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Publication database - Helmholtz-Zentrum Dresden-Rossendorf

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22135 Publications
Synthesis and characterization of MnAs and MnP nanoclusters embedded in III–V semiconductors
Khalid, M.; Prucnal, S.; Liedke, M. O.; Gao, K.; Facsko, S.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: We report on a systematic study of the synthesis and magnetism of hybrid ferromagnetic semiconductors comprised of MnAs and MnP nanoclusters embedded in GaAs and InP matrices, respectively. Samples were prepared by Mn-ion implantation followed by millisecond-range flash lamp annealing. X-ray diffraction and Auger electron spectroscopy results confirm the formation of MnAs nanoclusters of sizes 150 ± 50 nm. Ferromagnetic properties of MnAs: GaAs (MnP:InP) hybrid systems are studied by magnetic force microscopy and superconducting quantum interference device magnetometry. We show that the magnetization at saturation and the ferromagnetic transition temperature Tc, of MnAs:GaAs depend on the Mn-concentration and on the annealing energy density. While in the case of MnP:InP they are independent of the annealing energy density used. Ferromagnetism in such hybrid systems (ferromagnet–semiconductor) above 300 K makes them very attractive for applications in spintronic devices.
Keywords: magnetic semiconductor, flash lamp annealing, nanoclusters Registration No. 20305

Simulation of positron energy distribution generated by photons from channeled relativistic electrons on different crystallographic planes and axes of Si, C, Ge and W crystals with Mathematica and Geant 4
Azadegan, B.; Mahdipour, A.; Dabagov, S. B.; Wagner, W.
Abstract: A non-conventional positron source using the channeling radiation of relativistic electrons on different planes and axes of Si, C, Ge and W crystals which materialize into e+e- pairs in a tungsten amorphous converter is described. In this work we have calculated channeling radiation spectra from different planes and axes of Si, C, Ge and W crystals using the Doyle-Turner approximation for the continuum potentials of crystallographic planes and axes. The dependence of channeling radiation on the incidence angle of electrons are also investigated. The channeling radiation is then impinging on an amorphous tungsten target producing positrons by e+e- pair creation. The simulations are made with our developed Mathematica codes which realy calculate the photon energy spectrum of channeled electrons in the crystal target and Geant4 Monte Carlo code which calculates the the materialization of photons into e+e- pairs in an amorphous W target.
Keywords: channeling radiation, pair creation, positron source
  • Contribution to proceedings:
    5th International Conference on Charged & Neutral Particles Channeling Phenomena (Channeling 2012), 23.-28.09.2012, Alghero, Sardinia, Italy
    Proceedings, 5th International Conference on Charged & Neutral Particles Channeling Phenomena (Channeling 2012), Moscow, Russia: Publishing Office NRNU MEPhI, 978-5-7262-1864-9, 123-136
Registration No. 20301

Multiphase Flow System with Suspended Particles
Yeoh, G. H.; Lucas, D.; Cheung, S. C. P.; Tu, J.
Abstract: Industrial system that comprises flow of suspended particles in fluid generally requires an understanding of the multiscale physics occurring from micro/nanoscale to mesoscale and eventually to the macroscale phenomena. Because of the inherent complexities that are prevalent in such flow, investigations are certainly at the crossroads of intense research and development in the environment of significant advancements in experimentation as well as in computing power and performance. Much concerted development is nonetheless still needed to gain a better understanding of the complicated physics through the advancement of experimental techniques and computational methodologies and models and to specifically meet the increasing demand of improving efficiency of industrial multiphase flow system. The advances of experimental and modelling investigation of multiphase flow system are presented in this special issue.
Keywords: multiphase, particle, bubble Registration No. 20300

Tunnel magnetoresistance in double barrier magnetic tunnel junctions with different free layer deposition conditions
Fowley, C.; Feng, W.; Gan, H.; Hübner, R.; Kunz, A.; Lindner, J.; Fassbender, J.; Coey, J.; Deac, Alina M.
Abstract: Double barrier magnetic tunnel junctions (DB-MTJs) allow for operation at higher bias voltages than their single barrier counterparts, but their total tunnelling magnetoresistance (TMR) ratio is still less than in the single barrier case.[1] Here, we prepare CoFeB/MgO-based DB-MTJs with differing free layer deposition conditions. The deposition conditions for the outer CoFeB electrodes and the MgO barriers were kept the same. The middle CoFeB layer was deposited at differing sputtering power densities (from 1.3 to 4.4 W/cm2) to vary the B concentration.[2] Contributions of the upper and lower junction to the total TMR were compared as a function of sputtering power density and annealing temperature. As the sputtering power density of the free layer is increased the TMR response of the upper and lower junctions is opposite, indicating that the growth of both MgO on CoFeB as well as CoFeB on MgO is sensitive to B content. This is attributed to the suppression of B diffusion which is confirmed by transmission electron microscopy analysis. [1] T. Nozaki et al., Appl. Phys. Lett., 86, 082501 (2005). [2] H.D. Gan et al., IEEE Trans. Magn. 47, 1567 (2011).
Keywords: magnetic tunnel junctions, boron diffusion, CoFeB, tunneling magnetoresistance, sputtering power density
  • Lecture (Conference):
    Deutsche Physikalische Gesellschaft, 31.03.-04.04.2014, Dresden, Germany
Registration No. 20299

FDG PET/MR for lymph node staging in head and neck cancer
Platzek, I.; Beuthien-Baumann, B.; Schneider, M.; Gudziol, V.; Kitzler, Hagen H.; Maus, J.; Schramm, G.; Popp, M.; Laniado, M.; Kotzerke, J.; van den Hoff, J.
Abstract: Objective
To assess the diagnostic value of PET/MR (positron emission tomography/magnetic resonance imaging) with FDG (18F-fluorodeoxyglucose) for lymph node staging in head and neck cancer.

Materials and Methods
This prospective study was approved by the local ethics committee; all patients signed informed consent. Thirty-eight patients with squamous cell carcinoma of the head and neck region underwent a PET scan on a conventional scanner and a subsequent PET/MR on a whole-body hybrid system after a single intravenous injection of FDG. The accuracy of PET, MR and PET/MR for lymph node metastases were compared using receiver operating characteristic (ROC) analysis. Histology served as the reference standard.

Metastatic disease was confirmed in 16 (42.1%) of 38 patients and 38 (9.7%) of 391 dissected lymph node levels. There were no significant differences between PET/MR, MR and PET and MR (p > 0.05) regarding accuracy for cervical metastatic disease. Based on lymph node levels, sensitivity and specificity for metastatic involvement were 65.8% and 97.2% for MR, 86.8% and 97.0% for PET and 89.5% and 95.2% for PET/MR.

In head and neck cancer, FDG PET/MR does not significantly improve accuracy for cervical lymph node metastases in comparison to MR or PET.

Keywords: PET/MR; head and neck cancer; lymph node metastasis; staging Registration No. 20294

Electrical Characterization of a Switchable Molecular Wire via Mechanically Controllable Break Junctions
Sendler, T.; Wieser, M.; Wolf, J.; Huhn, T.; Scheer, E.; Moresco, F.; Grebing, J.; Gemming, S.; Erbe, A.
Abstract: Molecular electronics has been a eld of big interest for the last years. Using the technique of mechanically controllable break junctions we characterize the Switchable Molecular Wire Oligo(phenylene ethynylene)-embedded Difurylperuorocyclopentenes (SMW) in liquid environment. Via light irradiation the SMW can be switched between two well-defi ned conductance states. Conductance and hysteresis measurements allow us to identify the two states providing the basis for a comprehensive study of the in situ switching process. Based on the analysis with the transport model assuming transport through a single molecular level, we confi rm that a reliable contact of the molecules to the gold contacts is formed and extract the energy of the molecular levels and the coupling constants between molecule and electrodes.
Keywords: Molecular Electronics, MCBJ, Switchable Molecular Wire
  • Poster:
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland
Registration No. 20289

Nonlinear spin-wave scattering in a micro-structured magnonic crystal
Obry, B.; Meyer, T.; Pirro, P.; Brächer, Th.; Osten, J.; Chumak, A. V.; Serga, A. A.; Fassbender, J.; Hillebrands, B.
Abstract: We study the nonlinear multi-magnon processes in a micro-structured magnonic crystal consisting of a Ni81Fe19 waveguide, which has been periodically modulated in its saturation magnetization by localized ion implantation. A significant modification of the nonlinear magnon spectrum compared to a reference waveguide is determined, exhibiting a predominant scattering into modes with a frequency at the magnonic band gaps and an enhancement of the nonlinearities for some excitation frequencies. The results prove the feasibility to utilize nonlinear multi-magnon scattering for magnon spintronic applications on the micrometer scale.
Keywords: magnonic crystal permalloy magnon process spintronic
  • Lecture (Conference):
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland
Registration No. 20287

Subnanosecond relaxation of free carriers in compensated n- and p-type germanium
Deßmann, N.; Pavlov, S.; Shastin, V.; Zhukavin, R.; Tsyplenkov, V.; Winnerl, S.; Mittendorff, M.; Abrosimov, N.; Riemann, H.; Hübers, H.-W.
Abstract: The relaxation of free holes and electrons in highly compensated germanium doped with gallium (p-Ge:Ga:Sb) and antimony (n-Ge:Sb:Ga) has been studied by a pump-probe experiment with the free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf. The relaxation times vary between 20 ps and 300 ps and depend on the incident THz intensity and compensation level. The relaxation times are about five times shorter than previously obtained for uncompensated n-Ge:Sb and p-Ge:Ga. The results support the development of fast photoconductive detectors in the THz frequency range.
  • Lecture (Conference):
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland
Registration No. 20286

Polarization dependence of optical carrier excitation in graphene
Mittendorff, M.; Winzer, T.; Malic, E.; Knorr, A.; Schneider, H.; Helm, M.; Winnerl, S.
Abstract: We present near-infrared pump-probe measurements to investigate the polarization dependence of optical carrier excitation in graphene. Excitation with linearly polarized radiation leads to an anisotropic distribution of the nonequilibrium carriers in momentum space. This anisotropy can be revealed by the comparison of pump-probe signals for different polarization configurations. In parallel configuration the probe beam has the same polarization with respect to the pump beam, for the perpendicular configuration the polarization of the probe beam is rotated by 90°. The signal amplitude of the parallel configuration is about twice as large as compared to the perpendicular configuration. The initial relaxation process is faster for the parallel polarized probe beam, which leads to identical signals about 150 fs after excitation. At this time delay an isotropic carrier distribution is reached by electron-phonon scattering. These findings are confirmed by microscopic calculations.
  • Lecture (Conference):
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland
Registration No. 20285

Carrier dynamics in graphene under Landau quantization
Wendler, F.; Mittendorff, M.; Winnerl, S.; Helm, M.; Knorr, A.; Malic, E.
Abstract: We investigate the ultrafast dynamics of low-energetic Dirac electrons in graphene under Landau quantization [1]. In a joint experiment-theory study, we provide calculations based on the density matrix formalism [2] as well as measurements of the relaxation dynamics via differential transmission spectroscopy.

As a consequence of the linear dispersion at the Dirac points, graphene exhibits a non-equidistant Landau level spectrum which allows to address specific transitions by optical pumping. Exploiting this to selectively excite the energetically lowest Landau levels, we employ pump-probe spectroscopy to explore the carrier dynamics in this regime. A surprising sign reversal in differential transmission spectra is observed both in experiment and theory and provides evidence for strong Auger scattering on a picosecond timescale. Our calculations even predict the occurrence of a substantial carrier multiplication in Landau quantized graphene [3].

[1] M. Mittendorff et al., (in preparation).

[2] E. Malic, A. Knorr, Graphene and Carbon Nanotubes: Ultrafast Optics and Relaxation Dynamics, (Wiley-VCH, Berlin, 2013).

[3] F. Wendler, A. Knorr, and E. Malic, (submitted).
  • Lecture (Conference):
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 31.03.-04.04.2014, Dresden, Deutschland
Registration No. 20284

Terahertz Stimulated Emission from Silicon Doped by Hydrogenlike Acceptors
Pavlov, S.  G.; Deßmann, N.; Shastin, V.  N.; Zhukavin, R.  Kh.; Redlich, B.; van der Meer, A.  F.  G.; Mittendorff, M.; Winnerl, S.; Abrosimov, N.  V.; Riemann, H.; Hübers, H.-W.
Abstract: Stimulated emission in the terahertz frequency range has been realized from boron acceptor centers in silicon. Population inversion is achieved at resonant optical excitation on the 1Γ+8 → 1Γ−7, 1Γ−6, 4Γ−8 intracenter transitions with a midinfrared free-electron laser. Lasing occurs on two intracenter transitions around 1.75 THz. The upper laser levels are the 1Γ−7, 1Γ−6, and 4Γ−8 states, and the lower laser level for both emission lines is the 2Γ+8 state. In contrast to n-type intracenter silicon lasers, boron-doped silicon lasers do not involve the excited states with the longest lifetimes. Instead, the absorption cross section for the pump radiation is the dominating factor. The four-level lasing scheme implies that the deepest even-parity boron state is the 2Γ+8 state and not the 1Γ+7 split-off ground state, as indicated by other experiments. This is confirmed by infrared absorption spectroscopy of Si:B. Registration No. 20281

Temperature dependence of ion-beam mixing in crystalline and amorphous germanium
Radek, M.; Bracht, H.; Posselt, M.; Liedke, B.; Schmidt, B.
Abstract: not available, please contact the authors
Keywords: ion beam mixing, crystalline Ge, amorphous Ge, isotope multilayers
  • Lecture (Conference):
    49. Tagung des Arbeitskreises Punktdefekte, 04.-05.04.2014, Dresden, Germany
Registration No. 20275

Defects and sintering-induced diffusion processes in yttria-stabilised zirconia nanomaterials studied by positron annihilation spectroscopy
Prochazka, I.; Cizek, J.; Melikhova, O.; Anwand, W.; Konstantinova, T. E.; Danilenko, I. A.
Abstract: In the present work, zirconia (ZrO2) nanopowders doped with yttria (Y2O3) and chromia (Cr2O3) were prepared by a co-precipitation technique. The nanopowders were then subjected to a calcination and a successive sintering at elevated temperatures up to 1500 °C. The nanostructures in these nanomaterials were characterized by positron annihilation spectroscopy (positron lifetimes and Doppler broadening measurements) which is a non-destructive technique with a high sensitivity to atomic-scale open-volume defects. It was found that the zirconia-based nanomaterials studied contain vacancy-like defects and nano-scale pores. Diffusion processes induced in these nanomaterials by sintering were investigated also by depth sensitive positron annihilation studies using a variable energy slow positron beam. Sintering was found to cause intensive grain growth and a removal of porosity by a migration of pores from the sample interior toward its surface.
Keywords: Zirconia. Nanopowders. Sintering. Porosity. Positron annihilation Registration No. 20273

Phase analysis with HRPD and XAFS in the USiO4-ZrSiO4 solid solution system
Hennig, C.
Abstract: Invesigation the solid solution USiO4-ZrSiO4 is related with the problem to avoid the formation of the related oxides UO2 and ZrO2. In previous studies we have shown that the formation of UO2 can be relatively easy supressed by using an excess of SiO2 during the hydrothermal synthesis already at relatively low temperature. The formation of ZrO2 is obviously more pronounced in the same temperature range. A part of Zr enters the amorphous phase. The aim of this study is to investigate the Zr containing phases in crystalline and in amorphous state with HRPD and XAFS, respectively.
Keywords: solid solution, USiO4, ZrSiO4, HRPD, XAFS
  • Invited lecture (Conferences):
    TALISMAN Projekt meeting, 06.02.2014, Jülich, Germany
Registration No. 20272

Challenges in Detection, Structural Characterization and Determination of Complex Formation Constants of Uranyl-Arsenate Complexes in Aqueous Solutions
Gezahegne, W.; Hennig, C.; Geipel, G.; Planer-Friedrich, B.; Merkel, B. J.
Abstract: Uranium forms analogous minerals with phosphate and arsenate. In aqueous solutions an analogy is expected to govern the complexes that uranium builds with these ligands. Three uranyl arsenate complexes UO2H2AsO4+, UO2HAsO4 0 and UO2(H2AsO4)2 0 were identified and reported previously with TRLFS in the pH range 1 to 3. Using a similar detection system and elevating the pH range a negatively charged fourth uranyl-arsenate complex, UO2AsO4- was found under circum neutral pH. Determining the complex formation constant for this complex was not possible due to the susceptibility of the fluorescence intensity to external influences and the difficulty of resolving the measured spectra into individual fluorescence contributions. By immediate shock-freezing to 15K we succeeded to measure a reproducible EXAFS spectrum of a uranyl-arsenate species in an aqueous solution at pH 2.
Keywords: Arsenate, Uranyl, aqueous solution, EXAFS, TRLFS Registration No. 20271

Annual Report 2013 - Institute of Ion Beam Physics and Materials Research
Cordeiro, A. L.; Fassbender, J.; Heera, V.; Helm, M. (Editors)
Abstract: The year 2013 was the third year of HZDR as a member of the Helmholtz Association (HGF), and we have made progress of integrating ourselves into this research environment of national Research centers. In particular, we were preparing for the evaluation in the framework of the so-called program oriented funding (POF), which will hopefully provide us with a stable funding for the next five years (2015 – 2019). In particular, last fall we have submitted a large proposal in collaboration with several other research centers. The actual evaluation will take place this spring. Most of our activities are assigned to the program “From Matter to Materials and Life” (within the research area “Matter”). A large fraction of this program is related to the operation of large-scale research infrastructures (or user facilities), one of which is our Ion Beam Center (IBC). The second large part of our research is labelled “in-house research”, reflecting the work driven through our researchers without external users, but still mostly utilizing our large-scale facilities such as the IBC, and, to a lesser extent, the free-electron laser. Our in-house research is performed in three so-called research themes, as depicted in the schematic below. What is missing there for simplicity is a small part of our activities in the program “Nuclear Waste Management and Safety” (within the research area “Energy”).
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-049 2014
    ISSN: 2191-8708
Registration No. 20265

