation mask allows the fabrication of III-V NCs in a Si nanowire at defined positions [2].

In this presentation we extend our previous investigations to the case of Ge. In order to get a better understanding of the NC formation process, InAs and GaAs NCs were fabricated in Si and Ge by ion implantation and FLA, and their structural and electric properties were compared to each other. It will be shown that the recrystallization of the near-surface layer of amorphous substrate material (Si or Ge), together with the NC formation, is rather governed by liquid phase than by solid phase epitaxy. This scenario is supported by the evaluation of the corresponding segregation and diffusion coefficients, the temperature profile during FLA and the final size distribution of the NCs.

[1] S. Prucnal, S. Facsko, C. Baumgart, H. Schmidt, M.O. Liedke, L. Rebohle, A. Shalimov, H. Reuther, A. Kanjilal, A. Mucklich, M. Helm, J. Zuk, and W. Skorupa, Nano Lett. 11, Issue 7, 2814-2818 (2011)
[2] S. Prucnal, M. Glaser, A. Lugstein, E. Bertagnolli, M. Stöger-Pollach, S. Zhou, M. Helm, D. Reichel, L. Rebohle, M. Turek, J. Zuk, and W. Skorupa, Nano Res. 7, 1769 (2014)

Keywords: III-V integration, ion implantation, flash lamp annealing, silicon, germanium
  • Lecture (Conference)
    Gettering and Defect Engineering in Semiconductor Technology (GADEST) 2015, 20.-25.09.2015, Bad Staffelstein, Deutschland
Registration No. 22366

High-temperature photon-noise-limited performance terahertz quantum-well photodetectors
Jia, J. Y.; Wang, T. M.; Zhang, Y. H.; Shen, W. Z.; Schneider, H.
Abstract: In this paper, we propose using a terahertz quantumwell photodetector (THz QWP) in combination with a terahertz source to realize a detection system with photon-noise limited performance (PLIP) at high temperatures. Systematical investigations on the high-temperature performances of THz QWPs, including required signal power density for PLIP, detectivity, and the signal-to-noise ratio, have been carried out by elaborating their dark current mechanism and photocurrent response both experimentally and theoretically. We also present the optimal doping concentration of THz QWPs designed for different peak wavelengths and the resulting optimum performance regarding the above three key parameters. Numerical results show that optimal designed QWP with peak response frequency of 5.5 THz is expected to achieve PLIP at 77 K at signal power density at 819 W/cm and above. This work gives a precise description of PLIP performance of THz QWPs and will open ways for new applications for high-temperature detection in the THz regime.
Keywords: High temperature, detectivity, photon-noise limited, quantum-well photodetector (QWP), Terahertz (THz) Registration No. 22365

Tunneling breakdown of a strongly correlated insulating state in VO2 induced by intense multiterahertz excitation
Mayer, B.; Schmidt, C.; Grupp, A.; Bühler, J.; Oelmann, J.; Marvel, R. E.; Haglund, R. F.; Oka, T.; Brida, D.; Leitenstorfer, A.; Pashkin, A.
Abstract: We directly trace the near- and midinfrared transmission change of a VO2 thin film during an ultrafast insulator-to-metal transition triggered by high-field multiterahertz transients. Nonthermal switching into a metastable metallic state is governed solely by the amplitude of the applied terahertz field. In contrast to resonant excitation below the threshold fluence, no signatures of excitonic self-trapping are observed. Our findings are consistent with the generation of spatially separated charge pairs and a cooperative transition into a delocalized metallic state by THz field-induced tunneling. The tunneling process is a condensed-matter analog of the Schwinger effect in nonlinear quantum electrodynamics. We find good agreement with the pair production formula by replacing the Compton wavelength with an electronic correlation length of 2.1 A° . Registration No. 22363

Bispecific antibody releasing-mesenchymal stromal cell machinery for retargeting T cells towards acute myeloid leukemia blasts
Aliperta, R.; Cartellieri, M.; Feldmann, A.; Arndt, C.; Koristka, S.; Michalk, I.; von Bonin, M.; Ehninger, A.; Bachmann, J.; Ehninger, G.; Bornhäuser, M.; Bachmann, M. P.
Abstract: Bispecific antibodies (bsAbs) engaging T cells are emerging as a promising immunotherapeutic tool for the treatment of hematologic malignancies. Because their low molecular mass, bsAbs have short half-lives. To achieve clinical responses, they have to be infused into patients continously, for a long period of time. As a valid alternative we examined the use of mesenchymal stromal cells (MSCs) as autonomous cellular machines for the constant production of a recently described, fully humanized anti-CD33-anti-CD3 bsAb, which is capable of redirecting human T cells against CD33-expressing leukemic cells. The immortalized human MSC line SCP-1 was genetically modified into expressing bsAb at sufficient amounts to redirect T cells efficiently against CD33 presenting target cells, both in vitro and in an immunodeficient mouse model. Moreover, T cells of patients suffering from acute myeloid leukemia (AML) in blast crisis eliminated autologous leukemic cells in the presence of the bsAb secreting MSCs over time. The immune response against AML cells could be enhanced further by providing T cells an additional co-stimulus via the
CD137-CD137 ligand axis through CD137L expression on MSCs. This study demonstrates that MSCs have the potential to be used as cellular production machines for bsAb-based tumor immunotherapy in the future.
Registration No. 22361

