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28071 Publications
Ion-Beam-Induced Atomic Mixing in Ge, Si, and SiGe, Studied by Means of Isotope Multilayer Structures
Bracht, H.; Radek, M.; Posselt, M.; Liedke, B.; Schmidt, B.; Voelskow, M.; Bischoff, L.; Böttger, S.; Prucnal, S.; Hansen, J. L.; Larsen, A. N.; Bougeard, D.
Corresponding author: Bracht, H. Institute of Materials Physics, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
Abstract: Crystalline and preamorphized isotope multilayers are utilized to investigate the dependence of ion beam mixing in silicon (Si), germanium (Ge), and silicon germanium (SiGe) on the atomic structure of the sample, temperature, ion flux, and electrical doping by the implanted ions. The magnitude of mixing is determined by secondary ion mass spectrometry. Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy, and transmission electron microscopy provide information about the structural state after ion irradiation. Different temperature regimes with characteristic mixing properties are identified. A disparity in atomic mixing of Si and Ge becomes evident while SiGe shows an intermediate behavior. Overall, atomic mixing increases with temperature, and it is stronger in the amorphous than in the crystalline state. Ion-beam-induced mixing in Ge shows no dependence on doping by the implanted ions. In contrast, a doping effect is found in Si at higher temperature. Molecular dynamics simulations clearly show that ion beam mixing in Ge is mainly determined by the thermal spike mechanism. In the case of Si thermal spike, mixing prevails at low temperature whereas ion beam-induced enhanced self-diffusion dominates the atomic mixing at high temperature. The latter process is attributed to highly mobile Si di-interstitials formed under irradiation and during damage annealing.
Keywords: silicon; germanium; ion beam; atomic mixing; thermal spike; radiation enhanced diffusion; amorphization; recrystallization; molecular dynamics

Registration No. 25852 - Permalink


Modeling tumor control probability for spatially inhomogeneous risk of failure based on clinical outcome data
Lühr, A.; Löck, S.; Jakobi, A.; Stützer, K.; Bandurska-Luque, A.; Vogelius, I. R.; Enghardt, W.; Baumann, M.; Krause, M.
Corresponding author: Lühr, A. DKTK, OncoRay, DKFZ, HZDR
Abstract: Purpose

Objectives of this work are (1) to derive a general clinically relevant approach to model tumor control probability (TCP) for spatially variable risk of failure and (2) to demonstrate its applicability by estimating TCP for patients planned for photon and proton irradiation.
Methods and Materials

The approach divides the target volume into sub-volumes according to retrospectively observed spatial failure patterns. The product of all sub-volume TCPi values reproduces the observed TCP for the total tumor. The derived formalism provides for each target sub-volume i the tumor control dose (D50,i) and slope (γ50,i) parameters at 50% TCPi. For a simultaneous integrated boost (SIB) prescription for 45 advanced head and neck cancer patients, TCP values for photon and proton irradiation were calculated and compared. The target volume was divided into gross tumor volume (GTV), surrounding clinical target volume (CTV), and elective CTV (CTVE). The risk of a local failure in each of these sub-volumes was taken from the literature.
Results

Convenient expressions for D50,i and γ50,i were provided for the Poisson and the logistic model. Comparable TCP estimates were obtained for photon and proton plans of the 45 patients using the sub-volume model, despite notably higher dose levels (on average +4.9%) in the low-risk CTVE for photon irradiation. In contrast, assuming a homogeneous dose response in the entire target volume resulted in TCP estimates contradicting clinical experience (the highest failure rate in the low-risk CTVE) and differing substantially between photon and proton irradiation.
Conclusions

The presented method is of practical value for three reasons: It (a) is based on empirical clinical outcome data; (b) can be applied to non-uniform dose prescriptions as well as different tumor entities and dose-response models; and (c) is provided in a convenient compact form. The approach may be utilized to target spatial patterns of local failures observed in patient cohorts by prescribing different doses to different target regions. Its predictive power depends on the uncertainty of the employed established TCP parameters D50 and γ50 and to a smaller extent on that of the clinically observed pattern of failure risk.
Keywords: Radiotherapy, Dose–response modeling, TCP, Inhomogeneous dose, Head and neck cancer, Proton therapy

Registration No. 25851 - Permalink


Superconducting Ferromagnetic Nanodiamond
Zhang, G.; Samuely, T.; Xu, Z.; Jochum, J. K.; Volodin, A.; Zhou, S.; May, P. W.; Onufriienko, O.; Kačmarčík, J.; Steele, J. A.; Li, J.; Vanacken, J.; Vacík, J.; Szabó, P.; Yuan, H.; Roeffaers, M. B. J.; Cerbu, D.; Samuely, P.; Hofkens, J.; Moshchalkov, V. V.
Corresponding author: Zhang, G. INPAC-Insititute for Nanoscale Physics and Chemistry, KU Leuven, Celestijnenlaan 200D, Heverlee, Belgium
Abstract: Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the electronic entanglement between superconducting and ferromagnetic states in hydrogenated boron-doped nanodiamond films, which have a superconducting transition temperature Tc ∼ 3 K and a Curie temperature TCurie > 400 K. In spite of the high TCurie, our nanodiamond films demonstrate a decrease in the temperature dependence of magnetization below 100 K, in correspondence to an increase in the temperature dependence of resistivity. These anomalous magnetic and electrical transport properties reveal the presence of an intriguing precursor phase, in which spin fluctuations intervene as a result of the interplay between the two antagonistic states. Furthermore, the observations of high-temperature ferromagnetism, giant positive magnetoresistance, and anomalous Hall effect bring attention to the potential applications of our superconducting ferromagnetic nanodiamond films in magnetoelectronics, spintronics, and magnetic field sensing.
Keywords: anomalous Hall effect; giant positive magnetoresistance; nanodiamond; spin fluctuations; superconductivity and ferromagnetism

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  • Secondary publication expected from 16.05.2018

Registration No. 25850 - Permalink


Structural and optical properties of Gd implanted GaN with various crystallographic orientations
Macková, A.; Malinský, P.; Jagerová, A.; Sofer, Z.; Klímová, K.; Sedmidubský, D.; Pristovsek, M.; Mikulics, M.; Lorinčík, J.; Böttger, R.; Akhmadaliev, S.
Corresponding author: Macková, A. Nuclear Physics Institute of the Academy of Sciences of the Czech Republic, v. v. i., 250 68 Rez, Czech Republic
Abstract: Structure, morphology, and optical properties of Gd implanted GaN epitaxial layers were studied for (0001), (11 − 20), and (11 − 22) orientations. The GaN layers grown by MOVPE on sapphire were subsequently implanted with 200 keV Gd+ ions using fluences of 5 × 1015 and 5 × 1016 cm− 2. Dopant depth profiling was accomplished by Rutherford Back-Scattering spectrometry (RBS). Structural and optical changes during subsequent annealing were characterized by RBS, Raman spectroscopy, and photoluminescence measurements. Post-implantation annealing induced a structural reorganization of GaN structure in the buried layer depending on the introduced disorder level, i.e. depending on the implantation fluence and on crystallographic orientation. The defect density depth distribution was evaluated by RBS. The surface morphology and optical properties depend on particular crystallographic orientation.
Keywords: GaN implantation; RBS channelling; Optical properties of Gd implanted GaN

Registration No. 25849 - Permalink


Theranostic mercury 197(m)Hg: comparing different Hg/Au separation methods
Wang, C.; Červenák, J.; Walther, M.; Lebeda, O.; Preusche, S.; Pietzsch, H. J.; Steinbach, J.
Abstract: Objectives: The access to no-carrier-added 197(m)Hg for imaging and therapy research based on proton or deuteron irradiation of gold was recently reported1,2. The development of a rapid, reliable method for Hg/Au separation represents an important prerequisite for increasing yields. Ideally would be, a reversible interaction at least of one of the two metal ions, allowing for the product elution into a small volume. Besides the liquid-liquid extraction with methyl isobutyl keton (MIBK)1, the solid phase extraction using LN resin (LaNthanides) containing di(2-ethylhexyl)orthophosphoric acid as extractant was examined for this application2.
Methods: The gold target was irradiated for 120 minutes with a 25 µA beam current of 10 MeV protons resulting in 200 MBq of 197(m)Hg or with 15.6 MeV deuteron beam at 7.8 µA beam current for 180 min resulting in ca 800 MBq of of 197(m)Hg (EOB). The irradiated gold foil was dissolved after 1 h in 700 µl of aqua regia (freshly prepared 1 h before EOB from 525 µl 30% HCl + 175 µl 65% HNO3) at room temperature. The column preparation was carried out directly before use by loading 3.6 g LN resin slurried with 10 ml of 6M HCl onto the column and rinsing with additional 30 ml of 6M HCl. After dilution of the 700 µl product solution with 300 µl 6M HCl, this mixture was loaded onto the column and eluted with 6M HCl in 1 ml aliquots.
Results: Comparing with the previously described liquid-liquid extraction1, the solid phase extraction using the LN resin showed shorter performance time. After loading the mixture of chloroauric acid and n.c.a. mercury chloride, the colored gold solution was observed to rapidly distribute in the upper part of the column and then slowly proceeds down during the stepwise elution with 6M HCl. After the addition of 5–6 ml of HCl, the yellow chloroauric acid extended roughly two thirds down the column and almost stopped to move, while over 90% of n.c.a. radiomercury chloride (higher than 60-80% extracted with 4×500 µl MIBK) eluted in the following 2 ml of HCl. The separated 197(m)Hg has excellent radionuclidic purity with no detectable traces of 198Au. It is massively produced in the deuteron activation of gold and acts as a very sensitive tracer of the separation process efficiency.
Conclusions: In contrast to the liquid-liquid extraction, LN resin based method is significantly more efficient and provides product of high radionuclidic purity. Another major advantages compared to the liquid-liquid extraction are obviously 1) better handling and easy automation that shorten the separation time and minimize radiation burden, 2) negligible product losses 3) open possibility to collect and recycle the target material.
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland

Registration No. 25842 - Permalink


Strategies for the radiosynthesis of potent fluorinated Nε-acryloyllysines as potential PET tracers for transglutaminase 2
Wodtke, R.; Jäckel, E.; Bauer, D.; Lohse, M.; Wong, A.; Pufe, J.; Ruiz-Gómez, G.; Hauser, C.; Hauser, S.; Steinbach, J.; Teresa Pisabarro, M. T.; Pietsch, M.; Pietzsch, J.; Löser, R.
Corresponding author: Wodtke, Robert
Abstract: Objectives: Various kinds of tumour entities are characterised by increased activity of transglutaminase 2 (TGase 2), which contributes to enhanced invasive potential of the tumour cells and their resistance to chemo- and radiotherapy. Therefore, this enzyme represents an interesting target for the development of PET tracers for functional imaging of tumours. Among the TGase 2 inhibitors described in the literature, Nε-acryloyllysine 1 [1] seems to be most suitable for radiotracer development as this compound exhibits both strong inhibitory potential and selectivity towards human TGase 2. Extensive structure-activity relationship studies by our group revealed some potent fluorinated analogues of 1, of which compounds 2 and 4 were identified as potential candidates for PET tracer development due to their great inhibitory potencies and promising pharmacokinetic properties.
Methods: Reference compounds 2 and 4 as well as the precursor 3 were synthesised in a modular synthetic route. For the radiosynthesis of [18F]2, thienyl and anisyl iodonium salts were envisaged as precursors for prosthetic labelling groups, which were synthesised starting from iodophenylacetates. The fluorination reactions using [18F]F- were performed under various conditions to maximise the radiochemical yield (RCY).
Results: Although a wide range of conditions for radiolabelling of the phenylacetic acid-derived iodonium salts were applied, no incorporation of [18F]F- could be observed. To identify possible reasons for this, the two other regioisomeric phenylacetic acid-derived iodonium salts were synthesised and subjected to labelling with [18F]F-. As a result of these efforts, the CH acidity of the benzylic methylene group was supposed to have a detrimental effect on the labelling reaction. In contrast to this, labelling of precursor 3 was successful with RCYs (non-isolated crude product) of up to 15%. Due to the difficult separation of 3 and [18F]4, the nitro group was reduced to the respective amino group by tin(II) chloride prior to purification by RP-HPLC.
Conclusions: After identifying fluorinated Nε-acryloyllysines as potential PET tracer candidates, strategies for their radiosynthesis were developed. While attempts for the incorporation of fluorine-18 at the non-activated phenylacetic acid moiety revealed inherent structural limitations, labelling at the 2-nitropyridine-derived precursor led to a promising PET tracer candidate.
References:
[1] J. Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024-1028

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  • Secondary publication expected from 12.05.2018

Registration No. 25836 - Permalink


Improving Stability of Cathepsin B Endopeptidase Substrates as Potential Cleavage Sites in Activatable Cell-Penetrating Peptides
Kuhne, K.; Behring, L.; Birgit Belter, B.; Wodtke, R.; Steinbach, J.; Pietzsch, J.; Löser, R.
Corresponding author: Löser, Reik
Abstract: Objectives: The cysteine protease cathepsin B, whose expression in tumors correlates with increased metastasis, therapy resistance, and a generally poor prognosis, represents an excellent target for molecular imaging using radiotracers [1]. We aim to develop a cathepsin B specific, substrate-based radiotracer derived from poly-d-arginine-based activatable cell penetrating peptides [2]. With in vivo application of peptides being often limited by short biological half-life, stabilization against proteolytic degradation is a key aspect in the development of this agent.
Methods: Octapeptide substrates containing the FRET pair aminobenzoyl/dinitrophenyl (Abz/Dnp) were synthesized by solid phase peptide synthesis in high purities and good yields, using non-proteinogenic and N-methylated amino acids (AA) for stabilization. All substrates were evaluated for cleavage efficiency by cathepsin B in orientation to [3]. In vitro stability studies were performed in human serum, with analysis by UPLC-ESI-MS, using the UV absorbance of Dnp (λ = 365 nm) for quantification and subsequent ESI-MS analysis for identification of degradation products.
Results: Rapid degradation has been observed for the endopeptidase substrate Abz-Gly-Ile-Val-Arg-Ala-Lys(Dnp)-Gly-Ser-NH2 in the in vitro serum stability assay (T1/2 = 3.7 min), which was due to cleavage at the P1-P1’ cleavage site (Arg-Ala) as indicated by LC-MS analysis. In a first step, arginine was substituted by citrulline to decrease susceptibility to trypsin-like serum proteases, which increased serum stability (T1/2 = 8.9 min). The non-proteinogenic AA homoarginine, homocitrulline and O-carboxybenzylserine are being tested as further potential substitutes for arginine. Secondary cleavage sites, identified at P4-P3 (Gly-Ile) and P2’-P3’ (Lys-Gly), were suppressed by insertion of Nα-methyl-isoleucine and Nα-methyl-glycine.
Conclusions: After the optimization of the endopeptidase substrate with regards to cathepsin B-specific cleavage, substrate stabilization against other proteases is a crucial step to a peptide-based radiotracer. We have demonstrated the potential for stabilization by introduction of citrulline, with further stabilization by insertion of N-methylated and non-proteinogenic amino acids ongoing, which will pave the way to the envisaged substrate-based imaging probes.
References:
1. Löser & Pietzsch, Front. Chem. 2015, 3, 37
2. Jiang et al., PNAS 2004, 101, 17867
3. Cotrin et al., Anal. Biochem. 2004, 335, 244

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  • Secondary publication expected from 12.05.2018

Registration No. 25835 - Permalink


Thermal convection of liquid metal in the titanium reduction reactor
Teimurazov, A.; Frick, P.; Stefani, F.
Corresponding author: Teimurazov, Andrei ICMM Perm, Russia
Abstract: The structure of the convective flow of molten magnesium in a metallothermic titanium reduction reactor has been studied numerically in a three-dimensional non-stationary formulation with conjugated heat transfer between liquid magnesium and solids (steel walls of the cavity and titanium block). A nonuniform computational mesh with a total of 3.7 million grid points was used. The Large Eddy Simulation technique was applied to take into account the turbulence in the liquid phase. The instantaneous and average characteristics of the process and the velocity and temperature pulsation fields are analyzed. The simulations have been performed for three specific heating regimes: with furnace heaters operating at full power, with furnace heaters switched on at the bottom of the vessel only, and with switched-off furnace heaters. It is shown that the localization of the cooling zone can completely reorganize the structure of the large-scale flow. Therefore, by changing heating regimes, it is possible to influence the flow structure for the purpose of creating the most favorable conditions for the reaction. It is also shown that the presence of the titanium block strongly affects the flow structure.

