Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41354 Publications

Interfacial heat transfer models for flashing flows: a review

Liao, Y.; Lucas, D.

An extensive literature review on existing models for interfacial heat transfer in flashing of pure liquids was carried out. It reveals that recent numerical simulations rely still on empirical closures. A correlation in terms of the Jakob number, Reynolds number and Prandtl number might be the most promising one. However, all the validation against experiment is limited to single spherical droplet or bubble. For large deformed bubbles and high void fractions, there are still no direct validation due to the lack of experimental data and complicated intervening physics. Improvement regarding the effect of bubble interaction, interfacial morphology and turbulence is necessary.

Keywords: Flashing flow; Heat transfer; Models; Review

  • Contribution to proceedings
    13th international conference Multiphase Flow in Industrial Plant, 17.-19.09.2014, Genova, Italy
  • Lecture (Conference)
    13th international conference Multiphase Flow in Industrial Plant, 17.-19.09.2014, Genova, Italy

Publ.-Id: 20632

Assessment of CFD predictive capacity for flash boiling

Liao, Y.; Lucas, D.; Krepper, E.; Rzehak, R.

Flash boiling of water inside a converging-diverging nozzle and a vertical pipe under pressure release transients is investigated. Some representative assumptions and simplifications encountered in the literature are assessed. It is shown that a fully non-equilibrium model with two velocity fields and two temperature fields should be applied. Non-drag forces are necessary to predict the lateral distribution of bubbles, which is usually non-uniform. For large bubbles (dg>1mm), bubble translation has a significant contribution to the interphase heat transfer, and thus heat conduction would give a significant under-prediction. The most important point in the assessment of these interphase exchange closures is to have a reliable prediction of bubble size. On this topic there is still much to do, since a realistic modelling of bubble number density transport is still missing. Great efforts need to be invested in the development of generally applicable closure models for nucleation, bubble growth, coalescence and breakup, etc.

Keywords: CFD; Flash boiling; phase change; heat transfer

  • Contribution to proceedings
    CFD4NRS-5, 09.-11.09.2014, Zürich, Schweiz
  • Lecture (Conference)
    CFD4NRS-5, 09.-11.09.2014, Zürich, Schweiz

Publ.-Id: 20631

CFD simulations on TOPFLOW-PTS tests

Apanasevich, P.; Coste, P.; Merigoux, N.

Pressurized Thermal Shock (PTS) has been identified as one of the most important industrial needs related to nuclear reactor safety. The PTS analysis is required to assure the integrity of the Reactor Pressure Vessel (RPV) throughout the reactor life. One important part of the PTS analysis is the thermal hydraulic analysis which must predict the local temperature fields experienced by the structural parts of the cold leg and especially of the RPV wall close to the cold leg nozzle. Such results are applied as the input data for further structural analyses. Several scenarios that describe what could occur in Small Break Loss Of Coolant Accidents (SB-LOCA) result in an Emergency Core Cooling (ECC) water injection into the cold leg of a Pressurized Water Reactor (PWR). The cold water mixes there with the hot coolant, which is present in the primary circuit. The mixture flows to the downcomer where further mixing of the fluids takes place. Single-phase as well as two-phase PTS situations have to be considered. In case of two-phase PTS situations the water level in the RPV has dropped down to or below the height of the cold leg nozzle, which leads to a partially filled or totally uncovered cold leg. Pressurized Thermal Shock implies the occurrence of thermal loads on the Reactor Pressure Vessel wall. In order to predict thermal gradients in the structural components of the Reactor Pressure Vessel (RPV) wall, knowledge of transient temperature distribution in the downcomer is needed. The prediction of the temperature distribution requires reliable Computational Fluid Dynamic simulations. The CFD models should be able to model the complex mixing processes taking place in the cold leg and the downcomer of the reactor pressure vessel (IAEA, 2001; Lucas et al., 2008, 2009).

In the framework of the NURESAFE project attempts have been made to continue improvement and validation of CFD modeling for two-phase PTS situations. The NEPTUNE_CFD, ANSYS CFX and TransAT codes are used in the project for PTS investigations. A CFD benchmark test on a reference TOPFLOW-PTS steam-water experiment is a part of these activities within the project.

Keywords: TOPFLOW-PTS experiments; direct contact condensation; CFD

  • Lecture (Conference)
    NURESAFE 1st Open Seminar, 16.-17.06.2014, Budapest, Hungary

Publ.-Id: 20630

Ge(1-x)Sn(x) alloys synthesized by ion implantation and pulsed laser melting

Gao, K.; Prucnal, S.; Huebner, R.; Baehtz, C.; Skorupa, I.; Wang, Y.; Skorupa, W.; Helm, M.; Zhou, S.

The tunable bandgap and the high carrier mobility of Ge(1-x)Sn(x) alloys stimulate a large effort for bandgap and strain engineering for Ge based materials using silicon compatible technology. In this letter we present the fabrication of highly mismatched Ge(1-x)Sn(x) alloys by ion implantation and pulsed laser melting with Sn concentration ranging from 0.5 at. % up to 1.5 at. %. According to the structural investigations, the formed Ge(1-x)Sn(x) alloys are monocrystalline with high Sn-incorporation rate. The shrinkage of the bandgap of Ge(1-x)Sn(x) alloys with increasing Sn content is proven by the red-shift of the E1 and E1+Δ1 critical points in spectroscopic ellipsometry. Our investigation provides a chip technology compatible route to prepare high quality monocrystalline Ge(1-x)Sn(x) alloys.

Keywords: Ge(1-x)Sn(x) alloys; ion implantation; pulsed laser melting

Related publications

Publ.-Id: 20629

Uncertainties in the fluence determination in the surveillance samples of VVER-440

Konheiser, J.; Grahn, A.; Borodkin, P.; Borodkin, G.

The reactor pressure vessel (RPV) represents one of the most important safety components in a nuclear power plant. Therefore, surveillance specimen (SS) programs for the RPV material exist to deliver a reliable assessment of RPV residual lifetime. This report will present neutron fluence calculations for SS. These calculations were carried out by the codes TRAMO and DORT [1, 2]. This study was accompanied by ex-vessel neutron dosimetry experiments at Kola NPP. The main neutron activation monitoring reactions were Fe-54(n,p)Mn-54 and Ni-58(n,p)Co-85. Good agreement was found between the deterministic and stochastic calculation results and between the calculations and the ex-vessel measurements. The different influences on the monitors were studied. In order to exclude the possible healing effects of the samples due to excessive temperatures, the heat release in the surveillance specimens was determined based on the calculated gamma fluences. Under comparatively realistic conditions, the heating was up to 6 K.

Keywords: VVER440; reactor pressure vessel; surveillance specimen; activation monitors; Fe-54(n; p)Mn-54; Ni-58(n; p)Co-85

  • Lecture (Conference)
    Fifteenth International Symposium on Reactor Dosimetry, 18.-23.05.2014, Aix-en-Provence, France
  • Open Access Logo Contribution to proceedings
    Fifteenth International Symposium on Reactor Dosimetry, 18.-23.05.2014, Aix-en-Provence, France
    EPJ Web of Conferences, Les Ulis Cedex: EDP Sciences, 978-2-7598-1929-4
    DOI: 10.1051/epjconf/201610602006

Publ.-Id: 20627

Assessment of the best N3− donors in preparation of [M(N)(PNP)]-based (M = 99mTc-; 188Re) target-specific radiopharmaceuticals: Comparison among succinic dihydrazide (SDH), N-methyl-S-methyl dithiocarbazate (HDTCZ) and PEGylated N-methyl-S-methyl dithiocarbazate (HO2C-PEG600-DTCZ)

Carta, D.; Jentschel, C.; Thieme, S.; Salvarese, N.; Morellato, N.; Refosco, F.; Ruzza, P.; Bergmann, R.; Pietzsch, H.-J.; Bolzati, C.

Succinic dihydrazide (SDH), N-methyl-S-methyl dithiocarbazate (HDTCZ) and PEGylated N-methyl-S-methyl dithiocarbazate (HO2C-PEG600-DTCZ) are nitrido nitrogen atom donors employed for the preparation of nitride [M(N)]‐complexes (M = 99mTc and 188Re).
This study aims to compare the capability and the efficiency of these three N3− group donors, in the preparation of [M(N)PNP]-based target-specific compounds (M = 99mTc, 188Re; PNP = aminodiphosphine). For this purpose, three different kit formulations (SDH kit; HO2C-PEG600-DTCZ kit; HDTCZ kit) were assembled and used in the preparation of [M(N)(cys~)(PNP3)]0/+ complexes (cys~ = cysteine derivate ligands).
For each formulation, the radiochemical yield (RCY) of the [M(N)(~cys)(PNP3)] compounds, was determined by HPLC. The deviation of the percentage of RCY, due to changes in concentration of the N3− donors and of the
exchanging ligand, was determined.
For 99mTc, data clearly show that HDTCZ is the most efficient donor of N3−; however, SDH is the most suitable nitrido nitrogen atom donor for the preparation of [99mTc(N)(PNP)]-based target-specific agents with high specific activity. When HO2C-PEG600-DTCZ or HDTCZ are used in N3− donation, high amounts of the exchanging ligand (10−4 M) were required for the formation of the final complex in acceptable yield.
The possibility to usemicrogram amounts of HDTCZ also in [188Re(N)] preparation (0.050 mg) reduces its ability to compete in ligand exchange reactions, minimizing the quantity of chelators required to obtain the final complex in high yield. This finding can be exploit for increasing the radiolabeling efficiency in [188Re(N)]-radiopharmaceutical preparations compared to the previously reported HDTCZ-based procedure, notwithstanding a purification process could be necessary to improve the specific activity of the complexes.

Keywords: Rhenium; Technetium; 188Re; Diphosphinoamines; Peptide; Therapy

Publ.-Id: 20626

Influence of riboflavin on the reduction of radionuclides by Shewanella oneidenis MR-1

Cherkouk, A.; Law, G. T. W.; Rizoulis, A.; Law, K.; Renshaw, J. C.; Morris, K.; Livens, F. R.; Lloyd, J. R.

Uranium (as UO22+), technetium (as TcO4-) and neptunium (as NpO2+) are highly mobile radionuclides that can be reduced enzymatically by a range of anaerobic and facultatively anaerobic microorganisms, including Shewanella oneidensis MR-1, to poorly soluble analogues. The redox chemistry of Pu is more complicated, but the dominant oxidation state in most environments is poorly soluble Pu(IV), which can be reduced to the potentially more soluble Pu(III), which could enhance migration of Pu in the environment. Recently it was shown that flavins (riboflavin and flavin mononucleotide (FMN)) secreted by Shewanella oneidensis MR-1 can act as electron shuttles, promoting anoxic growth coupled to the accelerated reduction of poorly-crystalline Fe(III) oxides. Here we studied the role of riboflavin in mediating the reduction of radionuclides in cultures of Shewanella oneidensis MR-1. Our results demonstrate that the addition of 10 µM riboflavin enhances the reduction rate of Tc(VII) to Tc(IV) and Np(V) to Np(IV), but has no significant influence on the reduction rate of U(VI) by Shewanella oneidensis MR-1. The presence of riboflavin also accelerated Pu(IV) reduction, demonstrated by an increase in the percentage of Pu(IV) reduced to Pu(III), with and without riboflavin present (17 and 3%, respectively). Thus riboflavin can act as an extracellular electron shuttle to enhance rates of Tc(VII), Np(V) and Pu(IV) reduction, and may therefore play a role in controlling the oxidation state of key redox active actinides and fission products in natural and engineered environments. These results also suggest that the addition of riboflavin could be used to accelerate the bioremediation of radionuclide-contaminated environments.

Publ.-Id: 20625

Scalable, interactive 3D in-situ visualization of large-scale Simulations

Pausch, R.; Schneider, B.; Hettmanczyk, D.; Burau, H.; Huebl, A.; Schmitt, F.; Widera, R.; Grottel, S.; Gumhold, S.; Bussmann, M.

We present scalable, in-situ visualization of large-scale plasma simulations that allows for remote live visualization. We discuss the GPU rendering implementation, its interface to the simulation, scalable image composition on large clusters and the use of low-power visualisation clients attached to a server located at the HPC system. Such a setup challenges current HPC visualization paradigms and will potentially allow for explorative simulation surveys of large parameter spaces with strongly reduced storage footprint.

Keywords: in-situ visualization; PIConGPU; live visualization; GPU; HPC

  • Lecture (Conference)
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland

Publ.-Id: 20624

Computing Angularly-resolved Far Field Emission Spectra in Particle-in-cell Codes using GPUs

Pausch, R.; Burau, H.; Bussmann, M.; Couperus, J. P.; Cowan, T.; Debus, A.; Huebl, A.; Irman, A.; Köhler, A.; Schramm, U.; Steiniger, K.; Widera, R.

Angularly resolved far field radiation spectra computed from the Lienard Wiechert Potentials of accelerated electrons give information on the microscopic particle dynamics. We present recent results using our many-GPU, fully relativistic 3D3V particle-in-cell code PIConGPU for which we have developed fully synthetic radiation diagnostics that is capable of computing angularly-resolved radiation spectra of more than 10^10 electrons for several hundred to a thousand wavelengths and directions in a single simulation in less than a day on large-scale supercomputers. With such a technique it is possible to use precision spectroscopic methods for understanding the dynamics of electron acceleration in scenarios where other diagnostics fail. We present studies on laser-driven wakefield acceleration and astrophysical jet dynamics to underline the power of this new technique.

Keywords: far field radiation spectra; Lienard Wiechert potentials; PIConGPU; many-GPU; synthetic radiation diagnostics

  • Poster
    5th International Particle Accelerator Conference (IPAC 2014), 15.-20.06.2014, Dresden, Deutschland
  • Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC 2014), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, 978-3-95450-132-8, MOPRI069


Publ.-Id: 20623

Charakterisierung von anisotropen Magnetowiderstandseffekten in Nanostrukturen aus Permalloy und Eisenaluminium

Warnatz, T.

Magnetic field induced resistance effects are used in digital storage media - like hard- disk read heads [1]. To produce commercial devices it is of utmost importance to understand and tune the effect. The ion beam induced change of ferromagnetic or paramagnetic effects is known since 1986 [2,3]. However, most of the research was done on bulk material. Due to the increasing miniaturization of digital storage devices it is essential to investigate also the behavior in thin films. Taking into account that a commercial use of the devices is favored, it was focused on easy and reproducible sample geometries. The aim of this thesis was to produce, tune and character- ize magnetic field induced resistance changes in thin films of permalloy and iron-aluminum. Af- terwards, the results have been used to create well-defined nanostructures with potential giant magnetoresistance effects. It is shown, that magnetoresistance effects can be created (iron- aluminum) or reduced (permalloy) by ion beam irradiation. The measurements were performed by a self-programmed LabVIEW program with a precise four-terminal sensing setup at low tempera- tures and with a variable magnetic field up to 2.5 T. The variation of the angle between current flow and the magnetic field as well as measurements at different temperatures led to a very good understanding of the occurring phenomena.

Keywords: FeAl; anisotropic magnetoresistance

Related publications

  • Bachelor thesis
    Westsächsische Hochschule Zwickau, 2013

Publ.-Id: 20622

Herstellung und Charakterisierung eines Spinventils zur Untersuchung der Spindiffusionslänge von FeAl

Liersch, V.

Spintronic devices hold great potential for future applilcations in information technology. In this work, the design and fabrication of a lateral spin valve for investigating the spin diffusion length of paramagnetic Fe60Al40 will be discussed. Samples were prepared by defining polycrystalline circuits using electron beam lithography, thin film deposition, and lift-off processing. The developed sample layout allows for both local and non-local measurement routines. Cobalt was employed as ferromagnetic polarizing material, while aluminium holds for reference measurements of the spin diffusion length. The determination of the so far unknown spin diffusion length of paramagnetic Fe60Al40 shall then be performed by detecting resistance changes at different temperatures and for different polarizer distances. Highly sensitive electric transport measurements were carried out in a so-called probe station, which allows for achieving very low temperatures via liquid He cooling. Additionally, paramagnetic ferromagnetic heterostructures were investigated with respect to possible giant magneto resistance effects.

Keywords: FeAl; spin valve; spin diffusion length

Related publications

  • Bachelor thesis
    Westsächsische Hochschule Zwickau, 2014

Publ.-Id: 20621

Transverse Emittance Compensation for the Rossendorf SRF GUN II

Vennekate, H.; Lu, P.; Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.; Kneisel, P.; Kamps, T.

Superconducting RF particle sources combine the advantages of normal conducting RF sources and high duty cycle non-RF sources. The Rossendorf SRF gun was the first to demonstrate this injecting electrons into the ELBE accelerator at 13MHz. Recently, a new 3-1/2-gun cavity has been prepared at Jefferson Lab for its use in an updated injector which is expected to increase the electron energy from 2:4 to 7:5 MeV. Along with this new cavity, a new gun cryostat has been introduced. It combines several minor updates to the setup with the installation of a superconducting solenoid right at the exit of the gun, compensating the emittance growth of the electron bunch at an early stage. Hereby, the results of the commissioning of the new cryostat including the solenoid are concluded and compared to the prior concept of using a normal conducting solenoid outside the cryostat. As it is of great importance to this subject, studies of the magnetic shielding are going to be presented as well.

Keywords: SRF; superconducting radio frequency; injector; Rossendorf SRF Gun; ELBE; emittance

Related publications

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC'14), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, JACoW, 978-3-95450-132-8, TUPRI015


Publ.-Id: 20620

Simulation d ́écoulement multiphasique couplé aux effets magnétiques des batteries à métaux liquides

Barry, L.

Le stockage d’énergie électrique devient une nécessité avec le développement des énergies renouvelables en Allemagne. Dans cette perspective un nouveau type de batterie, composée de trois phases de métal liquide maintenues à plus de 500°C, semble prometteur pour une future utilisation. Cependant ces batteries sont le siège d’instabilités qui peuvent mener à un mélange non voulu des trois phases liquides. Ce projet étudie une instabilité particulière appelée instabilité de Tayler, et cherchera à savoir si celle-ci peut mener à une destruction de la batterie. Pour cela, un nouveau solveur numérique est utilisé, combinant à la fois les lois de l’électromagnétique et de la mécanique des fluides. Des simulations seront lancées à partir de diverses conditions initiales, et nous verrons qu’il est en effet possible d’arriver à une destruction de la batterie, sous réserves de conditions initiales particulières.

