Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

32227 Publications
Laser-Based Particle Accelerators at HZDR - Ions
Brack, F.-E.; Kroll, F.; Metzkes, J.; Obst, L.; Kraft, S.; Schlenvoigt, H.-P.; Gaus, L.; Ziegler, T.; Rehwald, M.; Zeil, K.; Schramm, U.;
Summary of the current status and carried out experiments of Laser-driven ion experiments at Draco
  • Lecture (Conference)
    Matter and Technology Student Retreat, 11.06.2018, Berlin, Deutschland

Publ.-Id: 28510 - Permalink


Medical Applications of Laser-driven Particle Sources - An Overview of Activities in Dresden
Kroll, F.; Zeil, K.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Brack, F.; Metzkes-Ng, J.; Bernert, C.; Gaus, L.; Ziegler, T.; Kluge, T.; Garten, M.; Hübl, A.; Kraft, S.; Schramm, U.; Beyreuther, E.; Karsch, L.; Pawelke, J.; Kunz-Schughart, L.;
The talk summarizes activities of HZDR on the topic of laser-driven particle sources for medical applications. The focus lies on a the development and characterization of a pulsed high-field beamline that allows to transport and spacially as well as spectrally shape a laser-driven ion beam and thereby prepare it for irradiation studies, e.g. on radiobiological studies.
  • Lecture (Conference)
    WHELMI Meeting 2018, 28.08.2018, Rehovot, Israel

Publ.-Id: 28509 - Permalink


Pulsed High-Field Magnets for a laser-driven Ion Beam shaping and Laboratory Astrophysics
Brack, F.-E.ORC; Kroll, F.; Metzkes-Ng, J.; Gaus, L.; Kraft, S.; Schlenvoigt, H.-P.; Karsch, L.; Pawelke, J.; Zherlitsyn, S.; Herrmansdörfer, T.; Zeil, K.; Schramm, U.
Pulsed high-field magnets have become a common, versatile research tool. We present a pulsed magnet technology platform that opens up new areas of application in the field of laser-driven plasma physics. Compact high-field magnets, generating ms-long magnetic field pulses with amplitudes ranging as high as 20 T, have been developed for operation under high vacuum and in close vicinity to the harsh laser-plasma environment. The combination of the presented magnet technology and portable pulsed power systems paves the way for novel experiments in laboratory astrophysics and enables unique studies on beam optics for laser-driven ion sources.
We implemented a tunable pulsed beamline at the Dresden laser acceleration source (Draco) for radiobiological irradiation studies. It consists of two pulsed solenoids for shaping laser-accelerated ion beams spatially and spectrally for application. We performed experiments with the PW beam of Draco to investigate the feasibility of worldwide first controlled volumetric in vivo tumour irradiations in a dedicated mouse model with laser-accelerated protons. The study shows the reliable generation of homogeneous dose distributions laterally and in depth. Practical issues, like magnet repetition rate and stability, mean dose rate and future radiobiological challenges will be discussed and an outlook on the already performed volumetric tumour irradiation experiments will be given.
Furthermore, a split-pair coil was developed that can be used for the investigation of magnetized plasma in the frame laboratory astrophysical phenomena. The magnet provides optical access to the magnetized laser-driven plasma via two bores perpendicular to the coil axis. These openings enable optical and X-ray probing as well as insertion of obstacles and/or laser targets from solids to gas jets.
  • Lecture (Conference)
    ECLIM 2018, 22.-26.10.2018, Kreta, Griechenland
  • Poster
    Matter & Technology Meeting, 12.-14.06.2018, Berlin, Deutschland
  • Poster
    45th Conference on Plasma Physics EPS, 02.-06.07.2018, Prag, Tschechische Republik

Publ.-Id: 28508 - Permalink


Theisenschlamm – Waste of the past, resource of the future: a hydrometallurgical approach
Helbig, T.;
A summary of the hydrometallurgical processing approach for "Theisenschlamm" was presented. The proposed approach was developed together with partners of the "Theisenschlamm" project. Limits and Challenges for the recovery of very low concentrated target elements were highlighted with examples of the solvent extraction processes.
  • Lecture (Conference)
    69. Berg- und Hüttenmännischer Tag – Freiberger Universitätsforum 2018, 06.-08.06.2018, Freiberg, Deutschland

Publ.-Id: 28507 - Permalink


Hydrometallurgical recovery of high-tech metals from a complex sulfidic flue dust with focus on the separation of rhenium and molybdenum by solvent extraction
Helbig, T.; Haseneder, R.; Werner, A.; Kelly, N.; Scharf, C.;
“Theisenschlamm”, a flue dust of the former copper shale processing in Germany, comprises high amounts of zinc and lead as well as a variety of low concentrated high-tech metals, such as rhenium, molybdenum, cobalt and germanium. A hydrometallurgical process route was investigated to recover the valuable metals with focus on rhenium and molybdenum. However, very low concentrations of some target elements (1 – 15 mg/L) had to be considered. The process includes an innovative combination of membrane filtration and solvent extraction. With the first processing step 95% molybdenum were extracted from the pregnant leach solution in a continuous mixer settler set-up with the extractant Cyanex 272. High selectivity over rhenium was obtained, with a coextraction of only 0.3%. Continuous membrane nanofiltration technology achieved a selective separation and enrichment of 97.3% zinc, 98.5% iron(III), 97.0% copper, 98.3% aluminium and 99.1% cobalt over rhenium (7.2%) and germanium (7.7%). From the permeate solution 98.4% germanium were separated from rhenium (0.1%) by a continuous reverse osmosis membrane process. Extraction of 99.9% rhenium was obtained by continuous solvent extraction with Alamine 336. Considerations for the selective enrichment of very low concentrated target elements by solvent extraction are discussed in detail. Moreover, potential solvent extraction processes are suggested for further processing of the cobalt, germanium, zinc and copper containing membrane process streams.
  • Contribution to proceedings
    Hi-Tech Metals '18, 22.-23.11.2018, Cape Town, South Africa
  • Lecture (Conference)
    Hi-Tech Metals '18, 22.-23.11.2018, Cape Town, South Africa

Publ.-Id: 28506 - Permalink


Exploration of Rare Earth Elements and Absorption-Emission Features in Rare Earth (La-Lu) Orthophosphates
Sharma, S. K.; Koehler, T.; Fuchs, M.; Beyer, J.; Seidel, P.; Lorenz, S.; Meyer, D. C.; Gloaguen, R.; Heitmann, J.;
Mining of rare earth elements (REEs) followed by application of mined REEs to wide range of application, has been of immense interest for both, geologists and phosphor engineers. In the present contribution, we will focus on a) exploring laser-induced fluorescence (LIF) for REE exploration in our project “inSPECtor”; and b) combining absorption-emission characteristics to understand f-f and f-d transitions in rare earth orthophosphates (La-Lu)PO4. Orthophosphate deposits in nature are important for technological and environmental challenges faced by high-tech industry. It has been shown recently that the phosphorites can be considered as the primary source of REEs to solve the global rare earth supply shortage [1]. The existing technologies in rare earth exploration are based on diffuse-reflectance measurements (for example, Hyperspectral Imaging). However, the spectral features of REEs are due to sharp 4f-4f intraconfigurational transitions, which are sufficiently distinct to enable spectral classification. LIF is an important technique which records REE features in spectral as well as the time domain. Recently, we started a project “inSPECtor” to develop a single sensor system, which combines hyperspectral imaging (or diffuse reflectance spectra) with laser induced fluorescence (for spectral and time resolution from ns to ms). From an application point of view, the Rare earth orthophosphates (REPO4) are important compounds for application in light emitting diodes (LEDs), plasma display panels (PDPs) and fluorescent lamps [2]. The lower atomic number lanthanides (La-Gd) based orthophosphates crystallise with monoclinic structure (P21/n space group) at moderately high temperatures; while the higher atomic number lanthanides based orthophosphates possess tetragonal xenotime-type structure (I41/amd space group). The luminescence properties in a lattice of orthophosphates are expected to be controlled by the type of REEs and their coordination around PO43- tetrahedra. However, PO43- (which forms host valence and conduction band), is transparent itself in visible-UV region and does not absorb, up to approximately 175 nm [3]. Hence, the type of rare earth ion, which increases in ionic radii by approximately 22% from La-Lu, control the electronic structure and optical properties therein. Some of the REPO4, for example-LaPO4, GdPO4, YPO4 and LuPO4; have been explored recently for their charge carrier trapping and relevant applications in storage devices [4]. However, information for other REPO4 is limited and no clear information, relevant to their absorption-emission features, charge storage/release could be found. We present results on our extensive investigation in both these directions; the new sensor and fundamental properties.

References:
[1] P. Emsbo, P.I.McLaughlin, G.N.Breit, E.A.du Bray, A.E.Koenig, Gondwana Res., 27 (2015) 776-785.
[2] J. George, C.Ryan, R.K.Brow, J. Am. Ceram. Soc. 97 (2014) 2249-2255.
[3] P.Melnikov, A.M.Massabni, O.Malta, Phosphorus, Sulfur and Silicon and Related Elements, 1996, pp. 1-1.
[4] T.Lyu, P.Dorenbos, J.Mater.Chem. C, 6 (2018) 369-379.
Keywords: Rare earth orthophosphates, laser induced fluorescence, exploration, diffuse reflectance
  • Lecture (Conference)
    The 5th International Conference on the Physics of Optical Materials and Devices (ICOM-2018), 27.-31.08.2018, Igalo, Montenegro, Montenegro

Downloads:

Publ.-Id: 28505 - Permalink


Modeling Hybrid Wakefield Accelerators with PIConGPU
Debus, A.ORC; Pausch, R.; Huebl, A.; Bastrakov, S.; Widera, R.; Martinez De La Ossa, A.; Irman, A.; Couperus, J.; Schramm, U.; Bussmann, M.
Hybrid LWFA-PWFA obtain high-charge beams of several 100pC with comparably large energy spread and divergence from a first LWFA stage. These beams are then used as a driver in a subsequent PWFA stage, where electron beams with less charge, but higher beam brightness are accelerated. Recent experiments at the HZDR, based on a LWFA-PWFA setup that includes an additional metal foil in between the gas jets, have provided promising results. The presence of very different regimes in hybrid LWFA-PWFAs ranging from underdense plasma to overdense plasma of the foil, interspersed with extended vacuum propagation distances is challenging for 3D-PIC simulations with regard to HPC resources, performance, numerical stability and the ability to iteratively compare with experimental results. The poster presents current simulation efforts at HZDR together with DESY collaborators in modeling experimental results using the open-source, 3D-PIC code PIConGPU. This includes simulation results from parameter scans, as well as the numerical techniques used.
Keywords: Laser-wakefield acceleration, Plasma-wakefield acceleration, PIC, PIConGPU, hybrid LPWFA, hybrid LWFA-PWFA, HPC, LWFA. PWFA
  • Poster
    Directions in particle beam-driven plasma wakefield acceleration, 04.-5.6.2018, Chicheley Hall, Großbrittannien

Publ.-Id: 28504 - Permalink


Traveling-Wave Electron Acceleration, Optical FELs and Thomson Scattering -- Designing laser pulses with a (pulse-front) tilt
Debus, A.ORC; Steiniger, K.; Siebold, S.; Bussmann, M.; Pausch, R.; Albach, D.; Loeser, M.; Roeser, F.; Huebl, A.; Widera, R.; Cowan, T.; Schramm, U.
Generating and controlling ultrashort, pulse-front tilted laser pulses is essential for Traveling-Wave Electron Acceleration (TWEAC), Traveling-Wave Thomson Scattering (TWTS) and Traveling-Wave Optical FELs (TWTS-OFELs). All these applications require controlling angular and group-delay dispersion, while keeping experimental setups as compact as possible. However, the varying requirements with respect to laser power, extent of focal region, incident angles and laser mode quality lead to differing strategies in designing experimental setups.

In this overview poster we provide answers to the question: What experimental efforts in terms of laser system and optics are necessary in current labs for first proof-of-principle realizations of the different applications of "Traveling-Wave" laser pulses -- ranging from low-bandwidth and yield-enhanced Thomson sources (TWTS), laser-based electron accelerators beyond the LWFA depletion and dephasing limits (TWEAC) and ultimately an optical free-electron laser (TWTS-OFEL)?
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC, optical FEL, traveling-wave, Thomson scattering, pulse-front tilt, out-of-focus interaction
  • Poster
    4. Annual MT Meeting, 12.-14.6.2018, Berlin, Deutschland

Publ.-Id: 28503 - Permalink


Breaking the dephasing and depletion limits of laser-wakefield acceleration with Traveling-Wave Electron Acceleration
Debus, A.ORC; Pausch, R.; Hübl, A.; Steiniger, K.; Widera, R.; Cowan, T.; Schramm, U.; Bussmann, M.
We show how to simultaneously solve several long standing limitations of laser-wakefield acceleration that have thus far prevented laser-plasma electron accelerators (LWFA) to extend into the energy realm beyond 10 GeV. Most prominently, our novel Traveling-Wave Electron Acceleration (TWEAC) approach eliminates both the dephasing and depletion constraints. The wakefield driver is a region of overlap of two obliquely incident, ultrashort laser pulses with tilted pulse-fronts in the line foci of two cylindrical mirrors, aligned to coincide with the trajectory of subsequently accelerated electrons. TWEAC leads to quasistatic acceleration conditions, which do not suffer from laser self-phase modulation, parasitic self-injection or other plasma instabilities. Particularly, and in contrast to LWFA and PWFA, a single TWEAC-stage can arbitrarily be extended in length to higher electron energies without changing the underlying acceleration mechanism. We introduce the new acceleration scheme, show results from 3D particle-in-cell simulations using PIConGPU, discuss energy scalability for both laser and electrons and elaborate on experimental realization requirements.
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC
  • Lecture (Conference)
    DPG-Frühjahrstagung 2018, 19.-23.3.2018, Würzburg, Deutschland

Publ.-Id: 28501 - Permalink


Predictive geometallurgy: An interdisciplinary key challenge for mathematical geosciences
van den Boogaart, K. G.; Tolosana-Delgado, R.;
Predictive geometallurgy tries to optimize the mineral value chain based on a precise and quantitative understanding of: the geology and mineralogy of the ores, the minerals processing, and the economics of mineral commodities. This chapter describes the state of the art and the mathematical building blocks of a possible solution to this problem. This solution heavily relies on all classical fields of mathematical geosciences and geoinformatics, but requires new mathematical and computational developments. Geometallurgy can thus become a new defining challenge for mathematical geosciences, in the same fashion as geostatistics has been in the first 50 years of the IAMG.
Keywords: Geostatistics; Statistical scales; Microstructure; Computational geometry; Processing optimisation; Value of information; Mineral liberation analyser; QUEMSCAN
  • Open Access LogoBook chapter
    Daya Sagar, B.S.; Cheng, Qiuming; Agterberg, Frits: Handbook of Mathematical Geosciences: Fifty Years of IAMG, Cham: Springer, 2018, 978-3-319-78998-9, 673-686
    DOI: 10.1007/978-3-319-78999-6_33

Publ.-Id: 28500 - Permalink


Control concepts for image-based structure tracking with ultrafast electron beam X-ray tomography
Windisch, D.ORC; Bieberle, M.; Bieberle, A.ORC; Hampel, U.ORC
In this paper, a novel approach for tracking moving structures in multiphase flows over larger axial ranges is presented, which at the same time allows imaging the tracked structures and their environment. For this purpose, ultrafast electron beam X-ray computed tomography (UFXCT) is being extended by an image-based position control. Application is scanning and tracking of e.g. bubbles, particles, waves and other features of multiphase flows within vessels and pipes. Therefore, the scanner has to be automatically traversed with the moving structure basing on real-time scanning, image reconstruction and image data processing. In this paper we discuss requirements and different strategies for reliable object tracking. Promising tracking strategies have been numerically implemented and evaluated.
Keywords: Ultrafast X-ray computed tomography, structure tracking, multiphase flow, model predictive control

