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33403 Publications

Charge Collection Efficiency in a segmented semiconductor detector interstrip region

Alarcon-Diez, V.; Vickridge, I.; Jakšić, M.; Grilj, V.; Schmidt, B.; Lange, H.
Charged particle semiconductor detectors have been used in Ion Beam Analysis (IBA) for over four decades without great changes in either design or fabrication. However one area where improvement is desirable would be to increase the detector solid angle so as to improve spectrum statistics for a given incident beam fluence. This would allow the use of very low fluences opening the way, for example, to increase the time resolution in real-time RBS or for analysis of materials that are highly sensitive to beam damage. In order to achieve this goal without incurring the costs of degraded resolution due to kinematic broadening or large detector capacitance, a single-chip segmented detector (SEGDET) was designed and built within the SPIRIT EU infrastructure project. In this work we present the Charge Collection Efficiency (CCE) in the vicinity between two adjacent segments focusing on the interstrip zone. Microbeam Ion Beam Induced Charge (IBIC) measurements with different ion masses and energies were used to perform X-Y mapping of (CCE), as a function of detector operating conditions (bias voltage changes, detector housing possibilities and guard ring configuration). We show the (CCE) in the edge region of the active area and have also mapped the charge from the interstrip region, shared between adjacent segments. The results indicate that the electrical extent of the interstrip region is very close to the physical extent of the interstrip and guard ring structure with interstrip impacts contributing very little to the complete spectrum. The interstrip contributions to the spectra that do occur, can be substantially reduced by an offline anti-coincidence criterion applied to list mode data, which should also be easy to implement directly in the data acquisition software.
Keywords: Segmented detector; IBIC; Charge Collection Efficiency; Interstrip

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Permalink: https://www.hzdr.de/publications/Publ-25103
Publ.-Id: 25103


Effect of glutamic acid on copper sorption onto kaolinite - batch experiments and surface complexation modeling

Karimzadeh, L.; Barthen, R.; Stockmann, M.; Gruendig, M.; Franke, K.; Lippmann-Pipke, J.
High carbonate content of the European Kupferschiefer ore deposits is a challenge for acid copper leaching (pH ≤ 2). Therefore investigating the mobility behavior of Cu(II) under conditions related to an alternative, neutrophil biohydrometallurgical Cu(II) leaching approach is of interest. As glutamic acid (Glu) might be present as a component in the growth media, we studied its effects on the adsorption of Cu(II) onto kaolinite. The binary and ternary batch sorption measurements of Cu(II) and Glu onto kaolinite were performed in the presence of 10 mM NaClO4 as background electrolyte and at a pH range from 4 to 9. Sorption experiments were modeled by the charge-distribution multi-site ion complexation (CD-MUSIC) model by using single sorption site (≡SOH) and monodentate surface complexation reactions. Glu sorption on kaolinite is weak (<10%) and independent of pH. Furthermore, Glu slightly enhances the Cu(II) sorption at low pH but strongly hinders (up to 50%) the sorption at higher pH and therewith enhances copper mobility. The results of isotherms show that Cu(II)-Glu sorption onto kaolinite mimics the Freundlich model. The proposed CD-MUSIC model provides a close fit to the experimental data and predicts the sorption of Cu(II), Cu(II)-Glu and Glu onto kaolinite as well as the effect of Glu on Cu(II) mobility.
Keywords: Copper mobility, Glutamic acid, Kaolinite, Sorption, Surface complexation modeling

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Permalink: https://www.hzdr.de/publications/Publ-25102
Publ.-Id: 25102


Provenance of uranium in a sediment core from a natural reservoir, South China: Application of Pb stable isotope analysis

Liu, J.; Luo, X.; Wang, J.; Xiao, T.; Yin, M.; Belshaw, N. S.; Lippold, H.; Kong, L.; Xiao, E.; Bao, Z.; Li, N.; Chen, Y.; Linghu, W.
As part of ongoing environmental investigations of U mining impacts, forty-two sediment samples of a nearly-half-meter-long sediment core retrieved from a natural reservoir near an active uranium (U) mining site, South China were analyzed to quantify the extent of U release and identify U release mechanism within the riverine catchment. Enrichment levels of U was dispersed not only in the surface sediments but also in deep sediments across the depth profile. Further analysis by SEM-EDS and XRD indicated that U partitioning in the depth profile was possibly controlled by complicated interplay of leaching and precipitation cycles of U-bearing minerals. Even with the relative complexity of U dispersal processes within the catchment, the Pb isotopic fingerprinting techniques allowed quantification of source inputs of the sediments by using a binary mixing model. The results revealed that along the depth profile, only 6%–50% of the sediment material is anthropogenically derived from the U ore tailing, with the other predominant proportions originated from geogenically natural weathering of granitic bedrocks. This study highlights the use of Pb isotopes as a powerful tool for quantitatively fingerprinting the sources of U dispersal in the sediment core, and natural-occurring U contamination that may become a hidden geoenvironmental health hazard in this area.
Keywords: uranium; Pb isotopes; source apportionment; binary mixing; radiogenic

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Permalink: https://www.hzdr.de/publications/Publ-25100
Publ.-Id: 25100


Self-Organized Semiconductor Patterning by Polyatomic Broad Beam Ion Irradiation

Pilz, W.; Bischoff, L.; Böttger, R.; Laufer, P.; Tajmar, M.
Surface patterning based on self-organized nano-structures on i.e. semiconductor materials formed by heavy mono - and polyatomic ion irradiation from Liquid Metal (Alloy) Ion Sources (LMAIS) is a very promising technique. To overcome the lack of only very small treated areas by applying a Focused Ion Beam (FIB) instrument this technology was transferred into larger single-end ion beam systems like an ion implanter. Main component is an ion beam injector based on high current LMAIS, developed for space propulsion systems combined with suited ion optics allocating ion currents in the µA range in a nearly parallel beam of a few mm in diameter. The mass selection of the needed ion species can be performed either by an introduced ExB mass separator (Wien filter) and/or the existing magnet of the ion implanter itself which also can define the final ion energy up to 200 keV.
Different types of LMAIS (needle, porous emitter, capillary) are presented and characterized. The ion beam injector design is specified as well as the implementation of this module into a high current ion implanter (Danfysik Series 1090) operating at the HZDR Ion Beam Center (IBC). Finally the obtained results of large area surface modification of Ge using Bi2+ polyatomic ions from a GaBi capillary LMAIS at room temperature will be presented and discussed.
Keywords: Self-Organized Patterning; Polyatomic Ions; Broad Beam Ion Irradiation
  • Lecture (Conference)
    Nationales Treffen der deutschen Ionenstrahl-PhysikerInnen und -MaterialwissenschaftlerInnen, 12.-15.02.2017, Göttingen, Germany

Permalink: https://www.hzdr.de/publications/Publ-25099
Publ.-Id: 25099


Defect-induced magnetism in SiC probed by nuclear magnetic resonance

Zhang, Z. T.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Y.; Helm, M.; Zhou, S.; Kühne, H.
We give evidence for intrinsic defect-induced bulk paramagnetism in SiC by means of 13C and 29Si nuclear magnetic resonance (NMR) spectroscopy. The temperature dependence of the internal dipole-field distribution, probed by the spin part of the NMR Knight shift and the spectral linewidth, follows the Curie law and scales very well with the macroscopic dc susceptibility. In order to quantitatively analyze the NMR spectra, a microscopic model based on dipole-dipole interactions was developed. The very good agreement between these simulations and the NMR data establishes a direct relation between the frequency distribution of the spectral intensity and the corresponding real-space volumes of nuclear spins. The presented approach by NMR can be applied to a variety of similar materials and, thus, opens a new avenue for the microscopic exploration and exploitation of diluted bulk magnetism in semiconductors.

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Permalink: https://www.hzdr.de/publications/Publ-25098
Publ.-Id: 25098


Thallium contamination in arable soils and vegetables around a steel plant – A newly-found significant source of Tl pollution in South China

Liu, J.; Luo, X.; Wang, J.; Xiao, T.; Chen, D.; Sheng, G.; Yin, M.; Lippold, H.; Wang, C.; Chen, Y.
Thallium (Tl) is a highly toxic rare element. Severe Tl poisoning can cause neurological brain damage or even death. The present study was designed to investigate contents of Tl and other associated heavy metals in arable soils and twelve common vegetables cultivated around a steel plant in South China, a newly-found initiator of Tl pollution. Potential health risks of these metals to exposed population via consumption of vegetables were examined by calculating hazard quotients (HQ). The soils showed a significant contamination with Tl at a mean concentration of 1.34 mg/kg. The Tl levels in most vegetables (such as leaf lettuce, chard and pak choy) surpassed the maximum permissible level (0.5 mg/kg) according to the environmental quality standards for food in Germany. Vegetables like leaf lettuce, chard, pak choy, romaine lettuce and Indian beans all exhibited bioconcentration factors (BCF) and transfer factors (TF) for Tl higher than 1, indicating a hyperaccumulation of Tl in these plants. Although the elevated Tl levels in the vegetables at present will not immediately pose significant non-carcinogenic health risks to residents, it highlights the necessity of a permanent monitoring of Tl contamination in the steel-making areas.
Keywords: thallium; soil; vegetable; ecological risk; steel plant

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Permalink: https://www.hzdr.de/publications/Publ-25097
Publ.-Id: 25097


Surface science using radioactive ions at ISOLDE: from metal surfaces to 2-dimensional materials

Potzger, K.; Molholt, T. E.; Fenta, A. S.; Pereira, L. M. C.
We review the research carried out using the apparatus for surface physics and interfaces (ASPIC), at ISOLDE, CERN. We give an overview of the research highlights since 2000, focusing on magnetic and non-magnetic metallic surfaces, and introduce the scientific program that will follow the upgrade which is currently underway, focusing on 2-dimensional materials.
ASPIC was formerly used for the growth of ultrathin metallic films and their characterization by means of perturbed angular correlation spectroscopy. Past research has mainly focused on the determination of the magnetic hyperfine field at the probe atom located on different sites at the surface such as terraces, kinks, steps as well as on the investigation of the static magnetic polarization at the interface between ferromagnetic and paramagnetic layers.
Future research on 2-dimensional materials using ASPIC is foreseen to focus on the investigation of structural and electronic properties of adatoms (adsorption sites, hybridization effects, intra-atomic charge transfer, magnetic moments, etc.). We emphasize, in this context, the exceptional capabilities of ASPIC in terms of broad applicability, high precision and low detection limits.
Keywords: Perturbed angular correlation spectroscopy, nuclear solid state physics

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Permalink: https://www.hzdr.de/publications/Publ-25096
Publ.-Id: 25096


Backward-forward reaction asymmetry of neutron elastic scattering on deuterium

Pirovano, E.; Beyer, R.; Junghans, A. R.; Nankov, N.; Nolte, R.; Nyman, M.; Plompen, A. J. M.
A new measurement of the angular distribution of neutron elastic scattering on deuterium was carried out at the neutron time-of-flight facility nELBE. The backward-forward asymmetry of the reaction was investigated via the direct detection of neutrons scattered at the laboratory angle of 15◦ and 165◦ from a polyethylene sample enriched with deuterium. In order to extend the measurement to neutron energies below 1 MeV, 6Li glass scintillators were employed. The data were corrected for the background and the multiple scattering in the target, the events due to scattering on deuterium were separated from those due to carbon, and the ratio of the differential cross section at 15◦ and 165◦ was determined. The results, covering the energy range from 200 keV to 2 MeV, were found to be in agreement with the theoretical predictions calculated by Canton et al. [Eur. Phys. J. A 14, 225 (2002)] and by Golak et al. [Eur. Phys. J. A 50, 177 (2014)]. The comparison with the evaluated nuclear data libraries indicated CENDL-3.1, JEFF-3.2, and JENDL-4.0 as the evaluations that best describe the asymmetry of n-d scattering.
ENDF/B-VII.1 is compatible with the data for energies below 700 keV, but above the backward to forward ratio is higher than measured. ROSFOND-2010 and BROND-2.2 resulted to have little compatibility with the data.
Keywords: nELBE, neutron, time-of-flight, elastic scattering, deuterium

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Permalink: https://www.hzdr.de/publications/Publ-25095
Publ.-Id: 25095


Guidelines to Design Electrolytes for Lithium-ion Batteries: Environmental Impact, Physicochemical and Electrochemical Properties

Flamme, B.; Rodriguez-Garcia, G.ORC; Weil, M.; Haddad, M.; Phansavath, P.; Ratovelomanana-Vidal, V.; Chagnes, A.
Electrolytes for lithium-ion batteries (LiBs) have been put aside for too long because few new solvents have been designed to match electrolyte specifications. Conversely, more attention has been paid to synthesize new electrode materials, and more especially positive electrodes. Particularly, most of the studies dedicated to the investigation of electrolytes for LiBs have been focused on mixing different molecules. Nowadays, the development of high-voltage materials for LiBs stimulates the synthesis of new solvents and new salts more stable against oxidation. Despite the challenges, only few teams are active in this field in developing a rational approach combining physicochemistry, electrochemistry and modelling from the molecular to the macromolecular levels. After assembling a critical collection of physicochemical and electrochemical data from the literature, this paper highlights the main trends between the chemical structure of organic dipolar aprotic solvents and their physicochemical and electrochemical properties in order to provide a guide for the chemists to design new electrolytes for LiBs. This guide also includes indicators to take into account the environmental impact of solvent production by including the life cycle assessment of eight different solvents.

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Permalink: https://www.hzdr.de/publications/Publ-25094
Publ.-Id: 25094


Elastic Moduli in Cadmium Selenide Doped with Chromium

Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Korostelin, Y. V.
Temperature dependence of elastic moduli (C11 − C12 ) / 2 , C33 , and C44, the latter for the piezo-active and non-piezo-active versions, have been measured in the interval of 4 - 180 K at 28 - 262 MHz in a CdSe: Cr2+ crystal. Anomalies below 40 K have been found for all the moduli, except C33 . The interpretation of the results has been carried out involving the Jahn-Teller effect and relaxation between the equivalent distortions of the tetrahedral CrSe4 centers.

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Permalink: https://www.hzdr.de/publications/Publ-25092
Publ.-Id: 25092


On the Interpretation of Principal Balances for Compositional Data Sets

Martin-Fernandez, J. A.; Pawlowsky-Glahn, V.; Egozcue, J. J.; Tolosana-Delgado, R.
To analyse compositional data (CoDa) sets it is advisable to apply the principle of working on orthonormal coordinates. Sequential Binary Partition (SBP) is a technique to construct an interpretable basis. The provided coordinates are called balances, and they are complemented with a descriptive tool, the CoDa-dendrogram. The goal of a Principal Balances method is to identify an orthonormal basis of the simplex such that the coordinates are balances approaching the properties of principal component analysis (PCA) of CoDa. PCA is one of the main tools for exploratory analysis and modelling of CoDa. However, the main shortcoming of PC's is the difficulty in interpreting the resulting coordinates because a PC is a function of all the original parts. Balances are log-contrasts resulting from a logratio of two geometric means of two groups of parts. Their interpretation is considerably simpler than the interpretation of PC's. The resulting procedures provide tools improving interpretability and intuitive dimension reduction. The algorithm to compute principal balances requires an exhaustive search along all possible sets of orthonormal balances. The consumption of computational time may be considerable for even a small number of parts. Here, to reduce this time, the sets of possible partitions for up to 15 parts is stored. For comparison, two suboptimal, but feasible, algorithms are introduced: (i) searching for balances following a constraint PC's approach; and (ii) a hierarchical cluster analysis of variables based on the Aitchison distance between parts. The properties and performance of these three algorithms are illustrated using a data set of geochemical composition of glacial sediments. Results obtained corroborate the theoretical properties of the methods: they approximate reasonably well the PC's improving the interpretability. However, the price payed is a smaller amount of variance explained by the first balances and the lack of uncorrelation between the coordinates.
  • Poster
    18th Annual Conference IAMG2017, 02.-09.09.2017, Perth, Australia

Permalink: https://www.hzdr.de/publications/Publ-25091
Publ.-Id: 25091


Ultrafast observation of lattice dynamics in laser-irradiated gold foils

Hartley, N. J.ORC; Ozaki, N.; Matsuoka, T.; Albertazzi, B.; Faenov, A.; Fujimoto, Y.; Habara, H.; Harmand, M.; Inubushi, Y.; Katayama, T.; Koenig, M.; Krygier, A.; Mabey, P.; Matsumura, Y.; Matsuyama, S.; Mcbride, E. E.; Miyanishi, K.; Morard, G.; Okuchi, T.; Pikuz, T.; Sakata, O.; Sano, Y.; Sato, T.; Sekine, T.; Seto, Y.; Takahashi, K.; Tanaka, K. A.; Tange, Y.; Togashi, T.; Umeda, Y.; Vinci, T.; Yabashi, M.; Yabuuchi, T.; Yamauchi, K.; Kodama, R.
We have observed lattice expansion before the onset of compression in an optical-laser-driven target, using diffraction of femtosecond X-ray beams generated by the SACLA X-ray Free Electron Laser. The change in diffraction angle provides a direct measure of the lattice spacing, allowing the density to be calculated with a precision of +-1%. From known equation of state relations this allows estimation of the temperature responsible for the expansion as <1000 K. The subsequent ablation-driven compression was observed with a clear rise in density at later times. This demonstrates the feasibility of studying the dynamics of preheating and shock formation with unprecedented detail.
Keywords: XFEL, Diffraction, Laser-matter interaction

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Permalink: https://www.hzdr.de/publications/Publ-25090
Publ.-Id: 25090


Energy dependence of the electron-boson coupling strength in the electron-doped cuprate superconductor Pr1.85Ce0.15CuO4−δ

Beck, M.; Klammer, M.; Rousseau, I.; Obergfell, M.; Leiderer, P.; Helm, M.; Kabanov, V. V.; Diamant, I.; Rabinowicz, A.; Dagan, Y.; Demsar, J.
The quest for a pairing boson in cuprate high-temperature superconductors is one of the outstanding Tasks of solid-state physics. Numerous time-resolved studies of pair breaking, related to pairing by time-reversal symmetry, have been performed using femtosecond optical pulses. By considering energy Relaxation pathways between charge, spin, and lattice degrees of freedom, evidence for both phonon and antiferromagnetic fluctuationmediated pairing has been obtained. Here we present a study of the superconducting-state depletion process in an electron-doped cuprate Pr1.85Ce0.15CuO4−δ , where the superconducting gap is smaller than the energy of relevant bosonic excitations. When pumping with above-gap terahertz pulses, we find that the absorbed energy density required to deplete superconductivity, Adep, matches the thermodynamic condensation energy. On the contrary, by near-infrared pumping, Adep is an order of Magnitude higher, as in the case of hole-doped, large-gap cuprates. These results imply that only a small subset of bosons, which are generated during the relaxation of optically excited carriers, contributes to pairing. This observation implies that, contrary to the common assumptions, electron-boson coupling in cuprates is strongly energy dependent.
Keywords: superconductor, terahertz, free electron laser

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Permalink: https://www.hzdr.de/publications/Publ-25089
Publ.-Id: 25089


Field-induced gapless electron pocket in the superconducting vortex phase of YNi2B2C as probed by magnetoacoustic quantum oscillations

Nössler, J.; Seerig, R.; Yasin, S.; Uhlarz, M.; Zherlitsyn, S.; Behr, G.; Drechsler, S.-L.; Fuchs, G.; Rosner, H.; Wosnitza, J.
By use of ultrasound studies we resolved magnetoacoustic quantum oscillation deep into the mixed state of the multiband nonmagnetic superconductor YNi2B2C. Below the upper critical field, only a very weak additional damping appears that can be well explained by the field inhomogeneity caused by the flux-line lattice in the mixed state. This is clear evidence for no or a vanishingly small gap for one of the bands, namely, the spheroidal α band. This contrasts de Haas–van Alphen data obtained by use of torque magnetometry for the same sample, with a rapidly vanishing oscillation signal in the mixed state. This points to a strongly distorted flux-line lattice in the latter case that, in general, can hamper a reliable extraction of gap parameters by use of such techniques.

