Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

The ratio of bulk to shear viscosity is expected to exhibit a different behaviour in weakly and in strongly coupled systems. This can be expressed by its dependence on the squared sound velocity. In the high temperature QCD plasma at small running coupling, the viscosity ratio is uniquely determined by a quadratic dependence on the conformality measure, whereas in certain strongly coupled and nearly conformal theories this dependence is linear. Employing an effective kinetic theory of quasiparticle excitations with medium-modified dispersion relation, we analyze the ratio of bulk to shear viscosity of the gluon plasma. We show that in this approach, depending on the temperature, the viscosity ratio exhibits either of these dependencies found by means of weak coupling perturbative or strong coupling holographic techniques. The turning point between the two different dependencies is located around the maximum in the scaled interaction measure.

The production of phi mesons in proton collisions with C, Cu, Ag, and Au targets has been studied via the phi -> K+K- decay at an incident beam energy of 2.83 GeV using the ANKE detector system at COSY. For the first time, the momentum dependence of the nuclear transparency ratio, the in-medium phi width, and the differential cross section for phi meson production at forward angles have been determined for these targets over the momentum range of 0.6 - 1.6 GeV/c. There are indications of a significant momentum dependence in the value of the extracted phi width, which corresponds to an effective phi-N absorption cross section in the range of 14 - 21 mb.

This paper reports results from a study of the reaction pp->pK0\Sigma+ at beam momenta of p_{beam} = 2950, 3059, and 3200 MeV/c (excess energies of \epsilon= 126, 161, and 206 MeV). Total cross sections were determined for all energies; a set of differential cross sections (Dalitz plots; invariant mass spectra of all two-body subsystems; angular distributions of all final state particles; distributions in helicity and Jackson frames) are presented for \epsilon= 161 MeV. The total cross sections are proportional to the volume of available three-body phase-space indicating that the transition matrix element does not change significantly in this range of excess energies. It is concluded from the differential data that the reaction proceeds dominantly via the N(1710)P_{11} and/or N(1720)P_{13} resonance(s); N(1650)S_{11} and \Delta(1600)P_{33} could also contribute.

Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.

The retardation of contaminants in aquifers is mainly determined by chemical reactions occurring at the solid/liquid interface. For a more detailed understanding of the molecular reactions of uranium(VI) at Al-hydroxide surfaces, the surface speciation of the radionuclide on gibbsite was studied in aqueous medium by a combined spectroscopic approach using time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. For the first time, the impact of the surface morphology and of atmospherically derived carbonate on the uranyl surface speciation was systematically investigated under environmentally relevant conditions, namely in the near neutral pH range, at maximum initial U(VI) concentrations of 20 µM, and at different surface loadings. Concordantly, the formation of a monomeric binary inner-sphere surface complex is derived from vibrational spectroscopic and EXAFS data irrespective of the prevailing atmospheric condition and surface loading. In addition, from infrared spectra it was found that U(VI) surface precipitation occurs at a micromolar concentration level after a relatively short contact time in an inert gas atmosphere. However, this is circumvented by lowering the initial U(VI) concentration or in the presence of atmospheric CO₂ due to the formation of ternary uranyl carbonato surface complexes. The ternary complex was identified as a dimeric inner-sphere uranyl surface species containing a bidentately coordinated carbonate ligand. The results of this work might be of relevance for a comprehensive description of the dissemination of uranium in groundwater systems.

The complexation between uranium(VI) and nitrate ions in a hydrophobic ionic liquid (IL), namely [BMI][NO3] (BMI = 1-butyl-3-methylimidazolium+), is investigated by EXAFS spectroscopy. It was performed by dissolution of uranyl nitrate UO2(NO3)2·6H2O or UO2(Tf2N)2 (Tf2N = bis(trifluoromethylsulfonyl) imide (CF3SO2)2N−). The formation of the complex UO2(NO3)4 2− is evidenced.

In the Cadarache von-Karman-Sodium (VKS) dynamo experiment magnetic field excitation is generated by
a turbulent flow of liquid sodium. In the experiment this so called von-Karman-like flow is driven by two
counter-rotating impellers that are located close to the end-caps of a cylindrical vessel.
Despite of extensive numerical and experimental efforts the very nature of the VKS dynamo and its surprising properties still remain unclear. Firstly, dynamo action is obtained only when (at least one of) the flow driving impellers are made of soft iron with a relative permeability around 65. Moreover, and in apparent contradiction with Cowling’s anti-dynamo theorem, the geometric structure of the observed magnetic field is dominated by an axisymmetric field.
Our kinematic simulations of an axisymmetric model of the Cadarache dynamo show a close connection between the exclusive occurrence of dynamo action with soft iron impellers and the axisymmetry of the magnetic field. We observe two distinct classes of axisymmetric eigenmodes, a purely toroidal mode that is amplified by paramagnetic pumping at the fluid-disk interface and a mixed mode consisting of a poloidal and a toroidal contribution that is rather insensitive to the disk permeability. In the limit of large permeability, the purely toroidal mode is close to the onset of dynamo action with a growth-rate that is rather independent of the flow field.
This mode is located near to and in the high permeability disks and becomes the leading mode when the disk permeability exceeds a critical value. However, since in our axisymmetric configuration the purely toroidal mode is decoupled from any poloidal field component no dynamo action can be expected from this mode. The purely toroidal mode and its strong amplification by paramagnetic pumping at the fluid-disks interface can be obtained only by explicitly considering the internal permeability distribution. This mode does not exist in case of highly conducting disks or in simulations that only apply idealized boundary conditions.
The separation into purely toroidal and mixed mode can be overcome e.g. by a non-axisymmetric permeability distribution that resembles an assembly of blades attached to the disks. Such a coupled eigenmode is even more likely to facilitate the occurrence of dynamo action when a further source term like the alpha-effect is considered that is necessary to break the restriction imposed by Cowling’s theorem. The particular coupling mechanism provided by such a non-axisymmetric permeability distribution might give a hint why dynamo action is absent in experiments when the fluid flow is driven by an impeller system composed of soft iron disks and stainless steel blades.

The M1 excitations in the nuclide 90Zr have been studied in a photon-scattering experiment with monoenergetic and linearly-polarized beams from 7 to 11 MeV. More than 40 J^pi = 1+ states have been identified from observed ground-state transitions, revealing the fine structure of the giant M1 resonance with centroid energy of 9 MeV and sum strength of 3.4(3) µ_N^2 . The result for the total M1 strength and its fragmentation are discussed in the framework of three-phonon quasi-particle model.

Radiation therapy by means of protons or heavier ions can improve the performance of radiotherapy for cancer treatment by delivering dose more locally to tumor tissue. Due to the inherent precision of this irradiation modality a dose deposition monitoring is desirable. It has been shown that positron emission tomography (PET) can be used for that by exploiting the decay of positron emitters which arise from nuclear fragmentations of projectile and target nuclei. This monitoring was implemented and successfully applied to the treatment by carbon ions for more than 440 patients at the pilot facility at GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany. However, it comes with inherent drawbacks, e.g. spatial blurring of the reconstructed dose distribution due to unpredictable metabolically driven transport of the positron emitters within the patient.

Alternatively, the imaging of prompt gamma-rays -- photons emitted at time and location of the beam-tissue interaction -- is proposed to estimate dose deposition distributions more precisely and probably in real-time. Determined by their origin, these gamma-ray emission distributions have certain properties, i.e. smoothly extended in the order of a decimeter and a continuous energy spectrum up to 10 MeV.

A Compton camera is a single photon imaging device measuring position and energy deposition according to incoherent scattering (Compton scattering) of a photon, and its trajectory afterwards. Since the scattering angle is related to the photon energy before and after scattering a conical surface can be spanned in patient space which covers all possible source locations of the gamma-ray. This surface of response is the Compton camera equivalent to the well known line of response in PET.

