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39294 Publications

Green up-conversion of swift C5+ ion irradiated planar waveguide in Er3+, MgO codoped nearly stoichiometric LiNbO3 crystal

Liu, H.; Jia, Y.; Ren, Y.; Akhmadaliev, S.; Zhou, S.; Chen, F.

We report on the green up-conversion emission from Er3+, MgO codoped nearly stoichiometric LiNbO3 planar waveguides fabricated by the swift C5+ ion irradiation. The characteristics of the waveguides are investigated by using a continuous wave laser at wavelength of 800 nm. The reconstructed distribution of the refractive index of the C ion irradiated waveguides shows a “barrier and well” profile. The up-conversion emissions of green light, corresponding to the transition of 4H11/2→4I15/2 and 4S3/2→4I15/2 bands, have been observed in the waveguides with intensity of 40% of that from the bulk.

Keywords: Optical waveguides; Swift heavy ion irradiation; Green up-conversion emission; LiNbO3 crystal

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Publ.-Id: 19623

Channel waveguide lasers at 1064  nm in Nd:YAG crystal produced by C5+ ion irradiation with shadow masking

Yao, Y.; Jia, Y.; Chen, F.; Akhmadaliev, S.; Zhou, S.

We report on the fabrication of channel waveguides in Nd:YAG crystals, using swift C5+ ion irradiation with ion energy of 15 MeV and fluence at 5×10^15  ions/cm2. A laser-cut shadow mask of a number of open stripes with varied width was covered on the sample surface during the ion irradiation. Channel waveguides were formed in the Nd:YAG crystal due to the refractive index increase along the ion trajectory. Room temperature waveguide laser oscillations at 1064 nm have been observed under 808 nm optical pumping, with laser slope efficiency at 38% and a maximum output power of 36 mW.

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Publ.-Id: 19622

Is silicide formation the decisive factor in impurity induced ion beam pattern formation?

Engler, M.; Müller, S.; Will, M.; Frost, F.; Feder, R.; Spemann, D.; Hübner, R.; Facsko, S.; Michely, T.

Recent experiments showed that metal deposition during ion beam erosion causes the pattern formation at low incidence angles.
We performed 2 keV Kr+ ion beam erosion of Si(001) experiments using a scanned fine focus ion source with simultaneous deposition of metal atoms. After ion beam erosion we analyzed our samples in-situ with scanning tunneling microscopy and ex-situ with atomic force microscopy and transmission electron microscopy. The metal concentration on the Si surface was analyzed ex-situ with Rutherford backscattering spectrometry.
To distinguish the effects of collision kinetics versus chemical interaction in metal co-deposition induced pattern formation on Si(001) we conducted Ag and Pd sputter co-deposition from a target mounted on the Si sample. This setup results in a flux and concentration gradient of the co-deposited metals on the Si sample. While for Pd a concentration dependent ripple pattern is observed, no pattern evolves for Ag co-deposition under ultra high vaccum conditions. Since Ag and Pd possess nearly the same nuclear charge and atomic mass, their different ability to form a pattern must be attributed to their different ability to form silicides. While Pd forms a variety of silicides, Ag forms none. Silicide formation of the co-deposited metal appears thus to be a necessary condition to induce a pattern on Si during ion exposure.

Related publications

  • Lecture (Conference)
    Nanocale Pattern Formation at Surfaces, 26.-30.05.2013, Copenhagen, Denmark

Publ.-Id: 19621

Enhanced growth and Cu diffusion barrier properties of thermal ALD TaNC films in Cu/low-k interconnects

Wojcik, H.; Hossbach, C.; Kubasch, C.; Verdonck, P.; Barbarin, Y.; Merkel, U.; Bartha, J. W.; Hübner, R.; Engelmann, H.-J.; Friedemann, M.

For thermal ALD TaxNyCz films improved growth behaviour and Cu diffusion barrier performance are demonstrated by applying a plasma treatment prior to film deposition, in particular on low-k dielectrics. Two different kinds of ALD processes for depositing thermal ALD TaxNyCz films are applied in this study, involving either TBTDET or PDMAT as a precursor. Ammonia is used as a reactant and Ar as a purging gas in both processes. Within the experiment, two types of pre-treatments prior to ALD are investigated: a wet-chemical pre-treatment using diluted (0.5%) HF, and plasma pre-treatments using Ar/H2 or N2 plasmas. It is examined by transmission electron microscopy (TEM) from a microstuctural perspective whether improved growth behaviour of thermal ALD TaxNyCz films can be achieved by applying a plasma treatment prior to film deposition. The Cu diffusion barrier properties of 10-15 nm ALD TaNC films are then evaluated by bias temperature stress (BTS) and triangular voltage sweep (TVS) measurements on metal-insulator-semiconductor (MIS) test structures, after annealing at up to 600 °C under H2/N2 atmosphere. The results imply that, from a process side, thermal ALD TaNC films can intrinsically achieve a Cu diffusion barrier performance similar to PVD TaN. However, if no treatment was applied, Cu drift occurred.

Keywords: ALD TaN; Cu diffusion barrier; Triangular voltage sweep; Plasma treatment; Low-k

Publ.-Id: 19620

The giant Shakhdara migmatitic gneiss dome, Pamir, India–Asia collision zone, II:Timing of dome formation, Tectonics

Stübner, K.; Ratschbacher, L.; Weise, C.; Chow, J.; Hofmann, J.; Khan, J.; Rutte, D.; Sperner, B.; Pfänder, J. A.; Hacker, B. R.; Dunkl, I.; Tichomirowa, M.; Stearns, M. A.; Bahram, I.; Gadoev, M.; Gloaguen, R.; Jonckheere, R.; Kanaev, E.; Minaev, V.; Oimahmadoc, I.; Rajabov, N.; Stanek, K. P.

Cenozoic gneiss domes—exposing middle-lower crustal rocks—cover ~30% of the surface exposure of the Pamir, western India-Asia collision zone; they allow an unparalleled view into the deep crust of the Asian plate. We use titanite, monazite, and zircon U/Th-Pb, mica Rb-Sr and 40Ar/39Ar, zircon and apatite fission track, and zircon (U-Th)/He ages to constrain the exhumation history of the ~350 × 90 km Shakhdara-Alichur dome, southwestern Pamir. Doming started at 21–20 Ma along the Gunt top-to-N normal-shear zone of the northern Shakhdara dome. The bulk of the exhumation occurred by ~NNW-ward extrusion of the footwall of the crustal-scale South Pamir normal-shear zone along the southern Shakhdara dome boundary. Footwall extrusion was active from ~18–15 Ma to ~2 Ma at ~10 mm/yr slip and with vertical exhumation rates of 1–3 mm/yr; it resulted in up to 90 km ~N-S extension, coeval with ~N-S convergence between India and Asia. Erosion rates were 0.3–0.5 mm/yr within the domes and 0.1–0.3 mm/yr in the horst separating the Shakhdara and Alichur domes and in the southeastern Pamir plateau; rates were highest along the dome axis in the southern part of the Shakhdara dome. Incision along the major drainages was up to 1.0 mm/yr. Thermal modeling suggests geothermal gradients as high as 60°C/km along the trace of the South Pamir shear zone and their strong N-S variation across the dome; the gradients relaxed to ≤40–45°C/km since the end of doming.

Keywords: Pamir; gneiss dome; synorogenic extension; low-angle detachment

Publ.-Id: 19619

The giant Shakhdara migmatitic gneiss dome, Pamir, India–Asia collision zone, I: Geometry and kinematics

Stübner, K.; Ratschbacher, L.; Rutte, D.; Stanek, K.; Minaev, V.; Wiesinger, M.; Gloaguen, R.; Bahram, I.; Gadoev, M.; Gordon, S. M.; Hacker, B. R.; Hofmann, J.; Kanaev, E.; Oimahmadoc, I.; Rajabov, N.

Cenozoic gneiss domes comprise one third of the surface exposure of the Pamir and provide a window into the deep crustal processes of the India-Asia collision. The largest of these are the doubly vergent, composite Shakhdara-Alichur domes of the southwestern Pamir, Tajikistan, and Afghanistan; they are separated by a low-strain horst. Top-to-SSE, noncoaxial pervasive flow over the up to 4 km thick South Pamir shear zone exhumed crust from 30–40 km depth in the ~250 × 80 km Shakhdara dome; the top-to-NNE Alichur shear zone exposed upper crustal rocks in the ~125 × 25 km Alichur dome. The Gunt shear zone bounds the Shakhdara dome in the north and records alternations of normal shear and dextral transpression; it contributed little to bulk exhumation. Footwall exhumation along two low-angle, normal-sense detachments resulted in up to 90 km syn-orogenic ~N-S extension. Extension in the southwestern Pamir opposes shortening in a fold-thrust belt north of the domes and in particular in the Tajik depression, where an evaporitic décollement facilitated upper crustal shortening. Gravitational collapse of the Pamir-plateau margin drove core-complex formation in the southwestern Pamir and shortening of the weak foreland adjacent to the plateau. Overall, this geometry defines a “vertical extrusion” scenario, comprising frontal and basal underthrusting and thickening, and hanging gravitationally driven normal shear. In contrast to the Himalayan vertical extrusion scenario, erosion in the Pamir was minor, preserving most of the extruded deep crust, including the top of the South Pamir shear zone at peak elevations throughout the dome.

Keywords: Pamir; gneiss dome; synorogenic extension; low-angle detachment

Publ.-Id: 19618

Remote Sensing Analysis of Lake Dynamics in Semi-Arid Regions: Implication for Water Resource Management. Lake Manyara, East African Rift, Northern Tanzania

Deus, D.; Gloaguen, R.

We show here that a remote sensing (RS) approach is a cost-efficient and accurate method to study water resource dynamics in semi-arid areas. We use a MODIS surface reflectance dataset and a Modified Normalized Difference Water Index (MNDWI) to map the variability of Lake Manyara’s water surface area using a histogram segmentation technique. The results indicate that Lake Manyara’s water surface coverage has been decreasing from 520.25 km2 to 30.5 km2 in 2000 and 2011 respectively. We observe that the lake water surface and the lake water balance displayed a similar pattern from 2006 to 2009, probably initiated by heavy rainfall and low temperature in 2006. Lake water surface area appears to have an inverse relationship with MODIS evapotranspiration (ET) and MODIS land surface temperature (LST). We imply that recent fluctuations of Lake Manyara’s surface water area are a direct consequence of global and regional climate fluctuations. We therefore conclude that, by means of RS it is possible to provide timely and up-to-date water resource information to managers and hence enable optimized and operational decisions for sustainable management and conservation. We suggest that the method employed in this research should be applied to monitor water resource dynamics provided that remotely sensed datasets are available.

Keywords: water resource management; lake dynamics; climate variability; lake extraction; water index; remote sensing

Publ.-Id: 19617

Tectonic and Climatic Forcing on the Panj River System During the Quaternary

Fuchs, M.; Gloaguen, R.; Pohl, E.

Surface processes involve complex feedback effects between tectonic and climatic influences in the high mountains of Pamir. The ongoing India–Asia collision provokes the development of east–west-trending mountain ranges that impose structural control on flow directions of the Pamir rivers. The evolving relief is further controlled by strong moisture gradients. The decreasing precipitations from the southern and western margins of the Pamir Plateau to its center, in their turn, control the emplacement of glaciers. Chronologies of glacial records from the Pamir Plateau attest for strong climatic variability during the Quaternary. Corresponding remnants of glacial advances suggest glacial morphodynamic restricted to 4,000 m a.s.l. since marine isotope stage 4. The Panj, the trunk river of Pamir, deflects from the predominant westward drainage, connecting its main tributaries at the western margin of the drainage basin. The geometry of the river network and the pattern of incision characterize the Panj as a composite river. River reaches of indicated low incision coincide with west-trending valleys, parallel to domes and their bounding faults. Valley shape ratios reflect increased incision in north-trending sections, but do not match with changes in the catchment geometry or erodibility of rock types. Modelled riverbed profiles distinguish three Panj reaches. The upstream increase in convexity suggests successive river captures in response to local base-level changes. The northward-deflected river reaches link the local base levels, which coincide with the southern boundaries of the Shakhdara and Yazgulom Dome and Darvaz Range. We argue that tectonics plays a large role controlling the drainage system of the Panj and hence surface processes in the Pamir mountains.

Keywords: Pamir; Panj river network; Tectonic; geomorphology; Glacial chronology; Fluvial incision; River profiles

Publ.-Id: 19616

Automatic Extraction and Size Distribution of Landslides in Kurdistan Region, NE Iraq.

Othman, A. A.; Gloaguen, R.

This study aims to assess the localization and size distribution of landslides using automatic remote sensing techniques in (semi-) arid, non-vegetated, mountainous environments. The study area is located in the Kurdistan region (NE Iraq), within the Zagros orogenic belt, which is characterized by the High Folded Zone (HFZ), the Imbricated Zone and the Zagros Suture Zone (ZSZ). The available reference inventory includes 3,190 landslides mapped from sixty QuickBird scenes using manual delineation. The landslide types involve rock falls, translational slides and slumps, which occurred in different lithological units. Two hundred and ninety of these landslides lie within the ZSZ, representing a cumulated surface of 32 km2. The HFZ implicates 2,900 landslides with an overall coverage of about 26 km2. We first analyzed cumulative landslide number-size distributions using the inventory map. We then proposed a very simple and robust algorithm for automatic landslide extraction using specific band ratios selected upon the spectral signatures of bare surfaces as well as posteriori slope and the normalized difference vegetation index (NDVI) thresholds. The index is based on the contrast between landslides and their background, whereas the landslides have high reflections in the green and red bands. We applied the slope threshold map to remove low slope areas, which have high reflectance in red and green bands. The algorithm was able to detect ~96% of the recent landslides known from the reference inventory on a test site. The cumulative landslide number-size distribution of automatically extracted landslide is very similar to the one based on visual mapping. The automatic extraction is therefore adapted for the quantitative analysis of landslides and thus can contribute to the assessment of hazards in similar regions.

Keywords: brightness Indicator; landslide; automatic extraction; landslide index; remote sensing; GIS; number-size distribution; Zagros

Publ.-Id: 19615

Water Balance Modeling in a Semi-Arid Environment with Limited in situ Data Using Remote Sensing in Lake Manyara, East African Rift, Tanzania.

Deus, D.; Gloaguen, R.; Krause, P.

The purpose of this paper is to estimate the water balance in a semi-arid environment with limited in situ data using a remote sensing approach. We focus on the Lake Manyara catchment, located within the East African Rift of northern Tanzania. We use a distributed conceptual hydrological model driven by remote sensing data to study the spatial and temporal variability of water balance parameters within the catchment. Satellite gravimetry GRACE data is used to verify the trends of the inferred lake level changes. The results show that the lake undergoes high spatial and temporal variations, characteristic of a semi-arid climate with high evaporation and low rainfall. We observe that the Lake Manyara water balance and GRACE equivalent water depth show comparable trends; a decrease after 2002 followed by a sharp increase in 2006–2007. Our modeling confirms the importance of the 2006–2007 Indian Ocean Dipole fluctuation in replenishing the groundwater reservoirs of East Africa. We thus demonstrate that water balance modeling can be performed successfully using remote sensing data even in complex climatic settings. Despite the small size of Lake Manyara, GRACE data showed great potential for hydrological research on smaller un-gauged lakes and catchments in similar semi-arid environments worldwide. The water balance information can be used for further analysis of lake variations in relation to soil erosion, climate and land cover/land use change as well as different lake management and conservation scenarios.

Keywords: semi-arid; water balance; remote sensing; rainfall; evapotranspiration; runoff; GRACE

Publ.-Id: 19614

River Courses Affected by Landslides and Implications for Hazard Assessment: A High Resolution Remote Sensing Case Study in NE Iraq–W Iran

Othman, A. A.; Gloaguen, R.

The objective of this study is to understand the effect of landslides on the drainage network within the area of interest. We thus test the potential of rivers to record the intensity of landslides that affected their courses. The study area is located within the Zagros orogenic belt along the border between Iraq and Iran. We identified 280 landslides through nine QuickBird scenes using visual photo-interpretation. The total landslide area of 40.05 km2 and their distribution follows a NW–SE trend due to the tectonic control of main thrust faults. We observe a strong control of the landslides on the river course. We quantify the relationship between riverbed displacement and mass wasting occurrences using landslide sizes versus river offset and hypsometric integrals. Many valleys and river channels are curved around the toe of landslides, thus producing an offset of the stream which increases with the landslide area. The river offsets were quantified using two geomorphic indices: the river with respect to the basin midline (Fb); and the offset from the main river direction (Fd). Hypsometry and stream offset seem to be correlated. In addition; the analysis of selected river courses may give some information on the sizes of the past landslide events and therefore contribute to the hazard assessment.

Keywords: landslides; river offset; hypsometry; remote sensing; GIS; Zagros

Publ.-Id: 19613

Geothermal activities in the Main Ethiopian Rift: Hydrogeochemical characterization of geothermal waters and geothermometry applications

Pürschel, M.; Gloaguen, R.; Stadler, S.