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Permalink: https://www.hzdr.de/publications/Publ-25088
Publ.-Id: 25088


Interatomic coulombic decay - the mechanism for rapid deexcitation of hollow atoms

Wilhelm, R. A.ORC; Gruber, E.; Schwestka, J.; Kozubek, R.; Madeira, T. I.; Marques, J. P.; Kobus, J.; Krasheninnikov, A. V.; Schleberger, M.; Aumayr, F.
The impact of highly charged ions onto a solid gives rise to charge exchange between the ions and target atoms, so that slow ions get neutralized in the vicinity of the surface. Using highly charged Ar and Xe ions and the surface-only material graphene as a target, we show that the neutralization and de-excitation of the ions proceeds on a sub-10 fs time scale. We further demonstrate that a multiple interatomic coulombic decay (ICD) model of highly charged ions can describe the observed ultrafast de-excitation. Other de-excitation mechanisms involving non-radiative decay and quasi- molecular orbitals formation during the impact are not important, as follows from the comparison of our experimental data with the results of first-principles calculations. Our method also enables the estimation of ICD rates directly.
Keywords: slow highly charged ion, HCI, graphene, interatomic coulombic decay, ICD
  • Open Access Logo Physical Review Letters 119(2017)10, 103401
    DOI: 10.1103/PhysRevLett.119.103401
  • Poster
    28th International Conference on Atomic Collisions in Solids - ICACS 2018, 01.-06.07.2018, Caen, Frankreich
  • Invited lecture (Conferences)
    19th International Conferences on the Physics of Highly Charged Ions - HCI 2018, 02.-07.09.2018, Lissabon, Portugal
  • Lecture (Conference)
    The International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces - MPS 2018, 21.-24.08.2018, Budapest, Ungarn
  • Poster
    German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities, 17.-19.09.2018, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-25087
Publ.-Id: 25087


Fluor-18-markierte Substrat-basierte Radiotracer zur In-vivo-Bildgebung der Lysyloxidase

Kuchar, M.
Die Bedeutung von Lysyloxidasen im Zusammenhang mit Krebserkrankungen begründet die Notwendigkeit der nichtinvasiven bildgebenden Darstellung dieser Enzyme mittels PET.
Bisher wurde über die ln-vivo-Bildgebung von Lysyloxidasen mittels PET nicht berichtet, wodurch die in dieser Arbeit verfolgten Ansätze einen hohen Neuigkeitswert aufweisen. Allgemein haben sich in der molekularen Bildgebung Radiotracer, deren Anreicherungsmechanismen auf irreversiblen kovalenten Wechselwirkungen beruhen, als sehr erfolgreich erwiesen. Demzufolge erschien das Konzept, Bildgebungssonden auf der Basis von Substraten der Lysyloxidase zu entwickeln, die nach enzymatischem Umsatz potentiell einer kovalenten Fixierung an Matrixproteinen unterliegen können, vielversprechend. Daher wurden Peptide (Abb. 78) für die ln-vivo-Bildgebung derextrazellulären Lysyloxidase auf Grundlage des alpha1(I)-N-Telopeptids als substratbasierte Radiotracer ausgewählt und im Rahmen dieser Arbeit als Präkursaren und Referenzverbindungen synthetisiert und ausführlich charakterisiert.
Diese Markierungsmethode wurde auf weitere, für die molekulare Bildgebung potentiell interessante Peptide übertragen und evaluiert.
Um als Substrate gegenüber Lysyloxidasen zu fungieren, müssen die als Radiotracer zum Einsatz kommenden Peptide in jedem Fall einen Lysinrest aufweisen. Der für die Radiomarkierung ausgewählte Markierungsbaustein N-Succinimidyi-4-[18F]fluorbenzoat resultiert in einer 18F-Fiuorbenzoylierung von primären Aminofunktionen, wie sie am N-Terminus bzw. den Lysinseitenketten zu finden sind. Aus diesem Grund wurde eine Methode etabliert, die die 18F-Markierung selektiv an einer spezifischen Aminofunktion, die keinem enzymatischen Umsatz unterliegt, ermöglicht.
Für die Radiomarkierung wurden folgende vier Markierungsstrategien ausgewählt und hinsichtlich ihrer Selektivität beurteilt:
I. Synthese in Lösung, Steuerung der fvlarkierungsposition über den pH-Wert
II. Synthese in Lösung mit vollständigem Seitenkettenschutz
III. Synthese in Lösung mit geschütztem LOX-relevanten Lysin
IV. Synthese an der festen Phase mit variablem Seitenkettenschutz.
Durch den Einsatz der mikrowellengestützten Festphasenpeptidsynthese (SPPS) wurde die Mehrzahl der Peptide und deren Vorläufer unkompliziert hergestellt. Notwendige Modifikationen wurden in hohen Ausbeuten mittels manueller SPPS durchgeführt. Neben den Synthesen der Peptide als Präkurseren und Referenzverbindungn für die Markierungsstrategien, wurden weitere Peptidderivate für die Entwicklung von funktionellen Assays hergestellt.
Markierungsstrategie I lieferte unabhängig vom gewählten pH-Wert ein Gemisch der mono-18F-fluorbenzoylierten Regioisomere. Neben den radiomarkierten Spezies befanden sich in jeder Produktmischung zwei Zersetzungsprodukte, die während der [18F]SFB-Synthese entstanden waren. Diese Produktzusammensetzung hatte nicht nur eine aufwendige Reinigung zur Folge, sondern brachte einen großen Ausbeuteverlust mit sich.
Für Markierungsstrategie II war die Präkursorsynthese nicht praktikabel, daher wurde diese Strategie nicht weiter verfolgt.
Markierungsstrategie III führte zu geringen Ausbeuten des Rohprodukts und erforderte zusätzlich zu Strategie I einen Entschützungsschritt.
Markierungsstrategie IV erwies sich als effektivste Variante, über welche reproduzierbar die markierten Peptide mit hoher Ausbeute und radiochemischer Reinheit synthetisiert werden konnten.
Es wurde gezeigt, dass mit Markierungsstrategie IV der N-Terminus bzw. jede beliebige primäre Aminofunktion selektiv markiert werden kann. Sie ist damit eine universelle Methode, welche auf andere Peptide mit ähnlicher Fragestellung übertragen werden kann. Zur Evaluierung der Markierungsstrategie IV wurden zusätzlich drei pharmakologisch relevante Beispielpeptide (SNEW als Peptid mit für die Ligandenaffinität essentiellem N-Terminus, k7-Fragment als Peptid mit 7 Lysinresten sowie das Fragment 290-319 des Clostridium perfringens-Enterotoxins als Peptid bestehend aus 30 Aminosäuren) ausgewählt.
Die spezifische Aktivität der markierten und gereinigten Peptide lag zwischen 1-3 GBq/µmol ausgehend von ca. 3 GBq [18F]SFB mit einer spezifischen Aktivität von 20-40 GBq/µmol.
ln der Literatur sind keine Angaben zur Stärke der Telopeptid-Kollagen-lnteraktion verfügbar. Aus diesem Grund wurde die Wechselwirkung der LOX-adressierenden Peptide mit Atelokollagen mithilfe der Oberflächenplasmonresonanz-Spektroskopie quantifiziert. Bei diesen Experimenten wurden KD-Werte im oberen mikromolaren Bereich für das originale alpha1(I)-N-Telopeptid 1a ermittelt. Affinitäten in diesem Bereich legen nahe, dass nicht mit einer spezifischen Anreicherung von n.c.a.-Radiotracern auf Basis der Telopeptid-Kollagen-lnteraktion zu rechnen ist. Dieser Befund ist als günstig zu betrachten, da es Ziel war, mithilfe von 18F-markierten Telepeptidderivaten die Voraussetzung zur Bildgebung der enzymatischen Aktivität von Lysyloxidasen zu entwickeln. Eine Anreicherung der Peptide an das in Säugetieren nahezu ubiquitär vorhandene Typ I-Kollagen ist nach diesen Ergebnissen ohne enzymatische Aktivität der Lysyloxidase nicht erwünscht und es ist damit nicht zu rechnen. Die abgeleiteten Derivate des alpha1(I)-N-Telopeptids besitzen eine geringfügig höhere Affinität zum Kollagen als das authentische N-Telopeptid. Dieses Resultat ist ebenso als positiv für den Einsatz der Peptide als Radiotracer zur Visualisierung der LOX-Aktivität zu werten.
Es wurden LOX-exprimierende Tumorzelllinien ausgewählt, zum einen für die Entwicklung von Tumormodellen und zum anderen, um diese als mögliche Quellen für die Präparation des LOX-Enzyms zu nutzen. Wegen der großen Bedeutung sowohl der LOX als auch der LOXL2 im Prozess der Tumorbildung und Metastasierung wurden die Experimente auch parallel für die LOXL2 durchgeführt. Die Vorauswahl resultierte in Zelltypen aus sechs verschiedenen Tumorzelllinien (A375, FaDu, EMT-6, MDA-MB- 231 , HT-29 und MCF-7). Western-Slot-Analysen zum Nachweis der LOX in diesen Zellen ergaben für das Enzym ein charakteristisches Bandenmuster, das sich über die verschiedenen Zelllinien hinweg als konstant erwies. Die LOXL2 wurde vor allem in A375- und FaDu-Zellen als Einzelbande nachgewiesen.
Vier dieser Zelllinien wurden auf Veränderungen der Expression und Sekretion sowohl der LOX als auch der LOXL2 unter hypoxischen Kulturbedingungen untersucht (A375, EMT-6, MDA-MB-231 und MCF-7). Im Ergebnis dieser Vergleiche wurde festgestellt, dass alle getesteten Zelllinien unabhängig von den Kulturbedingungen gleichmäßig LOX exprimieren. Jedoch reichte die Expression der LOX nicht für eine Isolierung. Für die LOXL2 gelang der Nachweis einer gesteigerten Sekretion in der Zelllinie MDA-MB-231 unter hypoxischen Bedingungen.
Zusätzlich wurde die Assoziation der LOX/LOXL2 mit Proteinen der Zellmembran bzw. extrazellulären Matrix untersucht. Die Ergebnisse dieser Experimente ließen eine Assoziation der LOX mit den genannten Proteinen vermuten, während für die LOXL2 dafür keine Anhaltspunkte vorlagen. Eine Internalisierung der Tracerpeptide wurde anhand von Zellaufnahmeexperimenten ausgeschlossen.
Aus den vier Zelllinien A375, EMT-6, MDA-MB-231 und MCF-7 wurden Tumortiermodelle durch Xenotransplantation entwickelt, zwei weitere Modelle der Zelllinien FaDu und HT-29 waren im Institut verfügbar. Western-Blot-Analysen der Tumorlysate bestätigten die Untersuchungen zur LOX-Expression der kultivierten Tumorzellen in vitro. Der Nachweis der LOXL2-Expression gelang nur für A375-Tumoren mit hoher Intensität. Die LOX- und LOXL2-Expression und deren Lokalisation im A375-Tumor wurden weiterhin mittels histochemischer Untersuchungen belegt.
Die radiopharmakologische Charakterisierung der drei Tracerpeptide [18F]1c, [18F]2b und [18F]3b in gesunden männlichen Wistar-Ratten zeigte eine kurze Blutverweildauer, eine zügige renale Ausscheidung und keine Anreicherung in bestimmten Organen und Geweben. Die Untersuchungen zum Metabolisierungsverhalten der drei Tracerpeptide haben das Cyclohexapeptid [18F]3b als metabolisch inert ausgewiesen, während das N-Telopeptid [18F]1c nach 5 min zu 50% metabolisiert war. Das DPK-Peptid [18F]2b erwies sich als überraschend stabil, denn bei den ln-vivo-Studien waren nach 60 min noch über 50% intaktes Peptid nachweisbar.
Mit A375-tumortragenden NMRI-(nu/nu)-Mäusen wurden Experimente zur Aufnahme der radiomarkierten Peptide in den Tumor durchgeführt. Die Auswertung der dynamischen Kleintier-PET-Messungen und Autoradiogramme zeigten einen temporären Anstieg der Aktivität in den Tumoren, welcher sich aber deutlich von den Werten im jeweiligen Vergleichsmuskelgewebe abhob. Die höchsten SUV und ein günstiges Tumor-zu-Muskel-Verhältnis ergaben sich für DPK-Peptid [18F]2b, welches daraufhin in weiteren fünf Tumormodellen untersucht wurde; wobei analoge Ergebnisse erzielt wurden. Insgesamt wurden die größten Unterschiede des Tumor-zu-Muskel-Verhältnisses in den A375-, EMT-6- und MDA-MB-231-Tumormodellen gefunden.
Um einen Bezug der katalytischen Aktivität der LOX zur Tumoraufnahme von [18F]2b herzustellen, wurden Hemmexperimente an A375- und EMT-6-tumorentragenden Mäusen durchgeführt. Zur Hemmung der aktiven Lysyloxidase wurde den Versuchstieren vier und 24 Stunden vor Injektion von [18F]2b der Inhibitor ß-Aminopropionitril verabreicht. ln beiden Fällen wurde eine Hemmung beobachtet, wobei die Hemmung vier Stunden vor Injektion effektiver ist. Dies deutet auf einen direkten Zusammenhang zwischen Tumoraufnahme der Tracerpeptide und LOX-Aktivität hin.
  • Doctoral thesis
    TU Dresden, 2016
    Mentor: Dr. Reik Löser
    262 Seiten

Permalink: https://www.hzdr.de/publications/Publ-25086
Publ.-Id: 25086


Interaction of uranium (VI) with cellulose degradation products

Brinkmann, H.; Moll, H.
Cellulosic material is present in low and intermediate level wastes in considerable amounts. In the case of ground water ingressing into cementitious backfill material a hyperalkaline environment will be established. Since cellulose will be relatively fast degraded under alkaline conditions, there is a high risk that small organic, water soluble molecules will be formed. These molecules can act as complexing agents for radionuclides and thereby affecting their sorption behavior and solubility adversely. Therefore the focus of current investigations is on the interaction of uranium (VI) with Isosaccharinic acid as main degradation product as well as with acetate. The progress and results of these investigations as part of the MIND project (work package 1) will be presented.
Keywords: Cellulose, Isosaccharinic acid, Acetate, Uranium
  • Lecture (others)
    TD-315 Joint BN, GD, HT, MA Meeting 2017, 06.-07.02.2017, St. Ursanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25085
Publ.-Id: 25085


Combined fractionated external radiotherapy and internal irradiation using 90Y-labelled-Cetuximab: optimization of treatment scheduling and proof of curative potential

Dietrich, A.; Andreeff, M.; Koi, L.; Schubert, M.; Schreiner, L.; Bergmann, R.; Löck, S.; Sihver, W.; Faulhaber, D.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.
Solid tumors can be precisely targeted with external beam radiotherapy (EBRT) but dose is limited by the surrounding tissue. The combination with radioimmunotherapy (= combination of internal and external radiotherapy - CIERT) mediates additional internal irradiation with the potential to strike also distant metastases but affecting different organs at risk. Furthermore, patient stratification is possible using corresponding PET-tracers [1].
We showed the effectiveness of CIERT using 90Y-labelled Cetuximab ([90Y]Y-Cet) and single dose EBRT in a head and neck squamous cell carcinoma xenograft model (FaDu, [2]). The presented project aimed to investigate CIERT using clinical relevant fractionated EBRT with 30 fractions (fx) over 6 weeks. However, the timing of [90Y]Y-Cet is crucial in such settings and was first optimized by modeling [90Y]Y-Cet uptake with near-infrared-labeled Cetuximab (NIR-Cet). The tracer was injected in FaDu-bearing mice at different time points during fxEBRT with differing doses. NIR-Cet uptake was longitudinally followed by in vivo optical imaging to find the optimal schedule for tumor control probability experiments to test the curative potential of CIERT.
NIR-Cet uptake was enhanced after applying low to moderate doses of fxEBRT. Thus, [90Y]Y-Cet was injected after 10 fx of EBRT in CIERT efficacy experiments. CIERT massively increased local control probability compared to EBRT alone or in combination with unlabeled Cetuximab. In the group with the lowest external dose (1 Gy/fx, total dose = 30 Gy) plus [90Y]Y-Cet all tumors were still permanently controlled (observation period = 120 d). In contrast, the total EBRT dose to cure 50% of the tumors without additional [90Y]Y-Cet injection was 63.9 Gy [58.7, 73.9].
Our results indicate a remarkably potential to improve treatment outcome if radiolabeled therapeutics are combined with fractionated external radiotherapy in a clinical relevant setting. Tumor uptake may be improved by application of some EBRT dose prior to injection. This scheduling would also enable patient stratification via a corresponding PET-tracer during ongoing therapy.

[1] A. Dietrich, L. Koi, K. Zöphel, W. Sihver, J. Kotzerke, M. Baumann, M. Krause, Br. J. Radiol. 2015, 88, 20150042
[2] L. Koi, R. Bergmann, K. Brüchner, J. Pietzsch, H.-J. Pietzsch, M. Krause, J. Steinbach, D. Zips, M. Baumann, Radiother. Oncol. 2014, 110, 362-369
  • Contribution to proceedings
    Wolfsberg Meeting 2017, 17.-19.06.2017, Ermatingen, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25084
Publ.-Id: 25084


High power laser-driven particle acceleration for radiotherapy

Pawelke, J.; Beyreuther, E.; Cowan, T. E.; Enghardt, W.; Gotz, M.; Herrmannsdörfer, T.; Karsch, L.; Kraft, S.; Krause, M.; Kroll, F.; Masood, U.; Sauerbrey, R.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Zeil, K.
The current status of developing ultra-high intensity laser-based particle acceleration for more compact and cost effective ion therapy facilities will be presented.
  • Invited lecture (Conferences)
    Conference on Lasers and Electro-Optics Europe (CLEO/Europe) & European Quantum Electronics Conference (EQEC), 25.-29.06.2017, München, Germany

Permalink: https://www.hzdr.de/publications/Publ-25083
Publ.-Id: 25083


Status of the development of compact laser-driven ion beam therapy

Pawelke, J.
For a decade we have been developing laser-based particle acceleration for more compact and cost effective ion therapy facilities. The current status will be presented, discussing not only high power laser systems and laser targets to generate therapeutically applicable beams but also technical solutions for dosimetry, beam transport and dose delivery along with the radiobiological consequences of the short ultra-intense pulses of laser-driven beams.
  • Invited lecture (Conferences)
    32nd Conference on Clinical and Experimental Research in Radiation Oncology, 14.-21.01.2017, Les Menuires, France

Permalink: https://www.hzdr.de/publications/Publ-25082
Publ.-Id: 25082


Ab initio study of interaction of helium with edge and screw dislocations in tungsten

Bakaev, A.; Terentyev, D.; Grigorev, P.; Posselt, M.; Zhurkin, E. E.
The interaction of a single He atom with edge and screw dislocations in tungsten has been studied using ab initio calculations. It was revealed that He is strongly attracted to the core of both dislocations with the interaction energy of -1.3 and -3.0 eV for screw and edge dislocations, respectively, which corresponds to the detrapping temperature in thermal desorption spectroscopy experiments of about 500 K and 1050 K, respectively. The lowest energy positions for He around the dislocation cores are identified and the atomic structures are rationalized on the basis of elasticity theory considerations. Both types of dislocations exhibit a higher binding energy for He as compared to the He-He binding (known as self-trapping) and are weaker traps as compared to a single vacancy. It is, thus, concluded that the strong attraction to dislocation lines can contribute to the nucleation of He clusters in the temperature range which already excludes He self-trapping.
Keywords: Dislocations Helium Tungsten Ab initio

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Permalink: https://www.hzdr.de/publications/Publ-25081
Publ.-Id: 25081


Visualization of the global flow structure in a modified Rayleigh-Bénard setup using contactless inductive flow tomography

Wondrak, T.; Pal, J.; Stefani, F.; Galindo, V.; Eckert, S.
Rayleigh-Bénard convection is not only a classical problem in fluid dynamics but plays also an important role in many metallurgical and crystal growth applications. The measurement of the flow field and of the dynamics of the emerging large-scale circulation in liquid metals is a challenging task due to the opaqueness and the high temperature of the melts. Contactless inductive flow tomography is a technique to visualize the mean three-dimensional flow structure in liquid metals by measuring the flow induced magnetic field perturbations under the influence of one or several applied magnetic fields. In this paper, we present first measurements of the flow induced magnetic field in a Rayleigh-Bénard setup, which are also used to investigate the dynamics of the large-scale circulation. Additionally, we investigate numerically the quality of the reconstruction of the three-dimensional flow field for different sensor configurations.
Keywords: Rayleigh-Bénard convection, contactless inductive flow tomography

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Permalink: https://www.hzdr.de/publications/Publ-25080
Publ.-Id: 25080


Zwitterionic Modification of Ultra-Small Iron Oxide Nanoparticles for Reduced Protein Corona Formation

Pombo-Garcia, K.; Rühl, C.; Lam, R.; Ang, C.-S.; Scammells, P. J.; Comba, P.; Spiccia, L.; Graham, B.; Joshi, T.; Stephan, H.ORC
Polyacrylic acid-coated ultra-small super-paramagnetic iron oxide nanoparticles have been surface-modified with low-molecular weight sulfobetaines or N,N-diethylaminopropylamine in order to generate nanoparticles with zwitterionic character (ZW-NPs). The ZW-NPs proved highly resistant to serum protein corona formation in vitro, as revealed by AFM, SDS-PAGE and proteomics analysis, and exhibited low cytotoxicity towards A431 and HEK293 cells. The presence of unreacted carboxylic acid groups enabled additional functionalization with fluorescent (Cy5) and radioactive (64Cu-dmptacn) moieties. Overall, the ZW-NPs represent promising platforms for the development of new multi-modal diagnostic/therapeutic agents possessing “stealth” properties.
Keywords: iron oxide nanoparticles • multimodal imaging • protein corona • proteomics • zwitterionic coatings

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Permalink: https://www.hzdr.de/publications/Publ-25079
Publ.-Id: 25079


Do spiroindolines have the potential to replace vesamicol as lead compound for the development of radioligands targeting the vesicular acetylcholine transporter?

Lindemann, M.; Deuther-Conrad, W.; Moldovan, R.; Sekhar, K. V. G. C.; Brust, P.; Wenzel, B.
The vesicular acetylcholine transporter (VAChT) is an important target for in vivo imaging of neurodegenerative processes using positron-emission-tomography. So far the development of VAChT radioligands is based on the single known lead compound vesamicol. In this study we investigated a recently published spiroindoline compound class (Sluder et al. 2012), which was suggested to have potential in the development of VAChT ligands. Therefore, we synthesized a small series of spiroindoline derivatives and determined their in vitro binding affinities toward the VAChT. In order to investigate the selectivity, the off-target binding toward 1 and 2 receptors were determined. The compounds possessed VAChT affinities with Ki values in the range of 39 to 376 nM. Binding affinities toward the 1 and 2 receptors are in a similar range indicating that the strong structural difference between the spiroindolines and vesamicol did not improve the selectivity. The observed potential to additionally bind to  receptors let us assume that the herein investigated spiroindolines are not suitable to replace vesamicol as lead compound for the development of VAChT ligands.
Keywords: VAChT, Vesamicol, Spiroindolines, PET, sigma receptors

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Permalink: https://www.hzdr.de/publications/Publ-25078
Publ.-Id: 25078


A fluorescence anisotropy‐based assay to determine the activity of tissue transglutaminase in human cancer cell lines

Ullm, S.; Wodtke, R.; Pietzsch, J.; Löser, R.
High activity of tissue transglutaminase (TGase 2) in various tumors is associated with both their increased metastatic and invasive potential and their resistance towards chemotherapy and radiation. This renders TGase 2 an attractive target for the development of agents that are capable of targeting the tumor-associated TGase 2 for both imaging and therapeutic approaches [1].
To identify Inhibitor-based compounds for these purposes, the establishment of activity assays that allow their characterization both in vitro and at the cellular level is essential. We previously reported a kinetic fluorescence anisotropy (FA)-based assay to determine the transamidase activity of guinea pig TGase 2 [2] which follows the incorporation of fluorescently labeled (either fluoresceine or rhodamine B) cadaverine derivatives into N,N-dimethylated casein (DMC) over time. Using this assay, we were able to show that the method of FA ensures the absence of background signal and a high reproducibility in a homogenous assay design.
Here we apply the FA assay using DMC and a newly developed rhodamine B-cadaverine conjugate to recombinant human TGase 2 for the kinetic characterization of selected inhibitors and the active-site titration of the enzyme. Due to the favorable signal-to-noise ratio, it was furthermore possible to apply the FA assay for determining cellular TGase 2 in 25 human cell models by measuring the enzyme activity in the whole cell lysate and calculating the respective protein amount. The obtained results were compared with those of a densitometric Western Blot analysis, showing a clear correlation between the two data sets. The human lung cancer cell line NCI-H292 and the human breast cancer cell line MDA-MB-231 were found to exhibit the highest amount of activatable TGase 2 among the tested cancer cell lines, whereas the human cerebral endothelial cell line hCMEC-D3 showed the highest activity among the tested non-cancerous cell lines. To prove that the observed FA signal is caused by TGase 2 activity, N2-phenylacetyl-N6-acryloyl-lysine-4-(6-methylpyridine-2-yl)piperazide [3], which has previously been characterized as irreversible inactivator of this enzyme, was utilized. Application of this inhibitor resulted in a substantial reduction of the FA signal.