Keywords: Tayler instability; liquid metal battery; multiphase simulation; OpenFOAM

  • Master thesis
    Arts et Métiers Paristech Bordeaux-Talence, 2014
    Mentor: Azita Ahmadi, Tom Weier

Publ.-Id: 20619

Experimental evidence for nonaxisymmetric magnetorotational instability in a rotating liquid metal exposed to an azimuthal magnetic field

Seilmayer, M.; Galindo, V.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Gellert, M.; Rüdiger, G.; Schultz, M.; Hollerbach, R.

The azimuthal version of the magnetorotational instability (MRI) is a nonaxisymmetric instability of a hydrodynamically stable differentially rotating flow under the influence of a purely or predominantly azimuthal magnetic field. It may be of considerable importance for destabilizing accretion disks, and plays a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers.

Publ.-Id: 20618

Magnetic fields in space: phenomena and related lab experiments

Stefani, F.

The magnetic fields of cosmic bodies are generated by the homogeneous dynamo effect in moving electrically conducting fluids. Cosmic magnetic fields also play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. In 1999 the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf.
The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    Space trips summer school on thermo-acoustic and space technologies, 17.-20.06.2014, Riga, Latvia

Publ.-Id: 20617

The azimuthal MRI in experiment: confirmations and surprises

Stefani, F.

The azimuthal magnetorotational instability (AMRI) may be of considerable importance for destabilizing accretion disks and plays also a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers. We also discuss some peculiarities of the experimental results which are connected with the slight symmetry breaking of the applied magnetic field.

  • Invited lecture (Conferences)
    General Meeting of the Max Planck/Princeton Center for Plasma Physics, 28.06.-01.07.2014, Berlin, Germany

Publ.-Id: 20616

Simulation of the ELBE SRF Gun II

Lu, P.; Arnold, A.; Lehnert, U.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

By combining the code of ASTRA and elegant in a user-friendly interface, a simulation tool is developed for the ELBE SRF Gun II. The photoelectric emission and first acceleration to several MeV in the gun cavity are simulated by ASTRA with a 1D Model, where the space charge effect is considered. The dependence of the beam quality on key parameters is studied, and a compromised optimization for a 77 pC beam is used for further elegant simulation of the beam transport through a dogleg and ELBE Linacs. Proper settings of the magnets and RF phases are the main targets of improving the beam quality. Up to now the best simulation result is an electron bunch with the energy of 47 MeV, energy spread of 66 keV, bunch length of 0.35 ps and transverse emittance of 1.9 μm and 2.7 μm in the two perpendicular directions.

Related publications

  • Open Access Logo Contribution to proceedings
    IPAC2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC2014, MOPRI023

Publ.-Id: 20615

Dynamo action and related magnetic instabilities in the liquid metal lab

Stefani, F.

Magnetic fields of cosmic bodies are generated by the hydromagnetic dynamo effect in moving electrically conducting fluids, such as liquid metals or plasmas. Once produced, cosmic magnetic fields are able to act back on moving fluids. This back-reaction may have dramatic consequences for cosmic structure formation, with the magnetorotational instability (MRI) in accretions disks as the most prominent example. Considerable theoretical and computational progress has been made in understanding both the dynamo effect as well as magnetically triggered flow instabilities. Complementary to this, the last fifteen years have seen much effort in studying both effects in liquid metal experiments.
In the talk, we summarize the history of these experiments, discuss their main results and their limitations, and give an outlook on future activities. As for dynamo action, we focus on the Riga, Karlsruhe and Cadarache experiments, and discuss the present status of a large-scale precession-driven dynamo experiment to be set-up in the framework of the DRESDYN project. As for magnetically triggered instabilities, we review the recent experiments on the helical and azimuthal versions of the MRI, as well as on the current-driven Tayler instability (TI). After discussing the astrophysical relevance of those basically induction-less instabilities, we motivate the set-up of a large-scale liquid sodium experiment for studying the continuous transition to the standard version of MRI.

  • Invited lecture (Conferences)
    EUROMECH Colloquium 561: Dimensionality of Turbulence, 19.-21.05.2014, Coventry, United Kingdom

Publ.-Id: 20614

Liquid metal experiments on dynamo action and related magnetic instabilities

Stefani, F.

The magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, cosmic magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both effects, i.e. hydromagnetic dynamo action and the magnetorotational instability, have been the subject of purely theoretical investigations. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf. The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, it asks for the lessons they have taught us about real cosmic dynamos and accretion disks, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    LSTM Fluid Mechanics Seminar, 07.02.2014, Erlangen, Germany

Publ.-Id: 20613

Properties of oxide nanoclusters in ODS ferritic steels: A combined DFT and Metropolis Monte Carlo simulation study

Devaraj, M.; Posselt, M.

The main structural characteristic of Oxide Dispersion Strengthened (ODS) Fe-Cr alloys is the finely dispersed distribution of nm-size clusters that may contain O, Y, and Ti. Many details of the structure and composition of these nanoclusters are not yet fully understood. Numerous experiments demonstrated that number and size of the nanoclusters do not change significantly when ODS alloys are exposed to high dose irradiation and/or high temperatures. Furthermore, it was shown that the fine dispersion of the nanoclusters prevents recrystallization, i.e. the increase of grain size, which usually occurs at elevated temperatures. The extraordinary properties of the nanoclusters are deemed to be the cause of the superior high-temperature creep strength and the high radiation resistance of the ODS Fe-Cr alloys. Therefore, these materials are promising candidates for applications as structural materials in extreme environments, i.e. at high temperature and intense particle irradiation, such as in advanced nuclear fission and fusion reactors.
In this work a multiscale modeling approach is developed and successfully applied to interpret a large number of experimental data on the properties of nanoclusters in the ODS Fe-Cr alloys. Extensive first-principle calculations on embedded clusters containing few O, Y, Ti, and Cr atoms as well as vacancies are performed to obtain interaction parameters to be applied in Metropolis Monte Carlo simulations, within the framework of a rigid lattice model. A novel description using both pair and triple parameters is shown to be more precise than the commonly used pair parameterization. Simulated annealing provides comprehensive data on the energetics, structure and stoichiometry of nm-size clusters at . The results are fully consistent with the experimental finding of negligible coarsening and a high dispersion of the clusters, with the observation that the presence of Ti reduces the cluster size, and with the reported radiation tolerance of the clusters. In alloys without vacancies clusters show a planar structure, whereas the presence of vacancies leads to three-dimensional configurations. Additionally, Metropolis Monte Carlo simulations are carried out at high temperature in order to investigate the dependence of nanocluster composition on temperature. A good agreement between the existing experimental data on the ratios (Y+Ti):O, Y:Ti, (Y+Cr):O, and Y:Cr, and the simulation results is found. In some cases it is even possible to draw the conclusion that the respective alloys contained a certain amount of vacancies, or that the clusters analyzed were frozen-in high-temperature configurations. The comparison of experimental data with those obtained by simulations demonstrates that the assumption of nanoclusters which are coherent with the bcc lattice of the Fe-Cr matrix leads to reasonable results.

Keywords: ODS ferritic alloys; DFT; Monte Carlo simulation

  • Lecture (Conference)
    2nd International Workshop on ODS Materials, 26.-27.06.2014, Dresden, Germany

Publ.-Id: 20612

Fluorinated phosphodiesterase 10A inhibitors with a potential use as 18F-labeled imaging agents

Wagner, S.; Scheunemann, M.; Egerland, U.; Hoefgen, N.; Brust, P.

Phosphodiesterases (PDEs) are a class of enzymes heavily involved in cellular signaling by inactivating the second messenger cAMP and cGMP. So far, 11 different PDE families are known, of which one, the dual substrate enzyme PDE10A is abundantly expressed in a particular brain region, the striatum. Since it is thought to be involved in the pathomechanism of schizophrenia, PDE10A inhibition represents a novel approach in the treatment of this disease. In-vivo imaging via positron emission tomography (PET) of PDE10A would allow investigating the enzyme and its expression in neuropathological processes.
Recently, 1 arylimidazo[1,5a]quinoxalines have been reported as potent and selective PDE10A inhibitors.1 Considering the potential use of these inhibitors as 18F-labeled imaging agents fluorinated PDE10A inhibitors based on 1-arylimidazo[1,5a]quinoxaline as lead structure have been synthesized.
The imidazo[1,5a]quinoxaline key structure was synthesized from 2,6-difluoroaniline over 7 steps in an total yield of 8%. Using the palladium catalyzed Suzuki-coupling different substituted 2-fluoropyridine boronic acids could be linked to brominated imidazo[1,5a]quinoxalines. This divergent step allows a quick and easy variation. Moreover 2-fluoropyridines could be introduced at two positions of the aromatic system.
The inhibitory potency of these compounds was tested towards human, recombinant PDE10A and other PDE families. All inhibitors showed a high affinity for PDE10A with moderate to good selectivity versus other PDEs.
Currently the most selective inhibitor is under further investigation to be developed as PET tracer.

[1] Malamas et. al. J. Med. Chem. 2011,54, 7621-7638.

  • Poster
    ORCHEM 2014, 15.-17.09.2014, Weimar, Deutschland

Publ.-Id: 20611

Liquid phase epitaxy of Ge(1-x)Sn(x) alloy using ion-implantation and pulsed laser melting

Gao, K.; Prucnal, S.; Huebner, R.; Skorupa, W.; Helm, M.; Zhou, S.

Group IV semiconductor alloys have drawn substantial attention for their potential applications in optoelectronic devices capable of integration with the existing Si IC circuitry. Single crystalline Ge1-xSnx alloys are promising for electronic and optical applications in virtue of their high carrier mobility. In this contribution we present the fabrication of Ge1-xSnx by ion-implantation and pulsed laser melting (PLM). Sn was implanted into commercial Ge wafers to form 0.2 µm thick layers with different atomic concentrations from 0.5 % 3.0 %. The as-implanted Ge layer becomes amorphous due to the bombardment of Sn ions with high kinetic energy. The regrowth of the Ge1-xSnx layer after PLM and the lattice expansion were confirmed by X-ray diffraction and micro-Raman spectroscopy. Field emission scanning electron microscopy was applied to determine the surface morphology. High resolution transmission electron microscopy and Rutherford backscattering and channeling analysis confirmed the monocrystalline structure of the Ge1-xSnx layer. Our investigation provides an efficient technique to prepare high quality monocrystalline Ge1-xSnx alloys.

Keywords: GeSn; ion implantation; pulsed laser melting

Related publications

  • Lecture (Conference)
    E-MRS 2014 SPRING MEETING, 26.05.-01.08.2014, Lille, France

Publ.-Id: 20610

Photoluminescence from GaAs(1-x)N(x) dilute nitride achieved by nitrogen-implantation and flash lamp annealing

Gao, K.; Prucnal, S.; Huebner, R.; Skorupa, W.; Helm, M.; Zhou, S.

Nitrogen atoms are isoelectronic substituents for arsenic in GaAs. A small amount of nitrogen doping can lead to a pronounced bandgap reduction. Therefore nitrogen-doping can be applied as a powerful technique to modify GaAs based materials for long wavelength optoelectronic devices. In this contribution we present the fabrication of dilute nitride material GaAs1-xNx by nitrogen-implantation and flash lamp annealing (FLA). N was implanted in to the commercial GaAs wafer to form a 0.2 ?m thick layer with atomic concentration of about 0.76 % and 0.38 %. The as-implanted GaAs layer becomes amorphous due to the bombardment of nitrogen ions with high kinetic energy. The GaAs1-xNx layer with compressive strain is epitaxially regrown on GaAs during FLA treatment as confirmed by X-ray diffraction and micro-Raman spectroscopy. In the meantime the bandgap shrinkage is proven by photoluminescence spectroscopy. Based on the redshift of the GaAs1-xNx near band-edge emission, up to 60 % of the implanted N atoms are successfully incorporated into the lattice after FLA. According to our investigation, ion-implantation followed by ultrashort flash lamp treatment, which is quite efficient and low-cost, exhibits a promising prospect on bandgap engineering of GaAs based semiconductors.

Keywords: GaAsN; ion implantation; flash lamp annealing

Related publications

  • Poster
    E-MRS 2014 SPRING MEETING, 26.05.-01.08.2014, Lille, France

Publ.-Id: 20609

Spatiotemporal process monitoring of conservative and reactive tracer transport in a synthetic soil column

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

Transport and retardation of chemical species in soils as observed by input-output approaches are commonly interpreted by process simulations and break-through curve (BTC) fitting. Positron emission tomography (PET) provides a direct quantitative spatiotemporal (4D) visualization method for the propagation of compounds labelled with a PET-tracer at intermediate resolution and molecular sensitivity (Kulenkampff et al. 2013).
In the framework of SPP 1315, we conducted transport experiments on an artificial soil column with both reactive and conservative tracers, which were monitored with sequential PET imaging. The soil column used (l: 94.5 mm, d: 40 mm; composition: 94% sand, 5% illite, 1% goethite; porosity: 29%) was prepared under CO2-atmosphere and structurally characterized by µCT imaging as widely homogeneous. For the conservative tracer experiment, 5 mL 0.001 M NaNO3 + 0.01 M [18F]KF was flown through the equilibrated column. For the reactive species experiment, 64Cu was produced at the Leipzig cyclotron by the nuclear reaction 64Ni(p,n)64Cu and separation by ion exchange. 5 mL of 0.0008 M [64Cu]Cu(MCPA)2 was produced from 2 mL 64Cu2+ in 0.1 M HNO3, 1 mg Cu(NO3)2•3H2O and 2 mg MCPA in synthetic pore water. The labeled solution was adjusted to pH 5 and flown through the column, which had no former contact with MCPA and had been preconditioned for 4 days with synthetic pore water at pH 5. In both experiments the flow rate was 0.1 ml/min.
In the conservative experiment, the break-through occurred after 140 min, and – in spite of the homogeneous packing of the column – the tracer propagation observed with PET showed a preferential flow field towards the rim of the sample. The reactive [64Cu]Cu(MCPA)2 pulse was strongly retarded with a break-through of the activity after 66 h. Fig. 1 shows a snapshot of both experiments after 110 min.
Preferential and superficial transport, commonly ignored in input-output approaches, controls the effective volume and reactive internal surface area, and thus impacts interpretation and inverse numerical modelling of BTCs. Such effects can be assessed and quantified with PET process tomography, especially when the pore structure is heterogeneously altered by microbial activity.

Kulenkampff, J., Gründig, M., Korn, N., Zakhnini, A., Barth, T., Lippmann-Pipke, J., 2013. Application of high-resolution positron-emission-tomography for quantitative spatiotemporal process monitoring in dense material.

Keywords: reactive transport; column experiments; tomography; PET; preferential flow

  • Lecture (Conference)
    International Symposium 2014 Biogeochemical Interfaces in Soil: Towards a Comprehensive and Mechanistic Understanding of Soil Functions, 06.-08.10.2014, Leipzig, Deutschland

Publ.-Id: 20608

Formation and photoluminescence of GaAs(1-x)N(x) dilute nitride achieved by N-implantation and flash lamp annealing

Gao, K.; Prucnal, S.; Skorupa, W.; Helm, M.; Zhou, S.

In this paper we present the fabrication of dilute nitride semiconductor GaAs(1-x)N(x) by nitrogen-ion-implantation and flash lamp annealing (FLA). N was implanted into the GaAs wafers with atomic concentration of about ximp1=0.38% and ximp2=0.76%. The GaAs1-xNx layer is regrown on GaAs during FLA treatment in a solid phase epitaxy process. Room temperature near band-edge photoluminescence (PL) has been observed from the FLA treated GaAs(1-x)N(x) samples. According to the redshift of the near band-edge PL peak, up to 80% and 44% of the implanted N atoms have been incorporated into the lattice by FLA for ximp1=0.38% and ximp2=0.76%, respectively. Our investigation shows that ion implantation followed by ultrashort flash lamp treatment, which allows for large scale production, exhibits a promising prospect on bandgap engineering of GaAs based semiconductors.

Keywords: GaAs(1-x)N(x); ion implantation; flash lamp annealing; photoluminescence

Related publications

Publ.-Id: 20607

Process tomography of diffusion, using PET, to evaluate anisotropy and heterogeneity

Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J.

Anisotropy, compositional and structural heterogeneity of clays cause considerable deviations from homogeneous diffusion, in particular direction dependent transport rates and preferred transport zones. Conventional diffusion experiments, treating the sample as homogeneous black box in a concentration gradient, are interminable and inappropriate to elucidate these spatial effects. In contrast, tomographic imaging methods are capable both to shorten the required observation time and to reveal space-dependent variations of the diffusion process.
Here we applied positron-emission-tomography (PET) as quantitative spatiotemporal imaging method with perfect characteristics for non-destructive diffusion process observations. We adopted this nuclear medical imaging method and developed its geoscientific applicability in the past ten years [1-3]. GeoPET visualizes the concentration of certain positron-emitting radiotracers in opaque media with ultimate sensitivity (picomoles) and reasonable resolution (1 mm) on the laboratory scale (100 mm). For diffusion experiments longer living nuclides are applicable, like 58Co (T1/2=70.86 d) and 22Na (T1/2=2.603 a), and we have to consider the higher density of our specimens, which causes attenuation and scattering of the radiation [4].
GeoPET revealed spatial particularities in diffusion experiments that have been conducted on Opalinus clay samples of different sizes, as well as on other rock types. Applying the Comsol Optimization Module, we derived anisotropic diffusion parameters from the tomograms [5, 6].


1. Richter, M., et al., Radiochimica Acta 93, 643-651, 2005.
2. Gründig, M., et al., Applied Geochemistry 22, 2334-2343, 2007.
3. Kulenkampff, J., et al., Physics and Chemistry of the Earth 33, 937-942, 2008.
4. Zakhnini, A., et al., Computers and Geosciences 57 183-196, 2013.
5. Schikora, J., Dresden Technical University, Diploma thesis, 2012.
6. Kulenkampff, J., et al. Clays in Natural and Engineered Barriers for Radioactive Waste Confinement (O/11B/2), 2012. Montpellier, France.

Keywords: diffusion; clay; tomography; pet

Publ.-Id: 20606

Influence of substrate on resistive switching behavior of YMnO3 films in bottom-top contact configuration

Bogusz, A.; Blaschke, D.; Skorupa, I.; Scholz, A.; Bürger, D.; Schmidt, O. G.; Schmidt, H.