Spanning this surface (which means performing a backprojection and constructing the system matrix) is the major part of the image reconstruction process of Compton camera imaging (CCI) in terms of design and implementation efforts, and computation time. As shown previously, its precision also strongly impacts the quality of the image reconstruction results. Furthermore, in CCI a realistic system matrix (SM) has to take into account the physical and technological characteristics of the camera like limited energy and spatial resolution as well as Compton camera specific features as: (i) the event and image space are of high dimensionality, i.e. due to the energy of the gamma-rays and multi attribute measurements, (ii) the backprojections are surfaces instead of lines (Anger SPECT, PET) and therefore the SM occupancy is high, and (iii) incompletely absorbed photons may lead to incorrect conclusions on the initial gamma energies and scattering angles and subsequently to misarranged backprojections.

These challenges of CCI including their impacts will be discussed. Approaches to overcome them will be proposed and evaluated. This is done by means of measurements using radioactive sources as well as via in-beam tests at the proton beam facility AGOR in at KVI Groningen, Netherlands. Complementary results by means of simulations will be shown.

The NeuLAND detector at the R3B experiment of the future FAIR facility in Darmstadt aims to detect fast neutrons (0.2-1.0 GeV) with high time and spatial resolutions (σt<100 ps, σx,y,z<1 cm).

Here, development work on a possible NeuLAND solution based on the multigap resistive plate chamber (MRPC) technology is presented. In this hypothesis, the final detector consists of 50 consecutive MRPC stacks. Each stack contains a 4 mm thick anode made of iron converter material, with an additional 4mm of converter material between two stacks. The secondary charged particles stemming from hadronic interactions of the high energetic neutrons in the converter will be detected in the MRPC's. A number of prototypes have been developed and built. They have been tested with a beam of single electrons, with picosecond time resolution at the superconducting linac ELBE (Dresden, Germany).

The present prototypes show good time resolution and efficiency. However, much better multihit capability is expected for a fully active cube of 2.5 × 2.5 × 3 m scintillator material, so this is the solution adopted for the NeuLAND detector in the meantime.

kein Abstract verfügbar

Objectives: The overexpression of the epidermal growth factor receptor (EGFR) in tumours underlines the recent interest in EGFR as an attractive target for the development of new cancer imaging agents. EGFR-tyrosine kinase inhibitors (EGFR-TKI) based on the 4-anilinoquinazoline scaffold have been explored as potential probes for EGFR imaging [1, 2]. However up to now, no optimal radiotracer is still available. Herein, we report the synthesis, radiosynthesis (¹²⁵I- and ¹⁸F) and biological evaluation of three novel halogenated 6-substituted 4-anilinoquinazoline based EGFR-TKI as potential biomarkers.
Methods: The halogenated 6-substituted-4-anilinoquinazolines (2a, 2b and 2c) were obtained by reaction of 6-amino-4-anilinoquinazoline (1) with 3-/4-iodobenzoyl and 4-fluorobenzoyl chlorides as depicted in Scheme 1 [3].
Studies to inhibit EGFR autophosphorylation and A431 cellular proliferation were performed by Western blot and MTT colorimetric assays, respectively. ¹²⁵I-radiolabelled anilinoquinazolines, [¹²⁵I]-2a/b were prepared via destannylation of the corresponding tributylstannyl precursors with [¹²⁵I]NaI. Cellular uptake studies were conducted in intact A431 cells. Optimization of the radiosynthesis of the ¹⁸F-radiolabeld anilinoquinazoline [¹⁸F]-2c was attempted by nucleophilic substitution of the trimethylammonium- and nitro-6-substituted 4-anilinoquinazoline precursors using different reaction temperatures and solvents.
Results: The 6-substituted-4-anilinoquinazolines (2a, 2b and 2c) were synthesised in high chemical yield (>90%) and fully characterized. The fluorinated quinazoline 2c with IC₅₀ < 0.1 μM was shown to be the most potent inhibitor of EGFR autophosphorylation. Furthermore the three compounds are potent inhibitors of A431 cell proliferation as demonstrated by IC₅₀ values (0.78µM (2a), 3.37 (2b), 2.43 µM (2c)). The ¹²⁵I-radioiodinated analogues, obtained in high radiochemical purity and specific activity, displayed a relative high celular uptake (>35%) in intact A431 cells. Despite of all attempts the radiofluorinated compound [¹⁸F]-2c was only formed in a modest labeling yield (4%) what, up to now has hampered further radiopharmacological investigation.
Conclusions: Three novel halogenated 4-anilinoquinazoline-based EGFR-TK inhibitors, 2a, 2b and 2c, have been successful prepared and radiolabelled. The in vivo inhibition study of EGFR autophosphorylation and A431 cell proliferation proved that all three compounds show inhibitory properties at the micromolar level. In summary, data from this study suggest that this class of quinazolines derivatives encompasses promising derivatives with the potential to act as EGFR-TKI and should be further explored as biomarkers for SPECT and PET.
Research Support: The authors acknowledge FCT and DAAD for financial support. C. Neto thanks FCT for a Ph.D. grant (SFRH/BD/31319/2006).
References:
[1] Noble MEM. et al., (2004), Science, 303, 5665, 1800-5.
[2] Levitzki A. et al., (2003), Acc Chem Res, 36, 6, 462-9. [3] Hicks JW. et al., Molecules (2010), 15, 11, 8260-78.
[3] Fernandes C. et al., Bioorg Med Chem, (2007), 15, 12, 3974-80.

Prostate stem-cell antigen (PSCA) is a cell-surface antigen expressed in the normal prostate and overexpressed in over 80% of prostate cancer tissues. PSCA overexpression is associated with increased tumor stage, grade, and bone metastasis, as well as androgen independence and higher resistance to treatment. The aim of this work was to prepare and characterize a humanized monoclonal anti PSCA antibody (anti-PSCA mAb) for near infrared fluorescence (NIRF) and PET imaging using a near infrared (NIR) dye Alexa Fluor 750 (AF) and [64Cu]Cu-NOTA as a prerequisite for combination of both imaging methods. We evaluated the imaging potential of the [64Cu]Cu-NOTA-AF-anti-PSCA mAb in human prostate cancer xenograft mouse models by using the androgenindependent recombinant cell line PC3-PSCA as target and the non-transfected cell line as control. anti-PSCA mAb was conjugated with the bifunctional chelator 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA) and Alexa Fluor succinimidyl carboxic acid (Ex 752 nm; Em 776 nm; AF). NOTA-AF-anti-PSCA mAb was labeled with 64Cu within 30 min with high
radiolabeling yield and radiochemical purity. The [64Cu]Cu-NOTA- AF-anti-PSCA mAb showed high accumulation in xenotransplanted prostate carcinomas in mice after 24 hours demonstrated with both small animal PET and NIRF. The comparison of both methods in living animals showed the high signal intensity and accumulation of the probe in tumors; however only PET allowed the quantitative characterization of the probe distribution in vivo. Subsequent whole body cryosectioning of the animals into 40-micrometer sections permitted the direct comparison of the autoradiograms and NIRF images of the tissue cuts. The quantitative comparison of the registered autoradiograms and the NIRF images showed a good correlation of the pixel intensities, however, the different geometric resolution did not allow a pixel vise comparison. The NIRF images showed a higher differentiation than the autoradiograms. This was used to study the stability of the radio- and NIR-label on the mAbs. Dual labeling of antibodies is a promising tool for quantitative evaluation of the long time distribution in animals using also NIRF of cryosections beyond the decay of the radionuclide used.
Acknowledgement: This project was partially supported by FP7 project “GIPIO”, Project Reference: 223057

We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au60 +. The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.

Sunitinib® (SU11248) is a highly potent tyrosine kinase inhibitor targeting vascular endothelial growth factor receptor (VEGFR). Radiolabeled inhibitors of RTKs might be useful tools for monitoring RTKs levels in tumour tissue giving valuable information for anti-angiogenic therapy. We report here the synthesis of a ¹²⁵I-labeled derivative of sunitinib® and its first radiopharmaceutical characterization.
The non-radioactive reference compound 5-iodo-sunitinib 4 was prepared by Knoevenagel condensation of 5-iodo-oxindole with the corresponding substituted 5-formyl-1H-pyrrole. In a competition binding assay against VEGFR-2 a binding constant (K_d) of 16 nM for 4 was found. The ability of 4 to inhibit tyrosine kinase activity was demonstrated on RTK expressing cells suggesting this radiotracer as a useful tool for monitoring VEGFR expression. 5-[¹²⁵I]lodo-sunitinib, [¹²⁵I]-4 was obtained via destannylation of the corresponding tributylstannyl precursor with [¹²⁵I]NaI in the presence of H₂O₂ in high radiochemical yield (>95%) and radiochemical purity (<98%) after HPLC purification. Determination of human plasma protein binding at time intervals of 0; 1; 2; 4 and 24h suggested a low non-specific binding of 5-10%. Preliminary biodistribution studies of [¹²⁵I]-4 in healthy CD-1 mice showed a relatively high uptake in VEGFR-2 rich tissues like kidney and lung followed by rapid washout (9.6 and 9.7; 4.5 and 3.8% ID/g of kidney and lung at 1 and 4 h, respectively).

