Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31735 Publications
Alfvén wave experiments with liquid Rubidium at the Dresden High Magnetic Field Laboratory
Gundrum, T.; Arnold, F.; Forbriger, J.; Gerbeth, G.; Herrmannsdörfer, T.; Putzke, C.; Stefani, F.;
We report on Alfvén wave experiments with liquid Rubidium at the Dresden High Magnetic Field Laboratory (HLD). With pulsed magnetic fields reaching up 62 T we enter the interesting region where the Alfvén speed crosses the sound speed.
  • Contribution to proceedings
    8th PAMIR International Conference on Fundamental and Applied MHD, 05.-09.09.2011, Borgo, Corsica, France
    Proceedings of the 8th PAMIR International Conference on Fundamental and Applied MHD, 411-415
  • Poster
    8th PAMIR International Conference on Fundamental and Applied MHD, 05.-09.09.2011, Borgo, Corsica, France

Publ.-Id: 15623 - Permalink


On the formation of Taylor-Görtler vortices in RMF-driven spin-up flows
Vogt, T.; Grants, I.; Räbiger, D.; Eckert, S.; Gerbeth, G.;
This paper is concerned with a liquid metal flow driven by a rotating magnetic field inside a stationary cylinder. We consider especially the secondary meridional flow during the time the fluid spins up from rest. The developing flow is investigated experimentally and by direct numerical simulations. The vertical profiles of the axial velocity are measured by means of the ultrasound Doppler velocimetry. Evolving instabilities in form of Taylor-Görtler vortices have been observed just above the instability threshold. The transition to a three-dimensional flow in the side layers results from the advection or a precession and splitting of the Taylor-Görtler vortex rings. The numerical simulations agree very well with the flow measurements.
Keywords: rotating magnetic field, Taylor-Görtler vortex, flow measurements, ultrasound Doppler method, direct numerical simulation

Publ.-Id: 15622 - Permalink


Tayler instability influenced by internal heating
Gellert, M.; Rüdiger, G.; Schultz, M.; Stefani, F.; Seilmayer, M.;
The kink-type instability of a toroidal magnetic field, also known as Tayler instability (TI) is a current-driven instability of a strong enough field due to non-axisymmetric perturbations. In astrophysical context the TI has been discussed as a principal ingredient of a dynamo mechanism (Taylor-Spruit dynamo). It is also a possible source of helicity, in particular of helical structures in galactic jets and outflows. TI is also widely used as a mechanism to enhance angular momentum transport in star evolution models even if there is not yet observational evidence for its existence. Nonetheless an ongoing laboratory experiment in cylindrical geometry indeed shows that TI exists in liquid metal flows influenced by a strong axial current.
  • Lecture (Conference)
    17th International Couette-Taylor Workshop, 25.-27.07.2011, Leeds, United Kingdom

Publ.-Id: 15621 - Permalink


Ultraschall-Doppler-Array-Meßsystem zur flächenhaften Untersuchung von Flüssigmetallströmungen
Büttner, L.; Franke, S.; Räbiger, D.; Eckert, S.; Czarske, J.;
Die Untersuchung des Strömungsverhaltens von flüssigen Metallen besitzt sowohl in der Grundlagenforschung als auch in der industriellen Anwendung eine besondere Bedeutung. Dieses liegt zum einen an den Eigenschaften des Fluids selbst, zum anderen an der interessanten Möglichkeit, daß sich diese Strömungen aufgrund ihrer hohen elektrischen Leitfähigkeit aktiv durch elektromagnetische Kräfte beeinflussen lassen. Für die Kristallzucht wird beispielsweise der Einsatz rotierender oder wandernder Magnetfelder verfolgt, um eine gute Durchmischung und damit eine hohe Homogenität der Schmelze zu erreichen. Die dort auftretenden Strömungsstrukturen können relativ komplex werden, was wiederum eine örtlich hochauflösende, bildgebende Meßtechnik erfordert, um z.B. numerische Simulationen zu validieren. Es wird ein bildgebendes Ultraschall-Meßsystem vorgestellt, daß durch Einsatz segmentierter Wandler und deren weitgehendem Parallelbetrieb sowohl eine hohe Zeit- als auch eine hohe Ortsauflösung ermöglicht. Kernelemente des Systems sind zwei orthogonal angeordnete Ultraschallwandler-Arrays, deren einzelne Wandlerelemente durch eine mikroprozessorgesteuerte Schaltmatrix nach einem speziellen Muster angesteuert und ausgelesen werden.
Keywords: flow measurements, flow mapping, ultrasound Doppler method, sensor array
  • Lecture (Conference)
    GALA 2011, 06.-08.09.2011, Ilmenau, Deutschland
  • Contribution to proceedings
    GALA 2011, 06.-08.09.2011, Ilmenau, Deutschland

Publ.-Id: 15620 - Permalink


Oscillating melt flow driven by a rotating magnetic field in a cylindrical column with oxidized surface
Eckert, S.; Shatrov, V.; Zhang, C.; Gerbeth, G.;
This paper considers the situation where the liquid metal flow with a free surface covered by an oxide layer is driven by a rotating magnetic field. The cylindrical configuration was investigated in an experiment accompanied by numerical simulations. The oxide layer feels the effect of the viscous force arising from the moving liquid beneath and the friction force from the side walls. A complex interaction occurs if both forces are in the same order of magnitude. Our measurements demonstrate that the occurrence of the oxide layer may lead to an unexpected oscillating behaviour of the bulk flow. Our numerical model was shown to be able to reproduce essential features of the phenomenon in a qualitative way.
Keywords: electromagnetic stirring, rotating magnetic field, flow measurements, ultrasound Doppler method
  • Lecture (Conference)
    8th International PAMIR conference on fundamental and applied MHD, 05.-06.09.2011, Borgo, France
  • Contribution to proceedings
    8th International PAMIR conference on fundamental and applied MHD, 05.-09.09.2011, Borgo, France
    Proc. of the 8th International PAMIR conference, 611-615

Publ.-Id: 15619 - Permalink


Liquid metal modeling of continuous steel casting – the LIMMCAST programme at HZDR
Gerbeth, G.; Eckert, S.; Stefani, F.; Timmel, K.; Miao, X.; Wondrak, T.; Lucas, D.;
We present the new experimental facility LIMMCAST for modelling the continuous casting process of steel using the alloy SnBi at temperatures of 200-400°C. In addition, a smaller set-up Mini-LIMMCAST operates with the room-temperature liquid alloy GaInSn. First results will be presented covering the following phenomena: fully contactless electromagnetic tomography of the flow in the mould, mould flow monitoring by an array of ultrasonic sensors, analysis of the flow in the mould under the influence of an electromagnetic brake and the injection of argon bubbles through the stopper rod. Numerical simulations using ANSYS-CFX were performed which basically confirm the measuring results.
Keywords: continuous casting, model experiments, flow measurements, electromagnetic brake, numerical simulation
  • Invited lecture (Conferences)
    8th International PAMIR conference on fundamental and applied MHD, 05.-09.09.2011, Borgo, France
  • Contribution to proceedings
    8th International PAMIR conference on fundamental and applied MHD, 05.-09.09.2011, Borgo, France
    Proc. of the 8th International PAMIR conference, 635-639

Publ.-Id: 15618 - Permalink


A liquid metal experiment on the Tayler instability
Seilmayer, M.; Gerbeth, G.; Gundrum, T.; Stefani, F.; Weier, T.; Gellert, M.; Rüdiger, G.;
We describe an experimental set-up for the investigation of the Tayler instability (TI), we show first results, and we discuss the possible relevance of the TI for large-scale liquid metal batteries as they are presently under consideration as cheap means for the storage of renewable energies.
  • Lecture (Conference)
    17th International Couette-Taylor Workshop, 25.-27.07.2011, Leeds, United Kingdom

Publ.-Id: 15617 - Permalink


Experiments on dynamo action, magnetorotational instability, and Alfvén waves
Stefani, F.;
At the end of 1999, the dynamo experiments in Riga and Karlsruhe initiated a period of strong activity to simulate the origin and the action of cosmic magnetic fields in the liquid metal laboratory. With main focus on our own efforts, we summarize the recent liquid metal experiments on homogeneous dynamo action and related magnetic instabilities. We delineate our plans for a new liquid sodium facility that will comprise a large scale dynamo experiment based on precession, and a Taylor-Couette experiment for the combined investigation of the magnetorotational instability and of the kink-type Tayler instability. We further discuss the capabilities of alkali metal experiments to study Alfvén waves in a parameter region where the Alfvén speed crosses the sound speed.
  • Invited lecture (Conferences)
    478th Heraeus Seminar: Fusion and Astrophysical Plasmas, 18.-20.04.2011, Bad Honnef, Germany

Publ.-Id: 15616 - Permalink


Dynamic effects induced by renormalization in anisotropic pattern forming systems
Keller, A.; Nicoli, M.; Facsko, S.; Cuerno, R.;
The dynamics of patterns in large two-dimensional domains remains a challenge in non-equilibrium phenomena. Often it is addressed through mild extensions of one-dimensional equations. We show that full 2D generalizations of the latter can lead to unexpected dynamical behavior. As an example we consider the anisotropic Kuramoto-Sivashinsy equation, that is a generic model of anisotropic pattern forming systems and has been derived in different instances of thin film dynamics. A rotation of a ripple pattern by 90◦ occurs in the system evolution when nonlinearities are strongly suppressed along one direction. This effect originates in non-linear parameter renormalization at different rates in the two system dimensions, showing a dynamical interplay between scale invariance and wavelength selection. Potential experimental realizations of this phenomenon are identified.
Keywords: anisotropy renormalization Kuramoto-Sivashinsky euqation pattern formation

Publ.-Id: 15615 - Permalink


Tuning the hydrophobicity of mica surfaces by hyperthermal Ar ion irradiation
Keller, A.; Fritzsche, M.; Ogaki, R.; Bald, I.; Facsko, S.; Dong, M. D.; Kingshott, P.; Besenbacher, F.;
The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K+ ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle > 80 degrees is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity.
Keywords: atomic-force-microscopy ray photoelectron-spectroscopy highly-charged ions sputtering yields solid-surfaces film growth energy plasma adsorption argon

Publ.-Id: 15614 - Permalink


Synthesis, characterization and biological evaluation of [188Re(N)(cys∼)(PNP)]+/0 mixed-ligand complexes as prototypes for the development of 188Re(N)-based target-specific radiopharmaceuticals
Thieme, S.; Agostini, S.; Bergmann, R.; Pietzsch, J.; Pietzsch, H.-J.; Carta, D.; Salvarese, N.; Refosco, F.; Bolzati, C.;
We report on an efficient procedure for the preparation of [188Re(N)(PNP)]-based complexes (where PNP is diphosphinoamine) useful in the development of target-specific radiopharmaceuticals. The radiochemical yield of the compounds was optimized considering such reaction parameters as nature of the nitrido nitrogen donor, reaction times and pH level. The chemical identity of the 188Re agents was determined by high-performance liquid chromatography comparison with the corresponding well-characterized cold Re compounds. 188Re(N) mixed compounds have been evaluated with regard to stability toward transchelation with GSH and degradation by serum enzymes. The clearance of selected radiocompounds from normal tissues and their in vivo stability were evaluated in rats by biodistribution and imaging studies. [188Re(N)(cys∼)(PNP)]+/0 mixed-ligand compounds were efficiently prepared in aqueous solution from perrhenate using a multistep procedure based on the preliminary formation of the labile 188ReIII–EDTA species, which easily undergo oxidation/ligand exchange reaction to afford the [188ReV≡N]2+ core in the presence of dithiocarbazate. The final mixed-ligand compounds were obtained, at 100°C, by adding the two bidentate ligands to the buffered [188ReV≡N]2+ solution (pH 3.2–3.6). However, a relatively high amount of cys∼ ligand was required to obtain a quantitative radiochemical yield. The complexes were stable toward reoxidation to perrhenate and ligand exchange reactions. In vivo studies showed rapid distribution and elimination of the complexes from the body. No specific uptakes in sensitive tissues/organs were detected. A positive correlation of the distribution of the complexes estimated with biodistribution studies (%ID) and with micro-SPECT semiquantification imaging analysis (standard uptake values) was observed. These results support the possibility of applying [188Re(N)(PNP)] technology to the preparation of target-specific agents.
Keywords: Rhenium; Technetium; 188Re-nitrido; Diphosphinoamines; Peptide; Therapy

Publ.-Id: 15613 - Permalink


Feasibility and performance of novel software to quantify metabolically active volumes and 3D partial volume corrected SUV and metabolic volumetric products of spinal bone marrow metastases on 18F-FDG-PET/CT.
Torigian, D. A.; Lopez, R. F.; Alapati, S.; Bodapati, G.; Hofheinz, F.; van den Hoff, J.; Saboury, B.; Alavi, A.;
Our aim was to assess feasibility and performance of novel semi-automated image analysis software called ROVER to quantify metabolically active volume (MAV), maximum standardized uptake value-maximum (SUVmax), 3D partial volume corrected mean SUV (cSUVmean), and 3D partial volume corrected mean MVP (cMVPmean) of spinal bone marrow metastases on fluorine-18 fluorodeoxyglucose-positron emission tomography/computerized tomography (18F-FDG-PET/CT). We retrospectively studied 16 subjects with 31 spinal metastases on FDG-PET/CT and MRI. Manual and ROVER determinations of lesional MAV and SUVmax, and repeated ROVER measurements of MAV, SUVmax, cSUVmean and cMVPmean were made. Bland-Altman and correlation analyses were performed to assess reproducibility and agreement. Our results showed that analyses of repeated ROVER measurements revealed MAV mean difference (D)=-0.03±0.53cc (95% CI(-0.22, 0.16)), lower limit of agreement (LLOA)=-1.07cc, and upper limit of agreement (ULOA)=1.01cc; SUVmax D=0.00±0.00 with LOAs=0.00; cSUVmean D=-0.01±0.39 (95% CI(-0.15, 0.13)), LLOA=-0.76, and ULOA=0.75; cMVPmean D=-0.52±4.78cc (95% CI(-2.23, 1.23)), LLOA=-9.89cc, and ULOA=8.86cc. Comparisons between ROVER and manual measurements revealed volume D= -0.39±1.37cc (95% CI (-0.89, 0.11)), LLOA=-3.08cc, and ULOA=2.30cc; SUVmax D=0.00±0.00 with LOAs=0.00. Mean percent increase in lesional SUVmean and MVPmean following partial volume correction using ROVER was 84.25±36.00% and 84.45±35.94% , respectively. In conclusion, it is feasible to estimate MAV, SUVmax, cSUVmean, and cMVPmean of spinal bone marrow metastases from 18F-FDG-PET/CT quickly and easily with good reproducibility via ROVER software. Partial volume correction is imperative, as uncorrected SUVmean and MVPmean are significantly underestimated, even for large lesions. This novel approach has great potential for practical, accurate, and precise combined structural-functional PET quantification of disease before and after therapeutic intervention.
Keywords: Bone marrow metastasis, 18F-FDG-PET/CT, Partial volume correction, Globval disease assessment, Quantitative analysis, Software analysis
  • Open Access LogoHellenic Journal of Nuclear Medicine 14(2011)1, 8-14

Publ.-Id: 15612 - Permalink


Elektrische Aktivierung von Dotanden durch Lasertempern oberhalb der Löslichkeitsgrenze
Bürger, D.;
Die Aktivierung flacher Dotanden stellt einen wichtigen Prozess in der Siliziumtechnologie dar. Typische Dotiermaterialien, wie z.B. Bor, Phosphor, Arsen oder Antimon, besitzen eine sehr hohe Löslichkeit in Silizium. Deswegen können in Silizium hohe Dotierkonzentrationen mit konventionellen Ausheilmethoden in der festen Phase auf der Millisekunden-Zeitskale erreicht werden.
Neuartige, mit Übergangsmetallen dotierte Halbleiter, benötigen für die gewünschte ferromagnetische Kopplung Dotierkonzentrationen weit oberhalb der geringen Löslichkeit magnetischer Dotanden. Ausreichend hohe Dotierkonzentrationen magnetischer Dotanden werden mittels Lasertempern in der flüssigen Phase erreicht. Lasertempern ist ein Prozess, welcher unter thermodynamischen Nichtgleichgewichtsbedingungen auf der ns-Zeitskale stattfindet und eine Diffusion der Dotanden extrem unterdrückt.
In dem Vortrag werden typische Anwendungsgebiete der Lasertemperung vorgestellt und ein Blick auf den aktuellen Stand der Forschung auf dem Gebiet der Lasertemperung zur Herstellung ferromagnetischer Halbleiter geworfen.
Keywords: Lasertemperung, Löslichkeit, Aktivierung
  • Lecture (Conference)
    29. Treffen der Nutzergruppe Heißprozesse und RTP, 12.05.2011, Erlangen, Deutschland

Publ.-Id: 15611 - Permalink


Photoluminescence dynamics in GaAs/AlGaAs quantum wells under pulsed intersubband excitation
Zybell, S.; Schneider, H.; Winnerl, S.; Wagner, M.; Köhler, K.; Helm, M.;
We investigate the time-resolved photoluminescence (PL) dynamics of an undoped GaAs/AlGaAs multiple quantum well under mid-infrared (MIR) irradiation. A time-delayed MIR laser pulse from a free electron laser, tuned to the intersubband transition energy of the quantum well, induces temporal quenching of the PL intensity with subsequent recovery. The experimental data can be accurately described by a simple rate-equation model, which accounts for the cooling of the non-radiative states to radiative states. By performing polarization sensitive measurements, we are able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is about 50 times more efficient.
Keywords: semiconductor quantum well, intersubband excitation, time-resolved photoluminescence, photoluminescence quenching, rate equation model

Publ.-Id: 15610 - Permalink


Hydrogen loss from elastomers subjected to ion irradiation
Jagielski, J.; Grambole, D.; Jozwik, I.; Bielinski, D. M.; Ostaszewska, U.; Pieczynska, D.;
Hydrogen release from various elastomers upon irradiation with H+, He+ and Ar+ ions has been studied using nuclear reaction analysis (NRA) method. A massive loss of hydrogen atoms upon irradiation has been noted, the results point to the saturation of hydrogen content at about 10 at.%. The analysis of the experimental data indicates that the hydrogen release is controlled by inelastic collisions between ions and target electrons.

