Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Approved and published publications
Only approved publications

39109 Publications

Magnetic nanomaterials

Josten, E.; Glavic, A.; Meertens, D.; Wetterskog, E.; Bersgtröm, L.; Brückel, T.; Lindner, J.

Magnetic nanomaterials and their assembly in highly correlated structures are of great interest for future applications as e.g. spin-based data storage media or as material for magnon-spintronics. These systems exhibit unique physical properties like superparamagnetism or symmetry breaking emerging due to their limited size. Individual nanomaterials can be combined as building blocks for so called superstructures where the combination of the different functionalities creates a novel multi-functional system.
Recently, more and more well-defined nanoobjects became available and the advances in measurement methods allow a characterization of these systems. For example, single micrometer-sized three-dimensional magnetic nanoparticle assemblies are available, exhibiting a high degree of structural order close to that of an atomic crystal [1,2]. These systems provide a good basis for the magnetic investigation of nanoparticle superstructures.
The work to be presented focuses on the fundamental structural and magnetic research on such objects and their functionalization. For the investigation we make use of different complementary measurement methods like small angle x-ray and neutron scattering or using microresonators, which provide the necessary sensitivity for the investigation of magnetic properties of a single nano- or micrometer-sized object using ferromagnetic resonance (FMR) [3].

Keywords: nanoparticles; scattering

  • Invited lecture (Conferences)
    JCNS Workshop 2017, 10.-13.10.2017, Tutzing, Deutschland

Publ.-Id: 26349

Highly ordered 3D nanoparticle superlattices investigated by microresonator ferromagnetic resonance

Josten, E.; Narkowicz, R.; Kakay, A.; Meertens, D.; Lennart, B.; Brückel, T.; Fassbender, J.; Lindner, L.

Magnetic nanoparticles and their assembly into highly correlated superstructures are of great interest for future applications, e.g. as material for magnon-spintronic. These systems are not only distinguished by the obvious miniaturization but by their novel physical properties emerging due to their limited size and ordered arrangement. These superstructures are formed from nanometer-sized building blocks ordered like atoms in a crystal, which render them a new class of materials.
Recently, single micrometer-sized three-dimensional magnetic nanoparticle assemblies became available, exhibiting a high degree of structural order close to that of an atomic crystal. These systems provide a good basis for the magnetic investigation of nanoparticle superstructures.

Novel microresonators, provide the necessary sensitivity for the investigation of magnetic properties of nano- and micrometer-sized objects using ferromagnetic resonance (FMR) [1,2]. Due to the much higher filling factor as compared to conventional microwave cavities, they offer several orders of magnitude increased sensitivity gain. A focused ion beam was used to isolate an individual 3D mesocrystal from an ensemble and to transfer it into the microresonator loop (Fig. 1). The FMR study reveals the magnetic anisotropy of the single mesocrystal (Fig. 2), which is corroborated by micromagnetic simulations. It was possible for us to functionalize the system and to set the magnetic easy axis of the mesocrystal via pre-defining their shape.

Keywords: nanoparticle

  • Lecture (Conference)
    INTERMAG Europe 2017, 24.-28.04.2017, Dublin, Irland

Publ.-Id: 26348

Direct measurement of the flow field with GeoPET as the starting point for reactive transport modelling

Kulenkampff, J.; Karimzadeh, L.; Eichelbaum, S.; Lippmann-Pipke, J.; Fischer, C.

We present a RTM workflow which is based on the direct experimental derivation of effective volume and velocity vector field from sequential positron emission tomograms (PET) of the tracer transport in geologic materials. The focus on tracer concentration incorporates unconstrained upscaling from molecular sensitivity to the millimeter scale. This workflow allows minimizing deviations from the experiment and computational expenses.

Keywords: tracer; dynamics of flow; process tomography; reactive transport

  • Lecture (Conference)
    Computational Methods in Water Resources (CMWR), 03.-07.06.2018, Saint Malo, France

Publ.-Id: 26347

Felsenkeller 5 MV underground accelerator: Towards the Holy Grail of Nuclear Astrophysics 12C(α,γ)16O

Bemmerer, D.

Underground ion accelerator laboratories such as the LUNA 0.4 MV accelerator in Italy are indispensable in order to precisely measure charged particle induced nuclear reaction cross sections. The rock overburden attenuates the cosmic ray induced background and enables the measurement of very low interaction rates. The first of the new generation of higher-energy underground accelerators is the Felsenkeller 5 MV machine in Dresden/Germany, under construction and due to open late 2017. The cross sections of several nuclear reactions relevant to nucleosynthesis in a supernova and/or its precursor are not well known, with effects on the nucleosynthetic output of these events. Of these reactions, it is planned to study the 12C(alpha,gamma), 22Ne(alpha,gamma), 40Ca(alpha,gamma), and several other cases at Felsenkeller. The scientific motivation and state of work will be reviewed. It is hoped that the Felsenkeller accelerator will be widely used, including researchers from as many German universities as possible.

Keywords: Underground nuclear astrophysics; Felsenkeller; Helium burning

  • Invited lecture (Conferences)
    Arbeitstreffen Kernphysik, 02.-09.03.2017, Schleching, Deutschland
  • Lecture (Conference)
    Workshop on Nuclear Astrophysics at the Dresden Felsenkeller, 26.-28.06.2017, Dresden, Deutschland
  • Lecture (Conference)
    Nuclear Physics in Astrophysics VIII, 20.06.2017, Catania, Italien
  • Invited lecture (Conferences)
    16th International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics (CGS16), 19.09.2017, Shanghai, China

Publ.-Id: 26346

Molecular encapsulator on the surface of magnetic nanoparticles. Controlled drug release from calcium Ferrite/Cyclodextrin–tethered polymer hybrid

Ramasamy, S.; Reuther, H.; Adyanpuram, M. N. M. S.; Enoch, I. V. M. V.; Potzger, K.; Samathanam, B.

Magnetic nanoparticles (MNPs) are intriguing due to their potency to deliver anti-cancer drugs. This paper presents the inference from our experimental attempts to add merit to the concept of magnetic drug carrier, by designing calcium ferrite nanoparticles and coating them with a biocompatible dextran tethered with a hydrophobic cavity-containing molecule, β-cyclodextrin (β-CD). The size, crystal system, and the morphology of the MNPs are studied. The magnetic properties are explored using vibrating sample magnetometry, SQUID and Mössbauer spectroscopy. The roughly 75 nm MNPs, encapsulated with the β-CD–dextran conjugate allows a slow and sustained in vitro release of the loaded anti-cancer drug, Camptothecin, from the polymer shell. The study of cytotoxicity reveals that the loaded Camptothecin retains its potency as efficient as an effective carrier of the anti-cancer drug. Further, the toxicity of the nanomaterial is tested on an organism which is highly sensitive to toxicity i.e., brine shrimp (Artemia salina). The polymer coating brings down the toxicity of the MNPs.

Keywords: Cyclodextrin; Drug release; Host-guest interface; Magnetic nanoparticles; Surface functionalization

Related publications


Publ.-Id: 26345

Felsenkeller 5 MV underground accelerator: Muon, neutron, 𝛾-ray background and project status

Bemmerer, D.

Motivated by the success of the world's only underground ion accelerator, LUNA 0.4 MV in Italy, a project for a higher-energy underground accelerator is underway in Dresden. A 5\,MV Pelletron accelerator with double charging chains and provision for intensive ^1H^+, ^4He^+, and ^{12}C^+ beams based on external and internal ion sources is currently being installed in the Felsenkeller underground site in Dresden. Civil construction work in Felsenkeller will be completed in August 2017. The nine Felsenkeller tunnels are shielded from cosmic rays by 45\,m rock overburden, attenuating the background in radiation detectors. New data on the muon, neutron, and $\gamma$ background in Felsenkeller will be shown, and used for a discussion on the feasibility of low-background experiments there. The new accelerator will be open for outside users, and its most important experimental capabilities will be summarized.

Keywords: Underground Nuclear Astrophysics; Felsenkeller

  • Lecture (Conference)
    Frühjahrstagung, 30.03.2017, Münster, Deutschland

Publ.-Id: 26344

Recent progress on hydrogen and helium burning at the LUNA 400 kV underground accelerator

Bemmerer, D.

n-beam radiative-capture experiments at low astrophysical energies require experiments in ultra-low background conditions. The Laboratory for Underground Nuclear Astrophysics (LUNA) 0.4\,MV accelerator at INFN Gran Sasso, Italy, is so far the only underground ion accelerator in the world. Recent progress at LUNA regarding the $^{22}$Ne(p,$\gamma$)$^{23}$Na [1,2], $^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg, and $^{17}$O(p,$\alpha$)$^{14}$N [3] reactions will be reviewed. The project for the new, 3.5 MV LUNA-MV accelerator is on track and will be summarized.

Keywords: Nuclear Astrophysics; Hydrogen burning

  • Lecture (Conference)
    Frühjahrstagung, 27.03.2017, Münster, Deutschland

Publ.-Id: 26343

Constraining the 7Be(p,gamma)8B S -factor with the new precise 7Be solar neutrino flux from Borexino

Takács, M. P.; Bemmerer, D.; Junghans, A. R.; Zuber, K.

Among the solar fusion reactions, the rate of the 7Be(p,γ)8B reaction is one of the most difficult to determine rates. In a number of previous experiments, its astrophysical S-factor has been measured at E = 0.1-2.5 MeV center-of-mass energy. However, no experimental data is available below 0.1 MeV. Thus, an extrapolation to solar energies is necessary, resulting in significant uncertainty for the extrapolated S-factor. On the other hand, the measured solar neutrino fluxes are now very precise. Therefore, the problem of the S-factor determination is turned around here: Using the measured 7Be and 8B neutrino fluxes and the Standard Solar Model, the 7Be(p,γ)8B astrophysical S-factor is determined at the solar Gamow peak. In addition, the 3He(α,γ)7Be S-factor is redetermined with a similar method.

Keywords: Nuclear Astrophysics; Solar neutrinos; Nuclear reaction rate; Solar fusion


Publ.-Id: 26342

LUNA: Status and Prospects

Broggini, C.; Bemmerer, D.; Caciolli, A.; Trezzi, D.

The essential ingredients of nuclear astrophysics are the thermonuclear reactions which shape the life and death of stars and which are responsible for the synthesis of the chemical elements in the Universe. Deep underground in the Gran Sasso Laboratory the cross sections of the key reactions responsible for the hydrogen burning in stars have been measured with two accelerators of 50 and 400 kV voltage right down to the energies of astrophysical interest. As a matter of fact, the main advantage of the underground laboratory is the reduction of the background. Such a reduction has allowed, for the first time, to measure relevant cross sections at the Gamow energy. The qualifying features of underground nuclear astrophysics are exhaustively reviewed before discussing the current LUNA program which is mainly devoted to the study of the Big-Bang nucleosynthesis and of the synthesis of the light elements in AGB stars and classical novae. The main results obtained during the study of reactions relevant to the Sun are also reviewed and their influence on our understanding of the properties of the neutrino, of the Sun and of the Universe itself is discussed. Finally, the future of LUNA during the next decade is outlined. It will be mainly focused on the study of the nuclear burning stages after hydrogen burning: helium and carbon burning. All this will be accomplished thanks to a new 3.5 MV accelerator able to deliver high current beams of proton, helium and carbon which will start running under Gran Sasso in 2019. In particular, we will discuss the first phase of the scientific case of the 3.5 MV accelerator focused on the study of 12C+12C and of the two reactions which generate free neutrons inside stars: 13C(α,n)16O and 22Ne(α,n)25Mg.

Keywords: Nuclear Astrophysics; LUNA; Laboratory Underground for Nuclear Astrophysics


Publ.-Id: 26341

Modification of surface properties of solids by femtosecond LIPSS writing: comparative studies on silicon and stainless steel

Varlamova, O.; Hoefner, K.; Ratzke, M.; Reif, J.; Sarker, D.

We investigate the implication of modified surface morphology on wettability of stainless steel (AISI 304) and silicon (100) targets covered by laser-induced periodic surface structures (LIPSS) on extended areas (10 × 10 mm2). Using multiple pulses from a Ti: Sapphire laser (790 nm/100 fs/1 kHz) at a fluence in the range of 0.35–2.1 J/cm2 on a spot of 1.13 × 10− 4 cm2, we scanned the target under the spot to cover a large area. A systematical variation of the irradiation dose by changing the scanning speed and thus dwelling time per spot results in the formation of surface patterns ranging from very regular linear structures with a lateral period of about 500–600 nm to complex patterns of 3D microstructures with several-µm feature size, hierarchically covered by nano-ripples.

Publ.-Id: 26340

Surface modifications of crystal-ion-sliced LiNbO3 thin films by low energy ion irradiations

Bai, X.; Shuai, Y.; Gong, C.; Wu, C.; Luo, W.; Böttger, R.; Zhou, S.; Zhang, W.

Single crystalline 128°Y-cut LiNbO3 thin films with a thickness of 670 nm are fabricated onto Si substrates by means of crystal ion slicing (CIS) technique, adhesive wafer bonding using BCB as the medium layer to alleviate the large thermal coefficient mismatch between LiNbO3 and Si, and the X-ray diffraction pattern indicates the exfoliated thin films have good crystalline quality. The LiNbO3 thin films are modified by low energy Ar+ irradiation, and the surface roughness of the films is decreased from 8.7 nm to 3.4 nm. The sputtering of the Ar+ irradiation is studied by scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy, and the results show that an amorphous layer exists at the surface of the exfoliated film, which can be quickly removed by Ar+ irradiation. A two-stage etching mechanism by Ar+ irradiation is demonstrated, which not only establishes a new non-contact surface polishing method for the CIS-fabricated single crystalline thin films, but also is potentially useful to remove the residue damage layer produced during the CIS process.

Keywords: 128°Y-cut LiNbO3; Single crystalline thin films; Crystal ion slicing; BCB bonding; Ar+ irradiation

Related publications

Publ.-Id: 26339

Die Bestimmung des neutroneninduzierten Spaltquerschnitts von ²⁴²Pu

Kögler, T.

Präzise neutroneninduzierte Spaltquerschnitte von Actinoiden wie den Plutoniumisotopen haben für die Entwicklung zukünftiger Transmutationstechnologien eine große Bedeutung. Die Unsicherheiten des ²⁴²Pu-Spaltquerschnitts im schnellen Bereich des Spektrums betragen derzeit etwa 21 %. Aktuelle Sensitivitätsstudien haben gezeigt, dass nur eine Reduzierung dieser Unsicherheiten auf unter 5 % verlässliche neutronenphysikalische Simulationen zulässt.
Diese anspruchsvolle Aufgabe konnte im Rahmen der vorliegenden Arbeit an der Neutronen-Flugzeitanlage nELBE durchgeführt werden. Dünne, homogene und großflächige Actinoiden-Proben wurden dem Helmholtz-Zentrum Dresden - Rossendorf innerhalb des TRAKULA-Verbundprojektes zur Verfügung gestellt. Eingesetzt in eine neu entwickelte Spaltionisationskammer ermöglichten sie eine akkurate Bestimmung des Spaltquerschnitts relativ zu ²³⁵U. Die Flächendichten der Plutoniumschichten wurden anhand der spontanen Spaltrate von ²⁴²Pu bestimmt. Aufwändige Teilchentransportsimula-
tionen (durchgeführt mit Geant 4, MCNP 6 und FLUKA) wurden genutzt, um die auftretende Neutronenstreuung zu korrigieren. Die gewonnenen Ergebnisse sind im Rahmen ihrer Unsicherheiten in guter Übereinstimmung mit aktuellen Kerndatenevaluierungen. /
Neutron induced fission cross sections of actinides like the Pu-isotopes are of relevance for the development of nuclear transmutation technologies. For ²⁴²Pu, current uncertainties are of around 21 \%. Sensitivity studies show that the total
uncertainty has to be reduced to below 5\% to allow for reliable neutron physics simulations. This challenging task was performed at the neutron time-of-flight facility of the new German National Center for High Power Radiation Sources at HZDR, Dresden. Within the TRAKULA project, thin, large and homogeneous deposits of ²³⁵U and ²⁴²Pu have been produced successfully. Using two consecutively placed fission chambers allowed the determination of the neutron induced fission cross section of ²⁴²Pu relative to ²³⁵U. The areal density of the Plutonium targets was calculated using the measured spontaneous fission rate. Experimental results of the fast neutron induced fission of ²⁴²Pu acquired at nELBE will be presented and compared to recent experiments and evaluated data. Corrections addressing the neutron scattering are discussed by using
results of different neutron transport simulations (Geant4, MCNP6 and FLUKA).