Ethiopia holds an enormous capacity to generate geothermal energy in the volcano-tectonically active zones of the East African Rift System. In this study, we investigate the potential of three geothermal prospect areas in the Main Ethiopian Rift (Dofan-Fantale, Gergede-Sodere, Aluto-Langano). We examine existing and new data from a water sampling campaign, both of which are evaluated in terms of geochemistry and applicability for the estimation of geothermal subsurface temperatures. Several solute geothermometers, Cl–SO4–HCO3 and Na–K–Mg ternary diagrams as well as silica-enthalpy and chloride-enthalpy mixing models were applied to the prevailing alkaline and Na–HCO3 or Na–Cl–HCO3 dominated waters. Mixing was most pronounced in the individual subregions of Dofan-Fantale and Gergede-Sodere, yet these areas still indicate high heat-generating capabilities. The applied enthalpy-chloride mixing model suggests a subsurface temperature of 190 ± 20 °C for these hot springs. This temperature estimate is in good agreement with those obtained from the Na–K and Na–K–Ca geothermometers (185 ± 20 °C) for both geothermal areas. Additionally, for Gergede-Sodere it agreed well with the silica-enthalpy mixing model hot spring water results with the assumption that steam loss occurs before mixing (170 ± 20 °C). Furthermore, the enthalpy-chloride mixing model refers to reservoir temperatures between 300 °C and 370 °C for the Aluto-Langano geothermal fluids, which are in the same magnitude than the ones obtained by the silica-enthalpy mixing model for hot springs, if no steam loss occurs before mixing (270 ± 30 °C). In addition, they are comparable with few known data collected in drilled wells in the Aluto-Langano geothermal field (231–282 °C for LA-4 and LA-8 as well as 315–363 °C for LA-3 and LA-6).

Keywords: Subsurface temperatures; Groundwater; Thermal waters; Geothermometry; Geothermal energy; Ethiopia

Publ.-Id: 19612

Environmental change detection in the central part of Iraq using remote sensing data and GIS

Othman, A. A.; Al-Saady, Y. I.; Al-Khafaji, A. K.; Gloaguen, R.

This study aims to assess the potential of sev-eral ancillary input data for the improvement of unsuper-vised land cover change detection in arid environments. The study area is located in Central Iraq where deserti-fication has been observed. We develop a new scheme based on known robust indices. We employ Landsat (multispectral scanner, thematic mapper, and enhanced thematic mapper) satellite data acquired in 1976, 1990, and 2002. We use the Normalized Deferential Vegetation Index, Normalized Differential Water Index (NDWI), Salinity Index (SI), and Eolian Mapping Index. Two new equations were applied for the SI and the NDWI indices. Validation was performed using ground truth data collected in 16 days. We show that such an ap-proach allows a robust and low-cost alternative for pre-liminary and large-scale assessments. This study shows that desertification has increased in the study area since 1990.

Keywords: Remote sensing; changes detection; NDVI; NDWI; SI; EMI; MSS; TM; ETM; Land cover; Iraq

Publ.-Id: 19611

Influence of rigid coregistration of PET and CT data on metabolic volumetry: a user's perspective

Steffen, I. G.; Hofheinz, F.; Rogasch, J. M. M.; Furth, C.; Amthauer, H.; Ruf, J.

While non-rigid fusion is by definition expected to alter the information of positron emission tomography (PET) data, we assessed whether rigid transformation also influences metabolic tumor volume (MTV) determination.

The PET/computed tomography (CT) data of 28 solid pulmonary lesions of 20 tumor patients examined with 18 F-Fluordeoxyglucose (FDG) was retrospectively analyzed. The original (OR) hardware-coregistered PET images were fused with contrast-enhanced diagnostic CT (CT1, 1 mm slices) and low dose CT (CT5, 5 mm slices). After automatic rigid transformation (Mirada Fusion7D) using two algorithms (rigid fast (RF), rigid slow (RS)), MTV and maximal standardized uptake value (SUVmax) were determined applying four different segmentation methods with either fixed or background-adapted thresholding and compared to OR-PET data.

Relative differences in SUVmax compared to OR data revealed no significant differences for RF (median, -0.1%; interquartile range (IQR), -1.1% to 0.9%; p = 0.75) and RS (median, 0.5%; IQR, -0.6% to 1.3%; p = 0.19) in CT1, whereas in CT5 significant deviations were observed for RF (median, -9.0%; IQR, -10.9 to -6.1; p < 0.001) and RS (median, -8.4%; IQR, -11.1 to -5.6; p < 0.001). Relative MTV differences were 0.7% (IQR, -3.0% to 2.7%; p = 0.76) for RF and -1.3% (IQR, -3.6% to 0.9%; p = 0.12) for RS in CT1. Coregistration led to significant MTV differences in RF (median, 10.4%; IQR, 7.4% to 16.7%; p < 0.001) and RS (median, 10.6%; IQR, 5.4% to 17.7%; p < 0.001) in CT5.

Rigid coregistration of PET data allows a quantitative evaluation with reasonable accuracy in most cases. However, in some cases, it can result in substantial deviations of MTV and SUVmax. Therefore, it is recommended to perform quantitative evaluation in the original PET data rather than in coregistered PET data.

Publ.-Id: 19610

Evaluating SAR polarization modes at L-band for forest classification purposes in Eastern Amazon, Brazil

Liesenberg, V.; Gloaguen, R.

Single, interferometric dual, and quad-polarization mode data were evaluated for the characterization and classification of seven land use classes in an area with shifting cultivation practices located in the Eastern Amazon (Brazil). The Advanced Land-Observing Satellite (ALOS) Phased Array L-band Synthetic Aperture Radar (PALSAR) data were acquired during a six month interval. A clear-sky Landsat-5/TM image acquired at the same period was used as additional ground reference and as ancillary input data in the classification scheme. We evaluated backscattering intensity, polarimetric features, interferometric coherence and texture parameters for classification purposes using support vector machines (SVM) and feature selection. Results showed that the forest classes were characterized by low temporal backscatter-ing intensity variability, low coherence and high entropy. Quad polarization mode performed better than dual and single polarizations but overall accuracies remain low and were affected by precipitation events on the date and prior SAR date acquisition. Misclassifications were reduced by integrating Landsat data and an overall accuracy of 85% was attained. The integration of Landsat to both quad and dual polarization modes showed similarity at the 5% significance level. SVM was not affected by SAR dimensionality and feature selection technique reveals that co-polarized channels as well as SAR derived parameters such as Alpha-Entropy decomposition were important ranked features after Landsat' near-infrared and green bands. We show that in absence of Landsat data, polarimetric features extracted from quad-polarization L-band increase classification accuracies when compared to single and dual polarization alone. We argue that the joint analysis of SAR and their derived parameters with optical data performs even better and thus encourage the further development of joint techniques under the Reducing Emissions from Deforestation and Degradation (REDD) mechanism.

Keywords: Polarization modes; secondary forest; successional forest; ALOS/PALSAR; SVM; Eastern Amazon

Publ.-Id: 19609

Beneficiation potential of low-grade iron ore from the Manganore Iron Formation through gravity concentration

Beyeme-Zogo, J. C.; Beukes, N. J.; Gutzmer, J.

About 84% of the high-grade iron ore produced in South Africa is hosted by the Manganore Iron Formation of the Ghaap Group of the Asbestos Hills Subgroup, Transvaal Supergroup. The Manganore Iron Formation (MIF) is slumped into sinkhole structures of the Campbellrand Subgroup and occurs exclusively on the Maremane Dome, an arcuate structure located between Postmasburg in the south and Sishen/Kathu in the north, in the Northern Cape Province of South Africa. In the absence of major discoveries of new high-grade iron ore deposits around the world, mining companies have to turn to materials that were once classified as waste. This study was initiated to assess the beneficiation potential of banded MIF and brecciated MIF, two texturally distinct types of partly ferruginized iron formation that occur along the contact of the MIF with the immediately underlying Wolhaarkop Breccia and the Campbellrand Subgroup. The stratigraphic thickness of the partly ferruginized materials in drill core varied between from 23.2 m to 101.9 m. Both material types were sampled in drill cores, and Hand specimen samples were also collected from dump stockpiles and open pits at the Beeshoek and Khumani mines.
Partly ferruginized banded MIF consists of alternating bands of haematite and microbanded chert varying in thickness from the millimetre to the centimetre scale, with specularite filling fissures and pore spaces. The brecciated and partly ferruginized MIF comprises angular fragments of chert, quartz, iron formation, jasper, and high-grade haematite ore with or without matrix. Light microscopy and X-ray diffraction studies revealed that haematite is the principal ore mineral and quartz (chert) the main gangue mineral. Iron- and silica-rich bands were separated using a diamond saw for density measurements and for major element geochemistry by X-ray fluorescence spectrometry. The bulk density varies between 2.7 and 5.2 , and correlates well with the iron concentration, which range from 13.5 to 69.4 wt.% Fe. Bulk samples of both raw material types were crushed using a jaw crusher, then sieved in different size ranges and a particle size range (-5.6+1.4 mm) was selected for gravity concentration. This crushed material was found to contain 35.9 wt% Fe (brecciated MIF) and 33.7 wt% Fe (banded MIF). The beneficiation potential of the Manganore low-grade raw material type was assessed using a mineral density separator. The Mintek fixed trailer jig was used with input parameters of 200 kpa pressure. Separation success was monitored by determining the iron concentration of different beds using X-ray fluorescence spectrometry (XRF). The best separation was observed for brecciated MIF, which yielded a gravity concentrate containing 60.7 wt.% Fe (1.69 enrichment ratio), while processing of banded MIF yielded gravity concentrates of up to 52.2 wt.% Fe (1.72 enrichment ratio). The results d e m o n s t r a t e clearly that partly ferruginized MIF holds potential to be processed into a high-grade iron ore concentrate. However, the texture of the low-grade iron formation impacts significantly on separation success.

Keywords: Manganore Iron Formation; Gravity Concentration; Beneficiation Potential; Iron Ore

  • Contribution to proceedings
    SAIMM Physical Beneficiation Conference, 19.-21.11.2013, Misty Hills, South Africa
    Physical Beneficiation 2013, Johannesburg: SAIMM, 1 919783 50 4, 1-28

Publ.-Id: 19608

Lithium-Erkundung in Zinnwald, Osterzgebirge

Neßler, J.; Seifert, T.; Gutzmer, J.; Müller, A.; Stute, S.; Henker, J.; Kühn, K.

Nach einem beinahe 70-jährigen Stillstand der bergmännischen Tätigkeiten im Revier der Li-Sn-W-Lagerstätte Zinnwald im Osterzgebirge gehen die Erkundungsbemühungen in die nächste Runde. Die Freiberger Firma SolarWorld Solicium GmbH, einhundertprozentige Tochter der SolarWorld AG, erkundet seit der Erteilung der Aufsuchungsgenehmigung durch das Sächsische Oberbergamt im Februar 2011 gemeinsam mit der TU Bergakademie Freiberg und der GEOS Ingenieurgesellschaft mbH Mitteleuropas größtes bekanntes Li-Vorkommen.

Keywords: exploration; Saxony; resource technology

  • Acamonta 20(2013), 33-35
    ISSN: 2193-309X

Publ.-Id: 19607

"Erzminerale sehen heißt verstehen" - automatisierte Mineralogie und ihre Anwendung

Schulz, B.; Gutzmer, J.

Die von der Industrie benötigten Rohstoffe, insbesondere Metalle und Halbmetalle liegen in der Natur nur selten in einer elementaren und unmittelbar nutzbaren Form vor. Metalle wie beispielsweise Kupfer (Cu), Chrom (Cr) und Platin (Pt) finden sich vielmehr in vielfältigen molekularen Verbindungen mit Schwefel (S), Sauerstoff (O) und vielen weiteren Elementen in Erzmineralen wie Chalkopyrit (CuFeS2), Chromit ((Mg,Fe)Cr2O4) oder Braggit ((Pt,Pd,Ni)S. Diese Wertminerale treten wiederum oftmals in nur geringen Anteilen in den dazugehörigen Erzen.

Keywords: automated mineralogy; geometallurgy; mineral liberation analysis; resource technology

  • Acamonta 20(2013), 30-33
    ISSN: 2193-309X

Publ.-Id: 19606

Heimische Geopotenziale II - E3 - Rohstofferkundung im Erzgebirge mittels Geophysik

Osbahr, I.; Buske, S.; Spitzer, K.; Eiermann, M.; Siemon, B.; Meyer, U.; Gutzmer, J.; Gloaguen, R.; Stein, S.; Lehmann, U.

Im Januar dieses Jahres hat das Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF) in Kooperation mit der Technischen Universität Bergakademie Freiberg, der Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), sowie dem Landesamt für Umwelt, Landwirtschaft und Geologie (LfULG) einen Antrag auf eine wissenschaftliche Aufsuchungsgenehmigung für ein Gebiet im Raum Geyer im Erzgebirgskreis beantragt. Das damit einhergehende Forschungsprojekt hat das Ziel, mittels geophysikalischer Verfahren das Rohstoffpotenzial des geologischen Untergrundes bis in eine Tiefe von ca. 500 m zu erfassen. Alle relevanten Daten, die im Rahmen dieser Aufsuchung erhoben werden, sollen genutzt werden, um ein 3D-Modell des geologischen Untergrunds im Aufsuchungsgebiet zu erstellen. Sowohl dieses Modell als auch die ihm zugrundeliegenden Daten sollen mit Abschluss des auf drei Jahre ausgelegten Projekts veröffentlicht werden.

Keywords: geophysics; exploration; Saxony; resource technology

  • Acamonta 20(2013), 28-30
    ISSN: 2193-309X

Publ.-Id: 19605

Heimische Geopotenziale I - Wertstoffe aus Bergbauhalden

Osbahr, I.; Buettner, P.; Gutzmer, J.; Bertau, M.; Fritze, M.; Heide, G.; Janneck, E.; Kleeberg, R.; Leißner, T.; Luhmer, R.

Im Erzgebirge wurde über Jahrhunderte hinweg Erzbergbau betrieben. Abhängig vom Stand der Technik wurden nicht auszubringende oder nicht verwertbare Bestandteile des geförderten Gesteins aufgehaldet. Daher existieren als Hinterlassenschaft des Erzbergbaus des vorigen Jahrhunderts auch heutzutage noch etliche große Bergehalden, Spülhalden und Waschsandhalden aus der Aufbereitung sowie Schlacke- und Flugstaubablagerungen aus der Verhüttung. Diese Halden enthalten noch für die damalige Aufbereitung zu fein verwachsenes Material bzw. Restkonzentrationen der abgebauten Erzmetalle – z. B. Zinn, Zink, Silber oder Wolfram – und Begleitelemente, wie Lithium oder Indium. Einige der Metalle, die bei der historischen Gewinnung wirtschaftlich von wenig Interesse waren, sind heute von wirtschaftsstrategischer Relevanz.

Keywords: resource technology; resource efficiency; mine tailings; Saxony

  • Acamonta 20(2013), 25-27
    ISSN: 2193-309X

Publ.-Id: 19604

Printing Nearly-Discrete Magnetic Patterns Using Chemical Disorder Induced Ferromagnetism

Bali, R.; Wintz, S.; Meutzner, F.; Hübner, R.; Boucher, R.; Ünal, A. A.; Valencia, S.; Neudert, A.; Potzger, K.; Bauch, J.; Kronast, F.; Facsko, S.; Lindner, J.; Fassbender, J.

Ferromagnetism in certain alloys consisting of magnetic and non-magnetic species can be activated by the presence of chemical disorder. This phenomenon is linked to an increase in the number of nearest-neighbour magnetic atoms and local variations in the electronic band structure due to the existence of disorder sites. An approach to induce disorder is through exposure of the chemically ordered alloy to energetic ions; collision cascades formed by the ions knock atoms from their ordered sites and the concomitant vacancies are filled randomly via thermal diffusion of atoms at room temperature. The ordered structure thereby undergoes a transition into a metastable solid solution. Here we demonstrate the patterning of highly resolved magnetic structures by taking advantage of the large increase in the saturation magnetization of Fe60Al40 alloy triggered by subtle atomic displacements. The sigmoidal characteristic and sensitive dependence of the induced magnetization on the atomic displacements manifests a sub-50 nm patterning resolution. Patterning of magnetic regions in the form of stripes separated by ~ 40 nm wide spacers was performed, wherein the magnet/spacer/magnet structure exhibits re-programmable parallel (↑/spacer/↑) and antiparallel (↑/spacer/↓) magnetization configurations in zero field. Materials in which the magnetic behavior can be tuned via ion-induced phase transitions may allow the fabrication of novel spin-transport and memory devices using existing lateral patterning tools.

Keywords: phase-transitions; chemical disorder; magnetic patterning; magnetic nanostructures; memory devices

Related publications

Publ.-Id: 19603

Preclinical PET/MRI – First time use and validation of a potential tool for image based dosimetry

Kranz, M.; Sattler, B.; Patt, M.; Donat, C. K.; Deuther-Conrad, W.; Hiller, A.; Smits, R.; Hoepping, A.; Sabri, O.; Brust, P.

Objectives :

PET image based preclinical dosimetry (ibPD) allows the dose assessment for new radiotracers. However, most of the small animal systems are combined with CT. The low soft tissue contrast results in poor organ delineation. Therefore, we like to evaluate a new preclinical PET/MRI system by comparing a recent ibPD in female mice (M) with a post mortem biodistribution (PMB) and previous PET/CT based studies in piglets (P) and humans (H), after i.v. injection of [18F]flubatine.

Methods :

Whole body ibPD was performed in 3 M (11 w, 27.8 g), 3 P (7 w, 14.0 kg) and 3 H (59.6 y, 74.3 kg). The anesthetized animals and the H were PET-imaged (M: MEDISO nanoScan PET/MRI; P, H: SIEMENS Biograph16 PET/CT) up to 7h post i.v. injection of 13.1 MBq, 183.5. MBq, 353.7 MBq [18F]flubatine, followed by iterative reconstruction including MR- and CT-based attenuation correction respectively. Exponential curves were fitted to the time-activity-data (%ID/organ). In M and P, time and mass were adapted to the human scale. The activity data from the PMB study was obtained by organ counting of 27 M (11 w, 28.2 g) in a γ-counter. The ODs were calculated with OLINDA and the ED using tissue weighting factors (ICRP103).