This paper presents some recent developments on CFD models suitable to simulate free surface flows, which so far represented an unresolved matter for industrial nuclear reactors issues. While the general dynamics of such a large interface should be simulated in a CFD approach all sub-grid scale effects have to be modelled. Depending on choice of the general approach – one-fluid or multi-fluid models different closures are required. The momentum transfer between the phases is usually reflected by a drag model in a two-fluid approach. The drag force depends on the local morphology (free surface or dispersed bubbles/drops) and has to be anisotropic at the free surface. Surface tension has to be considered at wavy surfaces. The situation becomes even more complex if mass transfer occurs at the interface. Three approaches with different detailedness are presented. Examples for CFD simulations for free surface flow using different CFD codes and approaches are discussed.

At the superconducting electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf the compact neutron time-of-flight facility nELBE has been built. There, neutrons in the kinetic energy region from some tens of keV to a few MeV are produced by means of electrons impinging onto a liquid lead target. The emitted neutron spectrum is well suited for measurements of cross sections of fast-neutron nuclear interactions relevant to the transmutation of nuclear waste. To study inelastic neutron scattering a rather unique double-time-of-flight was developed measuring both emitted particles, i.e., the scattered neutron and the de-excitation photon, in coincidence. By this method the inelastic scattering cross section can be measured with a continuous neutron source without the knowledge of the decay scheme of the sample nucleus. Beside inelastic scattering also transmission experiments to measure the total neutron cross section were performed and for the future neutron fission experiments are under preparation.

Superconducting Ga-rich layers in Ge are fabricated by Ga implantation through a thin SiO₂ cover layer. After annealing in a certain temperature window, Ga accumulation at the SiO₂/Ge interface is observed. However, no Ga containing crystalline phases are identified. Thus it is suggested that the volatile Ga is stabilized in an amorphous mixture of all elements available at the interface. Electrical transport measurements reveal p-type metallic conductivity and superconducting transition. The superconducting properties of the samples with high Ga concentration at the interface change dramatically with etching the amorphous surface layer. A critical temperature of 6 K is measured before, whereas after etching it drops below 1 K. Therefore, one can conclude that the superconducting transport is based on two different layers: a Ga-rich amorphous phase at the interface and a heavily Ga-doped Ge layer. Finally, the comparison of the transport properties of Ga-rich Ge with those of Si demonstrates distinct differences between the interface layers and even the deeper lying doped regions.

Recent experiments in the Trident laser facility (Los Alamos National Laboratory) have shown that hollow conical targets with a flat top at the tip can enhance the maximum energy of proton beams created during the interaction of an ultra-intense short laser pulse with the target (Gaillard S A et al 2011 Phys. Plasmas 18 056710). The proton energies that have been seen in these experiments are the highest energies observed so far in laser-driven proton acceleration. This is attributed to a new acceleration mechanism, direct light pressure acceleration of electrons (DLLPA), which increases the number and energy of hot electrons that drive the proton acceleration. This acceleration process of protons due to a two-temperature sheath formed at the flat-top rear side is very robust and produces a large number of protons per shot, similar to what is regularly observed in target normal sheath acceleration (Hatchett S P et al 2000 Phys. Plasmas 7 2076, Maksimchuk A et al 2000 Phys. Rev. Lett. 84 4108, Snavely R A et al 2000 Phys. Rev. Lett. 85 2945) with flat foils. In this paper, we investigate the electron kinetics during DLLPA, showing that they are governed by two mechanisms, both of which lead to continuous electron acceleration along the inner cone wall. Based on our model, we predict the scaling of the hot electron temperature and ion maximum energy with both laser and target geometrical parameters. The scaling of T_e^{DLLPA}=m_e c_0 \frac {a_0^2} {4} with the laser strength parameter a0 leads to an ion energy scaling that surpasses that of some recently proposed acceleration mechanisms such as radiation pressure acceleration (RPA), while in addition the maximum electron energy is found to scale linearly with the length of the cone neck. We find that when optimizing parameters, high proton energies suitable for applications can be reached using compact short-pulse laser systems with pulse durations of only a few tens to hundreds of laser periods.

Die Natur ist ausgesprochen erfinderisch und erfolgreich in der Herstellung und Nutzung nanoskaliger Strukturen. Aus diesem Grund sind in der Nanotechnologie biomolekulare und biologisch erzeugte Strukturen eine interessante Alternative zu technisch erzeugten Nanomaterialien. Im Rahmen des Vortrags werden mikrobiologische Forschungsarbeiten im Zusammenhang mit den Hinterlassenschaften des Uranerzbergbaus vorgestellt und an verschiedenen Beispielen ihr hohes Anwendungspotenzial in der Bionanotechnologie aufgezeigt.

The presentation will provide a short description of the Rossendorf Beamline at ESRF. Common results obtained with the University Burgundy will be discussed. The research is related with the formation of polynuclear Actinide(IV) carboxylates.

The magnetorotational instability (MRI) triggers turbulence and enables outward transport of angular momentum in hydrodynamically stable rotating shear flows, e.g., in accretion disks. What laws of differential rotation are susceptible to the destabilization by axial, azimuthal, or helical magnetic field? The answer to this question, which is vital for astrophysical and experimental applications, inevitably leads to the study of spectral and geometrical singularities on the instability threshold. The singularities provide a connection between seemingly discontinuous stability criteria and thus explain several paradoxes in the theory of MRI that were poorly understood since the 1950s.

This paper presents a concept for the CFD-modelling of multiphase flows where both segregated and dispersed flow structures occur simultaneously. Transitions between such morphologies, characterized by different scales of interfacial structures, are investigated and a new multi-field two-fluid strategy for a generalized two-phase flow (GENTOP) is presented. The GENTOP-approach extends the inhomogeneous Multiple Size Group (MUSIG) –model by adding an additional continuous gas phase. In the MUSIG-framework, mass transfers between different bubble size groups due to coalescence and –breakup as well as gas-liquid transfers are described. By modelling an additional mass transfer between the polydispersed and continuous gas phase, transitions between the different gas morphologies can be considered dependent on the flow situation. The continuous gas phase summarizes gas structures which are large enough to be resolved within the computed mesh. Therefore a free surface detection and generalized formulations for interfacial transfer models are introduced. The appearance of one particular gas phase due to mass transfer from another gaseous morphology is demonstrated by means of two demonstration cases: the impingement of a liquid jet on a free surface with an associated bubble entrainment as well as a vertical bubble column showing a wide spectrum of bubble sizes.

To study the role of sulfonate functional groups of humic substances in uranyl(VI) complexation, all-electron density functional calculations and time-resolved laser-induced fluorescence spectroscopy (TRLFS) were applied using small sulfonate ligands as models. A thiolate ligand was explored for comparison. As in an earlier experiment, 4-hydroxy¬benzenesulfonic acid (HBSA) and benzenesulfonic acid (BSA) were examined and compared to methylsulfonic acid (MSA). Structural parameters as well as energetic aspects of uranyl complexes by BSA and HBSA ligands were determined to be rather similar, in contrast to earlier experimental findings. The present TRLFS measurements show complexation of uranyl by both ligands in agreement with the computational results. Overall, the combined computational and experimental results indicate that sulfonate groups play only a minor role in uranyl complexation by sulfonate groups of humic substances because of the rather low stability constants.

