Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35179 Publications

Robust range prediction for arbitrary tissue mixtures based on dual-energy CT

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

The treatment planning of proton or ion radiation therapy is affected by uncertainties arising from the heuristic conversion of computed tomography (CT) images to stopping-power ratio (SPR) maps. In this work, we present how these uncertainties can potentially be reduced by the use of dual-energy CT (DECT), via a physics-based SPR prediction. According to the Bethe formula, the SPR is the product of the electron density and the stopping number relative to water. The latter ranges between 0.96 and 1.02 for human tissue at a therapeutic beam energy of 200 MeV/u and depends on the mean excitation energy (I-value).
As a first step, the relative electron density can be directly determined from DECT images in a universal and robust procedure, based on a simple assumption for the cross section parameterization. Secondly, we propose to infer the relative stopping number from the relative photon absorption cross section obtained from DECT scans - instead of using an effective atomic number as a proxy for the I-value, which has previously been suggested in literature. Our choice of variables makes a proper treatment of tissue mixtures possible, which inevitably occur in patient CT images, and allows for a convenient definition of the uncertainties.
A calculation-based analysis of tabulated body tissues and tissue base components - such as water, lipid, carbohydrates and protein - suggests a maximum uncertainty below one percent for arbitrary mixtures of human tissue. We performed first experiments, combining particle range measurements with DECT scans, to validate our method of stopping-number prediction.

Keywords: dual-energy CT; proton therapy; ion-beam therapy

  • Poster
    55th Annual Conference of the Particle Therapy Co-operative Group (PTCOG), 22.-28.05.2016, Prag, Czech Republic

Publ.-Id: 23909

Numerical simulations for the precession dynamo experiment in the framework of the DRESDYN project

Giesecke, A.; Stefani, F.

In a next generation dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquid sodium, solely driven by precession, will be considered as a possible source for magnetic field generation.

I will present results from hydrodynamic simulations of a precession driven flow in cylindrical geometry. In a second step, the velocity fields obtained from the hydrodynamic simulations have been applied to a kinematic solver for the magnetic induction equation in order to determine whether a precession driven flow will be capable to drive a dynamo at experimental conditions.

It turns out that excitation of dynamo action in a precessing cylinder at moderate precession rates is difficult, and future dynamo simulations are required in more extreme parameter regimes where a more complex fluid flow is observed in water experiments which is supposed to be beneficial for dynamo action.

Keywords: Dynamo; Precession; Magnetohydrodynamics; Geodynamo; DRESDYN

  • Lecture (Conference)
    European GDR Meeting 20016, 27.06.-01.07.2016, Barcelona, Spain

Publ.-Id: 23908

Innovative Technologien für Ressourceneffizienz - Strategische Metalle und Mineralien Ergebnisse der r³ Fördermaßnahme

Dürkoop, A.; Brandstetter, C.; Gräbe, G.; Rentsch, L.; (Editors)

Zum Abschluss der r³ Fördermaßnahme werden die Ergebnisse der r³ Verbundprojekte in einem gesammelten Buch veröffentlicht.

Keywords: Ressourceneffizienz; Sekundärrohstoffe; Recycling; Substitution; Urban Mining

  • Book (Editorship)
    Stuttgart: Fraunhofer Verlag, 2016
    ISBN: 978-3-8396-1102-9

Publ.-Id: 23906

Frustrated magnets in high magnetic fields—selected examples

Wosnitza, J.; Zvyagin, S. A.; Zherlitsyn, S.

An indispensable parameter to study strongly correlated electron systems is the magnetic field. Application of high magnetic fields allows the investigation, modification and control of different states of matter. Specifically for magnetic materials experimental tools applied in such fields are essential for understanding their fundamental properties. Here, we focus on selected high-field studies of frustrated magnetic materials that have been shown to host a broad range of fascinating new and exotic phases. We will give brief insights into the influence of geometrical frustration on the critical behavior of triangular-lattice antiferromagnets, the accurate determination of exchange constants in the high-field saturated state by use of electron spin resonance measurements, and the coupling of magnetic degrees of freedom to the lattice evidenced by ultrasound experiments. The latter technique as well allowed new, partially metastable phases in strong magnetic fields to be revealed.

Publ.-Id: 23905

Magnetic properties of HoFe6Al6H hydride: A single-crystal study

Andreev, A. V.; Pelevin, I. A.; Sebek, J.; Tereshina, E. A.; Gorbunov, D. I.; Drulis, H.; Tereshina, I. S.

Crystal structure and magnetic properties were studied on a single crystal of HoFe6Al6H and compared with those of the parent HoFe6Al compound with a tetragonal crystal structure of the ThMn126Al6 is a ferrimagnet with exact compensation of the Ho and Fe sublattices magnetizations at low temperatures. Both the hydride and the parent compound display a high magnetic anisotropy of the easy-plane type, a noticeable anisotropy exists also within the easy plane with the [110] axis as the easy magnetization direction. The hydrogenation increases slightly (from 10 to 10.45 µB) the magnetic moment of the Fe sublattice as a result of volume expansion. It leads to a decompensation of the Fe and Ho sublattices and HoFe6Al6H has a spontaneous moment 0.45 µB/f.u. The enhancement of the Fe-Fe intra-sublattice exchange interaction results in a higher Curie temperature (TC) value, 350 K in the hydride as compared to 315 K of HoFe6Al6. The Ho-Fe inter-sublattice interaction is also enhanced in the hydride. The molecular field Hmol created on Ho Ions by Fe sublattice is 38 T in HoFe6Al6 and 48 T in HoFe6Al6H. The inter-sublattice exchange constant nHoFe is 3.8 T/µB and 4.6 T/µB, respectively. High-field measurements confirm the enhancement of the Ho-Fe exchange interaction in the hydride found from the temperature dependence of magnetization.

Publ.-Id: 23904

Treatment of once rejected material - Investigating the recovery of cassiterite from tailings disposals using different flotation methods

Leistner, T.; Leissner, T.; Möckel, R.; Osbahr, I.; Rudolph, M.; Peuker, U. A.

Tin-mining activities have taken place in the region of the German Erzgebirge (Ore Mountains) for over hundreds of years up until the late 1980s. For long times, gravity separation processes used to be the main beneficiation approach in those mining districts to recover cassiterite, the main tin-bearing mineral. Since for fine and very fine particles these approaches might not represent effective techniques, much valuable material could not be recovered and reported to tailings, where it was subsequently disposed. Thus, there are substantial amounts of cassiterite still present in these disposals, most of it as very fine particles with already high degrees of liberation. That fact brings these disposals into focus for potential reprocessing using beneficiation approaches, which are more sensitive to fine and very fine particles.

In this paper we present results concerning the laboratory-scale treatment of material from an exemplary heap of the former Ehrenfriedersdorf mining site using various flotation methods. The material used is previously classified into different size ranges. Conventional froth flotation is applied to the fine particles (20µm – 100µm). For the very fine particle (< 20µm), special emphasis is put on oil-assisted flotation methods, including oil agglomeration flotation and two-liquid flotation. Therefore, an aliphatic oil phase of alkane basis is used to either selectively aggregate or collect the cassiterite particles. Recovery and flotation performance results are presented with respect to different process parameters: various collectors (e.g. sulphosuccinamates, phosphonic acids) and depressants (e.g. sodium fluorosilicate, oxalic acid) regime, oil dosage, oil/pulp agitation time and pulp density. Furthermore, the oil/particle aggregation behavior is analyzed via particle image analysis and, additionally, collector adsorption characteristics are investigated by contact angle measurements, zeta potential analysis and infrared spectroscopy. The data obtained is correlated with the testwork results achieved in order to interpret the flotation response of very fine cassiterite particles.

  • Contribution to proceedings
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Kanada

Publ.-Id: 23903

Investigations on the selective particle/oil-aggregation as a processing strategy for ultrafine particle systems

Leistner, T.; Rudolph, M.; Peuker, U. A.

Difficulties in the selective separation and recovery of ultrafine or even colloidal particles (ranging from 0.1 to 10µm in size) represent a common problem in various industrial fields, e.g. in the mineral processing industry. The difficulties arise due to the dominance of surface effects over bulk properties that strongly determine the behavior of such systems. In order to overcome these problems various physico-chemical process approaches, based on differences in particle wettability and the use of a non-polar, water-immiscible oil phase, are reported in different investigations. For these oil-assisted separation techniques, differing only in oil amount, addition and function, particle/oil aggregates could be achieved theoretically with a high degree of selectivity either by (selective) particle accumulation at the oil/water interface or even by (selective) particle transfer from the aqueous pulp into the oil phase.

In this paper we present investigations on the selective particle/oil aggregation behavior for various ultrafine model particle systems (e.g. quartz, magnetite, apatite) and aliphatic oil phases of alkane basis. Analytical investigations performed include the analysis of zeta potentials of oil droplets and solid particles in modifying reagent solution and reagent-free solution, the particle/oil aggregate structure by particle image analysis as well as wettability characterization by contact angle measurements. Experimental investigations include separation experiments using a modified laboratory-scale flotation column for different artificial solid mixtures. In order to selectively control the particle surface properties, different modifying reagents, including sodium oleate, CTAB, sodium silicate, citric acid, etc. were chosen to promote particle/oil aggregation for various target particles and more importantly the hindrance of particle/oil aggregation for the others. The degree of selectivity achieved as well as recovery and type of oil/particle aggregates formed are presented with regard to operational parameters like pH, electrolyte content, oil/water volume ratio and oil droplet size.

Keywords: ultrafine particle processing; particle/oil aggregation; oil-assisted flotation

  • Poster
    IMPC 2016 - XXVIII International Mineral Processing Congress, 11.-15.09.2016, Quebec, Kanada

Publ.-Id: 23902

Selective Separation of ultrafine particle systems - Chances and drawbacks when using non-polar oil as process aid

Leistner, T.; Rudolph, M.; Peuker, U. A.

Selective fine particle separation based on differences in particle surface properties represents a key unit operation in various industrial fields, e.g. in the mineral processing industry in the form of flotation processes. One of the main challenges today for separation processes is the efficient processing of ultrafine or even colloidal particles ranging from 0.1 to 10 µm in size, because these particles are usually poorly recovered by conventional froth flotation. A promising approach for ultrafines recovery is the use of a non-polar, water-immiscible oil phase, as reported in various investigations. In a particle mixture in which only selected particles are wetted by the oil phase, particle/oil aggregates could be achieved theoretically with a high degree of selectivity either by particle accumulation at the oil/water interface or even by particle transfer from the aqueous pulp into the oil phase. Hence, different techniques of oil-assisted separations can be distinguished, differing only in oil amount, addition and function. The principle of these approaches is directly related to the stabilization of emulsions by very fine solid particles (so called Pickering emulsions).

In this paper we present investigations on the potentially application of oil-assisted separation methods for ultrafines processing. The investigations performed involve the determination of the degree of particle/oil aggregation for ultrafine model particle systems in simple laboratory-scale batch trials as well as separation experiments using a modified separation column. Aliphatic oil phase of alkane basis and modifying reagents (to selectively control the particle surface properties and thus particle/oil aggregation) are used for the experiments. The response of the process, including recovery and selectivity is presented with regard to operational parameters like pH, oil droplet size, etc. Furthermore, analysis of zeta potentials of non-polar oil droplets and solid particles in modifying reagent solution and reagent-free solution are taken into account in order to interpret and physically model the particle/oil aggregation mechanism as well as the applicability of the processes.

  • Contribution to proceedings
    PARTEC 2016 - International Congress on Particle Technology, 19.-21.04.2016, Nürnberg, Deutschland

Publ.-Id: 23901

A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques

Leistner, T.; Embrechts, M.; Leissner, T.; Chehreh Chelgani, S.; Osbahr, I.; Möckel, R.; Peuker, U. A.; Rudolph, M.

This study investigates the reprocessing of once disposed tin tailings from a historic German tin operation through different surface properties based processing techniques. Froth flotation and agglomeration flotation, by using commercially available cassiterite collectors from Clariant, were chosen as processing techniques. Isooctane as a nonpolar oil was used to promote the collection of ultrafine (-10 µm) cassiterite by selective agglomeration, and thus, size enlargement. Results indicate that by using sulfosuccinamates as a collector, around 80% of the fine (-50 µm) to very fine (-20 µm) cassiterite can be recovered (representing ~50% of the total cassiterite in the tailings sample). Agglomeration flotation experiments showed inferior results for recovering the ultrafine cassiterite (for feed fractions in the -25 µm size range). Oil/froth interaction and increased pulp ion content are considered as the main contributing causes.

Keywords: Tailings; Reprocessing; Cassiterite; Flotation; Ultrafine; Oil-assisted flotation


Publ.-Id: 23900

Experimental discrimination of ion stopping models near the Bragg peak in highly ionized matter

Cayzac, W.; Frank, A.; Ortner, A.; Bagnoud, V.; Basko, M. M.; Bedacht, S.; Bläser, C.; Blazevic, A.; Busold, S.; Deppert, O.; Ding, J.; Ehret, M.; Fiala, P.; Frydrych, S.; Gericke, D. O.; Hallo, L.; Helfrich, J.; Jahn, D.; Kjartansson, E.; Knetsch, A.; Kraus, D.; Malka, G.; Neumann, N.; Pepitone, K.; Pepler, D.; Sander, S.; Schaumann, G.; Schlegel, T.; Schroeter, N.; Schumacher, D.; Seibert, M.; Tauschwitz, A.; Vorberger, J.; Wagner, F.; Weih, S.; Zobus, Y.; Roth, M.

The energy deposition of ions in dense plasmas is a key process in inertial confinement fusion that determines the alpha-particle heating expected to trigger a burn wave in the hydrogen pellet and the resulting thermonuclear gain. However, measurements of ion stopping in plasmas are scarce and mostly restricted to high ion velocities where the theory agrees with data. Here, we report experimental data at low projectile velocities where the stopping force reaches its maximum (Bragg peak). This parameter range features the largest theoretical uncertainties and conclusive data are missing until today. The precision of our measurements, combined with a reliable knowledge of the plasma parameters, allows to clearly rule out several standard models for the stopping power for beam velocities typically encountered in inertial fusion. On the other hand, our data support theories that include a detailed treatment of strong ion-electron collisions.

Keywords: plasma; warm dense matter; stopping power; fusion; strong collisions

Publ.-Id: 23899

Solid state spectroscopy with THz free electron lasers

Helm, M.

Some applications of infrared and THz free electron lasers in solid state spectroscopy are discussed. In particular, nonlinear experiments on semiconductor quantum well excitons and pump-probe studies on carrier relaxation in graphene are presented.

Keywords: free electron laser; infrared; terahertz; quantum well; graphene

  • Invited lecture (Conferences)
    Laser Optics 2016, 27.06.-01.07.2016, St. Petersburg, Russland

Publ.-Id: 23898

Interplay of the Open Circuit Potential-Relaxation and the Dissolution Behavior of a Single H2 Bubble generated at a Pt Microelectrode

Karnbach, F.; Yang, X.; Mutschke, G.; Fröhlich, J.; Eckert, J.; Gebert, A.; Tschulik, K.; Eckert, K.; Uhlemann, M.

The dissolution behavior of a single H2 bubble electrochemically generated at a Pt microelectrode in 1 M H2SO4, was studied. The open circuit potential (OCP) relaxation after the polarization end was recorded and correlated with the dissolved H2 concentration at the interface electrode/electrolyte/gas. Simultaneously, the shrinking of the bubble was followed optically by means of a high speed camera. In addition, analytical modelling and numerical simulations for the bubble dissolution were performed. Three characteristic regions are identified in the OCP and the bubble radius transients: (i) slow relaxation and shrinking, (ii) transition region and (iii) a long-term slowed down dissolution process. The high supersaturation after polarisation remains longer than theoretically predicted and feeds the bubble in region (i). This reduces the dissolution rate of the bubble which differs significantly from that of non-electrochemically produced bubbles. Numerical multi-species simulations prove that oxygen and nitrogen dissolved in the electrolyte additionally influence the bubble dissolution and slow down its shrinkage compared to pure hydrogen diffusion. In region (iii), a complete exchange of hydrogen gas with nitrogen and oxygen has occurred in the gas bubble.

Keywords: electrochemistry; electrolysis; hydrogen evolution; gas dissolution; open circuit potential; numerical simulation

Publ.-Id: 23897

Crystallization of multi-crystalline silicon in a cone-shaped, inductively heated crucible: MHD melt flow and seeded growth

Poklad, A.; Galindo, V.; Schmid, E.; Heinze, V.; Pätzold, O.; Stelter, M.; Gerbeth, G.

A novel, vertical Bridgman-type technique for growing multi-crystalline silicon ingots in an induction furnace is described. In contrast to conventional growth, a modified setup with a cone-shaped crucible and susceptor is used. A detailed numerical simulation of the setup is presented. It includes a global thermal simulation of the furnace and local simulation of the melt, which aims at the influence of the melt flow on the temperature and concentration fields. Furthermore, seeded growth of cone-shaped Si ingots using either a monocrystalline seed or a seed layer formed by pieces of poly-Si is demonstrated and compared to growth without seeds. The influences of the seed material on the grain structure and the dislocation density of the ingots are discussed.

Keywords: Bridgman growth; Dislocation density; Melt flow; Multi-crystalline silicon; Seeded growth

  • Contribution to proceedings
    10th PAMIR International Conference ‐ Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, Cagliari, 978-88-90551-93-2, 336-340
  • Poster
    10th PAMIR International Conference ‐ Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy

Publ.-Id: 23896

Transitions in a Magnetized Quasi-laminar Spherical Couette Flow

Kasprzyk, C.; Kaplan, E.; Seilmayer, M.; Stefani, F.

First results from a new magnetized spherical Couette experiment are presented.
For a line in the Re-Ha instability diagram with constant Reynolds Number Re = 1000 and increasing Hartmann number Ha we study the liquid metal movement in a spherical gap under the influence of a vertical magnetic field.
The resulting flow structures are inspected with comprehensive ultrasound technique.
Increasing the magnetic field strength until Ha = 60, we observe the equatorially anti-symmetric jet instability with azimuthal wave number m = 3 at low Ha.
At intermediate Ha, no dominant m is identifiable.
At high Ha, an unstable, equatorially symmetric state with various transitions between different azimuthal modes becomes visible.
Our observations are in agreement with numerical linear instability analysis.

Keywords: Magnetized spherical Couette flow; Instabilities

  • Contribution to proceedings
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, 9788890551932, 547-551
  • Lecture (Conference)
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy

Publ.-Id: 23894

Rotating magnetic field driven spin-up flow in a rectangular cavity

Galindo, V.; Nauber, R.; Franke, S.; Räbiger, D.; Czarske, J.; Eckert, S.

Numerical simulations of the rotating magnetic field (RMF) driven liquid metal flow and corresponding velocity measurements using a dual plane, two-component ultrasound array Doppler velocimeter were carried out in a rectangular cavity with an aspect ratio of unity. The liquid metal (GaInSn) was suddenly exposed to an azimuthal body force generated by a RMF. The measurements show a similar flow structure compared to the case of the RMF-driven flow in a cylindrical container, in particular the so-called initial adjustment phase followed by an inertial phase which is dominated by inertial oscillations of the secondary flow. The transition from the double vortex structure of the secondary flow to an oscillating regime was detected at a magnetic Taylor number of Ta_cr > 1.3×10^5. A proper orthogonal decomposition (POD) of the velocity field allows a detailed study of the structure and time development of the most important flow modes.

Keywords: Rotating magnetic field; Ultrasound velocity measurement; Spin-up; OpenFOAM; Proper orthogonal decomposition

  • Contribution to proceedings
    10th PAMIR International Conference - Fundamental and Applied Magnetohydrodynamics, 20.-24.06.2016, Cagliari, Italien
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, Cagliari, 978-88-90551-93-2, 82-86
  • Lecture (Conference)
    10th PAMIR International Conference - Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italien

Publ.-Id: 23893

Influence of magnetic fields on the behavior of single hydrogen bubbles generated via water electrolysis

Karnbach, F.; Uhlemann, M.; Yang, X.; Eckert, K.; Baczyzmalski, D.; Cierpka, C.; Mutschke, G.; Gebert, A.