Based on preclinical PET/MRI, the highest OD (μSv/MBq) was in kidneys (47.5) and urinary bladder (33.4). The highest contribution to the ED (μSv/MBq) was by stomach (1.8) and lungs (1.7), resulting in an ED of 12.1 which is almost identical with the results of the PMB (12.5). The ED based on the PET/CT data is 14.3 (P) and 22.6 in H.

Conclusions :

It was proven, exemplary for [18F]flubatine, that ibPD studies with a preclinical PET/MRI in mice for dose assessment to humans are possible, taking into account an underestimation of the ED of about 40% as shown by earlier studies[1]. The investigation of further radiotracers is required to confirm the reliability of this study.


[1] B. Sattler, M. Kranz, M. Patt et al. Incorporation dosimetry of F-18-Flubatine - Comparison of animal model data with first-in-man results. Journal of Nuclear Medicine 2012; 53(suppl): 1503.

  • Poster
    SNMMI 2014 Annual Meeting, 07.-11.06.2014, St. Louis, Missouri, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 55(2014)1, 1140

Publ.-Id: 19602

Triaryl-olefine based nitric oxide-releasing selective cyclooxygenase-2 inhibitors as potential radiosensitizers

Bechmann, N.; Sehn, F.; Tondera, C.; Mosch, B.; Kniess, T.; Pietzsch, J.

kein Abstract verfügbar

  • Poster
    40th Annual Meeting of the Europoean Radiation Research Society, 01.-05.09.2013, Dublin, Ireland
  • Contribution to proceedings
    40th Annual Meeting of the European Radiation Research Society, 01.-05.09.2013, Dublin, Ireland
    Congress Program and Abstracts, Dublin: ERR conference partner

Publ.-Id: 19601

Near-room-temperature photon-noise-limited quantum well infrared photodetector

Hao, M. R.; Yang, Y.; Zhang, S.; Shen, W. Z.; Schneider, H.; Liu, H. C.

With the modern development of infrared laser sources such as broadly tunable quantum cascade lasers and frequency combs, applications of infrared laser spectroscopy are expected to become widespread. Consequently, convenient infrared detectors are needed, having properties such as fast response, high efficiency, and room-temperature operation. This work investigated conditions to achieve near-room-temperature photon-noise-limited performance of quantum well infrared photodetectors (QWIPs), in particular the laser power requirement. Both model simulation and experimental verification were carried out. At 300 K, it is shown that the ideal performance can be reached for typical QWIP designs up to a detection wavelength of 10 μm. At 250 K, which is easily reachable with a thermoelectric Peltier cooler, the ideal performance can be reached up to 12 μm. QWIPs are therefore suitable for detection and sensing applications with devices operating up to or near room temperature.

Keywords: Quantum well infrared photodetector; QWIP; background limited performance; detectivity; signal-to-noise ratio

Publ.-Id: 19600

Strong Quadrupole-Strain Interaction of Vacancy Orbital in Boron-Doped Czochralski Silicon

Okabe, K.; Akatsu, M.; Baba, S.; Mitsumoto, K.; Nemoto, Y.; Yamada-Kaneta, H.; Goto, T.; Saito, H.; Kashima, K.; Saito, Y.

We have carried out ultrasonic measurements of a boron-doped silicon ingot grown by the Czochralski method in order to determine the quadrupole-strain interaction constant of a vacancy orbital. The low-temperature softening of the elastic constant C44 shows a remarkable variation depending on positions of the ingot, which reflects the distribution of vacancy concentration N in the ingot. An infrared laser scattering tomograph was employed to measure the density and size of voids in the silicon wafers by determining the vacancy concentration Ncons consumed in void formation. Using a combination of laser scattering tomography and low-temperature softening, we have found a sum rule in which the initially created vacancy concentration Ntotal corresponds to the sum of the residual vacancy concentration N and the consumed vacancy concentration Ncons as Ntotal = N + Ncons. Taking account of the sum rule, we deduce the interaction constant gΓ5 = (2.8±0.2)×105 K for the quadrupole-strain interaction HQS = -gΓ5Ozxεzx of the vacancy orbital. The huge deformation energy of 1.6×105 K per vacancy with the Γ8 ground state for unit strain εzx = 1 verified the strong electron–lattice interaction of the vacancy orbital. Employing the one-to-one correspondence between the softening of ΔC44/C44 = 1.0×10-4 down to 30 mK and the vacancy concentration of N = 1.5 ×1013 cm-3, we can determine the vacancy concentration by low-temperature ultrasonic measurements. The present work surely puts forward a novel semiconductor technology based on low-temperature ultrasonic measurements for evaluating vacancy concentration in silicon wafers.

Keywords: vacancy; boron-doped silicon wafer; ultrasound; quadrupole; softening

Publ.-Id: 19599

Chemical reactions between poly(carbonate) and poly(vinyl amine) thermally induced by a high magnetic field pulse

Zimmerer, C.; Heinrich, G.; Wolff-Fabris, F.; Koch, E.; Steiner, G.

A high magnetic field pulse with a magnetic flux density of Bmax = 60.5 T was used to induce chemical reactions between poly(carbonate) (PC) and poly(vinyl amine) (PVAm). PC and PVAm were prepared as a thin film composite onto calcium fluoride substrate. A silver ring structure of 30 am thickness and a mean diameter of 4.5 mm was embedded in the PC/PVAm interface. The applied magnetic pulse induced an Eddy current in the silver ring which results in a temperature of approx. 90 degrees C. Chemical reactions between PC and PVAm were investigated by Fourier transform infrared spectroscopic imaging and principal component data analysis. The spectroscopic results point to a formation of urethane bonds and degraded PC chains with phenolic end groups in the vicinity of the silver ring structure. The results are in accordance with differential scanning calorimetric experiments and demonstrate a thermally induced chemical reaction between PC and PVAm.

Publ.-Id: 19598

ESR of coupled spin-1/2 chains in copper pyrazine dinitrate: unveiling geometrical frustration

Validov, A. A.; Ozerov, M.; Wosnitza, J.; Zvyagin, S. A.; Turnbull, M. M.; Landee, C. P.; Teitel’Baum, G. B.

The spin dynamics of copper pyrazine dinitrate (Cu(C4H4N2)(NO3)2), a model spin-1/2 Heisenberg antiferromagnetic (AF) chain system, was investigated by means of electron spin resonance (ESR). Using the high-field ESR we evidenced the inequivalence of Cu sites belonging to adjacent spin chains in the ac planes of this compound. It was revealed that the dominating interchain interaction is of zig-zag-type. This interaction gives rise to geometrical frustration strongly affecting the character of AF ordering. Combining our experimental findings with the results of a quasiclassical approach we predict that at low temperatures the system orders in an incommensurate spiral state.

Publ.-Id: 19597

Magnetization, magnetic susceptibility and ESR in Tb3Ga5O12

Löw, U.; Zvyagin, S.; Ozerov, M.; Schaufuss, U.; Kataev, V.; Wolf, B.; Lüthi, B.

We report on the measurement of the magnetic susceptibility and of ESR transitions in the garnet substance Tb3Ga5O12 (TGG). The results are compared with a calculation in the framework of crystal field theory for the orthorhombic surroundings of the six inequivalent Tb ions of TGG. We also present a calculation of the magnetization for the three main crystal directions.

Publ.-Id: 19596

The "quiet" Goldschmidt reaction 2Al + α-Fe2O3 → 2Fe + α-Al2O3

Stӧßer, R.; Feist, M.; Willgeroth, C.; Emmerling, F.; Menzel, M.; Reuther, H.

The well-known Goldschmidt reaction, i.e. the reaction of (2 Al + α-Fe2O3), was investigated upon mechanochemical activation by employing Mössbauer and ESR spectroscopy in combination with thermal analysis (TA), magnetic susceptibility measurements and X-ray powder diffraction (XRD).

  • Poster
    International Conference on the Applications of the Mossbauer Effect - 2013, 01.-06.09.2013, Opatija, Kroatien

Publ.-Id: 19595

Thin layer analysis with electrons - AES, XPS, Mössbauer spectroscopy

Reuther, H.

Thin surface layers on a solid may refine properties like corrosion, friction or wear of the whole workpiece. There are a lot of methods for modification and the analysis of such layers is often based on different kinds of electron spectroscopy.

  • Invited lecture (Conferences)
    XXXIV Brazilian Congress of Vacuum Applications in Industry and Science, 21.-25.10.2013, Ilheus, Brasilien

Publ.-Id: 19594

Evidence of formation of the tridymite form of AlPO4 in some municipal sewage sludge ashes

Peplinski, B.; Adam, C.; Adamczyk, B.; Muller, R.; Schadrack, R.; Michaelis, M.; Emmerling, F.; Reuther, H.; Menzel, M.

Evidence is provided that the tridymite component observed in the X-ray diffraction patterns of some sewage sludge ashes (SSAs) should not be interpreted as the tridymite modification of SiO2 but as the tridymite form of AlPO4. This proof is based on a combined X-ray Powder Diffraction (XRD), X-ray fluorescence (XRF) and Mossbauer spectroscopy investigation of two SSAs produced at two fluidized bed incineration facilities, located in different municipalities and operated differently. The structural and chemical characterization was carried out on the 'as received' SSA samples as well as on the residues of these two SSAs pretreated by leaching in citric acid. In addition, direct proof is presented that the tridymite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T approximate to 850 °) typical for fluidized bed incinerators.

Publ.-Id: 19593

Comparison of CFD simulations on two-phase Pressurized Thermal Shock scenarios

Apanasevich, P.; Coste, P.; Ničeno, B.; Heib, C.; Lucas, D.

Small Break Loss of Coolant Accident (SB LOCA) is one of the most severe transients which may lead to pressurized thermal shock (PTS) on the reactor pressure vessel (RPV) wall. During postulated SB LOCA emergency core cooling (ECC) water is injected into the cold leg, where it mixes with the hot coolant. The mixture of cold and hot coolants flows towards the downcomer. Knowledge of transient temperature distribution in the downcomer is necessary to predict thermal gradients in the structural components of the RPV wall. For the prediction of the temperature fields and heat transfer coefficient between the fluid and wall in the cold leg and the downcomer, reliable computational fluid dynamics (CFD) simulations are needed. To validate CFD models for two-phase PTS scenarios numerical simulations of the TOPFLOW-PTS experiments were performed in the framework of the EU NURISP (NUclear Reactor Integrated Simulation Project) project. The paper presents the post CFD simulations of a steady-state TOPFLOW-PTS air/water experiment and the pre-test blind simulations of a steady-state TOPFLOW-PTS steam/water case with condensation. CFD simulations were performed with ANSYS FLUENT, ANSYS CFX and NEPTUNE_CFD. The simulations of the air/water test have shown that correct modeling of the ECC jet behavior is essential for the temperature prediction in the cold leg. For modeling these two-phase flows with rather smooth large free surfaces, Reynolds Averaged Navier-Stokes approach seems to be appropriate. The pre-test simulations of steam/water flow predicted a thermal stratification at the entrance of the downcomer. Finally, the simulations of the TOPFLOW-PTS experiments have depicted considerable differences between the codes and the models.

Keywords: Computational fluid dynamics (CFD); Stratified two-phase flow; Pressurized thermal shock (PTS); Direct contact condensation (DCC); TOPFLOW-PTS experiments

Publ.-Id: 19592

Depositional environment and lithostratigraphy of the Paleoproterozoic Mooidraai Formation, Kalahari Manganese Field, South Africa

Kunzmann, M.; Gutzmer, J.; Beukes, N. J.; Halverson, G. P.

The Paleoproterozoic Mooidraai Formation is an up to 220 m-thick succession of marine carbonate rocks that caps the Fe- and Mn-bearing Hotazel Formation in the Kalahari Manganese Field, South Africa. Although it occupies an important stratigraphic position within the upper Transvaal Supergroup, which records major perturbations of the early Paleoproterozoic biosphere, a detailed sedimentological study on the Mooidraai Formation has never been conducted. Here we present a detailed facies analysis that distinguishes eight carbonate and two iron formation lithofacies types. The lower Mooidraai Formation is dominated by carbonate rhythmites and slope breccias deposited on a foreslope, occasionally interbedded with oxide or carbonate facies iron formation. The upper part of the formation reflects various shelf and peritidal environments arranged in shallowing-upward parasequences. Clastic-textured massive dolarenites deposited in shelf and lagoonal environments typically form the base of parasequences and are overlain by subtidal thrombolites, lagoonal to intertidal microbialaminites, and upper intertidal to supratidal smoothly laminated stromatolites. Supratidal intraclast breccias cap shallowing-upward parasequences. Strong base level rise in the lower Mooidraai Formation reflects a transgressive systems tract tied to rapid early subsidence. Together with considerable lateral thickness variation in the following regressive systems tract, this suggests deposition in a basin with significant seafloor relief.

Keywords: no keywords required

Publ.-Id: 19591

Experimental study of the 14N(p,γ)15O reaction for solar fusion at 0.5-1.5 MeV

Wagner, L.; Bemmerer, D.; Anders, M.; Elekes, Z.; Junghans, A.; Marta, M.; Reinhardt, T.; Reinicke, S.; Schmidt, K.; Röder, M.; Schwengner, R.; Wagner, A.; Zuber, K.; Takács, M.; Szücs, T.

Die 14N(p,γ)15O-Reaktion bestimmt als langsamste Kernreaktion die Rate des Bethe-Weizsäcker-Zyklus. Für eine präzise Extrapolation des Wirkungsquerschnitts zu niedrigen Energien ist die genaue Kenntnis der Anregungsfunktion über einen weiten Energiebereich notwendig. Am 3 MV Tandetron des Helmholtz-Zentrums Dresden-Rossendorf wurde der nichtresonante Wirkungsquerschnitt der 14N(p,γ)15O-Reaktion im Bereich von 0,5-1,5 MeV Strahlenergie neu untersucht. In dem Vortrag werden vorbereitende Simulationen, die experimentellen Daten und die resultierenden S Faktoren präsentiert.

Keywords: Nuclear Astrophysics; solar fusion; CNO cycle; 3MV Tandetron; non resonant cross sections; 14N(p; γ)15O

Related publications

  • Lecture (Conference)
    NAVI annual meeting, 16.-17.12.2013, Darmstadt, Deutschland

Publ.-Id: 19590

Durchführung von Sorptions- und Desorptionsversuchen von Uran(VI) an Montmorillonit

Zehlike, L.

In dieser Arbeit wurde die Sorption und Desorption von U(VI) an dem Tonmineral Montmorillonit untersucht. Dies geschah zum einen in Abhängigkeit vom pH-Wert, welcher im Bereich 5 - 7 lag und zum anderen in Abhängigkeit von der Ionenstärke. Als Hintergrundelektrolyten wurden NaCl und CaCl2 verwendet.
Die Ergebnisse zeigen, dass das Sorptionsmaximum in beiden Systemen bei ca. pH 6 liegt, obwohl im NaCl-System bei der Ionenstärke 3,0 mol/kg eine Verschiebung des Sorptionsmaximums zu pH-Wert 7 auftritt. Bei pH 7 nimmt die Sorption im CaCl2-System auf Grund des stabilen Ca2UO2(CO3)3(aq)-Komplexes stark ab, im NaCl-System bleibt sie dagegen annähernd konstant. Außerdem ist im CaCl2-System bei pH 6 und 7 eine Ionenstärkeabhängigkeit zu beobachten, welche im NaCl-System nicht gegeben ist. Des Weiteren scheinen verschiedene Ausfällungen wie z. B. Silikatniederschläge im CaCl2-System eine wichtige Rolle zu spielen.
Die Desorptionsuntersuchungen zeigten, dass die Desorption dieselbe pH-Abhängigkeit wie die sorption aufweist. Bei pH 5 konnte bei beiden Systemen die stärkste Desorption festgestellt werden, bei pH 6 die geringste. Die Desorptionsvorgänge laufen überwiegend reversiebl ab, was darauf schließen lassen könte, dass die Komplexierungsmechanismen vorrangig an den schwachen Bindungsstellen des Montmorillonit auftreten. Im CaCl2-System sind jedoch große Unterschiede in den logKd-Werten zwischen Sorption und Desorption zu verzeichnen, was mit den schon genannten Ausfällungen in Verbindung gebracht werden kann. Im NaCl-System scheint der Desorptionsvorgang abhängig von der Ionenstärke reversibel oder irreversibel zu verlaufen.
Von den getätigten Untersuchungen ausgehend, ist der Montmorillonit besonders für ein Endlagersystem mit pH-Werten im Bereich 6-7 geeignet, wobei sich allerdings hohe Calciumkonzentration in Gegenwart von Carbonat-Ionen nachteilig auf das sorptionsverhalten auswirken. Hohe NaCl-Konzentrationen haben keinen erheblichen negativen Einfluss auf die Sorptions- und Deosprtionsfähigkeit des Montmorillonits.

Keywords: nuclear waste repositories; uranium sorption; argillaceous rock; clay; uranium; montmorillonite; high ionic strength; desorption

  • Bachelor thesis
    TU Dresden, 2013
    0048 Seiten

Publ.-Id: 19588

Hyperdoping semiconductors by ion implantation

Zhou, S.

Ion implantation followed by annealing is a well-established method to dope Si and has been maturely integrated with the IC industry production line. Nowadays, the demands for functional materials require a supersaturated doping of semiconductors, i.e., the dopant concentration should be in the percent range. For instance for spintronic applications one needs to prepare magnetic semiconductors which are doped with up to 5-10% Mn [1]. For multiband solar cells one needs to dope semiconductors with deep levels at a concentration large enough to form impurity bands in the bandgap of the semiconductor host material [2]. In this talk, I will make an overview of the activities in my group utilizing ion implantation and short time annealing. These activities include synthesizing full spectrum of III-V:Mn diluted magnetic semiconductors [3-5], optical property modification of GaAs [6-7] and metal-insulator transition in Se/S doped Si.

