Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

How robust are landslide susceptibility estimates?

Ozturk, U.; Pittore, M.; Behling, R.; Roessner, S.; Andreani, L.; Korup, O.

Much of contemporary landslide research is concerned with predicting and mapping susceptibility to slope failure. Many studies rely on generalised linear models with environmental predictors that are trained with data collected from within and outside of the margins of mapped landslides. Whether and how the performance of these models depends on sample size, location, or time remains largely untested. We address this question by exploring the sensitivity of a multivariate logistic regression—one of the most widely used susceptibility models—to data sampled from different portions of landslides in two independent inventories (i.e. a historic and a multi-temporal) covering parts of the eastern rim of the Fergana Basin, Kyrgyzstan. We find that considering only areas on lower parts of landslides, and hence most likely their deposits, can improve the model performance by >10% over the reference case that uses the entire landslide areas, especially for landslides of intermediate size. Hence, using landslide toe areas may suffice for this particular model and come in useful where landslide scars are vague or hidden in this part of Central Asia. The model performance marginally varied after progressively updating and adding more landslides data through time. We conclude that landslide susceptibility estimates for the study area remain largely insensitive to changes in data over about a decade. Spatial or temporal stratified sampling contributes only minor variations to model performance. Our findings call for more extensive testing of the concept of dynamic susceptibility and its interpretation in data-driven models, especially within the broader framework of landslide risk assessment under environmental and land-use change.

Keywords: landslide susceptibility; logistic regression; Southern Kyrgyzstan; Landslide inventory; Remote sensing

Publ.-Id: 31472

Ferromagnetism in B2-Ordered Alloys Induced via Lattice Defects

Bali, R.

This chapter considers the case of B2-ordered alloys that are initially non-ferromagnetic and where the introduction of lattice defects can cause the onset of ferromagnetism. This disorder-induced ferromagnetism is confined to the regions where the defects are concentrated. In general, the lattice can be thermally re-ordered, removing the defects and erasing the magnetized regions. Using B2 Fe60Al40 thin films as a prototype, the use of ion irradiation as well as pulsed laser irradiation for inducing antisite defects in the crystalline lattice is demonstrated. Ion beams can be applied as broad beams in combination with shadow masks for printing magnetic patterns over large areas, or focused down to approximately nanometer diameters for stylus-like writing of nanomagnets of desired geometries. The patterning resolution is limited by the lateral scattering of ions and can be estimated by semi-empirical modelling, described in this chapter. In the case of laser pulsing, disordering can be induced at thin film surfaces for pulse fluences above the melting threshold. Pulsing below the threshold can lead to surface re-ordering, erasing the magnetic regions and achieving all-laser re-writeable patterning. Localized disordering of B2 ordered systems thus enables a versatile path to embedding highly resolved non-volatile magnets at room temperature, with potential in magnetic device applications.

  • Book chapter
    Francis Chi-Chung Ling, Shengqiang Zhou, Andrej Kuznetsov: Defects in Functional Materials, Hong Kong: World Scientific Publishing Co Pte Ltd, 2020, 978-981-120-316-9, 201-239
    DOI: 10.1142/11352

Publ.-Id: 31471

Normal tissue reaction following proton irradiation of the mouse brain

Beyreuther, E.; Suckert, T.; Müller, J.; Azadegan, B.; Bodenstein, E.; Haase, R.; Schürer, M.; Krause, M.; Lühr, A.; von Neubeck, C.; Dietrich, A.

Background: Due to the beneficial inverse physical depth-dose profile, proton radiotherapy (PT) offers the potential to reduce normal tissue toxicity by depositing the maximum dose within the tumor volume while sparing the surrounding tissue. However, range uncertainties and necessary clinical safety margins in combination with varying relative biological effectiveness may result in a critical dose in the normal tissue. Dedicated preclinical studies are needed to assess and better understand potential adverse effects of PT and to develop potential biomarkers and countermeasures for backtranslation into clinics.
For this purpose, a high-precision image-guided proton irradiation setup for small animals was established at the University Proton Therapy Dresden that mimics the clinical workflow, including pre-treatment imaging, treatment planning and image-guided brain irradiation.
The right hippocampus of C57BL/6 and C3H/HeN mice was irradiated to study the dose- and time-dependent radiation response of mouse brain tissue after short or long-term follow-up analysis. A Monte Carlo model of the proton beam was designed in the simulation toolkit TOPAS to calculate the dose distributions in vivo and to correlate the outcome with proton dose and LET.
The geometric accuracy of proton irradiation, detailed dose simulations on mouse CT and cell-based assessment enable a biologically and spatially resolved analysis of short-term radiation response and RBE. In addition, the long-term follow up over six month provides first insights into the formation of normal tissue damage in mouse brain after PT.

  • Lecture (Conference) (Online presentation)
    digital-ERRs, 13.-17.09.2020, Lund, Sweden

Publ.-Id: 31470

Late side effects in normal mouse brain tissue after proton irradiation

Suckert, T.; Beyreuther, E.; Müller, J.; Azadegan, B.; Meinhardt, M.; Raschke, F.; Bodenstein, E.; von Neubeck, C.; Lühr, A.; Krause, M.; Dietrich, A.

Radiation induced late side effects such as cognitive decline and normal tissue complications can severely affect quality of life and outcome in long-term survivors of brain tumors. Proton therapy offers a favorable depth-dose deposition with the potential to spare tumor-surrounding normal tissue, thus potentially reducing such side effects. In this study, we describe a preclinical model to reveal underlying biological mechanisms caused by precise high-dose proton irradiation of a brain subvolume.
We studied the dose- and time-dependent radiation response of mouse brain tissue, using a high-precision image-guided proton irradiation setup for small animals established at the University Proton Therapy Dresden. The right hippocampal area of ten C57BL/6 and ten C3H/He mice was irradiated. Both strains consisted of four groups treated with increasing doses (0 – 85 Gy and 0 – 80 Gy, respectively). Follow-ups were performed up to six months, including longitudinal monitoring of general health status and regular contrast-enhanced magnetic resonance imaging (MRI) of mouse brains. These findings were related to comprehensive final histological analysis.
In mice of the highest dose group, first symptoms of blood-brain barrier (BBB) damage appeared one week after irradiation, while a dose-dependent delay in onset was observed for lower doses. MRI contrast agent leakage occurred in the irradiated brain areas and was progressive in the higher dose groups. Mouse health status and survival corresponded to the extent of contrast agent leakage. Histological analysis revealed tissue changes such as vessel abnormalities, gliosis, and granule cell dispersion, which also partly affected the non-irradiated contralateral hippocampus.
All observed effects depended strongly on the prescribed radiation doses and the outcome, i.e. survival, image changes and tissue alterations, within an experimental dose cohort was very consistent. A derived dose-response model will determine doses in future experiments and may support the formulation of clinical hypotheses on brain toxicity after proton therapy.

Keywords: Proton therapy; brain irradiation; preclinical mouse model; magnetic resonance imaging (MRI); late side effects; blood-brain barrier; brain tissue toxicity; radiation dose modelling

Related publications

Publ.-Id: 31469

Damages induced by synchrotron radiation-based X-ray microanalysis in chrome yellow paints and related Cr-compounds: assessment, quantification and mitigation strategies

Monico, L.; Cotte, M.; Vanmeert, F.; Amidani, L.; Janssens, K.; Nuyts, G.; Garrevoet, J.; Falkenberg, G.; Glatzel, P.; Romani, A.; Miliani, C.

Synchrotron radiation (SR)-based X-ray methods are powerful analytical tools for several purposes and we widely use them for probing the degradation mechanisms of inorganic artists’ pigments in paintings, including chrome yellows (PbCr1-xSxO4; 0 ≤x≤0.8), a class of compounds often found in Van Gogh masterpieces. However, the high intensity and brightness of SR beams raise important issues regarding potential damages of the analyzed samples. A thorough knowledge of the SR X-ray sensitivity of each class of pigment in the painting matrix is therefore required to find analytical strategies that contribute to minimize the damage for preserving the integrity of the analyzed sample and to avoid misinterpretation of the data. Here, we employ a combination of Cr K-edge X-ray absorption near edge structure (XANES) spectroscopy, Cr-Kβ X-ray emission spectroscopy (XES) and X-ray diffraction (XRD) to monitor and quantify the effects of SR X-rays on the stability of chrome yellows and related Cr-compounds and to define strategies for mitigating their damage. We found that the SR X-ray beam exposure induces changes in the oxidation state and local coordination environment of Cr-ions and leads to a loss of the compound’s crystalline structure. The extent of X-ray damage depends on some intrinsic properties of the samples (chemical composition of the pigment as well as the presence/absence and nature of the binder) and it can be minimized by optimizing the overall fluence/dose released to the samples and by working in vacuum and cryogenic conditions.


  • Secondary publication expected

Publ.-Id: 31468

Development of PSMA-1007 - Related Series of 18F-Labeled Glu-ureido type PSMA inhibitors.

Cardinale, J.; Roscher, M.; Schaefer, M.; Geerlings, M.; Benešová, M.; Bauder-Wüst, U.; Remde, Y.; Eder, M.; Novakova, Z.; Motlová, L.; Bařinka, C.; Giesel, F.; Kopka, K.

In recent years, a number of drugs targeting the prostate specific-membrane antigen (PSMA) have become important tools in the diagnosis and treatment of prostate cancer. In the present work, we report on the synthesis and preclinical evaluation of a series of 18F-labeled PSMA ligands for diagnostic application based on the theragnostic ligand PSMA-617. By applying modifications to the linker-structure, insight into the structure-activity relationship could be gained highlighting the importance of hydrophilicity and stereoselectivity on interaction with PSMA and hence the biodistribution. Selected compounds were co-crystallized with the PSMA-protein and analyzed by X-ray with mixed results. Amongst these, PSMA-1007 (compound 5) showed the best interaction with the PSMA protein. The respective radiotracer [18F]PSMA-1007 was translated into the clinic and is in the meantime subject of advanced clinical trials.

Keywords: PET Tracer; PSMA ligands; prostate cancer; PSMA-1007; PSMA inhibitors


Publ.-Id: 31467

Atomic Physics in Particle in Cell Algorithms(PIC)

Marre, B. E.; Garten, M.; Bussmann, M.; Kluge, T.

Simulations allow us to get a detailed understanding of processes inside plasmas not directly accessible to experiments. They are therefore a very important tool for theoretical and experimental research and are continually being improved.
One improvement in development is the direct inclusion of atomic physics in Particle in Cell(PIC) simulations, a specific simulation technic used for non fluid-like plasmas.
In this talk I will describe possible approaches to realise atomic physics in PIC and give a short introduction to PIC algorithms and atomic physics in plasmas.

Keywords: atomic physics; particel in cell; Atomphysik in Plasmen; plasma; PIConGPU

  • Lecture (others)
    Numerics Seminar, 06.08.2020, Görlitz, Deutschland

Publ.-Id: 31466

P1826 - Calix[n]aren-Derivate zur Komplexierung von Erdalkalimetallkationen

Mamat, C.; Bauer, D.; Reissig, F.; Pietzsch, H.-J.; Steinbach, J.

Die Erfindung betrifft eine Verbindung, die

  • eine Calixaren-Einheit, die n Phenoleinheiten aufweist, wobei n 4, 5, 6 oder 8 ist;
  • eine Ethereinheit, die unter Ausbildung eines Kronenethers an die Calixaren-Einheit gebunden ist; und
  • zumindest eine Sulfonsäureamid-Einheit der Formel
aufweist, wobei
die zumindest eine Sulfonsäureamid-Einheiten jeweils an die Calixaren-Einheit gebunden ist und R¹ jeweils aus der Gruppe ausgewählt ist, die aus einer perfluorierten verzweigten oder unverzweigten C₂-C₈-Alkylgruppe, einer perfluorierten Arylgruppe, und einer Gruppe Ar besteht, p eine Ganzzahl von 1 bis 4 ist und Ar eine Phenylgruppe ist, die mit einer oder mehreren perfluorierten verzweigten oder unverzweigten C₁-C₈-Alkylgruppen substituiert ist.
  • Patent
    DE102018132293 - Offenlegung 18.06.2020; Nachanmeldungen: WO

Publ.-Id: 31465

P1825 - Tomographievorrichtung und Tomographieverfahren

Iskander, K.; Bieberle, A.; Schleicher, E.

Die Erfindung betrifft eine Tomographievorrichtung und ein Tomographieverfahren zum Abbilden der inneren Struktur eines Untersuchungsobjekts, wobei aufeinanderfolgend in einer ersten, einer zweiten und einer dritten Scanebene Strahlung zum tomographischen Untersuchen des Untersuchungsobjekts erzeugt wird und die Strahlung mittels einer Detektorvorrichtung mit mehreren Detektorsegmenten erfasst wird, wobei jedes Detektorsegment einen in der ersten Scanebene angeordneten ersten Strahlungsdetektor, einen in der zweiten Scanebene angeordneten zweiten Strahlungsdetektor und einen in der dritten Scanebene angeordneten dritten Strahlungsdetektor zum Erfassen der Strahlung unter Erzeugung von Detektorsignalen aufweist, und wobei die Detektorsignale des ersten und des dritten Strahlungsdetektors mittels eines ersten Verstärkers verstärkt werden und die Detektorsignale des zweiten Strahlungsdetektors mittels eines zweiten Verstärkers verstärkt werden.

  • Patent
    DE102018131497 - Offenlegung 10.06.2020

Publ.-Id: 31464

P1824 - Rippenrohrwärmeübertrager mit konvexen Aussparungen der Rippenflächen und integrierten Materialaufdickungen

Unger, S.; Hampel, U.

Die Erfindung betrifft einen Wärmeübertrager mit wenigstens einer Trennwand und wenigstens von einer Seite der Trennwand abstehenden und die Oberfläche der Trennwand vergrößernden Oberflächenelementen, die von einem Fluid umströmbar sind. Dabei weisen die Oberflächenelemente Verstärkungswülste und zwischen den Verstärkungswülsten befindliche Flächenbereiche auf, wobei sich die Verstärkungswülste von der Trennwand ausgehend erstrecken und eine kreisrunde oder ovale Querschnittform haben. Die Verstärkungswülste erstrecken sich ausgehend von der Trennwand über mindestens einen Teil der Höhe des Oberflächenelementes und verjüngen sich von der Trennwand aus entlang der Höhe der Oberflächenelemente. Die Oberflächenelemente weisen eine Vielzahl konvexer Aussparungen auf, wobei jede der konvexen Aussparungen in einem der Flächenbereiche zwischen zwei Verstärkungswülsten angeordnet ist und sich von einer Außenkante des Oberflächenelementes erstreckt. Der Scheitelpunkt der konvexen Aussparung liegt bei einer Höhe größer als oder gleich 30% und kleiner als oder gleich 70% der gesamten Höhe des Oberflächenelementes, wobei die Höhe ausgehend von der Trennwand gemessen ist.

  • Patent
    DE102018129788 - Erteilung 24.10.2019; Nachanmeldungen: WO

Publ.-Id: 31463

P1823 - Pyrrolopyridin-Derivate und deren Verwendung

Moldovan, R.-P.; Fischer, S.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I worin Ar ein Pyridin-Ring ist; R¹ Wasserstoff oder Fluor ist; R² aus der Gruppe ausgewählt ist, die aus Wasserstoff, Hydroxy, Halogen, -CN, -NO₂, -N(R³R⁴), -(CR⁹R¹⁰)ₚ-C(O)-N(R⁵R⁶), -(CR⁹R¹⁰)q-CHO, -(CR⁹R¹⁰)r-C(O)-(CR⁹R¹⁰)s-R⁷, -(CR⁹R¹⁰)t-O-(CR⁹R¹⁰)v-R⁸ oder einer verzweigten oder unverzweigten, substituierten oder unsubstituierten C₁-C₁₂-Alkylgruppe besteht; R³, R⁴, R⁵, R⁶ und R⁷ unabhängig voneinander jeweils Wasserstoff oder eine verzweigte oder unverzweigte, substituierte oder unsubstituierte C₁-C₁₂-Alkylgruppe sind; R⁸ eine verzweigte oder unverzweigte, substituierte oder unsubstituierte C₁-C₁₂-Alkylgruppe ist; R⁹ und R¹⁰ unabhängig voneinander bei jedem Vorkommen Wasserstoff, Halogen, verzweigtes oder unverzweigtes, unsubstituiertes oder substituiertes C₁-C₁₂-Alkyl oder unsubstituiertes oder substituiertes C₂-C₆-Alkenyl sind; 1 1, 2, 3 oder 4 ist m 0, 1 oder 2 ist, mit der Maßgabe, dass 1 + m nicht größer als 4 ist; n 1, 2 oder 3 ist; und p, q, r, s, t und v unabhängig voneinander 0 oder eine Ganzzahl von 1 bis 6 sind. Außerdem ist eine Präkursor-Verbindung zur Herstellung einer Verbindung der Formel I vorgesehen, die anstelle einer Gruppe R¹ eine Abgangsgruppe aufweist.