INTRODUCTION
In the framework of recycling minor actinides (MA) in fast neutron reactors, americium can be transmuted either by adding it in a small amount to the fuel (e.g. (U,Pu,Am)O2-x) or by using dedicated blanket fuels (e.g. (U1-y,Amy)O2-x). In both strategies, the stoichiometry of the solid solution, commonly described as oxygen to metal atom ratio (O/M), is an important parameter affecting thermal, chemical, and physical properties of the fuel during irradiation. A thorough knowledge of its correlation with oxygen potential (µO2) during manufacturing and especially sintering is then of major interest. To better assess this issue, several thermodynamic descriptions have been developed1,2. Despite their differences, they all involve the valence state of actinide cations (e.g. U, Pu and Am) as an essential parameter. However, experimental data regarding actinide valence remains very limited in the literature.
As illustrated by our recent study of (U,Am)O2±x samples3, coupling X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements allows to determine actinide valence states and to describe the solid solution at both long-range and short range order as a function of oxygen potential. From these data, O/M ratio is eventually calculated using the cation molar fractions determined by XAS. In the present work, we realized a complete XAS characterization on (U,Am)O2±x and (U,Pu,Am)O2-x samples.

MATERIALS AND METHODS
Mixed oxide samples (U1-y,Amy)O2±x (y=0.10, 0.15, 0.20) and (U0.750Pu0.246Am0.004)O2-x were manufactured by conventional powder metallurgy process. By adding a controlled amount of either H2O or Ar/O2 to the furnace atmosphere (Ar/5%H2), oxygen potential were ranging from -520 kJ.mol-1 to -390 kJ.mol-1 during sintering. XAS measurements were performed at the ROssendorf Beam Line (BM20) located at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). For each samples, U, Pu and Am LII,III edges were collected simultaneously in fluorescence and transmission modes at 15K using a helium cryostat.

RESULTS
Concerning americium, a complete reduction of Am4+ to Am3+ is observed for both (U,Am)O2 and (U,Pu,Am)O2 samples whatever the oxygen potential and the Am content. Unexpected results were obtained in the case of (U,Am)O2 solid solutions as, even for the lowest value of µO2 (-520 kJ.mol-1), pentavalent uranium is found, highlighting a charge compensation mechanism as the cause of this partial oxidation of uranium cations3. As a consequence, the expected hypo-stoichiometry was not observed and the solid solution can be described as .
For (U0.750Pu0.246Am0.004)O2-x samples, a radical difference is observed since uranium and americium cations remain respectively tetravalent and trivalent, regardless of the sintering conditions. On the other hand, a partial reduction of Pu4+ to Pu3+ as a function of µO2 is responsible for the continuous decrease in O/M (1.97≤O/M≤1.99). Furthermore, local environments given by EXAFS confirmed that the defects in hypo stoichiometric MOX are only located around Pu cations.
In the presentation, we will detail and compare these results and discuss their consequences on thermodynamical modeling, especially the actual temperature fixing the O/M ratio of the final material.

CONCLUSION
Using XAS measurement on (U,Am)O2±x and (U,Pu,Am)O2-x samples, O/M values were obtained as a function of oxygen potential at high temperature. Comparing these two materials, we evidenced (1) a distinct cation charge mechanism and (2) how the deviation from stoichiometry is supported in the solid solution structure. These results proved useful to better assess the thermodynamical models developed for actinides mixed oxides systems.

REFERENCES
1 M. Osaka et al. (2005) J. Nucl. Mater., 344, 230-234.
2 M. Osaka et al. (2007) J. Alloys Compounds, 428, 355-361.
3 D. Prieur et al. (2011) Inorg. Chem., 50, 12437–12445

Die Erfindung beschreibt eine Anordnung zur Erzeugung ultrakurzer und kurzwelliger Lichtpulse mit Hilfe des Thomson-wave-scattering-Verfahrens, wobei dispersive Elemente zwischen einer Elektronen-, Teilchen- oder Strahlenquelle, die mit einem Lasersystem synchronisiert ist, und einem in einer Richtung fokussierendem optischen Element angeordnet sind und die Verwendung dieser Anordnung zur Überlagerung eines pulsfrontverkippten Lichtpulses hoher Leistung mit einem ultrakurzen Puls relativistischer Elektronen in einem Laserlinienfokus. Durch die Variierung der Laserpulsfrontverkippung erhält man schmalbandige Strahlungspulse hoher Photonenzahl in einem breiten Wellenlängenbereich von EUV bis zu Röntgenwellenlängen und kann zudem die Bandbreite und Kohärenzeigenschaften anpassen. Diese Anordnung kann u. a. bei der EUV-Lithographie, bei der Planung und optimalen Auslegung von Lasersystem und Elektronenquelle, bei der Materialanalyse mittels Phasen-Kontrast-Bildgebung (phase constrast imaging), der Supraleiterforschung verwendet werden. Die vorgeschlagene Anordnung ist kleiner und kostengünstiger als vergleichbare heutige Anordnungen realisierbar.

Hintergrund der Erfindung ist die Ausgestaltung von Reaktorkernen für natriumgekühlte schnelle Reaktoren wobei an verschiedenen Stellen im Reaktorkern feste Metall-Wasserstoff-Verbindungen eingefügt werden. Dadurch reduziert sich der Effekt der Verdampfung des Natriums deutlich und die Sicherheitskoeffizienten verbessern sich signifikant.

Die Erfindung beschreibt ein Herstellungsverfahren von auf Siliziumkarbid basierenden Dünnfilm-Solarzellen. Durch eine impulsartige, intensive Lichtbestrahlung können die Silizium oder Silizium/Germanium auf Silizium Grenzflächen der Substrate kurzzeitig und facettenartig aufgeschmolzen werden. Die dadurch entstehende reliefartige Grenzfläche führt zu einer erhöhten Lichtabsorbtion in der Siliziumkarbidschicht, wodurch die Effizienz der Solarzellen erhöht wird.

Die Erfindung betrifft eine Anordnung zur Verbesserung der Kontrolle während der Strahlentherapie und deren Verwendung. Kern der Erfindung ist die Integration eines kombinierten PET/CT-Scanners in den Bestrahlungsplatz bzw. in unmittelbarer Nähe.

Vorteil dieser Erfindung ist, dass es zu einer Zeitersparnis für den Bestrahlungsablauf kommt, man erhält sicherere Werte für die Bestimmung des Bestrahlungserfolges. Die Positionierung des Patienten muss nur einmal vor Therapiefraktion durchgeführt werden.

Die Erfindung beschreibt eine koaxialen schlitzgekoppelten Resonatordiplexer, basierend auf der Verwendung unterschiedlicher Eigenmoden eines elektromagnetischen Resonators für die Einkopplung von wenigstens zwei Hochfrequenzwellen hoher Leistung und unterschiedlicher Wellenlänge in einen koaxialen mehrmodigen Wellenleiter. Diese Funktion ist zum Beispiel an supraleitenden Hochfrequenzresonatoren zur Beschleunigung von Elementarteilchen von großem Interesse. Ein weiteres mögliches Anwendungsgebiet findet sich in der Radartechnik.