1. T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Ferrand, Science 287, 1019 (2000).
2. A. Luque and A. Martí, Phys. Rev. Lett. 78, 5014 (1997).
3. D. Bürger, S. Zhou, et al., Application of pulsed laser annealing to ferromagnetic GaMnAs, Phys. Rev. B 81, 115202 (2010).
4. S. Zhou, et al., The importance of hole concentration in establishing carrier-mediated ferromagnetism in Mn doped Ge, Appl. Phys. Lett. 96, 202105 (2010).
5. S. Zhou, et al. Ferromagnetic InMnAs on InAs Prepared by Ion Implantation and Pulsed Laser Annealing, Appl. Phys. Express 5, 093007 (2012)
6. S. Prucnal, …, S. Zhou, Temperature stable 1.3 μm emission from GaAs, Optics Express, 20, 26075-26081 (2012).
7. K. Gao, …, S. Zhou, Origin and enhancement of the 1.3 μm luminescence from GaAs treated by ion-implantation and flash lamp annealing, J. Appl. Phys. 114, 093511 (2013).

Related publications

  • Lecture (others)
    Invited seminar at Southeast University and Nanjing University, Nanjing, China, 07.-08.10.2013, Nanjing, China

Publ.-Id: 19587

Ion beam synthesis of ferromagnetic semiconductors

Zhou, S.

Ferromagnetic semiconductors are under intensive investigation in last decade. Until now, III-Mn-V based compound semiconductors are the only well accepted family. The prototype ferromagnetic semiconductor GaMnAs has revealed a variety of unique features induced by the combination of its magnetic and semiconducting properties. To prepare ferromagnetic semiconductors, one needs to dope the host with up to 5-10% Mn, which is far beyond the solid solubility of Mn in III-V compounds. As a non-equilibrium process, ion implantation can introduce enough dopants as required. However, the activation of dopants remains challenging due to the clustering of implanted ions during post-annealing. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. On the other hand, one notes that the solubility limit in the liquid phase is generally much larger than that in the solid phase. Short-time annealing in the millisecond or nanosecond regime allows the epitaxial growth from a liquid phase. The mature development and commercialization of ion implantation promise the versatility. The approach combining ion implantation and pulsed laser melting allows us to prepare ferromagnetic semiconductors covering the full spectrum of III-V compound semiconductors. We have successfully synthesized ferromagnetic Mn doped III-V from InAs to GaP with different bandgaps. The results of magnetization, magnetic anisotropy, resistivity, anomalous Hall effect, magnetoresistance and x-ray magnetic circular dichroism obtained from the synthesized samples confirm the intrinsic origin and the carrier-mediated nature of the ferromagnetism. These results could allow a panorama-like understanding of III-V:Mn based ferromagnetic semiconductors.

Related publications

  • Invited lecture (Conferences)
    7th Symposium on Vacuum based Science and Technology, 19.-21.11.2013, Kołobrzeg, Poland

Publ.-Id: 19586

Structural and magnetic properties of irradiated SiC

Wang, Y.; Chen, X.; Li, L.; Shalimov, A.; Tong, W.; Prucnal, S.; Munnik, F.; Yang, Z.; Skorupa, W.; Helm, M.; Zhou, S.

We present a comprehensive structural characterization of ferromagnetic SiC single crystals induced by Ne ion irradiation. The ferromagnetism has been confirmed by electron spin resonance and possible transition metal impurities can be excluded to be the origin of the observed ferromagnetism. Using X-ray diffraction and Rutherford backscattering/channeling spectroscopy, we estimate the damage to the crystallinity of SiC which mutually influences the ferromagnetism in SiC.

Related publications

  • Journal of Applied Physics 115(2014), 17C104
    DOI: 10.1063/1.4860659
    Cited 14 times in Scopus
  • Lecture (Conference)
    The 58th Annual Magnetism and Magnetic Materials (MMM) Conference, 04.-08.11.2013, Denver, USA

Publ.-Id: 19585

Defect-induced ferromagnetism in semiconductors: a controllable approach by particle irradiation

Zhou, S.

Making semiconductors ferromagnetic has been a long dream. One approach is to dope semiconductors with transition metals (TM). TM ions act as local moments and they couple with free carriers to develop collective magnetism. However, there are no fundamental reasons against the possibility of local moment formation from localized sp states. Recently, ferromagnetism was observed in nonmagnetically doped, but defective semiconductors or insulators including ZnO and TiO2. This kind of observation challenges the conventional understanding of ferromagnetism. Often the defect-induced ferromagnetism has been observed in samples prepared under non-optimized condition, i.e. by accident or by mistake. Therefore, in this field theory goes much ahead of experimental investigation. To understand the mechanism of the defect-induced ferromagnetism, one needs a better controlled method to create defects in the crystalline materials. As a nonequilibrium and reproducible approach of inducing defects, ion irradiation provides such a possibility. Energetic ions displace atoms from their equilibrium lattice sites, thus creating mainly vacancies, interstitials or antisites. The amount and the distribution of defects can be controlled by the ion fluence and energy. By ion irradiation, we have generated defect-induced ferromagnetism in ZnO, TiO2 and SiC. In this short review, we also summarize some results by other groups using energetic ions to introduce defects, and thereby magnetism in various materials. Ion Irradiation combined with proper characterizations of defects could allow us to clarify the local magnetic moments and the coupling mechanism in defective semiconductors. Otherwise we may have to build a new paradigm to understand the defect-induced ferromagnetism.

Keywords: Ion irradiation; Defects; Magnetism

Related publications

  • Nuclear Instruments and Methods in Physics Research B 326(2014), 55-60
    DOI: 10.1016/j.nimb.2013.10.049
    Cited 21 times in Scopus
  • Invited lecture (Conferences)
    The 17th International Conference on Radiation Effects in Insulators, 30.06.-05.07.2013, Helsinki, Finland

Publ.-Id: 19584

Transport phenomena and dynamics of externally and self-propelled colloids in confined geometry

Kreuter, C.; Siems, U.; Nielaba, P.; Leiderer, P.; Erbe, A.

Over the last decades, colloidal suspensions have been proven as powerful model systems to reveal fundamental questions in soft matter or general physics. In this work, we will focus on the influ- ence of interaction and confinement to the mobility of colloidal particles as well as to the transport behavior of particles over obstacles placed in a micro-channel. Both experiments are supported with Brownian dynamics simulations to complete the experimental work. The paper concludes with the investigation of the behavior of single active swim- mers close to a wall.

Keywords: colloidal model systems; active swimmers; transport phenomena

Publ.-Id: 19583

Formation of radiation damage and helium release in yttria-stabilized zirconia

Ou, X.; Kögler, R.; Zhou, H.; Anwand, W.; Grenzer, J.; Hübner, R.; Voelskow, M.; Butterling, M.; Zhou, S.; Skorupa, W.

The radiation damage induced by neutrons and α-decay in YSZ (yttria-stabilized zirconia) was simulated using synchronized Zr+ & He+ dual ion beam implantation. [1] The measured damage profiles consist of two peaks which agree well with the calculated profiles of excess point defects generated by the collision cascade. The spatial separation of vacancy and interstitial defects is known as the “½Rp” effect describing the vacancy accumulation in the region at half of the projected ion range. This special implantation-related effect has to be considered carefully during the evaluation of experimental investigations which simulate isotropic irradiation effects caused by α-decay. Comparing the amount and type of radiation defects in single and dual beam implanted YSZ reveals that the implanted helium is released from the sample during simultaneous dual beam irradiation instead to be trapped by the created open volume defects at ½Rp region. According to first-principles total energy calculations, helium is mobilized and released via a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. The release of helium during room temperature dual beam irradiation demonstrates one of the suitable characteristics of YSZ that contributes to its excellent radiation hardness, since helium in YSZ can accumulate in undesirable helium bubbles and results in local surface swelling and lift-off.
[1] Xin Ou et al. PHYSICAL REVIEW B 86, 224103 (2012)

Keywords: radiation damage; dual ion beam implantation

Related publications

  • Poster
    E-MRS 2013 Spring Meeting, 27.-31.05.2013, Strasbourg, France

Publ.-Id: 19582

Tuning the resistive switching characteristics of BiFeO3 by Ar+ irradiation (Best Poster Award)

Ou, X.; Shuai, Y.; Luo, W.; Kögler, R.; Fiedler, J.; Reuther, H.; Zhou, S.; Hübner, R.; Facsko, S.; Helm, M.; Schmidt, H.

Sufficient and stable read current is critical for the scalability of RRAM devices and designing of multilevel resistive switching devices.
Here, we report that a remarkable increase of the current density and retention stability of Au/BiFeO3/Pt/Ti resistance random access memory (RRAM) devices can be achieved by low-energy (≤ 1 keV) Ar+ ion irradiation of BiFeO3 films.
According to dynamic simulations and microstructure characterizations, oxygen atoms are preferentially sputtered from the BiFeO3 surface by Ar+ ion irradiation. The generation of oxygen vacancies acting as "dopants" modifies the Schottky contact of the Au/BiFeO3 interface and also may contribute to the formation of highly conductive "shunt" channels. These two effects are proposed as the reasons for the increased current density by more than two orders of magnitude and the improved retention stability. After Ar+ irradiation the retention stability was increased as the current density remaining after the retention time is improved from 7% to 85% of the initial value.

Keywords: RRAM; ion irradiation

Related publications

  • Poster
    European Materials Research Society Conference, 27.-31.05.2013, Strasbourg, France

Publ.-Id: 19581

Reverse Epitaxy of Ge Surface for Nanopattern Formation

Ou, X.; Mücklich, A.; Fassbender, J.; Facsko, S.

Periodical semiconductor nanostructure arrays have the potential for nano-electronic and nano-optoelectronic application. Besides the conventional low efficiency lithographic techniques broad ion beam erosion is a simple and potentially mass productive technique to fabricate nanostructure patterns on semiconductor surfaces.[1] Based on a “self-organized” erosion process, periodic ripple, hole, dot or tip arrays can be created on various semiconductor surfaces due to the interplay of different processes.[2] However, the main drawback of this method is that the irradiated semiconductor surfaces are amorphized. In this work we report the recent discovery of single crystal Ge nanopattern formation based on a “reverse epitaxy” process. The vacancies created during the ion beam irradiation distribute according to the crystallographic anisotropy, which results in orientation-dependent pattern formation on single crystal Ge surface. The formation of these patterns is interpreted as the result of a surface instability due to an Ehrlich-Schwoebel barrier for ion induced surface vacancies. The simulation of the pattern formation is performed by a continuum equation accounting for the effective surface currents.

[1] Stefan Facsko et al. Science 285, 1551 (1999).

Keywords: Nanopattern; ion irradiation

Related publications

  • Lecture (Conference)
    European Materials Research Society Conference, 27.-31.05.2013, Strasbourg, France

Publ.-Id: 19580

Formation of radiation damage and helium release in yttria-stabilized zirconia under dual ion beam irradiation

Ou, X.; Kögler, R.; Zhou, H. B.; Anwand, W.; Grenzer, J.; Hübner, R.; Voelskow, M.; Butterling, M.; Zhou, S.; Skorupa, W.; Facsko, S.

Fission gas retention or release has a critical impact on the function of advanced nuclear materials. Helium trapping in, and release from, radiation defects induced by neutrons and by α decay in YSZ (yttria-stabilized zirconia) is experimentally simulated using synchronized Zr+ and He+ dual ion beam irradiation. The measured damage profiles consist of two peaks which agree well with the calculated profiles of implantation induced excess point defects. This special implantation related effect has to be carefully considered in the Evaluation of experimental investigations which simulate isotropic irradiation effects such as α decay. First-principles calculations show that helium is energetically favorable to be trapped by Zr vacancies in YSZ. Implanted helium alone in YSZ is accumulated in undesirable helium bubbles and results in local surface swelling and lift-off. However, under dual beam irradiation helium is released from vacancy defects and is out-diffused at room temperature. Helium is mobilized by a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. This behavior avoids the deleterious helium bubble formation and contributes to the suitable application characteristics of YSZ which result in its excellent radiation hardness.

Keywords: radiation defects; ZrO2

Related publications

  • Lecture (Conference)
    German workshop on Ion Beam Research and Application, 12.-14.06.2013, Leipzig, Germany

Publ.-Id: 19579

Ion beam irradiation and doping effect on 1D and 2D materials

Ou, X.

In this lecture, I will give a brief review on the doping of the nanostructure by ion beam implantation and irradiation. Because of the high surface to volume ratio of the low-dimensional materials, the doping behavior is quite different from the bulk materials. Some examples on doping of nanowire1,2 and graphene by ion beam will be discussed. Meanwhile, ion beam irradiation can create the oxygen vacancy in functional oxide in a controllable way. The generation of oxygen vacancies acting as "dopants" modifies the properties of the oxide. An example of tuning the resistive switching characteristics of resistive switching oxide 3 by low energy ion irradiation will be discussed.4

Keywords: doping of the nanostructure; ion beam implantation and irradiation

Related publications

  • Invited lecture (Conferences)
    International School on Ion Beams in Material Science, 21.-22.10.2013, Jaipur, India

Publ.-Id: 19578

Nanopatterning of semidonductor surfaces by ion beam irradiation

Ou, X.; Keller, A.; Helm, M.; Fassbender, J.; Facsko, S.

Periodic semiconductor nanostructure arrays have the potential for nanoelectronic and optoelectronic application. Besides the conventional low efficiency lithographic techniques broad ion beam irradiation is a simple and potentially mass productive technique to fabricate nanostructure patterns on semiconductor surfaces.[1] Based on a “self-organized” erosion process, periodic ripple, hole, or dot arrays can be produced on various semiconductor surfaces. Moreover, an array of isolated nanostructures on insulator substrate can be fabricated by ion beam erosion of a thin Si or Ge layer deposited on insulator and precisely stopping the sputtering as soon the nanopattern meets the interface of the buried oxide layer.[2]
However, the main drawback of this method is that the irradiated semiconductor surfaces are amorphized. In this work we report the recent discovery of single crystal Ge nanopattern formation based on a “reverse epitaxy” process.[3] The vacancies created during ion beam irradiation distribute according to the crystallographic anisotropy, which results in an orientation-dependent pattern formation on single crystal Ge surface. The formation of these patterns is interpreted as the result of a surface instability due to an Ehrlich-Schwoebel barrier for ion induced surface vacancies. The simulation of the pattern formation is performed by a continuum equation accounting for the effective surface currents.

[1] Stefan Facsko et al. Science 285, 1551 (1999).
[2] Xin Ou et al., AIP Advances, 1, 042174 (2011).
[3] Xin Ou et al., Physical Review Letters 111, 016101 (2013).

Keywords: nanopatterning

Related publications

  • Invited lecture (Conferences)
    International Conference on Nanostructuring by Ion Beams, 23.-25.10.2013, Jaipur, India

Publ.-Id: 19577

Investigation of a packed bed in a mini channel with a low channel-to-particle diameter ratio: Flow regimes and mass transfer in gas–liquid operation

Langsch, R.; Zalucky, J.; Haase, S.; Lange, R.

This work analyzes flow regimes and mass transfer in a miniaturized packed bed reactor under reacting conditions. The reactor consisted of a cylindrical channel with an inner diameter of 2 mm which was filled with spherical catalyst particles having an outer diameter of 0.8 mm. The liquid phase hydrogenation of α-methylstyrene over a Pd/γ-Al2O3 catalyst was employed as reaction system. Based on experimental reaction rates, overall (gas–liquid–solid) volumetric mass transfer coefficients of hydrogen, which were between 0.5 s−1 and 6.0 s−1, were computed. Detailed discussions focus on the impact of the flow regime, the gas and liquid superficial velocities and, consequently, their ratio, as well as system pressure on overall mass transfer rates.

Keywords: Mass transfer; Multiphase reactors; Hydrodynamics; Packed bed; Catalysis; Gas–liquid–solid reaction

Publ.-Id: 19576

Dissolution and diffusion behaviors of hydrogen in copper: A first-principles investigation Dissolution and diffusion behaviors of hydrogen in copper: A first-principles investigation

Zhou, H. B.; Zhang, Y.; Ou, X.

We have investigated the dissolution and diffusion behaviors of hydrogen (H) in copper (Cu) based on first-principles calculations in combination with the classical thermodynamics models. A single H atom energetically prefers to occupy the octahedral interstitial site (OIS) instead of the tetrahedral interstitial site (TIS). This can be confirmed by the charge density results. The dissolved equilibrium concentration of H is 8.98 × 10−7 at a typical temperature 600 K. We demonstrate that the OIS → TIS → OIS path is the optimal diffusion path of H in Cu with diffusion barrier of 0.23 eV. Double H atoms tend to be paired up at the two neighboring OIS’s along the 〈1 1 0〉 direction with a distance of 2.59 Å and a binding energy of 0.07 eV. This suggests a weak attractive interaction between H atoms, with the implication that self-trapping of H and thus formation of the H2 molecules are quite difficult in the bulk Cu.

Keywords: first-principles calculations; diffusion behaviors

Related publications

  • Computational Materials Science 79(2013), 923

Publ.-Id: 19575

Effect of carbon on helium trapping in tungsten: a first-principles investigation

Zhou, H.; Ou, X.; Zhang, Y.; Shu, X.; Liu, Y.; Lu, G.