Registration No. 25832 - Permalink


Transitions in a magnetized quasi-laminar spherical Couette flow
Kasprzyk, C.; Kaplan, E.; Seilmayer, M.; Stefani, F.
Corresponding author: Stefani, Frank HZDR
Abstract: First results of a new spherical Couette experiment are presented. The liquid metal flow in a spherical shell is exposed to a homogeneous axial magnetic field. For a Reynolds number Re=1000, we study the effect of increasing Hartmann number Ha. The resulting flow structures are inspected by ultrasound Doppler velocimetry. With a weak applied magnetic field, we observe an equatorially antisymmetric jet instability with the azimuthal wave number m=3. As the magnetic field strength increases, this instability vanishes. When the field is increased further, an equatorially symmetric return flow instability arises. Our observations are shown to be in good agreement with linear stability analysis and non-linear flow simulations.
  • Magnetohydrodynamics 53(2017)2, 393-401

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  • Secondary publication expected from 13.07.2018

Registration No. 25830 - Permalink


Comparison of MLAA-derived attenuation maps with and without utilisation of time-of-flight information in the attenuation estimation step
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: INTRODUCTION
As is well known, quantitative combined PET/MR imaging depends on accurate MR-based attenuation correction (MRAC). While a mostly satisfactory state of affairs has been reached today, problems persist regarding segmentation
errors including unsatisfactory bone identification and residual systematic differences in comparison to PET/CT. Alternative or complementary strategies for attenuation correction (AC), therefore, are of considerable relevance. In this context, Maximum Likelihood reconstruction of Attenuation and Activity (MLAA) is one of the most promising approaches. As A. Rezaei et al. have shown [1], Time-Of-Flight (TOF) image reconstruction is required to eliminate possible ”crosstalk” between the estimated activity and attenuation distribution. On the other hand, it is widely believed that use of the TOF information during attenuation estimation does not result in image quality improvement and thus is unnecessary, see for example ref. [2]. However, so far this assumption has never been thoroughly tested. We address this issue in the present investigation. To this end, we have compared TOF and non-TOF versions of the attenuation estimation algorithm as part of MLAA within the framework of our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [3].

METHODS
MLAA is an image reconstruction algorithm, which maximizes the Likelihood function by alternately updating activity distribution and attenuation map. Maximum-Likelihood Estimation-Maximization (MLEM) is normally used for the
activity estimation and Maximum-Likelihood Transmission Reconstruction (MLTR) for the attenuation estimation. In order to investigate the potential impact of using TOF-MLTR instead of nonTOF-MLTR in the MLAA workflow both of them were implemented as a part of our THOR application. List-mode MLEM algorithm was used for activity reconstruction and accelerated by utilizing ordered subsets. For scatter correction (SC), the time-of-flight extension of the Single Scatter Simulation algorithm (SSS) was used, see ref [4]. Attenuation map reconstruction was performed by ordered subsets accelerated list-mode version of MLTR, which is equivalent to the standard sinograms based MLTR in the non-TOF case. For the initial attenuation map estimate the MR-derived outline of the scanned object was uniformly filled with the attenuation coefficient of water. During reconstruction, attenuation map estimates were augmented by a pre-computed template of the patient bed. The main difference between TOF- and nonTOF-MLTR is the way how scatter and randoms corrections are handled. TOF information allows to individually compute this correction for each event (or TOF-bin) depending on event position along the LOR, while this correction is assumed to be the same for all the events within the LOR in the non-TOF algorithm. Consequently, any differences between both MLTR versions should be most pronounced for high contrast objects as is the case, e.g., if the bladder is within the field-of-view. Therefore, two different configurations of the whole body phantom L981602 were used. The phantom in configuration A has two cylindrical air-filled inserts and one cylindrical bone-like insert. This phantom allows to assess accuracy of the attenuation map estimate under low-contrast conditions. The phantom in configuration B comprises a large spherical ”bladder” insert with high target-to-background contrast and a small ”lesion” insert with lower contrast. The attenuation map is uniform in this case, which facilitates detection of scatter-related artifacts in the MLAA reconstructed attenuation image. Transmission scans of the phantoms with the Siemens HR+ scanner were performed and used as ground-truth for the attenuation maps.

RESULTS
The whole body phantom in both configurations was scanned with the Time-Of-Flight capable Philips Ingenuity-TF PET/MR scanner (TOF resolution (FWHM): ∼600 ps). Acquired data were reconstructed with THOR MLAA and TOF-MLTR and nonTOF-MLTR, respectively. In the case of configuration A (low activity contrast, high attenuation contrast) TOF-MLTR does not improve attenuation coefficients estimate significantly. Reconstructed attenuation values differ by less than 1% for bone and less than 15% for air. The situation is different for configuration B (high activity contrast, homogeneous attenuation). Due to presence of the large hot object in the field-of-view a massive artifact appears in the transaxial plane of the reconstructed attenuation map containing the ”bladder” insert. In the coronal view this artifact appears as a rather large area of apparently reduced attenuation in the middle of the phantom. The difference between the attenuation coefficient of the water background in the central and the peripheral zones depends on the reconstruction method used. Specifically, the use of TOF-MLTR instead of nonTOF-MLTR yields twofold decrease of the artifact. On the other hand, the attenuation coefficient inside the ”bladder” is about 12% higher than the reference value with TOF-MLTR compared to a 6% overestimate with nonTOF-MLTR (where this reduced deviation probably is due to the influence of the mentioned attenuation artifact).

CONCLUSION
Our preliminary results indicate that the use of TOF-MLTR within the MLAA framework provides only small improvements in terms of attenuation map accuracy if activity contrasts are modest. However, it can distinctly decrease scatter related artifacts in the presence of high activity contrast such as is frequently observed in the pelvis region. We hypothesize the advantages of TOF-MLTR will become even more apparent with increasing TOF resolution. A more detailed investigation of the benefits of TOF-MLTR usage within the MLAA workflow is under way.

REFERENCES
[1] A. Rezaei, M. Defrise, G. Bal, C. Michel, M. Conti, C. Watson, and J. Nuyts, “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on Medical Imaging, vol. 31, no. 12, pp. 2224–33, dec 2012.
[2] A. Rezaei and J. Nuyts, “Simultaneous reconstruction of the activity image and registration of the CT image in TOF-PET,” IEEE Nuclear Science Symposium Conference Record, vol. 1852, p. 1852, 2016.
[3] A. Lougovski, F. Hofheinz, J. Maus, G. Schramm, E. Will, J. van den Hoff, and J. van den Hoff, “A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction,” Physics in Medicine and Biology, vol. 59, no. 3, pp. 561–577, feb 2014.
[4] C. C. Watson, “Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET,” IEEE Transactions on Nuclear Science, vol. 54, no. 5, pp. 1679–1686, 2007.
Keywords: PET, TOF-PET, PET/MR, MLAA, MRAC, Attenuation Correction
  • Poster
    PSMR 2017 - 6th Conference on PET-MRI and SPECT-MRI, 29.-31.05.2017, Lisbon, Portugal

Registration No. 25829 - Permalink


Sun - Batteries - Sun
Stefani, F.; Galindo, V.; Giesecke, A.; Weber, N.; Weier, T.
Abstract: Liquid metal batteries (LMBs) are presently discussed as cheap means for the storage of wind and solar energy. Among other drivers of undesired fluid motion that could destroy the three-fluids stratification, the Tayler instability (TI) sets some upper limit for the upscalability of LMBs. We present the principles of the TI, its possible effects on LMBs, and some simple ways to suppress it. We focus on the peculiar saturation mechanism of the TI at low magnetic Prandtl numbers, which relies on the change of the hydrodynamic base state. We discuss the recently found helicity oscillations of the m=1 velocity field of the TI which, in turn, might have consequences for stellar dynamo models for which the TI had originally been discussed. We show that these helicity oscillations can be resonantly excited by certain m=2 perturbations which would result, e.g., from planetary tidal forces. It is this high sensitivity of the helicity oscillations that could empower those very weak tidal forces to synchronize the entire solar dynamo.
  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics (LMBFD 2017), 16.-17.05.2017, Dresden, Germany

Registration No. 25828 - Permalink


The DRESDYN project: planned experiments and present status
Stefani, F.; Eckert, S.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Räbiger, D.; Seilmayer, M.; Weier, T.
Abstract: The Dresden sodium facility for dynamo and thermohydraulic studies (DRESDYN) is a platform for large-scale liquid sodium experiments devoted to fundamental geo- and astrophysical questions as well as to various applied problems related to the conversion and storage of energy. Its most ambitious part is a precession driven dynamo experiment, comprising 8 tons of liquid sodium supposed to rotate with up to 10 Hz and to precess with up to 1 Hz. Another large-scale set-up is a Tayler-Couette experiment with a gap width of 0.2 m and a height of 2 m, whose inner cylinder rotates with up to 20 Hz. Equipped with a coil system for the generation of an axial field of up to 120 mT and two different axial currents through the center and the liquid sodium, this experiment aims at studying various versions of the magnetorotational instability and their combinations with the Tayler instability. We discuss the physical background of these two experiments and delineate the present status of their technical realization. Other installations, such as a sodium loop and a test stand for In-Service-Inspection experiments, will also be sketched.
  • Lecture (Conference)
    88th GAMM Annual Meeting, 06.-10.03.2017, Weimar, Germany

Registration No. 25827 - Permalink


Ultrasound propagation in bond frustrated HgCr2S4 spinel in magnetic fields
Felea, V.; Prodan, L.; Stefanet, E.; Cong, P. T.; Zherlitsyn, S.; Tsurkan, V.
Corresponding author: Tsurkan, V. Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova & Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Augsburg, Germany
Abstract: Ultrasound and magnetization studies of bond frustrated spinel HgCr2S4 are performed as a function of temperature in static magnetic fields. Beside the anharmonic effect, the sound velocity shows pronounced anomaly at the antiferromagnetic (AFM) transition at TN = 23 K with an additional significant increase of the order of 0.5 % indicating a strong spin-lattice coupling. External magnetic fields enhance the ferromagnetic (FM) correlations and shift the anomalies to lower temperatures concomitantly with the reduction of the Néel temperature. The constructed H–T Phase diagram beside the long-range AFM states reveals the state with induced FM order and regimes with short-range AFM and FM correlations as well.

Registration No. 25826 - Permalink


Comparison of arterial spin labeling registration strategies in the multi-center GENetic frontotemporal dementia initiative (GENFI)
Mutsaerts, H. J. M. M.; Petr, J.; Thomas, D. L.; de Vita, E.; Cash, D. M.; van Osch, M. J. P.; Golay, X.; Groot, P. F. C.; Ourselin, S.; van Swieten, J.; Laforce, R.; Tagliavini, F.; Borroni, B.; Galimberti, D.; Rowe, J. B.; Graff, C.; D. Pizzini, F. B.; Finger, E.; Sorbi, S.; Castelo Branco, M.; Rohrer, J. D.; Masellis, M.; Macintosh, B. J.
Abstract: Purpose: To compare registration strategies to align arterial spin labeling (ASL) with 3D T1-weighted (T1w) images, with the goal of reducing the between-subject variability of cerebral blood flow (CBF) images.
Materials and Methods: Multi-center 3T ASL data were collected at eight sites with four different sequences in the multi-center GENetic Frontotemporal dementia Initiative (GENFI) study. In a total of 48 healthy controls, we compared the following image registration options: (I) which images to use for registration (perfusion-weighted images [PWI] to the segmented gray matter (GM) probability map (pGM) (CBF-pGM) or M0 to T1w (M0-T1w); (II) which transformation to use (rigid-body or non-rigid); and (III) whether to mask or not (no masking, M0-based FMRIB software library Brain Extraction Tool [BET] masking). In addition to visual comparison, we quantified image similarity using the Pearson correlation coefficient (CC), and used the Mann-Whitney U rank sum test.Results: CBF-pGM outperformed M0-T1w (CC improvement 47.2% 6 22.0%; P < 0.001), and the non-rigid transformation outperformed rigid-body (20.6% 6 5.3%; P < 0.001). Masking only improved the M0-T1w rigid-body registration (14.5% 6 15.5%; P 5 0.007).
Conclusion: The choice of image registration strategy impacts ASL group analyses. The non-rigid transformation is promising but requires validation. CBF-pGM rigid-body registration without masking can be used as a default strategy.
In patients with expansive perfusion deficits, M0-T1w may outperform CBF-pGM in sequences with high effective spatial resolution. BET-masking only improves M0-T1w registration when the M0 image has sufficient contrast.

Registration No. 25825 - Permalink


Scatter correction in TOF and non-TOF PET image reconstruction in THOR
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: INTRODUCTION
As is well known, quantitative combined PET/MR imaging depends on accurate MR-based attenuation correction (MRAC). While a mostly satisfactory state of affairs has been reached today, problems persist regarding segmentation errors including unsatisfactory bone identification and residual systematic differences in comparison to PET/CT. Alternative or complementary strategies for attenuation correction (AC), therefore, are of considerable relevance. In this context, Maximum Likelihood reconstruction of Attenuation and Activity (MLAA) is one of the most promising approaches but, as A. Rezaei et al. have shown [1], Time-Of-Flight (TOF) image reconstruction is then required to eliminate possible ”crosstalks” between the estimated activity and attenuation distribution. We are aiming at implementation of MLAA for the Philips Ingenuity-TF PET/MR scanner as part of our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [2]. As a prerequisite we are currently modifying THOR to make full use of the available TOF information. The most critical point in this context is accurate and computational efficient TOF Scatter Correction (TOF-SC). Here, we report on our approach to solving this issue and compare TOF-SC techniques with conventional non-TOF SC method.

METHODS
One possible implementation of TOF-SC uses a straight forward extension of Watson’s well-known Single Scatter Simulation (SSS) algorithm [3] but this approach results in about an order of magnitude increase of computational burden compared to standard SSS. Alternatively, one can use standard SSS to estimate the number of scattered events in each Line Of Response (LOR) and use an additional algorithm to estimate the shape of the time distribution of scattered events within each LOR (scatter mask). To integrate TOF-SC into our THOR reconstruction, four different approaches to scatter mask calculation have been investigated:
A. Simple scatter scaling
This approach assumes that scattered and unscattered events have identical time distribution within each single LOR.
B. Attenuation based SC
In this approach the object is modeled as a set of “scatter points” which are generated by SSS. Each scatter point is then also assumed to be a scatter source. For each detector pair and scatter point the geometric path difference from scatter source to both detectors is calculated and an effective position of the scattered event within the corresponding LOR is determined. By repeating this procedure for a large number of scatter points and post-processing the results by smoothing or using a TOF-binning technique one can compute the required scatter mask.
C. Attenuation and activity based SC
While approach B allows to properly handle the shape of the attenuating object it does not take into account the given activity distribution. To fix this issue scatter sources and scatter points should be separated. To do this in a simple and fast way we introduce a small set of “emission points” for approximation of the given activity distribution. The activity distribution/object is then described as superposition of suitable 3D Gaussian distributions around these emission
points. Calculation of the scatter masks is similar to the previous approach, but now scatter sources are determined as projections of emission points onto straight lines connecting selected scatter point and detectors. In this approach the intensity of each source is proportional to the intensity of corresponding emission point and decreases according to a Gaussian as a function of the distance between them.
D. TOF-SSS Time-Of-Flight extension of Single Scatter Simulation by Watson.

RESULTS
All four approaches have been integrated into THOR and tested in dedicated phantom and patient studies. Approach A does not yield quantitatively correct scatter distributions for big objects. Approach B is superior to A but notable artifacts remain in the presence of high-contrast. Approach C is able to eliminate part of these artifacts but requires more computation time. Approach D is the most accurate and computationally most expensive.

CONCLUSION
Our preliminary results indicate that attenuation based SC might be the best compromise between computation time and image quality for a wide range of applications.

REFERENCES
[1] A. Rezaei, M. Defrise, G. Bal, C. Michel, M. Conti, C. Watson, and J. Nuyts, “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on Medical Imaging, vol. 31, no. 12, pp. 2224–33, dec 2012.
[2] A. Lougovski, F. Hofheinz, J. Maus, G. Schramm, E. Will, J. van den Hoff, and J. van den Hoff, “A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction,” Physics in Medicine and Biology, vol. 59, no. 3, pp. 561–577, feb 2014.
[3] C. C. Watson, “Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET,” IEEE Transations on Nuclear Science, vol. 54, no. 5, pp. 1679–1686, 2007.
Keywords: PET, TOF-PET, Scatter Correction, TOF-SC, Single Scatter Simulation, SSS
  • Lecture (Conference)
    Seminar on PET image reconstruction, 28.-30.09.2016, Leuven, Belgium

Registration No. 25824 - Permalink


Effect of Brain Extraction of Low Resolution Arterial Spin Labeling (ASL) Fmri Images on Realignment and Coregistration
Liao, J.; Petr, J.; Lazar, R. M.; Marshall, R. S.; Asllani, I.
Abstract: ASL is an fMRI method that maps cerebral blood (CBF), which is a key parameter of brain physiology. In ASL, flow-weighted images are computed by subtracting a “labeled” image from a contiguously acquired unlabeled control image. The difference is then converted to a CBF image using partial volume (PV) maps obtained from the segmentation of the anatomical T1w image. It follows that the quality of ASL data is dependent on the quality of motion correction and coregistration of the high-resolution T1w image to the low-resolution ASL. We tested whether applying brain-extraction on the low-resolution ASL would improve both these processes. The test was performed on 8 patients with carotid occlusive disease. Improvement in motion realignment was defined as % change averaged over the 6 degrees of freedom and across patients; improvement in coregistration was assessed as a difference in the mutual information (MI) value between the T1w and extracted and original ASL, respectively. There was a noticeable effect of brain extraction on both realignment and coregistration.
Keywords: MR neuroimaging, Brain image analysis, Rigid-body image registration, ASL
  • Contribution to proceedings
    39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 11.-15.07.2017, Jeju Island, Korea
  • Poster
    39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 11.07.2017, Jeju Island, Korea

Registration No. 25823 - Permalink


SUR: a superior alternative to SUV as a surrogate of tumor glucose metabolism
van den Hoff, J.
Abstract: kein Abstract verfügbar
  • Invited lecture (Conferences)
    Symposium Nuclear Medicine & Molecular Imaging, Katholieke Universiteit Leuven, 10.01.2017, Leuven, Belgien

Registration No. 25822 - Permalink


Standardised Uptake Ratio (SUR): die robuste Variante des SUV
van den Hoff, J.
Abstract: kein Abstract verfügbar
  • Invited lecture (Conferences)
    Jahrestagung der Bayrischen Gesellschft für Nuklearmedizin, 01.07.2016, Regensburg, Deutschland

Registration No. 25821 - Permalink


Magnetohydrodynamic instabilities in liquid metal batteries
Stefani, F.
Abstract: The increasing deployment of strongly fluctuating renewable energies requires a corresponding large-scale expansion of electricity storage. Liquid metal batteries (LMBs) are presently discussed as a possible route of economical grid-scale energy storage. They consist of two liquid metal electrodes and a molten salt ionic conductor sandwiched between them. The density ratios allow for a stable stratification of the three layers. In the talk, we concentrate on the magnetohydrodynamic aspects of this cell type, with special focus on electro-vortex flows, the sloshing instability, and possible effects of the Tayler instability.
  • Lecture (Conference)
    XXth Winter School on Continuous Media Mechanics, 13.-16.02.2017, Perm, Russia

Registration No. 25820 - Permalink


Time efficient scatter correction in Time-Of-Flight PET image reconstruction
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: Aim
We are currently modifying our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [1], to make full use of the available Time-of-Flight (TOF) information. The most critical point in this context is accurate and computational efficient TOF Scatter Correction (TOF-SC). Here, we report on our approach to solving this issue.