Surface Modificationwith heavy Mon- and Polyatomic Ions
Bischoff, L.; Böttger, R.; Heinig, K.-H.
Abstract: Self-organization of nanopatterns on solid surfaces by ion irradiation is a well-established technique to create regular and ordered structures like ripples or dots. Characteristics of patterns can be controlled selecting different ion species as well as by varying their energy, fluence, incidence angle or the sample temperature during irradiation. To date, mostly monatomic ions with masses between 40 (Ar) and 131 amu (Xe) were used for self-organized nanopatterning or contrary for surface smoothing. A comprehensive review is given.Here, self-organization of periodic patterns by bombardment with polyatomic/cluster ion species with masses of up to ~835 amu is studied – a regime not explored so far. Each impact of a very heavy polyatomic projectile deposits within femtoseconds an extremely high energy density into a local, near-surface volume. The achieved energy density exceeds that of irradiation with monatomic ions of medium mass considerably, it is of the order of femtosecond laser irradiation or swift heavy ion bombardment. Therefore, compared to former ion-induced pattern formation, different pattern based on different mechanisms can be expected.A new quality of pattern on Ge surfaces are obtained by Bi2, Bi3, Bi4 and Au2, Au3 ion irradiation. Polyatomic ions are provided by liquid metal (alloy) ion sources (LM(A)IS) in a mass-separating 30 kV focused ion beam (FIB) system. Results are compared to monatomic Bi and Au ion irradiation using otherwise equivalent irradiation parameters. For this, SEM and AFM were applied to investigate the pattern formation in dependence on ion species, energy per projectile atom, fluence, incidence angle and target temperature. Finally, a consistent, qualitative model for the surface evolution relating on energy density deposition sufficient for localized, transient nano melt pool formation is discussed.
Keywords: Self-organization, ripples, dots, mon- and polyatomic ions, FIB
  • Invited lecture (Conferences)
    The 22nd International Conference on Ion-Surface Interactions, ISI - 2015, 20.-24.08.2015, Moscow, Russia
Registration No. 22360

Denudation rates across the Pamir based on 10Be concentrations in fluvial sediments: dominance of topographic over climatic factors
Fuchs, Margret C.; Gloaguen, R.; Merchel, S.; Pohl, E.; Sulaymonova, Vasila A.; Andermann, C.; Rugel, G.
Abstract: A clear understanding of erosion processes is fundamental in order to comprehend the evolution of actively deforming mountain ranges. However, the relative contributions of tectonic and climatic factors and their feedbacks remain highly debated. In order to contribute to the debate, we quantify basin-wide denudation rates from cosmogenic 10Be concentrations in modern river sediments in the Pamir. This mountain range is a unique natural laboratory because the ongoing India–Eurasia collision sustains high deformation rates and, on account of its position at the transition between Westerlies and monsoon, a strong regional climatic variability arises. Sample acquisition and preparation for accelerator mass spectrometry measurements were challenging due to difficult field accessibility, low quartz and high feldspar concentrations and crystal coating. Six samples along the main draining river, the Panj, and five samples within the major, east–west elongated tributary basins allow us to quantify basin-wide denudation rates for the first time in this orogen. An average denudation rate of 0.64 mm yr-1 reveals a rapid evolution of the entire Pamir. Denudation rates of tributary sub-basins highlight the strong contrast between the Pamir Plateau (0.05 to 0.16 mm yr-1) and its margins (0.54 to 1.45 mm -1). The intensity of denudation is primarily correlated with geometric properties of the surface, such as slope steepness (0.75 quartiles; R2 of 0.81), and to a lesser extent to climatic factors such as precipitation. We thus argue that either tectonic uplift or base-level lowering are the main contributors to denudation processes. Multiple linear regression analysis (best R2of 0.93) suggests that precipitation may act as a limiting factor to denudation.
The highest denudation rates coincide with areas of the northwestern Pamir margin that receive precipitation predominantly from the Westerlies during winter. There, the concentrated discharge during spring and early summer may sustain the pronounced denudation and allow the rapid sediment transport out of the basins. Low slope angles and dry conditions hamper the sediment flux on the plateau and, consequently, denudation. The magnitude of denudation in the Pamir is similar to rates determined in the southern Himalaya despite very different climatic and tectonic conditions. The discrepancy between rates of basin-wide denudation and the fluvial incision that is up to 10 times higher evidences a transient landscape in the Pamir. This underpins the hypothesis that river captures may have caused the strong base-level lowering that drives the enhanced incision of the Panj and its main tributaries.

Keywords: erosion, geomorphology, accelerator mass spectrometry, AMS, cosmogenic nuclide


Registration No. 22359

Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE
Schmidt, J.; Winnerl, S.; Seidel, W.; Bauer, C.; Gensch, M.; Schneider, H.; Helm, M.
Abstract: We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30μm is discussed. In addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.
Keywords: Pulse picking, plasma switch Registration No. 22356

Erbium-ion implantation into various crystallographic cuts of Al2O3
Nekvindova, P.; Mackova, A.; Malinsky, P.; Cajzl, J.; Svecova, B.; Oswald, J.; Wilhelm, R. A.
Abstract: This paper reports on the importance of crystallographic cuts with a different orientation on the luminescent properties and structural changes of Al2O3 implanted with Er+ ions at 190 keV and with a fluence of 1.0 × 1016 cm−2. Post-implantation annealing at 1000 °C in oxygen atmosphere was also done. The chemical compositions and erbium concentration-depth profiles of implanted layers were studied by Rutherford Backscattering Spectrometry (RBS) and compared to SRIM simulations. The same value of the maximum erbium concentration (up to 2 at.%) was observed at a depth of about 40 nm for all crystallographic cuts. The structural properties of the prepared layers were characterised by RBS/channelling. The relative amount of disordered atoms of 70–80% was observed in the prepared implanted layers and discussed for various cuts. It has been found that erbium is positioned randomly in the Al2O3 crystalline matrix, and no preferential positions appeared even after the annealing procedure. Erbium luminescence properties were measured in the wavelength range of 1440–1650 nm for all samples. As-implanted Al2O3 samples had a significant luminescence band at 1530 nm. The best luminescence was repeatedly observed in the 〈0 0 0 1〉 cut of Al2O3. The annealing procedure significantly improved the luminescent properties.
Keywords: Sapphire; Erbium; Ion implantation; Luminescence Registration No. 22355

Magnetoelectricity of the spin-ice compound Ho2Ti2O7
Herrmannsdörfer, T.; Schönemann, R.; Green, E.; Opherden, L.; Skrotzki, R.; Wang, Z.; Kaneko, H.; Suzuki, H.; Wosnitza, J.
  • Lecture (Conference)
    ICM2015 - 20th International Conference on Magnetism, 05.-10.07.2015, Barcelona, Espana
Registration No. 22354