Hydrogen production via water electrolysis is an established method for energy storage the efficiency of which is limited by the gas bubbles blocking the electrode surface during the process. The application of a magnetic field can be a promising solution for an increased bubble detachment due to the Lorentz force induced electrolyte convection. Therefore single hydrogen bubbles offer a nice possibility for a detailed analysis of the underlying mechanisms. To analyze the impact of the magnetic field single hydrogen bubbles were produced potentiostatically at different potentials via electrolysis of sulfuric acid at a Pt microelectrode (Ø 100 μm) with a magnetic field superimposed in two different field configurations to the electrode surface for varying magnetic field strengths. The bubble behavior was visualized by a CCD camera and the electrolyte flow analyzed via Particle Image Velocimetry and Astigmatism Particle Tracking Velocimetry. Significant changes in the current signal were obtained (Fig. 1), depending on field orientation and strength, and are discussed due to the impact of the Lorentz force induced flow around the bubble, which possibly also influences the mass transfer in the vicinity of the bubble surface. If the magnetic field is applied parallel, a different bubble behavior is observed in comparison to a perpendicular applied magnetic field what may result in a higher efficiency.

Keywords: electrochemistry; electrolysis; renewable energy; hydrogen production; water splitting; magnetic field; Lorentz force; particle tracking velocimetry

  • Poster
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia

Publ.-Id: 23892

Functional DNA origami nanotubes for nanoelectronics

Teschome, B.; Facsko, S.; Kerbusch, J.; Schönherr, T.; Hübner, R.; Gothelf, K.; Keller, A.

DNA origami [1] has become a key technique for designing well-defined nanostructures with any desired shape [2] and for the controlled arrangement of nanostructures with few nanometer scales [3]. These unique features of DNA origami make it a promising candidate for use as a scaffold for nanoelectronics [4] and nanophotonics [5] device fabrication.
In this work, we first demonstrate a compelling alternative approach to generate ordered arrays of DNA nanotubes on topographically patterned surfaces [6]. To this end, we combine two bottom-up techniques for nanostructure fabrication, i.e., DNA origami self-assembly and self-organized nanopattern formation on silicon surfaces during ion sputtering, thus avoiding the necessity of lithographic processing or chemical modifications. Then, we present the high-yield synthesis of high-density gold nanoparticle (AuNP) arrangements on DNA origami nanotubes with few unbound background nanoparticles and fabricate large arrays of aligned DNA origami nanotubes decorated with a high density of AuNPs [7]. The high yield of AuNP assembly was achieved by careful control of the buffer and the AuNPs concentrations and the hybridization time on Si surface. In addition, we optimize the metallization of DNA origami nanotubes to create DNA origami-templated nanowires and develop a platform for electrical contacting of those nanowires. We also demonstrate the assembly of heterogeneous nanostructures on a single DNA origami nanotube.

[1] P. W. K. Rothemund, Nature, 440, 297(2006).
[2] H. Dietz, S. M. Douglas and W. M. Shih, Science, 325, 725 (2009).
[3] B. Ding, Z. Deng, H. Yan, S. Cabrini, R. N. Zuckermann and J. Bokor, J. Am. Chem. Soc., 132, 3248 (2010).
[4] A. C. Pearson, J. Liu, E. Pound, B. Uprety, A. T. Woolley, R. C. Davis and J. N. Harb, J. Phys. Chem. B, 116, 10551(2012).
[5] J. Prinz, B. Schreiber, L. Olejko, J. Oertel, J. Rackwitz, A. Keller and I. Bald, J. Phys. Chem. Lett., 4, 4140 (2013).
[6] B. Teshome, S. Facsko and A. Keller, Nanoscale, 6, 1790 (2014).
[7] B. Teschome, S. Facsko, K. V. Gothelf and A. Keller, Langmuir, 31,12823 (2015).

  • Lecture (Conference)
    DNA-Based Nanotechnology, 19.-21.05.2016, Jena, Germany
  • Poster
    2nd Functional DNA Nanotechnology Workshop, 22.-24.06.2016, Rom, Italy

Publ.-Id: 23891

Comparative evaluation of SUV, tumor-to-blood standard uptake ratio (SUR), and dual time point measurements for assessment of the metabolic uptake rate in FDG PET

Hofheinz, F.; van den Hoff, J.; Steffen, I. G.; Lougovski, A.; Ego, K.; Amthauer, H.; Apostolova, I.


We have demonstrated recently that the tumor-to-blood standard uptake ratio (SUR) is superior to tumor standardized uptake value (SUV) as a surrogate of the metabolic uptake rate K m of fluorodeoxyglucose (FDG), overcoming several of the known shortcomings of the SUV approach: excellent linear correlation of SUR and K m from Patlak analysis was found using dynamic imaging of liver metastases. However, due to the perfectly standardized uptake period used for SUR determination and the comparatively short uptake period, these results are not automatically valid and applicable for clinical whole-body examinations in which the uptake periods (T) are distinctly longer and can vary considerably. Therefore, the aim of this work was to investigate the correlation between SUR derived from clinical static whole-body scans and K m-surrogate derived from dual time point (DTP) measurements.


DTP 18F-FDG PET/CT was performed in 90 consecutive patients with histologically proven non-small cell lung cancer (NSCLC). In the PET images, the primary tumor was delineated with an adaptive threshold method. For determination of the blood SUV, an aorta region of interest (ROI) was delineated manually in the attenuation CT and transferred to the PET image. Blood SUV was computed as the mean value of the aorta ROI. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values from the early time point of each DTP measurement were scan time corrected to 75 min postinjection (SURtc). As surrogate of K m, we used the SUR(T) slope, K slope, derived from DTP measurements since it is proportional to the latter under the given circumstances. The correlation of SUV and SURtc with K slope was investigated. The prognostic value of SUV, SURtc, and K slope for overall survival (OS) and progression-free survival (PFS) was investigated with univariate Cox regression in a homogeneous subgroup (N=31) treated with primary chemoradiation.


Correlation analysis revealed for both, SUV and SURtc, a clear linear correlation with K slope (P<0.001). Correlation SUR vs. K slope was considerably stronger than correlation SUV vs. K slope (R 2=0.92 and R 2=0.69, respectively, P<0.001). Univariate Cox regression revealed SURtc and K slope as significant prognostic factors for PFS (hazard ratio (HR) =3.4/ P=0.017 and HR =4.3/ P=0.020, respectively). For SUV, no significant effect was found. None of the investigated parameters was prognostic for OS.


Scan-time-corrected SUR is a significantly better surrogate of tumor FDG metabolism in clinical whole-body PET compared to SUV. The very high linear correlation of SUR and DTP-derived K slope (which is proportional to actual K m) implies that for histologically proven malignant lesions, FDG-DTP does not provide added value in comparison to the SUR approach in NSCLC.

Keywords: PET FDG Tumor-to-blood ratio SUR

Publ.-Id: 23888

Remarks on 3 years SSPA Operation at the Superconducting Linac ELBE

Büttig, H.; Arnold, A.; Kuntzsch, M.; Schurig, R.

Since January 2012 the superconducting Linac ELBE is in operation with 1.3 GHz Solid State Power Amplifiers (SSPA). One system can deliver up to 20 kW per cavity.
The presentation revues the experiences gained within 3 years of operation and problems that have been solved.

Keywords: ELBE RF; Superconducting Linac RF-SSPA; SSA 1.3GHz; Solid state power amplifiers 1.3GHz

  • Poster
    CWRF2016 - The Continuous Wave and High Average RF Power Workshop, 20.-24.06.2016, Grenoble, France

Publ.-Id: 23887

Upgrade of the 1.3 GHz Resonant Ring for High Power RF Test of Accelerator Components

Arnold, A.; Büttig, H.; Staats, G.

Since 2009 the ELBE center for high power radiation sources is using a 1.3 GHz resonant ring for RF conditioning of power couplers and to test different waveguide components. The poster describes the ring and two new features that are improving the ring significantly. First, a PLL system is used to stabilize the RF-power in the ring which normally drops with increasing temperature because the frequency of the structure shifts. And second, an adjustable test waveguide was designed that allows perfect matching of a pair of RF-couplers with different antenna tip lengths. All measurements are in good agreement with simulations and the ring is now routinely in use for travelling wave measurements of RF components up to 50 kW CW.

Keywords: Resonant Ring; RF-component tests; High power RF; Waveguide window test; RF Coupler tests

  • Poster
    CWRF2016 - The Continuous Wave and High Average RF Power Workshop, 20.-24.06.2016, Grenoble, France

Publ.-Id: 23886

Subsecond thermal processing for the advancement of thin layers and functional coatings

Skorupa, W.

This talk reviews the advances that subsecond thermal processing in the millisecond range using xenon-filled flash lamps (FLA) brings to the processing of the most advanced thin layer and coating materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. An important issue of our work was the formation and characterization of semiconductor materials and coatings for the green energy advancement. Regarding photovoltaic applications, we dealt with the ion beam doping and thermal processing of PV silicon demonstrating using FLA a distinct improvement of the minority carrier diffusion length compared to rapid thermal processing and furnace treatments. Moreover, we engineered the hydrogen content in photovoltaic silicon in correlation to the phosphorus doping using plasma immersion ion implantation and FLA. Recently, we demonstrated also FLA driven boron and phosphorus in-diffusion from surface coatings. Further, we prepared coarse grained dendritic crystal structures in thin silicon films on silicon dioxide to show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process. Finally the strongly developing field of large area electronics is represented by reporting on our activities in regard to transparent conductive oxide (TCO) and copper paste coatings.

Keywords: subsecond thermal processing; flash lamp annealing; ion implantation; photovoltaics; transparent conductive oxide; copper paste

  • Invited lecture (Conferences)
    SVC (Society of Vacuum Coaters) 59th Annual Technical Conference (TechCon), 09.-13.05.2016, Indianapolis, IN, USA

Publ.-Id: 23885

Fragment molecular orbital (FMO) method for studying actinide interaction with DNAs and proteins

Tsushima, S.; Ishikawa, T.; Tanaka, S.; Mori, H.; Saeki, M.; Nakano, T.; Komeiji, Y.; Mochizuki, Y.

Due to its potential health and environmental impacts, actinide binding to biomolecules has been a subject of intensive investigations. A large number of experimental works have been carried out but our understanding remains mostly in a macroscopic scale. Modeling actinide interaction with large biomolecules using ab initio quantum chemical calculations may drastically expand our molecular level knowledge but is challenged by a demand for huge computational resources.
Our strategy to overcome this difficulty is to apply fragment molecular orbital (FMO) method. In FMO, the molecular system of interest is partitioned into small fragments. Each fragment and fragment pair is subject to self-consistent field calculations under environmental electrostatic potentials and the electronic structure of the whole system is reconstituted [1]. This procedure drastically reduces computational cost of Hartree Fock calculations from N3 to N2 (or less) and is readily parallelizable. FMO has been extended to MP2 and to DFT to include electron correlation and was successfully applied to the systems such as hydrated DNA (~ 7500 atoms) [2].
Currently we are upgrading the FMO program Abinit-MP [3] to implement 5f elements into the program. We first choose uranyl-bound DNA for a case study. Calcu-lations are performed as follows. UO2 2+-bound d(CGCGAATTCGCG)2 (Dickerson-Drew dodecamer) with 20 Na+ ions and SPC/E water shell with 10 Å thickness (a to-tal of 15559 atoms in the system) is first thermally equilibrated and subsequently submitted to molecular dynamics (MD) simulation at 300 K for 100 ns interval using AMBER 14 program. Force field parameters for UO2 2+ and coordinating water are those developed by Pomogaev et al. [4]. At each 1 ns time step of MD simulation, the structure is extracted and submitted to FMO single point energy calculation at the MP2 level. In FMO, nucleic unit is appropriately divided into sugar, base, and phosphate fragments. Inter-fragment interaction energy analysis is performed to explore the binding affinity of uranyl to DNA and its influence on base pairing.
Binding of Eu3+ to Calmodulin and its comparison with Ca2+ binding is under in-vestigation.

FMO program Abinit-MP and its graphical user interface BioStationViewer are freely distributed online [5]. This project is funded by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT).

  • Lecture (Conference)
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS 2016), 07.-10.11.2016, Richland, USA

Publ.-Id: 23884

Ultrasonic flow measurement in liquid metal models of continuous steel casting

Timmel, K.; Wondrak, T.; Franke, S.; Eckert, S.

Model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in melt flows relevant for metallurgical applications. One very important industrial process is the continuous casting of steel. But there exist almost no measurement data of the inner mold flow from real casting plants and there are no satisfying measurement techniques available for those harsh conditions. By this, e.g. a detailed understanding of the action of electromagnetic brakes on the complex flow is missing. Therefore we built model experiments for the continuous casting process of steel by using low melting liquid metals and investigated the mold flow under different conditions. The main value of cold metal laboratory experiments consists in the capabilities to obtain quantitative flow measurements by ultrasonic flow measurements with a reasonable spatial and temporal resolution. Standard transducers were used at the model operating at room temperature with the eutectic alloy of GaInSn. Ultrasonic transducers for high temperatures and ultrasonic waveguide sensors were used at the big model, which uses the alloy Sn60Bi40 as model liquid and is operated at temperatures of 200-350 °C. Results from the mold flow measurement will be presented, showing the effect of a static magnetic field on the flow structure. It turned out, that the magnetic field can locally accelerate the flow, contrary to the expected action as a brake. The ultrasonic velocity measurement data were further used for validation and for comparison with other measurement techniques at the model experiment.

Keywords: Continuous casting of steel; electro-magnetic flow control; liquid metal models; applied Ultrasonic Doppler Velocimetry; ultrasonic wave-guides; high temperature transducers

  • Lecture (Conference)
    10th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD 10), 28.-30.09.2016, Tokyo, Japan
  • Contribution to proceedings
    10th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering (ISUD10), 28.-30.09.2016, Tokyo, Japan
    Proceedings of the 10th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Tokyo: Tokyo Institute of Technology, 17-20

Publ.-Id: 23883

Evaluierung iterativer Rekonstruktionsverfahren zur Optimierung der Bildqualität und Reduktion von Metallartefakten in der Computertomographie

Negwer, F.; Wohlfahrt, P.; Richter, C.

In dieser Studie wurde der Einfluss des iterativen Rekonstruktionsverfahrens SAFIRE und des iterativen Verfahrens zur Metallartefaktreduktion iMAR auf die Bildqualität untersucht. SAFIRE konnte das Bildrauschen um bis zu 50% oder die Dosis um bis zu 70% reduzieren. Der optische Bildeindruck verbessert sich durch die Metallartefaktreduktion iMAR signifikant, die quantitativen Parameter zur Beschreibung der Metallartefakte zeigen jedoch keine klare Verbesserung. Die erzielten Verbesserungen durch iMAR sind daher nicht ausreichend, um eine hochpräzise Protonentherapie gewährleisten zu können.

In this study the influence of the iterative reconstruction method SAFIRE and the iterative method for metal artifact reduction iMAR on the image quality was investigated. SAFIRE was able to reduce the noise by 50% or the dose by 70%. The visual impression could be significantly improved by iMAR, although the quantitative parameters for the description of metal artifacts depend strongly on the investigated scan region. The achieved improvements by iMAR are not sufficient to ensure high precision proton therapy.

CT-Aufnahmen, die zur Bestrahlungsplanung verwendet werden, müssen hohe Qualitätsanforderungen erfüllen. Dies gilt insbesondere bei der Anwendung in der Protonentherapie. Es ist dabei entscheidend, dass sich CT-Zahlen für spezifische Gewebe trotz unterschiedlicher Patientenanatomie, das heißt unterschiedliche Strahlaufhärtungsverhältnisse, nicht unterscheiden, da auf deren Grundlage die Protonreichweite im Patienten berechnet wird.
Zunehmend werden von den CT-Herstellern iterative Rekonstruktionsverfahren angeboten, deren Auswirkung auf die strahlentherapeutische Anwendung evaluiert werden sollte. Ein Ziel dieser Untersuchung war den Einfluss des iterativen Rekonstruktionsverfahrens SAFIRE (Siemens Healthcare, Forchheim, Deutschland) auf Strahlaufhärtung und Bildrauschen in Abhängigkeit von der applizierten CT-Dosis für Single-energy (SECT) und Dual-energy (DECT) CT-Scans zu quantifizieren. Weiterhin wurde das iterative Verfahren zur Metallartefaktreduktion iMAR (Siemens Healthcare, Forchheim, Deutschland) auf CT-Aufnahmen mit Metallimplantaten angewendet, um dessen Effekt auf die Ausprägung von Metallartefakten zu analysieren.

Material und Methoden
Für die klinische Charakterisierung von SAFIRE hinsichtlich Bildrauschen und Strahlaufhärtung wurden 11 gewebeäquivalente Materialien, 5 Kunststoffe und Aluminium in einem Siemens SOMATOM Definition AS CT-Scanner in drei verschiedenen Messaufbauten, die unterschiedliche Körperregionen simulieren, aufgenommen. Hierbei wurde zum Einen bei konstanter Dosis (CTDIvol32cm = 28.5 mGy) die Hochspannung (80, 100, 120, 140 kV) und zum Anderen bei konstanter Hochspannung (SECT: 120kV, DECT: 80/140kV) die Dosis variiert (CTDIvol32cm = 28.3, 18.3, 8.1 mGy")" . Außerdem wurde der Einfluss von SAFIRE auf aus DECT-Scans berechneten pseudo-monoenergetischen CT-Datensätzen unterschiedlicher Energie (gewichtete Summe beider DECT-Aufnahmen) quantifiziert.
Die Evaluierung von iMAR erfolgte mit Hilfe eines Kopfphantoms der Firma CIRS (Norfolk, Virginia, USA), welches aufgrund eines Metallimplantates im Wirbelkörper und eines austauschbaren Zahnes (mit und ohne Metallfüllung) unterschiedlich stark ausgeprägte Artefakte aufweist. Für die Analyse wurden in ausgewählten Bereichen des Phantomes Konturen festgelegt, die von Metallartefakten beeinflusst werden. Für jede Kontur wurde anhand der mittleren CT-Zahl sowie deren Standardabweichung die Artefaktausprägung quantitativ evaluiert. Des Weiteren wurde der optische Bildeindruck von CT-Datensätzen, die mit iMAR rekonstruiert wurden, durch drei Ärzte und sechs Medizinphysikexperten (MPEs) bewertet. Mit dem Mann-Whitney-U-Test wurden die unterschiedlichen Bildeindrücke auf Signifikanz überprüft.

Die Abweichungen materialspezifischer CT-Zahlen zwischen gefilterter Rückprojektion (FBP) und iterativer Rekonstruktion mit SAFIRE sind für alle Messaufbauten stets kleiner als 3 HU. Da SAFIRE somit keinen relevanten Einfluss auf die im Rekonstruktionskern integrierte Strahlaufhärtungskorrektur hat, enthält ein mit SAFIRE rekonstruierter CT-Scan dieselben Materialeigenschaften wie ein FBP-Datensatz. Durch die Anwendung von SAFIRE kann jedoch das Bildrauchen um bis zu 50% für SECT-Scans und pseudo-monoenergetische CT-Datensätze im Vergleich zur FBP reduziert werden (Abb. 1). Um ein vergleichbares Bildrauschen zwischen FBP und SAFIRE zu erreichen, kann die applizierte CT-Dosis für SAFIRE-Rekonstruktionen um bis zu 70% reduziert werden (Abb. 1a).
Das iterative Verfahren iMAR kann zur Reduktion von Metallartefakten beitragen, wobei der Effekt stark vom betrachteten Bildbereich und der nach Anwendungsgebiet optimierten Korrektur (z.B. für Zahn-, Hüft oder Wirbelimplantate) abhängen. In artefaktreichen Gebieten kann iMAR zu einer Verringerung von Metallartefakten von bis zu 75% führen, wobei in artefaktarmen Gebieten teilweise künstliche Bildfehler erzeugt werden, die sich in einer bis zu 4-fach erhöhten Standardabweichung widerspiegeln. Der optische Bildeindruck kann durch iMAR für Ärzte und MPEs signifikant (p < 0,01) verbessert werden.