Publ.-Id: 28499 - Permalink


Airlift Reactor – Experiment and CFD Simulation
Hessenkemper, H.; Ziegenhein, T.;
Airlift reactors are modified bubble columns, where internal walls separate the up- and downward flow sections. Since appropriate experiments with locally resolved flow parameters are hardly available, a CFD-grade dataset has been created to validate the HZDR baseline closure model set for an internal airlift reactor. The measurements include many important gas-liquid flow characteristics like gas volume fraction, liquid velocity, turbulence parameters and bubble size distributions for both, the riser and the downcomer. CFD simulations of the test facility were conducted using the URANS concept and compared to the experiments to show strengths and drawbacks of the used closure models. The results reveal that the CFD simulations are capable to predict void fraction in the riser as well as the liquid velocity over the whole cross section quite well. However, the void fraction along the downcomer could not be reproduced in the simulations.
  • Poster
    16th Multiphase Flow Conference and Short Course, 13.-16.11.2018, Dresden, Deutschland

Publ.-Id: 28495 - Permalink


Contamination effects on the lift force of ellipsoidal air bubbles rising in saline water solutions
Hessenkemper, H.; Ziegenhein, T.; Lucas, D.;
The lift force is known to strongly influence the lateral bubble distribution in bubbly flows and is therefore an important force that has to be modeled in corresponding CFD simulations. For ellipsoidal bubbles, which are mostly present in industrial cases, the strength as well as the direction in which the lift force acts is determined by the bubble deformation. The bubble deformation however, can strongly be reduced when surface-active contaminations like salts are present in the liquid bulk, which implies a change of the lift force by contaminations too. In the present work, lift coefficients for single bubbles rising in aqueous NaCl solutions were determined to investigate the influence of such an inorganic surfactant on the lift force. For this purpose, a recently developed method by Ziegenhein et al. [Int. J. Multiphase Flow, Vol. 108, 11-24 (2018)] is used, which is capable to measure the lift force in low viscous liquids. Besides the lift force, the bubble shape and slip velocity were studied in detail to connect the results to known contamination effects, which showed different behavior in dependence on the salt concentration. The results reveal that the contamination level plays an important role on changes of the lift force in comparison to clean bubbles. Up to a concentration of 1.0 mol/l the salt has only a weak effect on the lift force of larger bubbles. The lift coefficients of smaller bubbles however, clearly show significant changes, which were also reflected in a change of the bubble shape. However, some findings could only be connected to the slip velocity, which implies a connection of the lift force to more than just the shape.
Keywords: Lift coefficient; Bubbly flows; Contaminations; Bubble shape; Slip velocity; Sodium chloride

Publ.-Id: 28493 - Permalink


Radiometric Normalization of Multitemporal and Multisensor Remote Sensing Images Based on a Gaussian Mixture Model and Error Ellipse
Ghanbari, H.; Homayouni, S.; Ghamisi, P.; Safari, A.;
Relative radiometric normalization is often required in time series analysis of satellite Earth observations such as land cover change detection. Normalization process reduces the radiometric differences caused by changes in the environmental conditions during the acquisition of multitemporal satellite images. In this paper, we proposed an efficient and automatic method based on Gaussian mixture model (GMM) to find a set of subjectively chosen invariant pixels. A linear model, based on Error Ellipse, was then adjusted to normalize the subject image. The proposed method involves two main steps; in the first step, invariant pixels, which are known as most probable unchanged pixels, were obtained by analyzing image differences estimated by GMMs. Then, these pixels were used to model the relationship between two multitemporal images. To evaluate the proposed method in real analysis scenarios, three multitemporal datasets acquired by different satellite sensors such as Ikonos, Quickbird, SuperView-1, and Worldview-2 were analyzed. These images were collected before and after the 2011's Japan and the 2004's Indonesia Tsunamis, and the 2017's Iran–Iraq earthquake. Experimental results demonstrated that the proposed method can considerably improve the radiometric variations between temporal images for change detection applications.
  • IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 11(2018)11, 4526-4533
    DOI: 10.1109/JSTARS.2018.2871373

Publ.-Id: 28491 - Permalink


Feature importance analysis for Local Climate Zone classification using a residual convolutional neural network with multi-source datasets
Qiu, C.; Schmitt, M.; Mou, L.; Ghamisi, P.; Zhu, X. X.;
Global Local Climate Zone (LCZ) maps, indicating urban structures and land use, are crucial for Urban Heat Island (UHI) studies and also as starting points to better understand the spatio-temporal dynamics of cities worldwide. However, reliable LCZ maps are not available on a global scale, hindering scientific progress across a range of disciplines that study the functionality of sustainable cities. As a first step towards large-scale LCZ mapping, this paper tries to provide guidance about data/feature choice. To this end, we evaluate the spectral reflectance and spectral indices of the globally available Sentinel-2 and Landsat-8 imagery, as well as the Global Urban Footprint (GUF) dataset, the OpenStreetMap layers buildings and land use and the Visible Infrared Imager Radiometer Suite (VIIRS)-based Nighttime Light (NTL) data, regarding their relevance for discriminating different Local Climate Zones (LCZs). Using a Residual convolutional neural Network (ResNet), a systematic analysis of feature importance is performed with a manually-labeled dataset containing nine cities located in Europe. Based on the investigation of the data and feature choice, we propose a framework to fully exploit the available datasets. The results show that GUF, OSM and NTL can contribute to the classification accuracy of some LCZs with relatively few samples, and it is suggested that Landsat-8 and Sentinel-2 spectral reflectances should be jointly used, for example in a majority voting manner, as proven by the improvement from the proposed framework, for large-scale LCZ mapping.

Publ.-Id: 28490 - Permalink


Nonlinear plasmonic response of doped nanowires observed by infrared nanospectroscopy
Lang, D.ORC; Balaghi, L.; Winnerl, S.; Schneider, H.; Hübner, R.; Kehr, S. C.; Eng, L. M.ORC; Helm, M.; Dimakis, E.ORC; Pashkin, A.ORC
We report a strong shift of the plasma resonance in highly doped GaAs/InGaAs core/shell nanowires for intense infrared excitation observed by scattering-type scanning near-field infrared microscopy. The studied nanowires show a sharp plasma resonance at a photon energy of about 125 meV in the case of continuous-wave excitation by a CO₂ laser. Probing the same nanowires with the pulsed free-electron laser with peak electric field strengths up to several 10 kV/cm reveals a power-dependent redshift to about 95 meV and broadening of the plasmonic resonance. We assign this effect to a substantial heating of the electrons in the conduction band and subsequent increase of the effective mass in the nonparabolic Γ-valley.
Keywords: nonlinear plasmonics, infrared nanospectroscopy, s-SNIM, free-electron laser, nanowires, InGaAs

Publ.-Id: 28489 - Permalink


Hyperspectral and LiDAR Fusion Using Deep Three-Stream Convolutional Neural Networks
Li, H.; Ghamisi, P.; Soergel, U.; Zhu, X. X.;
Recently, convolutional neural networks (CNN) have been intensively investigated for the classification of remote sensing data by extracting invariant and abstract features suitable for classification. In this paper, a novel framework is proposed for the fusion of hyperspectral images and LiDAR-derived elevation data based on CNN and composite kernels. First, extinction profiles are applied to both data sources in order to extract spatial and elevation features from hyperspectral and LiDAR-derived data, respectively. Second, a three-stream CNN is designed to extract informative spectral, spatial, and elevation features individually from both available sources. The combination of extinction profiles and CNN features enables us to jointly benefit from low-level and high-level features to improve classification performance. To fuse the heterogeneous spectral, spatial, and elevation features extracted by CNN, instead of a simple stacking strategy, a multi-sensor composite kernels (MCK) scheme is designed. This scheme helps us to achieve higher spectral, spatial, and elevation separability of the extracted features and effectively perform multi-sensor data fusion in kernel space. In this context, a support vector machine and extreme learning machine with their composite kernels version are employed to produce the final classification result. The proposed framework is carried out on two widely used data sets with different characteristics: an urban data set captured over Houston, USA, and a rural data set captured over Trento, Italy. The proposed framework yields the highest OA of 92.57% and 97.91% for Houston and Trento data sets. Experimental results confirm that the proposed fusion framework can produce competitive results in both urban and rural areas in terms of classification accuracy, and significantly mitigate the salt and pepper noise in classification maps.

Publ.-Id: 28488 - Permalink


A Flow Pattern Adaptive Multi-field Two-fluid Concept for turbulent two-phase flows
Schlegel, F.; Meller, R.; Oertel, R.;
Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby the issue of a big range of different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multifluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research, including a state-of-the-art IT concept. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfill the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled either by an isotropic (Strubelj and Tiselj, 2011) or by an anisotropic drag. In both cases, the immensely strong phase coupling requires an adapted numerical method. State and evolution of bubble size distribution in disperse phase context is solved with either class or moment methods. The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.
  • Poster
    16th Multiphase Flow Conference and Short Course, 13.-16.11.2018, Dresden, Deutschland

Publ.-Id: 28487 - Permalink


Magnetoacoustic Relaxation by Cr2-+ Jahn–Teller Centers Revealed from Elastic Moduli
Gudkov, V. V.; Bersuker, I. B.; Zhevstovskikh, I. V.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Korostelin, Y. V.;
Magnetoacoustic investigations of the ZnSe:Cr2+ crystal with sphalerite structure, performed in Faraday geometry, show that there is a new channel of relaxation by the Cr2+ Jahn–Teller (JT) centers, induced by the magnetic field. A new method is worked out that allows to extract the relaxation time, either from the temperature changes of the elastic modulus in fixed magnetic field or from the magnetic field dependences at fixed temperatures. Application of both approaches to the imaginary part of the elastic modulus prove their efficiency and indicate that the magnetic field dependent relaxation rate reaches the magnitude of about 106s-1 at T = 1.3 K.

Publ.-Id: 28486 - Permalink


Technical note: Co-localized (colloidal probe) atomic force microscopy / Raman spectroscopy measurements for floatability characterization
Babel, B.; Rudolph, M.;
Atomic force microscopy measurements are chemically blind towards the underlying sample surface. On chemically heterogeneous samples e.g. ores the identification of regions of interest relies on the optical microscopic image and previous sample characterizations e.g. by a SEM + EDX combination. In this paper, we demonstrate for the first time the application of co-localized colloidal probe atomic force microscopy / Raman (CP-AFM-Raman) measurements, combining the wettability information of a cassiterite in a quartz matrix with the identification of the mineral phases by their Raman spectra at a high spatial resolution of only 1 µm. Additional topography measurements are performed highlighting the selective adsorption of sulfosuccinamate molecules, resulting in a nano-structuring of the cassiterite surface by collector molecules.
Keywords: Atomic force microscopy, hydrophobic interactions, Raman spectroscopy, flotation research, adsorption, cassiterite

Publ.-Id: 28485 - Permalink


Investigating reagent-mineral interactions by colloidal probe atomic force microscopy
Babel, B.; Rudolph, M.;
The characterization of reagent-mineral interactions in flotation systems of finely intergrown ores holds difficult challenges for the applicability of standard techniques like Hallimond tube tests and contact angle experiments or renders them impossible due to a lack of sufficient samples in terms of quality and quantity. This disadvantage may not apply to more sophisticated techniques, but these often do not work in an aqueous environment.
We present the utilization of an atomic force microscope with a hydrophobic colloidal probe to characterize the wettabilities of individual mineral domains of an ore sample, while additional spectral information is gathered by Raman spectroscopy. The exemplary ore sample investigated is mainly containing cassiterite and quartz, therefore the reference measurements like Hallimond tube tests and contact angle experiments were carried out with this binary system as a comparison.
The focus of the study lies in the correlation of data gathered by the atomic force microscope and the Raman spectrometer with data from standard techniques. Finally the applicability of the colloidal probe atomic force microcopy technique for reagent-mineral investigations is critically evaluated.
Keywords: Atomic force microscope, colloidal probe, hydrophobic interactions, Raman spectroscopy, cassiterite
  • Contribution to proceedings
    International Mineral Processing Congress, 17.-21.09.2018, Moskau, Russland
    International Mineral Processing Congress (IMPC 2018)
  • Lecture (Conference)
    International Mineral Processing Congress 2018, 19.09.2018, Moskau, Russland

Publ.-Id: 28483 - Permalink


Physical model of the Czochralski crystal growth in a horizontal magnetic field
Pal, J.; Grants, I.; Eckert, S.; Gerbeth, G.;
The horizontal magnetic field (HMF) may improve conditions in the melt during large silicon single crystal growth by the Czochralski technique. This observation is counter-intuitive as the HMF evidently breaks the rotational symmetry. A previous study has shown that the HMF is not able to
significantly delay the Rayleigh-Bénard instability in a rotating cylinder [1]. It has been observed [2] that an oscillating flow sets in soon after the linear onset. Can we expect a stabilizing effect of the HMF in the Czochralski growth? Why the symmetry breaking by the HMF is eventually not
so relevant? These are two central questions for our primarily experimental study using the room-temperature eutectic alloy GaInSn for dedicated model experiments, allowing an almost complete measurement of the velocity field inside the melt [3]. Besides, it is also meant as a benchmark for comparison with the numerical codes. To serve the latter purpose the boundary conditions should be preferably well defined. Having this in mind the temperature boundary conditions are defined as follows. An isothermal heating is applied at the bottom of a cylindrical cell filled with GaInSn
alloy. The side wall is thermally insulated. An optionally rotating isothermal cooler models the growing crystal. A water-cooled layer of an alkaline solution keeps the rest of the metal surface free from oxides and models the radiation heat loss. The maximum HMF strength is 0.3 T that
corresponds to a Hartmann number of about 1200. Velocity profiles are measured by ultrasound Doppler velocimetry. Temperatures are monitored in the vicinity of the triple point at the rim of the cooler, at the rim of the cell, inside of the cooler and of the heater. The Nusselt-Grashof number
dependency is obtained by controlling the total heat flux injected at the bottom and measuring the temperature difference between the bottom plate and the cooler. The critical cooler rotation rate is determined at which the rotation introduces a significant variation of the velocity field dominated by the HMF-aligned convection rolls.
Keywords: Czochralski, Physical model, horizontal magnetic field
  • Open Access LogoContribution to proceedings
    International Workshop on Modeling in Crystal Growth, 21.-24.10.2018, Kailua-Kona, Hawaii, USA
    Program of the 9 th International Workshop on Modeling in Crystal Growth
  • Lecture (Conference)
    International Workshop on Modeling in Crystal Growth, 21.-24.10.2018, Kailua-Kona, Hawaii, USA

Publ.-Id: 28481 - Permalink


Electroforming-free resistive switching in polycrystalline YMnO3 thin films
Rayapati, V. R.; Du, N.; Bürger, D.; Patra, R.; Skorupa, I.; Matthes, P.; Stöcker, H.; Schulz, S. E.; Schmidt, H.;
Polycrystalline YMnO3 thin films sandwiched between an un-patterned bottom electrode (Pt or Pt/Ti) and a circular top electrode (Au or Al) reveal an electroforming-free, unipolar resistive switching. We report YMnO3 resistive switching devices endurance depending on the bottom electrode and the top electrode. The number of loading cycles of the Al/YMnO3/Pt resistive switch is larger than 103. The resistance ratio between the high resistance (OFF) and the low resistance (ON) state is larger than 104, which can be further increased to 105 by decreasing the diameter of the Al top electrode.

Publ.-Id: 28480 - Permalink


Dissipation-Induced Instabilities in Magnetized Flows
Kirillov, O. N.;
We study local instabilities of a differentially rotating viscous flow of electrically conducting incompressible fluid subject to an external azimuthal magnetic field. A hydrodynamically stable flow can be destabilized by the magnetic field both in an ideal and a viscous and resistive system giving rise to the azimuthal magnetorotational instability. A special solution to the equations of ideal magnetohydrodynamics characterized by the constant total pressure, the fluid velocity parallel to the direction of the magnetic field, and by the magnetic and kinetic energies that are finite and equal—the Chandrasekhar equipartition solution—is marginally stable in the absence of viscosity and resistivity. Performing a local stability analysis, we find the conditions under which the azimuthal magnetorotational instability can be interpreted as a dissipation-induced instability of the Chandrasekhar equipartition solution.