Publ.-Id: 15608 - Permalink


Visualization of the focus in congenital hyperinsulinism by intraoperative sonography
von Rohden, L.; Mohnike, K.; Mau, H.; Eberhard, T.; Mohnike, W.; Blankenstein, O.; Empting, S.; Koch, M.; Fuechtner, F.; Barthlen, W.;
In surgery for focal congenital hyperinsulinism (CHI), the identification and complete resection of the focus without collateral damage is of utmost importance. In a pilot study we applied intra-abdominal high-frequency sonography during surgery for focal CHI in 2 infants. The focus could be identified, its relation to the pancreatic and common bile duct could be shown, and the typical octopus-like tentacles could be demonstrated. In one case the resection was successful; in the other it was not. These preliminary results suggest that intraoperative sonography could be a valuable tool in the surgical therapy of focal CHI and warrants further evaluation in a clinical study.
Keywords: Intraoperative sonography, Congenital hyperinsulinism, Pancreatic resection

Publ.-Id: 15606 - Permalink


Brouwer’s problem on a heavy particle in a rotating vessel: wave propagation, ion traps, and rotor dynamics
Kirillov, O. N.;
In 1918 Brouwer considered stability of a heavy particle in a rotating vessel. This was the first demonstration of a rotating saddle trap which is a mechanical analogue for quadrupole particle traps of Penning and Paul. We revisit this pioneering work in order to uncover its intriguing connections with classical rotor dynamics and fluid dynamics, stability theory of Hamiltonian and non-conservative systems as well as with the modern works on crystal optics and atomic physics. In particular, we find that the boundary of the stability domain of the undamped Brouwers problem possesses the Swallowtail singularity corresponding to the quadruple zero eigenvalue. In the presence of dissipative and non-conservative positional forces there is a couple of Whitney umbrellas on the boundary of the asymptotic stability domain. The handles of the umbrellas form a set where all eigenvalues of the system are pure imaginary despite the presence of dissipative and non-conservative positional forces.
Keywords: Rotating saddle; Dissipation-induced instabilities; Merkin theorem; Swallowtail; Whitney umbrella; Exceptional point

Publ.-Id: 15605 - Permalink


Array anisotropy in structured thin film arrays: Influence on the magnetodynamics
Wolf, M.; Patschureck, C.; Schafer, R.; Monch, I.; Schultz, L.; McCord, J.;
The dynamic magnetic properties of soft-ferromagnetic thin film element arrays are strongly influenced by long range interelement magnetostatic interaction. In order to estimate the effective array dipolar field a quantitative model is presented, which is based on the superposition of stray fields that arise from the neighborhood of a reference element. Kittel's equation, that describes the magnetodynamics, is generalized for magnetically saturated arrays by additional array dipolar field terms. Measurements of the magnetodynamic response of quasi-saturated arrays with a rectangular base agree with theoretical predictions. Thus, our model allows the estimation of the frequency of the uniform precessional mode in mesoscopic thin film arrays with non-negligible magnetostatic interaction.
Keywords: magnetization dynamics

Publ.-Id: 15604 - Permalink


Exceptional Points in a Microwave Billiard with Time-Reversal Invariance Violation
Dietz, B.; Harney, H. L.; Kirillov, O. N.; Miski-Oglu, M.; Richter, A.; Schaefer, F.;
We report on the experimental study of an exceptional point (EP) in a dissipative microwave billiard with induced time-reversal invariance (T) violation. The associated two-state Hamiltonian is non-Hermitian and nonsymmetric. It is determined experimentally on a narrow grid in a parameter plane around the EP. At the EP the size of T violation is given by the relative phase of the eigenvector components. The eigenvectors are adiabatically transported around the EP, whereupon they gather geometric phases and in addition geometric amplitudes different from unity.
Keywords: Microwave billiard, time-reversal symmetry, non-Hermitian hamiltonian, geometric phase, exceptional point, geometric amplitude, geometric pumping

Publ.-Id: 15603 - Permalink


TRLFS study on the speciation of uranium in seepage water and pore water of heavy metal contaminated soil
Baumann, N.; Arnold, T.; Lonschinski, M.;
In situ leaching of uranium ores with sulfuric acid during active uranium mining activity on the Gessenheap has caused longstanding environmental problems of acid mine drainage and elevated concentrations of uranium. To study there remediation measures the test site Gessenwiese, a recultivated former uranium mining heap near Ronnenburg/East Thuringia/Germany, was installed as a part of a research program of the Friedrich Schiller University Jena to study, amongs other techniques, the phytoremediation capacity of native and selected plants towards uranium. In a first step the uranium speciation in surface seepage and soil pore waters from the Gessenwiese, ranging in pH from 3.2 to 4.0, were studied by Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS). Both types of water samples showed a mono-exponential fluorescene decay, indicating the presence of only one major species. The detected emission bands were found at 477, 491, 513, 537, 562, and 591 nm (478 – 492 – 513 – 538 – 562 – 590). These characteristic peak maxima together with the observed mono-exponential decay revealed indicated that the uranium speciation in the seepage and soil pore waters is dominated by the uranium (VI) sulfate species UO2SO4(aq). Due to the presence of fluorescence quenchers in the natural water samples the measured fluorescence lifetimes of the UO2SO4(aq) species of 1.0 to 2.6 µs were reduced in comparison to pure uranium sulphate solutions, which show a fluorescence lifetime of 4.7µs.
This results convincingly show that in the pH range of 3.2 to 4.0 TRLFS is a suitable and very useful technique to study the uranium speciation in naturally occurring water samples.
Keywords: Time-resolved laser-induced fluorescence spectroscopy • TRLFS • Uranium(VI) • Speciation • Pore water • Seepage water

Publ.-Id: 15602 - Permalink


Traveling-wave Thomson scattering: a source of X-ray photons with high per-shot yield and tunable energy and bandwidth
Debus, A.; Bussmann, M.; Siebold, M.; Jochmann, A.; Irman, A.; Schramm, U.; Cowan, T. E.; Sauerbrey, R.;
Thomson sources, driven by laser-wakefield accelerated (LWFA) electrons or small linacs are compact in size and can provide ultrashort, hard X-ray pulses of high brilliance [1]. However, in head-on (180°) Thomson setups, the finite Rayleigh length at small interaction diameters ultimately prevents further advances in peak brilliance, since it becomes increasingly difficult to avoid the nonlinear Thomson regime.
Effectively, not the laser or electron properties, but the interaction geometry limits the performance of all future Thomson sources that aim for high single-shot photon yields.
In order to circumvent this bottleneck, we present a novel concept, which allows obtaining centimeter to meter long optical undulators, where interaction length and diameter are independent of each other.
With an ultrashort, high-power laser pulse in an oblique angle scattering geometry using tilted pulse fronts, electrons and laser remain overlapped while both beams travel over distances much longer than the Rayleigh length.
Such a Traveling-wave Thomson scattering (TWTS) design [2] is particularly interesting for future LWFA-driven Thomson sources with photon yields per pulse that can be orders of magnitudes beyond current designs. In addition, TWTS offeres unique advantages with respect to the minimum scattered bandwidth, which here is independent of the ultrashort laser pulse duration. Instead, it is controlled by the width of a cylindrically focused laser beam.
The possibility to freely choose a side-scattering angle -- from 0 to over 120° -- enables tuning of the photon energy without having to change the electron energy. For optimized LWFA electron sources operating within a narrow energy range, this opens up access to large parts of the X-ray spectrum and hence many applications.
Towards experimental realization, we show how a Traveling-wave setup has to be implemented. An emphasis is put on the use of varied-line spacing (VLS) gratings for dispersion precompensation of the laser beam at large interaction angles to achieve the required overlap between laser and electrons within the interaction region.

[1] A. D. Debus et al., Linear and non-linear Thomson-scattering x-ray sources driven by conventionally and laser plasma accelerated electrons, Proc. SPIE, Vol. 7359, 735908, 2009
[2] A. D. Debus et al., Traveling-wave Thomson scattering and optical undulators for high-yield EUV and X-ray sources, Applied Physics B: Lasers and Optics 100(1), 61-76, 2010
Keywords: Traveling-wave Thomson scattering, X-ray, VLS gratings
  • Lecture (Conference)
    Optics + Optoelectronics 2011 Harnessing Relativistic Plasma Waves as Novel Radiation Sources from Terahertz to X-rays and Beyond, 18.-21.04.2011, Prag, Tschechische Republik

Publ.-Id: 15601 - Permalink


Coupled neutronic thermo-hydraulic analysis of full PWR core with Monte-Carlo based BGCore system
Kotlyar, D.; Shaposhnik, Y.; Fridman, E.; Shwageraus, E.;
BGCore reactor analysis system was recently developed at Ben-Gurion University for calculating in-core fuel composition and spent fuel emissions following discharge. It couples the Monte Carlo transport code MCNP with an independently developed burnup and decay module SARAF. Most of the existing MCNP based depletion codes (e.g. MOCUP, Monteburns, MCODE) tally directly the one-group fluxes and reaction rates in order to prepare one-group cross sections necessary for the fuel depletion analysis. BGCore, on the other hand, uses a multi-group (MG) approach for generation of one group cross-sections. This coupling approach significantly reduces the code execution time without compromising the accuracy of the results.
Substantial reduction in the BGCore code execution time allows consideration of problems with much higher degree of complexity, such as introduction of thermal hydraulic (TH) feedback into the calculation scheme. Recently, a simplified TH feedback module, THERMO, was developed and integrated into the BGCore system. To demonstrate the capabilities of the upgraded BGCore system, a coupled neutronic TH analysis of a full PWR core was performed. The BGCore results were compared with those of the state of the art 3D deterministic nodal diffusion code DYN3D. Very good agreement in major core operational parameters including k-eff eigenvalue, axial and radial power profiles, and temperature distributions between the BGCore and DYN3D results was observed. This agreement confirms the consistency of the implementation of the TH feedback module.
Although the upgraded BGCore system is capable of performing both, depletion and TH analyses, the calculations were performed for the beginning of cycle state with pre-generated fuel compositions.
Keywords: Monte Carlo, DYN3D, PWR, 3D core analysis, Thermal Hydraulic analysis

Publ.-Id: 15600 - Permalink


High Resolution TEM Study of WS2 Nanotubes
Krause, M.; Mücklich, A.; Zak, A.; Seifert, G.; Gemming, S.;
Closed capped WS2 nanotubes with diameters from 30 to 110 nm are studied by high resolution transmission electron microscopy. The tubes exhibit preferentially a hexagonal stacking order. Atomic resolution images of a 30 nm diameter tube reveal a zigzag chirality. A lattice expansion in c-axis direction of ≤ 11% is found within the outermost triple layers. The tube caps often display regular polygon angles. Structural defects like grain boundaries, non-planar triple layers, dislocations, platelet-like fragments, terraces, and amorphous precipitates are identified.
Keywords: Inorganic Nanotubes, HRTEM, Microstructure, Structural Defects
  • Physica Status Solidi (B) 248(2011)11, 2716-2719

Publ.-Id: 15599 - Permalink


Time-resolved photoluminescence quenching measurements in InAs/GaAs quantum dots using terahertz laser pulses
Bhattacharyya, J.; Zybell, S.; Wagner, M.; Helm, M.; Hopkinson, M.; Wilson, L. R.; Schneider, H.;
Carrier dynamics and relaxation processes in self assembled quantum dots (QDs) are of fundamental interest due to their influences on the efficiency and performances of optoelectronic devices [1]. The intersublevel relaxation mechanisms influence the temporal response of the photoluminescence (PL) [2]. It is therefore interesting to study the carrier relaxation in a series of QD samples where the intersublevel separation varies, resulting in different relaxation times. In this paper we present our work on time-resolved PL quenching measurements on QD ensembles using terahertz pulses, to study the effect of carrier redistribution on PL. Interband quasi-resonant excitation was done by a Ti-Sapphire laser and the PL emission was measured using a spectrometer coupled to a streak camera. Terahertz pulses were obtained from a Free Electron Laser (FEL) synchronized to the Ti:Sapphire laser. The FEL wavelengths were tuned to excite intersublevel transitions in the QDs (ranging from 23 meV to 15 meV) which caused partial depletion of the electronic ground state resulting in quenching of the interband PL. The samples studied consisted of a series of self-assembled InAs/GaAs QDs for which the intersublevel relaxation times varied from few ps to ns, as a result of thermal annealing [3]. Simultaneous time and wavelength resolved measurements enabled us to study the carrier redistribution by the terahertz pulse and their dynamics. PL measurements were done with and without FEL pulses. Figure 1 shows the calculated difference of two such streak camera images measured for a typical QD sample. The blue regions show the PL quenching dip caused by the FEL excitation for two interband transition energies corresponding to the QD ensemble. The data was fitted using exponential functions convoluted with a Gaussian system response. From the fitting parameters the PL quenching depth and recovery times were extracted. The recovery times were found to be significantly shorter than the intersublevel relaxation times suggesting that other mechanisms like interdot transfer and multiphoton excitations were also involved. We performed measurements for different FEL excitation powers, which showed an eventual saturation of the PL quenching. We observed an increase in the PL signal for the lower energy transition after the recovery of the PL, as shown by the orange region in Figure 1. However the carrier redistribution was found to depend on the intersublevel properties of the samples. In this work we will present a comparative analysis for different QD samples, with emphasis on the effect of intersublevel relaxation times on the carrier dynamics.
Keywords: photoluminescence quenching, quantum dots, free electron laser
  • Lecture (Conference)
    International Workshop on Optical Terahertz Science and Technology, 13.-17.03.2011, Santa Barbara, USA
  • Lecture (Conference)
    DPG Frühjahrstagung der Sektion AMOP (SAMOP) und der Sektion Kondensierte Materie (SKM) 2011, 13.-18.03.2011, Dresden, Germany

Publ.-Id: 15598 - Permalink


Diameter dependent TEM and Raman study of WS2 nanotubes
Krause, M.; Mücklich, A.; Viršek, M.; Remškar, M.; Zak, A.; Seifert, G.; Gemming, S.;
Metal dichalcogenide (MX2) nanotubes and particles, commonly classified as inorganic fullerene-like (IF) materials, represent the inorganic counterparts of carbon nanotubes and fullerenes. They are usually constituted of several MS2 triple layers, whose curvature is provided by specific defect sites. WS2 and MoS2 IF's have recently attracted much interest as dry lubricants and grease additives due to friction coefficients lower than those of platelet based standard mineral oil additives.

In this study WS2 nanotubes with diameters in the range of 28 nm to 290 nm are studied by electron microscopy and resonant 1st and 2nd order Raman spectroscopy. The Raman response is compared to that of 2H-WS2 single crystals and microcrystalline 2H-WS2 powder. With decreasing tube diameter a disorder induced line in the A1g range, termed D-A1g line, is increasingly enhanced. For the thinnest tubes it is even stronger than the fundamental A1g crystal mode. The intensity ratio I (D-A1g)/ I (A1g) follows a simple functional relationship. It resembles that of the well known ID/ IG ratio in disordered carbon. The enhancement mechanism of the D-A1g line is discussed in terms of the increasing number of local defects, which is the consequence of the increasing curvature.

[1] M. Krause, M. Viršek, M. Remškar, N. Salacan, N. Fleischer, L. Chen, P. Hatto, A. Kolitsch, W. Möller, "Diameter and Morphology Dependent Raman Signatures of WS2 Nanostructures", ChemPhysChem, 10, 2221-2225 (2009)
  • Poster
    25th International Winterschool on: Electronic Properties of Novel Materials: “Molecular nanostructures”, 26.02.-04.03.2011, Kirchberg, Österreich

Publ.-Id: 15597 - Permalink


Beschleuniger zum Nachweis geringster Isotopenkonzentrationen
Merchel, S.; Akhmadaliev, S.; Rugel, G.;
Eingeladener Vortrag ohne Abstract
Keywords: accelerator mass spectrometry, AMS, radionuclides
  • Invited lecture (Conferences)
    Fachgespräch Strahlungsmesstechnik und Software, 05.-07.10.2011, Gelsenkirchen, Deutschland

Publ.-Id: 15595 - Permalink


Cosmogenic noble gases of the Gebel Kamil iron meteorite
Ott, U.; Merchel, S.; Folco, L.; D’Orazio, M.;
Introduction: The Kamil crater in southern Egypt was first identified during a Google Earth survey. A closer inspection during a geophysical expedition in February 2010 not only revealed details of its structure but also identified several thousand iron meteorite specimens with a total weight of ~1.7 tons [1, 2]. The meteorite is classified as an ungrouped Ni-rich ataxite [3]. He, Ne and Ar measurements have been performed on samples from the only regmaglypted 83 kg individual as well as from a piece of the shrapnel produced during the impact [1, 2].
Experimental:We measured two samples each from the individual and the shrapnel, separated by a distance of ~1 cm in each case. Material from in between is being used for accelerator mass spectrometry of long-lived cosmogenic radionuclides. Because of instabilities in the gain of the electron multiplier, the noble gas abundances were not determined by the (standard) peak height method, but rather by isotope dilution. For that, about 1/3 of the sample gas was “spiked” with a gas mixture (3He/4He/22Ne/36Ar ~ 1.2x10-8/1.1x10-6/1.0x10-10/3.8x10-9 cc, Ne and Ar isotopic compositions atmospheric).
Results: As normal for iron meteorites, noble gases are purely spallogenic. Relevant results are listed in Table 1 (concentrations in 10-8 cc/g units; uncertainties in the last digits in parentheses; I = individual, S = shrapnel).
Sample 3He 4He 21Ne 38Ar
I-C 147 (10) 622 (18) 1.59 (4) 9.47 (29)
I-g 138 (9) 604 (20) 1.58 (4) 8.20 (34)
S-C 44 (5) 214 (16) 0.42 (1) 2.39 (10)
S-f 41 (5) 193 (18) 0.35 (1) 2.31 (11)
Discussion: Using the model calculations of [4], we can derive bounds on the pre-atmospheric size of the object and can define a possible range of cosmic ray exposure ages. Most useful is the 4He/38Ar ratio (cf. Fig. 13 in [4]). Based on the maximum ratio of ~90 (S-C), a minimum radius for the meteoroid is ~85 cm. This implies a preatmospheric mass of >20,000 kg, in excellent agreement with the estimate of [1]. Furthermore, the shrapnel samples must originate from further inside the meteoroid than the individual (35-45 cm vs. 15-25 cm). To reach agreement between 4He/38Ar and 4He/21Ne, a sulfur / phosphorus content in the range 0.4-0.8 wt % contributing to 21Ne production is required ([4, 5; cf. Fig. 11 in [4]). Conflicting cosmic ray exposure ages, however, follow from the relation between 4He/38Ar ratio and 38Ar production rate according to [4]. While for the individual an age on the order of 400 to 500 Ma is indicated, estimates for the shrapnel samples are lower in the 200 to 300 Ma range. The discrepancy may be solved by the radionuclide measurements, which are in progress.
References: [1] Folco L. et al. 2010. Science 329:804. [2] Folco L. et al. 2011. Geology 39:179-182. [3] Weisberg M. K. et al. 2010. Meteoritics & Planetary Science 45:1530-1551. [4] Ammon K. et al. 2009. Meteoritics & Planetary Science 44:485-503; in detail at: http://noblegas.unibe.ch/index.php?content=noblegas/data. [5] Ammon K. et al. 2008. Meteoritics & Planetary Science 43:685-699.
Keywords: cosmogenic nuclides, accelerator mass spectrometry, AMS, exposure age
  • Abstract in refereed journal
    Meteoritics & Planetary Science 46(2011), 5012
  • Poster
    74th Annual Meeting of the Meteoritical Society, 08.-12.08.2011, London, UK