Synthese, 18F-Markierung und radiopharmakologische Charakterisierung eines 30mer-Peptids als potentieller Radiotracer für die molekulare Bildgebung von Claudin-4 mittels PET
Bader, M.; Kuchar, M.; Wodtke, R.; Lenk, J.; Bergmann, R.; Pufe, J.; Haase-Kohn, C.; Steinbach, J.; Pietzsch, J.; Löser, R.
Abstract: Der Zelloberflächenrezeptor Claudin-4 (Cld-4) wird in verschiedenen Tumoren überexprimiert und stellt daher ein potentielles Target sowohl für die Diagnose als auch die Therapie von Tumoren epithelialen Ursprungs dar. Dies lässt die Entwicklung von Sonden, die das in vivo-Imaging dieses Proteins ermöglichen, attraktiv erscheinen. Im Rahmen dieser Arbeit sollte untersucht werden, inwiefern sich das C-terminale Fragment der C-terminalen Domäne des Clostridium perfringens-Enterotoxins cCPE(290-319) für die PET-Bildgebung von Cld-4 eignet. Dieses Fragment besteht aus 30 Aminsäuren und weist die Sequenz SLDAGQYVLVMKANSSYSGNYPYSILFQKF auf, was den Positionen 290-319 im cCPE entspricht.
Die Synthese des cCPE(290-319) und davon abgeleiteter Analoga, insbesondere N-terminal fluorbenzoylierter und FITC-konjugierter Derivate sowie Varianten, in denen kritische Aminosäuren (Tyr 306 und Leu 315) ausgetauscht wurden, sollte durch Festphasenpeptidsynthese erfolgen. Unter verschiedenen erprobten Strategien erwies sich die sequentielle Festphasenpeptidsynthese unter Einsatz von drei Pseudoprolin-Dipeptiden am effizientesten, um cCPE(290-319) und dessen Derivate zugänglich zu machen. Die Affinität der erhaltenen Peptide zu einem artifiziellen Proteinkonstrukt bestehend aus beiden extrazellulären Domänen des Cld-4 wurde mit Hilfe der Oberflächen-Plasmonenresonanz (SPR) untersucht, wodurch ein Kd-Wert von 1.4 µM für das N-terminal 4-fluorbenzoylierte cCPE(290-319) ermittelt wurde. Die Markierung von CPE(290-319) mit Fluor-18 erfolgte an fester Phase mit Hilfe von N-Succinimidyl-4-[18F]fluorbenzoat ([18F]SFB) und 4-[18F]Fluorobenzoylchlorid. Dabei wurden die besten Resultate erzielt, wenn harzgebundenes cCPE(290-319) mit N-terminalem 6-Aminohexansäure-Spacer mit [18F]SFB zur Reaktion gebracht wurde. Die Inkubation des auf diese Weise erhaltenen Radiotracers mit Zellüberstand und Blutplasma ließ keine Anzeichen von Instabilität in diesen physiologischen Medien erkennen. Die Zellbindung von 18F-markiertem cCPE(290-319) wurde mit den Tumorzelllinien HT29, A375 und A431 untersucht. Dabei konnte die zeitabhängige Bindung des radiomarkierten Peptids an Cld-4-positive A375- und A431-Zellen beobachtet werden, die stärker war als im Fall der Cld-4-negativen HT29-Zellen. Dieses Ergebnis wird gestützt durch konfokale Fluoreszenzmikroskopie mit FITC-konjugiertem cCPE(290-319) an A431-Zellen. Das in vivo-Verhalten von 18F-markiertem cCPE(290-319) wurde durch dynamisches PET-Imaging und Radiometabolit-Analysen in NMRI nu/nu-Mäusen bzw. Wistar-Ratten evaluiert. Dabei hat sich gezeigt, dass 18F-markiertes cCPE(290-319) schnell metabolisiert wird und einer deutlichen Aufnahme in die Leber unterliegt.
  • Poster
    GDCh-Wissenschaftsforum 2015, 30.08.-02.09.2015, Dresden, Deutschland
Registration No. 22351

Targeting of tissue transglutaminase for functional tumour imaging: Studies on novel assay methods and inhibitors for this enzyme
Wodtke, R.; Hauser, C.; Jäckel, E.; Ruiz-Gómez, G.; Wong, A.; Steinbach, J.; Pietzsch, J.; Pietsch, M.; Löser, R.
Abstract: An increased activity of tissue transglutaminase (TGase 2) in tumours correlates with enhanced invasive potential as well as resistance to chemo- and radiotherapy. Therefore, this enzyme represents an interesting target for the development of PET tracers for functional in vivo imaging of tumours.
One important prerequisite for the identification and characterisation of TGase 2-binding compounds are reliable assay methods to measure the enzymatic activity. For this, a continuous fluorimetric activity assay was established, which allows the detection of the TGase 2-activity through the measurement of an increase in fluorescence. In this context, six novel water-soluble fluorogenic acyl donors containing either 7-hydroxycoumarin or 7-hydroxy-4-methylcoumarin (HMC) as fluorogenic leaving groups were developed and extensively characterised concerning their enzymatic hydrolysis and aminolysis. Within these substrates, the dipeptide Z-Glu(HMC)-Gly-OH exhibits not only the most favourable substrate properties of all compounds in this study but also within the peptidic acyl donors described for TGase 2 so far. In addition to that, a fluorescence anisotropy-based assay method was established where the TGase 2-mediated incorporation of either fluorescein- or rhodamine-conjugated cadaverine into N,N-dimethylcasein is quantified.
For the development of PET tracers for molecular imaging of TGase 2, different approaches are pursued. One of those exploits the use of irreversible inhibitors for this enzyme. Among the TGase 2 inhibitors described in the literature, the recently reported Nα-acyl-Nε-acryloyl-lysine-4-pyridylpiperazides seem to be most suitable for radiotracer development as these compounds exhibit strong inhibitory potential and selectivity towards TGase 2 as well as favourable pharmacokinetic properties. Hence, derivatives based on this class of compounds that allow the labelling with radionuclides such as fluorine-18 and iodine-124 were prepared and their inhibitory potential towards TGase 2 was evaluated by the two independent assay methods outlined above. The kinetic characterisation of the compounds revealed interesting structure-activity relationships. Particularly, the introduction of iodine into the C-terminal pyridyl moiety resulted in a significantly increased inhibitory potential towards TGase 2 compared to the lead structure. This was further illustrated by investigations on covalent docking of the lysine-derived inhibitors within the catalytic centre of TGase 2 which simultaneously will open strategies for the design of even more potent inhibitors.
  • Lecture (Conference)
    14th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2015, Wien, Österreich
Registration No. 22350