The influence of the bottom electrode/substrate on the resistive switching behavior of YMnO3 thin films was investigated. Unipolar resistive switching was observed when Pt/Ti/SiO2/Si and Pt/Al2O3 were employed as a bottom electrode/substrate. YMnO3 deposited on a SrTiO3 doped with Nb exhibits bipolar resistive switching characteristics. It was shown that the use of different substrate materials has got a decisive impact on the YMnO3 microstructure and current-voltage characteristics.

  • Contribution to proceedings
    12th International Conference on Solid-State and Integrated Circuit Technology (ICSICT 2014), 29.-31.10.2014, Guilin, China
    Proceedings of ICSICT-2014: IEEE, 978-1-4799-3296-2
    DOI: 10.1109/ICSICT.2014.7021530
  • Lecture (Conference)
    12th International Conference on Solid-State and Integrated Circuit Technology (ICSICT 2014), 28.-31.10.2014, Guilin, China

Publ.-Id: 20605

Nanoscale Transport Phenomena

Erbe, A.; Gemming, S.

The miniaturization and concurrent diversification of functional devices is one of the key technology drivers in science and technology. Following the ITRS roadmap the length scales of functional elements have shrunk to the nanoscale, permitting comparison between controlled experiments and a realistic, scale-adapted modeling of their physical properties.
In this presentation we show studies of transport properties in nanoscale systems, such as electrical current transport through single molecules, magnetic nanoparticles, and nanowires in experiment and simulation. Our results open possible routes towards new functional devices on the molecular and nanometer scale using effects like light-induced switching of single molecules or charging of single electrons to magnetic single electron transistors. Future integration of these nanostructures into micronsize electrical circuits requires structuring techniques, which form contacts by using combinations of self-assembly and top-down approaches. We demonstrate charge transport through self-organized structures and their placement on large electrodes.

Keywords: nanoscale transport; molecular electronics; charge transport; density-functional theory; functional oxides; nanocomposite materials

Related publications

  • Lecture (others)
    Abengoa Research Seminar, 20.05.2014, Sevilla, Spanien

Publ.-Id: 20604

Kleinste Strukturen ganz groß – Forschung mit Großgeräten

Gemming, S.

allg. Vorstellung der Forschungsanagen am HZDR

Related publications

  • Lecture (others)
    Seniorenkolleg der TU Chemnitz, 27.05.2014, Chemnitz, Deutschland

Publ.-Id: 20603

Selbstorganisation – Wie kommt das Muster auf die Oberfläche?

Gemming, S.

Muster auf Oberflächen können sich durch eine Vielzahl verschiedener Mechanismen ausbilden. Regelmäßige mikro- und nanoskalige Muster für mobile elektronische Geräte lassen sich zum Beispiel nach vorgegebenen Vorlagen durch aktive top-down Strukturierungsverfahren wie Lithographie oder Drucken erzeugen.

Aus der Natur ist demgegenüber spontane Musterbildung unter Gleichgewichtsbedingungen bekannt, wenn ordnende Wechselwirkungen mit entropischen Faktoren erfolgreich konkurrieren. Induzierte Musterbildung durch Einwirkung externer Faktoren wie den Ionenstrahl ergänzt die Palette möglicher Wege zur Bildung geordneter Oberflächenstrukturen.

Strukturelle Muster finden sich auf verschiedensten Längen- und Zeitskalen von der dreidimensionalen Anordnung von Materie in Galaxien bis hin zur Dekoration von Sensor- oder Katalysatoroberflächen mit Atomen und Molekülen. Gerade die Mustererkennung auf molekularer Ebene bildet die Basis vieler biologischer Prozesse. Darauf basierende Ansätze wie die DNA-Origami-Technik versprechen eine gezielte Strukturierung größerer, technologisch relevanter Oberflächen aus kleinen molekularen Bausteinen. Selbstorganisation auf atomarer Ebene treibt dagegen die Ausbildung von meso- und nanoskopischen Strukturen wie Quantenpunkten, Rippeln oder Nanokompositen durch Ionenstrahlerosion oder ionenstrahlgestützte Abscheidung. Hierbei ist die Strukturierung gekoppelt an das Entstehen funktionaler Muster, wie man sie auch bei Materialien beobachtet, in denen sich am Ordnungs-Unordnungs-Übergang Domänen spontaner Magnetisierung oder spontaner elektrischer Polarisation ausbilden. Einige Beispiele aus der aktuellen Materialforschung sollen verdeutlichen, dass die Musterbildung jenseits des rein Dekorativen eine Vielzahl fundamentaler Aspekte der Physik berührt.

Keywords: Musterbildung; crystal structure; space groups; frieze groupd; rod groups

  • Invited lecture (Conferences)
    Workshop Nanostrukturbildung, 15.04.2013, Dresden, Deutschland
  • Lecture (others)
    Physikalisches Kolloquium, 17.04.2013, Chemnitz, Deutschland

Publ.-Id: 20602

Strontium titanate: An all-in-one rechargeable energy storage material

Hanzig, J.; Zschornak, M.; Nentwich, M.; Hanzig, F.; Gemming, S.; Leisegang, T.; Meyer, D. C.

Redistribution of oxygen vacancies in a strontium titanate single crystal is caused by an external electric field. We present electrical measurements during and directly after electroformation, showing that intrinsic defect separation establishes a non-equilibrium state in the transition metal oxide accompanied by an electromotive force. A comprehensive thermodynamic deduction in terms of theoretical energy and entropy calculations indicate an exergonic electrochemical reaction after the electric field is switched off. Based on that driving force the experimental and theoretical proof of concept of an all-in-one rechargeable SrTiO3 single crystal energy storage is reported here.

Keywords: Solid state energy storage; Transition metal oxides; Defects; Density functional theory

Related publications

Publ.-Id: 20601

Probing a crystal's short-range structure and local orbitals by Resonant X-ray Diffraction methods

Zschornak, M.; Richter, C.; Nentwich, M.; Stöcker, H.; Gemming, S.; Meyer, D. C.

Diffraction Anomalous Fine Structure (DAFS) combines the long-range, crystallographic sensitivity of X-ray diffraction with the short-range sensitivity of X-ray Absorption Spectroscopy (XAS). In comparison to other spectroscopic methods, DAFS can additionally distinguish phases of different translational symmetry by choice of momentum transfer, or isolate spectra from chemically identical atoms on various Wyckoff sites of a crystal's structure using crystallographic weights. The Anisotropy of Anomalous Scattering (AAS) extends the concept of isotropically scattering atoms to a more general case, where the atom's scattering characteristics depend on the polarization as well as the wavevector of the incident and scattered X-rays. These can be written as tensors that reflect the local site symmetries of the resonant atom. Forbidden Reflection Near-Edge Diffraction (FRED) is an elegant way to measure AAS by using reflections that are extinguished in the special case of isotropically scattering atoms. They can only be observed due to the non-isotropic contributions at photon energies in the vicinity of an absorption edge where electronic transitions occur. Combining the site selectivity of DAFS with the information accessible through AAS allows probing the short-range order and local orbitals of selected atoms in a crystal structure of a chosen phase. The present condensed review gives a brief overview on the pioneer work, the theory and sensitivities as well as selected recent applications of these powerful and promising Resonant X-ray Diffraction (RXD) methods. Additionally, some recent work of the authors is included exemplarily for the model structure rutile TiO2 presenting the progress in measurement and interpretation.

Keywords: diffraction anomalous fine structure; anisotropic anomalous scattering; resonant elastic X-ray scattering; forbidden reflection near-edge diffraction

Related publications

Publ.-Id: 20600

Investigation of contaminated soil

Richter, C.; Fahmy, K.

Investigation of microbial growth in natural minerals using the TAM Air 3 channel calorimeter.

  • Lecture (Conference)
    ISBC Meeting, Lund 2014, 03.06.2014, Lund, Schweden

Publ.-Id: 20599

Single-crystalline Ga- and In- based compound semiconductor nanocrystals in Si by ion implantation and short time flash lamp annealing

Wutzler, R.; Rebohle, L.; Prucnal, S.; Bregolin, F.; Hübner, R.; Helm, M.; Skorupa, W.

The integration of III-V compound semiconductors into silicon is a substantial research field for the progress of micro- and optoelectronic device technology. We fabricated various III-V compound semiconductor nanocrystals (NCs) in Si and SOI substrates by sequential high fluence ion beam implantation and ultra-short flash lamp annealing (FLA). Single-crystalline GaAs, GaP, GaSb, InAs, InP and InSb NCs were grown by liquid phase epitaxy during FLA. Additionally, precise positioning of NCs was achieved by using a lithographically patterned aluminum mask layer for ion implantation.

The characterization of the NCs was performed by using Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Rutherford Backscattering (RBS). Raman measurements confirmed the formation of III-V NCs. AFM and SEM were used to control surface morphology and to investigate the lateral NC distribution. RBS monitored the distribution of the implanted ions. TEM images show distinct, single-crystalline NCs of various shapes. The shape and size of the NCs varies from large domes over small spherical precipitates to conical and pyramidal nanostructures depending on the processing conditions.

Keywords: Ion Implantation; Flash Lamp Annealing; III-V Integration; SOI

Related publications

  • Lecture (Conference)
    X-th International Conference Ion Implantation and other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland

Publ.-Id: 20598

In-situ spectroscopic characterization of Np(V) sorption complexes at manganese and iron oxide surfaces

Müller, K.; Rossberg, A.; Simon, B.; Berger, J.

Neptunium (Np) is one of the most important components of nuclear waste to consider for the long-term safety assessment of nuclear waste repositories, due to the increasing enrichment, the long half-life and the high toxicity of Np-237. Hence, great attention is attracted to its geochemistry [1]. Among the various geochemical reactions, the molecular processes occurring at the solid-water interface, e.g. sorption onto mineral phases, surface precipitation, and colloid formation strongly affect the migration behavior of the radioactive contaminant in the environment [2]. Thus, various components of geological materials, such as manganese and iron oxides and hydroxides play an important role in regulating the mobility of actinides in aquifers, due to their widespread environmental presence, high sorption capacity and tendency to form coatings on mineral surfaces [3]. In recent years, the sorption behavior of Np(V), the most relevant oxidation state under ambient conditions, onto iron oxides was mainly studied by macroscopic experiments [4]. Manganese oxides were rarely investigated [5]. For a better understanding of the molecular events occurring at the mineral’s surfaces, ATR FT-IR spectroscopy is a useful tool for the in-situ identification of surface species [5]. In addition, time-resolved measurements provide kinetic information on the surface reactions. Complementary information on molecule structure and atomic environment can be elucidated from EXAFS spectroscopy.

In this work, Np(V) sorption on the oxyhydroxides of Fe and Mn is investigated comprehensively by combining in-situ ATR FT-IR and EXAFS spectroscopy under a variety of environmentally relevant sorption conditions. As an example, upon sorption of micromolar Np(V) on Fe2O3, a band observed at 789 cm−1 is assigned to the antisymmetric stretching vibrational mode (ν3) of the neptunyl ion (Fig.1). The IR spectrum obtained at equal conditions in an aqueous solution shows the absorption of ν3(NpVO2) at 818 cm−1 [6]. The red shift of ν3 to 789 cm−1 upon sorption can be assigned to an inner-sphere sorption complex. Kinetic experiments have shown that only one sorption complex was formed independent from Np(V) loading. Furthermore, no impact of ionic strength (1- 10−4 M NaCl) and pH (≤ 10) on the sorbed species was found. By EXAFS structural analysis of batch samples the surface complex was further characterized being a binary edge-sharing Np(V) sorption species (Fig.2). From a comparison of Np(V) surface complexation on different mineral oxides of iron, manganese, silicon and titanium a very similar sorption behavior was elucidated.

[1] Kaszuba, J.P. et al. (1999) Environ. Sci. Technol. 33, 4427-4433.
[2] O'Day, P.A. (1999) Rev. Geophys. 37, 249-274.
[3] Tochiyama, O. et al. (1996) Radiochim. Acta 73, 191-198.
[4] Li, D. et al. (2012) J. Hazard. Mater. 243, 1-18.
[5] Wilk, P. A. et al. (2005) Environ. Sci. Technol. 39, 2608-2615.
[6] Müller, K. et al. (2009) Environ. Sci. Techn. 43, 7665-7670.
[7] Blake, R. al. (1966) Am. Mineral. 51, 123-129

Related publications

  • Poster
    International workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2014), 03.-07.11.2014, Dresden, Deutschland

Publ.-Id: 20597

Aligning 1D and 2D axial symmetric transport simulations with observations: consequences for the reactive transport

Lippmann-Pipke, J.; Stuhlfauth, C.; Lippold, H.; Kulenkampff, J.; Enzmann, F.

With 1D and axial symmetric 2D finite element simulations of tracer transport in porous media columns, we conducted systematic studies of increasing heterogeneity on the resulting break-through curves (BTC).

While preferential flow can still have comparably little effect on the BTC of non-reactive tracer substances, for strongly adsorbing tracer preferential flow can significantly shift the break-through towards earlier arrival times by reducing the reactive surface area.

Motivation for conducting this systematic simulation study is our unique GeoPET method (Positron Emission Tomography) that allows the visualization of the spatio-temporal tracer distribution in geologic media (Richter et al., 2000; Gründig et al., 2007; Kulenkampff et al., 2008). The real complexity of thus directly observed flow fields is always surprising. Even for non-reactive tracers quantitative transport simulations typically remain a challenge due to the need for detailed knowledge of hydrodynamic parameter values in 3D with a certain critical spatial resolution.

Here we show simulation results obtained by the COMSOL Multiphysics code coupled with PHREEQC (Wissmeier and Barry, 2011) and compare them with measurement results (BTC) from reactive transport (herbicide MCPA on goethite/sand). CD-MUSIC adsorption model parameter were obtained from Kersten et al., (2014). The underlying structural heterogeneity of the simulated column experiments reflects preferential flow along the column boundaries caused by locally elevated permeability in otherwise homogeneous sand packing as verified by the GeoPET images from both conservative and reactive tracer experiments.

Gründig, M., Richter, M., Seese, A. and Sabri, O., 2007. Tomographic radiotracer studies of the spatial distribution of heterogeneous geochemical transport processes. Applied Geochemistry, 22: 2334-2343.
Kersten, M., Tunega, D., Georgieva, I. and Vlasova, N., 2014. Surface complexation modeling of herbicide adsorption by goethite: 1. 4-chloro-2-methylphenoxyacetic acid (MCPA). Environmental Science & Technology, submitted.
Kulenkampff, J., Gründig, M., Richter, M. and Enzmann, F., 2008. Evaluation of positron emission tomography for visualisation of migration processes in geomaterials. Physics and Chemistry of the Earth, 33: 937-942.
Richter, M., Gründig, M. and Butz, T., 2000. Tomographische Radiotracerverfahren zur Untersuchung von Transport- und Sorptionsprozessen in geologischen Schichten. Zeitschrift für Angewandte Geologie, 46(2): 101.
Wissmeier, L. and Barry, D.A., 2011. Simulation tool for variably saturated flow with comprehensive geochemical reactions in two- and three-dimensional domains. Environmental Modelling & Software, 26(2): 210-218.

  • Poster
    International Symposium of the German Priority Programme SPP 1315 Biogeochemical Interfaces in Soil - Towards a Comprehensive and Mechanistic Understanding of Soil Functions, 06.-08.10.2014, Leipzig, Deutschland

Publ.-Id: 20595

Imaging of α7 nicotinic acetylcholine receptors in brain and cerebral vasculature of juvenile pigs with [18F]NS14490

Rötering, S.; Deuther-Conrad, W.; Cumming, P.; Donat, C. K.; Scheunemann, M.; Fischer, S.; Xiong, G.; Steinbach, J.; Peters, D.; Sabri, O.; Bucerius, J.; Brust, P.

Background: The α7 nicotinic acetylcholine receptor (nAChR) is an important molecular target in neuropsychiatry and oncology. Development of applicable highly-specific radiotracers has been challenging due to comparably low protein expression. To identify novel ligands as candidates for positron emission tomography (PET), a library of diazabicyclononane compounds was screened regarding affinity and specificity towards α7 nAChRs. From these, [18F]NS14490 has been shown to yield reliable results in organ distribution studies; however, dynamic PET investigations required the establishment of an automated radiosynthesis.

Methods: Automated radiosynthesis of [18F]NS14490 has been performed by [18F]fluoroalkylation of the tosylate precursor in the TRACERlabTM FX-N synthesis module. After optimization, the radiochemical yield of [18F]NS14490 was consistently ~35% and the total synthesis time was about 90 min. The radiotracer was prepared with >92% radiochemical purity, and the specific activity at the end of the synthesis was 226 ± 68 GBq µmol-1. PET measurements were performed in young pigs to investigate the metabolic stability and cerebral binding of [18F]NS14490 without and with administration of the α7 nAChR partial agonist NS6740 in baseline and blocking conditions.

Results: The total distribution volume relative to the metabolite-corrected arterial input was 3.5-4.0 mL g-1 throughout telencephalon, and was reduced to 2.6 in animals treated with NS6740. Assuming complete blockade, this displacement indicated a binding potential (BPND) of approximately 0.5 in brain of living pigs. In addition, evidence for specific binding in major brain arteries has been obtained.

Conclusion: [18F]NS14490 is not only comparable to other preclinically investigated PET radiotracers for imaging of α7 nAChR in brain but could besides be a potential PET radiotracer for imaging of α7 nAChR in vulnerable plaques of diseased vessels.

Keywords: Alpha7 nicotinic acetylcholine receptors; Alzheimer´s disease; Blood-brain barrier; Cancer; Diazabicyclononane; Metabolism; PET; Stroke

Publ.-Id: 20594

Recent improvement of Cs2Te photocathodes at HZDR

Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.

The ELBE SRF gun has been successfully operated for the radiation source at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. Meanwhile, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are produced for an accurate deposition rate. Furthermore, the cathode transfer system is improved for a better vacuum condition.

Keywords: SRF gun; high current; low beam emittance; Cs2Te photocathode

Related publications

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC'14, MOPRI025
  • Poster
    the 5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany

Publ.-Id: 20593

PET Imaging of the α4β2* Nicotinic Acetylcholine Receptors in Alzheimer's Disease

Sabri, O.; Meyer, P. M.; Gertz, H.-J.; Brust, P.; Barthel, H.; Hesse, S.