  • Patent
    DE102018129693 - Offenlegung 28.05.2020; Nachanmeldungen: WO

Publ.-Id: 31462

P1821 - Markierungsvorläufer mit Quadratsäure-Kopplung

Bergmann, R.; Johannes-Gutenberg-Universität Mainz

Ein Markierungsvorläufer umfasst einen Chelator oder eine Fluorierungsgruppe für die Radiomarkierung mit ⁴⁴Sc, ⁴⁷Sc, ⁵⁵Co, ⁶²Cu, ⁶⁴Cu, ⁶⁷Cu, ⁶⁶Ga, ⁶⁷Ga, ⁶⁸Ga, ⁸⁹Zr, ⁸⁶Y, ⁹⁰Y, ⁹⁰Nb, ⁹⁹ᵐTc, ¹¹¹In, ¹³⁵Sm, ¹⁴⁰Pr, ¹⁵⁹Gd, ¹⁴⁹Tb, ¹⁶⁰Tb, ¹⁶¹Tb, ¹⁶⁵Er, ¹⁶⁶Dy, ¹⁶⁶Ho, ¹⁷⁵Yb, ¹⁷⁷Lu, ¹⁸⁶Re, ¹⁸⁸Re, ¹¹³Bi und ¹¹⁵Ac beziehungsweise mit ¹⁸F, ¹³¹I oder ¹¹¹At und einen oder zwei biologische Targetingvektoren, die über eine oder mehrere Quadratsäuregruppen mit dem Chelator oder der Fluorierungsgruppe gekoppelt sind.

  • Patent
    DE102018126558 - Offenlegung 30.04.2020; Nachanmeldungen: WO

Publ.-Id: 31461

P1820 - Tomographievorrichtung und Tomographieverfahren

Barthel, F.

Die Erfindung betrifft eine Tomographievorrichtung und ein Tomographieverfahren zum Abbilden der inneren Struktur eines Untersuchungsobjekts, wobei ein Elektronenstrahl derart über ein erstes Target mit mehreren Durchtrittsöffnungen geführt wird, dass der Elektronenstrahl nacheinander mehrere der Durchtrittsöffnungen überstreicht, wobei an dem ersten Target erste Röntgenstrahlung zum Durchstrahlen des Untersuchungsobjekts entsteht, wenn der Elektronenstrahl abseits der Durchtrittsöffungen auf das erste Target trifft, und wobei der Elektronenstrahl durch das erste Target hindurchtritt und mittels einer zwischen das erste Target und ein zweites Target angelegten elektrischen Spannung auf das zweite Target beschleunigt wird, wenn der Elektronenstrahl auf eine der Durchtrittsöffnungen gerichtet ist, wobei an dem zweiten Target zweite Röntgenstrahlung zum Durchstrahlen des Untersuchungsobjekts

  • Patent
    DE102018125822 - Erteilung 02.01.2020

Publ.-Id: 31460

Data for: Enantiomerically pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

Fichter, S.; Kaufmann, S.; Kaden, P.; Brunner, T. S.; Stumpf, T.; Roesky, P. W.; März, J.

The synthesis of a tetravalent neptunium amidinate [NpCl((S)‐PEBA)3] (1) ((S)‐PEBA=(S,S)‐N,N′‐bis‐(1‐phenylethyl)‐benzamidinate) is reported. This complex represents the first structurally characterized enantiopure transuranic compound. Reactivity studies with halide/pseudohalides yielding [NpX((S)‐PEBA)3] (X=F (2), Br (3), N3 (4)) have shown that the chirality‐at‐metal is preserved for all compounds in the solid state. Furthermore, they represent an unprecedented example of a structurally characterized metal–organic Np complex featuring a Np−Br (3) bond. In addition, 4 is the only reported tetravalent transuranic azide. All compounds were additionally characterized in solution using para‐magnetic NMR spectroscopy showing an expected C3‐symmetry at low temperatures.

Keywords: transuranium chemistry; actinides; neptunium; coordination chemistry; amidinates

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-27
    DOI: 10.14278/rodare.465
    License: CC-BY-4.0


Publ.-Id: 31459

How does iron storage protein ferritin interact with plutonium (and thorium) ?

Zurita, C.; Tsushima, S.; Bresson, C.; Garcia-Cortes, M.; Solari, P. L.; Jeanson, A.; Creff, G.; Den Auwer, C.

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The Ferritin ‐ thorium load curve suggests that Th(IV) saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (Spectrophotometry, Infrared Spectroscopy and X‐ray Absorption Spectroscopy) were combined with Molecular Dynamics to provide a structural model of the interaction of Th(IV) and Pu(IV) with ferritin. Comparison of spectroscopic data together with MD calculations suggests that Th(IV) and Pu(IV) are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of Th(IV) and Pu(IV) interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology.

Publ.-Id: 31457

Numerical ferromagnetic resonance experiments in nanosized elements

Wagner, K.; Körber, L.; Stienen, S.; Lindner, J.; Farle, M.; Kakay, A.

We present a numerical approach to obtain the Ferromagnetic Resonance (FMR) spectra of micrometer- and nano-sized magnetic elements by micromagnetic simulations. Mimicking common experimental conditions, a static magnetic field is applied and a linearly polarized oscillating magnetic field is used to excite magnetization dynamics. A continuous single-frequency excitation is utilized, which permits to study the steady-state dynamics in space- and time-domain. This gives direct access to resonance fields, line widths and relative amplitudes as observed in the experiments, which is not easily accessible in pulsed schemes and allows for a one-to-one identification between simulation and experiment. Similar to numerical approaches using pulsed excitations the phases, ellipticity and spatial mode profiles of the spin-wave excitations may also be accessed. Using large excitation powers we then showcase that one can additionally study nonlinear responses by this method such as the nonlinear shift of the resonance fields and the fold-over of the absorption lines. Since the dynamic susceptibility is directly determined from standard outputs of common micromagnetic codes, the presented method is robust, efficient and easy-to-use, adding to its practical importance.

Keywords: Ferromagnetic resonance; Micromagnetic simulations; line width; nonlinear; fold-over

Related publications


  • Secondary publication expected from 29.01.2022

Publ.-Id: 31456

Non-linear Breit-Wheeler process with linearly polarized beams

Titov, A.; Kämpfer, B.

We study the non-linear Breit-Wheeler process γ⃗ ′+L⃗ →e++e− in the interaction of linearly polarized probe photons (γ⃗ ′) with a linearly polarized laser beam (L⃗ ). In particular, we consider the asymmetry of the total cross section and the azimuthal electron distributions when the polarizations of the photon and laser beams in the initial state are mutually perpendicular or parallel. Considering intense laser beams and the strong field asymptotic we explore essentially the multi-photon dynamics. The asymmetry exhibits some non-monotonic behavior depending on initial kinematic conditions; it depends sensitively on the laser pulse duration. Our results provide additional knowledge for studying non-linear multi-photon effects in quantum electrodynamics and may be used in planning experiments in upcoming laser facilities.

Publ.-Id: 31455

Quarkonia formation in a holographic gravity-dilaton background describing QCD thermodynamics

Zöllner, R.; Kämpfer, B.

A holographic model of probe quarkonia is presented, where the dynamical gravity-dilaton background is adjusted to the thermodynamics of 2 +1 flavor QCD with physical quark masses. The quarkonia action is modified to account for a systematic study of the heavy-quark mass dependence. We focus on the J/ψ and Υ spectral functions and relate our model to heavy quarkonia formation as a special aspect of hadron phenomenology in heavy-ion collisions at LHC.

Publ.-Id: 31454

Brittle-ductile transition temperature of recrystallized tungsten following exposure to fusion relevant cyclic high heat load

Shah, V.; van Dommelen, J. A. W.; Altstadt, E.; Das, A.; Geers, M. G. D.

The lifetime of tungsten (W) monoblocks under fusion conditions is ambivalent. In this work, the microstructure dependent mechanical behaviour of pulsed high heat flux (HHF) exposed W monoblock is investigated. Two different microstructural states, i.e. initial (deformed) and recrystallized, both machined from HHF exposed monoblocks are tested using tensile and small punch tests. The initial microstructural state reveals a higher fraction of low angle boundaries along with a preferred orientation of crystals. Following HHF exposure, the recrystallized state exhibits weakening of initial texture along with a higher fraction of high angle boundaries. Irrespective of the testing methodology, both the microstructural states display brittle failure for temperatures lower than 400∘C. For higher temperatures (>400∘C), the recrystallized microstructure exhibits more ductile behaviour as compared to the initial state. The observed microstructural state-dependent mechanical behaviour is further discussed in terms of different microstructural features. The estimated brittle-to-ductile transition temperature (BDTT) range is noticed to be lower for the recrystallized state as compared to the initial state. The lower BDTT in the recrystallized state is attributed to the high purity of the W in combination with its low defect density, thereby preventing segregation of impurities at the recrystallized boundaries and the related premature failure. Based on this observation, it is concluded that the common opinion of the aggravation of BDTT in W due to recrystallization is not unerring, and as a matter of fact, recrystallization in W could be instrumental for preventing the self-castellation of the monoblocks.

Keywords: Tungsten; High heat flux exposure; Tensile test; Small punch test; Recrystallization and embrittlement; Brittle-to-ductile transition temperature

Publ.-Id: 31453

An integrated approach combining soil profile, records and tree ring analysis to identify the origin of environmental contamination in a former uranium mine (Rophin, France)

Martin, A.; Hassan-Loni, Y.; Fichtner, A.; Péron, O.; David, K.; Chardon, P.; Larrue, S.; Gourgiotis, A.; Sachs, S.; Arnold, T.; Grambow, B.; Stumpf, T.; Montavon, G.

Uranium mining and milling activities raise environmental concerns due to the release of radioactive and other toxic elements. Their long-term management thus requires a knowledge of past events coupled with a good understanding of the geochemical mechanisms regulating the mobility of residual radionuclides. This article presents the results on the traces of anthropic activity linked to previous uranium (U) mining activities in the vicinity of the Rophin tailings storage site (Puy de Dôme, France). Several complementary approaches were developed based on a study of the site's history and records, as well as on a radiological and chemical characterization of soil cores and a dendrochronology. Gamma survey measurements of the wetland downstream of the Rophin site revealed a level of 1050 nSv.h−1. Soil cores extracted in the wetland showed U concentrations of up to 1855−1, which appears to be associated with the presence of a whitish silt loam (WSL) soil layer located below an organic topsoil layer. Records, corroborated by prior aerial photographs and analyses of 137Cs and 14C activities, suggest the discharge of U mineral particles while the site was being operated. Moreover, lead isotope ratios indicate that contamination in the WSL layer can be discriminated by a larger contribution of radiogenic lead to total lead. The dendroanalysis correlate U emissions from Rophin with the site's history. Oak tree rings located downstream of the site contain uranium concentrations ten times higher than values measured on unaffected trees. Moreover, the highest U concentrations were recorded not only for the operating period, but more surprisingly for the recent site renovations as well. This integrated approach corroborates that U mineral particles were initially transported as mineral particles in Rophin's watershed and that amajority of the deposited uranium appears to have been trapped in the topsoil layer, with high organic matter content.

Keywords: Uranium mining; Wetland; Records; Dendroanalysis; Radiochronology; U decay chain

Publ.-Id: 31452

Photoluminescence and Raman Spectroscopy Study on Color Centers of Helium Ion-Implanted 4H–SiC

Song, Y.; Xu, Z.; Li, R.; Wang, H.; Fan, Y.; Rommel, M.; Liu, J.; Astakhov, G.; Hlawacek, G.; Li, B.; Xu, J.; Fang, F.

Color centers in silicon carbide (SiC) are promising candidates for quantum technologies. However, the richness of the poly-type and defect coniguration of SiC makes the accurate control of the types and position of defects in SiC still challenging. In this study, helium ion-implanted 4H–SiC was characterized by atomic force microscopy (AFM), confocal photoluminescence (PL), and Raman spectroscopy at room temperature. PL signals of silicon vacancy were found and analyzed using 638-nm and 785-nm laser excitation by means of depth proiling and SWIFT mapping. Lattice defects (C–C bond) were detected by continuous laser excitation at 532 nm and 638 nm, respectively. PL/Raman depth proiling is helpful in revealing the three-dimensional distribution of produced defects. Diferences in the depth proiling results and SRIM simulation results were explained by considering the depth resolution of the confocal measurement setup, helium bubbles, as well as swelling.

Keywords: Helium ion implantation; Silicon Carbid (SiC); Color Center; Point defect; Silicon vacancy; Confocal photoluminescence spectroscopy; Raman spectroscopy; Atomic force Microscopy (AFM); Helium Ion Microscopy


Publ.-Id: 31451

Intracavity third-harmonic generation in Si:B pumped by intense terahertz pulses

Meng, F.; Thomson, M. D.; Ul-Islam, Q.; Klug, B.; Pashkin, O.; Schneider, H.; Roskos, H. G.

We observe third-harmonic generation (THG) in boron-doped silicon (Si:B) upon pumping with picosecond 1.56 THz pulses from a free-electon laser with a peak electric field strength of up to 12 kV/cm. The measurements are performed at cryogenic temperatures where the majority of holes are bound to the acceptor dopants. The dependence of the THG on the pump intensity exhibits a threshold-free power-law behavior with an exponent close to 4. The observations can be explained by THz emission by free holes accelerated in the non-parabolic valence band, under the assumption that the density of free holes increases with the pump intensity. A quantitative treatment supports that these carriers are generated by impact ionization, initiated by the population of thermally ionized carriers , as opposed to direct tunneling ionization. In addition, we also observe intracavity THG by embedding the Si:B in a one-dimensional photonic crystal cavity. The THG efficiency is increased by a factor of eight due to the field enhancement in the cavity, with the potential to reach a factor of more than 100 for pump pulses with a spectrum narrower than the linewidth of the cavity resonance.

Related publications


Publ.-Id: 31450

Measurement of the 2H(p, γ)3He S-factor at 265 - 1094 keV

Turkat, S.; Hammer, S.; Masha, E.; Akhmadaliev, S.; Bemmerer, D.; Grieger, M.; Hensel, T.; Julin, J.; Koppitz, M.; Ludwig, F.; Möckel, C.; Reinicke, S.; Schwengner, R.; Stöckel, K.; Szücs, T.; Wagner, L.; Zuber, K.

Recent astronomical data have provided the primordial deuterium abundance with percent pre- cision. As a result, Big Bang nucleosynthesis may provide a constraint on the universal baryon to photon ratio that is as precise as, but independent from, analyses of the cosmic microwave back- ground. However, such a constraint requires that the nuclear reaction rates governing the production and destruction of primordial deuterium are sufficiently well known.
Here, a new measurement of the 2H(p,γ)3He cross section is reported. This nuclear reaction dominates the error on the predicted Big Bang deuterium abundance. A proton beam of 400- 1650keV beam energy was incident on solid titanium deuteride targets, and the emitted γ-rays were detected in two high-purity germanium detectors at angles of 55◦ and 90◦, respectively. The deuterium content of the targets has been obtained in situ by the 2H(3He,p)4He reaction and offline using the Elastic Recoil Detection method.
The astrophysical S-factor has been determined at center of mass energies between 265 and 1094 keV, addressing the uppermost part of the relevant energy range for Big Bang nucleosynthesis and complementary to ongoing work at lower energies. The new data support a higher S-factor at Big Bang temperatures than previously assumed, reducing the predicted deuterium abundance.


Publ.-Id: 31449

Fate of contaminants from repositories for radioactive waste based in clay-rock?

Marques Fernandes, M.; Baeyens, B.; Daehn, R.; Scheinost, A. C.; Churakov, S. V.

Safe disposal of radioactive waste is one of the big challenges of modern society. The concept of final storage in deep geological formations has become internationally accepted as a means of safe waste management waste in order to isolate it from the Biosphere for hundreds of thousands of years. The safety case has hence to prove that migration from the disposal site into the Biosphere can be effectively prevented across this time span. The potential migration is primarily controlled by sorption/desorption processes onto mineral surfaces along the migration path. Clay minerals are major constituents in both the engineered barriers and in the argillaceous host rock formations being considered for the deep high-level radioactive waste (HLW) repository in Switzerland. Therefore it is critically important to develop an understanding of the uptake processes of radionuclides on clay minerals and other minerals under a wide range of relevant geochemical conditions, to quantify and characterize them with the aim of strengthening the confidence in the safety case. An overview of the work performed at the Laboratory for Waste Management on the retention of radionuclides on clay rich materials will be presented.

Keywords: nuclear waste; clay rock; XAFS; ROBL

  • Invited lecture (Conferences) (Online presentation)
    18th Swiss Geoscience Meeting, 06.-07.11.2020, Zurich, Switzerland

Publ.-Id: 31448

Crystal structure, phase transition and properties of indium (III) sulfide

Wyżga, P.; Carrillo-Cabrera, W.; Akselrud, L.; Veremchuk, I.; Wagler, J.; Hennig, C.; Tsirlin, A.; Leithe-Jasper, A.; Kroke, E.; Gumeniuk, R.

Poly- and single-crystalline samples of In0.670.33In2S4 thiospinel were obtained by various powder metallurgical and chemical vapor transport methods, respectively. All synthesized samples contained β-In0.670.33In2S4 modification only, independent from synthesis procedure. High-resolution powder X-ray diffraction (PXRD) experiment at 80 K enabled observation of split tetragonal reflections (completely overlapped at room temperature), which proves the correctness of crystal structure model accepted for β-polymorph. Combined single-crystal XRD, transmission electron microscopy and selected-area electron diffraction confirmed the presence of three twin domains in as-grown crystals. High temperature PXRD study revealed both abrupt (in full width at half maximum) and gradual (in intensity of satellites, c/a ratio and unit-cell volume) changes in the vicinity of the α-β phase transition. On the other hand, clear thermal effect in heat capacity, magnitude of enthalpy/entropy change and temperature dependence of electrical resistivity, associated with hysteresis, hinted towards the 1st order type of the transition. Two scenarios, based on Rietveld refinement analysis, were proposed for the description of crystal structure evolution from β- to α-modification. Seebeck coefficient, electrical resistivity and thermal conductivity were shown to be influenced not only by phase transition, but also by annealing conditions (S-poor or S-rich atmosphere). Theoretical density functional calculations predicted n-type semiconducting behavior of In0.670.33In2S4, as well as instability of fictitious InIn2S4 thiospinel.