Keywords: Kernspaltung; Wirkungsquerschnitt; schnelle Neutronen; nELBE; Spaltionisationskammern; fission; cross section; fast neutrons; nELBE; fission ionization chambers

Related publications

  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Dr. Arnd R. Junghans
    187 Seiten


Publ.-Id: 26338

Determination of the γ-Ray-Angular Distribution in the Inelastic Scattering of Fast Neutrons on ⁵⁶Fe at nELBE

Dietz, M.

The inelastic neutron scattering reaction on 56Fe was studied at the nELBE time-of-flight facility of HZDR. The incoming neutron energy ranges in the fast neutron spectrum from 100 keV to 10 MeV, where high precision nuclear data are needed. Regarding the recent CIELO evaluation on 56Fe, there is a great interest in improving the knowledge of inelastic scattering angular distribution and increasing the resolution on the few literature data of gamma-ray-angular distribution.
To investigate angular distributions of the emitted gamma-rays, a new detector setup has been installed. It contains five HPGe detectors and five LaBr3 scintillation detectors, which can be set under different angles. For this measurement they were positioned under 30°; 55°; 90°; 125° and 150°, relative to the beam axis. By cyclical measurement with and without the natural Fe-target the intrinsic and the neutron induced background from the setup, except the target, has been subtracted. Corrections for gamma-self-absorption inside the target and extended source effciency were achieved using GEANT4 simulations.
The gamma-ray-angular distribution data measured with the HPGe detectors are compared with data from D. L. Smith, Argonne, 1976. Due to the much better time resolution in LaBr3 detectors high resolution data have been obtained and very interesting resonant structures have been observed for the gamma-ray-angular distribution. In the end, the influence of angular distribution coeffcient a4 is demonstrated by a anisotropy correction factor for experiments, using only one detector under an angle of 125°.

Keywords: nELBE; inelastic neutron scattering; Fe-56; angular distribution

Related publications

  • Master thesis
    TU Dresden, 2016
    Mentor: Arnd R. Junghans


Publ.-Id: 26336

Untersuchungen zur katalytischen Aktivität von Au(III) Verbindungen

Patzschke, M.

In diesem Betrag stellen wir von uns durchgeführte Untersuchungen zur katalytischen Aktivität verschiedener Gold(III) Verbindungen vor.

We present our investigations on the catalytic activity of Au(III) complexes in organic synthesis.

Keywords: ab initio; DFT; computational chemistry; gold chemistry; catalysis

  • Lecture (others)
    Organisch-Chemisches Kolloquium, 12.12.2017, Dresden, Deutschland

Publ.-Id: 26335

Orca for computational actinide chemistry

Patzschke, M.

The program package Orca will be introduced and the use in computational actinide chemistry will be demonstrated.

Keywords: computational chemistry; ab initio; DFT; relativistic effects

  • Invited lecture (Conferences)
    ThUL School 2017, 16.-20.10.2017, Jülich, Deutschland

Publ.-Id: 26334

Computational Spectroscopy

Patzschke, M.

In the contribution we discuss the application of computational chemistry to calculate spectroscopical parameters. We first present the foundations of computational chemistry in a very short form. We will show problems and advantages of DFT. Then we will show how spectroscopical parameters (IR,UV-VIS,NMR) can be calculated and what accuracy can be expected.

Keywords: computational chemistry; DFT; ab initio; actinides; spin-orbit coupling; relativistic effects

  • Invited lecture (Conferences)
    ThUL School 2017, 16.-20.10.2017, Jülich, Deutschland

Publ.-Id: 26333

VVER-1000 RPV lower head model related to late in-vessel phenomena in case of hypothetical severe accident

Gencheva, R.; Grudev, P.; Stefanova, A.; Jobst, M.; Wilhelm, P.

This work discusses the progress in the development of an ASTEC computational model for investigation of molten corium pool behaviour in the lower head of a VVER-1000 reactor in case of a hypothetical accident with core degradation. The model was tested with variation of characterizing parameters which could have an influence on the molten pool behaviour and respectively the response behaviour of the reactor pressure vessel wall. An accident scenario with external cooling of the RPV wall was analysed. The preliminary code results give an estimation of the thermal load on the RPV wall. The sensitivity of the model depending on RPV wall nodalization was investigated. The analysis is performed in support to the numerical investigations realized within the frames of the EU HORIZON 2020 IVMR project (grant agreement number 662157).

Keywords: VVER-1000; severe accident; RPV; lower head; in-vessel

  • Contribution to proceedings
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland, 205-213
  • Lecture (Conference)
    27th Symposium of AER on VVER Reactor Physics and Reactor Safety, 17.-20.10.2017, München, Deutschland

Publ.-Id: 26332

Sorption competition and kinetics of trivalent cations (Eu, Y and Cm) on corundum (α-Al2O3): a batch sorption and TRLFS study

Virtanen, S.; Meriläinen, S.; Eibl, M.; Rabung, T.; Huittinen, N.

In this study we have combined batch sorption and laser spectroscopic investigations to study the sorption of Eu(III) and Cm(III), on the aluminum oxide corundum in single- and multi-metal systems. Experiments were performed using a constant equilibrium time as a function of pH (pH-edges) or at constant pH as a function of equilibrium time (kinetic experiments) in 0.01 M NaClO4 and carbonate free conditions. The objective was to investigate how the sorption behavior of trivalent actinides and lanthanides is affected by the presence of another trivalent metal, Y(III). Our hypothesis was that the addition of higher concentrations of trivalent Y(III) together with a chemically similar trivalent metal, would affect the sorption behavior of that metal. Batch experiments show that when the concentration of competing Y(III) is high enough (1×10-4 M) to occupy most of the surface sites, there is a clear shift in the position of the Eu(III) pH-edge to higher pH. Spectroscopic studies using time-resolved laser fluorescence spectroscopy (TRLFS) clearly confirm sorption competition between the trivalent metals Cm(III) and Y(III), but they also indicate a change in the surface speciation of the trivalent actinide in the presence of the competing metal if the concentration of that competing metal is high enough.

Keywords: Sorption competition; Eu(III); Cm(III); Y(III); TRLFS; corundum; α-Al2O3


Publ.-Id: 26331

The influence of bentonite colloids on neptunium(V) migration in granitic rock

Elo, O.; Hölttä, P.; Huittinen, N.

In Finland, the repository for spent nuclear fuel (SNF) will be excavated at a depth of about 500 meters in the fractured crystalline bedrock in Olkiluoto at Eurajoki implemented by Posiva Oy. The engineered barrier systems (EBS), consisting of a solid fuel capsule, a copper-iron canister and the bentonite buffer should prevent the migration of radionuclides to the biosphere. Montmorillonite, the main mineral of bentonite, is like other aluminosilicates known to retain radionuclides, thus, preventing them from migrating from the repository with the groundwater. Bentonite erosion resulting in the formation of colloids may have a direct impact on the overall performance of the bentonite buffer. The potential relevance of colloids for radionuclide transport is highly dependent on the formation of colloids, the stability and mobility of colloids in different chemical environments, and their interaction with radionuclides [1]. Stable and mobile bentonite colloids can be formed when the glacial meltwater dilutes the groundwater. In these mildly oxic conditions, neptunium(V) will be present in its pentavalent oxidation state as the neptunyl cation (NpO2+), which is rather soluble, highly mobile and poorly adsorbed. Due to the long half-life of Np-237 (2.144·106 y), it will be a major dose contributor after 100,000 years in the SNF repository.
In our previous study, the interaction of Np(V) with Na-montmorillonite purified from MX-80 bentonite and corundum was investigated [2]. Corundum was used as a reference mineral in order to study the aluminol surface sites present on clay minerals, which are regarded as the main adsorption sites for radionuclide attachment [3]. This study aimed at investigating two processes: retardation of Np(V) on the bentonite colloids and granitic rock and the effect of the stable and mobile bentonite colloids on the migration of Np(V) in intact and crushed granitic rock columns.
The materials used in this study were colloids prepared from MX-80 Volclay type bentonite (76% montmorillonite) and Kuru Grey granite. Np(V) sorption on these materials under stagnant conditions was studied as a function of pH, solid concentration, time, and Np(V) concentration. The sorption experiments as a function of pH (3-11), were performed at a constant Np(V) concentration of 10-6 M. The sorption isotherms as a function of Np(V) concentration were conducted at concentration from 10-9 to 5·10-6 M at pH 8, 9, and 10. Solid concentrations were 0.08 g/L and 0.8 g/L for colloids and 40 g/L for granite. The samples were prepared by adding a small aliquot of colloid stock solution or crushed granite, Np-237 tracer and the background electrolyte in 20 ml polypropylene vials. The solution was buffered to the desired pH and after one week equilibration time the solid phase was separated from the liquid by centrifugation and 1 ml aliquots were taken immediately for liquid scintillation counting (Perkin Elmer Tri-Carb 3100 TR or Quantulus liquid scintillation counter). All the batch sorption studies were conducted in 10 mM NaClO4 either in carbonate-free N2-atmosphere (bentonite colloids, 0.08 g/L) or under ambient air conditions (granite and bentonite colloids 0.8 g/L).
The effect of bentonite colloids on Np(V) migration was studied in column experiments, where the column material was either crushed granite (grain size 0.01-0.1 mm) or an intact drill core of the Kuru Grey granite. The crushed granite column diameter was 1.5 cm and the length 15 cm. Drill core columns were constructed from Kuru grey granite cores which were placed inside a tube to form a flow channel (L = 28 cm, w = 4.4 cm) representing an artificial fracture formed by the 0.5 mm gap between the core and the tube [3]. In the experiments, colloid solution was injected into the water flow and the colloid breakthrough was detected by photon correlation spectroscopy (PCS) measurements. The column experiments were performed under ambient air conditions in 10 mM NaClO4 solution using flowrates of 1.5 mL/h, 0.8 mL/h, and 0.3 mL/h. The Np-tracer was injected into the flow, through an injection loop of known volume. The flow conditions in the columns were determined using chloride (36Cl-) as a conservative tracer. The effect of bentonite colloids on Np(V) transport at pH 8 and pH 10 was determined in the absence and presence of colloids (0.7 and 0.9 g/L). The colloid concentration in the collected fractions was determined by PCS and the Np(V) concentration was determined after PCS measurements from the same samples by liquid scintillation counting.
Np(V) adsorption onto MX-80 bentonite colloids and crushed Kuru Grey granite in 10 mM NaClO4 is shown as a function of pH in Figure 1a and as a function of Np concentration in Figure 1b. Sorption onto colloids was rather weak (20%) at pH 8 and higher adsorption occurred only above pH 10. According to the pH-edge results, the sorption isotherms for bentonite colloids are as expected, linear and the slopes are close to one another. The weak sorption of Np(V) on the colloids indicates that Np(V) will be mobilized as a neptunyl cation in solution. Despite the low uptake of Np(V) by the bentonite colloids, the obtained column results show that Np(V) breakthrough from the granite columns is enhanced in the presence of colloids (Figure 2).

  • Poster
    16th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spain

Publ.-Id: 26330

Complexation of trivalent actinides and lanthanides with aqueous phosphates at elevated temperatures (25-80°C)

Huittinen, N.; Jordan, N.; Lösch, H.

The incorporation of actinides in solid lanthanide phosphates crystallizing in the monazite structure has been intensely investigated in the past decades due to the relevance of these monazites as potential ceramic phases for the immobilization of specific high level radioactive waste (HLW) streams [1-3]. In recent years, understanding the incorporation behaviour of trivalent dopants in the LnPO4×nH2O rhabdophane structure, which is the hydrated phosphate precursor in the synthesis of monazites through precipitation routes and a potential secondary mineral controlling actinide solubility in dissolution and re-precipitation reactions of monazite host-phases, has been given more attention [4,5]. Despite the large interest in lanthanide phosphates and the interaction of actinides with these solids, very little data is available on the complexation of lanthanides and actinides with aqueous phosphates, even though these complexation reactions precede any aqueous synthesis of monazite ceramics and are expected to occur in natural waters as well as in the proximity of monazite-containing HLW repositories. It also suffers from an almost systematic absence of independent spectroscopic validation of the stoichiometry of the proposed complexes. Both from the perspective of aqueous rhabdophane synthesis, which is often carried out at elevated temperatures, and heat-generating HLW immobilization in monazites, the lanthanide and actinide complexation reactions with aqueous phosphates under ambient conditions should be complemented with data obtained at higher temperatures.

In the present work, time-resolved laser fluorescence spectroscopy (TRLFS) has been employed to study the phosphate complexation of Eu3+ (5×10-6 M) and Cm3+ (5×10-7 M) as a function of total phosphate concentration (0-1 M ΣPO4) in the temperature regime 25-80°C, using NaClO4 as a background electrolyte. These studies have, in a first step, been conducted in the acidic pH-range (pH = 1) to avoid precipitation of solid Eu or Cm rhabdophane. Both trivalent metal cations form a complex with the anionic H2PO4- species, i.e. EuH2PO42+ and CmH2PO42+. As expected, the complexation reaction occurs at lower total phosphate concentration when increasing the temperature. In addition, our preliminary results show the presence of a second Eu-phosphate species which is tentatively assigned to Eu(H2PO4)2+. The presence of this species will be verified with mass-spectrometric methods.
Temperature-dependent complexation constants for the identified species will be derived from the recorded luminescence emission spectra. These will be recalculated to standard conditions with the van´t Hoff equation and the Specific Ion Interaction Theory. For this, the required ion interaction coefficients have been preliminary determined at 25 °C by varying the ionic strength (0.6 to 3 M).

  • Poster
    16th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spain

Publ.-Id: 26329

Charaterization of actinide(IV) complexes with imine type ligands

Radoske, T.

The progress on the PhD thesis is presented in an oral talk. The results include complexes of tetradentate and hexadentate salen complexes with several actinides in tetravalent state.

Keywords: actinide; salen; complex; thorium; uranium; SC-XRD

  • Lecture (others)
    FENABIUM Projekttreffen, 10.05.2017, Leipzig, Deutschland

Publ.-Id: 26328

European standard on small punch testing of metallic materials

Bruchhausen, M.; Holmström, S.; Altstadt, E.; Dymacek, P.; Jeffs, S.; Lancaster, R.; Lacalle, R.; Matocha, K.; Petzova, J.

Life extension of aging nuclear power plant components requires knowledge of the properties of the service-exposed materials. For instance, in long term service the tensile and creep properties might decline and the ductile-to-brittle transition temperature (DBTT) might shift towards higher temperatures. Monitoring of structural components in nuclear power plants receives much attention – in particular in the context of lifetime extension of current plants, where the amount of material available for destructive testing is limited. Much effort has therefore been invested in the development of miniature testing techniques that allow characterizing structural materials with small amounts of material. The small punch (SP) test is one of the most widely used of these techniques. It has been developed for nuclear applications but its use is spreading to other industries.