Methods
Four different, partly newly developed approaches to estimation of scatter time distribution have been investigated: A. Simple scatter scaling: this approach assumes that scattered and unscattered events have identical time distribution within each single LOR. B. Attenuation based SC (new approach): in this approach the object is modeled as a set of “scatter points”. Each scatter point is also assumed to be a scatter source. C. Attenuation and activity based SC (new approach): in this approach a small set of “emission points” for approximation of the given activity distribution is introduced. Calculations are similar to B except that scatter sources are determined as projections of emission points onto straight lines connecting selected scatter point and detectors. D. TOF-SSS Time-Of-Flight extension of Single Scatter Simulation by Watson.

Results
All four approaches have been integrated into THOR and tested in dedicated phantom and patient studies. Approach A does not yield quantitatively correct scatter distributions for big objects. Approach B is superior to A but notable artifacts remain in the presence of high-contrast. Approach C is able to eliminate part of these artifacts but requires more computation time. Approach D is the most accurate and computationally most expensive.

Conclusion
Our preliminary results indicate that attenuation based SC might be the best compromise between computation time and image quality for a wide range of applications.

Literature
[1] A. Lougovski, F. Hofheinz, J. Maus, et al., Physics in Medicine
and Biology 59(3), 561 (2014)
Keywords: PET, TOF-PET, Scatter Correction, TOF-SC
  • Poster
    NuklearMedizin 2017, 26.-29.04.2017, Dresden, Germany

Registration No. 25818 - Permalink


Liquid metal experiments on hydromagnetic dynamos and magnetically triggered flow instabilities
Stefani, F.
Abstract: The magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Magnetic fields play, in turn, an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both effects had been the subject of purely theoretical investigations. The lecture gives an overview about the recent liquid metal experiments on dynamo action and magnetically triggered instabilities. An outlook on 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, is also given.
  • Invited lecture (Conferences)
    XXth Winter School on Continuous Media Mechanics, 13.-16.02.2017, Perm, Russia

Registration No. 25817 - Permalink


Time efficient scatter correction in Time-Of-Flight PET image reconstruction
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: INTRODUCTION
As is well known, quantitative combined PET/MR imaging depends on accurate MR-based attenuation correction (MRAC). While a mostly satisfactory state of affairs has been reached today, problems persist regarding segmentation errors including unsatisfactory bone identification and residual systematic differences in comparison to PET/CT. Alternative or complementary strategies for attenuation correction (AC), therefore, are of considerable relevance. In this context, Maximum Likelihood reconstruction of Attenuation and Activity (MLAA) is one of the most promising approaches but, as A. Rezaei et al. have shown [1], Time-Of-Flight (TOF) image reconstruction is then required to eliminate possible ”crosstalks” between the estimated activity and attenuation distribution. We are aiming at implementation of MLAA for the Philips Ingenuity-TF PET/MR scanner as part of our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [2]. As a prerequisite we are currently modifying THOR to make full use of the available TOF information. The most critical point in this context is accurate and computational efficient TOF Scatter Correction (TOF-SC). Here, we report on our approach to solving this issue.

METHODS
One possible implementation of TOF-SC uses a straight forward extension of Watson’s well-known Single Scatter Simulation (SSS) algorithm [3] but this approach results in about an order of magnitude increase of computational burden compared to standard SSS. Alternatively, one can use standard SSS to estimate the number of scattered events in each Line Of Response (LOR) and use an additional algorithm to estimate the shape of the time distribution of scattered events within each LOR (scatter mask). To integrate TOF-SC into our THOR reconstruction, three different approaches to scatter mask calculation have been investigated which are modifications/improvements of key ideas from article [4]:
A. Simple scatter scaling
This approach assumes that scattered and unscattered events have identical time distribution within each single LOR.
B. Attenuation based SC
In this approach the object is modeled as a set of “scatter points” which are generated by SSS. Each scatter point is then also assumed to be a scatter source. For each detector pair and scatter point the geometric path difference from scatter source to both detectors is calculated and an effective position of the scattered event within the corresponding LOR is determined. By repeating this procedure for a large number of scatter points and post-processing the results by smoothing or using a TOF-binning technique one can compute the required scatter mask.
C. Attenuation and activity based SC
While approach B allows to properly handle the shape of the attenuating object it does not take into account the given activity distribution. To fix this issue scatter sources and scatter points should be separated. To do this in a simple and fast way we introduce a small set of “emission points” for approximation of the given activity distribution. The activity distribution/object is then described as superposition of suitable 3D Gaussian distributions around these emission
points. Calculation of the scatter masks is similar to the previous approach, but now scatter sources are determined as projections of emission points onto straight lines connecting selected scatter point and detectors. In this approach the intensity of each source is proportional to the intensity of corresponding emission point and decreases according to a Gaussian as a function of the distance between them.

RESULTS
All three approaches have been integrated into our THOR reconstruction and tested in phantom and patient studies. Simple scatter scaling (approach A) does not yield quantitatively correct scatter distributions for big objects such as whole body phantoms. Attenuation based SC (approach B) does not have this problem due to proper handling of the object shape, but notable artifacts appear in the presence of high-contrast such as in the pelvis/bladder region. The combined attenuation and activity based algorithm (approach C) is able to eliminate part of the latter artifacts but requires more computation time.

CONCLUSION
Our preliminary results indicate that attenuation based SC might be the best compromise between computation time and image quality for a wide range of applications. A more detailed investigation of the efficiency and accuracy of the implemented TOF-SC methods is currently in progress.

REFERENCES
[1] A. Rezaei, M. Defrise, G. Bal, C. Michel, M. Conti, C. Watson, and J. Nuyts, “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on Medical Imaging, vol. 31, no. 12, pp. 2224–33, dec 2012.
[2] A. Lougovski, F. Hofheinz, J. Maus, G. Schramm, E. Will, J. van den Hoff, and J. van den Hoff, “A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction,” Physics in Medicine and Biology, vol. 59, no. 3, pp. 561–577, feb 2014.
[3] C. C. Watson, “Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET,” IEEE Transations on Nuclear Science, vol. 54, no. 5, pp. 1679–1686, 2007.
[4] M. Conti, B. Bendriem, M. Casey, M. Chen, F. Kehren, C. Michel, and V. Panin, “First experimental results of time-of-flight reconstruction on an LSO PET scanner.” Physics in medicine and biology, vol. 50, no. 19, pp. 4507–4526, oct 2005.
Keywords: PET, TOF-PET, Scatter Correction, TOF-SC
  • Lecture (Conference)
    PSMR 2016 - 5th Conference on PET/MR and SPECT/MR, 23.-25.05.2016, Cologne, Germany

Registration No. 25816 - Permalink


DRESDYN: Liquid metal experiments on dynamo action and magnetorotational instability
Gundrum, T.; Eckert, S.; Gerbeth, G.; Stefani, F.; Steglich, C.
Abstract: We report on two large-scale liquid sodium experiments on precession-driven dynamo action and magnetorotational instability that are planned in the framework of the DRESDYN project.
  • Poster
    Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Germany

Registration No. 25815 - Permalink


Can planetary tides synchronize the solar dynamo?
Stefani, F.; Galindo, V.; Giesecke, A.; Weber, N.; Weier, T.
Abstract: While the traditional explanation of the Hale cycle of the solar magnetic field relies on intrinsic features of the solar dynamo, we presently witness an increased interest in the question of whether gravitational forces of planets could influence the length and intensity of the cycle. Although tidal forces are usually considered as much too weak to play any role, one should note the large gravitational acceleration at the tachocline that amounts to 500 m/s². This translates the apparently tiny tidal heights of the order of 1 mm to equivalent velocities of 1 m/s. Such velocities, when allowed to coherently develop in the quiet regions of the tachocline, might indeed be relevant for the dynamo.
In our quest for a viable physical mechanism that could link the weak planetary force with solar dynamo action, we focus on the helicity oscillations that were recently found in simulations of the current-driven, kink-type Tayler instability that is characterized by an m=1 azimuthal dependence. We show how these helicity oscillations can be resonantly excited by m=2 perturbations that reflect tidal oscillations. Specifically, we speculate that the 11.07 years tidal oscillation induced by the tidally dominant Venus--Earth--Jupiter system may lead to a 1:1 resonant excitation of the oscillation of the associated alpha-effect. In the framework of a reduced, zero-dimensional alpha-Omega dynamo model, including a weak non-oscillatory and a resonantly excited oscillatory part of alpha, we recover the 22.14-year cycle of the solar dynamo. We finally show that the synchronization model can produce the correct orientation of the butterfly diagram even in case that the product of the non-oscillatory part of alpha with Omega is positive.
  • Poster
    2nd Conference on Natural Dynamos, 25.06.-01.07.2017, Valtice, Czech Republic

Registration No. 25814 - Permalink


Laboratory experiments on dynamo action and magnetically triggered flow instabilities
Stefani, F.
Abstract: Magnetic fields of planets, stars and galaxies are known to be generated by the homogeneous dynamo effect in moving electrically conducting fluids, such as liquid metals or plasmas. Once generated, magnetic fields can foster cosmic structure formation by destabilizing, via the magnetorotational instability (MRI) or the Tayler instability (TI), those rotating flows that would be otherwise hydrodynamically stable. The mutual reinforcement of dynamo action and magnetic instabilities leads to interesting concepts such as the MRI-dynamo or the Tayler-Spruit-dynamo.
For a long time, all these topics had been the subject of purely theoretical and numerical research. 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 VKS dynamo experiment in Cadarache has successfully reproduced many features of geophysical interest such as reversals and excursions. Further liquid metal experiments in Grenoble, Madison, Maryland, Perm, Princeton, Perm, and Socorro have contributed important findings related to the alpha, beta and Omega effects as well as to various wave phenomena in magnetized rotating fluids. MRI-related research was partly successful with the observation of the helical MRI and the azimuthal MRI at the PROMISE facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). First evidence of the current-driven Tayler instability in a liquid metal was also obtained.
The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered flow instabilities. It concludes with an overview about future experiments, with special focus on the precession driven liquid sodium experiment and the large-scale Tayler-Couette experiment that are under construction in the framework of the DRESDYN project at HZDR.The prospects for experimental validation of the recently discussed magnetic destabilization of flows with positive shear are also discussed.
  • Invited lecture (Conferences)
    2nd Conference on Natural Dynamos, 25.06.-01.07.2017, Valtice, Czech Republic

Registration No. 25812 - Permalink


Evaluation of hemodynamic impairments in healthy elderly participants and patients with high-grade unilateral carotid artery stenosis
Kaczmarz, S.; Göttler, J.; Griese, V.; Petr, J.; van de Ven, K.; Helle, M.; Kooijman, H.; Kluge, A.; Karampinos, D.; Zimmer, C.; Sorg, C.; Preibisch, C.
Abstract: Internal carotid-artery stenosis (ICAS) causes complex and not yet well understood physiological impairments. We present preliminary data from an ongoing clinical study in ICAS patients and healthy, age-matched participants. The major aims were to evaluate the reliability of a multimodal MRI-protocol and investigate physiological changes. For ICAS patients, regionally impaired vascular-reactivity as well as hypo-perfusion were found. In accordance with literature, we did not find ICAS-induced changes in oxygen extraction on group level. The presented preliminary results thus imply successful application of multimodal MRI methods and are highly promising with respect to gaining a deeper insight into ICAS-related physiological changes.
Keywords: stenosis, ASL, perfusion, MRI
  • Contribution to proceedings
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.-27.04.2017, Honolulu, Hawaii, USA
    Proceedings of the 25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine
  • Lecture (Conference)
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.04.2017, Honolulu, Hawaii, USA

Registration No. 25811 - Permalink


Perfusion decrease during radiochemotherapy is not fully explained by volumetric gray matter changes
Petr, J.; Mutsaerts, H.; Hofheinz, F.; Asllani, I.; van Osch, M.; Platzek, I.; Seidlitz, A.; Krause, M.; van den Hoff, J.
Abstract: Radiochemotherapy in brain-tumor patients was shown to cause gray matter (GM) volume and cerebral blood flow (CBF) changes. The interaction of these two effects, however, remains unclear. Here, we investigated GM volume and ASL CBF changes and their interaction in the healthy hemisphere of 38 glioblastoma patients undergoing radiochemotherapy with Temozolomide. We found a statistically significant CBF decrease with dependence on the RT-dose. PV-corrected results indicated that, while to a certain extent the apparent CBF decrease measured by ASL is caused by GM atrophy, there still remain significant CBF changes that cannot be explained by structural changes alone.
Keywords: ASL, perfusion, glioblastoma, radiochemotherapy, atrophy, partial volume
  • Contribution to proceedings
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.-27.04.2017, Honolulu, Hawaii, USA
    Proceedings of the 25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine
  • Poster
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.04.2017, Honolulu, Hawaii, USA

Registration No. 25810 - Permalink


Brain volume loss in glioblastoma patients following photon and proton radiochemotherapy
Petr, J.; Hofheinz, F.; Gommlich, A.; Raschke, F.; Troost, E.; Beuthien-Baumann, B.; Seidlitz, A.; Platzek, I.; Baumann, M.; Krause, M.; van den Hoff, J.
Abstract: Gray matter (GM) atrophy in healthy brain tissue following radiochemotherapy was shown in brain-tumor patients in several studies. Here, we aimed to study GM and white matter (WM) changes in glioblastoma patients undergoing photon (n=43) and proton (n=12) radiochemotherapy. In photon-therapy patients, a statistically significant decrease of both GM (~2%) and WM (1.3-2.3%) volume was found with a positive influence of the RT-dose on the GM volume loss. In proton-therapy patients, no significant changes in GM and WM volumes were observed after therapy. This indicates that the proton-therapy has the potential to reduce structural GM changes in healthy tissue.
Keywords: radiochemotherapy, proton therapy, atrophy, morphometrics
  • Contribution to proceedings
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.-27.04.2017, Honolulu, Hawaii, USA
    Brain volume loss in glioblastoma patients following photon and proton radiochemotherapy
  • Lecture (Conference)
    25th Scientific Meeting and Exhibition of International Society for Magnetic Resonance in Medicine, 22.04.2017, Honolulu, Hawaii

Registration No. 25809 - Permalink


Kinetic Modeling
van den Hoff, J.
Abstract: A mathematical description of the time-dependent tissue uptake and tissue clearance after injection of contrast agents or radioactively labeled tracers with suitable models (kinetic modeling) allows a detailed analysis of transport processes and metabolism in vivo. Such an analysis can provide at once quantitative information for several interesting parame- ters such as local blood volume, blood flow, distribution volumes, metabolic rates, binding potentials, and so forth. While the mathematical techniques are – with some reservations – in principle suited for data analysis in other tomographic modalities as well (notably CT and MRI), the broadest field of application is found in PET. We will focus especially on small animal PET in the following.
Keywords: PET, Kinetic Modeling, Small Animal Imaging
  • Book chapter
    Fabian Kiessling, Bernd J. Pichler, Peter Hauff: Small Animal Imaging: Basics and Practical Guide, Heidelberg: Springer International Publishing, 2017, 978-3-319-42200-8, 559-580
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-42202-2_21