Keywords: In2S3; synchrotron diffraction; single-crystal diffraction; twinning; DFT calculations

Publ.-Id: 31446

Anisotropic spin-acoustic resonance in silicon carbide at room temperature

Hernandez-Minguez, A.; Poshakinskiy, A. V.; Hollenbach, M.; Santos, P. V.; Astakhov, G.

We report on acoustically driven spin resonances in atomic-scale centers in silicon carbide at room temperature. Specifically, we use a surface acoustic wave cavity to selectively address spin transitions with magnetic quantum number differences of 1 and 2 in the absence of external microwave electromagnetic fields. These spin-acoustic resonances reveal a nontrivial dependence on the static magnetic field orientation, which is attributed to the intrinsic symmetry of the acoustic fields combined with the peculiar properties of a half-integer spin system. We develop a microscopic model of the spin-acoustic interaction, which describes our experimental data without fitting parameters. Furthermore, we predict that traveling surface waves lead to a chiral spin-acoustic resonance that changes upon magnetic field inversion. These results establish silicon carbide as a highly promising hybrid platform for on-chip spin-optomechanical quantum control enabling engineered interactions at room temperature.

Keywords: Spin qubits; surface acoustic waves; quantum technology; SiC

Publ.-Id: 31445

Experimental and numerical analysis of the complex permittivity of open-cell ceramic foams

Hernandez, J. N. C.; Link, G.; Soldatov, S.; Füssel, A.; Schubert, M.; Hampel, U.

Open-cell ceramic foams are promising materials in the field of microwave heating. They can be manufactured from susceptor materials and can, therefore, be used as selective heating elements. In this study, the complex permittivities of ceramic foam materials, including silicon-infiltrated silicon carbide (SiSiC), pressureless sintered silicon carbide (SSiC), silicate bonded silicon carbide (SBSiC), and cordierite were determined. The dielectric properties of the foams were determined by the cavity perturbation technique using a TE104 WR340 waveguide resonator at 2.45 GHz. Samples were preheated in a tubular furnace, enabling temperature-dependent permittivity measurements up to 200 °C. The effective dielectric constant and effective loss factor were found to depend on the porosity and material composition of the foam. The SiSiC material had a higher effective dielectric constant than the SSiC and SBSiC ceramics. The effective dielectric constant of the foams showed a trend of gradual increase with increasing temperature. Some selected dielectric mixing relations were then applied to describe the effective permittivity of the foams and compare them with predictions from finite element simulations performed using the CST Studio Suite. The foam morphologies and simple block inclusions were used in the simulations.

Keywords: microwave processing; dielectric properties; silicon carbide; cordierite


Publ.-Id: 31444

Dimensional crossover in spin Hall oscillators

Smith, A.; Sobotkiewich, K.; Khan, A.; Montoya, E. A.; Yang, L.; Duan, Z.; Schneider, T.; Lenz, K.; Lindner, J.; An, K.; Li, X.; Krivorotov, I. N.

Auto-oscillations of magnetization driven by direct spin current have been previously observed in multiple quasi-zero-dimensional (0D) ferromagnetic systems such as nanomagnets and nanocontacts. Recently, it was shown that pure spin Hall current can excite coherent auto-oscillatory dynamics in quasi-one-dimensional (1D) ferromagnetic nanowires but not in quasi-two-dimensional (2D) ferromagnetic films. Here we study the 1D to 2D dimensional crossover of current-driven magnetization dynamics in wire-based Pt/Ni80Fe20 bilayer spin Hall oscillators via varying the wire width.We find that increasing the wire width results in an increase of the number of excited auto-oscillatory modes accompanied by a decrease of the amplitude and coherence of each mode. We also observe a crossover from a hard to a soft onset of the auto-oscillations with increasing wire width. The amplitude of auto-oscillations rapidly decreases with increasing temperature suggesting that interactions of the phase-coherent auto-oscillatory modes with incoherent thermal magnons play an important role in suppression of the auto-oscillatory dynamics. Our measurements set the upper limit on the dimensions of an individual spin Hall oscillator and elucidate the mechanisms leading to suppression of coherent auto-oscillations with increasing oscillator size.

Keywords: Spin hall oscillators; ferromagnetism; spin currents; magnetization dynamics; spin waves


Publ.-Id: 31443

Liquid Metal Alloy Ion Sources for magnetic nano-structures

Bischoff, L.; Pilz, W.; Klingner, N.; Hlawacek, G.; Mazarov, P.; Meyer, F.

Focused Ion Beam (FIB) is a modern tool for µm and sub-µm structure fabrication and analysis. Commercial systems work mostly with a Gallium - Liquid Metal Ion Source (LMIS) and can achieve a resolution lower than 10 nm and current densities more than 10 Acm-2. The use of alloy LMIS, mainly developed at HZDR, opens a broad field of new applications. In combination with modern FIB systems, like the VELION (Raith) the application field can be extended due to a broad spectrum of available ion species in high resolution ion beams and the stage properties. All these aspects will be concentrated to the ZIM project GRANT No.-ZF4330902 DF7 dealing with the prospective modern topic of nano-magnetic structures from basic research up to new applications. Main topics are: i) the local modification of magnetic single nano-structures using a FIB with Co, Ni, Fe, … ions and ii) the fabrication and investigation of magnonic crystals, made by writing FIB implantation with rare earth ions (Nd, Dy, Ho, Er, …).

Keywords: Focused Ion Beam; ion sources; magnetic nanostructures; magnonic crystals

  • Lecture (others)
    Kick-off meeting, ZIM Project No.-ZF4494801 DF7, 14.-16.09.2020, Dortmund, Germany

Publ.-Id: 31442

X-ray and neutron radiographic experiments on particle-laden molten metal flows

Lappan, T.; Sarma, M.; Heitkam, S.; Mannes, D.; Trtik, P.; Shevchenko, N.; Eckert, K.; Eckert, S.

In metallurgical processing, non-metallic inclusions in metallic materials are one highly relevant challenge. Bubble injection into molten metals boosts the inclusion control and removal, thus enhancing metal homogenisation and purification. Although this principle of bubble flotation has been used for a long time, the effects of bubble-inclusion interactions in molten metals are not yet well researched. Imaging measurements of multiphase metal flows are challenging for two main reasons: the metals’ high melting temperatures, and their opaqueness for visible light. This work focuses on X-ray and neutron radiographic experiments employing low-melting gallium alloys laden with model particles smaller than 1 mm in diameter. Both, bubbles and particles, are visualised simultaneously with high spatial and temporal resolution to analyse their motions by tracking algorithms. We demonstrate the capability of time-resolved X-ray and neutron radiography to image multiphase flows in particle-laden optically opaque liquid metal, thus contributing to pave the way for systematic investigations on bubble-inclusion interactions in molten metals.

Keywords: X-ray radiography; neutron radiography; bubble flotation; non-metallic inclusions; liquid metal

  • Lecture (Conference) (Online presentation)
    TMS2021 Virtual, 15.-18.03.2021, Orlando, Florida, USA
  • Book chapter
    Lee J., Wagstaff S., Anderson A., Tesfaye F., Lambotte G., Allanore A.: Materials Processing Fundamentals 2021, Cham: Springer, 2021, 978-3-030-65253-1, 13-29
    DOI: 10.1007/978-3-030-65253-1_2

Publ.-Id: 31441

Simulation of hard x-rays source produced by a picosecond laser irradiated solid target for Compton radiography

Meng-Ting, L.; Guang-Yue, H.; Huang, L.; Jian, Z.

A bremsstrahlung radiation hard x-ray source, produced by a picosecond intense laser irradiated solid target, was used to diagnose an implosion capsule at stagnation phase via Compton radiography in experiments. By performing Monte Carlo and particle-in-cell simulation, we investigated the influence of target materials and laser intensity on the >70 keV bremsstrahlung hard x-ray emission. We found that the brightness of the hard x-rays is proportional to the atomic number multiplied by area density (ZρL), which indicates that the higher Z and higher density gold or uranium material will produce the brightest hard x-rays source at the same thickness. In relativistic laser solid interactions, hot electron recirculation plays an important role in hard x-ray emission. Without recirculation, hard x-ray conversion efficiency decays when increasing the laser intensity. While the hard x-ray emission comes to the maximal saturated conversion efficiency at relativistic laser intensity if considering the electron recirculation.
These results provide valuable insights into the experimental design of Compton radiography

Keywords: Inertial confined fusion; Compton radiography; Numerical modeling


Publ.-Id: 31440

Three-dimensional cell culture systems in radiopharmaceutical cancer research

Doctor, A.; Seifert, V.; Ullrich, M.; Hauser, S.; Pietzsch, J.

In preclinical cancer research, three-dimensional (3D) cell culture systems such as multicellular spheroids and organoids are becoming increasingly important. They provide valuable information before studies on animal models begin and, in some cases, are even suitable for reducing or replacing animal experiments. Furthermore, they recapitulate microtumors, metastases and the tumor microenvironment much better than monolayer culture systems could. 3D models show higher structural complexity and diverse cell interactions, while reflecting (patho)physiological phenomena such as oxygen and nutrient gradients in the course of their growth or development. These interactions and properties are of great importance for understanding the pathophysiological importance of stromal cells and the extracellular matrix for tumor progression, treatment response or resistance mechanisms of solid tumors. Special emphasis is placed on co-cultivation with tumor-associated cells, which further increases the predictive value of 3D models, e.g. for drug development. The aim of this overview is to shed light on selected 3D models and their advantages and disadvantages, especially from the radiopharmacist´s point of view with focus on the suitability of 3D models for the radiopharmacological characterization of novel radiotracers and radiotherapeutics. Special attention is paid to pancreatic ductal adenocarcinoma (PDAC), as predestined target for the development of new radionuclide-based theranostics.

Keywords: Co-culture; organoids; pancreatic cancer; radiotherapeutics; radiotracer; spheroids; stromal cells; 3D model; tumor microenvironment

Publ.-Id: 31439

The dipole response of 87Rb and its impact on the 86Rb(n,γ)87Rb cross section

Wilhelmy, J.; Müscher, M.; Rusev, G.; Schwengner, R.; Beyer, R.; Bhike, M.; Erbacher, P.; Fiedler, F.; Friman-Gayer, U.; Glorius, J.; Greifenhagen, R.; Hammer, S.; Hensel, T.; Isaak, J.; Junghans, A. R.; Krishichayan, F.; Löher, B.; Müller, S. E.; Pietralla, N.; Reinicke, S.; Savran, D.; Scholz, P.; Sonnabend, K.; Szücs, T.; Tamkas, M.; Tornow, W.; Turkat, S.; Wagner, A.; Zilges, A.

Background: Detailed information on the low-lying dipole response in atomic nuclei along isotonic or isotopic chains is well suited to systematically investigate the structure and evolution of the Pygmy Dipole Resonance (PDR). Moreover, the dipole strength below and around the neutron separation energy Sn has impact on statistical model calculations for nucleosynthesis processes. Purpose: The photon strength function (PSF) of 87 Rb, which is directly connected to the photoabsorption cross section, is a crucial input for statistical model calculations constraining the Maxwellian-averaged cross section (MACS) of the neutron capture of the unstable s-process branching-point nucleus 86 Rb. Within this work, the photoabsorption cross section is investigated.
Methods: The photoabsorption cross section of the N = 50 nucleus 87 Rb was determined from photon-scattering experiments via the Nuclear Resonance Fluorescence (NRF) technique. Bremsstrahlung beams at the γELBE facility in conjunction with monoenergetic photon beams at the HIGS facility were used to determine the integrated cross sections Is of isolated states as well as the averaged cross section as function of the excitation energy. Decays to the ground state were disentangled from decays to first low-lying excited states. Statistical and experimental approaches for the γ-decay properties at various excitation energies were applied. The linearly polarized photon beams at HIGS provide information on the ratio of electric and magnetic type of radiation.
Results: Within this work, more than 200 ground-state decays and associated levels in 87Rb were identified. Moreover, transitions below the sensitivity limit of the state-by-state analysis were taken into account via a statistical approach from the bremsstrahlung data as well as model-independently from the HIGS data. The photoabsorption cross sections at various excitation energies were determined. The dipole response between 6 and 10 MeV of 87 Rb is in agreement with assuming contributions of electric multipolarity, only.
Conclusions: The photoabsorption cross section of 87Rb does not contradict with the trend of decreasing E1 strength with increasing proton number along the N = 50 isotonic chain but might also be associated with a constant trend. The experimental γ decay at various excitation energies of the HIGS data supports the statistical approach but does not provide a stringent proof due to the limited sensitivity in the decay channels. The additional E1 strength observed in the present experiments significantly enhances the MACSs compared to recent microscopic D1M HFB+QRPA calculations only. Moreover, theoretical estimations provided by the KADoN iS project could be significantly improved.

Publ.-Id: 31438

Uranium(VI) bioassociation by different fungi – a comparative study into molecular processes

Wollenberg, A.; Drobot, B.; Hübner, R.; Kretzschmar, J.; Freitag, L.; Lehmann, F.; Günther, A.; Stumpf, T.; Raff, J.

After the Chernobyl and Fukushima incidents it has become clear that fungi can take up and accumulate large quantities of radionuclides and heavy metals, but the underlying processes are not well understood yet. For this study, the molecular interactions of uranium(VI) with the white-rot fungi, Schizophyllum commune and Pleurotus ostreatus, and the soil-living fungus, Leucoagaricus naucinus, were investigated. First, the uranium concentration in the biomass was determined by time-dependent bioassociation experiments. To characterize the molecular interactions, uranium was localized in the biomass by transmission electron microscopy analysis. Second, the formed uranyl complexes in both biomass and supernatant were determined by fluorescence spectroscopy. Additionally, possible bioligands in the supernatant were identified. The results show that the discernible interactions between metals and fungi are similar, namely biosorption, accumulation, and subsequent crystallization. But at the same time, the underlying biochemical mechanisms are different and specific to the fungal species. In addition, Schizophyllum commune was found to be the only fungus that, under the chosen experimental conditions, released tryptophan and other indole derivatives in the presence of uranium(VI) as determined by nuclear magnetic resonance spectroscopy. These released substances most likely act as messenger molecules rather than serving the direct detoxification of uranium(VI).

Keywords: radionuclides; mycelium; microscopy; spectroscopy; metabolite; quorum sensing

Publ.-Id: 31437

Trapped-ion toolkit for studies of quantum harmonic oscillators under extreme conditions

Wittemer, M.; Schröder, J.-P.; Hakelberg, F.; Kiefer, P.; Fey, C.; Schützhold, R.; Warring, U.; Schaetz, T.

Many phenomena described in relativistic quantum field theory are inaccessible to direct observations, but analogue processes studied under well-defined laboratory conditions can present an alternative perspective. Recently, we demonstrated an analogy of particle creation using an intrinsically robust motional mode of two trapped atomic ions. Here, we substantially extend our classical control techniques by implementing machine-learning strategies in our platform and, consequently, increase the accessible parameter regime. As a proof of methodology, we present experimental results of multiple quenches and parametric modulation of an unprotected motional mode of a single ion, demonstrating the increased level of real-time control. In combination with previous results, we enable future experiments that may yield entanglement generation using a process in analogy to Hawking radiation. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.

Keywords: Trapped Ions; Qubits; Ion Traps (Instrumentation)

Publ.-Id: 31436

Prognostic value of baseline [18F]-fluorodeoxyglucose positron emission tomography parameters MTV, TLG and asphericity in an international multicenter cohort of nasopharyngeal carcinoma patients

Zschaeck, S.; Li, Y.; Lin, Q.; Beck, M.; Amthauer, H.; Bauersachs, L.; Hajiyianni, M.; Rogasch, J.; Ehrhardt, V. H.; Kalinauskaite, G.; Weingärtner, J.; Hartmann, V.; van den Hoff, J.; Budach, V.; Stromberger, C.; Hofheinz, F.


[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) parameters have shown prognostic value in nasopharyngeal carcinomas (NPC), mostly in monocenter studies. The aim of this study was to assess the prognostic impact of standard and novel PET parameters in a multicenter cohort of patients.

The established PET parameters metabolic tumor volume (MTV), total lesion glycolysis (TLG) and maximal standardized uptake value (SUVmax) as well as the novel parameter tumor asphericity (ASP) were evaluated in a retrospective multicenter cohort of 114 NPC patients with FDG-PET staging, treated with (chemo)radiation at 8 international institutions. Uni- and multivariable Cox regression and Kaplan-Meier analysis with respect to overall survival (OS), event-free survival (EFS), distant metastases-free survival (FFDM), and locoregional control (LRC) was performed for clinical and PET parameters.

When analyzing metric PET parameters, ASP showed a significant association with EFS (p = 0.035) and a trend for OS (p = 0.058). MTV was significantly associated with EFS (p = 0.026), OS (p = 0.008) and LRC (p = 0.012) and TLG with LRC (p = 0.019). TLG and MTV showed a very high correlation (Spearman’s rho = 0.95), therefore TLG was subesequently not further analysed. Optimal cutoff values for defining high and low risk groups were determined by maximization of the p-value in univariate Cox regression considering all possible cutoff values. Generation of stable cutoff values was feasible for MTV (p<0.001), ASP (p = 0.023) and combination of both (MTV+ASP = occurrence of one or both risk factors, p<0.001) for OS and for MTV regarding the endpoints OS (p<0.001) and LRC (p<0.001). In multivariable Cox (age >55 years + one binarized PET parameter), MTV >11.1ml (hazard ratio (HR): 3.57, p<0.001) and ASP > 14.4% (HR: 3.2, p = 0.031) remained prognostic for OS. MTV additionally remained prognostic for LRC (HR: 4.86 p<0.001) and EFS (HR: 2.51 p = 0.004). Bootstrapping analyses showed that a combination of high MTV and ASP improved prognostic value for OS compared to each single variable significantly (p = 0.005 and p = 0.04, respectively). When using the cohort from China (n = 57 patients) for establishment of prognostic parameters and all other patients for validation (n = 57 patients), MTV could be successfully validated as prognostic parameter regarding OS, EFS and LRC (all p-values <0.05 for both cohorts).