Annual Report 2013 - Institute of Resource Ecology
Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A. (Editors)
Abstract: The Institute of Resource Ecology (IRE) ISone of the eight institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The Research activities are mainly integrated into the program “Nuclear Safety Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”.
Additionally, various activities have been started investigating chemical and environmental aspects of processing and recycling of strategic metals, namely rare earth elements. These activities are located in the HGF program “Energy Efficiency, Materials and Resources (EMR)”. Both programs, and therefore all work which is done at IRE, belong to the research sector “Energy” of the HGF.
The research objectives are the protection of humans and the environment from hazards caused by pollutants resulting from technical processes that produce energy and raw materials. Treating technology and ecology as a unity is the major scientific challenge in assuring the safety of technical processes and gaining their public acceptance. Namely, we investigate the ecological risks exerted by radioactive and non-radioactive metals in the context of nuclear waste disposal, the production of energy in nuclear power plants and in processes along the value chain of metalliferous raw materials. A common goal is to generate better understanding about the dominating processes essential for metal mobilization and immobilization on the molecular level. This in turn enables us to assess the macroscopic phenomena, including models, codes and data for predictive calculations, which determine the transport and distribution of contaminants in the environment.
  • Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-048 2014
    ISSN: 2191-8708
10,3 MB PDF
Registration No. 20264

Inter-sublevel transitions in single InAs/GaAs quantum dots
Stephan, D. R.; Bhattacharyya, J.; Helm, M.; Huo, Y.; Rastelli, A.; Schmidt, O.; Schneider, H.
Abstract: In the past, inter-band transitions in quantum dots (QDs) have received an appreciable amount of scientific interest. However, inter-sublevel transitions have been studied much less extensively, likely because of their strongly non-radiative nature and because of limited availability of tunable sources for resonant excitation. In this work we explore the dynamics of inter-sublevel transitions in single InAs/GaAs self-assembled QDs. We combine the commonly used micro-photoluminescence (PL) technique with time-resolved detection and additional excitation by a free-electron laser. The experiment is carried out in the following way: the low-density QD sample is illuminated with a picosecond pulsed Ti:sapphire laser. PL from a single QD is coupled into a spectrometer, recording the spectrum with a CCD detector, as well as the time-resolved transient via the time-correlated single photon counting technique. Introducing a free-electron laser pulse tuned to the inter-sublevel transition energy excites carriers to a higher energy level, which decay back to the ground state non-radiatively with a relatively short time constant. These inter-sublevel dynamics causes quenching in the exponential PL decay of the energy of the ground state, which can be observed in timeresolved measurements. Whereas previous studies on inter-sublevel transitions have used QD ensembles[1-3], investigating single dots excludes many-dot effects such as inhomogeneous broadening and inter-dot transfer, which should lead to a better understanding of intersublevel carrier dynamics.
  • Poster:
    20th International Conference on Electronic Properties of Two-Dimensional Systems (EP2DS-20) and 16th International Conference on Modulated Semiconductor Structures(MSS-16), 03.07.2013, Wroclaw, Polska
Registration No. 20263

Investigation of the e ffective mass in GaAsN
Eßer, F.; Drachenko, O.; Schneider, H.; Patanè, A.; Hopkinson, M.; Helm, M.
Abstract: As a member of diluted nitrides, GaAsN is a highly interesting material system for many application purposes such as LEDs, lasers, solar cells, and infrared photodetectors because of the tuning possibility of these devices by the variation of the nitrogen content. For an accurate description of this material system, a profound knowledge of the band structure and in particular the e ffective mass (EM) is crucial. Because of the inconsistency of previous results, which can be traced down to the particular investigation method, we apply several methods on one sample series of GaAsN containing samples with 0.1 - 1 percent of nitrogen. Cyclotron resonance spectroscopy, beeing the most direct method, reveals that the EM is not signi cantly a ffected by the nitrogen doping. Photoluminescence, on the other hand, stems from several transitions, which are not resolved spectrally, but identifi ed in time-resolved measurements. We discuss the di fferent behaviour of the involved transitions in magnetic f ields up to 7 T (static) and 41 T (pulsed).
  • Lecture (Conference):
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Deutschland
Registration No. 20262

Nd:YAG waveguide laser Q-switched by evanescent-field interaction with graphene
Tan, Y.; Chen, C.; Akhmadaliev, Sh.; Zhou, S.; Chen, F.
Abstract: We report on the Q-switched laser operation by the evanescent-field interaction with the graphene layers deposited on a Nd:YAG surface planar waveguide, which was fabricated by the 15 MeV carbon ion irradiation. Based on the simple and compact design of the cavity with saturable-absorber features, the Q-switched pulsed waveguide laser operation was achieved at the wavelength of 1064 nm through the interaction between the graphene layer and the evanescent-field of the waveguide mode. The maximum output pulse repetition rate was ~29 kHz with the pulse duration of ~9.8 µs.
Keywords: Q-switched; Rare-earth-doped materials; Waveguides Registration No. 20259

Mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films
Fu, Y.; Barsukov, I.; Meckenstock, R.; Lindner, J.; Raanaei, H.; Hjörvarsson, B.; Farle, M.
Abstract: The mechanism of tailored magnetic anisotropy in amorphous Co68Fe24Zr8 thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m(3). The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy. Registration No. 20257

Potential clinical predictors of outcome after postoperative radiotherapy of non-small cell lung cancer
Buetof, R.; Kirchner, K.; Appold, S.; Loeck, S.; Rolle, A.; Hoeffken, G.; Krause, M.; Baumann, M.
Abstract: Abstract:
The aim of this analysis was to investigate the impact of tumour-,
treatment- and patient-related cofactors on local control and survival after postoperative adjuvant radiotherapy in patients with non-small cell lung cancer (NSCLC), with special focus on waiting and overall treatment times.
For 100 NSCLC patients who had received postoperative radiotherapy, overall, relapse-free and metastases-free survival was retrospectively analysed using Kaplan-Meier methods. The impact of tumour-, treatment- and patient-related cofactors on treatment outcome was evaluated in uni- and multivariate Cox regression analysis.
No statistically significant difference between the survival curves of the groups with a short versus a long time interval between surgery and radiotherapy could be shown in uni- or multivariate analysis.
Multivariate analysis revealed a significant decrease in overall survival times for patients with prolonged overall radiotherapy treatment times exceeding 42 days (16 vs. 36 months) and for patients with radiation-induced pneumonitis (8 vs. 29 months).
Radiation-induced pneumonitis and prolonged radiation treatment times significantly reduced overall survival after adjuvant radiotherapy in NSCLC patients. The negative impact of a longer radiotherapy treatment time could be shown for the first time in an adjuvant setting. The hypothesis of a negative impact of longer waiting times prior to commencement of adjuvant radiotherapy could not be confirmed.
Registration No. 20255

Aging of the (2+1)-dimensional Kardar-Parisi-Zhang model
Ódor, G.; Kelling, J.; Gemming, S.
Abstract: Extended dynamical simulations have been performed on a (2+1)-dimensional driven dimer lattice-gas model to estimate aging properties. The autocorrelation and the autoresponse functions are determined and the corresponding scaling exponents are tabulated. Since this model can be mapped onto the (2+1)-dimensional Kardar-Parisi-Zhang surface growth model, our results contribute to the understanding of the universality class of that basic system. Registration No. 20253

Elastic Properties of Nickel Carbides
Kelling, J.; Zahn, P.; Gemming, S.
Abstract: The nickel -- carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube growth and as a substrate for metal-induced crystallization of graphene and graphite.
Nickel carbides as bulk materials are out
of reach for experimental studies because of their meta-stability. Ab-initio studies are rare. We present our ab-initio -- frozen phonon results for the elastic properties of Ni3C, Ni2C and NiC.
  • Poster:
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 30.03.-04.04.2014, Dresden, Germany
Registration No. 20252

GPU-based Atomistic Simulations\\on spatio-temporal experimental Scales
Kelling, J.; Heinig, K.-H.; Gemming, S.
Abstract: The Kinetic Metropolis Lattice Monte-Carlo (KMC) method is a means of performing atomistic simulations of self-organization processes in solids at by far larger scales than those accessible via Molecular Dynamics. Employing a cellular automaton approach allows incorporation of many body interactions and external driving forces. Here, we present an efficient KMC implementation on single and multiple GPUs, which allows us to study phase separation and nanostructure-evolution at spatio-temporal experimental scales. The KMC implementation has been used to develop with industrial partners a new Si-based nanocomposite for next-generation thin-film solar cells.
  • Poster:
    GPU Technology Conference, 24.-27.03.2014, San Jose, California, USA
Registration No. 20251

Bulk viscosity of the gluon plasma in a holographic approach
Yaresko, R.; Kämpfer, B.
Abstract: A gravity-scalar model in 5-dimensional Riemann space is adjusted to the thermodynamics of SU(3) gauge field theory in the temperature range of 1–10 T/Tc to calculate holographically the bulk viscosity in 4-dimensional Minkowski space. Various settings are compared, and it is argued that, upon an adjustment of the scalar potential to reproduce exactly the lattice data within a restricted temperature interval above Tc, rather robust values of the bulk viscosity to entropy density ratio are obtained. Registration No. 20250

Experimental study of magnetic anisotropy in a layered CsNd(MoO4)2
Tkac, V.; Orendácová, A.; Cizmár, E.; Orendác, M.; Zvyagin, S.; Anders, A. G.; Pavlík, V.; Feher, A.
Abstract: Ground-state properties of Nd3+ ion in the magnetically concentrated CsNd(MoO4)2 lattice of orthorhombic symmetry have been investigated at low temperatures. Magnetic-field dependence of magnetization measured at 5 K in the magnetic field applied along the a, b, c crystallographic axes reflects slight deviations from the tetragonal symmetry of a local surrounding of Nd3+ ion. The analysis of the data performed within a model of an ideal paramagnet provided g-factor values, ga = 3.08, gb = 1.90, and gc = 1.95. Angular dependence of the electron paramagnetic resonance spectra studied at temperature 2.5 K was investigated in the ab, ac and bc planes. The spectra are dominated by a broad asymmetric line which is strongly deformed due to the formation of a fine structure ascribed to the presence of nonequivalent Nd3+ sites. The analysis of the spectra confirmed the easy-axis character of a magnetic anisotropy. In addition, nontrivial tilting of the local anisotropy axes from the crystallographic axes was revealed, indicating lowering of crystal symmetry at low temperatures. Registration No. 20244

Padé approximations for the magnetic susceptibilities of Heisenberg antiferromagnetic spin chains for various spin values
Law, J. M.; Benner, H.; Kremer, R. K.
Abstract: The temperature dependence of the spin susceptibilities of S = 1, 3/2 , 2, 5/2 and 7/2 Heisenberg antiferromagnetic 1D spins chains with nearest-neighbor coupling was simulated via Quantum Monte Carlo calculations, within the reduced temperature range of 0,005 ≤ T* ≤ 100, and fitted to a Padé approximation with deviations between the simulated and fitted data of the same order of magnitude as or smaller than the quantum Monte Carlo simulation error. To demonstrate the practicality of our theoretical findings, we compare these results with the susceptibility of the well known 1D chain compound TMMC ([(CH3)4N[MnCl3]], d5, S = 5/2) and find that different intra-chain spin–exchange parameters result if we consider the data above and below the structural phase transition reported for TMMC at ~126 K. The structural phase transition, which gives rise to an anomaly in the magnetic susceptibility, is independent of the magnetic field up to magnetic fields of 7 T. Additionally, we show that the S = 1 system NiTa2O6 with tri-rutile crystal structure can be very well described as a Heisenberg S = 1 spin chain. Registration No. 20243

Characterization of the spin-½ linear-chain ferromagnet CuAs2O4
Caslin, K.; Kremer, R. K.; Razavi, F. S.; Schulz, A.; Munoz, A.; Pertlik, F.; Liu, J.; Whangbo, M.-H.; Law, J. M.
Abstract: The magnetic and lattice properties of the S = 1/2 quantum-spin-chain ferromagnet CuAs2O4, mineral Name trippkeite, were investigated. The crystal structure of CuAs2O4 is characterized by the presence of corrugated CuO2 ribbon chains.Measurements of themagnetic susceptibility, heat capacity, electron paramagnetic resonance, and Raman spectroscopy were performed. Our experiments conclusively show that a ferromagnetic Transition occurs at ∼7.4 K. Ab initio DFT calculations reveal dominant ferromagnetic nearest-neighbor and weaker antiferromagnetic next-nearest-neighbor spin exchange interactions along the ribbon chains. The ratio of Jnn/Jnnn is near −4, placing CuAs2O4 in close proximity to a quantum critical point in the Jnn-Jnnn phase diagram. TMRG simulations used to analyze the magnetic susceptibility confirm this ratio. Single-crystal magnetization measurements indicate that a magnetic anisotropy forces the Cu2+ spins to lie in an easy plane perpendicular to the c axis. An analysis of the field- and temperature-dependent magnetization by modified Arrott plots reveals a 3d-XY critical behavior. Lattice perturbations induced by quasihydrostatic pressure and temperature were mapped via magnetization and Raman spectroscopy Registration No. 20242

Asphericity of pretherapeutic FDG uptake predicts outcome in NSCLC
Rogasch, J. M.; Steffen, I. G.; Furth, C.; Beyer, M.; Riedel, S.; Schreiber, J.; Buchert, R.; Amthauer, A.; Hofheinz, F.; Apostolova, I.
Abstract: Ziel/Aim:
FDG-PET/CT has become the standard for staging of local tumor extent, mediastinal lymph node involvement and distant metastatic disease in patients with non-small-cell lung cancer (NSCLC). However, its role for prognosis is less clear. The aim of the present study was to evaluate the prognostic value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP).

FDG-PET/CT had been performed in 47 patients (65.1±8.8y, 38 males) with newly diagnosed NSCLC prior to treatment. PET images of the primary tumor were segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducible intensity threshold after subtraction of local background. The ASP defined as the deviation of the tumor's shape from sphere symmetry was implemented in ROVER. Kaplan-Meier analysis with respect to overall (OS) and progression-free survival (PFS) was performed for localization (central vs. peripheral), SUVmax, metabolically active tumor volume (MTV), total lesion glycolysis (MTV*SUVmean) and ASP. OS and PFS curves were separated by the median value and compared by log-rank tests.

32 patients experienced tumor progression or recurrence after a median interval of 6.2 (range, 0.4-26.7) months. 19 of these patients died during a median follow-up of 8.7 (0.4-26.7) months. ASP was the only prognostic factor for PFS (p=0.01): the probability of 1-year PFS decreased from 69 % in the patients with low ASP to 37 % in the patients with high ASP. Furthermore, there was a tendency towards longer OS in case of small vs large ASP (p=0.06, 1-year-OS 81% vs 51%). The localization of the tumor was a strong predictor for OS (p=0.004, 1-year OS 78% vs 25% for peripheral vs central localization), but not for PFS (p=0.12).

The novel parameter asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and glycolytic tumor volume.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, D
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A13
Registration No. 20240

Correction of scan time dependence of standard uptake values in oncological PET
van den Hoff, J.; Lougovski, A.; Schramm, G.; Maus, J.; Oehme, L.; Petr, J.; Beuthien-Baumann, B.; Kotzerke, J.; Hofheinz, F.
Abstract: Background

Standard uptake values (SUV) as well as tumor-to-blood standard uptake ratios (SUR) measured with [18F-]fluorodeoxyglucose (FDG) PET are time dependent. This poses a serious problem for reliable quantification since variability of scan start time relative to the time of injection is a persistent issue in clinical oncological Positron emission tomography (PET). In this work, we present a method for scan time correction of, both, SUR and SUV.

Assuming irreversible FDG kinetics, SUR is linearly correlated to Km (the metabolic rate of FDG), where the slope only depends on the shape of the arterial input function (AIF) and on scan time. Considering the approximately invariant shape of the AIF, this slope (the `Patlak time?) is an investigation independent function of scan time. This fact can be used to map SUR and SUV values from different investigations to a common time point for quantitative comparison. Additionally, it turns out that modelling the invariant AIF shape by an inverse power law is possible which further simplifies the correction procedure. The procedure was evaluated in 15 fully dynamic investigations of liver metastases from colorectal cancer and 10 dual time point (DTP) measurements. From each dynamic study, three `static scans? at T = 20, 35, and 55 min post injection (p.i.) were created, where the last scan defined the reference time point to which the uptake values measured in the other two were corrected. The corrected uptake values were then compared to those actually measured at the reference time. For the DTP studies, the first scan (acquired at 78.1 ? 15.9 min p.i.) served as the reference, and the uptake values from the second scan (acquired 39.2 ? 9.9 min later) were corrected accordingly and compared to the reference.

For the dynamic data, the observed difference between uncorrected values and values at reference time was (?52 ? 4.5)% at T = 20 min and (?31 ? 3.7)% at T = 35 min for SUR and (?30 ? 6.6)% at T = 20 min and (?16 ? 4)% at T = 35 min for SUV. After correction, the difference was reduced to (?2.9 ? 6.6)% at T = 20 min and (?2.7 ? 5)% at T = 35 min for SUR and (1.9% ? 6.2)% at T = 20 min and (1.7 ? 3.3)% at T = 35 min for SUV. For the DTP studies, the observed differences of SUR and SUV between late and early scans were (48 ? 11)% and (24 ? 8.4)%, respectively. After correction, these differences were reduced to (2.6 ? 6.9)% and (?2.4 ? 7.3)%, respectively.