Registration No. 25808 - Permalink


Synthesis of two new 11C-labelled a7 nicotinic acetylcholine receptor ligands.
Patt, J.-T.; Deuther-Conrad, W.; Peters, D.; Brust, P.; Sabri, O.; Patt, M.
Abstract: Introduction
NS-9011 (4-[5-(4-Methoxy-phenyl)-[1,3,4]oxadiazol-2-yl]-1,4-diaza-bizyclo[3.2.2]nonane) and NS-9030 (4-[5-(3-Methoxy-phenyl)-[1,3,4]oxadiazol-2-yl]-1,4-diaza-the desmethyl precursor compounds with [11C]methyltriflate. The precursor compounds showed a high reactivity towards [11C]iodomethane, unfortunately not in the desired labelling position. In order to decrease the selectivity for the undesired compound(s) [11C]methyltriflate instead of [11C]iodomethane was used. The higher reactivity of the [11C]methyltriflate in combination with elevated temperature of 60 °C and using water as solvent should result in a considerable decrease in selectivity.
Methods
The radiosynthesis was carried out in a modified TracerLab C system (GEMS) equipped with a reaction loop instead of the glass reactor in the heating zone of the module. [11C]iodomethane was subsequently passed over silver triflate at 200 °C and through the reaction loop containing the precursor solution (prepared from 0.5 – 1.0 mg precursor and 30μl of 0.5 M NaOH solution) and 30 μl of water) heated to 60 °C. The reaction mixture was transferred with eluent into a HPLC valve and injected on a ReproSil-Pur 120 C18-Aq 5μ (125 mm x 10 mm) HPLC column. An eluent composed of 10 % Ethanol (NS-9011) or 13 % Ethanol (NS-9030) and buffer solution (40 ml sodium phosphate (Braun) per 1000 ml adjusted to pH 2 with phosphorc acid was used for purification.The product peak was collected, diluted and concentrated on a Phenomenex Strata X cartridge. The radiotracer was eluted with acetone (1.5 ml). Evaporation was performed manually in a heating block (70 °C) in a stream of nitrogen. The product was dissolved in 500 μl of physiological NaCl solution. Radiochemical purity was determined on a radio-HPLC system on a ReproSil-Pur 120 C18-Aq 5μ (250 mm x 4.6 mm) HPLC column.
Results and Discussion
By applying the reaction conditions described above, despite highly favoured competing labelling sites in the precursor molecule up to 0.5 GBq of tracer compound could be synthesized. The product was obtained in high radiochemical purity (>95 %). Comparison of the UV trace of authentic standard compound and the radioactivity signal of radiotracer spiked with standard compound showed a full match of radioactivity and UV signal. The yield was sufficient for first animal experiments and the reaction conditions were not further optimized.
  • Poster
    The 22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.05.2017, Dresden, Germany

Registration No. 25803 - Permalink


A clinical trial with (+)-[18F]Flubatine: evaluation of metabolism, plasma protein binding and parameters.
Patt, M.; Mishchenko, O.; Tiepolt, S.; Sattler, B.; Höpping, A.; Smits, R.; Becker, G. A. F.; Deuther-Conrad, W.; Steinbach, J.; Brust, P.; Sabri, O.
Abstract: Introduction
(+)-[18F]Flubatine ((+)[18F]NCFHEB), the enantiomer of the recently introduced radioligand for quantificati(-)-[18F]Flubatine, was investigated in a clinical trial with patients suffering from Alzheimer’s disease compared to healthy controls. In order to be able to apply full kinetic modelling biological parameters such as plasma protein binding, amount of parent compound over time and distribution between cellular and noncellular blood components, were determined. In addition the kinetics of the tracer distribution between plasma and whole blood was assessed.
Methods
Plasma protein binding was evaluated in vitro by means of ultracentrifugation using a blood sample from each subject prior to injection. The amount of unchanged tracer over time was determined at 11 time points ranging from 3 to 270 min p.i. by radio-HPLC analysis of protein free plasma obtained by centrifugation as described previously. The distribution of radioactivity between cellular and non-cellular blood components was determined at 11 time points p.i. after separation of the blood components by centrifugation.
Results/Discussion
Plasma protein binding of (-)-[18F]Flubatine was found to be 0.140.02 (meansd) without significant difference between AD and HC groups. Metabolic degradation of (+)-[18F]Flubatine was very low: the amount of parent compound was found to be 100 and 972 % at 90 and 270 min p.i., respectively. The activity distribution between plasma and whole blood was found to be 0.820.05 and did not change with time. Kinetics for the distribution of the tracer between plasma and whole blood was determined over a time period of 1.5 h and equilibrium was found to be reached instantaneously.
Conclusions Biological parameters such as plasma protein binding, metabolism and tracer/activity distribution between plasma and whole blood were investigated within a clinical trial using (+)-[1842 subtype of nAChRs. From the biological data obtained within this study we, conclude that (+)-[18F]Flubatine is a very suitable radiotracer for the determination of the 42 nAChRs by kinetic modelling since plasma protein binding is moderate and the equilibrium between whole blood and plasma is reached instantaneously. Furthermore, metabolic degradation of the radiotracer is negligible.
  • Poster
    The 22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.-19.05.2017, Dresden, Germany

Registration No. 25802 - Permalink


Superconductivity with broken time-reversal symmetry in ion irradiated Ba0.27K0.73Fe2As2 single crystals
Grinenko, V.; Materne, P.; Sarkar, R.; Luetkens, H.; Kihou, K.; Lee, C. H.; Akhmadaliev, S.; Efremov, D. V.; Drechsler, S.-L.; Klauss, H.-H.
Corresponding author: Grinenko, V. Institute for Solid State Physics, TU Dresden / IFW Dresden, Germany
Abstract: Over the last years a lot of theoretical and experimental efforts have been made to find states with broken time reversal symmetry (BTRS) in multi-band superconductors. In particular, it was theoretically proposed that in the Ba1−xKxFe2As2 system either an s + is or an s + id BTRS state may exist at high doping levels in a narrow region of the phase diagram. Here we report the observation of an enhanced zero field muon spin relaxation rate below the superconducting transition temperature for a high quality crystalline sample with x ≈ 0.73. This indicates that indeed the time reversal symmetry is broken in superconducting Ba1−xKxFe2As2 at this doping level.

Registration No. 25800 - Permalink


Positioning of cobalt atoms in amorphous carbon films by pre-selecting the hydrogen concentration
Gupta, P.; Williams, G. V. M.; Vajandar, S.; Osipowicz, T.; Becker, H.-W.; Heinig, K.-H.; Hübner, R.; Leveneur, J.; Kennedy, J.; Markwitz, A.
Corresponding author: Markwitz, A. National Isotope Centre, GNS Science, Lower Hutt, New Zealand
Abstract: Amorphous carbon and hydrogenated amorphous carbon layers were implanted at room temperature with Co ions to investigate the role of hydrogen on the Co distribution. Amorphous carbon (a:C) and hydrogenated amorphous carbon (a:C-H) films were prepared by mass selective ion beam deposition with a 5 kV acceleration voltage using C+ and C3H6+ ions, respectively. The typically 100 nm thin films were implanted with Co using a 30 kV acceleration voltage to a fluence of 4×1016 cm-2. Raman measurements showed that Co implantation in hydrogenated amorphous carbon causes increased sp2 clustering while in amorphous carbon there is significant rehybridisation of carbon from sp3 to sp2 bonding. High resolution Rutherford backscattering measurements indicated that in the absence of hydrogen in the base matrix, the implantation profile assumes a unimodal distribution as predicted by simulations. However, in the presence of hydrogen the effects of collision cascade enhanced diffusion are significant in altering the implantation profile resulting in a bimodal distribution. The difference in the Co depth distribution between a:C and a:C-H films is explained by the change in thermal conductivity of the carbon matrix in the presence of hydrogen. The ability to position Co (magnetic atoms) in the surface region of diamond-like carbon films offers great advantages for applications in novel magnetic devices.
Keywords: Atomic positioning, Bimodal distribution, Cobalt implantation, Diamond-like carbon, Hydrogen

Registration No. 25794 - Permalink


Bispidine ligands for the potential application in nuclear medicine
Comba, P.; Pietzsch, J.; Rück, K.; Starke, M.; Stephan, H.; Wadepohl, H.
Corresponding author: Comba, P. Universität Heidelberg
Abstract: Objectives
An important part of radiopharmaceuticals containing radiometals is the so-called bifunctional chelator (BFC). Bispidine ligands (3,7-diazabicyclo[3.3.1]nonane) (see Figure 1) developed in the Comba group are perfectly suited BFCs for the application in nuclear medicine. Due to their preorganisation and rigidity of the backbone with the donor atoms N3 and N7 they generally form complexes fastly and with high stability.[1]
Methods
By choosing suitable moieties at position R1 and R2 and by fine tuning of the pyridyl groups at C2 and C4,[2] bispidines can be tailored for the complexation of many different metal ions. Coupling to vector entities is performed at the ester groups at C1/5 or the hydroxyl group at C9.[3-4] One of the applications for bispidine ligands is 64CuII PET imaging (positron emission tomography).[3,5] We design bispidine ligand systems for PET and evaluate their potential in radiolabeling experiments and stability studies.
Results
First in vitro and in vivo studies show the high potential of the bispidine chelators for PET application.[3] The hexadentate ligands N2Py4, N2Py3Pdz and the isomers Hbispa1a/b with pyridyl, pyridazyl or picolinic acid groups at R1 and/or R2 (see Figure 1) are promising BFCs for 64CuII PET imaging.[6-7]
Conclusions
The hexadentate ligands shown in Figure 1 and derivatives are further investigated regarding the application in nuclear medicine.
References
[1] P. Comba, M. Kerscher, W. Schiek, Prog Inorg Chem 2007, 55, 613-704.
[2] P. Comba, S. Hunoldt, M. Morgen, J. Pietzsch, H. Stephan, H. Wadepohl, Inorg Chem 2013, 52, 8131-8143.
[3] S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem 2009, 20, 347-359.
[4] H. Stephan, M. Walther, S. Fahnemann, P. Ceroni, J. K. Molloy, G. Bergamini, F. Heisig, C. E. Muller, W. Kraus, P. Comba, Chem-Eur J 2014, 20, 17011-17018.
[5] A. Roux, A. M. Nonat, J. Brandel, V. Hubscher-Bruder, L. J. Charbonniere, Inorg Chem 2015, 54, 4431-4444.
[6] C. Bleiholder, H. Borzel, P. Comba, R. Ferrari, M. Heydt, M. Kerscher, S. Kuwata, G. Laurenczy, G. A. Lawrance, A. Lienke, B. Martin, M. Merz, B. Nuber, H. Pritzkow, Inorg Chem 2005, 44, 8145-8155.
[7] P. Comba, L. Grimm, C. Orvig, K. Rück, H. Wadepohl, Inorg Chem 2016, manuscript accepted.
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Germany
  • Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)Suppl 1, S500
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

Registration No. 25791 - Permalink


Optical Synchronization and Electron Bunch Diagnostic at ELBE
Kuntzsch, M.
Abstract: The talk summarizes the activities at ELBE in the fields of optical synchronization and electron bunch diagnostic.
Keywords: Optical Synchronization Diagnostic ELBE
  • Invited lecture (Conferences)
    Graduiertenkolleg "Accelence", 06.07.2017, Mainz, Deutschland

Registration No. 25781 - Permalink


DFO* - An Improved Chelating System for 89Zr-Immuno-PET Applications
Briand, M.; Zarschler, K.; Vugts, D.; Stephan, H.; Steinbach, J.; Gasser, G.; Mindt, T.
Abstract: Objectives
The potential of 89Zr-labelled antibodies as diagnostic probes for 89Zr-immuno-PET has been demonstrated by a number of clinical trials.[1] The only chelator used thus far in the clinic is the siderophore desferrioxamine (DFO). However, DFO does not satisfy the preferred ocatadentate coordination of zirconium-89, which results in vivo into unspecific uptake of the radiometal in, e.g., the bones. This can interfere with the detection of bone metastases and leads to additional radiation dose to non-targeted tissue.
We have previously reported the development of an extended, octadentate version of DFO, termed DFO*,[2] which provides complexes with [89Zr]Zr4+ of remarkably increased stability in vitro and in vivo. [2, 3] DFO* and derivatives thereof already fulfil a number of prerequisites to become a new standard chelator for zirconium-89; however, its solubility could be improved to facilitate further its application in conjugation chemistry. We here wish to report our efforts in developing novel DFO* derivatives which display an improved water solubility.

Methods
Based on the DFO* scaffold, new derivatives containing pharmacological modifiers to improve the water solubility were synthesized. In addition, different functional groups for bioconjugation chemistry were included. LogP values of the novel bifunctional chelating agents were determined by HPLC. First bioconjugations and radiolabelling experiments with 89Zr were performed according to published procedures. [1,3]

Results
All new derivatives exhibited an increased hydrophilicity and thus, enhanced water solubility in comparison to the original DFO* (as well as DFO) system. Preliminary results on their reactivity in bioconjugations, capability of 89Zr-complexation, and stability of radiometal complexes will be reported.

Conclusions
Structural modifications provided novel derivatives of DFO* with improved water solubility which could facilitate their application in bioconjugation chemistry for the 89Zr-labelling of delicate proteins under aqueous (e.g., organic solvent free) reaction conditions.

Acknowledgements
This work is supported by the Swiss National Sciences Foundation (grant N° 205321–157216).

References
[1] G.A.M.S. Van Dongen, M.C. Huisman, R. Boellaard et al. Q. J. Nucl. Med. Mol. Imaging 2015, 59, 18-38
[2] M. Patra, A. Bauman, C. Mari et al. Chem. Commun. 2014, 50, 11523-11525
[3] D. Vugts, C. Klaver, C. Sewing et al. Eur. J. Nucl. Med. Mol. Im. 2016, doi:10.1007/s00259-016-3499-x S394: Poster 22nd International Symposium on Radiopharmaceutical Sciences
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), 14.-19.05.2017, Dresden, Deutschland

Registration No. 25778 - Permalink


Biasing in MC transport calculations
Müller, S. E.ORC
Abstract: The method of biasing in radiation transport simulations is described.
Keywords: Radiation transport, variance reduction, biasing, simulation
  • Lecture (others)
    Mu2e software and simulations workshop, 21.06.2017, Batavia, USA

Registration No. 25771 - Permalink


The use of FLUKA in the Mu2e experiment
Müller, S. E.ORC
Abstract: The use of FLUKA in the mu2e experiment
Keywords: FLUKA, mu2e
  • Lecture (others)
    Mu2e Sotware and Simulation Meeting, 07.06.2017, Batavia, USA

Registration No. 25770 - Permalink


Preliminary combination of the KLOE08, KLOE10 KLOE12 ISR measurements
Keshavarzi, A.; Müller, S. E.ORC; Teubner, T.; Venanzoni, G.
Abstract: Preliminary combination of the KLOE08, KLOE10 KLOE12 ISR measurements
Keywords: KLOE, g-2, hadronic contribution
  • Invited lecture (Conferences)
    First Workshop of the muon g-2 Theory Initiative, 04.06.2017, St. Charles, USA

Registration No. 25768 - Permalink


Energy Transfer Kinetics in Photosynthesis as an Inspiration for Improving Organic Solar Cells
Nganou, C.; Lackner, G.; Teschome, B.; Deen, M. J.; Adir, N.; Pouhe, D.; Lupascu, D. C.; Mkandawire, M.
Corresponding author: Mkandawire, M. Verschuren Centre for Sustainability in Energy and the Environment, Cape Breton University, 1250 Grand Lake Road, Sydney, NS, Canada
Abstract: Clues to designing highly efficient organic solar cells may lie in understanding the architecture of light-harvesting systems and exciton energy transfer (EET) processes in very efficient photosynthetic organisms. Here, we compare the kinetics of excitation energy tunnelling from the intact phycobilisome (PBS) light-harvesting antenna system to the reaction center in photosystem II in intact cells of the cyanobacterium Acaryochloris marina with the charge transfer after conversion of photons into photocurrent in vertically aligned carbon nanotube (va-CNT) organic solar cells with poly(3-hexyl)thiophene (P3HT) as the pigment. We find that the kinetics in electron hole creation following excitation at 600 nm in both PBS and va-CNT solar cells to be 450 and 500 fs, respectively. The EET process has a 3 and 14 ps pathway in the PBS, while in va-CNT solar cell devices, the charge trapping in the CNT takes 11 and 258 ps. We show that the main hindrance to efficiency of va-CNT organic solar cells is the slow migration of the charges after exciton formation.
Keywords: Acaryochloris marina carbon nanotubes chromophore exciton photosynthesis photovoltaic polarons solar energy conversion

Registration No. 25765 - Permalink


Liquid metal based magnetic cooling: velocity measurements
Lei, Z.; Raebiger, D.; Eckert, S.; Eckert, K.ORC
Corresponding author: Lei, Z.
Abstract: Heat transfer enhancement in a segment of the active magnetic regenerator (AMR), consisting of a magnetocaloric material (Gadolinium) and a heat transfer fluid in between, which is periodically magnetized and demagnetized, is investigated in this work. After giving a brief account on how magnetohydrodynamic (MHD) convection can be used to enhance the heat transfer from flat plate gadolinium toward the heat transfer fluid we apply two different techniques for MHD flow generation. In the first approach, an electric current I was injected into an electrically conducting, aqueous heat transfer fluid (NaOH). A heat transfer enhancement of about 40% (I=3mA) was found by means of a Mach-Zehnder interferometer. In the second approach, a liquid metal (GaInSn) was used which is potentially an interesting candidate for a heat transfer fluid in an AMR operating with high cycling frequency. Velocity measurements by means of ultrasound doppler velocimetry with a quasi uniform static magnetic field (220mT) in the gadolinium channel are presented.
  • Magnetohydrodynamics 53(2017)2, 403-410

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  • Secondary publication expected from 10.07.2018

Registration No. 25761 - Permalink


Laser spectroscopy measurement of the 2s-hyperfinesplitting in lithium-like bismuth
Sánchez, R.; Lochmann, M.; Jöhren, R.; Andelkovic, Z.; Anielski, D.; Botermann, B.; Bussmann, M.; Dax, A.; Frömmgen, N.; Geppert, C.; Hammen, M.; Hannen, V.; Kuehl, T.; Litvinov, Y.; Coto, R. L.; Stoehlker, T.; Thompson, R.; Vollbrecht, J.; Wen, W.; Weinheimer, C.; Will, E.; Winters, D.; Noertershaeuser, W.
Corresponding author: Sánchez, R.
Abstract: We have recently reported on the first direct measurement of the 2s hyperfine transition in lithium-like bismuth (209Bi80+) at the GSI Helmholtz Centrefor Heavy Ion Research (GmbH) in Darmstadt, Germany. Combined with a newmeasurement of the 1s hyperfine splitting in hydrogen-like (209Bi82+) the so-called specific difference Δ’E = -61.37(36) meV could be determined and was found to bein good agreement with its prediction from strong-field bound-state QED. Here wereport on additional investigations performed to estimate systematic uncertainties of these results and on details of the experimental setup. We show that the dominating uncertainty arises from insufficient knowledge of the ion beam velocity which is determined by the electron-cooler (voltage). Two routes to obtain a cooler-voltage calibration are discussed and it is shown that agreement can be reached either of the experimental Δ’E with the theoretical result, or between the two measurements of the hyperfine splitting in hydrogen-like bismuth, but not both at the same time.
Keywords: qed, spectroscopy, bismuth, hyperfine, lithium-like, storage ring, laser

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  • Secondary publication expected from 29.03.2018

Registration No. 25756 - Permalink


Simulations of a precession driven flow in a cylindrical cavity
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.; Herault, J.
Abstract: The project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) conducted at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) provides a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics [1]. The most ambitious experiment will be a dynamo experiment which consists of a large precessing cylindrical cavity filled with liquid sodium. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo [2] or the ancient lunar dynamo [3].