We investigate the effect of carbon (C) on helium (He) trapping in tungsten (W) using a first-principles method. We show C can effectively reduce the solution energy of He in the bulk W originated from the charge density redistribution. This leads to a strong attraction between He and C in W. We demonstrate the C–vacancy (C–V) complex can serve as a trapping center by reducing charge density in its vicinity to induce He nucleation in comparison with the defect-free W. The maximal number of He atoms that can be trapped by such C–V complex is 5, and He diffusion into the C–V complex is kinetically feasible. Further, it is found the binding energy of He to a C–V complex is weaker than that to a C-free vacancy, suggesting C will decrease the He trapping capability of vacancy. We thus propose that C plays a key role in He trapping behavior.

Keywords: tungsten; first-principles method; trapping

Related publications

Publ.-Id: 19574

A Si-based nanocomposite absorber for thin film solar cells

Heinig, K.-H.; Aydinli, A.; Turan, R.; Hauschild, D.

Si-based thin film solar cells suffer from a rather low efficiency. This leads to a relative small market share, although their module prices are comparably low. RainbowEnergy aims at a novel nanostructured Si-based thin film PV cell absorber, which increases the efficiency substantially without increasing the module costs.
If after phase separation SiOx --> 0.5SiO2 + (1-0.5x)Si the volume fraction of Si exceeds ~30%, then Si forms a percolated nanowire network. Energy-Filtered Transmission Electron Microscopy (EFTEM) studies show that nanowires have diameters of a few nanometers with a narrow distribution. This is in excellent agreement with large-scale simulations based on kinetic Monte-Carlo.
As the wire diameters coarsens with time of heat treatment like d~t1/3, and because the Si bandgap opens for nm-structures by quantum confinement, a band gap engineering for PV cell optimization becomes feasible. It will be shown that up-scaling of the nanotechnology described above to large-scale PV cell production is under way with industrial partners.

Keywords: Solar Energy; thin film; nanocomposite; Si; SiO2; atomistic simulation; EFTEM

Related publications

  • Invited lecture (Conferences)
    2013 Energy Materials Nanotechnology (EMN Spring), 08.-11.04.2013, Orlando, USA

Publ.-Id: 19573

Key concepts behind forming-free resistive switching incorporated with rectifying transport properties

Shuai, Y.; Ou, X.; Luo, W.; Mücklich, A.; Bürger, D.; Zhou, S.; Wu, C.; Chen, Y.; Zhang, W.; Helm, M.; Mikolajick, T.; Schmidt, O.; Schmidt, H.

This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO3/Pt/Ti capacitor-like structures. Polycrystalline BiFeO3 thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO2/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600°C. The current-voltage (I–V) curves indicate that resistive switching can only be achieved in Au/BiFeO3/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO3 thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits.

Keywords: resistive switching; BiFeO3; Ti diffusion

Related publications

Publ.-Id: 19572

Forming-free resistive switching in multiferroic BiFeO3 thin films with enhanced nanoscale shunts

Ou, X.; Shuai, Y.; Luo, W.; Siles, P. F.; Kögler, R.; Fiedler, J.; Reuther, H.; Zhou, S.; Hübner, R.; Facsko, S.; Helm, M.; Mikolajick, T.; Schmidt, O. G.; Schmidt, H.

A controlled shunting of polycrystalline oxide thin films on the nanometer length scale opens the door to significantly modify their transport properties. In this paper, the low energy Ar(+) irradiation induced shunting effect of forming-free, non-volatile resistive switching in polycrystalline BiFeO3 thin film capacitor-like structures with macroscopic bottom and top contacts was investigated. Oxygen atoms at the BiFeO3 surface are preferentially sputtered by Ar(+) ion irradiation and oxygen vacancies and a metallic Bi phase are formed at the surface of the BiFeO3 thin film before deposition of the top contacts. A phenomenological model is that of nanoscale shunt resistors formed in parallel to the actual BiFeO3 thin film capacitor-like structure. This model fits the noticeable increase of the retention stability and current density after irradiation. The formation of stable and conductive shunts is further evidenced by conductive atomic force microscopy measurements.

Keywords: resistive switching; Ar irradiation; shunting; oxygen vacancy; current retention; BiFeO3

Related publications

Publ.-Id: 19571

Hollandite-type TiO2: a new negative electrode material for sodium-ion batteries

Perez-Flores, J. C.; Baehtz, C.; Kuhna, A.; Garcia-Alvaradoa, F.

The electrochemical properties of TiO2 with the hollandite structure (TiO2(H)) as a negative electrodematerial for sodium-ion batteries are reported. TiO2(H) was obtained from hollandite K0.21TiO2 by an oxidation–ion extraction process. Na/TiO2(H) cells exhibit a large first discharge capacity of 280 mA h g1 down to 0.2 V. After the first discharge the Na/TiO2(H) cells develop a reversible charge–discharge capacity of 85 mA h g1 at C/8 rate in the 2.5–0.2 V voltage range; this corresponds to the reversible insertion of 0.25 Na per TiO2(H) formula unit. Chronoamperometry and potentiostatic intermittent titration techniques were used to further characterize the electrochemical reaction mechanism. Structural changes in the TiO2(H) electrode upon sodium insertion and extraction have been studied by ex situ XRD and high resolution in situ synchrotron diffraction techniques, for which appropriately modified coin-type cells were used. It is seen that sodium insertion into TiO2(H) is commenced with a single-phase solid solution followed by a structural transition from tetragonal I4/m to monoclinic I2/m symmetry, in which the skeleton framework is retained. The reversible transition includes few structural changes with a small volume change of only 1.1%. Fourier difference maps deduced from SXRD patterns revealed the location of Na ions in 4i sites in the tunnel space. The coordination arrangement around Na ions is distorted capped trigonal prisms formed by seven oxygen atoms. Although still far from the theoretical capacity (335 mA h g1), the cycling properties at a low insertion potential together with the host framework stability indicate the feasibility of TiO2 with the hollandite structure as a negative electrode material for Na-ion batteries.

Keywords: sodium-ion batterie; in-situ XRD; hollandite

Related publications

Publ.-Id: 19570

Unusual crystallization behavior in Ga-Sb phase change alloys

Putero, M.; Coulet, M.-V.; Ouled-Khachroum, T.; Muller, C.; Baehtz, C.; Raoux, S.

Combined in situ X-ray scattering techniques using synchrotron radiation were applied to investigate the crystallization behavior of Sb-rich Ga-Sb alloys. Measurements of the sheet resistance during heating indicated a reduced crystallization temperature with increased Sb content, which was confirmed by in situ X-ray diffraction. The electrical contrast increased with increasing Sb content and the resistivities in both the amorphous and crystalline phases decreased. It was found that by tuning the composition between Ga:Sb = 9:91 (in at.%) and Ga:Sb = 45:55, the change in mass density upon crystallization changes from an increase in mass density which is typical for most phase change materials to a decrease in mass density. At the composition of Ga:Sb = 30:70, no mass density change is observed which should be very beneficial for phase change random access memory (PCRAM) applications where a change in mass density during cycling is assumed to cause void formation and PCRAM device failure.

Keywords: PCRAM; XRD; XRR; phase change material

Related publications

Publ.-Id: 19569

Phase transition in stoichiometric GaSb thin films: Anomalous density change and phase segregation

Putero, M.; Coulet, M.-V.; Ouled-Khachroum, T.; Muller, C.; Baehtz, C.; Raoux, S.

The crystallization of stoichiometric GaSb thin films was studied by combined in situ synchrotron techniques and static laser testing. It is demonstrated that upon crystallization, GaSb thin films exhibit an unusual behaviour with increasing thickness and concomitant decreasing mass density while its electrical resistance drops as commonly observed in phase change materials. Furthermore, beyond GaSb amorphous-to-crystalline phase transition, an elemental segregation and a separate crystallization of a pure Sb phase is evidenced.

Keywords: PCRAM; XRD; XRR; synchrotron

Related publications

Publ.-Id: 19568

Observing Graphene Grow: Catalyst−Graphene Interactions during Scalable Graphene Growth on Polycrystalline Copper

Kidambi, P. R.; Bayer, B. C.; Blume, R.; Wang, Z.-J.; Baehtz, C.; Weatherup, R. S.; Willinger, M.-G.; Schloegl, R.; Hofmann, S.

Complementary in situ X-ray photoelectron spectroscopy (XPS), X-ray diffractometry, and environmental scanning electron microscopy are used to fingerprint the entire graphene chemical vapor deposition process on technologically important polycrystalline Cu catalysts to address the current lack of understanding of the underlying fundamental growth mechanisms and catalyst interactions. Graphene forms directly on metallic Cu during the high-temperature hydrocarbon exposure, whereby an upshift in the binding energies of the corresponding C1s XPS core level signatures is indicative of coupling between the Cu catalyst and the growing graphene. Minor carbon uptake into Cu can under certain conditions manifest itself as carbon precipitation upon cooling. Postgrowth, ambient air exposure even at room temperature decouples the graphene from Cu by (reversible) oxygen intercalation. The importance of these dynamic interactions is discussed for graphene growth, processing, and device integration.

Keywords: Graphene; chemical vapor deposition (CVD); polycrystalline copper (Cu); in situ X-ray photoelectron spectroscopy; in situ X-ray diffractometry; environmental scanning electron microscopy; intercalation

Related publications

Publ.-Id: 19567

Introducing Carbon Diffusion Barriers for Uniform, High-Quality Graphene Growth from Solid Sources

Weatherup, R. S.; Baehtz, C.; Dlubak, B.; Bayer, B. C.; Kidambi, P. R.; Blume, R.; Schloegl, R.; Hofmann, S.

Carbon diffusion barriers are introduced as a general and simple method to prevent premature carbon dissolution and thereby to significantly improve graphene formation from the catalytic transformation of solid carbon sources. A thin Al2O3 barrier inserted into an amorphous-C/Ni bilayer stack is demonstrated to enable growth of uniform monolayer graphene at 600 °C with domain sizes exceeding 50 μm, and an average Raman D/G ratio of <0.07. A detailed growth rationale is established via in situ measurements, relevant to solid-state growth of a wide range of layered materials, as well as layer-by-layer control in these systems.

Keywords: Graphene; solid carbon; low temperature; diffusion barrier; in situ; XPS; XRD

Related publications

Publ.-Id: 19566

Interlaboratory study of the ion source memory effect in 36Cl accelerator mass spectrometry

Pavetich, S.; Akhmadaliev, S.; Arnold, M.; Aumaître, G.; Bourlès, D.; Buchriegler, J.; Golser, R.; Keddadouche, K.; Martschini, M.; Merchel, S.; Rugel, G.; Steier, P.

Understanding and minimization of contaminations in the ion source due to cross-contamination and long-term memory effect is one of the key issues for accurate accelerator mass spectrometry (AMS) measurements of volatile elements. The focus of this work is on the investigation of the long-term memory effect for the volatile element chlorine, and the minimization of this effect in the ion source of the Dresden accelerator mass spectrometry facility (DREAMS). For this purpose, one of the two original HVE ion sources at the DREAMS facility was modified, allowing the use of larger sample holders having individual target apertures. Additionally, a more open geometry was used to improve the vacuum level. To evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison had been initiated. The long-term memory effect of the four Cs sputter ion sources at DREAMS (two sources: original and modified), ASTER (Accélérateur pour les Sciences de la Terre, Environnement, Risques) and VERA (Vienna Environmental Research Accelerator) had been investigated by measuring samples of natural 35Cl/37Cl-ratio and samples highly-enriched in 35Cl (35Cl/37Cl ~1000). Besides investigating and comparing the individual levels of long-term memory, recovery time constants could be calculated. The tests show that all four sources suffer from long-term memory, but the modified DREAMS ion source showed the lowest level of contamination. The recovery times of the four ion sources were widely spread between 60 – 1390 s, where the modified DREAMS ion source with values between 155 – 260 s showed the fastest recovery in 80% of the measurements.

Keywords: Accelerator Mass Spectrometry (AMS); volatile elements; chlorine; negative ion sputter sources; long-term memory effect; interlaboratory comparison

Related publications

Publ.-Id: 19565

Performance of the modied DREAMS ion source for 36Cl applications

Pavetich, S.; Akhmadaliev, S.; Merchel, S.; Rugel, G.; Ziegenrücker, R.

First analyses of real 36Cl-AMS samples were performed with the newly developed low memory-eect ion source at the DREsden Accelerator Mass Spectrometry (DREAMS) facility [1, 2]. Considerable improvements have been reached with respect to the overall ion source performance. Especially, parameters like current output, ion source fractionation eects, normalization factors, blank values and sulphur suppression factors have been investigated to enhance accuracy of 36Cl data.
Applications cover a wide spectrum, which implies also highly variable 36Cl/35+37Cl-ratios ranging from nearly background level of ~10-15 up to 10-10. Samples from aquifers in arid regions for groundwater dating and modelling were analysed. Meteorite samples were measured to investigate the constancy of the galactic cosmic radiation, production rates from sulphur, and reconstruction of exposure histories of individual meteorites.
Acknowledgements: C. Wilske, B. Merkel (TUBAF), T. Müller (UFZ), U. Ott (MPI Mainz), T. Smith (U Bern), G. Domenech i Surinyach (U Barcelona), DREAMS-Operators.
[1] S. Pavetich et al., NIMB, submitted.
[2] Sh. Akhmadaliev et al., NIMB 294 (2013) 5.

Keywords: accelerator mass spectrometry; chlorine; sputter negative ion sources; meteorites; groundwater dating

Related publications

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 19563

Anisotropy of Hydrogen Diffusivity in ZnO

Čížek, J.; Lukáč, F.; Vlček, M.; Vlach, M.; Procházka, I.; Traeger, F.; Rogalla, D.; Becker, H.-W.; Anwand, W.; Brauer, G.; Wagner, S.; Uchida, H.; Pundt, A.; Bähtz, C.

Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a subsurface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the subsurface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.

Keywords: zinc oxide; hydrogen; nuclear reaction analysis; electrical resistivity; X-ray diffraction

Related publications

Publ.-Id: 19562

Development of a general coupling interface for the fuel performance code TRANSURANUS tested with the reactor dynamics code DYN3D

Holt, L.; Rohde, U.; Seidl, M.; Schubert, A.; van Uffelen, P.

A general interface is presented for coupling the TRANSURANUS fuel performance code with thermal hydraulics system codes, sub-channel codes or reactor dynamics codes. Beside its generality, other main characteristics of this interface are the calculation at either fuel assembly or fuel rod level, one-way or two-way coupling, automatic switch from steady to transient conditions in TRANSURANUS (including update of the material properties etc.), writing of all TRANSURANUS output files and manual pre- and post-calculations with TRANSURANUS in standalone mode. The TRANSURANUS code can be used in combination with this coupling interface in various scenarios: different fuel compositions in the reactor types BWR, PWR, VVER, HWR and FBR, time scales from milliseconds (i.e. RIA) over seconds/ minutes (i.e. LOCA) to years (i.e. normal operation) and thence different reactor states.

As first application of the interface the reactor dynamics code DYN3D was coupled in order to analyze the impact of a more detailed description of the fuel rod behavior during system transients. More precisely, the influence of the high burn-up structure formation, geometry changes and fission gas release are included. In the coupling, DYN3D provides only the time-dependent rod power and thermal hydraulics conditions to TRANSURANUS, which in turn transfers parameters like fuel temperature and cladding temperature back to DYN3D. Results of the coupled code system are presented for a control rod ejection transient in a German PWR, along with a sensitivity study for the full core. The results reveal that the detailed fuel rod behavior modeling influences the neutron kinetics in the core due to the Doppler reactivity effect of the fuel temperature. In particular it appears that for high burn-up fuel DYN3D-TRANSURANUS systematically calculates higher value for the node centerline fuel temperature compared to DYN3D standalone. The main reasons of the differences seem to be the UO2 material properties (e.g. thermal conductivity), and the radial power density profile over the fuel pellet radius.

Furthermore results of the DYN3D-TRANSURANUS code system are shown for the planed RIA experiment CIP3-1 in the CABRI water loop facility in France. The experimental data including time-dependent rod power was taken from the recent RIA fuel codes benchmark organized by the OECD/NEA. DNB is predicted by calculations under the typically PWR coolant conditions in CIP3-1.

No convergence problems occurred for DYN3D-TRANSURANUS. The coupled code system can improve the assessment of safety criteria, at a reasonable computational cost since it rises on average only by a factor 4 on the same workstation for RIA (determined from reaching the initial state of the transient), when compared to the DYN3D code standalone.

Publ.-Id: 19560

Two-way Coupling between the Reactor Dynamics Code DYN3D and the Fuel Performance Code TRANSURANUS at Assembly Level

Holt, L.; Rohde, U.; Seidl, M.; Schubert, A.; van Uffelen, P.; Macián-Juan, R.

In the last two decades the reactor dynamics code DYN3D was coupled to thermal hydraulics codes, sub-channel code and CFD codes. These earlier developed code systems allow modelling of the phenomena in higher degree of detail. Nevertheless all of them contain a simplified fuel behaviour model, i.e. without taking into account the fission gas release during normal operation, off-normal conditions and transient. Furthermore, no two-way coupling to a fuel performance code has so far been reported in the open literature for calculating a full core with detailed and well validated fuel behaviour correlations.

A new two-way coupling approach between DYN3D and the fuel performance code TRANSURANUS is presented. In the coupling, DYN3D provides only the time-dependent rod power and thermal hydraulics conditions to TRANSURANUS, which in turn transfers parameters like fuel temperature and cladding temperature back to DYN3D. The main part of the development is a so-called general TRANSURANUS coupling interface that is applicable for other reactor dynamics codes, thermal hydraulics codes and sub-channel codes. Beside its generality, other characteristics of this interface are the calculation at either fuel assembly or fuel rod level, one-way or two-way coupling, automatic switch from steady to transient conditions in TRANSURANUS (including update of the material properties etc.), writing of all TRANSURANUS output files and manual pre- and post-calculations with TRANSURANUS in standalone mode. The TRANSURANUS code can be used in combination with this coupling interface in various scenarios: different fuel compositions in the reactor types BWR, PWR, VVER, HWR and FBR, time scales from milliseconds (i.e. RIA) over seconds/ minutes (i.e. LOCA) to years (i.e. normal operation) and thence different reactor states.