Publ.-Id: 28479 - Permalink


A Flow Pattern Adaptive Multi-Field Two-Fluid Concept for Turbulent Two-Phase Flows
Meller, R.; Schlegel, F.; Lucas, D.;
Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby the issue of a big range of different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multifluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfill the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled by an isotropic drag (Strubelj and Tiselj, 2011). In this case, the immensely strong phase coupling requires an adapted numerical method. The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.
Keywords: computational fluid dynamics, two-fluid model, multiphase, numerical method
  • Lecture (others)
    Seminar des Instituts für Mathematik und Rechneranwendungen der Universität der Bundeswehr München, 09.02.2018, München, Deutschland

Publ.-Id: 28478 - Permalink


In vivo confirmation of altered hepatic glucose metabolism in patients with liver fibrosis/cirrhosis by 18F-FDG PET/CT
Verloh, N.; Einspieler, I.; Utpatel, K.; Menhart, K.; Brunner, S.; Hofheinz, F.; van den Hoff, J.; Wiggermann, P.; Evert, M.; Stroszczynski, C.; Hellwig, D.; Grosse, J.;
Objective: The aim of this study was to assess the value of 18F-FDG PET/CT for quantitative assessment of hepatic metabolism in patients with different stages of liver fibrosis/cirrhosis. Materials and methods: 18F-FDG PET/CT scans of 37 patients either with or without liver fibrosis/cirrhosis, classified according to the METAVIR score (F0-F4) obtained from histopathological analysis of liver specimen, were analyzed retrospectively and classified as follows: no liver fibrosis (F0, n = 6), mild liver fibrosis (F1, n = 11), advanced liver fibrosis (F2, n = 6), severe liver fibrosis (F3, n = 5), and liver cirrhosis (F4, n = 11). The liver-to-blood ratio (LBR, scan time corrected for a reference time of 75 min) was compared between patient groups. Results: Patients with liver fibrosis or cirrhosis (≥ F1; LBR 1.53 ± 0.35) showed a significant higher LBR than patients with normal liver parenchyma (F0, 1.08 ± 0.23; P = 0.004). In direct comparison, LBR increased up to the advanced stage of liver fibrosis (F2; 2.00 ± 0.40) and decreased until liver cirrhosis is reached (F4, 1.32 ± 0.14). Conclusion: Functional changes in liver parenchyma during liver fibrosis/cirrhosis affect hepatic glucose metabolism and significantly differ between stages of liver fibrosis/cirrhosis, classified according to the METAVIR scoring system, as demonstrated by LBR quantification by 18F-FDG PET/CT.
Keywords: 18F-FDG PET/CT, FDG kinetics, Hepatic metabolism, Liver cirrhosis, Liver fibrosis, METAVIR score

Publ.-Id: 28475 - Permalink


U(VI) sorption on Ca-bentonite at (hyper)alkaline conditions – Spectroscopic investigations of retention mechanisms
Philipp, T.; Shams Aldin Azzam, S.; Rossberg, A.; Huittinen, N.; Schmeide, K.ORC; Stumpf, T.
Environmental conditions in deep geological repositories for radioactive waste may involve high pH values due to the degradation of concrete. However, the U(VI) sorption at such (hyper)alkaline conditions is still poorly understood. In this study, batch sorption experiments with Ca-bentonite in the pH range 8–13 at different carbonate concentrations were combined with spectroscopic investigations in order to gain insight into the underlying retention mechanisms. It was found that U(VI) sorption strongly correlates with the aqueous U(VI) speciation determined by time-resolved laser-induced luminescence spectroscopy (TRLFS). Increasing retention with increasing pH was accompanied by a change in aqueous speciation from uranyl carbonates to uranyl hydroxides. The occurrence of luminescence line -narrowing and a decreased frequency of the symmetric stretch vibration, deduced from site-selective TRLFS, indicate the presence of adsorbed U(VI) surface complexes. X-ray absorption fine structure (EXAFS) spectroscopy confirms that surface precipitation does not contribute significantly to the removal of U(VI) from solution but that retention occurs through the formation of two non-equivalent U(VI)-complexes on the bentonite surface. The present study demonstrates that in alkaline environments, where often only precipitation processes are considered, adsorption can provide effective retention of U(VI), despite the anionic character of prevailing aqueous species.
Keywords: uranium, Ca-bentonite, sorption, (hyper)alkaline, site-selective TRLFS, EXAFS, speciation, surface complexation

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  • Secondary publication expected from 19.04.2020

Publ.-Id: 28474 - Permalink


Eulerian multiphase flow modelling: bubbly flow with phase change
Liao, Y.; Krepper, E.; Ding, W.;
Phase change phenomena such as evaporation and condensation are encountered frequently in daily life and technical applications. However, reliable numerical simulation of these processes is still challenging mainly due to insufficient knowledge on the mechanism of interfacial mass, momentum and energy exchanges. In the context of two-fluid model, developing and applying general closures for the representation of interfacial structures and exchanging processes is of great significance. In the presentation the HZDR baseline modelling approach for poly-dispersed bubbly flow with details on bubble size, interfacial area density, sub-cooled wall boiling as well as interphase heat transfer coefficient will be introduced. Application examples for condensing, flash evaporating and wall boiling flows will be presented.
  • Invited lecture (Conferences)
    Lectures on multiphase CFD at Central South University, 06.-08.06.2018, Changsha, China

Publ.-Id: 28473 - Permalink


Turbulence-Interface Interaction in Large-Eddy Simulations with a Two-Fluid Model
Meller, R.; Klein, M.ORC; Lucas, D.; Schlegel, F.
With the aim of a generalized model framework for two-phase flows, cases with large scale interfaces are modeled by means of a two-fluid model in the manner of large-eddy simulations. In this context a number of unclosed terms due to the filtering operation arise. One of them is the classical convective sub-grid scale turbulence stress term. Different closure models for the convective sub-grid scale term are adapted to the presented model framework and a-posteriori investigations are carried out in order to compare the influence of the different modeling approaches.
Keywords: computational fluid dynamics, two-fluid model, large-eddy simulation, multiphase, rising bubble
  • Contribution to proceedings
    12th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements, 26.-28.09.2018, Montpellier, Frankreich
  • Lecture (Conference)
    12th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements, 26.-28.09.2018, Montpellier, Frankreich

Publ.-Id: 28472 - Permalink


On numerical simulation of flashing flows
Liao, Y.; Lucas, D.;
Flashing of water into steam due to decompression or pressure loss is a familiar scenario during the LOCA accident of Light Water Reactors. Because of its relevance to the safety analysis there have been many research activities since the mid of last century. Nevertheless, the understanding of nucleation characteristics, bubble dynamics, as well as interphase exchanges remains insufficient, which makes it quite difficult to define the problem precisely in numerical simulations. As a result, a broad consensus on numerical methods for flashing flows is not available, and various models have been used even for the same case. For example, the critical flashing flow in a converging-diverging nozzle has been studied either with cavitation models or thermal phase change models, and there is little discussion on the contribution of mechanical and thermal effects under given temperature and pressure conditions. A guideline for selecting an appropriate model is desirable, which is clearly not an easy task due to complex physics and missing insights. Under the guidance of a baseline model concept presented in our previous work the present work will focus on the evaluation of existing numerical methods for flashing flows, and aim to discover the underlying laws with help of computational fluid dynamics and experimental data. The temporal and spatial distribution of evaporated steam will be reproduced numerically, and the effect of closure models for interphase exchanging rates as well as bubble dynamics will be discussed.
Keywords: closure model, computational fluid dynamics, flashing flow, numerical methods, phase change
  • Contribution to proceedings
    The 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-22.08.2019, Portland, USA
  • Lecture (Conference)
    The 18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-22.08.2019, Portland, USA

Publ.-Id: 28464 - Permalink


Euler-Euler Simulation of Fluid Dynamics and Mass Transfer in Bubbly Flows
Rzehak, R.; Kappelt, C.;
CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. To achieve predictive capability, all details of the closure models have to be fixed in advance without reference to any measured data.
Concerning the fluid dynamics of bubbly flows a baseline model has recently been proposed to this end and shown to work for a range of different applications in a unified manner1,2. This provides a reliable background which is well suited to add more complex physics. Concerning mass transfer in bubbly flows only few studies have been performed to date3. For the mass transfer coefficient, a variety of entirely different closures have been applied in rather similar situations. To facilitate predictive applications, a standard model which is validated for a broad range of conditions yet has to be developed.
The present contribution considers two test cases from the literature, where mass transfer takes place during the absorption of oxygen into water. The first case is a bubbly mixing layer4, the second is concerned with co-current bubble column flow5. The above mentioned baseline model is used for the fluid dynamical part of the simulation model. Two different correlations for the mass transfer coefficient are considered6, which had been used in previous work. Sources of uncertainty in both, models and data, are discussed. Taking into account possible measurement errors, reasonable agreement between simulations and measurements is found for the present situations. Needs for further experimental data to facilitate qualification of a generally applicable model are specified.
Keywords: Euler-Euler simulation, dispersed gas-liquid multiphase flow, mass-transfer
  • Lecture (Conference)
    12th European Fluid Mechanics Conference, 09.-13.09.2018, Wien, Österreich

Publ.-Id: 28463 - Permalink


Euler-Euler modelling of bubble dynamics in flashing flows
Liao, Y.; Lucas, D.;
A poly-disperse multiple-size-group approach, which is a class method of population balance, is developed for two-fluid modelling of the evolution of gas-liquid mixture during flash evaporation. Special efforts are dedicated to the development and validation of sub models for describing bubble nucleation, coalescence and breakup as well as interfacial heat transfer rates. The baseline model with a fixed set of closures for interphase momentum transfer and bubble-induced turbulence, which was proposed in the previous work and validated for isothermal cases, is extended by a mechanistic model for the overall heat transfer coefficient from liquid to gas-liquid interface, and the model for bubble growth and shrinkage due to phase change. The poly-disperse approach is applied to simulate evaporating pipe flow under pressure release transients, which is controlled by the operation of a blow-off valve. CFD-grade experimental data including local bubble size and void fraction as well as velocity distributions are available for model validation. The comparison demonstrates that the model is effective in capturing the temporal course of vapour bubbles’ generation and growth as well as their spatial distribution. The agreement between measured and simulated cross-section averaged flow parameters such as void fraction, liquid temperature and bubble size distribution is satisfying.
  • Contribution to proceedings
    10th International Conference on Multiphase Flow, ICMF2019, 19.-24.05.2019, Rio de Janeiro, Brazil
  • Lecture (Conference)
    10th International Conference on Multiphase Flow, ICMF2019, 19.-24.05.2019, Rio de Janeiro, Brazil

Publ.-Id: 28462 - Permalink


Euler-Euler Closure for Bubbly Flows with Full Reynolds Stress Model and Anisotropic Bubble-induced Turbulence
Rzehak, R.; Parekh, J.;
In the present work, Euler-Euler modeling of bubbly flows is combined with a full Reynolds stress model for the turbulence in the liquid carrier phase. Reynolds stress models have only rarely been explored in this context, although effects requiring this level of description are frequently encountered in industrial applications towards which the Euler-Euler approach is geared. In particular, source terms describing the additional bubble-induced contribution to the liquid phase turbulence with proper account for its anisotropy have not firmly been established yet. A formulation based on the direction of bubble motion relative to the liquid is given here. Two well-known variants of Reynolds stress models due to Launder, Reece and Rodi and Speziale, Sarkar and Gatski are compared. Closure relations for the bubble forces are applied that have been shown previously to work well over a range of conditions. The model is validated by comparison with a set of pipe flow data that contains variations of liquid and gas flow rates as well as different pipe diameters. An important criterion for the selection of the data was to provide measurements of individual components of the Reynolds stress tensor.
Keywords: Euler-Euler simulation, dispersed gas-liquid multiphase flow, turbulence modeling, Reynolds-strss model, bubble-induced turbulence
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe CFD, 06.-07.03.2018, Bremen, Deutschland

Publ.-Id: 28461 - Permalink


The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C
Matschiavelli, N.; Kluge, S.; Podlech, C.; Standhaft, D.; Grathoff, G.; Ikeda-Ohno, A.; Warr, L.; Chukharkina, A.; Arnold, T.; Cherkouk, A.;
In the multi-barrier concept for the deep geological disposal of high-level radioactive waste (HLW), bentonite is proposed as a potential barrier and buffer material for sealing the space between the steel-canister containing the HLW and the surrounding host rock. In order to broaden the spectra of appropriate bentonites, we investigated the metabolic activity and diversity of naturally occurring microorganisms as well as their time-dependent evolution within the industrial B25 Bavarian bentonite under repository-relevant conditions. We conducted anaerobic microcosm-experiments containing the B25 bentonite and a synthetic Opalinus Clay pore water solution, which were incubated for one year at 30 °C and 60 °C. Metabolic activity was only stimulated by the addition of lactate, acetate or H2. The majority of lactate- and H2-containing microcosms at 30 °C were dominated by strictly anaerobic, sulfate-reducing and spore-forming microorganisms. The subsequent generation of hydrogen sulfide led to the formation of iron-sulfur precipitations. Independent from the availability of substrates, thermophilic bacteria dominated microcosms that were incubated at 60 °C. However, in the respective microcosms, no significant metabolic activity occurred and there was no change in the analyzed bio-geochemical parameters.
Keywords: high-level radioactive waste repository, sulfate-reduction, spores, thermophiles

Publ.-Id: 28460 - Permalink


Bio-Angeln zum Recycling von Elektroschrott
Lederer, F.;
Bio-Angeln zum Recycling von Elektroschrott
  • Lecture (others)
    Geissinger Technikerstammtisch am HZDR, 7.11.2018, Dresden, Deutschland

Publ.-Id: 28459 - Permalink


Effect of pH on the Formation of Gibbsite-Layer Films at the Muscovite (001)−Water Interface
Lee, S. S.; Schmidt, M.ORC; Sturchio, N. C.; Nagy, K. L.; Fenter, P.
Aluminum (oxy)hydroxide films play an important role as sorbents of toxic elements in aqueous environments, where their heterogeneous nucleation and growth can be controlled by the speciation of dissolved Al species and the charge and structure of underlying mineral surfaces. The structure of gibbsite films nucleated at the interface between the muscovite (001) surface and 1 mM AlCl3 solutions was investigated as a function of pH using in situ X-ray reflectivity. Growth of well-ordered gibbsite films was observed at pH 3–4, even when the solutions were undersaturated with respect to gibbsite. The ordering of these gibbsite films likely resulted from the structural similarity (i.e., epitaxy) between the basal planes of gibbsite and muscovite. In contrast, no film growth was observed at pH 9–12 where the solutions were supersaturated with respect to gibbsite. These results indicate that adsorption and accumulation of aqueous Al(III) species (i.e., Al3+ and AlOH2+ at acidic pH) is a critical step for the formation of secondary minerals on the negatively-charged muscovite surface.
Keywords: Mica, Nucleation, Epitaxy; AFM; CTR/RAXR; X-ray Reflectivity

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  • Secondary publication expected from 26.02.2020

Publ.-Id: 28458 - Permalink


Transport properties of Cu-doped bismuth selenide single crystals at high magnetic fields up to 60 Tesla: Shubnikov–de Haas oscillations and π-Berry phase
Romanova, T. A.; Knyazev, D. A.; Wang, Z.; Sadakov, A. V.; Prudkoglyad, V. A.;
We report Shubnikov-de Haas (SdH) and Hall oscillations in Cu-doped high quality bismuth selenide single crystals. To increase the accuracy of Berry phase determination by means of the of the SdH oscillations phase analysis we present a study of n-type samples with bulk carrier density n ∼ 1019 − 1020 cm−3 at high magnetic field up to 60 Tesla. In particular, Landau level fan diagram starting from the value of the Landau index N = 4 was plotted. Thus, from our data we found π-Berry phase that directly indicates the Dirac nature of the carriers in three-dimensional topological insulator (3D TI) based on Cu-doped bismuth selenide. We argued that in our samples the magnetotransport is determined by a general group of carriers that exhibit quasi-two-dimensional (2D) behaviour and are characterized by topological π-Berry phase. Along with the main contribution to the conductivity the presence of a small group of bulk carriers was registered. For 3D-pocket Berry phase was identified as zero, which is a characteristic of trivial metallic states.