III-V nanocrystals in Silicon via Liquid Phase Epitaxy: Microstructure and related properties
Wutzler, R.; Rebohle, L.; Prucnal, S.; Böttger, R.; Hübner, R.; Grenzer, J.; Helm, M.; Skorupa, W.
Abstract: The integration of III-V compound semiconductors into existing semiconductor technology is a milestone in future development of micro- and opto-electronics. However, one of the main problems is the presence of defects both inside the III-V semiconductor and at its interfaces. In the present case, III-V compound semiconductor nanocrystals (NCs) were fabricated in Si based systems. For NC formation ion implantation and short-time flash lamp annealing (FLA) were used. After the implanted Si is molten by FLA, the NCs grow via liquid phase epitaxy (LPE) in a millisecond regime. Several binary and ternary III-V compounds have been produced using this approach. While binary compounds are fabricated stoichiometrically, ternary compounds can be achieved with varying compositions. Raman spectroscopy measurements confirmed the formation of III-V NCs within the particular, recrystallized matrices and Si doping. Microstructural properties were investigated by scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (TEM) and X-ray diffraction analysis. SEM and TEM images show crystalline, strained III-V nanocrystals in recrystallized Si layers.
Keywords: ion implantation, flash lamp annealing, III-V integration, silicon, liquid phase epitaxy
  • Poster
    28th International Conference on Defects in Semiconductors (ICDS), 27.-31.07.2015, Espoo, Finland
Registration No. 22349

Experimental investigations on the influence of adhesive oxides on the metal-ceramic bond
Enghardt, S.; Richter, G.; Richter, E.; Reitemeier, B.; Walter, M. H.
Abstract: The objective of this study was to test the influence of selected base metals, which act as oxide formers, on the metal-ceramic bond of dental veneer systems. Using ion implantation techniques, ions of Al, In and Cu were introduced into near-surface layers of a noble metal alloy containing no base metals. A noble metal alloy with base metals added for oxide formation was used as a reference. Both alloys were coated with a low-temperature fusing dental ceramic. Specimens without ion implantation or with Al2O3air abrasion were used as controls. The test procedures comprised the Schwickerath shear bond strength test (ISO 9693-1), profile height (surface roughness) measurements (ISO 4287; ISO 4288; ISO 25178), scanning electron microscopy (SEM) imaging, auger electron spectroscopy (AES) and energy dispersive X-ray analysis (EDX). Ion implantation resulted in no increase in bond strength. The highest shear bond strengths were achieved after oxidation in air and air abrasion with Al2O3 (41.5 MPa and 47.8 MPa respectively). There was a positive correlation between shear bond strength and profile height. After air abrasion, a pronounced structuring of the surface occurred compared to ion implantation. The established concentration shifts in alloy and ceramic could be reproduced. However, their positive effects on shear bond strength were not confirmed. The mechanical bond appears to be of greater importance for metal-ceramic bonding.
Keywords: Alloy; Chemical bond; Ion implantation; Mechanical bond; Metal-ceramic bond; Shear bond strength


Registration No. 22348

Linear magnetoresistance in mosaic-like bilayer graphene
Kisslinger, F.; Ott, C.; Heide, C.; Kampert, E.; Butz, B.; Spiecker, E.; Shallcross, S.; Weber, H. B.
Abstract: The magnetoresistance of conductors usually has a quadratic dependence on magnetic field, however, examples exist of non-saturating linear behaviour in diverse materials. Assigning a specific microscopic mechanism to this unusual phenomenon is obscured by the co-occurrence and interplay of doping, mobility fluctuations and a polycrystalline structure. Bilayer graphene has virtually no doping fluctuations, yet provides a built-in mosaic tiling due to the dense network of partial dislocations. We present magnetotransport measurements of epitaxial bilayer graphene that exhibits a strong and reproducible linear magnetoresistance that persists to B = 62 T at and above room temperature, decorated by quantum interference effects at low temperatures. Partial dislocations thus have a profound impact on the transport properties in bilayer graphene, a system that is frequently assumed to be dislocation-free. It further provides a clear and tractable model system for studying the unusual properties of mosaic conductors. Registration No. 22346

Solid-phase synthesis of selectively monofluorobenzoylated polyamines for targeting of transglutaminases and polyamine transporters in tumours
Wodtke, R.; Steinbach, J.; Pietzsch, J.; Pietsch, M.; Löser, R.
Abstract: Transglutaminases and polyamine transporters are promising targets for functional imaging of tumours. Therefore, our aim is to synthesise polyamine-based radiotracers that allow the in vivo imaging of the aforementioned targets by positron emission tomography (PET). Labelling with the radionuclide fluorine-18 can be accomplished via attaching a [18F]fluorobenzoyl group with the prosthetic labelling reagent N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB). To access the required non- radioactive analogues, a solid-phase synthesis was developed that enables selective fluorobenzoylation at distinct amino groups of various polyamines (e.g. cadaverine, spermidine, spermine) on the basis of a recently described synthetic concept for the selective functionalisation of polyamines. The established route can be directly applied to synthesise the 18F-labelled analogues.
The mono-fluorobenzoylated polyamines were obtained by solidphase synthesis of the corresponding oxopolyamines and subsequent reduction of the amide bond with BH3-THF. By applying Dde and Boc as orthogonal protecting groups and taking advantage of the selective reaction of 2-acetyldimedone with primary amino groups in the presence of secondary amines, the selective fluorobenzoylation (FBz) of different amino groups becomes possible.
Additionally, the selective mono-fluorobenzylation (FBn) of selected diamines by reaction with 4-fluorobenzaldehyde and subsequent reduction of the resulting imine using sodium triacetoxyborohydride was performed. Based on the established methodology, the following compounds among others were obtained in good yields: N-FBzcadaverine, N-FBn-cadaverine, N1-FBz- spermidine, N4-FBz-spermidine, N8-FBz-spermidine and N1-FBz-spermine. Furthermore, the naturally occurring diamine cadaverine was conjugated to different reporter groups such as biotin. The identity of the compounds was confirmed by NMR spectroscopy and mass spectrometry. The kinetic parameters towards transglutaminase 2-catalysed acyl transfer were determined for selected compounds with an in-house fluorimetric assay using the fluorogenic acyl donor Cbz–Glu(HMC)–Gly–OH.
  • Abstract in refereed journal
    Amino Acids 47(2015)8, 1630
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  • Poster
    14th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2015, Wien, Österreich
Registration No. 22345