The objective of this project was the study of basic interaction processes in the systems actinide - clay organics - aquifer and actinide - natural clay - clay organics - aquifer. Thus, complexation, redox, sorption and diffusion studies were performed.
To evaluate the influence of nitrogen, phosphorus and sulfur containing functional groups of humic acid (HA) on the complexation of actinides in comparison to carboxylic groups, the Am(III) and U(VI) complexation by model ligands was studied by UV-Vis spectroscopy and TRLFS. The results show that Am(III) is mainly coordinated via carboxylic groups, however, probably stabilized by nitrogen groups. The U(VI) complexation is dominated by carboxylic groups, whereas nitrogen and sulfur containing groups play a minor role. Phosphorus containing groups may contribute to the U(VI) complexation by HA, however, due to their low concentration in HA they play only a subordinate role compared to carboxylic groups. Applying synthetic HA with varying sulfur contents (0 to 6.9 wt.%), the role of sulfur functionalities of HA for the U(VI) complexation and Np(V) reduction was studied. The results have shown that sulfur functionalities can be involved in U(VI) humate complexation and act as redox-active sites in HA for the Np(V) reduction. However, due to the low content of sulfur in natural HA, its influence is less pronounced.
In the presence of carbonate, the U(VI) complexation by HA was studied in the alkaline pH range by means of cryo-TRLFS (-120°C) and ATR FT-IR spectroscopy. The formation of the ternary UO₂(CO₃)₂HA(II)⁴⁻ complex was detected. The complex formation constant was determined with log β_{0.1 M} = 24.57 ± 0.17.
For aqueous U(VI) citrate and oxalate species, luminescence emission properties were determined by cryo-TRLFS and used to determine stability constants. The existing data base could be validated.
The U(VI) complexation by lactate, studied in the temperature range 7 to 65°C, was found to be endothermic and entropy-driven. In contrast, the complex stability constants determined for U(VI) humate complexation at 20 and 40°C are comparable, however, decrease at 60°C.
For aqueous U(IV) citrate, succinate, mandelate and glycolate species stability constants were determined. These ligands, especially citrate, increase solubility and mobility of U(IV) in solution due to complexation.
The U(VI) sorption onto crushed Opalinus Clay (OPA, Mont Terri, Switzerland) was studied in the absence and presence of HA or low molecular weight organic acids, in dependence on temperature and CO₂ presence using OPA pore water as background electrolyte. Distribution coefficients (K_d) were determined for the sorption of U(VI) and HA onto OPA with (0.0222 ± 0.0004) m³/kg and (0.129 ± 0.006) m³/kg, respectively. The U(VI) sorption is not influenced by HA (50 mg/L), however, decreased by low molecular weight organic acids (> 1×10^-5 M), especially by citrate and tartrate. With increasing temperature, the U(VI) sorption increases both in the absence and in the presence of clay organics.
The U(VI) diffusion in compacted OPA is not influenced by HA at 25 and 60°C. Predictions of the U(VI) diffusion show that an increase of the temperature to 60°C does not accelerate the migration of U(VI). With regard to uranium-containing waste, it is concluded that OPA is suitable as host rock for a future nuclear waste repository since OPA has a good retardation potential for U(VI).

The stability of the steady laminar flow driven by the meridional electromagnetic force due to an electric current from a hemispherical electrode to a hemispherical cavity surface is studied using a multi-domain pseudospectral method. The most unstable azimuthal wave number is found as m = 4. Even in a low external magnetic field, the meridional flow in the main toroidal eddy changes its direction from counter-clockwise to clockwise due to the rotation in the azimuthal direction.

We study the production of Σ^±π^∓pK⁺ particle quartets in p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the HADES experiment at GSI. This report evaluates the contribution of resonances like Λ(1405), Σ(1385)⁰, Λ(1520), Δ(1232), N^∗ and K^∗0 to the Σ^±π^∓pK⁺ final state. The resulting simulation model is compared to the experimental data in several angular distributions and it shows itself as suitable to evaluate the acceptance corrections properly.

Accurate numerical prediction of void-fraction profiles in bubbly multiphase-flow relies on suitable closure models for the momentum exchange between liquid and gas phases. We here consider forces acting on the bubbles in the vicinity of a wall. A number of different models for this so-called wall-force have been proposed in the literature and are implemented in widely-used CFD-codes. Simulations using a selection of these models are compared with a set of experimental data on bubbly air-water flow in round pipes of different diameter. Based on the results, recommendations on suitable closures are given.

In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.
Essential for the momentum, mass and energy exchange between the phases is an adequate description of the interfacial area or respectively the bubble size. In a previous study (Krepper and Rzehak, 2011) it was shown that a monodisperse bubble size representation is not sufficient to this end. Therefore, in the present work a population balance approach is used, where bubbles are generated at the wall with a certain size that subsequently evolves due to both condensation / evaporation and coalescence / breakup processes. The results show the potential of this approach which is able to describe the observed bubble size increase after leaving the wall as well as the change of gas volume fraction profile from wall to core peaking with increasing inlet temperature.

kein Abstract verfügbar

We have investigated the Auger decay in xenon and krypton atoms in a terahertz streaking field. Linewidth asymmetries suggest a chirped Auger electron emission which can be understood by field-assisted post-collision interaction.

While life requires water, many organisms, known as anhydrobiotes, can survive in the absence of water for extended periods of time. Although discovered 300 years ago, we know very little about the fascinating phenomenon of anhydrobiosis. In this paper, we summarize our previous findings on the desiccation tolerance of the Caenorhabditis elegans dauer larva. A special emphasis is given to the role of trehalose in protecting membranes against desiccation. We also propose a simple mechanism for this process.

Introduction: The overexpression of epidermal growth factor receptor (EGFR) in tumors underlines the recent interest in EGFR as attractive target for the development of new cancer imaging agents. EGFR-tyrosine kinase inhibitors (EGFR-TKIs) based on the anilinoquinazoline scaffold have been explored as potential probes for EGFR imaging. However, up to now, no optimal radiotracer is available. Herein, we report the synthesis and biological evaluation of three novel halogenated 6-substituted 4-anilinoquinazoline based EGFR-TKIs. Radiosynthesis (¹²⁵I and ¹⁸F) of the corresponding analogues was also performed.
Methods: 6a, 6b and 8 were obtained by reaction of 6-amino-4-anilinoquinazoline (5) with 3-/4-iodobenzoyl and 4-fluorobenzoyl chlorides. Inhibition of EGFR autophosphorylation and A431 cellular proliferation were assessed by Western blot and MTT assays. ¹²⁵I-anilinoquinazolines [¹²⁵I]6a/b were prepared via destannylation of the corresponding tributylstannyl precursors with [¹²⁵I]NaI. Cellular uptake studies were conducted in A431 cells. Optimization of the radiosynthesis of the ¹⁸F-anilinoquinazoline [¹⁸F]8 was attempted by nucleophilic substitution of the trimethylammonium- and nitro-6-substituted 4-anilinoquinazoline precursors.
Results: 6a, 6b and 8 were synthesized in high chemical yield. All of them are inhibitors of EGFR autophosphorylation (0.1bIC50b1 μM) and A431 cell proliferation (IC₅₀ <3.5 μM). [¹²⁵I]6a/b, obtained in high radiochemical purity and specific activity, were highly taken up by A431 cells. Biodistribution profile in mice indicated fast blood clearance and hepatobiliary excretion. Despite all attempts, [¹⁸F]8 was only formed in 4% yield, hampering further biological evaluation.
Conclusions: This study suggests that these quinazoline derivatives can act as EGFR-TKI, warranting further modifications in the chemical structure in order to be explored as potential molecular imaging agents for single photon emission computerized tomography and positron emission tomography.

Recently, the effect of bubbles on the generation and destruction of turbulence in the liquid phase, the so-called Bubble-Induced Turbulence (BIT), is getting more and more attention in the numerical simulation of bubbly flows. There are several theories and models available in the literature, which helps much to understand the inherent characteristics of BIT. However, a systematic validation of these models is still missing. In the current work, popular models considering the additional BIT are implemented into a 1D Test Solver, where the standard k-epsilon model for traditional Shear-Induced Turbulence (SIT) is available. The Test Solver was developed specially for the case of vertical pipe flows by Lucas et al. (2001) and for the purpose of an efficient pre-test of closure models for CFD codes. Its applicability has been tested in an amount of previous work such as Lucas et al. (2005) and (2007).

In the current work, turbulence parameters as well as liquid velocity profiles, which are predicted by the modified k-epsilon model with the consideration of BIT, are compared with experimental data published by different investigators. To exclude other uncertainties, the k-epsilon model is tested firstly for several single-phase cases with different average velocities and pipe diameters. In general, satisfying agreements are achieved in these cases. Then the contribution of BIT and the effect of various models are investigated for mono-dispersed bubbly flows. The flow is assumed to be fully-developed and moreover, the radial gas volume fraction profile is taken from the measurement. The results prove that for test cases with high gas volume fractions (high superficial gas velocity or low superficial liquid velocity) the neglecting of BIT will lead to an obvious underestimation of turbulence parameters. Furthermore, noticeable inconsistency can be observed in the results delivered by different BIT models, which indicates a need for further improvement in this aspect.

