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< Seite 1 von 184 >   Gesamtzahl lt. Auswahl: 18350 Title records (100 Title records je Seite)
22610 Publications
Phase transitions of anisotropic and exchange origins in TmFe5Al7
Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Mushnikov, N. V.; Rosenfeld, E. V.; Skourski, Y.; Zherlitsyn, S.; Wosnitza, J.
Abstract: Magnetization and sound propagation reveal a number of unusual spontaneous and field-induced transformations in ferrimagnetic TmFe5Al7 (TC = 193 K). The rare-earth sublattice was found to provide a uniaxial magnetic anisotropy, whereas the iron sublattice favors an easy-plane anisotropy. A competition between them results in a first-order spin-reorientation transition at 64 K as the magnetic moments rotate from the c axis to the basal plane of a tetragonal structure. The transition is preceded by a first-order magnetization process of type II along the hard axis. Remarkably, the intersublattice Tm-Fe exchange interaction is weakened at the spin-reorientation transition. Concomitantly, the spontaneous magnetic moment disappears, and the ferrimagnetic state changes to antiferromagnetic. With increasing temperature, the strength of the Tm-Fe exchange is recovered, and the ferrimagnetism is restored at 82 K through another first-order phase transformation. Below 40 K, a first-order field-induced transition occurs for a magnetic field applied along the easy [001] axis. It reflects a rotation of the magnetic moments towards the forced ferromagnetic state observed above 30 T. Along the hard [100] axis the ferromagnetic saturation is not reached even at 60 T. Registration No. 20757

Observation of anisotropic exchange in a spin ladder by ESR
Čižmár, E.; Ozerov, M.; Krämer, K. W.; Rüegg, Ch.; Zvyagin, S. A.
Abstract: We report on high resolution X-band electron spin resonance (ESR) spectroscopy studies of the spinladder material (C5H12N)2CuBr4. Our experiments provide a direct evidence for the presence of anisotropy in (C5H12N)2CuBr4 in contrast to a fully isotropic spin-ladder model employed for this system previously. Low-temperature angular dependence of ESR transitions is analyzed employing a simple spin-1/2 dimer model with the symmetric anisotropic exchange interaction. Registration No. 20756

Uranyl sorption onto birnessite: A surface complexation modeling and EXAFS study
Rihs, S.; Gaillard, C.; Reich, T.; Kohler, S. J.
Abstract: This work investigates the mechanism of the uranyl interaction with birnessite, one of themost common layertype MnO2 mineral at the Earth's surface, by coupling macroscopic (surface complexation experiments) andmicroscopic (EXAFSmeasurements) approaches. The sorption of uranyl on synthetic hexagonal birnessite, the lowpH birnessite form, was studied under various conditions of pH (3–6), electrolyte backgrounds (0.1 M NaClO4, NaNO3 and Na2CO3), and solid/liquid ratios (from0.27 to 4.5 g/L). Sorption isotherms exhibit a complex form indicative of at least two types of sorption sites. EXAFS data reveal the presence of two equatorial O shells at ca. 2.32 Å and 2.46 Å for all the samples, and a Mn shell at ca. 3.38 Å in the low-pH (≤5) samples only. No U–U pair was detected, despite the presence of polynuclear dissolved species in some of the samples.
From the combination of the sorption isotherms and EXAFS results, a structural model for the sorption of uranyl onto hexagonal birnessite is proposed, in which two energetically different sites are involved. At low pH (≤5) a bidentate edge-sharing complex with Mn octahedra of the mineral edges can be inferred, whereas bidentate corner-sharing and/or monodentate complexation to layer vacancies would most likely describe EXAFS features of higher pH samples. A diffuse double layermodel of surface complexationwas developed for describing within the same framework the uranyl sorption against pH, involving both high-affinity (Mn octahedra edge) and lowaffinity (above layer vacancies) sites.
The comparison of the uranyl sorption onto hexagonal birnessite and various related environmental minerals shows that the affinity of uranyl for birnessite largely exceeds the sorption observed on montmorillonite and zeolite and turns out to be comparable to iron oxides, confirming the potential role of phyllomanganates to the control of uranyl mobility in post-oxic acidic environments.

Keywords: EXAFS U birnessite Registration No. 20755

Pathways for abiotic reduction in the FeS/Se(IV) and FeS2/Se(IV) systems
Breynaert, E.; Wangermez, W.; Dom, D.; Scheinost, A. C.; Parac-Vogt, T. N.; Kirschhock, C. E. A.; Maes, A.
Abstract: The geochemical behaviour and bio-availability of selenium have an unexpectedly intricate impact on modern society. While selenium is an essential micronutrient for many living organisms, the window between deficiency and toxicity is very narrow (0.04 ppm ; essential; 0.04 – 0.1 ppm beneficial; 3 ppm toxic). Due to its similarity to sulphur, it is commonly encountered in subsurface deposits such as coal and uranium, phosphate and sulphidic transitionmetal ores. The release of selenium to the environment is closely associated with the economic exploitation of such deposits. Because of its significant contribution to long-term radiation exposure, 79Se is considered as one of the important isotopes in the inventory of the long-lived radioactive waste produced by nuclear industry. In view of redox properties and abundant occurence in reducing soils and sediments, iron sulphides play an important role in the availability of mobile inorganic selenium in the environment.
While previous studies have demonstrated the formation of FeSe and Se0 upon reduction of Se(IV) with respectively iron monsulphides and iron disulphides, the mechanistic pathways explaining the different outcome are missing.
Combination of published results in a wide range of relevant systems [1-5] with new spectroscopic information (XAS and NMR spectroscopy) obtained for specifically synthesized key intermediates allows to rationalise all previous observations. These results allow to outline the different pathways and demonstrate how the intermediary selenium, sulphur and selenosulphur species determine the final outcome of the reactions.
[1] Scheinost et al (2008), ES&T, 42, 1984–1989
[2] Breynaert et al (2008), ES&T, 42, 3595–3601
[3] Scheinost et al (2008), J. Contam. Hydrol., 102, 228-245
[4] Breynaert et al (2010), ES&T, 44, 6649–6655
[5] Kang et al (2011), ES&T, 45, 2704–2710

Keywords: selenium EXAFS NMR nuclear waste
  • Lecture (Conference):
    Goldschmidt2014, 08.-13.06.2014, Sacramento, USA
Registration No. 20754

A radically new suggestion about the electrodynamics of water: Can the pH index and the Debye relaxation be of a common origin?
Volkov, A. A.; Artemov, V. G.; Pronin, A. V.
Abstract: The structure of pure water is commonly viewed as an openwork matrix of hydrogen-bonded H2O molecules with a Debye relaxation dynamics. The matrix is filled with free ions of low concentration, which makes water a weak electrolyte with pH = 7. Traditionally, the Debye relaxation is considered having no relevance to the dc water conductivity (or the pH index): while the Debye relaxation is caused by the dynamics of intact H2O molecules, the dc conductivity, in contrast, is due to self-dissociation of H2O into H3O+ and OH- ions. Here, we consider a microscopic mechanism, which could unify the Debye and the dc dynamics, namely the Brownian-like motion of strongly interacting ions. The model comprehensively describes the low-energy electrodynamics of water (up to 1011Hz) giving however an unexpected outcome: water behaves as if it had far more free ions than the standard model assumes. High concentration of counter charges results in a polarization structure of water. We recognize full well that such a radical model is contrary to many years of research on the dynamics, thermodynamics, and dielectric properties of water; but the results seem logically consistent and may prove stimulating. Registration No. 20751

Multiband transport and nonmetallic low-temperature state of K0.50Na0.24Fe1.52Se2
Ryu, H.; Wolff-Fabris, F.; Warren, J. B.; Uhlarz, M.; Wosnitza, J.; Petrovic, C.
Abstract: We report evidence for multiband transport and an insulating low-temperature normal state in superconducting K0.50Na0.24Fe1.52Se2 with Tc approximate to 20 K. The temperature-dependent upper critical field Hc2 is well described by a two-band BCS model. The normal-state resistance, accessible at low temperatures only in pulsed magnetic fields, shows an insulating logarithmic temperature dependence as T -> 0 after superconductivity is suppressed. This is similar as for high-Tc copper oxides and granular type-I superconductors, suggesting that the superconductor-insulator transition observed in high magnetic fields is related to intrinsic nanoscale phase separation. Registration No. 20750

Nonmetallic low-temperature normal state of K0.7Fe1.46Se1.85Te0.15
Wang, K.; Ryu, H.; Kampert, E.; Uhlarz, M.; Warren, J.; Wosnitza, J.; Petrovic, C.
Abstract: The normal-state in-plane resistivity below the zero-field superconducting transition temperature Tc and the upper critical field μ0Hc2 (T) was measured by suppressing superconductivity in pulsed magnetic fields for K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity ρab is found to increase logarithmically with decreasing temperature as (T/Tc) → 0. Similar to granular metals, our results suggest that a superconductor-insulator transition below zero-field Tc may be induced in high magnetic fields. This is related to the intrinsic real-space phase-separated states common to all inhomogeneous superconductors. Registration No. 20749

Controlling Magnetic Order and Quantum Disorder in Molecule-Based Magnets
Lancaster, T.; Goddard, P. A.; Blundell, S. J.; Foronda, F. R.; Ghannadzadeh, S.; Moeller, J. S.; Baker, P. J.; Pratt, F. L.; Baines, C.; Huang, L.; Wosnitza, J.; Mcdonald, R. D.; Modic, K. A.; Singleton, J.; Topping, C. V.; Beale, T. A. W.; Xiao, F.; Schlueter, J. A.; Barton, A. M.; Cabrera, R. D.; Carreiro, K. E.; Tran, H. E.; Manson, J. L.
Abstract: We investigate the structural and magnetic properties of two molecule-based magnets synthesized from the same starting components. Their different structural motifs promote contrasting exchange pathways and consequently lead to markedly different magnetic ground states. Through examination of their structural and magnetic properties we show that [Cu(pyz)(H2O)(gly)2](ClO4)2 may be considered a quasi-one-dimensional quantum Heisenberg antiferromagnet whereas the related compound [Cu(pyz)(gly)](ClO4), which is formed from dimers of antiferromagnetically interacting Cu2+ spins, remains disordered down to at least 0.03 K in zero field but shows a field-temperature Phase diagram reminiscent of that seen in materials showing a Bose-Einstein condensation of magnons.
  • Physical Review Letters 112(2014), 207201
Registration No. 20748

Evolution of the Pauli spin-paramagnetic effect on the upper critical fields of single-crystalline KxFe2-ySe2-zSz
Wolff-Fabris, F.; Lei, H.; Wosnitza, J.; Petrovic, C.
Abstract: We have studied the temperature dependence of the upper critical fields µ0Hc2 of KxFe2-ySe2-zSz single crystals up to 60 T. The µ0Hc2 for H parallel to ab and H parallel to c decrease with increasing sulfur content. The detailed analysis using Werthamer-Helfand-Hohenberg theory including the Pauli spin-paramagnetic effect shows that µ0Hc2 for H parallel to ab is dominated by the spin-paramagnetic effect, which diminishes with higher S content, whereas µ0Hc2 for H parallel to c shows a linear temperature dependence with an upturn at high fields. The latter observation can be ascribed to multiband effects that become weaker for higher S content. This results in an enhanced anisotropy of µ0Hc2 for high S content due to the different trends of the spin-paramagnetic and multiband effect for H parallel to ab and H parallel to c, respectively. Registration No. 20747

Fermi-surface topology of the iron pnictide LaFe2P2
Blackburn, S.; Prevost, B.; Bartkowiak, M.; Ignatchik, O.; Polyakov, A.; Foerster, T.; Cote, M.; Seyfarth, G.; Capan, C.; Fisk, Z.; Goodrich, R. G.; Sheikin, I.; Rosner, H.; Bianchi, A. D.; Wosnitza, J.
Abstract: We report on a comprehensive de Haas-van Alphen (dHvA) study of the iron pnictide LaFe2P2. Our extensive density-functional band-structure calculations can well explain the measured angular-dependent dHvA frequencies. As salient feature, we observe only one quasi-two-dimensional Fermi-surface sheet; i.e., a hole-like Fermi-surface cylinder around Gamma, essential for s+/- pairing, is missing. In spite of considerable mass enhancements due to many-body effects, LaFe2P2 shows no superconductivity. This is likely caused by the absence of any nesting between electron and hole bands.
  • Physical Review B 89(2014), 220505(R)
Registration No. 20745

Optical study of superconducting Pr2CuOx with x similar or equal to 4
Chanda, G.; Lobo, R. P. S. M.; Schachinger, E.; Wosnitza, J.; Naito, M.; Pronin, A. V.
Abstract: Superconducting Pr2CuOx, x similar or equal to 4 (PCO), films with T' structure and a Tc of 27 K have been investigated by various optical methods in a wide frequency (7 - 55 000 cm-1) and temperature (2 - 300 K) range. The optical spectra do not reveal any indication of a normal-state gap formation. A Drude-like peak centered at zero frequency dominates the optical conductivity below 150 K. At higher temperatures, it shifts to finite frequencies. The detailed analysis of the low-frequency conductivity reveals that the Drude peak and a far-infrared (FIR) peak centered at about 300 cm-1 persist at all temperatures. The FIR-peak spectral weight is found to grow at the expense of the Drude spectral weight with increasing temperature. The temperature dependence of the penetration depth follows a behavior typical for d-wave superconductors. The absolute value of the penetration depth for zero temperature is 1.6 mu m, indicating a rather low density of the superconducting condensate. Registration No. 20744

Neutron and EPR study of Cu(tn)Cl2 - A two-dimensional spatially anisotropic triangular-lattice antiferromagnet
Tarasenko, R.; Orendáčová, A.; Čižmár, E.; Mataš, S.; Orendáč, M.; Zeleňák, V.; Pavlík, V.; Siemensmeyer, K.; Zvyagin, S. E.; Wosnitza, J.; Feher, A.
Abstract: We have studied the temperature dependence of the lattice parameters and the influence of spin anisotropy on the electron paramagnetic spectra of Cu(tn)Cl2, an S = 1/2 quasi-two-dimensional spatially-anisotropic triangular-lattice Heisenberg antiferromagnet. The variation of the resonance fields with temperature reflects the presence of an easy-plane exchange anisotropy with Jz/Jx,y < 1 and g-factor anisotropy, gz/gx,y > 1. Registration No. 20743