Keywords: small punch test; tensile properties; fracture; creep; standardization

  • Contribution to proceedings
    ASME 2017 Pressure Vessels and Piping Conference PVP2017, 16.-20.07.2017, Hawaii, USA
    Proceedings of the ASME 2017 Pressure Vessels and Piping Conference PVP2017
    DOI: 10.1115/PVP2017-65396
    Cited 25 times in Scopus

Publ.-Id: 26327

Selective THz control of magnetic order: new opportunities from superradiant undulator sources

Kovalev, S.; Wang, Z.; Deinert, J.; Awari, N.; Chen, M.; Green, B.; Germanskiy, S.; de Oliveira, T. V. A. G.; Lee, J. S.; Deac, A.; Turchinovich, D.; Stojanovic, N.; Eisebitt, S.; Radu, I.; Bonetti, S.; Kampfrath, T.; Gensch, M.

Recent advancements of accelerator technology enable the generation of carrier-envelope-phase stable THz pulses with high-fields at adjustably high repetition rates. The appropriate choice of THz radiator allows generating narrow-band, spectrally dense, multicycle THz transients of tunable THz frequency which are ideally suited to selectively excite low-energy excitations such as magnons or phonons. They also allow one to study the frequency dependence of nonresonant THz-field interactions with various order parameters with high dynamic range. In this paper we discuss the future prospects of this new type of THz light sources for studying the coherent control of magnetic order based on recent results.

Keywords: Terahertz; THz control; magnetic order

Related publications


Publ.-Id: 26326

Structure Analysis of Pipe Section Reactor for Pipe-Wall Reaction: A Computational Fluid Dynamics Analysis Approach

Hua, P.; Ma, S.; Ding, W.; Zhang, J.

Pipe section reactor (PSR) is a well-controlled laboratory reactor, which is used to simulate the water quality variations in drinking water distribution systems. However, the hydraulics condition within PSR, which is an essential prerequisite of the water quality studies, still remains unclear. Consequently, the objective of this study is to analyze the hydraulic conditions within PSR by means of a computational fluid dynamics (CFD) approach. The influences of configuration parameters on the hydraulic conditions were tested including propeller diameter, inclined angle of the propeller, distance between the top and inner cylinder, distance between the bottom and inner cylinder, outer cylinder length, baffle length, number of the baffles, rotational speed of the propeller, and inner and outer cylinder diameters. According to the CFD analysis, an optimal structure of PSR was suggested. The data presented here could facilitate the PSR application and improve the simulation of water quality in distribution systems

Keywords: Chlorine decay; Computational fluid dynamics; Pipe section reactor; Structure optimization

Publ.-Id: 26325

Dynamics of a solid particle attachment to a gas bubble in a liquid

Baba, K.; Kotani, Y.; Lecrivain, G.; Yamamoto, R.; Taniguchi, T.

An extended smooth profile method which can deal with particle-dynamics dispersed in a binary fluid is presented. The smooth profile method, originally developed for the simulation of particle transport in a homogeneous fluid, has been successfully combined with a binary fluid model based on Ginzburg-Landau free energy functional. In this approach, the three types of interfaces among particles and two fluids are treated as diffuse interfaces. By using the method, we simulated the attachment and detachment dynamics of a colloidal particle to the surface of a position fixed bubble in a Newtonian fluid under various capillary numbers. It is found that the method can reproduce the three micro-processes associated with the particle attachment ((i) particle approach, (ii) collision, (iii) sliding down on the bubble surface) (Gregory et al, 2016). The present method will make it possible to simulate a froth flotation process, where the capture of hydrophobic particles by rising bubbles is of primary importance.
Keywords: Flotation; Direct Numerical Simulation; Smoothed Profile Method; Immersed Boundary Method

  • Contribution to proceedings
    49th Autumn Meeting of the Society of Chemical Engineers Japan, 20.-22.09.2017, Nagoya University, Japan
    Proceedings of the 49th Autumn Meeting of the Society of Chemical Engineers Japan

Publ.-Id: 26324

On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x

Tyrpekl, V.; Najii, M.; Holzhäuser, M.; Freis, D.; Prieur, D.; Martin, P.; Cremer, B.; Murray-Farthing, M.; Cologna, M.

The electric field has a large effect on the stoichiometry and grain growth of UO2+x during Spark Plasma Sintering. UO2+x is gradually reduced to UO2.00 as a function of sintering temperature and time. A gradient in the oxidation state within the pellets is observed in intermediate conditions. The shape of the gradient depends unequivocally on the direction of the electrical field. The positive surface of the pellet shows a higher oxidation state compared to the negative one. An area with larger grain size is found close to the positive electrode, but not in contact with it. We interpret these findings with the redistribution of defects under an electric field, which affect the stoichiometry of UO2+x and thus the cation diffusivity. The results bear implications for understanding the electric field assisted sintering of UO2 and non-stoichiometric oxides in general.

Keywords: UO2; SPS; XANES

Related publications

Publ.-Id: 26323

Serpent-DYN3D solution of the X2 benchmark: fresh core at HZP

Bilodid, Y.; Fridman, E.

In this work, the hot zero power experiments conducted during the startup of the fresh core of Khmelnitsky-2 NPP are modelled with the Serpent and DYN3D codes.

  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Publ.-Id: 26322

Nuclear data uncertainty quantification for the FREYA fast critical experiments

Fridman, E.; Aufiero, M.

This study summarizes some initial results of nuclear data uncertainty quantification for the FREYA fast critical experiments

  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Publ.-Id: 26321

Modeling of Phenix EOL experiments with Serpent-DYN3D

Nikitin, E.; Fridman, E.

This study presents the Serpent-DYN3D solution of the Phenix EOL benchmark

Keywords: Serpent; DYN3D; SFR; Phenix

  • Lecture (Conference)
    7th International Serpent User Group Meeting, 06.-09.11.2017, Gainesville, FL, USA

Publ.-Id: 26320

Software Concept for Automated Synthesis and Analysis of Resource-Technological Image Data in Scientific Large-Scale Infrastructures

Oertel, W.; Kaever, P.; König, S.; Pour, R.; Renno, A. D.; Rugel, G.; Ziegenrücker, R.; Zierer, R.

The document describes the concept of a software system that synthesises and analyses image data from multidimensional measurement data generated in scientific large-scale infrastructures. The aim is to reach a new level of efficiency, competency, and flexibility by combining highly efficient algorithms with domain-specific knowledge and changeable control structures. Applications are established to investigate samples or mass flows of rock, ore, material, or waste in ion beam analytics respectively recycling facilities.

Related publications

  • Poster
    Workshop 3D-NordOst 2017 20. Anwendungsbezogener Workshop zur Erfassung, Modellierung, Verarbeitung und Auswertung von 3D-Daten, 07.-08.12.2017, Berlin, Deutschland

Publ.-Id: 26319

Geostatistics with compositional data, an overview

Tolosana-Delgado, R.; Mueller, U.; van den Boogaart, K. G.; Pawlowsky-Glahn, V.; Egozcue, J. J.

This paper presents an overview of results for the geostatistical analysis of collocated multivariable data sets, in which the variables form a composition, i.e. where the components inform of the relative important of the parts forming a whole. Such data sets occur most often in mining, hydrogeochemistry and soil science, but the results gathered here are relevant for any regionalised compositional data set. The paper covers the basic definitions, the analysis of the spatial codependence between components, mapping methods of cokriging and cosimulation honoring the compositional constraints, the role of pre- and post-transformations like logratios or multivariate normal score transforms, and block-support upscaling. Proofs of all statements are included in an appendix.


Publ.-Id: 26318

Evaluation of gamma-ray strength functions

Schwengner, R.

Gamma-ray strength functions deduced from nuclear resonance fluorescence (NRF) and from light-ion induced reactions are compared.
Model assumptions in the analysis and differences in the reaction mechanisms and their influence on the results are considered.
New results from NRF experiments at ELBE and from calculations within the shell model are presented.

Keywords: Nuclear resonance fluorescence; light-ion induced reactions; absorption cross sections; dipole strength functions

Related publications

  • Invited lecture (Conferences)
    2nd Research Coordination Meeting of the Coordinated Research Project on Updating the Photonuclear Data Library and generating a Reference Database for Photon Strength Functions, 16.-20.10.2017, Wien, Österreich

Publ.-Id: 26317

Development of novel benzomidazotriazine derivatives for PET imaging of phosphodiesterase 2A (PDE2A)

Ritawidya, R.; Scheunemann, M.; Brust, P.

Ziel: Cyclic nucleotide phoshodiesterases (PDEs) are enzymes that hydrolyze cyclic AMP and cyclic GMP. These ubiquitous second messengers are involved in important cellular processes, such as proliferation, differentiation, migration, survival, and apoptosis. Accordingly PDEs are regarded as therapeutic targets to alter these processes. The expression of PDE2A was found to be related to a variety of tumors (1). Our aim was to synthesis novel PDE2A inhibitors based on the benzoimidazotriazine (BIT) moiety that might be prospective as a lead compound for the development of an F-18 labeled ligand for PDE2A imaging with PET.

Methodik: Three BIT derivatives (BIT1, BIT2, BIT3) were prepared (in 7-10 steps) by introducing different moieties to the C-1 and C-8 position of a BIT intermediate, using two-step Suzuki coupling and bromination. The derivatives were characterized by NMR, MS, and HPLC. Thereafter, the inhibitory potential of the three new compounds towards PDE2A and other PDE subtypes was estimated. Thereafter other derivatives were synthesized using a similar strategy. For radiolabeling, the nitro precursor of BIT1 was prepared employing a four-step synthesis, starting from Miyaura-Borylation instead of Suzuki coupling reaction.

Ergebnisse: BIT derivatives were successfully prepared in 6-8 % overall yield. The affinity and selectivity of BIT1 (82.9 % inhibition of PDE2A3 at 10 nM) was much higher than that of BIT2 and BIT3 (8.52 % and 13.2 % inhibition, respectively). Furthermore, BIT1 provided a promising IC50 of 3.33 nM. The precursor nitro-BIT1 was successfully obtained and is expected to be suitable for one-step radiofluorination via aromatic nucleophilic substitution.

Schlussfolgerungen: It is suggested that BIT1 if radiolabeled with the PET radionuclide F-18 using nitro-BIT1 precursor via aromatic nucleophilic substitution could be a promising PDE2A imaging agent.


(1) S. Schröder et al. Molecules 2016, 21, 650.

  • Poster
    56. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 18.-21.04.2018, Bremen, Deutschland

Publ.-Id: 26316

P1504 - Pockelszellen-Treiberschaltung mit ohmschen, induktiven oder kapazitiven Elementen

Bergmann, T.; Bergmann, F.; Siebold, M.; Löser, M.

Die Treiberschaltung umfasst einen ersten Knoten (J1), welcher mit einem ersten Anschluß der Pockelszelle (CP) verbindbar ist, einem zweiten Knoten (J2), welcher mit einem zweiten Anschluß der Pockelszelle (CP) verbindbar ist, wobei der erste Knoten (J1) über eine erste Schalteinheit (S1) mit einem ersten Potential (+HV) verbindbar ist und der zweite Knoten (J2) über eine zweite Schalteinheit (S2) mit dem ersten Potential (+HV) verbindbar ist, und wobei der erste Knoten (J1) über einen ersten Widerstand (R1) mit einem zweiten Potential (-HV) verbindbar ist und der zweite Knoten (J2) über einen zweiten Widerstand (R2) mit dem zweiten Potential (-HV) verbindbar ist, und wobei der erste Knoten (J1) mit dem zweiten Knoten (J2) über eine Serienschaltung aus einem dritten Widerstand (R3) und einer Induktivität (L1) verbunden ist.

Related publications

  • Patent
    EP3128673 - Offenlegung: 08.02.2017, Nachanmeldungen: US

Publ.-Id: 26315

Advanced inertial position tracking of sensor particles in fluid flows of large industrial containers

Arefin, S.; Reinecke, S.; Hampel, U.

In this paper, a concept for inertial position tracking of flow following sensor particles based on data fusion of inertial sensors is presented. The employed data fusion technique is quaternion based and uses an extended Kalman filter algorithm. A generalized sensor system kinematics has been developed to test the filter algorithm where three data conditions have been considered. Eventually, first simulation results are compared which shows the performance of the filter regarding sensor drift and noise are being discussed.

Keywords: data fusion; Kalman filter; position tracking; sensor particle; flow follower

  • Open Access Logo Contribution to proceedings
    13. Dresdner Sensor-Symposium 2017, 04.-06.12.2017, Dresden, Deutschland
    13. Dresdner Sensor-Symposium 2017, Wunstorf: AMA Service GmbH, 978-3-9816876-5-1, 213-218
    DOI: 10.5162/13dss2017/P2.08
  • Poster
    13. Dresdner Sensor-Symposium, 04.-06.12.2017, Dresden, Deutschland

Publ.-Id: 26312

Noncentrosymmetric Superconductor BeAu

Amon, A.; Svanidze, E.; Cardoso, R.; Wilson, M. N.; Rosner, H.; Bobnar, M.; Schnelle, W.; Lynn, J. W.; Gumeniuk, R.; Hennig, C.; Luke, G. M.; Borrmann, H.; Leithe-Jasper, A.; Grin, Y.

Noncentrosymmetric superconductors have attracted tremendous research interest due to the possibility of mixed spin-singlet and spin-triplet pairing in these materials. In this work, physical properties of a noncentrosymmetric superconductor BeAu were investigated. It was established that BeAu undergoes a structural phase transition from a room-temperature noncentrosymmetric FeSi structure type to a high-temperature CsCl structure type at Ts = 860 K. The room-temperature modification exhibits a superconducting transition below Tc = 3.3 K. The values of lower (Hc1 = 32 Oe) and upper (Hc2 = 335 Oe) critical fields are rather small, confirming that this Type II (κG−L=2.3) weakly coupled (λe−p= 0. ∆ Ce/γnTc≈1.26) superconductor can be well understood within the Bardeen-Cooper-Schrieffer theory. The muon spin relaxation analysis indicates that the time-reversal symmetry is preserved when the superconducting state is entered, supporting conventionalsuperconductivity in BeAu. From the density functional calculations, a considerable contribution of the Be electrons to the superconducting state was established. Moreover, on average, a rather small mass renormalization was found, consistent with the experimental data.

Related publications

Publ.-Id: 26311

FFLO States in Layered Organic Superconductors

Wosnitza, J.

In this short review, the recently found experimental evidence that Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states are realized in quasi-two-dimensional (2D) organic superconductors is reported. At low temperatures and when a high magnetic field is aligned parallel to the conducting organic layers, an upturn of the upper critical field much beyond the Pauli limit is observed, as proven by thermodynamic measurements. Under certain conditions, a second thermodynamic transition emerges inside the FFLO state. Nuclear magnetic resonance (NMR) work has added strong microscopic support for the realization of the FFLO state. The NMR spectra in the FFLO phase can very well be explained by a nonuniform one-dimensionally modulated superconducting order parameter. All These features, appearing only in a very narrow angular region close to parallel-field orientation, give robust evidence for the realization of the FFLO state in organic superconductors.

Publ.-Id: 26310

„Simulation based Life Cycle Assessment of Circular Economy Systems”

Reuter, M. A.

The ISO 14000 norm provides a framework in which a continuous improvement of the environmental performance of a process may be realised. Life Cycle Assessment (LCA) forms an integral part of ISO 14000, however, ist inventory analysis presently often simplifies process routes for metals processing to simple averaging black-boxes that represent whole process. This approach hardly makes it possible to capture the detail of complex interconnected material processing systems as found in metals processing.