References:
[1] Pietsch et al. Bioorg. Med. Chem. Lett. 2013, 23, 6528.
[2] Hauser et al. Amino Acids 2016 DOI: 10.1007/s00726-00016-02192-00725.
[3] Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024.
  • Poster
    Transglutaminases in Human Disease Processes, 10.-15.07.2016, Girona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25077
Publ.-Id: 25077


Expression and Activity of Tissue Transglutaminase in the Response to Gelatin-based Hydrogels in vitro and in vivo

Ullm, S.; Wodtke, R.; Tondera, C.; Löser, R.; Pietzsch, J.
Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial-cell or -tissue interactions due to its presence and versatile functions in the extracellular environment. For example, TGase 2 catalyzes the crosslinking of proteins of the extracellular matrix through its Ca2+-dependent transamidase activity or enhances the interactions between fibronectin, integrins, and syndecan-4 via its role as scaffold protein. Through these functions, TGase 2 mediates the adhesion, migration and motility of cells. Additionally, TGase 2 is a key player during the development of fibrosis. Consequently, TGase 2 might be a potential target for the improvement and visualization of tissue regeneration following biomaterial implantation. Here, we studied the expression pattern and activity of TGase 2 in the response to gelatin-based hydrogels with tailorable elastic properties and degradation behavior due to different degrees of crosslinking.
Solutions of 10 wt.-% gelatin were crosslinked with 3- (G10_LNCO3) or 8-fold (G10_LNCO8) excess of isocyanate groups of lysine diisocyanate ethyl ester compared to amino groups of gelatin. Primary human aortic endothelial cells (HAEC) and human leukemia THP-1 and HL-60 cells, differentiated to macrophages (Mɸ) or granulocytes (Gɸ), were seeded either directly on the hydrogel films or cultivated with material eluates in order to simulate hydrolytic or enzymatic hydrogel degradation in vivo. Expression levels of intracellular and secreted TGase 2 were analyzed via Western blotting [1]. Additionally, hydrogels were implanted subcutaneously in immunocompetent, hairless SKH-1 mice. TGase 2 expression at the implantation site was detected ex vivo by immunohistochemistry at several time points up to 112 days after implantation. The presence of activatable TGase 2 in tissue sections was confirmed in vitro by incorporation of fluorescently labelled cadaverine derivatives [2] at sites of TGase 2 expression. To prove that the incorporation is caused by TGase 2, the staining was performed in the presence and absence of a recently described irreversible inhibitor for TGase 2 [3].
HAEC showed high expression and secretion of TGase 2, independent from hydrogel contact. THP-1 Mɸ highly expressed TGase 2, and increased its secretion after direct hydrogel contact. In contrast, HL-60 Mɸ and Gɸ exhibited enhanced expression of TGase 2 after direct contact to the hydrogels, without secreting TGase 2. These results demonstrate that TGase 2 expression and secretion by Mɸ and Gɸ are influenced by contact to the hydrogel surface structure and not by hydrogel degradation products. Additionally, the hydrogels with higher content of diurealysine junction units (G10_LNCO8) induced higher effects than G10_LNCO3. Ex vivo analysis of tissue sections by immunohistochemistry revealed enhanced expression levels of activatable TGase 2 around the hydrogels 14 and 21 days after implantation, indicating a role of TGase 2 in hydrogel integration and tissue remodelling.
Our results revealed that contact to the gelatin-based hydrogels influenced TGase 2 expression and secretion by Mɸ and Gɸ in vitro, as well as expression of activatable TGase 2 in vivo. This underlines TGase 2 to be a promising theranostic target during processes of biomaterial integration.
References:
[1] Ullm et al. Biomaterials 2014, 35, 9755-9766
[2] Hauser et al. Amino Acids 2016, DOI 10.1007/s00726-00016-02192-00725
[3] Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024-1028
  • Poster
    Transglutaminases in Human Disease Processes, 10.-15.07.2016, Girona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25076
Publ.-Id: 25076


N6-Acryloyl-lysine piperazides as irreversible inhibitors of transglutaminase 2 ― synthesis and structure activity relationships

Wodtke, R.; Jäckel, E.; Wong, A.; Lohse, M.; Bauer, D.; Ullm, S.; Steinbach, J.; Pietzsch, J.; Löser, R.
Various kinds of tumour entities are characterised by an increased activity of transglutaminase 2 (TGase 2), which contributes to an enhanced invasive potential of the tumour cells and their resistance to chemo- and radiotherapy. Therefore, this enzyme represents an interesting target for the development of PET tracers for functional imaging of tumours in vivo [1].
Among the TGase 2 inhibitors described in the literature, N6-acryloyl-lysine-4-arylpiperazides reported by Wityak et al. [2] seem to be most suitable for radiotracer development as these compounds exhibit both strong inhibitory potential and selectivity towards human TGase 2 and show favourable pharmacokinetic properties. Based on this class of compounds, derivatives that allow for labelling with radionuclides such as fluorine-18 and iodine-124 were prepared and their inhibitory potential towards TGase 2 was evaluated.
The N2-acyl-N6-acryloyl-lysine-4-pyridylpiperazides were synthesised in a sequence consisting of N6-acrylation, PyBOP-mediated amide bond formation, Boc deprotection and N2-acylation starting from N2-Boc-lysine. The required pyridylpiperazines were obtained commercially or prepared in a few steps. All final compounds were evaluated in two independent kinetic assays, which detect either the transamidase [3] or hydrolase activity [4] of TGase 2, respectively, with N2-phenylacetyl-N6-acryloyl-lysine-4-(6-methylpyridine-2-yl)piperazide [2] serving as benchmark inhibitor.
Using the outlined synthetic route a series of more than 50 N2-acyl-N6-acryloyl-lysine-4-pyridylpiperazides was prepared in good yields. The kinetic characterisation of the compounds revealed some interesting structure-activity relationships. For example, replacing the 6-methylpyridine-2-yl moiety of the benchmark inhibitor by a 2-nitro-5-pyridyl moiety led to a significantly increased inhibitory effect towards human TGase 2. Furthermore, substitution of the methyl group by hydrogen or a halogen atom (F, Cl, Br and I) revealed a direct correlation between the van der Waals radius of the substituent and the inhibitory effect towards human TGase 2, with the inhibitor containing iodine being even more potent than the benchmark inhibitor. Covalent docking studies provided information about the binding mode of this inhibitor class for the first time and, thus, allowed for explaining the trends observed in the activity assays and give hints for further improvement of inhibitory potency by specific structural variations.
In addition to their interaction with TGase 2, the inhibitors are characterised for their pharmacokinetic properties by the determination of appropriate parameters in vitro.
References:
[1] Pietsch et al. Bioorg. Med. Chem. Lett. 2013, 23, 6528. [2] Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024. [3] Hauser et al. Amino Acids 2016 DOI 10.1007/s00726-00016-02192-00725. [4] Wodtke et al. ChemBioChem 2016 DOI 10.1002/cbic.201600048
  • Poster
    Transglutaminases in Human Disease Processes, 10.-15.07.2016, Girona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25075
Publ.-Id: 25075


Comparative analysis of radiolabeled monoclonal antibodies and antibody fragments for immunotherapy of Prostate Stem Cell Antigen expressing tumors

Oertel, F.; Arndt, C.; Feldmann, A.; Bachmann, M.; Bergmann, R.; Steinbach, J.; Pietzsch, H.-J.
Aim: Advances in antibody engineering have led to the development of a multiplicity of antibody types for radioimmunotherapy. Predominantly, this development was concentrated on generating variations in the antibody size, which evidently influences the pharmacokinetics and tumor uptake. However, it is still discussed, which size has most suitable properties for radioimmunotherapy approaches. Here, two different antibody types, monoclonal antibodies (mAbs, 150 kDa) and thereof derived single-chain variable fragments (scFv, 35 kDa), were compared, that are directed against the prostate stem cell antigen (PSCA). Due to its overexpression on the surface of various cancers, including prostate, pancreas and bladder cancer, PSCA is proposed to be a promising tumor target structure for antibody-based immunotherapy.

Methods: In this study, two different anti-PSCA mAb clones, RD1 and RD2, as well as their respective anti-PSCA scFvs were compared with regard to their binding properties towards PSCA, using flow cytometry analysis. Above, the anti-PSCA mAbs were conjugated with the radionuclide chelating agent CHX-A’'-DTPA and subsequently radiolabeled with 177Lu. The radiolabeled mAb-conjugates were, then, characterized regarding binding properties on PC3-PSCA cells in vitro.

Results: As determined by flow cytometry, non-radiolabeled anti-PSCA mAbs RD1 and RD2 show a high affinity, with a dissociation constant of 10 and 6 nM, respectively. Even though, the scFvs of RD1 and RD2 exhibit a lower affinity in comparison to their mAbs counterpart, they maintain a moderate Kd-value (170 and 98 nM) that is sufficient to proceed with conjugation and radiolabeling analogous to the mAbs. Conjugation of three CHX-A’’-DTPA-chelators to the mAbs had no influence on binding affinity towards the PSCA. Subsequent radiolabeling of the mAb-conjugates could be performed with high radiochemical purity (> 95%). Similar to the non-radiolabeled mAbs, the binding affinity of 177Lu-labeled (CHX-A’’-DTPA)3-RD1 or RD2 was high with 12 and 19 nM, respectively. Summing up, both anti-PSCA mAb were successfully radiolabeled with 177Lu without losing their binding properties to PSCA. Thus, these molecules are attractive candidates for radioimmunotherapy of PSCA-positive cancers.
  • Lecture (Conference)
    24. Jahrestagung der Arbeitsgemeinschaft Radiochemie/Radiopharmazie 2016, 29.09.-01.10.2016, Morschach, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25074
Publ.-Id: 25074


Toward high-energy laser-driven ion beams: Nanostructured double-layer targets

Passoni, M.; Sgattoni, A.; Prencipe, I.; Fedeli, L.; Dellasega, D.; Cialfi, L.; Choi, I. W.; Kim, I. J.; Janulewicz, K. A.; Lee, H. W.; Sung, J. H.; Lee, S. K.; Nam, C. H.
The development of novel target concepts is crucial to make laser-driven acceleration of ion beams suitable for applications. We tested double-layer targets formed of an ultralow density nanostructured carbon layer (∼7  mg/cm3, 8–12  μm–thick) deposited on a μm–thick solid Al foil. A systematic increase in the total number of the accelerated ions (protons and C6+) as well as enhancement of both their maximum and average energies was observed with respect to bare solid foil targets. Maximum proton energies up to 30 MeV were recorded. Dedicated three-dimensional particle-in-cell simulations were in remarkable agreement with the experimental results, giving clear indication of the role played by the target nanostructures in the interaction process.

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Permalink: https://www.hzdr.de/publications/Publ-25073
Publ.-Id: 25073


Investigation of microbial community in extreme saline environments

Franze, M.; Cherkouk, A.
In Germany, three kinds of potential host rock systems (clay, crystalline and rock salt) are considered for the long-term storage of highly radioactive waste in a deep geological repository. In this study the focus is on the habitat rock salt to get a more detailed understanding of the way of life of the microorganisms occurring there. Next to bacteria and fungi, extreme halophilic archaea are dominating this habitat. It is of interest to know what kind of microorganisms are living there, how active they are under repository relevant conditions and how these microorganisms can influence the safe storage of the waste. The microbial diversity of two different types of samples (rock salt from Germany & saline soil sample from Israel) was investigated with a combination of culture-dependent and -independent methods. From the two samples DNA was extracted, purified for PCR amplifications of 16S rRNA genes and finally sequenced with Illumina MiSeq by RTL Genomics. Additionally, a specific portion of each sample was incubated in three different sodium chloride concentrations of modified R2A resuscitation buffer and subsequently spread on corresponding agar plates (37°C) to get isolates which were further characterized. Different halophilic microorganisms could be isolated from both kinds of samples. The isolates from rock salt can all be assigned to different Halobacterium species. Whereas from the saline soil samples different archaeal genera such as Natrinema, Halorubrum as well as Halobacterium could be isolated. Bacterial isolates were related to different Bacilli such as Halobacillus and Aquibacillus species. The obtained isolates can be further used for investigations e.g. regarding their activity under repository relevant conditions.
  • Poster
    MiCom 6th International Conference on Microbial Communication for Young Scientists, 20.-23.03.2017, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25070
Publ.-Id: 25070


Towards atomic physics in particle in cell on GPUs (PIConGPU), photon scattering and nanometer and femtosecond probing of hot dense matter with SAXS

Kluge, T.
Ultrafast heating of solids or solid density plasmas can provide a unique, transient and non-thermal state of matter that enables the study e.g. of ultrafast ionization and excitation, recombination, photon and electron transport. Heating can be achieved directly and indirectly by irradiation with ultra-intense optical lasers or volumetrically with XFELs. Yet, the state-of-the-art theoretical description needed to simulate those processes in particle in cell (PIC) simulations is based on average and effective simplistic assumptions, and hence not reliable for ultrashort, non-thermal states. We present our approach and status of implementing explicit atomic physics in PIConGPU, and introduce the first spin-off tool ParaTAXIS that simulates explicitly photon scattering using PIC methods. This enables implementation of arbitrary scattering physics, multiple scattering, full treatment of X-ray beam properties and fast plasma dynamics. We also demonstrate a novel experimental method based on Small Angle X-ray Scattering to probe such physics on a few nanometer and few femtosecond level simultaneously in ultra-intensity optical laser heated solids.
  • Poster
    Radiative Properties of Hot Dense Matter Workshop, 05.-09.12.2016, Santa Barbara, USA (CA)

Permalink: https://www.hzdr.de/publications/Publ-25069
Publ.-Id: 25069


Nanometer-scale characterization of laser-driven plasmas, compression, shocks and phase transitions, by coherent small angle x-ray scattering

Kluge, T.; Rödel, M.; Pelka, A.; Mcbride, E. E.; Bussmann, M.; Fletcher, L.; Galtier, E.; Laso Garcia, A.; Gutt, C.; Lee, H. J.; Nagler, B.; Rödel, C.; Glenzer, S.; Schramm, U.; Cowan, T. E.
Combining ultra-intense short-pulse and high-energy long-pulse lasers, with hard X-ray FELs, such as the Helmholtz International Beamline for Extreme Fields (HIBEF) [1] at European XFEL [2], or MEC at LCLS [3], holds the promise to revolutionize our understanding of many High Energy Density Physics phenomena. Examples include the relativistic electron generation, transport, and bulk plasma response [4], and ionization dynamics and heating [5] in relativistic laser-matter interactions, or the dynamics of laser-driven shocks, quasi-isentropic compression, and the kinetics of phase transitions at high pressure [3,6]. Particularly interesting is Small Angle X-ray Scattering [4] and resonant scattering [5]. Their feasibility in laser-driven matter will be discussed for ultra-intense short pulse drive lasers and nanosecond lasers, including first results from demonstration experiments at LCLS (SLAC). Very sharp density changes from laser-driven compression are observed, having a step width of <10 nm, comparing to a resolution of several hundred nm achieved previously [6] with phase contrast imaging.
[1] www.hibef.eu
[2] www.xfel.eu
[3] J. Synchrotron Rad. 22, 520 (2015)
[4] Phys. Plasmas 21, 033110 (2014)
[5] http://arxiv.org/abs/1508.03988
[6] Sci. Rep. 3, 1633 (2013)
  • Invited lecture (Conferences)
    43rd EPS Conference on Plasma Physics, 04.-08.07.2016, Leuven, Belgium

Permalink: https://www.hzdr.de/publications/Publ-25068
Publ.-Id: 25068


Prospective Validation of a Prognostic Computed Tomography-Based Radiomic Signature in Stage IV Non-Small Cell Lung Cancer

de Jong, E.; van Elmpt, W.; Leijenaar, R. T. H.; Carvalho, S.; Troost, E. G. C.; Hendriks, L. E. L.; Dingemans, A. M. C.; Lambin, P.
there ist no abstract
  • Abstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 96(2016)2, S192
    DOI: 10.1016/j.ijrobp.2016.06.480

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Publ.-Id: 25067


Toward Shared Decision: Validated Clinical Nomogram for Personalized Long-Term Survival Prediction After Radiosurgery for Brain Metastases

Zindler, J. D.; Jochems, A.; Beumer, R.; Troost, E. G.; Lagerwaard, F.; Eekers, D. B.; Compter, I.; van der Toorn, P. P.; Essers, M.; Oei, B.; Hurkmans, C.; Bruynzeel, A.; Bosmans, G.; Lambin, P.
there ist no abstract
  • Abstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 96(2016)2, S181
    DOI: 10.1016/j.ijrobp.2016.06.453

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Permalink: https://www.hzdr.de/publications/Publ-25066
Publ.-Id: 25066


Toward Distributed Conduction of Large-Scale Studies in Radiation Therapy and Oncology: Open-Source System Integration Approach

Skripcak, T.; Just, U.; Simon, M.; Buttner, D.; Lühr, A.; Baumann, M.; Krause, M.
The conduct of multicenter studies in the field of radiation therapy and oncology is one of the key prerequisites for stimulating translational research and accelerating the application of healthcare innovations into day to day patient treatment. To effectively run such studies, the participating research institutions need access to radiotherapy-specific information technology (IT), which enables collection of case report forms (eCRFs) linked with medical imaging and treatment planning data. Existing commercial systems that provide multimodal data collection features may fit for industry funded clinical trials but do not consider academia needs for long-lasting and affordable IT infrastructure. This paper presents an alternative way for development of a sustainable clinical research IT platform based on open-source systems. The platform design is driven by an integration of its core components, namely, electronic data capture system (EDC), medical image archive (PACS), and patient identity management system (PIDG). Three deployment scenarios are described that allow setting up the platform in a central, virtually hosted or decentralized environment. The first production implementation of this infrastructure was established as RadiationDosePlan-Image/Biomarker-Outcome-platform (RadPlanBio) in September 2013. It is maintained by the German Cancer Consortium (DKTK), Dresden and the German Cancer Research Center (DKFZ), Heidelberg. Until now, it manages 9 studies across 11 sites with 600 enrolled subjects. This paper shows how the integration of open-source systems can drive the development of sustainable clinical research IT environment supporting translational research projects in the field of radiation therapy and oncology. © 2015 IEEE.
Keywords: Digital imaging and communication in medicine (DICOM); electronic data capture (EDC); open source; radiotherapy studies; software integration

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Publ.-Id: 25065


Personalized radiation oncology: Epidermal growth factor receptor and other receptor tyrosine kinase inhibitors

Higgins, G. S.; Krause, M.; Mckenna, W. G.; Baumann, M.
Molecular biomarkers are currently evaluated in preclinical and clinical studies in order to establish predictors for treatment decisions in radiation oncology. The receptor tyrosine kinases (RTK) are described in the following text. Among them, the most data are available for the epidermal growth factor receptor (EGFR) that plays a major role for prognosis of patients after radiotherapy, but seems also to be involved in mechanisms of radioresistance, specifically in repopulation of tumour cells between radiotherapy fractions. Monoclonal antibodies against the EGFR improve locoregional tumour control and survival when applied during radiotherapy, however, the effects are heterogeneous and biomarkers for patient selection are warranted. Also other RTK’s such as c-Met and IGF-1R seem to play important roles in tumour radioresistance. Beside the potential to select patients for molecular targeting approaches combined with radiotherapy, studies are also needed to evluate radiotherapy adaptation approaches for selected patients, i.e. adaptation of radiation dose, or, more sophisticated, of target volumes. © Springer-Verlag Berlin Heidelberg 2016.
Keywords: Biomarker; EGFR; HER-2; Radiotherapy; Receptor tyrosine kinases
  • Book chapter
    Baumann, M.; Krause, M.; Cordes, N.: Molecular Radio-Oncology, Volume 198 of the series Recent results in Cancer Research, Berlin Heidelberg: Springer Verlag, 2016, 107-122
    DOI: 10.1007/978-3-662-49651-0_5

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Publ.-Id: 25063


Low Cancer Stem Cell Marker Expression and Low Hypoxia Identify Good Prognosis Subgroups in HPV(-) HNSCC after Postoperative Radiochemotherapy: A Multicenter Study of the DKTK-ROG.

Linge, A.; Löck, S.; Gudziol, V.; Nowak, A.; Lohaus, F.; von Neubeck, C.; Jütz, M.; Abdollahi, A.; Debus, J.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Avlar, M.; Grosu, A. L.; Bayer, C.; Belka, C.; Pigorsch, S.; Combs, S. E.; Welz, S.; Zips, D.; Buchholz, F.; Aust, D. E.; Baretton, G. B.; Thames, H. D.; Dubrovska, A.; Alsner, J.; Overgaard, J.; Baumann, M.; Krause, M.
PURPOSE:

To investigate the impact of hypoxia-induced gene expression and cancer stem cell (CSC) marker expression on outcome of postoperative cisplatin-based radiochemotherapy (PORT-C) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC).
EXPERIMENTAL DESIGN:

Expression of the CSC markers CD44, MET, and SLC3A2, and hypoxia gene signatures were analyzed in the resected primary tumors using RT-PCR and nanoString technology in a multicenter retrospective cohort of 195 patients. CD44 protein expression was further analyzed in tissue microarrays. Primary endpoint was locoregional tumor control.
RESULTS:

Univariate analysis showed that hypoxia-induced gene expression was significantly associated with a high risk of locoregional recurrence using the 15-gene signature (P = 0.010) or the 26-gene signature (P = 0.002). In multivariate analyses, in patients with HPV16 DNA-negative but not with HPV16 DNA-positive tumors the effect of hypoxia-induced genes on locoregional control was apparent (15-gene signature: HR 4.54, P = 0.006; 26-gene signature: HR 10.27, P = 0.024). Furthermore, MET, SLC3A2, CD44, and CD44 protein showed an association with locoregional tumor control in multivariate analyses (MET: HR 3.71, P = 0.016; SLC3A2: HR 8.54, P = 0.037; CD44: HR 3.36, P = 0.054; CD44 protein n/a because of no event in the CD44-negative group) in the HPV16 DNA-negative subgroup.
CONCLUSIONS:

We have shown for the first time that high hypoxia-induced gene expression and high CSC marker expression levels correlate with tumor recurrence after PORT-C in patients with HPV16 DNA-negative HNSCC. After validation in a currently ongoing prospective trial, these parameters may help to further stratify patients for individualized treatment de-escalation or intensification strategies. Clin Cancer Res; 22(11); 2639-49. ©2016 AACR.