Ultrasonic investigations of the spin ices Dy2Ti2O7 and Ho2Ti2O7 in and out of equilibrium
Erfanifam, S.; Zherlitsyn, S.; Yasin, S.; Skourski, Y.; Wosnitza, J.; Zvyagin, A. A.; Mcclarty, P.; Moessner, R.; Balakrishnan, G.; Petrenko, O. A.
Abstract: We report ultrasound studies of spin-lattice and single-ion effects in the spin-ice materials Dy2Ti2O7 (DTO) and Ho2Ti2O7 (HTO) across a broad field range up to 60 T, covering phase transformations, interactions with low-energy magnetic excitations, and single-ion effects. In particular, a sharp dip observed in the sound attenuation in DTO at the gas-liquid transition of the magnetic monopoles is explained based on an approach involving negative relaxation processes. Furthermore, quasiperiodic peaks in the acoustic properties of DTO due to nonequilibrium processes are found to be strongly affected by macroscopic thermal-coupling conditions: the thermal runaway observed in previous studies in DTO can be suppressed altogether by immersing the sample in liquid helium. Crystal-electric-field effects having a higher energy scale lead to a renormalization of the sound velocity and sound attenuation at very high magnetic fields. We analyze our observations using an approach based on an analysis of exchange-striction couplings and single-ion effects. Registration No. 20742

Microstructural and mechanical characterisation of ODS ferritic alloys produced by mechanical alloying and spark plasma sintering
Hernández-Mayoral, M.; Serrano, M.; Oñorbe, E.; García-Junceda, A.; Hilger, I.; Kloeden, B.; Weissgaerber, T.; Ulbricht, A.; Bergner, F.; Radiguet, B.; Etienne, A.; Shariq, A.; Dewhurst, C. D.
Abstract: Powders with basic composition Fe-14Cr-2W-0.4Ti were mechanically alloyed (MA) with Y2O3 in a planetary ball mill under two different rotation speeds. Consolidation of the as-milled powders was performed by spark plasma sintering (SPS). As-milled powders showed a highly deformed microstructure with elongated nanometric grains, around 50nm and different nanoclusters were found depending upon the rotational speed that produces different stages on the nanoclusters evolution. In the case of SPS materials, grain growth occurred during the SPS process and it was possible to observe the influence of the MA parameters, with larger and more homogeneously distributed grains at the higher speed. The mechanical behavior of the SPS compacts was evaluated by tensile and small punch testing also showing the influence of the MA parameters in the material behavior.
Keywords: FeCr ODS alloys; Mechanical alloying; Spark plasma sintering; Nanostructured materials; Yttria; Microstructure; Tensile and small punch tests Registration No. 20737

Assessment of the diagnostic performance of 18F-FDG-PET/CT for detection and characterization of solid renal malignancies.
Nakhoda, Z.; Torigian, D. A.; Saboury, B.; Hofheinz, F.; Alavi, A.
Abstract: To evaluate the sensitivity of the positron emission tomography (PET) portion of fluorine-18 fluorodeoxyglucose- PET-computerized tomography (18F-FDG-PET/CT) to detect solid malignant renal masses, and to assess for metabolic differences based on histopathological type. Nineteen subjects with 25 known solid malignant renal masses who underwent 18F-FDG-PET/CT were retrospectively evaluated. Qualitative analysis of the PET portion only of 18F-FDG-PET/CT examinations to assess visual detection of renal masses was initially performed in blinded fashion. Subsequently, measurements of standardized uptake value (SUV) and lesion-to-background ratios were performed for all masses and compared between histopathological types. Of 25 solid malignant renal masses, 18 were renal cell carcinoma (RCC), 3 were renal lymphoma, and 4 were metastases. Twenty-two of 25 were detectable, and all were correctly spatially localized. Fifteen of 22 detectable lesions were exophytic in configuration. The three non-detectable masses were non-exophytic RCC's with average diameter of 2.0cm. Fifteen of 18 of RCC were detectable, whereas all renal lymphomas and metastases were detectable. None of the metabolic parameters were statistically significant between RCC and renal lymphoma. However, all metabolic parameters were statistically significantly greater for renal metastases compared to RCC and renal lymphoma, and for clear cell RCC compared to papillary RCC. In conclusion, the PET portion of 18F-FDG-PET/CT had a sensitivity of 88% for detection of solid malignant renal lesions in patients with known renal malignancy, and reveals differences in metabolic activity based on histopathological type, which may be useful for purposes of individualized medicine. Further studies are required for more in depth assessment of these preliminary observations.
  • Hellenic Journal of Nuclear Medicine 16(2013), 19-24
Registration No. 20734

Predictive value of asphericity of pretherapeutic FDG uptake in NSCLC
Apostolova, I.; Steffen, I.; Rogasch, J.; Furth, C.; Buchert, R.; Hofheinz, F.; Amthauer, H.
Abstract: Objectives: 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).

Methods: FDG-PET/CT had been performed in 68 patients (65.5±8.8y) 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. ASP defined as the deviation of the tumor's shape from sphere shape was computed. Kaplan-Meier analysis with respect to progression-free (PFS) and overall survival (OS) was performed for localization (central vs. peripheral), SUVmax, metabolically active tumor volume (MTV), total lesion glycolysis (TLG) and ASP. OS and PFS curves were separated by the median value and compared by log-rank tests.

Results: 38 patients experienced tumor progression or recurrence after a median interval of 6.2 months (range 1.4-23.7). 28 patients died after a median interval of 7.1 months (0.4-19.4). The localization of the tumor was a predictor of both PFS (p=0.04, 2-year PFS 58% vs 45% for peripheral vs central localization) and OS (p=0.02, 2-year OS 57% vs 33%). ASP was the only PET-based parameter with prognostic value for PFS (p=0.005): the probability of 2-year PFS decreased from 60 % in the patients with low ASP to 47 % in the patients with high ASP. None of the PET-based parameters was predictive for OS.

Conclusions: The asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and TLG.
  • Lecture (Conference):
    Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2014, 07.-11.06.2014, St. Louis, USA
  • Abstract in refereed journal:
    Journal of Nuclear Medicine 55(2014)Suppl. 1, 125
Registration No. 20733

Dynamic Ga-68 DOTATOC PET for segregation of tumor perfusion from somatostatin receptor expression on neuroendocrine tumor (NET)
Steffen, I.; Hofheinz, F.; Pavel, M.; Brenner, W.; Prasad, V.
Abstract: Objectives: To generate quantitative parameters from dynamic Ga-68 DOTATOC PET (PET) as new markers for tumor perfusion and somatostatin receptor expression on gastroenteropancreatic NET.

Methods: PET was performed in 8 patients (pts) Images were acquired in list mode for 15 minutes after i.v. bolus injection. 63 regions of interests (spleen/adrenals, n=21; normal liver tissue, n=8; primary tumor/metastases (mets); n=34) were evaluated to generate k1, k2, k3, k4 and the fractional blood volume (fbv) using a reversable two compartment model.

Results: Mets in pts with proliferation rate (Ki67) 5-20% showed (n=12) significant higher k1, k2, k3, k4 (all p<0.01) compared to pts with lower Ki67 (<5%) (n=22) but significantly lower fbv (p<0.05). In liver (not receptor-specific uptake), k2 was signficantly higher (p<0.05) than in mets (median, 0.50 vs 0.23). SUVmax in mets showed significant correlations with k1 (rho, 0.37; p<0.001) und fbv (rho, 0.51; p<0.01) but not with k3. SUVmax in spleen/adrenal glands (receptor-specific uptake) correlated significantly with k3 (rho, 0.51; p<0.05).

Conclusions: These preliminary results, within its limitations (low pts number) suggests that dynamic Ga-68 DOTATOC PET enables segregation of tumor perfusion (fbv) from receptor specific binding (k1) in mets. Both parameters, fbv and k1, are primarily correlated to SUVmax in mets. The internalization of receptor ligand (Ga-68 DOTATOC) complexes (k3) appears to be mainly responsible for specific uptake in spleen and adrenal glands, while in normal liver a significantly higher washout of the ligand (k2) was observed which is in line with non-specific peptide uptake due to peptide metabolism in the liver. Moreover, mets in pts with higher Ki67 showed higher receptor ligand dynamics as denoted by higher k1-4 values.
  • Abstract in refereed journal:
    Journal of Nuclear Medicine 55(2014)Suppl. 1, 558
  • Lecture (Conference):
    Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2014, 07.-11.06.2014, St. Louis, USA
Registration No. 20732

Asphericity of pretherapeutic tumour FDG uptake provides independent prognostic value in head-and-neck cancer
Apostolova, I.; Steffen, I. G.; Wedel, F.; Lougovski, A.; Marnitz, S.; Derlin, T.; Amthauer, H.; Buchert, R.; Hofheinz, F.; Brenner, W.
Abstract: Objective:
To propose a novel measure, namely the ‘asphericity’ (ASP), of spatial irregularity of FDG uptake in the primary tumour as a prognostic marker in head-and-neck cancer.

Methods:
PET/CT was performed in 52 patients (first presentation, n = 36; recurrence, n = 16). The primary tumour was segmented based on thresholding at the volume-reproducible intensity threshold after subtraction of the local background. ASP was used to characterise the deviation of the tumour’s shape from sphere symmetry. Tumour stage, tumour localisation, lymph node metastases, distant metastases, SUVmax, SUVmean, metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were also considered. The association of overall (OAS) and progression-free survival (PFS) with these parameters was analysed.

Results:
Cox regression revealed high SUVmax [hazard ratio (HR) = 4.4/7.4], MTV (HR = 4.6/5.7), TLG (HR = 4.8/8.9) and ASP (HR = 7.8/7.4) as significant predictors with respect to PFS/OAS in case of first tumour manifestation. The combination of high MTV and ASP showed very high HRs of 22.7 for PFS and 13.2 for OAS. In case of recurrence, MTV (HR = 3.7) and the combination of MTV/ASP (HR = 4.2) were significant predictors of PFS.

Conclusions:
ASP of pretherapeutic FDG uptake in the primary tumour improves the prediction of tumour progression in head-and-neck cancer at first tumour presentation.

Keywords: Head-and-neck cancer; Prognosis; FDG PET; Heterogeneity; Asphericity Registration No. 20731

Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition
Döring, J.; von Ribbeck, H.-G.; Fehrenbacher, M.; Kehr, S. C.; Eng, L. M.
Abstract: Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263 K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip. Registration No. 20730

Rates of river incision across the main tectonic units of the Pamir identified using optically stimulated luminescence dating of fluvial terraces
Fuchs, M. C.; Gloaguen, R.; Krbetschek, M.; Szulc, A.
Abstract: Calculated incision rates along the Panj, the main river of the Pamir, are used to investigate any influence by tectonics or climate on the architecture of the river. The depositional ages of Panj River terraces were calculated using optically stimulated luminescence (OSL) dating of terrace sand. Fluvial incision rates were generated by integrating the terrace depositional ages with accurate kinematic GPS measurements of terrace heights above the modern Panj. We investigated 16 terraces along the Panj at the western Pamir margin and one terrace from the Vakhsh River to the north of the Pamir. The results reveal brief periods of fluvial deposition over the past 26 kyr. The oldest Panj terrace depositional ages coincide with early MIS 2 and MIS 2/1 glaciations on the Pamir Plateau. Younger terrace ages have no apparent link with glacial cycles. Terraces with varying heights above the modern Panj at different localities yielded similar depositional ages. This suggests that local conditions have determined fluvial incision rates. Combining all of the terrace measurements, the average incision rate of the Panj over the last 26 kyr has been similar to 5.6 mm/yr. A high mean incision rate of similar to 7.3 mm/yr was calculated from terraces where the Panj has cut a steep-sided valley through the Shakhdara dome. Significantly lower incision rates (similar to 2-3 mm/yr) were calculated from terraces where the Panj flows along the southern boundaries of the Shakhdara and Yazgulom domes. At those localities, graded segments of the Panj River profile and increased valley widths are indicative of local base levels. Downstream of the Yazgulom dome, river incision rates are generally lower (similar to 4-5 mm/yr) than the Panj average.
However, there is one exception where higher incision rates (similar to 6 mm/yr) were calculated upstream of the Darvaz Fault Zone, a major tectonic feature that forms the western boundary of the Pamir. The Vakhsh River terrace to the north of the Pamir yielded a lower incision rate (similar to 3 mm/yr) compared to the Panj average. Variation in incision rates along the Panj does not correspond to changes in rock type or river catchment area. Instead, incision rates appear to have been primarily influenced by river capture across the southern and central metamorphic domes of the Pamir. Wherever the Panj cuts these domes it displays a convex river profile. The combination of localized river profile convexity and changes in incision rates across the Pamir domes indicates that the dome boundaries have been active recently.
Registration No. 20729

Seismotectonics of the Pamir
Schurr, B.; Ratschbacher, L.; Sippl, C.; Gloaguen, R.; Yuan, X.; Mechie, J.
Abstract: Based on a 2 year seismic record from a local network, we characterize the deformation of the seismogenic crust of the Pamir in the northwestern part of the India-Asia collision zone. We located more than 6000 upper crustal earthquakes in a regional 3-D velocity model. For 132 of these events, we determined source mechanisms, mostly through full waveform moment tensor inversion of locally and regionally recorded seismograms. We also produced a new and comprehensive neotectonic map of the Pamir, which we relate to the seismic deformation. Along Pamir's northern margin, where GPS measurements show significant shortening, we find thrust and dextral strike-slip faulting along west to northwest trending planes, indicating slip partitioning between northward thrusting and westward extrusion. An active, north-northeast trending, sinistral transtensional fault system dissects the Pamir's interior, connecting the lakes Karakul and Sarez, and extends by distributed faulting into the Hindu Kush of Afghanistan. East of this lineament, the Pamir moves northward en bloc, showing little seismicity and internal deformation. The western Pamir exhibits a higher amount of seismic deformation; sinistral strike-slip faulting on northeast trending or conjugate planes and normal faulting indicate east-west extension and north-south shortening. We explain this deformation pattern by the gravitational collapse of the western Pamir Plateau margin and the lateral extrusion of Pamir rocks into the Tajik-Afghan depression, where it causes thin-skinned shortening of basin sediments above an evaporitic décollement. Superposition of Pamir's bulk northward movement and collapse and westward extrusion of its western flank causes the gradual change of surface velocity orientations from north-northwest to due west observed by GPS geodesy. The distributed shear deformation of the western Pamir and the activation of the Sarez-Karakul fault system may ultimately be caused by the northeastward propagation of India's western transform margin into Asia, thereby linking deformation in the Pamir all the way to the Chaman fault in the south in Afghanistan.
Keywords: Pamir; seismotectonics; India-Asia collision; seismicity; moment tensors Registration No. 20728