If FDG kinetics is irreversible in the targeted tissue, correction of SUV and SUR for scan time variability is possible with good accuracy. The correction distinctly improves comparability of lesion uptake values measured at different times post injection.
Registration No. 20239

Spin Vortices in Magnetic Multilayers
Wintz, S.
Abstract: The focus of this thesis are spin vortices in magnetic multilayers. A spin vortex is a topological spin texture, characterized by a planar magnetization curl that tilts out- of-plane in the nanoscopic core region at the center. There are two different states possible for both the rotation sense of the curl (circulation) and the orientation of the core (polarity), leading to a binary vortex chirality. The spin vortex is typically the ground state of micron sized ferromagnetic thin film disks or square-shaped elements. During the past decades, spin vortices were studied intensively with respect to their magnetostatic and—in particular—their intriguing magneto-dynamic properties. Along with these fundamental studies, proposals were made for the application of vortices for example in data storage and radio-frequency oscillator technology. With respect to density and synchronization in both these application concepts—but also from a fundamental point of view—the interaction between vortices is a crucial issue to address. This holds true especially for the vertical geometry of trilayer vortices (ferromagnet/non-ferromagnet/ferromagnet) in which giant- or tunnel magneto resistance effects as well as spin-transfer torques are exploitable. However, the knowledge on such coupled vortices has been fairly limited. Therefore it was the aim of this work to investigate the magnetic properties of vertically coupled vortex pairs. Investigations were mainly made by means of synchrotron-based transmission x-ray microscopy. This method uniquely allows for a direct and element selective imaging of the magnetic orientation in spin textures with the lateral resolution required. The vortex pair samples were fabricated by electron beam lithography and thin film deposition techniques. Additional magnetometry measurements were employed to address the basic material and coupling properties. Also micromagnetic simulations were carried out in order to complement the experimental results. By this approach, different vortex pair configurations concerning the relative orientation of circulations and polarities, are identified. It is shown that interlayer exchange coupling can be exploited to deterministically set the relative circulation state, and that ion irradiation provides a method to finely tune this coupling after the multilayer has been deposited. In contrast, the polarity states are found not to be controllable by any of the interlayer coupling strengths accessible. Both states are stable in fact, with the parallel configuration representing the ground state. The field response of a vortex pair is evaluated to range from a quasi-independent behavior to a strict coupling between both layers, where the latter can be described by a single layer vortex response with effective magnetic properties. When a relevant non-collinear interlayer coupling is introduced to the vortex pair state, the system is found to exhibit radial magnetization components with opposing sign between both ferromagnetic layers, which in turn results in the formation of a three-dimensional torus vortex accompanied by a symmetry break of the polarity states. The findings achieved in this work mark a significant advance of the state of the art in the field of spin vortices and coupled spin textures, and they may also be of value for future vortex-based applications in technology.
Keywords: magnetism, vortex, multilayer, coupling, x-ray microscopy
  • Thesis / Students' report:
    TU Dresden, 2014
    Mentor: Prof. Dr. Jürgen Faßbender
    153 Seiten
Registration No. 20230

Ga-reiche Schichten in Si – vom Supraleiter zum Isolator
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.
Abstract: Es hat kein Abstract vorgelegen.
  • Lecture (Conference):
    51. Treffen der Nutzergruppe Ionenimplantation, 03.04.2014, Erlangen, Deutschland
Registration No. 20228

Supraleitende Schichten in Ge und Si – Einfluss der Ausheilbedingungen
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.
Abstract: Es hat kein Abstract vorgelegen.
  • Lecture (Conference):
    35. Treffen der Nutzergruppe Heißprozesse und RTP, 02.04.2014, Erlangen, Deutschland
Registration No. 20227

Combined PET/MR: Where Are We Now? Summary Report of the Second International Workshop on PET/MR Imaging April 8–12, 2013, Tubingen, Germany
Bailey, Dale L.; Barthel, H.; Beuthin-Baumann, B.; Beyer, T.; Bisdas, S.; Boellaard, R.; Czernin, J.; Drzezga, A.; Ernemann, U.; Franzius, C.; Gückel, B.; Handgretinger, R.; Hartenbach, M.; Hellwig, D.; Nadel, H.; Nekolla, Stephan G.; Pfluger, T.; Pichler, Bernd J.; Quick, Harald H.; Sabri, O.; Sattler, B.; Schäfer, J.; Schick, F.; Siegel, Barry A.; Schlemmer, Heinz P.; Schwenzer, Nina F.; van den Hoff, J.; Veit-Haibach, P.; Wehrl, Hans F.
Abstract: This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging modality. Discussions were focused on the search for truly novel, unique clinical and research applications as well as technical issues such as reliable and accurate approaches for attenuation and scatter correction of PET emission data. The workshop provided hands-on experience with PET and MR imaging. In addition, structured and moderated open discussion sessions, including six dialogue boards and two roundtable discussions, provided input from current and future PET/MR imaging users. This summary provides a snapshot of the current achievements and challenges for PET/MR.
Keywords: Combined imaging, Molecular imaging, PET/CT, PET/MR, Quantification, MRbased attenuation correction methods, Oncology, Paediatric oncology, Neurology, Cardiology Registration No. 20225

Ferromagnetism and impurity band in a magnetic semiconductor: InMnP
Khalid, M.; Weschke, E.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: We have synthesized ferromagnetic InMnP, a member of the III-Mn-V ferromagnetic semiconductor family,
by Mn ion implantation and pulsed laser annealing. Clear ferromagnetic hysteresis loops and a perpendicular
magnetic anisotropy are observed up to a Curie temperature of 42 K. Large values of negative magnetoresistance
and magnetic circular dichroism as well as an anomalous Hall effect are further evidence of a ferromagnetic
order in InMnP. An effort is made to understand the transport mechanism in InMnP using the theoretical models.
We find that the valence band of InP does not merge with the impurity band of the heavily doped ferromagnetic
InMnP. Our results suggest that impurity band conduction is a characteristic of Mn-doped III-V semiconductors
which have deep Mn-acceptor levels.

Keywords: diluted magnetic semiconductor, III-V semiconductor Registration No. 20209

Analyse von Artefakten in der MR-basierten Schwächungskorrektur am PET-MR
May, C.; Schramm, G.; Platzek, I.; Kotzerke, J.; Beuthien-Baumann, B.
Abstract: Ziel/Aim:
Ziel der Arbeit ist die Analyse von Artefakten in MR-basierten Schwächungsbildern (MRMaps) bei Patientenuntersuchungen am Philips Ingenuity TF PET/MR. Die Artefakte wurden auf Art und Häufigkeit untersucht.

Insgesamt wurden 723 PET/MR Untersuchungen des Körperstamms im Zeitraum 01.10.2012 bis 01.10.2013 ausgewertet. Fehlerhafte MRMaps wurden mit dem zugrundeliegenden Schwächungs-MRT parallel betrachtet. Die Segmentierungsfehler wurden in folgende Kategorien eingeteilt: 1. die Lunge wurde nicht erkannt, 2. die Lunge wies eine falsche Form auf, 3. durch Metallimplantate verursachte Artefakte (z.B. durch Hüft-/Knie-TEP, Sternalcerclagen, Ports oder Zahnfüllungen), 4. sonstige Artefakte.

Es wurden 52 MRMaps mit Segmentierungsfehlern gefunden, die nicht durch eine einfache Nachbearbeitung der MTRA korrigiert werden konnten. In 20 Fällen wurde die Lunge nicht erkannt. In 24 Fällen wurde die Form der Lunge falsch segmentiert, wobei die Form 5 mal zu klein und 19 mal zu groß war. 35 Artefakte fielen in die Kategorie Metallartefakte, 5 in die Kategorie sonstige Artefakte. Einzelne MRMaps wiesen eine Kombination von Segmentierungsfehlern auf. Zusätzliche PET Rekonstruktionen mit korrigierten MRMaps zeigten SUV Abweichungen von bis zu 50% in verschiedenen Körperarealen.

Aufgrund der beobachteten Artefakte und deren Auswirkungen sollten bei allen PET/MRT Untersuchungen die MRMap von der MTRA auf Fehler untersucht werden.Treten gröbere Artefakte in der MRMap auf, müssen diese korrigiert und das PET Bild neu rekonstruiert werden, um eine quantitativ korrekte Auswertung der PET-Daten zu gewährleisten.
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A102
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
Registration No. 20208

Asphericity as a measure of spatial heterogeneity is superior to SUVmax change as a predictor of therapy outcome in FDG-PET of patients with head and neck cancer
Hofheinz, F.; Zöphel, K.; Lougovski, A.; Oehme, L.; Beuthien-Baumann, B.; Maus, J.; Steffen, G.; Buchert, R.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.
Abstract: Ziel/Aim:
The prognostic value of SUV is unsatisfactory in head and neck carcinoma. The aim of the present study was to evaluate a new measure of spatial heterogeneity as prognostic factor in FDG PET investigations of this cancer type.

We define the asphericity of a lesion as ASP=[1/(36*pi)*S^3/V^2]^(1/3)-1 where S is the lesion's surface and V is it's volume. ASP is a dimensionless number having a simple interpretation: ASP represents the fractional increase of the surface of the lesion relative to the surface of a sphere possessing the same volume (i.e. ASP=0 for a spherical lesion). ASP was evaluated retrospectively in 36 FDG PETs of patients with head and neck squamous cell carcinoma prior to chemoradiotherapy. A second FDG PET/CT was performed one to two weeks after start of therapy. The baseline and interim FDG images of the primary tumor were segmented using the ROVER 3D segmentation tool. The change of SUVmax (dSUVmax) of the primary tumor was computed. ASP was computed in the baseline PET. Kaplan-Meier analysis with respect to overall survival (OAS) was performed for dSUVmax and ASP and were compared by log-rank tests.

Mean OAS was 20.7 month. ASP was prognostic for OAS (p=0.0001), as was dSUVmax but with distinctly lower significance (p=0.023). Higher tumor asphericity was associated with reduced survival. Patients with ASP>25% showed a 2-year OAS rate of 12% compared to 74% in patients with ASP < 25%.

ASP of the pretherapeutic FDG uptake pattern in the primary tumor is predictive for survival of patients with head-and-neck carcinoma. It is superior to changes of SUVmax during therapy. This is remarkable since ASP is derived from a single PET scan prior to therapy, while computation of dSUVmax requires at least two PET measurements. Further investigations are necessary to confirm these preliminary results.
  • Poster:
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A85-A86
Registration No. 20207

Dosimetrische Evaluation des therapeutischen Potentials von Hg-197m
Freudenberg, R.; Walther, M.; Wunderlich, G.; Kotzerke, J.
Abstract: Ziel/Aim:
Hg-197m emittiert beim Zerfall Photonen und Elektronen. Damit besitzt es Potential zur nuklearmedizinischen Anwendungen. Während die emittierte Gammastrahlung die Lokalisation ermöglicht, erfolgt durch Elektronen eine lokal begrenzte Dosisdeposition. In Abhängigkeit der Elektronenenergie können damit Läsionen mit Durchmessern bis zu einigen mm therapiert werden. Anhand theoretischer Betrachtungen zur Dosisdeposition erfolgt ein Vergleich mit dem Therapienuklid Lu-177.

Die Produktion von Hg-197m erfolgt durch Bestrahlung von Gold-Targets am Zyklotron über eine (p,n)-Reaktion. Hg-197m wandelt sich mit einer Halbwertszeit von 23,8 h im Wesentlichen über Hg-197 in stabiles Au-197 um. Die Bildgebungseigenschaften wurden an einer Philips „BrightView“ Gammakamera nachgewiesen, Emissionsspektren mit einem GeLi-Halbleiterdetektor gemessen. Durch Simulationen mit Geant4 wurden Dose-Point-Kernels (DPK) für Hg-197m, Hg-197 und Lu-177 generiert. Weiterhin erfolgten die Schätzung der Dosisdeposition in Läsionen verschiedener Größen sowie ein Vergleich mit MIRD S-Werten.

Die DPK zeigen für Hg-197m und Hg-197 bei einem radialen Abstand < 270 μm eine 10-fach höhere Dosisdeposition im Vergleich zu Lu-177 sowie einen 5-fach höheren Dosiseintrag > 1 mm infolge der intensiveren Photonenemission. Im Bereich dazwischen dominiert die β--Dosisdeposition durch Lu-177. Für eine Läsion mit 10 g resultiert eine 1,9-fach höhere Tumordosis durch Hg-197m bei gleicher Zerfallszahl, bei Komplettzerfall beträgt die zu erwartende Dosis 0,6 Gy/MBq für Hg-197m und 2 Gy/MBq für Lu‑177.

Die Eignung von Hg-197m für nuklearmedizinische Zwecke konnte gezeigt werden, die erreichbaren Dosen liegen in der Größenordnung von Lu-177. Die Synthese neuer Radiopharmaka kann vielversprechende neue Behandlungskonzepte ermöglichen. Zusätzlich ist infolge des hohen linearen Energietransfers der Auger-Elektronen von Hg-197 nach DNA-Bindung eine vermehrte Induktion von Doppelstrangbrüchen zu erwarten.
  • Poster:
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A79
Registration No. 20206

Radiopharmacology of an Anti-CEA Monoclonal Antibody-l-RNA / l-DNA Duplex Pretargeting System
Bergmann, R.; Schlesinger, J.; Koezle, I.; Förster, C.; Klussmann, S.; Vonhoff, S.; Pietzsch, H.-J.; Pietzsch, J.; Wüst, F.; Behrsin, O.; Micheel, B.; Steinbach, J.
Abstract: Ziel/Aim:
This current study is aimed at demonstrating of the applicability of l‑oligonucleotides as a novel recognition system for pretargeting using a radiolabeled 17mer l‑DNA and complementary l‑RNA bound to microspheres and an antibody as targeting vector.

Small animal PET, biodistribution and metabolite studies of Ga-68 and Y-86-labeled L-DNA were carried out in rats and mice. Hybridization in vivo was demonstrated through cl‑RNA-modified microspheres trapped in the lungs and injection of complementary Ga-68-labeled 17mer l‑DNA. Tumor accumulation and pharmocokinetics in the human colon carcinoma models LS174T (n=10) and LoVo (n=2) tumors on NMRI nu/nu mice were evaluated with a 17mer cl‑RNA modified anti CEACAM5 (CEA) antibody aCEA(IG1)D11-DG2 and Ga-68-L-DNA.

The Ga-68- and Y-86-labeled L-DNAs showed typical biodistributions pattern of hydrophylic compounds with fast renal elimination and displayed high metabolic stability in vivo. cl‑RNA-microspheres trapped in the lungs could be visualized (SUV=0.51), i.e. 1.5%ID of the Ga-68-labeled 17mer l‑DNA were hybridized with the cl‑RNA on the microspheres. The LS174T and LoVo tumors were clearly visible with SUVs (median, 25%; 75% percentile) of 0.20 (0.19; 0.31) and 0.18 (0.16; 0.19), respectively. The averaged tumor/muscle ratio was 5.4±0.4 by administering the DG2 immunoconjugate first and injection of radiolabeled L-DNA after a 24 h delay.

Preliminary results demonstrate that the recognition system has promising properties for pretargeting in vivo to improve molecular imaging and therapy of solid tumors.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A49
Registration No. 20205

Incorporation of position dependent detection probability into a tube-of-response based model for system matrix calculation in 3D PET imagereconstruction
Lougovski, A.; Maus, J.; Hofheinz, F.; Schramm, G.; van den Hoff, J.
Abstract: Ziel/Aim:
We have presented previously a model for fast on-the-fly volume-of-intersection (VOI) system matrix calculation for PET image reconstruction. The model replaces cubic voxels by spheres and the usual line of response by a cylindrical tube of response (TOR) whose diameter matches the size of the detector crystals. We now present a refined model which takes into account solid angle effects and position dependent detection efficiency across the crystal surface by using a TOR with a position-variant density.

We model the detection efficiency across the crystal surface as a radially symmetric function (superposition of two error functions) which leads to a TOR with a variable radial density. Additionally accounting for the solid angle effects results in a further modification of the TOR density that also varies in the axial direction. Consequently, the density-weighted VOI between TOR and spherical voxel now depends not only on the distance between the center of spherical voxel and line of TOR but also on the axial position along the TOR. The new model was integrated into our Tube-Of-Response High Resolution OSEM Reconstruction (THOR) and evaluated using a cylindrical phantom with spherical inserts. We have investigated several figures of merit (reconstructed spatial resolution, noise level, extend of Gibbs artifacts) and compared them between the original and modified TOR models.

The modified model maintains the high spatial resolution already demonstrated for the original TOR approach while showing an improved noise characteristics and reduction of residual Gibbs artifacts. The improvement of image quality overall is only modest.

The proposed modification of the TOR model for on-the-fly system matrix computation allows more accurate modelling of the scanner geometry and event detection and leads to reduced noise levels and Gibbs artifacts in the reconstructed image. However, it noticeably increases reconstruction times in comparison to the original model.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A35-A36
Registration No. 20204

Detektionraten von Skelettmetastasen neuroendokriner Tumore (NET) im F18-NaF-PET und MRT am PET/MR im Vergleich zur Somatostatin-Rezeptor-Szintigraphie (SSRS)
Beuthien-Baumann, B.; Platzek, I.; Strumpf, A.; Schramm, G.; Zessin, J.; van den Hoff, J.; Kotzerke, J.
Abstract: iel/Aim:
NET weisen in fortgeschrittenen Stadien häufig Skelettmetastasen auf. Die Skelettszintigraphie detektiert Metastasen die eine Alteration der Knochenmatrix ausgelöst haben; Knochenmarkmetastasen werden in der MRT frühzeitig erkannt. Erhöht die Kombination von NaF-PET und MRT bei NET die Detektionsrate ossärer Metastasen?

Untersucht wurden 15 Patienten (5w/ 10m; mittl. Alter 63 Jahre mit NET (n=12), medull. Schilddrüsen-Ca (n=1) und SSR-pos. Foll. Schilddrüsen-Ca (n=2) mittels F18-NaF-PET sowie MRT am sequenziellen PET/MR (Ingenuity PET/MR, Philips) im Vergleich zum „Goldstandard“ SSRS (Ga68 DOTATOC/ DOTATATE) am PET/CT (Biograph 16, Siemens). Die MRT-Sequenzen bestanden neben dem Schwächungs-MRT (T1 TFE) aus einer sag. Wirbelsäulenaufnahe (T1 TSE n=10), einer cor. Ganzkörperaufnahme (T1TFE n=9), einer DWIBS (n=3). Die Kombination mehrerer MR-Sequenzen wurde bei langen Untersuchungszeiten nicht von allen Patienten toleriert.

Ein Patient wies im SSRS und im NaF eine disseminierte Metastasierung auf. Bei 14 Pat. wurden mittels SSRS 200 Metastasen im Skelett detektiert. Im NaF-PET fanden sich 176 Matchbefunde (88%), in den MRT-Untersuchungen zeigten sich 116 Läsionen (58%). Bei der Betrachtung allein der Wirbelsäulenbefunde (n=105 im SSRS), wurden im NaF 87%, im MRT 63% der WS-Läsionen detektiert. Im MRT zeigten sich 10 WS-Läsionen, die im NaF nicht abgrenzbar waren. Die Zusammenschau von NaF-PET und MRT erleichterte die Differenzierung zwischen Metastase oder degenerativem Befund.