Results of DYN3D-TRANSURANUS are shown for a control rod ejection transient in a UO2 core of a German PWR. In particular it appears that for all burn-up levels DYN3D-TRANSURANUS systematically calculates higher values for the node fuel enthalpy (max. difference of 46 J/g) and node centerline fuel temperature (max. difference of 180 K) compared to DYN3D standalone in best estimate calculations. These differences can be completely explained by the more detailed TRANSURANUS modelling of fuel thermal conductivity, radial heat release profile and heat transfer in the gap. As known from fuel performance codes, the modelling of the heat transfer in the gap is sensitive and causes also larger differences in case of low burn-up.

No convergence problems occurred for DYN3D-TRANSURANUS. The coupled code system can improve the assessment of safety criteria, at a reasonable computational cost with a running time of less than six hours without parallelization.

  • Contribution to proceedings
    22nd International Conference on Nuclear Engineering (ICONE 2014), 07.-11.07.2014, Prague, Czech Republic

Publ.-Id: 19559

Completeness of DYN3D Coupling Approaches by the European Fuel Performance Code TRANSURANUS – Full Core Analysis for a Reactivity Initiated Accident (vorläufiger Titel)

Holt, L.

Es handelt sich um ein Compact.

  • Lecture (Conference)
    45th Annual Meeting on Nuclear Technology (Workshop Preserving Competence), 06.-08.05.2014, Frankfurt, Germany

Publ.-Id: 19558

Volatilisation of Lead by Using Chlorination Agent Magnesium Chloride

Scharf, C.; Lenzen, P.; Ditze, A.

Zinc- and lead-containing waste materials such as steel mill electric arc furnace dust are mainly processed by the Waelz process (volatilisation under reducing conditions). Especially, the addition of carbon as reducing agent to the initial mixture contributes to the desired reaction kinetics and progress. However, the removal of the element lead is not completely. It remains partly as water-soluble compounds in the Waelz slag in the order of magnitude of 3 mass % which prevents the use in road construction. Starting from the idea lead can be volatilised by using an additional chlorinating agent like magnesium chloride first principle investigations are made. Therefore the pure model substances PbO, MgCl2 and C are used. The formation and volatilisation of PbCl2 is assumed, because of its high vapor pressure. Favorable thermodynamic conditions exist in particular for MgCl2 as chlorinating agent. It should therefore be clarified how far PbO reacts with MgCl2 - also in the presence of C - to PbCl2 in a temperature range of 800 to 1000 °C. First experiments show promising results, not only for the pure substances but also for electric arc furnace dust.

Keywords: Lead; Lead chloride; Magnesium chloride; Recycling; Vapor pressure; Volatilisation

  • Open Access Logo Contribution to proceedings
    European Metallurgical Conference 2011, 26.-29.06.2011, Düsseldorf, Germany
    Proceeding of EMC 2011, 978-3-940276-37-7, 505-518

Publ.-Id: 19557

Recycling von Magnesium

Scharf, C.; Ditze, A.

Obwohl Magnesium das achthäufigste Element der Erde ist und die Rohstoffe für seine Gewinnung als reines Metall fast unbegrenzt verfügbar sind, ist seine Herstellung sehr energieintensiv. Dieses vor allem wegen der großen Bindungsaffinität zu Sauerstoff und Chlor. Folglich besitzt das Recycling [1] eine hohe Bedeutsamkeit, da der Metallschrott bereits den Energieinhalt der Reduktion zum Metall innehat.

  • Open Access Logo Book chapter
    K.J.Thomè-Kozmiensky, D.Goldmann: Recycling und Rohstoffe - Band 4, Berlin: TK Verlag Karl Thomè-Kozmiensky, 2011, 978-3-935317-67-2, 215-234

Publ.-Id: 19556

Fundamentals of Chlorination of Lead Oxide Using Magnesium Chloride

Scharf, C.; Ditze, A.

Zinc-and lead-containing waste materials such as steel mill electric arc furnace dust are mainly processed by the Waelz process (volatilisation of zinc under reducing conditions). However, the removal of the element lead is not completely. It remains partly as water-soluble compounds in the Waelz slag in the order of magnitude of 3 mass-% which prevents the use in road construction. - Starting from the idea lead can be volatilised by using an additional chlorinating agent like magnesium chloride first principle investigations with pure model substances PbO and MgCl 2 were made. Thereby, the formation and volatilisation of PbCl 2 is assumed, because of its high vapor pressure. Besides the favorable thermodynamic conditions using MgCl 2 as chlorinating agent the reaction kinetics are of special interest. Volatilisation experiments in the temperature range of 800 °C to 1000 °C showed promising results.

Keywords: Kinetics; Lead; Lead chloride; Magnesium chloride; Recycling; Vapor pressure; Volatilisation; Waelz process

  • Open Access Logo Worl of Metallurgy - ERZMETALL 64(2011)4, 205-209

Publ.-Id: 19555

Removal of nickel from magnesium melts by precipitation with zirconium

Ditze, A.; Scharf, C.

Magnesium scrap is often contaminated with nickel, copper and iron. Especially nickel is detrimental in regard to the corrosion properties of magnesium. Ways have to be found for the removal of nickel from magnesium to initiate actually the recycling of post consumer scrap. Experiments at 660, 720 and 770°C comprise the determination of the solubilities of nickel and zirconium in magnesium and the identification of the precipitates. Based on this, equlibrium constants and interaction parameters were calculated. These values enable the estimation of the necessary zirconium addition for the removal of nickel by precipitation to low contents in liquid magnesium.

  • Open Access Logo Contribution to proceedings
    9th International Conference on magnesium alloys and their applications, 08.-12.07.2012, Vancouver, Canada
    Proceedings of the 9th International Conference on magnesium alloys and their applications, 889-894

Publ.-Id: 19554

Presentation of patented secondary magnesium alloy – Subsequent basic research: Investigation of influence of dendritic microstructure on corrosion properties.

Scharf, C.; Lakoma, P.; Ditze, A.

As first step in the past a patented secondary magnesium alloy AZC1231 (Aluminium = 12mass.-%, Zinc = 3mass.-% and Cu = up to 1 mass.-%) was developed to close the loop of magnesium material flow. The impurity tolerant AZC1231 was tested in a real die casting process to prove feasibility resulting in navigation device housing. Corrosion properties show interesting effects because the noble copper was disposed by copper solving and copper encircling phases. The influence of the microstructure plays therefor a very important role. A new basic research project was started to investigate dendritic microstructure regarding grain size, dendrite formation, eutectic refinement and distribution of Mg17Al12(β)-phase of magnesium alloys with aluminium contents from 0 to 12 mass.-%. The aim is evaluation of secondary dendrite arm spacings at defined cooling conditions which are responsible for a columnar or equiaxed macrostructure containing dendritic microstructure. Subsequent corresponding corrosion behaviour has to be examined by immersion testing method.

Keywords: secondary magnesium alloy; AZC1231; corrosion properties; microstructure; secondary dendrite arm spacing

  • Contribution to proceedings
    International Conference "Recycling of Non-Ferrous Metals", 06.-08.02.2013, Krakow, Poland
    International Conference "Recycling of Non-Ferrous Metals"

Publ.-Id: 19553

Interaction between Nickel and Zirconium in liquid Magnesium

Ditze, A.; Scharf, C.

Magnesium scrap is often contaminated with nickel, copper and iron. Especially nickel is detrimental in regard to the corrosion properties of magnesium. Ways have to be found for the removal of nickel from magnesium to initiate actually the recycling of post consumer scrap. Experiments at 660,720 and 770 °C comprise the determination of the solubilities of nickel and zirconium in magnesium and the identification of the precipitates. Based on this, equilibrium constants and interaction parameters were calculated. These values enable the estimation of the necessary zirconium addition for the removal of nickel by precipitation to low contents in liquid magnesium.

Keywords: Activity; Activity coefficient; Equilibrium constant; Gibbs free energy; Interaction parameter; Intermetallic phases; Magnesium; Nickel; Refining; Zirconium

  • Open Access Logo Worl of Metallurgy - ERZMETALL 66(2013)3, 168-174

Publ.-Id: 19552

SHI induced enhancement in green emission from nanocrystalline CdS thin films for photonic applications

Kumar, P.; Saxena, N.; Chandra, R.; Gao, K.; Zhou, S.; Agarwal, A.; Singh, F.; Gupta, V.; Kanjilal, D.

Intense green emission is reported from nanocrystalline CdS thin films grown by pulsed laser deposition. The effect of ion beam induced dense electronic excitation on luminescence property of CdS films is explored under irradiation using 70 MeV 58Ni6+ ions. It is found that swift heavy ion beam irradiation enhances the emission intensity by an order of 1 and broadens the emission range. This feature is extremely useful to enhance the performance of different photonic devices like light emitting diodes and lasers, as well as luminescence based sensors. To examine the role of energy relaxation process of swift heavy ions in creation/annihilation of different defect levels, multi-peaks are fitted in photoluminescence spectra using a Gaussian function. The variation of contribution of different emissions in green emission with ion fluence is studied. Origin of enhancement in green emission is supported by various characterization techniques like UV-visible absorption spectroscopy, glancing angle X-ray diffraction, micro-Raman spectroscopy and transmission electron microscopy. A possible mechanism of enhanced GE due to ion beam irradiation is proposed on the basis of existing models.

Keywords: Ion beam irradiation; Nanocrystalline CdS thin films; Photoluminescence; Pulsed laser deposition

Publ.-Id: 19551

Preclinical dose assessment and biodistribution of [F-18]DBT-10, a new α7 nicotinic acetylcholine receptor (α7-nAChR) imaging ligand.

Kranz, M.; Sattler, B.; Deuther-Conrad, W.; Teodoro, R.; Donat, C. K.; Wenzel, B.; Scheunemann, M.; Patt, M.; Sabri, O.; Brust, P.

Objectives :

In vivo imaging of α7-nAChR provide important information for CNS disorders such as schizophrenia, Alzheimer disease, brain tumors etc. Due to the lack of suitable radiotracers a new structure, DBT-10 (Ki=0.3nM), was developed for brain imaging. To assess the radiation risk to humans after i.v. injection the biodistribution, organ doses (OD) and the effective dose (ED) were determined in mice (M) and piglets (P).

Methods :

Image based (M: Mediso nanoScan PET/MRI, P: SIEMENS Biograph16 PET/CT) whole body dosimetry was performed in 3 female M (age: 11 w, weight: 27.8 g) and 3 female P (age: 7 w, weight: 15.8 kg). The anesthetized animals were PET-imaged up to 5h post i.v. injection of 13.1 MBq, 165.5 MBq [18]DBT-10, followed by iterative reconstruction including MR- or CT-based attenuation correction respectively. The organs were defined by volumes of interest. Exponential curves were fitted to the time-activity-data (%ID/g). Time and mass were adapted to the human scale. The ODs were calculated using OLINDA and the ED using tissue weighting factors (ICRP103).


Following the i.v. injection of [18]DBT-10 no adverse effects on the basis of vital function monitoring were observed. The highest OD [µSv/MBq] was received in M by pancreas (35.5) and urinary bladder (30.0), in P by pancreas (60.8) and spleen (58.8). The highest contribution to ED [µSv/MBq] was in M by red marrow (2.4) and lungs (1.5), in P by liver (2.0) and lungs (1.9). The estimated ED [µSv/MBq] to humans is 12.7 (M), 13.7 (P).

Conclusions :

Considering an underestimation of 40% in preclinical dosimetry, the radiation risk, to humans (M: 6.4 mSv/300MBq, P: 6.8 mSv/300MBq) is well within the range of other F-18 labeled radiotracers. These results encourage to transfer [18]DBT-10 to the clinical study phase and further develop it as a clinical tool for imaging of α7-nAChR.


[1] M.Schrimpf, K. Sippy, C. Briggs et al., SAR of α7 nicotinic receptor agonists derived from tilorone: Exploration of a novel nicotinic pharmacophore, Bioorganic & Medicinal Chemistry Letters, Volume 22, Issue 4, 15 February 2012, Pages 1633-1638, ISSN 0960-894X.

[2] B. Sattler, M. Kranz, M. Patt et al. Incorporation dosimetry of F-18-Flubatine - Comparison of animal model data with first-in-man results. Journal of Nuclear Medicine 2012; 53(suppl): 1503.

  • Poster
    SNMMI 2014 Annual Meeting, 07.-11.06.2014, St. Louis, Missouri, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 55(2014)1, 1143

Publ.-Id: 19550

Synthesis and F-18 labeling of a 2-fluoro dibenzothiophene sulfone derivative, as a potential alpha-7 nicotinic acetylcholine receptor (α7 nAChR) imaging agent

Scheunemann, M.; Teodoro, R.; Wenzel, B.; Kranz, M.; Deuther-Conrad, W.; Brust, P.


The homopentameric α7 nAChR is proposed to be implicated in the pathophysiology of various diseases, e.g. schizophrenia, Alzheimer disease and tumors. Due to a relatively low concentration of α7 subtype binding sites in brain an appropriate PET radiotracer for quantitative molecular imaging requires a sufficiently high receptor affinity. Based upon a novel pharmacophoric lead structure (1) consisting of a diazabicyclononane as amine scaffold, connected to a tricyclic aromatic moiety we developed DBT-10, as potential PET radiotracer for imaging α7 nAChR in brain.


DBT-10 was prepared in four steps from 2-nitro-dibenzothiophene in 31% overall yield. Binding affinity for α7 nAChRs was evaluated in vitro by competitive inhibition experiments using H-3 methyllycaconitine. The radiotracer was synthesized by nucleophilic F-18 fluoro-for-nitro aromatic substitution. Animal PET/MR was performed to investigate the radiotracer kinetics in brain.


A preliminary α7 nAChR affinity of Ki=0.67±0.36 nM (n=4) was determined for DBT-10. For F-18 labeling, 0.5-1.4 mg of NO2-precursor was converted in the presence of F-18 fluoride, K222/K2CO3 in DMF for 10 min at 140°C with 67-87% labeling yield. F-18 DBT-10 was obtained after purification (30% ACN, H2O, 0.05% TFA, isocratic on Reprosil-Pur AQ 250x10 mm) in 99% RCP and identified by HPLC coinjection of DBT-10. Animal PET/MR revealed fast kinetics of F-18 DBT-10 in mice brain with SUVmax ~1.5 at 3´ p.i.


The 2-fluoro-dibenzothiophene based DBT-10 was readily prepared and radiolabeled (2). Product F-18 DBT-10 displayed a marked brain uptake in mice and about four-fold higher affinity than our previous α7 nAChR-selective radiotracers suggesting improved suitability for PET imaging.
(1) Schrimpf M. et al. Bioorg. Med. Chem. Lett. 2012, 22, 1633-38; (2) Concurrent to our work a recent paper describes two PET tracers based on the same pharmaceutical lead: Gao et al. J. Med. Chem. 2013, 56, 7574-89.

  • Lecture (Conference)
    NuklearMedizin2014, 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A26
    ISSN: 0029-5566


Publ.-Id: 19549

Präklinisches PET/MRT – Eine potentielle Methode zur Abschätzung der Strahlenexposition des Menschen durch neue Radioliganden

Kranz, M.; Sattler, B.; Patt, M.; Donat, C. K.; Deuther-Conrad, W.; Hiller, A.; Smits, R.; Hoepping, A.; Sattler, T.; Sabri, O.; Steinbach, J.; Brust, P.

Bildbasierte Dosimetrie mittels präklinischer hybrider PET Systeme ermöglicht die Abschätzung der Strahlenexposition durch neue Radiopharmazeutika für die Anwendung am Menschen. Bisherige Untersuchungen beschränken sich auf Kombinationen mit CT. Zur Evaluierung eines neuen präklinischen PET/MRT-Systems stellen wir an Mäusen erhobene Daten mit an Ferkeln (PET/CT) erhobenen Daten und einer post mortem Aktivitätsverteilung in Organen (AV) an Mäusen, nach Injektion von [18F]Flubatine, gegenüber.

Die Messung der kumulierten Organaktivität (OA) erfolgte an einem präklinischen PET/MRT (nanoScan®, Mediso) bzw. PET/CT (Biograph 16, Siemens). Es wurden 3 narkotisierte CD1 Mäuse (12 Wochen, 30g) bzw. 3 Ferkel (43 Tage, 14kg) bis zu 4 h nach i.v. Injektion von [18F]Flubatine dynamisch untersucht. Die Definition von Volumes of Interest erlaubte die Bestimmung der OA. Die AV von [18F]Flubatine in 27 CD1 Mäusen wurde mittels Sektion und Messung im γ-Counter bestimmt. Die Zeit-Aktivitäts Daten wurden auf die Verhältnisse im Menschen skaliert und durch exponentielle Anpassung dargestellt. Die Berechnung der Organdosis (OD) erfolgte mit OLINDA, die der effektiven Dosis (ED) nach ICRP 103.

Mit PET/MRT wurde die höchste OD (μSv/MBq) in den Nieren (47,5±2.0) und der Blase (33,4±0.06) berechnet, während der größte Beitrag zur ED (μSv/MBq) im Magen (1,8±0.1) sowie der Lunge (1,7±0.7) vorliegt. Die ED nach Injektion von [18F]Flubatine ist 12,1±0.7 und nahezu identisch mit dem Ergebnis der in vitro gewonnenen AV (12,5). Die ED beim Ferkelversuch mit PET/CT lag bei 14,3±0.7.