Improving the Estimation of Above Ground Biomass Using Dual Polarimetric PALSAR and ETM+ Data in the Hyrcanian Mountain Forest (Iran)
Attarchi, S.; Gloaguen, R.
Abstract: The objective of this study is to develop models based on both optical and L-band Synthetic Aperture Radar (SAR) data for above ground dry biomass (hereafter AGB) estimation in mountain forests. We chose the site of the Loveh forest, a part of the Hyrcanian forest for which previous attempts to estimate AGB have proven difficult. Uncorrected ETM+ data allow a relatively poor AGB estimation, because topography can hinder AGB estimation in mountain terrain. Therefore, we focused on the use of atmospherically and topographically corrected multispectral Landsat ETM+ and Advanced Land-Observing Satellite/Phased Array L-band Synthetic Aperture Radar (ALOS/PALSAR) to estimate forest AGB. We then evaluated 11 different multiple linear regression models using different combinations of corrected spectral and PolSAR bands and their derived features. The use of corrected ETM+ spectral bands and GLCM textures improves AGB estimation significantly (adjusted R2 = 0.59; RMSE = 31.5 Mg/ha). Adding SAR backscattering coefficients as well as PolSAR features and textures increase substantially the accuracy of AGB estimation (adjusted R2 = 0.76; RMSE = 25.04 Mg/ha). Our results confirm that topographically and atmospherically corrected data are indispensable for the estimation of mountain forest’s physical properties. We also demonstrate that only the joint use of PolSAR and multispectral data allows a good estimation of AGB in those regions.
Keywords: Landsat7/ETM+; ALOS/PALSAR; L-band; above ground biomass (AGB); DBH; linear multiple regression; topographic effects; Hyrcanian mountainous forest; Iran Registration No. 20727

Classifying Complex Mountainous Forests with L-Band SAR and Landsat Data Integration: A Comparison among Different Machine Learning Methods in the Hyrcanian Forest
Attarchi, S.; Glouagen, R.
Abstract: Forest environment classification in mountain regions based on single-sensor remote sensing approaches is hindered by forest complexity and topographic effects. Temperate broadleaf forests in western Asia such as the Hyrcanian forest in northern Iran have already suffered from intense anthropogenic activities. In those regions, forests mainly extend in rough terrain and comprise different stand structures, which are difficult to discriminate. This paper explores the joint analysis of Landsat7/ETM+, L-band SAR and their derived parameters and the effect of terrain corrections to overcome the challenges of discriminating forest stand age classes in mountain regions. We also verified the performances of three machine learning methods which have recently shown promising results using multisource data; support vector machines (SVM), neural networks (NN), random forest (RF) and one traditional classifier (i.e., maximum likelihood classification (MLC)) as a benchmark. The non-topographically corrected ETM+ data failed to differentiate among different forest stand age classes (average classification accuracy (OA) = 65%). This confirms the need to reduce relief effects prior data classification in mountain regions. SAR backscattering alone cannot properly differentiate among different forest stand age classes (OA = 62%). However, textures and PolSAR features are very efficient for the separation of forest classes (OA = 82%). The highest classification accuracy was achieved by the joint usage of SAR and ETM+ (OA = 86%).
However, this shows a slight improvement compared to the ETM+ classification (OA = 84%). The machine learning classifiers proved t o be more robust and accurate compared to MLC. SVM and RF statistically produced better classification results than NN in the exploitation of the considered multi-source data.

Keywords: Landsat; ALOS/PALSAR; L-band; maximum likelihood classification; support vector machines; neural networks; random forest; topographic effects; Hyrcanian mountainous forest; Iran Registration No. 20726

Improving Lithological Mapping by SVM Classification of Spectral and Morphological Features: The Discovery of a New Chromite Body in the Mawat Ophiolite Complex (Kurdistan, NE Iraq)
Othman, A. A.; Gloaguen, R.
Abstract: The mineral ore potential of many mountainous regions of the world, like the Kurdistan region of Iraq, remains unexplored. For logistical and sometimes political reasons, these areas are difficult to map using traditional methods. We highlight the improvement in remote sensing geological mapping that arises from the integration of geomorphic features in classifications. The Mawat Ophiolite Complex (MOC) is located in the NE of Iraq and is known for its mineral deposits. The aims of this study are: (I) to refine the existing lithological map of the MOC; (II) to identify the best discriminatory datasets for lithological classification, including geomorphic features and textures; and (III) to identify potential locations with high concentrations of chromite. We performed a Support Vector Machine (SVM) classification method to allow the joint use of geomorphic features, textures and multispectral data of the Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) satellite. The updated map allowed the identification of a new mafic body and a substantial improvement of the geometry of the known lithological units. The use of geomorphic features allowed for the increase of the overall accuracy from 73% to 79.3%. In addition, we detected chromite occurrences within the ophiolite by applying Spectral Angle Mapping (SAM) technique. We identified two new locations having high concentrations of chromite and verified one of these promising areas in the field. This new body covers ~0.3 km2 and has coarsely crystalline chromite within dunite host rock. The chromium (Cr2O3) concentration is ~8.46%. The SAM and SVM methods applied on ASTER satellite data show that these can be used as a powerful tool to explore ore deposits and to further improve lithological mapping in mountainous semi-arid regions
Keywords: Zagros; Mawat; ophiolite; chromite; SVM; SAM; ASTER; remote sensing; GIS Registration No. 20725

Growth of separated individual SWCNTs from metal:matrix templates
Melkhanova, S.; Kunze, T.; Haluska, M.; Hübner, R.; Keller, A.; Gemming, S.; Krause, M.
Abstract: Metal: matrix templates deposited by physical vapor deposition (PVD) were used to grow separated, individual single-walled carbon nanotubes (SWCNTs). The templates are thin films of 2 nm thickness, where the metal is either segregated as nanoparticles (NPs) or diluted in the matrix. The upper limit of the NP diameter was confined by the film thickness. The function of the matrix is to prevent the metal particle from coalescence during nanotube growth by chemical vapor deposition. SEM, TEM, AFM, and Raman mapping were used for template and carbon nanotube characterization. SWCNTs with a narrow, monomodal diameter distribution are obtained from templates with NPs of 2 nm diameter. About 50 % of the SWCNTs detected by Raman mapping have a diameter between 1.3 nm and 1.5 nm. Smaller SWCNT diameters down to 0.8 nm are obtained from templates where the metal is diluted in the matrix. For these templates a bimodal SWCNT diameter distribution was observed. The two maxima of the CNT diameter distribution were found at about 0.8 nm to 1.0 nm and at about 1.2 nm to 1.4 nm, respectively. The CNTs are in their majority separated each from other.
Keywords: Nanocomposites, Carbon Nanotubes, SEM, TEM, AFM, Raman
  • Poster:
    XXVIII. International Winterschool on Electronic Properties of Novel Materials, 08.-15.03.2014, Kirchberg, Österreich
Registration No. 20721

Periacetabular bone metabolism following hip revision surgery. PET-based evaluation of allograft osteointegration.
Bernstein, P.; Beuthien-Baumann, B.; Kotzerke, J.; Hofheinz, F.; Zessin, J.; Stiehler, M.; Günther, K.-P.
Abstract: The treatment of loosened total hip replacement (THR) acetabular components may require the management of severe bone defects. Although being applied for decades, there is only limited scientific data about the osteointegration of cancellous bone allografts (CBA) and other void fillers. Monitoring of periprosthetic bone regeneration could possibly help to optimize this process thereby reducing late failure rates. The aim of this study was to show osteometabolic changes in periprosthetic CBA after THR revision with the use of sodium-[18F]-fluoride (NaF) and positron emission tomography (PET). Patients, methods: Twelve patients undergoing THR revision with the use of CBA were prospectively enrolled in the study. Nine patients completed all necessary examinations and were included in the evaluation. The temporal pattern of osteointegration was assessed via NaF-PET at one (PET1) and six weeks (PET2) after surgery. CBA, tantalum implants, supraacetabular regions ipsilateral and contralateral, and parasymphyseal pubic bones were delineated as volumes of interest (VOI) in postop CT scans, which were then merged with the PET data. Results: In comparison to the contralateral supraacetabular reference bone, a significant 1.5-fold increase of osteometabolic activity from PET1 to PET2 was seen in the CBA region. Also, the ipsilateral supraacetabular host bone showed a higher NaF-influx in week 6, compared to the first postoperative week. The supraacetabular site exhibited a significantly 1.8- to 2-fold higher influx and uptake than bone regions in non-operated sites. Tantalum implants had a low NaF influx at both time points investigated.

Conclusion: Using NaF-PET osteometabolic changes of CBA and implant-bone-interfaces can be monitored. Applying this method we demonstrated early periprosthetic temporal bone regeneration patterns in THR cup revision patients.

Keywords: Allograft; NaF-PET, bone metabolism; endoprothesis; acetabular Registration No. 20720

Zwitterionic-Coated "Stealth" Nanoparticles for Biomedical Applications: Recent Advances in Countering Biomolecular Corona Formation and Uptake by the Mononuclear Phagocyte System
Pombo Garcia, K.; Zarschler, K.; Barbaro, L.; Barreto, J. A.; O'Malley, W.; Spiccia, L.; Stephan, H.; Graham, B.
Abstract: Nanoparticles represent highly promising platforms for the development of imaging and therapeutic agents, including those that can either be detected via more than one imaging technique (multi-modal imaging agents) or used for both diagnosis and therapy (theranostics). A major obstacle to their medical application and translation to the clinic, however, is the fact that many accumulate in the liver and spleen as a result of opsonization and scavenging by the mononuclear phagocyte system. This focused Review summarizes recent efforts to develop zwitterionic-coatings to counter this issue and render nanoparticles more biocompatible. Such coatings have been found to greatly reduce the rate and/or extent of non-specific adsorption of proteins and lipids to the nanoparticle surface, thereby inhibiting production of the "biomolecular corona" that is proposed to be a universal feature of nanoparticles within a biological environment. Additionally, in vivo studies have demonstrated that larger-sized nanoparticles with a zwitterionic coating have extended circulatory lifetimes, while those with hydrodynamic diameters of <= 5 nm exhibit small-molecule-like pharmacokinetics, remaining sufficiently small to pass through the fenestrae and slit pores during glomerular filtration within the kidneys, and enabling efficient excretion via the urine. The larger particles represent ideal candidates for use as blood pool imaging agents, whilst the small ones provide a highly promising platform for the future development of theranostics with reduced side effect profiles and superior dose delivery and image contrast capabilities. Registration No. 20719

Nonlinear PT−symmetric plaquettes --- and beyond
Günther, U.; Kevrekidis, P.; Li, K.; Malomed, B.
Abstract: Nonlinear 2-dimensional PT-symmetric plaquettes of various types are considered. A technique is developed to obtain explicit matrix representations for the parity (P) and for the time-reversal (T) operators starting from initially heuristically designed gain-loss setups of general 2D-type. The threshold behavior of the corresponding linear sub-systems is analyzed near PT-phase transition points in parameter space, the concrete type of exceptional point is established and the analytical construction of stationary solutions for the nonlinear setups is made explicit. The presentation is based on common work with Panayotis Kevrekidis, Kai Li and Boris Malomed [J. Phys. A 45, 444021 (2012)]. Next possible steps of technical extensions towards higher-dimensional soliton setups and required integrability tests via the search for Lax pairs of Zakharov-Shabat and Fordy-Kulish type are briefly sketched.
Keywords: PT symmetry, nonlinear 2-dimensional plaquettes, parity operator, time reversal operator, PT phase transition, exceptional point, Lax pair
  • Invited lecture (Conferences):
    SIAM Conference on Nonlinear Waves and Coherent Structures (SIAM-NW14), Churchill College, University of Cambridge, 11.-14.08.2014, Cambridge, United Kingdom
Registration No. 20715

Neuroimaging the PET experience
Brust, P.
Abstract: Positron Emission Tomography (PET) is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide that is routinely used in radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109,8 min. The administration of such radiotracers into the brain provides images of transport, metaboic and neurotransmission processes on the molecular level. After a short introduction into the principles of PET this talk will mainly focus on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as discussed in this talk provides molecular probes which are not only useful for imaging of human brain diseases. They allow also molecular neuroreceptor imaging studies in various small-animal models of disease including genetically engineerd animals. Futhermore, they provide a powerful tool for in vivo pharmacology during the process of preclinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the phramacokinetics and pharmacodynamics of drugs in vivo.
  • Invited lecture (Conferences):
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria
Registration No. 20710

Plasma based nanotechnology against corrosion of CuZn and TiAl alloys.
Pelic, B.; Bregolin, F. L.; Prucnal, S.; Yankov, R.; Skorupa, W.
Abstract: Experiments have been undertaken to explore the improvement of the aqueous corrosion and high temperature oxidation of CuZn and TiAl, respectively, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-Zn alloy (namely brass) is strongly enhanced by traces of VOC (acetic acid vapors) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits the replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PI3 process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), corrosion of reed organ pipes, CuZn alloys, TiAl alloys, oxidation protection.
  • Lecture (Conference):
    ION 2014 X-th INTERNATIONAL CONFERENCE on Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 20709

Importance of the blood-brain barrier for neuroimaging studies
Brust, P.
Abstract: The blood-brain barrier (BBB) is a control system to preserve homeostasis in the nervous system, facilitating the entry of necessary metabolites, but blocking the entry or facilitating the removal of unnecessary metabolites or toxic substances. For any solute the efficacy of the exclusion or transport is determined by the morphological and functional characteristics of the brain capillaries and by the biochemical and biophysical characteristics of the solute. This applies also for radiotracers which are used for brain imaging. Several transport routes across the BBB exist. Therfore, the transport of radiotracers depends on the functional status of the brain endothelium. Studies were performed to investigate the expression and function of various transport systems at the BBB, such as ABC transporters, aquaporins, glucose, amino acid, choline and serotonin transporters. The influence of drugs, hormones and brain development on transport processes has been explored. Our main findins are: (1) The brain uptake of certain 99m/99Tc-labelled radiotracers is reduced by the presence of drug efflux transporters, e.g: P-glycoprotein. (2) Peptide hormones selectively alter the water permeability and the transport of neutral amino acids at the BBB. (3) The BBB transport of neutral amino acids decreases during development. (4) The transport of basic drugs from blood to brain is partly mediated by the BBB choline transporter. (5) The transport of the PET radiotracer [11C]McN5652 is mediated by the serotonin transporter at the BBB but of no relevance for human PET studies. It is concluded that the transport of radiotracers across the BBB does not solely depend on the lipophilicity of the compounds. Active and regulated efflux systems need to be considered. For many radiotracers specific transport systems exist, which underlie developmental changes and physiological regulation. Nutrient transporter, e. g. for glucose, amino acids and choline, are of special importance.
  • Invited lecture (Conferences):
    5th Biennial Inernational Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria
Registration No. 20708