Publ.-Id: 28457 - Permalink


High-Field Magnetization Study of R2Fe17N2 (R = Ho and Er) Nitrides
Tereshina, I. S.; Tereshina-Chitrova, E. A.; Pelevin, I. A.; Doerr, M.; Law, J. M.; Verbetski, V. N.; Salamova, A. A.;
The structure and magnetic properties of the nitrided compounds R2Fe17N2 (R = Ho and Er) are studied. The type of crystal structure Th2Ni17 is preserved upon nitrogenation, and the relative unit cell volume ΔV/V increase exceeds 6%. Magnetic studies are performed in fields up to 60 T at 4.2 K on aligned powder samples. Field-induced spin-reorientation (SR) transitions are observed in the M(H) curves of R2Fe17N2. Unlike the parent R2Fe17 compounds, where the magnetization increases in steps as the field grows stronger, 2Fe17N2 demonstrate a gradual increase in magnetization. It is indicative of the change of the SR transition from first to the second type. Extrapolation of magnetization curves to the theoretical value of magnetization in the forced ferromagnetic state yields the coefficient of the inter-sublattice R–Fe exchange interaction. The inter-sublattice exchange is found to decrease upon nitrogenation.

Publ.-Id: 28456 - Permalink


MsRi-CCF: Multi-Scale and Rotation-Insensitive Convolutional Channel Features for Geospatial Object Detection
Wu, X.; Hong, D.; Ghamisi, P.; Li, W.; Tao, R.;
Geospatial object detection is a fundamental but challenging problem in the remote sensing community. Although deep learning has shown its power in extracting discriminative features, there is still room for improvement in its detection performance, particularly for objects with large ranges of variations in scale and direction. To this end, a novel approach, entitled multi-scale and rotation-insensitive convolutional channel features (MsRi-CCF), is proposed for geospatial object detection by integrating robust low-level feature generation, classifier generation with outlier removal, and detection with a power law. The low-level feature generation step consists of rotation-insensitive and multi-scale convolutional channel features, which were obtained by learning a regularized convolutional neural network (CNN) and integrating multi-scaled convolutional feature maps, followed by the fine-tuning of high-level connections in the CNN, respectively. Then, these generated features were fed into AdaBoost (chosen due to its lower computation and storage costs) with outlier removal to construct an object detection framework that facilitates robust classifier training. In the test phase, we adopted a log-space sampling approach instead of fine-scale sampling by using the fast feature pyramid strategy based on a computable power law. Extensive experimental results demonstrate that compared with several state-of-the-art baselines, the proposed MsRi-CCF approach yields better detection results, with 90.19% precision with the satellite dataset and 81.44% average precision with the NWPU VHR-10 datasets. Importantly, MsRi-CCF incurs no additional computational cost, which is only 0.92 s and 0.7 s per test image on the two datasets. Furthermore, we determined that most previous methods fail to gain an acceptable detection performance, particularly when they face several obstacles, such as deformations in objects (e.g., rotation, illumination, and scaling). Yet, these factors are effectively addressed by MsRi-CCF, yielding a robust geospatial object detection method.

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Publ.-Id: 28455 - Permalink


Element Selectivity in Second-Harmonic Generation of GaFeO3 by a Soft-X-Ray Free-Electron Laser
Yamamoto, S.; Omi, T.; Akai, H.; Kubota, Y.; Takahashi, Y.; Suzuki, Y.; Hirata, Y.; Yamamoto, K.; Yukawa, R.; Horiba, K.; Yumoto, H.; Koyama, T.; Ohashi, H.; Owada, S.; Tono, K.; Yabashi, M.; Shigemasa, E.; Yamamoto, S.; Kotsugi, M.; Wadati, H.; Kumigashira, H.; Arima, T.; Shin, S.; Matsuda, I.;
Nonlinear optical frequency conversion has been challenged to move down to the extreme ultraviolet and x-ray region. However, the extremely low signals have allowed researchers to only perform transmission experiments of the gas phase or ultrathin films. Here, we report second harmonic generation (SHG) of the reflected beam of a soft x-ray free-electron laser from a solid, which is enhanced by the resonant effect. The observation revealed that the double resonance condition can be met by absorption edges for transition metal oxides in the soft x-ray range, and this suggests that the resonant SHG technique can be applicable to a wide range of materials.We discuss the possibility of element-selective SHG spectroscopy measurements in the soft x-ray range.

Publ.-Id: 28454 - Permalink


Ultra-fast annealing manipulated spinodal nano-decomposition in Mn-implanted Ge
Liu, C.; Hübner, R.; Xie, Y.; Wang, M.; Xu, C.; Jiang, Z.; Yuan, Y.; Li, X.; Yang, J.; Li, L.; Weschke, E.; Prucnal, S.; Helm, M.; Zhou, S.;
In the present work, millisecond-range flash lamp annealing is used to recrystallize Mnimplanted Ge. Through systematic investigations of structural and magnetic properties, we find that the flash lamp annealing produces a phase mixture consisting of spinodally decomposed Mn-rich ferromagnetic clusters within a paramagnetic-like matrix with randomly distributed Mn atoms. Increasing the annealing energy density from 46, via 50, to 56 J cm−2 causes the segregation of Mn atoms into clusters, as proven by transmission electron microscopy analysis and quantitatively confirmed by magnetization measurements. According to x-ray absorption spectroscopy, the dilute Mn ions within Ge are in d5 electronic configuration. This Mn-doped Ge shows paramagnetism, as evidenced by the unsaturated magnetic-field-dependent x-ray magnetic circular dichroism signal. Our study reveals how spinodal decomposition occurs and influences the formation of ferromagnetic Mn-rich Ge–Mn nanoclusters.
Keywords: ion implantation, flash lamp annealing, spinodal decomposition, Ge–Mn nanoclusters

Publ.-Id: 28453 - Permalink


Femtosecond resonant magneto-optical Kerr effect measurement on an ultrathin magnetic film in a soft X-ray free electron laser
Yamamoto, S.; Kubota, Y.; Yamamoto, K.; Takahashi, Y.; Maruyama, K.; Suzuki, Y.; Hobara, R.; Fujisawa, M.; Oshima, D.; Owada, S.; Togashi, T.; Tono, K.; Yabashi, M.; Hirata, Y.; Yamamoto, S.; Kotsugi, M.; Wadati, H.; Kato, T.; Iwata, S.; Shin, S.; Matsuda, I.;
Time-resolved magneto-optical Kerr effect (MOKE) measurement was demonstrated on a sample of the Au/Fe/Au heterostructure with the Fe layer of 0.35nm thickness under Fe M-edge resonance condition. An ultrabrilliant free electron laser (FEL) in the soft X-ray range was facilitated for the detection of transient signals of resonant MOKE from the ultrathin Fe film. A variation in the Kerr rotation angle was successfully observed on the femtosecond timescale. This technique enables us to reveal the transient magnetization dynamics of such a-few-monolayer magnetic films, which promote the development of spintronic devices.

Publ.-Id: 28452 - Permalink


Neugier trifft Know-how: Erfahrungsaustausch für Wissenschaftlerinnen zu ERC und Marie-Sklodowska-Curie Maßnahmen
Lederer, F.;
Neugier trifft Know-How:
Erfahrungsaustusch für Wissenschaftlerinnen zu ERC und Marie-Sklodowska-Curie-Maßnahmen
  • Invited lecture (Conferences)
    Neugier trifft Know-how: Erfahrungsaustausch für Wissenschaftlerinnen zu ERC und Marie-Sklodowska-Curie-Maßnahmen, 12.11.2018, Dresden, Deutschland

Publ.-Id: 28451 - Permalink


Stochastic Modeling of Multidimensional Particle Properties Using Parametric Copulas
Furat, O.; Leißner, T.; Bachmann, K.; Gutzmer, J.; Peuker, U.; Schmidt, V.;
In this paper, a prediction model is proposed which allows the mineralogical characterization of particle systems observed by X-ray micro tomography (XMT). The model is calibrated using 2D image data obtained by a combination of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) in a planar cross-section of the XMT data. To reliably distinguish between different minerals the model is based on multidimensional distributions of certain particle characteristics describing, e.g., their size, shape and texture. These multidimensional distributions are modeled using parametric Archimedean copulas, since other approaches like kernel density estimation require much larger sample sizes and are thus less practical. Parametric copulas have the advantage of describing the correlation structure of complex multidimensional distributions with only a few parameters. With the help of such distributions the proposed prediction model is able to distinguish between different types of particles among the entire XMT image.
Keywords: X-ray micro tomography (XMT), mineral liberation analyzer (MLA), stereology, multidimensional particle characterization, parametric copula

Publ.-Id: 28450 - Permalink


Chromatopanning for the identification of gallium binding peptides
Schönberger, N.; Braun, R.; Matys, S.; Lederer, F. L.; Lehmann, F.; Flemming, K.; Pollmann, K.;
This study is concerned with a chromatography-based approach for the recovery of gallium binding peptide sequences from a recombinant phage display library.
The phage display technology is a promising tool for the identification of highly specific peptide biosorbents for the recognition and binding of gallium in aqueous solutions. However, the success of the peptide selection strongly depends on the chosen biopanning method. Stable target immobilization, as well as low unspecific interactions is a prerequisite for the enrichment of strong binding peptides. The underlying procedure of phage clone selection is sophisticated but has many advantages for biopanning experiments using metal ions as a target, such as an enhanced monitoring of process conditions and fractionation of eluates.
Here we report about the development of chromatography-based biopanning methods for gallium as target ion and the enrichment of putative gallium binding clone types.
The methods meet the requirements for stable immobilization of the target metal ions during the entire biopanning process and complete recovery of well interacting bacteriophage clones.
Phage clones expressing the peptide sequences TMHHAAIAHPPH, SQALSTSRQDLR and HTQHIQSDDHLA were identified and characterized to bind >10 fold better to a target that presents immobilized gallium ions, thus being promising sequence motifs for the development of peptide-based biosorbents.
Keywords: Phage display; gallium; peptides; chromatopanning

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  • Secondary publication expected from 30.08.2020

Publ.-Id: 28449 - Permalink


The role of functional imaging in lung cancer
Bütof, R.; Troost, E. G. C.;
Over the past decade, functional imaging by means of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET/CT) has improved tumor staging and treatment planning leading to somewhat higher survival rates, in particular in NSCLC patients. This review focuses on the recent insight gained and at current challenges encountered while pursuing improved outcome in patients suffering from NSCLC or SCLC. © 2018, Italian Association of Nuclear Medicine and Molecular Imaging.
Keywords: NSCLC, Positron emission tomography, Radiotherapy, SCLC, Selective nodal irradiation

Publ.-Id: 28448 - Permalink


Transition from antiferromagnetic ground state to robust ferrimagnetic order with Curie temperatures above 420 K in manganese-based antiperovskite-type structures
Zhang, X.; Yuan, Q.; Gao, T.; Ren, Y.; Wu, H.; Huang, Q.; Zhao, J.; Wang, X.; Yuan, Y.; Xu, C.ORC; Hu, Y.; Dynes, J. J.; Zhou, J.; Zhou, S.; Liu, Y.; Song, B.
Manganese (Mn)-based antiperovskite structures (Mn3AX, where A and X represent the 3d transition-metal elements and N or C atoms, respectively) have attracted growing attention because of their novel electronic and magnetic properties. However, the lack of an effective approach to regulate the magnetic coupling in Mn3AX crystal structure, particularly in antiferromagnetic ground states, hinders their further design and applications. Herein, robust high-temperature ferrimagnetic order with a Curie temperature (TC) in the range of B390–420 K was successfully achieved in Mn3GaxNx (x = 0.5, 0.6, and 0.7) via composition-deficient engineering. A systematic investigation, including synchrotron X-ray diffraction, neutron powder diffraction, pair distribution function, X-ray absorption near-edge structure, magnetic characterization, and first-principles calculations, convincingly indicated that the redistribution of partial atoms in the antiferromagnetic ground state was responsible for the observed long-range magnetic order. These results not only provide a new perspective into the design and construction of high-temperature ferrimagnets based on the Mn3AX structure, but also open up a promising avenue for the further design of Mn3AX-based spintronic or other multifunctional devices.

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Publ.-Id: 28447 - Permalink


Systematic study of multipactor suppression techniques for a superconducting rf gun
Tulu, E. T.; van Rienen, U.; Arnold, A.;
Future light sources such as synchrotron radiation sources driven by an energy recovery linac, free electron lasers, or THz radiation sources have in common that they require injectors, which provide high-brilliance, high-current electron beams in almost continuous operation. Thus, the development of appropriate highly brilliant electron sources is of key importance. With its superconducting radio-frequency photo-injector (SRF gun) the Helmholtz-Zentrum Dresden-Rossendorf provided a promising approach for this key component, which has since been adopted in other laboratories. Nevertheless, some limitations occur caused by electron multipacting, which should be suppressed in order to further improve the gun. In this contribution, we present a detailed analysis of multipacting in the critical area of the SRF gun and different suppression techniques for it. The analytical predictions on the threshold for multipacting are qualitatively comparable with numerical simulation results and experimental data. Finally, we present specific surface structuring as an effective method to mitigate the multipacting phenomenon from the photocathode channel.
Keywords: superconducting RF, electron source, SRF gun, multipacting

Publ.-Id: 28446 - Permalink


Ab-initio study of electronic and magneto-optical properties of InAs:Mn
Gan’Shina, E.; Kulatov, E.; Golik, L.; Kun’Kova, Z.; Uspenskii, Y.; Zykov, G.; Yuan, Y.; Zhou, S.ORC
Energy difference between the ferromagnetic and antiferromagnetic collinear orderings has been calculated for the uniform and dimer Mn-pair geometries in order to find the ground state distribution of the Mn atoms in InAs host. We find the preference of the dimer ferromagnetic configuration of Mn dopants and an importance of optimizing the atomic site positions. The frequency-dependent optical and magneto-optical properties, namely the dielectric tensor (on-and off-diagonal components), the electron energy loss spectra, and the transversal Kerr effect (TKE), are calculated. Calculated TKE resonance in In1-xMnxAs (x=0.0625) is found to be in good agreement with corresponding experimental magneto-optical spectra. The origin of the large TKE is discussed.
  • Open Access LogoContribution to proceedings
    Moscow International Symposium on Magnetism 2017, 01.-05.07.2017, Moscow, Russia
    Moscow International Symposium on Magnetism (MISM 2017): EPJ Web of Conferences, 185, 06008
    DOI: 10.1051/epjconf/201818506008

Publ.-Id: 28444 - Permalink


Bacillus safensis JG-B5T affects the fate of selenium
Fischer, S.; Jordan, N.; Krause, T.; Lederer, F.; Merroun, M. L.; Shevchenko, A.; Hübner, R.; Jain, R.;
Selenium is toxic to aquatic organisms even at µg L−1 range concentration. Further, the toxicity of selenium not only depends on its concentration but also on speciation. Thus, understanding the fate of the selenium in the environment is important. Micro-organisms are known to affect the speciation and hence mobility of selenium. This study, for the first time, evaluated the interaction of selenium oxyanions and strain Bacillus safensis JG-B5T, which was isolated from the Haberland uranium waste pile in Johanngeorgenstadt (Saxony) in 1997. The study showed that the B. safensis JG-B5T can reduce selenite, but not selenate, to selenium nanoparticles. Further, the growth of B. safensis JG-B5T is not affected by the presence of 2.5 mM of selenate and observed a lag of 8 h in presence of 2.5 mM selenite. The high resolution time-dependent TEM images has suggested that the extracellular production of Se NPs. The genomic data has pointed to the role of membrane associated reductases or extracellular reducing mechanism for the reduction of selenite. The high mobility, due to the presence of protein corona and negative zeta potential, and extracellular origin of Se NPs make them mobile. Thus, B. safensis JG-B5T can change the speciation and mobility of dissolved selenite and affect the fate of selenium in the environment.
Keywords: Selenium, speciation, availability, transformation
  • Invited lecture (Conferences)
    Research frontiers in chalcogen cycles science and technology, 06.-07.12.2018, Naples, Italy

Publ.-Id: 28443 - Permalink


Ion implantation + sub-second annealing: a route towards hyperdoped semiconductors
Zhou, S.ORC
Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortenedto millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-5], highly mismatched semiconductor alloys (Ge1-xSnx [6] and GaAs1-xNx [7]), n++ Ge [8, 9] and chalcogen doped Si [10-12].