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common form of dementia in the elderly. The subunits α4 and β2 of the nicotinic acetylcholine receptors (α4β2*-nAChRs) are widely abundant throughout the human Brain and play an important role as neuromodulators in different neuronal systems. They are particularly important for cognitive functions and the loss of α4β2*-nAChRs, especially in cholinergic neurons may underlie memory loss in AD. Postmortem autoradiographic and immunohistochemical studies identified cortical and subcortical reductions in α4β2*-nAChR binding in patients with AD. Recently, the α4β2*-nAChR-specific PET and SPECT tracers 2-[18F]FA-85380 (2-FA) and 5-[123I]IA-85380 (5-IA) were developed enabling to study the α4β2*nAChR availability in the living human brain. With such specific radioligands, α4β2*-nAChR binding and its association to cognitive symptoms can be quantitatively determined in patients with AD and mild cognitive impairment (MCI). Initial results show that α4β2*-nAChR availability is reduced in AD but also in amnestic MCI patients who progressed into AD. Hence, the prediction of conversion from MCI to AD seems to be feasible, and therefore, quantitative assessment of α4β2*-nAChR binding using 2-FA-PET or 5-IA-SPECT might become an early biomarker of mental dysfunction in AD. However, the devvelopment of new α4β2*-nAChR PET radioligands characterized by faster kinetics, higher receptor affinity and selectivity is needed and currently underway.

Publ.-Id: 20592

NEA-GaAs (Cs, O) Photocathodes for the ELBE SRF gun

Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.

At HZDR a preparation chamber for NEA-GaAs (Cs,O) has been built and tested. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te photocathode in last years. GaAs photocathodes are advantageous because of their high quantum efficiency (QE) with visible light and the extensive experiences of their use in DC guns. Furthermore, GaAs photocathodes provide the possibility to realize a polarized SRF gun in the future. In this presentation we will introduce the new preparation system and the first results of the GaAs tests. The new transfer system under construction will be also presented.

Keywords: NEA-GaAs (Cs; O); SRF gun; photocathode

Related publications

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC'14, MOPRI024
  • Poster
    the 5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany

Publ.-Id: 20591

Surface nanostructuring by ion-induced localized plasma expansion in zinc oxide

El-Said, A. S.; Moslem, W. M.; Djebli, M.

Creation of hillock-like nanostructures on the surface of zinc oxide single crystals by irradiation with slow highly charged ions is reported. At constant kinetic energy, the nanostructures were only observed after irradiation with ions of potential energies above a threshold between 19.1 keV and 23.3 keV. The size of the nanostructures increases as a function of potential energy. A plasma expansion approach is used to explain the nanostructures creation. The calculations showed that the surface nanostructures became taller with the increase of ionic temperature. The influence of charged cluster formation and the relevance of their polarity are discussed.

Keywords: Surface Nanostructuring; highly charged ions; Zinc oxide; plasma expansion

Related publications

Publ.-Id: 20590

Commissioning and First RF Results of the Second 3.5 Cell Rossendorf SRF Gun

Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.

As in 2007 the first 3.5 cell superconducting radio frequency (SRF) gun was taken into operation at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), it turned out that the specified performance to realize an electron energy gain of 9.4 MeV (E_peak=50 MV/m @ Q_0=1e10) has not been achieved. Instead, the resonator of the gun was limited by field emission to about one third of these values and the measured beam parameters remained significantly below the expectations. However, to demonstrate the full potential of this new electron source for the ELBE LINAC, a second and slightly modified SRF gun was developed and built in collaboration with Thomas Jefferson National Accelerator Facility (TJNAF). We will report on commissioning and first results of this new SRF gun. This includes in particular the characterization of the most important RF properties of the cavity as well as their comparison with previous vertical test results.

Keywords: superconducting radio frequency; SRF gun; cavity

Related publications

  • Poster
    5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Deutschland

Publ.-Id: 20589

Investigation of Cryomodules for the Mainz Energy-recovering Superconducting Accelerator MESA

Schlander, F.; Aulenbacher, K.; Heine, R.; Simon, D.; Arnold, A.

For the multiturn accelerator MESA it is planned to employ superconducting technology for the main linac, which is supposed to provide an energy gain of 50 MeV per turn. As continuous wave operation is mandatory for the experiments, it is important to minimise the cryogenic losses, hence to find cavities and the corresponding cryomodule meeting the framework conditions for the accelerator. The findings and the current statuts will be reported.

Keywords: superconducting technology; linac; cryomodule

Related publications

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference IPAC’14, 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC'14
  • Poster
    5th International Particle Accelerator Conference IPAC’14, 15.-20.06.2014, Dresden, Deutschland


Publ.-Id: 20588

The CBM Time-of-Flight wall - A conceptual design

Deppner, I.; Herrmann, N.; Akindinov, A.; Bartos, D.; Balaceanu, A.; Belogurov, S.; Cao, P.; Caragheorgheopol, G.; Chen, H.; Ciobanu, M.; Constantin, F.; Deng, Z.; Deppe, H.; Duta, V.; Flemming, H.; Frühauf, J.; Gebelein, J.; Heidel, K.; Hildenbrand, K.; Kebschull, U.; Kiš, M.; Kiselev, S.; Koch, K.; Koczon, P.; Kotte, R.; Laso Garcia, A.; Lehrbach, J.; Li, C.; Loizeau, P.-A.; Malkevich, D.; Manz, S.; Naumann, L.; Nedosekin, A.; Niebur, W.; Oancea, A.; Petris, M.; Petrovici, M.; Plotnikov, V.; Prokudin, M.; Radulescu, L.; Shao, M.; Simion, V.; Simon, C.; Sultanov, R.; Sun, Y.; Tang, Z.; Wang, J.; Wang, Y.; Wüstenfeld, J.; Xiang, C.; Xu, N.; Zhang, Y.; Zhou, D.; Zhu, X.

Charged hadron identification in the Compressed Baryonic Matter experiment (CBM) is realized via the Time-of-Flight method [1]. For this purpose the CBM-ToF collaboration designed a Time-of-Flight wall composed of Multi-gap Resistive Plate Chambers (MRPCs). Due to the high interaction rate in CBM of 10 MHz the key challenge is the development of high rate MRPCs above 25 kHz/cm² which become possible after the development of low resistive glass with extremely good quality. In this article we present the actual conceptual design of the ToF-wall which is subdivided in three parts namely the outer wall, the inner wall and the forward zone that are discussed in detail.

Related publications

Publ.-Id: 20587

New experimental upper limit of the electron-proton spin-flip cross-section

Oellers, D.; Weidemann, C.; Lenisa, P.; Meyer, H. O.; Rathmann, F.; Trusov, S.; Augustyniak, W.; Bagdasarian, Z.; Barion, L.; Barsov, S.; Bechstedt, U.; Bertelli, S.; Carassiti, V.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dalpiaz, P. F.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Goslawski, P.; Grigoriev, K.; Guidoboni, G.; Kacharava, A.; Khoukaz, A.; Kulikov, A.; Kleines, H.; Langenberg, G.; Lehrach, A.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Maier, R.; Marianski, B.; Martin, S.; Mchedlishvili, D.; Merzliakov, S.; Meshkov, I. N.; Mielke, M.; Mikirtychiants, M.; Mikirtychiants, S.; Nass, A.; Nikolaev, N.; Nioradze, M.; Papenbrock, M.; Pappalardo, L.; Pesce, A.; Prasuhn, D.; Sarkadi, J.; Schleichert, R.; Smirnov, A.; Seyfarth, H.; Statera, M.; Steffens, E.; Stein, H. J.; Stockhorst, H.; Ströher, H.; Tabidze, M.; Tagliente, G.; Thörngren Engblom, P.; Trzcinski, A.; Valdau, Y.; Vasiliev, A.; Wüstner, P.; Zupranski, P.

In a previous publication, measurements of the depolarization of a stored proton beam by interaction with a co-propagating unpolarized electron beam at low relative energy have been presented and an upper limit of about 3 ×107 b for the electron-proton spin-flip cross-section was determined. A refined analysis presented in this paper reduces the previous upper limit by a factor of three by the introduction of a new procedure that also makes use of non-identified particles.

Publ.-Id: 20586

Different Countermeasures of Electron Amplification in the Photocathode Unit

Tafa Tulu, E.; van Rienen, U.; Arnold, A.

Superconducting radio frequency (SRF) structures may be subjected to electron multipacting (MP). The electrons emitted from one of the structure’s wall under certain conditions are accelerated by the RF field, thereby they may impact the wall again based on the field pattern in the structure. Accordingly the number of electrons increases exponentially caused by secondary electron emission. The latter depends on the secondary emission coefficient of the surface material and the electron trajectory in the device under study. This phenomenon limits the accelerating gradient in the cavity, moreover, it might cause an impair of RF components and distortion of the RF signal. Therefore, there should be an efficient countermeasure to suppress MP in order to boost the performance of the SRF gun. In this paper, three techniques of suppression of MP from the vicinity of the cathode, such as DC-bias, geometric modification and the microstructure of the cathode's surface, in the Rossendorf SRF gun are presented. The simulation has been done using CST Microwave Studio® and CST Particle Studio®. Eventually, the efficient suppression method would be chosen for this particular case.

Keywords: SRF gun; multipacting; electron source

Related publications

  • Open Access Logo Contribution to proceedings
    5th International Particle Accelerator Conference IPAC’14, 15.-20.06.2014, Dresden, Deutschland
    Different Countermeasures of Electron Amplification in the Photocathode Unit
  • Poster
    5th International Particle Accelerator Conference IPAC’14, 15.-20.06.2014, Dresden, Deutschland


Publ.-Id: 20585

Defects and localized states in silica layers implanted with lead ions

Zatsepin, A. F.; Fitting, H.-J.; Buntov, E. A.; Pustovarov, V. A.; Schmidt, B.

The luminescence of silica films and glasses implanted with Pb+ ions was studied by means of time-resolved photoluminescence spectroscopy under synchrotron excitation. The ion-modified silica layers are "metal- dielectrics" composites the oxide part of which is represented by amorphous micro-heterogeneous phase with variable Pb2+ions. Two groups of emission centers are identified: such as: (1) radiation-induced oxygen-deficient centers (ODCs) and non-bridging oxygen atoms (NBOs) in the SiO2 matrix and (2) localized electronic states (LS) of the amorphous lead-silicate phase

Keywords: Lead ion implantation; Metal-dielectric composites; Photoluminescence excitation; Silica; UV-vis-photoluminescence

Related publications

Publ.-Id: 20584

Simulation Study of a Combined Pair Production - Compton Camera for In-Vivo Dosimetry During Therapeutic Proton Irradiation

Rohling, H.; Golnik, C.; Enghardt, W.; Hueso-González, F.; Kormoll, T.; Müller, A.; Pausch, G.; Fiedler, F.

Proton and light ion beams are applied to the therapeutic irradiation of cancer patients due to the favorable dose deposition of these particles in tissue. By means of accelerated ions, a high dose can be accurately deposited in the tumor while normal tissue is spared. Since minor changes in the patient’s tissue along the beam path can compromise the success of the treatment, an in-vivo monitoring of the dose deposition is highly desired. Cameras detecting the prompt gamma-rays emitted during therapy are under investigation for this purpose. Due to the energy spectrum of prompt gamma-rays with a range between a few keV and several MeV, it is reasonable to consider the utilization of electron-positron pair production events to reconstruct the origin of these prompt photons. We evaluated if a pair production camera could be suitable in this context by means of Monte-Carlo simulations. Modelling of the pair production events taking place in a prototype detector dedicated to Compton imaging were performed. We analyzed the efficiency of the detector system regarding pair production and Compton events. The most crucial property of this pair production camera is the angular resolution. The results of this work indicate that the spatial resolution of a pair production camera is, for principal reasons, insufficient for an application to range assessment in particle therapy. Furthermore, the efficiency of the pair production camera under study is one magnitude lower than the efficiency of the Setup applied to the detection of Compton events.

Keywords: Pair production camera; Compton camera; in-vivo dosimetry; Particle therapy

Publ.-Id: 20583

APPL proteins modulate DNA repair and radiation survival of pancreatic carcinoma cells by regulating ATM

Hennig, J.; Mcshane, M.; Cordes, N.; Eke, I.

Despite intensive multimodal therapies, the overall survival rate of patients with ductal adenocarcinoma of the pancreas is still poor. The chemo- and radioresistance mechanisms of this tumor entity remain to be determined in order to develop novel treatment strategies. In cancer, endocytosis and membrane trafficking proteins are known to be utilized and they also critically regulate essential cell functions like survival and proliferation. On the basis of these data, we evaluated the role of the endosomal proteins adaptor proteins containing pleckstrin homology domain, phosphotyrosine binding domain and a leucine zipper motif (APPL) 1 and 2 for the radioresistance of pancreatic carcinoma cells. Here, we show that APPL2 expression in pancreatic cancer cells is upregulated after irradiation and that depletion of APPL proteins by small interfering RNA (siRNA) significantly reduced radiation survival in parallel to impairing DNA double strand break (DSB) repair. In addition, APPL knockdown diminished radiogenic hyperphosphorylation of ataxia telangiectasia mutated (ATM). Activated ATM and APPL1 were also shown to interact after irradiation, suggesting that APPL has a more direct role in the phosphorylation of ATM. Double targeting of APPL proteins and ATM caused similar radiosensitization and concomitant DSB repair perturbation to that observed after depletion of single proteins, indicating that ATM is the central modulator of APPL-mediated effects on radiosensitivity and DNA repair. These data strongly suggest that endosomal APPL proteins contribute to the DNA damage response. Whether targeting of APPL proteins is beneficial for the survival of patients with pancreatic adenocarcinoma remains to be elucidated.

Publ.-Id: 20581

EGFR-Mediated Chromatin Condensation Protects KRAS-Mutant Cancer Cells against Ionizing Radiation

Wang, M.; Kern, A.; Hulskotter, M.; Greninger, P.; Singh, A.; Pan, Y.; Chowdhury, D.; Krause, M.; Baumann, M.; Benes, C.; Efstathiou, J.; Settleman, J.; Willers, H.

Therapeutics that target the epidermal growth factor receptor (EGFR) can enhance the cytotoxic effects of ionizing radiation (IR). However, predictive genomic biomarkers of this radiosensitization have remained elusive. By screening 40 non-small cell lung cancer cell (NSCLC) lines, we established a surprising positive correlation between the presence of a KRAS mutation and radiosensitization by the EGFR inhibitors erlotinib and cetuximab. EGFR signaling in KRAS-mutant NSCLC cells promotes chromatin condensation in vitro and in vivo, thereby restricting the number of DNA double-strand breaks (DSB) produced by a given dose of IR.
Chromatin condensation in interphase cells is characterized by an unexpected mitosis-like colocalization of serine 10 phosphorylation and lysine 9 trimethylation on histone H3. Aurora B promotes this process in a manner that is codependent upon EGFR and protein kinase C alpha (PKC alpha). PKC alpha, in addition to MEK/ERK signaling, is required for the suppression of DSB-inducible premature senescence by EGFR. Blockade of autophagy results in a mutant KRAS-dependent senescence-to-apoptosis switch in cancer cells treated with IR and erlotinib. In conclusion, we identify EGFR as a molecular target to overcome a novel mechanism of radioresistance in KRAS-mutant tumor cells, which stands in contrast to the unresponsiveness of KRAS-mutant cancers to EGFR-directed agents in monotherapy. Our findings may reposition EGFR-targeted agents for combination with DSB-inducing therapies in KRAS-mutant NSCLC. Cancer Res; 74(10); 2825-34. (C) 2014 AACR.

Publ.-Id: 20580

Bispidine dioxotetraaza macrocycles: a new class of bispidines for 64Cu PET imaging

Comba, P.; Kubeil, M.; Pietzsch, J.; Rudolf, H.; Stephan, H.; Zarschler, K.

The three new dioxo-tetraazamacrocyclic ligands with a fused, very rigid bispidine (3,7-diazabicyclo[3.3.1]nonane) group connecting the two tertiary amine donors, and ethyl, propyl, or benzene groups connecting the two amide donors are highly preorganized and lead to very stable, uncharged CuII complexes. Solution spectroscopy and solid state structures indicate that these are square pyramidal with a solvent molecule occupying the apical position. Cyclic voltammetry defines a reversible CuIII/II couple and a strongly negative irreversible CuII/I couple (ca. −2 V vs Fc/Fc+), indicating that the CuII complexes are very stable in solution. This is supported by superoxide dismutase (SOD) and human serum challenge experiments as well as the biodistribution, which all show that the benzene-based ligand has the highest in vitro and in vivo stability and that this was expected on the basis of the macrocycle ring size and shape and the highest degree of preorganization. This ligand is easy to functionalize for a possible coupling to biological vector molecules and/or fluorescence markers for PET (positron emission tomography) and multimodal imaging (i.e., PET and optical imaging).

Publ.-Id: 20579

Evaluation of Novel Fluorescence Probes for Conjugation Purposes Using the Traceless Staudinger Ligation

Wodtke, R.; König, J.; Pigorsch, A.; Köckerling, M.; Mamat, C.

A robust and versatile method for the synthesis of various azide, alkyne and phosphane functionalized coumarin derivatives from the corresponding 7-amino and 7-hydroxy analogs for an application in bioorthogonal conjugation and labeling reactions like the Staudinger Ligation or the Huisgen-Click reaction is presented. Further, the convenient preparation of modified coumarins was performed and subsequent regio–/chemoselective labeling reactions delivered the desired biologically active derivatives in high yields. These new compounds may thus constitute attractive scaffolds for designing novel fluorescence building blocks for various challenging biolabeling applications.

Publ.-Id: 20578

Uranium Redox processes – initiated by plant cells

Geipel, G.; Viehweger, K.

Recently we have shown that uranium can be taken up by plant cells. Fractionation studies showed that the uranium was present in nearly all cell compartments. Nevertheless, luminescence measurements showed that the speciation of the uranium in the several cell compartments differs from each other.
One of the major remaining questions concerns to the ways of uranium uptake. Recently published work [1, 2] proposed that the uranium uptake is influenced by the iron uptake. As it is known that the iron uptake occurs via reduction of the iron(III) into iron(II), we conclude that uranium uptake should also by accompanied by a redox process.
From electrochemical point of view the formation of uranium(V) is a reversible process and the redox potential uranium(VI)/uranium(V) is of the same order as the redox potential iron(III)/iron(II) (values for acidic solution).
The evaluation of Laser-Induced Photoacoustic Spectra (LIPAS) in the wavelength range 620 nm to 680 nm gave evidence for the formation of both reduced oxidation states in the media studied. The uranium(V) is assigned to an absorption at around 637 nm, while uranium(IV) absorbs light at ~660 nm.