Molecular Imaging of Neurodegeneration
Brust, P.
Abstract: Molecular imaging (MI) originated from the field of radiopharmacology due to the need to better understand the fundamental molecular pathways inside organisms in a noninvasive manner. It emerged in the early twenty-first century as a discipline at the intersection of molecular biology and in vivo imaging and enables the visualization of the cellular function and the follow-up of the molecular process in living organisms without perturbing them. Basic requirements for MI are probes whose concentration and/or spectral properties are altered by the specific biological process under investigation technology to monitor these probes in living organisms and to reconstruct images from their distribution patterns. Positron Emission Tomography (PET) ist the most sensitive molecular imaging tool and a well-established method for neuroimaging of neurodegeneration such as Alzheimer's disease (AD). An ideal PET biomarker for AD should allow a reliable estimation of disease risk and rate of disease progression long before first symptoms are clinically diagnosed. The main pathologic processes of AD, deposition of beta-amyloid, hyperphosphorylated tau protein, degeneration of cholinergic and other neurons, precede clinical symptoms by years providing potential targets for the identification of individuals at risk for AD. In the last few years, several PET tracers targeting beta-amyloid in AD have been developed. The suitability of these PET radiopharmaceuticals to differentiate AD patients and patients with mild cognitive impairment (MCI) from control subjects has been demonstrated and will be discussed. However beta-amyloid deposition has been found in about 20% of normal elderly subjects.
  • Invited lecture (Conferences):
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria
Registration No. 20707

Polyoxometalates as potent inhibitors of P2X receptors
Spanier, C.; Stephan, H.; Kortz, U.; Haider, A.; Hausmann, R.; Abdelrahman, A.; Müller, Christa E.
Abstract: P2X receptors are trimeric ion channels that are activated by ATP and are permeable for the cations Na+, K+ and Ca2+. Seven different subunits exist, which are assembled as homo- or heterotrimers of various stoichiometry.1,2 Polyoxometalates (POMs) are discrete, polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+), comprising edge- and corner-shared MO6 octahedra. They exhibit enormous flexibility with respect to shape, size, composition and charge.3 POMs are relatively large molecules (> 1 nm) and bear several negative charges. In this respect they bear similarity to ATP, which binds to P2X2 and P2X4 in its tetraanionic form (ATP4-) and to P2X1 and P2X3 possibly also in its dianionic state as a Mg2+ complex (MgATP2-).4 We previously found that certain POMs can inhibit alkaline phosphatase5 and ectonucleotidases,6, 7 enzymes that are capable of hydrolyzing nucleotides such as ATP and ADP. In the present study we investigated whether POMs can interact with P2X receptors. A series of POMs was investigated for their effects to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X1, P2X2, P2X3, P2X4 or P2X7 receptors. Several POMs were found to be highly potent inhibitors of P2X receptors with potency in the low nanomolar range. The compounds were found to be non-cytotoxic at pharmacologically active concentrations, whereas some POMs showed cytotoxic effects in an MTT assay at concentrations typically higher than 1 µM.


1 Young, MT (2010), Trends Biochem. Sci. 35: 83-90
2 Torres, GE, Egan, TM, Voigt, MM (1999), J Biol. Chem. 274: 6653-6659
3 Hasenknopf, B (2005), Front Biosci. 10: 275-28
4 Li, M, Silberberg, SD, Swartz, KJ (2013), Proc. Natl. Acad. Sci. USA: 110: E3455-E3463
5 Raza, R, Matin, A, Sarwar, S, Barsukova-Stuckart, M, Ibrahim, M, Kortz, U, Iqbal, J (2012), Dalton Trans. 41: 14329-14336
6 Müller, CE, Iqbal, J, Baqi, Y, Zimmermann, H, Röllich, A, Stephan, H (2006), Bioorg. Med. Chem. Lett. 16: 5943-5947
7 Stephan, H, Kubeil, M, Emmerling, F, Müller, CE (2013), Eur. J. Inorg. Chem. 1585-1594
  • Poster:
    Purines International Conference on Nucleotides Nucleosides and Nucleobases, 23.-27.07.2014, Bonn, Deutschland
Registration No. 20700

Potential mapping from geochemical surveys using a Cox process
Tolosana-Delgado, R.; van den Boogaart, K. Gerald; Schaeben, H.
Abstract: Punctual occurrence phenomena are often modeled as Poisson point processes, sometimes with an inhomogeneous, unknown intensity, that is desired to be estimated from some covariables. Within this setting, we study the case in which the covariables form a regionalized geochemical composition of stream sediments, and the known punctual occurrences are existing mineral deposits, not collocated with the available explanatory data. This is modeled by assuming a two-layer stochastic process, where the observed Poisson log-intensity is taken as a balanced log-linear function of the geochemical composition of stream sediments, which coefficients must be estimated. Estimation is possible through a pseudolikelihood device based on generalized loglinear models, though the result intensity function appears to be valid only up to arbitrary scaling and addition of constants.
  • Contribution to proceedings:
    GeoENV 2014 - 10th Conference on Geostatistics for Environmental Applications, 09.-11.07.2014, Paris, France
    Proceedings of geoENV 2014
Registration No. 20698

Applications in Compositional Data Analysis
Tolosana-Delgado, R.; van den Boogaart, K. G.
Abstract: Compositional data occur in all fields of science: from politics to materials engineering, from biomedical sciences to geochemistry. In all these fields, variables representing the relative contribution of some parts forming a whole are routinely acquired. Actually, compositions form their own scale, essentially characterized by their intrinsic multivariate nature and the closure to constant sum to 100%. Statistical techniques used with these data must then conform to that scale.

This contribution presents a comprehensive summary of how to adapt the most common statistical techniques, based on the principle of working on coordinates within the log-ratio approach. In application of this principle, data are represented in an one-to-one set of logratios of the original components, the scores are analysed with classical multivariate tools, and results are eventually back-transformed for interpretation. In particular, this contribution explores the uses of cluster analysis, principal components and linear regression to explain the natural variability on several data sets from the Earth sciences.

Keywords: biplot ; PCA ; linear model ; geochemical survey ; clr ; ilr
  • Lecture (Conference):
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA
Registration No. 20697

Spatial Analysis of Compositional Data
Pawlowsky-Glahn, V.; Tolosana-Delgado, R.; van den Boogaart, K. G.
Abstract: Spurious correlation is known to be a problem in statistics since Pearson's early warnings in 1897. The same problems arise in spatial statistics: bias towards negative values and non-zero cross-covariances and cross-covariograms; singular matrices of intrinsic co-dispersion; co-kriged regionalised vectors of proportions that do not satisfy the constant sum constraint. A way out is to use log-ratio transformations: the spatial structure can be described in terms of direct variograms of each possible pairwise logratio; variation-variograms can be estimated even in case of missing components; they can be modelled with standard tools; both the data and the spatial structure model can be expressed in isometric logratio coordinates, and standard co-kriging techniques can be applied to obtain interpolated logratios. These can be back-transformed to compositions, delivering interpolated maps of each component that satisfy the required constraints. Moreover, the result does not depend on which logratio transformation was used for the computations. This approach and its potentialities is illustrated with a data set of soil geochemistry.
Keywords: Aitchison geometry of the simplex ; co-kriging ; compositional data ; spurious spatial covariance ; variation-variogram
  • Lecture (Conference):
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA
Registration No. 20696

Single-domain antibodies as targeting moieties for nanomaterial-based cancer imaging
Zarschler, K.; Zscheppang, K.; Cordes, N.; Stephan, H.; Steinbach, J.
Abstract: ken Abstract verfügbar
  • Poster:
    DKTK Retreat 2014, 12.-13.05.2014, Heidelberg, Deutschland
Registration No. 20694

Ultrasmall silicon nanoparticles: preparation strategies and bioapplications
Licciardello, N.; Hsu, C.-W.; Prasetyanto, E. A.; Hunoldt, S.; Viehweger, K.; Stephan, H.; de Cola, L.
Abstract: The use of nanoparticles in multimodal bio-imaging is attracting increasing interest, but toxicity and accumulation in organs still limit their in vivo applications. Silicon nanoparticles (Si NPs) are very promising in this respect as their size, 1.5 - 4 nm, can allow body excretion. In addition Si NPs are photo- and chemical stable, possess bright tunable luminescence and can be covalently functionalized with desired molecules. Indeed several techniques have been described to obtain Si NPs [1-3] with different sizes and bearing various functional groups.
Here we report on some optimized wet chemistry techniques to prepare ultrasmall (< 5 nm) Si NPs and, in particular, the focus is on microemulsion methods and hydrothermal synthesis. The obtained Si NPs can bear different functional groups, allowing a wide spectrum of subsequent conjugations. Once functionalized and purified, Si NPs were characterized by HR-TEM and IR spectroscopy, and their photophysical properties were investigated. Reactivity and properties of the NPs obtained by various methods will be compared and the results of in vitro and in vivo experiments will be shown to demonstrate the great potentialities of such ultrasmall Si NPs.
This work was financially supported by Helmholtz Virtual Institute “Nano-Tracking”, Agreement No. VH-VI-421

1. J. H. Warner et al., Angew. Chem. Int. Ed. 2005, 44, 4550 –4554
2. M. Rosso-Vasic et al., Small, 2008, 4, 1835–1841
3. Y. Zhong et al., J. Am. Chem. Soc., 2013, 135, 8350-8356
  • Lecture (Conference):
    E-MRS Spring Meeting, 26.-30.05.2014, Lille, France
Registration No. 20693

Transport in Nanoelectronic Systems
Grebing, J.; Deb, D.; Grube, M.; Trommer, J.; Teshome, B.; Sendler, T.; Wieser, M.; Helm, M.; Weber, W.; Keller, A.; Erbe, A.
Abstract: Microelectronics today is still based on the silicon technology it has been employing for the past 40 years even though it has been highly optimised and iteratively refined. Yet, it will come to a point where new concepts will be needed when “More Moore” has been extended to its ultimate limits. This is why there is a high interest in researching different approaches, e.g., with added functionality (“More-than-Moore”) [1] or even completely different concepts going “beyond Moore” like molecular electronics.

In the first part of this paper we present recent work on the top-down fabrication of silicon nano wire field effect transistors (FET) with two gates allowing not only for the control of the current through the device as it is done in a conventional FET but also to switch between the conduction mechanism, i.e., p- or n-type behaviour. It has been demonstrated previously that this kind of device can be used to build circuits [2,3]. However, we want to extend the principle from single nano wire devices to complex integrated circuits.

The second part will then go “beyond Moore” to illustrate results from our research on two challenges in the field of molecular electronics: Joining bottom-up with top-down techniques to form electrical contacts to nano objects on the one hand. We employ ion beam treatment of the substrate to form a preferential alignment for DNA templated wires. These will ultimately be used for DNA templated quantum dot transistors. On the other hand we will present a single molecular switch sensitive to light in the UV/VIS regime [4].

[1] ITRS “More-than-Moore” White Paper (2010) – http://www.itrs.net/papers.html
[2] A. Heinzig et al., Nano Lett. 12 (1) 119–124 (2012)
[3] T. Mikolajick et al., Phys. Status Solidi Rapid Res. Lett. 7 (10), 793–799
[4] Y. Kim et al., Nano Lett. 12 (7) 3736–3742 (2012)

Keywords: nanoelectronics, DNA template, nanowire, molecular electronics
  • Invited lecture (Conferences):
    9. Silicon Saxony Day, 03.07.2014, Dresden, Deutschland
Registration No. 20691

An adaptive, load-balanced MPI/GPU-Code for calculating the gain in High Power Laser media
Zenker, E.; Eckert, C.; Albach, D.; Bussmann, M.
Abstract: We present an adaptive Monte Carlo approach for computing the amplified spontaneous emission (ASE) flux in a laser medium pumped by pulsed lasers. For high energy laser systems with large apertures sufficient spatial resolution requires high computational power. We have developed an adaptive multi-node GPU algorithm with load balancing that shows close to perfect strong scaling that allows for large speedups compared to previously existing CPU implementations. This code will allow to calculate the ASE flux in large size gain media as they will be used in the upcoming generation of high-power laser systems.
Keywords: CUDA, MPI, Monte Carlo, ASE flux, HPC, Cluster, laser, parallel, GPU
  • Lecture (Conference):
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland
Registration No. 20689

Evaluation of metabolism, plasma protein binding and other biological parameters after administration of (−)-[18 F]Flubatine in humans
Patt, M.; Becker, Georg A.; Grossmann, U.; Habermann, B.; Schildan, A.; Wilke, S.; Deuther-Conrad, W.; Graefe, S.; Fischer, S.; Smits, R.; Wagenknecht, G.; Steinbach, J.; Gertze, H.-J.; Hesse, S.; Schönknecht, P.; Brust, P.; Sabri, O.
Abstract: Introduction
(−)-[18 F]Flubatine is a PET tracer with high affinity and selectivity for the nicotinic acetylcholine α4β2 receptor subtype. A clinical trial assessing the availability of this subtype of nAChRs was performed. From a total participant number of 21 Alzheimer’s disease (AD) patients and 20 healthy controls (HCs), the following parameters were determined: plasma protein binding, metabolism and activity distribution between plasma and whole blood.

Methods
Plasma protein binding and fraction of unchanged parent compound were assessed by ultracentrifugation and HPLC, respectively. The distribution of radioactivity (parent compound + metabolites) between plasma and whole blood was determined ex vivo at different time-points after injection by gamma counting after separation of whole blood by centrifugation into the cellular and non-cellular components. In additional experiments in vitro, tracer distribution between these blood components was assessed for up to 90 min.

Results
A fraction of 15% ± 2% of (−)-[18F]Flubatine was found to be bound to plasma proteins. Metabolic degradation of (−)-[18F]Flubatine was very low, resulting in almost 90% unchanged parent compound at 90 min p.i. with no significant difference between AD and HC. The radioactivity distribution between plasma and whole blood changed in vivo only slightly over time from 0.82 ± 0.03 at 3 min p.i. to 0.87 ± 0.03 at 270 min p.i. indicating the contribution of only a small amount of metabolites. In vitro studies revealed that (−)-[18F]Flubatine was instantaneously distributed between cellular and non-cellular blood parts.

Discussion
(−)-[18F]Flubatine exhibits very favourable characteristics for a PET radiotracer such as slow metabolic degradation and moderate plasma protein binding. Equilibrium of radioactivity distribution between plasma and whole blood is reached instantaneously and remains almost constant over time allowing both convenient sample handling and facilitated fractional blood volume contribution assessment.

