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24338 Publications
European activities on crosscutting thermal-hydraulic phenomena for innovative nuclear systems
Cheng, X.; Batta, A.; Bandini, G.; Roelofs, F.; van Tichelen, K.; Gerschenfeld, A.; Prasser, M.; Papukchiev, A.; Hampel, U.; Ma, W. M.
Abstract: Thermal-hydraulics is recognized as a key scientific subject in the development of innovative reactor systems. In Europe, a consortium is established consisting of 24 institutions of universities, research centers and nuclear industries with the main objectives to identify and to perform research activities on important crosscutting thermal-hydraulic issues encountered in various innovative nuclear systems. For this purpose the large-scale integrated research project THINS (Thermal-Hydraulics of Innovative Nuclear Systems) is launched in the 7th Framework Programme FP7 of European Union. The main topics considered in the THINS project are (a) advanced reactor core thermal-hydraulics, (b) single phase mixed convection, (c) single phase turbulence, (d) multiphase flow, and (e) numerical code coupling and qualification. The main objectives of the project are:
Generation of a data base for the development and validation of new models and codes describing the selected crosscutting thermal-hydraulic phenomena.
Development of new physical models and modeling approaches for more accurate description of the crosscutting thermal-hydraulic phenomena.
Improvement of the numerical engineering tools for the design analysis of the innovative nuclear systems.
This paper describes the technical tasks and methodologies applied to achieve the objectives. Main results achieved so far are summarized.
Registration No. 22269

Formation of Ge-0 and GeOx nanoclusters in Ge+-implanted SiO2/Sithin-film heterostructures under rapid thermal annealing
Zatsepin, A. F.; Zatsepin, D. A.; Zhidkov, I. S.; Kurmaev, E. Z.; Fitting, H. J.; Schmidt, B.; Mikhailovich, A. P.; Lawniczak-Jablonska, K.
Abstract: The results of X-ray photoelectron spectra (XPS valence band and core levels) measurements for Ge+ implanted SiO2/Si heterostructures are presented. These heterostructures have a 30 nm thick Ge+ ion implanted amorphous SiO2 layer on p-type Si. The chemical-state transformation of the host-matrix composition after Ge+ ion implantation and rapid thermal annealing (RTA) are discussed. The XPS-analysis performed allows to conclude the formation of Ge-o and GeOx clusters within the samples under study. It was established, that the annealing time strongly affects the degree of oxidation states of Ge-atoms
Keywords: RAY PHOTOELECTRON-SPECTROSCOPY; OXYGEN; LAYERS; FILMS; SI+; CATHODOLUMINESCENCE; TRANSFORMATIONS; SIO2; XPS Registration No. 22267

Annual Report 2014 - Institute of Ion Beam Physics and Materials Research
Fassbender, J.; Heera, V.; Helm, M.; Zahn, P. (Editors)
Abstract: This past year 2014 was the year when we finally completely arrived as a “full member” in the Helmholtz Association. This is related to the successfully passed research evaluation in the framework of the Program Oriented Funding (POF), which will give us a stable and predictable funding for the next five years (2015 – 2019). This is particularly true for our large-scale user facilities, like the Ion Beam Center (IBC) and the electron accelerator ELBE with the free-electron laser. Most of our activities are assigned to the program “From Matter to Materials and Life” within the research area “Matter”, in cooperation with several other German Helmholtz Centers. Our in-house research is performed in three so-called research themes, as depicted in the schematic below. What is missing there for simplicity is a small part of our activities in the program “Nuclear Waste Management and Safety” within the research area “Energy”.

Our research and facilities were well appreciated by the evaluation committee, who made the following judgement about the Ion Beam Center:
“The Ion Beam Centre (IBC) of HZDR is an internationally leading ion-beam facility (with ion energies ranging from several eV to several tens of MeV). At both the national and international level it is one of the key players and is unique in its kind. The synergy between forefront research and user service has been leading to a very good publication output for both in-house research and user research. …
The very broad range of beam energies, the versatility of techniques and applications – both for ion beam modification of materials and for ion-beam analysis – makes the IBC unique in its kind. …
The strength of IBC is that its activities are based on a combination of forefront research and user service, which mutually interact in synergy and strengthen one another. In turn, this synergy has been leading to a very good publication output for both in-house research and user research.”
In order to make our Annual Report a bit more compact, we have decided to include only four full journal papers this year. This was also triggered by the fact that our publication activities have turned out be become more diverse, in more diverse journals than in the past, and often through longer papers, which would be too long to reprint them here. However, apart from the constantly quantitatively high publication output, we succeeded to publish in excellent journals such as Nature Physics, Nano Letters and Physical Review Letters, in fields as diverse as ion beam physics, magnetism and terahertz spectroscopy.
Two of our scientists, Dr. Artur Erbe and Dr. Alexej Pashkin obtained their Habilitation in 2014, both at University of Konstanz. For the first time, we are hosting an Emmy Noether Young Investigator Group funded by the Deutsche Forschungsgemeinschaft (DFG); the group works on the hot topic of magnonics and is headed by Dr. Helmut Schultheiß.
Finally we would like to cordially thank all partners, friends, and organizations who supported our progress in 2014. Special thanks are due to the Executive Board of the Helmholtz-Zentrum Dresden-Rossendorf, the Minister of Science and Arts of the Free State of Saxony, and the Minister of Education and Research of the Federal Government of Germany. Numerous partners from universities, industry and research institutes all around the world contributed essentially, and play a crucial role for the further development of the institute. Last but not least, the directors would like to thank again all IIM staff for their efforts and excellent contributions in 2014.
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-060 2015

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Registration No. 22263

Building a New Assessment Tool for Potential Rare Earth Underground Mining Projects
Barakos, G.; Mischo, H.
Abstract: Once an ore body has been probed and outlined and initial resource indications deserve further attention, the evaluation stage has to begin to determine the potential exploitation. This analysis is a sophisticated process, let alone when it comes to underground mining projects and especially on rare earth deposits that are governed by notable boundary conditions. However, the significant numbers of the parameters to be considered and their complexity, as well as the solvency of the outcomes, often result in questioning the suitability of common evaluation methods. This has created a necessity for a new evaluation procedure that focuses on potential rare earth underground mining projects. This paper describes the construction development of an assessment tool that considers not only the mining method selection process but identifies social, economic and environmental impact factors and Rare Earth Element industry-specific criteria as well. Based on the philosophy of previous linguistic and numerical approaches, this combined tool is based on a step-by-step numerical analytical hierarchical process with weighted criteria. The purpose of building this tool is to adjust to the specifications of rare earth underground mining projects and to contribute into having accurate and secure con-clusions for if and when investment decisions should be made and minimize the potential risks regarding the viability of any mining project.
Keywords: rare earths, underground mining method selection, viability, assessment tool
  • Contribution to proceedings
    7th Sustainable Development In Minerals Industry Conference (SDIMI 2015), 12.-15.07.2015, Vancouver, Canada
    Proceedings of SDIMI 2015, Vancouver: University of British Columbia
Registration No. 22260

Setting the REE industry-specific criteria and their significant role in the viability of rare earth underground mining projects
Barakos, G.; Mischo, H.
Abstract: To evaluate the feasibility of a future underground mining operation is a complex problem in itself, with several different parameters to be accounted for and evaluated to secure investment decisions over the viability of any potential underground mining project. This procedure gets even more complicated when it comes to exploiting rare earth deposits. Various concerns are expressed regarding the environmental impacts that an underground mining operation may cause due to the radioactivity of the rare earth elements during mining and in waste treatment. Furthermore, the fragile market and the diversified supply and demand of the different rare earth elements can significantly affect the viability of such a venture, among other factors. This paper deals with the definition and classification of the specific criteria that govern the REE mining industry. Moreover, a thorough investigation is made of how these criteria can determine not only the selection of the underground mining method to be applied, but also of the impact that they may have to the overall feasibility of any given potential project.
Keywords: rare earth elements, underground mining, sustainability, environmental impacts, balance problem
  • Contribution to proceedings
    26th Annual Meeting & Conference of the Society of Mining Professors, 21.-26.06.2015, Freiberg, Deutschland
    Proceedings of the 26th Annual Meeting & Conference of the Society of Mining Professors, Backnang, Stuttgart: WIRmachenDRUCK, 978-3-86012-505-2
Registration No. 22259

Simulation studies for the in-vivo dose verification of particle therapy
Rohling, H.
Abstract: An increasing number of cancer patients is treated with proton beams or other light ion beams which allow to deliver dose precisely to the tumor. However, the depth dose distribution of these particles, which enables this precision, is sensitive to deviations from the treatment plan, as e.g. anatomical changes. Thus, to assure the quality of the treatment, a non-invasive in-vivo dose verification is highly desired. This monitoring of particle therapy relies on the detection of secondary radiation which is produced by interactions between the beam particles and the nuclei of the patient’s tissue.
Up to now, the only clinically applied method for in-vivo dosimetry is Positron Emission Tomography which makes use of the beta+-activity produced during the irradiation (PT-PET). Since from a PT-PET measurement the applied dose cannot be directly deduced, the simulated distribution of beta+-emitting nuclei is used as a basis for the analysis of the measured PT-PET data. Therefore, the reliable modeling of the production rates and the spatial distribution of the beta+-emitters is required. PT-PET applied during instead of after the treatment is referred to as in-beam PET. A challenge concerning in-beam PET is the design of the PET camera, because a standard full-ring scanner is not feasible. For instance, a double-head PET camera is applicable, but low count rates and the limited solid angle coverage can compromise the image quality. For this reason, a detector system which provides a time resolution allowing the incorporation of time-of-flight information (TOF) into the iterative reconstruction algorithm is desired to improve the quality of the reconstructed images.
Secondly, Prompt Gamma Imaging (PGI), a technique based on the detection of prompt gamma-rays, is currently pursued. Concerning the emissions of prompt gamma-rays during particle irradiation, experimental data is not sufficiently available, making simulations necessary. Compton cameras are based on the detection of incoherently scattered photons and are investigated with respect to PGI. Monte Carlo simulations serve for the optimization of the camera design and the evaluation of criteria for the selection of measured events.
Thus, for in-beam PET and PGI dedicated detection systems and, moreover, profound knowledge about the corresponding radiation fields are required. Using various simulation codes, this thesis contributes to the modelling of the beta+-emitters and photons produced during particle irradiation, as well as to the evaluation and optimization of hardware for both techniques.
Concerning the modeling of the production of the relevant beta+-emitters, the abilities of the Monte Carlo simulation code PHITS and of the deterministic, one-dimensional code HIBRAC were assessed. The Monte Carlo tool GEANT4 was applied for an additional comparison. For irradiations with protons, helium, lithium, and carbon, the depth-dependent yields of the simulated beta+-emitters were compared to experimental data. In general, PHITS underestimated the yields of the considered beta+-emitters in contrast to GEANT4 which provided acceptable values. HIBRAC was substantially extended to enable the modeling of the depth-dependent yields of specific nuclides. For proton beams and carbon ion beams HIBRAC can compete with GEANT4 for this application. Since HIBRAC is fast, compact, and easy to modify, it could be a basis for the simulations of the beta+-emitters in clinical application. PHITS was also applied to the modeling of prompt gamma-rays during proton irradiation following an experimental setup. From this study, it can be concluded that PHITS could be an alternative to GEANT4 in this context.
Another aim was the optimization of Compton camera prototypes. GEANT4 simulations were carried out with the focus on detection probabilities and the rate of valid events. Based on the results, the feasibility of a Compton camera setup consisting of a CZT detector and an LSO or BGO detector was confirmed. Several recommendations concerning the design and arrangement of the Compton camera prototype were derived. Furthermore, several promising event selection strategies were evaluated. The GEANT4 simulations were validated by comparing simulated to measured energy depositions in the detector layers. This comparison also led to the reconsideration of the efficiency of the prototype. A further study evaluated if electron-positron pairs resulting from pair productions could be detected with the existing prototype in addition to Compton events. Regarding the efficiency and the achievable angular resolution, the successful application of the considered prototype as pair production camera to the monitoring of particle therapy is questionable.
Finally, the application of a PET camera consisting of Resistive Plate Chambers (RPCs) providing a good time resolution to in-beam PET was discussed. A scintillator-based PET camera based on a commercially available scanner was used as reference. This evaluation included simulations of the detector response, the image reconstructions using various procedures, and the analysis of image quality. Realistic activity distributions based on real treatment plans for carbon ion therapy were used. The low efficiency of the RPC-based PET camera led to images of poor quality. Neither visually nor with the semi-automatic tool YaPET a reliable detectability of range deviations was possible. The incorporation of TOF into the iterative reconstruction algorithm was especially advantageous for the considered RPC-based PET camera in terms of convergence and artifacts.
The application of the real-time capable back projection method Direct TOF for the RPCbased PET camera resulted in an image quality comparable to the one achieved with the iterative algorihms. In total, this study does not indicate the further investigation of RPC-based PET cameras with similar efficiency for in-beam PET application.
To sum up, simulation studies were performed aimed at the progress of in-vivo dosimetry. Regarding the modeling of the beta+-emitter production and prompt gamma-ray emissions, different simulation codes were evaluated. HIBRAC could be a basis for clinical PT-PET simulations, however, a detailed validation of the underlying cross section models is required. Several recommendations for the optimization of a Compton Camera prototype resulted from systematic variations of the setup. Nevertheless, the definite evaluation of the feasibility of a Compton camera for PGI can only be performed by further experiments. For PT-PET, the efficiency of the detector system is the crucial factor. Due to the obtained results for the considered RPC-based PET camera, the focus should be kept to scintillator-based PET cameras for this purpose.

Keywords: Monte-Carlo Simulation, Partikeltherapie, in-vivo Reichweitenkontrolle, GEANT4, PHITS, Prompt Gamma Imaging, Compton-Kamera, Positronen-Emissions-Tomographie, Paarbildungskamera, Monte Carlo simulation, particle therapy, in-vivo range verification, GEANT4, PHITS, Prompt Gamma Imaging, Compton camera, positron emission tomography
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-062 2015
    ISSN: 2191-8716

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Registration No. 22256

Polyatomic Focused Ion Beams – Origin and Applications
Bischoff, L.
Abstract: In the last four decades Focused Ion Beams (FIB) have evolved from a sophisticated idea to a distinguished standard technique for sample preparation for SEM and TEM, prototyping in research and development and analytics in fields like microelectronics or nanotechnology. Most of the FIB systems works with Ga beams, but liquid metal ion sources (LMIS) provide a much broader spectrum of other ion species using different source materials and an ion optical column equipped with an ExB mass separator [1]. From the source tip beside single and double charged monatomic ions also dimers, trimers and heavier projectiles are extracted, which play an increasing role due to their special properties, like slight penetration depth, enhanced sputtering efficiency and the huge energy deposition due to the simultaneous impact of several atoms in the same point of the surface.
Beside others heavy elements or alloys, those containing Au but in particular Bi are very appropriate for the emission of polyatomic ions. Such projectiles with masses up to about 1000 amu have an energy spread in the range of ΔEFWHM = 30 … 150 eV, which restrict the final FIB resolution (spot size) due to chromatic aberration to 10 to 100 nm. This is a result of the complex appearance of polyatomic species in the area around the emission point.
One of the main application fields at present is SIMS, which increasingly works with polyatomic Bi beams for defined surface erosion on inorganic as well as organic specimen [2]. A second exciting field of application is the surface modification in terms of surface patterning by heavy dimer and trimer ions (e.g. Aunm+, Binm+). Due to the enormous energy transfer by the cluster ions to the surface a self-organization process of hexagonal ordered dot arrays on Ge and Si could be found surprisingly for pure elemental targets at normal incidence, described by the formation of tiny melt pools [3] shown in the figure.

[1] L. Bischoff, Nucl. Instr. Meth. B 266 (2008) 1846.
[2] F. Kollmer, Appl. Surf. Sci. 231-232 (2004) 153.
[3] R. Böttger, L. Bischoff, K.-H. Heinig, W. Pilz and B. Schmidt, JVST B 30 (2012) 06FF12.

Keywords: FIB, Cluster ions, LMIS, self-assembly
  • Lecture (Conference)
    10. Dreiländer-FIB-Workshop, 29.-30.06.2015, Halle, Germany
Registration No. 22254

Spin-transfer effects in MgO-based tunnel junctions with an out-of-plane free layer and in-plane polarizer
Kowalska, E.; Sluka, V.; Fowley, C.; Kakay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Deac, A. M.
Abstract: Spin-torque nano-oscillators (STNOs) are novel devices which may be exploited for wireless communication applications [1-3]. In particular, it has recently been demonstrated that STNOs utilizing an in-plane (IP) magnetized polarizer (also acting as read-out layer) and out-of-plane (OOP) magnetized free layer allow for the full parallel (P)-to-antiparallel (AP) resistance variation to be exploited in the limit of 90° precession angle, thereby maximizing the output power [1]. However, for this specific geometry, steady-state precession can only be sustained if the spin-transfer torque exhibits an asymmetric dependence on the angle between the free and the polarizing layer, such as in the case of fully metallic devices [1]. Nevertheless, it has recently been reported that dynamics have been experimentally observed in similarly designed MgO-based MTJs under constant applied electrical current, in spite of the fact that such devices do not exhibit any asymmetry in the spin-torque angular dependence [4,5]. These results have so far been interpreted based on the formalism for metallic devices, including the spin-torque angular dependence.
Here, we explore potential mechanisms for sustaining steady-state precession in MgO-based MTJs with an IP polarizer and an OOP free layer. To this end, we analytically and numerically solve the Landau-Lifshitz-Gilbert-Slonczewski equation for a nano-pillar MTJ with circular cross-section, under a constant perpendicular applied current and field. To sustain steady-state precession, the energy supplied by the in-plane spin-torque term and energy dissipated through damping must compensate over a full precession period.
In an MgO-MTJ, the magnitude of the STT is determined by the voltage across the barrier [6]. As the magnetization of the free layer precesses around the put-of-plane direction, the angle between the magnetic moments of the two layers changes and through the magnetoresistance effect the voltage changes if the experiment is conducted at constant applied current [7,8]. This cosine-like angular dependence of the MTJ resistance effectively introduces a spin-torque angle dependence asymmetry. In addition, for a given angle, the resistance exhibits a specific bias dependence, with the resistance of the AP state decreasing approximately linearly with increasing bias, while remaining mostly constant in the P configuration. In this work, we demonstrate that the spin-torque angular asymmetry exhibited in such systems is sufficient to sustain STT-driven dynamics.
Fig. 1 shows dynamic and static phase diagrams of the STNO obtained when neglecting (Fig. 1(a) and 1(c)) and taking into account (Fig. 1(b) and 1(d)) the bias dependence of the AP state resistance. In both cases, stable dynamics occur only for positive currents (colored area), defined as electrons flowing from the free to the reference layer. In MTJs exhibiting no bias dependence of the resistance (dRAP/dV = 0 Ω/V), the onset current for steady-state dynamics (solid lines) scales linearly with the applied current. High output powers can be obtained for relatively low values of applied currents and fields for realistic MTJ parameters, which is beneficial from the point of view of applications. Introducing an experimentally realistic value of dRAP/dV affects mostly the steady-state dynamics, while most of the trends observed for static states are maintained (Fig. 1(b) and 1(d)). Indeed, in this case current-driven precession is only excited for fields lower than the effective anisotropy of the free layer (but still only for positive currents). Moreover, while the symmetry versus field sign is conserved, the onset current no longer increases linearly with the field, but rather exhibits a parabolic-like dependence.