  • HSC Chemistry platform may be used to create process flowsheet models and link them to Life Cycle Assessment (LCA) tools.
  • Environmental footprints - which are based on the physical process models – will meet element and energy balances.
  • Process models make it possible to optimize process yields and profits, and the connection to LCA will also optimize environmental footprints.
  • Outotec Silver refining process is used to demonstrate this procedure.
  • Exergy analysis of a power plant will show the thermodynamic basis.
  • Invited lecture (Conferences)
    European Congress and Exhibition on Advanced Materials and Processes - EUROMAT 2017, 17.-22.09.2017, Thessaloniki, Griechenland

Publ.-Id: 26309


Reuter, M. A.; Ballester, M.; van Schaik, A.

Fairphone is a social enterprise since 2013 using the power of business to tackle step by step the social and environmental challenges of the electronics industry.
By manufacturing our own products we are able to work with partners to increase the increase the sustainability in the supply chain at the same time that we grow the demand for such products in the market. Fairphone.

Keywords: Fairphone

  • Invited lecture (Conferences)
    Circular-CRM IdeaCamp on Innovation & Research in the E-waste Recycling Chain: Improving Circular Economy of Critical Raw Materials (CRMs) / IdeaCamp and Workshop, 13.-14.09.2017, Aachen, Deutschland

Publ.-Id: 26308

Pt and Au bimetallic and monometallic nanostructured amperometric sensors for direct detection of hydrogen peroxide: Influences of bimetallic effect and silica support

Liu, W.; Hiekel, K.; Hübner, R.; Sun, H.; Ferancova, A.; Sillanpää, M.

The non-enzyme direct electrochemical sensing of hydrogen peroxide (H2O2) by nanostructured electrodes of Pt- and Au-containing bimetallic or monometallic nanocatalysts including paramecium-like nanostructures of PtAu supported on silica nanorods, Pt and Au nanoparticles supported on silica nanorods, and the non-supported Pt and Au nanoparticles (NPs) is reported. The nanocatalysts modified electrodes were fabricated by simple self-assembling on 3-aminopropyl-trimethoxysilane (APTMS) modified glassy carbon. The cyclic voltammetric and amperometric results showed that PtAu supported on silica nanorods has superior performance over the corresponding monometallic counterparts, with a broad linear range from 5.0 µM to 72000 µM for H2O2, a detection limit of 2.6 µM, a sensitivity of 46.7 µA mM-1cm-2 at a lower working potential of -0.20 V vs SCE, and has good stability and reproducibility. In addition, a systematic test showed that the non-supported Pt NPs sensor has a surprisingly high performance, even better than the paramecium-like nanostructure of PtAu supported on silica nanorods, where the existence of silica nanorod templates in the nanocatalysts retards the electrocatalytic reduction/oxidation of H2O2. Among the nanocatalysts tested in this work, the Pt NPs sensor showed fastest response within 3 s, a broad linear response from 5 µM to 58000 µM, a detection limit of 4.2 µM, and the highest sensitivity of 110.3 µA mM-1cm-2 at the lowest working potential of -0.08 V vs SCE. Notably, the performance of the Pt NPs sensor is also among the best Pt-containing monometallic or bimetallic nanostructured electrochemical sensors toward H2O2 reported so far. This work shows a simple method to fabricate H2O2 electrochemical sensors of high performance and indicates the importance of considering not only bimetallic effects but also the influences of the nanostructure of nanocatalysts on the electrocatalytic performance and electrochemical sensing property.

Keywords: Platinum; Bimetallic effect; Support material; Electrocatalyst; Amperometric sensor; Hydrogen peroxide

Related publications

  • Sensors and Actuators B 255(2018), 1325-1334

Publ.-Id: 26307

Fast neutron measurements at the nELBE time-of-flight facility

Junghans, A. R.; Beyer, R.; Grosse, E.; Hannaske, R.; Kögler, T.; Massarczyk, R.; Schwengner, R.; Wagner, A.

The compact neutron-time-of-flight facility nELBE at the superconducting electron accelerator ELBE of Helmholtz-Zentrum Dresden-Rossendorf has been rebuilt. A new enlarged experimental hall with a flight path of up to 10 m is available for neutron time-of-flight experiments in the fast energy range from about 50 keV to 10 MeV.
nELBE is intended to deliver nuclear data of fast neutron nuclear interactions e.g. for the transmutation of nuclear waste and improvement of neutron physical simulations of innovative nuclear systems. The experimental programme consists of transmission measurements of neutron total cross sections, elastic and inelastic scattering cross section measurements, and neutron induced fission cross sections. The inelastic scattering to the first few excited states in 56Fe was investigated by measuring the gamma production cross section with an HPGe detector. The neutron induced fission of 242Pu was studied using fast ionisation chambers with large homogeneous actinide deposits.

Keywords: nELBE; neutron time of flight; transmission; total cross section; inelastic scattering; fission

Related publications


Publ.-Id: 26306

Generation of high-avidity, WT1-reactive CD8+ cytotoxic T cell clones with anti-leukemic activity by streptamer technology

Tunger, A.; Wehner, R.; von Bonin, M.; Kühn, D.; Heidenreich, F.; Matko, S.; Nauerth, M.; Rücker-Braun, E.; Dietz, S.; Link, C. S.; Eugster, A.; Odendahl, M.; Busch, D. H.; Tonn, T.; Bonifacio, E.; Germeroth, L.; Schetelig, J.; Bachmann, M. P.; Bornhäuser, M.; Schmitz, M.

Summary: In summary, we demonstrated that the expansion of WT1 peptide-specific CD8+ T cells by peptide-loaded MoDCs followed by streptamer-based selection represents an attractive strategy to significantly enrich such T cells prior to cloning. By using this technology, we generated high-avidity, WT1 peptide-reactive CD8+T cell clones with anti-leukemic activity. This strategy may be particular useful for the generation of CD8+T cell clones from healthy donors, in which blood circulating T cells recognizing tumor-associated antigens are rare or not detectable.

Keywords: WT1; CD8+ cytotoxic T cell clones; streptamer technology

Publ.-Id: 26305

On the estimation of ultimate tensile stress from small punch testing

Altstadt, E.; Houska, M.; Simonovski, I.; Bruchhausen, M.; Holmström, S.; Lacalle, R.

Finite element simulations of the small punch test are performed in order to critically evaluate and improve empirical correlations for the estimation of the ultimate tensile stress from force-deflection and force-displacement curves. For this purpose, generic elastic-plastic material properties are used. A systematic variation of the ultimate tensile stress and total uniform elongation is performed to investigate the effects of these parameters of the uniaxial stress-strain curve on the characteristics of small punch test curves. It is shown, that the maximum force Fm of the small punch test curve is not the appropriate parameter for the estimation of the ultimate tensile stress. Instead, the force Fi at a punch displacement of 1.29 times the specimen thickness (or alternatively at bottom deflection of 1.1 times the specimen thickness) should be used. This force is associated with the onset of plastic instability. A correlation between the force Fi and the ultimate tensile strength is proposed and validated by more than 100 small punch tests of nine different steel heats.

Keywords: small punch test; finite-element analysis; plasticity; hardening; ultimate tensile stress


Publ.-Id: 26303

Exploratory investigation of PSCA-protein expression in primary breast cancer patients reveals a link to HER2/neu overexpression.

Link, T.; Kuithan, F.; Ehninger, A.; Kuhlmann, J. D.; Kramer, M.; Werner, A.; Gatzweiler, A.; Richter, B.; Ehninger, G.; Baretton, G.; Bachmann, M.; Wimberger, P.; Friedrich, K.

Background: Prostate stem cell antigen (PSCA) has been suggested as biomarker and therapeutic target for prostate cancer. Recent advances showed that PSCA is upregulated in other cancer entities, such as bladder or pancreatic cancer. However, the clinical relevance of PSCA-expression in breast cancer patients has not yet been established and is therefore addressed by the current study.
Methods: PSCA-protein expression was assessed in 405 breast cancer patients, using immunohistochemistry (PSCA antibody MB1) and tissue microarrays.
Results: PSCA-expression was detected in 94/405 patients (23%) and correlated with unfavorable histopathological grade (p=0.011) and increased Ki67 proliferation index (p=0.006). We observed a strong positive correlation between PSCA-protein expression and HER2/neu receptor status (p<0.001). PSCA did not provide prognostic information in the analyzed cohort. Interestingly, the distribution of PSCA-expression among triple negative patients was comparable to the total population.
Conclusion: We identified a subgroup of PSCA-positive breast cancer patients, which could be amenable for a PSCA-targeted therapy. Moreover, given that we found a strong positive correlation between PSCA- and HER/neu expression, targeting PSCA may provide an alternative therapeutic option in case of trastuzumab resistance.

Keywords: breast cancer; PSCA; HER2/neu; therapeutic target

Publ.-Id: 26302

Local formation of InAs nanocrystals in Si by masked ion implantation and flash lamp annealing

Rebohle, L.; Wutzler, R.; Prucnal, S.; Hübner, R.; Georgiev, Y. M.; Erbe, A.; Böttger, R.; Glaser, M.; Lugstein, A.; Helm, M.; Skorupa, W.

The integration of high-mobility III-V compound semiconductors emerges as a promising route for Si device technologies to overcome the limits of further down-scaling. In this work, we investigate the possibilities to form InAs nanocrystals in a thin Si layer at laterally defined positions with the help of masked ion beam implantation and flash lamp annealing. In detail, a cladding layer was deposited on a silicon-on-insulator (SOI) wafer and patterned by electron beam lithography in order to serve as an implantation mask. The wafer was subsequently implanted with As and In, followed by flash lamp annealing leading to the formation of InAs nanoparticles in the implanted areas. The structures were investigated by Raman spectroscopy, scanning and transmission electron microscopy as well as energy-dispersive X-ray spectroscopy. Depending on the size of the implantation window, several, one or no nanoparticle is formed. Finally, the perspectives for using this technique for the local modification of Si nanowires are discussed.

Keywords: ion implantation; flash lamp annealing; III-V integration into silicon; nanocrystal; InAs; liquid phase epitaxy

Related publications

Publ.-Id: 26301

Deposition and properties of Fe(Se,Te) thin films on vicinal CaF2 substrates

Bryja, H.; Hühne, R.; Iida, K.; Molatta, S.; Sala, A.; Putti, M.; Schultz, L.; Nielsch, K.; Hänisch, J.

We report on the growth of epitaxial Fe1+δSe0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δSe0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H||ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength.

Publ.-Id: 26300

Acoustic Properties of Crystals with Jahn–Teller Impurities: Elastic Moduli and Relaxation Time. Application to SrF2:Cr2+

Averkiev, N. S.; Bersuker, I. B.; Gudkov, V. V.; Zhevstovskikh, I. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.

A new approach to evaluate the relaxation contribution to the total elastic moduli for crystals with Jahn–Teller (JT) impurities is worked out and applied to the analysis of the experimentally measured ultrasound velocity and attenuation in SrF2:Cr2+. Distinguished from previous work, the background adiabatic contribution to the moduli, important for revealing the impurity relaxation contribution, is taken into account. The temperature dependence of the relaxation time for transitions between the equivalent configurations of the JT centers has been obtained, and the activation energy for the latter in SrF2:Cr2+. as well as the linear vibronic coupling constant have been evaluated.

Publ.-Id: 26299

Mass spectrometry-based identification of a naturally presented receptor tyrosine kinase-like orphan receptor 1-derived epitope recognized by CD8+ cytotoxic T cells

Heidenreich, F.; Rücker-Braun, E.; Walz, J. S.; Eugster, A.; Kühn, D.; Dietz, S.; Nelde, A.; Tunger, A.; Wehner, R.; Link, C. S.; Middeke, J. M.; Stölzel, F.; Tonn, T.; Stevanovic, S.; Rammensee, H. G.; Bonifacio, E.; Bachmann, M.; Zeis, M.; Ehninger, G.; Bornhäuser, M.; Schetelig, J.; Schmitz, M.

Mass spectrometry-based identification of a naturally presented receptor tyrosine kinase-like orphan receptor 1-derived epitope recognized by CD8+ cytotoxic T cells

Publ.-Id: 26298

Isolation of Proteins from Polyacrylamide Gels

Koristka, S.; Arndt, C.; Bergmann, R.; Bachmann, M.

Minute amounts of proteins are required for immunization of mice for the development of antibodies including monoclonal antibodies. Here we describe a rapid procedure for the isolation of proteins from polyacrylamide gels after sodium dodecyl sulfate polyacrylamide gel electrophoresis in sufficient amounts for immunization of animals.

Keywords: Polyacrylamide gels; Isolation of proteins

  • Book chapter
    Kurien B., Scofield R.: Electrophoretic Separation of Proteins. Methods in Molecular Biology, Totowa, NJ, USA: Human Press, 2019, 461-465
    DOI: 10.1007/978-1-4939-8793-1_38

Publ.-Id: 26297

Gel drying methods

Feldmann, A.; Berndt, N.; Bergmann, R.; Bachmann, M.

There are several reasons for drying of polyacrylamide gels after gel electrophoresis. E.g. if autoradiography should be performed from radioactive-labeled proteins. Another reason may be to simply store the gel in the laboratory book. Aside laborious commercial solutions, especially for storage of the dried gel in the lab book the here presented simple and cheap drying protocol may be sufficient.

Keywords: Polyacrylamide gels; Proteins; Gel drying

Publ.-Id: 26296

Silver Staining Techniques of Polyacrylamide Gels

Berndt, N.; Bergmann, R.; Arndt, C.; Koristka, S.; Bachmann, M.

After SDS-polyacrylamide gel electrophoresis the separated proteins have to be visualized by staining in the gel. The same is true after transfer of separated proteins to a blotting membrane in order to verify an efficient transfer and to visualize the amount of protein(s) which remained in the gel. Several different staining techniques exist for staining of proteins in SDS-polyacrylamide gels. The sensitivity of these staining procedures are different, also the expenditure of time and other aspects. Still, silver staining is among the most sensitive and reliable staining.

Publ.-Id: 26295

Native Polyacrylamide Gels

Arndt, C.; Koristka, S.; Feldmann, A.; Bachmann, M.

Proteins can easily be separated by polyacrylamide gel electrophoresis (PAGE) in the presence of a detergent and under (heat-) denaturing and (non- or) reducing conditions. The most commonly used detergent is sodium dodecyl sulfate (SDS). The major function of SDS is to shield the respective charge of the proteins present in the mixture to be analyzed and to provide all proteins with a negative charge. As a consequence, the proteins will be separated according to their molecular weight. Electrophoresis of proteins can also be performed in the absence of SDS. Using such “native” conditions, the charge of each of the proteins, which will depend on the primary amino acid sequence of the protein (isoelectric point) and the pH during electrophoresis, will mainly influence the mobility of the respective protein during electrophoresis. Here we describe a starting protocol for “native” PAGE.

Keywords: “Native” polyacrylamide gels; “Blue native” polyacrylamide gels; Proteins

Publ.-Id: 26294

Coomassie-Brilliant Blue Staining of Polyacrylamide Gels

Arndt, C.; Koristka, S.; Feldmann, A.; Bergmann, R.; Bachmann, M.

Over the past a series of staining procedures for proteins were published. Still, the most commonly used staining dye for proteins is Coomassie-Brilliant Blue. The major reasons are: Coomassie-Brilliant Blue staining is simple, fast and sensitive. As Coomassie-Brilliant Blue is almost insoluble in water a series of procedures including colloidal aqueous procedures were described.

Keywords: Coomassie Brilliant Blue; Polyacrylamide gels; Proteins

Publ.-Id: 26293

Local formation of III-V nanocrystals in Si by ion implantation and flash lamp annealing

Rebohle, L.; Wutzler, R.; Prucnal, S.; Hübner, R.; Georgiev, Y.; Erbe, A.; Böttger, R.; Helm, M.; Skorupa, W.

This presentation gives a short overview of our recent investigations devoted to the formation of III-V nanocrystals in bulk Si, in SOI substrates and at laterally defined positions. The group III and group V elements are incorporated by ion beam implantation, and the formation of III-V nanocrystals is due to liquid phase epitaxy during flash lamp annealing.