Diskussion und Zusammenfassung
Das iterative Rekonstruktionsverfahren SAFIRE kann basierend auf den Ergebnissen dieser Studie für die Bestrahlungsplanung in der Protonentherapie eingesetzt werden. Die durch den CT-Scan in den Patienten eingetragene Dosis kann durch SAFIRE ohne Bildqualitätsverlust deutlich reduziert werden. -Dies ist insbesondere für notwendige engmaschige Kontroll-CT-Aufnahmen während der Protonentherapie von Bedeutung. Diese sind in vielen Fällen notwendig, um den hohen Präzisionsanspruch der Protonentherapie und gegebenenfalls die rechtzeitige Planadaptation zu gewährleisten.
Mit Hilfe des iterativen Verfahrens iMAR können Metallartefakte in Abhängigkeit vom Anwendungsgebiet reduziert werden. Aufgrund des signifikant verbesserten optischen Bildeindruckes kann iMAR zu einer besseren Abgrenzung von Tumor bzw. Risikoorganen beitragen, die anderweitig durch Metallartefakte überlagert werden. Jedoch sind die Verbesserungen nicht ausreichend, um eine präzise Protonenreichweite und Dosisberechnung gewährleisten zu können, wodurch Metallartefakte weiterhin ein Ausschlusskriterium für die Protonentherapie sind. Darüber hinaus ist eine ausschließliche Verwendung von iMAR aufgrund von Bildveränderungen in nicht betroffenen Gebieten nicht zu empfehlen. Es sollten stets die CT-Bilder mit der Standardrekonstruktion verglichen werden.

Keywords: CT imaging; iterative reconstruction; metal artifact reduction

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e.V., 07.-10.09.2016, Würzburg, Deutschland

Publ.-Id: 23882

Clinical implementation of dual-energy CT for proton treatment planning on pseudo-monoenergetic CT scans

Wohlfahrt, P.; Möhler, C.; Hietschold, V.; Menkel, S.; Greilich, S.; Krause, M.; Baumann, M.; Enghardt, W.; Richter, C.

Purpose: To determine whether a standardized clinical application of dual-energy CT (DECT) for proton treatment planning based on pseudo-monoenergetic CT scans (MonoCT) is feasible and leads to more reliable proton range predictions as compared to single-energy CT (SECT).

Methods and Materials: To define an optimized DECT protocol, CT scan settings were analyzed experimentally concerning beam hardening, image quality and influence on the heuristic conversion of CT numbers into stopping-power ratios (SPRs) using phantoms consisting of tissue surrogates and compared to SECT scans with identical CT dose. Differences in range prediction and dose distribution between SECT and MonoCT were quantified for phantoms and patients.

Results: Dose distributions planned on SECT and MonoCT datasets revealed mean range deviations of 0.3 mm, gamma passing rates (1%, 1 mm) greater than 99.9% and no clinically relevant changes in dose-volume histograms. However, image noise and CT-related uncertainties could be reduced by MonoCT compared to SECT with identical CT dose, which might result in a more reliable proton range prediction. Consequently, DECT was clinically implemented at the University Proton Therapy Dresden. 120 planning and 499 control DECT scans of overall 144 patients were acquired from April 2015 until May 2016.

Conclusions: A standardized clinical use of MonoCT for proton treatment planning is feasible, leads to improved image quality, extends diagnostic variety and enables a stepwise clinical implementation of DECT towards a physics-based, patient-specific, non-heuristic SPR determination. Further reductions of CT-related uncertainties, as expected from such SPR approaches, can be evaluated on the resulting DECT patient database.

Keywords: dual-energy CT; proton therapy; clinical implementation; pseudo-monoenergetic CT scans

Publ.-Id: 23881

Range prediction for tissue mixtures based on dual-energy CT

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

The use of dual-energy CT (DECT) potentially decreases range uncertainties in proton and ion therapy treatment planning via determination of the involved physical target quantities. For eventual clinical application, the correct treatment of tissue mixtures and heterogeneities is an essential feature, as they naturally occur within a patient’s CT. Here, we present how existing methods for DECT-based ion-range prediction can be modified in order to incorporate proper mixing behavior on several structural levels. Our approach is based on the factorization of the stopping-power ratio into the relative electron density and the relative stopping number. The latter is confined for tissue between about 0.95 and 1.02 at a therapeutic beam energy of 200 MeV/u and depends on the I-value. We show that convenient mixing and averaging properties arise by relating the relative stopping number to the relative cross section obtained by DECT. From this, a maximum uncertainty of the stopping-power ratio prediction below 1% is suggested for arbitrary mixtures of human body tissues.

Keywords: proton and ion radiation therapy; treatment planning; computed tomography; volume averaging

Publ.-Id: 23880

Clinical implementation of dual-energy CT for proton treatment planning to reduce CT-based range uncertainties

Wohlfahrt, P.; Möhler, C.; Baumann, M.; Enghardt, W.; Krause, M.; Greilich, S.; Richter, C.

Particle treatment planning is particularly afflicted by CT-based range uncertainties. A clinical application of dual-energy CT (DECT) provides additional tissue information to potentially achieve more precise range predictions compared to single-energy CT (SECT). Therefore, the clinical implementation of DECT was aimed to be reached in this study.

To define an optimal DECT protocol (Siemens Somatom Definition AS: 80/140kVp, kernel D34), CT scan settings were experimentally analyzed concerning beam hardening, image quality and influence on the heuristic conversion of CT numbers into stopping-power ratios (SPRs) per look-up table (HLUT) using phantoms consisting of tissues and tissue surrogates. Differences in range prediction and dose distribution between SECT and pseudo-monoenergetic CT datasets (MonoCT), derived by a weighted sum of both DECT scans, were quantified for phantoms and patients.

For treatment planning a DECT-based MonoCT of 79 keV is optimal, since CT-based HLUT uncertainties can be reduced (Figure 1). Dose distributions planned on SECT and MonoCT datasets reveal mean range deviations of 0.3mm, gamma passing rates (1%,1mm) greater than 99.9% and no clinically relevant changes in dose-volume histograms. Therefore, DECT was clinically implemented for patients treated with protons. 70 planning and 400 control DECT scans of overall 90 patients were acquired until January 2016.

More precise range predictions and a wider diagnostic variety are feasible with DECT-based MonoCTs. Further improvements are expected from a direct, patient-specific, non-heuristic SPR determination. To quantify their possible benefits, first investigations of intra- and interpatient variations were performed on the still growing patient database.

Keywords: dual-energy CT; proton therapy

  • Poster
    PTCOG - annual conference, 23.-28.05.2016, Prag, Czech Republic

Publ.-Id: 23879

Dual-energy CT for range prediction in proton and ion therapy

Möhler, C.; Wohlfahrt, P.; Richter, C.; Jäkel, O.; Greilich, S.

Proton and ion therapy require accurate prediction of particle ranges in tissue. In current clinical practice, computed tomography (CT) images are voxel-wise converted to ion-stopping power ratio maps using direct heuristic relations. The general validity of these approaches is, however, limited due to the different physical regimes of photon and ion interaction. Using a more sophisticated method based on dual-energy CT (DECT), which provides access to the physical quantities influencing photon attenuation, Hünemohr et al. (2014) reported an improved ion-range prediction for homogeneous tissue surrogates. Here, we present a major modification of the latter method, enabling a proper treatment of heterogeneities and mixtures on several structural levels, which represent a crucial feature of the realistic clinical situation.

Material and Methods:
We treat the stopping-power ratio as the product of the electron density relative to water and a correction factor that implicitly involves the logarithmic dependence on the mean excitation energy (I-value). The relative electron density, being an important parameter in both photon and ion energy loss, can be derived directly from DECT scans using a universal and robust method. The correction factor, however, has to be determined with an empirical method. For this purpose, we propose to use the information from CT images that is complementary to the relative electron density, i.e. the electronic photon absorption cross section relative to water. Using the attenuation sum rule and Bragg’s additivity rule, the relative cross sections and correction factors were calculated for single elements, tissue base materials like water, lipid, etc. and tabulated real tissues.

For a therapeutic beam energy of 200 MeV/u, the correction factor varies between 1.15 and 0.70 for single elements with atomic numbers between 1 and 100. Building up compounds from a certain number of elements, a maximum spread of possible values for the correction factor can be quoted for a given relative cross section, due to the mathematical structure of the variable space. In practice, this could be used as an uncertainty estimate for a given calibration. The accessible variable space is drastically reduced by admitting only tissue base materials such as water, lipids and hydroxylapatite. The space is further reduced by admitting only mixtures of real tissue materials. For human tissue, the correction factor is thus limited overall to a small range around one (0.96 - 1.02).

With the definition of the correction factor in the stopping-power ratio prediction and its relation to the relative cross section, a mathematically rigorous treatment of tissue mixtures was made possible. Such mixtures influence CT imaging of patients e.g. in the form of volume averaging in a CT voxel. This thorough treatment of mixtures, like the one presented here, is thus essential for the clinical applicability of DECT-based ion-range prediction.

Keywords: dual-energy CT; proton therapy

  • Poster
    ESTRO 35 - annual meeting, 29.04.-03.05.2016, Turin, Italy
  • Abstract in refereed journal
    Radiotherapy and Oncology 119(2016)Suppl.1, S869-S870

Publ.-Id: 23878

Trapping of hydrogen and helium at dislocations in tungsten: an ab initio study

Bakaev, A.; Grigorev, P.; Terentyev, D.; Bakaeva, A.; Zhurkin, E. E.; Posselt, M.

Retention of plasma gas components such as hydrogen (H) isotopes and helium (He) is one of the limiting factors in selection of plasma facing materials for future thermonuclear fusion devices. Tungsten (W) is one of the promising candidates for such materials and was chosen for the divertor armor for International Thermonuclear Experimental Reactor (ITER) and the first wall material for the design of the demonstrational fusion power plant - DEMO. For the analytical estimation of accumulation of H/He components in tungsten, it is important to understand the relevant physical mechanisms of their trapping in the material and thoroughly parameterize them numerically.
Experiments involving high flux plasma exposures of tungsten at temperature below 500 K conclude on significant amount of retained hydrogen, which unlike helium, does not agglomerate in the form of clusters in the bulk defect-free material. The observed hydrogen isotope trapping and deep diffusion is conventionally attributed to the trapping at the natural lattice defects such as dislocations and grain boundaries.
Computational assessment of trapping strength and capacity of the dislocations is the subject of this work. Here the electronic structure calculations using density functional theory (DFT) are done to evaluate the affinity of hydrogen and helium to the screw and edge dislocations. For this, we calculate the interaction energy map around the dislocation core for hydrogen and helium atoms. The energetically favorable positions are rationalized on the basis of charge density distribution and local stress concentraion. The results obtained help to refine the input parameters of the macro-scale models of retention of plasma components, such as mean field rate theory methods.
The additional molecular statics simulations are also performed to analyze whether the contempory atomistic models using the recently developed interatomic potentials for W-H-He system can grasp adequately the interaction of H and He with dislocations.

Keywords: H and He in W; trapping at dislocation; DFT

  • Lecture (Conference)
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK

Publ.-Id: 23877

Operation and sound field of an ultrasonic biplane-array

Hipp, R.; Gommlich, A.; Joneit, D.; Schubert, F.; Heuer, H.

For ultrasonic non-destructive testing several types of transducers are available based on single-channel or multi-channel technology. Transducers with more than two individual elements are usually called arrays. These arrays can differ in geometry and arrangement of their individual elements, e.g. linear, matrix and annular geometry. The advantage of arrays in contrast to single element transducers is the ability to tilt and focus the sound beam to a desired region inside the specimen. The biplane phased array is a new possibility in NDE for combining the advantages of linear phased arrays, regarding low costs and high compatibility to existing phased array electronics with the goal of matrix arrays to get signal information from the evaluated specimen in all three dimensions. The biplane array consists of a piezoelectric sensor with a conventional line electrode structure on the top and a second perpendicular line electrode structure rotated by 90° on the bottom side of the piezo layer. By using appropriate excitation and control techniques the biplane array is able to perform a conventional sector scan in two spatial directions. Moreover it is also possible to excite or receive with one single element or a choice of adjacent elements which allows flexible 3-D reconstruction techniques. All these features go along with significantly less technological effort compared to 2-D matrix arrays where each single element needs to be electrically connected and a large number of individual channels needs to supported by the used ultrasonic hardware. The paper describes and visualizes the operation of a biplane array by calculating its spatio-temporal sound field. The numerical simulations are performed by the CEFIT-PSS technique, a powerful combination of the axisymmetric Elastodynamic Finite Integration Technique (EFIT) with transient Point Source Synthesis (PSS).

Keywords: sound field simulation; biplane-array; cefit; pss

  • Open Access Logo Contribution to proceedings
    19th World Conference on Non-Destructive Testing 2016, 13.-17.06.2016, München, Deutschland


Publ.-Id: 23876

Kinetic Monte Carlo simulation of irradiation-induced nanostructure evolution in Oxide Dispersion Strengthened Fe alloys

Liedke, B.; Posselt, M.; Murali, D.; Claisse, A.; Olsson, P.

Rigid-lattice Kinetic Monte Carlo simulations are performed in order to investigate the modification of Y-Ti-O nanoclusters during irradiation, at selected temperatures, doses and dose rates. The simulations use input parameters for the atomic interactions and the migration barriers obtained by DFT calculations as well as data on representative examples of the cascade debris determined by Molecular Dynamics. Before irradiation the nanostructure is prepared by performing thermal relaxation of a system with randomly distributed Y, Ti, O atoms, and vacancies. The concentration of Y, Ti, and O is chosen according to the common 14 YWT ODS alloy and both low and high vacancy contents are considered. The nanostructures obtained in the preparation step were used subsequently in KMC simulations of irradiation. The results demonstrate the competition between ballistic effects leading to the dissolution and the growth of the clusters. While the former effect dominates at high doses and low temperatures the latter prevails at low doses and high temperatures. On the other hand, the nanoclusters formed in the preparation step show a very high stability under irradiation within the temperature and dose range relevant for the application of ODS alloys in advanced nuclear reactors. The findings of this work are consistent with the results of experimental studies of ion and neutron irradiation of ODS alloys.

Keywords: Oxide Dispersion Strengthened (ODS) Fe alloys; Kinetic Monte Carlo simulation; Irradiation

  • Lecture (Conference)
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK

Publ.-Id: 23875

Membrane Lateral Pressure Regulates Dipolar Relaxation Dynamics at the Active Site of an ATPase

Fischermeier, E.; Pospíšil, P.; Sayed, A.; Hof, M.; Solioz, M.; Fahmy, K.

Copper is an essential cofactor for redox enzymes but toxic when it accumulates in the cell. Copper homeostasis relies on transmembrane Cu+ transporting PIB-type ATPases. Molecular Dynamics simulations of the Cu-ATPase CopA from Legionella pneumophila[1] (LpCopA) suggest a water-accessible Cu+-binding site at the conserved CPC motif in the E2.Pi intermediate, where Cu+ occlusion is expected from homology with the Ca2+-ATPase, SERCAII[2,3]. However, the role of the additional physical constraints imposed by the biological membranes on LpCopA is not known. We have labeled the transmembrane cysteines of the copper-binding site with the polarity-sensitive fluorophore 6-bromoacetyl-2-dimethylaminonaphthalene (BADAN). Time-resolved dipolar relaxation studies of the dye show that membrane lateral pressure affects the hydration and dipole mobility of the ion binding site with high topological discrimination. The data show that the lipidic phase can contribute to the energetics of the ion transport cycle by providing lateral forces that affect hydration and dehydration events.

[1] P. Gourdon, P. et al. 2011, Nature 475, 59–64
[2] M. Andersson et al. 2014, Nature Struct.&Mol.Biol. 21, 43-48
[3] J. Møller et al. 2010, Biophys.Q. Rev. 43, 501–566

Keywords: time-resolved; fluorescence spectroscopy; membrane protein

  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 25.-30.09.2016, Erlangen, Germany

Publ.-Id: 23874

First-principles-based calculation of self- and solute diffusion in bcc-Fe

Posselt, M.; Abdou, J.; Murali, D.; Liedke, B.

DFT calculations were performed in order to study self-diffusion as well as oxygen and titanium diffusion in bcc Fe. It is commonly accepted that self-diffusion proceeds via the exchange of a Fe atom with a vacancy. The octahedral interstitial site is the most stable position of oxygen in bcc Fe. Therefore, it is assumed that O diffuses via the interstitial mechanism, i.e. an O atom moves from one octahedral site to the other. As for other substitutional solutes in bcc Fe, in the case of Ti the vacancy mechanism is considered. The migration barriers occurring in all these processes were calculated using the Nudged Elastic Band method. The corresponding attempt frequencies were obtained from the difference between the vibrational contribution to the free energy of the related equilibrium and saddle point configurations. While in the case of self- and O-diffusion only one saddle point and one attempt frequency are relevant, several barriers and frequencies must be determined to consider Ti diffusion by the vacancy mechanism. Different models were used to obtain the diffusion coefficient of Ti: (i) the original nine-frequency model [1], (ii) a modified nine-frequency model [2], and (iii) the Self-Consistent Mean Field model [3]. The comparison between the calculated self-, O-, and Ti-diffusion coefficients with experimental data shows significant differences. This is mainly due to fact that electron and magnon excitations were neglected in the calculations, whereas the phonon excitations were taken into account via the vibrational free energy. Under the assumption that electron excitations are small different phenomenological models are applied to consider the magnon excitations, which decrease the spontaneous magnetization of bcc Fe with increasing temperature. Choosing suitable model parameters a good agreement with measurements is obtained for self- and Ti-diffusion. On the other hand, the agreement with the few existing experimental data on O diffusion is poor. Possible reasons for this are discussed.

[1] A. D. Le Claire, in Physical chemistry: an advanced treatise, edited by H. Eyring
(Academic Press, New York, 1970).
[2] L. Messina, M. Nastar, T. Garnier, C. Domain, P. Olsson, Phys. Rev. B 90, 104203 (2014)
[3] M. Nastar, Philos. Mag. 85, 3767 (2005).

Keywords: Self- and solute diffusion; bcc-Fe; DFT

  • Poster
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK

Publ.-Id: 23873

On determination off focal laws for linear phased array probes as to the active and passive element size

Gommlich, A.; Schubert, F.

Ultrasonic linear phased array probes consist of several single transducer elements. By exciting each single element at a particular time wave fronts can be tilted, focused or both combined. The required set of time delays is called ''focal law''. Hence, the shape of the resulting wave front depends significantly on focal law calculation. The typical single transducer element in linear phased array probes has a rectangle shape with a width-to-length-ratio of approximately 0.1 to 0.5. The width of the short side is called ''active aperture size'', the larger one is called ''passive aperture size''. In state of the art calculations of the focal laws only the pitch between the single elements is considered and the elements are approximated by a point source in the centre of their aperture. Therefore, the real dimensions of the elements - both the active and the passive dimension - have no further influence. Moreover the wave propagation process itself is modelled by geometrical acoustics.
The numerical CEFIT (Cylindrical Elastodynamic Finite Integration Technique) in combination with transient PSS (Point Source Synthesis) enables flexible and fast simulation of 4-D spatio-temporal sound fields in homogeneous and layered half spaces, espectively. Thereby all wave physical effects like diffraction, scattering and mode conversion will be considered. The calculations with different geometrical parameters for the probes show that both the active as well as the passive aperture size influence the time and frequency characteristic of the signal in the focal point. Based on the focal laws calculated with and without respect to the aperture size, sound fields were simulated for selected focal points. The results were qualitatively and quantitatively compared whereby the differences between both methods are distinguishable. It becomes evident that geometrical focus and acoustical focus are different. The feasibility of corrections for the focal laws with respect to time and frequency characteristics in the focal point as well as the improvement of resolution will be discussed. The results further allow an estimation of the optimal width-tolength-ratio for single transducer elements of linear phased arrays.

Keywords: focal law; phased array; sound field simulation; cefit; pss

  • Open Access Logo Contribution to proceedings
    19th World Conference on Non-Destructive Testing 2016, 13.-17.06.2016, München, Deutschland


Publ.-Id: 23872

A comparison of adsorption, reduction, and polymerization of the plutonyl(VI) and uranyl(VI) ions from solution onto the muscovite basal plane

Hellebrandt, S.; Lee, S. S.; Knope, K. E.; Lussier, A. J.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P.; Schmidt, M.