Am Beispiel von [18F]Flubatine wurde gezeigt, dass es mit dem präklinischen PET/MRT-System möglich ist, eine Abschätzung der ED für den Menschen vorzunehmen. Die Untersuchung weiterer Radiotracer ist erforderlich, um diese Aussage zu erhärten. Die Studie bestätigt frühere Ergebnisse, nach denen die präklinische Inkorporationsdosimetrie die ED für den Menschen unterschätzt.

  • Lecture (Conference)
    NuklearMedizin2014, 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A69
    ISSN: 0029-5566


Publ.-Id: 19548

Thyrogener Einfluss auf die Aktivierung braunen Fettgewebes (BAT) bei Mäusen

Zeisig, V.; Kranz, M.; Krause, K.; Steinhoff, K.; Tönjes, A.; Deuther-Conrad, W.; Fasshauer, M.; Brust, P.; Sabri, O.; Hesse, S.


Braunes Fettgewebe (BAT) hat eine essentielle Funktion in der Wärmeregulation und im Energiehaushalt. Seine Aktivierung erfolgt über β3-adrenerge Rezeptoren, die auf zellulärer Ebene eine vermehrte Konversion von T4 in T3 bewirkt und hierüber die mitochondriale Wärmeerzeugung stimuliert. Eine direkte thyrogene BAT-Aktivierung wurde jedoch bislang nicht gezeigt. Ziel unserer Untersuchung war es daher, den direkten Einfluss peripherer Schilddrüsenhormone auf eine BAT-Aktivierung nachzuweisen.


Es wurden jeweils 3 hyper-, hypo- und euthyreote Black 6-Mäuse mit F-18-FDG im Kleintier PET/MRT (nanoScan®, Mediso) untersucht (i.p-Injektion; ID:15 MBq; Raumtemperatur). Die Tracerapplikation erfolgte intraperitoneal. Mittels MR-basierter VOI-Analyse (PMOD vers. 3.3) typischer Regionen von braunem Fettgewebe (nuchal) wurde die Glukoseaufnahme (SUVmean) bestimmt, um Rückschlüsse auf eine mögliche BAT-Aktivierung ziehen zu können.


Im SUVmean-Vergleich zeigten die hyperthyreoten Tiere eine bereits visuell erfassbare, FDG-Mehranreicherung gegenüber der euthyreoten Kontrollgruppe (8,61±2,05 vs 6,04±0,52; p=0,16; MV±SD) in den untersuchten Körperregionen. In den hypothyreoten Mäusen konnte ein verminderter FDG-Uptake beobachtet werden (SUVmean=3,2±0,04; p<0,002; MV±SD).


Unsere Ergebnisse bestätigen einen thyrogenen Einfluss auf die murine BAT-Aktivität. Es konnte gezeigt werden, dass eine Hypothyreose eine verminderte BAT-Aktivierung bewirkt, eine Hyperthyreose eine BAT-Stimulierung zur Folge hat. Inwieweit sich diese Ergebnisse auch im Menschen nachweisen lassen, soll gegenwärtig eine prospektive Studie zeigen.

  • Lecture (Conference)
    NuklearMedizin2014, 52. Jahrestagung der DGN, 26.-29.03.2014, Hannover, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 53(2014)A61

Publ.-Id: 19547

Formation and structure of polynuclear actinide(IV) carboxylates in aqueous solution

Hennig, C.

Polyanuclear An(IV) carboxylate complex were identified in aqueous solution. The related complex species were preserved in crystals and their structures were determined. The structural identity of the species in solution and in solid state was tested by EXAFS spectroscopy.

Keywords: actinides; carboxylates; EXAFS; XRD

Related publications

  • Invited lecture (Conferences)
    Laboratoire des Interactions Ligand-Actinide / CEA Marcoule, 19.12.2013, Marcoule, France

Publ.-Id: 19546

Processing of agglomerated red filter dust in the converter operation from metallurgical point of view

Scharf, C.; Ditze, A.

Red filter dust (RFD) from steel works contains up to 50 mass% iron, which therefore can serve as raw material for steel production. It should be possible to recycle a fraction of the RFD in the converter process of a steel works wherein also scrap for recycling is used. The aim was the investigation of the reduction behavior of the iron oxide in the RFD. This was accomplished by contact of the dust with pig iron containing up to 3.9 mass% carbon and also by addition of bio‐char to the dust, creating self‐reducing briquettes. The experimental results were compared to the theoretical achievable iron oxide reduction. The reaction time of selected briquettes was calculated by a kinetic approach. Additional the behavior of lead and zinc in the dust was investigated. The mass balance of the converter process indicated the influence of the dust recycling especially regarding the zinc mass flow.

Publ.-Id: 19545

Gas-Liquid distribution in tubular reactors with solid foam packings

Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.

The axial evolution of gas-liquid distribution patterns in co-current downward gas-liquid two-phase flow through solid foam packings of different pore density expressed by pores per inch was experimentally studied. The experimental results are based on time-averaged capacitance measurements of the liquid phase with embedded wire-mesh sensors, positioned at different axial heights of the solid foam packing. The measurements revealed the spatial distribution of the liquid phase saturation, which was applied to quantify the degree of liquid maldistribution. Both the spray nozzle and the multipoint distributor provide rather uniform initial liquid distributions across the foam packings with low maldistribution factors at superficial liquid velocities above 0.009 mis. However, the uniform initial irrigation deteriorates along the foam packing length, in particular for foams with low pore density. The gas flow rate does not significantly influence the liquid distribution. Furthermore, the foam's ability to radially spread the liquid phase in the cross-section downstream from a single drip point distributor was studied and found to be low, independent from the pore density.

Publ.-Id: 19544

Archaeometallurgical studies of bronze age objects from the romanian cultural heritage

Bugoi, R.; Constantinescu, B.; Popescu, A. D.; Munnik, F.

This paper reports the chemical composition of some ancient metallic objects dated to the Bronze Age period and found on Romanian territory.Preliminary ED-XRF measurements were performed on cleaned areas of artefacts, while the nuclear microprobe experiments were conducted on tiny fragments detached from the same zones. The identified trace-elements led to some speculations about the employed metallurgical procedures and raw materials. Thus, the chemical composition of the Early Bronze Age dagger found at Ocniţa suggests its manufacturing by smelting a mixture of copper and arsenic ores, while the Late Bronze Age artefacts have compositional patterns supporting the idea of connections and exchanges between the ancient populations living along the Danube river.

Keywords: PIXE; archaeometallurgy; chemical composition; bronze; arsenical copper; Bronze Age

Related publications

  • Open Access Logo Romanian Reports in Physics 65(2013)4, 1234-1245

Publ.-Id: 19543

Evaluation of Large 3600MWth Sodium-Cooled Fast Reactor Neutronic OECD Benchmarks

Buiron, L.; Rimpault, G.; Fontaine, B.; Fridman, E.; Keresztúri, A.; Pataki, I.; Kugo, K.; Sugino, K.; Uematsu, M. M.; Yamaji, A.; Gulliford, J.; Kim, T. K.; Stauff, N. E.; Taiwo, T. A.; Lin Tan, R.; Kozlowski, T.; Parisi, C.; Ponomarev, A.

In the frame of the Working Party on Reactor and System (WPRS), an international mandate has been proposed to work towards a shared neutronic analysis of several Generation-IV Sodium-cooled Fast Reactor (SFR) concepts. This paper summarizes the results obtained for large cores benchmark by participants from numerous institutes of different countries (ANL, CEA, ENEA, HZDR, JAEA, KFKI, KIT, UIUC). This paper gathers results using different calculation methods and systems to estimate the core reactivity and isotopic composition evolution, neutronic feedbacks and power distribution. For the different core concepts analyzed, a satisfactory agreement between participants was obtained despite the different schemes of calculation used. A good agreement is generally obtained when comparing compositions after burnup, the delayed neutron fraction, the Doppler coefficient, and the sodium void worth. However, some noticeable discrepancies between the k-effective values were observed and are explained in this paper. These are mostly due to the different neutronic libraries employed (JEFF3.1, ENDF/B-VII.0 or JENDL-4.0) and in a less extend calculations methods.

Keywords: 3600MWth SFR; oxide; carbide; OECD Benchmark

  • Contribution to proceedings
    PHYSOR2014, 28.09.-03.10.2014, Kyoto, Japan

Publ.-Id: 19542

Generation of One-Group Self-Shielded Cross Sections with Multi-Group Approach for Monte Carlo Burnup Codes

Kotlyar, D.; Shwageraus, E.; Fridman, E.

Allowing Monte Carlo (MC) codes to perform fuel cycle calculations requires coupling to a point depletion solver. In order to perform depletion calculations, one-group (1-g) cross sections must be provided in advance. This paper focuses on generating accurate 1-g cross section values that are necessary for evaluation of nuclide densities as a function of burnup. The proposed method is an alternative to the conventional direct reaction rate tally approach, which requires extensive computational efforts. The method presented here is based on the multi-group (MG) approach, in which pre-generated MG sets are collapsed with MC calculated flux. In our previous studies, we showed that generating accurate 1-g cross sections requires their tabulation against the background cross-section (σ0) to account for the self-shielding effect. However, in previous studies, the model that was used to calculate σ0 was simplified by fixing Bell and Dancoff factors. This work demonstrates that 1-g values calculated under the previous simplified model may not agree with the tallied values. Therefore, the original background cross section model was extended by implicitly accounting for the Dancoff and Bell factors. The method developed here reconstructs the correct value of σ0 by utilizing statistical data generated within the MC transport calculation by default. The proposed method was implemented into BGCore code system. The 1-g cross section values generated by BGCore were compared with those tallied directly from the MCNP code. Very good agreement (<0.05%) in the 1-g cross values was observed. The method does not carry any additional computational burden and it is universally applicable to the analysis of thermal as well as fast reactor systems.

Keywords: Monte Carlo; BGCore; Multi group; one-group cross sections

  • Contribution to proceedings
    PHYSOR2014, 28.09.-03.10.2014, Kyoto, Japan
    Proceedings of PHYSOR2014

Publ.-Id: 19541

Regioselective Synthesis of Trichloromethyl-Substituted Salicylates and Cyclohexenones by One-Pot Cyclizations of 1,3-Bis(trimethylsilyloxy)buta-1,3-dienes

Reimann, S.; Bunescu, A.; Petrosyana, A.; Sharif, M.; Erfle, S.; Mamat, C.; Ghochikyan, T. V.; Saghyan, A. S.; Spannenberg, A.; Villinger, A.; Langer, P.

A variety of 6-(trichloromethyl)salicylates (=2-hydroxy-6-(trichloromethyl)benzoates) were prepared by TiCl4-mediated cyclization of 1,3-bis(trimethylsilyloxy)buta-1,3-dienes with 1,1,1-trichloro-4,4-dimethoxybut-3-en-2-one. The employment of trimethylsilyl trifluoromethanesulfonate (Me3SiOTf) as Lewis acid resulted in the formation of trichloromethyl-substituted cyclohexenones. The cyclizations proceeded with good-to-very-good regioselectivities.

Publ.-Id: 19540

Towards a high field THz source operating at few 100 kHz repetition rates

Gensch, M.; Kovalev, S.; Green, B.; Bauer, C.; Kuntzsch, M.; Golz, T.; Al-Shemmary, A.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Asgekar, V.; Freitag, M.; Lehnert, U.; Teicher, J.; Justus, M.; Seidel, W.; Ilgner, C.; Winnerl, S.; Schneider, H.; Geloni, G.; Radu, I.; Kampfrath, T.; Wall, S.; Cavalleri, A.; Heberle, J.; Michel, P.; Fisher, A.; Mueller, A.-S.; Stojanovic, N.; Helm, M.; Schramm, U.; Cowan, T.

At the ELBE accelerator a unique super-radiant THz source is currently under developement. It aims at delivering fourier-limited THz pulses with pulse energies of up to 100 microJ at reprates of up to 500 kHz (cw). This corresponds to transient electric elds in the GV/m regime or transient magnetic elds in the few T regime. First results from the commissioning are discussed.

Related publications

  • Poster
    DPG Spring Meeting 2014, 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 19539

Analytical properties of the quark propagator from truncated Dyson-Schwinger equation in complex Euclidean space

Dorkin, S. M.; Kaptari, L. P.; Hilger, T.; Kämpfer, B.

In view of the mass spectrum of heavy mesons in vacuum the analytical properties of the solutions of the truncated Dyson-Schwinger equatio for the quark propagator within the rainbow approximation are analysed in some detail. In Euclidean space, the quark propagator is not an analytical function possessing, in general, an infinite number of singularities (poles) which hamper to solve the Bethe-Salpeter equation. However, for light mesons (with masses M_{q\bar q} <= 1 GeV) all singularities are located outside the region within which the Bethe-Salpeter equation is defined. With an increase of the considered meson masses this region enlarges and already at masses >= 1 GeV, the poles of propagators of u,d and s quarks fall within the integration domain of the Bethe-Salpeter equation. Nevertheless, it is established that for meson masses up to M_{q\bar q}~=3 GeV only the first, mutually complex conjugated, poles contribute to the solution. We argue that, by knowing the position of the poles and their residues, a reliable parametrisation of the quark propagators can be found and used in numerical procedures of solving the Bethe-Salpeter equation. Our analysis is directly related to the future physics programme at FAIR with respect to open charm degrees of freedom.

Publ.-Id: 19538

Baryon resonance production and dielectron decays in proton-proton collisions at 3.5 GeV

Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

We report on the investigation of baryon resonance extraction and their subsequent electromagnetic decays in proton-proton collisions at the kinetic energy of 3:5 GeV based on data measuer with HADES. The exclusive channels npπ+ and ppπ0 as well as ppe+e- are studied simultaneously for the first time. The invariant masses and angular distributions of the pion-nucleon system were studied and compared to simulations based on a resonance model ansatz assuming saturation of the pion production by an incoherent sum of baryonic resonances (R) with masses < 2 GeV/c2. A very good description of the one-pion production is achieved allowing for an estimate of individual Δ and N* production cross sections which are used to calculate the dielectron yields from R -> pe+e- decays. Two models of the resonance dielectron decays are examined assuming a point-like RNγ* coupling and the dominance of the ρ meson. The results of model calculations are compared to the data from the exclusive ppe+e- channel by means of the dielectron and pe+e- invariant mass distributions.

Publ.-Id: 19537

Residual gamma H2AX foci predict local tumour control after radiotherapy

Koch, U.; Hohne, K.; von Neubeck, C.; Thames, H. D.; Yaromina, A.; Dahm-Daphi, J.; Baumann, M.; Krause, M.

Purpose: Evaluation of micromilieu-dependent quantified gamma H2AX foci as a potential predictive biomarker in well-oxygenated tumour areas in 9 HNSCC xenograft models in vivo.

Materials & methods: GammaH2AX foci were quantified in perfused tumour areas 30 min (initial gamma H2AX foci) and 24 h (residual gamma H2AX foci) after exposure to a single dose of 4 Gy. The initial and residual normalised gamma H2AX foci were correlated with TCD50 after single dose irradiation under clamped blood flow (SDclamp) or a fractionated irradiation setting under ambient blood flow (fx).

Results: A significant negative correlation between initial and residual normalised gamma H2AX foci and TCD50 SDclamp and TCD50 fx for 9 HNSCC tumour xenograft models in vivo was found. Residual normalised gamma H2AX foci showed higher intertumoural variability and their correlation with TCD50 was more robust.

Conclusions: For the first time a significant negative correlation between gamma H2AX foci and local tumour control after irradiation has been demonstrated. Our results underline the potential of residual gamma H2AX foci as a predictive biomarker for local tumour control after radiotherapy

Keywords: gamma H2AX; Radiotherapy; DNA repair; Local tumour control; Tumour micromilieu; Biomarker

Publ.-Id: 19536

Clinical perspectives of cancer stem cell research in radiation oncology

Butof, R.; Dubrovska, A.; Baumann, M.

Radiotherapy has a proven potential to eradicate cancer stem cells which is reflected by its curative potential in many cancer types. Considerable progress has been made in identification and biological characterisation of cancer stem cells during the past years. Recent biological findings indicate significant inter- and intratumoural and functional heterogeneity of cancer stem cells and lead to more complex models which have potential implications for radiobiology and radiotherapy. Clinical evidence is emerging that biomarkers of cancer stem cells may be prognostic for the outcome of radiotherapy in some tumour entities. Perspectives of cancer stem cell based research for radiotherapy reviewed here include their radioresistance compared to the mass of non-cancer stem cells which form the bulk of all tumour cells, implications for image- and non-image based predictive bio-assays of the outcome of radiotherapy and a combination of novel systemic treatments with radiotherapy.

Keywords: Cancer stem cells; Radiation oncology; Radiobiology

Publ.-Id: 19535

Simultaneous PLK1 inhibition improves local tumour control after fractionated irradiation

Krause, M.; Kummer, B.; Deparade, A.; Eicheler, W.; Pfitzmann, D.; Yaromina, A.; Kunz-Schughart, L. A.; Baumann, M.