Keywords: ion implantation; flash lamp annealing; III-V integration into silicon; nanocrystal; liquid phase epitaxy

Related publications

  • Lecture (Conference)
    42. Treffen der Nutzergruppe Heißprozesse und RTP, 08.11.2017, Itzehoe, Deutschland

Publ.-Id: 26292

Microstructure and charge trapping in in ZrO2- and Si3N4-based superlattice layer systems with Ge nanoparticles

Seidel, S.; Rebohle, L.; Prucnal, S.; Lehninger, D.; Hübner, R.; Klemm, V.; Skorupa, W.; Heitmann, J.

Ge was deposited on silicon as a superlattice with 10 layers of Ge embedded in Si3N4 or ZrO2 matrices via plasma enhanced chemical vapor deposition or RF-sputtering, respectively. Raman spectroscopy, transmission electron microscopy and capacitance-voltage (CV) measurements were performed in order to investigate the structural and electrical properties of the superlattices. It will be shown that, in contrast to furnace annealing, flash lamp annealing of Ge-ZrO2-superlattices leads to crystalline Ge nanoparticles in an amorphous matrix. As revealed by CV measurements, these layers show excellent charge storage capabilities. In comparison, a higher thermal budget is needed to crystallize Ge in case of Si3N4-based superlattices, and no significant charge trapping could be detected during CV measurements.

Keywords: Ge nanocrystals; zirconium oxide; silicon nitride; superlattice; flash lamp annealing

Related publications


Publ.-Id: 26291

Quantification of MRI visibility and artefacts at 3T of liquid fiducial marker in a pancreas tissue mimicking phantom

Schneider, S.; Jølck, R. I.; Troost, E. G. C.; Hoffmann, A. L.


Image-guided radiotherapy (IGRT) of pancreatic ductal adenocarcinoma (PDAC) based on implanted fiducial markers and daily orthogonal kV X-ray imaging or cone-beam computed tomography (CBCT) has been shown to significantly reduce the setup error as compared to bony alignment1. In state-of-the-art IGRT solid gold markers are implanted into the pancreas using endoscopic ultrasonography (EUS), a procedure that is well established and generally well tolerated. However, solid gold markers not only deteriorate image quality in both CT and MRI, but additionally cause significant dose alterations in particle therapy, showing local dose perturbations up to 80% of the prescribed dose. Recently, a new biodegradable liquid marker has been developed, which forms a semisolid gel after injection into soft tissue. This marker may particularly benefit patients with PDAC who are scheduled for particle therapy, because it can be implanted using very thin (≤25 G) needles, its low Z-elemental (non-ferrous and non-magnetic) composition causes minimal proton dose perturbation in soft tissues, its size and visibility on X-ray images, CT and CBCT can be adjusted by controlling the injected volume and compound composition, and its soft-surface adhesiveness may decrease migration behaviour relative to solid markers. So far, the characteristics of the liquid marker on magnetic resonance imaging (MRI) have not been investigated.
It is the aim of the present work to provide a quantitative, pulse sequence-independent assessment of the visibility and artefacts of the new liquid fiducial marker on MRI and compare them against those of two gold markers commonly applied in IGRT of PDAC.
To quantify the propensity of the different markers to generate signal voids and signal shifts on MRI, a spherical gel phantom mimicking the relaxation properties of healthy pancreatic tissue at 3 Tesla was constructed. Different volumes (10 µL, 25 µL, 50 µL and 100 µL) of the liquid marker (BioXmark®, Nanovi Radiotherapy A/S) were casted into the gel as well as four Gold Anchor™ (Naslund Medical AB; 0.28 mm diameter, 10 mm and 20 mm length) and three VisiCoil™ (IBA Dosimetry; 0.35 mm diameter, 5 mm and 10 mm length) markers, implanted in different orientations. MR relaxometry was performed to quantify the size and magnitude of the decrease in the effective transversal relaxation time T2* and water proton density ρ(H) relative to pure water as a measure of potential visibility, and to quantify the size and magnitude of the increase in magnetic field inhomogeneity ΔB0 as a measure of potential signal artefacts. The phantom was scanned with a 3.0 T Philips Ingenuity TF PET/MR scanner using an 8-channel head coil.
The solid fiducial markers showed a direct linear relationship between the potentially visible size and artefact size. The liquid fiducial marker showed a tendency towards a potentially visible size at smaller artefacts. Liquid markers from 25-100 μL generated visible volumes comparable to the visible size of the solid markers. The visible magnitude was the largest for the liquid fiducial marker with volumes of 25μL – 100μL showing no correlation with the magnitude of artefact. The solid markers showed a strong non-linear correlation between magnitude of visibility and artefact. The gold-iron alloy marker induced the strongest artefacts.
The liquid fiducial marker causes signal voids on MRI due to its absence of water hydrogen atoms without strongly affecting the magnetic field in the surrounding tissue. The alteration of the static magnetic field was found to be the main effect leading to the visibility of the solid fiducial markers.
BioXmark® has beneficial MRI properties regarding the trade-off between potential visibility and artefacts compared to the tested solid gold markers that are currently being used for IGRT of PDAC. Contrary to the solid markers, an increase in visibility of BioXmark® was not directly coupled to an increase in artefact. Due to the proton density effect, BioXmark® behaves comparably in all pulse sequences if acquired at similar resolution.

  • Poster
    Joint annual meeting IMSRM-ESMRB 2018, 16.-21.06.2018, Paris, Frankreich

Publ.-Id: 26290

Topological Hall Effect in an Artificial Skyrmion Lattice

Murray, P.; Chen, Z.; Gilbert, D. A.; Zang, J.; Stuckler, T.; Lenz, K.; Maranville, B. B.; Fassbender, J.; Yu, H.; Borchers, J. A.; Liu, K.

Magnetic skyrmions have exciting potential for future device applications in low dissipation information storage [1-3]. While much research has been focused on DMI-stabilized skyrmions in bulk crystals or multilayers, we recently realized Bloch-type artificial skyrmion lattices which are stable at room temperature under zero magnetic field [4], offering a convenient platform for investigating transport characteristics such as the Topological Hall Effect (THE). Here, we report a study of the THE in a different type of planar skyrmion lattice, without any protruding magnetic dots on top.

Keywords: skyrmions; DMI; magnetism; topological hall effect

Related publications

  • Poster
    62nd Annual Conference on Magnetism and Magnetic Materials, MMM 2017, 06.-10.11.2017, Pittsburgh, USA

Publ.-Id: 26289

Synthesis and characterization of tetravalent actinide complexes with benzamidinates

Schöne, S.; März, J.; Kaden, P.

The synthesis and characterization of tetravalent actinide complexes with different amidinates is presented. The synthesized thorium and uranium amidinates were characterized in solution with NMR and UV-Visible spectroscopy and in solid state with SC-XRD and IR spectroscopy. The molecular structures were discussed in detail showing differences between the coordination behavior of different amidinates.

  • Lecture (others)
    FENABIUM Projekttreffen, 10.05.2017, Leipzig, Deutschland

Publ.-Id: 26288

Novel Radiolabeled Bisphosphonates for PET Diagnosis and Endoradiotherapy of Bone Metastases

Pfannkuchen, N.; Meckel, M.; Bergmann, R.; Bachmann, M.; Bal, C.; Sathekge, M.; Mohnike, W.; Baum, R. P.; Rösch, F.

Bone metastases, often a consequence of breast, prostate, and lung carcinomas, are characterized by an increased bone turnover, which can be visualized by positron emission tomography (PET), as well as single-photon emission computed tomography (SPECT). Bisphosphonate complexes of 99mTc are predominantly used as SPECT tracers. In contrast to SPECT, PET offers a higher spatial resolution and, owing to the 68Ge/68Ga generator, an analog to the established 99mTc generator exists. Complexation of Ga(III) requires the use of chelators. Therefore, DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), NOTA (1,4,7-triazacyclododecane-1,4,7-triacetic acid), and their derivatives, are often used. The combination of these macrocyclic chelators and bisphosphonates is currently studied worldwide. The use of DOTA offers the possibility of a therapeutic application by complexing the β-emitter 177Lu. This overview describes the possibility of diagnosing bone metastases using [68Ga]Ga-BPAMD (68Ga-labeled (4-{[bis-(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl)acetic acid) as well as the successful application of [177Lu]Lu-BPAMD for therapy and the development of new diagnostic and therapeutic tools based on this structure. Improvements concerning both the chelator and the bisphosphonate structure are illustrated providing new 68Ga- and 177Lu-labeled bisphosphonates offering improved pharmacological properties.

Keywords: bisphosphonates; bone metastases; diagnosis; therapy; 68Ga; 177Lu

Publ.-Id: 26287

Biological characterization of novel nitroimidazole-peptide conjugates in vitro and in vivo.

Bergmann, R.; Splith, K.; Pietzsch, J.; Bachmann, M.; Neundorf, I.

Recently, we reported on the design of a multimodal peptide conjugate useful as delivery platform for targeting hypoxic cells. A nitroimidazole (2-(2-nitroimidazol-1-yl)acetic acid, NIA) moiety, which is selectively entrapped in hypoxic cells, was coupled to a cell-penetrating peptide serving as the transporter. Furthermore, attachment of a bifunctional linker allowed the introduction of a diagnostic or therapeutic radiometal. However, although selective tumor accumulation could be detected in vivo, a fast renal clearance of the compound was observed. The present study aims to improve the system by using the more proteolytically stable all-d version of the peptide carrier (DsC18), by attaching two NIA moieties instead of one (DsC18(NIA)2 ) to enhance the tumor uptake, and by incorporating the bifunctional chelator NODAGA instead of DOTA (NODAGA-DsC18(NIA)2 ) to optimize labeling chemistry. First, we characterized in vitro the novel all-d peptide compared with its parent l-version. Then, in order to investigate and compare the pharmacological profiles of the peptides, these were radiolabeled with 64 CuII and 68 GaIII , and the biodistribution and kinetics were evaluated in vivo. Our results show the versatility of the d-peptide as cell-penetrating peptide and transporter. However, attaching two NIA groups modified the system in such a way that no selective tumor uptake could be observed compared with the peptide without NIA moieties. Still, this work highlights new pharmacokinetic data on the biodistribution of such compounds in vivo.

Keywords: cell-penetrating peptides; drug delivery; positron emission tomography (PET); proteolytic stability; tumor hypoxia; tumor theranostics

Publ.-Id: 26286

Detection of metal ions using fluorescent gold nanoclusters

Vogel, M.; Matys, S.; Pollmann, K.; Raff, J.

S-layer proteins appear to be suitable for wide variety of different technical applications due to their distinctive physico-chemical properties and their multifunctionality.Since several years the focus has been placed especially on their potential use for biosensor applications. There are many approaches under investigation to develop sensors that are highly specific and sensitive as well as robust, reliable and not expensive. Optical methods currently appear an attractive solution. Colloidal gold nanoparticle suspensions as sensory active systems, for instance, have been the subject of intensive investigations for many years. An additional promising approach is the use of proteins as template structures for the production of highly fluorescent, size-controlled gold nanoclusters. These gold nanoclusters can be synthesized directly at the protein by a simple chemical reaction. We present current investigations on different kind of proteins such as bovine serum albumin, calmodulin, and S-layer protein. In combination with the known S-layer or calmodulin mediated selective and specific binding of ionic analytes, e.g. rare earth elements as surrogates/analogues for intrinsic protein bound Ca2+, a subsequent analyte-induced change in the fluorescence intensity of the gold nanoclusters might be used as sensory system for the detection of such strategic relevant elements.

Keywords: S-layer proteins; BSA; gold nanoclusters; bio-sensing; fluorescence

  • Poster
    13. Sensor Symposium, 04.-06.12.2017, Dresden, Deutschland
  • Open Access Logo Contribution to proceedings
    13. Sensor Symposium, 04.-06.12.2017, Dresden, Deutschland
    AMA Proceedings 2017
    DOI: 10.5162/13dss2017/P4.08

Publ.-Id: 26285

Characterization of a switchable chimeric antigen receptor platform in a pre-clinical solid tumor model

Bejestani, E. P.; Cartellieri, M.; Bergmann, R.; Ehninger, A.; Loff, S.; Kramer, M.; Spehr, J.; Dietrich, A.; Feldmann, A.; Albert, S.; Wermke, M.; Baumann, M.; Krause, M.; Bornhäuser, M.; Ehninger, G.; Bachmann, M.; von Bonin, M.

The universal modular chimeric antigen receptor (UniCAR) platform redirects CAR-T cells using a separated, soluble targeting module with a short half-life. This segregation allows precise controllability and flexibility. Herein we show that the UniCAR platform can be used to efficiently target solid cancers in vitro and in vivo using a pre-clinical prostate cancer model which overexpresses prostate stem cell antigen (PSCA). Short-term administration of the targeting module to tumor bearing immunocompromised mice engrafted with human UniCAR-T cells significantly delayed tumor growth and prolonged survival of recipient mice both in a low and high tumor burden model. In addition, we analyzed phenotypic and functional changes of cancer cells and UniCAR-T cells in association with the administration of the targeting module to reveal potential immunoevasive mechanisms. Most notably, UniCAR-T cell activation induced upregulation of immune-inhibitory molecules such as programmed death ligands. In conclusion, this work illustrates that the UniCAR platform mediates potent anti-tumor activity in a relevant in vitro and in vivo solid tumor model.

Keywords: Chimeric antigen receptors; immune checkpoints; immunoevasion; prostate stem cell antigen; solid tumors; targeting module

Publ.-Id: 26282

Retargeting of UniCAR T cells with an in vivo synthesized target module directed against CD19 positive tumor cells

Bachmann, D.; Aliperta, R.; Bergmann, R.; Feldmann, A.; Koristka, S.; Arndt, C.; Loff, S.; Welzel, P. B.; Albert, S.; Kegler, A.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Bornhäuser, M.; von Bonin, M.; Werner, C.; Pietzsch, J.; Steinbach, J.; Bachmann, M.

Recent treatments of leukemias with T cells expressing chimeric antigen receptors (CARs) underline their impressive therapeutic potential but also their risk of severe side effects including cytokine release storms and tumor lysis syndrome. In case of cross-reactivities, CAR T cells may also attack healthy tissues. To overcome these limitations, we previously established a switchable CAR platform technology termed UniCAR. UniCARs are not directed against typical tumor-associated antigens (TAAs) but instead against a unique peptide epitope: Fusion of this peptide epitope to a recombinant antibody domain results in a target module (TM). TMs can cross-link UniCAR T cells with tumor cells and thereby lead to their destruction. So far, we constructed TMs with a short half-life. The fast turnover of such a TM allows to rapidly interrupt the treatment in case severe side effects occur. After elimination of most of the tumor cells, however, longer lasting TMs which have not to be applied via continous infusion would be more convenient for the patient. Here we describe and characterize a TM for retargeting UniCAR T cells to CD19 positive tumor cells. Moreover, we show that the TM can efficiently be produced in vivo from producer cells housed in a sponge-like biomimetic cryogel and, thereby, serving as an in vivo TM factory for an extended retargeting of UniCAR T cells to CD19 positive leukemic cells.

Keywords: CAR; CD19; Retargeting; T cell; T cell therapy; cryogel

Publ.-Id: 26281

3D modelling of the Epembe (Namibia) Nb-Ta-P-(LREE) carbonatite deposit: new insights into geometry related to rare metal enrichment

Unger, G.; Zimmermann, R.; Gloaguen, R.