Ausgehend vom „Goldstandard SSRS“ zeigte sich eine hohe Detektionsrate der ossären Metastasen im NaF-PET. Die Detektionsrate mit den durchgeführten MRT-Sequenzen fiel geringer aus, hier wird eine Optimierung der MRT-Sequenzen angestrebt. Die Kombination NaF-PET und MRT erleichtert die Differenzierung zwischen Metastase und Degeneration.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A30
Registration No. 20203

Compensation and evaluation of metal-implant-induced artifacts in MR-based attenuation correction
Schramm, G.; Maus, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.
Abstract: Ziel/Aim:
MR-based attenuation correction (MRAC) using tissue type segmentation suffers from metal-implant-induced artifacts (MAs) in the underlying MR scan. We propose an improved MRAC segmentation algorithm compensating MAs in MR-based attenuation maps (MRMaps) and evaluate the quantitative influence of these artifacts on the reconstructed PET images.

MA-based cavities in MRMaps are filled by the developed algorithm using a delineation of the patient's body contour that is derived from the PET emission image . PET emission data of 11 patients with MAs (endoprotheses, sternal cerlages) examined in a Philips Ingenuity PET/MR were reconstructed with the vendor-provided method for attenuation correction (MRMap1,PET1) and additionally with our MRAC algorithm (MRMap2,PET2). Both types of MRMaps were visually inspected for segmentation errors. The segmentation errors in MRMap1 were classified into four classes (L1 and L2 artifacts inside the lung, and B1 and B2 artifacts inside the remaining body depending on the assigned attenuation coefficients). The average relative SUV differences (eps_relav) between PET1 and PET2 in all regions showing erroneous attenuation coefficients in MRMap1 were calculated.

MRMap1 showed erroneous attenuation coefficients in regions near metal implants and inside the patient's lung in all 11 patients. In MRMap2, all MA regions were filled with the soft tissue attenuation coefficient and the lung was correctly segmented in all cases. MRMap2 showed small residual segmentation errors in 8 patients. eps_relav was (mean+-sd): (-57+-1)% in B1, (-43+-4)% in B2, (19+-19)% in L1 and (128+-50)% in L2 regions.

MAs severely disturb MR-based attenuation correction and SUV quantification in PET/MR. The developed algorithm is able to compensate for these artifacts, improves SUV quantification accuracy distinctly and is suitable for clinical application.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A29
Registration No. 20202

Development of a novel class of spirocyclic σ1 receptor ligands − structure-affinity relationships and fluorine-18 radiolabeling
Xie, F.; Kniess, T.; Deuther-Conrad, W.; Bergmann, R.; Mamat, C.; Brust, P.; Pietzsch, J.; Steinbach, J.; Jia, H.
Abstract: Ziel/Aim:
Two subtypes of sigma (σ) receptors were confirmed. While the expression of σ1 is mainly altered in several brain disorders, both of them are expressed in a number of tumor entities. Some radioligands for imaging of σ1 and σ2 have been developed but most of them suffer from lipophilicity too high for tumor targeting. The aim of this study was to synthesize a series of novel spirocyclic σ1 receptor ligands, and to develop by analyzing structure-affinity relationships a suitable hydrophilic radiotracer with high affinity and selectivity for σ1.

A series of novel spirocyclic σ1 receptor ligands was designed, synthesized, and characterized. The affinity to σ1 and σ2 receptors was assessed and the most superior compound chosen for radiolabeling with fluorine-18. The logD value of the radiotracer, its stability in vitro and in vivo as well the biodistribution in rats were investigated.

Six spirocyclic derivatives have been synthesized; Ki values were determined to be in the range of 3.26 - 11.2 nM for σ1 and 164.4 - 312.4 nM for σ2. Compound 1 (8-[4-(2-fluoroethoxy)benzyl]-1,4-dioxa-8-azaspiro[4.5]decane; Ki σ1=5.38±0.43 nM, Ki σ2=164±20.4 nM, was selected for fluorine-18 radiolabeling. [18F]1 was prepared by fluoroethylation via a two-step automated procedure in 20% yield after column purification. The radiochemical purity was >99% as determined by HPLC analysis, the specific activity was in the range of 25 - 45 GBq/μmol. The logD value of [18F]1 was determined as 0.81±0.13. [18F]1 was stable in saline, ethanol, and human plasma in vitro for up to 2h. In preliminary experiments an uptake in mice brain of 2.6% ID at 5 min p.i. was detected.

We designed a potential spirocyclic σ1 receptor ligand with high affinity, selectivity, and excellent hydrophilicity. The biological evaluation of the corresponding radiotracer in brain and selected tumor models is ongoing.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Nuklearmedizinischen Gesellschaft (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A25
Registration No. 20201

Radiosynthesis of 5-(2-[18F]fluoroethyl)-sunitinib, an inhibitor of VEGFR-2
Knieß, T.; Kuchar, M.; Pietzsch, J.; Steinbach, J.
Abstract: Ziel/Aim:
Sunitinib is a multi-tyrosine kinase inhibitor (TKI) targeting VEGFR, PDGFR and FLT-3. Radiolabeled sunitinib might be suitable probe for monitoring angiogenesis with PET and to facilitate the success of corresponding anti-angiogenic
chemotherapy for the individual patient. For this purpose we developed an fluorine-18 radiolabeled PET tracer, 5-(2-[18F]fluoroethyl)-sunitinib basing on the lead structure of sunitinib.
The reference compound 5-(2-fluoroethyl)-sunitinib was synthesized by Knoevenagel condensation of 5-(2-fluoroethyl)-indoline-2-one with N-[2-(diethylamino)ethyl]-2,4-dimethyl-5-formyl-1H-pyrrole-3-carboxamide. Two suitable precursors for radiolabeling were obtained by reacting 5-(2-bromoethyl)-substituted sunitinib with AgC7H7SO3 and AgCH3SO3, respectively. In a set of experiments for finding the optimal radiolabeling conditions 4 mg of each
precursor was reacted with [18F]fluoride at a scheduled temperature regime for 20 min in acetonitrile, DMF or DMSO.
In a competition binding assay against VEGFR-2 a Kd value of 9 nM for 5-(2-fluoroethyl)-sunitinib was determined. For radiolabeling with [18F]fluoride the methanesulfonyl-substituted precursor in acetonitrile gave radiochemical yields up to 8%. In large scale synthesis using a TracerLAB (GE) synthesiser 8mg of precursor were reacted with 10 GBq of [18F]fluoride in acetonitrile at 110°C for 12 min. After semi-preparative HPLC purification and SPE separation 115-135 MBq of 5-(2-[18F]fluoroethyl)-sunitinib could be obtained in radiochemical purity > 95% and in a specific activity of 38-62 GBq/[mu]mol.
The new VEGFR-2 targeted radiolabeled probe 5-(2-[18F]fluoroethyl)-sunitinib was successfully synthesized by radiofluorination of the corresponding methanesulfonyl-substituted precursor with [18F]fluoride. The radiotracer can be obtained in high chemical and radiochemical purity in 100 MBq scale.
  • Lecture (Conference):
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal:
    Nuklearmedizin 53(2014), A43-A44
Registration No. 20200

Application of Sub-second Annealing for Diluted Ferromagnetic Semiconductors
Zhou, S.; Bürger, D.; Schmidt, H.
Abstract: The dilute ferromagnetic semiconductor GaMnAs provides a great promise for its application in spintronics, which combines two degrees of freedom: charge and spin. Mn ions which substitute Ga sublattice sites provide both local magnetic moments and itinerant holes. The magnetic properties of GaMnAs can be controlled by manipulating free carriers via electrical gating. However, the preparation of ferromagnetic GaMnAs presents a big challenge due to the low solubility of Mn in GaAs. To overcome the low solid solubility limit of transition metal dopants in semiconductors, one needs highly nonequilibrium methods to introduce enough dopants and a short-time annealing to activate them. Both ion implantation and pulsed-laser (or flash-lamp) annealing occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants. The subsequent short-time annealing deposits energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Such a nonequilibrium process maintains the supersaturation induced by ion implantation. In this chapter, we review the application of sub-second annealing in the activation of Mn implanted GaAs as well as GaP.
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 297-314
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6_15
Registration No. 20196

Sub-nanosecond Thermal Spike Induced Nanostructuring of Thin Solid Films Under Swift Heavy Ion (SHI) Irradiation
Ghosh, S.; Kumar, H.; Singh, S. P.; Srivastava, P.; Kabiraj, D.; Avasthi, D. K.; Bürger, D.; Zhou, S.; Mücklich, A.; Schmidt, H.; Stouquert, J. P.
Abstract: The interaction between swift heavy ions (SHI) and a solid has been identified as one of the important physical processes to generate or modify nanostructures in thin solid films. The large part of the energy which is deposited in the electronic subsystem of a material by SHI is known as electronic energy loss and gets coupled to the lattice subsystem in a complex way resulting in a transient (picoseconds to sub-nanosecond) thermal spike within a few nanometer diameter region of the thin solid film along the ion path. The temperature of this narrow zone may raise up to 1000 K or more during this time. This transient heating process is known as lattice thermal spike and can be used as a tool to engineer materials down to the nanoscale. Here we address two important consequences of lattice thermal spike; (i) elongation of metal nanoparticles embedded in dielectric thin films and (ii) generation of a-Si/c-Si nanostructures in a silicon nitride matrix.

(i) Metal nanoparticles embedded in a thin film matrix belong to a class of materials that has potential applications as optical and magnetic sensors, storage, memory devices, field emission display etc. The nanoparticle size and shape, orientation, inter-particle separation and dielectric constant of the surrounding matrix are the crucial parameters which control their properties. Thermal spike generated by SHI in these nanoparticles and surrounding matrix can be used as a unique tool to tailor the shape of the embedded nanoparticles, eventually modifying the physical properties of these materials. Metal nanoparticles, which are mostly spherical in shape in as grown films, get elongated along the direction of SHI due to thermal spike induced melting and stress. After a brief introduction of some fundamental aspects and synthesis of these films, a detailed discussion on elongation of nearly spherical Ni nanoparticles embedded in SiO2 thin film matrix under 120 MeV Au ion irradiation is made. Various physical parameters influencing the shape modification of nanoparticles under the framework of thermal spike model are discussed.

(ii) a-Si/c-Si nanostructures embedded in different Si-based dielectric matrix have attracted researchers because of their potential application in low-cost Si-based optoelectronic devices. We report here the response of in-situ formed Si-nanostructures embedded in a Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation. Si-rich a-SiN x :H films have been prepared by Hg-sensitized Photo Chemical Vapor Deposition. Presence of elemental Si was confirmed from X-ray photoelectron spectroscopy. Irradiation with a fluence of 5×1012 ions/cm2 under normal incidence at room temperature leads to dissolution of these Si-nanostructures. However, irradiation with a relatively higher fluence of 1×1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures in the film. In addition, at the surface a novel effect i.e. partial crystallization of Si-nanostructures along the beam direction is observed. The results are explained on the basis of thermal spike model.
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 107-121
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6_6
Registration No. 20195

Nanonet Formation by Constitutional Supercooling of Pulsed Laser Annealed, Mn-Implanted Germanium
Bürger, D.; Zhou, S.; Höwler, M.; Ou, X.; Kovacs, G. J.; Reuther, H.; Mücklich, A.; Skorupa, W.; Schmidt, H.
Abstract: This subchapter presents interesting aspects of pulsed laser annealing. During this process, a laser pulse incorporates heat in the near surface region of a semiconductor or a metal. If the energy density is high enough, the system may melt near the surface. Because of the large temperature gradient, a very fast recrystallization may lead to novel physical material properties. Here we present interesting aspects of the formation of a Mn-rich nanonet in germanium. Important physical phenomena are explained in detail. The material has been fabricated by pulsed laser annealing of Mn implanted Ge wafers with a pulse duration of 300 ns. Due to a segregation instability during recrystallization, Mn segregates at the liquid-solid interface and an approximately 40 nm thick Ge:Mn surface layer is strongly enriched with Mn. Transmission electron microscopy plan-view images reveal a percolating Mn-rich nanonet after etching the top 10 nm surface layer. Hysteretic anomalous Hall effect has been observed up to 30 K, but it vanishes after etching away the 40 nm thick Mn-rich Ge:Mn layer. The nanonet seems to support the correlation between magnetization and hysteretic Hall resistance. Intrinsic charge carrier scattering in the threads or vertices of the Ge:Mn nanonet may lead to the observed anomalous Hall effect. In the outlook the nanonet formation is revealed for supercooled Mn-implanted Si.
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 15-33
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6_2
Registration No. 20194

High-Speed PIXE: A spatially resolved PIXE setup at the 6 MV Tandem accelerator
Buchriegler, J.; von Borany, J.; Hanf, D.; Munnik, F.; Nowak, Stansilaw H.; Renno, Axel D.; Scharf, O.; Ziegenrücker, R.
Abstract: kein Abstract eingereicht
Keywords: High-Speed PIXE, SLcam, Colour X-Ray Camera
  • Invited lecture (Conferences):
    SLcam(R) User Workshop, 16.01.2014, Berlin, Deutschland
Registration No. 20191

Investigation of vertical gas-liquid pipe flows using ultrafast X-ray tomography – An overview of methods, measurement series and previous results
Banowski, M.; Lucas, D.; Beyer, M.; Szalinski, L.; Hoppe, D.; Hampel, U.
Abstract: In this presentation, methods, measurement series and previous results of upward, counter-current as well as downward gas-liquid flows at the vertical titanium pipe of the TOPFLOW test facility are shown.
  • Lecture (Conference):
    German CFD Network of Competence, Workshop, 19.-20.03.2014, München-Garching, Deutschland
Registration No. 20184

Systematic investigation of terahertz-induced excitonic Rabi splitting
Teich, M.; Wagner, M.; Stehr, D.; Schneider, H.; Helm, M.; Böttge, C. N.; Klettke, A. C.; Chatterjee, S.; Kira, M.; Koch, S. W.; Khitrova, G.; Gibbs, H. M.
Abstract: Weak near-infrared and strong terahertz excitation are applied to study excitonic Rabi splitting in (GaIn)As/GaAs quantum wells. Pronounced anticrossing behavior of the split peaks is observed for different terahertz intensities and detunings relative to the intra-excitonic heavy-hole 1s–2p transition. At intermediate to high electric fields the splitting becomes highly asymmetric and exhibits significant broadening. A fully microscopic theory is needed to explain the experimental results. Comparisons with a two-level model reveal the increasing importance of higher excitonic states at elevated excitation levels.
Keywords: QW, FEL, Autler-Townes, THz Registration No. 20183

Experimente zu vertikalen Dampf-Wasser-Rohrströmungen mit ultraschneller Röntgentomographie
Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.
Abstract: Gas-Flüssigkeits-Zweiphasenströmungen in Rohrleitungen sind für die Entwicklung und Validierung neuer zweiphasiger CFD-Modelle ein geeigneter generischer Untersuchungsgegenstand. Der Grad an strömungsmorphologischer Komplexität ist relativ hoch, was sich insbesondere in der Ausprägung charakteristischer Strömungsregime mit ihren jeweils spezifischen Impulstransferbeziehungen an der Phasengrenze in Abhängigkeit von Leerrohrgeschwindigkeiten und Stoffwerten äußert. An der TOPFLOW-Versuchsanlage des HZDR werden gegenwärtig umfangreiche experimentelle Studien zu Zweiphasenströmungen in senkrechten Testsektionen für Wasser/Luft- und Wasser/Dampf-Strömungen bis 65 bar Druck durchgeführt. Diese Experimente dienen vordergründig der Erhebung von Messdaten für die CFD-Codeentwicklung. Als Messverfahren kommt in aktuellen Versuchen an einer vertikalen DN50 Testsektion die ultraschnelle Röntgentomographie zum Einsatz. Diese ermöglicht es, den Strömungsquerschnitt mit Bildraten von 2500 Bildern/Sekunde und einer räumlichen Auflösung von etwa 1 mm in zwei jeweils 10 mm entfernten Ebenen abzubilden. Verschiedene Strömungsregime werden durch Wahl der Leerohrgeschwindigkeiten für die Gas- und die Flüssigphase am Versuchsstand eingestellt. Neben der Aufklärung des Strömungsregimes und der Erfassung interessanter Detailstrukturen der Strömung können radiale Gasgehaltsprofile ebenso wie Gasphasengeschwindigkeiten durch automatisierte Auswerteroutinen extrahiert werden. Im Beitrag werden Ergebnisse von Dampf-Wasser-Experimenten zu auf- und abwärtsgerichteten Gleichströmungen bei verschiedenen Druckstufen vorgestellt.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.
  • Poster:
    ProcessNet Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland
Registration No. 20181

Experimentelle Untersuchung von aufwärtsgerichteten zweiphasigen Rohrströmungen mit ultraschneller Röntgentomographie
Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.
Abstract: Die Entwicklung von CFD-Modellen zur Berechnung von Zweiphasenströmungen für industrielle Anwendungen in der Prozessindustrie stellt eine große Herausforderung dar. Zweiphasenströmungen in Reaktions- oder Trennapparaten sind infolge der auf mehreren Skalen ablaufenden Transportprozesse für Impuls, Stoff und Wärme inhärent hoch komplex. Zur Validierung von CFD-Codes sind daher experimentelle quantitative Daten solcher Strömungen mit hoher zeitlicher und räumlicher Auflösung erforderlich.
An der TOPFLOW-Versuchsanlage des HZDR werden auf diesem Gebiet umfangreiche Versuche an einer vertikalen DN50-Testsektion mit Luft-Wasser und Dampf-Wasser-Strömungen bis zu p = 65 bar und einer weiten Variation der Leerrohrgeschwindigkeiten für Wasser- und Gasphase durchgeführt. Unter Verwendung der am HZDR entwickelten ultraschnellen Röntgentomographie können Strömungsquerschnitte mit Bildraten von bis zu 2500 frames/s und einer räumlichen Auflösung von etwa 1 mm rückwirkungsfrei erfasst und visualisiert werden. Neben der Ermittlung von Strömungsregimen und weiterer charakteristischer Strömunsgkenngrößen dienen diese Untersuchungen dem Erkenntnisgewinn über Strömungsdetails, wie etwa Blasenkoaleszenz und –zerfall, radiale Gasgehaltsprofile, Strömungsverhalten von Kleinblasen in Abhängigkeit benachbarter Blasen sowie Geschwindigkeitsinformationen, in hochturbulenten Zweiphasenströmungen bei industriell relevanten Gasgehalten. Mit Hilfe von speziell entwickelten Bildauswertungsroutinen können diese Daten analysiert und für die Zweiphasen-CFD-Modellvalidierung aufbereitet werden. In diesem Beitrag wird ein Überblick über bisherige Versuche und deren Ergebnisse gegeben.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.
  • Poster:
    ProcessNet Jahrestreffen der Fachgruppen Extraktion und Fluidverfahrenstechnik, 27.-28.03.2014, Fulda, Deutschland
Registration No. 20179

Design, synthesis, characterisation and in vitro studies of hydrophilic, colloidally-stable, 64Cu(II)-labelled, ultra-small iron oxide nanoparticles in a range of human cell lines
Pombo Garcia, K.; Zarschler, K.; Barreto, Jose A.; Spiccia, L.; Graham, B.; Stephan, H.
Abstract: The application of ultra-small super-paramagnetic iron oxide nanoparticles (USPIONs) as versatile diagnostic probes for multimodal imaging in biomedicine, including via magnetic resonance imaging (MRI) and positron emission tomography (PET), requires hydrophilic and biocompatible surface coatings. Herein, we describe the development of USPIONs stabilised by octylamine-modified polyacrylic acid (OPA) and the subsequent
conjugation of a 64Cu(II) chelator, N-(4-aminophenyl)-2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]- acetamide (amino-dmptacn), for radioactivity-based detection. Transmission electron microscopic analysis and dynamic light scattering measurements confirmed the monodispersity and stability of the OPA-USPIONs in aqueous media and revealed a hydrodynamic size of ca. 15 nm. Furthermore, the biocompatibility and cellular uptake efficiency of the functionalised USPIONs was investigated in a range of normal and tumour cell lines. The results clearly show a cell type- as well as time-dependent internalisation of the OPA-USPIONs via active energy-dependent pathways. Biocompatibility of OPA- USPIONs in the concentration range of 10–50 mg mL-1 was demonstrated, while impairment of cellular viability was observed for human umbilical vein endothelial cells at 100 mg mL-1. Upon exposure to human serum, several biomolecules cover the negatively-charged surface of the nanoparticles and a biomolecular corona is formed. Nonetheless, the nanoparticles represent a promising platform for the future development of a bimodal PET-MRI tumour-imaging agent.