Keywords: Uranium; oxidation states; redox process; plant cells

  • Contribution to proceedings
    International Workshop on Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Rossendorf, Deutschland
    Advanced Techniques in Actinide Spectrooscopy (ATAS 2014) Abstract Book, Dresden-Rossendorf: HZDR-054

Publ.-Id: 20577

Radiofluorination and first radiopharmacological characterization of a SWLAY peptide-based ligand targeting EphA2

Pretze, M.; Mosch, B.; Bergmann, R.; Steinbach, J.; Pietzsch, J.; Mamat, C.

Peptides labeled with short-lived positron-emitting radionuclides are of considerable interest as probes for molecular imaging by positron emission tomography (PET). Herein, the regioselective and convenient radiofluorination of a biologically relevant alkyne-modified SWLAY peptide bound on solid support with the radiolabeling building block 1-(3-azidopropyl)-4-(3-fluoropropyl)piperazine ([18F]AFP) is described.
The desired 18F-peptide could be prepared in a total synthesis time of 140 min including the removal of the catalytic copper species and was obtained with a RCY of 7–13% and a RCP > 98%. The method’s feasibility for a robust and bioorthogonal radiolabeling via the 1,3-dipolar Huisgen cycloaddition was demonstrated. Preliminary radiopharmacological studies regarding the metabolic stability of the peptides in cell culture supernatants and rat plasma were accomplished as well as the cellular association of the 18F-peptide in EphA2-overexpressing human melanoma cells in vitro. Furthermore, an initial in vivo PET experiment was performed which showed a fast metabolism of the novel 18F-peptide followed by an accumulation in the kidneys, followed by elimination into the bladder.

Publ.-Id: 20576

Development of New PET Tracers for Clinical Use: Challenges and Problems

Brust, P.

Es ist kein Abstract vorhanden.

  • Invited lecture (Conferences)
    4. Dresdner Workshop "Molekulare Bildgebung in den Lebenswissenschaften", 26.06.2014, Rossendorf, Deutschland

Publ.-Id: 20575

Aufbereitung von [18O]Wasser für die Produktion und Verwendung von [18F]Fluorid

Rötering, S.; Franke, K.; Zessin, J.; Brust, P.; Füchtner, F.; Fischer, S.; Steinbach, J.


Bestrahltes [18O]H2O kann nach Aufbereitung erneut für Bestrahlungen eingesetzt werden1. Wir berichten über einen einfachen Aufbereitungsprozess und eine genaue Charakterisierung des [18O]H2O.


1 l bestrahltes [18O]Wasser mit 396 mg l–1 Ethanol und 44 mg l–1 Aceton sowie Ionen im g-l–1-Bereich wurde in unterschiedlichen Ansätzen zur Oxidation der organischen Lösungsmittel mit KMnO4/NaOH bei 50°C bzw. mit UV-Strahlung1 (254 nm, 1 W) behandelt. Anschließend erfolgte eine Vakuumdestillation. Nach genauer Charakterisierung mit Gas- und Ionenchromatographie Pyknometrie wurde das gewonnene Wasser in einem Nirta®Fluor - Target an einem Cylcone®18/9 (IBA, Belgien) bestrahlt und die Produktionsaktivitäten mit denen von (verdünntem) [18O]Originalwasser verglichen. Das produzierte [18F]Fluorid wurde für die Entwicklung von Radiosynthesen und für standardisierte Herstellungsverfahren eingesetzt.
Für einen Vergleich der beiden Oxidationsmethoden wurde [16O]H2O mit Methanol, Ethanol, Aceton und Acetonitril kontaminiert und entsprechend aufbereitet.


Mit beiden Oxidationsmethoden wurden die organischen Lösungsmittel innerhalb von max. 2 Tagen unter einen Grenzwert von 50 mg l–1 abgebaut. Nach der Vakuumdestillation zeichneten sich die einzelnen Chargen durch übereinstimmende 18O-Anreicherungen sowie geringe Ionengehalte aus. Der Vergleich der Produktionsaktivitäten zeigt eine Übereinstimmung zu verdünntem Originalwasser. Die Verwendung des [18F]F– in radiochemischen Umsetzungen war erfolgreich.

Abbildung 1: Produktionsaktivitäten mit aufbereitetem Wasser und verdünntem Originalwasser
Die Aufbereitung von Modelllösungen mit [16O]H2O ergab, dass Acetonitril durch KMnO4/NaOH defakto nicht abgebaut wird. Es wurden für beide Methoden ≥97% des eingesetzten Wassers gewonnen.


Die Ergebnisse zeigen einen zuverlässigen, nahezu verlustfreien Aufbereitungsprozess von bestrahltem [18O]H2O. Dies ermöglicht einen ökonomisch sinnvollen Gebrauch von [18O]H2O.


[1] Gebrauchsmuster DE 29504388 U1 (15.03.95), Forschungszentrum Jülich GmbH

  • Lecture (Conference)
    22. Jahrestagung der AGRR 2014, 11.-13.09.2014, Mainz, Deutschland

Publ.-Id: 20574

Proinflammatory human 6-sulfo LacNAc-positive dendritic cells accumulate in intestinal acute graft-versus-host disease

Sommer, U.; Larsson, B.; Tuve, S.; Wehner, R.; Zimmermann, N.; Kramer, M.; Kloß, A.; Günther, C.; Babatz, J.; Schmelz, R.; Brückner, S.; Schetelig, J.; Bornhäuser, M.; Schäkel, K.; Bachmann, M. P.; Aust, D.; Baretton, G.; Schmitz, M.

kein Abstract verfügbar

Keywords: Acute graft versus host disease; b-sulfo LacNAc positive; Dendritic cells; Proinflammatory

Publ.-Id: 20573

Combined measurement of tumor perfusion and glucose metabolism for improved tumor characterization in advanced cervical carcinoma: A PET/CT pilot study using [15O]water and [18F]fluorodeoxyglucose

Apostolova, I.; Hofheinz, F.; Buchert, R.; Steffen, I. G.; Michel, R.; Rosner, C.; Prasad, V.; Köhler, C.; Derlin, T.; Brenner, W.; Marnitz, S.

Background and purpose:

The aim of this pilot study was (1) to evaluate the combination of [18F]fluorodeoxyglucose (FDG) and [ 15O]water for detection of flow-metabolism mismatch in advanced cervical carcinomas, i.e., increased glycolysis at low blood flow, as a possible parameter for prediction of response to treatment, and (2) to propose a method for automated quantification of its spatial extent.
Patients and methods:
The study retrospectively included 10 women with advanced cervical carcinoma in whom PET with both FDG and [15O]water had been performed prior to therapy. The metabolically active tumor volume was delineated automatically in the FDG images. For computation of the regional blood flow in the tumor, a recovery corrected image-derived arterial input function was used. A tumor voxel was classified as mismatched when the voxel SUV of FDG was larger than the median tumor SUV and the voxel perfusion (K1) was smaller than the median perfusion. The absolute mismatch volume (aMMV) was defined as the volume of all mismatched voxels in ml, and the relative mismatch volume (rMMV) as the ratio of the aMMV to the metabolic tumor volume in percent.
The tumors were quite heterogeneous with respect to both FDG uptake and perfusion. The aMMV clustered into 2 groups: "large aMMV" ∈10 ml in 40∈% of patients and "small aMMV" 5 ml in 60∈% of patients. The rMMV ranged from 12.7-24.9∈%. There was no correlation between rMMV and metabolic tumor volume. There was a tendency (p∈=∈0.126) for an association between rMMV and histological grading, rMMV being about 20∈% higher in G3 than in G2 tumors. rMMV did not correlate with SUV or perfusion.
These results suggest that combined PET with FDG and [15O]water allows detection and quantitative characterization of flow-metabolism mismatch in advanced cervical carcinomas.

Keywords: Positron emission tomography; Prognosis; Uterine cervical carcinoma

Publ.-Id: 20572

64Cu-labeling of dendritic polyglycerol derivatives for biodistribution studies

Pant, K.; Steinbach, J.; Stephan, H.; Gröger, D.; Nowag, S.; Haag, R.

Dendritic polyglycerols (dPG) and polyglycerol sulfates (dPGS) are promising compounds for biomedical applications due to their easy synthesis and high biocompatibility. Dendritic polyglycerol sulfate shows strong anti-inflammatory
properties [1, 2] which makes it a promising agent for diagnostic and therapeutic applications [3].

Information about the biodistribution and the metabolism of dendritic polyglycerol derivatives in living systems are quite scarce. In order to obtain quantitative information about the biodistribution of dPGS in vivo, methods like positron emission tomography (PET) will be applied. Among the metal-based positron emitting radionuclides, 64Cu is one of the most intensively evaluated isotopes. Incorporation of 64Cu into dPG/dPGS derivatives requires the use of chelate ligands capable of tightly binding the radionuclide.

Herein, we report the conjugation of bifunctional chelating agents (BFCA), based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) [4], on the dPG/dPGS scaffold. The structure of DMPTACN allows for the introduction of linker groups, such as carboxylic acids, maleimides or isothiocyanates, thereby facilitating coupling to the dendritic polyglycerol derivatives that contain amino and mercapto surface groups. 64Cu-labeling experiments and studies of the stability of the resulting radiocopper complexes in the presence of human serum or the competing ligand EDTA will be discussed.


[1] H. Türk et al., Bioconjugate Chem. 2004, 15, 162.
[2] J. Dernedde et al., PNAS 2010, 117, 19679.
[3] K. Licha et al., Bioconjugate Chem. 2011, 22, 2453.
[4] G. Gasser et al., Bioconjugate Chem.2008, 19, 719.

  • Poster
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Publ.-Id: 20571

Magnetic dipole strength in 128Xe and 134Xe in the spin-flip resonance region

Massarczyk, R.; Rusev, G.; Schwengner, R.; Dönau, F.; Bhatia, C.; Gooden, M. E.; Kelley, J. H.; Tonchev, A. P.; Tornow, W.

The magnetic dipole strength in the energy region of the spin-flip resonance has been investigated in {128}Xe and {134}Xe using quasi-monoenergetic and linearly polarized gamma-ray beams at the HI gamma S facility in Durham, USA. Absorption cross sections were deduced for the electric and magnetic Dipole distributions separately for various intervals of excitation energy, including the strength of states in the unresolved quasi-continuum. Spin-flip like resonance structures were found in the magnetic dipole strength distribution around an excitation energy of 8 MeV. The E1 strength distributions deduced from the present experiments are compatible with the data of an experiment using bremsstrahlung that are based on simulations of statistical gamma-ray cascades. The experimental E1 and M1 strengths are compared with phenomenological approximations and with deformed-basis quasiparticle-random-phase-approximation predictions.

Keywords: Photon scattering; nuclear resonance fluorescence; polarized $\gamma$-ray beams; electric and magnetic dipole strength functions; nuclear deformation; quasiparticle-random-phase-approximation

Related publications

Publ.-Id: 20570

64Cu-labelling and biodistribution of dendritic polyglycerol derivatives

Pant, K.; Stephan, H.; Bergmann, R.; Steinbach, J.; Gröger, D.; Haag, R.

Dendritic polyglycerols are highly biocompatible polymers which can be synthesized on a multi gram scale in a one-pot synthesis. The properties of these derivatives can be influenced by using various surface groups, such as sulfates, carbonates, phosphates etc. Some derivatives have been already known for inflammation and bone targeting [1]. Dendritic polyglycerol sulfates (dPGS) are promising candidates to be applied as anti-inflammation and anti-coagulation agents [2]. The presence of amine surface groups in dPGS derivatives allows the attachment of various fluorescence tags and/or radiolabels. Fluorescence imaging using near IR probes visualizes a specific accumulation of dendritic polyglycerol sulfates (dPGS) in inflamed lesions [3]. With respect to radioactive labelling, 35S-labelled dPGS amines have been prepared. This allows ex vivo experiments using autoradiography[4]. However, there is a need of detailed information about bio-distribution and pharmacokinetic properties for dendritic polyglycerol derivatives.

For this reason, appropriate imaging techniques should be applied to achieve reliable information about the bio-distribution and the metabolic fate of these macromolecules in vivo. Nuclear imaging, especially positron emission tomography (PET) is known to be one of the most reliable techniques to follow the fate of substances in vivo and to examine the biological and pathological processes considering the small dose requirement of the radiolabelled substances to diminish the pharmacological effects. 64Cu has suitable decay characteristics that allow for PET imaging and a variety of bifunctional chelator agents (BFCAs) are available for attachment to dendritic polyglycerol derivatives using appropriate anchor groups.

Herein, we report the synthesis, radiolabelling and biodistribution studies of the dPGS scaffolds using BFCAs on the basis of 1,4,7-triazacyclononane with various functional end groups (carboxylic, maleimide, isothiocyanate groups) for easy bioconjugation onto the dPGS scaffolds (amine/mercapto surface groups). 64Cu-labeling experiments confirmed rapid CuII complex formation under mild conditions. The stability of the 64Cu radiolabelled conjugates has been studied in the presence of competing ligands, human serum and super oxide dismutase (SOD)[5] For stability studies in the presence of human serum and SOD, two complementary in vitro assays have been applied. Small animal PET studies with 64Cu-labelled dPGS derivatives in male Wistar rats have been performed and discussed.

  • Poster
    Biodendrimer 2014, 4th International Symposium on Biomedical Applications of Dendrimers, 18.-20.06.2014, Lugano, Schweiz

Publ.-Id: 20569

Carbon redistribution and precipitation in high temperature ion-implanted strained Si/SiGe/Si multi-layered structures

Gaiduk, P. I.; Lundsgaard Hansen, J.; Larsen, A. N.; Korolik, O. V.; Bregolin, F. L.; Skorupa, W.

We report on the segregation of carbon atoms and structural transformations in strained multilayered Si/SiGe/Si structures after molecular-beam epitaxial (MBE) growth, carbon ion implantation and thermal treatment at different conditions. The idea behind this study was that due to their specific strain distribution, pseudomorphic layers of Si/SiGe promote spatial separation of vacancies and interstitials followed by segregation of foreign dopant atoms. High temperature ion implantation was used for injection of carbon atoms as well as point defects in the strained layers. The defects were investigated by transmission electron microscopy (TEM), dopant depth profiles by secondary-ion-mass spectrometry (SIMS), and optical properties by Raman scattering measurements. Based on SIMS data we demonstrate anomalous redistribution of the implanted carbon atoms around the strained SiGe/Si layers which results in their accumulation on the Si side and depletion on the SiGe side of the structure. The TEM study demonstrates formation of plate-like defects, stacking faults and thin carbon-precipitated flakes distributed along the Si/SiGe interfaces. Raman spectra reveal peaks at 1600 and 2700 cm -1 which might be associated with carbon-related phases. The concept of strain-enhanced separation of point defects and dopant precipitation is discussed.

Keywords: Carbon redistribution; Defects; Precipitates; Si-SiGe heterostructures; Voids

Related publications

Publ.-Id: 20568

Gangue mineralogy and deportment of titanium (Ti) and vanadium (V) in the Kiirunavaara iron ore deposit, Northern Sweden

Aupers, K.; Niiranen, K.; Birtel, S.; Höfig, T. W.; Krause, J.; Gutzmer, J.

The Paleoproterozoic Kiirunavaara Fe oxide-apatite intrusive body has long been known as the most productive iron ore deposit of Europe. Because of the production in the mine is advancing deeper levels and demand for iron ore is increasing, the importance of understanding the deposit from both mineralogical and geochemical point of view is obvious. Among other it is thus important to characterise the abundance and chemical composition of ore and gangue minerals in terms of their variable impact as potential Ti-V hosts, which might be critical elements for production in the future. For this purpose, 55 samples from deeper parts of the orebody were studied combining optical microscopy, SEM-based MLA, and EPMA. Three minerals with stoichiometric Ti-contents have been identified: titanite, ilmenite, and rutile. Moreover, phlogopite hosts Ti in significant amounts (Ø 4300 ppm). For the P-poor parts of the orebody (B-type ore), ilmenite and rutile form the major Ti-hosts in Fe-rich intervals (Fe > 66 wt. %), whereas titanite is predominant in P-poor intervals with slightly lower Fe contents. In contrast, Ti-minerals are fairly rare in P-rich zones of the orebody (P > 0.1 wt. %, D-type ore) and, if present, represented by titanite. Magnetite, being the major commodity at Kiirunavaara, has not revealed any significant Ti contents in its crystal structure. However, Ti is associated with magnetite in the form of Ti-rich exsolution lamellae, being restricted to magnetite crystals in B-type ore (Fig. 1). Incorporation of V has been exclusively detected in magnetite and titanite, revealing average concentrations of c. 600 ppm and 650 ppm respectively. Due to the exploration and grade control drilling the Ti-grade increases with depth. Consequently also the abundance of Ti-bearing silicate (titanite, phlogopite) and oxide (ilmenite, rutile) rises. In the future, additional flotation steps besides the reverse apatite flotation may be required to ensure their efficient elimination during the beneficiation process. It also appears unreasonable to mechanically separate the Ti-rich exsolution lamellae and lattice-bound V from the magnetite sinter feed product of the Kiruna Mine.

Keywords: deleterious elements; element deportment; geometallurgy

  • Lecture (Conference)
    92nd Annual Meeting Deutsche Mineralogische Gesellschaft, 21.-24.09.2014, Jena, Germany
  • Contribution to proceedings
    92nd Annual Meeting Deutsche Mineralogische Gesellschaft, 21.-24.09.2014, Jena, Germany
    Minerals at Focal Point, 115

Publ.-Id: 20567

Solution of the OECD/NEA neutronic SFR benchmark with Serpent-DYN3D and Serpent-PARCS code systems

Nikitin, E.; Fridman, E.; Mikityuk, K.

In this study, the Serpent Monte Carlo code was used as a tool for preparation of homogenized group constants for the nodal diffusion analysis of a large U-Pu MOX fueled Sodium-cooled Fast Reactor (SFR) core specified in the OECD/WPRS neutronic SFR benchmark. The group constants generated by Serpent were employed by DYN3D and PARCS nodal diffusion codes in 3D full core calculations. The DYN3D and PARCS results were verified against the references full core Serpent Monte Carlo solution. A good agreement between the reference Monte Carlo and nodal diffusion results was observed demonstrating the feasibility of using Serpent as a group constant generator for the deterministic SFR analysis.