Synthesis, 18F-labeling and radiopharmacological characterization of a 30mer peptide as potential radiotracer for PET imaging of claudin-4
Kuchar, M.; Bader, M.; Wodtke, R.; Lenk, J.; Pufe, J.; Bergmann, R.; Haase-Kohn, C.; Steinbach, J.; Pietzsch, J.; Löser, R.
Abstract: The cell surface receptor claudin-4 (Cld-4) represents a single-chain protein containing four transmembrane domains and constitutes cell–cell contacts of the tight-junction type by engaging in homophilic interactions. Cld-4 is upregulated in various tumors and represents a promising target for both diagnosis and treatment of solid tumors of epithelial origin. Therefore, the development of agents that allow imaging of Cld-4 in vivo such as 18F-labeled compounds for positron emission tomography (PET) appears to be attractive. A suitable ligand to target Cld-4 in vivo seems to be the C-terminal peptidic fragment of the C-terminal domain of the Clostridium perfringens enterotoxin cCPE(290-319). This fragment is of 30 amino acids in length and has the sequence SLDAGQYVLVMKANSSYSGNYPYSILFQKF corresponding to positions 290-319 of cCPE.
The synthesis of cCPE(290–319) and analogues derived thereof, such as N-terminally modified derivatives (fluorobenzoylated and FITC-conjugated) and variants in which critical amino acids (Tyr 306 and Leu 315) have been replaced, was envisaged to be accomplished by solid-phase peptide synthesis (SPPS). Among several approaches, sequential SPPS using three pseudoproline-dipeptide building blocks revealed to be the most efficient one to afford cCPE(290–319) and its derivatives. The affinity of the furnished peptides to a soluble protein construct that contains both extracellular loops of Cld-4 was studied by surface plasmon resonance (SPR), which allowed determining a Kd value of 1.4 lM for the N-terminally fluorobenzoylated cCPE(290-319). Labeling of cCPE(290–319) with fluorine-18 was achieved on solid phase using N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) and 4-[18F]fluorobenzoyl chloride as 18F-acylating agents. Most advantageous results were obtained when [18F]SFB was reacted with resin-bound cCPE(290–319) containing an N-terminal 6-aminohexanoic spacer. Stability assays in cell supernatants and plasma indicated no degradation of the resulting radiotracer in these physiological media. Cell binding of 18F-labeled cCPE(290–319) was investigated using the HT29, A375 and A431 tumor cell lines. Timedependent binding of the radiolabeled peptide to the Cld-4-positive A375 and A431 cells was observed, which was stronger than for the Cld-4-negative HT29 cell line. These findings are in accordance with results of confocal microscopy studies using FITC-conjugated cCPE(290–319) and A431 cells. The in vivo behavior of 18F-labeled cCPE(290–319) was studied in NMRI nu/nu mice and Wistar rats by dynamic PET imaging and radiometabolite analyses, respectively. These investigations have shown that 18F-labeled cCPE(290–319) is subject to substantial liver uptake and rapid metabolic degradation in vivo.
In conclusion, the synthesis and 18F-labeling of cCPE(290-319) were successfully established. Its binding to Cld-4 in vitro and in cellulo has been demonstrated. Initial radiopharmacological studies suggest the limited suitability of this peptide in its current non-stabilized form to target Cld-4 in vivo.
  • Abstract in refereed journal
    Amino Acids 47(2015)8, 1629-1630
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  • Poster
    14th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2015, Wien, Österreich
Registration No. 22344

A new fluorescence anisotropy-based assay for activity determination of tissue transglutaminase
Hauser, C.; Wodtke, R.; Löser, R.; Pietsch, M.
Abstract: Considerable evidence for the implication of tissue transglutaminase (TGase 2) in a variety of pathological processes, such as neurodegenerative diseases, disorders related to autoimmunity and inflammation as well as tumor progression, has been revealed over the recent years. This renders TGase 2 attractive for developing agents which allow the enzyme’s targeting for both therapeutic and imaging purposes. The development of such molecules requires the establishment of reliable methods to assess the interaction with TGase 2, which can be done most conveniently in continuous kinetic assays.
Several assays have been published over the last decades to determine TGase 2 activity, with only very few using the method of fluorescence anisotropy. Measurement of fluorescence anisotropy offers a better signal to noise ratio than other techniques, such as those based solely on fluorescence emission and does not need washing or separation of unbound fluorescent substance.
Here, we report a fluorescence anisotropy-based approach for the determination of TGase 2’s transamidase activity, established and validated by using fluorescein- and rhodamine B-labeled cadaverines as acyl acceptor substrates. The synthesis of the cadaverine derivatives has been accomplished in a solid-phase approach. To allow efficient conjugation of the rhodamine B moiety, different linkers providing secondary amine functions have been introduced between the cadaverine and xanthenyl entities.
The increase in fluorescence anisotropy resulting from covalent binding of the relatively small cadaverine derivatives to the much larger acyl donor substrate N,N-dimethylated casein was followed over time and enzyme activities were derived thereof. The assay was found to be highly reproducible and shows no background signal in the absence of the enzyme for all synthesized cadaverine derivatives. After characterization of the enzyme–substrate interaction by determination of the Michaelis constants, Km, and the maximum velocities of substrate conversion, Vmax, the assay was validated for screening of non-covalent and covalent inhibitors by using the literature-known substances GTP and iodoacetamide, respectively, as well as a recently reported L-lysine acrylamide derivative.
  • Abstract in refereed journal
    Amino Acids 47(2015)8, 1629
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  • Poster
    14th International Congress on Amino Acids, Peptides and Proteins, 03.-07.08.2015, Wien, Österreich
Registration No. 22343