X-ray scattering techniques [in situ resonant anomalous X-ray reflectivity (RAXR) and specular crystal truncation rods (CTR)] were used to compare muscovite (001) surfaces in contact with solutions containing either 0.1 mM plutonyl(VI) or 1 mM uranyl(VI) at pH = 3.2 ± 0.2, I(NaCl) = 0.1 M , as well as in situ grazing-incidence X-ray adsorption near-edge structure (GI XANES) spectroscopy and ex situ alpha spectrometry. Details of the surface coverage are found to be very different. In the case of Pu, alpha spectrometry finds a surface coverage of 8.3 Pu/AUC (AUC = 46.72 Å2, the unit cell area), far in excess of the 0.5 Pu/AUC expected for ionic adsorption of PuO22+. GI XANES results show that Pu is predominately tetravalent on the surface, and the CTR/RAXR results show that the adsorbed Pu is broadly distributed. Taken together with previous findings, the results are consistent with adsorption of Pu in the form of Pu(IV)-oxo-nanoparticles. In contrast, uranyl shows only negligible, if any, adsorption according to all methods applied. These results are discussed and compared within the context of known Pu and U redox chemistry.

Keywords: plutonium; uranium; surface chemistry; muscovite; surface x-ray diffraction

Publ.-Id: 23871

Liquid Metal Modelling Of The Continuous Casting Process

Timmel, K.; Willers, B.; Shevchenko, N.; Röder, M.; Wondrak, T.; Eckert, S.

The steel quality in continuous casting is greatly affected by the flow in the mould. Therefore, big efforts are made to adjust and control the flow in the mould. The tools for flow control are mainly the plant design and the use of contactless and flexible electromagnetic fields. Those electromagnetic actuators are already in use for decades in industry. Furthermore, for steel quality reasons argon can be added in the submerged entry nozzle to prevent nozzle clogging and to remove inclusions. But for both issues – electromagnetic fields and two-phase flow - an actual and detailed understanding about their action on the flow remained unclear due to inappropriate measuring techniques for liquid steel and the inadequate portability of water models for these special cases.
To get an insight into the effects of electromagnetic fields and argon bubbles on the mould flow, three experimental facilities were built up, operating with low melting liquid metals. The advantage of using these low melting metals is the availability of appropriate measurement techniques. First results already showed a strong influence of a static magnetic field on the spatial and temporal flow structure, where the conductivity of the walls plays an important role. Experiments with Argon injection revealed a complex flow and a complicated bubble creation mechanism. All the measurements provide valuable data for the validation of numerical models, which aimed to reproduce the continuous casting process of steel. The numerical models validated at model experiments can than simulate real casting machines more accurate. This paper will present the three experimental setups operating with liquid metals as model fluid and some measurement results. The three setups have slightly different scopes of investigation.

Keywords: Continuous Casting; Liquid metal model; mold flow; Ultrasonic-Doppler-Velocimetry (UDV)

  • Lecture (Conference)
    SCANMET V - 5th International Conference on Process Development in Iron and Steelmaking, 12.-16.06.2016, Luleå, Schweden
  • Contribution to proceedings
    SCANMET V - 5th International Conference on Process Development in Iron and Steelmaking, 12.-16.06.2016, Luleå, Schweden
    SCANMET V - 5th International Conference on Process Development in Iron and Steelmaking, 978-91-639-1232-7 (Book of abstracts), 132

Publ.-Id: 23869

Tuning pattern symmetry by choosing the substrate in reverse epitaxy

Engler, M.; Ou, X.; Facsko, S.

Ion beam erosion of solid surfaces is long known to yield regular surface morphologies, like periodic ripples or hexagonal dot patterns. At room temperature, semiconductors are amorphized by the ion beam. Pattern formation under these conditions has been studied extensively in the last decades.

Ion beam erosion above a material dependent dynamic recrystallization temperature allows the formation of crystalline nano scale patterns on semiconductor surfaces. At these elevated temperature pattern formation is driven by diffusion of vacancies created by sputtering of atoms. Anisotropic diffusion on the surface and diffusion barriers across step edges lead to the formation of pattern reflecting the symmetry of the irradiated surface. We will discuss how the surface symmetry determines the pattern symmetry.

Keywords: reverse epitaxy; ion beam; pattern; pattern formation; semiconductor

  • Lecture (Conference)
    80. Jahrestagung der DPG und DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Deutschland

Publ.-Id: 23868

Time-Resolved Two Million Year Old Supernova Activity Discovered in the Earth’s Microfossil Record

Bishop, S.; Ludwig, P.; Egli, R.; Chernenko, V.; Deveva, B.; Faestermann, T.; Famulok, N.; Fimiani, L.; Gomez, J.; Hain, K.; Korschinek, G.; Hanzlik, M.; Merchel, S.; Rugel, G.

Massive stars (M≥M⊙), which terminate their evolution as core collapse supernovae, are theoretically predicted to eject >10−5M⊙ of the radioisotope 60Fe (t1/2=2.6 Ma). If such an event occurs sufficiently close to our solar system, traces of the supernova debris could be deposited on Earth. Herein, we report a time-resolved 60Fe signal residing, at least partially, in a biogenic reservoir. Using accelerator mass spectrometry, this signal was found through the direct detection of live 60Fe atoms contained within secondary iron-oxides, among which are magnetofossils; the fossilized chains of magnetite crystals produced by magnetotactic bacteria. The magnetofossils were chemically extracted from two Pacific Ocean sediment drill cores. Our results show that the 60Fe signal onset occurs around 2.6−2.8 Ma, near the lower Pleistocene boundary, terminates around 1.7 Ma, and peaks at about 2.2 Ma.

Keywords: accelerator mass spectrometry; AMS

  • Invited lecture (Conferences)
    2016 Carpathian Summer School of Physics, 26.06.-09.07.2016, Sinaia, Romania


Publ.-Id: 23867

Validation of the surveillance concepts and trend curves by the investigation of decommissioned RPVs

Viehrig, H.-W.; Altstadt, E.; Houska, M.; Valo, M.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The paper presents test results measured on trepans taken from the multilayer beltline welding seam SN0.1.4. and forged base metal ring 0.3.1. located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The characterisation of the irradiation response is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seam SN0.1.4 and the forged base metal ring 0.3.1.
For the beltline welding seam we observed a large variation in the through thickness T0 values. The T0 values measured with the T-S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer beltline welding seam strongly depend on the intrinsic weld bead structure along the crack tip. In general, the fracture toughness values at cleavage failure, KJc-1T, measured on SE(B) specimens from beltline welding seam follow the Master Curve description, but more than the expected number lie outside the curves for 2 % and 98 % fracture probability. In this case the test standard ASTM E1921 indicates the investigated multi-layer weld metal as not uniform. The multi modal Master Curve based approach describes the temperature dependence of the specimen size adjusted KJc-1T values well.
The KJc values measured on L-S oriented Charpy size SE(B) specimens from defined thickness locations of the forged base metal ring 0.3.1. strongly scatter. The progression of the T0 values through the thickness lies in the range from 121 °C to 130 °C and indicate no irradiation induced embrittlement within the through the thickness fluence range from 5.38 to 1.20 ∙ 1019 n/cm2 (E > 0.5 MeV). The application of the multi modal extension [Wallin 2004, Viehrig 2006, Scibetta 2010] on the summarised dataset does essentially improve the situation. More than allowed 2% of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2% fracture probability. The reason for the occurrence of very low KJc values is seen in intergranular planes detected on the fractured surfaces of the specimens. The application of modified MC based evaluation methods indicates the material as non-homogeneous.
The investigation show that Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam and the forged base metal ring of the decommissioned Greifswald WWER-440 first generation RPV do not correspond to the forecast according to the current Russian code.

Keywords: reactor pressure vessel; multi-layer welding seam; forged base metal ring; neutron irradiation; hardness; tensile strength; fracture toughness; Master Curve approach; Charpy-V

  • Lecture (Conference)
    Workshop on Nuclear Reactor Pressure Vessel Surveillance Programs, 28.-29.06.2016, Chicago, USA
  • Book chapter
    Milan Brumovsky, William L. Server: International Review of Nuclear Reactor Pressure Vessel Surveillance Programs, ASTM STP1603, West Conshohocken, PA, USA: ASTM, 2018, 457-482
    DOI: 10.1520/STP160320160127

Publ.-Id: 23866

Zerstörungsfreie Analyse von Metallartefakten. Eine Fallstudie

Hahn, O.; Denker, A.; Merchel, S.; Radtke, M.; Reinholz, U.; Wolff, T.

Die naturwissenschaftliche Analyse historischer Materialen ermöglicht die Beantwortung kulturhistorischer Fragestellungen, die mit kunsthistorischen oder archäologischen Ansätzen allein nicht zu leisten sind. In dieser Studie wurden sechs römische Münzen mit unterschiedlich stark ausgeprägten Korrosionsschichten an unbehandelten und polierten Stellen mit vier zerstörungsfreien analytischen Methoden untersucht: Hoch- und Niederenergie Protonen Induzierter Röntgenemission (HE-/PIXE), Synchrotronstrahlungsinduzierte-Röntgenfluoreszenzanalyse (SY-RFA) und Mikro-Röntgenfluoreszenzanalyse (Mikro-RFA) mit einem mobilen Gerät. Aufgrund von Unterschieden in den Messbedingungen und dem Einfluss der Patina-Schichten auf diese ergaben sich nur für wenige Elemente Übereinstimmungen in den quantitativen Daten. Zur Validierung zukünftiger Messkampagnen mit verschiedenen Methoden sind daher Vergleichstudien unerlässlich.

Keywords: Zerstörungsfreie Prüfung; protoneninduzierte Röntgenemission; Röntgenfluoreszenzanalyse

  • Book chapter
    Barbara Armbruster, Heidemarie Eilbracht, Oliver Hahn, Orsolya Heinrich-Tamáska: Verborgenes Wissen: Innovation und Transformation feinschmiedetechnischer Entwicklungen im diachronen Vergleich, Berlin Studies of the Ancient World, Berlin: edition topoi, 2016, 978-3-9816751-5-3, 117-137


Publ.-Id: 23865

On a Long Term Strategy for the Success of Nuclear Power

Merk, B.; Litskevich, D.; Whittle, K. R.; Bankhead, M.; Taylor, R.; Mathers, D.

The current generation of nuclear reactors are evolutionary in design, mostly based on the technology originally designed to power submarines, and dominated by light water reactors. The aims of the Generation IV consortium are driven by sustainability, safety and reliability, economics, and proliferation resistance. The aims are extended here to encompass the ultimate and universal vision for strategic development of energy production, the "perpetuum mobile"-at least as close as possible.
We propose to rethink nuclear reactor design with the mission to develop an innovative system which uses no fresh resources and produces no fresh waste during operation as well as generates power safe and reliably in economic way. The results of the innovative simulations presented here demonstrate that, from a theoretical perspective, it is feasible to fulfil the mission through the direct reuse of spent nuclear fuel from currently operating reactors as the fuel for a proposed new reactor. The produced waste is less burdensome than current spent nuclear fuel which is used as feed to the system. However, safety, reliability and operational economics will need to be demonstrated to create the basis for the long term success of nuclear reactors as a major carbon free, sustainable, and applied highly reliable energy source.

Keywords: Nuclear; Reactor; Spent Fuel; P&T; Innovation Strategy

Publ.-Id: 23864

Characteristics of chemical bonding of pentavalent uranium in La-doped UO2

Butorin, S. M.; Kvashnina, K. O.; Prieur, D.; Rivenet, M.; Martin, P. M.

The effect of La doping on the electronic structure of U in UO2 was studied using an advanced technique, namely x-ray absorption spectroscopy (XAS) in the high-energy-resolution uorescence- detection (HERFD) mode at the U 3d3=2 (M4) edge. Thanks to a significant reduction of the core-hole lifetime broadening and distinct chemical shifts of the HERFD-XAS lines, the U(V) formation as a result of La doping was identified. The isolated contribution of U(V) in the M4 HERFD-XAS spectrum reveals the so-called charge-transfer satellites due to the U 5f -O 2p hybridization. The analysis of the experimental data within framework of the Andersson impurity model (AIM) indicates a significant change in the character and degree of covalency for the chemical bonding in the U(V) subsystem of UO2 as compared to undoped UO2 which is a Mott-Hubbard system. The results are also supported by AIM calculations of x-ray photoelectron and optical absorption data.

Publ.-Id: 23862

Protective effects of 2,3-diaryl-substituted indole-based cyclooxygenase-2 inhibitors on oxidative modification of human low density lipoproteins in vitro

Pietzsch, J.; Laube, M.; Bechmann, N.; Pietzsch, F.-J.; Kniess, T.

It has been suggested that 2,3-diaryl-substituted indole-based

cyclooxygenase-2 (COX-2) inhibitors (2,3-diaryl-indole coxibs) do not only appear as potent anti-inflammatory agents but also show the ability to scavenge reactive oxygen species (ROS). This led to the hypothesis that 2,3-diaryl-indole coxibs also may act as potent inhibitors of oxidative modification of low-density lipoprotein (LDL), which is considered a key factor in atherogenesis. The aim of this study was to explore i) the reactivity of a series of new synthesized 2,3-diaryl-indoles with several well characterized LDL oxidation systems and ii) subsequent effects on an inflammatory/atherogenic microenvironment. The results demonstrate that under the present experimental conditions 2,3-diaryl-indoles showed potent ROS scavenging activity and were able to markedly inhibit LDL oxidation. Subsequently, this led to a substantial decrease of modified LDL uptake by scavenger receptors in THP-1 macrophages in vitro and in rats in vivo. Moreover, modified LDL-mediated monocyte/neutrophil adhesion to endothelial cells, macrophage NF kappa B activation, as well as macrophage and endothelial cell cytokine release was diminished in vitro. The reduction of modified LDL-induced atherogenic effects by antioxidant 2,3-diaryl-indole coxibs may widen the therapeutic window of COX-2 targeted treatment.

Keywords: Antioxidants; atherogenesis; selective cyclooxygenase-2 (COX-2) inhibitors (coxibs); inflammation; lipid peroxidation; protein oxidation; radical scavenger; reactive oxygen species (ROS)

  • Open Access Logo Clinical Hemorheology and Microcirculation 61(2015)4, 615-632
    DOI: 10.3233/CH-141923


Publ.-Id: 23861

The HIV protease and PI3K/Akt inhibitor nelfinavir does not improve the curative effect of fractionated irradiation in PC 3 prostate cancer in vitro and in vivo

Liebscher, S.; Koi, L.; Löck, S.; Muders, M. H.; Krause, M.

Background: Radiotherapy has a high curative potential in localized prostate cancer, however, there are still patients with locally advanced tumours who face a considerable risk of recurrence. Radiosensitization using molecular targeted drugs could help to optimize treatment for this high-risk group. The PI3K/Akt pathway is overexpressed in many prostate cancers and is correlated to radioresistance. Nelfinavir, an HIV protease inhibitor (HPI), was found to block this pathway and to radiosensitize cancer cells of different origin. This is the first study examining the effect of nelfinavir in combination with irradiation on prostate cancer cell survival in vitro as well as on growth time and local tumour control in vivo.
Methods: The in vitro effect of nelfinavir on radioresponse of PC 3 was tested by colony formation assay with 10 µM nelfinavir. In vivo, the effect of nelfinavir alone and in combination with irradiation was tested in nude mice carrying PC 3 xenografts. For evaluating tumour growth time, mice were treated with 80 mg nelfinavir/kg body weight, daily at 5 days per week over 6 weeks. Simultaneous irradiation with 30 fractions and total doses between 30 and 120 Gy was applied to calculate local tumour control for day 180 after treatment.
Results: Nelfinavir inhibited Akt phosphorylation at Ser473 and showed a minor but significant effect on clonogenic cell survival in vitro with slightly higher cell survival rates after combined treatment. The treatment of PC 3 xenografts with nelfinavir alone led to no significant increase of tumour growth time and no improvement of local tumour control.
Conclusions: Despite promising growth delay effects of nelfinavir in other tumour models and first clinical applications of this drug as anti-cancer agent, PC 3 prostate cancer cells express no or only minor sensitivity to nelfinavir treatment alone and no radiosensitizing effect in vitro or in vivo.

Keywords: Nelfinavir; prostate cancer; PC-3; irradiation; radiosensitization; growth delay; local tumour control

Publ.-Id: 23860

Complexation and Adsorption of [152Eu]Eu to Superplasticizers and Bentonite at Variable Salt Concentrations

Becker, M.; Lippold, H.

The preferred method for the storage of spent nuclear fuel (HLW) is the disposal in deep geological formations. The repository will consist not only of the geological barrier but also of an engineered barrier and has to isolate the waste for at least 106 years from the biosphere [1]. In this barrier, several materials like concrete or bentonite are effective in retention of radionuclides. In modern concrete, several additives are used to improve the properties of the cement paste. Superplasticizers of the polycarboxylateether (PCE)-family are widely used for this purpose [2]. These organic materials might have an influence on the mobility of radionuclides. Hence, it is necessary to study their complexation and adsorption behaviour with radionuclides, cement-phases like C-S-H and buffer materials like bentonite considering a possible leaching of PCE from cement in consequence of water influx. In this study, the complexation and adsorption behaviour of the superplasticizer MasterGlenium® 51 was investigated by means of the radionuclide 152Eu, which is an analogue for trivalent actinides such as Cm(III) or Am(III), at a fixed pH and variable salt concentrations (NaCl, CaCl2). Complexation constant and loading capacity for the PCE with [152Eu]Eu were determined on the basis of the Langmuir isotherm equation as well as of the charge neutralisation model [3]. Furthermore the adsorption behaviour of [152Eu]Eu to bentonite with and without MasterGlenium51® in the presence of different background electrolytes was studied.

Keywords: Adsorption; Complexation; Superplasticizer

  • Poster
    2nd Petrus-OPERA Conference on Radioactive Waste Management and Geological Disposal, 27.06.-01.07.2016, Delft, Niederlande

Publ.-Id: 23858

Physical realization of a quantum spin liquid based on a complex frustration mechanism

Balz, C.; Lake, B.; Reuther, J.; Luetkens, H.; Schönemann, R.; Herrmannsdörfer, T.; Singh, Y.; Nazmul Islam, A. T. M.; Wheeler, E. M.; Rodriguez-Rivera, J. A.; Guidi, T.; Simeoni, G. G.; Baines, C.; Ryll, H.

Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. In the case of magnets with isotropic interactions, spin-liquid behaviour is sought in simple lattices with antiferromagnetic interactions that favour antiparallel alignments of the magnetic moments and are incompatible with the lattice geometries. Despite an extensive search, experimental realizations remain very few. Here we investigate the novel, unexplored magnet Ca10Cr7O28, which has a complex Hamiltonian consisting of several different isotropic interactions and where the ferromagnetic couplings are stronger than the antiferromagnetic ones. We show both experimentally and theoretically that it displays all the features expected of a quantum spin liquid. Thus spin-liquid behaviour in isotropic magnets is not restricted to the simple idealized models currently investigated, but can be compatible with complex structures and ferromagnetic interactions.

Publ.-Id: 23857

Visualization of trace-element zoning in apatite using BSE and CL imaging and EPMA and particle-induced X-ray/gamma-ray emission mapping

Gros, K.; Słaby, E.; Förster, H.-J.; Michalak, P. P.; Munnik, F.; Götze, J.; Rhede, D.