Keywords: Group constant generation; Monte-Carlo; SFR; Serpent; DYN3D; PARCS

Publ.-Id: 20566

Effect of [18F]FMISO stratified dose-escalation on local control in FaDu hSCC in nude mice

Schütze, C.; Bergmann, R.; Brüchner, K.; Mosch, B.; Yaromira, A.; Zips, D.; Hessel, F.; Krause, M.; Thames, H.; Kotzerke, J.; Steinbach, J.; Baumann, M.; Beuthien-Baumann, B.

Objective To investigate the effect of radiation dose-escalation on local control in hypoxic versus non-hypoxic hypoxic tumours defined using [18F]fluoromisonidazole ([18F]FMISO) PET. Materials and methods FaDu human squamous cell carcinomas (hSCCs) growing subcutaneously in nude mice were subjected to [18F]FMISO PET before irradiation with single doses of 25 or 35 Gy under normal blood flow conditions. [18F]FMISO hypoxic volume (HV) and maximum standardised uptake value (SUVmax) were used to quantify tracer uptake. The animals were followed up for at least 120 days after irradiation. The endpoints were permanent local tumour control and time to local recurrence. Results HV varied between 38 and 291 mm3 (median 105 mm3). Non-hypoxic tumours (HV below median) showed significantly better local control after single dose irradiation than hypoxic tumours (HV above median) (p = 0.046). The effect of dose was significant and not different in non-hypoxic and in hypoxic tumours (HR = 0.82 [95% CI 0.71; 0.93], p = 0.002 and HR = 0.86 [0.78; 0.95], p = 0.001, respectively). Dose escalation resulted in an incremental increase of local tumour control from low-dose hypoxic, over low-dose non-hypoxic and high-dose hypoxic to high-dose non-hypoxic tumours. SUVmax did not reveal significant association with local control at any dose level. Conclusions The negative effect of [18F]FMISO HV on permanent local tumour control supports the prognostic value of the pre-treatment [18F]FMISO HV. Making the assumption that variable [18F]FMISO uptake in different FaDu tumours which all have the same genetic background may serve as an experimental model of intratumoural heterogeneity, the data support the concept of dose-escalation with inhomogeneous dose distribution based on pre-treatment [18F]FMISO uptake. This result needs to be confirmed in other tumour models and using fractionated radiotherapy schedules.

Keywords: Dose escalation; Human tumour xenografts; Hypoxic volume; Local control; Single dose irradiation; Squamous cell carcinoma

Publ.-Id: 20565

Investigations of the liquid steel flow in slab casters with electromagnetic brakes and round bloom casters with electromagnetic stirring

Barna, M.; Willers, B.; Javurek, M.; Reiter, J.; Eckert, S.

In the continuous casting of steel the application of electromagnetic fields to modify the flow is steadily increasing. Electromagnetic stirring fields are used to excite a rotary motion in the strand thereby – among other benefits – promoting the columnar to equiaxed transition. In slab casters stationary fields shall break the submerged jets, dampen the turbulent movement and calm the liquid steel flow.
The influence of an electromagnetic brake onto the liquid steel flow is investigated through numerical simulations and experimental work. A 1:10 scale model of a continuous slab caster is built and flow measurements are conducted with Ga68In20Sn12 (Galinstan), a low melting point alloy. The results are then used for the validation of fully coupled numeric simulations, where the flow influences the magnetic field and vice versa.
For round bloom casting with electromagnetic stirring the impact of stirring frequency and stirring field current will be shown. From the results a simple analytical model can be deduced, which describes the average azimuthal velocity close to the wall. When combined with an estimation of the power losses, optimal stirring parameters can be chosen.

Keywords: Continuous casting of steel; electromagnetic braking; electromagnetic stirring; multiphysics; fully coupled numeric simulation; computational fluid dynamics (CFD); experiments; low melting point alloy Galinstan; Ultra Sound Doppler Velocimetry

  • Open Access Logo Contribution to proceedings
    8th European Continuous Casting Conference, 23.-26.06.2014, Graz, Austria
    Proceedings of ECCC

Publ.-Id: 20563

Multiscale and multiphysics simulation of pessurized thermal shock (PTS)

Lucas, D.

An overview on the activities related to the work package 32 on pressurized thermal shock in frame of the European project NURESAFE is given in this presentation

Keywords: CFD; PTS

  • Lecture (Conference)
    First NURESAFE open seminar, 16.-17.06.2014, Budqapest, Hungary

Publ.-Id: 20562

CFD-Modelle für Zweiphasenströmungen im Rahmen des Mehr-Fluid-Konzepts

Lucas, D.; Rzehak, R.; Krepper, E.; Höhne, T.; Liao, Y.; Montoya, G.; Hänsch, G.

Mehrphasenströmungen kommen u. a. in verschiedenen industriellen Prozessen der chemischen Verfahrenstechnik, der Energietechnik und der Ölindustrie vor. Zuverlässige Vorhersagen der zu erwartenden Strömungs- und Energietransfereigenschaften sind für die Auslegung, Optimierung und auch Sicherheitsbetrachtung dieser Prozesse wichtig. Für CFD-Simulationen von Strömungen in mittleren und großen Volumina wird meist das Zwei- bzw. Mehr-Fluid-Konzept (Euler-Euler-Modell) genutzt. Eine wesentliche Unsicherheit der Simulationsergebnisse resultiert dabei aus den Schließungsmodellen. Oft werden diese Modelle sowie damit verbundene freie Parameter so ausgewählt, dass eine gute Überstimmung mit vorhanden experimentellen Daten erzielt wird. Da die Vorhersagefähigkeit für unbekannte Strömungen dadurch nicht verbessert wird, wurden am HZDR so genannte Standardmodelle für polydisperse Blasenströmungen und separierte Strömungen definiert. Die allgemeine Strategie der Modellentwicklung sowie die Standardmodelle selbst werden in dem Vortrag vorgestellt. Weiterhin wird ein neuer Modellansatz diskutiert, der eine kombinierte Simulation der beiden Strömungsmorphologien einschließlich der Berücksichtigung von Übergängen zwischen diesen ermöglicht.

Keywords: CFD; Mehrphasenströmungen

  • Invited lecture (Conferences)
    Institutsseminar des Instituts für Kern- und Energietechnik (IKET) am Karlsruher Institut für Technologie (KIT), 08.07.2014, Karlsruhe, Deutschland

Publ.-Id: 20561

GENTOP – a multi-field 2-fluid model

Lucas, D.; Hänsch, S.; Krepper, E.; Höhne, T.; Montoya, G.

In this presentation the main ideas of the GENTOP-concept are presented. The concept allows the modelling of different morphologies of two-phase flows including transitions between them. Simulation results are shown for four different demonstration cases.

Keywords: CFD; two-phase; multi-scale

  • Invited lecture (Conferences)
    Joint Hungarian-Korean Laboratory (JHKL) Workshop, 19.-20.06.2014, Budapest, Hungary

Publ.-Id: 20560

Potential of a Cetuximab-based radioimmunotherapy combined with external irradiation manifests in a 3-D cell assay

Ingargiola, M.; Runge, R.; Heldt, J.-M.; Freudenberg, R.; Steinbach, J.; Cordes, N.; Baumann, M.; Kotzerke, J.; Brockhoff, G.; Kunz-Schughart, L. A.

Targeting epidermal growth factor receptor (EGFR)-overexpressing tumors with radiolabeled anti-EGFR antibodies is a promising strategy for combination with external radiotherapy. In this study, we evaluated the potential of external plus internal irradiation by [90Y]Y-CHX-A''-DTPA-C225 (Y-90-C225) in a 3-D environment using FaDu and SAS head and neck squamous cell carcinoma (HNSCC) spheroid models and clinically relevant endpoints such as spheroid control probability (SCP) and spheroid control dose 50% (SCD 50, external irradiation dose inducing 50% loss of spheroid regrowth). Spheroids were cultured using a standardized platform. Therapy response after treatment with C225, CHX-A''-DTPA-C225 (DTPA-C225), [ 90Y]Y-CHX-A''-DTPA (Y-90-DTPA) and Y-90-C225 alone or in combination with X-ray was evaluated by long-term monitoring (60 days) of spheroid integrity and volume growth. Penetration kinetics into spheroids and EGFR binding capacities on spheroid cells were identical for unconjugated C225 and Y-90-C225. Spheroid-associated radioactivity upon exposure to the antibody-free control conjugate Y-90-DTPA was negligible. Determination of the SCD50 demonstrated higher intrinsic radiosensitivity of FaDu as compared with SAS spheroids. Treatment with unconjugated C225 alone did not affect spheroid growth and cell viability. Also, C225 treatment after external irradiation showed no additive effect. However, the combination of external irradiation with Y-90-C225 (1 μg/ml, 24 hr) resulted in a considerable benefit as reflected by a pronounced reduction of the SCD50 from 16 Gy to 9 Gy for SAS spheroids and a complete loss of regrowth for FaDu spheroids due to the pronounced accumulation of internal dose caused by the continuous exposure to cell-bound radionuclide upon Y-90-C225-EGFR interaction.

Keywords: Cetuximab; EGFR; tumor spheroids; Y-90

Publ.-Id: 20559

Multiscale thermalhydraulic analyses performed in NURESAFE project

Bestion, D.; Lakehal, D.; Tregoures, N.; Lucas, D.; Anglart, H.; Niceno, B.; Hazi, G.; Vyskocil, L.

An overview on the activities on thermal hydraulics with in the NURESAFE project is given in this presentation.

Keywords: CFD; PTS; BWR; multi-scale modelling

  • Lecture (Conference)
    22th International Conference on Nuclear Engineering (ICONE22), 06.-10.07.2014, Prague, Czech Republic

Publ.-Id: 20558

Climatic vs tectonic forcing: the case of Pamir

Gloaguen, R.; Fuchs, M.; Pohl, E.; Sulaymonova, V.; Andreani, L.

Surface processes in Pamir are temporally and spatially extremely variables. Our collaborative research demonstrated that, (1) the controlling forces such as climate and tectonic deformation have evolved during the Quaternary, (2) Westerlies and Monsoon have varying domains of influence and (3) the rates of deformation, erosion and incision are locally extremely high. The determination of the localization and intensity of active tectonic structures was allowed by the production of remote sensing based geomorphometric maps combined with published GPS and seismological data. Incision rates were measured by OSL and cosmogenic dating of river terraces. Modern erosion rates were calculated using AMS 10Be concentrations in river sediments. Tectonic deformation principally occurs along the borders of the Pamir domes, probably along propagating strike-slip faults reactivating older structures such as sutures and dome bounding faults. Most rivers are in imbalance and witness a strong reorganization of the drainage system during the Late Quaternary. The Panj itself is built by the concatenation of rivers by successive captures, the last one probably younger than MIS2. The average incision rate of the Panj, the main river draining Pamir and its main tributaries is about 4 mm/yr. Peak incisions reach 10 mm/yr where river captures induced high offsets with respect to base levels. Erosion rates are high at the Pamir periphery (ca 0.7 mm/yr) and very low on the plateau (ca 0.005 mm/yr). The Pamir can be subdivided in zones in which specific controlling forces are dominating. The Pamir plateau is dominated by diffusive hillslope processes contributing to further flattening. The main rivers are located in or nearby active faults. High erosion rates are probably sustained by steep hillslopes generated by high incision rates. Highest erosion rates are found were both Monsoon and Westerlies occur.

Related publications

  • Lecture (Conference)
    EGU General Assembly 2014, 27.04.-02.06.2014, Vienna, Austria

Publ.-Id: 20557

A new set of MATLAB functions (TecDEM toolbox) to analyze erosional stages in landscapes and base-level changes in river profiles

Andreani, L.; Gloaguen, R.; Shahzad, F.

We implemented three new functions in the MATLAB-based TecDEM toolbox [1,2]: surface index, topographic position index, and the analysis of base-levels in river longitudinal profiles. These tools provide useful ways to understand the effects of base-level changes on topography such as stream captures, erosion or rejuvenation of pre-existing topographic features and anomalies in river longitudinal profiles. We developed a new index (referred as “surface index”) which provides a quick way to map simultaneously preserved and eroded portions of an elevated landscape. This index classifies landscapes according to their erosional stages using the combination of the hypsometric integral, which efficiently highlights flat surfaces, and the surface roughness, which substantially increases with incision. We also implemented the commonly used “topographic position index”. This index provides a simple way to classify the landscapes as valleys, ridges and flat areas. However, its application in tectonic geomorphology can go far beyond as it discriminates valleys shapes and reveals other important features such as wind gaps and knickpoints when associated to the extracted river system. Finally, we implemented a tool allowing the estimation of base-level changes using the reconstruction of river longitudinal profiles. River profiles can be decomposed in concave or convex segments. Relict base-levels are typically associated to gently concave segments in river profiles. By restoring the initial shape of these segments we are able to estimate the amount of incision between the present day base-level and the relict base-level. All these tools were successfully tested in different settings such as Central America, Central Europe and Pamir. In addition to the description of these tools we provide examples from these different areas.
[1] Shahzad, F., & Gloaguen, R. (2011). TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 1: Drainage network preprocessing and stream profile analysis. Computers & Geosciences, 37, 250–260.
[2] Shahzad, F., & Gloaguen, R. (2011). TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 2: Surface dynamics and basin analysis. Computers & Geosciences, 37, 261–271.

  • Poster
    EGU General Assembly 2014, 27.04.-02.05.2014, Vienna, Austria

Publ.-Id: 20556

Planned high-brightness channeling radiation experiment at FERMILAB’s Advanced Superconducting Test Accelerator

Blomberg, B.; Brau, C. A.; Choi, B. K.; Gabella, W. E.; Ivanov, B.; Mendenhall, M.; Lynn, C.; Mihalcea, D.; Panuganti, H.; Piot, P.; Sen, T.; Wagner, W.

In this contribution we describe the technical details and experimental setup toward the production of high-brightness channeling radiation (CR) at the Fermilab’s Advanced Superconducting Test Accelerator (ASTA). In the ASTA photoinjector area electrons are accelerated up to 40-MeV and focused to a sub-micron spot on a 40 micron thick diamond, the electrons channel through the crystal and emit CR up to 80-KeV. Our study utilizes ASTA’s long pulse train capabilities and ability to preserve ultra-low emittance, to produce the desired brightness.

Keywords: electron channeling; channeling radiation; ASTA

  • Open Access Logo Contribution to proceedings
    IPAC 2014 - 5th International Particle Accelerator Conference, 16.-20.06.2014, Dresden, Germany
    Proceedings of IPAC 2014, 1457

Publ.-Id: 20555

A new multi-region solver for liquid metal batteries

Weber, N.; Galindo, V.; Stefani, F.; Weier, T.

Liquid metal batteries (LMBs) are a very innovative approach intending to fill the gap of grid-scale electricity storage, as induced by the expand of highly fluctuating renewable energies. Earth-abundant raw materials, simple construction and easy scalability allow for very cheap batteries – the biggest advantage of LMBs.
A LMB is made up of two liquid metals, separated by a liquid salt electrolyte. Properly chosen densities ensure a stable stratification. Taking a Na/Bi LMB, on dis-charge, the Na will lose one electron. The ion Na+ will pass the electrolyte layer and alloy with the Bi to NaBi.
The high resistivity of the salt requires a very thin electrolyte layer, but thick enough to avoid a short-circuit. Fluid flows in LMBs may involve the risk of displacing the electrolyte, resulting in a short-circuit. One of the most important sources of motion are electro vortex flows: the different cross-sections of feeding lines, current collectors and the battery itself induces Lorentz forces in the liquid metal, which are driving a fluid flow.
The fluid flow is governed by the incompressible Navier-Stokes equation (NSE) with the Lorentz force as source term. In order to obtain the latter, we solve a Laplace equation for the electric potential in the liquid metal as well as the current collectors and compute it's gradient giving the current density. With the help of the Biot-Savart law we can compute the magnetic field. The cross product of both is the desired Lorentz force.
Our solver is modeled analogous to chtMultiRegionFoam. We solve the NSE by the PISO algorithm as electro vortex flows are instationary. Solving the Laplace equation for the electric potential we alternate between the liquid and solid regions. The interface condition is given by the demand that there is no jump of the electric potential, and that the normal electric current must be continuous. We combine these two conditions to a single Dirichlet boundary condition for fastest Dirichlet-Neumann partitioning. We stop the iteration between the regions, when both boundary conditions are fulfilled at all interfaces.
The last step, the computation of the magnetic induction using the Biot-Savart law, is a N x N problem. In order to speed up the computation we propose a fast MPI implementation.
Finally, we present some exemplary results and show how electro vortex flows scale in LMBs with the applied current, the current collectors aspect ratio and it's conductivity.

Keywords: liquid metal battery; electro vortex flow; instability; OpenFOAM

  • Lecture (Conference)
    OpenFOAM User Conference, 07.-09.10.2014, Berlin, Deutschland

Publ.-Id: 20554

Model experiments for investigations of heat transfer phenomena in the Czochralski crystal growth

Pal, J.; Cramer, A.; Eckert, S.; Gerbeth, G.; Grants, I.

A low temperature liquid metal model of the Czochralski crystal growth process is considered experimentally under conditions of high aspect ratio. We focus on the influence of a rotating magnetic field (RMF) and/or crystal rotation on temperature fluctuation near the crystal edge. The radial flow structure is observed by ultrasound Doppler velocimetry (UDV). It is concluded that the effect of RMF on the temperature fluctuation is less expressed than in a Rayleigh-Bénard cell.

Keywords: Czochralski crystal growth; electromagnetic processing; buoyant flow; heat transfer

  • Lecture (Conference)
    The 9th. International PAMIR conference on Fundamental and Applied MHD, Thermo Acoustic and Space Technologies, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    The 9th. International PAMIR Conference on Fundamental and Applied MHD, Thermo Acoustic and Space Technologies, 16.-20.06.2014, Riga, Latvia
    Proceedings, 110-114

Publ.-Id: 20553

Experimental Investigation of Rayleigh-Benard convection in a liquid metal layer exposed to a horizontal magnetic field

Igaki, K.; Tasaka, Y.; Yanagisawa, T.; Vogt, T.; Eckert, S.