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).
[6] K. Gao, et al., Appl. Phys. Lett.,105, 042107 (2014).
[7] K. Gao, et al., Appl. Phys. Lett.,105, 012107 (2014).
[8] S. Prucnal, et al., Sci.Reports 6, 27643(2016).
[9] S. Prucnal, et al., Semicond. Sci. Technol. 32 115006 (2017).
[10] S. Zhou, et al., Sci. Reports 5, 8329(2015).
[11] Y. Berencén, et al., Adv. Mater. Inter. 5, 1800101 (2018).
[12] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018).
  • Invited lecture (Conferences)
    International Conference on Radiation and Emission in Materials, 20.-23.11.2018, Chiang Mai, Thailand
  • Invited lecture (Conferences)
    Seminar at Hongkong University, 15.11.2018, Hong Kong, China
  • Lecture (Conference)
    Seminar at University Leipzig, 05.12.2018, Leipzig, Germany

Publ.-Id: 28442 - Permalink


Anomalous Hall-like transverse magnetoresistance in Au thin films on Y3Fe5O12
Kosub, T.; Velez, S.; Gomez-Perez, J. M.; Hueso, L. E.; Fassbender, J.; Casanova, F.; Makarov, D.;
Anomalous Hall-like signals in platinum in contact with magnetic insulators are common observations that could be explained by either proximity magnetization or spin Hall magnetoresistance (SMR). In this work, longitudinal and transverse magnetoresistances are measured in a pure gold thin film on the ferrimagnetic insulator Y3Fe5O12 (Yttrium Iron Garnet, YIG). We show that both the longitudinal and transverse magnetoresistances have quantitatively consistent scaling in YIG/Au and in a YIG/Pt reference system when applying the SMR framework. No contribution of an anomalous Hall effect due to the magnetic proximity effect is evident. Published by AIP Publishing.

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Publ.-Id: 28440 - Permalink


Efficient ion-slicing of InP thin film for Si-based hetero-integration
Lin, J.; You, T.; Wang, M.ORC; Huang, K.; Zhang, S.; Jia, Q.; Zhou, M.; Yu, W.; Zhou, S.; Wang, X.; Ou, X.
Integration of high quality single crystalline InP thin film on Si substrate has potential applications in Si-based photonics and high-speed electronics. In this work, the exfoliation of a 634 nm crystalline InP layer from the bulk substrate was achieved by sequential implantation of He ions and H ions at room temperature. It was found that the sequence of He and H ion implantations has a decisive influence on the InP surface blistering and exfoliation, which only occur in the InP pre-implanted with He ions. The exfoliation efficiency first increases and then decreases as a function of H ion implantation fluence. A kinetics analysis of the thermally activated blistering process suggests that the sequential implantation of He and H ions can reduce the InP thin film splitting thermal budget dramatically. Finally, a high quality 2 inch InP-on-Si(100) hetero-integration wafer was fabricated by He and H ion sequential implantation at room temperature in combination with direct wafer bonding.
Keywords: InP-on-Si, hetero-integration, ion-slicing, wafer bonding

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  • Secondary publication expected from 10.10.2019

Publ.-Id: 28439 - Permalink


Development of a Refined RTD-Based Efficiency Prediction Model for Cross-flow Trays
Vishwakarma, V.ORC; Schubert, M.ORC; Hampel, U.
The present work describes the mathematical formulation of a new tray efficiency model through refinement of the conventional residence time distribution (RTD) approach [Foss et al. AIChE J. 1958, 4(2), 231−239]. Geometrical partitioning of a tray into compartments along the main liquid flow direction is a prerequisite in the new model. This partitioning allows computation of the tray efficiency through quantification of the efficiency of the individual compartments. The new model ensures that the fluid dynamics of each compartment contributes toward the overall tray efficiency. This breaks the previous black-box convention of the existing models, which only refer to flow profiles at the tray boundaries. The tray segmentation further aids in analyzing the impact of vapor flow maldistribution on the tray efficiency. The capabilities of the new model are demonstrated in two separate case studies after the model validation for perfectly mixed liquid flow in the compartments and biphasic plug flow on the tray.

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  • Secondary publication expected from 16.01.2020

Publ.-Id: 28438 - Permalink


Effect of flow non-idealities and vapor-liquid equilibrium characteristics on tray column efficiency: a case study
Vishwakarma, V.; Rigos, N.; Schubert, M.; Hampel, U.;
Distillation columns are energy-intensive process equipments as they account for 10 to 15% of the global energy consumption.(1) According to a recent estimate, 50% of the existing columns in the world are equipped with cross-flow trays.(2) Such columns are cascades of trays with similar geometry and function. Thus, trays are considered as the fundamental unit in distillation columns.(3) This generalization has led to numerous experimental and numerical studies on hydrodynamics and separation efficiency of individual trays. The methods for integrating individual tray performances in a column with the overall column efficiency have been largely unexplored. Reasonable estimates of the column efficiency based on vapor-liquid equilibrium (VLE) characteristics and flow non-idealities on tray internals are possible to obtain during the column design phase. This can reduce column’s cost and energy consumption through design modification and process optimization.
In this work, two separate case studies are formulated for displaying the approach of the overall column efficiency prediction based on flow non-idealities and VLE characteristics of binary mixtures on column trays. Basically, the axial dispersion model is firstly used to assign non-idealities to the liquid flow on column trays. The VLE data for binary mixtures are then generated using the Soave-Redlich-Kwong (SRK) model and the Non-Random Two-Liquid (NRTL) model inbuilt in Aspen Plus. Thereafter, the mathematical models(3) are employed to obtain the tray efficiency based on given liquid dispersion and VLE data using an iterative procedure for the presumed point efficiencies. In the first study, this procedure is employed for different binary mixtures getting distilled in a theoretical column operating under total reflux condition as shown in Fig. 1.

Fig. 1. McCabe-Thiele diagram for Benzene-Toluene mixture in total reflux column at 1 atm with pseudo-VLE curves for tray Péclet number as 2 and 40 and EOV = 0.5.

In the second study, the same procedure is used to analyze real column data of binary mixtures taken from the literature. For both studies, the graphical stepping procedure of equilibrium and non-equilibrium trays in the McCabe-Thiele diagram is shown (Fig. 1) in this work. The relocation of the pseudo-VLE curve in this diagram with respect to liquid dispersion on trays signifies their impact on the overall column efficiency. This work also motivates for the formulation of better tray efficiency models in the future, as they are a key aspect of column efficiency calculations.

(1) D. S. Sholl, R. P. Lively. Seven chemical separations to change the world. Nature News, 532(7600), 435, 2016.
(2) A. Górak, Z. Olujić. Distillation: equipment and processes, Academic Press. 2014.
(3) V. Vishwakarma, M. Schubert, U. Hampel. Assessment of separation efficiency modeling and visualization approaches pertaining to flow and mixing patterns on distillation trays, Chemical Engineering Science, 185, 182-208, 2018.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Germany

Publ.-Id: 28437 - Permalink


A novel RTD compartment model for tray efficiency predictions
Vishwakarma, V.; Schubert, M.; Hampel, U.;
In the present work, a new model built through refinement of the existing residence time distribution model [Foss, PhD Thesis, University of Delaware, 1957] is proposed. In this new model, the tray is imaginarily partitioned into compartments along the liquid flow direction between tray inlet and outlet. This partitioning allows computing the tray efficiency through quantification of the efficiencies of the individual compartments. Therefore, the fluid dynamics of each compartment contribute towards the evolving tray efficiency, thereby breaking the tray’s black-box convention. The tray segmentation further supports in studying the effects of vapor maldistribution as well as flow path length on the tray efficiency. This indicates the versatility and advantage of the new model over the existing ones. In particular, the mathematical formulation of this model along with its theoretical validation and application through analysis of suitable case studies are presented.
  • Open Access LogoChemical Engineering Transactions 69(2018), 331-336
    DOI: 10.3303/CET1869056
  • Poster
    Distillation and Absorption 2018, 16.-19.09.2018, Florence, Italy

Publ.-Id: 28435 - Permalink


Advancement in tray efficiency modeling through RTD chambers
Vishwakarma, V.; Schubert, M.; Hampel, U.;
Cross-flow trays are widely favored vapor-liquid contacting devices in the process industry. It is approximated that distillation columns consume 3% of the worldwide energy, while half of them are equipped with trays. An accurate quantification of column performance is a prerequisite prior to process optimization through external measures. Since a column is a cascade of trays with more or less same function, it is appropriate to consider the trays as a fundamental unit of the column, and thus focus on understanding of their operation and performance.
Flow and mixing patterns on these trays strongly affect their separation efficiency. Mathematical models have been formulated in the literature to relate these patterns with the tray efficiency. Recent advances in imaging and simulation techniques have revealed the biphasic non-idealities existing on the trays. The available efficiency models, recently reviewed by Vishwakarma et al.(1), however, usually consider flow conditions at the tray boundaries only, and assume uniform homogenous vapor load on the tray. Such efficiency assessment conveys the impression of trays as a black-box.
A significant improvement in tray efficiency modeling can be achieved by mathematically segmenting the tray into an arbitrary number of chambers amidst inlet and outlet. A new model built upon the available residence time distribution (RTD) approach(2) is proposed in the present work, where the tray efficiency is computed through contribution of the RTD efficiencies of the individual chambers. This segmentation further complements in studying the impacts of vapor maldistribution and flow path length on the tray efficiency, thereby signifying the advantage of this new model over the existing ones. The mathematical construction of the proposed model along with its theoretical validation and analyses through case studies will be highlighted in this work. The cases studies will further attempt to break the black-box convention of the trays.

(1) V. Vishwakarma, M. Schubert and U. Hampel. ‘Distillation tray efficiency modelling: a forgotten chapter’, Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 16-17 March 2016, Garmisch-Partenkirchen (Germany).

(2) A. S. Foss, J. A. Gerster and R. L. Pigford. ‘Effect of liquid mixing on the performance of bubble trays’, AIChE Journal, 4(2):231-239, 1958.
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Membrantechnik und Mischvorgänge, 27.-28.02.2018, Munich, Germany

Publ.-Id: 28434 - Permalink


Speciation of U(IV) sulfate in aqueous solution – spectroscopic characterization and thermodynamic modelling
Lehmann, S.; Steudtner, R.; Gerber, U.; Zimmermann, T.; Brendler, V.;
For a high level radioactive waste disposal as well as former uranium mining sites after sealing U(IV) is expected to be the stable oxidation state due to reducing conditions. Thermodynamic data on U(IV) in aqueous solution is needed for a reliable safety assessment but still sparse by reason of its low solubility and a lack of appropriate measuring systems. By employing a combination of absorption- and fluorescence spectroscopy to study U(IV) sulfate complexation in acidic aqueous solution we gained complex formation constants, extinction coefficients and single component absorption spectra of U4+, UOH3+, U(SO4)2+ and U(SO4)2.
  • Lecture (others)
    Workshop of Doctoral Candidates (PhD student seminar), 13.12.2018, Zittau, Deutschland

Publ.-Id: 28432 - Permalink


Integration of VNIR-SWIR hyperspectral core scanning in predictive geometallurgical modelling
Tusa, L.; Andreani, L.; Gilbricht, S.; Ivascanu, P.; Gloaguen, R.; Gutzmer, J.;
Traditionally during exploration campaigns, geochemical and conventional drill-core logging data is acquired in order to understand the formation and zonality of mineral deposits. The zonality and variability of the mineralization are most commonly linked to the changes in alteration assemblages and therefore the development of a detailed alteration model would allow a better understanding of the distribution and mode of occurrence of mineralization – and provides important, early clues to processing characteristics. Here, we introduce a methodology for rapid extraction of mineralogical, textural and structural features from exploration core. Data obtained can be easily integrated into 3D numerical models and linked to other exploration data (e.g. grade). Mineralogical and structural information is acquired using innovative image classification and segmentation techniques on hyperspectral VNIR-SWIR core scans. Scanning electron microscopy (SEM)-based analyses performed on representative samples allow for thorough investigations of the modal mineralogy and microfabric attributes of specific mineralization styles – with samples selected based on the results of hyperspectral core scans. The methodology is applied to the Bolcana copper-gold porphyry deposit (Romania), where extensive drilling has been performed by Eldorado Gold. The system shows complex transitions between lithological and alteration assemblages thus representing a particularly suitable case study. Results obtained illustrate that the integration of hyperspectral data with conventional core logs and structural data (Reflex IQ-logger) provided by Eldorado Gold offers insight into the spatial and directional distribution of vein types and associated alteration assemblages. The integration of SEM-data permits unique insight into processing characteristics – thus enabling the construction of a predictive geometallurgical model to outline limits and opportunities of metallurgical testing already during the early exploration stage.
  • Contribution to proceedings
    Resources for future generations, 16.-21.06.2018, Vancouver, Canada
    Proceedings of Resources for future generations

Publ.-Id: 28431 - Permalink


Extraction of structural and mineralogical features from hyperspectral drill-core scans
Tusa, L.; Andreani, L.; Pohl, E.; Contreras, I. C.; Khodadadzadeh, M.; Gloaguen, R.; Gutzmer, J.;
For vein hosted mineralization such as encountered in porphyry systems, the documentation of the main alteration assemblages associated with specific vein generations is essential in understanding the geometry of the mineralized body. Hence, mineralogical and structural information are highly relevant for characterizing the mineralization. In this paper, we present an approach for the extraction of both mineralogical and structural information from hyperspectral scans. We propose a parallel framework which includes a typical mineral mapping technique for the extraction of mineralogical information as well as a ridge detection method for the extraction of veins applied on mineral abundance maps. In the proposed framework, the abundance maps are obtained from hyperspectral VNIR-SWIR drill-core scans using a linear spectral unmixing technique. Drill cores hosting porphyry stockwork type mineralization are used for the evaluation of the proposed technique and the experimental results show that the method offers a tool for accurately characterizing the mineralized body.
Keywords: core scanning, hyperspectral imaging, image segmentation, feature extraction, mineral mapping
  • Contribution to proceedings
    IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 23.-27.07.2018, Valencia, Spain
    Proceedings of IGARSS 2018
    DOI: 10.1109/IGARSS.2018.8517786

Publ.-Id: 28429 - Permalink


Robust intensity-modulated proton therapy with simultaneous integrated boost reduces the low-dose to surrounding tissues in pancreatic cancer patients
Stefanowicz, S.; Zschaeck, S.; Troost, E. G. C.ORC
Purpose or Objective
Neoadjuvant or primary radiochemotherapy (RCT) are treatment options for patients with borderline resectable or unresectable locally advanced non-metastatic pancreatic cancer, respectively. Currently, the potential of RCT is hampered by an insufficient dose prescription to the target, limited by the close-by radiosensitive organs at risk (OAR). Dose-escalation to the gross tumor volume (GTV) along with the current standard dose to the elective volume using a simultaneous integrated boost approach (SIB) may lead to improved therapeutic outcome. In this in-silico feasibility study on SIB dose-escalation, we compared volumetric modulated arc therapy (VMAT) using photons with robust intensity-modulated proton therapy (IMPT).

Material and Methods
For each of five locally advanced pancreatic cancer patients, a VMAT and a robust multi-field optimized IMPT treatment plan were optimized on free-breathing treatment planning CTs using the RayStation treatment planning system (V5.99, RaySearch Laboratories AB, Sweden). For the photon treatment plan, the doses prescribed to 95% of the GTV and of the planning target volume (PTV: clinical target volume, CTV, plus a 5 mm margin) were to be at least 95% of 66Gy and 51Gy respectively, both in 30 fractions. For the proton plan, robust optimization to the CTV (instead of the PTV) with a setup uncertainty of 5mm and a density uncertainty of 3.5% was chosen, thus prescribing the dose of 51Gy(RBE) to 95% of the CTV (GTV with a margin and elective volume). The OAR dose constraints adhered to local guidelines and QUANTEC. For each treatment plan, doses to GTV, CTV, and OARs as well as the volume of normal tissue outside the CTV receiving a dose of ≥ 20Gy(RBE) (V20Gy) were compared.