Geological 3D modelling delivers essential information on distribution of enrichment zones and structures in (complex) mineral deposits and fosters a better guidance to subsequent exploration stages. The Paleoproterozoic Epembe carbonatite complex showcases the close relation between enrichment of specific elements (Nb, Ta, P, TREE+Y) and shear zones by structural modelling combined with geochemical interpolation. Three-dimensional fault surfaces based on structural field observations, geological maps, cross-sections and drill-hole data are visualised. The model shows a complex, dextral transpressive fault system. Three dimensional interpolation of geochemical data demonstrates enrichment of Nb, Ta, P and TREE+Y in small isolated, lens shaped high-grade zones in close spatial distance to faults. Based on various indicators (e.g., oscillating variograms, monazite rims around the apatite) and field evidence, we see rather evidence for enrichment during hydrothermal (re-)mobilisation than due to magmatic differentiation related to the formation of the alkaline system. This is further supported by geostatistical analysis of three-dimensional distribution of Nb, Ta, P and LREE with respect to discrete shear zones.

Keywords: Namibia; carbonatite; 3D modelling; REE; GoCAD

Publ.-Id: 26280

Monovacancy paramagnetism in neutronirradiated graphite probed by 13C NMR

Zhang, Z. T.; Xu, C.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Y. T.; Helm, M.; Zhou, S.; Kühne, H.

We report on the magnetic properties of monovacancy defects in neutron-irradiated graphite, probed by 13C nuclear magnetic resonance spectroscopy. The bulk paramagnetism of the defect moments is revealed by the temperature dependence of the NMR frequency shift and spectral linewidth, both of which follow a Curie behavior, in agreement with measurements of the macroscopic magnetization. Compared to pristine graphite, the fluctuating hyperfine fields generated by the defect moments lead to an enhancement of the 13C nuclear spin-lattice relaxation rate 1/T1 by about two orders of magnitude. With an applied magnetic field of 7.1 T, the temperature dependence of 1/T1 below about 10 K can well be described by a thermally activated form, 1/T1 α exp(−Δ/kBT), yielding a singular Zeeman energy of (0.41 ± 0.01) meV, in excellent agreement with the sole presence of polarized, non-interacting defect moments.

Publ.-Id: 26279

Magnetic Properties of the Nanocrystalline Nd-Ho-Fe-Co-B Alloy at Low Temperatures: The Influence of Time and Annealing

Tereshina, I. S.; Kudrevatykh, N. V.; Ivanov, L. A.; Politova, G. A.; Tereshina, E. A.; Gorbunov, D.; Doerr, M.; Rogackie, K.

A study is made of the effects of various factors such as time (7 years), temperature, high magnetic field up to 580 kOe and heat treatment (HT) on the morphological structure and magnetic hysteresis properties of a high-coercive nanocrystalline (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2 alloy with a low temperature coefficient of remanence. We find a rather weak time effect on (Nd0.55Ho0.45)2.7(Fe0.8Co0.2)14B1.2. After 7 years, the loss in the maximum magnetic energy product (BH)max is no more than 5%. Annealing of the sample at 250 °C for 30 min decreases the amount of amorphous phase from 7.2 to 1.7%, while the grains’ size of the 2-14-1 phase increases from 83 to 109 nm. For the HT alloy, a magnetization jump is observed at H ~ 500 kOe. It can be attributed to the first-order magnetization process or a spin-flip magnetic transition. Rectangularity of the hysteresis loop degrades after annealing. In case of the short-time heat treatment, losses in (BH)maxare ~ 10%.

Publ.-Id: 26278

Influence of Co on the magnetism of HoFe5Al7

Andreev, A. V.; Gorbunov, D. I.; Sebek, J.; Nehnakhin, D. S.

Effects of the Co substitution for Fe on the strongly anisotropic ferrimagnet HoFe5Al7 are studied on single-crystalline samples with a tetragonal crystal structure of the ThMn12-type. For HoFe5-xCoxAl7, we found the homogeneity range up to x = 2.5. The Co substitution results in a shrinkage of the tetragonal lattice within the basal plane, whereas the c parameter does not change. The exchange interactions and magnetic anisotropy are strongly affected by the Co substitution. The detrimental effect of Co on the Curie temperature TC in HoFe5-xCoxAl7 compounds is very unusual. The Curie temperature linearly falls from 216 K for x = 0-67 K for x = 2.5, which is unexpected because the Co substitution for Fe in 3d-4f intermetallic compounds usually increases the magnetic ordering temperatures due to the strengthening of exchange interactions. At the same time, the compensation temperature changes very little between 65 K and 72 K. At 2 K, spontaneous magnetic moment increases from 2 µB at x = 0-4.2 µB at x = 2.5. Magnetization measurements have been performed in pulsed magnetic fields up to 58 T. The compounds exhibit a high magnetic anisotropy of the easy-plane type with the [110] axis as the easy-magnetization direction. Along the easy axis, two first-order field-induced magnetic transitions (at 17 T and 37 T) are observed for HoFe5Al7 and one transition at 27 T for HoFe4CoAl7. The magnetization curve has an S-shape for HoFe3Co2Al7.

Publ.-Id: 26273

Meniscus Asymmetry and Chemo-Marangoni Convection in Capillaries

Eckert, K.; Shi, Q.; Seidel, K.; Schwarzenberger, K.

A liquid-liquid system inside a capillary in which an interfacial reaction leads to in situ production of a surfactant was studied experimentally. The resulting chemo-Marangoni convection induces periodic spreading-dewetting cycles in laboratory experiments. By selected experiments in microgravity, the individual phenomena of the system dynamics could be isolated. The spreading-dewetting cycles result from a complex interplay between the decrease in interfacial tension due to the production of surfactant, the chemo-Marangoni convection, and the gravity-driven deformation of the meniscus shape.

Keywords: Capillaries; Interfacial reactions; Marangoni convection; Meniscus deformation; Microgravity

Publ.-Id: 26272

Dynamo action generated by a precession driven flow

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.

Since many years precession is regarded as an alternative flow driving mechanism that may account, e.g., for remarkable features of the ancient lunar magnetic field [Dwyer 2011; Noir 2013; Weiss 2014] or as a complementary power source for the geodynamo [Malkus 1968; Vanyo 1991]. Precessional forcing is also of great interest from the experimental point of view because it represents a natural forcing mechanism that allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a dynamo experiment is under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which a precession driven flow of liquid sodium with a magnetic Reynolds number of up to Rm=700 will be used to drive dynamo action.

Our present study addresses preparative numerical simulations and flow measurements at a small model experiment running with water. In dependence of precession ratio and Reynolds number the resulting flow patterns and amplitudes provide the essential ingredients for kinematic dynamo models that are used to estimate whether the particular flow is able to drive a dynamo.

In the strongly non-linear regime the flow essentially consists of standing inertial waves. Most remarkable feature is the occurrence of a resonant-like axisymmetric mode which emerges around a precession ratio of Omega_p/Omega_c = 0.1 on top of the directly forced recirculation flow. The combination of this axisymmetric mode and the forced m=1 Kelvin mode is indeed capable of driving a dynamo at a critical magnetic Reynolds number of Rm_c=430 which is well within the range achievable in the experiment. However, the occurrence of the axisymmetric mode slightly depends on the absolute rotation rate of the cylinder and future experiments are required to indicate whether this instability persists at the extremely large Re that will be obtained in the large scale experiment.

Keywords: Dynamo; Dresden

  • Poster
    AGU Fall Meeting, 11.-15.12.2017, New Orleans, USA
  • Open Access Logo Contribution to proceedings
    AGU Fall Meeting, 11.-15.12.2017, New Orleans, USA,


Publ.-Id: 26271

Kinematic dynamo models from hydrodynamic simulations and experiments of precession driven flows

Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.

We used a model water experiment and hydrodynamic simulations to estimate the flow in a precessing cylinder. The resulting velocity fields are dominated by standing inertial waves which makes them appropriate for the application in a kinematic dynamo model based on the time-averaged flow. We found dynamo action at magnetic Reynolds numbers of the order of Rm~500.
Essential for the dynamo is the coupling of the primary (directly forced) flow with azimuthal wave number m = 1 and a non-geostrophic axisymmetric mode which at Re = 10000 emerges in a narrow regime around Po = 0.10.

Our results point out a first promising – but narrow – regime
where we may expect dynamo action in the large scale dynamo
experiment currently under construction at HZDR.

Keywords: Dynamo; Dresdyn

  • Lecture (Conference)
    GDRI DYNAMO Meeting, 27.-29.11.2017, Paris, France

Publ.-Id: 26270

Magnetic and acoustic properties of CoCr2S4

Felea, V.; Cong, P. T.; Prodan, L.; Gritsenko, Y.; Wosnitza, J.; Zherlitsyn, S.; Tsurkan, V.

We report results of magnetic and ultrasound studies of the sulfide spinel CoCr2S4, for which the multiferroicity has recently been suggested. Clear anomalies in the magnetic and acoustic properties have been observed at TN = 222 K and in applied magnetic fields evidencing the important role of magnetoelastic interac-tions in this material. In contrast, no anomalies have been detected at TC = 28 K, where a spontaneous electric polarization and isostructural distortions have been reported. We have extracted the H–T phase diagram of CoCr2S4 from our experiments for magnetic fields applied along the <111> direction. We discuss our observa-tions in relation to our earlier results obtained for the oxide multiferroic spinel CoCr2O4.


Publ.-Id: 26269

Bulk Fermi surface of the Weyl type-II semimetallic candidate γ -MoTe2

Rhodes, D.; Schönemann, R.; Aryal, N.; Zhou, Q.; Zhang, Q. R.; Kampert, E.; Chiu, Y.-C.; Lai, Y.; Shimura, Y.; Mccandless, G. T.; Chan, J. Y.; Paley, D. W.; Lee, J.; Finke, A. D.; Ruff, J. P. C.; Das, S.; Manousakis, E.; Balicas, L.

The electronic structure of semimetallic transition-metal dichalcogenides, such as WTe2 and orthorhombic γ-MoTe2, are claimed to contain pairs of Weyl points or linearly touching electron and hole pockets associated with a nontrivial Chern number. For this reason, these compounds were recently claimed to conform to a new class, deemed type-II, of Weyl semimetallic systems. A series of angle-resolved photoemission experiments (ARPES) claim a broad agreem nt with these predictions detecting, for example, Fermi arcs at the surface of these crystals. We synthesized single crystals of semimetallic MoTe2 through a Te flux method to validate these predictions through measurements of its bulk Fermi surface (FS) via quantum oscillatory phenomena.We find that the superconducting transition temperature of γ-MoTe2 depends on disorder as quantified by the ratio between the room- and low-temperature resistivities, suggesting the possibility of an unconventional superconducting pairing symmetry. Similarly to WTe2, the magnetoresistivity of γ-MoTe2 does not saturate at high magnetic fields and can easily surpass 106%. Remarkably, the analysis of the de Haas–van Alphen (dHvA) signal superimposed onto the magnetic torque indicates that the geometry of its FS is markedly distinct from the calculated one. The dHvA signal also reveals that the FS is affected by the Zeeman effect precluding the extraction of the Berry phase. A direct comparison between the previous ARPES studies and density-functional-theory (DFT) calculations reveals a disagreement in the position of the valence bands relative to the Fermi level εF . Here, we show that a shift of the DFT valence bands relative to εF , in order to match the ARPES observations, and of the DFT electron bands to explain some of the observed dHvA frequencies, leads to a good agreement between the calculations and the angular dependence of the FS cross-sectional areas observed experimentally. However, this relative displacement between electron and hole bands eliminates their crossings and, therefore, the Weyl type-II points predicted for γ-MoTe2.

Publ.-Id: 26268

Methods of dilatometric investigations under extreme conditions and the case of spin-ice compounds

Doerr, M.; Granovsky, S.; Rotter, M.; Stöter, T.; Wang, Z.-S.; Zherlitsyn, S.; Wosnitza, J.

We give an overview on how dilatometric methods have been developed in the last decade. The concept of capacitive dilatometry was successfully adapted to dilution refrigerators with a resolution of 10-9. Miniaturized dilatometers with an overall diameter of 18 mm or less are optimally suited for measuring longitudinal and transversal components of the striction tensor. Going to another extreme, to the highest (pulsed) fields, optical methods, such as the FBG technology, were developed for investigations up to 100 T.
As examples for utilizing dilatometry at low temperatures we show results for the spin-ice materials Dy2Ti2O7 and Ho2Ti2O7. To characterise the magneto-elastic coupling in these materials, we investigated the thermal expansion and magnetostriction between 80 mK and 15 K and in magnetic fields aligned along the [111] direction and found field-induced phases and strong correlations below 500 mK. Our data demonstrate, that the formation of the field-induced phase is strongly influenced by lattice distortions: any change in interatomic distances will result in a variation of the exchange couplings.

Publ.-Id: 26267

Integrative interpretation of potential field data by 3D-modeling and visualization

Götze, H.-J.; Schmidt, S.; Menzel, P.

Any integrative interpretation by the aid of independent geophysical disciplines benefits from modern computational techniques. Today 3D seismic surveying and imaging, gradients of potential field (mostly aero- and/or satellite observations) are combined with on-/off-shore electro-magnetic surveys. In this paper we aim to describe new algorithms and software tools for 3D potential field and gradients of remanent and induced magnetization of complicated underground structures, the local stress field, and the distribution of stress beneath salt domes on base of constrained 3D models. E.g. the presence of salt domes causes a significant perturbation of in situ stress, which may cause serious implications e.g. for the stability of boreholes drilled in the vicinity of salt structures. Geological structures will be approximated by extremely flexible homogeneous polyhedrons (with respect to the domain’s density and/or susceptibility) and their fields and gradients are calculated by the transformation of volume integrals into a sum of line integrals. Alternatively, the approximating polyhedrons consist of variable density distributions which are recalculated from studies of seismic velocities. Magnetic modeling is possible by either applying Poisson’s Theorem or a modification of the derived formulas for gravity modeling. The inversion of potential fields is performed by the CMA-ES, the “covariance-matrix-adoption Evolution Strategy”. A new robust method was introduced for the reduction of edge effects of potential field data. Although the main structure of the new software already existed for 3D gravity modeling, it had be extended by a tool for magnetic modeling, a borehole gravity/susceptibility modeling tool and an immersive visualization of even complicated geological underground structures by 3D printing. Examples from the Gifhorn Trough and KTB are presented here to illustrate the user friendly newly developed software tools.

Keywords: potential field methods; geophysics; visualization; interactive modeling

  • Oil Gas European Magazine 43(2017)4, 202-208
    DOI: 10.19225/171206
    ISSN: 0342-5622

Publ.-Id: 26266

The mobility of thallium in sediments and source apportionment by lead isotopes

Liu, J.; Yin, M.; Luo, X.; Xiao, T.; Wu, Z.; Li, N.; Wang, J.; Zhang, W.; Lippold, H.; Belshaw, N.; Feng, Y.; Chen, Y.

Thallium (Tl) is a very toxic heavy metal. As a part of ongoing investigations, the mobility, sources and fate of Tl were investigated for sediments from a watershed in the northern part of the Pearl River, South China, whose catchment has been seriously impacted by large-scale Pb-Zn smelting activities onshore. A wide dispersion of severe Tl contamination was observed throughout the depth profiles. A modified IRMM (Institute for Reference Materials and Measurements, Europe) sequential extraction procedure of a selected depth profile uncovered an exceptionally high enrichment of Tl in geochemically-mobile fractions (i.e., weak-acid-exchangeable, reducible and oxidizable fractions), on average 5.94 ± 2.19 mg/kg (74.6% ± 5.1% of the total Tl content) not only in the surface sediments but also in deep sediments. The proximal quantitative source apportionment using Pb isotopic fingerprinting technique indicated that a majority (80% - 90%) of Tl contamination along the depth profiles is anthropogenically derived from the Pb-Zn smelting wastes. The results highlight the pivotal role of smelting activities in discharging huge amounts of geochemically-mobile Tl to the sediments down to approximately 1 m in length, which is quantitatively evidenced by Pb isotopic tracing technique. Lead isotopes combined with distribution of Tl and Pb contents identified a potential marker for a point source from the Pb-Zn smelter in the river catchment, which also provides a theoretical framework for source apportionment of metal contamination in a larger river/marine system and in other sulfide mining/smelting areas likewise.