In this study, the sorption properties of maghemite (γ-Fe2O3) towards selenium(VI) were studied for the first time both on the macroscopic and the molecular level. Using batch experiments, we found that the retention reaction was very fast. Both increase of pH and ionic strength led to a decrease of selenium(VI) sorption. Electrophoretic mobility measurements showed that selenium(VI) sorption had no significant effect on the isoelectric point of maghemite. These macroscopic results strongly suggested the formation of outer-sphere complexes across the investigated pH range (3.5 – 8.0). At the molecular level, the structure of the sorbed surface species was elucidated in situ using Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) spectroscopy and Extended X-ray Absorption Fine-Structure (EXAFS) spectroscopy. The ATR FT-IR results suggested the formation of outer-sphere complexes showing an unexpected bidentate symmetry, which possibly revealed the lack of accuracy of the actual widely-used classification of inner- and outer-sphere coordination for anionic species. EXAFS results revealed, that in addition to outer-sphere complexes, there is also a small (15%) contribution of an inner-sphere complex in binuclear corner-sharing geometry present.

We report x-ray absorption at Zn and Ni K-edges in 200 keV Ni(2+) ion implanted ZnO/sapphire films. The implantation fluences are 6 x 10(15) and 2 x 10(16) ions/cm(2), corresponding to 2% and 7% Ni in a ZnO matrix. The measurements reveal a marginal substitution of Ni in ZnO in both the films and also rule out the presence of ferromagnetic Ni metal clusters. The M-H and field cooled-zero field cooled measurements performed via SQUID magnetometry show that the films are ferromagnetic at room temperature, and the saturation magnetization of 2% Ni film is appreciably higher than that of 7% Ni film. The origin of ferromagnetism is understood on the basis of the oxygen vacancy mediated bound magnetic polaron model.

The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

no abstract available

Gemäß ihrer Wechselwirkung mit (belebter) Materie sollten Protonenund Ionenstrahlen das Potenzial besitzen, den Erfolg der Strahlentherapie deutlich zu erhöhen. Begründet wird dies durch physikalische Vorteile gegenüber konventionellen Strahlenarten (Photonen, Elektronen), welche i. a. zu einer reduzierten Normalgewebsdosis und zur Möglichkeit der Dosiseskalation im Tumor führen. Im Falle der leichten Ionen kommt zu diesen physikalischen Vorteilen eine Erhöhung der relativen biologischen Wirksamkeit, welche bei adäquater technologischer Umsetzung der Strahlführung (Rasteroder Spotscanning) nahezu auf das Tumorvolumen begrenzt werden kann. Bisher konnten diese physikalisch und biologisch offenkundigen Vorteile der Partikelstrahlen für viele Bestrahlungssituationen nicht in verbesserte Tumorheilung umgesetzt werden.
Dafür sind drei Gründe anzusprechen: (1) Die in der Partikeltherapie angewendeten Behandlungs- und Qualitätssicherungstechniken wurden zum überwiegenden Teil für die konventionellen Therapie an medizinischen Elektronen-Linearbeschleunigern entwickelt und von dort übernommen. Letzteres erscheint nicht adäquat, weil Dosisverteilungen von Partikelstrahlen, im Gegensatz zu Photonenstrahlen, nicht robust gegen Ungenauigkeiten in der gesamten Kette der Strahlentherapie von der CT-Diagnostik bis zur Dosisapplikation sind. (2) Die Zahl der bisher weltweit an technologisch ausgereiften Protonen- oder Ionen-Therapieanlagen in qualitativ hochwertigen klinischen Studien behandelten Patienten ist nach wie vor klein, so dass oftmals statistisch gut gesicherte Therapieergebnisse nicht vorliegen. Generelle Anforderungen der heutigen evidenzbasierten Medizin, insbesondere auch randomisierte Studien, finden nur geringe Berücksichtigung. (3) Die unter (1) und (2) genannten Gründe folgen zu einem großen Teil aus den hohen Investitions- und Betriebskosten für Partikeltherapie-Anlagen, welche jene mit konventioneller Bestrahlungstechnologie um ca. eine Größenordnung übersteigen.
Diese Analyse definiert die medizinischen, strahlenbiologischen und physikalisch-technischen Arbeitsfelder der im Aufbau befindlichen Hochtechnologieplattform am Nationalen Zentrum für Strahlenforschung in der Onkologie - OncoRay, Dresden: (1) Die Entwicklung von Technologien, welche auf die der Partikeltherapie inhärenten Präzision zugeschnitten sind (Bewegungskompensation, Bildführung, dreidimensionale Dosislokalisation, ortsaufgelöste in-vivo Dosimetrie in Echtzeit). (2) Den Einschluss aller Patienten in klinische Studien. (3) Die Entwicklung neuartiger auf der Laser-Teilchenbeschleunigung beruhender Partikeltherapie-Anlagen, die kompakt und kostengünstig sind.
Diese klinischen und wissenschaftlichen Zielstellungen bestimmen die Auslegung der Anlage. Sie wird auf dem Gelände des Universitätsklinikums Carl Gustav Carus Dresden errichtet und in die bestehende Klinik und Poliklinik für Strahlentherapie und Radioonkologie integriert. Sie wird mit einer konventionellen Zyklotron basierten Protonen-Bestrahlungsanlage (Hersteller: Fa. IBA, Louvain-la-Neuve, Belgien) ausgerüstet. Der Protonenstrahl bedient vorerst einen klinischen Bestrahlungsbunker mit isozentrischer Gantry, ausgestattet mit einer universellen Strahlführung für passive und aktive Bestrahlungsfeld-Formierung. Ferner wird für experimentelle Arbeiten der Protonenstrahl in einen Experimentalbunker geführt. Auf dessen Dach wird ein Reinraum für einen Dioden gepumpten Hochintensitäts-Laser der Petawatt-Klasse errichtet. Das Laserlicht wird in den Experimentalbunker geführt, so dass dort sowohl konventionell als auch Laser beschleunigte Protonenstrahlen zur Verfügung stehen werden. Dies wird für die Entwicklung und Validierung dedizierter Strahlführungssysteme, dosimetrischer Messverfahren, Echtzeit-Verifikations- und Qualitätssicherungs-Techniken sowie für die Durchführung strahlenbiologischer Experimente an Laser beschleunigten Protonenstrahlen ein bisher weltweit nicht vorhandenes Umfeld bieten.

Einleitung: Bevor die neue Technologie der Laser Beschleunigung in der Strahlentherapie eingesetzt werden kann, müssen Beschleuniger einen stabilen, steuerbaren Strahl mit genügender Strahlstärke liefern. Ausserdem müssen die entstehenden ultra kurzen, sehr intensiven Strahlpulse auf ihre biologische Wirksamkeit und dosimetrische Erfassung hin untersucht werden.
Methoden: Es wurde ein integriertes Dosimetrie- und Zellbestrahlungssystem (IDOCIS) entwickelt, getestet und umfangreich kalibriert.
Die Kombination verschiedener Dosimeter erlaubt eine präzise Absolutdosimetrie und Strahlüberwachung in Echtzeit. Nach zusätzlicher Modifizierung und Optimierung des 150 TW Lasersystems DRACO (FZD) wurden Zellbestrahlungen mit Laser beschleunigten Protonen durchgeführt.
Ergebnisse: Der Laserbeschleuniger lieferte überWochen einen stabilen und reproduzierbaren Protonenstrahl. Zusammen mit der präzisen dosimetrischen Erfassung mit Hilfe des IDOCIS wurden Dosiseffektkurven bestimmt.
Schlussfolgerung: Vor einem Einsatz Laser beschleunigter Protonen in der Strahlentherapie sind verschiedene Verbesserungen der Lasertechnik und die Durchführung von tierexperimentellen Studien notwendig.
ST 1.4

Modeling of bubble-induced turbulence in dispersed gas-liquid multiphase flow is an important but still unresolved issue. A common approach to its solution is to add source terms to the single phase two-equation turbulence models. We here report a comparison of different models of this type some of which have been used previously in the literature, some of which are new. Special care has been given to the selection of a set of reference data allowing to qualify the validity of the different models. Conclusions towards best practice guidelines for modeling bubbly turbulence are drawn and needs for further reasearch identified.