Our presentation addresses corresponding hydrodynamic simulations that provide characteristic properties of the precession-driven flow such as amplitudes or helicity and their implications for the dynamo effect. Our results show that the primary response of the fluid to the precession is an azimuthally rotating inertial wave, called Kelvin mode [4]. Increasing the precession ratio the fundamental Kelvin mode becomes unstable which goes along with the emergence of two free inertial waves due to a parametric resonance caused by the periodic perturbation of the primary flow [5]. The free inertial waves only exist within a narrow range of rather small precession ratios because increasing non-linear interactions give rise to the formation of an azimuthal circulation flow which alters the resonance condition (detuning effect) [6].

For large precession ratios, instead, we find a clear signature of Kelvin modes with the frequency of the forcing and higher azimuthal and/or axial wave numbers. In the turntable frame these Kelvin modes correspond to standing inertial waves that are caused by non-linear self-interaction of the fundamental forced mode. The contributions of these modes provide a breaking of the parity with respect to the equatorial plane which has proven to be beneficial for dynamo action [7].

Further considerations on the dynamo-ability of the precession driven flow require larger Reynolds numbers which are numerically no longer accessible. Therefore, they have to be based solely on data from the downscaled water experiment that currently is running at HZDR in preparation for the large liquid sodium facility (see contribution of T. Vogt). Comparisons of our simulations with experimental data from Ultrasonic Doppler Velocimetry (UDV) measurements at similar Reynolds number show a surprisingly good consistency thus providing a basis for the development of flow models at larger Reynolds numbers for future kinematic dynamo models.

[1] Stefani, F. et al., Magnetohydrodynamics, 48 (1), 103--114, 2012.
[2] Malkus, W. V. R., Science, 160, 259--264, 1968.
[3] Noir, J., and D. C{\'e}bron, J. Fluids Mech., 737, 412--439, 2013.
[4] Thomson W, Phil. Mag. J. Sci. 10 (61), 155--168, 1880.
[5] Kerswell, R. R., J. Fluids Mech., 382, 283--306, 1999.
[6] Herault, J. et al., Phys. Rev. Fluids, in preparation, 2017.
[7] Tilgner, A., Phys. Fluids, 17 (3), 034, 104, 2005.
Keywords: Dynamo DRESDYN precession
  • Lecture (Conference)
    Natural Dynamos, 26.-30.06.2017, Valtice, Tschechien

Registration No. 25753 - Permalink


Solvent extraction: fundamental equilibrium studies of neodymium and DEHPA
Scharf, C.; Ditze, A.
Abstract: This article presents equilibrium studies into the NdCl3–HCl (or NaOH)–H2O–DEHPA (di-(2-ethylhexyl) phosphoric acid)–kerosene system. The system plays a role in solvent extraction of rare earth elements from aqueous chloride solutions. Thereby neodymium is transferred into the organic phase consisting of DEHPA solved in kerosene. Measurements were taken at DEHPA concentrations between 1 and 40 vol.% and at concentrations of neodymium which prevent a gelatinous organic phase. Results are presented in tables. Three charts of process variables were evaluated which, under the assumption of ideal behaviour, should lead to slopes of 3 in double logarithmic scale in all three cases. Since the actual slopes of measured variables were 2.4, 2.5 and 3.8, ideal behaviour is only a first approximation, and non-ideal aspects need to be further studied. The plot of percentage extraction versus pH shows that neodymium is completely extracted at pH values above 1.
Keywords: solvent extraction / equilibrium system / neodymium / DEHPA / law of mass action

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Registration No. 25749 - Permalink


Experimental analysis of Taylor bubble behavior and mass transfer during lateral oscillation of a vertical milli-channel
Haghnegahdar, M.; Boden, S.; Hampel, U.
Corresponding author: Haghnegahdar, Mohammadreza Institute of Fluid Dynamics
Abstract: In this paper, we report on an experimental study on the influence of low-frequency horizontal vibration of a vertical millimeter-size channel with Taylor bubbles. We investigated the motion, shape and dissolution rate of individual elongated Taylor bubbles of air and CO2, which were freely rising in stationary water. Bubble size and dissolution rate were determined from microfocus X-ray radiographs. From the shrinking rate we calculated the liquid-side mass transfer coefficient. The rise velocity of bubbles and surface wave motion were analyzed using a videometric technique. The comparison of the results for the stationary and the oscillating channel showed that mechanical vibration of the channel is able to enhance the mass transfer coefficient from gas to the liquid phase by 80% to 186%, depending on the frequency and amplitude of vibration. It was found that channel oscillation causes the increase of free rise velocity of bubbles which is mainly attributed to the development of propelling interfacial waves and increase of liquid film flow rate. Furthermore, analyzing the surface wave motion of bubbles revealed that the enlargement of contact area between the phases and the increased mixing enhances the mass transfer additionally up to 30% compared to non-agitated bubbles of similar Peclet number.
Keywords: Vibration; Milli-channels; Mass transfer; Taylor bubble; Carbon dioxide

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  • Secondary publication expected from 23.05.2018

Registration No. 25746 - Permalink


Combining dynamic modelling codes with medium energy ion scattering measurements to characterise plasma doping
England, J.; Möller, W.; van den Berg, J. A.; Rossall, A.; Min, W. J.; Kim, J.
Corresponding author: England, J. Varian Semiconductor Equipment, Silicon Systems Group, Applied Materials Inc., USA
Abstract: Plasma doping ion implantation (PLAD) is becoming increasingly important in the manufacture of advanced semiconductor device structures but a fundamental understanding of PLAD is complicated. A model of PLAD into planar substrates has been constructed using the one dimensional computer code TRIDYN to predict collision cascades and hence substrate compositional changes during implantation. Medium Energy Ion Scattering (MEIS) measurements of dopant profiles in PLAD processed samples were used to calibrate the input ion and neutral fluxes to the model. Rules could then be proposed for how post implant profiles should be modified by a cleaning step. This learning was applied to a three dimensional TRI3DYN based model for PLAD implants into FinFET like structures. Comparison of the model to dopant profile measurements made by time of flight (TOF)-MEIS revealed the angular distributions of neutral species and doping mechanisms acting in three dimensional structures.
Keywords: FinFET, Ion beam modelling, Ion-Implantation, PLAD, Plasma Doping, TRI3DYN, TRIDYN

Registration No. 25743 - Permalink


Roughness-induced domain structure in perpendicular Co/Ni multilayers
Lee-Hone, N. R.; Thanhoffer, R.; Neu, V.; Schäfer, R.; Arora, M.; Hübner, R.; Suess, D.; Broun, D. M.; Girt, E.
Corresponding author: Lee-Hone, N. R. Simon Fraser University
Abstract: We investigate the correlation between roughness, remanence and coercivity in Co/Ni films grown on Cu seed layers of varying thickness. Increasing the Cu seed layer thickness of Ta/Cu/8×[Co/Ni] thin films increases the roughness of the films. In-plane magnetization loops show that both the remanence and coercivity increase with increasing seed layer roughness. Polar Kerr microscopy and magnetic force microscopy reveal that the domain density also increases with roughness. Finite element micromagnetic simulations performed on structures with periodically modulated surfaces provide further insight. They confirm the connection between domain density and roughness, and identify the microsocpic structure of the domain walls as the source of the increased remanence in rough films. The simulations predict that the character of the domain walls changes from Bloch-like in smooth films to Néel-like for rougher films
Keywords: Domain density, Domain structure, In-plane magnetization, Micromagnetic simulations, Modulated surfaces, Polar-Kerr, Seed layer thickness, Varying thickness

Registration No. 25741 - Permalink


High-field ESR in low-D spin systems
Zvyagin, S.
  • Invited lecture (Conferences)
    L. A. Prozorova Workshop on Spin Dynamics, 17.-18.05.2017, Moscow, Russia

Registration No. 25739 - Permalink


The determination of the fast neutron-induced fission cross section of Pu(242) at nELBE
Kögler, T.; Beyer, R.; Junghans, A. R.; Müller, S. E.; Schwengner, R.; Wagner, A.
Abstract: The fast neutron-induced fission cross section of 242Pu was determined in the range of 0.5 MeV to 10 MeV relative to 235U(n,f) at the neutron time-of-flight facility nELBE. The number of target nuclei was calculated by means of measuring the spontaneous fission rate of 242Pu. Neutron transport simulations with Geant 4 and MCNP 6 are used to correct the relative cross section for neutron scattering. The determined results are in good agreement with current experimental and evaluated data sets.
Keywords: neutron-induced fission cross section, neutron scattering corrections, fast neutrons, nELBE
  • Invited lecture (Conferences)
    Scientific Workshop on Nuclear Fission dynamics and the Emission of Prompt Neutrons and Gamma Rays, 19.-23.06.2017, Varna, Bulgaria

Registration No. 25737 - Permalink


Enhancement of superconductivity in FeSe thin crystals induced by biaxial compressive strain
Wang, X. F.; Zhang, Z. T.; Wang, W. K.; Zhou, Y. H.; Kan, X. C.; Chen, X. L.; Gu, C. C.; Zhang, L.; Pi, L.; Yang, Z. R.; Zhang, Y. H.
Corresponding author: Wang, X. F. High Magnetic Field Laboratory, Chinese Academy of Sciences
Abstract: We report on the enhancement of superconductivity in FeSe thin crystals induced by in-plane biaxial compressive strain, with an underlying scotch tape as an in-situ strain generator. It is found that, due to the compressive strain, the superconducting transition temperature Tc ≈ 9 K of FeSe is increased by 30%–40% and the upper critical field Hc2(0) ≈ 14.8 T is increased by ∼ 20%. In parallel, the T*, which characterizes an onset of enhanced spin fluctuations, is raised up from 69 K to 87 K. On the other hand, the structural transition temperature Ts ≈ 94 K, below which an orthorhombic structure and an electronic nematic phase settle in, is suppressed down by ∼ 5 K. These findings reveal clear evolutions of the orders/fluctuations under strain effect in FeSe, the structurally simplest iron-based superconductor where the lattice/spin/charge degrees of freedom are closely coupled to one another. Moreover, the presented research provides a simple and clean way to manipulate the superconductivity in the layered iron compounds and may promote applications in related materials. © 2017 Elsevier B.V.
Keywords: Biaxial compressive strains; FeSe; Superconductivity

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Registration No. 25736 - Permalink


Ultrasonic Study on the Hexagonal Antiferromagnet Dy3Ru4Al12
Ishii, I.; Takezawa, K.; Goto, H.; Kamikawa, S.; Andreev, A. V.; Gorbunov, D. I.; Henriques, M. S.; Suzuki, T.
Corresponding author: Ishii, I. Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, Japan
Abstract: In the distorted kagome lattice antiferromagnet Dy3Ru4Al12 with TN = 7 K, a crystal electric field (CEF) effect is expected at high temperatures. To investigate the CEF effect and the phase transition at TN, we performed ultrasonic measurements on a single-crystalline sample. At high temperatures, both the longitudinal elastic modulus C11 and the transverse modulus C44 increase monotonically with decreasing temperature. Below 60 K a characteristic elastic softening is observed in C44 in contrast to C11 with monotonic hardening down to TN. We analyzed C44 using the Curie-Weiss-type equation and obtained a negative parameter: Θ which is proportional to a quadrupole-quadrupole coupling constant under the hexagonal CEF. With further decreasing temperature, both moduli exhibit abrupt elastic hardening at TN due to a magnetostriction.

Registration No. 25735 - Permalink


Manifestation of the Jahn-Teller effect in elastic moduli of strontium fluorite crystals doped with chromium ions
Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.
Corresponding author: Gudkov, V. V. Ural Federal University, Ekaterinburg, Russia
Abstract: Attenuation and phase velocity of ultrasound have been measured in strontium fluoride single crystal doped with chromium in the temperature range of 4 – 185 K at 56 -162 MHz. Anomalies have been found for all the normal modes corresponding to the non-vanishing elastic moduli of a cubic crystal. Interpretation of the observed anomalies has been done in the frame work of relaxation in the system of Jahn-Teller (JT) complexes CrF8 subject to full T2g X (eg+t2g)JT problem. Relaxation time has been calculated from the experimental data on ultrasonic attenuation and adiabatic and isothermal contributions of the impurity subsystem to the total elastic moduli have been obtained.

Registration No. 25732 - Permalink


Anisotropic physical properties of single-crystal U2Rh2Sn in high magnetic fields
Prokes, K.; Gorbunov, D. I.; Reehuis, M.; Klemke, B.; Gukasov, A.; Uhlirova, K.; Fabreges, X.; Skourski, Y.; Yokaichiya, F.; Hartwig, S.; Andreev, A. V.
Corresponding author: Prokes, K. Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
Abstract: We report on the crystal and magnetic structures,magnetic, transport, and thermal properties of U2Rh2Sn single crystals studied in part in high magnetic fields up to 58 T. The material adopts a U3Si2-related tetragonal crystal structure and orders antiferromagnetically below TN = 25 K. The antiferromagnetic structure is characterized by a propagation vector k = (0 0 1/2). The magnetism in U2Rh2Sn is found to be associated mainly with 5f states. However, both unpolarized and polarized neutron experiments reveal at low temperatures in zero field non-negligible magnetic moments also on Rh sites. U moments of 0.50(2) μB are directed along the tetragonal axis while Rh moments of 0.06(4) μB form a noncollinear arrangement confined to the basal plane. The response to applied magnetic field is highly anisotropic. Above ∼15 K the easy magnetization direction is along the tetragonal axis. At lower temperatures, however, a stronger response is found perpendicular to the c axis. While for the a axis no magnetic phase transition is observed up to 58 T, for the field applied at 1.8 K along the tetragonal axis we observe above 22.5 T a field-polarized state. A magnetic phase diagram for the field applied along the c axis is presented.

Registration No. 25731 - Permalink


Nuclear Magnetic Resonance Signature of the Spin-Nematic Phase in LiCuVO4 at High Magnetic Fields
Orlova, A.; Green, E. L.; Law, J. M.; Gorbunov, D. I.; Chanda, G.; Krämer, S.; Horvatic, M.; Kremer, R. K.; Wosnitza, J.; Rikken, G. L. J. A.
Corresponding author: Green, E. L. Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report a 51V nuclear magnetic resonance investigation of the frustrated spin-1/2 chain compound LiCuVO4, performed in pulsed magnetic fields and focused on high-field phases up to 56 T. For the crystal orientations H‖c and H‖b, we find a narrow field region just below the magnetic saturation where the local magnetization remains uniform and homogeneous, while its value is field dependent. This behavior is the first microscopic signature of the spin-nematic state, breaking spin-rotation symmetry without generating any transverse dipolar order, and is consistent with theoretical predictions for the LiCuVO4 compound.