Keywords: spin-torque nano-oscillators (STNOs), magnetic tunnel junctions (MTJs)
  • Poster
    International Colloquium on Magnetic Films and Surfaces (ICMFS 2015), 12.-17.07.2015, Cracow, Poland
Registration No. 22252

Ion microprobe PIXE and PIGE analysis of standards’ trace elements for electron microprobe calibration.
Le Bras, L.; Munnik, F.; Renno, A. D.
Abstract: The purpose of this study is, with the recorded data, to be able to calibrate microanalytical methods, in particular electron microprobe with high precision chemical data standards. Analysis on selected standards by ion microprobe Particle-Induced-X-ray-Emission (PIXE) and Particle-Induced-Gamma-ray-Emission (PIGE) are used to detect and quantify the trace and light elements present in these samples. The presence of those elements makes a specific calibration of the machines necessary.
Electron- and X-ray measurements need good standards for a good quantification of the elements of interest. Actually, certified reference materials for microanalytical methods are very rare. In addition they are mainly glass samples. Utilisation of chosen minerals fixed in a matrix instead of glasses for calibration makes possible the application of the matrix-matched principle and the detection and quantification of trace elements in natural minerals for a resource technology application.
The widespread utilisation of Smithsonian Microbeam Standards makes this study relevant. That is why a 10 sample selection has been made in this collection. The samples’ theoretical compositions in major and trace elements are very important for the achievement of the analysis. In addition to the given element concentrations [1], a bibliographic study has also been performed for each standard in order to find possible trace elements which could be detected.
The standards received from the Smithsonian Institute are composed of crushed particles (500 µm diameter). The sample preparation is also essential. It consists in the fixation of three particles with epoxy resin into a 3 mm diameter messing cylinder.
The analyses are performed with an incident proton beam of 3.5 MeV in order to acquire simultaneously X- and Gamma-ray spectra. The data analysis is performed with GeoPIXE in order to add qualitative and quantitative data about trace elements to the given composition of the major elements. Preliminary results on apatite (NMNH 104021) are in agreement with the literature and show the presence of vanadium, arsenic, strontium, yttrium and light Rare Earth Elements such as lanthanum, cerium and neodymium. These trace elements are important for mineral resources analysis. Elemental mapping is also achieved in order to check the homogeneity of the samples’ particles.

Acknowledgements: Special thanks to Andreas Bartzsch, from the sample’s preparation laboratory of the Helmholtz Institute Freiberg, Germany, for his expertise.

[1] E. Jarosewich, J. A. Nelen, J. A. Norberg, Geostandards Newsletter 4 1980, p. 43-47

Keywords: Mineral standards, PIXE, PIGE, calibration, electron microprobe
  • Lecture (Conference)
    Workshop für Ionenstrahlen und Nanostrukturen, 22.-24.07.2015, Heidelberg, Germany
Registration No. 22249

A comprehensive study on iodine uptake by selected LDH phases via coprecipitation, anionic exchange and reconstruction
Iglesias, L.; Walther, C.; Medina, F.; Holzer, A.; Neumann, A.; Lozano-Rodriguez, M. Janeth; Alvarez, Mayra G.; Torapava, N.
Abstract: We explored the use of selected layered double hydroxides (LDHs) of different compositions and obtained by means of different routes (i.e., coprecipitation, anionic exchange and reconstruction) as iodine/iodate adsorbents. The influence of speciation (iodide vs. iodate) on iodine uptake was rather strong, resulting in much lower iodide incorporation. The Fourier transform of iodine K X-ray absorption edge data (EXAFS) of all iodate-LDHs showed a single I–O scattering path of 1.8 A ° . Thermal stability and leaching experiments showed that the incorporated iodate and iodide were rather loosely bound in the interlayer space and were easily released under heating to 180 C and leaching with Milli-Q water and brine solution.
Keywords: Iodine, Layered double hydroxide, Immobilization, Nuclear waste, Aqueous systems Registration No. 22248

Coffinite, USiO4, Is Abundant in Nature: So Why Is It So Difficult To Synthesize?
Mesbah, A.; Szenknect, S.; Clavier, N.; Lozano-Rodriguez, J.; Poinssot, C.; Den Auwer, C.; Ewing, R. C.; Dacheux, N.
Abstract: Coffinite, USIO4, is the second most abundant U4+ mineral on Earth, and its formation by the alteration of the UO2 in spent nuclear fuel in a geologic repository may control the release of radionuclides to the environment. Despite its abundance in nature, the synthesis and characterization of coffinite have eluded researchers for decades. On the basis of the recent synthesis of USiO4, we can now define the experimental conditions under which coffinite is most efficiently formed. Optimal formation conditions are defined for four parameters: pH, T, heating time and U/Si molar ratio. The adjustment pf pH between 10 and 12 leads probably to the formation of a uranium (IV) hydroxo-silicate complex that acts as a precursor of uranium (IV) silicate colloids and then of coffinite. Moreover, in this pH range, the largest yield of coffinite formation (as compared with those of the two competing byproduct phases, nanometer-scale UO2 and amorphous SiO2) is obtained for 250 C, 7 days and 100% excess silica.
Keywords: coffinite, PXRD, EXAFS, XANES, Raman spectra Registration No. 22247

Relationship Between Kolmogorov Entropy and Characteristic Mixing Length in Narrow Bubble Columns Operated in the Transition Flow Regime
Nedeltchev, S.; Schubert, M.; Donath, Th.; Rabha, S.; Hampel, U.
Abstract: The mixing performance of bubble column reactors depends strongly on the prevailing flow regime. Kawase and Tokunaga (Can. J. Chem. Eng. 69, 1228-1231, 1991) introduced the characteristic mixing length L as an important mixing parameter. In the homogeneous regime the liquid mixing is at the scale of the bubble diameter, whereas in the heterogeneous regime it is at the scale of the column diameter. Our research is aimed at determining the scale of liquid mixing in the transition flow regime by using some advanced methods.
The Kolmogorov entropies (KE) were extracted from gas holdup time series measured (at 2000 Hz) by a new type of wire mesh sensor. It was found that in a relatively narrow bubble column (0.15 m in ID, clear liquid height = 2 m) operated with an air-water system in the transition flow regime the KE values could be correlated to L. The KE in the transition flow regime decreases monotonously and can be correlated to the superficial gas velocity (KE=1.5Ug^-0.38). The same exponent (-0.38) for UG was reported by Kawase and Tokunaga (1991) in their correlation for prediction of L. Therefore, the KE and L values (in a narrow bubble column) are correlated as follows: KE=222.222L.
A new parameter called maximum number of visits per region Nv-max was also introduced and in the same way was related to L in the transition flow regime.

Keywords: Narrow bubble column, Transition flow regime, Kolmogorov entropy, Mixing length, New statistical parameter
  • Lecture (Conference)
    Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-26.03.2014, Fulda, Deutschland
Registration No. 22244

18F-FDG PET/MRI for therapy response assessment in sarcoma: Comparison of PET and MR imaging results
Schuler, M. Kajo; Platzek, I.; Beuthien-Baumann, B.; Fenchel, M.; Ehninger, G. E.; van den Hoff, J.
Abstract: Background: 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) has proven to be of substantial benefit in imaging of sarcoma patients. We therefore investigated the feasibility and benefit of combined PET/magnetic resonance imaging (MRI). Methods: Twelve patients with sarcoma who underwent FDG PET/MRI for staging and response assessment after chemotherapy were included. Results: Based on contrast-enhanced MRI and application of Choi criteria, therapy response was classified as stable disease in 6/12 patients (50%) and as partial remission in 6/12 patients (50%). Conclusion: In sarcoma patients, response assessment using Choi criteria based on contrast-enhanced MRI in comparison to FDG PET imaging only demonstrates slight correlation.
Keywords: Cancer imaging; Choi criteria; FDG PET/MRI; Sarcoma Registration No. 22243

New Methods for Flow Regime Identification in Bubble Columns and Fluidized Beds
Nedeltchev, S.
Abstract: New methods for flow regime identification were developed and applied to photon count time series measured in a bubble column (0.162 m in ID) and fluidized bed (0.438 m in ID). The signals in the bubble column (operated with an air-therminol system) were measured by means of Computed Tomography (CT), whereas the data in the fluidized bed (operated with an air-polyethylene system) were recorded by means of Nuclear Gauge Densitometry (NGD). The hidden information in the time series was extracted by means of two new parameters: entropy (bit/s) and information entropy (bit). Both of them were calculated on the basis of multiple reconstructions of the time series. In the case of the bubble column, the well-pronounced local minima were used for identification of three transition velocities (0.04, 0.08 and 0.13 m/s). They distinguished the boundaries of the bubbly flow, transition and churn-turbulent flow regimes. In the case of the fluidized bed, the minimum fluidization velocity (0.086 m/s) and minimum bubbling velocity (0.12 m/s) were also identified on the basis of the well-pronounced local minima in the profiles of the new parameters. They distinguished the boundaries of both the transition and bubbling fluidization regimes.
Keywords: Flow regime identification, Bubble column, Fluidized bed, Transition velocities, Entropy, Information entropy Registration No. 22241

Efficient Auger scattering in Landau-quantized graphene
Wendler, F. H. Funk; Mittendorff, M.; Winnerl, S.; Helm, M.; Knorr, A.; Malic, E.
Abstract: We present an analytical expression for the differential transmission of a delta-shaped light field in Landauquantized graphene. This enables a direct comparison of experimental spectra to theoretical calculations reflecting the carrier dynamics including all relevant scattering channels. In particular, the relation is used to provide evidence for strong Auger scattering in Landau-quantized graphene.
Keywords: Graphene, ultrafast spectroscopy, Landau quantization, Auger scattering
  • Lecture (Conference)
    Photonics West Conference, 07.-12.02.2015, San Francisco, USA
  • Contribution to proceedings
    Photonics West Conference, 07.-12.02.2015, San Francisco, USA
    Proceedings of SPIE, 936105
    DOI-Link: http://dx.doi.org/10.1117/12.2075458
Registration No. 22238

Theoretical Prediction of Mass Transfer Coefficients in Two-Phase and Slurry Bubble Columns
Nedeltchev, S.
Abstract: Two-phase and slurry bubble columns are characterized with high volumetric mass transfer coefficients kLa at low energy input. The design, modelling, optimization and scale-up of these reactors require precise knowledge of the mass transfer parameters. The mass transfer coefficients determine the efficiency and dimensions of (slurry) bubble columns. Nedeltchev et al. (2007) developed a correlation for prediction of mass transfer coefficients in gas-liquid bubble columns operated in the homogeneous flow regime. It was based on experimental gas holdups. On the other hand, Nedeltchev and Schumpe (2008) developed a correlation for prediction of gas holdups in gas-liquid bubble columns operated in the homogeneous regime. In this work, the theoretically calculated gas holdups were substituted in the mass transfer model (in the correlation for the interfacial area) of Nedeltchev et al. (2007) and the mass transfer coefficients were recalculated by means of a purely theoretical approach. The same gases and liquids (18 pure organic liquids, 14 adjusted liquid mixtures and tap water) were used and 263 kLa values (only in the homogeneous regime) were successfully predicted at ambient and high pressures (up to 1 MPa).
The same approach was tested in a slurry bubble column. Nedeltchev et al. (2014) predicted successfully the experimental mass transfer coefficients in a slurry bubble column based on bubble sizes which depended on the experimental gas holdups. On the other hand, Nedeltchev (2014) established a new approach for predicting the gas holdups in a slurry bubble column. When these theoretical gas holdups were substituted in the mass transfer model (in the correlations for prediction of bubble size and interfacial area), a purely theoretical kLa values in a slurry bubble column were obtained. The predictions were good not only in the homogeneous regime but also in the heterogeneous regime. The theoretical approach was applicable up to relatively high (18 %) solids concentrations. Six different liquid-solid systems were used and 66 kLa values were successfully predicted. In both mass transfer models, correction factors (a function of Eӧtvӧs numbers) were introduced due to the non-spherical (ellipsoidal) shape of the bubbles.

Keywords: Mass transfer coefficients, Penetration theory, New contact time, Gas-liquid bubble columns, Slurry bubble columns
  • Lecture (Conference)
    12th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York, USA
Registration No. 22237

Controllable Broadband Absorption in the Mixed Phase of Metamagnets
Pregelj, M.; Zaharko, O.; Zorko, A.; Gomilsek, M.; Sendetskyi, O.; Günther, A.; Ozerov, M.; Zvyagin, S. A.; Luetkens, H.; Baines, C.; Tsurkan, V.; Loidl, A.
Abstract: Materials with broad absorption bands are highly desirable for electromagnetic filtering and processing applications, especially if the absorption can be externally controlled. Here, a new class of broadband-absorption materials is introduced. Namely, layered metamagnets exhibit an electromagnetic excitation continuum in the magnetic-field-induced mixed ferro-and anti-ferromagnetic phase. Employing a series of complementary experimental techniques involving neutron scattering, muon spin relaxation, specific heat, ac and dc magnetization measurements, and electron magnetic resonance, a detailed magnetic phase diagram of Cu3Bi(SeO3)2O2Br is determined and it is found that the excitations in the mixed phase extend over at least ten decades of frequency. The results, which reveal a new dynamical aspect of the mixed phase in metamagnets, open up a novel approach to controllable microwave filtering. Registration No. 22232

Depth Resolved Structural and Compositional Characterization of Ion-Implanted Polystyrene that Enables Direct Covalent Immobilization of Biomolecules
Bilek, M. M. M.; Kondyurin, A.; Dekker, S. A.; Steel, B. C.; Wilhelm, R. A.; Heller, R.; Mckenzie, D. R.; Weiss, A. S.; James, M.; Möller, W.
Abstract: A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) in order to activate its surface for single step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)-visible (VIS) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characterization by FTIR, atomic force microscopy (AFM), ellipsometry and X-ray reflectometry shows that polystyrene films modified in this way immobilize dense layers of protein (tropoelastin) directly from solution. A substantial fraction of the immobilized protein layer remains after rigorous washing with sodium dodecyl sulfate solution, indicating that its immobilization is by covalent bonding.
Keywords: Plasma immersion ion implantation, polystyrene, protein immobilization, nuclear reaction analysis, X-ray reflectometry, neutron reflectometry, spectroscopic ellipsometry, Raman and FTIR spectroscopy Registration No. 22230

Response of GaN to energetic ion irradiation: conditions for ion track formation
Karlušić, M.; Kozubek, R.; Lebius, H.; Ban-D’Etat, B.; Wilhelm, R. A.; Buljan, M.; Siketić, Z.; Scholz, F.; Meisch, T.; Jakšić, M.; Bernstorff, S.; Schleberger, M.; Šantić, B.
Abstract: We investigated the response of wurzite GaN thin films to energetic ion irradiation. Both swift heavy ions (92 MeV Xe23+, 23 MeV I6+) and highly charged ions (100 keV Xe40+) were used. After irradiation, the samples were investigated using atomic force microscopy, grazing incidence small angle x-ray scattering, Rutherford backscattering spectroscopy in channelling orientation and time of flight elastic recoil detection analysis. Only grazing incidence swift heavy ion irradiation induced changes on the surface of the GaN, when the appearance of nanoholes is accompanied by a notable loss of nitrogen. The results are discussed in the framework of the thermal spike model.
Keywords: GaN, swift heavy ion, highly charged ion, ion track, thermal spike Registration No. 22226

Formation of shallow boron emitters in crystalline silicon using flash lamp annealing: Role of excess silicon interstitials
Riise, H. N.; Schumann, T.; Azarov, A.; Hübner, R.; Skorupa, W.; Svensson, B. G.; Monakhov, E.
Abstract: Shallow, Boron (B)-doped p+ emitters have been realized using spin-on deposition and Flash Lamp Annealing (FLA) to diffuse B into monocrystalline float zone Silicon (Si). The emitters extend between 50 and 140 nm in depth below the surface, have peak concentrations between 9x1019 cm-3 and 3x1020 cm-3, and exhibit sheet resistances between 70 and 3000 Ohm/Square. An exceptionally large increase in B diffusion occurs for FLA energy densities exceeding approximately 93 J/cm2 irrespective of 10 or 20 ms pulse duration. The effect is attributed to enhanced diffusion of B caused by Si interstitial injection following a thermally activated reaction between the spin-on diffusant film and the silicon wafer. Registration No. 22225

Mass of GaAsN in Pulsed Magnetic Fields up to 60 T with Free-Electron Laser IR Radiation
Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.
Abstract: We use the unique combination of the widely tunable (4 μm – 250 μm) Free-Electron laser (FEL) FELBE and pulsed magnetic fields up to 60T of the High Magnetic Field Laboratory HLD to perform spectroscopic investigations on the dilute nitride system GaAsN. We carry out systematic cyclotron resonance (CR) spectroscopy and analyze the dependence of the electron effective mass on the nitrogen content. The red triangles in Figure 1 illustrate our findings for the illumination wavelength 46 μm at 100 K. We observe a slight increase of the effective mass with nitrogen content, which is in very good agreement with the Band Anti-Crossing (BAC) model [1], the empirical Tight Binding (TB) calculations [2] and the Two band BAC model [3], which are represented in Figure 1 by dashed, dotted and dash-dotted black lines, respectively. We compare our results with magneto-photoluminescence (PL) investigations performed by Alberi et al. [4] and Masia et al. [5], which are presented with blue circles and stars respectively. Magneto-PL investigations reveal a very fast increase of the effective mass with nitrogen content, well above the mentioned models [1-3], but consistent with the modified k·p calculations by Lindsay and O’Reilly [6]. Our magneto-PL study (not shown) exhibits a very similar behavior as shown by Alberi et al. and Masia et al., which allows us to exclude the different samples as a source for the deviation.
It is well known that nitrogen tends to form pairs and clusters during the growth, which is only considered in the modified k·p calculations [4]. Magneto-PL is a method which is very sensitive to localization of the neighboring atoms and thus to clusters. For this reason the magneto-PL results are consistent with [4], but cannot be described by [1-3], which do not take clusters into account. On the other hand, CR spectroscopy is only sensitive to delocalized states and this is why our results are in such good agreement with [1-3].

[1] J. Wu et al. Phys. Rev. B 64, 085320 (2000).
[2] N. Shtinkov et al. Phys. Rev. B 67, 081202(R) (2003).
[3] Tomic et al. Phys. Rev. B 69, 245305 (2004).
[4] Alberi et al. Phys. Rev. Lett. 110, 156405 (2013).
[5] Masia et al. Phys. Rev. B 73, 073201, (2006).
[6] A. Lindsay and E. P. O’Reilly Phys. Rev. Lett. 93, 196402 (2004).

Keywords: GaAsN, effective mass, cyclotron resonance spectroscopy, THz spectroscopy in pulsed magnetic fields
  • Lecture (Conference)
    RHMF 2015; International Conference on Research in High Magnetic Fields 2015, 01.-04.07.2015, Grenoble, France
Registration No. 22221

Cyclotron Resonance Spectroscopy of GaAsN in Pulsed Magnetic Fields up to 60 T with Free-Electron Laser IR Radiation
Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Pettinari, G.; Helm, M.
Abstract: The unique combination of the high magnetic field laboratory Dresden (HLD) and the free-electron laser facility FELBE allow us to perform cyclotron resonance spectroscopy experiments with tunable, intense, coherent infrared radiation of high brilliance in the range of 4 - 250 µm in pulsed magnetic fields up to 60 T. The material system of interest is the dilute nitride GaAsN, a promising candidate for electro-optical applications, because of its band gap tunability. The incorporation of a few percent of nitrogen into GaAs enables the gradual decrease of the band gap, which is proportional to the nitrogen content. The description of the band structure and in particular of the effective mass are still challenging despite the number of experimental works (e.g. [1, 2]) that have been performed on this system. In order to contribute to a clarification of this problem, we apply different investigation methods on one sample series of GaAsN with different nitrogen contents (0%; 0.1%; 0.2%).
Probably the most direct and reliable method for the investigation of the effective mass is cyclotron resonance spectroscopy, which has never been applied to bulk GaAsN layers before, according to our best knowledge. Figure 1 illustrates our CR spectroscopy investigation of three samples with different nitrogen contents illuminated with the FEL at wavelengths of 30 µm and 70 µm. These wavelengths have been chosen intentionally to investigate the effective mass behavior below and above the Reststrahlenband of GaAs. We discuss the significance of these CR studies, which were conducted using a range of temperatures, illumination wavelengths and n-type doping of the GaAsN layers. Using a simple Drude-like absorption model we deduce the electron CR mass, the electron mobility, the density of free carriers and the electron relaxation time.

References
[1] F. Masia et al., Phys. Rev. B 73, 07320 (2006).
[2] K. Alberi et al., Phys. Rev. Lett. 110, 156405 (2013).