In this analysis, PET parameters were associated with outcome of NPC patients. MTV showed a robust association with OS, EFS and LRC. Our data suggest that combination of MTV and ASP may potentially further improve the risk stratification of NPC patients.

Publ.-Id: 31435

Unusual scandium enrichments of the Tørdal pegmatites, south Norway. Part I: Garnet as Sc exploration pathfinder

Steffenssen, G.; Müller, A.; Munnik, F.; Friis, H.; Erambert, M.; Kristoffersen, M.; Rosing-Schow, N.

The granitic pegmatites of the Tørdal area in southern Norway have been known for their Sc enrichment for about 100 years. Scandium is a compatible element in garnet. In this study, 32 garnet samples from 16 pegmatite localities across the Tørdal pegmatite field were investigated to determine the Sc distribution within garnets (crystal scale), within pegmatite bodies (pegmatite scale) and across the Tørdal pegmatite field (regional scale). In the Tørdal pegmatites, Sc content in garnet is representative for the Sc bulk composition of pegmatites, defining garnet as a reliable pathfinder mineral for the exploration of Sc mineralization in pegmatite fields. Garnets with highest Sc concentrations of up to 2197 µg/g have a spessartine component ranging from 50 to 60 mol.%. Since most garnets crystallized during the early stage of pegmatite formation (wall zone stage) Sc decreases in the remaining pegmatite melt, as documented by generally decreasing Sc from core to rim of crystals and by the occurrence of late-stage garnets (albite zone stage) with low Sc. Thus, with progressing crystallization Sc decreases in the melt. The regional Sc distribution in the Tørdal pegmatite field revealed that the Skardsfjell-Heftetjern-Høydalen pegmatites have highest Sc enrichments to sub-economic levels, with an average bulk Sc content of 53 µg/g and an average Sc content in garnet of about 1900 µg/g in the Heftetjern 2 pegmatite.
The assumed resources of the Skardsfjell-Heftetjern-Høydalen area are about 125,000 t ore grading c. 50 µg/g Sc resulting in a total of 625 t Sc, which is too small to have economic potential. However, the strong Sc enrichment of the Tørdal pegmatites is unusual for granitic pegmatites, making them a specific Sc deposit type. The amphibolitic host rocks of the Tørdal pegmatites are identified as the source rocks of Sc. The host rocks, which are part of the Nissedal Outlier supracrustals, are enriched in Sc (mean 34 µg/g) compared to average crustal compositions (mean 14 µg/g). Scandium of amphiboles was preferentially released at the onset of partial melting of the amphibolites. Thus, the Sc content in the pegmatite is strongly dependent on the degree of partial melting.

Keywords: scandium; pegmatite; garnet; Sveconorwegian orogeny; Tørdal

Publ.-Id: 31434

Applying tissue slice culture in cancer research—insights from preclinical proton radiotherapy

Suckert, T.; Rassamegevanon, T.; Müller, J.; Dietrich, A.; Graja, A.; Reiche, M.; Löck, S.; Krause, M.; Beyreuther, E.; von Neubeck, C.

A challenge in cancer research is the definition of reproducible, reliable, and practical models, which reflect the effects of complex treatment modalities and the heterogeneous response of patients. Proton beam radiotherapy (PBRT), relative to conventional photon-based radiotherapy, offers the potential for iso-effective tumor control, while protecting the normal tissue surrounding the tumor. However, the effects of PBRT on the tumor microenvironment and the interplay with newly developed chemo-and immunotherapeutic approaches are still open for investigation. This work evaluated thin-cut tumor slice cultures (TSC) of head and neck cancer and organotypic brain slice cultures (OBSC) of adult mice brain, regarding their relevance for translational radiooncology research. TSC and OBSC were treated with PBRT and investigated for cell survival with a lactate dehydrogenase (LDH) assay, DNA repair via the DNA double strand break marker γH2AX, as well as histology with regards to morphology. Adult OBSC failed to be an appropriate model for radiobiological research questions. However, histological analysis of TSC showed DNA damage and tumor morphological results, comparable to known in vivo and in vitro data, making them a promising model to study novel treatment approaches in patient-derived xenografts or primary tumor material.

Keywords: tumor biology; DNA damage; organotypic brain slice culture; head and neck cancer; proton beam radiotherapy; thin-cut tissue slices

Publ.-Id: 31432

Coherent Optical Signatures of Electron Microbunching in Laser-Driven Plasma Accelerators

Lumpkin, A. H.; Laberge, M.; Rule, D. W.; Zgadzaj, R.; Hannasch, A.; Zarini, O.; Bowers, B.; Irman, A.; Couperus Cabadağ, J. P.; Debus, A.; Köhler, A.; Schramm, U.; Downer, M. C.

We report observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched∼200-MeV electrons as they emerge from a laser-driven plasma accelerator. The divergence of the microbunched portion of electrons, deduced by comparison to a COTRI model, is ∼9× smaller than the ∼3 mrad ensemble beam divergence, while the radius of the microbunched beam, obtained from COTR images on the same shot, is <3 μm. The combined results show that the microbunched distribution has estimated transverse normalized emittance∼0.4mm mrad.

Keywords: Beam diagnostics; LWFA; COTRI; CTR; transition radiation


Publ.-Id: 31431

Freestanding and Supported MoS2 Monolayers under Cluster Irradiation: Insights from Molecular Dynamics Simulation

Ghaderzadeh, S.; Ladygin, V.; Ghorbani Asl, M.; Hlawacek, G.; Schleberger, M.; Krasheninnikov, A.

Two-dimensional (2D) materials with nanometer-size holes are promising systems for DNA sequencing, water purification, and molecule selection/separation. However, controllable creation of holes with uniform sizes and shapes is still a challenge, especially when the 2D material consists of several atomic layers as, e.g., MoS2, the archetypical transition metal dichalcogenide.We use analytical potential molecular dynamics simulations to study the response of 2D MoS2tocluster irradiation. We model both freestanding and supported sheets and assess the amount of damage created in MoS2by the impacts of noble gas clusters in a wide range of cluster energies and incident angles. We show that cluster irradiation can be used to produce uniform holes in 2DMoS2with the diameter being dependent on cluster size and energy. Energetic clusters can also beused to displace sulfur atoms preferentially from either top or bottom layers of S atoms in MoS2and also clean the surface of MoS2sheets from adsorbents. Our results for MoS2, which should be relevant to other 2D transition metal dichalcogenides, suggest new routes toward cluster beam engineering of devices based on 2Dinorganic materials.

Keywords: two-dimensional materials; MoS2; cluster irradiation; pore formation; sputtering yield; atomistic simulation

  • ACS Applied Materials and Interfaces 12(2020)33, 37454-37463
    Online First (2020) DOI: 10.1021/acsami.0c09255


  • Secondary publication expected

Publ.-Id: 31430

A supervised technique for drillcore mineral mapping using Hyperspectral data

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Gloaguen, R.

D rilling is a key task in exploration campaigns to characterize mineral deposits at depth. Drillcores are first logged in the field by a geologist and with regards to, e.g., mineral assemblages, alteration patterns, and structural features. The core-logging information is then used to locate and target the important ore accumulations and select representative samples that are further analyzed by laboratory measurements (e.g., Scanning Electron Microscopy (SEM), Xray diffraction (XRD), X-ray Fluorescence (XRF)). However, core-logging is a laborious task and subject to the expertise of the geologist. Hyperspectral imaging is a non invasive and non-destructive technique that is increasingly being used to support the geologist in the analysis of drill-core samples. Nonetheless, the benefit and impact of using hyperspectral data depend on the applied methods. With this in mind, machine learning techniques, which have been applied in different research fields, provide useful tools for an advance and more automatic analysis of the data. Lately, machine learning frameworks are also being implemented for mapping minerals in drill-core hyperspectral data. In this context, this work follows an approach to map minerals on drill-core hyperspectral data using supervised machine learning techniques, in which SEM data, integrated with the mineral liberation analysis (MLA) software, are used in training a classifier. More specifically, the high-resolution mineralogical data obtained by SEM-MLA analysis is resampled and co-registered to the hyperspectral data to generate a training set. Due to the large difference in spatial resolution between the SEM-MLA and hyperspectral images, a pre-labeling strategy is required to link these two images at the hyperspectral data spatial resolution. In this study, we use the SEM-MLA image to compute the abundances of minerals for each hyperspectral pixel in the corresponding SEM-MLA region. We then use the abundances as features in a clustering procedure to generate the training labels. In the final step, the generated training set is fed into a supervised classification technique for the mineral mapping over a large area of a drill-core. The experiments are carried out on a visible to near-infrared (VNIR) and shortwave infrared (SWIR) hyperspectral data set and based on preliminary tests the mineral mapping task improves significantly.

  • Open Access Logo Poster (Online presentation)
    European Geosciences Union (EGU) General Assembly, 04.-08.05.2020, Vienna, Austria


Publ.-Id: 31429

Fusion of VNIR-SWIR and LWIR for Mineral Mapping in a Machine Learning Framework

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Gloaguen, R.

Mineral mapping is an important task in exploration campaigns where it is required to obtain a preliminary idea about the composition of ore deposits. Hyperspectral imaging is becoming a trending technology within the mining community to map minerals during exploration campaigns. This is because minerals have unique spectral responses in specific parts of the electromagnetic spectrum. These responses depend on the bonds between the atoms and electron orbitals of the minerals. In other words, based on the molecular vibrations and composition of the minerals the light reflects differently from the minerals and therefore, the spectral responses vary. In general, alteration minerals (e.g., phyllosilicates) can be mapped using the visible to near-infrared (VNIR) and short-wave infrared (SWIR) parts of the electromagnetic spectrum, whereas rock-forming minerals, (e.g., feldspars and quartz) are better distinguishable using the long-wave infrared (LWIR). Therefore, fusing the VNIR-SWIR and LWIR parts of the electromagnetic spectrum provides a complete range of data for the mineral mapping task. The benefit of using hyperspectral data from both regions of the electromagnetic spectrum to map minerals is clear and it has been previously implemented in an independent manner. However, in this work, we focus on different machine learning strategies to fuse VNIR-SWIR and LWIR hyperspectral data for an accurate mineral mapping. We test two fusion scenarios: feature level fusion and decision-level fusion. For the feature-level fusion, we adopt a state-of-the-art multiple feature learning technique to adequately exploit the information containing in both data types. Hence, we take advantage of the complementary information using only one classifier. For the decision-level fusion, we integrate the independent classification results obtained using the VNIR-SWIR and LWIR data. In this way, higher robustness is expected from the combination of the classification results. The experiments are carried out on real hyperspectral datasets of drill core samples. With this contribution, we introduce a novel approach for the mining community to map minerals using a full range of hyperspectral data where not only alteration minerals but rock-forming minerals can be jointly mapped. Moreover, our proposed approach can accurately map minerals with weak spectral responses in both wavelength ranges. Based on preliminary attempts, the fusion of the VNIRSWIR and LWIR at both decision and feature levels performed better than considering both datasets independently.

  • Open Access Logo Lecture (Conference)
    European Geosciences Union (EGU) General Assembly, 07.-12.04.2019, Vienna, Austria


Publ.-Id: 31428

Multi-label Classification for Drill-core Hyperspectral Mineral Mapping

Contreras Acosta, I. C.; Khodadadzadeh, M.; Gloaguen, R.

A multi-label classification concept is introduced for the mineral mapping task in drill-core hyperspectral data analysis. As opposed to traditional classification methods, this approach has the advantage of considering the different mineral mixtures present in each pixel. For the multi-label classification, the well-known Classifier Chain method (CC) is implemented using the Random Forest (RF) algorithm as the base classifier. High resolution mineralogical data obtained from Scanning Electron Microscopy (SEM) instrument equipped with the Mineral Liberation Analysis (MLA) software are used for generating the training data set. The drillcore hyperspectral data used in this paper cover the visible-near infrared (VNIR) and the short-wave infrared (SWIR) range of the electromagnetic spectrum. The quantitative and qualitative analysis of the obtained results shows that the multi-label classification approach provides meaningful and descriptive mineral maps and outperforms the single-label RF classification for the mineral
mapping task.

Keywords: Mineral mapping; drill-core hyperspectral data; mineral liberation analysis; classifier chains; random forest; multi-label classification; machine learning

Publ.-Id: 31427

Geochemical and Hyperspectral Data Fusion for Drill-core Mineral Mapping

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Loidolt, C.; Tolosana Delgado, R.; Gloaguen, R.

Hyperspectral imaging is increasingly being used in the mining industry for the investigation of drill-core samples. It provides the means to analyze a large amount of cores considerably faster than traditional methods and in a non-invasive and non-destructive manner. Traditional approaches used to analyse drill-core hyperspectral data are mainly based on visual observations and need significant human interactions. Thus, they are time-consuming and subjective. In this paper, we explore the use of supervised machine learning techniques for mineral mapping in drill-core hyperspectral data. For this purpose, we suggest to use geochemical data for generating a training set. The main contribution of this work is to fuse geochemical and hyperspectral data within a machine learning framework. Moreover, for a more complete mineral mapping task, we integrate visible near-infrared (VNIR), short-wave infrared (SWIR) and long-wave infrared (LWIR) hyperspectral data. For the extraction of input features, the traditional Principal Component Analysis (PCA) is implemented. For classification, we propose to use Random Forest (RF) because of its significant performance in hyperspectral data classification when there are few training samples available. Experimental results show that the proposed method provides comprehensive mineral maps in which the distribution and patterns of different minerals are well characterised.

Keywords: Data fusion; mineral mapping; hyperspectral data; geochemical data; machine learning

  • Contribution to proceedings
    2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS), 24.-26.09.2019, Amsterdam, The Netherlands
    2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS): IEEE
    DOI: 10.1109/WHISPERS.2019.8921163

Publ.-Id: 31426

Drill-Core Hyperspectral and Geochemical Data Integration in a Superpixel-Based Machine Learning Framework

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gloaguen, R.

The analysis of drill-core samples is one of the most important steps in the mining industry for the exploration and discovery of mineral resources. Geochemical assays are a common approach to represent the abundance of different chemical elements and aid at quantifying the concentrations of the important ore accumulations. However, their acquisition is time-consuming and usually averages of long core portions. Hyperspectral data are increasingly being used in the mining industry to complement the analysis of drill-cores due to their efficiency and fast turn-around time. Moreover, hyperspectral imaging is a technique able to provide data with high spatial resolution. In this article, we propose to integrate the complementary information derived from hyperspectral and geochemical data via a superpixel-based machine learning framework. This framework considers the difference in spatial resolution through segmentation. We extract labels from the geochemical assays and select, from the hyperspectral data, representative samples for each measurement. A supervised machine learning classification (composite kernel support vector machine) is then used to extrapolate the elements relative abundance to the entire core length. We propose an innovative integration of hyperspectral data covering different regions of the electromagnetic spectrum in a kernel-based framework to facilitate the identification of a larger amount of elements. A qualitative and quantitative evaluation of the results demonstrates the capabilities of the proposed method, which provides approximately 20% more accurate results than the pixel-based approach. Results also imply that the method could be beneficial for the reduction of geochemical assays needed for the detailed analysis of the cores.

Keywords: Data integration; drill-cores; geochemical data; hyperspectral data; machine learning; superpixel segmentation

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13(2020), 4214-4228
    Online First (2020) DOI: 10.1109/JSTARS.2020.3011221

Publ.-Id: 31425

Mass Spectrum of Pseudo-Scalar Glueballs from a Bethe–Salpeter Approach with the Rainbow–Ladder Truncation

Kaptari, L. P.; Kämpfer, B.

We suggest a framework based on the rainbow approximation to the Dyson–Schwinger and Bethe–Salpeter equations with effective parameters adjusted to lattice QCD data to calculate the masses of the ground and excited states of pseudo-scalar glueballs. The structure of the truncated Bethe–Salpeter equation with the gluon and ghost propagators as solutions of the truncated Dyson–Schwinger equations is analyzed in Landau gauge. Both, the Bethe–Salpeter and Dyson–Schwinger equations, are solved numerically within the same rainbow–ladder truncation with the same effective parameters which ensure consistency of the approach. We found that with a set of parameters, which provides a good description of the lattice data within the Dyson–Schwinger approach, the solutions of the Bethe–Salpeter equation for the pseudo-scalar glueballs exhibit a rich mass spectrum which also includes the ground and excited states predicted by lattice calculations. The obtained mass spectrum contains also several intermediate excitations beyond the lattice approaches. The partial Bethe–Salpeter amplitudes of the pseudo-scalar glueballs are presented as well.

Publ.-Id: 31424

Ab initio results for the plasmon dispersion and damping of the warm dense electron gas

Hamann, P.; Vorberger, J.; Dornheim, T.; Moldabekov, Z.; Bonitz, M.