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Publ.-Id: 25060


Correlation of FMISO simulations with pimonidazole-stained tumor xenografts: A question of O2 consumption?

Wack, L. J.; Mönnich, D.; Yaromina, A.; Zips, D.; Baumann, M.; Thorwarth, D.
PURPOSE:

To compare a dedicated simulation model for hypoxia PET against tumor microsections stained for different parameters of the tumor microenvironment. The model can readily be adapted to a variety of conditions, such as different human head and neck squamous cell carcinoma (HNSCC) xenograft tumors.
METHODS:

Nine different HNSCC tumor models were transplanted subcutaneously into nude mice. Tumors were excised and immunoflourescently labeled with pimonidazole, Hoechst 33342, and CD31, providing information on hypoxia, perfusion, and vessel distribution, respectively. Hoechst and CD31 images were used to generate maps of perfused blood vessels on which tissue oxygenation and the accumulation of the hypoxia tracer FMISO were mathematically simulated. The model includes a Michaelis-Menten relation to describe the oxygen consumption inside tissue. The maximum oxygen consumption rate M0 was chosen as the parameter for a tumor-specific optimization as it strongly influences tracer distribution. M0 was optimized on each tumor slice to reach optimum correlations between FMISO concentration 4 h postinjection and pimonidazole staining intensity.
RESULTS:

After optimization, high pixel-based correlations up to R(2) = 0.85 were found for individual tissue sections. Experimental pimonidazole images and FMISO simulations showed good visual agreement, confirming the validity of the approach. Median correlations per tumor model varied significantly (p < 0.05), with R(2) ranging from 0.20 to 0.54. The optimum maximum oxygen consumption rate M0 differed significantly (p < 0.05) between tumor models, ranging from 2.4 to 5.2 mm Hg/s.
CONCLUSIONS:

It is feasible to simulate FMISO distributions that match the pimonidazole retention patterns observed in vivo. Good agreement was obtained for multiple tumor models by optimizing the oxygen consumption rate, M0, whose optimum value differed significantly between tumor models.

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Permalink: https://www.hzdr.de/publications/Publ-25058
Publ.-Id: 25058


Room-temperature short-wavelength infrared Si photodetector

Berencén, Y.; Prucnal, S.; Liu, F.; Skorupa, I.; Hübner, R.; Rebohle, L.; Zhou, S.; Schneider, H.; Helm, M.; Skorupa, W.
The optoelectronic applications of Si are restricted to the visible and near-infrared spectral range due to its 1.12 eV-indirect band gap. Sub-band gap light detection in Si, for instance, has been a long-standing scientific challenge for many decades since most photons with sub-band gap energies pass through Si unabsorbed. This fundamental shortcoming, however, can be overcome by introducing non-equilibrium deep-level dopant concentrations into Si, which results in the formation of an impurity band allowing for strong sub-band gap absorption. Here, we present steady-state room-temperature short-wavelength infrared p-n photodiodes from single-crystalline Si hyperdoped with Se concentrations as high as 9×1020 cm-3, which are introduced by a robust and reliable non-equilibrium processing consisting of ion implantation followed by millisecond-range flash lamp annealing. We provide a detailed description of the material properties, working principle and performance of the photodiodes as well as the main features in the studied wavelength region. This work fundamentally contributes to establish the short-wavelength infrared detection by hyperdoped Si in the forefront of the state-of-the-art of short-IR Si photonics.
Keywords: Extended Si photodetector, Hyperdoped Si, Chalcogens, FLA, non-equilibrium processing

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Publ.-Id: 25057


Local flow measurement in a continuous casting model test stand

Hernández, D.; Wondrak, T.; Karcher, C.
Local Lorentz force velocimetry (LFV) is a contactless local velocity measurement technique for liquid metals. Due to the interaction between an electrically moving liquid and an applied magnetic field, eddy currents and flow-braking Lorentz forces are induced within the fluid. Due to Newton’s third law, a counter force of the same magnitude acts on the source of the applied magnetic field which is in our case a permanent magnet. The magnet is connected to a new generation force/torque sensor that has been especially developed to record all force and torque components. This sensor has already been tested at a continuous casting model with a 15 mm cubic magnet providing an insight of the 3-D velocity distribution of GaInSn near the wide face of the mold [1]. For a better understanding of these results, especially regarding torque sensing, we propose a kinematic approach of ohm’s law where the velocity field is already given. In this case we avoid the variability and noise of the measurements meaning that the force depends just on the velocity distribution of the liquid metal. In this paper we present a comparison between our numerical model and the previous experiments.
  • Contribution to proceedings
    Workshop Elektroprozesstechnik, 22.-23.09.2016, Ilmenau, Deutschland
  • Lecture (Conference)
    Workshop Elektroprozesstechnik, 22.-23.09.2016, Ilmenau, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-25056
Publ.-Id: 25056


Elucidating the role of dissolution in CeO2 nanoparticle plant uptake by smart radiolabeling

Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.
The identification of major uptake pathways in plants is an important factor when evaluation the fate of manufactured nanoparticles in the environment and the associated risks. Using different radiolabeling techniques we were able to show a predominantly particulate uptake for CeO2 nanoparticles (NPs) in contrast to a possible uptake in the form of ionic cerium.
Keywords: Radiomarkierung, Radiolabeling Nanopartikel, Nanoparticle CeO2, CeO2 Pflanzenaufnahme, plant uptake

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Permalink: https://www.hzdr.de/publications/Publ-25055
Publ.-Id: 25055


Representing topology and geometry of 3D ore microstructures with GMaps

Menzel, P.; Teichmann, J.; van den Boogaart, K. G.
The determination of optimal processing chains of specific and complex ores is one of the main tasks in mineral processing. For this purpose, we want to simulate the complete process chain from ore body to flotation to optimize for specific input materials. The key issue is the knowledge of the 3D ore microstructure as starting point for crushing into mineral particles.
Based on statistical information of 2D samples from MLA images (mineral liberation analysis), 3D microstructure models founded on random mosaics are fitted using stochastic geometry.
Then again, simulated MLA data sets can be created from this 3D microstructure model and compared to real data to optimize simulation.
To represent the geometry and the topology of the microstucture models, a data structure is needed to perform the following main tasks. Firstly, we need to build a comprehensive, topologically consistent cell structure. Secondly, we need easy access to all geometric features for all k-cells (e.g. volume, surface, contact faces). Furthermore, operations like the breakup along defined particle borders, the creation of profiles along planes and the dual graph have to be provided in an eficient way. We decided to use our own Java-based implementation of the Generalized Maps (GMaps) data structure that supports the requested operations.
The opportunity of the GMaps concept is, that it only uses one specific data type, called Dart, and several associations between incident Darts, called involutions, to describe the complete topology. Thus, it allows an efficient traversal through all topological elements of our microstructure models.
The simulated microstructure, represented by a GMap, can be used for a milling simulation and the resulting particle streams might undergo, e.g., a flotation simulation. The 3D microstructure models are the essential linkage between the analytical and the processing part of our mineral processing simulation.
Keywords: GMaps, microsructures, stochastic geometry, data structures
  • Lecture (Conference)
    18th Annual Conference IAMG2017, 02.-09.09.2017, Fremantle, Australia

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Publ.-Id: 25053


Numerical calibration of a multicomponent local lorentz force flowmeter

Hernández, D.; Böck, T.; Karcher, C.; Wondrak, T.
Local Lorentz force velocimetry is a local velocity measurement technique for liquid metals. Due to the interaction between an electrically conductive liquid and an applied magnetic field, eddy currents and flow-braking Lorentz forces are induced within the fluid. Due to Newtons’s third law, a force of the same magnitude acts on the source of the applied magnetic field, which is a permanent magnet in our case. The magnet is attached to a gauge that has been especially developed to record all three force and three torque components acting on the magnet. This new-generation local Lorentz force flowmeter (L2F2) has already been tested at a test stand for continuous casting with a 15mm cubic magnet providing an insight into the three-dimensional velocity distribution of the model melt GaInSn near the wide face of the mold. For a better understanding of these results, especially regarding torque sensing, we propose dry experiments which consist in replacing the flowing liquid by a moving solid. Here, as the velocity field is fixed and steady, we are able to decrease considerably the variability and the noise of the measurements providing an accurate calibration of the system. In this paper we present a numerical study of this dry calibration proposal using a rotating disk made of aluminum and two different magnet systems that can be shifted along the rotation axis as well as in radial direction.
Keywords: local lorentz force velocimetry
  • Magnetohydrodynamics 53(2017)2, 233-243

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Publ.-Id: 25052


Synthese von Transglutaminase 2-Inhibitoren und Präkursoren für deren Markierung mit Fluor-18

Bauer, D.
Kein Abstract vorhanden
  • Master thesis
    TU Dresden, 2016
    Mentor: Dr. Reik Löser
    181 Seiten

Permalink: https://www.hzdr.de/publications/Publ-25051
Publ.-Id: 25051


Germanium Recovery from Optical Fiber Waste

Recksiek, V.; Scharf, C.
Germanium is an essential element for the European information technology. The increasing demand for high speed internet connections requires the application of optical fibers, which cannot be produced without Germanium. Because of high supply risks, the European Union added Germanium to the list of critical raw materials in 2010. The world refinery production of Germanium was approximately 165 metric tons in 2014. Thirty percent of this amount was used for the manufacturing of optical fibers. In the production process various Germanium containing scraps are generated, from some of these Germanium is not yet recovered.
This poster outlines methods for the recovery of Germanium from these waste materials. The necessary mechanical processing and a possible pyrometallurgical recovery process are discussed.
Keywords: Germanium, recovery, distillation, reduction, chlorination
  • Poster
    European Resources Forum, Nationales Ressourcen-Forum, 09.-11.11.2016, Berlin, Deutschland
  • Lecture (Conference)
    Aufbereitung und Recycling, 11.-12.11.2015, Freiberg, Deutschland

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Publ.-Id: 25050


Local Hydrodynamics, Mixing and Mass Transfer in Bubble Columns with Internals

Möller, F.; Macisaac, A.; Seiler, T.; Hampel, U.; Schubert, M.
Abstract
Bubble column reactors (BCRs) are apparatuses of choice for the chemical process industry due to their excellent heat and mass transport as well as their simple manufacturing and design without any moving part. They are commonly used for reactions, such as Fischer-Tropsch and methanol synthesis. Most of the reactions carried out in these devices are of exothermic nature and require an efficient heat removal, which can be achieved via internally placed tube bundle heat exchangers. For the Fischer-Tropsch synthesis, a specific heat exchanging surface area between 30 and 40 m²/m³ is needed, which can be provided, for instance, with dense tube bundles inserted in the reactor. Accordingly, the hydrodynamic behavior of the reactor is strongly affected and subsequently, mixing and mass transfer processes are altered, too. Hitherto, the influence of the most common configurations used for the design of shell and tube heat exchangers, i.e. triangular and square pitches, has not been subject of a comparative analysis. Therefore, a study was conducted to reveal global and local hydrodynamics in the equipped bubble column covering a comprehensive sub-channel analysis as well as to disclose the pattern’s influence on gas-liquid mass transfer and liquid mixing behavior.

Figure 1: a) Bubble column reactor with internals, b) with spacer layouts, and c) summary of the studied tube bundle configurations.
A bubble column reactor with an internal diameter of 0.1 m (ID) and 2 m height (clear liquid height of 1.1 m) was employed and operated with deionized water and air. For the internal tube bundles, two configurations, namely, triangular and square tube pitch of two tube diameters (8 and 13 mm), ensuring a similar cross-sectional coverage were chosen (Figure 1).
The ultrafast X-ray tomography was used to disclose the hydrodynamic parameters bubble size and gas holdup. In particular, characteristic sub-channels along the reactor diameter were analyzed (Fig. 2a) to study the effect of the sub-channel position compared with the cross-sectional averaged data in order to examine whether a single sub-channel analysis is sufficient to describe the whole bubble column behavior. In addition, a fast-responding oxygen needle probe was used for mass transfer measurements (Fig. 2b) and wire-mesh sensors (WMS) were applied to track the dispersion of conductive tracers throughout the column’s cross-sectional area (Fig. 2c). The study covered homogenous and heterogeneous flow conditions (2 – 20 cm s-1) in order to also reveal the influence of different regimes.

Figure 2: a) Sub-channel flow structure, b) Mixing analysis based on 2D tracer distributions and c) mass transfer evaluation via oxygen saturation.
The hydrodynamic behavior within the sub-channels was found to depend strongly on their position within the reactor’s cross-sectional area. Furthermore, the influence of tube pattern is also very pronounced. The square configurations show advantageous hydrodynamic behavior with regard to the gas-liquid mass transfer. The small bubbles of narrow size distribution are evenly-distributed over the cross-sectional area and rise with lower velocity, thus, resulting in higher gas holdup and longer bubble-liquid contact time. Triangular configurations, however, introduce a strong flow resistance for the moving bubbles and cause flow asymmetries.
The mixing behavior in the columns with internals was quantified considering axial and radial dispersion of the tracer (Forret et al., 2003). The resulting axial dispersion coefficient was subsequently used for the estimation of the overall volumetric mass transfer coefficient. The dispersion coefficient depends strongly on the internals’ geometry as well as on the bottom structure, i.e. mixing is strongly increased when U-tube bottom ends are used. The mass transfer, however, is lower, with respect to an empty BCR, when internals are inserted due to turbulence dampening.
References
A. Forret, J.-M. Schweitzer, T. Gauthier, R. Krishna and D. Schweich, Liquid Dispersion in Large Diameter Bubble Columns, with and without Internals, The Canadian Journal of Chemical Engineering, Volume 81, June-August 2003, 360-366
  • Lecture (Conference)
    13th International Conference on Gas–Liquid and Gas–Liquid–Solid Reactor Engineering (GLS-13), 20.-23.08.2017, Brussels, Belgium

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Publ.-Id: 25049


Synthese Lysin-abgeleiteter Inhibitoren der Transglutaminase 2 als potentielle Radiotracer zur funktionellen Charakterisierung dieses Enzyms

Lohse, M.
In der vorliegenden Bachelorarbeit wird die Synthese von irreversiblen Transglutaminase 2-Inhibitoren basierend auf einem N6-Acryloyl-L-lysin-Grundgerüst beschrieben. Dafür konnte ausgehend von einem N6-Acryloyl-L-lysin eine Reaktionssequenz aus den drei Schritten Amidkupplung, Boc-Entschützung und N2-Acylierung angewendet werden. Auf diesem Weg erfolgte die Synthese von 23 Inhibitoren mit einer Gesamtausbeute zwischen 2% und 17%. Die Inhibitoren sollen für die Ermittlung von Struktur-Aktivitätsbeziehungen sowie als Vorläuferverbindungen und Referenzverbindungen für PET-Radiotracer verwendet werden.
Weiterhin wird die Synthese eines Fluorophor-konjugierten Substrats der TGase 2 beschrieben. Die Festphasensynthese von 2’-((5-Aminopentyl)isonipecotyl)rhodamin B erfolgte durch eine dreistufige Synthese ausgehend von dem an das 2-Chlortritylchlorid-Harz angebundenen Cadaverin mit einer Gesamtausbeute von 24%. Diese Verbindung soll für ein Fluoreszenzpolarisations-Assay zur Ermittlung der inhibitorischen Potenz (IC50) der irreversiblen TGase 2-Inhibitoren verwendet werden.
  • Bachelor thesis
    Hochschule Zittau/Görlitz, 2016
    Mentor: Dr. Reik Löser
    147 Seiten

Permalink: https://www.hzdr.de/publications/Publ-25048
Publ.-Id: 25048


Molecular Targeting of Integrins and Integrin-Associated Signaling Networks in Radiation Oncology.

Vehlow, A.; Storch, K.; Matzke, D.; Cordes, N.
Radiation and chemotherapy are the main pillars of the current multimodal treatment concept for cancer patients. However, tumor recurrences and resistances still hamper treatment success regardless of advances in radiation beam application, particle radiotherapy, and optimized chemotherapeutics. To specifically intervene at key recurrence- and resistance-promoting molecular processes, the development of potent and specific molecular-targeted agents is demanded for an efficient, safe, and simultaneous integration into current standard of care regimens. Potential targets for such an approach are integrins conferring structural and biochemical communication between cells and their microenvironment. Integrin binding to extracellular matrix activates intracellular signaling for regulating essential cellular functions such as survival, proliferation, differentiation, adhesion, and cell motility. Tumor-associated characteristics such as invasion, metastasis, and radiochemoresistance also highly depend on integrin function. Owing to their dual functionality and their overexpression in the majority of human malignancies, integrins present ideal and accessible targets for cancer therapy. In the following chapter, the current knowledge on aspects of the tumor microenvironment, the molecular regulation of integrin-dependent radiochemoresistance and current approaches to integrin targeting are summarized.
Keywords: Focal adhesion signaling; Integrins; Molecular targeting; Radiochemosensitization
  • Book chapter
    Baumann, M.; Krause, M.; Cordes, N: Molecular Radio-Oncology, Volume 198 of the series Recent results in Cancer Research, Berlin Heidelberg: Springer Verlag, 2016, 89-106
    DOI: 10.1007/978-3-662-49651-0_4

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Publ.-Id: 25047


Optimisation of Cathepsin B Endopeptidase Substrates as Potential Cleavage Sites for Activatable Cell-Penetrating Peptides (ACPP)

Kuhne, K.; Behring, L.; Belter, B.; Wodtke, R.; Steinbach, J.; Pietzsch, J.; Löser, R.
High activity of the cysteine protease cathepsin B correlates with increased metastasis, therapy resistance, and a generally poor prognosis in neoplastic diseases [1,2] Therefore, the development of substrate-based radiotracers for in vivo imaging of this protease will be beneficial towards better diagnosis and improved therapy regimens. We aim at developingsuch a probe by combination of a polyarginine-based, activatable cell penetrating peptide, as described by Tsien and others, and newly optimised endopeptidase substrates for cathepsin B [3]. A unique feature of cathepsin B within the cysteine cathepsin family is the occluding loop, a flexible element consisting of 20 amino acids (aa), which is able to cover the active site of the enzyme and thereby regulates the substrate specificity in a pH-dependent manner [1,2]. This phenomenon is mediated by two histidine residues within the occluding loop, which play a crucial role in positioning a potential substrate for carboxydipeptidolytic cleavage.
Starting point for the development of endopeptidase substrates was the carboxydipeptidase substrate Abz‑GIVRAK(Dnp)‑OH (Abz - aminobenzoyl, Dnp - dinitrophenyl) described by Cotrin et al. in 2004, with the fluorophores Abz and Dnp constituting a FRET pair to enable fluorometric detection of the proteolytic cleavage [4]. Two structural changes were introduced to convert the exopeptidase substrate into an endopeptidase substrate for later use as an activator sequence in an aCPP: Firstly, C‑terminal amidation was performed to interrupt the interaction between the terminal carboxyl group and the two His residues within the occluding loop. This resulted in a reduced specificity constant (kcat/Km = 1179 mM‑1s‑1 vs. 139 mM‑1s‑1), indicating attenuated electrostatic/hydrogen bond interactions. Secondly, the peptide sequence was C‑terminally elongated to test longer substrates. Interestingly, the C‑terminal elongation resulted in a hysteretic progress of the enzymatic cleavage, likely a result of the steric displacement of the occluding loop. To evaluate the influence of size, polarity and charge of the C‑terminal aa on the enzymatic hysteresis, 14 variations of this position were synthesized and analysed for their kinetic parameters. The peptide Abz‑GIVRAK(Dnp)G‑V‑NH2 was determined to exhibit the highest specificity constant (kcat/Km = 260 mM‑1s‑1).
The optimised octapeptide sequence is currently inserted as recognition site in a fluorophore-labelled aCPP for monitoring cathepsin B-mediated activation and subsequent cellular uptake, and for investigating kinetics and in vitro stability analysis in future
experiments.
[1] Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8(5-6), 427-437
[2] Löser and Pietzsch, Front. Chem. 2015, 3, article 37
[3] Jiang et al., PNAS, 2004, 101(51), 17867-17872
[4] Cotrin et al., Anal. Biochem. 2004, 335, 244-252
  • Poster
    34th European Peptide Symposium, 04.-09.09.2016, Leipzig, Deutschland
  • Abstract in refereed journal
    Journal of Peptide Science 22(2016)S2, 177-178
    DOI: 10.1002/psc.2950

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Publ.-Id: 25046


N6-Acryloyl-lysine piperazides as irreversible inhibitors of transglutaminase 2 - synthesis and structure activity relationships