Keywords: GaAsN, effective mass, cyclotron resonance spectroscopy, THz spectroscopy in pulsed magnetic fields
  • Lecture (Conference)
    EDiSON'19 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures, 29.06.-02.07.2015, Salamanca, España
Registration No. 22219

THz free-electron laser investigation of GaAsN in pulsed magnetic fields up to 60 T
Eßer, F.; Schneider, H.; Winnerl, S.; Drachenko, O.; Patanè, A.; Helm, M.
Abstract: We use the unique combination of the free-electron laser FELBE and the High Magnetic Field Laboratory Dresden to perform cyclotron resonance (CR) spectroscopy on the dilute nitride alloy GaAsN. FELBE is a tunable (4 – 250 µm) laser source of high brilliance, which can be used in pulsed magnetic fields up to 60 T. Our CR studies enable us to measure fundamental electronic properties of GaAsN, a very interesting candidate for optoelectronic applications because of the tunability of its band gap energy in the range of 1.4 eV – 0.9 eV by the incorporation of a small concentration of N-atoms (~ 1%). Figure 1 illustrates a typical CR spectrum and our values of the CR electron mass at 100 K and 6.5 THz. We observe a slight increase of the electron CR mass with nitrogen content. This dependence is in very good agreement with that described by the band anticrossing (BAC) model [1] and the empirical tight binding (TB) calculations [2], which are represented in Figure 1 by dashed and dotted black lines, respectively. The comparison with magneto-photoluminescence (PL) investigations performed by Alberi et al. [3] and Masia et al. [4] reveal instead a steep increase of the electron effective mass with nitrogen content, which is consistent with a modified k·p calculation by Lindsay and O’Reilly [5]. This model assumes that nitrogen can form pairs and clusters, not considered in [1,2]. Since PL is very sensitive to carrier localization effects, the results in [3,4] can be well described by [5]. In contrast, CR spectroscopy is only sensitive to delocalized states, which explains the good agreement of the present results with [1,2].

[1] J. Wu et al. Phys. Rev. B 64, 085320 (2000).
[2] N. Shtinkov et al. Phys. Rev. B 67, 081202(R) (2003).
[3] Alberi et al. Phys. Rev. Lett. 110, 156405 (2013).
[4] Masia et al. Phys. Rev. B 73, 073201, (2006).
[5] A. Lindsay and E. P. O’Reilly Phys. Rev. Lett. 93, 196402 (2004).

Keywords: GaAsN, effective mass, cyclotron resonance spectroscopy, THz spectroscopy in pulsed magnetic fields
  • Poster
    German THz Conference 2015, 08.-10.06.2015, Dresden, Deutschland
Registration No. 22218

Design of compensated ferrimagnetic Heusler alloys for giant tunable exchange bias
Nayak, A. K.; Nicklas, M.; Chadov, S.; Khuntia, P.; Shekhar, C.; Kalache, A.; Baenitz, M.; Skourski, Y.; Guduru, V. K.; Puri, A.; Zeitler, U.; Coey, J. M. D.; Felser, C.
Abstract: Rational material design can accelerate the discovery of materials with improved functionalities. This approach can be implemented in Heusler compounds with tunable magnetic sublattices to demonstrate unprecedented magnetic properties. Here, we have designed a family of Heusler alloys with a compensated ferrimagnetic state. In the vicinity of the compensation composition in Mn–Pt–Ga, a giant exchange bias (EB) of more than 3 T and a large coercivity are established.
The large exchange anisotropy originates from the Exchange interaction between the compensated host and ferrimagnetic clusters that arise from intrinsic anti-site disorder. Our design approach is also demonstrated on a second material with a magnetic transition above room temperature, Mn–Fe–Ga, exemplifying the universality of the concept and the feasibility of room-temperature applications. These findings may lead to the development of magneto-electronic devices and rareearth-free exchange-biased hard magnets, where the second quadrant magnetization can be stabilized by the exchange bias.
Registration No. 22216

Ga, Ge, In and other trace elements in sphalerite from different geological deposit types, with reference to mineralisation events at Freiberg.
Frenzel, M.
Abstract: Sphalerite (ZnS) is an important source of a number of high-tech metals. However, while a large amount of analytical data on trace and minor element concentrations in sphalerite has been collected over the last decades, our understanding of the geological controls on their enrichment or depletion remains limited. No comprehensive meta-analysis of this data has ever been conducted. This talk presents the results of such a meta-analysis, based on an extensive collection of data from the scientific literature. Nine elements (Ag, Cd, Co, Cu, Fe, Ga, Ge, In and Mn) were considered. For five of these elements (Fe, Ga, Ge, In, Mn) significant differences were found between different geological types of deposits. The regularity of these differences suggests the operation of a single underlying control parameter – possibly formation temperature – with obvious implications for the identification of future sources of these elements.
  • Lecture (others)
    BHMZ Seminar, 06.05.2015, Freiberg, Deutschland
Registration No. 22214

Lattice location of deep level impurities in hyperdoped Si by ion implantation and short-time annealing
Liu, F.; Prucnal, S.; Gao, K.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Keywords: Ion implantation, deep level impurities
  • Poster
    Jaszowiec 2015, 20.-25.06.2015, Wisła, Poland
Registration No. 22206

Lattice location of deep level impurities in hyperdoped Si by ion implantation and short-time annealing
Liu, F.; Prucnal, S.; Gao, K.; Heller, R.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Impurities play an important role in determining the electrical, optical and structural properties of semiconductors. It has been proposed that deep level impurities, such as Titanium (Ti) or chalcogens in Si, can induce an impurity band inside the bandgap at high enough doping concentration. The insertion of an impurity band can enhance the absorption at a broader wavelength range and leads to applications in the so-called intermediate band solar cell. However, deep level impurities have relatively low solid solubility limit in Si. We prepared deep level impurities doped silicon to above the Mott insulator concentration by ion implantation followed by sub-second annealing. The degree of crystalline lattice recovery in implanted layers and the lattice location of impurities in Si were analyzed by Rutherford backscattering spectrometry/Channeling. Our results show that S and Se atoms are occupying substitutional lattice sites in Si [1], while Ti impurities have no ordered lattice occupation [2].

[1] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, W. Skorupa and M. Helm, Scientific Report 5, 8329 (2015).
[2] F. Liu, et al., in preparation (2015).

Keywords: Ion implantation, deep level impurities
  • Poster
    IBA 2015 - 22nd International Conference on Ion Beam Analysis, 14.-19.06.2015, Opatija, Croatia
Registration No. 22205

High temperature stable transparent conductive oxides for solar thermal applications
Lungwitz, F.; Schumann, E.; Guillen, E.; Escobar, R.; Krause, M.; Gemming, S.
Abstract: In solar thermal energy conversion systems, receivers containing the heat transfer fluid are coated by a solar selective coating which must exhibit high absorption in the solar region and low thermal emittance. Additionally, the coating materials have to be structurally, optically, and mechanically stable at high temperatures. Nowadays, temperatures of up to 450 °C and up to 550°C are reached using parabolic trough arrays and solar tower absorbers, respectively, whereas temperatures up to 800 °C could be reached if the receiver materials were stable enough. Solar selective coatings can be formed by a transparent conductive oxide (TCOs) film deposited on a black body absorber to have both, high absorption in the ultraviolet, visible and near infrared spectral range (300 nm – 2500 nm) as well as high reflectivity in the infrared (> 2500 nm). The former is to absorb as much sunlight as possible, the latter for preventing thermal radiation losses from the system to the environment. In this work Ta:TiO2 and Ta:SnO2 TCOs thin films are reactively magnetron sputtered from tantalum doped metallic targets. The oxygen flow during deposition is precisely controlled by a plasma emission unit which is crucial to obtain optimal electrical and therefore also optical properties by maintaining high sputtering rates. While the as-deposited films are amorphous and non-conductive, they are crystallized and therefore electrically activated upon a subsequent thermal treatment at 425 °C for 1 hour. The correlation between structural, optical, and electrical properties is shown by Rutherford Backscattering Spectroscopy (RBS), X-ray Diffraction (XRD), Raman Spectroscopy, Spectroscopic Ellipsometry (SE) (both at room- and high- temperatures), UV-VIS spectrometry, and Hall Effect measurements. Preliminary tests show that optical constants of Ta:TiO2 films are maintained after annealing at 700ºC.
Keywords: TCO, transparent conductive oxide, solar thermal, magnetron sputtering, TiO2, Cluster Tool, solar selectivity, high temperature
  • Lecture (Conference)
    ICMAT 2015 & IUMRS - ICA 2015, 28.06.-03.07.2015, Singapore, Singapore
Registration No. 22203

Optical and electrical characterization of TiO2- based transparent conductive oxides
Lungwitz, F.; Schumann, E.; Wenisch, R.; Neubert, M.; Guillen, E.; Escobar, R.; Krause, M.; Gemming, S.
Abstract: Transparent conductive oxides (TCOs) are already widely used in the optoelectronic industry e.g. as electrodes for liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), or thin film solar cells. Less attention has been devoted to their optical properties and thermal stability until now.
In this work, Tantalum doped TiO2 and SnO2 TCO films are investigated with respect to their structural, optical, and electrical properties at temperatures from RT to 700°C. The films are prepared at room temperature by direct current reactive magnetron sputtering from metallic as well as ceramic targets and subsequently isothermally annealed at temperatures of 425°C. For compositional and structural analysis x-ray diffraction (XRD), Raman spectroscopy, and Rutherford backscattering spectroscopy (RBS) are used. The optical properties are determined by spectroscopic ellipsometry, spectral photometry, and subsequent modelling. Hall effect measurements are used to determine the electrical properties of the TCO films.
The as-deposited layers are amorphous and isolating. By thermal annealing they are activated and become conductive.

Keywords: TCO, transparent conductive oxide, solar-thermal, thin film, high temperature, magnetron sputtering, energy materials, Cluster Tool
  • Poster
    Frühjahrstagung der DPG, 19.03.2015, Berlin, Deutschland
Registration No. 22202

Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Trin-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: Uranium(VI), aqueous solution, tri-n-butyl phosphate, UV/Vis, EXAFS Registration No. 22200

Fermi surface of SrCo2P2: A strongly enhanced Pauli paramagnet
Götze, K.; Klotz, J.; Bergmann, C.; Geibel, C.; Kraft, I.; Lorenz, V.; Rosner, H.; Sheikin, I.; Mccollam, A.; Bruin, J.; Wosnitza, J.
Abstract: es hat kein Abstract vorgelegen
  • Poster
    RHMF 2015, 11th International Conference on Research in High Magnetic Fields, 02.-04.07.2015, Grenoble, France
Registration No. 22193

NMR of the Shastry-Sutherland lattice SrCu2(BO3)2
Stern, R.; Kohlrautz, J.; Haase, J.; Kühne, H.; Green, E.; Zhang, Z.; Wosnitza, J.
Abstract: SrCu2(BO3)2 is a prominent realization of the Shastry-Sutherland lattice model [1]. In this quasi-two-dimensional compound, Cu2+ ions form orthogonal spin-singlet dimers with strong geometrical frustration of the next-nearest and nearest neighbor exchange interactions. SrCu2(BO3)2 has been studied extensively using a variety of techniques, such as nuclear magnetic resonance (NMR) spectroscopy, or recent magnetization measurements up to 118 T. These experiments reveal a complex sequence of magnetization plateaus with differing commensurate magnetic superstructure, stemming from a stripe type order of triplet states [2-4]. Due to its highly sensitive local probe character, NMR can provide deep insight into the spin-coupling mechanisms and excitations at highest magnetic fields. We present 11B NMR spectra measured in pulsed magnetic fields up to 56 T, and compare those with prior results obtained in highest static magnetic fields. Herewith, we prove the feasibility and efficacy of this new technique, yielding the capability for extended studies at highest magnetic fields up to the 100 T regime that determine the spin structure in the 1/3 magnetization plateau and beyond.
  • Poster
    RHMF 2015 - 11th International Conference on Research in High Magnetic Fields, 02.-04.07.2015, Grenoble, France
Registration No. 22192

III-V:Mn Ferromagnetic semiconductors prepared by ion implantation
Yuan, Y.; Sawicki, M.; Helm, M.; Zhou, S.
Abstract: Ferromagnetic semiconductors (FSs) have been under intensive investigation during the last decade. Until now, the prototype ferromagnetic semiconductor GaMnAs has revealed a variety of unique features induced by the combination of its magnetic and semiconducting properties. As a non-equilibrium process, ion implantation can overcome the difficulty that the Mn concentration in ferromagnetic III-V (FS) is far beyond the solid solubility of Mn in III-V compounds. However, the activation of dopants remains challenging due to the clustering of implanted ions during post-annealing. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. On the other hand, one notes that the solubility limit in the liquid phase is generally much larger than that in the solid phase. Short-time annealing within nanoseconds regime allows the epitaxial growth from a liquid phase. The approach combining ion implantation and pulsed laser melting allows us to prepare ferromagnetic semiconductors covering the full spectrum of III-V compound semiconductors.
We have successfully synthesized ferromagnetic Mn doped III-V from InAs and GaAs to InP and GaP with different bandgaps. The results of magnetization, magnetic anisotropy, resistivity, anomalous Hall effect, magnetoresistance and x-ray magnetic circular dichroism obtained from the synthesized samples confirm the intrinsic origin and the carrier-mediated nature of the ferromagnetism. Moreover, in different III-V hosts we observe distinct differences regarding the magnetic anisotropy and conduction mechanism which are related with the intrinsic parameters such as the lattice mismatch, energy gap and the acceptor level of Mn. These results could allow a panorama-like understanding of III-V:Mn based ferromagnetic semiconductors.
  • Poster
    Jaszowiec 2015, 20.06.2015, Wisla, Poland
Registration No. 22190

Hydrodynamic and mass transfer properties of a bubble column with vertically inserted tube bundles
Šimić, N.; Breiler, K.; Schubert, M.
Abstract: The objective of this study is to examine the influence of different vertical tube bundle designs on the bubble dynamics and on the mass transfer rates in a bubble column. The studies in the open literature examining the performance of bubble columns with vertically inserted tube bundles have focused primarily on the coverage of the cross-sectional area of the bubble column by the tube bundle (CSA). The most frequently used coverages are the 5% and the 25% (± 3%) which mimic the heat exchangers utilized in the processes of methanol and Fischer-Tropsch syntheses. Other than that, the designs of tube bundles seem to be arbitrarily chosen and feature a number of different configurations of layouts, tube diameters and tube lengths. From the current state of research, it is thus rather difficult to draw conclusions on the optimal design of a heat exchanger suitable for use in bubble columns (Youssef et al., 2013). Intuitively, it can be concluded that the most important design features of tube bundles affecting the flow are the distance between the tubes and the unit cell area enclosed by the tubes in their respective arrangements. Accordingly, the study aims on a systematic analysis on the effect of these geometric parameters.
Keywords: bubble column, internals, heat exchanger, tube bundle, hydrodynamics, gas holdup, bubble size distribution, mass transfer, X-ray tomography
  • Poster
    12th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York City, USA
Registration No. 22189

High Curie temperature and perpendicular magnetic anisotropy in homoepitaxial InMnAs films
Yuan, Y.; Wang, Y.; Gao, K.; Khalid, M.; Wu, C.; Zhang, W.; Munnik, F.; Weschke, E.; Baehtz, C.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: We have prepared the dilute magnetic semiconductor (DMS) InMnAs with different Mn concentrations by ion implantation and pulsed laser melting. The Curie temperature of the In1−xMnxAs epilayer depends on the Mn concentration x, reaching 82K for x = 0.105. The substitution of Mn ions at the indium sites induces a compressive strain perpendicular to the InMnAs layer and a tensile strain along the in-plane direction. This gives rise to a large perpendicular magnetic anisotropy, which is often needed for the demonstration of the electrical control of magnetization and for spin-transfer-torque induced magnetization reversal
Keywords: dilute magnetic semiconductors, InMnAs, ion implantation, pulsed laser melting, perpendicular magnetic anisotropy Registration No. 22182

P1402-Kontrolle einer therapeutischen Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl
Enghardt, W.; Fiedler, F.; Helmbrecht, S.
Abstract: Die Erfindung betrifft Verfahren und Einrichtungen zur Kontrolle einer therapeutischen Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen. Diese zeichnen sich insbesondere dadurch aus, dass eine therapeutische Bestrahlung durch eine Bestrahlungseinrichtung mit einem mikrogepulsten Teilchenstrahl mittels eines Positronen-Emissions-Tomografen während der Bestrahlung kontrollierbar ist. Dazu werden wahre Koinzidenzen mittels – des durch die erlaubte Zeitdifferenz des Auftreffens zweier Photonen in verschiedenen Detektoren des Tomografen bestimmten Koinzidenzzeitfensters und – der Differenz zwischen prompten Fenster und verzögerten Fenster ohne wahre Koinzidenzen ermittelt. Dabei sind sowohl das Koinzidenzzeitfenster als auch die Zeitdifferenz zwischen prompten und verzögerten Fenster ein ganzzahliges Vielfaches der durch die Frequenz der beschleunigenden Wechselspannung des Hochfrequenzbeschleunigers gegebenen Zeitdauer einer Mikropulsperiode des Teilchenstrahls. Die Mikropulsperiode ist durch den Mikropuls und die Pause zwischen Mikropulsen definiert. Diese Zeitdauer ist durch die Frequenz der die Teilchen des Teilchenstrahls beschleunigenden Wechselspannung gegeben und damit zu wählen.
  • Patent
    DE102014202828.0 - Erteilung 15.04.2015; Nachanmeldung: WO
Registration No. 22178

Biomimetic Magnetic Silk Scaffolds
Samal, S. K.; Dash, M.; Shelyakova, T.; Declercq, H. A.; Uhlarz, M.; Banobre-Lopez, M.; Dubruel, P.; Cornelissen, M.; Herrmannsdörfer, T.; Rivas, J.; Padeletti, G.; de Smedt, S.; Braeckmans, K.; Kaplan, D. L.; Dediu, V. A.
Abstract: Magnetic silk fibroin protein (SFP) scaffolds integrating magnetic materials and featuring magnetic gradients were prepared for potential utility in magnetic-field assisted tissue engineering. Magnetic nanoparticles (MNPs) were introduced into SFP scaffolds via dip-coating methods, resulting in magnetic SFP scaffolds with different strengths of magnetization. Magnetic SFP scaffolds showed excellent hyperthermia properties achieving temperature increases up to 8 °C in about 100 s. The scaffolds were not toxic to osteogenic cells and improved cell adhesion and proliferation. These findings suggest that tailored magnetized silk-based biomaterials can be engineered with interesting features for biomaterials and tissue-engineering applications. Registration No. 22176

Capture Gamma-Ray Spectroscopy and Related Topics, Proceedings of the Fifteenth International Symposium
Schwengner, R.; Zuber, K. (Editors)
Abstract: The Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS15) was organized by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Technische Universität (TU) Dresden and held at TU Dresden from August 25 to August 29, 2014.
CGS15 was the fifteenth symposium in a series that started in 1969.
This conference continued the general themes of earlier meetings with special emphasis on gamma-ray spectroscopy used in neutron capture and also in a wider context in nuclear structure, nuclear reactions, nuclear astrophysics, statistical properties of nuclei, nuclear probes for fundamental physics, nuclear data, novel techniques and applications.
These proceedings include a collection of articles from all these topics.

Keywords: Gamma-ray spectroscopy
  • Book (Editorship)
    France: EDP Sciences, 2015
    ISBN: 978-2-7598-1794-8

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Registration No. 22175

Commissioning and first RF results of the second 3.5 cell SRF gun for ELBE
Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Eremeev, Gr. V.; Kneisel, P.; Stirbet, M.; Turlington, L.
Abstract: As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at Helmholtz-Zentrum Dresden-Rossendorf, it turned out that the specified performance to realize an electron energy of 9.4 MeV has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of this value and the measured beam parameters remained significantly below its expectations.

However, to demonstrate the full potential of this electron source for the ELBE linear accelerator, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility.

We will report on commissioning and first RF results of this new SRF gun. This includes in particular the characterization of the most important RF properties as well as their comparison with previous vertical test results. Additionally, investigations are presented that try to explain a particle contamination that happened recently during the first cathode transfer.