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Registration No. 25729 - Permalink


Completely compensated ferrimagnetism and sublattice spin crossing in the half-metallic Heusler compound Mn1.5FeV0.5Al
Stinshoff, R.; Nayak, A. K.; Fecher, G. H.; Balke, B.; Ouardi, S.; Skourski, Y.; Nakamura, T.; Felser, C.
Corresponding author: Nayak, A. K. Max Planck Institute for Chemical Physics of Solids, Dresden & Max Planck Institute of Microstructure Physics, Halle, Germany
Abstract: The Slater-Pauling rule states that L21 Heusler compounds with 24 valence electrons never exhibit a total spin magnetic moment. In the case of strongly localized magnetic moments at one of the atoms (here Mn) they will exhibit a fully compensated half-metallic ferrimagnetic state instead, in particular, when symmetry does not allow for antiferromagnetic order. With the aid of magnetic and anomalous Hall effect measurements, it is experimentally demonstrated that Mn1.5V0.5FeAl follows such a scenario. The ferrimagnetic state is tuned by the composition. A small residual magnetization, which arises due to a slight mismatch of the magnetic moments in the different sublattices, results in a pronounced change of the temperature dependence of the ferrimagnet. A compensation point is confirmed by observation of magnetic reversal and sign change of the anomalous Hall effect. Theoretical models are presented that correlate the electronic structure and the compensation mechanisms of the different half-metallic ferrimagnetic states in the Mn-V-Fe-Al Heusler system.

Registration No. 25728 - Permalink


Sediment-bound trace metals in Golfe-Juan Bay, northwestern Mediterranean: Distribution, availability and toxicity
Tiquio, M. G. J.; Hurel, C.; Marmier, N.; Taneez, M.; Andral, B.; Jordan, N.; Francour, P.
Corresponding author: Tiquio, M. G. J. Université Côte d´Azur, CNRS, Ecomers, France
Abstract: The concentration, potential mobility, cation exchange capacity and toxicity of eight sediment-bound metals in Golfe-Juan Bay, France were examined. Results revealed significant spatial gradient of metal contamination along Golfe-Juan coast. The distribution and concentration of the metals appear to be influenced by the geochemical properties of the sediment, proximity to anthropogenic sources and general water circulation in the bay. The portion of trace metals found in the exchangeable, carbonate, oxidizable and reducible fractions of the sediment constitute 31%-58% ofthe total sediment-bound trace metal content, suggesting significant potential for remobilization of metals into the water column. Pb and Ni content ofthe sediment exceed the limits ofthe French marine sediment quality. Whole sediment extracts showed acute toxicity to marine rotifers. This study concludes that monitoring and management ofsediment-bound trace metals in Golfe-Juan Bay are important so as not to underestimate their availability and risk to the marine ecosystems.
Keywords: trace metals, sediment, mussels, remobilization

Registration No. 25727 - Permalink


Synthesis and radiopharmacological evaluation of a novel 18F-labeled cyclooxygenase-2 inhibitor based on dihydropyrrolo[3,2,1-hi]indole core structure
Laube, M.; Gassner, C.; Neuber, C.; Bergmann, R.; Kniess, T.; Steinbach, J.; Pietzsch, J.
Corresponding author: Laube, M.
Abstract: Objectives
Cyclooxygenase-2 (COX-2), a key player in inflammation, is an attractive target for functional characterization of solid tumors by PET because its overexpression has been associated with chemo-/radioresistance and poor prognosis in cancer. We recently developed a novel series of selective COX-2 inhibitors based on a tricyclic core structure with IC50 values in the nanomolar range1 and herein report on the 18F-labeling and evaluation of a promising candidate.
Methods
5-(4-[18F]Fluorophenyl)-4-[4-(methylsulfonyl)phenyl]-1,2-dihydropyrrolo[3,2,1-hi]indole ([18F]2) was synthesized according to our recently reported 18F-fluorination and McMurry cyclization approach2 with modifications reported herein. [18F]2 was evaluated in vitro in cell lines with different COX-1/COX-2 expression patterns. In vivo dynamic small animal PET imaging and biodistribution studies were performed in NMRI nu/nu mice bearing a COX-2-positive A2058 tumor-xenograft.
Results
18F-Fluorination under standard conditions2 was hampered by basic hydrolysis leading primarily to side product [18F]1b. Optimization experiments focused on the use of different bases with varying concentrations (K2CO3, KHCO3, KH2PO4) or no base using the ‘minimalist approach’3. As one result, the use of decreased amounts of K2CO3 (5 instead of 20 μmol) effectively suppressed hydrolysis and gave [18F]1a in high yield (Figure 1). An automated synthesis comprising mild 18F-fluorination, McMurry cyclization, and purification using a TracerLabFX-N module provided [18F]2 in 16% isolated RCY (d.c.) with a molar activity of 45-106 GBq/μmol at EOS. A LogDpH7.4 of 4.66 and a CHI IAM value of 48 indicated high lipophilicity and non-specific binding. Cell uptake was independent of COX-2 expression. Biodistribution and PET studies revealed highest uptake of [18F]2 in liver and adipose tissue but only low accumulation in A2058 tumors (tumor/muscle < 1) at 60 min post injection. Celecoxib pre-injection (20 mg/kg) did not significantly change tumor uptake although a trend towards decreased radiotracer uptake was observed by PET in a subset of mice.
Conclusions
Despite of a high COX-2 selectivity and metabolic stability, [18F]2 did not emerge as suitable radiotracer for imaging COX-2 in vitro and in vivo, likely due to its high lipophilicity and fast hepatobiliary excretion.4 Future efforts for the development of COX-2-targeted radiotracers should focus on adaption of lipophilicity and/or use of targeted delivery systems.
References
1Laube et al. J. Org. Chem. 2015, 80, 5611-5624. 2Kniess et al. Biorg. Med. Chem. 2012, 20, 3410-3421. 3Richarz et al. Org. Biomol. Chem. 2014, 12, 8094-8099. 4Gassner et al. ChemistrySelect, 2016, 1, 5812–5820.
Figure 1.: Radiosynthesis of [18F]2 by 18F-fluorination and McMurry cyclization. S156: Poster 22nd International Symposium on Radiopharmaceutical Sciences
J

Registration No. 25721 - Permalink


Celecoxib based fluorine-18 radiolabelled probes for cyclooxygenase-2 monitoring - COX-2 affinity, radiosynthesis and in vitro studies.
Kniess, T.; Bechmann, N.; Steinbach, J.; Pietzsch, J.
Corresponding author: Kniess, Torsten
Abstract: kein Abstract verfügbar

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  • Secondary publication expected from 14.05.2018

Registration No. 25718 - Permalink


Radio-U(H)PLC - the optimal flow cell for the gamma-detector ?
Kniess, T.; Fischer, S.; Ludwig, F.-A.; Steinbach, J.
Corresponding author: Kniess, Torsten
Abstract: kein Abstract verfügbar

Downloads:

  • Secondary publication expected from 14.05.2018

Registration No. 25717 - Permalink


Hydrous 18F-Fluoroethylation - leaving off the azeotropic drying
Kniess, T.; Laube, M.; Steinbach, J.
Corresponding author: Kniess, Torsten
Abstract: kein Abstract verfügbar

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  • Secondary publication expected from 14.05.2018

Registration No. 25716 - Permalink


Immersed transient eddy current flow metering: a calibration-free velocity measurement technique for liquid metals
Krauter, N.; Stefani, F.
Corresponding author: Krauter, Nico HZDR
Abstract: Eddy current flow meters (ECFM) are widely used for measuring the flow velocity of electrically conducting fluids. Since the flow induced perturbations of a magnetic field depend both on the geometry and the conductivity of the fluid, extensive calibration is needed to get accurate results. Transient eddy current flow metering (TECFM) has been developed to overcome this problem. It relies on tracking the position of an impressed eddy current system which is moving with the same velocity as the conductive fluid. We present an immersed version of this measurement technique and demonstrate its viability by numerical simulations and a first experimental validation.
Keywords: flow measurement, inductive methods, calibration-free

Registration No. 25714 - Permalink


Actinide Bonding Analysis in Position Space
Patzschke, M.
Abstract: Actinides are a fascinating class of elements. They are difficult to work with in the laboratory, but they are also very challenging for the theoretician. The open f-shell sometimes necessitates the use of multi-reference calculations. They contribute many electrons, making the calculation more demanding. And lastly, relativistic effects become important. These problems certainly contribute to the situation in which far less is known and understood about actinide chemistry compared to e.g. the lanthanides. In this contribution, we use analysis methods that work in real space, i.e. on the electronic density. We present different tools and the application to the bonding in BTP complexes on actinides and lanthanides . BTP complexes have been investigated for numerous years now and it is still not entirely understood, why they bind actinides more strongly than lanthanides. The presented data is hopefully a step towards the solution of that problem.
Keywords: DFT, CASPT2, Lanthanides, Actinides, Covalency
  • Poster
    Magical Mystery Tour of Electron Correlation - A Symposium in Honour of Jeppe Olsen on the Occasion of his 60th Birthday, 24.-27.10.2016, Oslo, Norwegen

Registration No. 25713 - Permalink


Modifications of the magnetization ordering in Co/Mo/Co layers by Ga+ ion irradiation
Wawro, A.; Kurant, Z.; Tekielak, M.; Jakubowski, M.; Pietruczik, A.; Böttger, R.; Maziewski, A.
Abstract: Molecular beam epitaxy-grown layered structures Co/Mo/Co exhibit an antiparallel coupling of Co films magnetization in the Mo spacer thickness range between 0.5 nm and 1.0 nm and parallel beyond this range. Magnetic properties are substantially modified by beam irradiation of 35 keV Gaþ ions. With the increase in ion fluence, antiparallel coupling switches to the parallel one. Further increase in fluence results in gradual suppression of ferromagnetic behavior of the system. Experimental results are correlated with numerical simulations of layered structure evolution driven by irradiation.
Keywords: ion irradiation, magnetic multilayers, molecular beam epitaxy, ion implantation

Registration No. 25709 - Permalink


Interactions of coolants with hot-dip galvanized materials after loss-of-coolant accidents in pressurized water reactors
Harm, U.; Kryk, H.; Hampel, U.
Abstract: During the sump recirculation phase after loss-of-coolant accidents (LOCA) in pressurized water reactors, coolant spilling out of the leak in the primary cooling circuit is collected in the reactor sump and recirculated to the reactor core by residual-heat removal pumps as part of the emergency core cooling system. The long-term contact of the boric acid containing coolant with hot-dip galvanized containment internals (e.g. grating treads, supporting grids of sump strainers) may cause corrosion of the corresponding materials.
Generic investigations regarding the influence of such corrosion processes on the coolant chemistry and possible resulting effects in the reactor core are subject of joint research projects of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), TU Dresden (TUD) and Zittau-Görlitz University of Applied Sciences (HSZG). Lab-scale experiments at HZDR and TUD are focused on elucidation of physico-chemical corrosion and precipitation processes [1].
Results of generic experiments in a lab-scale corrosion test facility suggest that there is a multi-stage corrosion process. The first stage comprises dissolution of the zinc layer in the coolant forming zinc ions and in turn affecting the coolant chemistry. During the second stage, the base material (steel) corrodes forming insoluble corrosion particles. The main influences on corrosion were identified as impact of the coolant leak jet onto the corroding surface, the coolant chemistry and the zinc surface / coolant volume ratio.
Furthermore, retrograde solubility of zinc corrosion products in boric acid containing coolants with increasing temperature was observed. Thus, formation and deposition of solid corrosion products cannot be ruled out if zinc containing coolant is heated up during its recirculation into hot downstream components (e.g. hot-spots in core). Corrosion experiments, which included formation of corrosion products at heated zircaloy cladding tubes, proved that zinc, dissolved in the coolant at low sump temperatures, turns into solid deposits of zinc borates when contacting heated zircaloy surfaces. Due to alternating heating and cooling of the coolant during sump recirculation operation, a cycle of zinc corrosion and zinc borate precipitation may be initiated.
Based on the experimental results, water chemical measures were tested to reduce corrosion and zinc borate precipitation effects [1]. Additionally, joint research projects have been established by the TUD and the HSZG dealing with local effects of corrosion, corrosion product precipitation and the interplay thereof at LOCA-specific conditions [1-2].
The investigations have been supported by the German Federal Ministry for Economic Affairs and Energy under contract nos. 1501363, 1501430, 1501467 and 1501496.

References
[1] Kryk, H. , Harm, U., Hampel, U.: Reducing in-core zink borate precipitation after loss-of-coolant accidents in pressurized water reactors, Proceedings of the Annual Meeting on Nuclear Technology (AMNT), Hamburg, 2016
[2] Seeliger, A.; Alt, S.; Kästner, W., Renger, S., Kryk, H., Harm, U. : Zinc corrosion after loss-of-coolant accidents in pressurized water reactors - thermo- and fluid- dynamic effects. Nuclear Engineering and Design, 2016, 305, 489-502
Keywords: Nuclear energy; Loss of coolant accident; corrosion; zinc release; experiments
  • Contribution to proceedings
    The Energy and Materials Research Conference (EMR 2017), 05.-07.04.2017, Lissabon (Lisbon), Portugal
    Book of Abstracts
  • Lecture (Conference)
    The Energy and Materials Research Conference (EMR 2017), 05.-07.04.2017, Lisabon (Lisbon), Portugal

Registration No. 25708 - Permalink


Where do the Actinides go? And why we should care…
Patzschke, M.
Abstract: Understanding the chemistry of actinides is crucial for the safety guarantees required for final repositories for nuclear waste. Pathways of distribution of actinides in the environment are discussed and calculations on model compounds to understand the bonding of actinides are presented.
Keywords: DFT, Real space analysis, actinide compounds
  • Invited lecture (Conferences)
    X. MMQC Mariapfarr, 06.-10.03.2017, Mariapfarr, Österreich

Registration No. 25703 - Permalink


Bond analysis of actinide complexes in real space
Patzschke, M.
Abstract: Subtle effects are important in the bonding of actinides. Understanding of these effects is crucial for the prediction of the fate of actinides in the environment. In this talk we will focus on QTAIM, NCI and ELI calculations to understand the difference in bonding between actinides and lanthanides.
Keywords: DFT, CASPT2, Real space analysis, QTAIM, ELF/ELI, NCI, actinide complexes
  • Invited lecture (Conferences)
    UCT und IOCB Seminar Prag, 31.03.2017, Prag, Tschechien

Registration No. 25702 - Permalink


Real Space Analysis of Ac-Ac bonds, the case of encaged U_2
Patzschke, M.
Abstract: Real space analysis of the chemical bond is a valuable tool for understanding the bonding in chemical compounds. Especially in the field of actinide complexes and actinide-actinide bonds, there is still much to be learned. In this talk we will shoe how encaged uranium is forced to bond and how the bond depends on the cage size.
Keywords: Real Space Analysis, DFT, CASPT2, Actinides
  • Invited lecture (Conferences)
    Chemical Bonding in Position Space, 27.11.-01.12.2016, Dresden, Deutschland

Registration No. 25701 - Permalink


Technetium Complexes with Arylselenolato and Aryltellurolato Ligands
Noschang Cabral, B.; Kirsten, L.; Hagenbach, A.; Piquini, P. C.; Patzschke, M.ORC; Schulz Lang, E.; Abram, U.
Corresponding author: Abram, U. Freie Universität Berlin, Institute of Chemistry and Biochemistry, Fabeckstr. 34/36, D-14195 Berlin, Germany
Abstract: Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates
give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl,
mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII
complexes) coordinated technetium atoms. Density Functional Theory calculations indicate that the Tc-chalcogen bonds in
the TcIII compounds have greater bond order than in the TcV compounds.
Keywords: Technetium, new compounds, crystal structure, DFT, bond analysis

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Registration No. 25700 - Permalink


Local aspects of hydrogen-induced metallization of the ZnO(10-10) surface
Deinert, J.-C.ORC; Hofmann, O. T.ORC; Meyer, M.; Rinke, P.ORC; Stähler, J.ORC
Corresponding author: Deinert, Jan-Christoph Fritz-Haber-Institut der Max-Planck-Gesellschaft
Abstract: This study combines surface-sensitive photoemission experiments with density functional theory to give a microscopic description of H-adsorption-induced modifications of the ZnO(10-10) surface electronic structure. We find a complex adsorption behavior caused by a strong coverage dependence of the H adsorption energies: Initially, O-H bond formation is energetically favorable and H acting as an electron donor leads to the formation of a charge accumulation layer and to surface metallization. The increase of the number of O-H bonds leads to a reversal in adsorption energies such that Zn-H bonds become favored at sites close to existing O-H bonds, which results in a gradual extenuation of the metallization. The corresponding surface potential changes are localized within a few nanometers both laterally and normal to the surface. This localized character is experimentally corroborated by using subsurface bound excitons at the ZnO(10-10) surface as a local probe. The pronounced and comparably localized effect of small amounts of hydrogen at this surface strongly suggests metallic character of ZnO surfaces under technologically relevant conditions and may, thus, be of high importance for energy level alignment at ZnO-based junctions in general.