Keywords: Flubatine; Plasma protein binding; Metabolism; Clinical trial; PET; Fluorine-18 Registration No. 20684

Automated recognition of quasi-planar ignimbrite sheets as paleosurfaces via robust segmentation of digital elevation models: an example from the Central Andes
Székely, B.; Koma, Z.; Karátson, D.; Dorninger, P.; Wörner, G.; Brandmeier, M.; Nothegger, C.
Abstract: Quasi-planar morphological surfaces may become dissected or degraded with time, but still retain original features related to their geologic-geomorphic origin. To decipher the information hidden in the relief, recognition of such features is required, possibly in an automated manner. In our study, using Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM), an existing algorithm has been adapted to recognize quasi-planar features fulfilling specified criteria. The method has been applied to a study area of the Central Andes with Miocene to Quaternary volcanic edifices, tilted ignimbrite surfaces, and basin-filling sediments. The result is a surface segmentation, whereas non-planar features (gullies, tectonic faults, etc.) are sorted out. The main types of geomorphic features that can be distinguished and interpreted are as follows. (1) The west-dipping western margin of the Altiplano is differentiated into segments of the lower sedimentary cover that of increased erosion by tectonic steepening at intermediate levels, and an upper plane with limited erosion. (2) In the central part of the Western Cordillera, the Oxaya ignimbrite block shows a ‘striped’ bulging pattern that results from a smoothly changing surface dip. This pattern is due to continuous folding/warping of the ignimbrite block possibly related to gravitational movements. (3) To the west, large, uniform planes correspond to flat, smooth, tectonically undisturbed surfaces of young sedimentary cover of the Central Basin. (4) The evolution of Taapaca volcanoes with sector collapse events and cone-building phases is shown by several segments with overlapping clastic aprons. (5) To the east, on the western margin of the Altiplano, young intermontane basins filled by Upper Miocene sediments show progressively increasing dip toward basin margins, reflected by a circular pattern of the segmentation planes. We show that the segmentation models provide meaningful images and additional information for geomorphometric analysis that can be interpreted in terms of geological and surface evolution models.
Keywords: geomorphometry;dissected surfaces;robust segmentation;digital elevation model;paleosurfaces Registration No. 20681

Plasma based nanotechnology against corrosion of CuZn and TiAl alloys
Bregolin, B. Pelic. F.; Prucnal, S.; Yankov, R.; Skorupa, W.
Abstract: Experiments have been undertaken to explore the improvement of the aqueous corrosion and high temperature oxidation of CuZn and TiAl, respectively, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-Zn alloy (namely brass) is strongly enhanced by traces of VOC (acetic acid vapors) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits the replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PI3 process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.

Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), corrosion of reed organ pipes, CuZn alloys, TiAl alloys, oxidation protection
  • Lecture (Conference):
    X-th INTERNATIONAL CONFERENCE - Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 20680

Thermal evolution of defects in undoped zinc oxide grown by pulsed laser deposition
Wang, Z.; Su, S.; Ling, F. C. C.; Anwand, W.; Wagner, A.
Abstract: Undoped ZnO films are grown by pulsed laser deposition on c-plane sapphire with different Oxygen pressures. Thermal evolutions of defects in the ZnO films are studied by secondary ion mass spectroscopy (SIMS), Raman spectroscopy, and positron annihilation spectroscopy (PAS), and with the electrical properties characterized by the room temperature Hall measurement. Oxygen deficient defect related Raman lines 560 cm^-1 and 584 cm^-1 are identified and their origins are discussed. Thermal annealing induces extensive Zn out-diffusion at the ZnO/sapphire interface and leaves out Zn-vacancy in the ZnO film. Two types of Zn-vacancy related defects with different microstructures are identified in the films. One of them dominates in the samples grown without oxygen. Annealing the sample grown without oxygen or growing the samples in oxygen would favor the Zn-vacancy with another microstructure, and this Zn-vacancy defect persists after 1100 °C annealing.
Keywords: undoped ZnO films, Raman spectroscopy, positron annihilation, green luminescence Registration No. 20678

Nature of red luminescence band in research-grade ZnO single crystals: A “self-activated” configurational transition
Chen, Y. N.; Xu, S. J.; Zheng, C. C.; Ning, J. Q.; Ling, F. C. C.; Anwand, W.; Brauer, G.; Skorupa, W.
Abstract: By implanting Zn+ ions into research-grade intentionally undoped ZnO single crystal for facilitating Zn interstitials (Zni) and O vacancies (VO) which is revealed by precise X-Ray diffraction rocking curves, we observe an apparent broad red luminescence band with a nearly perfect Gaussian lineshape. This red luminescence band has the zero phonon line at ~2.4 eV and shows distinctive lattice temperature dependence which is well interpreted with the configurational coordinate model. It also shows a low “kick out” thermal energy and small thermal quenching energy. A “selfactivated” optical transition between a shallow donor and the defect center of Zni-VO complex or VZnVO di-vacancies is proposed to be responsible for the red luminescence band. Accompanied with the optical transition, large lattice relaxation simultaneously occurs around the center, as indicated by the generation of multiphonons.
Keywords: ZnO, Zn Implantation, red luminescence, Zn interstitials, O vacancies Registration No. 20677

Quantification of brittle-ductile failure behavior of ferritic reactor pressure vessel steels using the Small-Punch-Test and micromechanical damage models
Linse, T.; Kuna, M.; Viehrig, H.-W.
Abstract: Two German ferritic pressure vessel steels are examined in the brittle to ductile transition regime as a function of temperature and irradiation.The experiments are done by a miniaturized Small-Punch-Test in hot cells within the temperature range of -185 °C up to 70 °C. From the load–displacement curve of the SPT,the yield curves and parameters of both a non-local GURSON-TVERGAARD-NEEDLEMAN ductile damage model and a modified BEREMIN model are identified. The influence of temperature and irradiation on the model parameters is analyzed. All parameters are verified by comparison with results from standard test methods. The parameters, identified from SPT,are used to simulate the failure behavior in standard fracture mechanics specimens.In the uppershelf, the non-local GTN-model is applied to simulate crack resistance curves,from where the fracture toughness data could be successfully predicted. In the lower shelf, the WEIBULL-stress of the specimens was computed to find out the statistics of fracture toughness values.Finally, the modified BEREMIN model and the non-local ductile damage model were combined to evaluate the failure of fracture specimens in the brittle-ductile transition region.This way, an acceptable agreement with Master-Curve data for non-irradiated steels could be achieved in the whole temperature range.
Keywords: Non-local ductiledamagemodel, Beremin-Model, Small-Punch-Test, Brittle-ductile transition Registration No. 20676

Investigations on the Discrimination of Nuclear Reactor Core State Changes by the external Gamma Radiation Field
Brachem, C.; Konheiser, J.; Hampel, U.
Abstract: Monte Carlo Simulations have been carried out to estimate the gamma radiation distributions outside the reactor pressure vessel of a generic pressurized water reactor for a set of simplified accident-like reactor states.
This is done as a first step towards the development of a non-invasive core monitoring system for light water reactors.
The results show a change in the shape of the gamma ray distributions for decreasing coolant levels as well as a vast increase in flux for corium accumulating inside the lower head.

Keywords: gamma radiation, Monte Carlo simulation, PWR, accident,
  • Lecture (Conference):
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2014, Berlin, Germany
Registration No. 20671

The Gamma Radiation emitted by a PWR Core under severe Accident Conditions
Brachem, C.; Konheiser, J.; Hampel, U.
Abstract: The gamma radiation emitted by a nuclear reactor core might contain information about the reactor state. This information may be used in a monitoring system for severe accidents.
The Technische Universit¨at Dresden and the Zittau/G¨orlitz University of Applied Sciences are currently carrying out feasibility studies for the development of such a system in a collaborative effort. As one part of such feasibility studies we performed Monte Carlo simulations on a simplified model of a generic pressurized water reactor. For a set of states which represent scenarios of a coolant level decrease and core melt, the gamma radiation distribution outside the reactor pressure vessel has been computed.
The results are presented in this paper.
They indicate that different coolant levels yield different gamma radiation distributions, and that an accumulation of corium inside the lower head is detectable from the outside.

Keywords: gamma radiation, Monte Carlo simulation, PWR, accident,
  • Contribution to proceedings:
    22nd International Conference on Nuclear Engineering (ICONE22), 07.-11.07.2014, Prague, Czech Republic
    Proceedings of the 22nd International Conference on Nuclear Engineering, ICONE22
Registration No. 20670

Sponge-like Si-SiO2 nanocomposite for PV applications
Liedke, B.; Heinig, K.-H.; Friedrich, D.; Schmidt, B.; Mücklich, A.; Keles, U.; Bulutay, C.
Abstract: The aim of this talk is to explain method of fabrication, modification and optimization of Sponge-like Si-SiO2 nanocomposite.
It consists of Si embedded in SiO2 fabricated by spinodal decomposition of sputter-deposited silicon-rich oxide SiOx≈1. Thermal treatment using rapid thermal processing and oven annealing requires annealing times of few tens of sec. up to few tens of min. However, in a thin film technology the phase separation of SiOx at high temperatures requires a very rapid thermal processing of few tens of ms in order to avoid substrate damage.
Here, the structure of the Si-SiO2 nanocomposite was investigated by energy-filtered transmission electron microscopy (EFTEM), EFTEM tomography and atom probe tomography, which revealed a percolated Si morphology. This is in excellent agreement with atomistic simulations using kinetic Monte-Carlo method. Depending on the annealing time and temperature a feature size in the range of 2...5 nm was found, which is small enough for band gap widening due to quantum confinement.
We show that the favorable properties of Si-SiO2 nanocomposite, e.g. quantum size effect and percolated morphology, make it a suitable material for PV absorber.

Keywords: sponge-like nanocomposite, SiOx, photovoltaic, absorber, phase separation, band-gap engineering
  • Lecture (others):
    Seminar an der TU Bergakademie Freiberg, 15.07.2014, Freiberg, Germany
Registration No. 20668

Stabilität des Hypoxietracers [18F]-FMISO während sequentieller PET-Untersuchungen bei Patienten mit radiochemotherapierten HNO-Tumoren und Korrelation von funktionellen Tumor-Subvolumina zur Rezidivlokalisation
Zschaeck, S.; Haase, R.; Zöphel, K.; Abolmaali, N.; Perrin, R.; Kotzerke, J.; Steinbach, J.; Zips, D.; Krause, M.; Baumann, M.
Abstract: Fragestellung.
Untersucht wurde die Verteilung der Aktivitätskonzentration des Hypoxietracers FMISO in sequentiellen PET-Untersuchungen bei Patienten mit primär radiochemotherapierten Kopf-Hals-Tumoren. Patienten mit residueller Hypoxie während der zweiten Behandlungswoche erleiden fast immer ein Lokalrezidiv im Hochdosis-Bereich. Zur Erhöhung der Strahlendosis werden unter anderem FMISO-PET-basiert adaptierte Dosisverschreibungen (Dose-painting) diskutiert. Für eine erste Plausibilitätsprüfung dieses Ansatzes wurde die Stabilität der FMISO-Verteilung und die Lokalisation von Lokalrezidiven mit, während der Therapie erfassten, PET-Parametern untersucht.
Methodik.
Von 25 Patienten, die während der primären Radiochemotherapie sequentielle FMISO Aufnahmen erhielten (FMISO1 vor Therapie, FMISO2 in der ersten, FMISO3 in der zweiten und FMISO4 in der fünften Woche) zeigten 12 eine ausgeprägte residuelle Hypoxie (bestimmt als TBRmax>1,9). Sechs dieser Patienten hatten ein auswertbares Lokalrezidiv (2 x in der CT und 4 x in der FDG-PET-CT). Die Rezidivbildgebung und darauf basierende Konturen wurden auf die FMISO- und FDG PET-Untersuchungen vor Therapie fusioniert und die PET-Konturen auf ein Überlappen überprüft.
Ergebnis.
Die wiederholten FMISO-PET-Untersuchungen während der Radiochemotherapie zeigten ein sehr heterogenes volumetrisches Verhalten der hypoxischen Subvolumina zu Beginn der Therapie. In der FMISO4-Bildgebung war nur noch selten Hypoxie nachzuweisen. Trotz der Größenvariationen innerhalb der ersten beiden Wochen war die Überlappung der sequentiellen Sub-Volumina ausgeprägt, bestimmt als mittlerer Dice-Index von 62% zwischen FMISO1 und FMISO2 und 58% zwischen FMISO2 und FMISO3. Die Lokalisation des Aktivitäts-Hot-Spots SUVmax zeigte demgegenüber dramatische Veränderungen, der mittlere Abstand betrug zwischen FMISO2 und FMISO3 13,5
mm. Die vorhandenen, registrierten Rezidive zeigten sowohl ein Überlappen mit dem initialen FDG-PET, als auch mit FMISO1 und FMISO3 (medianer Dice-Index 27, 24 und 28%). Zur Überprüfung ob es wirklich eine reproduzierbare und stabile FMISO-PET-positive Region gibt, die sich zur Dosiseskalation eignet, wurden die überlappenden Konturen verschiedener FDG und FMISO-Konturen zu einer gemeinsamen Kontur zusammengefasst (FDG, FMISO1, FMISO3). Nur in 2 Fällen trat das Rezidiv in der so eingegrenzten Region auf.
Schlussfolgerung.
Die FMISO-Verteilung variiert während der ersten beiden Therapiewochen erheblich, es erfolgt jedoch keine komplette Verschiebung des hypoxischen Subvolumens sondern eine unterschiedlich ausgeprägte Volumenveränderung. Die Überlappung der FMISO-PET-basierten Subvolumina mit dem Lokalrezidiv stärken die Hypothese, dass radioresistente Zellen in diesen Regionen das Rezidiv verursachen können. Die Variabilität des SUVmax und die geringe Rate an Rezidiven innerhalb einer reproduzierbar abgrenzbaren FDG und FMISO aviden Region sprechen jedoch gegen eine, rein voxelbasierte, Dosisverschreibung.
  • Poster:
    20. Jahrestagung der Deutschen Gesellschaft für Radioonkologie (DEGRO), 03.-06.07.2014, Düsseldorf, D
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl. 1, 52
Registration No. 20664

Spin dynamics in triangular-lattice antiferromagnets Cs2CuBr4 and Cs2CuCl4: high-field ESR studies
Zvyagin, S.
Abstract: A spin-1/2 Heisenberg antiferromagnet (AF) on a triangular lattice is the paradigmatic model in quantum magnetism, which was intensively studied. In spite of numerous theoretical studies (which predict a rich variety of grounds states, ranging from a gapless spin liquid to Néel order), many important details of the phase diagram of triangular-lattice AFs remain controversial or even missing. In order to test the theory experimentally, a precise information on the spin-Hamiltonian parameters for the materials of interest is highly demanded. Here, we present results of high-field electron spin resonance (ESR) studies of spin-1/2 Heisenberg AFs Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures in magnetic fields up to 50 T [1]. In the magnetically saturated phase (H>Hsat), 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 first proven by applying it to Cs2CuCl4, revealing good agreement with inelastic neutron-scattering 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 coupling parameters in this frustrated spin system. The approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered Dzyaloshinskii-Moriya interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode above Hsat
  • Invited lecture (Conferences):
    Fifth Workshop on Current Trends in Molecular and Nanoscale Magnetism, 26.-29.05.2014, Larnaca, Cyprus
Registration No. 20662