Wodtke, R.; Jäckel, E.; Wong, A.; Lohse, M.; Bauer, D.; Ullm, S.; Steinbach, J.; Pietzsch, J.; Löser, R.
Various kinds of tumour entities are characterised by an increased activity of transglutaminase 2 (TGase 2), which contributes to an enhanced invasive potential of the tumour cells and their resistance to chemo- and radiotherapy. Therefore, this enzyme represents an interesting target for the development of PET tracers for functional imaging of tumours in vivo [1].
Among the TGase 2 inhibitors described in the literature, N6-acryloyl-lysine-4-arylpiperazides reported by Wityak et al. [2] seem to be most suitable for radiotracer development as these compounds exhibit both strong inhibitory potential and selectivity towards human TGase 2 and show favourable pharmacokinetic properties. Based on this class of compounds, derivatives that allow for labelling with radionuclides such as fluorine-18 and iodine-124 were prepared and their inhibitory potential towards TGase 2 was evaluated.
The N2-acyl-N6-acryloyl-lysine-4-pyridylpiperazides were synthesised in a sequence consisting of N6-acrylation, PyBOP-mediated amide bond formation, Boc deprotection and N2-acylation starting from N2-Boc-lysine. The required pyridylpiperazines were obtained commercially or prepared in a few steps. All final compounds were evaluated in two independent kinetic assays, which detect either the transamidase or hydrolase activity of TGase 2, respectively, with N2-phenylacetyl-N6-acryloyl-lysine-4-(6-methylpyridine-2-yl)piperazide [2] serving as benchmark inhibitor.
Using the outlined synthetic route a series of more than 40 N2-acyl-N6-acryloyl-lysine-4-pyridylpiperazides were prepared in good yields. The kinetic characterisation of the compounds revealed some interesting structure-activity relationships. For example, replacing the 6-methylpyridine-2-yl moiety of the benchmark inhibitor by a 2-nitro-5-pyridyl moiety led to a significantly increased inhibitory effect towards human TGase 2.
Furthermore, substitution of the methyl group by hydrogen or a halogen atom (F, Cl, Br and I) revealed a direct correlation between the van der Waals radius of the substituent and the inhibitory effect towards human TGase 2, with the inhibitor containing iodine being even more potent than the benchmark inhibitor. Covalent docking studies provided information about the binding mode of this inhibitor class for the first time and, thus, allowed for explaining the trends observed in the activity assays and give hints for further improvement of inhibitory potency by specific structural variations.
References:
[1] Pietsch etal. Bioorg. Med. Chern. Lett. 2013, 23, 6528. [2] Wityak etal. ACS Med. Chem. Lett. 2012, 3, 1024.
  • Poster
    Frontiers in Medicinal Chemistry, 13.-16.03.2016, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25045
Publ.-Id: 25045


Erbium ion implantation into diamond – measurement and modelling of the crystal structure

Cajzl, J.; Nekvindová, P.; Mackova, A.; Malinský, P.; Sedmidubsky, D.; Hušák, M.; Remeš, Z.; Varga, M.; Kromka, A.; Böttger, R.; Oswald, J.
Diamond is proposed as extraordinary material usable for interdisciplinary fields, especially for optics and photonics. In this contribution we focus on the doping of diamond with erbium as optically active centre. In the theoretical part of study based on DFT simulations we have developed two Er-doped diamond structure models with 0 to 4 carbon vacancies in the vicinity of Er atom and performed geometry optimizations with calculation of cohesive energies and defect formation energies. The theoretical results showed an excellent agreement between the calculated and experimental cohesive energy for the parent diamond. The highest values of cohesive energies and lowest values of defect formation energies were obtained for models with erbium in the substitutional carbon position with 1 or 3 vacancies in the vicinity of erbium atom. From the geometry optimization the structure model with 1 vacancy had an octahedral symmetry whereas the model with 3 vacancies had a coordination of 10 forming a trigonal structure with hexagonal ring. In the experimental part, erbium doped diamond crystal samples were prepared by ion implantation of Er+ ions using ion implantation fluences ranging from 1×1014 ions/cm2 to 5×1015 ions/cm2. The experimental results revealed a high degree of diamond structure damage after the ion implantation process reaching up to 69% of disordered atoms in the samples. The prepared Er-doped diamond samples annealed at the temperatures of 400, 600 and 800 °C in vacuum revealed clear luminescence, where the 〈110〉 cut sample was having approximately 6-7 times higher luminescence intensity than 〈001〉 cut sample with the same ion implantation fluence. The reported results are the first demonstration of the Er luminescence in the single crystal diamond structure for the near-infrared spectral region.
Keywords: diamond, erbium, ion implantation, luminescence, DFT

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Evaluation of tumour hypoxia during radiotherapy using [18F]HX4 PET imaging and blood biomarkers in patients with head and neck cancer

Zegers, C. M. L.; Hoebers, F. J. P.; van Elmpt, W.; Bons, J. A.; Öllers, M. C.; Troost, E. G. C.; Eekers, D.; Balmaekers, L.; Arts-Pechtold, M.; Mottaghy, F. M.; Lambin, P.
BACKGROUND AND PURPOSE:

Increased tumour hypoxia is associated with a worse overall survival in patients with head and neck squamous cell carcinoma (HNSCC). The aims of this study were to evaluate treatment-associated changes in [18F]HX4-PET, hypoxia-related blood biomarkers, and their interdependence.
MATERIAL AND METHODS:

[18F]HX4-PET/CT scans of 20 patients with HNSCC were acquired at baseline and after ±20Gy of radiotherapy. Within the gross-tumour-volumes (GTV; primary and lymph nodes), mean and maximum standardized uptake values, the hypoxic fraction (HF) and volume (HV) were calculated. Also, the changes in spatial uptake pattern were evaluated using [18F]HX4-PET/CT imaging. For all patients, the plasma concentration of CAIX, osteopontin and VEGF was assessed.
RESULTS:

At baseline, tumour hypoxia was detected in 69 % (22/32) of the GTVs. During therapy, we observed a significant decrease in all image parameters. The HF decreased from 21.7 ± 19.8 % (baseline) to 3.6 ± 10.0 % (during treatment; P < 0.001). Only two patients had a HV > 1 cm3 during treatment, which was located for >98 % within the baseline HV. During treatment, no significant changes in plasma CAIX or VEGF were observed, while osteopontin was increased.
CONCLUSIONS:

[18F]HX4-PET/CT imaging allows monitoring changes in hypoxia during (chemo)radiotherapy whereas the blood biomarkers were not able to detect a treatment-associated decrease in hypoxia.
Keywords: CAIX; Hypoxia; Osteopontin; PET; VEGF

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Synthese und enzymkinetische Prüfung von N6-Acryloyllysinpiperaziden als potentielle Radiotracer zur Bildgebung der Transglutaminase 2 (TGase 2)

Wodtke, R.; Hauser, C.; Jäckel, E.; Ruiz-Gomez, G.; Ullm, S.; Wong, A.; Lohse, M.; Steinbach, J.; Pietzsch, J.; Pietsch, M.; Löser, R.
Ziel/Aim: Zahlreiche Krebsarten zeichnen sich durch eine deutlich erhöhte Aktivität der TGase 2 aus, die vor allem mit einer gesteigerter Chemo- und Strahlenresistenz der Krebszellen korreliert. Daher stellt dieses Enzym ein interessantes Target für die Entwicklung von PET-Tracern zur funktionellen Bildgebung derartiger Tumoren dar. Unter den bekannten Inhibitoren der TGase 2 erscheinen die N6-Acryloyllysin-4-arylpiperazide für die Entwicklung von Radiotracern als besonders geeignet, da sie über eine hohe inhibitorische Potenz und Selektivität verfügen (1). Daher sollten ausgehend von dieser Verbindungsklasse Derivate zugänglich gemacht werden, die eine Markierung mit Radionukliden wie F-18 oder Radioiod erlauben.
Methodik/Methods: Ausgehend von N2-Boc-Lysin wurden in einer Sequenz bestehend aus N6-Acrylierung, Amidknüpfung, Boc-Entschützung und N2-Acylierung verschiedene N2-Acyl-N6-acryloyllysin-4-arylpiperazide synthetisiert. Alle Zielverbindungen wurden in zwei unabhängigen enzymkinetischen Assays, welche die Transamidase- bzw. Hydrolaseaktivität der TGase 2 erfassen, evaluiert.
Ergebnisse/Results: Bisher wurde eine Serie von mehr als 40 Inhibitoren synthetisiert, deren enzymkinetische Charakterisierung interessante Struktur-Wirkungsbeziehungen aufdeckte. So führt der Ersatz des 6-Methyl-2-pyridyl-Restes im literaturbekannten Referenzinhibitor N2-Phenylacetyl-N6-acryloyllysin-4-(6-methylpyridin-2-yl)piperazid gegen einen 2-Nitro-5 pyridyl-Rest zu einer deutlich höheren Hemmwirkung gegenüber der TGase 2. Untersuchungen zum kovalenten Docking der Inhibitoren im aktiven Zentrum der TGase 2 geben erstmals Aufschluss über deren Bindungsmodus.
Schlussfolgerungen/Conclusions: Die gefundenen Struktur-Wirkungs-Beziehungen können gezielt genutzt werden, um potentielle Radiotracer hinsichtlich ihrer Hemmkinetik zu verbessern, was für ihre Anwendung zur molekularen Bildgebung in vivo vorteilhaft ist.
Literatur/References:
[1] Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024.
  • Poster
    54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 20.-23.04.2016, Dresden, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 55(2016)2, A77-A77

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Publ.-Id: 25042


Simulating laser wakefield acceleration with PIConGPU - from modeling the laser plasma dynamic to in-situ radiation calculation

Pausch, R.; Debus, A.; Burau, H.; Huebl, A.; Garten, M.; Steiniger, K.; Widera, R.; Bussmann, M.; Schramm, U.
We recent simulations of laser wakefield acceleration on recent experiments performed at HZDR. We focus on how to best approximate the experimental setup using newly developed laser-models, as well as particle creation- and ionization-methods. Furthermore, we elaborate on predicting experimentally observable radiation signatures from the simulation.

We discuss in detail the influence of various ionization mechanisms, including BSI, ADK and Keldysh, and how to model the initial gas or plasma distribution. Furthermore, we present recent improvements in the laser implementation, that added Laguerre-Gauss modes, which drastically reduces discrepancies between previous simulations and experiments. On top of simulating plasma dynamics, we present how to predict experimental observables using PIConGPU’s in-situ synthetic diagnostics, especially the classical Liénard-Wiechert potential- and QED-based radiation. It allows predicting both coherent and incoherent radiation spectrally from infrared to x-rays and provides the capability to resolve the radiation polarization as well as determine its temporal and spatial origin.

On the examples of a large-scale LWFA simulation, we illustrate how we reduce the gap between simulated plasma dynamics and radiation observed in experiments and discuss valuable spectral signatures which allow conclusions on the micrometer femtosecond electron dynamics occurring during acceleration.
Keywords: PIConGPU, LWFA, radiation, GPU, ionization, laser, synthetic diagnostics
  • Poster
    3rd Annual Matter and Technologies Meeting, Darmstadt 2017, 30.01.-02.02.2017, Darmstadt, Deutschland
  • Lecture (Conference)
    3rd Annual Matter and Technologies Meeting, Darmstadt 2017, 30.01.-02.02.2017, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25041
Publ.-Id: 25041


Multiscale structured germanium nanoripples as templates for bioactive surfaces

Dell'Anna, R.; Masciullo, C.; Iacob, E.; Barozzi, M.; Giubertoni, D.; Böttger, R.; Cecchini, M.; Pepponi, G.
Nanostructured germanium substrates are produced by gold ion implantation; they show periodic ripples of nanometer size, decorated on the top and partially on one side with a forest of curled nanowires that end with gold-rich nanoparticles. For the first time, through a novel two-step soft lithography transfer process, the multi-scale nanopatterns are replicated, with features well below 100 nm, on biocompatible 2-norbornene ethylene cyclic olefin copolymer substrates. Given the suitable aspect ratio of the nanoripples and the peculiarity of their multiscale structure, the final substrates are available for cell–material interaction studies that can shed light on the role of the hierarchy of nanostructured materials in controlling the large-scale cellular behavior on biocompatible scaffolds. This work also presents an original combination of numerical analyses of scanning force microscopy images, which allows an accurate quantitative description of the outputs of the two-step transfer process.
Keywords: nanostructures, germanium, ion irradiation, lithography, transfer process

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Publ.-Id: 25040


Impact of pre- and early per-treatment FDG-PET based dose-escalation on local tumour control in fractionated irradiated FaDu xenograft tumours.

Jentsch, C.; Bergmann, R.; Brüchner, K.; Mosch, B.; Yaromina, A.; Krause, M.; Zips, D.; Troost, E. G. C.; Löck, S.; Kotzerke, J.; Steinbach, J.; Thames, H.; Baumann, M.; Beuthien-Baumann, B.
OBJECTIVE:

To investigate local tumour control after dose-escalation based on [18F]2-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) obtained before and early during fractionated irradiation.
MATERIALS AND METHODS:

85 mice bearing FaDu xenografts underwent FDG-PET twice: first immediately prior to the first 2-Gy fraction of irradiation (PET1_0) and second after 18°Gy (PET2_18). After these 9 fractions, animals were randomly allocated to: (1) continuation of 2-Gy fractions (cumulative dose of 60°Gy; n=31), (2) dose-escalation with 3-Gy fractions (cumulative EQD2-dose 86.25°Gy [α/β-value: 10]; n=25), or (3) with 4-Gy fractions (cumulative EQD2-dose 116°Gy; n=29). The effects of SUVmax0°Gy, SUVmax18°Gy, and dose on local tumour control were analysed in two ways. First, the Cox proportional hazards model was used with two covariates: continuous SUVmax values and dose. Second, the Kaplan-Meier method was used, with tumours classified according to SUVmax greater than or less than (1) median maximum standardized uptake value (SUVmax) at PET1_0 and PET2_18, or (2) the cut-off value 2.5.
RESULTS:

The multivariate Cox analysis revealed a significant negative association between higher SUVmax determined before start of treatment and local control (HR=1.59, [95% CI 1.04, 2.42], p=0.031), whereas higher dose had a significant positive effect (HR=0.95, [0.93, 0.98], p<0.001). In contrast, FDG uptake at 18Gy did not correlate with local control (HR=1.14, [0.53, 2.45], p=0.73). Neither FDG uptake prior to irradiation nor at 18Gy correlated with local control irrespective of the delivered dose (log-rank test) when using the median SUVmax values for stratification (SUVmax0Gy: 60Gy: p=0.25, 86.25Gy: p=0.47, 116Gy: p=0.88 and SUVmax18Gy: 60Gy: p=0.42, 86.25Gy: p=0.34, 116Gy: p=0.99). By contrast, stratifying the animals by the cut-off 2.5 at PET1_0 reveals a significant difference in local control for the 60Gy group (p=0.034), but not for the other dose groups. At PET2_18, no significant effect for any dose group was detected.
CONCLUSIONS:

The multivariate Cox analysis revealed a significantly higher hazard of recurrence for mice with higher SUVmax determined before start of treatment. These results support the hypothesis that patients with high pre-therapeutic FDG uptake should be considered at increased risk of local failure and therefore as possible candidates for dose escalation strategies.
Keywords: Dose escalation; FDG positron emission tomography; FaDu xenografts; Fractionated irradiation; Local tumour control; Squamous cell carcinoma

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Publ.-Id: 25039


HPV status, cancer stem cell marker expression, hypoxia gene signatures and tumour volume identify good prognosis subgroups in patients with HNSCC after primary radiochemotherapy: A multicentre retrospective study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG).

Linge, A.; Lohaus, F.; Löck, S.; Nowak, A.; Gudziol, V.; Valentini, C.; von Neubeck, C.; Jütz, M.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Combs, S. E.; Mönnich, D.; Zips, D.; Buchholz, F.; Aust, D. E.; Baretton, G. B.; Thames, H. D.; Dubrovska, A.; Alsner, J.; Overgaard, J.; Krause, M.; Baumann, M.
OBJECTIVE:

To investigate the impact of the tumour volume, HPV status, cancer stem cell (CSC) marker expression and hypoxia gene signatures, as potential markers of radiobiological mechanisms of radioresistance, in a contemporary cohort of patients with locally advanced head and neck squamous cell carcinoma (HNSCC), who received primary radiochemotherapy (RCTx).
MATERIALS AND METHODS:

For 158 patients with locally advanced HNSCC of the oral cavity, oropharynx or hypopharynx who were treated at six DKTK partner sites, the impact of tumour volume, HPV DNA, p16 overexpression, p53 expression, CSC marker expression and hypoxia-associated gene signatures on outcome of primary RCTx was retrospectively analyzed. The primary endpoint of this study was loco-regional control (LRC).
RESULTS:

Univariate Cox regression revealed a significant impact of tumour volume, p16 overexpression, and SLC3A2 and CD44 protein expression on LRC. The tumour hypoxia classification showed a significant impact only for small tumours. In multivariate analyses an independent correlation of tumour volume, SLC3A2 expression, and the 15-gene hypoxia signature with LRC was identified (CD44 protein n/a because of no event in the CD44-negative group). Logistic modelling showed that inclusion of CD44 protein expression and p16 overexpression significantly improved the performance to predict LRC at 2years compared to the model with tumour volume alone.
CONCLUSIONS:

Tumour volume, HPV status, CSC marker expression and hypoxia gene signatures are potential prognostic biomarkers for patients with locally advanced HNSCC, who were treated by primary RCTx. The study also supports that the individual tumour volumes should generally be included in biomarker studies and that panels of biomarkers are superior to individual parameters.
Keywords: Biomarkers for radiotherapy; Cancer stem cells; HNSCC; HPV; Hypoxia; Primary radiochemotherapy

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Publ.-Id: 25037


Ionization and Reflux Dependence of Magnetic Instabilities Generation and Probing Inside Laser-Irradiated Thin Solid Foils

Huang, L. G.; Schlenvoigt, H.-P.; Takebe, T.; Cowan, T. E.
The effects of ionization and hot electron reflux on magnetic instabilities generation inside solid thin foils driven by ultra-fast relativistic laser pulses are presented. We also show the Faraday rotation method to probe the magnetic fiels in the bulk target by using XFELs.
Keywords: ionization, reflux,magnetic instabilities,plasma physics,xfel,faraday rotation
  • Poster
    2017 European XFEL Users' Meeting and Satellite Meetings, 24.-27.01.2017, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-25036
Publ.-Id: 25036


Internal and external validation of an ESTRO delineation guideline - dependent automated segmentation tool for loco-regional radiation therapy of early breast cancer.

Eldesoky, A. R.; Yates, E. S.; Nyeng, T. B.; Thomsen, M. S.; Nielsen, H. M.; Poortmans, P.; Kirkove, C.; Krause, M.; Kamby, C.; Mjaaland, I.; Blix, E. S.; Jensen, I.; Berg, M.; Lorenzen, E. L.; Taheri-Kadkhoda, Z.; Offersen, B. V.
BACKGROUND AND PURPOSE:

To internally and externally validate an atlas based automated segmentation (ABAS) in loco-regional radiation therapy of breast cancer.
MATERIALS AND METHODS:

Structures of 60 patients delineated according to the ESTRO consensus guideline were included in four categorized multi-atlas libraries using MIM Maestro™ software. These libraries were used for auto-segmentation in two different patient groups (50 patients from the local institution and 40 patients from other institutions). Dice Similarity Coefficient, Average Hausdorff Distance, difference in volume and time were computed to compare ABAS before and after correction against a gold standard manual segmentation (MS).
RESULTS:

ABAS reduced the time of MS before and after correction by 93% and 32%, respectively. ABAS showed high agreement for lung, heart, breast and humeral head, moderate agreement for chest wall and axillary nodal levels and poor agreement for interpectoral, internal mammary nodal regions and LADCA. Correcting ABAS significantly improved all the results. External validation of ABAS showed comparable results.
CONCLUSIONS:

ABAS is a clinically useful tool for segmenting structures in breast cancer loco-regional radiation therapy in a multi-institutional setting. However, manual correction of some structures is important before clinical use. The ABAS is now available for routine clinical use in Danish patients.
Keywords: Atlas based automated segmentation; Breast cancer; ESTRO consensus guideline; Multi-center study; Target volume delineation; Validation

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Permalink: https://www.hzdr.de/publications/Publ-25035
Publ.-Id: 25035


Limits on 60Fe/26Al nucleosynthesis ratios from deep-sea AMS measurements

Feige, J.; Wallner, A.; Fifield, L. K.; Golser, R.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S.; Winkler, S. R.
The long-lived radionuclide 26Al (t1/2=~0.7 Myr) has been observed throughout our galaxy, reflecting ongoing nucleosynthesis over the past few million years [1]. It is produced and ejected into the interstellar medium by stellar winds and during supernova explosions. A nearby supernova may leave an imprint of 26Al in terrestrial archives, complementing the observation of supernova-produced 60Fe in deep-sea samples. The same set of sediment samples from the Indian Ocean that showed a distinct 60Fe-signature in layers of ages between 1.7 and 3.2 Myr [2] was also analyzed for 26Al. However, additional terrestrial sources producing 26Al on Earth, such as cosmogenic production in the atmosphere and in-situ production within the sediment, may obscure a supernova imprint. We used our experimental 26Al data to infer lower limits on 60Fe/26Al nucleosynthesis ratios by comparing the width and the strength of the previously measured 60Fe-signal to our 26Al data. We find that our results generally favour the higher theoretical isotopic supernova ratios and deviate from the observed galactic 60Fe/26Al flux ratio by 2-3 times of the measurement uncertainty.