Registration No. 25697 - Permalink


Using cosmogenic 10Be surface exposure dating to constrain the timing of deglaciation on the northern Swiss Plateau
Groos, A. R.; Struck, J.; Wüthrich, L.; Veit, H.; Gnägi, C.; Merchel, S.; Scharf, A.; Rugel, G.; Zech, R.
Keywords: LGM, AMS, 10Be Surface Exposure Dating
  • Poster
    Annual CH-QUAT Meeting Faculty of Science, University of Neuchâtel Topic: "Quaternary topics in the Jura Mountains and the Seeland region", 01.04.2017, Neuchâtel, Schweiz

Registration No. 25692 - Permalink


Structural Distortions and Charge Density Waves in Iodine Chains Encapsulated inside Carbon Nanotubes
Komsa, H.-P.; Senga, R.; Suenaga, K.; Krasheninnikov, A. V.ORC
Corresponding author: Komsa, H.-P. Aalto University
Abstract: Atomic chains are perfect systems for getting fundamental insights into the electron dynamics and coupling between the electronic and ionic degrees of freedom in one-dimensional metals. Depending on the band filling, they can exhibit Peierls instabilities (or charge density waves), where equally spaced chain of atoms with partially filled band is inherently unstable, exhibiting spontaneous distortion of the lattice that further leads to metal−insulator transition in the system. Here, using high-resolution scanning transmission electron microscopy, we directly image the atomic structures of a chain of iodine atoms confined inside carbon nanotubes. In addition to long equidistant chains, the ones consisting of iodine dimers and trimers were also observed, as well as transitions between them. First-principles calculations reproduce the experimentally observed bond lengths and lattice constants, showing that the ionic movement is largely unconstrained in the longitudinal direction, while naturally confined by the nanotube in the lateral directions. Moreover, the trimerized chain bears the hallmarks of a charge density wave. The transition is driven by changes in the charge transfer between the chain and the nanotube and is enabled by the charge compensation and additional screening provided by the nanotube.
Keywords: carbon nanotubes, Peierls instabilities, charge density waves, TEM, DFT

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Registration No. 25691 - Permalink


Revisiting hollandites: channels filling by main-group elements together with transition metals in Bi2-yVyV8O16
Lebedev, O. I.; Hébert, S.; Roddatis, V.; Martin, C.; Turner, S.; Krasheninnikov, A. V.ORC; Grin, Y.; Maignan, A.
Abstract: Starting from the nominal BixV8O16 formula, state-of-the-art transmission electron microscopy investigation has been made to propose the new chemical formula Bi2-yVyV8O16 for this hollandite structure. This results from the filling of the channels by main-group elements together with vanadium (V5+) species, with variable content of Bi and V inside the channels. The influence of the Bi content and of this local disorder on the magnetic and transport properties has been investigated in polycrystalline samples of BixV8O16 with nominal composition x = 1.6 and x = 1.8. The rather x-independent electrical resistivity (≈ 5 m·cm) and Seebeck coefficient at high T (-35 μV·K-1 at 900 K) is discussed in terms of an unchanged V oxidation state resulting from the filling-up of the wide channels with Bi and V. It is proposed that this local disorder hinders the charge/orbital setting below 60 K on the V ions of the V8O16 framework. Hollandites exhibit complex electronic and magnetic properties with potential applications in the field of batteries, photocatalysis or nuclear waste storage, and these results show that a careful and detailed investigation of the nature and content of the cations inside the channels is crucial to better understand the doping and disorder impact on their properties.
Keywords: hollandites, defects, TEM, DFT calculations

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Registration No. 25690 - Permalink


Open Science with openPMD
Huebl, A.ORC; Lehe, R.; Vay, J.-L.ORC; Grote, D. P.; Sbalzarini, I. F.ORC; Kuschel, S.; Bussmann, M.ORC
Abstract: Nobody needs yet an other data format for HPC. But why have so-called self-describing data formats never provided out-of-the-box cross application portability? Why are most open-access datasets not self-describing for both the domain scientist and after-use? And why do communities need to implement their data readers in various post-processing, visualization and analysis frameworks over and over again?

We present the open meta data format openPMD for data format agnostic markup of particle-mesh data. Based on a minimal kernel of meta information and enriched with domain-specific extensions, we develop an open ecosystem of interoperable simulations and data processing frameworks from the domains of laser-plasma interaction, X-ray photon sciences, astrophysics up to systems biology. This poster presents our efforts to enable & establish workflows suitable to frictionless transposition between those domains, using highly scalable I/O methods (e.g. ADIOS BP or HDF5), a truly self-describing data markup and peer reviewed participation.
Keywords: I/O OpenScience OpenData HPC OpenAccess HDF5 ADIOS metadata

Registration No. 25686 - Permalink


Data Management in Small Animal Imaging: Conceptual and Technical Considerations
Maus, J.ORC; Hofheinz, F.
Abstract: Small animal imaging in general and multimodal tomographic imaging in particular generate a substantial amount of heterogeneous data that can be challenging to handle. Besides computed tomographic images, there are also the primarily acquired raw data such as listmode data in positron emission tomography (PET), projection data in X-ray computed tomography (CT), or even k-space data in magnetic resonance imaging (MRI). Additionally, further image data might be created by postprocessing (e.g., filtering) or by using alternative image reconstruction methods. All these data have to be stored; thus, the required disk space can easily exceed several terabyte (TB) over time. Therefore, good data storage planning and management strategies are required. In this context, data management obviously does not just mean storing the data. Rather, the data have to be easily accessible for all involved researchers, they also have to remain accessible years after the measurement, and the data have to be backed up in a save and secured place.
Keywords: PET, Small Animal Imaging
  • Book chapter
    Fabian Kiessling, Bernd J. Pichler, Peter Hauff: Small Animal Imaging: Basics and Practical Guide, Heidelberg: Springer International Publishing, 2017, 978-3-319-42200-8, 581-590
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-42202-2_22

Registration No. 25685 - Permalink


Hyperdoping silicon with tellurium by ion implantation and ultra-short annealing for optoelectronics
Wang, M.; Liu, F.; Yuan, Y.; Prucnal, S.; Berencén, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption exhibited by the resulting materials, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped silicon layers have been fabricated by ion implantation followed by flash lamp annealing (FLA) or pulsed-laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted silicon by both FLA and PLM. From the transport measurements, an insulator-to-metal transition is observed with increasing tellurium concentration. Moreover, the ellipsometry measurements show that the band gap narrows with increasing doping concentration. And the Fourier transform infrared (FTIR) spectroscopy show that tellurium hyperdoped Si has strong infrared absorption. All these results give us a signal that hyperdoped silicon with tellurium could enable silicon-based optoelectronics in the infrared band.

[1] Kim, T. G., et al., Appl. Phys. Lett. 88, 241902 (2006)
[2] Tabbal, M., et al., Appl. Phys. A 98, 589–594 (2010)
[3] Umezu, I., et al., J. Appl. Phys. 113, 213501 (2013)
Keywords: Hyperdoping silicon, infrared absorption, ion implantation
  • Lecture (Conference)
    DPG-Frühjahrstagung (DPG Spring Meeting), 19.-24.03.2017, Dresden, Germany, Germany

Registration No. 25682 - Permalink


Bentonite – geotechnical barrier and source for microbial life
Matschiavelli, N.; Kluge, S.; Cherkouk, A.
Abstract: Due to their properties, namely a high swelling capacity and a low hydraulic conductivity, bentonites fulfil as geotechnical barrier a sealing and buffering function in a high-level waste repository. Depending on the mineral composition, bentonites contain many suitable electron-donors and –acceptors, enabling potential microbial life. For the potential repository of highly radioactive waste, the microbial mediated transformation of bentonite could influence its properties as a barrier material. Microcosms were set up containing bentonite and anaerobic synthetic Opalinus-clay pore water solution under an N2/CO2 gas atmosphere to elucidate the microbial potential within selected bentonites. Substrates like acetate, lactate and hydrogen were supplemented as electron donors to stimulate potential microbial activity. First results show that bentonites represent a source for microbial life, demonstrated by the consumption of lactate and the formation of pyruvate and hydrogen sulphide.
Keywords: bentonite, sulfate reduction, redox potential
  • Lecture (Conference)
    PETRUS-ANNETTE PhD Conference, 23.-30.06.2017, Lissabon, Portugal

Registration No. 25680 - Permalink


Quantum criticality in the coupled two-leg spin ladder Ba2CuTeO6
Glamazda, A.; Choi, Y. S.; Do, S.-H.; Lee, S.; Lemmens, P.; Ponomaryov, A. N.; Zvyagin, S. A.; Wosnitza, J.; Sari, D. P.; Watanabe, I.
Corresponding author: Choi, Y. S. Department of Physics, Chung-Ang University, Seoul 156-756, Republic of Korea
Abstract: We report on zero-field muon spin rotation, electron-spin resonance, and polarized Raman scattering measurements of the coupled quantum spin ladder Ba2CuTeO6. Zero-field muon spin rotation and electron spin resonance probes disclose a successive crossover from a paramagnetic through a spin-liquid-like into a magnetically ordered state with decreasing temperature. More significantly, the two-magnon Raman response obeys a T -linear scaling relation in its peak energy, linewidth, and intensity. This critical scaling behavior presents an experimental signature of proximity to a quantum-critical point from an ordered side in Ba2CuTeO6.

Registration No. 25676 - Permalink


Bose-Einstein condensation of triplons in the S = 1 tetramer antiferromagnet K2Ni2(MoO4)3: A compound close to a quantum critical point
Koteswararao, B.; Khuntia, P.; Kumar, R.; Mahajan, A. V.; Yogi, A.; Baenitz, M.; Skourski, Y.; Chou, F. C.
Abstract: The structure of K2Ni2(MoO4)3 consists of S = 1 tetramers formed by Ni2+ ions. The magnetic susceptibility χ(T ) and specific heat CP (T ) data on a single crystal show a broad maximum due to the low dimensionality of the system with short-range spin correlations. A sharp peak is seen in χ(T ) and CP (T ) at about 1.13 K, well below the broad maximum. This is an indication of magnetic long-range order, i.e., the absence of spin gap in the ground state. Interestingly, the application of a small magnetic field (H >0.1 T) induces magnetic behavior akin to the Bose-Einstein condensation (BEC) of triplon excitations observed in some spin-gap materials. Our results demonstrate that the temperature-field (T -H) phase boundary follows a power law (T − TN) ∝ H1/α with the exponent 1/α close to 2/3 , as predicted for the BEC scenario. The observation of BEC of triplon excitations in small H infers that K2Ni2(MoO4)3 is located in the proximity of a quantum critical point, which separates the magnetically ordered and spin-gap regions of the phase diagram.

Registration No. 25675 - Permalink


Forced-ferromagnetic state in a Tm2Fe17H5 single crystal
Tereshina, E. A.; Kuz´Min, M. D.; Skourski, Y.; Doerr, M.; Iwasieczko, W.; Wosnitza, J.; Tereshina, I. S.
Abstract: We report the attainment of the ferromagnetic state in an interstitially modified heavy rareearth-iron intermetallic compound in an external magnetic field. The starting composition is E2Fe17, which is the RE–Fe binary richest in iron. We concentrate on the Tm–Fe compound, which is the most sensitive to magnetic field. The maximum possible amount of hydrogen (5 at.H/f.u.) is inserted into a Tm2Fe17 single crystal. We demonstrate that in a magnetic field of 57 T Tm2Fe17H5 reaches the ferromagnetic state with an enviably high polarization of 2.25 T.
Keywords: single crystal, hydride, forced-ferromagnetic state, rare-earth-iron intermetallic compound

Registration No. 25674 - Permalink


Relativistic Electron Streaming Instabilities Modulate Proton Beams Accelerated in Laser-Plasma Interactions
Göde, S.; Rödel, C.; Zeil, K.; Mishra, R.; Gauthier, M.; Brack, F.-E.; Kluge, T.; Macdonald, M.  J.; Metzkes, J.; Obst, L.ORC; Rehwald, M.; Ruyer, C.; Schlenvoigt, H.-P.; Schumaker, W.; Sommer, P.; Cowan, T.  E.; Schramm, U.; Glenzer, S.; Fiuza, F.
Abstract: We report experimental evidence that multi-MeV protons accelerated in relativistic laser-plasma interactions are modulated by strong filamentary electromagnetic fields. Modulations are observed when a preplasma is developed on the rear side of a μm-scale solid-density hydrogen target. Under such conditions, electromagnetic fields are amplified by the relativistic electron Weibel instability and are maximized at the critical density region of the target. The analysis of the spatial profile of the protons indicates the generation of B>10  MG and E>0.1  MV/μm fields with a μm-scale wavelength. These results are in good agreement with three-dimensional particle-in-cell simulations and analytical estimates, which further confirm that this process is dominant for different target materials provided that a preplasma is formed on the rear side with scale length ≳0.13λ0√a0. These findings impose important constraints on the preplasma levels required for high-quality proton acceleration for multipurpose applications.

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Registration No. 25665 - Permalink


Optimization of liquid metal flow pattern generated by rotating magnetic field and the effect on solidification structure of wrought aluminium alloys
Räbiger, D.; Willers, B.; Eckert, S.; Rosefort, M.; Dang, T.; Koch, H.
Abstract: AC magnetic fields provide a contactless method to control the flow inside a liquid metal. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, melt convection may also produce segregation freckles on the macroscale. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification. Previous investigations considered the use of time-modulated AC magnetic fields to control the heat and mass transfer at the solidification front. It has been shown that an accurate tuning of the magnetic field parameters can avoid segregation effects. The present study examines the directional solidification of wrought aluminium alloys from a water-cooled copper chill. Rotating magnetic fields were used to agitate the melt.
  • Lecture (Conference)
    XVIII International UIE-Congress on Electrotechnologies for Material Processing, 06.-09.06.2017, Hannover, Deutschland
  • Contribution to proceedings
    XVIII International UIE-Congress on Electrotechnologies for Material Processing, 06.-09.06.2017, Hannover, Deutschland
    XVIII International UIE-Congress Electrotechnologies for Material Processing: Vulkan-Verlag GmbH, 978-3-8027-3095-5, 255-260

Registration No. 25662 - Permalink


Bulk production and evaluation of high specific activity 186gRe for cancer therapy using enriched 186WO3 targets in a proton beam
Mastren, T.; Radchenko, V.; Bach, H.; Balkin, E.; Birnbaum, E.; Brugh, M.; Engle, J.; Gott, Matthew; Guthrie, J.; Hennkens, H.; John, K.; Ketring, A.; Kuchuk, M.; Maassen, J.; Naranjo, C.; Nortier, M.; Phelps, T.; Jurisson, S.; Wilbur, S.; Fassbender, M.
Corresponding author: Fassbender, Michael Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, 87545
Abstract: Introduction

Rhenium-186g (t1/2 = 3.72 d) is a β− emitting isotope suitable for theranostic applications. Current production methods rely on reactor production by way of the reaction 185Re(n,γ)186gRe, which results in low specific activities limiting its use for cancer therapy. Production via charged particle activation of enriched 186W results in a 186gRe product with a higher specific activity, allowing it to be used more broadly for targeted radiotherapy applications. This targets the unmet clinical need for more efficient radiotherapeutics.

Methods

A target consisting of highly enriched, pressed 186WO3 was irradiated with protons at the Los Alamos National Laboratory Isotope Production Facility (LANL-IPF) to evaluate 186gRe product yield and quality. LANL-IPF was operated in a dedicated nominal 40 MeV mode. Alkaline dissolution followed by anion exchange chromatography was used to isolate 186gRe from the target material. Phantom and radiolabeling studies were conducted with the produced 186gRe activity.

Results

A 186gRe batch yield of 1.38 ± 0.09 MBq/μAh or 384.9 ± 27.3 MBq/C was obtained after 16.5 h in a 205 μA average/230μA maximum current proton beam. The chemical recovery yield was 93% and radiolabeling was achieved with efficiencies ranging from 60–80%. True specific activity of 186gRe at EOB was determined via ICP-AES and amounted to 0.788 ± 0.089 GBq/μg (0.146 ± 0.017 GBq/nmol), which is approximately seven times higher than the product obtained from neutron capture in a reactor. Phantom studies show similar imaging quality to the gold standard 99mTc.

Conclusions

We report a preliminary study of the large-scale production and novel anion exchange based chemical recovery of high specific activity 186gRe from enriched 186WO3 targets in a high-intensity proton beam with exceptional chemical recovery and radiochemical purity.
Keywords: Theranostic; 186gRe; 186WO3 target; High specific activity; Radiolabeling; SPECT phantom images

Registration No. 25659 - Permalink


Breaking the Electrical Barrier between Copper and Carbon Nanotubes
Milowska, K. Z.; Ghorbani-Asl, M.ORC; Burda, M.; Wolanicka, L.; Catic, N.; Bristowe, P. D.; Kozioł, K. K. K.
Corresponding author: Milowska, K. Z. University of Cambridge
Abstract: Improving the interface between copper and carbon nanotubes (CNTs) offers a straightforward strategy for the effective manufacturing and utilisation of Cu-CNT composite material that could be used in various industries including microelectronics, aerospace and transportation. Motivated by a combination of structural and electrical measurements on Cu-M-CNT bimetal systems (M = Ni, Cr) we show, using first principles calculations, that the conductance of this composite can exceed that of a pure Cu-CNT system and that the current density can even reach 10 11 A/cm2 . The results show that the proper choice of alloying element (M) and type of contact facilitate the fabrication of ultra-conductive Cu-M-CNT systems by creating a favourable interface geometry, increasing the interface electronic density of states and reducing the contact resistance. In particular, a small concentration of Ni between the Cu matrix and the CNT using either an "end contact" and or a "dot contact" can significantly improve the electrical performance of the composite. Furthermore the predicted conductance of Ni-doped Cu-CNT "carpets" exceeds that of an undoped system by ∼200%. Cr is shown to improve CNT integration and composite conductance over a wide temperature range while Al, at low voltages, can enhance the conductance beyond that of Cr.
Keywords: carbon nanotubes, copper, composite, electrical properties

Registration No. 25657 - Permalink


Holographic Entanglement Entropy in the QCD Phase Diagram with a Critical Point
Knaute, J.; Kämpfer, B.
Abstract: We calculate the holographic entanglement entropy for the holographic QCD phase diagram in [Knaute, Yaresko, K\"ampfer (2017), arXiv:1702.06731] and explore the resulting qualitative behavior over the temperature-chemical potential plane. In agreement with the thermodynamic result, the phase diagram exhibits the same critical point as the starting point of a first-order phase transition curve. We compare the phase diagram of the entanglement entropy to that of the thermodynamic entropy density and find a striking agreement in the vicinity of the critical point. Thus, the holographic entanglement entropy qualifies to characterize different phase structures. The scaling behavior near the critical point is analyzed through the calculation of critical exponents.