Keywords: SRF gun, superconducting radio frequency electron injector, ELBE linear accelerator
  • Lecture (Conference)
    The 56th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 07.-12.06.2015, Stony Brook, NY 11794, USA
Registration No. 22171

Radiation Effects in Solid Nitrogen and Nitrogen-Containing Matrices: Fingerprints of N4+ Species
Savchenko, E. V.; Khyzhniy, I. V.; Uyutnov, S. A.; Barabashov, A. P.; Gumenchuk, G. B.; Beyer, M. K.; Ponomaryov, A. N.; Bondybey, V. E.
Abstract: The radiation effects and relaxation processes in solid N2 and N2-doped Ne matrices, preirradiated by an electron beam, have been studied in the temperature range of 5–40 and 5–15 K, respectively. The study was performed using luminescence methods: cathodoluminescence CL and developed by our group nonstationary luminescence NsL, as well as optical and current activation spectroscopy methods: spectrally resolved thermally stimulated luminescence TSL and exoelectron emission TSEE. An appreciable accumulation of N radicals, N+, N2+ ions, and trapped electrons is found in nitrogen-containing Ne matrices. Neutralization reactions were shown to dominate relaxation scenario in the low-temperature range, while at higher temperatures diffusion-controlled reactions of neutral species contribute. It was conceived that in α-phase of solid N2, the dimerization reaction (N2+ + N2 → N4+) proceeds: “hole self-trapping”. Tetranitrogen cation N4+ manifests itself by the dissociative recombination reaction with electron: N4+ + e → N2*(a’1Σu) + N2 → N2 + N2 + hν. In line with this assumption, we observed a growth of the a’1Σu → X1Σg+ transition intensity with an exposure time in CL spectra and the emergence of this emission in the course of electron detrapping on sample heating in the TSL and NsL experiments. Registration No. 22170

Dependence of the inverse magnetocaloric effect on the field-change rate in Mn3GaC and its relationship to the kinetics of the phase transition
Scheibel, F.; Gottschall, T.; Skokov, K.; Gutfleisch, O.; Ghorbani-Zavareh, M.; Skourski, Y.; Wosnitza, J.; Cakir, Ö.; Farle, M.; Acet, M.
Abstract: We study the dependence of the magnetocaloric effect on the magnetic field-change-rate the first order magnetostructural transition in Mn3GaC by measuring the adiabatic temperature change ΔT at three different time scales: 11 mTs-1, 700 mTs-1, and ~1000 Ts-1. We find that the Maximum adiabatic temperature-change of about 5 K is reached in the 11 mTs-1 and 700 mTs-1 rates, whereas for the ~1000 Ts-1 the transition lags the change in the magnetic field so that the maximum adiabatic temperature-change is not attained. Registration No. 22169

Optical conductivity evidence of clean-limit superconductivity in LiFeAs
Lobo, R. P. S. M.; Chanda, G.; Pronin, A. V.; Wosnitza, J.; Kasahara, S.; Shibauchi, T.; Matsuda, Y.
Abstract: We measured the optical conductivity of superconducting LiFeAs. In the superconducting state, the formation of the condensate leads to a spectral-weight loss and yields a penetration depth of 225 nm. No sharp signature of the superconducting gap is observed. This suggests that the system is likely in the clean limit. A Drude-Lorentz parametrization of the data in the normal state reveals a quasiparticle scattering rate supportive of spin fluctuations and proximity to a quantum critical point. Registration No. 22168

Doping effects of Sb in FeTe1-xSbx single crystals
Wang, X. F.; Zhang, Z. T.; Chen, X. L.; Kan, X. C.; Li, L.; Sun, Y. P.; Zhang, L.; Xi, C. Y.; Pi, L.; Yang, Z. R.; Zhang, Y. H.
Abstract: We investigated the doping effects of Sb on the magnetic, transport and structural properties in FeTe1-xSbx single crystals. Resistivity, magnetic susceptibility and heat capacity experiments consistently reveal that the magnetic/structural transition temperature TN ~ 70 K in undoped Fe1.05Te is gradually suppressed by Sb doping, but no superconductivity is observed for x up to 10%. It is found that the electronic heat capacity coefficient gamma increases with Sb content, implying the increase of the density of states at Fermi level. Referring to previous calculation reports, this means that the Sb substituent plays a role of hole carrier doping, which is consistent with our measurements on Hall coefficient. Structural Analysis shows that Sb doping induces an expansion of the lattice along the a axis and a shrinkage along the c axis. Our work suggests that the antiferromagnetism in Fe1+yTe may be different in nature with other parent compounds of FeAs-based systems. Registration No. 22167

First evidence of low energy enhancement in Ge isotopes
Renström, T.; Nyhus, H.-T.; Utsunomiya, H.; Larsen, A. C.; Siem, S.; Guttormsen, M.; Filipescu, D. M.; Gheorghe, I.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Glodariu, T.; Görgen, A.; Hagen, T. W.; Lui, Y.-W.; Negi, D.; Ruud, I. E.; Sahin, E.; Schwengner, R.; Shima, T.; Takahisa, K.; Tesileanu, O.; Tornyi, T. G.; Tveten, G. M.; Wiedeking, M.
Abstract: The γ-strength functions and level densities of 73,74 Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74 Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ~ 1-13 MeV for 74 Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ~ 3 MeV towards lower γ energies. The obtained data show that both 73,74 Ge display an increase in strength at low γ energies.
Keywords: gamma-ray strength

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Registration No. 22165

Low-Energy Magnetic Radiation
Frauendorf, S.; Beard, M.; Mumpower, M.; Schwengner, R.; Wimmer, K.
Abstract: A pronounced spike at low energy in the strength function for magnetic radiation (LEMAR) is found by means of Shell Model calculations, which explains the experimentally observed enhancement of the dipole strength. LEMAR originates from statistical low-energy M1-transitions between many excited complex states.
Re-coupling of the proton and neutron high-j orbitals generates the strong magnetic radiation. LEMAR is predicted for nuclides with A ~ 132 participating in the r-process of element synthesis. It increases the reaction rates by a factor of 2.5. The spectral function of LEMAR follows Planck's Law. A power law for the size distribution of the B(M1) values is found.

Keywords: Magnetic dipole radiation, shell model,

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Registration No. 22163

Neutron-capture experiment on 77Se with EXILL at ILL Grenoble
Lorenz, Ch.; John, R.; Massarczyk, R.; Schwengner, R.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Urban, W.; Valenta, S.; Belgya, T.
Abstract: The neutron capture reaction at 77 Se has been studied with cold neutrons in the course of the EXILL campaign at the high-flux reactor of the Institut Laue-Langevin Grenoble. A simulation of the detector array with Geant4 has been accomplished and evaluated. The detector response has been deduced and measured spectra were unfolded, which have been compared with simulations using γDex to determine strength functions.
Keywords: Neutron capture, gamma-spectroscopy

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Registration No. 22160

Investigation of dipole strength up to the neutron separation energy at γELBE
Massarczyk, R.; Schwengner, R.; Bemmerer, D.; Beyer, R.; Hannaske, R.; Junghans, A. R.; Kempe, M.; Kögler, T.; Schramm, G.; Wagner, A.
Abstract: The bremsstrahlung facility at the ELBE accelerator offers the possibility to investigate dipole strength distributions up to the neutron-separation energies with photon up to 16 MeV in energy. The facility and various results for nuclides measured during recent years are presented. One example is the study of the N = 80 nuclide 136 Ba. The other presented example is the study of the chain of xenon isotopes from N = 70 to N = 80 which aimed to investigate the influence of nuclear deformation an neutron excess on the dipole strength in the pygmy region. An overview of the analysis is given. GEANT4 simulations were performed to determine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasi-continuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground-state transitions are compared with theoretical predictions and results within the chain of isotopes. With the help of the measured dipole distribution it is possible to describe gamma-ray spectra following neutron capture more precisely.
Keywords: photon scattering, nuclear structure, photon strength

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Registration No. 22159

Combined study of the gamma-ray strength function of 114Cd with (n,γ) and (γ,γ’) reactions
Belgya, T.; Massarzyk, R.; Szentmiklósi, L.; Schramm, G.; Schwengner, R.; Junghans, A. R.; Wagner, A.; Grosse, E.
Abstract: Collaboration on strength function measurements and level density determinations is ongoing between the Budapest Prompt Gamma Neutron Activation Analysis and the ELBE Nuclear Physics groups within the framework of EU FP6 EFNUDAT project. The idea is to prove that good theoretical fits to the measured gamma-ray spectra collected in the (n,γ) and (γ,γ’) reactions can be carried out using common photon strength and level density functions over a wide spectral energy range from 1 to 10 MeV for the same residual nucleus. Here, preliminary results on the isotope pair of 113,114Cd are presented for which the neutron capture state in 114Cd has 1+ or 0+ spin and parity.
Keywords: electromagnetic strength function neutron capture resonance fluorescence

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Registration No. 22158

Spin decoherence processes in the S=1/2 scalene triangular cluster (Cu3(OH))
Ponomaryov, A. N.; Kim, N.; Jang, Z. H.; van Tol, J.; Koo, H.-J.; Law, J. M.; Suh, B. J.; Yoon, S.; Choi, K. Y.
Abstract: We report the synthesis and magnetic properties of the molecular cluster Cu33−OH)(μ-OH)(μ-O2Ar4F-Ph)2(py)3(OTf)2, abbreviated as (Cu3(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu3(OH)) and measure the electron T1 and T2 relaxation times. The Cu2+ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J1 = −43.5 K, J2 = −53.0 K, and J3 = −37.7 K. At T = 1.5 K T1 is of the order of 10−4 s and T2 is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T1 and 1/T2 is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.

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Registration No. 22157

Paramagnetic moments and time effects in melt-textured NdBaCuO system with Nd422 inclusions
Dias, F. T.; Vieira, V. N.; Silva, D. L.; Wolff-Fabris, F.; Kampert, E.; Almeida, M. L.; Mesquita, F.; Hneda, M.; Roa, J. J.
Abstract: We have performed magnetic measurements in two melt-textured NdBa2Cu3O7-δ samples with Nd422 inclusions under magnetic fields from 0.05 up to 14 T, applied parallel to the ab planes. The measurements were made with a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Paramagnetic moments could be observed during FCC (field-cooled cooling) and FCW (field-cooled warming) experiments. This effect, known as Paramagnetic Meissner Effect (PME), persisted up to 14 T and strong irreversibilities were observed among FCC and FCW experiments, revealing the presence of time effects. These time effects were confirmed by specific magnetic relaxation experiments in different cooling rates and temperatures, showing an anomalous and curious paramagnetic behavior. We explain our results based on the flux-compressed state generated within nonsuperconducting regions of the sample, such as the Nd422 inclusions dispersed into the superconducting matrix. These inclusions may produce a strong vortex pinning that stabilize the paramagnetic state, allowing the admission of extra vortices into the sample responsible for the positive moments during the relaxation experiments.

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Registration No. 22156

Electron-tunneling measurements of low-Tc single-layer Bi2+xSr2−yCuO6+δ: Evidence for a scaling disparity between superconducting and pseudogap states
Jacobs, Th.; Katterwe, S. O.; Motzkau, H.; Rydh, A.; Maljuk, A.; Helm, T.; Putzke, C.; Kampert, E.; Kartsovnik, M. V.; Krasnov, V. M.
Abstract: We experimentally study intrinsic tunneling and high magnetic field (up to 65 T) transport characteristics of the single-layer cuprate Bi2+xSr2−yCuO6+δ, with a very low superconducting critical temperature Tc ≲ 4 K. It is observed that the superconducting gap, the collective bosonic mode energy, the upper critical field, and the fluctuation temperature range are scaling down with Tc, while the corresponding pseudogap characteristics remain the same as in high-Tc cuprates with 20 to 30 times higher Tc. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins. Registration No. 22155

Repeatability of tumor SUV quantification: the role of variable blood SUV
van den Hoff, J.; Hofheinz, F.
Abstract: kein Abstract verfügbar Registration No. 22151

Novel (pyrazolyl)benzenesulfonamides with a nitric oxide-releasing moiety as selective cyclooxygenase-2 inhibitors
Bechmann, N.; Kniess, T.; Köckerling, M.; Pigorsch, A.; Steinbach, J.; Pietzsch, J.
Abstract: Inhibition of cyclooxygenase-2 (COX-2) is a promising anti-inflammatory therapeutic strategy, but longterm medication with COX-2-inhibitors (coxibs) may be associated with adverse cardiovascular effects. Functionalization of existing lead structures with nitric oxide (NO)-releasing moieties is an auspicious approach to minimize these effects. In this regard, an organic nitrate (–O–NO2) substituent was introduced at a (pyrazolyl)benzenesulfonamide lead structure. The novel NO-coxibs selectively inhibited COX-2 in a low micromolar range (IC50(COX-2): 0.22–1.27 lM) and are supposed to be promising antiinflammatory compounds with, in parallel, positive effects on vascular homeostasis.
Keywords: Anti-inflammatory therapy; Cardiovascular side effects; Celecoxib; Direct/indirect NO coupling; Griess assay; Organic nitrate Registration No. 22150

Rational design of dual peptides targeting ghrelin and Y2 receptors to regulate food intake and body weight
Kilian, T. M.; Klöting, N.; Bergmann, R.; Els-Heindl, S.; Babilon, S.; Clément-Ziza, M.; Zhang, Y.; Beck-Sickinger, Annette G.; Chollet, C.
Abstract: Ghrelin and Y2 receptors play a central role in appetite regulation inducing opposite effects. The Y2 receptor induces satiety, while the ghrelin receptor promotes hunger and weight gain. However, the food regulating system is tightly controlled by interconnected pathways where redundancies can lead to poor efficacy and drug tolerance when addressing a single molecule. We developed a multitarget strategy to synthesize dual peptides simultaneously inhibiting the ghrelin receptor and stimulating the Y2 receptor. Dual peptides showed dual activity in vitro, and one compound induced a slight diminution of food intake in a rodent model of obesity. In addition, stability studies in rats revealed different behaviors between the dual peptide and its corresponding monomers. The Y2 receptor agonist was unstable in blood, while the dual peptide showed an intermediate stability compared to that of the highly stable ghrelin receptor inverse agonist. Registration No. 22149

On the relation between Kaiser-Bessel blob and tube of response based modelling of the system matrix in iterative PET image reconstruction
Lougovski, A.; Hofheinz, F.; Maus, J.; Schramm, G.; van den Hoff, J.
Abstract: We investigate the question of how the blob approach is related to tube of response based modelling of the system matrix. In our model, the tube of response (TOR) is approximated as a cylinder with constant density (TOR-CD) and the cubic voxels are replaced by spheres. Here we investigate a modification of the TOR model that makes it effectively equivalent to the blob model, which models the intersection of lines of response (LORs) with radially variant basis functions ('blobs') replacing the cubic voxels. Implications of the achieved equivalence regarding the necessity of final resampling in blob-based reconstructions are considered. We extended TOR-CD to a variable density tube model (TOR-VD) that yields a weighting function (defining all system matrix elements) which is essentially identical to that of the blob model. The variable density of TOR-VD was modelled by a Gaussian and a Kaiser-Bessel function, respectively. The free parameters of both model functions were determined by fitting the corresponding weighting function to the weighting function of the blob model. TOR-CD and the best-fitting TOR-VD were compared to the blob model with a final resampling step (BLOB-RS) and without resampling (BLOB-NRS) in phantom studies. For three different contrast ratios and two different voxel sizes, resolution noise curves were generated. TOR-VD and BLOB-NRS lead to nearly identical images for all investigated contrast ratios and voxel sizes. Both models showed strong Gibbs artefacts at 4 mm voxel size, while at 2 mm voxel size there were no Gibbs artefacts visible.
The spatial resolution was similar to the resolution with TOR-CD in all cases. The resampling step removed most of the Gibbs artefacts and reduced the noise level but also degraded the spatial resolution substantially. We conclude that the blob model can be considered just as a special case of a TOR-based reconstruction. The latter approach provides a more natural description of the detection process and allows for modifications that are not readily representable within the blob framework.
Registration No. 22148

Positron-Annihilation Lifetime Spectroscopy using Electron Bremsstrahlung
Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Fritz, F.; Kempe, M.; Krause-Rehberg, R.
Abstract: A new type of an intense source of positrons for materials research has been set up at the superconducting electron linear. The source employs hard X-rays from electron-bremsstrahlung production generating energetic electron-positron pairs inside the sample under investigation. CW-operation allows performing experiments with significantly reduced pile-up artefacts in the detectors compared to pulsed mode operation in conventional accelerators. The high-resolution timing of the accelerator with bunch lengths below 10 ps full width at half maximum (FWHM) allows positron annihilation lifetime spectroscopy (PALS) measurements with high time resolution. A single-component annihilation lifetime of Kapton has been measured as (381.3 ± 0.3) ps. Employing segmented detectors for the detection of both annihilation photons allows for the first time to perform a 4D tomographic reconstruction of the annihilation sites including the annihilation lifetime.
Keywords: positrons materials research ELBE linac superconducting tomography

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Registration No. 22147

Coulomb Dissociation Experiment of P-27
Marganiec, J.; Beceiro-Novo, S.; Typel, S.; Wimmer, C.; Alvarez-Pol, H.; Aumann, T.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Cortina Gil, D.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Rodriguez Tajes, C.; Rossi, D.; Simon, H.; Stanoiu, M.; Stroth, J.; Sümmerer, K.; Wagner, A.; Wamers, F.; Weick, H.
Abstract: The 26Si(p;gamma)27P reaction, which might play an important role in the rp process, was studied by the Coulomb Dissociation method. The experiment was performed at GSI, Darmstadt. A secondary 27P ion beam of 500 MeV/nucleon was directed onto a Pb target. From this experiment, the Coulomb Dissociation cross section will be deduced and then converted to the photoabsorption cross section, and the radiative-capture cross section. Also information on the structure of 27P will be obtained. The analysis is in progress.
Keywords: Coulom dissociation radiative-capture radioactive beams

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Registration No. 22141

Depth-resolved slow positron beam analysis of ECR proton and argon implanted graphite and boron nitride system
Ganguly, B. N.; Menon, R.; Yalagoud, N. P.; Bandyopadhyay, S. K.; Anwand, W.; Brauer, G.
Abstract: Layered materials and sp2 hybridized structures like graphite and hexagonal-boron nitride (h-BN) have been subjected to electron cyclotron resonance (ECR) ion beam implantation of proton and argon ions at different fluences and studied primarily employing slow positron beam technique using positron annihilation Doppler broadening spectroscopy (DBS). The results show remarkable structural perturbation effects in the implantation areas around the depth of 200–300 nm from the top surface, in both the systems but with glaring differences in the trends of the line shape analysis in terms of S and W parameters. Due to proton and argon ion implantation, structurally damaged lattice with open volume defects exists in graphite. But, for both the ion implantations at the high fluence, profound clustering effect of the respective atoms within the interstitial space are evident in h-BN. The structural effects of both graphite and h-BN lattice after the said implantation have been studied and corroborated through grazing incidence X-ray diffraction (GI-Xray) method and Raman scattering spectroscopy as complementary analytical techniques.
Keywords: BN, graphite, grazing incidence X-ray diffraction, positron beams, Raman spectroscopy, slow positrons Registration No. 22140

How radio-ecological research helps to develop innovative nanobiomaterials
Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.
Abstract: The presentation introduces the Institute of Resource Ecology and the Helmholtz Institute Freiberg for Resource Technology and provides an insight into the work of the Biotechnology Group.
Keywords: radio-ecology, resource technology, nano-biotechnology,
  • Lecture (others)
    Arbeitskreisseminar Technische Chemie, 03.07.2015, Paderborn, Deutschland
Registration No. 22139

Investigating hadronic resonances in pp interactions with HADES
Przygoda, W.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc3, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Yu. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.
Abstract: In this paper we report on the investigation of baryonic resonance production in proton-proton collisions at the kinetic energies of 1.25 GeV and 3.5 GeV, based on data measured with HADES. Exclusive channels npπ+ and ppπ0 as well as ppe+e− were studied simultaneously in the framework of a one-boson exchange model. The resonance cross sections were determined from the one-pion channels for Δ(1232) and N(1440) (1.25 GeV) as well as further Δ and N* resonances up to 2 GeV/c2 for the 3.5 GeV data. The data at 1.25 GeV energy were also analysed within the framework of the partial wave analysis together with the set of several other measurements at lower energies. The obtained solutions provided the evolution of resonance production with the beam energy, showing a sizeable non-resonant contribution but with still dominating contribution of Δ(1232)P33. In the case of 3.5 GeV data, the study of the ppe+e− channel gave the insight on the Dalitz decays of the baryon resonances and, in particular, on the electromagnetic transition form-factors in the time-like region. We show that the assumption of a constant electromagnetic transition form-factors leads to underestimation of the yield in the dielectron invariant mass spectrum below the vector mesons pole. On the other hand, a comparison with various transport models shows the important role of intermediate ρ production, though with a large model dependency. The exclusive channels analysis done by the HADES collaboration provides new stringent restrictions on the parameterizations used in the models.