1. K. Pombo-Garcia, K. Zarschler, J. A. Barreto, J. Hesse, L. Spiccia, B. Graham, H. Stephan, RSC Advances 2013, 3, 22443.
2. M. P. Monopoli, D. Walczyk, A. Campbell, G. Elia, I. Lynch, F. B. Bombelli and K. A. Dawson, J Am Chem Soc, 2011, 133, 2525-2534.

Acknowledgements: Helmholtz Initiative and Networking Fund (Functional nanomaterials for multimodality cancer imaging (NanoTracking), project ID: VH-VI-421). Australian Research Council Discovery Grant and a Discovery Outstanding Researcher Award and a Senior Research Award by the Humboldt Foundation are gratefully acknowledged by L.S.
  • Poster:
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy
Registration No. 20177

Ultrasmall and radiolabelled upconverting nanophosphors – ready for challenge of multimodal cancer imaging
Hesse, J.; Graham, B.; Geipel, G.; Grenzer, J.; Spiccia, L.; Steinbach, J.; Stephan, H.
Abstract: The increasing interest in nanomaterials for medical applications is mainly attributed to their unique and structural properties. Based on different materials like polymers, inorganic or organic-inorganic hybrid substances such nanomaterials are investigated for applications in biological systems. Regarding this upconverting nanophosphors exhibit a high potential because of their bright luminescence. With their exceptional characteristic to convert near infrared to visible light (upconversion) these inorganic lanthanide-doped nanoparticles are very attractive as probes for optical imaging with the possibiliy for elucidation of even cellular processes[1]. In addition the surface of the nanoparticles offer the chance for rather multiple functionalisation such as radiometall chelates for PET and SPECT as well as for tumor affine units (peptides, aptamers, antibodies).
We want to present the synthesis and photophysical properties of ultrasmall (<10 nm) upconverting nanophosphors based on a host lattice of NaYF4: (Nd3+),Yb3+, Er3+/Tm3+ which are excited at 800 nm or 980 nm. To generate watersoluble biocompatible nanoparticles the material was coated with different polymers and afterwards functionalized with DMPTACN, a picolyl derivative of the macrocyclic ligand 1,4,7-triazacyclononane. An initial point for further investigations in vitro and in vivo was achieved by radiolabelling with the positron emitter Cu-64.

1. Cheng, L. , Wang, C. , Liu, Z. Nanoscale. 2013, 5, 23-37.

Acknowledgements: This work was funded by the Helmholtz Initiative and Networking Fund „Functional nanomaterials for multimodality cancer imaging“ (NanoTracking, project ID: VH-VI-421).
  • Poster:
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy
Registration No. 20176

Metastatic potential of B16-F10 melanoma cells is enhanced by extracellular S100A4 derived from RAW264.7 macrophages
Haase-Kohn, C.; Wolf, S.; Herwig, N.; Mosch, B.; Pietzsch, J.
Abstract: S100A4, synthesized and secreted from both tumor and stroma cells, modulates an aggressive tumor phenotype in various cancers by intracellular and extracellular interactions which are not completely understood. Because of the high content of tumor-associated macrophages in melanoma, here, a syngeneic model (coculture of mouse B16-F10 melanoma cells (Mel) and RAW264.7 macrophages (Mϕ); administration (i.v.) of Mel and Mϕ/Mel in NMRI nu/nu mice) was used to investigate synthesis and secretion of a) S100A4, b) S100A4-mediated signaling and activation of NFκB, and c) S100A4-mediated modulation of Mel invasiveness in vitro (transwell assay, transwell matrigel assay) and in vivo (metastatic lung colonization), respectively. In this model substantial S100A4 synthesis and secretion is demonstrated in Mϕ. Macrophage-derived S100A4 promotes Mel invasiveness in a paracrine manner in vitro, which is further substantiated in control experiments using recombinant human S100A4 and Mel stably transfected with mouse S100A4. Moreover, the participation of S100A4-mediated signaling, e.g., via the receptor for advanced glycation endproducts (RAGE), resulting in activation of NFκB was demonstrated in all experimental settings. Finally, we demonstrated that interaction of macrophage-derived S100A4 with Mel results in increased metastatic lung colonization in vivo.
Keywords: Melanoma metastasis; Receptor for advanced glycation; endproducts (RAGE); S100 proteins; Tumor-associated macrophages (TAM) Registration No. 20174

Concept for individualized patient allocation: ReCompare-remote comparison of particle and photon treatment plans
Lühr, A.; Löck, S.; Roth, K.; Helmbrecht, S.; Jakobi, A.; Petersen, J. B.; Just, U.; Krause, M.; Enghardt, W.; Baumann, M.
Abstract: Background: Identifying those patients who have a higher chance to be cured with fewer side effects by particle beam therapy than by state-of-the-art photon therapy is essential to guarantee a fair and sufficient access to specialized radiotherapy. The individualized identification requires initiatives by particle as well as non-particle radiotherapy centers to form networks, to establish procedures for the decision process, and to implement means for the remote exchange of relevant patient information. In this work, we want to contribute a practical concept that addresses these requirements.Methods: We proposed a concept for individualized patient allocation to photon or particle beam therapy at a non-particle radiotherapy institution that bases on remote treatment plan comparison. We translated this concept into the web-based software tool ReCompare (REmote COMparison of PARticlE and photon treatment plans).Results: We substantiated the feasibility of the proposed concept by demonstrating remote exchange of treatment plans between radiotherapy institutions and the direct comparison of photon and particle treatment plans in photon treatment planning systems. ReCompare worked with several tested standard treatment planning systems, ensured patient data protection, and integrated in the clinical workflow.Conclusions: Our concept supports non-particle radiotherapy institutions with the patient-specific treatment decision on the optimal irradiation modality by providing expertise from a particle therapy center. The software tool ReCompare may help to improve and standardize this personalized treatment decision. It will be available from our website when proton therapy is operational at our facility. © 2014 Lühr et al.; licensee BioMed Central Ltd.
Keywords: Particle therapy, Patient selection; Proton therapy; Treatment plan comparison Registration No. 20168

Visualizing inflammation activity in rheumatoid arthritis with Tc-99 m Anti-CD4-mAb fragment scintigraphy
Steinhoff, K.; Pierer, M.; Siegert, J.; Pigla, U.; Laub, R.; Hesse, S.; Seidel, W.; Sorger, D.; Seese, A.; Künstler, J.-U.; Pietzsch, H.-J.; Lincke, T.; Rullmann, M.; Emmrich, F.; Sabri, O.
Abstract: Purpose:
T-cell-located CD4 antigen represents one of the therapeutic targets in rheumatoid arthritis (RA). However, up to now there is no established imaging tool to visualize this target in vivo. The aim of our study was to assess the safety and tolerability of a technetium-99 m labelled murine anti-human CD4 IgG1-Fab fragment ([99mTc]-anti-CD4-Fab, [99mTc]-EP1645) in patients with active synovitis due to RA, and to evaluate its potential as a marker of disease activity.
In the present phase I proof of principle study five patients with RA were examined. Planar scans of the whole body, hands, and feet were taken 30 min up to 24 h after application of 550 ± 150 MBq [99mTc]-anti-CD4-Fab, followed by visual analyses, comparison with clinical data in 68 joints per patient and semiquantitative analysis of hand and wrist joints.
Neither infusion related adverse events nor adverse events during follow up were observed. No increase in human anti-murine antibody titres was seen. All patients had positive scans in almost 70% of clinically affected joints. Positive scans were also found in 8% of joints without evidence of swelling or tenderness.
Scintigraphy with [99mTc]-anti-CD4-Fab is a promising technique for evaluation of inflammatory activity in patients with RA, pre-therapeutical evaluation of CD4 status and therapy control. Tracer uptake in clinically inconspicuous joints strongly indicates diagnostic potential of [99mTc]-anti-CD4-Fab. Whether this technique is eligible as a prognostic factor in RA needs to be analysed in further studies as well as the pathophysiological background of clinically affected joints lacking tracer uptake.

Keywords: CD4; Monoclonal antibodies; Technetium-99 m scintigraphy; Rheumatoid arthritis; Molecular imaging Registration No. 20166

Influence of different chelators on the radiochemical properties of a 68-Gallium labelled bombesin analogue.
Asti, M.; Iori, M.; Capponi, Pier C.; Atti, G.; Rubagotti, S.; Martin, R.; Brennauer, A.; Müller, M.; Bergmann, R.; Erba, Paola A.; Versari, A.
Abstract: The radiolabelled bombesin analogue AMBA shows high potential for diagnosis and treatment of prostate and breast cancer, but the influence of different chelators, which differ in terms of radiochemical reactivity and stability, have not been explored so far. In order to find the best suitable chelator for labelling of AMBA, we synthesized AMBA analogues linked to the most commonly used chelators DOTA, NOTA and NODAGA and compared their reactivity and stability after labelling with 68-Gallium.
Keywords: 68Ga-labelling, AMBA-chelators, Bombesin analogues, 68Ga-NODAGA-AMBA, Gallium radionuclides Registration No. 20165

Radiolabeled anti-EGFR-antibody improves local tumor control after external beam radiotherapy and offers theragnostic potential
Koi, L.; Bergmann, R.; Brüchner, K.; Pietzsch, J.; Pietzsch, H.-J.; Krause, M.; Steinbach, J.; Zips, D.; Baumann, M.
Abstract: PURPOSE:
The effect of radioimmunotherapy (RIT) using the therapeutic radionuclide Y-90 bound to the anti-EGFR antibody cetuximab combined with external beam irradiation (EBRT) (EBRIT) on permanent local tumor control in vivo was examined.
Growth delay was evaluated in three human squamous cell carcinoma models after RIT with [(90)Y]Y-(CHX-A''-DTPA)4-cetuximab (Y-90-cetuximab). The EBRT dose required to cure 50% of the tumors (TCD50) for EBRT alone or EBRIT was evaluated in one RIT-responder (FaDu) and one RIT-non-responder (UT-SCC-5). EGFR expression and microenvironmental parameters were evaluated in untreated tumors, bioavailability was visualized by PET using ([(86)Y]Y-(CHX-A''-DTPA)4-cetuximab (Y-86-cetuximab) and biodistribution using Y-90-cetuximab.
In UT-SCC-8 and FaDu but not in UT-SCC-5 radiolabeled cetuximab led to significant tumor growth delay. TCD50 after EBRT was significantly decreased by EGFR-targeted RIT in FaDu but not in UT-SCC-5. In contrast to EGFR expression, parameters of the tumor micromilieu and in particular the Y-90-cetuximab biodistribution or Y-86-cetuximab visualization in PET correlated with the responsiveness to RIT or EBRIT.
EGFR-targeted EBRIT can improve permanent local tumor control compared to EBRT alone. PET imaging of bioavailability of labeled cetuximab appears to be a suitable predictor for response to EBRIT. This theragnostic approach should be further explored for clinical translation.

Keywords: Cetuximab, Combined treatment, Epidermal growth factor receptor (EGFR) inhibition, Radioimmunotherapy, Radiotherapy Registration No. 20164

Investigations on multi phase flow in inline separators using ultra fast X-ray tomography and wire mesh sensors
Schäfer, T.; Schleicher, E.; Hampel, U.
Abstract: The optimization of separation processes with respect to the capacity and efficiency and the decreasing of the required residence time for the separation is significant for production of raw materials for petrochemical industries and in numerous operations of process engineering. Compact inline separators with swirl elements provide a smart technology for fast and robust mechanical separation of gases and liquids. A significant advantage of these separators is their small size and their applicability directly in pipes. However, unfavorable operating states in terms of separation quality (selectivity) appearing under specific conditions, caused by flow instabilities. They are leading to gas and liquid carry over effects. For the here presented tomographic investigations, it was a main objective to analyze the fluid dynamics inside and in the surrounding area of these separators, to improve the quality and efficiency of these separators. Therefore, ultrafast X-ray tomography and wire mesh sensor technology were used. Applying these tomographic measurement techniques, hydrodynamic characteristics, like the local distribution of the phase fractions, can be captured with very high spatial and temporal resolution. Thus it was possible, to evaluate the separation quality as well as critical flow regimes. Additionally, the obtained data are a basis for the modeling of the separation processes and the effects occurring thereby. Based on this, CFD simulations of the processes can be executed more accurately and design modifications and optimizations of the inline separators can be derived.

Die Optimierung von Separationsverfahren hinsichtlich Leistungsstärke und Effizienz bei Verringerung der notwendigen Verweilzeiten für die Separation hat eine hohe Bedeutung für die Gewinnung von Rohstoffen für die petrochemische Industrie und in einer Vielzahl verfahrenstechnischer Prozesse. Kompakte Inline-Separatoren mit Drallelementen bieten dabei eine elegante Möglichkeit für eine schnelle und robuste mechanische Separation von Gasen und Flüssigkeiten. Ein wesentlicher Vorteil dieser Separatoren ist ihre geringe Größe und die Möglichkeit des direkten Einsatzes in Rohrleitungen. Dabei treten unter bestimmten Umständen jedoch auch ungünstige Zustände hinsichtlich der Qualität der Separation (Trennschärfe), verursacht durch Strömungsinstabilitäten, auf. Diese führen zu Gas- und Liquid-carry-over Effekten. Ein wesentliches Ziel der hier vorgestellten tomographischen Untersuchungen war es, die Strömungsdynamik in der Umgebung und innerhalb solcher Separatoren aufzuklären, um damit Qualität und Effizienz der Separation weiter zu verbessern. Für diese Untersuchungen wurde neben der ultraschnellen Röntgentomographie auch die Gittersensormesstechnik eingesetzt. Mit diesen beiden tomographischen Messtechniken können hydrodynamische Größen, wie die lokale Verteilung der einzelnen Phasenanteile, mit sehr hoher örtlicher und zeitlicher Auflösung gemessen werden. Mit diesen Messdaten war es möglich, die Separationsqualität zu beurteilen und kritische Strömungsregime zu erkennen. Die gewonnenen Daten bilden zudem die Grundlage für eine Modellierung des Separationsprozesses und dabei auftretender Effekte. Darauf aufbauend können genauere CFD-Simulationen der Prozesse durchgeführt werden und konstruktive Optimierungen für die Inline-Separatoren abgeleitet werden.