Warm dense matter (WDM) is an exotic state on the border between condensed matter and dense plasmas. Important occurrences of WDM include dense astrophysical objects, matter in the core of our Earth, as well as matter produced in strong compression experiments. As of late, x-ray Thomson scattering has become an advanced tool to diagnose WDM. The interpretation of the data requires model input for the dynamic structure factor S(q,ω) and the plasmon dispersion ω(q). Recently the first \textit{ab initio} results for S(q,ω) of the homogeneous warm dense electron gas were obtained from path integral Monte Carlo simulations, [Dornheim et al., Phys. Rev. Lett. 121, 255001 (2018)]. Here, we analyse the effects of correlations and finite temperature on the dynamic dielectric function and the plasmon dispersion. Our results for the plasmon dispersion and damping differ significantly from the random phase approximation and from earlier models of the correlated electron gas. Moreover, we show when commonly used weak damping approximations break down and how the method of complex zeros of the dielectric function can solve this problem for WDM conditions.

Keywords: warm dense matter; electron gas; correlation; exchange; plasmon dispersion; plasmon width; collective effects; dynamic structure factor

Publ.-Id: 31423

Highly ordered silicide ripple patterns induced by medium-energy ion irradiation

Redondo-Cubero, A.; Palomares, F. J.; Hübner, R.; Gago, R.; Vázquez, L.

We study the nanopatterning of silicon surfaces under near-normal 40-keV Ar+ sputtering with simultaneous Fe oblique codeposition. The ion-beam incidence was kept at 15°, for which no pattern is produced in the absence of metal incorporation. Morphological and compositional analyses were performed by atomic force microscopy, in its morphological and electrical modes, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, scanning Auger, as well as transmission and scanning electron microscopy. Initially, nanodot structures randomly emerge, which, with increasing ion fluence, become progressively aligned along the perpendicular direction to the Fe flux. With increasing fluence, they coalesce, leading to a ripple pattern. The pattern dynamics and characteristics are faster and enhanced, respectively, as the distance to the metal source decreases (i.e., as the metal content increases). For the highest metal flux, the ripples can become rather large (up to 18 μm) and straighter, with few defects, and a pattern wavelength close to 500 nm, while keeping the surface roughness close to 15 nm. Furthermore, for a fixed ion fluence, the pattern order is improved for higher metal flux. In contrast, the pattern order enhancement rate with ion fluence does not depend on the metal flux. Our experimental observations agree with the predictions and assumptions of the model by Bradley [R. M. Bradley, Phys. Rev. B 87, 205408 (2013)] Several compositional and morphological studies reveal that the ripple pattern is also a compositional one, in which the ripple peaks have a higher iron silicide content, in agreement with the model. Likewise, the ripple structures develop along the perpendicular direction to the Fe flux, and the pattern wavelength increases as the metal flux decreases with a behavior qualitatively consistent with the model predictions.

Publ.-Id: 31422

Towards Bacteria Counting in DI Water of Several Microliters or Growing Suspension Using Impedance Biochips

Kiani, M.; Tannert, A.; Du, N.; Hübner, U.; Skorupa, I.; Bürger, D.; Zhao, X.; Blaschke, D.; Rebohle, L.; Cherkouk, C.; Neugebauer, U.; Schmidt, O. G.; Schmidt, H.

We counted bacterial cells of E. coli strain K12 in several-microliter DI water or in several-microliter PBS in the low optical density (OD) range (OD = 0.05-1.08) in contact with the surface of Si-based impedance biochips with ring electrodes by impedance measurements. The multiparameter fit of the impedance data allowed calibration of the impedance data with the concentration cb of the E. coli cells in the range of cb = 0.06 to 1.26 × 109 cells/mL. The results showed that for E. coli in DI water and in PBS, the modelled impedance parameters depend linearly on the concentration of cells in the range of cb = 0.06 to 1.26 × 109 cells/mL, whereas the OD, which was independently measured with a spectrophotometer, was only linearly dependent on the concentration of the E. coli cells in the range of cb = 0.06 to 0.50 × 109 cells/mL.

Publ.-Id: 31421

Sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase: Batch experiments, Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) and Surface Complexation Modeling (SCM)

Brinkmann, H.; Neumann, J.; Britz, S.; Brendler, V.; Stumpf, T.; Schmidt, M.

Sorption is one of the main processes, which determine the retention of radionuclides (RN) in a repository for nuclear waste. In a multi-barrier system, the host rock poses the ultimate barrier retarding the release of RN into the environment. Feldspars (e.g. orthoclase) are one of the main constituents of crystalline rock (e.g. granite), which is considered one potential host rock type in many countries (e.g. Finland, Sweden, Germany). In this study, the sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase (K feldspar) is investigated. For reliable predictions concerning the migration of RN, a process understanding on the molecular level of such processes is necessary. To achieve this, batch sorption experiments are combined with TRLFS and SCM.
Batch experiments were performed covering a broad range of experimental conditions (pH 4-11, oxic and anoxic conditions, [M3+] = 10-6-10-4 M, 3-50 g/L orthoclase (grain size: < 21 and 63-200 µm; SSA: 4.2 and 0.2 m2g-1)). Weak retardation below pH 5, followed by a strong increase between pH 5 and 7 and complete removal from solution at pH ≥ 8 was observed for all investigated metals. Cm- and Eu-TRLFS-measurements suggested the formation of an outer-sphere surface complex at lower (pH<5) and two different inner-sphere surface complexes at higher pH values (pH > 5 and pH > 7.5, respectively). Surface precipitation was observed for higher metal concentrations (10-4 M). As the investigated metals revealed a similar behavior over a broad range of conditions, a generic approach was used for the SCM to describe the system as a whole. Experimental data of different series with different metals were simultaneously fitted by coupling PHREEQC with UCODE using the same underlying speciation model. Resulting generic stability constants for the involved surface complexes will be presented.
The identification of comparable processes and their unified description with one suitable model is important to map the complexity of natural systems onto simplified geochemical models. This step is crucial for large-scale reactive transport calculations needed for a reliable safety assessment of potential repository sites, as they require enormous computing efforts.

Keywords: Actinides; Sorption; Orthoclase; Spectroscopy; Modeling

Publ.-Id: 31420

Analysis of technetium immobilization and its molecular retention mechanisms by Fe(II)-Al(III)-Cl layered double hydroxide.

Mayordomo, N.; Rodriguez Hernandez, D. M.; Roßberg, A.; Foerstendorf, H.; Heim, K.; Brendler, V.; Müller, K.

Layered double hydroxides (LDH) play a decisive role in regulating the mobility of contaminants in natural and engineered environments. In this work, the retention of an Fe(II)-Al(III)-Cl LDH towards pertechnetate (TcO₄⁻ ), which is the most stable and highly mobile form of Tc under aerobic conditions, is investigated comprehensively as a function of pH, Tc concentration and ionic strength. For a technetium initial concentration of 5 µM, its retention yield is higher than 80% from pH 3.5 to pH 10.5, especially at NaCl concentration below 0.1 M. A combination of vibrational and X-ray absorption spectroscopy provides structural information on the retention mechanism on a molecular scale. X-ray absorption near edge spectroscopy (XANES) confirms that most of the Tc uptake is due to Tc(VII) reduction to Tc(IV). The analysis of the extended X-ray absorption fine structure (EXAFS) reveals two different mechanisms of Tc(IV) interaction with hematite (sub-product of the LDH oxidation and confirmed by Raman microscopy). At low pH, sorption of Tc(IV) dimers via inner-sphere monodentate complexation on hematite dominates. In contrast, under alkaline conditions, Tc(IV) is incorporated into the structure of hematite. Additionally, in situ attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR) evidences a small contribution of the total uptake corresponding to Tc(VII) anion exchange.
The derived molecular structures increase confidence in predictive modelling of Tc migration patterns in subsurface environments, e.g. in the vicinity of a radioactive waste repository and treatment sites or in polluted areas due to other anthropogenic Tc sources.

Keywords: LDH; hematite; reduction; retardation; XAS; ATR FT-IR


  • Secondary publication expected from 15.03.2022

Publ.-Id: 31419

Mapping the stray fields of a micromagnet using spin centers in SiC

Bejarano, M.; Trindade Goncalves, F. J.; Hollenbach, M.; Hache, T.; Hula, T.; Berencen, Y.; Faßbender, J.; Helm, M.; Astakhov, G.; Schultheiß, H.

We report the use of optically addressable spin qubits in SiC to probe the static magnetic stray fields generated by a ferromagnetic microstructure lithographically patterned on the surface of a SiC crystal. The stray fields cause shifts in the resonance frequency of the spin centers. The spin resonance is driven by a micrometer-sized microwave antenna patterned adjacent to the magnetic element. The patterning of the antenna is done to ensure that the driving microwave fields are delivered locally and more efficiently compared to conventional, millimeter-sized circuits. A clear difference in the resonance frequency of the spin centers in SiC is observed at various distances to the magnetic element, for two different magnetic states. Our results offer a wafer-scale platform to develop hybrid magnon-quantum applications by deploying local microwave fields and the stray field landscape at the micrometer lengthscale.

Keywords: Quantum sensing; Magnonics; Spin qubits in SiC; Microwave circuits; electron beam lithography

Related publications

  • IEEE Magnetics Letters 12(2021), 9380379
    DOI: 10.1109/LMAG.2021.3066341
  • Poster (Online presentation)
    Magnetism and Magnetic Materials Conference 2020 (MMM2020), 02.-06.11.2020, Online, United States


  • Secondary publication expected from 17.03.2022

Publ.-Id: 31418

Studies of Big Data Processing at Linear Accelerator Sources Using Machine Learning

Bawatna, M.; Green, B. W.

In linear accelerator sources such as the electron beam of the super-conducting linear accelerator at the radiation source Electron Linear accelerator for beams with high Brilliance and low Emittance (ELBE), different kinds of secondary radiation can be produced for various research purposes from materials science up to medicine. A variety of different beam detectors generate a huge amount of data, which take a great deal of computing power to capture and analyse. In this contribution, we will discuss the possibilities of using Machine Learning method to solve the big data challenges. Moreover, we will present a technique that employ the machine learning strategy for the diagnostics of high-field terahertz pulses generated at the ELBE accelerator with extremely flexible parameters such as repetition rate, pulse form and polarization.

Keywords: Cloud computing; Machine learning; Big data; Deep neural networks

  • Contribution to proceedings
    Computer Science On-line Conference, CSOC 2020: Artificial Intelligence and Bioinspired Computational Methods, 20.-24.05.2020, Berlin, Germany
    Advances in Intelligent Systems and Computing, Volume 1225 AISC, 2020, Pages 450-460: Springer, 978-3-030-51970-4
    DOI: 10.1007/978-3-030-51971-1_37

Publ.-Id: 31417

Real-Time Data Compression System for Data-Intensive Scientific Applications Using FPGA Architecture

Bawatna, M.; Knodel, O.; Spallek, R.

Particle accelerators are continually advancing and offer insights into the world of molecules, atoms, and particles on the ever shorter length and timescales. A variety of detectors, which are connected to different front-end electronics are installed in various kinds of Data Acquisition (DAQ) systems, to collect a huge amount of raw data. This goes along with a rapid and highly accurate transformation of analog quantities into discrete values for electronic storage and processing with exponentially increasing amounts of data. Therefore, data reduction or compression is an important feature for the DAQ systems to reduce the size of the data transmission path between the detectors and the computing units or storage devices. The flexibility of the Field Programmable Gate Arrays (FPGAs) allows the implementation of real-time data compression algorithms inside these DAQ systems. In this contribution, we will present our developed real-time data compression technique for continuous data recorded by high-speed imaging detectors at the terahertz source facility at ELBE particle accelerator. The hardware implementation of the algorithm proved its real-time suitability by compressing one hundred thousand consecutive input signals without introducing dead time.

Keywords: Lossless data compression; FPGA; Real-time; Data-intensive

  • Contribution to proceedings
    Computer Science On-line Conference, Applied Informatics and Cybernetics in Intelligent Systems, 20.-24.05.2020, Berlin, Germany
    CSOC 2020: Applied Informatics and Cybernetics in Intelligent Systems: Springer, 978-3-030-51974-2, 304-313
    DOI: 10.1007/978-3-030-51974-2_29

Publ.-Id: 31416

Possibilities and Challenges for Reconfigurable Hardware and Cloud Architectures in Data-Intensive Scientific Applications

Bawatna, M.; Knodel, O.; Spallek, R.

Advances in process technology and new design tools have expanded the scope of embedded systems. This ranges from the implementation in several chips on board to module groups in integrated circuits. Reconfigurable hardware and, in particular, FPGAs are used more frequently in scientific applications, where they enable the development of complex and intelligent field devices. Furthermore, this increased the use of a platform-based design approach that facilitates the development and verification of complex FPGAs through the full reuse of hardware and software modules. Especially in the area of heterogeneous accelerators, which can improve the exploitation of modern data centers. Another critical aspect in the evolution of embedded systems is the trend towards networking embedded nodes using specialized computational and networking technologies called cloud computing. In this paper, we will present our data-intensive experiments at the terahertz source at ELBE accelerator-based light source, and its integration into a reproducible data management workflow at the heterogeneous cluster in our data centre

Keywords: Reconfigurable computing; cloud; data-intensive scientific applications

  • Contribution to proceedings
    Seventh International Conference on Software Defined Systems (SDS), 20.-23.04.2020, Paris, France
    Proceedings of Seventh International Conference on Software Defined Systems: IEEE, 978-1-7281-7218-7
    DOI: 10.1109/SDS49854.2020.9143904

Publ.-Id: 31415

In silico finding of key interaction mediated α3β4 and α7 nicotinic acetylcholine receptor ligand selectivity of quinuclidine-triazole chemotype

Arunrungvichian, K.; Chongruchiroj, S.; Sarasamkan, J.; Schüürmann, G.; Brust, P.; Vajragupta, O.

The selective binding of six (S)-quinuclidine-triazole and their (R)-enantiomers to nicotinic acetylcholine receptor (nAChR) subtypes α3β4 and α7, respectively, was analyzed by in silico docking to provide the insight into the molecular basis for the observed stereospecific subtype discrimination. Homology modeling follwed by molecular docking and molecular dynamics (MD) simulations revealed that unique amino acid residues in the complementary subunits of the nAChR subtypes are involved in subtype-specific selectivity profiles. In the complementary β4-subunit of the α3β4 nAChR binding pocket, non-conserved AspB173 through a salt bridge was found to be the key determinant for the α3β4 selectivity of the quinuclidine-triazole chemotype, explaining the 47-327-fold affinity of the (S)-enantiomers as compared to their (R)-enantiomer counterparts. Regarding the α7 nAChR subtype, the aminio acids promoting a however significantly lower preference for the (R)-enantiomers were the conserved TyrA93, TrpA149 and TrpB55 residues. The non-conserved amino acid residue in the complementary subunit of nAChR subtypes appeard to play a significant role for the nAChR subtype-selective binding, particularly at the heteropentameric subtype, wheras the conserved amino acid residues in both principal and complementary subunits are essential for ligand potency and efficacy.

Keywords: stereoselectivity; anti-1,2,3-triazole; α7 nAChR; α3β4 nAChR; quinuclidine

Publ.-Id: 31414

Effects of Acquisition Parameter Modifications and Field Strength on the Reproducibility of Brain Perfusion Measurements Using Arterial Spin-Labeling

Baas, K.; Petr, J.; Kuijer, J.; Nederveen, A.; Mutsaerts, H.-J.; van de Ven, K.

Background and Purpose: To encourage clinical adoption of ASL-based perfusion MRI, we investigated the reproducibility of CBF measurements and the effects of protocol variations at clinical field strengths in adult participants with a broad age range. This study increases the knowledge on the tolerance to variations in scan parameters compared to the recommended ASL implementation.
Materials and Methods: Thirty-four volunteers (mean age 57.8±17.0y, range 22-80y) underwent two separate scan sessions on clinical field strengths (1.5T and 3T, single vendor), using a fifteen channel head coil. Both sessions contained repeated 3D and 2D pseudo-continuous ASL (pCASL) vendor-recommended protocols, followed by three 3D pCASL scans; two with post-labeling delays (PLD) of 1600ms and 2000ms and one with increased spatial resolution. All pCASL scans were acquired with a single PLD. The effect of scan parameter variations on CBF and spatial coefficient of variation (CoV) was examined, as well as the reproducibility of the recommended protocols, both intrasession (two identical protocols scanned 5 min apart) and intersession (first 2D and 3D protocol of the first and second session).
Results: Intrasession CBF reproducibility was similar across image readouts and field strengths ( coefficient of variation (CV) ranging from 4.0% to 6.9%) and did not show a statistically significant correlation with age. Intersession wsCV ranged from 6.8% to 14.8%, scanning twice at 3T versus mixed 3T-1.5T respectively. At 3T, there is sufficient SNR to increase the spatial resolution of the 3D protocol, causing less mixing of gray matter (GM) and white matter signal, therewith decreasing the bias in GM CBF between 2D and 3D protocols (ΔCBF = 2.49 (p<0.001) ml/100g/min. Changes in PLD resulted in a modest bias (ΔCBF ranging from -3.78 (p<0.001) to 2.83 (p<0.001) ml/100g/min).
Conclusion: Our data shows that ASL imaging is reproducible at both field strengths and does not show a statistically significant correlation with age. Furthermore, 3T offers more tolerance for scan parameter variations and allows for protocol optimizations such that 3D and 2D protocols can be compared.

  • American Journal of Neuroradiology 42(2021)1, 109-115
    Online First (2020) DOI: 10.3174/ajnr.A6856

Publ.-Id: 31413

GliMR: Cross-border collaborations to promote advanced MRI biomarkers in glioma

Clement, P.; Borovecki, F.; Emblem, K. E.; Figueiredo, P.; Hirschler, L.; Jancalek, R.; Keil, V. C.; Maumet, C.; Ozsunar, Y.; Pernet, C.; Petr, J.; Pinto, J.; Smits, M.; Warnert, E. A. H.