Publ.-Id: 15594 - Permalink


Decisive role of oxygen vacancy in ferroelectric versus ferromagnetic Mn-doped BaTiO3 thin films
Shuai, Y.; Zhou, S.; Bürger, D.; Reuther, H.; Skorupa, I.; John, V.; Helm, M.; Schmidt, H.;
Single-phase perovskite 5 at.% Mn-doped and undoped polycrystalline BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. Ferroelectricity is only observed for the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Compared to undoped BaTiO3, Mn-doped BaTiO3 reveals a low leakage current, increased dielectric loss, and a decreased dielectric constant. Ferromagnetism is seen on Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is attributed to the formation of bound magnetic polarons (BMPs). This BMP formation is enhanced by oxygen vacancies. The present work confirms a theoretical work from C. Ederer and N. Spaldin on ferroelectric perovskites [Nature Mat. 3, 849 (2004)] which shows that the existence of ferroelectricity is incompatible with the existence of a spontaneous magnetization in Mn-doped BaTiO3 thin films.
Keywords: multiferroic, Mn-BaTiO₃

Publ.-Id: 15593 - Permalink


How plants cope with heavy metals
Viehweger, K.;
Heavy metals are naturally occurring in the earth‘s crust but anthropogenic and industrial activities have led to drastic environmental pollutions in distinct areas. Plants are able to colonize such sites due to several mechanisms of heavy metal tolerance. Understanding of these pathways enables different fruitful approaches like phytoremediation and biofortification.
Therefore, this review addresses mechanisms of heavy metal tolerance and toxicity in plants possessing a sophisticated network for maintenance of metal homeostasis. Key elements of this are chelation and sequestration which result either in removal of toxic metal from sensitive sites or conduct essential metal to their specific cellular destination. This implies shared pathways which can result in toxic symptoms especially in an excess of metal. These overlaps go on with signal transduction pathways induced by heavy metals which include common elements of other signal cascades. Nevertheless, there are specific reactions some of them will be discussed with special focus on the cellular level.
Keywords: heavy metals, tolerance, toxicity, signaling, sequestration, chelation

Publ.-Id: 15592 - Permalink


Flow structures arising from melt stirring by means of modulated rotating magnetic fields
Räbiger, D.; Eckert, S.; Gerbeth, G.; Franke, S.; Czarske, J.;
Electromagnetic stirring during solidification has been proved to be a striking method for achieving a purposeful alteration of the microstructure of casting ingots, such as grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic groth (CET). However, the imposition of a rotating (RMF) or a travelling magnetic field (TMF) also causes problems like the occurrence of typical segregation pattern or a deflection of the upper free surface. A permanent radial inward (RMF and downward TMF) or outward (upward TMF) flow along the solidification front is responsible for the transport of solute to the axis or the wall of the ingot resulting in typical freckle segregation pattern filled with alloy of eutectic composition. Recent studies have shown, that modulated AC magnetic fields are appropriate to overcome these problems.
We present an experimental study concerning measurements of the flow inside a liquid metal column exposed to a pulsed rotating magnetic field. A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane. It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution. The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures. The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.
Keywords: Electromagnetic stirring, ultrasound Doppler velocimetry, modulated magnetic field, liquid metal flow
  • Magnetohydrodynamics 48(2012)1, 213-220

Publ.-Id: 15591 - Permalink


SP3 solution versus diffusion solution in nodal codes – which improvement can be expected
Merk, B.; Duerigen, S.;
A detailed analysis of the differences between the diffusion and the SP3 method is given. The analysis is based on one dimensional analytical solutions for the one and two group diffusion and SP3 method. Different cases from a benchmark core configuration are analyzed with the help of the one dimensional analytical solutions. It is shown that only a limited part of the gain achievable due to the use of the SP3 approximation will be seen in nodal calculations.
Keywords: SP3 method, diffusion, transport, analytical solutions
  • Contribution to proceedings
    International Conference on Transport Theory, 11.-15.09.2011, Portland, USA
  • Lecture (Conference)
    International Conference on Transport Theory, 11.-15.09.2011, Portland, USA

Publ.-Id: 15590 - Permalink


Importance of unified control for a holding groups motives fulfillment
Joehnk, P.; Hodulikova, P.; Snircová, J.;
The article focuses on forming of holding groups and unified economic control in the frame of them. The globalization of markets leads to a need for bigger and stronger companies. Therefore, we can talk about dramatic increases in the frequency and volume of corporate groups. The most important reason for these combinations is to acquire advantages, which can have economic and noneconomic character. Another important is the limitation or elimination of competitive influences. [1] A holding group as a form of corporate group is a reality, which can go behind the borders of the European Union nowadays. Although, holding groups have been in advanced industrial countries for more than several decades, this type of structure has a relatively brief history in Slovakia. Also the theoretical background of this issue is, in Slovak literature, relatively poor.
Keywords: holding group, synergism, unified control
  • Lecture (others)
    International Doctoral Seminar, 15.-17.05.2011, Smolenice, Slovak
  • Contribution to proceedings
    International Doctoral Seminar, 15.-17.05.2011, Smolenice, Slovak
    Proceeding, 154-161

Publ.-Id: 15589 - Permalink


Study of the 2H(α,γ)6Li reaction at LUNA
Anders, M.; Bemmerer, D.;
Observations of very metal-poor stars have yielded evidence for the less abundant lithium isotope 6Li in several cases. These findings prompt the question whether there is a non-negligible primordial contribution to the observed 6Li abundances. Network calculations show that the 2H(α,γ)6Li reaction dominates 6Li production in the Big Bang. A recent Coulomb dissociation work on this reaction produced only an upper limit for the astrophysical S-factor. At the 400 kV underground accelerator LUNA in Gran Sasso/Italy, an experiment is underway to gain direct cross section data, but the background is formidable. Preliminary data of the first phase of the LUNA experiment will be shown, and an outlook will be given.
Keywords: LUNA, LNGS, Laboratori Nazionali del Gran Sasso, nucleosynthesis, Big Bang, nuclear astrophysics, lithium, beam induced background
  • Lecture (Conference)
    DPG-Frühjahrstagung Münster 2011, 22.03.2011, Münster, Deutschland

Publ.-Id: 15588 - Permalink


Direct measurement d(α,γ)6Li at LUNA
Anders, M.;
The talk summarizes the first phase of the direct d(alpha,gamma)6Li cross section measurement at energies of astrophysical interest by the LUNA collaboration at Laboratori Nazionali del Gran Sasso. The role of 6Li during primordial nucleosynthesis, the current problems of explaining its abundance in very old stars, the measurement approach, details about the beam induced background and ideas to control it are the main topics.
Keywords: LUNA, LNGS, Laboratori Nazionali del Gran Sasso, nuclear astrophysics, nucleosynthesis, beam induced background
  • Lecture (Conference)
    8th Russbach Workshop on Nuclear Astrophysics 2011, 13.03.2011, Rußbach am Pass Gschütt, Österreich

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Publ.-Id: 15587 - Permalink


Superconducting nanolayers in Ge and Si fabricated by Ga+ ion implantation and rapid thermal annealing
Heera, V.; Fiedler, J.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Schmidt, B.; Skorupa, W.;
Superconducting nanolayers in Ge and Si can be fabricated by high fluence Ga ion implantation and subsequent rapid thermal annealing.
Keywords: superconducting Ge, superconducting Si, Ga ion implantation, rapid thermal annealing
  • Lecture (others)
    29. Treffen der Nutzergruppe Heißprozesse und RTP, 12.05.2011, Erlangen, Deutschland

Publ.-Id: 15586 - Permalink


Eukaryotic life in Biofilms formed in a Uranium Mine
Zirnstein, I.; Arnold, T.; Krawczyk-Bärsch, E.; Jenk, U.; Bernhard, G.; Röske, I.;
The underground uranium mine Königstein (Saxony, Germany), currently in the process of remediation, represents a underground acid mine drainage environment (AMD), i.e. low pH conditions and high concentrations of heavy metals including uranium, in which eye-catching biofilm formations were observed. During active uranium mining from 1967-1990 technical leaching with sulphuric acid was applied underground on-site resulting in a change of the underground mine environment and initiated the formation of AMD and also the growth of AMD-related copious biofilms.
Biofilms grow underground in the mine galleries in a depth of 250 m (50 m above sea level) either as stalactite-like slime communities or as acid streamers in the drainage channels. The eukaryotic diversity of these biofilms was analyzed by microscopic investigations and by molecular methods, i.e. 18S rDNA PCR, cloning and sequencing. The biofilm communities of the Königstein environment showed a low eukaryotic biodiversity and consisted of a variety of groups belonging to nine major taxa: ciliates, flagellates, amoebae, heterolobosea, fungi, apicomplexa, stramenopiles, rotifers and arthropoda and a large number of uncultured eukaryotes, denoted as acidotolerant eukaryotic cluster (AEC). In Königstein the flagellates Bodo saltans, the stramenopiles Diplophrys archeri and the phylum of rotifers, class Bdelloidea were detected for the first time in an AMD environment characterized by high concentrations of uranium. This study shows that not only bacteria and archaea may live in radioactive contaminated environments, but also species of eukaryotes, clearly indicating their potential influence on carbon cycling and metal immobilization within AMD affected environment.
Keywords: eukaryote, uranium, acid mine drainage, biofilm, microbial diversity, acid streamer, 18S rDNA PCR, light microscopy

Publ.-Id: 15585 - Permalink


Cathepsin S inhibitors: WO2010070615
Löser, R.;
This article evaluates a patent application of the company Medivir (SE/UK) describing the synthesis of dipeptide-derived alpha alpha-ketoamides containing a propylene glycine moiety in P1 as selective inhibitors of cathepsin S for the potential treatment of various systemic human diseases such as several autoimmune diseases, MS, rheumatoid arthritis, endometriasis and chronic pain. The claims of the patent are discussed in light of recent results in the field of cathepsin S research.

Publ.-Id: 15584 - Permalink


Application of a new drag coefficient model at CFD-simulations on free surface flows relevant for the nuclear reactor safety analysis
Deendarlianto; Höhne, T.; Apanasevich, P.; Lucas, D.; Vallée, C.; Beyer, M.;
This paper presents different CFD-simulations on flows which are relevant for nuclear reactor safety using a new modelling approach for the interfacial drag at free surfaces. The developed drag coefficient model was implemented together with the Algebraic Interfacial Area Density (AIAD) model (Höhne, 2009) into the three-dimensional (3-D) computational fluid dynamics (CFD) code ANSYS-CFX. The applications considered include the prediction of counter-current flow limitations (CCFL) in a PWR hot leg, the development of hydraulic jump during the air-water co-current flow in a horizontal channel, and pressurized thermal shock (PTS) phenomena in a PWR cold leg and downcomer. For the modelling of these tasks, an Euler–Euler approach was used. This approach allows the use of different models depending on the local morphology. In the frame of an Euler-Euler simulation, the local morphology of the phases has to be considered in the drag model.

To demonstrate the feasibility of the present approach, the computed main parameters of each case were compared with experimental data. It is shown that the CFD calculations agree well with the experimental data. This indicates that the AIAD model combined with new drag force modeling is a promising way to simulate the phenomena in frame of the Euler-Euler approach. Moreover the further validation of the model by including mass transfer effects should be carried out.
Keywords: Computational fluid dynamics (CFD), Algebraic interfacial area density (AIAD) model, Drag coefficient, Pressurized water reactor (PWR), Hot leg, Cold leg, Counter-current flow limitation (CCFL), Hydraulic jump, Slug flow, Stratified flow, Pressurized thermal shocks (PTS), Downcomer.

Publ.-Id: 15583 - Permalink


Scanning near-field infrared microspectroscopy on semiconductor structures
Jacob, R.;
Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source.
In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems.
In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from literature. While the structures of the first system were in the micrometer regime, the capability to probe buried nanostructures is demonstrated at a sample of indium arsenide quantum dots. Those dots are covered by a thick layer of gallium arsenide. For the first time ever, it is shown experimentally that transitions between electron states in single quantum dots can be investigated by near-field microscopy. By monitoring the near-field response of these quantum dots while scanning the wavelength of the incident light beam, it was possible to obtain characteristic near-field signatures of single dots. Near-field contrasts up to 30 % could be measured for resonant excitation of electrons in the conduction band of the indium arsenide dots.
Keywords: Spectroscopy, Near-field microscopy, Infrared, Semiconductor materials, quantum dots
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-009 2011

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Publ.-Id: 15582 - Permalink


Miniaturisierte BeO-OSL-Detektoren für die Dosimetrie in Zellkulturen und Organismen: Anwendung und Herausforderungen
Anders, M.;
Dosimetrie in Organismen oder in Zellkulturen erfordert Detektoren mit einer angepassten Größe, die zugleich chemisch und biologisch völlig inert sind. In Rahmen der an der Technischen Universität Dresden angefertigten Diplomarbeit wurden miniaturisierte Detektoren aus gesintertem Berylliumoxid mit positivem Ergebnis auf ihre Anwendbarkeit in der OSL-Dosimetrie und der Biotechnologie untersucht. Die Dosischarakteristik, die typische Messabweichung und die untere Erkennungsgrenze wurden bestimmt. Die Ergebnisse werden in Zusammenhang zur Theorie der Dosimetrie und der Wechselwirkungen der Strahlungsfelder gebracht. In Zusammenarbeit mit der Karlsruhe Beryllium Handling Facility wurde eine weitere Miniaturisierung der Detektoren erreicht, die aber mit einer erhöhten Erkennungsgrenze und einer zunehmend schwierigen Handhabung verbunden ist.
Keywords: BeO, Berylliumoxid, Dosimetrie, Optisch stimulierte Lumineszenz, OSL
  • Lecture (others)
    Institutsseminar des Instituts für Kern- und Teilchenphysik, Technische Universität Dresden, 22.07.2010, Dresden, Deutschland

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Publ.-Id: 15581 - Permalink


Towards an understanding of the Von-Karman-Sodium dynamo experiment
Giesecke, A.; Gerbeth, G.; Stefani, F.;
Numerical simulations of kinematic dynamo action have been carried out in a setup that resembles the configuration of the Von-Karman-Sodium (VKS) dynamo experiment. The results show that the high permeability domains introduced by soft iron impellers essentially determine the field generation process and are also responsible for the selection of the dominating azimuthal dynamo mode.

The material heterogeneity within the fluid give rise to three distinct effects that may influence the dynamo process. In addition to the local decrease of the magnetic diffusivity eta=(mu_0\mu_r\sigma)(-1) so called paramagnetic pumping occurs which is proportional to the gradient of the permeability and describes the suction of magnetic field into domains with high permeability. Beside the modifications of the induction equation itself, jump conditions of the magnetic field (respectively the electric field) are enforced on the material interfaces between fluid and impellers. These jump conditions and the pumping term are responsible for the distinct behavior of high conducting(i.g. copper) and soft iron impellers.

At reasonable values for the magnetic Reynolds number (i.e around Rm=30) and rather moderate permeability (around values of 60 as suggested from recent measurements) the simulated magnetic field is dominated by an axisymmetric component. However, to obtain a growing axisymmetric eigenmode still an alpha-effect is necessary that parametrizes the induction effects of helical small scale motions. In contrast to preliminary mean field models for the VKS dynamo that have been based solely on an alpha-omega mechanism, the necessary magnitude for the alpha effect remains reasonable small if soft iron impellers are utilized.
Keywords: Dynamo, VKS, Numerical Simulations, Magnetohydrodynamics, Permeability
  • Poster
    8th PAMIR International Conference on Fundamental and Applied MHD, 05.-09.09.2011, Borgo – Corsica, France
  • Open Access LogoContribution to proceedings
    8th PAMIR International Conference on Fundamental and Applied MHD, 05.-09.09.2011, Borgo – Corsica, France
    Towards an understanding of the Von-Karman-Sodium dynamo experiment

Publ.-Id: 15580 - Permalink


The LUNA experiment at the Gran Sasso Laboratory in Italy
Anders, M.;
The LUNA experiment is dedicated to measure low energy cross sections of reactions of astrophysical interest. Motivating these measurements with the question about the origin and the different abundances of isotopes in our universe, the reason to perform them in a deep underground laboratory is also mentioned. Using the example of the 2H(alpha, gamma)6Li reaction, the measurement approach and the apparatus are introduced.
Keywords: LUNA, LNGS, Laboratori Nazionali del Gran Sasso, low background, nuclear astrophysics
  • Lecture (Conference)
    Gran Sasso-South Dakota-Princeton Physics Summer School - 2010, 13.07.2010, Laboratori Nazionali del Gran Sasso, Italia

Publ.-Id: 15579 - Permalink


Resonanzstärken in der 40Ca(alpha,gamma)44Ti-Reaktion
Schmidt, K.; Akhmadaliev, C.; Anders, M.; Bemmerer, D.; Boretzky, K.; Caciolli, A.; Elekes, Z.; Fülöp, Z.; Gyürky, G.; Hannaske, R.; Junghans, A.; Marta, M.; Schwengner, R.; Szücs, T.; Wagner, A.; Zuber, K.;
Das Nuklid 44Ti (Halbwertszeit 59 Jahre) wird in Supernovae erzeugt. Die Gamma-Strahlung aus seinem Zerfall lässt sich in weltraumgestützten Gamma-Teleskopen nachweisen und kann als Werkzeug zum Test von Supernova-Modellen genutzt werden. Hierfür ist eine genaue Kenntnis der Kernreaktionsraten für die Erzeugung und Zerstörung von 44Ti erforderlich. Die 40Ca(alpha,gamma)44Ti-Reaktion dominiert die Erzeugung von 44Ti. Ihre Rate wird von einer Vielzahl von Resonanzen bestimmt. Um präzise Daten zu gewinnen, wurde die Stärke des Resonanztripletts bei 4.5MeV Gamma-Energie am Dresdner 3MV Tandetron sowohl mittels in-beam Gamma-Spektrometrie als auch durch eine Aktivierungsmessung im Felsenkeller-Niederniveaumesslabor gemessen. Eine Untersuchung der bestrahlten Proben mittels Beschleunigermassenspektrometrie ist geplant. – Gefördert von der EU (FP7-SPIRIT 227012) und der DFG (BE 4100/2-1).
Keywords: 44Ti Supernova 40Ca(alpha,gamma)44Ti 3MV Tandetron Felsenkeller
  • Lecture (Conference)
    DPG Frühjahrstagung Münster 2011, 21.-25.03.2011, Münster, Deutschland
  • Lecture (others)
    Institutsseminar (Kolloquium)am Institut für Kern- und Teilchenphysik, TU Dresden, 28.04.2010, Dresden, Deutschland
  • Lecture (Conference)
    2nd workshop on Exotic Radionuclides from Accelerator Waste for Science and Technology (ERAWAST II), 02.09.2011, Paul Scherrer Institute, Switzerland
  • Lecture (Conference)
    496. Wilhelm und Else Heraeus-Seminar - Astrophysics with modern small-scale accelerators, 05.-10.02.2012, Bad Honnef, Deutschland