Purpose: Polo-like kinase 1 (PLK1) plays an important role in mitotic progression, is frequently overexpressed and associated with a poor prognosis of cancer patients, thus providing a promising target in anticancer treatment. Aim of the current project was to evaluate the effect of the novel PLK1 inhibitor BI 6727 in combination with irradiation.
Material and methods: In vitro proliferation and radiation cell survival assays as well as in vivo local tumour control assays after single treatment and combined radiation and drug application were carried out using the squamous cell carcinoma models A431 and FaDu. In addition, cell cycle phases were monitored in vitro and in vivo.
Results: BI 6727 showed a dose-dependent antiproliferative effect and an increase in the mitotic fraction. BI 6727 alone reduced clonogenic cell survival, while radiosensitivity in vitro (SF2) and in vivo (single-dose TCD50 under clamped hypoxia) was not affected. In contrast, local tumour control was significantly improved after application of BI 6727 simultaneously to fractionated irradiation (A431: TCD50 = 60.5 Gy [95% C.I. 57; 63] after IR alone and <30 Gy after combined treatment; FaDu: 49.5 Gy [43; 56 Gy] versus 32.9 Gy 126; 40]).
Conclusions: Despite the lack of direct cellular radiosensitisation, PLK1 inhibition with BI 6727 during fractionated irradiation significantly improves local tumour control when compared to irradiation alone. This result is likely explained by a considerable effect on cell cycle and an independent cytotoxic potential of BI 6727.

Keywords: Radiotherapy; PLK1 inhibition; Cell cycle; Local tumour control; Combined treatment

Publ.-Id: 19534

Implementation of Cascade Gamma and Positron Range Corrections for I-124 Small Animal PET

Harzmann, S.; Braun, F.; Zakhnini, A.; Weber, W. A.; Pietrzyk, U.; Mix, M.

Small animal Positron Emission Tomography (PET) should provide accurate quantification of regional radiotracer concentrations and high spatial resolution. This is challenging for non-pure positron emitters with high positron endpoint energies, such as I-124: On the one hand the cascade gammas emitted from this isotope can produce coincidence events with the 511 keV annihilation photons leading to quantification errors. On the other hand the long range of the high energy positron degrades spatial resolution. This paper presents the implementation of a comprehensive correction technique for both of these effects.
The established corrections include a modied sinogram-based tail-fitting approach to correct for scatter, random and cascade gamma coincidences and a compensation for resolution degradation effects during the image reconstruction. Resolution losses were compensated for by an iterative algorithm which incorporates a convolution kernel derived from line source measurements for the microPET Focus 120 system. The entire processing chain for these corrections was implemented, whereas previous work has only addressed parts of this process. Monte Carlo simulations with GATE [1] and measurements of mice with the microPET Focus 120 show that the proposed method reduces absolute quantication errors on average to to 2.6% compared to 15.6% for the ordinary Maximum Likelihood Expectation Maximization algorithm. Furthermore resolution was improved in the order of 11-29% depending on the number of convolution iterations.
In summary, a comprehensive, fast and robust algorithm for the correction of small animal PET studies with I-124 was developed which improves quantitative accuracy and spatial resolution.

Keywords: Monte Carlo simulations; cascade gamma coincidences; non-pure positron emitter; positron range; positron emission tomography (PET); image resolution

Publ.-Id: 19533

Discovery of the cancer stem cell related determinants of radioresistance

Peitzsch, C.; Kurth, I.; Kunz-Schughart, L.; Baumann, M.; Dubrovska, A.

Tumors are known to be heterogeneous containing a dynamic mixture of phenotypically and functionally different tumor cells. The two concepts attempting to explain the origin of intratumor heterogeneity are the cancer stem cell hypothesis and the clonal evolution model. The stochastic model argues that tumors are biologically homogenous and all cancer cells within the tumor have equal ability to propagate the tumor growth depending on continuing mutations and selective pressure. By contrast, the stem cells model suggests that cancer heterogeneity is due to the hierarchy that originates from a small population of cancer stem cells (CSCs) which are biologically distinct from the bulk tumor and possesses self-renewal, tumorigenic and multilineage potential. Although these two hypotheses have been discussed for a long time as mutually exclusive explanations of tumor heterogeneity, they are easily reconciled serving as a driving force of cancer evolution and diversity. Recent discovery of the cancer cell plasticity and heterogeneity makes the CSC population a moving target that could be hard to track and eradicate. Understanding the signaling mechanisms regulating CSCs during the course of cancer treatment. can be indispensable for the optimization of current treatment strategies.

Keywords: Cancer stem cells; Radioresistance; Biomarkers; Microenvironment

Publ.-Id: 19532

Comment on: "Transconvolution and the virtual positron emission tomograph: A new method for cross calibration in quantitative PET/CT imaging"

Hofheinz, F.; van den Hoff, J.

kein Abstract verfügbar - "Letter to the Editor"

Publ.-Id: 19531

Performance Evaluation of Stationary and Semi-Stationary Acquisition with a Non-Stationary Small Animal Multi-Pinhole SPECT System

Lange, C.; Apostolova, I.; Lukas, M.; Huang, K. P.; Hofheinz, F.; Gregor-Mamoudou, B.; Brenner, W.; Buchert, R.

Step-and-shoot mode with many angular steps results in long frame duration limiting the capability of single-photon emission computed tomography (SPECT) for fast dynamic scans. The present study evaluates acquisition with reduced angular sampling for fast imaging in preclinical research with the nanoSPECT/CTplus four-head multi-pinhole system.
Measurements with line sources, homogeneity phantoms and a Jaszczak phantom filled with 99mTc or 123I were performed to evaluate the ‘stationary’ and ‘semi-stationary’ acquisition mode (one or two detector positions, respectively) with respect to spatial resolution, quantification, noise properties and image artefacts. An in vivo mouse study was performed with 99mTc-MAG3.
The fast acquisition modes resulted in only minor degradation of spatial resolution and quantification accuracy. Statistical noise in reconstructed images was significantly reduced compared to conventional SPECT, particularly at low count statistics. Stationary acquisition resulted in streak artefacts and spatial distortion.
The semi-stationary acquisition mode of the nanoSPECT/CTplus allows fast dynamic SPECT with tolerable loss of image quality.

Keywords: SPECT; Dynamic imaging; Stationary; Performance evaluation

Publ.-Id: 19530

Nickel Induced Crystallization of Carbon During Deposition

Wenisch, R.; Hübner, R.; Krause, M.; Gemming, S.; Abrasonis, G.

Crystallization kinetics of ion beam sputtered carbon on polycrystalline nickel thin films is investigated. The process temperature is significantly reduced in comparison to annealing of an amorphous carbon film without the aid of a transition metal. The degree of graphitization and the average grain size of the resulting films are examined by means of Raman-spectroscopy and high resolution transmission electron microscopy. The chemical state of the carbon atoms is analyzed by X-ray photoelectron spectroscopy. Additionally, nuclear reaction analysis confirms the temperature independence of the carbon absorption on the nickel surface. We believe that the process holds a potential for the synthesis of crystalline thin films or single layers of different 2D nanomaterials.

Keywords: nickel; carbon; graphite; amorphous carbon; physical vapor deposition; Rutherford back-scattering; nuclear reaction analysis; X-ray photoelectron spectroscopy; Raman spectroscopy; transmission electron spectroscopy

Related publications

  • Poster
    2013 MRS Fall Meeting & Exhibit, 01.-06.12.2013, Boston, USA

Publ.-Id: 19529

Nickel Induced Crystallization of Carbon During Deposition

Wenisch, R.; Gemming, S.; Abrasonis, G.

A single-step process for the preparation of very thin polycrystalline carbon films on uniform nickel thin films is presented. The process temperature is significantly reduced in comparison to annealing of an amorphous carbon film without the aid of a transition metal. The degree of graphitization and the average grain size of the resulting films are examined by means of Raman-spectroscopy and transmission electron microscopy. The chemical state of the carbon atoms is analyzed by X-ray photoelectron spectroscopy. Additionally, nuclear reaction analysis is employed to confirm the temperature independence of the carbon absorption on the nickel surface. We believe that the process holds a potential for the synthesis of crystalline thin films or single layers of different 2D nanomaterials.

Keywords: nickel; carbon; physical vapor deposition; graphite; amorphous carbon; Rutherford back-scattering; nuclear reaction analysis; X-ray photoelectron spectroscopy; Raman spectroscopy; transmission electron microscopy

Related publications

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie 2013, 10.-15.03.2013, Regensburg, Deutschland

Publ.-Id: 19528

Fluence calculation and reaction rates determination at the reactor pressure vessel Kola 3

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

In this work, different geometric positions which have influence on the radiation conditions of the samples are investigated. Thus, the uncertainties can be determined in the fluence values of surveillance specimens. The fluence calculations were carried out by the codes TRAMO and DORT. This study was accompanied by ex-vessel neutron dosimetry experiments at at Kola NPP, Unit 3 (VVER-440/213), which provide the basis for validation of calculated neutron fluences. The main neutron-activation monitoring reactions were 54Fe(n,p)54Mn and 58Ni(np)58Co. The activity measurements were carried out by SEC NRS.
Good agreement as between the deterministic and stochastic calculation results and between the calculations and the ex-vessel measurements was found. The average difference between measured and calculated values is 5%. The influence of the channels for surveillance specimens and the shielding effect of a baffle rib on the monitors and on the Monte-Carlo calculated results was studied.
The differences of fast neutron fluences in the depth of surveillance specimens could be up to 30% depending on the direction to the core. Based on these calculations the lead factor of specimens is very large and has high uncertainty. The maximum fluence of RPV may be achieved after two cycles. These uncertainties should be taken into account during validation of calculated results by SS neutron dosimetry.

Keywords: Neutron fluence monitor; Monte-Carlo; surveillance specimens; TRAMO; VVER440

  • Lecture (others)
    13. AAA Usergroup Meeting, 02.12.2013, Garching bei München, Deutschland

Publ.-Id: 19527

Development of Radioligands for PET Imaging of Neurodegeneration

Brust, P.

  • Invited lecture (Conferences)
    Kolloquiumsreihe des Universitätsklinikums Tübingen, 22.07.2013, Tübingen, Deutschland

Publ.-Id: 19526

SP3 solution versus diffusion solution in pin-by-pin calculations and conclusions concerning advanced methods

Litskevich, D.; Merk, B.

Opportunities for and limitations of the use of the SP3 solution instead of the diffusion solution are given and discussed. Due to existing limitations, the use of a hybrid method consisting of nodal full core calculations coupled with an advanced transport solution based on the current coupling collision probability method with an orthonormal flux expansion is proposed. The method seems to be promising compared to adaptive mesh using refined geometry but without refined detail information, which is deleted by the homogenization process and compared to brute force full core pin-by-pin using advanced transport solvers.

Keywords: SP3 approximation; diffusion approximation; current coupling collision probability; transport equation

Publ.-Id: 19525

Ultrafast spectroscopy of super high frequency mechanical modes of doubly clamped beams

Ristow, O.; Merklein, M.; Grossmann, M.; Hettich, M.; Schubert, M.; Bruchhausen, A.; Grebing, J.; Erbe, A.; Mounier, D.; Gusev, V.; Scheer, E.; Dekorsy, T.; Barretto, E. C. S.

We use ultrafast pump-probe spectroscopy to study the mechanical vibrations in the time Domain of doubly clamped silicon nitride beams. Beams with two different clamping conditions are investigated. Finite element method calculations are performed to analyse the mode spectra of both structures. By calculating the strain integral on the surface of the resonators, we are able to reproduce the effect of the detection mechanism and identify all the measured modes. We Show that our spectroscopy technique combined with our modelling tools allow the investigation of several different modes in the super high frequency range (3-30 GHz) and above, bringing more information about the vibration modes of nanomechanical resonators.

Keywords: nanomechanical resonators; ASOPS; Optical spectroscopy

Publ.-Id: 19523

On the role of fluoro-substituted nucleosides in DNA radiosensitization for tumor radiation therapy

Kopyra, J.; Keller, A.; Bald, I.

Gemcitabine (2’,2’-difluorocytidine) is a well-known radiosensitizer routinely applied in concomitant chemoradiotherapy. During irradiation of biological media with high-energy radiation secondary low-energy (< 10 eV) electrons are produced that can directly induce chemical bond breakages in DNA by dissociative electron attachment (DEA). Here, we investigate and compare DEA to the three molecules 2’-deoxycytidine, 2’-deoxy-5-fluorocytidine, and gemcitabine. Fluorination at specific molecular sites, i.e., nucleobase or sugar moiety, is found to control electron attachment and subsequent dissociation pathways. The presence of two fluorine atoms at the sugar ring results in more efficient electron attachment to the sugar moiety and subsequent bond cleavages. For the formation of the dehydrogenated nucleobase anion, we obtain an enhancement factor of 2.8 upon fluorination of the sugar, whereas the enhancement factor is 5.5 when the nucleobase is fluorinated. The observed fragmentation reactions suggest enhanced DNA strand breakage induced by secondary electrons when gemcitabine is incorporated into DNA.

Related publications

Publ.-Id: 19522

Bacterial Diversity at Abandoned Uranium Mining and Milling Sites in Bulgaria as Revealed by 16S rRNA Genetic Diversity Study

Radeva, G.; Kenarova, A.; Bachvarova, V.; Flemming, K.; Popov, I.; Vassilev, D.; Selenska-Pobell, S.

Radionuclide and heavy metal contamination influences the composition and diversity of bacterial communities, thus adversely affecting their ecological role in impacted environments. Bacterial communities from uranium and heavy metal-contaminated soil environments andmine waste piles were analyzed using 16S rRNA gene retrieval. A total of 498 clones were selected, and their 16S rDNA amplicons were analyzed by restriction fragment length polymorphism, which suggested a total of 220 different phylotypes. The phylogenetic analysis revealed Proteobacteria, Acidobacteria, and Bacteroidetes as the most common bacterial taxa for the three sites of interest. Around 20–30 % of the 16S rDNA sequences derived from soil environments were identified as Proteobacteria, which increased up to 76 % (mostly Gammaproteobacteria) in bacterial communities inhabiting the mine waste pile. Acidobacteria, known to be common soil inhabitants, dominated in less contaminated environments, while Bacteroidetes were more abundant in highly contaminated environments regardless of the type of substratum (soil or excavated gravel material). Some of the sequences affiliated with Verrucomicrobia, Actinobacteria, Chloroflexi, Planctomycetes, and Candidate division OP10 were site specific. The relationship between the level of contamination and the rate of bacterial diversity was not linear; however, the bacterial diversity was generally higher in soil environments than in the mine waste pile. It was concluded that the diversity of the bacterial communities sampled was influenced by both the degree of uranium and heavy metal contamination and the site-specific conditions.

Keywords: Bacterial diversity; 16S rRNA gene; Uranium and heavy metal contamination

Publ.-Id: 19521

Radiosynthesis of 5-(2-[18F]fluoroethyl)-sunitinib as inhibitor of VEGFR-2-first results

Knieß, T.; Kuchar, M.; Bergmann, R.; Steinbach, J.; Pietzsch, J.


Radiolabeled inhibitors of receptor tyrosine kinases (RTK) might be suitable probes for monitoring pathophysiological situations related to enhanced expression of the vascular endothelial growth factor receptor (VEGFR). Imaging of angiogenesis with PET could facilitate for the individual patient the evaluation of e.g. the success of corresponding anti-angiogenic chemotherapy or monitoring the stimulation of the endogenous adaptive vessel growth after implantation of
bioMaterials. For this purpose we developed an 18F-radiolabeled probe, 5-(2-[18F]fluoroethyl)-sunitinib basing on the lead structure of sunitinib®, a multi-kinase inhibitor selective to VEGFR-2.
Materials and Methods:
The non-radioactive reference compound 5-(2-fluoroethyl)-sunitinib was synthesized by Knoevenagel condensation of 5-(2-fluoroethyl)-indoline-2-one with N-[2-(diethylamino)ethyl]-2,4-dimethyl-5-formyl-1H-pyrrole-3-carboxamide. Two suitable precursors for radiolabeling, A and B were obtained by reacting a 5-(2-bromoethyl)-substituted sunitinib derivative with silver 4-toluenesulfonate and silver methanesulfonate, respectively. [18F]Fluoride was produced by the 18O(p,n)18F reaction from [18O]H2O in a 18/9 cyclotron (IBA), separated by an anion exchange cartridge (QMA, Waters) and activated by azeotropic drying with acetonitrile in a stream of nitrogen before use. In a set of radiolabeling experiments 4 mg of precursor A or B were reacted with [18F]fluoride in 500μL of solvent at a scheduled temperature regime for 20 min. The yield of 5-(2-[18F]fluoroethyl)-sunitinib was determined by radio-TLC (silicagel, THF/TEA=9/1).
The non-radioactive 5-(2-fluoroethyl)-sunitinib was investigated in a competition binding assay against VEGFR-2; a Kd value of 9 nM is justifying its classification as specific inhibitor. The radiolabeling reaction of the precursors A and B was performed at temperatures varying from 60, 90, and 120°C in one of the following solvents: acetonitrile, DMF, and DMSO. As result it turned out that for both precursors in DMF and DMSO only poor labeling yields about 2% could be achieved, whereas by using acetonitrile at 90°C the yield of 5-(2-[18F]fluoroethyl)-sunitinib increased to 7-9%. Reaction temperatures higher than 90°C lead to fast and complete decomposition of the precursors as monitored by several non-radioactive by-products on TLC. Notably no difference in yield was observed by using the methanesulfonyl- or the 4-toluenesulfonyl-precursor.
The new VEGFR-2 targeted radiolabeled probe 5-(2-[18F]fluoroethyl)-sunitinib was successfully synthesized by radiofluorination of the corresponding methanesulfonyl- or 4-toluenesulfonyl-substituted precursor with [18F]fluoride. First attempts to transfer the labeling method to a remote-controlled system were successful. By now a procedure for the purification of the radiotracer by semipreparative HPLC and SPE is under development to enable the radiopharmacological evaluation.

  • Poster
    Annual Congress of the European Association of Nuclear Medicine, 19.-23.10.2013, Lyon, France
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 40(2013), S316
    ISSN: 1619-7070

Publ.-Id: 19520

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