18F-Labeled 1,4-Dioxa-8-azaspiro[4.5]decane Derivative: Synthesis and Biological Evaluation of a σ1 Receptor Radioligand with Low Lipophilicity as Potent Tumor Imaging Agent
Xie, F.; Bergmann, R.; Kniess, T.; Deuther-Conrad, W.; Mamat, C.; Neuber, C.; Liu, B.; Steinbach, J.; Brust, P.; Pietzsch, J.; Jia, H.
Abstract: We report the syntheses and evaluation of series of novel piperidine compounds with low lipophilicity as σ1 receptor ligands. 8-(4-(2-Fluoroethoxy)benzyl)-1,4-dioxa-8-azaspiro[4.5]decane (5a) possessed high affinity (Ki = 5.4 ± 0.4 nM) for σ1 receptors and selectivity for σ2 receptors (30-fold) and the vesicular acetylcholine transporter (1404-fold). [18F]5a was prepared using a one-pot, two-step labeling procedure in an automated synthesis module, with a radiochemical purity of >95%, and a specific activity of 25−45 GBq/μmol. Cellular association, biodistribution, and autoradiography with blocking experiments indicated specific binding of [18F]5a to σ1 receptors in vitro and in vivo. Small animal positron emission tomography (PET) imaging using mouse tumor xenograft models demonstrated a high accumulation in human carcinoma and melanoma. Treatment with haloperidol significantly reduced the accumulation of the radiotracer in tumors. These findings suggest that radiotracer with suitable lipophilicity and appropriate affinity for σ1 receptors could be used for tumor imaging.
Keywords: 8 [4 (2 fluoroethoxy)benzyl) 1,4 dioxa 8 azaspiro[4.5]decane f 18; fluorine 18; haloperidol; piperidine derivative; radioligand; radiopharmaceutical agent; sigma 1 opiate receptor; sigma 2 opiate receptor; unclassified drug; vesicular acetylcholine transporter Registration No. 22342

Complex antiferromagnetic structure in the intermediate-valence intermetallic Ce2RuZn4
Hartwig, S.; Prokes, K.; Hansen, T.; Ritter, C.; Gerke, B.; Pöttgen, R.; Mydosh, J. A.; Förster, T.
Abstract: Neutron powder diffraction experiments were performed on the intermediate-valence Ce2RuZn4 intermetallic compound and combined with magnetic bulk measurements including high magnetic field experiments up to 58 T. Previous theoretical studies suggest that only one (here Ce1) out of two inequivalent Ce sites ismagnetically active. Ce2RuZn4 orders antiferromagnetically at TN = 2.3 K. The magnetic structure is characterized by an incommensurate propagation vector qm = (0.384, 0.384, 1/2). Assuming that the Ce2 site does not carry any substantial moment, Ce1 magnetic moments are confined to the (110)-type planes and transversely modulated with an amplitude of 1.77(3) μB. Registration No. 22341

Atomic scale interface design and characterisation
Bittencourt, C.; Ewels, C.; Krasheninnikov, A. V.
Abstract: There is no abstract
Keywords: nanotechnology


Registration No. 22339

Development and Validation of Advanced Theoretical Modeling for Churn-Turbulent Flows and Subsequent Transitions
Montoya Zabala, G. A.
Abstract: The applicability of CFD codes for two-phase flows has always been limited to special cases due to the very complex nature of its interface. Due to its tremendous computational cost, methods based on direct resolution of the interface are not applicable to most problems of practical relevance. Instead, averaging procedures are commonly used for these applications, such as the Eulerian-Eulerian approach, which necessarily means losing detailed information on the interfacial structure. In order to allow widespread application of the two-fluid approach, closure models are required to reintroduce in the simulations the correct interfacial mass, momentum, and heat transfer.
It is evident that such closure models will strongly depend on the specific flow pattern. When considering vertical pipe flow with low gas volume flow rates, bubbly flow occurs. With increasing gas volume flow rates larger bubbles are generated by bubble coalescence, which further leads to transition to slug, churn-turbulent, and annular flow. Considering, as an example, a heated tube producing steam by evaporation, as in the case of a vertical steam generator, all these flow patterns including transitions are expected to occur in the system. Despite extensive attempts, robust and accurate simulations approaches for such conditions are still lacking.
The purpose of this dissertation is the development, testing, and validation of a multifield model for adiabatic gas-liquid flows at high gas volume fractions, for which a multiple-size bubble approach has been implemented by separating the gas structures into a specified number of groups, each of which represents a prescribed range of sizes. A fully-resolved continuous gas phase is also computed, and represents all the gas structures which are large enough to be resolved within the computational mesh. The concept, known as GENeralized TwO Phase flow or GENTOP, is formulated as an extension to the bubble population balance approach known as the inhomogeneous MUltiple SIze Group (iMUSIG). Within the polydispersed gas, bubble coalescence and breakup allow the transfer between different size structures, while the modeling of mass transfer between the polydispersed and continuous gas allows including transitions between different gas morphologies depending on the flow situations. The calculations were performed using the computational fluid dynamic code from ANSYS, CFX 14.5, with the support of STAR-CCM+ v8.06 and v9.02. A complete three-field and four-field model, including a continuous liquid field and two to three gas fields representing bubbles of different sizes, were first tested for numerical convergence and then validated against experimental data from the TOPFLOW and MT-Loop facilities.