Keywords: Thallium mobility; Lead isotopes; Source apportionment; Pb-Zn smelting

Publ.-Id: 26265

Bubble breakup inside a bubble chain

Keplinger, O.; Shevchenko, N.; Eckert, S.

Liquid metal two-phase flows are widely used in metallurgy and continuous casting. For example Argon gas is injected during metal casting to enhance mixing of the melt and for the floatation process in which Argon gas bubbles separate undesired inclusions from the melt by transporting them towards the slag layer at the free surface improving the melt cleanliness. The floatation process is highly dependent not only on the properties of the inclusions but also on the size and surface characteristics of the dispersed gas phase. The bubble size distribution and interfacial area inside the melt are strongly influenced by the bubble coalescence and breakup. Despite a considerable number of numerical studies on bubble coalescence and breakup in liquid metals only few experimental data exists. Therefore, direct investigation of bubble coalescence and breakup in liquid metals becomes crucial.
Bubble breakup processes in a bubble chain ascending in non-transparent liquid metal were examined by X-ray radiography through high-speed video imaging. The Argon gas bubbles were injected through a single bevel-shaped nozzle positioned in the middle at the bottom of a flat Plexiglas vessel filled with eutectic GaInSn alloy at isothermal conditions. The bubble breakup mechanisms observed in the chosen experimental geometry were mainly initiated by bubble collisions or by the interaction of the bubbles with the flow pattern developed in the vessel due to viscous shear forces influencing the bubble interface. We present experimental results accompanied by statistical analysis of the bubble breakup frequency, number of daughter bubbles and their size distribution, bubble velocities before and after the breakup process, etc. for a broad range of Argon gas flow rates.

Keywords: Bubble breakup; bubble chain; two-phase flow; liquid metal; GaInSn

  • Poster
    15th Multiphase Flow Conference & Short Course, 15.-17.11.2017, Helmholtz-Zentrum Dresden-Rossendorf, Germany

Publ.-Id: 26264

Biomarkers in Malignant Melanoma: Recent Trends and Critical Perspective

Belter, B.; Haase-Kohn, C.; Pietzsch, J.

The worldwide incidence of malignant melanoma is steadily increasing, suggesting a probable melanoma “epidemic.” From a clinical point of view, malignant melanoma still is an unpredictable disease and, once in the advanced stage, allows only scarce therapeutic options. There is an urgent need to identify, characterize, and validate informative biomarkers, biomarker patterns, or surrogate markers in order to not only improve early diagnosis of melanoma but also for differential diagnosis, staging, prognosis, therapy selection, and therapy monitoring.
In this chapter, an update on the ongoing debate on serologic and histologic markers such as lactate dehydrogenase, tyrosinase, S100 family of calcium-binding proteins, cyclooxygenase-2, matrix metalloproteinases, and stem and/or progenitor cell markers are presented, and novel, innovative, and promising trends currently being explored are discussed.

Keywords: Cyclooxygenase-2; Lactate dehydrogenase; Malignant melanoma; Matrix metalloproteinases; S100 proteins; Tyrosinase

  • Open Access Logo Book chapter
    William H. Ward; Jeffrey M. Farma: Cutaneous Melanoma: Etiology and Therapy, Brisbane, Australia: Codon Publications, 2017, 978-0-9944381-4-0, 39-56
    DOI: 10.15586/codon.cutaneousmelanoma.2017

Publ.-Id: 26263

High Temperature Stability of BaZrO3: An Ab Initio Thermodynamic Study

Raja, N.; Murali, D.; Posselt, M.; Satyanarayana, S. V. M.

BaZrO3 exhibits excellent proton conductivity and good high-temperature stability. It is therefore a promising electrolyte material for solid oxide fuel cells. The stability of BaZrO3 at high temperatures is generally explained by the low diffusivity of O vacancy. Present first principle density functional theory calculations show that the slow migration of the doubly charged O vacancy at high temperature cannot be solely caused by the ground-state migration energy but by the contribution of phonon excitations to the free migration energy. With increasing temperature, the effective barrier for oxygen vacancy migration increases. At about 1000 K, which is the operating temperature of fuel cells, the calculated O vacancy diffusivity is more than one order of magnitude lower than that determined using ground-state migration barrier. The calculated diffusivity data agree well with experimental results from literature. The present work reveals that the high-temperature stability of BaZrO3 is mainly due to the phonon contribution to the free migration energy of the O vacancy.

Keywords: perovskite; high-temperature stability; ab-initio calculation; O vacancy

Publ.-Id: 26262

Achievement of a table-like magnetocaloric effect in the dual-phase ErZn2/ErZn composite

Li, L.; Yuan, Y.; Qi, Y.; Wang, Q.; Zhou, S.

Dual-phase ErZn2/ErZn composite was obtained by induction-melting method. The composite crystallizes in the phases of ErZn2 and ErZn with the weight ratio of 53.8:46.2. The composite undergoes two successive magnetic phase transitions. And accordingly two peaks (partly overlapped) are appeared in the temperature dependence of magnetic part of entropy change SM(T) curves which resulting in a table-like magnetocaloric effect (MCE) and large refrigerant capacity (RC). The MCE parameters are comparable or even larger than most of the recently reported potential magnetic refrigerant materials at similar temperature region, making the dual-phase ErZn2/ErZn composite attractive for low-temperature magnetic refrigeration.

Publ.-Id: 26261

Ion beams for the creation of magnonic circuits

Fassbender, J.

Ion beams for the Creation of magnonic circuits

Keywords: ions; magnetism; magnonics

Related publications

  • Invited lecture (Conferences)
    Magnonics - quo vadis?, 27.10.2017, Kaiserslautern, Deutschland

Publ.-Id: 26260

Temperature measurement of hohlraum radiation for energy loss experiments in indirectly laser heated carbon plasma

Schumacher, D.; Bedacht, S.; Blazevic, A.; Busold, S.; Cayzac, W.; Frank, A.; Heßling, T.; Kraus, D.; Ortner, A.; Schaumann, G.; Roth, M.

For ion energy loss measurements in plasmas with near solid densities, an indirect laser heating scheme for carbon foils has been developed at GSI Helmholtzzentrum für Schwerionenforschung GmbH (Darmstadt, Germany). To achieve an electron density of 10^22 cm^3 and an electron temperature of 10–30 eV, two carbon foils with an areal density of 100 μg/cm^2 heated in a double-hohlraum configuration have been chosen. In this paper we present the results of temperature measurements of both primary and secondary hohlraums for two different hohlraum designs. They were heated by the PHELIX laser with a wavelength of 527 nm and an energy of 150 J in 1.5 ns. For this purpose the temperature has been investigated by an x-ray streak camera with a transmission grating as the dispersive element.


  • Secondary publication expected

Publ.-Id: 26259

Dynamische Belüftung zur Optimierung von Sauerstoffeintrag und Durchmischung für die biologische Abwasserbehandlung

Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

In fast 10.000 kommunalen Kläranlagen in Deutschland werden jährlich 4.400 GWh Strom benötigt, um den Nährstoffgehalt des Abwassers zu reduzieren. Der höchste Energiebedarf besteht dabei mit einem Anteil von bis zu 80 % bei dem Prozess-schritt der biologischen Abwasserreinigung. Während der Nitrifikation benötigen die Mikroorganismen Sauerstoff, welcher durch Druckbelüftung vom Beckenboden bereitgestellt wird. Die Gebläse müssen den Druckverlust der Belüftungselemente und den hydrostatischen Druckverlust aufgrund von 4 bis 6 m Wassertiefe überwinden, woraus der hohe Energieaufwand resultiert. Jedoch wird aufgrund des limitierten Stoffübergangs nicht der gesamte Sauerstoff der im Nitrifikationsbecken aufsteigenden Blasen in die flüssige Phase übertragen. Durch einen verbesserten Sauerstoffübergang kann der benötigte Luftvolumenstrom und somit die Gebläse-leistung reduziert werden. Dafür wird die dynamische Belüftung vorgeschlagen.
Die dynamische Belüftung beruht auf einer zeitlichen Dynamik im Gasvolumen-strom, welcher durch die Belüftungselemente geleitet wird. Der Volumenstrom kann harmonisch oder gepulst variiert sein. Dies hat zur Folge, dass die Blasenfahne über dem Belüfter diskontinuierlich wird. Im Vergleich zur kontinuierlichen Blasenfahne entstehen Bereiche, in denen die Flüssigphase vermischt wird und Konzentrationsgradienten größer werden.
Im Rahmen dieser Arbeit werden optimale Belüftungsregime für dynamische, gepulste Belüftung untersucht, welche in Stoffübergang und Durchmischung der kontinuierlichen Belüftung überlegen sein sollen. Hierfür werden in transienten Euler-Euler Simulationen die wichtigsten Parameter variiert. Dazu zählen die Parameter Pulsfrequenz, Pulsweite, Pulshöhe und Pulsoffset. Die simulativ gefundenen Regime werden experimentell überprüft. Weiterhin wird das Sedimen-tationsverhalten von Belebtschlamm simuliert, um dessen Ablagerung am Beckenboden bei dynamischer Belüftung untersuchen und geeignete Kriterien zur Verhinderung der Sedimentation ableiten zu können.

Keywords: Dynamische Belüftung; Abwasserreinigung; Stoffübergang

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen, Wärme- und Stoffübertragung und Computational Fluid Dynamics, 06.03.2018, Bremen, Deutschland

Publ.-Id: 26258

Effect of pH on the mobility of the herbicide MCPA in a sand-goethite column: 1D and 2D reactive transport modeling

Lippold, H.; Karimzadeh, L.; Kulenkampff, J.; Wissmeier, L.; Stuhlfauth, C.; Stoll, M.; Lippmann-Pipke, J.

Adsorption and transport of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in a homogeneous sand-goethite system were investigated as a function of pH. Interaction of MCPA with the solid surface was geochemically modeled according to the charge distribution multisite complexation (CD-MUSIC) approach. Based on this calibration, retardation of MCPA transport in column experiments was significantly underestimated by conventional 1D simulations.
As a new approach, Positron Emission Tomography (PET) was employed to analyze the flow field, using 18F as a radiotracer. The observed heterogeneity was reproduced in 2D simulations assuming increased permeability and porosity at the periphery of the column. With this flow model, predicted retardation factors for MCPA were in agreement with the experimental data. Thus, this study demonstrates quantitatively that inconsistencies between static (batch) and dynamic (column) systems can be caused by heterogeneities in fluid flow, i.e., not necessarily by non-equilibrium conditions, which are commonly taken into account. This in turn highlights the need to consider realistic flow fields in studies of contaminant transport in natural matrices.

Keywords: CD-MUSIC model; Column experiments; Heterogeneous flow; Phenoxy acid herbicides; Positron Emission Tomography; 1D 2D transport modeling


Publ.-Id: 26257

Residual tumour hypoxia in head-and-neck cancer patients undergoing primary radiochemotherapy, final results of a prospective trial on repeat FMISO-PET imaging

Löck, S.; Perrin, R.; Seidlitz, A.; Bandurska-Luque, A.; Zschaeck, S.; Zöphel, K.; Krause, M.; Steinbach, J.; Kotzerke, J.; Zips, D.; Troost, E. G. C.; Baumann, M.


Hypoxia is a well recognised parameter of tumour resistance to radiotherapy, a number of anticancer drugs and potentially immunotherapy. In a previously published exploration cohort of 25 head and neck squamous cell carcinoma (HNSCC) patients on [18F]fluoromisonidazole positron emission tomography (FMISO-PET) we identified residual tumour hypoxia during radiochemotherapy, not before start of treatment, as the driving mechanism of hypoxia-mediated therapy resistance. Several quantitative FMISO-PET parameters were identified as potential prognostic biomarkers. Here we present the results of the prospective validation cohort, and the overall results of the study.

FMISO-PET/CT images of further 25 HNSCC patients were acquired at four time-points before and during radiochemotherapy (RCHT). Peak standardised uptake value, tumour-to-background ratio, and hypoxic volume were analysed. The impact of the potential prognostic parameters on loco-regional tumour control (LRC) was validated by the concordance index (ci) using univariable and multivariable Cox models based on the exploration cohort. Log-rank tests were employed to compare the endpoint between risk groups.

The two cohorts differed significantly in several baseline parameters, e.g., tumour volume, hypoxic volume, HPV status, and intercurrent death. Validation was successful for several FMISO-PET parameters and showed the highest performance (ci=0.77-0.81) after weeks 1 and 2 of treatment. Cut-off values for the FMISO-PET parameters could be validated after week 2 of RCHT. Median values for the residual hypoxic volume, defined as the ratio of the hypoxic volume in week 2 of RCHT and at baseline, stratified patients into groups of significantly different LRC when applied to the respective other cohort.

Our study validates that residual tumour hypoxia during radiochemotherapy is a major driver of therapy resistance of HNSCC, and that hypoxia after the second week of treatment measured by FMISO-PET may serve as biomarker for selection of patients at high risk of loco-regional recurrence after state-of-the art radiochemotherapy.

Copyright © 2017 Elsevier B.V. All rights reserved.

Keywords: Advanced stage HNSCC; FMISO-PET; Hypoxia; Prognostic biomarker; Radiochemotherapy

Publ.-Id: 26256

Quality assessment of delineation and dose planning of early breast cancer patients included in the randomized Skagen Trial 1

Francolini, G.; Thomsen, M. S.; Yates, E. S.; Kirkove, C.; Jensen, I.; Blix, E. S.; Kamby, C.; Nielsen, M. H.; Krause, M.; Berg, M.; Mjaaland, I.; Schreiber, A.; Kasti, U. M.; Boye, K.; Offersen, B. V.


To report on a Quality assessment (QA) of Skagen Trial 1, exploring hypofractionation for breast cancer patients with indication for regional nodal radiotherapy.

Deviations from protocol regarding target volume delineations and dose parameters (Dmin, Dmax, D98%, D95% and D2%) from randomly selected dose plans were assessed. Target volume delineation according to ESTRO guidelines was obtained through atlas based automated segmentation and centrally approved as gold standard (GS). Dice similarity scores (DSC) with original delineations were measured. Dose parameters measured in the two delineations were reported to assess their dosimetric outcome.

Assessment included 88 plans from 12 centres in 4 countries. DSC showed high agreement in contouring, 99% and 96% of the patients had a complete delineation of target volumes and organs at risk. No deviations in the dosimetric outcome were found in 76% of the patients, 82% and 95% of the patients had successful coverage of breast/chestwall and CTVn_L2-4-interpectoral. Dosimetric outcomes of original delineation and GS were comparable.

QA showed high protocol compliance and adequate dose coverage in most patients. Inter-observer variability in contouring was low. Dose parameters were in harmony with protocol regardless original or GS segmentation.

Keywords: Delineation; Quality assessment; Skagen Trial 1

Publ.-Id: 26255

CFD Studies on the gas-liquid flow in the swirl generating device

Putra, R. A.; Schäfer, T.; Neumann, M.; Lucas, D.

In this work, CFD simulations using the Euler-Euler approach were performed to model the gas-liquid flow in a swirl-generating device. The computational work was based on experiments, which are conducted in a vertical pipe packed with a static swirl element. Measurements of gas volume fractions at several planes within the swirl element were taken using high-resolution gamma-ray computed tomography (HireCT).
The simulations were carried out for the experimental conditions with defined inlet gas volumetric flow rates of 5 and 10 %. The profile of several key parameters (e.g pressure, liquid and gas velocities and gas fraction) are used to understand the flow behavior inside the device. The radial gas phase distribution obtained from the simulations assuming different mono-disperse and bi-modal bubble sizes is compared against the experimental results. The significant influence of the selected bubble sizes on the profile is shown and discussed within this paper. In general, the radial profile of gas fraction is well captured by the CFD simulations except in the transition zone where a significant discrepancy to the experiment is observed.