In this paper, zonation patterns of trace elements in apatite were visualized using four analytical techniques, namely back-scattered electrons (BSE) and cathodoluminescence (CL) imaging and electron probe micro-analysis (EPMA) and micro-proton-induced X-ray/gamma-ray emission (μPIXE/μPIGE) mapping. Each method demonstrates the in-grain compositional variations in a slightly different way. Both BSE and CL provide qualitative data, and the internal textures are displayed in most detail. Additionally, CL points to specific elements enriched in certain growth zones. Qualitative EPMA maps show detailed zonation patterns for specific elements (with high spatial resolution), which are in general correspondence with the patterns observed in BSE and CL images. The µPIXE/µPIGE maps are fully quantitative and the detection limits are relatively low compared to EPMA mapping. In present spot measurements µPIXE demonstrates lower detection limits than EPMA, however, the latter could be considerably improved by extending the acquisition times. There is no significant overlap of REE (rare earth elements) peaks in the acquired µPIXE energy spectra, however, when multiple REEs are present with sufficiently high concentrations, peak deconvolution may pose some difficulties. Spatial resolution of µPIXE/µPIGE images is not sufficiently high to reflect minor textural features, which also result from the greater interaction depth of the proton beam. However, major growth zones are distinguishable. Even though each method has their advantages and limitations, when applied together, they provide an almost complete characterization of compositional variability in trace-element-bearing minerals.

Keywords: trace-element zoning; apatite; BSE; CL; EPMA; µPIXE/µPIGE

Publ.-Id: 23856

Mg and Cs2Te photocathodes in ELBE SRF-gun

Xiang, R.; Teichert, J.

For the accelerator-based light sources and the electron colliders, the development of photo injectors has become a key technology. Especially for the superconducing radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. The “perfect” photocathodes require four important aspects: high efficiency, long life time, small transverse emittance and prompt time response.
To use Metallic photocathodes for ELBE SRF Gun is the primary choice to prevent the contamination of the SC cavity. In this contribution, we will report the investigation of magnesium (Mg) cathode in ELBE SRF gun, including the laser cleaning treatment and the measurement on quantum efficiency, Schottkey effect, dark current and damage threshold. From our experience, Mg cathode can reach high QE of 0.1% and produce up to 300 pC bunch charge in SRF gun, which is suitable for the applications with medium beam current.
However, semiconductor photocathodes in the SRF gun-I gave out very positive results. For high bunch charge and high current application, Cs2Te photocathode will be applied in the SRF gun-II soon in 2016.

Keywords: Mg; Cs2Te; photocathode; SRF-gun

  • Invited lecture (Conferences)
    European Workshop on Photocathodes for Particle Accelerator Applications, 06.-08.06.2016, Daresbury, United Kingdom

Publ.-Id: 23855

Metallic Photocathodes as an Alternative to Semiconductor Cathodes for SRF Photo-injectors

Xiang, R.; Teichert, J.

We report the Status of Mg and Cu Photocathodes used in the HZDR SRF Photo-injector.

Keywords: metallic photocathode; Mg; SRF gun; Quantum efficiency

  • Lecture (Conference)
    Matter and Technology 2nd Annual Meeting, 08.-10.03.2016, Karlsruhe, Germany

Publ.-Id: 23854

Qualification of CFD-models for multiphase flows in medium and large scale industrial applications

Lucas, D.

Multiphase flows are frequently applied in industrial processes as e.g. in chemical engineering, oil industries or power plants. Reliable predictions of the flow characteristics such as local concentration of species, interfacial area density or heat transfer in gas-liquid flows can contribute to an optimization of the design of corresponding apparatuses and processes. Computational Fluid Dynamics (CFD) in principle allows the simulation of such flows and provides local flow characteristics. While it is frequently used for industrial problems in case of single phase flows it is not yet mature for two-phase flows. The reason is the complex gas-liquid interface. For medium and large scale flow domains it is not feasible to resolve all details of this interface. Averaging procedures have to be applied and in most cases the so-called two- or multi-fluid approach is used. It assumes interpenetrating phases and the information on the interface gets lost by these averaging procedures. This information has to be added to the basic balance equations by so-called closure models. The development and validation of such models is done at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) to obtain tools for reliable predictions of multiphase flow characteristics in medium and large industrial scales.
One difficulty for the model development and validation results from the fact that we still have a lack of knowledge on local phenomena which determine the two-phase flow characteristics and which should be considered in the closure models. Experimental data with high resolution in space and time are required. To get such information on the gas-liquid interface new innovative measuring techniques as wire-mesh sensors and ultrafast X-ray tomography were developed at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) and extensively used to establish comprehensive databases. The corresponding experiments were conducted at the TOPFLOW-facility of HZDR. It can be operated for air-water and steam-water flows with a pressure up to 7 MPa and the corresponding saturation temperature of 286 °C. An electrical steam generator with a power of 4 MW is able provide up to 1.5 kg steam per second.
In this lecture the strategy of the CFD-model development and validation for multiphase flows is presented. This includes the corresponding experimental work and development of innovative measuring techniques.

Keywords: CFD; two-phase flow; TOPFLOW

  • Invited lecture (Conferences)
    Lecture series of the Energy Department of Politecnico die Milano, 15.06.2016, Milano, Italy

Publ.-Id: 23853

BEMER electromagnetic field therapy reduces cancer cell radioresistance by enhanced ROS formation and induced DNA damage

Storch, K.; Dickreuter, E.; Artati, A.; Adamski, J.; Cordes, N.

Each year more than 450,000 Germans are expected to be diagnosed with cancer subsequently receiving standard multimodal therapies including surgery, chemotherapy and radiotherapy. On top, molecular-targeted agents are increasingly administered. Owing to intrinsic and acquired resistance to these therapeutic approaches, both a better molecular understanding of tumor biology and an intensive consideration of alternative and complementary therapeutic support are warranted and open up broader and novel possibilities for therapy personalization. Particularly the latter is clearly underpinned by the increasing utilization of non-invasive complementary and alternative medicine by the population. One intensively investigated approach is the application of low-dose electromagnetic fields (EMF) to modulate cellular processes. A particular system is the BEMER therapy as a Physical Vascular Therapy for which a normalization of the microcirculation has evidently been demonstrated by a unique EMF pattern. Open remained whether this EMF pattern impacts on cancer cell survival upon treatment with radiotherapy, chemotherapy and the molecular-targeted agent Cetuximab inhibiting the epidermal growth factor receptor. Using more physiological, three-dimensional, matrix-based cell culture models and cancer cell lines originating from lung, head and neck, colorectal and pancreas, we show significant changes in distinct intermediates of the glycolysis and tricarboxylic acid cycle pathways and enhanced cancer cell radiosensitization associated with increased DNA double strand break numbers and higher levels of reactive oxygen species upon BEMER treatment relative to controls. Intriguingly, exposure of cells to the BEMER EMF pattern failed to result in sensitization to chemotherapy and Cetuximab. Further studies are necessary to better understand the mechanisms underlying the cellular alterations induced by the specific BEMER EMF pattern and clarify the application areas for human disease.

Keywords: Magnetic field therapy; radiotherapy; cancer; ROS

Publ.-Id: 23852

Radiation-Hard Ceramic Resistive Plate Chambers for Forward TOF and T0 Systems

Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kiselev, S.; Kotte, R.; Laso Garcia, A.; Malkevich, D.; Naumann, L.; Nedosekin, A.; Plotnikov, V.; Stach, D.; Sultanov, R.; Voloshin, K.

Resistive Plate Chambers with ceramic electrodes are the main candidates to be used in precise multi-channel timing systems operating in high-radiation conditions. We report the latest R&D results on these detectors aimed to meet the requirements of the forward T0 counter at the CBM experiment. RPC design, gas mixture, limits on the bulk resistivity of ceramic electrodes, efficiency, time resolution, counting rate capabilities and ageing test results are presented.


Publ.-Id: 23851

Methoden zur Charakterisierung und Optimierung von Belebungsbecken

Reinecke, S. F.; Hampel, U.

Für den Großteil der in Deutschland betriebenen Kläranlagen übersteigt die aufgewendete Energie zur Durchmischung und Belüftung des Abwassers oftmals den tatsächlich notwendigen Energiebedarf. Dies wird oft durch eine nicht-optimale Auslegung bzw. Anordnung der Begasungs- und Dispergierorgane im Belebtschlammbecken hervorgerufen. Im Vortrag werden die am HZDR durchgeführten Forschungsvorhaben zur Effizienzsteigerung von Abwasseraufbereitungsanlagen vorgestellt.

  • Lecture (Conference)
    25. Lehrer-Obmann-Tag der Kläranlagen- und Kanal-Nachbarschaften, 15.-16.03.2016, Dresden, Deutschland

Publ.-Id: 23850

Strömungsfolgende Sensorpartikel zur Charakterisierung von Bioreaktoren

Reinecke, S.; Hampel, U.

Die Kenntnis der in Bioreaktoren und speziell in großen Behältern, wie Biogasfermentern, Belebtschlammbecken und Hefefermentern, ablaufenden hydrodynamischen und biochemischen Prozesse ist begrenzt. Der Zugang für Messtechnik ist durch die Behälter und die rauen mechanischen und chemischen Umgebungsbedingungen stark eingeschränkt. Daher sind bekannte bildgebende Messverfahren zur Strömungscharakterisierung, wie Hochgeschwindigkeitsvideometrie, Particle Image Velocimetry (PIV) und Prozesstomografie, nicht anwendbar.
Zur räumlichen Erfassung der Prozessparameter in Bioreaktoren wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1,2]. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Nach der Rückgewinnung der Sensorpartikel aus dem Prozess werden die Daten ausgewertet. Die Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit ausgestattet sind (siehe Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung, die Drehrate und das Magnetfeld. Das Konzept ist zudem offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z.B. für pH-Wert und Gelöst-Sauerstoff. Eine Auftriebseinheit erlaubt zum einen die automatisierte Tarierung der Sensorpartikel im ruhenden Prozessmedium und weiterhin eine erleichterte Rückgewinnung der Sensorpartikel von der Flüssigkeitsoberfläche nach Beendigung der Messung [3].
Die Sensorpartikel wurden bereits unter realen Bedingungen von Biogasfermentern getestet und es wurden erste Strömungsanalysen erstellt [2,4]. Ein weiteres aktuelles Anwendungsfeld der Sensorpartikel sind Kläranlagen und speziell Belebtschlammbecken zur biologischen Abwasserreinigung. Erste Tests mit Sensorpartikeln wurden bereits durchgeführt (siehe Abb. 2). Der Beitrag stellt neben dem Konzept der Sensorpartikel deren Anwendungsmöglichkeiten in Bioreaktoren und damit verbundene technische Herausforderungen vor.

  • Lecture (Conference)
    AHMT 2016 – XXX. Messtechnisches Symposium des Arbeitskreises der Hochschullehrer für Messtechnik, 15.-16.09.2016, Hannover, Deutschland
  • Contribution to proceedings
    XXX. Messtechnische Symposium des Arbeitskreises der Hochschullehrer für Messtechnik, 15.-16.09.2016, Hannover, Deutschland
    Tagungsband XXX. Messtechnisches Symposium 2016, Oldenburg: De Gruyter, 978-3-11-049487-7, 19-27

Publ.-Id: 23849

Tomographic Interrogation of Gas-Liquid Flows in Inclined Risers

Lokman, A. A.; Escrig, E.; Reinecke, S.; Hewakandamby, B. N.; Azzopardi, B. J.

Measurements have been made with Electrical Capacitance Tomography (ECT) and a Wire Mesh Sensor (WMS) using air-silicone
oil (viscosity 5 mPa s) on a 67 mm diameter pipe. The experiments were carried out in a facility at Nottingham University different
inclinations. The cross-sectional distribution of gas fraction is obtained from the WMS and from the ECT the latter after post -
processing. The combined data is used to provide information on the size, frequency and velocity of large bubbles (Taylor bubbles
and spherical cap bubbles) and how they are influenced by the phase flow rates and the pipe inclinations. The boundary for spherical
cap bubbles is identified. In addition, WMS output presents the results for a radial void fraction, as well as bubble size distribution, in
particular that gives the percentage of void fraction in relation to bubble diameter. It is concluded that moving from horizontal to
inclined to vertical, there is an increase in the percentage of smaller bubbles. There are also large diameter bubbles forming for all the
inclinations. The cross-section averaged void fraction and its variation in time were measured. Taylor bubble frequency increases
with increasing of liquid flow rate and inclination angle of the pipe

Keywords: wire mesh sensor; electrical capacitance tomography; two phase flow; inclined riser

  • Contribution to proceedings
    ICMF-2016 - 9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien
    Proceedings of ICMF-2016
  • Lecture (Conference)
    ICMF-2016 - 9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien

Publ.-Id: 23848

Dipole strength in 80Se for s process and nuclear transmutation of 79Se

Makinaga, A.; Massarczyk, R.; Beard, M.; Schwengner, R.; Otsu, H.; Al-Abdullah, T.; Anders, M.; Bemmerer, D.; Hannaske, R.; John, R.; Junghans, A. R.; Müller, S. E.; Röder, M.; Schmidt, K.; Wagner, A.

The dipole strength distribution of 80Se was studied in a photon-scattering experiment using bremsstrahlung produced with an electron beam of energy 11.5 MeV at the linear accelerator ELBE. We identified 180 gamma transitions up to an energy of 9.6 MeV, and analyzed the strength in the quasicontinuum of the spectrum. Simulations of statistical gamma-ray cascades were performed to estimate intensities of inelastic transitions, and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section below the neutron-separation energy derived in this way was combined with the photoabsorption cross section obtained from an earlier (gamma, n) experiment and used as an input for the calculation of 79 Se(n, gamma) reaction rates on the basis of the statistical reaction model.

Keywords: Nuclear structure; statistical reactions; gamma spectroscopy; photon scattering; nuclear resonance fluorescence; photoabsorption cross section; gamma-ray strength function


Publ.-Id: 23847

Untersuchung der Hydrodynamik von ovalen Biogasreaktoren mit instrumentierten Strömungsfolgern

Reinecke, S. F.; Hampel, U.

Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Diese Daten werden nach der Rückgewinnung der Sensorpartikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung gestellt. Die erweiterten Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit zur Tarierung und Rückgewinnung ausgestattet sind (Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung und das Magnetfeld und offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z.B. für pH-Wert und Gelöst-Sauerstoff.
Zur Erweiterung der Positionserfassung wurde die Detektion eines festen Positionsmarkers mit den Sensorpartikeln realisiert. Als Positionsmarker wird eine eigens entwickelte Tauschspule eingesetzt, deren kodiertes Anregungssignal über das entstehende Magnetfeld von den vorbeiströmenden Sensorpartikeln empfangen wird.
Die Sensorpartikel mit magnetischer Positionsdetektion wurden erstmals in einer hydrodynamischen Studie von drei Fermentern mit ovalen Behältergeometrien genutzt . Die Fermenter haben ein Füllvolumen von 1,5 m³, 2 m³ und 32 m³ und wurden mit je zwei horizontalen Rührwerken bei zwei Umfangsgeschwindigkeiten (5,5 m/s und 6,7m/s) in einer Xanthan-Lösung (5 g/L) betrieben (Abb. 2).
Mit der Positionsdetektion im Scheitelpunkt der Fermenter wurden die Zirkulationszeitverteilungen der Fluidelemente bestimmt (Abb. 3). Dies lässt Aussagen über das Mischverhalten in den Behältern zu. In Kombination mit den extrahierten vertikalen Aufenthaltsprofilen der Sensorpartikel erfolgt ein Vergleich der drei Fermenter.

  • Poster
    Jahrestreffen Reaktionstechnik 2016 zusammen mit der Fachgruppe Mischvorgänge, 02.-04.05.2016, Würzburg, Deutschland

Publ.-Id: 23846

Instrumented flow-following sensor particles with magnetic position detection and buoyancy control

Reinecke, S. F.; Hampel, U.

A concept for buoyancy control and magnetic position detection has been developed for the improvement of instrumented flow-following sensor particles. The sensor particles are used for investigation of hydrodynamic and biochemical processes in large-scale vessels such as biogas fermenters, bioreactors and aerated sludge basins. Neutral buoyancy of the sensor particles is required for tracing of the fluid flows. Buoyancy control is performed by adjustment of the sensor particles’ volume, which is altered by an integrated piston. A miniaturized linear actuator, namely a stepper motor with linear transmission, is operated by a microcontroller to drive the piston. The buoyancy control unit enables accurate automated taring of the sensor particles in the stagnant process fluid to achieve neutral buoyancy. Therefore, the measured vertical position of the sensor particle as a function of the hydrostatic pressure is used as feedback. It has an incremental density change of 0.0136 % as compared to water and a residual drift velocity of approximately 3.6 × 10−3 m s−1. Furthermore, a minimum density of 926 kg m−3 can be set by full extension of the piston, which allows floating of the sensor particles after a defined event, namely critical charge of battery, full data storage or the end of a fixed time cycle. Thus, recovery of the sensor particles can proceed easily from the fluid level. The sensor particles with a buoyancy control unit are tested for depths up to 15 m. Also, detection of a local magnetic position marker by the sensor particles has been implemented to enhance movement tracking. It was tested in a lab-scale biogas digester and was used for estimation of the liquid circulation time distribution and Peclét number to describe the macro-flow.

Keywords: Flow follower; sensor particle; autonomous sensor; position detection; buoyancy


Publ.-Id: 23845

In-situ study of high temperature stability and optical properties of aluminum-titanium oxynitride thin films

Heras, I.; Guillén, E.; Wenisch, R.; Krause, M.; Escobar-Galindo, R.

Aluminum-titanium oxynitride AlTiO(x)N(y) thin films were investigated in order to understand the influence of the oxygen/nitrogen ratio on the optical properties and their failure mechanisms at high temperatures. The optical properties of oxynitride thin films as well as their high temperature stability showed a wide range of different responses according the oxygen/nitrogen ratio and the deposition pressure. AlTiO(x)N(y) thin films were deposited by cathodic vacuum arc and characterized at different temperatures to follow the temperature dependence of the composition and the optical constants. The samples were heated in vacuum from room temperature up to 800°C inside a multi-chamber cluster tool and the analysis of the thin films was carried out in-situ without intermittent sample exposure to air. Ellipsometry and Rutherford backscattering spectrometry (RBS) results showed the influence of the as-deposited oxygen content in the sample with the inward diffusion of oxygen into the coating and therefore oxidation resistance at high temperatures. Likewise, ex-situ annealing in air was performed to compare the results observed when exposed to ambient conditions. The low emittance properties of AlTiO(x)N(y) enabled in-situ RBS analysis at temperatures higher than 750°C. No significant changes of the optical properties and composition were found when heating in vacuum demonstrating excellent stability at high temperatures.

Keywords: solar-selective coatings; concentrated solar power; in situ RBS; cluster tool

  • Lecture (Conference)
    EMRS 2016 Spring Meeting, 02.-06.05.2016, Lille, Frankreich

Publ.-Id: 23844

High-field paramagnetic Meissner effect up to 14 T in melt-textured YBa2Cu3O7–δ

Dias, F. T.; Vieira, V. N.; Wolff-Fabris, F.; Kampert, E.; Gouvea, C. P.; Campos, A. P. C.; Archanjo, B. S.; Schaf, J.; Obradors, X.; Puig, T.

We have performed magnetization experiments in a melt-textured YBa2Cu3O7-δ (Y123) sample with Y2BaCuO5 (Y211) inclusions, under magnetic fields up to 14 T applied parallel or perpendicular to the ab plane. Magnetic anisotropy and paramagnetic moments were observed in both FC (field-cooling) and FCW (field-cooled warming) procedures and these features correspond to the so-called High-Field Paramagnetic Meissner Effect (HFPME). The HFPME effect increases monotonically as the magnetic field rises and a strong paramagnetic relaxation, toward increasing paramagnetic moment was additionally observed as a function of time. Microscopy analysis revealed a complex and correlated microstructure of the Y211 particles. These correlated defects are well known to cause strong flux pinning. Our results suggest a scenario of strong flux compression within weak or non-superconducting regions of the samples, developed as a consequence of the Meissner effect and assisted by strong flux pinning by the Y211 particles. This scenario is observed up to 14 T and clearly persists beyond.


Publ.-Id: 23843

Confined catalytic Janus swimmers in a crowded channel: geometry-driven rectification transients and directional locking

Yu, H.; Kopach, A.; Misko, V. R.; Vasylenko, A. A.; Makarov, D.; Marchesoni, F.; Nori, F.; Baraban, L.; Cuniberti, G.