Every year, 50.000 new glioma cases occur in Europe. The optimal treatment strategy is highly personalised, depending on tumour type, grade, spatial localization, and tissue infiltration level. In research settings, advanced magnetic resonance imaging (MRI) has shown great promise to inform personalised treatment decisions. However, the use of advanced MRI in clinical practice is still scarce, due to a scattered imaging research landscape, a limited representation of MRI in established consortia for glioma, and the lack of tools and expertise for advanced MRI, available in standard clinical settings. These shortcomings delay the translation of scientific breakthroughs into novel treatment strategy developments, and limit the progression of personalised medicine.
Therefore, in this work, the network Glioma MR Imaging 2.0 (GliMR) is presented. GliMR aims to build a pan-European and multidisciplinary network of experts and progress beyond the state-of-the-art in glioma imaging, by accelerating the use of advanced MRI in glioma. The Action ‘Glioma MR Imaging 2.0 (GliMR)’ was granted funding by the European Cooperation in Science and Technology (COST) in June 2019.
GliMR’s first grant period ran from September 2019 to April 2020, during which several networking meetings were held and projects were initiated by the different working groups, such as reviewing of the current knowledge on advanced MRI, developing a GDPR-compliant consent form, initiating relationships with European scientific organisations, and setting up several dissemination channels, including the website The action is funded until September 2023 and is accepting new members during its entire duration.

Publ.-Id: 31412

Integrated Geological and Geophysical Mapping of a Carbonatite-Hosting Outcrop in Siilinjärvi, Finland, Using Unmanned Aerial Systems

Jackisch, R.; Lorenz, S.; Kirsch, M.; Zimmermann, R.; Tusa, L.; Pirttijärvi, M.; Saartenoja, A.; Ugalde, H.; Madriz Diaz, Y. C.; Savolainen, M.; Gloaguen, R.

Mapping geological outcrops is a crucial part of mineral exploration, mine planning and ore extraction. With the advent of unmanned aerial systems (UAS) for rapid spatial and spectral mapping, opportunities arise in fields where traditional ground-based approaches are established and trusted, but fail to cover sufficient area or compromise personal safety. Multi-sensor UAS are a technology that change geoscientific research, but they are still not routinely used for geological mapping in exploration and mining due to lack of trust in their added value, missing expertise and guidance in the selection and combination of drones and sensors. To address these limitations and highlight the potential of using UAS in exploration settings, we present a UAS multi-sensor mapping approach based on the integration of drone-borne photography, multi- and hyperspectral imaging, and magnetics. Data are processed with conventional methods as well as innovative machine-learning algorithms and validated by geological field mapping, yielding a comprehensive and geologically interpretable product. As a case study, we chose the northern extension of the Siilinjärvi apatite mine in Finland, in a brownfield exploration setting with plenty of ground truth data available and a survey area that is only partly covered by vegetation. We conducted rapid UAS surveys from which we created a multi-layered dataset to investigate properties of the ore-bearing carbonatite-glimmerite body. Our resulting geologic map discriminates between the principal lithologic units and distinguishes ore-bearing from waste rocks. Structural orientations and lithological units are deduced based on high-resolution, hyperspectral image-enhanced point clouds. UAS-based magnetic data allow an insight into their subsurface geometry through modelling based on magnetic interpretation. We validate our results via ground survey including rock specimen sampling, geochemical and mineralogical analysis and spectroscopic point measurements. We are convinced that the presented non-invasive, data-driven mapping approach can complement traditional workflows in mineral exploration as a flexible tool. Mapping products based on UAS data increase efficiency and maximize safety of the resource extraction process, reduce expenses and incidental wastes.

Keywords: unmanned aerial vehicles; hyperspectral; multispectral; magnetic; geologic mapping; drones; UAV

Publ.-Id: 31411

Live-cell Imaging with Aspergillus Fumigatus-specific fluorescent Siderophore Conjugates

Pfister, J.; Lichius, A.; Summer, D.; Haas, H.; Kanagasundaram, T.; Kopka, K.; Decristoforo, C.

Live-cell imaging allows to analyse the subcellular localisation dynamics of physiological processes with high spatial-temporal resolution in vivo. So far, only few fluorescent dyes have been custom-designed to facilitate species-specific live-cell imaging approaches in filamentous fungi. Therefore, we developed fluorescent dye conjugates based on the sophisticated iron acquisition system of Aspergillus fumigatus by chemical modification of the siderophore Triacetylfusarinine C (TAFC).
Various fluorophores (FITC, NBD, Ocean Blue, BODIPY 630/650, SiR, TAMRA and Cy5) were conjugated to Diacetylfusarinine C (DAFC). Gallium-68 labelling enabled in-vitro and in-vivo characterisations. LogD, uptake assays and growth assays were performed and complemented by live-cell imaging in different Aspergillus species.
Siderophore conjugates were specifically recognised by the TAFC transporter MirB and utilized in growth assays as an iron source. Fluorescence microscopy revealed uptake dynamics and differential subcellular accumulation patterns of all compounds inside fungal hyphae. [Fe]DAFC-NBD and -Ocean Blue accumulated in vacuoles, whereas [Fe]DAFC-BODIPY, -SiR and -Cy5 localised to mitochondria. [Fe]DAFC -FITC showed a uniform cytoplasmic distribution, whereas [Fe]DAFC-TAMRA was not internalised at all. Co-staining experiments with commercially available fluorescent dyes confirmed these findings.
Overall we developed a new class of fluorescent dyes varying in intracellular fungal targeting providing novel tools for live-cell imaging applications for Aspergillus fumigatus.

Keywords: Live-cell Imaging; Aspergillus Fumigatus; Fluorescence Microscopy; Siderophores; Fluorescent Dyes

Publ.-Id: 31410

Data for: An analysis for detecting potential relocation of the inventory of dry storage containers during prolonged interim storage via changes in the wall temperature fields

Wagner, M.; Reinicke, S.

Geometry files of the performed simulations (ANSYS Fluent).

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-06
    DOI: 10.14278/rodare.416
    License: CC-BY-4.0


Publ.-Id: 31409

Radiomics-based prediction of tumor phenotype from tumor microenvironment and medical imaging

Müller, J.; Leger, S.; Zwanenburg, A.; Suckert, T.; Beyreuther, E.; von Neubeck, C.; Lühr, A.; Krause, M.; Löck, S.; Dietrich, A.; Bütof, R.

Magnetic resonance imaging (MRI) and immunohistochemical tissue stainings are pivotal for radiotherapeutic workflows. Yet, recent efforts herald a paradigm shift: Radiomic methods are used to extract a large number of quantitative features from image data to detect high-dimensional patterns, which are correlated with relevant clinical endpoints. Preclinical experiments help to understand underlying mechanisms, yet require the backtranslation of clinically used methods and their application to a heterogeneous patient cohort. In the present preclinical experiment, we determine the tumor phenotype from MRI and tumor microenvironment (TME) features in a patient cohort of xenograft tumor models of the head and neck.
An artificial heterogeneous patient population was created by mixing two tumor models of different radiosensitivity (SAS & UT-SCC-14) in pooled cohort (N = 108) and exposure to one week of fractionated irradiation with photons and protons. After irradiation, contrast agent-enhanced T1-weighted 3D gradient-echo MRI scans were acquired, tumors were excised and characterized immunohistochemically regarding vascularity (CD31), hypoxia (Pimonidazole) and morphology (H&E). Approximately 200 quantitative features were extracted from MRI and light-microscopy image data with an automated medical image radiomics processor and trainable image segmentation, respectively. TME parameters were analyzed regarding effects of radiation with two-sided t-tests. A fully automated radiomic framework was used for feature selection, model generation using leave-one-out cross validation with the individual tumor model’s identity (i.e. its phenotype) as endpoint. Model performance was assessed through area under the curve (AUC).
The used image quantification methods allowed for robust feature extraction. No effects of radiation on the TME were detected except for changes in vessel-adjacent hypoxia. Radiomic analysis was able to predict the tumor model based on TME features (AUC = 0.86), MRI features (AUC = 0.90) or combined features (AUC = 0.86).
We demonstrated backtranslation of radiomic methods in a preclinical setting with multi-modal image data. Further analysis of automatically extracted MRI and TME features may allow for a more biologically informed interpretation of MRI data.

Keywords: Radiomics; Medical Imaging; Preclinical; Microenvironment; Hypoxia; Radiation

  • Lecture (Conference) (Online presentation)
    Virtual Meeting 2020, 18.-21.10.2020, (Virtual), (Virtual)

Publ.-Id: 31408

A convolutional neural network for fully automated blood SUV determination in oncological FDG-PET

Nikulin, P.; Hofheinz, F.; Maus, J.; Pietsch, J.; Li, Y.; Bütof, R.; Lange, C.; Furth, C.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.

Aim: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor's glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.

Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), namely U-Net. 632 FDG PET/CT scans from 4 different sites were used for network training (N=208) and testing (N=424). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.

Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Notably, using both CT and PET data as input for network training allows the trained network to derive unbiased BSUVs by detecting and excluding aorta segments affected by attenuation artifacts or spill-over. Comparison of manually (M) and automatically (A) derived BSUVs shows excellent concordance: the mean paired M-A difference in the 424 test cases is (mean +/- SD)=(0.2 +/- 3.1)% with a 95% confidence interval of [-6.6, 5.7]%. For a single test case the M-A difference exceeded 10%.

Conclusion: CNNs offer a viable approach for automatic BSUV determination. Our trained network exhibits a performance comparable to an experienced human observer and might already be considered suitable for supervised clinical use.

Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network

  • Poster (Online presentation)
    Nuklearmedizin 2020, 07.-09.07.2020, Online, Online
  • Lecture (Conference) (Online presentation)
    EANM’20 Congress, 22.-30.10.2020, Online, Online


Publ.-Id: 31407

A convolutional neural network for fully automated blood SUV determination to facilitate SUR computation in oncological FDG-PET

Nikulin, P.; Hofheinz, F.; Maus, J.; Li, Y.; Bütof, R.; Lange, C.; Furth, C.; Zschaeck, S.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.

Purpose: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor’s glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.
Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), using the U-Net architecture. 946 FDG PET/CT scans from several sites were used for network training (N = 366) and testing (N = 580). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.
Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Comparison of manually and automatically derived BSUVs shows excellent concordance: the mean relative BSUV difference was (mean ± SD) = (-0.5± 2.2)% with a 95% confidence interval of [−5.1, 3.8]% and a total range of [-10.0, 12.0]%. For four test cases the derived ROIs were unusable (<1 ml).
Conclusion: CNNs are capable of performing robust automatic image-based BSUV determination. Integrating automatic BSUV derivation into PET data processing workflows will significantly facilitate SUR computation without increasing the workload in the clinical setting.

Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network

  • Open Access Logo European Journal of Nuclear Medicine and Molecular Imaging 48(2021), 995-1004
    Online First (2020) DOI: 10.1007/s00259-020-04991-9

Publ.-Id: 31406

Hierarchical Sparse Subspace Clustering (HESSC): An Automatic Approach for Hyperspectral Image Analysis

Rafiezadeh Shahi, K.; Khodadadzadeh, M.; Tusa, L.; Ghamisi, P.; Tolosana Delgado, R.; Gloaguen, R.

Hyperspectral imaging techniques are becoming one of the most important tools to remotely acquire fine spectral information on different objects. However, hyperspectral images (HSIs) require dedicated processing for most applications. Therefore, several machine learning techniques were proposed in the last decades. Among the proposed machine learning techniques, unsupervised learning techniques have become popular as they do not need any prior knowledge.
Specifically, sparse subspace-based clustering algorithms have drawn special attention to cluster the HSI into meaningful groups since such algorithms are able to handle high dimensional and highly mixed data, as is the case in real-world applications. Nonetheless, sparse subspace-based clustering algorithms usually tend to demand high computational power and can be time-consuming.
In addition, the number of clusters is usually predefined. In this paper, we propose a new hierarchical sparse subspace-based clustering algorithm (HESSC), which handles the aforementioned problems in a robust and fast manner and estimates the number of clusters automatically. In the experiment, HESSC is applied to three real drill-core samples and one well-known rural benchmark (i.e., Trento) HSI datasets. In order to evaluate the performance of HESSC, the performance of the new proposed algorithm is quantitatively and qualitatively compared to the state-of-the-art sparse subspace-based algorithms. In addition, in order to have a comparison with conventional clustering algorithms, HESSC’s performance is compared with K-means and FCM. The obtained clustering results demonstrate that HESSC performs well when clustering HSIs compared to the other applied clustering algorithms.

Keywords: hyperspectral images; subspace-based clustering; hierarchical structure; unsupervised learning; sparse representation; ensemble learning

Publ.-Id: 31405

Magnetic properties of biogenic selenium nanomaterials

Dixit, R.; Gupta, A.; Jordan, N.; Zhou, S.; Schild, D.; Weiß, S.; Guillon, E.; Jain, R.; Lens, P.

The properties of biogenic elemental selenium (BioSe) need to be studied in order to understand its environmental fate. In this paper, the magnetic properties of biogenic elemental selenium nanospheres (BioSe-Nanospheres) and nanorods (BioSe-Nanorods) obtained via the reduction of selenium(IV) using anaerobic granular sludge were investigated. The study indicated that the BioSe nanomaterials have a strong paramagnetic contribution with some ferromagnetic component due to the incorporation of Fe(III) (high spin and low spin species) as indicated by Electron Paramagnetic Resonance (EPR). X-Ray Photoelectron Spectroscopy (XPS) also confirmed the weak presence of Fe(III) and combined with EPR data, the Fe(III) availability through the nanomaterial was established. It is likely that Fe(III) being abundantly present in sludge got entrapped in the extracellular polymeric substances (EPS) coating the biogenic nanomaterials. The presence of Fe(III) in BioSe nanomaterials increases the mobility of Fe(III) and can have an effect on phytoplankton growth in the environment. Further, there is a potential to exploit the magnetic properties of BioSe nanomaterials in drug delivery system as well as in space refrigeration.

Publ.-Id: 31404

Thermal kinetics of free volume in porous spin-on dielectrics: exploring the network- and pore-properties

Elsherif, A. G. A.; Koehler, N.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Ecke, R.; Schulz, S. E.; Wagner, A.

Comprehensive ex-situ and in-situ investigations of thermal curing processes in spin-on ultra-low-k thin films conducted by positron annihilation spectroscopy and Fourier transform infrared spectroscopies are presented. Positron annihilation lifetime spectroscopy of ex-situ cured samples reveals an onset of the curing process at about 200 °C, which advances with increasing curing temperature. Porogen agglomeration followed by diffusive migration to the surface during the curing process leads to the generation of narrow channels across the film thickness. The size of those channels is determined by a pore size distribution analysis of positron lifetime data. Defect kinetics during in-situ thermal curing has been investigated by means of Doppler broadening spectroscopy of the annihilation radiation, showing several distinct partially superposed and subsequent curing stages, i.e., moisture and residual organic solvents removal, SiOx network cross-linking, porogen decomposition, and finally creation of a stable porous structure containing micropore channels interconnecting larger mesopores formed likely due to micelle like interaction between porogen molecules, for curing temperatures not larger than 500 °C. Static (sequencing curing) states captured at specific temperature steps confirm the conclusions drawn during the dynamic (continuous curing) measurements. Moreover, the onset of pore inter-connectivity is precisely estimated as pore interconnectivity sets in at 380–400 °C.

Keywords: In-situ curing; Positron annihilation spectroscopy; Porogen removal; Porosimetry; FTIR; Dielectrics; Pore size distribution; Positronium

Related publications

Publ.-Id: 31402

Transition from steady to oscillating convection rolls in Rayleigh-Bénard convection under the influence of a horizontal magnetic field

Yang, J.; Vogt, T.; Eckert, S.

In this study we consider the effect of a horizontal magnetic field on the Rayleigh-Bénard convection in a finite liquid metal layer contained in a cuboid vessel (200x200x40 mm^3) of aspect ratio Gamma = 5. Laboratory experiments are performed for measuring temperature and flow field in the low melting point alloy GaInSn at Prandtl number Pr = 0.03 and in a Rayleigh number range 2.3x10^4 < Ra < 2.6x10^5. The field direction is aligned parallel to one pair of the two side walls. The field strength is varied up to a maximum value of 320 mT (Ha = 2470, Q = 6.11x10^6, definitions of all non-dimensional numbers are given in the text). The magnetic field forces the flow to form two-dimensional rolls whose axes are parallel to the direction of the field lines. The experiments confirm the predictions made by Busse and Clever (J. Mécanique Théorique et Appliquée, 1983 [1]) who showed that the application of the horizontal magnetic field extends the range in which steady two-dimensional roll structures exist (‘Busse balloon’) towards higher Ra numbers. A transition from the steady to a time-dependent oscillatory flow occurs when Ra exceeds a critical value for a given Chandrasekhar number Q, which is also equivalent to a reduction of the ratio Q/Ra. Our measurements reveal that the first developing oscillations are clearly of two-dimensional nature, in particular a mutual increase and decrease in the size of adjacent convection rolls is observed without the formation of any detectable gradients in the velocity field along the magnetic field direction. At a ratio of Q/Ra = 1, the first 3D structures appear, which initially manifest themselves in a slight inclination of the rolls with respect to the magnetic field direction. Immediately in the course of this, there arise also disturbances in the spaces between adjacent convection rolls, which are advected along the rolls due to the secondary flow driven by Ekman pumping. The transition to fully-developed three-dimensional structures and then to a turbulent regime takes place with further lowering Q/Ra.