Results
All treatment plans reached the prescribed doses to the GTV and CTV/PTV, irrespective of the technique. In some patients, doses to the bowel, stomach and liver exceeded the constraints since that OARs were next to or within the target volume. While the VMAT technique reduced the V50Gy of the bowel (median V50Gy: VMAT 20.4ccm vs. IMPT 23.3ccm) and stomach (median V50Gy: VMAT 1.2ccm vs. IMPT 4.5ccm), the radiation doses to the remaining gastrointestinal organs were lower for IMPT, e.g. liver (median V30Gy: VMAT 93.6ccm vs. IMPT 39.2ccm) and kidneys (median V20Gy of left/right kidney: VMAT 21.0ccm/16.1ccm vs. IMPT 13.8ccm/12.1ccm). Overall, the IMPT technique showed a lower dose deposition outside the targets for the surrounding normal tissue (median V20Gy: VMAT 1483.4ccm vs. IMPT 756.2ccm).

Conclusion
Disregarding the inter- and intra-fractional organ motion, dose escalation is possible for both treatment techniques. In comparison to VMAT, IMPT reduced the dose to the surrounding normal tissue, including relevant organs at risk. However, robust optimization increased the high-dose level to OARs overlapping with the target volume. Further patients will be included in this study and presented during the DKFK 2019.
  • Poster
    1. Deutscher KrebsForschungsKongress (DKFK), 04.-05.02.2019, Heidelberg, Deutschland

Publ.-Id: 28428 - Permalink


Status of the Digital Low Level RF at ELBE
Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.;
Status of the Digital Low Level RF at ELBE is presented.
Keywords: ELBE, MicroTCA.4, LLRF, OPC UA, ChimeraTK
  • Lecture (others)
    6th ARD ST3 Workshop, 27.09.2018, Dresden, Deutschland

Publ.-Id: 28426 - Permalink


Ab Initio Path Integral Monte Carlo Results for the Dynamic Structure Factor of Correlated Electrons: From the Electron Liquid to Warm Dense Matter
Dornheim, T.; Groth, S.; Vorberger, J.; Bonitz, M.;
The accurate description of electrons at extreme density and temperature is of paramount importance for, e.g., the understanding of astrophysical objects and inertial confinement fusion. In this context, the dynamic structure factor S(q,w) constitutes a key quantity as it is directly measured in X-ray Thomson (XRTS) scattering experiments and governs transport properties like the dynamic conductivity. In this work, we present the first ab initio results for S(q,w) by carrying out extensive path integral Monte Carlo simulations and developing a new method for the required analytic continuation, which is based on the stochastic sampling of the dynamic local field correction G(q,w).
In addition, we find that the so-called static approximation constitutes a promising opportunity to obtain high-quality data for S(q; !) over substantial parts of the warm dense matter regime.
Keywords: warm dense matter, quantum Monte Carlo, electron gas, dynamic structure factor, local field correction

Publ.-Id: 28425 - Permalink


Digital Low Level RF at ELBE
Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.;
The upgrade of the Low Level RF (LLRF) system of the Electron Linac for beams with high Brilliance and low Emittance (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is ongoing. A digital system based on MTCA.4 will replace the analogue system, which is operated since almost 20 years.The digital LLRF controller is implemented on a FPGA. The parametrisation and monitoring of the controller is performed by a ChimeraTK server application. ChimeraTK is a control system and hardware interface tool kit, which among others can provide an OPC-Unified Architecture (OPC-UA) interface. On the one hand, this interface is used to integrate the digital LLRF into the existing ELBE control and machine protection system, that is based on a Siemens PLC (S7) infrastructure. On the other hand, it is used to implement different additional clients of the ChimeraTK server application, such as the ELBE human machine interface used by the operators (WinCC, SCADA) or expert panels (e.g. LabView or Python). An overview of the new system including hardware as well as software components is given. In addition, first results of the full integration test including LLRF controller optimization and amplitude and phase noise measurements are presented.
Keywords: ELBE, MicroTCA.4, LLRF, OPC UA, ChimeraTK
  • Invited lecture (Conferences)
    MAMI Seminar, 08.11.2018, Mainz, Deutschland

Publ.-Id: 28424 - Permalink


Upgrade of the LLRF system at ELBE
Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.;
The upgrade of the Low Level Radio Frequency (LLRF) system at the superconducting linear accelerator ELBE is about to being finished. A digital system based on MTCA.4 has been implemented and is going to replace the analogue system which is in operation since 20 years by the end of 2018. The digital system is capable for continuous wave (CW) operation and single cavity control. The server application uses the open source project ChimeraTK and its OPC-UA adapter, that is based on the open source project open62541. This allows to integrate the digital LLRF into the existing ELBE control and machine protection system, that is based on a Siemens PLC (S7) infrastructure. Furthermore, the OPC-UA adapter of ChimeraTK allows to implement different additional clients of the ChimeraTK server application, such as the ELBE human machine interface used by the operators (WinCC, SCADA) or expert panels (e.g. LabView or Python). The talk summarizes first results of the full integration test including LLRF controller optimization and amplitude and phase noise measurements. Furthermore, latest developments of the OPC-UA adapter and contributions to ChimeraTK are presented.
Keywords: ELBE, MicroTCA.4, LLRF, OPC UA, ChimeraTK
  • Lecture (others)
    7th MicroTCA Workshop for Industry and Research, 05.-06.12.2018, Hamburg, Deutschland

Publ.-Id: 28423 - Permalink


Preparation of animal irradiation experiments with laser-accelerated protons and pulsed high-field magnets
Brack, F.-E.; Kroll, F.; Metzkes, J.; Obst, L.; Kraft, S.; Schlenvoigt, H.-P.; Beyreuthe, E.; Karsch, L.; Pawelke, J.; Enghardt, W.; Zeil, K.; Schramm, U.;
Laser-driven ion acceleration has been considered a potential alternative for conventional accelerators like cyclotrons or synchrotrons and thus could provide a more compact and cost-efficient particle therapy solution in the future. Instead of continuous ion beams, laser-driven ions exhibit fs to ps bunch length, carrying up to 1013 particles with broad energy spectrum and are highly divergent. Pulsed high-field magnets are a versatile and efficient way of shaping those bunches both spatially and spectrally for application, while preserving the short pulse lengths and high intensities leading to high dose rates when stopped in matter.
We performed experiments with the PW beam of the Dresden laser acceleration source Draco to investigate the feasibility of worldwide first controlled volumetric tumour irradiations with laser-accelerated protons. Therefore, a setup of up to two solenoid magnets was used to efficiently capture and shape the proton beam, matching the radiobiological demands, which was then analysed by means of a Thomson parabola spectrometer, scintillator, ionization chamber and radiochromic film.
  • Lecture (Conference)
    DPG Frühjahrstagung 2018, 19.-23.03.2018, Würzburg, Deutschland

Publ.-Id: 28421 - Permalink


Structural and magnetic susceptibility characterization of Pu(V) aqua ion using sonochemistry as a facile synthesis method
Dalodiere, E.; Virot, M.; Dumas, T.; Guillaumont, D.; Illy, M.; Berthon, C.; Guerin, L.; Rossberg, A.; Venault, L.; Moisy, P.; Nikitenko, S.;
Since the past few years, Pu(V) has gained much attention due to its potential contribution to the environmental migration of actinides. However, the preparation of concentrated (up to mM) and pure Pu(V) solutions is quite difficult and often hindered by its great instability towards disproportionation, thus limiting the accessibility to physical and chemical property data. This work describes the rapid and facile sonochemical preparation of relatively stable Pu(V) solutions in the millimolar range free from the admixtures of the other oxidation states of plutonium. The mechanism deals with the sonochemical reduction of Pu(VI) in weakly acidic perchloric solutions by using the in situ generated H2O2, where the kinetics can be dramatically enhanced under high frequency ultrasound and an Ar/O2 atmosphere. The quasi-exclusive presence of the Pu(V) aqua ion in solution was evidenced by UV-vis absorption spectroscopy. The prepared solutions were found to be stable for more than one month which allowed the accurate XAFS and NMR investigations of Pu(V). EXAFS spectra revealed the presence of two trans dioxo Pu[double bond, length as m-dash]O bonds at 1.81 Å and 4–6 equatorial Pu–Oeq interactions at 2.47 Å characteristic of coordinated water molecules. The exact number of water molecules (N[Oeq(H2O)] = 4) was determined by simulating the EXAFS spectra of the PuO2+ aqua complexes using DFT calculations (geometry and the Debye–Waller factor) and comparing them with experimental signals. For the first time, the magnetic susceptibility of the pentavalent state of plutonium in aqueous solutions was also determined (χM = 16.3 × 10−9 m3 mol−1 at 25 °C) and the related Curie constant was estimated (C = 6.896 × 10−6 m3 K mol−1).

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  • Secondary publication expected

Publ.-Id: 28420 - Permalink


First application studies at the laser-driven LIGHT beamline: Improving proton beam homogeneity and imaging of a solid target
Jahn, D.; Schumacher, D.; Brabetz, C.; Ding, J.; Weih, S.; Kroll, F.; Brack, F.-E.ORC; Schramm, U.; Blažević, A.; Roth, M.
In the last two decades, the generation of intense ion beams based on laser-driven sources has become an extensively investigated field. The LIGHT collaboration combines a laser-driven intense ion source with conventional accelerator technology based on the expertise of laser, plasma and accelerator physicists. Our collaboration has installed a laser-driven multi-MeV ion beamline at the GSI Helmholtzzentrum für Schwerionenforschung delivering intense proton bunches in the subnanosecond regime. We investigate possible applications for this beamline, especially in this report we focus on the imaging capabilities. We report on our proton beam homogenization and on first imaging results of a solid target.
Keywords: Laser-driven ion acceleration; Laser-driven proton beam homogeneity; Proton imaging; LIGHT collaboration
  • Contribution to proceedings
    3rd European Advanced Accelerator Concepts Workshop, 24.-28.09.2017, La Biodola, Isola d'Elba, Italien
    3rd European Advanced Accelerator Concepts workshop (EAAC2017)
    DOI: 10.1016/j.nima.2018.02.026

Publ.-Id: 28419 - Permalink


Heterogeneous modeling approach for gas-limited reactions in an inclined rotating fixed bed reactor
Timaeus, R.; Hampel, U.; Schubert, M.;
A heterogeneous modeling approach for an inclined rotating fixed bed reactor with concentric internal tube is introduced. The novel reactor is designed to intensify the mass transfer of gas-limited heterogeneous catalyzed reactions by intermittent catalyst wetting, which is enabled exposing the packed bed to rotation and inclination. A simulation study for the hydrogenation of α-methylstyrene is presented. In particular, the influence of period length and different wetting-draining cycles on the space-time-yield of the reactor is analyzed.
Keywords: Inclined fixed bed, multiphase reactor, particle modeling, process intensification, reactor modeling

Downloads:

  • Secondary publication expected from 01.05.2020

Publ.-Id: 28418 - Permalink


Inclined rotating fixed bed reactors – a process intensification concept for heterogeneous catalytic multiphase reactions
Timaeus, R.; Schubert, M.; Hampel, U.;
The inclined rotating tubular fixed bed reactor has been introduced recently as a concept for the implementation of multiphase processes, in particular for heterogeneously catalysed gas-liquid reactions with mass transfer limitations.
Often, trickle bed reactors suffer from liquid maldistribution and low mass and heat transfer rates and have therefore been subject to process intensification. Periodic liquid flow rate modulation at the reactor inlet was introduced, which leads to elevated space-time-yields in comparison to the steady-state operation. However, the beneficial effects decay rapidly along the reactor length and maldistribution is not effectively counterbalanced.
To fully utilise the positive effects of such modulation strategy with the new reactor concept, the tubular reactor with the fixed catalyst packing is inclined against the vertical to establish a stratified flow. The superimposed continuous reactor rotation around the axis ensures a wetting intermittency via periodic immersion of the whole catalyst packing in the stratified liquid phase. Furthermore, it enables also tuning the liquid residence time at constant gas and liquid flow rates.
The wetting intermittency results in a complete utilization of the catalyst on the reactor scale and in periodically thinned liquid films at the catalyst surface, which enhances the accessibility of the gaseous reactants to the active sites. The latter is proven by an increased space-time-yield compared to conventional trickle bed reactor operation for the hydrogenation of α methylstyrene to cumene.
In this presentation, the performance of the new reactor concept will be assessed based on reactive studies. Furthermore, the results will be discussed with respect to the prevailing flow regimes investigated via gamma-ray computed tomography, as well as liquid residence time and axial dispersion obtained by a stimulus-response technique using embedded wire-mesh sensors.
Keywords: Inclined rotating fixed bed reactors, process intensification, innovative reactor concepts
  • Invited lecture (Conferences)
    International Congress of Chemical and Process Engineering (CHISA 2018), 26.08.2018, Prag, Tschechische Republik

Publ.-Id: 28417 - Permalink


Ultra-high-speed X-ray imaging of laser-driven shock into solid materials using synchrotron light
Olbinado, M. P.; Grenzer, J.; Rack, A.; de Resseguier, T.; Danilewsky, A.; Kraus, D.; Cowan, T.;
A high-power, pulsed laser impacting the surface of a material can generate surface ablation, shock waves and crack propagation; while X-ray imaging can provide a time-resolved probe. Hard X-rays are perfectly suitable for visualizations of transient processes in optically opaque materials even for objects of several mm in size. The MHz pulsed time structure, tunable energy bandwidth, high brilliance, and the high degree of spatial coherence of hard X-rays (E > 30keV) from third generation synchrotron sources allowing transient processes to be tracked directly using ultra-high-speed image acquisition systems.
We report on an in-situ real time investigation of ns single-pulsed laser-driven processes studied by combined diffraction-direct-space-imaging experiments exploiting the single bunch structure at the hard X-ray imaging beam line ID19 of the ESRF investigating the process of laser hole drilling into single crystalline silicium.
Whereas macroscopic changes in bulk materials can be quite easily deduced from X-ray phase contrast imaging; information probing changes at the lattice level can be obtained using diffraction imaging. The whole process was followed for 120sec with a maximum frame rate of up to 100kHz.
We have developed an experimental methods that allow to synchronize on the ns level the single shot laser operation with the high speed camera system matching the 4- and 16-bunch structure of the ESRF.
Keywords: X-ray imaging laser
  • Lecture (Conference)
    Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten (SNI2018), 17.-19.09.2018, München, Germany

Publ.-Id: 28416 - Permalink


Computational modelling approach of an inclined rotating fixed bed reactor
Timaeus, R.; Schubert, M.; Hampel, U.;
In the last decades several research groups investigated the dynamic operation of trickle bed reactors to intensify mass transfer-limited multiphase reactions. This process intensification strategy is realized via a cyclic flow rate modulation of the liquid phase, which results in a spatial and time-dependent liquid holdup in the catalytic fixed bed. Here, the variation of the liquid holdup causes an enhanced accessibility of the limited components to the catalyst, whereby a higher overall reaction rate is achieved. Although promising enhancements of the overall reaction rate in lab-scale trickle bed reactors were proved, the forced liquid cycling suffers from pulse attenuation along the reactor, thus the beneficial flow conditions mitigate at lower axial reactor positions (Atta et al., 2014).
Recently, an inclined rotating fixed bed reactor was developed, which ensures a permanent wetting intermittency of the catalyst within the stratified flow. The latter is caused by the reactor inclination. A twofold increase of the conversion for the α-methylstyrene hydrogenation was obtained, compared to the trickle bed operation, which highlights the potential of the new reactor concept (Härting et al., 2015).
In this contribution, a feasible hybrid model approach for the prediction of the space-time yield is proposed. The model consists of a three-dimensional two-phase Eulerian-Eulerian model and a heterogeneous continuum model to describe the hydrodynamics and the mass transfer and reaction phenomena, respectively. In this hybrid framework, the Eulerian-Eulerian model provides information about the wetting intermittency in terms of the dynamic holdup, which is incorporated in the heterogeneous continuum model by time-dependent boundary conditions at the particle scale.
The hydrodynamic model is based on a recently modified permeability approach with permeability coefficients of the gas phase depending on the flow pattern to approximate the solid-gas interactions of the phases (Subramanian et al., 2016). In this contribution different reactor geometries are studied and operated with α-methylstyrene, cumene and hydrogen. Additionally, the influence of the interfacial area density and the drag coefficient in the gas-liquid closure is examined via simulation studies.
The heterogeneous continuum model consists of a stationary reactor model considering the Danckwerts boundary conditions and of a transient particle model accounting for the intraparticle concentration gradients.
Eventually, the implemented hybrid model approach is applied for simulation studies to extend the knowledge of the new reactor concept and to support the optimal design and operation.
Keywords: Inclined rotating fixed bed reactors, process intensification, innovative reactor concepts
  • Lecture (Conference)
    International Congress of Chemical and Process Engineering (CHISA 2018), 27.08.2018, Prag, Tschechische Republik