Self-propelled Janus particles, acting as microscopic vehicles, have the potential of performing complex tasks on a microscopic scale, suitable, e.g., for environmental applications, on-chip chemical information processing or in vivo drug delivery. Development of these smart nano-devices requires a better understanding of how synthetic swimmers move in crowded and confined environments that mimic actual biosystems, of blood vessels. Here the dynamics of self-propelled Janus particles interactingwith catalytically passive silica beads in a narrow channel isstudied both experimentally and through numerical simulations. Upon varying the area density of thesilica beads and the width of the channel, active transport reveals a number of intriguing properties, which range from distinct bulk and boundary-free diffusivity at low densities, to directional “locking” and channel “unclogging” at higher densities, whereby a Janus swimmer is capable of transporting large clusters of passive particles.

Keywords: Janus particles motors; microswimmers; microfluidic channel; catalytic propulsion

Publ.-Id: 23842

Development of interatomic potential for bcc FeCrNi and its validation

Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.

Vac-Ni dragging possible
DFT logic substitutional configs reproduced
Most stable interstitial configs reproduced
Defect free Monte Carlo simulations:
Cr and Ni precipitate as separate fractions
Cr precipitation is independent of Ni content (<2%Ni)
Ni precipitation is enhanced by Cr

Keywords: FeCrNi alloy; interatomic potential

  • Lecture (Conference)
    8th N-FAME Workshop on modelling and modelling-oriented experiments in Fe alloys for nuclear applications, 13.-14.06.2016, Brussels, Belgium

Publ.-Id: 23841

Radiation-induced segregation in FeNiCr model alloys

Bakaev, A.; Posselt, M.; Terentyev, D.; Bonny, G.; Zhurkin, E. E.

Defect-free FeNiCr alloys:
No influence of Ni on Cr solubility, limited effect of Cr on Ni at 2%Ni : ↗100 K
Ni and Cr precipitate as separate fractions. Ni forms B2 FeNi clusters with {100} facets while the Cr atoms form pure Cr clusters with {110} facets
FeNiCr alloys with dislocation loops:
No mixing of Ni and Cr precipitates: Ni moves to compressive regions, Cr - tensile regions
Dislocation loops stabilize by 100-200 K Ni clusters only at Ni content in the alloy >=0.5%
Ni decreases significantly the segregation of Cr, cancelling the segregation or causing the depletion at Ni>=1%
Cr decreases the segregation of Ni at ½<111> loops for low Ni (0.25%) alloys, strongly enhances the Ni segregation at <100> loops for high Ni (2%) at T < 800 K due to Cr depletion
Enrichment values for Cr and Ni at ½<111 > loops at T = 600 K are consistent with experiments:
small ½<111> loops can serve as nucleus for NiCr(Si/P)-rich clusters

Keywords: FeCrNi alloys; radiation-induced segregation; Metropolis Monte Carlo simulation

  • Lecture (Conference)
    8th N-FAME Workshop on modelling and modelling-oriented experiments in Fe alloys for nuclear applications, 13.-14.06.2016, Brussels, Belgium

Publ.-Id: 23840

Spatially-resolved sorption studies of Eu(III) on granite surface with time-resolved laser fluorescence microscopy (TRLFM)

Zesewitz, K.; Schmidt, M.

The finding of an appropriate long-term repository for high-level nuclear waste is a highly relevant topic. To that end, it is required to research the interaction of occurring radionuclides with mineral phases contained in possible host rocks and construction materials. On a time scale of up to a million years, especially the scenario of a water intrusion into the repository and thus dissolution of radionuclides has to be considered. To investigate the sorption behavior of actinides and lanthanides, time-resolved laser fluorescence spectroscopy (TRLFS) is a widely used method, because of its trace concentration sensitivity and capability to distinguish multiple species in complex systems. On one hand this method gives the spectral information of the emitted fluorescence light, which allows determining the symmetry and the grade of complexation of the sorbed Ln/Ac. On the other hand the lifetimes of the excited electron states provide information about the surrounding quenchers, mainly water. Typically, TRLFS investigations will focus on the interaction of an actinide with one relevant mineral phase. For a real rock formation, e.g. granite, sorption will however be a competitive process involving multiple mineral phases at the same time.
In this study a new method called time-resolved laser fluorescence microscopy (TRLFM) is introduced, which will add a spatial dimension to TRLFS. By doing so, it is possible to separate the multi-phase system into discrete single-phase systems and therefore to make a step beyond model systems by researching, for example whole natural granite rock with TRLFS. Because of its advantageous fluorescence properties we use europium as an analogue for the trivalent actinides americium and curium. Sorption experiments with Eu(III) on granite under different solution conditions, regarding metal concentration and pH will be presented. These samples are excited by a focused pulsed laser beam at a wavelength of 394 nm, and scanned through the laser’s focal point by an XYZ-Stage with a resolution in the micrometer range. The sample is subsequently mapped by Raman-Microscopy to distinguish the different phases and the TRLFM data is then compared to the combination of Raman-data with TRLFS data of the single phases.
First results show that the different sorption behavior of the single phases can be resolved by this method. Lifetimes and emission spectra have been measured for quartz, feldspar and mica phases on granite plates, which evidence that the spatial resolution is sufficient to distinguish mineral grains in natural granite. XRD and XFA are done for the samples to determine all possible constituents. Partial maps of the europium distribution and speciation are presented together with phase identification by Raman microscopy and a comparison to optical microscopy images.

Keywords: TRLFS; granite; TRLFM; europium; speciation

  • Lecture (Conference)
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 07.-10.11.2016, EMSL, Richland, Washington, USA

Publ.-Id: 23839

Coulomb dissociation of 27P at 500 MeV/u

Marganiec, J.; Beceiro Novo, S.; Typel, S.; Langer, C.; Wimmer, C.; Alvarez-Pol, H.; Aumann, T.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y. A.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Rodriguez Tajes, C.; Rossi, D. M.; Simon, H.; Stanoiu, M.; Stroth, J.; Sümmerer, K.; Wagner, A.; Wamers, F.; Weick, H.; Wiescher, M.

The proton-capture reaction 26Si(p,γ)27P was studied via Coulomb dissociation (CD) of 27P at an incident energy of about 500 MeV / u. The three lowest-lying resonances in 27P have been populated and their resonance strengths have been measured. In addition, a nonresonant direct-capture component was clearly identified and its astrophysical S factor measured. The experimental results are compared to Monte Carlo simulations of the CD process using a semiclassical model. Our thermonuclear reaction rates show good agreement with the rates from a recent compilation. With respect to the nuclear structure of 27P we have found evidence for a negative-parity intruder state at 2.88-MeV excitation energy.

Keywords: proton capture radioactive beam thermonuclear

Publ.-Id: 23837

Frequency- and Amplitude Modulation of Spin-Wave Signals emitted from Topological Spin Textures

Wintz, S.; Finizio, S.; Schultheiss, K.; Liersch, V.; Kilibarda, F.; Warnatz, T.; Suszka, A. K.; Warnicke, P.; Wohlhüter, P.; Erbe, A.; Lindner, J.; Fassbender, J.; Raabe, J.

The investigation of spin-wave phenomena, dubbed magnonics, is an important branch of present magnetism research. This is in particular the case since spin waves are seen as promising signal carriers for future spintronic information and communication technology devices. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths (striplines or point-contacts) or to generate such spin waves parametrically by a spatially uniform double-frequency microwave signal. Recently, however, a new mechanism for the local excitation of spin waves has been found, which overcomes the lower wavelength limit given by the minimum patterning size. This method utilizes the translation of layered topological magnetic defects, i.e. the gyration of coupled spin vortex cores to generate propagating spin waves. In the present contribution we will show that a system similar to the one used in can be exploited to excite spin-wave signals with frequency- and amplitude modulation. With respect to a certain high-frequency spin-wave carrier signal, frequency and amplitude were periodically modulated encoding a lower frequency information signal. The resulting spin-wave dynamics was directly imaged by means of time-resolved scanning transmission x-ray microscopy. By demonstrating a very high agility for the vortex core based spin-wave generation mechanism, our findings further underline the potential applicability of this concept.

  • Poster
    61st Annual Conference on Magnetism and Magnetic Materials, 31.10.-04.11.2016, New Orleans, USA

Publ.-Id: 23836

Band structure modification in silicon hyperdoped with tellurium for optoelectronics

Wang, M.; Liu, F.; Yuan, Y.; Prucna, S.; Berencen, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.

Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption exhibited by these materials, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped Si layers have been fabricated by ion implantation followed by either millisecond range flash lamp annealing (FLA) or nanosecond range pulsed-laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted Si by both FLA and PLM. From the transport measurements, the conductivity increases with increasing tellurium concentration and the high tellurium concentration samples show a finite conductivity if temperature tends to zero. This indicates that the high concentration doping of tellurium induces an insulator-to-metal transition in silicon although tellurium introduces a deep donor in Si. Moreover, the ellipsometry measurements show that the band gap narrows with increasing doping concentration, which could enable silicon-based optoelectronics in the infrared spectral range.

[1] Kim, T. G., et al., Appl. Phys. Lett. 88, 241902 (2006)
[2] Tabbal, M., et al., Appl. Phys. A 98, 589–594 (2010)
[3] Umezu, I., et al., J. Appl. Phys. 113, 213501 (2013)

Keywords: Hyperdoping silicon; Flash lamp annealing; Pulsed-laser melting; Band structure modification

  • Lecture (Conference)
    The 2016 E-MRS Spring Meeting, 02.-06.05.2016, Lille, France

Publ.-Id: 23835

Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles

Pidchenko, I.; Kvashnina, K. O.; Yokosawa, T.; Finck, N.; Schild, D.; Polly, R.; Bohnert, E.; Rossberg, A.; Göttlicher, J.; Dardenne, K.; Rothe, J.; Schäfer, T.; Geckeis, H.; Vitova, T.

Uranium redox states and speciation in magnetite nanoparticles co-precipitated with U(VI) for uranium loadings varying from 1,000 to 10,000 ppm are investigated by X-ray absorption spectroscopy (XAS). It is demonstrated that the U M4 high energy resolution X-ray absorption near edge structure (HR-XANES) method is capable to clearly characterize U(IV), U(V) and U(VI) existing simultaneously in the same sample. The contributions of the three different uranium redox states present in the samples are quantified with the iterative transformation factor analysis (ITFA) method. U(V) incorporated in octahedral magnetite sites remains stable over 226 days under ambient conditions as unambiguously shown for the magnetite nanoparticles containing 1,000 ppm uranium. U L3 XAS and transmission electron microscopy (TEM) studies reveal that initially precipitated U(VI) phases recrystallize to non-stoichiometric UO2+x nanoclusters within 147 days when stored under anoxic conditions. XAS results are supported by density functional theory (DFT) calculations. Further characterization of the samples include powder X-ray diffraction (pXRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

Keywords: Uranium; actinides; redox state; magnetite; HR-XANES


Publ.-Id: 23834

Tellurium hyperdoped Si: Flash lamp annealing vs. Pulsed laser melting

Wang, M.; Liu, F.; Yuan, Y.; Prucna, S.; Berencen, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.

Chalcogen-hyperdoped silicon has been a topic of great interesting due to its potential properties of sub-band gap optical and optoelectronic [1-3]. Tellurium hyperdoped Si was fabricated by the ion-implantation with different doses ranging from 1.09×1015 to 1.25×1016 atom/cm2 followed by two ultra-short annealing processing: flash lamp annealing (FLA) and pulsed laser melting (PLM). The structural properties of Te doped Si were characterized by Rutherford backscattering spectrometry / Channeling and Raman scattering. The Raman results show the high quality recrystallization of tellurium implanted Si by both FLA and PLM. In addition the Electrical properties of Tellurium hyperdoping silicon were measured by using a commercial Lakeshore Hall System. The differentiation of conductivity occurs with increasing tellurium concentration, which indicated that upon high concentration doping the insulator-metal transition was observed in tellurium doped Si. Moreover the carrier concentration and Hall mobilities measured at 300 K for different FLA and PLM samples with increasing tellurium concentration were measured. The PLM samples generally have a larger carrier concentration than the FLA samples, the mobility is around 2 times smaller.

Keywords: Hyperdoped Si; Ion-implantation; Flash lamp annealing; Pulsed laser melting

  • Lecture (Conference)
    80. Jahrestagung der DPG und DPG-Frühjahrstagung (80th Annual Conference of the DPG and DPG Spring Meeting), 06.-11.03.2016, Universität Regensburg, Regensburg, Germany

Publ.-Id: 23833

Dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses

Huang, L. G.; Kluge, T.; Cowan, T. E.

The dynamics of bulk heating and ionization is investigated both in simulations and theory, which determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. During laser-plasma interactions, the solid density plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A portion of the electrons with relativistic kinetic energy goes through the solid density plasma and transfers energy into the bulk electrons, which results in bulk electron heating. The bulk electron heating is finally translated into the processes of bulk collisional ionization inside the solid target. A simple model based on the Ohmic heating mechanism indicates that the local and temporal profile of bulk return current is essential to determine the temporal evolution of bulk electron temperature. A series of particle-in-cell simulations showing the local heating model is robust in the cases of target with a preplasma and without a preplasma. Predicting the bulk electron heating is then benefit for understanding the collisional ionization dynamics inside the solid targets. The connection of the heating and ionization inside the solid target is further studied using Thomas-Fermi model.

Keywords: bulk heating; ionization; local; temporal; Ohmic heating; return current

Publ.-Id: 23832

Putaminal dopamine turnover in de novo Parkinson disease predicts later motor complications

Loehle, M.; Mende, J.; Wolz, M.; Beuthien-Baumann, B.; Oehme, L.; van den Hoff, J.; Kotzerke, J.; Reichmann, H.; Storch, A.

Objective: To investigate the predictive value of striatal dopamine turnover in patients with de novo Parkinson disease (PD) for the onset of later motor complications.

Methods: This retrospective, observer-blinded cohort study followed up 31 patients with early PD who completed quantitative 18F-dopa PET imaging to measure striatal 18F-dopa uptake (Kocc) and effective distribution volume ratio (EDVR) as the inverse of dopamine turnover prior to antiparkinsonian treatment. The onset of wearing-off and dyskinesias was determined based on blinded clinical assessments and patient records. The predictive value of baseline PET measures for motor complications was evaluated using Cox proportional hazard models.

Results: During a mean follow-up time of 6.8 years, 18 (58.1%) patients developed wearing-off, 11 (35.5%) dyskinesia, and 20 (64.5%) any motor complication. Patients with dyskinesia and any motor complication showed lower baseline EDVR (higher dopamine turnover) in the putamen than those without dyskinesias and any motor complication, with differences most markedly present in the posterior putamen. Baseline EDVR in the whole and the posterior putamen predicted development of motor complications with an increasing risk with lower EDVR (higher dopamine turnover), whereas EDVR in other regions and Kocc did not correlate with motor complications. Correspondingly, Kaplan-Meier curves showed reduced survival from motor complications in patients with lower baseline EDVR (higher dopamine turnover) in the posterior putamen with ongoing levodopa treatment and disease duration.

Conclusions: Elevated putaminal dopamine turnover in de novo PD is associated with an increased risk for later motor complications and comprises a disease-intrinsic predisposing factor for their development.

Publ.-Id: 23830

General switching voltages for magnetic tunnel junctions with in-plane and/or perpendicular-to-plane anisotropy free layers

Bernert, K.; Sluka, V.; Fowley, C.; Lindner, J.; Deac, A. M.; Fassbender, J.

We analytically calculate the switching voltages for MgO-based magnetic tunnel junctions for the generalized case where the free layer has two generic “intrinsic” fields oriented along orthogonal directions. The magnetization of the reference layer and the applied field are assumed to be parallel to one of the two intrinsic field axis. Both the in-plane and the field-like spin-torque terms are taken into account, with the field-like torque assumed to have a quadratic dependence on the applied voltage and to favour the antiparallel state [1]. The switching voltages thus determined can be particularized for different geometries by replacing the two generic intrinsic field terms with the appropriate expressions for the anisotropy and demagnetizing fields, according to the specific free and reference layer configuration considered. The results are consistent with numerical integration of the Landau-Lifshitz-Gilbert equation with the relevant spin-torque terms.
For in-plane MgO-based magnetic tunnel junctions, one of the two intrinsic fields of the free layer corresponds to the (negative) demagnetizing field, which pulls the magnetization of the free layer towards the film plane. The orthogonal intrinsic field component is the easy-axis anisotropy, parallel to the current polarization and the external field direction. We demonstrate that in this configuration the quadratic dependence of the field-like torque on the applied voltage can cause back-hopping (a somewhat obscure behaviour characteristic to tunnel junctions, whereby reliable switching to the desired state is achieved for applied voltages of the order of the critical voltage, but a larger applied bias induces a telegraph-noise behaviour [2, 3]). For perpendicular anisotropy tunnel junctions without in-plane shape anisotropy, the only intrinsic field present in the free layer is parallel the effective anisotropy, parallel to the reference layer direction. In this case, we find that neither back-hopping, nor spin-transfer driven steady stare precession are expected, as evidenced by experimental results [4]. Finally, if an in-plane shape anisotropy is considered in addition to the effective perpendicular anisotropy, a variety of canted states are predicted [5].
[1] C. Heiliger and M. Stiles, Ab Initio Studies of the Spin-Transfer Torque in Magnetic Tunnel Junctions, Phys. Rev. Lett. 100, 186805 (2008).
[2] J. Z. Sun, , M. C. Gaidis, G. Hu, E. J. O’Sullivan, S. L. Brown, J. J. Nowak, P. L. Trouilloud and D. C. Worledge, High-bias backhopping in nanosecond time-domain spin-torque switches of MgO-based magnetic tunnel junctions, J. Appl. Phys. 105, 07D109 (2009).
[3] T. Min, J. Z. Sun, R. Beach, D. Tang and P. Wang, Back-hopping after spin torque transfer induced magnetization switching in magnetic tunneling junction cells, J. Appl. Phys. 105, 07D126 (2009).
[4] J.J. Nowak, R. P. Robertazzi, J. Z. Sun, G. Hu, David W. Abraham, P. L. Trouilloud, S. Brown, M. C. Gaidis, E. J. O’Sullivan, W. J. Gallagher, and D. C. Worledge, Demonstration of Ultralow Bit Error Rates for Spin-Torque Magnetic Random-Access Memory With Perpendicular Magnetic Anisotropy, IEEE Magn. Lett. 2, 3000204 (2011).
[5] K. Bernert, V. Sluka, C. Fowley, J. Lindner, J. Fassbender and A. M. Deac, Phase diagrams of MgO magnetic tunnel junctions including the perpendicular spin-transfer torque in different geometries, Phys. Rev. B 89, 134415 (2014).

Keywords: spin-transfer torque; magnetic tunnel junctions

  • Invited lecture (Conferences)
    New Horizons for Memory Storage: Advancing Non-volatile Memory with Atomistic Simulations, 29.06.-01.07.2016, Dublin, Ireland

Publ.-Id: 23829

An outlook on the rare earth elements mining industry

Barakos, G.; Mischo, H.; Gutzmer, J.

How learning from the mistakes of the past can contribute to building a strong global rare earth elements supply chain

  • Other report
    Carlton Victoria, Australia: The Australasian Institute of Mining and Metallurgy, 2016


Publ.-Id: 23828

Legislation; Challenges and Policy Strategies: In search for a regulatory framework for sustainable development in the Rare Earths mining industry

Barakos, G.; Mischo, H.; Gutzmer, J.

One of the major issues that the Rare Earth Elements Mining Industry has to deal with is the legislation vacuum that exists in many countries around the world. Among these, are countries which have long history and tradition in mining. In many cases the lack of direct legislation for REE mine management as well as for other potentially polluting industries can be a barrier to sustainable development. Moreover, the case of lax legislation in China has led to environmental pollution problems and extended smuggling of rare earth elements.
This paper looks into the current regulatory status on the mining of REEs, identifies the loopholes and suggests some elements for a new global legislation framework for sustainable development in the REE mining industry. The setting of this regulatory framework will be in line with the present and future challenges of the rare earths market as well as with the policy strategies that are defined internationally. The aim of such a legislative framework will be to strengthen the global rare earth elements supply chain, appease social concerns and ensure the preservation and conservation of the environment.