Experimentelle Untersuchungen zur Ablagerung und Remobilisierung von Aerosolpartikeln in turbulenten Strömungen
Barth, T.
Abstract: Im Rahmen dieser Dissertation werden eine Serie von Grundlagenexperimenten zur Ablagerung (Deposition) und Remobilisierung (Resuspension) von Aerosolpartikeln in turbulenten Strömungen beschrieben. Die Kernmotivation stellt die Quelltermanalyse von Druckentlastungsstörfällen von Hochtemperaturreaktoren (HTR) dar. Im Primärkreislauf früherer HTR-Forschungsanlagen wurden größere Mengen an radiologisch belastetem Graphitstaub gefunden. Dieser Staub scheint größtenteils durch Abrieb zwischen den graphitischen Kernstrukturen entstanden zu sein und verteilte sich während des fortlaufenden Reaktorbetriebs über sämtliche Oberflächen des Primärkreislaufs. Während eines Druckentlastungsstörfalls kann dieser Staub durch die Gasströmung remobilisiert und aus dem Primärkreislauf ausgetragen werden. Eine Quelltermanalyse solch eines Störfallszenarios erfordert die Kenntnis über die Menge und die räumliche Verteilung des Staubs, die radiologische Belastung sowie das Remobilisierungsverhalten in Bezug auf die zu erwartenden Strömungstransienten. Nach dem heutigen Stand von Wissenschaft und Technik kann die räumlich-zeitliche Verteilung des Staubs im Primärkreislauf für stationären Reaktorbetrieb unter Verwendung eindimensionaler Systemcodes abgeschätzt werden. Jedoch ist unbekannt, welcher Anteil des Staubinventars durch die Gasströmung remobilisiert und aus dem Primärkreislauf ausgetragen werden würde.
Zur systematischen Untersuchung des Staubtransportverhaltens in turbulenten Strömungen wurden zwei kleinskalige Versuchsanlagen entwickelt und eine Serie von Depositions- und Resuspensionsexperimenten durchgeführt. Die partikelbeladene Strömung in der Heißgasumgebung des HTR-Primärkreislaufs wurde über die Verwendung von Ähnlichkeitskennzahlen auf eine Luftströmung bei Umgebungsbedingungen herunterskaliert. Die Strömung und die Partikel wurden mittels hochauflösender, bildgebender und nichtinvasiver Messverfahren räumlich und zeitlich vermessen, um eine umfangreiche Datenbasis für die Analyse der Partikeltransportprozesse zu erstellen. Inhaltlich lassen sich die durchgeführten Untersuchungen in drei Teile gliedern. Der erste Teil besteht aus zwei Studien über die Deposition und Resuspension monodisperser, sphärischer Einzelpartikel in einer ungestörten, horizontalen Kanalströmung. Die systematische Variation experimenteller Randbedingungen wie der Partikelgröße, der Oberflächenrauheit und der Strömungsgeschwindigkeit ermöglichte die Quantifizierung der einzelnen Einflussgrößen. Im zweiten und dritten Teil der Dissertation wurden die Deposition und Resuspension einer mehrschichtigen Ablagerung (Partikel-Multilayer) zwischen periodischen Stufen und in einer Kugelschüttung untersucht, um die komplexe Interaktion zwischen der turbulenten Strömung und der Multilayer-Ablagerung weiter zu erforschen.
Die gewonnenen Erkenntnisse leisten einen Beitrag für die Quelltermanalyse des Staubtransports im HTR-Primärkreislauf und können für die Weiterentwicklung numerischer Strömungssimulationen des Partikeltransports in turbulenten Strömungen verwendet werden.

Keywords: turbulent flows, aerosol particle, deposition, resuspension, high temperature reactor
  • Thesis / Students' report:
    TU Dresden, 2014
    Mentor: Prof. Dr.-Ing. habil. Uwe Hampel
    155 Seiten
Registration No. 20660

Development of substrate-based radiotracers for imaging of tumour-associated lysyl oxidase activity by positron emission tomography
Kuchar, M.; Bergmann, R.; Wodtke, R.; Mosch, B.; Lenk, J.; Steinbach, J.; Pietzsch, J.; Löser, R.
Abstract: kein Abstract verfügbar
  • Poster:
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal:
    European Journal of Cancer 50(2014)Suppl. 5, S204
Registration No. 20659

EphB4 negatively regulates blood vessel network formation and perfusion in human A375 melanoma xenografts
Neuber, C.; Hofheinz, F.; Bergmann, R.; Meister, S.; Steinbach, J.; Mosch, B.; Pietzsch, J.
Abstract: kein Abstract verfügbar
  • Poster:
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal:
    European Journal of Cancer 50(2014)Suppl. 5, S62-S63
Registration No. 20658

A novel animal model of phaeochromocytoma for preclinical therapy evaluation
Ullrich, M.; Bergmann, R.; Pietzsch, J.; Cartellieri, M.; Peitzsch, M.; Eisenhofer, G.; Bornstein, S. R.; Ziegler, C. G.
Abstract: kein Abstract verfügbar
  • Poster:
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal:
    European Journal of Cancer 50(2014)Suppl. 5, S53
Registration No. 20657

Role of extracellular S100A4 in stimulation of melanoma cells crossing the blood-brain barrier in vitro and in vivo
Herwig, N.; Wolf, S.; Haase-Kohn, C.; Steinbach, J.; Pietzsch, J.
Abstract: kein Abstract verfügbar
  • Poster:
    23rd Biennial Congress of the European Association for Cancer Research (EACR), 05.-08.07.2014, München, D
  • Abstract in refereed journal:
    European Journal of Cancer 50(2014)Suppl. 5, S49
Registration No. 20656

Variability and lower bound of fracture toughness of welds in the ductile-to-brittle transition regime
Hans-Jakob, S.; Dietmar, K.; Hans-Werner, V.
Abstract: The reference temperature T0 was measured for both T-S and T-L- specimen orientation in 24 layers across the thickness of the beltline weld of a reactor pressure vessel. It turned out to vary in a bandwidth of more than 40K. Because of a high scatter, no clear pattern of T0 as a function of the thickness position could be recognized. A more detailed analysis revealed that the median of KJc was considerably steeper than predicted by the Master-Curve, which leads to a bias of T0 with respect to the testtemperature relative to T0. By a modified evaluation procedure, the scatter of the reference temperature could be significantly reduced, which enabled the global pattern of T0 to be recognized. By comparing the theoretical lower bound to KJc-data of the used specimens with the individual measured KJc a representative T0 that characterizes the overall toughness behaviour of the weld was determined. It turned out to be about 10 K lower than the maximum local T0.
Keywords: welding seam, fracture toughness, ductile-tobrittle, Master Curve, Registration No. 20655

Uniaxial anisotropy and its manipulation in amorphous Co68Fe24Zr8 thin films
Fu, Y.; Barsukov, I.; Meckenstock, R.; Lindner, J.; Zhai, Y.; Hjörvarsson, B.; Farle, M.
Abstract: We have proven that the growth of Co68Fe24Zr 8 layers under external field yields a uniaxial anisotropy, defined by the direction of the field. No magnetic coupling is present between Co 68Fe24Zr8 layers when separated by a 3nm of Al70Zr30. The anisotropy axis can therefore be manipulated at will and the direction can be tailored, layer by layer in multilayers, by the choice of the direction of the applied field during growth. The g-factor (2.13) and the anisotropy constant, obtained from ferromagnetic resonance, support the existence of short-range order. The relation between the temperature dependences of magnetic anisotropy and magnetization are partially captured by Callen-Callen power law. Registration No. 20653

Strong Auger scattering in Landau-quantized graphene investigated by infrared pump-probe experiments
Mittendorff, M.; Wendler, F.; Malic, E.; Knorr, A.; Orlita, M.; Potemski, M.; Berger, C.; de Heer, Walter A.; Schneider, H.; Helm, M.; Winnerl, S.
Abstract: The non-equidistant Landau-level (LL) spectrum of graphene enables the investigation of the carrier dynamics of distinct LL transitions. We present pump-probe measurements on multilayer epitaxial graphene, complemented by microscopic modelling. The free-electron laser (FEL) FELBE served as radiation source at a wavelength of 16.5 µm, which corresponds to a photon energy of 75 meV. At a magnetic field of 4.2 T, the photon energy gets resonant with the energetically degenerate LL transitions LL-1 → LL0 and LL0 → LL1. Circularly polarized radiation allows one to address one of these transitions selectively.
Besides a strong increase of the pump-probe signal at 4.2 T, we observe a complex set of pump-probe signals for all four combinations of pump and probe polarization. For contrarily polarized pump and probe radiation, one would expect negative pump-probe signals, as the initial state of the probed transition is populated (pump: σ+; probe: σ-) or the final state of the probe gets depopulated.
Our measurements show the counterintuitive result of positive pump-probe signals for the case of σ+-polarized pump radiation. The experimental findings are well described by microscopic calculations based on the density matrix formalism, which helped to reveal the origin of this behavior.

Keywords: Landau quantization; relaxation dynamics; graphene
  • Lecture (Conference):
    High Magnetic Fields in Semiconductor Physics, 03.-08.08.2014, Panama City Beach, USA
Registration No. 20652

Kurzzeitspektroskopie: Kürzeste Laserpulse für Materialuntersuchungen
Mittendorff, M.
Abstract: Mit Hilfe der Kurzzeitspektroskopie ist es möglich die Ladungsträgerdynamik in unterschiedlichen Materialsystemen direkt zu untersuchen. Bei sog. „Pump-Probe-Messungen“ werden z.B. Ladungsträger oder Moleküle mit einem sehr intensiven, aber auch sehr kurzen Laserpuls angeregt. Ein zweiter, wesentlich schwächerer Puls wird verwendet um die verursachte Änderung zu messen. Durch eine zeitliche Verschiebung des zweiten Pulses kann gemessen werden, wie lange das System braucht um die Energie wieder abzugeben. Eine einfache Skizze eines Aufbaus für Pump-Probe-Messungen, sowie ein Beispiel für das Ergebnis einer Messung sind in Abb. 1 gezeigt. Diese Untersuchungen sind beispielsweise besonders wichtig zur Entwicklung und Optimierung elektro-optischer Bauelemente wie z. B. Detektoren oder optische Modulatoren.
Die erreichbare zeitliche Auflösung bei diesen Messungen hängt im Wesentlichen von der Pulsdauer des Lasersystems ab. In diesem Vortrag werden verschieden Lasersysteme zur Erzeugung ultra-kurzer Laserpulse in einem breiten Spektralbereich vom nahen bis zum fernen Infrarot vorgestellt (800 nm – 250 µm). Zu jedem vorgestellten System wird als Beispiel eine Messung der Ladungsträgerdynamik in Graphen gezeigt, das aus einem zweidimensionalen Gitter aus Kohlenstoffatomen besteht. Dieses relativ neue Material, für dessen Untersuchung der Nobelpreis für Physik 2010 verliehen wurde, ist neben der Verwendung in der Elektronik speziell für Anwendungen in der Optoelektronik interessant. Durch die Verwendung verschiedener Wellenlängen können in diesem Material unterschiedliche physikalische Effekte untersucht werden.
  • Lecture (others):
    2. Fortbildungsveranstaltung zu Optotechnik und Bildverarbeitung, 27.06.2014, Darmstadt, Deutschland
Registration No. 20651

Microscopic Description of Intraband Absorption in Graphene: The Occurrence of Transient Negative Differential Transmission
Kadi, F.; Winzer, T.; Malic, E.; Knorr, A.; Göttfert, F.; Mittendorff, M.; Winnerl, S.; Helm, M.
Abstract: We present a microscopic explanation of the controversially discussed transient negative differential transmission observed in degenerate optical pump-probe measurements in graphene. Our approach is based on the density matrix formalism allowing a time- and momentum-resolved study of carrier-light, carrier-carrier, and carrier-phonon interaction on microscopic footing. We show that phonon-assisted optical intraband transitions give rise to transient absorption in the optically excited hot carrier system counteracting pure absorption bleaching of interband transitions. While interband transition bleaching is relevant in the first hundreds of fs after the excitation, intraband absorption sets in at later times. In particular, in the low excitation regime, these intraband absorption processes prevail over the absorption bleaching resulting in a zero crossing of the differential transmission. Our findings are in good qualitative agreement with recent experimental pump-probe studies.
Keywords: graphene, carrier-dynamics, ultrafast spectroscopy Registration No. 20649

Magnetization reversal in Co zigzag nanocolumns grown by glancing angle deposition
Buchta, K.; Lewandowski, M.; Bischoff, L.; Synoradzki, K.; Błaszyk, M.; Toliński, T.; Luciński, T.
Abstract: A Co zigzag nanocolumn sample was grown by glancing angle deposition using molecular beam epitaxy. A structural study was carried out using scanning electron microscopy and the magnetic properties and the magnetoresistance were investigated at room temperature. Each zigzag consisted of six arms tilted with respect to each other by approx. 60°, had a club-like shape, diameter in the range of 20-100 nm, a single arm length of about 150 nm and a total height of approx. 370 nm. The magnetization hard axis was observed for the magnetic field oriented parallel to the zigzag long axis and the easy axis for the field oriented perpendicular to the long axis. The system exhibited very high maximum coercivity values, which could find potential applications. The angular dependences of the coercive field and the remanent to saturation magnetization ratio, as well as magnetoresistance curves, indicated the presence of curling magnetization reversal mode.
Keywords: Glancing Angle Deposition; Magnetization Reversal Mechanisms; Magnetic Anisotropy; Magnetic Properties; Zigzag Nanostructures; Sculptured Thin Films Registration No. 20648

A Survivin-XIAP regulates Complexity of the Signaling Molecules FAK and Aktl Radiation Sensitivity as well as Motility of Colorectal Tumor Cells
Hehlgans, S.; Petraki, C.; Cordes, N.; Oppermann, J.; Rodel, C.; Rodel, F.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 35-35
Registration No. 20647

Effect of EGF Receptor and beta 1-Integrin Inhibition on the Radiosensitivity three dimensions growing colorectal Cancer cells / Einfluss von EGF Rezeptor und β1-Integrin Hemmung auf die Strahlenempfindlichkeit dreidimensional wachsender kolorektaler Karzinomzellen
Poschau, M.; Zscheppang, K.; Cordes, N.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 44-44
Registration No. 20646

Pharmacological Inhibition of Focal Adhesion Kinase affects Cell Survival and Cell death but not Radiosensitivity of human Glioblastoma Cells / Pharmakologische Hemmung der Fokalen Adhäsionskinase beeinflusst Zellüberleben und Zelltod aber nicht Strahlenempfindlichkeit von humanen Glioblastomzellen
Sagerer, A.; Storch, K.; Cordes, N.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl. 1, 35-35
Registration No. 20645

Fractionated radiotherapy and cetuximab: EGFR amplification and histological markers as potential biomarkers / Fraktionierte Bestrahlung und Cetuximab: EGFR-Amplifikation und histologische Marker als potenzielle Biomarker
Gurtner, K.; Thurow, C.; Koi, L.; Yaromina, A.; Eicheler, W.; Baumann, M.; Krause, M.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 27-27
Registration No. 20644