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Registration No. 22138

Specific binding biomolecules
Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Hofinger, J.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.
Abstract: During evolution nature has evolved different kinds of specific binding macro-molecules being crucial for cell metabolism and their interaction with the environment. Most important examples therefore are proteins and nucleic acids. But beside biogenic molecules, specific proteins and nucleic acids can also be selected by doing an in vitro evolution using large molecule libraries. In this way specific ligands for various targets can be obtained allowing the development of new materials for different industrial applications.
Keywords: Sepcific binding, proteins, peptides, aptamers
  • Invited lecture (Conferences)
    Professur-Seminar Biomaterialien, 01.07.2015, Dresden, Deutschland
Registration No. 22137

Developed turbulence and nonlinear amplification of magnetic fields in laboratory and astrophysical plasmas
Meinecke, J.; Tzeferacos, P.; Bell, A.; Bingham, R.; Clarke, R.; Churazov, E.; Crowston, R.; Doyle, H.; Drake, R. Paul; Heathcote, R.; Koenig, M.; Kuramitsu, Y.; Kuranz, C.; Lee, D.; Macdonald, M.; Murphy, C.; Notley, M.; Park, H.-S.; Pelka, A.; Ravasio, A.; Reville, B.; Sakawa, Y.; Wan, W.; Woolsey, N.; Yurchak, R.; Miniati, F.; Schekochihin, A.; Lamb, D.; Gregori, G.
Abstract: The visible matter in the universe is turbulent and magnetized. Turbulence in galaxy clusters is produced by mergers and by jets of the central galaxies and believed responsible for the amplification of magnetic fields. We report on experiments looking at the collision of two laser-produced plasma clouds, mimicking, in the laboratory, a cluster merger event. By measuring the spectrum of the density fluctuations, we infer developed, Kolmogorov-like turbulence. From spectral line broadening, we estimate a level of turbulence consistent with turbulent heating balancing radiative cooling, as it likely does in galaxy clusters. We show that the magnetic field is amplified by turbulent motions, reaching a nonlinear regime that is a precursor to turbulent dynamo. Thus, our experiment provides a promising platform for understanding the structure of turbulence and the amplification of magnetic fields in the universe.
Keywords: galaxy clusters, laboratory analogues, lasers, magnetic fields, turbulence Registration No. 22136

Recycling of magnesium chips
Ohmann, S.; Ditze, A.; Scharf, C.
Abstract: Magnesium chips were processed by means of re-melting. An important requirement of re-melting the chips is the removal of oil and moisture. The results show that using acetone in a soxhlet as an organic solvent is a more efficient method to obtain good results compared to vacuum distillation with a rotational evaporator. The subsequent re-melting has been successfully performed without the addition of flux between temperatures of 580 °C and 600°C. At this temperature range, the exothermic reaction of magnesium with the oxygen present in the surrounding atmosphere was avoided. Results show that more than 95 % of the magnesium chips were able to be recovered as metal. Experiments were performed at different scales to obtain production parameters for the recycling process. Larger particle size of magnesium chips were able to be faster remelted than the smaller ones. In the case of added lime for oil removal, the yield of recovered magnesium was lower due to the reaction towards magnesium foam. The ability of re-melting at low temperatures without the need for flux demonstrates the possibility of recovering virtually all of the metal from the chips.
Keywords: Magnesium, Chips, Recycling, Remelting, Analysis
  • Contribution to proceedings
    European Metallurgical Conference, 14.-17.06.2015, Düsseldorf, Germany
    EMC 2015 Volume 1, 978-3-940276-61-2
Registration No. 22134

Understanding Cu mobilisation from Kupfershale leaching: [64Cu]CuS: Ligand identification, kinetic rates and modelling Preliminary Results.
Lippmann-Pipke, J.; Barthen, R.; Gründig, M.; Karimzadeh, L.; Schössler, C.; Mansel, A.; Grenzer, J.; Scholz, A.; Bischoff, L.; Schymura, S.; Kulenkampff, J.; Franke, K.; Lippold, H.
Abstract: Es ist kein Abstract vorhanden.
  • Poster
    General Meeting 3, Ecometals, 23.-24.06.2015, Halle/Saale, Deutschland
Registration No. 22133

Liquid phase epitaxy of binary III-V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Bregolin, F.; Hübner, R.; Voelskow, M.; Helm, M.; Skorupa, W.
Abstract: The integration of III-V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III-V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO2/Si/SiO2 layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III-V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.
Keywords: ion implantation, flash lamp annealing, III-V integration into silicon, nanostructure, liquid phase epitaxy, compound semiconductor Registration No. 22132

Flash-Enhanced Atomic Layer Deposition: Basics, Opportunities, Review, and Principal Studies on the Flash-Enhanced Growth of Thin Films
Henke, T.; Knaut, M.; Hossbach, C.; Geidel, M.; Rebohle, L.; Albert, M.; Skorupa, W.; Bartha, J.
Abstract: Within this work, flash lamp annealing (FLA) is utilized to thermally enhance the film growth in atomic layer deposition (ALD). First, the basic principles of this flash-enhanced ALD (FEALD) are presented in detail, the technology is reviewed and classified. Thereafter, results of our studies on the FEALD of aluminum-based and ruthenium thin films are presented. These depositions were realized by periodically flashing on a substrate during the precursor exposure. In both cases, the film growth is induced by the flash heating and the processes exhibit typical ALD characteristics such as layer-by-layer growth and growth rates smaller than one angstrom/cycle. The obtained relations between process parameters and film growth parameters are discussed with the main focus on the impact of the FLA-caused temperature profile on the film growth.

Similar, substrate-dependent growth rates are attributed to the different optical characteristics of the applied substrates. Regarding the ruthenium deposition, a single-source process was realized. It was also successfully applied to significantly enhance the nucleation behavior in order to overcome substrate-inhibited film growth. Besides, this work addresses technical challenges for the practical realization of this film deposition method and demonstrates the potential of this technology to extend the capabilities of thermal ALD.

Keywords: flash lamp annealing, atomic layer deposition

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Registration No. 22131

Uranyl(VI) hydrolysis studied by luminescence spectroscopy
Drobot, B.; Steudtner, R.; Raff, J.; Brendler, V.; Geipel, G.; Tsushima, S.
Abstract: Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the [UO2(H2O)5]2+ cation (aquo complex, 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified. Refined structural and thermodynamical data of uranyl(VI) hydrolysis is thus acquired.
  • Poster
    Second Joint Student Workshop on f-Element Chemistry, 09.-10.06.2015, Karlsruhe, Deutschland
Registration No. 22130

XAS and XMCD studies of magnetic properties modifications of Pt/Co/Au and Pt/Co/Pt trilayers induced by Ga+ ions irradiation
Mazalski, P.; Sveklo, I.; Kurant, Z.; Ollefs, K.; Rogalev, A.; Wilhelm, F.; Fassbender, J.; Baczewski, L.; Wawro, A.; Maziewski, A.
Abstract: Magnetic and magneto-optical properties of Pt/Co/Au and Pt/Co/Pt trilayers subjected to 30 keV Ga+ ion irradiation are compared. In two-dimensional maps of these properties as a function of cobalt thickness and ion fluence, two branches with perpendicular magnetic anisotropy (PMA) for Pt/Co/Pt trilayers are well distinguished. The replacement of the Pt capping layer with Au results in the two branches still being visible but the in-plane anisotropy for the low-fluence branch is suppressed whereas the high-fluence branch displays PMA. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) spectra are discussed and compared with non-irradiated reference samples. The changes of their shapes and peak amplitude, particularly for the high-fluence branch, are related to the modifications of the local environment of Co(Pt) atoms and the etching effects induced by ion irradiation. Additionally, in irradiated trilayers the XMCD measurements at the Pt L-2,L-3-edge reveal an increase of the magnetic moment induced in Pt atoms. Registration No. 22126

Kinematic dynamos resulting from the interaction of high permeability material and flows of liquid sodium
Giesecke, A.; Stefani, F.
Abstract: We perform numerical simulations of the dynamo effect driven by various flow fields of a conducting liquid interacting with "magnetic material" characterized by a large relative permeability. The examinations are motivated by the key role of soft iron impellers for the Von-Kármán-Sodium (VKS) dynamo [1] and by the repeatedly expressed idea to make use of Oxide Dispersion Strengthened (ODS) ferritic/martensitic alloys in the core of a fast reactor which may exhibit a permeability much larger than one [2].

The results of our simulations that consider a localized distribution with finite permeability clearly differ from computations using simplyfying pseudo-vacuum boundary conditions (vanishing tangential field conditions) in order to mimic the impact of infinite permeability. Our kinematic simulations of an axisymmetric model of the VKS dynamo show a close connection between the exclusive occurrence of dynamo action in the presence of soft iron impellers and the observed axisymmetry of the magnetic field [3]. We qualitatively explain this effect by paramagnetic pumping at the fluid-disk interface and propose a simplified analytical model that quantitatively reproduces numerical results. In order to fully explain the observation of growing magnetic fields in the VKS dynamo we resort to mean-field dynamo theory [4] in terms of an α-effect caused by helical outflows between adjacent blades attached to the impeller disks.

In order to examine the properties of the α- and β-effect (which is closely related to the turbulent diffusivity) under influence of magnetic material [5] we use an idealized helical flow field (a modified Roberts flow). We compute the mean-field coefficients using the test-field method [6] and proof that the corresponding mean-field models are indeed capable to reproduce growth-rates and principle field structure of the fully resolved model by requiring much less computational efforts.

Further remarkable results are the observed reduction of the critical magnetic Reynolds number by roughly 30 percent independently of configuration or flow geometry when the permeability is sufficiently large. However, this universality is not reflected in the behavior of the mean-field coefficients. In particular, the β-effect strongly depends on the geometry and the permeability. A striking feature is the occurrence of negative β which has previously been observed in simulations [7] and, more recently, in experiments [8].

Our results for the mean-field coefficients allow the development of dynamo models for nearly arbitrary systems of various sizes consisting of a large number of helical small scale flow cells embedded into some large flow structure.


[1]Monchaux, R. et al., Phys. Rev. Lett. 98 (2007), 044502
[2]Dubuisson, P., de Carlan, Y., Garat, V. and Blat, M., J. Nucl. Mater. 428 (2012), 6–12
[3]Giesecke, A. et al., New J. Phys. 14 (2012), 053005
[4]Krause, F. and Rädler, K.-H. Mean-field Magnetohydrodynamics and dynamo theory, Pergamon Press 1980
[5]Giesecke, A. et al., New J. Phys. 16 (2014), 073034
[6]Schrinner, M. et al., Astron. Nachr. 326 (2005), 245-249
[7]Rädler, K.-H. and Brandenburg, A., Phys. Rev. E 67 (2003), 026401
[8]Frick, P., Noskov, V., Denisov, S. and Stepanov ,R., Phys. Rev. Lett. 105 (2010), 184502

Keywords: dynamo
  • Lecture (Conference)
    Russian Conference on Magnetohydrodynamics, 22.-25.06.2015, Perm, Russia
Registration No. 22124

In vivo Demonstration of an Active Tumor Pretargeting Approach with Peptide Nucleic Acid Bioconjugates as Complementary System
Leonidova, A.; Foerster, C.; Zarschler, K.; Schubert, M.; Pietzsch, H.-J.; Steinbach, J.; Bergmann, R.; Metzler-Nolte, N.; Stephan, H.; Gasser, G.
Abstract: A novel, promising strategy for cancer diagnosis and therapy is the use of a pretargeting approach. For this purpose, the non-natural DNA/RNA analogues Peptide Nucleic Acids (PNAs) are ideal candidates as in vivo recognition units due to their high metabolic stability and lack of unspecific accumulation. In the pretargeting approach, an unlabeled, highly specific antibody-PNA conjugate has sufficient time to target a tumor before administration of a small fast-clearing radiolabeled complementary PNA that hybridizes with the antibody-PNA conjugate at the tumor site. Herein, we report the first successful application of this multistep process using a PNA-modified epidermal growth factor receptor (EGFR) specific antibody (Cetuximab) and a complementary 99mTc-labeled PNA. In vivo studies on tumor bearing mice demonstrated a rapid and efficient in vivo hybridization of the radiolabeled PNA with the antibody-PNA conjugate. Decisively, a high specific tumor accumulation was observed with a tumor-to-muscle ratio of >8, resulting in a clear visualization of the tumor by single photon emission computed tomography (SPECT). Registration No. 22118

Tomographic investigations on the effects of gas entrainment on centrifugal pumps
Schäfer, T.
Abstract: High-resolution gamma-ray computed tomography (HireCT) was applied to clarify the two phase flow distribution inside the impeller wheel of a running pump. Thus, the accumulated gas holdup inside the impeller of an industrial centrifugal pump was investigated and analysed, depending on the suction side gas volume fraction and type of two phase flow regime. Using time-averaging rotation-synchronized tomographic imaging technique, effects on the conveying performance of the centrifugal pump could be clarified. The obtained results contributes to a better understanding of the flow behavior and its effects inside the impeller of a centrifugal pump, which is running under two phase flow conditions due to gas entrainment. Moreover, the results can help to develop improved pump designs to avoid loss of conveying performance due to gas entrainment.
Keywords: centrifugal pump, gas entrainment, two-phase flow, advanced gamma-ray computed tomography, phase fraction visualization
  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology (AMNT), 05.-07.05.2015, Berlin, Deutschland
Registration No. 22114

Untersuchung von Zweiphasenströmungen in einer Kreiselpumpe mittels tomographischer Bildgebungsverfahren
Schäfer, T.; Neumann, M.; Bieberle, A.; Hampel, U.
Abstract: Zentrifugalpumpen sind sehr weitverbreitet und werden in vielfältiger Weise unter anderem in der Prozessindustrie oder im Kraftwerksbereich eingesetzt. Beispielweise nutzt man Kreiselpumpen in Raffinerien als Speisepumpen oder in Kraftwerken als Umwälzpumpen in Kühlkreisläufen. Erfolgt der Einsatz auch in sicherheitsrelevanten Bereichen, wie z.B. in der Reaktornotkühlung von Kernkraftwerken, muss unbedingt ein störungsfreier und zuverlässiger Betrieb gewährleistet werden. Obwohl diese Pumpen einfach aufgebaut sind, bieten sie eine Reihe von Vorteilen, wie zum Beispiel hohe Effizienz bei geringem Energieverbrauch, ruhiger und kontinuierlicher Förderstrom und hohe Haltbarkeit und Beständigkeit. Es ist bekannt, dass sowohl Gaseintrag als auch Dampfbildung durch Kavitation schädlich und kritisch für den Betrieb von Kreiselpumpen sind, welche eigentlich für den einphasigen Betrieb ausgelegt sind. Gaseintrag kann beispielsweise in Situationen entstehen, wo Flüssigkeiten aus Reservoirs mit einem zu niedrigen Füllstand gefördert werden. Hier können sich als Konsequenz aus der unzureichenden Überdeckung des Pumpenansaugstutzens und der Anwesenheit von Initialwirbeln an der Flüssigkeitsoberfläche Hohlwirbel ausprägen. Derartige Situationen sind insbesondere in Kernkraftwerken, wo beispielsweise Notkühlmittel aus einem Reservoir wie der Kondensationskammer gefördert wird, unbedingt zu vermeiden. Der Gaseintrag führt zu einer verminderten Förderleistung der Pumpe, bis hin zum vollständigen Zusammenbruch der Förderrate. Außerdem kann vorhandenes Gas in Pumpen unter anderem zum Verlust der Kühlung der Lager und der Gleitringdichtung führen, was zu einer früheren Abnutzung bis hin zum Versagen der Pumpe führt. Auch starke Vibrationen welche ebenfalls zur Schädigung der Lager beitragen, sowie Abnutzungserscheinungen an den Laufradschaufeln können eintreten. Die vorgestellte Arbeit leistet mit quantitativen Messungen, Visualisierungen und Analysen der Gas-Flüssigkeits-Phasenverteilungen innerhalb des Laufrades und des umgebenden Pumpengehäuses einer fördernden Kreiselpumpe einen Beitrag zum fundamentalen Verständnis der Auswirkungen von Gaseintrag in Zentrifugalpumpen.
Keywords: Kreiselpumpe, Gaseintrag, Zweiphasenströmung, erweiterte Gammastrahlen-Computertomographie, Visualisierung der Phasenanteile centrifugal pump, gas entrainment, two-phase flow, advanced gamma-ray computed tomography, phase fraction visualization
  • Invited lecture (Conferences)
    2. Projektstatusgespräch zur BMBF-geförderten Nuklearen Sicherheitsforschung, 25.-26.03.2015, Dresden, Deutschland
Registration No. 22113

Synthesis and First Evaluation of [18F]Fluorocyano- and [18F]Fluoronitroquinoxalinedione as Putative AMPA Receptor Antagonists
Olma, S.; Ermert, J.; Sihver, W.; Coenen, H.-H.
Abstract: Derivatives of quinoxalinedione (QX) were chosen as chemical lead for the development of new radioligands of the AMPA receptor, since there are several examples of QX-derivatives with high affinity. The radiosyntheses of the new compounds 6-[18F]fluoro-7-nitro-QX ([18F]FNQX) and 7-[18F]fluoro-6-cyano-QX ([18F]FCQX) with radiochemical yields of 8 ± 2 and 3 ± 2 %, respectively, as well as the evaluation of their binding properties to the AMPA-receptor were performed. A comparison of the Ki-values of the new QX-derivatives FCQX and FNQX with mono-substituted cyanoand nitro-QX shows negligibly small differences of affinity (within the range of 1.4 to 5 µM), but exhibits a tenfold lower affinity than derivatives with two electron withdrawing groups like the 7-cyano-6-nitro-compound CNQX and the 6,7- dinitro compound DNQX. Thus, with respect to the low affinity and a high non-specific binding with in vitro and ex vivo autoradiographic studies, the new compounds do not lend themselves for in vivo imaging.
Keywords: AMPA receptor, fluorine-18, glutamate receptor, positron emission tomography, quinoxalinedione, radiofluorination. Registration No. 22111

Nichtinvasive Zustandsüberwachung von Kernreaktoren zur Detektion von Füllstandsänderungen und Deformationen des Kerns
Hampel, U.; Brachem, C.; Lange, C.; Kratzsch, A.; Schmidt, S.; Fiß, D.; Härtel, S.; Konheiser, J.
Abstract: Der Vortrag stell das laufende BMBF-Vorhaben "Nichtinvasive Zustandsüberwachung von Kernreaktoren zur Detektion von Füllstandsänderungen und Deformationen des Kerns" vor. Berichtet wird über den Hintergrund des Vorhabens, Zielstellungen im Rahmen der Reaktorsicherheitsforschung und Nachwuchsförderung in der Kerntechnik sowie über aktuelle Projektergebnisse.
Keywords: Nuclear Safety, Reactor Safety, Reactor Monitoring, Monte-Carlo Simulation
  • Invited lecture (Conferences)
    Projektstatusgespräch zu BMBF-geförderten FuE-Arbeiten auf dem Gebiet der Nuklearen Sicherheits- und Entsorgungsforschung sowie Strahlenforschung, 25.03.2015, Dresden, Deutschland
Registration No. 22109

Toward polarized antiprotons: Machine development for spin-filtering experiments
Weidemann, C.; Rathmann, F.; Stein, H.; Lorentz, B.; Bagdasarian, Z.; Barion, L.; Barsov, S.; Bechstedt, U.; Bertelli, S.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Goslawski, P.; Grigoriev, K.; Guidoboni, G.; Kacharava, A.; Kamerdzhiev, V.; Khoukaz, A.; Kulikov, A.; Lehrach, A.; Lenisa, P.; Lomidze, N.; Macharashvili, G.; Maier, R.; Martin, S.; Mchedlishvili, D.; Meyer, H.; Merzliakov, S.; Mielke, M.; Mikirtychiants, M.; Mikirtychiants, S.; Nass, A.; Nikolaev, N.; Oellers, D.; Papenbrock, M.; Pesce, A.; Prasuhn, D.; Retzlaff, M.; Schleichert, R.; Schroer, D.; Seyfarth, H.; Soltner, H.; Statera, M.; Steffens, E.; Stockhorst, H.; Stroher, H.; Tabidze, M.; Tagliente, G.; Engblom, P.; Trusov, S.; Valdau, Y.; Vasiliev, A.; Wustner, P.
Abstract: The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3 MeV in COSY. The implementation of a low-β insertion made it possible to achieve beam lifetimes of τb=8000  s in the presence of a dense polarized hydrogen storage-cell target of areal density dt=(5.5±0.2)×1013  atoms/cm2. The developed techniques can be directly applied to antiproton machines and allow the determination of the spin-dependent p¯p cross sections via spin filtering.