Publ.-Id: 15578 - Permalink


Aus alt mach neu – wie Bakterien beim Recycling von Handys & Co helfen können
Raff, J.;
Eine der größten Herausforderungen der Gegenwart ist der verantwortungsvolle Umgang mit den Ressourcen unseres Planeten. In diesem Zusammenhang ist die Entwicklung neuartiger Verfahren zur Gewinnung und vor allem Rückgewinnung von seltenen Metallen aus Industrieprodukten als wichtige Rohstoffe zahlreicher Zukunftstechnologien von besonderer Relevanz.
  • Invited lecture (Conferences)
    Tage der Wissenschaften, 06.07.2011, Radebeul, Deutschland

Publ.-Id: 15577 - Permalink


Cu-61 production with increased SA
Thieme, S.;
kein Abstrakt verfügbar
  • Lecture (others)
    Seminarvortrag, Turku PET Centre, 31.03.2011, Turku, Finland

Publ.-Id: 15576 - Permalink


Radiopharmazeutische Werkzeuge zur molekularen Bildgebung und Therapie von Tumoren
Thieme, S.;
kein Abstract verfügbar
  • Lecture (others)
    Wissenschaftstage der Hochschule Lausitz, 26.11.2009, Senftenberg, D

Publ.-Id: 15575 - Permalink


Adenosine is released per se under physiological conditions from the rat striatum in vivo
Pedata, F.; Melani, A.; Corti, F.; Stephan, H.; Müller, C. E.; Vannucchi, M. G.;
In this study, extracellular concentrations of adenosine and ATP from the rat striatum were estimated by the microdialysis technique under physiological conditions and during focal cerebral ischemia induced by middle cerebral artery occlusion (MCAo). Under these conditions, adenosine and ATP concentrations were in the range of 130 nM and 30 nM, respectively. Blocking the ecto-ATPases with the novel inhibitor polyanion [TiW11CoO40]8- (PV4: 100 μM), recently synthesized and characterized by Stephan and Müller, we could demonstrate that the extracellular concentration of ATP increased 12-fold and that adenosine concentration was not modified. This result indicates that, under physiological conditions, adenosine is released per se from cells. In the presence of PV4 and of the adenosine equilibrative transporter inhibitor dipyridamole (100 μM), adenosine extracellular concentration was increased 3-fold. This result excludes the possibility that adenosine is carried out of cells by a carrier mediated efflux. By using immunolabeling and electron microscopy, we showed the presence of the CNT2 on plasma membrane of synaptic terminals and on vesicle membranes. Results suggest that under in vivo physiological conditions adenosine is transported in vesicles and is released in an excitation-secretion manner.
In the first 4 hours after in vivo ischemia induced by MCAo, adenosine increased to ~690 nM and ATP to ~50 nM. In the presence of PV4 the extracellular concentration of ATP increased to ~440 nM and extracellular adenosine decreased to ~270 nM. An upregualtion of ecto-nucleotidases after ischemia might represent an important mechanism in hydrolysis of ATP and formation of extracellular adenosine in the first hours after ischemia.
  • Lecture (Conference)
    International Conference on Purinergic Drugs and Targets 2011, 22.-25.07.2011, Bonn, D
  • Open Access LogoAbstract in refereed journal
    Purinergic Signalling 8(2012)1, 132

Publ.-Id: 15574 - Permalink


Modes of the use of high intensity plasma beams for ceramic surface modification
Barlak, M.; Piekoszewski, J.; Werner, Z.; Sartowska, B.; Pisarek, M.; Walis, L.; Starosta, W.; Kolitsch, A.; Gröetzchel, R.; Pochrybniak, K.; Bochenska, C.;
Wetting properties of ceramic materials may be enhanced by treating them with high-intensity plasma pulses carrying a substantial fraction of metallic ions. Rod Plasma Injectors (RPI), developed originally for fusion studies, may generate such plasma pulses containing the working gas used for discharge initiation and the metal ions eroded from the discharge electrodes. We examined the plasma pulse technology and concluded that it is possible to extend the range of system parameters appropriate for wetting enhancement. We also studied the physical properties of plasma treated carbon and silicon carbide samples in an attempt to disclose the origin of wettability differences between them. We finally conclude that these differences are due to the morphology of the treated surfaces.
Keywords: wettability; high intensity pulsed plasma beams; ceramic

Publ.-Id: 15573 - Permalink


Radiopharmaka: Herstellung, Charakterisierung und Anwendungsmöglichkeiten
Stephan, H.;
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Kolloquium Hochschule Zittau/Görlitz, 20.04.2011, Zittau, D

Publ.-Id: 15572 - Permalink


Nanoclusters in bcc-Fe containing vacancies, copper and nickel: Structure and energetics
Al-Motasem, A. T.; Posselt, M.; Bergner, F.;
The most stable atomic configuration of coherent nanoclusters in bcc-Fe formed by vacancies, Cu and Ni as well as the corresponding energetics are determined by on-lattice simulated annealing and subsequent off-lattice relaxation. Ternary v_l Cu_m Ni_n clusters show a core-shell structure with vacancies in the core coated by a shell of Cu atoms, followed by a shell of Ni atoms. In binary Cu_m Ni_n clusters the Cu core is covered by a shell of Ni atoms. On the contrary, binary v_l Ni_n clusters consist of a pure vacancy cluster surrounded by an agglomeration of Ni atoms. The latter is similar to a pure Ni cluster (Ni_n) and consists of Ni atoms at the second nearest neighbor distance. In all clusters investigated Ni atoms may be nearest neighbors of Cu atoms but never nearest neighbors of vacancies or other Ni atoms. The structure obtained for Cu_m Ni_n clusters is in agreement with previous theoretical results and with indications from measurements while for the other clusters reference data are not available. It is shown that the presence of Ni atoms promotes the nucleation of clusters containing vacancies and Cu. This is in agreement with experimental observations and recent theoretical results Compact and rather accurate analytical formulae for the total binding energy have been derived from the results of the atomistic simulations. These relations can be used in rate theory or object kinetic Monte Carlo simulations of nanocluster evolution.
Keywords: Fe-Cu-Ni alloy, Nanostructures, Defects, Monte Carlo simulation, Molecular dynamics simulations

Publ.-Id: 15570 - Permalink


Influence of the developing magnetic order on the transport properties of epitaxial Zn1-xCoxO films
Ye, S.; Ney, V.; Kammermeier, T.; Ollefs, K.; Zhou, S.; Schmidt, H.; Ney, A.;
A series of high quality Zn1-xCoxO films prepared by reactive magnetron sputtering displays altered magnetic properties ranging from paramagnetic (PM) to ferromagnetic (FM)- like at room temperature. With tuning the properties of the Zn1-xCoxO films from PM- to FMlike, the temperature dependent resistivity of the films changes from a Mott variable-range hopping to an Efros variable-range hopping process. This indicates the emergence of a Coulomb gap, which can be explained by the presence of nanoclusters. Moreover, the anhysteretic M (H)-curves above the blocking temperature for superparamagnetic (SPM) films can be described by a Langevin function, which confirms the existence of FM nanoclusters. The investigation on the magneto-transport of these films shows no spin-dependent transport behaviour associated with the observed FM-like/SPM properties.

Publ.-Id: 15569 - Permalink


The 14N(p,gamma)15O reaction studied with a composite germanium detector
Marta, M.; Formicola, A.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Corvisiero, P.; Costantini, H.; Elekes, Z.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Imbriani, G.; Junker, M.; Lemut, A.; Limata, B.; Mazzocchi, C.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.; Vomiero, A.;
The rate of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning is controlled by the 14N(p,gamma)15O reaction. The reaction proceeds by capture to the ground states and several excited states in O-15. In order to obtain a reliable extrapolation of the excitation curve to astrophysical energy, fits in the R-matrix framework are needed. In an energy range that sensitively tests such fits, new cross section data are reported here for the four major transitions in the 14N(p,gamma)15O reaction. The experiment has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy. Using a composite germanium detector, summing corrections have been considerably reduced with respect to previous studies. The cross sections for capture to the ground state and to the 5181, 6172, and 6792 keV excited states in O-15 have been determined at 359, 380, and 399 keV beam energy. In addition, the branching ratios for the decay of the 278 keV resonance have been remeasured.
Keywords: Nuclear astrophysics, LUNA, CNO cycle, Sun, solar fusion

Publ.-Id: 15568 - Permalink


Coupling of the CFD code ANSYS CFX with the 3D neutron kinetic core model DYN3D for VVER applications
Kliem, S.; Grahn, A.; Rohde, U.; Schütze, J.; Frank, T.;
The CFD code ANSYS CFX has been coupled with the neutron-kinetic core model DYN3D. ANSYS CFX calculates the fluid dynamics and related transport phenomena in the reactor’s coolant and provides the corresponding data to DYN3D. In the fluid flow simulation of the coolant, the core itself is modeled within the porous body approach. DYN3D calculates the neutron kinetics and the fuel behavior including the heat transfer to the coolant. The physical data interface between the codes is the volumetric heat release rate into the coolant. In the prototype that is currently available, the coupling is restricted to single-phase flow problems. In the time domain an explicit coupling of the codes has been implemented so far.
Steady-state and transient verification calculations for a small-size test problem confirm the correctness of the implementation of the prototype coupling. The test problem was a mini-core consisting of seven real-size VVER-1000 fuel assemblies. Comparison was performed with the DYN3D stand-alone code. In the steady state, the effective multiplication factor obtained by the DYN3D/ANSYS CFX codes shows a deviation of 0.2 pcm from the DYN3D stand-alone solution. The transient test case simulated the withdrawal of the control rod from the central fuel assembly at hot zero power in the same mini-core. Power increase during the introduction of positive reactivity and power reduction due to fuel temperature increase are calculated in the same manner by the coupled and the stand-alone codes. The maximum values reached during the power rise differ by about 3 MW at a power level of 240 MW. These differences are caused by the use of different flow solvers.
After this verification a steady-state full power calculation for a full VVER-1000 reactor was carried out in order to show the applicability of the new code system to real problems. A CFX grid consisting of about 1.3 106 nodes was created. The main difference to a pure DYN3D calculation with its 1D thermal hydraulic model is the presence of a lateral coolant flow at a velocity in the order of 1 cm/s from the circumference of the core centre. It is driven by the acceleration of the liquid in the centre due to the stronger heating. This flow increases the exchange of heat in the lateral direction by advection and leads to a ‘smearing’ of the step-like temperature profile that has been found in a pure DYN3D calculation.
  • Contribution to proceedings
    7th International Conference “Safety Assurance of NPP with VVER”, 17.-20.05.2011, Podolsk, Russland
    Proceedings of the 7th International Conference “Safety Assurance of NPP with VVER” paper 007, Podolsk: Gidropress
  • Lecture (Conference)
    7th International Conference “Safety Assurance of NPP with VVER”, 17.-20.05.2011, Podolsk, Russland

Publ.-Id: 15567 - Permalink


Environment Controlled De-wetting Kinetics of Rh-Pd Bilayer Thin Films
Abrasonis, G.; Wintz, S.; Liedke, M. O.; Aksoy, F.; Liu, Z.; Kuepper, K.; Krause, M.; Gemming, S.;
The control of morphology and surface composition of nanoalloys is the key factor in order to tune or to extend the range of their optical, magnetic and chemical properties. Therefore it is one of the major tasks in nanoalloy materials science. The de-wetting dynamics and kinetics dependence of a Rh-Pd bilayer/alloy thin film model system on chemical environment (CO and NO) is investigated in-situ by means of high pressure x-ray photoelectron spectroscopy. Independently of the initial state, the film surface shows an enrichment of Pd upon heating in vacuum. De-wetting caused by heating in NO or CO shows significant differences in the surface chemical composition evolution and, consequently, in the de-wetting onset temperature. Alternating exposure to NO or CO results in the surface enrichment with either Rh or Pd, respectively, and subsequent film rupture. The results are discussed on the basis of the interplay between thermodynamic and kinetic factors. The study demonstrates the effect of the chemical environment on the morphology as well as on the composition of supported nanostructures.
  • Lecture (Conference)
    DPG Spring Meeting 2011, 13.-18.03.2011, Dresden, Germany

Publ.-Id: 15566 - Permalink


P0714 - Verfahren und Anordnung zur Messung des Durchflusses elektrisch leitfähiger Medien
Gerbeth, G.; Priede, J.; Buchenau, D.;
Die Erfindung betrifft ein Verfahren und eine Anordnung zur kontaktlosen Messung des Durchflusses elektrisch leitfähiger Medien durch Strömungskanäle. Durch die Erfindung soll eine Durchflussmessung ohne mechanischen oder elektrischen Kontakt zum fließenden Medium zu ermöglicht werden, ohne die zu messende Strömung zu beeinflussen und die unabhängig von möglichen Temperaturänderungen des fließenden Mediums eine direkte Durchflussmessung erlaubt. Erreicht wird das durch Ausbilden eines am Strömungskanal drehbaren einfach polarisierten Magnetfeldes eines Magneten (4), derart, dass die Strömung im Strömungskanal (1) ein Drehmoment auf das Magnetfeld der Magneten (4) ausübt, das proportional zum Produkt aus der elektrischen Leitfähigkeit des strömenden Mediums und dessen mittleren Geschwindigkeit ist und das den Magneten (4) in Drehung versetzt, derart, dass ein Drehmoment auf das strömende Medium im Strömungskanal (1) ausgeübt wird, welches proportional zur elektrischen Leitfähigkeit des strömenden Mediums und zur Drehzahl des sich drehenden Magneten (4) ist und nachfolgende Messung der Drehzahl des einfach polarisierten Magnetfeldes im weitgehend drehmomentlosen Zustand.
  • Patent
    DE102007046881A1 - 16.04.2009
  • Patent
    DE102007046881B4 - 24.05.2012

Publ.-Id: 15565 - Permalink


Structure-induced coexistence of ferromagnetic and superconducting states of single-phase Bi3Ni seen via magnetization and resistance measurements
Herrmannsdörfer, T.; Skrotzki, R.; Wosnitza, J.; Köhler, D.; Boldt, R.; Ruck, M.;
We demonstrate the coexistence of superconductivity and ferromagnetism in Bi3Ni nanostructures that have been prepared by making use of novel chemical-reaction paths. We have characterized their magnetic and superconducting properties by means of magnetometry and electrical-transport measurements. Other than in bulk geometry, submicrometer-sized particles and quasi-one-dimensional nanoscaled strains of single-phase Bi3Ni undergo ferromagnetic order. Superconductivity in confined Bi3Ni emerges in the ferromagnetically ordered phase and is stable up to remarkably high magnetic fields. Uniquely, ferromagnetic hysteresis at zero resistance is observed in nanostructured Bi3Ni.
  • Physical Review B 83(2011), 140501(R)

Publ.-Id: 15564 - Permalink


Magnetoelectric effects in an organometallic quantum magnet
Zapf, V. S.; Sengupta, P.; Batista, C. D.; Nasreen, F.; Wolff-Fabris, F.; Paduan-Filho, A.;
Metal-organic materials constitute a new field in which to search for ferroelectricity and coupling between electricity and magnetism. We observe a magnetic field-induced change in the electric polarization, ΔP(H), that reaches 50 μC/m2 in single crystals of NiCl2–4SC(NH2)2 (DTN). DTN forms a tetragonal structure that breaks inversion symmetry with the electrically polar thiourea molecules [SC(NH2)] all tilted in the same direction along the c axis. The field H induces canted antiferromagnetism of the Ni S = 1 spins between 2 and 12 T and our measurements show that the electric polarization increases monotonically in this range, saturating above 12 T. By modeling the microscopic origin of this magnetoelectric effect, we find that the leading contribution to ΔP comes from the change in the crystal electric field, with a smaller contribution from magnetic exchange striction. The finite value of ΔP induced by magnetostriction results from the polar nature of the thiourea molecules bonded to the Ni atoms, and it is amplified by the softness of these organic molecules.
  • Physical Review B 83(2011), 140405(R)