Effects of a Combined Radio (chemo) therapy and HMG-CoA Reductase-Inhibition in Patients with Head-and-neck-Cancer / Effekte einer kombinierten Radio(chemo)therapie und HMG-CoAReduktase-Inhibition bei Patienten mit Kopf-Hals-Tumoren
Ebert, N.; Thiele, C.; Gurtner, K.; Dorr, W.; Lock, S.; Baumann, M.; Krause, M.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 144-144
Registration No. 20643

Influence of Chromatin Condensation on cellular Radiosensitivity in three dimensions growing human Tumor Cells / Einfluss der Chromatinkondensierung auf die zelluläre Strahlenempfindlichkeit dreidimensional wachsender humaner Tumorzellen
Storch, K.; Borgmann, K.; Eke, I.; Krause, M.; Becker, K.; Schrock, E.; Cordes, N.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 45-45
Registration No. 20642

Radiation sensitization of human squamous by alpha3 integrin Inhibition / Strahlensensibilisierung humaner Plattenepithelkarzinomzellen durch alpha3 Integrin Hemmung
Steglich, A.; Eke, I.; Vehlow, A.; Cordes, N.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 22-22
Registration No. 20641

The LIM only Protein FHL2 modulates the MAPK Signal Pathways and influences the Radiation Sensitivity of growing 3D Pancreatic Carcinoma Cells / Das LIM only Protein FHL2 moduliert MAPK Signalwege und beeinflusst die Strahlenempfindlichkeit von 3D wachsenden Pankreaskarzinomzellen
Zienert, E.; Eke, I.; Cordes, N.
Abstract: kein Abstract vorhanden
  • Abstract in refereed journal:
    Strahlentherapie und Onkologie 190(2014)Suppl 1, 14-15
Registration No. 20640

From a non-magnet to a ferromagnet: Mn implantation into different TiO2 structures
Yildirim, O.; Cornelius, S.; Butterling, M.; Anwand, W.; Wagner, A.; Smekhova, A.; Baehtz, C.; Potzger, K.
Abstract: As one of the most promising candidates for a diluted magnetic oxide material for spintronic and magneto optic applications, transition metal (TM) doped titanium dioxide (TiO2) has been extensively studied for last two decades. Up to date room temperature ferromagnetism (RTFM) has been reported for different types of TM dopants and also different types of preparation methods, such as ion implantation [1] or magnetron sputtering [2]. There is an ongoing debate on the origin of the ferromagnetic properties of TiO2, whether RTFM arises from unwanted clustering of the TM atoms, magnetic contamination from sample handling or the desired substitution of Ti by the TM dopants.
We have investigated Mn implanted TiO2 films with respect to the effect of the crystalline structure of the pristine film on the magnetic properties of the doped films. The films were prepared by DC magnetron sputtering using a high purity oxygen deficient ceramic TiO2-x target in Ar/O2 atmosphere. SrTiO3 (100) single crystals were used as substrates. In order to achieve different structures of TiO2, namely amorphous, polycrystalline anatase and epitaxial anatase, different substrate temperatures and post-growth annealing were applied. The as-prepared TiO2 samples have been implanted with Mn ions of 30 keV to 190 keV kinetic energy and variable fluence resulting in a homogenous Mn concentration of 5 at.% within a 150 nm thin layer below the film surface.
The structural changes upon implantation were followed by means of X-ray diffraction (XRD) measurements. Comparison of the diffraction patterns indicates ion-induced damage in the epitaxial film and the formation of Mn containing secondary phases in the polycrystalline material. Depth resolved defect concentration profiles of as-grown and Mn implanted films were determined by means positron annihilation spectroscopy (PAS) measurements based on Doppler broadening spectroscopy. Magnetometry measurements of Mn implanted films reveal ferromagnetism for amorphous and polycrystalline films whereas paramagnetism is observed for epitaxial films. The local environments of implanted Mn ions in different TiO2 structures were probed by X-ray absorption spectroscopy (XAS) in fluorescence mode.
In summary, we have found a significant influence of the as-grown film structure on the magnetic properties of Mn:TiO2. During the presentation the PAS and XAS data will be discussed with respect to the presence of defects and secondary phases in the Mn doped TiO2 films.
  • Lecture (Conference):
    Moscow International Symposium on Magnetism MISM-2014, 29.06.-03.07.2014, Moscow, Russia
Registration No. 20639

Angular dependent ferromagnetic resonance analysis in a single micron sized cobalt stripe
Schoeppner, C.; Wagner, K.; Stienen, S.; Meckenstock, R.; Farle, M.; Narkowicz, R.; Suter, D.; Lindner, J.
Abstract: We demonstrate how planar microresonators (PMRs) can be utilized to investigate the angular dependent magnetic resonance response of single magnetic nanostructures. In contrast to alternative detection schemes like electrical or optical detection, the PMR approach provides a classical means of investigating the high frequency dynamics of single magnetic entities, enabling the use of well-established analysis methods of ferromagnetic resonance (FMR) spectroscopy. To demonstrate the performance of the PMR-based FMR setup for angular dependent measurements, we investigate the microwave excited magnons in a single Co stripe of 5x1x0.02 µm^3 and compare the results to micromagnetic simulations. The evolution of excited magnons under rotation of one individual stripe with respect to a static magnetic field is investigated. Besides quasi uniform excitations, we observe magneto-static as well as localized excitations. We find a strong influence of inhomogeneous dynamic and static demagnetizing fields for all modes. Registration No. 20638

Efficiency determination of resistive plate chambers for fast quasi-monoenergetic neutrons
Röder, M.; Elekes, Z.; Aumann, T.; Bemmerer, D.; Boretzky, K.; Caesar, C.; Cowan, T. E.; Hehner, J.; Heil, M.; Kempe, M.; Maroussov, V.; Nusair, O.; Prokofiev, A. V.; Reifarth, R.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.; Zilges, A.; Zuber, K.; for the R3B collaboration
Abstract: Composite detectors made of stainless-steel converters and multigap resistive plate chambers have been irradiated with quasi-monoenergetic neutrons with a peak energy of 175 MeV. The neutron detection efficiency has been determined using two different methods. The data are in agreement with the output of Monte Carlo simulations. The simulations are then extended to study the response of a hypothetical array made of these detectors to energetic neutrons from a radioactive ion beam experiment. Registration No. 20637

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

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

Keywords: TOPFLOW-PTS experiments, direct contact condensation, CFD
  • Lecture (Conference):
    NURESAFE 1st Open Seminar, 16.-17.06.2014, Budapest, Hungary
Registration No. 20630

Ge(1-x)Sn(x) alloys synthesized by ion implantation and pulsed laser melting
Gao, K.; Prucnal, S.; Huebner, R.; Baehtz, C.; Skorupa, I.; Wang, Y.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: The tunable bandgap and the high carrier mobility of Ge(1-x)Sn(x) alloys stimulate a large effort for bandgap and strain engineering for Ge based materials using silicon compatible technology. In this letter we present the fabrication of highly mismatched Ge(1-x)Sn(x) alloys by ion implantation and pulsed laser melting with Sn concentration ranging from 0.5 at. % up to 1.5 at. %. According to the structural investigations, the formed Ge(1-x)Sn(x) alloys are monocrystalline with high Sn-incorporation rate. The shrinkage of the bandgap of Ge(1-x)Sn(x) alloys with increasing Sn content is proven by the red-shift of the E1 and E1+Δ1 critical points in spectroscopic ellipsometry. Our investigation provides a chip technology compatible route to prepare high quality monocrystalline Ge(1-x)Sn(x) alloys.
Keywords: Ge(1-x)Sn(x) alloys, ion implantation, pulsed laser melting Registration No. 20629

Uncertainties in the fluence determination in the surveillance samples of VVER-440
Konheiser, J.; Grahn, A.; Borodkin, P.; Borodkin, G.
Abstract: The reactor pressure vessel (RPV) represents one of the most important safety components in a nuclear power plant. Therefore, surveillance specimen (SS) programs for the RPV material exist to deliver a reliable assessment of RPV residual lifetime. This report will present neutron fluence calculations for SS. These calculations were carried out by the codes TRAMO and DORT [1, 2]. This study was accompanied by ex-vessel neutron dosimetry experiments at Kola NPP. The main neutron activation monitoring reactions were Fe-54(n,p)Mn-54 and Ni-58(n,p)Co-85. Good agreement was found between the deterministic and stochastic calculation results and between the calculations and the ex-vessel measurements. The different influences on the monitors were studied. In order to exclude the possible healing effects of the samples due to excessive temperatures, the heat release in the surveillance specimens was determined based on the calculated gamma fluences. Under comparatively realistic conditions, the heating was up to 6 K.
Keywords: VVER440, reactor pressure vessel, surveillance specimen, activation monitors, Fe-54(n,p)Mn-54, Ni-58(n,p)Co-85
  • Lecture (Conference):
    Fifteenth International Symposium on Reactor Dosimetry, 18.-23.05.2014, Aix-en-Provence, France
Registration No. 20627

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

Keywords: Rhenium; Technetium; 188Re; Diphosphinoamines; Peptide; Therapy Registration No. 20626

Scalable, interactive 3D in-situ visualization of large-scale Simulations
Pausch, R.; Schneider, B.; Hettmanczyk, D.; Burau, H.; Huebl, A.; Schmitt, F.; Widera, R.; Grottel, S.; Gumhold, S.; Bussmann, M.
Abstract: We present scalable, in-situ visualization of large-scale plasma simulations that allows for remote live visualization. We discuss the GPU rendering implementation, its interface to the simulation, scalable image composition on large clusters and the use of low-power visualisation clients attached to a server located at the HPC system. Such a setup challenges current HPC visualization paradigms and will potentially allow for explorative simulation surveys of large parameter spaces with strongly reduced storage footprint.
Keywords: in-situ visualization, PIConGPU, live visualization, GPU, HPC
  • Lecture (Conference):
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland
Registration No. 20624

Computing Angularly-resolved Far Field Emission Spectra in Particle-in-cell Codes using GPUs
Pausch, R.; Burau, H.; Bussmann, M.; Couperus, J.; Cowan, T.; Debus, A.; Huebl, A.; Irman, A.; KöHler, A.; Schramm, U.; Steiniger, K.; Widera, R.
Abstract: Angularly resolved far field radiation spectra computed from the Lienard Wiechert Potentials of accelerated electrons give information on the microscopic particle dynamics. We present recent results using our many-GPU, fully relativistic 3D3V particle-in-cell code PIConGPU for which we have developed fully synthetic radiation diagnostics that is capable of computing angularly-resolved radiation spectra of more than 10^10 electrons for several hundred to a thousand wavelengths and directions in a single simulation in less than a day on large-scale supercomputers. With such a technique it is possible to use precision spectroscopic methods for understanding the dynamics of electron acceleration in scenarios where other diagnostics fail. We present studies on laser-driven wakefield acceleration and astrophysical jet dynamics to underline the power of this new technique.
Keywords: far field radiation spectra, Lienard Wiechert potentials, PIConGPU, many-GPU, synthetic radiation diagnostics
  • Contribution to proceedings:
    5th International Particle Accelerator Conference (IPAC 2014), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, 978-3-95450-132-8, MOPRI069
Downloads:
PDF
Registration No. 20623

Charakterisierung von anisotropen Magnetowiderstandseffekten in Nanostrukturen aus Permalloy und Eisenaluminium
Warnatz, T.
Abstract: Magnetic field induced resistance effects are used in digital storage media - like hard- disk read heads [1]. To produce commercial devices it is of utmost importance to understand and tune the effect. The ion beam induced change of ferromagnetic or paramagnetic effects is known since 1986 [2,3]. However, most of the research was done on bulk material. Due to the increasing miniaturization of digital storage devices it is essential to investigate also the behavior in thin films. Taking into account that a commercial use of the devices is favored, it was focused on easy and reproducible sample geometries. The aim of this thesis was to produce, tune and character- ize magnetic field induced resistance changes in thin films of permalloy and iron-aluminum. Af- terwards, the results have been used to create well-defined nanostructures with potential giant magnetoresistance effects. It is shown, that magnetoresistance effects can be created (iron- aluminum) or reduced (permalloy) by ion beam irradiation. The measurements were performed by a self-programmed LabVIEW program with a precise four-terminal sensing setup at low tempera- tures and with a variable magnetic field up to 2.5 T. The variation of the angle between current flow and the magnetic field as well as measurements at different temperatures led to a very good understanding of the occurring phenomena.
Keywords: FeAl, anisotropic magnetoresistance
  • Thesis / Students' report:
    Westsächsische Hochschule Zwickau, 2013
Registration No. 20622

Herstellung und Charakterisierung eines Spinventils zur Untersuchung der Spindiffusionslänge von FeAl
Liersch, V.
Abstract: Spintronic devices hold great potential for future applilcations in information technology. In this work, the design and fabrication of a lateral spin valve for investigating the spin diffusion length of paramagnetic Fe60Al40 will be discussed. Samples were prepared by defining polycrystalline circuits using electron beam lithography, thin film deposition, and lift-off processing. The developed sample layout allows for both local and non-local measurement routines. Cobalt was employed as ferromagnetic polarizing material, while aluminium holds for reference measurements of the spin diffusion length. The determination of the so far unknown spin diffusion length of paramagnetic Fe60Al40 shall then be performed by detecting resistance changes at different temperatures and for different polarizer distances. Highly sensitive electric transport measurements were carried out in a so-called probe station, which allows for achieving very low temperatures via liquid He cooling. Additionally, paramagnetic ferromagnetic heterostructures were investigated with respect to possible giant magneto resistance effects.
Keywords: FeAl, spin valve, spin diffusion length
  • Thesis / Students' report:
    Westsächsische Hochschule Zwickau, 2014
Registration No. 20621

Transverse Emittance Compensation for the Rossendorf SRF GUN II
Vennekate, H.; Lu, P.; Arnold, A.; Murcek, P.; Teichert, J.; Xiang, R.; Kneisel, P.; Kamps, T.
Abstract: Superconducting RF particle sources combine the advantages of normal conducting RF sources and high duty cycle non-RF sources. The Rossendorf SRF gun was the first to demonstrate this injecting electrons into the ELBE accelerator at 13MHz. Recently, a new 3-1/2-gun cavity has been prepared at Jefferson Lab for its use in an updated injector which is expected to increase the electron energy from 2:4 to 7:5 MeV. Along with this new cavity, a new gun cryostat has been introduced. It combines several minor updates to the setup with the installation of a superconducting solenoid right at the exit of the gun, compensating the emittance growth of the electron bunch at an early stage. Hereby, the results of the commissioning of the new cryostat including the solenoid are concluded and compared to the prior concept of using a normal conducting solenoid outside the cryostat. As it is of great importance to this subject, studies of the magnetic shielding are going to be presented as well.
Keywords: SRF, superconducting radio frequency, injector, Rossendorf SRF Gun, ELBE, emittance
  • Contribution to proceedings:
    5th International Particle Accelerator Conference (IPAC'14), 15.-20.06.2014, Dresden, Deutschland
    Proceedings of IPAC2014, JACoW, 978-3-95450-132-8, TUPRI015
Downloads:
PDF
Registration No. 20620