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Registration No. 25655 - Permalink


Efficient Parallel Monte-Carlo Simulations for Large-Scale Studies of Surface Growth Processes
Kelling, J.
Abstract: Lattice Monte Carlo methods are used to investigate far from and out-of-equilibrium systems, including surface growth, spin systems and solid mixtures. Such studies require observations of large systems over long times scales, to allow structures to grow over orders of magnitude, which necessitates massively parallel simulations. This talk presents work done to address the problem of parallel processing introducing correlations in Monte Carlo updates. Studies of the effect of correlations on scaling and dynamical properties of surface growth systems and related lattice gases is investigated further by comparing results obtained by correlation-free and intrinsically correlated but highly efficient simulations using a stochastic cellular automaton. The primary subject of study is the Kardar-Parisi-Zhang surface growth in (2+1) dimensions. Key physical insights about this universality class, like precise universal exponent values and exponent relations, obtained from large-scale simulations are presented.
Keywords: Lattice Monte Carlo, GPU, Surface Growth, Kardar-Parisi-Zhang
  • Lecture (others)
    Seminar Topical Problems, 14.06.2017, Chemnitz, Deutschland

Registration No. 25653 - Permalink


Magnesium photocathodes in the SRF photo-injector at HZDR
Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.
Abstract: Magnesium photocathodes in the SRF photo-injector at HZDR
Keywords: Magnesium photocathode, SRF photoinjector
  • Poster
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Germany

Registration No. 25652 - Permalink


Improvements of the photoemission efficiency of magnesium photocathodes
Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.; Patra, P.
Abstract: To improve the quality of photocathodes is one of the critical issues in enhancing the stability and reliability of photo-injector systems. Presently the primary choice is to use metallic photocathodes for the ELBE SRF Gun II to reduce the risk of contamination of the superconducting cavity. Magnesium has a low work function (3.6 eV) and shows high quantum efficiency (QE) up to 0.3 % after laser cleaning. The SRF Gun II with an Mg photocathode has successfully provided electron beam for ELBE users. However, the present cleaning process with a high intensi-ty laser (activation) is time consuming and generates unwanted surface roughness. This paper presents the investigation of alternative surface cleaning procedures, such as thermal treatment. The QE and topography of Mg samples after treatment are reported.
Keywords: magnesium photocathodes, quantum efficiency, SRF photoinjector
  • Open Access LogoContribution to proceedings
    The 8th International Particle Accelerator Conference (IPAC’17), 14.-19.05.2017, Copenhagen, Danmark
    Proceedings of IPAC'17
  • Poster
    The 8th International Particle Accelerator Conference (IPAC’17), 14.-19.05.2017, Copenhagen, Denmark

Registration No. 25651 - Permalink


Tailoring Optical Properties of Atomically-Thin WS2 via Ion Irradiation
Tan, L. N.; Tan, Y.; Ghorbani-Asl, M.ORC; Boettger, R.; Kretschmer, S.; Zhou, S. Q.; Huang, Z. Y.; Krasheninnikov, A. V.ORC; Chen, F.
Abstract: Two-dimensional transition metal dichalcogenides (TMDCs) exhibit excellent optoelectronic properties. However, the large band gaps in many semiconducting TMDCs make optical absorption in the near-infrared (NIR) wavelength regime impossible, which prevents applications of these materials in optical communications. In this work, we demonstrate that Ar+ ion irradiation is a powerful post-synthesis technique to tailor the optical properties of the semiconducting tungsten disulfide (WS2) by creating S vacancies and thus controlling material stoichiometry. First-principles calculations reveal that the S-vacancies give rise to deep states in the band gap, which determine the NIR optical absorption of the WS2 monolayer. As the density of the S-vacancies increases, the enhanced NIR linear and saturable absorption of WS2 is observed, which is explained by the results of first-principles calculations. We further demonstrate that by using the irradiated WS2 as a saturable absorber in a waveguide system, the passively Q-switched laser operations can be optimized, opening thus new avenues for tailoring the optical response of TMDCs by defect-engineering through ion irradiation.
Keywords: Ion irradiation, WS2, optical properties

Registration No. 25650 - Permalink


Asymmetric spin-wave dispersion in ferromagnetic nanotubes induced by surface curvature
Otálora, J. A.; Yan, M.; Schultheiss, H.; Hertel, R.; Kákay, A.
Corresponding author: Otálora, J. A. IFW Dresden
Abstract: We present a detailed analytical derivation of the spin wave (SW) dispersion relation in magnetic nanotubes with magnetization along the azimuthal direction. The obtained formula can be used to calculate the dispersion relation for any longitudinal and azimuthal mode. The obtained dispersion is asymmetric for all azimuthal modes traveling along the axial direction. As reported in our recent publication [Phys. Rev. Lett. 117, 227203 (2016)], the asymmetry is a curvature-induced effect originating from the dipole-dipole interaction. Here, we discuss the asymmetry of the dispersion for azimuthal modes by analyzing the SW asymmetry deltaf (kz) = fn(kz) − fn(−kz), where fn(kz) is the eigenfrequency of a magnon with a longitudinal and azimuthal wave vectors, kz and n, respectively; and the dependence of the maximum asymmetry with the nanotube radius R. The analytical results are in perfect agreement with micromagnetic simulations. Furthermore, we show that the dispersion relation simplifies to the thin-film dispersion relation with in-plane magnetization when analyzing the three limiting cases: (i) kz = 0, (ii) kz>>1/R, and (iii) kz<<1/R. In the first case, for the zeroth-order modes the thin-film Kittel formula is obtained. For modeswith higher order the dispersion relation for the Backward-Volume geometry is recovered. In the second case, for the zeroth-order mode the exchange dominated dispersion relation for SW in Damon-Esbach configuration is obtained. For the case kz<<1/R, we find that the dispersion relation can be reduced to a formula similar to the Kalinikos-Slavin [J. Phys. C: Sol. State Phys. 19, 7013 (1986)] type.
Keywords: Spin waves, curvature, mangnonics

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Registration No. 25646 - Permalink


Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by Small Angle X-Ray Scattering using XFELs
Kluge, T.; Rödel, M.; Metzkes, J.; Pelka, A.; Laso Garcia, A.; Prencipe, I.; Hartley, N.; Nakatsutsumi, M.; Gutt, C.; Galtier, E.; Nam, I.; Lee, H. J.; Zacharias, M.; Garten, M.; Bussmann, M.; Zeil, K.; Rödel, C.; Mcbride, E.; Schramm, U.; Cowan, T. E.
Abstract: Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by Small Angle X-Ray Scattering using XFELs
  • Lecture (Conference)
    2017 European XFEL Users' Meeting and Satellite Meetings, Satellite Meeting: Status of the HED science instrument & Meeting of the HIBEF user consortium, 24.01.2017, Hamburg, Deutschland

Registration No. 25644 - Permalink


Start-to-end simulations for photon interaction in ultra-high intensity short pulse laser experiments with solids
Kluge, T.; Burau, H.; Garten, M.; Grund, A.; Huebl, A.; Matthes, A.; Jung, F.; Widera, R.; Zacharias, M.; Fortmann-Grote, C.; Bussmann, M.
Abstract: EUCALL annual meeting poster
  • Poster
    EUCALL annual meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Registration No. 25642 - Permalink


The need for detailed scattering simulations for Small Angle X-Ray Scattering on laser driven solids
Thomas Kluge; Burau, H.; Garten, M.; Grund, A.; Huebl, A.; Matthes, A.; Jung, F.; Widera, R.; Zacharias, M.; Fortmann-Grote, C.; Bussmann, M.
Abstract: SIMEX progress report June 2017
  • Lecture (Conference)
    EUCALL annual meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Registration No. 25641 - Permalink


1‑(4‑[18F]Fluorobenzyl)-4-[(tetrahydrofuran-2-yl)methyl]piperazine: A Novel Suitable Radioligand with Low Lipophilicity for Imaging σ1 Receptors in the Brain
He, Y.; Xie, F.; Ye, J.; Deuther-Conrad, W.; Cui, B.; Wang, L.; Lu, J.; Steinbach, J.; Brust, P.; Huang, Y.; Lu, J.; Jia, H.
Abstract: We have designed and synthesized novel piperazine compounds with low lipophilicity as σ1 receptor ligands. 1-(4-Fluorobenzyl)-4-[(tetrahydrofuran-2-yl)methyl]piperazine (10) possessed a low nanomolar σ1 receptor affinity and a high selectivity toward the vesicular acetylcholine transporter (>2000-fold), σ2 receptors (52-fold), and adenosine A2A, adrenergic α2, cannabinoid CB1, dopamine D1, D2L, γ-aminobutyric acid A (GABAA), NMDA, melatonin MT1, MT2, and serotonin 5-HT1 receptors. The corresponding radiotracer [18F]10 demonstrated high brain uptake and extremely high brain-to-blood ratios in biodistribution studies in mice. Pretreatment with the selective σ1 receptor agonist SA4503 significantly reduced the level of accumulation of the radiotracer in the brain. No radiometabolite of [18F]10 was observed to enter the brain. Positron emission tomography and magnetic resonance imaging confirmed suitable kinetics and a high specific binding of [18F]10 to σ1 receptors in rat brain. Ex vivo autoradiography showed a reduced level of binding of [18F]10 in the cortex and hippocampus of the senescence-accelerated prone (SAMP8) compared to that of the senescence-accelerated resistant (SAMR1) mice, indicating the potential dysfunction of σ1 receptors in Alzheimer’s disease.

Registration No. 25640 - Permalink


Quantifying the relative availability of high-tech by-product metals – The cases of gallium, germanium and indium
Frenzel, M.; Mikolajczak, C.; Reuther, M. A.; Gutzmer, J.
Abstract: There are considerable concerns about the supply security of certain high-tech elements produced as by-products. To determine in how far these concerns are justified by the actual availability of these elements, we compare the supply potentials for three particularly relevant examples – gallium, germanium and indium – to current and historic production volumes. Our assessment is based on detailed estimates of the amounts extractable from various raw materials given contemporary market prices and technologies. While the estimate for gallium is taken from a previous publication, the estimate for germanium is recalculated from an earlier estimate of recoverable germanium in reserves and resources, and the estimate for indium is compiled as part of this article.

We find that the supply potentials of all three elements significantly exceed current primary production. However, the degree to which this is the case varies from element to element. While both the supply potentials of gallium and germanium are ~10 times higher than primary production, the supply potential of indium is ~3 times higher.

Differences also exist in historic growth trends, with indium showing the fastest growth rate of the utilised supply potential. This makes it the most likely of the three to reach its maximum production level in the future. Based on these considerations we propose a new quantitative indicator for the future availability of by-products, time-to-maximum extraction as a by-product (TMEB), and show its utility in discriminating between the different supply situations of the three by-product elements.
Keywords: Scarcity; Critical raw materials; Indium; Companion metals; By-products; Supply potential

Registration No. 25636 - Permalink


PIConGPU Particle-in-Cell Simulations of Transient High Energy Density Plasmas
Huebl, A.ORC; Kluge, T.; Garten, M.; Grund, A.; Pausch, R.; Widera, R.ORC; Matthes, A.ORC; Debus, A.; Vorberger, J.; Fortmann-Grote, C.ORC; Chung, H.-K.; Bussmann, M.ORC
Abstract: This talk shows the progress of PIConGPU on modeling transient high-energy density plasmas for the EUCALL annual workshop. We report on new features in PIConGPU, challenges in HPC-scale I/O for PIC simulations and how we interact with simex_platform and our approach for collisional-radiative non-LTE modeling within the scope of particle-in-cell.
Keywords: PIConGPU EUCALL non-LTE HPC I/O transient plasma processes
  • Lecture (Conference)
    EUCALL Annual Meeting 2017, 07.-09.06.2017, Grenoble, Frankreich

Registration No. 25635 - Permalink


Studying tracer metabolism by LC-MS: (+)-[18F]flubatine and (S)-[18F]fluspidine – two different radioligands showing similar metabolic pathways in vitro and in vivo
Ludwig, F.-A.; Fischer, S.; Smits, R.; Hoepping, A.; Houska, R.; Patt, M.; Hesse, S.; Wünsch, B.; Sabri, O.; Brust, P.; Steinbach, J.
Abstract: Objectives: Radiometabolites can affect PET imaging dramatically due to their expected different properties. Therefore identification of radiometabolites is an important step to understand the metabolic fate of a radioligand. The approach presented demonstrates how LC-MS supports in vitro experiments and contributes to explore the metabolic profile of two tracers recently studied in human brain [1, 2].
Methods: (+)-[18F]Flubatine ([18F]1) and (S)-[18F]Fluspidine ([18F]2) (Figure 1), as well as nonradioactive references were incubated with human liver microsomes (HLM) in presence of NADPH and/or activated glucuronic acid (UDPGA) at 37°C. Radiometabolite patterns were monitored by radio-HPLC and structures were identified by LC-MS of non-radioactive incubations using different MS-methods (EPI, MS3). Plasma (30 min p.i.) and urine (90 min p.i.) from human subjects receiving [18F]1 or [18F]2 during clinical studies were investigated and compared with results von microsomal incubations.
Results: During HLM incubations in presence of NADPH, mono-hydroxylation was predominant for both, 1 and 2, beside debenzylation of 2. In presence of UDPGA 1 and 2 underwent glucuronidation, but only after previous hydroxylation. Corresponding in vitro radiometabolites were detected by radio-HPLC and assigned regarding their structure. Samples obtained from humans showed high stability of both tracers, whereby [18F]1 (97.0% in plasma 30 min p.i, n=6) proved to be more stable than [18F]2 (85.3% in plasma 30 min p.i, n=3). However, hydroxylation and subsequent glucuronidation was found to be the major metabolic pathway of both tracers.
Conclusions: Using in vitro studies and LC-MS, in vivo radiometabolites could be identified. Beside high metabolic stability, [18F]1 and [18F]2 show similar major pathways, namely glucuronidation after previous hydroxylation.
Acknowledgements: Supported by the Helmholtz Validation Fund (HVF) and the German Research Foundation (DFG).
References: [1] Sattler et al. (2015), J Nucl Med, 56, suppl. 3, 1020; [2] Sattler et al. (2016), J Nucl Med, 57, suppl. 2, 1022.
Keywords: PET, LC-MS, Microsomes, Flubatine, Fluspidine, Metabolism, Fluorine-18
  • Lecture (Conference)
    XIV Turku PET symposium, 27.-30.5.2017, Turku, Finnland

Registration No. 25633 - Permalink


Prompt-gamma based range verification with a slit camera: Sensitivity and first clinical experiences
Richter, C.
Abstract: Overview of PGI slit camera activities in Dresden
  • Invited lecture (Conferences)
    ENLIGHT Annual Meeting 2017, 12.-13.06.2017, Aarhus, Danmark

Registration No. 25624 - Permalink


Following our DREAMS (DREsden Accelerator Mass Spectrometry)
Merchel, S.; Dreams-Team (S. Pavetich, G. Rugel, A. Scharf, R. Ziegenrücker,...); Dreams-Users; Dreams-Friends
Abstract: no abstract necessary
Keywords: AMS
  • Poster
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland

Registration No. 25623 - Permalink


From Space to Earth to Accelerator Mass Spectrometry: Applications at Dresden AMS
Rugel, G.; Merchel, S.; DREAMS; Cooperation partners
Abstract: no abstract necessary
Keywords: AMS, astrophysics
  • Poster
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland

Registration No. 25622 - Permalink


Strain and particle size analysis in ion beam synthesized SiC nanoparticles using Raman scattering studies
Saravanan, K.; Jayalakshmi, G.; Panigrahi, B. K.; Hübner, R.
Abstract: We study the strain and particle size analysis of ion beam synthesized SiC nanoparticles (NPs) embedded in Si matrix using Raman and low-frequency Raman scattering (LFRS). 300 keV C+ ions with the fluence of 2 × 1017 ions/cm2 were implanted on Si substrate at three different substrate temperatures (300, 500 and 650 °C). Raman scattering analyses confirm the formation of 3C-SiC NPs in Si matrix. Relative strain in 3C-SiC NPs estimated from Raman scattering was found to decrease with increase of substrate temperature. The particle size distribution of 3C-SiC NPs was estimated from the signature of localized acoustic phonon modes observed in the low frequency region (ω<40cm-1) of LFRS spectra. The estimated particle size of the SiC is found to be in good agreement with the TEM analysis.
Keywords: Acoustic phonon modes; Ion beam synthesis; SiC nanoparticles; Strain

Registration No. 25620 - Permalink


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