The development of proton and ion acceleration by ultra-high intensity lasers for cancer therapy promises the realisation of compact and economic particle accelerators that can be integrated in already existing clinics. However, particle acceleration with high intensity lasers leads in comparison to the conventional used acceleration technique to ultra short beam pulses, generated with low pulse frequency, that apply a very high pulse dose. Prior to a clinical application the radiobiological consequences of laser accelerated and therewith ultra short pulsed particle beams have to be investigated.
For this in vitro dose effect curves have been determined, which required a high power laser system with a stable and reproducible acceleration of protons, precise beam monitoring and the technical ability to apply a prescribed dose to a cell sample and to determine the absolute dose received by the cells.
Systematic cell irradiations were performed at the 150 TW Ti:Sapphire laser system DRACO at HZDR that delivered laser pulseswith an energy of 3.5 J, a pulse duration of 30 fs and a frequency of 0.1 Hz. By focusing the laser on a 2 μm thin Ti foil, protons were accelerated from the target rear surface. The generated exponential energy spectrum was limited downwards to 6-20 MeV. An in-house developed integrated dosimetry and cell irradiation system was tested and calibrated, allowing precise dosimetry as well as the exact positioning of each cell sample.
In the present experiment radiosensitive head and neck tumour cells (SKX) were irradiated in a dose range from 0.5-4 Gy with an average pulse dose of 80 mGy and a mean dose rate of 0.5 Gy/min.
Investigated biological endpoints were the clonogenic cell survival and residual DNA-double strand breaks (DSB) 24 h post irradiation via γ-H2AX /p53BP1 assay.
Reference irradiation was performed with continuous, conventional accelerated 7.2 MeV proton beams at the Tandem accelerator at HZDR with a dose rate of 1.1 Gy/min.
The measured dose effect curves show no difference in biological effectiveness between laser accelerated ultra short pulsed and conventional continuous proton beams in clonogenic cell survival and residual DNA DSB.

no abstract available

Abstract not available

no abstract available

The calculation of impinging liquid jets and the associated bubble entrainment is a challenging problem in two-fluid model applications. The various mechanisms behind these phenomena are not well understood and a better appreciation of them is vitally important for industrial and scientific issues. The difficulty of simulation arises from the fact that impinging jets show a mixture of both segregated and dispersed flow regimes. Therefore they demand a multi-fluid simulation to capture larger gas structures with resolved interfaces as well as many small bubbles of different sizes that require an averaged treatment. In order to deal with the complexity of these mechanisms a new CMFD-strategy of a generalized two-phase flow (GENTOP) is presented.
Currently, the GENTOP-concept combines a three-field simulation with the recently developed inhomogeneous Multiple Size Group (MUSIG)-approach. The flow is represented by a liquid phase, a polydispersed gas phase, containing different bubble size groups, and a continuous gas phase. Within the MUSIG-framework, transfers between the different bubble size groups due to bubble coalescence and -breakup are described. By modelling an additional mass transfer between the continuous and the polydispersed gas phase, transitions between different gas morphologies can be considered. The continuous gas phase summarizes all gas structures larger than a certain bubble diameter so that for these structures the gas-liquid interfaces are resolved. In order to blend the gaseous morphology basic ideas of the Algebraic Interfacial Area Density (AIAD)-model are used. Generalized formulations for interfacial area density and drag are introduced considering free surfaces within a multi-fluid simulation. This new concept can provide more detailed information about complex flow situations with higher gas fractions such as the impinging jet being just one particular application.
First results computed by the CFD-code CFX 13.0 are compared to experiments carried out at the HZDR and empirical correlations from literature. The flow field is adapted to the experiments considering inlet velocity of the jet v0=1.7m/s, jet length Lj=10mm and jet diameter d0=16mm as well as the dimensions of the water tank. The computational results show good qualitative agreement with the experiments regarding typical continuous and polydispersed gas structures. The values of air entrainment rate and bubble plume length are determined as quantitative values characterizing the results. Further developments consist of new generalized closure models for bubble coalescence and –breakup processes between continuous and dispersed gas phases.

no abstracts available

Purpose: Before laser particle accelerators can be used for radiation therapy, the supply of stable, reliable and reproducible beams with sufficient particle intensity and useable energy spectra is required. Moreover, consequences on dosimetry as well as on radiobiological effectiveness have to be investigated for laser-accelerated and therefore ultra-shortly pulsed particle beams with very high pulse dose rate.
Method and Materials: In vitro cell irradiations have been established and performed within the German multi-institutional research project onCOOPtics for both laser-accelerated electron and proton beams.
The experimental setups at two lasers, the 10 TW JETI laser for electron and the 150 TW DRACO laser for proton beams, includes a dedicated system for routine cell sample irradiation and precise determination of applied dose. After extensive tuning and optimization of the laser systems and particle beams as well as test and calibration of all dosimetric components, systematic radiobiological experiments with several tumor and normal tissue cell lines have been performed over the last three years measuring dose-effect-curves for cell survival and DNA double strand break induction.
Results: No significant differences in biological effectiveness between laser-accelerated and conventional electron beams were found, apart from one cell line at one end point. The evaluation of the recently finished proton irradiation campaign is in progress.
Conclusion: Laser accelerators can be used for radiobiological experiments, meeting all necessary requirements like homogeneity, stability and precise dose delivery. Nevertheless, before fulfilling the much higher requirements for clinical application, several improvements concerning i.e. proton energy, spectral shaping and patient safety are necessary.

We investigate on the basis of new photon scattering measurements and photoneutron and average neutron resonance capture data how well Lorentzians adjusted to photoneutron data in the giant dipole resonances give a good description of the photon strength also below the neutron threshold. If deformation effects are properly taken into account it is verified that down to about 4 MeV for various nuclei with A £¾ 80 the previously employed differentiation between deformed and non-deformed nuclei is no longer necessary.

The advent of high power laser systems providing pulse rates of a few pulses per minute in the field of laser ion acceleration has brought medical applications such as ion therapy of cancer closer into reach. Although the proton energies are still not high enough for patient treatment, they are sufficient to start first experiments on dosimetry and the biological effectiveness. In contrary to conventional accelerators, the laser ion acceleration delivers proton bunches with a very high charge in short times with a broad energy spectrum. Thus new concepts in dosimetry and irradiation are necessary.
It is evident, that applications with biological material have demanding requirements to the proton energy spectrum and its stability. In this paper we present a robust scheme to provide stable energy spectra for first cell irradiation experiments performed with the Dresden 150 TW laser system DRACO at a dose rate of about 1 Gy/min. A second paper will concentrate on the radiobiological aspects of the experiment and the complex dosimetry issues.
In addition to the production of a reproducible proton spectrum the scheme involves magnetic filtering. Based on a simple non-focusing magnetic dipole equipped with two apertures it makes use of an energy dependent angular asymmetry of the proton spectra and protons with energies above 7 MeV originating from a 2 μm thick Titanium foil are led to the cell sample.
S.D. Kraft, et al., Dose dependent biological damage of tumour cells by laser-accelerated proton beams, New Journal of Physics 12, 085003(2010)

KAERI (Korea Atomic Energy Research Institute) is developing a neutron TOF facility by using KAERI's electron accelerator. KAERI has a superconducting electron accelerator which can produce 17 MeV pulsed electron beams with a pulse width of 20 ps. The pulse current and maximum frequency of the electron accelerator are 20 A and 2 MHz respectively. Fast neutrons can be used for cross-section measurements. A short pulse width can provide a good neutron energy resolution for fast neutrons at relatively short flight lengths. The time resolution related to a neutron source target should be small enough to utilize the short pulse width. We adopted the liquid Pb target which was developed by FDZ (Forschungszentrum Dresden-Rossendorf). The first step of the neutron source development is to simulate a neutron production. MCNPX was used to simulate the neutron production when electron beams irradiate the Pb target. Those simulations were performed by varying beam energies and target sizes to find out optimal variables related to the beam and target. The information of heat deposition in the target was studied by MCNPX since a proper cooling system should be considered to operate the liquid Pb target safely. The thermal-hydraulic analysis was performed based on the result of heat deposition calculation. The study of the detection system is under progress. The design of an experimental hall and a collimator system is also being progressed with the development of the detection system.