Experimental evidence for nonaxisymmetric magnetorotational instability in a rotating liquid metal exposed to an azimuthal magnetic field
Seilmayer, M.; Galindo, V.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Gellert, M.; Rüdiger, G.; Schultz, M.; Hollerbach, R.
Abstract: The azimuthal version of the magnetorotational instability (MRI) is a nonaxisymmetric instability of a hydrodynamically stable differentially rotating flow under the influence of a purely or predominantly azimuthal magnetic field. It may be of considerable importance for destabilizing accretion disks, and plays a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers. Registration No. 20618

Magnetic fields in space: phenomena and related lab experiments
Stefani, F.
Abstract: The magnetic fields of cosmic bodies are generated by the homogeneous dynamo effect in moving electrically conducting fluids. Cosmic magnetic fields also play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. In 1999 the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf.
The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.
  • Invited lecture (Conferences):
    Space trips summer school on thermo-acoustic and space technologies, 17.-20.06.2014, Riga, Latvia
Registration No. 20617

The azimuthal MRI in experiment: confirmations and surprises
Stefani, F.
Abstract: The azimuthal magnetorotational instability (AMRI) may be of considerable importance for destabilizing accretion disks and plays also a central role in the concept of the MRI dynamo. We report the results of a liquid metal Taylor-Couette experiment that shows the occurrence of an azimuthal MRI in the expected range of Hartmann numbers. We also discuss some peculiarities of the experimental results which are connected with the slight symmetry breaking of the applied magnetic field.
  • Invited lecture (Conferences):
    General Meeting of the Max Planck/Princeton Center for Plasma Physics, 28.06.-01.07.2014, Berlin, Germany
Registration No. 20616

Simulation of the ELBE SRF Gun II
Lu, P.; Arnold, A.; Lehnert, U.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.
Abstract: By combining the code of ASTRA and elegant in a user-friendly interface, a simulation tool is developed for the ELBE SRF Gun II. The photoelectric emission and first acceleration to several MeV in the gun cavity are simulated by ASTRA with a 1D Model, where the space charge effect is considered. The dependence of the beam quality on key parameters is studied, and a compromised optimization for a 77 pC beam is used for further elegant simulation of the beam transport through a dogleg and ELBE Linacs. Proper settings of the magnets and RF phases are the main targets of improving the beam quality. Up to now the best simulation result is an electron bunch with the energy of 47 MeV, energy spread of 66 keV, bunch length of 0.35 ps and transverse emittance of 1.9 μm and 2.7 μm in the two perpendicular directions.
  • Contribution to proceedings:
    IPAC2014 - 5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC2014, MOPRI023
Registration No. 20615

Dynamo action and related magnetic instabilities in the liquid metal lab
Stefani, F.
Abstract: Magnetic fields of cosmic bodies are generated by the hydromagnetic dynamo effect in moving electrically conducting fluids, such as liquid metals or plasmas. Once produced, cosmic magnetic fields are able to act back on moving fluids. This back-reaction may have dramatic consequences for cosmic structure formation, with the magnetorotational instability (MRI) in accretions disks as the most prominent example. Considerable theoretical and computational progress has been made in understanding both the dynamo effect as well as magnetically triggered flow instabilities. Complementary to this, the last fifteen years have seen much effort in studying both effects in liquid metal experiments.
In the talk, we summarize the history of these experiments, discuss their main results and their limitations, and give an outlook on future activities. As for dynamo action, we focus on the Riga, Karlsruhe and Cadarache experiments, and discuss the present status of a large-scale precession-driven dynamo experiment to be set-up in the framework of the DRESDYN project. As for magnetically triggered instabilities, we review the recent experiments on the helical and azimuthal versions of the MRI, as well as on the current-driven Tayler instability (TI). After discussing the astrophysical relevance of those basically induction-less instabilities, we motivate the set-up of a large-scale liquid sodium experiment for studying the continuous transition to the standard version of MRI.
  • Invited lecture (Conferences):
    EUROMECH Colloquium 561: Dimensionality of Turbulence, 19.-21.05.2014, Coventry, United Kingdom
Registration No. 20614

Liquid metal experiments on dynamo action and related magnetic instabilities
Stefani, F.
Abstract: The magnetic fields of planets, stars and galaxies are generated by self-excitation in moving electrically conducting fluids. Once produced, cosmic magnetic fields can play an active role in cosmic structure formation by destabilizing rotational flows that would be otherwise hydrodynamically stable. For a long time, both effects, i.e. hydromagnetic dynamo action and the magnetorotational instability, have been the subject of purely theoretical investigations. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the Cadarache dynamo experiment has successfully reproduced many features of geophysical interest such as reversals and excursions. In the same year, the helical version of the magnetorotational instability was observed in the PROMISE facility in Dresden-Rossendorf. The lecture gives an overview about liquid metal experiments on dynamo action and magnetically triggered instabilities, it asks for the lessons they have taught us about real cosmic dynamos and accretion disks, and it concludes with an overview about future experiments, including a precession driven dynamo and a large-scale Tayler-Couette experiment to be set-up in the framework of the DRESDYN project.
  • Invited lecture (Conferences):
    LSTM Fluid Mechanics Seminar, 07.02.2014, Erlangen, Germany
Registration No. 20613

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

Keywords: ODS ferritic alloys, DFT, Monte Carlo simulation
  • Lecture (Conference):
    2nd International Workshop on ODS Materials, 26.-27.06.2014, Dresden, Germany
Registration No. 20612

Liquid phase epitaxy of Ge(1-x)Sn(x) alloy using ion-implantation and pulsed laser melting
Gao, K.; Prucnal, S.; Huebner, R.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Group IV semiconductor alloys have drawn substantial attention for their potential applications in optoelectronic devices capable of integration with the existing Si IC circuitry. Single crystalline Ge1-xSnx alloys are promising for electronic and optical applications in virtue of their high carrier mobility. In this contribution we present the fabrication of Ge1-xSnx by ion-implantation and pulsed laser melting (PLM). Sn was implanted into commercial Ge wafers to form 0.2 µm thick layers with different atomic concentrations from 0.5 % 3.0 %. The as-implanted Ge layer becomes amorphous due to the bombardment of Sn ions with high kinetic energy. The regrowth of the Ge1-xSnx layer after PLM and the lattice expansion were confirmed by X-ray diffraction and micro-Raman spectroscopy. Field emission scanning electron microscopy was applied to determine the surface morphology. High resolution transmission electron microscopy and Rutherford backscattering and channeling analysis confirmed the monocrystalline structure of the Ge1-xSnx layer. Our investigation provides an efficient technique to prepare high quality monocrystalline Ge1-xSnx alloys.
Keywords: GeSn, ion implantation, pulsed laser melting
  • Lecture (Conference):
    E-MRS 2014 SPRING MEETING, 26.05.-01.08.2014, Lille, France
Registration No. 20610

Photoluminescence from GaAs(1-x)N(x) dilute nitride achieved by nitrogen-implantation and flash lamp annealing
Gao, K.; Prucnal, S.; Huebner, R.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Nitrogen atoms are isoelectronic substituents for arsenic in GaAs. A small amount of nitrogen doping can lead to a pronounced bandgap reduction. Therefore nitrogen-doping can be applied as a powerful technique to modify GaAs based materials for long wavelength optoelectronic devices. In this contribution we present the fabrication of dilute nitride material GaAs1-xNx by nitrogen-implantation and flash lamp annealing (FLA). N was implanted in to the commercial GaAs wafer to form a 0.2 ?m thick layer with atomic concentration of about 0.76 % and 0.38 %. The as-implanted GaAs layer becomes amorphous due to the bombardment of nitrogen ions with high kinetic energy. The GaAs1-xNx layer with compressive strain is epitaxially regrown on GaAs during FLA treatment as confirmed by X-ray diffraction and micro-Raman spectroscopy. In the meantime the bandgap shrinkage is proven by photoluminescence spectroscopy. Based on the redshift of the GaAs1-xNx near band-edge emission, up to 60 % of the implanted N atoms are successfully incorporated into the lattice after FLA. According to our investigation, ion-implantation followed by ultrashort flash lamp treatment, which is quite efficient and low-cost, exhibits a promising prospect on bandgap engineering of GaAs based semiconductors.
Keywords: GaAsN, ion implantation, flash lamp annealing
  • Poster:
    E-MRS 2014 SPRING MEETING, 26.05.-01.08.2014, Lille, France
Registration No. 20609

Formation and photoluminescence of GaAs(1-x)N(x) dilute nitride achieved by N-implantation and flash lamp annealing
Gao, K.; Prucnal, S.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: In this paper we present the fabrication of dilute nitride semiconductor GaAs(1-x)N(x) by nitrogen-ion-implantation and flash lamp annealing (FLA). N was implanted into the GaAs wafers with atomic concentration of about ximp1=0.38% and ximp2=0.76%. The GaAs1-xNx layer is regrown on GaAs during FLA treatment in a solid phase epitaxy process. Room temperature near band-edge photoluminescence (PL) has been observed from the FLA treated GaAs(1-x)N(x) samples. According to the redshift of the near band-edge PL peak, up to 80% and 44% of the implanted N atoms have been incorporated into the lattice by FLA for ximp1=0.38% and ximp2=0.76%, respectively. Our investigation shows that ion implantation followed by ultrashort flash lamp treatment, which allows for large scale production, exhibits a promising prospect on bandgap engineering of GaAs based semiconductors.
Keywords: GaAs(1-x)N(x), ion implantation, flash lamp annealing, photoluminescence Registration No. 20607

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

Keywords: nanoscale transport, molecular electronics, charge transport, density-functional theory, functional oxides, nanocomposite materials
  • Lecture (others):
    Abengoa Research Seminar, 20.05.2014, Sevilla, Spanien
Registration No. 20604

Kleinste Strukturen ganz groß – Forschung mit Großgeräten
Gemming, S.
Abstract: allg. Vorstellung der Forschungsanagen am HZDR
Keywords: -
  • Lecture (others):
    Seniorenkolleg der TU Chemnitz, 27.05.2014, Chemnitz, Deutschland
Registration No. 20603

Selbstorganisation – Wie kommt das Muster auf die Oberfläche?
Gemming, S.
Abstract: Muster auf Oberflächen können sich durch eine Vielzahl verschiedener Mechanismen ausbilden. Regelmäßige mikro- und nanoskalige Muster für mobile elektronische Geräte lassen sich zum Beispiel nach vorgegebenen Vorlagen durch aktive top-down Strukturierungsverfahren wie Lithographie oder Drucken erzeugen.

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

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

Keywords: Musterbildung, crystal structure, space groups, frieze groupd, rod groups
  • Invited lecture (Conferences):
    Workshop Nanostrukturbildung, 15.04.2013, Dresden, Deutschland
  • Lecture (others):
    Physikalisches Kolloquium, 17.04.2013, Chemnitz, Deutschland
Registration No. 20602

Strontium titanate: An all-in-one rechargeable energy storage material
Hanzig, J.; Zschornak, M.; Nentwich, M.; Hanzig, F.; Gemming, S.; Leisegang, T.; Meyer, D. C.
Abstract: Redistribution of oxygen vacancies in a strontium titanate single crystal is caused by an external electric field. We present electrical measurements during and directly after electroformation, showing that intrinsic defect separation establishes a non-equilibrium state in the transition metal oxide accompanied by an electromotive force. A comprehensive thermodynamic deduction in terms of theoretical energy and entropy calculations indicate an exergonic electrochemical reaction after the electric field is switched off. Based on that driving force the experimental and theoretical proof of concept of an all-in-one rechargeable SrTiO3 single crystal energy storage is reported here.
Keywords: Solid state energy storage; Transition metal oxides; Defects; Density functional theory Registration No. 20601

Investigation of contaminated soil
Richter, C.; Fahmy, K.
Abstract: Investigation of microbial growth in natural minerals using the TAM Air 3 channel calorimeter.
  • Lecture (Conference):
    ISBC Meeting, Lund 2014, 03.06.2014, Lund, Schweden
Registration No. 20599

Single-crystalline Ga- and In- based compound semiconductor nanocrystals in Si by ion implantation and short time flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Bregolin, F.; Hübner, R.; Helm, M.; Skorupa, W.
Abstract: The integration of III-V compound semiconductors into silicon is a substantial research field for the progress of micro- and optoelectronic device technology. We fabricated various III-V compound semiconductor nanocrystals (NCs) in Si and SOI substrates by sequential high fluence ion beam implantation and ultra-short flash lamp annealing (FLA). Single-crystalline GaAs, GaP, GaSb, InAs, InP and InSb NCs were grown by liquid phase epitaxy during FLA. Additionally, precise positioning of NCs was achieved by using a lithographically patterned aluminum mask layer for ion implantation.

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

Keywords: Ion Implantation, Flash Lamp Annealing, III-V Integration, SOI
  • Lecture (Conference):
    X-th International Conference Ion Implantation and other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland
Registration No. 20598

Imaging of α7 nicotinic acetylcholine receptors in brain and cerebral vasculature of juvenile pigs with [18F]NS14490
Rötering, S.; Deuther-Conrad, W.; Cumming, P.; Donat, C. K.; Scheunemann, M.; Fischer, S.; Xiong, G.; Steinbach, J.; Peters, D.; Sabri, O.; Bucerius, J.; Brust, P.
Abstract: Background: The α7 nicotinic acetylcholine receptor (nAChR) is an important molecular target in neuropsychiatry and oncology. Development of applicable highly-specific radiotracers has been challenging due to comparably low protein expression. To identify novel ligands as candidates for positron emission tomography (PET), a library of diazabicyclononane compounds was screened regarding affinity and specificity towards α7 nAChRs. From these, [18F]NS14490 has been shown to yield reliable results in organ distribution studies; however, dynamic PET investigations required the establishment of an automated radiosynthesis.

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

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

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

Keywords: Alpha7 nicotinic acetylcholine receptors; Alzheimer´s disease; Blood-brain barrier; Cancer; Diazabicyclononane; Metabolism; PET; Stroke Registration No. 20594

Recent improvement of Cs2Te photocathodes at HZDR
Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.
Abstract: The ELBE SRF gun has been successfully operated for the radiation source at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. Meanwhile, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are produced for an accurate deposition rate. Furthermore, the cathode transfer system is improved for a better vacuum condition.
Keywords: SRF gun, high current, low beam emittance, Cs2Te photocathode
  • Contribution to proceedings:
    5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany
    Proceedings of IPAC'14, MOPRI025
  • Poster:
    the 5th International Particle Accelerator Conference (IPAC’14), 15.-20.06.2014, Dresden, Germany
Registration No. 20593
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