Publ.-Id: 15563 - Permalink


Uranantwort von Bakterien und Pilzen
Schindler, F.; Günther, A.; Freihorst, D.; Haferburg, G.; Raff, J.; Kothe, E.;
Um die hohen Bindungskapazitäten und schnelle Mutationsrate von Bakterien, aber auch die bekanntermaßen hohen Aufnahmekapazitäten von Pilzen als Modell zu nutzen, werden die generellen, molekularen Aufnahmesysteme für Uran und die Bindungsformen in der Zelle beispielhaft für Bakterien und Pilze mit ihrer guten Bearbeitbarkeit untersucht. Dazu werden Mikroorganismen verwendet, für die molekulare Werkzeuge und Genomsequenzen vorliegen. Stämme mit Schwermetallresistenz werden genutzt, um die hier besonders stark ausgeprägten Systeme zur Entgiftung von Schwermetallen und damit auch der schweren Radioisotope zu nutzen. Der Nachweis der Aufnahme in die Zelle erfolgt durch Analyse der einzelnen zellulären Fraktionen, die mit spektroskopischen und mikroskopischen Methoden auf die vorherrschenden, molekularen Bindungsformen hin untersucht werden. Dabei werden die Modellorganismen Arthrobacter sp. JG37-Iso2 und Streptomyces acidiscabies E13 als Bakterien sowie der Weißfäulepilz Schizophyllum commune genutzt. Die Genomsequenz von Schizophyllum konnte genutzt werden, um Gene zu annotieren, die mit der Uranaufnahme zusammenhängen könnten. Dies ist nur durch Experimente wirklich möglich, da bisher keine Urantransporter in Eukarya gefunden wurden. Wir haben daher Proteomanalysen und Transkriptomanalysen durchgeführt, um die Expression unter verschiedenen Bedingungen zu testen, in denen der Pilz auf uranhaltigen Medien wächst. In Mikroarrays zeigen sich eine hohe Anzahl unterschiedlich regulierter Gene, deren Funktion experimentell überprüft wird. Ergänzend dazu wurde die Wechselwirkung von Schizophyllum mit Uran auf molekularer und zellulärer Ebene untersucht. Dabei konnte eine dominierende Wechselwirkung von Uran mit organischen Phosphatverbindungen auf und in der Zelle nachgewiesen werden. Bei der Untersuchung der Arthrobacter-Referenzstämme stellte sich heraus, dass eine Zellsorption der angebotenen U(VI) Spezies der dominante Prozess ist. Fluoreszenzspektroskopische Untersuchungen ergaben deutliche Unterschiede zwischen den U(VI) Spezies in den mineralischen Ausgangsmedien (freies U(VI), Uranylhydroxide bzw.Uranylhydroxocarbonat) und der sich über Carboxyl- und organischen Phosphatgruppen bildenden U(VI)- Spezies an der Bakterienzelle. Es konnten von schwermetallhaltigen Arealen der ehemaligen Wismut Region Pilzfruchtkörper gewonnen werden, die extrem hohe Anreicherungsfaktoren für Uran und Cäsium zeigen. Weiterhin konnte gezeigt werden, dass aus Pilzen sowie Gram-positiven und Gram-negativen Bakterien vom Standort lediglich 2 Isolate auf 50 μM Uranylacetat wachsen konnten. Diese beiden Stämme zeigten in der Laserablations-ICP-MS eine deutlich signifikante Urananreicherung im Bereich des Wachstums. Daneben wurden Streptomyces-Stämme auf ihre Resistenz gegenüber Uran getestet. Hier scheint sich ein anderer Mechanismus als bei Arthrobacter herauszustellen.
  • Lecture (Conference)
    10. Internationales Symposium "Konditionierung radioaktiver Betriebs- und Stilllegungsabfälle", 06.-08.04.2011, Dresden, BRD
  • Poster
    10. Internationales Symposium "Konditionierung radioaktiver Betriebs- und Stilllegungsabfälle", 06.-08.04.2011, Dresden, BRD

Publ.-Id: 15562 - Permalink


P0718 - Anordnung zur optischen Tomographie
Hoppe, D.;
Die vorliegende Erfindung beschreibt eine Anordnung zur optischen Tomographie mit mindestens einem optischen Aufnehmer 5 und einem Untersuchungsobjekt 2 unter Verwendung von Spiegeln 1. Damit können sich schnell zeitlich verändernde oder bewegende Untersuchungsobjekte untersucht werden, ohne dass örtliche Veränderungen der optischen Aufnehmer (Kamera) oder der Spiegel notwendig sind.
  • Patent
    DE102007054669A1 - 28.05.2009

Publ.-Id: 15561 - Permalink


P0813 - Prozessmikroskop
Hampel, U.; Barthel, F.; Tschofen, M.;
Die Erfindung betrifft eine Anordnung zur optischen Visualisierung und Vermessung von mikroskopischen Vorgängen in Prozessen bei hoher Temperatur und/oder hohem Druck. Die Kamera- und die Beleuchtungseinheit sind in einem oder in getrennten Wärmeleitzylindern untergebracht um diese Einheiten vor unzulässig hohen Temperaturen, die am Prozessort auftreten, zu schützen ohne gleichzeitig einen starken Wärmeentzug aus dem Prozessmedium zu verursachen.
  • Patent
    DE102008058785 - Offenlegung 27.05.2010, Erteilung 16.02.2016

Publ.-Id: 15560 - Permalink


P0812 - Tetrathiol-Liganden, Metallkomplexe, Konjugate und Kits, deren Verwendung in der nuklearmedizinischen Diagnostik und Endoradionuklidtherapie sowie Verfahren zur Herstellung der Tetrathiol-Liganden und Metallkomplexe
Suhr, M.; Förster, C.; Pietzsch, H.-J.;
Ligand der Formel F1 worin (CH-R1) und (CH-R1') substituierte oder unsubstituierte Methylenbrücken darstellen, die einzelnen R1 und R1', sowie R3 und R3' jeweils unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Arylgruppen, m und n positive ganze Zahlen sind, wobei m die Anzahl der Gruppen (CH-R1') und n die Anzahl der Gruppen (CH-R1) repräsentiert, wobei die Summe aus m und n im Bereich von 4 bis 10 liegt, R2 und R2' unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Carboxylgruppen, substituierten oder unsubstituierten Arylgruppen oder Z, X eine substituierte oder unsubstituierte Methylenbrücke mit der Formel CHR4 oder eine unsubstituierte Aminogruppe (N-H) oder substituierte Aminogruppe (N-Z) ist, wobei Z für -(CH-R5)p-A steht, worin (CH-R5) eine substituierte oder unsubstituierte Methylenbrücke darstellt und p eine ganze Zahl ist, die für die Anzahl der Gruppen (CH-R5) steht, wobei p im Bereich von 2 bis 8 liegt, A eine kopplungsfähige Einheit darstellt, wobei R4 und die einzelnen R5 jeweils unabhängig voneinander ausgewählt sind aus Wasserstoff, substituierten oder unsubstituierten Alkylgruppen, substituierten oder unsubstituierten Arylgruppen.
  • Patent
    DE102009029033A1 - 24.06.2010

Publ.-Id: 15559 - Permalink


P0814 - Anordnung und Verfahren zur Erzeugung einzelner relativistischer Elektronen
Naumann, L.; Lehnert, U.; Kotte, R.; Wagner, A.;
The arrangement has an electron accelerator with accelerator cavities, and strewing targets (3) positioned between the accelerator cavities. The strewing targets are electron-optically thin. Multiple strewing targets are used between the cavities. An independent claim is also included for a method for producing individual relativistic electrons.
  • Patent
    DE102008054676A1 - 01.07.2010
  • Patent
    DE 102008054676 B4 - 30.06.2011

Publ.-Id: 15558 - Permalink


P0816 - Verfahren und Anordnung zur kontaktlosen Bestimmung von Geschwindigkeitsverteilungen eines flüssigen Metalls in einer Stranggießkokille
Stefani, F.; Wondrak, T.; Gundrum, T.; Timmel, K.; Gerbeth, G.;
Die vorliegende Erfindung dient der kontaktlosen Bestimmung von Geschwindigkeitsverteilungen eines flüssigen Metalls in einer Stranggießkokille. Ein bevorzugtes Einsatzgebiet der Einrichtung ist die Geschwindigkeitsbestimmung im Strangguss von Stahl und Aluminium, insbesondere beim Brammengießen. Die Bestimmung erfolgt dadurch, dass ein primäres Magnetfeld das Flüssigmetallvolumen in der Kokille durchdringt, dass die durch die Flüssigkeitsbewegung induzierten Magnetfelder gemessen und aus diesen die Geschwindigkeit durch Lösung eines inversen Problems berechnet wird. Die Berechnung benutzt das Prinzip der kleinsten Quadrate, wobei als zu minimierendes Funktional die mittlere quadratischen Abweichungen der durch die angenommene Geschwindigkeit induzierten Magnetfelder von den gemessenen Werten benutzt wird. Dabei wird die Tichonov-Regularisierung eingesetzt, wobei als Regularisierungsfunktional die mittlere quadratische Krümmung des Geschwindigkeitsfeldes oder die mittlere quadratische Geschwindigkeit verwendet wird. Des Weiteren wird die Divergenzfreiheit des Geschwindigkeitsfeldes durch Verwendung eines zusätzlichen Funktionals gewährleistet. Die Anordnung besteht aus einem ein Magnetfeld erzeugenden Spulensystem, einer Mess- und Steuereinheit für die Ströme in diesem Spulensystem, mit welcher die Richtung des Magnetfeldes in der Flüssigkeit geändert werden kann, einer Mehrzahl von Magnetfeldsensoren im Außengebiet der Flüssigkeit zur Bestimmung der durch die Flüssigkeitsbewegung induzierten Magnetfelder sowie aus Mitteln zur Signalweiterleitung, -verarbeitung und -darstellung.
  • Patent
    DE102008055034 - Offenlegung: 01.07.2010, Nachanmeldungen: WO, EP

Publ.-Id: 15557 - Permalink


P0815 - Anordnung und Verfahren zur Mehrphasendurchflussmessung
Hampel, U.; Da Silva, M. J.;
Gegenstand der Anmeldung ist eine Anordnung und ein Verfahren zur Messung der Partikelvolumenströme von Mehrphasengemischen in einem Strömungskanal, die aus einem innerhalb eines Strömungskanals eingebrachten Kanalkörper besteht, wobei über dem Kanalkörper ein Differenzdrucksensor oder vor und hinter dem Kanalkörper jeweils ein Drucksensor angeordnet ist, aus dem der Differenzdruck der beiden Drucksensoren ermittelt wird; der Kanalkörper aus einer Vielzahl von in Strömungsrichtung verlaufenden durchgängigen Kanälen mit geringem hydraulischem Durchmesser besteht; an jedem der Kanäle mindestens zwei Phasensensoren zur Identifikation der stofflichen Phase in Strömungsrichtung hintereinander angeordnet sind; alle Phasensensoren signaltechnisch mit einer zugeordneten Messelektronik verbunden sind, die gleichzeitig die Phasenindikatorsignale der Phasensensoren sowie den Messwert des Differenzdrucksensors mit hoher Abtastrate erfasst; ein in der Messelektronik integrierter oder dieser nachgeschalteter Mikrocontroller oder Rechner die Partialvolumenströme in den Kanälen sowie die mittleren Partialvolumenströme des gesamten Querschnitts des Strömungskanals aus den erfassten Messwerten berechnet.
  • Patent
    DE102008055032 - Offenlegung: 01.07.2010, Erteilung: 24.12.2014, Nachanmeldungen: WO

Publ.-Id: 15556 - Permalink


Collision Dynamics
Knoll, J.; Randrup, J.; Fuchs, C.; Aichelin, J.; Bleicher, M.; Bratkovskaya, E.; Cassing, W.; Danielewicz, P.; Ivanov, Y.; Kämpfer, B.; Larionov, A.; Toneev, V.;
"Collision Dynamics" is part of the CBM Physics Book.

Publ.-Id: 15555 - Permalink


In-Medium Excitations
Rapp, R.; Kämpfer, B.; Andronic, A.; Blaschke, D.; Fuchs, C.; Harada, M.; Hilger, T.; Kitazawa, M.; Kunihiro, T.; Petreczky, P.; Riek, F.; Sasaki, C.; Thomas, R.; Tolos, L.; Zhuang, P.; van Hees, H.; Vogt, R.; Zschocke, S.;
"In-Medium Excitations" is part of the CBM Physics Book.

Publ.-Id: 15554 - Permalink


Bulk Properties of Strongly Interacting Matter
Leupold, S.; Redlich, K.; Stephanov, M.; Andronic, A.; Blaschke, D.; Bluhm, M.; Dumitru, A.; Fodor, Z.; Friman, B.; Fuchs, C.; Kämpfer, B.; Karsch, F.; Katz, S. D.; Klähn, T.; Randrup, J.; Ratti, C.; Rebhan, A.; Rischke, D.; Rummukainen, K.; Sasaki, C.; Schaefer, B.-J.; Shuryak, E.; Thaler, M.; Wambach, J.; Weber, F.; Weise, W.; Typel, S.;
"Bulk Properties of Strongly Interacting Matter" is part of the CBM Physics Book.

Publ.-Id: 15553 - Permalink


P0904 - E. coli-Sekretionssystem auf der Basis von S-Layer-Proteinen
Pollmann, K.; Lederer, F.; Raff, J.;
Die vorliegende Erfindung betrifft ein E. coli-Sekretionssystem auf Basis einer S-Layer-Gensequenz, deren Expressionsprodukt die Sekretion von rekombinanten Proteinen aus E. coli-Zellen vermittelt. Das Sekretionssystem eignet sich für die Anwendung in der Molekularbiologie und in der Biotechnologie. Das erfindungsgemäße Sekretionssystem basiert auf der Verwendung eines S-Layer-Proteins, einer Teilsequenz davon oder einer dazu homologen Sequenz als Sekretionssignal. Die Erfindung umfasst weiter ein Fusionsprotein, welches ein zu exprimierendes Zielprotein und das erfinungsgemäße Sekretionssignal enthält, eine Nukleinsäuresequenz, welche für ein erfindungsgemäßes Fusionsprotein kodiert, einen Expressionsvektor oder einen Klonierungsvektor für die Herstellung eines erfindungsgemäßen Fusionsproteins, eine Wirtszelle für die Expression eines erfindungsgemäßen Fusionsproteins und einen Kit sows erfindungsgemäßen Fusionsproteins aus einer Wirtszelle.
  • Patent
    DE102009032646A1: Offenlegung-05.01.2011
  • Patent
    EP2270029A1: Offenlegung - 05.01.2011; Erteilung-19.11.2014 (Validierung in AT, CH, DE, FR, GB)

Publ.-Id: 15552 - Permalink


P0905 - Hochfrequenz-Fotoelektronenquelle mit supraleitendem Hohlraumresonatorsystem stabilisierter Eigenfrequenz
Teichert, J.; Murcek, T.; Möller, K.; Arnold, A.;
Die Erfindung betrifft das Hohlraumresonatorsystem (HRS) supraleitender Hochfrequenz-Fotoelektronenquellen (SHFE), die in Elektronenbeschleunigern eingesetzt werden können. Die beschleunigten Elektronen können direkt genutzt oder mittels nachgelagerter Anordnungen zur Erzeugung von Sekundärstrahlen, wie Gamma-, Röntgen- oder Laserstrahlung dienen. Der Erfindung liegt die Aufgabe zugrunde, die bei den bisherigen supraleitenden Hochfrequenz-Fotoelektronenquellen unbefriedigende Frequenzstabilität wesentlich zu erhöhen. Die Aufgabe wird durch eine spezielle Konstruktion zur mechanischen Stabilisierung des Hohlraumresonanzsystems gelöst, wobei die für das supraleitende System erforderliche hohe Effektivität für die Kühlung weiterhin gewährleistet wird und eine einfache Montage des Systems unterstützt wird.
  • Patent
    DE102009028182B3 - 24.02.2011

Publ.-Id: 15551 - Permalink


P0903 - Mikroröhren, umfassend Bestandteile der äußeren Membran von E. coli Zellen und rekombinant exprimierte S-Layer-Proteine, Verfahren zu ihrer Herstellung und Verwendung
Pollmann, K.; Raff, J.; Lederer, F.;
Die vorliegende Erfindung betrifft röhrenartige biologische Strukturen, die sich aus der äußeren Membran von E. coli zusammensetzen und durch heterolog exprimierte rekombinante S-Layer-Proteine stabilisiert werden. Die neuartigen Mikroröhren eignen sich für die Anwendung in der Biotechnologie, Pharmazie, in der chemischen Katalyse und in der Nanotechnologie. Die erfindungsgemäßen Mikroröhren umfassen Bestandteile der äußeren Membran von E. coli Zellen und rekombinant exprimierte S-Layer-Proteine. Die Erfindung umfasst weiter ein Verfahren zur Herstellung der erfindungsgemäßen Mikroröhren, bei dem S-Layer-Proteine in E. coli-Zellen exprimiert werden und anschließend die E. coli-Zellen ggf. aus den gebildeten Mikroröhren entfernt werden, die E. coli-Zellen, welche die rekombinanten S-Layer-Proteine exprimieren, und die Verwendung der erfindungsgemäßen Mikroröhren zur Bindung von Metall aus einer wässrigen Lösung, zur Herstellung funktionalisierter Schichten, als Carrier für Enzyme oder für pharmazeutische Wirkstoffe oder als Katalysator.
  • Patent
    DE102009032645 - Erteilung 17.03.2011, Nachanmeldungen: EP (validiert in AT, DE, GB)

Publ.-Id: 15550 - Permalink


Sump simulations
Cartland Glover, G.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which
undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations in the containment sump. Two dispersed phases were conditions to determine the influence of entrained air from a jet on the transport of fibre agglomerates through the sump. The strainer model of A. Grahn was implemented to observe the impact that the accumulation of the fibres have on the pressure drop across the strainers. The geometry considered is similar to the containment sump configurations found in Nuclear Power Plants.
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Contribution to proceedings
    Fachkolloquium "Partikelströmung" CD Rom, 17.-18.03.2011, Zittau and Dresden, Dresden
    Fachkolloquium "Partikelströmung" CD Rom

Publ.-Id: 15549 - Permalink


Simulations of agglomerate sedimentation and suspension
Cartland Glover, G.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Application of such a model to sedimentation in a quiescent column and a horizontal flow are examined. The scenario also presents the suspension and horizontal transport of a single fiber agglomerate phase in a racetrack type channel.
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Lecture (others)
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau and Dresden, Germany
  • Contribution to proceedings
    Fachkolloquium "Partikelströmung", 17.-18.03.2011, Zittau and Dresden, Germany
    Fachkolloquium "Partikelströmung"

Publ.-Id: 15548 - Permalink


Numerical models used for the modelling of the transport of fibrous insulation debris
Cartland Glover, G. M.; Krepper, E.; Renger, S.; Seeliger, A.; Kästner, W.; Kryk, H.;
Mineral wool insulation material applied to the primary cooling circuit of a nuclear reactor maybe damaged in the course of a loss of coolant accident (LOCA). The insulation material released by the leak may compromise the operation of the emergency core cooling system (ECCS), as it maybe transported together with the coolant in the form of mineral wool fiber agglomerates (MWFA) suspensions to the containment sump strainers, which are mounted at the inlet of the ECCS to keep any debris away from the emergency cooling pumps. In the further course of the LOCA, the MWFA may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fiber cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Therefore, it is essential to understand the transport characteristics of the insulation materials in order to determine the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a primary circuit coolant leak. The study entails the generation of fiber agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effects that particles formed due to corrosion of metallic containment internals by the coolant medium have on the strainer pressure drop.
The focus of this presentation is on the numerical models that are used to predict the transport of MWFA by CFD simulations. A number of pseudo-continuous dispersed phases of spherical wetted agglomerates can represent the MWFA. The size, density, the relative viscosity of the fluid-fiber agglomerate mixture and the turbulent dispersion all affect how the fiber agglomerates are transported. In the cases described here, the size is kept constant while the density is modified. This definition affects both the terminal velocity and volume fraction of the dispersed phases. Only one of the single effect experimental scenarios is described here that are used in validation of the numerical models. The scenario examines the suspension and horizontal transport of the fiber agglomerates in a racetrack type channel. The corresponding experiments will be described in an accompanying presentation (see abstract of Seeliger et al.).
Keywords: Mineral Wool Fiber Agglomerates, Loss of Coolant Accidents, Containment Sump, Computational Fluid Dynamics, Multiphase Flow
  • Lecture (Conference)
    Euromech Coloquium 513 on non-spherical particles in fluid turbulence, 06.-08.04.2011, Udine, Italy
  • Contribution to WWW
    http://158.110.32.35/Euromech/PRESENTATIONS/CartlandGlover.pdf
  • Lecture (Conference)
    Euromech Coloquium 513 on non-spherical particles in fluid turbulence, 06.-08.04.2011, Udine, Italy