[1] Diehl et al., New Astron. Rev., 52, 440 (2008)
[2] Wallner, Feige et al., Nature, 532, 69 (2016)
Keywords: AMS, supernova
  • Lecture (Conference)
    8th Nuclear Physics in Astrophysics International Conference, 18.-23.06.2017, Catania, Italy

Permalink: https://www.hzdr.de/publications/Publ-25034
Publ.-Id: 25034


Top-Down Fabrication and Characterization of SiNW RFETs

Deb, D.; Georgiev, Y.; Löffler, M.; Weber, W.; Helm, M.; Erbe, A.
The following work illustrates top-down fabrication and characterization of reconfigurable, undoped silicon nanowire field effect transistors with Schottky junctions on silicon on insulator (SOI) substrate. The fabrication scheme is based on electron beam lithography (EBL) on a SOI substrate followed by reactive ion etching (RIE) with HSQ etch mask. In best case we fabricated nanowires with 20 nm width and 60 nm pitch.
Nickel-silicide Schottky junctions were created inside the nanowire by ni-sputtering followed by forming gas annealing. Diffusion of nickel in silicon nanowire is precisely controlled by optimizing the time of annealing. Detailed morphological analyses of the nanowires were done by transmission electron microscopy (TEM) at Dresden Center for Nanoanalysis to identify the strained deformation in silicon crystal structure due to silicidation.
Keywords: EBL, ICP, SiNW, RFETs
  • Lecture (Conference)
    IHRS NanoNet Annual Workshop 2015, 02.10.2015, Bastei, Germany

Permalink: https://www.hzdr.de/publications/Publ-25033
Publ.-Id: 25033


Top-down fabrication and characterization of reconfigurable silicon nanowires

Deb, D.; Khan, M. B.; Georgiev, Y.; Löffler, M.; Weber, W.; Helm, M.; Erbe, A.
The following work illustrates characterization of reconfigurable, undoped silicon nanowire field effect transistors with Schottky junctions fabricated on silicon on insulator (SOI) substrate by top-down process. The fabrication scheme is based on electron beam lithography (EBL) using hydrogen silsesquioxane (HSQ), a negative tone electron beam resist, followed by inductively coupled plasma (ICP) etching. The etch recipe was optimised in context of selectivity, sidewall roughness and anisotropy by selecting an appropriate gas chemistry (SF6/C4F8) and controlling the ICP hardware parameters like gas flow, mixed gas ratio, plasma power and chamber pressure. We produced silicon nanowires of 20 nm width and nanowire arrays with pitch of 200 nm. 50 nm thick nickel (Ni) layer was sputtered on the SiNWs at lithographically defined areas followed by lift-off and thermal annealing to create Nickel-Silicide Schottky junctions inside the nanowires. In this way, the source and drain region was formed creating silicide-silicon-silicide contacts. Transport properties of these nanowires can be modulated from P-type to N-type and vice-versa by changing polarity of the back gate
Keywords: RFETs, ICP etching, EBL, Silicon nanowire, HSQ resist
  • Lecture (Conference)
    DPG Frühjahrstagung 2016, 06.-11.03.2016, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-25032
Publ.-Id: 25032


Analysis of NixSiy-Si Nanowires for Next Generation Electronics

Loffler, M.; Deb, D.; Muhle, U.
Si Nanowires are one of the foremost candidates for “beyond CMOS” technology, both from the point of miniaturization (more Moore) but also from the point of added function (more-than-Moore). NiSi2-Si Schottky junctions in nanowires are the building blocks for the design of reconfigurable logic on the hardware level [1]. However, the device parameters depend very sensitively on the geometry of the interface and the transistor makeup.
Here we present the analysis of NixSiy-Si nanowires fabricated on silicon-on-insulator (SOI) substrate using a top-down approach and silicidized using thermal Ni diffusion from lithographically patterned electrodes. We employed both SEM and TEM techniques to identify regions of interest to be prepared by the standard FIB technique followed by 1kV FIB cleaning to preserve the crystal structure.
We observed that the interface forms {111} facets (Figure 1). Furthermore, we observed grain boundaries, nanotwins and multiple silicide phases between the Ni source and the Si part of the nanowire.
Keywords: TEM, RFETs, Nanaowires
  • Poster
    Scandem 2016, 07.-10.06.2016, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-25031
Publ.-Id: 25031


Characterization of silicon nanowires with NiSi2 Schottky contacts fabricated by top-down process

Deb, D.; Fuchs, F.; Georgiev, Y.ORC; Gemming, S.ORC; Schuster, J.; Erbe, A.
We report on characterization of reconfigurable, undoped silicon nanowire field effect transistors (FETs) with an axial heterostructure (metal/intrinsic-silicon/metal) fabricated on silicon on insulator (SOI) substrates by top-down process. Reconfigurable Si nanowire transistors with Schottky junctions can be reversely configured as p-FET or n-FET simply by the application of back gate electric signal. The fabrication scheme is based on electron beam lithography (EBL) using hydrogen silsesquioxane (HSQ), a negative-tone electron beam resist, followed by inductively-coupled plasma (ICP) etching. We produced silicon nanowires of 20 nm width and nanowire arrays with a pitch of ≈ 200 nm.
Nickel was sputtered on the Si nanowires at lithographically defined areas followed by thermal annealing to create nickel-silicide Schottky junctions inside the nanowires which also act as source-drain contacts. Diffusion of Ni in Si nanowires was precisely controlled by the radial crystal orientation of the nanowires, which was checked by transmission electron microscopy (TEM). TEM images show atomic sharp NiSi2-silicon junctions. Quantum transport simulations using non-equilibrium Green’s functions show changes in local density of states at the NiSi2-Si interface. Calculations also confirm that at the NiSi2-Si junction the Schottky barrier, heights for electron and holes are equal.
Keywords: NiSi2, Schottky Junctions, TEM
  • Poster
    Physics on Boat 2016, 31.05.-02.06.2016, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-25030
Publ.-Id: 25030


Top-down fabrication and characterization of reconfigurable silicon nanowire-based field effect transistors with Schottky contacts

Deb, D.; Khan, M. B.; Georgiev, Y. M.; Löffler, M.; Weber, W.; Helm, M.; Erbe, A.
In the last 60 years the size of a transistor has been reduced from few centimeters to few nanometers. Smarter, faster and cheaper: these are the three factors that motivated the miniaturization crusade in the silicon chip industry. Now we reach the end of physical scaling and it is expected that future development will be based on new ideas1: (i) new materials (high-mobility channel materials accompanied by metal gates with high-k gate dielectrics), (ii) new architectures (e.g. 3D integration), (iii) new functionality (e.g. reconfigurability), (iv) new computation principles (e.g. spintronics, quantum computing), etc.
In this work we deal with this problem by introducing reconfigurability in transistors. We report on characterization of reconfigurable, undoped silicon nanowire field effect transistors (FETs) with Schottky junctions fabricated on silicon on insulator (SOI) substrates by an industry compatible top-down process. Reconfigurable transistors employ an axial nanowire heterostructure (metal/intrinsic-silicon/metal) with independent gating of the two Schottky junctions and can be reversely configured as p-FET or n-FET simply by the application of an electric signal2.
The fabrication scheme is based on electron beam lithography (EBL) using hydrogen silsesquioxane (HSQ), a negative-tone electron beam resist, followed by inductively-coupled plasma (ICP) etching. The etch recipe was optimized with respect to selectivity, sidewall roughness and anisotropy by selecting an appropriate gas chemistry (SF6/C4F8) and controlling the ICP hardware parameters such as gas flow, mixed gas ratio, plasma power and chamber pressure. We produced silicon nanowires of 20 nm width and nanowire arrays with a pitch of ≈ 200 nm.
A nickel (Ni) layer of 50 nm thickness was sputtered on the Si nanowires at lithographically defined areas followed by lift-off and thermal annealing to create nickel-silicide Schottky junctions inside the nanowires. In this way, the source and drain regions were formed creating silicide-silicon-silicide contacts. Diffusion of Ni in Si nanowires was precisely controlled by the radial crystal orientation of the nanowires, which was checked by transmission electron microscopy (TEM). The Schottky junctions were electrostatically modulated by a back gate potential. Transport properties of these nanowires could be switched from p-type to n-type and vice-versa by changing the polarity of the back gate.

References
1. L. Risch, Solid-State Electronics. 50, 527 (2006).
2. A. Heinzig, T. Mikolajick, J. Trommer, D. Grimm and W. M. Weber, Nano Letters. 13, 4176 (2013).
Keywords: Nanowires, FETs, Schotky Junctions, Silicides
  • Lecture (Conference)
    ICSNN 2016 - 19th International Conference on Superlattices, Nanostructures and Nanodevices, 25.-29.07.2016, Hong Kong, China

Permalink: https://www.hzdr.de/publications/Publ-25029
Publ.-Id: 25029


Characterisation of top-down fabricated NixSiy-Si hetrostructure undoped nanowires

Deb, D.; Loffler, M.; Khan, M. B.; Georgiev, Y. M.; Erbe, A.
Semiconductor industry reaches the end of physical scaling soon and it is expected that future development will be based on new concepts: (i) new materials (high-mobility channel materials accompanied by metal gates with high-k gate dielectrics), (ii) new architectures (e.g. 3D integration), (iii) new functionality (e.g. reconfigurability), (iv) new computation principles (e.g. spintronics, quantum computing), etc [1]. In our work we focus on new functionality, specifically reconfigurable logic. The most promising industry compatible hardware for this logic is silicon nanowire based Schottky junction FET [2]. However, NiSi2-Si Schottky junctions in axial heterostructures (metal/intrinsic silicon/metal) are still complex and detailed studies of these structures are essential.
We report on heterostructure (NixSiy-Si) characterisation of reconfigurable, undoped silicon nanowire Schottky junction FETs. The nanowires are fabricated on silicon on insulator (SOI) substrates by electron beam lithography (EBL) using hydrogen silsesquioxane (HSQ), a negative-tone electron beam resist, followed by inductively-coupled plasma (ICP) etching. We produced silicon nanowires of 20 nm width and arrays of them with a pitch of ≈ 200 nm. Nickel was sputtered on the Si nanowires at lithographically defined areas followed by thermal annealing to create nickel-silicide Schottky junctions inside the nanowires, which also act as source-drain contacts. Silicidation was done on single nanowires and nanowire arrays with varying cross-sections and also for different annealing times.
We investigated the corresponding devices using SEM and TEM concerning their morphology and silicidation and determined the necessary parameters to allow for a reproducible scaling of these structures.
Furthermore, some cross-sections of nanowire samples were prepared by the standard FIB technique followed by low voltage FIB cleaning to preserve the crystal structure. We observed that the interface between the Ni silicide and the intrinsic silicon forms {111} facets. In contrast to common expectations, also features such as grain boundaries, nanotwins and multiple silicide phases between the Ni source and the Si part of the nanowire have been observed. Those features pose a technological challenge towards large-scale integration in future reconfigurable semiconductor devices and need to be properly studied and taken into account.
[1] L. Risch, Solid-State Electronics. 50 (2006) 527-535.
[2] A. Heinzig, T. Mikolajick, J. Trommer, D. Grimm and W. M. Weber, Nano Lett. 13 (2013) 4176-4181.
Keywords: Nanowires, TEM, silicon on insulator, Schottky junction, FETs, Silicidation
  • Poster
    42nd Micro and Nano Engineering international conference (MNE 2016), 19.-23.09.2016, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-25028
Publ.-Id: 25028


Open volume defects in annealed and ion irradiated SrTiO3 systems

Liedke, M. O.; Potzger, K.; Srinivasan, N.; Wagner, A.
The formation of vacancies in SrTiO3 due to annealing in vacuum [1] or low-energy ion irradiation [2] also leads to the modification of electronic properties that could be exploited in applications like resistivity switching. Here, we employ both these modification methods combined with in-situ defects evolution analysis by means of Doppler Broadening Positron Annihilation Spectroscopy (DB-PAS). Two reference SrTiO3 single crystals, undoped and Nb-doped have been investigated. Vacuum annealing of undoped SrTiO3 increases the defect concentration which can be attributed to the creation of oxygen and strontium vacancies close to the sample surface and deeper inside the substrate, respectively. Variable energy DB-PAS reveals the depth-dependent open volume defects concentration. Second, in-situ room and low temperature (about 165K) Ar+ irradiation has been utilized as a preliminary attempt to understand a vacancy migration process beneath the kinetical ion penetration depth. For that purpose, a frozen vacancy state is required, which could be achieved by lowering the system temperature below the vacancy activation energy. Although, that part of the experiment has been not entirely successful due to not low enough temperature realized during ion irradiation, however, a strong conclusion has been drawn about necessity of performing such type of experiments in-situ. A clear indication of oxygen deficiency at the sample surface due to ion irradiation, as found from DB-PAS is diminished after repeated ex-situ measurements.
Keywords: strontium titanate, annealing, PAS, Doppler broadening, AIDA
  • Poster
    MEMRIOX International Workshop 2016, 25.-27.09.2016, Bastei, Germany

Permalink: https://www.hzdr.de/publications/Publ-25027
Publ.-Id: 25027


Positron annihilation spectroscopy of ion and laser irradiation driven spin reorientation transitions in Pt/Co/Pt systems

Liedke, M. O.; Sveklo, I.; Jakubowski, M.; Anwand, W.; Yuan, Y.; Zhou, S.; Kurant, Z.; Wawro, A.; Maziewski, A.; Wagner, A.
Multilayer ultrathin-films with perpendicular magnetic anisotropy (PMA) show a perspective as candidates for spintronic devices. The effective magnetic anisotropy strongly depends on the magnetic layer thickness – spin reorientation transition (SRT) at a critical thickness takes place from the inplane to out-of-plane magnetization direction. Moreover, SRT can be shifted to higher thicknesses by means of ion [1] and fs-laser irradiation [2]. Here, we employ variable energy positron annihilation spectroscopy (PAS) that is sensitive to open volume defects and their atomic surrounding to compare these two methods of the SRT inducement. Molecular beam epitaxy deposited films with different bottom Pt layer thicknesses and growth temperatures have been investigated. In case of Ar+ ion irradiated trilayers magnetization can be driven to the out-of-plane state twice as a function of ion fluence [1], whereas our preliminary studies of UV laser irradiation suggest only one SRT.
PAS analysis (Fig. 1) of the as-grown samples reveal slight differences in crystal quality and defect concentration that is likely due to a thicker bottom Pt layer used for the ion irradiation experiment.
Films utilized for the laser irradiation exhibit larger initial positron diffusion length, L+ that is close to L+ of the substrate (~60nm). In case of lower ion and laser fluences only minor and no interface intermixing has been found, respectively. The sample irradiated with lower ion fluence shows a slight increase of S (for E~1.5keV) being likely due to Co-vacancy increase, which could be responsible for first SRT. The sample irradiated with lower laser fluence shows no difference compare to the asgrown stacks, where only increase of magnetic anisotropy was found. The larger ion and laser fluences reorients magnetization to the out-of-plane state that is evidenced by both magneto-optical and PAS studies – S(E) curves nicely overlap. Moreover, large intermixing is expected, thus creation of the CoPt alloy with PMA. To elucidate stoichiometry and atomic surrounding of open volume defect coincidence Doppler broadening investigations will be presented.
*Corresponding author. E-mail address: m.liedke@hzdr.de
[1] A. Maziewski et al., Phys. Rev. B. 85, 054427 (2012)
[2] J. Kisielewski et al., J. Appl. Phys. 115, 053906 (2014)
Keywords: perpendicular magnetic anisotropy, positron annihilation spectroscopy, Doppler broadening, ion irradiation, UV ns-laser irradiation
  • Poster
    Joint European Magnetic Symposia (JEMS), 21.-26.08.2016, Glasgow, United Kligdom

Permalink: https://www.hzdr.de/publications/Publ-25026
Publ.-Id: 25026


Positron annihilation lifetime spectroscopy study of self-assembled porous low-k films

Kraatz, M.; Clausner, A.; Gall, M.; Zschech, E.; Liedke, M. O.; Anwand, W.; Wagner, A.; Krause-Rehberg, R.; Pakbaz, K.
We investigated advanced, self-assembled, porous organosilicate glasses with varying porogen level, resulting in varying dielectric constants (k-values ranging from 1.8 to 2.7, including a non-porous reference sample with 3.0). We used positron annihilation lifetime spectroscopy (PALS) to determine the pore size. The pores are fabricated by self-assembly into the OSG by a sol-gel process. The pore size is a critical parameter to characterize the quality of the OSG thin film. Other critical parameters, which were not investigated in this study are connectedness of pores and pore size distribution. Porous OSG is used in the microelectronic industry as insulating material for the wiring of microchips. Since pores not only lower the k-value, but also degrade mechanical stability of film stacks in microchips, knowledge of pore characteristics is crucial. Low-k materials are a necessity to lower microchip power consumption, maintain signal speed and reduce coupling in the relentless icroelectronics miniaturization process.
Keywords: positron annihilation spectroscopy, low-k, dielectrics, porous materials, positron lifetime
  • Poster
    14th International Conference Reliability and Stress-Related Phenomena in Nanoelectronics – Experiment and Simulation, 30.05.-01.06.2016, Bad Schandau, Germany

Permalink: https://www.hzdr.de/publications/Publ-25025
Publ.-Id: 25025


P1608 - Ionenmikroskopievorrichtung

Klingner, N.; Heller, R.; Hlawacek, G.; Facsko, S.; von Borany, J.; Wilhelm, R. A.
Die Erfindung betrifft eine Ionenmikroskopievorrichtung mit einer Ionenquelle zum Erzeugen eines Ionenstrahls, einem Detektor, einer Spannungsquelle und einem Photonenpuls-Generator, wobei die Ionenmikroskopievorrichtung zum Bestrahlen eines Objekts mit dem Ionenstrahl unter Erzeugung von Wechselwirkungsteilchen ausgebildet ist, wobei die Ionenquelle eine Gasionisationskammer, eine in derselben angeordnete spitzenförmige Elektrode und eine Gegenelektrode aufweist, der Detektor zum Erfassen der Wechselwirkungsteilchen dient, die Spannungsquelle zum Anlegen einer elektrischen Spannung zwischen die Elektrode und die Gegenelektrode dient, und der Photonenpuls-Generator zum Erzeugen von in die Ionisationskammer gerichteten Photonenpulsen dient.
  • Patent
    DE102016112328 - Erteilung: 05.01.2017

Permalink: https://www.hzdr.de/publications/Publ-25024
Publ.-Id: 25024


Single Molecule Level Measurements

Kilibarda, F.; Ahmed, O.; Öktem, G.; Kiriy, A.; Cuniberti, G.; Erbe, A.
In the quest for miniaturizing the transistor nodes, the technology does not look so promising and alternates have to be done in order to sustain the ‘Beyond CMOS’ trend. One of the promising technology can be the use of ‘Molecular Electronics’. In recent years, microelectronics industry is reaching its limits with transistor miniaturization. One of the possibilities is to abandon standard silicon technologies and start using single molecules and atoms as building blocks. By taking this route, it is first important to characterize and choose the right molecular candidates for future implementation. Till recent years this area was very slow in development, but as the techniques of electronic lithography, nanoscale manufacture and chemical synthesis continue to improve, it is accelerating in progress. In our research we are working with Mechanically Controlled Break Junctions (MCBJ) as a method of characterizing electrical properties of molecules and apply Landauer theoretical approach to model the behavior of the junctions. In parallel to that, we are examining possibilities to gate the molecules while they are being characterized. Our experiments show successful coupling to the molecules and accompanying change in conductance. In regard to gating we show possibility of manufacturing sub-20nm gaps for side gating of the molecular system.The developed techniques presented here may prove to be important in future many-level measurements and transistor implementation.
Keywords: Molecular electronics; MCBJ; electronic lithography; gating; nanogaps
  • Poster
    NanoNet International Workshop 2016, 30.08.-02.09.2016, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-25023
Publ.-Id: 25023


P1511 - Thermisches Anemometer

Schleicher, E.; Berger, R.; Arlit, M.
Die Erfindung betrifft ein thermisches Anemometer zum Charakterisieren einer Fluidströmung, wobei das Anemometer ein Sensorelement zum Einbringen in die Fluidströmung aufweist, das mittels einer Spannung elektrisch beheizbar ist; wobei das Anemometer zum abwechselnden Betreiben des Sensorelements mit einer kleineren ersten und einer größeren zweiten Spannung ausgebildet ist, sodass ein abwechselndes Erwärmen und Abkühlen des Sensorelements erfolgt; wobei beim Betreiben des Sensorelements mit der ersten Spannung beim Erreichen eines unteren Temperatur-Schwellenwertes ein Umschalten zu der zweiten Spannung erfolgt, beim Betreiben des Sensorelements mit der zweiten Spannung beim Erreichen eines oberen Temperatur-Schwellenwertes ein Umschalten zu der ersten Spannung erfolgt, und das Anemometer zum Charakterisieren der Fluidströmung basierend auf den Zeitabständen zwischen den Umschalt-Zeitpunkten, an denen ein Umschalten der Spannung erfolgt, ausgebildet ist.
  • Patent
    DE102015114139 - Erteilung: 08.12.2016

Permalink: https://www.hzdr.de/publications/Publ-25022
Publ.-Id: 25022


The influence of local ion implantation on magnetic domains, magnetoresistance and spin wave propagation

Osten, J.; Hula, T.; Wagner, K.; Henschke, A.; Lenz, K.; Schultheiss, H.; Lindner, J.; Fassbender, J.ORC
The influence of ion induced magnetic patterning on the anisotropic magnetoresistance (AMR) is investigated in the first part. The AMR directly depends on the angle between the applied current and the magnetization of the material. To investigate this relationship a Kerr microscope for visualizing the magnetic domains is combined with magneto-transport measurements. The investigated samples are magnetic hybrid structures from irradiated and non-irradiated permalloy.