Rayleigh-Benard convection has been investigated inside a liquid metal layer under the influence of a DC magnetic field. Similar configurations can be found in geophysical or steel production. Our group reported recently that spontaneous flow reversals of quasi two-dimensional rolls randomly occur in Rayleigh-Benard convection of liquid metal exposed to a horizontal magnetic field (Yanagisawa, et al., PRE, 2011). In fluid layers with relatively large aspect ratios the flow pattern consisting of several convection rolls appears to be almost isotropic. However, the rolls are aligned with the magnetic field direction if the Lorentz force becomes either comparable to the buoyancy or larger. In our experiment, where the fluid layer has a dimension of 200x200x40 mm (corresponding to an aspect ratio of 5), the convection pattern can show 3, 4 or 5 rolls regimes depending on the Rayleigh number Ra and the Chandrasekhar number Q. Flow reversals occur spontaneously between these steady states in the Ra-Q parameter space.

Keywords: Rayleigh-Benard

  • Contribution to proceedings
    9th International Pamir Conference, 16.-20.06.2014, Riga, Latvia
  • Poster
    9th International Pamir Conference, 16.-20.06.2014, Riga, Latvia

Publ.-Id: 20552

Application of magnetically driven tornado-like vortex for stirring floating particles into liquid metal

Grants, I.; Räbiger, D.; Vogt, T.; Eckert, S.; Gerbeth, G.

A tornado-like vortex is driven by magnetic body forces. A continuously applied rotating magnetic field provides source of the angular momentum. A pulse of a much stronger travelling magnetic field drives a converging flow that temporarily focuses this angular momentum towards the axis of the container. A highly concentrated vortex forms that produces a funnel-shaped surface depression. The ability of this vortex to entrain floating unwetted particles in liquid metal is investigated experimentally.

Keywords: Electromagnetic processing of materials; magnetohydrodynamics

  • Lecture (Conference)
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    9th PAMIR conference on Fundamental and Applied MHD, 16.-20.06.2014, Riga, Latvia

Publ.-Id: 20551

Experimental investigation of inertial waves inside a cylindrical liquid metal column

Vogt, T.; Räbiger, D.; Eckert, S.

The dynamics of free inertial waves inside a cylindrical volume was investigated experimentally in this study. The liquid metal GaInSn was chosen as fluid in order to enable a contactless stimulation of the flow inside the cylinder by means of a rotating magnetic field which generates a supercritical rotating motion of the liquid. The experiment demonstrates that inertial waves may be excited spontaneously by turbulent structures in the rotating flow. The ultrasound Doppler velocimetry was used to record the flow structure and to identify the inertial waves occurring in the setup.

Keywords: inertial waves; rotating flow

  • Lecture (Conference)
    9th International PAMIR Conference, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    9th International PAMIR Conference, 16.-20.06.2014, Riga, Latvia
    Proceedings of the 9th International PAMIR Conference

Publ.-Id: 20550

Regime transition in viscous and pseudo viscous systems: A comparative study

Rabha, S.; Schubert, M.; Hampel, U.

A comprehensive quantitative study on the effect of liquid viscosity (1 ≤ µL ≤ 1149 mPa-s) on the local flow phenomena of the gas phase in a small diameter bubble column is performed using ultrafast electron beam X-ray tomography. The internal dynamic flow structure and the bubble size distribution have proven a dual role of the liquid viscosity on the hydrodynamics. Further, effect of solid concentration (Cs = 0.05, 0.20) on the local flow behavior of the gas phase is studied for the pseudo (slurry) viscosities similar to the liquid viscosities of the gas-liquid systems. The effects of liquid and pseudo (slurry) viscosity on flow structure, bubble size distribution and gas phase distribution are compared. The bubble coalescence is significantly enhanced with the addition of particles as compared to the system without particles for apparently same viscosity. The superficial gas velocity at which transition occurs from homogeneous bubbly to slug flow regime is initiated by the addition of particles as compared to the particle free system for apparently same viscosity.

Keywords: Liquid viscosity; Pseudo (slurry) viscosity; Gas holdup; Bubble size distribution; Ultrafast electron beam X-ray tomography

Publ.-Id: 20548

Methods for extraction of velocity information from ultrafast X-ray tomography

Barthel, F.; Bieberle, M.; Hoppe, D.; Hampel, U.

The ultrafast electron beam X-ray tomography scanner “ROFEX” is widely used for investigations on multiphase flows, such as two-phase pipe flow, bubble columns, flows in structured packings, in monolith ceramics, in foams, in rod bundle geometries and others. The use of X-rays allows to discriminate phases, i.e. to distinguish between gas and liquid, gas and solid, liquid and solid and so on. It is, however, more difficult, to obtain velocity information from two-phase flows. Measuring velocities in the continuouse phase is only possible, if there is density contrast in it. In case of disperse flows the disperse phase self may act as a tracer. This gives rise to application of velocity measurement methods, which are based on correlation techniques. Adding liquid contrast agents to the continuous liquid phase is another choice. The paper introduces three methods of velocity measurements along with the associated data processing and gives some demonstration examples to discuss capabilities and limits of the methods.

Keywords: Ultrafast X-ray Tomography; velocity measurement; cross correlation; ROFEX

  • Lecture (Conference)
    5th International Workshop on Process Tomography (IWPT5), 16.-18.09.2014, Jeju, Korea
  • Contribution to proceedings
    5th International Workshop on Process Tomography (IWPT5), 16.-18.09.2014, Jeju, Korea
    Proceedings of IWPT5

Publ.-Id: 20547

Effective spin meron pairs in ferromagnetic multilayer elements

Wintz, S.; Raabe, J.; Fassbender, J.

Topological spin textures, such as vortices or skyrmions, are attracting significant attention because of both their intriguing fundamental properties and their promising applicability in memory devices or spin torque oscillators. A particular topological texture that was theoretically predicted is the two-dimensional hedgehog state, also known as a ’spin meron’. It had been unclear, however, whether this kind of highly divergent magnetization structure may exist in real systems. Only recently, evidence for the occurrence of meron-like pair states was reported for the case of trilayer elements consisting of two ferromagnetic layers and a non-ferromagnetic interlayer.On this background we present a direct proof for the existence of meron-like states in trilayer elements via direct magnetic imaging. We also show that in the presence of biquadratic interlayer exchange coupling, such meron-like pair states may even represent the magnetic ground state of the system. Interestingly, the highly divergent magnetization distribution induces an additional, three-dimensional torus vortex that in-turn causes a symmetry break for the allowed topological pair configurations.In the second part of our presentation we will address the dynamic properties of vertically coupled topological spin textures, where the focus will be on spin wave emission processes in such systems.

Keywords: vortex multilayer meron

  • Invited lecture (Conferences)
    59th Annual Magnetism & Magnetic Materials Conference, 03.-07.11.2014, Honolulu, USA

Publ.-Id: 20545

Cluster models for random particle aggregates-Morphological statistics and collision distance

Teichmann, J.; van den Boogaart, K. G.

In this paper, new models for particle-cluster and cluster-cluster-like aggregates are investigated trough detailed Monte Carlo simulation to model aggregation of micro-sized particles in turbulent flows.
These structures are built up by mechanisms which occur for instance in homogeneous isotropic turbulence flows with absence of Brownian motion and can be studied without a predefined motion field. The models are compared among each other in two and three dimensions with respect to several morphological properties, such as Feret diameter, radius of gyration, convexity, aspect ratio, fractal dimension and coordination number averaged over hundreds of thousands of aggregates of each size. An important part is devoted to approximation of these aggregates by spherical particles. For this, a particular radius, based on the collision distance to other particles is used, measured and approximated for both aggregate models. It can be useful for calculations related to agglomeration kernels in the framework of Smoluchowski’s coagulation equation.

Keywords: agglomeration; cluster-cluster aggregation; morphology; coagulation; micro-sized

Publ.-Id: 20544

Simultane Messung des Geschwindigkeitsfeldes und der Blasentrajektorien in einer ungeteilten Elektrolysezelle

Baczyzmalski, D.; Weier, T.; Kähler, C. J.; Cierpka, C.

Die Effizienz bei der Wasserstoffelektrolyse wird durch die Bedeckung der aktiven Elektrodenoberfläche durch die entstehenden Wasserstoff- und Sauerstoffblasen beeinträchtigt. Zur Effizienzsteigerung werden derzeit Strömungsbeeinflussungsmethoden untersucht, die zum beschleunigten Ablösen der Gasblasen von den Elektrodenoberflächen führen und so die Oberfläche schneller zur erneuten Reaktion freigeben. Zur Entwicklung solcher Strömungsbeeinflussungsmethoden müssen die hierdurch hervorgerufenen Strömungseffekte verstanden werden. Dies setzt die Kenntnis des Strömungsfeldes an der Elektrode und um die Gasblasen voraus. Im Sinne einer Machbarkeitsstudie zur gemeinsamen Messung von Gasblasenbewegung und umgebenden Strömungsfeld wurden hierzu im Rahmen der dargelegten Experimente in einer Wasserstoffelektrolysezelle simultane Messungen des Geschwindigkeitsfeldes und der Gasblasenbeladung durchgeführt. Zur Geschwindigkeitsmessung wurden fluoreszente Partikel mit einer sCMOS-Kamera beobachtet und deren Bewegung mittels PIV (Particle Image Velocimetry) ausgewertet. Die Gasblasen wurden hingegen durch Hintergrundbeleuchtung im Durchlichtverfahren mit einer weiteren sCMOS-Kamera aufgenommen und deren Bewegung mittels PTV (Particle Tracking Velocimetry) bestimmt. Zur Strömungsbeeinflussung wurden mit Hilfe eines Permanentmagneten Lorentzkräfte erzeugt. Abhängig von der vorherrschenden Stromstärke kann eine deutliche Beschleunigung der Strömung und Gasblasen durch die Lorentzkräfte festgestellt werden. Sowohl die Messung der Strömungsgeschwindigkeiten als auch der Blasenbewegung in unmittelbarer Wandnähe war aufgrund der dort vorherrschenden hohen Gasbeladung mit großen Unsicherheiten behaftet. Außerhalb dieses Bereiches konnten die Blasenbewegungen bestimmt und deren Einfluss auf das umgebende Strömungsfeld visualisiert werden. In Abhängigkeit des Blasendurchmessers führen die Blasen eine wellenförmige Aufwärtsbewegung parallel zur Elektrode aus, die mit dem elektrodennahen wellenförmigen Blasenteppich zusammenhängen oder auf Nachlaufinstabilitäten zurückzuführen sein könnte.

Keywords: two-phase flow; gas bubbles; water electrolysis

  • Open Access Logo Contribution to proceedings
    22. Fachtagung "Lasermethoden in der Strömungsmesstechnik", 09.-11.09.2014, Karlsruhe, Deutschland, 9783981676402, 51-1-51-8
  • Lecture (Conference)
    Fachtagung "Lasermethoden in der Strömungsmesstechnik", 09.-11.09.2014, Karlsruhe, Deutschland

Publ.-Id: 20543

URANS simulation of continuous casting mold flow: Assessment of revised turbulence models

Kratzsch, C.; Timmel, K.; Eckert, S.; Schwarze, R.

A time-resolved numerical model of the mini-LIMMCAST facility is investigated in the frame of RANS simulations. Three revised eddy viscosity turbulence models besides the often used Standard k-epsilon model for steady and unsteady RANS simulations are evaluated with the CFD software tool OpenFOAM. The data is compared with experimental results focusing the jet flow[1]. Different turbulence models lead to slight deviations from the experimental data in the case of steady state calculation with first order accuracy. For the time-averaged URANS results a crucial in uence by the discretization order is observed. In case of unsteady results a mix between first and higher order accuracy schemes is necessary for representative results. The use of the Standard k-epsilon model and the Realizable k-epsilon model can lead to unstable behavior in the case of URANS simulations. Conclusively, the study shows, that in case of qualitative temporal resolved informations and temporal averaged results an unsteady RANS simulation can keep up with a LES.

Keywords: unsteady mold flow; RANS; URANS; OpenFOAM; mini-LIMMCAST

Publ.-Id: 20542

Impedance analysis of secondary phases in a Co-implanted ZnO single crystal

Younas, M.; Zou, L. L.; Nadeem, M.; Ur-Rehman, N.; Su, S. C.; Wang, Z. L.; Anwand, W.; Wagner, A.; Hao, J. H.; Leung, C. W.; Lortz, R.; Ling, F. C. C.

Co ions with 100 keV energy with a fluence of 1 x 10^15 cm-2 are implanted into ZnO(0001) single crystals at 300 °C under vacuum. The resulting Co-implanted ZnO single crystals and the subsequent 750 °C and 900 °C annealed samples are analysed with respect to their structural, optical, electronic, magnetic and ac electrical properties. Photoluminescence and X-ray photoelectron spectroscopy results indicate the signatures of the Co^2+ state and its substitution at the tetrahedrally coordinated Zn-sites. X-ray diffraction and X-ray photoelectron spectroscopy identify the presence of the ZnCo2O4 and Co3O4 phases in the 900 °C annealed sample. By comparing the resistance response of the identified phases towards different magnetic environments, the impedance spectroscopy results successfully identify two magnetic phases (ZnCo2O4 and Co3O4) and a paramagnetic (CoZn) phase for the 750 °C and 900 °C annealed samples, implying the extrinsic nature of room temperature erromagnetism. The observed ferromagnetism in each sample is not of single origin, instead the mutual effects of the secondary phases embedded in the paramagnetic host matrix are in competition with each other.

Keywords: ZnO; Co implantation; secondary phases; impedance analysis

Related publications

Publ.-Id: 20541

Surface-near modifications of SrTiO3 local symmetry due to nitrogen implantation investigated by grazing incidence XANES

Stöcker, H.; Zschornak, M.; Richter, C.; Hanzig, J.; Hanzig, F.; Hinze, V.; Potzger, K.; Gemming, S.; Meyer, D. C.

Nitrogen ion implantation into strontium titanate single crystals causes a slight shift of the Ti-K edge position compared to pristine SrTiO3 and a strong increase of the second pre-edge peak in X-ray absorption near-edge spectroscopy (XANES) using graz- ing incidence geometry. Calculations by a finite difference method demonstrate that the strong increase of the second pre-edge fea- ture in the defect distorted phase can be attributed to a static displacement of the Ti atom relative to the surrounding oxygen octahedron.

Keywords: ferroic functional oxides; density functional theory; doping; strontium titanate

Related publications

Publ.-Id: 20540

Multiple point statistics understood in Matheronian principles

van den Boogaart, K. G.

In the last years the conditional simulation of geological structures with the multiple point statistics (MPS) approach has created new opportunities for a better description of the uncertainty in inference from spatial observations to knowledge and uncertainty about the geological reality. A new paradigm of geostatistics has been created based on simulation algorithms rather than on stochastic theory. The talk thus aims at discussing MPS in the light of the ideas behind Matheron’s geostatistic. Matheron simplified the problem to linear functions due to the lack of computer power. MPS now allows incorporating nonlinearities. The normal distribution assumption was a tool to teach uncertainty to the computer. MPS now allows new tools like the training image to take that role. In this perspective MPS can be seen as the extension of Matheron’s ideas to new computational possibilities. On the other hand some of the stochastic background of Matheron’s geostatistic has been lost in the fast course of development of MPS. The talk aims at rebuilding these basics. This stochastic view to MPS allows to discuss strengths and weaknesses of various MPS applications and to ask new questions potentially improving their future performance: Which of two simulation algorithms is better? Is the training image large enough to capture the uncertainty? Does the training image adequately describe the reality? Which criteria can be used to describe the performance of a conditional simulation algorithm for a specific purpose? How large should search neighborhoods be? Adding these stochastic viewpoints is a step towards not only having good algorithms, but also good tools to judge the appropriateness of an algorithm, to anticipate possible artefacts and to see MPS as the natural evolution of Materon’s geostatistic, rather than as an alternate approach.

Keywords: Multiple Point Statistics; Uncertainty Modelling

  • Invited lecture (Conferences)
    IAMG 2014, 16th conference of the international association for mathematical geosciences, 17.-20.10.2014, New Dehli, India

Publ.-Id: 20539

1-Arylimidazo[1,5a]chinoxalines as lead compounds for a PDE10A PET tracer

Wagner, S.; Scheunemann, M.; Fischer, S.; Egerland, U.; Ludwig, F.-A.; Hoefgen, N.; Steinbach, J.; Brust, P.

Aim: Phosphodiesterase 10A (PDE10A) plays a key role in cellular signaling by inactivation of the second messengers cAMP and cGMP. The abundant expression of PDE10A in the striatum makes this enzyme a prime target in the therapy of diseases related to this brain area, e.g. schizophrenia and movement disorders. Imaging by PET would allow to investigate the pathomechanism of such diseases and the relation to PDE10A and its expression. Therefore our aim is to develop a PET tracer for PDE10A. Recently 1-arylimidazo[1,5a]quinoxalines have been reported as very potent and selective PDE10A inhibitors.[1] This structural motif was selected as lead structure for the development of a new PET tracer.
Methods: To enable an easy incorporation of F-18 fluoride the 2-fluoropyridine moiety was chosen as fluorine containing building block. For synthesis of the reference compounds different 2-fluoropyridine boronic acids were linked to the tricyclic key intermediate by a palladium catalyzed Suzuki coupling. Characterization of these compounds was done by NMR, HRMS and HPLC. The inhibitory potency of these new fluorinated derivatives was tested in an enzyme assay towards PDE10A and further PDEs. For one candidate which was selected to be labeled with F-18 a precursor was synthesized likewise by a Suzuki coupling with 2-bromopyridine boronic acid. Different reaction conditions were tested for the one step F-18 fluoro-for-bromo substitution.
Results: A small library of reference compounds was synthesized. All compounds possess a high affinity for PDE10A (IC50 < 10 nM) with good to moderate selectivity versus other PDEs. The most selective inhibitor (IC50 = 2.91 nM) was chosen to be further developed as PET tracer. The logD7.4 value of the inhibitor (2.41 ± 0.33) was estimated by HPLC. When the precursor was reacted with F-18 fluoride in DMSO at 140°C under standard conditions (K2CO3, K222) radiolabeling efficiency of 30-50% was obtained within 10 min. At longer reaction times the labeling efficiencies decreased. A purification process including semi-preparative HPLC was established to isolate the radiotracer.
Conclusion: A new fluorinated, potent and selective PDE10A inhibitor was identified. The bromo precursor proved to be a suitable precursor for the F-18 labeling. Good conditions for the nucleophilic aromatic bromo-to-fluoro exchange were found. Further investigations of the tracer including small animal PET studies are currently underway.
Reference: [1] Malamas et. al. J. Med. Chem. 2011,54, 7621-7638.