Publ.-Id: 28415 - Permalink


Ultra-high-speed X-ray imaging of laser driven processes using synchrotron light
Grenzer, J.; Rack, A.; Olbinado, M. P.; de Resseguier, T.; Danilewsky, A.; Kraus, D.; Cowan, T.;
Time-resolved in-situ or/and in-operando X-ray experiments open a very direct, natural way to study the formation and transformation of materials during relevant technological processes. High-brilliance, fs-pulsed X-rays generated by XFels demonstrate the highest temporal and spatial resolutions, but the maximum X-ray energy is currently limited to ~25 keV. Despite the possibility to illuminate macroscopic objects with large beams (~100mm2) synchrotron light sources produce X-rays pulses with much lower temporal resolution (~100ps), spatial coherence and brilliance but are able to reach X-ray energies higher than achieved at current FELs. MHz pulse repetition rates (ESRF:up to 5.6MHz in the 16 bunch mode) are characteristic to synchrotrons, allowing transient processes to be tracked using ultra-high-speed image acquisition systems with multiple frames, that are even able to visualize transient processes that are stochastic or a-periodic.
Here, we report on an in-situ real time investigation into high-power (>1J), ns single-pulsed (Nd:YAG, = 532 nm; pulse length ~10 ns) laser-driven irradiation processes leading either to surface ablation, crack propagation or shock generation [1] studied by a combined diffraction-direct-space-imaging experiment exploiting the single bunch structure. Whereas macroscopic changes (i.e. density changes or cracks) in bulk materials can be quite easily deduced from X-ray phase contrast imaging, information probing changes at the lattice level can be obtained using diffraction imaging.
As an example is in the figure shown such a combined experiment [2]: The first laser shot of an in-situ real-time laser hole-drilling experiment into a 0.50 mm thick Si (001) single crystalline wafer that was carried out for about 120sec. The sample was placed by about 45° with respect to the laser and the X-ray beam. Both beams intersect horizontally at the same height at an angle of 90° at the rotation center of the sample. The laser light was directed to the sample using a focusing lens. The synchronization of the cameras with laser and X-ray pulses are described in [1]. The X-ray beam fully illuminates the 10×10 mm2 wafer. The diffraction angle was tuned so that the Si (333) reflection in transmission geometry was recorded by the diffraction imaging detector.
Keywords: X-ray imaging laser
  • Lecture (Conference)
    XTOP 2018. XIV Biennial Conference of High Resolution X-ray Diffraction and Imaging, 03.-07.09.2018, Bari, Italy

Publ.-Id: 28414 - Permalink


Heterogeneous modeling approach for gas-limited reactions in an inclined rotating fixed bed reactor with stratified flow
Timaeus, R.; Schubert, M.; Hampel, U.;
Mass transfer limitations in multiphase reactions are a widespread phenomenon in reaction engineering. Particularly in trickle bed reactors, space-time yield is limited due to the low accessibility of the gaseous educts to the solid catalyst. The inclined rotating fixed bed reactor is a new intensification strategy for trickle bed reactors to circumvent this bottleneck. The superposition of reactor inclination and rotation results in a stratified flow, which causes wetting intermittency of the catalytic fixed bed with alternatingly unhindered access of gas and liquid educts to the catalyst. The conversion for the α-methylstyrene hydrogenation has been doubled with the new reactor concept compared to the trickle bed operation, which highlights the potential of the process intensification strategy [1].
Within a DFG-funded project, a feasible model approach for the prediction of the space-time yield of the process intensification strategy is developed. In order to identify the most beneficial process windows and proper design parameters, a reactor model framework consisting of a two-phase Eulerian-Eulerian model and a heterogeneous continuum model to describe the hydrodynamics and to capture mass transfer and reaction phenomena, respectively, is proposed. In this contribution, the heterogeneous one-dimensional continuum model accounting for intraparticle gradients with time-dependent Neumann boundary conditions at particle scale is implemented. While the catalyst wetting intermittency leads to dynamic species concentrations at the particle scale, the species concentrations of the liquid bulk phase are stationary. Coupling of the different scales is realized by a two-way approach, using the species concentrations on each scale. The implemented model is applied for simulation studies considering the hydrogenation of α-methylstyrene to cumene in order to investigate the influence of period length via reactor rotation velocity and the wetting/draining cycle via flow stratification defined as split on the space-time yield.
Keywords: Inclined rotating fixed bed reactor, process intensification, modeling
  • Poster
    Jahrestreffen Reaktionstechnik 2018, 07.05.2018, Würzburg, Deutschland

Publ.-Id: 28413 - Permalink


Formation and evolution of porosity pattern in a potential host rock
Bollermann, T.;
The major goal of the iCross project is to link experimental results and reactive transport modelling across scale to get a fundamental understanding of processes in the multi barrier system of a potential nuclear waste repository. This poster shows how the mapping of surface topography via vertical scanning interferometer results in quantitative information about the surface reactivity. Furthermore, it highlights how Positron emission tomography can be used to characterize transport patterns in geomaterials.
Keywords: iCross, analysis of surface reactivity, positron emission tomography
  • Poster
    KompOst Doktorandenseminar 2018, 13.12.2018, Zittau, Deutschland

Publ.-Id: 28412 - Permalink


Materials science: in-situ, in-operando, time-resolved
Grenzer, J.; Bähtz, C.; Rack, A.;
The development of new materials is today closely related to the “creation” of new functional nano structures. Structural investigations are the key to establish a connection between the functional and structural properties generating these functions. This knowledge makes it possible to design new materials with precisely predetermined properties. The function of nano structures is not only determined by their internal structure, but in large part by their morphology and surface properties.


Time-resolved in-situ or/and in-operando X-ray experiments open a very direct, natural way to study the formation and transformation of materials during the relevant technological processes. The talk will build a bridge from classical material science problems, like the formation of 3-dimensional Germanium nano crystal arrays embedded in a dielectric matrix using synchrotron radiation, or the crystallization process during a rapid thermal annealing (RTA) of an amorphous GeSn thin film using a laboratory setup, to experiments exploiting a µsec-time resolution and even behind that.

For example, material processing by laser beams is a widely used technology in industry. Many applications, like the fabrication of thin solar cells, require a large area processing in short times with a limited heat exposure. Therefore time resolved studies of laser driven processes are again of great scientific interest. If thousand of frames are needed to follow the materials evolution on an atomic level the regular bunch structure of a synchrotron source turns out to be an ideal probe to sense changes in the morphology and crystal structure during and after a laser-sample(target) interaction.
Keywords: in-situ, time-resolved, synchrotron
  • Invited lecture (Conferences)
    EPDIC16 – The 16th European Powder Diffraction Conference, 01.-04.07.2018, Edinburgh, GB
  • Lecture (others)
    Materials science: in-situ, in-operando, time-resolved, 08.11.2018, Prag, CZ

Publ.-Id: 28411 - Permalink


Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by SAXS using XFELs
Kluge, T.; Rödel, M.; Metzkes-Ng, J.; Pelka, A.; Laso Garcia, A.; Rehwald, M.; Prencipe, I.; Galtier, E.; Lee, H. J.; Glenzer, S.; Zeil, K.; Schramm, U.; Cowan, T. E.;
Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by SAXS using XFELs
  • Lecture (Conference)
    EUCALL Joint Foresight Topical Workshop: Theory and Simulation of Photon-Matter Interaction, 01.-05.07.2018, Szeged, Ungarn
    DOI: 10.5281/zenodo.1308068

Publ.-Id: 28410 - Permalink


3D Local Manipulation of the Metal-Insulator Transition Behavior in VO2 Thin Film by Defect-Induced Lattice Engineering
Jia, Q.; Grenzer, J.; He, H.; Anwand, W.; Ji, Y.; Yuan, Y.; Huang, K.; You, T.; Yu, W.; Ren, W.; Chen, X.; Liu, M.; Facsko, S.; Wang, X.; Ou, X.;
The ability to manipulate the metal-insulator transition (MIT) of metal oxides is of critical importance for fundamental investigations of electron correlations and practical implementations of power efficient tunable electrical and optical devices. Most of the existing techniques including chemical doping and epitaxial strain modification can only modify the global transition temperature, while the capability to locally manipulate MIT is still lacking for developing highly integrated functional devices. Here, lattice engineering induced by the energetic noble gas ion allowing a 3D local manipulation of the MIT in VO2 films is demonstrated and a spatial resolution laterally within the micrometer scale is reached. Ion-induced open volume defects efficiently modify the lattice constants of VO2 and consequently reduce the MIT temperature continuously from 341 to 275 K. According to a density functional theory calculation, the effect of lattice constant variation reduces the phase change energy barrier and therefore triggers the MIT at a much lower temperature. VO2 films with multiple transitions in both in-plane and out-of-plane dimensions can be achieved by implantation through a shadow mask or multienergy implantation. Based on this method, temperature-controlled VO2 metasurface structure is demonstrated by tuning only locally the MIT behavior on the VO2 surfaces.
Keywords: Metal–insulator transition VO2

Publ.-Id: 28409 - Permalink


Laser-driven ion acceleration at the Draco PW laser
Obst, L.ORC; Bernert, C.; Brack, F.; Branco, J.; Bussmann, M.; Cowan, T. E.; Garten, M.; Gaus, L.; Huebl, A.; Kluge, T.; Kraft, S. D.; Kroll, F.; Metzkes-Ng, J.; Rehwald, M.; Schlenvoigt, H.; Schramm, U.; Ziegler, T.; Zeil, K.
Presentation of past and ongoing campaigns aimed at the efficient generation of high energy proton beams at the Draco PW laser facility of Helmholtz-Zentrum Dresden - Rossendorf (HZDR).
  • Lecture (Conference)
    High-field laser-plasma interaction EPS DPP satellite workshop, 14.07.2018, Dolní Břežany, Tschechische Republik

Publ.-Id: 28408 - Permalink


Stress control of tensile-strained In1-xGaxP nanomechanical string resonators
Bueckle, M.; Hauber, V. C.; Cole, G. D.; Gaertner, C.; Zeimer, U.; Grenzer, J.; Weig, E. M.;
We investigate the mechanical properties of freely suspended nanostrings fabricated from tensilestressed, crystalline In1-xGaxP. The intrinsic strain arises during epitaxial growth as a consequence of the lattice mismatch between the thin film and the substrate, and is confirmed by x-ray diffraction measurements. The flexural eigenfrequencies of the nanomechanical string resonators reveal an orientation dependent stress with a maximum value of 650 MPa. The angular dependence is explained by a combination of anisotropic Young's modulus and a change of elastic properties caused by defects. As a function of the crystal orientation, a stress variation of up to 50% is observed. This enables fine tuning of the tensile stress for any given Ga content x, which implies interesting prospects for the study of high Q nanomechanical systems.
Keywords: nanomechanical string resonators

Publ.-Id: 28407 - Permalink


Advances in indirect detector systems for ultra high-speed hard X-ray imaging with synchrotron light
Olbinado, M. P.; Grenzer, J.; Pradel, P.; de Resseguier, T.; Vagovic, P.; Zdora, M.-C.; Guzenko, V. A.; David, C.; Rack, A.;
We report on indirect X-ray detector systems for various full-field, ultra high-speed X-ray imaging methodologies, such as X-ray phase-contrast radiography, diffraction topography, grating interferometry and speckle-based imaging performed at the hard X-ray imaging beamline ID19 of the European Synchrotron - ESRF. Our work highlights the versatility of indirect X-ray detectors to multiple goals such as single synchrotron pulse isolation, multiple-frame recording up to millions frames per second, high efficiency, and high spatial resolution. Besides the technical advancements, potential applications are briefly introduced and discussed.
Keywords: Inspection with x-rays; X-ray detectors; X-ray diffraction detectors

Publ.-Id: 28406 - Permalink


Einfluss der Rohrleitungsführung auf die Strömungsmorphologie in Feedleitungen von Destillationskolonnen
Döß, A.ORC; Schubert, M.; Hampel, U.; Mehringer, C.; Geipel, C. Keywords: Strömungsmorphologie, Feedleitung, Distillation, Gittersensor, TERESA
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik 2019, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 28405 - Permalink


MVT deposits
Gutzmer, J.;
This presentation provides an overview of current concepts of MVT deposit formation. As an in-depth case study, MVT-style deposits in South Africa are used to illustrate variations to the common theme.
  • Invited lecture (Conferences)
    16th Freiberg Short Course in Economic Geology, 02.-06.12.2018, Freiberg, Germany

Publ.-Id: 28404 - Permalink


The essence of time – fertile skarn formation in the Variscan Orogenic Belt
Burisch, M.; Gerdes, A.; Meinert, L.; Albert, R.; Seifert, T.; Gutzmer, J.;
Extending from Northern America to Central China the Variscan belt is a Paleozoic Orogen exceptionally well endowed in magmatic-hydrothermal ore deposits, including skarn deposits. Yet, the genesis of fertile skarns and their distinction from barren equivalents in orogenic zones is only poorly constrained. Here, we present innovative U-Pb laser-ablation inductively-coupled-plasma mass-spectrometry geochronology of garnet from different skarns in the Erzgebirge, a classic metallogenic province in central Europe. Garnet ages obtained not only constrain the timing of fertile skarn formation and associated Sn, W, Fe, Zn, Cu and In mineralization, but also clearly distinguish these from barren skarn bodies. We show that barren skarns formed during times of peak regional metamorphism at ∼340 Ma whereas mineralized skarns are temporally associated with late-orogenic magmatism at ∼325-313 Ma as well as post-orogenic magmatism at ∼308-295 Ma. The recognition of discrete mineralization events associated with the largest and economically most important skarn deposits provides valuable insight into the punctuated evolution of magmatic-hydrothermal systems in ancient collisional orogens on a regional scale; this has important implications to direct future mineral exploration.
Keywords: LA-ICP-MS U-Pb geochronology, metasomatism, hydrothermal ore deposit, garnet, Erzgebirge

Publ.-Id: 28403 - Permalink


An introduction to the thematic issue on “Ore deposits in the Variscan basement of Central Europe”
Gutzmer, J.; Markl, G.;
Much of the basement geology of Central Europe is characterized by volcanosedimentary successions of Late Precambrian and Early Paleozoic age that have been variably deformed and metamorphosed during the Variscan orogeny, followed by the intrusion of voluminous granites. The Variscan orogen records the closure of the Rheic ocean and the collision of Laurussia with Gondwana to form the Supercontinent Pangaea, and occurred as a series of protracted geotectonic events providing a suitable framework for the formation of a diverse range of ore deposits.

It comes as no surprise that the Variscan basement is host to most significant ore deposits of Central Europe. These ore deposits did not only provide the raw materials needed for industrial development in the past, but their mining yielded the need for scientific research and technological innovation. This need was also expressed by the publication of the world’s first textbook dedicated to economic geology as a distinct subdiscipline of the geosciences (Cotta 1855).