Keywords: multi phase flow, inline cyclonic separator, swirl element, x-ray tomography, wire mesh sensor
  • Poster:
    Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland
Registration No. 20163

High-field magnetization and magnetic phase diagrams in Nd2RhIn8 and Tb2RhIn8
Javorský, P.; Pajskr, K.; Klicpera, M.; Cermák, P.; Skourski, Y.; Andreev, A. V.
Abstract: We present magnetic phase diagrams of Nd2RhIn8 and Tb2RhIn8 determined by magnetization and magnetoresistivity measurements on single crystals, including high-field magnetization up to 60 T. Both compounds order antiferromagnetically with the c-axis as the easy magnetization axis. Their magnetic Phase diagrams are qualitatively rather similar. At low temperatures up to 1/2TN, when applying the field along the tetragonal c-axis, we observe first-order transition to another magnetic phase prior to transition to the ferromagnetic order. The magnetic phase diagrams resemble those of other R2RhIn8 or RRhIn5 compounds. Registration No. 20159

High-field magnetization and magnetoelasticity of single crystalline HoFe5Al7
Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Skourski, Y.; Arnold, Z.; Zherlitsyn, S.; Wosnitza, J.
Abstract: Magnetization and ultrasound measurements have been performed in pulsed magnetic fields up to 60 T on a ferrimagnetic HoFe5Al7 single crystal (Curie temperature TC = 216 K, compensation point Tcomp = 65 K) with a tetragonal crystal structure of the ThMn12-type. The compound exhibits a high magnetic anisotropy of the easy-plane type. A large anisotropy is also observed within the basal plane having an easy-magnetization direction along the [110] axis with the spontaneous magnetic moment Ms = 2 μB/f.u. at T = 2 K. Along the easy axis, two first-order field-induced magnetic transitions are observed. At both transitions sharp anomalies in the acoustic properties are found. The critical fields of the transitions depend on temperature in a different manner. Within molecular-field theory and using the high-field magnetization data the Ho-Fe inter-sublattice exchange parameter has been determined to be nHoFe ≈ 4 T/μB. The magnetoelasticity has also been probed by magnetization measurements under hydrostatic pressure. TC decreases with a rate dTC/dp = −10 K/GPa, whereas Tcomp increases with dTcomp/dp = 3.5 K/GPa. Registration No. 20157

Strongly correlated one-dimensional magnetic behavior of NiTa 2O6
Law, J. M.; Koo, H.-J.; Whangbo, M.-H.; Brücher, E.; Pomjakushin, V.; Kremer, R. K.
Abstract: The magnetic properties of NiTa2O6 were investigated by magnetic susceptibility, specific heat, electron paramagnetic resonance, neutron powder diffraction, and pulse field magnetization measurements. Accompanying ab initio DFT calculations of the spin-exchange constants complemented and supported our experimental findings that NiTa2O6 must be described as a quasi-1D Heisenberg S=1 spin chain system with a nearest-neighbor only antiferromagnetic spin-exchange interaction of 18.92(2) K. Interchain coupling is by about two orders of magnitude smaller. Electron paramagnetic resonance measurements on Mg1-xNixTa2O6 (x≈1%) polycrystalline samples enabled us to estimate the single-ion zero-field splitting of the S=1 states which amounts to less than 4% of the nearest-neighbor spin-exchange interaction. At 0 T NiTa2O6 undergoes long-range antiferromagnetic ordering at 10.3(1) K evidenced by a λ-type anomaly in the specific heat capacity. On application of a magnetic field the specific heat anomaly is smeared out. We confirmed the magnetic structure by neutron powder diffraction measurements and at 2.00(1) K refined a magnetic moment of 1.93(5) μB per Ni2+ ion. Additionally, we followed the magnetic order parameter as a function of temperature. Last, we found saturation of the magnetic moment at 55.5(5) T with a g factor of 2.14(1), with an additional high field phase above 12.8(1) T. The onset of the new high field phase is not greatly affected by temperature, but rather smears out as one approaches the long-range ordering temperature. Registration No. 20156

Signature of the topological surface state in the thermoelectric properties of Bi2Te3
Rittweger, F.; Hinsche, N. F.; Zahn, P.; Mertig, I.
Abstract: We present electronic structure calculations based on density functional theory for the thermoelectric properties of Bi2Te3 films. Conductivity and thermopower are computed in the diffusive limit of transport based on the Boltzmann equation. Bulk and surface contributions to the transport coefficients are separated by a special projection technique. As a result we show clear signatures of the topological surface state in the thermoelectric properties.
Keywords: PACS: 71.15.Mb, 73.50.Lw, 72.20.−i, 03.65.Vf Registration No. 20154

Magnetization dynamics of magnetic domain wall imprinted magnetic films
Hamann, C.; Mattheis, R.; Mönch, I.; Fassbender, J.; Schultz, L.; McCord, J.
Abstract: The influence of micromagnetic objects on the dynamic magnetic excitation in magnetic thin films is studied by imprinting periodic domain wall patterns through selective ion irradiation in exchange biased Ni81Fe 19/IrMn structures. For high domain wall densities an increased precessional frequency is achieved. The zero field resonance of the domain wall state hereby depends directly on the stripe period, showing a pronounced increase with decrease of domain wall spacing. With the abrupt annihilation of magnetic domain walls with an applied bias field a jump-like decrease in precessional frequency takes place. The experimental data and micromagnetic simulations prove that the characteristic collective dynamic mode for the domain wall configurations is attributed to strongly coupled tilted magnetization structure. This is evidenced by an overlapping Néel wall structure for the narrowly spaced imprinted antiparallel unidirectional anisotropy state. The controlled introduction of high density frozen-in micromagnetic objects is a novel way to control the dynamic magnetic properties of continuous magnetic thin films.
Keywords: magnetism, dynamics, domain wall, ion irradiation Registration No. 20148

Packaging for radiation resistant X-ray detectors
Lohse, T.; Oppermann, M.; Metasch, R.; Zerna, T.; Seilmayer, M.; Wolter, K.-J.
Abstract: Today non-destructive evaluation techniques become more and more important. Consequently, X-ray detectors are suitable tools to get information about specimens. In comparison to the already established scintillation principle, the direct converting method on the basis of semiconductor materials delivers several advantages. Hence, it is necessary to speed this measurement method and develop appropriate packages for these assemblies. In this paper the method of direct converting X-ray line detectors as well as their packaging and relevant aspects are introduced.
Keywords: X-ray detection electronics packaging silicon radiation detectors measurement method nondestructive evaluation techniques radiation resistant X-ray detectors scintillation principle semiconductor materials Absorption Anodes Detectors Integrated circuits Materials Packaging X-ray detectors
  • Contribution to proceedings:
    33rd International Spring Seminar on Electronics Technology (ISSE 2010), 12.-16.05.2010, Odrębna 4 04-867 Warsaw, Poland
    33rd International Spring Seminar on Electronics Technology (ISSE 2010): Institute of Electrical and Electronics Engineers, 9781424478491, 138-142
Registration No. 20138

Development of MMRPC prototype for the NeuLAND detector of the R3B collaboration
Datta Pramanik, U.; Chakraborty, S.; Basu, P.; Basu, J.; Banerjee, P.; Bemmerer, D.; Bose, S.; Chatterjee, S.; Elekes, Z.; Kempe, M.; Leifels, Y.; Panja, J.; Mukherjee, A.; Rahaman, A.; Roy, S.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.
Abstract: A prototype of Multi-strip Multi-gap Resistive Plate chamber (MMRPC) with active area 40 cm×20 cm has been developed at SINP, Kolkata as a new Time-Of-Flight (TOF) system with timing resolution σt<120ps and position resolution σx∼0.58cm. The intention is to use multilayers of this type together with converter materials as a high energy neutron (1GeV>En>200MeV) TOF system for the R3B collaboration at the FAIR facility. The design of the detector elements is as follows: a double stack MMRPC with float glass plates and two gas gaps of 0.3 mm per stack. The response of this MMRPC has been studied with cosmic muons and γ-raysγ-rays from a standard radioactive source (60Co) in coincidence with fast inorganic scintillators at SINP laboratory. Recently, response of developed MMRPC has been studied using pulsed electron beam at ELBE, FZD. The details of the MMRPC construction , experimental set-up for investigation of its response and first results are presented.
Keywords: Multi-strip Multi-gap Resistive Plate chamber high energy neutron R3B FAIR Registration No. 20134

Establishment of two complementary in vitro assays for radiocopper complexes achieving reliable and comparable evaluation of in vivo stability
Zarschler, K.; Kubeil, M.; Stephan, H.
Abstract: The development of novel radiopharmaceuticals for imaging and therapy requires rapid and reproducible in vitro assays to estimate their in vivo stability and dissociation behaviour. In general, these assays should allow an assessment of dissociation of the radiometal from the radiopharmaceuticals. In the past, a series of chemical challenges has been widely used to estimate complex stability under non-physiological and non-radiotracer conditions providing limited information on the potential in vivo stability. In contrast, we herein present two independent in vitro methods to measure the stability of radiocopper complexes under physiologically relevant conditions. To quantify and compare the dissociation behaviour of six well-established 64Cu chelates (TETA, DOTA, NOTA, Cyclam, diamSar and EDTA), we combine a protein challenge experiment considering the stability of the chelates in the presence of human superoxide dismutase with a serum assay measuring the stability of the radiometal complexes against human serum. Unlike HPLC- and TLC-based analytical techniques, we describe the stability assessments by standard gel electrophoretic procedures, which allow a timesaving workflow as well as simultaneous processing and comparative analysis of a variety of copper-containing chelates and conjugates thereof. [64Cu]Cu-diamSar is the most kinetically stable ligand, whereas the acyclic chelate [64Cu]Cu-EDTA underwent an almost complete complex dissociation. Furthermore, kinetic stability studies in human serum carried out for [64Cu]Cu-diamSar revealed no substantial time-dependent influence under commonly used labelling conditions. Both described assays, the protein challenge experiment as well as the serum stability assay, are not restricted to radiocopper, but may be adopted for other radiometal containing chelates. © 2014 The Royal Society of Chemistry. Registration No. 20133

Transverse wobbling: A collective mode in odd- A triaxial nuclei
Frauendorf, S.; Dönau, F.
Abstract: The wobbling motion of a triaxial rotor coupled to a high-j quasiparticle is treated semiclassically. Longitudinal and transverse coupling regimes can be distinguished depending on, respectively, whether the quasiparticle angular momentum is oriented parallel or perpendicular to the rotor axis with the largest moment of inertia.
Simple analytical expressions for the wobbling frequency and the electromagnetic E2 and M1 transition probabilities are derived assuming rigid alignment of the quasiparticle with one of the rotor axes and harmonic oscillations (HFA). Transverse wobbling is characterized by a decrease of the wobbling frequency with increasing angular momentum. Two examples for transverse wobbling, 163 Lu and 135 Pr, are studied in the framework of the full triaxial particle-rotor model and the HFA. The signature of transverse wobbling, decreasing wobbling frequency, and enhanced E2 interband transitions, is found in agreement with experiment.

Keywords: Nuclear structure, triaxial particle-rotor model, E2 transitions Registration No. 20132

SiΛvio: A trigger for Λ-hyperons
Münzer, R.; Berger, M.; Fabbietti, L.; Averbeck, R.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Buehler, P.; Cargnelli, M.; Čaplar, R.; Carevic, I.; Charviakova, V.; Crochet, P.; Deppner, I.; Dupieux, P.; Dželalija, M.; Fodor, Z.; Gasik, P.; Gašparić, I.; Grishkin, Y.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kang, T. I.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Kiš, M.; Kienle, P.; Koczon, P.; Kotte, R.; Lebedev, A.; Leifels, Y.; Liu, J. L.; Lopez, X.; Manko, V.; Marton, J.; Matulewicz, T.; Petrovici, M.; Piasecki, K.; Rami, F.; Reischl, A.; Reisdorf, W.; Ryu, M. S.; Schmidt, P.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczyńska, K.; Smolyankin, V.; Suzuki, K.; Tyminski, Z.; Wagner, P.; Widmann, E.; Wiśniewski, K.; Xiao, Z. G.; Yamazaki, T.; Yushmanov, I.; Zhang, X. Y.; Zhilin, A.; Zinyuk, V.; Zmeskal, J.
Abstract: As online trigger for events containing Λ hyperons in p+p collisions at 3.1 GeV a silicon-based device has been designed and built. This system has been integrated close to the target region within the FOPI spectrometer at GSI and was also employed as a tracking device to improve the vertex reconstruction of secondary decays. The design of the detector components, read-out, the trigger capability as well as the tracking performance are presented. An enrichment factor of about 14 was achieved for events containing a Λ-hyperon candidate. Registration No. 20127

Azimuthal Emission Patterns of K+ and of K- Mesons in Ni+Ni Collisions near the Strangeness Production Threshold
Zinyuk, V.; Kang, T. I.; Leifels, Y.; Herrmann, N.; Hong, B.; Averbeck, R.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Berger, M.; Buehler, P.; Cargnelli, M.; Čaplar, R.; Carevic, I.; Crochet, P.; Deppner, I.; Dupieux, P.; Dželalija, M.; Fabbietti, L.; Fodor, Z.; Gasik, P.; Gašparić, I.; Grishkin, Y.; Hartmann, O. N.; Hildenbrand, K. D.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Kiš, M.; Koczon, P.; Kotte, R.; Lebedev, A.; Le Fèvre, A.; Liu, J. L.; Lopez, X.; Manko, V.; Marton, J.; Matulewicz, T.; Münzer, R.; Petrovici, M.; Piasecki, K.; Rami, F.; Reischl, A.; Reisdorf, W.; Ryu, M. S.; Schmidt, P.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczyńska, K.; Smolyankin, V.; Suzuki, K.; Tyminski, Z.; Wagner, P.; Widmann, E.; Wiśniewski, K.; Xiao, Z. G.; Yushmanov, I.; Zhang, Y.; Zhilin, A.; Zmeskal, J.; Bratkovskaya, E.; Hartnack, C.
Abstract: Azimuthal emission patterns of $K^\pm$ mesons have been measured in Ni + Ni collisions with the FOPI spectrometer at a beam kinetic energy of 1.91 A GeV. The transverse momentum $p_{T}$ integrated directed and elliptic flow of $K^{+}$ and $K^{-}$ mesons as well as the centrality dependence of $p_{T}$ - differential directed flow of $K^{+}$ mesons are compared to the predictions of HSD and IQMD transport models. The data exhibits different propagation patterns of $K^{+}$ and $K^{-}$ mesons in the compressed and heated nuclear medium and favor the existence of a kaon-nucleon in-medium potential, repulsive for $K^{+}$ mesons and attractive for $K^{-}$ mesons. Registration No. 20124

Laborexperimente zur Entstehung und Wirkung kosmischer Magnetfelder
Stefani, F.
Abstract: Bekanntermaßen entstehen planetare, stellare und galaktische Magnetfelder durch den hydromagnetischen Dynamoeffekt, d.h. durch Selbsterregung in strömenden elektrisch leitfähigen Fluiden. Weniger bekannt ist, dass Magnetfelder auch eine aktive Rolle in der kosmischen Strukturbildung spielen, indem sie Akkretionsscheiben in der Umgebung von Protosternen und Schwarzen Löchern destabilisieren. Der Artikel gibt einen Überblick über die Flüssigmetallexperimente der letzten 15 Jahre, in denen sowohl der Dynamoeffekt als auch die destabilisierende Wirkung von Magnetfeldern auf rotierende Strömungen nachgewiesen worden ist.
  • Praxis der Naturwissenschaften - Physik in der Schule 63(2014)2, 31-37
Registration No. 20116

Terahertz spectroscopy of nanostructures with a free electron laser
Helm, M.
Abstract: I will start describing the Dresden free-electron laser (FEL) as an intense, tunable, pulsed and narrowband source of infrared and THz radiation and the unique opportunities it offers for the spectroscopy of low-energy excitations in nanostructures. In particular, the FEL can be used for nonlinear optical experiments, for time-resolved pump-probe studies, and also for near-field microscopy. I will mainly discuss experiments studying electronic relaxation processes in semiconductor quantum dots with their totally quantized energy levels, and in graphene with its zero energy gap and linear band dispersion.
Keywords: free electron laser, terahertz, nanostructures, quantum dots, graphene
  • Invited lecture (Conferences):
    Annual BuildMoNa Conference, 04.03.2014, Leipzig, Germany
Registration No. 20115

Optical waveguides in LiTaO3 crystals fabricated by swift C5+ ion irradiation
Liu, G.; He, R.; Akhmadaliev, Sh.; de Aldana, J.; Zhou, S.; Chen, F.
Abstract: We report on the optical waveguides, in both planar and ridge configurations, fabricated in LiTaO3 crystal by using carbon (C5+) ions irradiation at energy of 15 MeV. The planar waveguide was produced by direct irradiation of swift C5+ ions, whilst the ridge waveguides were manufactured by using femtosecond laser ablation of the planar layer. The reconstructed refractive index profile of the planar waveguide has showed a barrier-shaped distribution, and the near-field waveguide mode intensity distribution was in good agreement with the calculated modal profile. After thermal annealing at 260 °C in air, the propagation losses of both the planar and ridge waveguides were reduced to 10 dB/cm.
Keywords: Ion irradiation; LiTaO3 crystal; Optical waveguide Registration No. 20113

Hochauflösende Positronen Emissions Tomographie für quantitative, raumzeitliche Prozessvisualisierung in geologischem Material (GeoPET)
Kulenkampff, J.; Lippmann-Pipke, J.
Abstract: Positronen-Emissions-Tomographie (PET) ist das empfindlichste bildgebende Verfahren der Medizin, um Körperfunktionen in ihrem räumlich-zeitlichen Verlauf sichtbar zu machen. Seit der klinischen Einführung der PET vor etwa 40 Jahren gibt es auch einige Beispiele für den erfolgreichen Einsatz klinischer PET-Scanner in den Geowissenschaften. Explizit wird seit über 10 Jahren die Entwicklung der „GeoPET“-Methode n in der Forschungsstelle Leipzig des HZDR vorangetrieben (Gründig et al., 2007; Kulenkampff et al., 2008; Richter et al., 2000; Richter et al., 2005). Mittels eines kommerziellen hochauflösenden biomedizinischen PET-Scanners (ClearPET) einerseits und ausgereifter Korrektur- und Rekonstruktionsverfahren andererseits haben wir unsere GeoPET-Methode Alleinstellungsmerkmal zur (Transport-)Prozesstomographie in dichtem Medium (z.B. Gesteinen) entwickelt.

PET nutzt die räumliche Detektion der Annihilationsstrahlung (zwei antiparallele Gammas mit jeweils 511 keV), die durch den β+-Zerfall geeigneter Radiotracer entsteht. Beim ClearPET wird die physikalisch maximal mögliche räumliche Auflösung von etwa 1 mm erreicht. Dieser – verglichen mit den Möglichkeiten der Röntgen-CT – geringen räumlichen Auflösung steht die der PET immanente, überragende Empfindlich-keit gegenüber: Die Detektion und Quantifizierung von Tracerkonzentrationen ist auf atomarer Skala möglich: Transport-vorgänge, die sich auf der Nanometerskala abspielen (z.B. gelöste oder nanopartikulär getragene Stoffe) können detektiert und räumlich verortet werden, wenn der Stofftransport eine hinreichende Aktivitäts-konzentration von ca. 0,1 kBq pro Voxel bewirkt (etwa 109 Atome/1 mm³, pikomolar). Diese außergewöhnliche Sensitivität (und Selektivität) ist mit keiner anderen Bildgebungsmodalität erreichbar, insbe-sondere, da wir in repräsentativen Volumen von um 1 L arbeiten, also 106 Voxel. Der Einfluss des Materials – Schwächung und Streuung – ist dabei von zweitrangiger Bedeutung bzw. wird mittels systematischer Verfahren reduziert (Zakhnini et al., 2013).
Sinnvolle Anwendungen liegen in der direkten Visualisierung und Quantifizierung realer chemisch-physikalischer Prozesse (Abb.2a und b). Solche Prozesse können sonst nur über modellhafte Prozess-Simulationen dargestellt werden, indem etwa statistische a-priori-Strukturmodelle oder strukturelle Information aus CT-Bildern oder als Grundlage für LBM- oder FEM-Simulationen genutzt werden (zu letzteren zwei Beispiele in Abb. 3). Bei der direkten Beobachtung chemisch-physikalischer Prozesse in Gesteinen mittels GeoPET zeigen sich regelmäßig Abweichungen von den für Simulationen angenommene Versuchsbedingungen, etwa bezüglich der Homogenität des Probekörpers, der Topologie des Fließpfades oder der Auswirkungen geringster – aber wirkungsvoller – Abweichungen von Idealbedingungen (nicht-Dirac-Injektionsimpulsen, nicht-Punkt-/Linien- oder Flächenhaft homogener Zufuhr von Tracern). Zielparameter sind prozessabhängige, effektive Größen (effektives Transportvolumen, wirksame innere Oberfläche, Geschwindigkeitsverteilung, lokale Retardation), sowie räumlich und tensoriell aufgelöste Dispersions- und Diffusionskoeffizienten.