no abstract available

Einleitung: Bevor die neue Technologie der Laser Beschleunigung in der Strahlentherapie eingesetzt werden kann, müssen Beschleuniger einen stabilen, steuerbaren Strahl mit genügender Strahlstärke liefern. Ausserdem müssen die entstehenden ultra kurzen, sehr intensiven Strahlpulse auf ihre biologische Wirksamkeit und dosimetrische Erfassung hin untersucht werden.
Methoden: Es wurde ein integriertes Dosimetrie- und Zellbestrahlungssystem (IDOCIS) entwickelt, getestet und umfangreich kalibriert.
Die Kombination verschiedener Dosimeter erlaubt eine präzise Absolutdosimetrie und Strahlüberwachung in Echtzeit. Nach zusätzlicher Modifizierung und Optimierung des 150 TW Lasersystems DRACO (FZD) wurden Zellbestrahlungen mit Laser beschleunigten Protonen durchgeführt.
Ergebnisse: Der Laserbeschleuniger lieferte überWochen einen stabilen und reproduzierbaren Protonenstrahl. Zusammen mit der präzisen dosimetrischen Erfassung mit Hilfe des IDOCIS wurden Dosiseffektkurven bestimmt.
Schlussfolgerung: Vor einem Einsatz Laser beschleunigter Protonen in der Strahlentherapie sind verschiedene Verbesserungen der Lasertechnik und die Durchführung von tierexperimentellen Studien notwendig.

Production cross sections and longitudinal velocity distributions of the projectilelike residues produced in the reactions 112Sn+112Sn and 124Sn+124Sn, both at an incident beam energy of 1A GeV, were measured with the high-resolution magnetic spectrometer, the Fragment Separator of GSI. For both reactions the characteristics of the velocity distributions and nuclide production cross sections were determined for residues with atomic number Z≥10. A comparison of the results of the two reactions is presented.

We have investigated the temperature-dependent, intraexcitonic AC Stark effect that manifests itself in a line splitting of the heavy-hole 1s exciton transition in a GaAs/AlGaAs multi quantum well when the 1s-2p intraexciton transition is driven by intense THz light. The observed wavelength-dependent splitting at Helium temperature can still be distinguished at elevated temperatures up to 200 K. Although the thermal energy exceeds the exciton binding energy by a factor of 1.7, thermal exciton ionization influences the coherent nonlinear effect only indirectly via thermal line broadening. With a threefold transmission change on ultrafast timescales in a region accessible to Peltier-cooling the scheme could be promising for optical modulators.

no abstract available

This thesis addresses the metal nanocluster growth process on prepatterned substrates, the development of atomistic simulation method with respect to an acceleration of the atomistic transition states, and the continuum model of the ion-beam inducing semiconductor surface pattern formation mechanism.
Experimentally, highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO^2 surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well-separated. The first topic is the investigation of this growth process with a continuum theoretical approach to the surface gas condensation as well as an atomistic cluster growth model. The atomistic simulation model is a lattice-based kinetic Monte-Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature.
An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag monomers and ≈1 nm square surface migration ranges of Ag monomers. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns.
The second topic specifies the acceleration scheme utilized in the metallic cluster growth model. Concerning the atomistic movements, a classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multi-dimensional Boolean valued functions in three dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion.
The third topic is the formation of ripple structures on ion bombarded semiconductor surfaces treated in the first topic as the prepatterned substrate of the metallic deposition. This intriguing phenomenon has been known since the 1960's and various theoretical approaches have been explored. These previous models are discussed and a new non-linear model is formulated, based on the local atomic flow and associated density change in the near surface region. Within this framework ripple structures are shown to form without the necessity to invoke surface diffusion or large sputtering as important mechanisms. The model can also be extended to the case where sputtering is important and it is shown that in this case, certain \lq magic' angles can occur at which the ripple patterns are most clearly defined. The results including some analytic solutions of the nonlinear equation of motions are in very good agreement with experimental observation.

Recent progress in generating high-energy (>50 MeV) protons from intense laser–matter interactions (1018–1021Wcm2; refs 1–7) has opened up new areas of research, with applications in radiography8, oncology9, astrophysics10, medical imaging11, high-energy-density physics12–14, and ion-proton beam fast ignition15–19. With the discovery of proton focusing with curved surfaces20,21, rapid advances in these areas will be driven by improved focusing technologies. Here we report on the first investigation of the generation and focusing of a proton beam using a cone-shaped target.We clearly show that the focusing is strongly affected by the electric fields in the beam in both open and enclosed (cone) geometries, bending the trajectories near the axis. Also in the cone geometry, a sheath electric field effectively ‘channels’ the proton beam through the cone tip, substantially improving the beam focusing properties. These results agree well with particle simulations and provide the physics basis for many future applications.

Strahlentherapie zur Krebsbehandlung nutz ionisierende Strahlung um letale Schäden im Tumor zu applizieren. Aufgrund der Art der Energiedeposition von Protonen in Materie kann dies, vergliechen mit konventioneller Therapie mit Photonen oder Elektronen, wesentlich schonender für umliegendes gesundes Gewebe realisiert werden.

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Parallel zu den Experimenten mit laserbeschleunigten Elektronen wurde das 150 TW Lasersystem DRACO (Dresden laser acceleration source) am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) aufgebaut und in Betrieb genommen. Die im Vergleich zum JETI Lasersystem mehr als zehnfach höhere Laserleistung ermöglicht die Beschleunigung von Protonen bis zu einer Maximalenergie von 20 MeV und damit deren strahlenbiologische Charakterisierung in vitro (3,4). Die für die Bestimmung von Dosis-Effekt-Kurven am laserbeschleunigten Protonenstrahl zu erfüllenden Anforderungen, sowie deren Realisierung werden zusammen mit ersten strahlenbiologischen Ergebnissen sowie einem Ausblick auf die weitere Entwicklung im Beitrag präsentiert.

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Motivation
Kompakte Protonen- und Ionenbeschleuniger
Physik der Laserbeschleunigung
Stand von Forschung und Entwicklung

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The structures of the complex of 2,2'-(methylimino)bis(N,N-dioctylacetamide) (MIDOA) with M-(VII)O-4(-) (M = Re and Tc), which were prepared by liquid-liquid solvent extraction, were investigated by using H-1 nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS), and infrared (IR) spectroscopy. The H-1 NMR spectra of the complex of MIDOA with Re(VII)O-4(-) prepared in the organic solution suggest the transfer of a proton from aqueous to organic solution and the formation of the H(+)MIDOA ion. The EXAFS spectra of the complexes of H(+)MIDOA with Re(VII)O-4(-) and Tc(VII)O-4(-) show only the M-O coordination of the aquo complexes, suggesting that the chemical state of M(VII)O-4(-) was unchanged during the extraction process. The results from H-1 NMR and EXAFS, therefore, provide evidence of M(VII)O-4(-)center dot center dot center dot H(+)MIDOA complex formation in the organic solution. The IR spectra of Re(VII)O-4(-)center dot center dot center do!
t H(+)MIDOA and Tc(VII)O-4(-)center dot center dot center dot H(+)MIDOA were analyzed based on the structures and the IR spectra that were calculated at the B3LYP/cc-pVDZ level. Comparison of the observed and calculated IR spectra demonstrates that an intramolecular hydrogen bond is formed in H(+)MIDOA, and the M(VII)O-4(-) ion interacts with H(+)MIDOA through multiple C-H-n center dot center dot center dot O hydrogen bonds.

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1. Physikalische Eigenschaften von Ionenstrahlen
2. Bestrahlungsfeld-Formierung für Ionenstrahlen
3. Kernreaktionen
4. Exotische Strahlen

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1.Die Wechselwirkung ionisierender Strahlung mit (belebter) Materie
2.Die Formen der Strahlentherapie
3.Exkurs in die Radionuklid- und Brachytherapie
4.Teletherapie
4.1. Die Erzeugung von Photonen- und Elektronenstrahlen für
die Strahlentherapie (Elektronen-Linearbeschleuniger)
4.2. Ionenstrahl-Therapie
4.3. Adaptive Strahlentherapie

1. Die Wechselwirkung ionisierender Strahlung mit (belebter) Materie
2. Moderne strahlentherapeutische Techniken
3. Photonen- und Elektronenstrahlen für die Therapie
4. Ionenstrahl-Therapie
5. Adaptive Strahlentherapie

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