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Registration No. 22107

Analysing powers and spin correlations in deuteron–proton charge exchange at 726 MeV
Dymov, S.; Azaryan, T.; Bagdasarian, Z.; Barsov, S.; Carbonell, J.; Chiladze, D.; Engels, R.; Gebel, R.; Grigoryev, K.; Hartmann, M.; Kacharava, A.; Khoukaz, A.; Komarov, V.; Kulessa, P.; Kulikov, A.; Kurbatov, V.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Mchedlishvili, D.; Merzliakov, S.; Mielke, M.; Mikirtychyants, M.; Mikirtychyants, S.; Nioradze, M.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Seyfarth, H.; Shmakova, V.; Stroeher, H.; Tabidze, M.; Trusov, S.; Tsirkov, D.; Uzikov, Yu.; Valdau, Yu.; Weidemann, C.; Wilkin, C.
Abstract: The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td=726 MeV. By selecting two fast protons at low relative energy Epp, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron–proton charge-exchange amplitudes at a neutron kinetic energy of Tn≈1/2 Td=363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both Epp and the momentum transfer. This lends broad support to the current neutron–proton partial wave solution that was used in the estimation. Registration No. 22106

Biodistribution, cellular localization, and in vivo tolerability of S-35-labeled antiinflammatory dendritic polyglycerol sulfate amine
Holzhausen, C.; Groger, D.; Mundhenk, L.; Donat, C. K.; Schnorr, J.; Haag, R.; Gruber, A. D.
Abstract: Antiinflammatory dendritic polyglycerol sulfate (dPGS) holds great potential in the treatment and imaging of inflammatory processes. Here, we studied its biokinetic behavior, biodistribution, target cells, and in vivo toxicology. Following intravenous or subcutaneous application of (35)sulfur-labeled dPGS amine with a molecular weight of 10.05 kDa and a hydrodynamic diameter of 5.7 +/- 1.5 nm to mice, tissues were collected at specific time points (2, 15 min; 1, 24 h; 5, 21 days) and analyzed by liquid scintillation counting, autoradiography, radioluminography, and light microscopic autoradiography. The blood half-life of dPGS amine was 12 days. The major route of elimination was via the bile and feces.
Elimination via the kidney and urine was only initially observed after i.v., but not after s.c. injection. Regardless of the administration mode, liver and spleen were late target organs where dPGS amine accumulated in phagocytic cells. Despite bioaccumulation, toxicological histopathology failed to identify any adverse effects at any time and in any tissues examined suggesting a high in vivo biocompatibility and encouraging future investigation for biomedical applications.
Registration No. 22104

Felsenkeller shallow-underground accelerator laboratory for nuclear astrophysics (at p-process workshop)
Szücs, T.
Abstract: A very low background level is a key requirement for low-energy nuclear astrophysics experiments. A series of detailed high energy (E> 3 MeV) laboratory gamma-background study with escape-suppressed HPGe detectors has been performed at the surface of the Earth [1,2], at shallow underground (110 m w. e.) in the Felsenkeller laboratory in Dresden, Germany [2,3], at medium deep underground (400 m w. e.) in the Reiche Zeche mine in Freiberg, Germany [3], and at deep underground (3800 m w. e.) in LNGS in Gran Sasso, Italy [1]. 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 [2,3].
Benefiting from these low background conditions, a used 5 MV Pelletron tandem accelerator with external high-current sputter ion source for hydrogen and carbon beams is currently being refurbished for installation in Felsenkeller [4]. Installation of an additional radio-frequency ion source on the high voltage terminal is under way. The ions will be injected into the acceleration tube by an electrostatic deflector, thus the tandem mode of operation will be kept. With the RF-source up to 100A alpha beam is foreseen. Similarly high proton current either from the external or the internal source will be available. In addition, also a large, well-shielded HPGe detector for offline counting will be included in the new laboratory, enabling activation experiments.

The Felsenkeller accelerator will be used in part for in-house research by HZDR and TU Dresden, aiming for complementarity with the LUNA-MV project and science program. In addition, external users from any field of science will be highly welcome at Felsenkeller. Users are to be selected based on the recommendations of an independent group of outside advisers judging the scientific merits of the proposals.
Owing to the high current of the 5 MV Pelletron and the low laboratory background, the Felsenkeller laboratory may be suited to study p-process related nuclear reactions.

In addition to the detailed introduction of the new Felsenkeller accelerator laboratory, the talk will flash the recent status of the KADoNiS-p database [5].

- Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (NAVI, HGF VH-VI-417)

[1] T. Szücs et al., Eur. Phys. J. A 44, (2010) 513
[2] T. Szücs et al., Eur. Phys. J. A 48, (2012) 8
[3] T. Szücs et al., Eur. Phys. J. A 51, (2015) 33
[4] D. Bemmerer et al., Procc. of Sciences NIC XIII, (2015) 044
[5] T.Szücs et al., Nucl. Data Sheets 120, (2014) 191
http://www.kadonis.org/pprocess/

Keywords: Felsenkeller, Underground, accelerator, nuclear astrophysics
  • Lecture (Conference)
    p-process workshop 2015: status and outlook, 10.-13.06.2015, Limassol, Cyprus
Registration No. 22103

Cysteine cathepsins: their role in tumor progression and recent trends in the development of imaging probes
Löser, R.; Pietzsch, J.
Abstract: Papain-like cysteine proteases bear an enormous potential as drug discovery targets for both infectious and systemic human diseases. The considerable progress in this field over the last two decades has also raised interest in the visualization of these enzymes in their native context, especially with regard to tumor imaging.
After a short introduction to structure and general functions of human cysteine cathepsins, we highlight their importance for drug discovery and development and provide a critical update on the current state of knowledge towards their involvement in tumor progression, with a special emphasis on their role in therapy response. In accordance with a radiopharmaceutical point of view, the main focus of this review article will be the discussion of recently developed fluorescence and radiotracer-based imaging agents together with related molecular probes.

Keywords: Cancer, Carcinogenesis, extracellular enzymes, Fluorescence-based probes, Lysosomal cysteine proteases, metastasis, Molecular Imaging, radiotracers Registration No. 22101

Flexible Antigen-Specific Redirection of Human Regulatory T Cells Via a Novel Universal Chimeric Antigen Receptor System
Koristka, S.; Cartellieri, M.; Feldmann, A.; Arndt, C.; Loff, S.; Michalk, I.; Aliperta, R.; von Bonin, M.; Bornhäuser, M.; Ehninger, A.; Ehninger, G.; Bachmann, M. P.
Abstract: Based on compelling evidence from a vast number of in vitro and in vivostudies, Tregs have become an attractive cell population to treat or even prevent auto- and alloimmunity including Graft-versus-Host disease (GvHD). However, several safety concerns still exist as for example the risk of global immunosuppression using polyclonal Tregs. In fact, experiments in mice showed that adoptive transfer or induction of antigen-specific Tregs is more potent regarding suppression of pathogenic immune responses when compared to polyclonal Treg populations. Unfortunately, the isolation and expansion of naturally occurring antigen-specific Tregs is technically difficult, labour-intensive, and time-consuming. An attractive way to overcome these limitations and to endow polyclonal Treg populations with a desired antigen-specificity is their engraftment with chimeric antigen receptors (CARs). In this context, CAR-modification represents a promising approach to redirect polyclonal Tregs in an antigen-specific manner to suppress ongoing self-destructive immune responses at the site of inflammation.

Nevertheless, until now redirection of CAR-engineered T cells is limited to a single target antigen, restricting this approach to an unflexible monospecific therapy. Therefore, we developed a more flexible universal CAR (UCAR) platform that allows redirection of T cells to an in principal unrestricted number of surface antigens. T cells are engrafted with UCARs that bind to a small peptide epitope derived from a human nuclear protein. Cross-linkage to target cells is mediated by independent target modules that provide antigen-specificity and comprise the peptide epitope recognized by the UCAR. In order to target different tissue antigens, the target modules can easily be exchanged. Thereby, once established, the treatment strategy can easily be applied to various auto- and alloimmune diseases.

At present, the CD45RA+ population is the Treg subset of choice for a clinical application as these cells have the highest capacity to maintain phenotypic and functional Treg properties upon prolonged ex vivo expansion. Here we show that highly pure, sorted CD4+CD25+CD127lowCD45RA+ Tregs can be genetically manipulated using lentiviral gene transfer, resulting in approximately 70 % of UCAR-expressing Treg cells. The transduction procedure itself did not affect the phenotype of UCAR-engineered Tregs as it was similar to non-transduced wildtype cells. Both Treg populations presevered FOXP3 expression even after prolonged in vitro cultivation (> 95 % FOXP3+). Upon incubation with antigen-positive target cells and a respective target module UCAR-engineered Tregs upregulate the activation markers CD69 and LAP demonstrating that the cells can be restimulated antigen-specifically. Most importantly, UCAR-engrafted Tregs were functionally activated upon antigen encounter, demonstrated by suppression of proliferation and expansion of cocultured autologous T effector cells.

Taken together, our results pave the way towards an application of UCAR technology for a site-specific recruitment of CAR-modified Tregs into inflamed tissues aiming at re-establishing immune homeostasis. Due to its high flexibility UCAR-engrafted Tregs can easily and universally be used for treatment of various autoimmune diseases or GvHD just by exchanging the tissue-specific target modules.

Disclosures Cartellieri: Cellex Patient Treatment GmbH: Employment. Ehninger: GEMoaB GmbH: Employment, Patents & Royalties. Ehninger: GEMoaB GmbH: Consultancy, Patents & Royalties. Bachmann: GEMoaB GmbH: Consultancy, Patents & Royalties.
  • Abstract in refereed journal
    BLOOD 124(2014)21, 3494
  • Poster
    56th ASH Annual Meeting, 06.-09.12.2014, San Francisco, USA
Registration No. 22099

Novel indole-based sigma-2 receptor ligands: synthesis, structure–affinity relationship and antiproliferative activity
Xie, F.; Kniess, T.; Neuber, C.; Deuther-Conrad, W.; Mamat, C.; Liebermann, Brain P.; Liu, B.; Mach, Robert H.; Brust, P.; Steinbach, J.; Pietzsch, J.; Jia, H.
Abstract: We report the synthesis and biological evaluation of a series of indole-based σ2 receptor ligands derived from siramesine. In vitro competition binding assays showed that these analogues possessed high to moderate affinity and selectivity for σ2 receptors. Structure–affinity relationship analyses of these indole-based σ2 receptor ligands were performed. In the 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, 1a and 1b displayed significant and comparable antiproliferative activity in DU145, MCF7 and C6 cells to siramesine. In cell cycle analyses, compounds 1a, 1b and siramesine were found to induce a G1 phase cell cycle arrest in DU145 cells using flow cytometry. The combination of 5,6-dimethoxyisoindoline scaffold and N-(4-fluorophenyl)indole moiety was identified as a new σ2 receptor ligand deserving further investigation as an antitumor agent. Registration No. 22096

The origin and crust/mantle mass balance of Central Andean ignimbrite magmatism constrained by oxygen and strontium isotopes and erupted volumes
Freymuth, H.; Brandmeier, M.; Wörner, G.
Abstract: Volcanism during the Neogene in the Central Volcanic Zone (CVZ) of the Andes produced 1) stratovolcanoes, 2) rhyodacitic to rhyolitic ignimbrites which reach volumes of generally less than 300 km3 and 3) large volume monotonous dacitic ignimbrites of up to several thousand cubic kilometres. We present models for the origin of these magma types using O and Sr isotopes to, constrain crust/mantle proportions for the large volume ignimbrites and explore the relationship to the evolution of the Andean crust.
Oxygen isotope ratios were measured on phenocrysts in order to avoid the effects of secondary alteration. Our results show a complete overlap in the Sr-O isotope compositions of lavas from stratovolcanoes and low-volume rhyolitic ignimbrites as well as older (>9 Ma) large-volume dacitic ignimbrites. This suggests that the mass balance of crustal and mantle components are largely similar. By contrast, younger (<10 Ma) large-volume dacitic ignimbrites from the southern portion of the Central Andes have distinctly more radiogenic Sr and heavier O isotopes and thus contrast with older dacitic ignimbrites in northernmost Chile and southern Peru.
Results of assimilation and fractional crystallization (AFC) models show that the largest chemical changes occur in the lower crust where magmas acquire a base-level geochemical signature that is later modified by middle to upper crustal AFC. Using geospatial analysis we estimated the volume of these ignimbrite deposits throughout the Central Andes during the Neogene and examined the spatiotemporal pattern of so- called "ignimbrite flare-ups". We observe a N-S migration of maximum ages of the onset of large volume "ignimbrite pulses" through time: Major pulses occurred at 19-24 Ma (e.g. Oxaya, Nazca Group), 13-14 Ma (e.g. Huaylillas and Altos de Pica ignimbrites), <10 Ma (Altiplano and Puna ignimbrites). Such "flare-ups" represent magmatic production rates of 25 to >70 km3 Ma-1 km-1 (assuming plutonic:volcanic ratios of 1:5) which are additional to, but within the order of, the arc background magmatic flux. Comparing our results to average shortening rates observed in the Andes, we observe a "lag-time" with large-volume eruptions occurring after accelerated shortening. A similar delay exists between the ignimbrite pulses and the subduction of the Juan-Fernandez ridge. This is consistent with the idea that large-volume ignimbrite eruptions occurred in the wake of the N-S passage of the ridge after slab steepening has allowed hot asthenospheric mantle to ascend into and cause the melting of the mantle wedge.
In our model, the older large-volume dacitic ignimbrites in the northern part of the CVZ have lower (15 to 37 %) crustal contributions because they were produced at times when the Central Andean crust was thinner and colder, and large-scale melting in the middle crust could not be achieved. Younger ignimbrite flare-ups further south (< 10 Ma, > 22°S) formed with a significantly higher crustal contribution (22 to 68 %) because at that time the Andean crust was thicker and hotter and, therefore primed for more extensive crustal melting. The rhyolitic lower-volume ignimbrites are more equally distributed in the Central Volcanic Zone (CVZ) in time and space and are produced by mechanisms similar to those operating below large stratovolcanoes, but at times of higher melt fluxes from the mantle wedge.
Registration No. 22094

Melanoma targeting with [99mTcN(PNP3)]-labeled α-MSH peptide analogs: Preliminary studies
Gao, F.; Carta, D.; Salvarese, N.; Sihver, W.; Pietzsch, H.-J.; Biondi, B.; Ruzza, P.; Refosco, F.; Bolzati, C.
Abstract: Objectives: The purpose of this study was to examine the effect of cyclization on the biological profiles of [99mTcN(PNP3)]-labeled α-MSH analogs.
Methods: The linear peptide H-Cys-Ahx-bAla-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2 (NAP-NS1) (1) and a corresponding lactam bridge-cyclized peptide, H-Cys-Ahx-bAla3-c[Lys4-Glu-His-D-Phe-Arg-Trp-Glu10]-Arg11-Pro-Val-NH2 (NAP-NS2) (2), were synthesized, characterized by ESI-MS, and their melanocortin-1 receptor (MC1R) binding affinity was determined in B16F10 melanoma cells. In vitro stability and pharmacological parameters of [99mTc(N)(NAP-NS1)(PNP3)]+ (1a) and [99mTc(N)(NAP-NS2)(PNP3)]+ (2a) were assessed. Challenges with an excess of glutathione and cysteine and LogD values were also investigated. Furthermore, 1a and 2a were applied to study in vivo stability and the pharmacokinetic profiles on healthy rats.
Results: 1a and 2a were obtained in high yield (RCY > 90%). LogD values demonstrated the hydrophilic nature of the radiolabeled peptides: -1.43 for 1a; - 2.09 for 2a. No significant variations in RCPs of both the complexes were
observed. Both complexes showed high stability after incubation in human and rat sera as well as in rat liver homogenate. A fast degradation of 2a was detected in kidneys homogenate. 1a retained a high receptor affinity (Kd: 7.1±0.5 nM). Biodistribution of 1a displayed a favorable pharmacokinetic profile with fast blood clearance and elimination from normal tissues. Rapid renal excretion of 1a was observed due to the high hydrophilic
character. The pharmacokinetic profile of 2a was reflected in reduction of the blood clearance and the elimination from the other organs; especially the kidneys showed restraint elimination.
Conclusions: Compared with the linear peptide 1, cyclization affected the pharmacological properties of 2 negatively by reducing its stability, its binding affinity to MC1Rs (Ki: 0.9±0.3 nM for 1; 7.1±2.4 nM for 2) and decreasing the overall excretion rate of the corresponding [99mTcN(PNP3)]-labeled peptide from the body. Thus, only the linear labeled peptide 1a will be considered for further investigations in tumor bearing mice.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S359
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22091

(Radio)pharmacological characterization of novel α-MSH derivatives
Gao, F.; Sihver, W.; Bergmann, R.; Haase-Kohn, C.; Steinbach, J.; Carta, D.; Bolzati, C.; Calderan, A.; Pietzsch, J.; Pietzsch, H.-J.
Abstract: Objectives: Melanocortin-1 receptor (MC1R) is well known to be overexpressed in melanoma. Thus, it has been a great interest in targeting this receptor for diagnosis of human metastasized melanoma. We aimed at investigating
(radio)pharmacological properties of novel derivatives of the α-melanocyte-stimulating hormone (α-MSH) and selecting most promising candidates for further studies in melanoma models in vivo.
Methods: Linear and cyclic α-MSH derivatives (NAP-NS1(1), NOTA-NAP-NS1(2), natCu-NOTA-NAP-NS1(3), NAP-NS2(4), NOTA-NAP-NS2(5), natCu-NOTA-NAP-NS2(6), DPA-NAP-NS1(7) and Re-tricarbonyl-DPA-NAPNS1(8)) were investigated in competition assays in both murine B16F10 and human MeWo cells. In vitro stabilities of [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 were tested in phosphate buffer (pH=7.4) and human serum at 37°C for 1h and 24h. Transchelation and octanol/water partition coefficients of radiolabeled peptides were also investigated. Additionally, [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 with high radiochemical purities and specific activities were applied in saturation assays and kinetic studies.
Results: Linear α-MSH derivatives (1, 2, 3, 7 and 8) showed higher affinities on both murine and human cells than cyclic α-MSH derivatives (4, 5, 6). Linking the chelator to the peptide and coordinating the chelator-peptide with
natCu or Re were accompanied by some loss of affinity. [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 were stable in phosphate buffer and serum at 37°C after incubation for 1h and 24h. No transchelation of radiolabeled peptides was observed in cysteine and histidine challenge experiments. LogD values suggested that [64Cu]Cu-2 (-2.30±0.01) and [64Cu]Cu-5 (-3.39±0.04) had higher hydrophilicity than 99mTc-tricarbonyl-7 (-0.43±0.01). Saturation studies in both cell lines resulted in Kd values (nM) in the lower nanomolar ranges for [64Cu]Cu-2 (B16F10: 1.7±0.2; MeWo: 2.6±0.5) and 99mTc-tricarbonyl-7 (B16F10: 6.0±0.5; MeWo: 4.5±0.8). But Bmax (fmol/mg protein) of [64Cu]Cu-2 on murine and human cells (B16F10: 46.6±3.9; MeWo: 16.6±1.6) was notably lower than that of 99mTc-tricarbonyl-7 (B16F10: 403.5±46.1; MeWo: 50.3±6.4). Kinetic study of [64Cu]Cu-2 in murine cells showed rapid cellular association and dissociation in vitro.
Conclusions: [64Cu]Cu-2 showed high stability, hydrophilicity, binding affinities and rapid cellular association and dissociation in vitro, which made it promising for further investigations in melanoma models.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S345
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22090