Keywords: Swirling flow; Multiphase flow; Swirl-vane separator; CFD simulation; Euler-Euler model


Publ.-Id: 26254

Beam operation with ELBE SRF gun using Mg photo cathodes

Xiang, R.; Teichert, J.; Arnold, A.; Murcek, P.; Lu, P.; Vennekate, H.

In this presentation the latest results of SRF gun-II with Mg photocathode is overviewed. The stable beam from SRF gun was guided into ELBE linac for a whole week of neutron beam time and THz beam time without unexperted breakdown.

Related publications

  • Lecture (Conference)
    The 3rd annual meeting of Matter and Technologies, 31.01.-02.02.2017, Darmstadt, Germany

Publ.-Id: 26253

Status of SRF-gun-II and Photocathodes at HZDR

Xiang, R.

In this presentation the latest results of ELBE SRF gun-II with Mg photocathodes are overviewed. And the status of Cs2Te photocathode for SRF gun is also summaried.

Related publications

  • Invited lecture (Conferences)
    HOPE-II annual meeting, 11.10.2017, Rostock, Germany

Publ.-Id: 26252

Cs2Te and metallic photocathodes for SRF gun at HZDR

Xiang, R.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.

Quality of photocathode is one of the critical issues for the stability and reliability of the photoinjector system. SRF Gun II with Mg photocathode has successfully provided stable electron beams for ELBE users at HZDR. In this work, we present the various cleaning processes (activation) for Mg photocathodes, e.g. high intensity laser cleaning and thermal treatment. Furthermore, we show the first result of the photoemission study on the alternative metallic cathode, for instance MgY alloy.

To generate higher bunch charge up to 0.5nC, Cs2Te photocathode is planned for SRF gun II. Up to now three Cs2Te photocathodes have been used in SRF gun II, however, they show abnormal phenomena and unwanted contamination for the superconducting cavity.

Related publications

  • Poster
    European Workshop on Photocathodes for Particle Accelerator Applications (EWPAA 2017), 20.-22.09.2017, Berlin, Germany

Publ.-Id: 26251

Compatibility of SC cavity and "foreigner" photocathodes in SRF gun

Xiang, R.

More and more electron accelerator projects ask for “super” electron beams with high brightness, low emittance, and high average current. Under this background, much attention is paid on the research and development of new electron sources potentially providing electron beams with better quality. Superconducting RF photoinjectors allow CW operation and meanwhile provide high E-field on cathode to generator high bunch charge and low emittance beam, thus it is a promising candidate for such kind of high current and high brightness electron source.

However, because Nb itself has too low quantum efficiency, the normal conducting photocathodes, such as alkali photocathodes, are the best photoemitter with high quantum efficiency for SRF gun. The compatibility of photocathodes made of ‘foreigner materials’ inside the sensitive Nb cavity is of the biggest difficulty for the designer of SRF gun. One has to solve a lot of unwanted problems like compatibility, particle contamination, multipacting, dark current etc.

In this presentation we collect the running results of SRF guns with normal conducting photocathodes at HZDR and BNL, share the experience gained during the long term development experiments, and discuss the relative problems in the future development.

Related publications

  • Invited lecture (Conferences)
    Workshop "Operating SRF in a "dirty" machine", 14.-15.09.2017, Berlin, Germany

Publ.-Id: 26250

Simulation of bubbly flows with special numerical treatments of the semi-conservative and fully conservative two-fluid model

Dongyue, L.; Hasse, C.

Bubbly flows are found in a large number of chemical engineering applications. For the computational fluid dynamics (CFD) simulations of such multi-phase flows, both physical models and numerical treatment are crucial to obtain robust and accurate results. In this numerical study, we investigate the twofluid model (TFM) under challenging conditions such as phase segregation and inversion. For the phase segregation, a singular problem arises in the phase momentum and the two-phase k-e equations when one phase fraction approaches zero. Another numerical issue is the accurate calculation of the drag coefficient, e.g., during the phase inversion. To address the singular problem, previous studies used a nonconservative formulation after dividing by the phase fraction; in our approach, we present a robust methodology for semi-conservative and fully conservative formulations. A special numerical treatment is introduced to the phase momentum equations and the turbulence equations, which avoids the singular problem in case of phase segregation. Concerning the drag force, two novel methods, the linear and the hyperbolic blending method, respectively, are presented to obtain accurate results. For testing the new numerical treatment, the analytical solution of a two-dimensional test case is first compared with the results predicted using a semi-conservative and a fully conservative formulation. The second test case investigated is a bubble column with different superficial velocities. The results from threedimensional simulations using the novel formulations show good agreement with the literature data.
Especially when phase segregation occurs, the semi-conservative and the fully conservative formulations using the two-phase k-e model formulation converge.

Keywords: Bubble column; Two-fluid model; CFD; Drag force; OpenFOAM

Publ.-Id: 26249

Multiphase CFD with OpenFOAM at HZDR

Schlegel, F.

Presentation of the activities at HZDR in the field of simulation of multiphase flows with OpenFOAM.

Keywords: OpenFOAM; Multiphase; CFD; Simulation

  • Lecture (Conference)
    OpenFuelCell Workshop, 24.-25.10.2017, Jülich, Deutschland

Publ.-Id: 26248

Hyperdoping of silicon: A last niche of defect engineering?

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

Hyperdoping of silicon using ion implantation and short time annealing of chalcogen atoms and transition metals (e.g. S, Se, Te, Au and Ti) appears as a challenging and promising research topic for developing Si-based infrared photodetectors and intermediate band solar cells [i.e.1-3].
The specific physical properties, such as a near-unity broadband absorption (particularly below the Si bandgap), a large enhancement of sub-band-gap photocurrent generation, and the insulator-to-metal transition, are based on this type of doping much above the solid solubility limit of dopants in Si. We have recently been demonstrated that both, laser annealing via the liquid phase and flash lamp annealing via the solid phase can be used to process such high-dose chalcogen-implanted layers [2]. Such kind of non-equilibrium processing needs a careful adjustment of the processing parameters, especially in regard to the “thermal engineering” with processing times at or below the millisecond range, to optimize the defect engineering of this specific type of hyperdoped material. We will report on the microstructural, optical and electrical properties of this new type of silicon material as well as first applications for room-temperature extended infrared Si p-n photodiodes.
[1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014).
[2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015).
[3] F. Liu, S Prucnal, R. Hübner, Ye Yuan, W Skorupa, M Helm, and S. Zhou, J.Phys.D: Appl.Phys. 49 (2016) 245104.

Keywords: hyperdoping; silicon; ion implantation; flash lamp annealing; chalcogen atoms; transition metals

Related publications

  • Lecture (Conference)
    17th Conference on Gettering and Defect Engineering in Semiconductor Technology (GADEST 2017), 01.-06.10.2017, Tbilisi, Georgia

Publ.-Id: 26247

Toward higher precision in radiooncology: Tackling the range problem in particle therapy

Pausch, G.

The promise of particle therapy at ultimate precision can only be fulfilled once the particle range can be controlled and verified with millimeter precision. In spite of considerable efforts made by research groups and commercial enterprises throughout the world means or devices for routinely measuring the particle range during treatments are still missing. On the one hand prompt gamma-ray imaging, proposed almost 15 years ago, has become widely accepted as the most promising strategy for online range verification. On the other hand none of the Compton camera concepts pursued by several groups, including our group at HZDR/OncoRay, could prove to be applicable under treatment conditions so far. The only prototype system ever used in a clinical trial is the passively collimated knife-edge slit camera by IBA. This “camera” cannot provide 3D images but measures one-dimensional prompt gamma-ray intensity profiles that allow quantifying possible shifts of the distal edge of high-weighted single pencil beam spots. Alternative, potentially less expensive approaches have been proposed by MGH (prompt gamma spectroscopy) and OncoRay (prompt gamma timing). Efforts to translate these ideas in applicable technologies and instruments are underway.
The talk will review the state-of-the art in prompt-gamma based range verification, with a focus on previous and present activities at OncoRay: (1) the lessons learned from the Compton camera project, (2) the first-in-man application of a passively collimated prompt gamma camera, and (3) the exploration and stepwise development of an alternative approach, the prompt gamma-ray timing technique.

Keywords: Particle therapy; proton therapy; treatment verification; range verification; prompt gamma rays; prompt gamma imaging; prompt gamma timing; gamma spectroscopy; Compton camera

Related publications

  • Lecture (others)
    Physikalisches Kolloquium (eingeladener Vortrag), 14.12.2017, Siegen, Deutschland

Publ.-Id: 26246

IAEA CRP benchmark of ROCOM PTS test case for the use of CFD in reactor design using the CFD-codes ANSYS CFX and TRIOCFD

Höhne, T.; Kliem, S.; Bieder, U.

Over the last 15 years, considerable effort has been expended in assembling the available information on the use of CFD in the nuclear reactor safety field. Typical application areas here are heterogeneous mixing and heat transfer in complex geometries, buoyancy-induced natural and mixed convection, etc., with specific reference to Nuclear Reactor Safety (NRS) accident scenarios such as Pressurized Thermal Shock (PTS), boron dilution, hydrogen build-up in containments, thermal fatigue and thermal striping issues, etc. The development, verification and validation of CFD codes in respect to Nuclear Power Plant (NPP) design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. Therefore, a set of ROCOM CFD-grade test data were made available to set up an International Atomic Energy Agency (IAEA) benchmark, relating to PTS scenarios. The benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification. Data obtained from the PTS experiment were compared in the study presented here with predictions obtained from the CFD software ANSYS CFX and TrioCFD. In addition a test case without buoyancy forces was selected to show the influence of density differences.

The results of the two test cases and the numerical calculations show that mixing efficiency is strongly influenced by buoyancy effects. At higher mass flow rates without density differences the injected slug propagates in the circumferential direction around the core barrel. Buoyancy forces reduce this azimuthal propagation. The ECC water falls in an almost vertical path and reaches the lower down¬comer sen¬sor below the inlet nozzle. Therefore, density effects play an important role during natural convection with ECC injection in PWRs. Both CFD codes were able to predict the observed flow patterns and mixing phenomena.

Keywords: ROCOM; PTS; PWR; RDB; Mixing; CFD

Publ.-Id: 26245

Ge/Si core/shell quantum dots in alumina: Tuning the optical absorption by the core and shell size(Article)

Nekić, N.; Sancho-Parramon, J.; Bogdanović-Radović, I.; Grenzer, J.; Hübner, R.; Bernstorff, S.; Ivanda, M.; Buljan, M.

Ge/Si core/shell quantum dots (QDs) recently received extensive attention due to their specific properties induced by the confinement effects of the core and shell structure. They have a type II confinement resulting in spatially separated charge carriers, the electronic structure strongly dependent on the core and shell size. Herein, the experimental realization of Ge/Si core/shell QDs with strongly tunable optical properties is demonstrated. QDs embedded in an amorphous alumina glass matrix are produced by simple magnetron sputtering deposition. In addition, they are regularly arranged within the matrix due to their self-assembled growth regime. QDs with different Ge core and Si shell sizes are made. These core/shell structures have a significantly stronger absorption compared to pure Ge QDs and a highly tunable absorption peak dependent on the size of the core and shell. The optical properties are in agreement with recent theoretical predictions showing the dramatic influence of the shell size on optical gap, resulting in 0.7 eV blue shift for only 0.4 nm decrease at the shell thickness. Therefore, these materials are very promising for light-harvesting applications.

Keywords: absorption; Ge/Si core/shell quantum dots; quantum confinement; self-assembly

Related publications

Publ.-Id: 26244

Effect of broken axial symmetry on the electric dipole strength and the collective enhancement of level densities in heavy nuclei

Grosse, E.; Junghans, A. R.; Wilson, J. N.

The basic parameters for calculations of radiative neutron capture, photon strength functions and nuclear level densities near the neutron separation energy are determined based on experimental data without an ad hoc assumption about axial symmetry—at variance to previous analysis. Surprisingly few global fit parameters are needed in addition to information on nuclear deformation, taken from Hartree Fock Bogolyubov calculations with the Gogny force, and the generator coordinator method assures properly defined angular momentum. For a large number of nuclei the GDR shapes and the photon strength are described by the sum of three Lorentzians, extrapolated to low energies and normalised in accordance to the dipole sum rule. Level densities are influenced strongly by the significant collective enhancement based on the breaking of shape symmetry. The replacement of axial symmetry by the less stringent requirement of invariance against rotation by 180° leads to a novel prediction for radiative neutron capture. It compares well to recent compilations of average radiative widths and Maxwellian average cross sections for neutron capture by even target nuclei. An extension to higher spin promises a reliable prediction for various compound nuclear reactions also outside the valley of stability. Such predictions are of high importance for future nuclear energy systems and waste transmutation as well as for the understanding of the cosmic synthesis of heavy elements.

Keywords: nuclear structure; nuclear level density; giant resonances; nuclear astrophysics; nuclear waste transmutation


Publ.-Id: 26243

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

Bakaev, A.; Grigorev, P.; Terentyev, D.; Bakaeva, A.; Zhurkin, E. E.; Mastrikov, Y. A.

The interaction of H or He atoms with a core of edge and screw dislocations (SDs), with Burgers vector a0/2 < 111 > s are stronger traps for H and He compared to the SDs, while the H/He affinity to both types of dislocation is significantly weaker than to a single vacancy. The lowest energy atomic configurations are rationalized on the basis of the charge density distribution and elasticity theory considerations. The results obtained contribute to the rationalization of the thermal desorption spectroscopy analysis by attributing certain peaks of the release of plasma components to the detrapping from dislocations. Complementary molecular statics (MS) calculations are performed to validate the accuracy of the recently developed W-H-He embedded atom method (EAM) and bond-order potentials. It is revealed that the EAM potential can reproduce correctly the magnitude of the interaction of H with both dislocations as compared to the ab initio results. All the potentials underestimate significantly the He-dislocation interaction and cannot describe correctly the lowest energy positions for H and He around the dislocation core. The reason for the discrepancy between ab initio and the MS results is rationalized by the analysis of the fully relaxed atomic configurations.

Keywords: tungsten; plasma; hydrogen; helium; dislocations; ab initio; molecular statics

Publ.-Id: 26241

Magnetic excitations and continuum of a possibly field-induced quantum spin liquid in α-RuCl3

Wang, Z.; Reschke, S.; Hüvonen, D.; Do, S.-H.; Choi, K.-Y.; Gensch, M.; Nagel, U.; Rõõm, T.; Loidl, A.

We report on terahertz spectroscopy of quantum spin dynamics in α-RuCl3, a system proximate to the Kitaev honeycomb model, as a function of temperature and magnetic field. An extended magnetic continuum develops below the structural phase transition at Ts2=62K. With the onset of a long-range magnetic order at TN=6.5K, spectral weight is transferred to a well-defined magnetic excitation at ℏω1=2.48meV, which is accompanied by a higher-energy band at ℏω2=6.48meV. Both excitations soften in magnetic field, signaling a quantum phase transition at Bc=7T where we find a broad continuum dominating the dynamical response. Above Bc, the long-range order is suppressed, and on top of the continuum, various emergent magnetic excitations evolve. These excitations follow clear selection rules and exhibit distinct field dependencies, characterizing the dynamical properties of a possibly field-induced quantum spin liquid.


Publ.-Id: 26240

Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

Reschke, S.; Wang, Z.; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

We report on THz time-domain spectroscopy on multiferroic GeV4S8, which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8, this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.


Publ.-Id: 26239

Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.]