Keywords: Rayleigh-Benard convection; liquid metal; horizontal magnetic field; convection rolls; oscillatory instability


Publ.-Id: 31399

Strengthening of ods silver wires

Wasserbäch, W.; Skrotzki, W.; Chekhonin, P.

The present work is part of an experimental program in which the mechanical behavior and the evolution of microstructure and texture of different industrially manufactured oxide-dispersion strengthened silver alloys upon different processing steps like hot-extrusion, cold-working and further annealing have been investigated. The investigations reveal that the incoherent oxide particles strongly influence the evolution of microstructure and texture during processing and consequently the deformation behavior at room temperature. Small oxide particles cause a high strengthening of the material but only a small change of the microstructure and texture. Increasing the oxide particle size subsequently reduces the strength and changes the original microstructure and texture in a more pronounced way. The yield strength at room temperature can be explained with a linear superposition of the Orowan stress for bypassing of oxide particles by dislocations and grain boundary strengthening according to Hall-Petch. The impact of texture of the materials on the yield strength is accounted for.

Keywords: Silver; Metal matrix composites; Cold-working; Strain hardening; Texture


Publ.-Id: 31397

Keap1 inhibition sensitizes head and neck squamous cell carcinoma cells to ionizing radiation via impaired non-homologous end joining and induced autophagy

Deville, S.; Luft, S.; Kaufmann, M.; Cordes, N.

The function of Keap1 (Kelch-like ECH-associated protein 1), a sensor of oxidative and electrophilic stress, in the radiosensitivity of cancer cells remains elusive. Here, we investigated the effects of pharmacological inhibition of Keap1 with ML344 on radiosensitivity, DNA double strand break (DSB) repair and autophagy in head and neck squamous cell carcinoma (HNSCC) cell lines. Our data demonstrate that Keap1 inhibition enhances HNSCC cell radiosensitivity. Despite elevated, Nrf2-dependent activity of non-homologous end joining (NHEJ)-related DNA repair, Keap1 inhibition seems to impair DSB repair through delayed phosphorylation of DNA-PKcs. Moreover, Keap1 inhibition elicited autophagy and increased p62 levels when combined with X-ray irradiation. Our findings suggest HNSCC cell radiosensitivity, NHEJ-mediated DSB repair and autophagy to be co-regulated by Keap1.

Keywords: HNSCC; radiosensitivity; Keap1; autophagy

Publ.-Id: 31395

c-Abl tyrosine kinase is regulated downstream of the cytoskeletal protein synemin in head and neck squamous cell carcinoma radioresistance and DNA repair

Deville, S.; Delgadillo, L.; Vehlow, A.; Cordes, N.

The intermediate filament synemin has been previously identified as novel regulator of cancer cell therapy resistance and DNA double strand break (DSB) repair. c-Abl tyrosine kinase is involved in both of these processes. Using PamGene technology, we performed a broad-spectrum kinase activity profiling in three-dimensionally, matrix grown head and neck cancer cell cultures. Upon synemin silencing, we identified 86 deactivated tyrosine kinases, including c-Abl, in irradiated HNSCC cells. c-Abl hyperphosphorylations on tyrosine (Y) 412 and threonine (T) 735 upon irradiation were significantly reduced after synemin inhibition prompting us to hypothesize that c-Abl tyrosine kinase is an important signaling component of the synemin-mediated radioresistance pathway. Simultaneous targeting of synemin and c-Abl resulted in similar radiosensitization and DSB repair compared with single synemin depletion suggesting synemin as an upstream regulator of c-Abl. Immunoprecipitation assays revealed a protein complex formation between synemin and c-Abl pre- and post-irradiation. Upon pharmacological inhibition of ATM, synemin/c-Abl protein-protein interactions were disrupted implying synemin function to depend on ATM kinase activity. Moreover, deletion of the ∆SH2 domain in c-Abl demonstrated a decrease in interaction indicating the dependency of the protein-protein interaction on this domain. Mechanistically, impairment of DNA repair seems to be related with radiosensitization upon synemin knockdown via regulation of non-homologous end joining, independent of c-Abl function. Our data generated in more physiological 3D cancer cell culture models suggest c-Abl as further key determinant of radioresistance downstream of synemin.

Keywords: Ionizing radiation; HNSCC; Synemin; DNA repair

Publ.-Id: 31394

Comparative proton and photon irradiation combined with pharmacological inhibitors in 3D pancreatic cancer cultures

Görte, J.; Beyreuther, E.; Danen, E.; Cordes, N.

Pancreatic ductal adenocarcinoma (PDAC) is a highly therapy resistant tumor entity of unmet need. Over the last decades, radiotherapy has been considered as additional treatment modality to surgery and chemotherapy. Owing to radiosensitive abdominal organs, high precision proton beam radiotherapy has been regarded superior to photon radiotherapy. To further elucidate the potential of combination therapies, we employed a more physiological 3D, matrix-based cell culture model to assess tumoroid formation capacity after photon and proton irradiation. Additionally, we investigated proton and photon irradiation-induced phosphoproteomic changes for identifying clinically exploitable targets. Here, we show that proton irradiation elicits a higher efficacy to reduce 3D PDAC tumoroid formation and a greater extent of phosphoproteome alterations compared with photon irradiation. Targeting of proteins identified in the phosphoproteome that were uniquely altered by protons or photons failed to cause radiation type-specific radiosensitization. Targeting DNA repair proteins associated with non-homologous endjoing, however, revealed a strong radiosensitizing potential independent from the radiation type. In conclusion, our findings suggest proton irradiation to be potentially more effective in PDAC than photons without additional efficacy when combined with DNA repair inhibitors.

Keywords: PDAC; radiotherapy; proton beam irradiation; 3D cell culture; molecular targeting

Publ.-Id: 31393

Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions

Schwestka, J.; Inani, H.; Tripathi, M.; Niggas, A.; Mcevoy, N.; Libisch, F.; Aumayr, F.; Kotakoski, J.; Wilhelm, R. A.

The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van-der-Waals heterostructures. Tailoring of heterostructure properties post-growth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van-der-Waals MoS2/graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nm-sized pores that appear only in the MoS2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS2 underneath. Our main focus is here on monolayer MoS2, but we also analyzed areas with few-layer structures, and observed that the perforation is limited to the two topmost MoS2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono(or bi-)layer manipulation of van-der-Waals heterostructures when also the localized potential energy deposition of highly charged ions is added to the toolbox.

Keywords: 2d material modification; ion beam surface modification; monolayer precision; van der Waals heterostructure

Publ.-Id: 31392

The role of contaminations in ion beam spectroscopy with freestanding 2D materials: A study on thermal treatment

Niggas, A.; Schwestka, J.; Creutzburg, S.; Gupta, T.; Eder, D.; Bayer, B. C.; Aumayr, F.; Wilhelm, R. A.

As surface-only materials, freestanding 2D materials are known to have a high level of contamination—mostly in the form of hydrocarbons, water, and residuals from production and exfoliation. For well-designed experiments, it is of particular importance to develop effective clean- ing procedures, especially since standard surface science techniques are typically not applicable. We perform ion spectroscopy with highly charged ions transmitted through freestanding atomically thin materials and present two techniques to achieve clean samples, both based on thermal treatment. Ion charge exchange and energy loss are used to analyze the degree of sample contamination. We find that even after cleaning, heavily contaminated spots remain on single layer graphene. The contamination coverage, however, clusters in strand-like structures leaving large clean areas. We present a way to discriminate clean from contaminated areas with our ion beam spectroscopy if the heterogeneity of the surface is increased sufficiently enough. We expect a similar discrimination to be necessary in most other experimental techniques.

Publ.-Id: 31391

PIMC data for the nonlinear electronic density response in warm-dense matter (WDM)

Dornheim, T.

This repository contains the PIMC raw data for the actual density response of the harmonically perturbed electron gas.

The data can be freely re-used. Please cite:

T. Dornheim, J. Vorberger, and M. Bonitz, Nonlinear Electronic Density Response in Warm Dense Matter, Phys. Rev. Lett. (in press), arXiv:2004.03229

Keywords: PIMC, density response, warm dense matter

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-03
    DOI: 10.14278/rodare.408
    License: CC-BY-4.0


Publ.-Id: 31390

Trimeric uranyl(VI)–citrate forms Na+, Ca2+, and La3+ sandwich complexes in aqueous solution

Kretzschmar, J.; Tsushima, S.; Drobot, B.; Steudtner, R.; Schmeide, K.; Stumpf, T.

Basile et al. (Chem. Commun., 2015, 51, 5306–5309) showed that a sodium ion is sandwiched by the uranyl(VI) oxygen atoms of two 3:3 uranyl(VI)–citrate complex molecules in single-crystals. By means of NMR spectroscopy supported by DFT calculation we provide unambiguous evidence for this complex to persist in aqueous solution above a critical concentration of 3 mM uranyl citrate. Unprecedented Ca2+ and La3+ coordination by a bis-(η3-uranyl(VI)-oxo) motif advances the understanding of uranium’s aqueous chemistry. As determined from 17O NMR, Ca2+ and especially La3+ cause strong O=U=O polarization which opens up new ways for uranyl(VI)-oxygen activation and functionalization.

Keywords: uranium; uranyl; U(VI); citric acid; NMR; DFT; spectroscopy; molecular structure

Related publications

  • Chemical Communications 56(2020), 13133-13136
    Online First (2020) DOI: 10.1039/D0CC05460G

Publ.-Id: 31389

Tumor markers as an entry for SARS-CoV-2 infection?

Pu, X.; Dubrovska, A.

Coronavirus disease 2019 (COVID-19), the highly contagious illness caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the globe, becoming one of the most challenging public health crisis of our times. SARS-CoV-2 can cause severe disease associated with multiple organ damage. Cancer patients have a higher risk of SARS-CoV-2 infection and death. While the virus uses angiotensin-converting enzyme 2 (ACE2) as the primary entry receptor, the recent experimental and clinical findings suggest that some tumor markers, including CD147 (Basigin), can provide a new entry for SARS-CoV-2 infection through binding to the viral spike (S) protein. In the absence of specific viral drugs, blocking of CD147 might be a way to prevent virus invasion. Identifying other target proteins is of high importance as targeting the alternative receptors for SARS-CoV-2 might open up a promising avenue for the treatment of COVID-19 patients, including those who have cancer.

Keywords: SARS-CoV-2; COVID-19; CD147; Basigin; Emmprin; spike protein

Publ.-Id: 31388

Metal dissociation from humic colloids: Kinetics with time-dependent rate constants

Lippold, H.; Zedek, L.

The mobility of contaminant metals in aqueous subsurface environments is largely controlled by their interaction with humic substances as colloidal constituents of Dissolved Organic Matter. Transport models for predicting carrier-bound migration are based on a competitive partitioning process between solid surface and colloids. However, it has been observed that dissociation of multivalent metals from humic complexes is a slow kinetic process, which is even more impeded with increasing time of contact. Based on findings obtained in isotope exchange experiments, the convoluted time dependence of dissociation was fully described by a complex two-site approach, integrating rate “constants” that are in turn time-dependent. Thus, this study presents the treatment of a particular phenomenon: kinetics within kinetics. The analysis showed that the inertization process does not lead to irreversible binding. Consequently, thermodynamic concepts using equilibrium constants remain applicable in speciation and transport modeling if long time frames are appropriate.

Keywords: Colloids; Desorption; Humic complexes; Kinetic model; Metal binding; Natural organic matter


  • Secondary publication expected from 22.02.2022

Publ.-Id: 31387

Quantitative isotopic fingerprinting of thallium associated with potentially toxic elements (PTEs) in fluvial sediment cores with multiple anthropogenic sources

Liu, J.; Zhou, Y.; She, J.; Tsang, D. C. W.; Lippold, H.; Wang, J.; Jiang, Y.; Wei, X.; Yuan, W.; Luo, X.; Zhai, S.; Song, L.

Thallium (Tl) is a dispersed trace metal showing remarkable toxicity. Various anthropogenic activities may generate Tl contamination in river sediments, posing tremendous risks to aquatic life and human health. This paper aimed to provide insight into the vertical distribution, risk assessment and source tracing of Tl and other potentially toxic elements (PTEs) (lead, cadmium, zinc and copper) in three representative sediment cores from a riverine catchment impacted by multiple anthropogenic activities (such as steel-making and Pb-Zn smelting). The results showed high accumulations of Tl combined with associated PTEs in the depth profiles. Calculations according to three risk assessment methods by enrichment factor (EF), geoaccumulation index (Igeo) and the potential ecological risk index (PERI) all indicated a significant contamination by Tl in all the sediments. Furthermore, lead isotopes were analyzed to fingerprint the contamination sources and to calculate their quantitative contributions to the sediments using the IsoSource software. The results indicated that a steel-making plant was the most important contamination source (~56%), followed by a Pb-Zn smelter (~20%). The natural parental bedrock was found to contribute ~24%. The findings highlight the importance of including multiple anthropogenic sources for quantitative fingerprinting of Tl and related metals by the lead isotopic approach in complicated environmental systems.

Keywords: Thallium contamination; Spatial distribution; Pollution risk assessment; Multiple end-members; Isotopic tracing

Publ.-Id: 31386

gmGeostats: an R package for Geostatistics for Compositional Analysis with R

Tolosana Delgado, R.; van den Boogaart, K. G.; Mueller, U.; Talebi, H.

The package provides support for geostatistical analysis of multivariate data, in particular data with restrictions, e.g. positive amounts data, compositional data, distributional data, microstructural data, as occur in Geometallurgy. It includes descriptive analysis and modelling for such data, both from a two-point Gaussian perspective and multipoint perspective, in an unified integrated approach.

Keywords: R programming; Geostatistics; Compositional data analysis; 3D modelling; Uncertainty

  • Software in external data repository
    Publication year 2020
    Programming language: R
    System requirements: multiplatform
    License: CC BY-SA 4.0 | GPL (≥ 2)
    Hosted on CRAN: Link to location

Publ.-Id: 31384

Data for: The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?

Eftekhari, M.; Schwarzenberger, K.; Javadi, A.; Eckert, K.

The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-09
    DOI: 10.14278/rodare.406


Publ.-Id: 31383

All-THz pump-probe spectroscopy of the intersubband AC-Stark effect in a wide GaAs quantum well

Schmidt, J.; Winnerl, S.; Dimakis, E.; Hübner, R.; Schneider, H.; Helm, M.

We report the observation of the intersubband AC-Stark effect in a single wide GaAs/AlGaAs quantum well. In a three-level configuration, the n = 2 to n = 3 intersubband transition is resonantly pumped at 3:5 THz using a free-electron laser. The induced spectral changes are probed using THz time-domain spectroscopy with a broadband pulse extending up to 4 THz. We observe an Autler Townes splitting at the 1 -> 2 intersubband transition as well as an indication of a Mollow triplet at the 2 -> 3 transition, both evidencing the dressed states. For longer delay times, a relaxation of the hot-electron system with a time constant of around 420 ps is measured.

Keywords: AC Stark effect; Autler Townes splitting; high-field physics; intersubband transitions

Publ.-Id: 31382

Modelling of late side effects following cranial proton beam therapy

Dutz, A.; Lühr, A.; Agolli, L.; Bütof, R.; Valentini, C.; Troost, E. G. C.; Baumann, M.; Vermeren, X.; Geismar, D.; Lamba, N.; Lebow, E.; Bussière, M.; Daly, J.; Bussière, M.; Krause, M.; Timmermann, B.; Shih, H.; Löck, S.

The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies that can be based on normal tissue complication probability (NTCP) models. We developed and externally validated NTCP models for common late side-effects following PBT in brain tumour patients to optimise patients’ quality of life.
Cohorts from three PBT centres (216 patients) were investigated for several physician-rated endpoints at 12 and 24 months after PBT: alopecia, dry eye syndrome, fatigue, headache, hearing and memory impairment, and optic neuropathy. Dose-volume parameters of associated normal tissues and clinical factors were used for logistic regression modelling in a development cohort. Statistically significant parameters showing high area under the receiver operating characteristic curve (AUC) values in internal cross-validation were externally validated. In addition, analyses of the pooled cohorts and of time-dependent generalised estimating equations including all patient data were performed.
In the validation study, mild alopecia was related to high dose parameters to the skin [e.g. the dose to 2% of the volume (D2%)] at 12 and 24 months after PBT. Mild hearing impairment at 24 months after PBT was associated with the mean dose to the ipsilateral cochlea. Additionally, the pooled analyses revealed dose-response relations between memory impairment and intermediate to high doses to the remaining brain as well as D2% of the hippocampi. Mild fatigue at 24 months after PBT was associated with D2% to the brainstem as well as with concurrent chemotherapy. Moreover, in generalised estimating equations analysis, dry eye syndrome was associated with the mean dose to the ipsilateral lacrimal gland.
We developed and in part validated NTCP models for several common late side-effects following PBT in brain tumour patients. Validation studies are required for further confirmation.

Keywords: NTCP models; brain tumours; late side-effects; proton beam therapy

Publ.-Id: 31380

Practice recommendations for lung cancer radiotherapy during the COVID-19 pandemic: An ESTRO-ASTRO consensus statement

Troost, E. G. C.; Nestle, U.; Putora, P.; Bussink, J.

COVID-19 Rapid Letter

Publ.-Id: 31378

Nonlinear Electronic Density Response in Warm Dense Matter

Dornheim, T.; Vorberger, J.; Bonitz, M.