Synthesis, 18F-labeling and radiopharmacological characterization of a claudin-targeting peptide
Löser, R.; Bader, M.; Kuchar, M.; Wodtke, R.; Bergmann, R.; Lenk, J.; Haase-Kohn, C.; Pufe, J.; Steinbach, J.; Pietzsch, J.
Abstract: Objectives: The cell surface receptor claudin-4 (Cld-4) is upregulated in various tumors and represents a promising target for both diagnosis and treatment of solid tumors of epithelial origin [1]. A suitable ligand to address Cld-4 in
vivo seems to be the C-terminal fragment of the Clostridium perfringens enterotoxin cCPE(290-319) (1; Figure 1)
[2].
Methods: 1 and N-terminally modified (fluorobenzoylated and FITC-conjugated) as well as other analogs were synthesized by microwave-assisted solid-phase peptide synthesis (SPPS). Their affinity to a protein construct containing both extracellular loops of Cld-4 was studied by surface plasmon resonance (SPR). Labeling of 1 with fluorine-18 was achieved on solid phase using [18F]SFB and 4-[18F]fluorobenzoyl chloride as 18F-acylating agents [3]. The stability of the resulting radiotracer was evaluated in different physiological media. Its cell binding was investigated using the HT29, A375 and A431 tumor cell lines. The in vivo behavior of 18F-labeled 1 was studied in NMRI nu/nu mice and Wistar rats by dynamic PET imaging and radiometabolite analyses, respectively. Furthermore, the binding of FITC-conjugated 1 was investigated by fluorescence microscopy.
Results: Among several approaches tried, sequential SPPS using three pseudoproline-dipeptide building blocks revealed as the most efficient one to afford 1 and its derivatives. Their affinities to the Cld-4 mimicking construct are in the low micromolar range. 18F-labeling was most advantageous when [18F]SFB was reacted with resin-bound 1 containing an N-terminal aminohexanoic spacer. The resulting radiotracer was sufficiently stable in cell supernatants and plasma. Its cell binding was time-dependent and higher to the Cld-4-positive A375 and A431 compared to the negative HT29 line. Results of confocal microscopy using FITC-1 and A431 cells are in
accordance with these findings. 18F-labeled 1 is subject to substantial liver uptake and rapid metabolic degradation in vivo.
Conclusions: The synthesis and 18F-labeling of 1 was 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 form to target Cld-4 in vivo.
References
[1] Neese A, et al (2012) Arch. Biochem. Biophys. 524, 64–70.
[2] Ling J, et al (2008) J. Biol. Chem. 283, 30585–30595.
[3] Kuchar M, et al (2012) Amino Acids 43, 1431-1443.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S205
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22089

Targeting lysyl oxidase for molecular imaging in breast cancer
Wuest, M.; Kuchar, M.; Sharma, S. K.; Richter, S.; Wankg, M.; Vos, L.; Mackey, John R.; Wuest, F.; Löser, R.
Abstract: Objectives: Lysyl oxidase (LOX, EC 1.4.3.13) and its family members LOX-like 1-4 are copper-dependent matrixmodifying enzymes [1]. The expression of LOX is elevated in many human cancers, including breast cancer and
correlates with tissue hypoxia. The enzyme plays a critical role in breast cancer metastasis [2]. The goal of the current study was to target LOX with fluorescent and radiolabeled oligopeptides to visualize LOX in preclinical
models of breast cancer.
Methods: mRNA expression of all 5 LOX family members was analyzed by gene expression microarray analysis on samples from 176 breast cancer patients. The peptidic substrate GGGDPKGGGGG was selected to target LOX
[3]. The peptide was labeled with either FITC for confocal microscopy experiments or with the positron emitter fluorine-18 for molecular imaging in vivo using positron emission tomography (PET) (Figure 1). The preclinical
breast cancer models utilized were the murine breast cancer cell line EMT-6 and xenografts of MCF-7 and MDAMB-231.
Results: Immunofluorescence with a LOX-specific antibody confirmed that LOX protein expression is enhanced in hypoxic EMT-6 cells. FITC-labeled oligopeptide binds to several cell compartments of EMT6 cells under hypoxic
conditions. After injection of 18F-labeled oligopeptide, radioactivity uptake was visible in all three breast cancer models in vivo with SUV5min values of: 0.70±0.07 (n=3) in EMT-6, 0.57±0.01 (n=3) in MCF-7 and 0.68 (n=2) in MDA-MB-231. The following continuous washout of radioactivity led to SUV60min values of: 0.18±0.03 (n=3) in EMT-6, 0.14±0.02 (n=3) in MCF-7 and 0.13 (n=2) in MDA-MB-231. Tumor uptake was reduced by pre-dosing with the irreversible LOX inhibitor BAPN 4 h and 24 h prior to injection of the radiotracer.
Conclusions: These data support further investigations towards the development of LOX-binding peptides as molecular probes for imaging of LOX expression in breast cancer.
Acknowledgements: The access to the Alberta Cancer Foundation-supported CBCF Tumor Bank is well appreciated.
References
[1] Payne SL, et al (2007) J. Cell. Biochem.101, 1338-54.
[2] Erler JT, et al (2006) Nature 440, 1222-6.
[3] Nagan N and Kagan HM (1994) J. Biol. Chem. 269, 22366-71.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S204
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22088

Fast 18F-fluoroethylation without azeotropic drying in the radiosynthesis of cyclooxygenase-2 inhibitors
Kniess, T.; Laube, M.; Pietzsch, J.; Steinbach, J.
Abstract: Objectives: 18F-Fluoroethylation is a basic approach in PET labeling chemistry and 2-[18F]fluoroethyl tosylate ([18F]FETs) is one of the mostly used agents. Usual protocols with [18F]FETs are covering the azeotropic drying of [18F]fluoride, nucleophilic substitution, purification and 18F-fluoroethylation within 60-90 min synthesis time. We developed a fast 18F-fluoroethylation avoiding azeotropic drying to yield e.g. 18F-fluoroethylated cyclooxygenase-2 (COX-2) inhibitors within 25 min.
Methods: Our approach is based on the finding that [18F]fluoride trapped on SAX cartridges can be completely eluted by a mixture of K222/K2CO3/acetonitrile/2% water and is bsufficiently reactive for 18F-labeling. [1,2] [18F]Fluoride, trapped on the SAX cartridge is eluted with 0.7 mL K222/K2CO3/acetonitrile/H2O into a vial containing 20 μmol bis-tosylate precursor. The vial is heated 10 min at 100°C, than 20 μmol hydroxyl precursor and 40 μmol Cs2CO3 dissolved in 0.5 mL DMF are added. Additional heating for 10 min at 110°C yields the 18Ffluoroethylated COX-2 radiotracers, by almost complete consumption of [18F]FETs. We used three different precursors to build COX-2 inhibitors (Fig) as model compounds to elucidate 18F-fluoroethylation.
Results: By elution of the SAX cartridge (46 mg) with K222/K2CO3/acetonitrile/H2O (42 μmol, 21 μmol, 679 μL, 21 μL) the adsorbed activity could be tranferred nearly quantitatively (93-95%). [18F]FETs was formed in 79-88% rcy as confirmed by radio-TLC. Subsequent 18F-fluoroethylation of the corresponding hydroxyl precursors resulted in yields of 77-92% (n=7) in case of the cyclopentene (1), 54-65% (n=3) for the pyrazolo[1,5-b]pyridazine (2), and 44-70% (n=3) for the indomethacine (3).
Conclusions: The [18F]KF/K222/K2CO3/H2O complex, formed without azeotropic drying is highly reactive to form [18F]FETs in yields up to 88%. Hence the reaction time can be shortened resulting in fast 18F-fluoethylations with total radiochemical yields up to 92% as exemplified for three radiolabeled COX-2 inhibitors.
References
[1] Wessmann S.H. et al., Nuklearmedizin, 2012, 51, 1-8
[2] Kolb H.C. et al., J.Label.Compd.Radiopharm.,2011, 54, S518
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S169
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22087

18F-Radiolabeling of Second Generation EphB4 Inhibitors Based on Bis-anilinopyrimidines
Mamat, C.; Wiemer, J.; Mosch, B.; Pietzsch, J.; Steinbach, J.
Abstract: Objectives: Ephrins and its Eph receptors are dysregulated in several human tumor entities including malignant melanoma. In this regard, the EphB4/ephrinB2 system seems to play a major role in melanoma angiogenesis [1].
Thus,we developed a fluorine-18-containing peptide [2] extracellularly binding to EphB4 and a small 18F-labeled molecule which intracellularly binds to the EphB4 kinase domain with high affinity [3] in the past. However, the results showed low binding/uptake in A375EphB4 melanoma cells in vitro and in vivo. Therfore, a “second generation” lead structure based on bis-anilinopyrimidines (IC50 = 1.3 nM) [4] was chosen for novel EphB4-targeted radioligands.
Methods: The lead compound is based on two substructures (part A and B) which were synthesized independently. Two positions of the original inhibitor for the best position of the radiolabel were figured out using docking studies. Based on this, references 2 and 4 as well as precursors 1 and 3 were obtained. In order to introduce [18F]fluoride by ring opening, precursors 1 and 3 were prepared as azetidinium mesylates and lead to high RCYs.
The radiolabeling was done in anhydrous acetonitrile for 30 min at 100°C. Afterwards, the EOE protecting group, which is mandatory for the successful introduction, was cleaved under acidic conditions. The subsequent purification should be easy done by cartridges due to the ionic nature of the precursors [5].
Results: Interestingly, radiofluorination of the first precursor 1 did not lead to the desired tracer [18F]2. The delocalization of the positive charge over both aromatic rings might be the reason for this result. On the other hand, radiofluorination of diazaspirononane precursor 3 was successful and gives the desired [18F]4 in a radiochemical yield of 34% (n.d.c.) and high purity (>95%).
Conclusions: [18F]4 as novel potential EphB4-targeted radioligand based on the bis-anilinopyrimidine scaffold has been successfully synthesized and radiolabeled. Ongoing work is focused on the alternative preparation of radiotracer [18F]2 and on the biological evaluation of both radiotracers to be a suitable target for diagnostic applications.
References
[1] Mosch, B. et al. (2010), J. Oncol., DOI: 10.1155/2010/135285,
[2] Pretze, M., et al. (2013) ChemMedChem, 8, 935–945,
[3] Mamat, C., et al. (2012) ChemMedChem, 7, 1991–3002,
[4] Bardelle, C., et al. (2010) Bioorg. Med. Chem. Lett., 20, 6242–6245,
[5] Grosse-Gehling, P., et al. (2011) Radiochim. Acta 99, 365–373
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S166
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22086

18F-Labeling and Radiopharmacological Evaluation of Novel Purinedione Multi-Eph Inhibitors
Mamat, C.; Pretze, M.; Neuber, C.; Mosch, B.; Steinbach, J.; Pietzsch, J.
Abstract: Objectives: The overexpression of various Eph receptors in tumors provokes the recent interest in highly affine inhibitors as attractive leads for the development of new targeted radioligands to image cancer [1]. Selective Ephtyrosine
kinase inhibitors based on the purinedione skeleton have been explored in the past as potential probes for imaging of EphB4 [2] and a SNEW peptide for EphB2 [3]. However up to now, there is still no optimal radiotracer
available. Herein, we report the synthesis, radiofluorination and biological evaluation of two novel purinedione derivatives as potential multi Eph inhibitor radioligands.
Methods: Based on known positions for affinity-related interactions of the lead structure with the receptor [4] two positions are favorable for the labeling with fluorine-18. Two precursors 1 and 3 as well as their reference compounds 2 and 4 were prepared. The radiolabeling was done in dry ACN at 100°C for 30 min. First cell association studies were performed using various Eph expressing melanoma cells (A375wt/mock, A375EphB4,
A375EphB6, A375EphB4) and Eph-negative controls (HL-60).
Results: After labeling, both tracers [18F]2 and [18F]4 were obtained in 10 – 15 % RCY (n.d.c.) after HPLC separation (RCP: > 95%). Cell experiments in vitro revealed a substantial cell association of both [18F]2 and [18F]4 ranging from 40 to 50 %ID/mg protein at 120 min in all cell lines used. The lack of any significant difference between wild type, recombinant and control cells is indicative for cell association of, as expected, low selectivity, but also of low specificity. The latter is consistent with the observation that preincubation with 100 μM of nonradioactive compound did not result in substantial inhibition of cell association.
Conclusions: [18F]2 and [18F]4 were synthesized successfully and first in vitro experiments were accomplished showing substantial cell association for both tracers in various melanoma cells. However, the cell experiments revealed data on specificity of purinedione derivatives that are contradictory to data from literature [4]. These observations will be elucidated in ongoing studies.
Acknowledgements
References
[1] Mosch, B. et al. (2010), J. Oncol., DOI: 10.1155/2010/135285;
[2] Mamat, C. et al. (2012), ChemMedChem, 7, 1991–2003;
[3] Pretze, M., et al. (2013) ChemMedChem, 8, 935–945; [4] Lafleur, K. et al.
(2009) J. Med. Chem., 52, 6433–6446.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S165
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22085

First-in-human PET quantification study of cerebral α4β2* nicotinic acetylcholine receptors using the novel specific radioligand (−)-[18F]Flubatine
Sabri, O.; Becker, G.-A.; Meyer, P. M.; Hesse, S.; Wilke, S.; Graef, S.; Patt, M.; Luthardt, J.; Wagenknecht, G.; Hoepping, A.; Smits, R.; Franke, A.; Sattler, B.; Habermann, B.; Neuhaus, P.; Fischer, S.; Tiepolt, S.; Deuther-Conrad, W.; Barthel, H.; Schönknecht, P.; Brust, P.
Abstract: α4β2* nicotinic receptors (α4β2* nAChRs) could provide a biomarker in neuropsychiatric disorders (e.g., Alzheimer's and Parkinson's diseases, depressive disorders, and nicotine addiction). However, there is a lack of α4β2* nAChR specific PET radioligands with kinetics fast enough to enable quantification of nAChR within a reasonable time frame. Following on from promising preclinical results, the aim of the present study was to evaluate for the first time in humans the novel PET radioligand (−)-[18F]Flubatine, formerly known as (−)-[18F]NCFHEB, as a tool for α4β2* nAChR imaging and in vivo quantification.
Dynamic PET emission recordings lasting 270 min were acquired on an ECAT EXACT HR+ scanner in 12 healthy male non-smoking subjects (71.0 ± 5.0 years) following the intravenous injection of 353.7 ± 9.4 MBq of (−)-[18F]Flubatine. Individual magnetic resonance imaging (MRI) was performed for co-registration. PET frames were motion-corrected, before the kinetics in 29 brain regions were characterized using 1- and 2-tissue compartment models (1TCM, 2TCM). Given the low amounts of metabolite present in plasma, we tested arterial input functions with and without metabolite corrections. In addition, pixel-based graphical analysis (Logan plot) was used. The model's goodness of fit, with and without metabolite correction was assessed by Akaike's information criterion. Model parameters of interest were the total distribution volume VT (mL/cm3), and the binding potential BPND relative to the corpus callosum, which served as a reference region.
The tracer proved to have high stability in vivo,with 90% of the plasma radioactivity remaining as untransformed parent compound at 90 min, fast brain kinetics with rapid uptake and equilibration between free and receptor bound tracer. Adequate fits of brain TACs were obtained with the 1TCM. VT could be reliably estimated within 90 min for all regions investigated, and within 30 min for low-binding regions such as the cerebral cortex.
The rank order of VT by region corresponded well with the known distribution of α4β2* receptors (VT [thalamus] 27.4±3.8, VT [putamen] 12.7±0.9, VT [frontal cortex] 10.0±0.8, and VT [corpus callosum] 6.3±0.8). The BPND, which is a parameter of α4β2* nAChR availability, was 3.41±0.79 for the thalamus, 1.04±0.25 for the putamen and 0.61 ± 0.23 for the frontal cortex, indicating high specific tracer binding. Use of the arterial input function without metabolite correction resulted in a 10% underestimation in VT, and was without important biasing effects on BPND.

Keywords: (−)-[18F]Flubatine [(−)-[18F]NCFHEB] PET α4β2* nicotinic acetylcholine receptors Human brain Kinetic modeling Registration No. 22084

Radiosynthesis of [18F]cabozantinib and [18F]fluoroethyl-sunitinib: two RTK-inhibitors of VEGFR-2
Schwebe, M.; Bergmann, R.; Steinbach, J.; Pietzsch, J.; Kniess, T.
Abstract: Objectives: Radiolabeled inhibitors of the angiokinase VEGFR-2 might be suitable probes for monitoring induction of angiogenesis and anti-angiogenic therapy response in vivo with PET. [1,2]. We selected two VEGFR-2
inhibitors, cabozantinib (IC50, 0.03 nM) and sunitinib (IC50, 9.0 nM), both bearing a fluorine substituent, as lead
structures for 18F-radiolabeled PET tracers.
Methods: [18F]Cabozantinib is synthesized by a 3-step radiosynthesis with final condensation of 4-[18F]fluoroaniline with an acyl chloride precursor. 4-[18F]Fluoroaniline is formed by substitution of 1,4-dinitrobenzene with [18F]fluoride, subsequent reduction of the intermediate 4-[18F]fluoro-nitrobenzene with Pd/C and NaBH4. Since [18F]sunitinib is not accessible via direct nucleophilic 18F-substitution, we developed the 5-fluoroethylated derivative (IC50, 9 nM) as well the corresponding radiolabeled analogue.
Results: 4-[18F]fluoroaniline was obtained in >60% rcy starting from [18F]fluoride after SPE purification. [18F]Cabozantinib was formed by reaction of 4-[18F]fluoroaniline with 10 mg of acyl precursor in THF at rt in >90% rcy. HPLC purification delivered [18F]cabozantinib in 95% purity and specific activity >20 GBq/μmol. Reaction of the methanesulfonyl-substituted sunitinib precursor with [18F]fluoride resulted in 8% 18F-incorporation. HPLC purification yielded [18F]fluoroethyl-sunitinib in 100 MBq scale. First in vitro investigations on VEGFR-2 expressing human A 2058 melanoma cell line showed cellular uptake of [18F]cabozantinib up to 790±100 %ID/mg protein at 60 min that could be significantly blocked by 46±3% by its non-radioactive counterpart (10 μM). For
[18F]fluoroethyl-sunitinib the uptake reached 340±48 %ID/mg protein at 60 min. Stability tests in rat blood over 60 min revealed almost no metabolism for both radiotracers.
Conclusions: With the reliable radiosynthesis of [18F]cabozantinib and [18F]fluoroethyl-sunitinib two radiolabeled VEGFR-2 inhibitors with nano- and sub-nanomolar affinity and high in vivo stability are available.
Acknowledgements
References [1] Slobbe P. et al (2012) Drug Discov. Today, 17, 1175-1187
[2] Kniess T. (2012) Curr Pharm Des, 18, 2867-2874
  • Poster
    21st Internation Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S159
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22083