  • Open Access Logo Contribution to proceedings
    SME Annual Meeting 2016, 21.-24.02.2016, Phoenix, United States of America
    SME Annual Meeting 2016, Phoenix, USA: SME

Publ.-Id: 23827

Status Quo and Future Evaluations of Global Rare Earth Mining (with Respect to Special Rare Earth Element-industry Criteria)

Barakos, G.; Mischo, H.; Gutzmer, J.

The continuously growing demand for rare earth elements (REEs), in combination with the crisis of 2009 and the price spike of 2011, has initiated a treasure hunt for rare earth deposits all over the world in recent years. Since then, commodity prices have declined and are now quite stable, yet the world is still dependent on China’s dominance of the market and its export policies. Exploration is unremitting and numerous resources of potential interest have already been revealed in many countries; however, proceeding to mining operations is not that simple, especially when it comes to the exploitation of rare earth deposits. Evaluating the feasibility of a mining project is always a unique, sensitive and rather complex process that depends on multiple criteria. This paper focuses on clarifying the present and future global situation in the development of respective deposits and on identifying rare earth-specific criteria that influence the overall feasibility assessments of any potential (especially underground) mining projects. Environmental impacts, legislation issues and the presence of radioactive pollutants are some of the notable boundary conditions that govern rare earth mining operations and need to be taken into consideration. Furthermore, the balance problem between the supply and demand of the different REEs can determine decisively whether a deposit of specific REEs is economically exploitable. For this reason, evaluations are made regarding the future strategies to be enacted in order for the rest of the world to detach itself from this situation. The ultimate goal of these evaluations is for them to be incorporated in an overall assessment tool for rare earth underground mining procedures that will be implemented in real case studies to determine their sustainability.

  • Open Access Logo Contribution to proceedings
    Third International Future Mining Conference, 04.-06.11.2015, Sydney, Australia
    Third International Future Mining Conference, Carlton Victoria, Australia: The Australasian Institute of Mining and Metallurg, 978 1 925100 40 2

Publ.-Id: 23826

Strategic evaluations and mining process optimization towards a strong global ree supply chain

Barakos, G.; Gutzmer, J.; Mischo, H.

Rare earth elements (REE) have turned from an inconspicuous group of raw materials to critical commodities in the last decade. The insatiable and continuously growing demand for rare earths combined with their small and opaque market has resulted in a global exploration boom that has led to the delineation of extensive resources on every continent. Nevertheless, the special boundary conditions that govern the REE industry require second thoughts and careful evaluations when it comes to the potential exploitation of such resources. Past mistakes, with respect to environmental impacts and uncertain investments, have resulted in an overall uncertainty whether the mining and beneficiation of rare earth elements can be a viable industry in a free market context. This paper attempts to record the erroneous practices of the past and use them as guidelines to strengthen the global REE supply-chain. Moreover, the paper focuses on the assessments that need to be made in order to optimize the mining process and reinforce the growth prospects of the market. An overall assessment tool for the mineability of rare earth deposits is also used to consolidate these evaluations and answer the question, if REE mining can be sustainable.

Keywords: Rare earth elements; Global supply chain; Mining optimization; Mining sustainability

Publ.-Id: 23825

Improved progression free survival for patients with diabetes and locally advanced non-small cell lung cancer (NSCLC) using metformin during concurrent chemoradiotherapy.

Wink, K. C. J.; Belderbos, J. S. A.; Dieleman, E. M. T.; Rossi, M.; Rasch, C. R. N.; Damhuis, R. A. M.; Houben, R. M. A.; Troost, E. G. C.


The aim was to investigate whether the use of metformin during concurrent chemoradiotherapy (cCRT) for locally advanced non-small cell lung cancer (NSCLC) improved treatment outcome.

A total of 682 patients were included in this retrospective cohort study (59 metformin users, 623 control patients). All received cCRT in one of three participating radiation oncology departments in the Netherlands between January 2008 and January 2013. Primary endpoint was locoregional recurrence free survival (LRFS), secondary endpoints were overall survival (OS), progression-free survival (PFS) and distant metastasis free survival (DMFS).

No significant differences in LRFS or OS were found. Metformin use was associated with an improved DMFS (74% versus 53% at 2years; p=0.01) and PFS (58% versus 37% at 2years and a median PFS of 41months versus 15months; p=0.01). In a multivariate cox-regression analysis, the use of metformin was a statistically significant independent variable for DMFS and PFS (p=0.02 and 0.03).

Metformin use during cCRT is associated with an improved DMFS and PFS for locally advanced NSCLC patients, suggesting that metformin may be a valuable treatment addition in these patients. Evidently, our results merit to be verified in a prospective trial.

Keywords: Chemotherapy; Diabetes; Metformin; NSCLC; Radiotherapy

Publ.-Id: 23824

An Epigenetic Reprogramming Strategy to Resensitize Radioresistant Prostate Cancer Cells.

Peitzsch, C.; Cojoc, M.; Hein, L.; Kurth, I.; Mäbert, K.; Trautmann, F.; Klink, B.; Schröck, E.; Wirth, M. P.; Krause, M.; Stakhovsky, E. A.; Telegeev, G. D.; Novotny, V.; Toma, M.; Muders, M.; Baretton, G. B.; Frame, F. M.; Maitland, N. J.; Baumann, M.; Dubrovska, A.

Radiotherapy is a mainstay of curative prostate cancer treatment, but risks of recurrence after treatment remain significant in locally advanced disease. Given that tumor relapse can be attributed to a population of cancer stem cells (CSC) that survives radiotherapy, analysis of this cell population might illuminate tactics to personalize treatment. However, this direction remains challenging given the plastic nature of prostate cancers following treatment. We show here that irradiating prostate cancer cells stimulates a durable upregulation of stem cell markers that epigenetically reprogram these cells. In both tumorigenic and radioresistant cell populations, a phenotypic switch occurred during a course of radiotherapy that was associated with stable genetic and epigenetic changes. Specifically, we found that irradiation triggered histone H3 methylation at the promoter of the CSC marker aldehyde dehydrogenase 1A1 (ALDH1A1), stimulating its gene transcription. Inhibiting this methylation event triggered apoptosis, promoted radiosensitization, and hindered tumorigenicity of radioresistant prostate cancer cells. Overall, our results suggest that epigenetic therapies may restore the cytotoxic effects of irradiation in radioresistant CSC populations. Cancer Res; 76(9); 2637-51. ©2016 AACR.

Publ.-Id: 23823

[Melanoma brain metastases : Treatment options]. [Hirnmetastasen des malignen Melanoms].

Rauschenberg, R.; Tabatabai, G.; Troost, E. G. C.; Garzarolli, M.; Beissert, S.; Meier, F.

Hirnmetastasen treten bei der Mehrheit der Patienten mit metastasiertem Melanom auf und sind die häufigste Todesursache. Bis vor Kurzem war die Lokaltherapie die einzige Option für die Kontrolle von Hirnmetastasen. Inzwischen stehen wirksame systemische Therapieoptionen zur Verfügung. Bei Verdacht auf Hirnmetastasen sind eine Staging-Diagnostik mit Craniale Magnetresonanztomographie (cMRT) sowie eine neurologische Untersuchung indiziert. Für die Therapieplanung sollten prognostische Faktoren wie Anzahl und Symptomatik der zerebralen Metastasen, der LDH- und S100-Wert im Serum, die extrazerebrale Metastasierung sowie der ECOG (Eastern Cooperative Oncology Group)-Status einbezogen werden. Die Therapieentscheidung bzw. -durchführung sollte interdisziplinär bzw. multimodal erfolgen. Bei singulären Hirnmetastasen sind die neurochirurgische Resektion und die stereotaktische Radiatio etabliert. Das Behandlungsspektrum hat sich durch die Neuzulassung von wirksamen Immuntherapien (CTLA-4- und PD-1-Antikörper) sowie zielgerichteten Therapien (BRAF-und MEK-Inhibitoren) erheblich erweitert. Die palliative Ganzhirnradiatio wird bei multiplen symptomatischen Hirnmetastasen eingesetzt, wobei bisher kein signifikanter Vorteil für das Gesamtüberleben gezeigt werden konnte. Bei erhöhtem intrakraniellem Druck und epileptischen Anfällen sind Kortikosteroide und Antikonvulsiva indiziert. In aktuellen klinischen Studien werden für Melanompatienten mit Hirnmetastasen neue Therapieoptionen wie PD-1-Antikörper, Ipilimumab plus Nivolumab, BRAF-Inhibitoren plus MEK-Inhibitoren sowie stereotaktische Radiatio in Kombination mit Immuntherapie bzw. zielgerichteter Therapie untersucht.

Keywords: Resektion Radiatio Systemtherapie BRAF-Inhibitor Immuntherapie

Publ.-Id: 23822

Efficacy of Beta1 Integrin and EGFR Targeting in Sphere-Forming Human Head and Neck Cancer Cells

Zscheppang, K.; Kurth, I.; Wachtel, N.; Dubrovska, A.; Kunz-Schughart, L. A.; Cordes, N.


Resistance to radiotherapy continues to be a limiting factor in the treatment of cancer including head and neck squamous cell carcinoma (HNSCC). Simultaneous targeting of β1 integrin and EGFR was shown to have a higher radiosensitizing potential than mono-targeting in the majority of tested HNSCC cancer models. As tumor-initiating cells (TIC) are thought to play a key role for therapy resistance and recurrence and can be enriched in sphere forming conditions, this study investigated the efficacy of β1 integrin/EGFR targeting without and in combination with X-ray irradiation on the behavior of sphere-forming cells (SFC).

HNSCC cell lines (UTSCC15, UTSCC5, Cal33, SAS) were injected subcutaneously into nude mice for tumor up-take and plated for primary and secondary sphere formation under non-adhesive conditions which is thought to reflect the enrichment of SFC and their self-renewal capacity, respectively. Treatment was accomplished by inhibitory antibodies for β1 integrin (AIIB2) and EGFR (Cetuximab) as well as X-ray irradiation (2 - 6 Gy single doses). Further, flow cytometry for TIC marker expression and cell cycling as well as Western blotting for DNA repair protein expression and phosphorylation were employed.

We found higher primary and secondary sphere forming capacity of SAS cells relative to other HNSCC cell lines, which was in line with the tumor up-take rates of SAS versus UTSCC15 cells. AIIB2 and Cetuximab administration had minor cytotoxic and no radiosensitizing effects on SFC. Intriguingly, secondary SAS spheres, representing the fraction of surviving SFC upon passaging, showed greatly enhanced radiosensitivity compared to primary spheres. Intriguingly, neither AIIB2 nor Cetuximab significantly altered basal sphere forming capacity and radiosensitivity. While an increased accumulation of G0/G1 phase cells was observable in secondary SAS spheres, DNA double strand break repair indicated no difference on the basis of significantly enhanced ATM and Chk2 dephosphorylation upon irradiation.

In the HNSCC model, sphere-forming conditions select for cells, which are unsusceptible to both anti-β1 integrin and anti-EGFR inhibitory antibodies. With regard to primary and secondary sphere formation, our data suggest that both of these SFC fractions express distinct survival strategies independent from β1 integrin and EGFR and that future work is warranted to better understand SFC survival and enrichment before and after treatment to untangle the underlying mechanisms for identifying novel, druggable cancer targets in SFC.

Keywords: EGFR; Sphere formation; beta1 integrin; head and neck squamous cell carcinoma; radiosensitivity

Publ.-Id: 23821

Comparative analysis of transcriptomics based hypoxia signatures in head- and neck squamous cell carcinoma.

Tawk, B.; Schwager, C.; Deffaa, O.; Dyckhoff, G.; Warta, R.; Linge, A.; Krause, M.; Weichert, W.; Baumann, M.; Herold-Mende, C.; Debus, J.; Abdollahi, A.


Hypoxia renders tumors resistant to radiotherapy. However, the paucity of sensitive and reliable methods for detection of tumor hypoxia limits the translation of novel therapy strategies targeting this well-known resistance factor. We sought to investigate the ability of three previously discovered transcriptomics based hypoxia signatures to identify hypoxic tumors and consequently discriminate between patients with poor- vs. good prognosis.

Three different hypoxia gene signatures developed by Toustrup et al., Eustace et al. and Lendahl et al. were evaluated in an independent cohort consisting of 302 patients with head and neck squamous cell carcinoma (HNSCC). Clinical data as well as genome-wide RNA-sequencing based gene expression data were retrieved from The Cancer Genome Atlas (TCGA). Clustering and statistical analysis were performed using Statistical Utilities for Microarray and Omics data (SUMO) software package.

The 15 gene hypoxia signature developed by Toustrup et al. as well as the 30 gene signature by Lendahl et al. successfully discriminated between HNSCC patients with poor vs. good prognosis. The 26 gene signature developed by Eustace et al. was prognostic in HNSCC patients treated with radiotherapy. The best prognostic value was achieved when a consensus cohort of patients was assigned, i.e., low- or high- degree of tumor hypoxia was found, by all three signatures. Interestingly, the number of signature genes could be successfully reduced to the only common gene across all three signatures, i.e., P4HA1, encoding prolyl-4-hydroxylase, alpha polypeptide I.

This is the first independent proof for the feasibility of hypoxia gene expression signatures as a prognostic tool in HNSCC patients.

Keywords: Gene signatures; Head and neck squamous cell carcinoma; Hypoxia; Transcriptomics

Publ.-Id: 23820

Prognostic value of blood-biomarkers related to hypoxia, inflammation, immune response and tumour load in non-small cell lung cancer - A survival model with external validation.

Carvalho, S.; Troost, E. G. C.; Bons, J.; Menheere, P.; Lambin, P.; Oberije, C.


Improve the prognostic prediction of clinical variables for non-small cell lung cancer (NSCLC), by selecting from blood-biomarkers, non-invasively describing hypoxia, inflammation and tumour load.

Model development and validation included 182 and 181 inoperable stage I-IIIB NSCLC patients treated radically with radiotherapy (55.2%) or chemo-radiotherapy (44.8%). Least absolute shrinkage and selection operator (LASSO), selected from blood-biomarkers related to hypoxia [osteopontin (OPN) and carbonic anhydrase IX (CA-IX)], inflammation [interleukin-6 (IL-6), IL-8, and C-reactive protein (CRP)], and tumour load [carcinoembryonic antigen (CEA), and cytokeratin fragment 21-1 (Cyfra 21-1)]. Sequent model extension selected from alpha-2-macroglobulin (α2M), serum interleukin-2 receptor (sIL2r), toll-like receptor 4 (TLR4), and vascular endothelial growth factor (VEGF). Discrimination was reported by concordance-index.

OPN and Cyfra 21-1 (hazard ratios of 3.3 and 1.7) significantly improved a clinical model comprising gender, World Health Organization performance-status, forced expiratory volume in 1s, number of positive lymph node stations, and gross tumour volume, from a concordance-index of 0.66 to 0.70 (validation=0.62 and 0.66). Extension of the validated model yielded a concordance-index of 0.67, including α2M, sIL2r and VEGF (hazard ratios of 4.6, 3.1, and 1.4).

Improvement of a clinical model including hypoxia and tumour load blood-biomarkers was validated. New immunological markers were associated with overall survival. Data and models can be found at ( and

Keywords: Blood-biomarkers; NSCLC; Prognostic model

Publ.-Id: 23819

Improved Killing of AML Blasts By Dual-Targeting of CD123 and CD33 Via Unitarg a Novel Antibody-Based Modular T Cell Retargeting System

Arndt, C.; Feldmann, A.; Koristka, S.; Cartellieri, M.; von Bonin, M.; Ehninger, A.; Bornhäuser, M.; Ehninger, G.; Bachmann, M. P.

Acute myeloid leukemia (AML) is a hematologic malignancy of the myeloid line with high prevalence in older patients. As complete eradication of metastatic cancer cells is often not achieved by standard therapies, alternative treatment modalities are urgently needed.
In recent years, bispecific antibodies (bsAbs) and chimeric antigen receptors (CARs) emerged as promising candidates for an antigen-specific cancer immunotherapy. Both bsAbs and CARs are able to redirect T cells for efficient tumor cell lysis. Nevertheless, the development of a novel TAA specific bsAb or a CAR is a long lasting process. Therefore, we recently introduced a novel antibody-based modular platform (UniTARG) that can be rapidly and easily adapted for redirection of T cells to any TAA in both a bsAb or CAR related manner. The modular UniTARG system distributes the effector arm (the anti-CD3 domain or CAR) and the anti-TAA binding domain to two separate molecules: (I) an exchangeable target module (TM) comprising an anti-TAA binding moiety and a short peptide epitope (E5B9), and (II) a universal effector unit. The effector systems represent either a bsAb with specificity for CD3 and a peptide epitope (E5B9) termed UniMAB or a CAR directed to the E5B9 epitope (UniCAR). Thus, TMs can form a complex with the respective effector system that facilitates the cross-linkage of tumor and T cells similar to conventional bsAbs or CARs. For redirection of T cells to any kind of TAA only the binding moiety of the TM has to be adapted what saves costs and time. To increase tumor specificity and to reduce the risk of tumor escape variants, the modular UniTARG system further offers the possibility to apply simultaneously different monospecific or even bispecific TMs recognizing two TAAs.

For proof of concept of a dual targeting using the UniTARG system we selected as TAA on AML blasts the molecules CD33 and CD123. They represent promising target antigens as they are overexpressed on both rapidly proliferating terminal AML blasts and leukemic stem cells which might be responsible for disease relapse after initial chemotherapy. Thus, we generated an anti-CD123 TM and anti-CD33 TM that can be applied within the modular system for single-targeting or that can be combined for dual-targeting of AML blasts. By fusion of the anti-CD123 and anti-CD33 domains via the E5B9 epitope a bispecific TM was further constructed. As revealed by cytotoxicity assays with CD33+CD123+ AML cell lines, the novel mono- and bispecific TMs can be easily applied to the modular systems to trigger highly potent tumor cell lysis at low E:T ratios and picomolar Ab concentrations. By using the dual-targeting approach we can show that lysis of CD123+CD33+ AML blasts can be considerably improved in comparison to the mono-specific strategy.

Overall, due to the ease and cost-effectiveness of development the UniTARG platform technology represents a promising tool in the field of both bsAbs and CARs with the advantage of simultaneous or consecutive dual or even multispecific targeting. This approach might additionally improve anti-tumor activity by increasing tumor specificity and diminishing off-target effects.

  • BLOOD 126(2015), 2565


Publ.-Id: 23818

„Qualifizierung von CFD-Programmen für Fragestellungen der Reaktorsicherheit“

Höhne, T.

The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.
The nuclear industry now also recognizes that CFD codes have reached the desired level of maturity (at least for single-phase applications) for them to be used as part of the Nuclear Power Plant (NPP) design process, and it is the objective the research and development teams to assess the current capabilities of such codes in this regard, and contribute to the technology advance in respect to their verification and validation. CFD is already well-established in addressing certain safety issues in NPPs, as reported and discussed at various international workshops. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. In parallel, it remains an overriding necessity to benchmark the performance of the CFD codes, and for this experimental databases need to be established, first for separate-effect tests but especially for full-size integral tests.
In order to validate the CFD Code ANSYS CFX for reactor safety relevant flow phenomena it is essential to use the UPTF experiments, since they are full scale tests. All other separate effect test rigs and test facilities like ROCOM (Höhne, 2000) are scaled. Scaling parameters of flow conditions are one of the still open topics for the use of CFD codes in nuclear reactor safety. Three UPTF tests were selected and post-test calculation were performed. The major focus was analyzing the qualitative flow behavior.


  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2016
    44 Seiten
    ISSN: 2191-8708, eISSN: 2191-8716

Publ.-Id: 23817

Bioassociation of uranium on halophilic archaea analyzed with microscopic and spectroscopic methods

Bader, M.; Müller, K.; Foerstendorf, H.; Schmidt, M.; Musat, N.; Stumpf, T.; Cherkouk, A.