Die mittels der GeoPET-Methode beobachteten Prozesse können mit Alteration der Struktur durch Auflösung oder Ausfällung einhergehen, welche mit CT oder MRT mit höherer Auflösung, eventuell auch prozessbegleitend-zeitaufgelöst, sichtbar gemacht werden können. Dies entspricht der üblichen Vorgehensweise bei der nuklearmedizinischen PET-CT. Direkte und rückwirkungsfreie ortsaufgelöste Information über das chemische Milieu als Ursache der Alteration kann dagegen nur die PET liefern. Nur hierdurch werden viele bisher deduzierte Parameter direkt messbar und die Ergebnisse von Modellsimulationen verifizierbar.
Begleitend zur Prozessbeobachtung mit der GeoPET wird der Kontrollbereich und das Zyklotron des HZDR in Leipzig zur Produktion von Radiotracern genutzt (siehe z.B. (Mansel et al.)). Hier werden grundlegende geochemische Transport- und Wechselwirkungsstudien durchgeführt, die ebenfalls durch die Anwendung von Radiomarkierungen besonders empfindlich sind, wodurch die geochemische Parametrisierung von Modellen für reaktive Transportvorgänge ermöglicht wird.


Bittner, L., Kulenkampff, J., Gründig, M., Lippmann-Pipke, J. and Enzmann, F., 2014. Direct Observation of Waterglass Impregnation of Fractured Salt Rock with Positron Emission Tomography, International Conference on the Performance of Engineered Barriers: Backfill, Plugs & Seals, BGR, Hannover, Germany.
Gründig, M., Richter, M., Seese, A. and Sabri, O., 2007. Tomographic radiotracer studies of the spatial distribution of heterogeneous geochemical transport processes. Applied Geochemistry, 22: 2334-2343.
Kulenkampff, J., Gründig, M., Richter, M. and Enzmann, F., 2008. Evaluation of positron emission tomography for visualisation of migration processes in geomaterials. Physics and Chemistry of the Earth, 33: 937-942.
Lippmann-Pipke, J., Kulenkampff, J., Gründig, M. and Richter, M., 2011. Matching PET data with COSMOL Multiphysics simulation results, COMSOL Conference, 26.-28.10.2011, Ludwigsburg, Germany.
Mansel, A., Gruhne, S., Franke, K. and Fischer, S., Production of 85Sr at a 18 MeV-cyclotron and purification for geochemical investigations. Submitted to Applied Radiation and Isotopes, submitted.
Richter, M., Gründig, M. and Butz, T., 2000. Tomographische Radiotracerverfahren zur Untersuchung von Transport- und Sorptionsprozessen in geologischen Schichten. Zeitschrift für Angewandte Geologie, 46(2): 101.
Richter, M., Gründig, M., Zieger, K., Seese, A. and Sabri, O., 2005. Positron Emission Tomography for modelling of geochmical transport processes in clay. Radiochimica Acta, 93: 643-651.
Schikora, J., 2012. Simulation of diffusion-adsorption processes in natural geological media by means of COMSOL Multiphysics, Dresden Technical University, Diploma thesis, Dresden, Germany, 95 pp.
Zakhnini, A., Kulenkampff, J., Sauerzapf, S., Pietrzyk, U. and Lippmann-Pipke, J., 2013. Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (18F, 124I and 58Co) in Opalinus Clay, anhydrite and quartz. Computers and Geosciences, 57 183-196.
  • Lecture (Conference):
    International Conference on the Performance of Engineered Barriers: Backfill, Plugs & Seals, 06.-07.02.2014, Hannover, Deutschland
Registration No. 20111

Preclinical Aspects of Nicotinic Acetylcholine Receptor Imaging
Brust, P.; Deuther-Conrad, W.; Donat, C. K.; Barthel, H.; Riss, P.; Paterson, L.; Höpping, A.; Sabri, O.; Cumming, P.
Abstract: Recent developments in radiochemistry have opened new vistas for investigations of nicotinergic acetylcholine receptors (nAChRs) in living brain by positron emission tomography (PET) and by single photon emission computed tomography (SPECT). In parallel, dedicated instrumentation for molecular imaging in small animals has facilitated preclinical investigations in a number of models in which perturbations in nAChR signalling are implicated, notably Alzheimer’s disease and other neurodegenerative conditions, schizophrenia and other neuropsychiatric disorders, substance abuse and traumatic brain injury. The nAChRs are members of a family of ligand-gated ion channels composed of five subunits, most commonly occurring in the central nervous system as heteropentamers designated α4β2, with lesser amounts of the α7 homopentamer. We present a systematic review of preclinical findings with the diverse nAChR ligands which have been investigated to date. Molecular imaging of the α4β2 nAChR subtype by PET has been successfully achieved by 2-[18F]fluoro-A-85380. Newer agents such as (−)-[18F]flubatine permit quantitation of α4β2 receptors with PET recordings not exceeding 90 min, without the toxicity characteristic of earlier epibatidine derivatives. Imaging studies of α7 nAChRs have been hampered by inadequate pharmacological specificity of available ligands and by the low natural abundance of this receptor subtype in the brain. However, a continued search for optimal ligands is justified by the particular association of α7 nAChRs with aspects of cognitive function. We note that no molecular imaging ligands have been developed for α6-containing nAChRs, despite their importance for the psychopharmacology of nicotine actions in the basal ganglia. Finally, we review the competitive binding model, in which the availability of α4β2 binding sites is altered by competition from endogenous acetylcholine, noting that this approach has yet to be applied for monitoring acetylcholine release in disease models.
  • Book chapter:
    Rudi A.J.O. Dierckx, A. Otte, E. F.J. de Vries, A. van Waarde: PET and SPECT of Neurobiological Systems, Heidelberg: Springer, 2014, 978-3-642-42013-9, 465-512
    DOI-Link: http://dx.doi.org/10.1007/978-3-642-42014-6
Registration No. 20109

Overview and current status of the PENELOPE project
Siebold, M.
Abstract: PENELOPE (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments) is designed for a pulse energy of 150 J, a repetition rate of 1Hz and a pulse duration of 120 fs after compression. Yb:CaF2 is chosen as gain medium, while each amplifier head consists four He-cooled slabs having a thickness of 5mm and a doping concentration of 1.4mol% Yb3+. The slab diameter of the final 150 J amplifier and its 10 J pre-amplifier is 110 and 55 mm, respectively. A total laser diode peak-power of 1.2 MW is installed for pumping at 980 nm. As front-end a 60 fs Yb:KGW oscillator, a regenerative Yb:CaF2 amplifier and two active mirror Yb:CaF2 multi-pass amplifiers with a pulse energy of 300µJ, 100mJ and 1J are used. The compressor is based on multilayer dielectric (MLD) gratings with a dimension of 94×42cm2, a groove density of 1760 l/mm, a grating distance of 220cm, a hard-clip bandwidth of 50nm, and a output beam diameter of 25cm.
  • Lecture (others):
    Science Palaver talk, 12.02.2014, Jena, Deutschland
Registration No. 20108

Astrophysical and experimental implications from the magnetorotational instability of toroidal fields
Rüdiger, G.; Gellert, M.; Schultz, M.; Hollerbach, R.; Stefani, F.
Abstract: The interaction of differential rotation and toroidal fields that are current-free in the gap between two corotating axially unbounded cylinders is considered. It is shown that non-axisymmetric perturbations are unstable if the rotation rate and Alfven frequency of the field are of the same order, almost independent of the magnetic Prandtl number Pm. For the very steep rotation law Omega proportional to R^2 (the Rayleigh limit) and for small Pm, the threshold values of rotation and field for this azimuthal magnetorotational instability (AMRI) scale with the ordinary Reynolds number and the Hartmann number, respectively. A laboratory experiment with liquid metals like sodium or gallium in a Taylor-Couette container has been designed on the basis of this finding. For fluids with more flat rotation laws, the Reynolds number and the Hartmann number are no longer typical quantities for the instability. For the weakly non-linear system, the numerical values of the kinetic energy and the magnetic energy are derived for magnetic Prandtl numbers <= 1. We find that the magnetic energy grows monotonically with the magnetic Reynolds number Rm, while the kinetic energy grows with Rm/root Pm. The resulting turbulent Schmidt number, as the ratio of the 'eddy' viscosity and the diffusion coefficient of a passive scalar (such as lithium), is of the order of 20 for Pm = 1, but for small Pm it drops to the order of unity. Hence, in a stellar core with fossil fields and steep rotation law, the transport of angular momentum by AMRI is always accompanied by an intense mixing of the plasma, until the rotation becomes rigid. Registration No. 20105

An analytic approach to modeling the optical response of anisotropic nanoparticle arrays at surfaces and interfaces
Persechini, L.; Verre, R.; Mcalinden, N.; Wang, J.; Ranjan, M.; Facsko, S.; Shvets, I.; Mcgilp, J.
Abstract: Anisotropic nanoparticle (NP) arrays with useful optical properties, such as localized plasmon resonances (LPRs), can be grown by self-assembly on substrates, but these systems often have significant dispersion in NP dimensions and distribution, which makes a numerical approach to modeling the LPRs very difficult. An improved analytic approach to this problem is discussed in detail and applied successfully to NP arrays from three systems that differ in NP metal, shape and distribution, and in substrate and capping layer. The materials and anisotropic NP structures that will produce LPRs in desired spectral regions can be determined using this approach.
Keywords: metallic nanoparticles, plasmonics Registration No. 20102

Electrical Characterization of Single Molecules via Mechanically Controllable Break Junctions
Wieser, M.; Sendler, T.; Weisbrod, S.; Tang, Z.; Marx, A.; Wolf, J.; Huhn, T.; Scheer, E.; Moresco, F.; Grebing, J.; Erbe, A.
Abstract: Molecular electronics has been a field of big interest for the last years. Using the technique of mechanically controllable break junctions we characterize different organic molecules, e.g. 1,4-Diethoxy-2,5-bis(4-sulfanyl-phenylethynyl)-benzene (PEEB) and switchable molecular wires, dissolved in an organic non-polar solvent. IV-curves taken from the molecules connected to single gold atom contacts show the expected tunneling behavior described by the single-level model: weak coupling of the molecules to the gold atoms implies an off-resonant tunneling process and a transport through a single channel. Varying the end-groups of the molecules leads to a different transport behavior. Figure 1 shows a 2D histogram of IV-curves of PEEB with amino end-groups. Based on the single-level transport model the analysis of the current-voltage characteristics delivers the energy of the molecular level and the coupling between electrode and molecule. It also indicates a reliable contact of the molecules to the gold atoms. A further goal is the investigation of an electric gate effect on the transport behavior through the molecules.
Keywords: Molecular Electronics, Electronic Transport
  • Poster:
    IHRS NANONET Annual Workshop 2013, 10.10.2013, Dresden, Deutschland
Registration No. 20097

Electrical Characterization of Single Organic Molecules via Mechanically Controllable Break Junctions
Sendler, T.; Wieser, M.; Liu, S.-P.; Weisbrod, S.; Tang, Z.; Marx, A.; Wolf, J.; Huhn, T.; Scheer, E.; Moresco, F.; Grebing, J.; Erbe, A.
Abstract: Molecular electronics has been of big interest for the last years. To allow an electrical characterization of single molecules a reliable contact to gold atoms is required. We ensure this by using single organic molecules with a plain structure, in particular 1,4-Diethoxy-2,5-bis (4-sulfanyl-phenylethynyl)-benzene and single stranded DNA fragments, dissolved in an organic non-polar solvent. For measurements we use the technique of mechanically controllable break junctions. IV-curves taken from single molecules connected to single gold atom contacts show the expected tunneling behavior, from which we gain the energy of the molecular level and the coupling between electrode and molecule.
Keywords: Molecular Electronics, Electronic Transport
  • Poster:
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 10.-15.03.2013, Regensburg, Deutschland
Registration No. 20096

Direct Determination of Exchange Parameters in Cs2CuBr4 and Cs2CuCl4: High-Field Electron-Spin-Resonance Studies
Zvyagin, S. A.; Kamenskyi, D.; Ozerov, M.; Wosnitza, J.; Ikeda, M.; Fujita, T.; Hagiwara, M.; Smirnov, A. I.; Soldatov, T. A.; Shapiro, A. Ya.; Krzystek, J.; Hu, R.; Ryu, H.; Petrovic, C.; Zhitomirsky, M. E.
Abstract: Spin-1/2 Heisenberg antiferromagnets Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures are studied by means of electron spin resonance spectroscopy in magnetic fields up to the saturation field and above. In the magnetically saturated phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their Exchange parameters. The viability of the proposed method was proven by applying it to Cs2CuCl4, yielding J/kB = 4.7(2) K, J'/kB = 1.42(7) K, [J'/J ≃ 0.30] and revealing good agreement with inelastic neutronscattering results. For the isostructural Cs2CuBr4, we obtain J/kB = 14.9(7) K, J'/kB = 6.1(3) K, [J'/J ≃ 0.41], providing exact and conclusive information on the exchange couplings in this frustrated spin system. Registration No. 20095

Radiation Thermometry—Sources of Uncertainty During Contactless Temperature Measurement
Reichel, D.; Schumann, T.; Skorupa, W.; Lerch, W.; Gelpey, J.
Abstract: Short Time Annealing on a microsecond to nanosecond scale presents new challenges to temperature measurement. Pyrometers are widely used owing to their commercial availability, short response time, easy handling and contactless operation. However, they hold a source for considerable measurement errors. False readings are easily gained producing large errors during temperature measurement.
This chapter intends to give the reader an overview on characteristic features associated with Radiation Thermometry in a broader sense and more specifically with Pyrometry.

Keywords: short time annealing, temperature measurement, pyrometry, flash lamps
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 211-228
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6_12
Registration No. 20094

All-optical helicity dependent magnetic switching in an artificial zero moment magnet
Schubert, C.; Hassdenteufel, A.; Matthes, P.; Schmidt, J.; Helm, M.; Bratschitsch, R.; Albrecht, M.
Abstract: Low remanent magnetization as key prerequisite for the ability of helicity dependent all-optical magnetic switching (AOS) is demonstrated for an artificial zero moment magnet. A heterostructure consisting of two amorphous ferrimagnetic Tb36Fe64 and Tb19Fe81 alloy layers is designed to yield a zero remanent net magnetization at room temperature by means of an antiparallel interfacial exchange coupling of the dominant magnetic moments. The canceling layer magnetizations provide vanishing demagnetization fields and the ability of AOS. Contrary to this, no all-optical switching is observed for single Tb36Fe64 and Tb19Fe81 films. This study provides further evidence that the ability for all-optical magnetic switching is correlated to the remanent sample magnetization and thus to the difference in magnetic moment of the rare-earth and transition-metal sublattices.
Keywords: optical switching, magnetic switching, magnetic film, Registration No. 20092

TCR/CD3 activation and co-stimulation combined in one T cell retargeting system improve anti-tumor immunity
Cartellieri, M.; Arndt, C.; Feldmann, A.; von Bonin, M.; Ewen, E.-M.; Koristka, S.; Michalk, I.; Stamova, S.; Berndt, N.; Gocht, A.; Bornhäuser, M.; Ehninger, G.; Schmitz, M.; Bachmann, M.
Abstract: We have recently described a novel modular targeting platform for T cell recruitment that not only efficiently replaces but also is superior to conventional T cell-engaging bispecific antibodies as it allows for the flexible targeting of several antigens and the delivery of co-stimulatory ligands to malignant lesions, thereby enhancing the antitumor potential of redirected T cells.
Keywords: acute myeloid leukemia, CD33, CD137, co-stimulatory ligands, immunotherapy, modular targeting system, single-chain bispecific antibodies, T-cell retargeting Registration No. 20091

III-V/Si on silicon-on-insulator platform for hybrid nanoelectronics
Prucnal, S.; Zhou, S.; Ou, X.; Facsko, S.; Liedke, M. O.; Bregolin, F.; Liedke, B.; Grebing, J.; Fritzsche, M.; Hübner, R.; Mücklich, A.; Rebohle, L.; Helm, M.; Turek, M.; Drozdziel, A.; Skorupa, W.
Abstract: The unique properties of SOI wafers enable the integration of heterogeneous materials with distinct functionalities in different layers. In particular, III-V compound semiconductors are very attractive for low-noise and high-speed electronic and photonic components integrated on a single chip. We have developed a CMOS compatible and fully integrated solution for the integration of III-V compound semiconductors with silicon technology for optoelectronic applications. InAs compound semiconductor nanostructures are synthesized in SOI wafers using the combined ion beam implantation and millisecond liquid-phase epitaxial growth. Optoelectronic and microstructural investigations carried out on implanted, annealed and selectively etched samples confirm the formation of high-quality III-V compound semiconductor nanostructures.
Keywords: Ion Implantation, Flash Lamp Annealing, InAs, SOI, heterojunction Registration No. 20090

Zero- field spin-transfer oscillators combining in-plane and out-of-plane magnetized layers
Fowley, C.; Sluka, V.; Bernert, K.; Lindner, J.; Fassbender, J.; Rippard, W. H.; Pufall, M. R.; Russek, S. E.; Deac, A. M.
Abstract: Excited magnetization dynamics in a spin-valve device consisting of an in-plane polarizer and an out-of-plane free layer were studied numerically. In the case where the free layer is assumed to lack any in-plane anisotropy components, a finite external field is required to generate steady-state dynamics, in agreement with previous reports. We demonstrate that this constraint can be removed and precession can be stabilized in zero applied field by introducing an additional in-plane anisotropy axis. Moreover, the in-plane anisotropy offers an additional degree of freedom for tuning the frequency response of the device.
Keywords: spin transfer torque, spin valve, spin transfer oscillator, magnetisation dynamics, zero-field oscillator, perpendicular magnetic anisitropy Registration No. 20089