Publ.-Id: 15547 - Permalink


Experiments to assess the transport of fibrous insulation debris
Seeliger, A.; Cartland Glover, G. M.; Renger, S.; Krepper, E.; Kästner, W.; Kryk, H.;
Loss of coolant accidents (LOCA) in the primary cooling circuit of a nuclear reactor may result in damage to insulation materials that are located near to the leak. The insulation materials released may compromise the operation of the emergency core cooling system (ECCS). Insulation material in the form of mineral wool fibre agglomerates (MWFA) maybe transported to the containment sump strainers mounted at the inlet of the emergency cooling pumps, where the insulation fibres may block or penetrate the strainers. In addition to the impact of MWFA on the pressure drop across the strainers, corrosion products formed over time may also accumulate in the fibre cakes on the strainers, which can lead to a significant increase in the strainer pressure drop and result in cavitation in the ECCS. Thus, knowledge of transport characteristics of the damaged insulation materials in various scenarios is required to help plan for the long-term operability of nuclear reactors, which undergo LOCA.
An experimental and theoretical study performed by the Helmholtz-Zentrum Dresden-Rossendorf and the Hochschule Zittau/Görlitz1 is investigating the phenomena that maybe observed in the containment vessel during a LOCA. The study entails the generation of fibre agglomerates, the determination of their transport properties in single and multi-effect experiments and the long-term effect that corrosion of the containment internals by the coolant has on the strainer pressure drop.
The focus of this presentation is on the experiments performed that characterize the horizontal transport of MWFA, whereas the corresponding CFD simulations are described in an accompanying contribution (see abstract of Cartland Glover et al.). The experiments were performed a racetrack type channel that provided a near uniform horizontal flow. The channel is 0.1 wide by 1.2 m high with a straight length of 5 m and two bends of 0.5 m. The measurement techniques include particle imaging (both wide-angle and macro lens), concurrent particle image velocimetry, ultravelocimetry, laser detection sensors to sense the presence of absence of MWFA and pertinent measurements of the MWFA concentration and quiescent settling characteristics. The transport of the MWFA was observed at velocities of 0.1 and 0.25 m s-1 to verify numerical model behaviour in and just beyond expected velocities in the containment sump of a nuclear reactor.
Keywords: Mineral Wool Fibre Agglomerates, Loss of Coolant Accidents, Containment Sump, Particle Imaging, Particle Image Velocimetry

Publ.-Id: 15546 - Permalink


F-18 Labelled cathepsin inhibitors as potential radiotracers for tumour imaging
Löser, R.; Frizler, M.; Bergmann, R.; Dombrowski, L.; Knieß, T.; Gütschow, M.; Steinbach, J.;
Ziel/Aim:
The enzyme class of thiol-dependent cathepsins has been shown to be linked to the progression of cancer in multiple ways. Particularly crucial is their involvement in proteolytic pathways that are related to tumour invasion and metastasis (1).
The aim was the design of a fluorine-containing inhibitor of the azadipeptide nitrile chemotype (2) and the labelling with the radionuclide F-18 to evaluate the potential of this inhibitor class for functional tumour imaging by PET and to gain insight into the pharmacokinetic behaviour of these inhibitors.

Methodik/Methods:
The fluorine atom was connected by an ethylene bridge to the inhibitor core structure and the affinities of the resulting compound to its targets were determined in kinetic enzyme assays. Labelling with F-18 was achieved by fluoroethylation with different substituted [18F]2-fluoroethyl benzenesulfonates (3). The stability of the tracer against chemical and enzymatic degradation as well as its metabolic fate in rat blood was investigated and its biodistribution was studied in vivo by small animal PET.

Ergebnisse/Results:
The fluorine containing azadipeptide nitrile Gue2011 exhibits inhibition constant in the single-digit to subnanomolar range against the oncologically relevant cathepsins L, S, and B. Among the various F-18 fluoroethylating agents tested, [18F]2-fluoroethyl nosylate revealed as the most efficient one. This enabled the two-step radiosynthesis of [18F]Gue2011 in an average RCY (dc) of 24 % (n = 6). Metabolite analysis in rat blood showed the rapid conversion of the tracer into its glutathione conjugate as indicated by HPLC. Studies towards the pharmacological prevention of this conjugate formation are under current investigation.

Schlussfolgerungen/Conclusions:
With Gue2011 a highly potent fluorine-containing cathepsin inhibitor was found and its labelling with fluorine-18 could be successfully established. The compounds suitability as PET tracer for functional tumour imaging seems to be limited due to its inherent thiol reactivity. The radiolabelling of other cathepsin inhibitors is underway.

Literatur/References:
(1) Mohamed, M. M.; Sloane B. F. Nat. Rev. Cancer 2006, 6, 764-775
(2) Löser, R. et al. Angew. Chem. Int. Ed. 2008, 47, 4331-4334
(3) Musachio, J. L.; Shah, J.; Pike V. W. J. Label. Compd. Radiopharm. 2005, 48, 735-747
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A118

Publ.-Id: 15545 - Permalink


Einfluss der Datenfilterung auf die Bestimmung von Tumor-Volumen und SUVmax in der PET: Vergleich von einfacher Glättung und lokal adaptiver Filterung.
Beuthien-Baumann, B.; Hofheinz, F.; Oehme, L.; Langner, J.; van den Hoff, J.;
Ziel/Aim:
Bei der FDG-PET kann die Bildqualität bzg. des Signal/Rausch-Verhältnisses (SN-ratio) deutlich eingeschränkt sein (z.B. Adipositas, Atemgating). Der Einsatz üblicher glättender Filter (MAF: „Moving Average Filter“) verbessert das SN-ratio, reduziert aber die räumliche Auflösung, woraus verminderte Detailerkennbarkeit und Kontrastverlust v.a. bei Strukturen nahe der Auflösungsgrenze resultieren. Eine Alternative zu MAF sind lokal adaptive Filter, welche eine Rauschunterdrückung kombiniert mit Kantenerhaltung in den Bildern bewirken, aber bisher wenig verbreitet sind. Ziel: Einfluß der Bildbearbeitung mittels MAF und einem lokalen adaptiven Filter (LAF ) auf das abgegrenzte Tumorvolumen und den maximalen Standard Uptake Value (SUVmax) zu ermitteln.

Methodik/Methods:
10 Patienten mit nicht-kleinzelligem Bronchial-Karzinom und mind. einer Metastase, BMI 29,5 (23,9 – 40,4), mittl. injizierte Aktivität 384 MBq F18-FDG. Akquisition ab 60 min p.i., PET-Scanner ECAT EXACT HR+ (Siemens/ CTI). Iterative Rekonstruktion OSEM 6/16, Gauss 6mm. Vergleich von 5 Datensätzen: Original-Daten, MAF (3x3x3 Gaussfilter, FWHM = 8 mm) sowie LAF optimiert für 3 Rauschamplituden (NR20, NR40, NR60). Ermittlung von Tumorvolumen und SUVmax über 3D Regions Of Interest mittels ROVER (ABX, Radeberg). Ausgewertet wurde die Änderung des Volumens und des SUVmax in Abhängigkeit von der Filterung.

Ergebnisse/Results:
Es wurden insgesamt 29 Läsionen ausgewertet. 9 Läsionen zeigten eine Volumen < 3 ccm, 12 Läsionen zwischen >3 ccm und < 10c cm, 5 Läsionen <10 und >20 ccm, und 5 Läsionen > 20 ccm. Der SUVmax lag im Mittel bei 6,5 für Läsionen < 3 ccm, SUVmax 8,3 bei Läsionen zwischen >3 und < 10 ccm, SUVmax 12,1 bei Läsionen <10 und >20 ccm und SUVmax 19,4 bei Läsionen > 20 ccm. MAF führte zu einer Zunahme des ermittelten Volumens zwischen 2 und 18%, wobei die kleinen Läsionen eine relativ größere Volumenzunahme aufwiesen. Der SUVmax sank auf 85% bis 95% des Ausgangswertes, wobei kleine Läsionen eine deutlichere Reduktion des SUVmax zeigten. LAF führte zu keiner wesentlichen Volumenänderung im Vergleich zum Originaldatensatz. Der SUVmax lag bei einer noise reduction von 60% zwischen 92% und 98% des Ausgangswertes, bei NR20 und NR40 waren die Abweichunegn noch geringer.

Schlussfolgerungen/Conclusions:
Der Einsatz glättender Filter reduziert die effektive räumliche Auflösung der Bilddaten und ist problematisch im Hinblick auf die visuelle und quantitative Bewertung von kleinen Läsionen nahe der Auflösungsgrenze, selbst bei nur geringfügiger Glättung. Kantenerhaltende lokal adaptive Filter bieten eine vielversprechende Alternative und führen visuell wie quantitativ zu überlegenen Ergebnissen. Dies erscheint insbesondere von Bedeutung für Verlaufsuntersuchungen, bei denen möglicherweise die prozentuale Änderung des SUVmax nach Chemotherapie für eine weitere Therapiestratifizierung genutzt wird.
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A104

Publ.-Id: 15544 - Permalink


A new segmentation approach for F-18-fluoromisonidazole positron emission tomography data based on Ant Colony Optimization: Considering Reproducibility
Haase, R.; Hietschold, V.; Andreeff, M.; Böhme, H. J.; Kotzerke, J.; Steinbach, J.; Zips, D.; Baumann, M.; Abolmaali, N.;
Ziel/Aim:
Hypoxia imaging using F-18-fluoromisonidazole (FMISO) positron emission tomography (PET) is of increasing interest in the field of radiation oncology. But for analysis of FMISO PET data a reliable and accurate delineation technique of hypoxic subvolumes is still needed. Due to the inability of threshold based segmentation approaches to deliver reliable results when applied to data sets with small, inhomogeneous or non spherical target volumes, more complex algorithms may be preferred (1). We propose an Ant-Colony-Optimization (ACO) approach for segmentation of FMISO PET data sets. This investigation was performed to validate the reproducibility of the algorithm processing patient data sets.

Methodik/Methods:
Our analysis included 28 patients from an ongoing prospective study on head and neck cancers. FMISO PET images were acquired 4 hours p.i. of ~266 MBq. Patients were investigated by FMISO PET before radiochemotherapy (RCT) and the resulting data sets were further processed by the proposed ACO approach. Virtual ants were operating autonomously in the PET volume searching for regions with signal intensity above average. When an ant is located in such a region, it emits pheromone, attracting more ants to go to the marked region. More ants emit more pheromone and in that way the pheromone field shows the target objects with higher contrast than the original data set. Afterwards the pheromone fields were segmented into positive and negative regions using a histogram based threshold algorithm. Each data set was processed for 3 times and the resulting delineations were compared pair wise using the Jaccard-Index (JI). Mean JI and standard deviation were calculated from the resulting three JI values for each data set.

Ergebnisse/Results:
The JI over all data sets was 0.81 (+- 0.1) indicating highly reproducible volume delineations. The mean segmented volume was 182 ml with a mean deviation of 10 %. In 19 patient data sets volumes outside the presumptive tumour volume were segmented as positive, especially in the cerebellar region. This finding is well comparable to the clinical experience and these volumes were also segmented with high reproducibility.

Schlussfolgerungen/Conclusions:
The results show that the ACO approach delivers reproducible volume delineations when applied to FMISO PET patient data sets. Further development of the proposed algorithm will face excluding positive regions outside the presumptive tumour volume and comparison of automatically generated delineations with manual segmentations by experienced physicians.

Literatur/References:
(1) Lee J.A. (2010) Segmentation of positron emission tomography images: Some recommendations for target delineation in radiation oncology.
Radiotherapy & Oncology, Vol. 96, Issue 3, pp 302-307
  • Poster
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A95

Publ.-Id: 15543 - Permalink


Dynamics of PBF changes in regions of aspiration-induced acute lung injury
Bergmann, R.; Richter, T.; Ragaller, M.; Pietzsch, J.;
Ziel/Aim:
Aspiration of gastric contents is the second most common clinical event associated with the development of the adult respiratory distress syndrome (ARDS) and the mortality for ARDS resulting from acid aspiration ranges from 40-50%. Regions of aspiration induced injury matches regions of high pulmonary blood flow (PBF) in the early stage of acute lung injury, as recently shown by us. The aim of this project was to characterize the dynamics of regional PBF distribution in dependence on time after injury.

Methodik/Methods:
The protocol was approved by the Animal Study Committee of the Landesdirektion Dresden. In 11 desflurane anesthetized, spontaneously breathing male Wistar rats the lung injury was achieved by instillation of 0.1 HCl (0.4 ml/kg body weight) through a tracheostomy tube. The animals were scanned with a dedicated small animal CT scanner before and after injury. The pulmonary blood flow in the lungs was imaged by dedicated positron emission tomography (PET) using intravenously infused Ga-68-labeled DOTA-modified microspheres (diameter 20 µm) at 10 (6 animals) and 120 min (5 animals) after aspiration. CT- and PET-images were co-registered. Areas of injury, identified as new high density regions in lung CT-images after aspiration, were marked with a spherical mask and regions of interest (ROI) were derived using a threshold of 80% of maximum activity in the mask. Identical masks were used at the contralateral lung as reference. PBF in the injury ROI was calculated as activity fraction of the reference PBF region. The PBF in injury was compared with the reference side using the Wilcoxon matched-pairs signed rank test. The PBF-fraction at different time points was compared between the groups by unpaired t-test with Welch's correction.

Ergebnisse/Results:
CT images after aspiration showed areas of lung injury different in location and size within the two groups. Fraction of PBF in injured regions was higher at 10 min {1.34 (1.15-1.45) (median (interquartile range)} compared to 120 min (0.9 (0.85-1.06); P=0.0014) after aspiration. The intra-individual difference was determined by a high PBF in injured lung regions compared to the contralateral reference side at 10 min after injury (P = 0.03), whereas at 120 min after aspiration, injured regions have shown similar PBF compared to the contralateral reference side (P=0.81).

Schlussfolgerungen/Conclusions:
Regional PBF was increased 10 minutes after acid aspiration in regions of injury. This effect disappears within two hours after injury in anesthetized rats. This observed change in PBF after aspiration-induced acute lung injury seems to be important in early targeted treatment of acid aspiration.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizn 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A76-A77

Publ.-Id: 15542 - Permalink


Optimierung der Pharmakokinetik radioaktiv markierbarer L-Oligonukleotide durch PEGylierung
Pietzsch, H.-J.; Förster, C.; Schubert, M.; Bergmann, R.; Vonhoff, S.; Klussmann, S.; Steinbach, J.;
Ziel/Aim:
Komplementäre L-Oligonukleotide (L-ON) stellen einen alternativen Ansatz zur Realisierung von Pretargeting-Technologien dar. Im Vergleich zu natürlichen D‑Oligonukleotiden besitzen L-Oligonukleotide eine sehr hohe metabolische Stabilität; allerdings werden sie sehr schnell aus der Blutbahn entfernt und in hohem Maße in den Nieren angereichert.Ziel des Forschungsvorhabens ist die gezielte Einflussnahme auf die Pharmakokinetik durch systematische PEGylierung einer L-ON-Leitstruktur. Schwerpunkte sind die Erhöhung der Bioverfügbarkeit durch Reduzierung der Blutclearance sowie die Verringerung der Nierenakkumulation.

Methodik/Methods:
Als Leitstruktur wurde das L-Oligonukleotid HO-C6H12-S-S-C6H12-5’GCG-GCT-GTG-CGG-TGC-GG3’ verwendet. Das 3’-Ende wurde mit PEG unterschiedlicher Größen (2, 5, 10, 20 kDa) derivatisiert. Nach Spaltung der Disulfidbindung und Funktionalisierung der PEG-L-ON-Konjugate mit maleinimidfunktionalisierten NOTA- bzw. DOTA-Chelatoren wurden die resultierenden Konstrukte mit Ga-68 bzw. Cu-64 markiert. Die Pharmakokinetik der Radiotracer wurde durch dynamische PET-Scans und simultane Organverteilungsstudien in Wistar-Ratten bestimmt.

Ergebnisse/Results:
Die Zunahme der PEG-Molmassen bewirkte eine stetige Reduzierung der Nierenaufnahme nach 60 min von 56,3 ± 4,1 %ID (Cu-64; 2 kDa PEG) und 52,4 ± 6,1 %ID (Ga-68; 2 kDa PEG) zu 6,5 ± 0,4 %ID (Cu-64; 20 kDa PEG) und 6,9 ± 0,6 % (Ga-68; 20 kDa PEG).Mit zunehmender PEG-Größe zeigte sich eine ansteigende Leberaufnahme nach 60 min p.i. von 4,8 ± 0,2 %ID (Cu-64; 2 kDa PEG) und 2,6 ± 0,4 %ID (Ga-68; 2 kDa PEG) zu 13,3 ± 2,1 %ID (Cu-64; 20 kDa PEG) und 10,7 ± 2,7 %ID (Ga-68; 20 kDa PEG). In den restlichen Organen, mit Ausnahme des Blutes, war die Radiotraceraufnahme nach 60 min p.i. sehr gering (<0,5 %ID/g bzw. <1 SUV). Aus den dynamischen PET-Untersuchungen wurden die Halbwertszeiten der einzelnen Radiotracer im Blutkreislauf bestimmt, diese betrugen 10,8 min (2 kDa PEG), 9,6 min (5 kDa PEG), 27,7 min (10 kDa PEG) und 39,4 min (20 kDa PEG).