Salt rock is one potential host rock formation for the final disposal of radioactive waste in Germany. Next to geochemical and physical parameters in salt rock indigenous microorganisms have to be taken into account for the safety performance of the deep geological repository. The halophilic archaeon Halobacterium noricense DSM-15987 is indigenous in salt rock and was originally isolated from a salt mine in Austria [1]. This extreme halophilic archaeon was used to study its interactions with uranium. ICP-MS analyses of the supernatant were performed to document the bioassociation kinetic of uranium to cells of Hbt. noricense, which showed a so far unknown behavior. More detailed information about the formed complexes were gained by using different spectroscopic and microscopic methods. All experiments with Hbt. noricense have to be performed at 3 M NaCl which leads to a limited selection of methods or makes their application complicated. Hence, different approaches to generate samples for electron microscopy have been performed and will be the focus of the talk. For example preparation steps like fixation as well as washing steps to get rid of the salt have been varied to obtain SEM and TEM samples which are unaffected by the preparation steps. The used electron microscopic methods have been a useful tool for various reasons. First, by using SEM coupled with EDX a localization of uranium was possible. Second, changes in cell agglomeration as well as uranium bioassociation over time were visible supporting the so far unknown multi-stage bioassociation process. In combination with spectroscopic tools like infrared spectroscopy and laser fluorescence spectroscopy the applied microscopic methods were essential for a better understanding of the bioassociation process of uranium to cells of the halophilic archaeon.

  • Lecture (others)
    Open ProVIS Meetings, 16.06.2016, Leipzig, Deutschland

Publ.-Id: 23816

Profiling Performance of hybrid applications with Score-P and Vampir

Juckeland, G.; Dietrich, R.

OpenACC aims at providing a relatively easy and straightforward way to describe parallelism for exploitation on platforms with hardware accelerators. It is by design also an approach for porting legacy HPC applications to this novel architecture. Especially such legacy applications, but also newly developed applications that require more resources than a single node can offer, use MPI for inter-node communication and coarse work distribution, thus, becoming so-called hybrid applications. It is also possible to combine OpenACC with OpenMP on the host side to utilize all resources of a compute node or to even use all three levels of parallelism concurrently. Tuning application performance for one parallelization paradigm is challenging, adding the second or third level of parallelism introduces a whole new layer of potential performance problems from the interaction of all parallelization paradigms. It is, however, possible to extend the previously mentioned profile-guided development to also cover this usage scenario.
Profiling tools from compiler or accelerator vendors are usually limited to the scheme the product address, e.g. only OpenACC or CUDA/OpenCL activity. Almost all vendor tools cannot record MPI activity leaving the programmer in the dark how well hybrid applications perform over all used levels of parallelism. Research based performance tools cover this gap. HPCtoolkit, Tau, and Score-P are the most prominent ones that also offer hardware accelerator support. Out of the three Score-P is the one that covers the most parallelization paradigms, can record the most concurrent activity and, as a result, can provide the most complete performance picture even for very complex applications. Therefore, Score-P will be used as the example performance recording tool for this chapter. The other tools can provide similar results. Vampir will be use for visualizing the performance data since it is by far the most capable trace visualizer and profile generator.

  • Book chapter
    Farber, Rob: OpenACC - Parallel Programming with OpenACC, Amsterdam: Elsevier, 2016, 978-0-12-410397-9, 55-68

Publ.-Id: 23815

Reshaping on demand

Makarov, D.

The emergent field of flexible magneto-electronics is reviewed with respect to its application potential for e-mobility, personal appliances and medicine.

Keywords: shapeable magnetoelectronics

Publ.-Id: 23814

Bunch arrival-time monitoring for laser particle accelerators and Thomson scattering x-ray sources.

Krämer, J.; Kuntzsch, M.; Zarini, O.; Köhler, A.; Lehnert, U.; Michel, P.; Irman, A.; Schramm, U.; Couperus, J. P.

The ELBE center of high power radiation sources at Helmholtz-Zentrum Dresden-Rossendorf combines a superconducting CW linear accelerator with Terawatt- and Petawatt- level laser sources. Key experiments rely on precise timing and synchronization between the different radiation pulses. An online single shot monitoring system has been set up in order to measure the timing between the high-power Ti:Sa laser DRACO and electron bunches generated by the conventional SRF accelerator. This turnkey timing system is suitable for timing control of Thomson scattering x-ray sources and external injection of electron bunches into a laser wakefield accelerator. It uses a broadband RF pickup to acquire a probe of the particle bunch’s electric field and modulates a fraction of the high power laser pulse in a fast electro-optical modulator. The amplitude modulation gives a direct measure for the timing between both beams. Using this setup a resolution of <200 fs RMS has been demonstrated. The contribution will show the prototype, first measurement results and will discuss future modification in order to improve the resolution of the system.

Keywords: ELBE BAM arrival time diagnostic Thomson

  • Poster
    International Beam Instrumentation Conference IBIC, 11.-15.09.2016, Barcelona, Spain
  • Open Access Logo Contribution to proceedings
    International Beam Instrumentation Conference IBIC, 11.-15.09.2016, Barcelona, Spain

Publ.-Id: 23813

Role of solvents in the electronic transport properties of single-molecule junctions

Luka-Guth, K.; Hambsch, S.; Bloch, A.; Ehrenreich, P.; Briechle, B. M.; Kilibarda, F.; Sendler, T.; Sysoiev, D.; Huhn, T.; Erbe, A.; Scheer, E.

We report on an experimental study of the charge transport through tunnel gaps formed by adjustable gold electrodes immersed into different solvents which are commonly used in the field of molecular electronics (ethanol, toluene, mesitylene, 1,2,4-trichlorobenzene, isopropanol, toluene/tetrahydrofuran mixtures) for the study of single-molecule contacts of functional molecules. We present measurements of the conductance as a function of gap width, conductance histograms as well as current-voltage characteristics of narrow gaps and discuss them in terms of the Simmons model, which is the standard model for describing transport via tunnel barriers, and the resonant single-level model, often applied to single-molecule junctions. One of our conclusions is that stable junctions may form from solvents as well and that both conductance-distance traces and current-voltage characteristics have to be studied to distinguish between contacts of solvent molecules and of molecules under study.

Keywords: mechanically controllable break junction; polar solvent; molecular electronics; electrochemical environment; single-molecule junctions

Publ.-Id: 23812

Radiolabelling of nanoparticles for the use in environmental fate studies in waste water treatment and beyond

Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.

Radiolabeling is a strong tool for the research of nanoparticle fate in the environment as it allows sensitive detection at very low concentrations. We introduced radiolabels into commerical TiO2, CeO2 and multi-wall carbon nanotubes using various cyclotron and non-cyclotron techniques. The so-labelled nanoparticles can be used in fate studies of nanoparticle beahavior in waste water treatment and their possible uptake into plants.

Keywords: Radiomarkierung; radiolabelling; Nanopartikel; nanoparticles; Zyklotron; Cyclotron

  • Lecture (Conference)
    CYCLEUR 2016, 23.-24.06.2016, Bern, Schweiz

Publ.-Id: 23811

First experience using a MTCAMicroTCA.4-based LLRF-controller driving the SSPA-based high power RF system at ELBE.

Kuntzsch, M.; Rutkowski, I.; Hierholzer, M.; Grzegrzółka, M.; Rybaniec, R.; Schmidt, C.; Hoffmann, M.; Büttig, H.; Schurig, R.

The ELBE center for high power radiation sources is operating a superconducting RF accelerator in CW mode. Since 2012 solid state amplifiers are used to drive the accelerating structures at ELBE. New experiments which are in preparation need a better temporal resolution and therefore a higher beam stability. Since 2013 a test series has been performed to evaluate a MicroTCA.4-based digital LLRF (low level RF) system foreseen to replace the analogue controllers. The contribution gives an overview of the setup, reports first performance results and discusses challenges and experience gained during commissioning.

Keywords: ELBE SSPA high power RF LLRF

  • Poster
    Continuous Wave and High Average Power RF Workshop, 21.-24.06.2016, Grenoble, France

Publ.-Id: 23810

The molecular switching mechanism at the conserved D(E)RY motif in class-A GPCRs

Sandoval, A.; Eichler, S.; Madathil, S.; Reeves, P. J.; Fahmy, K.; Boeckmann, R. A.

The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the photoreceptor rhodopsin, this is accompanied by proton uptake at Glu134 in the class-conserved E(D)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed here by molecular dynamics (MD) simulations on TM3 model peptides in a DOPC bilayer. We show that protonation of the conserved glutamic acid alters its side chain rotamer preferences and stabilizes the C-terminal helical structure. Both factors contribute to the rise of the side chain pKa (> 6) and to reduced polarity around the TM3 C-terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved FTIR spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu134- and Gln134-containing opsin mutants and demonstrates that the E(D)RY motif is a hydrated microdomain. 25 The function of the E(D)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface.

Keywords: infrared; fluorescence; membrane protein; hydration


Publ.-Id: 23809

Measuring techniques for experimental investigations and monitoring of liquid metal flows

Ratajczak, M.; Wondrak, T.; Klotsche, K.; Zürner, T.; Martin, R.; Stefani, F.; Gundrum, T.; Franke, S.; Räbiger, D.; Eckert, S.

Flow measurements in hot liquid metals using the ultrasound Doppler method (UDV)
Contactless Inductive Flow Tomography

  • Invited lecture (Conferences)
    SCK CEN Heavy Metal Summer School 2016, 13.-17.06.2016, Mol, Belgium

Publ.-Id: 23808

New insights into the petrogenesis of the Jameson Range layered intrusion and associated Fe-Ti-P-V-PGE-Au mineralisation, West Musgrave Province, Western Australia

Karykowski, B. T.; Polito, P. A.; Maier, W. D.; Gutzmer, J.; Krause, J.

The Mesoproterozoic Jameson Range intrusion forms part of the Giles Complex, Musgrave Province, Western Australia. It is predominantly mafic in composition comprising olivine-bearing gabbroic lithologies with variable amounts of magnetite and ilmenite. Lithologies containing more than 50 vol% magnetite and ilmenite are classified as magnetitites. The Jameson Range hosts several of these magnetitites forming laterally extensive layers, which can be traced for at least 19 km as continuous magnetic anomalies. Similar occurrences of magnetitites are known from the upper parts of other layered intrusions, such as the Bushveld Complex. In addition, the intrusion hosts several P-rich zones, one of which is at least 59 m in thickness containing 1.0 wt% P2O5. The P-rich zones are not directly associated with the magnetitites, but they mostly occur slightly above them. The mineral chemistry of the Jameson Range cumulates is relatively evolved with olivine compositions ranging from Fo44 to Fo60 and plagioclase compositions varying between An56 and An59. The Mg# (100 × Mg / (Mg + Fe)) of ortho- and clinopyroxene ranges from 60 to 61 and from 70 to 75, respectively. Magnetite compositions are characterised by low TiO2 concentrations varying from 0.39 to 3.04 wt% representing near end-member magnetite with up to 1.2 wt% Cr and 1.3 wt% V, respectively. The basal magnetite layer reaches up to 68.8 wt% Fe2O3(t) and 24.2 wt% TiO2, and it is also markedly enriched in Cu (up to 0.3 wt% Cu), V (up to 1.05 wt% V2O5) and platinum-group elements (PGE) (up to 2 ppm Pt + Pd). Sulphide minerals comprising bornite, chalcopyrite and minor pentlandite occur finely disseminated in the magnetitite and account for the elevated base metal and PGE concentrations. Modelling indicates that the PGE mineralisation was formed at very high R factors of up to 100,000, which is typical for PGE reefs in layered intrusions. Whole rock geochemical and mineralogical data of the magnetite layers and their host rocks further allow for a refinement of current formation models of layered igneous sequences. Several lines of evidence suggest that the magnetite layers formed in response to primarily density-controlled mineral sorting within crystal slurries, although the grain size also affects the sorting process.

Keywords: Giles Complex; Layered intrusion; Magnetite layers; Musgrave Province; Platinum-group elements

Publ.-Id: 23807

Excitonic mobility edge and ultra-short photoluminescence decay time in n-type GaAsN

Eßer, F.; Winnerl, S.; Patanè, A.; Helm, M.; Schneider, H.

We use time-resolved photoluminescence (PL) spectroscopy to study the recombination dynamics in Si-doped GaAsN semiconductor alloys with a nitrogen content up to 0.2%. The PL decay is predominantly monoexponential and exhibits a strong energy dispersion. We find ultra-short decay times on the high-energy side and long decay times on the low-energy side of the photoluminescence spectrum. This asymmetry can be explained by the existence of an additional non-radiative energy transfer channel and is consistent with previous studies on intrinsic GaAsN epilayers. However, the determined maximum decay times of GaAsN:Si are significantly reduced in comparison to undoped GaAsN. The determined excitonic mobility edge energy constantly decreases with increasing N content, in agreement with the two-level band anticrossing model.

Keywords: dilute nitride; mobility edge; recombination dynamics; time-resolved photoluminescence


Publ.-Id: 23806

Secondary Neutron Fields During Modern Cancer Treatments -- Simulation and Measurement of the Secondary Radiation Field at the University Proton Therapy Dresden (UPTD)

Lutz, B.; Reginatto, M.; Zboril, M.; Swanson, R.; Enghardt, W.; Fiedler, F.

Particle therapy is a strongly growing field in cancer therapy. More than 60 treatment centres are currently operating worldwide and the total number will reach more than 90 by 2017(1). The majority of the centres uses protons to treat patients.

With the increasing importance of particle therapy, the development of application-specific monitoring systems has received a significant boost. On the one side, there are the radio-protection questions like the secondary dose to patients or to radio-sensitive equipment. On the other side, there are the methods that intend to verify the correct application of the treatment dose, during or short after the treatment, like prompt-gamma-imaging or -timing, or PET. For both groups of measurements, a good understanding of the secondary radiation field is crucial.

The greatest challenge in determining the secondary radiation field comes from neutrons. The spectra of the neutrons, generated by protons of therapeutic energies, extend far beyond the specification of most commercially available dosimeters. Additionally, the generated neutron fields are spatially non-uniform and in case of passive field formation strongly dependent on the operational setting. Combined with the very limited spatial and spectral resolution of the available neutron detectors, many details of the field cannot be experimentally resolved. Therefore, a dependable measurement of the neutron field requires a detailed simulation of the neutron generation in the treatment system.

The talk gives an overview of the passive proton field formation used at the University Proton Therapy Dresden. The challenges in modelling and measuring the resulting neutron fields are discussed. The current status of the simulation model is presented. The predicted neutron fields are also compared to first experimental measurements with a neutron REM meter and an extended Bonner sphere spectrometer.

(1) Particle Therapy Co-Operative Group (PTCOG),

Keywords: neutron simulation; neutron experiment; UPTD

  • Lecture (others)
    Lunch seminar University of Michigan, 15.06.2016, Ann Arbor, USA
  • Lecture (others)
    Fachgespräches des Fachbereichs Strahlenschutz des VKTA, 23.11.2016, Dresden, Deutschland
  • Lecture (others)
    Institutsseminar des Instituts für Kern- und Teilchenphysik der TU-Dresden, 29.06.2017, Dresden, Deutschland

Publ.-Id: 23805

P1219 - Funktionalised silicon nanoparticles

Stephan, H.; Bergmann, R.; Ruffani, A.; de Cola, L.

The present invention is related to silicon nanoparticles, a pharmaceutical composition comprising silicon nanoparticles, a method for synthesis of the silicon nanoparticles and their use for in vivo diagnostics, visualization of drug delivery or staining of cells, biological processes or pathways. The silicon nanoparticles are characterised that they comprise a silicon core of a size of 1 to 10 nm and are terminated with allylamine or poly(allylamine) comprising up to 10 allylamine groups.

  • Patent
    WO2013087734 - Offenlegung 20.06.2013, Nachanmeldungen: CN, EP, US

Publ.-Id: 23804

Systematic XAS study on the reduction and uptake of Tc by magnetite and mackinawite

Yalcintas, E.; Scheinost, A. C.; Gaona, X.; Altmaier, M.

The mechanisms for the reduction and uptake of Tc by magnetite (Fe3O4) and mackinawite (FeS) are investigated using XAS techniques (XANES, EXAFS), in combination with thermodynamic calculations of the Tc/Fe systems and accurate characterization of the solution properties (pHm, pe, [Tc]). Batch sorption experiments were performed in the presence of freshly prepared magnetite and mackinawite in 0.1 M NaCl solutions with varying [Tc(VII)]0 (2·10–5 – 2·10–4 M) and loading of Tc (400–900 ppm ). XANES confirms the complete reduction of Tc(VII) to Tc(IV) in all investigated systems, as predicted by experimental (pHm + pe) measurements and thermodynamic calculations. Two Tc pure endmember species are identified by EXAFS in the magnetite system, corresponding to fully incorporated Tc in the magnetite structure and (likely) to a Tc-Tc dimeric structure with triple-bonding to the magnetite {111} faces. The latter endmember is favoured at higher [Tc], whereas incorporation prevails at low [Tc] and less alkaline pH conditions. The key role of pH in the uptake mechanism is interpreted in terms of magnetite solubility, with higher [Fe] and greater recrystallization rates occurring with decreasing pH values. A TcS2-like phase prevails in all investigated mackinawite systems, although the contribution of up to  20% of TcO2xH2O(s) (likely as surface precipitate) is observed for the highest investigated loadings (900 ppm). These results provide key inputs for an accurate mechanistic interpretation of the Tc uptake by magnetite and mackinawite, so far controversially discussed in the literature, and represent a very relevant contribution in the context of nuclear waste disposal.

Keywords: Tc; nuclear waste; XAS; XAFS; XANES; magnetite; mackinawite

Publ.-Id: 23803

Phosphorene under electron beam: from monolayer to one-dimensional chains

Vierimaa, V. V.; Krasheninnikov, A. V.; Komsa, H.-P.

Phosphorene, a single sheet of black phosphorus, is an elemental two-dimensional material with unique properties and potential applications in semiconductor technology. While few-layer flakes of the material have been characterized using transmission electron microscopy, very little is known about its response to electron irradiation, which may be particularly important in the context of top-down engineering of phosphorus nanostructures using a focused electron beam. Here, using first-principles simulations, we study the production of defects in a single phosphorene sheet under impacts of energetic electrons. By employing the McKinley–Feshbach formalism and accounting for the thermal motion of atoms, we assess the cross section for atom displacement as a function of electron energy. We further investigate the ener- getics and dynamics of point defects and the stability of ribbons and edges under an electron beam. Finally, we show that P atomic chains should be surprisingly stable, and their atomic structure is not linear giving rise to the absence of a gap in the electronic spectrum.

Keywords: Phosphorene; 2D materials; first-principles simulations; defect; irradiation

Publ.-Id: 23802

Biologische Laugung von Kupfer aus Kupferschiefer

Kostudis, S.; Bachmann, K.; Kutsche, S.; Pollmann, K.; Gutzmer, J.

Die Kupferschiefervorkommen Mitteleuropas stellen eine anspruchsvolle lokale Ressource von Basismetallen wie Kupfer, aber auch strategischen Elementen wie Gallium oder Molybdän dar. Um diese Wertstoffe aus dem Kupferschiefer umweltfreundlich und effizient zu gewinnen, werden biotechnologische Laugungsverfahren untersucht. Die klassische Biolaugung, die säureliebende Mikroorganismen verwendet, stößt beim Kupferschiefer aufgrund hoher Karbonatgehalte von bis zu 18 % (Material aus Polkowice, Polen)an ihre Grenzen, da der optimale mikrobielle pH-Bereich um pH 2 überschritten wird. Daher werden alternative Verfahren getestet; so beispielsweise die Produktion organischer Säuren wie Glutamin- oder Zitronensäure durch Mikroorganismen. Hier wurden mithilfe von Schimmelpilzen bereits gute Kupferausbeuten aus Material des Kupferschiefertyps erzielt. Allerdings konnte in eigenen Arbeiten gezeigt werden, dass bei der Verwendung organischer Säuren die Laugungseffektivität im neutralen pH-Bereich höher ist als im schwach sauren Milieu. Daher stellt der Beitrag Ergebnisse zur Biolaugung von Kupfer aus Kupferschiefer im neutralen pH-Bereich vor. Dabei werden sowohl geochemische als auch mineralogische Daten präsentiert.

  • Poster
    Jahrestagung Aufbereitung und Recycling, 11.-12.11.2015, Freiberg, Deutschland

Publ.-Id: 23801

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