Industrial exploitation of most ore deposits of the Variscan basement in Central Europe ceased towards the end of the 20th century, typically due to subdued metal prices, but not motivated by a lack of mineral resources. Yet, following the demise of the mining sector there was the prevailing perception that Central Europe had little to offer for future exploration. This erroneous perception has seen a surprising reversal in the last decade. Renewed exploration interest is attributable not only to higher commodity prices but also to the realization of the significant geostrategic risk of highly industrialized countries to be entirely dependent on raw materials imports (EU 2008).

Publ.-Id: 28402 - Permalink


Recovery of REEs, Zr(+Hf), Mn and Nb by H2SO4 leaching of eudialyte concentrate
Balinski, A.; Atanasova, P.; Wiche, O.; Kelly, N.; Reuter, M. A.; Scharf, C.;
In this study three hydrometallurgical methods are described for leaching of a eudialyte concentrate with H2SO4: (i) direct leaching, (ii) fast leaching and (iii) water leaching of dehydrated acid/concentrate mixture. It is demonstrated how to obtain a silica free solution, how parameter variations impact the properties of precipitated silica and which processes lead to losses of valuable components during leaching. Furthermore, the acid solubility of gangue minerals in the concentrate is analyzed and the resulting consequences in terms of leach solution contamination and acid consumption are discussed. The best result in terms of the average yield of value components (REEs, Zr(+Hf), Mn and Nb) of 86 % is obtained by direct leaching under mild conditions (cH2SO4=1 mol/L; TL=60 °C). However, released silicic acid does not precipitate and aggregates at pulp density ϱPD,L=100 kg/m3 by gelling. Fast leaching allows the efficient removal of silica at high solid-liquid ratios in the pre-treatment stage. Due to mass transfer limitations, high efficiency stirrers are crucial for achieving high yields in short reaction times. Dehydration of the acid/concentrate mixture before water leaching can be a good alternative if well-defined amount of acid is used; however, high energy input is needed.
Keywords: eudialyte concentrate, silicate raw materials, aggregation of polysilicic acid, kinetic inhibition, gelling, leaching, mass transfer limitations, rare earth elements, zirconium, hafnium, niobium, manganese.

Publ.-Id: 28400 - Permalink


Bioangeln zum Recycling Seltener Erden Selektive Trennung von Mineralen durch Phagen-gebundene Peptide
Lederer, F. L.;
Selten-Erd-Elemente (SEE) sind 17 verschiedene Elemente (Scandium, Yttrium sowie die sog. Lanthanoide), die weltweit in nur wenigen Regionen in abbauwürdigen Mengen zu finden sind. SEE gelten als Schlüsselkomponenten der Hightech-Industrie und werden unter anderem in Windturbinen, Smartphones und Energiesparlampen eingesetzt.
Keywords: SEE, Phage Surface Display
  • GIT Laborfachzeitschrift 69(2019)2, 27-29

Publ.-Id: 28399 - Permalink


X-ray and neutron imaging studies on particle-laden liquid metal flow
Lappan, T.; Eckert, S.;
In metallurgy, the achievement of inclusion cleanliness is a major challenge for the production of high-performance structural and functional metallic materials like aluminium alloys and steels. Ladle treat-ment of molten metal by gas injection has been employed for a long time as the processing stage is mainly responsible for the control of non-metallic inclusions in metal alloys. In these ladles, inclusion are separated by the combination of settling down and floating up. Since bigger inclusion aggregates are eliminated more easily, agglomeration is supposed to play an essential role. In case of the floata-tion process, the probabilities of collision as well as attachment between gas bubbles and solid in-clusions is strongly dependent on their sizes.
This work is focussed on the visualization of three-phase particle-laden liquid metal flow in model experiments, applying 2D X-ray and neutron transmission imaging. Low-melting gallium-based alloys are employed for the imaging studies at room temperature. Modell particles containing tungsten and gadolinium are used due to their excellent attenuation characteristics for polychromatic X-ray and thermal neutrons, respectively. Injection of inert argon gas drives the liquid metal flow in a rectangular shaped vessel having a gap size of up to 20 mm. For both X-ray and neutron imaging, the time-resolved measurements are performed by means of a scintillation screen in combination with a sCMOS camera. The captured trajectories of rising millimetre-sized gas bubbles and submillimetre-sized solid particles, carried by the bubbly liquid metal flow, are analysed regarding bubble - particle and particle - particle interactions.
Keywords: X-ray transmission imaging; neutron transmission imaging; inclusions; liquid metal
  • Lecture (Conference)
    Materials Science and Engineering Congress 2018 (MSE 2018), 26.-28.09.2018, Darmstadt, Deutschland

Publ.-Id: 28398 - Permalink


Scanning Transmission Ion Detection in the Helium Ion Microscope
Serralta, E.ORC; Klingner, N.ORC; Hlawacek, G.ORC
The helium ion microscope has already proven its value for high-resolution imaging, composition analysis, nanofabrication, and material modification. However, imaging in transmission mode remains not fully explored. Mass-thickness contrast has been studied using a conversion plate below the specimen and collecting secondary electrons with an ET detector. Changing from bright to dark field regime was demonstrated using an annular microchannel plate and changing the acceptance angle by adjusting the distance between the sensor and the sample. Channeling and diffraction phenomena provide information about the crystal structure and can be recorded by a position-sensitive detector. In this report, we present our approach to explore this imaging mode, the challenges and main figures of merit. Our test setup with a position-sensitive detector will be shown, and simulations of the contrast mechanism will be presented.
  • Poster
    2nd international HeFIB conference on Helium and emerging Focused Ion Beams, 11.-13.06.2018, Dresden, Deutschland

Publ.-Id: 28397 - Permalink


Application of marine amphiphilic siderophores in froth flotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.;
Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process. The hydrophilic part, carrying hydroxamate groups is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested, that siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubbles and avoid additional chemicals and further working steps for making the target mineral particles hydrophobic. The aim of this study is to show the usage of amphiphilic siderophores in froth flotation process in different scales and with different minerals.
  • Lecture (others)
    UCT Biohydrometallurgy meeting, 19.06.2018, Cape Town, South Africa

Publ.-Id: 28396 - Permalink


Enhanced photoresponses of an optically driven VO₂-based terahertz wave modulator near percolation threshold
Zhai, Z.-H.; Zhu, H.-F.; Shi, Q.; Chen, S.-C.; Li, J.; Li, Z.-R.; Schneider, H.; Zhu, L.-G.;
We proposed and demonstrated a method to enhance photoresponses in the timescale from nanoseconds to microseconds of an all optically driven VO₂-based terahertz (THz) wave modulator by driving the initial VO₂ close to percolation threshold (via externally heating the initial VO₂ thin film near insulator-to-metal transition temperature). We experimentally realized 10-fold, 3-fold, and 3-fold improvement of photosensitivity, photoresponsivity, and optical modulation bandwidth of the VO₂-based THz wave modulator, respectively. Percolation theory, along with the macroscopic conductivity response, was used to explain the mechanism for photomodulation response enhancement. The enhanced photomodulation response is promising especially for optical modulators and photodetectors. This approach is also compatible with other optimization methods and can be further used to enhance other VO₂-based optoelectronic devices.
Keywords: Vanadiumdioxide, terahertz modulator

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Publ.-Id: 28395 - Permalink


Thermodynamic and structural studies on the Ln(III)/An(III) malate complexation
Taube, F.; Drobot, B.; Roßberg, A.; Foerstendorf, H.ORC; Acker, M.; Patzschke, M.; Trumm, M.; Taut, S.; Stumpf, T.
The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi−method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (logβ0, ΔrH0m,2, ΔrS0m, ΔrG0m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X–ray absorption fine structure spectroscopy complemented with quantum-mechanical ab–initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV–Vis, laser fluorescence and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal:malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding logβ10 and logβ20 of about 6 and 9, respectively. The respective complexation enthalpies ΔrH0m,1 and ΔrH0m,2 showed average values of 5 kJ·mol−1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f–/ 5f–element homology.

Publ.-Id: 28394 - Permalink


Ln(III)/An(III) Retention on CSH Phases and the Influence of Malate
Taube, F.; Roßberg, A.; Acker, M.; Foerstendorf, H.; Taut, S.; Stumpf, T.;
Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...
  • Lecture (Conference)
    4th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 06.-09.11.2018, Nice, France

Publ.-Id: 28393 - Permalink


Am3+ Malate Sorption on CSH Phases
Taube, F.; Acker, M.; Roßberg, A.; Taut, S.; Stumpf, T.;
Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...
  • Poster
    2nd Workshop on Calcium-Silicate Hydrates Containing Aluminium: C-A-S-H II, 23.-24.04.2018, Dübendorf, Schweiz

Publ.-Id: 28391 - Permalink


Lithium Ion Beams from Liquid Metal Alloy Ion Sources
Pilz, W.; Mazarov, P.; Klingner, N.; Bauerdick, S.; Bischoff, L.;
In recent years Focused Ion Beam (FIB) processing has been developed into a well-established and promising technique in nearly all fields of nanotechnology for patterning and prototyping on the µm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the FIB application fields beside all other source concepts. The need of light elements like Li was investigated using various alloys. A promising candidate is a Ga35Bi60Li5 based LMAIS which is introduced in more detail and operates stable for more than 1000 µAh. It enables high resolution imaging and patterning using Li and sample modification using Ga or heavy polyatomic Bi clusters, all coming from one ion source.
Keywords: Focused Ion Beam, Liquid Metal Alloy Ion Source, Li ions
  • Open Access LogoJournal of Vacuum Science & Technology B 37(2019)2, 021802-1-021802-4
    DOI: 10.1116/1.5086271

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Publ.-Id: 28390 - Permalink


Is hydroxypyridonate 3,4,3‐LI(1,2‐HOPO) a good competitor of fetuin for uranyl metabolism?
Younes, A.; Creff, G.; Beccia, M. R.; Moisy, P.; Roques, J.; Aupiais, J.; Hennig, C.; Solari, P. L.; Den Auwer, C.; Vitaud, C.;
Uranium is widespread in the environment, resulting both from natural occurrences and anthropogenic activities. Its toxicity is mainly chemical rather than radiological. In the blood it is transported as uranyl UO22+ cation and forms complexes with small ligands like carbonates and with some proteins. From there it reaches the skeleton, its main target organ for accumu lation. Fetuin is a serum protein involved in biomineralization processes which was demonstrated to be the main UO22+‐binder in vitro. Fetuin’s life cycle ends in bone. It is thus suspected to be a key protagonist of U accumulation in this organ. Up to now, there has been no effective treatment for the removal of U from the body and studies devoted to the interactions involving chelating agents with both UO22+ and its protein targets are lacking. The present work aims at studying the potential role of the 3,4,3‐LI(1,2‐HOPO) as a promising chelating agent in competition with fetuin. The apparent affinity constant of the 3,4,3‐LI(1,2‐HOPO) was first determined, giving evidence for its very high affinity similarity to that of fetuin. Chromatography experiments, aimed at identifying the complexes formed and quantify their UO22+ content, and spectroscopic structural investigations (XAS) were carried out, demonstrating that the 3,4,3‐LI(1,2‐HOPO) inhibits/limits the formation of fetuin‐uranyl complexes in stoichiometric conditions. But surprisingly, possible ternary complexes stable enough to remain present after the process, were identified for sub stoichiometric conditions of HOPO versus fetuin. These results contribute to the understanding of the mechanisms accounting for U residual accumulation despite the chelation therapy after internal contamination.

Publ.-Id: 28389 - Permalink


Compositional Data Analysis - Mineral Chemistry
Frenzel, M.ORC
Short introduction to general principles for the statistical analysis of mineral chemistry data.
  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 09.10.2018, Freiberg, Deutschland

Publ.-Id: 28388 - Permalink


Compositional Data Analysis - General Principles
Frenzel, M.ORC
Any data measured (or reported) in terms of proportions of a whole is called ‘compositional’. Virtually all geochemical data falls under this category. Because such data has a number of special properties, specific procedures are required for its statistical analysis. Generally, it cannot be meaningfully analyzed by methods designed for the analysis of multivariate Gaussian data, such as the standard regression analysis still used by many geologists.

This lecture is intended to give a brief overview of the most important mathematical characteristics of compositional data, and what consequences these have for the statistical analysis of such data. It will provide the theoretical foundations for the next lecture(s) in which the specific problems associated to the analysis of mineral chemistry data (lecture 2) and hierarchical data structures (lecture 3) will be considered in somewhat more detail. These later two lectures are intended as more practical guides to actual data analysis.
  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 18.09.2018, Freiberg, Deutschland

Publ.-Id: 28387 - Permalink


Field-Driven Hopping Transport of Oxygen Vacancies in Memristive Oxide Switches with Interface-Mediated Resistive Switching
Du, N.; Manjunath, N.; Li, Y.; Menzel, S.; Linn, E.; Waser, R.; You, T.; Burger, D.; Skorupa, I.; Walczyk, D.; Walczyk, C.; Schmidt, O. G.; Schmidt, H.;
We investigate the hopping transport of positively charged mobile oxygen vacancies V(o)(+)in electroforming-free bipolar memristive BiFeO3 switches by conducting impedance spectroscopy and quasistatic state-test measurements. We demonstrate that BiFeO3 switches with mobile oxygen vacancies (V-o(+)) and fixed substitutional Ti4+ donors on Fe3+ lattice sites close to the bottom electrode have a rectifying top electrode with an unflexible barrier height and a rectifying and/or nonrectifying bottom electrode with a flexible barrier height. The field-driven hopping transport of the oxygen vacancies determines the recon- figuration of the flexible barrier and the dynamics of the resistive switching. Average activation energies of 0.53 eV for trapping and of 0.31 eV for the release of oxygen vacancies by the Ti4+ donors during application of the SET and RESET excitation pulses are extracted, respectively. The larger activation energy during SET is experimentally verified by impedance spectroscopy measurements and evidences the local enhancement of the electrostatic potential profile at the bottom electrode due to the Ti4+ donors on Fe3+ lattice sites.
Keywords: BIFEO3; KINETICS; CONDUCTIVITY; TEMPERATURES; ELECTRODES; FILMS

Publ.-Id: 28384 - Permalink


A Novel Statistical Insight to Selection of the Best flotation Kinetic Model
Hassanzadeh, A.; Cagirici, S.; Ozturk, Z.;
Many flotation kinetics models have been studied in the literature. Their applicability was extensively investigated and argued in detail. However, model selection criteria were not adequately discussed from the statistical points of view. In this investigation, the kinetic behavior of a complex copper sulfide ore was studied in a mechanical Denver flotation cell focusing on flotation kinetics of chalcopyrite, pyrite and molybdenite. Different flotation kinetics models including nine common empirical models and four mathematical models namely Hill, Chapman (Sigmodial function), single rectangular (Hyperbola equation) and exponential were applied to the experimental data. In addition to assessment of the goodness of fit criterion for each model, a factor of model complexity was considered using information criteria (IC) (i.e. Bayesian information (BIC), low of iterated logarithm (LILC) and Akaike information (AIC) indices). The obtained results showed that the IC indices could simply manifest the best-fitted model to the experimental data. Whereas, the coefficient of determination values (R2) were relatively same for all models. By taking the R2 and model complexity criteria into account, the exponential model was chosen as the best representative mathematical model to demonstrate chalcopyrite kinetic behavior. However, Chapman model was selected as the best one for the flotation of pyrite and molybdenite. In case of the common first-order flotation kinetics models, fast and slow flotation kinetic model (Kelsall) was reasonably fitted the best to the given data of chalcopyrite. However, the gas/solid kinetics adsorption model was chosen as the best-fitted one for pyrite and molybdenite. Furthermore, it was found that mathematical models represent better results in association with flotation kinetic behavior of chalcopyrite, pyrite and molybdenite due to the consideration of more parameters in modeling. Finally, it was concluded that the IC indices must be applied to the process of model selection due to consideration of goodness of fit, complexity of a model and model consistency.
Keywords: Flotation kinetics model, information criteria (IC), modeling, Akaike information criterion (AIC)
  • Contribution to proceedings
    XXIX International Mineral Processing Conference (IMPC), 15.09.-21.12.2018, Moscow, Russia
    A Novel Statistical Insight to Selection of the Best flotation Kinetic Model

Publ.-Id: 28383 - Permalink


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