Keywords: CFD, GENTOP, Surface Tension, MT-Loop, TOPFLOW
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-063 2015


Registration No. 22338

Solubility of boron, carbon, and nitrogen in transition metals: getting insight into trends from first-principles calculations
Hu, X.; Björkman, T.; Lipsanen, H.; Sun, L.; Krasheninnikov, A. V.
Abstract: Efficient chemical vapor deposition synthesis of two-dimensional (2D) materials such as graphene, boron nitride, and mixed BCN systems with tunable band gaps requires precise knowledge of the solubility and mobility of B/C/N atoms in the transition metals (TMs) used as substrates for the growth. Yet, surprisingly little is known about these quantities either from experiments or simulations. Using first-principles calculations, we systematically study the behavior of B/C/N impurity atoms in a wide range of TMs. We compute formation energies of B/C/N interstitials and demonstrate that they exhibit a peculiar but common behavior for TMs in different rows of the periodic table, as experimentally observed for C. Our simulations indicate that this behavior originates from an interplay between the unit cell volume and filling of the d- shell electronic states of the metals. We further assess the vibrational and electronic entropic contributions to the solubility, as well as the role of anharmonic effects. Finally, we calculate the migration barriers, an important parameter in the growth kinetics. Our results not only unravel the fundamental behavior of interstitials in TMs but also provide a large body of reference data, which can be used for optimizing the growth of 2D BCN materials.
Keywords: graphene, solubility, interstitials Registration No. 22337

Broadband THz detection from 0.1 to 22 THz with large area field-effect transistors
Regensburger, S.; Mittendorff, M.; Winnerl, S.; Lu, H.; Gossard, A. C.; Preu, S.
Abstract: We report on ultrafast detection of radiation between 100 GHz and 22 THz by field-effect transistors in a large area configuration. With the exception of the Reststrahlenband of GaAs, the spectral coverage of the GaAs-based detectors is more than two orders of magnitude, covering the entire THz range (100 GHz - 10 THz). The temporal resolution of the robust devices is yet limited by the 30GHz oscilloscope used for read out. The responsivity roll-off towards higher frequencies is weaker than expected from an RC-roll-off model. Terahertz pulses with peak powers of up to 65 kW have been recorded without damaging the devices.
Keywords: terahertz detetector, field-effect transistor, braodband and fast THz detection


Registration No. 22334

X-ray Absorption Spectroscopy for Actinide Chemistry - Basics, Experiments and Applications
Ikeda-Ohno, A.
Abstract: Synchrotron-based X-ray spectroscopy is an emerging and powerful tool for actinide chemistry. This lecture focuses particularly on X-ray absorption spectroscopy, and will provide a comprehensive overview of the basics and experiments of this technique, as well as their applications to actinide chemistry.
Keywords: X-ray absorption spectroscopy; XAS; XANES; EXAFS; synchrotron; actinide; chemistry; overview; introduction
  • Invited lecture (Conferences)
    The ThUL School in Actinide Chemistry, 28.09.-02.10.2015, Karlsruhe, Germany
Registration No. 22332

Targeting lysyl oxidase for molecular imaging in breast cancer
Wuest, M.; Kuchar, M.; Sharma, S. K.; Richter, S.; Hamann, I.; Wang, M.; Vos, L.; Mackey, John R.; Wuest, F.; Löser, R.
Abstract: Introduction: Lysyl oxidase (LOX; ExPASy ENZYME entry: EC and members of the LOX-like family, LOXL1–LOXL4, are copper-dependent enzymes that can modify proteins of the extracellular matrix. Expression of LOX is elevated in many human cancers, including breast cancer. LOX expression correlates with the level of tissue hypoxia, and it is known to play a critical role in breast cancer metastasis. The goal of the present study was to target LOX with (1) molecular probe fluorescent labeling to visualize LOX in vitro and (2) a radiolabeled peptide to target LOX in vivo in three different preclinical models of breast cancer.
Methods: Gene expression of all five members of the LOX family was analyzed at the transcript level via microarray analysis using tissue biopsy samples from 176 patients with breast cancer. An oligopeptide sequence (GGGDPKGGGGG) was selected as a substrate-based, LOX-targeting structure. The peptide was labeled with fluorescein isothiocyanate (FITC) for confocal microscopy experiments with the murine breast cancer cell line EMT-6. In vivo molecular imaging experiments were performed using a C-terminal amidated peptide, GGGDPKGGGGG, labeled with a short-lived positron emitter, fluorine-18 (18F), for positron emission tomography (PET) in three different breast cancer models: EMT6, MCF-7 and MDA-MB-231. The PET experiments were carried out in the presence or absence of β-aminopropionitrile (BAPN), an irreversible inhibitor of LOX.
Results: Immunostaining experiments using a LOX-specific antibody on EMT-6 cells cultured under hypoxic conditions confirmed the elevation of LOX expression in these cells. An FITC-labeled oligopeptide, FITC-Ava- GGGDPKGGGGG-NH2, was found to be localized in different cellular compartments under these conditions. After injection of [18F]fluorobenzoate-GGGDPKGGGGG-NH2, radioactivity uptake was visible in all three breast cancer models in vivo. Tumor uptake was reduced by predosing the animals with 2 mg of BAPN 4 h or 24 h before injection of the radiotracer.
Conclusions: The present data support further investigation into the development of LOX-binding radiolabeled peptides as molecular probes for molecular imaging of LOX expression in cancer.