Schlussfolgerungen/Conclusions:
Die Modifikation des pharmakokinetischen Profils der L-ON-Leitstruktur ist durch sukzessive PEGylierung möglich. Im optimalen Fall verringerte sich die Nierenanreicherung der PEG-L-ON nach 60 min auf ein Neuntel des Wertes der nicht-PEGylierten L-ON, bei gleichzeitiger Erhöhung der Verweilzeiten im Blut. Weiterhin bewirkte die PEGylierung eine Erhöhung der Leberaufnahme, während alle anderen Gewebe und Organe auf sehr niedrigem Radioaktivitätsniveau blieben. Durch PEGylierung von L-ON ist eine gezielte Beeinflussung der Pharmakokinetik möglich, jedoch ergeben sich entgegengesetzte Effekte bezüglich der Nieren- und Leberaufnahme. Die absoluten Anreicherungen in den genannten Organen müssen noch weiter reduziert werden, um die L-ON in Pretargeting-Technologien für Diagnostik und Therapie anwenden zu können.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A74

Publ.-Id: 15541 - Permalink


Molecular imaging of radio- and NIR-labeled EGFR-antibody in tumor bearing mice
Bergmann, R.; Zenker, M.; Pietzsch, J.; Walther, M.; Heldt, J.-M.; Pietzsch, H.-J.; Steinbach, J.;
Ziel/Aim:
The epidermal growth factor receptor (EGFR) is often overexpressed in human malignancies. This phenotype is associated with tumor aggressiveness, treatment resistance, and biological heterogeneity with potential to bypass the blockade of the EGFR signaling pathways. Cetuximab (C225) as a chimeric monoclonal antibody specifically targets the EGFR was modified for radio- and near infrared fluorescence (NIRF) imaging as well as for potential applications in radiotherapy using DTPA-, DOTA-, NOTA-modification, radio-labeling with Cu-64, Y-86, Y-90, Lu-177, and for modification with X-SIGHT Large Stokes Shift Dye (X-SIGHT 670 LSS Dye).

Methodik/Methods:
C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Ergebnisse/Results:
C225 was conjugated with bifunctional chelators based on SCN-Bz and -DTPA, -DOTA, -NOTA, and the C225-NOTA derivative was additionally modified with the X-SIGHT 670 Large Stokes Shift Dye, TFP Ester (XS670). The receptor binding and cell (A431 cells expressing high amounts of EGFR) uptake of Cu-64-NOTA-XS670-C225 was studied in vitro. The EGFR-affinity of the immune-conjugates was measured by a competitive radio-ligand binding assay. The conjugates were labeled with Cu-64, Y-86, Y-90, Lu-177 within 30 min with high radiolabeling yield and radiochemical purity. The biodistribution and –kinetics in vivo were studied by small animal PET or SPECT and ex vivo by autoradiography. Whole body cryo-sectioning of the animals into 40 micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue sections.

Schlussfolgerungen/Conclusions:
PET allows the quantitative kinetic characterization of biodistribution in small animals, which will be a prerequisite to estimate the dosimetry in animals. SPECT and autoradiography allowed the fine distribution imaging. The dual-labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using NIRF of cryo-sections beyond the decay of the radionuclide used. Dual-labeled immune-conjugates represent a potential probe for translational application in tumor detection.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A41-A42

Publ.-Id: 15540 - Permalink


Erste Ergebnisse zur Untersuchung des Uptakes von Y-90-Cetuximab in vitro an FaDu-Monolayer-Zellen
Runge, R.; Ingargiola, M.; Förster, C.; Freudenberg, R.; Wunderlich, G.; Heldt, J.-M.; Zenker, M.; Steinbach, J.; Cordes, N.; Kunz-Schughart, L.; Kotzerke, J.;
Ziel/Aim:
In einer Vielzahl menschlicher Tumore ist die Expression des Epidermal-Growth-Factor-Receptor (EGFR) nachweisbar und geht mit einer schlechteren Prognose onkologisch behandelter Patienten einher. Der EGFR wird durch seine natürlichen Liganden oder ligandenunabhängig durch Bestrahlung aktiviert. Zu den Substanzen, die den EGFR hemmen gehören monoklonale Antikörper (mAb) z.B. Cetuximab (C225). Die Markierung des C-225 mit dem Beta-Strahler Y-90 ermöglicht eine zielgerichtete Induktion von DNA-Schäden. Es sollte untersucht werden, welchen Einfluss der Zusatz von kaltem C225 auf den Uptake von Y-90-C225 in FaDu-Monolayer-Zellen hat.

Methodik/Methods:
FaDu-Zellen wurden in 6-Well-Mikrotiterplatten (MTP) ausgesät (1x105 und 3x105 Zellen pro well). Die Inkubation erfolgte mit Y-90-C225 über 24 h bei 37°C mit unterschiedlichen Dosen (0-6 Gy, Geant4 Monte Carlo Toolkits). Y-90-C225 wurde mit unmarkiertem C225 auf C225-Konzentrationen von 1 µg/ml und 5 µg/ml eingestellt und Proben ohne Zusatz von unmarkiertem C225 mitgeführt. Die Bestimmung des zellulär gebundenen Y-90-C225 (Uptake) erfolgte durch Messung der Radioaktivität des ungebunden Y-90-C225 sowie des gebundenen Y-90-C225 im Zelllysat an einem Gammacounter (CobraTM II).

Ergebnisse/Results:
Der Uptake von Y-90-C225 in FaDu-Zellen zeigte eine Abhängigkeit von der Zellzahl. Der absolute Uptake von Y-90-C225 ohne Zusatz von unmarkiertem C-225 stieg bei Dosissteigerung bzw. Konzentrationserhöhung des mAb nur marginal an, die relativen Werte (bezogen auf die eingesetzte Radioaktivität) zeigten bei 1 Gy den höchsten Uptake (1 Gy: 18,63%, 6 Gy: 3,6 %). Die Kompetition von Y-90-C225 und unmarkiertem C225 um die Bindungsstellen auf der Zellmembran konnte durch die Reduzierung des Y-90-C225-Uptakes mit zunehmendem Anteil von unmarkiertem C225 an der Gesamtantikörperkonzentration nachgewiesen werden.

Schlussfolgerungen/Conclusions:
Bei höheren Dosen bzw. Antikörperkonzentrationen wurde kein höherer Y-90-C225-Uptake erzielt, was auf eine Sättigung der Rezeptoren/Bindungsstellen hinweist. Die lineare Abnahme der zellulären Bindung des Y-90-C225 bei Erhöhung der Konzentration des unmarkierten C225 deutet auf die gleiche Affinität des markierten und unmarkierten Antikörpers an die EGFR-Bindungsstellen der FaDu-Zellen hin.Zur Verifizierung der Ergebnisse sind weitere Experimente geplant.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A37

Publ.-Id: 15539 - Permalink


Inkorporationsdosimetrie mit (-)-F18-NCFHEB, einem neuen PET-Tracer zur Darstellung von zerebralen α4β2 nikotinischen Acetylcholinrezeptoren.
Sattler, B.; Wilke, S.; Starke, A.; Seese, A.; Patt, M.; Schildan, A.; Smits, R.; Hoepping, A.; Brust, P.; Steinbach, J.; Gräf, S.; Gertz, H. J.; Sabri, O.;
Ziel/Aim:
(-)-F18-Norchloro-fluoro-homoepibatidin ((-)-F18-NCFHEB) ist ein neuer und vielversprechender Radioligand für die Darstellung von alpha4beta2 nikotinischen Acetylcholinrezeptoren mit PET. Um das Strahlenrisikio durch diesen Tracer abzuschätzen, wurden die resultierenden Organdosen (OD) und die effektive Dosis (ED) im Rahmen einer Machbarkeitsstudie inkorporationsdosimetrisch ermittelt.

Methodik/Methods:
Die inkorporationsdosimetrische Untersuchung von (-)-F18-NCFHEB wurde an 3 Probanden (2 männlich, 1 weiblich; Alter: 59,6±3,9a; Gewicht: 74,3±3,1Kg) vorgenommen. Die Probanden unterzogen sich nach intravenöser Injektion von 353,7±10,2 MBq (-)-F18-NCFHEB einer sequentiellen PET-CT-Untersuchung bis zu 7h nach Injektion an einem SIEMENS Biograph16 PET-CT-System (9 Bettpositionen pro Frame, 1,5-6min/Bettposition, CT-Schwächungskorrektur, iterative Rekonstruktion). Bis zu 7h p.i. wurde sämtlicher Urin gesammelt und dessen Aktivitätskonzentration bestimmt. Alle den Tracer aufnehmenden Organe wurden CT-geführt mit dreidimensionalen Regionen (VOIs) markiert, und ihr Aktivitätsinhalt als Zeit-Aktivitäts-Verlauf dargestellt. Mit dem EXM-Modul von OLINDA [1] wurden Zeit-Aktivitäts-Kurven an diese Daten angepasst. Der Aktivitätsverlauf in der Blase wurde anhand der Urinabgaben bestimmt. ODs wurden unter Verwendung des 73,7kg-"adult male model" mit OLINDA bestimmt. Die ED wurde unter Verwendung der Gewebewichtungsfaktoren in der ICRP 103 von 2007 berechnet [2].

Ergebnisse/Results:
Die Harnblaseblase erhält die höchste OD (80,2±37,8µSv/MBq), gefolgt von der Leber (44,7±5,4µSv/MBq), den Nieren (38,6±5,1µSv/MBq), der Milz (38,4±11,6µSv/MBq), der Schilddrüse (32,8±11,9µSv/MBq) und den Lungen (31,1±5,3µSv/MBq). Die höchsten Beiträge zur ED leisten die Lunge (3,7±0,6µSv/MBq), die Harnblase (3,2±1,5µSv/MBq), der Magen (2,9±0,7µSv/MBq), das rote KM (2,3±0,2µSv/MBq), der absteigende Dickdarm (1,9±0,2µSv/MBq) und die Leber (1,8±0,2µSv/MBq). Die ED durch i.v. Applikation von (-)-F18-NCFHEB ergibt sich zu 22,9±0,7µSv/MBq.

Schlussfolgerungen/Conclusions:
Die effektive Dosis als Maß für das summarische Risiko durch i.v. Applikation von 300 MBq (-)-F18-NCFHEB) ergibt sich zu 6,8±0,2mSv. Dies liegt im Bereich der Strahlenexposition durch andere F18-markierte Radioliganden. Diese günstigen dosimetrischen Ergebnisse unterstützen die weitere Entwicklung von (-)-F18-NCFHEB) als klinischen Hirn-PET-Tracer.

Literatur/References:
[1] Stabin et. al.: OLINDA/EXM: The Second-Generation Personal Computer Software for Internal Dose Assessment in Nuclear Medicine; JNM 46/6, 2005
[2] International Commission on Radiological Protection. Recommendations of the International Commission on Radiological Protection. ICRP Publication 103, Pergamon Press, New York, 2007
Die Studie wird vom Bundesministerium für Bildung und Forschung gefördert (Nr. 01EZ0820)
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutsche, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A36

Publ.-Id: 15538 - Permalink


Ein Verfahren zur modellfreien Recovery-Korrektur fokaler Strukturen in der PET
Hofheinz, F.; Langner, J.; Will, E.; Oehme, L.; Beuthien-Baumann, B.; van den Hoff, J.;
Ziel/Aim:
Der Partialvolumeneffekt beeinträchtigt die Bestimmung der wahren Aktivitätskonzentration einer Zielstruktur (sowie hiervon abgeleiteter Größen, wie z.B. SUV-Werte). Bereits bei Strukturabmessungen, die noch deutlich größer als die rekonstruierte räumliche Auflösung der Bilddaten sind, tritt eine gravierende Unterschätzung der wahren Werte auf, insbesondere, wenn ROI-Mittelwerte betrachtet werden (beschränkte Signal-Recovery). Werden quantitative Parameter wie SUV-Werte zur Beurteilung des Therapieansprechens herangezogen, muss daher eine Recovery-Korrektur durchgeführt werden Ziel dieser Arbeit war es, eine routinefähige modellfreie Methode zur Recovery-Korrektur zu entwickeln und diese anhand von Phantommessungen zu validieren.

Methodik/Methods:
Die entwickelte Methode arbeitet in 2 Schritten. Schritt 1: Bestimmung des wahren Objektvolumens V unter Benutzung eines automatischen thresholdbasierten Verfahrens inklusive einer Berücksichtigung des lokalen Untergrundes (ROVER, ABX) und der entsprechenden Gesamtaktivität A innerhalb von V. Schitt 2: Bestimmung des infolge des Partialvolumeneffektes ausserhalb der Objektgrenze abgebildeten untergrundbereinigten(!) Aktivtätsanteils B. Der Recoverykoeffizient
ergibt sich hiermit zu R = A/(A+B). Es wurden Messungen mit einem Zylinderphantom (Durchmesser: 20 cm, Höhe: 18 cm) durchgeführt. Die im Zylinder befindlichen 6 Kugeleinsätze besitzen Volumina von 2,5 ml bis 27 ml. In 3 Phantommessungen mit einem ECAT EXACT HR+ (Siemens/CTI, Knoxville, Tennessee) wurden der Zylinder und die Kugeln mit unterschiedlichen Aktivitätsmengen (Fluor-18) befüllt, um das Signal-Untergrund-Verhältnis und damit den Bildkontrast zu variieren. Zum Vergleich wurden die Recovery-Koeffizienten aus der Faltung der Objektfunktion (homogene Kugel) mit der bekannten/gemessenen Point Spread Function der Bilddaten berechnet. Die berechneten Recovery-Koeffizienten wurden mit den aus den Bilddaten gewonnenen Koeffizienten verglichen.

Ergebnisse/Results:
Die in den Bilddaten mit dem beschriebenen Verfahren bestimmten Recovery-Koeffizienten stimmmen bei praktisch relevanten Target/Background Kontrastverhältnissen sehr gut mit den berechneten Koeffizienten überein (Abweichungen im Mittel 5%).

Schlussfolgerungen/Conclusions:
Die vorgestellte Methode liefert bei praktisch relevanten Kontrastverhältnissen und homogenem Untergrund gute Ergebnisse. Die genauen Gültigkeitsgrenzen des Verfahren (inhomogener Untergrund, geringer Kontrast usw.) müssen noch genauer untersucht werden.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A28

Publ.-Id: 15537 - Permalink


Perfusion measurements using Arterial Spin Labeling and MRI in small animals: comparison with radioactive and fluorescent microspheres
Bos, A.; Bergmann, R.; Hofheinz, F.; van den Hoff, J.;
Ziel/Aim:
Regional tissue perfusion is a fundamental physiological parameter controlling delivery of oxygen and nutrients to tissue. Arterial Spin Labeling (ASL) is a Magnetic Resonance Imaging (MRI) technique used for perfusion quantification. ASL has been shown to work reasonably well in human brain investigations. In other organs and especially in small animal imaging, however, ASL is not yet well established and validation against other methods is missing. The purpose of this work was to evaluate ASL in the brain of the rat by comparison with microspheres-derived regional perfusion using dedicated small animal PET and Optical Imaging (OI) systems.

Methodik/Methods:
Catheters were implanted through the right carotid artery in the left ventricle of the heart for administration of labeled microspheres (20μm) and in the left femoral artery for blood sampling. Microspheres were double-labeled with Cu-64 (or Ga-68) for PET (microPET P4, Siemens) and and X-sight 670 LSS for OI (Kodak FX). ASL measurements were performed in a 7T small animal MRI system (BioSpec 70/30, BRUKER) using a FAIR (Flow-sensitive Alternating Inversion Recovery) sequence with an adiabatic hyperbolic secant inversion pulse (length-bandwidth product: 80) and EPI (Echo Planar Imaging) acquisition. Global and selective T1 images were used for calculation of the perfusion values.

Ergebnisse/Results:
Perfusion in two brain slices was determined in three different ways (PET, MRI, OI). For the catheterized rat under anesthesia the whole brain perfusion values range from 0.2 to 1.19 ml/min/g for PET measurements and from 0.3 to 1.15 ml/min/g for OI calculations. In the normal rat brain (no catheter) under anesthesia perfusion values from FAIR-ASL ranged from 0.8 to 1.4 ml/min/g in both hemispheres (caudate putamen region). Catheter implantation created left/right differences between hemispheres of 10-30 %. The Pearson correlation factor varies between 0.88 and 0.9 for ASL vs. PET.

Schlussfolgerungen/Conclusions:
Overall the regional perfusion contrast is concordant between ASL and microspheres measurements. However, substantial quantitative deviations exist and are currently investigated. In order to become a useful routine applications in small animal imaging, ASL data acquisition and data evaluation needs to be further optimized. A thorough calibration via a quantitative comparison with radio- and fluorescent-labeled microspheres is mandatory. Altogether, perfusion quantification in the rat brain with ASL seems possible.
  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A10

Publ.-Id: 15536 - Permalink


Countercurrent gas-liquid flow in a PWR hot leg (Effects of channel shape and size)
Kinoshita, I.; Murase, M.; Utanohara, Y.; Lucas, D.; Vallée, C.; Tomiyama, A.;
A numerical study is presented to examine the effects on countercurrent flow limitation (CCFL) of shape and size of hot leg models with rectangular cross-section. Using the CFD software FLUENT 6.3.26, numerical simulations were conducted for CCFL experiments in a 1/3 scale rectangular channel (HxW = 0.25x0.05 m2), and results were compared with CCFL data and simulation results in a 1/5 scale rectangular channel (HxW = 0.15x0.01 m2). Comparing CCFL characteristics in rectangular channels with those in circular channels, the hydraulic diameter was turned out to be a major factor of cross-section geometry influencing the CCFL characteristics in hot legs.
Keywords: PWR hot leg, countercurrent gas-liquid flow, CCFL, rectangular channel, numerical simulation
  • Contribution to proceedings
    Japan Society of Multiphase Flow (JSMF) Annual Meeting 2011, 06.-08.08.2011, Koto, Japan

Publ.-Id: 15535 - Permalink


Radiolabelling of engineered nanomaterials as a tool for sensitive particle tracking
Hildebrand, H.; Franke, K.;
Engineered nanoparticles (NPs) are present in a wide variety of consumer products, occasionally in significant quantities. During aging, abrasion or disposal of such products, NPs-release is likely - accompanied with effects for the environment that have to be investigated in more detail. The aim of this study is to quantify the amount of NPs (TiO2 and Ag0) released from composite coatings due to weathering, aging or mechanical stress and to follow the NPs along their further fate in the environment.
Generally, particle tracking may provide information on the transport behavoir of the particles in aqueous media or on their interactions with biota. Since NPs are possibly released in tiny amounts and into very complex natural systems, we suggest the radiolabelling of NPs as a tool for their very sensitive detection throughout their life cycle including complex media such as aquifer sands, soil or cells.
Within this study, a novel radiolabelling technique for TiO2 (P 25, Evonik Degussa) and Ag0 (Sigma-Aldrich) NPs is under development. During this labelling process, significant changes of the chemical composition and properties of the particles are avoided to the greatest possible extend.
Stability of the NPs in different media has been studied and results contribute to first estimates concerning their transport behaviour in the aquatic environment. Batch tests including sediment materials were conducted to describe interactions of Ag0 and TiO2 NPs with natural matrices.
Interactions of engineered NPs and natural colloids have been studied as well. Results show that natural colloids have a strong influence on stability and transport of engineered NPs under environmental conditions.
Based on these data, radiolabelling of engineered NPs may open up the chance for sensitive tracking of particles not only in environmental media but also in other complex systems.
  • Lecture (Conference)
    Goldschmidt2011, 14.-19.08.2011, Prag, Tschechische Republik

Publ.-Id: 15534 - Permalink


Interdiffusion in Fe/Pt Multilayers: In-situ high-temperature synchrotron radiation reflectivity study
Zotov, N.; Feydt, J.; Savan, A.; Ludwig, A.; von Borany, J.;
Thermal annealing of Fe/Pt multilayers (ML) is reported to reduce significantly the formation temperature of FePt hard magnetic thin films. The transformation mechanisms of [Fe 1.38 nm/Pt 2.24 nm]50 ML, prepared by magnetron sputtering, is investigated in the present communication by high temperature X-ray reflectivity using synchrotron radiation. Complete degradation of the ML periodic structure is observed at about 610 K. The variation with annealing temperature of the intensity of the first Bragg peak, the correlated vertical roughness, and the lateral correlation length of the ML show that the ML transform in two stages with a cross-over temperature of about 515 ± 15 K. This behavior cannot be simply explained by the change in the measured interdiffusion coefficient below and above the cross-over temperature, suggesting the formation of FePt nanograins along the interfaces.