An attractive method for radiolabeling antibodies with Tc-99m
Wunderlich, G.; Naumann, A.; Schubert, M.; Pietzsch, H.-J.
Abstract: Objectives: Radiolabeled Cetuximab (C225, Ab) is an attractive tool for tumor targeting and delivering of particles for therapy or imaging applications of EGFR positive tumors. The labeling of Ab with radionuclides requires
suitable chelating agents for a stable binding of the radionuclides. Well known is the Ab labeling with In-111 (imaging) and Y-90 (therapy). The aim of the present study was to develop a sufficient radiolabeling technique of
this Ab with Tc-99m for SPECT imaging. A second label with a fluorescent dye (Alexa 488) enables to track the uptake of the compound with fluorescent microscopy.
Methods: NOTA (2,2',2''-(1,4,7-triazonane-1,4,7-triyl)triacetic-acid) was linked to C225 and labeled with the [Tc-99m]Tc(H2O)3(CO)3 complex that was made by a standard tricarbonylkit preparation [1]. For preparation of [Tc-99m]Tc(CO)3-NOTA-C225-Alexa(488) (figure 1) and [Tc-99m]Tc(CO)3-NOTA-C225 1 nM of the modified antibody was incubated with up to 1 GBq [Tc-99m]Tc(H2O)3(CO)3 complex and was shaken for 2 h at 40°C. The product was isolated by gelfiltration and tested for yield and stability with ITLC (Silica gel impregnated glass fiber
sheets, Varian) in 5% acetic acid. The cell membrane binding and cell uptake of the compound was detected with Cetuximab receptor positive A431 cells and Cetuximab negative MDA cells. For comparison the pure NOTA
ligand and unmodified Cetuximab were labeled with [Tc-99m]Tc(H2O)3(CO)3.
Results: NOTA-C225-Alexa(488), NOTA-C225 and NOTA ligand were successfully labeled with [Tc-99m]Tc(H2O)3(CO)3. Sufficient radiolabeling of Cetuximab was achieved and determined by ITLC. Yields: [Tc-99m]Tc-NOTA-C225-Alexa(488) 25-30% and [Tc-99m]Tc-NOTA-C225 50-60%. After purification the labeled compound is stable in cell culture medium and phosphate buffered saline to 24 h with a release of about 20%. Maximum membrane uptake at A431cells is determined after 1 h followed by a partly internalization into the cells. The affinity constant was found Kd = 3.71 nM and Bmax = 35 nM. Already after 1 h the localisation of NOTAC225-Alexa(488) is visualized with fluorescence microscope at cell membrane.
Conclusions: NOTA-Cetuximab can be radiolabeled with Tc-99m which is an interesting approach for SPECT studies in Nuclear Medicine besides the Ab labeling with Ga-68 or Cu-64.
Acknowledgements
References [1] Alberto, R. et al. (1998) J. Am. Chem. Soc., 120, 7987-7988.
  • Poster
    21st Internatioonal Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S105
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22082

Potential labeling strategies with NCA 197(m)Hg
Walther, M.; Wang, C.; Bergmann, R.; Pietzsch, H.-J.; Steinbach, J.
Abstract: Objectives: The decay properties of both nuclear isomers, like convenient half life 197mHg (T1/2 = 23.8 h, Eγ 133.98 keV, 33.5%) and 197Hg (T1/2 = 64.14 h, Eγ 77.4 keV, 18.7%), low energy gamma radiations for imaging and numerous Auger- and conversion electrons useful for therapy combined with unique chemical and physical properties of mercury and its compounds represent the motivation for this project. The no carrier added (NCA) radionuclide 197(m)Hg is accessible in sufficient quantity and quality for radiopharmaceutical research by irradiation of gold with protons using a cyclotron [1]. As the following logical step after examination of the production feasibility, the search for a suitable labeling tool was intensified.
Methods: Three different approaches to prepare a stable labeling unit at NCA level with 197(m)Hg were studied. The reactivity of the mercury(II) ions towards sulfur containing ligands (a), solvomercuration of alkenes (b) and electrophilic aromatic substitution (c) were investigated in this context. Prepared characteristic representatives of all three groups are shown in Figure 1.
Results: For all studied reactions the desired 197(m)Hg labeled compounds were detected. The mercury thiolate complexe (a) and the product of solvomercuration (b) show low stability in the presence of competing thiol ligands and therefore the suitability for radiopharmaceutical applications is not given. In contrast, diphenylmercury (c) as the simplest representative for symmetric diarylmercury compounds shows high stability against competing
ligands.
Conclusions: As a basis for the development of a convenient labeling method different kinds of mercury compounds were prepared and characterized at NCA level. After nuclide production this was the required succeeding part of the evaluation of the cyclotron-based NCA 197(m)Hg regarding their suitability for diagnostics and therapy of tumors. First promising results of investigations concerning the development of mercury compounds stable in vivo will be reported.

References: [1] Walther, M., Preusche, S., Bartel, S., Wunderlich, G., Freudenberg, R., Steinbach, J., Pietzsch, H.-J., Theranostic mercury: 197(m)Hg with high specific activity for imaging and therapy (2014) Appl. Radiat. Isot. submitted
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S99
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_2
Registration No. 22081

68Ga-DATATOC: Synthesis, radiolabeling and first in vivo studies
Waldron, B.; Seemann, J.; Sinnes, J.-P.; Bergmann, R.; Nagel, J.; Rösch, F.
Abstract: Objectives: 68 Ga-DOTATOC is currently used as standard for diagnostic imaging of neuroendocrine tumors (NETs) and its metastases. Radiolabeling can be performed manually and automated at 95 °C. In order to approach application of 68 Ga following a kit-type procedure, a DATA-based chelator (6-Amino-1,4-diazepine-triacetate) was used as it has shown to radiolabel under very mild conditions. Conjugation with TOC may enable radiolabeling of the peptide at room temperature.
Methods: DATATOC was synthesized in a seven step synthesis. Radiolabeling with 68 Ga was performed manually at room temperature and stability was assessed in human serum. An automated setup was also examined, using the Modular-Lab eazy (Eckert & Ziegler, Berlin, Germany). First in vivo studies using MPC-mCherry tumor bearing mice were performed and compared with 68 Ga-DOTATATE.
Results: Radiolabeling was performed at room temperature using N2 solution, NaOAc-buffer and 14 nmol DATATOC. Within 3 min a RCY of 96.3 ± 1.2 % was obtained. Stability was tested in human serum over a period
of 2 h (Δ = 1.3 %). Automated labeling with 23 nmol precursor achieved quantitative complexation of 68 Ga (> 99 %). In vivo PET/CT-studies with 68Ga-DATATOC indicate a high specific uptake in the tumor region after 10 min (SUV of 3.73 ± 1.49). In a blocking study with OC, the SUV in the tumor was reduced to 0.45 ± 0.15. In addition, 68 Ga-DATATOC showed high stability in mouse plasma with 93.7 % of the tracer remaining intact after 120 min. Compared to 68 Ga-DOTATATE a faster renal excretion of the tracer was observed.
Conclusions: DATATOC can be labeled with 68 Ga in a manual or automated setup rapidly at room temperature, offering significant advantages over similar DOTA-based derivatives. Because of quantitative labeling yields, product purification is unnecessary. Furthermore, first in vivo studies confirm excellent targeting and excretion characteristics for the novel tracer. With the perspective towards a kit-type formulation, the superior characteristics
of this new compound pave the way for a new generation of 68 Ga radiopharmaceuticals.
  • Lecture (Conference)
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S15
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_1
Registration No. 22080

A novel pretargeting system based on complementary L-oligonucleotides
Schubert, M.; Foerster, C.; Bergmann, R.; Sihver, W.; Vonhoff, S.; Klussmann, S.; Bethge, L.; Walther, M.; Pietzsch, J.; Pietzsch, H.-J.; Steinbach, J.
Abstract: Objectives: High metabolic stability, low immunogenicity and negligible specificity for naturally binding partners are predominant characteristics of L-configured oligonucleotides. These advantages predestine this substance class
for its use in pretargeted radioimmunotherapy as in vivo recognition system between a tumor-specific antibody and a radiolabeled chelate. We evaluated this new pretargeting system consisting of 64Cu labeled NOTA-L-DNA-10kDa-PEG and c-L-DNA modified Cetuximab (C225) in vitro and in vivo.
Methods: C225 was functionalized with NOTA, maleimide moieties and thiol-bearing c-L-DNA. Competition studies were carried out against 64Cu labeled standard NOTA3-C225 in FaDu and A431-cell lysates. In vitro pretargeting studies were done in intact FaDu and A431 cells. PET and biodistribution studies were performed both in FaDu and A431 tumor bearing mice by intravenous injection of 4 nmol NOTA3-C225-(c-L-DNA)1,5 and 1 nmol [64Cu]Cu-NOTA-L-DNA-10kDa-PEG 24 h later.
Results: We synthesized two Cetuximab derivatives with 1.5 and respective 5 c-L-DNA molecules per antibody. Competition assays showed that affinities are not affected as a result of conjugation with NOTA and c-L-DNA.
PET studies injecting only [64Cu]Cu-NOTA3-C225-(c-L-DNA)1.5 revealed that a pretargeting interval of 24 h is the best compromise between tumor accumulation, blood background as well as liver uptake. Biodistribution in pretargeted A431 tumor mice is characterized by decreased tumor uptake (see figure). Internalization of antibody within waiting period is the obvious reason and could be confirmed by cellular uptake studies. After 24 h over 2/3 of surface bound antibody was internalized.
Conclusions: The present pretargeting concept shows high potential for further preclinical studies. Use of a noninternalizing antibody is necessary to enhance both tumor uptake and tumor to background ratios.
  • Lecture (Conference)
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S14
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3302_1
Registration No. 22079

Evidence of a distinct Permian thermal event by EMP-Th-Pb-monazite ages in metapelites of the polymetamorphic Austroalpine basement
Schulz, B.; Zimmermann, R.; Krenn, E.
Abstract: During the Alpine orogeny, the Austroalpine basement complex of the Eastern Alps was thrusted upon the Penninic ophiolites and the European basement, now exposed in the Tauern and Engadine tectonic windows. The Austroalpine basement underwent a polymetamor- phic evolution since the Early Paleozoic. An Ordovi- cian-Silurian event, the Devonian-Carboniferous Var- iscan orogeny, as well as the Cretaceous and Tertiary Alpine orogenic periods have been recognised in many parts. Although a wealth of radiometric data on these events exist, a distinct Permian metamorphic episode has not yet been established. Corresponding mica cool- ing ages were considered as Variscan-to-Alpine “mixed ages” in this polymetamorphic frame. However, the intrusion of Permian pegmatites between 270-250 Ma is an important marker of the tectonic and magmatic activity (Schuster et al. 2001).

The Permian pegmatites can be traced from the Ortler- Campo basement through the basement to the south of the Tauern Window toward the East into the Saualpe and Koralpe units. The electron microprobe (EMP) Th-U-Pb monazite dating method (Montel et al. 1996) has been applied to the garnet-bearing metapelitic host rocks of these Permian pegmatites. In the Saualpe, the Permian pegmatites were strongly deformed during the eclogite-facies Cretaceous event. In the metapelitic host rocks, the Permian monazites have the largest grain sizes and abundance. They are often character- ised by spectacular coronas of apatite and allanite of a partial decomposition.

In the Schobergruppe and the Defereggen Alps to the south of the Tauern Window, the Permian monazites are a less prominent population, but clearly distinct from the Carboniferous monazites (Krenn et al. 2012). The characteristic coronas around the Permian mona- zites are lacking. Permian monazites occur mainly in a zone with fibrolitic sillimanite and andalusite in the vicinity of the pegmatites.

The Oetztal-Stubai basement to the W of the Tauern Window is characterised by a Cretaceous metamor- phic overprint. Permian pegmatites have not yet been reported. The monazite Th-U-Pb EMP ages in the Sellrain area and in the central Oetztal valley (Umhau- sen, Sölden) in the northern vicinity of the Cretaceous metamorphic zone are mostly Carboniferous. They are interpreted to be related to a Variscan amphibolite- to-eclogite-facies garnet crystallisation (Rode et al. 2012). Recent investigations in the Stubai valley re- vealed garnet metapelites with exclusively Permian monazites. These monazites are often surrounded and partly replaced by coronas of apatite and allanite. The mineral-chemical properties and the special character of the dating method allow the conclusion that the Permian monazites represent a distinct crystallisation event at low pressures, apparently in an occasional association to the pegmatites.

References

Krenn, E., Schulz, B. & Finger, F. (2012): Three generations of monazite in Austroalpine basement rocks to the south of the Tauern Window – evidences for Variscan, Permian and Alpine metamorphism. – Swiss Journal of Geosci- ences, 105, DOI 10.1007/s00015-012-0104-6.

Montel, J.-M., Foret, S., Veschambre, M., Nicollet, C. & Provost, A. (1996): A fast, reliable, inexpensive in-situ dating technique: Electron microprobe ages on monazite. – Chem. Geol., 131: 37-53.

Rode, S., Rösel, D. & Schulz, B. (2012): Constraints on the Variscan P-T evolution by EMP Th-U-Pb monazite dat- ing in the polymetamorphic Austroalpine Oetztal-Stubai basement (Eastern Alps). – Z. Dt. Ges. Geowiss. 163: 43- 67; Stuttgart.

Schuster, R., Scharbert, S., Abart, R. & Frank, W. (2001): Permo-Triassic extension and related HT/LP metamor- phism in the Austroalpine - Southalpine realm. – Mitt. Ges. Geol. Bergbaustud. Österr., 45: 111-141; Wien.
  • Poster
    GeoFrankfurt 2014, 21.-24.09.2014, Frankfurt/Main, Deutschland
Registration No. 22077

Simulation of the Gamma Radiation Distribution Emitted from a PWR Core under Severe Accident-Like Conditions
Brachem, C.; Schmidt, S.; Konheiser, J.; Hampel, U.
Abstract: Using a generic model of a pressurized water reactor, we have defined a set of severe accident-like reactor states depicting various degrees of coolant level decrease and core degradation. We then computed the gamma radiation distribution which would occur outside the reactor pressure vessel in each of the previously defined states using stationary Monte Carlo simulations. This is done in an effort to understand if it is possible to detect the occurrence of certain phenomena from outside the RPV and to eventually develop a system for state detection.
Keywords: accident, Monte Carlo simulation, gamma radiation,
  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Germany
Registration No. 22075

Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tubingen, Germany
Bailey, D. L.; Antoch, G.; Bartenstein, P.; Barthel, H.; Beer, A. J.; Bisdas, S.; Bluemke, D. A.; Boellaard, R.; Claussen, C. D.; Franzius, C.; Hacker, M.; Hricak, H.; La Fougere, C.; Guckel, B.; Nekolla, S. G.; Pichler, B. J.; Purz, S.; Quick, H. H.; Sabri, O.; Sattler, B.; Schafer, J.; Schmidt, H.; van den Hoff, J.; Voss, S.; Weber, W.; Wehrl, H. F.; Beyer, T.
Abstract: This paper summarises the proceedings and discussions at the third annual workshop held in Tubingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".
Keywords: Hybrid imaging, Molecular imaging, PET/CT, PET/MRI, PET, MRI, Quantification, Attenuation correction, Oncology, Paediatric oncology, Neurology, Cardiology Registration No. 22071

The association of tumor-to-background ratios and SUVmax deviations related to point spread function and time-of-flight F18-FDG-PET/CT reconstruction in colorectal liver metastases
Rogasch, Julian M. M.; Steffen, Ingo G.; Hofheinz, F.; Großer, O. S.; Furth, C.; Mohnike, K.; Hass, P.; Walke, M.; Apostolova, I.; Amthauer, Holger W.
Abstract: Methods: Fifteen patients (f, 6; m, 9; median age, 59 years; range, 32 to 72 years) with 28 liver metastases were included retrospectively. FDG-PET/CT imaging (median activity, 237 MBq; range, 231 to 252 MBq; median uptake, 61 min; range, 55 to 67 min) was performed on a Siemens Biograph mCT 64 followed by image reconstruction using 3D-ordered subset expectation maximization (3D-OSEM) or 3D-OSEM with PSF modeling - both with and without TOF information. Differences in SUVmax were analyzed using the Friedman test and Wilcoxon test for paired non-parametric data. The correlation of inter-method differences with the lesions’ TBR was studied using Spearman’s rank correlation coefficient (rho). Differences between lesions with low (<4.8) and high (>4.8) TBR were analyzed using the Mann-Whitney U test (TBR measured with 3D-OSEM; binarized by its median).
Background: The maximum standardized uptake value (SUVmax) is a common clinical parameter for quantification in F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), but it is influenced by image reconstruction. The aim of this study was to analyze the association of SUVmax deviations related to point spread function (PSF) and time-of-flight (TOF) reconstruction with tumor-to-background ratios (TBR) in colorectal liver metastases (CRLM).
Results: There was a significant correlation of the lesions’ TBR with relative SUVmax differences related to PSF (PSF + TOF vs. 3D-OSEM + TOF, rho = 0.61; PSF vs. 3D-OSEM, rho = 0.52) or TOF (PSF + TOF vs. PSF, rho = −0.58; 3D-OSEM + TOF vs. 3D-OSEM, rho = −0.61). Accordingly, PSF algorithms only showed higher SUVmax than non-PSF algorithms in lesions with a high TBR (median differences at low/high TBR, +2.6%/+9.1% [PSF + TOF vs. 3D-OSEM + TOF]; +0.7%/+6.4% [PSF vs. 3D-OSEM]). TOF integration also led to higher SUVmax but mainly at low TBR (low/high TBR, +10.4%/+1.8% [PSF + TOF vs. PSF]; +8.6%/−0.1% [3D-OSEM + TOF vs. 3D-OSEM]).
Conclusions: Both PSF and TOF reconstruction resulted in a substantial alteration of SUVmax in CRLM. TOF provided the highest SUVmax increase in low-contrast lesions while - vice versa - PSF showed the most relevant increase in high-contrast lesions. Thus, one should be aware that quantitative analyses of lesions with varying TBR, e.g., in radiotherapy or follow-up studies, may be mainly affected by either PSF or TOF reconstruction, respectively.

Keywords: Colorectal liver metastases; F18-FDG-PET/CT; PSF; Reconstruction algorithm; SUVmax; Target volume definition; TOF; Tumor-to-background ratio

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Registration No. 22070

Cutting-edge analytics at DREAMS: Cool application stuff using tandem accelerators
Merchel, S.; Pavetich, S.; Rugel, G.; Ziegenrücker, R.; Dreams-Users; Dreams-Friends
Abstract: The DREsden Accelerator Mass Spectrometry facility (DREAMS) is in routine operation since autumn 2011 [1, Figure 1].

Figure 1. DREAMS incl. planned Time-of-Flight (ToF) and SIMS connection for TEAMS/Super-SIMS.

Here, long-lived so-called cosmogenic radionuclides such as 10Be, 26Al, 36Cl, 41Ca and 129I can be quantified at the 10-14 (radionuclide/stable nuclide) level. Applications are performed within interdisciplinary cooperations with users from universities and research centres. Hence, research is focussed on topics from e.g. astrophysics [2], climate, cosmochemistry [3,4], geomorphology [5-7], hydrogeology and nuclear decommissioning [8].

To keep DREAMS a state-of-the-art facility in-house research such as the development of a low cross-contamination and memory-effect ion source [9], a high-current ion source and expansion to stable nuclides with (Super-Secondary Ion Mass Spectrometry (SIMS)) or without spatial resolution (Trace Element AMS = TEAMS) is performed. This kind of technology development is partially based on our own research interests, but also driven by the steadily increasing demands of our users.

Quality assurance incl. the use of primary or traceable standards and dedicated AMS chemistry labs accessible for users make DREAMS especially attractive for experienced cosmogenic nuclide researchers but even more for newcomers. Thus, training on the job e.g. in the chemistry labs is an essential tool of our “mission” to widen the fields of AMS applications and user communities.

Ackn.: Operators, S. Akhmadaliev, S. Enamorado Baez & A. Renno for help; DFG/DAAD for funding.

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. Phys. Res. B 2013, 294, 5. [2] J. Feige et al., EPJ Web of Conferences 2013, 63, 03003. [3] U. Ott et al., Meteorit. Planet. Sci. 2014, 49, 1365. [4] J. Llorca, et al., Meteorit. Planet. Sci. 2013, 48, 493. [5] M.C. Fuchs et al., Earth Surf. Dynam. Discuss. 2015, 3, 83. [6] K. Hahne et al., System Erde. GFZ-Journal 2013, 3 (2), 44. [7] R. Zech et al., Palaeogeography, Palaeoclimatology, Palaeoecology 2013, 369, 253. [8] D. Hampe et al., J. Radioanal. Nucl. Chem. 2013, 296, 617. [9] S. Pavetich et al., Nucl. Instr. Meth. Phys. Res. B 2014, 329, 22.

Keywords: accelerator mass spectrometry, radionuclide
  • Poster
    Workshop für Ionenstrahlen und Nanostrukturen 2015, 22.-24.07.2015, Heidelberg, Deutschland
Registration No. 22069
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