Environmental fate of TiO2 nanoparticles
Hildebrand, H.; Schymura, S.; Franke, K.
Abstract: Vortrag im Rahmen des IRE STATUS-SEMINAR 2013 „Nuclear Safety Research – From Reactors to Disposal“ 11. - 13.12.2013 in Dresden
Präsentation von Ergebnissen aus den Projekten NanoTrack und QNano
  • Lecture (Conference):
    STATUS-SEMINAR 2013 „Nuclear Safety Research – From Reactors to Disposal“, 11.-13.12.2013, Rossendorf, Deutschland
Registration No. 20088

In-medium QCD sum rules for D mesons: A projection method for higher order contributions
Buchheim, T.; Hilger, T.; Kämpfer, B.
Abstract: D mesons serve as excellent probes of hot and/or dense strongly interacting matter. They can provide insight into the restoration of chiral symmetry. The chiral condensate as well as other chirally odd condensates, such as certain four-quark condensates, are linked to order parameters of spontaneous chiral symmetry breaking. Thus, the evaluation of these higher order condensate contributions in the framework of QCD sum rules is of high interest. We present a general method for projecting Lorentz indices of ground state expectation values providing a crucial step towards a comprehensive calculation of higher order corrections to the operator product expansion of hadrons, especially D mesons, in a strongly interacting medium. Registration No. 20086

Evaluation of PET quantification accuracy in vivo - Comparison of measured FDG concentration in the bladder with urine samples / In-vivo-Evaluation der Quantifizierungsgenauigkeit der PET - Vergleich der gemessenen FDG-Konzentration in der Blase mit Urinproben
Maus, J.; Hofheinz, F.; Schramm, G.; Oehme, L.; Beuthien-Baumann, B.; Lukas, M.; Buchert, R.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.
Abstract: Summary
Quantitative positron emission tomography (PET) requires accurate scanner calibration, which is commonly performed using phantoms. It is not clear to what extent this procedure ensures quantitatively correct results in vivo, since certain conditions differ between phantom and patient scans.
Aim: We, therefore, have evaluated the actual quantification accuracy in vivo of PET under clinical routine conditions.
Patients, methods: We determined the activity concentration in the bladder in patients undergoing routine [18F]FDG whole body investigations with three different PET scanners (Siemens ECAT EXACT HR+ PET: n = 21; Siemens Biograph 16 PET/CT: n = 16; Philips Gemini-TF PET/CT: n = 19). Urine samples were collected immediately after scan. Activity concentration in the samples was determined in well counters cross-calibrated against the respective scanner. The PET (bladder) to well counter (urine sample) activity concentration ratio was determined.
Results: Activity concentration in the bladder (PET) was systematically lower than in the urine samples (well counter). The patient-averaged PET to well counter ratios for the investigated scanners are (mean ± SEM): 0.881 ± 0.015 (ECAT HR+), 0.898 ± 0.024 (Biograph 16), 0.932 ± 0.024 (Gemini-TF). These values correspond to underestimates by PET of 11.9%, 10.2%, and 6.8%, respectively.
Conclusions: The investigated PET systems consistently underestimate activity concentration in the bladder. The comparison of urine samples with PET scans of the bladder is a straightforward means for in vivo evaluation of the expectable quantification accuracy. The method might be interesting for multi-center trials, for additional quality assurance in PET and for investigation of PET/MR systems for which clear proof of sufficient quantitative accuracy in vivo is still missing.

Für die Bestimmung quantitativer Parameter mittels Positronenemissionstomo graphie (PET) ist eine genaue Kalibrierung des PET-Scanners mit Hilfe geeigneter Phantommessungen notwendig. Auf Grund der offensichtlichen Unterschiede zwischen Phantom- und Patientenmessungen bestehen jedoch Unsicherheiten im Bezug auf die In- vivo- Genauigkeit einer solchen phantom-basierten Kalibrierung. Ziel dieser Studie war es daher die Genauigkeit
einer solchen Kalibrierung mittels klinischer Routinemessungen in vivo zu evaluieren.
Patienten, Methoden: Wir bestimmten die Aktivitätskonzentration in der Blase bei Patienten die an unterschiedlichen PET-Scannern eine [18F]FDG-Ganzkörperuntersuchung erhielten (Siemens ECAT EXACT HR+ PET: n = 21; Siemens Biograph 16 PET/CT: n = 16; Philips Gemini-TF PET/CT: n = 19). Unmittelbar nach Messung der Blasenregion gaben alle Patienten Urinproben ab. Die Aktivitätskonzentration der Urinproben wurde mit Hilfe eines kreuzkalibrierten Bohrlochzählers bestimmt. Im Anschluss wurde das Verhältnis zwischen Aktivitätskonzentration PET (Blase) zu Bohrlochzähler (Urinprobe) berechnet.
Ergebnisse: Die Aktivitätskonzentration in der Blase (PET) war systematisch niedriger als die der Urinproben (Bohrlochzähler). Das über die jeweiligen Patienten gemittelte Verhältnis zwischen PET und Bohrlochzähler war für die untersuchten Scanner (Mittelwert ± SEM): 0,881 ± 0,015 (ECAT HR+), 0,898 ± 0,024 (Biograph 16), 0,932 ± 0,024 (Gemini-TF). Diese Werte entsprechen Unterschätzungen der Aktivitätskonzentration durch die PET von jeweils 11,9%, 10,2% und 6,8%.
Schlussfolgerungen: Die untersuchten PETSysteme unterschätzen die Aktivitätskonzentration in der Blase. Der direkte Vergleich von Urinproben und PET-Bildern der Blase stellt eine einfache Art der In-vivo-Evaluation der zu erwartenden Quantifizierungsgenauigkeit eines PET-Scanners dar. Die vorgestellte Methode kann für Multicenterstudien, für eine zusätzliche Qualitätssicherung in der PET sowie für eine Untersuchung von PET/MRSystemen
interessant sein, für die es hinsichtlich einer ausreichenden Quantifizierungsgenauigkeit in vivo noch keine belastbaren Zahlen gibt.

Keywords: PET, quantification, accuracy, in vivo, multicenter, QA PET, Quantifizierung, Genauigkeit, in vivo, Multicenter, QA Registration No. 20085

The Ion Beam Center at the HZDR, nanocomposite growth with ions, and cluster tool setting up
Krause, M.
Abstract: The talk will first emphasize the role of the Ion Beam Center as large scale facility within our research center. Recent results of ion-assisted growth of carbon:metal nanocomposite thin films will be shown in the second part. In the third part of the talk the concept and the current state of the setting up of the cluster tool at the Ion Beam Center will be presented. Examples for possible in situ experiments are given. They include the layer exchange in carbon: nickel double layers, the growth mechanism of carbon on metals at different temperatures, the thermal stability and graphitization of carbon: metal films, and the graphitization of carbon implanted in metals.
  • Lecture (others):
    Seminar at Abengoa Research, 12.02.2014, Seville, Spain
Registration No. 20082

Associate K0 production in p+p collisions at 3.5 GeV: The role of Δ(1232)++
Agakishiev, G.; Arnold, O.; Balanda, A.; Belver, D.; Belyaev, A. V.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O. V.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbe, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y. V.
Abstract: An exclusive analysis of the 4-body final states  Λ+p+π+K0 and Σ0+p+π++K0 measured with HADES for p+p collisions at a beam kinetic energy of 3.5 GeV is presented. The analysis uses various phase space variables, such as missing mass and invariant mass distributions, in the four particle event selection (p, π+, π+, π-) to fi nd cross sections of the di fferent production channels, contributions of the intermediate resonances Δ++ and Σ(1385)+ and corresponding angular distributions. A dominant resonant production is seen, where the reaction Λ+Δ+++K0 has an about ten times higher cross section (29.45 ±0.08 +1.67-1.46 ±2.06 μb) than the analougous non-resonant reaction (2.57 ±0.02 +0.21-1.98 ±0.18 μb). A similiar result is obtained in the corresponding Σ0 channels with 9.26 ±0.05 +1.41-0.31 ±0.65 μb in the resonant and 1.35 ±0.02 +0.10-1.35 ±0.09 μb in the non-resonant
Registration No. 20080

Ab-initio investigation of carbides and of CNT junctions at finite temperature and under stress.
Kelling, J.; Gemming, S.
Abstract: With the presented work we lay the foundation for ab-initio studies of contacted carbon nanotubes with both metal and metal--carbide leads. We Focus on applying the frozen phonon method on top density-functional-theory calculations for electronic the system. Here we show our ab-initio results on the elastic and electronic properties of Al4C3 and the metastable Ni3C.

Furthermore we present an alternative non-perturbative approach to calculating the quantum conductance in CNT/molecular junctions at finite temperature. Strictly employing the Born--Oppenheimer approximation, we aim to calculate the influence of phonons on the conductance of such a system by averaging over a representative sample drawn from snapshots of thermal fluctuation of the lattice.
  • Poster:
    NanoNet Workshop, 10.10.2013, Rossendorf, Deutschland
Registration No. 20079

Millisecond-range liquid-phase processing of silicon-based hetero-nanostructures
Prucnal, S.; Skorupa, W.
Abstract: The downscaling and stressor technology of Si based devices is extending the performance of the silicon channel to its limits. Further downsizing of CMOS devices below 16 nm will need to solve some of the practical limits caused by one of the integration issues, such as chip performance, cost of development and production, power dissipation, reliability, etc. One solution for the performance progress which can overcome the downsizing limit in silicon technology is the integration of different functional optoelectronic elements within one chip.
We have realized a compact, CMOS compatible and fully integrated solution for the integration of III-V compound semiconductors with silicon technology for optoelectronic applications. The III-V nanostructured semiconductors are synthesized in either silicon or SOI wafers using the combined ion implantation and millisecond flash lamp annealing (FLA) techniques [1]. The FLA appears to be the most suitable one for this purpose. The energy budget introduced to the sample during FLA is sufficient to recrystallize silicon amorphized during implantation and to form III-V nanocrystals (NCs). In this paper we will present research results of the microstructural, optical and electrical properties of III-V quantum dots (InAs, GaAs and InP) formed in silicon and on SOI wafers. The influence of the annealing conditions and the lattice mismatch between III-V semiconductors and silicon on the shape of the III-V quantum dots will be examined. The annealing is performed at temperatures by far exceeding the melting point of bulk compound semiconductors, which leads to the formation of III-V nanostructures due to liquid phase epitaxy and enhances the probability for the incorporation of silicon atoms into III-V NCs. Silicon atoms are commonly used as n-type dopants in most III-V semiconductors. Therefore, liquid phase processing leads to the formation of heavily n-type doped single crystalline III-V nanostructures on silicon. If we consider that the synthesized NCs are n-type, by using a p-type silicon substrate a heterojunction can be formed between the III-V NCs and p-type Si. Conventional selective etching has been used to form the n-III-V/p-Si heterojunction. Current-voltage measurements confirm the heterojunction diode formation between n-type III-V quantum dots and p-type Si. The main advantage of our method is its ability to be integrated into large-scale silicon technology, which also allows applying it to Si-based optoelectronic devices.

Keywords: liquid phase epitaxy, Flash Lamp Annealing, ion implantation, compound semiconductors, silicon
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 189-210
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6_11
Registration No. 20078

Effect of solvent exchange on the stability of sterically functionalized magnetite nanoparticles in poly(methyl methacrylate)-solutions and resulting spray dried composites
Bremerstein, T.; Rudolph, M.; Peuker, U. A.
Abstract: In this study highly filled nanoparticle-polymer-composites consisting of the polymer poly(methyl methacrylate) and magnetite nanoparticles are synthesized via the solution and spray drying method. The synthesis process is carried out for two different solvents, dichloromethane and ethyl acetate, and the resulting suspensions and composites are compared to each other. The preparation of the composites consists of the following steps: First the magnetite nanoparticles are precipitated in an aqueous phase. In the next step the nanoparticles are coated with ricinoleic acid for stabilization and are transferred to the organic solvent dichloromethane. In a rotating evaporator the solvent dichloromethane is exchanged with ethyl acetate. Finally, the nanoparticles in the respective solvent and dissolved polymer are mixed and spray dried.
The stability of the nanoparticle suspensions is characterized using thermogravimetric and photometric analyses. The specific surface of spray dried composites is determined via BET measurements and the distribution of the nanoparticles is assessed with BSE-SEM imaging and laser diffraction.
The stability of the nanoparticles is independent of the examined solvents. Both solvents provide a homogeneous distribution of nanoparticles in the composite at high filler concentrations.

Keywords: Polymer nanocomposites Spray drying Magnetite nanoparticles Solvent Ethyl acetate Dichloromethane Registration No. 20077

Low-cost and large-area electronics, roll-to-roll processing and beyond
Wiesenhütter, K.; Skorupa, W.
Abstract: In the following chapter, the authors conduct a literature survey of current advances in state-of-the-art low-cost, flexible electronics. A new emerging trend in the design of modern semiconductor devices dedicated to scaling-up, rather than reducing, their dimensions is presented. To realize volume manufacturing, alternative semiconductor materials with superior performance, fabricated by innovative processing methods, are essential. This review provides readers with a general overview of the material and technology evolution in the area of macroelectronics. Herein, the term macroelectronics (MEs) refers to electronic systems that can cover a large area of flexible media. In stark contrast to well-established micro- and nano-scale semiconductor devices, where property improvement is associated with downscaling the dimensions of the functional elements, in macroelectronic systems their overall size defines the ultimate performance (Sun and Rogers in Adv. Mater. 19:1897–1916, 2007). The major challenges of large-scale production are discussed. Particular Attention has been focused on describing advanced, short-term heat treatment approaches, which offer a range of advantages compared to conventional annealing methods. There is no doubt that large-area, flexible electronic systems constitute an important research topic for the semiconductor industry. The ability to fabricate highly efficient macroelectronics by inexpensive processes will have a significant impact on a range of diverse technology sectors. A new era “towards semiconductor volume manufacturing. . .” has begun.
The chapter is organized in three main sections. The candidate materials for flexible, large-area electronics (LAEs) are discussed in Sect. 14.1. Given the Limitation of this chapter, only selected groups of the semiconductors are presented. The target materials are Si-based inorganic thin-films and their intriguing, organic competitors. The general attributes of the materials suitable for macroelectronics are revised. The challenges associated with volume manufacturing with emphasis on the evolution of the heating technologies are demonstrated in Sect. 14.2. The final conclusions along with the authors’ considerations on the LAEs’ perspectives are given in Sect. 14.3.

Keywords: large-area semiconductor manufacturing, low-cost and flexible electronics, laser and flash lamp annealing, millisecond annealing, plastic foils, roll-to-roll processing, organic semiconductors
  • Book chapter:
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 271-295
    DOI-Link: http://dx.doi.org/10.1007/978-3-319-03131-6
Registration No. 20067

Mapping of Hydrophobic Interactions for Investigating the Floatability of Mineral Using Atomic Force Microscopy and Raman Spectroscopy
Rudolph, M.
Abstract: The novel method of measuring the floatability of individual mineral phases on an ore cross section is presented. Combining atomic force microscopy with Raman spectroscopy can make use of hydrophobic effects to evaluate the hydrophobization of surfaces, a crucial microprocess of flotation. This paper presents comparative results of classic microflotation experiments and the new method looking at pure mineral samples of magnetite and quartz using simple anionic and cationic collectors. The mapping capabilities and identification of mineral phases with Raman spectroscopy is presented for a silicate type or from southern Sweden containing the mineral eudialyte rich in heavy rare earth elements. We show theoretically and experimentally the different possibilities to determine hydrophobic effects using force spectroscopy and the colloidal probe technique with a hydrophobic colloid attached to the cantilever of an atomic force microscope. This novel concept shall not only be a plain research tool but should help to simplify the investigation of the right flotation reagent and thus optimize flotation processes.
Keywords: AFM, Raman, Nanobubbles, Hydrophobic Interactions, Minerals
  • Lecture (Conference):
    Conference in Minerals Engineering 2014, 04.-05.02.2014, Lulea, Sverige
Registration No. 20066

Actinyl(V/VI) complexes at water-mineral interfaces investigated by vibrational spectroscopy and complementary techniques.
Müller, K.; Foerstendorf, H.; Steudtner, R.; Rossberg, A.
Abstract: For the long-term safety assessment of nuclear waste repositories, neptunium and uranium are two of the most environmentally relevant components of nuclear waste to be considered. Hence, great attention is attracted to their geochemistry and migration behavior. Among the various geochemical processes, the migration of radioactive contaminants in the environment is strongly affected by molecular reactions in aqueous solution and at the solid-water interface, e.g. complexation with organic/inorganic ligands, sorption onto mineral phases, surface precipitation, and colloid formation. A detailed description of these interactions on a molecular level is required for a reliable modeling of the contaminants dissemination in the environment.
In the past decade, vibrational spectroscopy has been developed to a powerful tool for the study of dissolved complexes of heavy metal ions with a variety of inorganic and organic ligands and surface complexes on solid phases. In particular, a combined approach of in situ vibrational, time-resolved laser fluorescence and X-ray absorption spectroscopy potentially provides comprehensive molecular information. A survey of very recent spectroscopic results obtained from geochemical reactions of radionuclides, namely Np(V) and U(VI), is given.
  • Lecture (others):
    Institutskolloquium, 28.02.2014, Umea, Schweden
Registration No. 20064

An attempt to simulate multilayer particle resuspension in a cavity
Lecrivain, G.; Vitsas, A.; Hampel, U.
Abstract: The present work deals with particle re-entrainment from a multilayer deposit exposed to a sudden flow increase. An early model is suggested to simulate the multilayer remobilisation of solid aerosol particles. The work is decomposed in two parts: 1. an algorithm is first developed for the virtual reconstruction of the multilayer deposit given its porosity and 2. particle detachment off the deposit is coupled with computational fluid mechanics. Experimental observations have shown that the clustering effect plays an important role in multilayer resuspension. Particle aggregates, and not individual particles, tend to reenter the turbulent flow. A cluster identification procedure is therefore suggested to work out resuspendable particle clusters. The condition of cluster dislocation is based on a force-balance model. The cluster detachment off the multilayer deposit occurs whenever the aerodynamic force overcomes the adhesive force. The turbulent flow was computed with a large eddy simulation. The numerical results showed satisfactory agreement with experimental data. Findings from that study showed that the wall shear stress is a main resuspension agent. Results have a direct impact for the safety assessment of gas-cooled high temperature reactor, in which the remobilisation of radioactive graphite particles occurs.
  • Contribution to proceedings:
    International Workshop on Thermal Hydraulics of Innovative Nuclear Systems, 20.-22.01.2014, Modena, Italy
Registration No. 20063
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