Publ.-Id: 15533 - Permalink


Die Nutzung der Hochenergie-Ionenimplantation für die Verbesserung des Schaltverhaltens von Leistungshalbleiter- Bauelementen
von Borany, J.;
Im Vortrag werden die Möglichkeiten zur Verbesserung des Schaltverhaltens von Leistungshalbleiter-Bauelementen mittels einer Ionenbestrahlung vorgestellt. Die grundlegenden physikalischen Effekte und gerätetechnischen Voraussetzungen werden diskutiert und die anwendungsrelevanten Vorteile am Bespiel von schnellen Schaltdioden aufgezeigt.
Keywords: Ion-beam irradiation, Power electronics, Fast Switching Diodes
  • Lecture (others)
    2. Mitteldeutscher Innovationstag, 14.04.2011, Dresden, Deutschland

Publ.-Id: 15532 - Permalink


Superconductivity in quasi-two-dimensional organic charge-transfer salts
Wosnitza, J.;
Since the discovery of the first organic superconductor, more than 30 years ago, these materials revealed many fascinating properties and allowed to study fundamental low-dimensional physics. Besides superconductivity, the organic metals show a wealth of different ground states such as antiferromagnetic, spin-Peierls, spin-density-wave, and charge-density-wave phases. These ground states are accessible by tuning the structure, counter anion, magnetic field, temperature, and pressure. The study of these fertile phase diagrams has led to new theoretical concepts; however, a solid understanding of some of these states still remains a challenge and especially the nature of the superconducting state is a controversially discussed issue since many years. Even the normal metallic phase of these electronically low-dimensional metals reveals unusual properties sometimes not in line with conventional Fermi-liquid theory. Here, a review on selected normal-state and superconducting properties of the layered quasi-two-dimensional organic superconductors will be given. Thereby, the focus will be laid on the superconducting properties of the charge-transfer salts based on bisethylenedithio-tetrathiafulvalene, BEDT-TTF or ET for short, the building block of most of the to-date known organic superconductors. Some basic features of the crystallographic structure, the highly anisotropic electronic properties, and of the superconductivity in the organics will be highlighted. In more detail the recently reported evidence for the existence of a Fulde Ferrell Larkin Ovchinnikov state for exactly aligned in-plane magnetic fields will be presented
  • Invited lecture (Conferences)
    477. Wilhelm und Else Heraeus Seminar, 11.-13.04.2011, Bad Honnef, Deutschland

Publ.-Id: 15531 - Permalink


Spectroscopic study of influence of silica on the stability of actinide(IV) colloids at near-neutral pH
Banerjee, D.; Weiss, S.; Zaenker, H.; Scheinost, A. C.; Hennig, C.;
The migration of tetravalent actinides in natural waters occurs predominantly as sorption complexes at the surface of colloidal particles like clay, but also by the formation of actinide oxyhydroxide colloids (MOn(OH)4-2n•mH2O where M = Th or U [1]). Colloid-facilitated migration of plutonium has also been documented in subsurface groundwater conditions [2]. In a recent study it was observed that the stability of U(IV) and Th(IV) oxyhydroxide colloids is dramatically enhanced by the presence of silica [3]. In this study we investigate the influence of silica on the formation and stability of U and Th colloids at near-neutral pH conditions, which might have important environmental implications due to the uniquitous nature of silica in aquifers and surface waters.
U and Th colloids with varying U/Si and Th/Si ratios were synthesized and characterized using a range of spectroscopic and microscopic techniques. TEM and XRD measurements indicated that the structure of thorium/silica colloids is highly amorphous, which is clearly different from the ordered actinide(IV) oxyhydroxide colloids which are stable at pH < 3 but agglomerate and precipitate at near neutral pH within minutes. Comparison of O 1s X-ray photoelectron spectra (XPS) of actinide(IV)-silica and actinide(IV)-oxyhydroxide colloids revealed that two types of oxygen bonds (oxo and hydroxo) occur in presence of silica, which may explain the high degree of structural disorder. Moreover, the presence of O-Si bonds at near-neutral pH values suggest that silica is able to stabilize such colloids through modification of the structure by replacing the An-O(H)-An bonds of the oxyhydroxide structure with An-O(H)-Si bonds and consequently influencing the surface charge. These observations are consistent with X-ray absorption spectroscopy (XAS) data which demonstrate higher An-Si interaction and lower An-An interaction with increasing silica content in these colloids.

[1] Rothe et al. (2002) Inorg. Chem. 41, 249-258.
[2] Kersting et al. (1999) Nature 397, 56-59.
[3] Dreissig et al. (2011) GCA 75, 352-367.
  • Abstract in refereed journal
    Mineralogical Magazine 75(2011)3, 478-478
  • Lecture (Conference)
    Goldschmidt2011, 14.-19.08.2011, Prague, Czech Republic

Publ.-Id: 15530 - Permalink


Wechselwirkung von wasserlöslichen Calixarenen mit divalenten Kationen (85Sr, 56Co)
Paulik, S.; Mansel, A.; Schnorr, R.; Haupt, S.; Bernhard, G.; Kersting, B.;
Das vom BMBF (Bundesministerium für Bildung und Forschung) geförderte Forschungsprojekt „Multifunktionelle Komplexbildner mit N, O, S-Donorfunktionen für d- und f-Elemente: Synthese, Komplexbildung, Struktur und Transportverhalten“ beschäftigt sich im Teilprojekt II mit der „Steuerung des Migrationsverhaltens von Radionukliden mit Hilfe makrozyklischer, multifunktionaler Chelatliganden“. Die Arbeitspakete Radionukliderzeugung, Radiomarkierung, Komplexbildungs- und Transportstudien in Geosystemen des Teilprojekts II werden in der Abteilung Reaktiver Transport des Instituts für Radiochemie untersucht.

Für die Sicherheitsbewertung von Schadstoffen in Untertagedeponien bestehen teilweise Defizite – insbesondere das Sorptions- und Komplexierungsverhalten von langlebigen radiotoxischen Schwermetallen unter naturnahen Bedingungen bedarf noch genauerer Aufklärung, was auch anhand fehlender Einträge in der RES3T-Datenbank zu sehen ist.[1] Das Sorptions- und Komplexierungsverhalten der Radionuklide wird sowohl durch das Milieu des Wirtsgesteins, als auch durch die Präsenz von anorganischen Komplexbildnern bestimmt.[2]

Für die Trennung von schwach-radioaktivem und hoch-radioaktivem Abfall werden hauptsächlich organische Komplexierungsverbindungen eingesetzt, die durch ihre teilweise hohe Elementselektivität mittels Extraktion oder Ionenaustausch diese Trennung ermöglichen. Für diese Trennung haben sich auch die Stoffgruppe der Calixarene als sehr nützlich erwiesen.[3] Die Calixarene werden nun so modifiziert, dass sie einerseits eine gute Wasserlöslichkeit und andererseits eine selektive Komplexierung von 85Sr bzw. 56Co aufweisen. Somit sollte eine gezielte Steuerung des Transports von Radionukliden mit Hilfe von Calixarenen ermöglicht werden.

Literatur:

[1] RES3T-Datenbank, URL: http://www.hzdr.de/db/res3t.login [13.04.2011] [2] M. Dozol, Pure & Appl. Chem. 1993, 65, 1081-1102. [3] J. F. Dozol, J. Incl. Phenom. Macrocycl. Chem. 2000, 38, 1-22.
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2011, 04.-07.09.2011, Bremen, Deutschland

Publ.-Id: 15529 - Permalink


Magneto-acoustic study of single crystalline UCu0.95Ge
Yasin, S.; Andreev, A. V.; Skourski, Y.; Wosnitza, J.; Zherlitsyn, S.; Zvyagin, A. A.;
We present results of a magneto-acoustic study of UCu0.95Ge. This compound exhibits antiferromagnetic ordering at 48 K and shows a metamagnetic phase transition at 38 T for the magnetic field applied along the c direction, seen as a jump in themagnetization. The sound velocity and sound attenuation demonstrate pronounced anomalies in the vicinity of both magnetic phase transitions proving the important role of magnetoelastic interactions in the physics of this actinide compound.
  • Physical Review B 83(2011), 134401

Publ.-Id: 15528 - Permalink


Novel Phase Transition Probed by Sound Velocity in Quasi-One-Dimensional Ising-Like Antiferromagnet BaCo2V2O8
Yamaguchi, H.; Yasin, S.; Zherlitsyn, S.; Omura, K.; Kimura, S.; Yoshii, S.; Okunishi, K.; He, Z.; Taniyama, T.; Itoh, M.; Hagiwara, M.;
We have performed magnetostriction and ultrasound measurements on the quasi-one-dimensional S ¼ 1=2 Ising-like antiferromagnet BaCo2V2O8 in high magnetic fields of up to 51 T. The magnetostriction shows lattice shrinking along the c-axis, and we interpret it as the lattice distortion caused by exchange striction and Van-Vleck paramagnetism. It is clarified that the field dependence of sound velocity is correlated to the magnetostriction. We observed a pronounced softening in the sound velocity of the longitudinal-acoustic c33 mode and found a novel phase transition.
  • Journal of the Physical Society of Japan 80(2011), 033701

Publ.-Id: 15527 - Permalink


Microstructure of superconducting films fabricated by high-fluence Ga implantation in Si
Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Mücklich, A.; Skorupa, W.; Gobsch, G.; Helm, M.; Wosnitza, J.;
The feasibility of embedding extrinsic superconducting nanolayers in commercial (100) silicon due to Ga precipitation is presented. To be far beyond the solid solubility limit of 0.1 at.% a high Ga fluence of 4x1016cm-2 is introduced in silicon by the ion-implantation technique. This leads to 100 nm thick amorphous silicon layers with a Ga peak concentration of 16 at.%. Subsequent recrystallization and Ga precipitation is initiated via rapid thermal annealing (RTA) for 60 seconds at temperatures of 500 – 800°C. A 30 nm sputter deposited SiO2 cover layer is used to protect the silicon surface during implantation and prevent Ga out-diffusion during annealing. It was shown that optimized annealing conditions (600 – 700°C) lead to superconducting layers with critical temperatures of 7 K and in plane critical fields up to 14 T [1]. Details of the layer microstructure investigations using of RBS/C and TEM as well as depth dependent XPS will be presented. The presented structural investigations reveal poly-crystalline silicon layers and show a strong Ga enrichment at the Si/SiO2 interface. Even if no crystalline Ga clusters were detected it is shown that the superconductivity arises due to a high density of amorphous Ga-rich precipitates at the Si/SiO2 interface. Since all involved processing steps are fully compatible with standard microelectronic technology and high criti-cal current densities of more than 2 kA/cm2 are reached, the proposed material system may implicate a high potential for future microelectronic applications.
[1] Skrotzki R. et al., Appl. Phys. Lett. 97 (2010) 192505
  • Lecture (Conference)
    Workshop Ionen- und Positronenstrahlen, 04.-05.07.2011, Neubiberg, Deutschland

Publ.-Id: 15526 - Permalink


Uranium(VI) Complexation with Lactate and Citrate in Dependence on Temperature (7-65°C)
Steudtner, R.; Schmeide, K.; Bernhard, G.;
After disposal in nuclear waste repositories the chemical and migration behavior of actinides depends on many factors. It is estimated that maximum temperatures in the near field of a repository could reach 300°C in dependence on the waste forms [1] and the host rock [2]. Thus, for the long-term safety assessment, knowledge of the interaction of actinides such as uranium with inorganic and organic ligands at elevated temperatures is required. The amount of organic matter in a repository can be separated in humic substances and in low molecular weight organic substances. A not negligible component of low molecular weight organic substances is the group of carboxylic acid. For example, citric acid is used in nuclear reprocessing [3] and acetic, lactic and formic acid were identified in rock extracts and pore water of Opalinus Clay [4]. Reliable experimental data on the complexation of U(VI) in solution at elevated temperatures are still needed.
Therefore, we studied the U(VI) complexation by lactic acid (pH 3) and citric acid (pH 0-10) in the temperature range from 7 to 65°C. Species distribution and complex formation constants were determined by means of UV-Vis and time-resolved laser-induced fluorescence spectroscopy. In the U(VI) lactate system, we identified the formation of 1:1- and 1:2-complexes. In the presence of citrate, we could characterize five U(VI) complexes in dependence on pH value. The complex formation between U(VI) and these both ligands was found to be endothermic and entropy-driven. The complex stability constants of the U(VI) complexes increase with increasing temperature. This could lead to an increased mobility of U(VI) at higher temperatures.
Keywords: Uranium(VI), Lactate, Citrate, Complexation, higher Temperatures
  • Contribution to proceedings
    Goldschmidt 2011, 14.-19.08.2011, Prag, Czech Republic
    Mineralogical Magazine 75, 1940
  • Poster
    Goldschmidt 2011, 14.-19.08.2011, Prag, Czech Republic

Publ.-Id: 15525 - Permalink


High Efficiency Nanosecond Pulse Amplication Based on Diode-Pumped Cryogenic-Cooled Yb:YAG
Koerner, J.; Hein, J.; Kahle, M.; Liebtrau, H.; Kaluza, M.; Siebold, M.;
An output energy of 1.1 J of amplified nanosecond pulses was obtained by utilizing a diode-pumped Yb:YAG laser amplifier with the crystal cooled to 125 K. An all-mirror relay imaging was implemented to accomplish a low loss multi-pass scheme, where a three dimensional folding compensates the astigmatism of spherical mirrors at non-normal incidence. Without the need of diode-wavelength stabilization a for this type of amplifier record high total diode output to amplifier efficiency of 45 % was achieved.
Keywords: Lasers and laser optics
  • Lecture (Conference)
    Advanced Solid-State Photonics (ASSP), 13.-16.02.2011, Istanbul, Turkey

Publ.-Id: 15524 - Permalink


Broadband, diode-pumped Yb:SiO2 multicomponent glass laser
Roeser, F.; Reichelt, A.; Kroll, F.; Siebold, M.; Schramm, U.; Grimm, S.; Kirchhof, J.; Litzkendorf, D.;
We successfully demonstrated cw lasing of ytterbium-doped silica multicomponent glass bulk material. A slope efficiency of 43% and a tuning range from 1010-1080 nm have been achieved.
Keywords: Lasers, diode-pumped; Lasers, ytterbium; Lasers, tunable; Lasers, solid-state; Laser materials; Rare earth and transition metal solid-state lasers
  • Lecture (Conference)
    Advanced Solid-State Photonics (ASSP), 13.-16.02.2011, Istanbul, Turkey

Publ.-Id: 15523 - Permalink


Analysis of a high-energy, diode-pumped Yb:CaF2 disk laser
Loeser, M.; Siebold, M.; Kroll, F.; Roeser, F.; Koerner, J.; Hein, J.; Schramm, U.;
We present gain measurements and a time-resolved thermal lens analysis of a diode pumped, joule-class Yb:CaF2 disk laser. A thermal lens power of 0.05dpt at a single disk and small-signal gain of 5.2 in a two-disk amplifier were achieved at full pump power.
Keywords: Lasers, diode-pumped; Lasers Ytterbium; Laser amplifiers
  • Lecture (Conference)
    Advanced Solid-State Photonics ASSP, 13.-16.02.2011, Istanbul, Turkey

Publ.-Id: 15522 - Permalink


Adsorption of thallium(I) onto geological materials: Effect of pH and humic matter
Liu, J.; Lippold, H.; Wang, J.; Lippmann-Pipke, J.; Chen, Y. H.;
Thallium (Tl) is a typical toxic heavy metal, with higher toxicity than Hg, Cd, Pb. Anthropogenic sources such as coal combustion or mining/smelting activities generated high enrichments of Tl in some areas. For long-term risk assessments, the mobility in geochemical systems is a topic of major interest. Adsorption onto mineral surfaces can be considerably affected by dissolved humic acids (HAs), which are ubiquitous in natural waters. By using radioactive tracers, we were able to investigate co-adsorption of Tl and HAs at low concentration levels to be considered in real scenarios.
Two natural HAs were extracted from river sediments collected in a contaminated mining area in South China (regions of Guangzhou and Yunfu City). They were radiolabeled by an azo-coupling reaction with 14C-aniline. 204Tl(I) was employed as a radiotracer for Tl(I). The geological materials used in this study were goethite, pyrolusite and a natural sediment sample taken from Yunfu City.
For all these substrates, metal adsorption was found to be promoted with increasing pH since more binding sites are provided by deprotonation of surface hydroxyl groups. In contrast, adsorption of HAs was counteracted with increasing pH, which is explained by increasing electrostatic repulsion as a consequence of deprotonation. As expected, the extent of Tl(I)-HA complexation turned out to be very low, with a slight increase at higher pH.
Based on these data, a combined distribution model (Linear Additive Model) was tested for suitability in predicting the pH-dependent influence of HAs on Tl(I) adsorption. Our experimental results could not be reproduced in this way. In view of the fact that the approach worked well in other studies, criteria for its applicability need to be identified. Selectivities within the multicomponent system of humic material, regarding adsorption as well as complexation, are one possible reason for a failure of the model.
  • Lecture (Conference)
    Goldschmidt 2011, 14.-19.08.2011, Praha, Ceska Republika

Publ.-Id: 15521 - Permalink


Time-of-flight detection of fast neutrons
Bemmerer, D.;
The methods of time of flight detection of fast neutrons are reviewed, with an emphasis on the planned NeuLAND detector at FAIR.
  • Invited lecture (Conferences)
    XLII. Arbeitstreffen "Kernphysik" in Schleching/Obb., 24.02.-03.03.2011, Schleching, Deutschland

Publ.-Id: 15520 - Permalink


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