In the second part ion implantation is used to create spin wave channels. Fe60Al40films in the B2 phase is paramagnetic. Starting from a FeAl film in the paramagnetic state the incident ions randomize the site occupancies and, thereby, transform it to the chemically disordered, ferromagnetic A2 phase. Spin waves, the eigen-excitations of ferromagnets, are promising candidates for spin transport in lateral devices. The aim is to investigate spin wave propagation in this ferromagnetic material in free standing structure as well as in structure within a paramagnetic matrix.
  • Lecture (others)
    Hard Condensed Matter Theory Seminar, 24.01.2017, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25021
Publ.-Id: 25021


P1413 - Verfahren zur Metallisierung von Kunststoffteilen sowie Lösung

Hofinger, J.; Roos, S.; Günther, T.; Maffert, A.
Die Erfindung umfasst ein Verfahren zur Metallisierung von Kunststoffteilen mit den Schritten Vorbehandlung der Kunststoffoberfläche, chemische Metallisierung, wobei zur Vorbehandlung, die Oberfläche des Kunststoffteiles mit mindestens einer niedrig siedenden organischen Flüssigkeit angelöst und/oder angequollen wird, sodass anschließend die angelöste und/oder angequollene Kunststoffoberfläche durch Verdampfen der mindestens einen niedrig siedenden organischen Flüssigkeit strukturiert wird und sodass die so strukturierte Oberfläche ohne Chromsäure-Schwefelsäure-Lösung hydrophiliert wird.
  • Patent
    DE102015201562 - Offenlegung: 04.08.2016, Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-25020
Publ.-Id: 25020


German Resource Research Institute (GERRI): Concept and Aims of a Raw Materials Network

Köpf, H.; Rasenack, K.
The German Resource Research Institute “GERRI” was founded as a virtual institute and a national network in 2015 by five leading German research institutions of the raw materials sector. The founding partners of GERRI - TU Bergakademie Freiberg, RWTH Aachen University, Clausthal University of Technology, Fraunhofer project group materials recycling and resource strategies IWKS at the Fraunhofer Institute ISC and the Helmholtz-Institute Freiberg for Resource Technolo-gy (HIF) at the HZDR – offer broad knowledge and experience in the following fields of expertise: exploration & mining, processing, hydrometallurgy, pyrometallurgy, materials, waste management, machinery, modeling and special analytics. The main goal of GERRI is to strengthen transdiscipli-nary research along the entire value chain of mineral metalliferous and raw materials. Furthermore, GERRI is intended to become a central nucleus for innovation between politics, industry and aca-demic research.
GERRI´s unique feature of GERRI is competence mapping, which bundles the available knowledge and experience within all competence fields of this network. There methods and processes of tech-nical infrastructure are directly linked to relevant elements of periodic table and material flows.
GERRI is embedded in the "Research for Sustainable Development (FONA)" program of the Ger-man Federal Ministry of Education and Research (BMBF), which is part of the funding program "r4 - Innovative Technologies for Resource Efficiency - Research on the Provision of Economic Strate-gic Raw Materials". After the expiry of the five-year funding period, GERRI is envisioned to persist independently as a network and will be financed, amongst others, by industrial and research funds.
Keywords: Competence mapping, infrastructure sharing, interdisciplinary research, network, synergies
  • Contribution to proceedings
    European Metallurgical Conference (EMC) 2017, 25.-28.06.2017, Leipzig, Deutschland
    German Resource Research Institute (GERRI): Concept and Aims of a Raw Materials Network
  • Lecture (Conference)
    European Metallurgical Conference 2017, 25.-28.06.2017, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25019
Publ.-Id: 25019


Das virtuelle Rohstoffforschungsinstitut GERRI: Innovationskatalysator für Deutschland

Köpf, H.; Güth, C.; Rasenack, K.; Rombach, E.; Schmid, E.; Friedrich, B.; Goldmann, D.; Reuter, M. A.; Stauber, R.; Stelter, M.
Das German Resource Research Institute GERRI ist ein nationales Netzwerk im Bereich metallischer und mineralischer Rohstoffe. Ziel ist die Bündelung und Koordination der Akteure für eine optimierte gemeinsame Forschung entlang der Rohstoffkette. GERRI hat erstmals eine Methodik entwickelt, über die Kompetenzen strukturiert erfasst, ausgewertet und verfügbar gemacht werden können. Dadurch schafft GERRI Transparenz und legt die Grundlage zur Realisierung von Synergien.
Keywords: Wirtschaftsstrategische Rohstoffe, Rohstoffstrategie, KIC EIT RawMaterials, German Ressource Research Institute (GERRI), strategische Forschungskooperation, Kompetenzmapping
  • Contribution to proceedings
    Berliner Rohstoff- und Recyclingkonferenz, 06.-07.03.2017, Berlin, Deutschland
    Proceedings der Berliner Rohstoff- und Recyclingkonferenz

Permalink: https://www.hzdr.de/publications/Publ-25018
Publ.-Id: 25018


P1412 - Pockelszellen-Treiberschaltung mit Induktivitäten

Bergmann, T.; Siebold, M.; Löser, M.
Die Treiberschaltung enthält eine erste Leitung, welche mit einem ersten Anschluss der Pockelszelle (18; CP) zu verbinden ist, und eine zweite Leitung, welche mit einem zweiten Anschluss der Pockelszelle (18; CP) zu verbinden ist, wobei die erste Leitung und/oder die zweite Leitung eine Induktivität 10 (14, 15; 24, 25) aufweist.
  • Patent
    EP3023832 - Offenlegung: 25.05.2016, Nachanmeldungen: US

Permalink: https://www.hzdr.de/publications/Publ-25017
Publ.-Id: 25017


Micro reactor experiments on the partial isobutane oxidation as a multiphase process.

Willms, T.; Kryk, H.; Hampel, U.
Tertiary butyl hydroperoxide (TBHP), as an intermediate for the production of propylene oxide according to the Oxirane process, is currently produced at industrial scale by the partial oxidation of liquid isobutane using bubble columns or bubble tray reactors. In this process, liquid isobutane reacts with oxygen at temperatures of 120 to 140 °C and pressures of 25 to 37 bar at high residence times of up to 12 hours. The conversion is limited to 35 to 50 % in order to obtain a TBHP selectivity of 50 to 60 % minimizing the formation of by-products, which are caused by the decomposition of the TBHP due to the complex reaction mechanism. Besides safety aspects, the high reaction enthalpy of the oxidation as well as heat and mass transport problems are further issues of this process. In the frame of the Helmholtz-Energy-Alliance project “Energy efficient chemical multiphase processes“, this reaction is investigated for the first time as a Taylor-Flow process in a broad range of flow rates, temperatures and pressures in a micro reactor with the aim to enhance the space-time yield of the process. The advantage of micro reactors are the high surface – volume ratio for an efficient heat transfer, the related, improved – nearly inherent – safety and the resulting possibility to investigate yet unexplored process windows for instance within the explosive region of a reaction mixture. A number of levers for the process intensification have been identified. In addition to the parameter ranges studied so far, higher pressures of up to 100 bar and uninvestigated initiator types, especially e.g hydrogen peroxide and high oxidation concentrations (50 to 100%) are applied, which have not been studied yet. Also, the influence of process parameters on the start-up time is investigated. Finally, the reaction medium characteristics of the isobutane – oxidant flow is modified by adding additives to the liquid phase or inert gases to the gas phase. For all parameters, the selecti¬vity and conversion of the reaction is studied. Therefore, the reaction course is followed by sampling and analyzing the reaction by GC/MS and GC–TCD where analytical methods have been developed to detect a maximum of by-products and intermediates. In the frame of the presentation, the results of preliminary investigations and the first multiphase flow oxidation experiments are given and discussed with respect to the reaction characteristics.
Keywords: isobutane oxidation, microreactor, t-butyl hydroperoxide, two phase process
  • Poster
    10th European Congress of Chemical Engineering, 3rd European Congress of Applied Biotechnology, 5th European Process Intensification Conference ECCE10+ECAB3+EPIC5, 27.09.-01.10.2015, Nice, France
  • Contribution to proceedings
    10th European Congress of Chemical Engineering, 3rd European Congress of Applied Biotechnology, 5th European Process Intensification Conference ECCE10+ECAB3+EPIC5, 27.09.-01.10.2015, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-25016
Publ.-Id: 25016


Fabrication of sub-50 nm silicon nanowires using inductively coupled plasma etching

Khan, M. B.; Deb, D.; Georgiev, Y. M.; Erbe, A.
Development of an etching process for fabrication of ultrathin silicon nanowires (SiNWs) with inductively coupled plasma (ICP) source and C4F8/SF6 mixed gas recipe at 18 oC is reported. Etch selectivity of silicon (SOI) to hydrogen silsesquioxane (HSQ), a negative tone electron beam resist and selectivity of silicon (SOI) to SiO2 are investigated to identify suitable process window. Effects of ICP power, RF power, chamber pressure, flow rates and ratio of C4F8/SF6 on etch rate, selectivity and surface roughness are examined. Atomic force microscopy (AFM) is used for identifying surface roughness of the plain silicon (SOI) substrates after etching. Thereafter etching of HSQ patterned substrates is performed. Scanning electron microscopy is performed to observe the etch profile. Parameters such as flow rates of C4F8/SF6 are optimized to attain sub-50 nm SiNWs with smooth and vertical sidewalls.
  • Poster
    DPG Regensburg, 06.-11.03.2016, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-25015
Publ.-Id: 25015


Ge-doped GaSb thin films with zero mass density change upon crystallization for applications in phase change memories

Putero, M.; Coulet, M. V.; Muller, C.; Baehtz, C.; Raoux, S.; Cheng, H. Y.
In order to optimize materials for phase change random access memories (PCRAM), the effect of Ge doping on Ga-Sb alloy crystallization was studied using combined in situ synchrotron x-ray techniques, electrical measurements, and static laser testing. The present data emphasize that the crystallization temperature can be increased up to 390C with subsequent higher thermal stability of the amorphous phase; phase segregation is evidenced with GaSb, Sb, and Ge phases that crystallize in a two-step crystallization process. The Ge-doped GaSb films exhibit a larger electrical contrast as compared to undoped GaSb alloy (up to 100). The optical contrast measured by laser testing is shown to follow the mass density change variations upon crystallization, with a negative contrast (higher value in amorphous state) whatever Ge-doping levels. In situ x-ray reflectivity measurements show that zero mass density change can be achieved by low Ge-doping. Ge-doped GaSb alloys look promising since a phase change material with zero mass density change and higher crystallization temperature satisfactorily fulfills the specifications for reliable PCRAM cells in terms of endurance and data retention.
Keywords: phase change memories; thin films

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Permalink: https://www.hzdr.de/publications/Publ-25014
Publ.-Id: 25014


In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites

Bayer, B. C.; Bosworth, D. A.; Michaelis, F. B.; Blume, R.; Habler, G.; Abart, R.; Weatherup, R. S.; Kidambi, P. R.; Baumberg, J. J.; Knop-Gericke, A.; Schloegl, R.; Baehtz, C.; Barber, Z. H.; Meyer, J. C.; Hofmann, S.
Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputterdeposited nanocomposites of metastable nickel carbide (Ni3C) nanocrystals in an amorphous carbon (a-C) matrix during thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ Xray photoelectron spectroscopy. At low annealing temperatures (300 °C) we observe isothermal Ni3C decomposition into face-centered-cubic Ni and amorphous carbon, however, without changes to the initial finely structured nanocomposite morphology. Only for higher temperatures (400−800 °C) Ni-catalyzed isothermal graphitization of the amorphous carbon matrix sets in, which we link to bulk-diffusion-mediated phase separation of the nanocomposite into coarser Ni and graphite grains. Upon natural cooling, only minimal precipitation of additional carbon from the Ni is observed, showing that even for highly carbon saturated systems precipitation upon cooling can be kinetically quenched. Our findings demonstrate that phase transformations of the filler and morphology modifications of the nanocomposite can be decoupled, which is advantageous from a manufacturing perspective. Our in situ study also identifies the high carbon content of the Ni filler crystallites at all stages of processing as the key hallmark feature of such metal−carbon nanocomposites that governs their entire thermal evolution. In a wider context, we also discuss our findings with regard to the much debated potential role of metastable Ni3C as a catalyst phase in graphene and carbon nanotube growth.
Keywords: nickel carbide, carbon nano tubes; in-situ xray diffraction

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Controlling Catalyst Bulk Reservoir Effects for Monolayer Hexagonal Boron Nitride CVD

Caneva, S.; Weatherup, R. S.; Bayer, B. C.; Blume, R.; Cabrero-Vilatela, A.; Braeuninger-Weimer, P.; Martin, M. B.; Wang, R.; Baehtz, C.; Schloegl, R.; Meyer, J. C.; Hofmann, S.
Highly controlled Fe-catalyzed growth of monolayer hexagonal boron nitride (h-BN) films is demonstrated by the dissolution of nitrogen into the catalyst bulk via NH3 exposure prior to the actual growth step. This “pre-filling” of the catalyst bulk reservoir allows us to control and limit the uptake of B and N species during borazine exposure and thereby to control the incubation time and h-BN growth kinetics while also limiting the contribution of uncontrolled precipitation-driven h-BN growth during cooling. Using in situ X-ray diffraction and in situ X-ray photoelectron spectroscopy combined with systematic growth calibrations, we develop an understanding and framework for engineering the catalyst bulk reservoir to optimize the growth process, which is also relevant to other 2D materials and their heterostructures.
Keywords: hexagonal boron nitride (h-BN), chemical vapor deposition (CVD), borazine (HBNH)3

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Publ.-Id: 25012


Micro structure and strain relaxation in thin nanocrystalline platinumfilms produced via different sputtering techniques

Gruber, W.; Baehtz, C.; Horisberger, M.; Ratschinski, I.; Schmidt, H.
In this study we investigated the correlation between microstructure and residual strain relaxation innanocrystalline Pt films with a thickness of about 20 nm produced by different deposition techniques:magnetron sputtering and ion beam sputtering. X-ray diffractometry was carried out using synchrotronradiation. The out-of-plane interplanar distance was measured during isothermal in situ annealing attemperatures between 130◦C und 210◦C. The thermoelastic expansion coefficient is equal for both types of nanocrystalline Pt films and slightly lower than for coarse grained Pt. The relaxation of residual out-of-plain strain depends on temperature and is significantly stronger in the case of the magnetron sputteredfilms than for the ion beam sputtered films. Different relaxation of compressive stress is ascribed tothe different microstructures which evolve during deposition via the corresponding deposition tech-nique. Thickness fringes around the (1 1 1) Bragg peak deposited via magnetron sputtering reveal thatthese films are essentially composed of columnar (1 1 1) oriented grains which cover the whole filmthickness. In contrast, no thickness fringes are observed around the (1 1 1) Bragg peak of films preparedby ion beam sputtering indicating a significantly different microstructure. This is confirmed by ElectronBackscatter Diffraction which reveals a (1 1 1) texture for both types of films. The (1 1 1) texture, however,is significantly stronger in the case of the magnetron sputtered films. Grain growth at low homologoustemperatures is considered to be an important contribution to relaxation of residual stress.
Keywords: microstructure sputtering diffraction

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Measurements of the diameter of rising gas bubbles by means of the ultrasound transit time technique

Richter, T.; Keplinger, O.; Strumpf, E.; Wondrak, T.; Eckert, K.; Eckert, S.; Odenbach, S.
This study presents ultrasound transit time technique (UTTT) measurements of single Ar bubbles rising in Galinstan under an applied magnetic field. Two setups were used to analyze the bubble rise, which led to differently oriented zig-zag trajectories. UTTT is able to visualize the bubble trajectory and to measure the variations of the apparent bubble diameters associated with the zig-zag trajectory. Due to the straightening of the bubble trajectories with increasing magnetic field, an increase of the apparent bubble diameter was detected.
Keywords: ultrasound transit time technique, single bubble, bubble diameter, Galinstan
  • Open Access Logo Magnetohydrodynamics 53(2017)2, 383-392

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Publ.-Id: 25010


Microstructure of multilayer heterosystems containing molecules of Ge quantum dots in Si on the stages of nucleation and growth as revealed by EXAFS spectroscopy

Erenburg, S. B.; Trubina, S. V.; Zvereva, V. V.; Zinov’Ev, V. A.; Dvurechenskiy, A. V.; Kuchinskaya, P. A.; Kvashnina, K. O.
GeK edge EXAFS (Extended X-Ray Absorption Fine Structure) spectra have been measured for multilayer semiconducting heterosystems containing interacted groups of quantum dots (“molecules from quantum dots”) ordered in rings on different stages of their growth depending on topologic parameters and growth conditions. In accordance with our results obtained previously for the quantum dots of SiGe, for the molecules of quantum dots it was found that deformation at the interface leads to decrease in the interatomic distance of Ge–Ge by ~0.03 Å. Effect of heterosystem topology and temperature at different stages of their growth on interlayer diffusion was investigated. It was found that at the first growth stage (growth of “seeded islands” serving as a basis for obtaining the molecules) at 700°C a concentration of Ge atoms in the system is ~38%. With further growth of the vertically-matched quantum dots groups the concentration of Ge increases up to ~43-47% depending on the growth conditions. Comparable analysis of different modes of EXAFS measurements was performed to determine precisely structural parameters of heterosystem SiGe with different thickness grown on Si(100) surface.
Keywords: microstructure, semiconductor heterosystem, molecules of quantum dots GeSi, EXAFS spectra

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P1410 - Elektromagnet zur Führung von Teilchenstrahlen zur Strahlentherapie

Schürer, M.; Karsch, L.; Pawelke, J.; Zschetzsche, J.; Kroll, F.
Die Erfindung betrifft Elektromagnete zur Führung von Teilchenstrahlen zur Strahlentherapie mit einer Spule in Verbindung mit einer elektrischen Energiequelle zur Ausbildung eines magnetischen Feldes. Die Elektromagnete zeichnen sich insbesondere dadurch aus, dass die Führung der Teilchenstrahlen mit einem gepulsten Magnetfeld erfolgt. Dazu besteht die Spule aus mindestens einem aus einem elektrisch nichtleitenden Material bestehenden Grundkörper mit wenigstens einem elektrischen und flexiblen Leiter mit mindestens einer Biegung. Weiterhin ist die Spule mit einer eine gepulste Energie liefernden Energiequelle verbunden. Die Spule besteht damit im Wesentlichen aus dem elektrischen Leiter und dem Grundkörper, wobei der Grundkörper ausschließlich als Träger fungiert. Der Grundkörper besitzt damit keine elektrischen Eigenschaften.
  • Patent
    DE102015200213 - Offenlegung: 14.07.2016

Permalink: https://www.hzdr.de/publications/Publ-25008
Publ.-Id: 25008


Electrical characterization of two-dimensional materials and their heterostructures

Arora, H.; Seifert, G.; Cuniberti, G.; Helm, M.; Erbe, A.
Two-dimensional (2D) materials have gained enormous attention in recent years owing to their excellent transport properties and mechanical flexibility. Several 2D materials like graphene, MoS2, h-BN are under intense study in the areas of electronics, optics and sensing. Apart from these materials, 2D polymers are also rapidly gaining attention due to easy tuning of their properties by altering their synthesis parameters. Polymers and inorganics together, allow us to develop 2D nanostructures whose electrical properties can be controlled. Thus, in this project, we aim to investigate novel 2D materials followed by their structural and electrical characterizations w.r.t transistor properties. Another focus will be to fabricate vertical heterostructures by stacking different 2D materials together and investigate resulting functionalities of the stack.
Keywords: Two-dimensional (2D) materials, 2D polymers, nanostructures, heterostructures
  • Open Access Logo Contribution to proceedings
    2016 Radio and Antenna Days of the Indian Ocean (RADIO), 10.-13.10.2016, Reunion Island, France
    IEEE Xplore Digital Library: IEEE, 978-1-5090-2580-0
    DOI: 10.1109/RADIO.2016.7772014
  • Lecture (Conference)
    2016 Radio and Antenna Days of the Indian Ocean (RADIO), 10.-13.10.2016, Reunion Island, France
  • Poster
    Tailor-made 2D-materials and functional devices, 27.06.-01.07.2016, Bremen, Germany
  • Poster
    IHRS NanoNet International Workshop 2016, 30.08.-02.09.2016, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-25007
Publ.-Id: 25007


Retention of uranium(VI) by Ca-bentonite at high ionic strength and high pH studied by batch sorption tests and TRLFS

Philipp, T.; Schmeide, K.; Stumpf, T.
The retention behavior of U(VI) by Ca-bentonite was studied in saline and alkaline solution via batch sorption experiments and TRLFS. At pH 8.5-9.5 sorption is lower in the presence of CO2 due to the formation of weakly sorbing uranyl carbonate species, which have been observed to dominate speciation up to pH 10 by TRLFS. In the pH range10-12 the U(VI) retention is almost complete both in the absence as well as in the presence of CO2 (carbonate concentrations between 1∙10-4 and 1∙10-3 M). This retention appears to be a combination of adsorption of uranyl hydroxo complexes and precipitation of uranium due to an altered solubility of U(VI) induced by ions leached out of the bentonite. At pH > 12 the U(VI) retention decreases again, pre-sumably due to the formation of the strongly negatively charged 1:4 uranyl hydroxo complex.
  • Poster
    7th International Conference on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 24.-27.09.2017, Davos, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-25006
Publ.-Id: 25006


Electrical characterization of atomically thin InSe layers

Arora, H.; Schönherr, T.; Erbe, A.
Two-dimensional (2D) materials have gained enormous attention in recent years owing to their huge potential in future electronics and optics. On the one hand, conventional 2D materials like graphene, MoS2, h-BN are being intensively studied, on the other hand, search for novel 2D materials is at a rapid pace. In this study, we have investigated electrical properties of 2D nanosheets of ultrathin Indium Selenide (InSe), a member of the family of III-VI chalcogenides. The InSe layers were prepared via micromechanical cleavage of its bulk crystal and were integrated into a field-effect transistor (FET) device as the transport channel. On characterizing the InSe-based FET, InSe showed n-type conductance with the mobility of 2.1x10-4 cm2V-1s-1.
Keywords: Two-dimensional (2D) materials, Indium Selenide, Field-effect transistors, micromechanical cleavage
  • Open Access Logo Contribution to proceedings
    IEEE Radio and Antenna Days of the Indian Ocean 2016, 10.-13.10.2016, Reunion Island, France
    IoP Conference Series: Materials Science and Engineering.: IEEE
    DOI: 10.1088/1757-899X/198/1/012002
  • Poster
    MRS Spring Meet 2017, 17.-21.04.2017, Phoenix, USA

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Towards an Electronic Model for Reconfigurable Transistors

Fuchs, F.; Schuster, J.; Gemming, S.
In contrast to conventional CMOS transistors, reconfigurable field effect transistors (RFETs) can be switched between n- and p-type behavior, which allows more compact and flexible circuit designs [1, 2]. Symmetry between n- and p-current is required and this can be achieved by strain engineering as experimentally demonstrated in Ref. [2]. However, a detailed understanding of the electron transport across the strained interface is not yet available and requires electronic models to capture all relevant transport mechanism.
We investigate the relation between strain and electron transport properties of planar interfaces between metallic NiSi 2 and semiconducting Si in <110> crystal orientation. We apply the non-equilibrium Green’s functions formalism together with density functional theory as implemented in Atomistix ToolKit [3] to calculate the transmission spectra. Using a modified version of the Landauer formula, we than obtain an expression for the current through the RFET and hence, the transfer characteristic can be investigated. A comparison between the calculated transfer characteristic using this model and experimental reference data [2] are performed. A very good agreement can be seen which verifies our model. However, in the experiment, the RFET was compressed during the oxidation process. Because the structure in the simulation was supposed to be unstrained, some pre-strain might be present in the simulation. We also study how strain, either applied perpendicular or parallel to the transport direction, alters the current. It can be seen that a small amount of strain is sufficient to change the ratio between n- and p-current and that symmetry can be achieved. Considering the above-mentioned pre-strain in the simulation, the general trend is also in agreement with experimental studies [1, 2].