  • Lecture (Conference)
    EANM'14 - Annual Congress of the European Association of Nuclear Medicine, 17.-22.10.2014, Göteborg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014)2, 197

Publ.-Id: 20538

Development, synthesis and F-18 labelling of a fluoroalkylated triazine derivative for PET imaging of phosphodiesterase 2A

Schröder, S.; Wenzel, B.; Kranz, M.; Egerland, U.; Teodoro, R.; Deuther-Conrad, W.; Fischer, S.; Höfgen, N.; Steinbach, J.; Brust, P.


Phosphodiesterases (PDEs) are a class of enzymes expressed in mammalian cells using the cyclic nucleotides cAMP and/or cGMP as secondary messengers. Inhibitors of PDEs prevent the breakdown of these molecules and thus affect various physiological processes. The PDE2A is highly and specifically expressed in the brain and in certain tumours and is involved in the pathophysiology of related diseases (e.g. neurodegenerative and highly proliferative processes). With this project we aim to develop a radiolabelled inhibitor of PDE2A for PET imaging of this new target.
Materials and Methods:
Starting from a triazine key compound [1] a new fluoropropyl derivative (9-(2-fluoro-5-(3-fluoropropoxy)phenyl)-2-methoxy-7-methylimidazo[5,1-c]pyrido[2,3-e][1,2,4]triazine) as reference structure for in vitro studies and the corresponding tosylate precursor for a one-step radiosynthesis strategy were designed and synthesised. The nucleophilic F-18 labelling was performed in acetonitrile at 80°C for 15 minutes. After isolation by semi-preparative HPLC the radioligand was purified using a Sep-Pak® C18 Plus light cartridge and formulated in 0.9% NaCl. The final product was analysed by radio-TLC and radio-HPLC. In vitro autoradiography was accomplished by incubating sagittal sections of rat brain with 1 MBq of the radioligand for
60 minutes at ambient temperature. Blocking studies were performed by addition of the triazine compound [1] in different concentrations.
The triazine key compound [1] (IC50 hPDE2A: 4.1 nM), the new fluoropropyl derivative
(IC50 hPDE2A: 11.4 nM) and the tosylate precursor were obtained with overall yields of 70 - 80%. The radioligand was synthesised with a labelling yield of 75.4 ± 4.9% (n = 5), a radiochemical yield of 57.2 ± 0.4% (end of synthesis; n = 3), a specific activity of 60.4 ± 11.6 GBq/µmol (n = 3) and a radiochemical purity of ≥ 99.5%. In first autoradiographic experiments a high and specific accumulation of the radioligand in cortex and striatum and a low uptake in cerebellum was observed, which is consistent with the distribution pattern of PDE2A protein in the brain.
A new F-18 labelled and highly affine PDE2A inhibitor was successfully developed and synthesised. Further characterisation of this new radioligand is currently performed by small animal PET/MR, metabolism studies and autoradiography.
[1] Patent WO2010/054253 A1

  • Lecture (Conference)
    EANM'14 - Annual Congress of the European Association of Nuclear Medicine, 18.-22.10.2014, Göteborg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014)2, 197

Publ.-Id: 20537

Development of a suitable PET ligand for the vesicular acetylcholine transporter (vAChT) - an extensive qualitative structure affinity relationship study

Barthel, C.; Wenzel, B.; Sorger, D.; Schweiger, S.; Deuther-Conrad, W.; Jäckel, P.; Roghani, A.; Schüürmann, G.; Steinbach, J.; Sabri, O.; Brust, P.

Aim: The vesicular acetylcholine transporter (vAChT) is an interesting target for in vivo imaging of cholinergic deficits. Vesamicol (2-(4-phenylpiperidin-1-yl)cyclohexanol) acts as a highly potent inhibitor for this transporter and thus represents the chemical lead for the development of vAChT radioligands. Due to its comparably high affinity towards σ1/σ2 receptors and hence its lack of selectivity it is not suitable for in vivo imaging of cholinergic neurons. The aim of our studies was to develop a selective ligand by varying the vesamicol skeleton in a systematic manner and determining the binding profile of the resulting derivatives. These in vitro data were correlated with the various chemical structures leading to an extensive qualitative structure affinity relationship study.
Materials and methods: Based on suitable epoxide precursors, the derivatives were synthesised by nucleophilic ring opening using structurally varied amines. The regioisomers resulting from asymmetrical epoxides were separated by semi-preparative HPLC and all analogues were characterised using MS, NMR, and HPLC. To obtain the binding profile of all compounds, competitive binding assays were performed in vitro with rvAChT-cDNA stably transfected PC12 cells, rat cortex (σ1), and rat liver (σ2) using (-)-[H-3]vesamicol, (+)-[H-3]pentazocine and [H-3]DTG as radioligands for vAChT, σ1, and σ2 receptor, respectively.
Results: 57 new analogues and seven reference compounds from literature were synthesised and characterised regarding to their in vitro binding profile. Based on different epoxide precursors, the lead structure of vesamicol was modified at the cyclohexyl ring A. Variations on the piperidinyl ring B and phenyl ring C, respectively, were achieved using several amines. In vitro binding studies showed vAChT affinities in the range of low nanomolar to micromolar Ki values. As expected, we found a strong variability regarding affinity and selectivity within each class of derivatives (modified in ring B and C). But surprisingly, also similar analogues from different classes (modified in ring A) varied substantially in their affinities. The resulting selectivity factors (Ki(σ1)/Ki(vAChT) and Ki(σ2)/Ki(vAChT)) ranged from 0.003 to 72.7 indicating none to moderate selectivities towards vAChT.
Conclusion: The results show a great variability of the in vitro binding profile of ligands based on the vesamicol lead structure. Even small structural changes led to unexpected changes in affinities and selectivities towards vAChT and we obtained evidence that an increased vAChT affinity correlated with an increase of σ1/σ2 receptor affinity. Based on our results we conclude that future development of a selective vAChT radioligand might be based on another lead compound.

  • Poster
    EANM'14 - Annual Congress of the European Association of Nuclear Medicine, 18.-22.10.2014, Göteborg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014)2, 452

Publ.-Id: 20536

The surface speciation of the ternary sorption system U(VI)/phosphate/silica

Foerstendorf, H.; Steudtner, R.; Comarmond, M. J.; Heim, K.; Müller, K.

The impact of inorganic ligands on the sorption behavior of actinide ions is commonly known. However, detailed knowledge of the molecular events occurring during the sorption processes is often lacking. In particular, the presence of inorganic anions forming actinide complexes of low solubility hampers the application of many spectroscopic approaches due to the formation of binary complexes precipitating from the aqueous solutions.
This study sustains our preliminary results on the ternary sorption system U(VI)/phosphate/silica introduced at ATAS 2012 [1]. The advanced results obtained from a combined approach of in situ vibrational and luminescence spectroscopy provide a more detailed insight into the surface speciation of this ternary sorption system.
From in situ vibrational spectroscopic sorption experiments of the binary system U(VI)/silica, infrared data exhibit the formation of a uranyl inner sphere complex at the silica surface, whereas from the ternary sorption system, spectra showing great homologies to spectra of solid U(VI)phosphate phases are obtained. The results obtained from the in situ IR experiments strongly suggest the formation of a solid U(VI)phosphate as a surface precipitate on the silica phase.
Laser fluorescence spectroscopy reveals the presence of U(VI) phosphate species in aqueous solution most probably solid or colloidal (UO2)(PO4)2∙4H2O. For the U(VI) sorption samples, two different surface species were derived from luminescence spectra irrespective of the absence or presence of phosphate [2]. However, the spectral differences became more apparent after prolonged equilibration of the solid phase with a stable U(VI) phosphate solution suggesting chemical rearrangements of the sorbed U(VI) ion towards a ternary surface species.
In summary, IR and luminescence data suggest the formation of a ternary surface species where the U(VI) acts as a bridging ion to the SiO2 surface with subsequent formation of the ternary surface species SiO2–U(VI)-phosphate. This ternary species most likely constitutes a precursor of the formation of a surface precipitate showing spectral properties similar to U(VI) phosphate minerals.

  • Poster
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden, Deutschland

Publ.-Id: 20535

Evaluation and automatic correction of metal-implant-induced artifacts in MR-based attenuation correction in whole-body PET/MR imaging

Schramm, G.; Maus, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.

The aim of this paper is to describe a new automatic method for compensation of metal-implant-induced segmentation errors in MR-based attenuation maps (MRMaps) and to evaluate the quantitative influence of those artifacts on the reconstructed PET activity concentration. The developed method uses a PET-based delineation of the patient contour to compensate metal-implant-caused signal voids in the MR scan that is segmented for PET attenuation correction. PET emission data of 13 patients with metal implants examined in a Philips Ingenuity PET/MR were reconstructed with the vendor-provided method for attenuation correction (MRMap(orig), PETorig) and additionally with a method for attenuation correction (MRMap(cor), PETcor) developed by our group. MRMaps produced by both methods were visually inspected for segmentation errors. The segmentation errors in MRMap(orig) were classified into four classes (L1 and L2 artifacts inside the lung and B1 and B2 artifacts inside the remaining body depending on the assigned attenuation coefficients). The average relative SUV differences (epsilon(av)(rel)) between PETorig and PETcor of all regions showing wrong attenuation coefficients in MRMap(orig) were calculated. Additionally, relative SUVmean differences (epsilon(rel)) of tracer accumulations in hot focal structures inside or in the vicinity of these regions were evaluated. MRMap(orig) showed erroneous attenuation coefficients inside the regions affected by metal artifacts and inside the patients' lung in all 13 cases. In MRMap(cor), all regions with metal artifacts, except for the sternum, were filled with the soft-tissue attenuation coefficient and the lung was correctly segmented in all patients. MRMap(cor) only showed small residual segmentation errors in eight patients. (epsilon(av)(rel)) (mean +/- standard deviation) were: (-56 +/- 3)% for B1, (-43 +/- 4)% for B2, (21+/- 18)% for L1, (120 +/- 47)% for L2 regions. epsilon(rel) (mean +/-standard deviation) of hot focal structures were: (-52 +/- 12)% in B1, (-45 +/- 13)% in B2, (19 +/- 19)% in L1, (51 +/- 31)% in L2 regions.
Consequently, metal-implant-induced artifacts severely disturb MR-based attenuation correction and SUV quantification in PET/MR. The developed algorithm is able to compensate for these artifacts and improves SUV quantification accuracy distinctly.

Publ.-Id: 20534

Modellierung und numerische Berechnung monodisperser Blasenströmungen: Ein Vergleich zweier CFD Programme

Kriebitzsch, S.; Rzehak, R.; Lucas, D.

Die numerische Simulation von der Mehrphasenströmungen in technischen Apparaten kann einen wertvollen Beitrag zum Design und zur Optimierung der Prozesse liefern, da man detaillierte Informationen über lokale Strömungsgrößen erhält. Üblicherweise sind die Apparateabmessungen deutlich größer als die charakteristische Größe der dispersen Phase, weshalb das sogenannte Zwei-Fluid-Modell verwendet wird. In diesem werden die verschiedenen Phasen als sich gegenseitig durchdringende Kontinua modelliert. Hierbei muss Wechselwirkung der Phasen durch geeignete Schließungsansätze beschrieben werden und üblicherweise stehen viele unterschiedliche Ansätze in kommerziellen CFD Programmen zu Auswahl. Ein für die Berechnung adiabater, monodisperser Blasenströmungen geeigneter Satz von Schließungsmodellen wurde in einer früheren Studie (Rzehak & Krepper, 2013) identifiziert und in der kommerziellen Software Ansys CFX verwendet.
Diese physikalischen Modelle wurden nun in das frei verfügbare Programmpaket OpenFOAM übertragen und verschiedene aufwärtsgerichtete Rohrströmungen von Luft-Wasser Gemischen berechnet und mit Experimenten verglichen. Insgesamt zeigen die Ergebnisse der Berechnungen beider Programmpakete eine vergleichbare, zufriedenstellende Übereinstimmung mit den Experimenten. Abweichungen findet man insbesondere in Wandnähe und in den turbulenten Größen.

Keywords: multiphase flow; CFD; bubbly flow

  • Poster
    ProcessNet-Jahrestagung und 31. DECHEMA-Jahrestagung der Biotechnologen 2014 - GENERALTHEMA: ProcessNet 21plus - Zukunft gestalten, 30.09.-02.10.2014, Aachen, Deutschland

Publ.-Id: 20533

Combining Luminescence Spectroscopy, Parallel Factor Analysis and Quantum Chemistry to Reveal Metal Speciation - a Case Study of Uranyl (VI) Hydrolysis

Drobot, B.; Steudtner, R.; Raff, J.; Geipel, G.; Brendler, V.; Tsushima, S.

This study of aqueous metal speciation is an advanced combination of theoretical and experimental methods. 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 M) 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 region is extreme ligand sensitive and not unspecific. Combining findings from PARAFAC and DFT the UO22+ cation (aquo complex 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified.

Keywords: U(VI); uranyl hydrolysis; TRLFS; continuous wave spectroscopy; site selective excitation; TD-DFT; PARAFAC

Publ.-Id: 20532

Superconducting RF Guns: Emerging Technology for Future Accelerators

Teichert, J.

This talk should give an overview of Superconducting photo injectors (SRF guns) and focus on the present status of SRF gun development, the technical requirements and the critical issues like cavity design, photocathode integration, and emittance compensation methods.

Keywords: photo injector; superconducting RF; electron source; SRF gun

Related publications

  • Invited lecture (Conferences)
    IPAC'14 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany
  • Open Access Logo Contribution to proceedings
    IPAC'14 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC'14: Jacow

Publ.-Id: 20531

TecLines: A MATLAB-Based Toolbox for Tectonic Lineament Analysis from Satellite Images and DEMs, Part 1: Line Segment Detection and Extraction

Rahnama, M.; Gloaguen, R.

Geological structures, such as faults and fractures, appear as image discontinuities or lineaments in remote sensing data. Geologic lineament mapping is a very important issue in geo-engineering, especially for construction site selection, seismic, and risk assessment, mineral exploration and hydrogeological research. Classical methods of lineaments extraction are based on semi-automated (or visual) interpretation of optical data and digital elevation models. We developed a freely available Matlab based toolbox TecLines (Tectonic Lineament Analysis) for locating and quantifying lineament patterns using satellite data and digital elevation models. TecLines consists of a set of functions including frequency filtering, spatial filtering, tensor voting, Hough transformation, and polynomial fitting. Due to differences in the mathematical background of the edge detection and edge linking procedure as well as the breadth of the methods, we introduce the approach in two-parts. In this first study, we present the steps that lead to edge detection. We introduce the data pre-processing using selected filters in spatial and frequency domains. We then describe the application of the tensor-voting framework to improve position and length accuracies of the detected lineaments. We demonstrate the robustness of the approach in a complex area in the northeast of Afghanistan using a panchromatic QUICKBIRD-2 image with 1-meter resolution. Finally, we compare the results of TecLines with manual lineament extraction, and other lineament extraction algorithms, as well as a published fault map of the study area.

Keywords: TecLines; Matlab; tectonic; lineament; edge detection; tensor voting

Publ.-Id: 20530

How Forward Integration Along the Rare Earth Value Chain Threatens the Global Economy

van den Boogaart, K. G.; Klossek, P.; Klossek, A.

At the moment the first steps of the REE value chain are already dominated by a monopolistic power. Current developments, however, show a tendency of a monopolistic takeover of the subsequent steps of the value chain with finally having control over the whole chain. Such tendency, in our view, represents a serious threat to the key industries in the ROW and, therefore, to the global economy.

The takeover of subsequent steps is induced by the price differences between domestic prices and the world market price, which is dominated by the monopolist’s FOB (free on board) price, and executed by so created market forces. The rebuilding of the first steps in ROW (rest of world) like REE mining, processing and soon separation is demotivated by the de facto monopoly on the subsequent steps controlling the products markets and, possibly, by a well chosen price policy. The strategic dominance of the monopolist creates enormous price risks scaring off independent investment into the ROW value chain. Likewise, it generates a default risk scaring off strategic investors. Investment in ROW enterprises and JVs (joint ventures) are other important tools of the monopolist to gain control over the value chain with respect to technological know-how, business relations, and production capacity. This takeover seems to be a part of a well-planned long-term strategy of a major state actor and requires cooperative actions of industry and state in ROW in order to stop this dangerous trend.

  • Invited lecture (Conferences)
    Critical Minerals 2014, Rare earths and beyond, mines, markets, and manufacturing, 03.-05.08.2014, Denver, USA

Publ.-Id: 20528

Surface modifications of BaF2 and CaF2 single crystals by slow highly charged ions

El-Said, A. S.; Heller, R.; Wilhelm, R.; Facsko, S.; Aumayr, F.

Ion-irradiation of solid surfaces is considered as one of the promising and powerful techniques for material nanostructuring. Recently, slow highly charged ions (HCI) have shown their potential in creating surface nanostructures in various solids. Here, we focus on the surface modifications of BaF2 and CaF2 single crystals by HCI. Despite the fact that both materials belong to alkaline-earth fluorides with the same crystalline structure, they exhibit different sensitivity for HCI-induced nanostructure. We discuss similarities and differences for the creation of HCI-induced nanohillocks and etch pits in both materials and their dependence on potential and kinetic energy deposition. Furthermore, we compare the results with modifications induced by swift heavy ions (SHI), in order to reach a better understanding of the mechanisms responsible for the creation of nanostructures in ionic fluoride single crystals.

Keywords: Highly charged ions; Nanostructures; Ion–surface interaction; BaF2; CaF2

Related publications

Publ.-Id: 20527

Investigation of H+ implanted Fe-Al alloys

Lukac, F.; Cizek, J.; Prochazka, I.; Jiraskova, Y.; Janickovic, D.; Simeg Veternikova, J.; Anwand, W.; Butterling, M.

In the present work hydrogen interaction with vacancies was investigated in Fe-Al alloys with various concentration of vacancies. The Fe-Al samples were implanted with low energy H+ ions (100 keV). This procedure introduced high hydrogen concentration into relatively narrow sub-surface region in the depth of ~500 nm. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of hydrogen interaction with vacancies in the sub-surface region. This study revealed formation of vacancy hydrogen complexes in the sub-surface region. Thermal stability of vacancy-hydrogen complexes was investigated as well.

Keywords: FeAl alloys; hydrogen implantation; vacancies; positron annhilation

Related publications

Publ.-Id: 20526

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