Registration No. 22331

Ultrasound Doppler flow measurements in a liquid metal column under the influence of a strong axial electric current
Starace, M.; Weber, N.; Seilmayer, M.; Kasprzyk, C.; Weier, T.; Stefani, F.; Eckert, S.
Abstract: Magnetohydrodynamic instabilities can constitute a serious hazard to the functionality of liquid metal batteries. Here we consider the Tayler instability, which appears when the electric current, passing through a conducting fluid, reaches a critical value. The experiment discussed in this article involves a column of a eutectic GaInSn alloy, along whose axis an electric current passes. Ultrasound transducers encased in a copper electrode bounding the top of the column were used to obtain the vertical component of fluid flow, once a noise suppression system had been devised. The data thus retrieved will be discussed here.
  • Magnetohydrodynamics 51(2015)2, 249-256
    Button zum Volltext
Registration No. 22330

Ion acceleration enhanced by target ablation
Zhao, S.; Lin, C.; Wang, H. Y.; Lu, H.; Tu He, X.; Chen, J.; Cowan, T. E.; Q. Yan, X.
Abstract: Laser proton acceleration can be enhanced by using target ablation, due to the energetic electrons generated in the ablation preplasma. When the ablation pulse matches main pulse, the enhancement gets optimized because the electrons' energy density is highest. A scaling law between the ablation pulse and main pulse is confirmed by the simulation, showing that for given CPA pulse and target, proton energy improvement can be achieved several times by adjusting the target ablation. Registration No. 22329

Caustic structures in the spectrum of x-ray Compton scattering off electrons driven by a short intense laser pulse
Seipt, D.; Surzhykov, A.; Fritzsche, S.; Kämpfer, B.
Abstract: We study the Compton scattering of x-rays off electrons that are driven by a relativistically intense short optical laser pulse. The frequency spectrum of the laser-assisted Compton radiation shows a broad plateau in the vicinity of the laser-free Compton line due to a nonlinear mixing between x-ray and laser photons. Special emphasis is placed on how the shape of the short assisting laser pulse affects the spectrum of the scattered x-rays. In particular, we observe sharp peak structures in the plateau region, whose number and locations are highly sensitive to the laser pulse shape. These structures are interpreted as spectral caustics by using a semiclassical analysis of the laser-assisted QED matrix element. Registration No. 22328

Post-test calculations of UPTF experiments with ANSYS CFX
Höhne, T.
Abstract: The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.
The nuclear industry now also recognizes that CFD codes have reached the desired level of maturity (at least for single-phase applications) for them to be used as part of the Nuclear Power Plant (NPP) design process, and it is the objective the research and development teams to assess the current capabilities of such codes in this regard, and contribute to the technology advance in respect to their verification and validation. CFD is already well-established in addressing certain safety issues in NPPs, as reported and discussed at various international workshops. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. In parallel, it remains an overriding necessity to benchmark the performance of the CFD codes, and for this experimental databases need to be established, first for separate-effect tests but especially for full-size integral tests.
In order to validate the CFD Code ANSYS CFX for reactor safety relevant flow phenomena it is essential to use the UPTF experiments, since they are full scale tests. All other separate effect test rigs and test facilities like ROCOM (Höhne, 2000) are scaled. Scaling parameters of flow conditions are one of the still open topics for the use of CFD codes in nuclear reactor safety. Three UPTF tests were selected and post-test calculation were performed. The major focus was analyzing the qualitative flow behavior.

Keywords: UPTF, CFX, LOCA, PTS
  • Other report
    Dresden: HZDR, 2015
    25 Seiten
Registration No. 22324

H trapping and mobility in nanostructured tungsten grain boundaries: A combined experimental and theoretical approach
González, C.; Panizo-Laiz, M.; Gordillo, N.; Tejado, E.; Munnik, F.; Guerrero, C.; Piaggi, P.; Iglesias, R.; Perlado, J. M.; González-Arrabal, R.
Abstract: The H trapping and mobility in nanostructured W grain boundaries has been studied by combining experimental and density functional theory (DFT) data. Experimental results show that nanostructured W coatings with a columnar structure and a large number of (110)/(211) interfaces retain more H than the coarsed grained W tungsten samples do. To investigate the possible influence of grain boundaries on the H retention, a complete energetic analysis has been done in a semi-coherent W(110)/W(112) interface built by DFT. Our results show that this kind of non-coherent interface largely attract points defects (both H atom and metallic monovacancy separately) and that the presence of these interfaces contribute to decrease the migration energy of the H atoms with respect to the bulk. When both W monovacancy and H atom are introduced together into the system, the HV complex results the most stable configuration suggesting an explanation to the H retention in the GB observed experimentally.
Keywords: Fusion, H trapping Registration No. 22323

Terahertz spectroscopy of 0D and 2D semiconductors with a free-electron laser
Schneider, H.
Abstract: This talk reviews recent experimental studies carried out using the free-electron laser (FEL) facility FELBE in Dresden, Germany. Intense, nearly transform-limited ps pulses in the mid-infrared and terahertz (THz) regimes provide unique research opportunities to study novel materials and devices.
Keywords: free-electron laser, terahertz spectroscopy
  • Lecture (others)
    Seminar, Xi'an University of Technology, 04.05.2015, Xi'an, China
  • Lecture (others)
    Seminar, CAEP, 07.05.2015, Mianyang, China
Registration No. 22321

In Situ Tuning the Conductance of Single Molecular Diarylethene Switches
Sendler, T.; Luka-Guth, K.; Wieser, M.; Lokamani, M.; Wolf, J.; Huhn, T.; Scheer, E.; Kerbusch, J.; Gemming, S.; Erbe, A.
Abstract: A major goal of molecular electronics is the development and implementation of molecular electronic devices such as single molecular switches. In this work we present a detailed study of single diarylethene molecules that were in situ switched from their non-conductive to conductive state in the presence of gold nanoelectrodes via controlled light irradiation. The molecules were dissolved in two different solvents and measured with two different side-groups. Histograms of conductance traces were taken and complemented by extracting the relative position of the current carrying molecular level and its level broadening from current-voltage characteristics by means of the single level transport model. The obtained results show a clear light-induced ring forming isomerization, which is almost independent of the side-groups, while electron withdrawing side groups lead to a reduction of conductance, a decrease of the level broadening and an increased difference between the molecular level and the Fermi energy of the metals. Quantum chemical calculations of the light-induced switching processes correlate these observations with the fundamentally different low-lying electronic states of the opened and closed forms and their comparably small modification by the electron-withdrawing substituents.
  • Poster
    Annual Workshop IHRS NanoNet 2014, 29.-30.09.2014, Lohmen/Bastei, Deutschland
  • Poster
    DCCMS Annual Workshop and General Assembly 2014, 20.10.2014, Dresden, Deutschland
Registration No. 22316
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