[1] A. Heinzig et al., Reconfigurable Silicon Nanowire Transistors. Nano Letters 12, 119 (2012)
[2] A. Heinzig et al., Dually Active Silicon Nanowire Transistors and Circuits with Equal Electron and Hole Transport. Nano Letters 13, 4176 (2013)
[3] Atomistix ToolKit 15, QuantumWise A/S (www.quantumwise.com)
Keywords: reconfigurable transistor, silicon, density functional theory, non-equilibrium Green's function formalism, strain
  • Poster
    NanoNet International Workshop 2016, 30.08.-02.09.2016, Praha, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-25004
Publ.-Id: 25004


Businesskontept für die Wirtschaftlichkeitsprüfung einer Haldensanierung der Tiefenbachhalde in Altenberg

Scholz, A.
Die vorliegende Masterarbeit beschäftigt sich mit dem Thema eines "Businesskonzepts für die Wirtschaftlichkeitsprüfung einer Haldensanierung der Tiefenbachhalde in Altenberg".
Es geht um die Frage, ob ein Re-mining, sprich eine Haldensanierung der Tiefenbachhalde mit Rohstoffrückgewinnung, wirtschaftlich durchgeführt werden und sich selbst finanzieren kann. Um die Wirtschaftlichkeit des Vorhabens überprüfen zu können, wurden alle schon vorhandenen Daten der möglichen Erlöse und der anfallenden Kosten recherchiert und zusammengetragen. Bei noch fehlenden Daten sollten Möglichkeiten zur Informationsbeschaffung aufgezeigt werden. Im Laufe der Arbeit hat sich gezeigt, dass genügend Daten für eine Wirtschaftlichkeitsbetrachtung vorhanden sind. Somit konnten im Anschluss daran verschiedene Szenarien bearbeitet werden. Das Ergebnis ist eine Gegenüberstellung der Erlöse zu den Kosten, wobei die Kosten um den Faktor 2,29 höher sind als die Erlöse. Auch bei den betrachteten Szenarien sind die Kosten jeweils höher als die Erlöse. Um eine Wirtschaftlichkeit erreichen zu können, müsste der Zinnpreis sehr stark ansteigen. Insgesamt sind die Ergebnisse kritisch zu beurteilen, da Annahmen das Ergebnis beeinflussen und die Aufbereitung auf einem Prozess von 1982 basiert.

Feasibility study to remediate the Tiefenbachhalde in Altenberg The Tiefenbachhalde Altenberg is a tailing of a former tin mine in the Erzgebirge. An extensive exploration conducted by researchers from HIF and TUBAF showed that the dump still contains about 8000 tons of valuable tin. However there are also about 4000 tons of arsenic, which could be an environmental hazard, if the tailing is treated improperly.
The idea is to remediate the dump and cover the costs by Re-mining of the tin. In this master thesis the economic feasibility of this concept is evaluated by a feasibility calculation.
Keywords: Wirtschaftlichkeitsprüfung, Haldensanierung, Re-mining, feasibility calculation, dump remediation, re-mining
  • Master thesis
    TU Bergakademie Freiberg, 2016
    Mentor: Prof. Dr. Michael Höck, Prof. Dr. Karl Gerald van den Boogaart
    0105 Seiten

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3D-geologische Modellierung der Nb-Ta-P-(LREE-) Lagerstätte Epembe, Namibia

Unger, G.
Das aus den vorhandenen Daten erstellte Modell der Nb-Ta-P-(LREE)-Lagerstätte Epembe in Nordwest-Namibia, beinhaltet die Störungssysteme, sowie flexible 3D-Stratigraphische Grids (SGrids) der Sektoren B und K. Das Modell lässt Aussagen über die räumlichen Beziehungen zwischen Anreicherungszonen und Störungen im Untergrund zu. Die im Untersuchungsgebiet vorkommenden Lithologien wurden in Lithoeinheiten zusammengefasst und mit den geochemischen Daten verglichen. Dabei stellte sich heraus, dass die Anreicherungszonen der Elemente nicht mit den anstehenden Lithoeinheiten korrelieren. Des Weiteren ergaben sich lineare Zusammenhänge der Elemente U-Ta, U-Nb, Ta-Nb, HREE-LREE aus den geochemischen Daten der Bohrungen. Dies unterstreicht eine Intrusion von Magmen, die mit inkompatiblen Elementen angereichert waren. Die linearen Zusammenhänge der Elemente, spiegeln sich in den gleichen Anreicherungszonen der SGrids wieder. Die Korrelationen mit Uran werden im Modell nicht bestätigt, aufgrund der aufsummierten Darstellung der Gehalte von Uran, Thorium und Kalium. Eine weitere Ausnahme bilden die Anreicherungszonen von HREE-LREE im Sektor B. Da die Gehalte der schweren Seltenen Erden in den Anreicherungszonen der leichten Erden sehr gering sind. Diese Zonen wurden wahrscheinlich hydrothermal überprägt und es kam zur Auslaugung der HREE. Mit dem Modell konnte eine störungsgebundene Anreicherung von inkompatiblen Elementen (HFSE) nachgewiesen werden.
Mithilfe des Modells können Thesen der Genese der Lagerstätte aufgestellt werden:
1) Bei der Intrusion (vor 1215 MA) von gabbroiden, syenitischen Magmen in den Epupa Komplex, bildete sich der Karbonatit Dyke aus. Die Magmen waren vermutlich mit inkompatiblen Elementen angereichert.
2) Infolge der tektonischer Überprägung des Epembe Karbonatit Syenit Komplexes wurden diese Elemente wahrscheinlich durch hydrothermale Prozesse aus dem Umgebungsgestein gelaugt und kristallisierten dann entlang von Störungen aus. Dabei bildeten sich die modellierten Anreicherungszonen der Lagerstätte.
3) Die Auslaugung bildete Anreicherungszonen von Elementen, aber auch Zonen mit extrem geringen Elementgehalten (HREE). Da einige Elemente mobiler sind als andere.
4) Tektonische Strukturen spielten bei der Genese der Lagerstätte eine zentrale Rolle für Aufstiegs- und Platznahmemöglichkeiten von alkalischen oder karbonatischen Magmen und assoziierten REE-reichen Fluiden.
Die vorliegende Arbeit unterstreicht den Fakt, dass Seltene Erden Lagerstätten nicht ausschließlich durch magmatische Prozesse entstehen, sondern auch in Kombination mit hydrothermalen Prozessen. Des Weiteren wurde bewiesen das zur Genese von REE Lagerstätten, tektonische Strukturen eine entscheidende Rolle spielen.
  • Bachelor thesis
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institut Freiberg, 2015
    Mentor: Dr. Richard Gloaguen
    46 Seiten

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Publ.-Id: 25002


Hyperspectral remote sensing for mineral mapping of structural related mineralizations around Mount Isa, Queensland, Australia

Jakob, S.
The present report demonstrates the possibilities and limitations of remote sens- ing, especially hyperspectral data, for mineral mapping purposes, using the example of the Mount Isa Inlier. This geological area is situated in Northern Queensland, Australia, and is known for its considerable ore deposits and consequent mining of predominantly copper, zinc, lead, silver and gold. Beside hyperspectral HyMap data, multispectral Landsat 8 and SRTM digital elevation data were analyzed. A three-week field study supported the investigations by data delivered from rock sampling and field spectral measurements. The observations were concentrated on four study areas and four main objectives: the location of orebodies near Mount Isa mine by mapping their altered outcrops, the targeting of critical elements at the Mary Kathleen U-REE deposit, the investigation of the dependency between the shear and fault-controlled vein-copper deposits of Mount Isa inlier and main deep-crustal faults and the testing of a fixed-wing drone for 3D-photogrammetry of geological features.
Throughout the study, mineral mapping using remote sensing data, especially hyperspectral data, turned out to deliver high qualitative results when it is supported by additional infor- mation. In situ investigation of the observed mineralizations for validation is important and can deliver such data, for instance by the investigation of rock samples or spectral measure- ments. Since mineralizations and alterations are often related to structures, their analysis and consideration can provide crucial hints. Without additional data it is very difficult up to impossible to create and interpret mineral mapping results accurately. The most significant result throughout the study was the determination of a new site of gossanous, silicified ridges south of the Mount Isa mining complex. They coincide with the outcrops of mineralized parts of the Urquhart Shale, which form the mined Pb-Zn-Ag deposits and are probably related to structures. Their occurrence was validated through fieldwork observations including rock sampling and spectral measurements. The gathered information additionally supported the mapping of those ridges using HyMap data, which confirmed the connection between the north-south trending ridges and the Mount Isa mine deposits.
  • Master thesis
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institut Freiberg, 2014
    Mentor: Dr. Richard Gloaguen
    75 Seiten

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Publ.-Id: 25001


Hyperspectral remote sensing of carbonatite hosted REE-deposits in Namibia

Zimmermann, R.ORC
In this thesis, two case-studies for exploration of carbonatite hosted REE-deposits in Namibia using hyperspectral remote sensing data are presented. REEs have enormous economic importance because they are the major constituents of high-tech electronic devices and are non-substitutable.
The two areas of interest in Namibia are Epembe/Kunene region and Lofdal/Bergville Farm close to Khorixas. Namibia is convenient because of less vegetation, a good data coverage, and a good geological knowledge.
Multi- and hyperspectral data of multiple source and scale in combination with tectonic geomorphology were used for data analysis. In a first step, spectral signatures and geomorphic indices were extracted, followed by expert classification made by a Decision Tree approach. The detailed processing chain is shown in figure 1.
Standard procedures for spectral unmixing (e.g. Spectral Feature Fitting, Matched Filtering) are well suited to map the abundances of carbonate minerals. However, calcretes, meta-sedimentary units, and amphibolites have similar spectral signatures in the SWIR range and are difficult to distinguish.
More advantageous approaches, like Self-Organizing maps and Decision Trees, were used to discriminate the carbonatite from surrounding rocks with similar signatures. The carbonatites are associated to specific textural, geomorphic and structural patterns. Incorporating these features into hyperspectral data analysis improve classification results and reduce misclassifications for carbonatite.
  • Master thesis
    Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institut Freiberg, 2014
    Mentor: Dr. Richard Gloaguen
    67 Seiten

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Publ.-Id: 25000


Exploration mit Drohnen

Gloaguen, R.
Am Helmholtz-Institut Freiberg für Ressourcentechnologie entwickeln wir neue Methoden zur Erkundung mineralischer Rohstoffe mittels Drohnen. Unser Hexacopter transportiert beispielsweise eine hyperspektrale Kamera, die uns die Kartierung von Schlüsselmineralen erlaubt und so mögliche Lagerstätten identifizieren lässt. Einsätze in Namibia, Grönland und Spanien haben diese Erwartungen bestätigt.
  • Invited lecture (Conferences)
    Future Technologies - Innovationen aus den Technikwissenschaften, 26.01.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24999
Publ.-Id: 24999


Sorption of NpO2+ on montmorillonite: influence of ferrous iron

Marques, M. M.; Scheinost, A. C.; Baeyens, B.
The interaction of radionuclides with clay minerals, major constituents of the multi-barrier system of a radioactive waste repository (i.e. host rocks and backfill materials), is a key process in retarding their migration. It is very important to develop a fundamental understanding of the uptake processes of (radio-)contaminants onto clay minerals and to implement sorption models to reliably predict their fate in the near- and far-fields of radioactive waste repositories. 
Redox phenomena play an important role for radionuclide retention in the safety case. In the near-field, the corrosion of steel canisters will release large amounts of ferrous iron (FeII) and produce H2 with a strong influence on the redox potential (Eh). In the undisturbed bentonite it is anticipated that FeII concentrations in the porewater will lie typically between 10-5 and 10-4 M, controlled by the solubility of siderite, and Eh is predicted to be ~-200 mV [1]. The presence of high concentrations of FeII and reducing conditions in the interstitial porewater of bentonite can potentially influence the sorption behaviour of redox-sensitive nuclides. The mobility of elements such as U, Np and Tc highly depends on their oxidation state. In their most oxidized form +V, +VI (as oxocations NpO2+, UO2+2+) and +VII (as oxoanion TcO4-) these radionuclides are highly mobile, whereas their transport is strongly decreased when reduced to the oxidation state +IV.
With respect to reduction reactions of inorganic and organic compounds, FeII bound to oxide/clay minerals (surface mediated reduction) has been observed to be much more reactive than dissolved FeII [2-6]. Not only the kinetics of reaction is faster but also the redox potential of the clay/oxide associated FeII/FeIII redox couple is lower than this of dissolved iron. 

The aim of this study is to investigate the sorption of the long-lived neptunium (237Np, t1/2 = 2.14·106 a) on montmorillonite under reducing conditions mimicking “in situ” geochemical repository conditions. Most of sorption, modelling and spectroscopic studies on clay minerals so far have focused on the uptake of the mobile and very soluble NpO2+ under oxic and anoxic conditions. Sorption data for Np under reducing conditions or in the presence of FeII on clay minerals are sparse. 

The sorption of NpV on montmorillonite (Na-STx) was measured under electrochemically established reducing conditions in a bulk electrolysis cell composed of a three electrode system at a fixed redox potential in the absence and presence of varying ferrous iron concentrations (up to 44 mmol·kg-1). Fig. 1a shows the temporal evolution of the sorption of NpV in the absence and presence of ~44 mmol·kg-1 FeII at pH 7.8 and Eh -291 mV (vs SHE). If no Fe is added the sorption of Np remained nearly constant and no noticeable increase of sorption compared to anoxic conditions could be observed. In the presence of Fe, the sorption of Np steadily increased up to log Rd ~ 3.8 L/kg, suggesting the reduction of NpV at the clay surface. 

Evidence for the oxidation state and type of surface complex formed was obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy (Fig. 1b). The derived structural parameters confirm that under the above mentioned experimental conditions, Np sorbed on montmorillonite is fully reduced to NpIV and is strongly associated to surface bound Fe. 
The results of this study (i.e. influence of different FeII concentrations, nature of surface complex) will be presented at the conference.

Figs. 1: Sorption of NpO2+ on Na-STx under anoxic conditions and under reducing conditions (-291 mV) in the absence and presence of FeII. a) Temporal evolution and b) Fourier Transforms of the Np-LIII edge EXAFS spectra of Np adsorbed to Na-STx.

References:
1. Nagra (2014). Montmorillonite stability under near-field conditions. Nagra Technical Report NTB 14-12, Nagra, Wettingen, Switzerland.
2. Charlet, L., Liger, E. and Gerasimo, P. (1998). Decontamination of TCE- and U-rich waters by granular iron: role of sorbed Fe(II). Journal of Environmental Engineering, 124: 25–30.
3. Charlet, L., Scheinost, A. C., Tournassat, C., Grenèche, J. M., Géhin, A., Fernandez-Martinez, A., Coudert, S., Tisserand, D. and Brendlé, J. (2007). Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay. Geochimica et Cosmochimica Acta, 71: 5731–5749.
4. Felmy, A. R., Ilton, E. S., Rosso, K. M. and Zachara, J. M. (2011). Interfacial reactivity of radionuclides: emerging paradigms from molecular-level observations. Mineralogical Magazine, 75: 2379–2391.
5. Hofstetter, T. B., Neumann, A and Schwarzenbach, R.P. (2006). Reduction of nitroaromatic compounds by Fe(II) species associated with iron-rich smectites. Environmental Science and Technology, 40: 235–242.
6. Liger, E, Charlet, L. and Van Cappellen, P. (1999). Surface catalysis of uranium(VI) reduction by iron(II). Geochimica Cosmochimica Acta, 63: 2939–2955.
Keywords: clay montmorillonite nuclear radioactive waste EXAFS Neptunium Redox
  • Lecture (Conference)
    7th International Conference on Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, 24.-27.09.2017, Davos, Switzerland
  • Lecture (Conference)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

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Permalink: https://www.hzdr.de/publications/Publ-24998
Publ.-Id: 24998


Novel Nanoelectronic Devices and Technologies for Their Fabrication

Georgiev, Y.ORC
The traditional scaling of microelectronic devices was over in 2003 (130 nm node). New “performance boosters” are being used since then: (i) strained silicon (Si) since 2004 (90 nm node), (ii) high-k gate dielectrics + metal gates (HKMG) instead of SiO2 + poly-Si gates since 2008 (45 nm node) and (iii) non-planar 3D (tri-gate) transistor architecture since 2012 (22 nm node). Further improvements are expected by the implementation of (i) new device architectures, (ii) high-mobility channel materials such as silicon-germanium (SiGe), Ge, III-Vs, carbon nanotubes (CNTs), graphene and/or other 2D materials, etc., (iii) new (non-digital) functionalities (e.g. sensing), usually referred to as “More than Moore”, and (iv) new computational principals such as spintronics, quantum computing, etc.

In this talk I will present three novel nanoelectronics devices that have been proposed and demonstrated for the first time in the last 5-6 years: (i) junctionless nanowire transistors (JNTs) [1], (ii) 3D vertically stacked nanowire field effect transistors (VSNFETs) [2] and (iii) reconfigurable field effect transistors (RFETs) [3]. These devices embody to some extent the first three of the above-mentioned future “performance boosters”: (i) they have advanced transistor architecture, (ii) JNTs have been fabricated not only in Si but also in Ge as a high-mobility channel material and (iii) JNTs and VSNFETs have been implemented as chemical and biosensors demonstrating excellent sensing performance.
I will briefly discuss the specifics in the functioning of those devices, outlining their advantages and disadvantages. I will then consider the technologies for their fabrication and the challenges that they are facing. Finally, I will present examples of the devices fabricated for some particular applications, showing results of their structural and electrical characterisation. In the case of JNTs and VSNFETs I will focus mostly on their application as chemo/biosensors [4-8]. Additionally, I will also show the first Ge-based JNTs [9]. In the case of RFETs I will present the recent results of top-down fabrication and characterisation of such devices on silicon-on-insulator (SOI) wafers.

[1] J.P. Colinge, C.-W. Lee, A. Afzalian, N.D. Akhavan, R. Yan, I. Ferain, P. Razavi, B. O’Neill, A. Blake, M. White, A.-M. Kelleher, B. McCarthy and R. Murphy, Nanowire transistors without junctions. Nat. Nanotechnol. 5 (2010) 225.
[2] E. Buitrago, M. Fernández-Bolaños, A.M. Ionescu, Vertically stacked Si nano-structures for biosensing applications, Microelectron. Eng. 97 (2012) 345–348.
[3] A. Heinzig, T. Mikolajick, J. Trommer, D. Grimm and W. M. Weber, Nano Lett. 13 (2013) 4176-4181.
[4] Y. M. Georgiev, N. Petkov, B. McCarthy, R. Yu, V. Djara, D. O'Connell, O. Lotty, A. M. Nightingale, N. Thamsumet, J. C. deMello, A. Blake, S. Das, J. D. Holmes. Fully CMOS-compatible top-down fabrication of sub-50 nm silicon nanowire sensing devices. Microelectron. Eng. 118 (2014) pp. 47-53.
[5] Y. M. Georgiev, R. Yu, N. Petkov, O. Lotty, A. M. Nightingale, J. C. deMello, R. Duffy, J. D. Holmes. Silicon and Germanium Junctionless Nanowire Transistors for Sensing and Digital Electronics Applications. In "Functional Nanomaterials and Devices for Electronics, Sensors and Energy Harvesting.", A. Nazarov, F. Balestra, V. Kilchytska, D. Flandre eds. Springer International Publishing AG, Cham, Switzerland, 2014, pp. 367-388.
[6] E. Buitrago, G. Fagas, M. Fernández-Bolanos Badia, Y.M. Georgiev, M. Berthomé, A.M. Ionescu. Junctionless silicon nanowire transistors for the tunable operation of a highly sensitive, low power sensor. Sens. Actuators B 183 (2013) 1– 10.
[7] E. Buitrago, M. Fernández-Bolaños, Y. M. Georgiev, R. Yu, O. Lotty, J. D. Holmes, A. M. Nightingale, H. M. Guerin, A. M. Ionescu. Electrical Characterization of High Performance, Liquid Gated Vertically Stacked SiNW-Based 3D FET for Biosensing Applications. Sens. Actuators B 199 (2014) pp. 291-300.
  • Invited lecture (Conferences)
    IEEE 25th International Scientific Conference Electronics - ET2016, 12.-14.09.2016, Sozopol, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-24997
Publ.-Id: 24997


High Resolution Nanofabrication

Georgiev, Y.ORC
The aim of nanofabrication is to create structures and devices with minimum dimensions lower than 100 nm. There are two main nanofabrication approaches, bottom-up and top-down. In the former, the structures and devices are created from small to large in an additive fashion, which relies to a great extent on self-organisation processes. In the latter, the fabrication goes from large to small where nanostructures and devices are carved from a larger piece of material in a subtractive fashion. It is much more mature than the bottom-up approach and is based on two long-established processes: (i) nanolithography, where a stencil with the required pattern is created in a sacrificial layer called “resist”, deposited on the main working material, and (ii) pattern transfer through the resist stencil into the base material.

In the present paper we will present results on high-resolution nanofabrication of structures and devices with critical dimensions (CD) below 10 nm on silicon (Si), silicon-on-insulator (SOI), germanium (Ge) and germanium-on-insulator (GeOI) substrates. The fabrication was mainly within the frames of the top-down approach and was based on electron beam lithography (EBL) with positive and negative resists followed by a pattern transfer with both additive (metal deposition and lift-off) and subtractive (dry etching) methods. Moreover, high-end results on combination of bottom-up and top-down approaches will also be presented such as (i) contacting of bottom-up grown and randomly distributed nanostructures and fabrication of devices out of them as well as (ii) pattern density multiplication by directed self assembly (DSA) of block-copolymers (BCP). We believe that these results are showing some of the promising trends for future development of high-resolution nanofabrication.
  • Lecture (Conference)
    12th International Conference "Electron Beam Technologies" (EBT 2016), 13.-18.06.2016, Varna, Bulgaria

Permalink: https://www.hzdr.de/publications/Publ-24996
Publ.-Id: 24996


Top-down fabrication of silicon nanowires

Georgiev, Y.ORC
Results on top-down fabrication of silicon (Si) nanowires (Ws) towards junctionless nanowire transistors, Si NW-based biosensors and reconfigurable field effect transistors have been presented at the SENTECH "Plasma Process Technology” seminar.
  • Invited lecture (Conferences)
    SENTECH "Plasma Process Technology” seminar, 07.04.2016, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-24995
Publ.-Id: 24995


A new precision measurement of the α-decay half-life of 190Pt

Braun, M.; Georgiev, Y.ORC; Schönherr, T.; Wilsenach, H.; Zuber, K.
A laboratory measurement of the alpha-decay half-life of 190Pt has been performed using a low background Frisch grid ionisation chamber. A total amount of 216.60(17) mg of natural platinum has been measured for 75.9 days. The resulting half-life is (4.97+-0.16)x10e11 years, with a total uncertainty of 3.2%. This number is in good agreements with the half-life obtained using the geological comparison method.

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Publ.-Id: 24994


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