Warm dense matter (WDM)—an extreme state with high temperatures and densities that occurse.g. in astrophysical objects—constitutes one of the most active fields in plasma physics and materials science. These conditions can be realized in the lab by shock compression or laser excitation, and the most accurate experimental diagnostics is achieved with lasers and free electron lasers which is theoretically modeled using linear response theory. Here, we present first ab initio path integral Monte Carlo results for the nonlinear density response of correlated electrons in WDM and show that for many situations of experimental relevance nonlinear effects cannot be neglected.

Keywords: Warm dense matter; Nonlinear effects; path integral Monte Carlo

Related publications


Publ.-Id: 31377

Imaging and Milling Resolution of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs

Klingner, N.; Hlawacek, G.; Mazarov, P.; Pilz, W.; Meyer, F.; Bischoff, L.

The application of Focused Ion Beams (FIB) has become a well-established and promising technique for patterning and prototyping on the nm-scale in research and development. Light ions in the range of m = 1 … 28 u (hydrogen to silicon) are of increasing interest due to the available high beam resolution in the nm range and their special chemical and physical behavior in the substrate. In this work helium and neon ion beams from a Helium Ion Microscope (HIM) are compared with ion beams like beryllium, lithium, boron, carbon and silicon obtained from a mass separated FIB using Liquid Metal Alloy Ion Sources (LMAIS) with respect to their imaging and milling resolution.

Keywords: Focused Ion Beam; Helium Ion Microscope; Gas Field Ion Source; Liquid Metal Alloy Ion Sources; resolution

Publ.-Id: 31376

Mapping the Future of Particle Radiobiology in Europe: The INSPIRE Project

Henthorn, N.; Sokol, O.; Durante, M.; de Marzi, L.; Pouzoulet, F.; Miszczyk, J.; Olko, P.; Brandenburg, S.; van Goethem, M.-J.; Barazzuol, L.; Tambas, M.; Langendijk, J. A.; Davídková, M.; Vondráček, V.; Bodenstein, E.; Pawelke, J.; Lomax, A. J.; Weber, D. C.; Dasu, A.; Stenerlöw, B.; Poulsen, P. R.; Sørensen, B. S.; Grau, C.; Sitarz, M. K.; Heuskin, A.-C.; Lucas, S.; Warmenhoven, J. W.; Merchant, M. J.; Mackay, R. I.; Kirkby, K. J.

Particle therapy is a growing cancer treatment modality worldwide. However, there still remains a number of unanswered
questions considering differences in the biological response between particles and photons. These questions, and probing of biological mechanisms in general, necessitate experimental investigation. The “Infrastructure in Proton International Research” (INSPIRE) project was created to provide an infrastructure for European research, unify research efforts on the topic of proton and ion therapy across Europe, and to facilitate the sharing of information and resources. This work highlights the radiobiological capabilities of the INSPIRE partners, providing details of physics (available particle types and energies), biology (sample preparation and post-irradiation analysis), and researcher access (the process of applying for beam time). The collection of information reported here is designed to provide researchers both in Europe and worldwide with the tools required to select the optimal center for their research needs. We also highlight areas of redundancy in capabilities and suggest areas for future investment.

Keywords: Proton theraphy; Radiotherapy; Radiobiology; Beamline; Irradiation

Publ.-Id: 31375

A computational method to simulate mono- and poly-disperse two-dimensional foams flowing in obstructed channel

Carl Lavoratti, T.; Heitkam, S.; Hampel, U.; Lecrivain, G.

A modified phase-field model is presented to numerically study the dynamics of flowing foam in an obstructed channel. The bubbles are described as smooth deformable fields interacting with one another through a repulsive potential. A strength of the model lies in its ability to simulate foams with wide range of gas fraction. The foam motion, composed of about hundred two-dimensional gas elements, was analyzed for gas fractions ranging from 0.4 to 0.99, that is below and beyond the jamming transition. Simulations are preformed near the quasi-static limit, indicating that the bubble rearrangement in the obstructed channel is primarily driven by the soft collisions and not by the hydrodynamics. Foam compression and relaxation upstream and downstream of the obstacle are reproduced and qualitatively match previous experimental and numerical observations. Striking dynamics, such as bubbles being squeezed by their neighbors in negative flow direction, are also revealed at intermediate gas fractions.

Keywords: Flowing foam; Computational method; Phase-field method; Obstructed channel

Related publications

Publ.-Id: 31374

Benchmark hyperspectral field and laboratory data against X-ray diffraction (XRD), Portable X-ray fluorescence (pXRF) and Scanning Electron Microscopy with Mineral Liberation Analysis (SEM-MLA) data.

de La Rosa Ferna; Tolosana Delgado, R.; Gloaguen, R.

A benchmarking databank based on different spectral, multiscale, multisensor exploration technologies was created. The benchmarking is composed of 63 rock samples from drill cores from a polymetallic (Cu-Zn-Pb) massive sulphide deposit in the Iberian Pyrite Belt. The samples had been analyzed by portable XRF, point hyperspectral spectrometer, portable FTIR, VNIR-SWIR imaging hyperspectral sensor and a LWIR imaging thermal hyperspectral sensor.

The mineralogical information from the boreholes will be complemented with mineral chemistry extracted from the spectral features of the alteration minerals that display chemical variations. The chemical variations in minerals generate shifts on the position of the metal-OH vibrational absorptions. This systematic variation can be recorded using the SWIR wavelength region of hyperspectral data. The shifts sometimes occur systematically with respect to ore deposits and hence mineral chemical information extracted from hyperspectral surveys can be used for mineral exploration. The mineral chemistry of the samples will be validated using scanning electron microscopy data integrated with the mineral liberation analysis (SEM-MLA).

In order to apply this type of research techniques aiming at a 3D model of the alteration areas of the entire deposit based on the hyperspectral data, it is essential to have the availability of drill cores along the whole extension of the mineral deposit. Consequently, the research was focused in a study area in the Southern Spain, the Elvira deposit of the MATSA–VALORIZA mining company, where 7 km of drill core were scanned with the hyperspectral sensors.

New exploration technologies (NEXT) is a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement nº 776804.

Keywords: Benchmarking; Hyperspectral; Drill core scanner; pFTIR; PXRF; VNIR - SWIR - LWIR

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-07-02
    DOI: 10.14278/rodare.392


Publ.-Id: 31373

Advanced Sandwich Composite Cores for Patient Support in Advanced Clinical Imaging and Oncology Treatment

Morris, R. H.; Geraldi, N. R.; Pike, L. C.; Pawelke, J.; Hoffmann, A. L.; Doy, N.; Stafford, J. L.; Spicer, A.; Newton, M. I.

Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as PET-CT and PET-MRI when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper we present a range of materials which are suitable for such purposes and evaluate the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We find that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins.

Keywords: Composite; Core; Clinical imaging; PET; CT; MRI; Proton

Publ.-Id: 31372

Brain geometry matters in Alzheimer disease progression: a simulation study

Hoore, M.; Kelling, J.; Sayadmanesh, M.; Mitra, T.; Schips, M.; Meyer-Hermann, M.

The Amyloid cascade hypothesis (ACH) for Alzheimer's disease (AD) is modeled over the whole brain tissue with a set of partial differential equations. Our results show that the amyloid plaque formation is critically dependent on the secretion rate of amyloid β(Aβ), which is proportional to the product of neural density and neural activity. Neural atrophy is similarly related to the secretion rate of Aβ. Due to a heterogeneous distribution of neural density and brain activity throughout the brain, amyloid plaque formation and neural death occurs heterogeneously in the brain. The geometry of the brain and microglia migration in the parenchyma bring more complexity into the system and result in a diverse amyloidosis and dementia pattern of different brain regions. Although the pattern of amyloidosis in the brain cortex from in-silico results is similar to experimental autopsy findings, they mismatch at the central regions of the brain, suggesting that ACH is not able to explain the whole course of AD without considering other factors, such as tau-protein aggregation or neuroinflammation.

Keywords: Neurdegenerative disease; Alzheimer's disease; Amyloid cascade hypothesis; mult-phase model


Publ.-Id: 31371

Multiscale Tomographic Analysis for Micron-Sized Particulate Samples

Ditscherlein, R.; Furat, O.; de Langlard, M.; Martins De Souza E. Silva, J.; Sygusch, J.; Rudolph, M.; Leißner, T.; Schmidt, V.; Peuker, U. A.

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

Keywords: multidimensional particle characterization; multiscale X-ray tomography; parametric copula; statistical image analysis

Publ.-Id: 31370

Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond

Zhang, G.; Samuely, T.; Iwahara, N.; Kačmarčík, J.; Wang, C.; May, P. W.; Jochum, J. K.; Onufriienko, O.; Szabó, P.; Zhou, S.; Samuely, P.; Moshchalkov, V. V.; Chibotaru, L. F.; Rubahn, H.-G.

The combination of different exotic properties in materials paves the way for the emergence of their new potential applications. An example is the recently found coexistence of the mutually antagonistic ferromagnetism and superconductivity in hydrogenated boron-doped diamond, which promises to be an attractive system with which to explore unconventional physics. Here, we show the emergence of Yu-Shiba-Rusinov (YSR) bands with a spatial extent of tens of nanometers in ferromagnetic superconducting diamond using scanning tunneling spectroscopy. We demonstrate theoretically how a two-dimensional (2D) spin lattice at the surface of a three-dimensional (3D) superconductor gives rise to the YSR bands and how their density-of-states profile correlates with the spin lattice structure. The established strategy to realize new forms of the coexistence of ferromagnetism and superconductivity opens a way to engineer the unusual electronic states and also to design better-performing superconducting devices.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-25
    DOI: 10.14278/rodare.341
    License: CC-BY-4.0


Publ.-Id: 31369

Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Ajayakumar, M.; Fu, Y.; Liu, F.; Komber, H.; Tkachova, V.; Xu, C.; Zhou, S.; Popov, A.; Liu, J.; Feng, X.

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-25
    DOI: 10.14278/rodare.343
    License: CC-BY-4.0


Publ.-Id: 31366

Revisiting the complexation of Cm(III) with aqueous phosphates: what can we learn from the complex structures using luminescence spectroscopy and ab initio simulations?

Huittinen, N. M.; Jessat, I.; Réal, F.; Vallet, V.; Starke, S.; Eibl, M.; Jordan, N.

The coordination chemistry of Cm(III) with aqueous phosphates was investigated by means of laser–induced luminescence spectroscopy and ab initio simulations.
For the first time, in addition to the presence of Cm(H2PO4)2+, the formation of Cm(H2PO4)2+ was unambiguously established from the luminescence spectroscopic data collected at various H+ concentrations (–log10[H+] = 2.52, 3.44, and 3.65), ionic strengths (0.5 – 3.0 mol∙L−1 NaClO4), and temperatures (25 – 90 °C). Complexation constants for both species were derived and extrapolated to standard conditions using the specific ion interaction theory.
The molal enthalpy ∆_R H_m^0 and molal entropy ∆_R S_m^0 of both complexation reactions were derived using the integrated van’t Hoff equation, and indicated an endothermic and entropy driven complexation. For the Cm(H2PO4)2+ complex, a more satisfactory description could be obtained when including the molal heat capacity term.
While monodentate binding of the H2PO4– ligand(s) to the central curium ion was found to be the most stable configuration for both complexes in our ab initio simulations and luminescence lifetime analyses, a different temperature–dependent coordination to hydration water molecules could be deduced from the electronic structure of the Cm(III)–phosphate complexes. More precisely, where the Cm(H2PO4)2+ complex could be shown to retain an overall coordination number of 9 over the entire investigated temperature range, a coordination change from 9 to 8 was established for the Cm(H2PO4)2+ species with increasing temperature.

Keywords: Cm(III); phosphate; complexation; luminescence; temperature; ab initio


  • Secondary publication expected from 30.06.2022

Publ.-Id: 31365

HIF2α supports pro-metastatic behavior in pheochromocytomas/paragangliomas

Bechmann, N.; Moskopp, M. L.; Ullrich, M.; Calsina, B.; Wallace, P. W.; Richter, S.; Friedemann, M.; Langton, K.; Fliedner, S. M. J.; Timmers, H. J. L. M.; Nölting, S.; Beuschlein, F.; Fassnacht, M.; Preijbisz, A.; Pacak, K.; Ghayee, H. K.; Bornstein, S. R.; Dieterich, P.; Pietzsch, J.; Wielockx, B.; Robledo, M.; Qin, N.; Eisenhofer, G.

Mutations that drive the stabilization of hypoxia inducible factor 2α (HIF2α) and downstream pseudohypoxic signaling are known to predispose to the development of pheochromocytomas and paragangliomas (PPGLs). However, any role of HIF2α in predisposition to metastatic disease remains unclear. To assess such a role we combined gene-manipulations in pheochromocytoma cell lines with retrospective analyses of patient data and gene expression profiling in tumor specimens. Among 425 patients with PPGLs identified with mutations in tumor-susceptibility genes, those with tumors due to activation of pseudohypoxic pathways had a higher frequency of metastatic disease than those with tumors due to activation of kinase- signaling pathways, even without inclusion of patients with mutations in SDHB (18.6% vs. 4.3% in, p<0.0001). Three out of nine (33%) of patients with gain-of-function mutations in HIF2α had metastatic disease. In cell line studies, elevated expression of HIF2α enhanced cell proliferation and led to increased migration and invasion capacity. Moreover, HIF2α expression in HIF2α-deficient cells resulted in increased cell motility, diffuse cluster formation and emergence of pseudopodia indicating changes in cell adhesion and cytoskeletal remodeling. In a mouse liver metastasis model, HIF2α enhanced the metastatic load. Transcriptomics data revealed alterations in focal adhesion and extracellular matrix-receptor interactions in HIF2α-mutated PPGLs. Our translational findings demonstrate that HIF2α supports pro-metastatic behavior in PPGLs, though other factors remain critical for subsequent transition to metastasis. We identified LAMB1 and COL4A2 as new potential therapeutic targets for HIF2α-driven PPGLs. Identified HIF2α downstream targets might open a new therapeutic window for aggressive HIF2α-expressing tumors.


  • Secondary publication expected

Publ.-Id: 31364

Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions

Mohseni, E.; Jose Kalayathine, J.; Reinecke, S.; Hampel, U.

Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve fine gas dispersion is to downsize the openings from which gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We have found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using relevant dimensionless numbers.

Keywords: Bubble Formation; Submillimeter Orifices; Bubbling Regime; Bubbling Dynamics; Stainless Steel Orifice

Related publications

Publ.-Id: 31363

Sorption of Europium on Diatom Biosilica as Model of a “Green” Sorbent for f-Elements

Kammerlander, K. K. K.; Köhler, L.; Huittinen, N. M.; Bok, F.; Steudtner, R.; Oschatz, C.; Vogel, M.; Stumpf, T.; Brunner, E.

Removing f-elements from anthropogenically contaminated sites is a challenging, but ecologically important task. Some of these elements are not only radioactive, but also chemically toxic and can spread through various pathways in the environment. The present work investigates f-element sorption on biogenic silica, which may be a promising “green” material for remediation. Commercially available diatomaceous earth (DE) and the cleaned cell walls of the diatom species Stephanopyxis turris (S.t.) and Thalassiosira pseudonana (T.p.) are compared with artificial mesocellular foam (MCF) as porous silica reference material. Trivalent europium was chosen as model sorptive for chemically similar trivalent actinides. Accordingly, Eu(III) in concentrations of 10-3 M and 10-5 M was sorbed on the four silica materials at varying pH values. The zeta potentials of the implemented sorbents under the same conditions were determined. In addition, the sorption reaction and the aqueous speciation of Eu(III) in the (bio)silica suspensions were modeled using the Diffuse Double Layer (DDL) model. With time-resolved laser-induced fluorescence spectroscopy (TRLFS), two different uptake mechanisms can be discerned, surface adsorption and incorporation/precipitation.

Keywords: biosilica; diatoms; europium; fluorescence; sorption


  • Secondary publication expected from 14.11.2021

Publ.-Id: 31362

Magnetocaloric effect in GdNi2 for cryogenic gas liquefaction studied in magnetic fields up to 50 T

Taskaev, S.; Khovaylo, V.; Skokov, K.; Liu, W.; Bykov, E.; Ulyanov, M.; Bataev, D.; Basharova, A.; Kononova, M.; Plakhotskiy, D.; Bogush, M.; Gottschall, T.; Gutfleisch, O.

Natural gases have played a significant role in different sectors of the global economy. Recent analyses have shown that the world’s gas consumption doubled over the last three decades; further growth of the gas consumption is predicted, rising to be 23%–28% of the total primary energy demand by 2030. Therefore, liquefaction of natural gases rapidly gains global importance. In this context, magnetic refrigeration emerges as a modern energy-saving technique, which is an alternative to the traditional gas-compression refrigeration. This paper is devoted to the study of the magnetocaloric effect in magnetic fields up to 10 T on a representative of the Laves phase alloys, GdNi2, which is considered as a perspective material for liquefaction of natural gases. For a magnetic field change of 10 T, the magnetic entropy change ΔSm≈−17 J/kg K and the adiabatic temperature change ΔTad ≈ 6.8 K was attained around Curie temperature TC = 70 K. The maximal value of the adiabatic temperature change measured directly in pulsed magnetic fields up to 50 T is ΔTad ≈ 15 K.

Publ.-Id: 31361

Effect of uniaxial stress on the electronic band structure of NbP

Schindler, C.; Noky, J.; Schmidt, M.; Felser, C.; Wosnitza, J.; Gooth, J.

The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov–de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov–de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov–de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the a axis.

Publ.-Id: 31360

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